JP2014087702A - Resin composition for golf ball cover, golf ball, and method for manufacturing golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition for golf balls containing an ionomer resin and having excellent resilience and fluidity, and to provide a golf ball using the ionomer resin for a cover and having excellent ball hitting property, durability, and resilience.SOLUTION: The resin composition for golf ball covers contains: a resin component; and (C) a zinc compound. The resin component contains only (A) a ternary ionomer resin with a melt flow rate of 0.1 g/10 min-20 g/10 min, and (B) a binary copolymer and/or a ternary copolymer. A content ratio of the (A) component to the (B) component is (A)/(B)=50/50-80/20 in a mass ratio. A content of the (C) component is 0.1 pts.mass to 20 pts.mass with respect to a total 100 pts.mass of the (A) component and the (B) component, and the (C) component has the melt flow rate of 5 g/10 min or more, and includes no fatty acid and/or no metal salt thereof.

Description

  The present invention relates to a resin composition for a golf ball cover containing an ionomer resin and a golf ball using the same.

  As the structure of the golf ball, for example, a two-piece golf ball having a core and a cover, a three-piece golf ball having a core composed of a center and a single intermediate layer covering the center, and a cover covering the core, a center And a core composed of at least two or more intermediate layers covering the center and a cover covering the core. An ionomer resin is used as a material constituting each layer of the golf ball. The ionomer resin has high rigidity, and when used as a component of a golf ball, a golf ball having a large flight distance can be obtained. For this reason, ionomer resins are widely used as materials for golf ball intermediate layers and covers. However, there is room for improvement in the rigidity and fluidity of ionomer resins, and proposals have been made to improve these properties.

  For example, Patent Document 1 discloses, as an ionomer resin component, (a) a ternary ionomer resin made of a metal ion neutralized product of an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer having an acid content of 12% by weight or less; (B) an ionomer resin component containing a binary ionomer resin composed of a metal ion neutralized product of an olefin-unsaturated carboxylic acid copolymer having an acid content of 15% by weight or less in a weight ratio of 40:60 to 100: 0; And (c) a base resin containing an unneutralized random copolymer having an olefin and an unsaturated carboxylic acid as a monomer in a weight ratio of 75:25 to 100: 0, and (d) having 29 carbon atoms The main component is a mixture of metal soaps obtained by neutralizing the following organic acids with 1 to 3 metal ions at a weight ratio of 95: 5 to 80:20, and the melt index. MI) is the golf ball cover material is disclosed which is characterized in that at 1 dg / sec or more.

  Patent Document 2 includes a core and a cover, and the cover substantially includes 100 parts by mass of at least one ionomer resin, and more than 25 parts by mass and up to about 100 parts by mass of a metal stearate, A golf ball is disclosed in which the ionomer resin is a reaction product of an olefin having 2 to 8 carbon atoms and an unsaturated monocarboxylic acid having 3 to 8 carbon atoms.

  Patent Document 3 has a core and a cover, and the cover includes substantially 100 parts by mass of at least one ionomer resin and a fatty acid metal salt of more than 25 parts by mass and up to about 100 parts by mass, and the ionomer A golf ball is disclosed in which the resin is a reaction product of an olefin having 2 to 8 carbon atoms and an unsaturated monocarboxylic acid having 3 to 8 carbon atoms.

  Patent Document 4 includes 15 to 90 parts by weight of a metal salt (A) having a neutralization degree of 25 mol% or more of an ethylene / unsaturated carboxylic acid binary copolymer having an unsaturated carboxylic acid content of 10 to 30% by weight. And (meth) acrylic acid ester content of 12 to 45% by weight and unsaturated carboxylic acid content of 0.5 to 5% by weight of ethylene / (meth) acrylic acid ester / unsaturated carboxylic acid terpolymer ( B) A composition for a golf ball skin material containing 85 to 10 parts by weight is disclosed.

  Patent Document 5 discloses a multi-piece golf ball comprising a solid core, an intermediate layer formed on the solid core, and a cover formed on the intermediate layer. (A) 100 mass parts of olefin-unsaturated carboxylic acid random copolymer and / or olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester random copolymer, (b) fatty acid having a molecular weight of 280 or more or a derivative thereof 5 ~ 80 parts by mass, (c) a basic inorganic metal compound capable of neutralizing the acid groups in the above components (a) and (b), containing 0.1 to 10 parts by mass, and having a melt index of 1 And the intermediate layer has a Shore D hardness of 40 to 63, and the cover has a Shore D hardness of 45 to 68. A multi-piece golf ball is disclosed in which each Shore D hardness of the solid core center, intermediate layer and cover satisfies the relationship of solid core center hardness ≦ intermediate layer hardness ≦ cover hardness. .

  Patent Document 6 includes (a) a metal ion neutralized product of an olefin-unsaturated carboxylic acid binary random copolymer and / or an olefin-unsaturated carboxylic acid binary random copolymer, and (b) an olefin-unsaturated product. 100: 0 of a saturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymer and / or a metal ion neutralized product of an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymer in a mass ratio of 100: 0. With respect to 100 parts by mass of a resin component formulated so as to be 100: 0 to 50:50 by mass ratio of the base resin compounded to ˜25: 75 and (e) non-ionomer thermoplastic elastomer ( c) 5-80 parts by mass of a fatty acid having a molecular weight of 280-1500 and / or a derivative thereof, and (d) a base capable of neutralizing an unneutralized acid group in the base resin and component (c). Golf ball material, characterized in that an inorganic metal mixture by blending the compound 0.1 to 10 parts by weight as essential components is disclosed.

JP 2000-157646 A US Pat. No. 5,306,760 US Pat. No. 5,312,857 JP-A-6-292740 JP 2001-218873 A JP 2002-219195 A

  A golf ball using a highly rigid ionomer resin as a cover is excellent in resilience, but tends to have a low shot feeling. In order to improve the feel at impact, it has been studied to employ a soft ternary ionomer resin for the cover. However, the soft ternary ionomer resin has low fluidity and it is difficult to mold a thin cover. When the cover made of the soft ternary ionomer resin is thick, the core portion having high resilience cannot be increased in diameter, and the resilience of the golf ball is lowered. As a result, the flight distance of the golf ball decreases. Further, as a method for increasing the flight distance, there is a method of using a highly neutralized ionomer resin having high resilience. However, a highly neutralized ionomer resin has low fluidity, and for example, it is extremely difficult to injection mold a thin cover. As a technique for improving the fluidity of an ionomer resin, for example, a low molecular material such as a fatty acid or a metal salt thereof is added. However, in order to improve the fluidity, it is necessary to add a considerable amount of a low molecular material, and the low molecular material 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. Further, when the amount of the low-molecular material added is not more than a certain amount, the effect of improving the fluidity is low, and when it is more than a certain amount, the mechanical properties of the material are lowered, and the durability of the golf ball is lowered.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a soft resin composition for a golf ball cover that contains an ionomer resin and has excellent resilience and fluidity. Another object of the present invention is to provide a golf ball using an ionomer resin as a cover, which is excellent in feel at impact, durability, resilience, and coating film adhesion.

  The resin composition for a golf ball cover according to the present invention that has solved the above-mentioned problems includes (A) an olefin, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an α, β-unsaturated carboxylic acid. An ionomer resin comprising a metal ion neutralized product of a ternary copolymer with an acid ester, (B) a binary copolymer of an olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and And / or a terpolymer of an olefin, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α, β-unsaturated carboxylic acid ester, and (C) a zinc compound, The content ratio of the component (A) to the component (B) is (A) / (B) = 50/50 to 80/20 by mass ratio, and the content of the component (C) B) 0.1 parts by mass to 20 parts by mass with respect to 100 parts by mass in total of the components, 0 ° C., 2.16 kg load) is equal to or is 5 g / 10min or more.

  The (A) ternary ionomer resin contained in the resin composition for a golf ball cover of the present invention as a main component is soft and improves the feel at impact of the resulting golf ball. And (B) a binary copolymer of an olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and / or an α, β-unsaturated carboxylic acid having an olefin and 3 to 8 carbon atoms. The terpolymer of an acid and an α, β-unsaturated carboxylic acid ester improves the fluidity of the golf ball cover resin composition. (C) A zinc compound is used in order to neutralize the unneutralized carboxyl group which exists in (A) component and (B) component, and to improve the resilience of a resin composition. If the (C) zinc compound, which has a relatively slow neutralization reaction, is used, good fluidity can be maintained without the progress of the neutralization reaction in the process of melt mixing or extruding the golf ball cover resin composition. However, the neutralization reaction proceeds in the process of molding in the mold, and a golf ball resin composition having a resilience comparable to that obtained using a highly neutralized ionomer resin is obtained. As a result, the golf ball cover resin composition of the present invention can achieve both fluidity and resilience.

  Examples of the (C) zinc compound include zinc oxide, zinc hydroxide, and zinc carbonate. The slab hardness of the resin composition for a golf ball cover of the present invention is preferably a Shore D hardness of 35 to 55.

  The present invention includes a resin composition for a golf ball cover before neutralizing the carboxyl groups present in the components (A) and (B) with the (C) zinc compound, and a golf ball cover in which neutralization has progressed A resin composition is included. The golf ball cover resin composition having undergone neutralization includes those in which neutralization has partially progressed. Further, in the present invention, the golf ball cover resin composition before neutralization is referred to as “golf ball cover non-neutralized resin composition”, and the golf ball resin composition subjected to neutralization is “golf ball cover use”. The term “neutralized resin composition” is sometimes used, and the term “golf ball cover resin composition” includes any aspect unless otherwise specified.

Golf ball cover resin composition of the present invention, the peak area in the vicinity of 1600 cm ^-1 as measured by FT-IR before injection molding the peak area in the vicinity of A1,1700cm ^-1 and B1, in FT-IR after the injection molding the peak area around 1600 cm ^-1 when measuring the peak area in the vicinity of A2,1700cm ^-1 is taken as B2, A1, B1, A2 and B2 may satisfy the following expression. When the following formula is satisfied, the resilience of the obtained golf ball becomes good.
P1 = A1 / (A1 + B1)
P2 = A2 / (A2 + B2)
0.3 ≦ P1 ≦ 1.0
0.3 ≦ P2 ≦ 1.0
1.1 ≦ P2 / P1 ≦ 2.5
A1 and A2 are peak areas attributed to neutralized carboxyl groups, and B1 and B2 are peak areas attributed to unneutralized carboxyl groups. P1 and P2 indicate the degree of neutralization of the carboxyl group of the resin component. In the present invention, P2 / P1 is preferably within the above range. If it is lower than the lower limit, the effect of improving the resilience by neutralization with the zinc compound is increased, and if it is lower than the upper limit, the neutralization reaction does not proceed excessively, the fluidity can be maintained, and injection molding becomes easy. is there.

  The present invention includes a golf ball having a cover formed by injection molding the resin composition for a golf ball cover. The cover preferably has a thickness of 0.5 mm to 1.5 mm.

  According to the present invention, a soft golf ball cover resin composition containing an ionomer resin and excellent in resilience and fluidity can be obtained. In addition, a golf ball excellent in feel at impact, flight distance, durability and coating film adhesion can be obtained.

FT-IR measurement chart of one embodiment of resin composition for golf ball cover of the present invention

  The resin composition for a golf ball cover of the present invention is a ternary copolymer of (A) an olefin, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an α, β-unsaturated carboxylic acid ester. An ionomer resin composed of a neutralized metal ion of the coalescence, (B) a binary copolymer of an olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and / or an olefin and a carbon number of 3 -A ternary copolymer of eight [alpha], [beta] -unsaturated carboxylic acids and [alpha], [beta] -unsaturated carboxylic acid esters, and (C) a zinc compound, (A) component and (B) component Is a mass ratio of (A) / (B) = 50/50 to 80/20, and the content of the component (C) is 100 parts by mass in total of the component (A) and the component (B). The melt flow rate (190 ° C., 2.16 kg load) is 5 parts by mass with respect to 0.1 to 20 parts by mass. Characterized in that at / 10min or more.

  First, in the metal ion of the terpolymer of (A) olefin used in the present invention, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an α, β-unsaturated carboxylic acid ester. An ionomer resin made of a Japanese product (in the present invention, simply referred to as “ternary ionomer resin”) will be described. Examples of the (A) ternary ionomer resin include a terpolymer of an olefin, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an α, β-unsaturated carboxylic acid ester. And those obtained by neutralizing at least a part of the carboxyl groups with metal ions. The olefin is preferably an olefin having 2 to 8 carbon atoms, and examples thereof include ethylene, propylene, butene, pentene, hexene, heptene, octene and the like, and ethylene is particularly preferable. Examples of the α, β-unsaturated carboxylic acid include acrylic acid, methacrylic acid, fumaric acid, maleic acid, crotonic acid and the like, and acrylic acid or methacrylic acid is particularly preferable. Examples of the α, β-unsaturated carboxylic acid ester include methyl, ethyl, propyl, n-butyl, isobutyl ester and the like such as acrylic acid, methacrylic acid, fumaric acid and maleic acid, and particularly acrylic acid ester. Or a methacrylic acid ester is preferable. Among these, the (A) ternary ionomer resin is preferably a metal ion neutralized product of an ethylene- (meth) acrylic acid- (meth) acrylic acid ester terpolymer.

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

The neutralization degree of the carboxyl group of the (A) ternary ionomer resin is preferably 20 mol% or more, more preferably 30 mol% or more, preferably 90 mol% or less, more preferably 85 mol% or less. is there. If the degree of neutralization is 20 mol% or more, the resilience and durability of the golf ball obtained using the resin composition of the present invention will be good, and if it is 90 mol% or less, the resin composition of the present invention will be. The fluidity of the is improved (moldability is good). In addition, the neutralization degree of the carboxyl group of ionomer resin can be calculated | required by a following formula.
Degree of neutralization of ionomer resin = 100 × number of moles of neutralized carboxyl groups in ionomer resin / total number of moles of carboxyl groups in ionomer resin

  Examples of the metal ion that neutralizes at least a part of the carboxyl group of the ternary ionomer resin (A) include monovalent metal ions such as sodium, potassium, and lithium; 2 such as magnesium, calcium, zinc, barium, and cadmium. Valent metal ions; trivalent metal ions such as aluminum; and other ions such as tin and zirconium. The (A) ternary ionomer resin used in the present invention is preferably neutralized with zinc. This is because the use of the (A) ternary ionomer resin neutralized with zinc improves the durability and low temperature durability of the golf ball.

  A specific example of the ternary ionomer resin is exemplified by trade names such as “Himilan (registered trademark)” (for example, Himilan AM7327 (Zn), Himilan 1855 (Zn) available from Mitsui DuPont Polychemical Co., Ltd. ), Himilan 1856 (Na), Himilan AM7331 (Na), etc.). Further, as ternary ionomer resins commercially available from DuPont, “Surlin 6320 (Mg), Surlyn 8120 (Na), Surlyn 8320 (Na), Surlyn 9320 (Zn), Surlyn 9320W (Zn), etc.)” Can be mentioned. Examples of the ternary ionomer resins commercially available from ExxonMobil Chemical Co., Ltd. include “Iotech 7510 (Zn), Iotech 7520 (Zn), etc.)”. In addition, Na, Zn, Mg, etc. described in parentheses after the trade name indicate the type of neutralized metal ion. The ternary ionomer resins may be used alone or in combination of two or more.

  The flexural modulus of the (A) ternary ionomer resin is preferably 10 MPa or more, more preferably 11 MPa or more, further preferably 12 MPa or more, preferably 100 MPa or less, more preferably 97 MPa or less, and still more preferably 95 MPa or less. It is. If the bending rigidity of the (A) ternary ionomer resin is too low, the spin rate on driver shots tends to increase and the flight distance tends to decrease. If the bending rigidity is too high, the durability of the golf ball May decrease.

  The melt flow rate (190 ° C., 2.16 kg load) of the ternary ionomer resin (A) is preferably 0.1 g / 10 min or more, more preferably 0.3 g / 10 min or more, still more preferably 0.5 g / It is 10 min or more, preferably 20 g / 10 min or less, more preferably 15 g / 10 min or less, still more preferably 10 g / 10 min or less. When the melt flow rate (190 ° C., 2.16 kg load) of the ternary ionomer resin (A) is 0.1 g / 10 min or more, the fluidity of the golf ball cover resin composition is improved, and the thin cover Molding becomes possible. Further, when the melt flow rate (190 ° C., 2.16 kg load) of the (A) ternary ionomer resin is 20 g / 10 min or less, the durability of the obtained golf ball becomes better.

  The slab hardness of the (A) ternary ionomer resin is preferably 20 or more in Shore D hardness, more preferably 25 or more, further preferably 30 or more, preferably 70 or less, more preferably 65 or less, still more preferably. Is 60 or less. If the slab hardness is 20 or more in Shore D hardness, the resulting cover will not be too soft and the resilience of the golf ball will be good. Further, if the slab hardness is 70 or less in Shore D hardness, the obtained cover will not be too hard, and the durability of the golf ball will be better.

  Next, (B) a binary copolymer of an olefin and a C 3-8 α, β-unsaturated carboxylic acid, and / or an olefin and a C 3-8 α, β-unsaturated The terpolymer of carboxylic acid and α, β-unsaturated carboxylic acid ester will be described. In the present invention, (B) a binary copolymer of an olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and / or an olefin and an α, β having 3 to 8 carbon atoms. -A terpolymer of an unsaturated carboxylic acid and an α, β-unsaturated carboxylic acid ester is simply referred to as a “binary and / or ternary copolymer”, and an olefin and an α having 3 to 8 carbon atoms. , Β-unsaturated carboxylic acid is referred to simply as “binary copolymer”, which is an olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α, β-unsaturated carboxylic acid. A terpolymer with a saturated carboxylic acid ester is sometimes simply referred to as a “terpolymer”. The binary and / or ternary copolymer enhances the fluidity of the resin composition for a golf ball cover.

  The binary copolymer is a binary copolymer of an olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and is a nonionic one whose carboxyl group is not neutralized. It is. The terpolymer is a terpolymer of an olefin, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an α, β-unsaturated carboxylic acid ester, the carboxyl group of which is It is non-neutralized and nonionic. Examples of the olefin, the α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and the α, β-unsaturated carboxylic acid ester are exemplified as constituting “(A) ternary ionomer resin”. The same can be used. As the binary copolymer used in the present invention, a binary copolymer of ethylene and (meth) acrylic acid is preferable, and as the ternary copolymer, ethylene, (meth) acrylic acid and (meth) acrylic are used. Ternary copolymers with acid esters are preferred.

  The content of the α, β-unsaturated carboxylic acid component having 3 to 8 carbon atoms in the (B) binary and / or ternary copolymer is preferably 4% by mass or more, more preferably 5% by mass. Above, 25 mass% or less is preferable, More preferably, it is 20 mass% or less.

  The melt flow rate (190 ° C., 2.16 kg load) of the (B) binary and / or ternary copolymer is preferably 5 g / 10 min or more, more preferably 10 g / 10 min or more, and further preferably 15 g / 10 min. It is above, 1700 g / 10min or less is preferable, More preferably, it is 1500 g / 10min or less, More preferably, it is 1300 g / 10min or less. If the melt flow rate (190 ° C., 2.16 kg load) of the (B) binary and / or terpolymer is 5 g / 10 min or more, the fluidity of the resin composition will be good and a thin cover will be molded. It becomes easy to do. Further, when the melt flow rate (190 ° C., 2.16 kg load) of the (B) binary and / or ternary copolymer is 1700 g / 10 min or less, the durability of the obtained golf ball becomes better. .

Specific examples of the binary copolymer are exemplified by trade names, for example, trade names “NUCREL® (for example,“ Nucrel N1050H ”,“ Nucrel N2050H ”,“ Nucrel ”from Mitsui DuPont Polychemical Co., Ltd.). An ethylene-methacrylic acid copolymer marketed under the trade name “PRIMACOR (registered trademark) 5980I” from Dow Chemical Co., Ltd. An acrylic acid copolymer etc. can be mentioned.
Specific examples of the ternary copolymer are exemplified by trade names: “Nucrel (registered trademark)” (for example, “Nucrel AN4318” and “Nucrel AN4319”) commercially available from Mitsui DuPont Polychemical Co., Ltd. Trade name "NUCREL" (registered trademark) (for example, "Nuclele AE") commercially available from DuPont, trade name "PRIMACOR (registered trademark) (for example, commercially available from Dow Chemical Company) , “PRIMACOR AT310”, “PRIMACOR AT320”) ”and the like. The binary and / or ternary copolymers may be used alone or in combination of two or more.

Next, (C) a zinc compound will be described. (C) A zinc compound is used in order to neutralize the unneutralized carboxyl group which exists in (A) component and (B) component, and to improve the resilience of a resin composition. (C) Zinc compound with relatively slow neutralization reaction By using a zinc compound, the neutralization reaction does not proceed in the process of melting and mixing the resin composition for golf ball cover or the process of extrusion, and maintains good fluidity However, in the process of molding in the mold, the neutralization reaction proceeds, and a golf ball resin composition having the same degree of resilience as using a highly neutralized ionomer resin can be obtained. (C) Examples of the zinc compound include zinc powder, oxide (zinc oxide), hydroxide (zinc hydroxide), sulfide (zinc sulfide), phosphide, halide (zinc fluoride, zinc chloride) , Zinc bromide, zinc iodide), oxo acid salts (such as zinc sulfate, zinc carbonate, zinc phosphate), organic zinc compounds (such as dimethyl zinc and diphenyl zinc), complex compounds, and the like. Among these, as the (C) zinc compound, zinc oxide (ZnO), zinc hydroxide (Zn (OH) ₂ ), or zinc carbonate (ZnCO ₃ ) is preferable. This is because (B) the binary and / or ternary copolymer can be neutralized without reducing the fluidity of the resin composition. The shape of the zinc compound particles is not particularly limited, and examples thereof include granular shapes, plate shapes, needle shapes, and tetrapot shapes (for example, “Panatetra” manufactured by Amtec Corporation). Zinc oxide is sometimes used as a specific gravity adjusting agent or pigment for the cover, but zinc oxide used as a pigment or specific gravity adjusting agent is subjected to a surface treatment in order to increase the dispersibility in the resin. There are many cases. On the other hand, the zinc oxide that can be suitably used in the present invention is preferably not surface-treated or lightly surface-treated in order to enhance the neutralizing ability.

Golf ball cover resin composition of the present invention, the peak area in the vicinity of 1600 cm ^-1 as measured by FT-IR (Fourier transform infrared spectrophotometer) before injection molding the peak area in the vicinity of A1,1700cm ^-1 B1 When P1 is calculated by the following equation, P1 is preferably 0.3 or more, more preferably 0.31 or more, preferably 1.0 or less, and more preferably 0.99 or less. When P1 is within the above range, the fluidity of the resin composition during injection molding is good.
P1 = A1 / (A1 + B1)
In the formula, A1 is a peak area attributed to a neutralized carboxyl group, and B1 is a peak area attributed to an unneutralized carboxyl group. P1 is the ratio of the neutralized carboxyl group in the entire carboxyl group, and indicates the degree of neutralization of the resin component.

Golf ball cover resin composition of the present invention, the peak area in the vicinity of A2,1700cm ^-1 peak area around 1600 cm ^-1 when measured at FT-IR (Fourier transform infrared spectrophotometer) after the injection molding When B2 is calculated by the following formula, P2 is preferably 0.3 or more, more preferably 0.31 or more, preferably 1.0 or less, and more preferably 0.99 or less. If P2 is within the above range, the resulting golf ball has good resilience.
P2 = A2 / (A2 + B2)
In the formula, A2 is a peak area attributed to a neutralized carboxyl group, and B2 is a peak area attributed to an unneutralized carboxyl group. P2 is the ratio of neutralized carboxyl groups in the entire carboxyl group, and indicates the degree of neutralization of the resin component.

  Further, P2 / P1 is preferably 1.1 or more, more preferably 1.2 or more, further preferably 1.3 or more, preferably 2.5 or less, more preferably 2.4 or less, and 2.3 or less. Further preferred. P2 / P1 indicates a change in the neutralization degree of the golf ball before and after injection molding. If P2 / P1 is equal to or higher than the lower limit, the effect of improving the resilience by neutralization with the zinc compound is increased, and if it is equal to or lower than the upper limit, the neutralization reaction does not proceed excessively and the fluidity can be maintained. This is because injection molding is facilitated.

  In the golf ball cover resin composition of the present invention, the content ratio of (A) ternary ionomer resin to (B) binary and / or ternary copolymer is expressed by mass ratio, Component (B) is preferably 50/50 to 80/20, more preferably 55/45 to 75/25, and still more preferably 60/40 to 70/30. It is because it becomes easy to make high fluidity and a softness | flexibility compatible by making content ratio of (A) component and (B) component into the said range.

  The content of the (C) zinc compound in the golf ball cover resin composition of the present invention is preferably 0.1 parts by mass or more with respect to 100 parts by mass in total of the component (A) and the component (B). More preferably, it is 0.2 parts by mass or more, more preferably 0.5 parts 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 or less. If the content of the (C) zinc compound is 0.1 parts by mass or more with respect to 100 parts by mass in total of the components (A) and (B), the durability of the resulting golf ball is improved. It is. Moreover, if the content of the (C) zinc compound is 20 parts by mass or less with respect to a total of 100 parts by mass of the component (A) and the component (B), the fluidity of the resin composition can be secured. is there.

  The resin composition for a golf ball cover of the present invention further includes a pigment component such as a white pigment (titanium oxide) and a blue pigment, a weight adjuster, a dispersant, an anti-aging agent, an ultraviolet absorber, a light stabilizer, a fluorescent material, You may contain a fluorescent whitening agent etc. in the range which does not impair the performance of a golf ball. Further, the resin composition for a golf ball cover of the present invention may use a fatty acid and / or a metal salt thereof as a fluidity modifier as long as the effects of the present invention are not impaired. Therefore, it is preferable not to use low molecular weight materials such as fatty acids and / or metal salts thereof in combination.

  The content of the white pigment (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, with respect to 100 parts by mass of the resin component. More preferred. By making the content of the white pigment 0.5 parts by mass or more, the golf ball cover can be concealed. Further, when the content of the white pigment exceeds 10 parts by mass, the durability of the obtained golf ball may be lowered.

  The resin composition for a golf ball cover of the present invention preferably contains only (A) a ternary ionomer resin and (B) a binary and / or ternary copolymer as the resin component. Other thermoplastic elastomers and thermoplastic resins may be contained within a range that does not impair the effect. In this case, the total content of (A) ternary ionomer resin and (B) binary and / or ternary copolymer in the resin component contained in the resin composition is preferably 50% by mass or more. It is preferably at least 90% by mass, more preferably at least 90% by mass.

  Specific examples of the other thermoplastic elastomer include, for example, a thermoplastic polyamide elastomer marketed by Arkema Co., Ltd. under the trade name “Pebax (for example,“ Pebax 2533 ”)”, and a trade name “BASF Japan Ltd.” Thermoplastic polyurethane elastomer marketed by Elastollan (for example, “Elastollan XNY85A”), commercially available under the trade name “Hytrel” (for example, “Hytrel 3548”, “Hytrel 4047”) from Toray DuPont Co., Ltd. And thermoplastic polystyrene elastomers commercially available from Mitsubishi Chemical Corporation under the trade name “Lavalon (for example,“ Lavalon T3221C ”). As said other thermoplastic resin, the ionomer resin of the binary copolymer system which consists of an olefin and C3-C8 alpha, beta-unsaturated carboxylic acid can be mentioned.

  The resin composition for a golf ball cover of the present invention is obtained by, for example, dry blending (A) a ternary ionomer resin, (B) a binary and / or ternary copolymer, and (C) a zinc compound. can get. Further, the dry blended mixture may be extruded to be pelletized. For dry blending, for example, it is preferable to use a mixer capable of blending pellet-shaped raw materials, and more preferably a tumbler type mixer. For the extrusion, a known extruder such as a single screw extruder, a twin screw extruder, or a twin screw single screw extruder can be used. Examples of extrusion conditions include a screw diameter of 45 mm, a screw rotation speed of 50 rpm to 400 rpm, a screw L / D = 35, and a cylinder temperature of 140 ° C. or higher and 200 ° C. or lower when a twin screw extruder is used. . If it is 200 ° C. or higher, the neutralization reaction proceeds and the fluidity is lowered.

  The melt flow rate (190 ° C. × 2.16 kg load) of the resin composition for a golf ball cover of the present invention is preferably 5 g / 10 min or more, more preferably 6 g / 10 min or more, preferably 100 g / 10 min or less, and 75 g / 10 min. The following is more preferable, and 50 g / 10 min or less is more preferable. If the melt flow rate of the resin composition is within the above range, molding into a thin layer is facilitated.

  The slab hardness of the resin composition for a golf ball cover of the present invention is preferably 35 or more in Shore D hardness, more preferably 36 or more, further preferably 37 or more, preferably 55 or less, more preferably 54 or less, and 53 or less. Further preferred. By using a resin composition having a slab hardness of Shore D hardness of 35 or more, the rigidity is increased and excellent resilience (flying distance) is obtained. On the other hand, by using a resin composition having a slab hardness of 55 or less in Shore D hardness, the shot feeling and durability of the obtained golf ball are further improved. Here, the slab hardness of the resin composition is a hardness measured by molding the resin composition into a sheet shape, and is measured by a measurement method described later.

  The flexural modulus of the resin composition for a golf ball cover of the present invention is preferably 10 MPa or more, more preferably 20 MPa or more, further preferably 30 MPa or more, preferably 150 MPa or less, more preferably 145 MPa or less, still more preferably 140 MPa. It is as follows. If the bending rigidity of the golf ball cover resin composition is too low, the spin rate on driver shots tends to increase and the flight distance tends to decrease. If the bending rigidity is too high, the durability of the golf ball decreases. There is a case.

  The golf ball of the present invention is particularly limited as long as it is a golf ball having a cover formed by injection molding the resin composition for a golf ball cover of the present invention (hereinafter sometimes simply referred to as “cover composition”). Not. For example, a two-piece golf ball having a single-layer core and a cover disposed so as to cover the core; a core comprising a center and a single-layer intermediate layer disposed so as to cover the center; A three-piece golf ball having a cover disposed to cover the core; or a core comprising a center and one or more intermediate layers disposed to cover the center; and covering the core A golf ball in which a cover constituting a multi-piece golf ball having the cover arranged in this manner (including the three-piece golf ball) is formed by injection molding the resin composition for golf ball cover can be given.

  The cover of the golf ball of the present invention is formed from a cover composition. As a method of molding the cover, for example, a method of molding a hollow shell from the cover composition, and covering and compressing the core with a plurality of shells (preferably molding a hollow half shell from the cover composition And a method in which the core is covered with two half shells and compression-molded), and a cover composition is directly injection-molded on the core. The golf ball cover of the present invention is preferably formed by injection molding. This is because the cover can be more easily produced by injection molding.

  When the cover composition is directly injection-molded on the core to form a cover, the cover-like cover composition obtained by extrusion may be used for injection molding, or a base resin component or pigment Direct injection molding may be performed by dry blending a cover material such as. As the upper and lower molds for forming the cover, it is preferable to use a cover mold having a hemispherical cavity and having a pimple and also serving as a hold pin in which a part of the pimple can advance and retreat. The cover can be formed by injection molding by projecting the hold pin, inserting the core, holding the cover, injecting the cover composition, and cooling.

  When a cover is molded using an injection molding machine having an injection device and a molding die, the temperature (set temperature of the device) at the cylinder (barrel) portion of the injection device is preferably 200 ° C or higher, and 210 ° C or higher. More preferably, 270 ° C. or lower is preferable, and 260 ° C. or lower is preferable. By setting the temperature in the cylinder (barrel) portion within the above range, the fluidity of the golf ball resin composition can be maintained, and the (A) component and the (B) component non-neutralized carboxyl group ( C) The neutralization reaction with the zinc compound proceeds.

  Further, when molding the cover, a depression called dimple is usually formed on the surface. Further, it is preferable that the golf ball main body with the cover formed is taken out from the mold and subjected to surface treatment such as deburring, washing, and sand blasting as necessary. Moreover, a coating film and a mark can also be formed if desired. 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 thickness of the golf ball cover is preferably 1.5 mm or less, more preferably 1.3 mm or less, and even more preferably 1.0 mm or less. By setting the thickness to 1.5 mm or less, the outer diameter of the core can be increased, so that the resilience can be improved. Although the minimum of the thickness of a cover is not specifically limited, For example, 0.5 mm is preferable, 0.6 mm is more preferable, and 0.7 mm is further more preferable. If it is less than 0.5 mm, it may be difficult to form the cover.

  Next, the core used for the golf ball of the present invention will be described. Examples of the structure of the core include a single-layer core and a core having a center and one or more intermediate layers covering the center. Examples of the core having a center and one or more intermediate layers covering the center include, for example, a core composed of a center and a single-layer intermediate layer covering the center; There are cores composed of layers. The core shape is preferably spherical. When the core shape is not spherical, the thickness of the cover is not uniform. As a result, the cover performance may partially deteriorate. 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 intermediate | middle 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. When providing the ridge, the concave portion partitioned by the ridge is filled with a plurality of intermediate layers or a single intermediate layer covering each of the concave portions, and the shape of the core is made spherical. 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 core or center of the golf ball of the present invention includes, for example, a rubber composition containing a base rubber, a crosslinking initiator, a co-crosslinking agent, and, if necessary, a filler (hereinafter simply referred to as “center rubber composition”). In some cases).

  As the base rubber, natural rubber or synthetic rubber can be used. For example, natural rubber, polybutadiene rubber, polyisoprene rubber, styrene polybutadiene rubber, ethylene-propylene-diene rubber (EPDM) or 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, and sodium, and zinc is preferably used because resilience increases.

  The amount of the co-crosslinking agent used is 10 parts by mass or more, more preferably 20 parts by mass or more, and 50 parts by mass or less, more preferably 40 parts by mass or less with respect to 100 parts by mass of the base rubber. desirable. When the amount of the co-crosslinking agent used is less than 10 parts by mass, the amount of the organic peroxide 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 center 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, and is necessary. It may be blended according to. 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 2 parts by mass or more, more preferably 3 parts by mass or more, and 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. desirable. 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, the center rubber composition may further contain an organic sulfur compound, an antioxidant, a peptizer, and the like as appropriate.

  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 with respect to 100 parts by mass of the base rubber. More preferably, it 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. Moreover, it is preferable that the compounding quantity of a peptizer is 0.1 to 5 mass parts with respect to 100 mass parts of base rubber.

  The hot-press molding conditions for the center rubber composition may be appropriately set according to the rubber composition, but are usually heated at 130 to 200 ° C. for 10 to 60 minutes, or at 130 to 150 ° C. for 20 to 40 minutes. After heating, it is preferable to heat at 160 to 180 ° C. for 2 to 5 minutes.

  When the core structure of the golf ball of the present invention is a core comprising a center and one or more intermediate layers covering the center, the diameter of the center is preferably 34.8 mm or more, more preferably 35.0 mm or more. 41.2 mm or less is preferable, and 41.0 mm or less is more preferable. If the diameter of the center is smaller than 34.8 mm, the intermediate layer or the cover needs to be thicker than desired, and as a result, the resilience may decrease. On the other hand, when the diameter of the center exceeds 41.2 mm, it is necessary to make the intermediate layer or cover thinner than a desired thickness, and the function of the intermediate layer or cover layer is not sufficiently exhibited.

  When the diameter of the center is 34.8 mm to 41.2 mm, the amount of compressive deformation (the amount that the center contracts in the compression direction) from when the initial load 98 N is applied to when the final load 1275 N is applied is 1.90 mm or more. More preferably, it is 2.00 mm or more, More preferably, it is 2.10 mm or more, 5.00 mm or less is preferable, More preferably, it is 4.90 mm or less, More preferably, it is 4.80 mm or less. When the amount of compressive deformation is 1.90 mm or more, the feel at impact is better, and when the amount is 5.00 mm or less, the resilience is better.

  The surface hardness of the center is preferably 45 or more in Shore D hardness, more preferably 50 or more, still more preferably 55 or more, and preferably 65 or less, more preferably 62 or less, and still more preferably 60 or less. By setting the surface hardness of the center to 45 or more in Shore D hardness, the center does not become too soft and good resilience can be obtained. Further, by setting the surface hardness of the center to 65 or less in Shore D hardness, the center does not become too hard and a good shot feeling can be obtained.

  Examples of the material for the intermediate layer include a cured product of a rubber composition, an ionomer resin, and a thermoplastic polyamide commercially available from Arkema Co., Ltd. under the trade name “Pebax (registered trademark)” (for example, “Pebax 2533”). Elastomer, a thermoplastic polyester elastomer marketed under the trade name “Hytrel (registered trademark)” (for example, “Hytrel 3548” and “Hytrel 4047”) by Toray DuPont Co., Ltd. Thermoplastic polyurethane elastomer marketed by Elastollan (registered trademark) (for example, “Elastollan XNY97A”), thermoplastic polystyrene elastomer marketed by Mitsubishi Chemical Corporation under the trade name “Lavalon (registered trademark)” Etc. The material for the intermediate layer can be used alone or in combination.

  As the ionomer resin, in particular, an ionomer resin in which at least a part of a carboxyl group in a binary copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms is neutralized with a metal ion, ethylene, What neutralized at least one part of the carboxyl group in the ternary copolymer of C3-C8 alpha, beta-unsaturated carboxylic acid and alpha, beta-unsaturated carboxylic acid ester with a metal ion, or And mixtures thereof.

  Specific examples of the ionomer resin are illustrated by trade names, such as “Himilan (registered trademark)” (for example, Himilan 1555 (Na), Himilan 1557 (Zn), Himilan, which is commercially available from Mitsui DuPont Polychemical Co., Ltd.). 1605 (Na), HiMilan 1706 (Zn), HiMilan 1707 (Na), HiMilan AM3711 (Mg), etc., and terpolymer ionomer resins include HiMilan 1856 (Na), HiMilan 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 the ionomer resin include Surlyn 8120 (Na), Surlyn 8320 (Na), Surlyn 9320 (Zn), Surlyn 6320 (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. The intermediate layer may further contain a specific gravity adjusting agent such as barium sulfate or tungsten, an antiaging agent, or a pigment.

  The method for forming the intermediate layer is not particularly limited. For example, the intermediate layer composition is formed in advance into a half shell, the two are used to wrap the center, and the intermediate layer is formed. For example, a method of directly molding the composition for injection onto the center and wrapping the center can be employed.

  When using an intermediate layer composition comprising a rubber composition as a main component (50% by mass or more), the thickness of the intermediate layer is preferably 1.2 mm or more, more preferably 1.8 mm or more, and still more preferably It is 2.4 mm or more, 6.0 mm or less is preferable, More preferably, it is 5.2 mm or less, More preferably, it is 4.4 mm or less.

  Moreover, when using the composition for intermediate | middle layers which has resin as a main component (50 mass% or more), the thickness of an intermediate | middle layer has preferable 0.3 mm or more, More preferably, it is 0.4 mm or more, More preferably It is 0.5 mm or more, 2.5 mm or less is preferable, More preferably, it is 2.4 mm or less, More preferably, it is 2.3 mm or less. If the thickness of the intermediate layer exceeds 2.5 mm, the resilience performance of the resulting golf ball may be reduced. Moreover, if it is less than 0.3 mm, there is a possibility that an excessive amount of spin at the time of a driver shot cannot be suppressed.

  The hardness of the mid layer of the golf ball of the present invention is preferably 30 or more in Shore D hardness, more preferably 34 or more, further preferably 37 or more, preferably 65 or less, more preferably 62 or less, and further preferably 60 or less. By setting the hardness of the intermediate layer to 30 or more in Shore D hardness, it contributes to increasing the degree of outer-hard / inner-softness of the core, so that a high launch angle and low spin are achieved and a high flight distance is achieved. On the other hand, when the hardness of the intermediate layer is set to 65 or less in Shore D hardness, an excellent shot feeling can be obtained, the spin performance can be improved, and the controllability can be improved. Here, the hardness of the intermediate layer is a slab hardness measured by molding the intermediate layer composition into a sheet shape, and is measured by a measurement method described later. Moreover, the hardness of the said intermediate | middle layer can be adjusted by selecting suitably the combination of the resin component or rubber composition mentioned above, content of an additive, etc.

  The diameter of the core used in the golf ball of the present invention is preferably 40.4 mm or more, more preferably 40.6 mm or more, further preferably 40.8 mm or more, preferably 42.4 mm or less, more preferably 42.3 mm or less. 42.2 mm or less is more preferable. When the core diameter is less than the above lower limit, the cover becomes too thick and the resilience is lowered.On the other hand, when the core diameter exceeds the above upper limit, the cover is too thin, so the cover is molded. Because it becomes difficult.

  When the core has a diameter of 40.4 mm to 42.4 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 1.9 mm. The above is preferable, 2.0 mm or more is more preferable, 2.1 mm or more is further preferable, 4.7 mm or less is preferable, and 4.5 mm or less is more preferable. When the amount of compressive deformation is less than 1.9 mm, the feel at impact is hard and worse, and when it exceeds 4.7 mm, the resilience may be lowered.

  The center hardness of the core is preferably 30 or more in Shore D hardness, more preferably 32 or more, and still more preferably 35 or more. If the center hardness of the core is less than 30 in Shore D hardness, the core may become too soft and the resilience may decrease. Further, the center hardness of the core is preferably 50 or less in Shore D hardness, more preferably 48 or less, and further preferably 45 or less. This is because if the center hardness exceeds 50 in Shore D hardness, the hardness becomes too hard and the shot feeling tends to decrease. 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 of the core is preferably 20 or more in Shore D hardness, more preferably 25 or more, and further preferably 30 or more. If the surface hardness is less than 20, it may become too soft and the resilience may be lowered. The surface hardness of the core is preferably 70 or less in Shore D hardness, more preferably 69 or less, and even more preferably 68 or less. This is because if the surface hardness exceeds 70 in Shore D hardness, the core becomes too hard and the feel at impact may be lowered.

  It is also preferable to make the surface hardness of the core larger than the center hardness. The difference in hardness between the surface hardness and the center hardness of the core (surface hardness-center hardness) is preferably 4 or more, more preferably 7 or more in Shore D hardness. By making the surface hardness of the core greater than the center hardness, the launch angle is increased, the spin rate is decreased, and the flight distance is improved. In this case, the hardness difference (surface hardness-center hardness) is preferably 40 or less, and more preferably 35 or less. This is because if the hardness difference becomes too large, the durability may be lowered.

  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 this case, as the thread winding core, for example, a thread core formed by curing the center 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.

  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 without departing from the gist of the present invention are not limited thereto. Included in range.

(1) Center, core hardness (Shore D hardness)
The Shore D hardness measured at the surface of the center or core using the automatic rubber hardness meter P1 manufactured by Kobunshi Keiki Co., Ltd. equipped with the Shore D type spring type hardness meter specified in ASTM-D2240 is the center surface hardness or the core surface. 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) center hardness.

(2) Slab hardness (Shore D hardness)
Using the cover composition or intermediate layer composition, a sheet having a thickness of about 2 mm was prepared by injection molding (cylinder temperature 230 ° C.) and stored at 23 ° C. for 2 weeks. An automatic rubber hardness tester P1 type manufactured by Kobunshi Keiki Co., Ltd. equipped with a spring type hardness tester Shore D type as defined in ASTM-D2240 in a state where three or more sheets are stacked so as not to affect the measurement substrate. It measured using.

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

(4) 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.

(5) Flexural rigidity (MPa)
Using the cover composition, a sheet having a thickness of about 2 mm was prepared by injection molding (cylinder temperature 230 ° C.) and stored at 23 ° C. for 2 weeks. The bending rigidity was measured according to JIS K 7106. The measurement was performed at a temperature of 23 ° C. and a humidity of 50% RH.

(6) Feeling of hitting Ten amateur golfers (advanced players) performed a hitting test using a driver, and evaluated the feeling of hitting the ball at the following four stages.
A: Soft B: Slightly soft (allowable range)
C: Slightly hard D: Hard

(7) 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 23 ° C. for 12 hours in a thermostat. After each golf ball was taken out of the thermostat, it was hit immediately and the number of hits until the golf ball was broken was measured. The measurement was performed 12 pieces for each golf ball. The durability of each golf ball is determined according to the golf ball no. The number of hits of 11 was set to 100, and the number of hits for each golf ball was shown as an index value. The larger the indexed value, the more excellent the golf ball is.

(8) Resilience Each golf ball is impacted with 198.4 g of a metal cylinder at a speed of 40 m / second, and the speed of the cylinder and the golf ball before and after the collision is measured. The coefficient of restitution 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 11 is taken as 100 and is shown as an indexed value.

(9) Coating film adhesion A driver (1W) is attached to a swing robot manufactured by Trutemper, and a golf ball is repeatedly hit 100 times at a head speed of 45 m / s, and the degree of peeling of the coating film is observed. evaluated.
○: There was no peeling in the coating film, or peeling of less than 1 mm ² occurred in the coating film.
X: Peeling of 1 mm ² or more occurred in the coating film.

(10) Measurement of FT-IR Pellet before injection molding and after injection molding by a macro ATR method (germanium prism, observation diameter of about 1 mm) with an infrared spectrophotometer (AutoIMAGE FT-IR) manufactured by PerkinElmer. the cover was taken from the measured chart to determine the peak area in the vicinity of 1600 cm ^-1 and 1700 cm ^-1 vicinity of the peak area B. FIG. 1 shows a golf ball no. It is the chart which measured FT-IR about the cover of 1 (a vertical axis | shaft is a light absorbency). Each of 1600 cm ^-1 vicinity of the peak A and 1700 cm ^-1 peak near B, and calculating the area and subtracting the baseline as shown in FIG. The peak A near 1600 cm ⁻¹ may be slightly shifted depending on the type of metal neutralizing the carboxyl group.

[Production of golf balls]
(1) Production of Center A rubber center composition having the composition shown in Table 1 was kneaded and heated and pressed at 170 ° C. for 15 minutes in an upper and lower mold having hemispherical cavities to obtain a spherical center. An appropriate amount of barium sulfate was added so that the mass of the obtained golf ball was 45.4 g.

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」
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」
ジフェニルジスルフィド：住友精化社製
硫酸バリウム：堺化学社製、「硫酸バリウムＢＤ」

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”
Dicumyl peroxide: NOF Corporation, “Park Mill (registered trademark) D”
Diphenyl disulfide: manufactured by Sumitomo Seika Co., Ltd. barium sulfate: manufactured by Sakai Chemical Industry Co., Ltd., “barium sulfate BD”

(2) Preparation of intermediate layer composition and cover composition The blended materials shown in Tables 2 and 3 were mixed by a twin-screw kneading extruder to form a pellet-like intermediate layer composition and cover resin. A composition was prepared. The cover resin composition was extruded at a screw diameter of 45 mm, a screw rotation speed of 200 rpm, a screw L / D = 35, and a cylinder temperature of 140 to 200 ° C. The extrusion conditions for the intermediate layer composition 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、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

Surlyn 8945: Sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by DuPont Himira AM7329: Zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by Mitsui DuPont Polychemical Co., Ltd.

(3) Production of Golf Ball Body The intermediate layer (thickness: 1.0 mm) covering the center is formed by injection molding the intermediate layer composition obtained above onto the spherical center obtained as described above. Formed. Subsequently, a cover was formed by injection molding a cover composition on the intermediate layer, thereby producing 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 was protruded and held after the core was inserted. The resin composition for the cover is heated to 200 ° C. to 260 ° C. in the cylinder portion of the injection device, injected into a mold clamped at a pressure of 15 MPa, and then cooled for 30 seconds to open the mold and take out the golf ball It was. 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 550 U (manufactured by Sumika Bayer Urethane: branched polyol having a molecular weight of 550) are 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)

High Milan AM7327: Mitsui-DuPont Polychemical Co., Ltd., zinc ion neutralized ethylene-methacrylic acid-butyl acrylate terpolymer ionomer resin (melt flow rate (190 ° C. × 2.16 kg): 0.7 g / 10 min, bent (Rigidity: 35 MPa)
Surlyn 6320: DuPont, magnesium ion neutralized ethylene-methacrylic acid-butyl acrylate terpolymer ionomer resin (melt flow rate (190 ° C. × 2.16 kg): 1.0 g / 10 min, flexural rigidity: 53 MPa )
High Milan AM7331: manufactured by Mitsui DuPont Polychemical Co., Ltd., sodium ion neutralized ethylene-methacrylic acid-butyl acrylate terpolymer ionomer resin (melt flow rate (190 ° C. × 2.16 kg): 1.3 g / 10 min, bent (Rigidity: 25 MPa)
High Milan 1855: Mitsui-DuPont Polychemical Co., Ltd., zinc ion neutralized ethylene-methacrylic acid-butyl acrylate terpolymer ionomer resin (melt flow rate (190 ° C. × 2.16 kg): 1.0 g / 10 min, bending (Rigidity: 87 MPa)
High Milan AM7329: Mitsui DuPont Polychemical Co., Ltd., zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin (melt flow rate (190 ° C. × 2.16 kg): 5 g / 10 min, flexural rigidity: 221 MPa)
NUCLEL 1050H: manufactured by Mitsui DuPont Polychemical Co., Ltd., ethylene / methacrylic acid copolymer (melt flow rate (190 ° C. × 2.16 kg): 500 g / 10 min, flexural rigidity: 79 MPa)
Nucrel 2050H: manufactured by Mitsui DuPont Polychemical Co., Ltd., ethylene / methacrylic acid copolymer (melt flow rate (190 ° C. × 2.16 kg): 500 g / 10 min, flexural rigidity: 82 MPa)
PRIMACOR 5980I: Ethylene / acrylic acid copolymer manufactured by Dow Chemical Co. (melt flow rate (190 ° C. × 2.16 kg): 300 g / 10 min, flexural rigidity: 80 MPa)
Nukurel AN4319: made by Mitsui DuPont Polychemical Co., Ltd., ethylene / methacrylic acid / butyl acrylate copolymer (melt flow rate (190 ° C. × 2.16 kg): 55 g / 10 min, bending rigidity: 21 MPa)
Zinc oxide: Yoneyama Pharmaceutical Co., Ltd. (no surface treatment)
Zinc hydroxide: Yoneyama Pharmaceutical Co., Ltd. Zinc carbonate: Yoneyama Pharmaceutical Co., Ltd. Magnesium stearate: Nitto Kasei Kogyo Titanium oxide: Ishihara Sangyo A220

(A) an ionomer resin comprising a metal ion neutralized product of a terpolymer of an olefin, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an α, β-unsaturated carboxylic acid ester; ,
(B) a binary copolymer of an olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and / or an olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms A ternary copolymer with an α, β-unsaturated carboxylic acid ester and (C) a zinc compound are contained, and the content ratio of the component (A) to the component (B) is (A) / (B) = 50/50 to 80/20, and the content of the component (C) is 0.1 parts by mass to 20 parts by mass with respect to 100 parts by mass in total of the components (A) and (B). In addition, the resin composition for a golf ball cover having a melt flow rate (190 ° C., 2.16 kg load) of 5 g / 10 min or more is excellent in fluidity and can form a thin cover. Moreover, since both P2 / P1 is 1.1 or more, it can confirm that neutralization by the (C) zinc compound is performed. Golf ball No. 1 using these resin compositions for golf ball covers. 1-No. 10 and no. No. 16 was excellent in feel at impact, durability flight distance (coefficient of restitution), and coating film adhesion. Golf ball No. No. 16 had a slightly lower shot feeling because the Shore D hardness of the cover composition was 56.

  Golf ball no. 11 is a case where (A) a ternary ionomer resin and (B) a binary and / or ternary copolymer are included, but (C) a zinc compound is not included. Golf ball no. No. 12 is a case where a fatty acid metal salt is used in order to improve fluidity, but durability and coating film adhesion decreased. Golf ball no. 13 is a case where the content of the (C) zinc compound is high, but could not be molded because the fluidity was too low. Golf ball no. No. 14 has a low durability because the content ratio of the component (A) is too low. Golf ball no. No. 15 could not be molded because the content ratio of the component (A) was too high and the fluidity decreased. Golf ball no. 17 is a case where a binary ionomer resin was used in place of the (A) ternary ionomer resin, but the shot feeling decreased.

The present invention is suitable for a golf ball having an ionomer cover.

Claims (16)

A resin component and (C) a zinc compound,
The resin component is (A) a metal ion neutralized product of a terpolymer of an olefin, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an α, β-unsaturated carboxylic acid ester. An ionomer resin having a melt flow rate (190 ° C., 2.16 kg load) of 0.1 g / 10 min to 20 g / 10 min, and (B) an olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms. Contains only a binary copolymer with an acid and / or a terpolymer of an olefin, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α, β-unsaturated carboxylic acid ester And
The content ratio of the component (A) and the component (B) is (A) / (B) = 50/50 to 80/20 in mass ratio,
(C) Content of a component is 0.1 mass part-20 mass parts with respect to a total of 100 mass parts of (A) component and (B) component,
The melt flow rate (190 ° C., 2.16 kg load) is 5 g / 10 min or more,
A resin composition for a golf ball cover, which does not contain a fatty acid and / or a metal salt thereof.   The golf ball cover resin composition according to claim 1, wherein the (C) zinc compound is zinc oxide, zinc hydroxide, or zinc carbonate.   The resin composition for a golf ball cover according to claim 1 or 2, wherein the slab hardness is 35 to 55 in Shore D hardness. The peak area around 1600 cm ^-1 measured by FT-IR before injection molding the peak area in the vicinity of A1,1700cm ^-1 and B1, the peak area in the vicinity of 1600 cm ^-1 as measured by FT-IR after the injection molding The golf ball cover according to any one of claims 1 to 3, wherein A1, A2, B1, and B2 satisfy the following formula, where A2 and a peak area near 1700 cm ^-1 are defined as B2. Resin composition.
P1 = A1 / (A1 + B1)
P2 = A2 / (A2 + B2)
0.3 ≦ P1 ≦ 1.0
0.3 ≦ P2 ≦ 1.0
1.1 ≦ P2 / P1 ≦ 2.5   The resin composition for a golf ball cover according to any one of claims 1 to 4, wherein the flexural modulus is 10 MPa to 150 MPa.   The resin composition for a golf ball cover according to claim 1, wherein the flexural modulus of the component (A) is 10 MPa to 100 MPa.   The resin composition for a golf ball cover according to claim 1, wherein the melt flow rate (190 ° C., 2.16 kg load) of the component (B) is 5 g / 10 min to 1700 g / 10 min.   A golf ball having a cover formed by injection molding the resin composition for a golf ball cover according to claim 1.   The golf ball according to claim 8, wherein the cover has a thickness of 0.5 mm to 1.5 mm. A golf ball manufacturing method for molding a cover by injection molding a resin composition for a golf ball cover,
The golf ball cover resin composition contains a resin component and (C) a zinc compound,
The resin component is (A) a metal ion neutralized product of a terpolymer of an olefin, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an α, β-unsaturated carboxylic acid ester. An ionomer resin having a melt flow rate (190 ° C., 2.16 kg load) of 0.1 g / 10 min to 20 g / 10 min, and (B) an olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms. Contains only a binary copolymer with an acid and / or a terpolymer of an olefin, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α, β-unsaturated carboxylic acid ester The content ratio of the component (A) and the component (B) is (A) / (B) = 50/50 to 80/20 in terms of mass ratio, and the content of the component (C) is (A) It is 0.1 to 20 parts by mass with respect to 100 parts by mass in total of the component and the component (B) Melt flow rate (190 ° C., 2.16 kg load) is not less 5 g / 10min or higher, fatty acids and / or method of manufacturing a golf ball characterized in that it does not contain a metal salt thereof.   The method for producing a golf ball according to claim 10, wherein the (C) zinc compound is zinc oxide, zinc hydroxide, or zinc carbonate.   The method for producing a golf ball according to claim 10, wherein the bending rigidity is 10 MPa to 150 MPa.   The method for manufacturing a golf ball according to claim 10, wherein the component (A) has a flexural modulus of 10 MPa to 100 MPa.   The method for producing a golf ball according to claim 10, wherein the melt flow rate (190 ° C., 2.16 kg load) of the component (B) is 5 g / 10 min to 1700 g / 10 min.   The said injection molding is performed using the injection molding machine which has an injection device and a metal mold | die, and the temperature of the cylinder part of the said injection device is 200 degreeC or more and 270 degrees C or less. Golf ball manufacturing method. 1600cm when the peak area in the vicinity of 1600cm ^-1 of the cover composition was measured by FT-IR before injection molding the peak area in the vicinity of A1,1700cm ^-1 and B1, the cover after the injection molding was measured by FT-IR the peak area of around ^-1 peak area in the vicinity of A2,1700cm ^-1 is taken as B2, A1, A2, B1 and B2, any one of claims 10 to 15 is intended to satisfy the following equation A method for producing the golf ball described in 1.
P1 = A1 / (A1 + B1)
P2 = A2 / (A2 + B2)
0.3 ≦ P1 ≦ 1.0
0.3 ≦ P2 ≦ 1.0
1.1 ≦ P2 / P1 ≦ 2.5

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