Catalyst for polymerizing aromatic vinyl compound and process for producing polymer of aromatic vinyl compound

Abstract: A catalyst for polymerizing an aromatic vinyl compound, comprising a transition metal compound as a catalyst component (A) represented by the general formula (1): where M is an element of Transition Group IV; X¹ and X² are respectively halogen; R¹, R², R³, R⁴, R⁵ and R⁶ are respectively hydrogen or an alkyl group of from 1 to 6 carbon atoms; and m is an integer of 1 to 6; and an aluminoxane as a catalyst component (B) represented by the general formula (2) or (3): where n is an integer of from 4 to 60; and R⁷ is an alkyl of from 1 to 6 carbon atoms, phenyl or benzyl, preferably methyl, and a process for producing a polymer of an aromatic vinyl compound, comprising polymerizing the aromatic vinyl compound in the presence of the catalyst.

Description: The present invention relates to a catalyst for polymerizing an aromatic vinyl compound, and a process for producing a polymer of the aromatic vinyl compound. More particularly, the present invention relates to a catalyst and a process for producing a polymer of an aromatic vinyl compound mainly in syndiotactic configuration with high catalyst activity. Polymers of aromatic vinyl compounds include polymers of three types of configuration, namely syndiotactic, isotactic and atactic polymers. Among them, polymers of syndiotactic configuration are useful as heat-resistant polymers because of the higher melting point and the larger crystallization rate in comparison with polymers in other types of configuration. A syndiotactic polymer of an aromatic vinyl compound was produced, for example, by employing a catalyst composed of a titanium compound such as titanium halide and alkoxytitanium and a reaction product of an organoaluminum compound with a condensing agent such as a methylaluminoxane as disclosed in Japanese Patent Application Laid-Open No. Sho 62-104818. The catalyst systems of prior art, however, exhibit unsatisfactorily low catalytic activity, and are required to be improved substantially in the catalyst activity. Additionally, methylaluminoxane which is a reaction product of an organic aluminum compound with water as a condensing agent is extremely expensive, so that the amount to be used of the methylaluminoxane is desired to be less in view of the cost. The present invention intends to provide a catalyst for producing a polymer of an aromatic vinyl compound mainly constituted in syndiotactic configuration with high catalyst activity, and a process for producing the polymer. The present invention provides a catalyst for producing an aromatic vinyl compound, comprising a transition metal compound as a catalyst component (A) represented by the general formula (1): where M is an element of Transition Group IV; X¹ and X² are respectively halogen; R¹, R², R³, R⁴, R⁵ and R⁶ are respectively hydrogen or an alkyl group of from 1 to 6 carbon atoms; and m is an integer of 1 to 6; and an aluminoxane as a catalyst component (B) represented by the general formula (2) or (3): where n is an integer of from 4 to 60; and R⁷ is an alkyl group, a phenyl group or a benzyl group. The present invention also provides a process for producing a polymer of an aromatic vinyl compound in syndiotactic configuration with high catalyst activity by employing the above specified catalyst. The component (A) of the catalyst for polymerizing an aromatic vinyl compound of the present invention is a transition metal compound represented by the general formula below: where M is an element of Transition Group IV; X¹ and X² are respectively halogen; R¹, R², R³, R⁴, R⁵ and R⁶ are respectively hydrogen or an alkyl group of from 1 to 6 carbon atoms; and m is an integer of 1 to 6. The transition metal (M) is an element of Transition Group IV of the periodic table, including titanium, zirconium, and hafnium, of which titanium is preferable. X¹ and X² are respectively a halogen, preferably chlorine. The substituents, R¹ to R⁶, are respectively hydrogen or an alkyl of 1 to 6 carbons. The alkyl of 1 to 6 carbons include specifically linear and branched alkyl groups such as methyl, ethyl, propyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, n-hexyl and isohexyl. The size (m) of the bridge between the two cyclopentadienyl rings is from 1 to 6, preferably from 1 to 2. The catalyst component (A) specifically includes methylene-bis(cyclopentadienyl)titanium dichloride and ethylene-bis(2,3,4,5-tetramethylcyclopentadienyl)titanium dichloride. The catalyst component (B) is an aluminoxane represented by the general formula (2) or (3): R⁷ is an alkyl of from 1 to 6 carbon atoms, phenyl or benzyl, preferably methyl. "n" is an integer of from 4 to 60, preferably not less than 6. These compounds may be commercial products, or may be prepared according to a known method. The preparation of the compound is conducted, for example, by adding an aluminum compound into a suspension of a crystalline-water-containing salt (such as copper sulfate hydrate or aluminum sulfate hydrate) in a hydrocarbon medium. The ratio of the catalyst component (B) to the catalyst component (A) to be used, [(B)/(A)], is within the range of from 10 to 1000 in molar ratio. With the catalyst system of the present invention, polymers of sufficiently high stereoregularity can be obtained at the molar ratio, Al/Ti, of less than 300, or further, as low as less than 100. The aromatic vinyl compounds to be polymerized in the present invention include styrene or derivatives thereof. The derivatives of styrene include alkylstyrenes such as methylstyrene, ethylstyrene and dimethylstyrene; halogenated styrenes such as chlorostyrene, bromostyrene and fluorostyrene; halogen-substituted alkylstyrenes such as chloromethylstyrene; alkoxystyrenes such as methoxystyrene; carboxymethylstyrene, alkyl ether styrene and alkylsilylstyrene. The polymerization of the aromatic vinyl compound in the presence of the aforementioned catalyst in the present invention may be conducted in bulk, or in a medium of an aliphatic hydrocarbon such as pentane, hexane and heptane; an alicyclic hydrocarbon such as cyclohexane; or an aromatic hydrocarbon such as benzene, toluene and xylene. The catalyst component (A) is used at a concentration in the range of from 0.1 to 1000 mmol/l in the solution. The polymerization temperature is not specially limited, but preferably in the range of from -70°C to 150°C. As described above, the use of the catalyst of the present invention gives a polymer of an aromatic vinyl compound having syndiotactic configuration with a high catalyst activity. Further, the catalyst system of the present invention exhibits not only improved activity of the main catalyst but also sufficient effect at a less amount of aluminoxane as the cocatalyst in comparison with the catalyst systems of prior art, and is advantageous economically. Example 1 In a Schlenk type reaction vessel having been purged with nitrogen, 26.2 mg (0.10 mmol) of methylene-bis(cyclopentadienyl)titanium dichloride was weighed out, and 10 ml of toluene was added. Further thereto, 15.0 g (144 mmol) of styrene, and 4 mmol of methylaluminoxane (made by Tosoh-Akzo Co.) were added, and polymerization was conducted at 15°C for 5 hours. At the end of the reaction, 0.5 ml of methanol was added to decompose the catalyst. The reaction product was put into a mixture of 200 ml of methanol with 2 ml of hydrochloric acid, and was stirred sufficiently. The resulting white polymer was collected by filtration, and washed with 50 ml of methanol twice. The yield of the dried polymer was 13.7 g. Subsequently the polymer was extracted with methyl ethyl ketone by Soxhlet extraction for 12 hours, giving 12.1 g of a residual polymer. The resulting polymer had a weight-average molecular weight of 52000 and a number-average molecular weight of 14000 according to gel permeation chromatography (GPC), and had a melting point of 267°C according to DSC measurement. Configuration analysis of the polymer by ¹³C-NMR in o-dichlorobenzene showed that the polymer had the pentad rrrr at a level of not less than 99% as calculated from the peak of 145.5 ppm originating from the syndiotactic configuration. Example 2 In a Schlenk type reaction vessel having been purged with nitrogen, 26.2 mg (0.10 mmol) of methylene-bis(cyclopentadienyl)titanium dichloride was weighed out, and 20 ml of toluene was added. Further thereto, 13.6 g (131 mmol) of styrene, and 20 mmol of methylaluminoxane (made by Tosoh-Akzo Co.) were added, and polymerization was conducted at 15°C for 5 hours. At the end of the reaction, 0.5 ml of methanol was added to decompose the catalyst. The reaction product was put into a mixture of 200 ml of methanol with 2 ml of hydrochloric acid, and was stirred sufficiently. The resulting white polymer was collected by filtration, and washed with 50 ml of methanol twice. The yield of the dried polymer was 12.0 g. Subsequently the polymer was extracted with methyl ethyl ketone by Soxhlet extraction for 12 hours, giving 11.1 g of a residual polymer. Configuration analysis of the polymer by ¹³C-NMR in o-dichlorobenzene showed that the polymer had the pentad rrrr at a level of not less than 99% as calculated from the peak of 145.5 ppm originating from the syndiotactic configuration. Example 3 In a Schlenk type reaction vessel having been purged with nitrogen, 38,7 mg (0.10 mmol) of ethylene-bis(2,3,4,5-tetramethylcyclopentadienyl)titanium dichloride was weighed out, and 10 ml of toluene was added. Further thereto, 13.6 g (131 mmol) of styrene, and 4 mmol of methylaluminoxane (made by Tosoh-Akzo Co.) were added, and polymerization was conducted at 15°C for 5 hours. At the end of the reaction, 0.5 ml of methanol was added to decompose the catalyst. The reaction product was put into a mixture of 200 ml of methanol with 2 ml of hydrochloric acid, and was stirred sufficiently. The resulting white polymer was collected by filtration, and washed with 50 ml of methanol twice. Subsequently the polymer was extracted with methyl ethyl ketone by Soxhlet extraction for 12 hours, giving 0.113 g of a residual polymer. Configuration analysis of the polymer by ¹³C-NMR in o-dichlorobenzene showed that the polymer had the pentad rrrr at a level of 96% as calculated from the peak of 145.5 ppm originating from the syndiotactic configuration. Comparative Example 1 Polymerization of styrene was conducted in the same manner as in Example 1 except that 0.10 mmol of titanocene dichloride was used in place of the methylene-bis(cyclopentadienyl)titanium dichloride. As the result, the yield of the dried polymer was 0.062 g. Comparative Example 2 Polymerization of styrene was conducted in the same manner as in Example 1 except that 0.10 mmol of pentamethylcyclopentadienyltitanium dichloride was used in place of the methylene-bis(cyclopentadienyl)titanium dichloride. As the result, the yield of the dried polymer was 0.063 g.

Claims: A catalyst for polymerizing an aromatic vinyl compound, comprising a transition metal compound as a catalyst component (A) represented by the general formula (1): where M is an element of Transition Group IV; X¹ and X² are respectively halogen; R¹, R², R³, R⁴, R⁵ and R⁶ are respectively hydrogen or an alkyl group of from 1 to 6 carbon atoms; and m is an integer of 1 to 6; and an aluminoxane as a catalyst component (B) represented by the general formula (2) or (3): where n is an integer of from 4 to 60; and R⁷ is an alkyl of from 1 to 6 carbon atoms, phenyl or benzyl. A process for producing a polymer of an aromatic vinyl compound, comprising polymerizing the aromatic vinyl compound in the presence of a catalyst comprising a transition metal compound as a catalyst component (A) represented by the general formula (1): where M is an element of Transition Group IV; X¹ and X² are respectively halogen; R¹, R², R³, R⁴, R⁵ and R⁶ are respectively hydrogen or an alkyl group of from 1 to 6 carbon atoms; and m is an integer of 1 to 6; and an aluminoxane as a catalyst component (B) represented by the general formula (2) or (3): where n is an integer of from 4 to 60; and R⁷ is an alkyl of from 1 to 6 carbon atoms, phenyl or benzyl. A catalyst according to claim 1, wherein R⁷ in the general formula (2) or (3) of catalyst component (B) is methyl. A process according to claim 2, wherein R⁷ in the general formula (2) or (3) of catalyst component (B) is methyl.

Inventors: MIYASHITA AKIRA, MIYASHITA, AKIRA
Applicants: TOSOH CORP, TOSOH CORPORATION
Application year: 1991
Main classification: C08F4
IPC codes: C08F4, C08F12, C07F7