JPH0363075A - Tennis ball - Google Patents

Abstract

PURPOSE:To improve the hardness of a ball without hardly changing the rebound of the ball by providing a rubbery compound having a hollow core and containing a specified rate of basic magnesium carbonate having a specified surface are a to the rubber. CONSTITUTION:While natural rubber is used mainly for the rubbery compound, a butadiene rubber, a styrene butadiene rubber or the like can also be used other than the natural rubber. 40-120wt. parts of a filler in 100wt. parts of rubber contains 10-50wt. parts of magnesium carbonate having 10m<2>/g-20m<2>/g of specific surface area. A tennis ball is obtained by covering a hollow core with a cover and the hollow core is obtained by compression molding a rubbery compound containing the said rate of the magnesium carbonate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to tennis balls, and more particularly to improvements in the hollow core thereof.

[Conventional technology]

The hollow core of a tennis ball is generally made of natural rubber, butadiene rubber, white carbon, clay calcium carbonate, basic magnesium carbonate (in rubber compounding agents, ``magnesium carbonate'' refers to ``basic magnesium carbonate'', so In the following, it is obtained by molding a rubber & iron ball to which a reinforcing agent such as "magnesium carbonate" has been added, but the ball properties are greatly influenced by the type of reinforcing agent. In particular, the ball's rebound and forward deformation are the most important ball characteristics for tennis balls, and they also have a significant impact on the feel of the ball when it is actually hit.

In other words, if the forward deformation of the ball is small (in other words, if the ball is hard), the rebound when hitting the ball will be good and it will have a solid feel, but if the forward deformation is too small (in other words, if the ball is hard) If the ball becomes too hard), the impact when hitting the ball increases, resulting in a ``clunk'' feeling.

Due to these circumstances, a tennis ball needs to have a certain degree of hardness, and it is necessary to reduce the forward deformation to a certain extent to make the ball harder, but if the forward deformation is reduced, the rebound generally tends to be lower. There is.

For example, it is known to increase the amount of sulfur to reduce the forward differential and increase the hardness of the ball, but in this case, the ball properties deteriorate, such as a decrease in rebound, and the ball deteriorates over time. The disadvantage is that the changes are large.

[Problem to be solved by the invention]

As mentioned above, in order to improve the feeling when hitting a ball, it is necessary to reduce the forward deflection of the ball to a certain extent and increase the hardness of the ball to an appropriate degree. If the pitch is lowered by this means, ball characteristics generally tend to deteriorate, such as a decrease in rebound.

Therefore, an object of the present invention is to provide a tennis ball that has a good feel and good ball properties by reducing the forward deflection and increasing the hardness of the ball without changing the rebound of the ball. shall be.

[Means to solve the problem]

The present invention has been developed by focusing on reinforcing agents that affect ball properties, and has developed a specific surface area of 1Onf/g to 20n (when 7g of magnesium carbonate is used as a reinforcing agent, the rebound of the ball is hardly changed, It was completed by discovering that it was possible to increase the hardness of the ball by reducing the forward deformation.

That is, magnesium carbonate used in the rubber composition of the hollow core of conventional tennis balls has a specific surface area of 24
rrf/g to about 30nf/g, and the magnesium carbonate used in the present invention has a smaller specific surface area than conventionally used magnesium carbonate, and this small specific surface area hardly changes the rebound of the ball. This is a factor that can reduce forward deformation.

In the present invention, the specific surface area is 10 m2/g to 20 nf.
/g of magnesium carbonate is contained in the rubber composition constituting the hollow core of the tennis ball in an amount of 10 to 50 parts by weight per 100 layers of rubber.

That is, the specific surface area is 10nf/g to 20rr
If the blending amount of magnesium carbonate in f/g is less than 10 parts by weight per 100 parts by weight of rubber, a significant effect of reducing forward deformation without almost changing the rebound of the ball cannot be expected;
Further, the amount of magnesium carbonate having a specific surface area of 10rrf/g to 20mm/g is 50% by weight per 100 parts by weight of rubber.
If the amount exceeds parts by weight, the kneading process becomes difficult and impractical.

In the present invention, the specific surface area of magnesium carbonate used is specified to be 10 m2/g to 20 rrf/g, which means that if the specific surface area of magnesium carbonate is larger than 2 On (7 g), it will not be much different from normal magnesium carbonate. This is because the effect of reducing forward deformation cannot be expected without almost changing the rebound of the ball.Furthermore, if the specific surface area of magnesium carbonate becomes smaller, it is estimated that the modulus will decrease. The reason why the specific surface area is specified to be 10%/g or more is because
This is because magnesium carbonate having a specific surface area smaller than 1 orrf/g cannot be obtained on an industrially usable scale. In addition, in the present invention, 1 of magnesium carbonate
The specific surface area of 0 bo/g to 20 rrf/g is the specific surface area measured by the BET method.

The rubber that makes up the hollow core is usually made of 100% rubber.
Based on parts by weight, fillers (including reinforcing agents such as clay, magnesium carbonate, activated calcium carbonate, and silica such as zinc white) are 40 to 120 parts by weight, sulfur is 2 to 4 parts by weight, guanidine type, thiazole type. , 2 to 5 parts by weight of a sulfenamide-based accelerator.

As the rubber, natural rubber is mainly used, but other than natural rubber, butadiene rubber, styrene-butadiene rubber, etc. can also be used.

Then, in 40 to 120 parts by weight of filler to 100 parts by weight of the above rubber, a specific surface area of 10rrf/g to 20rl (
7 g of magnesium carbonate account for 10-50 parts by weight.

A tennis ball is obtained by covering a hollow core with a cover, and the hollow core has a specific surface area of 10rr.
It is obtained by compression molding (molding under heat and pressure, so-called vulcanization) rubber containing magnesium carbonate in a specific proportion of r/g to 20 bo/g.

As a specific method, for example, a pair of half shells is produced by putting rubber &ll acid in a mold for half shells and compression molding, and concave in one half shell of the pair of half shells obtained. Fill the space with a gas generating agent, stack the other half shell on top of it to form a spherical shape,
A hollow core is produced by pressing the core with a mold for forming the core.

Moreover, it may be used as a core for a pressureless tennis ball without adding a gas generating agent as described above. The pressure w1 for producing the above half shell is, for example, the heating temperature 1
The heating time is 1 to 6 minutes, and the thickness of the half shell is, for example, 3.1 to 3.60.
be reduced to a certain degree. In addition, compression molding for producing a hollow core is performed at a heating temperature of 140 to 160' C1 for a heating time of 1
The duration ranges from 0 to 25 minutes.

A tennis ball is produced by covering the hollow core obtained as described above with a cover such as a Melton cover, placing it in a ball mold, and pressing it into shape.

Compression molding for producing tennis balls is performed at a heating temperature of 130 to 150° C. and a heating time of 15 to 20 minutes, for example.

〔Example〕

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

However, the present invention is not limited to the examples.

Examples 1 to 3 and Comparative Examples 1 to 2 Five types of rubber compositions shown in Table 1 were prepared, hollow cores were prepared using these rubbers and [acids, and the physical properties of the rubber were measured. A tennis ball was made using the obtained hollow core, and the ball properties were measured. Table 2 shows the measurement results of rubber physical properties and ball properties.

Note that the tennis ball was produced as shown below.

That is, the rubber composition prepared by kneading is put into a mold for half shells, compression molded at 150 ° C. for 2 minutes to produce a pair of half shells, and the obtained half shells are stacked to form a spherical shape. Compression molding was performed at 155'C for 10 minutes in a core mold, the obtained hollow core was covered with a Melton force bar, and compression molding was performed at 130'C for 15 minutes in a ball mold to produce a tennis ball. was created.

As shown in Tables 1 and 2, the specific surface area is 20rr? In Examples 1 to 3 using magnesium carbonate with a specific surface area of 20 m2/g or less, the rebound is almost the same as in Comparative Examples 1 to 2 using magnesium carbonate with a specific surface area larger than 20 m2/g, but the forward deformation is small. , it was shown that it is possible to increase the hardness of the ball and improve the feel without degrading the ball properties.

〔Effect of the invention〕

As explained above, in the present invention, by containing a specific proportion of magnesium carbonate having a specific surface area of 1 Onf/g to 20 nf/g in the hollow core rubber composition, forward deformation can be achieved without almost changing the rebound. By reducing the diameter and increasing the hardness of the ball, it was possible to provide a tennis ball with good ball properties and a good feel.

Claims (1)

[Claims] (1) A tennis ball consisting of a hollow core made of a rubber composition and a cover covering the hollow core, wherein the rubber composition of the hollow core has a diameter of 10 m^2/g to 20 m
A tennis ball characterized by containing 10 to 50 parts by weight of basic magnesium carbonate having a specific surface area of ^2/g based on 100 parts by weight of rubber.