JPS614742A - Silica-compounded rubber composition - Google Patents

Abstract

PURPOSE:A rubber composition having excellent workability and processability, obtained by incorporating a silicate filler and a silane coupling agent into a rubber. CONSTITUTION:A silica-compounded rubber composition prepared by incorporating 1-100pts.wt. silicate filler which has a mean primary particle diameter measured with an electron microscope of 30mmu or smaller and a specific surface area measured by BET method of 130m<2>/g or greater and contains at least 80% SiO2, and 0.1-20pts.wt. coupling agent of formula I (where R<1> and R<2> each are a 1-4C alkyl, a 5-8C cycloalkyl or phenyl; R<3> is a 1-8C bivalent straight- chain, branched or cyclic hydrocarbon group; m is 1, 2 or 3; n is 2-6; X is a group of formula II or III; R<4> and R<5> each are a 1-4C straight-chain or branched hydrocarbon group or phenyl) (e.g. a compound of formula IV or V) into 100pts.wt. natural rubber and/or diene rubber. This composition has excellent workability and processability and can be used widely as various tire members, especially a tread rubber and a side-tread rubber, and as various industrial goods such as a hose, a belt, and a rubber vibration isolator.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a work in which a silicate filler and a silane coupling agent are blended with at least one rubber selected from the group consisting of natural rubber and diene synthetic rubber. The present invention relates to a rubber composition with excellent properties and processability.

(Prior Art) Conventionally, methods of replacing part or all of carbon black with silica to improve the reinforcing properties of rubber compositions containing carbon black, and methods of using silane coupling agents to improve this have been studied. For example, the Tokuko Sho 5
No. 0-29741 describes the use of a silica coupling agent as a reinforcing agent. However, even this silica coupling agent-based reinforcing agent is insufficient to achieve high levels of fracture characteristics, workability, and processability of rubber compositions. Moreover, a rubber composition using a silica-silane coupling agent as a reinforcing agent is described in Japanese Patent Publication No. 51-20208 and the like. Such silica-silane coupling agent-based reinforcement can significantly improve the reinforcing properties of the compounded rubber and improve the fracture properties, but the fluidity of the compounded rubber when unvulcanized is significantly poor, and the workability and It has the disadvantage of decreasing workability.

(Object of the Invention) The object of the present invention is to eliminate the above-mentioned drawbacks of a silica-silane coupling agent-based reinforcing rubber composition, to have fracture properties superior to carbon blank reinforcement, and at the same time, to have improved workability and processability. An object of the present invention is to provide a rubber composition.

(Problems to be Solved by the Invention) The present inventors have conducted extensive research into the causes of deterioration in workability and processability of rubber compositions when a silica-silane coupling agent is used as a reinforcing agent, and have found that, for example, Said Tokuko Sho 5
1-20208, a silane coupling agent (
Z -Alk -Sn -A4k -Z, where 2 is a silane group, Alk is an alkylene group, and n is 2 to 6). Sulfur promoters, such as dibenzothiazyl sulfide (DI), diphenylguanidine (DPG),
The silane coupling agent is consumed by the bonding between polymers and polymers through a complementary reaction with N-oxydiethylenebenzothiazylsulfenamide (NOBS), N-cyclohexylbenzothiazylsulfenamide (CZ), etc. In addition, the reaction between the surface of the silica compounded in the rubber and the end group of the silane coupling agent is inhibited, the reinforcing properties of the filler are reduced, and the surface of the silica itself has the potential to easily form physical bonds with the polymer. It was found that, in combination with this, the unvulcanized viscosity of the compounded rubber (Mooney viscosity increases), workability, and processability decrease.

(Means for solving the problem) Next, based on the above knowledge, research was conducted on a method for preventing the above-mentioned mutual reaction. When using silane coupling in which the reactive group of the accelerator, thiazole group or thiocarbamyl group is simultaneously included in one molecule, only the bond between the silane coupling agent and the silica takes place during crosstalk, and the bond between the polymers The present invention was achieved by confirming that the reaction was carried out in the vulcanization process and that a rubber composition with improved workability and processability while maintaining a high level of reinforcing properties could be obtained.

Therefore, in the present invention, the average basic particle diameter measured with an electron microscope is 30 mμ for 100 parts by weight of at least one rubber selected from the group consisting of natural rubber and diene-based synthetic rubber.
Below, specific surface area M (more than O" Schiff, measured by BET method,
Silica CSin, ) 1 to 100 parts by weight of a silicate filler (fine powder activated precipitated silicic acid, hereinafter referred to as silica) having a content of 80 or more and the following general formula (in the formula, R1; carbon number 1 to 4 alkyl group cycloalkyl group or phenyl group having 5 to 8 carbon atoms R''i Alkyl group having 1 to 4 carbon atoms cycloalkyl group having 5 to 8 carbon atoms or phenyl group R8; divalent group having 1 to 8 carbon atoms Straight chain or branched chain optionally cyclic hydrocarbon group nil, 2 or 8 ni 2 to 6 values where R4 and R5 are straight chain or branched hydrocarbon group having 1 to 4 carbon atoms or phenyl group 0.1 to 20
This relates to a rubber composition containing silica in a proportion by weight of silica.

Here, the BET method refers to the Brunauer-Emmett-Teller (Brunauer-Emmett-Teller) method.
) method, the measurement method of which is specified in ASTM D-3087-81.

The silica used in the present invention has a BET adsorption specific surface area of I
F30'm2/; 2 or more, and the average basic particle diameter measured by an electron microscope is 30 mμ or less, because by specifying it in this way, the breaking strength of the rubber composition can be maintained at a high level. Furthermore, in order to increase the bond between the OH groups on the silica surface and the coupling agent polymer and thereby maintain high breaking strength, the silica content must be 80% or more.

If the blending amount of silica is less than 1 part by weight per 100 parts by weight of rubber, it will not be effective; if it exceeds 100 parts by weight, the viscosity of the unvulcanized state will increase, and the processability and workability of the rubber composition will deteriorate. The amount is set at 1 to 100 parts by weight.

In the present invention, as the rubber component, one or more of natural rubber and diene-based synthetic rubber are used, but diene-based rubber is understood in a broad sense; For example, styrene butadiene rubber (SBR)
, polybutadiene rubber (BR), polyisoprene rubber (
It includes not only IR), acrylonitrile) IJ/l/-butadiene rubber, but also ethylene propylene rubber (EPDM) and halogenated butyl rubber.

Next, the silane coupling agent as a binder that is blended with silica is shown by the general formula above, and has a completely different structure from that used in conventional silica-silane coupling agent systems, and has a terminal One molecule has a group R10 that reacts with silica and a residue X of a vulcanization accelerator on the other end, and during kneading, the group R10 bonds to the silica surface, and during vulcanization, the group X is vulcanized. It functions as a promoter and has the effect of bonding between polymers by sulfur in the molecule, and includes, for example, the following compounds.

If the above-mentioned binder is added in an amount exceeding 20 parts by weight per 100 parts by weight of the rubber content, the breaking strength of the rubber after vulcanization decreases, and 0.
If it is less than 1 part by weight, the added effect cannot be obtained, so if it is added 0.
The amount is 1 to 20 parts by weight.

To the rubber composition of the present invention, 0.1 to 5.0 parts by weight of a stiffening accelerator is usually added to 100 parts by weight of rubber, but 5.
．． If it is more than 0 part by weight, the modulus of the vulcanized rubber becomes too high, causing rubber burning, and if it is less than 0.1 part by weight, no effect can be obtained. Further, sulfur does not necessarily need to be blended, but it can be blended in an amount of 4 parts or less while maintaining a balance with the vulcanization accelerator to adjust rubber crosslinking.

Other commonly used compounding agents, such as pouches oil, anti-aging agents, antioxidants, etc., may be appropriately added to the rubber composition of the present invention.

The rubber composition of the present invention having the above structure has significantly improved reinforcement/strengthening properties, improved fracture properties, and excellent workability and processability, so it can be used for various tire components, especially tread rubber and side tread rubber. It can also be widely used as various industrial products such as hoses, belts, vibration-proof rubber, vibration-damping materials, etc.

(Example of the invention) Next, the present invention will be explained with reference to Examples and Comparative Examples.

Twenty-one types of rubber compositions were made with the formulations (parts by weight) shown in Table 1. In addition, the following silica species were used in the table.

The compositions in Table 1 also contain the following silane coupling agents as shown in Tables 2 and 8: 1. H8-OH, .CH8.OH, .Si.(OCH
3) 8 Manufactured by Nippon Nijika Co., Ltd., product name A-189 n, s, mo (3H2・OH,・OH2・Si・(00
2H, ), ), Degussa product name SI 69 (If there is one sulfur atom, the vulcanization rate will be significantly delayed,
It is difficult to exhibit sufficient physical properties under normal vulcanization conditions.

) were blended in an amount of 6.0 parts by weight as shown in Table 2 for rubber compositions A1 to A14, and 12 parts by weight as shown in Table 8 for rubber compositions A1 to A21. Tables 2 and 8 show the results of measuring the breaking strength and Mooney viscosity of the rubber composition thus obtained and the rubber composition containing no silane coupling.

Here, the breaking strength is a value measured according to JIS K6801, and the Mooney viscosity is a value measured according to JIS K6800.

(Effects of the Invention) The rubber composition of the present invention has a structure in which a specific silica and a silane coupling agent represented by the above general formula are blended as a binder. The material used to bond the filler and the polymer is used between the polymers, reducing the reinforcing effect of the filler and improving workability and processability.

In contrast, in the silane coupling agent used in the present invention, a reactive moiety with silica as a binder and a reactive group, which is a residue of a vulcanization accelerator, are present in one molecule to stabilize the silane coupling agent. As shown in Tables 2 and 8, the silane coupling agent used in the present invention is liquid at room temperature. Since it has a softening effect similar to aroma oil, spindle oil, etc., it avoids the essential problem of physical bonding of the surface of silica itself with the polymer, and has the effect of significantly improving workability and processability. is obtained.

Patent applicant: Brideston Co., Ltd. Same applicant: Shin-Etsu Chemical Co., Ltd.

Claims (1)

[Scope of Claims] 1. Based on 100 parts by weight of at least one rubber selected from the group consisting of natural rubber and diene-based synthetic rubber, the average basic particle diameter measured with an electron microscope is 30 mμ or less, and BE
1 to 100 parts by weight of a silicate filler with a specific surface area of 130 m^2/g or more measured by the T method and a silica (SiO_2) content of 80% or more, and the following general formula ▲ Numerical formula, chemical formula, table etc. ▼ (In the formula, R^1: an alkyl group having 1 to 4 carbon atoms; a cycloalkyl group having 5 to 8 carbon atoms; or a phenyl group; R^2; an alkyl group having 1 to 4 carbon atoms; a cycloalkyl group having 5 to 8 carbon atoms; Alkyl group or phenyl group R^3; divalent straight chain or branched chain, optionally cyclic hydrocarbon group having 1 to 8 carbon atoms m; 1, 2 or 3 n; value X from 2 to 6; ▲ There are mathematical formulas, chemical formulas, tables, etc.▼ or ▲mathematical formulas,
There are chemical formulas, tables, etc. ▼ (benzothiazole group) (thiocarbamyl group) In this case, R
^4 and R^5 represent a straight or branched hydrocarbon group having 1 to 4 carbon atoms or a phenyl group, and may be the same or different. A silica-blended rubber composition containing 0.1 to 20 parts by weight of a binder represented by