JPH08196661A - Rubber composition for solid golf ball - Google Patents

Abstract

PURPOSE: To provide a rubber composition for a solid golf ball which is provided with excellent impact resilience and proper compression and gives a soft hitting feeling. CONSTITUTION: A rubber composition for a solid golf ball consists of 100 parts by weight of base rubber containing butadiene rubber, which is provided with 40% or more of cis 1,4-configulation, and 15-50 parts by weight of unsaturated carboxylic acid metallic salt whose average grain size is 5.0μm or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has an appropriate hardness (compression) and a soft shot feeling when hit,
The present invention also relates to a rubber composition for solid golf balls, which has excellent impact resilience (flying distance) and is excellent.

[0002]

2. Description of the Related Art A solid golf ball is a uniform rubber ball (core itself) consisting of one component, a so-called one-piece golf ball, a two-piece golf ball having a core covered with a cover, and a suitable intermediate portion between the core and the cover. There is a multi-layer golf ball having three or more layers.

Conventionally, the core material of a solid golf ball is
Obtained by heat-pressurizing a rubber composition obtained by blending a butadiene rubber with an unsaturated carboxylic acid metal salt as a co-crosslinking agent, zinc oxide as a weight modifier, and a free radical initiator such as dicumyl peroxide. To be In this rubber composition, the unsaturated carboxylic acid metal salt is grafted to the polybutadiene main chain by a free radical initiator such as dicumyl peroxide and acts as a co-crosslinking agent. But,
In this case, the unsaturated carboxylic acid metal salt is generally blended in a considerably large amount of 15 to 60 parts by weight with respect to 100 parts by weight of polybutadiene. Kneading work is difficult, and dispersibility is poor because it easily forms agglomerates in the rubber, and the compounded unsaturated carboxylic acid metal salt is not effectively used, resulting in an unexpectedly low ball hardness. In addition, the resilience does not increase to a desired value, and the hitting sound and feel of the obtained golf ball are deteriorated.

[0004]

The object of the present invention is to incorporate an unsaturated carboxylic acid, but it has good resilience and appropriate compression (force required for 2.54 mm compression), and has a soft impact. It is intended to provide a rubber composition for a solid golf ball capable of giving a feeling. This rubber composition is useful as a constituent material of a one-piece golf ball and as a core material of a two-piece golf ball or a golf ball having a multilayer structure.

[0005]

The rubber composition for solid golf balls according to the present invention has an average particle size of 5. 5 with respect to 100 parts by weight of a base rubber containing a butadiene rubber having a cis 1,4-structure of 40% or more. Unsaturated carboxylic acid metal salt of 0 μm or less 15
It is characterized by being mixed up to 50 parts by weight. As described above, by using the finely powdered unsaturated carboxylic acid metal salt having an average particle size of 5.0 μm or less, the workability during kneading and the dispersibility in rubber are remarkably improved and the hardness is appropriate. In addition, a golf ball having excellent resilience performance and a good feel on impact can be obtained.

The term "average particle size" as used herein means the particle size measured by a conventional sedimentation particle size distribution measuring method. Less than,
The configuration of the present invention will be described in detail. (1) Base Rubber The base rubber used in the present invention is a rubber containing polybutadiene having a cis-1,4 structure of at least 40%, preferably 90% or more. This is because if the cis-1,4 structure is less than 40%, good resilience (flying distance) cannot be maintained.

As the base rubber, it is preferable to use the above polybutadiene alone, but if necessary, a rubber component conventionally used as a base rubber for solid golf balls, such as natural rubber, isoprene rubber, or styrene. -Butadiene copolymer rubber and the like may be appropriately blended. (2) Unsaturated Carboxylic Acid Metal Salt As the unsaturated carboxylic acid in this case, various carboxylic acids having an unsaturated bond are used, and more preferable one is α,
Examples of β-unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid and phthalic acid, with acrylic acid being particularly preferred.

The metal species of the metal salt include metal ions having a valence of 1 to 3, and examples thereof include zinc, sodium, magnesium, calcium and aluminum, with zinc being particularly preferred. The average particle size of the unsaturated carboxylic acid metal salt is 5.0 μm or less, preferably 2.0 to 4.5 μm. When the average particle size is less than 2.0 μm, the particles are too fine and are scattered during kneading, resulting in poor mixability. On the other hand, if it exceeds 5.0 μm, agglomerates are easily formed in the rubber, the dispersibility is deteriorated, and the properties of the obtained golf ball are deteriorated. (3) 15 to 50 parts by weight, preferably 20 to 40 parts by weight of the unsaturated metal salt of a carboxylic acid is added to 100 parts by weight of the base rubber. If it is less than 15 parts by weight, the hardness of the ball will be insufficient,
If it exceeds the weight part, the ball hardness becomes too hard and the feel on impact is impaired.

Other core preparations typically include peroxides,
Fillers, antioxidants, etc. are used. Examples of peroxides include dicumyl peroxide. Examples of the filler include zinc oxide, barium sulfate and the like, and other compounding agents can be appropriately compounded as necessary.

[0010]

EXAMPLES Rubber compositions were prepared according to the formulation (parts by weight) shown in Table 1 (Examples 1 to 8 and Comparative Examples 1 to 7). Each of the obtained rubber compositions was press-molded at 160 ° C. for 20 minutes to form a spherical solid core having a diameter of 38.3 mm, and this solid core was coated with ionomer Surlyn 1707 as a cover (thickness: about 2.5 mm) to form two layers. A two-piece golf ball having a structure was manufactured. The physical properties of these golf balls are shown in the lower row of Table 1.

[0011]

[Table 1]

Note) * 1 Commercially available polybutadiene rubber manufactured by Japan Synthetic Rubber Co., Ltd. (cis 1,4-structure 97%) * 2 Zinc acrylate: average particle size 0.8 μm * 3 zinc acrylate by sedimentation particle size distribution measurement method : Average particle size by sedimentation particle size distribution measurement method 2.5 μm * 4 Zinc acrylate: Average particle size by sedimentation particle size distribution measurement method 2.8 μm * 5 Zinc acrylate: Average particle size by sedimentation particle size distribution measurement method 4.0 μm * 6 Acrylic acid Zinc: average particle size by sedimentation particle size distribution measurement method 5.3 μm * 7 Zinc methacrylate: average particle size by sedimentation particle size distribution measurement method 4.0 μm * 8 Swanox BHT manufactured by Seiko Chemical Co., Ltd. * 9 Driver using a swing robot (Wood #
In Comparative Example 1, the initial speed ratio of the golf ball to the head speed when hit at a head speed of 43 m / sec in 1)
Relative value when set to 100.

* 10 Force required to deform a golf ball 1/10 inch (2.54 mm) at a compression speed of 10 mm / min (kg
f). * 11 Feeling during a trial shot by a professional golfer. * Average particle size measured by a natural / centrifugal sedimentation type automatic particle size distribution analyzer CAPA-300 (Horiba) after crushing commercial zinc acrylate with an average particle size of 5.3 μm with a lab jet mill. As is clear from Table 1, the golf ball made of the rubber composition of the present invention has excellent initial velocity efficiency (resilience), good compression, and good feel on impact.

[0014]

As described above, according to the present invention, since the unsaturated carboxylic acid metal salt having an average particle size of 5.0 μm or less is used, the resilience is good, the compression is moderate, and the hit feeling is good. It is possible to provide a soft rubber composition for solid golf balls.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Kobayashi 2-1, Oiwake, Hiratsuka-shi, Kanagawa Yokohama Rubber Co., Ltd. Hiratsuka Factory

Claims (4)

[Claims] 1. 100 parts by weight of a base rubber containing a butadiene rubber having a cis 1,4-structure of 40% or more is mixed with 15 to 50 parts by weight of an unsaturated carboxylic acid metal salt having an average particle size of 5.0 μm or less. A rubber composition for a solid golf ball. 2. The rubber composition for a solid golf ball according to claim 1, wherein the average particle size is 2.0 to 4.5 μm. 3. The solid golf according to claim 1, wherein the unsaturated carboxylic acid of the unsaturated carboxylic acid metal salt is at least one selected from acrylic acid, methacrylic acid, maleic acid and phthalic acid. Rubber composition for balls. 4. The metal of the unsaturated carboxylic acid metal salt is
The rubber composition for a solid golf ball according to claim 1, wherein the rubber composition is at least one selected from zinc, sodium, magnesium, calcium, and aluminum.