JPH0748477A - Core composition for two piece golf ball - Google Patents

Abstract

PURPOSE:To obtain the composition having proper compression and soft driving feeling and excellent in resilience and durability by blending a rubber composition consisting of a base material rubber, an unsaturated carboxylic acid salt, etc. CONSTITUTION:This composition is obtained by further blending a rubber composition obtained by blending (A) 100 pts.wt. of a substrate rubber containing a butadiene having <=40% cis 1,4-structure with (B) 9-18 pts.wt. (5-10 pts.wt. as unsaturated carboxylic acid) of an unsaturated carboxylic acid metal salt, (C) 5-30 pts.wt. of urethaneacrylate and (D) 0.5-3 pts.wt. of an organic peroxide (e.g. dicumyl peroxide) with (E) an ultrafine fiber or fine particles (e.g. nylon fiber) having amide group. The blend ratio of the component E is preferably 1-8 pts.wt. based on 100 pts.wt. of the component A. Furthermore, as the component B, e.g. zinc acrylate is exemplified.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention has an appropriate compression (hardness), a soft feel at impact, a good impact resilience (flying distance), and excellent durability (breaking strength). The present invention relates to a core composition for a two-piece golf ball.

[0002]

2. Description of the Related Art Golf balls generally used include a wound golf ball and a two-piece golf ball. A two-piece golf ball is constructed by covering a core made of a rubber composition with a cover material such as an ionic ethylene copolymer resin having excellent impact resistance and impact resilience. Two-piece golf balls are used by many golfers because of their great flight distance and excellent durability. However, because the feel when hit is hard,
Many golfers prefer the soft feel of a wound golf ball, and the development of a two-piece golf ball having a soft feel has been desired.

Conventionally, in order to soften a two-piece golf ball to give a soft feel at impact, the core has been softened. However, when a soft core is used as the core, there is a problem that durability of the ball deteriorates because the ball is largely deformed when hit.

[0004]

DISCLOSURE OF THE INVENTION The present invention has a proper compression (less than 130 kgf) and a soft shot feeling close to that of a thread-wound golf ball, and has good impact resilience and durability. An object is to provide an excellent two-piece golf ball core composition.

[0005]

The core composition for a two-piece golf ball according to the present invention comprises a base rubber containing a butadiene rubber having a cis 1,4-structure of 40% or more, fine fibers or fine particles having an amide group, It is characterized by comprising a metal salt of a saturated carboxylic acid, a urethane acrylate, and an organic peroxide.

As described above, in the present invention, since the fine fibers or fine particles having an amide group are used, the reinforcing effect is enhanced, and it becomes possible to improve the durability while maintaining a good impact resilience, and an appropriate hardness ( Provided is a core composition for a two-piece golf ball, which has a soft feel at impact. Hereinafter, the configuration of the present invention will be described in detail.

(1) Base Rubber The base rubber used in the present invention contains a butadiene rubber having a cis-1,4 structure of at least 40%, preferably 90% or more. If the cis-1,4 structure is less than 40%, a good flight distance cannot be maintained. As the base rubber, the butadiene rubber may be used alone, but if necessary, a rubber component conventionally used as a base rubber for two-piece golf balls, for example, natural rubber, isoprene rubber,
You may mix | blend styrene-butadiene copolymer rubber etc. suitably.

(2) Fine Fiber or Fine Particle Having Amide Group The fine fiber having an amide group is, for example, nylon fiber.
(Fibers such as nylon 6, nylon 610, nylon 12, nylon 611, nylon 612) are fine. Further, the fine particles having an amide group are, for example, fine particles of these nylons. Fine fibers have a diameter of 0.
The size is 3 μm, the length is about 300 μm, and the size of the fine particles is about 4 μm.

That is, nylon and natural rubber are graft-bonded through an alkylphenol-formaldehyde resin as a cross-linking agent. The alkylphenol-formaldehyde resin is a resin crosslinking agent, and examples thereof include a resol-type initial condensate obtained by reacting an alkylphenol such as cresol with formaldehyde or acetaldehyde and a modified product thereof. In particular, as the alkylphenol-formaldehyde resin, one having two or more methylol groups in the molecule is preferably used.

The mixing ratio of such natural rubber and fine fibers or fine particles having an amide group is, for example, fine fiber: natural rubber = 33% by weight: 67% by weight, fine particle: natural rubber = 29% by weight: 71% by weight. %. An example of such a mixture is UBEPOL-HE manufactured by Ube Industries, Ltd. Fine fibers or fine particles having an amide group are difficult to mix with butadiene rubber alone. Therefore, a mixture with natural rubber is used, and in this case, since butadiene rubber and natural rubber are bound via a crosslinking agent (organic peroxide), these fine fibers or fine particles in the rubber composition are This is because the dispersibility is enhanced.

(3) Metal salts of unsaturated carboxylic acids For example, zinc salts of α, β-ethylenically unsaturated carboxylic acids such as methacrylic acid and acrylic acid. For example, zinc acrylate is a compound having the formula:

[0012] Examples of the zinc acrylate include zinc diacrylate sold under the trade name of RT manufactured by Sartoma Company, USA. The unsaturated carboxylic acid and the metal oxide such as zinc white may be used alone to form the metal salt in the rubber composition.

(4) Urethane Acrylate This urethane acrylate is a (meth) acrylate group-containing urethane compound obtained by reacting an isocyanate or an isocyanate prepolymer with a di- or poly (meth) acrylate having a hydroxyl group. In this case, the isocyanate prepolymer is a polyol such as glycol, triol, or tetrol, or has a molecular weight of 20
00 or less polyether diol, polyether triol, polyester diol, polyester triol,
It is a prepolymer having an isocyanate group at the terminal obtained by reacting polycaprolactone ester diol or polycaprolactone triol with di- or triisocyanate.

The isocyanates include, for example, tolylene diisocyanate (2,4-, 2,6-isomer).
80%, 20% included, 65%, 35% included, or 2,
4, 4'-diphenylmethane diisocyanate, toluidine diisocyanate, xylylene diisocyanate, diisocyanates having a saturated hydrocarbon ring obtained by hydrogenating these, isophorone diisocyanate, dimer acid diisocyanate, 1, 6
A polyisocyanate polymer obtained from hexamethylene diisocyanate, lysine diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, polymethylene polyphenylene polyisocyanate and tolylene diisocyanate.

The di- or poly (meth) acrylate having a hydroxyl group is obtained by reacting acrylic acid or methacrylic acid or a derivative thereof with a polyhydric alcohol, or acrylic acid or methacrylic acid or a derivative thereof and an epoxy. For example, those obtained by reaction with a compound having a group. Such di or poly (meta)
Examples of the acrylate include ethylene glycol mono (meth) acrylate, propylene glycol (meth) acrylate, 1,3-propanediol mono (meth) acrylate, 1,4-butanediol mono (meth) acrylate, and 1,6-hexane. Diol mono (meth) acrylate, diethylene glycol mono (meth)
Mono (meth) acrylates of dihydric alcohols such as acrylates, dipropylene glycol mono (meth) acrylates, polyethylene glycol mono (meth) acrylates, polypropylene glycol mono (meth) acrylates; trimethylolethane mono (meth) acrylates, trimethylolpropane Mono (meth) acrylate, trimethylolethane bis (meth) acrylate,
Glycerin mono (meth) acrylate, glycerin bis
Mono (meth) acrylates of trihydric alcohols such as (meth) acrylates; and bis (meth) acrylates,
4 such as pentaerythritol bis (meth) acrylate and pentaerythritol tris (meth) acrylate
Examples thereof include bis or tris (meth) acrylates of polyhydric alcohols having a valence of 3 or more. Furthermore, a reaction product of glycidyl (meth) acrylate and an aromatic carboxylic acid, or
A reaction product of (meth) acrylic acid and phenyl glycidyl ether (or phenyl glycidyl ether) can be mentioned. Other reaction products of (meth) acrylic acid and glycidyl compound in a molar ratio of 1: 1 may be used. Specifically, these reaction products can be represented by the following formula.

[0016] In the above formula, R ₁ represents H or CH ₃ , and R ₂ represents an alkyl group, an aryl group, an allyl group, a (meth) acryloyl group or a derivative thereof. The above-mentioned di- or poly (meth) acrylate having a hydroxyl group easily reacts with isocyanates to form urethane acrylate. This reaction is represented by the following formula.

[0017] In the above formula, R ₃ is an alkyl group in isocyanates,
An allyl group and other substituents are shown. Furthermore, a urethane acrylate obtained by reacting a glycol or a polyol with a diisocyanate to form an adduct having an isocyanate group and reacting this with a di- or poly (meth) acrylate having a hydroxyl group described above is used as the urethane in the present invention. It can be used as an acrylate.
This urethane acrylate is represented by the following formula.

[0018] Furthermore, an isocyanate group-terminated prepolymer obtained by reacting a polyol having a molecular weight of 2000 or less with a diisocyanate, and a urethane acrylate obtained by reacting the above-mentioned di- or poly (meth) acrylate having a hydroxyl group are also included in the present invention. Can be used as the urethane acrylate in. Here, the reason why the molecular weight is 2000 or less is that when the molecular weight exceeds 2000, the crosslinking density becomes low and the hardness (or improvement in compression) aimed at by the present invention cannot be expected, which is not preferable. As the polyol having a molecular weight of 2000 or less used here, polytetramethylene ether glycol, polyoxypropylene glycol, pooxyethylene propylene glycol, polyethylene adipate glycol, polybutylene adipate glycol, polyethylene propylene adipate glycol, polyethylene terephthalate glycol,
Examples thereof include polybutylene terephthalate glycol, polycaprolactone glycol, and copolymers thereof.

(5) Organic peroxide For example, it is an alkyl peroxide such as dicumyl peroxide and is not particularly limited. This organic peroxide acts as a polymerization initiator or a crosslinking agent. In the present invention, sulfur is not used as a cross-linking agent in place of the organic peroxide because the impact resilience decreases when sulfur is used.

(6) In the present invention, a rubber composition comprising the above base rubber, fine fibers or fine particles having an amide group, a metal salt of an unsaturated carboxylic acid, urethane acrylate, zinc oxide, and an organic peroxide. To form the core. In this case, the compounding ratio is 1 to 8 parts by weight of fine fibers or fine particles having an amide group with respect to 100 parts by weight of the base rubber. If it is less than 1 part by weight, there is almost no effect, and if it exceeds 8 parts by weight, the durability is improved but the impact resilience is lowered. In addition, the Mooney viscosity becomes too high, resulting in poor processability and causing problems during production.

The amount of the unsaturated carboxylic acid metal salt compounded is 5 to 10 parts by weight as the amount of unsaturated carboxylic acid. If it is less than 5 parts by weight, there is no effect, and if it exceeds 10 parts by weight, the compression becomes high and it becomes too hard. This is because the impact resilience is significantly reduced accordingly. The compounding amount of urethane acrylate is 5 to 30 parts by weight. If it is less than 5 parts by weight, there is no effect and workability is poor. This is because if it exceeds 30 parts by weight, the compression will be too high and it will be too hard.

The compounding amount of the organic peroxide is 0.5 to 3 parts by weight. This is because if it is less than 0.5 parts by weight, no effect is obtained, and if it exceeds 3 parts by weight, the compression is excessively increased and becomes too hard. The compounding amount of zinc oxide is 5 to 50 parts by weight. Within this range, the weight of the obtained golf ball may be adjusted so as to be the specified weight.

In addition to these, silicon dioxide and a bismaleimide compound may be blended as necessary for adjusting the compression. Preferably, the base rubber 100
The amount of silicon dioxide is preferably 10 to 30 parts by weight and the bismaleimide is 0 to 20 parts by weight with respect to parts by weight. This is because if the compounding amount of silicon dioxide is less than 10 parts by weight, there is almost no effect, and if it exceeds 30 parts by weight, the compression becomes high and it becomes too hard. Also, the impact resilience is reduced, and good performance cannot be obtained. Furthermore, the purity of silicon dioxide is 99% or more, and if it is less than 99%, compression will be insufficient. The specific surface area by the BET method is 160 to 340 m ² / g, and 1
If it is less than 60 or more than 340, the compression is insufficient and becomes unpleasant. For example, Aerosil 200 (trade name), Aerosil
200V (trade name), Aerosil 300 (trade name), Reolosil
QS-102 (trade name) is an example.

This is because if the amount of the bismaleimide compound added exceeds 20 parts by weight, the compression becomes high and the hardness becomes too high. Examples of the bismaleimide compound include N,
N'-ethylene bismaleimide, N, N'-trimethylene bismaleimide, N, N-hexamethylene bismaleimide, N, N'-m-phenylene bismaleimide, N, N'-
4,4'-diphenylmethane bismaleimide, N, N'-
4,4'-diphenyl ether bismaleimide, N, N'-
Examples include 4,4'-diphenyl sulfone bismaleimide.

To form a core from the rubber composition obtained as described above, this rubber composition may be uniformly kneaded by a conventional method, and heat-vulcanized under pressure to integrally mold it.
By covering the core with a cover, a two-piece golf ball having a double structure can be manufactured. Examples of the material of the cover include balata, polyurethane, nylon, and ionomer, but are not particularly limited. Ionomer is usually used in a thickness of about 1.0 to 3.0 mm. The above rubber composition can be used not only for two-piece golf balls but also for cores of one-piece golf balls, three-piece golf balls and the like.

[0026]

EXAMPLE A rubber composition was prepared according to a conventional method according to the compounding contents (parts by weight) shown in Tables 1 and 2. The rubber compositions obtained were each press-molded at 160 ° C. for 20 minutes to give a diameter of 3
A spherical solid core (core) of 8.3 mm was prepared, and this solid core was coated with an ionomer (Sarlin 1707) as a cover.
Two-layer two-piece golf balls (thickness: about 2.5 mm) were manufactured (Examples 1-12, Comparative Examples 1-9).

These two-piece golf balls were evaluated for durability (breaking strength), initial velocity efficiency (rebound resilience), compression, and feel at impact (hit feeling). The results are shown in Tables 1 and 2.

[0028]

[0029] Note) * 1 Polybutadiene rubber (cis 1,4-structure 97%) manufactured by Nippon Synthetic Rubber Co., Ltd. * 2 Ube Industries, Ltd., a fine particle-natural rubber composite material having an amide group. "3" in "3 (1)" in Table 1
Indicates the total amount, and "1" indicates the amount of fine particles.

The same applies hereinafter. * 3 Ube Industries, Ltd., amide group-containing fine fiber
Natural rubber composite material. In “3 (1)” in Table 1
"3" represents the total amount and "1" represents fine fibers. same as below. * 4 Reaction product of isocyanurate of hexamethylene diisocyanate and glycerin di (mono) methacrylate, number of functional groups: 4.

* 5 AEROSIL 2 manufactured by Nippon Aerosil Co., Ltd.
00. * 6 N, N'-4,4'-diphenylmethane bismaleimide manufactured by Mitsui Toatsu Chemicals, Inc. * 7 The force required to break a golf ball when compressed at a compression speed of 10 mm / min. It is represented by an index with Comparative Example 1 as 100. The larger the number, the better.

* 8 The initial velocity ratio of the golf ball to the head speed when hit with a driver using a swing robot at a head speed of 43 m / sec. * 9 1/10 inch golf ball at a compression speed of 10 mm / min
(2.54mm) Force required to deform (kgf). * 10 The force (kgf) required to deform a golf ball by 10 mm at a compression speed of 10 mm / min.

It is close to the amount of deformation at the time of actual impact. * 11 Three types of impact, soft, slightly hard, and hard at the wood club No. 1 by professional golfers. "Soft" corresponds to less than 130kgf compression (A), "slightly hard" corresponds to 130-150kgf compression (A), and "hard" corresponds to more than 150kgf compression (A). As is clear from Tables 1 and 2, the two-piece golf balls (Examples 1 to 12) of the present invention have durability, initial velocity efficiency,
It can be seen that both compression and feeling are good.

[0034]

As described above, according to the present invention, a base rubber containing a butadiene rubber having a cis 1,4-structure of 40% or more, fine fibers or fine particles having an amide group, and a metal of an unsaturated carboxylic acid. Since the core of the two-piece golf ball is formed of the rubber composition including the salt, the urethane acrylate, and the organic peroxide, it is possible to improve the compression, feel at impact, impact resilience, and durability.

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Claims (3)

[Claims] 1. 9 to 18 parts by weight of a metal salt of an unsaturated carboxylic acid (5 to 5 parts as an unsaturated carboxylic acid) based on 100 parts by weight of a base rubber containing a butadiene rubber having a cis 1,4-structure of 40% or more. 10 parts by weight), 5 to 30 parts by weight of urethane acrylate, and 0.5 to 3 parts by weight of organic peroxide, and a fine composition or fine particles having an amide group in a rubber composition, and a core composition for a two-piece golf ball. . 2. The fine fibers or fine particles having an amide group are blended in an amount of 1 to 8 parts by weight with respect to 100 parts by weight of a base rubber containing a butadiene rubber having a cis 1,4-structure of 40% or more. A core composition for a two-piece golf ball as described above. 3. The core composition for a two-piece golf ball according to claim 1, wherein the fine fibers or fine particles are graft-bonded with another rubber component having compatibility with the base rubber during kneading.