JP6119195B2 - Golf ball manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a golf ball having good hitting durability, soft hit feeling, and excellent abrasion resistance of a cover, and a golf ball manufactured using the manufacturing method.

  Conventional golf balls generally have a cover structure in which a material mainly composed of ionomer resin is coated around a core mainly composed of diene rubber by an injection molding method. In recent years, attempts have been made to use a resin material other than an ionomer resin as a cover material in order to improve the feeling at the time of impact and the abrasion resistance at the time of approach shot.

  For example, in Japanese Patent Laid-Open No. 11-104273 (Patent Document 1), in a multi-layered solid golf ball having a solid core and two inner and outer cover layers covering the same, a thermoplastic polyurethane elastomer is used as the main material for the outer layer. A golf ball coated with the cover layer is disclosed. Japanese Patent Laid-Open No. 10-219053 (Patent Document 2) discloses the use of a polyamide elastomer as one component of a golf ball cover material.

  These golf balls have good hitting feeling and high scratch resistance, but have poor adhesion to the diene rubber, which is the main component of the core, compared to ionomer resins, There is a problem that delamination is likely to occur between the surface and the adjacent cover layer.

  In the golf ball industry, it is known to perform plasma treatment or corona discharge treatment as a means of improving adhesion such as painting, but these treatments are used to improve the adhesion between the core surface and the adjacent cover layer. In such a case, the functional groups introduced by these treatments are relatively small functional groups such as hydroxyl groups and carboxyl groups, and these functional groups are introduced to the soft rubber surface. When the cover resin covers the core surface, many of the introduced functional groups move from the core surface to the inside of the core, and the expected adhesive improvement effect cannot be obtained. JP-A-5-317459 (Patent Document 3) discloses that the core surface is treated with an aqueous solution containing active chlorine (chlorine, concentrated hydrochloric acid, hypochlorous acid metal salt, etc.). Is difficult and has an adverse effect on the environment, and is not as effective as the plasma treatment.

  As another method, there is a primer treatment for applying a solution containing a hot-melt resin as a main component to a surface to be bonded, as disclosed in JP-A-11-253581 (Patent Document 4). There is a concern that high-temperature molten resin that flows on the core surface during injection molding will flow while melting the hot-melt resin of the primer component, causing bleeding to the parting line, etc., and adversely affecting durability and appearance quality. The

  On the other hand, when a cover layer is formed by thermocompression molding or cast molding using a thermosetting polyurethane resin, the isocyanate contained as a component of the cover contains unsaturated carboxylic acid and / or a trace amount present on the core surface. By reacting with a functional group containing active hydrogen derived from the metal salt, etc., the adhesion to the core surface is slightly improved, but the reaction takes a long time, and its productivity is far from injection molding. Absent.

  In addition, the applicant disclosed in Japanese Patent Application Laid-Open No. 2009-131431 (Patent Document 5) that the core and the cover are formed by subjecting the core formed of the rubber composition to a surface treatment with a solution using a halogenated isocyanuric acid. Proposes a technique to improve adhesion to the layer. However, since an organic solvent such as acetone is used as a solvent for the treatment liquid, it is necessary to pay attention to the influence on the environment.

  Therefore, there is still room for improvement in terms of achieving high impact durability in response to the demand for golf balls having both good feel and scratch resistance, and also consider the environmental impact. There must be.

Japanese Patent Laid-Open No. 11-104273 Japanese Patent Laid-Open No. 10-219053 JP-A-5-317459 JP 11-253581 A JP 2009-131631 A

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a golf ball having good hitting feeling, scuff resistance, and high hitting durability while reducing the burden on the environment. to.

As a result of intensive studies to achieve the above object, the inventors of the present invention, in a method for producing a multi-layer golf ball having a solid core formed of a rubber composition and one or more layers covering it,
A cover material is prepared by dissolving a halogenated isocyanuric acid and / or a metal salt thereof in water, adjusting the pH of the obtained aqueous solution to a specific range to prepare a treatment liquid, and treating the core surface with the treatment liquid. It has been found that the adhesion between the core surface and the cover is greatly improved by covering the surface with a very high impact durability. Furthermore, the use of water as the solvent for the treatment liquid has realized a reduction in environmental burden. Also, in this case, the use of a cover material mainly composed of urethane resin or polyamide resin for the cover makes it possible to obtain an excellent solid golf ball having a very good feel and scratch resistance as compared with conventional golf balls. Has been found to yield the present invention.

That is, the present invention is to provide a manufacturing how the golf ball follows.
[1] In a method for producing a golf ball having a solid core formed of a rubber composition and one or more covers covering the core,
A core forming process for forming a solid core;
A step of dissolving a halogenated isocyanuric acid and / or a metal salt thereof in water, and adjusting a pH of the obtained aqueous solution to 1 to 3 to prepare a treatment liquid;
A golf ball comprising: a surface treatment step of treating the surface of the obtained core with the treatment liquid prepared in the above step ; and a cover formation step of covering the core surface with a cover material to form a cover. Manufacturing method.
[2] The method for producing a golf ball according to [1], wherein the pH of an aqueous solution in which the halogenated isocyanuric acid and / or metal salt thereof is dissolved in water is adjusted with hydrochloric acid.
[3] The golf ball manufacturing method according to [1] or [2], wherein a polishing step of polishing the core surface is performed before the surface treatment step.
[4] The method for manufacturing a golf ball according to any one of [1] to [3], wherein in the surface treatment step, an aqueous solution in which dichloroisocyanuric acid or sodium dichloroisocyanurate is dissolved in water is used as the treatment liquid.
[5] The method for producing a golf ball according to any one of [1] to [4], wherein the core is formed of a rubber composition mainly composed of a diene rubber.
[6] In the cover forming step, the cover in contact with the core is formed of a material mainly composed of one or more selected from a thermoplastic polyurethane elastomer, a thermosetting polyurethane resin, and a polyamide elastomer [1] to [5 ] The manufacturing method of the golf ball of any one of.
[7] The golf ball manufacturing method according to any one of [1] to [6], wherein the surface treatment step is performed by an immersion method.
[8] The golf ball manufacturing according to any one of [1] to [7], further including a cleaning step of cleaning the surface of the surface-treated core using a cleaning liquid after performing the surface treatment step. Method.
[9] The golf ball manufacturing method according to [8], wherein water is used as a cleaning liquid in the cleaning step.
[10] The golf ball manufacturing method according to [8] or [9], wherein the cleaning step is performed by an immersion method .

According to the golf ball manufacturing method of the present invention, the core surface formed of the rubber composition is prepared using an aqueous solution in which a halogenated isocyanuric acid having a pH adjusted to a specific range and / or a metal salt thereof is dissolved in water. By processing, the adhesion between the core surface and the cover can be greatly improved, and a golf ball having very high hitting durability can be obtained. Furthermore, the use of water as a solvent for the treatment liquid has a very low environmental impact. Also, in this case, the use of a cover material mainly composed of urethane resin or polyamide resin for the cover makes it possible to obtain an excellent solid golf ball having a very good feel and scratch resistance as compared with conventional golf balls. Can be obtained.

Hereinafter, the production method of the present invention will be described in more detail.
The method for producing a golf ball of the present invention can be suitably used for producing a golf ball having a solid core formed of a rubber composition and one or more covers covering the core, A core forming step for forming a solid core, a step of dissolving a halogenated isocyanuric acid and / or a metal salt thereof in water, and adjusting the pH of the obtained aqueous solution to 1 or more and 3 or less to prepare a treatment liquid, and the obtained core Surface treatment step for treating the surface of the core with an aqueous solution in which a halogenated isocyanuric acid and / or metal salt thereof is dissolved in water, a washing step for washing the surface of the surface-treated core, and a cover material on the surface of the washed core A cover covering step for covering the surface.

First, in the core forming step of forming a solid core, the solid core needs to be formed of a rubber composition. About the blending of the rubber composition, it can be set as appropriate according to the required performance of the ball and is not particularly limited, but in the present invention, the following components,
(A) a base rubber containing 60 to 100% by mass of polybutadiene containing 60% or more of cis-1,4-bonds,
(B) an organic peroxide,
(C) an unsaturated carboxylic acid and / or a metal salt thereof,
(E) A rubber composition containing an inorganic filler can be suitably used.
In addition, (D) organic sulfur compound can be mix | blended with the said rubber composition as needed.

  In the base rubber containing 60 to 100% by mass of polybutadiene containing 60% or more of (A) cis-1,4-bond, the content of cis-1,4-bond contained in the polybutadiene is particularly limited. Although not, it is 60% or more, preferably 80% or more, more preferably 90% or more, and most preferably 95% or more. When the content of cis-1,4-bonds contained in the polybutadiene is less than 60%, suitable resilience may not be obtained. The range of the molecular weight distribution Mw / Mn (Mw: weight average molecular weight, Mn: number average molecular weight) is not particularly limited, but can be 1.0 or more, preferably 2.0 or more. The upper limit is not particularly limited, but is preferably 8.0 or less, preferably 7.5 or less, more preferably 4.0 or less, and most preferably 3.4 or less. When Mw / Mn is too small, workability may be reduced, and when Mw / Mn is too large, resilience may be reduced.

  Although the said polybutadiene is not specifically limited, What was synthesize | combined with the rare earth element-type catalyst is used preferably from the point of high resilience. As the rare earth element-based catalyst, known catalysts can be used. For example, a catalyst comprising a combination of a lanthanum series rare earth element compound, an organoaluminum compound, an alumoxane, a halogen-containing compound, and a Lewis base as necessary. Can be mentioned.

  Examples of the lanthanum series rare earth element compounds include metal halides having an atomic number of 57 to 71, carboxylates, alcoholates, thioalcolates, and amides.

Examples of the organoaluminum compound include AlR ¹ R ² R ³ (wherein R ¹ , R ² and R ³ may be the same or different, and each represents a hydrogen atom or a hydrocarbon residue having 1 to 8 carbon atoms. That represents a group) can be used.

  Preferred examples of the alumoxane include compounds having a structure represented by the following formula (I) or the following formula (II). In this case, Fine Chemicals, 23, (9), 5 (1994), J. Am. Am. Chem. Soc. 115, 4971 (1993); Am. Chem. Soc. 117, 6465 (1995).

（式中、Ｒ⁴は炭素数の炭素原子を含む１〜２０の炭化水素基、ｍは２以上の整数である。）

(In the formula, R ⁴ is a hydrocarbon group having 1 to 20 carbon atoms containing carbon atoms, and m is an integer of 2 or more.)

Examples of the halogen-containing compound include AlX _n R _3-n (where X represents a halogen atom, R is a hydrocarbon residue having 1 to 20 carbon atoms, such as an alkyl group, an aryl group, and an aralkyl group. And strontium halides such as Me ₃ SrCl, Me ₂ SrCl ₂ , MeSrHCl ₂ , and MeSrCl ₃ (Me represents a methyl group), wherein n is 1, 1.5, 2 or 3) In addition, metal halides such as silicon tetrachloride, tin tetrachloride, and titanium tetrachloride are used.

  The Lewis base can be used to complex a lanthanum series rare earth element compound, and examples thereof include acetylacetone and ketone alcohol.

  In the present invention, in particular, the use of a neodymium-based catalyst using a neodymium compound as a lanthanum series rare earth element compound is excellent in polybutadiene rubber having a high content of 1,4-cis bonds and a low content of 1,2-vinyl bonds. Since it is obtained by polymerization activity, it is preferable, and specific examples of these rare earth element-based catalysts include those described in JP-A No. 11-35633.

When butadiene is polymerized in the presence of a rare earth element-based catalyst using a lanthanum series rare earth element compound, the cis bond content and the molecular weight distribution Mw / Mn (Mw: weight average molecular weight, Mn: number average molecular weight) are within the above ranges. Therefore, the molar ratio of the butadiene / lanthanum series rare earth element compound is preferably 1,000 to 2,000,000, particularly 5,000 to 1,000,000, and the AlR ¹ R ² R ³ / lanthanum series rare earth element compound is The ratio is preferably 1 to 1000, particularly 3 to 500. Furthermore, the molar ratio of the halogen compound / lanthanum series rare earth element compound is preferably 0.1 to 30, and particularly preferably 0.2 to 15. The Lewis base / lanthanum series rare earth element compound is preferably in a molar ratio of 0 to 30, particularly 1 to 10. In the polymerization, a solvent may be used, or bulk polymerization or gas phase polymerization may be performed without using a solvent. In addition, polymerization temperature is -30-150 degreeC normally, Preferably it is 10-100 degreeC.

The Mooney viscosity (ML _{1 + 4} (100 ° C.)) of the polybutadiene used in the present invention is not particularly limited, but is preferably 20 or more, more preferably 30 or more, and still more preferably 35 or more. it can. The upper limit is not particularly limited, but is preferably 140 or less, more preferably 120 or less, still more preferably 100 or less, and most preferably 80 or less. When the Mooney viscosity is out of the above range, workability may be deteriorated or resilience may be reduced.

The Mooney viscosity referred to in the present invention is an industrial viscosity index (JIS K 6300) measured with a Mooney viscometer, which is a kind of rotational plasticity meter, and has ML _{1 + 4} as a unit symbol. (100 ° C.) is used. M represents Mooney viscosity, L represents a large rotor (L-type), 1 + 4 represents a preheating time of 1 minute, and a rotor rotation time of 4 minutes, and the measurement was performed at 100 ° C.

  The polybutadiene may be obtained by reacting a terminal modifier with the active terminal of the polymer subsequent to the polymerization using the rare earth element-based catalyst.

  Here, a well-known thing can be used for the said terminal modifier, The terminal modifier described in following [1]-[7] can be used.

[1] First, a compound having an alkoxysilyl group is exemplified. As the compound having an alkoxysilyl group, an alkoxysilane compound having at least one epoxy group or isocyanate group in the molecule is preferably used. Specific examples include 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, (3-glycidyloxypropyl) methyldimethoxysilane, (3-glycidyloxypropyl) methyldiethoxysilane, β- (3 , 4-epoxycyclohexyl) trimethoxysilane, β- (3,4-epoxycyclohexyl) triethoxysilane, β- (3,4-epoxycyclohexyl) methyldimethoxysilane, β- (3,4-epoxycyclohexyl) ethyldimethoxy Epoxy group-containing alkoxysilanes such as silane, 3-glycidyloxypropyltrimethoxysilane condensate, (3-glycidyloxypropyl) methyldimethoxysilane condensate; 3-isocyanatopropyltrimethoxysilane, 3 Isocyanatopropyltriethoxysilane, (3-isocyanatopropyl) methyldimethoxysilane, (3-isocyanatopropyl) methyldiethoxysilane, condensate of 3-isocyanatopropyltrimethoxysilane, (3-isocyanatopropyl) methyl Examples include isocyanate group-containing alkoxysilane compounds such as dimethoxysilane condensates.

  In addition, when the compound having an alkoxysilyl group is reacted with the active terminal, a Lewis acid can be added to accelerate the reaction. The Lewis acid acts as a catalyst to promote the coupling reaction, improving the cold flow of the modified polymer and improving the storage stability. Specific examples of the Lewis acid include dialkyl tin dialkyl malate, dialkyl tin dicarboxylate, aluminum trialkoxide and the like.

（式中、Ｚは、酸素原子、チッ素原子又はイオウ原子を示す。）
〔５〕ハロゲン化イソシアノ化合物、
〔６〕Ｒ⁸−（ＣＯＯＨ）_q、Ｒ⁹（ＣＯＸ）_q、Ｒ¹⁰−（ＣＯＯ−Ｒ¹¹）_q、Ｒ¹²−ＯＣＯＯ−Ｒ¹³、Ｒ¹⁴−（ＣＯＯＣＯ−Ｒ¹⁵）_q、又は下記式（ＩＶ）で示されるカルボン酸、酸ハロゲン化物、エステル化合物、炭酸エステル化合物又は酸無水物、

（式中、Ｒ⁸〜Ｒ¹⁶は、同一でも異なっていてもよく、炭素数１〜５０の炭素原子を含む炭化水素基、Ｘはハロゲン原子、ｑは１〜５の整数を示す。）
〔７〕Ｒ¹⁷ _rＭ″（ＯＣＯＲ¹⁸）_4-r、Ｒ¹⁹ _rＭ″（ＯＣＯ−Ｒ²⁰−ＣＯＯＲ²¹）_4-r、又は下記式（Ｖ）で示されるカルボン酸の金属塩

（式中、Ｒ¹⁷〜Ｒ²³は、同一でも異なっていてもよく、炭素数１〜２０の炭素原子を含む炭化水素基、Ｍ″はスズ原子、ケイ素原子又はゲルマニウム原子、ｒは０〜３の整数を示す。）
等を挙げることができる。 [2] _{^{R 5 p M'X 4-p,}} M'X 4, M'X 3, R 5 p M '(- R 6 -COOR 7) 4-p or _{^{R 5 p M' (- R}} 6 - COR ⁷ ) _4-p (wherein R ⁵ and R ⁶ may be the same or different and each represents a hydrocarbon group containing 1 to 20 carbon atoms, R ⁷ is a carbon atom having 1 to 20 carbon atoms) Which may contain a carbonyl group or an ester group in the side chain, M ′ is a tin atom, silicon atom, germanium atom or phosphorus atom, X is a halogen atom, p is an integer of 0 to 3 A halogenated organometallic compound, a halogenated metal compound, or an organometallic compound containing an ester group or a carbonyl group in the molecule,
[3] Heterocumlene containing Y = C = Z bond in the molecule (wherein Y represents a carbon atom, oxygen atom, nitrogen atom or sulfur atom, and Z represents an oxygen atom, nitrogen atom or sulfur atom) Compound,
[4] A hetero three-membered ring compound containing a bond represented by the following formula (III) in the molecule,

(In the formula, Z represents an oxygen atom, a nitrogen atom or a sulfur atom.)
[5] Halogenated isocyano compound,
[6] _{^{R 8 - (COOH) q,}} R 9 (COX) q, R 10 - (COO-R 11) q, R 12 -OCOO-R 13, R 14 - (COOCO-R 15) q, or the following Carboxylic acid, acid halide, ester compound, carbonate compound or acid anhydride represented by the formula (IV)

(In formula, R < ⁸ > -R < ¹⁶ > may be same or different, A hydrocarbon group containing a C1-C50 carbon atom, X is a halogen atom, q shows the integer of 1-5.)
[7] R ¹⁷ _r M ″ (OCOR ¹⁸ ) _4-r , R ¹⁹ _r M ″ (OCO—R ²⁰ —COOR ²¹ ) _4-r , or a metal salt of a carboxylic acid represented by the following formula (V)

(In formula, R < ¹⁷ > -R < ²³ > may be same or different, A hydrocarbon group containing a C1-C20 carbon atom, M "is a tin atom, a silicon atom, or a germanium atom, r is 0-3. Indicates an integer.)
Etc.

Specific examples of the terminal modifier and the method of reacting the above-described examples include, for example, specific examples described in JP-A Nos. 11-35633, 7-268132, 2002-293996, and the like. A method can be mentioned.
Among the above-mentioned catalysts, rare earth element-based catalysts, particularly Nd-based catalysts are preferable.

  The component (A) is a base rubber mainly composed of polybutadiene as described above, and the content of polybutadiene in the main material is 60% by mass or more, preferably 70% by mass or more in the base rubber. More preferably, it is 80 mass% or more. Further, 100% by mass of the base rubber may be the polybutadiene, and the content may be 95% by mass or less, and in some cases 90% by mass or less. If the polybutadiene content is less than 60% by mass, the resilience may be inferior.

  Examples of the rubber component other than polybutadiene contained in the component (A) include styrene butadiene rubber, natural rubber, isoprene rubber, and ethylene propylene diene rubber.

  The content of the rubber component other than the polybutadiene in the base rubber can be the balance of the content of the polybutadiene, and is 40% by mass or less, more preferably 30% by mass or less, and still more preferably 20% by mass or less. is there.

  Next, as (B) the organic peroxide, specifically, dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,5,5-trimethylcyclohexane, α, α′- Bis (t-butylperoxy) diisopropylbenzene and the like can be mentioned. Commercially available products of these organic peroxides can be used. For example, Park Mill D (manufactured by NOF Corporation), Trigonox 29-40 (manufactured by Akzo Nobel), Perhexa 3M (manufactured by NOF Corporation), Luperco 231XL (Atchem Corporation) Manufactured), and the like. These can be used alone or in admixture of two or more.

  The amount of the organic peroxide is not particularly limited, but is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more with respect to 100 parts by mass of the component (A). More preferably, it can be 0.3 parts by mass or more. The upper limit is not particularly limited, but is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and still more preferably 2 parts by mass or less. If the blending amount of the component (B) is too small, the time required for crosslinking becomes long, the productivity is greatly reduced, and the compression may be greatly reduced. If the amount is too large, the resilience and durability may decrease.

  Next, in (C) unsaturated carboxylic acid and / or its metal salt, as unsaturated carboxylic acid, acrylic acid, methacrylic acid, maleic acid, fumaric acid, etc. are mentioned, Acrylic acid and methacrylic acid are especially preferable. Examples of the metal salt of the unsaturated carboxylic acid include a zinc salt and a magnesium salt. Among them, zinc acrylate is preferably used.

  The blending amount of the component (C) is not particularly limited, but is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and further preferably 20 parts by mass with respect to 100 parts by mass of the component (A). Or more. The upper limit is not particularly limited, but is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, still more preferably 45 parts by mass or less, and most preferably 40 parts by mass or less. When the blending amount of the component (C) is out of the above range, the resilience and feel may be reduced (inferior).

  The organic sulfur compound as the component (D) is an optional component for enhancing the resilience of the ball, and examples thereof include thiophenols, thionaphthols, halogenated thiophenols, and metal salts thereof. More specifically, pentachlorothiophenol, pentafluorothiophenol, pentabromothiophenol, parachlorothiophenol or zinc salts thereof, diphenyl polysulfide having 2 to 4 sulfur atoms, dibenzyl polysulfide, dibenzoyl polysulfide, dibenzo Examples include thiazoyl polysulfide, dithiobenzoyl polysulfide, alkylphenyl disulfides, sulfur compounds having a furan ring, sulfur compounds having a thiophene ring. In particular, zinc salts of pentachlorothiophenol and diphenyl disulfide are preferably used. Can do.

  The compounding amount of the component (D) is not particularly limited, but is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and more preferably 100 parts by mass of the component (A). Preferably it is 0.4 mass part or more, Most preferably, it can be 0.5 mass part or more. The upper limit is not particularly limited, but is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and still more preferably 3 parts by mass or less. If the blending amount is too small, the effect of improving the resilience may be lost. If the blending amount is too large, the hardness will be too low and sufficient resilience may not be obtained.

  Examples of the inorganic filler of the component (E) include zinc oxide, barium sulfate, and calcium carbonate. The blending amount is not particularly limited, but is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and further preferably 8 parts by mass or more with respect to 100 parts by mass of the component (A). Can do. The upper limit is not particularly limited, but is preferably 80 parts by mass or less, more preferably 65 parts by mass or less, and still more preferably 50 parts by mass or less. If the amount is too large or too small, the proper weight and suitable resilience may not be obtained.

  Moreover, an anti-aging agent can be further added to the rubber composition comprising the components (A) to (E) as necessary. The addition amount of the anti-aging agent is not particularly limited, but is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and still more preferably with respect to 100 parts by mass of the component (A). It can be 0.2 parts by mass or more. Further, the upper limit is not particularly limited, but preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and still more preferably 1 part by mass or less. A commercial item can be used as said anti-aging agent, for example, Nocrack NS-6, Nocrack NS-30 (made by Ouchi Shinsei Chemical Co., Ltd.), Yoshinox 425 (made by Yoshitomi Pharmaceutical Co., Ltd.), etc. are mentioned.

  When a solid core is formed using the above rubber composition, it can be formed by vulcanization and curing in the same manner as a known golf ball rubber composition. Examples of the vulcanization conditions include a vulcanization temperature of 100 to 200 ° C. and a vulcanization time of 10 to 40 minutes.

  Further, the local hardness of the solid core formed as described above can be adjusted as appropriate, and is not particularly limited. The local hardness distribution is equivalent from the center to the surface of the molded product. Even if it is hardness, there may be a hardness difference between the center and the surface of the molded product.

  The diameter of the solid core obtained in the core forming step is preferably 35 mm or more, more preferably 37 mm or more. The upper limit is not particularly limited, but is preferably 42 mm or less, more preferably 41 mm or less, and still more preferably 40 mm or less. If the diameter of the solid core is too small, the feel and resilience may be deteriorated. On the other hand, if the diameter is too large, the durability to cracking may be deteriorated.

  The amount of bending deformation of the solid core is not particularly limited, but the amount of deformation from when the initial load 98N (10 kgf) is applied to the solid core to when the final load 1275N (130 kgf) is applied is 2 0.0 mm or more, preferably 3.0 mm or more. The upper limit is not particularly limited, but is 5.5 mm or less, preferably 5.0 mm or less. When the amount of flexure deformation is less than 2.0 mm, the feeling of hitting becomes worse, and in particular, when a long shot in which large deformation occurs in a ball such as a driver, the spin increases excessively and does not fly, while when it exceeds 5.5 mm, While the hit feeling becomes dull, the resilience becomes insufficient and does not fly, and the crack durability due to repeated hitting may deteriorate.

  The specific gravity of the solid core is not particularly limited, but is preferably 0.9 or more, more preferably 1.0 or more, and even more preferably 1.1 or more. The upper limit is not particularly limited, but it is recommended that the upper limit is 1.4 or less, preferably 1.3 or less, and more preferably 1.2 or less.

Next, the solid core formed in the core forming step is subjected to a surface treatment using an aqueous solution in which halogenated isocyanuric acid and / or a metal salt thereof is dissolved in water as a treatment liquid. Hereinafter, the surface treatment step using an aqueous solution in which the halogenated isocyanuric acid and / or metal salt thereof is dissolved in water will be described in detail.

  First, the halogenated isocyanuric acid and its metal salt contained in the treatment liquid used in the surface treatment step are compounds represented by the following formula (VI).

（ここで、Ｘは、水素原子、ハロゲン原子又はアルカリ金属原子を表す。Ｘの少なくとも１個はハロゲン原子である。ハロゲン原子としては、Ｆ、Ｃｌ、Ｂｒが好ましく、特にＣｌが好ましい。アルカリ金属原子としては、Ｌｉ、Ｎａ、Ｋが好ましい。）

(Here, X represents a hydrogen atom, a halogen atom or an alkali metal atom. At least one of X is a halogen atom. F, Cl and Br are preferable, and Cl is particularly preferable. Alkali metal. (As atoms, Li, Na, and K are preferable.)

  Specific examples of the halogenated isocyanuric acid and / or its metal salt include chloroisocyanuric acid, sodium chloroisocyanurate, potassium chloroisocyanurate, dichloroisocyanuric acid, sodium dichloroisocyanurate, sodium dichloroisocyanurate dihydrate, dichloroisocyanuric Examples thereof include salts of potassium acid, trichloroisocyanuric acid, isocyanuric tribromide, isocyanuric dibromide, isocyanuric bromide, sodium isocyanurate dibromide, hydrates thereof, difluoroisocyanuric acid and the like. Among these, chloroisocyanuric acid, sodium chloroisocyanurate, potassium chloroisocyanurate, dichloroisocyanuric acid, sodium dichloroisocyanurate, potassium dichloroisocyanurate, and trichloroisocyanuric acid are preferable. This is because they are easily hydrolyzed by moisture to generate an acid and chlorine and serve as an initiator for an addition reaction to a double bond in a diene rubber molecule. In the present invention, dichloroisocyanuric acid and sodium dichloroisocyanurate can be particularly preferably used because of its high solubility in water and easy reaction with the core surface.

  In the surface treatment step, an aqueous solution of the above-mentioned halogenated isocyanuric acid and / or a metal salt thereof is used as a treatment liquid. In the present invention, since water is used as the solvent for the treatment liquid, the burden on the environment can be reduced as compared with conventionally used organic solvents such as acetone. Moreover, since water can be easily obtained and is low-cost, it is preferable not only from the environmental aspect but also from the viewpoint of productivity. In addition, many organic solvents such as acetone are designated as hazardous materials, but water is not so easy to handle.

  The content of the halogenated isocyanuric acid and / or the metal salt thereof in the treatment liquid is not particularly limited, but can be preferably 0.5% by mass or more. If the content of halogenated isocyanuric acid and / or metal salt thereof is too low, the effect of improving adhesiveness expected after the core surface treatment cannot be obtained, and the impact durability may be poor. Moreover, although the upper limit is a saturated solution density | concentration, it is 10 mass%. Further, the immersion time of the core in the treatment liquid is not particularly limited, but is preferably 0.3 seconds or more, more preferably 3 seconds or more, and further preferably 10 seconds or more. Also, the upper limit is not particularly limited, but is preferably within 5 minutes, more preferably within 4 minutes. If it is too short, the treatment effect may not be obtained, and if it is too long, the productivity may be impaired.

  In the present invention, it is necessary to adjust the pH of the treatment liquid to 1 or more and less than 5. The upper limit of the pH of the treatment liquid is preferably 4 or less, more preferably 3 or less, and still more preferably 2 or less. If the pH of the treatment liquid is too high, scratch resistance and impact durability may be reduced. Further, the pH of the treatment liquid may be appropriately adjusted using an acid such as hydrochloric acid, nitric acid, sulfuric acid or the like, and hydrochloric acid can be particularly preferably used. The acid content in the treatment liquid is not particularly limited as long as the pH can be adjusted within the above range, but is 0.5% by mass or more, preferably 1% by mass or more, more preferably 3% by mass or more. is there. Moreover, although the upper limit is a saturated solution density | concentration, it is 10 mass%.

  As a method of treating the core surface with the treatment liquid, a method of applying the aqueous solution to the core surface by brushing or spraying, a method of immersing the core in the treatment liquid, or the like can be employed. In the present invention, the dipping method can be suitably employed particularly from the viewpoint of productivity and high permeability of the treatment liquid to the core surface.

  In addition, before the surface treatment is performed on the solid core, the adhesion between the core surface and the adjacent cover material can be further improved by performing a polishing step for polishing the core surface.

  By performing the polishing step, it is possible to remove the skin layer from the core surface after vulcanization, increase the permeability of the treatment liquid to the core surface, and increase the contact area with the adjacent cover material. Specific methods include buffing, barrel polishing, centerless polishing, and the like.

  The solid core subjected to the above-described surface treatment is cleaned to remove excess treatment liquid on the surface. Hereinafter, the cleaning process will be described in detail.

In the cleaning step, water or an aqueous solution in which halogenated isocyanuric acid and / or a metal salt thereof having a lower concentration than the processing solution used in the surface treatment step is dissolved in water can be used as the cleaning solution. Moreover, when using the aqueous solution which dissolved the halogenated isocyanuric acid and / or its metal salt in water as a washing | cleaning liquid, the aqueous solution which dissolved dichloroisocyanuric acid or sodium dichloroisocyanurate in water can be used suitably.

  The content of the halogenated isocyanuric acid and / or the metal salt thereof in the cleaning liquid is not particularly limited as long as the concentration is lower than that of the processing liquid used in the surface treatment step. More specifically, the concentration of the cleaning liquid is preferably less than 0.5% by mass on the assumption that the concentration is lower than that of the treatment liquid. When the content of halogenated isocyanuric acid and / or metal salt thereof is too high, the appearance may be deteriorated.

In the cleaning process, the core surface can be cleaned by running water, spraying, or soaking using a cleaning tank, but it is not only for cleaning, but also for the purpose of starting and promoting a desired treatment reaction. For this reason, a too rapid cleaning method is not suitable. Therefore, in the present invention, pickling soaking with a washing basket is preferably used. In this case, it is preferable to put in water or a washing basket containing a predetermined concentration of washing liquid about 1 to 5 times. Moreover, when using the aqueous solution which melt | dissolved the low concentration halogenated isocyanuric acid and / or its metal salt in water as a washing | cleaning liquid, it is also arbitrary to change the density | concentration of aqueous solution for every step of washing | cleaning. For example, the concentration of the cleaning liquid may be gradually decreased every time the number of cleanings is followed. If the above cleaning treatment is not performed after the surface treatment step, excess halogenated isocyanuric acid and / or metal salt thereof remaining on the core surface partially yellows the ball surface after the cover is formed. There is a case to let you.

  In the present invention, the adhesion with the cover is greatly improved by treating the core surface with a halogenated isocyanuric acid and / or a metal salt thereof. The reason is not clear, but the following can be considered.

  First, the halogenated isocyanuric acid and / or its metal salt penetrates into the diene rubber forming the core together with the solvent, and approaches the double bond of the main chain. Thereafter, water enters the core surface, and the halogenated isocyanuric acid and / or its metal salt is hydrolyzed with water to release halogen. The halogen attacks the double bond of the nearby diene rubber main chain, and the addition reaction proceeds. In the course of the addition reaction, liberated isocyanuric acid is added to the diene rubber main chain together with chlorine while maintaining the ring structure. The added isocyanuric acid has three —NHCO— structures in the molecule.

  Accordingly, the core surface treated with the halogenated isocyanuric acid and / or metal salt thereof is given a structure of -NHCO-, so that the adhesion to the cover material is further improved, so that the hitting durability as a golf ball is improved. It is thought that it is done. Further, when a polyurethane elastomer or a polyamide elastomer having the same —NHCO— structure in the polymer molecule is used as the cover material, it is considered that the impact durability is further increased because the affinity is further increased.

  Further, the material of the surface portion of the solid core after the surface treatment does not show any exothermic or endothermic peak from room temperature to 300 ° C. by differential scanning calorimetry (DSC). This means that the introduced functional group is kept stable in this temperature range. In other words, in the process in which the introduced functional group forms the cover, it does not cause thermal decomposition, etc., and maintains its effectiveness, and does not cause melting like a hot melt resin, and bleeds into the parting line. This means that there is no concern about adverse effects on durability and appearance quality. In addition, as described above, the stability of the material of the surface portion of the solid core after the surface treatment is one of the evidence that isocyanuric acid having a melting point of 300 ° C. or higher was added while maintaining its molecular structure. It can be said that there is.

  Next, a cover is formed by covering the solid core washed in the washing step with a cover material. Hereinafter, the cover forming step will be described in detail.

  In the cover forming step, one or more kinds selected from thermoplastic polyurethane elastomers, thermosetting polyurethane resins, and polyamide elastomers can be used as the main component of the cover material. These resins have the same —NHCO— molecular structure as isocyanuric acid in the resin skeleton, and are firmly adhered to the solid core surface subjected to the above treatment by a strong intermolecular force.

  The polyurethane elastomer is not particularly limited as long as it is a thermoplastic resin or thermosetting resin containing polyurethane as a main component. The polymer polyol compound that constitutes the soft segment, the diisocyanate that constitutes the hard segment, and the monoisocyanate. It is preferable that it is composed of a molecular chain extender.

  First, the thermoplastic polyurethane elastomer will be described. The polymer polyol compound is not particularly limited, and examples thereof include polyester-based polyols and polyether-based polyols. From the viewpoint of rebound resilience or low-temperature characteristics Polyether polyols are preferably used.

  Examples of the polyether polyol include polytetramethylene glycol and polypropylene glycol, and polytetramethylene glycol is particularly preferably used. Further, these number average molecular weights are not particularly limited, but are preferably 1000 or more, more preferably 1500 or more. Also, the upper limit is not particularly limited, but is preferably 5000 or less, more preferably 3000 or less.

  The diisocyanate is not particularly limited. For example, aromatic diisocyanates such as 4,4′-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, and 2,6-toluene diisocyanate, and aliphatics such as hexamethylene diisocyanate. Diisocyanate is mentioned. In the present invention, 4,4'-diphenylmethane diisocyanate is preferably used from the viewpoint of reaction stability with the isocyanate mixture when an isocyanate mixture described later is blended.

  Although it does not restrict | limit especially as a monomolecular chain extender, A normal polyhydric alcohol and amines can be used, for example, 1, 4- butylene glycol, 1, 2- ethylene glycol, 1, 3 -Propylene glycol, 1,3-butanediol, 1,6-hexylene glycol, 2,2-dimethyl-1,3-propanediol, 1,3-butylene glycol, dicyclohexylmethylmethanediamine (hydrogenated MDA), isophorone A diamine (IPDA) etc. are mentioned. These chain extenders preferably have an average molecular weight of 20 to 15000.

  As such a thermoplastic polyurethane elastomer, commercially available products can be used. For example, Pandex T7298, Pandex TR3080, Pandex T8190, Pandex T8195 (manufactured by DIC Bayer Polymer), Resamine 2593, Resamine 2597 (large) Nissei Kagaku Kogyo Co., Ltd.). These may be used individually by 1 type and may use 2 or more types together.

  These thermoplastic polyurethane elastomers include other components as desired, such as pigments, dispersants, antioxidants, ultraviolet absorbers, ultraviolet stabilizers, plasticizers, and inorganic fillers (such as zinc oxide, barium sulfate, and titanium dioxide). Can also be blended.

  The blending amount of the additive is not particularly limited, but is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and still more preferably with respect to 100 parts by mass of the thermoplastic polyurethane elastomer. It can be 1 part by mass or more. The upper limit is not particularly limited, but is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and still more preferably 6 parts by mass or less. If the amount of the additive is too large, the durability may decrease, and if the amount of the additive is too small, the effect of the additive may not be obtained.

  The material hardness (Shore D) of the cover material is not particularly limited, but can be preferably 40 or more. The upper limit is not particularly limited, but is preferably 70 or less, more preferably 60 or less. If the material hardness is too low, the resilience may be poor. On the other hand, if the material hardness is too high, improvement in feel and controllability may not be observed. In the present invention, the material hardness is measured using a type D durometer in accordance with ASTM D2240 by pressing a cover material into a sheet shape having a thickness of 2 mm, and superposing the molded sheets to a thickness of 6 mm or more. Hardness.

  On the other hand, the thermosetting polyurethane resin cover is obtained by covering the core surface with a mixture of the main components of the thermoplastic polyurethane elastomer and reacting and curing on the core surface by heating or the like. The difference from the thermoplastic polyurethane elastomer is that the polymer is polymerized to a molecular weight or higher that does not have a melting point by reaction.

  The thermosetting polyurethane resin may contain other components as desired, such as pigments, dispersants, antioxidants, ultraviolet absorbers, ultraviolet stabilizers, plasticizers, and inorganic fillers (zinc oxide, barium sulfate, titanium dioxide). Etc.), a hardening accelerator, etc. can be mix | blended.

  The blending amount of the additive is not particularly limited, but is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, with respect to 100 parts by mass of the thermosetting polyurethane resin main component. More preferably, it can be 1 mass part or more. The upper limit is not particularly limited, but is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and still more preferably 6 parts by mass or less. If the amount of the additive is too large, the durability may decrease, and if the amount of the additive is too small, the effect of the additive may not be obtained.

  The polyamide elastomer is not particularly limited as long as it is a thermoplastic resin having a polyamide component in its molecule. This polyamide elastomer has a characteristic that the lower its hardness is, the higher its resilience is. Therefore, it is a very suitable material for softening a golf ball cover material and designing a golf ball with high resilience. is there.

  The polyamide elastomer has a polyamide component such as nylon 6, nylon 66, nylon 11, nylon 12 and aromatic polyamide as a hard segment, and a poly segment such as polyoxytetramethylene glycol and polyoxypropylene glycol as a soft segment. A block copolymer having components such as oxyalkylene glycol or aliphatic polyester can be used.

  The material hardness (Shore D) of the cover material is not particularly limited, but is preferably 20 or more, more preferably 40 or more. The upper limit is not particularly limited, but is preferably 70 or less, more preferably 60 or less. If the material hardness is too low, the content of the polyamide component in the hard segment is small, so that the compatibility with the modified core surface is deteriorated, and the interlayer adhesion may be reduced. If the material hardness is too high, good hitting feeling and controllability may not be improved.

  Commercially available products can be used for this polyamide elastomer, for example, PEBAX 2533, PEBAX 3533, PEBAX 4033 from ARKEMA, Daiamid-PAE E40, Daiamid-PAE E47 from Daicel Huls, Grilon, Grillamide from Ems Japan, Examples include Gleasing A manufactured by DIC, Novamid EL manufactured by Mitsubishi Chemical, UBE-PAE manufactured by Ube Industries.

  These polyamide elastomers may contain other components as desired, such as pigments, dispersants, antioxidants, UV absorbers, UV stabilizers, plasticizers, inorganic fillers (such as zinc oxide, barium sulfate, and titanium dioxide). Can be blended.

  The amount of the additive is not particularly limited, but is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and further preferably 1 part by mass with respect to 100 parts by mass of the polyamide elastomer. Or more. The upper limit is not particularly limited, but is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and still more preferably 6 parts by mass or less. If the amount of the additive is too large, the durability may decrease, and if the amount of the additive is too small, the effect of the additive may not be obtained.

  The above-mentioned cover material exhibits very good scratch resistance and realizes a good hit feeling.

  The golf ball obtained by the production method of the present invention is a golf ball in which a cover layer adjacent to the core is formed of the cover material. The golf ball of the present invention may be a two-piece solid golf ball in which a single layer cover is formed with the cover material on the surface of the solid core surface-treated with the treatment liquid, or the core surface with the cover material. After the inner layer cover is formed by coating, a multilayer structure solid golf ball in which one or more outer layer covers are formed on the outside with another cover material, and two or more cover layers are formed on the core surface. Good.

  As other cover materials, materials known as cover materials for golf balls can be used, and are not particularly limited, but specifically, ionomer resins, polyester elastomers, polyurethane used for inner layer covers Examples of the elastomers and polyamide elastomers include polyurethane elastomers and polyamide elastomers, polyolefin elastomers, or mixtures thereof having different physical properties.

  As a method for forming the cover, a known method can be used, and is not particularly limited.For example, a core prepared in advance is disposed in a mold, and the cover material is heated and melted or heated and mixed and melted. An injection molding method or the like can be employed.

  Moreover, you may use the method of forming a pair of hemispherical half cups beforehand with a cover material, wrapping a core with this half cup, and press-molding at 120-170 degreeC for 1 to 5 minutes. When a thermosetting resin is used, a method such as RIM molding or LIM molding can be employed.

  On the other hand, when the cover is formed by an injection molding method, it is preferable to adjust the melt flow rate of the material from the viewpoint of ensuring fluidity suitable for the injection molding method and improving the moldability. . In the present invention, although not particularly limited, the melt flow rate (MFR) when measured under conditions of a test temperature of 190 ° C. and a test load of 21.18 N (2.16 kgf) in accordance with JIS K 6760, It is usually recommended to adjust to 0.5 dg / min or more, preferably 1 dg / min or more, more preferably 1.5 dg / min or more, and even more preferably 2 dg / min or more. Also, the upper limit is not particularly limited, but it is recommended that it is usually adjusted to 20 dg / min or less, preferably 10 dg / min or less, more preferably 5 dg / min or less, and further preferably 3 dg / min or less. If the melt flow rate is too large or too small, the workability may be significantly reduced.

  The thickness of the cover formed by the cover material is not particularly limited, but is preferably 0.5 mm or more, more preferably 1.0 mm or more. The upper limit is not particularly limited, but is preferably 4.0 mm or less, more preferably 2.5 mm or less. If the cover thickness is too large, the resilience may decrease, and if the cover thickness is too small, the durability may decrease.

  In the golf ball obtained by the production method of the present invention, it is preferable to form a large number of dimples on the surface of the cover, and to perform various treatments such as ground treatment, stamping and painting on the cover. When arranging the dimples, it is preferable to arrange the dimples so that there is no single great circular line that does not intersect the dimples. If there is a great circle line that does not intersect the dimples, there may be variations in flight.

  It is preferable that the number of dimples and the total number of dimples are optimized, and the trajectory is more stable due to the synergistic effect of optimization of the number and total number of dimples, and the flight distance performance is excellent. Golf balls can be obtained.

  Here, the number of types of dimples refers to the number of types of dimples having different diameters and / or depths, and it is recommended that the number is preferably 2 or more, more preferably 3 or more. In addition, it is recommended that the upper limit is 8 or less, particularly 6 or less.

  Further, the total number of dimples is not particularly limited, but is preferably 250 or more, more preferably 300 or more. The upper limit is not particularly limited, but it is recommended that the upper limit be 500 or less, preferably 455 or less. Even if the total number of dimples is too small or the total number of dimples is too large, the optimal lift may not be obtained and it may not fly.

  Further, in the present invention, when the above coating is performed, the coating composition disclosed in JP-A-10-234848, that is, a hydroxyl group-containing product obtained by reacting a polyhydric alcohol component and a polybasic acid component. A golf ball coating composition containing polyester and non-yellowing polyisocyanate, wherein at least part of the polyhydric alcohol component has an alicyclic structure in the molecule, or JP-A-2003-253201 A coating composition for golf balls comprising a disclosed coating composition, that is, a polyester and / or polyether-containing acrylic polyol having a hydroxyl value of 30 to 180 mg KOH / g (solid content), and a polyisocyanate. Is composed of a main chain made of an acrylic polymer and a side chain made of polyester and / or polyether. , The molar ratio of isocyanate groups and hydroxyl groups be used [NCO] / [OH] = 0.5~1.5 golf ball coating composition is particularly suitable. The coating composition has excellent cohesive fracture strength, impact resistance to withstand repeated hits by golf clubs, sand wear resistance to withstand bunker shots, excellent grass juice stain resistance, weather resistance and water resistance However, it has been found that it can be satisfactorily adhered to the cover layer in the present invention.

  The multi-layer structure solid golf ball obtained by using the manufacturing method of the present invention can conform to the golf rules for competition and can be formed to have a diameter of 42.67 mm or more. The weight is not particularly limited, but is usually 45.0 g or more, preferably 45.2 g or more. The upper limit is not particularly limited, but is preferably 45.93 g or less.

  The multi-layer structure solid golf ball includes the core and the cover, and preferably includes a large number of dimples on the cover surface. In this case, the amount of deflection of the entire ball is not particularly limited, but is preferably a deformation amount from a state in which an initial load of 98 N (10 kgf) is applied to a ball to a case in which a final load of 1275 N (130 kgf) is applied. Can be made 2.0 mm or more, more preferably 3.0 mm or more. The upper limit is not particularly limited, but is preferably 5.0 mm or less, more preferably 4.5 mm or less. If the amount of deformation is too small, the hit feeling will be worse, and the spin may increase and will not fly especially during long shots where large deformation occurs in the ball of the driver, etc., whereas if it is too large, the hit feeling will be dull. At the same time, the resilience is not sufficient and the air does not fly, and the crack durability due to repeated impacts may be deteriorated.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[Examples 1 to 6, Reference Example 1 , Comparative Examples 1 and 2]
A rubber composition shown in Table 1 below was prepared, and the resulting composition was vulcanized and molded at 155 ° C. for 17 minutes to form a solid core having an outer diameter of 39.3 mm. Next, the surface of the solid core was polished by centerless polishing.

The details of each component in Table 1 are as follows.
BR01: manufactured by JSR, polybutadiene rubber synthesized with Ni catalyst, cis-1,4-bond content 95%, Mooney viscosity (ML _{1 + 4} (100 ° C.)) 45, molecular weight distribution Mw / Mn 4.1
Zinc oxide: manufactured by Sakai Chemical Industry Co., Ltd., trade name "Zinc oxide 3 types"
Barium sulfate: manufactured by Sakai Chemical Industry Co., Ltd., trade name “Precipitated Barium Sulfate # 100”
NOCRACK NS-6: Ouchi Shinsei Chemical Co., Ltd., 2,2′-methylenebis (4-methyl-6-tert-butylphenol)
Zinc acrylate: Nippon Distillation Kogyo Co., Ltd. Pentachlorothiophenol zinc salt: Tokyo Chemical Industry Co., Ltd. Park mill D: NOF Co., Ltd., Dicumyl peroxide Trigonox 29-40: Akzo Nobel Co., Ltd., Dicumyl peroxide

  The solid core obtained above was immersed in a surface treatment tank containing the treatment liquid shown in Table 2 under the conditions shown in Table 4. The pH in Table 2 is a value measured using a pH meter “Navih D-52” manufactured by HORIBA, Ltd.

Details of the components in Table 2 are as follows.
Neochlor 60G: manufactured by Shikoku Kasei Kogyo Co., Ltd., sodium dichloroisocyanurate

  Next, the solid core after the surface treatment was immersed in a cleaning bowl containing water under the conditions shown in Table 4. After immersion for a predetermined time, the solid core was taken out from the washing tank and allowed to dry naturally at room temperature.

  Next, each component shown in Table 3 was mixed with a kneading type twin screw extruder at 200 ° C. to obtain a pellet-shaped cover material. The obtained cover material was injected into a mold in which the solid core obtained above was arranged, and a cover having a thickness of 1.7 mm was formed to produce a two-piece solid golf ball.

The details of each component in Table 3 are as follows.
Pandex T8195: manufactured by DIC Bayer Polymer, thermoplastic polyurethane elastomer titanium oxide: manufactured by Ishihara Sangyo Co., Ltd.

  Table 4 shows various performances of the produced golf balls.

[Evaluation of various physical properties of balls]
Core outer diameter (mm)
Average value obtained by measuring 5 points on the surface.
Cover thickness (mm)
It was calculated as (ball outer diameter−core outer diameter) ÷ 2.
Hardness of cover material Hardness measured by press-molding a cover material into a sheet having a thickness of 2 mm, overlaying the formed sheets on a thickness of 6 mm or more, and using a type D durometer according to ASTM D2240.
Ball outer diameter (mm)
Average value of 5 points measured without dimples.
Scratch resistance (peel test)
A tensile tester composed of a gripper, a drive device, a force meter, and a recording device was used as a test device.
The golf ball was attached to a rotatable fixing jig, and cut into a band shape having a width of 4 ± 0.3 mm. Note that if the measurement site includes a cover layer by injection molding using a hemispherical mold, a cut is made to include at least one injection gate and at least one pole. In this case, the above “pole part” means the north pole or the south pole, assuming that the part where one or more injection gates are surrounded by a great circle is the equator.
A cut was made in the pole and peeled off by about 20 mm so that it could be fixed to the gripping tool of the test apparatus.
A golf ball with a notch is placed on a fixing jig with a bearing, and the end of the strip-shaped test piece is fixed to the gripping tool at the upper opening, and is pulled at a test speed of 50 mm / min in an environment of 23 ± 2 ° C. Test measurement was performed, and an average value of three measurement pieces was obtained.
The results obtained above were evaluated according to the following criteria.
(Double-circle): Even if the average value of the sample exceeded 1.5 kgf, load reduction was not seen by all the balls.
A: The average value of the sample was less than 1.5 kgf, and a decrease in load was observed in 1 to 2 of the 3 balls.
(Triangle | delta): The load fall was seen by all the balls when the average value of the sample was less than 1.5 kgf.
Durability of hitting The durability of the golf ball was evaluated by ADC Ball COR Durability Tester manufactured by Automated Design Corporation. This test machine has a function of causing a golf ball to be blown with air pressure and then continuously colliding with two metal plates installed in parallel. The incident speed on the metal plate was 43 m / s. For each ball, the number of times when the initial speed was 97% or less compared to the average initial speed of 10 times was judged as a decrease in durability. Table 4 shows the average value of three measured samples.
In Table 4, all balls for which no decrease in durability was confirmed even when the number of shots exceeded 1000 were indicated as “1000”.

Claims (10)

In a method for producing a golf ball having a solid core formed of a rubber composition and one or more layers covering the core,
A core forming process for forming a solid core;
A step of dissolving a halogenated isocyanuric acid and / or a metal salt thereof in water, and adjusting a pH of the obtained aqueous solution to 1 to 3 to prepare a treatment liquid;
A golf ball comprising: a surface treatment step of treating the surface of the obtained core with the treatment liquid prepared in the above step ; and a cover formation step of covering the core surface with a cover material to form a cover. Manufacturing method. 2. The method for producing a golf ball according to claim 1, wherein the pH of an aqueous solution in which the halogenated isocyanuric acid and / or a metal salt thereof is dissolved in water is adjusted with hydrochloric acid.   The golf ball manufacturing method according to claim 1, wherein a polishing step of polishing the core surface is performed before the surface treatment step. The method for producing a golf ball according to claim 1, wherein in the surface treatment step, an aqueous solution in which dichloroisocyanuric acid or sodium dichloroisocyanurate is dissolved in water is used as the treatment liquid.   The method for producing a golf ball according to claim 1, wherein the core is formed of a rubber composition containing a diene rubber as a main material.   In the cover forming step, the cover in contact with the core is formed of a material mainly composed of one or more selected from a thermoplastic polyurethane elastomer, a thermosetting polyurethane resin, and a polyamide elastomer. A method for producing a golf ball according to Item.   The golf ball manufacturing method according to claim 1, wherein the surface treatment step is performed by an immersion method.   The golf ball manufacturing method according to any one of claims 1 to 7, further comprising a cleaning step of cleaning the surface of the surface-treated core using a cleaning liquid after performing the surface treatment step.   The golf ball manufacturing method according to claim 8, wherein water is used as a cleaning liquid in the cleaning step.   The golf ball manufacturing method according to claim 8, wherein the cleaning step is performed by an immersion method.