KR0173374B1 - Rubber composition for vulcanizing bladder of tire having high thermal conductivity - Google Patents

Abstract

The present invention relates to 2 to 10 phr of reactive resin, 0.2 to 2.0 phr of sulfur, 5 to 30 phr of copper and copper alloy, and 1.0 to 2.5 phr of vulcanization accelerator and conventional vulcanization bladder for 100 phr of halogenated polyisobutylene-para methylstyrene copolymer rubber. It relates to a rubber composition for vulcanizing bladder of a tire, characterized in that the zero.

The rubber composition for the vulcanizing bladder of a tire prepared by using a mixture of copper and / or copper alloy and carbon black as a filler according to the present invention improves productivity by greatly improving the thermal conductivity of the vulcanizing bladder to shorten the tire vulcanization time, It is possible to improve the physical properties and quality of the tire by reducing the difference in vulcanization for each part of the tire.

Description

Rubber composition for vulcanizing bladder of tire having high thermal conductivity

1 is a schematic diagram showing chemical bonds (Cu-S-Rb; S sulfur atom, Rb rubber chain) of copper, copper alloy and rubber in the rubber composition,

2 is a graph showing the quantitative relationship and the adhesive force relationship of sulfides depending on the copper content of the copper alloy.

The present invention relates to a rubber composition for vulcanizing bladder of a tire having high thermal conductivity, and more particularly, to a rubber composition for vulcanizing bladder of a tire having improved thermal conductivity using copper and / or a copper alloy as a filler.

Conventionally, a thermal conductive black or the like was used as a filler for the purpose of improving the thermal conductivity of a tire vulcanization bladder, and as the amount of the filler is increased, the thermal conductivity increases almost linearly, but at an appropriate level, high heat generation characteristics in a dynamic state This deepens the heat accumulation inside the bladder and causes physical property deterioration, which eventually leads to destruction. Therefore, since the amount of the thermally conductive black is limited, the increase in thermal conductivity is also limited.

In order to overcome the limitations of thermal conductivity, when the metal powder or the like is used as a filler, the effect of increasing the thermal conductivity is very great. These physical bonds were unbearable and easily broken in vulcanizing bladders that would be under harsh conditions subjected to repeated fatigue deformation under 25 kgf). In addition, due to the different thermal expansion coefficients (butyl rubber; 57 × 10 ⁻⁵ / ° C., metal powder; 5 to 6 × 10 ⁻⁵ / ° C.) between the rubber and the metal powder, the thermal expansion of the rubber chains on the surface of the metal powder is very large and the interface is large. The spaces are separated from each other to form a space, which becomes a crack initiation point under severe conditions, and the cracks continuously grow and lead to destruction, resulting in problems such as a decrease in the life of the bladder and an increase in tire defects. The use of metal powders in rubber compositions for bladder was considered almost impossible.

On the contrary, carbon black is the most widely used to reinforce the rubber composition and to increase the physical properties of the rubber composition because the carbon black particles can form a three-dimensional network with each other with a unique structure having strong physical and chemical bonds with the rubber chain. Being a filler.

Therefore, as a filler for improving the thermal conductivity of the rubber composition for vulcanizing bladder of a tire, a material having high thermal conductivity and a property such as carbon black is required.

In the past, sulfur was used as a crosslinking agent for rubber compositions for vulcanizing bladder in tires. However, in general, when sulfur is used as a crosslinking agent, sulfide bonds have good physical properties but have very poor heat resistance. Sulfur is rarely used as a crosslinking agent of the rubber composition for vulcanizing bladder because problems such as poor vulcanization bladder life and poor tires occur due to failure.

In order to make up for the above disadvantages, a reactive resin capable of crosslinking with excellent hysteresis has been developed, and has been used as a vulcanizing agent for almost all vulcanizing bladder rubber compositions.

However, the reactive resin does not have any reactivity with the metal powders, so that the use of the metal powder in the rubber composition for the vulcanizing bladder has not been attempted to date.

The present inventors use a copper and copper alloy powder having excellent thermal conductivity as a filler in the rubber composition for vulcanizing bladder of a tire to induce a sulfidation reaction between copper and sulfur in the composition to form a Cu-S-Rb layer directly with rubber at the interface. The present invention has been found to significantly increase the thermal conductivity while preserving the physical properties of the vulcanized bladder rubber composition.

Hereinafter, the present invention will be described in detail.

The present invention relates to 2 to 10 phr of reactive resin, 0.2 to 2.0 phr of sulfur, 5 to 30 phr of copper and copper alloy, 1.0 to 2.5 phr of vulcanization accelerator and conventional vulcanization bladder for 100 phr of halogenated polyisobutylene-para methylstyrene copolymer rubber. It is a rubber composition for vulcanizing bladder of a tire characterized by consisting of a compounding agent.

Hereinafter, the present invention will be described in more detail.

As the rubber base material of the rubber composition for vulcanizing bladder of a tire having high thermal conductivity according to the present invention, a halogenated polyisobutylene-para methylstyrene copolymer rubber developed for the purpose of increasing heat resistance may be used. Isobutylene-paramethylstyrene copolymer rubber can be used.

When the above-mentioned halogenated polyisobutylene-para methylstyrene copolymer rubber is used as a vulcanization bladder rubber for tires and only reactive resin as a crosslinking agent, the crosslinked rubber structure is formed due to the aromatic ring present in the copolymer rubber side chain. It becomes very hard and greatly improves heat resistance, but fatigue property tends to be disadvantageous. In the present invention, in order to improve this point, sulfur is added to provide a flexible sulfide bond (Rb-S-Rb) in the rubber composition.

In addition, when the copolymer rubber is used as a rubber for the vulcanizing bladder of the tire, it is possible to simultaneously form some sulfur crosslinks together with the crosslinking with the reactive resin, and when the copper and the copper alloy powder are added, the copper reacts with the sulfur as described above. And by connecting the rubber chains with chemical bonds on the surface of the copper alloy particles to maintain the physical properties of the rubber composition for vulcanizing bladder to significantly improve the thermal conductivity.

The reactive resin used in the present invention is preferably an alkyl phenol aldehyde resin.

As is known in tire technology, copper alloy coated steel cords used as tire reinforcements form chemical bonds with rubber chains. That is, a sulfidation reaction between the copper element and sulfur on the surface of the copper alloy coated steel cord results in the formation of a Cu-S-Rb layer, which is a sulfide bond, on the surface of the copper alloy, which depends on the copper content present in the copper alloy. It is known.

In all vulcanization systems where sulfur or sulfur-promoting agent is partially used as a crosslinking agent of the rubber composition for crosslinking bladder, when copper and copper alloy powders are used, sulfidation reaction between sulfur-copper occurs according to the following reaction path and thus the surface of copper and copper alloy particles The chemical bond between and the rubber chains increases the adhesion between the rubber and the metal particles very much.

Adhesion occurs due to the intimate bonding of Cu-S-Rb (S; sulfur atom, Rb; rubber chain), which is an organometallic substance formed by the vulcanization reaction, and Cu-S through the formation of Cu _2- xS as described above. The first step of the reaction as -Rb bonds is the formation of a Cu _2- xS layer, which grows through cation diffusion. Here, the step of controlling the reaction rate is the diffusion step of Cu + in the sulfide layer, the positive hole (hole) is formed due to the lack of electrons in the Cu ₂ S lattice through which the donor in the form of Cu _2- xS-S-Rb Receptor binding occurs. That is, the sulfidation reaction (Cu _2- xS generation) and vulcanization (Sy-Rb radical generation) reaction occurs at the same time to generate the adhesive force by the chemical bond between them.

1 shows chemical bonds (Cu-S-Rb; S sulfur atoms, Rb rubber chains) of rubber with copper and copper alloys that can be formed in the rubber composition.

As shown in FIG. 2, in the quantitative relationship of the sulfide depending on the average amount of copper in the copper alloy layer and the adhesion formation relationship, when the copper element in the copper alloy is 50% or more, the adhesion force increases sharply, and when the 70% is about It is the maximum.

The properties of the fillers affecting the physical properties of the rubber composition for vulcanizing bladder include many factors such as particle size, distribution, particle shape, specific gravity, volume, specific heat, thermal conductivity, surface active group, acidity, solubility, and elongation. Have. When the copper and copper alloy powder is selected, it may be appropriately selected and used in consideration of the physical properties and thermal conductivity of the rubber composition.

Since the thermal conductivity of the rubber composition for the vulcanization bladder determines the tire vulcanization time and vulcanization degree, if the thermal conductivity is improved, the tire vulcanization productivity can be improved, and the difference in vulcanization degree between the tire parts can be improved, thereby improving the quality of the product.

Generally, it is known that the thermal conductivity of about 90% or more is improved when the carbon black is added to the pure rubber by volume 2.0, and the thermal conductivity is improved by about 30% when the same amount of carbon black is replaced by the high thermal conductivity black. When 1/2 copper and copper alloy + 1/2 ISAF carbon black are used, the thermal conductivity of the rubber composition for vulcanizing bladder is improved by 40% or more, similarly 1/4 copper and copper alloy with volume% 2.0 + 3/4 The use of ISAF carbon black as a filler improves about 60% or more.

In case of using fine thin plate or fibrous copper and / or copper alloy, the thermal conductivity is improved by about 15% compared with the use of spherical powder. Especially, the smaller the particle size (≤10㎛), the better the physical properties of the vulcanizing bladder composition. do.

The rubber composition for the vulcanizing bladder of a tire prepared by using a mixture of copper and / or copper alloy and carbon black as a filler according to the present invention improves productivity by greatly improving the thermal conductivity of the vulcanizing bladder to shorten the tire vulcanization time, It is possible to improve the physical properties and quality of the tire by reducing the difference in vulcanization for each part of the tire.

Hereinafter, the present invention will be described in detail by way of examples.

Example 1

For 100 phr of synthetic rubber (EXXPRO, manufactured by EXXON Chemicals), zinc oxide 3.0 phr, stearic acid 0.5 phr, carbon black 55.0 phr, copper powder 5.0 phr, castor oil 6.0 phr, reactive resin (SP 1045) 10.0 phr, insoluble sulfur 0.75 phr And 1.40 phr of MBTS (dibenzothiazyl disulfide) were mixed to prepare a rubber composition for a vulcanization bladder of a tire.

Physical properties of the obtained rubber composition were measured, and the results are shown in Table 1.

Example 2

For 100 phr of synthetic rubber (EXXPRO, manufactured by EXXON Chemicals), zinc oxide 3.0 phr, stearic acid 0.5 phr, carbon black 55.0 phr, copper powder 30.0 phr, castor oil 6.0 phr, reactive resin (SP 1045) 10.0 phr, insoluble sulfur 1.15 phr And 2.15 phr of MBTS were mixed to prepare a rubber composition for a vulcanization bladder of a tire.

Physical properties of the obtained rubber composition were measured, and the results are shown in Table 1.

Comparative Example 1

A rubber composition for a vulcanizing bladder of a tire was prepared in the same manner as in Example 1 except that no copper powder was added.

Physical properties were measured about the obtained rubber composition, and the result is shown in Table 1.

Claims (4)

Consisting of 2 to 10 phr of reactive resin, 0.2 to 2.0 phr of sulfur, 5 to 30 phr of vulcanization accelerator and 1.0 to 2.5 phr of vulcanization accelerator and conventional compounding agent for vulcanizing bladder to 100 phr of halogenated polyisobutylene-para methylstyrene copolymer rubber A rubber composition for a vulcanizing bladder of a tire. The rubber composition for a vulcanizing bladder of claim 1, wherein the reactive resin is an alkyl phenol aldehyde resin. The rubber composition for a vulcanizing bladder of claim 1, wherein a sulfur accelerator is used in place of the sulfur. The rubber composition for a vulcanizing bladder of claim 1, wherein the copper alloy contains 50% or more of copper.