JPS5986679A - Foaming agent - Google Patents

Abstract

PURPOSE:To provide a foaming agent capable of preventing cracking when striking a ball and suitable for hollow balls with an internal pressure, by adding a material serving as a core in the formation of crystals of sodium chloride to a sodium nitrite/ammonium chloride foaming agent. CONSTITUTION:A material serving as a core in the formation of crystals of sodium chloride produced by the reaction of sodium nitrite with ammonium chloride is added to a sodium nitrite/ammonium chloride foaming agent. Crystalline cellulose, agar-agar, powdered devil's tongue, gelatin, vinyl acetate, magnesium stearate, silicic anhydride, clay, talc, etc. are used as said core material. By adding a binder, the resultant foaming agent can be well tabletted. Said binder includes shellac, polyvinylpyrrolidone, and hydroxypropylcellulose.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in sodium nitrite-ammonium chloride foaming agents, and particularly provides a foaming agent suitable for use in hollow balls with internal pressure, such as hard tennis ball cores. The purpose is to

For example, hard tennis balls are manufactured by covering a hollow rubber core, which has an internal pressure of about twice atmospheric pressure, with a fabric called Melton.

There is also a so-called Pressure Les Paul that does not have this internal pressure for practice, but it has a poor feel at impact and is not generally liked.

There are two methods for applying internal pressure to the tennis hole core. One is a method in which two hemispherical rubber molded products called half shells are superimposed and bonded together in pressurized air (air inflation method). The other half shell is filled with a tablet-shaped foaming agent that generates gas such as nitrogen gas when decomposed by heat or chemical reaction, and is overlapped with the other half shell, causing the enclosed foaming agent to undergo a decomposition reaction. This is a method (chemical inflation method) in which internal pressure is applied by generating

The above-mentioned reactive blowing agent is usually nitrite)
An ammonium chloride foaming agent is used.

In this sodium nitrite-ammonium chloride foaming agent, sodium nitrite and ammonium chloride react as shown in the following formula to generate nitrogen gas.

N5tNO,-)-NH4C1-→NaC1+N2-1
-2H2O The reaction is usually accelerated by the addition of a small amount of water and heating. The sodium chloride produced by the reaction exists in a dissolved state in water immediately after its formation, but as time passes and water permeates through the core and decreases, the amount that can no longer be dissolved will precipitate and form crystals. . Particularly when the ball is left undisturbed for a long time in a warehouse or the like, coarse single crystals are formed, and when the ball is hit, these coarse crystals hit the inner wall of the core, producing a so-called "rattling" sound.

In view of these circumstances, the present inventors have conducted various studies and found that a sodium nitrite-ammonium chloride foaming agent contains nuclei during the crystallization of sodium chloride produced by the reaction between sodium nitrite and ammonium chloride. It has been discovered that by adding a substance such that the formation of coarse single crystals of sodium chloride can be suppressed and a large number of fine crystals can be generated, thereby preventing the generation of noise when hitting a ball, and the present invention has been developed. was completed.

In the present invention, as mentioned above, substances added for the purpose of forming nuclei during crystal formation of sodium chloride (hereinafter referred to as additives) include, for example, crystalline cellulose, agar, konjac powder, gelatin, vinyl acetate, magnesium stearate, Silicic anhydride, clay, talc, etc. are used.

In order to use foaming agents for tennis ball cores, etc., they are molded into tablets, but when the additives mentioned above are added, the tablets become brittle, making it difficult for tablets to be formed well by a molding machine. It may disappear. Therefore, the present inventors conducted further research and found that the above-mentioned drawbacks could be overcome by adding the following binder.

Examples of binders added for such purposes include shellac, polyvinylpyrrolidone, and hydroxypropylcellulose.

Even if these additives and binders are added, a predetermined internal pressure can be obtained as long as the amounts of sodium nitrite and ammonium chloride, which are the main ingredients, are the same as conventional ones.

The ratio of sodium nitrite and ammonium chloride to be used may be the same as conventional ones, and for example, the reaction molar ratio may be around 1:1 so that a predetermined internal pressure can be obtained in the core.

Preferably, the amount of the additive is 0.6 to 8.0% (by weight, hereinafter the same) in the blowing agent.

Furthermore, by appropriately combining these additives and binders, the hardness and disintegration time of the blowing agent, that is, the time required for the tablet to dissolve in water and for the reaction to proceed rapidly, can be freely adjusted. For example, the foaming agents shown in the examples have greater hardness and are adjusted to take longer to disintegrate than conventional products, so tablets are less likely to crack or chip during use, and variations in internal pressure are reduced. Additionally, there is no possibility that the foaming agent will decompose before the half shells are firmly bonded together and some of the internal gas will leak out, making it possible to manufacture tennis balls with more stable quality than before. be able to.

The foaming agent of the present invention is particularly suitably used for imparting internal pressure to hollow balls for play, such as tennis ball cores, which have an internal pressure higher than atmospheric pressure, but the use is not limited thereto. Further, when used for applying internal pressure to a tennis ball core, it is usually molded into a tablet shape, but the shape is not limited to the tablet shape, and may be molded into other shapes such as a pellet shape.

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

Examples 1 to 2 and Comparative Example 1 A blowing agent having the composition shown in Table 1 was prepared and molded into tablets with a diameter of approximately 6+w+ and a thickness of approximately 6− using a rotary tablet press, and their hardness and disintegration time were determined. was measured.

Next, the tablet-shaped foaming agent obtained as described above is placed in a half shell made of a rubber composition having the composition shown in Table 2, and the half shells having the same composition are overlapped and vulcanized (heated and pressure molded). I got a koala for a tennis ball. Next, a melton dumbbell was bonded to the core and vulcanized to produce a tennis ball.

The tennis balls obtained were stored under the conditions shown in Table 1, and after storage, the balls were cut to examine the presence or absence of coarse crystals. The results are shown in Table 1.

The amounts of each component in the table are all parts by weight. In Example 1, ammonium chloride, crystalline cellulose, hydroxypropylcellulose, and magnesium stearate were mixed in advance, and the mixture was mixed with sodium nitrite. Further, in Example 2, ammonium chloride, silicic anhydride, polyvinylpyrrolidone,
A blowing agent was prepared by mixing white shellac and magnesium stearate, and separately mixing sodium nitrite, silicic anhydride, polyvinylpyrrolidone, vinyl acetate, and magnesium stearate, and further mixing these mixtures with each other. .

The hardness was measured by measuring the compressive strength in the diametrical direction using a Monsanto type hardness tester, and the disintegration time was measured at 8.
This was done by immersing it in 5°C warm water and measuring the time until it completely dissolved.

Table 2 Patent applicant Sumitomo Rubber Industries Co., Ltd. Patent attorney
Three wheel iron Yugeki 2 ÷'t Go ゛Douto, -2

Claims (1)

[Claims] 1. A blowing agent comprising sodium nitrite, ammonium chloride, and a substance that serves as a nucleus during crystal formation of sulfur chloride produced by the reaction of sodium nitrite and ammonium chloride. 2. The substance that becomes the nucleus during crystal formation of IJium chloride is selected from the group consisting of crystalline cellulose, agar, konjac powder, gelatin, vinyl acetate, magnesium stearate, silicic anhydride, clay, and talc. The blowing agent according to claim 1, which is at least one blowing agent. 8. The foaming agent according to claim 1 or 2, which is formed into a tablet or pellet shape by adding a binder. 4. The blowing agent according to claim 8, wherein the binder is at least one selected from the group consisting of shellac, polyvinylpyrrolidone, and hydroxypropyl cellulose.