JPH06327794A - Golf ball - Google Patents

Abstract

PURPOSE:To provide the golf ball which substantially prevents the generation of rough surface by using a polymer consisting of a mixture composed of the zinc salt, etc., of an ethylene-(meth)acrylate copolymer having a modulus of elasticity in flexure of a specific value and an ethylene-vinyl acetate copolymer having the modulus of elasticity in flexure of a specific value as the essential components of the core and cover of the golf ball. CONSTITUTION:The cover of the golf ball having the core and the cover for coating the core consists essentially of the polymer consisting of 60 to 95wt.% mixture composed of the zinc salt or sodium salt or zinc salt and sodium salt of the ethylene-(meth)acrylate copolymer having 20000 to 56000psi modulus of elasticity in flexure and 5 to 40wt.% ethylene-vinyl acetate copolymer having 1000 to 10000psi modulus of elasticity in flexure. This golf ball has the good hitting characteristic and spin characteristic, a good initial speed and excellent durability and is less damaged in hitting with iron clubs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a golf ball having a core and a cover covering the core, and more particularly to an improvement of the cover.

[0002]

BACKGROUND OF THE INVENTION Ionomer resins of ethylene / (meth) acrylic acid copolymers are used in two-piece golf balls and some thread-wound golf balls because of their excellent impact durability and cut resistance. Widely used and accepted as cover material. However, this type of ionomer resin has a harder feel when compared to the balata rubber that has been conventionally used as a cover material, and has a high hardness relative to the balata rubber, which makes it difficult to spin freely on iron shots. It has been said that it is inferior in sex.

Therefore, as an improvement of such a point, ethylene (meth), which is a relatively flexible ionomer resin, is used.
It is possible to use a mixture of an acrylic acid / (meth) acrylic acid ester terpolymer with an ionomer resin of ethylene / (meth) acrylic acid copolymer having a certain physical property within a certain range as a soft / hard ionomer blend golf ball cover. Proposed (US Pat. No. 48848)
No. 14, Japanese Patent Laid-Open No. 1-308577).

This proposal is very effective as a technique for greatly improving hitting hardness and controllability, which are problems of a golf ball using a conventional ionomer resin of ethylene / (meth) acrylic acid copolymer as a cover. It can be said that.

[0005]

However, the soft / hard ionomer blend golf ball cover according to this proposal has the following problems. That is, the softness of the cover and the tendency to spin on the iron shot mean that the frictional force between the club face and the cover is large. Therefore, a hard core material such as a two-piece solid golf ball is used. In the case of a ball using the (core), the cover surface is scraped off by the groove of the iron club at the time of iron shot, and the phenomenon that the ball surface rises up easily occurs.

Further, since the hardness of the ionomer cover is lowered, the resilience of the cover itself is also lowered, and the resilience as a ball is greatly reduced.

Therefore, when it is applied to a solid golf ball such as a two-piece golf ball, it has a good feeling, an excellent spin characteristic, a good controllability, a swelling phenomenon hardly occurs, and a good repulsion property. A golf ball that does not impair the flight distance peculiar to this is desired.

[0008]

Therefore, the present inventors have a soft feeling, have good spin characteristics, and do not significantly reduce the repulsion property of the ball. As a result of diligently studying a golf ball having improved resistance to fraying, an intermediate hardness ionomer resin in the intermediate region of the hard ionomer resin or the soft / hard ionomer resin or a mixture thereof, and a resin having a relatively low hardness. A polymer obtained by blending an ethylene-vinyl acetate copolymer having flexibility and elasticity in a specific ratio, specifically, a flexural modulus of 20,0.
Ethylene- (meth) from 00 psi to 56,000 psi
60 to 95% by weight of zinc salt or sodium salt of acrylic acid copolymer or a mixture of zinc salt and sodium salt,
By forming a cover using as a main component a polymer composed of an ethylene-vinyl acetate copolymer having a flexural modulus of 1,000 psi to 10,000 psi and 5 to 40% by weight,
It has been found that when the hardness is the same as that of the soft / hard ionomer resin cover, the resilience is high, and the golf ball using the cover has good feel and spin characteristics and little damage on iron shots. The present invention has been completed.

The present invention will be described in more detail below. The golf ball of the present invention is a golf ball having a core and a cover that covers the core, wherein the cover has an elastic modulus of 20,000 psi to 56,000 psi of ethylene-
(Meth) acrylic acid copolymer zinc salt or sodium salt or a mixture of zinc salt and sodium salt 60 to 95% by weight, and flexural modulus 1,000 psi to 10,000 p
The main component is a polymer composed of 5 to 40% by weight of an ethylene-vinyl acetate copolymer of si.

In this case, as the Zn salt and Na salt of the former ethylene- (meth) acrylic acid copolymer, any one may be used as long as it has the above-mentioned flexural modulus, and these are two or more kinds thereof. However, if the flexural modulus of the mixture is within the above range, the Zn salt and Na salt of each copolymer may be out of the above range.

As the Zn salt and Na salt of the ethylene- (meth) acrylic acid copolymer, Himilan which is commercially available from DuPont Mitsui Polychemical Co., Ltd., a corresponding grade of DuPont Co., USA, and EXON Co. An ethylene-acrylic acid copolymer ionomer "Iotek" or the like can also be used. Specifically, those shown in Table 1 can be exemplified.

[0012]

[Table 1]

On the other hand, the ethylene-vinyl acetate copolymer has a flexural modulus in the range of 1,000 to 10,000 psi, and such a copolymer has a vinyl acetate content of 10 to 32 in the copolymer. What is in weight percent is used.

The weight ratio of the Zn salt or Na salt of the ethylene- (meth) acrylic acid copolymer to the ethylene-vinyl acetate copolymer is 60:40 to 95: 5, more preferably 70:30 to 90. When the amount of ethylene-vinyl acetate exceeds 40% in the polymer, the impact durability is deteriorated, and when it is less than 5%, there is no effect of improving the feel at impact and spin characteristics.

The cover according to the present invention comprises a Zn salt, Na salt and ethylene-containing ethylene- (meth) acrylic acid copolymer.
The main component is a polymer which is used in combination with the vinyl acetate copolymer in the above proportions, but the cover of the present invention may contain a dye, a pigment such as titanium dioxide, zinc oxide, barium sulfate, or the like, if necessary. Agents, antioxidants and other materials, as well as dispersing aids such as metal soaps, etc. can be added, and these materials can be mixed by ordinary mixing, for example, in a closed kneader (Banbury, kneader), in an extruder. After mixing with
It can be molded according to a conventional method.

The cover of the present invention is particularly suitable as a cover for a solid golf ball such as a two-piece ball and a three-piece ball. The core of this solid golf ball has a base rubber, an unsaturated carboxylic acid metal salt and a peroxide. It is preferable to use a core composition containing a compound added with pentachlorothiophenol or a metal salt thereof as an essential component. In this case, as the base rubber, cis-1,4 having a cis structure of 90% or more is used.
-Polybutadiene rubber is particularly preferably used from the viewpoint of high resilience. Natural rubber, polyisoprene rubber and the like can be appropriately blended with the cis-1,4-polybutadiene rubber, if desired, but the high cis-1,4-polybutadiene rubber is contained in the base rubber component at 80% by weight. It is preferable to contain the above, and if it is less than 80% by weight, excellent resilience of the high cis-1,4-polybutadiene rubber may be impaired. The metal salt of unsaturated carboxylic acid is added as a co-crosslinking agent, and zinc acrylate is particularly preferable, and 25 to 40 parts by weight is preferably used with respect to 100 parts by weight of the base rubber. Examples of the peroxide include dicumyl peroxide, t-butyl peroxybenzoate, di-t-butyl peroxide,
1,1-bis (t-butylperoxy) -3,3,5-
Trimethylcyclohexane and the like can be used. The amount to be blended is preferably 0.5 to 3 parts by weight, particularly 0.8 to 2 parts by weight, based on 100 parts by weight of the base rubber. Pentachlorothiophenol or its metal salt is preferably added in an amount of 0.2 to 1.5 parts by weight with respect to 100 parts by weight of the base rubber in order to achieve a clear high repulsion property in this compounding system. When compounded, the case where the crosslinking reaction of the core composition of the present invention is inhibited may occur.

Further, in this core composition, zinc oxide,
If necessary, a component which can be usually used in a core ball of a two-piece solid golf ball such as an antiaging agent or barium sulfate can be appropriately blended. This core rubber composition is kneaded with a Banbury or a kneader or the like, and can be cured and molded as a core material of a sphere by high temperature pressure vulcanization according to a conventional method, but in the present invention, as the hardness of the vulcanized product core, The amount of deflection when a 100 kg load is applied to the core is 2.3 to 3.
It is preferable to use one that is 3 mm. 2.3 m
If it is smaller than m, the ball after covering with the cover tends to be hard and the feel on impact tends to be poor, and if it is larger than 3.3 mm, the rebound may be low.

The golf ball of the present invention can be molded by a conventional molding method,
For example, the leaf cup may be molded in advance with the cover material, and the solid core may be coated with the cover material by thermal compression molding, or the cover material may be coated around the solid core by direct injection molding.

After molding in this manner, various finishing operations such as buffing, painting and stamping can be performed on the surface.

[0020]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples 1 to 5, Comparative Examples 1 and 2] The following compositions
A rubber composition having a diameter of 38.5 mm is prepared by a conventional method using
A core of a large size two-piece golf ball was manufactured.Rubber composition JSR BR01 100 parts by weight Zinc acrylate 33 〃 Zinc white 9.7 〃 Barium sulfate 9.7 〃 Anti-aging agent (Norak NS-6) 0.2〃 Dicumyl peroxide 1.0〃

Next, using the cover material having the composition shown in Table 2, a cover having a thickness of 2.1 mm was formed on the core by injection molding.

With respect to the obtained two-piece golf ball,
The following properties were evaluated. The results are shown in Table 2. The results are average values of 12 balls. Ball hardness Deflection when a load of 100 kg is applied to the ball (m
m). The larger this number, the softer the ball. Measured using an initial velocity meter with the same type ball initial velocity of a golf ball accredited institutions R & A (USGA) (m / sec). Striking Feeling Three professional golfers were shot by clubs of W # 1 and I # 7, and the feel of striking was evaluated according to the following criteria. ◎: Soft (similar to balata thread-wound balls) ○: Soft ×: Hard (similar to a normal two-piece ball) Backspin amount Swing robot machine with pitching wedge, hit at 37m / sec head speed, and ball behavior immediately after impact Was photographed and analyzed. Under the same conditions as the evaluation of the stopping backspin amount on the green , evaluation was made by the distance difference between the falling position and the stopping position when the ball was hit so as to directly fall on the green. In addition, "+" indicates a case of moving forward from the drop position, and "-" indicates a case of moving backward. Under the same conditions as the evaluation of the amount of backspin test with an iron , three hits of the ball were hit once each, and the hit parts at these three places were observed, and evaluated according to the following criteria in three levels. ◯: A slight mark on the club face is left, but it is hardly noticeable. △: A clear mark on the club face is left, but there is no feathering on the cover surface. ×: The surface is flaky or noticeable feathering.

[0024]

[Table 2] Note: Evaflex 150: ethylene-vinyl acetate copolymer, vinyl acetate amount 33%, flexural modulus 1,200 psi Evaflex 260: ethylene-vinyl acetate copolymer, vinyl acetate amount 28%, flexural modulus 2,500 psi

[0025]

The golf ball of the present invention has good hitting and spin characteristics and a good initial velocity.
Moreover, it has excellent durability and little damage on iron shots.

Claims (1)

[Claims] 1. A golf ball having a core and a cover for covering the core, wherein the cover has a bending elastic modulus of 2.
Ethylene from 50,000 psi to 56,000 psi
(Meth) acrylic acid copolymer zinc salt or sodium salt or a mixture of zinc salt and sodium salt 60 to 95% by weight, and flexural modulus 1,000 psi to 10,000 p
A golf ball comprising, as a main component, a polymer composed of 5 to 40% by weight of ethylene-vinyl acetate copolymer of si.