JP3133229B2 - Two-piece solid golf ball - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-piece solid golf ball having the feel and spin of a thread-wound ball and the flying distance and durability of a two-piece ball.

[0002]

2. Description of the Related Art Conventionally, many professional golfers have used wound balls. The wound ball is excellent in feeling and controllability. The wound ball has a center core (solid or liquid) with a diameter of about 30 mm at the center, and a thread rubber stretched around it has a diameter of about 40 mm.
It has a structure wound around. for that reason,
The center core part is hard, and the thread winding part has a hard → soft structure from the center where it becomes softer and inclined from the center to the surface. It is considered that this S / H (soft / hard) structure produces a feeling peculiar to a wound ball. However, the core of the two-piece ball is made of integrally molded hard rubber, but during press molding with a mold, the surface is controlled by the mold temperature, so it is appropriately cross-linked. Is excessively elevated, resulting in over-crosslinking. As a result, the center is soft and the surface is hard.
It has become. The stiff feel of the two-piece ball created by this structure is not preferred. However, two-piece balls are used by many amateur golfers because they can fly far less than wound balls for less powerful amateur golfers.

In order to improve the feeling which is a drawback of the two-piece ball, the core is made as soft as possible to improve the feeling, and the cover material is made softer to improve the feeling at the time of putting so that spin is easily applied. are doing. However, the former is inferior in durability because the deformation amount of the ball is too large, and the latter has been supported by professional golfers. However, the feeling other than putting is hard and the cover is easily damaged.

In order to solve such problems, attention is paid to the hardness distribution of the inner core and various performances of the cover. By softening the surface of the inner core and covering it with a thin cover, the area in contact with the club at the time of hitting the ball is improved. The golf ball has a large golf ball with a high cover hardness, a good spin, and a soft inner core surface, so that a golf ball that absorbs impact and has a soft feeling has been developed (Japanese Patent Publication No. 6-4103).
issue). However, since this golf ball has a high cover hardness, the spin performance is still poor, and since the core and cover are hard to approach the feeling of other wound balls,
There is still a problem that it is insufficient.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a two-piece solid golf ball having excellent feeling, spin, flight distance, resilience, and durability.

[0006]

The present invention relates to a two-piece solid golf ball comprising an inner core and a cover, wherein the cover has a thickness of 0.6 to 2.4 mm and a flexural modulus of 2000 to 34.
The inner core has a surface hardness of 45 to 65 as measured by a JIS-C hardness tester, and the cross-sectional hardness of a portion at least 1.5% from the center with respect to the total volume of the inner core is 7 kg / cm ^2.
5 to 90, the outer peripheral portion excluding a maximum of 15% from the center with respect to the whole volume has a gradient structure in which the cross-sectional hardness increases gradually from the surface to the center portion, and the maximum hardness of the gradient structure portion Is in the range of 70 to 90.

In the present invention, a soft feeling can be obtained by forming the two-piece core from the same center as the thread winding to the surface to form a hard-to-soft structure, and the spin characteristics can be improved without using a soft cover material that is easily damaged. An excellent two-piece ball can be obtained. Further, in terms of durability, excellent durability can be obtained in the same manner as a conventional hard two-piece ball. That is, in the present invention, the inner core of the two-piece ball has a substantially uniform hard portion with a center portion of about 1.5%, a surface layer portion with a tilted structure of about 85%, and a buffering function of 13 to 14% therebetween. It has been found that the excellent two-piece solid golf ball of the present invention can be obtained by adopting a volume structure (S / H structure) having a neutral zone. FIG. 1 shows a cross-sectional view of such a golf ball of the present invention.

In the two-piece solid golf ball of the present invention, the inner core is obtained by, for example, blending a base rubber, a crosslinkable monomer, a crosslinker, an inert filler and the like and vulcanizing the mixture. As the rubber component of the base rubber of the present invention, various known rubbers can be used. For example, natural rubber (N
R), isoprene rubber (IR), styrene-butadiene rubber (SBR), etc., and especially cis 1,4
-Polybutadiene rubber (BR) having a structure of 30% or more (particularly preferably 90% or more) is preferred. SB
R and nitrile rubber (NBR), silicon rubber (SiR)
Etc. can be mixed.

In the present invention, unsaturated carboxylic acids, salts thereof, and other unsaturated vinyl compounds can be used as the crosslinkable monomer. As the unsaturated carboxylic acid, for example, acrylic acid, methacrylic acid, and the like, and metal salts thereof are preferable. Representative examples thereof include zinc, magnesium, and calcium, and zinc acrylate is particularly preferable. The amount of the crosslinkable monomer is not particularly limited, but is 20 to 45 parts by weight, preferably 30 to 40 parts by weight, per 100 parts by weight of the rubber component.

The crosslinking agent of the present invention includes organic peroxides, and particularly preferred are dicumyl peroxide and t-butyl peroxide. The compounding amount is arbitrarily selected depending on the kind of rubber to be used, the purpose of use of the rubber composition, and the like, but is usually preferably about 0.5 to 1.5 parts by weight based on 100 parts by weight of rubber. As the inert filler, zinc oxide, magnesium oxide, metal oxides such as lead oxide, urethane resin,
Examples thereof include crosslinkable resins such as polyester resins and epoxy resins, and low molecular weight or modified products thereof. The compounding amount is usually about 5 parts per 100 parts by weight of rubber.
Preferably, the amount is up to 30 parts by weight. In the present invention, it is possible to add various known additives, for example, a vulcanization accelerator,
Add a vulcanization retarder, polymerization inhibitor, antioxidant, plasticizer, peptizer, tackifier, antiblocking agent, foaming agent, dispersant, powdering, mold release agent, solvent, softener, etc. as necessary. be able to. Further, carbon black, calcium carbonate, titanium oxide, potassium titanate and the like can be added as a reinforcing material.

The composition for the inner core obtained by blending the above components is kneaded using a conventional kneader, for example, a kneader, a Banbury mixer or a roll, and is compressed or injection-molded into a mold for the inner core, and the molded product is crosslinked. Heat curing at a temperature sufficient for the functional monomer and the cross-linking agent to act (eg, about 130-170 ° C. when zinc acrylate is used as the cross-linking monomer and dicumyl peroxide is used as the cross-linking agent), Is about 38.5 to about 41.4mm for large size
Prepare inner core of In the present invention, in particular, the surface hardness of the inner core measured by a JIS-C hardness tester is 45 to 65, and the cross-sectional hardness of at least 1.5% from the center to the total volume of the inner core is 75 to 90. , Up to 1 from center for total volume
The vulcanization conditions and compounding ratio are such that the outer peripheral portion except for 5% has a gradient structure in which the cross-sectional hardness increases gradually from the surface to the center portion, and the maximum hardness of the gradient structure portion is 70 to 90. Is adjusted appropriately. Both the surface hardness and the cross-sectional hardness are measured with a JIS-C type hardness meter. Measurement method is JISK6
This is performed by the method of 301. As for the surface hardness, a pressing surface of a JIS-C type hardness meter is brought into contact with the pressing surface so as to be perpendicular to the inner core surface, and the scale is immediately read. The cross-sectional hardness is a measured value when the same measurement is performed on the cross section of the inner core.

The inner core obtained as described above has a thickness of 0.
It is covered with a cover of 6 to 2.4 mm, preferably 1.0 to 2.0 mm. As the cover, one containing an ionomer resin as a main material and optionally containing an inorganic filler (for example, titanium dioxide, barium sulfate, etc.) for the purpose of coloring or the like is usually used. Preferred ionomer resins are polymers of a monoolefin and at least one selected from the group consisting of unsaturated mono- or dicarboxylic acids having 3 to 8 carbon atoms and esters thereof (unsaturated mono- or dicarboxylic acids and / or esters thereof). (Containing 4 to 30% by weight). As such an ionomer resin, various types of “Hylamin” (for example, Hylamin 1555, 1557, 1707, 1706, 16) which are commercially available from Mitsui DuPont Polychemicals, Inc.
05 or the like or a combination thereof).

In the present invention, the cover has a flexural modulus of 2000.
~3400kg / cm ^2, preferably 2400~3200kg
/ Cm ² . Flexural modulus is ASTM D-790
Is the value measured by Various bending elastic modulus products are commercially available as the ionomer resin, and those having a predetermined bending elastic modulus can be obtained by selecting or mixing these. If the flexural modulus is less than 2000 kg / cm ^{2, the} cover becomes too soft, the flight distance becomes short, and 3400
If it is larger than kg / cm ^2, the feel when hitting the ball becomes too hard, which is not appropriate. In the present invention, the rubber component, the crosslinkable monomer, the crosslinking agent, the inert filler, the various additives that are added as required, and the like are kneaded by a usual method, and then are cross-linked simultaneously with molding into a core material shape. To
A two-piece solid golf ball can be obtained by coating, molding and, if necessary, vulcanizing the coating layer of the present invention.

[0014]

The present invention will be described below with reference to examples and comparative examples. Examples 1 to 5 and Comparative Examples 1 to3  Each component described in Tables 1-2 was charged into a kneader and kneaded.
After that, it is shown in Tables 1 and 2 with a mold for a core material of a normal golf ball.
The core material obtained by pressing under the vulcanization conditions
Fat (flexural modulus 2800kg / cm^Two) To cover and inject
Injection molding was performed with a traction device. Of the resulting golf ball
The surface hardness at the eight locations described in Tables 1 and 2 from the center to the surface is determined by
-Measured with a C-type hardness tester. This hardness distribution is graphed
Those are shown in FIG. In FIG. 2, part A is the scope of the present invention.
The shaded area of B indicates the range of Japanese Patent Publication No. 6-4103.
Is shown. The hit feeling (feeling) of each golf ball
Was measured by actual impact. Spin and rebound
The number and durability were measured mechanically. Tables 1 and 2 show the results.
It was shown to. The coefficient of restitution is 40m / sec.
Calculated from the rebound speed when colliding with
A ball hits a rigid wall with a wall angle of 20 ° at 40 m / sec.
Spin amount and durability when using a swing robot
When the driver hit with a head speed of 45m / sec
Is the index when the fracture strength is 100 in Comparative Example 4.
You. In the table, * 1 Polybutadiene BR210 manufactured by Ube Industries, Ltd. * 2 Antioxidant Sandan 425 manufactured by Sanshin Chemical * 3 Hydroquinone Nocrack NS-7 manufactured by Ouchi Shinko Chemical

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

According to the present invention, a soft feeling can be obtained by forming a two-piece core from the same center as the thread winding to the surface to form a hard-to-soft structure, and without using a soft cover material that is easily damaged. A two-piece ball with excellent spin characteristics can be obtained. As a result, a two-piece solid golf ball excellent in feeling, spin, flight distance, resilience, and durability can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a two-piece solid golf ball of the present invention.

FIG. 2 is a graph showing the hardness distribution of the golf ball of the embodiment and Japanese Patent Publication No. 6-4103.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Kiso 6-2-1 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo ASICS Sports Engineering Laboratory Co., Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) A63B 37/00 A63B 37/02 A63B 37/12

Claims (2)

(57) [Claims] 1. A two-piece solid golf ball comprising an inner core and a cover, wherein the cover has a thickness of 0.6 to 2.4.
mm, a flexural modulus of 2000 to 3400 kgf / cm ² , and the inner core has a surface hardness of 45 measured by a JIS-C type hardness tester.
65, the cross-sectional hardness of at least 1.5% from the center with respect to the total volume of the inner core is 75 to 90, and the outer peripheral portion excluding a maximum of 15% from the center to the total volume is the center from the surface. A two-piece solid golf ball having an inclined structure in which the cross-sectional hardness increases gradually toward the center, and the maximum hardness of the inclined structure portion is 70 to 90. 2. 1.5% from the center to the total volume of the inner core
Section hardness is 75-90, section hardness at 15% section is 70-90, section hardness at 40% section is 50-80.
The two-piece solid golf ball of claim 1, wherein