JPS6060866A - Two-piece golf ball and its production - 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 The present invention relates to a two-piece golf ball and a method for manufacturing the same.
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Two-piece golf balls are easy to manufacture and inexpensive.''-1 Two-piece golf balls have become widely popular in recent years because they provide a product of consistent quality, but their impact resistance and feel at impact are superior to that of conventional thread-wound golf balls. It has some disadvantages compared to the ball.

In order to improve the impact resistance of this two-piece golf ball, we have recently used polybutadiene as a base rubber and co-crosslinked α,β-monoethylenically unsaturated carboxylic acid and its metal salt as a co-crosslinking agent. Techniques for manufacturing two-piece golf balls have been proposed (for example, Japanese Patent Publication No. 55-1
Publication No. 9615). A carboxylic acid metal salt that has attracted particular attention as a metal salt of these α,β-monoethylenically unsaturated carboxylic acids is an acrylic acid metal salt, which is usually polybutadiene 100! The use limit is about 10 to 20 parts by weight, or 25 parts by weight at most, based on part i. If more than this amount of acrylic acid metal salt is used alone, it may cause damage during vulcanization due to the polymerization heat of gold acrylate BFA. The heat generation is delayed, and the amount of effective heat generated within a certain vulcanization time is reduced, resulting in variations in the degree of vulcanization and making it impossible to obtain a uniform golf ball, so it is rarely used in practice. There is no.

However, in order to improve the physical properties (especially impact resistance) of golf balls, it is desirable to use more acrylic acid [
)stomach.

The present inventors investigated means for blending more acrylic acid, and found that the addition of methacrylic acid promoted heat generation during vulcanization, and that the blending ratio of acrylic acid metal salts and methacrylic acid metal salts was reduced. It has been found that by maintaining the degree of vulcanization within a certain range, it is possible to blend more metal acrylic salts while maintaining a uniform degree of vulcanization. It has been found that the thus obtained golf ball has extremely excellent impact resistance due to the synergistic effect of the metal acrylate and the metal methacrylate.

On the other hand, in the core of a conventional two-piece golf ball (well, i
! +711jl i-% Initiators such as dicumyl peroxide, butyl peroxybenzoate, t-butyl cumyl peroxide, etc. are used as golf ball base rubber 10
Approximately 0.5 to 5 R parts are used per 0 single hanging part. In addition, in order to prevent golf balls from aging due to oxidation, various antioxidants are added at a concentration of 0.3 to 0 per 100 parts of the base rubber.
．． 7 hanging part (for the 'lfi leaving group initiator, mffl ratio has been used at about 0.2 to 0.8).

However, when acrylic acid metal salts are added to row seedlings,
In order to effectively react the added metal salts and to control the surface hardness and compression of the golf ball within an appropriate range, it is necessary to reduce the amount of free radical initiator used. Reactive metal salts are produced (1), making it difficult to control vulcanization and making it difficult to control the surface hardness of the golf ball and the compression of the golf ball within appropriate ranges.

The present inventors have identified acrylic acid metal salts and methacrylic acid metal salts by using a certain type of antioxidant, which has traditionally been used only to prevent the aging of golf balls, in a way that exceeds conventional wisdom. By adding it to highly compounded rubber within the range of It has been determined that a two-piece golf ball having surface hardness can be obtained. That is, in the present invention, per 100 parts of the base rubber, 30 to 50 parts by weight of metal salts of acrylic acid, 1 to 10 parts by weight of metal salts of methacrylic acid, 1 free radical;
3.0! A two-piece golf ball having as a core a vulcanizate of a rubber composition containing 0.63 to 2.0 parts by weight of a phenolic antioxidant per 1 part by weight of the free radical initiator. .

As the rubber, any suitable natural rubber and/or synthetic rubber conventionally used in solid golf balls may be used, but in the present invention, borobutazine rubber, especially one containing at least a cis-1,4 bond, may be used. A polybutadiene rubber containing 40%, preferably 90% or more is suitable. Natural rubber, polyisoprene rubber, styrene-butadiene rubber, etc. may be appropriately blended with the polybutadiene.

In the present invention, the metal salt of acrylic acid is used as the base material GoA10.
It can be added in an amount of 30 to 50 parts by weight based on 0Ifa parts, thereby significantly improving the impact resistance of golf holes. The reason for this is, as mentioned above, that high blending of acrylic acid, for example, the use of 25 parts or more, delays the heat generation during vulcanization of the rubber composition and reduces the effective calorific value required for vulcanization, resulting in uniform vulcanization. This is because, although it is not possible to obtain the degree of vulcanization, the combined use of a metal methacrylate accelerates heat generation and makes it possible to obtain a predetermined degree of vulcanization.

The amount of the metal salt of acrylic acid varies slightly depending on the type of metal salt, but it is usually 30 to 100 parts by weight per 100 parts by weight of the base rubber.
If the amount is 50 parts by weight, preferably 32 to 36 parts by weight, and 30 parts by weight or less, the two-piece ball has excellent impact resistance while maintaining various properties such as the initial velocity of the ball and the feel of the ball at impact 1. Can't get the golf ball. Also 5
If the amount is 0 parts by weight or more, the hardness of the golf ball becomes too high.

The methacrylic acid metal salt used in combination with the acrylic acid metal salt varies depending on the type of metal jB and the amount of methacrylic acid, but
The amount is usually 1 to 10 parts by weight, preferably 2 to 5 parts by weight, per 100 parts by weight of the base rubber. If the amount is less than 1 part by weight, it is difficult to obtain the effects of the present invention, and if it is more than 1 part by weight, the repulsion characteristics of the resulting two-piece golf ball will be significantly reduced.

The weight ratio of metal acrylate and metal methacrylate is
98/2 to 75/25, preferably 96/4 to 90/1
It is 0.

Metal salts of acrylic acid and methacrylic acid include calcium salts, magnesium salts, zinc salts, aluminum salts,
Examples include tin salts, and zinc acrylate and zinc methacrylate are particularly preferred.

In the present invention, a free radical initiator and a phenolic antioxidant are further added. Examples of free radical initiators include:
Particularly preferred are dicumyl peroxide, which includes dicumyl peroxide, t-butyl baroxybenzoate, t-butyl cumyl peroxide, and the like. i, H
l [The amount of the base initiator added is not particularly limited, but it is usually 0.5 to 20 parts by weight or 1.0 to 3.0 parts by weight per 100 parts by weight of the rubber material. , it is difficult to obtain a two-piece golf ball of optimum hardness when using a free radical initiator outside this range.

In addition to the above ingredients, the rubber composition according to the present invention contains a free radical initiator and a phenolic antioxidant. The amount ratio of phenolic antioxidant to free radical initiator is 0.
8 to 2.1. Preferably it is 1.0 to 1.5.

If it is less than 0.8, the effect of the present invention cannot be sufficiently obtained, and 2.
When it is 0 or more, the economic disadvantage is too large compared to the effect obtained. When the phenolic antioxidant is added within this range, vulcanization can be easily controlled, and the compression and surface hardness of the resulting two-piece golf ball can be easily controlled within appropriate ranges.

In the present invention, the phenolic antioxidants that act as vulcanization control agents include 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 2,6-
Di-tert-butyl-4-butylphenol, 2,5-di-
Examples include t-butylhydroquinone. Preferably, 2,2'-methylenebis(4-ethyl-6-t-
butylphenol). The effects obtained in the present invention cannot be achieved with antioxidants other than phenolic antioxidants.

The rubber composition according to the present invention may contain an inert filler in addition to the above-mentioned ingredients. Examples of inert fillers include barium sulfate, zinc oxide, calcium oxide, zinc carbonate, silica, and the like.

The amount of the inert filler added is also not particularly limited, but is usually about 30 to 70 parts by weight, preferably 40 to 55 parts by weight, per 100 parts by weight of the base rubber.

The rubber composition according to the present invention may further contain other conventional additives, if desired.

The method for producing a two-piece golf ball from the rubber composition of the present invention is not particularly limited, and any conventional method may be used.

For example, the above-mentioned polybutadiene, unsaturated carboxylic acid metal, etc. are thoroughly kneaded at about 60 to 110°C using a conventional kneader, and the temperature of the kneaded material is lowered to the decomposition temperature of the free radical initiator. Add a free radical initiator and mix well.
This is filled into a pressurized top mold and heated to form a core. The obtained core is covered with a cover material such as Zarlin to a thickness of about 2 mm to form a two-piece golf ball.The two-piece golf ball obtained from the rubber composition of the present invention has extremely excellent core hardness, surface hardness, etc. .

It also has a good feel at impact, excellent repulsion characteristics, and impact resistance f1, and can fully meet the preferences and demands of players.

Hereinafter, the present invention will be explained in detail with reference to Examples.

9 Examples 1 to 10 and Comparative Examples 1' to 12' Rubber compositions were prepared according to the formulations shown in Table 1.

The prepared rubber composition was manufactured according to the above manufacturing method to obtain a core for a two-piece golf ball.

Table 2 shows the core hardness and surface hardness of the core of the obtained two-piece golf ball.

The above core was mixed with Zarlin 1601 (100 parts), TiO2
A two-piece golf ball was obtained by covering the golf ball to a thickness of 2 mm using a cover material consisting of (1 part). Table 2 shows the repulsion index and durability index of these balls.

In addition, a flight test of the golf balls of Example 4 and Examples 6 to 8 was conducted using a driver at a head speed of 451+1.
/Sec. The results are shown in Table-3.

Example 13' and 14' Conventional loading of antioxidant 11-agent (0.3 parts by weight of antioxidant per 1 part by weight of free radical initiator) with or without addition of zinc methacrylate The additives are shown in Tables 1 and 2 in the same manner as in the above example.

Claims (1)

[Claims] 1. 30 to 50 parts of metal salt of acrylic acid, 1 to 1 part of metal salt of methacrylic acid per 100 parts of base rubber.
0 parts by weight, 0.5 to 3.0 parts by weight of a free radical Bil initiator, and 0.8 to 2.0 parts by weight of a phenolic antioxidant per 1 part by weight of the free radical initiator. A two-piece golf ball having a core made of a vulcanized product. 2. The base rubber is made of cis-1,4M4 structure with at least 40
% or more of 1,4-polybutadiene. 3. The first metal salt of acrylic acid is zinc acrylate.
The two-piece golf ball described in Section 1. 4. The two-piece golf ball according to item 1, wherein the gold Ji1 salt of methacrylic acid is zinc methacrylate. 5. The antioxidant is 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 2゜6-di-L-
Butyl-4-methylphenol, or 2,5-di-t
- The two-piece golf ball of item 1, which is butyl hydroquinone. 6. λ (per 100 parts by weight of raw rubber, 30 to 50 parts by weight of metal salts of acrylic acid, 1 to 10 parts of metal salts of methacrylic acid)
J
, 0 parts by weight (containing 0.8 to 2.0 parts by weight of b and phenolic antioxidant per 1 part by weight of the free radical initiator)
1. A method for manufacturing a two-piece golf ball, which comprises vulcanizing a rubber composition to form a core, and then coating the core with a coating material such as 1Norin.