JP2000239447A - Silica-mixed rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition showing good silica dispersion and possessing satisfactory mechanical strength by making a conjugated-diene-based elastomer contain a specific amount of silica and a specific amount of a polymer silane coupling agent obtained by adding a specific silane compound to a butadiene- based elastomer. SOLUTION: A conjugated diene-based elastomer is a rubbery polymer containing a conjugated diene as a major component. Silica to be used preferably has specific surface area of 50-400 m2/g. An amount of silica is referably 10-100 pts.wt. per 100 pts. of the elastomer and an amount of a silane coupling agent is 1-30 pts.wt. per 100 pts.wt. of the elastomer. The specific silane compound is represented by formula (R1 is 1-6C divalent alkylene group; and R2-R4 are methoxy, methyl and the like provided that at least one of R2-R4 is methoxy or phenoxy) and such an example is 3-mercaptopropyltrimethoxysilane. The coupling agent is obtained by adding 10-300 pts.wt. of the silane compound to 100 pts.wt. of a butadiene-based polymer having number average molecular weight of 500-10,000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a silica-containing rubber composition containing silica as an inorganic filler in a good dispersion state and having excellent mechanical strength.

[0002]

2. Description of the Related Art Silica has long been used as a white filler for rubber, but when kneading it with rubber,
Due to the remarkable increase in viscosity, it was extremely difficult to uniformly disperse this in rubber. In order to solve this problem, a method of adding a low-molecular silane coupling agent such as alkylsilane, vinylsilane, aminosilane, mercaptosilane or bis (3-triethoxysilylpropyl) polysulfide at the time of kneading silica has conventionally been adopted. Was. However, all of the above compounds are disadvantageous in that, in addition to being expensive, an odor is generated at the time of kneading, and an undesirable crosslinking reaction occurs upon heating (poor scorch properties). Not only that,
Silica-containing rubber compositions prepared using low-molecular coupling agents do not always have sufficient mechanical strength.
On the other hand, as the polymer silane coupling agent, polyorganosiloxanes described in JP-A-9-194638 and JP-A-10-53707 or modified products thereof are known. However, these conventional polymer-based silane coupling agents do not contain any structural units capable of chemically bonding to rubber in the molecule, or the amount thereof is extremely small. If the agent alone is used, a silica-containing rubber composition having satisfactory mechanical strength cannot be obtained. Therefore, it is premised that the above-mentioned polymer silane coupling agent is used in combination with a low-molecular silane coupling agent. In addition, polyorganosiloxanes or modified products thereof have regrets that they lack compatibility with rubber molecules because their structures are significantly different from those of general rubbers.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel rubber composition which has solved various problems which have been recognized in conventional rubber compositions containing silica.
The present inventors have conducted intensive studies to develop a silane-containing rubber composition suitable for this purpose, and as a result, by using a specific polymer silane coupling agent, not only is silica excellent in dispersibility, but also It has been found that a novel silica-containing rubber composition exhibiting satisfactory mechanical strength can be obtained at low cost.

[0004]

According to the present invention, 10 to 300 parts by mass of mercaptosilane represented by the following general formula (1) is added to 100 parts by mass of a butadiene polymer having a number average molecular weight of 500 to 10,000. A polymer silane coupling agent obtained by the above is used. Hereinafter, this polymer silane coupling agent is referred to as a coupling agent X.

Embedded image (In the formula, R ¹ represents a divalent alkylene group having 1 to 6 carbon atoms, and R ² , R ³ , and R ⁴ may be the same or different, and each may be a methoxy group, an ethoxy group, a phenoxy group, or a methyl group. , An ethyl group or a phenyl group, provided that
At least one of R ² , R ³ and R ⁴ is a methoxy group, an ethoxy group or a phenoxy group. That is, the silane-containing rubber composition according to the present invention comprises (a) a conjugated diene-based elastomer, (b) 10 to 100 parts by mass of silica per 100 parts by mass of the conjugated diene-based elastomer, and (c) a conjugated diene. It contains 1 to 30 parts by mass of the coupling agent X per 100 parts by mass of the system elastomer, and its main performance characteristics are that it shows good vulcanization properties, high tensile strength and high modulus.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The conjugated diene-based elastomer used in the present invention is not particularly limited as long as it is a rubbery polymer containing a conjugated diene as a main component. Cis 1,4-polyisoprene rubber, 3,4-polyisoprene rubber, emulsion-polymerized styrene / butadiene copolymer rubber, solution-polymerized styrene / butadiene copolymer rubber, isoprene / butadiene copolymer rubber, styrene / isoprene copolymer rubber, styrene / isoprene /
Butadiene terpolymer rubber. Cis 1,4-polybutadiene rubber, trans 1,4-polybutadiene rubber (70
~ 95% trans), low vinyl polybutadiene rubber (1
0-30% vinyl), medium vinyl polybutadiene rubber (3
0-50% vinyl), high vinyl polybutadiene rubber (5
0-90% vinyl), emulsion polymerized styrene / butadiene /
One or more of acrylonitrile terpolymer rubber and butadiene / acrylonitrile copolymer rubber can be used. The silica used in the present invention is not particularly limited. One or more of colloidal silica, precipitated silica and the like can be used. There is no special restriction on the specific surface area of the silica, preferably 50 to 400 m ² / g, more preferably 100 to 250 m ² / g, particularly preferably 1
It is in the range of 20 to ²⁰⁰ m ² / g. The specific surface area referred to herein is a nitrogen adsorption specific surface area (BET method) by a measuring method according to ASTM D3037-81. The mixing amount of silica is 10 per 100 parts by mass of the conjugated diene elastomer.
To 100 parts by mass, preferably 15 to 90 parts by mass. It is not preferable that the amount of silica deviates from this range, because the abrasion resistance and the like of the obtained rubber composition are significantly reduced.

The coupling agent X used in the present invention is
Provides good processability and mechanical strength to Rica compound rubber composition
It is an indispensable ingredient in doing. Coupling agent X
Is the carbon-carbon unsaturated in the butadiene polymer
A mercaptosilane represented by the general formula (1)
Radical reaction of mercapto group (HS-)
Is a compound obtained by In the general formula (1), R
¹Represents a divalent alkylene group having 1 to 6 carbon atoms,
Typically, -CH_Two−, − (CH_Two)_Two-,-(CH_Two)_Three−, −
(CH_Two)_Four-,-(CH_Two) _Five-Or-(CH_Two)₆Indicates-. Ma
R^Two, R^Three, R^FourAre the same or different
Well, methoxy, ethoxy, phenoxy respectively
A methyl group, a methyl group, an ethyl group or a phenyl group. However,
R^Two, R^Three, R^FourAt least one is a methoxy group, an ethoxy group
It is a silyl group or a phenoxy group. Represented by the general formula (1)
Preferred specific examples of the mercaptosilane compound include:
Can be exemplified.

Embedded image

In synthesizing the coupling agent X, the amount of the mercaptosilane of the general formula (1) added to the butadiene-based polymer is selected in the range of 10 to 300 parts by mass per 100 parts by mass of the butadiene-based polymer. . When the amount of the silane compound is less than 10 parts by mass, the reactivity between the addition reaction product and the silica is reduced, so that the rubber composition finally obtained cannot have satisfactory mechanical strength. On the other hand, when the amount of the silane compound is more than 300 parts by mass, the crosslinking reactivity between the addition reaction product and the rubber decreases, which is not preferable. It is not economically preferable to use a large amount of the silane compound. On the other hand, general formula (1)
The butadiene-based polymer to which mercaptosilane is added is selected from those having a number average molecular weight of 500 to 10,000, preferably 500 to 5,000. An addition reaction product obtained by using a polymer having a number average molecular weight of less than 500 cannot obtain a silica-containing rubber composition having sufficient mechanical strength even if it is added to the composition. When a polymer having a number average molecular weight of more than 10,000 is used, the viscosity of the addition reaction system is significantly increased, which hinders the execution of the addition reaction.

The butadiene polymer used in the addition reaction preferably has a vinyl group content of 50 mol% or more and 80 mol% or less, more preferably 55 mol% or more and 75 mol% or less of the total double bonds present in the polymer. Is more preferable. More specifically, the butadiene-based polymer used in the addition reaction has a number average molecular weight in the range of 500 to 5,000 and a vinyl group content in the range of 50 to 80 mol% of the total double bonds present in the polymer. Preferably, it is a certain polybutadiene. The vinyl group in the butadiene-based polymer has higher reactivity than the internal olefin. Therefore, the vinyl group content is 5% of the total double bonds present in the butadiene-based polymer.
If the amount is less than 0 mol%, it takes a long time to add a predetermined amount of mercaptosilane, so that side reactions such as a cross-linking reaction occur simultaneously. For this reason, the addition reaction product obtained using a butadiene-based polymer having a low vinyl group content has a reduced performance as a silane coupling agent. If the vinyl group content exceeds 80 mol%, the use of a butadiene-based polymer significantly increases the viscosity of the addition reaction system, which hinders the progress of the reaction. In other words, the vinyl group content is 8
To obtain a butadiene-based polymer exceeding 0 mol%, anionic polymerization at a low temperature is required, and as a result, the price of the butadiene-based polymer used as a raw material of the coupling agent X is increased.

The addition reaction between the polybutadiene-based polymer and the silane compound (i) for obtaining the coupling agent X can proceed by simply heating, but in order to proceed more quickly, it is necessary to coexist with a radical generator. Is preferred.
By using a radical generator, the desired addition reaction can be completed in a short time under mild reaction conditions, and a reaction product with a high addition rate can be obtained.
The radical generator used is not particularly limited, and commercially available organic peroxides, azo compounds, hydrogen peroxide and the like can be used.

Specific examples of the organic peroxide include methyl ethyl ketone peroxide, cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide,
Acetylacetone peroxide, 1,1, -bis (tert-butylperoxy) -3,3,5-trimethylcyclohexane 1,1, -bis (tert-butylperoxy) -3,3,5-cyclohexane, 2, 2-
Bis (tertiarybutylperoxy) butane, tertiarybutylhydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, paramenthane hydroperoxide,
2,5-dimethylhexane 2,5-dihydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, ditertiary butyl peroxide, tertiary butyl cumyl peroxide, dicumyl peroxide, bis ( Tert-butylperoxyisopropyl) benzene, 2,5-dimethyl-2,5
-Di (tert-butylperoxy) hexane, 2,
5-hexanoyl peroxide, lauroyl peroxide, succinic acid peroxide, benzoyl peroxide and its substituted product, 2,4-dichlorobenzoyl peroxide, metatoluoyl peroxide, diisopropylperoxydicarbonate, tertiary butyl-2 -Ethylhexanoate, di-2-ethylhexylperoxydicarbonate, dimethoxyisopropylperoxycarbonate, di (3-methyl-3-methoxybutyl) peroxydicarbonate, tertiary butyl peroxocia acetate, tertiary butyl par Oxypivalate, tertiary butyl peroxy neodecanoate,
Tertiary butyl peroxyoctanoate, tertiary butyl peroxy 3,3,5-trimethylhexanoate, tertiary butyl peroxy laurate,
Tertiary butyl peroxycarbonate, tertiary butyl peroxybenzoate, tertiary butyl peroxyisobutyrate, and the like.

Specific examples of the azo initiator include 2, 2 '
-Azobisisobutyronitrile, 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'-
Azobis (2-methylbutyronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2 ′
-Azobis (2,4-dimethyl-4-methoxyvaleronitrile), 2,2'-azobis (2- (2-imidazolin-2-yl) propane), 2,2'-azobis (2,
4,4-trimethylpentane), 2,2'-azobis (2-methylpropane), 2,2'-azobis (2-hydroxymethylpropionnitrile), 4,4'-azobis (4-cyanovaleric acid) , Dimethyl 2,
There are 2′-azobis (2-methylpropionate), 2-cyano-2-propylazoformamide, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, and the like. Then, the desired addition reaction can be performed under ultraviolet irradiation or visible light irradiation.
The addition reaction can be carried out without solvent, but a radical-inactive solvent can be used for the purpose of suppressing the increase in the viscosity of the reaction system and removing the heat of reaction. As the solvent, benzene, toluene, xylene, aromatic hydrocarbon solvents such as mixed xylene, or hexane, heptane,
Aliphatic hydrocarbon solvents such as ligroin can be used.

In the composition of the present invention, a coupling agent
The compounding amount of X is selected in the range of 1 to 30 parts by mass, more preferably 2 to 15 parts by mass per 100 parts by mass of the conjugated diene elastomer. When the amount of the coupling agent X is less than 1 part by mass, the effect as a silane coupling agent cannot be exhibited. On the other hand, if the compounding amount exceeds 30 parts by mass, the vulcanization characteristics of the obtained silica-containing rubber composition deteriorate. The basic constituent components of the silica-containing rubber composition according to the present invention are a conjugated diene-based elastomer, silica and a coupling agent X, and other additives in the composition include, for example, zinc oxide, stearic acid, and aging. An inhibitor, a vulcanization accelerator, bis (3-triethoxysilylpropyl) tetrasulfide (Si-69) and the like can be added. The addition amount of these is preferably 1 to 10 parts by mass per 100 parts by mass of the conjugated diene elastomer.
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[0013]

EXAMPLES Synthesis Example 1 of Polymeric Silane Coupling Agent A polybutadiene having a number average molecular weight of 930 and a vinyl group content of 65% (Nippon Petrochemical Co., Ltd.) was placed in a reactor equipped with a stirrer, a thermometer and a nitrogen inlet tube. Nisseki Polybutadiene B-10
00) 100 parts by mass, 3-mercaptopropyltrimethoxysilane (KBM-803 manufactured by Shin-Etsu Chemical Co., Ltd.)
After 100 parts by mass and 5 parts by mass of di-tert-butyl peroxide as an initiator, the inside of the reactor was purged with nitrogen using a nitrogen inlet tube. Then, under nitrogen atmosphere, 120 ° C
For 5 hours. After completion of the reaction, volatile components in the reaction product were removed under reduced pressure while maintaining the temperature at 80 ° C. The obtained pale yellow transparent liquid was used as polymer silane coupling agent A. Synthesis example 2 of polymer silane coupling agent Synthesis example except that polybutadiene as a raw material was changed to polybutadiene having a number average molecular weight of 2000 and a vinyl group content of 65% (Nippon Petrochemical Co., Ltd. Nisseki polybutadiene B-2000). Polymer silane coupling agent B was obtained in the same manner as in 1. Synthesis Example 3 of Polymeric Silane Coupling Agent A synthesis example except that the raw material polybutadiene was changed to polybutadiene having a number average molecular weight of 3000 and a vinyl group content of 65% (Nippon Petrochemical Co., Ltd. Nisseki polybutadiene B-3000) Polymer silane coupling agent C was obtained in the same manner as in 1. Synthesis Example 4 Synthesis of Polymeric Silane Coupling Agent A raw material was prepared by using a number average molecular weight of 2000 and a vinyl group content of 65%.
100 parts by mass of polybutadiene (Nippon Petrochemical Co., Ltd. Nisseki polybutadiene B-2000), 3-mercaptopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.)
KBM-803) Polymer silane coupling agent D was obtained in the same manner as in Synthesis Example 1 except that the amount was changed to 250 parts by mass.

Examples 1 to 4 and Comparative Examples 1 to 2 (Blending / Kneading of Rubber Composition) Kneading was carried out according to JIS K 6383 with the blending shown in Table 1 (the numerical values indicate parts by mass). A rubber composition was prepared. The components used in the compounding are as follows. SBR (1512) JSR zinc oxide 2 types Mitsui Kinzoku Mining Co., Ltd. Stearic acid Nippon Yushi Co., Ltd. Antioxidant Norac 810-NA Ouchi Shinko Chemical Co., Ltd. Vulcanization accelerator Noxeller DM Ouchi Shinko Chemical Co., Ltd. Sulfur Kawagoe Chemical Co., Ltd. Silica Nipsil VN-3 Nippon Silica Co., Ltd. Si-69 Degussa Co., Ltd. (Used roll) Dimensions φ6 × 16 inches, rotation speed 20 rpm (f), rotation ratio 1: 1: 22

[0015]

[Table 1]

(Vulcanization Test) Examples 1 to 4 and Comparative Examples 1 to
The vulcanization test for each sample obtained in 2 was measured by the following method. Test method JIS K 6300 Curastometer type III 170 ° C Amplitude ± 1 °, frequency 1.67 Hz (100 cpm) The results of the vulcanization test are shown in Table 2.

[0017]

[Table 2]

(Tensile test) Examples 1 to 3 and Comparative Examples 1 to
170 ° C. × 2 for each sample obtained in
After performing the vulcanization operation for 0 minutes, a test piece was prepared and JIS
Tensile test measurement was performed according to the method of K6251. Table 3 shows the results of the tensile test.

[0019]

[Table 3]

As is clear from the test results shown in Tables 2 and 3, Comparative Example 1 in which no polymeric silane coupling agent was added was used.
However, the strength of the rubber composition is insufficient because no bond exists between silica and rubber. On the other hand, in Comparative Example 2 using a low-molecular-weight silane coupling agent, although the effect as the coupling agent is recognized, the T10 value is short, and a problem remains in workability. In addition, elongation and strength of the rubber composition are not sufficiently improved due to an undesired crosslinking reaction caused by the reactive group (tetrasulfide). In contrast,
In the rubber composition of the present invention, a favorable improvement effect is recognized in both the vulcanization characteristics and the mechanical properties.

[0021]

As described above, in the silica-containing rubber composition of the present invention, by using a specific polymer silane coupling agent, the mechanical properties of the silica-containing rubber composition can be improved without impairing its processability. Can be improved.

Claims (4)

[Claims] Claims 1. A conjugated diene-based elastomer contains 100 to 100 parts by mass of silica and 1 to 30 parts by mass of a polymer silane coupling agent per 100 parts by mass of a conjugated diene elastomer. Average molecular weight 500-10
The silane compound represented by the following general formula (1) is used in an amount of 10 to 300 with respect to 100 parts by mass of a butadiene-based polymer of 000
A silica-containing rubber composition which is a coupling agent obtained by adding parts by mass. Embedded image (Wherein R ¹ is a divalent alkylene group having 1 to 6 carbon atoms, and R ² , R ³ , and R ⁴ may be the same or different, and each may be a methoxy group, an ethoxy group, a phenoxy group, a methyl group, Represents an ethyl group or a phenyl group, provided that
At least one of R ² , R ³ and R ⁴ is a methoxy group, an ethoxy group or a phenoxy group. ) 2. The conjugated diene elastomer is cis 1,4.
-Polyisoprene rubber, 3,4-polyisoprene rubber,
Styrene / butadiene copolymer rubber, isoprene / butadiene copolymer rubber, styrene / isoprene copolymer rubber, styrene / isoprene / butadiene terpolymer rubber, cis 1,4-polybutadiene rubber, trans 1,4-polybutadiene rubber (70-95% trans), Low vinyl polybutadiene rubber (10-30% vinyl), medium vinyl polybutadiene rubber (30-50% vinyl), high vinyl polybutadiene rubber (50-90% vinyl), emulsion polymerized styrene / butadiene / acrylonitrile terpolymer rubber and butadiene / acrylonitrile The silica-containing rubber composition according to claim 1, which is selected from the group consisting of a copolymer rubber. 3. The method according to claim 1, wherein the silane compound is The silica-containing rubber composition according to claim 1, which is 4. The butadiene-based polymer forming the polymer silane coupling agent has a number average molecular weight of 500 to 5,000.
And the vinyl group content is 50 to
The silica-containing rubber composition according to claim 1, which is in a range of 80 mol%.