JPH0280068A - Solid golf ball - Google Patents

Abstract

PURPOSE:To present a golf ball with high hardness and destructive strength further with a good hitting feeling by combining specific unsaturated carboxyilic acid ester with unsaturated carboxyilic acid metal salt. CONSTITUTION:For 100 pts.wt. polybutadiene rubber containing 40% or more cis 1, 4 structure, 7 to 14 pts.wt. unsaturated carboxyilic acid metal salt, 5 to 30 pts.wt. unsaturated carboxyilic acid ester of pentavalent or more alcohol or epoxyresin and 1 to 5 pts.wt. organic peroxide are compounded, forming a rubber composition, and its hardened material serves as a core. The unsaturated carboxyilic acid metal salt in use is preferably zinc diacrylate or zinc methacrylate with the quantity of use 7 to 14 pts.wt. for 100 pts.wt. rubber base material. The unsaturated carboxyilic acid ester in use is unsaturated carboxyilic acid ester of pentavalent or more alcohol or epoxyresin.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to solid golf balls. More specifically, the present invention relates to a cured product of a specific rubber composition constituting the core of a solid golf ball.

BACKGROUND OF THE INVENTION Compositions used for the core of solid golf balls are broadly classified into the following three types.

The first is a rubber composition containing an unsaturated carboxylic acid metal salt in the rubber I material (see Japanese Patent Publication No. 55-19F315 and Japanese Patent Publication No. 59-26310@), and a cured product of such a composition is used as a core. The golf ball described above satisfies most golfers in terms of hardness and feel at impact, and the current amount is also commonly used.

The first rubber composition is prepared by kneading a metal oxide (zinc oxide in the shell) into a rubber base material using a kneading machine such as a roll, mixer, or kneader, and then further kneading the unsaturated carbon M(
In this method, an unsaturated carboxylic acid metal salt is produced in 5itti in a rubber substrate by kneading acrylic acid or methacrylic acid in the shell, but in this method, Due to the low flash point of unsaturated carboxylic acids [acrylic acid = 54.4°C (open), methacrylic acid = 77°C (open)], there is a risk of fire during cross-mixing work, and the reaction may not proceed as desired due to evaporation loss. There is a drawback that it does not progress.

As a method to improve the above-mentioned drawbacks, a pre-synthesized unsaturated carboxylic acid metal salt (inside the shell is a zinc diacrylate salt or a zinc dimethacrylate salt) is finely pulverized to a powder of 300 mesh or less, A method has been proposed in which this is kneaded into a rubber base material using a roll or a kneader. In the case of this method, there is a disadvantage that when the unsaturated carboxylic acid metal salt is kneaded into the base rubber, the unsaturated carboxylic acid metal salt coagulates and solidifies and sticks to the roll surface or the inner wall of the mixer in a plate shape. If the kneading operation is continued, the stuck substances will fall off and the
Since the unsaturated carboxylic acid metal salt is crushed into granules and mixed into the rubber composition in that state, it has the disadvantage that the unsaturated carboxylic acid metal salt cannot be well dispersed in the rubber base material.

In order to improve dispersibility, a method has been proposed in which a dispersion aid such as a fatty acid metal salt is added and the surface of the unsaturated carboxylic acid metal salt is coated with the dispersion aid, but even this method is not satisfactory. No effect has been obtained.

At present, no effective means other than frequent removal of stuck substances has been proposed.

The second is a rubber composition containing an unsaturated carboxylic acid ester (e.g., ethylene dimethacrylate, 1,3-butylene dimethacrylate, trimethylolpropane trimethacrylate, or tetramethylolmethanetetramethacrylate) in the rubber base material. Yes (Tokuko Showa 44-2291
1 @ Publication and JP-A No. 52-136043),
A golf ball having a core made of a cured product of such a composition is softer than a golf ball having a core made of the first composition, has a lower breaking strength, has a shorter flight distance, and has a poor feel on impact, and is therefore used less frequently.

The third is an unsaturated carboxylic acid ester (ethylene glycol dimethacrylate) in a rubber base containing metal oxides (with zinc oxide in the shell).

unsaturated carboxylic acid (selected from trimethylolpropane trimethacrylate and tetramedylolmethane monoacrylate) and an unsaturated carboxylic acid using a mixer to produce in s+tu in a rubber base material. This is a rubber composition containing an acid metal salt (see Japanese Patent Laid-Open No. 57-25337), and golf balls made of a cured product of such a composition were soft and had insufficient feel on impact.

An object of the present invention is to eliminate the drawbacks of the prior art described above.

Another object of the present invention is to provide a golf ball that has high hardness and breaking strength and has a good feel when hit.

Another object of the invention is to provide a golf ball that is easy to manufacture.

SUMMARY OF THE INVENTION The present inventor has discovered that the above object can be achieved by combining a specific unsaturated carboxylic acid ester with an unsaturated carboxylic acid metal salt, leading to the present invention.

The present invention requires 7 to 14 i [parts] of an unsaturated carboxylic acid metal salt to 1001 ffi parts of polybutadiene rubber containing 40% or more of cis-1,4 structure, and an unsaturated carboxylic acid ester of a pentahydric or higher alcohol or an epoxy resin. A solid golf ball having a core made of a cured rubber composition containing 5 to 30 parts by weight and 1 to 5 fi (3 parts by weight) of an organic peroxide is provided.

In the present invention, polybutadiene rubber containing 40% or more of cis-1,4 structure, which is commonly used as a rubber base material for golf balls, is used, but if necessary, other cross-fertile rubber polymers such as butadiene-styrene may be used. rubber. Polyisoprene rubber, polyurethane rubber, natural rubber, etc. may be blended with polybutadiene rubber. When using the rubber polymer, the amount used should be cis 1, 4 in consideration of impact resilience.
The amount is preferably 5 to 20% by weight based on the polybutadiene rubber containing 40% or more of the structure.

The unsaturated carboxylic acid metal salts used in the present invention may be those used in the prior art described above, and are preferably zinc diacrylate or zinc dimethacrylate.

The amount of the unsaturated carboxylic acid metal salt used is 7 to 14 parts by weight based on 100 parts by weight of the rubber base material. When less than 7 parts by weight of the unsaturated carboxylic acid metal salt is used, a soft core is obtained, and when more than 14 parts by weight is used, the core becomes too hard. Therefore, the use of the unsaturated carboxylic acid ester used in the present invention m must be reduced to 5 parts by weight or less. In this case, the dispersion of the unsaturated carboxylic acid metal salt becomes poor, which is not preferable.

The unsaturated carboxylic acid ester used in the present invention is an unsaturated carboxylic acid (eg, acrylic acid, methacrylic acid, crotonic acid) ester of a pentahydric or higher alcohol or an epoxy resin. Examples of alcohols having a valence of 5 or more and F include tosorbitol, D-mannitol, dipentaerythritol, and dipentaerythritol derivatives (for example, alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide, or ε-caprolactone, γ-valerolactone, etc.). Examples of epoxy resins include addition reaction products of pentaerythritol and heterocyclic compounds having one or more oxygen atoms as heteroatoms such as lactones. Examples of epoxy resins include phenols (e.g. phenol, cresol, p-t- Monohydric phenols such as butylphenol, bisphenol A, bisphenol F, bisphenol S
, hydroquinone, polyhydric phenols such as trihydroxybenzene) and aldehydes (e.g. formaldehyde).

Examples include epoxy resins derived from condensates of aliphatic aldehydes such as acetaldehyde and acrolein, and aromatic aldehydes such as benzaldehyde. Particularly preferred epoxy resins include novolac epoxy resins. Some of the above unsaturated carboxylic acid esters are
to AYARA mouth DPH 800 to YARAD DPCA-20, to AYARAD C
-0011■ (all manufactured by Nippon Kayaku ■).

The amount of unsaturated carboxylic acid ester used is 5 to 30 parts by weight, preferably 7 to 25 parts by weight, based on 100 parts by weight of the rubber base material. 5m of unsaturated carboxylic acid ester! ! If less than 1 part of m is used, the dispersion of the unsaturated carboxylic acid metal salt will be poor, and if more than 30 parts by weight of m is used, the surface hardness of the resulting core will be too high and the feel on impact will be too hard, which is undesirable.

In the present invention, the organic peroxide is mainly used as a polymerization initiator for graft polymerization between a rubber base material and an unsaturated carboxylic acid metal salt and an unsaturated carboxylic acid ester. Peroxyketals and dialkyl peroxides are preferred, and n-butyl-4,4- whose half-life temperature is 105°C
Bis(t-butylperoxy)valerate is particularly preferably used.

The amount of organic peroxide used is 1 to 5 parts by weight, preferably 2 to 3 parts by weight, based on 100 parts by weight of the rubber base material. When less than 1 part by weight of the matrix is used, the reaction rate is too low and curing takes a long time, which is impractical.

Even if more than 5 parts by weight is used, not only will there be almost no difference in reaction rate, but physical properties such as repulsion and flight performance will be impaired.

Other conventionally used ingredients, such as antioxidants, may be incorporated into the rubber composition. Antioxidants are used to prevent double bonds in rubber molecules from being broken at the start of polymerization and to prevent aging. Phenolic antioxidants are usually used, preferably 2,2'-methylenebis(4-methyl-〇-1-butylphenol) and 2,2'-methylenebis(4-ethyl-6-t-
butylphenol).

The amount of antioxidant used is 0.3 to 1.0 parts by weight, preferably 0.4 to 0.7 parts by weight, per 1 part by weight of the rubber base material.

Inert fillers may be used to adjust weight.

For example, barium sulfate is used. Further, hydrated silicic acid or the like is used as a reinforcing filler.

The core of the golf ball of the present invention is produced by mixing each component in a mixer until uniform, extruding the obtained rubber composition into a rod shape using an extruder, cutting it into a certain volume, and then filling it into a mold. It is obtained by heating and pressure molding. The heating and pressurization is continued until the composition in the mold is cured, usually at 140 to 180°C.
It is carried out for 15-25 minutes under a pressure of 50-200 to 9/lri.

A solid two-piece golf ball is obtained by coating the core thus produced with an outer skin. The resin constituting the outer skin is not particularly limited, but ionomer resin is preferable, and trans isoprene rubber or thermosetting or thermoplastic resin can also be used.

Of course, the core obtained using the rubber composition of the present invention can be applied not only to the solid two-piece golf balls described above, but also to solid one-piece golf balls and solid three-piece golf balls.

The present invention will be further explained below with reference to Examples.

100 parts by weight (35N!F) of cis-1,4-polybutadiene [BR-Of■Nihon Gosei Rubber Baku Co., Ltd.] as a rubber base material was placed in a 51 type kneader [Shokude Seisakusho @J]. 2.2'-methylenebis(4-methyl-6-t-butylphenol) [TSCRACK MS-6]
■; Ouchi Shinko Chemical Industry ■] 0.5 parts by weight and zinc oxide [
- No. zinc white; Hakusui Chemical Industry ■] 16 parts by weight was added, 3
Kneaded for a minute. After confirming that no zinc oxide was attached to the inner wall and blade of the kneader, we added zinc diacrylate having a particle size of 300 mesh or less as an unsaturated carboxylic acid metal salt [Asada Kagaku Kogyo FI 113 parts by weight and unsaturated carboxylic acid] At the same time, 20 parts by weight of AYARADDPH 80 [to Nippon Kayaku ■] was added as an ester and kneaded for 3 minutes. In addition, hydrated silicate [vN3; Japan Silicani Industry ■] 15
[1 part was added, kneaded for 3 minutes, taken out, allowed to cool, and then kneaded on an 18-inch roll.
A rubber composition was obtained by adding a butylperoxy)murelate diplex.

The dispersion of zinc diacrylate was good. That is, zinc diacrylate was not adhered to the inner wall of the kneader, and no lumps of zinc diacrylate were observed in the rubber composition subjected to tq.

The rubber composition was extruded into a rod shape with a diameter of 29±1 rNR using an extruder and then cut to obtain a cylindrical material for one core weighing 37±0.5 g. This material has a sphere diameter of 39.5IllllII.
Put it in a hemispherical two-part mold, heat harden it at 160℃ for 20 minutes under pressure of 13ON9/α2, take it out, cool it, remove the paris, polish the surface with a centerless polisher, and make a sphere with a diameter of 38. A core of .3 m+ and weight of 134.39 (7) was obtained.

The above-mentioned core was placed in a hemispherical golf ball mold with a diameter of 43 m, and Himilan 1706 (manufactured by DuPont Polychemicals) containing 1% titanium oxide was injected using an injection molding method, and then covered with an outer skin. Ta.

In accordance with a conventional method, the ball was removed, painted, and a mark was printed, and then a transparent paint was applied again to obtain a solid two-piece golf ball.

The physical properties of the core and golf ball obtained as described above were investigated.

The results are shown in Table 1 below.

The surface hardness of the core was measured using a Shore D hardness meter according to 6301-1975, and was found to be 54.

The breaking strength of the core and golf ball was measured using a compression tester with a capacity of 20 m+/min at a speed of 20 m+/min.
．． 1t, 14. It was Ot.

The compression of the golf ball was measured with a PGA compression meter (Addy, Inc., USA) and was found to be 100.

In addition, the flight performance of the golf ball was measured using a swing machine (Two Temper Inc., USA) using a driver (Mizuno, Driver MS-1)1, and the carry when hit at a head speed of 45 m/s was 190.2.
m, run 14.8 TrL1 distance 206.5 doors.

Furthermore, as a result of test shots by 20 golf players with handicaps of 2 to 15, it was reported that the feel at impact was very good, comparable to that of the currently preferred solid sea piece golf ball with Comparative Example 2 as its core. Ta.

Examples 2 to 5 Rubber compositions were obtained in the same manner as in Example 1 using the components shown in the table.

When the unsaturated carboxylic acid ester and zinc diacrylate were introduced and kneaded, they did not adhere to the inner wall of the kneader or the blade. There was no lump of zinc diacrylate in the obtained rubber composition.

Table 1 also shows the results of a hitting feel test conducted by players in the same manner as in Example 1.

Comparative Example 1 YARAD DP as unsaturated carboxylic acid ester
A rubber composition having the same composition as in Example 1 was obtained, except that trimethylolpropane trimethacrylate was used in place of IIA and the amount of zinc oxide was increased to adjust the weight.

Although zinc diacrylate did not adhere to the inner wall of the kneader or the blade, the core was soft and its breaking strength was low.

In addition, the PGA compression and breaking strength of golf balls having this core were low, the flight distance was short, and the feel at impact was poor.

Comparative Example 2 Example 1 except that zinc diacrylate whose surface was coated with 14 parts by weight of zinc stearate was used as the unsaturated carboxylic acid metal salt, and the unsaturated carboxylic ester was not used.
A rubber composition having the same composition was obtained.

When the antioxidant and zinc oxide were added to the rubber base material and kneaded for 3 minutes, no adhesion was observed on the inner wall and blade of the kneader, but when the zinc diacrylate was subsequently added and kneaded for 3 minutes, the kneader - White plate-like deposits were partially formed on the inner wall and blade.

As a result of scraping off this adhered substance and measuring the loss on burning, it was confirmed that the adhered substance was zinc dimethacrylate.

(1) Japan Synthetic Rubber ■ B 01 (2) 2.2'-Melunbis (4-Mejirou (i-
t-Butylphenol): Iriuchi Shinko Kagaku Kogyo ■ Tsukuraku N5-6 ■ Hakusui Chemical Industry - No. 1 Zinc White 6) Zinc diacrylate (particle size 300 mesh or less): Asada Chemical Co., Ltd. ■ ■ Coated with 14-fold isomorphic O zinc stearate Zinc diacrylate (particle size 300 mesh or less): Asada Chemical Co., Ltd. ■ ■ Dipentaerythritol Pentaacrylate: Nippon Kayaku ■ ^YAR^◎ DPHA ■ Epoxy acrylate: Nippon Kayaku ■ AYARAD C-0011 ■ Dipentaerythritol AYARAD D to the acrylic acid ester of the addition reaction product of ε-kabu[]lactone and Nippon Kayaku
PC^-20 ■ Trimethylolpropane trimethacrylate: Shin Nakamura Chemical Industry ■ 08 Silicani Industry 1lvN3 6e Chemical Nouri ■ Trigonox 17 (1/), lower margin) As shown in Comparative Example 2 of Effect of Invention, zinc diacrylate Although coating with zinc stearate generally provides a satisfactory golf ball, there are problems with the incorporation of the zinc diacrylate into the rubber substrate.

As shown in Comparative Example 1, the problem of kneading zinc diacrylate into the rubber base material can be solved by using zinc diacrylate and trimethylolpropane trimethacrylate together, but the resulting core and golf ball are soft and have low breaking strength. The ball is also low, so the feel of the shot is also poor.

In the present invention, by using zinc diacrylate and a specific unsaturated carboxylic acid ester in combination, the problem of kneading zinc diacrylate into a rubber base material was solved, and a core and golf ball having satisfactory physical properties were obtained. .

Claims (3)

[Claims] (1) For 100 parts by weight of polybutadiene rubber containing 40% or more of cis-1,4 structure, 7 to 14 parts by weight of unsaturated carboxylic acid metal salt, 5 to 5 parts by weight of unsaturated carboxylic acid ester of pentahydric or higher alcohol or epoxy resin A solid golf ball having a core made of a cured product of a rubber composition containing 30 parts by weight and 1 to 5 parts by weight of an organic peroxide. (2) The golf ball according to claim 1, wherein the unsaturated carboxylic acid metal salt is zinc diacrylate or zinc dimethacrylate. (3) The golf ball according to claim 1, wherein the pentahydric or higher alcohol is dipentaerythritol or a derivative thereof.