JPH06198005A - Two-piece golf ball - Google Patents

Abstract

PURPOSE:To provide the two-piece golf which is soft in feeling at the time of hitting, and also, excellent in durability (shock resistance) and repellency. CONSTITUTION:The two-piece golf ball consists of a two-layer structure of a core of the center part and a cover its outside, and the core is constituted of a core material whose compression value at the time of deformation of 2.54mm is <=50kgf, and also, the cover is constituted of a cover material whose tensile elongation and 50% modulus are >=400%, and >=1.5kgf/mm<2>, respectively, and the compression value at the time of deformation of 2.54mm is <=95kgf.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-piece golf ball which has a soft feel when hit and is excellent in durability (impact resistance) and resilience.

[0002]

2. Description of the Related Art Golf balls generally used include a wound golf ball and a two-piece golf ball. A two-piece golf ball is constructed by covering a core made of a rubber composition with a cover made of an ionic ethylene copolymer resin having excellent impact resistance and resilience. Two-piece golf balls are used by many golfers because of their great flight distance and excellent durability. However, since the feel at the time of hitting is hard, many golfers prefer the soft hitting feeling of a thread-wound golf ball with regard to the hitting feeling, and the development of a two-piece golf ball having a soft hitting feeling has been desired. Also, when using a soft core material for the core to soften the two-piece golf ball,
There is a problem that durability is lowered because of large deformation on impact.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a two-piece golf ball which has a soft shot feeling close to that of a thread-wound golf ball and which is excellent in durability (impact resistance) and resilience. To aim.

[0004]

Therefore, the present invention comprises a two-layer structure of a core at the center and a cover on the outside thereof, and the core has a compression value of 50 kgf at the time of deformation of 2.54 mm.
A two-piece golf consisting of the following core material, the cover having a tensile elongation of 400% or more and a 50% modulus of 1.5 kgf / mm ² or more, and a compression value of 95 kgf or less when deformed by 2.54 mm. The main point is the ball.

As described above, according to the present invention, the physical properties of the core material and the cover material are determined, and the compression value of the two-piece golf ball itself is determined. Therefore, the feel at the time of hitting becomes soft and the durability (impact resistance) is further improved. And, it becomes possible to improve the resilience. Hereinafter, the configuration of the present invention will be described in detail.

(1) Core material. The core material usually contains polybutadiene rubber as a main component, and further comprises a crosslinking agent and a reinforcing material. As a cross-linking agent,
An α, β-ethylenically unsaturated carboxylic acid such as (meth) acrylic acid, a bismaleimide compound, and a urethane (meth) acrylate are used. Silicon dioxide or a metal oxide is used as a reinforcing material.

Although the composition of the core material used in the present invention is not limited, the compression value at the time of deformation of 2.54 mm is 50 kgf or less, preferably 30 kgf to 50 kgf. If the compression value exceeds 50 kgf, a soft shot feeling cannot be obtained. The compression value can be adjusted by increasing or decreasing the amount of the crosslinking agent. Here, the compression value means the force (kgf) required to deform 2.54 mm at a compression speed of 10 mm / min (hereinafter the same).

As the composition constituting the core material used in the present invention, specifically, the following materials are preferably used. (a) Polybutadiene rubber. At least 40%, preferably 90%, of cis-1,4 bond
It is a polybutadiene rubber having the above. When the cis-1,4 bond is less than 40%, the resilience decreases, and it is not suitable for use in the core material of the present invention. It is preferable to use the above polybutadiene rubber alone, but if necessary, a normal polybutadiene rubber or a rubber component conventionally used as a base rubber for solid golf balls, for example,
Natural rubber, isoprene rubber, styrene-butadiene rubber, etc. can be blended.

(B) α, β-ethylenically unsaturated carboxylic acid. The unsaturated carboxylic acid is, for example, acrylic acid or methacrylic acid. The salt is, for example, zinc acrylate or zinc methacrylate. (c) Bismaleimide compound. Examples of the bismaleimide compound include N, N'-ethylene bismaleimide, N, N'-trimethylene bismaleimide, N, N'-m-phenylene bismaleimide, N,
N'-4,4'-diphenylmethane bismaleimide, N,
N-4,4'-diphenyl ether bismaleimide, N,
N'-4,4'- diphenyl sulfone bismaleimide is mentioned.

(D) Urethane (meth) acrylate. Urethane (meth) acrylate is a (meth) acrylate group-containing urethane compound obtained by reacting one or more polyisocyanates with a poly (meth) acrylate having a hydroxyl group. (e) Silicon dioxide.

As the silicon dioxide, those having a specific surface area of 160 to 340 m ² / g by the BET method and a purity of 99% or more are preferable. (f) Metal oxide. For example, zinc oxide. Generally, a commercially available one may be used, and it is mainly used for adjusting the weight of the golf ball.

The core material is obtained by adding an organic peroxide as a polymerization initiator to the above composition and performing a conventional method such as press molding. (2) Cover material. The cover material used in the present invention is not limited in composition, but has a tensile elongation of 400% or more, preferably
400% to 600%, 50% modulus 1.5kgf / mm ² or more,
Preferably from ^{1.5kgf / mm 2 ~3kgf / mm 2} . An ionic ethylene copolymer is used.

If the tensile elongation is less than 400%, the required impact resistance cannot be obtained. Also, even if the tensile elongation is 400% or more, if the 50% modulus is less than 1.5 kgf / mm ² ,
Excellent impact resistance but poor resilience. As the composition constituting the cover material used in the present invention, specifically, the following materials are preferably used.

(A) Ionic ethylene copolymer. It is obtained from an ethylene-unsaturated carboxylic acid copolymer and a metal compound capable of supplying a cation, or an organic amine.
The manufacturing method is not particularly limited, and a known method can be used. For example, Mitsui DuPont Polychemical Co., Ltd., Himilan, HPR, Dupont Co., Surlyn, Exxon Chemical Co., Ltd.
Such as OTEC. These ionic ethylene copolymers may be used alone or as a mixture of several kinds.

Ethylene-unsaturated carboxylic acid copolymer. For example, ethylene and an unsaturated carboxylic acid having 3 to 6 carbon atoms,
For example, it is a copolymer with acrylic acid, methacrylic acid, maleic acid, fumaric acid, vinyl benzoate or the like. A metal compound capable of supplying a cation.

Examples thereof include formates, acetates, nitrates, carbonates, hydrogencarbonates, oxides, hydroxides and alkoxides of alkali metals, alkaline earth metals, transition metals and the like. The types of metals include Na, Zn, Li, Mg, Mn, Ca, Co, and K 2. Amines. It is an aromatic or alicyclic compound having a bisaminoalkyl group. For example, m-xylenediamine, o-xylenediamine, p-xylenediamine, or hydrogenated products of 1,3-bisaminomethylcyclohexane, 1,
2-bisaminomethylcyclohexane, 1,4-bisaminomethylcyclohexane and the like are used.

(B) White pigment. As the white pigment, titanium oxide, zinc oxide, calcium carbonate, lead white, zinc sulfide, barium sulfate, gypsum, precipitated silica or the like is used. Titanium oxide is preferable. When compounding, it is advisable to carry out melt-kneading at a temperature of 100 to 250 ° C. In addition, if necessary, an antioxidant, a stabilizer, a lubricant,
You may add additives, such as a coloring agent, suitably. More specifically, Himiran 1605, Himiran 1605 and Himiran 18
A blend of 55, a blend of Himilan 1605 and Himilan 1705, and the like are preferable.

[0018]

EXAMPLES The rubber compositions for cores (A to D) were mixed according to a conventional method according to the formulation (in parts by weight) shown in Table 1. Each of the obtained rubber compositions was press-molded at 160 ° C. for 20 minutes to obtain a spherical core material having a diameter of 38.3 mm. Using the compounding recipes (parts by weight) shown in Table 2, cover materials (af) were obtained by melt-kneading at a temperature of 200 ° C using a twin-screw extruder. As a sample for measuring the characteristics of the cover material, the obtained cover material was press-molded at 170 ° C to obtain a sample.

A golf ball for characteristic measurement was obtained by coating the above core material by injection molding so that the cover material had a thickness of 2.5 mm. The characteristics of each core material, cover material and golf ball are shown in Table 3.

[0020] Note) * 1 BR01, polybutadiene rubber: cis 1,4 structure 97%
(Made by Japan Synthetic Rubber Co., Ltd.). * 2 Reaction product of hexamethylene diisocyanate and glycerin dimethacrylate: 4 functional groups.

* 3 N, N'-4,4'-diphenylmethane bismaleimide (manufactured by Mitsui Toatsu). * 4 AEROSIL 200 (manufactured by Nippon Aerosil Co., Ltd.). * 5 Dicumyl peroxide.

[0022] Note) * 6 Sodium ionic ethylene copolymer (manufactured by Mitsui DuPont Polychemical Co., Ltd.).

* 7 Zinc ionic ethylene copolymer
(Mitsui DuPont Polychemical Co., Ltd.). * 8 Zinc ionic ethylene copolymer (manufactured by Mitsui DuPont Polychemical Co., Ltd.). * 9 Sodium ionic ethylene copolymer (Mitsui DuPont Polychemical Co., Ltd.). * 10 Zinc ionic ethylene copolymer (manufactured by Mitsui DuPont Polychemical Co., Ltd.). * 11 Taipaque CR-60-2, titanium dioxide: average particle size 0.2
1 μm (made by Ishihara Sangyo Co., Ltd.).

[0024] Note) * 12 1/10 inch golf ball at a compression speed of 10 mm / min.
(2.54mm) The force required to deform (kgf).

* 13 Elongation at break (%) during tensile test. JIS
According to K7113. Sample shape: JIS2 for plastic
No., pulling speed: 100 mm / min. * 14 Stress value at 50% deformation in the above measurement (kgf / mm ² ). * 15 Relative value when the number of hits to a crack when hitting with a driver (Wood Club No. 1) at a head speed of 43 mm / sec using a swing robot is 100 when Comparative Example 1 is set.

* 16 The initial speed ratio of a golf ball to the head speed when a driver (Wood club No. 1) was hit with a head sud of 43 mm / sec using a swing robot, and is a relative value when Comparative Example 1 is 100. * 17 A feeling of hitting at No. 1 wood club by a professional golfer. As is clear from Table 3, Examples 1 to 5 are conventional examples 1 to 1.
It can be seen that it has a soft feel at impact as compared with 2. Also, as in Comparative Example 1, the tensile elongation is
When the cover material of less than 400% is covered, the feel on impact is soft, but the durability is poor. On the other hand, even if a cover material having a tensile elongation of more than 400% is simply coated as in Comparative Example 2, the modulus value is 1.5 kg.
When it is less than f / mm ² , it is found that the durability is excellent, but the resilience is poor.

That is, in order to obtain a two-piece golf ball having a soft shot feeling as in the present invention, when a low compression core material is used, it is covered with a cover material having high elongation and high modulus as described above. I know I need to

[0028]

As described above, the two-piece golf ball of the present invention has excellent durability (impact resistance), impact resilience, and a soft feel at impact.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Toshiya Hase 2-1, Oiwake, Hiratsuka-shi, Kanagawa Yokohama Rubber Co., Ltd. Hiratsuka Factory

Claims (1)

[Claims] 1. A two-layer structure comprising a core at the center and a cover outside the core, the core is made of a core material having a compression value of 50 kgf or less when deformed at 2.54 mm, and the cover has a tensile elongation. A two-piece golf ball composed of a cover material with a modulus of 400% or more and a modulus of 50% of 1.5 kgf / mm ² or more, and a compression value of 95 kgf or less when deformed by 2.54 mm.