JPH0571710B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to rubber reinforcing fibers. (Prior Art) Reinforcing fibers such as glass fiber yarn are widely used to increase the strength of rubber products such as rubber belts and tires. Rubber products such as rubber belts are subjected to repeated bending stress, resulting in bending fatigue, resulting in decreased performance, and peeling between the reinforcing material and the rubber matrix is likely to occur. In order to prevent such peeling or performance deterioration and obtain a sufficient reinforcing effect, it is necessary to increase the compatibility and adhesive strength between the reinforcing fibers and the rubber. be done. Various compositions of processing agents have been proposed. For example, various processing agents have been proposed, such as a processing agent using a combination of a vinylpyridine-styrene-butadiene terpolymer latex and a water-soluble condensate of resorcinol and formalin, or a processing agent containing rubber latex (Japanese Unexamined Patent Application Publication No. 1983-1999). (See No. 114551). Furthermore, a treatment liquid containing a polyisocyanate, a polynitroso aromatic compound, and an acidic halogen-containing polymer has also been proposed (see Japanese Patent Application Laid-Open No. 14546/1983). Furthermore, a treatment liquid containing a polyisocyanate, a polynitroso aromatic compound, and an acidic halogen-containing polymer has also been proposed (see Japanese Patent Application Laid-Open No. 14546/1983). Further, a first liquid (RFL liquid) containing a water-soluble condensate of resorcin formaldehyde and rubber latex is applied to the rubber reinforcing fibers to form a first layer containing the resorcin formaldehyde condensate and rubber on the fibers, and then the rubber latex is coated with a first layer containing the resorcin formaldehyde condensate and rubber. It is also known to form a second layer containing isocyanate and rubber by treating with an overcoat liquid containing isocyanate (see JP-A-49-14546). Furthermore, it has been proposed to use H-NBR latex as the rubber latex to be contained in RFL (see Japanese Patent Laid-Open No. 270877/1983). (Problems to be Solved by the Invention) Conventional treatment liquids for rubber reinforcing fibers and conventional methods for treating rubber reinforcing fibers have the following problems. (1) Sufficient adhesive strength cannot be obtained. (2) It is difficult to obtain rubber products with sufficient bending strength. (3) Adhesiveness decreases when used at high temperatures. That is,
Heat resistance is insufficient. Recently, with the rise in temperature near automobile engines, heat-resistant rubbers such as chlorosulfonated polyethylene and hydrogenated nitrile rubber have come to be used as rubber for timing belts. Since such heat-resistant rubber has lower adhesion than ordinary rubber, the above-mentioned drawbacks tend to be greater than that of ordinary rubber, and a timing belt that can withstand long-distance running has not been obtained. Treat the rubber reinforcing fibers with RFL liquid, then
Although the above-mentioned problems can be solved to some extent by treating with an overcoat liquid containing rubber latex and isocyanate, this method has the following problems. (1) Adhesive strength decreases over time. (2) In order to obtain sufficient effects, it is necessary to use a large amount of isocyanate; increasing the amount of isocyanate deteriorates the stability of the solution, and it is necessary to prepare a small amount of overcoat solution each time it is used. . (3) The interfacial adhesion between the RFL layer (first layer) and the overcoat liquid (second layer) is poor, and peeling easily occurs between the first and second layers. Although the method of using an RFL liquid containing H-NBR latex is particularly effective when the matrix rubber is H-NBR, this method also has the following drawbacks. That is, it is necessary to use an aqueous emulsion as the rubber latex to be contained in the RFL liquid. Although it is technically possible to produce an aqueous solution containing H-NBR, the complexity of the production process significantly increases costs. The present invention solves the problems of the prior art described above,
The purpose is to provide rubber reinforcing fibers that do not lose adhesive strength over time even when used under high temperature conditions such as being subjected to repeated bending stress, have high heat resistance, and have low manufacturing costs. It is said that (Means for solving the problem) In order to achieve the above object, the present invention includes:
As a rubber reinforcing fiber for reinforcing the matrix rubber, a second layer containing a halogen-containing polymer and an isocyanate is formed on the first layer containing a water-soluble condensate of resorcin formaldehyde and rubber formed on the fiber, A fiber is used in which a third layer containing the same rubber as the matrix rubber is further formed on the second layer. In a preferred embodiment of the present invention, a second compound containing a halogen-containing polymer, an isocyanate, and a vulcanizing agent is used.
layer, or a second layer containing an inert fine powder such as a halogen-containing polymer, isocyanate, vulcanizing agent, carbon black, or silica, or the same rubber, vulcanizing agent, carbon black, or silica as the matrix rubber. A reinforcing fiber formed with a third layer containing an inert fine powder such as the following is used. Next, the present invention will be explained in more detail. In the present invention, the first layer is formed by applying a liquid containing a resorcin formaldehyde condensate and rubber latex (RFL liquid) onto the rubber reinforcing fibers. A water-soluble condensate of resorcin formaldehyde (hereinafter simply referred to as a condensate) is a resorcin and formaldehyde rich in oxymethyl groups obtained by reacting resorcin and formaldehyde in the presence of an alkaline catalyst such as an alkali hydroxide, ammonia, or an amine. Water-soluble initial addition condensates (resols) can be preferably used. In particular, the molar ratio of resorcinol and formaldehyde is 1:0.3 to 2.5.
It is preferable to react at a ratio of . As the rubber latex used in the RFL liquid (first liquid), a latex with a relatively low degree of polymerization that is used as a treatment agent for rubber reinforcing fibers can be suitably used, and there is no limitation, but in particular, butadiene rubber latex, Among vinylpyridine-styrene-butadiene terpolymer latexes (hereinafter referred to as terpolymer latexes), terpolymer latexes are preferred. As a terpolymer latex, the weight ratio of vinylpyridine, styrene, and butadiene is 10 to 10.
20:10~20:60~80 is particularly suitable,
Pyratex (product name, manufactured by Sumitomo Nogatatsuku Co., Ltd.), 0650
(trade name, Nippon Synthetic Rubber Co., Ltd.), Nipol2518FS (trade name, Nippon Zeon Co., Ltd.), etc. can be suitably used. As the butadiene latex, butadiene latex, butadiene-styrene copolymer latex, butadiene-nitrile copolymer latex, etc. are suitable, such as 0700 (trade name, manufactured by Japan Synthetic Rubber Co., Ltd.), Nipol LX111, Nipol 1562. (Product name,
(manufactured by Nippon Zeon) etc. can be suitably used. Although the above-mentioned terpolymer latex and butadiene latex can be used alone, it is preferable to use both in combination and in a mixture with chlorosulfonated polyethine (CSM) latex described below. As CSM latex, the chlorine content is 20~
40wt%, preferably 25-35wt%, S content in the sulfon group is 0.5-2.0wt%, preferably 1.1-35wt%
A raw rubber having a Mooney viscosity of 30 to 95 is suitably used. In addition, some of the CSM latex (50wt% or less,
Chloroprene (CR) (preferably 25wt% or less)
Alternatively, it can also be replaced with a latex of hydrogenated nitrile rubber (H-NBR). Rubber reinforcing fiber treatment liquid 1 containing each of the above-mentioned components
The concentrations of terpolymer latex, butadiene latex, CSM latex, and condensate in the liquid are 10 to 30 wt%, 3 to 25 wt%, and 0.5 to 6 wt%, respectively.
Preferably 15-25wt%, 5-15wt%, 1-3wt
%, the total amount of these is 10 to 50 wt%, preferably 20 to 40 wt%, and the amount of the first liquid applied to the reinforcing fibers is 12 to 50 wt% of the fiber weight as solid content.
A suitable amount is 25 wt%, preferably 16 to 22 wt%. Incidentally, a latex stabilizer, an anti-aging agent, etc. may be added to the first liquid if necessary. Although there are no particular limitations on the reinforcing fibers used in the present invention, it is practical to use glass fibers.
For example, glass fibers with a thickness of 9 μm that are bundled with a sizing agent and about 200 glass fibers can be suitably used. Arrange three such reinforcing fibers and add the first
The liquid is applied in an amount of 12 to 25 wt%, preferably 16 to 22 wt%, according to a conventional method. After the first liquid is applied and dried, the second liquid is applied according to a conventional method. It is desirable to dry the first liquid at a temperature of 200 to 350°C. In the present invention, a second layer containing a halogen-containing polymer and an isocyanate is formed on the first layer thus formed. The second layer can be suitably formed by applying a second liquid as described below. The amount of second liquid applied is 0.5 to 5wt to the reinforcing fiber.
%, preferably 1 to 4 wt%. Preferably at 100-200℃ after applying the second liquid
Dry in . In addition, 2.54
After applying S or Z twist (pre-twist) of about 0.5 to 4.0 per cm (1 inch), pull together about 2 to 13 more strands and twist in the opposite direction to the pre-twist, about 0.5 to 3.0 per 2.54 cm. It is desirable to apply the second liquid to the yarn by giving it a ply twist. As the second liquid, one containing a halogen-containing polymer and an isocyanate is used. A liquid containing a halogen-containing polymer, an isocyanate, and a vulcanizing agent, preferably a halogen-containing polymer, an isocyanate, a vulcanizing agent, and an inert fine powder such as carbon black or silica, particularly the liquid described below, is suitably used. As the halogen-containing polymer, chlorinated rubber, chloroprene, chlorinated polyethylene, chlorinated ethylene-propylene copolymer, chlorinated polyvinyl chloride, chlorosulfonated polyethylene, etc. can be used, but chlorosulfonated polyethylene is particularly preferred. Give results. The chlorosulfonated polyethylene (CSM) latex has a chlorine content of 20 to 40 wt%, preferably 25 to 35 wt%, and an S content of 0.5 to 2.0 wt%, preferably 1.1 to 1.4 wt% in the sulfon group. is appropriate, and the Mooney viscosity of raw rubber is 30 to 95.
Those can be suitably used. Also, the amount of halogen-containing polymer in the second liquid is
1 to 10 wt% as solid content, preferably 2 to 5 wt%
It is appropriate to If this amount is too small, the effect will not be sufficient, and if this amount is too large, the adhesive force will decrease. Isocyanate is added to the second liquid. The amount of isocyanate is suitably 0.5 to 2.0 wt%, preferably 1 to 15 wt%, and can improve adhesion. The amount of isocyanate is sufficient to be about 50% of that of conventional technology, and there is no deterioration in bending fatigue or heat resistance that would occur if too much isocyanate is used, and the stability of the overcoat liquid is increased. do. The weight percent of the total amount of isocyanate and halogen-containing polymer in the second liquid is suitably 3 to 15 wt%, preferably 5 to 10 wt%; if this concentration is too large, the viscosity of the liquid will increase; Unevenness tends to occur, and if this concentration is too low, the amount of adhesion decreases, making it impossible to obtain a sufficient effect. Furthermore, by containing a vulcanizing agent in the second liquid, the adhesion can be further improved and more suitable results can be obtained. Polynitroso aromatic compound A as a vulcanizing agent
(e.g. p-dinitrosobenzene), tetrachlorobenzoquinone, poly p-dinitrosobenzene,
Examples include p,p'-dibenzoyl, benzoquinone dioxime, and p-benzoquinone oxime,
Particularly preferred are tetrachlorobenzoquinone, polyp-dinitrosobenzene, p,p'-dibenzoylbenzoquinone dioxime, and p-benzoquinone dioxime. It is appropriate that the amount of the vulcanizing agent in the second liquid be 0.3 to 3 wt%, preferably about 0.6 to 2.5 wt%.If this amount is too small, the effect will not be sufficient, and the Peeling between the layers is likely to occur. The second liquid further contains litharge, lead maleate,
A lead compound such as lead phthalate can also be added, which has the effect of improving water resistance. The amount of lead compound in the second liquid is suitably 0.5 to 5 wt%, preferably 1 to 3 wt%. Furthermore, even better results can be obtained by adding methacrylate or acrylate as a vulcanization aid to the second liquid. As the methacrylate and acrylate, lead methacrylate, zinc methacrylate, aluminum methacrylate, silver methacrylate, and similar metal salts of acrylic acid can be suitably used. The amount of methacrylate or acrylate to be suspended in the second liquid is 3 to 0.001 wt%, preferably
It is appropriate to set it as 1.5-0.05wt%. Inert fine powder of carbon black, silica, titanium, etc. has a particle size of 10 to 200 mμ, preferably 20 mμ.
~100 mμ can be suitably used. It is practical to knead inert fine powders such as carbon black and silica into the rubber in advance. The amount of inert fine powder such as carbon black or silica is 10 to 50 wt%, preferably 20 to 50 wt%, based on the rubber.
It is appropriate to set it at 40wt%. The strength of the second layer can be increased by adding carbon black or an inert fine powder such as silica. The amount of the second liquid to be applied is suitably 0.5 to 5 wt%, preferably 2 to 4 wt%, based on the solid content, based on the reinforcing fibers. In the present invention, after drying the second layer thus formed, a third layer containing the same rubber as the matrix rubber is formed thereon. Rubbers include chlorosulfonated polyethine, nitrile rubber, and hydrogenated nitrile rubber (H-
NBR), ethylene-propylene rubber (EPDM)
is exemplified. The third layer can be suitably formed by applying the third liquid as described below. The third liquid will be explained below. As the third liquid, it is appropriate to use an organic solvent solution of the same rubber as the matrix rubber. As the organic solvent, toluene, MEK, xylene, trichloroethane, trichloroethylene, etc. can be suitably used. Also, the concentration is 3~20wt
%, preferably 5 to 15 wt%. It is desirable that the third liquid further contains carbon black, inert fine powder such as silica, and a vulcanizing agent. Inert fine powder such as carbon black, silica, titanium, etc. has a particle size of 10 to 200 mμ, preferably 20 to 200 mμ.
Use a 100 mμ sample and suspend it in the third liquid. The amount of inert fine powder such as carbon black and silica is 10 to 50 wt%, preferably 20 to 40 wt% of the rubber.
It is appropriate to do this, and it is practical to knead it into the rubber in advance. By adding these, the strength of the third layer can be increased. As the vulcanizing agent, the vulcanizing agents mentioned in the second liquid or peroxides such as sulfur and dicumyl peroxide can be suitably used, and the vulcanizing aids mentioned in the second liquid are used together. You can also obtain better results. The amounts of the vulcanizing agent and the vulcanizing aid are 0.5 to 15 wt%, 0.1 to 1.5 wt%, preferably 1 to 1.5 wt%, respectively, based on the rubber.
~10wt%, 0.2~1wt%, and the amount of the third liquid applied is suitably 0.5~5wt%, preferably 1~4wt% as a solid content, based on the reinforcing fibers. (Function) A second layer containing a halogen-containing polymer and an isocyanate is formed on the first layer containing a water-soluble condensate of resorcin formaldehyde and rubber formed on a rubber reinforcing fiber for reinforcing the matrix rubber. By forming a third layer containing the same rubber as the matrix rubber on top of the two layers, the adhesive force between the matrix rubber and the reinforcing fibers is increased, and the adhesive force between the rubber and the reinforcing fibers is subjected to repeated stress. Even when used under such conditions, it prevents deterioration over time, reinforcing fibers,
The interfacial adhesion between the second layer, the third layer, and the matrix rubber is increased to prevent peeling. Further, by using a second layer containing a halogen-containing polymer, an isocyanate, and a vulcanizing agent, the amount of isocyanate used can be reduced, and deterioration of flex fatigue resistance and heat resistance that would occur if too much isocyanate is used can be prevented. Further, performance deterioration due to aging of the second liquid itself is prevented. Furthermore, the effects of the present invention can be obtained by containing inert fine powder such as carbon black or silica in the second layer and by containing inert fine powder such as a vulcanizing agent or carbon black or silica in the third layer. Increase it further. (Example) Vinylpyridine, styrene and butadiene
65 parts by weight of vinylpyridine-styrene-butadiene terpolymer latex (Pyratex, trade name, manufactured by Sumitomo Naugatatsu Co., Ltd., terpolymer content 41wt%) containing a ratio of 15:15:70, butadiene latex (0700, Product name, Japan Synthetic Rubber Co., Ltd., 8 parts by weight of butadiene content (57 wt%), 20 wt% of an addition condensate of resorcinol and formaldehyde (resol) is added to a mixture of 15 parts by weight and 12 parts by weight of water, and further anti-aging. As agents, 1 part by weight of a mineral oil emulsion (mineral oil content: 55 wt%) and 1 part by weight of aqueous ammonia (concentration: 18 wt%) were added to obtain a first liquid (RFL liquid). 0.8 parts by weight of zinc methacrylate, 6 parts by weight of chlorosulfonated polyethylene (Hypalon 40, trade name, manufactured by Showa Denko DuPont), polyisocyanate (MR-200, trade name, manufactured by Nippon Polyurethane Co., Ltd.)
1.1 parts by weight, 1.5 parts by weight of p,p'-dibenzoylbenzoquinone dioxime (vulcanizing agent), and toluene were added to obtain a second liquid having a concentration of 10 wt%. In a toluene solution of ethylene-propylene rubber (concentration 7.5 wt%), carbon black with a particle size of 50 mμ was suspended at 50 wt% relative to the rubber, and 1.0 wt% of sulfur was added.
% was added to obtain a third solution. The first liquid was applied to three glass fiber bundles made of 200 9μ glass fibers in a conventional manner (solid content: 17 wt%). After drying at 250℃ for 1 minute,
This glass fiber bundle was given 4.0 Z twists (pre-twist) per 2.54 cm, and 13 of the fiber bundles that had been given this pre-twist were then aligned and subjected to S twists (pre-twist) 2.1 times per 2.54 cm. 2% solids content of the second liquid
After application, it was dried at 140°C for 1 minute, and 2wt% of the third liquid was added as a solid content, heated at 140°C for 1 minute, and dried. A test piece was prepared using the same method. Composition of matrix rubber: 100 parts by weight of ethylene-propylene rubber: 50 parts by weight of carbon black, 5 parts by weight of stearic acid, 2.5 parts by weight of anti-aging agent, 1 part by weight of vulcanizing agent, 1.5 parts by weight of vulcanization accelerator, 5 parts by weight of plasticizer Contains parts by weight. Preparation of test piece The following test piece was prepared using rubber having the above composition. Test piece 1 One of the above reinforcing fibers was sandwiched between rubber sheets with a thickness of 1 mm, a width of 10 mm, and a length of 500 mm, pressed, and heated at 160°C.
Vulcanize for 30 minutes. Test piece 2 The above reinforcing fibers were arranged without gaps between rubber sheets with a thickness of 3 mm, width of 25.4 mm, and length of 100 mm, pressed, and vulcanized at 160°C for 20 minutes. Using this test piece 1, the number of times it was bent until it broke was measured using a bending fatigue tester at room temperature. This test piece 2 was measured at 50mm/
The adhesive force was measured by peeling at a pulling speed of min. The results of the above tests are shown in the attached table. (Comparative example) Using only the first and second liquids of the above example, the third liquid
The same experiment was conducted without using the liquid (Comparative Example 1). A similar experiment was also conducted in the case where the first liquid of the example was used and the second and third liquids were not used at all (Comparative Example 2). The results of these experiments are shown in the attached table.

[Table] (Effects of the invention) Even when used for a long time under conditions that provide repeated bending strength, the decrease in adhesive strength is small, and even when chlorosulfonated polyethylene, hydrogenated nitrile rubber, etc. are used as the matrix rubber, the adhesive strength is large. It has great strength and greatly improves bending fatigue resistance.

Claims (1)

[Scope of Claims] 1. In a rubber reinforcing fiber for reinforcing matrix rubber, a halogen-containing polymer, an isocyanate, etc. A rubber reinforcing fiber comprising: a second layer containing the same rubber as the matrix rubber; and a third layer containing the same rubber as the matrix rubber formed on the second layer. 2. The rubber reinforcing fiber according to claim 1, wherein the second layer contains a halogen-containing polymer, an isocyanate, and a vulcanizing agent. 3. The rubber reinforcing fiber according to claim 1, wherein the second layer contains a halogen-containing polymer, an isocyanate, a vulcanizing agent, carbon black, or an inert fine powder such as silica. 4. The rubber reinforcing fiber according to claim 1, 2 or 3, wherein the third layer contains the same rubber as the matrix rubber, a vulcanizing agent, carbon black, or inert fine powder such as silica.