JPH0220644B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a styrene-butadiene copolymer, and more specifically, in copolymerizing styrene and 1,3-butadiene in a hydrocarbon solvent using an organolithium initiator, a Lewis base and a specific anionic obtained by adding surfactants and carrying out polymerization at elevated temperatures, at least
The present invention relates to a method for producing a random styrene-butadiene copolymer having a vinyl content distribution width of 20% and an average vinyl content of 20% or more and less than 70%. In the presence of a Lewis base in a hydrocarbon solvent,
The fact that polybutadiene, which is obtained by polymerizing 1,3-butadiene at elevated temperatures and has a distribution of vinyl content in its molecular chain, has a well-balanced wet skid property and abrasion property as a tire material was reported in Japanese Patent Publication No. 1973- Shown in 43267. but,
The above-mentioned polybutadiene has a practical problem in its breaking characteristics. On the other hand, random styrene-butadiene copolymers can be obtained by copolymerizing 1,3-butadiene and styrene under isothermal polymerization conditions in the presence of a Lewis base, but polymerization at elevated temperatures often results in block copolymerization. A styrene-butadiene copolymer containing styrene is produced, and its vulcanizate also has poor heat generation properties, making it undesirable as a tire material. The inventors of the present invention have conducted extensive research to find a material that has low rolling friction resistance, which is a measure of fuel efficiency, and high wet skid resistance, which is a measure of running safety, as well as a material that is well-balanced in terms of wear resistance and fracture properties. , a random styrene-butadiene copolymer with a Mooney viscosity (ML ₁₊₄ at 100℃) of 10 to 150, an average vinyl content of 20% to less than 70%, and a bound styrene content of 5 to 35% by weight. It has been found that polymers with a vinyl content distribution of at least 20% are suitable for these purposes. Based on this knowledge, the present invention provides the above-mentioned styrene-
This was achieved as a result of intensive research into methods for producing butadiene copolymers. That is, in the present invention, when producing a styrene-butadiene copolymer by copolymerizing styrene and butadiene in the presence of an organolithium initiator in a hydrocarbon solvent, a Lewis base and -
SO ₃ M group or -OSO ₃ M group (M is Na, K, Rb
or Cs), the polymerization is carried out under elevated temperature conditions, the average vinyl content is 20% or more and less than 70%, and the distribution width of the vinyl content is at least 20%; A method for producing a styrene-butadiene copolymer, characterized in that a random styrene-butadiene copolymer having a Mooney viscosity (ML ₁₊₄ , 100°C) of 10 to 150 and a styrene content of 5 to 35% by weight is obtained. be. The organolithium initiators used in the present invention include methyllithium, ethyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, amyllithium, phenyllithium, tolyllithium, vinyllithium, propenyl Lithium, tetramethylene dilithium, pentamethylene dilithium, hexamethylene dilithium, decamethylene dilithium, 1,3-bis(1
-lithio-3-methylpentyl)benzene, 1,
3-bis(1-lithio-1,3-dimethylpentyl)benzene, 1,1,4,4-tetraphenyl-1,4-dilithiobutane, etc. can be used. The amount of organolithium initiator to be used is determined by the molecular weight and Mooney viscosity of the resulting polymer, but it is usually in the range of 0.05 to 10 milligram atoms, preferably 0.1 to 5.0 milligram atoms, as lithium atoms per 100 g of monomer. used in Ethers and tertiary amines are preferably used as Lewis bases. Specific examples include diethyl ether, dibutyl ether, dioctyl ether, tetrahydrofuran, 2-methoxytetrahydrofuran, 2-methoxymethyltetrahydrofuran, 2,5-dimethoxymethyltetrahydrofuran, dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether. , ether compounds such as diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, and tetraethylene glycol dimethyl ether;
Tertiary compounds such as N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetraethylethylenediamine, triethylenediamine, N-methylmorpholine, N-ethylmorpholine, trimethylamine, triethylamine, pyridine, etc. Amine compounds are used. Among them, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, 2-methoxymethyltetrahydrofuran, 2,5-dimethoxymethyltetrahydrofuran. When using polyethers such as N,N,N',N-tetramethylethylenediamine, N,N,N',N'-tetraethylethylenediamine, etc., the average vinyl Content is 70%
The above is preferable because a random copolymer can be obtained. The amount of Lewis base used varies depending on the type of Lewis base, but is used in the range of 0.05 to 500 moles per gram atom of lithium in the organolithium initiator. -SO ₃ M group or -OSO ₃ M group (M is Na, K,
Examples of anionic surfactants having Rb, Cs) include alkylaryl sulfonates shown in Japanese Patent Publication No. 54-44315, amide bond sulfonates, ester bond sulfonates, higher alcohol sulfate ester salts, and ester bond Sulfate ester salts are used. The anionic surfactant is used in an amount of 0.005 to 1.0 gram atom based on the alkali metal atom per gram atom of lithium of the initiator. Polymerization solvents include aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene, alicyclic hydrocarbons such as cyclohexane, methylcyclopentane, and cyclooctane, propane, butane,
Aliphatic hydrocarbons such as pentane, hexane, heptane, octane, decane are used. Two or more kinds of these hydrocarbons may be used in combination. Among these hydrocarbons, alicyclic hydrocarbons and aliphatic hydrocarbons are preferred as polymerization solvents. The solvent is used in an amount of 1 to 20 parts by weight per 1 part by weight of the monomer. The average vinyl content of the styrene-butadiene copolymer obtained in the present invention depends on the type and amount of Lewis base used, the type of polymerization solvent, the polymerization temperature, etc. The content is 20% or more and less than 70%, preferably 30-60
% range. If the average vinyl content is less than 20%, sufficient wet skid properties cannot be obtained, and if it is more than 70%, wear resistance properties and
Not sufficient in terms of breaking properties. Furthermore, since the distribution of vinyl content is determined by the history of polymerization temperature during polymerization, the distribution of vinyl content under elevated temperature polymerization conditions is at least 20%, preferably 30%.
% or more must be set. If the distribution width of the vinyl content is less than 20%, the wet skid properties, abrasion resistance, and fracture properties cannot be harmonized. That is, even if the wet skid properties are good, the wear resistance and fracture properties are poor, and conversely, even if the wear resistance and fracture properties are good, the wet skid properties are poor. The vinyl content distribution width referred to here means that once the type of Lewis base, the amount added, and the polymerization solvent are determined, there is a correlation between the polymerization temperature and the vinyl content of the polymer, so it can be used to track changes in polymerization temperature over time during polymerization at elevated temperatures. However, it refers to the polymerization initiation temperature (Ti), that is, the difference between the vinyl content at the lowest polymerization temperature and the vinyl content at the highest temperature (Tm) during polymerization, expressed in %. In Figure 1, n-butyllithium was used as a polymerization initiator, diethylene glycol dimethyl ether was used as a Lewis base, potassium dodecylbenzenesulfonate was used as an anionic surfactant in a molar ratio of 1:0.3:0.05, and cyclohexane was used as a solvent. The relationship between the vinyl content in a styrene-butadiene copolymer containing 25% by weight of bound styrene and the polymerization temperature is shown below. The bound styrene content of the copolymer of the present invention is 5 to 35
% by weight, preferably 10-30% by weight. A bound styrene content of less than 5% by weight is unfavorable in terms of wear resistance and fracture resistance. Moreover, if it exceeds 35% by weight, it is unfavorable in terms of rolling friction resistance. The Mooney viscosity (ML ₁₊₄ , 100° C.) is preferably 10 to 150, particularly 3 to 120. If it is less than 10, it is unfavorable in terms of tensile strength and rolling friction resistance, and if it exceeds 150, it is unfavorable in terms of processability. In the present invention, the polymerization temperature is not particularly limited, but
The polymerization initiation temperature (Ti) is preferably 10 to 60°C. On the other hand, the temperature difference (ΔT) between the polymerization initiation temperature (Ti) and the maximum temperature (Tm) during or at the end of polymerization is set at 40% in order to make the vinyl content distribution width 20% or more.
It is preferable that the temperature is at least ℃. Further, the maximum temperature (Tm) is preferably 130°C or lower. If the temperature exceeds 130°C, the low molecular weight portion of the polymer increases, making it unfavorable in terms of rolling friction resistance. Polymerization under the condition of increasing temperature from the start of polymerization to the end of polymerization can be carried out by batch polymerization or continuous polymerization using various temperature increasing methods. For example, an adiabatic polymerization method in which the temperature rises linearly with the polymerization conversion rate by minimizing heat loss from the start of polymerization to the end of polymerization; A method in which isothermal polymerization is carried out to a predetermined polymerization conversion rate by adjusting removal, and then polymerization is carried out at an elevated temperature until the end of the polymerization, and a method in which the polymerization temperature is increased stepwise at each predetermined polymerization conversion rate. Various polymerization methods can be used, such as the polymerization method described below. Initiation of the polymerization of the present invention is preferably carried out by adding an organolithium initiator to a system in which a hydrocarbon solvent, a monomer, a Lewis base, and an anionic surfactant are present. Polymerization may be initiated by introducing a surfactant into which a hydrocarbon solvent and monomer are present. When the polymerization reaction reaches the desired conversion rate, an antiaging agent and a polymerization terminator such as water, alcohol, or phenols are added to stop the polymerization, and then the polymer solution is desolvented and dried to obtain the desired polymerization. You can get a combination. The styrene-butadiene copolymer obtained by the method of the present invention has a glass transition temperature measured by differential scanning calorimetry (DSC) and a peak width of attenuation (tan δ) of the attenuation temperature curve measured by kinetic measurement. The broadening of the vinyl content also supports the fact that the distribution width of the vinyl content is widening. The random styrene-butadiene copolymer of the present invention is described by IM Kolthoff et al. J. Polymer Sei. Vol. 1
When measured by an oxidative decomposition method such as p429 (1946), the blocked styrene content in bound styrene is 10
% by weight or less of styrene-butadiene copolymer. The styrene-butadiene copolymer obtained by the method of the present invention can provide a rubber material that is well balanced in terms of wet skid properties, rolling friction resistance properties, wear properties and fracture properties. The present invention will be explained in more detail with reference to Examples below. In each example, the microstructure of the polybutadiene moiety was determined by the method of D. Morero [chim e Ind. 41 758
(1959)], the styrene content in the copolymer is
It was determined from a calibration curve using absorbance at 699 cm ^-1 . The polymerization conversion rate was calculated by evaporating the polymer solution and determining the total solid content. The glass transition point was measured using a low-temperature DSC manufactured by Rigaku Denki Co., Ltd.
(This was carried out using a differential scanning calorimeter (heating rate: 20°C/min). In addition, the rebound elasticity at 70°C and the heat generation temperature measured by a wet skid flexometer were used as indicators of the rolling friction resistance properties. Wet skid resistance measured by a skid tester was used as an index. Examples 1 to 3, Comparative Examples 1 to 5 Cyclohexane, styrene, diethylerone glycol, dimethyl ether, potassium dodecylbenzenesulfonate, 1,
After charging 3-butadiene and adjusting it to a predetermined polymerization initiation temperature, n-butyllithium was added and 1
Time polymerization was carried out. With the exception of Comparative Example-1, polymerization was carried out at elevated temperatures without heat removal from outside the reactor. In Comparative Example 1, heat was removed from the outside of the reactor using a refrigerant, and polymerization was carried out under isothermal conditions. The polymerization recipe and polymerization conditions are shown in Table 1. The polymerization conversion rate was 100% in all cases. Polymerization conversion rate of 30% in Example 1 and Comparative Example 1
The combined styrene in the body obtained when
They were 25.5% and 23.0% by weight. The polymer is 2,6-ditertially added to the polymer solution.
After adding 25 g of butyl P-cresol, the solvent was removed by steam stripping and dried on a roll at 110°C. Table 3 shows the main properties of the polymer and the properties of the vulcanizate. The vulcanizate was obtained by kneading according to the formulation shown in Table 2 and vulcanizing at 145°C for 45 minutes. FIG. 2 shows a chart of the glass transition temperatures of the copolymer of Example 1 and the copolymer of Comparative Example 1 measured by differential scanning calorimetry. Examples 1, 2, and 3 are superior to the polymer of Comparative Example 1, which is obtained by isothermal polymerization and has no vinyl content distribution, in terms of tensile strength, elongation, abrasion, and wet skid. Furthermore, compared to the polymer of Comparative Example 2 which does not contain an anionic surfactant and contains blocked styrene, it is superior in terms of tensile strength, elongation, and heat generation (grid-strength). Examples 1, 2, and 3 are superior to the polymer of Comparative Example 3 in terms of tensile strength, elongation, and abrasion, and the polymer of Comparative Example 4 with 40% bound styrene and the polymer of Comparative Example 5 with an average vinyl content of Compared to 13% polymers, it is well balanced in terms of wet skid, repulsion properties, and heat generation.

【table】

【table】 Table 2 Combination prescription Weight part Styrene-butadiene copolymer rubber 100 Carbon black (ISAF) 50 Highly aromatic process oil 10 Stearic acid 2 Zinc flower 4 Accelerator (MSA) 0.54 Accelerator (DM) 0.86 I Ou 2.0

【table】

【table】 [Brief explanation of drawings]

Figure 1 shows the relationship between the vinyl content in a styrene-butadiene copolymer containing 25% by weight of bound styrene and the polymerization temperature, and Figure 2 shows the difference between the copolymer of Example 1 and the copolymer of Comparative Example 1. Figure 2 shows a chart of glass transition temperatures measured from a scanning calorimeter.

Claims (1)

[Claims] 1. In producing a styrene-butadiene copolymer by copolymerizing styrene and butadiene in the presence of an organolithium initiator in a hydrocarbon solvent, a Lewis base and -SO ₃ are added to the polymerization system. M group or -
OSO ₃ M group (M represents Na, K, Rb or Cs)
polymerization is carried out under elevated temperature conditions in the presence _of an anionic surfactant having A method for producing a styrene-butadiene copolymer, which comprises obtaining a random styrene-butadiene copolymer having a temperature of 10 to 150 ( ₊₄ , 100°C) and a styrene content of 5 to 35% by weight. 2. Claim 1, which is an elevated temperature polymerization condition in which the polymerization initiation temperature (Ti) is 10 to 60°C and the temperature interval (△T) between the maximum temperature during polymerization (Tm) and Ti is at least 40°C or more. A method for producing a styrene-butadiene copolymer as described in 1.