JPH0425029B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION The present invention relates to thread-wound golf balls. In recent years, many two-piece golf balls have been commercially available. A two-piece golf ball has a longer flight distance than a conventional thread-wound golf ball, but the ball has a higher hardness and has an extremely poor feel when hit. In addition, since the amount of spin of the ball is extremely small, the ball tends to become a so-called drop ball, which has the disadvantage that it is difficult for the ball to stop on the green. On the other hand, thread-wound golf balls are commercially available with two types of cover materials (balata and ionomer), and balata is often used because it has better feel, controllability, and ease of stopping on the green than ionomer. However, as mentioned above, it is inferior to two-piece golf balls in terms of flight distance. This is because the launch angle of a thread-wound golf ball is smaller than that of a two-piece golf ball, so in order to increase flight distance, it is necessary to increase the spin and raise the trajectory from the middle, and the angle at the time of fall is large, resulting in less run. This is one of the reasons. Therefore, it is desired to develop a golf ball that has the advantages of a thread-wound golf ball, such as the feel at impact, and has the flight distance of a two-piece golf ball. The present inventors have discovered that a golf ball with excellent characteristics can be obtained by using a specific ionomer resin for the cover material and making the thread-wound core soft and large in diameter. That is, in the case of a 1.62 inch size ball, a rubber ball core having an outer diameter of about 27 to about 30 mm, a JIS-A hardness of 75 to 85, and a weight of about 20.5 to about 23.5 g is used.
For inch size balls, the outer diameter is approximately 28 to 32.
mm, JIS-A hardness 70 to 80 and weight approximately 17.5 to approximately
A rubber ball core with a weight of 21.0g is used, and a thread-wound core with a rubber thread wound around the rubber ball core has a Shore D hardness of 65.
The above describes a thread-wound golf ball coated with an ionomer resin having a softening point of 50° C. or higher to a thickness of 1.5 to 2.0 mm. The rubber ball core used in the present invention is within the following range: (1) For a 1.62-inch golf ball, the outer diameter is approximately
27 to about 30mm, preferably 28.0mm to 29.5mm, JIS
-A hardness 75 to 85, weight approximately 20.5 g to approximately 23.5 g, (2) 1.68 inch size golf ball, outer diameter approximately
28 to about 32mm, preferably 29mm to 31.5mm, JIS-
A hardness 70 to 80, weight approximately 17.5g to approximately 21.0g. If the outer diameter of the rubber ball core is larger than the above range, the required ball hardness will not be obtained and the repulsion will be reduced. If it is smaller than the above range, the effects of the present invention cannot be obtained. If the JIS-A hardness of the rubber ball core is harder than the above range,
As the spin at the time of hitting increases, the impact is also large, resulting in a poor hitting feel. If it is softer than the above range, the ball core will deform more during thread winding and sufficient hardness will not be obtained. If the weight of the rubber ball core exceeds the above range, a golf ball with an appropriate weight cannot be obtained. The rubber used to obtain the above-mentioned rubber ball core is not particularly limited, but high-cis polybutadiene, which has high repellency, is preferred. Generally, to 100 parts by weight of high-cis polybutadiene, 8 to 12 parts by weight of sulfur, 5 to 9 parts by weight of vulcanization aid, 1 to 2 parts by weight of vulcanization accelerator, and the desired amount of weight adjuster are mixed in a Banbury mixer or roll. Knead at 155-165℃ for 15 minutes.
Obtain by vulcanization molding for ~20 minutes. Any commonly used vulcanization aids, vulcanization accelerators, and weight adjusters may be used, but
As the weight adjuster, barium sulfate, which has a high specific gravity, is preferable in order to increase the rubber fraction of the rubber ball core and obtain low hardness. The above-mentioned rubber ball core is wound around a conventional rubber thread by applying a stretching force. The rubber thread is not particularly limited as long as it is commonly used as a rubber thread for golf balls. The cover material of the golf ball of the present invention is Shore D
It is an ionomer resin with a hardness of 65 or higher and a softening point of 50°C or higher. The ionomer resin is a polymer (unsaturated mono/
or dicarboxylic acid and/or their ester (containing 4 to 30% by weight) with cross-metal bonds. In order to obtain the above physical properties of the ionomer resin,
It is preferred to blend various ionomer resins. For example, the following formulation examples may be mentioned:. Ingredient weight parts Surlyn 1706 ¹ 40-45 Surlyn 1605 ² 40-45 Surlyn 1555 ³ 5-10 Surlyn 1557 ⁴ 5-10 1 Shore D hardness 65 or more, tensile strength 250-300 Kg/cm ² , commercially available from Dupont. Brittle temperature −110
Ionomer resin with ~-100℃, MI=0.7~2.0, and melting point of about 88℃. 2 Commercially available from Dupont, Shore D hardness 65 or higher, tensile strength 275 to 320 Kg/cm ² , embrittlement temperature -110
Ionomer resin with ~-100℃, MI=2.3~3.3, melting point about 90℃. 3 Shore D hardness 60 ~ commercially available from Dupont
64, tensile strength 200~230Kg/ ^cm2 , embrittlement temperature -80~
-70℃, MI=8-12, ionomer resin with melting point of about 96℃. 4 Shore D hardness 60 ~ commercially available from Dupont
64, tensile strength 190~220Kg/ ^cm2 , embrittlement temperature -80~
-75℃, MI=4.5~8.0, ionomer resin with melting point of about 94℃. The method of covering the core with the above-mentioned cover is not particularly limited, but usually two
The core is wrapped in two covers and molded under heat and pressure. Alternatively, the cover composition may be injection molded to enclose the core. In addition to the above-mentioned ionomer resin, the cover composition may contain various conventional additives such as a vulcanizing agent, a vulcanization accelerator, a vulcanization aid, a weight regulator, and an antioxidant. The golf ball of the present invention has a large launch angle due to the high hardness cover, and a reduced spin rate due to the rubber core having a large diameter. Therefore, the launch angle of the ball,
The amount of spin is between that of a conventional thread-wound golf ball and a two-piece golf ball, and flight distance is significantly improved compared to a conventional thread-wound golf ball without sacrificing controllability. In addition, since the rubber ball core is soft and has a large diameter,
Even when the rubber thread, which is the cause of the high repulsion of thread-wound balls, is wound with high tension, it remains structurally soft and does not become unnecessarily hard. Therefore, high repulsion can be imparted without increasing compression, and the feel at impact is improved compared to not only two-piece golf balls but also conventional thread-wound golf balls. The present invention will be explained in more detail with reference to Examples. Example 1 A rubber ball core and rubber thread were obtained using the following formulation. [Rubber core] Parts by weight of components High-cis polybutadiene 100 Sulfur 10 Vulcanization aid 7 Vulcanization accelerator 1.5 Weight adjusting agent (barium sulfate) 200 [Thread rubber] Parts by weight of components IR (Isoprene rubber) 50 NR (Natural rubber) ) 50 Sulfur 2.7 Vulcanization accelerator 0.7 Anti-aging agent 1.2 After sufficiently kneading the above components, the mixture was vulcanized at a temperature of 155 to 165°C to obtain a rubber core and rubber thread. The outer diameter, hardness and weight of the rubber ball core are shown in Table-1. A thread rubber is wound around a rubber ball core to obtain a thread-wound core, and the thread-wound core is wrapped with two pieces of cover material previously formed into a hemispherical grain shape having the formulation and physical properties shown in Table 1, and heated at about 160°C and about 25°C. A 1.62-inch golf ball was obtained by heating and pressurizing for a minute. Table 1 shows the flight performance and ball repulsion coefficient of the obtained ball. Examples 2 to 4 Example 1 except that the outer diameter of the rubber ball core was approximately 28.3 mm and approximately 29.3 mm, and the amount of weight adjuster was changed.
A golf ball was created in the same way. flight performance,
Table 1 shows the ball restitution coefficient. Comparative Examples 1-2 Golf balls were made in the same manner as in Example 2 except that the composition of the cover material was changed. Flight performance and ball repulsion coefficient are shown in Table 1. Comparative Examples 3 and 4 Rubber ball cores were created using the following formulations. Ingredient parts by weight High-cis polybutadiene 100 Zinc white 44 Methacrylic acid 14 Dicumyl peroxide 2.0 Barium sulfate 145 The preparation was the same as in Example 1. A 1.62-inch golf ball was prepared using the obtained hard rubber ball core using the cover material of Example 1 for Comparative Example 3 and the cover material of Comparative Example 2 for Comparative Example 4. Flight performance etc. are shown in Table-1. Comparative Examples 5 to 9 Commercially available first-class golf balls were used. The results are shown in Table-1.

【table】

[Table] From Example 2 and Comparative Examples 1 to 3, as the hardness of the cover material becomes harder at No. 1 wood, the spin decreases, the launch angle increases, and the carry and total increase. In Examples 1 to 4, as the outer diameter of the ball center increases with Wood No. 1, the spin decreases and the launch angle increases, and although there is almost no change in carry, the total increases due to an increase in run. showed that. The feel of the shot is based on the results obtained by a professional golfer using the wood No. 1. Comparative Examples 3 and 4, in which the ball core was made of hard rubber, felt like hitting a stone and were the worst. As is clear from the flight performance of Example 2, the run, which is the difference between total and carry, is smaller than that of Comparative Examples 8 and 9, which are two-piece golf balls. It was confirmed that the ball was easy to stop at the top. Examples 5 to 7 The outer diameter of the rubber ball core is approximately 28.3 mm and approximately 29.3 mm, respectively.
and approximately 30.8 mm, and a 1.68-inch golf ball was prepared in the same manner as in Example 1 except for the amount of weight adjuster in the core composition. Measurements similar to those in Table 1 were performed. The results are shown in Table-2. Comparative Example 10 Using the same ball core mold as in Example 5, a 1.68-inch golf ball was produced in the same manner as in Example 5, except that a slightly harder ball core was used. Displays flight performance, etc.
2 is shown. Comparative Example 11 A golf ball was prepared in the same manner as in Example 5, except that the cover material of Comparative Example 1 was used. Measurements similar to those in Table 1 were performed. The results are shown in Table-2. Comparative Examples 12 to 16 Similar evaluations were performed on golf balls that are already commercially available as first-class golf balls. Display the results -
Shown in 2.

【table】

[Table] (1)(2)(3) are the same as Table-1.
It was found that Examples 5 to 7 had the same tendency as Examples 1 to 4. Comparative Example 10 is only slightly inferior to Example 7 in terms of carry and total, but it is only slightly inferior to Example 7 in terms of carry and total.
I didn't like the feel of the ball when I hit it because it felt like there was a core inside.

Claims (1)

[Claims] 1. In the case of a 1.62 inch size ball, the outer diameter is approximately
27~30mm, JIS-A hardness 75~85 and weight approx.
When using a rubber ball core with a weight of 20.5 to about 23.5 g, and a 1.68 inch size ball, the outer diameter is about 28 to about 32
mm, JIS-A hardness 70 to 80 and weight approximately 17.5 to approximately
A rubber ball core with a weight of 21.0g is used, and a thread-wound core with a rubber thread wound around the rubber ball core has a Shore D hardness of 65.
The above is a thread-wound golf ball coated with an ionomer resin having a softening point of 50° C. or higher to a thickness of 1.5 to 2.0 mm. 2. The thread-wound golf ball according to item 1, wherein the rubber core has an outer diameter of 28.0 to 29.5 mm in the case of a 1.62 inch size ball. 3. The thread-wound golf ball according to item 1, wherein the rubber core has an outer diameter of 29.0 to 31.5 mm in the case of a 1.68-inch size ball.