JPH1176464A - Method of manufacturing hollow golf ball - Google Patents

Abstract

(57) Abstract: The present invention provides a method for producing a hollow golf ball having a good production yield. SOLUTION: The present invention comprises (i) a step of producing a hollow center (5), and (ii) a semi-vulcanization molding of a rubber composition for forming an outer shell layer to produce two half-vulcanized rubber half shells. Enclosing a hollow center therein, pressurizing and heating in an upper and lower mold to form a hollow core (6), and (iii) covering a cover, ) And an inner shell layer (2) and a hollow core (5) and an outer shell layer (3)
(6) and a method for manufacturing a hollow golf ball comprising the cover (4), wherein the pressurizing pressure in the step (ii) is such that the inner shell layer (2) is cut when the hollow center is bisected in a plane. The pressure applied to the entire hollow core per area is 20 to 80 kgf / cm
^{The present} invention relates to a method for producing a hollow golf ball, which is performed in the range of ² .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a hollow solid golf ball, and more particularly, to a method for manufacturing a hollow golf ball having a good production yield.

[0002]

2. Description of the Related Art In the recent development of golf balls, the improvement in resilience characteristics has reached its limit, and its development policy is shifting to a direction in which the launch angle is increased and the spin is reduced. As a method of reducing the spin, it is conceivable to increase the moment of inertia by hollowing the center of the golf ball. By increasing the moment of inertia, the attenuation of the spin during flight can be reduced, so that the lift can be increased from the highest point of the trajectory and the flight distance can be increased.

The present inventors have already proposed a hollow golf ball in which a solid core of a two-piece golf ball is made hollow and an ionomer cover is coated on the hollow core (Japanese Patent Application Nos. 8-288131 and 8-288131). 8-288136). Since the hollow golf ball can increase the moment of inertia as described above, it has the effect of suppressing the initial spin and the effect of suppressing the spin attenuation during flight, so that the flight distance increases. However, forming a core made of a rubber material into a hollow core with good yield has many points to be overcome in manufacturing, and there is no hollow golf ball put on the market yet.

[0004]

The present inventors have already made a hollow center (5) made of rubber or thermoplastic resin and a rubber outer shell layer (3) covering the hollow center (2) with the core part as two layers. (Japanese Patent Application No. 8-288099). In this method, after a hollow center (5) is formed in advance, a rubber composition for forming an outer shell layer is separated from the hollow center and a mold (7) for forming an outer shell layer and a core mold as shown in FIG. Semi-vulcanization molding is performed using (8) to form a half-vulcanized rubber half shell (9) as shown in FIG. The hollow center (5) is inserted into the two recesses of the half-vulcanized rubber half shell (9) thus obtained as shown in FIG.
By inserting and vulcanizing as shown in FIG.
A hollow golf ball as shown in FIG. 1 can be manufactured by forming a hollow core (6) having a cross section shown in FIG. 1 and covering it with a cover (4).

[0005] If this manufacturing method is carried out under the conditions usually carried out by a person skilled in the art, the center hollow portion frequently collapses during the pressure vulcanization molding performed in the step shown in FIG. If the hollow portion is crushed, not only the hollowing effect cannot be achieved, but also eccentricity of the golf ball occurs, and the commercial value is lost.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an effective means for preventing a hollow portion from being crushed at the time of manufacturing a hollow golf ball, and to improve the yield at the time of manufacturing.

[0007]

That is, the present invention provides (i) a step of producing a hollow center (5) containing rubber or a resin or a mixture thereof as a main component, and (ii) a rubber composition for forming an outer shell layer. To form a semi-vulcanized rubber half shell having a recess having the same shape as the hollow center, and enclose the hollow center in the two half-vulcanized rubber half shells to form an outer shell layer. Pressing and heating in the upper and lower molds, (iii) if necessary, repeating step (ii) to form a hollow core (6), and (iv) coating a cover on the hollow core A hollow center (5) comprising a hollow portion (1) and an inner shell layer (2) around the hollow portion, and one or more outer shell layers (3) formed on the hollow center. In the method for manufacturing a hollow golf ball comprising a hollow core (6) and a cover (4) formed on the hollow core (6), the step (ii) Definitive pressurization pressure is, the inner shell layer when the bisecting the hollow center plane
When the sectional area of ( ² ) is S (cm ² ) and the pressure applied to the entire hollow core is F (kgf), F / S (kgf / cm ² ) is 20 to 80.
Provided is a method for producing a hollow golf ball, which is performed in a range of kgf / cm ² .

The collapse of the hollow portion during the production of the hollow golf ball described above is expected to be caused by a combination of the pressure applied during the vulcanization molding of the outer shell layer and the expansion of the hollow portion.
Under what conditions can the hollow collapse be prevented,
Moreover, it is not known at all whether sufficient vulcanization of the outer shell layer is performed.

The present inventors clarified the relationship between the pressure applied during vulcanization of the outer shell layer and the cross-sectional area of the inner shell layer (2) of the hollow center (5). It has been found that the collapse of the portion can be effectively prevented and the vulcanization proceeds to a sufficient extent, and the present invention has been achieved.

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, hollow part (1)
An outer shell layer (3) is formed on a spherical hollow center (5) comprising an inner shell layer (2) and the hollow center (5) and the outer shell layer (3).
Together form a core (hollow core) (6). The cover (4) is covered on the hollow core (6).

The inner shell layer (2) is formed from a composition mainly composed of rubber or resin or a mixture thereof, and may have a multilayer structure of two or more layers. 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, when complete vulcanization is performed at 150 ° C. for 30 minutes, vulcanization is performed at 150 ° C. for about 15 minutes.

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, a bowl-shaped hemisphere may be formed using a core having the same size as the hollow portion. Further, a method such as injection molding may be used.

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 (5) is made of rubber, the internal pressure of the hollow center is reduced to the atmospheric pressure in order to further improve the sphericity when vulcanizing and molding the outer shell layer (3). It is preferable to fill a gaseous gas such as air or nitrogen so that the pressure exceeds, specifically, 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 (5) is formed of a resin, a bowl-shaped hemisphere is formed by a method using a normal mold or the like,
These may be joined together by a method such as adhesive or welding. The resin is preferably a thermoplastic resin that can be injection-molded, a thermoplastic elastomer composed of a soft phase (soft segment) and a hard phase (hard segment), or a mixture thereof, and further has a melting point of 150 ° C. that's all,
Further, those having a temperature of 160 ° C. or higher, more preferably 170 ° C. or higher are preferred. The use of a resin having a high melting point makes it difficult for the hollow core to be deformed when the outer shell layer is vulcanized on the hollow center.

Examples of the thermoplastic resin include, for example, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polymethyl methacrylate, polyacetal, polyamide, polyoxymethylene, polycarbonate, polyester, polyphenylene oxide, polysulfone, polyimide or a mixture thereof. It is also possible to use a polyester-based thermoplastic elastomer, a urethane-based thermoplastic elastomer, a styrene-based thermoplastic elastomer, a polyamide-based thermoplastic elastomer, or a mixture thereof. It is preferable to use a polyester-based thermoplastic elastomer or a urethane-based thermoplastic elastomer capable of achieving high resilience as a golf ball. Further, a filler for adjusting specific gravity, rubber fine particles for imparting flexibility, a crosslinking agent for rubber fine particles, and the like can be blended in the resin.

The hollow center (5) of the present invention preferably has a Shore D hardness of 30 to 90, more preferably 30 to 80, still more preferably 30 to 60, and most preferably 30 to 50. If the Shore D hardness is larger than 90, the feeling at the time of impact is deteriorated, and if it is smaller than 30, it is too soft and the hollow portion is easily deformed. The size of the hollow center is not particularly limited, but in order to increase the moment of inertia, the hollow portion diameter is 5 to 30 mm, preferably 10 to 20 mm, more preferably 10 to 15 mm, and the inner shell layer thickness is 0.5 to Preferably it has a length of 15 mm. When the hollow part diameter is larger than 30 mm, the outer shell layer
In (3), it is necessary to use a large amount of filler for adjusting the specific gravity, and the rebound is too low, and if it is less than 5 mm, the hollow effect cannot be seen. If the inner shell layer thickness is larger than 15 mm, the hollow part will be too small, so the hollow effect will not be seen.If it is smaller than 0.5 mm, it will not be able to withstand external pressure, and the sphericity of the hollow part will not be maintained. . Further, since the diameter of the hollow core (5) is 36 to 41 mm, the thickness of the outer shell layer (3) is 5 to 16 mm.

The outer shell layer (3) of the present invention is obtained by vulcanizing a rubber composition usually used for a golf ball core. The rubber composition usually contains a base rubber, a salt of an unsaturated metal carboxylate, an organic peroxide, a filler and the like. As the base rubber, natural rubber and / or synthetic rubber conventionally used for solid golf balls are used. In particular, the cis-1,4-structure is at least 40% or more, preferably 80%.
The so-called high cis polybutadiene rubber having the above is preferable, and if desired, natural rubber, polyisoprene rubber,
Styrene polybutadiene rubber, ethylene-propylene-diene rubber (EPDM) and the like may be blended.

The metal salts of unsaturated carboxylic acids act as co-crosslinking agents, especially zinc, magnesium salts and the like of α, β-unsaturated carboxylic acids having 3 to 8 carbon atoms such as acrylic acid or methacrylic acid. Although a monovalent or divalent metal salt is mentioned, zinc methacrylate 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, and may be an inorganic salt (for example, zinc oxide,
Barium sulfate, calcium carbonate, silica gel), 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.

As shown in FIG. 2, the hollow core (6) of the present invention comprises a mold (7) for forming an outer shell layer and a core mold (8) having the same recess as the hollow center (5). The rubber composition for forming the outer shell layer is used to form a semi-vulcanized rubber half shell (9) having the same shape as the hollow center (5) (FIG. 3), and as shown in FIG. When joining the two half-vulcanized rubber half shells (9) and (9 ′) using the layer forming molds (7) and (7 ′), the hollow center (5) is sealed. The cross-sectional area of the inner shell layer (2) when the pressure of the hollow center (5) is bisected by a plane is S (cm ² ), and the pressure applied to the entire hollow core (6) is lower than usual. When pressure is F (kgf), F
The hollow core (6) is obtained by vulcanizing press molding so that / S is 20 to 80 kgf / cm ² . By using the method of the present invention, a hollow golf ball having a multilayer structure can be formed without deforming or breaking the hollow portion. If the pressure is less than 20 kgf / cm ² , a concave portion due to an air pocket called a bear is formed on the surface of the hollow core to deteriorate the appearance, and if it is more than 80 kgf / cm ² , the hollow portion is deformed or crushed. When a golf ball is produced using the hollow core (5) having a bear on the surface, the adhesion to the outer shell layer (3) is reduced, and the durability of the golf ball is reduced. Also,
When the hollow portion (1) is crushed, the hollow core (5) is also deformed. When a golf ball is manufactured using the hollow core (5), the thickness of the cover or the like is partially reduced, and the durability of the golf ball is reduced. Semi-vulcanization has the same meaning as in the case of a hollow center, but it is more preferable to shorten the time than in the case of a hollow center (1/1).
About 10). This is to further improve the adhesion with the hollow center. In the method for producing the hollow core, when an unvulcanized outer shell layer forming composition is used, when the hollow center is sealed and press-formed, the expansion is large at the time of vulcanization in a mold and the hollow portion is formed. Easy to deform. Therefore, if a half-vulcanized rubber half shell is used, the expansion is smaller than in the case of unvulcanized, and the deformation of the hollow portion is reduced. Further, when the above method is used, the effect of preventing the deformation of the hollow portion as described above, as well as the ease of setting the composition for forming the outer shell layer on the hollow core, the productivity is improved, and in addition, the uniformity is previously formed on the hollow center in advance. Since the composition for forming the outer shell layer can be coated on the surface, no bear or the like is generated at the time of vulcanization molding, and the pressure applied to the hollow core at the time of vulcanization molding is made uniform, and the effect of preventing deformation of the hollow portion is further improved. improves.

The outer shell layer (3) of the present invention may have a multilayer structure of two or more layers.
The same outer shell layer coating process is repeated on the member coated with the outer shell layer to coat two or more outer shell layers. In this case, the F / S is 20 to 80 kgf / cm ² . It is preferable to press-mold under such a constant pressure.

The inner shell layer having a multilayer structure and the outer shell layer having a multilayer structure require more manufacturing steps and increase manufacturing costs. Therefore, the inner shell layer is preferably a single-layer structure. The layer preferably has a one-layer structure.

Next, a cover (4) is placed on the hollow core (5).
Is coated. 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. Further, the composition for the cover, fillers such as barium sulfate and additives such as titanium dioxide for coloring, and other additives, such as ultraviolet absorbers, light stabilizers and fluorescent materials or fluorescent brighteners And the like may be contained within a range that does not impair the desired properties of the golf ball cover, but usually, the amount of the coloring agent is 0.1 to 100 parts by weight of the cover resin.
~ 0.5 parts by weight is preferred.

The cover layer 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 1 to 3 mm.
Many depressions called dimples are formed on the surface.
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.

By using the method of the present invention, there is provided a hollow golf ball having a true spherical hollow portion and a good hit feeling.

[0029]

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 The rubber composition shown in the following Table 1 was molded at 150 ° C. for 1 minute to form a bowl-shaped hemisphere, and these two bowl-shaped hemispheres were joined.
By vulcanizing at 140 to 170 ° C. for 15 minutes, a hollow center having a hollow part diameter of 17 mm, a rubber thickness of 2 mm and an outer diameter of 21 mm was prepared.
By changing the vulcanization temperature to 140 to 170 ° C., a hollow center having a Shore D hardness of 20 to 80 was obtained.

Preparation of Core A rubber composition similar to the hollow center shown in Table 1 below was used.
Using the outer shell layer forming mold (7) and the core mold (8) as shown in FIG. 2, a half-shell (9) was prepared by preforming at 160 ° C. for 30 seconds under a pressure of 1000 kgf. The core mold (8) was pulled out, and the hollow center (5) obtained as described above was sealed in two half shells (9) and (9 ') as shown in FIG. By performing vulcanization molding at 160 ° C for 20 minutes at a constant pressure such that the pressure applied to the entire core per sectional area of the inner shell layer when the center is bisected in a plane is 15 to 90 kgf / cm ² , A hollow core having an outer diameter of 38 mm was obtained. The above pressure is 20,
Examples 40, 80 kgf / cm ² were used in Examples 1, 2, 3
The golf ball cores of Comparative Examples 1 and 2 were respectively 15 and 90 kgf / cm ² .
The shape and appearance of the hollow portion of the obtained hollow core were evaluated, and the results are shown in Tables 3 and 4, respectively. The test method was performed as described below.

[0032]

[Table 1] Ingredients Parts by weight BR-18 (Note 1) 100 Zinc methacrylate 30 Zinc oxide 47 Dicumyl peroxide 0.3 (Note 1) Hicis-1,4-polybutadiene manufactured by Nippon Synthetic Rubber Co., Ltd.

(Examples 1 to 3 and Comparative Examples 1 and 2) Cover Coating A cover layer having the composition shown in Table 2 below was coated on the hollow core obtained as described above to form a cover layer. By applying paint, a hollow solid golf ball having a diameter of 42.7 mm was produced. The feeling of the obtained golf ball at the time of hitting was evaluated, and the results are shown in Table 5. The test method was performed as described below.

[0034]

[Table 2] Type Weight parts Himilan # 1605 (Note 2) 50 Himilan # 1706 (Note 3) 50 Titanium dioxide 2 (Note 2) Mitsui-DuPont Polychemical Co., Ltd. sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin (Note 3) ) Mitsui DuPont Polychemical Co., Ltd. zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin

(Test Method) Hollow Portion The obtained hollow core was cut, and the shape of the hollow portion was visually evaluated according to the following criteria. Judgment Criteria…: True sphere △: Deformation (not true sphere) ×: Damaged (hollow portion is crushed) Core appearance The appearance of the obtained hollow core was visually evaluated according to the following criteria. Judgment criteria 〇: Good ×: There is a bear (recess due to air pocket) on the core surface ××: Deformation (not a true sphere) Feeling at the time of hitting Ten professional golfers hit the ball with a driver to evaluate. 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 ×… One or less respondents are good

(Test results)

[Table 3] Hollow part shape Example Comparative example Hollow center 1 2 3 1 2 Shore D hardness Core molding pressure (kgf / cm ² ) 20 40 80 15 90 20 〇 △ △ △ × 30 〇 〇 〇 〇 × 50 〇 【 〇 〇 × 60 〇 〇 〇 〇 × 80 〇 〇 〇 〇 △

[0037]

[Table 4] Core appearance Example Comparative example Hollow center 1 2 3 1 2 Shore D hardness Core molding pressure (kgf / cm ² ) 20 40 80 15 90 20 〇 〇 〇 × ×× 30 〇 〇 〇 × ×× 50 〇 〇 〇 × ×× 60 〇 〇 × × ×× 80 〇 〇 〇 × ××

[0038]

[Table 5] Example of feeling at impact Hollow center 1 2 3 Shore D hardness Core molding pressure (kgf / cm ² ) 20 40 80 20 ◎ ◎ ◎ ◎ 30 ◎ ◎ ◎ 50 ◎ ◎ ◎ 60 〇 △ △ 80 × × ×

From the above results, the molding pressure was 20 to 80 kgf / cm
^The hollow golf ball (Examples 1 to 3) using the production method of the present invention which is No. 2 is compared with the hollow golf ball (Comparative Examples 1 and 2) using the method in which the molding pressure is out of the range. It was confirmed that the hollow portion was close to a true sphere without being crushed, and that the core had a good appearance. Furthermore, a hollow golf ball using the production method of the present invention preferably has a hollow center having a Shore D hardness of 30 to 50, because if the hardness of the hollow center is large, the feel at the time of hitting is deteriorated.

[0040]

According to the present invention, there is provided a method for manufacturing a hollow golf ball having a hollow portion having a perfect sphere and a good production yield, and having a good hit feeling.

[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 cross-sectional view of a mold for forming an outer shell layer of a hollow golf ball of the present invention.

FIG. 3 is a schematic perspective view of a half shell for an outer shell layer of the hollow golf ball of the present invention.

FIG. 4 is a schematic cross-sectional view illustrating a method of forming a hollow core of a hollow golf ball of the present invention.

FIG. 5 is a schematic sectional view of a hollow core of the hollow golf ball of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Hollow part 2 ... Inner shell layer 3 ... Outer shell layer 4 ... Cover 5 ... Hollow center 6 ... Hollow core 7, 7 '... Die for forming outer shell layer 8 ... Core die 9, 9' ... Half shell

Claims (1)

[Claims] (1) a step of producing a hollow center (5) containing rubber or a resin or a mixture thereof as a main component; and (ii) semi-vulcanization molding of a rubber composition for forming an outer shell layer to form a hollow center. A half-vulcanized rubber half shell having the same shape of the recess is produced, and a hollow center is sealed inside the two half-vulcanized rubber half shells, and pressurized and heated in an upper and lower mold for forming an outer shell layer. (Iii) if necessary, repeating step (ii), hollow core (6)
And (iv) covering the hollow core with a cover, comprising: a hollow center (5) comprising a hollow portion (1) and an inner shell layer (2) around the hollow portion (1); A method for manufacturing a hollow golf ball, comprising: a hollow core (6) having at least one outer shell layer (3) formed thereon; and a cover (4) formed on the hollow core (6). The pressurizing pressure in the step (ii) is such that the sectional area of the inner shell layer (2) when the hollow center is bisected in a plane is S (cm ² ), and the pressing force applied to the entire hollow core is F ( kg
A method for producing a hollow golf ball, wherein, when f) is satisfied, F / S (kgf / cm ² ) is performed in a range of ²⁰ to 80 kgf / cm ² .