JPS6363671B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method of adhering carbon fibers and rubber compounds, and more specifically, a method of adhering carbon fibers and rubber compounds that has excellent fatigue resistance and adhesive properties of carbon fibers in rubber. Regarding. (Prior art) Because carbon fiber has excellent properties such as high modulus of elasticity, high strength, dimensional stability, and heat resistance, it is attracting attention as a reinforcing material for rubber products such as power transmission belts. It has not yet been put into practical use due to poor adhesion to rubber. Therefore, various measures to improve this adhesion have been proposed in the past, such as the
As disclosed in Japanese Patent Publication No. 57-46427 and Japanese Patent Publication No. 53-33998, carbon fibers are treated with water-soluble epoxy resin or hydrophobic epoxy resin, heat treated, and then bonded with resorcinol-formalin-rubber latex. A method of treating with liquid or rubber glue containing polyisocyanate has been proposed. (Problems to be Solved by the Invention) However, although the above-mentioned conventional methods improved the adhesion to rubber, they lacked the fatigue resistance or bending stability of the carbon fibers in the rubber. The present invention improves these points, and provides a method for adhering carbon fibers and rubber compounds that have excellent adhesive strength and also have the fatigue resistance of carbon fibers in rubber. The purpose is to provide the following. (Means for Solving the Invention) That is, the feature of the present invention is that carbon fibers are immersed in an epoxy urethane resin solution and heat treated, and then treated with a rubber glue containing an acrylate compound having an acryloyl group and an epoxy group. , there is a method of adhering carbon fibers and a rubber compound, which are obtained by closely vulcanizing this with unvulcanized rubber. The carbon fibers used in the present invention are PAN (polyacrylonitrile) type, pitch type, and rayon type, and their shapes are cord, woven, knitted, or nonwoven. Carbon fibers commonly available on the market today are sized with a surfactant solution containing an epoxy compound, and the carbon fibers used in the method of the present invention are preferably treated in this way. Rubber compounds used as adherends include ethylene-propylene rubber (EPR), ethylene-propylene terpolymer (EPT), chloroprene rubber (CR), styrene-butadiene rubber (SBR), and chlorosulfonated polyethylene ( CSM), nitrile rubber (NBR), hydrogenated
NBR, isoprene rubber (IR), etc. alone or a blend thereof can be peroxide vulcanized, and among these, a rubber compound using CSM and hydrogenated NBR is most preferred. The peroxides added to the above rubber compound include dicumyl peroxide, di-t-butyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,
These include cyclohexanone peroxide, toluoyl peroxide, benzoyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, and t-butyl hydroperoxide. In addition, the epoxy urethane resin used in the pretreatment liquid of the present invention is a liquid material that has multiple urethane bonds in the molecule and an epoxy group at the end of the molecule, and specifically has the following molecular structure. ing. This epoxyurethane resin does not contain isocyanate groups or blocked isocyanates and is stable at room temperature. However, at temperatures above about 150°C, the epoxy groups may ring open and react with various active groups, and on the other hand, the amino groups of the urethane in epoxy urethane resins may react with the epoxy groups of other epoxy urethane resins. It has the property of self-crosslinking. The pretreatment liquid is used in the form of a solution, suspension, or emulsion in which the above epoxy urethane resin is mixed with a solvent, etc., but at this time, the solid content concentration of the epoxy urethane resin is adjusted to be 1 to 20%. do. Furthermore, a catalyst such as a tertiary amine may be added to the pretreatment liquid in order to speed up the curing speed of the epoxy urethane resin. Carbon fibers are immersed in the pretreatment liquid prepared in this manner, dried at approximately 120 to 220℃, and then further heated at approximately 120 to 220℃.
Although the carbon fiber is heat-treated at ℃, if the carbon fiber is sized with a surfactant liquid containing an epoxy compound during the spinning process, it has relatively good compatibility with the pretreatment liquid containing an epoxy urethane resin. As a result, the epoxy urethane resin easily adheres to the surface of the carbon fiber, and the amount of the epoxy urethane resin attached to the carbon fiber is 1 to 10% by weight, and if it is less than 1% by weight, the adhesive strength is poor; If it exceeds this limit, a thick film of hardened epoxy urethane resin will be formed on the surface of the carbon fiber, resulting in a lack of fatigue resistance. In addition, the acrylate compound having an acryloyl group and an epoxy group used in the post-treatment of the present invention is
An alicyclic diepoxide partial acrylate compound consisting of the following structural formula, which is normally liquid at room temperature,
Cured by heating or amines. (Here, X is OH, COOH,

[Formula] _-CH2 -CH= _CH2 ,

[Formula] etc., and n=1 to 5. ) The post-treatment liquid is mainly used for EPR, EPT, CR, as well as the rubber compound used as the adherend.
SBR, CSM, NBR, hydrogenated NBR, IR, etc., including peroxide compounds, carbon black,
A rubber paste obtained by dissolving a rubber compound such as an anti-aging agent, a filler, etc. and the above acrylate compound in a solvent, or a rubber paste obtained by adding the above acrylate compound to SBR or CR rubber latex containing various compounds. The amount of the acrylate compound added is 10 to 100% by weight as a solid content concentration. The carbon fibers that have already been immersed in the pre-treatment liquid and heat-treated are immersed again in the post-treatment liquid prepared in this way, and then heat-treated at 180 to 240°C. In this case, the appropriate amount of solid adhesion of the post-treatment liquid on the carbon fibers is 2 to 15% by weight; if it is less than 2% by weight, the adhesion to the rubber is insufficient, while if it exceeds 15% by weight, the amount of solids attached to the carbon fibers is lacks flexibility. The surface of carbon fiber treated as above has
Two layers: epoxy urethane resin layer adhered and hardened by pre-treatment liquid and rubber glue layer adhered and hardened by post-treatment liquid.
A layer is formed, and first, the epoxy urethane resin is compatible with carbon fibers and adheres well, and since it contains elastic urethane, the treated fibers maintain their flexibility. Furthermore, in the rubber paste of the post-treatment liquid, there is a high possibility that the epoxy group contained in the acrylate compound reacts with the amino group of the urethane contained in the epoxy urethane resin of the first layer, so that it bonds well with the first layer. As a result, the adhesive-treated carbon fiber has good adhesion to the rubber adherend, and also forms a flexible coating layer, so it has good bending resistance and is suitable for power transmission. Applies to products used under dynamic conditions such as belts, conveyor belts, tires, etc. The present invention will be explained in more detail with reference to Examples below. Example 1 A carbon fiber cord (Torika T-300 manufactured by Toray Industries, Inc.) consisting of 1800D/1×4 was immersed and heat-treated in the pre-treatment liquid and heat treatment conditions shown in Table 1 below. Adhesion treatment was performed using the post-treatment liquid and heat treatment conditions shown in the table. The carbon fiber cord treated in this way is then spun onto an adhesive tape wrapped around a drum.
A cross-sulfonated polyethylene compound having a thickness of 0.5 mm shown in Table 3 was laminated thereon, and then the laminated sample was cut and vulcanized at 150°C for 30 minutes.
After vulcanization, the sample was cut to a width of 2.5 mm and tested at a tensile speed of 50 using a peel tester (Autograph manufactured by Shimadzu Corporation).
Peel adhesion was measured in mm/min. The results are shown in Table 4.

【table】

【table】

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[Table] Example 2 Each cord treated in Example 1 was spun onto the chlorosulfonated polyethylene rubber compound (1) of Table 3 having a thickness of 1.0 mm, which was separately wound on a drum.
A chlorosulfonated polyethylene rubber compound of the same thickness and composition was laminated thereon, and steam vulcanization was performed at 8 kg/cm ² for 40 minutes to produce a sample in which two cords were embedded in the vulcanizate. This sample was wrapped around a rotating bending bar positioned vertically, one end of the sample was fixed to a frame, a load of 2 kg was applied to the other end, and the rotating bending bar was reciprocated up and down 50,000 times for a bending test. Ivy. Thereafter, the strength of this sample was measured at a tensile speed of 50 mm. The results are shown in Table 5. The strength retention rate (%) shown in Table 5 is the value obtained by dividing the strength before the bending test by the strength after the bending test. Example 3 Cords treated by appropriately changing the weight ratio of the acrylate compound having an acryloyl group and an epoxy group to the chlorosulfonated polyethylene rubber in the post-treatment liquid (D) of Example 1 were treated with the rubber compound shown in Table 1.
Example 1 and Example 2 using (1) as the adherend rubber
The material was treated in the same manner as described above, and an adhesion test and a bending test were conducted. The results are shown in Table 6. Example 4 The pre-treatment liquid (A) of Example 1 was used, and the post-treatment liquid (D) was used.
A treatment solution was created using hydrogenated NBR shown in Table 7 instead of the chlorosulfonated polyethylene rubber.
The cords treated with these treatment solutions were used as samples in the same manner as in Example 1, using the hydrogenated NBR rubber compounds shown in Table 7 as adherends, and the samples were used as samples in Example 1.
An adhesion test and a bending test were conducted under the same conditions as in Example 2. As a result, the adhesive strength was 31.2Kg/mm.
Strong retention rate (%) was 89%.

【table】

[Table] Table 7 (Parts by weight) Hydrogenated NBR 100 Stearic acid 1 Carbon black 45 Process oil 10 ZnO 2 MgO 4 Diphenylamine derivative 3 Trimethylolpropane trimethacrylate
3 Dicumyl peroxide 4 (Effects of the invention) As described above, in the method of the present invention, the pre-treatment liquid and the post-treatment liquid adhere to the surface of the carbon fiber in a hardened state, and this pre-treatment liquid is used in the post-treatment. The rubber compound has the function of firmly adhering the liquid to the carbon fibers, and since the epoxy urethane resin of the pre-treatment liquid is flexible, it does not inhibit the flexibility of the carbon fibers, and the post-treatment liquid is the adherend. Because it is compatible with carbon fibers, the adhesive strength between the resulting rubber compound and carbon fibers is improved.
Furthermore, the strength retention rate after the bending test is good, and it has extremely good fatigue resistance. Therefore, the present invention can be fully applied to a method of adhering reinforcing bodies for dynamic products such as power transmission belts, conveyor belts, and tires.

Claims (1)

[Scope of Claims] 1 Carbon fibers are immersed in an epoxy urethane resin solution and heat-treated, then immersed in a rubber glue containing an acrylate compound having an acryloyl group and an epoxy group, and then heat-treated, and then used as an adherend. A method for adhering carbon fibers and a rubber compound, characterized by vulcanizing the rubber compound in close contact with an uncured rubber compound. 2. The method of bonding carbon fibers and a rubber compound according to claim 1, wherein the unvulcanized rubber compound as the adherend can be peroxide vulcanized.