JP2001178851A - Solid golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a golf ball wherein a feel of a soft shot can be obtained and a good flying performance and durability can be achieved. SOLUTION: In the solid golf ball comprising a core of one layer or multilayer construction and a cover layered over the core, at least one layer of the core is a vulcanized molded item of a rubber composition containing a base rubber of 100 parts by mass and a silane coupling agent of 0.1-5.0 parts by mass.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid golf ball comprising a core and a cover, which provides a soft hit feeling, and is excellent in flight performance and durability.

[0002]

2. Description of the Related Art In recent years, many golfers have tended to prefer golf balls having a soft impact when hit. A thread-wound golf ball is known as a golf ball having a soft hit feeling. However, thread-wound golf balls are inferior in flight performance and durability to solid golf balls typified by two-piece golf balls due to their structural characteristics, so that average golfers may use solid golf balls. Many.

Therefore, many studies have been made to soften the hit feeling of solid golf balls. Methods for softening the feel include a method of softening the solid core and a method of softening the cover.

A solid golf ball having a soft cover has a large launching angle and an increased spin rate due to a large frictional force with the golf club when shot with a golf club. Since an increase in the spin amount leads to an improvement in control performance, professional golfers and advanced amateur golfers tend to use solid golf balls with a soft cover. On the other hand, when the launch angle is reduced and the spin amount is increased, the trajectory is like a blow-up, so that the flight distance is likely to be reduced. For this reason, the average golfer does not want to use a solid golf ball with a soft cover.

[0005] For average golfers,
There is a high demand for golf balls that have a soft feel at impact and that do not impair flight performance. In order to satisfy such demands, various researches have been made on golf balls having a soft feeling without deteriorating the resilience of the balls, in particular, a soft and high resilience core material.

For example, Japanese Patent Application Laid-Open No. 10-80503 proposes to add a specific organic sulfur compound to a core material. However, when the core is softened by adding an organic sulfur compound to the core material, there is a problem that the amount of deformation at the time of hitting becomes large, so that the durability is reduced. Especially in the case of a multi-piece golf ball consisting of a core and a cover, if the core is softened and the cover is hardened to ensure impact resistance, the core and cover will easily peel off due to the difference in the amount of deformation at the time of impact, and durability will be reduced. descend.

On the other hand, as a core material having improved resilience and durability, a core material to which a titanate coupling agent is added has been proposed (Japanese Patent Application Laid-Open No. H10-108925). However, since the rubber composition to which the titanate coupling agent is added has improved durability and resilience by hardening the core, the hit feeling is hard, which can satisfy golfers who prefer a soft feeling. Can not.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a soft hit feeling, excellent flight performance, and durability. Is to provide a good golf ball.

[0009]

Means for Solving the Problems In a golf ball having a solid core covered with a cover, the present inventors reduced the hardness by including a silane coupling agent in a rubber composition constituting the solid core. Even so, the inventor has found that the adhesiveness to the cover is excellent and the flight performance does not need to be reduced, and the present invention has been completed.

That is, the solid golf ball of the present invention is a solid golf ball including a core having a one-layer structure or a multilayer structure of two or more layers, and a cover covering the core, wherein at least one layer of the core has Base rubber 1
It is a vulcanized molded product of a rubber composition containing 00 parts by mass and 0.1 to 5.0 parts by mass of a silane coupling agent.

The rubber composition further comprises an α, β-unsaturated carboxylic acid and / or 100 parts by mass of the base rubber.
Alternatively, it is preferable to contain 10 to 50 parts by mass of a metal salt thereof, 0.1 to 5.0 parts by mass of an organic peroxide, and 5 to 50 parts by mass of zinc oxide.

Preferably, the difference between the JIS-C hardness of the core surface and the JIS-C hardness of the center of the core is 20 degrees or more.

It is preferable that a deformation amount of the core when an initial load of 98N is applied to the core and a final load of 1275N is applied is 2.5 to 5 mm.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The golf ball of the present invention is a multi-piece type golf ball in which a core is covered with a cover, and a rubber composition (core rubber composition) as a core material has a base material. Contains rubber and silane coupling agent.

The base rubber may be a diene rubber having a diene component in the molecule. Specifically, butadiene rubber (BR), ethylene propylene diene terpolymer (EPDM) , Isoprene rubber (I
One or more of R), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR) and the like can be used, and among these, butadiene rubber is preferably used as a main component. As the butadiene rubber, a high cis polybutadiene having a cis-1,4 bond content of 40% or more, preferably 70% or more, more preferably 90% or more is preferably used.

The silane coupling agent used in the present invention is a compound represented by the following general formula. (RO) _a —Si—X _{b In the} formula, R is a saturated alkyl group having 1 to 3 carbon atoms, which may be the same or different. a and b are both 1
Satisfies a + b = 4. A combination in which a is 3 and b is 1 is preferable. X is an organic group having a vinyl group, an amino group, an epoxy group, a methacryloxy group, a chloropropyl group, or a mercapto group. It is sufficient that the organic group represented by X has at least one of these functional groups, and it may be at the terminal or inside the molecule.

Accordingly, examples of the silane coupling agent having a vinyl group include vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltris (β-methoxyethoxy) silane. Examples of the silane coupling agent having an epoxy group include β- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycid Xypropyltriethoxysilane and the like can be mentioned. Examples of the silane coupling agent having a methacryloxy group include γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, and γ-methacryloxypropyltriethoxysilane. . Examples of the silane coupling agent having an amino group include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, and N-β (aminoethyl) γ-aminopropyl Methyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β
(Aminoethyl) γ-aminopropyltriethoxysilane and the like. Examples of the silane coupling agent having a chloropropyl group include γ-chloropropyltrimethoxysilane, and examples of the silane coupling agent having a mercapto group include γ-mercaptopropyltrimethoxysilane. These silane coupling agents may be used alone or in combination of two or more.

These silane coupling agents affect the crosslinked structure to create a more optimal crosslinked form, and can reduce the hardness while ensuring resilience.
Furthermore, the silane coupling agent present on the surface of the solid core has an affinity for the cover material covering the solid core, and contributes to the improvement in the adhesion between the solid core and the cover. This makes it possible to prevent a decrease in durability due to a difference in the amount of deformation between the core and the cover due to the lower hardness of the core. Further, the increase in the adhesion between the core and the cover can reduce the energy loss due to the relative movement between the core and the cover that occurs at the time of hitting the ball, thereby improving the resilience performance. Although the reason is not well understood, the center hardness of the core using the rubber composition containing the silane coupling agent is as follows:
The core hardness becomes lower than the center hardness of the core using the rubber composition containing no silane coupling agent. Therefore, if a rubber composition for a core using a silane coupling agent is used, it is possible to increase the hardness difference between the center and the surface of the solid core, thereby increasing the launch angle at the time of shot and reducing the spin rate. be able to. In other words, since the spin amount is not too large and not too small, it does not blow up against a headwind and has a trajectory called a so-called ball and ball, so that the flight distance increases. Also, if the difference in hardness is large, the amount of deformation near the center when hitting the ball is large, achieving a soft feeling, while reducing the difference in the amount of deformation between the cover and the core surface layer and contributing to improved durability it can.

The silane coupling agent is a base rubber 100
0.1 parts by mass or more, preferably 0.5 parts by mass or more and 5.0 parts by mass or less, preferably 4.5 parts by mass or less with respect to parts by mass, is contained in the core rubber composition. If the content of the silane coupling agent is too large, the hardness is reduced not only at the center of the core but also over the entire core, resulting in a decrease in resilience. Also, if the core surface is softened, the core will be easily deformed when hit, so the difference in deformation amount with the cover will be too large, and it will not be possible to compensate for the increase in adhesion with the silane coupling agent, resulting in reduced durability. Because it becomes.

Japanese Patent Application Laid-Open No. 9-48880 discloses a rubber composition containing a silane coupling agent for dispersing silica particles. This is a composition in which a silane coupling agent is blended to improve the dispersibility of silica particles blended as a reinforcing agent for rubber products, and reduces energy loss and increases resilience. However, the rubber composition containing silica cannot be used as a rubber material for golf balls aiming at a soft feeling because the hardness increase due to the silica mixing is too large.

The rubber composition for a core used in the present invention contains, in addition to the base rubber and the silane coupling agent, an organic peroxide as a cross-linking initiator and 3 carbon atoms as a co-cross-linking agent.
It is preferable that the composition contains α to 8 unsaturated carboxylic acids and / or metal salts thereof.

Examples of the organic peroxide include dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,
5-trimethylcyclohexane, 2,5-dimethyl-
2,5-di (t-butylperoxy) hexane, di-t
Organic peroxides such as -butyl peroxide;
Of these, dicumyl peroxide is preferably used. The content of the organic peroxide is preferably at least 0.1 part by mass, particularly preferably at least 0.2 part by mass with respect to 100 parts by mass of the diene rubber. Further, the upper limit of the content is preferably 5.0 parts by mass, particularly preferably 3.0 parts by mass. If the amount is less than 0.1 part by mass, the material becomes too soft, and if it exceeds 5.0 parts by mass, the material becomes too hard.

As the α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, acrylic acid and methacrylic acid are preferably used, and as the metal salts, zinc salts and magnesium salts are preferably used. The content of such a co-crosslinking agent,
It is preferably at least 10 parts by mass, particularly preferably at least 15 parts by mass, based on 100 parts by mass of the base rubber, and the upper limit of the content is preferably 50 parts by mass, particularly preferably 45 parts by mass. If it is less than 10 parts by mass,
This is because the material becomes too soft, and the amount of deformation at the time of impact increases, energy loss increases, and resilience decreases. 5
If the amount is less than 0 parts by mass, the ball becomes too hard and the shot feeling becomes hard, which is not practical for golfers who prefer a soft shot feeling and is not practical.

The rubber composition for the core used in the present invention may further contain a filler for the purpose of adjusting the specific gravity.
It is preferable to mix 5 to 50 parts by mass of the specific gravity adjuster with respect to 00 parts by mass. When using a filler with a low specific gravity,
This is because a large amount of filler is added to the core, so that the rubber fraction is reduced and the resilience is reduced. As the specific gravity adjusting agent, those having a specific gravity of 2.5 or more, more preferably 3.5 or more are mainly used. When a filler having a specific gravity of less than 2.5 is blended, the specific gravity relative to the total content of the whole specific gravity adjusting agent is 2.
The ratio of the specific gravity adjusting agent of less than 5 is preferably at most 0.3, more preferably at most 0.15.

As the specific gravity adjusting agent having a specific gravity of 2.5 or more, zinc oxide (specific gravity: about 5.6) and titanium oxide (specific gravity: about 3.
8), metal oxides such as barium sulfate (specific gravity: about 4.3), calcium carbonate (specific gravity: 2.6), and metal powders such as tungsten (specific gravity: about 19) can be used. Of these, zinc oxide which also functions as a vulcanization aid is preferably used. The content of zinc oxide in the rubber composition for the core is
It is preferably at least 5 parts by mass, particularly at least 10 parts by mass, per 100 parts by mass of the base rubber, and the upper limit of the content is preferably 50 parts by mass, particularly preferably 40 parts by mass.

The rubber composition for a core used in the present invention may further contain, if desired, an antioxidant, a pigment and the like.

A solid core is formed by kneading the above rubber composition and heat-molding it in a mold.
The solid core may have a single-layer structure or a multilayer structure of two or more layers (multi-core). In the case of a multi-piece core, at least one layer may be composed of a vulcanized molded article of the core rubber composition containing the silane coupling agent. However, it is preferable that the entire core is constituted by a vulcanized molded article of the rubber composition for a core containing a silane coupling agent.

It is preferable that the core of the present invention has the softest center hardness, becomes harder as it approaches the surface layer, and has the hardest surface layer, that is, a so-called outer-hard inner-softness hardness distribution. By softening the inside and softening the shot feeling and increasing the hardness of the surface layer, the difference in the amount of deformation with the cover at the time of hitting can be reduced, and the reduction in resilience and durability can be prevented. is there.

The difference between the hardness at the center of the core and the hardness at the core surface is preferably at least 20 degrees in JIS-C hardness. The reason is that by setting the hardness distribution of the outer hard and inner soft having such a hardness difference, conflicting demands of a soft feel at impact, a decrease in resilience and a prevention of a decrease in durability can be satisfied. In addition, with such a hardness distribution, the launch angle can be increased, the spin rate can be reduced, and the flight performance can be improved.

The hardness at the center of the core is 30 in JIS-C hardness.
It is preferably from 70 to 70 degrees, and more preferably from 40 to 65 degrees. If it is less than 30 degrees, it is too soft and the resilience performance deteriorates.
If it exceeds 0 degree, it is difficult to obtain a soft feel at impact, and it becomes difficult to obtain a hardness distribution of outer hard and inner soft in which the difference between the hardness of the core central portion and the hardness of the core surface is 20 or more.

The surface hardness of the core of the present invention is preferably 70 to 90 degrees in JIS-C hardness, more preferably 75 to 8 degrees.
8 degrees. If the surface hardness is less than 70 degrees, the resilience decreases, and if it is more than 90 degrees, the feeling becomes hard.

The outer diameter of the core of the golf ball of the present invention (the outer diameter of the surface layer core in the case of a multi-piece core) is 30 to 41.
mm is preferred, and more preferably 32 to 40 mm.

The core of the golf ball of the present invention (in the case of a multi-piece core, the multi-piece core) has a lower limit of deformation of 2.5 mm when an initial load of 98 N is applied and a final load of 1275 N is applied. It is preferably, more preferably, 3.0 mm, and the upper limit of the deformation is preferably 5.0 mm, more preferably 4.5 mm. If it is smaller than 2.5 mm, the core becomes too hard, and a soft shot feeling cannot be obtained. If it is larger than 5.0 mm, the core becomes soft and easily deformed, so that the resilience and durability are reduced. It is. Incidentally, when a core having a deformation amount of 2.5 mm or more, particularly 3.0 mm or more is produced with a conventional rubber composition containing no silane coupling agent, it is possible to achieve high resilience like the core of the present invention. Although difficult, the use of the rubber composition for a core of the present invention can provide a ball and ball trajectory even with a soft core having a deformation of about 2.5 mm, so that the flight distance does not decrease. .

The golf ball of the present invention is obtained by covering the above-mentioned core with a cover. The cover may have a single layer or a multilayer structure of two or more layers (ie, a multi-piece core). You may.

As the material used for the cover, a conventionally used cover material can be used, and a resin composition using a thermoplastic resin as a base resin is preferably used.

As the thermoplastic resin, an ionomer resin is preferably used. This is because covers mainly composed of ionomers have a high rebound. In addition to the ionomer resin, a polyethylene elastomer, a polyester elastomer, a polyamide elastomer, a polyurethane elastomer, a styrene-butadiene elastomer, and the like can be used, and a mixture of the ionomer resin and these elastomers may be used. When an ionomer and another resin are mixed and used, the resin component 5 of the resin composition for a cover may be used.
It is preferable that the ionomer is 0% by weight or more, preferably 80% by weight or more.

The cover resin composition used in the present invention may contain, if necessary, a filler such as titanium oxide, barium sulfate, calcium carbonate, an ultraviolet absorber, an antioxidant,
Additives such as pigments and optical brighteners may be appropriately blended.

As a method for covering the core with the cover, a conventionally known method may be used, for example, an injection molding method, a compression molding method or the like is employed. When forming the cover, desired dimples are formed as necessary.

The thickness of the cover is preferably from 1.0 to 6.0 mm, more preferably from 1.3 to 4.0 mm.

After the cover is formed, paint or marking is applied as necessary. Before marking or painting,
A paint pretreatment known to those skilled in the art (for example, surface polishing treatment, shot blast treatment, framing treatment, plasma treatment, corona discharge treatment, etc.) may be performed.

The paint used for the paint coating may be a white and desired enamel paint or a clear paint. In any case, urethane paint is preferred as the paint because of good elongation and adhesion. If necessary, additives such as an ultraviolet absorber, a light stabilizer, a fluorescent brightener, a lubricant, and a pigment may be added to the paint.

The golf ball of the present invention has a diameter of not less than 42.67 mm and a weight of not more than 45.63 g according to the Rules of Golf in the state of final finishing.

[0043]

Example [Evaluation method] Amount of compressive deformation of core (mm) From a state where an initial load of 98 N was applied to the core, a final load of 1275
The amount of deformation of the core when N was applied was measured.

Hardness distribution A solid core was cut along a plane passing through the center, and the hardness of the core center, a position of 5 mm from the center, a position of 10 mm from the center, a position of 15 mm from the center, and the hardness of the core surface were measured using a JIS-C hardness tester. Was measured.

Coefficient of Restitution A cylindrical project tile made of aluminum was made to collide with the ball at a speed of 45 m / s, and a coefficient of restitution calculated from the speed of the ball and the project tile after the collision was obtained.
No. The coefficient of restitution of 8 is expressed as an index, with 100 as the coefficient. The larger the index, the greater the resilience.

Driver launch angle and spin rate A driver was attached to a swing robot manufactured by True Temper Co., Ltd. A photograph was taken of the golf ball after impact when hit at a head speed of 45 m / s, and the launch angle and spin rate were calculated.

Driver Carry (m) A driver was attached to a swing robot manufactured by True Temper Corporation, and the distance (carry) to the drop point of the golf ball when the golf ball was hit at a head speed of 45 m / s was measured.

Hitting Feeling Ten golfers, professional golfers or amateur top golfers, actually hit with a driver, and the hitting feeling was evaluated based on the magnitude of impact at the time of hitting and the presence or absence of rebound. When the impact is large, there is no resilience, and when the ball feels heavier at the time of hitting, it is evaluated as a bad shot feeling. A ball evaluated as poor by 5 or more is evaluated as "x", and two or more and less than 5 are evaluated as bad. The ball that was evaluated as “○” was evaluated as “bad”, and the case where one or less evaluated it as poor was evaluated as “◎”.

Durability Test A ball was repeatedly applied to an iron impact plate having a face groove at a speed of 45 m / s, and the number of repetitions until the ball was broken was measured. Here, breaking of the ball means a state in which the ball is cracked, the cover is peeled off, or the core is cracked and the external shape of the ball is deformed.

[Preparation of Core] The rubber composition for a core shown in Table 1 was kneaded using a kneader and a roll, and then was heated and molded at 160 ° C. for 30 minutes using a mold to have a diameter of 38.4 mm.
Solid core No. 1 to 9 were produced. Solid core No. In Nos. 1 to 9, the type (silane coupling agent, titanate coupling agent, sulfide) and the amount of the resilience improver were changed as shown in Table 2. However,
No. 7 is a core produced using a rubber composition containing no resilience improver. For each of the cores thus prepared, the amount of compressive deformation and hardness distribution were measured in accordance with the above evaluation method.

The following were used as the resilience improver.

Silane coupling agent 1: K manufactured by Shin-Etsu Chemical
BM403 (γ-glycidoxypropyltriethoxysilane), silane coupling agent 2: KBM manufactured by Shin-Etsu Chemical
603 (N-β (aminoethyl) γ-aminopropyltrimethoxysilane) titanate coupling agent: Prenact KR TTS sulfide manufactured by Ajinomoto Co., Inc .: diphenyl disulfide

[0053]

[Table 1]

In Table 1, the butadiene rubber is JSR
BR-01 (cis 1,4 bond content: 96%) was used. As the zinc acrylate, one manufactured by Asada Chemical Co., Ltd. was used. The zinc white used was made by Toho Zinc Co., Ltd.
"Park Mill D" manufactured by NOF Corporation was used as dicumyl peroxide.

[Preparation of Cover] Two kinds of ionomers (Himilan 1605 and Himilan 1706: both trade names of Mitsui Dupont Polychemical Co., Ltd.) were mixed by 50 parts by mass, and 4 parts by mass of titanium oxide were further mixed with a twin-screw extruder. And a pelletized resin composition for a cover was obtained with a pelletizer.

[Production of golf ball] The resin composition for a cover was injection-molded and coated on the core prepared above. Next, the usual processing for producing a golf ball such as deburring, paint pretreatment, and paint was performed to obtain a finished golf ball having a weight of 45.4 g and a diameter of 42.8 mm (cover thickness 2.2 mm).

With respect to the golf balls produced as described above, the coefficient of restitution, launch angle, spin rate, carry, durability and shot feeling were measured based on the above evaluation methods.
The results are shown in Table 2 together with the type and amount of the resilience improver.

[0058]

[Table 2]

[Evaluation] No. Nos. 1 to 6 (golf balls using a rubber composition containing a silane coupling agent) and No. 1 7
Compared to both, the shot feel is almost the same, but the flight distance,
No. for both durability. Golf balls 1 to 4 were more excellent. Therefore, the silane coupling agent has the effect of increasing the flight distance and improving the durability by increasing the launch angle while reducing the spin rate without hardening the golf ball. I understand.

No. From 1 to 4, as the content of the silane coupling agent increases, the core hardness can be reduced without lowering the coefficient of restitution, and the shot feeling, flight distance,
It can be seen that all of the durability is improved. However, if the content of the silane coupling agent is too large, the core becomes too soft, the durability is reduced, and the coefficient of restitution is reduced, resulting in a reduced flight distance. Had poor resilience and a heavy shot feeling.

No. 1 and No. Comparing No. 8, when sulfide is mixed in place of the silane coupling agent, the hardness of the entire core is softened, so that the shot feeling can be improved, but the durability decreases. In addition, since the spin rate is increased and the launch angle is reduced, the repulsion and the shot feeling are almost the same. The flight distance was inferior to the golf ball No. 3.

When the titanate coupling agent was blended (No. 9), the durability was improved because the entire core was hardened, but the shot feeling was reduced, and the spin rate was increased to increase the launch angle. Of the golf ball of the present invention having a similar coefficient of restitution because The flight distance was inferior to 1 and 2.

In addition, No. Nos. 1 to 6; From the comparison with 7 to 9, the difference in hardness between the center and the surface of the core of 20 or more can suppress the spin amount, increase the launch angle, and even when the restitution coefficient is almost the same. It can be seen that the flight distance can be extended.

[0064]

As described above, the golf ball of the present invention improves the durability by improving the adhesion between the core and the cover while softening the center of the core to soften the shot feeling. It is a golf ball with excellent flight performance that can be drawn and fly.

Accordingly, the golf ball is suitable for a golfer who desires both a soft feeling and an increased flight distance.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J002 AC031 AC061 AC071 AC081 BB151 DA119 DE109 DE139 DE239 DG049 EF047 EG037 EG047 EX036 EX038 EX066 EX076 EX086 FD019 FD146 FD147 GC01

Claims (4)

[Claims] 1. A solid golf ball including a core having a one-layer structure or a multilayer structure of two or more layers, and a cover covering the core, wherein at least one layer of the core is composed of 100 parts by mass of a base rubber and silane. A solid golf ball, which is a vulcanized molded product of a rubber composition containing 0.1 to 5.0 parts by mass of a coupling agent. 2. The rubber composition further comprises 10 to 50 parts by mass of an α, β-unsaturated carboxylic acid and / or a metal salt thereof and 100 parts by mass of an organic peroxide per 100 parts by mass of the base rubber. 2. The solid golf ball according to claim 1, wherein the solid golf ball contains about 5.0 parts by mass and 5 to 50 parts by mass of zinc oxide. 3. The solid golf ball according to claim 1, wherein the difference between the JIS-C hardness of the core surface and the JIS-C hardness of the center of the core is 20 degrees or more. 4. The solid golf according to claim 1, wherein an amount of deformation of the core when an initial load of 98N is applied to the core and a final load of 1275N is applied is 2.5 to 5 mm. ball.