JP2776962B2 - Golf ball - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a golf ball with improved shot feeling and controllability.

[Background Art] Ionomer resins are particularly used for two-piece golf balls as golf ball cover materials because of their durability, cut resistance, good resilience, and ease of molding. On the other hand, the disadvantage of this ionomer resin as a cover material is that it has higher hardness and higher rigidity than trans polyisoprene, which is a cover material that has been used mainly for thread-wound golf balls, so the shot feeling and control performance (spin)
Is inferior in terms of

In order to solve this drawback, it has been attempted to soften the ionomer resin by various methods, for example, as disclosed in Japanese Patent Application Laid-Open No. 1-2952, but a large decrease in the rebound distance by the softening can be avoided. And nothing was satisfactory.

[Problems to be Solved by the Invention] An object of the present invention is to provide a golf ball with improved shot feeling and controllability.

[Means for Solving the Problems] To achieve the above object, an ionomer in which each carboxyl group of an ethylene- (meth) acrylic acid copolymer and a liquid rubber having a carboxyl group at a molecular terminal is co-cross-linked with each other by a metal ion. The present inventors have found that when a resin is blended into a composition for a golf ball cover, excellent effects are achieved, and the present invention has been accomplished.

That is, the present invention provides a golf ball comprising a core and a cover covering the core, wherein the cover comprises: (A) a carboxyl group of an ethylene- (meth) acrylic acid copolymer containing 10 to 20% by weight of (meth) acrylic acid; 20 to
To a mixture of (B) a liquid polybutadiene or a liquid acrylonitrile-butadiene copolymer having carboxyl groups at both ends of the molecule, and a metal hydroxide, carbonate, or A golf ball characterized by being prepared by adding acetate and heating.

The resin (A) used as a raw material of the golf ball cover composition of the present invention is obtained by partially neutralizing a carboxyl group of an ethylene- (meth) acrylic acid copolymer with a metal ion. As the ethylene- (meth) acrylic acid copolymer, a copolymer of ethylene and acrylic acid and / or methacrylic acid (hereinafter, simply referred to as “(meth) acrylic acid”) is used as a base resin, and the carboxylic acid Is used in an amount of 10 to 20% by weight. When the carboxylic acid is less than 10% by weight, the amount of the carboxylic acid is insufficient, and a resin having excellent neutralization of metal ions cannot be obtained. Is difficult to obtain, and the rigidity is too high, resulting in a brittle resin, which is not practical.

The resin (A) contains 20 to 70 mol%, preferably 20 to 70 mol% of the carboxyl groups of the ethylene- (meth) acrylic acid copolymer.
~ 50 mol% is neutralized with metal ions. As metal ions, for example, sodium ions, zinc ions,
Magnesium ion and the like. Examples of these metal ion sources include hydroxides, carbonates, and acetates of these metals. Neutralization can be easily obtained by blending a metal ion source in an ethylene- (meth) acrylic acid copolymer and melt-mixing. If the neutralization amount is less than 20 mol%, there are disadvantages such as insufficient rigidity and reduced rebound resilience. If it exceeds 70 mol%, the rigidity becomes too high, and the feeling is deteriorated. In addition, the fluidity is extremely reduced, the formability is deteriorated, and the impact resistance is further deteriorated.

As such a resin (A), commercially available products, for example, Himilan 1605, 1706, and 1707 (all of which are manufactured by Du Pont-Mitsui Polychemicals) may be used. In particular, Himilan 1605, which has a low degree of neutralization and high resilience, is suitable because of the ease of the co-crosslinking reaction described below.

The liquid polymer (B) used as the other raw material of the golf ball cover composition of the present invention is a liquid polybutadiene or a liquid acrylonitrile-butadiene copolymer having carboxyl groups at both ends of the molecular chain and having an average molecular weight of 1,000. Those with ~ 10,000 are suitable. A specific example of such a liquid polymer (B) is Ube Industries, Ltd.
Reactive liquid polymer "Hiker CTB", "Hiker C
And those marketed under the trade name "TBN".

The golf ball cover composition of the present invention is prepared by co-crosslinking at least a part of each of the carboxyl groups of the resin (A) and the liquid polymer (B) with metal ions to form an ionomer resin. You. The composition for the cover is easily prepared, for example, by adding a metal ion source to a mixture of the resin (A) and the liquid polymer (B) and mixing by heating.

Magnesium ions as the metal ions for crosslinking,
Zinc ions, sodium ions, potassium ions, lithium ions and the like can be mentioned. Examples of these metal ion sources include hydroxides, basic or neutral carbonates of these metals.

In the composition, the resin (A) and the liquid polymer (B)
Is preferably 95/5 to 70/30. If the amount of the liquid polymer (B) is less than 5 parts, the softening is insufficient, and there is no feeling. If it exceeds 30 parts, it becomes too soft, and durability and rebound are reduced. The amount of the metal ion source is preferably, for example, 0.5 to 2.0 parts by weight based on 100 parts by weight of the total weight of the resin (A) and the liquid polymer (B). If it is less than 0.5 part by weight, co-crosslinking due to metal ions is small and rebound is low. If it exceeds 2.0, the melt index (MI) becomes too small, and the formlessness of the cover deteriorates.

In addition, pigments, dispersants, antioxidants, ultraviolet absorbers and the like may be added as additives for preparing the cover composition.

The method for preparing the cover composition is carried out, for example, by mixing the above ingredients with a plastic extruder or an internal mixer such as a Banbury or kneader at a resin temperature of 200 to 250 ° C. A twin-screw kneading extruder is most suitable for uniformly and efficiently performing the mixing and crosslinking reactions.

The golf ball is formed by coating the core of the golf ball with the cover material in a conventional manner. As the core, both a solid core formed integrally with a rubber component as a main component and a wound core obtained by winding a thread rubber on a core material can be used.

(Effect of the Invention) The golf ball obtained by the present invention has improved shot feeling and controllability.

(Examples) The present invention will be described in more detail with reference to examples. It should not be understood that the present invention is limited to these examples.

Molding of core 100 parts by weight of polybutadiene ("BR01", manufactured by JSR Corporation), 35 parts by weight of zinc acrylate, 20 parts by weight of zinc oxide, 1 part by weight of dicumyl peroxide, and an antioxidant ("Koshinox"
425 ") The composition containing 0.5 parts by weight was vulcanized at 165 ° C. for 20 minutes to obtain a solid core. The average diameter of the solid core was 38.4 mm.

Preparation of cover composition (Preparation Examples 1 and 2 and Comparative Preparation Examples 1 to 3) Each compounding agent having the composition shown in Table 1 was mixed with a screw-type twin-screw extruder to obtain each cover composition. Extrusion conditions are screw diameter 45mm, screw rotation 200rpm, screw L / D
= 30 and extruded at a resin temperature of 200-260 ° C. For cylinder temperature conditions, Was used. Further, the set temperatures of the adapter and the die were both 250 ° C.

1): Mitsui Dupont Polychemical Co., Ltd., sodium-neutralized ethylene-methacrylic acid copolymer (high rigidity type), MI
= 2.8.

2): Ube Industries, reactive liquid carboxy-terminated polybutadiene, viscosity (cps, 27 ° C) = 40,000, molecular weight 4,000,
Functional group number = 2.01 / mol.

3): Ube Industries, Ltd., reactive liquid carboxy-terminated acrylonitrile-butadiene copolymer, viscosity (cps, 27 ° C.) =
55,000, molecular weight = 3,500, number of functional groups = (1.9 / mol), amount of bound nitrile = 10%.

4): DuPont-made, sodium-neutralized ethylene-methacrylic acid-methacrylic acid ester terpolymer (low rigid type), MI = 1.9.

5): DuPont-made, sodium-neutralized ethylene-methacrylic acid-methacrylic acid ester terpolymer (low rigidity type), MI = 0.8.

Production of Golf Balls (Examples 1 and 2 and Comparative Examples 1 to 3) Each cover composition prepared above was coated around the produced core by injection molding to obtain each golf ball. The resins in Table 2 were mixed with a screw-type twin-screw extruder in the same manner as in the preparation of the ionomer resin.

Perform each physical property test on each obtained golf ball,
Table 2 shows these results.

When a flight distance test was performed on each of these golf balls with a true temper swing robot under a condition of a driver of 45 m / s, the flight distances of Examples 1 and 2 were equal to those of Comparative Example 3. On the other hand, Comparative Examples 1 and 2 were inferior by 5 to 10 yards.

The shot feeling of these balls in the actual professional hit test,
Controllability was confirmed. As a result, in Examples 1 and 2 and Comparative Examples 1 and 2, the hit feeling and controllability were close to those of a thread-wound golf ball coated with trans polyisoprene, but the ball of Comparative Example 3 had a hard hitting feel and poor controllability. The evaluation was bad.

Claims (1)

(57) [Claims] 1. A golf ball comprising a core and a cover covering the core, wherein the cover comprises: (A) a carboxyl group of an ethylene- (meth) acrylic acid copolymer containing 10 to 20% by weight of (meth) acrylic acid; 20 to
To a mixture of (B) a liquid polybutadiene or a liquid acrylonitrile-butadiene copolymer having carboxyl groups at both ends of the molecule, and a metal hydroxide, carbonate, or A golf ball characterized by being prepared by adding acetate and heating.