JPS59129238A - Rubber composition for core of playing ball - Google Patents

Abstract

PURPOSE:To provide the titled rubber compsn. which give proper compression without increasing the quantity of a vulcanizing agent, by blending a specified quantity of liquid polyisoprene rubber to a base rubber. CONSTITUTION:The titled rubber compsn. is obtd. by blending 1-10pts.wt. liquid polyisoprene rubber such as one having an average MW of 20,000-70,000 with 100pts.wt. base rubber such as natural rubber or a mixture thereof with butadiene rubber. By using low-molecular liquid polyisoprene rubber in place of a conventional softening agent, proper compression can be obtd. without increasing the quanaity of a vulcanizing agent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rubber composition for the fur of play balls such as tennis balls and racquet balls.

In general, rubber compositions require softeners to improve the ease of mixing and dispersion of compounding ingredients, improve rubber flow, and facilitate molding operations such as extrusion and rolling. It contains higher fatty acids such as cottonseed oil, higher fatty acid esters such as castor oil, vegetable oil softeners such as pine cool and tall oil, petroleum softeners such as spindle oil and process oil, etc. In rubber compositions for the core of play poles such as poles, the above-mentioned softeners have the disadvantage of softening compression, which is important in core properties.

Therefore, the amount of vulcanizing agent is increased to control the degree of vulcanization and achieve the appropriate combibrection. This will reduce the ring (hit feel).

In view of such circumstances, the present invention uses low molecular weight liquid polyisoprene rubber in place of conventional softeners, thereby making it possible to obtain appropriate compression without increasing the amount of vulcanizing agent. .

That is, the present invention relates to a rubber composition for the core of a play ball, characterized in that 1 to 10 parts by weight of liquid polyisoprene rubber is blended with 100 parts by weight of base rubber.

In the present invention, liquid polyisoprene rubber is vulcanized by a vulcanizing agent, unlike conventional softening agents that do not participate in the process, and after vulcanization it itself has some rubber-like elasticity. Unlike softeners, it does not cause a large deterioration in rubber properties, and has a good softening effect when unvulcanized, so it can be used satisfactorily as a softener.

In the present invention, it is preferable to use liquid polyisoprene rubber having an average molecular weight in the range of 20,000 to 70,000. This is because those with an average molecular weight of less than 20,000 deteriorate the physical properties of the vulcanized rubber, while those with an average molecular weight of more than 70,000 have little effect on improving ease of mixing, dispersibility, and molding workability such as extrusion. It is.

The base rubber is preferably natural rubber or a mixture of natural rubber and butadiene rubber, ethylene propylene diene rubber, styrene butadiene rubber, etc., and it is particularly preferable to use natural rubber alone.

As mentioned above, the amount of liquid polyisoprene rubber blended into the base rubber is 1 to 10 parts of liquid polyisoprene rubber per 100 parts of the base rubber, and the range of 1 to 7 parts of liquid polyisoprene rubber is particularly heavy. However, if the amount of liquid polyimprene rubber blended is less than the above range, it will have little effect on improving ease of mixing, dispersibility, and molding workability such as extrusion, and conversely, if it exceeds the above range, the physical properties of the vulcanized rubber will be affected. This is because it lowers the

The composition of the present invention is prepared by blending 1 to 10 parts of liquid polyisoprene rubber with respect to 100 parts of the base rubber7 as described above, and further blending zinc oxide, sulfur, a vulcanization accelerator, etc., and carbonic acid if necessary. It can be obtained by appropriately blending fillers such as lucium, magnesium carbonate, silicate compounds, clay, and other rubber compounding agents.

In order to obtain a core for a tennis ball from the rubber composition of the present invention, the rubber composition is usually formed into a hemispherical shell shape, the hollow part is filled with a gas generating agent, and two pieces are bonded together to form a ball shape. Vulcanize. A preferred blending example for obtaining a core for a tennis ball is 100 parts of natural rubber, 1-10 parts of liquid polyisoprene rubber, 3-20 parts of zinc oxide, 20-60 parts of filler such as magnesium carbonate or clay, and 2-20 parts of sulfur. 5th part,
It consists of 1 to 5 parts of accelerator.

In addition, the core for racquetballs is usually obtained by vulcanization molding a rubber composition into a solid spherical shape, and racquetballs are made by using the core ball as it is, or by using a cover of the core pole. Obtained by receiving the award. A preferred compounding example for obtaining a core for racquetball is 100 parts of natural rubber, 1 to 10 parts of liquid polyisoprene rubber, 3 to 20 parts of zinc oxide, lucium carbonate, magnesium carbonate, a silicate compound, etc. It consists of 5 to 25 parts of filler, 2 to 5 parts of sulfur, and 1 to 5 parts of accelerator. The core for racquetballs differs from the core for tennis balls in terms of ratio, weight, etc.
Other characteristics do not change much.

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

Examples 1 to 2 and Comparative Examples 1 to 3 Rubber compositions having the compositions shown in Table 1 were prepared, and their Mooney viscosity and physical properties after vulcanization were measured. The results are shown in Table 2.

In the kneading, the rubber and compounding ingredients other than sulfur and the accelerator were kneaded in a Banbury mixer, and the sulfur and the accelerator were added to the above-mentioned kneaded material using a roll and kneaded. 1xJ sulfur is 30 at 141°C
The physical properties of vulcanized rubber are measured using JIS
The test was conducted according to the test method specified in K6801.

＼ ＼ Notes to Table 1 *1: 2-Mercaptobenzothiazole *2:
Dibenzothiazyl disulfide Table 2 As shown in Table 2, the composition of the present invention has a lower Mooney viscosity than the composition of Comparative Example 3, which did not contain a softener. Ease of mixing, dispersibility,
It has been revealed that molding workability such as extrusion properties is good. Furthermore, the composition of the present invention has a higher modulus than the compositions of Comparative Examples 1 to 20 containing conventional softeners, and is clearly suitable as a core rubber.

Next, cores for tennis balls were manufactured using the rubber compositions of Examples 1 and 2 and Comparative Examples 1 and 2, and their properties were measured. The results are shown in Table 3. The core was manufactured by molding the rubber composition into a hemispherical shell shape, filling the hollow space with a gas generating agent made of a mixture of Acimonicum salt and nitrite, and pasting them together to form a spherical shape.
This was done by vulcanization under pressure at °C for 10 minutes. The outer diameter of the core ball after vulcanization is 60.5M.

No. 3 Table Note *1: Compression is the initial load on the core ball 3.
From the time you multiply 5 bonds (],, 575 by 9), 1
When a load of 8 pounds (8,165 kg) is applied, the amount of change (struggle) in the sword is caused.

*2: Determine the rebound height of the core ball when it is dropped naturally from a field with a repulsion height of 254 ant onto a flat concrete surface with a thickness of 6G or more.

The smaller the compression value, the harder the core ball will be, but it is considered that a range of 6.8 to 02 is good for tennis balls.

Therefore the target value! -1-6,8, but both the compositions of the present invention iri:, rigu glabella 1 and 2 fall within the above range,
In terms of compression, it can be said that it is a good composition for tennis pole cores.

In addition, the rebound height is 174mm, which is considered to be good as a core for tennis balls, and the target value is t/1174α.
However, both the composition ID Examples 1 and 2 of the present invention are close to the target value, and from this point of view, it can be said that the compositions are suitable as compositions for tennis ball cores.

Claims (1)

Claims: (1) A rubber composition for a core of a play ball, characterized in that 1 to 10 parts by weight of liquid polyisoprene rubber is blended with 100 parts by weight of base rubber. 2. The rubber composition according to claim 1, wherein the base rubber is natural rubber. 3. The average molecular weight of liquid polyisoprene rubber is 20.0.
00 to 70,000. The rubber composition according to claim 1 or claim 2.