JPH0214386B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in sodium nitrite-ammonium chloride foaming agents, and an object of the present invention is to provide a foaming agent suitable for use in hollow balls having internal pressure, such as hard tennis ball cores. 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 metton.
There are so-called pressureless balls for practice that do not have this internal pressure, but they have a poor feel at impact and are generally not preferred. There are two ways to apply internal pressure to the tennis ball core.
There are two types: one is a method (air inflation method) in which two hemispherical rubber molded products called half shells are glued together in pressurized air; A tablet-shaped foaming agent that generates gas such as nitrogen gas when decomposed by heat or chemical reaction is placed in the half-shell and overlapped with the other half-shell, causing the enclosed foaming agent to undergo a decomposition reaction and apply internal pressure. method (chemical inflation method). As the above-mentioned reactive foaming agent, a sodium nitrite-ammonium chloride foaming agent is usually used. In this sodium nitrite-ammonium chloride foaming agent, sodium nitrite and ammonium chloride react as shown in the following equation to generate nitrogen gas. NaNO ₂ +NH ₄ Cl→NaCl + N ₂ +2H ₂ O 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 cannot be dissolved will precipitate. to produce crystals. Especially under conditions where it is left undisturbed for a long time in a warehouse etc., coarse single crystals are produced.
When the ball is hit, these coarse crystals collide with the inner wall of the core, producing a 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 crystal formation of ammonium chloride, which is produced by the reaction between sodium nitrite and ammonium chloride. By adding a substance that causes I have completed my invention. 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. When used as a foaming agent for tennis ball cores, etc., it is molded into tablets, but when the additives mentioned above are added, the tablets become brittle and cannot be properly formed by a molding machine. There are cases. 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 hydroxypropyl cellulose. 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. When a foaming agent is used to impart internal pressure to the core of a tennis ball, etc., it is molded into a tablet. The component containing ammonium chloride and the component containing ammonium chloride are molded separately, the tablet-shaped molded product of the sodium nitrite-containing component and the tablet-shaped molded product of the ammonium chloride-containing component are placed in a half shell, and a small amount of water is added, Inside the half shell, sodium nitrite and ammonium chloride react to generate nitrogen gas. The reason why the sodium nitrite-containing component and the ammonium chloride-containing component are molded separately in this way is that the sodium nitrite and ammonium chloride react with each other during molding or when they are mixed before molding, resulting in their properties as a blowing agent. This is to prevent loss. In addition, the reason why molded products such as tablets are made is that before the joint surfaces of the half shells are firmly bonded, the gas generated by the reaction of sodium nitrite and ammonium chloride flows from the unbonded joint surface to the half shells. This is to prevent leakage to the outside. In other words, when used in the core of a tennis ball, if it is in powder form, the sodium nitrite and ammonium chloride will react and generate nitrogen gas before the joint surfaces of the half shells are firmly bonded. The nitrogen gas leaks out from the unbonded joint surface to the outside of the half shell, making it impossible to obtain the desired internal pressure. This is to slow down the reaction and prevent the reaction between sodium nitrite and ammonium chloride from occurring until the joint surfaces of the half shells are firmly bonded. Note that the ratio of sodium nitrite and ammonium chloride used may be the same as conventional ones, and for example, it is sufficient to set a reaction molar ratio of about 1:1 so that a predetermined internal pressure can be obtained in the core. And the additive is in the foaming agent
It is preferable to set the binder to 0.5 to 8.0% (weight%, the same applies hereinafter), and when adding a binder, the binder is added to the foaming agent at a concentration of 0.5 to 8.0%, although it varies depending on the amount of additive added.
It is preferable to set it to about 10.0%. In addition, by appropriately combining these additives and binders, the hardness and disintegration time of the blowing agent, that is, tablets containing sodium nitrite and ammonium chloride, dissolve in water and the reaction proceeds rapidly. You can freely adjust the time. For example, the effervescent agents shown in the examples are adjusted so that the tablets have greater hardness and longer disintegration time than conventional products, so the tablets are less likely to crack or chip during use, and variations in internal pressure are reduced. In addition, the foaming agent does not decompose before the half shells are firmly bonded together and some of the internal gas leaks out, which also has the effect of producing tennis balls with more stable quality than before. can be achieved. 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 Blowing agents having the compositions shown in Table 1 were prepared. However, in Example 1, ammonium chloride, crystalline cellulose, hydroxypropyl cellulose, and magnesium stearate were mixed in advance, and this ammonium chloride-containing component was then molded into tablets of approximately 6 mm in diameter and approximately 6 mm in thickness using a rotary tablet press. Molded into tablets, sodium nitrite alone was molded into tablets with a diameter of about 6 mm and a thickness of about 6 mm using the above molding machine, and the hardness and disintegration time of these tablets were measured to determine the hardness of the tablets containing ammonium chloride. and disintegration time are shown in Table 1. In the case of Example 2, ammonium chloride, silicic anhydride, polyvinylpyrrolidone, white shellac, and magnesium stearate were mixed, and separately, sodium nitrite, silicic anhydride, polyvinylpyrrolidone,
Vinyl acetate and magnesium stearate are mixed, and the mixture of the ammonium chloride-containing component and the sodium nitrite-containing component are separately molded into tablets with a diameter of about 6 mm and a thickness of about 6 mm using the molding machine. The hardness and disintegration time of the tablets were measured and are shown in Table 1. In addition, in Comparative Example 1, ammonium chloride and sodium nitrite were separately molded into tablets with a diameter of about 6 mm and a thickness of about 6 mm using the molding machine, and the hardness and disintegration time of the tablets were measured. Table 1 shows the hardness and disintegration time of ammonium chloride tablets. In addition, all the amounts of each component in the table are based on parts by weight. In addition, the hardness and disintegration time were shown only for tablets containing ammonium chloride, because the tablets containing ammonium chloride had lower hardness than the tablets containing sodium nitrite.
This is because the collapse time is short. Next, the blowing agents obtained as described above (that is, tablets containing ammonium chloride and tablets containing sodium nitrite) were each placed in a half shell made of a rubber composition having the composition shown in Table 2. , 1.2 cc of water was added to each half shell, and half shells of the same composition were stacked and vulcanized (heated and pressure molded) at 155°C for 10 minutes to obtain a core 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 hardness was measured by measuring the compressive strength in the diametrical direction using a Monsanto type hardness tester, and the disintegration time was measured by immersing it in 85°C hot water and measuring the time until it completely dissolved. . As shown in Table 1, Example 1 in which crystalline cellulose was added as a core substance during crystal formation of sodium chloride produced by the reaction between sodium nitrite and ammonium chloride, and Example 1 in which silicic anhydride was added. Compared to Comparative Example 1 in which these were not added, Sample No. 2 produced fewer crude water crystals, as seen in the measurement results after storage at 20° C. for 1 year and 6 months.

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Claims (1)

[Scope of Claims] 1. A blowing agent comprising sodium nitrite, ammonium chloride, and a substance that serves as a nucleus during crystal formation of sodium chloride produced by the reaction of sodium nitrite and ammonium chloride. 2. The substance that serves as the core during crystal formation of the sodium chloride is at least one 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. 3. 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 3, wherein the binder is at least one selected from the group consisting of shellac, polyvinylpyrrolidone, and hydroxypropylcellulose.