JP3735403B2 - Multi-piece solid golf ball - Google Patents

Description

【表２】

【００２７】
1)日本合成ゴム社製BR-01 7) (重量部)
2)大内新興化学工業社製ノクラック300 ポリブタジエン 100
3)ジクミルパーオキサイド アクリル酸亜鉛 32
4)三井ポリケミカル社製アイオノマー樹脂 酸化亜鉛 20
5)住友化学社製EPDM 老化防止剤 0.3
6)東レデュポン社製ハイトレル ＤＣＰ 1.0
【００２８】
得られた各ゴルフボールについて、プロゴルファーによる打撃時フィーリング、耐久性指数、およびドライバー(ウッド１番クラブ)による飛距離(キャリー(落下点)およびトータル)、について評価を行い、その結果を表３(実施例)および表４(比較例)に示す。試験方法は以下の通り行った。
(試験方法)
▲１▼打撃時のフィーリング
プロゴルファーによりドライバーで実打して評価する。評価基準は下記の通りである。
評価基準
◎ …非常に良い
○ …良い
△ …普通
× …悪い
▲２▼耐久性指数
ゴルフボールを速度45m/秒にて衝突板に繰り返し衝突させ、ゴルフボールが割れるまでの回数を比較例４を100とした指数で表した。
▲３▼飛距離およびスピン
ツルーテンパー社製スイングロボットにドライバーを取付け、ゴルフボールをヘッドスピード45m/秒で打撃し、落下点までの距離(キャリー)およびトータルを飛距離として測定した。
【００２９】
【表３】

１）外層コアに分散され動的架橋されたゴムエラストマーの粒径
【表４】

１）外層コアに分散され動的架橋されたゴムエラストマーの粒径
【００３０】
表３および表４において、コア全体の直径、コア重量、コア圧縮変形量とは、内層コア(1)上に外層コア(2)を被覆することにより得られたソリッドコアの直径、重量、圧縮変形量である。コア圧縮変形量とは、コアに10kgfの荷重負荷時の変形量を基準として、130kgfの荷重を負荷した時のコアの変形量である。
【００３１】
以上の結果より、本発明の実施例１〜10は、打撃時フィーリング、飛び性能、更に優れた耐久性を有し、量産性に優れ、材料のリサイクル可能なマルチピースソリッドゴルフボールを提供し得ることがわかる。
【００３２】
【発明の効果】
多層構造のソリッドコアをカバーで被覆した本発明のマルチピースソリッドゴルフボールにおいて、上記外層コアをエチレン-(メタ)アクリル酸共重合体のアイオノマー中にゴムエラストマーが分散され架橋剤により動的架橋された材料で形成することにより、打撃時フィーリング、飛距離および耐久性、並びに製造上の効率および材料リサイクル性を向上させたものである。
【図面の簡単な説明】
【図１】 本発明のゴルフボールの断面概略図である。
【符号の説明】
１ … 内層コア
２ … 外層コア
３ … カバー[0001]
【Definition of terms】
As used herein, “dynamic cross-linking” means that rubber is cross-linked while being kneaded with a molten thermoplastic resin, and that rubber is dispersed in the thermoplastic resin by this dynamic cross-linking. For example, it is disclosed in Japanese Patent Publication No. 5-29553.
[0002]
BACKGROUND OF THE INVENTION
The present invention relates to a multi-piece solid golf ball having good flight performance, feeling at impact, durability, excellent mass productivity, and recyclable materials.
[0003]
[Prior art]
Conventionally, golf balls are classified into the following two types. One is a solid golf ball such as a two-piece ball, which is composed of a solid 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 central solid or liquid core is wound with a rubber thread winding, and then covered with a cover of ionomer resin or balata having a thickness of 1 to 2 mm. Among the above-mentioned solid golf balls, the two-piece solid golf ball comprising a solid rubber core and cover is easy to manufacture and can be mass-produced, so it occupies the main part of the commercially available solid golf balls. Yes.
[0004]
The two-piece solid golf ball has a long flight distance due to its durability and a high ball speed at the time of hitting, and has excellent flight characteristics. In particular, it is used by many golfers, particularly amateur golfers. On the other hand, a two-piece solid golf ball is spun due to its hard feeling when hitting, high ball speed when hitting, and low spin area due to a small contact area with the hitting surface of the golf club. It was difficult and lacked controllability of the approach. Further, when the ball compression is reduced to obtain a soft hit feeling, the rebound is reduced and the flight distance is also reduced.
[0005]
As a means of improving the disadvantages of such two-piece solid golf balls, the solid solid core part is now divided into two or more layers, hardness, specific gravity, thickness (diameter) of each layer, etc. This is a multi-piece solid golf ball in which As described above, this multi-piece solid golf ball has a multi-layered rubber solid core and is difficult to mass-produce in production. This is because the rubber material is basically poor in fluidity, it is difficult to finish the core outer layer part to a uniform thickness, and the vulcanization process is indispensable as long as it is rubber, which is positive for the production of the core inner layer part. This is because it takes time to manufacture and vulcanize the core outer layer portion.
[0006]
In order to improve such defects, it has been proposed to improve the manufacturing process by blending a thermoplastic material in the core outer layer portion. For example, in Japanese Patent Laid-Open No. 4-244174, the core outer layer portion is molded using a thermoplastic material containing an amide block copolymer of at least 10% by weight, preferably at least 35% by weight of the total weight of the composition. However, there is a demand for a material that is inferior in ball characteristics and more efficient in the manufacturing process.
[0007]
Japanese Patent Laid-Open No. 6-14228 also discloses the use of a thermoplastic material similar to the above in the core outer layer portion, and the material has a Shore D hardness of 30 to 50, and differential thermal analysis ( DSC) from 100 to 50% of polyether ester type thermoplastic elastomer having a glass transition temperature of -25 ° C or less and 0 to 50% of acrylic acid of ethylene- (meth) acrylic acid copolymer having a flexural modulus of 200 to 400 MPa A mixture mainly composed of However, this is a so-called thermoplastic rubber in which the crystalline part of the polyether ester type thermoplastic elastomer has a pseudo-crosslinking role, and is not stable against environmental thermal changes or long-term repeated impacts. I am worried about the shape maintenance. Further, in the case of a blend of an ethylene- (meth) acrylic acid copolymer with an ionomer, there is a problem that both are poor in compatibility and inferior in durability. In selecting the material for the core outer layer, the continuous impact durability of the outer layer itself and the adhesion to the cover material are important.
[0008]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the conventional multi-piece solid golf ball as described above, and to provide a multi-piece solid golf ball made of a material excellent in long-term stable performance and mass productivity.
[0009]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present inventors have covered a solid core having a multilayer structure in which an inner layer core (1) is coated with one or more outer layer cores (2). In the multi-piece solid golf ball coated with (3), the outer core is formed of a material in which a rubber elastomer is dispersed in an ionomer of an ethylene- (meth) acrylic acid copolymer and dynamically cross-linked by a cross-linking agent. The present invention has been completed by finding that a multi-piece solid golf ball excellent in feel at impact, flight distance, and durability can be obtained and also in terms of manufacturing efficiency.
[0010]
The present invention provides a rubber elastomer that is simply crosslinked by using a dynamic crosslinking technique in which an ionomer of an ethylene- (meth) acrylic acid copolymer is used as a matrix and the crosslinked rubber elastomer can be dispersed extremely finely. Finer particles can be dispersed than pulverized and mixed, and durability that has been a problem in the past, particularly durability due to continuous impact and stable performance against long-term impact stimulation can be maintained. Further, an ionomer of an ethylene- (meth) acrylic acid copolymer has already been known for its high durability as a golf ball cover material. Furthermore, the adhesion between the outer core and the cover material has also been a problem in the past, but by using the same ionomer of ethylene- (meth) acrylic acid copolymer as the cover material for the matrix, the interlayer between the cover and the outer core is used. It has been found that problems such as ball deformation or breakage due to peeling, etc., or performance degradation due to energy loss, in particular repulsion and flight distance, can be solved.
[0011]
The present invention will be described in detail below. For the inner layer core, the rubber composition for the core used in current two-piece balls is most suitable. A rubber composition containing polybutadiene rubber, a metal salt of unsaturated carboxylic acid, and peroxide as an essential component is heated under pressure. It is preferable that the outer diameter is 30 to 37 mm. The rubber composition may further contain a filler such as zinc oxide, an antiaging agent, and the like.
[0012]
The polybutadiene used for the inner layer core (1) is preferably a so-called high cis polybutadiene having a cis-1,4-structure of at least 40% or more, preferably 90% or more. If desired, natural rubber, polyisoprene rubber, styrene- Butadiene rubber, EPDM or the like may be blended.
[0013]
Examples of peroxides include organic peroxides such as dicumyl peroxide or t-butyl peroxide, with dicumyl peroxide being preferred. A compounding quantity is 0.3-5.0 weight part with respect to 100 weight part of base rubbers, Preferably it is 0.5-3.0 weight part.
[0014]
The rubber composition used for the inner layer core (1) of the present invention is blended with a metal salt of an unsaturated carboxylic acid. Examples of the metal salt of the unsaturated carboxylic acid include monovalent or divalent metal salts of unsaturated carboxylic acids having 3 to 8 carbon atoms such as acrylic acid or methacrylic acid. Zinc acid is preferred. The blending amount is preferably 10 to 40 parts by weight with respect to 100 parts by weight of the polybutadiene base rubber. If it is more than 40 parts by weight, it becomes too hard and the feeling becomes worse, and if it is less than 10 parts by weight, the rebound becomes worse.
[0015]
In the inner layer core, an inert filler such as zinc oxide, barium sulfate, calcium carbonate, etc .; an anti-aging agent; and other components that can be normally used for the structure of the core of the solid golf ball may be appropriately blended. The blending amount is preferably 15 to 50 parts by weight of the inert filler and 0.2 to 0.5 parts by weight of the anti-aging agent with respect to 100 parts by weight of the polybutadiene base rubber.
[0016]
The inner layer core is obtained by heat-molding the above composition using the method and conditions generally used for a solid core.
[0017]
The ionomer of the ethylene- (meth) acrylic acid copolymer used for the outer core (2) of the golf ball of the present invention is a conventionally known ionomer and is a carboxylic acid group of a copolymer of ethylene and (meth) acrylic acid. Is partially neutralized with metal ions. The flexural modulus is preferably 200 to 450 MPa, more preferably 300 to 400 MPa. If the flexural modulus is less than 200 MPa, the ball hardness decreases, and the feeling and durability at the time of hitting deteriorate. On the other hand, if it is larger than 450 MPa, the ball becomes too hard and the feeling at the time of hitting becomes worse. The ionomer of ethylene- (meth) acrylic acid copolymer used in the present invention is obtained by neutralizing a part of the carboxylic acid of the copolymer of α-olefin and α, β-unsaturated carboxylic acid with a metal ion. Is used. The α-olefin is preferably ethylene or propylene, and the α, β-unsaturated carboxylic acid is preferably acrylic acid or methacrylic acid. Further, the metal ions to be neutralized include alkali metal ions such as Na ions, K ions, Li ions, etc .; divalent metal ions such as Zn ions, Ca ions, Mg ions, etc .; trivalent metal ions such as Al ions, Nd ions, etc. are mentioned, but Na ions, Zn ions, Li ions, etc. are often used from the viewpoint of repulsion and durability. Recently, a grade having excellent moldability has been developed in consideration of injection molding, and this type of dynamic crosslinking is often used because the fluidity is lowered by the addition of a rubber elastomer. Furthermore, a plasticizer or oil may be added to improve fluidity.
[0018]
The rubber elastomer is not particularly limited as long as it can be crosslinked by a crosslinking agent, and examples thereof include butadiene rubber, isoprene rubber, styrene butadiene rubber, nitrile butadiene rubber, ethylene propylene rubber, ethylene propylene diene rubber, urethane rubber, and silicone rubber. In particular, those having good heat resistance such as ethylene propylene diene rubber are preferable from the viewpoint of processing. In addition, diene rubbers are also used because of their good crosslinkability. Regarding the rubber elastomer, the mixing ratio of the ionomer of the ethylene- (meth) acrylic acid copolymer and the rubber elastomer is 90/10 to 30/70, preferably 80/20 to 40/60. The mixing ratio of the rubber elastomer is less than 90/10, and if it is less, the effect of the rubber elastomer blend is small and the durability is good but the feeling at the time of hitting is bad. If the amount of rubber elastomer is larger than 30/70, the ball becomes too soft, feeling at impact, durability or rebound is poor, and the flight distance is also reduced. If the amount of rubber elastomer further increases, the flow of the resin is poor during actual molding, leading to a decrease in processability. The cross-linking agent used for dynamic cross-linking is not limited as long as it does not impair the performance of the matrix resin, but oximes, sulfur and vulcanization accelerators in combination, sulfur alone, vulcanization accelerators alone, etc. are used. It is done. Examples of the vulcanization accelerator include dithiomorpholine, dibenzothiazyl disulfide, mercaptobenzothiazole, tetramethylthiuram disulfide, tetraethylthiuram disulfide and the like. Dithiomorpholine and dibenzothiazyl disulfide are preferable. The amount of the crosslinking agent is 0.2 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of the rubber elastomer.
[0019]
In addition to the above components, the outer layer core of the present invention may contain other components, for example, a filler, a colorant, an antiaging agent, and the like as necessary.
[0020]
In the present invention, the ionomer and the rubber elastomer are subjected to crosslinking while being melted and kneaded to perform dynamic crosslinking. Dynamic cross-linking is industrially performed mainly using an extruder, and an ionomer resin, a rubber elastomer, and a cross-linking agent are introduced, and the temperature is generally set to 150 to a temperature set in accordance with the reaction temperature of the cross-linking agent. It is carried out by crosslinking the rubber elastomer while kneading at 220 ° C. Further, by blending or extruding an ionomer resin and a rubber elastomer in advance, more uniform dynamic crosslinking is performed. In the dynamically crosslinked composition, the rubber elastomer is preferably present with a particle size of 10 μm or less, preferably 5 μm or less. If it exceeds 10 μm, the particles cause stress concentration due to repeated impacts, leading to a decrease in durability. Furthermore, it has been found that the smaller the minimum level, the better the durability.
[0021]
In the present invention, the outer layer core (2) is formed on the inner layer core (1). The outer layer core (2) can easily cover the inner layer core (1) with the dynamically cross-linked outer layer core material by injection molding or the like. The outer layer core material dynamically cross-linked in the present invention has good fluidity at the time of coating and good moldability, and can be injection-molded. Of course, it may be coated by other methods. The outer layer core (2) may not be a single layer but a multilayer. In the case of one layer, the three-piece solid golf ball shown in FIG. 1 is obtained.
A cover (3) is formed by coating the core obtained by coating the outer layer core (2) as described above with a cover material made of an ethylene- (meth) acrylic acid copolymer ionomer resin. The multi-piece solid golf ball of the invention is obtained. The thickness of the cover (3) is preferably 1,5 to 2.7 mm.
The cover material is mainly made of an ionomer resin, but may contain a colorant (for example, titanium dioxide), an ultraviolet absorber, or the like as necessary. In the present invention, the cover (3) has a flexural modulus of 200 to 450 MPa, preferably 250 to 400 MPa. Examples of ionomers that satisfy such conditions include HiMilan 1707, 1601, 1605, 1706, AM7315, AM7317, and the like available from Mitsui DuPont Chemical Co., Ltd.
The cover layer of the present invention is formed by a generally known method used for forming a golf ball cover, such as injection molding or press molding. When the cover (3) is covered, many depressions called dimples are usually 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 the beauty and increase the commercial value.
[0022]
The present invention provides a multi-piece solid golf ball that has good flight performance, feel at impact and durability, is excellent in mass productivity, and can recycle the outer core material together with the cover material.
[0023]
【Example】
The present invention will be described in further detail with reference to examples. However, the present invention is not limited to these examples.
(Examples 1 to 10 and Comparative Examples 1 to 6 ) The compositions for the inner core of the composition shown in Table 1 (Example) and Table 2 (Comparative Example) were kneaded and pressure-molded at 160 ° C. for 20 minutes. Inner cores with diameters as shown in Table 3 (Examples) and Table 4 (Comparative Examples) were produced. Concentrically on this inner layer core, the composition for outer layer core having the composition shown in Table 1 (Example) and Table 2 (Comparative Example) was provided by injection molding, and Table 3 (Example) and Table 4 (Comparative) A two-piece solid core with a diameter as shown in Example) was obtained. Tables 3 and 4 show the weight of the obtained two-piece solid core, the amount of compressive deformation, and the particle size of the rubber elastomer dispersed and dynamically crosslinked in the outer layer core. The cover composition shown in Table 1 and Table 2 was injection-molded on the obtained two-piece solid core to cover the cover to obtain a three-piece solid golf ball. Tables 3 and 4 show the thickness and hardness of the obtained cover, and the weight, compression deformation, and outer diameter of the three-piece solid golf ball.
[0024]
(Comparative Example 7 ) Three-piece solid as in Examples 1 to 10 and Comparative Examples 1 to 6 , except that the same material as the inner layer core was used in the composition for the outer layer core in the amount shown in Table 2. A golf ball was obtained.
[0025]
(Comparative Example 8 ) A commercially available three-piece solid golf ball was used.
[0026]
[Table 1]

[Table 2]

[0027]
1) BR-01 manufactured by Nippon Synthetic Rubber Co. 7) (parts by weight)
2) Nouchi 300 Polybutadiene 100 manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
3) Dicumyl peroxide Zinc acrylate 32
4) Ionomer resin made by Mitsui Polychemical Co., Ltd.Zinc oxide 20
5) EPDM anti-aging agent manufactured by Sumitomo Chemical Co., Ltd.0.3
6) Hytrel DCP 1.0 manufactured by Toray DuPont
[0028]
Each golf ball obtained was evaluated in terms of feeling when hit by a professional golfer, durability index, and flight distance (carry (falling point) and total) by the driver (wood No. 1 club), and the results are shown in Table 3. (Example) and Table 4 (comparative example). The test method was as follows.
(Test method)
(1) Evaluation by hitting with a driver by a feeling professional golfer at the time of hitting. The evaluation criteria are as follows.
Evaluation criteria ◎… very good ○… good △… ordinary ×… bad ▲ 2 ▼ durability index The golf ball is repeatedly collided with the collision plate at a speed of 45 m / sec. Expressed with an index of 100.
(3) Flying distance and a driver was attached to a swing robot manufactured by Spin True Temper, and a golf ball was hit at a head speed of 45 m / second, and the distance to the falling point (carry) and the total were measured as the flying distance.
[0029]
[Table 3]

1) Particle size of rubber elastomer dispersed in outer core and dynamically cross-linked [Table 4]

1) Particle size of rubber elastomer dispersed in outer core and dynamically cross-linked
In Table 3 and Table 4, the diameter, weight, and compression amount of the entire core are the diameter, weight, and compression of the solid core obtained by coating the outer core (2) on the inner core (1). The amount of deformation. The amount of core compression deformation is the amount of deformation of the core when a load of 130 kgf is applied to the core based on the amount of deformation when a load of 10 kgf is applied.
[0031]
From the above results, Examples 1 to 10 of the present invention provide a multi-piece solid golf ball that has a feel at impact, flying performance, and excellent durability, is excellent in mass productivity, and can be recycled. I know you get.
[0032]
【The invention's effect】
In the multi-piece solid golf ball of the present invention in which a multi-layer solid core is covered with a cover, the outer layer core is dynamically cross-linked by a cross-linking agent in which a rubber elastomer is dispersed in an ethylene- (meth) acrylic acid copolymer ionomer. By using the same material, the feeling at the time of hitting, the flight distance and durability, the manufacturing efficiency and the material recyclability are improved.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a golf ball of the present invention.
[Explanation of symbols]
1 ... Inner layer core 2 ... Outer layer core 3 ... Cover

Claims (1)

A multi-piece solid golf ball comprising a core and a cover (3) formed on the core, wherein the core has a multilayer structure of an inner layer core (1) and one or more outer layer cores (2).
The inner layer core ( 1 ) is obtained by pressurizing and curing a rubber composition containing polybutadiene rubber, zinc acrylate and peroxide as essential components, and has an outer diameter of 30 to 37 mm.
The outer layer core (2) is formed of a material in which a rubber elastomer is dispersed in an ionomer of an ethylene- (meth) acrylic acid copolymer and dynamically cross-linked by a cross-linking agent, and the ethylene- ( meth ) acrylic acid copolymer The mixing ratio of the ionomer and the rubber elastomer is 90/10 to 30/70 (ionomer / rubber elastomer), the particle diameter of the dispersed and dynamically crosslinked rubber elastomer is 10 μm or less, and the ethylene- ( meta ) The ionomer of the acrylic acid copolymer has a flexural modulus of 200-450 MPa,
A multi-piece solid golf ball, wherein the cover (3) is formed of an ionomer of an ethylene- (meth) acrylic acid copolymer having a flexural modulus of 200 to 450 MPa.

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