US20160193505A1

US20160193505A1 - Golf ball incorporating steep hardness gradient and high compression thermoset rubber core

Info

Publication number: US20160193505A1
Application number: US15/072,511
Authority: US
Inventors: Mark L. Binette; David A. Bulpett; Douglas S. Goguen; Brian Comeau; Robert Blink; Michael J. Sullivan
Original assignee: Acushnet Co
Current assignee: Acushnet Co
Priority date: 2007-02-16
Filing date: 2016-03-17
Publication date: 2016-07-07

Abstract

A golf ball comprising a core comprising at least one layer that consists of a mixture of a plurality of synthetic flocks and a thermoset rubber composition. The plurality of synthetic flocks has a melting temperature that is greater than a mixing temperature at which the mixture is formed. Additionally, the at least one layer comprises an outer surface having an outer surface hardness of about 80 Shore C or greater and the outer surface hardness is greater than a center hardness of a geometric center of the core by at least 20 Shore C. A cover having at least one layer is disposed about the core. The synthetic flocks may be included in the mixture in an amount of from about 0.5 parts to about 15 parts of the total mixture. Examples of suitable synthetic flocks include nylon, polyester, polypropylene, aramid, or acrylic flocks, or combinations thereof.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending, co-assigned U.S. patent application Ser. No. 14/021,818, filed on Sep. 9, 2013, now allowed, which is a continuation-in-part of co-assigned U.S. patent application Ser. No. 13/309,085 filed on Dec. 1, 2011, now U.S. Pat. No. 8,529,378, which is divisional of U.S. patent application Ser. No. 12/143,879, filed on Jun. 23, 2008, now U.S. Pat. No. 8,070,626, which is a continuation-in-part of U.S. patent application Ser. No. 11/707,493, filed on Feb. 16, 2007, now U.S. Pat. No. 7,722,483, the entire disclosure of each of which is hereby incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

Golf balls incorporating high compression, steep hardness gradient thermoset rubber cores with controlled resilience.

BACKGROUND OF THE INVENTION

Golf balls are made in a variety of constructions and compositions. In recent years, virtually all golf balls are of a solid construction, generally including a solid core encased by a cover, both of which can have multiple layers, such as a dual core having a solid center and an outer core layer, or a multi-layer cover having an inner and outer cover layer. Examples of golf ball materials range from balata to polybutadiene, ionomer resins, polyurethanes, polyureas, and/or polyurethane/polyurea hybrids. Typically, outer layers are formed about the spherical outer surface of an inner golf ball component via compression molding, casting, or injection molding.
Golf ball cores are often formed at least in part from a thermoset rubber composition with polybutadiene as the base rubber. The cores are usually heated and crosslinked to create a core having certain pre-determined characteristics, such as compression or hardness, which result in a golf ball having the properties for a particular group of players, whether it be professionals, low-handicap players, or mid-to-high handicap golfers. From the perspective of a golf ball manufacturer, it is desirable to have cores exhibiting a wide range of properties, such as resilience, durability, spin, and “feel,” because this enables the manufacturer to make and sell golf balls suited to differing levels of ability.
Therefore, golf ball manufacturers continuously experiment with golf ball constructions and material formulations in order to target and improve aerodynamic and/or inertial properties and achieve desired feel without sacrificing durability. For example, spin performance can be enhanced by employing a golf ball construction using a steep gradient core (solid or multi-piece), meaning the hardness (JIS C or Shore D) increases considerably from the center point to the surface of the core. Steep hardness gradients usually produce a lower driver spin while still maintaining the desired approach and wedge spin. Meanwhile, better players often like higher compression golf balls—having faster swing speeds, they are capable of compressing the ball and still achieve the distance while gaining better control.
Steep hardness gradient cores may be created by employing a dual core construction wherein the inner core layer and an outer core layer are made from rubber formulations having differing physical properties. For example, a softer, less stiff inner core layer may be surrounded by a hard, stiffer outer core layer. The hardness and stiffness of each thermoset layer and the overall gradient of the core are conventionally modified by adding or subtracting coagents such as ZDA, ZDMA, HVA etc.; by adjusting the amount or type of peroxide crosslinker used; by incorporating chemical additives such as antioxidants, organosulfurs, etc.; and/or by changing cure time/temperature. However, such modifications can cause durability issues, such as crack propagation, which can result from changes in the crosslink density of the cured thermoset rubber material.
Yet, it can also be difficult to increase the compression of a rubber-based core by adding fillers without meanwhile also undesirably reducing resiliency/coefficient of restitution (CoR) of the core material. For example, poor coupling can occur between the filler and the rubber which can decrease the core's ability to rebound. Generally, a lower core CoR is undesirable, given that a golf ball's principal source of resiliency is typically in the rubber-based core, and high CoR values (i.e., closer to 1) will favorably correspond to a golf ball having a higher initial velocity and ultimately, greater overall distance.
And adding fillers that are known for increasing both compression and CoR are equally undesirable, since rubber-based cores are typically already abundantly resilient—unlike ionomeric layers, for example, which can protect the rubber core but generally lack resilience without combining ionomeric matrix material with some type of resilience-improving additive.
Accordingly, there is a need for durable golf balls incorporating high compression, steep hardness gradient rubber-based cores with controlled resilience/CoR that can be manufactured efficiently and cost effectively. The present inventive golf balls and methods of making same address and solve these needs.

SUMMARY OF THE INVENTION

Advantageously, a golf ball of the invention incorporates a high compression thermoset rubber core having a high outer surface hardness, steep hardness gradient from geometric center to the outer surface, and controlled resilience/CoR (not substantially decreasing or increasing CoR).
In one embodiment, a golf ball of the invention comprises a core comprising an inner core layer and an outer core layer; wherein the outer core layer consists of a mixture of a plurality of synthetic flocks and a first thermoset rubber composition. The plurality of synthetic flocks has a melting temperature that is greater than a mixing temperature at which the mixture is formed. The inner core layer does not contain said flocks.
The outer core layer comprises an outer surface having an outer surface hardness of about 80 Shore C or greater; and the outer surface hardness is greater than a center hardness of a geometric center of the core by at least 20 Shore C. In one alternative embodiment, the outer surface hardness is about 90 Shore C or greater and is greater than the center hardness by greater than 30 Shore C. Meanwhile, a cover comprising one or more layers is disposed about the core.
The synthetic flocks may be included in the mixture in an amount of from about 0.5 parts to about 15 parts of the total mixture. Non-limiting examples of suitable synthetic flocks include nylon, polyester, polypropylene, aramid, or acrylic flocks, or combinations thereof. The plurality of flocks is the only thermoplastic ingredient in the mixture.
In one embodiment, the first thermoset rubber composition comprises polybutadiene. In another embodiment, the first thermoset rubber composition comprises a blend of polybutadiene and at least one of polyoctenemer, natural rubber, ethylene propylene diene monomer (EPDM), cis-polyisoprene, trans-polyisioprene, and/or styrene-butadiene rubber (SBR).
In yet another embodiment, the first thermoset rubber composition further comprises at least one of zinc oxide, reactive coagent(s), peroxide(s), soft and fast agent(s), fatty acid(s)/fatty acid salt(s), inorganic filler(s), antioxidant(s), and antiozonants.
In one embodiment, the outer core layer has a compression of greater than 72. In another embodiment, the outer core layer has a compression of at least 75.
In one embodiment, the outer core layer surrounds and is adjacent to the inner core layer.
In one embodiment, the inner core layer consists of a thermoset composition. For example, the thermoset composition may in one embodiment be a second thermoset rubber composition different than the first thermoset rubber composition.
Alternatively, the inner core layer may consist of a thermoplastic composition. In one embodiment, the thermoplastic composition comprises an ionomer. In other embodiments, the thermoplastic composition may comprise a polyether-ester, a polyester-amide, or blends thereof.
In another embodiment, an intermediate core layer is disposed between the inner core layer and the outer core layer. In one embodiment, the intermediate layer comprises a thermoplastic composition.
Meanwhile, in one embodiment, the cover may comprise an inner cover layer disposed about the outer core layer and comprising an ionomeric material and having a first hardness; and an outer cover layer disposed about the inner cover layer and comprising a polyurea or a polyurethane and having a second hardness less than the first.
In one embodiment, each of the plurality of synthetic flocks has a length in the range of about 0.5 mm (500 μm or 0.02 inches) to about 2.0 mm (2000 μm or 0.08 inches). In a particular embodiment, each of the plurality of synthetic flocks has a length in the range of about 0.5 mm (500 μm or 0.02 inches) to about 1.016 mm (1016 μm or 0.04 inches).
In a different embodiment, a golf ball of the invention comprises a core comprising at least one layer that consists of a mixture of a plurality of synthetic flocks and a thermoset rubber composition. The plurality of synthetic flocks has a melting temperature that is greater than a mixing temperature at which the mixture is formed.
Additionally, the at least one layer comprises an outer surface having an outer surface hardness of about 80 Shore C or greater, and the outer surface hardness is greater than a center hardness of a geometric center of the core by at least 20 Shore C. A cover having at least one layer is disposed about the core.
A golf ball of the invention may be made, for example, by: (i) providing an inner core layer; (ii) forming an outer core layer that consists of a mixture of a plurality of synthetic flocks and a thermoset rubber composition about the inner core layer; wherein the plurality synthetic flocks have a melting temperature that is greater than a mixing temperature at which the mixture is formed; and wherein the plurality of synthetic flocks are included in the mixture in an amount such that the outer core layer comprises an outer surface having an outer surface hardness of about 80 Shore C or greater and the outer surface hardness is greater than a center hardness of a geometric center of the core by at least 20 Shore C; and (iii) forming at least one cover layer about the outer core layer.
Embodiments are also envisioned wherein the method further comprises forming at least one intermediate core layer about the inner core layer and forming the outer core layer about the intermediate core layer. One or more intermediate layers may be formed between the outer core layer and at least one cover layer.
Alternatively, the method for making a golf ball of the invention may comprise: (i) forming a core by providing at least one layer consisting of a mixture of a plurality of synthetic flocks and a thermoset rubber composition; wherein the plurality of synthetic flocks has a melting temperature that is greater than a mixing temperature at which the mixture is formed; and wherein the synthetic flocks are included in the mixture in an amount such that the core has an outer surface having an outer surface hardness of about 80 Shore C or greater; and wherein the outer surface hardness is greater than a center hardness of a geometric center of the core by at least 20 Shore C; and (ii) forming at least one cover layer about the outer core layer.
Although it preferred the core has at least two layers, embodiments are envisioned wherein the core might entirely consist of the mixture.
In some embodiments, the method may further comprise forming at least one intermediate layer about the core and then forming the at least one cover layer about the at least one intermediate layer.

DETAILED DESCRIPTION

A golf ball of the invention is an improved steep positive hardness gradient multi-piece golf ball incorporating at least one outer core layer that consists of a mixture of a thermoset rubber composition and a plurality of synthetic flocks such as nylon or polyester to enhance properties such as increasing compression and surface hardness without causing crack propagation in the cured core or reducing resilience/CoR significantly. Meanwhile, the inner core layer does not contain said flocks. Greater physical property differences can be achieved between the outer core layer and inner core layer without sacrificing or otherwise substantially changing core resiliency and meanwhile providing increased design flexibility with controlled manufacturing costs.
In this regard, four inventive spheres Ex. 1, Ex. 2, Ex. 3, and Ex. 4 were formed and compared with three comparative spheres Comp. Ex. 1, Comp. Ex. 2 and Comp. Ex. 3. The exact formulations for inventive cores Ex. 1, Ex. 2, Ex. 3, and Ex. 4 and comparative cores Comp. Ex. 1, Comp. Ex. 2 and Comp. Ex. 3 are as follows:

TABLE I

INGRE-					Comp.	Comp.	Comp.
DIENTS PHR	EX. 1	EX. 2	EX. 3	EX. 4	EX. 1	EX. 2	EX. 3

Polybutadiene	100	100	100	100	100	100	100
ZnO	5	5	5	5	5	5	5
ZDA	30	30	30	30	30	30	30
ZnPCTP	0.7	0.7	0.7	0.7	0.7	0.7	0.7
Dicumyl	0.5	0.5	0.5	0.5	0.5	0.5	0.5
Peroxide
Polyester	2	5	0	0	0	0	0
Flock¹
Nylon Flock²	0	0	2	5	0	0	0
Cotton Flock³	0	0	0	0	0	2	5

Barium Sulfate	varied to adjust weight

¹Akroflock PW #31 White Polyester, available from Akrochem Corporation.
²Akroflock ND 109 Dark Nylon, available from Akrochem Corporation.
³Akroflock CDV - 2 Dark Cotton, available from Akrochem Corporation.

All seven spheres included the same rubber matrix set forth in Table I. Inventive spheres Ex. 1, Ex. 2, Ex. 3, and Ex. 4 were formed by mixing this rubber matrix with synthetic flocks (polyester or nylon), whereas comparative core Comp. Ex. 1 was formed solely from the rubber matrix ingredients, and comparative spheres Comp. Ex. 2 and Comp. 3 included natural flocks (cotton) rather than synthetic flocks. The ingredients for each of the seven spheres were compounded and mixed in a Brabender mixer.
The resulting rubber compositions were molded for 11 minutes at 350° F. and then subjected to centerless grinding to a diameter of 1.550″. Subsequently, all finished spheres were evaluated for hardness, compression and CoR. The test results are set forth in TABLE II as follows:

TABLE II

					Comp.	Comp.	Comp.
Property	EX. 1	EX. 2	EX. 3	EX. 4	EX. 1	EX. 2	EX. 3

Compression	76	84	75	82	72	65	62
Surface	82.5	83.5	82.8	84.0	82.0	81.5	79.9
Hardness Shore C
Center	60.5	59.7	58.2	55.0	57.3	61.1	62.0
Hardness Shore C
Shore C Gradient	22.0	23.8	24.6	29.0	24.7	20.4	17.9
CoR	0.811	0.806	0.811	0.808	0.813	0.804	0.789

As is shown in TABLE II, all of cured inventive spheres Ex. 1, Ex. 2, Ex. 3, Ex. 4, incorporating synthetic flocks, have high outer surface hardnesses and desirably steep Shore C hardness gradients as well as favorably higher compressions than each of the three comparative cores Comp. Ex. 1 (no flocks), Comp. Ex. 2 (2 phr of natural flock (cotton) flocks) and Comp. Ex. 3 (5 phr of natural (cotton) flocks). And meanwhile, resulting inventive spheres Ex. 1, Ex. 2, Ex. 3, Ex. 4 also advantageously have controlled CoRs not substantially different than the CoRs of comparative spheres Comp. Ex. 1 and Comp. Ex. 2.
In further contrast, comparative core Comp. EX. 3 containing 5 phr cotton flock has a lower outer surface Shore C hardness than all six other spheres as well as an undesirably lower Shore C hardness gradient of less than 20 (17.9), with its compression and CoR also being substantially below that of not only comparative core Comp. EX. 1, which is formed solely of the rubber matrix, but also less than those of all five other spheres.
Accordingly, inventive outer core layer materials Ex. 1, Ex. 2, Ex. 3, and Ex. 4, formed from a mixture of a rubber matrix and synthetic flocks, advantageously have a high outer surface hardness, a steep hardness gradients of at least 20, and higher compressions over the other rubber matrixes—whether containing no flocks or natural cotton flocks—meanwhile without sacrificing or otherwise substantially changing core resiliency or CoR. In this regard, non-substantial CoR differences such as between outer core layer materials Ex. 1, Ex. 2, Ex. 3, and Ex. 4 compared with Comp. EX. 1 (not including flock) can generally be addressed by targeting the resilience of outer golf ball layers (e.g. inner cover layers) to achieve a particular desired overall golf ball CoR. And meanwhile, golf balls of the invention incorporating core materials Ex. 1, Ex. 2, Ex. 3, and Ex. 4 would not typically be subject to increased crack propagation.
A golf ball of the invention may therefore comprise a multi-layer core and one or more cover layers. For example, a soft inner core layer may be surrounded by at least one stiff outer core layer that is formed from the thermoset rubber composition mixed with a plurality of synthetic fibers such as nylon, polyester, polypropylene, aramid, acrylic flocks, or combinations thereof. The synthetic flocks may be mixed with the ingredients of the rubber matrix (thermoset rubber composition) in an amount of from about 0.5 parts to about 15 parts of the total mixture or from about 1 part to about 10 parts of the total mixture or from about 2 parts to about 7 parts of the total mixture or from about 2 parts to about 5 parts of the total mixture or from about 1 parts to about 5 parts of the total mixture. Once again, the plurality of flocks is the only thermoplastic ingredient in the mixture. And embodiments are envisioned wherein at least some of the flocks are surface-activated in order to improve compatibility, dispersibility, and/or durability.
In one embodiment, each of the plurality of synthetic flocks has a length in the range of about 0.5 mm (500 μm or 0.02 inches) to about 2.0 mm (2000 μm or 0.08 inches). In a particular embodiment, each of the plurality of synthetic flocks has a length in the range of about 0.5 mm (500 μm or 0.02 inches) to about 1.016 mm (1016 μm or 0.04 inches). Embodiments are also envisioned wherein each of the plurality of synthetic flocks has a length in the range of about 0.1 mm (100 μm or 0.004 inches) to about 5.0 mm (5000 μm or 0.2 inches).
The inner core layer(s) can be formed from a thermoplastic or thermoset material. In one embodiment, the inner core layer comprises a thermoset rubber composition having different physical properties (lower hardness/lower compression/lower modulus) than the outer core layer.
The outer core layer should have a surface hardness of about 80 Shore C or greater, more preferably about 85 Shore C or greater, or greater than 85 Shore C, and most preferably about 88 Shore C or greater. In one particular embodiment, the surface hardness is greater than 82 Shore C. Alternatively, the outer core layer may have a surface hardness of about 50 shore D or greater, more preferably about 55 Shore D or greater, and most preferably about 60 Shore D or greater.
The core should also have a steep positive gradient from the outer surface of the outer core layer and preferably to the geometric center of the core. In such case, the steep positive gradient is defined by the outer surface hardness of the outer core layer minus the center hardness of the core geometric center as explained/defined more fully further below.
The core in a golf ball of the invention may for example have a Shore C (or JIS C) hardness gradient of at least about 20 hardness points, or at least about 25 hardness points, or about 30 hardness points or greater, and may even be about 35 hardness points, or about 45 hardness points or greater. Using the Shore D scale, the steep positive gradient may be, for example, about 15 Shore D or greater, about 20 shore D or greater, or about 25 Shore D or greater.
The thermoset rubber composition part/portion of the mixture may include for example at least one base rubber such as a polybutadiene rubber, cured with at least one peroxide and at least one reactive co-agent (which can be a metal salt of an unsaturated carboxylic acid, such as acrylic acid or methacrylic acid, a non-metallic coagent, or mixtures thereof). An optional ‘soft and fast agent’ (and sometimes a cis-to-trans catalyst) such as an organosulfur or metal-containing organosulfur compound can also be included in the thermoset rubber composition formulation. To form the steep “positive hardness gradient”, a gradient-promoting additive is preferably added as detailed further below. Other ingredients that are known to those skilled in the art may be used, and are understood to include, but not be limited to, density-adjusting fillers, process aides, plasticizers, blowing or foaming agents, sulfur accelerators, and/or non-peroxide radical sources.
The base thermoset rubber, which can be blended with other rubbers and polymers, typically includes a natural or synthetic rubber. A preferred base rubber is 1,4-polybutadiene having a cis structure of at least 40%, preferably greater than 80%, and more preferably greater than 90%. Non-limiting examples of suitable commercially available base rubbers are Buna CB high-cis neodymium-catalyzed polybutadiene rubbers, such as Buna CB 22, Buna CB 23, Buna CB24, and Buna CB high-cis cobalt-catalyzed polybutadiene rubbers, such as Buna CB 1203, 1220 and 1221, commercially available from Lanxess Corporation; SE BR-1220, commercially available from The Dow Chemical Company; Europrene® NEOCIS® BR 40 and BR 60, commercially available from Polimeri Europa®; UBEPOL® 360L and UBEPOL® 150L and UBEPOL-BR® rubbers, commercially available from UBE Industries, Inc.; BR 01, BR 730, BR 735, BR 11 and BR 51, commercially available from Japan Synthetic Rubber Co., Ltd.; Neodene high-cis neodymium-catalyzed polybutadiene rubbers, such as Neodene BR 40, commercially available from Karbochem; BUNA® CB Nd40 from Lanxess; and KARBOCHEM® ND40, ND45, and ND60, commercially available from Karbochem; TP-301 transpolyisoprene, commercially available from Kuraray Co., Ltd.; Vestenamer® polyoctenamer, commercially available from Evonik Industries; Butyl 065 and Butyl 288 butyl rubbers, commercially available from ExxonMobil Chemical Company; Butyl 301 and Butyl 101-3, commercially available from Lanxess Corporation; Bromobutyl 2224 and Chlorobutyl 1066 halobutyl rubbers, commercially available from ExxonMobil Chemical Company; Bromobutyl X2 and Chlorobutyl 1240 halobutyl rubbers, commercially available from Lanxess Corporation; BromoButyl 2255 butyl rubber, commercially available from Japan Synthetic Rubber Co., Ltd.; Vistalon® 404 and Vistalon® 706 ethylene propylene rubbers, commercially available from ExxonMobil Chemical Company; Dutral CO 058 ethylene propylene rubber, commercially available from Polimeri Europa; Nordel® IP NDR 5565 and Nordel® IP 3670 ethylene-propylene-diene rubbers, commercially available from The Dow Chemical Company; EPT1045 and EPT1045 ethylene-propylene-diene rubbers, commercially available from Mitsui Corporation; Buna SE 1721 TE styrene-butadiene rubbers, commercially available from Lanxess Corporation; Afpol 1500 and Afpol 552 styrene-butadiene rubbers, commercially available from Karbochem; Plioflex PLF 1502, commercially available from Goodyear Chemical; Nipol® DN407 and Nipol® 1041L acrylonitrile butadiene rubbers, commercially available from Zeon Chemicals, L.P.; Neoprene GRT and Neoprene AD30 polychloroprene rubbers; Vamac® ethylene acrylic elastomers, commercially available from E. I. du Pont de Nemours and Company; Hytemp® AR12 and AR214 alkyl acrylate rubbers, commercially available from Zeon Chemicals, L.P.; Hypalon® chlorosulfonated polyethylene rubbers, commercially available from E. I. du Pont de Nemours and Company; and Goodyear Budene® 1207 polybutadiene, commercially available from Goodyear Chemical. In a particular embodiment, the core is formed from a rubber composition comprising as the base rubber a blend of Neodene BR 40 polybutadiene, Budene® 1207 polybutadiene, and Buna SB 1502 styrene butadiene rubber. In another particular embodiment, the core is formed from a rubber composition comprising as the base rubber a blend of Neodene BR 40 polybutadiene, Buna CB 1221, and core regrind.
The base rubber may also comprise high or medium Mooney viscosity rubber, or blends thereof. The measurement of Mooney viscosity is defined according to ASTM D-1646. The Mooney viscosity range is preferably greater than about 40, more preferably in the range from about 40 to about 80 and more preferably in the range from about 40 to about 60. Polybutadiene rubber with higher Mooney viscosity may also be used, so long as the viscosity of the polybutadiene does not reach a level where the high viscosity polybutadiene clogs or otherwise adversely interferes with the manufacturing machinery. It is contemplated that polybutadiene with viscosity less than 65 Mooney can be used with the present invention. In one embodiment of the present invention, golf ball core layers made with mid- to high-Mooney viscosity polybutadiene material exhibit increased resiliency (and, therefore, distance) without increasing the hardness of the ball.
Commercial sources of suitable mid- to high-Mooney viscosity polybutadiene include BUNA® CB23 (Nd-catalyzed), which has a Mooney viscosity of around 50 and is a highly linear polybutadiene, and BUNA® CB 1220 (Co-catalyzed). If desired, the polybutadiene can also be mixed with other elastomers known in the art, such as other polybutadiene rubbers, natural rubber, styrene butadiene rubber, and/or isoprene rubber in order to further modify the properties of the core. When a mixture of elastomers is used, the amounts of other constituents in the core composition are typically based on 100 parts by weight of the total elastomer mixture.
In one embodiment, the base rubber comprises a Nd-catalyzed polybutadiene, a transition metal polybutadiene rubber, or blends thereof. If desired, the polybutadiene can also be mixed with other elastomers known in the art such as natural rubber, polyisoprene rubber and/or styrene-butadiene rubber in order to modify the properties of the core. Other suitable base rubbers include thermosetting materials such as, ethylene propylene diene monomer rubber, ethylene propylene rubber, butyl rubber, halobutyl rubber, hydrogenated nitrile butadiene rubber, nitrile rubber, and silicone rubber.
Suitable rubber compositions include a base rubber selected from natural and synthetic rubbers, including, but not limited to, polybutadiene, polyisoprene, ethylene propylene rubber (“EPR”), ethylene propylene diene rubber (“EPDM”), styrene butadiene rubber, styrenic block copolymer rubber, butyl rubber, halobutyl rubber, copolymers of isobutylene and para-alkylstyrene, halogenated copolymers of isobutylene and para-alkylstyrene, acrylonitrile butadiene rubber, polychloroprene, alkyl acrylate rubber, chlorinated isoprene rubber, acrylonitrile chlorinated isoprene rubber, polystyrene elastomers, polyethylene elastomers, polyurethane elastomers, polyurea elastomers, metallocene-catalyzed elastomers and plastomers, polyalkenamer, phenol formaldehyde, melamine formaldehyde, polyepoxide, polysiloxane, alkyd, polyisocyanurate, polycyanurate, polyacrylate, and combinations of two or more thereof. Diene rubbers are preferred, particularly polybutadiene, styrene butadiene, acrylonitrile butadiene, and mixtures of polybutadiene with other elastomers wherein the amount of polybutadiene present greater than 40 wt % based on the total polymeric weight of the mixture.
The rubber is crosslinked using, for example, a peroxide or sulfur cure system, C—C initiators, high energy radiation sources capable of generating free radicals, or a combination thereof. The rubber composition optionally includes one or more of the following: scorch retarder, antioxidant, soft and fast agent, filler, processing aid, processing oil, coloring agent, fluorescent agent, chemical blowing and foaming agent, defoaming agent, stabilizer, softening agent, impact modifier, free radical scavenger, and antiozonant (e.g., p-phenylenediames). Suitable types and amounts of rubber, initiator agent, coagent, filler, and additives are more fully described in, for example, U.S. Pat. Nos. 6,566,483, 6,695,718, 6,939,907, 7,041,721 and 7,138,460, the entire disclosures of which are hereby incorporated herein by reference. Particularly suitable diene rubber compositions are further disclosed, for example, in U.S. Pat. No. 7,654,918, the entire disclosure of which is hereby incorporated herein by reference.
Additional thermoset polymers may also optionally be incorporated into the base rubber, including for example, thermoset elastomers such as core regrind.
Suitable peroxide initiating agents include dicumyl peroxide; 2,5-dimethyl-2,5-di(t-butylperoxy) hexane; 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne; 2,5-dimethyl-2,5-di(benzoylperoxy)hexane; 2,2′-bis(t-butylperoxy)-di-iso-propylbenzene; 1,1-bis(t-butylperoxy)-3,3,5-trimethyl cyclohexane; n-butyl 4,4-bis(t-butyl-peroxy)valerate; t-butyl perbenzoate; benzoyl peroxide; n-butyl 4,4′-bis(butylperoxy) valerate; di-t-butyl peroxide; or 2,5-di-(t-butylperoxy)-2,5-dimethyl hexane, lauryl peroxide, t-butyl hydroperoxide, α-α bis(t-butylperoxy) diisopropylbenzene, di(2-t-butyl-peroxyisopropyl)benzene, di-t-amyl peroxide, di-t-butyl peroxide. Preferably, the rubber composition includes from about 0.1 to about 5.0 parts by weight peroxide per 100 parts by weight rubber (phr), or from about 0.25 phr to about 4.0 phr, or from about 0.5 phr to 3 phr, or from about 0.5 phr to about 1.5 phr. These ranges of peroxide are given assuming the peroxide is 100% active, without accounting for any carrier that might be present. Because many commercially available peroxides are sold along with a carrier compound, the actual amount of active peroxide present must be calculated. Commercially-available peroxide initiating agents include DICUP™ family of dicumyl peroxides (including DICUP® R, DICUP® 40C and DICUP® 40KE) available from Crompton (Geo Specialty Chemicals). Similar initiating agents are available from AkroChem, Lanxess, Flexsys/Harwick and R.T. Vanderbilt. Another commercially-available and preferred initiating agent is TRIGONOX® 265-50B from Akzo Nobel, which is a mixture of 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane and di(2-t-butylperoxyisopropyl) benzene. TRIGONOX® peroxides are generally sold on a carrier compound.
Suitable reactive co-agents include, but are not limited to, metal salts of acrylic acid or methacrylic acid wherein the metal is zinc, magnesium, calcium, barium, tin, aluminum, lithium, sodium, potassium, iron, zirconium, and bismuth. Zinc diacrylate (ZDA) is preferred, but the present invention is not limited thereto. ZDA provides golf balls with a high initial velocity. The ZDA can be of various grades of purity. For the purposes of this invention, the lower the quantity of zinc stearate present in the ZDA the higher the ZDA purity. ZDA containing less than about 10% zinc stearate is preferable. More preferable is ZDA containing about 4-8% zinc stearate. Suitable, commercially available zinc diacrylates include those from Total S.A.
In one embodiment of a golf ball of the invention incorporating a core comprised of an inner core layer and the outer core layer, the inner core layer may for example comprise the coagent such as ZDA in an amount of from about 10 phr to about 30 parts by weight peroxide per 100 parts by weight rubber (phr), while the outer core layer comprises coagent in an amount of from about 25 phr to about 55 parts by weight peroxide per 100 parts by weight rubber (phr).
The ZDA amount can be varied to suit the desired compression, spin and feel of the resulting golf ball.
Additional preferred co-agents that may be used alone or in combination with those mentioned above include, but are not limited to, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, and the like. It is understood by those skilled in the art, that in the case where these co-agents may be liquids at room temperature, it may be advantageous to disperse these compounds on a suitable carrier to promote ease of incorporation in the rubber mixture.
The cure regime can generally have a temperature range between from about 290° F. to about 390° F., more preferably about 320° F. to about 375° F., and the stock is held at that temperature for at least about 10 minutes to about 30 minutes.
To form the steep “positive” hardness gradient across the core, it is preferred that a gradient-promoting additive is present. Suitable agents include, but are not limited to benzoquinones, resorcinols, catechols, quinhydrones, and hydroquinones. Those, and other methods and material for creating a steep “positive” hardness gradient are disclosed in U.S. patent application Ser. Nos. 12/168,979; 12/168,987; 12/168,995; and 12/169,002, which are incorporated herein by reference thereto.
The thermoset rubber composition of the present invention may also include an optional soft and fast agent. As used herein, “soft and fast agent” means any compound or a blend thereof that that is capable of making a core 1) softer (lower compression) at constant COR or 2) have a higher CoR at equal compression, or any combination thereof, when compared to a core equivalently prepared without a soft and fast agent. Preferably, the composition of the present invention contains from about 0.05 phr to about 10.0 phr soft and fast agent. In one embodiment, the soft and fast agent is present in an amount of about 0.05 phr to about 3.0 phr, preferably about 0.05 phr to about 2.0 phr, more preferably about 0.05 phr to about 1.0 phr. In another embodiment, the soft and fast agent is present in an amount of about 2.0 phr to about 5.0 phr, preferably about 2.35 phr to about 4.0 phr, and more preferably about 2.35 phr to about 3.0 phr. In an alternative high concentration embodiment, the soft and fast agent is present in an amount of about 5.0 phr to about 10.0 phr, more preferably about 6.0 phr to about 9.0 phr, most preferably about 7.0 phr to about 8.0 phr. In a most preferred embodiment, the soft and fast agent is present in an amount of about 2.6 phr.
Suitable soft and fast agents include, but are not limited to, organosulfur or metal-containing organosulfur compounds, an organic sulfur compound, including mono, di, and polysulfides, a thiol, or mercapto compound, an inorganic sulfide compound, a Group VIA compound, or mixtures thereof. The soft and fast agent component may also be a blend of an organosulfur compound and an inorganic sulfide compound.
Suitable soft and fast agents of the present invention include, but are not limited to those having the following general formula:
where R₁-R₅can be C₁-C₈alkyl groups; halogen groups; thiol groups (—SH), carboxylated groups; sulfonated groups; and hydrogen; in any order; and also pentafluorothiophenol; 2-fluorothiophenol; 3-fluorothiophenol; 4-fluorothiophenol; 2,3-fluorothiophenol; 2,4-fluorothiophenol; 3,4-fluorothiophenol; 3,5-fluorothiophenol 2,3,4-fluorothiophenol; 3,4,5-fluorothiophenol; 2,3,4,5-tetrafluorothiophenol; 2,3,5,6-tetrafluorothiophenol; 4-chlorotetrafluorothiophenol; pentachlorothiophenol; 2-chlorothiophenol; 3-chlorothiophenol; 4-chlorothiophenol; 2,3-chlorothiophenol; 2,4-chlorothiophenol; 3,4-chlorothiophenol; 3,5-chlorothiophenol; 2,3,4-chlorothiophenol; 3,4,5-chlorothiophenol; 2,3,4,5-tetrachlorothiophenol; 2,3,5,6-tetrachlorothiophenol; pentabromothiophenol; 2-bromothiophenol; 3-bromothiophenol; 4-bromothiophenol; 2,3-bromothiophenol; 2,4-bromothiophenol; 3,4-bromothiophenol; 3,5-bromothiophenol; 2,3,4-bromothiophenol; 3,4,5-bromothiophenol; 2,3,4,5-tetrabromothiophenol; 2,3,5,6-tetrabromothiophenol; pentaiodothiophenol; 2-iodothiophenol; 3-iodothiophenol; 4-iodothiophenol; 2,3-iodothiophenol; 2,4-iodothiophenol; 3,4-iodothiophenol; 3,5-iodothiophenol; 2,3,4-iodothiophenol; 3,4,5-iodothiophenol; 2,3,4,5-tetraiodothiophenol; 2,3,5,6-tetraiodothiophenoland; and their zinc salts. Preferably, the halogenated thiophenol compound is pentachlorothiophenol, which is commercially available in neat form or under the tradename STRUKTOL®, a clay-based carrier containing the sulfur compound pentachlorothiophenol loaded at 45 percent (correlating to 2.4 parts PCTP). STRUKTOL® is commercially available from Struktol Company of America of Stow, Ohio. PCTP is commercially available in neat form from eChinachem of San Francisco, Calif. and in the salt form, also from eChinachem. Most preferably, the halogenated thiophenol compound is the zinc salt of pentachlorothiophenol, which is commercially available from eChinachem.
As used herein when referring to the invention, the term “organosulfur compound(s)” refers to any compound containing carbon, hydrogen, and sulfur, where the sulfur is directly bonded to at least 1 carbon. As used herein, the term “sulfur compound” means a compound that is elemental sulfur, polymeric sulfur, or a combination thereof. It should be further understood that the term “elemental sulfur” refers to the ring structure of S₈and that “polymeric sulfur” is a structure including at least one additional sulfur relative to elemental sulfur.
Additional suitable examples of soft and fast agents (that are also believed to be cis-to-trans catalysts) include, but are not limited to, 4,4′-diphenyl disulfide; 4,4′-ditolyl disulfide; 2,2′-benzamido diphenyl disulfide; bis(2-aminophenyl) disulfide; bis(4-aminophenyl) disulfide; bis(3-aminophenyl) disulfide; 2,2′-bis(4-aminonaphthyl) disulfide; 2,2′-bis(3-aminonaphthyl) disulfide; 2,2′-bis(4-aminonaphthyl) disulfide; 2,2′-bis(5-aminonaphthyl) disulfide; 2,2′-bis(6-aminonaphthyl) disulfide; 2,2′-bis(7-aminonaphthyl) disulfide; 2,2′-bis(8-aminonaphthyl) disulfide; 1,1′-bis(2-aminonaphthyl) disulfide; 1,1′-bis(3-aminonaphthyl) disulfide; 1,1′-bis(3-aminonaphthyl) disulfide; 1,1′-bis(4-aminonaphthyl) disulfide; 1,1′-bis(5-aminonaphthyl) disulfide; 1,1′-bis(6-aminonaphthyl) disulfide; 1,1′-bis(7-aminonaphthyl) disulfide; 1,1′-bis(8-aminonaphthyl) disulfide; 1,2′-diamino-1,2′-dithiodinaphthalene; 2,3′-diamino-1,2′-dithiodinaphthalene; bis(4-chlorophenyl) disulfide; bis(2-chlorophenyl) disulfide; bis(3-chlorophenyl) disulfide; bis(4-bromophenyl) disulfide; bis(2-bromophenyl) disulfide; bis(3-bromophenyl) disulfide; bis(4-fluorophenyl) disulfide; bis(4-iodophenyl) disulfide; bis(2,5-dichlorophenyl) disulfide; bis(3,5-dichlorophenyl) disulfide; bis (2,4-dichlorophenyl) disulfide; bis(2,6-dichlorophenyl) disulfide; bis(2,5-dibromophenyl) disulfide; bis(3,5-dibromophenyl) disulfide; bis(2-chloro-5-bromophenyl) disulfide; bis(2,4,6-trichlorophenyl) disulfide; bis(2,3,4,5,6-pentachlorophenyl) disulfide; bis(4-cyanophenyl) disulfide; bis(2-cyanophenyl) disulfide; bis(4-nitrophenyl) disulfide; bis(2-nitrophenyl) disulfide; 2,2′-dithiobenzoic acid ethylester; 2,2′-dithiobenzoic acid methylester; 2,2′-dithiobenzoic acid; 4,4′-dithiobenzoic acid ethylester; bis(4-acetylphenyl) disulfide; bis(2-acetylphenyl) disulfide; bis(4-formylphenyl) disulfide; bis(4-carbamoylphenyl) disulfide; 1,1′-dinaphthyl disulfide; 2,2′-dinaphthyl disulfide; 1,2′-dinaphthyl disulfide; 2,2′-bis(1-chlorodinaphthyl) disulfide; 2,2′-bis(1-bromonaphthyl) disulfide; 1,1′-bis(2-chloronaphthyl) disulfide; 2,2′-bis(1-cyanonaphthyl) disulfide; 2,2′-bis(1-acetylnaphthyl) disulfide; and the like; or a mixture thereof. Preferred organosulfur components include 4,4′-diphenyl disulfide, 4,4′-ditolyl disulfide, or 2,2′-benzamido diphenyl disulfide, or a mixture thereof. A more preferred organosulfur component includes 4,4′-ditolyl disulfide. In another embodiment, metal-containing organosulfur components can be used according to the invention. Suitable metal-containing organosulfur components include, but are not limited to, cadmium, copper, lead, and tellurium analogs of diethyldithiocarbamate, diamyldithiocarbamate, and dimethyldithiocarbamate, or mixtures thereof.
Suitable substituted or unsubstituted aromatic organic components that do not include sulfur or a metal include, but are not limited to, 4,4′-diphenyl acetylene, azobenzene, or a mixture thereof. The aromatic organic group preferably ranges in size from C₆to C₂₀, and more preferably from C₆to C₁₀. Suitable inorganic sulfide components include, but are not limited to titanium sulfide, manganese sulfide, and sulfide analogs of iron, calcium, cobalt, molybdenum, tungsten, copper, selenium, yttrium, zinc, tin, and bismuth.
A substituted or unsubstituted aromatic organic compound is also suitable as a soft and fast agent. Suitable substituted or unsubstituted aromatic organic components include, but are not limited to, components having the formula (R₁)_c—R₃-M-R₄—(R₂)_y, wherein R₁and R₂are each hydrogen or a substituted or unsubstituted C_1-20linear, branched, or cyclic alkyl, alkoxy, or alkylthio group, or a single, multiple, or fused ring C₆to C₂₄aromatic group; x and y are each an integer from 0 to 5; R₃and R₄are each selected from a single, multiple, or fused ring C₆to C₂₄aromatic group; and M includes an azo group or a metal component. R₃and R₄are each preferably selected from a C₆to C₁₀aromatic group, more preferably selected from phenyl, benzyl, naphthyl, benzamido, and benzothiazyl. R₁and R₂are each preferably selected from a substituted or unsubstituted C₁to C₁₀linear, branched, or cyclic alkyl, alkoxy, or alkylthio group or a C₆to C₁₀aromatic group. When R₁, R₂, R₃, or R₄, are substituted, the substitution may include one or more of the following substituent groups: hydroxy and metal salts thereof; mercapto and metal salts thereof; halogen; amino, nitro, cyano, and amido; carboxyl including esters, acids, and metal salts thereof; silyl; acrylates and metal salts thereof; sulfonyl or sulfonamide; and phosphates and phosphites. When M is a metal component, it may be any suitable elemental metal available to those of ordinary skill in the art. Typically, the metal will be a transition metal, although preferably it is tellurium or selenium. In one embodiment, the aromatic organic compound is substantially free of metal, while in another embodiment the aromatic organic compound is completely free of metal.
The soft and fast agent can also include a Group VIA component. Elemental sulfur and polymeric sulfur are commercially available from Elastochem, Inc. of Chardon, Ohio Exemplary sulfur catalyst compounds include PB(RM-S)-80 elemental sulfur and PB(CRST)-65 polymeric sulfur, each of which is available from Elastochem, Inc. An exemplary tellurium catalyst under the tradename TELLOY® and an exemplary selenium catalyst under the tradename VANDEX® are each commercially available from RT Vanderbilt.
Other suitable soft and fast agents include, but are not limited to, hydroquinones, benzoquinones, quinhydrones, catechols, and resorcinols. Suitable compounds include, but are not limited to, those disclosed in U.S. patent application Ser. No. 11/829,461, the disclosure of which is incorporated herein in its entirety by reference thereto.
Fillers may also be added to the thermoset rubber composition of the core to adjust the density of the composition, up or down. Typically, fillers include materials such as tungsten, zinc oxide, barium sulfate, silica, calcium carbonate, zinc carbonate, metals, metal oxides and salts, regrind (recycled core material typically ground to about 30 mesh particle), high-Mooney-viscosity rubber regrind, trans-regrind core material (recycled core material containing high trans-isomer of polybutadiene), and the like. When trans-regrind is present, the amount of trans-isomer is preferably between about 10% and about 60%. In a preferred embodiment of the invention, the core comprises polybutadiene having a cis-isomer content of greater than about 95% and trans-regrind core material (already vulcanized) as a filler. Any particle size trans-regrind core material is sufficient, but is preferably less than about 125 μm.
Fillers added to one or more portions of the golf ball typically include processing aids or compounds to affect rheological and mixing properties, density-modifying fillers, tear strength, or reinforcement fillers, and the like. The fillers are generally inorganic, and suitable fillers include numerous metals or metal oxides, such as zinc oxide and tin oxide, as well as barium sulfate, zinc sulfate, calcium carbonate, barium carbonate, clay, tungsten, tungsten carbide, an array of silicas, and mixtures thereof. Fillers may also include various foaming agents or blowing agents which may be readily selected by one of ordinary skill in the art. Fillers may include polymeric, ceramic, metal, and glass microspheres may be solid or hollow, and filled or unfilled. Fillers are typically also added to one or more portions of the golf ball to modify the density thereof to conform to uniform golf ball standards. Fillers may also be used to modify the weight of the center or at least one additional layer for specialty balls, e.g., a lower weight ball is preferred for a player having a low swing speed.
Materials such as tungsten, zinc oxide, barium sulfate, silica, calcium carbonate, zinc carbonate, metals, metal oxides and salts, and regrind (recycled core material typically ground to about 30 mesh particle) are also suitable fillers.
The polybutadiene and/or any other base rubber or elastomer system may also be foamed, or filled with hollow microspheres or with expandable microspheres which expand at a set temperature during the curing process to any low specific gravity level. Other ingredients such as sulfur accelerators, e.g., tetra methylthiuram di, tri, or tetrasulfide, and/or metal-containing organosulfur components may also be used according to the invention. Suitable metal-containing organosulfur accelerators include, but are not limited to, cadmium, copper, lead, and tellurium analogs of diethyldithiocarbamate, diamyldithiocarbamate, and dimethyldithiocarbamate, or mixtures thereof. Other ingredients such as processing aids e.g., fatty acids and/or their metal salts, processing oils, dyes and pigments, as well as other additives known to one skilled in the art may also be used in the present invention in amounts sufficient to achieve the purpose for which they are typically used.
Core or core layers comprising synthetic flocks, preferably polyester or nylon flocks, include a base rubber such as a polybutadiene or a blend of polybutadienes, zinc oxide, reactive coagents such as ZDA, ZDMA, HVA, SR-350, SR-351 or other coagents sold by Cray Valley company, a peroxide or blends of peroxides, a soft and fast agent such as Zn PCTP, or PCTP, fatty acids/salts thereof, fillers such as calcium carbonate or barium sulfate, antioxidants, and antiozonants. The polybutadiene may be blended with other rubbers such as polyoctenamer, natural rubber, EPDM, cis-polyisoprene, trans-polyisoprene, SBR and other diene rubbers to name a few.
The preferred level of flock blended into the uncured stock is 0.5 to 15 phr, more preferably 1 to 10 phr and the preferred flock is nylon or polyester. A preferred rubber composition for the outer core is 100 phr by weight of a base rubber such as CB 23, 20 to 50 phr of a cogent, 5 to 50 phr of zinc oxide, 10 to 60 phr of an inorganic filler, 0.1 to 5 phr an organic peroxide, 0.05 phr to 3 phr of an organosulfur, 1 to 10 phr of a nylon flock. The fiber should be blended together with the other components at a temperature below the melting point of the fiber to preserve fibrous shape. Blends of fibers, including blends of different materials and sizes and can be used in combination with other types of reinforcing fillers. Preferred fibers are polymeric types with melting points greater than mixing temperature used to pre-blend the ingredients. Commercially available examples of suitable flocks include those sold by Akrochem Corp. as Akroflocks, such as nylon, polyester, polypropylene, aramid, or acrylic flocks.
A preferred outer core layer containing the flock should have 25-45 phr of a crosslinking coagent (ZDA for example) and the center should have about 10 to 30 phr of coagent.
It is envisioned that a golf ball of the invention incorporating the flock-containing core layer may otherwise have any known construction (e.g., inner core layer, intermediate core layer, inner cover layer, outer cover layer, etc.), and that each other layer may comprise any known golf ball material such as ionomers, polyurethanes, polyureas, TPE, HNP, crosslinked rubber, etc., or blends/mixtures/combinations thereof.
In this regard, where one or more of these other layers comprises a rubber composition, suitable base rubbers may include for example those identified above in connection with the flock-containing core layer. And suitable thermoplastic materials for these other golf ball layers include for example ionomers (more specifically HNP type ionomers as described for example in U.S. Pat. No. 7,867,106) and non-ionomeric materials such as polyether-esters and polyester-amides, or blends thereof. Additional suitable compositions for these other layers are disclosed, for example, in U.S. Pat. Nos. 6,953,820 and 6,939,907, and U.S. Pat. Nos. 5,919,100, 6,653,382, 6,872,774, 7,074,137, and 7,300,364, the entire disclosures of which are hereby incorporated herein by reference.
Suitable ionomer compositions for these other layers include partially neutralized ionomers and highly neutralized ionomers, including ionomers formed from blends of two or more partially neutralized ionomers, blends of two or more highly neutralized ionomers, and blends of one or more partially neutralized ionomers with one or more highly neutralized ionomers. Preferred ionomers are salts of O/X- and O/X/Y-type acid copolymers, wherein O is an α-olefin, X is a C₃-C₈α,β-ethylenically unsaturated carboxylic acid, and Y is a softening monomer. O is preferably selected from ethylene and propylene. X is preferably selected from methacrylic acid, acrylic acid, ethacrylic acid, crotonic acid, and itaconic acid. Methacrylic acid and acrylic acid are particularly preferred. As used herein, “(meth) acrylic acid” means methacrylic acid and/or acrylic acid. Likewise, “(meth) acrylate” means methacrylate and/or acrylate. Y is preferably selected from (meth) acrylate and alkyl (meth) acrylates wherein the alkyl groups have from 1 to 8 carbon atoms, including, but not limited to, n-butyl (meth) acrylate, isobutyl (meth) acrylate, methyl (meth) acrylate, and ethyl (meth) acrylate. Particularly preferred O/X/Y-type copolymers are ethylene/(meth) acrylic acid/n-butyl (meth) acrylate, ethylene/(meth) acrylic acid/isobutyl (meth) acrylate, ethylene/(meth) acrylic acid/methyl (meth) acrylate, and ethylene/(meth) acrylic acid/ethyl (meth) acrylate. The acid is typically present in the acid copolymer in an amount of 6 wt % or greater, or 9 wt % or greater, or 10 wt % or greater, or 11 wt % or greater, or 15 wt % or greater, or 16 wt % or greater, or 19 wt % or greater, or 20 wt % or greater, or in an amount within a range having a lower limit of 1 or 4 or 6 or 8 or 10 or 11 or 12 or 15 wt % and an upper limit of 15 or 16 or 17 or 19 or 20 or 20.5 or 21 or 25 or 30 or 35 or 40 wt %, based on the total weight of the acid copolymer. The acid copolymer is at least partially neutralized with a cation source, optionally in the presence of a high molecular weight organic acid, such as those disclosed in U.S. Pat. No. 6,756,436, the entire disclosure of which is hereby incorporated herein by reference. In a particular embodiment, less than 40% of the acid groups present in the composition are neutralized. In another particular embodiment, from 40% to 60% of the acid groups present in the composition are neutralized. In another particular embodiment, from 60% to 70% of the acid groups present in the composition are neutralized. In another particular embodiment, from 60% to 80% of the acid groups present in the composition are neutralized. In another particular embodiment, from 70% to 80% of the acid groups present in the composition are neutralized. In another embodiment, from 80% to 100% of the acid groups present in the composition are neutralized. Suitable cation sources include, but are not limited to, metal ion sources, such as compounds of alkali metals, alkaline earth metals, transition metals, and rare earth elements; ammonium salts and monoamine salts; and combinations thereof. Preferred cation sources are compounds of magnesium, sodium, potassium, cesium, calcium, barium, manganese, copper, zinc, tin, lithium, and rare earth metals. In a particular embodiment, the ionomer composition includes a bimodal ionomer, for example, DuPont® AD1043 ionomers, and the ionomers disclosed in U.S. Pat. No. 7,037,967 and U.S. Pat. Nos. 6,562,906, 6,762,246 and 7,273,903, the entire disclosures of which are hereby incorporated herein by reference. Suitable ionomers are further disclosed, for example, in U.S. Pat. Nos. 5,587,430, 5,691,418, 5,866,658, 6,100,321, 6,653,382, 6,756,436, 6,777,472, 6,815,480, 6,894,098, 6,919,393, 6,953,820, 6,994,638, 7,230,045, 7,375,151, 7,429,624, and 7,652,086, the entire disclosures of which are hereby incorporated herein by reference.
Suitable ionomer compositions also include blends of one or more partially- or fully-neutralized polymers with additional thermoplastic and thermoset materials, including, but not limited to, non-ionomeric acid copolymers, engineering thermoplastics, fatty acid/salt-based highly neutralized polymers, polybutadienes, polyurethanes, polyureas, polyesters, polyamides, polycarbonate/polyester blends, thermoplastic elastomers, maleic anhydride-grafted metallocene-catalyzed polymers (e.g., maleic anhydride-grafted metallocene-catalyzed polyethylene), and other conventional polymeric materials.
Suitable ionomeric compositions are further disclosed, for example, in U.S. Pat. Nos. 6,653,382, 6,756,436, 6,777,472, 6,894,098, 6,919,393, and 6,953,820, the entire disclosures of which are hereby incorporated herein by reference.
Also suitable are polyester ionomers, including, but not limited to, those disclosed, for example, in U.S. Pat. Nos. 6,476,157 and 7,074,465, the entire disclosures of which are hereby incorporated herein by reference.
Also suitable are thermoplastic elastomers comprising a silicone ionomer, as disclosed, for example, in U.S. Pat. No. 8,329,156, the entire disclosure of which is hereby incorporated herein by reference.
Also suitable are the following non-ionomeric polymers, including homopolymers and copolymers thereof, as well as their derivatives that are compatibilized with at least one grafted or copolymerized functional group, such as maleic anhydride, amine, epoxy, isocyanate, hydroxyl, sulfonate, phosphonate, and the like:
(a) polyesters, particularly those modified with a compatibilizing group such as sulfonate or phosphonate, including modified poly(ethylene terephthalate), modified poly(butylene terephthalate), modified poly(propylene terephthalate), modified poly(trimethylene terephthalate), modified poly(ethylene naphthenate), and those disclosed in U.S. Pat. Nos. 6,353,050, 6,274,298, and 6,001,930, the entire disclosures of which are hereby incorporated herein by reference, and blends of two or more thereof;
(b) polyamides, polyamide-ethers, and polyamide-esters, and those disclosed in U.S. Pat. Nos. 6,187,864, 6,001,930, and 5,981,654, the entire disclosures of which are hereby incorporated herein by reference, and blends of two or more thereof;
(c) polyurethanes, polyureas, polyurethane-polyurea hybrids, and blends of two or more thereof;
(d) fluoropolymers, such as those disclosed in U.S. Pat. Nos. 5,691,066, 6,747,110 and 7,009,002, the entire disclosures of which are hereby incorporated herein by reference, and blends of two or more thereof;
(e) non-ionomeric acid polymers, such as E/X- and E/X/Y-type copolymers, wherein E is an olefin (e.g., ethylene), X is a carboxylic acid such as acrylic, methacrylic, crotonic, maleic, fumaric, or itaconic acid, and Y is an optional softening comonomer such as vinyl esters of aliphatic carboxylic acids wherein the acid has from 2 to 10 carbons, alkyl ethers wherein the alkyl group has from 1 to 10 carbons, and alkyl alkylacrylates such as alkyl methacrylates wherein the alkyl group has from 1 to 10 carbons; and blends of two or more thereof;
(f) metallocene-catalyzed polymers, such as those disclosed in U.S. Pat. Nos. 6,274,669, 5,919,862, 5,981,654, and 5,703,166, the entire disclosures of which are hereby incorporated herein by reference, and blends of two or more thereof;
(g) polystyrenes, such as poly(styrene-co-maleic anhydride), acrylonitrile-butadiene-styrene, poly(styrene sulfonate), polyethylene styrene, and blends of two or more thereof;
(h) polypropylenes and polyethylenes, particularly grafted polypropylene and grafted polyethylenes that are modified with a functional group, such as maleic anhydride of sulfonate, and blends of two or more thereof;
(i) polyvinyl chlorides and grafted polyvinyl chlorides, and blends of two or more thereof;
(j) polyvinyl acetates, preferably having less than about 9% of vinyl acetate by weight, and blends of two or more thereof;
(k) polycarbonates, blends of polycarbonate/acrylonitrile-butadiene-styrene, blends of polycarbonate/polyurethane, blends of polycarbonate/polyester, and blends of two or more thereof;
(l) polyvinyl alcohols, and blends of two or more thereof;
(m) polyethers, such as polyarylene ethers, polyphenylene oxides, block copolymers of alkenyl aromatics with vinyl aromatics and poly(amic ester)s, and blends of two or more thereof;
(n) polyimides, polyetherketones, polyamideimides, and blends of two or more thereof;
(o) polycarbonate/polyester copolymers and blends; and
(p) combinations of any two or more of the above thermoplastic polymers.
In general, polyurea compositions contain urea linkages formed by reacting an isocyanate group (—N═C═O) with an amine group (NH or NH₂). The chain length of the polyurea prepolymer is extended by reacting the prepolymer with an amine curing agent. The resulting polyurea has elastomeric properties, because of its “hard” and “soft” segments, which are covalently bonded together. The soft, amorphous, low-melting point segments, which are formed from the polyamines, are relatively flexible and mobile, while the hard, high-melting point segments, which are formed from the isocyanate and chain extenders, are relatively stiff and immobile. The phase separation of the hard and soft segments provides the polyurea with its elastomeric resiliency. The polyurea composition contains urea linkages having the following general structure:
where x is the chain length, i.e., about 1 or greater, and R and R₁are straight chain or branched hydrocarbon chains having about 1 to about 20 carbon atoms.
Meanwhile, a polyurea/polyurethane hybrid composition is produced when the polyurea prepolymer (as described above) is chain-extended using a hydroxyl-terminated curing agent. Any excess isocyanate groups in the prepolymer will react with the hydroxyl groups in the curing agent and create urethane linkages. That is, a polyurea/polyurethane hybrid composition is produced.
In a preferred embodiment, a pure polyurea composition, as described above, is prepared. That is, the composition contains only urea linkages. An amine-terminated curing agent is used in the reaction to produce the pure polyurea composition. However, it should be understood that a polyurea/polyurethane hybrid composition also may be prepared in accordance with this invention as discussed above. Such a hybrid composition can be formed if the polyurea prepolymer is cured with a hydroxyl-terminated curing agent. Any excess isocyanate in the polyurea prepolymer reacts with the hydroxyl groups in the curing agent and forms urethane linkages. The resulting polyurea/polyurethane hybrid composition contains both urea and urethane linkages. The general structure of a urethane linkage is shown below:
where x is the chain length, i.e., about 1 or greater, and R and R₁are straight chain or branched hydrocarbon chains having about 1 to about 20 carbon atoms.
Two techniques for making the polyurea and polyurea/urethane compositions include: a) one-shot technique, and b) prepolymer technique. In the one-shot technique, the isocyanate blend, polyamine, and hydroxyl and/or amine-terminated curing agent are reacted in one step. On the other hand, the prepolymer technique involves a first reaction between the isocyanate blend and polyamine to produce a polyurea prepolymer, and a subsequent reaction between the prepolymer and hydroxyl and/or amine-terminated curing agent. As a result of the reaction between the isocyanate and polyamine compounds, there will be some unreacted NCO groups in the polyurea prepolymer. The prepolymer should have less than 14% unreacted NCO groups. Preferably, the prepolymer has no greater than 8.5% unreacted NCO groups, more preferably from 2.5% to 8%, and most preferably from 5.0% to 8.0% unreacted NCO groups. As the weight percent of unreacted isocyanate groups increases, the hardness of the composition also generally increases.
Either the one-shot or prepolymer method may be employed to produce the polyurea and polyurea/urethane compositions; however, the prepolymer technique is preferred because it provides better control of the chemical reaction. The prepolymer method provides a more homogeneous mixture resulting in a more consistent polymer composition. The one-shot method results in a mixture that is inhomogeneous (more random) and affords the manufacturer less control over the molecular structure of the resultant composition.
In the casting process, the polyurea and polyurea/urethane compositions can be formed by chain-extending the polyurea prepolymer with a single curing agent or blend of curing agents as described further below. The compositions of the present invention may be selected from among both castable thermoplastic and thermoset materials. Thermoplastic polyurea compositions are typically formed by reacting the isocyanate blend and polyamines at a 1:1 stoichiometric ratio. Thermoset compositions, on the other hand, are cross-linked polymers and are typically produced from the reaction of the isocyanate blend and polyamines at normally a 1.05:1 stoichiometric ratio. In general, thermoset polyurea compositions are easier to prepare than thermoplastic polyureas.
The polyurea prepolymer can be chain-extended by reacting it with a single curing agent or blend of curing agents (chain-extenders). In general, the prepolymer can be reacted with hydroxyl-terminated curing agents, amine-terminated curing agents, or mixtures thereof. The curing agents extend the chain length of the prepolymer and build-up its molecular weight. Normally, the prepolymer and curing agent are mixed so the isocyanate groups and hydroxyl or amine groups are mixed at a 1.05:1.00 stoichiometric ratio.
A catalyst may be employed to promote the reaction between the isocyanate and polyamine compounds for producing the prepolymer or between prepolymer and curing agent during the chain-extending step. Preferably, the catalyst is added to the reactants before producing the prepolymer. Suitable catalysts include, but are not limited to, bismuth catalyst; zinc octoate; stannous octoate; tin catalysts such as bis-butyltin dilaurate, bis-butyltin diacetate, stannous octoate; tin (II) chloride, tin (IV) chloride, bis-butyltin dimethoxide, dimethyl-bis[1-oxonedecyl)oxy]stannane, di-n-octyltin bis-isooctyl mercaptoacetate; amine catalysts such as triethylenediamine, triethylamine, and tributylamine; organic acids such as oleic acid and acetic acid; delayed catalysts; and mixtures thereof. The catalyst is preferably added in an amount sufficient to catalyze the reaction of the components in the reactive mixture. In one embodiment, the catalyst is present in an amount from about 0.001 percent to about 1 percent, and preferably 0.1 to 0.5 percent, by weight of the composition.
The hydroxyl chain-extending (curing) agents are preferably selected from the group consisting of ethylene glycol; diethylene glycol; polyethylene glycol; propylene glycol; 2-methyl-1,3-propanediol; 2-methyl-1,4-butanediol; monoethanolamine; diethanolamine; triethanolamine; monoisopropanolamine; diisopropanolamine; dipropylene glycol; polypropylene glycol; 1,2-butanediol; 1,3-butanediol; 1,4-butanediol; 2,3-butanediol; 2,3-dimethyl-2,3-butanediol; trimethylolpropane; cyclohexyldimethylol; triisopropanolamine; N,N,N′,N′-tetra-(2-hydroxypropyl)-ethylene diamine; diethylene glycol bis-(aminopropyl) ether; 1,5-pentanediol; 1,6-hexanediol; 1,3-bis-(2-hydroxyethoxy) cyclohexane; 1,4-cyclohexyldimethylol; 1,3-bis-[2-(2-hydroxyethoxy) ethoxy]cyclohexane; 1,3-bis-{2-[2-(2-hydroxyethoxy) ethoxy]ethoxy}cyclohexane; trimethylolpropane; polytetramethylene ether glycol (PTMEG), preferably having a molecular weight from about 250 to about 3900; and mixtures thereof.
Suitable amine chain-extending (curing) agents that can be used in chain-extending the polyurea prepolymer of this invention include, but are not limited to, unsaturated diamines such as 4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-dianiline or “MDA”), m-phenylenediamine, p-phenylenediamine, 1,2- or 1,4-bis(sec-butylamino)benzene, 3,5-diethyl-(2,4- or 2,6-) toluenediamine or “DETDA”, 3,5-dimethylthio-(2,4- or 2,6-)toluenediamine, 3,5-diethylthio-(2,4- or 2,6-)toluenediamine, 3,3′-dimethyl-4,4′-diamino-diphenylmethane, 3,3′-diethyl-5,5′-dimethyl4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-bis(2-ethyl-6-methyl-benezeneamine)), 3,3′-dichloro-4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-bis(2-chloroaniline) or “MOCA”), 3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-bis(2,6-diethylaniline), 2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-bis(3-chloro-2,6-diethyleneaniline) or “MCDEA”), 3,3′-diethyl-5,5′-dichloro-4,4′-diamino-diphenylmethane, or “MDEA”), 3,3′-dichloro-2,2′,6,6′-tetraethyl-4,4′-diamino-diphenylmethane, 3,3′-dichloro-4,4′-diamino-diphenylmethane, 4,4′-methylene-bis(2,3-dichloroaniline) (i.e., 2,2′,3,3′-tetrachloro-4,4′-diamino-diphenylmethane or “MDCA”), 4,4′-bis(sec-butylamino)-diphenylmethane, N,N′-dialkylamino-diphenylmethane, trimethyleneglycol-di(p-aminobenzoate), polyethyleneglycol-di(p-aminobenzoate), polytetramethyleneglycol-di(p-aminobenzoate); saturated diamines such as ethylene diamine, 1,3-propylene diamine, 2-methyl-pentamethylene diamine, hexamethylene diamine, 2,2,4- and 2,4,4-trimethyl-1,6-hexane diamine, imino-bis(propylamine), imido-bis(propylamine), methylimino-bis(propylamine) (i.e., N-(3-aminopropyl)-N-methyl-1,3-propanediamine), 1,4-bis(3-aminopropoxy)butane (i.e., 3,3′-[1,4-butanediylbis-(oxy)bis]-1-propanamine), diethyleneglycol-bis(propylamine) (i.e., diethyleneglycol-di(aminopropyl)ether), 4,7,10-trioxatridecane-1,13-diamine, 1-methyl-2,6-diamino-cyclohexane, 1,4-diamino-cyclohexane, poly(oxyethylene-oxypropylene) diamines, 1,3- or 1,4-bis(methylamino)-cyclohexane, isophorone diamine, 1,2- or 1,4-bis(sec-butylamino)-cyclohexane, N,N′-diisopropyl-isophorone diamine, 4,4′-diamino-dicyclohexylmethane, 3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane, 3,3′-dichloro-4,4′-diamino-dicyclohexylmethane, N,N′-dialkylamino-dicyclohexylmethane, polyoxyethylene diamines, 3,3′-diethyl-5,5′-dimethyl-4,4′-diamino-dicyclohexylmethane, polyoxypropylene diamines, 3,3′-diethyl-5,5′-dichloro-4,4′-diamino-dicyclohexylmethane, polytetramethylene ether diamines, 3,3′,5,5 ‘-tetraethyl-4,4’-diamino-dicyclohexylmethane (i.e., 4,4′-methylene-bis(2,6-diethylaminocyclohexane)), 3,3′-dichloro-4,4′-diamino-dicyclohexylmethane, 2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-dicyclohexylmethane, (ethylene oxide)-capped polyoxypropylene ether diamines, 2,2′,3,3′-tetrachloro-4,4′-diamino-dicyclohexylmethane, 4,4′-bis(sec-butylamino)-dicyclohexylmethane; triamines such as diethylene triamine, dipropylene triamine, (propylene oxide)-based triamines (i.e., polyoxypropylene triamines), N-(2-aminoethyl)-1,3-propylenediamine (i.e., N₃-amine), glycerin-based triamines, (all saturated); tetramines such as N,N′-bis(3-aminopropyl)ethylene diamine (i.e., N₄-amine) (both saturated), triethylene tetramine; and other polyamines such as tetraethylene pentamine (also saturated). One suitable amine-terminated chain-extending agent is Ethacure 300™ (dimethylthiotoluenediamine or a mixture of 2,6-diamino-3,5-dimethylthiotoluene and 2,4-diamino-3,5-dimethylthiotoluene.) The amine curing agents used as chain extenders normally have a cyclic structure and a low molecular weight (250 or less).
When the polyurea prepolymer is reacted with amine-terminated curing agents during the chain-extending step, as described above, the resulting composition is essentially a pure polyurea composition. On the other hand, when the polyurea prepolymer is reacted with a hydroxyl-terminated curing agent during the chain-extending step, any excess isocyanate groups in the prepolymer will react with the hydroxyl groups in the curing agent and create urethane linkages to form a polyurea/urethane hybrid.
This chain-extending step, which occurs when the polyurea prepolymer is reacted with hydroxyl curing agents, amine curing agents, or mixtures thereof, builds-up the molecular weight and extends the chain length of the prepolymer. When the polyurea prepolymer is reacted with amine curing agents, a polyurea composition having urea linkages is produced. When the polyurea prepolymer is reacted with hydroxyl curing agents, a polyurea/urethane hybrid composition containing both urea and urethane linkages is produced. The polyurea/urethane hybrid composition is distinct from the pure polyurea composition. The concentration of urea and urethane linkages in the hybrid composition may vary. In general, the hybrid composition may contain a mixture of about 10 to 90% urea and about 90 to 10% urethane linkages. The resulting polyurea or polyurea/urethane hybrid composition has elastomeric properties based on phase separation of the soft and hard segments. The soft segments, which are formed from the polyamine reactants, are generally flexible and mobile, while the hard segments, which are formed from the isocyanates and chain extenders, are generally stiff and immobile.
In an alternative embodiment, at least one layer may be formed from a polyurethane or polyurethane/urea hybrid composition. As discussed above, in general, polyurethane compositions contain urethane linkages formed by reacting an isocyanate group (—N═C═O) with a hydroxyl group (OH). The polyurethanes are produced by the reaction of a multi-functional isocyanate (NCO—R—NCO) with a long-chain polyol having terminal hydroxyl groups (OH—OH) in the presence of a catalyst and other additives. The chain length of the polyurethane prepolymer is extended by reacting it with short-chain diols (OH—R′—OH). The resulting polyurethane has elastomeric properties because of its “hard” and “soft” segments, which are covalently bonded together. This phase separation occurs because the mainly non-polar, low melting soft segments are incompatible with the polar, high melting hard segments. The hard segments, which are formed by the reaction of the diisocyanate and low molecular weight chain-extending diol, are relatively stiff and immobile. The soft segments, which are formed by the reaction of the diisocyanate and long chain diol, are relatively flexible and mobile. Because the hard segments are covalently coupled to the soft segments, they inhibit plastic flow of the polymer chains, thus creating elastomeric resiliency.
Suitable isocyanate compounds that can be used to prepare the polyurethane or polyurethane/urea hybrid material are described above. These isocyanate compounds are able to react with the hydroxyl or amine compounds and form a durable and tough polymer having a high melting point. The resulting polyurethane generally has good mechanical strength and cut/shear-resistance. In addition, the polyurethane composition has good light and thermal-stability.
When forming a polyurethane prepolymer, any suitable polyol may be reacted with the above-described isocyanate blends in accordance with this invention. Exemplary polyols include, but are not limited to, polyether polyols, hydroxy-terminated polybutadiene (including partially/fully hydrogenated derivatives), polyester polyols, polycaprolactone polyols, and polycarbonate polyols. In one preferred embodiment, the polyol includes polyether polyol. Examples include, but are not limited to, polytetramethylene ether glycol (PTMEG), polyethylene propylene glycol, polyoxypropylene glycol, and mixtures thereof. The hydrocarbon chain can have saturated or unsaturated bonds and substituted or unsubstituted aromatic and cyclic groups. Preferably, the polyol of the present invention includes PTMEG. In another embodiment, polyester polyols are included in the polyurethane material. Suitable polyester polyols include, but are not limited to, polyethylene adipate glycol; polybutylene adipate glycol; polyethylene propylene adipate glycol; o-phthalate-1,6-hexanediol; poly(hexamethylene adipate) glycol; and mixtures thereof. The hydrocarbon chain can have saturated or unsaturated bonds, or substituted or unsubstituted aromatic and cyclic groups. In still another embodiment, polycaprolactone polyols are included in the materials of the invention. Suitable polycaprolactone polyols include, but are not limited to: 1,6-hexanediol-initiated polycaprolactone, diethylene glycol initiated polycaprolactone, trimethylol propane initiated polycaprolactone, neopentyl glycol initiated polycaprolactone, 1,4-butanediol-initiated polycaprolactone, and mixtures thereof. The hydrocarbon chain can have saturated or unsaturated bonds, or substituted or unsubstituted aromatic and cyclic groups. In yet another embodiment, polycarbonate polyols are included in the polyurethane material of the invention. Suitable polycarbonates include, but are not limited to, polyphthalate carbonate and poly(hexamethylene carbonate) glycol. The hydrocarbon chain can have saturated or unsaturated bonds, or substituted or unsubstituted aromatic and cyclic groups. In one embodiment, the molecular weight of the polyol is from about 200 to about 4000.
In a manner similar to making the above-described polyurea compositions, there are two basic techniques that can be used to make the polyurethane compositions of this invention: a) one-shot technique, and b) prepolymer technique. In the one-shot technique, the isocyanate blend, polyol, and hydroxyl-terminated and/or amine-terminated chain-extender (curing agent) are reacted in one step. On the other hand, the prepolymer technique involves a first reaction between the isocyanate blend and polyol compounds to produce a polyurethane prepolymer, and a subsequent reaction between the prepolymer and hydroxyl-terminated and/or amine-terminated chain-extender. As a result of the reaction between the isocyanate and polyol compounds, there will be some unreacted NCO groups in the polyurethane prepolymer. The prepolymer should have less than 14% unreacted NCO groups. Preferably, the prepolymer has no greater than 8.5% unreacted NCO groups, more preferably from 2.5% to 8%, and most preferably from 5.0% to 8.0% unreacted NCO groups. As the weight percent of unreacted isocyanate groups increases, the hardness of the composition also generally increases.
Either the one-shot or prepolymer method may be employed to produce the polyurethane compositions of the invention. In one embodiment, the one-shot method is used, wherein the isocyanate compound is added to a reaction vessel and then a curative mixture comprising the polyol and curing agent is added to the reaction vessel. The components are mixed together so that the molar ratio of isocyanate groups to hydroxyl groups is in the range of about 1.01:1.00 to about 1.10:1.00. Preferably, the molar ratio is greater than or equal to 1.05:1.00. For example, the molar ratio can be in the range of 1.05:1.00 to 1.10:1.00. In a second embodiment, the prepolymer method is used. In general, the prepolymer technique is preferred because it provides better control of the chemical reaction. The prepolymer method provides a more homogeneous mixture resulting in a more consistent polymer composition. The one-shot method results in a mixture that is inhomogeneous (more random) and affords the manufacturer less control over the molecular structure of the resultant composition.
The polyurethane compositions can be formed by chain-extending the polyurethane prepolymer with a single curing agent (chain-extender) or blend of curing agents (chain-extenders) as described further below. The compositions of the present invention may be selected from among both castable thermoplastic and thermoset polyurethanes. Thermoplastic polyurethane compositions are typically formed by reacting the isocyanate blend and polyols at a 1:1 stoichiometric ratio. Thermoset compositions, on the other hand, are cross-linked polymers and are typically produced from the reaction of the isocyanate blend and polyols at normally a 1.05:1 stoichiometric ratio. In general, thermoset polyurethane compositions are easier to prepare than thermoplastic polyurethanes.
As discussed above, the polyurethane prepolymer can be chain-extended by reacting it with a single chain-extender or blend of chain-extenders. In general, the prepolymer can be reacted with hydroxyl-terminated curing agents, amine-terminated curing agents, and mixtures thereof. The curing agents extend the chain length of the prepolymer and build-up its molecular weight. Normally, the prepolymer and curing agent are mixed so the isocyanate groups and hydroxyl or amine groups are mixed at a 1.05:1.00 stoichiometric ratio.
A catalyst may be employed to promote the reaction between the isocyanate and polyol compounds for producing the polyurethane prepolymer or between the polyurethane prepolymer and chain-extender during the chain-extending step. Preferably, the catalyst is added to the reactants before producing the polyurethane prepolymer. Suitable catalysts include, but are not limited to, the catalysts described above for making the polyurea prepolymer. The catalyst is preferably added in an amount sufficient to catalyze the reaction of the components in the reactive mixture. In one embodiment, the catalyst is present in an amount from about 0.001 percent to about 1 percent, and preferably 0.1 to 0.5 percent, by weight of the composition. Suitable hydroxyl chain-extending (curing) agents and amine chain-extending (curing) agents include, but are not limited to, the curing agents described above for making the polyurea and polyurea/urethane hybrid compositions. When the polyurethane prepolymer is reacted with hydroxyl-terminated curing agents during the chain-extending step, as described above, the resulting polyurethane composition contains urethane linkages. On the other hand, when the polyurethane prepolymer is reacted with amine-terminated curing agents during the chain-extending step, any excess isocyanate groups in the prepolymer will react with the amine groups in the curing agent. The resulting polyurethane composition contains urethane and urea linkages and may be referred to as a polyurethane/urea hybrid. The concentration of urethane and urea linkages in the hybrid composition may vary. In general, the hybrid composition may contain a mixture of about 10 to 90% urethane and about 90 to 10% urea linkages.
Examples of commercially available thermoplastics suitable for forming thermoplastic layers include, but are not limited to, Pebax® thermoplastic polyether block amides, commercially available from Arkema Inc.; Surlyn® ionomer resins, Hytrel® thermoplastic polyester elastomers, and ionomeric materials sold under the trade names DuPont® HPF 1000, HPF 2000, HPF AD 1035, HPF AD 1040, all of which are commercially available from E. I. du Pont de Nemours and Company; Iotek® ionomers, commercially available from ExxonMobil Chemical Company; Amplify® IO ionomers of ethylene acrylic acid copolymers, commercially available from The Dow Chemical Company; Clarix® ionomer resins, commercially available from A. Schulman Inc.; Elastollan® polyurethane-based thermoplastic elastomers, commercially available from BASF; and Xylex® polycarbonate/polyester blends, commercially available from SABIC Innovative Plastics.
Suitable plasticized polymer compositions include a plasticizer in an amount sufficient to substantially change the stiffness and/or hardness of the composition, and typically comprise from 20 to 99.5 wt % of the polymer and from 0.5 to 80 wt % of the plasticizer, based on the combined weight of the polymer and the plasticizer. In a particular embodiment, the plasticizer is present in an amount of 0.5% or 1% or 3% or 5% or 7% or 8% or 9% or 10% or 12% or 15% or 18% or 20% or 22% or 25% or 30% or 35% or 40% or 42% or 50% or 55% or 60% or 66% or 71% or 75% or 80%, by weight based on the combined weight of the polymer and the plasticizer, or the plasticizer is present in an amount within a range having a lower limit and an upper limit selected from these values. Suitable polymers include acid copolymers, partially neutralized acid copolymers, highly neutralized acid polymers (“HNPs”), polyesters, polyamides, thermosetting and thermoplastic polyurethanes.
Suitable plasticized acid copolymer compositions, plasticized partially neutralized acid copolymer compositions, and plasticized HNP compositions, and particularly suitable golf ball constructions utilizing such compositions, are further disclosed, for example, in U.S. Patent Application Publ. No. 2015/0031475, U.S. Patent Application Publ. No. 2015/0005108, U.S. patent application Ser. No. 14/576,800, and U.S. patent application Ser. No. 14/588,317, the entire disclosures of which are hereby incorporated herein by reference.
Suitable plasticized polyester compositions, and particularly suitable golf ball constructions utilizing such compositions, are further disclosed, for example, in U.S. patent application Ser. No. 14/532,141, the entire disclosure of which is hereby incorporated herein by reference.
Suitable plasticized polyamide compositions, and particularly suitable golf ball constructions utilizing such compositions, are further disclosed, for example, in U.S. Patent Application Publ. No. 2014/0302947, U.S. Patent Application Publ. No. 2014/0323243, U.S. Patent Application Publ. No. 20150057105, and U.S. patent application Ser. No. 14/576,324, the entire disclosures of which are hereby incorporated herein by reference.
Suitable plasticized polyurethane compositions, and particularly suitable golf ball constructions utilizing such compositions, are further disclosed, for example, in U.S. patent application Ser. No. 14/672,538, U.S. patent application Ser. No. 14/672,523, U.S. patent application Ser. No. 14/672,485, and U.S. patent application Ser. No. 14/691,720, the entire disclosures of which are hereby incorporated herein by reference. Further suitable plasticized compositions include for example those disclosed in U.S. patent application Ser. Nos. 14/571,610, 14/576,324, and 14/707,028.
And it is contemplated that a golf ball of the invention may have any known construction and have any number of layers with any known properties with the foremost limitation being a high or steep hardness gradient in the core as discussed herein.
The core may have a dual core arrangement having a total diameter of from about 1.40 in. to about 1.65 in, for example, wherein the inner core may has a diameter of from about 0.75 inches to about 1.30 in. and the outer core has a thickness of from about 0.05 in. to about 0.45 in. Cover thicknesses generally range from about 0.015 in. to about 0.090 inches, although a golf ball of the invention may comprise any known thickness. Meanwhile, casing layers and inner cover layers each typically have thicknesses ranging from about 0.01 in. to about 0.06 in. A golf ball of the invention may also have one or more film layers, paint layers or coating layers having a combined thickness of from about 0.1 μm to about 100 μm, or from about 2 μm to about 50 μm, or from about 2 μm to about 30 μm. Meanwhile, each coating layer may have a thickness of from about 0.1 μm to about 50 μm, or from about 0.1 μm to about 25 μm, or from about 0.1 μm to about 14 μm, or from about 2 μm to about 9 μm, for example.
In some embodiments, the core may have an overall diameter within a range having a lower limit of 0.500 or 0.700 or 0.750 or 0.800 or 0.850 or 0.900 or 0.950 or 1.000 or 1.100 or 1.150 or 1.200 or 1.250 or 1.300 or 1.350 or 1.400 or 1.450 or 1.500 or 1.600 or 1.610 inches and an upper limit of 1.620 or 1.630 or 1.640 inches. In a particular embodiment, the core is a multi-layer core having an overall diameter within a range having a lower limit of 0.500 or 0.700 or 0.750 or 0.800 or 0.850 or 0.900 or 0.950 or 1.000 or 1.100 or 1.150 or 1.200 inches and an upper limit of 1.250 or 1.300 or 1.350 or 1.400 or 1.450 or 1.500 or 1.600 or 1.610 or 1.620 or 1.630 or 1.640 inches. In another particular embodiment, the multi-layer core has an overall diameter within a range having a lower limit of 0.500 or 0.700 or 0.750 inches and an upper limit of 0.800 or 0.850 or 0.900 or 0.950 or 1.000 or 1.100 or 1.150 or 1.200 or 1.250 or 1.300 or 1.350 or 1.400 or 1.450 or 1.500 or 1.600 or 1.610 or 1.620 or 1.630 or 1.640 inches. In another particular embodiment, the multi-layer core has an overall diameter of 1.500 inches or 1.510 inches or 1.530 inches or 1.550 inches or 1.570 inches or 1.580 inches or 1.590 inches or 1.600 inches or 1.610 inches or 1.620 inches.
The inner core can have an overall diameter of 0.500 inches or greater, or 0.700 inches or greater, or 1.00 inches or greater, or 1.250 inches or greater, or 1.350 inches or greater, or 1.390 inches or greater, or 1.450 inches or greater, or an overall diameter within a range having a lower limit of 0.250 or 0.500 or 0.750 or 1.000 or 1.250 or 1.350 or 1.390 or 1.400 or 1.440 inches and an upper limit of 1.460 or 1.490 or 1.500 or 1.550 or 1.580 or 1.600 inches, or an overall diameter within a range having a lower limit of 0.250 or 0.300 or 0.350 or 0.400 or 0.500 or 0.550 or 0.600 or 0.650 or 0.700 inches and an upper limit of 0.750 or 0.800 or 0.900 or 0.950 or 1.000 or 1.100 or 1.150 or 1.200 or 1.250 or 1.300 or 1.350 or 1.400 inches. In one embodiment, the inner core consists of a single layer formed from a thermoset rubber composition. In another embodiment, the inner core consists of two layers, each of which is formed from the same or different thermoset rubber compositions. In another embodiment, the inner core comprises three or more layers, each of which is formed from the same or different thermoset rubber compositions. In another embodiment, the inner core consists of a single layer formed from a thermoplastic composition. In another embodiment, the inner core consists of two layers, each of which is formed from the same or different thermoplastic compositions. In another embodiment, the inner core comprises three or more layers, each of which is formed from the same or different thermoplastic compositions.
In a particular embodiment, the overall core of a golf ball of the invention has one or more of the following properties:

a) a geometric center hardness within a range having a lower limit of 20 or 25 or 30 or 35 or 40 or 45 or 50 or 55 Shore C and an upper limit of 60 or 65 or 70 or 75 or less than about 79 Shore C;
b) an outer surface hardness within a range having a lower limit of 80 or 85 or 90 or 95 Shore C;
c) a positive hardness gradient of at least 20 Shore C; and
d) an overall compression of about 75 or greater, or greater than 75, or about 80 or greater, or greater than or 80.

An intermediate core layer can have an overall thickness within a range having a lower limit of 0.005 or 0.010 or 0.015 or 0.020 or 0.025 or 0.030 or 0.035 or 0.040 or 0.045 inches and an upper limit of 0.050 or 0.055 or 0.060 or 0.065 or 0.070 or 0.075 or 0.080 or 0.090 or 0.100 inches. In one embodiment, the intermediate core consists of a single layer formed from a thermoset rubber composition. In another embodiment, the intermediate core consists of two layers, each of which is formed from the same or different thermoset rubber compositions. In another embodiment, the intermediate core comprises three or more layers, each of which is formed from the same or different thermoset rubber compositions. In another embodiment, the intermediate core consists of a single layer formed from a thermoplastic composition. In another embodiment, the intermediate core consists of two layers, each of which is formed from the same or different thermoplastic compositions. In another embodiment, the intermediate core comprises three or more layers, each of which is formed from the same or different thermoplastic compositions.
The outer core layer can have an overall thickness within a range having a lower limit of 0.010 or 0.020 or 0.025 or 0.030 or 0.035 inches and an upper limit of 0.040 or 0.070 or 0.075 or 0.080 or 0.100 or 0.150 inches, or an overall thickness within a range having a lower limit of 0.025 or 0.050 or 0.100 or 0.150 or 0.160 or 0.170 or 0.200 inches and an upper limit of 0.225 or 0.250 or 0.275 or 0.300 or 0.325 or 0.350 or 0.400 or 0.450 or greater than 0.450 inches. The outer core layer may alternatively have a thickness of greater than 0.10 inches, or 0.20 inches or greater, or greater than 0.20 inches, or 0.30 inches or greater, or greater than 0.30 inches, or 0.35 inches or greater, or greater than 0.35 inches, or 0.40 inches or greater, or greater than 0.40 inches, or 0.45 inches or greater, or greater than 0.45 inches, or a thickness within a range having a lower limit of 0.005 or 0.010 or 0.015 or 0.020 or 0.025 or 0.030 or 0.035 or 0.040 or 0.045 or 0.050 or 0.055 or 0.060 or 0.065 or 0.070 or 0.075 or 0.080 or 0.090 or 0.100 or 0.200 or 0.250 inches and an upper limit of 0.300 or 0.350 or 0.400 or 0.450 or 0.500 inches or greater.
It is envisioned that the outer core layer may have more than one layer, as long as each of the layers forming the outer core layer consist of a mixture of a plurality of synthetic flocks and a first thermoset rubber composition; with the plurality of synthetic flocks has a melting temperature that is greater than a mixing temperature at which the mixture is formed; and the outer core layer as a whole has an outermost surface having an outer surface hardness of about 80 Shore C or greater; that is greater than a center hardness of the geometric center of the core by at least 20 Shore C. Of course, it is also envisioned that in a multi-layered outer core layer, each core layer thereforming may consist of a different mixture of a plurality of synthetic flocks and a first thermoset rubber composition. For example, in one embodiment, the outer core layer may have two differing layers, an inner layer that differs from an outer layer only by the type of flock mixed (e.g., the inner layer may contain nylon flocks whereas the outer layer contains polyester flocks). Or, the inner layer and outer layer may contain the same flocks but in differing amounts (phr) thereof. Additionally or alternatively, the inner and outer layers may include differing thermoset rubber compositions. And in different embodiments, the outer core layer may have three or more layers, some or all of which differ with respect to the type of flock used and/or the particular thermoset rubber composition included in the mixture.
The outer core layer may meanwhile have any thickness known in the art for outer core layers.
And it is recognized that a layer consisting of the mixture of a plurality of synthetic flocks and a thermoset rubber composition may also be useful for targeting other desired golf ball properties when used in different layers such as in an intermediate core layer that is disposed between an inner core layer and an outer core layer for example. In such an embodiment the intermediate core layer consists of the mixture of a plurality of synthetic flocks and a thermoset rubber composition; with the plurality of synthetic flocks having a melting temperature that is greater than a mixing temperature at which the mixture is formed; and the intermediate core layer having an outer surface with an outer surface hardness of about 80 Shore C or greater and greater than the hardness of the geometric center of the core by at least 20 Shore C. In this embodiment, the outer core layer might be formed from any known material such as a thermoplastic composition.
The multi-layer core is enclosed with a cover, which may be a single-, dual-, or multi-layer cover, preferably having an overall thickness within a range having a lower limit of 0.010 or 0.020 or 0.025 or 0.030 or 0.040 or 0.045 inches and an upper limit of 0.050 or 0.060 or 0.070 or 0.075 or 0.080 or 0.090 or 0.100 or 0.150 or 0.200 or 0.300 or 0.500 inches. In a particular embodiment, the cover is a single layer having a thickness of from 0.010 or 0.020 or 0.025 inches to 0.035 or 0.040 or 0.050 inches. In another particular embodiment, the cover consists of an inner cover layer having a thickness of from 0.010 or 0.020 or 0.025 inches to 0.035 or 0.050 inches and an outer cover layer having a thickness of from 0.010 or 0.020 or 0.025 inches to 0.035 or 0.040 inches.
In one embodiment, the cover is a single layer having a surface hardness of 60 Shore D or greater, or 65 Shore D or greater. In a particular aspect of this embodiment, the cover is formed from a composition having a material hardness of 60 Shore D or greater, or 65 Shore D or greater.
In another particular embodiment, the cover is a single layer having a thickness of from 0.010 or 0.020 inches to 0.035 or 0.050 inches and formed from an ionomeric composition having a material hardness of from 60 or 62 or 65 Shore D to 65 or 70 or 72 Shore D.
In another particular embodiment, the cover is a single layer having a thickness of from 0.010 or 0.025 inches to 0.035 or 0.040 inches and formed from a thermoplastic composition selected from ionomer-, polyurethane-, and polyurea-based compositions having a material hardness of 62 Shore D or less, or less than 62 Shore D, or 60 Shore D or less, or less than 60 Shore D, or 55 Shore D or less, or less than 55 Shore D.
In another particular embodiment, the cover is a single layer having a thickness of from 0.010 or 0.025 inches to 0.035 or 0.040 inches and formed from a thermosetting polyurethane- or polyurea-based composition having a material hardness of 62 Shore D or less, or less than 62 Shore D, or 60 Shore D or less, or less than 60 Shore D, or 55 Shore D or less, or less than 55 Shore D.
In another particular embodiment, the cover comprises an inner cover layer formed from an ionomeric composition and an outer cover layer formed from a thermosetting polyurethane- or polyurea-based composition. The inner cover layer composition preferably has a material hardness of from 60 or 62 or 65 Shore D to 65 or 70 or 72 Shore D. The inner cover layer preferably has a thickness within a range having a lower limit of 0.010 or 0.020 or 0.030 inches and an upper limit of 0.035 or 0.040 or 0.050 inches. The outer cover layer composition preferably has a material hardness of 62 Shore D or less, or less than 62 Shore D, or 60 Shore D or less, or less than 60 Shore D, or 55 Shore D or less, or less than 55 Shore D. The outer cover layer preferably has a thickness within a range having a lower limit of 0.010 or 0.020 or 0.025 inches and an upper limit of 0.035 or 0.040 or 0.050 inches.
In another particular embodiment, the cover comprises an inner cover layer formed from an ionomeric composition and an outer cover layer formed from a thermoplastic composition selected from ionomer-, polyurethane-, and polyurea-based compositions. The inner cover layer composition preferably has a material hardness of from 60 or 62 or 65 Shore D to 65 or 70 or 72 Shore D. The inner cover layer preferably has a thickness within a range having a lower limit of 0.010 or 0.020 or 0.030 inches and an upper limit of 0.035 or 0.040 or 0.050 inches. The outer cover layer composition preferably has a material hardness of 62 Shore D or less, or less than 62 Shore D, or 60 Shore D or less, or less than 60 Shore D, or 55 Shore D or less, or less than 55 Shore D. The outer cover layer preferably has a thickness within a range having a lower limit of 0.010 or 0.020 or 0.025 inches and an upper limit of 0.035 or 0.040 or 0.050 inches.
In another particular embodiment, the cover is a dual- or multi-layer cover including an inner or intermediate cover layer formed from an ionomeric composition and an outer cover layer formed from a polyurethane- or polyurea-based composition. The ionomeric layer preferably has a surface hardness of 70 Shore D or less, or 65 Shore D or less, or less than 65 Shore D, or a Shore D hardness of from 50 to 65, or a Shore D hardness of from 57 to 60, or a Shore D hardness of 58, and a thickness within a range having a lower limit of 0.010 or 0.020 or 0.030 inches and an upper limit of 0.045 or 0.080 or 0.120 inches. The outer cover layer is preferably formed from a castable or reaction injection moldable polyurethane, polyurea, or copolymer or hybrid of polyurethane/polyurea. Such cover material is preferably thermosetting, but may be thermoplastic. The outer cover layer composition preferably has a material hardness of 85 Shore C or less, or 45 Shore D or less, or 40 Shore D or less, or from 25 Shore D to 40 Shore D, or from 30 Shore D to 40 Shore D. The outer cover layer preferably has a surface hardness within a range having a lower limit of 20 or 30 or 35 or 40 Shore D and an upper limit of 52 or 58 or 60 or 65 or 70 or 72 or 75 Shore D. The outer cover layer preferably has a thickness within a range having a lower limit of 0.010 or 0.015 or 0.025 inches and an upper limit of 0.035 or 0.040 or 0.045 or 0.050 or 0.055 or 0.075 or 0.080 or 0.115 inches.
In another particular embodiment, the cover comprises an inner cover layer formed from an ionomeric composition and an outer cover layer formed from a thermosetting polyurethane- or polyurea-based composition. The inner cover layer composition preferably has a material hardness of from 60 or 62 or 65 Shore D to 65 or 70 or 72 Shore D. The inner cover layer preferably has a thickness within a range having a lower limit of 0.010 or 0.020 or 0.030 inches and an upper limit of 0.035 or 0.040 or 0.050 inches. The outer cover layer composition preferably has a material hardness of 62 Shore D or less, or less than 62 Shore D, or 60 Shore D or less, or less than 60 Shore D, or 55 Shore D or less, or less than 55 Shore D. The outer cover layer preferably has a thickness within a range having a lower limit of 0.010 or 0.020 or 0.025 inches and an upper limit of 0.035 or 0.040 or 0.050 inches.
In another particular embodiment, the cover comprises an inner cover layer formed from an ionomeric composition and an outer cover layer formed from a thermoplastic composition selected from ionomer-, polyurethane-, and polyurea-based compositions. The inner cover layer composition preferably has a material hardness of from 60 or 62 or 65 Shore D to 65 or 70 or 72 Shore D. The inner cover layer preferably has a thickness within a range having a lower limit of 0.010 or 0.020 or 0.030 inches and an upper limit of 0.035 or 0.040 or 0.050 inches. The outer cover layer composition preferably has a material hardness of 62 Shore D or less, or less than 62 Shore D, or 60 Shore D or less, or less than 60 Shore D, or 55 Shore D or less, or less than 55 Shore D. The outer cover layer preferably has a thickness within a range having a lower limit of 0.010 or 0.020 or 0.025 inches and an upper limit of 0.035 or 0.040 or 0.050 inches.
In another particular embodiment, the cover is a dual- or multi-layer cover including an inner or intermediate cover layer formed from an ionomeric composition and an outer cover layer formed from a polyurethane- or polyurea-based composition. The ionomeric layer preferably has a surface hardness of 70 Shore D or less, or 65 Shore D or less, or less than 65 Shore D, or a Shore D hardness of from 50 to 65, or a Shore D hardness of from 57 to 60, or a Shore D hardness of 58, and a thickness within a range having a lower limit of 0.010 or 0.020 or 0.030 inches and an upper limit of 0.045 or 0.080 or 0.120 inches. The outer cover layer is preferably formed from a castable or reaction injection moldable polyurethane, polyurea, or copolymer or hybrid of polyurethane/polyurea. Such cover material is preferably thermosetting, but may be thermoplastic. The outer cover layer composition preferably has a material hardness of 85 Shore C or less, or 45 Shore D or less, or 40 Shore D or less, or from 25 Shore D to 40 Shore D, or from 30 Shore D to 40 Shore D. The outer cover layer preferably has a surface hardness within a range having a lower limit of 20 or 30 or 35 or 40 Shore D and an upper limit of 52 or 58 or 60 or 65 or 70 or 72 or 75 Shore D. The outer cover layer preferably has a thickness within a range having a lower limit of 0.010 or 0.015 or 0.025 inches and an upper limit of 0.035 or 0.040 or 0.045 or 0.050 or 0.055 or 0.075 or 0.080 or 0.115 inches.
The compressions and CoRs of each golf ball layer may meanwhile also be targeted and coordinated with each other to form an overall golf ball possessing/displaying desired playing characteristics.
For purposes of the present invention, “compression” refers to Atti compression and is measured according to a known procedure, using an Atti compression test device, wherein a piston is used to compress a ball against a spring. The travel of the piston is fixed and the deflection of the spring is measured. The measurement of the deflection of the spring does not begin with its contact with the ball; rather, there is an offset of approximately the first 1.25 mm (0.05 inches) of the spring's deflection. Very low compression cores will not cause the spring to deflect by more than 1.25 mm and therefore have a zero or negative compression measurement. The Atti compression tester is designed to measure objects having a diameter of 1.680 inches; thus, smaller objects, such as golf ball cores, must be shimmed to a total height of 1.680 inches to obtain an accurate reading. Conversion from Atti compression to Riehle (cores), Riehle (balls), 100 kg deflection, 130-10 kg deflection or effective modulus can be carried out according to the formulas given in Compression by Any Other Name, Science and Golf IV, Proceedings of the World Scientific Congress of Golf (Eric Thain ed., Routledge, 2002).
CoR, as used herein, is determined according to a known procedure wherein a sphere is fired from an air cannon at two given velocities and calculated at a velocity of 125 ft/s. Ballistic light screens are located between the air cannon and the steel plate at a fixed distance to measure ball velocity. As the sphere travels toward the steel plate, it activates each light screen, and the time at each light screen is measured. This provides an incoming transit time period inversely proportional to the sphere's incoming velocity. The sphere impacts the steel plate and rebounds through the light screens, which again measures the time period required to transit between the light screens. This provides an outgoing transit time period inversely proportional to the sphere's outgoing velocity. CoR is then calculated as the ratio of the outgoing transit time period to the incoming transit time period, CoR=V_out/V_in=T_in/T_out. For example, the CoR value can be targeted in a thermoset rubber core by varying peroxide and antioxidant types and amounts as well as the cure temperature and duration.
The center hardness of a core is obtained according to the following procedure. The core is gently pressed into a hemispherical holder having an internal diameter approximately slightly smaller than the diameter of the core, such that the core is held in place in the hemispherical portion of the holder while concurrently leaving the geometric central plane of the core exposed. The core is secured in the holder by friction, such that it will not move during the cutting and grinding steps, but the friction is not so excessive that distortion of the natural shape of the core would result. The core is secured such that the parting line of the core is roughly parallel to the top of the holder. The diameter of the core is measured 90 degrees to this orientation prior to securing. A measurement is also made from the bottom of the holder to the top of the core to provide a reference point for future calculations. A rough cut is made slightly above the exposed geometric center of the core using a band saw or other appropriate cutting tool, making sure that the core does not move in the holder during this step. The remainder of the core, still in the holder, is secured to the base plate of a surface grinding machine. The exposed ‘rough’ surface is ground to a smooth, flat surface, revealing the geometric center of the core, which can be verified by measuring the height from the bottom of the holder to the exposed surface of the core, making sure that exactly half of the original height of the core, as measured above, has been removed to within ±0.004 inches. Leaving the core in the holder, the center of the core is found with a center square and carefully marked and the hardness is measured at the center mark according to ASTM D-2240. Additional hardness measurements at any distance from the center of the core can then be made by drawing a line radially outward from the center mark, and measuring the hardness at any given distance along the line, typically in 2 mm increments from the center. The hardness at a particular distance from the center should be measured along at least two, preferably four, radial arms located 180° apart, or 90° apart, respectively, and then averaged. All hardness measurements performed on a plane passing through the geometric center are performed while the core is still in the holder and without having disturbed its orientation, such that the test surface is constantly parallel to the bottom of the holder, and thus also parallel to the properly aligned foot of the durometer.
Hardness points should only be measured once at any particular geometric location.
The surface hardness of a golf ball layer is obtained from the average of a number of measurements taken from opposing hemispheres, taking care to avoid making measurements on the parting line of the core or on surface defects such as holes or protrusions. Hardness measurements are made pursuant to ASTM D-2240 “Indentation Hardness of Rubber and Plastic by Means of a Durometer.” Because of the curved surface of the golf ball layer, care must be taken to ensure that the golf ball or golf ball subassembly is centered under the durometer indentor before a surface hardness reading is obtained. A calibrated digital durometer, capable of reading to 0.1 hardness units, is used for all hardness measurements. The digital durometer must be attached to and its foot made parallel to the base of an automatic stand. The weight on the durometer and attack rate conforms to ASTM D-2240. It should be understood that there is a fundamental difference between “material hardness” and “hardness as measured directly on a golf ball.” For purposes of the present invention, material hardness is measured according to ASTM D2240 and generally involves measuring the hardness of a flat “slab” or “button” formed of the material. Surface hardness as measured directly on a golf ball (or other spherical surface) typically results in a different hardness value. The difference in “surface hardness” and “material hardness” values is due to several factors including, but not limited to, ball construction (that is, core type, number of cores and/or cover layers, and the like); ball (or sphere) diameter; and the material composition of adjacent layers. It also should be understood that the two measurement techniques are not linearly related and, therefore, one hardness value cannot easily be correlated to the other.
It should be understood that there is a fundamental difference between “material hardness” and “hardness as measured directly on a golf ball.” For purposes of the present disclosure, material hardness is measured according to ASTM D2240 and generally involves measuring the hardness of a flat “slab” or “button” formed of the material. Hardness as measured directly on a golf ball (or other spherical surface) typically results in a different hardness value. This difference in hardness values is due to several factors including, but not limited to, ball construction (i.e., core type, number of core and/or cover layers, etc.), ball (or sphere) diameter, and the material composition of adjacent layers. It should also be understood that the two measurement techniques are not linearly related and, therefore, one hardness value cannot easily be correlated to the other.
It is understood that the golf balls of the invention incorporating at least one core layer consisting of a mixture of a plurality of synthetic flocks and a thermoset rubber composition, as described and illustrated herein, represent only some of the many embodiments of the invention. It is appreciated by those skilled in the art that various changes and additions can be made to such golf balls without departing from the spirit and scope of this invention. It is intended that all such embodiments be covered by the appended claims.
A golf ball of the invention may further incorporate indicia, which as used herein, is considered to mean any symbol, letter, group of letters, design, or the like, that can be added to the dimpled surface of a golf ball.
It will be appreciated that any known dimple pattern may be used with any number of dimples having any shape or size. For example, the number of dimples may be 252 to 456, or 330 to 392 and may comprise any width, depth, and edge angle. The parting line configuration of said pattern may be either a straight line or a staggered wave parting line (SWPL), for example.
And the cover hardness and the hardness of any intermediate layers may be targeted depending on desired playing characteristics. As a general rule, all other things being equal, a golf ball having a relatively soft cover will spin more than a similarly constructed ball having a harder cover.
Other than in the operating examples, or unless otherwise expressly specified, all of the numerical ranges, amounts, values and percentages such as those for amounts of materials and others in the specification may be read as if prefaced by the word “about” even though the term “about” may not expressly appear with the value, amount or range. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Furthermore, when numerical ranges of varying scope are set forth herein, it is contemplated that any combination of these values inclusive of the recited values may be used.
Although the golf ball of the invention has been described herein with reference to particular means and materials, it is to be understood that the invention is not limited to the particulars disclosed and extends to all equivalents within the scope of the claims.
When numerical lower limits and numerical upper limits are set forth herein, it is contemplated that any combination of these values may be used.
All patents, publications, test procedures, and other references cited herein, including priority documents, are fully incorporated by reference to the extent such disclosure is not inconsistent with this invention and for all jurisdictions in which such incorporation is permitted.
While the illustrative embodiments of the invention have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those of ordinary skill in the art without departing from the spirit and scope of the invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein, but rather that the claims be construed as encompassing all of the features of patentable novelty which reside in the present invention, including all features which would be treated as equivalents thereof by those of ordinary skill in the art to which the invention pertains.

Claims

What is claimed is:

1. A golf ball comprising:

a core comprising an inner core layer and an outer core layer;

wherein the outer core layer consists of a mixture of a plurality of synthetic flocks and a first thermoset rubber composition;

wherein the plurality of synthetic flocks has a melting temperature that is greater than a mixing temperature at which the mixture is formed; and

wherein the outer core layer comprises an outer surface having an outer surface hardness of about 80 Shore C or greater; and

wherein the outer surface hardness is greater than a center hardness of a geometric center of the core by at least 20 Shore C; and

a cover having one or more layers disposed about the core.

2. The golf ball of claim 1, wherein the synthetic flocks are included in the mixture in an amount of from about 0.5 parts to about 15 parts of the total mixture.

3. The golf ball of claim 2, wherein the synthetic flocks are selected from the group consisting of nylon flocks, polyester flocks, or a combinations thereof.

4. The golf ball of claim 1, wherein the first thermoset rubber composition comprises polybutadiene.

5. The golf ball of claim 4, wherein the first thermoset rubber composition comprises a blend of the polybutadiene and at least one of polyoctenemer, natural rubber, ethylene propylene diene monomer (EPDM), cis-polyisoprene, trans-polyisioprene, and styrene-butadiene rubber (SBR).

6. The golf ball of claim 1, wherein the first thermoset rubber composition is formed from at least one rubber and at least one of zinc oxide, reactive coagent(s), peroxide(s), soft and fast agent(s), fatty acid(s)/fatty acid salt(s), inorganic filler(s), antioxidant(s), and antiozonants.

7. The golf ball of claim 1, wherein the outer core layer surrounds and is adjacent to the inner core layer.

8. The golf ball of claim 1, wherein the outer core layer has a compression of greater than 72.

9. The golf ball of claim 1, wherein the outer core layer has a compression of 75 or greater.

10. The golf ball of claim 8, wherein the outer surface hardness is greater than 82 Shore C.

11. The golf ball of claim 1, wherein the outer surface hardness is greater than 85 Shore C.

12. The golf ball of claim 1, wherein the outer surface hardness is about 90 Shore C or greater and is greater than the center hardness by greater than 30 Shore C.

13. The golf ball of claim 8, wherein the inner core layer consists of a thermoset composition.

14. The golf ball of claim 13, wherein the thermoset composition is different than the first thermoset rubber composition.

15. The golf ball of claim 8, wherein the inner core layer consists of a thermoplastic composition.

16. The golf ball of claim 15, wherein the thermoplastic composition comprises an ionomer.

17. The golf ball of claim 15, wherein the thermoplastic composition comprises a polyether-ester, a polyester-amide, or blends thereof.

18. The golf ball of claim 1, wherein an intermediate core layer is disposed between the inner core layer and the outer core layer.

19. The golf ball of claim 18, wherein the intermediate core layer comprises a thermoplastic composition.

20. The golf ball of claim 1, wherein the cover comprises an inner cover layer disposed about the outer core layer and comprising an ionomeric material and having a first hardness; and an outer cover layer disposed about the inner cover layer and comprising a polyurea or a polyurethane and having a second hardness less than the first.

21. The golf ball of claim 1, wherein each of the plurality of synthetic flocks has a length in the range of about 0.004 inches to about 0.2 inches.

22. The golf ball of claim 1, wherein each of the plurality of synthetic flocks has a length in the range of about 0.02 inches to about 0.08 inches.

23. The golf ball of claim 1, wherein each of the plurality of synthetic flocks has a length in the range of about 0.02 inches to about 0.04 inches.

24. A golf ball comprising:

a core comprising at least one layer that consists of a mixture of a plurality of synthetic flocks and a thermoset rubber composition;

wherein the at least one layer comprises an outer surface having an outer surface hardness of about 80 Shore C or greater; and

a cover disposed about the core.

25. The golf ball of claim 24, wherein the synthetic flocks are selected from the group consisting of nylon flocks, polyester flocks, or combinations thereof.

26. The golf ball of claim 24, wherein the at least one layer has a compression of greater than 72.

27. The golf ball of claim 24, wherein the at least one layer has a compression of at least 75.

28. The golf ball of claim 24, wherein each of the plurality of synthetic flocks has a length in the range of about 0.004 inches to about 0.2 inches.

29. The golf ball of claim 24, wherein each of the plurality of synthetic flocks has a length in the range of about 0.02 inches to about 0.08 inches.

30. The golf ball of claim 24, wherein each of the plurality of synthetic flocks has a length in the range of about 0.02 inches to about 0.04 inches.

31. The golf ball of claim 26, wherein the outer surface hardness is greater than 82 Shore C.

32. The golf ball of claim 24, wherein the outer surface hardness is greater than 85 Shore C.