JPH0527656B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a rubber composition suitable for tire treads comprising a styrene-butadiene copolymer containing three different block polymer components in the molecular chain. <Conventional technology> Recently, there has been an increase in demand for automobile running safety and fuel efficiency, and in addition to the fracture properties such as abrasion resistance that have traditionally been required for rubber materials for tire treads, wet skid resistance and ice skid resistance are also required. Moreover, rubber with low rolling friction resistance has become desirable. However, it is difficult to satisfy these properties at the same time, and in particular, wet skid properties and rolling friction properties, and wet skid properties and ice skid properties, are in an antinomic relationship. Conventionally, emulsion polymerization has good wet skid properties.
SBR, high cis 1,4-polybutadiene, low cis 1,4-polybutadiene with good ice skid properties and wear resistance
- Two or more rubber materials such as polybutadiene, natural rubber with good fracture properties and rolling friction resistance, and cis-1,4-polyisoprene were selected and blended to obtain a rubber composition in which contradictory properties were harmonized. . However, although a certain degree of harmonization has been achieved, it has not yet reached the level that currently requires standards. <Problems to be solved by the invention> In recent years, attempts have been made to modify polybutadiene (BR) and styrene-butadiene copolymer (SBR) obtained mainly using organolithium polymerization initiators.
BR with relatively high vinyl content in the butadiene moiety,
SBR is emulsion polymerized SBR, natural rubber, high cis 1,
It has come to be improved compared to 4BR and low cis 1,4BR (Japanese Patent Laid-Open Nos. 54-62248, 56-110753, 56-143209, 55-12133, etc.). However, the above polymers have poor ice skid properties and poor running safety in cold regions. In the styrene-butadiene copolymer obtained using a lithium-based polymerization initiator, the present inventors
In order to improve the wet skid properties, rolling friction properties, and ice skid properties, we investigated the results by introducing three block polymer components with different glass transition temperatures into the molecular chain and introducing a tin-carbon bond. It has been found that the wet skid properties, rolling friction properties and ice skid properties of sulfur can be improved to a high level. <Means for Solving the Problems> That is, the present invention provides a polymerization system in which the bound styrene content is 5 to 30% by weight and the vinyl content of the butadiene moiety is 40 to 40% by weight, which is obtained using a lithium-based polymerization initiator in a hydrocarbon solvent. 80% styrene-butadiene copolymer block part (A) 10-70% by weight and a styrene-butadiene copolymer or polybutadiene block part (B) with a bound styrene content of 0-15% by weight and a vinyl content in the butadiene part of less than 40%. ) 20 to 75% by weight and a styrene-butadiene copolymer block portion having an engaged styrene content of 50% by weight or more (C) A block polymer portion consisting of 5 to 20% by weight, b average The bound styrene content of c is 5 to 25% by weight, and the average vinyl content of the butadiene moiety is 20 to 50%.
%, d Mooney viscosity (ML _{1+4 100} °C) 20-150,
and e the tin atoms bonded to the carbon atoms are 100 ppm ~
1000 ppm, a styrene-butadiene copolymer of: It is something. The styrene-butadiene copolymer of the present invention is
Although it is composed of block polymer components (A), (B), and (C), the vinyl content of the bonded styrene and butadiene moieties of each component does not necessarily have to be uniform throughout the molecular chain. That is, there may be a gradual increase or decrease along the molecular chain. Furthermore, there is no particular restriction on the combination of bonds between block polymers (A), (B), and (C). The above component (A) is a random copolymer with a bound styrene content of 5 to 30% by weight and a vinyl content of the butadiene moiety of 40 to 80%, and its glass transition temperature is -70°C.
~-10°C, and its proportion in the copolymer is 10-70%, preferably 15-45% by weight. If the bound styrene content and vinyl content of component (A) are outside the above ranges, the ice skid properties and wet skid properties cannot be harmonized. Furthermore, if the proportion of component (A) in the copolymer is less than 10% by weight, the ice skid properties and wet skid properties cannot be balanced, and if the proportion of component (A) is more than 70% by weight, the ice skid properties are poor. Component (B) is a random styrene-butadiene copolymer or polybutadiene with a bound styrene content of 0 to 15% by weight and a vinyl content of the butadiene moiety of less than 40%, and its glass transition temperature ranges from -110°C to -70°C. The proportion thereof is 20 to 75% by weight, preferably 40 to 75% by weight in the copolymer. If the bound styrene content of component (B) exceeds 15% by weight, if the vinyl content exceeds 40%, or if the proportion of component (B) is less than 20% by weight, the ice skid properties and abrasion resistance will be poor. If the proportion of component (B) exceeds 75% by weight, the proportions of components (A) and (C) will decrease, resulting in poor wet skid properties. Component (C) is a random or partially blocked styrene-butadiene copolymer with a bound styrene content of 50% by weight or more, and its glass transition temperature is -
The temperature ranges from 10 DEG to +50 DEG C., and its proportion is 5 to 20%, preferably 5 to 15% by weight, in the copolymer. If the bound styrene content is less than 50% by weight and the proportion of component (C) in the copolymer is less than 5% by weight, the wet skid properties will be poor, and if it exceeds 20% by weight, the rolling friction properties and ice skid properties will be poor. The average bound styrene content of the styrene-butadiene copolymer of the present invention is 5 to 25% by weight, and 5% by weight.
If it is less than that, wet skid resistance and fracture strength will be poor. Moreover, if it exceeds 25% by weight, the ice skid properties will be poor. The average vinyl content of the butadiene part of styrene-butadiene copolymer is 20-50%, and the vinyl content is 20%.
If it is less than %, the wet skid resistance will be poor. If it exceeds 50%, wear resistance and fracture strength will be poor. The Mooney viscosity (ML ₁₊₄ , ₁₀₀ °C) of the styrene-butadiene copolymer is 20 to 150; below 20, the breaking strength and rolling friction properties are poor, and above 150, the processability is poor. It is important that tin atoms are contained in the styrene-butadiene copolymer in the form of carbon bonds in order to improve rolling friction properties and fracture properties. Such introduction of a tin atom in the form of a tin-carbon bond is usually carried out by reacting a styrene-butadiene copolymer anion with a halogenated tin compound. The tin atom content in the styrene-butadiene copolymer is 100ppm to 1000ppm, preferably 150ppm
~600ppm. If it is less than 100 ppm, it is insufficient in terms of rolling friction resistance and breaking strength. In addition, the coupling efficiency due to the tin modifier is
When the Mooney viscosity is about 20 at 100%, the tin atom content is about 1000 ppm. The styrene-butadiene copolymer of the present invention can be obtained by various methods, but the first method is to polymerize styrene and 1,3-butadiene using a lithium-based polymerization initiator in a hydrocarbon solvent in a batch or continuous polymerization method. Ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, N, N, N, 'N'-
When the polymerization temperature of tetramethylethylenediamine, dipiperidinoethane, etc. increases, the vinyl content of the butadiene moiety decreases, and styrene and 1,3-
In the presence of polyethers and polyamines that reduce the randomness of butadiene, the polymerization initiation temperature is -10 to 50.
After polymerization at elevated temperature at a maximum temperature of 80 to 120°C, (A-B-C)xSnRy(x:1
A styrene-butadiene copolymer consisting of A-B-C is obtained. The second method involves polymerizing 1,3-butadiene, styrene, tetrahydrofuran, dibutyl ether, ethylene glycol dibutyl ether, etc. at 10 to 100°C using a lithium-based polymerization initiator in a batch or continuous polymerization process in a hydrocarbon solvent. diethylene glycol diethyl ether, dimethoxybenzene,
Polymerization is carried out in the presence of an ether such as N,N,N,'N'-tetramethyl, ethylenediaminepyridine, dipiperidinoethane, or a tertiary amine to obtain an incompletely random styrene-butadiene copolymer. After this, 1,3-butadiene is further added and polymerized at 80 to 120°C, and by reacting with a tin halide compound, (A-C-B)
Styrene-butadiene copolymer consisting of xSnRy (x: an integer of 1 to 4, x+y=4, R: a substituent selected from an alkyl group having 1 to 8 carbon atoms, a phenyl group, and a benzyl group) and ABC is obtained. The third method is to polymerize 1,3-butadiene at 30 to 100°C using a lithium polymerization initiator in a hydrocarbon solvent, and then combine styrene/1,3-butadiene in a weight ratio of 5/95 to 30/70. Polymerization is carried out by adding the ether or tertiary amine of the second method, and the weight ratio of styrene/1,3-butadiene is 50/50 to 50/50.
After polymerizing by adding styrene and 1,3-butadiene in a ratio of 80/20, (B-A-C) xSnRy
(x: integer from 1 to 4, x+y=4, R: number of carbon atoms 1
A styrene-butadiene copolymer consisting of B-A-C and a substituent selected from alkyl groups, phenyl groups, and benzyl groups (8) is obtained. In the above method, pentane, hexane, heptane, cyclohexane, methylcyclopentane, etc. are used as the hydrocarbon solvent. As the lithium-based polymerization initiator, sec-butyllithium, n-butyllithium, tert-butyllithium, amyllithium, hexyllithium, etc. are used. Examples of tin halide compounds include tin dichloride,
Tin tetrachloride, methyltrichlorotin, butyltrichlorotin, dibutyldichlorotin, dimethyldichlorotin, tributylmonochlorotin, triphenylmonochlorotin, dibenzyldichlorotin, and the like are used. The styrene-butadiene copolymer of the present invention comprises natural rubber, cis 1,4-polyisoprene, high cis 1,
4 polybutadiene, low cis 1,4 polybutadiene, other solution polymerized styrene butadiene copolymers,
It is blended with one or more rubbers selected from emulsion polymerized styrene butadiene copolymer, ethylene propylene diene copolymer, and halogenated butyl rubber. That is, the rubber composition for tire tread of the present invention comprises the styrene-butadiene copolymer of the present invention,
This is a rubber composition comprising other rubber components as described above. It is necessary that the content of the styrene-butadiene copolymer of the present invention in the rubber composition of the present invention is at least 30% by weight.
Ice skid characteristics cannot be improved to a high level. The rubber composition containing the styrene-butadiene copolymer obtained by the present invention has good wet skid properties, ice skid properties, and rolling friction properties, and is also excellent in breaking properties, so it can be used as a rubber material for tire treads. It can be suitably used. Furthermore, it can be used for vibration isolators, fenders, window frames, and other industrial products. Carbon blocks, process oils (aromatic oils, naphthenic oils, paraffinic oils), fillers,
Vulcanization accelerators and vulcanizing agents can be used. The present invention will be described in more detail with reference to Examples below, but the present invention does not exceed the gist thereof.
The invention is not limited to these examples. In addition, various measurements in the examples were performed by the following methods. Tensile properties were measured according to JIS K 6301. 70°C rebound resilience as an indicator of rolling friction resistance (resilience measured by Danlopt Lipsometer)
was used. Wet skid resistance was measured on a wet asphalt road surface at 25°C using a portable skid tester manufactured by Stanley, UK. Ice skid resistance is on an icy road surface at -20℃.
Measurements were made using a portable skid tester manufactured by Stanley, UK. The microstructure of the butadiene portion of the styrene-butadiene copolymer was determined by an infrared method (Morello method). In addition, the bound styrene content was determined by infrared method at a wave number of 699 cm.
It was determined from a calibration curve based on the absorption peak of the phenyl group appearing at ^-1 . The tin atom content in the styrene-butadiene copolymer was determined by an atomic absorption spectrometer after dissolving it in toluene and performing reprecipitation purification twice in methanol. Examples 1 to 12 Comparative Examples 1 to 12 <About Polymers A to K and Q to S> Cyclohexane, monomer, and catalyst were charged into a reactor No. 5 purged with nitrogen, and polymerization was carried out in three stages. For those in which the coupling reaction was carried out after the polymerization was completed, a coupling agent was added. Then, ditertiary-butyl-P-cresol was added to the rubber.
Add 1 part by weight to 100 parts, desolute in the usual manner,
I did drying. The analysis results for each polymer are shown in Table 4. <About Polymers L and M> Cyclohexane, a monomer, and a catalyst were charged into a reactor No. 5 purged with nitrogen, and polymerization was carried out by changing the polymerization temperature of each block portion as shown in Table 2. A coupling agent was added and an anti-aging agent was added in a conventional manner, followed by desolvation and drying. The analysis results are shown in Table-4. <Regarding Polymers N and O> Cyclohexane, a monomer, and a catalyst were charged into a reactor No. 5 purged with nitrogen, and the A and C blocks were polymerized at the polymerization temperature shown in Table 3. After the conversion rate reaches 100%, butadiene is newly converted to Table 3.
A polymer was obtained under the following polymerization conditions. Table 4 shows the analysis results.
It was shown to. <About Polymer-P> In a reactor with an internal volume of 10 equipped with a stirrer and a heating jacket, 7.5 g/min of butadiene as a monomer, 75 g/min of cyclohexane as a solvent, and 0.005 g/min of tetrahydrofuran were added as monomers.
g/min, with n-butyllithium as catalyst
0.07 g per 100 g of total monomer was continuously supplied by a pump, and the reactor temperature was controlled at 70°C. The conversion rate at the reactor outlet was over 95%. At the inlet of the second reactor, add 0.1 g/min of tetrahydrofuran and 4.8 g/min of butadiene.
Styrene was continuously supplied at a rate of 1.2 g/min, and the temperature of the second reactor was controlled at 70°C. The conversion rate at the outlet of the second reactor is 95%.
That's all. At the reactor inlet in the third stage, add butadiene at 0.45 g/min and styrene at 1.05 g/min.
g/min continuously. The temperature of the third reactor was controlled at 70°C. Supply is from 95
It was within the 100% range. Tin tetrachloride was continuously added as a coupling agent to the outlet of the third reactor at a ratio of 1/4 mole to n-butyllithium, and then di-tert-butyl-P-cresol was added to 100 g of polymer. 0.7 g was added and desolubilized and dried in a conventional manner. The analysis results are shown in Table-4. The obtained polymer was mixed according to the formulation shown in Table 5.
The mixture was kneaded in a 250 c.c. plastomill and vulcanized at 150° C. for 30 minutes. The evaluation results of physical properties and workability are shown in Table 6. As shown in the comparative example, the rubber compositions of Examples 1 to 12 containing the styrene-butadiene copolymer of the present invention had a good balance of wet skid properties, ice skid properties, and rolling friction resistance, and also had good fracture properties. , has excellent wear resistance,
Suitable for tire treads and other rubber industrial products.

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[Table] Table 5 (Composition) Part by weight Polymer 100 HAF carbon 50 Aromatic oil 10 Stearic acid 2 Zinc white 3 Antioxidant 810SA ^*1 1 Accelerator CZ ^*2 0.6 〃 M ^*3 0.6 〃 D ^*4 0.4 Sulfur 1.5 *1 N-phenyl-N'-isopropyl-P-
Phenylene diamine *2 N-cyclohexyl-2-benizothiazolylsulfenamide *3 N-mercaptobenzothiazole *4 1,3-diphenylguanidine

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[Table] ←Good

Claims (1)

[Scope of Claims] 1. A styrene-butadiene copolymer having a bound styrene content of 5 to 30% by weight and a vinyl content of the butadiene moiety of 40 to 80%, obtained using a lithium-based polymerization initiator in a hydrocarbon solvent. Block part (A) 10-70% by weight
and a styrene-butadiene copolymer or polybutadiene block part (B) with a bound styrene content of 0 to 15% by weight and a vinyl content of the butadiene part of less than 40%, and a bound styrene content of 20 to 75% by weight.
A styrene-butadiene copolymer with bonded block moieties consisting of a styrene-butadiene copolymer block moiety (C) of 50 wt.% or more, 5-20 wt.%, b. an average bound styrene content of 5-25 wt.%, c. Average butadiene moiety vinyl content is 20-50
%, d Mooney viscosity (ML _1+4,100 °C) is 20~150, and e tin atoms bonded to carbon atoms are 100 ppm~
1000 ppm of a styrene-butadiene copolymer, and other rubber components, the rubber composition comprising at least 30 ppm of the styrene-butadiene copolymer.
A rubber composition for tire tread, characterized in that it contains % by weight.