Process for producing polybutadiene

Abstract: A process for producing a polybutadiene, which comprises polymerizing 1,3-butadiene in an inert organic solvent with a catalyst comprising (A) a cobalt compound, (B) an organoaluminum compound consisting essentially of an aluminoxane and, if necessary, (C) a tertiary phosphine compound, (D) at least one compound selected from the group consisting of an ester compound, an alcohol compound, a phenolic compound, a sulfoxide compound, a nitrogen-containing heterocyclic compound, water and a tertiary amine compound and (E) at least one compound selected from the group consisting of carbon disulfide, a xanthogen compound and a thioisocyanide. By this process, there can be produced, as desired, a cis-1,4-polybutadiene, a 1,2-polybutadiene having a desired vinyl content, a crystalline 1,2-polybutadiene or a polybutadiene containing crystalline 1,2-polybutadiene segments.

Description: The present invention relates to a process for producing a polybutadiene. More particularly, the present invention relates to a process for producing a cis-1,4-polybutadiene, a 1,2-polybutadiene having a desired vinyl content, a crystalline 1,2-polybutadiene or a polybutadiene containing crystalline 1,2-polybutadiene segments. The structure of a butadiene polymer composed mainly of 1,3-butadiene depends largely upon the catalyst system used in the production of the polymer. For example, it is known that a cis-1,4- or trans-1,4-polybutadiene is obtained when a catalyst system consisting of a transition metal compound and an alkylaluminum is used. It is also known that a syndiotactic 1,2-polybutadiene is obtained when a catalyst system consisting of CoBr 2 (PPh 3 ) 2 , Al(C 2 H 5 ) 3 and water is used (Japanese Patent Application Kokoku No. 44-32426). Meanwhile, it is known that when a catalyst system consisting of BuLi or Cr(acac) 3 -Al(C 2 H 5 ) 3 is used, an atactic 1,2-polybutadiene or an isotactic 1,2-polybutadiene is obtained, respectively [A.F. Halasa et al., J. Polym. Sci. Polym. Chem. Ed., 19 , 1357 (1981); G. Natta et al., Chem. Ind. (Millan), 41 , 1163 (1959)]. With the above catalyst systems, however, it is impossible to produce a cis-1,4-polybutadiene, a 1,2-polybutadiene having a desired vinyl content, a crystalline 1,2-polybutadiene and a polybutadiene containing crystalline 1,2-polybutadiene segments. That is, with the above catalyst systems, it is impossible to control the microstructure and stereoregurality over a wide range. Further, the above catalyst systems have such problems that in producing a crystalline 1,2-polybutadiene, the catalyst activity is high in a halogenated hydrocarbon solvent but is low in a hydrocarbon solvent and the polymer obtained in a hydrocarbon solvent has a low melting point and a lower molecular weight than the practical level. The Journal of Polymer Science 907, Polymer Chemistry Edition, Volume 21 (1983) July No. 7 pages 1951-1972 discloses a process for polymerizing 1,3-butadiene in benzene with the following catalyst: Co(octoate) 2 -AlEt 2 Cl/H 2 O-Additive-CS 2 GB-A-2,029,427 discloses a process for polymerising 1,3-butadiene in an organic solvent in the presence of a catalyst comprising a cobalt compound, a trialkylaluminium compound, water and an organic phosphine. The present inventors have made extensive research for solving the above-mentioned problems of the prior art and, as a result, found that when a catalyst system containing both transition metal compound and organoaluminum compound is used, a cis-1,4-polybutadiene, a 1,2-polybutadiene having a desired vinyl content, a crystalline 1,2-polybutadiene and a polybutadiene containing crystalline 1,2-polybutadiene segments can be produced, and a crystalline 1,2-polybutadiene having a high and desirably controlled melting point and a highly controlled molecular weight in a practical level can be produced at a high catalyst activity even in a hydrocarbon solvent and that butadiene polymers having various microstructures and stereoreguralities can be produced as desired by the appropriate selection of an electron donor compound which is one of the catalyst components. According to the present invention, there is provided a process for producing a polybutadiene, which comprises polymerizing 1,3-butadiene in the presence of a catalyst consisting essentially of (A) a cobalt-phosphine complex in an amount of 0.001-1 millimole in terms of cobalt per mole of 1,3-butadiene and (B) an organoaluminium compound consisting essentially of an aluminoxane represented in formula (I) or (II): wherein R is methyl, and m is an integer of 5 to 100, in a hydrocarbon solvent, wherein the Al/Co atomic ratio is 4-10 7 . In the present invention, there can be used, as the cobalt complex (A), cobalt complexes having an apparent O-valence to the maximum valence. The cobalt complex (A) is, for example, a complexed cobalt salt of an inorganic acid or a complexed cobalt salt of an organic acid. The salts are typically halides, sulfate, nitrate, carbonate, phosphate, sulfide, hydroxide, cyanide, thiocyanide, naphthenate and salts of organic acids (e.g. octanoate, stearate, benzoate and the like). Of these cobalt complexes (A), preferable are complexes such as cobalt bis(triphenylphosphine) dibromide, cobalt bis(triphenylphosphine) dichloride, cobalt bis(tri-m-methylphenylphosphine) dibromide, cobalt bis(tri-m-methylphenylphosphine) dichloride, cobalt bis(tri-p-methylphenylphosphine) dibromide, cobalt bis(tri-p-methylphenylphosphine) dichloride, cobalt bis(tri-p-methoxyphenylphosphine) dibromide, cobalt bis(tri-p-methoxyphenylphosphine) dichloride, cobalt bis(dicyclohexylphenylphosphine) dibromide, cobalt bis(dicyclohexylphenylphosphine) dichloride, cobalt bis(tri-m-dimethylphenylphosphine) dibromide, cobalt bis(3,5-dimethyl-4-methoxyphenylphosphine) dibromide and cobalt bis(3,5-dimethyl-4-methoxyphenylphosphine) dichloride. In the aluminoxane represented by general formula (I) or (II), m is an integer of 5-100, preferably 10-100. In the present invention, the cobalt compound [the catalyst component (A)] is used in an amount of 0.001-1 millimole, preferably about 0.01-0.5 millimole in terms of cobalt atom, per mole of 1,3-butadiene. The organoaluminum compound [the catalyst component (B)] is used as to give an Al/Co atomic ratio [a ratio of aluminum atoms in component (B) to cobalt atoms in component (A)] of 4-10 7 , preferably 10-10 6 . The catalyst used in the present invention is prepared by adding individual components in any desired order and mixing them in a hydrocarbon solvent. The preparation may be effected before the catalyst contacts with 1,3-butadiene, or may be effected by mixing the components in the presence of 1,3-butadiene in a polymerization reactor. In the present invention, 1,3-butadiene is polymerized in an inert organic solvent in the presence of the catalyst components (A) and (B). The polymerization solvent is an inert organic solvent and includes aromatic hydrocarbon solvents such as benzene, toluene, xylene and cumene; aliphatic hydrocarbon solvents such as pentane, hexane and butane; alicyclic hydrocarbon solvents such as methylcyclopentane and cyclohexane; and mixtures thereof. In the present process, it is also possible to produce a polybutadiene by slurry polymerization using an aliphatic hydrocarbon as the polymerization solvent. Also, there may be used polymerization of a C 4 fraction freed from polymerization-inhibiting components such as 1,2-butadiene and acetylene, and bulk polymerization of butadiene at a low conversion at a controlled polymerization rate. The polymerization temperature is preferably -50°C to 120°C, more preferably -20°C to 50°C. The polymerization reaction may be batchwise or continuous. The monomer concentration in solvent is preferably 5-50% by weight, more preferably 10-35% by weight. In producing a polymer according to the present invention, in order to prevent the deactivation of the catalyst used and the polymer formed, measures must be taken to avoid or minimize the incorporation of deactivating compounds such as oxygen, water, carbon dioxide and the like into the polymerization system. Hydrogen may be used as a molecular weight-modifier to control the molecular weight of the polymer obtained. When the polymerization reaction has reached a desired stage, there are added to the reaction mixture an alcohol or other polymerization terminator, an age resister, an antioxidant, an ultraviolet absorber, etc. Then, the polymer formed is separated, washed and dried according to usual methods to obtain a desired polybutadiene. According to the present process, since a specific catalyst is used, the vinyl content in the polybutadiene obtained can be easily controlled over a wide range by, for example, controlling the polymerization temperature. For example, when two polybutadienes are produced under the same specific conditions but at different polymerization temperatures of 20°C and 40°C, the vinyl contents of these polybutadienes differ by about 30%. Thus, in the polybutadiene obtained with a catalyst comprising the components (A) and (B) as the essential components, the vinyl content of butadiene portion is in the range of 5-90% and the cis-1,4 content is in the range of 10-95%. With the cobalt-phosphine complex compound used in the invention, there can be obtained a polybutadiene in which a cis-1,4 configuration and a 1,2 configuration coexist or a 1,2 configuration is present in a large proportion. In the polybutadiene obtained in the present invention, the molecular weight can be varied over a wide range but the polystyrene-reduced number-average molecular weight is preferably 5,000-1,000,000, more preferably 10,000-800,000. When the molecular weight is less than 5,000, the polymer has insufficient strength. On the other hand, when the molecular weight is more than 1,000,000, the polymer has inferior processability; consequently, a large torque is required during kneading on rolls or in a Banbury mixer and dispersion of compounding chemicals or reinforcing agents (e.g. carbon black) becomes unsatisfactor, and the properties of the vulcanizate become inferior. The Mooney viscosity (ML 1+4 , 100°C) of the polybutadiene obtained in the present invention is preferably 20-150, more preferably 30-80 when it is used as rubber products for industrial applications, in particular. When the Mooney viscosity is less than 20, the physical properties of vulcanizate are inferior for the same reasons as mentioned above. On the other hand, when the viscosity is more than 150, the polymer has inferior processability. Further, the ratio of weight-average molecular weight ( M w) to the polystyrene-reduced number-average molecular weight ( M n), i.e. the molecular weight distribution ( M w/ M n) of the polybutadiene obtained in the present invention can be varied over a wide range; however, it is usually 1.5-5.0. It is difficult technically to obtain a molecular weight distribution of less than 1.5. When the molecular weight distribution is larger than 5.0 the physical properties are inferior and the amount of a low molecular weight polymer is increased. The polybutadiene obtained in the present invention is used as a material rubber alone or in admixture with other synthetic rubbers or natural rubber. It necessary, it can be extended with a process oil and then mixed with conventional compounding agents for vulcanized rubbers, such as filler (e.g. carbon black), vulcanizing agent, vulcanization accelerator and the like to obtain a rubber composition. The composition is vulcanized, and the vulcanizate thus obtained can be used in rubber applications where mechanical properties and abrasion resistance are required, for example, tire, hose, belt and other industrial rubber products. The present invention is more specifically described below with reference to Examples. However, the present invention is by no means restricted to these Examples. In the Examples, parts and % are by weight unless otherwise specified. In the Examples, measurements of properties were made in accordance with the following methods. The vinyl content of polybutadiene was measured by an infrared absorption spectrum method (Morero method). The melting point of polybutadiene was measured using a DSC (differential scanning calorimeter), in accordance with ASTM D 3418. Weight-average molecular weight and number-average molecular weight were measured by gel permeation chromatography [C-4A of Shimadzu Corporation], at 40°C using a tetrahydrofuran as a solvent. Glass transition temperature and melting point were measured using a DSC [SSC5200H manufactured by Seiko Instruments Inc.], in accordance with ASTM D 3418. Reference Example (Preparation of 1,3-butadiene, catalysts and polymerization solvent) 1,3-Butadiene: 1,3-Butadiene manufactured by Japan Synthetic Rubber Co., Ltd. was subjected to distillation and then dried with a Molecular Sieve 4A. Cobalt bis(triphenylphosphine) dibromide: A dichloromethane solution of cobalt bis(triphenylphosphine) dibromide synthesized by a method described in J. Chatt et al., J. Chem. Soc., 1961, 285 Methylaluminoxane: A toluene solution of methylaluminoxane manufactured by TOSOH AKZO CORPORATION Triisobutylaluminum: A toluene solution of triisobutylaluminum manufactured by TOSOH AKZO CORPORATION Triisobutylaluminoxane: A n-hexane solution of triisobutylaluminoxane manufactured by TOSOH AKZO CORPORATION Polymerization solvent: Degassed using dry nitrogen and then dried with Molecular Sieve 4A. Examples 1-3 In a 100-ml stainless steel autoclave containing a rotor were placed methylaluminoxane and cobalt bis(triphenylphosphine) dibromide together with 60 g of toluene as a solvent and 10 g of 1,3-butadiene in a dry nitrogen atmosphere so that the molar ratio of 1,3-butadiene/Co and the atomic ratio of Al/Co became 1×10 4 and 1×10 3 , respectively. Then, polymerization of 1,3-butadiene was conducted at 20°C for a varying period of time as shown in Table 1. After the completion of the polymerization, a hydrochloric acid-methanol solution was added to the polymerization mixture to terminate the polymerization, after which the polybutadiene formed was separated by filtration and vacuum-dried at 60°C. The results of measurement are shown in Table 1. As is clear from Table 1, when the polymerization temperature is constant, the molecular weight and vinyl content of the polybutadiene obtained are each substantially constant, even when the conversion is varied by varying the polymerization time. Example 4 The same procedure as in Example 1 was repeated, except that the polymerization temperature was changed to 0°C and the polymerization time was changed to 8 hours. The results of measurement are shown in Table 2. Examples 5-8 The same procedure as in Example 1 was repeated, except that methylaluminoxane and cobalt bis(triphenylphosphine) dibromide were added so as to give an Al/Co atomic ratio of 2.5×10 4 and the polymerization temperature was changed as shown in Table 2. As is clear from Table 2, when the polymerization temperature is varied, the vinyl content is high when the polymerization temperature is low, but becomes lower as the polymerization temperature gets higher. Thus, it can be seen that the vinyl content of the polybutadiene obtained can be easily controlled by varying the polymerization temperature. Example 1 Example 2 Example 3 Polymerization time (hr) 1 2 4 Conversion (%) 13 23 39 Number-average molecular weight ( M n) 1.41×10 5 1.36×10 5 1.34×10 5 Weight-average molecular weight ( M w) 2.56×10 5 2.61×10 5 2.61×10 5 M w/ M n 1.82 1.91 1.94 Vinyl content (%) 65 66 67 Example 4 5 6 7 8 Polymerization temperature (°C) 0 20 30 40 80 Conversion (%) 24 12 13 9 14 Number-average molecular weight ( M n) 1.70×10 5 2.05×10 5 1.58×10 5 0.98×10 5 0.30×10 5 Weight-average molecular weight ( M w) 3.35×10 5 3.92×10 5 3.15×10 5 3.84×10 5 1.01×10 5 M w/ M n 1.97 1.91 2.00 3.91 3.41 Vinyl content (%) 61 63 60 28 11 Reference Example 1 In a 100-ml pressure bottle made of a hard glass were placed a methylaluminoxane solution in toluene and a cobalt octylate-triphenylphosphine-toluene mixture, together with 60 g of toluene and 10 g of 1,3-butadiene, in a dry nitrogen atmosphere so that the molar ratio of 1,3-butadiene/cobalt octylate (Co), and the atomic ratios of methylaluminoxane (Al)/cobalt octylate (Co) and triphenylphosphine (P)/cobalt octylate (Co) became 10,000, 50 and 2.5, respectively. The resulting mixture was subjected to polymerization at 10°C for 10 minutes. The reaction was terminated by adding, to the polymerization system, a small amount of methanol containing 2,6-di-tert-butyl-p-cresol as a reaction terminator. The resulting reaction mixture was poured into a large amount of methanol to coagulate a polymer. The polymer thus coagulated was vacuum-dried at 40°C and the amount of the polymer was then measured to determine the yield. The polymer was measured for 1,2-vinyl content (%), melting point (°C), weight-average molecular weight ( M w), number-average molecular weight ( M n) and molecular weight distribution ( M w/ M n). Comparative Example 1 The same procedure as in Reference Example 1 was repeated, except that the polymerization solvent used in Reference Example 1 was replaced by methylene chloride and water, triisobutylaluminum and bis(triphenylphosphine)cobalt dibromide were added in place of the catalyst components in Reference Example 1 so that BD (butadiene)/Co = 10,000 (molar ratio), Al/Co = 50 (atomic ratio) and H 2 O/Al = 0.8 (molar ratio). The results of measurement are shown in Table 3. Comparative Example 2 The same procedure as in Comparative Example 1 was repeated, except that the polymerization solvent was replaced by toluene. The results of measurement are shown in Table 3. Comparative Examples 3-6 The same procedure as in Example 9 was repeated, except that the methylaluminoxane used as the component (B) in Reference Example 1 was replaced by triisobutylaluminum, water + triisobutylaluminum (water/aluminum molar ratio = 0.8), triethylaluminum, or water + triethylaluminum (water/aluminum molar ratio = 0.8). The results of measurement are shown in Table 3.

Claims: A process for producing a polybutadiene, which comprises polymerizing 1,3-butadiene in the presence of a catalyst consisting essentially of (A) a cobalt-phosphine complex in an amount of 0.001-1 millimole in terms of cobalt per mole of 1,3-butadiene and (B) an organoaluminium compound consisting essentially of an aluminoxane represented by formula (I) or (II): wherein R is methyl, and m is an integer of 5 to 100, in a hydrocabon solvent, wherein the Al/Co atomic ratio is 4-10. The process according to Claim 1, wherein the hydrocarbon is an aliphatic hydrocarbon and the polymerization is conducted by slurry polymerization. The process according to Claim 1, wherein the cobalt-phosphine complex is cobalt bis(triphenylphosphine) dibromide, cobalt bis(triphenylphosphine) dichloride, cobalt bis(tri-m-methylphenylphosphine) dibromide, cobalt bis(tri-m-methylphenylphosphine) dichloride, cobalt bis(tri-p-methylphenylphosphine) dibromide, cobalt bis(tri-p-methylphenylphosphine) dichloride, cobalt bis(tri-p-methoxyphenylphosphine) dibromide, cobalt bis(tri-p-methoxyphenylphosphine) dichloride, cobalt bis (dicyclohexylphenylphosphine) dibromide, cobalt bis(dicyclohexylphenylphosphine) dichloride, cobalt bis(tri-m-dimethylphenylphosphine) dibromide, cobalt bis(3,5-dimethyl-4-methoxyphenylphosphine) dibromide or cobalt bis(3,5-dimethyl-4-methoxyphenylphosphine) dichloride. The process according to Claim 1, wherein the cobalt-phosphine complex is cobalt bis(triphenylphosphine) dibromide.

Inventors: GOTO KOHEI, HATTORI IWAKAZU, MICHINO YOSHIYUKI, OGASAHARA SHOJI, SHIBATA MASAHIRO, SHIONO TAKESHI, SOGA KAZUO, GOTO, KOHEI, HATTORI, IWAKAZU, MICHINO, YOSHIYUKI, OGASAHARA, SHOJI, SHIBATA, MASAHIRO, SHIONO, TAKESHI, SOGA, KAZUO
Applicants: JAPAN SYNTHETIC RUBBER CO LTD, JAPAN SYNTHETIC RUBBER CO., LTD.
Application year: 1992
Main classification: C08F136
IPC codes: C08F36, C08F4, C08F136