JP6513146B2 - Golf ball - Google Patents

Description

  The present invention relates to a golf ball having a large flight distance of driver shots.

  As a method of extending the flight distance of the golf ball of the driver shot, there are, for example, a method using a core with high resilience and a method using a core having a hardness distribution in which the hardness increases from the center of the core toward the surface. The former has the effect of increasing the initial velocity of the golf ball, and the latter has the effect of increasing the launch angle and achieving low spin. A golf ball with a high launch angle and a low spin has a long flight distance.

  As a technique which raises the resilience of a core, there are patent documents 1-6, for example. In Patent Documents 1 and 2, the reaction is performed with zinc acrylate as a co-crosslinking agent, palmitic acid, stearic acid or myristic acid as a co-crosslinking agent, and zinc oxide as a co-crosslinking agent with respect to 100 parts by weight of rubber. A solid golf ball is disclosed having an inner core formulated with a velocity retarder.

  In Patent Document 3, 15 to 35 parts by weight of an α, β-unsaturated carboxylic acid per 100 parts by weight of a base rubber, and a metal compound 7 which reacts with the α, β-unsaturated carboxylic acid to form a salt There is disclosed a solid golf ball obtained from a rubber composition containing 60 to 60 parts by weight and 1 to 10 parts by weight of a higher fatty acid metal salt.

  In Patent Document 4, a filler, an organic peroxide, an α, β-unsaturated carboxylic acid and / or a metal salt thereof is contained as an essential component in a base rubber, and a copper salt of a saturated or unsaturated fatty acid is added thereto. A golf ball is disclosed, characterized in that it comprises as a component a crosslinked molding of a rubber composition as prepared.

  U.S. Pat. No. 5,956,095 describes base elastomers selected from the group consisting of polybutadiene and mixtures of polybutadiene with other elastomers, salts of at least one metal of unsaturated monocarboxylic acids, free radical initiators, and nonconjugated dienes. A golf ball, or a component thereof, is disclosed which is molded from a composition containing the monomer of

In Patent Document 6, a master batch of unsaturated carboxylic acid and / or metal salt thereof prepared by mixing unsaturated carboxylic acid and / or metal salt thereof with rubber material is prepared in advance, and the above rubber material is used by using this master batch. What is claimed is: 1. A method of producing a golf ball, comprising: preparing a rubber composition containing the rubber composition; and using a thermoformed product of the rubber composition as a component of a golf ball, the masterbatch of the unsaturated carboxylic acid and / or its metal salt Disclosed is a method for producing a golf ball comprising the following (A) to (C).
(A) A polybutadiene having an active end, having a vinyl content of 0 to 2% and a cis 1,4-bond content of 80% or more, wherein the active end is modified with at least one alkoxysilane compound 20 to 100 mass%
(B) A diene rubber other than the above (A) rubber component 80 to 0 mass%
[The above-mentioned number shows the mass% when the total amount of (A) and (B) is set to 100. ]
(C) unsaturated carboxylic acid and / or metal salt thereof

  For example, Patent Documents 7 to 10 disclose a core having a hardness distribution. Patent Document 7 discloses a two-piece golf ball comprising a core formed of a rubber composition containing a base rubber, a co-crosslinking agent and an organic peroxide, and a cover, wherein the core is a JIS-C type hardness meter. The display has a hardness distribution with a center hardness of 1: 58 to 73, a hardness of 5 to 10 mm from the center 2: 65 to 75, a hardness of 15 mm from the center 3: 74 to 82, and a surface hardness of 4: 76 to 84. There is disclosed a two-piece golf ball in which the hardness 2 is substantially constant within the hardness range and the other satisfies the relation 1 <2 <3 ≦ 4.

  According to Patent Document 8, in a solid golf ball comprising a solid core and a cover layer covering the solid core, the solid core contains 60% or more of cis-1,4-bond and uses a rare earth element based catalyst. Organic sulfur compound 0.1-5 parts by mass, unsaturated carboxylic acid or metal salt thereof, inorganic filler and anti-aging agent with respect to 100 parts by mass of rubber base containing 60 to 100% by mass of polybutadiene rubber synthesized by And the deformation amount of the solid core when loaded from an initial load of 10 kgf to a final load of 130 kgf is 2.0 to 4.0 mm, and the solid core has the hardness distribution in the following table. Golf balls are disclosed.

  In Patent Document 9, in a solid golf ball having a solid core and a cover layer covering the solid core, the solid core contains 60% or more of cis-1,4-bond, and uses a rare earth element-based catalyst. Rubber composition containing 0.1 to 5 parts by mass of an organic sulfur compound, an unsaturated carboxylic acid or a metal salt thereof, and an inorganic filler with respect to 100 parts by mass of a rubber base containing 60 to 100 parts by mass of polybutadiene rubber synthesized Solid golf ball which is formed from a solid core and has a deformation amount of 2.0 to 4.0 mm when loaded from an initial load of 10 kgf to a final load of 130 kgf of the solid core, and the solid core has the hardness distribution in the table below. It is disclosed.

  Patent Document 10 discloses a multi-piece solid golf ball comprising a core, a surrounding layer covering the core, the intermediate layer covering the core, and a cover covering the core and having a large number of dimples formed on the surface. In the above, the core is formed mainly of a rubber material, the hardness gradually increases from the center of the core to the core surface, the hardness difference between the core center and the core surface is 15 or more in JIS-C hardness, and the core center When the average of the cross-sectional hardness between a position about 15 mm away from the core and the core center is (I) and the cross-sectional hardness at a position about 7.5 mm away from the core center is (II) A multi-piece solid characterized in that the hardness of the surrounding layer, the intermediate layer and the cover satisfies the condition of cover hardness> intermediate layer hardness> surrounding layer hardness, while II) is within ± 2 in JIS-C hardness Golf bo There has been disclosed.

Japanese Patent Application Laid-Open No. 61-37178 JP-A-61-113475 Japanese Patent Application Laid-Open No. 61-253079 JP, 2008-212681, A Japanese Patent Application Publication No. 2008-523952 JP, 2009-119256, A Japanese Patent Application Laid-Open No. 6-154357 JP, 2008-194471, A JP, 2008-194473, A JP, 2010-253268, A

  The core having the outer hard inner soft structure has a low spin rate and an increased flight distance, but may reduce the initial velocity of the obtained golf ball. However, it is expected that a core having a large outer velocity as well as an outer-rigid inner-flexible structure further increases the flight distance of driver shots. The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a golf ball having a novel core structure and having a great flight distance of driver shots.

  The golf ball of the present invention is a golf ball having a core comprising a spherical center and an envelope layer, and at least one cover disposed outside the core, wherein the maximum hardness and the minimum hardness inside the spherical center are provided. The hardness difference between them is less than 5 in JIS-C hardness, and the envelope layer is (a) base rubber, (b) α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms as a co-crosslinking agent It is formed from a rubber composition for an envelope layer containing an acid and / or a metal salt thereof, (c) a crosslinking initiator, (d) an acid and / or a salt thereof, and the outermost cover is a golf ball composition. It is characterized by having the highest hardness among the members.

  In the spherical center of the golf ball of the present invention, the hardness difference between the maximum hardness and the minimum hardness inside the spherical center is less than 5 in JIS-C hardness. A center with a low hardness distribution increases the golf ball initial velocity of driver shots. Also, by providing the surrounding layer around the spherical center, the spherical core has an outer rigid inner flexible structure. The spherical core having the outer rigid inner flexible structure reduces the spin rate of the driver shot and increases the flight distance. In addition, the outermost cover has the highest hardness among the constituent members of the golf ball, thereby increasing the flight distance to the driver shot.

  According to the present invention, it is possible to obtain a golf ball having a large flight distance of driver shots.

FIG. 1 is a partially cutaway cross-sectional view of a golf ball according to an embodiment of the present invention.

  The golf ball of the present invention is a golf ball having a core comprising a spherical center and an envelope layer, and at least one cover disposed outside the core, wherein the maximum hardness and the minimum hardness inside the spherical center are provided. The hardness difference between them is less than 5 in JIS-C hardness, and the envelope layer is (a) base rubber, (b) α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms as a co-crosslinking agent It is formed from a rubber composition for an envelope layer containing an acid and / or a metal salt thereof, (c) a crosslinking initiator, (d) an acid and / or a salt thereof, and the outermost cover is a golf ball composition. It is characterized by having the highest hardness among the members.

  The golf ball of the present invention has a core comprising a spherical center and an envelope layer, and at least one cover disposed on the outside of the core. Hereinafter, the golf ball of the present invention will be described based on a preferred embodiment with reference to the drawings as appropriate.

  FIG. 1 is a partially cutaway cross-sectional view of a golf ball 2 according to an embodiment of the present invention. The golf ball 2 has a core 7 comprising a spherical center 4 and a surrounding layer 6 disposed outside the spherical center 4, an inner cover 8 disposed outside the core 7, and an inner cover 8. And an outermost cover 12 disposed on the outside. A reinforcing layer 10 may be provided between the inner cover 8 and the outermost cover 12 to improve the adhesion between the inner cover 8 and the outermost cover 12. A large number of dimples 14 are formed on the surface of the outermost cover 12. The portion of the surface of the golf ball 2 other than the dimple 14 is a land 16. Although this golf ball 2 is provided with a paint layer and a mark layer on the outside of the cover, the illustration of these layers is omitted.

  In the spherical center of the golf ball of the present invention, the hardness difference between the maximum hardness and the minimum hardness inside the spherical center is less than 5 in JIS-C hardness. A golf ball using a spherical center having a small hardness distribution has a high initial velocity. From this point of view, the hardness difference between the maximum hardness and the minimum hardness inside the spherical center is preferably less than 4 in JIS-C hardness, and more preferably less than 3. The difference in hardness between the maximum hardness and the minimum hardness inside the spherical center is obtained by dividing an arbitrary radius of the spherical center at intervals of 2.0 mm to 2.5 mm in a cross section obtained by dividing the spherical center into two equal parts. The hardness at the point is measured and the difference in hardness between the maximum hardness and the minimum hardness obtained.

  The central hardness (Ho) of the spherical center is preferably 40 or more, more preferably 45 or more, and still more preferably 50 or more in JIS-C hardness. When the center hardness is 40 or more in JIS-C hardness, the resilience is improved. Further, from the viewpoint of spin suppression of driver shots, the center hardness is preferably 80 or less, more preferably 76 or less, and even more preferably 72 or less in JIS-C hardness.

  The diameter of the spherical center is preferably 5 mm or more, more preferably 8 mm or more, and still more preferably 10 mm or more. If the diameter of the spherical center is 5 mm or more, a golf ball having a larger initial velocity of driver shots can be obtained. Moreover, 30 mm or less is preferable, as for the diameter of the said spherical center, 28 mm or less is more preferable, and 25 mm or less is more preferable. If the diameter of the spherical center is 30 mm or less, the degree of outer hard and internal softness of the core can be further increased, and a golf ball with a low driver shot spin rate can be obtained.

  The core of the golf ball of the present invention has the spherical center and an envelope layer disposed outside the spherical center. The surrounding layer is preferably formed to cover the entire spherical center. The shape of the core is preferably spherical.

  The thickness of the envelope layer is preferably 3 mm or more, more preferably 4 mm or more, still more preferably 5 mm or more, preferably 18 mm or less, more preferably 16 mm or less, still more preferably 14 mm or less. If the thickness is more than 18 mm, the center diameter becomes too small, and the effect of improving the initial velocity by the center becomes difficult to be obtained. If the thickness is less than 3 mm, the surrounding layer becomes too thin. It is difficult to obtain.

  The surface hardness (Hs) of the core is preferably 70 or more, more preferably 75 or more, and even more preferably 80 or more in JIS-C hardness. If the surface hardness is 70 or more in JIS-C hardness, the spin amount of the driver shot is further reduced. From the viewpoint of durability, the surface hardness is preferably 96 or less, more preferably 94 or less, and even more preferably 92 or less in JIS-C hardness.

  The hardness difference (Hs-Ho) between the surface hardness (Hs) of the core (synonymous with the surface hardness of the envelope layer) and the central hardness (Ho) (synonymous with the central hardness of the spherical center) is 18 or more in JIS-C hardness 19 or more is preferable, 20 or more is further preferable, 40 or less is preferable, 38 or less is more preferable, and 36 or less is more preferable. The outer hard inner soft core reduces the spin rate of the driver shot and gives a great flight distance.

  The diameter of the spherical core is preferably 36.0 mm or more, more preferably 37.0 mm or more, and still more preferably 38.0 mm or more. If the diameter of the spherical core is 36.0 mm or more, the effect of the spin reduction by the outer hard and the inner soft and the effect of improving the resilience performance of the ball are compatible. Moreover, 41.5 mm or less is preferable, as for the diameter of the said spherical core, 41 mm or less is more preferable, and 40.5 mm or less is more preferable. If the diameter of the spherical core is 41.5 mm or less, the thickness of the cover will not be too thin, and molding of the cover can be performed more easily.

  When the spherical core has a diameter of 36.0 mm to 41.5 mm, the amount of compressive deformation (the amount by which the core shrinks in the compression direction) from when the initial load 98 N is applied to when the final load 1275 N is applied is 2.0 mm. The above is preferable, More preferably, 2.2 mm or more and 5.0 mm or less are preferable, More preferably, it is 4.8 mm or less. If the amount of compressive deformation is 2.2 mm or more, the feel at impact becomes better, and if it is 5.0 mm or less, the resilience becomes better.

  The golf ball of the present invention has at least one cover disposed on the outside of the spherical core. The cover may be a single layer or two or more layers. In the golf ball of the present invention, the cover of the outermost layer has the highest hardness among the components of the golf ball. Since the outermost cover has the highest hardness among the constituent members of the golf ball, the golf ball as a whole has an outer-hard / inner-soft structure, and the spin rate of driver shots is reduced. As a result, the flight distance of the driver shot is increased. The golf ball component means a spherical center, an envelope layer, and an inner cover other than the outermost layer. From this viewpoint, the hardness difference between the outermost cover and the component having the next highest hardness is preferably 2 or more, more preferably 6 or more, and still more preferably 8 or more.

  The hardness of the cover of the outermost layer is not particularly limited as long as it is the highest hardness among the constituent members of the golf ball, but JIS-C hardness is preferably 83 or more, more preferably 84 or more, and further 85 or more. Preferably, 96 or less is preferable, 95 or less is more preferable, and 93 or less is more preferable.

  The thickness of the at least one cover is preferably 2.5 mm or less, more preferably 2.3 mm or less, and still more preferably 2.1 mm or less. When the thickness of the cover is 2.5 mm or less, the feel at impact is good. The thickness of the cover is preferably 0.3 mm or more, more preferably 0.5 mm or more, and still more preferably 0.8 mm or more. If the cover is too thin, the durability and the abrasion resistance may be reduced. In addition, when a cover consists of several covers, it is preferable that the sum total thickness of a cover is in the said range.

  The cover is usually formed with depressions called dimples on the surface. The total number of dimples is preferably 200 or more and 500 or less. If the total number of dimples is less than 200, it is difficult to obtain dimple effects. In addition, when the total number of dimples exceeds 500, the size of each dimple becomes small, and it is difficult to obtain the effect of dimples. The shape (planar shape) of the dimple to be formed is not particularly limited, and circular shape; polygonal shape such as substantially triangular shape, substantially rectangular shape, substantially pentagonal shape, substantially hexagonal shape, etc .; They may be used in combination of two or more.

  The golf ball of the present invention may have a reinforcing layer between the outermost cover and the inner cover present inside the outermost cover. The reinforcing layer is in intimate contact with the inner cover and in intimate contact with the outermost cover. The reinforcing layer suppresses peeling of the outermost cover from the inner cover. In particular, when a golf ball having a thin outermost cover is hit with the edge of the club face, it is prone to wrinkles. The reinforcing layer suppresses wrinkles.

  When the golf ball of the present invention has a diameter of 40 mm to 45 mm, the amount of compressive deformation (the amount of compression in the compression direction) when a final load of 1275 N is applied from an initial load of 98 N is 1.8 mm or more More preferably, it is 2.0 mm or more, more preferably 2.2 mm or more, most preferably 2.4 mm or more, and preferably 4.8 mm or less, more preferably 4.6 mm or less. is there. The golf ball having a compressive deformation of 1.8 mm or more does not become too hard and has a good feel at impact. On the other hand, by setting the amount of compressive deformation to 4.8 mm or less, the resilience becomes high.

  It is preferable that a coating film is provided on the surface of the golf ball body. Although the film thickness of the said coating film is not specifically limited, 5 micrometers or more are preferable, 7 micrometers or more are more preferable, 50 micrometers or less are preferable, 40 micrometers or less are more preferable, and 30 micrometers or less are more preferable. When the film thickness is less than 5 μm, the coating film is apt to wear away due to continuous use, and when the film thickness exceeds 50 μm, the effect of the dimples is reduced and the flight performance of the golf ball is reduced.

  The golf ball of the present invention includes, for example, a three-piece golf ball having a spherical core comprising a spherical center and an envelope layer, and a single-layer cover disposed outside the spherical core; Four-piece golf ball having a spherical core, an inner cover layer provided outside the spherical core, and an outermost cover provided outside the inner cover layer; a spherical body comprising a spherical center and a surrounding layer A multi-piece golf ball (five or more pieces) having a core and a cover of three or more layers disposed outside the spherical core may be mentioned.

  Next, materials constituting the golf ball of the present invention will be described. The spherical center of the golf ball of the present invention is preferably formed from a resin composition for the center containing a resin component or a rubber composition for a center containing a rubber component. Examples of the rubber composition for center include (a) a base rubber, (b) a co-crosslinking agent, and (c) a rubber composition containing a crosslinking initiator. As the (a) base rubber, (b) co-crosslinking agent, and (c) crosslinking initiator, those similar to the rubber composition for envelope layer described later can be used. In addition to (a) base rubber, (b) co-crosslinking agent and (c) crosslinking initiator, the rubber composition for center is (e) metal compound, (f) organic sulfur compound, filler, anti-aging agent Agents, peptizers, etc. can be suitably blended. As these components, the same ones as the envelope layer rubber composition can be used. In addition, it is preferable not to mix | blend the (d) acid and / or its salt which are mentioned later with the rubber composition for centers.

  It does not specifically limit as a resin component which the resin composition for centers contains, For example, It is marketed by ionomer resin and Alkema Co., Ltd. under the brand name "Pebax (registered trademark) (for example," Pebax 2533 ")". Thermoplastic polyamide elastomer, thermoplastic polyester elastomer commercially available from Toray DuPont Co., Ltd. under the trade name "Hytrel (registered trademark) (for example," Hytrel 3548 "," Hytrel 4047 "), trade name from BASF Japan Thermoplastic polyurethane elastomers commercially available as Elastlan (registered trademark); thermoplastic styrene elastomer commercially available from Mitsubishi Chemical Co., Ltd. under the trade name “Lavaron (registered trademark)”. These resin components may be used alone or in combination of two or more.

  As a resin component contained in the resin composition for centers, a binary copolymer of (A) (a-1) olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, (a- 2) Ionomer resin composed of metal ion neutralized product of binary copolymer of olefin and α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, (a-3) olefin and 3 to 8 carbon atoms Terpolymers of α, β-unsaturated carboxylic acids and α, β-unsaturated carboxylic acid esters, and (a-4) olefins and α, β-unsaturated hydrocarbons having 3 to 8 carbon atoms At least one resin component selected from the group consisting of ionomer resins consisting of metal ion neutralized products of terpolymers of carboxylic acid and α, β-unsaturated carboxylic acid ester is preferred.

  The component (a-1) is a binary copolymer of an olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, wherein the carboxyl group is not neutralized and is nonionic. It is a thing. Moreover, as said (a-2) component, at least one part of the carboxyl group in the binary copolymer of an olefin and a C3-C8 alpha, beta- unsaturated carboxylic acid is neutralized with a metal ion. And ionomer resins.

  The component (a-3) is a ternary copolymer of an olefin, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an α, β-unsaturated carboxylic acid ester, and the carboxyl group thereof Is a non-neutralized one. The component (a-4) is a carboxyl group of a ternary copolymer of an olefin, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an α, β-unsaturated carboxylic acid ester. Mention may be made of ionomer resins neutralized at least in part with metal ions.

  In the present invention, the “binary copolymer of (a-1) olefin and α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms” is simply referred to as “binary copolymer”, (A-2) An ionomer resin consisting of a metal ion neutralized product of a binary copolymer of an olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms is referred to as “a binary ionomer resin” "(A-3) a ternary copolymer of an olefin, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an α, β-unsaturated carboxylic acid ester", simply "a ternary copolymer" Metal ion neutralized product of terpolymer of (a-4) olefin, α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and α, β-unsaturated carboxylic acid ester The ionomer resin which consists of these may be called "ternary ionomer resin."

  The olefin is preferably an olefin having 2 to 8 carbon atoms, and examples thereof include ethylene, propylene, butene, pentene, hexene, heptene, octene and the like, and ethylene is particularly preferable. As said C3-C8 alpha, beta- unsaturated carboxylic acid, acrylic acid, methacrylic acid, fumaric acid, maleic acid, crotonic acid etc. are mentioned, for example, Especially acrylic acid or methacrylic acid is preferable. Further, as the α, β-unsaturated carboxylic acid ester, for example, methyl such as acrylic acid, methacrylic acid, fumaric acid and maleic acid, ethyl, propyl, n-butyl, isobutyl ester and the like are used, and in particular acrylic acid ester. Or methacrylic acid esters are preferred.

  As the (a-1) binary copolymer, a binary copolymer of ethylene and (meth) acrylic acid is preferable, and as the (a-2) binary ionomer resin, ethylene- (meth) Metal ion neutralized products of acrylic acid binary copolymers are preferred. As said (a-3) ternary copolymer, the ternary copolymer of ethylene, (meth) acrylic acid, and (meth) acrylic acid ester is preferable. As the (a-4) ternary ionomer resin, a metal ion neutralized product of a ternary copolymer of ethylene, (meth) acrylic acid and (meth) acrylic acid ester is preferable. Here, (meth) acrylic acid means acrylic acid and / or methacrylic acid.

  The content of the α, β-unsaturated carboxylic acid component having 3 to 8 carbon atoms in the (a-1) binary copolymer or the (a-3) ternary copolymer is 4% by mass or more. The content is preferably 5% by mass or more, more preferably 30% by mass or less, and still more preferably 25% by mass or less.

  The melt flow rate (190 ° C., 2.16 kg load) of the (a-1) binary copolymer or (a-3) ternary copolymer is preferably 5 g / 10 min or more, more preferably 10 g / 10 min The amount is more preferably 15 g / 10 min or more, preferably 1700 g / 10 min or less, more preferably 1500 g / 10 min or less, and still more preferably 1300 g / 10 min or less. If the melt flow rate (190 ° C., 2.16 kg load) of the (a-1) binary copolymer or the (a-3) ternary copolymer is 5 g / 10 min or more, the flow of the composition for the center The properties are improved and the molding of the component members is facilitated. Also, if the melt flow rate (190 ° C., 2.16 kg load) of the (a-1) binary copolymer or the (a-3) ternary copolymer is 1700 g / 10 min or less, the obtained golf ball The durability of is better.

  If the specific example of a binary copolymer is illustrated by a brand name, the brand name "Nucrel (NUCREL) (registered trademark)" (eg, "Nucrel N1050H", "Nucrel N2050H", "Nuclell N1110H", for example, from Mitsui Dupont Polychemical Co., Ltd.) And ethylene-methacrylic acid copolymer marketed under "Nuclell N 0 200 H"). If the specific example of a ternary copolymer is illustrated by a brand name, the brand name "Nucrel (NUCREL) (trademark) (for example," Nucrel AN4318 "," Nuclel AN4319 ") etc. which are marketed from Mitsui Dupont Polychemicals Co., Ltd. etc. Can be mentioned.

  A specific example of the binary ionomer resin can be exemplified by trade name “Himilan (registered trademark) (for example, HIMIRAN 1555 (Na), HIMIRAN 1557 (Zn) which is commercially available from Dupont Polychemicals Co., Ltd. HIMIRAN 1605 (Na), HIMIRAN 1706 (Zn), HIMIRAN 1707 (Na), HIMIRAN AM 7311 (Mg), HIMIRAN AM 7329 (Zn), etc.] Specific examples of ternary ionomer resins are exemplified by trade names. Then, “HIMILAN (registered trademark) (for example, HIMIRAN AM 7327 (Zn), HIMIRAN 1855 (Zn), HIMIRAN 1856 (Na), HIMIRAN AM 7331 (Na), etc. commercially available from Mitsui DuPont Polychemicals Co., Ltd.) ) Is mentioned

  When a binary copolymer or ternary copolymer is used as a resin component, a metal compound may be blended. As a metal compound, the (e) metal compound used for the rubber composition for surrounding layers is mentioned.

  The resin component for center may further contain an anionic sulfur-containing surfactant having an anionic site, an amphoteric surfactant having a cationic site and an anionic site, a basic fatty acid metal salt, and the like. This is because the resilience of the obtained spherical center is increased.

  As the anionic sulfur-containing surfactant, for example, an anionic surfactant having an S = O bond is preferable, and an anionic surfactant such as a sulfate or a sulfonate is more preferable. Specific examples of the anionic sulfur-containing surfactant include, for example, alkyl sulfuric acid ester salt, polyoxyethylene polycyclic phenyl ether sulfuric acid ester salt, polyoxyethylene alkyl ether sulfuric acid ester salt, polyoxyethylene aryl ether sulfuric acid ester salt Sulfuric acid ester salts such as polyoxyethylene castor oil ether sulfuric acid ester salt; alkyl benzene sulfonic acid and / or salt thereof, alkylene disulfonic acid and / or salt thereof, monoalkyl sulfosuccinic acid and / or salt thereof; dialkyl sulfosuccinic acid and / or salt Salt thereof, alkyl diphenyl ether disulfonic acid and / or salt thereof, alkanesulfonic acid and / or salt thereof; sulfonic acid such as salt of formalin condensate of naphthalenesulfonic acid and / or the like And the like.

  Examples of sulfates or sulfonates include salts of alkali metals such as sodium and potassium; divalent metal salts such as magnesium and calcium; and ammonium salts such as ammonia and triethanolamine. The anionic sulfur-containing surfactant is preferably a neutralized salt, but may be a free acid which can be easily dissociated to form an anion like sulfonic acid.

  Examples of the alkyl sulfate ester salt include sodium lauryl sulfate, higher alcohol sodium sulfate, triethanolamine lauryl sulfate, ammonium lauryl sulfate and the like. Examples of polyoxyethylene alkyl ether sulfate ester salts include sodium polyoxyethylene lauryl ether sulfate, sodium polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl ether sulfate triethanolamine and the like. Examples of the alkylbenzenesulfonic acid and / or a salt thereof include dodecylbenzenesulfonic acid, sodium dodecylbenzenesulfonate and the like.

  It is preferable to use a dialkyl sulfosuccinic acid and / or a salt thereof as the anionic sulfur-containing surfactant. Three or more are preferable, as for carbon number of the alkyl group of dialkyl sulfo succinic acid and / or its salt, five or more are more preferable, 30 or less are preferable, and 28 or less are more preferable. If the carbon number of the alkyl group is in the above range, the mobility of the molecular chain is high, and high repulsion is obtained while maintaining the flexibility. Also, the two alkyl groups may be the same or different. Examples of the dialkyl sulfosuccinic acid and / or a salt thereof include di (2-ethylhexyl) sulfosuccinic acid, sodium di (2-ethylhexyl) sulfosuccinate, magnesium di (2-ethylhexyl) sulfosuccinate and the like.

  Examples of amphoteric surfactants having a cationic site and an anionic site include betaine-type amphoteric surfactants such as alkylbetaine type, amidobetaine type, imidazolium betaine type, alkylsulfobetaine type, amidosulfobetaine type and the like; Amide amino acid type amphoteric surfactant, alkylamino fatty acid salt; alkylamine oxide; β-alanine type amphoteric surfactant, glycine type amphoteric surfactant; sulfobetaine type amphoteric surfactant; phosphobetaine type amphoteric surfactant etc It can be mentioned.

  Specific examples of amphoteric surfactants include dimethyl lauryl betaine, oleyl betaine, dimethyl oleyl betaine, dimethyl stearyl betaine, stearyl dihydroxy methyl betaine, stearyl dihydroxyethyl betaine, lauryl dihydroxy methyl betaine, lauryl dihydroxyethyl betaine, myristyl dihydroxy methyl betaine, Behenyl dihydroxymethyl betaine, palmityl dihydroxyethyl betaine, oleyl dihydroxymethyl betaine, coconut oil fatty acid amidopropyl betaine, lauric acid amide alkyl betaine, 2-alkyl-N-carboxyalkyl imidazolinium betaine, lauric acid amide alkylhydroxysulfobetaine, Coconut oil fatty acid amide dialkyl hydroxy alkyl sulfo betai N-alkyl-β-aminopropionate, N-alkyl-β-iminodipropionate, alkyldiaminoalkylglycine, alkylpolyaminoalkylglycine, sodium alkylamino fatty acid, N, N-dimethyloctylamine oxide, N, N-dimethyl lauryl amine oxide, N, N- dimethyl stearyl amine oxide and the like can be mentioned.

  The content of the anionic surfactant or amphoteric surfactant is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and still more preferably 10 parts by mass or more with respect to 100 parts by mass of the resin component. 200 parts by mass or less is preferable, more preferably 150 parts by mass or less, and still more preferably 100 parts by mass or less.

  The basic fatty acid metal salt can be obtained by a known production method in which a fatty acid and a metal oxide or hydroxide are reacted, and a common fatty acid metal salt is a fatty acid and a metal oxide or hydroxide of a reaction equivalent. In contrast to the reaction, the basic fatty acid metal salt is obtained by adding a metal oxide or hydroxide in excess with the fatty acid and the reaction equivalent, and the metal content of the product, the melting point, etc. It is different from fatty acid metal salt.

  The basic fatty acid metal salt is preferably a basic saturated fatty acid metal salt. The basic fatty acid metal salt is preferably a basic fatty acid metal salt having 4 to 22 carbon atoms, and is preferably a basic fatty acid metal salt having 5 to 18 carbon atoms. Specific examples of basic fatty acid metal salts include basic magnesium caprylate, basic calcium caprylate, basic caprylate zinc, basic magnesium magnesium laurate, basic calcium laurate, basic zinc laurate, basic myristic acid Magnesium, basic calcium myristate, basic zinc myristate, basic magnesium magnesium palmitate, basic calcium calcium palmitate, basic zinc zinc palmitate, basic magnesium oleate, basic calcium oleate, basic zinc oleate, Basic magnesium stearate, basic calcium stearate, basic zinc stearate, basic 12-hydroxystearate magnesium, basic 12-hydroxystearate calcium, basic 12-hydroxystearate zinc Basic magnesium behenate, basic behenate calcium, and basic behenic acid zinc. As the basic fatty acid metal salt, basic fatty acid zinc is preferable, and basic zinc stearate, basic zinc laurate and basic zinc caprylate are more preferable. The basic fatty acid metal salt can be used alone or as a mixture of two or more.

  The content of the basic fatty acid metal salt is preferably 25 parts by mass or more, more preferably 33 parts by mass or more, still more preferably 50 parts by mass or more, and 100 parts by mass or less with respect to 100 parts by mass of the resin component. preferable.

  The envelope layer of the golf ball of the present invention comprises (a) a base rubber, (b) an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms as a co-crosslinking agent and / or a metal salt thereof (c) It is formed from a rubber composition for an envelope layer containing a crosslinking initiator, (d) an acid and / or a salt thereof. In the envelope layer formed of the above-mentioned envelope layer rubber composition, the hardness tends to increase from the spherical center surface side to the core surface side of the envelope layer.

  The reason why the hardness of the envelope layer increases from the spherical center surface side to the core surface side is considered as follows. (B) The metal salt of an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms which is compounded in the rubber composition for envelope layer forms an ion cluster inside the envelope layer to metal-crosslink rubber molecular chains It is believed that. By blending (d) an acid and / or a salt thereof into the rubber composition for a surrounding layer, (d) the acid and / or a salt thereof can be (b) α, β having 3 to 8 carbon atoms. The cation is exchanged with the ion cluster formed by the metal salt of unsaturated carboxylic acid, and the metal bridge is broken by the metal salt of α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms. In this cation exchange reaction, the internal temperature of the surrounding layer is likely to occur on the center surface side and less likely to occur on the core surface side. The heat of reaction of the curing reaction of the rubber composition for the envelope layer tends to be accumulated on the center surface side, and the internal temperature of the envelope layer at the time of molding the core is high on the center surface side and decreased toward the core surface side. is there. That is, cleavage of metal crosslinks by (d) carboxylic acid and / or a salt thereof is likely to occur on the center surface side and less likely to occur on the core surface side. As a result, since the crosslink density inside the envelope layer increases from the center surface side toward the core surface side, the hardness is considered to increase from the center surface side toward the core surface side.

  As the (a) 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), etc. It can be used. These may be used alone or in combination of two or more. Among these, high-cis polybutadiene having a cis-1,4-bond advantageous for repulsion is preferably 40% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more.

  The content of the 1,2-vinyl bond in the high-cis polybutadiene is preferably 2% by mass or less, more preferably 1.7% by mass or less, and still more preferably 1.5% by mass or less. If the content of the 1,2-vinyl bond is too large, the resilience may decrease.

  The high-cis polybutadiene is preferably synthesized with a rare earth element-based catalyst, and in particular, the use of a neodymium-based catalyst using a neodymium compound which is a lanthanum series rare earth element compound is high in 1,4-cis bond content A 1,2-vinyl bond is preferable because a low content of polybutadiene rubber can be obtained with excellent polymerization activity.

The high cis polybutadiene preferably has a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of 30 or more, more preferably 32 or more, still more preferably 35 or more, preferably 140 or less, more preferably It is 120 or less, more preferably 100 or less, and most preferably 80 or less. The Mooney viscosity (ML _{1 + 4} (100 ° C.)) referred to in the present invention is the condition of 100 ° C., with a preheating time of 1 minute, a rotor rotation time of 4 minutes, using an L rotor according to JIS K6300. It is the value measured below.

  As said high cis polybutadiene, it is preferable that molecular weight distribution Mw / Mn (Mw: weight average molecular weight, Mn: number average molecular weight) is 2.0 or more, More preferably, it is 2.2 or more, More preferably, 2. It is 4 or more, most preferably 2.6 or more, and preferably 6.0 or less, more preferably 5.0 or less, still more preferably 4.0 or less, most preferably 3.4 or less. When the molecular weight distribution (Mw / Mn) of the high cis polybutadiene is too small, the workability may be lowered, and when it is too large, the resilience may be lowered. The molecular weight distribution is determined by gel permeation chromatography (manufactured by Tosoh Corp., “HLC-8120GPC”) using a differential refractometer as a detector, column: GMHHXL (manufactured by Tosoh Corp.), column temperature: 40 ° C., mobile phase : Measured under conditions of tetrahydrofuran and calculated as standard polystyrene equivalent value.

  Next, the (b) co-crosslinking agent will be described. As the (b) co-crosslinking agent, (b1) α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or (b2) α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms Containing metal salts of Hereinafter, (b1) an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or (b2) a metal salt of an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, b) It may be generically referred to as ".alpha.,. beta.-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or its metal salt". (B) An α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or a metal salt thereof is added to the rubber composition as a co-crosslinking agent, and is grafted onto the base rubber molecular chain By polymerizing, it acts to crosslink the rubber molecules. When the rubber composition for the envelope layer used in the present invention contains only (b1) an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms as a co-crosslinking agent, the rubber composition for the envelope layer is It is preferable to contain the (f) metal compound mentioned later. By neutralizing (b1) an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms with (f) a metal compound in the rubber composition, (b2) having 3 to 8 carbon atoms as a co-crosslinking agent This is because substantially the same effect can be obtained as in the case of using metal salts of .alpha.,. Beta.-unsaturated carboxylic acids. Moreover, you may use (f) metal compound, also when using together (b2) C3-C8 alpha, (beta)-unsaturated carboxylic acid and its metal salt as a co-crosslinking agent.

  Examples of (b1) α, β-unsaturated carboxylic acids having 3 to 8 carbon atoms include acrylic acid, methacrylic acid, fumaric acid, maleic acid, crotonic acid and the like.

  (B2) The metal constituting the metal salt of α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms includes monovalent metal ions such as sodium, potassium and lithium; magnesium, calcium, zinc, barium, Examples include divalent metal ions such as cadmium; trivalent metal ions such as aluminum; and other ions such as tin and zirconium. The metal components can also be used alone or as a mixture of two or more. Among these, as the metal component, divalent metals such as magnesium, calcium, zinc, barium and cadmium are preferable. By using a divalent metal salt of an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, metal crosslinking is likely to occur between rubber molecules. In particular, zinc acrylate is preferable as the divalent metal salt because the resilience of the obtained golf ball is increased. In addition, (b) A C3-C8 alpha, beta- unsaturated carboxylic acid and / or its metal salt may be used individually or in combination of 2 or more types.

  The content of (b) an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or a metal salt thereof is preferably 15 parts by mass or more with respect to 100 parts by mass of (a) base rubber, 20 mass parts or more are more preferable, 50 mass parts or less are preferable, 45 mass parts or less are more preferable, and 40 mass parts or less are more preferable. (B) When the content of the α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or the metal salt thereof is less than 10 parts by mass, the member formed of the rubber composition has an appropriate hardness. In addition, the amount of the crosslinking initiator (c) described below must be increased, and the resilience of the golf ball tends to decrease. On the other hand, when the content of (b) the α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or the metal salt thereof exceeds 50 parts by mass, the member formed from the rubber composition becomes too hard. Therefore, the feel at impact of the golf ball may be reduced.

  The crosslinking initiator (c) is blended to crosslink the (a) base rubber component. (C) As a crosslinking initiator, an organic peroxide is suitable. Specifically, the organic peroxide is dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di And organic peroxides such as (t-butylperoxy) hexane and di-t-butylperoxide. These organic peroxides may be used alone or in combination of two or more. Among these, dicumyl peroxide is preferably used.

  The content of the crosslinking initiator (c) is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, and 5.0 parts by mass with respect to 100 parts by mass of the (a) base rubber. The amount is preferably at most parts, more preferably at most 2.5 parts by mass. If the amount is less than 0.2 parts by mass, the member formed from the rubber composition tends to be too soft and the resilience of the golf ball tends to decrease, and if it exceeds 5.0 parts by mass, the rubber composition is formed from the rubber composition. In order to make the member have an appropriate hardness, it is necessary to reduce the use amount of the (b) co-crosslinking agent described above, and there is a risk that the golf ball will have insufficient resilience and durability may deteriorate.

  Next, (d) the acid and / or the salt thereof will be described. (D) The acid and / or the salt thereof has the function of breaking the metal crosslink by the metal salt of an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms inside the envelope layer at the time of the envelope layer formation Conceivable.

  (D) Aliphatic acids and / or salts thereof as long as they can exchange the cation component with metal salts of α, β-unsaturated carboxylic acids having 3 to 8 carbon atoms (d) Alternatively, it may be any of an aromatic acid and / or a salt thereof. As the acid (d) and / or a salt thereof, for example, a protonic acid and / or a salt thereof is preferable. Examples of the protonic acid include oxo acids such as carboxylic acid, sulfonic acid and phosphoric acid; and hydrogen acids such as hydrochloric acid and hydrofluoric acid. Among these, oxo acids are preferable, and carboxylic acids are more preferable. That is, as (d) an acid and / or a salt thereof, a carboxylic acid and / or a salt thereof is suitable.

  (D) Carboxylic acid and / or a salt thereof is any of aliphatic carboxylic acids (sometimes referred to simply as “fatty acids” in the present invention) and / or salts thereof, or aromatic carboxylic acids and / or salts thereof Although aliphatic carboxylic acids and / or salts thereof are preferred. The carboxylic acid and / or the salt thereof is preferably a carboxylic acid having 1 to 30 carbon atoms and / or a salt thereof, more preferably a carboxylic acid having 4 to 30 carbon atoms and / or a salt thereof, and having 5 carbon atoms Further preferred is a carboxylic acid of 25 and / or a salt thereof. (D) Carboxylic acid and / or salt thereof does not include (b) α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or metal salt thereof which is used as a co-crosslinking agent It shall be.

  The fatty acid may be either a saturated fatty acid or an unsaturated fatty acid, but is preferably a saturated fatty acid. Specific examples of the saturated fatty acid (IUPAC name) include methane acid (C1), ethanoic acid (C2), propanoic acid (C3), butanoic acid (C4), pentanoic acid (C5), hexanoic acid (C6), heptane Acid (C7), octanoic acid (C8), nonanoic acid (C9), decanoic acid (C10), undecanoic acid (C11), dodecanoic acid (C12), tridecanoic acid (C13), tetradecanoic acid (C14), pentadecanoic acid C15), hexadecanoic acid (C16), heptadecanoic acid (C17), octadecanoic acid (C18), nonadecanoic acid (C19), icosanoic acid (C20), henicosanoic acid (C21), docosanoic acid (C22), trichosanic acid (C23) , Tetracosanoic acid (C24), pentacosanoic acid (C25), hexacosanoic acid (C26), heptacosanoic acid (C27), octo Concentrated acid acid (C28), nonacosanoic acid (C29), triacontanoic acid (C30).

  Examples of unsaturated fatty acids (IUPAC name) include ethenoic acid (C2), propenoic acid (C3), butene acid (C4), pentenoic acid (C5), hexenoic acid (C6), heptenoic acid (C7), octene Acid (C8), nonenic acid (C9), decenoic acid (C10), undecenoic acid (C11), dodecenoic acid (C12), tridecenoic acid (C13), tetradecenoic acid (C14), pentadecenoic acid (C15), hexadecenoic acid (C) C16), heptadecenoic acid (C17), octadecenoic acid (C18), nonadecenoic acid (C19), icosenoic acid (C20), hexicosenoic acid (C21), docosenoic acid (C22), tricosenoic acid (C23), tetracosenoic acid (C24) , Pentacosenoic acid (C25), hexacosenoic acid (C26), heptacosenoic acid (C27), octacosenoic acid (C28) Nonacosenoic acid (C29), and triacontenoic acid (C30).

  Specific examples (common names) of the fatty acid include, for example, formic acid (C1), acetic acid (C2), propionic acid (C3), butyric acid (C4), valeric acid (C5), caproic acid (C6), enanthate (C6) C7), caprylic acid (C8), pelargonic acid (C9), capric acid (C10), lauric acid (C12), myristic acid (C14), myristoleic acid (C14), pentadecyl acid (C15), palmitic acid (C16) Palmitoleic acid (C16), margaric acid (C17), stearic acid (C18), elaidic acid (C18), succenic acid (C18), oleic acid (C18), linoleic acid (C18), linolenic acid (C18), 12-hydroxystearic acid (C18), arachidic acid (C20), gaderic acid (C20), arachidonic acid (C20), eicosenic acid C20) Behenic acid (C22), erucic acid (C22), lignoceric acid (C24), nervonic acid (C24), serotic acid (C26), montanic acid (C28), melissic acid (C30), etc. it can. The fatty acids can also be used alone or as a mixture of two or more. Among these, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid or oleic acid is preferable as the fatty acid.

  The aromatic carboxylic acid is not particularly limited as long as it is a compound having an aromatic ring and a carboxyl group. Specific examples of the aromatic carboxylic acid include, for example, benzoic acid (C7), phthalic acid (C8), isophthalic acid (C8), terephthalic acid (C8), hememiritic acid (benzene-1,2,3-tricarboxylic acid) (C9), trimellitic acid (benzene-1,2,4-tricarboxylic acid) (C9), trimesic acid (benzene-1,3,5-tricarboxylic acid) (C9), merophanoic acid (benzene-1,2, 3,4-tetracarboxylic acid) (C10), planitic acid (benzene-1,2,3,5-tetracarboxylic acid) (C10), pyromellitic acid (benzene-1,2,4,5-tetracarboxylic acid) ) (C10), mellitic acid (benzenehexacarboxylic acid) (C12), diphenic acid (biphenyl-2,2'-dicarboxylic acid) (C12), toluic acid (methylbenzoic acid) (C10) ), Xylyl acid (C9), planytylic acid (2,3,4-trimethylbenzoic acid) (C10), γ-isodururic acid (2,3,5-trimethylbenzoic acid) (C10), dulylic acid (2,4 5-trimethylbenzoic acid (C10), β-isodururic acid (2,4,6-trimethylbenzoic acid) (C10), α-isodururic acid (3,4,5-trimethylbenzoic acid) (C10), cumin Acid (4-isopropylbenzoic acid) (C10), ubitic acid (5-methylisophthalic acid) (C9), α-toluic acid (phenylacetic acid) (C8), hydrotroparic acid (2-phenylpropanoic acid) (C9), Hydrocinnamic acid (3-phenylpropanoic acid) (C9) etc. can be mentioned.

  Moreover, as an aromatic carboxylic acid substituted by a hydroxyl group, an alkoxy group, or an oxo group, for example, salicylic acid (2-hydroxybenzoic acid) (C7), anisic acid (methoxybenzoic acid) (C8), cresothic acid (C8) Hydroxy (methyl) benzoic acid) (C8), o-homosalicylic acid (2-hydroxy-3-methylbenzoic acid) (C8), m-homosalicylic acid (2-hydroxy-4-methylbenzoic acid) (C8), p Homosalicylic acid (2-hydroxy-5-methylbenzoic acid) (C8), o-pyrocatechic acid (2,3-dihydroxybenzoic acid) (C7), β-resorcylic acid (2,4-dihydroxybenzoic acid) (C7) ), Γ-resorcylic acid (2,6-dihydroxybenzoic acid) (C7), protocatechuic acid (3,4-dihydroxybenzoic acid) (C7), Lucillic acid (3,5-dihydroxybenzoic acid) (C7), vanillic acid (4-hydroxy-3-methoxybenzoic acid) (C8), isovanillic acid (3-hydroxy-4-methoxybenzoic acid) (C8), belatrum Acid (3,4-dimethoxybenzoic acid) (C9), o-veratulmic acid (2,3-dimethoxybenzoic acid) (C9), orsellinic acid (2,4-dihydroxy-6-methylbenzoic acid) (C8), m-Hemipinic acid (4,5-dimethoxyphthalic acid) (C10), gallic acid (3,4,5-trihydroxybenzoic acid) (C7), silicic acid (4-hydroxy-3,5-dimethoxybenzoic acid) (C9), asaronic acid (2,4,5-trimethoxybenzoic acid) (C10), mandelic acid (hydroxy (phenyl) acetic acid) (C8), vanil mandelic acid (hydroxy ( -Hydroxy-3-methoxyphenyl) acetic acid) (C9), homoanisic acid ((4-methoxyphenyl) acetic acid) (C9), homogentisic acid ((2,5-dihydroxyphenyl) acetic acid) (C8), homoprotocatechuic acid (( 3,4-Dihydroxyphenyl) acetic acid) (C8), homovanillic acid ((4-hydroxy-3-methoxyphenyl) acetic acid) (C9), homoisovanillic acid ((3-hydroxy-4-methoxyphenyl) acetic acid) ( C9), homoberatolumic acid ((3,4-dimethoxyphenyl) acetic acid) (C10), o-homoberatolumic acid ((2,3-dimethoxyphenyl) acetic acid) (C10), homophthalic acid (2- (carboxymethyl) benzoic acid ) (C9), homoisophthalic acid (3- (carboxymethyl) benzoic acid) (C9), homoterephthalic acid (4-) (Carboxymethyl) benzoic acid (C9), Phthalonic acid (2- (Carboxycarbonyl) benzoic acid) (C9), Isophthalic acid (3- (Carboxycarbonyl) benzoic acid) (C9), Terephthalic acid (4- (Carboxy) (Carbonyl) benzoic acid) (C9), benzylic acid (hydroxydiphenylacetic acid) (C14), atrolactic acid (2-hydroxy-2-phenylpropanoic acid) (C9), tropic acid (3-hydroxy-2-phenylpropanoic acid) ) (C9), melilotic acid (3- (2-hydroxyphenyl) propanoic acid) (C9), phlorettic acid (3- (4-hydroxyphenyl) propanoic acid) (C9), hydrocaffeic acid (3- (3) , 4-Dihydroxyphenyl) propanoic acid) (C9), hydroferulic acid (3- (4-hydroxy-3-methoxy) (Nyl) propanoic acid) (C10), hydroisoferulic acid (3- (3-hydroxy-4-methoxyphenyl) propanoic acid) (C10), p-coumaric acid (3- (4-hydroxyphenyl) acrylic acid) C9), umbellic acid (3- (2,4-dihydroxyphenyl) acrylic acid) (C9), caffeic acid (3- (3,4-dihydroxyphenyl) acrylic acid) (C9), ferulic acid (3- (4) -Hydroxy-3-methoxyphenyl) acrylic acid) (C10), isoferulic acid (3- (3-hydroxy-4-methoxyphenyl) acrylic acid) (C10), sinapinic acid (3- (4-hydroxy-3,5) -Dimethoxyphenyl) acrylic acid) (C11) etc. can be mentioned.

  The cation component of the (d) acid salt may be any of metal ions, ammonium ions, and organic cations. Examples of the metal ion include monovalent metal ions such as sodium, potassium, lithium and silver; divalent metal ions such as magnesium, calcium, zinc, barium, cadmium, copper, cobalt, nickel and manganese; aluminum, iron And other trivalent metal ions such as tin, zirconium and titanium. As a cation component of the said carboxylate, a zinc ion is preferable. The cationic component may be used alone or in combination of two or more.

  The organic cation is a cation having a carbon chain. The organic cation is not particularly limited, and examples thereof include organic ammonium ions. Examples of the organic ammonium ion include primary ammonium ions such as stearyl ammonium ion, hexyl ammonium ion, octyl ammonium ion, 2-ethylhexyl ammonium ion, and secondary ions such as dodecyl (lauryl) ammonium ion and octadecyl (stearyl) ammonium ion. Ammonium ions; tertiary ammonium ions such as trioctyl ammonium ions; and quaternary ammonium ions such as dioctyl dimethyl ammonium ions and distearyl dimethyl ammonium ions. These organic cations may be used alone or in combination of two or more.

  The content of the (d) acid and / or the salt thereof is preferably 1.0 parts by mass or more, more preferably 1.5 parts by mass or more, still more preferably 2 parts by mass with respect to 100 parts by mass of the (a) base rubber. It is not less than 0 parts by mass, preferably less than 40 parts by mass, more preferably 38 parts by mass or less, and still more preferably 36 parts by mass or less. If the content is too low, the effect of adding (d) an acid and / or a salt thereof may not be sufficient, and the hardness distribution of the surrounding layer may be reduced. On the other hand, when the content is too large, the hardness of the obtained envelope layer may be reduced as a whole, and the resilience may be reduced.

  The surface of zinc acrylate used as a co-crosslinking agent may be treated with (d) an acid and / or a salt thereof in order to improve the dispersibility in rubber. In the case of using zinc acrylate surface-treated with (d) an acid and / or a salt thereof, in the present invention, the amount of the (d) acid and / or a salt thereof which is a surface treatment agent comprises the component (d) It shall not be included in the quantity. This is because (d) the acid and / or the salt thereof used for the surface treatment of zinc acrylate is considered to contribute little to the cation exchange reaction with the (b) co-crosslinking agent.

  The content of the (d) acid and / or the salt thereof is preferably set as appropriate depending on the type of the acid and / or the salt thereof used and the combination thereof. In particular, the content of (d) the acid and / or the salt thereof is preferably set as appropriate depending on the carbon number of the acid and / or the salt thereof and the combination thereof. (D) The action of the acid and / or the salt thereof to cleave the metal bridge is considered to be influenced by the number of moles of the acid and / or the salt thereof to be added. At the same time, the acid and / or its salt act as a plasticizer for the envelope layer. As the blending amount (mass) of the added acid (d) and / or the salt thereof increases, the entire envelope layer is softened. This plasticizing effect is influenced by the amount (mass) of the added acid and / or the salt thereof. In consideration of these effects, for example, using a small carbon number (small molecular weight) acid and / or a salt thereof, as compared with using a large carbon number (large molecular weight) acid and / or a salt thereof Therefore, the number of moles to be added can be increased with the same blending amount (mass). That is, the low carbon number acid and / or the salt thereof can enhance the effect of breaking the metal crosslink while suppressing the softening of the entire envelope layer by the plasticizing effect.

  For example, when (d) a carboxylic acid having 1 to 14 carbon atoms and / or a salt thereof is used as the acid and / or the salt thereof, the amount is 1.0 mass with respect to 100 mass parts of the (a) base rubber Part or more is preferable, more preferably 1.2 parts by mass or more, still more preferably 1.4 parts by mass or more, and preferably 20 parts by mass or less, more preferably 18 parts by mass or less, still more preferably 16 parts by mass Part or less. The carbon number of the carboxylic acid salt having 1 to 14 carbon atoms is the carbon number of the carboxylic acid component, and the carbon number in the organic cation is not included.

  For example, when (d) a carboxylic acid having 15 to 30 carbon atoms and / or a salt thereof is used as the acid and / or the salt thereof, 5 parts by mass or more relative to 100 parts by mass of the (a) base rubber Is more preferably 6 parts by mass or more, still more preferably 7 parts by mass or more and less than 40 parts by mass, more preferably 35 parts by mass or less, and still more preferably 30 parts by mass or less. In addition, carbon number of a C15-C30 carboxylic acid salt is carbon number of a carboxylic acid component, and carbon number in an organic cation is not contained.

  The envelope layer rubber composition preferably further contains (e) an organic sulfur compound. The outer layer and inner layer can be further promoted by using the rubber composition for the envelope layer in combination with (d) an acid and / or a salt thereof and (e) an organic sulfur compound. (E) The organic sulfur compound is not particularly limited as long as it is an organic compound having a sulfur atom in the molecule, and, for example, a thiol group (-SH) or a polysulfide bond having 2 to 4 sulfur atoms (- Organic compounds having S-S-, -S-S-S-, or -S-S-S-S-), or metal salts thereof (-SM, -S-M-S-, -S-) M-S-S-, -S-S-M-S-S-, -S-M-S-S-S-, etc., M is a metal atom). Further, (e) the organic sulfur compound is an aliphatic compound (aliphatic thiol, aliphatic thiocarboxylic acid, aliphatic dithiocarboxylic acid, aliphatic polysulfide, etc.), heterocyclic compound, alicyclic compound (alicyclic thiol) And alicyclic thiocarboxylic acid, alicyclic dithiocarboxylic acid, alicyclic polysulfide and the like) and aromatic compounds.

  (E) Examples of the organic sulfur compounds include thiophenols, thionaphthols, polysulfides, thiocarboxylic acids, dithiocarboxylic acids, sulfenamides, thiurams, dithiocarbamates, thiazoles and the like. . From the viewpoint that the hardness distribution of the spherical core becomes large, as the organic sulfur compound (e), an organic sulfur compound having a thiol group (-SH) or a metal salt thereof is preferable, and thiophenols, thionaphthols, or These metal salts are preferred. As metal salts, for example, monovalent metal salts such as sodium, lithium, potassium, copper (I), silver (I), zinc, magnesium, calcium, strontium, barium, titanium (II), manganese (II), Divalent metal salts such as iron (II), cobalt (II), nickel (II), zirconium (II), tin (II) and the like can be mentioned.

  As thiophenols, for example, thiophenol; 4-fluorothiophenol, 2,5-difluorothiophenol, 2,4,5-trifluorothiophenol, 2,4,5,6-tetrafluorothiophenol, penta Fluorophenol-substituted thiophenols such as fluorothiophenol; 2-chlorothiophenol, 4-chlorothiophenol, 2,4-dichlorothiophenol, 2,5-dichlorothiophenol, 2,6-dichlorothiophenol Chlorothio substituted thiophenols such as 2,4,5-trichlorothiophenol, 2,4,5,6-tetrachlorothiophenol and pentachlorothiophenol; 4-bromothiophenol, 2,5- Dibromothiophenol, 2,4,5-tribromothiophenol Bromo substituted thiophenols such as 2,4,5,6-tetrabromothiophenol and pentabromothiophenol; 4-iodothiophenol, 2,5-diiodothiophenol, 2,4,5- An iodo group-substituted thiophenol such as triiodothiophenol, 2,4,5,6-tetraiodothiophenol, pentaiodothiophenol, or a metal salt thereof. As a metal salt, a zinc salt is preferable.

  As thionaphthols, for example, 2-thionaphthol, 1-thionaphthol, 2-chloro-1-thionaphthol, 2-bromo-1-thionaphthol, 2-fluoro-1-thionaphthol, 2-cyano-1 -Thionaphthol, 2-acetyl-1-thionaphthol, 1-chloro-2-thionaphthol, 1-bromo-2-thionaphthol, 1-fluoro-2-thionaphthol, 1-cyano-2-thionaphthol, 1 Mention may be made of -acetyl-2-thionaphthol or metal salts thereof, with 1-thionaphthol, 2-thionaphthol or zinc salts thereof being preferred.

  As a sulfenamide type organic sulfur compound, for example, N-cyclohexyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzothiazole sulfenamide, N-t-butyl-2-benzothiazole sulfate Fenamide is mentioned. Examples of the thiuram-based organic sulfur compound include tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, and dipentamethylenethiuram tetrasulfide. Examples of dithiocarbamates include zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc ethylphenyldithiocarbamate, sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, copper (II) dimethyldithiocarbamate, and dimethyldithiocarbamate Iron (III), selenium diethyl dithiocarbamate, tellurium diethyl dithiocarbamate and the like can be mentioned. Examples of the thiazole organic sulfur compounds include 2-mercaptobenzothiazole (MBT), dibenzothiazyl disulfide (MBTS), sodium salt, zinc salt, copper salt or cyclohexylamine salt of 2-mercaptobenzothiazole, 2- Examples include (2,4-dinitrophenyl) mercaptobenzothiazole, 2- (2,6-diethyl-4-morpholinothio) benzothiazole and the like.

  (E) The organic sulfur compounds may be used alone or in combination of two or more.

  The content of the (e) organic sulfur compound is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and 5.0 parts by mass with respect to 100 parts by mass of the (a) base rubber. The amount is preferably at most parts, more preferably at most 2.0 parts by mass. If the amount is less than 0.05 parts by mass, the effect of the addition of the (e) organic sulfur compound can not be obtained, and the resilience of the golf ball may not be improved. On the other hand, if it exceeds 5.0 parts by mass, the amount of compressive deformation of the obtained golf ball becomes large, and the resilience may be reduced.

  The rubber composition for an envelope layer used in the present invention may, if necessary, contain additives such as a pigment, a filler for weight adjustment and the like, an antiaging agent, a peptizer and a softener. Further, as described above, when the rubber composition for the envelope layer used in the present invention contains only (b1) α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms as a co-crosslinking agent, the envelope layer The rubber composition preferably further contains (f) a metal compound.

  (F) The metal compound is not particularly limited as long as it can neutralize (b1) an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms in the rubber composition for an envelope layer. I will not. (F) Examples of the metal compound include metal hydroxides such as magnesium hydroxide, zinc hydroxide, calcium hydroxide, sodium hydroxide, lithium hydroxide, potassium hydroxide and copper hydroxide; magnesium oxide, calcium oxide And metal oxides such as zinc oxide and copper oxide; and metal carbonates such as magnesium carbonate, zinc carbonate, calcium carbonate, sodium carbonate, lithium carbonate and potassium carbonate. (F) Preferred as the metal compound is a divalent metal compound, more preferably a zinc compound. This is because (b1) the divalent metal compound reacts with an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms to form a metal bridge. Further, by using a zinc compound, a golf ball having high resilience can be obtained. These (f) metal compounds may be used alone or in combination of two or more. The content of the metal compound (f) may be appropriately adjusted according to the degree of neutralization of the desired (b) α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms.

  As a pigment mix | blended with the rubber composition for envelope layers, a white pigment, a blue pigment, a purple pigment etc. can be mentioned, for example. As the white pigment, titanium oxide is preferably used. The type of titanium oxide is not particularly limited, but it is preferable to use rutile because it has good hiding power. The content of titanium oxide is preferably 0.5 parts by mass or more, more preferably 2 parts by mass or more, and preferably 8 parts by mass or less, per 100 parts by mass of (a) base rubber. Preferably, it is 5 parts by mass or less.

  It is also a preferred embodiment that the envelope layer rubber composition contains a white pigment and a blue pigment. The blue pigment is blended to make the white look vivid, and examples thereof include ultramarine blue, cobalt blue, phthalocyanine blue and the like. Moreover, as said purple pigment, anthraquinone violet, dioxazine violet, methyl violet etc. can be mentioned, for example.

  The content of the blue pigment is preferably 0.001 parts by mass or more, more preferably 0.05 parts by mass or more, and 0.2 parts by mass or less with respect to 100 parts by mass of the (a) base rubber. Preferably, it is 0.1 parts by mass or less. If it is less than 0.001 part by mass, it looks bluish and yellowish, and if it exceeds 0.2 parts by mass, it becomes too blue to have a bright white appearance.

  The filler used for the envelope layer rubber composition is mainly blended as a weight regulator for adjusting the weight of the golf ball obtained as a final product, and may be blended as needed. Examples of the filler include inorganic fillers such as zinc oxide, barium sulfate, calcium carbonate, magnesium oxide, tungsten powder and molybdenum powder. Particularly preferred as the filler is zinc oxide. Zinc oxide is believed to function as a coagent to increase the overall hardness of the spherical core. The content of the filler is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 30 parts by mass or less, and 25 parts by mass or less with respect to 100 parts by mass of the base rubber. More preferably, 20 parts by mass or less is more preferable. If the content of the filler is less than 0.5 parts by mass, weight adjustment becomes difficult, and if it exceeds 30 parts by mass, the weight fraction of the rubber component tends to be small and the resilience tends to be reduced.

  It is preferable that content of the said anti-aging agent is 0.1 mass part or more and 1 mass part or less with respect to 100 mass parts of (a) base rubber. Moreover, it is preferable that content of a peptizing agent is 0.1 mass part or more and 5 mass parts or less with respect to 100 mass parts of (a) base rubber.

  The cover of the golf ball of the present invention is formed from a cover composition containing a resin component. Examples of the resin component include ionomer resins, thermoplastic polyamide elastomers commercially available from Arkema Co., Ltd. under the trade name “Pebax (registered trademark) (for example,“ Pebax 2533 ”)”, Toray DuPont Co., Ltd. Thermoplastic polyester elastomer marketed under the trade name "Hytrel (R) (e.g.," Hytrel 3548 "," Hytrel 4047 "), commercially available from BASF Japan under the trade name" Erastran (R) " Thermoplastic polyurethane elastomers; thermoplastic styrene elastomers commercially available from Mitsubishi Chemical Co., Ltd. under the trade name "Lavaron (registered trademark)" and the like. These resin components may be used alone or in combination of two or more.

  As the ionomer resin, for example, those obtained by neutralizing at least a part of carboxyl groups in a binary copolymer of an olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms with a metal ion, an olefin Or at least a portion of the carboxyl groups of a ternary copolymer of an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α, β-unsaturated carboxylic acid ester neutralized with a metal ion, or And mixtures thereof. The olefin is preferably an olefin having 2 to 8 carbon atoms, and examples thereof include ethylene, propylene, butene, pentene, hexene, heptene, octene and the like, and ethylene is particularly preferable. Examples of the α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms include acrylic acid, methacrylic acid, fumaric acid, maleic acid, crotonic acid and the like, with acrylic acid and methacrylic acid being particularly preferable. Further, as the α, β-unsaturated carboxylic acid ester, for example, methyl such as acrylic acid, methacrylic acid, fumaric acid and maleic acid, ethyl, propyl, n-butyl, isobutyl ester and the like are used, and in particular acrylic acid ester. Or methacrylic acid esters are preferred. Among these, as the ionomer resin, metal ion neutralized products of ethylene- (meth) acrylic acid binary copolymer, ethylene- (meth) acrylic acid- (meth) acrylic acid ester ternary copolymer Metal ion neutralized products are preferred.

  When the specific example of the said ionomer resin is illustrated by a brand name, "HIMILAN (trademark) (For example, HIMIRAN 1555 (Na), HIMIRAN 1557 (Zn), HIMILAN, which is commercially available from Mitsui DuPont Polychemical Co., Ltd.) is commercially available. 1605 (Na), HIMIRAN 1706 (Zn), HIMIRAN 1707 (Na), HIMIRAN AM 3711 (Mg), etc., and examples of terpolymer ionomer resins include HIMIRAN 1856 (Na), HIMIRAN 1855 (Zn), etc.) "Is mentioned.

  Furthermore, as an ionomer resin commercially available from DuPont, “Surlyn (registered trademark) (eg, Surlyn 8945 (Na), Surlyn 9945 (Zn), Surlyn 8140 (Na), Surlyn 8150 (Na), Surlyn) Examples include 9120 (Zn), surlyn 9150 (Zn), surlyn 6910 (Mg), surlyn 6120 (Mg), surlyn 7930 (Li), surlyn 7940 (Li), surlyn AD 8546 (Li), etc., and a terpolymer Examples of the ionomer resin include Surlyn 8120 (Na), Surlyn 8320 (Na), Surlyn 9320 (Zn), Surlyn 6320 (Mg), HPF 1000 (Mg), HPF 2000 (Mg) and the like.

  Further, as an ionomer resin commercially available from Exxon Mobil Chemical Co., Ltd., “Iotek (registered trademark) (eg, IOTEC 8000 (Na), IOTEC 8030 (Na), IOTEC 7010 (Zn), IOTEC 7030 ( Zn) and the like, and examples of terpolymer ionomer resins include IOTEC 7510 (Zn), IOTEC 7520 (Zn) and the like.

  In addition, Na, Zn, Li, Mg, etc. which were described in the parenthesis after the trade name of the above-mentioned ionomer resin show metal species of these neutralization metal ions. The ionomer resins may be used alone or in combination of two or more.

  The cover composition constituting the cover of the golf ball of the present invention preferably contains a thermoplastic polyurethane or an ionomer resin as a resin component. 50 mass% or more is preferable, as for the content rate of the thermoplastic polyurethane or ionomer resin in the resin component of the composition for cover, 60 mass% or more is more preferable, and 70 mass% or more is more preferable.

  The composition for the cover includes, in addition to the above-described resin components, pigment components such as white pigment (for example, titanium oxide), blue pigment, red pigment, specific gravity adjusting agent such as zinc oxide, calcium carbonate and barium sulfate, and dispersing agent An anti-aging agent, an ultraviolet light absorber, a light stabilizer, a fluorescent material, a fluorescent whitening agent, etc. may be contained in the range which does not impair the performance of a cover.

  The content of the white pigment (for example, 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 with respect to 100 parts by mass of the resin component constituting the cover. More preferably, it is 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 provided with concealability. In addition, when the content of the white pigment exceeds 10 parts by mass, the durability of the obtained cover may be reduced.

  The golf ball of the present invention may have a reinforcing layer between the outermost cover and the inner cover present inside the outermost cover. The reinforcing layer is formed of a composition for a reinforcing layer containing a resin component. As the resin component, a two-component curable thermosetting resin is suitably used. An epoxy resin, a urethane resin, an acrylic resin, a polyester-based resin, and a cellulose resin are mentioned as a specific example of two-component curing type thermosetting resin. From the viewpoint of strength and durability of the reinforcing layer, a two-part curable epoxy resin and a two-part curable urethane resin are preferable.

  The composition for the reinforcing layer may contain an additive such as a colorant (for example, titanium dioxide), a phosphoric acid based stabilizer, an antioxidant, a light stabilizer, a fluorescent brightening agent, an ultraviolet light absorber, an antiblocking agent, etc. . The additive may be added to the main component of the two-part curable thermosetting resin, or may be added to the curing agent.

  Next, a method of producing the golf ball of the present invention will be described. The spherical center used in the present invention is produced using the rubber composition for center or the resin composition for center. When the spherical center is formed from the rubber composition for center, the spherical center can be obtained by thermoforming the rubber composition for center after kneading in a mold. 120 degreeC or more is preferable, as for the temperature shape | molded to a spherical center, 150 degreeC or more is more preferable, 160 degreeC or more is further more preferable, and 170 degrees C or less is preferable. Moreover, as for the pressure at the time of shaping | molding, 2.9 MPa-11.8 MPa are preferable. The molding time is preferably 10 minutes to 60 minutes.

  When the spherical center is formed of the resin composition for center, the spherical center can be molded by injection molding. The molding by injection molding can be performed by injecting the resin composition for center and cooling it, and for example, the center heated to 60 ° C. to 260 ° C. in a mold clamped at a pressure of 1 MPa to 100 MPa. The resin composition is injected in 1 second to 100 seconds, cooled for 30 seconds to 300 seconds, and opened.

  The rubber composition for the envelope layer comprises (a) a base rubber, (b) an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or a metal salt thereof, (c) a crosslinking initiator, (d ) It is obtained by mixing and kneading an acid and / or a salt thereof and, if necessary, other additives and the like. The method of kneading is not particularly limited, and may be performed using, for example, a known kneader such as a kneader roll, a Banbury mixer, or a kneader.

  As a method of forming the envelope layer, for example, a method of forming a hollow shell-like shell from the rubber composition for envelope layer, covering a spherical center with a plurality of shells and compression molding (preferably, rubber composition for envelope layer) And molding a hollow shell-like half shell, covering the spherical center with two half shells, and compression molding). Examples of the conditions for compression molding the envelope layer rubber composition into a half shell include a molding temperature of 10 ° C. or more and 100 ° C. or less under a pressure of 1 MPa or more and 20 MPa or less. As a method of forming an envelope layer using a half shell, for example, a method of covering a spherical center with two half shells and performing compression molding can be mentioned. Examples of the conditions for compression molding the half shell into the envelope layer include a molding pressure of 100 ° C. or more and 200 ° C. or less under a molding pressure of 2 MPa or more and 25 MPa or less. By setting the molding conditions, it is possible to form an envelope layer having a uniform thickness.

  As a method of molding the cover of the golf ball of the present invention, for example, a method of molding a hollow shell-like shell from the composition for cover, covering a spherical core with a plurality of shells and compression molding (preferably for cover Method of molding a hollow shell-like half shell from the composition, covering the spherical core with two half shells and compression molding), or mentioning a method of directly injection molding the cover composition on the spherical core Can.

  When the cover is formed by the compression molding method, the half shell can be formed by either the compression molding method or the injection molding method, but the compression molding method is preferable. 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 temperature of −20 ° C. or more and 70 ° C. or less with respect to the flow start temperature of the cover composition. The molding temperature can be mentioned. By setting the molding conditions, it is possible to mold a half shell having a uniform thickness. The conditions for forming the cover by compression molding the half shell include, for example, a molding pressure of 0.5 MPa or more and 25 MPa or less and -20 ° C. or more and 70 ° C. or less with respect to the flow start temperature of the cover composition. The molding temperature can be mentioned. By setting the molding conditions, it is possible to mold a golf ball cover having a uniform thickness.

  When the cover composition is injection-molded to form a cover, injection molding may be performed using a pellet-like cover composition obtained by extrusion, or materials such as a base resin component and a pigment may be used. It is possible to dry blend and direct injection molding. As the upper and lower molds for molding, it is preferable to use a mold which has a hemispherical cavity and is equipped with pimples and which also serves as a hold pin capable of advancing and retracting a part of the pimples. The cover can be molded by injection molding by extruding a hold pin, inserting and holding the core, injecting the composition for the cover, and cooling the cover, for example, 9 MPa to 15 MPa. The cover composition heated to 200 ° C. to 250 ° C. is injected in 0.5 seconds to 5 seconds into a pressure-molded mold, cooled for 10 seconds to 60 seconds, and opened.

  The golf ball main body with the cover molded is preferably taken out of the mold and subjected to surface treatment such as deburring, washing, sand blasting and the like as required. Also, if desired, a coating film or a mark can be formed.

  EXAMPLES Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited by the following examples, and all changes and embodiments within the scope of the present invention are within the scope of the present invention. It is included in the range.

[Evaluation method]
(1) Compressive deformation (mm)
The amount of deformation in the compression direction (the amount of shrinkage of the core or the golf ball in the compression direction) from when the initial load 98N was loaded to the core or golf ball to when the final load 1275N was loaded was measured.

(2) Slab hardness (Shore D hardness)
A sheet having a thickness of about 2 mm was produced by press molding using the composition for a cover, and stored at 23 ° C. for 2 weeks. This type of automatic rubber hardness tester P1 type manufactured by Kobunshi Keiki Co., Ltd. equipped with a spring type hardness tester Shore D type specified in ASTM-D2240 in a state where three or more sheets are stacked so that the influence of a measurement substrate etc. is not exerted It measured using.

(3) Spherical core (spherical center) hardness distribution (JIS-C hardness)
Spring-type hardness meter JIS-C hardness measured on the surface portion of the spherical core using the automatic rubber hardness meter P1 type manufactured by Kobunshi Keiki Co., Ltd. equipped with JIS-C type was taken as the spherical core surface hardness. Further, the spherical core (spherical center) was cut into a hemispherical shape, and the JIS-C hardness was measured at a predetermined location of the obtained cross section. The hardness difference between the maximum hardness and the minimum hardness of the spherical center is obtained by measuring the hardness at each point obtained by dividing an arbitrary radius of the spherical center at intervals of 2.0 mm to 2.5 mm, and the obtained maximum hardness and the minimum hardness And the difference in hardness.

(4) Flying distance of driver shot (m), initial velocity of golf ball, and spin amount (rpm)
Attach a screwdriver (manufactured by Dunlop Sports Co., Ltd., XXIO S loft 11.0 °) to a swing robot M / C manufactured by Trutemper, and hit a golf ball at a head speed of 40 m / sec. The golf ball's spin speed, initial speed, and flight distance (distance from the launch point to the stationary point) were measured. The measurement was performed ten times for each golf ball, and the average value was taken as the measurement value of the golf ball. The spin speed of the golf ball immediately after the impact was measured by continuously photographing the impacted golf ball.

[Preparation of Golf Ball]
(1) Preparation of Spherical Center Case of Resin Composition for Center The compounding materials shown in Table 3 were dry-blended, mixed by a twin-screw kneading extruder, and extruded into cold water in the form of strands. The extruded strand was cut by a pelletizer to prepare a pellet-like center resin composition. The extrusion conditions were: screw diameter 45 mm, screw rotation speed 200 rpm, screw L / D = 35, and the mixture was heated to 160 ° -230 ° C. at the die position of the extruder. The obtained pellet-like resin composition for center was injection-molded at 220 ° C. to obtain a spherical center.
In the case of using the rubber composition for center The rubber composition of the composition shown in Table 3 was kneaded by a kneading roll and heat pressed at 170 ° C. for 20 minutes in upper and lower molds having hemispherical cavities to obtain a spherical center .

ハイミランＡＭ７３２７：三井・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−アクリル酸ブチル三元共重合体アイオノマー樹脂
ニュクレルＡＮ４３１９：三井・デュポンポリケミカル社製、エチレン−メタクリル酸−アクリル酸ブチル三元共重合体
塩基性オレイン酸マグネシウム：日東化成工業社製（金属含有量１．７モル％）
塩基性オレイン酸マグネシウム：日東化成工業社製（金属含有量１．４モル％）
水酸化マグネシウム：和光純薬工業社製
オレイルベタイン（オレイルジメチルアミノ酢酸ベタイン）：ルーブリゾール社製「Ｃｈｅｍｂｅｔａｉｎｅ ＯＬ」の精製品（水分と塩分を除去）
ポリブタジエンゴム：ＪＳＲ社製ＢＲ−７３０、ハイシスポリブタジエン（シス−１，４−結合含有量＝９６質量％、１，２−ビニル結合含有量＝１．３質量％、ムーニー粘度（ＭＬ₁₊₄（１００℃））＝５５、分子量分布（Ｍｗ／Ｍｎ）＝３）
アクリル酸亜鉛：三新化学工業社製サンセラーＳＲ（１０質量％ステアリン酸コーティング品）
マグサラット１５０ＳＴ：協和化学工業製 酸化マグネシウム
メタクリル酸：三菱レイヨン社製
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」
酸化亜鉛：東邦亜鉛社製「銀嶺Ｒ」
硫酸バリウム：堺化学社製「硫酸バリウムＢＤ」、最終的に得られるゴルフボールの質量が４５．４ｇとなるように調整した。
２−チオナフトール：東京化成工業社製
ノクラック２００：大内新興化学工業社製、２，６−ジ−ｔ−ブチル−４−メチルフェノール

HIMIRAN AM 7327: made by Mitsui Dupont Polychemicals, zinc ion neutralized ethylene-methacrylic acid-butyl acrylate terpolymer ionomer resin nucrel AN4319: made by Mitsui Dupont Polychemicals, ethylene-methacrylic acid-butyl acrylate 3 Former copolymer basic magnesium oleate: Nitto Kasei Kogyo Co., Ltd. (metal content: 1.7 mol%)
Basic magnesium oleate: Nitto Kasei Kogyo Co., Ltd. (metal content 1.4 mol%)
Magnesium hydroxide: Oleyl betaine (oleyl dimethylaminoacetic acid betaine) manufactured by Wako Pure Chemical Industries, Ltd .: A purified product of “Chembetaine OL” manufactured by Lubrizol (removal of water and salt)
Polybutadiene rubber: BR-730 manufactured by JSR, high cis polybutadiene (cis-1,4-bond content = 96% by mass, 1,2-vinyl bond content = 1.3% by mass, Mooney viscosity (ML _{1 + 4)} (100 ° C.)) = 55, molecular weight distribution (Mw / Mn) = 3)
Zinc acrylate: SANSERA SR (10% by mass stearic acid coated product) manufactured by Sanshin Chemical Industry Co., Ltd.
Magsalat 150ST: manufactured by Kyowa Chemical Industry Magnesium oxide methacrylic acid: manufactured by Mitsubishi Rayon Dicumyl peroxide: manufactured by NOF Corporation, "Parkmill (registered trademark) D"
Zinc oxide: "Ginko R" manufactured by Toho Zinc
Barium sulfate: "Barium sulfate BD" manufactured by Sakai Chemical Co., Ltd., and the weight of the finally obtained golf ball was adjusted to 45.4 g.
2-Thionaphthol: Noclac 200 manufactured by Tokyo Chemical Industry Co., Ltd. 2: 2,6-di-t-butyl-4-methylphenol manufactured by Ouchi Emerging Chemical Industry Co., Ltd.

(2) Preparation of Core The rubber composition for an envelope layer shown in Table 4 was kneaded, and a half shell was formed from the rubber composition for an envelope layer. In forming the half shell, the rubber composition for envelope layer was charged into each recess of the lower mold of the half shell forming mold and pressurized. Compression molding was performed under the conditions of a molding temperature of 25 ° C., a molding time of 3 minutes, and a molding pressure of 15 MPa. The spherical center obtained above was covered with two half shells. The spherical center and the half shell were placed in a mold consisting of an upper mold and a lower mold both having hemispherical cavities, and heat pressed at 150 ° C. and 12 MPa for 20 minutes to obtain a spherical core. The blending amount of barium sulfate was adjusted so that the mass of the finally obtained golf ball was 45.4 g.

Polybutadiene rubber: BR-730 manufactured by JSR, high cis polybutadiene (cis-1,4-bond content = 96% by mass, 1,2-vinyl bond content = 1.3% by mass, Mooney viscosity (ML _{1 + 4)} (100 ° C.)) = 55, molecular weight distribution (Mw / Mn) = 3)
Zinc acrylate: SANSERA SR (10% by mass stearic acid coated product) manufactured by Sanshin Chemical Industry Co., Ltd.
Zinc oxide: "Ginko R" manufactured by Toho Zinc Co., Ltd.
Barium sulfate: "Barium sulfate BD" manufactured by Sakai Chemical Co., Ltd., and the weight of the finally obtained golf ball was adjusted to 45.4 g.
2-Thionaphthol: Dicumyl peroxide manufactured by Tokyo Chemical Industry Co., Ltd .: NOF Corporation "Parkmill (registered trademark) D"
Zinc octanoate: manufactured by Mitsutsu Chemical Co., Ltd. (purity 99% or more)
Zinc laurate: manufactured by Mitsutsu Chemical Co., Ltd. (purity 99% or more)
Zinc myristate: manufactured by NOF Corporation (purity 90% or more)
Zinc stearate: Wako Pure Chemical Industries (purity 99% or more)

(3) Preparation of composition for cover The compounding material shown in Table 10 was mixed by a twin-screw kneader-type extruder to prepare a composition for cover in the form of pellets. The extrusion conditions were: screw diameter 45 mm, screw rotation speed 200 rpm, screw L / D = 35, and the mixture was heated to 160 ° -230 ° C. at the die position of the extruder.

HIMIRAN AM 7337: made by Mitsui-Dupont Polychemicals, sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin HIMIRAN 1555: made by Mitsui-Dupont Polychemicals, sodium neutralized ethylene-methacrylic acid copolymer ionomer resin HIMIRAN 1605: Sodium ion-neutralized ethylene-methacrylic acid copolymer ionomer resin HIMIRAN AM7329 manufactured by Du Pont Polychemical Co., Ltd .: Zinc ion-neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by DuPont Polychemical Co., Ltd. Ethylene-methacrylic acid copolymer Lavalon T3221 manufactured by Polychemical Co., Ltd .: Styrene elastomer titanium dioxide manufactured by Mitsubishi Chemical Co., Ltd .: A220 manufactured by Ishihara Sangyo Co., Ltd.
Tinuvin 770: BASF Japan Ltd., hindered amine stabilizer

(4) Preparation of Golf Ball Body The cover composition obtained above was injection-molded on the spherical core obtained as described above to form an inner cover and an outermost cover covering the spherical core. . At the time of cover molding, hold pins are pushed out, the core is put and held, and the resin heated to 210 ° C to 260 ° C is injected in 0.3 seconds into a mold clamped at a pressure of 80 tons and cooled for 30 seconds. The mold was opened and the golf ball was taken out. The surface of the obtained golf ball 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 weight of 45.4 g. The The evaluated results of the obtained golf balls are summarized in Tables 5 to 9.

  From the results of Tables 5 to 9, it is a golf ball having a core comprising a spherical center and a surrounding layer, and at least one cover disposed on the outer side of the core, wherein any two points of the spherical center Hardness difference in JIS-C hardness is less than 5, and the envelope layer is (a) base rubber, (b) α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms as a co-crosslinking agent And / or a metal composition for an envelope layer containing (c) a crosslinking initiator, (d) an acid and / or a salt thereof, and the outermost cover is a component of a golf ball. It can be seen that the golf ball having the highest hardness among them has a great flight distance for driver shots.

  The golf ball of the present invention has a large flight distance.

2: Golf ball, 4: spherical center, 6: surrounding layer, 8: middle layer, 10: reinforcing layer, 12: cover, 14: dimple, 16: land

Claims (12)

A golf ball comprising a core comprising a spherical center and an envelope layer, and at least one cover disposed on the outside of the core,
The spherical center contains a base rubber, a co-crosslinking agent, and a crosslinking initiator, and a carboxylic acid and / or a salt thereof (excluding an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and a metal salt thereof The rubber composition for the center which does not contain.
The difference in hardness between the maximum hardness and the minimum hardness in the spherical center is less than 5 in JIS-C hardness,
The envelope layer comprises (a) a base rubber, (b) an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms as a co-crosslinking agent and / or a metal salt thereof, and (c) a crosslinking initiator, d) containing a carboxylic acid and / or a salt thereof (excluding an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and a metal salt thereof);
(D) a carboxylic acid and / or a salt thereof is a carboxylic acid having 1 to 14 carbon atoms and / or a salt thereof,
Those formed from a rubber composition for an envelope layer containing 1.0 part by mass or more and 20 parts by mass or less of (d) carboxylic acid and / or a salt thereof with respect to 100 parts by mass of (a) base rubber And
The envelope layer has a hardness distribution which increases from the spherical center surface side to the core surface side by the action of the (d) carboxylic acid and / or a salt thereof,
The hardness difference (Hs-Ho) between the surface hardness (Hs) of the core and the center hardness (Ho) is 18 to 40 in JIS-C hardness,
A golf ball characterized in that the outermost cover has the highest hardness among components of the golf ball. A golf ball comprising a core comprising a spherical center and an envelope layer, and at least one cover disposed on the outside of the core,
The spherical center contains a base rubber, a co-crosslinking agent, and a crosslinking initiator, and a carboxylic acid and / or a salt thereof (excluding an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and a metal salt thereof The rubber composition for the center which does not contain.
The difference in hardness between the maximum hardness and the minimum hardness in the spherical center is less than 5 in JIS-C hardness,
The envelope layer comprises (a) a base rubber, (b) an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms as a co-crosslinking agent and / or a metal salt thereof, and (c) a crosslinking initiator, d) containing a carboxylic acid and / or a salt thereof (excluding an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and a metal salt thereof);
(D) a carboxylic acid and / or a salt thereof is a carboxylic acid having 15 to 30 carbon atoms and / or a salt thereof,
It is formed from the rubber composition for surrounding layers containing 6 parts by mass or more and less than 40 parts by mass of (d) carboxylic acid and / or salt thereof with respect to 100 parts by mass of (a) base rubber ,
The envelope layer has a hardness distribution which increases from the spherical center surface side to the core surface side by the action of the (d) carboxylic acid and / or a salt thereof,
The hardness difference (Hs-Ho) between the surface hardness (Hs) of the core and the center hardness (Ho) is 18 to 40 in JIS-C hardness,
A golf ball characterized in that the outermost cover has the highest hardness among components of the golf ball. The central hardness (Ho) of the spherical center is 40 to 80 in JIS-C hardness,
The golf ball according to claim 1 , wherein a surface hardness (Hs) of the core is 70 to 96 in JIS-C hardness . The golf ball according to claim 3, wherein the hardness of the outermost cover is 83 to 96 in JIS-C hardness .   The golf ball according to any one of claims 1 to 4, wherein the (d) carboxylic acid and / or the salt thereof is a fatty acid and / or a salt thereof.   The golf ball according to any one of claims 1 to 5, wherein the envelope layer rubber composition further comprises (e) an organic sulfur compound.   The golf ball according to claim 6, wherein the organic sulfur compound (e) is a thiophenol, a polysulfide having 2 to 4 sulfur, a thionaphthol, a thiuram, or a metal salt thereof.   The golf ball according to claim 6, wherein the rubber composition for an envelope layer contains 0.05 parts by mass to 5 parts by mass of the organic sulfur compound (e) with respect to 100 parts by mass of the base rubber (a). .   The rubber composition for an envelope layer contains 15 parts by mass to 50 parts by mass of the (b) co-crosslinking agent with respect to 100 parts by mass of (a) the base rubber. Golf balls.   When the rubber composition for the envelope layer contains only the α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms as the co-crosslinking agent (b), it further contains a metal compound (f) The golf ball according to any one of claims 1 to 9.   The rubber composition for an envelope layer contains 0.2 parts by mass to 5 parts by mass of the crosslinking initiator (c) with respect to 100 parts by mass of the base rubber (a). The golf ball according to claim 1.   The golf ball according to any one of claims 1 to 11, wherein a total thickness of at least one cover is 2.5 mm or less.

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