JPS6194666A - Solid golf ball - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is directed to improving the polishing workability during true sphere processing (hereinafter referred to as centerless processing) after forming and hardening the core body (hereinafter referred to as core) of a golf pole. Improve quality by improving
Concerning a solid golf ball that is designed to be stable.

[Prior art]

Generally, when manufacturing a solid golf ball such as a two-piece golf ball, the core is made by mixing rubber such as polybutadiene and/or synthetic resin with zinc acrylate and other additives using a mixer such as a kneader, Banbury mixer, or roll. The mixture is kneaded under heat using a press molding machine, and then heated and molded into a spherical shape using a press molding machine and hardened. This spherical core has f! The ball is puffed by centerless processing using an fS machine, and the mold release agent attached during press molding is removed to roughen the spherical surface. This core is optionally surface-treated with an adhesive or the like.

Thereafter, the cover material is coated by injection molding or compression molding, and at the same time dimples are formed on the surface of the cover material to form a solid golf ball. The final product is then processed through processes such as polishing, painting, and marking.

In these processes, centerless processing after heat forming the core is one of the important processes for the product quality of solid golf balls, and the true spherical finish and uniform puff finish here are important for the homogeneity of the solid golf ball. Strength,
It has a big impact on lifespan and flight.

Conventionally, the polishing condition in centerless machining is checked by measuring sphericity or by visual inspection, but it is difficult to achieve uniform polishing in a short time, and as a result, polishing residue is often left on the parting line caused by core press molding. This tendency is particularly noticeable in cores with low hardness. In particular, cores of soft type solid golf balls having a core combination fusion (crab unit kg required to compress a spherical core by 1/10 inch) of 60 or less are extremely poorly polished.

If the cover material is covered with polishing residue without sufficient spherical processing, a thin part will appear in the cover material, which is responsible for the impact strength of the solid golf ball, and this will cause problems when using the solid golf ball. This may cause deformation (distortion) or a decrease in the strength of the cover material. In addition, since the release material remains attached to the surface of the unpolished portion, the adhesion with the cover material is poor, and the dirt not only causes deformation of the solid golf ball when hit hard,
Slippage occurs between the core and the cover material when the ball is hit, resulting in energy loss when the ball is hit, which ultimately causes a reduction in the flight distance of the solid golf ball.

This problem has been dealt with by extending the centerless machining time, but this is still insufficient and it is difficult to perform satisfactory centerless machining.

[Purpose of the invention]

The present invention improves the polishing processability during centerless processing of the core, thereby improving productivity by shortening the processing time of solid golf balls, stabilizing quality, and improving durability and flight characteristics. The purpose of the present invention is to provide a solid golf ball.

[Structure of the invention]

Therefore, the present invention provides a core made of a composition in which a core material made of rubber and/or synthetic resin is further blended with a heat-resistant resin or vulcanized rubber having a melting point higher than the temperature at the time of mixing the core material. The gist of the invention is a solid golf ball having the following characteristics.

Hereinafter, the configuration of the present invention will be explained in detail.

The core material made of rubber and/or synthetic resin used in the present invention is a compound known for use in solid golf ball cores. For example, ■Polybutadiene is blended with zinc acrylate, etc.;■Polybutadiene is blended with α,β-ethylenically unsaturated carboxylic acid such as methacrylic acid or acrylic acid and a metal oxide such as zinc white. A metal salt of carboxylic acid is formed in
5-19615), and (2) Chinoku JP-A No. 53-8383, in which polybutadiene rubber is blended with zinc methacrylate, etc.

In the present invention, a composition in which this core material is further blended with a heat-resistant resin or vulcanized rubber having a melting point higher than the temperature at which the core material is mixed is used for the core of a solid golf ball.

In this case, the temperature at which the core material is mixed is the temperature at which the core material raw materials are mixed. Since the temperature at the time of mixing the core material is generally about 80 to 135°C, the melting point of the heat-resistant resin or vulcanized rubber may be 80'C or higher.

The melting point of the heat-resistant resin or vulcanized rubber may be selected based on the timing of mixing these into the core material. For example, if the core material is mixed in the primary mixing (so-called non-pro; mixing without the addition of a vulcanizing agent), it should have a melting point of 120°C or higher. If it is mixed during mixing with a sulfur agent, it may have a melting point of 80° C. or higher.

Examples of heat-resistant resins include nylon resin, acrylic resin,
polyacecool, polycarbonate, polypropylene,
These include polyurethane, epoxy resin, phenol+1 resin, melamine resin, and silicone resin.

Vulcanized rubber is a rubber with high hardness, such as ebonite.

The amount of the heat-resistant resin or vulcanized rubber added to the core material is preferably 3 to 15 parts by weight based on 100 parts by weight of the core material, taking into consideration the impact on the flight and compressive fracture strength of the resulting solid golf ball. and preferably 3 to 10 parts by weight.

The heat-resistant resin or vulcanized rubber is a coarse powder with a particle size of approximately 60 to 300 μm, preferably 60 μm to 300 μm.
0 to 200μ is good. This is because if the powder is too fine, the VF polishing efficiency described below will be poor, and if the powder is too coarse, the compressive fracture strength of the core will decrease and the life of the solid golf ball will be shortened.

In this way, a core can be made from a composition in which a heat-resistant resin or vulcanized rubber is blended with a core material by any conventional method. The resulting core has a rough surface because the heat-resistant resin or vulcanized rubber that does not melt is scattered in the molten matrix. Therefore, during centerless processing, the frictional force between the polishing machine and the core surface increases, so the polishing efficiency increases and the polishing processability improves.

〔Effect of the invention〕

As explained above, according to the present invention, since the core material made of rubber and/or synthetic resin is further blended with a heat-resistant resin with a high melting point or vulcanized rubber, the core material is polished after hardening to form a true sphere. This makes it easier to apply the powder (puffing).
The polishing efficiency during centerless processing can be significantly improved, thereby eliminating instability in the quality of solid golf balls caused by poor polishing. In particular, the effect of the present invention is remarkable when the core has low hardness.

EXAMPLES The effects of the present invention will be specifically explained below with reference to Examples.

Examples Various rubber compositions (Examples 1 to 5,
Standard Example 1 and Comparative Examples 1 to 2) were prepared. In addition, in Table 1, the numerical values for each compounding component are expressed in parts by weight based on 100 parts by weight of the rubber component for compounding components 1 to 6, and for additional components 1 to 6.
and 2 are expressed in parts by weight based on the total amount of 100 parts by weight of components 1 to G.

In Example 1, acrylic resin was used as a heat-resistant resin coarse powder.
Acrybase MH-101-5” (Gensan Kasei (41+)
5 parts by weight of
3.4.5 and Comparative Example 1.2, nylon resin coarse powder "Diamide T-250, P-2" was used instead of acrylic resin.
(manufactured by Daicel) at 3.5°10, 15 and 20.2
The amount was varied within a range of 5 parts by weight.

The method of mixing these rubber compositions is to mix polybutadiene (component 1) to silica (component 5) at a mixing temperature of 80°C to 130°C for 5 to 10 minutes using a conventional closed mixer such as a kneader. After mixing and cooling for half a day, this mixture was mixed with dicumyl peroxide as component 6 and coarse resin powder as additional component 1 or 2 at 60°C to 80°C. . As a result, a plate-like sheet of unvulcanized compound was obtained.

This plate-like sheet is heated to a temperature of 140°C to 160° using a core mold.
C. for 20 to 30 minutes to harden and mold a spherical core material. This core material is processed by a centerless polishing machine.
After performing centerless processing to make a true sphere, it was covered with a thermoplastic elastomer such as an ionomer using an injection molding method to obtain a two-piece golf ball.

The polishing condition during centerless polishing was confirmed, and the compression, compressive fracture strength, and flight distance of the resulting two-piece golf ball were measured and evaluated. This result is the first
Shown in the table.

(Margins below this page) As can be seen from Table 1, the polishing workability of the spherical core in centerless processing is higher than that of standard example 1 in which the heat-resistant resin coarse powder is not mixed. The Examples and Comparative Examples in which coarse powder was mixed were extremely good, and there was no polishing residue after one centerless processing, and the effect of centerless processing could be obtained in a short time. However, as the amount of heat-resistant resin increases, the compressive fracture strength of the golf ball tends to decrease, and when the amount of the heat-resistant resin increases to 20 or more, as in Comparative Examples 1 and 2, this tendency becomes noticeable and has a negative impact on the life of the golf ball. Ta.

The two-piece golf ball obtained here was adjusted to a head speed of 34 m/sec to 46 m/sec with a driver using a swing robot manufactured by Tsuru Temper.
As a result of trial hitting at five levels up to C, a slight decrease in flight distance was observed with a blending amount of 20.25 parts by weight, but with a blending amount of 15 parts by weight.
Below the weight part, there was almost no decrease in flight distance at any head speed level.

In addition, the influence of the particle size of the heat-resistant resin coarse powder to be blended was investigated. The results are shown in Table 2 below.

The polishing effect in centerless processing depends on the particle size, but the effect is small with fine powder, and if it is too rough, the polished surface will be too rough, and the compressive fracture strength of the core sphere is lower than that of heat-resistant resin. It decreased as the particle size became coarser. From these results, it can be seen that the appropriate particle size is 60μ to 300μ, preferably 60μ to 200μ.

(Margin below this page) Table 2 $2. $3 X: Bad, Δ: Fairly good, O: Good, ◎
: An even better agent Patent attorney Shin Ogawa − Kenshosai Noguchi Kazuhiko Shimo

Claims (1)

[Claims] A solid golf ball having a core made of a composition in which a core material made of rubber and/or synthetic resin is further blended with a heat-resistant resin or vulcanized rubber having a melting point higher than the temperature at which the core material is mixed.