JPS61168376A - Tennis 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 [Field of Industrial Application] The present invention relates to a hard tennis ball suitable for practicing hitting speed balls.

[Conventional technology]

Hardball tennis balls have a hollow core with a pressure lower than atmospheric pressure.
．． 6 to 1.0 kg/J Pressure rise tennis ball filled with air or other gas that applies high pressure There are two types of balls.

Among these, there are first-class balls that pass the International Tennis Federation standards, and low-priced practice balls whose shot feel and characteristics are slightly lower than those of the first-class balls. However, even though it is a practice ball, it is only slightly inferior in shot feel and characteristics, and its characteristics are not significantly different or essentially different from those of a first-class ball.

By the way, there are various ways to practice to improve your tennis skills, but in order to get used to the speedball in baseball, the pitcher throws the ball in front of the normal position, shortening the distance from the pitching position to the batter. be. This method of improving by practicing under conditions that are more severe than the actual situation can be applied to any sport.

Tennis has also recently become faster around the world, and various training methods have been adopted as a countermeasure. The basic technique for ground strokes is to quickly get to the point where you want to hit the ball, pull the racket quickly, and lower your hips (bend your knees) to hit a fast ball that slides.

The quickest way to master these basics is to practice under the harsher conditions mentioned above. Specifically, there are various methods, but as far as current balls are used, the most common method is to use the ball at a faster speed than at short distances.

[Problem that the invention seeks to solve]

In the above case, the person throwing out the ball just throws out a large number of balls one after another, but never continues a normal rally. This is because, as mentioned above, practice balls are made with the goal of making them as close as possible to balls that pass the International Tennis Federation standards, so if you continue to rally,
This is because unless the opponent is an expert who can easily hit a speedball with good control, it will not be a practice for hitting a speedball.

[Means for solving problems]

Therefore, in practicing ground strokes, the present inventor continued to rally each other, in other words, practiced more realistically, while at the same time, the bounce was low and the horizontal velocity after the bounce was high. As a result of various studies to obtain a tennis ball that can be used for hitting practice against speed balls, we found that the epoxidation rate of 1 in the entire polymer was
0-60 mol% epoxidized natural rubber 3-50% by weight
When making a core with the rubber composition containing the rubber composition, the diameter is within the range that passes the International Tennis Federation standard and the weight is 54.0.
~58.0 g, forward deformation amount is 5.90~7.5
0 mm, return deformation amount is 8.5 to 10.0 mm, and has characteristics that pass or are close to the standard values stipulated by the International Tennis Federation standards, while rebound is 70 to 10.0 mm.
130 ell, lower than the International Tennis Federation standard value (, The feel and flight of the ball are very different from first-class tennis balls that pass the International Tennis Federation standard (, The reflection angle of the ball after bouncing is smaller than conventional balls, The inventors have also discovered that a tennis ball can be obtained that has a higher horizontal speed after bouncing than conventional balls, and has completed the present invention.

When a tennis ball having the above characteristics is actually hit, it exhibits ball behavior after bouncing that cannot be obtained with a conventional tennis ball, as described above. That is,
The speed after the bounce is fast (and the ball exhibits a low sliding behavior. As a result, by using the tennis ball of the present invention, the bounce is low and the horizontal speed after the bounce is high, which cannot be obtained with conventional balls. This will allow you to practice ground strokes under harsh conditions, and will help you more reliably master the aforementioned basics of improving speed balls, such as pulling the racket quickly and hitting the ball with a lowered back (bending your knees). Therefore, if you can reliably return the tennis ball of the present invention as intended, you will be able to return the ball with ground strokes without difficulty even in a match with a player who is several steps faster than the opponent with whom you regularly practice. In other words, the tennis ball of the present invention can be said to be an optimal practice ball for improving ball returns against speed balls.

Epoxidized natural rubber is a part of natural rubber that has been epoxidized, and was developed by the Malaysian Rubber Research Institute. 60 mol% epoxidized natural rubber is used.

The amount of the above epoxidized natural rubber used is 3-5% of the total polymer.
0% by weight, but this is because if the amount of epoxidized natural rubber used is less than 3% by weight, the rebound will become too large and it will be difficult to keep the rebound within the range of 70 to 130 mouths. This is because if the amount used is more than 50% by weight, the reflection angle after bouncing becomes small at the end of the rod, making it difficult to practice.

Within the above range, when the usage ratio of epoxidized natural rubber in the total polymer is A weight % and the epoxidation rate of epoxidized natural rubber is B mol %, A×B has the relationship shown below. The most favorable results are obtained when

AXB 1.5 ≦ □ ≦9 Polymers constituting the core other than the above-mentioned epoxidized natural rubber include natural rubber, polybutadiene, styrene-butadiene rubber (SBR), high styrene resin, and ethylene-propylene-diene rubber (EPDM). ), etc., but natural rubber or high-cis polybutadiene is usually preferred.

The core is made by adding fillers such as clay, magnesium carbonate, calcium carbonate, and silica fillers, vulcanization accelerators such as zinc oxide and stearic acid, vulcanizing agents, vulcanization accelerators, etc. to the above polymer. It can be obtained by vulcanizing a rubber composition prepared as follows.

Specifically, the polymer, filler, and vulcanization accelerator are kneaded using a kneading machine such as a panburi mixer or a roll, and then a vulcanizing agent and a vulcanization accelerator are mixed and kneaded. The obtained rubber composition is formed into a sheet shape, which is formed into a rod shape using an extruder.The obtained rod-shaped rubber composition is put into a half shell mold and compression molded to form a pair of hemispherical shell bodies. A gas generating agent made of a mixture of ammonium salt and nitrite is filled into the recess of one of the obtained hemispherical shells, and the other hemispherical shell is filled into the recess so that the other hemispherical shell becomes spherical. The core is produced by superimposing and compression molding. Further, it may be used as a core for a pressureless tennis ball without adding a gas generating agent as described above. Compression molding to produce hemispherical shells is usually performed at 140-160°C.
, within the range of 3 to 6 minutes, and the thickness of the hemispherical shell is usually 3.1 to 3.6 mta. Compression molding for core production is usually carried out at 140 to 160°C for 15 to 25 minutes.

A tennis ball is produced by covering the core obtained as described above with a felt cover such as a melton cover and compression molding it in a ball mold.

Compression molding for making tennis balls is usually 130~
It is carried out at 150°C for 15 to 20 minutes, and the ball diameter is usually 64 to 66.5 mm.

In the present invention, the weight of the tennis ball obtained is 54.
0 to 58.0 g, forward deformation amount to 5.90 to 7.
50mm, return deformation amount 8.5~10. The reason for specifying the ball as a ball is that the characteristics of the ball must meet or be as close as possible to the International Tennis Federation's standard values, but since it is a practice ball, slight deviations from the International Tennis Federation's standard values are actually acceptable. Based on. And the rebound is specified as 70-130 cm.
If the rebound is less than 70 cm, the flight and feel of the ball will be too far from the ball that passes the International Tennis Federation standards, and if the rebound is greater than 130 am, the angle of reflection after the bounce will be small and the horizontal speed after the bounce will be increased. This is because you will not be able to do it.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Examples 1 to 3 and Comparative Example 1 Make a pipe into a panot shape, mold it into a rod shape with an extruder, put it into a half shell mold, Compression molded at ℃ for 5 minutes to a thickness of 3.
A pair of hemispherical shells of 3 m+++ were obtained. The amounts of each component in Table 1 are based on parts by weight.

Of the pair of hemispherical shells obtained as described above, a gas generating agent made of a mixture of ammonium salt and nitrite is filled into the recess of one of the hemispherical shells, and the other hemispherical shell is shaped into a sphere. Place them in a core mold at 150°C.
Compression molding was performed for 20 minutes to obtain a core for a tennis ball.

The core was coated with a Melton force bar in a conventional manner, placed in a tennis ball mold, and compression molded at 140° C. for 18 minutes to obtain a pressurized tennis ball with a diameter of 65+wm.

The weight, forward deformation, return deformation, and rebound of the tennis balls obtained were measured in accordance with International Tennis Federation standards, and the ball was also lined to examine the feel and flight of the ball, and the results are shown in Table 2. .

The bounce characteristics of a groundstroke made by hitting a ball flat on a hard court with a Suka-On^h Roku-ko Nispaul were investigated, and the results are shown in Table 3.

As shown in Table 2, the weight, forward deformation amount, and return deformation amount of the tennis balls of Examples 1 to 3 of the present invention are all within the International Tennis Federation standard values, but the rebound is within the International Tennis Federation standard values. As shown in Table 3, the reflection angle is smaller than the standard value, and as shown in Table 3, the reflection angle is smaller than the ball of Comparative Example 1 whose ball properties meet the International Tennis Federation standards.
Also, the ball speed in the horizontal direction was high.

〔Effect of the invention〕

As explained above, in the present invention, by using a specific proportion of epoxidized natural rubber in the polymer constituting the core, the rebound of the ball is lower than the International Tennis Federation standard value, and the angle of reflection after the bounce is reduced. It is smaller than conventional balls and has a higher horizontal speed after bouncing. Therefore, according to the tennis ball of the present invention, even when continuing a normal rally, it is possible to practice hitting against a speed ball that has a low bounce and a high horizontal speed after bouncing, which was impossible with conventional balls. Now you can. In addition, if you release the ball one after another at a faster speed than before from close range, the bounce that could not be obtained with a conventional ball will be lower.
In addition, it is possible to practice under more severe conditions for a speed ball that has a high horizontal speed after bouncing, and it is possible to practice more appropriately when returning a speed ball with a ground stroke.

Claims (1)

[Claims] (1) A core made of a rubber composition containing 3 to 50% by weight of epoxidized natural rubber with an epoxidation rate of 10 to 60 mol% in the total polymer, and a cover covering the core,
4.0~58.0g, forward deformation amount is 5.90~
7.50mm, return deformation amount is 8.5~10.0mm
A tennis ball characterized by a rebound of 70 to 130 cm.