Golf ball material, method for producing the same, and golf ball

Abstract

SOLUTION: To provide a golf ball material including, following components (i), (ii): (i) fine particles which are formed of a multidimensional copolymer cross-link object formed of, a conjugate diene unit, non conjugate olefin unit, and an aromatic vinyl unit and whose average particle diameter is less than 300 μm; (ii) a thermoplastic resin, in which the conjugate diene unit has a butadiene unit, the non conjugate olefin unit includes a unit selected from, an ethylene unit, a propylene unit, and 1-butene unit, the aromatic vinyl unit includes a styrene unit, and content of the conjugate diene unit with respect to the multidimensional copolymer is 5 mass% or greater, and to provide a production method thereof and a golf ball using the same material.EFFECT: According to a material for golf ball of the present invention, the material is soft and excellent in rebound resilience and is also excellent in molding processing ability.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a material for a golf ball, a method for manufacturing the same, and a golf ball, and more particularly, to a material for a golf ball suitably used as a material for each layer (intermediate layer or outermost layer) of a cover in a golf ball covered with one or more layers of a cover covering a core, and a golf ball using the same.

Background Art

[0002] In order to realize a golf ball having both a soft feeling and high resilience, a material in which a hydrogenated aromatic vinyl-based elastomer such as styrene-ethylene / butylene-styrene block copolymer (SEBS) is added to an ionomer resin has been proposed. For example, Japanese Patent Application Laid-Open No. 2001-95948 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2001-32763 (Patent Document 2) propose a resin composition in which a thermoplastic elastomer such as SEBS and a tackifier are blended with an ionomer resin.

[0003] However, although adding SEBS to an ionomer resin can impart a soft feeling, if the addition amount of SEBS is large, there is a drawback that the resilience is lowered.

[0004] In addition, a material that completely neutralizes the acid in an ionomer resin composition by adding a fatty acid has been proposed as a material for a golf ball. For example, Japanese Patent Application Laid-Open No. 2001-120686 (Patent Document 3) and Japanese Patent Application Laid-Open No. 2001-348467 (Patent Document 4) propose a highly neutralized ionomer resin material in which a fatty acid and a basic inorganic metal compound are blended with an ionomer resin composition.

[0005] However, although the above highly neutralized ionomer resin material exhibits high resilience, it cannot be said that softening is sufficient.

Prior Art Documents

Patent Documents

[0006] Patent Document 1 Japanese Patent Application Laid-Open No. 2001-95948 Patent Document 2 Japanese Patent Application Laid-Open No. 2001-32763 Patent Document 3 Japanese Patent Application Laid-Open No. 2001-120686 Patent Document 4 Japanese Patent Application Laid-Open No. 2001-348467 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] The present invention has been made in view of the above circumstances, and an object thereof is to provide a golf ball material excellent in soft and resilient elasticity, a method for producing the same, and a golf ball. MEANS FOR SOLVING THE PROBLEMS

[0008] As a result of intensive studies to achieve the above object, the present inventors have found that, as a golf ball material, fine particles having an average particle diameter of less than 300 μm and composed of a crosslinked product of a multi-component copolymer having a conjugated diene unit, a non-conjugated olefin unit, and an aromatic vinyl unit are mixed with a thermoplastic resin such as an acid-containing copolymer, whereby even if the hardness is low, the resilient elasticity can be unexpectedly maintained high and the processability is good. Furthermore, when a golf ball is constituted using this material as a cover, a golf ball can be provided that sufficiently imparts a soft feeling and has excellent resilient elasticity and high flight performance. The present invention has been completed based on this finding.

[0009] Therefore, the present invention provides the following golf ball materials, a method for producing the same, and a golf ball. 1. The following component (i) and component (ii) (i) Fine particles having an average particle diameter of less than 300 μm and composed of a crosslinked product of a multi-component copolymer having a conjugated diene unit, a non-conjugated olefin unit, and an aromatic vinyl unit, and (ii) Acid-containing copolymer comprising, wherein the conjugated diene unit contains a butadiene unit, the non-conjugated olefin unit contains a unit selected from the group consisting of an ethylene unit, a propylene unit, and a 1-butene unit, the aromatic vinyl unit contains a styrene unit, and the content of the conjugated diene unit in the above-mentioned multi-block copolymer is 5% by mass or more and and the content of the component (ii) is 50 to 80% by mass based on the total amount of the component (i) and the component (ii), and it is used as a cover material for a golf ball A material for a golf ball, characterized by the above. 2 . The content of the conjugated diene unit in the multi-block copolymer as the component (i) is 10% by mass or more, and the content of the non-conjugated olefin unit is 85 % by mass or less, and the content of the aromatic vinyl unit is 30% by mass or less. The material for a golf ball according to Item 1 above. 3 . The non-conjugated olefin unit is an ethylene unit in the above 1 or 2 The material for a golf ball according to the description. 4 . The multi-block copolymer as the component (i) is a copolymer polymerized by a gadolinium metallocene complex catalyst. The material for a golf ball according to any one of Items 1 to 3 above. 5 . The material hardness is 25 to 65 in Shore D hardness. The material for a golf ball according to any one of Items 1 to 4 above. 6. The golf ball material according to claim 2, wherein the content of the conjugated diene unit is 10 to 50% by mass, the content of the non-conjugated olefin unit is 40 to 80% by mass, and the content of the aromatic vinyl unit is 10 to 20% by mass 7 . (a1) A multi-block copolymer having a conjugated diene unit, a non-conjugated olefin unit, and an aromatic vinyl unit, wherein the conjugated diene unit contains a butadiene unit, the non-conjugated olefin unit contains a unit selected from the group consisting of an ethylene unit, a propylene unit, and a 1-butene unit, the aromatic vinyl unit contains a styrene unit, and the content of the conjugated diene unit in the multi-block copolymer is 5% by mass or more. Using the multi-block copolymer, adding a crosslinking agent thereto to obtain a crosslinked product of the multi-block copolymer; (a2) A step of pulverizing the crosslinked product of the multi-block copolymer to obtain fine particles having an average particle diameter of less than 300 μm; (a3) The acid-containing copolymer and the fine particles are kneaded, and their mixing ratio is adjusted to 80 to 50:20 to 50 in terms of acid-containing copolymer:fine particles (mass ratio) Step and A method for manufacturing a golf ball material, comprising obtaining the golf ball material according to claim 1 by the steps of (a1) to (a3). 8 . In the copolymer of step (a1), the content of the conjugated diene unit with respect to the copolymer is 10% by mass or more, and the content of the non-conjugated olefin unit is 85 % by mass or less, and the content of the aromatic vinyl unit is 30% by mass or less. The manufacturing method of the golf ball material described above. 7 9 . The manufacturing method of the golf ball material described above, wherein the non-conjugated olefin unit is an ethylene unit. 7 or 8 10. The method for producing the golf ball material according to the above 8, wherein the content of the conjugated diene unit is 10 to 50% by mass, the content of the non-conjugated olefin unit is 40 to 80% by mass, and the content of the aromatic vinyl unit is 10 to 20% by mass 11. A golf ball having a core composed of one layer or a plurality of layers and a cover composed of one layer or a plurality of layers covering the core, wherein at least one layer of the cover is formed of the golf ball material according to any one of 1 to 6 .

Advantages of the Invention

[0010] The golf ball material of the present invention is soft and excellent in resilience, and moreover, it is excellent in kneading processability. A golf ball using the golf ball material of the present invention for the cover is advantageous in competition for golfers.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Best Mode for Carrying Out the Invention

[0012] Hereinafter, the present invention will be described in more detail. The material for a golf ball of the present invention is characterized by containing the following components (i) and (ii). (i) Fine particles having an average particle diameter of less than 300 μm, which are cross-linked products of a multi-block copolymer having a conjugated diene unit, a non-conjugated olefin unit, and an aromatic vinyl unit, and (ii) A thermoplastic resin

[0013] The multi-block copolymer in the component (i) has a conjugated diene unit, a non-conjugated olefin unit, and an aromatic vinyl unit. This multi-block copolymer is the multi-block copolymer described in Japanese Patent No. 6780827 and is described as follows.

[0014] <Conjugated Diene Unit> The multi-block copolymer contains a conjugated diene unit. The conjugated diene unit is a constitutional unit derived from a conjugated diene compound as a monomer. Since the multi-block copolymer can be polymerized using a conjugated diene compound as a monomer, it has excellent cross-linking properties compared to a copolymer polymerized using a non-conjugated diene compound such as known EPDM. The conjugated diene compound includes a butadiene unit. The butadiene unit is a constitutional unit derived from a butadiene compound. Specific examples of the butadiene compound include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, and the like. Further, the conjugated diene unit in the multi-block copolymer preferably contains a 1,3-butadiene unit, and more preferably consists only of a 1,3-butadiene unit.

[0015] Furthermore, the multi-block copolymer preferably has a cis-1,4 bond content of 50% or more, more preferably 70% or more, still more preferably 80% or more, and particularly preferably 90% or more in the total conjugated diene units. Such a multi-block copolymer with a high cis-1,4 bond content in the total conjugated diene units can be obtained by using a conjugated diene compound, a non-conjugated olefin compound, and an aromatic vinyl compound as monomers. On the other hand, the vinyl bond (such as 1,2-vinyl bond, 3,4-vinyl bond, etc.) content in the total conjugated diene units is preferably 30% or less, more preferably 15% or less, still more preferably 10% or less, and particularly preferably 6% or less. Also, the trans-1,4 bond content in the total conjugated diene units is preferably 30% or less, more preferably 15% or less, still more preferably 10% or less. The content of each of the cis-1,4 bond, trans-1,4 bond, and vinyl bond can be determined by the integral ratio from the measurement results of 1H-NMR and 13C-NMR.

[0016] The conjugated diene compound may be used alone or in combination of two or more. That is, the multi-block copolymer may contain one kind of conjugated diene unit alone or two or more kinds. The content of the conjugated diene unit is required to be 5% by mass or more, preferably 10% by mass or more, and more preferably 15% by mass or more of the total multi-block copolymer. Also, the content of the conjugated diene unit is preferably 80% by mass or less, more preferably 60% by mass or less, and still more preferably 50% by mass or less of the total multi-block copolymer.

[0017] <Non-conjugated olefin unit> The multi-block copolymer contains non-conjugated olefin units. The non-conjugated olefin units are structural units derived from a non-conjugated olefin compound as a monomer. Examples of the non-conjugated olefin compound include those selected from the group consisting of ethylene, propylene, and 1-butene. In particular, in order to sufficiently impart the resilience and softness to the golf ball material, the non-conjugated olefin unit is preferably an ethylene unit.

[0018] The non-conjugated olefin compound may be used alone or in combination of two or more. That is, the above-mentioned multi-block copolymer may contain one type of non-conjugated olefin unit alone or two or more types. The content of the non-conjugated olefin unit is preferably more than 20% by mass and less than 90% by mass of the whole multi-block copolymer, more preferably 30 to 85% by mass, still more preferably 40 to 80% by mass, and most preferably 45 to 75% by mass.

[0019] <Aromatic vinyl unit> The above-mentioned multi-block copolymer contains an aromatic vinyl unit. The aromatic vinyl unit is a structural unit derived from an aromatic vinyl compound as a monomer. Examples of the aromatic vinyl compound include styrene compounds, specifically, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o,p-dimethylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene and the like. The aromatic vinyl unit in the above-mentioned multi-block copolymer includes a styrene unit, and it is more preferably composed of only styrene units. Note that the aromatic ring in the aromatic vinyl unit is not included in the main chain of the copolymer unless it is bonded to an adjacent unit.

[0020] The aromatic vinyl compound may be used alone or in combination of two or more. That is, the above-mentioned multi-block copolymer may contain one type of aromatic vinyl unit alone or two or more types. The content of the aromatic vinyl unit is 3 to 30% by mass of the whole multi-block copolymer. If the content of the aromatic vinyl unit is less than 3% by mass or exceeds 30% by mass, the length of the non-conjugated olefin part of the copolymer cannot be suppressed, and the improvement in durability derived from non-conjugated olefin crystals cannot be achieved. The content of the aromatic vinyl unit is preferably 3 to 30% by mass of the whole multi-block copolymer, more preferably 5 to 25% by mass, and still more preferably 10 to 20% by mass.

[0021] As for the number of types of monomers of the above-mentioned multi-component copolymer, there is no particular limitation as long as the multi-component copolymer contains a conjugated diene unit, a non-conjugated olefin unit, and an aromatic vinyl unit. The multi-component copolymer may have other constitutional units other than the conjugated diene unit, the non-conjugated olefin unit, and the aromatic vinyl unit. From the viewpoint of obtaining a desired effect, the content of the other constitutional units is preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less, and particularly preferably not contained, that is, the content is 0% by mass, based on the entire multi-component copolymer.

[0022] The multi-component copolymer is a multi-component copolymer containing at least one type of conjugated diene unit, one type of non-conjugated olefin unit, and one type of aromatic vinyl unit. Further, from the viewpoint of making the fracture characteristics favorable, the multi-component copolymer is preferably a polymer obtained by polymerizing using at least one type of conjugated diene compound, one type of non-conjugated olefin compound, and one type of aromatic vinyl compound as monomers. And it is more preferable that the multi-component copolymer is a terpolymer composed only of one type of conjugated diene unit, one type of non-conjugated olefin unit, and one type of aromatic vinyl unit, and still more preferable that it is a terpolymer composed only of 1,3-butadiene unit, ethylene unit, and styrene unit. Here, it is assumed that the "one type of conjugated diene unit" includes conjugated diene units with different bonding modes.

[0023] The multi-block copolymer contains a conjugated diene unit, a non-conjugated olefin unit, and an aromatic vinyl unit, and one of the major features is that the main chain consists only of an acyclic structure. If the main chain has a cyclic structure, the fracture properties (especially the elongation at break) will decrease. For the confirmation of whether the main chain of the multi-block copolymer has a cyclic structure or not, NMR is used as the main measurement means. Specifically, when the peak derived from the cyclic structure existing in the main chain (for example, the peak appearing at 10 to 24 ppm for three-membered to five-membered rings) is not observed, it indicates that the main chain of the multi-block copolymer consists only of an acyclic structure. Furthermore, the multi-block copolymer can be synthesized in one reaction vessel, that is, one-pot synthesis, as described in its manufacturing method below, and can be manufactured by a simplified process.

[0024] The multi-block copolymer preferably has a polystyrene-reduced weight average molecular weight (Mw) of 10,000 to 10,000,000, more preferably 100,000 to 9,000,000, and even more preferably 150,000 to 8,000,000. When the Mw of the multi-block copolymer is 10,000 or more, the standard strength as a golf ball material can be sufficiently ensured, and when the Mw is 10,000,000 or less, high workability can be maintained. The above-mentioned weight average molecular weight and molecular weight distribution are determined by gel permeation chromatography (GPC) using polystyrene as the standard substance.

[0025] The chain structure of the multi-component copolymer is not particularly limited and can be appropriately selected according to the purpose. For example, when the conjugated diene unit is A, the non-conjugated olefin unit is B, and the aromatic vinyl unit is C, a block copolymer having a structure such as Ax-By-Cz (x, y, and z are integers of 1 or more), a random copolymer having a structure in which A, B, and C are randomly arranged, a tapered copolymer in which the above random copolymer and block copolymer are mixed, and an alternating copolymer having a structure such as (A-B-C)w (w is an integer of 1 or more) can be used. Further, the multi-component copolymer may have a structure in which the conjugated diene unit, the non-conjugated olefin unit, and the aromatic vinyl unit are linearly linked (linear structure), or a structure in which at least one of the conjugated diene unit, the non-conjugated olefin unit, and the aromatic vinyl unit forms a branched chain and is linked (branched structure). When the multi-component copolymer has a branched structure, the branched chain can also be binary or multi-component (that is, the branched chain can contain at least two of the conjugated diene unit, the non-conjugated olefin unit, and the aromatic vinyl unit). Therefore, among multi-component copolymers, a multi-component copolymer having a branched structure with a binary or multi-component branched chain can be clearly distinguished from a conventional graft copolymer in which the main chain and the side chain are formed of different types of units.

[0026] Regarding the production method, polymerization process, and production conditions such as the polymerization catalyst used for the multi-component copolymer, the content described in the specification of Japanese Patent No. 6780827 can be adopted. The above multi-component copolymer is preferably polymerized by a gadolinium metallocene complex catalyst.

[0027] For the component (i) of the present invention, the above-described multi-component copolymer is crosslinked by adding a crosslinking agent to obtain a crosslinked product, and then, by performing a pulverization treatment, fine particles having an average particle diameter of less than 300 μm can be obtained.

[0028] As the above crosslinking agent, radical polymerization initiators such as organic peroxides, co-crosslinking agents such as zinc acrylate and zinc methacrylate can be used. The blending amount of these crosslinking agents is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 5 parts by mass, based on 100 parts by mass of the above-mentioned multi-component copolymer.

[0029] As the conditions for obtaining the above crosslinked product, a composition obtained by adding a crosslinking agent to the multi-component copolymer can be obtained, for example, by molding at a heating temperature and heating time of 100 to 200 ° C for 1 to 60 minutes.

[0030] Next, the crosslinked product of the above multi-component copolymer is pulverized to obtain fine particles having an average particle diameter of less than 300 μm. Specific means for obtaining fine particles having a predetermined average particle diameter from the crosslinked product of the multi-component copolymer include, for example, milling machines such as a milling machine, a ball mill pulverizer, a roller mill, a jet mill, a high-speed rotary pulverizer, a container-driven mill, and ultrafine pulverizers such as a medium stirring mill. The object to be pulverized is pulverized by applying forces such as compression, impact, and rotation. By appropriately adjusting these forces, fine particles having an average particle diameter of less than 300 μm can be obtained. In addition to causing the particles of the object to be pulverized to collide with each other, it is also effective to cause the object to be pulverized to collide with the pulverizing medium. Before granulating with a pulverizer, the crosslinked product of the multi-component copolymer may be finely cut and cut.

[0031] As described above, the average particle diameter of the fine particles of the multi-component copolymer crosslinked product is 300 μm, preferably 50 to 250 μm. If this average particle diameter is exceeded, the kneading processability with the thermoplastic resin described later deteriorates, and it may be difficult to finish into a high-quality golf ball. That is, in the present invention, the multi-component copolymer is not simply mixed (kneaded) with the thermoplastic resin described later, but is mixed with the thermoplastic resin in the form of crosslinked fine particles of the multi-component copolymer. For this reason, the kneading processability is improved, the molding processability is improved in the manufacturing method of the golf ball, high-quality material characteristics can be surely obtained, and thus the physical properties of the golf ball are improved.

[0032] Regarding the average particle diameter of the above microparticles, it can be measured using a microscope. For example, using a digital microscope "VHX-2000" manufactured by KEYENCE, the major axis of the particles can be measured and taken as the particle diameter.

[0033] Next, the crosslinked microparticles of the above-described copolymer obtained as described above are mixed with a thermoplastic resin as the component (ii) of the present invention. In this case, as the above thermoplastic resin, a resin material generally used as a material for golf balls can be used. Specifically, resins selected from the group consisting of acid-containing copolymers, polyester resins, thermoplastic polyester elastomers, polyamide resins, thermoplastic polyamide elastomers, polyurethane resins, and unsaturated polyester resins are exemplified.

[0034] The above acid-containing copolymer is a resin in which the acid is selected from carboxylic acids (including anhydrous carboxylic acids and their derivatives), dicarboxylic acids (hereinafter also including their half-ester carboxylic acids), sulfonic acids, and phosphoric acids, and particularly preferably a carboxylic acid. Specific examples of such acid-containing copolymers include olefin-α,β-unsaturated carboxylic acid copolymers or olefin-α,β-unsaturated carboxylic acid-α,β-unsaturated carboxylic acid ester copolymers.

[0035] The olefin of the above copolymer preferably has usually 2 or more and at most 8, particularly at most 6 carbon atoms, and specifically includes ethylene, propylene, butene, pentene, hexene, heptene, octene, etc., and ethylene is particularly preferable. Examples of the unsaturated carboxylic acid of the component (a) include acrylic acid, methacrylic acid, maleic acid, fumaric acid, etc., and acrylic acid and methacrylic acid are particularly preferable. Further, as the unsaturated carboxylic acid ester of the above copolymer, lower alkyl esters of the above unsaturated carboxylic acids are suitable, and specifically include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, etc., and butyl acrylate (n-butyl acrylate, i-butyl acrylate) is particularly preferable.

[0036] The acid-containing copolymer may be neutralized with metal ions, and specifically, it can be obtained by partially neutralizing the acid groups of the above olefin-unsaturated carboxylic acid (-unsaturated carboxylic acid ester) copolymer with metal ions. Examples of the metal ions for neutralizing the acid groups include Na+, K+, Li+, Zn++, Cu++, Mg++, Ca++, Co++, Ni++, Pb++, etc., and particularly, Na+, Li+, Zn++, Mg++, Ca++, etc. are preferably used. Such neutralized products can be obtained by known methods. For example, neutralized products can be obtained by using compounds such as formates, acetates, nitrates, carbonates, bicarbonates, oxides, hydroxides, and alkoxides of the above metal ions with respect to the above copolymer.

[0037] As the acid-containing copolymer, known ones can be used. For example, as commercially available products, as acid copolymers, Nuclel N1560, N1214, N1035, N2060, AN4221C, AN4311, AN4319 (all manufactured by Mitsui Dow Polychemical Co., Ltd.) and the like can be mentioned. Further, as metal ion neutralized products of acid copolymers, for example, Himilan 1554, 1557, 1601, 1605, 1706, AM7311, 1855, 1856, AM7316, AM7318, AM7327 (all manufactured by Mitsui Dow Polychemical Co., Ltd.), Surlyn 7930, 6320, 8660, 8320, 9320, 8120 (manufactured by Dow Company) and the like can be respectively mentioned.

[0038] The mixing ratio of the thermoplastic resin of the above component (ii) and the fine particles of the above component (i) is preferably in the range of (i):(ii) = 20 - 80:80 - 20 by mass ratio. That is, the content of component (ii) is in the range of 20 - 80% by mass with respect to the total amount of component (i) and component (ii).

[0039] In the golf ball material of the present invention, various additives can be blended as necessary. For example, pigments, dispersants, antioxidants, light stabilizers, ultraviolet absorbers, mold release agents and the like can be appropriately blended.

[0040] The golf ball material of the present invention can be obtained, for example, by using various kneaders such as a kneading type twin-screw extruder, Banbury, kneader, and Laboplastomill to mix all of the above-mentioned component (i), component (ii), and various additives as necessary simultaneously or stepwise. Further, as the production extruder, either a single-screw extruder or a twin-screw extruder may be used, and a twin-screw extruder is more preferable.

[0041] The resilience modulus of the golf ball material of the present invention is preferably 45% or more, more preferably 49% or more, as measured according to the JIS-K 6255 standard. If the above-mentioned resilience modulus is too small, a decrease in the initial ball speed during an approach shot can be achieved, but the flight distance during a driver shot is significantly reduced.

[0042] Regarding the material hardness, from the viewpoints of the spin characteristics and soft feeling obtained as a golf ball, the Shore D hardness is preferably 25 or more, more preferably 35 or more, and the upper limit thereof is preferably 75 or less, more preferably 65 or less, and still more preferably 60 or less.

[0043] The golf ball material of the present invention can be used particularly as a cover material (intermediate layer and outermost layer) in a two-piece solid golf ball composed of a core and a cover covering the core, or a multi-piece solid golf ball composed of one or more cores and a multi-layer cover covering the core.

[0044] The description of each component in the golf ball to which the golf ball material of the present invention is applied is as follows.

[0045] The core can be formed using a known rubber material as a base material. As the base rubber, a known base rubber of natural rubber or synthetic rubber can be used. More specifically, it is recommended to mainly use polybutadiene, particularly cis-1,4-polybutadiene having at least 40% or more of a cis structure. Further, in the base rubber, natural rubber, polyisoprene rubber, styrene-butadiene rubber, etc. can be used in combination with the above-mentioned polybutadiene as desired.

[0046] In addition, polybutadiene can be synthesized by a metal catalyst such as a rare earth element-based catalyst of an Nd catalyst, a cobalt catalyst, and a nickel catalyst.

[0047] To the above base rubber, a co-crosslinking agent such as an unsaturated carboxylic acid and its metal salt, an inorganic filler such as zinc oxide, barium sulfate, and calcium carbonate, and an organic peroxide such as dicumyl peroxide and 1,1-bis(t-butylperoxy)cyclohexane can be blended. Further, if necessary, a commercially available anti-aging agent or the like can be appropriately added.

[0048] The diameter of the above core is appropriately selected according to the structure of the ball and is not particularly limited. Preferably, it is 20 mm or more, more preferably 25 mm or more, still more preferably 30 mm or more. As the upper limit value, preferably it is 41 mm or less, more preferably 40 mm or less.

[0049] An intermediate layer can be provided between the above core and the outermost layer of the cover. In this case, the material hardness of the above intermediate layer is not particularly limited, but it can be 50 or more, preferably 55 or more, more preferably 60 or more in Shore D hardness. Also, the upper limit is not particularly limited, but preferably it can be 70 or less, more preferably 65 or less.

[0050] The thickness of the outermost layer of the above cover is not particularly limited, but preferably it is 0.3 mm or more, more preferably 0.4 mm or more, still more preferably 0.5 mm or more. As the upper limit, preferably it is 1.2 mm or less, more preferably 1.0 mm or less, still more preferably 0.8 mm or less.

[0051] Note that one or two or more kinds of a large number of dimples can be formed on the surface of the above cover. Also, various paints can be further applied to the cover surface. As this paint, a two-component curable urethane paint, particularly a non-yellowing urethane paint, is preferably cited because it needs to withstand the severe use conditions of a golf ball.

[0052] To obtain the above cover, for example, a single-layer or multi-layer core prepared in advance according to the type of the ball is arranged in a mold, the above mixture is heated, mixed, and melted, and injection molding is performed to coat the periphery of the core with a desired cover. A method or the like can be adopted. In this case, the production of the cover can be carried out in a state where excellent thermal stability, fluidity, and moldability are ensured. As a result, the finally obtained golf ball has high resilience and good hitting feeling. Also, as a method for forming the cover, in addition to the above, for example, a method of molding a pair of hemispherical half-cups in advance with a cover material, wrapping the core with this half-cup, and performing pressure molding at 120 to 170 °C for 1 to 5 minutes can also be adopted.

Example

[0053] Hereinafter, examples and comparative examples will be shown to specifically describe the present invention, but the present invention is not limited to the following examples.

[0054] [Examples 1 - 8, Comparative Examples 1 - 12] Using a rubber composition mainly composed of polybutadiene common to all the examples and comparative examples shown in Table 1 below, a solid core of each example with a diameter of 38.7 mm is created by vulcanization at 152°C for 19 minutes.

[0055]

Table 1

[0056] Note that the details of the above core material are as follows. · "Polybutadiene" manufactured by JSR Corporation, product name "BR51" · "Zinc acrylate" manufactured by Nippon Catalyst Co., Ltd., product name "ZN - DA85S" · "Organic peroxide" dicumyl peroxide, manufactured by NOF Corporation, product name "Perkyl D" · "Antioxidant" manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "No Crack NS - 6" · "Zinc oxide" manufactured by Sakai Chemical Industry Co., Ltd., product name "Three - type zinc oxide" · "Zinc pentachlorothiophenolate" manufactured by Wako Pure Chemical Industries, Ltd. · "Zinc dimethacrylate" manufactured by Wako Pure Chemical Industries, Ltd. · "Water" pure water (manufactured by Shoei Pharmaceutical Co., Ltd.)

[0057] Formation of the cover layer (intermediate layer and outermost layer) Next, the resin composition shown in Table 2 below is coated around the core obtained above by an injection molding method to produce a sphere (intermediate - layer - coated sphere) with an intermediate layer having a thickness of 1.2 mm and a Shore D hardness of "66".

[0058]

Table 2

[0059] The details in the above table are as follows. "AM7318", an ionomer resin manufactured by Mitsui Dow Chemical Co., Ltd. "Himilan 1706", an ionomer resin manufactured by Mitsui Dow Chemical Co., Ltd. "Trimethylolpropane", manufactured by Tokyo Chemical Industry Co., Ltd.

[0060] Next, the resin compositions shown in Tables 3 and 4 below were kneaded in a lab plastomill at 160 °C for 30 minutes, and then coated around the intermediate layer-coated sphere by an injection molding method to produce a sphere (three-piece golf ball) with an outermost layer having a thickness of 0.8 mm. At this time, although not particularly shown, common dimples are formed on the cover surfaces of each example and comparative example.

[0061] The materials in Tables 3 and 4 are as follows. "AM7318", an ionomer resin manufactured by Mitsui Dow Chemical Co., Ltd. "AM7327", an ionomer resin manufactured by Mitsui Dow Chemical Co., Ltd. "Diamide E62", a polyamide 12 elastomer manufactured by Daicel Evonik Co., Ltd. "Multicomponent copolymer A", the following description "Multicomponent copolymer B", the following description "Crosslinked multicomponent copolymer A", the following description "Crosslinked multicomponent copolymer B", the following description

[0062] Multicomponent copolymer A Add 95 g of styrene and 400 mL of toluene to a sufficiently dried 1,000 mL pressure-resistant stainless steel reactor. In a glove box under a nitrogen atmosphere, in a glass container, mono(bis(1,3-tert-butyldimethylsilyl)indenyl)bis(bis(dimethylsilyl)amide)gadolinium complex (1,3-[(t-Bu)Me 2 Si] 2 C 9 H 5 Gd[N(SiHMe 2 )2 2 ) 0.17 mmol, dimethylanilinium tetrakis(pentafluorophenyl)borate [Me 2 NHPhB(C 6 F 5 ) 4 ) 0.187 mmol, and diisobutylaluminum hydride 1.4 mmol are charged, and 40 mL of toluene is added to form a catalyst solution. The catalyst solution is added to the above-mentioned pressure-resistant stainless steel reactor and heated to 70 °C. Next, ethylene is introduced into the pressure-resistant stainless steel reactor at a pressure of 1.5 MPa, and then a toluene solution of 150 mL containing 27 g of 1,3-butadiene is introduced into the pressure-resistant stainless steel reactor over 30 minutes, and copolymerization is carried out at 70 °C for 6 hours. Then, a toluene solution of 150 mL containing 27 g of 1,3-butadiene is introduced into the pressure-resistant stainless steel reactor over 30 minutes, and copolymerization is further carried out at 70 °C for 1 hour. Next, 1 mL of an isopropanol solution containing 5% by mass of 2,2'-methylene-bis(4-ethyl-6-t-butylphenol) (NS-5) is added to the pressure-resistant stainless steel reactor to stop the reaction. Next, a large amount of methanol is used to separate the copolymer, and it is dried in vacuo at 50 °C to obtain copolymer A.

[0063] Multicomponent copolymer B 80 g of styrene and 600 mL of toluene are added to a sufficiently dried 1,000 mL pressure-resistant stainless steel reactor. In a glove box under a nitrogen atmosphere, in a glass container, mono(bis(1,3-tert-butyldimethylsilyl)indenyl)bis(bis(dimethylsilyl)amide) gadolinium complex (1,3-[(t-Bu)Me 2 Si] 2 C 9 H 5 Gd[N(SiHMe 2 ) 2 ) 2 ) 0.25 mmol, dimethylanilinium tetrakis(pentafluorophenyl)borate [Me 2 NHPhB(C 6 F 5 )​4 Charge 0.275 mmol and 1.1 mmol of diisobutylaluminum hydride, and add 40 mL of toluene to make a catalyst solution. Add the catalyst solution to the pressure-resistant stainless steel reactor and heat it to 70 °C. Next, introduce ethylene into the pressure-resistant stainless steel reactor at a pressure of 1.5 MPa, and then introduce 80 mL of a toluene solution containing 20 g of 1,3-butadiene into the pressure-resistant stainless steel reactor over 8 hours, and carry out copolymerization at 70 °C for a total of 8.5 hours. Next, add 1 mL of an isopropanol solution containing 5% by mass of 2,2'-methylene-bis(4-ethyl-6-t-butylphenol) (NS-5) to the pressure-resistant stainless steel reactor to stop the reaction. Next, separate the copolymer using a large amount of methanol and dry it under vacuum at 50 °C to obtain copolymer B.

[0064] For each of the copolymers "multicomponent copolymer A" and "multicomponent copolymer B", measure and evaluate the contents (mass%) of butadiene, ethylene, and styrene by the following method. <Contents of butadiene, ethylene, and styrene> Determine the contents of butadiene, ethylene, and styrene in each copolymer 1 by the H-NMR method. The results are as follows. · "Multicomponent copolymer A" ··· butadiene / ethylene / styrene = 32 / 49 / 19 (mass%) weight average molecular weight (Mw) 375×10 3 · "Multicomponent copolymer B" ··· butadiene / ethylene / styrene = 14 / 70 / 16 (mass%) weight average molecular weight (Mw) 273×10 3

[0065] Powder of crosslinked type · Multicomponent copolymer A To 100 parts by mass of the "multicomponent copolymer A" obtained above, 1.0 part by mass of dicumyl peroxide as an organic peroxide is blended, and the resulting composition is heat-molded into a sheet at 160 °C for 30 minutes. The obtained sheet-shaped crosslinked molded product is ground and pulverized using a milling machine and a ball mill, and powders having an average particle size in the range of 50 to 200 μm are collected. The particle size is measured using a CCD camera with a magnifying lens, and those within the above-specified range are collected. In the table, it is described as "multicomponent A crosslinked powder".

[0066] Powder of crosslinked type · Multicomponent copolymer B To 100 parts by mass of the "multicomponent copolymer B" obtained above, 1.0 part by mass of dicumyl peroxide as an organic peroxide is blended, and the resulting composition is heat-molded into a sheet at 160 °C for 30 minutes. The obtained sheet-shaped crosslinked molded product is ground and pulverized using a milling machine and a ball mill, and powders having an average particle size of 200 μm or less are collected. The particle size is measured using a CCD camera with a magnifying lens, and those within the above-specified range are collected. In the table, it is described as "multicomponent B crosslinked powder".

[0067] The material hardness and rebound resilience of the cover in the above three-piece golf ball are measured as follows, and the results shown in Table 3 and Table 4 below are obtained.

[0068] Hardness of the cover material (Shore D hardness) The resin material of the cover is molded into a sheet with a thickness of 2 mm and left for two weeks or more. Then, the Shore D hardness is measured in accordance with the ASTM D2240-95 standard.

[0069] Rebound resilience The resin material is molded into a sheet with a thickness of 2 mm using a press machine, stacked to a thickness of 4 mm, temperature-controlled to 23 ± 1 °C, and then measured using a tripson-type rebound resilience device based on JIS-K 6255 (2013) (note that the drop angle described in the JIS-K 6255 standard is adjusted to 30 degrees to measure the above-mentioned rebound resilience).

[0070] Processability during kneading The resin components of each example are blended, and the processability during kneading is evaluated according to the following criteria. 〔Evaluation〕 〇 ··· Good kneadability and excellent processability. △ ··· The powder during kneading is slightly difficult to disperse and difficult to process. - ··· Since it is a single substance, kneading is not required.

[0071]

Table 3

[0072]

Table 4

[0073] Figure 1 shows a graph indicating the relationship between the material hardness and the rebound resilience of the golf ball materials in Examples 1 to 3 and Comparative Examples 1 to 3, 6, and 7 in Tables 3 and 4. The difference between these examples and comparative examples lies in whether the multi-component copolymer B is directly blended into the ionomer resin or blended in the form of crosslinked microparticles (powder). As a result, as shown in Figure 1, Examples 1 to 3 have a higher rebound resilience compared to Comparative Examples 6 and 7.

[0074] Figure 2 shows a graph indicating the relationship between the material hardness and the rebound resilience of the golf ball materials in Examples 4 and 5 and Comparative Examples 1, 4, 8, and 9 in Tables 3 and 4. The difference between these examples and comparative examples lies in whether the multi-component copolymer A is directly blended into the ionomer resin or blended in the form of crosslinked microparticles (powder). As a result, as shown in Figure 2, Examples 4 and 5 have a higher rebound resilience compared to Comparative Examples 8 and 9.

[0075] Figure 3 shows a graph showing the relationship between the material hardness and the coefficient of restitution of the golf ball materials in Examples 6 to 8 and Comparative Examples 10 to 12 of Tables 3 and 4. The difference between these Examples and Comparative Examples lies in whether the multi-component copolymer B is directly blended into the polyamide elastomer or blended in the form of crosslinked fine particles (powder). As a result, as shown in Figure 3, Examples 6 to 8 have a higher coefficient of restitution compared to Comparative Examples 10 to 12.

Claims

1. The following component (i) and component (ii): (i) Fine particles having an average particle diameter of less than 300 μm, which are composed of a cross-linked product of a multi-block copolymer having a conjugated diene unit, a non-conjugated olefin unit, and an aromatic vinyl unit, and (ii) An acid-containing copolymer A golf ball material characterized by containing the above, wherein the conjugated diene unit contains a butadiene unit, the non-conjugated olefin unit contains a unit selected from the group consisting of an ethylene unit, a propylene unit, and a 1-butene unit, the aromatic vinyl unit contains a styrene unit, and the content of the conjugated diene unit in the multi-block copolymer is 5% by mass or more, and the content of the component (ii) with respect to the total amount of the component (i) and the component (ii) is 50 to 80% by mass, and it is used as a cover material for a golf ball.

2. The golf ball material according to claim 1, wherein the content of the conjugated diene unit in the multi-block copolymer as the component (i) is 10% by mass or more, the content of the non-conjugated olefin unit is 85% by mass or less, and the content of the aromatic vinyl unit is 30% by mass or less.

3. The golf ball material according to claim 1 or 2, wherein the non-conjugated olefin unit is an ethylene unit.

4. The golf ball material according to any one of claims 1 to 3, wherein the multi-block copolymer as the component (i) is a copolymer polymerized by a gadolinium metallocene complex catalyst.

5. The golf ball material according to any one of claims 1 to 4, wherein the material hardness is 25 to 65 in Shore D hardness.

6. The golf ball material according to claim 2, wherein the content of the conjugated diene unit is 10 to 50% by mass, the content of the non-conjugated olefin unit is 40 to 80% by mass, and the content of the aromatic vinyl unit is 10 to 20% by mass.

7. (a1) A step of using a multi-block copolymer having a conjugated diene unit, a non-conjugated olefin unit, and an aromatic vinyl unit, wherein the conjugated diene unit contains a butadiene unit, the non-conjugated olefin unit contains a unit selected from the group consisting of an ethylene unit, a propylene unit, and a 1-butene unit, the aromatic vinyl unit contains a styrene unit, and the content of the conjugated diene unit in the multi-block copolymer is 5% by mass or more, adding a cross-linking agent thereto to obtain a cross-linked product of the multi-block copolymer. Step (a2) of pulverizing the crosslinked product of the above-mentioned copolymer to obtain fine particles having an average particle diameter of less than 300 μm; Step (a3) of kneading the acid-containing copolymer and the above-mentioned fine particles and adjusting the mixing ratio thereof to 80 to 50:20 to 50 in terms of acid-containing copolymer:fine particles (mass ratio); A method for producing a material for a golf ball, comprising the steps (a1) to (a3) and obtaining the material for a golf ball according to claim 1 by the steps (a1) to (a3).

8. In the copolymer of step (a1), the content of the conjugated diene unit with respect to the copolymer is 10% by mass or more, the content of the non-conjugated olefin unit is 85% by mass or less, and the content of the aromatic vinyl unit is 30% by mass or less. The method for producing a material for a golf ball according to claim 7.

9. The method for producing a material for a golf ball according to claim 7 or 8, wherein the non-conjugated olefin unit is an ethylene unit.

10. The method for producing a material for a golf ball according to claim 8, wherein the content of the conjugated diene unit is 10 to 50% by mass, the content of the non-conjugated olefin unit is 40 to 80% by mass, and the content of the aromatic vinyl unit is 10 to 20% by mass.

11. A golf ball having a core composed of one layer or a plurality of layers and a cover composed of one layer or a plurality of layers covering the core, wherein at least one layer of the cover is formed of the material for a golf ball according to any one of claims 1 to 6.

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