JP5238486B2 - Golf ball - Google Patents

Description

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

  As a golf ball 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 viewpoint, various improved techniques have been proposed for golf ball materials using ionomer resins. For example, Patent Document 1 discloses a golf ball material having (i) an ionomer polymer and (ii) a metal stearate. Patent Document 2 discloses a blend composition including reaction products of three components (A), (B), and (C), wherein component (A) is ethylene and / or α-olefin, and one or A polymer comprising a plurality of α, β-ethylenically unsaturated carboxylic acids, sulfonic acids or phosphoric acids, component (B) is represented by the general formula (R ₂ N) _m —R ′ — (X (O) _n OR _y ) _m Disclosed is a blend composition wherein the compound having component (C) is a basic metal ion salt having the ability to neutralize acidic groups present in components (A) and (B).

  Patent Document 3 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. -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, (c) (a) above, (B) A golf ball material is disclosed that contains a basic inorganic metal compound capable of neutralizing an acid group in the component and contains a heated mixture having a melt index of 1.0 dg / min or more. Yes.

  Patent Document 4 discloses a blend of a high molecular weight ternary ionomer (molecular weight of about 80,000 to 500,000) having a different molecular weight and a low molecular weight binary ionomer (molecular weight of about 2000 to 30000), while maintaining durability and flight distance. A golf ball having improved flexibility and scratch resistance is disclosed.

Patent Document 5 has a highly neutralized acid polymer having a water vapor transmission rate (MVTR) of 4.0 g · mil / 100 in ² / day or less, a melt flow index of 1.0 g / 10 min or more, and And further comprising at least one layer made from a moisture resistant composition having an organic acid salt selected from zinc stearate and calcium stearate, wherein the highly neutralized acid polymer comprises a total weight of the polymer. A golf ball is disclosed which is an ethylene / acrylic acid (methacrylic acid) polymer having 0 to 19 weight percent acrylic acrylate (acrylic methacrylate) as a base.

Patent Document 6 discloses that in a golf ball having a core, an intermediate layer, and a cover, the intermediate layer has a specific gravity of 1.05 or less, the intermediate layer is manufactured from a moisture-resistant composition, and the moisture-resistant composition has water vapor. The transmittance (MVTR) is 12.5 g · mil / 100 in ² / day or less, and the moisture-resistant composition has a highly neutralized acid polymer, and the acid groups present in the moisture-resistant composition A golf ball is disclosed in which at least 80% of this is neutralized into a salt.
Special Table 2002-514112 JP 2006-28517 A Japanese Patent No. 3767683 Special table 2006-500995 gazette JP 2008-68080 A JP 2008-55176 A

  In order to improve the resilience of the golf ball, the cover and the intermediate layer are thinned. However, in order to form the cover and the intermediate layer thinly, the ionomer resin used as a material 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 has a problem of causing smoke during molding. Further, in order to improve the flight distance, it is preferable to increase the rigidity of the intermediate layer. However, if the rigidity of the intermediate layer is increased, there is a problem that the durability and feel of the golf ball are lowered.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a golf ball having excellent flight distance, durability, and feel at impact.

  The golf ball of the present invention that has solved the above problems is a golf ball having a core, at least one intermediate layer that covers the core, and a cover that covers the intermediate layer, wherein at least one piece or one layer of the intermediate layer As a resin component, (A) as a base resin, (a-1) a metal ion neutralized product of a binary copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, ethylene An ionomer resin comprising a neutralized metal ion of a terpolymer of an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α, β-unsaturated carboxylic acid ester, or a mixture thereof, And / or (a-2) a binary copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms And α, β-unsaturated carboxylic acid ester A nonionic resin comprising an original copolymer or a mixture thereof; and (B) a polyglycerol fatty acid ester, wherein the content of the (B) polyglycerol fatty acid ester is the above (A) base resin 1 part by weight to 45 parts by weight with respect to 100 parts by weight, and the slab hardness (Hm) is formed from a highly fluid intermediate layer composition having a Shore D hardness of 35 to 57; The thickness of the cover is 0.5 mm to 1.6 mm, the thickness of the cover is 0.3 mm to 1.6 mm, and the slab hardness (Hc) of the cover composition forming the cover is 56 Shore D hardness. It is the above.

  That is, in the present invention, the fluidity of the cover composition is improved by blending (B) polyglycerin fatty acid ester with (A) base resin. Moreover, since (A) ionomer resin and / or (a-2) nonionic resin used as a base resin and (B) polyglycerin fatty acid ester are highly compatible, (B ) Bleed out of the polyglycerin fatty acid ester component on the surface of the golf ball body is suppressed. The present invention uses the above composition for high fluidity intermediate layer to reduce the thickness of the intermediate layer, soften the outer and inner cores, and reduce the cover thickness and increase the rigidity, thereby improving the flight distance and durability. A golf ball having excellent properties and feel at impact is obtained.

  As said (B) polyglyceryl fatty acid ester, what is represented by following formula (1) is preferable.

［式中、Ｒ^１、Ｒ^２、Ｒ^３は、同一または異なって、水素原子、または、炭素数６〜３０の脂肪酸残基を表し、ｎは２〜２０の整数を表す。なお、複数存在するＲ^３は、同一でも異なっていてもよい。］

[Wherein, R ¹ , R ² and R ³ are the same or different and represent a hydrogen atom or a fatty acid residue having 6 to 30 carbon atoms, and n represents an integer of 2 to 20]. Incidentally, R ³ present multiple may be the same or different. ]

It is preferable that at least one of R ¹ , R ² and R ^{3 in} the above formula (1) is a stearic acid residue or a behenic acid residue. Examples of the (B) polyglycerin fatty acid ester include diglycerin monostearate, tetraglycerin pentastearate, hexaglycerin pentastearate, decaglycerin tristearate, decaglycerin decastate, decaglycerin heptabehenate, hexaglycerin. More preferably, it is at least one selected from the group consisting of dibehenate, hexaglycerin tetrabehenate, hexaglycerin hexabehenate, hexaglycerin octabehenate and decaglycerin dodecavehenate.

  The high fluidity intermediate layer composition further comprises (C) a metal ion source capable of neutralizing the carboxyl group in the base resin (A) in 100 parts by weight of the base resin (A). On the other hand, it is preferable to contain 0.1-10 mass parts. (C) By mix | blending a metal ion source, the neutralization degree of the carboxyl group in (A) base-material resin becomes high. As a result, the resilience of the intermediate layer composition is improved.

The density of the intermediate layer is preferably 1.10 g / cm ^{3 to} 1.50 g / cm ³ . By adding a high specific gravity filler to the intermediate layer composition to increase the density, it is possible to increase the moment of inertia of the golf ball and reduce back spin and side spin for a shot of a driver or the like. Thereby, the flight distance and direction stability at the time of impact can be improved more.

  The core preferably has a diameter of 38.0 mm or more. The melt flow rate (190 ° C. × 2.16 kg) of the composition for high fluidity intermediate layer is preferably 1 g / 10 min or more.

  The high fluidity intermediate layer composition comprises (A) only an ionomer resin (A-1) as a base resin; (A) only (a-2) a nonionic resin as a base resin. The aspect which performs is also suitable. In the composition for high fluidity intermediate layer, (A) ionomer resin and (a-2) nonionic resin are used as (A) base resin, and (a-1) ionomer resin / (a-2). It is preferable to contain in the ratio of nonionic resin = 1 mass%-90 mass% / 99 mass%-10 mass%.

  According to the present invention, a golf ball excellent in flight distance, durability, and feel at impact can be obtained.

  The golf ball of the present invention is a golf ball having a core, at least one intermediate layer covering the core, and a cover covering the intermediate layer, wherein at least one piece or one layer of the intermediate layer is a resin component (A) As a base resin, (a-1) a metal ion neutralized product of a binary copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, ethylene and 3 to 3 carbon atoms An ionomer resin comprising a neutralized metal ion of a terpolymer of eight α, β-unsaturated carboxylic acids and an α, β-unsaturated carboxylic acid ester, or a mixture thereof, and / or ( a-2) A binary copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and α, β- Terpolymers with unsaturated carboxylic esters, and A nonionic resin composed of a mixture thereof; and (B) a polyglycerin fatty acid ester, and the content of the (B) polyglycerin fatty acid ester is based on 100 parts by mass of the (A) base resin. 1 part by mass to 45 parts by mass, and the slab hardness (Hm) is formed from a highly fluid intermediate layer composition having a Shore D hardness of 35 to 57, and the intermediate layer has a thickness of 0.5 mm. The cover has a thickness of 0.3 to 1.6 mm, and the cover composition forming the cover has a slab hardness (Hc) of 56 or more in Shore D hardness. And

  First, the high fluidity intermediate layer composition will be described.

  The “(a-1) ionomer resin” used as the (A) base resin of the resin component of the high fluidity intermediate layer composition will be described.

  The (a-1) 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, ethylene And a neutralization of at least a part of the carboxyl group of a terpolymer of an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α, β-unsaturated carboxylic acid ester, or And a mixture of these.

  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, Divalent 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 preferable. Zinc and magnesium are more preferable. This is because the use of a divalent metal ion improves the durability and low temperature durability of the resulting golf ball.

  Among these, as the (a-1) ionomer resin used in the present invention, a resin obtained by neutralizing at least a part of a carboxyl group of a binary copolymer of ethylene and (meth) acrylic acid with a metal ion, ethylene It is preferable to use those obtained by neutralizing at least part of the carboxyl groups of the terpolymer of methacrylic acid and (meth) acrylic acid and (meth) acrylic acid ester with metal ions, or a mixture thereof. . In addition, in this application, (meth) acrylic acid shows acrylic acid and / or methacrylic acid.

  Furthermore, as the (a-1) ionomer resin used in the present invention, (a-1-1) at least part of the carboxyl group of the binary copolymer of ethylene and (meth) acrylic acid is a monovalent metal. Those neutralized with ions, or those obtained by neutralizing at least part of the carboxyl groups of a terpolymer of ethylene, (meth) acrylic acid and (meth) acrylic acid ester with a monovalent metal ion, (A-1-2) A copolymer obtained by neutralizing at least part of the carboxyl group of a binary copolymer of ethylene and (meth) acrylic acid with a divalent metal ion, or ethylene and (meth) acrylic acid It is a preferred embodiment to use an ionomer resin obtained by mixing at least a part of the carboxyl group of the terpolymer with (meth) acrylic acid ester with a divalent metal ion.

  By using the mixture of ionomer resins as described above, the impact resilience of the cover composition can be further improved. As the monovalent metal ion, sodium, lithium, potassium, rubidium, cesium and francium are preferable, and as the divalent metal ion, magnesium, calcium, zinc, beryllium, strontium, barium and radium are preferable. In this case, the blending ratio of (a-1-1) and (a-1-2) is (a-1-1) / (a-1-2) = 20% by mass to 80% by mass / 80. It is preferably 20% by mass to 20% by mass, more preferably 25% by mass to 77% by mass / 75% by mass to 23% by mass, and still more preferably 30% by mass to 75% by mass / 70% by mass to 25% by mass.

  The content of the α, β-unsaturated carboxylic acid component having 3 to 8 carbon atoms in the (a-1) ionomer resin is preferably 2% by mass or more, more preferably 3% by mass or more, and 30% by mass. % Or less is preferable, and more preferably 25% by mass or less.

  The neutralization degree of the carboxyl group of the (a-1) 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. It is. If the degree of neutralization is 20 mol% or more, the resilience and durability of the resulting cover will be good, and if it is 90 mol% or less, the fluidity of the cover composition will be good (good moldability). ). In addition, the neutralization degree of the carboxyl group of (a-1) 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

  A specific example of the (a-1) ionomer resin is exemplified by trade names such as “Himilan (registered trademark)” (for example, Himilan 1555 (Na), Himilan 1557, commercially available from Mitsui DuPont Polychemical Co., Ltd.). (Zn), High Milan 1605 (Na), High Milan 1702 (Zn), 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)). In addition, Na, Zn, Li, Mg, etc. described in parentheses after the trade name indicate the metal species of these neutralized metal ions.

  The “(a-2) nonionic resin” that can be used as the (A) base resin of the resin component of the high fluidity intermediate layer composition will be described.

  The (a-2) nonionic resin is one in which a carboxyl group of a binary copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms is not neutralized, ethylene and carbon Those in which the carboxyl group of a terpolymer of several to eight α, β-unsaturated carboxylic acid and α, β-unsaturated carboxylic acid ester is not neutralized, or a mixture thereof It is.

  Examples of the α, β-unsaturated carboxylic acid and α, β-unsaturated carboxylic acid ester having 3 to 8 carbon atoms are the same as those exemplified as constituting “(a-1) ionomer resin”. Can be used.

  Among these, as the (a-2) nonionic resin used in the present invention, a binary copolymer of ethylene and (meth) acrylic acid, ethylene, (meth) acrylic acid and (meth) acrylic acid ester are used. It is preferable to use a terpolymer of the above or a mixture thereof.

  The content of the α, β-unsaturated carboxylic acid component having 3 to 8 carbon atoms in the nonionic resin (a-2) is preferably 2% by mass or more, more preferably 3% by mass or more. 30 mass% or less is preferable, More preferably, it is 25 mass% or less.

  Specific examples of the above (a-2) nonionic resin are exemplified by trade names such as “NUCREL” (registered trademark) manufactured by Mitsui DuPont Polychemical Co., Ltd. (for example, Nucrel AN4214C, Nucrel AN4225C, Nucrel AN4318, Nucrel AN42115C, Nucrel N0903HC, Nucrel N0908C, Nucrel AN42012C, Nucrel N410, Nucrel N1035, Nucrel N1050H, Nucrel N2050H, Nucrel N1108C, Nucrel N1110H, Nucrel N1207C, Nucrel N1214C Nuclerel N4213C, Nuclerel Ethylene commercially available, etc.) "035C - and the like acrylic acid copolymer - methacrylic acid copolymer, ethylene commercially available trade name Dow Chemical Company under the" PRIMACOR (TM) 5990I ".

  As said (A) base resin, the said (a-1) ionomer resin or (a-2) nonionic resin may be used independently, and these may be used together. (A) When (a-1) ionomer resin and (a-2) nonionic resin are used in combination as the base resin, the blending ratio of these is (a-1) ionomer resin / (a-2) non Ionic resin = 1% by mass to 90% by mass / 99% by mass to 10% by mass, preferably 5% by mass to 80% by mass / 95% by mass to 20% by mass, and more preferably 10% by mass to 70% by mass. % / 90% by mass to 30% by mass. By setting the blending ratio within the above range, the moldability to a golf ball is improved, and in particular, the intermediate layer can be easily formed into a thin wall.

  The “(B) polyglycerin fatty acid ester” used in the composition for high fluidity intermediate layer will be described.

  The (B) polyglycerol fatty acid ester is a compound in which at least a part of hydroxyl groups in the polyglycerol molecule is esterified with a fatty acid. In addition, (B) polyglyceryl fatty acid ester is not contained in the resin component which comprises the composition for highly fluid intermediate | middle layers.

  As said (B) polyglyceryl fatty acid ester, what is represented by following formula (1) is preferable.

［式中、Ｒ^１、Ｒ^２、Ｒ^３は、同一または異なって、水素原子、または、炭素数６〜３０の脂肪酸残基を表し、ｎは２〜２０の整数を表す。なお、複数存在するＲ^３は、同一でも異なっていてもよい。］

[Wherein, R ¹ , R ² and R ³ are the same or different and represent a hydrogen atom or a fatty acid residue having 6 to 30 carbon atoms, and n represents an integer of 2 to 20]. Incidentally, R ³ present multiple may be the same or different. ]

  Thus, if the polyglycerin skeleton has a linear structure and the fatty acid residue has 6 to 30 carbon atoms, the compatibility with (A) the base resin is increased, and after the cover molding (B) Since the polyglycerin fatty acid ester is difficult to bleed out, the coating film adhesion is further improved.

  Examples of the fatty acid residue having 6 to 30 carbon atoms in the above formula include, for example, hexanoic acid residue, heptanoic acid residue, octanoic acid residue, pelargonic acid residue, decanoic acid residue, lauric acid residue, myristic acid Saturated fatty acid residues such as residues, palmitic acid residues, heptadecanoic acid residues, stearic acid residues, icosanoic acid residues, behenic acid residues, lignoceric acid residues, serotic acid residues; palmitoleic acid residues, olein Examples thereof include unsaturated fatty acid residues such as acid residues, linoleic acid residues, α-linolenic acid residues, γ-linolenic acid residues, and arachidonic acid residues. Among these, saturated fatty acid residues are preferable, and stearic acid residues and behenic acid residues are more preferable.

  The degree of polymerization of glycerin represented by n in the above formula is not particularly limited as long as it is 2 or more, but is preferably 3 or more, more preferably 4 or more, and preferably 20 or less, more preferably 18 or less. By setting the degree of polymerization of glycerin to 2 or more and 20 or less, it becomes difficult to bleed out after cover molding, and the coating film adhesion is further improved.

  The (B) polyglycerin fatty acid ester used in the present invention preferably has an HLB (Hydrophile-Lipophile Balance) of 0 or more, more preferably 0.5 or more, still more preferably 1 or more, and 10 or less. Preferably, it is 9 or less, more preferably 8 or less. (B) By setting the HLB of the polyglycerin fatty acid ester within the above range, compatibility with the (A) base resin component is improved, and (B) the polyglycerin fatty acid ester is uniform in the (A) base resin component. And the fluidity of the cover composition is further improved.

  In the present invention, (B) HLB of polyglycerol fatty acid ester is HLB = 20 × {1- (S / A)} (S: saponification value of polyglycerol fatty acid ester, A: polyglycerol fatty acid ester. (Acid value of fatty acid).

  Examples of the (B) polyglycerin fatty acid ester include diglycerin monostearate, tetraglycerin pentastearate, hexaglycerin pentastearate, decaglycerin tristearate, decaglycerin decastate, decaglycerin heptabehenate, hexaglycerin. More preferred is at least one selected from the group consisting of dibehenate, hexaglycerin tetrabehenate, hexaglycerin hexabehenate, hexaglycerin octabehenate and decaglycerin dodecavehenate.

  Specific examples of the (B) polyglycerin fatty acid ester are illustrated by trade names, for example, “SY Glyster DAS-7S (decaglycerin decastate)”, “SY glycerin PS-5S (hexaglycerin penta) manufactured by Sakamoto Pharmaceutical Co., Ltd. Stearate) "," SY Glycer PS-3S (tetraglycerin pentastearate) "," SY Glyster HB-750 (decaglycerin heptabehenate) "," SY glycerine TS-7S (decaglycerin tristearate) " , “SY Glyster MS-150 (diglycerin monostearate)” and the like.

  The content of the (B) polyglycerin fatty acid ester in the composition for high fluidity intermediate layer is 1 part by mass or more, preferably 1.5 parts by mass or more, with respect to 100 parts by mass of the (A) base resin. More preferably, it is 2 parts by mass or more, 45 parts by mass or less, preferably 40 parts by mass or less, more preferably 30 parts by mass or less. (B) If content of polyglyceryl fatty acid ester is the said range, the fluidity | liquidity of the composition for highly fluid intermediate | middle layers will improve, and thickness reduction of an intermediate | middle layer will be attained. As a result, the resilience and durability of the resulting golf ball are improved.

  The high fluidity intermediate layer composition further comprises (C) a metal ion source capable of neutralizing the carboxyl group in the base resin (A) in 100 parts by weight of the base resin (A). On the other hand, it is preferable to contain 0.1-10 mass parts.

  The (C) metal ion source is a basic metal compound capable of neutralizing an unneutralized carboxyl group in the (A) base resin. In addition, (C) a metal ion source is not contained in the resin component which comprises the composition for highly fluid intermediate | middle layers.

  Examples of the metal ion source (C) include metal hydroxides such as magnesium hydroxide, calcium hydroxide, sodium hydroxide, lithium hydroxide, potassium hydroxide, and copper hydroxide; magnesium oxide, calcium oxide, and zinc oxide. Metal oxides such as copper oxide; metal carbonates such as magnesium carbonate, calcium carbonate, sodium carbonate, lithium carbonate, and potassium carbonate. These (C) metal ion sources may be used alone or in combination of two or more. Among these, as the metal ion source (C), a metal hydroxide is preferable, and magnesium hydroxide and calcium hydroxide are particularly preferable.

  Further, the content of the (C) metal ion source in the composition for high fluidity intermediate layer is preferably 0.1 parts by mass or more, more preferably 0 with respect to 100 parts by mass of the base resin (A). .2 parts by mass or more, more preferably 0.3 parts by mass or more, preferably 10 parts by mass or less, more preferably 9 parts by mass or less, still more preferably 8 parts by mass or less. (C) When the content of the metal ion source is within the above range, the resilience performance of the obtained golf ball is further improved. In addition, the moldability of the highly fluid intermediate layer composition into a golf ball is also improved.

  Further, the content of the component (C) is preferably adjusted so that the neutralization degree of all the carboxyl groups of the base resin (A) is 50 mol% or more, more preferably 75 mol% or more, More preferably, it is 80 mol% or more.

  In the present invention, the high fluidity intermediate layer composition preferably includes only the base resin (A) as a resin component, but further to the extent that the effects of the present invention are not impaired (A) You may contain (D) thermoplastic resins and / or thermosetting resins other than base resin.

  In this case, the content of the (D) thermoplastic resin and / or thermosetting resin in the resin component is preferably more than 0 parts by mass, more preferably 1 part by mass with respect to 100 parts by mass of the (A) base resin. Part or more, more preferably 5 parts by weight or more, preferably 100 parts by weight or less, more preferably 70 parts by weight or less, and still more preferably 50 parts by weight or less. (D) If content of a thermoplastic resin and / or a thermosetting resin is the said range, it will be easy to obtain physical properties, such as hardness and resilience characteristics, of the desired composition for high fluidity intermediate | middle layers.

  Examples of the thermoplastic resin (D) and / or thermosetting resin include thermoplastic polyamides commercially available from Arkema Co., Ltd. under the trade name “Pebax (registered trademark)” (for example, “Pebax 2533”). Elastomer; Thermoplastic polyester elastomer commercially available from Toray DuPont Co., Ltd. under the trade name “Hytrel (registered trademark)” (for example, “Hytrel 3548” and “Hytrel 4047”); trade name “Mitsubishi Chemical Co., Ltd.” Thermoplastic polystyrene-based elastomer marketed under Lavalon (registered trademark) (for example, “Lavalon T3221C”) or thermoplastic polyester marketed under the trade name “Primalloy® (for example,“ Primalloy B1942N ”) -Based elastomer; from BASF Polyurethane Elastomers Thermoplastic resins such as thermoplastic polyurethane elastomers marketed under the product name “Elastolan (registered trademark)” (for example, “Elastolan ET880”); Resins formed by crosslinking a rubber composition with sulfur, organic peroxide, etc. And thermosetting resins such as thermosetting polyurethane resins, epoxy resins, and phenol resins.

  In the present invention, the composition for high fluidity intermediate layer includes, in addition to the resin component described above, pigment components such as a white pigment (titanium oxide), a blue pigment, and a red pigment, a specific gravity adjuster, a dispersant, an anti-aging agent, and an ultraviolet ray. You may contain an absorber, a light stabilizer, a fluorescent material, a fluorescent whitening agent, etc. in the range which does not impair the effect of this invention.

  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 10 parts by mass or less, more preferably 8 parts by mass with respect to 100 parts by mass of the resin component. The following is desirable. By setting the content of the white pigment to 0.5 parts by mass or more with respect to 100 parts by mass of the resin component, concealability can be imparted to the intermediate layer. Moreover, when content of a white pigment exceeds 10 mass parts with respect to 100 mass parts of resin components, durability of the intermediate | middle layer obtained may fall.

  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 1 part by mass or more, more preferably 2 parts by mass or more, further preferably 3 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 47 parts by mass, still more preferably not more than 44 parts by mass. If the blending amount of the specific gravity adjusting agent is 1 part 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, the dispersibility with respect to the resin component becomes good.

Density of the intermediate layer is preferably 1.10 g / cm ³ or more, more preferably 1.15 g / cm ³ or more, still more preferably 1.20 g / cm ³ or more, 1.50 g / cm ³ or less is preferable More preferably, it is 1.45 g / cm ³ or less, and further preferably 1.40 g / cm ³ or less. If the density of the intermediate layer is 1.10 g / cm ³ or more, the moment of inertia of the golf ball can be further increased, and the effect of lowering the backspin and side spin on the shot of a driver or the like is further increased, and the flying Distance and direction stability is further improved. Further, if the density of the intermediate layer is 1.50 g / cm ³ or less, the amount of the specific gravity adjusting agent to be blended does not increase too much, and the resilience of the resulting golf ball becomes good. The intermediate layer having a high density is preferably arranged on the outside of the golf ball as much as possible. Here, the density of the intermediate layer is measured by the method described later.

In this case, the density of the core to be described later is preferably from 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 described later 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 melt flow rate (190 ° C. × 2.16 kg) of the composition for high fluidity intermediate layer is preferably 1 g / 10 min or more, more preferably 2 g / 10 min or more, further preferably 3 g / 10 min or more, and 70 g / It is preferably 10 min or less, more preferably 60 g / 10 min or less, still more preferably 50 g / 10 min or less. If the melt flow rate of the composition for high fluidity intermediate layer is 1 g / 10 min or more, the moldability becomes high, and the intermediate layer can be made thinner.

  The bending rigidity of the composition for high fluidity intermediate layer 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, still more preferably 400 MPa or less. It is. If the bending rigidity of the composition for high fluidity intermediate layer is 100 MPa or more, the obtained golf ball can have an outer-hard / inner-soft structure, and the flight distance is improved. Moreover, if the bending rigidity of the composition for high fluidity intermediate layer is 450 MPa or less, the obtained golf ball becomes appropriately soft and the shot feeling becomes good.

  The rebound resilience of the high fluidity intermediate layer composition is preferably 40% or more, more preferably 41% or more, and still more preferably 42% or more. By setting the rebound resilience of the composition for high fluidity intermediate layer to 40% or more, the flight distance of the obtained golf ball is increased. Here, the bending rigidity and rebound resilience of the composition for high fluidity intermediate layer are the bending rigidity and rebound resilience measured by molding the composition for high fluidity intermediate layer into a sheet shape, which will be described later. Measure by the measuring method.

  The slab hardness (Hm) of the composition for high fluidity intermediate layer is preferably 35 or more, more preferably 40 or more, further preferably 45 or more, preferably 57 or less, more preferably 55 or less in Shore D hardness. More preferably, it is 52 or less. When the slab hardness (Hm) of the composition for high fluidity intermediate layer is 35 or more in Shore D hardness, the rigidity of the obtained intermediate layer is increased, and a golf ball having excellent resilience (flying distance) can be obtained. On the other hand, when the slab hardness (Hm) of the composition for high fluidity intermediate layer is 57 or less in Shore D hardness, the feel at impact of the obtained golf ball is further improved. Here, the slab hardness (Hm) of the composition for high fluidity intermediate layer is hardness measured by molding the composition for high fluidity intermediate layer into a sheet shape, and is measured by a measurement method described later.

  The melt flow rate, flexural modulus, rebound resilience, and slab hardness of the high fluidity intermediate layer composition are (A) base resin, (B) polyglycerin fatty acid ester, (C) metal ion source. And (D) It can adjust by selecting suitably the combination of a thermoplastic resin and / or a thermosetting resin, content of an additive, etc.

  As a method for forming an intermediate layer using the high fluidity intermediate layer composition, for example, a core is coated with the high fluidity intermediate layer composition to form an intermediate layer. The method for forming the intermediate layer is, for example, a method in which the composition for high fluidity intermediate layer is directly injection-molded on the core, or a hollow shell-like shell is formed from the composition for high fluidity intermediate layer, and the core is formed. A method of compression molding by coating with a plurality of shells (preferably a method of molding a hollow shell-shaped half shell from the composition for high fluidity intermediate layer and then coating the core with two half shells for compression molding) Can be mentioned.

  When forming the intermediate layer by injection molding the composition for high fluidity intermediate layer on the core, the upper and lower molds for forming the intermediate layer have hemispherical cavities, with pimples, and a part of the pimples. It is preferable to use one that also serves as a hold pin that can be advanced and retracted. The intermediate layer is formed by injection molding by protruding the hold pin, inserting the core, holding it, and then injecting the heat-melted composition for a high fluidity intermediate layer and cooling it. For example, in a mold clamped at a pressure of 980 kPa to 1,500 kPa, a high fluidity intermediate layer composition heated and melted at 150 ° C. to 230 ° C. is injected in 0.1 seconds to 1 second. The mold is opened by cooling for 15 to 60 seconds.

  When the intermediate layer is formed 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 high fluidity intermediate layer composition into a half shell are, for example, -20 with a pressure of 1 MPa or more and 20 MPa or less with respect to the flow start temperature of the high fluidity intermediate layer composition. A molding temperature of from ℃ to +70 ℃ can be mentioned. By setting the molding conditions, a half shell having a uniform thickness can be molded. As a method for forming the intermediate layer using the half shell, for example, a method in which the core is covered with two half shells and compression-molded can be mentioned. As conditions for compression-molding the half shell into the intermediate layer, for example, at a molding pressure of 0.5 MPa or more and 25 MPa or less, the flow start temperature of the composition for high fluidity intermediate layer is −20 ° C. or more. And a molding temperature of + 70 ° C. or lower. By setting it as the said molding conditions, the intermediate | middle layer which has uniform thickness can be shape | 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 composition for high fluidity intermediate layers was obtained by using a “flow tester CFT-500” manufactured by Shimadzu Corporation, using a pellet-shaped intermediate layer composition with a plunger area of 1 cm ² and DIE LENGTH of 1 mm. , DIE DIA: 1 mm, load: 588.399 N, starting temperature: 30 ° C., heating rate: 3 ° C./min.

  The intermediate layer has a thickness of 0.5 mm or more, preferably 0.6 mm or more, more preferably 0.7 mm or more, and 1.6 mm or less, preferably 1.2 mm or less, more preferably 1.0 mm or less. . When the thickness of the intermediate layer is 0.5 mm or more, the durability of the resulting golf ball is further improved. Further, if the thickness of the intermediate layer is 1.6 mm or less, the core is relatively enlarged in diameter, and the resilience and feel at impact of the obtained golf ball become better.

  Examples of the mode of covering the core described later with the intermediate layer include a mode of covering the core with a single layer of the intermediate layer; a mode of covering the core with a plurality of pieces or a plurality of layers of the intermediate layer.

  The shape after the core is covered with the intermediate layer is preferably spherical. When the shape of the intermediate layer is not spherical, the thickness of the cover is not uniform. As a result, a part in which the cover performance is partially reduced occurs. On the other hand, the shape of the core is generally spherical, but a ridge may be provided so as to divide the surface of the spherical core, for example, the ridge so as to divide the surface of the spherical core equally. May be provided. As an aspect which provides the said protrusion, the aspect which provides a protrusion integrally with an envelope layer on the surface of an envelope layer, the aspect which provides the envelope layer of an protrusion on the surface of a spherical center, etc. can be mentioned, for example.

  For example, when the spherical core is regarded as the earth, the protrusions are preferably provided along the equator and an arbitrary meridian that equally divides the spherical core surface. For example, when the spherical core surface is divided into 8 parts, 90 degrees east longitude, 90 degrees west longitude, east longitude (west longitude) with reference to the equator, an arbitrary meridian (longitude 0 degrees), and a meridian of such longitude 0 degrees It may be provided along the meridian of 180 degrees. When providing protrusions on the core surface, the recesses partitioned by the protrusions are filled with a plurality of intermediate layers or a single intermediate layer covering each of the recesses so as to have a spherical shape. It is preferable to make it. 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).

  As the intermediate layer, when the core is covered with a single layer or a plurality of intermediate layers, at least one of the intermediate layers is partitioned by a protrusion provided on the surface of the center. When the recess is filled with a plurality of intermediate layers, at least one of the plurality of intermediate layers is formed from the composition for high fluidity intermediate layer. When the core is covered with a plurality of intermediate layers or a plurality of intermediate layers, the core is formed from the intermediate layer composition other than the high fluidity intermediate layer composition as long as the effects of the present invention are not impaired. An intermediate layer may be included. In this case, it is preferable that the outermost intermediate layer is an intermediate layer formed from the composition for high fluidity intermediate layer, and a plurality of pieces or a plurality of intermediate layers are all made of the high fluidity intermediate layer. More preferably, it is formed from a composition for a conductive intermediate layer.

  Examples of the intermediate layer composition other than the high fluidity intermediate layer composition include a rubber composition for a center described later, and an ionomer resin exemplified as the component (a-1) (for example, “Surlin (registered trademark)”). ) "), Ethylene-methacrylic acid copolymer exemplified as the component (a-2) (for example," Nucrel (registered trademark) "), and trade name" Pebax (registered trademark) "(for example, from Arkema Co., Ltd.) , "Pebax 2533"), a commercially available thermoplastic polyamide elastomer, commercially available from Toray DuPont Co., Ltd. under the trade name "Hytrel (registered trademark)" (for example, "Hytrel 3548", "Hytrel 4047") " The product name "Elastolan (registered trademark)" (for example, "Elastolan X Y97A ")", a thermoplastic polyurethane elastomer marketed under the trade name "Lavalon (registered trademark)" from Mitsubishi Chemical Corporation, and barium sulfate, tungsten, etc. Specific gravity adjusters, anti-aging agents, pigments and the like may be blended.

  Next, the cover of the golf ball of the present invention will be described.

  As the resin component of the cover composition forming the cover, polyurethane resin, ionomer resins exemplified as the component (a-1) (for example, “Surlin (registered trademark) 8945”, “Himiran (registered trademark) AM7329” In addition to the ethylene-methacrylic acid copolymer exemplified as the component (a-2) (for example, “Nuclele (registered trademark) N1050H”, etc.), the trade name “Pebax (registered trademark) ( For example, a thermoplastic polyamide elastomer marketed under the name “Pebax 2533”), commercially available under the trade name “Hytrel® (eg“ Hytrel 3548 ”,“ Hytrel 4047 ”) from Toray DuPont Co., Ltd. Product name "Lavalon" from Mitsubishi Chemical Corporation. Recording TM) (e.g., a thermoplastic polystyrene elastomer having a commercial "Rabalon T3221C") "can be mentioned. These resin components may be used alone or in combination of two or more. Among these, from the viewpoint of resilience, it is preferable to mix an ionomer resin and an ethylene-methacrylic acid copolymer as a resin component; or it is preferable to mix an ionomer resin and a thermoplastic polystyrene elastomer.

  In the present invention, in addition to the resin component described above, the cover is a pigment component such as a white pigment (titanium oxide), a blue pigment (ultramarine blue), a red pigment, or a specific gravity adjuster such as zinc oxide, calcium carbonate, or barium sulfate. Further, a dispersant, an anti-aging agent, an ultraviolet absorber, a light stabilizer, a fluorescent material, or a fluorescent brightening agent 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 setting the content of the white pigment to 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.

  The slab hardness (Hc) of the cover composition is 56 or more, preferably 58 or more, more preferably 59 or more in Shore D hardness, 65 or less, preferably 64 or less, more preferably 63 or less. If the slab hardness (Hc) of the cover composition is 56 or more in Shore D hardness, it is possible to achieve low spin for a shot of a driver and the like, and the flight distance is improved. Moreover, if the slab hardness (Hc) of the composition for a cover is 65 or less in Shore D hardness, a shot feeling will improve.

  As a method of forming a cover using the cover composition, for example, the cover is formed by covering the intermediate layer with the cover composition. The method of molding the cover is not particularly limited. For example, the cover composition is previously molded into a hemispherical half-shell, and two of them are used to wrap and compress the intermediate layer, or A method of wrapping the intermediate layer by injection molding the cover composition directly on the intermediate layer is used.

  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 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.

  The cover has a thickness of 0.3 mm or more, preferably 0.5 mm or more, more preferably 0.7 mm or more, and 1.6 mm or less, preferably 1.2 mm or less, more preferably 1.0 mm or less. If the cover has a thickness of 0.3 mm or more, the cover can be formed more easily. In addition, when the cover has a thickness of 1.6 mm or less, the core becomes relatively large in diameter, and the resilience of the obtained golf ball becomes good. 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).

  Next, 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. Examples of the structure of the core include a single-layer core; a multilayer core composed of a center and an envelope layer covering the center. Among these, a single layer core is preferable.

  The center of the single-layer core or the center of the multilayer core composed of the center and the envelope layer 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 0.3 parts by mass or more, more preferably 0.4 parts by mass or more, and preferably 5 parts by mass or less, more preferably 100 parts by mass of the base rubber. 3 parts by mass or less. If the amount is less than 0.3 parts by mass, the core tends to be too soft and the resilience tends to decrease. If the amount exceeds 5 parts by mass, it is necessary to increase the amount of co-crosslinking agent used 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 15 parts by mass or more, still more preferably 20 parts by mass or more, and preferably 55 parts by mass or less with respect to 100 parts by mass of the base rubber. More preferably, it is 50 mass parts or less, More preferably, it is 48 mass parts or less. 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 55 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 0.5 parts by mass or more, more preferably 1 part by mass or more, and 30 parts by mass or less, more preferably 20 parts by mass or less with respect to 100 parts by mass of the base rubber. It is desirable. This is because if the blending amount of the filler is less than 0.5 parts by mass, it is difficult to adjust the weight, and if it exceeds 30 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 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 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. For example, the rubber composition is heated at 130 ° C. to 200 ° C. for 10 minutes to 60 minutes, or after being heated at 130 ° C. to 150 ° C. for 20 minutes to 40 minutes, Heating is preferably performed in two stages of 160 ° C. to 180 ° C. for 5 minutes to 15 minutes.

  The envelope layer in the multilayer core composed of the center and the envelope layer covering the center will be described.

  Examples of the envelope layer composition forming the envelope layer include the above-described core rubber composition, the ionomer resin exemplified as the component (a-1), and the ethylene- exemplified as the component (a-2). In addition to methacrylic acid copolymer, thermoplastic polyamide elastomer marketed by Arkema Co., Ltd. under the trade name “Pebax (registered trademark)” (for example, “Pebax 2533”), trade name “Toray DuPont” A thermoplastic polyester elastomer commercially available under the name Hytrel (registered trademark) (for example, “Hytrel 3548”, “Hytrel 4047”), trade name “Elastollan” (for example, “Elastollan XNY97A” from BASF Japan). ) ", A commercially available thermoplastic polyurethane elastomer, trade name from Mitsubishi Chemical Corporation Examples include thermoplastic polystyrene elastomers marketed under Lavalon (registered trademark) (for example, “Lavalon T3221C”), and specific gravity adjusting agents such as barium sulfate and tungsten, antiaging agents, and pigments. May be.

  The diameter of the core is preferably 38.0 mm or more, more preferably 38.5 mm or more, and further preferably 39.0 mm or more. When the diameter of the core is 38.0 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 center hardness (Ho) of the core to 36 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 a Shore D hardness of 60 or less, the core does not become too hard and a good shot feeling can be obtained.

  The golf ball of the present invention is not particularly limited as long as it has a core, at least one 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, a single-layer intermediate layer covering the single-layer core, and a cover covering the intermediate layer; the center and the center A four-piece golf ball comprising a two-layer core comprising an envelope layer covering the core, a single-layer intermediate layer covering the core, and a cover covering the intermediate layer; a single-layer core and the single-layer core A multi-piece golf ball having a plurality of pieces or a plurality of intermediate layers to be covered and a cover for covering the intermediate layers can be exemplified. Among these, the present invention is preferably 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 2.9 mm or more, 4.0 mm or less is preferable, More preferably, it is 3.8 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) Core hardness (Shore D hardness)
Using an automatic rubber hardness tester P1 type made by Kobunshi Keiki Co., Ltd. equipped with a Shore D type spring type hardness tester specified in ASTM-D2240, the Shore D hardness measured at the surface of the core is defined as the core surface hardness, and the core is hemispheric The Shore D hardness measured at the center of the cut surface was taken as the core center hardness.

(2) Slab hardness of intermediate layer composition, slab hardness of cover composition (Shore D hardness)
Using the cover composition or intermediate layer composition, a sheet having a thickness of about 2 mm was produced by hot press molding 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) 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.

(4) Flexural rigidity (MPa)
Using the cover composition or the intermediate layer composition, a sheet having a thickness of about 2 mm was produced by hot press molding 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.

(5) Rebound resilience (%)
By using a cover composition or an intermediate layer composition, a sheet having a thickness of about 2 mm is produced by hot press molding, and six sheets of the sheet punched into a circular shape having a diameter of 28 mm are stacked. A cylindrical specimen having a diameter of about 12 mm and a diameter of 28 mm was produced. A Rüpke-type rebound resilience test (test temperature and humidity of 23 ° C., 50 RH%) was performed on this test piece. The test piece was prepared and tested in accordance with JIS K6255.

(6) Density of intermediate layer Pellets were produced using the composition for intermediate layer, and the density of the pellet was measured. The measurement was performed using ARCHIMEDES made by Chyo balance Corporation, the measurement temperature was 23 ° C., and ethanol was used as the solvent.

(7) 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 1274N was applied was measured.

(8) Flying distance Mount a W # 1 driver (SRI Sports, XXIO S Loft 10 °) on a swing robot made by True Temper, hit a golf ball at a head speed of 45m / s, and fly away (starting point) 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.

(9) Durability After producing each golf ball, it was stored at 23 ° C. for 1 month.
Attach a metal head W # 1 driver to a swing robot made by True Temper, set the head speed to 45m / sec, hit each golf ball stored at 23 ° C, and hit repeatedly until the golf ball breaks The number of times 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 durability of each golf ball is determined according to the golf ball no. The number of hits in 2 was taken as 100, and the hit count for each golf ball was shown as an index value. The larger the indexed value, the more excellent the golf ball is.

(10) 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)

[Production of golf balls]
(1) Production of Core A rubber composition having 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 a center. An appropriate amount of barium sulfate was added so that the mass of the obtained golf ball was 45.4 g.

ＢＲ−７３０：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」

BR-730: manufactured by JSR, "BR730 (High cis polybutadiene)"
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 cover composition and intermediate layer composition Using the compounding materials shown in Tables 2 and 4, mixing with a twin-screw kneading extruder, pellet-shaped intermediate layer composition and cover Each composition was prepared. 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
ニュクレルＮ１０５０Ｈ：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
ラバロンＴ３２２１Ｃ：三菱化学社製のスチレン系エラストマー
ウルトラマリンブルー：第一化成工業社製、群青Ｎｏ．１５００

Surlyn 8945: Sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin Himiran AM 7329 manufactured by DuPont Zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin Nucrel N1050H manufactured by Mitsui DuPont Polychemical Co., Ltd .: Mitsui DuPont Polychemical Co., Ltd., ethylene / methacrylic acid copolymer Lavalon T3221C: Mitsubishi Chemical Corporation styrene elastomer Ultramarine Blue: Daiichi Kasei Kogyo Co., Ltd., ultramarine No. 1500

(3) Production of Golf Ball Body The intermediate layer composition obtained above is injection-molded on the core obtained as described above to form an intermediate layer covering the core, and the spherical core is formed. Produced. Subsequently, a cover was formed by injection molding a cover composition on the spherical core to produce a golf ball. The molding upper and lower molds for molding the intermediate layer and the cover have hemispherical cavities, have pimples, and also serve as hold pins in which a part of the pimples can advance and retreat.

  At the time of forming the intermediate layer, the hold pin is protruded, the center is inserted and held, and the intermediate layer composition heated to 260 ° C. is injected into the mold clamped at a pressure of 80 tons in 0.3 seconds, and 30 seconds. After cooling, the mold was opened and the core was taken out.

  At the time of molding the cover, the hold pin is protruded, the core is inserted and held, and a mold heated at a pressure of 80 tons is injected with a resin heated to 210 ° C. in 0.3 seconds, cooled for 30 seconds and opened. The golf ball was taken out. The surface of the obtained golf ball main body is sandblasted and marked, and then a clear paint is applied and the paint is dried in an oven at 40 ° C. to obtain a golf ball having a diameter of 42.8 mm and a mass of 45.4 g. It was.

  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 “curvature radius” is a curvature radius of the bottom curved surface of the dimple, and the “area” is calculated by area = (Di / 2) 2 × π. “Occupancy ratio” is the ratio of the total area of all the dimples 10 to the surface area of the phantom sphere 14.

得られたゴルフボール圧縮変形量、飛距離、耐久性および打球感について評価した結果を表４に示した。

Table 4 shows the results of evaluation of the obtained golf ball compression deformation, flight distance, durability, and feel at impact.

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（メルトフローレイト（１９０℃×２．１６ｋｇ）：１０ｇ／１０ｍｉｎ）
サーリン８１５０：デュポン社製、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（メルトフローレイト（１９０℃×２．１６ｋｇ）：４．５ｇ／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（メルトフローレイト（１９０℃×２．１６ｋｇ）：５ｇ／１０ｍｉｎ）
サーリン９１５０：デュポン社製、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（メルトフローレイト（１９０℃×２．１６ｋｇ）：４．５ｇ／１０ｍｉｎ）
サーリン６３２０：デュポン社製、マグネシ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（メルトフローレイト（１９０℃×２．１６ｋｇ）：１．１ｇ／１０ｍｉｎ）
ＨＰＦ１０００：デュポン社製、マグネシ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（メルトフローレイト（１９０℃×２．１６ｋｇ）：０．６５ｇ／１０ｍｉｎ）
ニュクレルＮ２０５０Ｈ：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（メルトフローレイト（１９０℃×２．１６ｋｇ）：５００ｇ／１０ｍｉｎ）
ニュクレルＡＮ４３１８：三井・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（メルトフローレイト（１９０℃×２．１６ｋｇ）：３０ｇ／１０ｍｉｎ）
ラバロンＴ３２２１Ｃ：三菱化学社製のスチレン系エラストマー
ＰＳ−３Ｓ：阪本薬品工業社製、テトラグリセリンペンタステアレート（ＨＬＢ：２．６）
ＨＢ−７５０：阪本薬品工業社製、デカグリセリンヘプタベヘネート（ＨＬＢ：３．５）
ＭＳ−１５０：阪本薬品工業社製、ジグリセリンモノステアレート（ＨＬＢ：５．５）
ベヘン酸：日油社製、「ＮＡＡ−２２２Ｓ粉末」
ステアリン酸：日油社製、「粉末ステアリン酸つばき」
Ｍｇ（ＯＨ）_２：米山薬品工業社製
Ｃａ（ＯＨ）_２：米山薬品工業社製
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

High Milan 1555: Mitsui DuPont Polychemical Co., Ltd., sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin (melt flow rate (190 ° C. × 2.16 kg): 10 g / 10 min)
Surlyn 8150: manufactured by DuPont, sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin (melt flow rate (190 ° C. × 2.16 kg): 4.5 g / 10 min)
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)
Surlyn 9150: DuPont, zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin (melt flow rate (190 ° C. × 2.16 kg): 4.5 g / 10 min)
Surlyn 6320: manufactured by DuPont, magnesium ion neutralized ethylene-methacrylic acid copolymer ionomer resin (melt flow rate (190 ° C. × 2.16 kg): 1.1 g / 10 min)
HPF1000: manufactured by DuPont, magnesium ion neutralized ethylene-methacrylic acid copolymer ionomer resin (melt flow rate (190 ° C. × 2.16 kg): 0.65 g / 10 min)
Nukurel N2050H: manufactured by Mitsui DuPont Polychemical Co., Ltd., ethylene / methacrylic acid copolymer (melt flow rate (190 ° C. × 2.16 kg): 500 g / 10 min)
Nucleel AN4318: manufactured by Mitsui DuPont Polychemical Co., Ltd., ethylene / methacrylic acid copolymer (melt flow rate (190 ° C. × 2.16 kg): 30 g / 10 min)
Lavalon T3221C: Styrene elastomer manufactured by Mitsubishi Chemical Corporation PS-3S: Sakamoto Yakuhin Kogyo Co., Ltd., tetraglycerin pentastearate (HLB: 2.6)
HB-750: Sakamoto Pharmaceutical Co., Ltd., decaglycerin heptabehenate (HLB: 3.5)
MS-150: diglycerin monostearate (HLB: 5.5) manufactured by Sakamoto Pharmaceutical Co., Ltd.
Behenic acid: “NAA-222S powder” manufactured by NOF Corporation
Stearic acid: manufactured by NOF Corporation
Mg (OH) ₂ : Yoneyama Pharmaceutical Co., Ltd. Ca (OH) ₂ : Yoneyama Pharmaceutical Co., Ltd. Tungsten: Allied Material Co., tungsten powder C50G

  Golf ball no. In Nos. 1 to 9, the intermediate layer is formed from the composition for high fluidity intermediate layer, the intermediate layer has a thickness of 0.5 mm to 1.6 mm, and the cover has a thickness of 0.3 mm to 1.6 mm. The slab hardness (Hc) of the cover composition forming the cover is a Shore D hardness of 56 or more. All of these are excellent in flight distance, durability and feel at impact.

  Golf ball no. 10 is a case where the slab hardness (Hm) of the intermediate layer composition exceeds 57 in Shore D hardness, but the flight distance is excellent, but the durability and feel at impact are inferior. Golf ball no. 11 is a case where the composition for an intermediate layer does not contain a component (B) and a low molecular material such as a fatty acid, but the fluidity was poor and the intermediate layer could not be formed.

  Golf ball no. 12 and 13 are cases where the intermediate layer composition contains a fatty acid instead of the component (B), and the slab hardness (Hm) exceeds 57 in Shore D hardness. These golf balls are excellent in flight distance but are inferior in durability and feel at impact. In these golf balls, it is presumed that the fatty acid bleeds out during the molding of the intermediate layer, and the bleed out of the fatty acid is also considered to be a factor of lowering the durability.

  Golf ball no. 14 to 16 are golf ball Nos. 4 is used, but when the slab hardness (Hc) of the cover composition is less than 56 in Shore D hardness (golf ball No. 14), the thickness of the intermediate layer is When the thickness exceeds 1.6 mm (golf ball No. 15), the thickness of the cover exceeds 1.6 mm (golf ball No. 16). Golf ball no. Although 14 is excellent in durability and feel at impact, the flight distance is inferior. Golf ball no. Although 15 and 16 are excellent in durability, the flight distance is inferior and the shot feeling is also slightly inferior.

  The present invention relates to a golf ball, and more specifically, is suitable for a technique for improving the characteristics of an intermediate layer and a technique for forming an intermediate layer.

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, De: Dimple deepest point, Di: Dimple diameter, Ed: Edge, P: Pole, T: Tangent

Claims (10)

A golf ball having a core, at least one intermediate layer covering the core, and a cover covering the intermediate layer,
At least one piece or one layer of the intermediate layer is a resin component,
(A) As a base resin, (a-1) a metal ion neutralized product of a binary copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, ethylene and 3 to 8 carbon atoms An ionomer resin comprising a metal ion neutralized product of a terpolymer of α, β-unsaturated carboxylic acid and α, β-unsaturated carboxylic acid ester, or a mixture thereof, and / or (a -2) A binary copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, ethylene, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and α, β-unsaturated A terpolymer with a saturated carboxylic acid ester, or a nonionic resin comprising a mixture thereof; and (B) a polyglycerin fatty acid ester,
The (B) polyglycerin fatty acid ester is represented by the following formula (1):

[Wherein, R ¹ , R ² and R ³ are the same or different and represent a hydrogen atom or a fatty acid residue having 6 to 30 carbon atoms, and n represents an integer of 2 to 20]. A plurality of R ³ may be the same or different. ]
It is represented by
The content of the (B) polyglycerin fatty acid ester is 1 part by mass to 45 parts by mass with respect to 100 parts by mass of the base resin (A),
Slab hardness (Hm) is formed from the composition for high fluidity intermediate | middle layers whose Shore D hardness is 35-57,
The intermediate layer has a thickness of 0.5 mm to 1.6 mm,
A golf ball, wherein the cover has a thickness of 0.3 mm to 1.6 mm, and the cover composition forming the cover has a slab hardness (Hc) of 56 or more in Shore D hardness. ^2. The golf ball according to claim 1 , wherein at least one of R ¹ , R ² , and R ^{3 in} the formula (1) is a stearic acid residue or a behenic acid residue. The (B) polyglycerol fatty acid ester is diglycerol monostearate, tetraglycerol pentastearate, hexaglycerol pentastearate, decaglycerol tristearate, decaglycerol decastate, decaglycerol heptabehenate, hexaglycerol dibe. Heneto, hexaglycerin tetra behenate, hexamethylene hexabehenate, according to claim 1 or 2 is at least one selected from the group consisting of hexaglycerol octa behenate and decaglycerol dodeca behenate Golf ball. The high fluidity intermediate layer composition further comprises (C) a metal ion source capable of neutralizing the carboxyl group in the base resin (A) in 100 parts by mass of the base resin (A). the golf ball according to any one of claims 1 to 3 containing 10 parts by 0.1 parts by weight for. The golf ball according to any one of the preceding claims density of the intermediate layer is ^{1.10g / cm 3 ~1.50g / cm 3} 1~ 4. The golf ball according to any one of claims 1 to 5 the diameter of the core is not less than 38.0 mm. Melt flow rate (190 ℃ × 2.16kg) The golf ball according to any one of claims 1 to 6 in 1 g / 10min or more of the high fluidity intermediate layer composition. The golf ball according to any one of claims 1 to 7 , wherein the composition for a high fluidity intermediate layer contains only (a-1) an ionomer resin as the (A) base resin. The high fluidity intermediate layer composition The golf ball according to any one of claims 1 to 7 containing only (a-2) a non-ionic resin as (A) base resin. The high fluidity intermediate layer composition comprises (A) ionomer resin and (a-2) nonionic resin as (A) base resin, and (a-1) ionomer resin / (a-2). The golf ball according to any one of claims 1 to 7 , which is contained in a ratio of nonionic resin = 1% by mass to 90% by mass / 99% by mass to 10% by mass.

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