JPS6137178A - 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] [Industrial application field] The present invention relates to solid golf balls.

[Conventional technology]

Conventionally, regarding the composition of the inner core of solid golf balls such as two-piece golf balls, for example,
-19615 Publication, Japanese Patent Publication No. 56-9347, Japanese Patent Application Publication No. 51-92225, Japanese Patent Publication No. 53-83834
No. 1, JP-A-52-21933, JP-A-52-21933, JP-A-52-21933
A large number of patent applications have been filed, such as in Japanese Patent No. 21932, which describe the use of a metal salt of acrylic acid or a metal salt of methacrylic acid as a co-crosslinking agent to obtain a sled/7-dove golf ball with good flight characteristics. It is reported that

[Problem that the invention seeks to solve]

However, although the solid golf ball has good flight characteristics, it gives a hard feel and is disliked by some users. For example, most solid golf balls on the market today have a ball combination resolution of between 95 and 105, which is higher than the ball compression of a wound golf pole of 80.
This is higher than ~100 and causes a hard feel when hitting the ball. However, solid golf poles with ball compression comparable to those of thread-wound golf balls are rarely seen, but because they are soft, they have a low coefficient of repulsion and poor flight characteristics. The emergence of a solid golf ball with good properties is desired.

[Means for solving problems]

The present inventor has conducted various studies in view of the above circumstances, and has found that when forming an inner core, when 25 to 45 parts by weight of zinc acrylate is used as a co-crosslinking agent per 100 M parts of rubber, Valmitic acid, stearic acid or myristic acid as an agent is 5 to 25% by weight based on zinc acrylate.
When 20% by weight or more of zinc oxide is added to zinc acrylate as a co-crosslinking aid, and 1 to 3% by weight of a reaction rate retardant to zinc acrylate, the ball compression is 80 to 95 in PGA. It was discovered that a solid golf ball with good flight characteristics could be obtained by using the method, and the present invention was completed.

In other words, it is believed that the zinc acrylate causes a polymerization and grafting reaction with a peroxide-based initiator such as dicumyl peroxide, and functions as a co-crosslinking agent, as well as a reactive filler. However, in order to obtain higher impact resilience, it is desirable to reduce the amount as much as possible. In consideration of such circumstances, the present invention has discovered factors that increase ball compression, as shown in Experimental Examples 1 to 3 below, and has improved the set value of ball compression while reducing the amount of zinc acrylate blended. 80 to 95, which is lower than conventional solid golf balls, and as shown in Experimental Examples 4 to 5, a reaction rate retardant is added to suppress the runaway reaction of acrylic acid and reduce the width of the hardness distribution of the inner core. A solid golf ball with low ball compression, good feel, and good flight characteristics can be obtained.

In the present invention, zinc acrylate is blended in an amount of 25 to 45 parts by weight per 100 parts by weight of rubber; however, if the amount of zinc acrylate is less than 25 parts by weight, the ball compression and restitution coefficient will be low, and if it exceeds 45 parts by weight, the ball compression and restitution coefficient will be low. This is because gin becomes too expensive.

In addition, higher fatty acids such as valmitic acid, stearic acid, and myristic acid are 5 to 25% by weight based on zinc acrylate.
However, if the amount of higher fatty acids such as valmitic acid is less than 5% by weight, it will be difficult to achieve the desired ball compression and the durability will be low. This is because if it exceeds this, the volume fraction of rubber such as polybutadiene becomes small and the impact resilience is inhibited.

Zinc oxide is blended at least 20% by weight with respect to zinc acrylate;
This is because if it is less than % by weight, it becomes difficult to achieve the desired ball compression.

In addition to acting as a co-crosslinking aid, zinc oxide also functions as a weight adjuster for the inner core, so the upper limit of its amount is not particularly limited and may vary depending on other ingredients, the size of the golf pole, etc. Although it can be changed in various ways, it is usually rubber 10
It is blended up to about 60 parts by weight with respect to 0 parts by weight.

As the reaction rate retardant, for example, 2,5-di-ter
T-butylhydroquinone is used, and this reaction rate retardant is blended in an amount of 1 to 3% by weight based on zinc acrylate as described above. This is because if the reaction rate retardant is less than 1% by weight, it will have little effect in suppressing the crosslinking reaction in the center of the inner core, and it will be difficult to obtain an inner core with a narrow hardness distribution. This is because if the amount exceeds % by weight, the crosslinking reaction becomes too slow, resulting in poor production efficiency.

In the present invention, the ball compression is specified as 80 to 95 on the PGA scale because in order to obtain a golf pole with good feeling, it is necessary to keep the ball compression to 95 or less, and the ball compression is less than 80. This is because it is difficult to obtain a golf ball with good flight characteristics due to its high rebound resilience.

In order to obtain the inner core of the solid golf ball of the present invention, a rubber serving as a base material, an initiator, and the like are required in addition to the above-mentioned components. As the rubber, for example, butadiene rubber such as high-cis-1,4-polybutadiene, or a blend of butadiene rubber and natural rubber or styrene-butadiene rubber can be used, but especially those containing 90% by weight or more of high-cis-1,4-polybutadiene are used. preferable.

Examples of the initiator include dicumyl peroxide-11,1-bis(tert-butylperoxy) 3
, 3,5-trimethylcyclohexane and the like are preferably used. The amount of these initiators used is the same as before.
The amount is usually 0.5 to 5.0 parts by weight.

In addition, the rubber composition for the inner core may optionally contain additives such as anti-aging agents, fillers such as barium sulfate, calcium carbonate, silica, etc. in addition to the above-mentioned components.

The cover that covers the inner core is preferably made of, for example, an ionomer as the main material, to which other polymers such as nylon or additives such as titanium dioxide, dyes, pigments, and anti-aging agents are added. Ru.

The present invention is applicable not only to two-piece solid golf poles as described above, but also to solid golf poles with a multilayer structure of three or more layers, such as a three-piece solid golf ball in which an intermediate layer is formed on the inner core and a cover is coated on the intermediate layer. also applies.

〔Example〕

Next, the present invention will be explained in more detail with reference to experimental examples and examples. In addition, all the blending parts in the experimental examples and examples are based on parts by weight.

Experimental Example 1 Using zinc acrylate as a co-crosslinking agent, the relationship between the amount of zinc acrylate blended and ball hardness (ball compression measured by PGA) was investigated, and the results are shown in FIG. In addition, the amount of zinc acrylate blended on the horizontal axis in FIG. 1 is the number of parts blended with respect to 100 parts by weight of rubber (cis-1°4~polybutadiene).

Based on the formulations A and B shown in Table 1, the resulting rubber composition was kneaded with a roll, and a diameter of about 30 mm and a length of about 50 mm was obtained.
A plug with a diameter of 38.1 mm was prepared and crosslinked by heating and compression molding at 165°C for 30 minutes (hereinafter referred to as vulcanization).
We obtained a solid inner core of . In addition, the cis-1,4 used
-Polybutadiene is BROI manufactured by Nippon Gosei Rubber Co., Ltd., and the same applies to subsequent formulations.

Table 1 Next, the solid inner core was covered with a cover by injection molding to obtain a two-piece solid golf ball having a diameter of 42.8 mm. Note that Kahaha Surlin 1707 (trade name, an ionomer manufactured by DuPont) was used.

The composition for forming the inner core of a two-piece solid golf pole is determined by considering the hardness, weight, rebound, and crank resistance of the inner core, and the first consideration is weight and hardness. It should be noted that the hardness here refers to the hardness of the ball after being covered with a cover, and will hereinafter be expressed in terms of ball compression using PGA.

As shown in Figure 1, in order to achieve a ball compression of 80 to 95 on the PGA scale with formulation A, 35 to 45 parts by weight of zinc acrylate is required, but the filler was changed from barium sulfate to zinc oxide. In formulation B, the zinc acrylate was 30 to 40 parts by weight and the ball compression was 80 to 40 parts by weight.
95, which is less zinc acrylate than in the case of formulation A.

From this result, it can be seen that: 1) Increasing the amount of zinc acrylate (the amount of initiator remains constant) increases the ball compression. ■
Combining zinc acrylate and zinc oxide ink and ball complex, John found that it was even higher.

In other words, the more zinc acrylate that is graft-crosslinked to polybutadiene and has a three-dimensional structure, the higher the crosslinking density becomes. When zinc oxide is added to the polybutadiene, pseudo-ionic bonds are formed with the grafted zinc acrylate, creating a network structure. It is estimated that because the ball becomes denser, the hardness, that is, the ball compression, further increases. Note that this phenomenon was unique to zinc acrylate and was not observed in any other zinc acrylate.

Experimental Example 2 The effects of adding various fillers containing zinc oxide were investigated, and the results are shown in FIG.

The formulation used was formulation C shown in Table 2, and the ball compression was measured on a two-piece solid golf ball obtained by preparing a solid inner core in the same manner as in Experimental Example 1 and then covering it.

Table 2 As shown in Figure 2, the addition of substances that reduce ball compression (for example, Ca(OH)2, Mg0
), those with little change in ball compression (e.g. S'i02, BaSO4, Fe2O3, CaCO3
, 7, r02, PE powder, Zn powder, MgC03), which has the effect of slightly increasing ball compression (Z
n 02 ), but zinc oxide (Z n O)
is by far the most effective at increasing ball compression.

Experimental Example 3 Next, the effect of adding valmitic acid was investigated, and the results were used in the third experiment.
Shown in the figure.

The formulations were as shown in Table 3 and E, and the composure solution was measured on a two-piece solid golf pole obtained by producing a solid inner core in the same manner as in Experimental Example 1 and then covering it with a cover. .

Table 3 As shown in Figure 3, in formulations containing zinc oxide without l or M, palmitic acid is added to each f, kf, etc.
It inhibits vulcanization and causes ball compression (heating). However, zinc oxide
Even if more than 100% of zinc acrylate, zinc oxide, and valmitic acid are added, the price will increase as the amount of lumitic acid is added. Only when zinc oxide is present in the system does the cross-linked structure become stronger and an excellent highly elastic material is obtained. Ball compression decreases as the amount of palmitic acid increases because it makes the atmosphere in the rubber acidic and suppresses the generation of peroxide radicals. It is thought that this causes the crosslinked structure to become stronger, resulting in a ball with high compression and high elasticity.

In addition, in order to investigate whether zinc salts of higher fatty acids have the effect of increasing ball compression even in the absence of zinc oxide, the amount of zinc stearate added was determined using Formulation F containing zinc stearate. We investigated the relationship between
As shown in the figure, when zinc stearate alone does not contain zinc oxide, it does not have an ionic bonding effect and only acts as a plasticizer, and as the amount of added zinc stearate increases, ball compression increases. has become lower.

Experimental Example 4 Using the formulation GL shown in Table 4, a solid inner core was prepared in the same manner as in Experimental Example 1, and then covered with a cover to obtain a two-piece solid golf ball. The ball compression and restitution coefficient of these two-piece solid golf balls were measured, and the results are shown in Table 4.

As shown in formulations G-J in Table 4, the coefficient of restitution is approximately proportional to the ball compression, and the lower the ball compression, the lower the coefficient of restitution. therefore,
If you place emphasis on feel and make the ball softer, that is, lower the ball compression, the rebound will decrease. However, as an anti-aging agent, it has the effect of retarding the reaction rate.
, 2.5-di-tert-butylhydroquinone), L showed a high restitution coefficient even though the ball compression was lower than that of Formulation I.

Based on the above findings, we conducted various studies on hindered phenol-based anti-aging agents to determine whether they have the effect of increasing the repulsion coefficient.
In addition to tert-butylhydroquinone, 2,4-di-
Tert-butyl-4-methylphenol, 4,4-thiobis(5-tert-butyl-3-methylphenol), mono(α-methylbenzyl)phenol, mercaptobenzimidazole, dihydroxybisphenol, etc. are also effective, but In particular, the aforementioned 2,5-di-te
It was found that rt-butylhydroquinone is highly effective.

When these anti-aging agents are used, golf poles with a high coefficient of restitution despite low ball compression can be obtained because these anti-aging agents act as reaction rate retarders and slow down the vulcanization rate. This is thought to be based on suppressing the polymerization and grafting reactions of zinc acrylate, which are runaway reactions.

Experimental Example 5 In order to examine the vulcanization characteristics of individual materials using the formulations shown in Table 5, a test was first conducted using a curelastometer, and the results are shown in FIG. Test at 160℃, Arc ±
It was performed at 1°.

As shown in Table 5 and Figure 4, blend P vulcanizes more slowly and has a lower degree of vulcanization than blends M and H. Usually, such a formulation has a low degree of vulcanization, making it difficult to achieve ball compression, and is often not suitable for golf balls. However, in reality,
As shown below, a golf ball with a high coefficient of restitution can be obtained even though the ball compression is low.

That is, using the above formulations M, N, and P, a solid inner core was obtained by vulcanization at 160° C. for 30 minutes in the same manner as in Experimental Example 1, and then a cover was applied. The coefficients were measured and the results are shown in Table 6. In addition, the hardness distribution of the inner core of the golf ball was investigated, and the results are shown in Table 6. Note that the hardness of the inner core is determined by a JIS-C type hardness meter.

Table 6 As shown in Table 6 above, in the case of formulation P, the coefficient of restitution is higher than in the cases of formulations M and H, although the ball compression is lower.

This is because the hardness distribution of their inner cores is that in compound M1N, the surface part is hard and the center part is soft, and there is a considerable difference in the degree of vulcanization, whereas in compound P, the hardness is low overall, and The width of the hardness distribution is narrow (this is thought to be due to uniform vulcanization).

In other words, in the case of the inner core of a golf ball, there is a distance from the surface to the center, so under normal conditions the vulcanization rate between the surface and the center is quite different. However, in the center of the inner core, the pressing temperature is reached once due to the amount of heat given from the outside, and the polymerization and grafting reaction of zinc acrylate progresses, and once the reaction begins, the reaction stops due to self-heating. begins to progress rapidly. Therefore, the reaction rate is faster at the center than at the surface, and when the surface is brought to the desired degree of vulcanization, the center becomes over-vulcanized, resulting in a hardness distribution of outer hardness and inner softness. By adding tert-butylhydroquinone, the runaway reaction of zinc acrylate in the center is suppressed, and a homogeneous vulcanizate with a narrow hardness distribution from the surface to the center can be obtained.

Examples 1 to 3 and Comparative Examples 1 to 2 Rubber compositions for inner cores having the formulations shown in Table 7 were heated at 160°C for 30 minutes.
A solid inner core was prepared by vulcanization for a minute, and then a cover was covered by injection molding to obtain a two-piece solid golf ball having a diameter of 42.8 mm.

Ball weight, pole compression, and restitution coefficient were measured for the resulting two-piece solid golf pole. The results are shown in Table 7. The Naori bar composition is 100 parts by weight of Surlyn 1707 (mentioned above) and 2 parts by weight of titanium dioxide.
As shown in Table 7, the balls of Examples 1 to 3 of the present invention had a high coefficient of restitution, good feel, and good flight characteristics despite having low ball compression. shows that it is excellent. On the other hand, the ball of Comparative Example 1 is the mainstream of conventional two-piece solid golf balls, but although it has a high coefficient of restitution and good flight characteristics, it has high ball compression, gives a hard feel when hit, and has a hard feel. The ring is bad. Further, the ball of Comparative Example 2 had low ball compression and good feel, but had a low repulsion coefficient and poor flight characteristics.

〔Effect of the invention〕

As explained above, according to the present invention, the feel of a solid golf ball is improved, and a solid golf ball with good feel and good flight characteristics can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the blending amount of zinc acrylate and ball compression, and FIG. 2 is a diagram showing the influence of the addition of various fillers on ball compression. FIG. 3 is a diagram showing the relationship between the amount of valmitic acid added and ball compression, and FIG. 4 is a diagram showing the vulcanization characteristics of blends M, N, and P in Experimental Example 5. Patent applicant Sumitomo Rubber Industries, Ltd. Figure 1 25 ao a540 45 Amount of zinc acrylate (number of parts) Figure 2 Amount of filler added (number of parts) Figure 3 Amount of palmitic acid added (number of parts) Figure 4 Time (Minutes) Procedural amendment (spontaneous) September 20, 1980 1, Indication of the case 1982 Patent Application No. 158241 2, Name of the invention Solid Golf Pole 3, Person making the amendment Relationship to the case Patent applicant Address: 1-1 Tsutsui-cho, Chuo-ku, Kobe, Hyogo Prefecture
), 27 Address: 1-23 Kitahorie-chome, Nishi-ku, Osaka Yoda Building Yotsubashikan Column 6 of "Detailed explanation of the invention" of the specification, No. 7 on page 26 of the specification of the contents of the amendment Correct the body as follows.

Claims (3)

[Claims] (1) When blending 25 to 45 parts by weight of zinc acrylate to 100 parts by weight of rubber as a co-crosslinking agent, 5 to 25 parts of palmitic acid, stearic acid or myristic acid to zinc acrylate as a co-crosslinking aid. It has an inner core containing 20% by weight or more of zinc oxide based on zinc acrylate as a co-crosslinking aid and 1 to 3% by weight of a reaction rate retardant based on zinc acrylate, and the ball compression is P.
A solid golf ball having a GA rating of 80 to 95. (2) The solid golf ball according to claim 1, wherein the reaction rate retardant is 2,5-di-tert-butylhydroquinone. (3) The solid golf ball according to claim 1 or 2, wherein the rubber contains 90% by weight or more of high-cis polybutadiene.