JPH0328243A - Hard rubber composition - Google Patents

Abstract

PURPOSE:To obtain a hard rubber composition improved in flex crack resistance, prevention of heat build-up and hardness by mixing a diene rubber with specified fibrils of a polyamide pulp, a thermosetting resin and a curing agent. CONSTITUTION:100 pts.wt. diene rubber (e.g. cis-1,4-polyisoprene rubber) is mixed with 1-30 pts.wt. fibrils of an aromatic polyamide pulp having a diameter of 0.1-1mum and a length of 3-1000mum, 2-40 pts.wt. thermosetting resin selected from among a phenolic resin, a cresol resin and a modified resin thereof and 1-20 pts.wt. curing agent which can donate methylene groups when used in vulcanization under usual vulcanization conditions (e.g. hexamethylenetetramine).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides hard rubber &llrIi. It relates to hard rubber & II soles suitable for products, especially bead apex or clincheapex, and more specifically, it is made by blending vulcanizable diene rubber with aromatic boria pulp, thermosetting resin, and curing agent. This invention relates to a hard rubber composition. -a In the radial tire, the cords of Kerr force splies are arranged in parallel to each other at almost right angles to the tire equatorial plane, and both ends are folded back around the bead wire, and the cords are surrounded by the folded ends of the braai and the carcass. A bead apex extending in the direction of the sidewall is disposed on the inside, and a clinch apex is disposed on the outside of the turn of the ply in a region adjacent to the rim flange.

Tires with a radial structure like this have a difference in rigidity at the folded end of the ply, which is prone to damage, and because it is a radial structure, it inherently has poor lateral rigidity. Therefore, it has been proposed that the bead apex or clincheapex has particularly high hardness (or dynamic elastic modulus). (Unexamined Japanese Patent Publication No. 53-4059). Therefore, as a method of controlling vulcanized rubber with high hardness or complex modulus, it is possible to increase the blending amount of thermosetting resin or carbon, or to increase the crosslinking density by using large amounts of sulfur or vulcanization accelerator. It is being said. However, the former has a high heat generation property when the rubber is kneaded in a banbari kisser, which may cause the rubber to scorch, and the composition itself has a high viscosity, causing an excessive load during kneading and extrusion. Furthermore, in the latter case, when processing the kumikaimono, sulfur blooms and impairs the adhesiveness of the rubber, as well as deteriorating the physical properties of the vulcanized rubber. The present invention aims to solve these problems, and proposes a rubber assembly or article that has extremely high hardness without problems such as workability.

In the present invention, 100 parts by weight of at least one type of diene rubber and aromatic polyamide pulp having a diameter of 0.00 parts by weight are added. A hard rubber assembly for bead apex characterized by blending 1 to 30 parts by weight of fibrils having a diameter of 1 to 1μ and a length of 3 to 1000μ, 2 to 40 parts by weight of a thermosetting resin, and 1 to 20 parts by weight of a curing agent. It is a precept.

The aromatic polyamide valve used in the present invention can be manufactured from aromatic polyamide fibers, or can be manufactured at the stage of synthesizing aromatic polyamide polymer, but this pulp has a diameter of 0.1 to 1μ and a length of 3 to It has fibrils of 1000μ. This aromatic boria ξ depulp has fine fractionation technology, so by kneading it into rubber, it can be mixed with rubber at the molecular level, achieving more effective reinforcement than when mixing fiber cords or short fibers. can. If the diameter is less than 0.1 μm or the length is less than 3 μm, it will be difficult to blend into rubber, and it will not be possible to secure the necessary rigidity when used in bead apex. In addition, if the diameter exceeds 1 μ and the length is 1000
If it exceeds μ, poor dispersion in the rubber will occur.

The aromatic polyamide valve must be blended in an amount of 1 to 30 parts by weight, preferably 5 to 20 parts by weight; if it is less than 1 part by weight, the reinforcing effect will not be sufficient and workability will deteriorate.

Next, the present invention requires blending a thermosetting resin and a curing agent. Here, thermosetting resins are phenolic resins, cresol resins, or modified resins thereof, such as cashew varnish modified resins, oil-modified resins modified with oils such as linoleic acid, linolenic acid, and oleic acid, and modified with alkylbenzenes such as xylene. alkylbenzene-modified phenols, epoxy-modified resins, aniline-modified resins,
Resins that harden by heat, such as melatan-modified resins, can be used alone or in combination of two or more in any ratio.
This thermosetting resin contains 2 to 100 parts by weight of rubber compound.
It is blended in an amount of 40 parts by weight, preferably 10 to 20 parts by weight.

If it is less than 2 parts by weight, the reinforcing effect will not be sufficient;
If the amount exceeds 1 part by weight, the kneading workability will be significantly impaired. Next, the curing agent used in the present invention is one that cures the thermosetting resin, and is a compound that provides methylene groups when vulcanized at 40 to 200'C, especially under normal vulcanization conditions. It is a so-called methylene donor. For example, hexamethylenetetramine, polyvalent methylolmelamine derivatives, oxazolidine, bis(l13oxazolidine), bis(1,3
oxazolidine) derivatives, etc. The amount of this curing agent needs to be adjusted depending on the amount of thermosetting resin, but it is blended in an amount of 0.5 to 7 parts by weight per 100 parts by weight of the rubber component. Note that by using a thermosetting resin and a curing agent together with the aromatic polyamide bulp, the hardness and complex modulus of the vulcanized rubber can be further increased.

The diene rubber used in the present invention may be natural rubber, cis-1,4-polyisobrene rubber, cis-1,4-polyptadiene rubber, styrene-butadiene copolymer rubber, etc., and may be used alone or in a blend of two or more. can. Furthermore, the composition of the present invention may contain commonly used additives such as carbon,
It goes without saying that fillers such as silica, softeners, anti-aging agents, vulcanization accelerators, plasticizers, etc. can be added as appropriate.

However, by vulcanizing the rubber composition according to the present invention by a conventional method, properties such as flex crack resistance, low heat build-up, and high hardness are maintained, while properties such as kneading workability and extrusion workability are further improved. This makes it possible. Example 1 Various rubber formulations for bead apex shown in Table 1 were vulcanized at 150'C for 30 minutes, and their modulus, hardness, complex modulus, etc. were measured, and the results are shown in Table 2. It is recognized that the performance is improved by the combined use of aromatic boria pulp and phenolic resin.

Claims (4)

[Claims] (1) 100 parts by weight of at least one type of diene rubber and aromatic polyamide pulp with a diameter of 0.1 to 1μ and a length of 3 to
A hard rubber composition for bead apex, characterized in that it contains 1 to 30 parts by weight of 1000μ fibrils, 2 to 40 parts by weight of a thermosetting resin, and 1 to 20 parts by weight of a curing agent. (2) The hard rubber composition for bead apex according to claim 1, wherein the thermosetting resin is a phenol resin, a cresol resin, or a modified resin thereof. (3) The hard rubber composition according to claim 1, wherein the curing agent is an oxazolidine derivative. (4) The hard rubber composition according to claim 1, wherein the curing agent is hexamethylenetetramine.