JPH0450938B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a solid-state golf ball made of a compounded composition which has excellent impact resistance and improved ball initial velocity to increase flight distance through three-dimensional network crosslinking, and a method for manufacturing the same. Golf balls used for competitions and practice are broadly classified into three types: triple-structured balls (spin-wound balls), double-structured balls (two-piece balls), and monolithic-structured balls (one-piece balls). In general, balls with a triple structure have poor cut resistance in irons, and even in balls with a double structure, the Surlyn resin on the skin is thermoplastic, so it is easily scratched, and the core is also prone to cracking. It is a known fact that it was difficult to achieve both flight distance and durability. In recent years, solid golf balls have been used for competitions and practice, and although such solid golf balls have been published, for example, in Japanese Patent Publication No. 19615/1987, these have deteriorated in impact resistance over time. Its properties had significantly decreased, and cracking had occurred over time. In addition, in JP-A-54-60033, the impact resistance was improved by a rubber composition, but the present invention improves these because it is economically unfavorable in the action and kneading of MG rubber. This invention was developed with the aim of solving these problems with a ball of one-piece construction. In particular, the drawback of cis-1.4 polybutadiene, which deteriorates over time and has poor impact resistance, has been overcome by the combined use of natural rubber, ethylene propylene rubber, and ethylene-vinyl acetate copolymer, resulting in improved impact resistance. The present invention first provides (a) a polybutadiene having a cis structure of at least 85%, preferably 97% or more;
Polybutadiene with cis-1.4 structure of more than 70%
(b) 3-15% by weight of natural rubber, (c) 2-5% by weight of ethylene propylene rubber, and (d) ethylene-vinyl acetate copolymer, preferably with a vinyl acetate content of 35% or more. 5 to 10% by weight of the rubber composition (a+b+c+
d) 100 parts by weight, (e) 20 to 45 parts by weight of a di- to tetravalent metal oxide, preferably zinc oxide (however, zinc oxide other than that used for neutralizing methacrylic acid is (used for adjusting the weight of the ball), (f) 26 to 32 parts by weight of an unsaturated monocarboxylic acid having 3 to 4 carbon atoms, preferably methacrylic acid, (g) 3 to 5 parts by weight of an organic peroxide. parts by weight, and (h) 1 to 5 parts by weight of an organic accelerator thiazole (a+b+c+d+e+f+g
To provide a solid-state golf ball characterized by comprising +h), which has excellent impact resistance and ball initial velocity improved by cross-linking a three-dimensional network, thereby increasing flight distance. This is what I am trying to do. The present invention furthermore provides (a) 70 to 90% by weight of 1.4 polybutadiene having a cis structure of at least 85%, (b) 3 to 15% by weight of natural rubber, and (c) 2 to 5% by weight of ethylene propylene rubber. , and further (d) 5 to 10% by weight of ethylene vinyl acetate copolymer, and (e) 20 to 20 to 40% of di- to tetravalent metal oxide to 100 parts by weight of the total amount (a+b+c+d) of the rubbery composition. (f) 26 to 32 parts by weight of an unsaturated monocarboxylic acid having 3 to 4 carbon atoms, (g) 3 to 5 parts by weight of an organic peroxide, and (h) organic promoter thiazoles.

[Formula] Preferably, 2-mercaptoben Zothiazole

A blended composition (a+b+c+d+
This is a manufacturing method for solid-state golf balls characterized by using three-dimensional network cross-linking (e+f+g+h), which provides excellent impact resistance, improved ball initial velocity, increased flying distance, and improvements in all aspects. Our goal is to provide a solid state golf ball that will satisfy your needs. The main configuration and its numerical limitations will now be explained. If the natural rubber (b) is less than 3% by weight, the impact resistance will be poor, and if it exceeds 15% by weight, it will be too soft to be used. (c) Ethylene propylene rubber If it is less than 2% by weight, the impact feel will be poor, and if it exceeds 5% by weight, the impact properties will be poor. (d) Ethylene vinyl acetate copolymer 5
If it is less than 10% by weight, the impact sound will be poor, and if it exceeds 10% by weight, the sound will be too high, which is not desirable. If the above (e) di- to tetravalent metal oxide is less than 20 parts by weight, both hardness and weight will be insufficient and the ball performance will deteriorate, and if it exceeds 45 parts by weight, it will become hard and overweight, so both are preferable. do not have. (f) As the unsaturated monocarboxylic acid having 3 to 4 carbon atoms, for example,

[Formula] [Here, R is a hydrogen atom and R' is a hydrogen atom or an ethyl group]. If the amount of methacrylic acid is less than 26 parts by weight, a suitable compression value will not be obtained, and if it exceeds 32 parts by weight, the elasticity will decrease and the impact sound will be low, which is not preferable. (g) As the organic peroxide, 1,1-bis(t-butylperoxy)3,3,5-tonomethylcyclohexane or the like is used. If it is less than 3 parts by weight, the crosslinking effect will be insufficient, and if it exceeds 5 parts by weight, it will become brittle, which is also undesirable due to economical issues. (h) Organic accelerator thiazole If less than 1 part by weight, no significant effect is observed, and if it exceeds 5 parts by weight, it becomes soft, which is not preferable. Also, considering its effect, there is no need for it in terms of quantity. By cross-linking the three-dimensional network with the above-mentioned compounded composition, extremely high repulsion characteristics, excellent impact resistance, ball initial velocity are improved, distance is increased, and durability is especially required for competition balls. It is useful and popular as a practice ball. By sufficiently cross-linking the three-dimensional network in the compounded composition composed of the above, it has extremely high repulsion characteristics, excellent impact resistance, and improves the ball's initial velocity and increases flight distance, making it useful as a competition ball. In addition, there is an advantage that the performance as a practice ball that particularly requires durability is improved. Firstly, the cis content of cis-1,4 polybutadiene in the rubber composition is 85% or more, preferably 97% or more, which guarantees high repulsion, but since impact resistance and cuttability are poor, in the present invention, acetic acid is not used. Vinyl content 35%
Cut resistance has been improved by adding the above ethylene vinyl acetate copolymers. However, ethylene-vinyl acetate copolymer increases strength and improves cutability, which makes it difficult to elongate, but it also makes noise, so adding ethylene-propylene rubber improves hardness, impact sound, and improves impact resistance and natural repulsion. gender is corrected. Second, if an organic accelerator thiazole, especially 2-mercaptobenzothiazole (for example, Sanshin Kagaku Co., Ltd. product name Suncellar M, etc. can be used) is added to the composition, organic It was crosslinked with peroxide alone, causing variations in hardness and impact resistance, and lacking in crosslinking stability.
Addition of organic accelerator thiazoles such as mercaptobenzothiazole makes the degree of crosslinking of the crosslinked product uniform and improves hardness, natural rebound and impact resistance. In addition, thiazoles such as 2-mercaptobenzothiazole have the characteristic of softening.
1,1-bis(t-butylperoxy)3,3,
It is corrected by adding 5-trimethylcyclohexane or the like. A solid state golf ball according to the present invention is manufactured as follows. First, mix the blended rubber of the rubbery composition (a+b+c+d) and zinc oxide adjusted to an appropriate amount with a Banbury mixer or mixing roll, etc.
Mix thoroughly for about 10 minutes at a temperature of 120℃, and methacrylic acid is gradually added to the state in which zinc oxide is well dispersed in the blended rubber (a + b + c + d), and the zinc oxide and methacrylic acid react in the rubber. to produce metal salts. Thereafter, 1,1-bis(t-butylperoxy) 3,
Add 3,5 trimethylcyclohexane and 2-mercaptobenzothiazole M and knead for about 5 minutes until uniform. The rubber composition thus obtained is heated and molded in a desired mold to obtain a solid state golf ball. The crosslinking temperature is 140°C to 180°C and the crosslinking time is 10 to 30 minutes. Next, examples according to the present invention and their physical properties will be shown. Regarding the crosslinking temperature, the ball was crosslinked at 160°C for 12 minutes. Breaking value (impact resistance) is the number of times a 5 kg weight is dropped from a height of 150 cm onto a golf ball placed on a flat iron plate (equivalent to a driver) until it breaks, and is the average of 20 balls tested. It is a value.
Also, for balls that did not break after 500 hits, the test was discontinued after the number of falls reached 500 times. Repulsion elasticity is expressed as the value (%) when a ball is dropped from a height of 120 cm onto a 25 mm thick iron plate and bounces back up. Compression values are based on the USA established stroke system compression meter called (Accu-TEST). The initial velocity of the ball is 50m/s using a golf hitting test machine.
The initial velocity of the ball when hit with a head speed of is expressed in m/sec.

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[Table] The above table and the rubbery polymer (a+b+c+
Comparison of the effect of adding ethylene propylene rubber in (c) to d), the table shows a comparison of methacrylic acid,
The tables show the effect of adding the organic promoter thiazoles.

Claims (1)

[Claims] 1 (a) Having at least 85% cis structure
1.4 Polybutadiene 70-90% by weight, (b) Natural rubber 3
~15% by weight, (c) 2 to 5% by weight of ethylene propylene rubber, and (d) ethylene vinyl acetate copolymer 5
(e) 2 to 4 parts by weight per 100 parts by weight of the total amount of rubber composition (a+b+c+d) composed of ~10% by weight.
20 to 45 parts by weight of valent metal oxide, (f) 3 to 4 carbon atoms
26 to 32 parts by weight of an unsaturated monocarboxylic acid having
A solid state golf ball comprising a blended composition (a+b+c+d+e+f+g+h) comprising (g) 3 to 5 parts by weight of an organic peroxide and (h) 1 to 5 parts by weight of an organic accelerator thiazole. . 2 (a) Has at least 85% cis structure
1.4 Polybutadiene 70-90% by weight, (b) Natural rubber 3
~15% by weight, (c) 2 to 5% by weight of ethylene propylene rubber, and (d) ethylene vinyl acetate copolymer 5
(e) 2 to 4 parts by weight per 100 parts by weight of the total amount of rubber composition (a+b+c+d) composed of ~10% by weight.
20 to 45 parts by weight of valent metal oxide, (f) 3 to 4 carbon atoms
26 to 32 parts by weight of an unsaturated monocarboxylic acid having
(g) 3 to 5 parts by weight of an organic peroxide and (h) 1 to 5 parts by weight of an organic accelerator thiazole (a+b+c+d+e+f+g+h) are used to effect three-dimensional network crosslinking. A method of manufacturing a solid state golf ball.