JPH10192447A - Solid golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid golf ball having a core easy to manufacture and excellent in recycling property, and having flying performance equal to or higher than in the past. SOLUTION: In a solid golf ball formed of a core 1 and a cover 2 covering the core 1, the core 1 is formed of a molded body of a thermoplastic elastomer composite having a bending elasticity of 400-3000kgf/cm<2> obtained by dispersing diene rubber in a thermoplastic resin, and dynamically cross-linking the diene rubber by a cross-linking agent to disperse a of the 10μm or less in the thermoplastic resin. Further, the ball cross-linked diene rubber grain having an average grain size compression (the deformation quantity from the state where an initial load of 10kgf is added to tire ball to tire state where a final load of 130kgf is added thereto) is set to 2.2-4.5mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a golf ball comprising a core and a cover for covering the core, and more particularly to a golf ball which is easy to manufacture, has excellent core recyclability, and is equal to or better than the conventional one. The present invention relates to a solid golf ball having the above flight performance.

[0002]

2. Description of the Related Art Solid golf balls are roughly classified into one-piece solid golf balls and two-piece solid golf balls. Round golf balls are mainly covered with a core made of a cross-linked molded article of a rubber composition. A two-piece solid golf ball is used.

However, since the core of the two-piece solid golf ball is usually formed by cross-linking a rubber composition mainly composed of butadiene rubber, the cross-linking takes time and is not suitable for continuous production. In addition, there is a problem that after use, they must be disposed of by incineration or the like, and cannot be recycled (reused).

For this reason, Japanese Patent Application Laid-Open No. Hei 4-359025 discloses a resin composition obtained by dynamically crosslinking a mixture of an ethylene / unsaturated carboxylic acid ester copolymer and rubber and then ionizing the mixture as a material for a golf ball core. It has been proposed that a core be produced by injection molding without using and crosslinking.

However, since the resin composition is ionized after the dynamic crosslinking, its flowability deteriorates. Therefore, it is necessary to improve the flowability by adding a polyether elastomer or a polyamide elastomer. There was a problem that there were multiple stages.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the problems of the solid golf ball using the above-mentioned core, and the core can be easily manufactured, and the core can be easily recycled. It is an object of the present invention to provide a solid golf ball having higher flight performance.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, dispersed a diene rubber in a thermoplastic resin, and dynamically dispersed the diene rubber with a crosslinking agent. Crosslink, average particle size 10μ in thermoplastic resin
m of a thermoplastic elastomer composition having a flexural modulus of 400 to 3000 kgf / cm ² in which crosslinked diene rubber particles are dispersed, and ball compression (final load from a state in which an initial load of 10 kgf is applied to the ball). The amount of deformation up to a load of 130 kgf) is 2.2.
When the distance is set to 4.5 mm, the inventors have found that the above problem can be easily solved, and have completed the present invention.

That is, in the thermoplastic elastomer composition, fine particles of dynamically crosslinked diene rubber are dispersed in a thermoplastic resin, and the dynamically crosslinked diene rubber particles have rubber elasticity. Because it has excellent restoring force, it does not cause plastic deformation, and the thermoplastic resin matrix forms a continuous layer and retains without impairing the excellent resilience performance of the thermoplastic resin, etc. Has high resilience performance. Therefore, a solid golf ball using a core made of the thermoplastic elastomer composition has a flight performance equal to or higher than that of a conventional solid golf ball.

The thermoplastic elastomer composition can be injection-molded and has excellent recyclability. That is, in the thermoplastic elastomer composition, the dynamically cross-linked diene-based rubber particles are finely dispersed in the thermoplastic resin, and the diene-based rubber particles behave like an inorganic filler. Flowability in molding does not deteriorate. Therefore, the injection molding of the core becomes possible, and the production of the core is facilitated and the productivity is improved as compared with the case where the cross-linking molding is performed by the conventional compression molding using a press or the like. Further, since the thermoplastic elastomer composition has a matrix component of a thermoplastic resin, even if it is repeatedly heated and melted, there is almost no decrease in fluidity and resilience performance, and therefore, recycling becomes possible.

In the present invention, the term “dynamic crosslinking” means that a diene rubber is crosslinked by a crosslinking agent while being kneaded together with a molten thermoplastic resin.

In the present invention, the thermoplastic elastomer composition in which the dynamically crosslinked diene rubber particles are dispersed in a thermoplastic resin has a flexural modulus of 400-3.
000 kgf / cm ² ,
This is based on the following reasons.

That is, when the flexural modulus of the thermoplastic elastomer composition is lower than 400 kgf / cm ² , the core is too soft, and even if the cover is covered, the ball compression is out of the proper range, and the flight performance and the like are reduced. descend. When the flexural modulus of the thermoplastic elastomer composition is higher than 3000 kgf / cm ² , when the golf ball is covered with the cover, the ball compression is out of an appropriate range, and the shot feeling becomes hard. This will cause inconvenience.

In the present invention, the average particle size of the crosslinked diene rubber particles dispersed in the thermoplastic resin of the thermoplastic elastomer composition is required to be 10 μm or less. When the average particle size of the particles is larger than 10 μm, the effect of absorbing the impact at the time of hitting the ball to soften the shot feeling is not sufficiently exhibited, and the resilience performance of the thermoplastic elastomer composition is reduced, resulting in high rebound. This is because a thermoplastic elastomer composition having high performance cannot be obtained, and the flowability at the time of injection molding may be reduced.

Furthermore, in the present invention, the ball compression needs to be 2.2 to 4.5 mm, which is based on the following reason. When the ball compression is smaller than 2.2 mm, the ball is too hard and the shot feeling is deteriorated. When the ball compression is larger than 4.5 mm, the ball is too soft and the flight performance is deteriorated. Become. This ball compression applies an initial load of 10 kg to the ball.
This is obtained by measuring the amount of deformation of the ball from the state where f is applied to the time when a final load of 130 kgf is applied.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a thermoplastic resin having a melting point of 250 ° C. or less is suitable as a constituent of a thermoplastic elastomer composition. When a thermoplastic resin having a melting point higher than 250 ° C. is used, the diene rubber is thermally deteriorated during melting and mixing with the diene rubber, that is, burning occurs. A plastic resin does not cause such inconvenience.

The above-mentioned thermoplastic resin is called an ionomer resin, and a metal ion neutralized product of ethylene-acrylic acid copolymer and ethylene-methacrylic acid copolymer which have been conventionally used as a base resin for a golf ball cover. Neutralized metal ion of polymer, ethylene-acrylate-
A metal ion neutralized product of a methacrylic acid terpolymer is particularly suitable. And, as the metal ions for neutralizing the copolymer, sodium ions, potassium ions, alkali metal ions such as lithium ions, zinc ions,
Examples thereof include divalent metal ions such as calcium ion, magnesium ion, copper ion, and manganese ion, and trivalent metal ions such as aluminum ion and neodymium ion. Particularly, sodium ion, lithium ion, magnesium ion, and zinc ion are repelled. It is preferable because it can be an ionomer resin having good elasticity.

Specific examples of the ionomer resin as described above include, for example, a commercially available product marketed by Mitsui DuPont Polychemicals Co., Ltd. under the trade name of “Himilan”,
There are a commercial product marketed by Exxon Chemical under the trade name "IOTEC" and a commercial product marketed by DuPont under the trade name of "Surlyn", and any of them can be suitably used in the present invention.

In addition to the above ionomer resins, thermoplastic resins such as polyethylene, polypropylene, polyamide, polycarbonate, polyester, and polyacetal can be used as long as the melting point is 250 ° C. or less.

The diene rubber is not particularly limited to a specific one. For example, ethylene-propylene-diene rubber (EPDM), butadiene rubber (B
R), isoprene rubber (IR), butyl rubber (II
R), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR) and the like are used.

When these diene rubbers are used, high resilience rubbers such as butadiene rubber and isoprene rubber are suitably used when resilience performance is important, and ethylene-propylene rubber is good when processability is important. It is suitable to use heat-resistant and highly fluid rubber such as diene rubber.

The ratio of the thermoplastic resin to the diene rubber is from 30:70 to 95: 5 by weight, especially 30:70.
70-85: 15 is preferable. If the proportion of the thermoplastic resin is less than the above range, the resilience performance of the thermoplastic resin and the like is reduced, it becomes difficult to obtain a golf ball excellent in flight performance, and the proportion of the thermoplastic resin is more than the above range In this case, the restoring force is reduced due to the decrease in the diene rubber, and the ball may be plastically deformed by hitting.

The crosslinking agent for dynamically crosslinking the diene rubber is not particularly limited, and sulfur, a crosslinking agent, a crosslinking accelerator, and the like commonly used in rubber compounding can be used.
One or more kinds of oximes and resin crosslinking agents can be used. Specific examples thereof include, for example, dibenzothiazyl disulfide, N, N'-dicyclohexyl-2-benzothiazylsulfenamide, hexamethylenetetramine, mercaptobenzothiazole, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutyl Crosslinking accelerators such as thiuram disulfide, oximes such as p-benzoylquinone dioxime, p, p'-dibenzoylquinone dioxime, 4,4'-dithio-bis-dimorpholine, alkylphenol formaldehyde resin, bromonatated alkylphenol formaldehyde resin , Brominated dimethylol phenol formaldehyde resin, dimethylol alkyl phenol resin, phenol resin, cumarone resin, zinc acrylate, methacrylate Suitable examples include metal salts of α, β-unsaturated carboxylic acids such as zinc luate, and peroxides such as zinc oxide and dicumyl peroxide. However, it is not limited to these.

The amount of the crosslinking agent is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the diene rubber in the mixture of the thermoplastic resin and the diene rubber. If the amount of the crosslinking agent is less than 0.05 part by weight based on 100 parts by weight of the diene rubber, the crosslinking of the diene rubber is not sufficiently performed, so that the rubber particles are not sufficiently refined, and thus the restoration is performed. When the force is not sufficiently improved and the amount of the crosslinking agent is more than 10 parts by weight with respect to 100 parts by weight of the diene rubber, an excessive crosslinking agent unnecessary for crosslinking causes blooming on the ball surface or crosslinking proceeds excessively. This causes inconvenience, such as loss of thermoplasticity.

In preparing the thermoplastic elastomer composition, the system containing the thermoplastic resin, the diene rubber, and the crosslinking agent may contain a filler, a pigment, a processing aid, a plasticizer, and the like as necessary. Good.

For the kneading for preparing the thermoplastic elastomer composition and the dynamic crosslinking of the diene rubber, various kneading means such as a closed kneader, an extruder, and an open roll can be employed. From the viewpoint of production efficiency, it is preferable to use an extruder, particularly a twin-screw extruder for plastics, a continuous kneading extruder, or the like.

The temperature at the time of kneading the composition containing the crosslinking agent as described above, that is, the temperature at the time of dynamic crosslinking, is suitably in the range of 20 ° C. lower than the activation temperature of the crosslinking agent to 250 ° C. For example, when sulfur and a vulcanization accelerator are used in combination, the activation temperature is generally about 150 ° C., so that the temperature during dynamic crosslinking is preferably 130 to 250 ° C. Also,
In the case of an oxime-based crosslinking agent, the activation temperature is generally 180 ° C.
Therefore, the temperature at the time of dynamic crosslinking is 160 to 2
A range of 50 ° C. is suitable. In particular, a temperature higher than the activation temperature of the cross-linking agent by 10 to 30 ° C. is preferable, but not limited to this.

When performing the dynamic crosslinking, it is preferable that the temporarily increased torque is reduced by the crosslinking of the diene rubber, and the dynamic crosslinking is terminated immediately before or immediately after stabilization. Although the end of the dynamic crosslinking is appropriately controlled by the torque value as described above, in terms of time, the type of the crosslinking agent, the composition, the amount of the compound, the kneading method, etc., vary greatly, but usually, , About 0.3 to 60 minutes, for example, about 0.5 to 30 minutes when sulfur and a vulcanization accelerator are used in combination, and about 3 to 60 minutes when an oxime-based crosslinking agent is used, When a metal salt of an α, β-unsaturated carboxylic acid and a peroxide are used in combination, the time is about 0.3 to 10 minutes.

In the present invention, as described above, the thermoplastic elastomer composition has a flexural modulus of 400 to 30.
It is necessary to be 00 kgf / cm ² . this is,
Flexural modulus of thermoplastic elastomer composition is 400 kg
If it is lower than f / cm ² , the core is too soft,
Even if the cover is covered, the ball compression falls outside the appropriate range, the flight performance and the like are reduced, and the flexural modulus of the thermoplastic elastomer composition is 3000 kgf / cm ^2.
If the height is higher, the core is harder, so that when the cover is covered, the ball compression is out of the proper range, which causes inconveniences such as a harder and worse hit feeling.

In the present invention, the crosslinked diene rubber particles dispersed in the thermoplastic resin of the thermoplastic elastomer composition must have an average particle size of 10 μm or less. The purpose is to obtain a thermoplastic elastomer composition or to soften the feel at impact by absorbing the impact at the time of hitting the ball. The crosslinked diene-based rubber particles have a smaller particle size, which is advantageous for softening the feel at impact and preventing a reduction in resilience performance. Is reduced, and the effect of improving the feel at impact is lost. Therefore, practically, the average particle diameter is preferably 0.001 μm or more.

Further, in the present invention, the ball compression needs to be 2.2 to 4.5 mm. This is because when the ball compression is smaller than 2.2 mm, the ball is too hard, and Gets worse,
When the ball compression is larger than 4.5 mm, it is because the ball is too soft and the flight performance is reduced. However, the ball compression is particularly preferably 2.5 to 4 mm.

A golf ball is produced by covering the above-mentioned core with a cover. The cover is not particularly limited to a specific one, and various types can be used. In order to take advantage of the above feature, a resin cover mainly composed of an ionomer resin that can be injection-molded is suitable.

The cover is not limited to a one-layer structure, but may be a multi-layer structure such as a two-layer cover composed of an inner cover and an outer cover.

Next, an example of the solid golf ball of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing one example of the solid golf ball of the present invention.
In the figure, 1 is a core, 2 is a cover for covering the core, and 2a is a dimple provided on the cover 2.

The core 1 is formed by dynamically cross-linking a diene rubber dispersed in a thermoplastic resin with a cross-linking agent and dispersing crosslinked diene rubber particles having an average particle size of 10 μm or less in the thermoplastic resin. Elastic modulus is 400-3000kgf / c
m ² of a molded article of the thermoplastic elastomer composition. Usually, the core 1 is manufactured by injection molding. Alternatively, the core 1 may be manufactured by, for example, compression molding.

The cover 2 is formed by injection molding a cover composition mainly composed of an ionomer resin around the core 1. In the solid golf ball shown in FIG. Although a cover having a single-layer structure is illustrated, the cover may have a multilayer structure having two or more layers.

The solid golf ball has a ball compression within a range of 2.2 to 4.5 mm. The dimples 2a are provided on the cover 2 in an appropriate number and in an appropriate form so that required or desired characteristics can be obtained. May be painted or marked.

[0037]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

Examples 1 to 5 and Comparative Examples 1 to 4 The following were used as the thermoplastic resin, the diene rubber, and the crosslinking agent, respectively. In Examples 1 to 5, and Comparative Examples 2 and 4, mixing and kneading were carried out while changing the ratio of the diene rubber to the thermoplastic resin, the type of the crosslinking agent, and the like with the compounding amounts of Tables 1 to 4 as shown in Table 2. In Comparative Examples 1 and 3, which did not contain a diene rubber or a crosslinking agent, only kneading was performed.

Thermoplastic resin: ionomer resin: Himilan 1555 [trade name, sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin, manufactured by Du Pont-Mitsui Polychemicals Co., Ltd.]

Diene rubber: EPDM: Esprene 586 [trade name, manufactured by Sumitomo Chemical Co., Ltd., ethylene-propylene-diene rubber (EPD)
M)]

Crosslinking agent: Takiroll 250-3 [trade name, Taoka Chemical Industry Co., Ltd.]
, Brominated dimethylol phenol formaldehyde resin] Sulfur accelerator NS [Ouchi Shinko Chemical Co., Ltd., Noxeller N
S (trade name), N-tert-butyl-2-benzothiazylsulfenamide]

The numerical values indicating the blending amounts of the respective materials in Tables 1 and 2 are based on parts by weight, and the ethylene-propylene-diene rubber is represented by EPDM, which is a simplified symbol, in the table of each material. indicate.

The kneading of each material, the dynamic crosslinking of the diene rubber, and the ball molding are all carried out by a twin-screw kneading type extruder.
To obtain a pellet-shaped thermoplastic elastomer composition. The residence time of the compound in the extruder, that is, the kneading time is slightly different between each Example and Comparative Example, but is 1.5 to
Within 3 minutes.

Using a part of the obtained thermoplastic elastomer composition, a sheet having a thickness of about 2 mm was formed by hot pressing, and the formed sheet was stored in a constant temperature room at 23 ° C. for 2 weeks, and then subjected to ASTM D-747. The flexural modulus was measured according to.

The particle size of the crosslinked diene rubber particles in the thermoplastic resin of the obtained thermoplastic elastomer composition was measured. The measuring method is as follows.

First, a sample for particle size measurement was prepared by pulverizing the above thermoplastic elastomer composition to 3 to 5 mm.
For 3 minutes under pressure. The particle size was measured by using a scanning electron microscope (T-220A manufactured by JEOL) to take a backscattered electron image photograph, measure the vertical length of any of the 50 rubber particles, and measure the length. The numerical value based on the number average was defined as the average particle size.
In Comparative Example 1, since the ionomer resin alone was used, the particle size of the crosslinked diene-based rubber particles was not measured. In Comparative Example 3, dynamic crosslinking was not performed, so that the ionomer resin and the diene-based rubber were respectively continuous. Since the layer was formed, the particle size of the crosslinked diene rubber particles could not be measured.

Next, the above Examples 1 to 5 and Comparative Example 1
The thermoplastic elastomer compositions of Nos. To 4 were filled in an injection molding machine, and the mixture was injection molded to produce a core having an outer diameter of 39 mm. Then, the moldability of the thermoplastic elastomer composition for producing this core was evaluated. Evaluation of moldability
Each thermoplastic elastomer composition is injected, and the flowability and the surface state at the time of molding the core are visually determined, and the results are indicated according to the following evaluation criteria.

Evaluation criteria: ：: Sufficiently flowed, and no wrinkles or the like due to poor flow were found on the surface of the core. ：: The core can be molded sufficiently, but the flow is slightly poor, so molding at a high temperature (about 230 to 250 ° C.) is required. Δ: The core can be molded, but large depressions occur even when injection molding is performed at a high temperature. X: It is difficult to flow and injection molding of the core cannot be performed.

Next, the cover composition was injection-molded around the core, the core was covered with a cover, paint-finished, and had an outer diameter of 42.5 mm and a weight of 45.2 to 45.6 g.
Was manufactured. The reason why the weight of the ball is shown in the range as described above is because the specific gravity of the material is different in each example. The cover composition used in forming the cover was 50 parts by weight of Himilan 1605 (trade name) and Himilan 1706.
(Trade name) A mixture of 50 parts by weight and 2 parts by weight of titanium dioxide. The above-mentioned Himilan 1605 (trade name) is a sodium ion neutralized ethylene-methacrylic acid copolymer manufactured by DuPont Mitsui Polychemicals, Inc. A polymer ionomer resin, Himilan 1706 (trade name) is a zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by DuPont-Mitsui Polychemicals.

Regarding the obtained solid golf ball,
The ball compression, coefficient of restitution, and feel at impact were examined. The results are the measurement results of the flexural modulus of the thermoplastic elastomer composition and the average particle size of the crosslinked diene rubber particles,
Tables 1 and 2 show the moldability and the like of the thermoplastic elastomer composition during core molding. The method for measuring the ball compression, the coefficient of restitution, and the method for evaluating the feel at impact are as follows.

Ball compression: The amount of deformation from the state where an initial load of 10 kgf is applied to the ball until the final load of 130 kg is applied is examined.

Coefficient of restitution: weight 1 due to resilience gun
A 98 g stainless steel cylinder was launched at an initial velocity of 45 m / s, and collided with a ball in front of it. The velocity of the cylinder and the ball before and after the collision were measured by two photoelectric tubes, and the coefficient of restitution was calculated from each velocity and weight. I do. The larger the coefficient of restitution, the higher the ball's resilience performance and the better the flight performance.

The coefficient of restitution of each of the examples and comparative examples is indicated in the table by an index with the coefficient of restitution of a commercially available two-piece solid golf ball being 100. This commercially available two-piece solid golf ball uses a cross-linked molded body of a rubber composition containing butadiene rubber as a core for the core, and the core is generally heated at a temperature of 140 to 170 ° C. for 10 to 40 minutes. Is done by doing. When the cover of this commercially available two-piece solid golf ball was analyzed by X-ray fluorescence analysis, IR analysis and the like, the base resin was an ionomer resin as in Examples 1 to 5, and the commercially available two-piece solid golf ball was used. The ball compression of the golf ball was 3.1 mm.

Shot feeling: The ball was hit with a No. 1 wood club by 10 top professionals and evaluated. The evaluation criteria are as follows, and when the evaluation results are displayed in the table, the same evaluation symbols are used, which indicates that 8 or more out of 10 persons have made the evaluation.

Judgment criteria: A : Good. ○ H: Slightly hard, but still within a good range. ○ S: Slightly soft, but still within a good range. × H: too hard and bad. × S: too soft and bad.

[0056]

[Table 1]

[0057]

[Table 2]

As is clear from the results shown in Table 1, Examples 1 to 5 had good core moldability, a larger coefficient of restitution than commercially available two-piece solid golf balls, and were superior in resilience performance.

On the other hand, as shown in Table 2, Comparative Example 1 was composed of only the ionomer resin, and thus the shot feeling was hard and poor. In Comparative Example 2, EPDM (ethylene-propylene-diene rubber) was blended and dynamically crosslinked, but the flexural modulus was 3100 kgf / cm ^2.
And the hit feeling was hard and poor, and Comparative Example 3 was EPDM
However, the core was not sufficiently moldable and the resilience performance was poor due to no dynamic crosslinking. In Comparative Example 4, EPDM was blended and dynamically crosslinked. However, since the flexural modulus was too low at 370 kgf / cm ² , the resilience performance and shot feeling were poor, and the EPDM ratio was high. The core was produced by compression molding because of poor molding properties and inability to perform injection molding.

Embodiment 6 In this embodiment 6, the recyclability of the core is examined. That is, the core of Example 3 was pulverized, the pulverized material was melt-mixed, injection molded to produce a core having an outer diameter of 39 mm, and the same cover composition as in Example 1 was injection-molded on the core. Then, a solid golf ball having an outer diameter of 42.5 mm was prepared by paint finish.

The moldability at the time of injection molding of the core is such that the core can be sufficiently molded by injection molding at a high temperature, and has a moldability corresponding to “O” when indicated by the same evaluation criteria as in Example 1. I was

The ball compression of the obtained golf ball was 2.97 mm, and the coefficient of restitution (index) was 1
06, which is superior to a commercially available two-piece solid golf ball in resilience performance, and also has a good shot feeling.

Examples 7 to 9 In Examples 7 to 9, the types of diene rubbers were changed from those in Examples 1 to 5, and some of the diene rubbers were changed in the cross-linking agent. The ball's coefficient of restitution, feel at impact, and the like were evaluated.

Examples of the thermoplastic resin include those described in Examples 1 to 5 above.
Himilan AM15 belonging to the ionomer resin as well as
55 (trade name) and IR2250 (trade name, manufactured by Nippon Zeon Co., Ltd.) belonging to isoprene rubber and BR-11 (trade name, manufactured by Nippon Synthetic Rubber Co., Ltd.) belonging to butadiene rubber as diene rubbers. Used, as a crosslinking agent,
In Examples 7 and 8, the aforementioned sulfur and the accelerator NS were used, and in Example 9, zinc acrylate and dicumyl peroxide were used.
Dynamic crosslinking was performed while kneading the crosslinking agent in the same manner as in Example 1. In addition, in the display in Table 3, isoprene rubber is indicated by its simplified symbol IR, butadiene rubber is indicated by its simplified symbol BR, and zinc acrylate is Z
Indicated by DA, dicumyl peroxide is indicated by DCPO.

The flexural modulus of the obtained thermoplastic elastomer composition was measured in the same manner as in Example 1 and the like.
The average particle size of the crosslinked diene rubber particles was determined. Further, the obtained thermoplastic elastomer composition was filled in an injection molding machine and injection molded to prepare a core having an outer diameter of 39 mm.

The same cover composition as in Example 1 was injection-molded around the obtained core and paint-finished to produce a solid golf ball having an outer diameter of 42.5 mm.

The moldability at the time of molding the core and the ball compression, restitution coefficient and shot feeling of the obtained solid golf ball were examined in the same manner as in Example 1 and the like. Table 3 shows the results together with the measurement results of the flexural modulus of the thermoplastic elastomer composition and the average particle size of the crosslinked diene rubber particles.

[0068]

[Table 3]

As is evident from the results shown in Table 3, Examples 7 to 9 had good core moldability, and the resilience of the ball was larger than that of a commercially available two-piece solid golf ball, and the resilience was excellent.

Examples 10 to 12 In Examples 10 to 12, the types of the thermoplastic resin were mainly changed and the characteristics were evaluated.

Regarding the thermoplastic resin, in Example 10, nylon [Nylon 12 manufactured by Ube Industries, Ltd. (product number: 3)
024U)], and in Example 11, PC [polycarbonate, Panlite L-1225 manufactured by Teijin Chemicals Ltd.]
(Trade name)], and in Example 12, POM [Polyacetal, Tenac 3010 (trade name) manufactured by Asahi Kasei Corporation) was used. Their amounts are as shown in Table 4.

As the diene rubber, Example 10
EPDM [Ethylene-propylene-diene rubber, Esplen 586 manufactured by Sumitomo Chemical Co., Ltd.]
(Trade name)] and the compounding amounts are as shown in Table 4.

As a cross-linking agent, in Example 10, Tackilol 250-3 (trade name, manufactured by Taoka Chemical Industry Co., Ltd., brominated dimethylol phenol formaldehyde resin) was used. In Example 11, sulfur and an accelerator MBT (mercapto) were used. In Example 12, sulfur and a promoter DM (mercaptobenzothiazyl disulfide) were used. Their amounts are as shown in Table 4.

In each of Examples 10 to 12, kneading and dynamic crosslinking of the diene rubber were performed in the same manner as in Example 1 and the like, and the flexural modulus of the obtained thermoplastic elastomer composition was measured. The average particle size of the crosslinked diene rubber particles was determined. The obtained thermoplastic elastomer composition was charged into an injection molding machine, injection-molded to produce a core having an outer diameter of 39 mm, and a cover composition similar to that of Example 1 was injection-molded around the core. , Paint finish, outer diameter 42.5m
m was produced.

The moldability at the time of molding the core and the ball compression, restitution coefficient and shot feeling of the obtained golf ball were examined in the same manner as in Example 1 and the like. The results are shown in Table 4 together with the measurement results of the flexural modulus and the average particle size of the crosslinked diene rubber particles.

[0076]

[Table 4]

As is evident from the results shown in Table 4, Examples 10 to 12 had good core moldability and resilience performance superior to those of a commercially available two-piece solid golf ball, and also had a good shot feeling.

As described above, in the solid golf ball of the present invention, since the core can be manufactured by injection molding (or can be manufactured by compression molding as well), a conventional crosslinked molded product of a rubber composition mainly containing butadiene rubber can be obtained. As compared with a solid golf ball having a core as the core, the production of the core was easier, the productivity could be improved, and the recyclability of the core was excellent as clarified in Example 6.

Further, as is clear from the measurement results of the coefficient of restitution in each of the examples, the solid golf ball of the present invention had a flight performance equal to or higher than that of a commercially available two-piece solid golf ball.

[0080]

As described above, the present invention provides a solid golf ball having a core and a cover for covering the core, in which the core can be easily manufactured, the core has excellent recyclability, and the flight performance is improved. It was possible to provide a solid golf ball equal to or more than.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of a solid golf ball of the present invention.

[Explanation of symbols]

 1 core 2 cover

Claims (1)

[Claims] 1. A solid golf ball comprising a core and a cover covering the core, wherein the core disperses a diene rubber in a thermoplastic resin and dynamically cross-links the diene rubber with a crosslinking agent. Average particle size 1 in thermoplastic resin
A molded article of a thermoplastic elastomer composition having a flexural modulus of 400 to 3000 kgf / cm ² in which crosslinked diene rubber particles having a particle size of 0 μm or less is dispersed, and ball compression (ends from a state where an initial load of 10 kgf is applied to the ball) A solid golf ball characterized in that the deformation amount before a load of 130 kgf is applied is 2.2 to 4.5 mm.