KR19980078894A - Rubber composition preventing physical property degradation by altered alkylphenol crosslinking resin - Google Patents

Abstract

The present invention relates to a rubber composition containing 0.1 to 1.0 phr of magnesium oxide relative to 100 phr of the raw rubber component in a conventional rubber composition containing an alkylphenol crosslinked resin modified with a quinone methide structure as a crosslinking agent.

Description

Rubber composition preventing physical property degradation by altered alkylphenol crosslinking resin

The present invention oxidizes when using modified alkylphenol crosslinked resin to improve the deterioration of processability caused by shortening the scorch generation time caused by the deterioration of the alkylphenol crosslinked resin added as a crosslinking agent in the manufacture of bladder rubber of a tire and to maintain stable rubber properties. By adding a certain amount of magnesium together, the rubber composition improves the process problem by increasing the scorch time and obtain a stable physical property to improve the bladder life.

At present, a bladder of a tire using butyl rubber having low unsaturation and excellent air permeability generally uses an alkylphenol crosslinking resin as a crosslinking agent for high temperature and heat stability. The general formula of the alkylphenol crosslinking resin is as follows. same.

(Wherein R is an alkyl group and R 'represents methylol (-CH ₂ OH) or hydrogen.)

As can be seen from the above formula, the alkylphenol crosslinked resin has a resin structure in which methylene or dimethyl ether is connected between alkylphenol molecules.

As is known, the alkylphenol crosslinking resin forms a strong carbon-carbon bond between the crosslinking agent and the rubber molecule, and since the carbon-carbon bond has a much higher atomic-to-atomic force than the carbon-sulfur bond or sulfur-sulfur bond, This excellent feature makes it an effective crosslinking method for bladders that must withstand high temperatures for a long time. The reaction site of the alkylphenol crosslinked resin chemically linked to the rubber molecule is methylol (-CH ₂ OH) linked to the phenol molecule and forms a strong binding force by the carbon-carbon bond between the carbon of the methylol and the carbon of the rubber molecule. Depending on the molecular structure of the alkylphenol crosslinked resin before blending, the reaction with rubber occurs by several different routes. In other words, if the end group of the alkylphenol crosslinked resin exists in methylol state before rubber blending, it becomes carbonium ion by Lewis acid added at the time of compounding, and carbon of methylol and isoprene double bond in butyl rubber. Single bonds form between them, resulting in long scorch times. In this case, there is no problem in the process.

However, alkylphenol crosslinked resins are easily deteriorated in nature, and usually, at about 30 ° C. for about 6 months, the molecular weight of the alkylphenol in the molecular structure of the alkylphenol is substantially changed to other forms. Here, alteration refers to a change in molecular structure, in which water is produced by hydroxyl groups of methylol and phenol in the molecule and gradually changes to a quinone methide structure. When the modified alkylphenol crosslinked resin reacts with the isoprene rubber molecule, it reacts by forming a carbon ring with two carbons forming a double bond of the isoprene rubber molecule. At this time, since the quinone methide structure shows a very fast reaction rate after rubber compounding, crosslinking reaction occurs rapidly in the process. That is, partial crosslinking occurs during processing, and scorch is generated to prevent processing. In addition, the crosslinking reaction with rubber occurring in the quinone methide structure has two carbons forming double bonds of rubber molecules, oxygen of phenol of alkylphenol crosslinking resin, and carbon of methylene, respectively. Modulus, Tensile strength is greatly increased and elongation is decreased, which causes big change in the original physical properties. In addition, the bladder manufactured by the modified crosslinked resin has a problem in that the service life of the tire is greatly reduced.

Therefore, when the modified alkylphenol crosslinked resin is used as a crosslinking agent, the present inventors add a certain amount of magnesium oxide together to lengthen the scorch time of the compounded rubber to maintain stable processability, and to suppress the increase in modulus and tensile strength after crosslinking and to increase elongation rate. The present invention was completed by finding that stable physical properties were obtained by increasing.

That is, the rubber composition of the present invention is characterized by containing 0.1 to 1.0 phr of magnesium oxide with respect to 100 phr of the raw rubber component in a conventional rubber composition containing an alkylphenol crosslinked resin modified with a quinone methide structure as a crosslinking agent. If the content of magnesium oxide is more than 1.0phr, the physical properties of the bladder rubber is greatly reduced, and if the content is less than 0.1phr, its effect is very insignificant. Magnesium oxide in the present invention serves to lower the reactivity of the alkylphenol resin modified by the quinone methide structure, which acts as an acid scavenger, so that its reaction rate is slowed (scorching time is increased). The reaction amount will be less.

Hereinafter, the present invention will be described in detail through examples.

EXAMPLE

To prepare a rubber specimen in accordance with the composition of Table 1 and then measured the physical properties thereof are shown in Table 2 below.

TABLE 1

Rubber ingredient list

[Table 2] Property test results

¹⁾ Number of bladder usage on industrial tires

As shown in Table 2 above, when magnesium oxide was added during crosslinking with the modified alkylphenol crosslinking resin, the scorch generation time could be increased by 37%, and the increase in modulus and tensile strength could be suppressed. By increasing the elongation rate, it was possible to maintain stable physical properties and improve the number of times the bladder was used.

Claims (1)

A rubber composition containing, as a crosslinking agent, an alkylphenol crosslinked resin modified with a quinone methide structure, the rubber composition comprising 0.1 to 1.0 phr of magnesium oxide with respect to 100 phr of the raw rubber component.