JP6996296B2 - Golf ball - Google Patents

Description

The present invention relates to a golf ball, and more particularly to a technique for improving the impact durability of a golf ball containing an ionomer resin as a resin component of a cover.

Conventionally, it has been known that by using a high hardness ionomer resin for the cover layer (outermost layer cover, inner layer cover), high repulsion and low spin are realized, and as a result, the flight distance such as a driver shot is increased. There is. However, on the other hand, there is also a problem that the shot feeling is deteriorated. On the other hand, attempts have been made to add a soft resin (soft ionomer, soft elastomer, etc.) for the purpose of improving the shot feeling.

For example, Patent Document 1 comprises (a) an α-olefin-unsaturated carboxylic acid copolymer resin, (b) one or more polymer blocks A composed of an aromatic vinyl compound, and a conjugated diene compound. , 70% or more of the carbon-carbon double bond derived from the conjugated diene compound has one or more polymer blocks B hydrogenated, and is composed of a block copolymer having a hydroxyl group at the terminal, and the weights of both. A resin composition for a golf ball cover, characterized in that the ratio is (a) / (b) = 98/2 to 50/50, is described (see Patent Document 1 (claim 1, paragraph 0021)). ..

Further, in Patent Document 2, in a golf ball in which an intermediate layer is interposed between a core and a cover, the intermediate layer comprises at least one polymer block A made of (a) an aromatic vinyl compound and conjugated. It is characterized in that it is a cured product of a thermoplastic resin composition containing (b) a mixture of a block copolymer having at least one polymer block B made of a diene compound or a hydrogenated product thereof and (b) ionomer as a polymer component. A golf ball to be used is described (see Patent Document 2 (claim 1, paragraphs 0032, 0042, 0046)).

Japanese Unexamined Patent Publication No. 10-57527 Japanese Unexamined Patent Publication No. 2000-185114

When a soft resin is blended with a cover material containing an ionomer resin having a high hardness, there is a problem that the impact durability is improved but the resilience is lowered. Therefore, in the conventional technique in the ionomer compounding system, high flight distance and impact durability are contradictory required characteristics.

Here, Patent Documents 1 and 2 describe a technique for blending a soft block copolymer or a hydrogenated additive thereof with an ionomer resin. However, these technologies pursue flexibility, and it is thought that if these technologies are adopted, the resilience of the cover material will decrease, and as a result, the flight distance will decrease.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a golf ball having excellent resilience performance and impact durability.

The golf ball of the present invention that has been able to solve the above problems has a spherical core and at least one layer of a cover that covers the spherical core, and at least one layer of the cover is (A) as a resin component. It is formed from an olefin-based ionomer resin and a cover resin composition containing (B) a block copolymer and / or a hydrogenated product thereof, and the (B) block copolymer and / or a hydrogenated product thereof. Is a copolymer having a block having a structural unit derived from an aromatic vinyl compound and a block having a structural unit derived from a conjugated diene compound and having a hydroxy group at the molecular terminal and / or a hydrogenated product thereof. Yes, the content of the (B) block copolymer and / or its hydrogenated material in the resin component is 0.1 part by mass to 20 parts by mass with respect to 100 parts by mass of the (A) olefin-based ionomer resin. The slab hardness of the cover resin composition is 57 or more in shore D hardness.

The golf ball of the present invention is excellent in resilience performance and impact durability.

A partially cutaway sectional view showing a golf ball according to an embodiment of the present invention. A partially cutaway sectional view showing a golf ball according to another embodiment of the present invention.

The golf ball of the present invention has a spherical core and at least one layer of a cover covering the spherical core. At least one layer of the cover is formed of a cover resin composition containing (A) an olefin-based ionomer resin and (B) a block copolymer and / or a hydrogenated additive thereof as resin components. , The block copolymer and / or its hydrogenated material has a block having a structural unit derived from an aromatic vinyl compound and a block having a structural unit derived from a conjugated diene compound, and has a molecular terminal. A copolymer having a hydroxy group and / or a hydrogenated product thereof, and the content of the (B) block copolymer and / or the hydrogenated product thereof in the resin component is the (A) olefin-based ionomer. It is 0.1 part by mass to 20 parts by mass with respect to 100 parts by mass of the resin, and the slab hardness of the resin composition for covering is 57 or more in shore D hardness.

The resin composition for a cover will be described. The cover resin composition contains (A) an olefin-based ionomer resin, and (B) a block copolymer and / or a hydrogenated product thereof as resin components.

((A) Olefin-based ionomer resin)
The (A) olefin-based ionomer resin is an ionomer resin using a copolymer of an olefin and an unsaturated carboxylic acid as a base polymer, and at least a part of the carboxy groups of the copolymer neutralized with metal ions. The copolymer may contain other monomer components other than the olefin and the unsaturated carboxylic acid. The (A) olefin-based ionomer resin is preferably thermoplastic. The (A) olefin-based ionomer resin may be used alone or in combination of two or more.

The (A) olefin-based ionomer resin is a metal ion-neutralized product of a binary copolymer of (a1) an olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms (hereinafter, “(). It may be referred to as "a1) binary ionomer resin") and / or (a2) an olefin, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an α, β-unsaturated carboxylic acid. A metal ion neutralized product of a ternary copolymer with an acid ester (hereinafter, may be referred to as "(a2) ternomer ionomer resin") is preferable.

As the olefin, an olefin having 2 to 8 carbon atoms is preferable, and examples thereof include ethylene, propylene, butene, pentene, hexene, heptene, and octene, and ethylene is particularly preferable.

Examples of the α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms include acrylic acid, methacrylic acid, fumaric acid, maleic acid, crotonic acid and the like, and acrylic acid or methacrylic acid is particularly preferable.

As the α, β-unsaturated carboxylic acid ester, an alkyl ester having 3 to 8 carbon atoms and an α, β-unsaturated carboxylic acid is preferable, and an alkyl ester of acrylic acid, methacrylic acid, fumaric acid or maleic acid is more preferable. Acrylic acid alkyl esters or methacrylic acid alkyl esters are particularly preferred. Examples of the alkyl group constituting the ester include a methyl group, an ethyl group, a propyl group, an n-butyl group, an isobutyl group and the like.

As the (a1) binary ionomer resin, a metal ion neutralized product of an ethylene- (meth) acrylic acid binary copolymer is preferable. As the (a2) ternary ionomer resin, a metal ion neutralized product of a ternary copolymer of ethylene, (meth) acrylic acid and (meth) acrylic acid ester is preferable. Here, (meth) acrylic acid means acrylic acid and / or methacrylic acid.

The content of the α, β-unsaturated carboxylic acid component having 3 to 8 carbon atoms in the (a1) binary ionomer resin is preferably 15% by mass or more, more preferably 16% by mass or more, and 17% by mass. The above is more preferable, 30% by mass or less is preferable, and 25% by mass or less is more preferable. When the content of the α, β-unsaturated carboxylic acid component having 3 to 8 carbon atoms is 15% by mass or more, the desired hardness of the obtained cover can be easily obtained. Further, when the content of the α, β-unsaturated carboxylic acid component having 3 to 8 carbon atoms is 30% by mass or less, the hardness of the obtained cover does not become too high, and the impact durability and shot feeling are good. become.

The degree of neutralization of the carboxy group of the (a1) binary ionomer resin is preferably 15 mol% or more, preferably 20 mol% or more, and preferably 100 mol% or less. When the degree of neutralization is 15 mol% or more, the resilience and impact durability of the obtained cover are good. The degree of neutralization of the carboxy group of the ionomer resin can be calculated by the following formula. In addition, a metal component may be contained so that the degree of neutralization of the carboxy group in the theoretical ionomer resin exceeds 100 mol%.
Degree of neutralization of ionomer resin (mol%) = 100 × number of moles of neutralized carboxy groups in ionomer resin / total number of moles of carboxy groups in ionomer resin

Examples of the metal ion that neutralizes at least a part of the carboxy group of the (a1) binary ionomer resin include monovalent metal ions such as sodium, potassium, and lithium; and 2 such as magnesium, calcium, zinc, barium, and cadmium. Valuable metal ions; trivalent metal ions such as aluminum; other ions such as tin and zirconium.

The melt flow rate (MFR) (190 ° C., 2.16 kg load) of the (a1) binary ionomer resin is preferably 0.1 g / 10 min or more, more preferably 0.5 g / 10 min or more, still more preferably 1 It is 0.0 g / 10 min or more, particularly preferably 3.0 g / 10 min or more, preferably 30 g / 10 min or less, more preferably 20 g / 10 min or less, still more preferably 15 g / 10 min or less. When the MFR (190 ° C., 2.16 kg load) of the (a1) binary ionomer resin is 0.1 g / 10 min or more, the fluidity of the cover resin composition becomes good, for example, molding of a thin layer. Is possible. Further, when the MFR (190 ° C., 2.16 kg load) of the (a1) binary ionomer resin is 30 g / 10 min or less, the durability of the obtained cover becomes better. MFR is measured according to JIS K7210 using a flow tester.

The slab hardness of the (a1) binary ionomer resin is preferably 40 or more, more preferably 45 or more, still more preferably 50 or more, particularly preferably 55 or more, and preferably 90 or less, more preferably 90 or less, in terms of shore D hardness. Is 80 or less, more preferably 70 or less. When the slab hardness is 40 or more in the shore D hardness, the obtained cover does not become too soft and the resilience becomes good. Further, when the slab hardness is 90 or less in the shore D hardness, the obtained cover does not become too hard and the impact durability becomes better.

The content of the α, β-unsaturated carboxylic acid component having 3 to 8 carbon atoms in the (a2) ternary ionomer resin is preferably 2% by mass or more, more preferably 3% by mass or more, and 30. It is preferably 5% by mass or less, more preferably 25% by mass or less.

The degree of neutralization of the carboxy group of the (a2) ternary ionomer resin is preferably 20 mol% or more, more preferably 30 mol% or more, and preferably 100 mol% or less. When the degree of neutralization is 20 mol% or more, the resilience and durability of the obtained cover are good.

Examples of the metal ion that neutralizes at least a part of the carboxy group of the (a2) ternary ionomer resin include monovalent metal ions such as sodium, potassium, and lithium; and 2 such as magnesium, calcium, zinc, barium, and cadmium. Valuable metal ions; trivalent metal ions such as aluminum; other ions such as tin and zirconium.

The MFR (190 ° C., 2.16 kg load) of the (a2) ternary ionomer resin is preferably 0.1 g / 10 min or more, more preferably 0.3 g / 10 min or more, still more preferably 0.5 g / 10 min or more. It is preferably 20 g / 10 min or less, more preferably 15 g / 10 min or less, and further preferably 10 g / 10 min or less. When the MFR (190 ° C., 2.16 kg load) of the (a3) ternary ionomer resin is 0.1 g / 10 min or more, the fluidity of the cover resin composition is good, and the thin layer can be easily formed. Become. Further, when the MFR (190 ° C., 2.16 kg load) of the (a2) ternary ionomer resin is 20 g / 10 min or less, the impact durability of the obtained cover becomes better.

The slab hardness of the (a2) ternary ionomer resin is preferably 20 or more, more preferably 25 or more, still more preferably 30 or more, preferably 70 or less, more preferably 65 or less, still more preferably 65 or less in terms of shore D hardness. Is 60 or less. When the slab hardness is 20 or more in the shore D hardness, the obtained cover does not become too soft and the resilience becomes good. Further, when the slab hardness is 70 or less in the shore D hardness, the obtained cover does not become too hard and the impact durability becomes better.

As the (a1) binary ionomer resin and (a2) ternary ionomer resin, a pre-neutralized ionomer resin may be used, or an olefin and α, β- having 3 to 8 carbon atoms may be used. A binary copolymer with an unsaturated carboxylic acid and / or a ternomer of an olefin with an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α, β-unsaturated carboxylic acid ester. And a metal compound may be mixed and used. Further, the (a1) binary ionomer resin and the (a2) ternomer ionomer resin may be used alone or in combination of two or more.

As the (A) olefin-based ionomer resin, (a1) a binary ionomer resin is preferable. In particular, it is preferable to use a binary ionomer resin neutralized with a monovalent metal ion and a binary ionomer resin neutralized with a divalent metal ion in combination.

Examples of the (a1) binary ionomer resin include Hymilan (registered trademark) 1555 (Na), 1557 (Zn), 1605 (Na), 1706 (Zn), 1707 (Na), AM7311 (Mg), and AM7329 (Zn). ) (Mitsui, DuPont Polychemical); Sarlin (registered trademark) 8945 (Na), 9945 (Zn), 8140 (Na), 8150 (Na), 9120 (Zn), 9150 (Zn), 6910 (Mg). ), 6120 (Mg), 7930 (Li), 7940 (Li), AD8546 (Li) (manufactured by DuPont); Iotech® 8000 (Na), 8030 (Na), 7010 (Zn), 7030 (Zn). ) (Manufactured by Exxon Mobile Chemical Co., Ltd.).

Examples of the (a2) ternary ionomer resin include Hymilan AM7327 (Zn), 1855 (Zn), 1856 (Na), AM7331 (Na) (manufactured by Mitsui, DuPont, Polychemical); Sarlin 6320 (Mg), 8120. (Na), 8320 (Na), 9320 (Zn), 9320W (Zn), HPF1000 (Mg), HPF2000 (Mg) (manufactured by DuPont); Iotech 7510 (Zn), 7520 (Zn) (manufactured by Exxon Mobile Chemical Co., Ltd.) ) And so on. Na, Zn, Li, Mg and the like described in parentheses after the trade name indicate the metal species of these neutralizing metal ions.

Examples of the binary copolymer include Nuclel (registered trademark) N1050H, N2050H, N1110H, N0200H, N1560, N2060 (manufactured by Mitsui DuPont Polychemical); Primacol (registered trademark) 5980I (manufactured by Dow Chemical). And so on. Examples of the ternary copolymer include Nuclel AN4318, AN4319 (manufactured by Mitsui DuPont Polychemical Co., Ltd.), Primacol AT310, AT320 (manufactured by Dow Chemical Co., Ltd.) and the like.

((B) Block copolymer and / or its hydrogenated agent)
The block copolymer (B) may be divided into a block having a structural unit derived from (b1) an aromatic vinyl compound (hereinafter, may be referred to as "(b1) block") and (b2) a conjugated diene compound. It has a block having a structural unit from which it is derived (hereinafter, may be referred to as "(b1) block"), and has a hydroxy group at the molecular terminal.

The block copolymer constituting the component (B) may be linear (b1-b2 type, b1-b2-b1 type, multi-block type), branched (T-shaped, star-shaped, etc.) or these. Any combination of the above can be mentioned.

Examples of the aromatic vinyl compound constituting the (b1) block include styrene, α-methylstyrene, 4-propylstyrene, 1,3-dimethylstyrene, vinylnaphthalene, vinylanthracene and the like, and styrene and α-methylstyrene. Is preferable. These aromatic vinyl compounds may be used alone or in combination of two or more. In addition, in order to enhance crystallinity, a block of homopolymer is preferable, and polystyrene or poly (α-methylstyrene) is particularly preferable.

(B) The content of the block (b1) in the block copolymer is preferably 5% by mass or more, more preferably 10% by mass or more, preferably 75% by mass or less, and more preferably 65% by mass or less. Is.

Examples of the conjugated diene compound constituting the (b2) block include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene and the like. 1,3-butadiene and isoprene are preferable. These conjugated diene compounds may be used alone or in combination of two or more. When 1,3-butadiene is polymerized, it may be any of 1,4-polymer, 1,2-polymer, or a mixture of 1,4-bond and 1,2-bond. The block (b2) is preferably polybutadiene, or a random copolymer of isoprene and butadiene.

In the hydrogenated product of the (B) block copolymer, at least a part of the carbon-carbon double bond of the (b2) block is hydrogenated. Therefore, the block (b2) after hydrogenation becomes a polyethylene block or an ethylene / propylene random copolymer block.

The block copolymer (B) and / or a hydrogenated product thereof has a hydroxy group at the end of the molecular chain. A block copolymer having a hydroxy group bonded to the end of a molecule is softer than a block copolymer having no hydroxy group bonded, but has high breaking strength, breaking elongation, and high resilience. It has the feature.

The hydroxy group may be introduced into either the (b1) block or the (b2) block, but it is preferably added to the end of the (b1) block, and more preferably to the end of the polystyrene block. preferable. Therefore, preferred (B) block copolymers and / or hydrogen additives thereof include polystyrene-polybutadiene-polystyrene-OH, polystyrene-polyisoprene-polystyrene-OH, polystyrene-butadiene / isoprene random polymer block-polystyrene-OH, And, these hydrogen additives are mentioned, and the most preferable is the polystyrene-butadiene / isoprene random polymer block-polystyrene-OH hydrogen additive and the polystyrene-polyisoprene-polystyrene-OH hydrogen additive.

The content of hydroxy groups in the (B) block copolymer and / or its hydrogenated product is preferably 0.5 or more per molecule of the (B) block copolymer and / or its hydrogenated product, more preferably. The number is preferably 0.6 or more.

The number average molecular weight of the block copolymer (B) and / or its hydrogenated product is not particularly limited, but is preferably 30,000 or more, more preferably 40,000 or more, preferably 1,000,000 or less, and more. It is preferably 300,000 or less.

The slab hardness of the block copolymer (B) and / or its hydrogenated product is the shore A hardness, preferably 5 or more, more preferably 10 or more, still more preferably 15 or more, and particularly preferably 50 or more. It is preferably 97 or less, more preferably 95 or less, and even more preferably 90 or less. (B) The slab hardness of the block copolymer and / or its hydrogenated product should be measured using an automatic hardness tester in a state where a sheet is prepared and the sheets are stacked so as not to be affected by the measuring substrate or the like. Just do it.

The MFR (230 ° C., 2.16 kg) of the (B) block copolymer and / or its hydrogenated product is preferably 0.1 g / 10 min or more, more preferably 0.5 g / 10 min or more, still more preferably 1 It is 9.0 g / 10 min or more, particularly preferably 10.0 g / 10 min or more, preferably 100 g / 10 min or less, more preferably 90 g / 10 min or less, still more preferably 80 g / 10 min or less.

(Resin composition for cover)
The content of the (B) block copolymer and / or its hydrogenated product in the resin component is preferably 0.1 part by mass or more with respect to 100 parts by mass of the (A) olefin ionomer resin. It is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, particularly preferably 1.0 part by mass or more, preferably 20 parts by mass or less, more preferably 15 parts by mass or less, still more preferably 10 parts by mass. It is less than the mass part. When the content of the component (B) is 0.1 part by mass or more, the impact durability of the golf ball is improved, and when it is 20 parts by mass or less, the resin composition is not too soft and the repulsion of the cover is lowered. Can be suppressed.

The cover resin composition may contain a resin component other than the component (A) and the component (B) as the resin component. In this case, the total content of the component (A) and the component (B) in the resin component is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, and particularly preferably 90% by mass. It is mass% or more. It is also preferable that the cover resin composition contains only the component (A) and the component (B) as the resin component.

Examples of the other resin component include thermoplastic resins, and examples thereof include thermoplastic resins such as thermoplastic polyurethane resins, thermoplastic polyamide resins, thermoplastic styrene resins, thermoplastic polyester resins, and thermoplastic acrylic resins. Can be done. Among the thermoplastic resins, a thermoplastic elastomer having rubber elasticity is preferable. Examples of the thermoplastic elastomer include thermoplastic polyurethane elastomers, thermoplastic polyamide elastomers, thermoplastic polyester elastomers, and thermoplastic acrylic elastomers.

Examples of the thermoplastic polyurethane resin and the thermoplastic polyurethane elastomer include the thermoplastic resin having a plurality of urethane bonds in the main chain of the molecule and the thermoplastic elastomer. The polyurethane is preferably obtained by reacting a polyisocyanate component with a polyol component. Examples of the thermoplastic polyurethane elastomer include the trade names "Elastran (registered trademark) XNY85A", "Elastran XNY90A", "Elastran XNY97A", "Elastran ET885", and "Elastran ET885" manufactured by BASF Japan Ltd. Lastran ET890 "and the like.

The thermoplastic polyamide is not particularly limited as long as it is a thermoplastic resin having a plurality of amide bonds (-NH-CO-) in the main chain of the molecule. Examples thereof include products in which an amide bond is formed in the molecule by reacting with an acid component.

Examples of the polyamide resin include aliphatic polyamides such as polyamide 6, polyamide 11, polyamide 12, polyamide 66, polyamide 610, polyamide 6T, polyamide 6I, polyamide 9T, polyamide M5T, and polyamide 612; poly-p-phenylene terephthal. Examples thereof include aromatic polyamides such as amide and poly-m-phenylene isophthalamide. These may be used alone or in combination of two or more. Among these, aliphatic polyamides such as polyamide 6, polyamide 66, polyamide 11, and polyamide 12 are suitable.

Specific examples of the polyamide resin may be described by trade name. For example, "Lilsan (registered trademark) B (for example, Lilsan BESN TL, Lilsan BESN P20 TL, Lilsan BESN P40 TL, Lilsan MB3610, Lilsan MB3610" commercially available from Arkema Co., Ltd. BMF O, Lilsan BMN O, Lilsan BMN O TLD, Lilsan BMN BK TLD, Lilsan BMN P20 D, Lilsan BMN P40 D, etc.) "and the like.

The polyamide elastomer has a hard segment portion and a soft segment portion composed of a polyamide component. Examples of the soft segment portion of the polyamide elastomer include a polyether ester component or a polyether component. The polyamide elastomer includes, for example, a polyether ester amide obtained by reacting a polyamide component (hard segment component) with a polyether ester component (soft segment component) composed of polyoxyalkylene glycol and dicarboxylic acid; a polyamide component (hard). Examples thereof include a polyether amide obtained by reacting a segment component) and a polyether (soft segment component) composed of a dicarboxylic acid or a diamine, which is obtained by aminating or carboxylating both ends of a polyoxyalkylene glycol.

Examples of the polyamide elastomer include "Pevax (registered trademark) 2533", "Pebax 3533", "Pebax 4033", and "Pebax 5533" manufactured by Arkema.

The cover resin composition further comprises a pigment component such as a white pigment (eg, titanium oxide), a blue pigment, a weight adjuster, a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent material or a fluorescence increase. It can contain additives such as whitening agents. Examples of the weight adjusting agent include inorganic fillers such as zinc oxide, barium sulfate, calcium carbonate, magnesium oxide, tungsten powder, and molybdenum powder.

The content of the white pigment (for example, titanium oxide) is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 parts by mass or less, based on 100 parts by mass of the component (A). More preferably, it is by mass or less. By setting the content of the white pigment to 0.5 parts by mass or more, concealing property can be imparted to the obtained cover. Further, when the content of the white pigment exceeds 10 parts by mass, the durability of the obtained cover may decrease.

The cover resin composition is obtained, for example, by dry-blending the component (A), the component (B), and if necessary, other additives. Alternatively, the dry-blended mixture may be extruded and pelletized. For the dry blend, for example, it is preferable to use a mixer capable of blending pellet-shaped raw materials, and more preferably a tumbler type mixer is used. For extrusion, a known extruder such as a single-screw extruder, a twin-screw extruder, or a twin-screw single-screw extruder can be used.

The slab hardness of the cover resin composition is a shore D hardness of 57 or more, preferably 61 or more, more preferably 63 or more, still more preferably 65 or more, preferably 90 or less, and more preferably 85 or less. When the slab hardness of the resin composition for the cover is 57 or more with the shore D hardness, the obtained cover does not become too soft and the resilience of the golf ball becomes good. Further, when the slab hardness of the resin composition for the cover is 90 or less with the shore D hardness, the obtained cover does not become too hard and the shot feeling of the golf ball becomes better.

The flexural modulus of the cover resin composition is preferably 100 MPa or more, more preferably 110 MPa or more, further preferably 120 MPa or more, particularly preferably 300 MPa or more, preferably 2000 MPa or less, still more preferably 1900 MPa or less, still more preferably. Is 1800 MPa or less. When the flexural modulus is 100 MPa or more, the repulsion of the golf ball becomes good, and when it is 2000 MPa or less, the obtained cover does not become too hard and the shot feeling of the golf ball becomes better. The flexural modulus is measured according to ISO178 (2001).

The MFR (190 ° C., 2.16 kg) of the cover resin composition is preferably 0.1 g / 10 min or more, more preferably 0.2 g / 10 min or more, still more preferably 0.5 g / 10 min or more, and particularly preferably 0.5 g / 10 min or more. It is 3.0 g / 10 min or more, preferably 100 g / 10 min or less, more preferably 90 g / 10 min or less, and further preferably 80 g / 10 min or less. When the MFR is 0.1 g / 10 min or more, the moldability is good, and when the MFR is 100 g / 10 min or less, the hitting durability of the golf ball does not decrease.

(Golf ball)
The structure of the golf ball of the present invention is not particularly limited as long as at least one layer of the cover is formed from the cover resin composition. The structure of the golf ball includes, for example, a golf ball having a core and a cover arranged to cover the core; a single-layer inner layer cover arranged to cover the core and the core. A golf ball having an outer layer cover arranged to cover the inner layer cover; or one or more inner layer covers arranged to cover the core and the core, and to cover the inner layer cover. A multi-piece golf ball (including the three-piece golf ball) having an arranged outermost layer cover can be mentioned. The core structure may be either a single-layer core or a multi-layer core.

As an aspect of the golf ball, the outermost layer cover is formed from the resin composition for the cover (first aspect); the cover has at least two layers, and at least one layer of the cover other than the outermost layer cover is formed. , A mode (second aspect) formed from the cover resin composition. As the first aspect, in a golf ball having a core and a single-layer cover arranged so as to cover the core, the cover is preferably formed from the cover resin composition. As a second aspect, in a multi-piece golf ball having a core, one or more inner layer covers arranged to cover the core, and an outermost layer cover arranged to cover the inner layer cover, an inner layer is used. It is preferable that the outermost layer of the cover is formed from the cover resin composition.

For the golf ball, a conventionally known material can be used for a portion other than the cover molded from the cover resin composition.

A known rubber composition (hereinafter, may be simply referred to as "rubber composition for core") can be used for the core, and for example, a rubber composition containing a base rubber, a co-crosslinking agent, and a cross-linking initiator. Can be heat-pressed and molded.

As the base rubber, it is particularly preferable to use high cis polybutadiene having a cis bond advantageous for repulsion of 40% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more. The co-crosslinking agent is preferably an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms or a metal salt thereof, and more preferably a metal salt of acrylic acid or a metal salt of methacrylic acid. As the metal of the metal salt, zinc, magnesium, calcium, aluminum and sodium are preferable, and zinc is more preferable. The amount of the co-crosslinking agent used is preferably 20 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the base rubber. Organic peroxides are preferably used as the cross-linking initiator. Specifically, dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t-butylperoxy). Examples thereof include organic peroxides such as hexane and di-t-butyl peroxide, and among these, dicumyl peroxide is preferably used. The blending amount of the crosslinking initiator is preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, and more preferably 5 parts by mass or less, more preferably 5 parts by mass, based on 100 parts by mass of the base rubber. It is 3 parts by mass or less.

Further, the rubber composition for a core may further contain an organic sulfur compound. As the organic sulfur compound, diphenyl disulfides, thiophenols, and thionaphthols can be preferably used. The blending amount of the organic sulfur compound is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, and more preferably 5.0 parts by mass or less with respect to 100 parts by mass of the base material rubber. It is preferably 3.0 parts by mass or less. The rubber composition for a core may further contain a carboxylic acid and / or a salt thereof. As the carboxylic acid and / or a salt thereof, a carboxylic acid having 1 to 30 carbon atoms and / or a salt thereof is preferable. As the carboxylic acid, either an aliphatic carboxylic acid or an aromatic carboxylic acid (benzoic acid or the like) can be used. The blending amount of the carboxylic acid and / or a salt thereof is 1 part by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the base rubber.

In the rubber composition for a core, in addition to a base rubber, a co-crosslinking agent, a cross-linking initiator, and an organic sulfur compound, a weight adjusting agent such as zinc oxide or barium sulfate, an antiaging agent, a colored powder, or the like is appropriately added. Can be blended. The heating press molding conditions of the rubber composition for the core may be appropriately set according to the rubber composition, but are usually heated at 130 ° C. to 200 ° C. for 10 minutes to 60 minutes, or at 130 ° C. to 150 ° C. 20. After heating for 1 to 40 minutes, it is preferable to heat at 160 ° C to 180 ° C for 5 to 15 minutes in two steps.

The diameter of the spherical core is preferably 34.8 mm or more, more preferably 36.8 mm or more, further preferably 38.8 mm or more, preferably 42.2 mm or less, more preferably 41.8 mm or less, still more preferably. It is 41.2 mm or less, and most preferably 40.8 mm or less. When the diameter of the spherical core is 34.8 mm or more, the thickness of the cover does not become too thick, and the resilience becomes better. On the other hand, when the diameter of the spherical core is 42.2 mm or less, the cover does not become too thin and the function of the cover is more exhibited.

When the diameter of the spherical core is 34.8 mm to 42.2 mm, the amount of compression deformation (the amount at which the center shrinks in the compression direction) from the state where the initial load of 98 N is applied to the time when the final load of 1275 N is applied is 1.90 mm. The above is preferable, more preferably 2.00 mm or more, further preferably 2.10 mm or more, preferably 5.00 mm or less, still more preferably 4.80 mm or less, still more preferably 4.60 mm or less. When the amount of compression deformation is 1.90 mm or more, the shot feeling is better, and when it is 5.00 mm or less, the resilience is better.

The hardness difference (Hs-Ho) between the surface hardness Hs and the center hardness Ho of the spherical core is the shore D hardness, preferably 5 or more, more preferably 8 or more, still more preferably 10 or more, and preferably 50 or less. , 45 or less is more preferable, and 40 or less is further preferable. When the hardness difference is large, a golf ball having a high launch angle and a low spin distance can be obtained.

The center hardness Ho of the spherical core is the shore D hardness, preferably 5 or more, more preferably 10 or more, and further preferably 15 or more. When the center hardness Ho of the spherical core is 10 or more in the shore D hardness, it does not become too soft and the resilience is good. The central hardness Ho of the spherical core is preferably 70 or less, more preferably 60 or less, and further preferably 50 or less in terms of shore D hardness. When the center hardness Ho is 70 or less in shore D hardness, the hardness is not too hard and the shot feeling is good.

The surface hardness Hs of the spherical core is the shore D hardness, preferably 15 or more, more preferably 25 or more, further preferably 35 or more, preferably 90 or less, more preferably 80 or less, still more preferably 70 or less. be. By setting the surface hardness of the spherical core to 15 or more in shore D hardness, the spherical core does not become too soft and good resilience can be obtained. Further, by setting the surface hardness of the spherical core to 90 or less in shore D hardness, the spherical core does not become too hard and a good shot feeling can be obtained.

Examples of the cover material other than the cover resin composition include thermoplastic resins such as polyurethane resin, ionomer resin, polyamide resin and polyethylene; thermoplastic elastomers such as styrene elastomer, polyolefin elastomer, polyurethane elastomer, polyamide elastomer and polyester elastomer. And so on. Here, as the ionomer resin, for example, at least a part of the carboxyl group in the copolymer of ethylene and α, β-unsaturated carboxylic acid is neutralized with a metal ion, or ethylene and α, β-non-residence. Examples thereof include those in which at least a part of the carboxyl groups in the ternary copolymer of saturated carboxylic acid and α, β-unsaturated carboxylic acid ester is neutralized with metal ions. The inner layer cover may further contain a weight adjusting agent such as barium sulfate or tungsten, an antiaging agent, a pigment or the like.

The method for forming the inner layer cover is not particularly limited, but for example, a method in which a resin composition for a cover is formed in advance into a hemispherical shell-shaped half shell, two of which are used to wrap the sphere, and pressure molding is performed. , A method of injecting a resin composition for a cover directly onto a sphere to wrap the sphere can be mentioned.

When the inner layer cover is formed by injection molding the cover resin composition onto a sphere, it is preferable to use a molding having a hemispherical cavity as the upper and lower molds for molding. In the molding of the inner layer cover by injection molding, the inner layer cover can be molded by sticking out a hold pin, throwing in a coated sphere to hold the cover, injecting a heat-melted resin composition for a cover, and cooling the inner layer cover. can.

When the inner layer cover is molded by a compression molding method, the half shell can be molded by either a compression molding method or an injection molding method, but the compression molding method is preferable. The conditions for compression molding the cover resin composition into a half shell are, for example, −20 ° C. or higher and + 70 ° C. with respect to the flow start temperature of the cover resin composition at a pressure of 1 MPa or higher and 20 MPa or lower. The following molding temperatures can be mentioned. By setting the molding conditions, a half shell having a uniform thickness can be molded. As a method of molding the inner layer cover using the half shell, for example, a method of covering a sphere with two half shells and compression molding can be mentioned. The conditions for compression molding the half shell to form the inner layer cover are, for example, −20 ° C. or higher and + 70 ° C. with respect to the flow start temperature of the cover resin composition at a molding pressure of 0.5 MPa or higher and 25 MPa or lower. The following molding temperatures can be mentioned. By setting the molding conditions, an intermediate layer having a uniform thickness can be molded.

The molding temperature means the maximum temperature reached by the surface of the concave portion of the lower mold between the mold clamping and the mold opening. The flow start temperature of the composition was set to a pellet-shaped cover resin composition using Shimadzu's "Flow Tester CFT-500" with a plunger area of 1 cm ² , DIE LENGTH: 1 mm, DIE DIA: 1 mm, and so on. It can be measured under the conditions of load: 588.399N, starting temperature: 30 ° C., and heating rate: 3 ° C./min.

The embodiment of molding the outermost layer cover using the cover composition is not particularly limited, but is an embodiment of injection molding the cover composition directly onto the spherical core or the inner layer cover, or a hollow shell shape from the cover composition. A mode in which a shell is formed and a spherical core or a sphere on which an inner layer cover is formed is covered with a plurality of shells and compression-molded (preferably, a hollow shell-shaped half shell is formed from a cover composition, and two spherical cores are formed. A method of covering with a half shell of the above and compression molding) can be mentioned. It is preferable that the golf ball body on which the outermost layer cover is formed is taken out from the mold and, if necessary, surface-treated such as deburring, cleaning, and sandblasting. Also, if desired, a mark can be formed.

The total number of dimples formed on the cover is preferably 200 or more and 500 or less. If the total number of dimples is less than 200, it is difficult to obtain the effect of dimples. Further, when the total number of dimples exceeds 500, the size of each dimple becomes small, and it is difficult to obtain the effect of the dimples. The shape of the dimples to be formed (planar shape) is not particularly limited, and a circle; a polygon such as a substantially triangle, a substantially quadrangle, a substantially pentagon, and a substantially hexagon; and other indefinite shapes; are used alone. Alternatively, two or more kinds may be used in combination.

It is preferable to remove the golf ball from which the cover is formed from the mold and, if necessary, perform surface treatment such as deburring, cleaning, and sandblasting. Further, if desired, a coating film or a mark can be formed. The film thickness of the coating film is not particularly limited, but is preferably 5 μm or more, more preferably 7 μm or more, more preferably 50 μm or less, still more preferably 40 μm or less, still more preferably 30 μm or less. This is because if the film thickness is less than 5 μm, the coating film is likely to wear away due to continuous use, and if the film thickness exceeds 50 μm, the effect of dimples is reduced and the flight performance of the golf ball is deteriorated.

The diameter of the golf ball of the present invention is preferably 40 mm to 45 mm. A diameter of 42.67 mm or more is particularly preferred from the perspective of meeting the standards of the United States Golf Association (USGA). From the viewpoint of suppressing air resistance, the diameter is more preferably 44 mm or less, and particularly preferably 42.80 mm or less. The mass of the golf ball is preferably 40 g or more and 50 g or less. From the viewpoint of obtaining a large inertia, the mass is more preferably 44 g or more, and particularly preferably 45.00 g or more. From the viewpoint that the USGA standard is satisfied, the mass is particularly preferably 45.93 g or less.

When the golf ball of the present invention has a diameter of 40 mm to 45 mm, the amount of compression deformation (the amount of shrinkage of the golf ball in the compression direction) when the final load of 1275 N is applied from the state where the initial load of 98 N is applied is 2.0 mm or more. It is preferably 2.4 mm or more, more preferably 2.5 mm or more, most preferably 2.8 mm or more, preferably 5.0 mm or less, and even more preferably 4. It is 5 mm or less. A golf ball having a compression deformation amount of 2.0 mm or more does not become too hard and has a good shot feeling. On the other hand, by setting the amount of compression deformation to 5.0 mm or less, the resilience becomes high.

In the first aspect, the slab hardness of the cover resin composition forming the outermost layer cover is preferably 57 or more, more preferably 61 or more, still more preferably 63 or more, and preferably 90 or less in terms of shore D hardness. , 85 or less is more preferable. If the slab hardness of the resin composition for the cover is a shore D hardness of 57 or more, a golf ball with a high launch angle and a low spin can be obtained in a driver shot and an iron shot, and the flight distance becomes large, even if it is 90 or less. For example, a golf ball having excellent impact durability can be obtained.

In the first aspect, the thickness of the outermost layer cover is preferably 0.3 mm or more, more preferably 0.5 mm or more, further preferably 1.0 mm or more, preferably 4.0 mm or less, and more preferably 3. It is 5.5 mm or less, more preferably 3.0 mm or less. When the thickness of the outermost layer cover is 0.3 mm or more, the hitting durability and wear resistance of the cover are improved, and when the thickness is 4.0 mm or less, the repulsion and shot feeling of the obtained golf ball are improved.

In the second aspect, the slab hardness Hm of the cover resin composition forming the inner layer cover is preferably 57 or more, more preferably 63 or more, still more preferably 65 or more, and preferably 90 or less in terms of shore D hardness. , 85 or less is more preferable. If the slab hardness of the resin composition for the cover is the shore D hardness of 57 or more, it contributes to increasing the degree of the outer rigid inner flexible structure of the golf ball, resulting in a high launch angle, low spin, and high flight distance. If it is achieved and 90 or less, the shot feeling is improved.

In the second aspect, the hardness difference (Hm-Ho) between the slab hardness Hm of the cover resin composition forming the inner layer cover and the center hardness Ho of the spherical core is preferably 5 or more in shore D hardness. It is more preferably 10 or more, preferably 50 or less, and more preferably 45 or less. Further, in the second aspect, the hardness difference (Hm-Hs) between the slab hardness Hm of the cover resin composition forming the inner layer cover and the surface hardness Hs of the spherical core is 1 or more in the shore D hardness. It is preferably 3 or more, preferably 25 or less, and more preferably 20 or less.

In the second aspect, the thickness of the inner layer cover formed from the cover resin composition is preferably 0.3 mm or more, more preferably 0.4 mm or more, still more preferably 0.5 mm or more, and 2. It is preferably 5 mm or less, more preferably 2.4 mm or less, still more preferably 2.3 mm or less.

In the second aspect, the ratio (Tm / Tc) of the thickness (Tm) of the inner layer cover formed from the resin composition for the cover to the thickness (Tc) of the outermost layer cover is preferably 0.5 or more. , More preferably 1.0 or more, still more preferably 1.5 or more, preferably 5 or less, more preferably 4 or less, still more preferably 3 or less.

In the second aspect, the slab hardness Hc of the resin composition forming the outermost layer cover is the shore D hardness, preferably 20 or more, more preferably 25 or more, preferably 50 or less, and more preferably 40 or less. More preferably, it is 35 or less.

In the second aspect, the hardness difference (Hm-Hc) between the slab hardness Hm of the cover resin composition forming the inner layer cover and the slab hardness Hc of the resin composition forming the outermost layer cover is the shore D hardness. It is preferably 10 or more, more preferably 20 or more, preferably 60 or less, and more preferably 50 or less.

In the second aspect, it is preferable that the outermost layer cover is formed of a resin composition containing a thermoplastic polyurethane resin. The content of the thermoplastic polyurethane resin in the resin component in this resin composition is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more.

FIG. 1 is a partially cutaway sectional view showing a golf ball 1 according to an embodiment of the present invention. The golf ball 1 has a spherical core 2 and a cover 4 that covers the spherical core 2. A large number of dimples 41 are formed on the surface of the cover 4. The portion of the surface of the golf ball other than the dimple 41 is the land 42. The cover 4 is formed of the cover resin composition.

FIG. 2 is a partially cutaway sectional view showing a golf ball 1 according to another embodiment of the present invention. The golf ball 1 has a spherical core 2, an inner layer cover 3 that covers the spherical core 2, and an outermost layer cover 4 that covers the inner layer cover 3. A large number of dimples 41 are formed on the surface of the outermost layer cover 4. The portion of the surface of the golf ball other than the dimple 41 is the land 42. The inner layer cover 3 is formed of the cover resin composition.

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited to the following examples, and changes and embodiments within the scope not deviating from the gist of the present invention are all of the present invention. Included within range.

[Evaluation methods]

(1) Core hardness (shore D hardness)
The hardness measured on the surface of the core was defined as the core surface hardness. In addition, the core was cut into a hemispherical shape, and the hardness was measured at the center of the cut surface. The surface hardness was calculated by measuring the hardness at four points on the core surface and averaging these points. The hardness was measured using an automatic hardness tester (Digitest II, manufactured by H. Burleys). As the detector, "Shore D" was used.

(2) Compressive deformation amount (mm)
The amount of deformation in the compression direction (the amount of shrinkage of the core or golf ball in the compression direction) from the state in which the initial load of 98N was applied to the core or the golf ball to the time when the final load of 1275N was applied was measured.

(3) Slab hardness (Shore D hardness)
A sheet having a thickness of about 2 mm was prepared by injection molding using the resin composition for a cover, and stored at 23 ° C. for 2 weeks. The hardness was measured using an automatic hardness tester (Digitest II, manufactured by H. Burleys) with three or more of these sheets stacked so as not to be affected by the measuring substrate or the like. As the detector, "Shore D" was used.

(4) Coefficient of restitution A 198.4 g metal cylindrical object is made to collide with each golf ball at a speed of 40 m / sec, the speeds of the cylindrical object and the golf ball before and after the collision are measured, and each golf is obtained from the respective speeds and masses. The coefficient of restitution of the ball was calculated. Twelve measurements were made for each golf ball, and the average value was used as the coefficient of restitution of the golf ball. The coefficient of restitution is the golf ball No. For 1 to 9, golf ball No. It is shown as an exponential value with the coefficient of restitution of 1 as 100. Golf ball No. For 10 to 18, golf ball No. It is shown as an exponential value with the coefficient of restitution of 10 as 100.

(5) Durability Twelve golf balls were collided with a metal plate at a speed of 45 m / sec using an air gun, and the number of repetitions until the golf balls broke was measured. The durability is the golf ball No. For 1 to 9, golf ball No. The durability of 1 is set to 100, and it is shown as an indexed value. Golf ball No. For 10 to 18, golf ball No. The durability of 10 is set to 100, and it is shown as an indexed value.

[Two-piece golf ball No. Preparation of 1 to 9]
(1) Preparation of Spherical Core No. 1 of the composition shown in Table 1. The rubber composition of A was kneaded and heated and pressed at 170 ° C. for 20 minutes in an upper and lower die having a hemispherical cavity to obtain a spherical core having a diameter of 39.8 mm.

Polybutadiene rubber: JSR Corporation, "BR730 (Hisys Polybutadiene)"
Zinc acrylate: "ZN-DA90S" manufactured by Nikko Techno Fine Chemical Co., Ltd.
Zinc oxide: "Ginmine R" manufactured by Toho Zinc Co., Ltd.
Barium Sulfate: "Barium Sulfate BD" manufactured by Sakai Chemical Industry Co., Ltd.
Diphenyl disulfide: manufactured by Sumitomo Seika Chemical Co., Ltd., diphenyl disulfide disulfide disulfide: manufactured by NOF CORPORATION, "Park Mill (registered trademark) D (diphenyl peroxide)"

(2) Preparation of Cover The compounding materials shown in Table 2 were mixed with a twin-screw kneading extruder to prepare a pellet-shaped cover composition. The extrusion conditions were a screw diameter of 45 mm, a screw rotation speed of 200 rpm, and a screw L / D = 35, and the compound was heated to 160 to 230 ° C. at the position of the die of the extruder. By injection molding the cover composition on the spherical core, a cover (thickness 1.5 mm) covering the core was formed. The cover composition is heated to 200 ° C. to 260 ° C. in the cylinder portion of the injection device, is injected into a mold molded at a pressure of 15 MPa, cooled for 30 seconds, and opened to form a cover. Was taken out.

Sarlin (registered trademark) 8150: Sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin (MFR (190 ° C., 2.16 kg load): 4.5 g / 10 min) manufactured by DuPont.
Sarlin 9150: Zinc ion-neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by DuPont (MFR (190 ° C., 2.16 kg load): 4.5 g / 10 min)
Hymilan (registered trademark) 1605: Sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by Mitsui DuPont Polychemical Co., Ltd. (MFR (190 ° C., 2.16 kg load): 2.8 g / 10 min)
Hymilan AM7329: Zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin (MFR (190 ° C., 2.16 kg load): 4.0 g / 10 min) manufactured by Mitsui DuPont Polychemical Co., Ltd.
Hymilan AM7327: Zinc ion neutralized ethylene-methacrylic acid-acrylic acid ester copolymer ionomer resin (MFR (190 ° C., 2.16 kg load): 3.2 g / 10 min) manufactured by Mitsui DuPont Polychemical Co., Ltd.
Septon® HG252: Polystyrene block-isoprene / butadiene random polymer block-polystyrene block copolymer hydrogenated by Claret, block copolymer having a hydroxy group at the end of the molecule (Shore A hardness) : 80, styrene content: 28% by mass, hydrogenation rate: 90% or more, melt flow rate (230 ° C, 2.16 kg): 26 g / 10 min)
Elastran (registered trademark) XNY80A: Thermoplastic polyurethane elastomer manufactured by BASF Japan Ltd. (Shore A hardness: 80)

Golf ball No. In Nos. 2 to 5 and 8, the cover resin composition contains (A) an olefin-based ionomer resin and a predetermined amount of (B) a block copolymer and / or a hydrogenated additive thereof, and the slab hardness of the cover resin composition. Has a shore D hardness of 57 or more. These golf balls No. Nos. 2 to 5 and 8 are golf ball Nos. No. 2 in which the resin composition for the cover does not contain the component (B). Compared with 1 and 7, durability is improved while maintaining resilience.
Golf ball No. No. 6 contains the component (B) in which the cover resin composition exceeds a predetermined amount. This golf ball No. In No. 6, the resilience is lowered and the durability is also greatly lowered.
Golf ball No. In 9, the cover resin composition contains a polyurethane elastomer instead of the (B) block copolymer and / or a hydrogenated product thereof. This golf ball No. In No. 9, the resilience is maintained, but the durability is greatly reduced.

[Three-piece golf ball No. Preparation of 10-18]
(1) Preparation of core No. 1 of the composition shown in Table 1. The rubber composition of B was kneaded and heated and pressed at 170 ° C. for 20 minutes in an upper and lower die having a hemispherical cavity to obtain a spherical core having a diameter of 39.7 mm.

(2) Preparation of Cover Composition The compounding materials shown in Tables 3 and 4 were mixed by a twin-screw kneading extruder to prepare a pellet-shaped cover composition. The extrusion conditions were a screw diameter of 45 mm, a screw rotation speed of 200 rpm, and a screw L / D = 35, and the compound was heated to 160 to 230 ° C. at the position of the die of the extruder.

Elastran XNY82A: Made by BASF Japan, Thermoplastic Polyurethane Elastomer Titanium Oxide: Made by Ishihara Sangyo, A220

(3) Preparation of Inner Layer Cover An inner layer cover (thickness 1.0 mm) covering the core was formed by injection molding the cover composition shown in Table 4 on the spherical core. The cover composition is a sphere heated to 200 ° C. to 260 ° C. in the cylinder portion of the injection device, injected into a mold molded at a pressure of 15 MPa, cooled for 30 seconds and opened to form an inner layer cover. Was taken out.

(4) Preparation of outer layer cover At the time of molding the outer layer cover, a cover composition in which a hold pin is projected, a sphere on which an inner layer cover is formed is put in and then held, and then heated to 260 ° C. in a mold compacted with a pressure of 80 tons. Was injected in 0.3 seconds, cooled for 30 seconds, opened, and the golf ball was taken out. The surface of the obtained golf ball body was sandblasted and marked, then clear paint was applied, and the paint was dried in an oven at 40 ° C. to obtain a golf ball having a diameter of 42.7 mm.

Golf ball No. In 11 to 14 and 17, the resin composition for the inner layer cover contains (A) an olefin-based ionomer resin and a predetermined amount (B) a block copolymer and / or a hydrogenated product thereof, and the resin composition for the inner layer cover is contained. The slab hardness is 57 or more in the shore D hardness. These golf balls No. Nos. 11 to 14 and 17 are golf ball Nos. Nos. 11 to 14 and 17 in which the resin composition for the cover does not contain the component (B). Compared with 10 and 16, durability is improved while maintaining resilience.
Golf ball No. Reference numeral 15 contains the component (B) in which the resin composition for the inner layer cover exceeds a predetermined amount. This golf ball No. In No. 15, the resilience is lowered and the durability is also greatly lowered.
Golf ball No. In 18, the cover resin composition contains a polyurethane elastomer instead of the (B) block copolymer and / or a hydrogenated product thereof. This golf ball No. In No. 18, the resilience is maintained, but the durability is greatly reduced.

1: Golf ball 2: Spherical core 3: Inner layer cover 4: Cover (outermost layer cover), 41: Dimple, 42: Land

Claims (7)

It has a spherical core and at least one layer of cover covering the spherical core.
At least one layer of the cover is formed of a cover resin composition containing (A) an olefin-based ionomer resin and (B) a block copolymer and / or a hydrogenated product thereof as resin components.
The block copolymer (B) and / or a hydrogenated product thereof has a block having a structural unit derived from an aromatic vinyl compound and a block having a structural unit derived from a conjugated diene compound, and has a block at the molecular terminal. A copolymer having a hydroxy group and / or a hydrogenated product thereof.
The content of the (B) block copolymer and / or its hydrogenated product in the resin component is 0.1 part by mass to 20 parts by mass with respect to 100 parts by mass of the (A) olefin-based ionomer resin. can be,
The slab hardness of the cover resin composition is 57 or more in Shore D hardness.
A golf ball having a flexural modulus of the resin composition for a cover of 300 MPa to 2000 MPa . The golf ball according to claim 1, wherein the slab hardness of the resin composition for a cover is 61 or more in shore D hardness. The (A) olefin-based ionomer resin is a metal ion neutralized product of a binary copolymer of (a1) an olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and / or ( a2) Claim 1 or a metal ion neutralized product of a ternary copolymer of an olefin, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an α, β-unsaturated carboxylic acid ester. The golf ball according to 2. The golf ball according to any one of claims 1 to 3, wherein the outermost layer cover is formed of the resin composition for a cover. The cover has at least two layers
The golf ball according to any one of claims 1 to 3, wherein at least one layer of a cover other than the outermost cover is formed of the resin composition for a cover. The golf ball according to claim 5, wherein the slab hardness of the resin composition forming the outermost layer cover is 20 to 50 in shore D hardness. 5. The hardness difference (Hm-Hc) between the slab hardness Hm of the cover resin composition and the slab hardness Hc of the resin composition forming the outermost layer cover is 10 to 60 in shore D hardness. Or the golf ball according to 6.

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