JP4387849B2 - Tennis ball and manufacturing method thereof - Google Patents

Description

  The present invention relates to a tennis ball in which the pressure inside the core is increased by a gas generated by a chemical reaction inside the core.

Some tennis balls have a gas generated by a chemical reaction inside the core and the pressure inside the core is made higher than atmospheric pressure (see, for example, Patent Document 1). Such a tennis ball is manufactured, for example, by the following procedures (a) to (c).
(A) After forming a rubber composition kneaded with raw rubber, filler, vulcanizing agent, vulcanization accelerator, etc. into a sheet shape, etc., extrusion molding is carried out so that the amount of the molded product is approximately half of the core. Disconnect. Next, the cut extruded product is placed in a half shell mold and vulcanized to obtain a hemispherical half shell made of vulcanized rubber.
(B) The two half shells are combined, and both the half shells are vulcanized and bonded together with ammonium chloride and sodium nitrite as an aqueous solution or solid in the hollow portion between the two half shells. In addition to molding, nitrogen gas is generated by the following reaction between ammonium chloride and sodium nitrite, and the pressure inside the core is increased to about twice the atmospheric pressure with this nitrogen gas to increase the repulsive force of the ball.
NH ₄ Cl + NaNO ₂ → NaCl + N ₂ + 2H ₂ O
(C) A felt-like melton is bonded to the surface of the molded core using an adhesive, and the resultant is put into a molding machine and heated to complete a tennis ball.

US Pat. No. 1,415,437

  In a tennis ball in which the pressure inside the core is increased by the gas generated by the chemical reaction inside the core described above, sodium chloride is generated together with nitrogen gas by the reaction between ammonium chloride and sodium nitrite inside the core. This by-product sodium chloride is in a state dissolved in the water present in the core immediately after the reaction, but as time elapses, the water evaporates and the water in the core decreases. Begins to crystallize. When this crystal grows and grows, the sodium chloride crystal that grows when the tennis ball is moved rolls inside the core, causing a phenomenon that makes a sound of noise, and the product value of the tennis ball and the player The evaluation from was reduced.

  The present invention has been made in view of the above-described circumstances. In a tennis ball in which the pressure inside the core is increased by a gas generated by a chemical reaction, the solid matter generated inside the core due to the chemical reaction is tennis. An object of the present invention is to provide a tennis ball that can be prevented from rolling inside the core when the ball is moved and thereby generating sound from the inside of the core, and a method for manufacturing the same.

  As a result of conducting various studies to solve the above-described problems, the present inventors have found that when a tackifier that imparts tackiness to the solid matter inside the core is sealed inside the core, the surface of the solid matter inside the core The tackifier substance adheres, and the solid substance adheres to the inner peripheral wall of the core due to the action of the tackifier substance. Therefore, even when the tennis ball is moved, the solid substance does not roll inside the core. It was found that no sound due to solid matter was generated from the inside.

The present invention has been made on the basis of the above-described knowledge, and in a tennis ball in which the pressure inside the core is made higher than the atmospheric pressure by the gas generated by the chemical reaction inside the core, the inside of the core is generated by the chemical reaction. Provided is a tennis ball characterized in that at least one selected from polyethylene glycol, polypropylene glycol and glycerin is enclosed in a core as a tackifier that imparts tackiness to a solid.

The present invention also provides a method for manufacturing a tennis ball in which the pressure inside the core is made higher than atmospheric pressure by a gas generated by a chemical reaction inside the core, and the raw material of the chemical reaction and the inside of the core by the chemical reaction. Tennis characterized by causing the chemical reaction to be carried out in a state in which at least one selected from polyethylene glycol, polypropylene glycol and glycerin is enclosed in the core as a tackifier that imparts tackiness to the generated solid. A method for manufacturing a ball is provided.

  According to the tennis ball and the manufacturing method thereof according to the present invention, it is possible to prevent a phenomenon in which a solid generated due to a gas generation chemical reaction rolls inside the core to generate a sound, and thus the generation of the sound. It is possible to prevent a decline in the product value of the tennis ball and evaluation from the player.

Hereinafter, the present invention will be described in more detail. In the present invention, as the chemical reaction for generating gas inside the core, in addition to the above-described reaction for generating nitrogen gas by the reaction of ammonium chloride and sodium nitrite, for example, nitrogen gas by the reaction of ammonium sulfate and sodium nitrite The following reactions can be mentioned. In this reaction, sodium sulfate is formed as a by-product, and solid sodium sulfate is generated inside the core by evaporation of moisture.
(NH ₄ ) ₂ SO ₄ + 2NaNO ₂ → Na ₂ SO ₄ + 2N ₂ + 4H ₂ O

  The chemical reaction raw material (gas generating agent) for generating the gas, that is, ammonium chloride, ammonium sulfate, sodium nitrite, etc., may be put into the hollow part between the half shells as an aqueous solution to carry out the reaction, and the half as a solid The reaction may be carried out by putting in a hollow portion between the shells and injecting water into the hollow portion.

Further, as the tackifier used in the present invention, it adheres to the solid generated inside the core to give the solid, and when the solid contacts the inner peripheral wall of the core, it can be used to become fixed to the peripheral wall. In this case, since water is used when the gas generating raw material is put into the core, a tackifier that dissolves or mixes in water or a tackifier that absorbs water and forms a gel will generate sound. This is preferable because it has a high effect of suppressing the production of the ball and can maintain the productivity of ball production.

As tackifying agent, specifically, use at least one selected from the port triethylene glycol, polypropylene glycol and glycerin. Of these , polyethylene glycol is preferred . The polyethylene glycol preferably has an average molecular weight of about 200 to 600, and particularly preferably about 200 to 300.

  The amount of the tackifier substance enclosed in the core can be appropriately set according to the type of the tackifier substance, etc., but usually solids (sodium chloride, It is appropriate that the mass is 0.2 to 2 times, particularly 0.3 to 0.8 times the mass of the sodium sulfate crystals.

  There is no limitation on the method of enclosing the tackifier inside the core, but when the gas generating agent, that is, ammonium chloride, ammonium sulfate, sodium nitrite, etc. is put in the hollow part between the half shells as an aqueous solution, the gas generating agent A method of previously dissolving the tackifier in any of the aqueous solutions, or a method of putting an aqueous solution of the tackifier in the hollow portion between the half shells separately from the aqueous solution of the gas generating agent can be employed. In addition, when the gas generating agent is put in the hollow portion between the half shells as a solid, a method in which an aqueous solution of a tackifier is put into the hollow portion between the half shells separately from the solid of the gas generating agent can be employed.

  A rubber composition is prepared by kneading 80 parts by mass of natural rubber, 20 parts by mass of polybutadiene rubber, 10 parts by mass of zinc oxide, 55 parts by mass of a filler, 2.5 parts by mass of a vulcanization accelerator and 5 parts by mass of sulfur. Then, this rubber composition was formed into a sheet shape. Thereafter, extrusion molding was performed, and the sheet-like molded product was cut into an amount approximately equivalent to a half core. The cut extruded product was put in a half shell mold and vulcanized to obtain a hemispherical half shell made of vulcanized rubber.

  Next, the two half shells are put together, and in a state where an aqueous solution of ammonium chloride and an aqueous solution of sodium nitrite are put in the hollow part between the two half shells, rubber shells are attached to both half shells and vulcanized to form a spherical core. In addition, nitrogen gas was generated by the reaction of ammonium chloride and sodium nitrite, and the pressure inside the core was increased to about twice the atmospheric pressure with this nitrogen gas. Furthermore, a tennis ball was manufactured by laminating a melton with an adhesive attached to the core surface, placing it in a molding machine and heating.

  At this time, ammonium chloride aqueous solutions (1) and (2) shown in Table 1 below were prepared as the ammonium chloride aqueous solution, and sodium nitrite aqueous solutions (1) to (4) shown in Table 2 below as the sodium nitrite aqueous solution. While producing these ammonium chloride aqueous solution and sodium nitrite aqueous solution in the hollow portion between both half shells in the combinations shown in Table 3, the reaction of Examples 1 to 4 and Comparative Example shown in Table 3 was performed. I got a tennis ball. In addition, as the polyethylene glycol in Table 1 and Table 2, those having an average molecular weight of 200 were used.

Three holes each having a diameter of 3 mm were formed in each of the ten tennis balls of Examples 1 to 4 and the comparative example, and the tennis balls were left in a constant temperature bath at 40 ° C. for 3 weeks. The noise was evaluated by examining the specific occurrence of the noise. The results are shown in Table 3. From the results shown in Table 3, it was confirmed that according to the present invention, it was possible to prevent a phenomenon in which solids (crystals of sodium chloride) produced due to a gas generation chemical reaction roll inside the core and generate sound.

Claims (4)

In a tennis ball in which the pressure inside the core is made higher than atmospheric pressure with a gas generated by a chemical reaction inside the core , polyethylene is used as a tackifier that gives the solid matter produced inside the core by the chemical reaction. A tennis ball characterized in that at least one selected from glycol, polypropylene glycol and glycerin is enclosed in a core.   The tennis ball according to claim 1, wherein the chemical reaction is a reaction in which nitrogen gas is generated by a reaction between ammonium chloride and sodium nitrite. In a method for manufacturing a tennis ball in which the pressure inside the core is made higher than atmospheric pressure with a gas generated by a chemical reaction inside the core, the raw material material of the chemical reaction and the solid matter generated inside the core by the chemical reaction are adhered. A method for producing a tennis ball, characterized in that the chemical reaction is carried out in a state where at least one selected from polyethylene glycol, polypropylene glycol and glycerin is encapsulated in the core as a tackifying substance for imparting properties. 4. The method for manufacturing a tennis ball according to claim 3 , wherein the chemical reaction is a reaction in which nitrogen gas is generated by a reaction between ammonium chloride and sodium nitrite.