JPS61200138A - Rubber composition - Google Patents

Abstract

PURPOSE:To provide a rubber composition having excellent processability in unvulcanized state and giving a vulcanized product having high hardness, by compounding a liquid phenolic compound having double bond on a side chain. CONSTITUTION:100pts.(wt.) of natural rubber, diene rubber, diene copolymer rubber,or their blended rubber is compounded with 1-50pts. of a liquid phenolic compound having double bond on a side chain. A phenolic compound existing in cashew oil is most effective. Preferably, the composition is further compounded with <=30pts. of a novolac phenolic resin and <=8pts. of morpholine disulfide.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a high hardness rubber composition used for tire treads, bead fillers, etc.

(Prior art and its problems) In a rubber compound that has high hardness in the vulcanized rubber state, as the hardness and dynamic modulus of the vulcanized rubber increase, the hardness and tensile stress in the unvulcanized rubber state also increase. It tends to get bigger.

Figure 1 shows this situation, and shows that the hardness and dynamic modulus of vulcanized rubber are in a linear relationship with the hardness and tensile stress in the unvulcanized rubber state, and rubber compounds that have high hardness after vulcanization. It can be seen that the hardness and tensile stress in the unvulcanized rubber state of the products (for example, those in the range indicated by D) are also very high. For this reason, in rubber compounds that require high hardness,
There was a problem in that the processability in extrusion, bending, etc. at the stage of unvulcanized rubber was significantly reduced, making processing difficult.

(Objective of the Invention) An object of the present invention is to provide a rubber composition which has good processability in the unvulcanized rubber stage and which provides high hardness after vulcanization.

(Disclosure of the Invention) The rubber composition according to the present invention is a natural rubber, a diene rubber, a diene copolymer rubber, or a blend rubber obtained by blending 2N or more of these rubbers (hereinafter, these are collectively referred to as rubber). It is characterized in that 1 to 50 parts by weight of a liquid phenol having a double bond in the side chain is blended per 100 parts by weight.

By adding liquid phenols having double bonds in their side chains to rubber within a certain range, it is possible to improve processability in the unvulcanized state and achieve the desired high hardness after vulcanization. A rubber composition having the following characteristics is obtained. In this case, if the amount of liquid phenols having a double bond in the side chain is less than 1 part by weight per 100 parts by weight of rubber, the expected effect of reducing hardness in the uncured state cannot be obtained, and processing Sexuality also becomes bad. On the other hand, if the proportion of the phenols exceeds 50 parts by weight, the viscosity of the unvulcanized rubber decreases too much, impeding processability, which is undesirable. According to the results of the experiment, it was most effective to use the phenols contained in cashew oil as a main component as the liquid phenols having double bonds in their side chains.

In addition to these rubbers and phenols, good results can also be obtained by adding novolac type phenolic resin, which has conventionally been mainly used as a curing agent, in an amount of 30 parts by weight or less per 100 parts by weight of rubber. Obtained. Furthermore, as a vulcanizing agent, in addition to sulfur, morpholine disulfide was added to the rubber.
Similarly good results were obtained even when the amount was added in an amount of 8 parts by weight or less per 00 parts by weight.

(Examples and Comparative Examples) Below, the Examples and Comparative Examples of the present invention will be explained. Table 1 shows the properties of vulcanized rubber and unvulcanized rubber in various formulations. Although the amount of carbon black blended is smaller than that of Comparative Example 1, the hardness and dynamic elastic modulus of the vulcanized rubber are the same as those of Comparative Example 1. Also,
It can be seen that the hardness and tensile stress of unvulcanized rubber are low, and it has excellent workability.

Example 2 is an example in which a liquid phenol having a double bond in the side chain and a curing agent were used in place of the novolak type phenolic resin and curing agent that have been conventionally mainly used as a curing agent. The hardness and dynamic modulus of elasticity are almost the same as those of Comparative Example 2, and the processability of the unvulcanized rubber is that of Comparative Example 2.
It can be seen that it is significantly improved.

Example 3 shows an example in which the above-mentioned liquid phenols and 7-Pollack type phenol resin were used in combination, and Example 4 shows an example in which morpholine disulfide was used in combination with sulfur as a vulcanizing agent. Example 3.4 In both cases, the processability of the unvulcanized rubber is improved without impairing the physical properties of the vulcanized rubber, as in the case of Example 1.2.

(Effects of the Invention) As explained in H below, the rubber composition according to the present invention has excellent processability in the unvulcanized rubber state and is capable of obtaining a rubber composition with high hardness after vulcanization. It became. This rubber composition can be suitably used as a raw material for tire treads, bead fillers, and other rubber products that require high hardness.

[Brief explanation of drawings]

FIG. 1 is a graph showing the correlation between the physical properties of unvulcanized rubber and vulcanized rubber. (Margin below)

Claims (4)

[Claims] (1) 1 to 50 parts by weight of a liquid phenol having a double bond in the side chain is added to 100 parts by weight of natural rubber, diene rubber, diene copolymer rubber, or a blended rubber of two or more of these. A rubber composition comprising: (2) A rubber composition in which liquid phenols having double bonds in side chains are phenols contained as a main component in cashew oil. (3) Claims comprising 30 parts by weight or less of a novolac-type phenolic resin mixed with 100 parts by weight of natural rubber, diene rubber, diene copolymer rubber, or a blended rubber of two or more of these. The rubber composition according to item 1. (4) 8 parts by weight or less of morpholine disulfide is blended with 100 parts by weight of natural rubber, diene rubber, diene copolymer rubber, or a blended rubber of two or more of these. The rubber composition described in .