CN1076734C - Catalyst for preparing syndiotactic polystyrene - Google Patents

Abstract

The present invention relates to a catalyst for the preparation of syndiotactic polystyrene (sPS), comprising an organometallic titanium compound Cp ^* Ti(OCH ₂ CH=CR ₁ R ₂ ) ₃ and an alkylaluminoxane, wherein Cp ^* is five Methylcyclopentadienyl, R ₁ and R ₂ are hydrogen or an alkyl group containing 1 to 16 carbon atoms. When the catalytic system is used for the syndiotactic polymerization of styrene, it has high catalytic activity and catalytic efficiency, and the molecular weight can be controlled in a relatively high range (M _w =1.5×10 ⁵ ~1.0×10 ⁶ ), which can be used in industrial in production.

Description

Catalysts for the preparation of syndiotactic polystyrene

This invention relates to catalysts for the preparation of syndiotactic polystyrene.

Styrene polymers can be classified into atactic polystyrene (aPS), isotactic polystyrene (iPS) and syndiotactic polystyrene (sPS). The synthesis of syndiotactic polystyrene usually uses a catalytic system composed of organometallic titanium compounds and polymethylaluminoxane (MAO), in which the organometallic compounds are mainly titanocene compounds. Documents EP210615, US5252693, JP0291104 and EP389981 etc. report that the structure is CpTiCl ₃ /MAO, Cp ^* TiCl ₃ /MAO catalytic system is used in the case of syndiotactic polymerization of styrene, but its catalytic activity and catalytic efficiency are not high, and it is not suitable for industrial application .

The purpose of the present invention is to provide a new catalyst for preparing syndiotactic polystyrene in order to overcome the low catalytic activity and catalytic efficiency existing in the above-mentioned documents. The catalyst has high catalytic activity and catalytic efficiency, and the molecular weight It can be controlled in a relatively high range (M _w =1.5×10 ⁵ ~1.0×1O ⁶ ).

The purpose of the present invention is achieved by the following technical solutions: a catalyst for the preparation of syndiotactic polystyrene, comprising organometallic titanium compound I and alkylaluminoxane II:

Cp ^* Ti(OCH ₂ CH=CR ₁ R ₂ ) ₃ I

In the formula, Cp ^* is pentamethylcyclopentadienyl;

R ₁ is hydrogen or an alkyl group containing 1 to 16 carbon atoms;

_R2 is hydrogen or an alkyl group containing 1 to 16 carbon atoms;

R ₃ is an alkyl group containing 1 to 4 carbon atoms;

n is the degree of oligomerization of alkylaluminoxane, and its value is 6-40.

In the above-mentioned technical scheme, the preferred versions of _R1 and _R2 are hydrogen; the preferred version of _R3 is methyl. The preferred value of the degree of oligomerization n is 10-30, and the molar ratio of aluminum to organometallic titanium compound I in the alkylaluminoxane II is 50-2000.

Polyalkylaluminoxanes are prepared from alkylaluminum by controlled hydrolysis. The reactant water can be the water in the inorganic salt containing crystal water, and the inorganic salt containing crystal water can be CaCl ₂ 6H ₂ O, MgCl ₂ 6H ₂ O, CuSO ₄ 5H ₂ O, CaSO ₄ 2H ₂ O , Al ₂ (SO ₄ ) ₃ ·18H ₂ O, MgSO ₄ ·7H ₂ O, FeSO ₄ ·7H ₂ O, Ti(SO ₄ ) ₂ ·4H ₂ O, Ti ₂ (SO ₄ ) ₃ ·8H ₂ O and ZnSO ₄ ·7H ₂ O, etc. The molar ratio of trimethylaluminum (TMA) to water is 1:1-1:3, the reaction temperature is -20-100° C., and the reaction time is 10-40 hours. Commonly used aluminum alkyls include trimethylaluminum, triethylaluminum, and triisobutylaluminum. The specific steps are as follows: slowly add Al ₂ (SO ₄ ) ₃ ·18H ₂ O toluene dropwise at -20 to 0°C to mix the alkyl aluminum according to the molar ratio of Al/H ₂ O in the range of 1:1 to 1:2. solution, the dropwise addition time is 0.5 to 4 hours. Then gradually increase the temperature to 20-100° C., and continue the reaction at this temperature for 5-40 hours. The reaction mixture was filtered under the protection of nitrogen to remove the solid, and the solvent was evaporated under reduced pressure to obtain a white solid product, that is, an alkylaluminoxane with structure II.

The preparation method of the organometallic titanium compound I is as follows: it is prepared by reacting the corresponding pentamethylcyclocenetitanium trichloride with the corresponding alkenyl alcohol in the presence of a hydrogen chloride absorbent and using a hydrocarbon as a solvent. The hydrogen chloride absorbent can be various amine compounds, among which trialkylamine is suitable, such as triethylamine. Hydrocarbons can be aliphatic hydrocarbons or aromatic hydrocarbons, and it is better to use aromatic hydrocarbons, such as benzene, toluene, etc. The specific steps are: slowly add the mixed solution of triethylamine and corresponding alkenyl alcohol dropwise to the benzene solution of pentamethylcenyl titanium trichloride; The molar ratio is 1.0:3.0, the molar ratio of pentamethylcenyltitanium trichloride to triethylamine is 1.0:3.0-4.5, the reaction temperature is 0-50°C, and the reaction time is 4-30 hours. The solid was removed by filtration under the protection of an inert gas, the solvent was distilled off under reduced pressure, and the obtained crude product was extracted with hexane. After removing volatile matter, an orange-red mucus was obtained.

When R ₁ and R ₃ are both hydrogen, the elemental analysis of organometallic titanium compound I, the results of hydrogen nuclear magnetic resonance spectrum ¹ H NMR and carbon nuclear magnetic resonance spectrum ¹³ C NMR are shown in the following data:

Element analysis

Calcd for C ₁₉ H ₃₀ O ₃ Ti: C: 64.44; H: 8.47. Found: C: 64.13; H: 8.24

Proton NMR [ ¹ H NMR(CDCl ₃ TMS intern)]

δ1.34(s, 15H, Cp ^* ), 2.07～2.09(s, 6H, (OCH ₂ ) ₃ ); 7.42(s, 9H, (CH=CH ₂ ) ₃ ).

Carbon ¹³ NMR [ ¹³ C NMR(CDCl ₃ )]

δ11.3(—CH ₃ ), 74.5(—OCH ₂ —), 77.6～78.4(Cp ^* C), 121.3～128.1((CH＝CH ₂ ) ₃ ).

Mass spectrum [MS (m/z, % intensity)] 27 (CH=CH ₂ ⁺ ), 41 (CH ₂ CH=CH ₂ ⁺ ), 57 (OCH ₂ CH=CH ₂ ⁺ ), 64 (TiO ⁺ ), 79 (TiOCH ⁺ ), 93 (TiOCH ₂ CH ⁺ ), 107 (TiOCH ₂ CH=CH ₂ ⁺ ), 135 (C ₁₀ H ⁺ ₁₅ [Cp ^* ] ⁺ ), 183 (Cp ^* Ti ⁺ ), 199 (Cp ^* TiO ⁺ ), 240(Cp ^* TiOCH ₂ CH=CH ₂ ⁺ ), 297(Cp ^* Ti(OCH ₂ CH=CH ₂ ) ₂ ⁺ ), 354(Cp ^* Ti(OCH ₂ CH=CH ₂ ⁺ )).

Catalyst components I and II can be reacted at 0-50°C, preferably 30°C, under the protection of an inert gas (such as nitrogen, argon, etc.).

The polymerization reaction is carried out at 30-100°C, preferably 60-90°C. In order to obtain a polymer with ideal properties, the polymerization needs a certain time, ranging from a few minutes to several hours, preferably 0.5 to 6 hours. The ideal polymerization time depends on the polymerization temperature, solvent and other polymerization conditions. The polymerization method can adopt solution polymerization, slurry polymerization and bulk polymerization. For solution polymerization and slurry polymerization, the solvents used are aliphatic or aromatic hydrocarbons, such as hexane, heptane, cyclohexane, benzene, toluene, etc. The concentration of styrene in the solvent is in the range of 5-100%.

The present invention adopts a new organometallic titanium compound as the main catalyst for preparing syndiotactic polystyrene, so that the catalytic activity of the catalyst reaches 121 kg polymer/g titanium/hour, and the catalytic efficiency reaches 121 kg polymer/g titanium. The molecular weight of the compound can be adjusted in the range of M _w =1.5×10 ⁵ ~1.0×10 ⁶ , and good results have been achieved.

The present invention will be further elaborated below just by embodiment [embodiment 1]

Preparation of organometallic titanium compounds

Put 1.68g (5.63mmol) of pentamethylcenyl titanium trichloride into a dry 250ml reaction bottle protected by nitrogen, add 50ml of dry benzene, and slowly add 50ml of The dried benzene solution of 1.72g (16.9mmol) triethylamine and 0.98g (16.9mmol) allyl alcohol was allowed to react at a temperature of 30°C for 24h, and the solid was removed by filtration under nitrogen protection, the solvent was distilled off under reduced pressure, and then Extract with dry hexane at 40°C, let it stand at constant temperature for 4 hours, transfer the supernatant to a dry container under nitrogen protection, then distill off the solvent and volatiles under reduced pressure at 60°C to obtain 1.55 g of orange-red oil Product, yield 77.6%. Dubbed 0.02M toluene solution for later use. [Example 2]

Preparation of MAOs

Add 30g of milled Al ₂ (SO ₄ ) ₃ ·18H ₂ O and 80ml of toluene into a 500ml reactor equipped with electromagnetic stirring, and add 200ml of trimethyl Aluminum (TMA) solution in toluene. The dropping speed is 5ml/min, and the dripping is completed in 60 minutes. Then gradually increase the reaction temperature, reaching 60°C within 2h, and continue the reaction for 24h. The reaction mixture was filtered under the protection of nitrogen to remove the solid, and the filtrate was evaporated under reduced pressure at 30° C. to remove part of the solvent, and then evaporated to dryness under reduced pressure at 50° C. to obtain 15.4 g of white solid MAO with a yield of 39.0%. The content of TMA in MAO was determined to be 25.0% by ¹ H NMR, and the molecular weight of MAO was determined to be 1100 by freezing point depression method. [Example 3]

The airtight 100ml two-necked flask with the feeding hole and gas inlet tube was vacuum-dried and deoxygenated, and under the protection of nitrogen, 0.11g of MAO prepared in Example 2, 10ml of toluene and 0.1ml of the organometallic titanium compound prepared in Example 1 were added successively, 25 After magnetic stirring for 10 min at °C, 10 ml of styrene was injected. After polymerization at 80°C for 1 hour, the reaction was terminated with 10% ethanol hydrochloric acid solution to obtain 7.4 g of polymer with a catalytic activity of 7.72×10 ⁴ gPS/gTi.h, polymer molecular weight M _w =4.8×10 ⁵ , and syndiotacticity of 97 %, the melting temperature is 269.5°C. 【Example 4】

Preparation of organometallic titanium compounds

Put 1.16g (3.89mmol) pentamethylcenyl titanium trichloride into a dry, nitrogen-protected 150ml reaction bottle, add 30ml of dry benzene, and slowly add 30ml of The dry benzene solution of 1.78g (17.5mmol) triethylamine and 0.68g (11.7mmol) allyl alcohol was allowed to react at a temperature of 30°C for 24h, and the solid was removed by filtration under nitrogen protection, and the solvent was distilled off under reduced pressure. Then extract with dry hexane at 40°C, let stand at constant temperature for 4h, transfer the supernatant to a dry container under the protection of nitrogen, and then distill off the solvent and volatiles under reduced pressure at 60°C to obtain 1.12g of orange-red oily product. The rate is 88.1%. Dubbed 0.01M toluene solution for later use. [Example 5]

The airtight 100ml two-necked flask with the feeding hole and the gas inlet tube was vacuum-dried and deoxygenated, and under the protection of nitrogen, 17.5mg of MAO, 10ml of styrene, 0.15ml of 1M triisobutylaluminum hexane solution and 0.1ml of the organometallic titanium compound prepared in Example 4 was polymerized at 90°C for 1 hour, and the reaction was terminated with 10% ethanol hydrochloric acid solution to obtain 5.8g of a polymer with a catalytic activity of 1.21×10 ⁵ gPS/gTi.h, and a molecular weight of M _w =5.2×10 ⁵ , syndiotacticity is 98%, melting temperature is 270.2°C. [Example 6]

The airtight 100ml two-necked flask with the feeding hole and gas inlet tube was vacuum-dried and deoxygenated, and under the protection of nitrogen, 11.6mg of MAO, 10ml of styrene, 0.2ml of 1M triisobutylaluminum hexane solution and 0.1ml of the organometallic titanium compound prepared in Example 4 was polymerized at 90°C for 1 hour, and the reaction was terminated with 10% ethanol hydrochloric acid solution to obtain 4.8g of the polymer, with a catalytic activity of 1.0×10 ⁵ gPS/gTi.h, and a molecular weight of the polymer M _w =3.1×10 ⁵ , the syndiotacticity is 97%, and the melting temperature is 269.2°C. [Example 7]

Preparation of MAOs

Add 41.3g of milled Al ₂ (SO ₄ ) ₃ ·18H ₂ O and 80ml of toluene into a 500ml reactor equipped with electromagnetic stirring, and add 200ml of trimethylmethanol with a concentration of 3.1mol/L dropwise at -10°C aluminum (TMA) solution in toluene. The dropping speed is 5ml/min, and the dripping is completed in 60 minutes. Then gradually increase the reaction temperature, reaching 60°C within 2h, and continue the reaction for 24h. The reaction mixture was filtered under nitrogen to remove solids, and the filtrate was evaporated under reduced pressure at 30°C to remove part of the solvent, and then evaporated to dryness under reduced pressure at 50°C to obtain 12.3 g of white solid MAO, with a yield of 37.0%. The content of TMA in MAO was determined to be 20.0% by ¹ H NMR, and the molecular weight of MAO was determined to be 1210 by freezing point depression method. [Embodiment 8]

The airtight 100ml two-necked flask with the feeding hole and the gas inlet tube was vacuum-dried and deoxygenated, and under the protection of nitrogen, 0.11g of MAO prepared in Example 2, 10ml of toluene and 0.1ml of the organometallic titanium compound prepared in Example 1 were added successively, 30 After magnetic stirring for 10 min at °C, 10 ml of styrene was injected. After polymerization at 80°C for 2 hours, the reaction was terminated with 10% ethanol hydrochloric acid solution to obtain 2.1 g of polymer with a catalytic efficiency of 2.19×10 ⁴ gPS/gTi, polymer molecular weight M _w =6.1×10 ⁵ , and syndiotacticity of 98%. The melting temperature is 269.1°C.

Claims (6)

1. A catalyst for preparing syndiotactic polystyrene, comprising organometallic titanium compound I and alkylaluminoxane II: Cp ^* Ti(OCH ₂ CH=CR ₁ R ₂ ) ₃ I

In the formula, Cp ^* is pentamethylcyclopentadienyl; R ₁ is hydrogen or an alkyl group containing 1 to 16 carbon atoms; _R2 is hydrogen or an alkyl group containing 1 to 16 carbon atoms; R ₃ is an alkyl group containing 1 to 4 carbon atoms; n is the oligomerization degree of alkylaluminoxane, and its value is 6-40. 2. The catalyst for preparing syndiotactic polystyrene according to claim 1, characterized in that R ₁ is hydrogen. 3. The catalyst for preparing syndiotactic polystyrene according to claim 1, characterized in that R ₂ is hydrogen. 4. The catalyst for preparing syndiotactic polystyrene according to claim 1, characterized in that _R3 is methyl. 5. The catalyst for preparing syndiotactic polystyrene according to claim 1, characterized in that the degree of oligomerization n of the alkylaluminoxane ranges from 10 to 30. 6. The catalyst for preparing syndiotactic polystyrene according to claim 1, characterized in that the molar ratio of aluminum to organometallic titanium compound I in the alkylaluminoxane II is 50-2000.