JPH045059B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a rubber composition with large hysteresis loss, excellent breaking strength, and good processability. Conventionally, butyl rubber, halogenated butyl rubber, ethylene propylene diene rubber, emulsion polymerized styrene-butadiene copolymer rubber with a high styrene content, and polybutadiene rubber with a high 1,2 content have been used as rubber materials with large hysteresis loss such as tires, anti-vibration rubber, and industrial products. , high 3,4 content polyisoprene rubber, etc. have been used. However, these rubber materials with large hysteresis loss are inferior in terms of co-vulcanization with diene rubbers such as high-cis polyisoprene rubber, natural rubber, high-cis polybutadiene, and emulsion polymerized styrene-butadiene rubber, and are also inferior in breaking strength. In addition, for tires and anti-vibration rubber, it is preferable that the temperature dependence of hysteresis loss, that is, the loss tangent (tan δ) value, be small in the range of 25° to 70°C. It is large and cannot be said to have satisfactory performance. JP-A-57-70134, JP-A No. 57-70136, JP-A No. 57-
Publication No. 70137 describes the use of SBR with high styrene content and high vinyl bond content to improve processability, wet skid properties, and wear resistance, but these SBRs have high hysteresis loss properties over a wide range. cannot be maintained. Furthermore, by blending polymers with different molecular weights to obtain a polymodal molecular weight distribution, wet skid characteristics, rolling friction characteristics, and processability can be improved, for example, in JP-A-57-180615.
As described in Japanese Patent No. 57-180646, No. 59-4633, and No. 59-4644, these diene rubber compositions have high hysteresis loss characteristics or a good balance between hysteresis loss characteristics and fracture characteristics. The current situation is that it has not been obtained. The purpose of the present invention is to have excellent co-vulcanization with other diene rubbers, large hysteresis loss, and
The object of the present invention is to provide a butadiene-based copolymer rubber composition that has small temperature dependence of hysteresis loss in the range of 70°C and has good breaking strength and processability. The rubber composition of the present invention has a) a vinyl bond content of 40 to 70% in the polybutadiene moiety, a) a bonded vinyl aromatic compound content of 25 to 50% by weight, and a) gel permeation chromatography (GPC). ) method: The ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) in terms of polystyrene, Mw/
Mn is 1.8 to 5 and has a unimodal molecular weight distribution, weight average molecular weight in terms of polystyrene
The proportion of 100,000 or less is 10 to 30% by weight, and the proportion of polystyrene equivalent weight average molecular weight of 2 million or more is
A rubber composition containing at least 30% by weight of a butadiene-based copolymer, characterized in that the amount is 10-30% by weight, and the Mooney viscosity (ML ₁₊₄ at 100°C) is 20-100. In the present invention, the above-mentioned butadiene-based copolymer may be used alone as a rubber component, or may be used as a blend with other diene-based rubbers. Preferred examples of such diene rubber include natural rubber, synthetic polyisoprene rubber, and high 1,4-bond polybutadiene rubber. The amount used is 70% by weight.
The following are preferred. In the butadiene copolymer of the present invention, the vinyl bond content of the polybutadiene portion is 40 to 70%.
If the vinyl content is less than 40%, the amount of polyvinyl aromatic compound blocks produced increases, hardness increases, and physical properties are adversely affected. Furthermore, if the vinyl content exceeds 70%, the breaking strength will be poor, which is not preferable. In addition, the content of bound vinyl aromatic compounds is 25 to 50
% by weight, preferably 30-50% by weight. If it is less than 25%, the hysteresis loss will be small, while if it exceeds 50%, the rebound resilience will be highly dependent on temperature in the range of 25°C to 70°C, and the breaking strength will be poor, which is not preferable. Examples of vinyl aromatic compounds include styrene, vinyltoluene, p-methylstyrene, o-methylstyrene, and vinylnaphthalene. The content of the polyvinyl aromatic compound block in the butadiene-based copolymer of the present invention is determined by the oxidative decomposition method of IM Kolthoff et al. (J. Polymer Sci Vol 1 P429).
(1946)) and accounts for 5% by weight or less of all bonded vinyl aromatic compounds. The butadiene copolymer in the present invention is 25 to 70
Reduces the temperature dependence of hysteresis loss in °C,
In addition, in order to provide good processability and fracture strength, it is important that the material contains specific amounts of low molecular weight components and high molecular weight components, and that the molecular weight distribution is wide and unimodal. The low molecular weight component is necessary to obtain high hysteresis loss with little temperature dependence and to improve processability, especially during roll work, and the high molecular weight component is necessary to obtain good breaking strength and extrusion processability. It is necessary for If either of the two components is out of the range of the present invention, the processability and physical properties cannot be balanced. Furthermore, in order to achieve both fracture strength and workability, it is important that the molecular weight distribution be unimodal. Although it is possible to improve processability and physical properties to some extent with a polymer having a bimodal or polymodal molecular weight distribution in which the molecular weight distribution (/), the amount of low molecular weight components, and the amount of high molecular weight components fall within the scope of the present invention, it is still possible to improve processability and physical properties to some extent. Not satisfied. The ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) of the butadiene copolymer is Mw/Mn.
1.8 to 5, preferably 2.5 to 5, and contains 10 to 30% by weight of low molecular weight components with a weight average molecular weight of 100,000 or less in terms of polystyrene, and 10 to 30% by weight of high molecular weight components with a weight average molecular weight of 2 million or more in terms of polystyrene. It is necessary. When Mw/Mn is less than 1.8, the temperature dependence of hysteresis loss is large, and Mw/Mn
If it exceeds 5, it is difficult to bring the low molecular weight component or high molecular weight component within the above range. Furthermore, if the amount of low molecular weight components is less than 10%, processability such as roll winding will be poor, while if it exceeds 30%, breaking strength will decrease. If the amount of high molecular weight is less than 10%, processability such as roll winding will be poor, while if it exceeds 30%, processability during extrusion molding will be poor. The Mooney viscosity (ML ₁₊₄ at 100°C) of the butadiene copolymer is 20 to 100. If it is less than 20, the breaking strength will be poor, and if it exceeds 100, the processability in extrusion, rolling work, etc. will be poor. The butadiene-based copolymer of the present invention can be obtained using various methods, but the most industrial method is to use a tank or column reactor to obtain ether or tertiary amine in a hydrocarbon solvent. It can be obtained by continuously copolymerizing 1,3-butadiene, including 1,2-butadiene, and a vinyl aromatic compound in the presence of an organolithium compound initiator. If necessary, silicon halide, adipic acid diester, alkylene carbonate, divinylbenzene, etc. can be added at the final stage of the copolymerization reaction to perform a coupling reaction, and catalysts and monomers can also be added during the polymerization. can. However, it is not preferable to use tin tetrachloride as a coupling agent from the viewpoint of hysteresis loss characteristics. Examples of hydrocarbon solvents used include hexane, heptane, cyclohexane, benzene and mixtures thereof. It is used in an amount of 200 to 1000 parts by weight per 100 parts by weight of monomer. As the organolithium compound initiator, n-butyllithium,
sec-butyllithium, tert-butyllithium, etc. are used in a proportion of 0.02 to 2 parts by weight per 100 parts by weight of monomer. Ethers or tertiary amines include dimethoxybenzene, tetrahydrofuran,
Dimethoxyethane, ethylene glycol dibutyl ether, pyridine, NNN'N'-tetramethylethylenediamine, etc. are used. The polymerization temperature is preferably in the range of 30 to 100°C. The rubber composition containing the butadiene-based polymer obtained in the present invention can be used as a rubber material for tire treads and various vibration damping materials by taking advantage of its good fracture properties, processability, and high hysteresis loss properties. In fact, since the copolymer has a relatively high glass transition temperature, rubber materials to be blended with the butadiene copolymer of the present invention include natural rubber, synthetic polyisoprene rubber, and rubber materials with a low glass transition temperature, which have good compatibility. Polybutadiene rubber having 1,4 bonds is preferred. As compounding agents, commonly used compounding agents can be used, such as carbon black, process oils (aromatic oils, naphthenic oils, paraffin oils, etc.), fillers, vulcanization accelerators, and vulcanizing agents. The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples unless the gist thereof is exceeded. Examples 1 to 7; Comparative Examples 1 to 8 Polymers used in the following Examples and Comparative Examples were obtained by the following method. Sample A: 1 as monomer into a reactor with an internal volume of 20, equipped with a stirrer and a jacket.
Butadiene containing 100ppm of 2-butadiene
20g/min, styrene at 10g/min, cyclohexane as a solvent at 150g/min, tetrahydrofuran at 1.5g/min, n-butyllithium as a catalyst at a rate of 0.055g per 100g of monomer by continuously pumping the reactor temperature. was controlled at 70°C. At the top outlet of the reactor, silicon tetrachloride was continuously added at a ratio of 1/4 mole to n-butyllithium, and this was introduced into a second reactor connected to the above-mentioned quactor to perform a coupling reaction. . Di-tert-butyl-p- at the outlet of the second reactor
Cresol was added in an amount of 0.7 parts by weight per 100 parts of rubber, and the solvent was removed and dried in a conventional manner. Table 1 shows the analysis results. Sample B: A polymer was obtained in the same manner as Sample A except for changing the monomer charge composition. The analysis results are shown in Table-1. Sample C: A polymer was obtained in the same manner as Sample A using 0.038 g of n-butyllithium. No coupling reaction was performed. The analysis results are shown in Table-1. Sample D: Polymerization was carried out in the first reactor using the same recipe as Sample A, and in the second reactor, 15 g of butadiene was added as a monomer.
Polymerization was carried out at 70° C. with continuous charge of styrene at 7 g/min and n-butyllithium. No coupling reaction was performed, and the di-tert
A predetermined amount of -butyl-p-cresol was added, and the solvent was removed and dried in a conventional manner. Table 1 shows the analysis results. Sample E: Butadiene 13.5g/min, styrene
A polymer was obtained in the same manner as Sample A except that the charge was 16.5 g/min. Table 1 shows the analysis results. Sample F: 24 g/min of butadiene, 6 g/min of styrene
A polymer was obtained in the same manner as Sample A except that the charge was changed to g/min. Table 1 shows the analysis results. Sample G: A polymer was obtained in the same manner as Sample A except that tetrahydrofuran was charged at 0.4 g/min. Table 1 shows the analysis results. Sample H: A polymer was obtained in the same manner as Sample A except that tetrahydrofuran was charged at 10 g/min. Table 1 shows the analysis results. Samples I, J, K; 5 Put 2000 g of cyclohexane, 335 g of butadiene, and 165 g of styrene into an autoclave, add 25 g of tetrahydrofuran, and add n-butyllithium at the polymerization temperature to the specified vinyl bond content and bound styrene content. I is 70℃, 0.23g, sample J is 70℃, 0.35
Sample K was polymerized at 70°C and adjusted to 0.15 g. The analysis results are shown in Table-1. Sample L: Using the same continuous polymerization apparatus as Sample A, the addition speed of monomer, solvent, and catalyst was lowered, and the polymerization temperature was lowered to 90° C. to obtain a polymer. No coupling reaction was performed, and the amount of tetrahydrofuran used was 4.5 g/min. The analysis results are shown in Table-1. A formulation was prepared according to the formulation shown in Table 2. The vulcanization conditions were 145°C for 30 minutes. Table 3 shows the properties of the vulcanized product obtained and the roll processability of the unvulcanized compound. Sample M: Comparing the polymerization recipe of Sample A using 0.045g of n-butyllithium for 100g of monomer,
Polymerization was carried out at a charge speed of 0.7 times the monomer and solvent. Table 1 shows the analysis results. Examples 1 to 4 and 6 are superior to Comparative Examples 1 to 7 in that they have well-balanced fracture strength, hysteresis loss characteristics, and roll workability. Comparative Examples 1 and 4 have large temperature dependence of hysteresis loss, and Comparative Examples 2, 5, and 7 have small hysteresis loss at high temperatures. Moreover, Comparative Examples 3 and 6 are inferior in breaking strength. Example 5 is superior to Comparative Example 8 in that the temperature dependence of hysteresis loss is smaller. Example 7 was the same as the formulation shown in Table 2 except that 60 parts by weight of HAF carbon and 40 parts by weight of aromatic oil were used.

[Table] Used. Tetrahydrofuran was used as a solvent.
Table 2 Compounding Disposal Weight parts Polymer 100 HAF carbon 50 Aromatic oil 10 Stearic acid 2 Zinc white 3 Anti-aging agent 810NA ^*1 1 Accelerator CZ ^*2 0.6 〃 M ^*3 0.6 〃 C ^*4 0.4 Sulfur 1.5 *1 N-phenyl-N'-isopropyl-p-
Phenylenediamine*2 N-cyclohexyl-2-benzothiazolylsulfenamide*3 2-mercaptobenzothiazole*4 1,3-diphenylguanidine

【table】

【table】 [Brief explanation of drawings]

Figure 1 shows the GPC charts of samples A, C, and I.

Claims (1)

[Claims] 1. The vinyl bond content of the polybutadiene portion is
The content of the bound vinyl aromatic compound is 25 to 50% by weight, and the ratio Mw/Mn of the polystyrene equivalent weight average molecular weight Mw to the number average molecular weight Mn by gel permeation chromatography is 1.8. 5.0 and has a unimodal molecular weight distribution, the proportion of polystyrene equivalent weight average molecular weight of 100,000 or less is 10 to 30% by weight, and the proportion of polystyrene equivalent weight average molecular weight of 2 million or more is 10 to 30% by weight, A rubber composition containing at least 30% by weight of a butadiene-based copolymer, characterized in that it has a Mooney viscosity ML ₁₊₄ and a temperature of 20 to 100 at 100°C.