JP5322571B2 - Golf ball - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a golf ball with good low-temperature endurance and normal temperature endurance, and with good flying distance, directional stability, and a ball-hitting sensation at the time of hitting a ball. <P>SOLUTION: The golf ball is provided with a core composed of a center and an enclosure layer which covers the center, one or more inner layers which cover the core, and a cover which covers the inner layers. The cover is formed of (A) highly-elastic polyamide resin with 700-5,000 MPa of flexural modulus, (B) metal neutralizing material of ethylene methacrylic acid binary copolymer and/or metal neutralizing material of ethylene methacrylic acid-methacrylic ester ternary copolymer, and (C) a composition for cover, which contains a specific amount of resin containing a polar functional group as resin component. The thickness of the cover is 0.3 to 1.0 mm, the slab hardness of the composition for cover is 65 to 75 of shore D hardness, the diameter of the center is 35 mm or less, and the difference in hardness (H3-H1) between the hardness of the center of the core (H1) and the hardness of the surface of the core (H3) is 10 or more in shore D hardness. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a golf ball, and more particularly, to a technique for maintaining a normal temperature durability and a low temperature durability and improving a flight distance, a directional stability, and a shot feeling at the time of hitting.

  Conventionally, a method for improving the flight distance of a golf ball by thinning the cover of the golf ball and enlarging a core made of a rubber composition having high resilience is known. However, as the cover is made thinner, the volume of the cover layer is reduced, so that the rigidity of the cover layer is lowered, and there is a problem that the spin rate is increased when a driver or the like is shot.

  In order to solve such a problem, it has been proposed to use a highly rigid resin for the cover composition forming the cover. For example, Patent Documents 1 and 2 disclose a golf ball using a high acid ionomer as a resin component of a cover composition. Patent Document 3 discloses a golf ball using a diamine complex ionomer resin as a resin component of the cover composition. However, when an ionomer resin or a diamine complex ionomer resin having a high acid content is used as the cover composition, there is a problem that the durability of the golf ball is lowered. Further, when an ionomer resin having a high degree of neutralization is used, there is a problem that the moldability of the cover composition is lowered.

  In view of this, there has been proposed a technique for achieving high rigidity without using an ionomer resin having a high acid content or a high degree of neutralization as described above. For example, U.S. Patent No. 6,057,051 contains about 4 to 95 wt.% Of one or more ionomer resins, about 95 to 4 wt.% Of one or more nonionic polymers, and about 100 parts to 100 parts of ionomer resins and nonionic polymers. 1 to 15 phr of a non-carboxylic acid compatibilizer comprising a material selected from the group consisting of one or more functionalized block and graft polymers, oligomers, and mixtures thereof, It is disclosed to use a compatibilized blend that is at least partially miscible with one or more ionomers and at least a portion of the non-carboxylic acid compatibilizer is miscible with one or more nonionic polymers. ing.

  U.S. Patent No. 6,057,051 uses a composition comprising a blend substantially free of about 10 to about 80 wt% of at least one ionomer and about 90 to about 20 wt% of at least one polyamide polymer. Is disclosed. Patent Document 6 discloses a golf ball mainly composed of a rubber-modified thermoplastic resin composition obtained by blending a functional rubber-like copolymer with a base resin composed of an ionomer resin, a non-ionomer thermoplastic elastomer, or a mixture thereof. A cover material is disclosed.

Patent Document 7 includes one or more selected from the group consisting of the following components (I) to (III), (I) ionomer, (II) diene polymer, thermoplastic polymer and thermosetting polymer. A golf ball material comprising a resin composition and (III) a thermoplastic resin composition having an acid group as essential components is disclosed.
JP-A-6-80718 Japanese Patent Laid-Open No. 9-10357 Japanese Patent Laid-Open No. 10-127822 Special table 2001-509204 gazette JP-T-2001-514561 JP-A-10-314341 JP 2007-622 A

  Conventionally, attempts have been made to solve the problem that the rigidity of the cover layer decreases with the thin cover by increasing the rigidity of the cover material. However, the durability of the golf ball is poor in the thin cover structure. As it became sufficient or the resilience was insufficient, further improvement was necessary for practical use.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a golf ball that is excellent in low temperature durability and normal temperature durability, and excellent in flight distance, directional stability and feel at impact. And

  The golf ball of the present invention that has solved the above-described problem has a core comprising a center and an envelope layer that covers the center, one or more intermediate layers that cover the core, and a cover that covers the intermediate layer. A golf ball, wherein the cover comprises, as a resin component, (A) a highly elastic polyamide resin having a flexural modulus of 700 MPa to 5000 MPa, (B) a metal neutralized product of an ethylene- (meth) acrylic acid binary copolymer And / or a metal neutralized product of ethylene- (meth) acrylic acid- (meth) acrylic acid ester terpolymer and (C) a resin having a polar functional group, and (A) a highly elastic polyamide resin. And (B) the content ratio (total 100% by mass) of the metal neutralized product of the binary copolymer and / or the metal neutralized product of the ternary copolymer is (A) a highly elastic polyamide resin / B) Metal neutralized product of binary copolymer and / or metal neutralized product of ternary copolymer = 5% by mass to 80% by mass / 95% by mass to 20% by mass, and (A) high elasticity (C) Resin having a polar functional group is 0 with respect to 100 parts by mass in total of polyamide resin and (B) neutralized metal of binary copolymer and / or neutralized metal of ternary copolymer. The cover composition is formed from 1 part by mass to 20 parts by mass, the cover has a thickness of 0.3 mm to 1.0 mm, and the slab hardness (H5) of the cover composition is Shore. The D hardness is 65 to 75, the diameter of the center is 35 mm or less, and the hardness difference (H3−H1) between the center hardness (H1) of the core and the surface hardness (H3) of the core is the Shore D hardness And 10 or more.

  That is, the present invention provides a cover composition having a high elasticity (A) a highly elastic polyamide resin; a high resilience and good fluidity (B) a metal neutralized binary copolymer and / or three Metal neutralized product of the original copolymer; (C) By adding a predetermined amount of resin having a polar functional group, the (A) component increases the elasticity of the cover composition and further improves the low temperature characteristics. The repulsion and fluidity of the cover composition are improved by the component (B), and the fluidity of the cover composition is not impaired by the component (C). Interfacial strength is improved. As a result, a cover having high elasticity and improved low-temperature characteristics can be obtained by forming a cover from the cover composition. The present invention uses the above cover composition to maintain the normal temperature durability and low temperature durability of the golf ball, while reducing the thickness of the cover, softening the inner and outer cores, and reducing the diameter of the center. The main point is that the spin distance is reduced to improve the flight distance and the directional stability, and even if the cover has a high hardness, the hit feeling is not impaired.

The density of the intermediate layer is preferably 1.10 g / cm ³ or more. 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.

  As for the slab properties of the cover composition, it is preferable that the bending elastic modulus is 300 MPa to 1000 MPa, and the tensile elastic modulus is 400 MPa to 1500 MPa.

  The (A) high-elasticity polyamide resin is composed of polyamide 6, polyamide 11, polyamide 12, polyamide 66, polyamide 610, polyamide 6T, polyamide 6I, polyamide 9T, polyamide M5T, polyamide 612, and a polyether block amide copolymer. It is preferable to contain at least one selected from

  The resin having (C) polar functional group is at least one selected from the group consisting of an ethylene-glycidyl methacrylate copolymer, an ethylene-acrylic acid-glycidyl methacrylate copolymer, and a methyl methacrylate-glycidyl methacrylate copolymer. Species are preferred.

  It is preferable that the center hardness (H1) of the core, the slab hardness (H4) of the intermediate layer, and the surface hardness (H3) of the core satisfy the relationship of H1 ≦ H4 <H3.

  The main component of the center composition forming the center and the envelope layer composition forming the envelope layer is preferably a rubber component, and the main component of the intermediate layer composition forming the intermediate layer Is preferably a thermoplastic material.

  According to the present invention, a golf ball having excellent low temperature durability and normal temperature durability, and excellent flight distance, directional stability and feel at impact can be obtained.

  The golf ball of the present invention is a golf ball having a core composed of a center and an envelope layer covering the center, one or more intermediate layers covering the core, and a cover covering the intermediate layer, And (A) a highly elastic polyamide resin having a flexural modulus of 700 MPa to 5000 MPa, (B) a metal neutralized ethylene- (meth) acrylic acid binary copolymer and / or ethylene- (meth) acrylic as a resin component. A metal neutralized acid- (meth) acrylic ester terpolymer and (C) a resin having a polar functional group, the (A) highly elastic polyamide resin and (B) a binary copolymer The content ratio of the metal neutralized product and / or the ternary copolymer to the metal neutralized product (total 100% by mass) in the metal of (A) highly elastic polyamide resin / (B) binary copolymer Japanese And / or metal neutralized product of ternary copolymer = 5% by mass to 80% by mass / 95% by mass to 20% by mass of (A) the highly elastic polyamide resin and (B) the binary copolymer. For a cover containing 0.1 to 20 parts by mass of a resin having a polar functional group (C) with respect to 100 parts by mass in total with the metal neutralized product and / or the metal neutralized product of the terpolymer. The cover has a thickness of 0.3 mm to 1.0 mm, and the cover composition has a slab hardness (H5) of Shore D hardness of 65 to 75, and the center. The diameter of the core is 35 mm or less, and the hardness difference (H3−H1) between the center hardness (H1) of the core and the surface hardness (H3) of the core is 10 or more in Shore D hardness.

  The (A) highly elastic polyamide resin having a flexural modulus of 700 MPa to 5000 MPa will be described.

  The (A) high-elasticity polyamide resin is not particularly limited as long as it is a polyamide-based resin or polyamide-based elastomer containing polyamide and has a flexural modulus of 700 MPa to 5000 MPa. Here, the polyamide is a polymer having a plurality of amide bonds (—NH—CO—) in the main chain. By using such a highly elastic polyamide resin, it is possible to increase the elastic modulus of the cover composition, and it is possible to suppress a decrease in resilience even if the cover is thin. Moreover, the low temperature durability of a cover can also be improved by using the polyamide resin which is excellent in a low temperature characteristic.

  Examples of the polyamide contained in the (A) high-elasticity polyamide resin include fats such as polyamide 6, polyamide 11, polyamide 12, polyamide 66, polyamide 610, polyamide 6T, polyamide 6I, polyamide 9T, polyamide M5T, and polyamide 612. Aromatic polyamides such as poly-p-phenylene terephthalamide and poly-m-phenylene isophthalamide; polyether block amide copolymers, polyester amide copolymers, polyether ester amide copolymers, polyamide imides Examples thereof include amide copolymers such as copolymers. These may be used alone or in combination of two or more. Among these, aliphatic polyamides such as polyamide 6, polyamide 11, and polyamide 12 are preferable.

  The flexural modulus of the (A) highly elastic polyamide resin is 700 MPa or more, preferably 750 MPa or more, more preferably 800 MPa or more. When the flexural modulus of the (A) high-elasticity polyamide resin is 700 MPa or more, the cover has a high rigidity, and the effect of reducing the spin rate for shots of a driver or the like is increased. The flexural modulus of the (A) high-elasticity polyamide resin is 5000 MPa or less, preferably 4500 MPa or less, more preferably 4000 MPa or less. If the flexural modulus of the (A) high-elasticity polyamide resin is 5000 MPa or less, the cover will not be excessively rigid, and the shot feel and durability will be good. In the present invention, the flexural modulus of the highly elastic polyamide resin is a value measured according to ISO 178, and details of the measuring method will be described later.

  The embrittlement temperature of the (A) highly elastic polyamide resin is preferably −20 ° C. or lower, more preferably −30 ° C. or lower, and further preferably −50 ° C. or lower. When the embrittlement temperature of the (A) highly elastic polyamide resin is −20 ° C. or lower, the low temperature durability of the cover can be further improved, and the low temperature durability of the resulting golf ball can be further improved. In the present invention, the embrittlement temperature of the highly elastic polyamide resin means a value measured according to JIS K7216.

  Specific examples of the (A) high-elasticity polyamide resin are indicated by trade names, for example, “Novamid (registered trademark) ST220, Novamid 1010C2, Novamid ST145” manufactured by Mitsubishi Engineering, and “Pebax (registered trademark)” manufactured by Arkema. 4033SA ”,“ UBE Nylon 1018I, UBE Nylon 1030J ”manufactured by Ube Industries, Ltd.,“ UBESTA (registered trademark) P3014U, UBESTA3035JU6, UBESTA PAE1200U2 ”,“ Zytel (registered trademark) FN716, Zytel ST811HS ”manufactured by DuPont “Amilan (registered trademark) U441, Amilan U328, Amilan U141” manufactured by Asahi Kasei Co., Ltd., and “Leona (registered trademark) 1300S” manufactured by Asahi Kasei are listed.

  The content of the (A) highly elastic polyamide resin in the resin component constituting the cover composition is preferably 8% by mass or more, more preferably 15% by mass or more, and further preferably 25% by mass or more. It is preferably 75% by mass or less, more preferably 70% by mass or less, and still more preferably 60% by mass or less. If the content of the (A) high-elasticity polyamide resin in the resin component constituting the cover composition is 8% by mass or more, the elastic modulus of the cover is high, and the launch angle is increased with respect to shots such as drivers. On the other hand, if the effect of lowering spin is greater, on the other hand, if it is 75% by mass or less, the elastic modulus of the cover will not be too high, and the durability and feel at impact of the golf ball will be better.

  (B) Metal-neutralized product of ethylene- (meth) acrylic acid binary copolymer and / or metal-neutralized product of ethylene- (meth) acrylic acid- (meth) acrylic acid ester ternary copolymer The “(B) copolymer metal neutralized product” will be simply described. In addition, in this application, (meth) acrylic acid shows acrylic acid and / or methacrylic acid.

  The (B) copolymer metal neutralized product is a binary copolymer obtained by copolymerizing a monomer composition containing ethylene and (meth) acrylic acid, and the binary Monomer composition containing a metal neutralized product in which at least a part of the carboxyl group of the copolymer is neutralized with a metal ion; and / or ethylene, (meth) acrylic acid and (meth) acrylic acid ester A ternary copolymer obtained by copolymerizing a product, wherein at least a part of carboxyl groups of the ternary copolymer is neutralized with a metal ion.

  Examples of the (meth) acrylic acid ester include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, isobutyl (meth) acrylate, n-butyl (meth) acrylate, ( Examples include isooctyl (meth) acrylate and 2-ethylhexyl (meth) acrylate.

  The content of the (meth) acrylic acid component in the ethylene- (meth) acrylic acid copolymer constituting the (B) copolymer metal neutralized product is preferably 2% by mass or more, more preferably 3% by mass. It is above, 30 mass% or less is preferable, More preferably, it is 25 mass% or less.

  Further, the copolymer constituting the (B) copolymer metal neutralized product is an amount other than ethylene, (meth) acrylic acid, and (meth) acrylic acid ester, as long as the effects of the present invention are not impaired. It may be a multi-component copolymer in which a monomer is copolymerized. Examples of other monomers that can be used in the copolymer include vinyl esters such as vinyl acetate and vinyl propionate; unsaturated carboxylic acid esters such as dimethyl maleate and diethyl maleate; carbon monoxide; Examples include sulfur dioxide.

  When the other monomer is used, the content of these other monomer components in the copolymer is preferably 40% by mass or less, more preferably 30% by mass or less, and still more preferably It is 20 mass% or less.

  Examples of the metal (ion) used in the (B) copolymer metal neutralized product include monovalent metals (ions) such as sodium, potassium and lithium; divalent metals such as magnesium, calcium, zinc, barium and cadmium. Metal (ion); trivalent metal (ion) such as aluminum; other metal (ion) such as tin and zirconium. Among these, sodium, zinc, and magnesium (ion) are particularly preferably used from the viewpoint of resilience and durability.

  The neutralization degree of the carboxyl group contained in the (B) copolymer metal neutralized product is preferably 20 mol% or more, more preferably 30 mol% or more, and preferably 90 mol% or less, more preferably 85 mol%. It is less than mol%. In addition, the neutralization degree of the carboxyl group in (B) copolymer metal neutralized material can be calculated | required by a following formula.

  The flexural modulus of the (B) copolymer metal neutralized product is preferably 250 MPa or more, more preferably 260 MPa or more, further preferably 270 MPa or more, preferably 1000 MPa or less, more preferably 800 MPa or less, still more preferably 600 MPa. It is as follows. If the bending elastic modulus of the (B) neutralized copolymer metal is 250 MPa or more, the elastic modulus of the cover will be high, and the effect of increasing the launch angle and reducing the spin will be greater for shots such as drivers. If the bending elastic modulus is 1000 MPa or less, the elastic modulus of the cover does not become too high, and the durability and feel at impact of the golf ball become better.

  A specific example of the (B) copolymerized metal neutralized product is exemplified by a trade name, “Himiran (registered trademark)” (for example, Himiran 1555 (Na), commercially available from Mitsui DuPont Polychemical Co., Ltd., High Milan 1605 (Na), High Milan 1706 (Zn), High Milan 1707 (Na), High Milan AM 7311 (Mg), High Milan AM 7329 (Zn), High Milan 1856 (Na), High Milan 1855 (Zn), etc.).

  Furthermore, “Surlyn (registered trademark)” commercially available from DuPont (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), Surlyn 6320 (Mg), Surlyn 8120 (Na), Surlyn 8320 (Na), Surlyn 9320 (Zn), Surlyn 9320W (Zn), etc.) "," HPF 1000 (Mg), HPF 2000 (Mg) ".

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

  In addition, Na, Zn, Li, Mg, etc. described in parentheses after the above-mentioned trade names indicate the metal species of these neutralized metal ions.

  The content of the (B) copolymer metal neutralized product in the resin component constituting the cover composition is preferably 25% by mass or more, more preferably 35% by mass or more, and still more preferably 40% by mass. % Or more, preferably 92% by mass or less, more preferably 85% by mass or less, and still more preferably 75% by mass or less. When the content of the (B) copolymer metal neutralized product in the resin component constituting the cover composition is 25% by mass or more, the resilience and durability of the golf ball become better, while 92% by mass. If it is less than or equal to%, the elastic modulus of the cover will be in an appropriate range, and the effect of increasing the launch angle and reducing the spin will be greater with respect to shots from drivers and the like.

  The (C) resin having a polar functional group will be described.

  The (C) resin having a polar functional group is not particularly limited as long as it is a polymer into which a polar functional group has been introduced. For example, a monomer having a polar functional group and a monomer having no polar functional group are used. It is a resin obtained by copolymerizing with a monomer. Here, the polar functional group is a functional group having polarity, and a functional group that causes the resin to generate polarity. For example, an epoxy group, a hydroxyl group, an amino group, a nitro group, a carboxyl group, a formyl group , A nitrile group, a sulfonic acid group, and the like. Among these, an epoxy group and a carboxyl group are preferable.

  (C) Since a resin having a polar functional group has a low polarity in the main skeleton constituting the resin, this main skeleton has good compatibility with (A) a highly elastic polyamide resin, and the polar functional group introduced into the resin is Since the polarity is high, this polar functional group (side chain portion) has good compatibility with the (B) neutralized copolymer metal. Therefore, dispersibility of the (A) highly elastic polyamide resin and the (B) neutralized copolymer metal is improved by including (C) a resin having a polar functional group in the cover composition. Thus, the normal temperature durability and low temperature durability of the golf ball can be further improved.

  Examples of the monomer having a polar functional group include epoxy group-containing monomers such as glycidyl (meth) acrylate, 2-vinyloxirane, and (allyloxy) oxirane; 2-hydroxyethyl (meth) acrylate, 2-hydroxy Hydroxyl-containing monomers such as propyl (meth) acrylate, vinyl alcohol, allyl alcohol, 2-hydroxyethyl vinyl ether; sulfonic acid group-containing monomers such as vinyl sulfonic acid; (meth) acrylic acid, itaconic acid, maleic anhydride And carboxyl group-containing monomers such as Only 1 type may be used for the monomer which has these polar functional groups, and it may use 2 or more types together. Among these, as the monomer having the polar functional group, an epoxy group-containing monomer is preferable, and glycidyl (meth) acrylate is particularly preferable. Since the epoxy group has reactivity with the carboxyl group of the (B) copolymer metal neutralized product, the (A) highly elastic polyamide resin and the (B) copolymer metal neutralized product It is possible to further improve the interfacial strength.

  Examples of the monomer having no polar functional group include olefins such as ethylene, propylene, 1-butene, isobutene, and 1-pentene; methyl (meth) acrylate, ethyl (meth) acrylate, and propyl (meth) acrylate. And alkyl (meth) acrylates such as n-butyl (meth) acrylate and isobutyl (meth) acrylate. Only 1 type may be used for the monomer which does not have these polar functional groups, and 2 or more types may be used together. Among these, ethylene and methyl (meth) acrylate are preferred as monomers having no polar functional group.

  The content of the monomer component having a polar functional group in the resin having the (C) polar functional group is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and further preferably 1% by mass. % Or more, preferably 30% by mass or less, more preferably 25% by mass or less, and still more preferably 20% by mass or less. By setting the content of the monomer component having a polar functional group in the resin having the (C) polar functional group within the above range, the (A) highly elastic polyamide resin and (B) in the copolymer metal Dispersibility with Japanese products can be sufficiently enhanced.

  Examples of the resin having the (C) polar functional group include (meth) acrylic acid ester-glycidyl (meth) acrylate copolymer, epoxy group-containing (meth) acrylic polymer, ethylene-glycidyl (meth) acrylate copolymer. Copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid- (meth) acrylic acid ester copolymer, ethylene- (meth) acrylic acid ester-glycidyl (meth) acrylate copolymer, maleic Acid-modified styrene-ethylene-butylene-styrene block polymer (SEBS), maleic acid-modified styrene-ethylene-butylene-olefin crystal block polymer (SEBC), maleic acid-modified polyethylene (PE), maleic acid-modified polypropylene (PP), maleic acid Modified ethylene-vinyl acetate Alcohol copolymer (EVA), and maleic acid-modified ethylene - propylene - diene rubber (EPDM), an epoxy group-containing styrene polymer can be exemplified. These resins having a polar functional group (C) may be used alone or in combination of two or more. Among these, an ethylene-glycidyl (meth) acrylate copolymer, an ethylene- (meth) acrylate ester-glycidyl (meth) acrylate copolymer, and a methyl (meth) acrylate-glycidyl (meth) acrylate copolymer are preferable, In particular, an ethylene-glycidyl methacrylate copolymer or a mixture of an ethylene-glycidyl methacrylate copolymer and a resin having another (C) polar functional group is preferable.

  Specific examples of the resin having a polar functional group (C) are exemplified by trade names, for example, “LOTADER AX8840” manufactured by Arkema Co., Ltd., “Alphon (registered trademark) UG-” manufactured by Toa Gosei Co., Ltd. 4030 "," Bond Fast (registered trademark) E "manufactured by Sumitomo Chemical Co., Ltd.," Tuff Tech (registered trademark) M1913, Tuftec M1943 "manufactured by Asahi Kasei Co., Ltd.," FUSABOND (registered trademark) NM052D "manufactured by DuPont, manufactured by JSR “Dynalon (registered trademark) 4630P” manufactured by Mitsui Dupont Polychemical Co., Ltd. Nucrel N410, Nucrel N1035, NUCREL N1050H, Nucrel N1108C, Nucrel N1110H, Nucrel N1207C, Nucrel N1214, Nucrel AN4221C, Nucrel N1525, Nucrel N1560, Nucrel N0200H, Nucrel AN4228C, Nucrel N4213C, etc. NUCREL N035C) ", and the like.

  The content ratio of (A) high-elasticity polyamide resin and (B) neutralized copolymer metal in the cover composition (when 100% by mass in total) is (A) high-elasticity polyamide resin / ( B) Copolymer metal neutralized product = 5% by mass to 80% by mass / 95% by mass to 20% by mass. By setting the content ratio of the (A) highly elastic polyamide resin and the (B) copolymer metal neutralized product within the above range, the cover has a desired elastic modulus, and a high launch angle with respect to shots such as drivers. And low spin, and the flight distance of the golf ball is improved. The content ratio (total 100% by mass) of (A) highly elastic polyamide resin and (B) neutralized copolymer metal in the cover composition is more preferably (A) highly elastic polyamide resin / (B ) Copolymer metal neutralized product = 10 mass% to 75 mass% / 90 mass% to 25 mass%, more preferably 30 mass% to 70 mass% / 70 mass% to 30 mass%.

  The content of the resin having the (C) polar functional group in the cover composition is 20 with respect to a total of 100 parts by mass of the (A) highly elastic polyamide resin and the (B) neutralized copolymer metal. It is below mass parts. (C) If content of resin which has a polar functional group is 20 mass parts or less, the fluidity | liquidity of the composition for a cover will not fall too much, and a moldability will become favorable. (C) Content of resin which has a polar functional group becomes like this. Preferably it is 15 mass parts or less, More preferably, it is 10 mass parts or less. The content of the resin having (C) polar functional group is 0.1 parts by mass or more with respect to 100 parts by mass in total of (A) highly elastic polyamide resin and (B) neutralized copolymer metal. is there. (C) If content of resin which has polar functional group is 0.1 mass part or more, the improvement effect of the mutual dispersibility of (A) highly elastic polyamide resin and (B) copolymer metal neutralized product will be Become bigger. (C) Content of resin which has a polar functional group becomes like this. Preferably it is 2 mass parts or more.

  The cover composition is a resin component other than (A) a highly elastic polyamide resin, (B) a copolymer metal neutralized product, and (C) a resin having a polar functional group, as long as the effects of the present invention are not hindered. However, it is preferable that the resin component contains only the (A) highly elastic polyamide resin, (B) neutralized copolymer metal, and (C) a resin having a polar functional group. .

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

  The content of the white pigment (titanium oxide) is 0.5 parts by mass or more, more preferably 1 part by mass or more, and more preferably 10 parts by mass or less, with respect to 100 parts by mass of the resin component constituting the cover. Is desirably 8 parts by mass or less. By 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.

  In the method for producing a golf ball of the present invention, the (A) highly elastic polyamide resin, (B) neutralized copolymer metal, (C) a resin having a polar functional group, and an additive as necessary are blended. To obtain a cover composition. For the blending of the composition for the cover, for example, a mixer capable of blending pellet-shaped raw materials is preferably used, and a tumbler mixer is more preferably used. For example, (A) a highly elastic polyamide resin, (B) a copolymer metal neutralized product, (C) a resin having a polar functional group, and an additive such as titanium oxide are mixed as a cover composition. And extruding to prepare pellets; (B) an additive such as titanium oxide is mixed with the copolymer metal neutralized product and extruded to prepare white pellets in advance, and the white pellets (A) A mode in which a highly elastic polyamide resin and (C) a pellet of a resin having a polar functional group are dry-blended can be exemplified.

  The slab hardness (H5) of the cover composition is 65 or more in Shore D hardness, preferably 66 or more, more preferably 67 or more, 75 or less, preferably 73 or less, more preferably 70 or less. It is. When the slab hardness (H5) of the cover composition is 65 or more in Shore D hardness, the cover hardness is not too low, and the effect of increasing the launch angle and reducing the spin is greater with respect to shots such as drivers. As a result, the flight distance is further improved. On the other hand, if it is 75 or less, the cover will not be too hard and the feel at impact of the golf ball will be better.

  The bending elastic modulus of the cover composition is preferably 300 MPa or more, more preferably 350 MPa or more, further preferably 450 MPa or more, preferably 1000 MPa or less, more preferably 800 MPa or less, still more preferably 700 MPa or less, particularly preferably. 600 MPa or less. If the bending elastic modulus of the cover composition is 300 MPa or more, the effect of increasing the launch angle and reducing the spin rate for shots of a driver or the like is greater, whereas if it is 1000 MPa or less, the cover composition The moldability of the product is good, and the durability of the golf ball becomes better.

  The tensile elastic modulus of the cover composition is preferably 400 MPa or more, more preferably 410 MPa or more, still more preferably 420 MPa or more, preferably 1500 MPa or less, more preferably 1400 MPa or less, and further preferably 1300 MPa or less. If the tensile modulus of the cover composition is 400 MPa or more, the effect of increasing the launch angle and reducing the spin rate for shots of a driver or the like is greater. The durability becomes better.

  Here, the slab hardness, bending elastic modulus, and tensile elastic modulus of the cover composition are measured by a measuring method described later. The slab hardness, flexural modulus, and tensile modulus of the cover composition are the same as those of (A) highly elastic polyamide resin, (B) neutralized copolymer metal, and (C) resin having polar functional groups. Adjustment can be made by appropriately selecting the combination, the content of additives, and the like.

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

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

  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.

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

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

  The golf ball of the present invention is a golf ball having a core composed of a center and an envelope layer covering the center, one or more intermediate layers covering the core, and a cover covering the intermediate layer, The cover composition has a thickness of 0.3 to 1.0 mm, and the cover composition has a slab hardness (H5) of 65 to 75 in Shore D hardness. The diameter of the center is 35 mm or less, and the hardness difference (H3−H1) between the center hardness (H1) of the core and the surface hardness (H3) of the core is 10 or more in Shore D hardness. And

  The core used in the present invention is a two-layer core comprising a center and an envelope layer covering the center. By configuring the core from the center and the envelope layer, the hardness difference (H3−H1) between the center hardness (H1) of the core and the surface hardness (H3) of the core can be easily adjusted. As a result, the hardness difference (H3−H1) can be increased, and the effect of increasing the launch angle and reducing the spin rate can be obtained for shots of a driver or the like.

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

  The center rubber composition preferably contains a rubber component as a main component. That is, the base rubber content in the center rubber composition is preferably 50% by mass or more. 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 3 parts per 100 parts by mass of the base rubber. It is below mass parts. 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, there exists a possibility that a center may become hard too and a shot feeling may fall.

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

  Subsequently, the envelope layer constituting the two-layer core will be described.

  Examples of the envelope layer composition forming the envelope layer include a rubber composition such as the center composition, or a trade name “HIMILAN (registered trademark)” (for example, HIMILAN 1605, HIMILAN 1706) ”, a thermoplastic resin such as an ionomer resin commercially available from DuPont under the trade name“ Surlyn® (for example, Surlyn 8140, Surlyn 9120) ”, and the trade name“ Pebax from Arkema Co., Ltd. (Registered trademark) (for example, “Pebax 2533”), a commercially available thermoplastic polyamide elastomer from Toray DuPont Co., Ltd. ) ", A commercially available thermoplastic polyester elastomer, BA Thermoplastic polyurethane elastomer marketed by F Japan under the trade name “Elastollan (registered trademark)” (for example, “Elastollan XNY97A”); And thermoplastic elastomers such as thermoplastic polystyrene elastomers. The thermoplastic resin and the thermoplastic elastomer can be used alone or in admixture of two or more. Among these, since the composition for the envelope layer is required to have relatively low hardness and high resilience, a rubber composition containing a rubber component as a main component, such as the center composition, is preferable. From the viewpoint of resilience, it is preferable to use, as the base rubber, a high cis polybutadiene having a cis bond advantageous for resilience of 40% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more.

  As a method for forming the envelope layer, for example, the envelope layer is formed by covering the center with the envelope layer composition. The method of forming the envelope layer is not particularly limited. For example, after the preform for the envelope layer composition is formed into a hollow shell half shell, the upper and lower molds having hemispherical cavities are covered with a pair of upper and lower centers. A method of forming an envelope layer by heating and pressing in a mold at 170 ° C. for 20 minutes can be mentioned.

  Next, the structure of a two-layer core composed of a center and an envelope layer covering the center will be described.

  The center has a diameter of 35 mm or less. By setting the diameter of the center to 35 mm or less, the thickness of the envelope layer can be ensured, and the effect of lowering spin can be obtained for shots of a driver or the like. The center has a diameter of preferably 33 mm or less, more preferably 32 mm or less, preferably 10 mm or more, and more preferably 15 mm or more. If the diameter of the center is 33 mm or less, the envelope layer can be made thicker, so that the effect of lowering the spin on the shot of a driver or the like is greater. If the diameter is 10 mm or more, the core hardness (H1) Since the difference in hardness (H3-H1) from the surface hardness (H3) can be increased, the effect of suppressing spin on a shot of a driver or the like is further increased.

  When the center has a diameter of 15 mm to 32 mm, the amount of compressive deformation (the amount by which 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 preferably 2.5 mm or more. Preferably it is 2.7 mm or more, More preferably, it is 3.0 mm or more, 7.0 mm or less is preferable, More preferably, it is 6.5 mm or less, More preferably, it is 6.0 mm or less. If the amount of compressive deformation is 2.5 mm or more, the effect of suppressing spin and hit feeling at the time of a driver shot are further improved. On the other hand, if it is 7.0 mm or less, the resilience will be better.

  The envelope layer preferably has a thickness of 15 mm or less, more preferably 10 mm or less, still more preferably 5 mm or less, preferably 2 mm or more, and more preferably 2.5 mm or more. When the thickness of the envelope layer is 15 mm or less, the shot feeling of a driver or the like is better when shot, and when the thickness is 2 mm or more, the center diameter can be increased, so that the spin for a shot of a driver or the like is reduced. The effect becomes larger.

  The diameter of the core is preferably 37 mm or more, more preferably 38 mm or more, further preferably 38.5 mm or more, preferably 41 mm or less, more preferably 40.5 mm or less, and still more preferably 40 mm or less. If the diameter of the core is within the above range, the effect of suppressing the spin at the time of a driver shot is further improved.

  When the diameter of the core is 38.5 mm to 40 mm, the amount of compressive deformation (the amount by which the core contracts in the compression direction) from when the initial load 98N is applied to when the final load 1275N is applied is preferably 2.7 mm or more. More preferably, it is 2.9 mm or more, More preferably, it is 3.2 mm or more, 4.5 mm or less is preferable, More preferably, it is 4.2 mm or less, More preferably, it is 3.8 mm or less. If the amount of compressive deformation is 2.7 mm or more, the effect of suppressing spin and shot feel at the time of a driver shot and the like are further improved. On the other hand, if it is 4.5 mm or less, the resilience will be better.

  The center hardness (center hardness) (H1) of the core is preferably 22 or more in Shore D hardness, more preferably 25 or more, and further preferably 28 or more. By setting the center hardness (H1) of the core to 22 or more in Shore D hardness, the core does not become too soft and good resilience is obtained. Further, the center hardness (H1) of the core is preferably 42 or less in Shore D hardness, more preferably 40 or less, and still more preferably 38 or less. By setting the central hardness (H1) to a Shore D hardness of 42 or less, the center hardness (H1) 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 (H2) of the center is preferably 44 or more in Shore D hardness, more preferably 46 or more, and still more preferably 48 or more. By setting the surface hardness (H2) to 44 or more in Shore D hardness, the center does not become too soft and good resilience is obtained. Further, the surface hardness (H2) of the center is preferably 60 or less in Shore D hardness, more preferably 58 or less, and still more preferably 56 or less. By setting the surface hardness (H2) to a Shore D hardness of 60 or less, the center does not become too hard, and a good shot feeling can be obtained.

  The surface hardness (H3) of the core is preferably 55 or more in Shore D hardness, more preferably 57 or more, and still more preferably 59 or more. By setting the surface hardness (H3) to 55 or more in Shore D hardness, it is not too soft and good resilience can be obtained. Further, the surface hardness (H3) of the core is preferably 65 or less in Shore D hardness, more preferably 64 or less, and still more preferably 63 or less. By setting the surface hardness (H3) to a Shore D hardness of 65 or less, the difference in hardness from the intermediate layer can be increased, so that the effect of reducing the spin at the time of driver shot is further enhanced.

  The core used for the golf ball of the present invention has a Shore D hardness of 10 or more in hardness difference (H3−H1) between the center hardness (H1) of the core and the surface hardness (H3) of the core. If the hardness difference (H3−H1) is 10 or more in Shore D hardness, the effect of reducing spin on a shot of a driver or the like becomes greater. The hardness difference (H3−H1) is preferably 15 or more, more preferably 20 or more in Shore D hardness. The hardness difference (H3-H1) is Shore D hardness, preferably 35 or less, more preferably 32 or less, and particularly preferably 30 or less. This is because if the hardness difference becomes too large, the durability may be lowered.

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

  Examples of the intermediate layer composition forming the intermediate layer include a rubber composition such as the center composition or a resin composition containing a resin component. The intermediate layer composition preferably contains a resin component as a main component. That is, the resin component content in the intermediate layer composition is preferably 50% by mass or more. The resin component is commercially available from Mitsui DuPont Polychemical Co., Ltd. under the trade name “High Milan (registered trademark)” (eg, High Milan AM7329) and from DuPont under the trade name “Surlyn® (eg, Surlyn 8945)”. A thermoplastic polyamide elastomer, such as a commercially available ionomer resin, from Arkema Co., Ltd. under the trade name “Pebax (registered trademark)” (for example, “Pebax 2533”), from Toray DuPont Co., Ltd. A thermoplastic polyester elastomer marketed under the trade name “Hytrel® (for example,“ Hytrel 3548 ”,“ Hytrel 4047 ”), a product name“ Elastollan® ”(for example,“ E Last-run XNY97A ")" Examples thereof include thermoplastic polyurethane elastomers and thermoplastic polystyrene elastomers commercially available from Mitsubishi Chemical Corporation under the trade name “Lavalon (registered trademark)” (for example, “Lavalon T3221C”), and these may be used alone. Two or more kinds may be used in combination. Among these, from the viewpoint of resilience, the intermediate layer composition preferably includes an ionomer resin and a thermoplastic styrene elastomer as a resin component.

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

  Examples of the specific gravity adjusting agent include zinc oxide, barium sulfate, calcium carbonate, magnesium oxide, tungsten, and molybdenum. The blending amount of the specific gravity adjusting agent is preferably 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 composition is preferably from 1.10 g / cm ³ or more, more preferably 1.20 g / cm ³ or more, further preferably 1.30 g / cm ³ or more. If the density of the intermediate layer composition is 1.10 g / cm ³ or more, the moment of inertia of the golf ball can be further increased, and the effect of lowering spin on shots of a driver or the like is further increased. Stability is further improved. On the other hand, the upper limit of the density of the intermediate layer composition is not particularly limited, but is preferably 1.8 g / cm ³ , more preferably 1.6 g / cm ³ , and even more preferably 1.5 g / cm ³ . is there. The intermediate layer having a high density is preferably arranged on the outside of the golf ball as much as possible.

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

  The slab hardness (H4) of the intermediate layer composition is Shore D hardness, preferably 35 or more, more preferably 40 or more, further preferably 45 or more, preferably 55 or less, more preferably 53 or less, and further Preferably it is 50 or less. When the slab hardness (H4) of the intermediate layer composition is a Shore D hardness of 35 or more, the rebound of the golf ball becomes better. On the other hand, if the slab hardness of the intermediate layer composition is 55 or less in Shore D hardness, the feel at impact of the golf ball becomes better. Here, the slab hardness (H4) of the intermediate layer is a hardness measured by molding the intermediate layer composition into a sheet shape, and is measured by a measurement method described later.

  Moreover, it is preferable that the slab hardness (H4) of the said composition for intermediate | middle layers, the center hardness (H1) of the said core, and the surface hardness (H3) of the said core satisfy the relationship of H1 <= H4 <H3. By satisfying this relationship, a softer feel at impact can be obtained.

  As a method for forming the intermediate layer, for example, the intermediate layer is formed by covering the core with the intermediate layer composition. The method for forming the intermediate layer is not particularly limited. For example, the composition for a high elastic intermediate layer is previously formed into a hemispherical half shell, and the two are used to wrap the center. A method of pressure molding at 170 ° C. for 1 minute to 5 minutes or a method of wrapping the center by directly injection-molding the highly elastic intermediate layer composition onto the center is used.

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

  Examples of the form of the core and the intermediate layer include an aspect in which the core is covered with a single layer of the intermediate layer; and an aspect in which the core is covered 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 made spherical by being filled with a plurality of intermediate layers, or a single layer intermediate layer covering each recess. 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 golf ball of the present invention is not particularly limited as long as it has a core comprising a center and an envelope layer covering the center, one or more intermediate layers 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 four-piece golf ball having a core comprising a center and an envelope layer covering the center, an intermediate layer covering the core, and a cover covering the intermediate layer; And a multi-piece golf ball having a core made of an envelope layer covering the center, a plurality of pieces or a plurality of intermediate layers covering the core, and a cover covering the intermediate layer. Among these, the present invention can be suitably applied to a four-piece golf ball having a core composed of a center and a surrounding layer covering the center, an intermediate layer covering the core, and a cover covering the intermediate layer.

  When the golf ball of the present invention has a diameter of 40 mm to 45 mm, the amount of compressive deformation (the amount by which the golf ball shrinks in the compression direction) from when the initial load 98 N is applied to when the final load 1275 N is applied is 2.5 mm or more. More preferably, it is 2.7 mm or more, More preferably, it is 3.0 mm or more, 4.0 mm or less is preferable, More preferably, it is 3.7 mm or less, More preferably, it is 3.4 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, better resilience is obtained.

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

(1) Slab hardness 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. Three or more sheets of this sheet are stacked so as not to be affected by the measurement substrate, etc., and an automatic rubber hardness meter LA1 type manufactured by Kobunshi Keiki Co., Ltd. equipped with a spring type hardness meter Shore D type as defined in ASTM-D2240. It measured using.

(2) Center center hardness, core surface hardness, center surface hardness (Shore D hardness)
The Shore D hardness measured at the center or the surface of the core using the automatic rubber hardness meter LA1 manufactured by Kobunshi Keiki Co., Ltd. equipped with the Shore D type spring type hardness tester specified in ASTM-D2240 is the center surface hardness, the core surface. Hardness. Further, the core was cut into a hemisphere, and the Shore D hardness measured at the center of the cut surface was defined as the center center hardness.

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

(4) Flexural modulus (MPa)
(A) A test piece having a length of 80.0 ± 2 mm, a width of 10.0 ± 0.2 mm, and a thickness of 4.0 ± 0.2 mm is produced by injection molding using dry pellets of a highly elastic polyamide resin, Immediately kept in a moisture-proof container at 23 ° C. ± 2 ° C. for 24 hours or more. After removing the test piece from the moisture-proof container, the flexural modulus was measured according to ISO 178 promptly (within 15 minutes). The measurement was performed at a temperature of 23 ° C. and a humidity of 50% RH.
(B) A test of length 80.0 ± 2 mm, width 10.0 ± 0.2 mm, thickness 4.0 ± 0.2 mm by injection molding using a copolymer metal neutralized product or a cover composition. Pieces were prepared and stored at 23 ° C. and 50% RH for 2 weeks. The flexural modulus of this test piece was measured according to ISO 178. The measurement was performed at a temperature of 23 ° C. and a humidity of 50% RH.

(5) Tensile modulus (MPa)
Using the cover composition, a sheet having a thickness of about 2 mm was produced by injection molding and stored at 23 ° C. for 2 weeks. A dumbbell-shaped test piece was prepared from this sheet, and the tensile elastic modulus of the test piece was measured according to ISO 527-1.

(6) 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.

(7) 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.

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

(9) Durability at normal temperature 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 made to collide with the collision plate, and the number of hits repeatedly until the golf ball was broken was measured. Although the intermediate layer may be cracked even though it is not broken in appearance, in such a case, whether or not it is broken is determined from the deformation of the golf ball and the difference in the hitting sound.
The durability of each golf ball is determined according to the golf ball no. The number of hits of 20 was set as 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.

(10) Low Temperature Durability A metal head W # 1 driver was attached to a swing robot M / C manufactured by True Temper, and the head speed was set to 45 m / sec. Each golf ball was stored at −10 ° C. for 24 hours in a thermostat. After each golf ball was taken out of the thermostat, it was hit immediately and made to collide with the collision plate, and the number of hits repeatedly until the golf ball was broken was measured. Although the intermediate layer may be cracked even though it is not broken in appearance, in such a case, whether or not it is broken is determined from the deformation of the golf ball and the difference in the hitting sound.
The low temperature durability of each golf ball is determined according to the golf ball no. The number of hits for each golf ball is shown as an index value, with the number of 20s being 100. The larger the indexed value, the more excellent the golf ball is.

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

[Production of golf balls]
(1) Production of Center 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.

Polybutadiene rubber: “BR-730 (High cis polybutadiene)” manufactured by JSR Corporation
Zinc acrylate: “ZNDA-90S” manufactured by Nippon Distillation Co., Ltd.
Zinc oxide: Toho Zinc Co., Ltd.
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”

  An appropriate amount of barium sulfate was added so that the mass of the obtained golf ball was 45.4 g.

(2) Preparation of composition for envelope layer The composition for envelope layer obtained by mixing and kneading the compounding materials shown in Table 2 was preformed into a hollow shell-shaped half shell, and then obtained as described above. A pair of upper and lower parts were placed on the center, and an envelope layer was formed by heating and pressing at 170 ° C. for 20 minutes in an upper and lower mold having a hemispherical cavity to obtain a spherical two-layer core.

Polybutadiene rubber: “BR-730 (High cis polybutadiene)” manufactured by JSR Corporation
Zinc acrylate: “ZNDA-90S” manufactured by Nippon Distillation Co., Ltd.
Zinc oxide: Toho Zinc Co., Ltd.
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”

(3) Preparation of cover composition and intermediate layer composition Using the compounding materials shown in Tables 3, 5 and 6, they were mixed by a twin-screw kneading type extruder to form a pellet cover composition and intermediate layer Each layer 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.

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 Lavalon T3221C manufactured by Mitsui Chemicals Styrene elastomer tungsten: Allied Materials, tungsten powder C50G

(4) Production of Golf Ball Main Body The intermediate layer covering the core was formed by injection molding the intermediate layer composition obtained above onto the core obtained as described above. Subsequently, a cover was formed by injection molding a cover composition on the intermediate layer to produce a golf ball. The upper and lower molds for molding have hemispherical cavities, are provided with pimples, and also serve as hold pins in which a part of the pimples can advance and retreat. The hold pin is protruded, the core is inserted and then held, and a resin heated to 210 ° C. is injected into a mold clamped at a pressure of 80 tons in 0.3 seconds, cooled for 30 seconds, and the mold is opened to open a golf ball Was taken out. 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 4 and FIGS. 2 and 3 was formed on the surface of the golf ball. In Table 4, “diameter” of the dimple means Di in FIG. 1, and “depth” means the distance between the tangent line T and the deepest point De.

  Tables 5 and 6 show the results of evaluation of the obtained golf ball compression deformation, flight distance, directional stability, normal temperature durability, low temperature durability, and feel at impact.

Surlyn 8945: Sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin made by DuPont Himiran AM 7329: Zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin Surlyn 8140 made by Mitsui DuPont Polychemical Co., Ltd. Sodium ion-neutralized ethylene-methacrylic acid copolymer ionomer resin Surlyn 9120: Zinc ion-neutralized ethylene-methacrylic acid copolymer ionomer resin Novamid ST220 manufactured by DuPont: Polyamide resin (high impact grade, manufactured by Mitsubishi Engineering Plastics) Flexural modulus: 2000 MPa)
Amilan U141: manufactured by Toray Industries, Inc., polyamide resin (super high impact type, flexural modulus: 1500 MPa)
LOTADER AX8840: manufactured by Tokyo Materials Co., Ltd., ethylene-acrylic acid-glycidyl methacrylate copolymer (content of monomer having polar functional group: 8% by mass)
ARUFON UG-4030: manufactured by Toagosei Co., Ltd., methyl methacrylate-glycidyl methacrylate copolymer (content of monomer having polar functional group: 0.02 mass%, epoxy value: 1.8 meq / g)
Ultramarine Blue: manufactured by Daiichi Kasei Kogyo Co., Ltd. 1500

  Golf ball no. 1 to 15, the cover is formed from a cover composition containing a predetermined amount of the components (A), (B) and (C), and the cover has a thickness of 0.3 mm to 1.0 mm. The slab hardness (H5) of the cover composition is 65 to 75 in Shore D hardness, and the hardness difference (H3−H1) between the center hardness (H1) of the core and the surface hardness (H3) of the core is This is a case where the Shore D hardness is 10 or more. In any of these golf balls, the cover is formed from a cover composition containing only an ionomer resin as a resin component. Compared to 20, flight distance, directional stability, normal temperature durability, low temperature durability and feel at impact are improved. Among these, golf ball no. Comparing 2 and 10, it can be seen that the higher the density of the intermediate layer composition, the better the directional stability. Golf ball No. No. 6 had a slightly inferior feel at impact because the slab hardness of the cover composition was high.

  Golf ball no. No. 16 is a case where the cover has a thickness of less than 0.3 mm, but the flying distance and feel at impact are excellent, but the effect of improving normal temperature durability and normal temperature durability is small. Golf ball no. 17 is a case where the thickness of the cover exceeds 1.0 mm, but the shot feeling is slightly inferior although it is excellent in normal temperature durability and low temperature durability.

  Golf ball no. 18 is a case where the slab hardness (H5) of the cover composition is less than 65, but the room temperature durability, low temperature durability and feel at impact are improved, but the flight distance is not improved. Golf ball no. 19 is a case where the slab hardness (H5) of the cover composition exceeds 75, but the shot feel is inferior although the flight distance is excellent.

  Golf ball no. Although 21 is a case where (C) component is not contained, all of a flight distance, normal temperature durability, low temperature durability, and a hit feeling are inferior. Golf ball no. 22 is the case where the content of the component (C) exceeds 20 parts by mass with respect to a total of 100 parts by mass of the component (A) and the component (B), but is excellent in normal temperature durability, low temperature durability and feel at impact. The flight distance is not improved and the direction stability is inferior.

  Golf ball no. No. 23 is a case where the center diameter exceeds 35 mm. However, although the room temperature durability, the low temperature durability and the shot feeling are excellent, the flight distance is not improved and the directional stability is inferior. Golf ball no. No. 24 is a case where the hardness difference (H3-H1) is less than 10 in Shore D hardness, but the flight distance is inferior although it is excellent in directional stability, normal temperature durability, low temperature durability and feel at impact.

  The present invention is useful for a golf ball having excellent low temperature durability and normal temperature durability, and excellent flight distance, directional stability and feel at impact.

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

Explanation of symbols

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

Claims (5)

A golf ball having a core comprising a center and a surrounding layer covering the center, one or more intermediate layers covering the core, and a cover covering the intermediate layer,
The cover is a resin component,
(A) Highly elastic polyamide resin (excluding polyamide-based elastomer) having a flexural modulus of 700 MPa to 5000 MPa, (B) Metal-neutralized product of ethylene- (meth) acrylic acid binary copolymer and / or ethylene- (meta ) A metal neutralized product of acrylic acid- (meth) acrylic acid ester terpolymer, and (C) a resin having an epoxy group,
The content ratio (total 100% by mass) of the (A) highly elastic polyamide resin and the (B) metal neutralized product of the binary copolymer and / or the metal neutralized product of the ternary copolymer is (A ) Highly elastic polyamide resin / (B) Metal neutralized product of binary copolymer and / or Metal neutralized product of ternary copolymer = 5 mass% to 80 mass% / 95 mass% to 20 mass% ,
With respect to a total of 100 parts by mass of the (A) highly elastic polyamide resin and the (B) metal neutralized product of the binary copolymer and / or the metal neutralized product of the ternary copolymer, Formed from a cover composition containing 0.1 to 20 parts by mass of a resin having
The cover has a thickness of 0.3 mm to 1.0 mm,
The slab hardness (H5) of the cover composition is 65 to 75 in Shore D hardness,
The diameter of the center is 35 mm or less,
Hardness difference center hardness between (H1) and the core of the surface hardness (H3) of said core (H3-H1), in Shore D hardness, der 10 above is, center hardness of the core (H1), said intermediate layer The slab hardness (H4) and the surface hardness (H3) of the core satisfy the relationship of H1 ≦ H4 <H3, the center hardness (H1) of the core is 22 or more in Shore D hardness, and the intermediate layer The golf ball is characterized by having a density of 1.10 g / cm ³ or more . The golf ball according to claim 1 , wherein the cover composition has a slab physical property of a bending elastic modulus of 300 MPa to 600 MPa and a tensile elastic modulus of 400 MPa to 875 MPa. The (A) high-elasticity polyamide resin is at least one selected from the group consisting of polyamide 6, polyamide 11, polyamide 12, polyamide 66, polyamide 610, polyamide 6T, polyamide 6I, polyamide 9T, polyamide M5T and polyamide 612. the golf ball according to claim 1 or 2 containing. (C) The resin having an epoxy group is at least one selected from the group consisting of an ethylene-glycidyl methacrylate copolymer, an ethylene-acrylic acid-glycidyl methacrylate copolymer, and a methyl methacrylate-glycidyl methacrylate copolymer. The golf ball according to any one of claims 1 to 3 . The main component of the center composition forming the center and the envelope layer composition forming the envelope layer is a rubber component, and the main component of the intermediate layer composition forming the intermediate layer is a thermoplastic material The golf ball according to any one of claims 1 to 4 .