JPH0149362B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a diene copolymer rubber having improved rebound elasticity.
More specifically, the present invention relates to a method for producing a diene copolymer rubber, which is characterized by reacting a diene copolymer rubber having an active dienyl-alkali metal bond terminal with a specific compound. [Prior Art] In recent years, due to demands for lower fuel consumption and driving safety for automobile tires, rubber materials with low rolling friction resistance and high wet skid resistance have been strongly desired as rubber for automobile tire treads. In order to reduce rolling friction resistance, it is necessary to increase the rebound elasticity of the rubber material. However, these two properties are contradictory, and various methods for improving polymers have been proposed in order to harmonize these two properties. For example, a method for adjusting the vinyl content and styrene content of a styrene-butadiene copolymer to a specific ratio (Japanese Patent Laid-Open No. 54-62248), a method for achieving a specific styrene chain distribution (Japanese Patent Laid-Open No. 56-143209), A method for creating a bonded chain distribution (Japanese Patent Application Laid-Open No. 149413/1983),
A method of introducing a dienyl-tin bond into the molecular chain (Japanese Unexamined Patent Publication No. 87407/1983) has been proposed. [Problems to be solved by the invention and means for solving the problems]

[Formula] It has been found that the above properties are improved in diene polymers in which a specific atomic group is introduced into the polymer chain by reacting with a compound having a bond (in the formula, M is O or S). (Special request 1982)
−249100). In order to develop a copolymer of a conjugated diene monomer and an aromatic vinyl monomer that has further improved high resilience, the present inventors have investigated various improvements to the above-mentioned method of introducing specific atomic groups. Ta. As a result, by reacting the copolymer with a dienyl-alkali metal bond terminal with a specific compound, a diene copolymer rubber with a better balance of rolling resistance (rebound elasticity) and wet skid resistance was produced. The present invention was achieved based on the discovery that the following can be obtained. An object of the present invention is to provide a method for producing diene copolymer rubber with an excellent balance of rolling resistance (rebound elasticity) and wet skid resistance.
Polymerize a conjugated diene monomer and an aromatic vinyl monomer in a hydrocarbon solvent using an organic alkali metal initiator to produce a conjugated diene-aromatic vinyl copolymer rubber in which the end of the molecular chain is a dienyl-alkali metal. After that, the copolymer rubber and

This is achieved by reacting a compound having a bond of the formula (in the formula, M represents an O atom or an S atom). The feature of the present invention is to react a conjugated diene-aromatic vinyl copolymer rubber whose polymer chain ends are dienyl-alkali metal with the above-mentioned compound. The rebound resilience is significantly improved compared to when copolymer rubber is used. Generally, when a conjugated diene monomer and an aromatic vinyl monomer are copolymerized in a hydrocarbon solvent using an organic alkali metal initiator, the copolymerization reactivity of the former is overwhelmingly greater than that of the latter. For example, M.
According to Morton, in benzene solvent, r ₁ (butadiene) = 4.5, r ₂ (styrene) = 0.08 to 0.41, Journal of Polymer Science (J. Polymer. Sci.), Vol. 61, 25. (1962). Such a large difference in copolymerization reactivity is due to the fact that the conjugated diene monomer is consumed in the first half of the polymerization, so at the end of the polymerization, a large amount of the aromatic vinyl monomer remains in the polymerization system, and the active end with the aromatic vinyl-alkali metal bond is This means that there will be more. For example, when butadiene and styrene are polymerized in a hydrocarbon solvent using n-butyllithium as a catalyst, at low polymerization rates, the color of the polymerized system is light yellow, which is characteristic of butadienyl anions. It is clear from the observation that when the polymerization rate increases, most of the butadiene is consumed, and a large amount of styrene remains, the color of the system changes to the reddish-orange color characteristic of styryl anions, and the polymerization rate also increases. The present invention is characterized in that a conjugated diene-aromatic vinyl copolymer rubber having a dienyl-alkali metal bond terminal is reacted with a specific compound, and the monomer unit immediately before the dienyl-alkali metal bond terminal is a conjugated diene. It may be aromatic vinyl. In addition, the method of adding a conjugated diene monomer to the terminal end of the copolymer rubber is, for example, a method of adding a conjugated diene monomer after the completion of copolymerization (usually, the amount of the monomer added is equal to or more than the equivalent amount to the active alkali metal end). It is fine, but preferably about 10 to 100 times the mole), and is not particularly limited, as long as it is a method in which the end of the polymer chain becomes a diene, such as copolymerization in a polymerization tank equipped with a reflux condenser. . Conjugated diene monomers used in the present invention include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, and 1,3-hexadiene.
Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, vinylnaphthalene, and the like. The ratio of conjugated diene monomer to aromatic vinyl monomer is
Used in a weight ratio of 95-50:5-50, preferably
A weight ratio of 95-65:5-35 is used. As the organic alkali metal initiator used in the present invention, those used in ordinary solution polymerization may be used.
Particularly preferred are organolithium initiators. For example, methyllithium, ethyllithium, n-propyllithium, i-propyllithium, n-butyllithium, sec-butyllithium, t-butyllithium,
Octyllithium, n-decyllithium, phenyllithium, 2-naphthyllithium, 2-butyl-phenyllithium, 4-phenyl-butyllithium, cyclohexyllithium, 4-cyclopentyllithium, 1,4-dilithio-butene-2, etc. can be mentioned. The amount of organic alkali metal initiator used usually ranges from 0.2 to 20 mmol per 100 grams of total monomer. Polar compounds such as ether compounds, amine compounds and phosphine compounds can be used with the organic alkali metal initiator for the purpose of randomizing the copolymer or controlling the proportion of vinyl bonds in the conjugated diene monomer units. The hydrocarbon solvent used in the present invention is selected from aliphatic hydrocarbons, aromatic hydrocarbons, and alicyclic hydrocarbons, such as propane, n-butane, i-butane, n-pentane, i-pentane, n- -hexane, cyclohexane, propane, 1-butene, i
Preferred solvents include -butene, trans-2-butene, cis-2-butene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, benzene, toluene, xylene, and ethylbenzene. Moreover, two or more types of these solvents can also be used in combination. The ratio of monomer to solvent is determined by the viscosity of the polymerization solution, the stirring power and heat removal capacity of the polymerization vessel, and is generally used at a weight ratio of 1:10 to 1:1. The polymerization temperature is carried out in the range of -20°C to 150°C, preferably in the range of 40 to 120°C. Polymerization can be carried out either at elevated or constant temperature. In the molecules used in the present invention

[Formula] Bond (However, M in the formula represents an O atom or an S atom)
Formamide, N, N
-dimethylformamide, acetamide, N,N
-diethylacetamide, aminoacetamide,
N,N-dimethyl-N,N'-dimethylaminoacetamide, N,N-dimethylaminoacetamide, N,N'-ethylaminoacetamide, N,
N-dimethyl-N'-ethylaminoacetamide,
Acrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, nicotinamide, isonicotinamide, picolinic acid amide, N,N-dimethylisonicotinamide, succinic acid amide, phthalic acid amide, N,N,N ′、
N′-tetramethylphthalic acid amide, oxamide,
N,N,N',N'-tetramethyloxamide, 2
-Furancarboxylic acid amide, N,N-dimethyl-
Amide compounds such as 2-furancarboxylic acid amide, quinoline-2-carboxylic acid amide, N-ethyl-N-methyl-quinolinecarboxylic acid amide, succinimide, N-methylsuccimide, maleimide, N-methylmaleimide, phthalimide, N −
Imide compounds such as methylphthalimide, ε-caprolactam, N-methyl-ε-caprolactam, 2-pyrrolidone, N-methyl-2-pyrrolidone, 2-piperidone, N-methyl-2-piperidone, 2-quinolone, N-methyl -lactam compounds such as 2-quinolones, urea, N,N'-dimethylurea, N,N-diethylurea, N,N,N',
N'-tetramethylurea, N,N-dimethyl-N',
Urea compounds such as N'-diphenyl urea and N,N'-dimethylethylene urea, methyl carbamate,
Carbamic acid derivatives such as methyl N,N-diethylcarbamate, isocyanuric acid, N,N′,
Examples include isocyanuric acid derivatives such as N''-trimethylisocyanuric acid and thiocarbonyl-containing compounds corresponding to these, but there are no particular limitations as long as the compound has the bond that reacts with the alkali metal at the end of the polymer chain. The amount of the compound used is preferably 0.5 mol or more per mol of the diene copolymer rubber having active dienyl-alkali metal bond terminals.
If the amount is less than 0.5 mol, the improvement in the rebound elasticity is insufficient, and if it is used in an amount greater than 1.0 mol, it does not participate in the reaction and there is no further improvement in the rebound elasticity. The temperature and reaction time of the reaction with the diene copolymer rubber having a dienyl-alkali metal bond can be selected over a wide range, but are generally from room temperature to 100°C for several seconds to several hours. After the reaction is complete, the modified diene polymer rubber can be coagulated by adding a coagulant such as alcohol such as methanol or ethanol to the reaction solution, or by coagulating the coagulation method used in conventional solution polymerization rubber production, such as steam coagulation. It can be used as is, and the solidification temperature is not particularly limited. For drying the crumb separated from the reaction system, a band dryer, an extrusion type dryer, etc., which are commonly used in the production of synthetic rubber, can be used, and the drying temperature is not particularly limited. The diene copolymer rubber thus obtained has an excellent balance between rebound resilience and wet skid resistance, and is useful as a rubber material for tire treads. Next, the present invention will be explained in more detail with reference to Examples. Example 1 (1) A stainless steel polymerization reactor with an internal volume of 2 was washed, dried, and replaced with dry nitrogen.
-Butadiene 120g, styrene 40g, cyclohexane 840g, tetramethylethylenediamine
0.4 mmol and 1.0 mmol of n-butyllithium (n-hexane solution) were added, and polymerization was carried out at 45° C. for 5 hours while stirring the contents. Then, add 50 g of a mixed solution of butadiene and cyclohexane with a butadiene concentration of 1% by weight at 45°C.
After reacting for 15 minutes, 1 mmol of the compound shown in Table 1 was further added, and the addition reaction was carried out for 30 minutes. Thereafter, 5 ml of methanol was added to stop the reaction, and the polymer solution was taken out into a methanol solution containing 1.5 weight percent of 2,6-di-t-butyl-p-cresol (BHT) to coagulate the resulting copolymer rubber. Thereafter, it was dried under reduced pressure at 60°C for 24 hours (rubber Nos. A, B, C, D, E, F). (2) A copolymer rubber was obtained under the same conditions as in (1) except that the compounds shown in Table 2 were added immediately after the copolymerization reaction of butadiene and styrene was completed without adding butadiene (Rubber No. G, H). The vinyl bond content and styrene content of the polymer thus obtained were determined by infrared spectroscopy [Hampton, Anal.Chem, 21 , 923 (1949)]. The results are shown in Table 1 along with the Mooney viscosity of the polymer.

[Table] These copolymer rubbers were kneaded and mixed with each compounding agent in a Brabender type mixer having a capacity of 250 ml according to the formulation shown in Table 2 to obtain a rubber compound composition. This material was press-vulcanized at 160°C for 25 minutes to prepare a test piece. The rebound elasticity of the vulcanized rubber was measured at 50°C using a Dunlop tripsomer. Wet skid resistance was tested on a road surface at 23°C (ASTME-
303-74, 3M outdoor type B, black,
Safety Walk). The results are shown in Table 3. Table 2 Compounding recipe Copolymer rubber 100 Parts by weight Zinc white No. 3 3 Stearic acid 2 Sulfur 1.75 N-cyclohexyl-2-benzo 1.1 Thiazole sulfenamide HAF carbon black 50 Aromatic process oil 5

【table】

[Table] From the results in Table 3, the butadiene-styrene copolymer rubber obtained by the method of the present invention has extremely high rebound resilience, and tires using this rubber for the tire tread have a good balance of rolling resistance and wet skid resistance. Conceivable. Example 2 (1) Copolymerization and post-added butadiene were copolymerized under the same conditions as in Example 1 (1) except that the amounts of butadiene and styrene charged were changed to those shown in Table 4. 1.0 mmol of N,N,N',N'-tetramethylurea was added and reacted to obtain a copolymer rubber (rubber No. J, K). (2) Copolymerization under the same conditions as in Example 1 (1) except that the amount of tetramethylethylenediamine added was changed to the amount shown in Table 4, polymerization of post-added butadiene,
and 1.0 mmol of N,N,N',N'-tetramethylurea to obtain copolymer rubbers (Rubber Nos. L and M).

[Table] These copolymer rubbers were prepared into a compound using the same formulation as in Example 1, and the rebound elasticity and wet skid resistance of each vulcanizate were measured. The results are shown in Table 5.

【table】

Claims (1)

[Claims] 1. Polymerization of a conjugated diene monomer and an aromatic vinyl monomer in a hydrocarbon solvent using an organic alkali metal initiator results in a polymerization process in which the end of the molecular chain is dienyl-
A conjugated diene-aromatic vinyl copolymer rubber which is an alkali metal is produced, and then the copolymer rubber and a compound having a [formula] bond (wherein M represents an O atom or an S atom) in the molecule. A method for producing a diene copolymer rubber, the method comprising reacting with.