KR20000025203A - Rubber composition with improved high temperature curing property of natural rubber - Google Patents

Abstract

PURPOSE: A rubber composition is provided to improve the high temperature curing property of a common natural rubber composition and to reduce the time required for the curing, thereby to increase the productivity. CONSTITUTION: A rubber composition comprises 100 parts by weight of a natural rubber which contains a synthetic rubber; 30-60 parts by weight of carbon black with a nitrogen adsorption surface of 60-140 square meter per gram; 0.5-3.0 parts by weight of BCL-MX (1,3-bis(citraconidomethyl)benzene); 0.2-3.0 parts by weight of alkyl phenol disulfide (APD); and common additives. The synthetic rubber can be contained in the rubber composition to the amount of 30 parts by weight, and is selected from butadiene rubbers and styrene butadiene rubbers.

Description

Rubber composition with improved high temperature vulcanization properties of natural rubber

In general, natural rubber has more double bonds than synthetic rubber such as styrene butadiene rubber (SBR), so that polysulfide crosslinked structure formed at the beginning of vulcanization at high temperature is decomposed by heat to form additional crosslinks in unreacted double bonds, or Or to form zinc sulfide or form cyclic-monosulfides, cyclic-disulfites, conjugated double bonds, triple bonds in the main chain. Therefore, when vulcanized at 150 ° C. or higher, the physical property is remarkably decreased. The vulcanization conditions which can obtain optimum physical properties without deteriorating such physical properties are 138 to 150 ° C. for natural rubber compositions and 150 to 180 ° C. for synthetic rubber systems. If the vulcanization temperature is increased, the vulcanization speed is high, so that the vulcanization time can be shortened, which can contribute to productivity improvement.

Until now, a method of improving the vulcanization properties of natural rubber has a method of increasing the ratio of the accelerator and the vulcanizing sulfur to increase the formation of mono-sulfide crosslinks, but this has not been practically used because it is ineffective and expensive.

Accordingly, the present invention is to increase the external vulcanization temperature of the tire using the natural rubber-based rubber composition than the current 150 ℃, in order to shorten the vulcanization time in order to obtain a natural rubber composition without deterioration of physical properties even when vulcanized at a higher temperature than 150 ℃ 1,3-bis (citraconidomethyl) benzene (hereafter referred to as BCL-MX) and a crosslinking agent in natural rubber and alkylphenol disulfide (SULFUR DONOR) crosslinking agent ( When APD) is used together and vulcanized at a high temperature, it is possible to prevent the deterioration of physical properties, to allow vulcanization at a high temperature, and to shorten the vulcanization time to improve productivity.

The present invention relates to a rubber composition having improved high-temperature vulcanization properties of natural rubber, and more particularly to 30 to 60 parts by weight of carbon black, 1,3-bis (citraconidomethyl) benzene, based on 100 parts by weight of natural rubber. It relates to a rubber composition consisting of 0.5 to 3.0 parts by weight, alkyl phenol disulfide 0.2 to 3.0 parts by weight and conventional additives.

Hereinafter, the present invention will be described in detail.

The natural rubber may be made by mixing up to 30 parts by weight of synthetic rubber. Synthetic rubber may be selected from butadiene rubber and styrene butadiene rubber.

Carbon black used in the present invention has a nitrogen adsorption surface area of 60 to 140 m ² / g.

The 1,3-bis (citraconidomethyl) benzene (hereinafter referred to as BCL-MX) acts as a crosslinking aid, which, unlike sulfur, an inorganic crosslinking agent, forms an organic crosslinking agent and crosslinks with a polymer in a single molecule state. Even when vulcanized at high temperature, the crosslinking form does not change, and thus physical properties do not decrease.

In addition, the alkylphenol disulfide (hereinafter referred to as APD) is also a SULFUR DONOR crosslinking agent, and forms cross-links of mono-sulfide or di-sulfide upon crosslinking to prevent deterioration of physical properties with BCL-MX.

Conventional additives that may be used in the present invention include vulcanization accelerators, pressure-sensitive adhesives, vulcanizing agents, anti-aging agents and the like.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Examples 1-5

Following the composition ratio as shown in Table 1, natural rubber, carbon black, and additives were mixed and mixed for 4 minutes and 30 seconds with a 2.7 liter half-barrier mixer, and then the vulcanization accelerators TBBS, sulfur, BCL-MX and APD were added. The mixture was added and kneaded with an 8 "(inch) test kneading roller for 4 minutes to obtain a rubber composition, which was compressed and vulcanized at 150 ° C for 30 minutes and at 160 ° C for 30 minutes to prepare a rubber specimen.

Comparative Examples 1 and 2

By using the composition ratio shown in Table 1 below, except that the crosslinking agents 1,3-bis (citraconidomethyl) benzene and alkyl phenol disulfide were not added, a rubber composition was prepared by compression and vulcanization in the same manner as in the above example. Rubber specimens were prepared.

Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Natural rubber 100 100 100 100 100 100 100 Carbon black 55 55 55 55 55 55 55 Zinc oxide 3 3 3 3 3 3 3 Stearic acid 2 2 2 2 2 2 2 Labor 2 2 2 2 2 2 2 brimstone 1.5 1.5 1.5 1.0 1.0 1.5 1.5 ¹⁾ TBBS 1.4 1.4 1.4 1.4 1.4 1.4 2.5 ²⁾ BCL-MX 0.5 1.0 1.5 1.0 1.5 0.0 0.0 ³⁾ APD 0.0 0.0 0.0 0.5 1.0 0.0 0.0

1) TBBS: N-tert-butyl-2-benzothiazyl sulfenamide

2) BCL-MX: 1,3-bis (citraconidomethyl) benzene

3) APD: Alkyl Phenol Disulfide

Test Example

Rubber specimens of Examples 1 to 5 and Comparative Examples 1 and 2 were measured as follows, 100% modulus, breaking strength and crosslink density, and the results are shown in Table 2 below.

Breaking strength and 100% modulus

It was measured according to K678 M6782 "Tension Test Method for Vulcanized Rubber".

Crosslinking density

After precipitation for 96 hours in benzene 40 ℃ ℃ vacuum was dried for 72 hours at 50 ℃ was weighed to determine the swelling crosslink density by Flory-Lenner equation.

Vulcanization condition Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 A B A B A B A B A B A B A B 100% Modulus (Kg / cm ² ) 40 36 42 40 43 41 45 43 46 44 37 31 45 35 Breaking Strength (Kg / cm ² ) 302 278 299 302 297 306 300 304 298 298 264 305 305 289 Crosslinking density (E-5 mol / ml) 6.8 5.3 7.3 6.7 7.5 6.9 7.8 7.2 7.9 7.3 6.5 4.7 7.8 5.9

Vulcanization Condition A: 150 ℃ 30 minutes

Vulcanization condition B: 160 ℃ 30 minutes

As shown in Table 2, the natural rubber composition filled with a conventional carbon black is significantly lower in physical properties than the rubber composition vulcanized at 150 ℃ when vulcanized at a temperature higher than 150 ℃, for example 160 ℃ (1 and 2 in comparison).

This is because the natural rubber-based rubber composition decomposes the polysulfur (DI-SULFUR) bond or the disulfur (DI-SULFUR) bond in the structure of the sulfur crosslinked bond formed at the beginning of the vulcanization when vulcanized at a temperature higher than the normal vulcanization temperature. Is converted to a monosulfur bond and the other part is a cyclic monosulfide, cyclic disulfide, conjugated double bond and triple bond formed in the main chain, resulting in a drop in sulfur crosslink.

However, the vulcanized rubber composition to which BCL-MX is added can be seen that the decrease in physical properties gradually decreases when vulcanized at 160 ° C. as the blending amount of BCL-MX is added at 0.5 to 1.5 parts by weight (see Examples 1 to 3). . In addition, it can be seen that the replacement of sulfur with APD, a sulfur donor crosslinking agent, further reduces the deterioration of high temperature vulcanizability (see Examples 4 and 5).

That is, the compounding agent BCL-MX, unlike sulfur, an inorganic crosslinking agent, forms an organic crosslinking agent with a single molecule to form a crosslink with the polymer, and does not change its crosslinking form even when heated to a high temperature, thereby not deteriorating physical properties. In addition, APD, which is a sulfur donor crosslinking agent, forms crosslinks of monosulfide and disulfide during crosslinking, so that even when vulcanized at a high temperature, there is little change in crosslink density.

Rubber compositions added with 1,3-bis (citraconidomethyl) benzene and alkylphenol disulfide (APD) prepared according to the present invention are vulcanized to high temperatures because the deterioration of physical properties during high temperature vulcanization is reduced compared to conventional natural rubber compositions. As a result, the vulcanization time can be shortened and the productivity can be greatly improved.

Claims (2)

To 100 parts by weight of natural rubber containing up to 30 parts by weight of synthetic rubber, 30 to 60 parts by weight of carbon black having a nitrogen adsorption surface area of 60 to 140 m ² / g, BCL-MX 0.5 to 3.0 parts by weight, alkyl phenol disulfide 0.2 to Rubber composition consisting of 3.0 parts by weight and conventional additives. The rubber composition according to claim 1, wherein the synthetic rubber is selected from butadiene rubber and styrene butadiene rubber.