JPS6342950B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an adhesive suitable for adhering melton dumbbells to tennis balls. Tennis balls are manufactured by bonding flat Melton dumbbells to a spherical core ball. To apply the adhesive to the melton dumbbells, stack a plurality of melton dumbbells 1 as shown in Figure 1, dip the melton pack 3 sandwiched between the end plates 2 into the adhesive, let it dry, and then apply the adhesive to the end. This is done by removing the plate and peeling off the Melton dumbbells one by one. As for the adhesive for Melton dumbbells as mentioned above, (1) the Melton dumbbells can be peeled off one by one from the Melton pack after the adhesive has dried, and (2) the adhesive will definitely adhere to the sides of the Melton dumbbells that have been peeled off. and (3) have appropriate initial surface adhesion for bonding a flat Melton dumbbell to a spherical core ball. In order to satisfy requirements (1) and (2), the internal cohesive force of the adhesive itself must be weakened to an extent that does not impair adhesive performance. Therefore, conventional adhesives for melton dumbbells are made by repeatedly masticating natural rubber or synthetic rubber for a long time using a kneading roll machine, etc., resulting in excessive molecular scission, and then dissolving it in an organic solvent such as naphtha. death,
A solvent-based adhesive containing a vulcanizing agent, a vulcanization accelerator, a vulcanization accelerator, an anti-aging agent, a filler, etc. is used. However, since this solvent-based adhesive exhibits Newtonian viscosity as its flow characteristic, it sag during drying, resulting in different adhesive amounts on the top and bottom of the melton pack, and the viscosity is high compared to the concentration. The amount of adhesive deposited in a single dipping is reduced, so that multiple dippings, at least two, must be carried out and each time the melton pack must be turned upside down to dry. There have been proposals to use latex-based adhesives to improve the above-mentioned drawbacks of solvent-based adhesives, but
Latex-based adhesives usually undergo prevulcanization during storage, which tends to reduce initial adhesive strength and increase internal cohesive strength over time (ie, shorten pot life). Further, the dispersion medium of such latex adhesives is usually water, which is difficult to dry and has the disadvantage that a thin film is formed on the surface in the early stage of drying, further reducing the drying rate. The present invention aims to improve the above-mentioned drawbacks of conventional adhesives for melton dumbbells. That is, the present invention is an adhesive comprising rubber latex mixed with a high-temperature decomposition type vulcanizing agent and a heat-sensitive gelling agent,
The high-temperature decomposition type vulcanizing agent does not decompose when the adhesive is heated and dried, but decomposes at a temperature higher than the heat-sensitive gelling temperature of the heat-sensitive gelling agent, and the heat-sensitive gelling agent does not decompose when the adhesive is heated and dried; This occurs at a low temperature due to the decomposition temperature of the decomposable vulcanizing agent.
Provides adhesive for tennis ball melton dumbbells. The rubber latex used in the present invention generally has a weak internal cohesive force and preferably has a high surface adhesive force. Such adhesive components include natural and/or synthetic rubbers such as polyisoprene,
Polybutadiene, polychloroprene, nitrile rubber, styrene-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, or mixtures thereof, or their depolymerization treatment,
For example, heating in the coexistence of peroxides or azo compounds, radical reactions using redox initiators containing persulfates, or X-rays, α-rays, β-rays, etc.
It can be obtained by irradiation with radiation such as rays and gamma rays. Particularly preferred rubbers are natural rubber, synthetic polyisoprene rubber latex, or depolymerized products thereof. The above rubber latex is not particularly limited, but
Usually JIS-Z-1522 (cellophane adhesive tape test) and JIS-Z-1528 (double-sided adhesive tape test)
For example, in the case of natural rubber latex, an adhesive force of 15 to 200 g/cm (at 25°C) is preferable, and in general, if the adhesive force is less than 20 g/cm, the initial adhesive force required for the adhesive is too small, the internal cohesive force is too large, and when it exceeds 180 g/cm, the surface adhesive force is too large, making work such as bonding difficult. Various conventional additives are appropriately blended into the rubber latex thus prepared. Such additives include tackifiers, e.g.
QE6503B (commercial product from Zeon Corporation), Claprene
LIR-700 (commercial product from Clarei Soprene Chemical Company),
Vulcanizing agents (sulfur), vulcanization accelerators such as 2-mercaptobenzothiazole zinc salt, zinc diethyldithiocarbamate, vulcanization accelerators such as zinc oxide, stearic acid, oleic acid, triethanolamine, fillers such as Calcium carbonate, kaolin, clay, barium sulfate, anti-aging agents such as 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-
ethyl-6-t-butylphenol), thickener,
For example, carboxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose,
Examples include polyvinyl alcohol and polyethylene oxide. The total amount of these additives is the same as the rubber component.
It is usually 20 to 60 parts by dry weight per 100 parts by dry weight. The viscosity of the adhesive prepared as described above is usually preferably adjusted to 3,000 to 70,000 cps (20° C.) [BM type viscometer No. 4 rotor: 12 or 6 rpm]. The adhesive according to the present invention exhibits chicken-tropic properties as its flow properties [Figs.
(wt%), any amount of adhesive can be applied uniformly to a predetermined area such as the seam of Melniton even with a single dip coating process, and since the zero shear viscosity is high, it is difficult to apply when left to dry. There is little downward dripping of the adhesive, and the amount of adhesive applied between the top and bottom can be kept uniform. The vulcanizing agent used in the present invention is of a high-temperature decomposition type, and does not decompose when the adhesive is heated and dried, but decomposes at a temperature higher than the heat-sensitive gelation temperature. Preferred vulcanizing agents are disulfide-based high-temperature decomposition compounds, such as morpholine disulfide (4,
4′-dithiodimorpholine), alkylphenol disulfide, methoxyphenyl disulfide,
Ethoxyphenyl disulfide, hydroxybenzyl disulfide, etc., especially with a decomposition temperature of 60~
A temperature of 160°C is preferred. If the decomposition temperature is too low, it may decompose during storage and cause the rubber components in the adhesive to vulcanize and coagulate, while if it is too high, a high temperature will be required when bonding the melton dumbbell to the ball. The amount of high-temperature decomposition type vulcanizing agent added is 2 to 2 of the total solid content.
10% by weight, preferably 3-8% by weight. The heat-sensitive gelling agent used in the present invention is preferably a substance that causes the fusion of latex particles when heated; specific examples thereof include polysiloxane having a polyvinyl methyl ether functional group; is preferably below the decomposition temperature of the high-temperature decomposition type vulcanizing agent. When such a heat-sensitive gelling agent is used, the latex particles are fused and gelled at a temperature below the decomposition temperature of the high-temperature decomposition type vulcanizing agent and above the heat-sensitive gelling temperature of the heat-sensitive gelling agent, and moisture etc. are absorbed from the coated surface. Not only does it precipitate on top of the adhesive, making it easier to dry, but it also allows heating and air blowing at a temperature below the decomposition temperature of the high-temperature decomposition type vulcanizing agent, allowing the adhesive to dry more quickly. The amount of heat-sensitive gelling agent added is 3 to 15% by weight, preferably 5 to 12% by weight of the total solid content. Melton packs are immersed in the adhesive thus obtained and dried by heating at a temperature below about 60°C. After thoroughly drying the melton pack, attach one melton dumbbell.
After peeling off the sheets one by one and pasting them onto a core ball, they are heated to a temperature higher than the decomposition temperature of the vulcanizing agent to vulcanize and bond them. It goes without saying that the adhesive of the present invention may contain components other than those mentioned above, such as fillers, surfactants, viscosity modifiers, etc. By the method of the present invention, the concentration of the adhesive can be easily controlled, a highly concentrated adhesive can be obtained, and sufficient and uniform adhesive adhesion can be achieved with a single dipping.
Further, vulcanization does not occur during heating and drying, so the above-mentioned troubles due to internal aggregation do not occur, and the adhesive itself gels when heated and dries easily because water is expelled. Furthermore, the adhesive of the present invention has many advantages such as good storage stability and long pot life. The present invention will be explained below with reference to Examples. In the examples, parts and percentages are expressed by weight unless otherwise specified. Examples 1 and 2 and Comparative Examples 1 and 2 Tennis ball melton dumbbell adhesives were blended according to the formulations shown in Table 1. The latex adhesive was applied to a thickness of 1.0 mm on a polyester film, immediately heated at 50°C for 1 minute, and then heated at 35°C.
It was dried by blowing air at ℃. The water content of the coated latex layer was measured over time and the results are shown in FIG. Curve 4 in FIG. 2 is the moisture content curve of Examples 1 and 2, and curve 5 is the moisture content curve of Comparative Examples 1 and 2. Additionally, the above adhesive (within 12 hours of mixing)
Nominal thickness 25 specified in polyester film (JIS C 2318 (Polyester film for electrical use))
No.) to a thickness of 20 to 25 μm, and while drying in the same manner as the drying test above, apply the JIS-
Z-1522 (cellophane adhesive tape test), JIS-Z-
Adhesive strength was measured in accordance with 1528 (double-sided adhesive tape test). The results are shown in Figure 3. In the figure, curve 6 shows the change in adhesive strength over time of Example 1 and Comparative Example 1, curve 7 shows the change in adhesive strength of Example 2, and curve 8 shows the change in adhesive strength of Comparative Example 2. That is, it is shown that when morpholine disulfide, which is a high-temperature decomposition type vulcanizing agent, is used, no decrease in adhesive strength is observed over time. Furthermore, the latex adhesives of Example 1 and Comparative Example 2 were stored at room temperature, and changes in their adhesive strength over time were measured. The results are shown in Figure 4. In the figure, curve 9 shows the results of Example 1, and curve 10 shows the results of Comparative Example 2. This result shows that the use of a high temperature decomposition type vulcanizing agent significantly increases the pot life of the rubber latex type adhesive.

【table】

【table】 [Brief explanation of drawings]

Figure 1 shows a Melton pack made by stacking Melton dumbbells sandwiched between end plates, Figure 2 shows changes in the water content of the applied latex over time, Figure 3 shows the relationship between adhesive strength and drying time, and Figure 4 shows the relationship between adhesive strength and drying time. The figure is a graph showing the relationship between the adhesive strength of the adhesive and the number of storage days. In the figure, 1 is a melton dumbbell, 2 is an end plate, 3 is a melton pack, 4 is Examples 1 and 2, 5 is Comparative Examples 1 and 2, 6 is Example 1, Comparative Examples 1 and 7 are Example 2, 8 shows the results of Comparative Example 2, 9 shows the results of Example 1, and 10 shows the results of Comparative Example 2, respectively.

Claims (1)

[Scope of Claims] 1. An adhesive comprising rubber latex mixed with a high-temperature decomposition type vulcanizing agent and a heat-sensitive gelling agent, wherein the high-temperature decomposition type vulcanizing agent does not decompose when the adhesive is heated and dried, and the heat-sensitive gelling agent For tennis balls and melton dumbbells, the heat-sensitive gelling agent decomposes at a temperature higher than the heat-sensitive gelling temperature of the agent, and the heat-sensitive gelling agent causes gelation of rubber latex at a temperature lower than the decomposition temperature of the high-temperature decomposition type vulcanizing agent. glue. 2. The adhesive according to item 1, wherein the high-temperature decomposition type vulcanizing agent is a disulfide compound having a decomposition temperature of 60 to 160°C. 3. The adhesive according to claim 1, wherein the heat-sensitive gelling agent is a polysiloxane having polyvinyl methyl ether functional groups. 4 Heat-sensitive gelling agent improves gelling of rubber latex 60
2. The adhesive according to claim 1, which is capable of forming at a temperature lower than .degree. 5. The adhesive according to item 1, wherein the rubber latex is a latex of natural rubber, synthetic polyisoprene rubber, or a depolymerized product thereof.