JPS648016B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention uses 20 to 100% by weight of amorphous polybutadiene having a bond between at least one metal selected from silicon, germanium, and tin and carbon at the end of the molecular chain, and 80% by weight of amorphous polybutadiene having no such bond.
The present invention relates to a rubber composition suitable for tire treads, comprising at least 20% by weight of amorphous polybutadiene of 0% to 0% by weight and a 1,2 bond content of 70% or more. Due to demands for lower fuel consumption and driving safety for automobiles, there is a strong demand for rubber materials for tire treads that have low rolling friction resistance and high resistance on wet roads (wet skid resistance).
However, these properties are contradictory, and until now there has been no rubber that satisfies all of these properties at the same time. Therefore, in order to balance these properties, blend compositions of different rubbers have been used. Blend compositions of styrene-butadiene copolymers, such as emulsion-polymerized styrene-butadiene copolymers and solution-polymerized styrene-butadiene copolymers, and polybutadienes, such as high-cis polybutadiene and low-cis polybutadiene, are widely used as tire tread rubber for passenger cars. has been used. However, these blend compositions are not necessarily sufficient in terms of wet skid properties and rolling friction resistance properties. Recently, a composition containing polybutadiene with a high content of 1 and 2 bonds has been proposed as meeting the above objectives (Japanese Patent Application Laid-Open No. 55-12133), but this composition has good wet skid properties and rolling friction resistance. Although this has been improved, it is still insufficient in terms of fracture properties and wear resistance, and there are also practical problems in terms of rolling friction resistance. Therefore, the present inventors conducted research to obtain a rubber material that has low rolling friction resistance, which is a measure of tire fuel efficiency, high wet skid resistance, which is a measure of running stability, and also has good breaking and wear characteristics. , containing at least 20% by weight of amorphous polybutadiene having at least one metal-carbon bond chain selected from silicon, germanium, and tin, having a 1,2 bond content of 70% or more, and a Mooney viscosity of 20 to 150. It has been found that rubber compositions containing at least 20% by weight of regular polybutadiene meet these objectives. The present invention will be explained in detail below. The amorphous polybutadiene of the present invention is made from natural rubber, cis-polyisoprene rubber, polybutadiene rubber with 1 to 60% of 1 and 2 bonds, styrene-butadiene copolymer rubber, ethylene-propylene-diene terpolymer rubber, and butyl rubber. It is blended with one or more selected other rubbers. Among these, natural rubber, cis-polyisoprene rubber, polybutadiene rubber containing 1 to 60% of 1 and 2 bonds, or styrene-butadiene rubber are preferred. The rubber composition of the present invention is characterized by containing at least 20% by weight, preferably 40% by weight or more of amorphous polybutadiene having a bond chain of at least one metal selected from silicon, germanium and tin, and 1 , using an amorphous polybutadiene having a 2-bond content of 70% or more, preferably 80% or more, and using a polybutadiene in which the amount of metal-carbon bond chains is less than 20% by weight or does not contain metal-carbon bond chains. It is superior in terms of fracture properties and rolling friction resistance properties. The metal compound used to obtain the amorphous polybutadiene having a chain containing carbon and at least one metal selected from silicon, germanium, and tin is a metal compound containing at least two metal halide or vinyl groups. silicon tetrachloride, dimethyl silicon dichloride, dibutyl silicon dichloride, germanium tetrabromide, germanium tetrachloride, tin tetrachloride, butyl tin trichloride, methyl tin trichloride, dibutyl tin dichloride, diphenyl tin dichloride, dichloride Dimethyltin, tetravinyltin, divinyldiphenyltin, bis(trichlorostannyl)ethane,
One or two compounds such as tin tetrachloride are used, and the amount used is 0.25 to 1.5 equivalents of halide or vinyl group per lithium atom of the organolithium compound described later. Among these, amorphous polybutadiene containing a tin-carbon bond chain is particularly superior in terms of rolling friction resistance compared to amorphous polybutadiene containing a silicon-carbon bond chain or a germanium-carbon bond chain. The amorphous polybutadiene of the present invention can be prepared in a hydrocarbon solvent in the presence of an ether or a tertiary amine.
It is obtained by polymerizing 3-butadiene using an organolithium compound as a catalyst, and then coupling it with a halide of the metal mentioned above, a metal compound containing at least two vinyl groups, or the like. Here, the content of amorphous polybutadiene with metal-carbon bond chains is determined by gel permeation chromatography (GPC).
It can be easily determined from the proportion of high molecular weight components measured by the method. Here, the hydrocarbon solvent used is one or two selected from hexane, heptane, octane, 2-methylbutene-2, 2-methylbutene-1, isopentane, benzene, xylene, ethylbenzene, cyclohexane, methylpentane, and the like. The ether or tertiary amine used in the present invention is used as a control agent for the content of 1 and 2 bonds in amorphous polybutadiene, and specifically, diethyl ether, dibutyl ether, dioxane, tetrahydrofuran, 2-methoxymethyltetrahydrofuran, Ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, dimethoxybenzene, triethylamine, pyridine, N,N-dimethylaniline, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetraethylethylenediamine etc. are used, and the amount used is 1 to 2 of the target amorphous polybutadiene.
The amount varies depending on the bond content, but is in the range of 0.2 to 2000 mol, preferably 1.0 to 1000 mol, per 1 atom of lithium in the organolithium compound. Examples of organic lithium compounds used as catalysts include ethyllithium, n-butyllithium,
sec-butyllithium, tert-butyllithium,
amyl lithium, phenyl lithium, tetramethylene dilithium, pentamethylene dilithium,
1,3-bis(1-lithio-3-methylpentyl)penzene, 1,1,4,4-tetraphenyl-1,4-dilithiobutane, and the like can be used. The amount used is determined by the molecular weight of the amorphous polybutadiene produced, but it is used in the range of 0.05 to 10 milligram atoms, preferably 0.1 to 5 milligram atoms, as lithium atoms per 100 g of 1,3-butadiene. More preferably, during polymerization, the polymerization initiation temperature (Ti)
is -20 to +50℃, and the difference between the highest polymerization temperature (Tm) and the polymerization initiation temperature (Ti) is at least 30℃ or more,
It is obtained by carrying out the polymerization under elevated temperature conditions of 120°C or less. By conducting the polymerization at such elevated temperature, the distribution width of the 1- and 2-bond content in the amorphous polybutadiene molecular chain is at least
Amorphous polybutadiene with a content of 10% or more can be obtained.
Such amorphous polybutadiene is preferred in terms of blend compatibility with other rubbers. The 1,2 bond content of the amorphous polybutadiene of the present invention needs to be 70% or more, preferably 80% or more. If the 1,2 bond content is less than 70%, the rubber composition will not have sufficient wet skid properties. In addition, the Mooney viscosity (ML ¹⁰⁰ ℃ ₁₊₄ ) is preferably 20 to 150,
If it is less than 20, it is unfavorable in terms of fracture properties and rolling friction resistance properties, and if it exceeds 150, it is unfavorable in terms of workability. In the rubber composition of the present invention, the content of the amorphous polybutadiene of the present invention must be at least 20% by weight, preferably 30 to 80% by weight. 20% by weight
If it is less than that, the purpose of the present invention cannot be achieved. The amorphous polybutadiene of the present invention can also be obtained by batch polymerization or continuous polymerization using a tank reactor, tower reactor, tube reactor, or the like. The molecular weight distribution of the polymer can be freely controlled not only by the type and amount of the coupling agent but also by the polymerization method. The rubber composition obtained by the present invention not only has excellent wet skid properties and rolling friction resistance properties, but also has improved fracture properties and wear properties, so it can be suitably used as a rubber material for tire treads. In the rubber composition of the present invention, carbon black is added per 100 parts by weight of raw rubber.
It contains 30 to 110 parts by weight, preferably 35 to 90 parts by weight. Furnace black with high reinforcement properties is preferable as carbon black, and SAF, ISAF,
Particle sizes such as HAF, FEF, and SRF grade and various structures are used. Iodine adsorption amount 30
Carbon black having a DBP oil absorption of 60 to 160 cm ² /100 g and a nitrogen specific surface area of 30 to 150 m ² /g is used singly or in combination of two or more. If the amount of carbon black is less than 30 parts by weight per 100 parts by weight of raw rubber, the reinforcing effect will be small and the tensile strength will be poor. On the other hand, if it exceeds 110 parts by weight, impact resilience decreases, which is not preferable. Further, the process oil that can be used in the rubber composition of the present invention is 0 to 50% per 100 parts by weight of raw rubber.
Parts by weight. The process oil may be aromatic, naphthenic, or paraffinic. If the process oil exceeds 50 parts by weight, the tensile strength, abrasion resistance, and impact resilience will decrease, which is not preferable. The vulcanizing agent used in the composition of the present invention mainly contains sulfur, and peroxides and sulfur-donating substances can also be used. Vulcanizing agent is raw rubber
It is preferable to use it in a range of 0.05 to 5.0 parts by weight per 100 parts by weight. Furthermore, in the composition of the present invention, various rubber compounding chemicals may be used as necessary. For example, vulcanization aids such as stearic acid and zinc white, vulcanization accelerators such as sulfenamide, thiuram, and guanidine, amine and phenol anti-aging agents, ozone deterioration inhibitors, processing aids, etc. Raw rubber 100 It is used in a range of 0.05 to 10 parts by weight. Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by these Examples unless the gist of the invention is exceeded. In each example, the microstructure of the amorphous polybutadiene was determined by the method of D.Morero et al.
Ind 41 758 (1959)]. Wet skid resistance measured by a skid tester was used as an index of wet skid characteristics.
Repulsion elasticity at 70°C was used as an index of rolling friction resistance. Examples 1 to 4, Comparative Examples 1 to 2 Polybutadiene - Polymerization of 1,3-butadiene using n-butyllithium in cyclohexane containing 3% tetrahydrofuran at an increasing temperature with a starting temperature of 5°C and a maximum reaching temperature of 70°C. After polymerization, tin tetrachloride was added and coupling was performed. Mooney viscosity (ML ¹⁰⁰ ℃ ₁₊₄ ) 60, 1, 2 bonds 87%
Content of amorphous polybutadiene containing tin-carbon bonds determined by GPC: 45% Polybutadiene - Obtained by polymerization at elevated temperature in the same manner as polybutadiene. Coupling with tin tetrachloride was not performed. Mooney viscosity (ML ¹⁰⁰ °C ₁₊₄ ) 63, 1, 2 bonds 87% Polybutadiene Polymerization was carried out in the same manner as polybutadiene.
Coupling was performed using silicon tetrachloride. Mooney viscosity (ML ¹⁰⁰ ℃ ₁₊₄ ) 61, 1, 2 bonds 87% Content of amorphous polybutadiene containing silicon-carbon bonds determined from GPC 47% Compounding and vulcanization conditions 100 parts by weight of the polymer shown in Table 1 On the other hand, HAF
Carbon 50, stearic acid 2, zinc white 3, anti-aging agent 810NA (N-phenyl-N'-isopropyl-
p-phenylenediamine) 1, accelerator CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) 0.6, M (2-mercaptobenzothiazole) 0.6, D (1,3-diphenylguanidine)
0.4 parts by weight and 1.5 parts by weight of sulfur were mixed and compounded using a Brabender and a roll, and vulcanization was performed at 145°C for 35 minutes. The rubber compositions containing the amorphous polybutadiene coupled with SnCl ₄ of Examples 1, 2, and 3 are excellent in tensile strength, Dunlop rebound (70° C.), and wet skid resistance. Comparative Example 1 is inferior to Examples 1, 2, and 3 in terms of tensile strength and Dunlop rebound resilience. Comparative Example 2 is inferior in wet skid resistance because the amorphous polybutadiene content of the present invention is less than 20%. Example 4 is an example in which SiCl ₄ is used as the coupling agent, and although it is slightly inferior to that using SnCl ₄ , it is clear that the rebound resilience, wet skid resistance, and tensile strength are well-balanced.

[Table] Examples 5 to 7, Comparative Examples 3 to 4 Polybutadiene - After polymerizing polybutadiene using a large amount of n-butyllithium, tin tetrachloride was added to increase the Mooney viscosity (ML ¹⁰⁰ °C). ₁₊₄ ) 18, 1, 2 bond
86% amorphous polybutadiene containing tin-carbon bonds
52% polybutadiene was obtained. Polybutadiene - After polymerizing polybutadiene with a slightly larger amount of n-butyllithium, dibutyltin dichloride was added to increase the Mooney viscosity (ML ¹⁰⁰ °C ₁₊₄ ) 35,
Amorphous polybutadiene containing 86% of 1,2 bonds and 30% of tin-carbon bonds was obtained. After polymerizing polybutadiene with a reduced amount of n-butyllithium, tin tetrachloride was added to give a Mooney viscosity (ML ¹⁰⁰ °C ₁₊₄ ) of 160, 86% of 1 and 2 bonds, and tin - Amorphous polybutadiene containing carbon bonds 48% polybutadiene was obtained. Polybutadiene - Polymerization was carried out using 5.0 mmol of n-butyl lithium, 2000 g of n-hexane, 500 g of 1,3-butadiene, and 10 mmol of ethylene glycol dibutyl ether at an elevated temperature with a polymerization initiation temperature of 15°C and a maximum temperature of 85°C. After that, add 1.0 mmol of tin tetrachloride to obtain Mooney viscosity (ML ¹⁰⁰ ℃ ₁₊₄ ) 70, 1, 2 bond.
74% amorphous polybutadiene containing tin-carbon bonds
70% butadiene was obtained. The physical properties were measured using the formulation and vulcanization conditions described above, and the results shown in Table 2 were obtained.

【table】

Claims (1)

[Claims] 1. 20 to 100% by weight of amorphous polybutadiene having at least one metal selected from silicon, germanium, and tin and carbon bond at the end of the molecular chain.
and amorphous polybutadiene 80~ that does not have the bond
1 and 2 bond content consisting of 0% by weight is 70% or more,
A rubber composition suitable for tire treads, characterized in that it contains at least 20% by weight of amorphous polybutadiene having a Mooney viscosity of 20 to 150. 2. The rubber composition according to claim 1, wherein the metal-carbon bond chain of the amorphous polybutadiene is tin-carbon. 3 The 1 and 2 bond content of amorphous polybutadiene is
80% or more of the rubber composition according to claim 1. 4 The amorphous polybutadiene is obtained by polymerizing at a polymerization initiation temperature of -20 to 50°C and at an elevated temperature of at least 30°C or more and 120°C or less above the polymerization initiation temperature, as described in claim 1. rubber composition.