JP2007289777A - Multipiece solid golf ball - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a golf ball giving a soft and good hitting feeling and having a highly excellent flight performance. <P>SOLUTION: The golf ball comprises a core, an inner layer cover, and an outer layer cover. The core is made of a rubber composition made by compounding, to a base rubber consisting of (a) polybutadiene made by using a rare earth element catalyst, having the cis-1,4 and 1,2 vinyl content within a specified range and satisfying the relationship, 10×B+5≤A≤10×B+45, wherein the viscosity of a toluene solution η is (mPa s) 500 or under, the Mooney viscosity is A and the ratio (Mw/Mn) of the weight-average molecular weight and the number average molecular weight is B, and (b) another diene rubber, a predetermined amount of unsaturated carboxylic acid and/or its metallic salt, an organic sulfur compound, an inorganic filler and an organic peroxide. In addition, the thickness of the inner layer cover, the shore D hardness of the inner layer cover, the thickness of the outer layer cover and the shore D hardness of the outer layer cover are controlled to an appropriate value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a multi-piece solid golf ball that can obtain a soft and good feel and a very good flying performance.

  Conventionally, in order to impart excellent resilience to golf balls, various improvements have been made in the composition of polybutadiene used as a base rubber.

  For example, JP-A-62-89750 discloses a polybutadiene having a Mooney viscosity of 70 to 100 synthesized using a Ni, Co catalyst as a base rubber and a Mooney viscosity of 30 to 90 synthesized using a lanthanum catalyst. A rubber composition for solid golf balls has been proposed which is blended with polybutadiene synthesized with a polybutadiene or a Ni, Co catalyst and having a Mooney viscosity of 20 to 50.

  However, the above proposal calls for further material improvements that can provide excellent flight performance.

  JP-A-2-268778 proposes a golf ball formed by blending a polybutadiene having a Mooney viscosity of less than 50 synthesized with a Group VIII catalyst and a polybutadiene having a Mooney viscosity of less than 50 synthesized using a lanthanide catalyst. However, it is not possible to obtain excellent flight performance.

  Further, JP-A-11-70187 discloses a multi-piece solid golf ball in which an intermediate layer is formed of polybutadiene having a low Mooney viscosity, and JP-A-11-319148 uses a Ni, Co catalyst. A solid golf ball formed of a rubber composition comprising a polybutadiene having a Mooney viscosity of 50 to 69 and a polybutadiene having a Mooney viscosity of 20 to 90 synthesized using a lanthanoid catalyst, Japanese Patent Application Laid-Open No. 11-164912 A solid golf ball made of a rubber composition having a 1,2 vinyl bond of 2.0% or less and a ratio Mw / Mn of weight average molecular weight to number average molecular weight of 3.5 or less, JP-A 63-275356 Japanese Patent Publication No. HEI 3 (1999) discloses a golf ball formed of a rubber composition in which polybutadiene having a high Mooney viscosity is blended. Japanese Patent No. 51985 proposes a golf ball formed of a rubber composition formed by blending a polybutadiene having a high number average molecular weight and a polybutadiene having a low number average molecular weight. It cannot be said that spin performance is imparted and the flight distance can be increased.

  JP-A-2-228978, JP-A-6-142287, JP-A-7-24084, JP-A-9-10358, JP-A-11-253578, JP-A-11-253579, JP-A-11-319149, Special Japanese Unexamined Patent Publication Nos. 2000-70408, 2000-70409, 2000-70410, and 2000-70411 propose golf balls having a cover whose inner layer is relatively soft and whose outer layer is relatively hard. However, both proposals leave room for improvement in flight distance, and further improvement in flight distance is desired.

JP-A-62-89750 JP-A 63-275356 JP-A-2-268778 JP-A-2-228978 Japanese Patent Laid-Open No. 3-151985 JP-A-6-142287 JP-A-7-24084 Japanese Patent Laid-Open No. 9-10358 JP-A-11-70187 Japanese Patent Laid-Open No. 11-253578 Japanese Patent Laid-Open No. 11-253579 JP 11-319149 A JP 11-319148 A JP 2000-70408 A JP 2000-70409 A JP 2000-70410 A JP 2000-70411 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a multi-piece solid golf ball that can achieve a soft and good feel and an increase in flight distance.

As a result of intensive studies in order to achieve the above object, the present inventor has found that in a multi-piece solid golf ball comprising a solid core, an inner layer cover, and an outer layer cover, the solid core is: A polybutadiene synthesized using a rare earth element-based catalyst having 60% or more of cis 1,4 bonds and 2% or less of 1,2 vinyl bonds, and having a viscosity η ( mPa · s) is 500 or less, the Mooney viscosity (ML _{1 + 4} (100 ° C.)) is A, and the ratio (Mw) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) / Mn) is B, 20-100 mass% of polybutadiene satisfying the relationship of 10 × B + 5 ≦ A ≦ 10 × B + 45, and (b) 0-80 mass% of other diene rubbers (C) 10-60 parts by mass of unsaturated carboxylic acid and / or metal salt thereof, (d) 0.5-5 parts by mass of organic sulfur compound, (e) inorganic filling with respect to 100 parts by mass of base rubber to be compounded 5 to 80 parts by weight of the agent, (f) 0.1 to 3.0 parts by weight of the organic peroxide, and the thickness of the inner layer cover is 1.7 to 3.0 mm. The Shore D hardness is 10 to 60, the Shore D hardness of the outer layer cover is 56 to 80, the thickness is 0.7 to 2.0 mm, and the Shore D hardness of the outer layer cover is greater than the Shore D hardness of the inner layer cover. The multi-piece solid golf ball obtained by increasing the height of the soft and good hit feeling and increase of the flight distance by optimizing the material of the solid core and the synergistic effect by optimizing the hardness between the inner layer cover and the outer layer cover Maru that can be planned The present inventors have found out that the golf ball is a chiped solid golf ball and have made the present invention.

Accordingly, the present invention provides the following multi-piece solid golf ball.
[Claim 1] In a multi-piece solid golf ball comprising a solid core, an inner layer cover, and an outer layer cover, the solid core has (a) 60% or more of cis 1,4 bonds, A polybutadiene synthesized using a rare earth element-based catalyst having 2% or less of a 2-vinyl bond, the viscosity η (mPa · s) of a 5% by mass toluene solution at 25 ° C. being 500 or less, and the Mooney viscosity When (ML _{1 + 4} (100 ° C.)) is A and the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is B, 10 × B + 5 ≦ A With respect to 100 parts by mass of the base rubber compounding 20 to 100% by mass of polybutadiene satisfying the relationship of ≦ 10 × B + 45 and (b) 0 to 80% by mass of other diene rubbers,
(C) 10-60 parts by mass of unsaturated carboxylic acid and / or metal salt thereof,
(D) 0.5 to 5 parts by mass of an organic sulfur compound,
(E) 5-80 parts by weight of inorganic filler,
(F) Organic peroxide formed with a rubber composition containing 0.1 to 5 parts by mass, the inner cover has a thickness of 1.7 to 3.0 mm, and a Shore D hardness of 10 to 60 And the outer layer cover has a Shore D hardness of 56-80, a thickness of 0.7-2.0 mm, and the outer layer cover has a Shore D hardness higher than that of the inner layer cover. Solid golf ball.
[2] The multi-piece solid golf ball of [1], wherein the polybutadiene in the component (b) is synthesized using a Group VIII catalyst.

  The multi-piece solid golf ball of the present invention is soft and has a good feel and high resilience.

  Hereinafter, the present invention will be described in more detail. The golf ball of the present invention is formed of a solid core of a rubber composition having polybutadiene as a base rubber. In the base rubber, (a) As the component polybutadiene, the contents of cis 1,4 bonds and 1,2 vinyl bonds, the viscosity η of a 5% by weight toluene solution at 25 ° C., and the relationship between Mooney viscosity and the above η are optimized, respectively. It is necessary to be blended.

  Here, the polybutadiene of component (a) has a cis 1,4 bond of 60% or more, preferably 80% or more, more preferably 90% or more, most preferably 95% or more, and 1,2 vinyl. It is necessary that the bond has 2% or less, preferably 1.7% or less, more preferably 1.5% or less, and most preferably 1.3% or less. When deviating from the above range, the resilience decreases.

  The polybutadiene as the component (a) of the present invention requires that the viscosity η (mPa · s) of a 5 mass% toluene solution at 25 ° C. is 500 or less. Here, the viscosity η (mPa · s) of a 5% by mass toluene solution at 25 ° C. of the present invention is obtained by dissolving 2.28 g of polybutadiene to be measured in 50 ml of toluene, and then using a standard solution for constituting a viscometer as a standard solution ( It shall mean the value measured under the condition of 25 ° C. with a predetermined viscometer using JIS Z8809).

  The polybutadiene as the component (a) needs to have a viscosity η (mPa · s) of a 5% by mass toluene solution at 25 ° C. of 500 or less, preferably 450 or less, and most preferably 400 or less. If it is too high, workability will deteriorate. Further, the lower limit of η is recommended to be 50 or more, preferably 100 or more, more preferably 150 or more, and most preferably 200 or more. If η is too low, the resilience may be lowered.

The polybutadiene of component (a) has a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of A, a weight average molecular weight of Mw and a number average molecular weight of Mn, and a ratio between the weight average molecular weight and the number average molecular weight ( When Mw / Mn) is B,
10 × B + 5 ≦ A
Preferably, 10 × B + 7 ≦ A,
More preferably, 10 × B + 8 ≦ A,
Most preferably 10 × B + 9 ≦ A
And the upper limit,
A ≦ 10 × B + 45
It is necessary to satisfy this relationship. If it is too low, the resilience will be low, and if it is too high, workability will be poor.

The polybutadiene of component (a) has a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of 20 or more, preferably 30 or more, more preferably 40 or more, most preferably 50 or more, and an upper limit of 80 or less, preferably 70. In the following, it is recommended that it is 65 or less, most preferably 60 or less.

The Mooney viscosity referred to in the present invention is an industrial viscosity index (JIS-K6300) measured with a Mooney viscometer, which is a kind of rotational plasticity meter, and ML _{1 + 4} as a unit symbol. (100 ° C.) is used. M represents Mooney viscosity, L represents a large rotor (L-type), 1 + 4 represents a preheating time of 1 minute, and a rotor rotation time of 4 minutes, and the measurement was performed at 100 ° C.

  The polybutadiene as component (a) is synthesized with a rare earth element-based catalyst, and a known one can be used as the rare earth element-based catalyst.

  For example, a catalyst comprising a combination of a lanthanum series rare earth element compound, an organoaluminum compound, an alumoxane, a halogen-containing compound and, if necessary, a Lewis base can be used.

  Examples of the lanthanum series rare earth element compounds include metal halides having an atomic number of 57 to 71, carboxylates, alcoholates, thioalcolates, and amides.

Examples of the organoaluminum compound include AlR ¹ R ² R ³ (wherein R ¹ , R ² and R ³ may be the same or different, and each represents hydrogen or a hydrocarbon residue having 1 to 8 carbon atoms. Can be used.

（式中、Ｒ⁴は、炭素数１〜２０の炭素原子を含む炭化水素基、ｎは２以上の整数である。） Preferred examples of the alumoxane include compounds having a structure represented by the following formula (I) or the following formula (II). In this case, Fine Chemicals, 23, (9), 5 (1994), J. Am. Am. Chem. Soc. 115, 4971 (1993); Am. Chem. Soc. 117, 6465 (1995).

(In the formula, R ⁴ is a hydrocarbon group containing a carbon atom having 1 to 20 carbon atoms, and n is an integer of 2 or more.)

Examples of the halogen-containing compound include AlX _n R _3-n (where X represents halogen, R is a hydrocarbon residue having 1 to 20 carbon atoms, such as an alkyl group, an aryl group, and an aralkyl group. And n represents 1, 1.5, 2 or 3), strontium halides such as Me ₃ SrCl, Me ₂ SrCl ₂ , MeSrHCl ₂ and MeSrCl ₃ , and others, silicon tetrachloride, tetrachloride Metal halides such as tin and titanium tetrachloride are used.

  The Lewis base can be used to complex a lanthanum series rare earth element compound, and examples thereof include acetylacetone and ketone alcohol.

  In the present invention, in particular, the use of a neodymium-based catalyst using a neodymium compound as a lanthanum series rare earth element compound is superior in polybutadiene rubber having a high content of 1,4-cis bonds and a low content of 1,2-vinyl bonds. Since it is obtained by polymerization activity, it is preferable, and specific examples of these rare earth element-based catalysts include those described in JP-A No. 11-35633.

  When butadiene is polymerized in the presence of a rare earth element-based catalyst, a solvent may be used, bulk polymerization or gas phase polymerization may be performed without using a solvent, and the polymerization temperature is usually −30 ° C. to 150 ° C., preferably Can be 10-100 degreeC.

  The polybutadiene as the component (a) of the present invention may be obtained by reacting a terminal modifier with the active terminal of the polymer subsequent to the polymerization using the rare earth element-based catalyst.

（式中、Ｙは、酸素原子、チッ素原子又はイオウ原子を示す）、
（４） ハロゲン化イソシアノ化合物、
（５） Ｒ⁸−（ＣＯＯＨ）_m、Ｒ⁹（ＣＯＸ）_m 、Ｒ¹⁰−（ＣＯＯ−Ｒ¹¹）、Ｒ¹²−ＯＣＯＯ−Ｒ¹³、Ｒ¹⁴−（ＣＯＯＣＯ−Ｒ¹⁵）_m 、又は下記式で示されるカルボン酸、酸ハロゲン化物、エステル化合物、炭酸エステル化合物又は酸無水物

（式中、Ｒ⁸〜Ｒ¹⁶は、同一でも異なっていてもよく、炭素数１〜５０の炭素原子を含む炭化水素基、Ｘはハロゲン原子、ｍは１〜５の整数を示す）、
（６） Ｒ¹⁷ _l Ｍ″（ＯＣＯＲ¹⁸）_4-l 、Ｒ¹⁹ _lＭ″（ＯＣＯ−Ｒ²⁰−ＣＯＯＲ²¹）_4-l、又は下記式で示されるカルボン酸の金属塩

（式中、Ｒ¹⁷〜Ｒ²³は、同一でも異なっていてもよく、炭素数１〜２０の炭素原子を含む炭化水素基、Ｍ″はスズ原子、ケイ素原子又はゲルマニウム原子、ｌは０〜３の整数を示す）等を挙げることができる。 Here, a well-known thing can be used for a terminal modifier, For example, the compound described in following (1)-(6) can be mentioned.
(1) R ⁵ _n M′X _4-n , M′X ₄ , M′X ₃ , R ⁵ _n M ′ (—R ⁶ —COOR ⁷ ) _4-n or R ⁵ _n M ′ (—R ⁶ — COR ⁷ ) _4-n (wherein R ⁵ and R ⁶ may be the same or different and each represents a hydrocarbon group containing 1 to 20 carbon atoms, R ⁷ is a carbon atom having 1 to 20 carbon atoms) Which may contain a carbonyl group or an ester group in the side chain, M ′ is a tin atom, silicon atom, germanium atom or phosphorus atom, X is a halogen atom, and n is an integer of 0 to 3 A halogenated organometallic compound, a halogenated metal compound or an organometallic compound,
(2) A heterocumulene containing a Y = C = Z bond in the molecule (wherein Y represents a carbon atom, oxygen atom, nitrogen atom or sulfur atom, and Z represents an oxygen atom, nitrogen atom or sulfur atom). Compound,
(3) Hetero 3-membered ring compound containing the following bond in the molecule

(Wherein Y represents an oxygen atom, a nitrogen atom or a sulfur atom),
(4) a halogenated isocyano compound,
^{(5) R 8 - (COOH} ) m, R 9 (COX) m, R 10 - (COO-R 11), R 12 -OCOO-R 13, R 14 - (COOCO-R 15) m, or the following formula Carboxylic acid, acid halide, ester compound, carbonate compound or acid anhydride represented by

(In formula, R < ⁸ > -R < ¹⁶ > may be same or different, The hydrocarbon group containing a C1-C50 carbon atom, X is a halogen atom, m shows the integer of 1-5),
(6) R ¹⁷ _l M ″ (OCOR ¹⁸ ) _4-l , R ¹⁹ _l M ″ (OCO-R ²⁰ —COOR ²¹ ) _4-l , or a metal salt of a carboxylic acid represented by the following formula

(Wherein R ^{17 to} R ²³ may be the same or different, a hydrocarbon group containing a carbon atom having 1 to 20 carbon atoms, M ″ is a tin atom, a silicon atom or a germanium atom, and l is 0 to 3) And the like).

  Specific examples of the terminal modifiers shown in the above (1) to (6) and the reaction method thereof include, for example, those described in JP-A-11-35633 or JP-A-7-268132 and the like. be able to.

  In the base rubber, the component (a) of the present invention is 20% by mass or more, preferably 25% by mass or more, more preferably 30% by mass or more, most preferably 35% by mass or more, and the upper limit is 100% by mass or less. Preferably, it is 90% by mass or less, more preferably 80% by mass or less, and most preferably 70% by mass or less.

  Further, in the base rubber of the present invention, in addition to the component (a), the diene rubber of the component (b) can be blended as desired within the range not impairing the achievement of the object of the present invention. Specific examples of the diene rubber include polybutadiene rubber, styrene butadiene rubber (SBR), natural rubber, polyisoprene rubber, and ethylene propylene diene rubber (EPDM). These can be used individually by 1 type or in combination of 2 or more types.

  The diene rubber of component (b) of the present invention is usually 80% by mass or less, preferably 75% by mass or less, more preferably 70% by mass or less, most preferably in the base rubber combined with component (a). 65% by mass or less, the lower limit being 0% by mass or more, preferably 10% by mass or more, more preferably 20% by mass or more, and most preferably 30% by mass or more.

  In the present invention, as the component (b), polybutadiene rubber is particularly preferably used. In particular, the content of cis 1,4 bond and 1,2 vinyl bond, Mooney viscosity of polybutadiene itself, Mooney viscosity and the above η It is recommended that each of these is appropriately formulated.

  Here, the polybutadiene in the component (b) has a cis 1,4 bond of 60% or more, preferably 80% or more, more preferably 90% or more, and most preferably 95% or more. It is recommended to have a vinyl bond of 5% or less, preferably 4.5% or less, more preferably 4.0% or less, and most preferably 3.5% or less.

  It is recommended that the polybutadiene in the component (b) has a Mooney viscosity of 55 or less, preferably 50 or less, more preferably 45 or less, the lower limit is 10 or more, preferably 20 or more, more preferably 25 or more, Most preferably it is recommended to be 30 or more.

  It is recommended that the polybutadiene in component (b) of the present invention is further synthesized with a Group VIII catalyst, and specific examples of the Group VIII catalyst include the following nickel-based catalyst and cobalt-based catalyst. Can do.

  Here, examples of the nickel-based catalyst include a one-component system such as nickel diatomaceous earth, a two-component system such as Raney nickel / titanium tetrachloride, and a three-component system such as nickel compound / organometallic / boron trifluoride etherate. Can be mentioned. As the nickel compound, reduced nickel with support, Raney nickel, nickel oxide, nickel carboxylate, organic nickel complex salt, or the like is used. Examples of the organic metal include trialkylaluminum such as triethylaluminum, tri-n-propylaluminum, triisobutylaluminum, and tri-n-hexylaluminum, n-butyllithium, sec-butyllithium, tert-butyllithium, 1, Examples include alkyl lithium such as 4-dilithium butane, and dialkyl zinc such as diethyl zinc and dibutyl zinc.

  In addition, as cobalt-based catalysts, cobalt and its compounds include Raney cobalt, cobalt chloride, cobalt bromide, cobalt iodide, cobalt oxide, cobalt sulfate, cobalt carbonate, cobalt phosphate, cobalt phthalate, cobalt carbonyl, cobalt acetyl. Examples thereof include acetonate, cobalt diethyldithiocarbamate, cobalt anilinium nitrite, cobalt dinitrosilkyl chloride and the like. -Trialkylaluminum such as n-propylaluminum, triisobutylaluminum, tri-n-hexylaluminum, ethylaluminum sesquik Aluminum alkyl sesquichloride of chloride etc., can be preferably exemplified a combination of aluminum chloride and the like.

  When the polymerization is performed using the above group VIII-based catalyst, particularly a nickel-based catalyst or a cobalt-based catalyst, usually, the reactor is continuously charged together with a solvent and a butadiene monomer, for example, the reaction temperature is 5 to 60 ° C, A method of operating the reaction pressure so as to obtain the Mooney viscosity can be exemplified by appropriately selecting the reaction pressure within the range of atmospheric pressure to 70 atm.

In the polybutadiene of the component (b) of the present invention, the Mooney viscosity (ML _{1 + 4} (100 ° C.)) is A, and the viscosity of a 5 mass% toluene solution at 25 ° C. is η (mPa · s). When
η ≦ 20 × A-550
In particular, η ≦ 20 × A-560
Preferably, η ≦ 20 × A-580
More preferably, η ≦ 20 × A-590
And the upper limit,
Usually, η ≧ 20 × A-750
Preferably, η ≧ 20 × A-700
More preferably, η ≧ 20 × A-680
Most preferably, η ≧ 20 × A−650
It is recommended that polybutadiene satisfy the above relationship, and the use of polybutadiene with η and A optimized in this way provides the linearity, ie, resilience and workability of the polybutadiene molecule. It is valid.

  The diene rubber in the component (b) of the present invention is usually 100% by mass or less, preferably 90% by mass or less, more preferably 80% by mass or less, and the lower limit is 30% by mass or more, preferably 50%. More than 70% by mass, more preferably 70% by mass or more can be blended. When the polybutadiene is blended in the component (b) within the above-described range, the extrudability is improved and the further excellent property of improving the workability can be imparted.

  The solid core of the present invention comprises (c) an unsaturated carboxylic acid and / or a metal salt thereof, (d) an organic sulfur compound, (e) an inorganic filler, and (f) an organic compound, based on 100 parts by mass of the base rubber. It is formed of a rubber composition containing a predetermined amount of peroxide as an essential component.

  Specific examples of the unsaturated carboxylic acid (c) include acrylic acid, methacrylic acid, maleic acid, and fumaric acid, and acrylic acid and methacrylic acid are particularly preferable.

  In addition, as the metal salt of (c) unsaturated carboxylic acid, zinc salts of unsaturated fatty acids such as zinc methacrylate and zinc acrylate, magnesium salts and the like can be blended, and particularly, zinc acrylate can be preferably used. .

  The (c) unsaturated carboxylic acid and / or metal salt thereof is 10 parts by mass or more, preferably 15 parts by mass or more, more preferably 20 parts by mass or more, and 60 parts by mass as an upper limit with respect to 100 parts by mass of the base rubber. Or less, preferably 50 parts by mass or less, more preferably 45 parts by mass or less, and most preferably 40 parts by mass or less. If the blending amount is too large, it becomes too hard, resulting in an unbearable feel, and if it is too small, the resilience decreases.

  (D) The organic sulfur compound is an essential component for imparting excellent resilience. Specifically, it is recommended that thiophenol, thionaphthol, halogenated thiophenol, or a metal salt thereof be blended. Specifically, zinc salts such as pentachlorothiophenol, pentafluorothiophenol, pentabromothiophenol, parachlorothiophenol, pentachlorothiophenol, diphenyl polysulfide having 2 to 4 sulfur atoms, dibenzyl polysulfide, dibenzoyl Polysulfide, dibenzothiazoyl polysulfide, dithiobenzoyl polysulfide and the like can be mentioned, and in particular, zinc salt of pentachlorothiophenol and diphenyl disulfide can be preferably used.

  (D) The organic sulfur compound is 0.5 parts by mass or more with respect to 100 parts by mass of the base rubber, and the upper limit is 5 parts by mass or less, preferably 4 parts by mass or less, and more preferably 3 parts by mass or less. Preferably 2 mass parts or less are mix | blended. If the amount is too large, the hardness becomes too soft, and if the amount is too small, improvement in resilience cannot be expected.

  (E) As an inorganic filler, zinc oxide, barium sulfate, calcium carbonate etc. can be mentioned, for example, The compounding quantity is 5 mass parts or more with respect to 100 mass parts of said base rubbers, Preferably it is 7 masses. Part or more, more preferably 10 parts by weight or more, most preferably 13 parts by weight or more, and the upper limit is 80 parts by weight or less, preferably 50 parts by weight or less, more preferably 45 parts by weight or less, and most preferably 40 parts by weight or less. . If the amount is too large or too small, an appropriate weight and suitable resilience cannot be obtained.

  (F) As an organic peroxide, a commercial item can be mentioned, for example, park mill D (made by NOF Corporation), perhexa 3M (made by NOF Corporation), Luperco 231XL (made by Atochem Corporation), etc. are mentioned. If necessary, two or more different organic peroxides may be mixed and used.

  (F) The organic peroxide is 0.1 parts by mass or more, preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and most preferably 0.00 parts by mass, relative to 100 parts by mass of the base rubber. 7 parts by mass or more and 5 parts by mass or less as an upper limit, preferably 4 parts by mass or less, more preferably 3 parts by mass or less, and most preferably 2 parts by mass or less. If the blending amount is too large or too small, it is not possible to obtain suitable feel, durability and resilience.

  Moreover, an anti-aging agent can be mix | blended as needed, for example, as a commercial item, NOCRACK NS-6, NS-30 (made by Ouchi Shinsei Chemical Co., Ltd.), Yoshinox 425 (Yoshitomi Pharmaceutical Co., Ltd.) And the like). 0 parts by mass or more, preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, most preferably 0.2 parts by mass or more, and 3 parts by mass as the upper limit, based on 100 parts by mass of the base rubber. In the following, it is recommended that the rebound and durability are preferably 2 parts by mass or less, more preferably 1 part by mass or less, and most preferably 0.5 parts by mass or less.

  The solid core of the present invention can be obtained by vulcanizing and curing the above-described rubber composition in the same manner as a known solid core rubber composition. The vulcanization conditions can be carried out, for example, at a vulcanization temperature of 100 to 200 ° C. and a vulcanization time of 10 to 40 minutes.

  In the present invention, the hardness of the heat-molded product can be appropriately adjusted according to the use mode of various golf balls described later, and is not particularly limited. The cross-sectional hardness is flat from the center to the surface of the molded product. Even in this case, there may be a difference in hardness between the center and the surface of the molded product.

  Further, the above-mentioned solid core has a deflection amount under a load of 980 N (100 kg) of usually 2.0 mm or more, preferably 2.5 mm or more, more preferably 2.8 mm or more, and most preferably 3.2 mm or more. Is 6.0 mm or less, preferably 5.5 mm or less, more preferably 5.0 mm or less, and most preferably 4.5 mm or less. If the amount of deformation is too small, the feel will be worsened, When a long shot that causes a large deformation of the ball of a driver or the like, the spin increases and does not fly, and if it is too soft, the hit feeling becomes dull and the rebound is not sufficient and does not fly, and the cracking durability due to repeated hitting deteriorates There is.

  The diameter of the solid core of the present invention is 30.0 mm or more, preferably 32.0 mm or more, more preferably 34.0 mm or more, most preferably 35.0 mm or more, and the upper limit is 40.0 mm or less, preferably 39.5 mm. Hereinafter, it is recommended that the thickness be 39.0 mm or less.

  The specific gravity of the solid core is usually 0.9 or more, preferably 1.0 or more, more preferably 1.1 or more, and the upper limit is 1.4 or less, preferably 1.3 or less, more preferably 1.2 or less. It is recommended that there be.

  The golf ball of the present invention is a multi-piece solid golf ball having a cover of two or more layers comprising an inner layer cover and an outer layer cover, and these covers can be manufactured using a known cover material. In any case, as a main material, specifically, thermoplastic or thermosetting polyurethane elastomer, polyester elastomer, ionomer resin, ionomer resin having a relatively high degree of neutralization, polyolefin An elastomer or a mixture thereof can be exemplified. These can be used alone or in admixture of two or more. Particularly preferred are thermoplastic polyurethane elastomers, ionomer resins, ionomer resins having a relatively high degree of neutralization, and polyester elastomers. be able to.

  Commercially available products can be used as the thermoplastic polyurethane elastomer, for example, diisocyanates such as Pandex T7298, T7295, T7890, TR3080, T8290, T8295, T1288 (DIC Bayer Polymer). In which is aliphatic or aromatic. Commercially available ionomer resins include Surlyn 6320, 8945, 9945, and 8120 (made by DuPont, USA), High Milan 1706, 1605, 1855, 1557, 1601, and AM7316 (Mitsui / Dupont Poly). Chemical) and the like. Moreover, as a commercial item of a polyester-type elastomer, Hytrel 4047, the same 3078 (made by Toray DuPont) etc. are mentioned.

  Furthermore, a polymer such as a thermoplastic elastomer other than the above can be blended as an optional component in the main material of the cover. Specifically, as an optional polymer, a polyamide-based elastomer, a styrene-based block elastomer, a hydrogenated polybutadiene, an ethylene-vinyl acetate (EVA) copolymer, or the like can be blended.

  The multi-piece solid golf ball of the present invention can be manufactured by a known method and is not particularly limited. However, the solid core is disposed in a predetermined molding die, and the intermediate layer material is provided. A method of injecting according to a predetermined method in the order of the cover material, making a pair of half cups with these cover materials, encapsulating the solid core, and compressing and compressing them can be suitably employed.

  In the golf ball of the present invention, the hardness of the outer layer cover is required to be higher than the Shore D hardness of the inner layer cover.

  Here, the Shore D hardness of the inner layer cover is usually 10 or more, preferably 20 or more, more preferably 25 or more, most preferably 30 or more, and the upper limit is 60 or less, preferably 55 or less, more preferably 50 or less, most preferably. Is recommended to be 45 or less.

  Further, it is recommended that the Shore D hardness of the outer layer cover is 56 or more, preferably 59 or more, and the upper limit is 80 or less, preferably 75 or less, more preferably 70 or less, and most preferably 65 or less.

  In the present invention, the Shore D hardness of the outer layer cover and the inner layer cover needs to be higher than the Shore D hardness of the inner layer cover, and the Shore D hardness difference between the hardness of the outer layer cover and the inner layer cover is usually It is recommended that it is 2 or more, especially 5 or more, preferably 7 or more, more preferably 9 or more, and the upper limit is 30 or less, particularly 25 or less, more preferably 20 or less.

  The thickness of the inner layer cover of the present invention is 1.7 mm or more and the upper limit is 3.0 mm or less, preferably 2.5 mm or less, more preferably 2.0 mm or less, and most preferably 1.6 mm or less. Recommended. Further, it is recommended that the thickness of the outer cover of the present invention is 0.7 mm or more, preferably 1.0 mm or more, and the upper limit is 2.0 mm or less, preferably 1.6 mm or less.

  The multi-piece solid golf ball of the present invention may conform to the golf rules for competition purposes, and may be formed with a diameter of 42.67 mm or more and a weight of 45.93 g or less. The upper limit of the diameter is preferably 44.0 mm or less, more preferably 43.5 mm or less, most preferably 43.0 mm or less, and the lower limit of the weight is preferably 44.5 g or more, particularly preferably 45.0 g or more, more preferably 45. It is recommended that it be at least 1 g, most preferably at least 45.2 g.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[Examples 1-4, Comparative Examples 1-4]
The core material shown in Table 2 is appropriately used with a kneader or a roll for 100 parts by mass of each polybutadiene prepared by mixing the polybutadiene materials shown in Table 1 of the following types (1) to (7) in combinations shown in Table 2. After kneading, pressure molding was performed at 150 ° C. for 20 minutes to produce a solid core having a diameter of about 35.3 mm.

Polybutadiene type (1) Polybutadiene: BR01 manufactured by JSR
(2) Polybutadiene: BR11 manufactured by JSR Corporation
(3) Polybutadiene: UBE101 manufactured by Ube Industries
(4) Polybutadiene: Prototype grade HCBN-4 manufactured by JSR
(5) Polybutadiene: Prototype grade HCBN-2 manufactured by JSR
(6) Polybutadiene: Prototype grade # 9100081 manufactured by Firestone
(7) Polybutadiene: Prototype grade # 9100069 manufactured by Firestone

The obtained solid core was examined for deformation amount and resilience when loaded with 980 N (100 kg) as follows. The results are shown in Table 4.
Deflection amount under load of 980N Solid core deformation amount under load of 980N (100kg) (mm)
The resilience when measured with the initial speedometer of the same type as the officially recognized resilience agency USGA was examined using a predetermined measuring instrument. Based on Comparative Example 2, the difference was expressed.

The obtained solid core was placed in a predetermined mold, the resin shown in Table 3 was injection-molded to produce an inner layer coated core having a diameter of about 38.7 mm, and then transferred to the predetermined mold and shown in Table 3 The resin was injection molded to produce a three-piece solid golf ball having a diameter of about 42.7 mm and a weight of about 45.3 g. The main product names are as follows.
High Milan: Mitsui DuPont Polychemical Ionomer Resin Hytrel: Toray DuPont Thermoplastic Polyester Elastomer Surlyn: U.S. DuPont Ionomer Resin Primaloloy: Mitsubishi Chemical's Thermoplastic Polyester Elastomer
Pandex: A polyurethane elastomer manufactured by DIC Bayer Polymer.

The performance of the obtained golf ball was examined as follows. The results are shown in Table 4.
The Shore D hardness of the material physical property inner layer and outer layer cover was measured by the ASTM D2240 test method.
A golf ball physical property hitting machine was used to measure the carry and total when hitting with a driver (W # 1) at a head speed of 40 m / s.
Based on an actual hitting test with 1st wood (driver) and putter by 5 golfers of feeling professionals and top amateurs, (1) Too hard, (2) Good, (3) Too soft The most frequent evaluation was taken as the evaluation of each ball.

Claims (2)

In a multi-piece solid golf ball comprising a solid core, an inner layer cover, and an outer layer cover, the solid core has (a) 60% or more of cis 1,4 bonds and 2 1,2 vinyl bonds. % Polybutadiene synthesized using a rare earth element-based catalyst having a viscosity of η (mPa · s) of 5 mass% toluene solution at 25 ° C. of 500 or less and the Mooney viscosity (ML _{1 + 4} (100 ° C.)) is A, and the ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) is B, 10 × B + 5 ≦ A ≦ 10 × B + 45 With respect to 100 parts by mass of base rubber compounding 20 to 100% by mass of polybutadiene satisfying the relationship and 0 to 80% by mass of other diene rubber,
(C) 10-60 parts by mass of unsaturated carboxylic acid and / or metal salt thereof,
(D) 0.5 to 5 parts by mass of an organic sulfur compound,
(E) 5-80 parts by weight of inorganic filler,
(F) Organic peroxide formed with a rubber composition containing 0.1 to 5 parts by mass, the inner cover has a thickness of 1.7 to 3.0 mm, and a Shore D hardness of 10 to 60 And the outer layer cover has a Shore D hardness of 56-80, a thickness of 0.7-2.0 mm, and the outer layer cover has a Shore D hardness higher than that of the inner layer cover. Solid golf ball.   The multi-piece solid golf ball according to claim 1, wherein the polybutadiene in the component (b) is synthesized using a Group VIII catalyst.