JP4751924B2 - Golf ball - Google Patents

Description

  The present invention relates to a golf ball, and more particularly to a technique for improving cover characteristics.

  As a golf ball cover material, an ionomer resin excellent in durability and resilience is used. However, when processing a golf ball using an ionomer resin, thermal stability and workability are also required, and the characteristics of the obtained golf ball include shot feeling, controllability, resilience and durability. It is also required to have excellent properties.

  From such a point of view, various improved techniques have been proposed for golf balls using ionomer resin as a cover material. For example, Patent Document 1 discloses (a) an olefin-unsaturated carboxylic acid as a golf ball material capable of obtaining a high-performance golf ball having good thermal stability, fluidity and moldability and excellent resilience. Binary random copolymer and / or metal ion neutralized product of olefin-unsaturated carboxylic acid binary random copolymer and (b) olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymer And / or a base resin blended with a metal ion neutralized product of an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ternary random copolymer in a mass ratio of 100: 0 to 25:75; e) With respect to 100 parts by mass of the resin component blended with the non-ionomer thermoplastic elastomer in a mass ratio of 100: 0 to 50:50, (c) the molecular weight is 280 to 5 to 80 parts by mass of 500 fatty acids and / or derivatives thereof, and (d) a basic inorganic metal compound capable of neutralizing an unneutralized acid group in the base resin and component (c) 0.1 to 10 parts by mass Is disclosed as an essential component, and a golf ball material is disclosed.

  Patent Document 2 discloses (a) an olefin as a golf ball material using a highly neutralized ionomer resin capable of obtaining a high-performance golf ball having good thermal stability, fluidity and moldability and excellent resilience. -100 mass parts of unsaturated carboxylic acid random copolymer and / or olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester random copolymer, (b) 5-80 parts by mass of a fatty acid having a molecular weight of 280 or more, or a derivative thereof, (C) It contains 0.1 to 10 parts by mass of a basic inorganic metal compound capable of neutralizing the acid groups in the components (a) and (b), and has a melt index of 1.0 dg / min or more. There is disclosed a golf ball material comprising a heated mixture as described above.

In Patent Document 3, a high molecular weight ternary ionomer (molecular weight of about 80000 to 500,000) having a different molecular weight and a low molecular weight binary ionomer (molecular weight of about 2000 to 30000) are blended to maintain durability and flight distance. A golf ball having improved flexibility and scratch resistance is disclosed.
Japanese Patent No. 3767683 Japanese Patent No. 3729243 Special table 2006-500995 gazette

  In order to improve the resilience of the golf ball, the cover is thinned. However, in order to make the cover thin, the ionomer resin needs to have high fluidity. As a technique for improving the flowability of an ionomer resin while maintaining the resilience performance, for example, it is known to add a low molecular weight material such as a fatty acid to a highly neutralized ionomer resin. However, the addition of a low molecular weight material such as a fatty acid causes smoke during molding. In addition, the low molecular material component tends to bleed out on the surface of the golf ball body. As a result, when coating the surface of the golf ball body, there arises a problem that the adhesion of the coating film is lowered.

  The present invention has been made in view of the above circumstances, and has improved the moldability of the cover, is excellent in coating film adhesion and low temperature durability, and has excellent flight distance and feel at impact. The purpose is to provide. Another object of the present invention is to provide a golf ball having excellent directional stability at the time of hitting.

  The golf ball of the present invention that has solved the above problems is a golf ball having at least one core, an intermediate layer that covers the core, and a cover that covers the intermediate layer, the cover being a resin component (A) a copolymer obtained by neutralizing at least a part of a carboxyl group of a binary copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms with ethylene and 3 to 3 carbon atoms From one obtained by neutralizing at least part of the carboxyl group of a terpolymer of eight α, β-unsaturated carboxylic acids and α, β-unsaturated carboxylic acid ester with a metal ion, or a mixture thereof A high melt viscosity ionomer resin having a melt viscosity (190 ° C.) of 500 Pa · s to 100,000 Pa · s by a flow tester, and (b) an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and ethylene. A copolymer obtained by neutralizing at least part of the carboxyl group of the binary copolymer with ethylene, ethylene, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α, β-unsaturated carboxylic acid ester And a mixture thereof obtained by neutralizing at least part of the carboxyl group of the terpolymer with a metal ion, or a melt viscosity (190 ° C.) by a Brookfield viscometer of 1 Pa · s to 10 Pa. A low melt viscosity ionomer resin having s and a melt flow rate (190 ° C. × 2.16 kg) of 100 g / 10 min to 2000 g / 10 min, (a) high melt viscosity ionomer resin / (b) low melt viscosity ionomer resin = 55% by mass to 99% by mass / 45% by mass to 1% by mass, (a) high melt viscosity ionomer resin and / or (b) low melt viscosity The composition for a cover, wherein at least one of the metal ions neutralizing the carboxyl group of the ionomer resin is a divalent metal ion, and the content of the divalent metal ion in 100 g of the resin component is 0.020 mol or more. The cover has a thickness of 0.3 mm to 1.0 mm, and the slab hardness of the intermediate layer composition forming the intermediate layer is a Shore D hardness of 35 to 55. It is characterized by.

  That is, the present invention has (a) a high melt viscosity ionomer resin component having a high resilience as a main component and (a) a structure similar to a high melt viscosity ionomer resin as a component for improving fluidity. Since the melt viscosity ionomer resin is blended, the compatibility of both is high, and (b) the low melt viscosity ionomer resin component is suppressed from bleeding out to the surface of the golf ball body. In addition, at least one of the metal ions neutralizing the carboxyl group of the (a) high melt viscosity ionomer resin and / or (b) the low melt viscosity ionomer resin is a divalent metal ion, By setting the content of the valent metal ion to 0.020 mol or more, the low temperature durability of the obtained golf ball is improved. The present invention improves the moldability of the cover, the adhesion of the golf ball to the coating film and the low temperature durability by using the cover composition, and is suitable for shots such as drivers by thinning the cover and optimizing the intermediate layer hardness. On the other hand, there is a gist in that the spin distance is reduced to improve the flight distance and the direction stability, and the hit feeling is improved by optimizing the intermediate layer hardness.

  The cover composition further includes (c) a nonionic thermoplastic resin having a melt viscosity (190 ° C.) of 5 Pa · s to 3000 Pa · s by a flow tester as a resin component, and each component in the resin component (A) high melt viscosity ionomer resin: 45 mass% to 70 mass%, (b) low melt viscosity ionomer resin: 5 mass% to 25 mass%, and (c) nonionic thermoplastic resin : It is also a preferable aspect that it is 10 mass%-40 mass%.

The density of the intermediate layer is preferably 1.10 g / cm ³ or more. It is preferable that the slab hardness of the cover composition is 57 or more in Shore D hardness. The center preferably has a diameter of 39.1 mm or more. The melt flow rate (190 ° C. × 2.16 kg) of the cover composition is preferably 10 g / 10 min to 100 g / 10 min.

  According to the present invention, a golf ball having improved cover moldability, excellent coating film adhesion and low temperature durability, and excellent flight distance and feel at impact is obtained. Furthermore, according to the present invention, a golf ball having excellent directional stability upon hitting can be obtained.

  The golf ball of the present invention is a golf ball having at least one core, an intermediate layer covering the core, and a cover covering the intermediate layer, wherein the cover includes (a) ethylene as a resin component Is obtained by neutralizing at least a part of a carboxyl group of a binary copolymer of a α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms with a metal ion, ethylene and α having 3 to 8 carbon atoms, It consists of a ternary copolymer of β-unsaturated carboxylic acid and α, β-unsaturated carboxylic acid ester, wherein at least a part of the carboxyl group is neutralized with a metal ion, or a mixture thereof. A high melt viscosity ionomer resin (hereinafter simply referred to as “(a) high melt viscosity ionomer resin”) having a melt viscosity (190 ° C.) of 500 Pa · s to 100,000 Pa · s, and (b) A copolymer obtained by neutralizing at least a part of a carboxyl group of a binary copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms with ethylene and α having 3 to 8 carbon atoms , Β-unsaturated carboxylic acid and α, β-unsaturated carboxylic acid ester ternary copolymer having at least a part of the carboxyl group neutralized with a metal ion, or a mixture thereof, Low melt viscosity ionomer resin (hereinafter simply referred to as a melt viscosity (190 ° C.) of 1 Pa · s to 10 Pa · s and a melt flow rate (190 ° C. × 2.16 kg) of 100 g / 10 min to 2000 g / 10 min as measured by a field viscometer. “(B) low melt viscosity ionomer resin” may be referred to as (a) high melt viscosity ionomer resin / (b) low melt viscosity ionomer resin = 55 mass%. -99 mass% / 45 mass%-1 mass%, and (a) high melt viscosity ionomer resin and / or (b) at least one metal ion that neutralizes the carboxyl group of the low melt viscosity ionomer resin Is a divalent metal ion, and the content of the divalent metal ion in 100 g of the resin component is 0.020 mol or more, and the cover has a thickness of 0.00. It is 3 mm-1.0 mm, The slab hardness of the composition for intermediate | middle layers which forms the said intermediate | middle layer is 35-55 in Shore D hardness, It is characterized by the above-mentioned.

  First, “(a) high melt viscosity ionomer resin” contained in the cover composition will be described.

  The (a) high melt viscosity ionomer resin is obtained by neutralizing at least part of the carboxyl group of a binary copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms with a metal ion. , Which is obtained by neutralizing at least part of carboxyl groups of a terpolymer of ethylene, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α, β-unsaturated carboxylic acid ester with a metal ion Or a mixture thereof.

  Examples of the α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms include acrylic acid, methacrylic acid, fumaric acid, maleic acid, and crotonic acid, and acrylic acid or methacrylic acid is particularly preferable. As the α, β-unsaturated carboxylic acid ester, for example, methyl, ethyl, propyl, n-butyl, isobutyl ester, etc. such as acrylic acid, methacrylic acid, fumaric acid, maleic acid, etc. are used. Methacrylic acid esters are preferred.

  A binary copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, or an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and α, β-unsaturated ethylene. Examples of the metal ion that neutralizes at least a part of the carboxyl group in the ternary copolymer with a saturated carboxylic acid ester include monovalent alkali metal ions such as sodium, potassium, and lithium; magnesium, calcium, zinc, barium, Bivalent metal ions such as cadmium; Trivalent metal ions such as aluminum; and other ions such as tin and zirconium, but divalent metal ions such as magnesium, calcium, zinc, barium, and cadmium are preferred. Zinc is more preferred. This is because the use of a divalent metal ion improves the durability and low temperature durability of the resulting golf ball.

  Among these, the (a) high melt viscosity ionomer resin used in the present invention includes those obtained by neutralizing at least part of the carboxyl groups of ethylene and (meth) acrylic acid copolymer with metal ions, ethylene and (meta It is preferable to use those obtained by neutralizing at least part of the carboxyl groups of the terpolymer of acrylic acid and (meth) acrylic acid ester with metal ions, or a mixture thereof.

  Furthermore, as the (a) high melt viscosity ionomer resin used in the present invention, (a-1) at least a part of the carboxyl group of the binary copolymer and / or ternary copolymer is a monovalent metal ion. An ionomer obtained by mixing a neutralized product with (a-2) a copolymer obtained by neutralizing at least part of the carboxyl groups of the binary copolymer and / or ternary copolymer with a divalent metal ion. It is a preferred embodiment to use a resin.

  By using the mixture of ionomer resins as described above, the impact resilience of the cover composition is increased. In the above, (meth) acrylic acid refers to acrylic acid or methacrylic acid. The monovalent metal ion is preferably sodium, lithium, potassium, rubidium, cesium or francium, and the divalent metal ion is preferably magnesium, calcium, zinc, beryllium, strontium, barium or radium. In this case, the blending ratio of (a-1) and (a-2) is preferably (a-1) / (a-2) = 20% by mass to 80% by mass / 80% by mass to 20% by mass. More preferably, they are 25 mass%-77 mass% / 75 mass%-23 mass%, More preferably, they are 30 mass%-75 mass% / 70 mass%-25 mass%.

  The content of the α, β-unsaturated carboxylic acid component in the (a) high melt viscosity ionomer resin is preferably 2% by mass or more, more preferably 3% by mass or more, and preferably 30% by mass or less. Preferably it is 25 mass% or less.

  Further, the neutralization degree of the carboxyl group of the (a) high melt viscosity ionomer resin is preferably 10 mol% or more, more preferably 15 mol% or more, preferably 90 mol% or less, more preferably 85 mol%. It is as follows. When the degree of neutralization is 10 mol% or more, the resilience and durability of the resulting golf ball are improved, and when it is 90 mol% or less, the fluidity of the cover composition is improved (formability). Is good). In addition, the neutralization degree of the carboxyl group of (a) high melt viscosity ionomer resin can be calculated | required by a following formula.

  Degree of neutralization of high melt viscosity ionomer resin (mol%) = 100 × number of moles of neutralized carboxyl groups in high melt viscosity ionomer resin / total number of carboxyl groups in high melt viscosity ionomer resin

  The melt viscosity (190 ° C.) of the (a) high melt viscosity ionomer resin by a flow tester is 500 Pa · s or more, preferably 1000 Pa · s or more, more preferably 1500 Pa · s or more, preferably 100,000 Pa · s or less, preferably 95000 Pa · s or less, more preferably 92000 Pa · s or less. By setting the melt viscosity to 500 Pa · s or more, the durability of the obtained golf ball is improved, and by setting the melt viscosity to 100000 Pa · s or less, the moldability of the cover composition is improved.

  Specific examples of the above (a) high melt viscosity ionomer resin are exemplified by trade names such as “Himilan (registered trademark)” (for example, Himilan 1555 (Na), Himilan, available from Mitsui DuPont Polychemical Co., Ltd.). 1605 (Na), High Milan 1706 (Zn), High Milan 1707 (Na), High Milan AM 7311 (Mg), High Milan AM 7329 (Zn), High Milan 1856 (Na), High Milan 1855 (Zn), etc.).

  Further, ionomer resins commercially available from DuPont include “Surlyn (registered trademark)” (for example, Surlyn 8945 (Na), Surlyn 9945 (Zn), Surlyn 8140 (Na), Surlyn 8150 (Na), Surlyn 9120 (Zn), Surlyn 9150 (Zn), Surlyn 6910 (Mg), Surlyn 6120 (Mg), Surlyn 7930 (Li), Surlyn 7940 (Li), Surlyn AD8546 (Li) and the like, and terpolymers Examples of ionomer resins include Surlyn 6320 (Mg), Surlyn 8120 (Na), Surlyn 8320 (Na), Surlyn 9320 (Zn), Surlyn 9320W (Zn), etc.), “HPF 1000 (Mg), HPF 2000 (Mg). ".

  Examples of ionomer resins commercially available from ExxonMobil Chemical Co., Ltd. include “Iotek (registered trademark)” (for example, Iotech 8000 (Na), Iotech 8030 (Na), Iotech 7010 (Zn), Iotech 7030 ( Zn) and the like, and examples of the ternary copolymer ionomer resin include Iotech 7510 (Zn) and Iotech 7520 (Zn)).

  Note that Na, Zn, Li, Mg, and the like described in parentheses after the trade name of the ionomer resin indicate the metal species of these neutralized metal ions.

  Next, “(b) low melt viscosity ionomer resin” used in the present invention will be described.

  (B) The low melt viscosity ionomer resin is obtained by neutralizing at least a part of a carboxyl group of a binary copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms with a metal ion, What neutralized at least one part of the carboxyl group of the terpolymer of ethylene, C3-C8 alpha, beta-unsaturated carboxylic acid, and alpha, beta-unsaturated carboxylic acid ester with a metal ion, Or a mixture of these. As the α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, the same ones exemplified as those constituting “(a) high melt viscosity ionomer resin” can be used.

  A binary copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, or an α, β-unsaturated carboxylic acid having ethylene and 3 to 8 carbon atoms and an α, β-unsaturated Examples of metal ions that neutralize at least a part of the carboxyl group of the terpolymer with a carboxylic acid ester include monovalent alkali metal ions such as sodium, potassium, and lithium; magnesium, calcium, zinc, barium, and cadmium. Divalent metal ions such as aluminum; trivalent metal ions such as aluminum; and other ions such as tin and zirconium. Among these, (b) the low melt viscosity ionomer resin is preferably neutralized with a divalent metal ion such as magnesium, calcium, zinc, barium or cadmium.

  The melt viscosity (190 ° C.) of the (b) low melt viscosity ionomer resin by a Brookfield viscometer is preferably 1 Pa · s or more, more preferably 2 Pa · s or more, further preferably 3 Pa · s or more, and 10 Pa · s. The following is preferable, 9 Pa · s or less is more preferable, and 8 Pa · s or less is more preferable. By setting the melt viscosity (190 ° C.) of the (b) low melt viscosity ionomer resin to 1 Pa · s or more, the compatibility with the component (a) is increased, and the durability of the resulting golf ball is improved. It is because the improvement effect of the fluidity | liquidity of the composition for a cover becomes large by setting it as 10 Pa * s or less.

  The melt flow rate (190 ° C. × 2.16 kg) of the (b) low melt viscosity ionomer resin is preferably 100 g / 10 min or more, more preferably 150 g / 10 min or more, further preferably 200 g / 10 min or more, and 2000 g / 10 min or less. Is preferably 1900 g / min or less, more preferably 1800 g / 10 min or less. By improving the melt flow rate of the low melt viscosity ionomer resin to 100 g / 10 min or more, the effect of improving the fluidity of the cover composition is increased, and by setting the melt flow rate to 2000 g / 10 min or less, (a) This is because the durability of the golf ball that can increase the compatibility with the components is improved.

  The content of the α, β-unsaturated carboxylic acid component in the (b) low melt viscosity ionomer resin is preferably 2% by mass or more, more preferably 3% by mass or more, and preferably 30% by mass or less. Preferably it is 20 mass% or less.

  The neutralization degree of the carboxyl group contained in the (b) low melt viscosity ionomer resin is preferably 10 mol% or more, more preferably 15 mol% or more, still more preferably 20 mol% or more, most preferably 100 mol%.

  In addition, the neutralization degree of the carboxyl group in (b) low melt viscosity ionomer resin can be calculated | required by a following formula.

  Degree of neutralization of low melt viscosity ionomer resin (mol%) = 100 × (number of moles of neutralized carboxyl groups in low melt viscosity ionomer resin) / total number of moles of carboxyl groups in low melt viscosity ionomer resin)

  Specific examples of the (b) low melt viscosity ionomer resin include “Aclyn (registered trademark) 201 (Ca)”, “Aclyn 246 (Mg)”, and “Aclyn 295 (Zn)” manufactured by Honeywell. Can do.

  The blending ratio of (a) high melt viscosity ionomer resin and (b) low melt viscosity ionomer resin in the cover composition used in the present invention is as follows: (a) high melt viscosity ionomer resin / (b) low melt viscosity ionomer resin = 55 mass% to 99 mass% / 45 mass% to 1 mass%. By setting it as the said range, the fluidity | liquidity of the composition for a cover improves and a thin cover is attained. As a result, the resilience and durability of the resulting golf ball are improved. (A) High melt viscosity ionomer resin / (b) Low melt viscosity ionomer resin = 58 mass% -90 mass% / 42 mass% -10 mass% is preferable, More preferably, 60 mass% -85 mass% / 40 mass% More preferably, it is -15 mass%.

  In the cover composition used in the present invention, at least one metal ion that neutralizes the carboxyl group of the (a) high melt viscosity ionomer resin and / or (b) the low melt viscosity ionomer resin is a divalent metal. It is ion and content of the said bivalent metal ion in 100 g of resin components is 0.020 mol or more.

  Examples of the divalent metal ion include Ca, Mg, and Zn, and among these, Zn is preferable. By using Zn as a divalent metal ion, durability, particularly low temperature durability, is improved.

  The content of the divalent metal ion that neutralizes the carboxyl group includes (a) a divalent metal ion that neutralizes the carboxyl group of the high melt viscosity ionomer resin and (b) a carboxyl group of the low melt viscosity ionomer resin. This is the total amount of divalent metal ions to be neutralized, and can be determined by the following formula by the method described later.

  The content of the divalent metal ion that neutralizes the carboxyl group in 100 g of the resin component of the cover composition is preferably 0.020 mol or more, more preferably 0.025 mol or more, still more preferably 0.030 mol or more, Especially preferably, it is 0.035 mol or more. When the content of the divalent metal ion that neutralizes the carboxyl group is 0.020 mol or more, the durability, particularly low temperature durability, of the obtained golf ball is improved. On the other hand, the amount of the divalent metal ion that neutralizes the carboxyl group is preferably 0.16 mol or less, more preferably 0.15 mol or less, and still more preferably 0.12 mol or less. This is because if the amount of the divalent metal ion neutralizing the carboxyl group is too large, the fluidity of the cover composition may be lowered.

  In the present invention, it is preferable that the resin component of the golf ball cover composition is composed only of (a) a high melt viscosity ionomer resin and (b) a low melt viscosity ionomer resin. In addition to (a) a high melt viscosity ionomer resin and (b) a low melt viscosity ionomer resin as a resin component, (c) a non-ion whose melt viscosity (190 ° C.) by a flow tester is 5 Pa · s to 3000 Pa · s. It is also a more preferable aspect to contain a heat-resistant thermoplastic resin (hereinafter, simply referred to as “(c) nonionic thermoplastic resin”). Here, nonionic means that the acidic component (preferably carboxyl group) does not have an ion center neutralized.

  In this case, the content ratio of each component in the resin component is (a) high melt viscosity ionomer resin: 45 mass% to 70 mass%, (b) low melt viscosity ionomer resin: 5 mass% to 25 mass%, and (C) Nonionic thermoplastic resin: preferably 10% by mass to 40% by mass, (a) High melt viscosity ionomer resin: 50% by mass to 68% by mass, (b) Low melt viscosity ionomer resin: 6 It is more preferable that they are mass%-20 mass%, and (c) nonionic thermoplastic resin: 11 mass%-35 mass%.

  Examples of the (c) nonionic thermoplastic resin that can be contained in the golf ball cover composition of the present invention include, for example, the trade name “PEBAX” (registered trademark) (for example, “Pebax 2533” from Arkema Co., Ltd.). "") ", A commercially available thermoplastic polyamide elastomer;" NUCREL "(registered trademark) manufactured by Mitsui Dupont Polychemical Co., Ltd. N0200H ")" or an ethylene-acrylic acid copolymer marketed by "PRIMACOR (registered trademark) 5990I"; trade name "Toray DuPont" Hytrel® (eg, “Hytrel 3548” “Hytrel 4047”) ”, a thermoplastic polyester elastomer commercially available from Mitsubishi Chemical Co., Ltd. under the trade name“ Lavalon (registered trademark) ”, or the product name“ Primalloy (registered trademark) ” A thermoplastic polyester elastomer available from BASF Polyurethane Elastomers Co., Ltd. under the trade name “Elastolan (registered trademark)” (for example, “Elastolan ET880”). Can do.

  The melt viscosity (190 ° C.) of the nonionic thermoplastic resin (c) by a Brookfield viscometer is 5 Pa · s or more, preferably 10 Pa · s or more, more preferably 15 Pa · s or more, and 3000 Pa · s. Hereinafter, it is preferably 2800 Pa · s or less, more preferably 2500 Pa · s or less. If the melt viscosity (190 ° C.) of the nonionic thermoplastic resin (c) is 5 Pa · s or more, the durability of the resulting golf ball is improved, and if it is 3000 Pa · s or less, the cover composition This is because the moldability of is improved.

  In the present invention, the cover composition includes, in addition to the resin component described above, a pigment component such as a white pigment (for example, titanium oxide), a blue pigment (for example, ultramarine blue), a red pigment, zinc oxide, calcium carbonate, Specific gravity adjusting agents such as barium sulfate, dispersants, anti-aging agents, ultraviolet absorbers, light stabilizers, fluorescent materials or fluorescent whitening agents may be contained within a range that does not impair the performance of the cover.

  The content of the white pigment (titanium oxide) is 0.5 parts by mass or more, more preferably 1 part by mass or more, and more preferably 10 parts by mass or less, with respect to 100 parts by mass of the resin component constituting the cover. Is desirably 8 parts by mass or less. By making the content of the white pigment 0.5 parts by mass or more, the cover can be concealed. Moreover, it is because durability of the cover obtained may fall when content of a white pigment exceeds 10 mass parts.

  In the present invention, the melt flow rate (190 ° C. × 2.16 kg) of the cover composition is preferably 10 g / 10 min or more, more preferably 15 g / 10 min or more, further preferably 22 g / 10 min or more, and 100 g / 10 min or less. Preferably, 95 g / 10 min or less is more preferable, and 90 g / 10 min or less is still more preferable. This is because the moldability is enhanced by setting the melt flow rate of the cover composition to 10 g / 10 min or more.

  The bending rigidity of the cover composition is preferably 100 MPa or more, more preferably 110 MPa or more, further preferably 120 MPa or more, preferably 450 MPa or less, more preferably 420 MPa or less, and still more preferably 400 MPa or less. By setting the bending rigidity of the cover composition to 100 MPa or more, the obtained golf ball has an outer-hard / inner-soft structure, and a flight distance is increased. Moreover, by setting it as 450 Mpa or less, the hit feeling of the golf ball obtained when a cover becomes moderately soft becomes favorable.

  The rebound resilience of the cover composition is preferably 40% or more, more preferably 41% or more, and still more preferably 42% or more. By setting the impact resilience of the cover composition to 40% or more, the flight distance of the obtained golf ball is increased. Here, the bending rigidity and rebound resilience of the cover composition are the bending rigidity and rebound resilience measured by molding the cover composition into a sheet shape, and are measured by the measurement method described later.

  The slab hardness of the cover composition is 57 or more in Shore D hardness, more preferably 59 or more, and still more preferably 61 or more. When the slab hardness of the cover composition is 57 or more in Shore D hardness, the effect of lowering the spin on a shot of a driver or the like is increased, and the flight distance is further improved. The slab hardness of the cover composition is Shore D hardness and is preferably 66 or less. When the slab hardness of the cover composition is 66 or less in Shore D hardness, the feel at impact of the golf ball becomes better. Here, the slab hardness of the cover is a hardness measured by molding the cover composition into a sheet shape, and is measured by a measurement method described later.

  Although the aspect which shape | molds a cover using the composition for a cover is not specifically limited, the aspect which directly inject-molds the composition for a cover on a core, or shape | molds a hollow shell-like shell from a composition for a cover, and a core And a method of compression molding by coating with a plurality of shells (preferably a method of molding a hollow shell-shaped half shell from a cover composition and coating a core with two half shells) Can do. When forming a cover by injection molding the cover composition onto the core, the upper and lower molds for cover molding have hemispherical cavities, with pimples, which also serve as hold pins that allow part of the pimples to advance and retract. It is preferable to use what is. The cover can be molded by injection molding by protruding the hold pin, inserting the core and holding it, and then injecting the heat-melted composition for the cover and cooling, for example, In a mold clamped at a pressure of 9.8 MPa to 15.0 MPa, a cover composition heated and melted at 150 ° C. to 230 ° C. is injected in 0.1 seconds to 1 second, and cooled for 15 seconds to 60 seconds. And then open the mold.

  When the cover is molded by the compression molding method, the half shell can be molded by either the compression molding method or the injection molding method, but the compression molding method is preferred. The conditions for compression molding the cover composition into a half shell include, for example, a pressure of 1 MPa or more and 20 MPa or less and a flow start temperature of the cover composition of −20 ° C. or more and 70 ° C. or less. A molding temperature can be mentioned. By setting the molding conditions, a half shell having a uniform thickness can be molded. As a method for forming a cover using a half shell, for example, a method in which a core is covered with two half shells and compression-molded can be mentioned. As a condition for compression-molding the half shell into a cover, for example, at a molding pressure of 0.5 MPa or more and 25 MPa or less, a flow start temperature of the cover composition is −20 ° C. or more and 70 ° C. or less. A molding temperature can be mentioned. By setting the molding conditions, a golf ball cover having a uniform cover thickness can be molded.

The molding temperature means the maximum temperature that the surface of the concave portion of the lower mold reaches between the mold clamping and the mold opening. Moreover, the flow start temperature of the cover material is “Plur tester CFT-500” manufactured by Shimadzu Corporation, and the pellet-shaped cover material has a plunger area: 1 cm ² , DIE LENGTH: 1 mm, DIE DIA: 1 mm, load: 588.399N, start temperature: 30 ° C., temperature increase rate: 3 ° C./min.

  When a golf ball body is manufactured by covering a cover, a depression called dimple is usually formed on the surface. FIG. 1 is an enlarged cross-sectional view illustrating a dimple of the golf ball 2. In this figure, a cross section passing through the deepest portion De of the dimple 10 and the center of the golf ball 2 is shown. The vertical direction in FIG. 1 is the depth direction of the dimple 10. The depth direction is a direction from the center of gravity of the dimple 10 toward the center of the golf ball 2. In FIG. 1, an alternate long and two short dashes line 14 indicates a virtual sphere. The surface of the phantom sphere 14 is the surface of the golf ball 2 when it is assumed that the dimple 10 does not exist. The dimple 10 is recessed from the phantom sphere 14. The surface of the land 12 coincides with the surface of the phantom sphere 14.

  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, the dimple effect is difficult to obtain. Further, when the total number of dimples exceeds 500, the size of each dimple becomes small and it is difficult to obtain the dimple effect. The shape (plan view shape) of the dimple formed is not particularly limited, and a circular shape; a polygon such as a substantially triangular shape, a substantially square shape, a substantially pentagonal shape, or a substantially hexagonal shape; Alternatively, two or more kinds may be used in combination. Further, it is preferable that the golf ball main body with the cover formed is taken out of the mold and subjected to surface treatment such as deburring, washing, and sand blasting as necessary. Moreover, a mark can be formed if desired.

  Further, the golf ball of the present invention comprises a golf ball body having at least one core, an intermediate layer covering the core, and a cover covering the intermediate layer, and a coating film covering the golf ball body. It may be a painted golf ball.

  The resin component constituting the coating film (paint layer) is not particularly limited, and an acrylic resin, an epoxy resin, a polyurethane resin, a polyester resin, a cellulose resin, or the like can be used, but a two-component curable polyurethane resin described later is used. It is preferable to do. This is because when a two-component curable polyurethane resin is used, a coating film with further excellent durability can be obtained.

  The two-component curable polyurethane resin is a polyurethane resin obtained by reacting and curing a main agent and a curing agent, and examples thereof include those obtained by curing a main component containing a polyol component with a polyisocyanate compound and a derivative thereof. The main component containing the polyol component preferably contains urethane polyol. Urethane polyol is synthesized by a reaction between a polyisocyanate compound and a polyol.

  The film thickness of the coating film is not particularly limited, but is preferably 5 μm or more, more preferably 7 μm or more and 25 μm or less, and more preferably 18 μm or less. This is because if the film thickness is less than 5 μm, the coating film tends to wear and disappear due to continuous use, and if the film thickness exceeds 25 μm, the dimple effect decreases and the flight performance of the golf ball decreases.

  In the present invention, the golf ball cover has a thickness of 0.3 mm or more, preferably 0.4 mm or more, more preferably 0.5 mm or more, 1.0 mm or less, preferably 0.9 mm or less, more preferably 0.00 mm. 8 mm or less. If the thickness of the cover is 0.3 mm or more, the cover layer can be easily formed and workability is improved. In addition, if the cover thickness is 1.0 mm or less, the intermediate layer having a high specific gravity is disposed on the outer side of the golf ball relatively, so that a light structure is achieved within the outer weight, and when shot by a driver or the like The effect of lowering the spin is greater. Note that the thickness of the cover is an average value obtained by measuring at least four points of the thickness of the cover where the dimples are not formed, that is, immediately below the land 12 (see FIG. 1).

  The structure of the golf ball of the present invention will be described.

  A golf ball having at least one core, an intermediate layer covering the core, and a cover covering the intermediate layer, wherein the cover is formed from the cover composition, and the thickness of the cover Is 0.3 mm to 1.0 mm, and the slab hardness of the intermediate layer composition forming the intermediate layer is 35 to 55 in Shore D hardness.

  The core used for the golf ball of the present invention will be described.

  The core of the golf ball of the present invention is not particularly limited as long as it consists of at least one layer. As the structure of the core, for example, a single-layer core; a multilayer core composed of a center and a single-layer envelope layer covering the center; a multilayer composed of a center and a plurality of pieces or a plurality of envelope layers covering the center A core etc. can be mentioned. Among these, a single layer core is preferable.

  The core shape is preferably spherical. When the core shape is not spherical, the thickness of the intermediate layer and / or the cover becomes non-uniform. As a result, a portion where the intermediate layer and / or the cover performance is deteriorated partially occurs. On the other hand, the shape of the center is generally spherical, but a ridge may be provided so as to divide the surface of the spherical center, for example, the ridge so as to divide the surface of the spherical center equally. May be provided. As an aspect which provides the said protrusion, the aspect which provides a protrusion integrally with a center on the surface of a spherical center, the aspect which provides the envelope layer of a protrusion on the surface of a spherical center, etc. can be mentioned, for example.

  For example, when the spherical center is regarded as the earth, the ridge is preferably provided along an equator and an arbitrary meridian that equally divides the surface of the spherical center. For example, when the spherical center surface is divided into 8 parts, 90 degrees east longitude, 90 degrees west longitude, and east longitude (west longitude) with reference to the equator, an arbitrary meridian (longitude 0 degrees), and the meridian of such longitude 0 degrees It may be provided along the meridian of 180 degrees. In the case of providing the ridge, the concave portion partitioned by the ridge is filled with a plurality of envelope layers or a single envelope layer covering each of the recesses, so that the core has a spherical shape. It is preferable to do so. The cross-sectional shape of the protrusion is not particularly limited, and examples thereof include an arc shape or a substantially arc shape (for example, a shape in which notched portions are provided at portions intersecting or orthogonal to each other).

  The center of the single-layer core, or the center in the multilayer core composed of the center and one or more surrounding layers covering the center will be described.

  For the single-layer core or center, a conventionally known rubber composition (hereinafter sometimes simply referred to as “core rubber composition”) may be employed. For example, a base rubber, a crosslinking initiator, a co-crosslinking A rubber composition containing an agent and a filler can be molded by hot pressing.

  As the base rubber, natural rubber and / or synthetic rubber can be used. For example, polybutadiene rubber, natural rubber, polyisoprene rubber, styrene polybutadiene rubber, ethylene-propylene-diene rubber (EPDM) and the like can be used. Among these, it is particularly preferable to use a 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 said crosslinking initiator is mix | blended in order to bridge | crosslink a base rubber component. As the crosslinking initiator, an organic peroxide is suitable. Specifically, dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, Examples thereof include organic peroxides such as di-t-butyl peroxide, among which dicumyl peroxide is preferably used. The amount of the crosslinking initiator is preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, and preferably 3 parts by mass or less, more preferably 100 parts by mass of the base rubber. 2 parts by mass or less. If it is less than 0.2 parts by mass, the core tends to be too soft and the resilience tends to decrease. If it exceeds 3 parts by mass, it is necessary to increase the amount of co-crosslinking agent used in order to obtain an appropriate hardness. There is a lack of resilience.

  The co-crosslinking agent is not particularly limited as long as it has a function of crosslinking rubber molecules by graft polymerization to a base rubber molecular chain. For example, α, β- having 3 to 8 carbon atoms. Unsaturated carboxylic acid or its metal salt can be used, Preferably, acrylic acid, methacrylic acid, or these metal salts can be mentioned. Examples of the metal constituting the metal salt include zinc, magnesium, calcium, aluminum, sodium and the like, and zinc is preferably used because resilience increases. The amount of the co-crosslinking agent used is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and preferably 50 parts by mass or less, more preferably 40 parts by mass or less, relative to 100 parts by mass of the base rubber. It is. When the amount of the co-crosslinking agent used is less than 10 parts by mass, the amount of the crosslinking initiator must be increased in order to obtain an appropriate hardness, and the resilience tends to decrease. On the other hand, when the usage-amount of a co-crosslinking agent exceeds 50 mass parts, a core may become hard too much and there exists a possibility that a shot feeling may fall.

  The filler contained in the core rubber composition is mainly blended as a specific gravity adjusting agent for adjusting the specific gravity of the golf ball obtained as a final product to a range of 1.0 to 1.5. What is necessary is just to mix | blend as needed. Examples of the filler include inorganic fillers such as zinc oxide, barium sulfate, calcium carbonate, magnesium oxide, tungsten powder, and molybdenum powder. The blending amount of the filler is preferably 2 parts by mass or more, more preferably 3 parts by mass or more, and preferably 50 parts by mass or less, more preferably 35 parts by mass or less with respect to 100 parts by mass of the base rubber. It is. If the blending amount of the filler is less than 2 parts by mass, it is difficult to adjust the weight, and if it exceeds 50 parts by mass, the weight fraction of the rubber component tends to decrease and the resilience tends to decrease.

  In addition to the base rubber, the crosslinking initiator, the co-crosslinking agent, and the filler, an organic sulfur compound, an antiaging agent, a peptizer, and the like can be appropriately added to the core rubber composition.

  As the organic sulfur compound, diphenyl disulfides can be preferably used. Examples of the diphenyl disulfides include diphenyl disulfide; bis (4-chlorophenyl) disulfide, bis (3-chlorophenyl) disulfide, bis (4-bromophenyl) disulfide, bis (3-bromophenyl) disulfide, bis (4- Mono-substituted products such as fluorophenyl) disulfide, bis (4-iodophenyl) disulfide, bis (4-cyanophenyl) disulfide; bis (2,5-dichlorophenyl) disulfide, bis (3,5-dichlorophenyl) disulfide, bis ( 2,6-dichlorophenyl) disulfide, bis (2,5-dibromophenyl) disulfide, bis (3,5-dibromophenyl) disulfide, bis (2-chloro-5-bromophenyl) disulfide, bis (2-cyano Disubstituted compounds such as 5-bromophenyl) disulfide; trisubstituted compounds such as bis (2,4,6-trichlorophenyl) disulfide and bis (2-cyano-4-chloro-6-bromophenyl) disulfide; bis (2 , 3,5,6-tetrachlorophenyl) disulfide and the like; bis (2,3,4,5,6-pentachlorophenyl) disulfide, bis (2,3,4,5,6-pentabromophenyl) Examples include penta-substituted products such as disulfide. These diphenyl disulfides have some influence on the vulcanized state of the rubber vulcanizate and can improve the resilience. Among these, it is preferable to use diphenyl disulfide and bis (pentabromophenyl) disulfide from the viewpoint that a highly repulsive golf ball can be obtained. The compounding amount of the organic sulfur compound is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and preferably 5.0 parts by mass or less, more preferably 100 parts by mass of the base rubber. Is 3.0 parts by mass or less.

  The blending amount of the anti-aging agent is preferably 0.1 parts by mass or more and 1 part by mass or less with respect to 100 parts by mass of the base rubber. The content of the peptizer is preferably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the base rubber.

  The single layer core or center can be obtained by mixing, kneading and molding the above rubber composition in a mold. The conditions at this time are not particularly limited, but are usually performed at 130 ° C. to 180 ° C. and a pressure of 2.9 MPa to 11.8 MPa for 10 minutes to 40 minutes. For example, the rubber composition is heated at 130 ° C. to 200 ° C. It is preferable to heat for 10 minutes to 60 minutes, or after heating at 130 ° C. to 150 ° C. for 20 minutes to 40 minutes and then at 160 ° C. to 180 ° C. for 5 minutes to 15 minutes.

  An envelope layer in a multilayer core composed of a center and one or more envelope layers covering the center will be described.

  Examples of the envelope layer composition forming the envelope layer include the core rubber composition described above, the ionomer resin exemplified as the component (B), and a trade name “Pebax (registered trademark)” from Arkema Co., Ltd. ) (For example, “Pebax 2533”), a thermoplastic polyamide elastomer available from Toray DuPont Co., Ltd. under the trade name “Hytrel® (eg,“ Hytrel 3548 ”,“ Hytrel 4047 ”)” A commercially available thermoplastic polyester elastomer, a thermoplastic polyurethane elastomer marketed by BASF Japan under the trade name “Elastolan (registered trademark)” (for example, “Elastolan XNY97A”), and a trade name from Mitsubishi Chemical Corporation. Commercially available under “Lavalon®” (eg “Lavalon T3221C”) And a thermoplastic polystyrene elastomers may be mentioned are, further, barium sulfate, weighting agent, such as tungsten, an antioxidant, a pigment may be blended.

  The diameter of the core is preferably 39.1 mm or more, more preferably 39.4 mm or more, and further preferably 39.8 mm or more. When the diameter of the core is 39.1 mm or more, the core becomes large and the resilience becomes better. In addition, if the core is increased, a relatively high specific gravity intermediate layer is disposed on the outer side of the golf ball, and the golf ball is further lightened in the outer weight, thereby further reducing the spin and improving the flight distance. . On the other hand, the diameter of the core is preferably 40.7 mm or less, more preferably 40.5 mm or less, and still more preferably 40.1 mm or less. When the diameter of the core is 40.7 mm or less, the intermediate layer or the cover layer does not become too thin, and the function of the intermediate layer or the cover layer is more exhibited.

  As a core of the golf ball of the present invention, it is also a preferable aspect to use a core having a surface hardness (Hs) larger than the center hardness (Ho). The hardness difference (Hs−Ho) between the surface hardness (Hs) and the center hardness (Ho) of the core is preferably 7 or more in Shore D hardness, more preferably 10 or more, and still more preferably 13 or more. By making the surface hardness of the core larger than the center hardness, the effect of lowering the spin is increased, and the flight distance is further improved. The Shore D hardness difference between the core surface hardness and the center hardness is preferably 25 or less, more preferably 20 or less, and still more preferably 17 or less. This is because if the hardness difference becomes too large, the durability may be lowered. The hardness difference of the core can be provided by appropriately selecting the thermoforming conditions for the core or by using a multilayer core.

  The core has a center hardness (Ho) of preferably 30 or more in Shore D hardness, more preferably 33 or more, and still more preferably 36 or more. By setting the central hardness (Ho) of the core to 30 or more in Shore D hardness, the core does not become too soft and good resilience can be obtained. Further, the center hardness (Ho) of the core is preferably 50 or less in Shore D hardness, more preferably 47 or less, and further preferably 43 or less. By setting the center hardness (Ho) to 50 or less in Shore D hardness, the core does not become too hard and a good shot feeling can be obtained. In the present invention, the center hardness of the core means a hardness measured by a spring type hardness tester Shore D type at a center point of the cut surface by cutting the core into two equal parts.

  The surface hardness (Hs) of the core is preferably 44 or more in Shore D hardness, more preferably 47 or more, and still more preferably 50 or more. By setting the surface hardness Hs to 44 or more in Shore D hardness, the core does not become too soft and good resilience can be obtained. Further, the surface hardness Hs of the core is preferably 60 or less, more preferably 57 or less, and further preferably 55 or less in Shore D hardness. By setting the surface hardness Hs to 60 or less in Shore D hardness, the core does not become too hard and a good shot feeling can be obtained.

  Next, the intermediate layer covering the core will be described.

  Examples of the resin component of the intermediate layer composition forming the intermediate layer include, for example, a trade name “Himiran (registered trademark) (for example, Himiran AM7329)” from Mitsui DuPont Polychemical Co., Ltd. and a trade name “Surlyn” from DuPont. (Registered trademark) (for example, Surlyn 8945) as well as an ionomer resin commercially available under the trade name “Pebax (registered trademark)” (for example, “Pebax 2533”) from Arkema Co., Ltd. Polyamide elastomer, a thermoplastic polyester elastomer marketed by Toray DuPont Co., Ltd. under the trade name “Hytrel (registered trademark)” (for example, “Hytrel 3548” and “Hytrel 4047”). Last Run (registered trademark) (for example, “Elasto Run XNY 7A ")", a thermoplastic polyurethane elastomer commercially available under the trade name "Lavalon (registered trademark)" (for example, "Lavalon T3221C") from Mitsubishi Chemical Corporation, and the like. These may be used alone or in combination of two or more. Among these, from the viewpoint of resilience, the intermediate layer composition is preferably mixed with an ionomer resin and a thermoplastic styrene-based elastomer as a resin component.

  In addition to the resin component, the intermediate layer composition may contain a specific gravity adjusting agent, an antiaging agent, a pigment and the like as appropriate.

  Examples of the specific gravity adjusting agent include zinc oxide, barium sulfate, calcium carbonate, magnesium oxide, tungsten, and molybdenum. The blending amount of the specific gravity adjusting agent is preferably 15 parts by mass or more, more preferably 25 parts by mass or more, further preferably 30 parts by mass or more, with respect to 100 parts by mass of the resin component of the intermediate layer composition. The amount is preferably not more than part by mass, more preferably not more than 45 parts by mass, still more preferably not more than 40 parts by mass. If the blending amount of the specific gravity adjusting agent is 15 parts by mass or more, the density of the intermediate layer composition can be adjusted more easily, and if it is 50 parts by mass or less, without impairing the durability of the golf ball, The density of the intermediate layer can be increased.

  The slab hardness (Hm) of the intermediate layer composition is preferably 35 or more in Shore D hardness, more preferably 40 or more, still more preferably 45 or more, preferably 55 or less, more preferably 53 or less, even more preferably. Is 50 or less. By setting the slab hardness (Hm) of the intermediate layer composition to 35 or more, the resilience of the golf ball becomes better. On the other hand, when the slab hardness of the intermediate layer composition is 55 or less, the shot feeling becomes better. Here, the slab hardness (Hm) of the intermediate layer composition is a hardness measured by molding the intermediate layer composition into a sheet, and is measured by a measurement method described later.

Density of the intermediate layer composition is preferably from 1.10 g / cm ³ or more, more preferably 1.20 g / cm ³ or more, further preferably 1.30 g / cm ³ or more. If the density of the intermediate layer composition is 1.10 g / cm ³ or more, the moment of inertia of the golf ball can be further increased. The upper limit of the density of the intermediate layer composition is not particularly limited, is preferably 2.00 g / cm ^3, more preferably 1.80 g / cm ^3, more preferably at 1.60 g / cm ³ is there. The intermediate layer having a high density is preferably disposed on the outer side of the golf ball as much as possible.

In this case, the density of the core is preferably 1.15 g / cm ³ or less, more preferably 1.13 g / cm ³ or less, further preferably 1.10 g / cm ³ or less. If the density of the core is 1.15 g / cm ³ or less, the moment of inertia of the golf ball can be further increased. Further, the density of the cover composition is preferably 0.96 g / cm ³ or more, more preferably 0.98 g / cm ³ or more, and further preferably 1.00 g / cm ³ or more. In addition, it is preferable that the density of the composition for a cover is high, but since a high specific gravity filler is usually a colored thing, it is not preferable to mix | blend with a cover composition in large quantities.

  The slab hardness and specific gravity of the intermediate layer composition can be adjusted by appropriately selecting a combination of the above-described resin component or rubber composition, an additive content, and the like.

  As a method for forming the intermediate layer, for example, the intermediate layer is formed by covering the center with the intermediate layer composition. The method of forming the intermediate layer is not particularly limited. For example, the intermediate layer composition is formed into a half-shell half shell in advance, and the two are used to wrap the center, and 130 ° C to 170 ° C. Or a method of wrapping the center by injection molding the intermediate layer composition directly on the center, or the like.

  The thickness of the intermediate layer is preferably 1.2 mm or less, more preferably 1.0 mm or less, still more preferably 0.9 mm or less, preferably 0.5 mm or more, more preferably 0.6 mm or more. If the thickness of the intermediate layer is 1.2 mm or less, the center becomes relatively large, so the rebound of the golf ball becomes better. If the thickness is 0.5 mm or more, the effect of the high specific gravity intermediate layer is achieved. Since the moment of inertia becomes larger and the moment of inertia becomes larger, the spin can be further reduced.

  The golf ball of the present invention is not particularly limited as long as it has at least one core, an intermediate layer covering the core, and a cover covering the intermediate layer. As a specific example of the structure of the golf ball of the present invention, a three-piece golf ball having a single-layer core, an intermediate layer that covers the single-layer core, and a cover that covers the intermediate layer; a center and the center are covered A four-piece golf ball having a multi-layer core comprising an envelope layer, an intermediate layer covering the core, and a cover covering the intermediate layer; comprising a center and a plurality or multiple envelope layers covering the center A multi-piece golf ball having a multilayer core, an intermediate layer that covers the core, and a cover that covers the intermediate layer can be given. Among these, the present invention can be suitably applied to a three-piece golf ball having a single layer core, an intermediate layer covering the single layer core, and a cover covering the intermediate layer.

  When the golf ball of the present invention is a thread wound golf ball, a thread wound core may be used as the core. In such a case, as the thread wound core, for example, a thread core composed of a center formed by curing the core rubber composition described above and a thread rubber layer formed by winding the thread rubber around the center in a stretched state is used. do it. The thread rubber wound on the center may be the same as that conventionally used for the thread wound layer of a thread wound golf ball, for example, natural rubber or natural rubber and synthetic polyisoprene with sulfur, You may use what was obtained by vulcanizing the rubber composition which mix | blended the vulcanization adjuvant, the vulcanization accelerator, the anti-aging agent, etc. The thread rubber is stretched about 10 times on the center and wound to form a thread wound core.

  When the golf ball of the present invention has a diameter of 40 mm to 45 mm, the amount of compressive deformation (the amount by which the golf ball shrinks in the compression direction) from when the initial load 98 N is applied to when the final load 1275 N is applied is 2.5 mm or more. More preferably, it is 2.7 mm or more, More preferably, it is 3.0 mm or more, 4.0 mm or less is preferable, More preferably, it is 3.7 mm or less, More preferably, it is 3.5 mm or less. When the amount of compressive deformation is 2.5 mm or more, a good feel at impact is obtained, and when it is 4.0 mm or less, good resilience is obtained.

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

(1) Slab hardness (Shore D hardness) of the intermediate layer composition and the cover composition
A sheet having a thickness of about 2 mm was produced by hot press molding using the intermediate layer composition or the cover composition, and stored at 23 ° C. for 2 weeks. Three or more sheets of this sheet are stacked so as not to be affected by the measurement substrate, etc., and an automatic rubber hardness meter LA1 type manufactured by Kobunshi Keiki Co., Ltd. equipped with a spring type hardness meter Shore D type as defined in ASTM-D2240 It measured using.

(2) Core surface hardness, center hardness (Shore D hardness)
Using an automatic rubber hardness meter LA1 manufactured by Kobunshi Keiki Co., Ltd. equipped with a spring type hardness meter Shore D type as defined in ASTM-D2240, the Shore D hardness measured at the surface of the core was defined as the core surface hardness. The core was cut into a hemispherical shape, and the Shore D hardness measured at the center of the cut surface was defined as the core center hardness.

(3) Density of intermediate layer Pellet was produced using the composition for intermediate layer, and the density of this pellet was measured. The measurement was performed using ARCHIMEDES made by Chyo balance Corporation, and the solvent was ethanol.

(4) Melt viscosity (Pa · s) by flow tester
The melt viscosity was measured for the pellet-like sample under the following conditions using a flow characteristic evaluation apparatus (manufactured by Shimadzu Corporation, flow tester CFT-500D).
Measurement conditions DIE LENGTH: 1mm
DIE DIA: 1mm
Load: 294N
Temperature: 190 ° C

(5) Melt viscosity (Pa · s) by Brookfield viscometer
Using a Brookfield viscometer (manufactured by Tokyo Keiki Co., Ltd., BL type viscometer), the melt viscosity of the (b) low melt viscosity ionomer resin heated to 190 ° C. was measured. The measurement conditions were rotor No. 4 was used, and the rotation speed was 6 rpm.

(6) Melt flow rate (MFR) (g / 10 min)
MFR was measured according to JIS K7210 using a flow tester (manufactured by Shimadzu Corporation, Shimadzu flow tester CFT-100C). The measurement was performed under the conditions of a measurement temperature of 190 ° C. and a load of 2.16 kg.

(7) Divalent metal content (mol)
The mass of the divalent metal contained in the cover composition was quantified using an ICP emission analyzer (“P-4010” manufactured by Hitachi, Ltd.). Specifically, 6 ml of concentrated sulfuric acid was added to 100 mg of the cover composition, and water was added to the solution obtained by extraction (acid decomposition) using a microwave decomposition apparatus (manufactured by Microstone, ETHOS). A 250 ml sample was used as a measurement sample for ICP analysis.
From the obtained measured value, the divalent metal content per 100 g of the resin component constituting the cover composition was determined using the following formula.

(8) Compression deformation (mm)
The amount of deformation in the compression direction (the amount by which the golf ball shrinks in the compression direction) from when the initial load 98N was applied to the golf ball to when the final load 1275N was applied was measured.

(9) Flight distance A W # 1 driver (SRI Sports, XXIO S Loft 10 °) is attached to a swing robot manufactured by Trutemper, and a golf ball is hit at a head speed of 45 m / sec. To the resting point). The measurement was performed 10 times for each golf ball, and the average value was taken as the measured value of the golf ball.

(10) Directional stability A W # 1 driver (SRI Sports Corp., XXIO S Loft 10 °) is attached to a swing robot manufactured by True Temper so that the club face is perpendicular to the striking direction, and a head speed of 45 m / Set to seconds. Next, the ball was hit with the club face opened by 2 ° and the club face closed by 2 °. Then, the distance between the resting point when the club face was hit with 2 ° opened and the resting point when the club face was hit with 2 ° closed was measured. Two parallel lines passing through each stationary point were drawn so that the distance between the two stationary points was parallel to the striking direction, and the interval between these two parallel lines was measured. The measurement was performed 10 times for each golf ball, and the average value was taken as the measured value of the golf ball.

(11) Low Temperature Durability A metal head W # 1 driver was attached to a swing robot M / C manufactured by True Temper, and the head speed was set to 45 m / sec. Each golf ball was stored at −10 ° C. for 24 hours in a thermostat. After each golf ball was taken out of the thermostat, it was hit immediately and made to collide with the collision plate, and the number of hits repeatedly until the golf ball was broken was measured. Although the intermediate layer may be cracked even though it is not broken in appearance, in such a case, whether or not it is broken is determined from the deformation of the golf ball and the difference in the hitting sound.
The low temperature durability of each golf ball is determined according to the golf ball no. The number of hits for each golf ball was shown as an index value with the number of times 22 as 100. The larger the indexed value, the more excellent the golf ball is.

(12) Coating film adhesion (coating film durability)
A driver (1 W) was attached to a swing robot manufactured by True Temper, and a golf ball was repeatedly hit 100 times at a head speed of 45 m / s. The degree of peeling of the coating film was observed and evaluated based on the following criteria.
(Double-circle): There was no peeling in a coating film.
○: Peeling of less than 1 mm ² occurred on the coating film.
Δ: Peeling of less than 1 to 4 mm ² occurred on the coating film.
X: Peeling of 4 mm ² or more occurred in the coating film.

(13) Feeling of hitting An actual hitting test using a driver by 10 amateur golfers (advanced players) was performed, and the hitting feeling at the time of hitting was evaluated according to the following four levels.
A: Very good (soft)
○: Good (slightly soft)
Δ: Slightly poor (slightly hard)
X: Defect (hard)

(14) Restitution coefficient Each golf ball was impacted with 198.4 g of a metal cylinder at a speed of 40 m / sec, and the speeds of the cylinder and the golf ball before and after the collision were measured. The coefficient of restitution of the ball was calculated. The measurement was performed 12 pieces for each golf ball, and the average value was used as the coefficient of restitution of each golf ball. The coefficient of restitution is the golf ball no. The repulsion coefficient of 22 is shown as an indexed value with 100.0.

[Production of golf balls]
(1) Preparation of core The rubber composition for cores of the composition shown in Table 1 was kneaded and heated and pressed at 170 ° C. for 20 minutes in an upper and lower mold having hemispherical cavities to obtain spherical cores.

ポリブタジエンゴム：ＪＳＲ社製、「ＢＲ７３０（ハイシスポリブタジエン）」
アクリル酸亜鉛：日本蒸溜工業社製、「ＺＮＤＡ−９０Ｓ」
酸化亜鉛：東邦亜鉛社製、「銀嶺（登録商標）Ｒ」
硫酸バリウム：堺化学社製、「硫酸バリウムＢＤ」
ジフェニルジスルフィド：住友精化社製
ジクミルパーオキサイド：日油社製、「パークミル（登録商標）Ｄ」

Polybutadiene rubber: “BR730 (High cis polybutadiene)” manufactured by JSR Corporation
Zinc acrylate: “ZNDA-90S”, manufactured by Nippon Distillery Co., Ltd.
Zinc oxide: Toho Zinc Co., Ltd., “Ginseng (registered trademark) R”
Barium sulfate: Sakai Chemical Co., Ltd. “Barium sulfate BD”
Diphenyl disulfide: Dicumyl peroxide manufactured by Sumitomo Seika Co., Ltd .: NOF Corporation, “Park Mill (registered trademark) D”

(2) Preparation of intermediate layer composition and cover composition Using the compounding materials shown in Tables 2, 4 and 5, mixing with a twin-screw kneading extruder to prepare a pellet cover composition did. 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 blend was heated to 160-230 ° C. at the die position of the extruder.

サーリン８９４５：デュポン社製のナトリウムイオン中和エチレン−メタクリル酸共重合体系アイオノマー樹脂
ハイミランＡＭ７３２９：三井デュポンポリケミカル社製の亜鉛イオン中和エチレン−メタクリル酸共重合体系アイオノマー樹脂
ラバロンＴ３２２１Ｃ：三井化学社製のスチレン系エラストマー
タングステン：アライドマテリアル社製、タングステン粉末Ｃ５０Ｇ

Surlyn 8945: DuPont sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin Himira AM7329: Mitsui DuPont Polychemical Co., Ltd. zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin Lavalon T3221C: Mitsui Chemicals Styrene elastomer tungsten: Allied Materials, tungsten powder C50G

(3) Production of Golf Ball Main Body The intermediate layer covering the core was formed by injection molding the intermediate layer composition obtained above onto the spherical core obtained as described above. Subsequently, a cover was formed by injection molding a cover composition on the intermediate layer to produce a golf ball. The upper and lower molds for molding have hemispherical cavities, are provided with pimples, and also serve as hold pins in which a part of the pimples can advance and retreat. The hold pin is protruded, the core is inserted and then held, and a resin heated to 210 ° C. is injected into a mold clamped at a pressure of 80 tons in 0.3 seconds, cooled for 30 seconds, and the mold is opened to open a golf ball Was taken out. After the surface of the obtained golf ball body is sandblasted and marked, a clear paint is applied, and the paint is dried in an oven at 40 ° C. to form a 10 μm thick paint layer having a diameter of 42.8 mm. A golf ball having a mass of 45.4 g was obtained. The following were used as the clear paint.

[Preparation of clear paint]
(1) Main agent: urethane polyol 60 parts by mass of PTMG250 (manufactured by BASF: polyoxytetramethylene glycol, molecular weight 250) and 54 parts by mass of 550U (manufactured by Sumika Bayer Urethane: branched polyol having a molecular weight of 550) 120 masses of solvent It was dissolved in a part (toluene and methyl ethyl ketone), and dibutyltin dilaurate was added to this so that it might become 0.1 mass% with respect to the whole main ingredient. While maintaining this polyol at 80 ° C., 66 parts by mass of isophorone diisocyanate was added dropwise to prepare urethane polyol (solid content 60% by mass, hydroxyl value 75 mgKOH / g, weight average molecular weight 7808).
(2) Curing agent: Isophorone diisocyanate (Suika Bayer Urethane)
(3) Compounding ratio: NCO of curing agent / OH of main agent = 1.2 (mol ratio)

  The dimple pattern shown in Table 3, FIG. 2, and FIG. 3 was formed on the surface of the golf ball. In Table 3, “diameter” of the dimple means Di in FIG. 1, and “depth” means the distance between the tangent line T and the deepest point De.

  The results of evaluating the golf ball characteristics are shown in Tables 4 and 5.

ハイミラン１５５５：三井デュポンポリケミカル社製、ナトリウムイオン中和エチレン−メタクリル酸共重合体アイオノマー樹脂（フローテスターによる溶融粘度（１９０℃）：５４０Ｐａ・ｓ、メルトフローレイト（１９０℃×２．１６ｋｇ）：１０ｇ／１０ｍｉｎ）
ハイミランＡＭ７３２９：三井デュポンポリケミカル社製、亜鉛イオン中和エチレン−メタクリル酸共重合体アイオノマー樹脂（フローテスターによる溶融粘度（１９０℃）：１１００Ｐａ・ｓ、メルトフローレイト（１９０℃×２．１６ｋｇ）：５ｇ／１０ｍｉｎ）
なお、ハイミラン１５５５とハイミランＡＭ７３２９の混合物（質量比１：１）のフローテスターによる溶融粘度（１９０℃）は８５０Ｐａ・ｓである。
Ａｃｌｙｎ２９５：ハネウェル社製、エチレンと炭素数３〜８個のα，β−不飽和カルボン酸の二元共重合体の亜鉛中和物（ブルックフィールド型粘度計による溶融粘度（１９０℃）：４．５Ｐａ・ｓ、メルトフローレイト（１９０℃×２．１６ｋｇ）：１２００ｇ／１０ｍｉｎ）
Ａｃｌｙｎ２０１：ハネウェル社製、エチレンと炭素数３〜８個のα，β−不飽和カルボン酸の二元共重合体のカルシウム中和物（ブルックフィールド型粘度計による溶融粘度（１９０℃）：５．５Ｐａ・ｓ、メルトフローレイト（１９０℃×２．１６ｋｇ）：１８５ｇ／１０ｍｉｎ）
ベヘニン酸：日油社製、「ＮＡＡ−２２２Ｓ粉末」
ニュクレル１０５０Ｈ：三井・デュポンポリケミカル社製、エチレン・メタクリル酸共重合体（フローテスターによる溶融粘度（１９０℃）：６Ｐａ・ｓ、メルトフローレイト（１９０℃×２．１６ｋｇ）：１５ｇ／１０ｍｉｎ）
ウルトラマリンブルー：第一化成工業社製、群青Ｎｏ．１５００

High Milan 1555: Made by Mitsui DuPont Polychemical Co., Ltd., sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin (melt viscosity (190 ° C.) by flow tester: 540 Pa · s, melt flow rate (190 ° C. × 2.16 kg): 10g / 10min)
High Milan AM7329: Mitsui DuPont Polychemical Co., Ltd., zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin (melt viscosity (190 ° C.) by flow tester: 1100 Pa · s, melt flow rate (190 ° C. × 2.16 kg): 5g / 10min)
In addition, the melt viscosity (190 degreeC) by the flow tester of the mixture (mass ratio 1: 1) of high Milan 1555 and high Milan AM7329 is 850 Pa.s.
Aclyn 295: manufactured by Honeywell, a zinc neutralized binary copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms (melt viscosity with a Brookfield viscometer (190 ° C.): 4. 5 Pa · s, melt flow rate (190 ° C. × 2.16 kg): 1200 g / 10 min)
Aclyn 201: manufactured by Honeywell, a neutralized calcium copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms (melt viscosity (190 ° C.) by Brookfield viscometer): 5. 5 Pa · s, melt flow rate (190 ° C. × 2.16 kg): 185 g / 10 min)
Behenic acid: “NAA-222S powder” manufactured by NOF Corporation
NUCLEL 1050H: manufactured by Mitsui DuPont Polychemical Co., Ltd., ethylene / methacrylic acid copolymer (melt viscosity with a flow tester (190 ° C.): 6 Pa · s, melt flow rate (190 ° C. × 2.16 kg): 15 g / 10 min)
Ultramarine Blue: manufactured by Daiichi Kasei Kogyo Co., Ltd. 1500

  Golf ball no. 1 to 12, the cover contains a predetermined amount of (a) high melt viscosity ionomer resin and (b) low melt viscosity ionomer resin as the resin component, and the content of the divalent metal ion in 100 g of the resin component It is formed from a cover composition having an amount of 0.020 mol or more, and the thickness of the cover and the slab hardness of the intermediate layer composition are within the specified range of the present invention. 13 to 17 are cases where a predetermined amount of (c) a nonionic thermoplastic resin is further contained. The cover compositions used for these materials have a high melt flow rate and excellent fluidity despite their high resilience, and low molecular weight materials such as fatty acids do not bleed out during molding. It was. As a result, all these golf balls were excellent in the coefficient of restitution, flight distance, low temperature durability, coating film adhesion, and feel at impact.

Among these, the golf ball No. 1 in which the density of the intermediate layer is 1.10 g / cm ³ or more. 2-17 were excellent also in directional stability. Golf ball No. Since the slab hardness of the intermediate layer composition is high, the shot feeling is slightly inferior. No. 11 has a slightly inferior feel at impact because the cover is thick. Golf ball no. Nos. 7 and 14 have a low melt flow rate due to the high content of the component (a), and the workability is slightly inferior. Golf ball no. Since No. 17 has a large content of the component (c), the flight distance is slightly inferior.

  Golf ball no. 18 is a case where the slab hardness of the intermediate layer composition is less than 35 in Shore D hardness, but the coefficient of restitution is low and the flight distance is inferior. Golf ball no. 19 is a case where the slab hardness of the intermediate layer composition exceeds 55 in Shore D hardness, but the shot feeling is inferior.

  Golf ball no. No. 20 is a case where the component corresponding to (b) low melt viscosity ionomer resin is not contained, but the flowability of the cover composition was poor, and a cover having a thickness of 0.7 mm could not be formed. Golf ball no. 21 is a case where the ratio of the component (a) to the component (b) is small, but the coefficient of restitution is low and the flight distance is inferior. Golf ball no. 22 is a case where the component (b) is not contained and the component (c) is contained, but the cover can be molded, but since the amount of the divalent metal in the resin component is small, the low temperature durability is improved. Not done.

  Golf ball no. 23 is a case where a fatty acid was used, but bleed out occurred on the surface of the golf ball main body, and the coating film adhesion was not good.

  Golf ball no. Although 24 is a case where the thickness of a cover exceeds 1.0 mm, it is inferior to a shot feeling. In addition, since the cover is thick and the intermediate layer having a high density is relatively disposed on the inner side of the golf ball, the effect of lowering the spin is small for a shot of a driver or the like, and the flight distance and direction stability are also inferior. . Golf ball no. 25 is a golf ball No. 25. This is a case where a cover having a thickness of 0.2 mm was formed using the same cover composition as in No. 3, etc., but the fluidity was insufficient and the cover could not be molded.

  The present invention can provide a golf ball that improves the moldability of the cover, has excellent coating film adhesion and low temperature durability, and has an excellent flight distance and feel at impact. It is possible to provide a golf ball having excellent directional stability.

2 is an enlarged view of a cross section of a dimple formed on a golf ball surface. FIG. It is a top view of the dimple pattern formed on the golf ball surface. It is a front view of the dimple pattern formed on the golf ball surface.

Explanation of symbols

  2: Golf ball, 10: Dimple, 12: Land, 14: Virtual sphere, A: Dimple A, B: Dimple B, C: Dimple C, D: Dimple D, E: Dimple E, F: Dimple F, G: Dimple G, H: Dimple H, Ed: Edge, De: Dimple deepest part, Di: Dimple diameter, Ed: Edge, P: Pole, T: Tangent

Claims (6)

A golf ball having at least one core, an intermediate layer covering the core, and a cover covering the intermediate layer,
The cover is a resin component,
(A) A copolymer obtained by neutralizing at least a part of a carboxyl group of a binary copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms with ethylene and 3 to 8 carbon atoms A mixture of these α, β-unsaturated carboxylic acid and α, β-unsaturated carboxylic acid ternary copolymer neutralized at least part of the carboxyl groups with metal ions, or a mixture thereof. A high melt viscosity ionomer resin having a melt viscosity (190 ° C.) by a flow tester of 500 Pa · s to 100,000 Pa · s,
(B) A copolymer obtained by neutralizing at least part of a carboxyl group of a binary copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms with ethylene and 3 to 8 carbon atoms A ternary copolymer of α, β-unsaturated carboxylic acid and α, β-unsaturated carboxylic acid ester having at least a part of the carboxyl group neutralized with a metal ion, or a mixture thereof. A low melt viscosity ionomer resin having a melt viscosity (190 ° C.) of 1 Pa · s to 10 Pa · s and a melt flow rate (190 ° C. × 2.16 kg) of 100 g / 10 min to 2000 g / 10 min as measured by a Brookfield viscometer; The
(A) high melt viscosity ionomer resin / (b) low melt viscosity ionomer resin = 55 mass% to 99 mass% / 45 mass% to 1 mass%
At least one of the metal ions neutralizing the carboxyl group of the (a) high melt viscosity ionomer resin and / or (b) the low melt viscosity ionomer resin is a divalent metal ion, The valence metal ion content is formed from a cover composition that is 0.020 mol or more,
The cover has a thickness of 0.3 mm to 1.0 mm,
The golf ball according to claim 5, wherein the intermediate layer composition forming the intermediate layer has a slab hardness of 35 to 55 in Shore D hardness. The cover composition further includes (c) a nonionic thermoplastic resin having a melt viscosity (190 ° C.) by a flow tester of 5 Pa · s to 3000 Pa · s as a resin component. The content ratio of
(A) High melt viscosity ionomer resin: 45 mass% to 70 mass%
(B) Low melt viscosity ionomer resin: 5% by mass to 25% by mass, and
(C) Nonionic thermoplastic resin: The golf ball according to claim 1, which is 10% by mass to 40% by mass. The density of the intermediate layer is 1.10 g / cm ³ or more, golf ball according to claim 1 or 2 is 2.00 g / cm ³ or less. The golf ball according to any one of claims 1 to 3, wherein the slab hardness of the cover composition is 57 or more and 66 or less in Shore D hardness.   The golf ball according to claim 1, wherein the core has a diameter of 39.1 mm or more.   The golf ball according to claim 1, wherein the cover composition has a melt flow rate (190 ° C. × 2.16 kg) of 10 g / 10 min to 100 g / 10 min.

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