JPS63220889A - Two-piece 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 two-piece solid golf ball comprised of a solid core and a cover.

(Prior art and its problems) Conventional 1. A thread-wound golf ball, in which a cover is placed on a thread-wound core, is commonly used.

However, thread-wound golf balls do not increase flight distance very much, and instead, so-called two-piece solid golf balls have been developed, which consist of a solid core and a cover integrally molded from a rubber composition.

The two-piece solid golf ball is characterized by its low spin rate and high launch angle, which creates an ideal parabolic trajectory and increases flight distance. In addition, since the ball has a low landing angle due to the parabolic trajectory, the ball tends to roll a lot.

However, these characteristics of the two-piece solid golf ball conversely make it difficult for the ball to spin when it is in the iron seat, making it difficult for the ball to stop. Additionally, it is disliked by some golfers because of its hard feel when hitting the ball.

In order to overcome the shortcomings of this two-piece solid golf ball several times over, we lowered the bending elastic modulus of the two-piece solid golf ball's cover to eliminate the hardness when hitting it, and also increased the contact area of the ball when hitting it to reduce spin. It has been proposed to make it easier to
(See JP-A-61-149178). However, although these methods make it easier to hit the ball and improve the feel of the ball, the trajectory is no longer parabolic and has a slightly floating trajectory like a conventional thread-wound ball, which is a characteristic of two-piece golf balls. The flying distance decreases.

Therefore, at present, a two-piece solid golf ball with necessarily satisfactory performance has not been obtained.

(Means for Solving the Problems) The present inventors have focused on the compressive strength of a two-piece solid golf ball, the hardness distribution of the solid core, and various performances of the cover, and have improved the performance of the ball when hitting the ball by improving these. It has been found that a two-piece solid golf ball can be obtained that has a soft ring and maintains the flight distance obtained with a conventional two-piece golf ball.

That is, the present invention provides a two-piece solid golf ball comprising a solid core and a cover formed from a rubber composition containing a base rubber, a co-crosslinking agent, an organic peroxide, and a crosslinking accelerator. 101
The hardness of the part less than m is 60 to 7 on the JI S-C type hardness tester.
9.Hardness of the part exceeding 10+u from the center is 80-90
, the cover has a thickness of 1.5 to 2.0 cm, and the resulting ball has a compressive deformation ff of 11.9 to 2 when the initial load 10 is multiplied by 9 to the light load 130 by 9, 4 a
To provide a two-piece solid golf ball characterized by having a m.

The golf ball of the present invention is designed so that the solid core is integrated with the solid core, but has the performance of a double structure, and is further covered with a thin cover, with a large number of dimples arranged on the surface of the solid core. In this way, the designed golf ball does not generate too much spin when hit, and when hit with a driver, it flies along a conventional parabolic trajectory, extending flight distance. In addition, the hardness of the center of the solid core is softer than that of the outer periphery, and as a result, shock is absorbed at the center, providing a soft touch feel.

The base rubber used in the present invention may be any suitable material conventionally used in two-piece solid cores. Preferably, cis-
1,4-polybutadiene rubber is particularly preferred, and if desired, natural rubber, polyisoprene rubber, styrene-butadiene rubber, etc. may be appropriately blended with the polybutadiene rubber.

Examples of organic peroxides to be incorporated into the rubber composition include dicumyl peroxide and di-butyl peroxide, with dicumyl peroxide being particularly preferred. The blend m of the organic peroxide is 0.5 to 3.0 parts by weight, preferably 1.0 to 2.0 parts by weight, based on 100 parts by weight of the listed rubber.
Parts by weight are preferred.

The co-crosslinking agent is not particularly limited, but metal salts of unsaturated carboxylic acids, especially -valent or divalent unsaturated carboxylic acids having 3 to 8 carbon atoms (for example, acrylic acid, methacrylic acid, etc.) Examples include metal salts. Particularly preferred is zinc acrylate. The co-crosslinking agent, in addition to the original crosslinking of the base rubber by vulcanization, reacts with the unsaturated bonds of the base rubber to create a straw-bridge-like bond between the same atoms.
Improve ball performance. The amount of the co-crosslinking agent is 25 to 35 parts by weight, preferably 2 parts by weight, based on 100 parts by weight of the base rubber.
It is 8 to 32 parts by weight. If it is less than 25 parts by weight, the ball will not have enough hardness, and if it exceeds 35 parts by weight, it will become too hard, resulting in disadvantages such as impairing the feel when hitting.

The rubber composition used in the two-piece solid golf ball of the present invention further contains a crosslinking accelerator. Examples of crosslinking accelerators include N,N'-m-phenylene bismaleimide and the like. The amount of crosslinking accelerator added to the base rubber is 1
A suitable amount is 0.5 to 1.5 parts by weight per 0.00 parts by weight. There is no effect if the output is less than this range, and 1,5 M
If the amount is more than m parts, vulcanization is accelerated too much, leading to overvulcanization, which impairs impact resilience, which is not desirable.

The rubber composition used in the golf ball of the present invention may contain additives such as fillers and antioxidants, if necessary. Zinc oxide, barium oxide, etc. are common examples of fillers, and the blending amount depends on the specific gravity and size of the cover and solid core, the ball weight standard, etc., and is not particularly limited, but it is usually based on the base material. Rubber+oOffiff1
10 to 60 parts by weight. .

The rubber composition is prepared by kneading the above components in a conventional kneading machine, such as a Nigu,
Thoroughly knead using an internal mixer or roll,
Compression or injection molding is performed in a mold for a solid core, and the molded product is heated and cured at a temperature sufficient for curing, for example, 130 to 170 ° C. If the diameter is large size, it is about 38.8 to about 39.8 xx , in the case of a small size golf ball, a solid core of about 37°3-3B, 3xx is obtained.

In the present invention, in particular, the solid core is
The hardness of the center part is 60 to 79, preferably 65 to 75, and about 10z from the center.
The outer circumference beyond z is 80-90, preferably 82-85
Adjust the vulcanization conditions and other conditions as appropriate so that the Although this difference in hardness distribution is not particularly clear, it cannot be produced solely by vulcanization conditions such as vulcanization temperature and pressure. It is thought that this can be achieved by using 0.5 to 1.5 parts by weight.

The hardness is determined by a method based on JIS-6301.
Measure with an S-C type hardness meter. The hardness meter is a polymer meter (
A JC type manufactured by Co., Ltd. was used. If the hardness of the central portion is less than 60, the durability of the solid core deteriorates, which is not preferable. If it is larger than 79, the impact upon hitting will be large, which is unfavorable in terms of feel.

If the hardness of the outer periphery is less than 80, even if the hardness of the center is in the range of 60 to 79, the inner core as a whole will be slightly under-vulcanized and the compressive strength of the ball will be low, and the amount of compressive deformation will be large, resulting in poor performance. Unfavorable on the ring surface.

The solid core obtained in the above manner has a thickness of 1.5
Covered with ~2.0 x m cover. The cover is usually made of an ionomer resin and contains a filler (for example, titanium dioxide, barium sulfate, etc.) for coloring purposes, if necessary. The thickness of the cover is 1,
If the ball is thinner than 5zx, spin will be more likely to occur, and the feel will be undesirable as it will feel like a one-piece ball. If it exceeds 2.0 dragon, the feeling when hitting is hard and undesirable.

In the present invention, the flexural modulus of the cover is a, o o.

It is desirable to set it to 5,000 kg/cx”.

Flexural modulus was measured according to ASTM D-790. If the flexural modulus is less than 3,000 kg/cm", the cover becomes soft and spin increases, which is undesirable. If it is greater than 5,000 kv/ay", the feeling when hitting the ball becomes hard. It's too inappropriate.

The method of coating the solid core with the cover is not particularly limited, but usually the solid core is wrapped with two covers that have been previously formed into a hemispherical shell shape and then heated and pressure molded, but it is also possible to inject the cover composition. It may also be molded to enclose a solid core.

The amount of compressive deformation of the resulting golf ball also affects the feel at impact and spin performance. The amount of compressive deformation referred to here is from an initial load of 10 to 9 to a final load of 1 for a golf ball.
It is the amount of deformation of the ball when 30 is multiplied by 9, and in the case of the present invention, it is preferably 1.9 to 2.4 mm. ! , 9■, the ball is too hard and the feeling when hitting is poor. If the ball exceeds 2°4jIjI, the ball becomes too soft and the feel becomes worse.

(Example) Examples will be described below.

°-Processing 11 and Comparison H2 Solid cores were kneaded with the formulations shown in Table 1, slags were prepared, and then vulcanized to obtain solid cores with a diameter of 39.0 x m. The hardness of each cross section of the solid core is JIS-C
Measured using a mold hardness meter.

The above solid core was covered by injection molding using Himilan 1707 (commercially available from DuPont Mitsui Chemicals, Inc.) to produce a two-piece solid golf ball with a diameter of 42.83!11. Table 1 shows the various physical properties of the obtained ball. Naori bar thickness is 1,9 sty,
Met.

Table 1 ■) Antioxidant: 2,2'-methylenebis-(4-ethyl-6-t-butylphenol) 2) Initial ball speed: Head speed of 45 g/s and driver conditions using a True Temper swing robot. Initial velocity of the ball 3) Flight distance: Average value of 20 strikes carried in a batting test using a swing robot manufactured by True Temper, with a head speed of 45 wing/ss with no wind.

4) Ball durability: Index display Example 11 Comparative example when Example 1 is set as 100 for the number of times it takes for the ball to break when repeatedly collided with the impact plate at a ball speed of 45*/s! , 2, in Example 1, only the center portion of the solid core has low hardness, and the outer peripheral portion has relatively high hardness □. A solid core with such a hardness distribution has high rebound resilience, the ball's initial velocity is actually higher than that of the comparative example, and the hardness of the center portion is low, giving it a light feel when hit.

Comparative example! , 2. The outside hardness of the solid core is high and the inside hardness is low. In the embodiment, the hardness is different between the center portion and the outer peripheral portion, and the hardness does not have a constant slope. In the comparative example, the hardness decreases in order from the outside to the inside, and a solid core with such a hardness distribution has low impact resilience and poor durability.

-Execution J2.3 and Proportions 3 to 6 Next, two-piece solid golf balls were manufactured by using solid cores with the same hardness distribution as in Example 1 with different diameters, and with different cover thicknesses and compressive deformation amounts. Example 1
Created in the same way. The cover used was Hymilan 1707, available from Mitsui DuPont Bolichemicals.

When changing the diameter of the solid core, the weight of the ball was adjusted by appropriately adjusting the amount of zinc oxide as a filler in order to adjust the specific gravity of the solid core. The flight distance, feel test, and spin of the golf balls obtained were measured, and the results are shown in Table 2.

Example 4 A solid core was created in the same manner as in Example 1, and covered with cover materials having various bending moduli to have a diameter of 42.8 mm.
A two-piece solid golf ball was prepared in the same manner as in Example 1.

The compression change, flight distance, spin, and feel of the resulting two-piece solid golf ball were measured in the same manner as in Example 1. The results are shown in Table-3.

Claims (1)

[Scope of Claims] 1. A two-piece solid golf ball comprising a solid core and a cover formed from a rubber composition containing a base rubber, a co-crosslinking agent, an organic peroxide, and a crosslinking accelerator; The hardness of the part less than about 10 mm from the center is 60 to 79 on a JIS-C type hardness meter, and 10 from the center.
The hardness of the part exceeding mm is 80 to 90, the cover has a thickness of 1.5 to 2.0 mm, and the amount of compressive deformation when the obtained ball is subjected to an initial load of 10 kg to a final load of 130 kg. A two-piece solid golf ball having a diameter of 1.9 to 2.4 mm. 2. The two-piece solid golf ball according to item 1, wherein the base rubber is cis-1,4-polybutadiene. 3. The two-piece solid golf ball according to item 1, wherein the co-crosslinking agent is an α,β-ethylenically unsaturated carboxylic acid metal salt. 4. The first organic peroxide is dicumyl peroxide
The two-piece solid golf ball described in Section 1. 5. The two-piece solid golf ball according to item 1, wherein the crosslinking accelerator is N,N'-m-phenylene bismaleimide. 6. Crosslinking accelerator: 0.5 parts by weight per 100 parts by weight of base rubber
2. The two-piece solid golf ball according to item 1, containing ~1.5 parts by weight.