JPH0550558A - Rubber-aramide cord composite - Google Patents

Abstract

PURPOSE:To obtain not only rubber having the high dynamic modulus of elasticity and suppressed in heat generation but also a rubber-aramide cord composite excellent in interlaminar bonding strength by coating an aramide fiber treated with an adhesive with a rubber composition wherein a specific epoxy resin is compounded with specific raw material rubber. CONSTITUTION:The compounding amount of a cresole novolac type epoxy resin in a rubber composition is 3-19 pts.wt. per 100 pts.wt. of raw material rubber. When the compounding amount is below 3 pts.wt., the enhancement degree of the dynamic modulus of elasticity is low. When the compounding amount exceeds 10 pts.wt., the dynamic modulus of elasticity is enhanced but loss tangent becomes large to exceed a tolerance limit and heat generation is not suppressed and the interlaminar bonding strength of a rubber-aramide cord composite is lowered. A methylene donor such as a melamine derivative, a methylene acceptor such as resolmine, sulfur as a vulcanizer, a vulcanization accelerator or a filler are appropriately compounded with a rubber composition.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rubber-aramid cord composite comprising an aramid cord and a rubber composition.

[0002]

2. Description of the Related Art Conventionally, a fiber having a rigid skeleton structure such as an aramid fiber is twisted into a cord and treated with an epoxy compound and then resorcin / formaldehyde resin / rubber latex. There is known a rubber-cord composite which is treated with an adhesive (RFL adhesive) and embedded in a rubber composition (for example, JP-A-63-203333).

When these rubber-cord composites are used in tires, belts, etc., they are repeatedly deformed to generate shear stress between the non-extensible cord and the extensible rubber. Below, fully satisfactory performance has been obtained with such rubber-cord composites.

However, in recent years, low fuel consumption of tires,
There has been a demand for weight reduction, and in particular, high performance has been demanded for rubber-aramid cord composites using aramid fibers. Therefore, as the rubber that covers the aramid cord, the rigidity of the belt is increased, the shear strain between the rubber and the cord is reduced, and the dynamic elastic modulus is large so that the heat generation level can be suppressed, and the adhesion with the aramid cord There is a demand for excellent rubber.

Conventionally, the amount of carbon black has been increased in order to increase the elastic modulus of rubber, but when this is done, the exothermic property is not increased and the rubber-aramid cord composite layer is formed. There was a problem because the inter-adhesion strength also decreased.

An object of the present invention is to provide a rubber having a high dynamic elastic modulus (high rigidity) and suppressed heat generation (loss tangent),
In addition, a rubber-aramid cord composite having excellent interlayer adhesion is provided to solve the above problems.

[0007]

In the rubber-aramid cord composite of the present invention, 3 to 10 parts by weight of a cresol novolac type epoxy resin is blended with 100 parts by weight of raw material rubber in an aramid fiber treated with an adhesive. It is characterized in that it is coated with a rubber composition.

In the present invention, as a method of treating the aramid fiber with an adhesive, a method of pretreating with an epoxy compound or an isocyanate compound and then treating with an RFL adhesive (Journal of Applied Po) is used.
Lymer Science, Vol. 22, pp. 801 to 812, 1987) and the like.

The raw rubber in the present invention means natural rubber or synthetic rubber such as polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer rubber, butyl rubber, halogenated butyl rubber, or a blended rubber thereof. Particularly, natural rubber alone or a blended rubber of natural rubber and synthetic rubber is preferable.

The cresol novolac type epoxy resin in the present invention is not particularly limited, but cresol novolac glycidyl ether is preferable, and for example, the one represented by the following structural formula [Chemical formula 1] is preferably used.

[0011]

[Chemical 1]

The compounding amount of the cresol novolac type epoxy resin in the rubber composition used in the present invention is 1
It is 3 to 10 parts by weight with respect to 00 parts by weight. Compounding amount is 3
When the amount is less than the weight part, the degree of improvement in the dynamic elastic modulus is small. If the blending amount exceeds 10 parts by weight, the dynamic elastic modulus is improved, but the loss tangent exceeds the allowable limit and becomes large.
This is not practical because the interlayer adhesion of the rubber-aramid cord composite is low with the increase in heat generation.

The rubber composition used in the present invention preferably contains an epoxy curing agent. The type of epoxy curing agent is not particularly limited, but for example, 2-undecylimidazole, 2-pentadecylimidazole, 2-
Ethyl-4-methylimidazole and the like are preferable. The compounding amount of the epoxy curing agent varies depending on the types of the cresol novolac type epoxy resin and the epoxy curing agent, but is usually 5 to 15% by weight of the cresol novolac type epoxy resin.

In the rubber composition used in the present invention, a methylene donor such as a melamine derivative, a methylene acceptor such as resorcin, sulfur as a vulcanizing agent, a vulcanization accelerator, a vulcanization accelerating aid, an antiaging agent. Agents or fillers are appropriately mixed.

The rubber-aramid cord composite of the present invention comprises:
It can be used as a tire for a vehicle that travels a long distance under a heavy load, a tire for a vehicle that runs at a high speed, a belt or a hose used under high temperature, and the like.

[0016]

The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to such examples.

Examples 1 to 3 and Comparative Examples 1 to 5 The aramid cords were pretreated with an IPD-38 compounding adhesive treatment liquid of du Pont and then treated with an IPD-39 compounding adhesive treatment liquid of du Pont. ..

The aramid cords treated with the adhesive as described above are arranged in parallel at a rate of 20 cords per 2.5 cm and coated on both sides with a rubber sheet having the composition (parts by weight) shown in [Table 1] below. Then, two of these were stacked and vulcanized at a temperature of 160 ° C. for 20 minutes to obtain a composite.

The adhesive strength of this composite and the physical properties of the vulcanized rubber of the rubber used for coating the aramid cord are shown in Table 1.

The evaluation method was carried out as follows.

(1) Adhesion between layers The above composite was cut into a width of 2.5 cm parallel to the cord to prepare a test piece, and the peeling force was determined according to JIS K6301.

(2) Interlayer adhesion after aging The test piece prepared in the same manner as in (1) was subjected to accelerated aging at a temperature of 90 ° C for 4 days, and then the peeling force was determined in the same manner as in (1).

(3) Dynamic elastic modulus and loss tangent (tan)
δ) After vulcanizing each rubber composition having the composition shown in Table 1 at 160 ° C. for 20 minutes, a sample having a length of 20 mm, a width of 5 mm, and a thickness of 1 mm was prepared, and using a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho, It was measured under the conditions of a frequency of 50 Hz, a dynamic strain of 2%, and 80 ° C.

[0024]

[Table 1]

As is apparent from the table, Example 1 of the present invention
In Nos. 3 to 3, the rubber had a large hardness and a high dynamic elastic modulus, and the loss tangent increased, but it was within the allowable limit (0.2 or less). Also, the interlayer adhesion between the aramid cord and the rubber was excellent. On the other hand, in Comparative Examples 1 to 3, the epoxy resin was not compounded or the compounding amount was small, so that the hardness and dynamic elastic modulus of the rubber were inferior. Comparative Example 4
In Example 1, since the amount of the epoxy resin compounded was too large, the loss tangent exceeded the permissible limit and increased, and the interlayer adhesive strength was poor. In Comparative Example 5, the hardness and the dynamic elastic modulus were improved because the compounding amount of carbon black was increased without compounding the epoxy resin in the rubber composition, but the loss tangent exceeded the allowable limit, and the layer The adhesive strength between them was also poor.

Observation of the state of the fractured surface after the interlayer adhesion test (including the aged interlayer adhesion test) revealed that only Comparative Example 5 failed at the interface between the coated rubber and the coated rubber. In Comparative Examples 1 to 3 and Comparative Examples 1 to 4, the coated rubber was cohesively broken. That is, the state of adhesion was clearly inferior to Comparative Example 5.

[0027]

As described above, the rubber-aramid cord composite of the present invention has a high dynamic elastic modulus (and therefore a high rigidity) while maintaining the interlayer adhesive force, and has an exothermic property (loss tangent).
It is extremely useful in many fields because it suppresses

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Claims (1)

[Claims] 1. A rubber composition characterized by coating an adhesive-treated aramid fiber with a rubber composition comprising 100 parts by weight of raw material rubber and 3 to 10 parts by weight of a cresol novolac type epoxy resin. Aramid code complex.