JP4935975B2 - Method for producing rubber crosslinked molded product for golf ball - Google Patents

Description

  The present invention relates to a rubber cross-linked molded article suitably used as a core material for a solid golf ball such as a one-piece golf ball material, a two-piece golf ball, and a three-piece golf ball, and a method for producing the same.

  Conventionally, a golf ball has a solid golf ball or rubber composition in which a single-layer or multiple-layer cover is formed on a solid core obtained by crosslinking a rubber composition containing various rubber compounding materials. A one-piece golf ball having the entire spherical object as a ball is known. In these golf balls, a rubber composition mainly composed of a base rubber is vulcanized to produce a core which is a spherical cross-linked molded product. By adjusting the hardness difference between the central portion and the surface portion, The degree of freedom of ball hardness distribution can be increased. Therefore, as a means for increasing the surface hardness of the ball, Japanese Patent Application Laid-Open No. 10-43330 (Patent Document 1) proposes a golf ball having a core containing silica particles on the core surface.

  However, the proposed golf ball has a problem in that since the silica particles are merely an inorganic filler, an interface loss occurs, resulting in poor resilience.

Japanese Patent Laid-Open No. 10-43330

The present invention has been made in view of the above circumstances, it aims to provide a manufacturing method of the degree of freedom even more golf ball rubber crosslinked molded product enhanced hardness design hardness distribution from the surface to the interior of the core And

As a result of intensive investigations to achieve the above object, the present inventors have determined that a rubber composition containing a base rubber, a filler, a rubber such as an organic peroxide, and a compounded material thereof is one layer or two layers. In a golf ball rubber cross-linked molded article obtained by cross-linking molding into a spherical body comprising the above, acrylic acid, methacrylic acid, and their alkyl esters, amino groups are used in the cross-linked molded article using a metal oxide as the filler. At least one monomer selected from the group of containing ester, alicyclic ring-containing ester, aromatic ring-containing ester, vinyl group-containing ester, and carboxylic acid-containing ester by a dipping method under a predetermined condition, and the monomer and rubber or a compounding material thereof The depth at which the monomer impregnates from the surface of the crosslinked molded product to the inside is adjusted to 0.3 mm or more. By doing so, the cross-sectional hardness at a predetermined depth from the surface of the cross-linked molded product can be changed more than the surface hardness, succeeding in further increasing the degree of freedom in designing the ball hardness compared to the conventional, the present invention That led to

Accordingly, the following method for producing a crosslinked rubber molded product for golf balls is provided.
A step of crosslinking and molding a rubber composition containing a rubber such as a base rubber, a metal oxide and an organic peroxide, and a compounded material thereof, and acrylic acid, methacrylic acid, and their alkyl esters, amino group-containing esters, fats Spherical cross-linking molding of one layer or two or more layers obtained by the above-described process in an impregnating liquid containing at least one monomer selected from the group of ring-containing esters, aromatic ring-containing esters, vinyl group-containing esters, and carboxylic acid-containing esters A step of immersing the product under conditions of 0 to 40 ° C./5 to 200 hours to impregnate the monomer to a depth of 0.3 mm or more from the surface, and a crosslinked molded article impregnated with the monomer at 80 ° C. or more, 20 A golf ball characterized in that a crosslinked molded product having a surface hardness of 7.4 to 63.3 higher in JIS-C hardness than before impregnation is obtained. Method for producing a crosslinked rubber molded product.

According to manufacturing method for a golf ball for cross-linked rubber molded product of the present invention, it is possible to freely adjust the hardness distribution of the cross-sectional hardness at a predetermined depth from the surface hardness and the surface of the cross-linked rubber molded product, in particular, When the rubber cross-linked molded product is used as a core for a golf ball, the degree of freedom in designing the hardness of the core surface-cross section hardness distribution can be increased. Therefore, when the rubber cross-linked molded product of the present invention is applied to a ball, the spin performance, resilience, etc. of the ball can be easily controlled or adjusted, and various golf balls can be manufactured according to golfers' requests. Can do.

In the present invention, the hardness of the rubber cross-linked molded product prior to impregnation with monomer, has been described by focusing on the hardness of the rubber cross-linked molded product after the impregnation and chemical reactions, other than the hardness of the rubber cross-linked molded product It can be inferred that various physical properties have also changed greatly.

It is described more fully below manufacturing method of the golf ball rubber crosslinked molded product of the present invention.

  The golf ball rubber molded product for a golf ball of the present invention can be applied as a one-piece golf ball material or as a core material of a two-piece or three-layer or more multi-piece solid golf ball. A rubber composition containing a rubber compounding material such as an organic peroxide is heat-molded, and further, a monomer is impregnated in the rubber cross-linked molded article and heated to cause a specific chemical reaction inside the rubber cross-linked molded article. The hardness distribution of the rubber cross-linked molded product is changed.

  Here, as the base rubber, a diene rubber conventionally used for solid golf balls can be used. For example, butadiene rubber (BR), styrene-butadiene rubber (SBR), isoprene rubber (IR), It is selected from chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), ethylene-propylene-diene rubber (EPDM), silicone rubber, and modified products thereof, and one kind is used alone, or two or more kinds are used in combination. Can do. There are no particular restrictions on conditions such as the synthetic catalyst, Mooney viscosity, and molecular weight of these rubbers. In particular, it is preferable to use a high cis polybutadiene rubber having cis-1,4-bonds of 40% or more, more preferably 90% or more. In addition, a high cis polybutadiene synthesized using a lanthanoid catalyst system is preferably used from the viewpoint of high resilience, and high cis polybutadiene obtained using a nickel or cobalt catalyst can also be used. Specific examples include commercially available products such as “BR01” and “BR730” manufactured by JSR, “CB22” and “CB24” manufactured by Bayer.

  Moreover, an inorganic filler is blended as an essential component in the base rubber. Examples of the inorganic filler include zinc oxide, calcium carbonate, calcium oxide, magnesium oxide, barium sulfate, and silica. In particular, it is preferable to use metal oxides such as zinc oxide, calcium oxide, and magnesium oxide. In this case, the average particle diameter of the metal oxide is preferably 0.8 μm or less, more preferably 300 nm or less.

  Specific examples of the organic peroxide include cyclohexanone peroxide, methylcyclohexanone peroxide, acetylacetone peroxide, 1,1-di (t-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1 -Di (t-hexylperoxy) cyclohexane, 1,1-di (t-butylperoxy) -2-methylcyclohexane, 1,1-di (t-butylperoxy) cyclohexane, 2,2-di (t -Butylperoxy) butane, n-butyl 4,4-di- (t-butylperoxy) halate, 2,2-di (4,4-di- (t-butylperoxy) cyclohexyl) propane, p- Methane hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl Dropper oxide, cumene hydroperoxide, t-butyl hydroperoxide, di (2-t-butylperoxyisopropyl) benzene, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) ) Hexane, t-butylcumyl peroxide, di-t-hexyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane-3, diisobutyryl per Oxide, di (3,3,5-trimethylhexanoyl) peroxide, di-n-octanoyl peroxide, dilauroyl peroxide, distearoyl peroxide, disuccinic acid peroxide, di- (3-methylbenzoyl) Peroxide), dibenzoyl peroxide, (4-methylbenzoyl) peroxide, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di (4-t-butylcyclohexyl) peroxydicarbonate, di (2-ethoxyethyl) peroxydicarbonate Di (3-methoxybutyl) peroxydicarbonate, di-sec-butylperoxydicarbonate, cumylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, 1 -Cyclohexyl-1-methylethylperoxyneodecanoate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexa Noate, 2,5-dimethyl-2,5-di (2-e Tylhexanoylperoxy) hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-hexylperoxyisopropylmono Carbonate, t-butylperoxymaleic acid, t-butylperoxy-3,3,5-trimethylhexanoate, t-butylperoxylaurate, 2,5-dimethyl-2,5-di (3- Methylbenzoylperoxy) hexane, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-di (benzoylperoxy) ) Hexane, t-butyl peroxyacetate, -Butylperoxy-3-methylbenzoate, t-butylperoxybenzoate, t-butylperoxyallyl monocarbonate, t-butyltrimethylsilyl peroxide, 3,3 ', 4,4',-tetra (t-butylperoxide Oxycarbonylbenzophenone), 2,3-dimethyl-2,3-dienylbutane, and the like.

  The compounding amount of the organic peroxide is not particularly limited, but is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and preferably 5 as the upper limit with respect to 100 parts by mass of the base rubber. 0.0 part by mass or less, more preferably 3 parts by mass or less.

  The rubber composition may contain α, β-unsaturated carboxylic acid such as acrylic acid and methacrylic acid, and / or a metal salt thereof, and the metals include zinc, sodium, potassium, magnesium, lithium, Calcium can be exemplified. Furthermore, in combination with the above compound or alone, an ester of unsaturated carboxylic acid such as butyl acrylate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, triallyl isocyanurate, glycidyl methacrylate, etc. it can.

  The compounding amount of the compound is not particularly limited, but is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, and preferably 60 parts by mass or less, more preferably as an upper limit, with respect to 100 parts by mass of the base rubber. The blending is 40 parts by mass or less.

  In the present invention, as other rubber compounding materials, sulfur, inorganic sulfur compounds, and various inorganic compounds other than those described above can be appropriately compounded.

  As other optional components of the rubber composition, for example, an organic sulfur compound can be blended for the purpose of improving the resilience of the spherical cross-linked molded product. Specific examples of such organic sulfur compounds include thiophenols, thionaphthols, halogenated thiophenols or metal salts thereof, more specifically, pentachlorothiophenol, pentafluorothiophenol, pentabromothiophenol. , Parachlorothiophenol or metal salts thereof, in particular zinc salts. In this case, the compounding amount of the organic sulfur compound is preferably 0.2 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the base rubber. In addition, elemental sulfur or inorganic sulfur compounds may be added to increase the cross-sectional hardness distribution of the spherical crosslinked product. Further, a known processing aid for improving the processability of the rubber composition, specifically, a processing aid such as a trade name “Akiplast” (manufactured by Rhein Chemie) can be added. You may add the ground material, the ground material of a cover material, the ground material of a used golf ball, and the thing which grind | pulverized the waste of rubber | gum and resin which generate | occur | produces in a manufacturing process.

  In addition, an anti-aging agent can also be mix | blended as needed. In this case, the blending amount of the antioxidant is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 3 parts by mass or less as an upper limit with respect to 100 parts by mass of the base rubber. Can do. Commercially available products can be used as the anti-aging agent, and examples thereof include NOCRACK NS-6, NS-30 (manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.), Yoshinox 425 (manufactured by Yoshitomi Pharmaceutical Co., Ltd.), and the like. .

  In addition to the rubber composition, silicone powder can be blended in an appropriate amount. In this case, the particle size of the silicone powder and the functional group to be modified are not particularly limited. Furthermore, in addition to the rubber composition, various thermoplastic resins can be blended in appropriate amounts.

  The crosslinked rubber molded article of the present invention can be obtained by crosslinking and curing the above-described rubber composition in the same manner as a known golf ball composition. For example, the rubber composition may be kneaded with an appropriate kneader such as a roll, a kneader, or a Banbury mixer, and heated and pressed using a mold. In addition, although there is no restriction | limiting in particular about temperature and time as bridge | crosslinking conditions, Implementing at 100-200 degreeC and 10 to 40 minutes is suitable.

  Here, in the present invention, a monomer is impregnated into a crosslinked molded product obtained by crosslinking the above rubber composition. The monomer is selected from the group consisting of acrylic acid, methacrylic acid, and alkyl esters thereof, amino group-containing esters, alicyclic ring-containing esters, aromatic ring-containing esters, vinyl group-containing esters, alkoxy group-containing esters, and carboxylic acid-containing esters. At least one compound can be employed.

  The means for impregnating the monomer varies depending on the type of monomer. For example, when the monomer is liquid, the liquid monomer is used as it is as the impregnating liquid, and the crosslinked molded product is preferably added to the impregnating liquid at 0 to 40 ° C. The method of immersing within the range of -200 hours is mentioned. The longer the immersion time, the greater the amount of chemicals to be immersed, and the surface is immersed from the surface to the deep part toward the center of the crosslinked molded product. That is, in order to increase the hardness near the center of the crosslinked molded product, it is necessary to immerse for a longer time. As described above, the dipping conditions can be appropriately selected according to the desired hardness distribution including the center hardness, surface hardness, hardness difference, and the like of the cross-linked molded product.

  In addition, if a monomer is a liquid, what is necessary is just to immerse with respect to a crosslinked molding as it is as above-mentioned, and if a monomer is a solid, it can melt | dissolve in various solvents and can use the said chemical | medical agent.

  Further, it is desired that the monomer penetrates within a range in which the depth of impregnation from the surface to the center of the crosslinked molded product is 0.3 mm or more, preferably 0.3 mm or more and 10 mm or less. Further, when the monomer rubber is infiltrated into the cross-linked molded product, the monomer may be immersed in a state where the cross-linked molded product is semi-vulcanized.

In the crosslinked molded product of the present invention, the following (i) and (ii) are obtained by heating the product in which the monomer has penetrated the crosslinked molded product.
(I) Chemical reaction between monomer and rubber and / or compounding material thereof (ii) Either chemical reaction of the monomer itself or both chemical reactions. However, the chemical reaction inside the cross-linked molded product does not occur only by allowing the monomer to permeate the cross-linked molded product, and heating is required.

The chemical reaction (i) (ii) above is specifically a chemical reaction selected from the following (1) to (4).
(1) Chemical reaction between monomer and base rubber (2) Chemical reaction of monomer itself (3) Chemistry of monomer and metal oxide such as zinc oxide when monomer is acid group-containing monomer such as acrylic acid The reaction produces an unsaturated carboxylic acid metal salt. In this case, the chemical reaction between the metal salt of the unsaturated carboxylic acid and the base rubber (4) The chemical reaction of the metal salt of the unsaturated carboxylic acid generated as described above In the present invention, the crosslinked molded product impregnated with the monomer is heated. Thus, at least one chemical reaction among the above (1) to (4) occurs alone, or these chemical reactions occur simultaneously by any combination of the above (1) to (4). The details of the mechanism are not clear, but it is thought that these chemical reactions cause a change in hardness.

  In the present invention, by heating the crosslinked molded article impregnated with the monomer, the hardness distribution of the crosslinked molded article can be changed to freely adjust the surface hardness and the difference in hardness between the center and the surface. That is, when the molded article is impregnated from the surface of the crosslinked molded article and heated, the surface hardness can be improved at least by the chemical reactions (1) to (4) described above. About heating temperature and heating time, although it changes with kinds of monomer, it is preferred to carry out within the range of 100-180 ° C and 1 minute-2 hours, and it is more preferable to carry out in 80 ° C or more and 20 minutes or more especially. Is preferred.

  The drying step is not an essential step of the present invention, but can be performed for the purpose of removing excess monomer. Specifically, after impregnating the monomer under atmospheric pressure or reduced pressure, 0 to 30 ° C. , And preferably dried within 0.5 to 240 hours.

  Specifically, in the heating step, the crosslinked molded product can be heated by pressurization or non-pressurization using a mold composed of an upper mold and a lower mold.

  In addition, the JIS-C hardness of the crosslinked molded product after impregnated with the monomer, dried if necessary, and heated is JIS-C hardness of 5 or more, particularly 10 or more higher than that of the crosslinked molded product before impregnation. It is preferable.

  The diameter of the crosslinked molded article impregnated with the monomer as described above and subjected to heat treatment (hereinafter abbreviated as “impregnated thermoformed article”) is preferably 30.0 mm or more, more preferably 32.0 mm or more. Preferably, it is adjusted to 35.0 mm or more. On the other hand, the upper limit is preferably adjusted to 41.0 mm or less, more preferably 40.5 mm or less, and still more preferably 40.0 mm or less.

  The center hardness of the impregnated thermoformed product is preferably 30 to 80, more preferably 40 to 72 in terms of JIS-C hardness. In addition, JIS-C hardness is measured according to JIS-K 6301-1993.

  The surface hardness of the impregnated thermoformed product is preferably 75 or more in terms of JIS-C hardness. In addition, since it is difficult to measure the hardness of the JIS-C hardness tester at 90 to 100 or more, a Shore D hardness tester (type D durometer according to ASTM D 2240) can be used for further hardness measurement. In this case, it is preferable that the surface hardness of the impregnated thermoformed product does not exceed 85 in Shore D hardness.

  The difference in hardness between the central portion and the surface of the impregnated thermoformed product thus obtained becomes large. Specifically, the value obtained by subtracting the center hardness from the surface hardness of the impregnated thermoformed product is preferably 15 to 45 in JIS-C hardness, and more preferably 17 to 40. When the hardness difference is small, the spin amount increases when the driver (W # 1) is hit, and as a result, the flight distance may not be sufficiently obtained.

  The amount of deflection of the impregnated thermoformed product under a load of 980 N (100 kg) is appropriately selected according to the type of the target golf ball, but is preferably 2.0 mm or more, more preferably 2.8 mm or more. The upper limit is preferably 7 mm or less, more preferably 5 mm or less.

  The use of the impregnated thermoformed product is mainly for golf balls. Specifically, the one-piece solid golf ball to which the impregnated thermoformed product is directly applied, the impregnated thermoformed product as a solid core, and its A two-piece solid golf ball having a one-layer cover on the surface, a three-piece or more multi-piece solid golf ball having a solid core made of an impregnated thermoformed product, and two or more layers on the outer side thereof, etc. be able to.

  When the impregnated thermoformed product is a one-piece golf ball or a core for a two-piece or three-piece or more multi-piece golf ball, the diameter of the golf ball is preferably 42.67 mm or more, more preferably 42.67 to 43. 0.000 mm, and the mass can be preferably 45.0 to 45.93 g. Also, when the above impregnated thermoformed product is applied to a solid core, the cover layer and / or intermediate layer that covers the core is made of a commonly used cover material such as ionomer resin, polyester, polyurethane, nylon, etc. can do. Furthermore, in this case, various known dimples can be formed on the surface of the golf ball by a known method. As a method of covering the core with the cover, a known method of forming by compression molding, injection molding or the like can be employed.

  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 and 2, Comparative Example 1]
The rubber compositions based on the core composition shown in Table 1 below were kneaded and vulcanized and molded under the conditions of 155 ° C. for 30 minutes for each of the examples and comparative examples. A product was prepared, and a monomer (that is, acrylic acid) shown in Table 1 below was impregnated into a crosslinked molded product and heated to change the hardness distribution. The results of measuring the cross-sectional hardness of this impregnated thermoformed product are shown in Table 2 below.

The rubber compounding shown in the above table for the impregnation and drying steps is molded under the above crosslinking conditions to obtain a spherical crosslinked molded product.
The molded product is put into a beaker containing a sufficient amount of acrylic acid. After soaking for 19.7 hours, remove from the beaker and dry at 23 ° C. and atmospheric pressure. After drying for 96 hours, the film was further dried at 23 ° C. under reduced pressure to make the total drying time 120 hours.
When the core obtained by impregnation and thermoforming is cut on the surface including the center of the sphere, the color of the impregnated part (impregnated layer) in the core layer by impregnation and heat treatment is the layer of the part not immersed Since it is different from the color, the depth, volume and mass of the impregnated layer can be calculated from this color difference.

  For convenience, assuming that the depth of the impregnation layer during the impregnation is the same as the depth of the impregnation layer measured as described above, the mass part of the impregnation liquid with respect to the polybutadiene in the impregnation layer during the impregnation step can be calculated. Moreover, in Examples 1 and 2, the surface hardness and cross-sectional hardness of the obtained core are different. As described above, when the acrylic acid monomer is immersed in the cross-linked molded product, the amount of acrylic acid to be immersed can be controlled by neutralizing the acrylic acid impregnating solution with zinc oxide or the like. Moreover, adjusting the amount of acrylic acid immersed is effective in adjusting the surface hardness of the core obtained and the hardness of the portion inside the surface. It is possible to neutralize and trap the acrylic acid impregnating liquid with zinc oxide and acrylic acid. In this case, since the amount of zinc oxide is always a constant amount, it is considered that each cross-sectional hardness of the core layer obtained by impregnation and thermoforming has a certain correlation with the amount of acrylic acid impregnation.

The description of Table 2 above is as follows.
-JIS-C hardness measured the hardness of each Example according to JISK6301-1993.
The surface hardness is an average value of values obtained by randomly measuring two points on the core surface.
-The core cross-section hardness was measured by measuring the hardness at a predetermined position described in Table 2 by cutting the core in half. The numbers in the table indicate the average of two points that are equally different from the center (the measurement points are on two orthogonal straight lines that pass through the center of the cross section).

[Examples 3 to 7]
The rubber composition based on the core composition shown in Table 3 below was kneaded and vulcanized and molded at 155 ° C. for 30 minutes for each example to produce spherical cross-linked molded products of Examples 3-7. The hardness distribution was changed by impregnating the cross-linked molded article with the monomer shown in (1). The results of measuring the cross-sectional hardness of this impregnated thermoformed product are shown in Table 4 below.

[Examples 8 to 11, Comparative Example 2]
The rubber composition based on the core composition shown in Table 5 below was kneaded and vulcanized and molded under the conditions of 160 ° C. and 15 minutes for each example to produce spherical crosslinked molded products of Examples 8-11 and Comparative Example 2. Then, the monomer (glycidyl methacrylate ester) shown in Table 5 below was impregnated into the crosslinked molded product to change the hardness distribution. The results of measuring the cross-sectional hardness of this impregnated thermoformed product are shown in Table 6 below.

※メタクリル酸グリシジルエステル（１００質量％）

* Glycidyl methacrylate (100% by mass)

The main trade names and materials described in the table are as follows.
Cis-1,4-polybutadiene: BR730 (Nd-based catalyst, ML1 + 4100 ° C. “55
“) Cis-1,4-polybutadiene manufactured by JSR: BR01 (Ni-based catalyst, ML1 + 4100 ° C.“ 43 ”)
) JSR Co., Ltd., Zinc Acrylate: Nippon Distillation Industry Co., Ltd., Zinc Oxide: Sakai Chemical Co., Ltd., 2,2'-methylenebis (4-methyl-6-t-butylphenol): Ouchi Shinsei Chemical Co., Ltd., Organic Peroxide 1: Dicumyl peroxide, trade name “Park Mill D”: Nippon Oil & Fats Co., Ltd. Organic peroxide 2: 1,1-di (t-butylperoxy) cyclohexane, trade name “Perhexa C” −40 ”: manufactured by Nippon Oil & Fats Co., Ltd.“ Acrylic acid ”used as impregnation liquid is manufactured by Nippon Shokubai Co., Ltd., and“ glycidyl methacrylate ”is manufactured by Mitsubishi Rayon Co., Ltd.

Claims (1)

A step of crosslinking and molding a rubber composition containing a base rubber, a rubber such as a metal oxide and an organic peroxide, and a compounded material thereof;
Impregnation liquid containing at least one monomer selected from the group of acrylic acid, methacrylic acid, and alkyl esters thereof, amino group-containing esters, alicyclic ring-containing esters, aromatic ring-containing esters, vinyl group-containing esters, and carboxylic acid-containing esters In addition, one or two or more spherical cross-linked molded products obtained by the above process are immersed under conditions of 0 to 40 ° C./5 to 200 hours to impregnate the monomer to a depth of 0.3 mm or more from the surface. Process,
Heating the crosslinked molded article impregnated with the monomer at 80 ° C. or more for 20 minutes or more,
A method for producing a crosslinked rubber molded article for a golf ball, characterized in that a crosslinked molded article having a surface hardness of 7.4 to 63.3 higher in JIS-C hardness than before impregnation is obtained.