JPS61290969A - Solid golf ball - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a solid golf ball, and particularly to a solid golf ball whose flight distance is improved by changing the structure of the cover of the golf ball.

(Background of the Invention) High-grade solid golf balls for rounds include multilayer solid golf balls and two-piece solid golf balls.
Both are covered with covers to protect the bumps.

The core of this solid golf ball is usually manufactured by vulcanizing and molding the core of polybutadiene, which has high repellency, using a metal salt of an unsaturated fatty acid as a co-crosslinking agent. The cover is usually formed by adding a small amount of white filler to an ionomer resin to adjust the specific gravity to about 0.92 to 1.2 and covering the core.

On the other hand, golf balls have a weight standard (45,919 or less)
However, it is generally adjusted to around the maximum value of the weight standard in order to increase flight distance. Therefore, a large amount of filler (eg, zinc oxide, barium sulfate, etc.) is added to the core rubber composition as a weight regulator.

However, the addition of such a large amount of weight adjuster does not take advantage of the inherent repulsion performance of butadiene rubber, reducing the flight distance of the golf ball. Furthermore, as the specific gravity of the core increases, the moment of inertia decreases, spin is more likely to occur, the spin decays faster during flight, and flight distance becomes shorter.

JP-A No. 60-53164 discloses that by increasing the specific gravity of the cover by adding high specific gravity materials (iron powder, metal oxides, etc.) to the cover, the rebound resilience of the core is increased and flight performance is improved. It is proposed that. However, the addition of high specific gravity materials to the entire cover, especially the addition of heavy metals or their salts (which usually have a dark color), can result in coloring the cover, even if the cover is painted. It shows off and is not suitable for practical use. Furthermore, in order to increase the specific gravity of the cover, a large amount of additives must be added, which tends to reduce the durability of the cover against impact from the club, which poses a practical problem.

The present invention was made with the aim of developing a golf ball that does not have the above-mentioned drawbacks.

(Structure of the Invention) That is, the present invention provides a solid golf ball consisting of a core and a cover covering the core, wherein the cover has two layers, an outer layer and an inner layer, and the outer layer and the inner layer have the following characteristics: A solid golf ball is provided.

The present invention will be explained with reference to the drawings.

The outer cover layer (1) of the solid golf ball of the present invention is prepared in exactly the same manner as conventionally used covers. Cover materials that can be used include various ionomer resins. Preferred ionomer resins include at least one polymer selected from the group consisting of monoolefins, unsaturated mono- or dicarboxylic acids having 3 to 8 carbon atoms, and esters thereof (unsaturated mono- or dicarboxylic acids and/or esters thereof). It is a thermoplastic resin with cross-metal bonding added to (containing ~30% by weight).

Examples of such resins include various types of "HIMILAN" commercially available from Mitsui Polychemical Co., Ltd., such as 1554.1.
555.1601.1605.1650.1652.1
702.1557.1706.1707.1855.1
856 is mentioned. The material used for the outer layer of this cover is
In particular, it is preferable to use a material that is hard and has a high elastic modulus that makes it difficult for the ball to spin when hit. For example, Shore D hardness 58-72, preferably 60-66, flexural modulus 23
0 to 600 MPa, preferably 280 to 500 MPa is preferred. Examples of resins with such properties include Himilan 1605.1706.1.
707, a mixture of these and Himilan resin of the above-mentioned properties, and the like.

The inner cover layer (2) is manufactured using substantially the same resin as the outer cover layer (1), but the specific gravity is adjusted to 1.2 or more, preferably 1.4 to 2.5. A high specific gravity filler is added to adjust the specific gravity. High specific gravity filler (preferably specific gravity 1
0 to 20) include metal powder, metal oxide, metal nitride,
Examples include metal carbides. For example, tungsten (black, specific gravity: 19.3), tungsten carbide (blackish brown, specific gravity: 15.8), molybdenum (gray, specific gravity: lO
, 2), lead (gray, specific gravity: 11.3), lead oxide (dark gray, specific gravity: 9.3), nickel (silver gray, specific gravity: 8.
9) and copper (reddish brown, specific gravity: 8.9) or a mixture thereof.

It is preferable to use the above-mentioned high specific gravity filler, but barium sulfate, titanium dioxide, or zinc white, which have a relatively low specific gravity, may also be used. In this case, in order to increase the specific gravity of the cover inner layer, the resin:filler weight ratio is added at a ratio of about 1:0.8 to 1:1.5. Since the cover inner layer (2) does not receive direct force from the club when hit, it does not need to be particularly hard and have a high modulus of elasticity, and may be made of a material such as conventionally used balata.

In addition to the above-mentioned ingredients, other additive amounts may be added to the Ryoryokuba layer. Other addition amounts include, for example, white pigments such as titanium dioxide, coloring agents, anti-aging agents, lubricants, dispersants, stabilizers, ultraviolet absorbers, etc., which are appropriately selected and used. In particular, when preparing a composition for a balata cover, sulfur, a vulcanization accelerator, and the like are used in addition to the above-mentioned amounts to be added to the cover.

The preparation of the cover composition and the method for coating the core of the cover are as follows:
This can be done by conventional means. For example, the cover composition is prepared by uniformly mixing the cover main material, if necessary, a high specific gravity filler, and the desired cover compounding agent using a roll, mixer, extruder, etc., and the core is coated by injection. This is done by molding or compression molding.

The thickness of both layers (1) and (2) is 0.5 to 2 mm.
It is. It is necessary to ensure that the two covers have a sufficient thickness as the cover of a solid golf ball, and that the cover inner layer (2) has a sufficient resin composition and thickness to mix the necessary amount of heavy metal filler.

The weight of the core (3) in a solid golf ball increases due to the addition of high-density fillers in the cover inner layer (2), making it possible to reduce the amount of fillers that were previously added to adjust the weight. can.

The components of the solid core include a base rubber, a crosslinking agent, a co-crosslinking agent, an inert filler, and the like.

As the base rubber, 1,4-polybutadiene having at least 40% cis structure is particularly preferred, and if desired, natural rubber, polyisoprene rubber,
Styrene-butadiene rubber or the like may be blended as appropriate.

Examples of crosslinking agents include organic peroxides such as dicumyl peroxide and t-butyl peroxide, and azo compounds such as azobisisobutylnitrile.
Particularly preferred is dicumyl peroxide.

The amount of crosslinking agent is usually 0 per 100 parts by weight of the base rubber.
．． 5 to 3.0 parts by weight, preferably 1. θ˜2.5 parts by weight.

Examples of the co-crosslinking agent include, but are not particularly limited to, metal salts of unsaturated fatty acids, particularly zinc salts and magnesium salts of unsaturated fatty acids having 3 to 8 carbon atoms (for example, acrylic acid, methacrylic acid, etc.). Zinc acrylate (normal salt)
is particularly suitable, and the blending amount is 30 to 38 parts by weight, preferably 32 to 36 parts by weight, based on 100 parts by weight of the base rubber.

Although the addition of inert fillers to the core can be reduced as described above, they may also have the function of promoting rubber crosslinking, so it is preferable to add a small amount of zinc oxide or the like.

The core (3) of the solid golf ball can be obtained by a conventional method, for example, by kneading the mixture using a roll or a negotiator, compression molding it in a mold, and crosslinking it.

The weight of the core (3) is reduced by the amount of filler added to adjust the weight, so the weight of the core (3) is normally 25% for small size balls.
~35g1 For large size balls, usually 30~
35g is preferred.

(Effects of the Invention) According to the present invention, the addition of an inert filler to the core is reduced, the repellency inherent to butadiene is fully exhibited, and the flight distance is increased. In addition, the weight of the center of the solid golf ball is reduced,
The increased weight of the outer portion increases the moment of inertia of the ball, reduces the initial spin when the ball is hit, suppresses spin attenuation during flight, and increases flight distance.

In particular, if a hard resin is used for the outer layer of the cover, the initial spin will be further reduced and the flight distance will be increased. In addition, since the inner layer is made of a layer with a large amount of filler and poor durability, and the inner layer is covered with a layer with a small amount of filler and good durability as an outer layer, the durability of the entire cover is sufficient for practical use.

(Examples) Examples 1 to 5 and Comparative Example 1 Core Preparation The rubber composition shown in Table 1 was vulcanized in a mold at 160° C. for 25 minutes to produce a solid core with an outer diameter of 36.8 mi+. In preparing the composition, the weight of the core was adjusted so that the total weight of the golf ball obtained was approximately 45.4 g. The blended parts of the compositions in Table 1 are based on parts by weight for both the cover and the core. Preparation of Cover Inner Layer The ionomer listed in Table 1 was dissolved and kneaded using a roll, and a predetermined amount of a high specific gravity filler was added thereto and mixed.

After mixing, the mixture was extruded into a sheet, stored at 150° C., and then a half shell for a ball was produced by a compression molding method and coated on the core. Next, the core coating was produced by heating at 155° C. for 2.5 minutes using a compression molding method.

Preparation of cover outer layer and ball A cover outer layer pellet was prepared by extrusion molding using the formulation shown in Table 1, and the pellet was coated on the core covering material by injection molding method to form a pellet with a diameter of 41.2 mm.
I got a two-piece golf ball.

The physical properties of the obtained golf ball were measured and the results are shown in Table 2.

(note) 凰 Ball hardness: Hardness display according to the USGA method.

2 Coefficient of repulsion: 198.4g cylindrical object on the ball
It was calculated from the ball speed when colliding at a speed of m/sea.

3 Flying distance: Funao M (carry) data when using True Temper's swing robot with No. 1 wood club and head speed of 45 m/s.

4. Initial spin: Measured using a photographic method when measuring flight distance.

5 Durability: 45 am on metal plate with air gun
The number of times it takes for one layer of the cover to crack after collision at a speed of /sec is expressed as an index, with Comparative Example 1 set as 100, and the larger the number, the better the durability.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the solid golf ball of the present invention, in which (1) two cover outer layers, (2) two cover inner layers, (
3); Indicates the core.

Claims (1)

[Claims] 1. A solid golf ball consisting of a core and a cover covering the core, wherein the cover has two layers, an outer layer and an inner layer.
A solid golf ball having a layer, the outer layer and the inner layer having the following properties. 2. The solid golf ball according to item 1, wherein the cover outer layer is made of a hard resin with a high modulus of elasticity. 3. The solid golf ball according to item 1, wherein the cover inner layer contains a high specific gravity filler. 4. The solid golf ball according to item 3, wherein the high specific gravity filler has a specific gravity of 10 to 20.