JPH0352310B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION This invention relates to an improved three-piece solid golf ball and method of manufacturing the same. Conventional technology Solid golf balls developed to improve the durability of thread-wound golf balls have the disadvantage that increasing repulsion reduces durability, and conversely, increasing durability deteriorates repulsion. Therefore, a two-piece solid core is usually used in which a relatively elastic solid core is covered with a relatively durable cover, but none of them are fully satisfactory. Problems to be Solved by the Invention In order to eliminate these drawbacks, a three-piece solid golf ball has been developed in which the solid core is divided into two layers: an inner layer with excellent rebound and an outer layer with excellent durability. However, in such a three-piece solid golf ball, it is not only difficult to obtain a ball of uniform quality because uneven thickness of the outer rubber layer tends to occur during the press process that combines the inner and outer layers of the solid core, but also the inner and outer layers are Difficulties regarding durability, such as relatively early cracking and deterioration of repulsion properties due to the difficulty of imparting sufficient adhesion between the materials, have not yet been overcome. The present invention has been made to overcome the drawbacks of such three-piece solid golf balls. Means for Solving the Problems According to the present invention, as shown in the schematic cross-sectional view of FIG. A three-piece solid golf ball and a method for manufacturing the same, characterized in that a protrusion 1' having a height comparable to the thickness of the outer layer 2 and integrally formed with the inner layer 1 is provided on the surface of the inner layer 1, and a method for manufacturing the same. Regarding. Although the compositions of the inner layer 1 and the outer layer 2 constituting the core of the three-piece solid golf ball according to the present invention are generally the same, they may be changed as desired. The components of the solid core include a base rubber, a crosslinking agent, a co-crosslinking agent, an inert filler, and the like. As the base rubber, any suitable natural rubber and/or synthetic rubber that has been conventionally used in solid golf balls can be used, but in the present invention, 1,4- Polybutadiene is particularly preferred, and if desired, natural rubber, polyisoprene rubber, styrene-butadiene rubber, etc. may be appropriately blended with the polybutadiene. Dicumyl peroxide and t-
Examples include organic peroxides such as butyl peroxide, but dicumyl peroxide is particularly preferred. The amount of the crosslinking agent blended is usually 0.5 to 3.0 parts by weight, preferably 1.0 to 2.5 parts by weight, based on 100 parts by weight of the base rubber. The co-crosslinking agent is not particularly limited, but includes metal salts of unsaturated fatty acids, especially metal salts having 3 carbon atoms.
Examples include zinc salts and magnesium salts of unsaturated fatty acids (e.g. acrylic acid, methacrylic acid, etc.) of 8 to 8, but zinc acrylate (normal salt) is particularly preferred, and the amount is based on 100 parts by weight of the base rubber. 20 to 38 parts by weight, preferably 25 to 36 parts by weight. Examples of inert fillers include zinc oxide, barium sulfate, silica, calcium carbonate, and zinc carbonate, but zinc oxide is common, and its amount depends on the specific gravity of the inner and outer layers, the weight standard of the ball, etc. Usually, but not exclusively, the base rubber
The amount is 3 to 150 parts by weight per 100 parts by weight. The core inner layer composition obtained by blending the above components is kneaded using a conventional kneading machine, such as a Banbury mixer or a roll, and then compressed or injected into a core inner layer mold having recesses corresponding to the protrusions 1'. The temperature is sufficient for the crosslinking agent and co-crosslinking agent to act (for example, approximately 150 to 170°C when dicumyl peroxide is used as the crosslinking agent and zinc acrylate is used as the co-crosslinking agent). ) to prepare a solid core inner layer having protrusions 1' on the surface. The shape, height, number, arrangement method, etc. of the protrusions are not particularly limited, but usually, for example, cylindrical protrusions with rounded tips (about 2 to 3 mm in diameter; about 1 to 3 mm in height) are placed on the inner layer surface of the solid core. Arrange 6 to 20 pieces evenly. The surface of the solid core inner layer with protrusions is then subjected to buffing and/or chemical treatment. The buffing treatment is performed by, for example, sandblasting, iron powder blasting, vibrating barrel treatment, or the like. Further, the chemical treatment is performed using, for example, a chlorine compound (for example, chlorine water, etc.), chromic acid, etc. at a concentration of about 0.1 to 5%. The chemically treated inner layer surface is washed with water and then dried. Other examples include plasma treatment. The solid core of the three-piece solid golf ball according to the present invention is formed by further providing an outer layer on the inner layer prepared as described above. That is, a core outer layer composition obtained by blending and kneading the above components is provided concentrically on the core inner layer by in-mold compression or injection molding, and this two-layer molded body is then mixed with the crosslinked material contained in the outer layer. A two-piece solid core is formed by heating and curing at a temperature sufficient for the action of the crosslinking agent and co-crosslinking agent. In this step, the outer layer 2 is placed on the surface of the inner layer 1.
Due to the presence of the protrusions 1' having almost the same height as the inner layer, uneven thickness of the outer layer rubber is effectively prevented, and the effect of the treatment on the surface of the inner layer and the anchoring effect of the protrusions 1' combine to prevent the inner layer from becoming uneven. The interfacial adhesion of the outer layer is significantly improved without the use of adhesives. The two-piece solid core obtained as described above is covered with a cover having a thickness of 1.4 to 2.7 mm. The cover is usually made of an ionomer resin and contains an inorganic filler (for example, titanium dioxide, zinc oxide, etc.) for the purpose of coloring, if necessary. A preferred ionomer resin is a polymer of a monoolefin and at least one member selected from the group consisting of unsaturated mono- or dicarboxylic acids having 3 to 8 carbon atoms and esters thereof (unsaturated mono- or dicarboxylic acids and/or esters thereof). It is a thermoplastic resin with cross-metal bonds added to (contains 4 to 30% by weight of ester). Such ionomer resins include various "Surlyn" commercially available from DuPont (for example, Surlyn 1601, 1707, 1605).
etc. or a combination thereof). The method of coating the solid core with the cover is not particularly limited, but usually the solid core is wrapped with two covers formed in advance into a hemispherical shell shape and molded under heat and pressure, but the cover composition is injection molded to form the solid core. You can also wrap it around. Hereinafter, the present invention will be explained with reference to Examples. Examples Example 1 The core inner layer composition according to the formulation shown in Table 1 was kneaded using a kneading roll, and the core inner layer composition was mixed into cylindrical recesses (12; spherical was divided into dodecahedrons, and one protrusion was arranged on each face.) was pressure-molded at 160°C for 20 minutes in a spherical mold with a diameter of 31 mm in which the protrusions were arranged evenly to form protrusions on the surface. A solid core inner layer was prepared. The surface of this core inner layer is buffed using sandblasting, and then a core outer layer composition kneaded according to the formulation shown in Table 1 is applied concentrically on the core inner layer by compression molding, and this two-layer molding is performed. body 160
A two-piece solid core was obtained by heat treatment at ℃ for 20 minutes. The obtained two-piece solid core was wrapped with two hemispherical shell-like covers (approximately 2.3 mm thick) prepared according to the formulation shown in Table 1, and pressure molded at 150°C for 2 minutes to form a 41.3 mm diameter solid core. A three-piece solid golf ball was manufactured. I punched out the inner layer of the solid core of this ball using a hole puncher (8mmφ) and tried to peel off the interface between the inner and outer layers with an awl, but the adhesion between the inner and outer layers was good and I could not peel it off, so I tried to force it. As a result, material failure of the solid core occurred.
This good adhesion between the inner and outer layers makes the ball 45
It remained undamaged even after hitting the impact plate 100 times at a speed of m/s. Also, the initial coefficient of repulsion of the ball and the ball
The repulsion coefficient after hitting the impact plate 100 times at a speed of 45 m/sec was examined at a club head speed of 45 m/sec. Furthermore, the ball was repeatedly hit against the collision plate at a speed of 45 m/sec, and the number of hits until the ball cracked was determined. The above measurement results are shown in Table-2. Example 2 Solid core inner layer surface treatment with 0.5% chromic acid
The procedure of Example 1 was repeated except that a solution was used, and the measurement results are shown in Table 2. Note that, as in Example 1, the adhesion between the inner layer and the outer layer of the solid core was extremely good. Comparative Example 1 The same procedure as in Example 1 was repeated except that a solid core inner layer without surface treatment and without protrusions was used, and the measurement results are shown in Table 2. In this case, there was no adhesion between the inner layer and the outer layer of the solid core, and when the core was cut into two, the outer layer came off. Also, when we investigated the maximum and minimum difference in external thickness, we found that it was 1.2m/m. Comparative Example 2 The procedure of Comparative Example 1 was repeated except that the inner layer and outer layer of the solid core were bonded together using an adhesive (neoprene adhesive), and the measurement results are shown in Table 2. In this case, although the adhesion between the inner layer and the outer layer of the solid core was relatively good, the rebound resilience of the ball was reduced.

【table】

[Table] Effects of the Invention The three-piece solid golf ball according to the present invention improves the adhesion between the inner layer and the outer layer of the solid core, which was insufficient in conventional similar products, without using an adhesive, and also improves the adhesion between the inner layer and the outer layer of the solid core, which was insufficient in conventional similar products, and also improves the adhesion between the inner layer and the outer layer of the solid core without using an adhesive. It is a uniform solid golf ball with no uneven thickness, exhibits improved durability while maintaining the same or better repulsion characteristics than conventional products, and also has an extremely good feel when hit.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing one embodiment of a three-piece solid golf ball according to the present invention. 1 is an inner layer of the solid core, 1' is a protrusion, 2 is an outer layer of the solid core, and 3 is a cover.

Claims (1)

[Claims] 1. A three-piece solid golf ball comprising a two-piece solid core consisting of an inner layer 1 and an outer layer 2 and covered with a cover 3, in which on the surface of the inner layer 1,
A three-piece solid golf ball characterized in that a protrusion 1' having a height comparable to the thickness of the outer layer 2 and integrally formed with the inner layer is provided. 2. The three-piece solid golf ball according to item 1, wherein the cover is mainly made of iomer resin. 3. The surface of the inner layer 1, in which the composition for the inner layer is compressed or injection molded in a spherical mold having recesses corresponding to the protrusions 1', is subjected to buffing and/or chemical treatment, and the composition for the outer layer is applied on the inner layer. The outer layer 2 is provided by compression or injection molding the composition concentrically in a spherical mold, and the two-piece solid core obtained by heating and curing this two-layer molded product is covered with a cover. A method for manufacturing a three-piece solid golf ball.