JPH10179805A - Hollow golf ball and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the feeling at the impact of ball without decreasing the flying characteristic thereof by sealing a hollow center having a completely spherical hollow part therein inside a core. SOLUTION: A rubber layer 3 for a core is formed on a spherical hollow center 2, and the two 2, 3 form a hollow core A which is covered with a cover 4. The hollow center 2 is made of material selected from a group of rubber, thermoplastic resin or a mixture thereof. The layer 3 is obtained by vulcanizing a rubber composite used for a core of a golf ball. The core A is obtained by forming semi-spherical rubber shells with a similar recess to that of the center 2 by use of material similar to that of the center 2, sealing the center 2 therein at the time of joining the two semi-spherical shells, and applying complete vulcanization thereto. Thereafter the core A is covered with the cover 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow solid golf ball and a method for manufacturing the same.
The present invention relates to a hollow golf ball having a hollow portion that is a true sphere, has excellent durability, does not impair flight performance, has a small impact force, and has a good feeling when hitting, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In the prior art, there are mainly two types of golf balls. One is a solid golf ball such as a solid two-piece ball, and is composed of a core made of an integrally molded rubber member and a thermoplastic resin cover such as an ionomer resin coated on the core. The other is a thread-wound golf ball, in which a solid or liquid core at the center is wound with a rubber thread winding, and then 1-2.
It is covered with a cover made of ionomer resin or balata with a thickness of mm. Two-piece solid golf balls
Compared to thread-wound golf balls, the ball has a longer flight distance and superior flight characteristics due to its higher durability and ball speed at the time of hitting, and is used by many golfers, especially amateur golfers. On the other hand, the two-piece solid golf ball has a problem that the feel when hit is hard.

[0003]

In order to solve such a problem, the present inventors made the core of a solid golf ball hollow so as to increase the moment of inertia of the ball and improve the flight performance. A new method to improve the feel when hitting without impairing it was proposed.

Here, the spin retention of a two-piece golf ball is affected by the shape of the dimple, but also by the moment of inertia of the ball. In general, the larger the moment of inertia, the harder it is to spin,
Easy to be held. In other words, a ball having a larger moment of inertia is less likely to be spun at the time of launch on a driver shot, so that the ball does not blow up and the flight distance is increased. More specifically, the ball receives lift during flight, and the horizontal component of the lift has a positive effect after passing the highest point. In other words, until the ball reaches the highest point immediately after the driver's shot, spin is difficult to apply, and the smaller the spin amount, the smaller the lift, so the force of the component trying to pull back the ball becomes smaller, the flight distance increases, and the highest point After that, the greater the spin (the greater the spin holding ratio), the greater the lift, and the greater the force component in the flight direction, the longer the flight distance. Therefore, the larger the moment of inertia of the ball,
The flight distance will be extended aerodynamically. Also, at the time of the approach shot, as the moment of inertia is larger, the backspin once applied is more likely to be retained and stops well. In the feel at impact, if the hardness of the core is softened, a soft and good feeling is obtained, but if it is made too soft, repulsion performance is reduced.

However, making the core hollow is
This leads to manufacturing problems. For example, a core 10 as shown in FIG.
The core rubber composition is vulcanized and molded by press molding or injection molding to form a bowl-shaped hemisphere 12, and two vulcanized bowl-shaped hemispheres are used. Is bonded with rubber glue or the like, since the impact at the time of hitting with the golf club is very large, there is a problem that it is broken at the bonding surface and durability is reduced. Further, the core rubber composition is semi-vulcanized by press molding or injection molding using a core mold 11 as shown in FIG. 2 to form a bowl-shaped hemispherical body 12. When two bowl-shaped hemispheres are further vulcanized and joined using a mold as shown in FIG. 3, the amount of rubber expansion increases in proportion to the thickness of the core, and the core deforms during vulcanization. The hollow part does not become a true spherical shape, causing a variation in the thickness of the core.
This causes variations in feeling, flight performance, and the like.

The present invention solves the above-mentioned problems, and has a hollow portion of a true sphere, and has an improved feeling at impact without deteriorating the excellent flight performance characteristic of a solid golf ball. An object of the present invention is to provide a golf ball and a method for manufacturing the same.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, in a method for manufacturing a solid golf ball comprising a hollow core and a cover layer covering the core, By enclosing a hollow center with a true sphere hollow part, the hollow part is maintained in a true sphere, and has excellent durability, without impairing flight performance, a hollow golf ball with improved feeling at impact We have found what we can achieve and based on it we have completed the present invention.

That is, the present invention provides a spherical hollow center made of a material selected from the group consisting of rubber, thermoplastic resin and a mixture thereof, at least one core rubber layer formed on the hollow center, and the rubber And a cover formed on the layer. Also, the present invention provides (a) a step of producing a spherical hollow center made of rubber or thermoplastic resin, (b) at least one layer of a rubber composition for a golf ball core is coated on the hollow center, and vulcanized. A method for producing a hollow golf ball, comprising the steps of: forming a spherical hollow core by molding; and (c) covering a cover on the hollow core.

According to the present invention, a hollow core having a hollow center formed by forming a spherical hollow center made of a rubber or a resin or a mixture of both in advance and coating a rubber composition for a core thereon is formed. The hollow part is not deformed when the core rubber composition is formed by coating. Further, the hollow center is molded using a core mold as shown in FIG. 2 and a rubber composition for the hollow center is press-molded or semi-vulcanized by injection molding to form a bowl-shaped hemisphere. Even if two vulcanized bowl-shaped hemispheres are further vulcanized and joined by using a mold as shown in FIG. 3, the thickness of the hollow center is the same as that of a hollow core without the hollow center. Can be made thinner than the thickness of the core,
The amount of expansion of the rubber during vulcanization molding is small, the hollow portion is not deformed, and the hollow portion is maintained in a true spherical shape.

The structure of the golf ball of the present invention will be described with reference to FIG. FIG. 1 is a diagram schematically showing a cross section of a hollow golf ball of the present invention. As shown in FIG. 1, a core rubber layer 3 is formed on a spherical hollow center 2, and the hollow center 2 and the core rubber layer 3 form a core (hollow core) A. The cover 4 is covered on the hollow core A.

The hollow center 2 is formed from a material selected from the group consisting of rubber, thermoplastic resin or a mixture thereof. When formed from rubber, it is formed by a method of making a normal hollow rubber ball. For example, after preparing a rubber composition, the rubber composition is molded into a bowl-shaped hemisphere and simultaneously semi-vulcanized. The semi-vulcanization refers to a state in which the rubber composition is not completely vulcanized, but the vulcanization is temporarily stopped before the crosslinking reaction is completed. When the semi-vulcanized product is heated again, crosslinking proceeds further, and the crosslinking reaction can be completed. The condition of semi-vulcanization is about half the vulcanization time of the condition of complete vulcanization. For example, if the full vulcanization is performed at 150 ° C for 30 minutes,
It will cure for about 15 minutes at ℃.

In the case of the hollow center of the present invention, complete vulcanization is usually carried out at 150 to 170 ° C. for 10 to 30 minutes. A method of forming a bowl-shaped hemisphere is known. For example, as shown in FIG. 2, a bowl-shaped hemisphere may be formed using a core having the same size as a hollow portion. Further, a method such as injection molding may be used. In addition, the bowl-shaped hemisphere is not necessarily completely hollow center 2
It is not necessary to divide the hollow center into two equal parts.
Various shapes can be used, and only one kind of bowl-shaped hemisphere is prepared.
It is better to divide them equally.

When the two semi-vulcanized bowl-shaped hemispheres thus formed are joined together and vulcanization is completed, a hollow center is formed. At the time of hemisphere bonding, apply an organic solvent to the bonding surface,
Improving the adhesion is generally performed.

The rubber composition used for the hollow center is as follows:
It contains a base rubber (for example, polybutadiene, natural rubber, cis isoprene rubber, or a mixture thereof), a vulcanizing agent, a filler, and the like. The vulcanizing agent is sulfur when performing sulfur vulcanization, and in the case of peroxide vulcanization, an organic peroxide (for example, dicumyl peroxide) and a vulcanization aid (for example,
A combination with a metal salt of an α, β-unsaturated carboxylic acid, specifically, a divalent metal salt of acrylic acid or methacrylic acid) is used.

As described above, when the hollow center is made of rubber, in order to further improve the sphericity when vulcanizing and molding the core rubber layer 3, the internal pressure of the hollow center exceeds the atmospheric pressure, specifically, Is preferably filled with a gaseous gas such as air or nitrogen so that the pressure becomes 1 to 2 atm. Although a method for filling the gas is known, for example, the gas may be injected into a completed hollow center with a syringe and then sealed. When forming the hollow center, a gas generating agent may be enclosed.

When the hollow center is formed of a thermoplastic resin, a bowl-shaped hemisphere is formed by a usual molding method (for example, injection molding), and two bowl-shaped hemispheres are joined by an adhesive or welding. Is also good.

The thermoplastic resin is not only a general thermoplastic resin that can be injection-molded, but also a thermoplastic elastomer composed of a soft phase (soft segment) and a hard (hard segment), or a mixture thereof. It is a concept including At room temperature (room temperature), a thermoplastic elastomer exhibits properties similar to a vulcanized rubber, and at elevated temperatures, is plasticized and can be molded by ordinary plastic molding equipment. The thermoplastic elastomer is generally classified according to the shape of the hard segment. For example, when the hard segment is polystyrene, it is referred to as a polystyrene type thermoplastic elastomer. In this case, the soft segment is butadiene rubber or isoprene rubber. All thermoplastic elastomers are known, and combinations of soft and hard segments are also known. The melting point of thermoplastic resin is 150
C. or higher, preferably 160.degree. C. or higher, more preferably 170.degree. C. or higher, but the upper limit of the melting point is preferably 230.degree. By using a resin having a high melting point, the hollow core is less likely to be deformed when the core rubber layer is vulcanized on the hollow center. Examples of thermoplastic resins include, for example, polyethylene, polypropylene, polystyrene, polyvinyl chloride,
Polymethyl methacrylate, polyacetal, polyamide, polyoxymethylene, polycarbonate, polyester, polyphenylene oxide, polysulfone, polyimide and the like or a mixture thereof can be used.As the thermoplastic elastomer, polyester-based thermoplastic elastomer, urethane-based heat A thermoplastic elastomer, a styrene-based thermoplastic elastomer, a polyamide-based thermoplastic elastomer, or a mixture thereof can be used. A polyester-based thermoplastic elastomer or a urethane-based thermoplastic elastomer that can achieve high resilience as a golf ball is preferable. In addition, a filler for adjusting specific gravity, rubber fine particles for imparting flexibility, a cross-linking agent for rubber fine particles, and the like can be added to the resin. The hardness of the thermoplastic resin (including the thermoplastic elastomer) is preferably 30 to 80 ° in Shore D. If the hardness is less than 30 °, the resilience decreases, and if it exceeds 80 °, the shot feeling decreases.

Although the size of the hollow center is not particularly limited, it is preferable that the diameter of the hollow portion is 5 to 30 mm. When the diameter of the hollow portion is larger than 30 mm, when the golf ball is hit, the deformation of the golf ball becomes too large, the energy loss increases, the resilience of the golf ball tends to decrease, and the specific gravity is adjusted. It is necessary to mix a large amount of filler in the core rubber layer, and the resilience of the golf ball is reduced. Therefore, the diameter of the hollow portion is preferably 25 mm or less. In addition, hollow part diameter is 5m
If the diameter is less than m, the effect of increasing the moment of inertia of the golf ball and improving the shot feeling cannot be sufficiently achieved by providing the hollow portion. Therefore, the diameter of the hollow portion is preferably 10 mm or more.

The thickness of the hollow center preferably ranges from 0.1 to 12.5 mm. When the thickness of the hollow center is less than 0.1 mm, the hollow center is easily deformed in the step of coating the core rubber layer on the hollow center. Therefore, the thickness of the hollow center is preferably 0.5 mm or more, more preferably 1.0 mm
The above is preferred. Also, if the thickness of the hollow center exceeds 12.5 mm, if the hollow center is made of resin, it is difficult to obtain a good shot feeling as a golf ball, and if the hollow center is made of rubber, the hollow center is vulcanized. In the manufacturing process, the amount of expansion due to vulcanization increases, the hollow center is easily deformed, and defects such as the shape of the hollow portion not becoming a true sphere tend to occur. Therefore, the thickness of the hollow center is preferably 6.0 mm or less, more preferably 4.0 mm or less.

The diameter of the hollow core having the hollow center is
In order to secure the thickness of the cover layer, the thickness is preferably 35 to 41 mm, preferably 36 to 39 mm.

The thickness of the hollow core including the hollow center (total thickness of the hollow center and the core rubber layer) is 2.5 to 18 mm
Good to be. When the thickness of the hollow core is less than 2.5 mm, the cover layer is too thick, or the diameter of the hollow portion is too large, and when the cover layer is too thick, the shot feeling tends to be reduced as described above. If the diameter of the hollow portion is too large, the resilience decreases as described above. Therefore, the thickness of the hollow core is preferably 3 mm or more, more preferably 7 mm or more. Also, the thickness of the hollow core is 18m
The diameter of the hollow part exceeding m becomes too small or the thickness of the cover becomes too small.If the diameter of the hollow part becomes too small, the moment of inertia of the golf ball increases as described above, and the shot feeling is improved. If the effect cannot be sufficiently achieved, and the thickness of the cover is too small, the durability is reduced as described above. Therefore, the thickness of the hollow core is preferably 15 mm or less.

The thickness of the core rubber layer is preferably 5 to 16 mm. When the thickness of the core rubber layer is less than 5 mm, when the hollow center is made of resin, or when the rubber is made of high rigidity, the shot feeling as a golf ball tends to decrease, and when the thickness of the core rubber layer exceeds 16 mm, The diameter of the hollow part becomes too small,
Or, if the thickness of the cover becomes too small and the diameter of the hollow portion becomes too small, the effect of increasing the moment of inertia of the golf ball as described above and improving the shot feeling cannot be sufficiently achieved, and the cover If the thickness is too small, the durability will be reduced as described above.

The core rubber layer 3 of the present invention is obtained by vulcanizing a rubber composition used for a golf ball core. The rubber composition usually contains a base rubber, a metal salt of an unsaturated carboxylic acid, an organic peroxide, a filler and the like. As the base rubber, natural rubber and / or synthetic rubber conventionally used for solid golf balls is used, and particularly, a so-called high cis having a cis-1,4-structure of at least 40% or more, preferably 80% or more. Polybutadiene rubber is preferred, and if desired, natural rubber, polyisoprene rubber, styrene polybutadiene rubber, EPDM, and the like may be blended.

The metal salt of an unsaturated carboxylic acid acts as a co-crosslinking agent, and particularly a zinc or magnesium salt of an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms such as acrylic acid or methacrylic acid. Although a monovalent or divalent metal salt is mentioned, zinc acrylate which gives high repulsion is suitable. The amount is preferably 25 to 55 parts by weight based on 100 parts by weight of the base rubber. If it is more than 55 parts by weight, it will be too hard and the feeling will be poor. If it is less than 25 parts by weight, rebound will be poor and the flight distance will be reduced.

The organic peroxide acts as a cross-linking or curing agent and includes, for example, dicumyl peroxide or t-butyl peroxide, with dicumyl peroxide being preferred. The compounding amount is 0.5 to 100 parts by weight of the base rubber.
Preferably it is 3.03.0 parts by weight. If it is less than 0.5 parts by weight, it becomes too soft and rebound becomes poor, resulting in a reduced flight distance.
If it exceeds 3.0 parts by weight, it will be too hard and the feeling will be poor.

The filler may be any one which is usually compounded in the core of a golf ball. For example, an inorganic salt (specifically,
Zinc oxide, barium sulfate, calcium carbonate), high specific gravity metal powder (for example, tungsten powder, molybdenum powder, etc.) and mixtures thereof. Since the weight of the hollow core used in the present invention tends to be less than that of a normal solid core, it is preferable to use a mixture of an inorganic salt and a high specific gravity metal powder. The compounding amount is preferably 10 to 120 parts by weight based on 100 parts by weight of the base rubber. If the amount is less than 10 parts by weight, the effect of the filler will not be seen, and if it exceeds 120 parts by weight, the repulsion performance will be too low.

In the hollow core A of the present invention, similarly to the hollow center 2, a semi-vulcanized rubber shell having a recess having the same shape as the hollow center 2 is formed from the rubber composition for the core, and the two semi-vulcanized rubber shells are formed. At the time of joining, it is obtained by sealing the hollow center 2 and performing complete vulcanization. Semi-vulcanization has the same meaning as described for the hollow center, but it is more preferable to shorten the time than for the hollow center (1/1 /
About 10). This is to further improve the adhesion with the hollow center.

Next, the cover 4 is covered on the hollow core A. The cover can be formed of an ionomer resin or balata commonly used as a cover material for a solid golf ball, and a small amount of another resin may be added. Also,
In the composition for the cover, fillers such as barium sulfate and additives such as titanium dioxide for coloring, and other additives such as an ultraviolet absorber, a light stabilizer and a fluorescent material or a fluorescent whitening agent. Although it may be contained within a range that does not impair the desired properties of the golf ball cover,
The amount of the coloring agent is preferably 0.1 to 0.5 part by weight.

The cover of the present invention is formed by a generally known method used for forming a cover of a golf ball, for example, injection molding, press molding or the like. The thickness of the cover layer is preferably from 1 to 4 mm. When the cover layer is coated, usually, many depressions called dimples are formed on the surface. When the thickness of the cover layer is less than 1 mm, the strength of the cover layer is insufficient, the durability as a golf ball tends to decrease, and when the thickness of the cover layer exceeds 4 mm, it is difficult to obtain a good shot feeling as a golf ball. . The golf ball of the present invention is usually coated with paint and put on the market in order to enhance aesthetic appearance and commercial value. Incidentally, the cover may be composed of two or more cover layers.

According to the method of the present invention, there is provided a hollow golf ball having a true spherical hollow portion, excellent durability, and improved feeling upon impact without impairing flight performance.

[0031]

The present invention will be described in more detail with reference to examples.
However, the present invention is not limited to these examples.

Preparation of Hollow Center Hollow Center I: Using a rubber composition A shown in Table 1 below, a mold having a predetermined size shown in the schematic diagram of FIG.
Vulcanization molding for 2 minutes to produce a semi-vulcanized bowl-shaped rubber hemisphere having a rubber thickness of 2 mm and a hollow portion diameter of 20 mm. This bowl-shaped rubber hemisphere 2
These were preliminarily bonded using an acetone solution of the rubber composition A shown in Table 1, inserted into a mold having predetermined dimensions shown in the schematic diagram of FIG. 3, and vulcanized and bonded at 155 ° C. for 20 minutes. A hollow rubber ball having a diameter of 24 mm was produced. The hollow rubber ball was filled with air using a syringe, and sealed with a rubber sheet of the same material as the center to which the adhesive was applied in a state where the internal pressure was equal to or higher than the atmospheric pressure, to obtain a hollow center I. Hollow center II: Thermoplastic polyacetal homopolymer resin (trade name: Tenac 7010, manufactured by Asahi Kasei Corporation) is injection molded at 250 ° C. into a mold having a predetermined shape shown in the schematic diagram of FIG. A bowl-shaped hemisphere having a diameter of 20 mm was prepared, and the two were adhered with an adhesive to obtain a hollow center II having an outer diameter of 22 mm. Hollow center III: The same manufacturing method as that of the hollow center I was used as the hollow center III without filling with an air syringe. The resulting hollow center is
It had a wall thickness of 2 mm, a hollow diameter of 20 mm, and an outer diameter of 24 mm. Hollow Center IV: In the manufacturing method of Hollow Center II, thermoplastic polyacetal polymer resin is converted to a thermoplastic polyester elastomer (Gleep EH700 manufactured by Dainippon Ink Co., Ltd.)
Was used to obtain a hollow center IV in the same manner. The obtained hollow center had a thickness of 1 mm, a hollow portion diameter of 20 mm, and an outer diameter of 22 mm.

Hollow Solid Golf Ball of Example 1 The rubber composition A shown in Table 1 below is molded in a mold as shown in FIG. 4 in which a hemispherical convex core is sandwiched between core press dies.
Preforming at 165 ° C. for 2 minutes to produce a semi-vulcanized bowl-shaped hemisphere, extracting the core, sealing the hollow center I in the obtained two bowl-shaped hemispheres, A hollow core having an outer diameter of 38.4 mm was obtained by placing in a mold having predetermined dimensions shown in the figure and press vulcanizing at 165 ° C. × 20 minutes. Thereafter, a cover layer having the composition shown in Table 2 below was coated on the obtained hollow core to form a cover layer, and paint was applied to the hollow core.
A large solid hollow golf ball of 42.7 mm was produced.

[Table 1] (parts by weight) Type AB BR-11 (Note 1) 100 100 Zinc acrylate 37 37 Zinc oxide 55 Barium sulfate 56.8 18.6 Antioxidant (Note 2) 0.5 0.5 Dicumyl peroxide 1.0 1.0

[Table 2] Type Weight part Himilan # 1805 (Note 3) 50 Himilan # 1706 (Note 4) 50 Titanium dioxide 2

(Note 1) High-cis-1,4-polybutadiene having a cis content of 96% manufactured by Nippon Synthetic Rubber Co., Ltd. (Note 2) Yoshitomi Pharmaceutical (Note 3) Ionomer resin manufactured by Mitsui Polychemicals (Note 4) Mitsui Poly Chemical company ionomer resin

Each of the golf balls obtained in Example 1 was evaluated for variations in hollow diameter, moment of inertia, impact force, flight performance by a driver (No. 1 wood club), feeling at impact, and durability. Table 3 shows the results
Shown in The test method was performed as follows.

(Test Method) Hollow Diameter Variation Three points as shown in FIG. 1 (aa ', bb', cc 'orthogonal to each other)
Was measured and the difference between the maximum value and the minimum value was indicated. Moment of inertia The average value in two perpendicular directions (pole direction, seam direction) was measured using a measuring machine of model number 005-002 manufactured by INERTIA DYNAMICS. Impact force Using a swing robot manufactured by True Temper, measure the acceleration generated in the direction opposite to the head's direction of travel by attaching an accelerometer to the back of the golf club head when hitting with a driver at a head speed of 45 m / sec with a driver Then, the maximum value of the acceleration was obtained by converting the value into a force, and the value was shown when the ball without the hollow portion was set to 100. Flying distance (carry) A driver is attached to a swing robot manufactured by True Temper, and the golf ball is hit at a head speed of 45 m / sec.
The distance to the drop point (carry) was measured as the flight distance. Feeling at the time of impact Evaluate by hitting with a driver by 10 professional golfers. The evaluation criteria are as follows. Evaluation criteria ◎… Eight or more respondents are good ○… Five to seven respondents are good △… Two to four respondents are good ×… Two or less respondents are good Durability Driver to True Temper swing robot And hit the golf ball at a head speed of 45 m / sec.
The collision plate is repeatedly hit and evaluated. The evaluation criteria are as follows. Evaluation criteria ○… No cracks after 50 times ×… Cracks within 50 times

Hollow solid golf balls of Examples 2 to 4
A hollow solid golf ball was obtained in the same manner as in Example 1 except that the hollow centers II, III and IV were used. The same evaluation was performed on the obtained golf balls, and the results are shown in Table 3.

Hollow Solid Golf Ball of Comparative Example 1 The rubber composition A shown in Table 1 was subjected to core preforming conditions of 165 ° C. for 2 minutes in a core hemispherical mold having predetermined dimensions shown in FIG. It is preformed to produce a semi-vulcanized bowl-shaped hemisphere, and the obtained two bowl-shaped hemispheres are combined (without enclosing the hollow center), and a mold having a predetermined size shown in the schematic diagram of FIG. The mixture was press-vulcanized under the core forming conditions of 165 ° C. × 20 minutes to obtain a hollow core having a hollow portion diameter of 20 mm and an outer diameter of 38.4 mm. Thereafter, a cover layer was formed by coating the obtained hollow core with a cover composition having the composition shown in Table 2.
A large solid hollow golf ball having a diameter of 42.7 mm was obtained by painting.

A hollow solid golf ball was obtained in the same manner as in Comparative Example 1 except that the conditions for preforming the hollow solid golf ball core of Comparative Example 2 were 165 ° C. for 7 minutes.
The same evaluation test was performed, and the results are shown in Table 3.

The hollow solid golf ball core of Comparative Example 3 was preformed at 165 ° C. for 20 minutes, and before the two bowl-shaped hemispheres were combined, an acetone solution of the same rubber composition as the core was used on the mating surface. A hollow solid golf ball was obtained in the same manner as in Comparative Example 1, except that the core molding condition was 165 ° C. for 20 minutes. The same evaluation test was performed, and the results are shown in Table 3.

Solid Golf Ball of Comparative Example 4 A solid core which was vulcanized at 165 ° C. for 20 minutes in a core mold shown in FIG. And a cover layer was similarly formed on the core to obtain a solid golf ball which was not hollow. The same evaluation test was performed, and the results are shown in Table 3.

(Test results)

TABLE 3 Example Comparative Example 1 2 3 4 1 2 3 4 hollow center I II III IV - - - - core rubber composition compounded A A A A A A A B hollow portion diameter (mm) 20 20 20 20 20 20 200 0 Hollow part diameter variation (mm) 0.8 0.7 1.0 0.7 10.2 3.4 1.6 − Moment of inertia (gcm ² ) 86.70 86.83 86.69 86.84 * 86.75 86.75 80.64 Impact force index 92 92 92 92 * 92 92 100 Flight distance (carry) ( (Yard) 232.5 233.2 232.3 232.3 * 232.0 Damage 233.5 Hitting feeling at impact ◎ ◎ ◎ ◎ * ◎ Damage △ Blow test 〇 〇 〇 〇 * × × 〇 * The uniformity of the golf ball is extremely poor, and no measurement

From the above results, it is recognized that the hollow solid golf ball manufacturing method of the present invention has a hollow portion which is closer to a true sphere and has excellent durability as compared with other methods. In terms of performance, it was recognized that the impact strength was smaller and the feel when hitting was better than that of a normal solid golf ball.

[0044]

According to the present invention, the hollow portion is a true sphere,
Provided is a hollow golf ball having excellent durability, low impact force and good feeling at impact without impairing flight performance, and a method of manufacturing the same.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a hollow golf ball of the present invention.

FIG. 2 is a schematic view showing a cross section of a core mold.

FIG. 3 is a schematic sectional view of a mold for vulcanizing a hollow center.

FIG. 4 is a schematic sectional view of a mold for producing a semi-vulcanized bowl-shaped hemisphere of a core.

FIG. 5 is a schematic sectional view of a mold for vulcanizing a core enclosing a hollow center.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Hollow part 2 ... Hollow center 3 ... Core 4 ... Cover layer 10 ... Core 11 ... Core mold 12 ... Bowl-shaped hemisphere

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // C08K 5/09 C08K 5/09 C08L 21/00 C08L 21/00 (72) Inventor Keiji Moriyama 165 Snakeishi, Shirakawa-shi, Fukushima Sumitomo Rubber Industries Co., Ltd. Company house 101 (72) Inventor Kiyoto Maruoka 3-7-24-403 Karibadai, Nishi-ku, Kobe-shi, Hyogo

Claims (12)

[Claims] 1. A spherical hollow center made of a material selected from the group consisting of rubber, thermoplastic resin, and a mixture thereof, at least one core rubber layer formed on the hollow center, and formed on the rubber layer. Cover, comprising a hollow golf ball. 2. The rubber forming the hollow center is a natural rubber and / or a synthetic rubber containing sulfur and / or an unsaturated carboxylic acid metal salt, an organic peroxide, a filler and the like. Hollow golf ball. 3. The hollow golf ball according to claim 1, wherein the thermoplastic resin forming the hollow center is a resin that melts at 150 ° C. or higher. 4. The hollow golf ball according to claim 1, wherein the core rubber layer is obtained by vulcanizing a rubber composition containing a base rubber, a metal salt of an unsaturated carboxylic acid, an organic peroxide and a filler. 5. The hollow golf ball according to claim 1, wherein the cover is formed from an ionomer resin or balata. 6. A step of producing a spherical hollow center made of a material selected from the group consisting of rubber, thermoplastic resin and a mixture thereof, and (b) a rubber for a golf ball core on the hollow center. A method for producing a hollow golf ball, comprising a step of producing at least one layer of the composition and vulcanizing and forming a spherical hollow core, and (c) a step of covering a cover on the hollow core. 7. When the hollow center in the step (a) is rubber,
Step (a) comprises: (i) semi-vulcanizing and molding a rubber composition for a hollow center to form a semi-vulcanized bowl-shaped hemisphere; and (ii) two semi-vulcanized bowl-shaped hemispheres. 7. A method for producing a hollow golf ball according to claim 6, comprising the steps of joining and vulcanizing. 8. The method of manufacturing a hollow golf ball according to claim 6, wherein when the hollow center is made of rubber, the inside of the hollow center is filled with a gas so that the internal pressure is equal to or higher than the atmospheric pressure. 9. When the hollow center of the step (a) is made of a thermoplastic resin, the step (a) comprises: (i) molding a thermoplastic resin to form a bowl-shaped hemisphere; and (ii) 7. A step of joining the two bowl-shaped hemispheres.
Method for manufacturing hollow golf balls. 10. In the step (b), a rubber composition for a core is semi-vulcanized to form a semi-vulcanized rubber shell having a recess having the same shape as the hollow center, and a hollow center is formed inside the two semi-vulcanized rubber shells. 7. The method according to claim 6, further comprising the steps of:
A method for producing the hollow golf ball described in the above. 11. The method according to claim 6, wherein the core rubber composition contains a base rubber, a metal salt of an unsaturated carboxylic acid, an organic peroxide and a filler. 12. The method according to claim 6, wherein the cover is an ionomer resin or a balata.