CN1067689C - Metallocene catalyst for polymerizing high molecular weight polyethylene and preparation thereof - Google Patents

Abstract

A metallocene catalyst for synthesizing high-molecular-weight polyethylene and a preparation method thereof. The main catalyst is a compound with two molecules of tetrahydrofuran and 1,3-(1-indenyl)dihydrofuran generated from a transition metal halide in tetrahydrofuran. It is formed by the reaction of dilithium salt of siloxane. Adopting the catalyst of the present invention to carry out ethylene polymerization or ethylene-α-olefin (containing 3-12 carbon-α-olefin) copolymerization has high activity, and the polymer is a low-density polymer with ultra-high molecular weight and a high melting point of 120-140°C. vinyl.

Description

A metallocene catalyst for synthesizing high molecular weight polyethylene and its preparation method

The invention relates to a catalyst for synthesizing high molecular weight polyethylene and a preparation method thereof.

Ziegler-Natta heterogeneous catalysts have been used in industry to synthesize ultra-high molecular weight polyethylene with common alkylaluminum compounds as cocatalysts. Titanium compounds are mostly used, with magnesium chloride as the carrier, the titanium content in the catalyst is ~3wt%, the ethylene polymerization activity can reach one million times per mole of titanium (106g PE/MTi.h.bar), and the weight average molecular weight of PE is Mw 6 million (CN1076456A), but the molecular weight distribution is broad MWD > 14 (Journal of PolymerScience: PartA: Polymer Chemistry, 28,15-38 (1990).

Using a metallocene-based compound as the main catalyst and aluminoxane (usually methylaluminoxane, MAO) as a homogeneous catalyst system to synthesize polyethylene and linear low-density polyethylene is a new technology developed in recent years. It is characterized by high catalytic activity, narrow polymer MWD, neat branched chain structure, and good processing performance, but its molecular weight is generally low in phase catalytic systems. For example, in the Cp ₂ Z ₅ Cl ₂ /MAO system, the ethylene polymerization activity can reach 1×10 ⁶ g PE/MZr.h.bar, but its Mw does not exceed 300,000 (Polymer 35,4,808-818(1994), B-C The viscosity-average molecular weight Mη of the copolymer is less than 10,000. Even if it is polymerized at low temperature (-15°C), its Mw is only 150,000 (Macromolecules 27, 1325-1328 (1994), using ethylene bridged zirconocene The ethylene polymerization activity of Et(Ind) ₂ ZrCl ₂ /MAO system can reach 10 ⁷ , but the Mw is only below 20,000 (Macromol. The ethylene polymerization activity of the ₂ ZrCl ₂ (acac=Acetylacetonate)/MAO system is 1×10 ⁶ , and the Mw is about 500,000 (Macromol. Rapid Commun 15, 655-658 (1994).

The purpose of the present invention is to overcome the shortcoming that heterogeneous catalyst PE molecular weight distribution is wide and homogeneous catalyst PE molecular weight is low, and a kind of metallocene catalyst of synthesizing has the high polymerization activity of homogeneous catalytic system concurrently, and polymer has narrow molecular weight distribution and It has the high molecular weight possessed by the heterogeneous catalyst, and the ethylene polymerization activity in the homogeneous catalytic system composed of the metallocene catalyst and MAO of the present invention is nearly 10 ⁷ , and the polyethylene weight-average molecular weight can be adjusted from 1 to 2 million.

The metallocene catalyst for ethylene polymerization and ethylene-alpha-olefin copolymerization of the present invention includes two components of a main catalyst and a cocatalyst, wherein the main catalyst component is a transition metallocene group of the IV or V transition metal group containing a siloxane bridging group compound. has the following structure.

Mt=titanium Ti or zirconium Zr or hafnium Hf or vanadium V or niobium Nb or tantalum Ta.

Y ₁ and Y ₂ are respectively the same or different indenyl or tetrahydroindenyl or cyclopentadienyl or fluorenyl or the above groups with alkyl or silyl substituents.

R ₁ , R ₂ , R ₃ , and R ₄ are the same or different C ₁ -C ₁₀ alkyl or alkoxy groups or aryl groups, and the aryl groups are phenyl or substituted phenyl or aralkyl groups or Aryloxy. Preferably they are the same or different C ₁ -C ₃ alkyl or alkoxy groups.

X ₁ and X ₂ are the same or different halogens, preferably chlorine or alkyl or benzyl or alkoxy.

The catalyst can be 1,3-tetramethyldisiloxane bridged bis(1-indenyl)zirconium dichloride or 1,3-tetramethyldisiloxane bridged bis(1-tetrahydro Indenyl)zirconium dichloride or 1,3-tetramethyldisiloxane bridged bis(1-indenyl)titanium dichloride or 1,3-tetramethyldisiloxane bridged bis(1- Tetrahydroindenyl) titanium dichloride.

The cocatalyst component is an organoaluminum compound. Can be aluminoxanes and alkylaluminum compounds, said alumoxanes have the following structure

Where R=-CH ₃ ,-C ₂ H ₅ ,-i-Butyl, n=5-30;

Described aluminum alkyls have the following molecular formula

AlR _n X _3-n

where R=-CH ₃ ,-C ₂ H ₅ ,-i-Butyl

X=R,F,Cl,Br

n=1-3

Or a cation generating agent, the above-mentioned cation generating agent is an ion-pair compound containing tetraperfluorophenyl boron anion. has the following molecular formula

[Ph ₃ C] ⁺ [B(C ₆ F ₅ ) ₄ ] ^-

The preparation technology feature of catalyst of the present invention is as follows:

1. The catalyst of the present invention is prepared by reacting a compound (I) of a transition metal halide and tetrahydrofuran (THF) with a dilithium salt of 1,3-bis(1-indenyl)-disiloxane (II).

2. The transition metal halide is preferably chloride. A complex with two molecules of THF is generated in THF solvent and used as reactant (I) after separation.

3. Add 1,3-bis(1-indenyl)disiloxane dropwise to n-BuLi hexane solution in THF medium at -2°C-40°C, preferably at 0°C, in which 1,3-bis(1 -indenyl)disiloxane:n-BuLi=1:2～3 molar ratio, preferably 1:2. Raise the temperature to room temperature and react for 1-4h, preferably 2h, to obtain 1,3-bis(1-indenyl)disiloxanedilithium salt solution (II).

4. In the THF solution of (I), add the solution of (II) dropwise at 0°C-40°C, preferably at 25°C. After the addition, heat and reflux for 2-24h, preferably 12h. After removing the solvent, use Ether extraction yielded the product.

The present invention adopts the preparation method of the synthetic high molecular weight polyethylene of metallocene catalyst as follows:

Add organoaluminum compound, preferably methylaluminoxane, and metallocene catalyst respectively in toluene medium, and keep the molar ratio at 1000-5000, preferably at 2500, at -20-90°C, preferably at 20- At 60°C, carry out ethylene homopolymerization or ethylene-α-olefin copolymerization under ethylene atmosphere or in the presence of C ₃ -C ₁₂ α-olefin monomers. The polymerization time is 10 minutes to 3 hours. The polymerization reaction is terminated with acidified methanol, and polyethylene with an ultrahigh molecular weight of 1.5 million to 2 million is obtained after washing and drying.

Using the catalyst system of the present invention for ethylene polymerization or ethylene-α-olefin (α-olefin containing 3-12 carbons) copolymerization has a high activity of up to 10 ⁷ g PE/mol.Mt.h.bar, and the polymer has ultra-high The molecular weight Mw1-2 million is adjustable, the high melting point Tm is 120-140℃, the high crystallinity is 65-96%, the molecular weight distribution is narrow MWD2.7-5.2, and the low-density polyethylene with a density range of 0.91-0.925 can be synthesized.

Example 1: 1,3-Tetramethyldisiloxane bridged bis(1-indenyl)zirconium dichloride (catalyst 1)

To the suspension of 8.33g (22.08mmol) ZrCl ₄ ·2THF and 100mL THF, add dropwise 8g (22.08mmol) 1,3-bis(1-indenyl)tetramethyldisiloxane and 44.16mmoln-BuLi The dilithium salt solution prepared from alkane solution was heated to reflux for 12h. The solvent was evaporated _under reduced pressure, followed by extraction with _CH2Cl2 . The extract was concentrated to obtain a crude product. Recrystallization from CH ₂ Cl ₂ and petroleum ether gave 3.33 g (28.85%) rac-1 and 1.27 g (10.40%) meso-1.

rac-1:mp 195-6°C. C ₂₂ H ₂₄ Cl ₂ OSi ₂ Zr elemental analysis (%, calculated value):

C50.60 (50.55); H4.70 (4.63). m/z: 522 (M ⁺ , 38.85%).

^-1 HNMR (CDCl ₃ , TMS external standard, 200MHz), δ: 7.82(d,2H), 7.64(d,

2H),7.40-7.20(m,4H),6.68(d,J=3.6Hz,2H),6.08(d,J=3.6Hz,

2H), 0.65(s, 6H). 0.44(s,6H).

meso-1: ^-1 HNMR(CDCl ₃ , TMS external standard, 200MHz), δ:7.63(d,2H),7.48(d,2H),7.30-7.10(m,4H),7.02(d,J=3.4 Hz,2H),6.56(d,J=3.4Hz,2H),0.57(s,6H),0.50(s,6H). Homopolymerization of ethylene:

In a 250cc three-neck reaction flask equipped with stirring which has been replaced by nitrogen and ethylene, add 100ml of toluene distilled after the metal nano reflux to remove water, raise the temperature to 50°C under stirring, and feed ethylene to keep the reaction flask The internal pressure is 0.1MPa. Add 0.625ml MAO toluene solution (11.6wt%, 1.25mmole), stir for 5 minutes, then add catalyst 1 toluene solution (0.5μmole) Al/Zr. The molar ratio was 2500, and the ethylene pressure was kept constant for 60 minutes to polymerize, 10 ml of acidified methanol (3% HCl) was added to terminate the polymerization reaction, and excess ethanol was added to continue stirring for 1 hour. Filter and wash the polymer with acidified methanol, ethanol and distilled water, respectively. Vacuum drying at 60°C for 4 hours yielded 3.5 g of polymer. The weight-average molecular weight Mw is 513,000 g/mol by viscosity method, the melting point of polymer is Tm136.5°C by differential scanning calorimeter (DSC), the crystallinity X is 96.0%, and the density D is 0.9255g/ ^cm3 by density gradient instrument .

Example 2: As a comparative example of Example 1, add MAO 2.5mmole, Cp ₂ ZrCl ₂ , 1.0μmole, Al/Zr2500, polymerize at 50°C for 13 minutes to obtain 1.90g of polymer, measured Mw162000, Tm132.6°C The crystallinity is 91.8%, and the density is 0.9343.

Example 3-7 The polymerization conditions of Catalyst 1 and Example 1 are the same, and the polymerization results are shown in Table 1 at different polymerization temperatures.

Table 1 Ethylene polymerization of catalyst 1 at different temperatures example Catalyst (μmole) Al/Zr ratio time (minutes) temperature(℃) Polymer (g) Polymer Mw(10) Tm(°C) Crystallinity (%) MWD 34567 0.50.50.52.00.5 25002500250025002500 6060603060 806040200 1.173.271.8O4.251.34 7.430.078.6114.5l98.8 131.6134.6138.9139.6 89.595.687.687.6 2.69

Example 8: 1,3-tetramethyldisiloxane bridged bis(1-tetrahydroindenyl) zirconium dichloride (catalyst 2) was formed by 1,3-tetramethyldisiloxane bridged di (1-Indenyl) zirconium dichloride is obtained by hydrogenation and recrystallization.

Add 1.598g rac-1, 80mg PtO ₂ and 100mL CH ₂ Cl ₂ into a 250mL autoclave, and hydrogenate at 8.4MPaH ₂ for 8h at room temperature. After filtration, the filtrate was concentrated to dryness, and recrystallized with CH ₂ Cl ₂ and petroleum ether to obtain 1.164 g (71.73%) of light yellow crystal rac-2. mp130-1°C. C ₂₂ H ₃₂ Cl ₂ OSi ₂ Zr Elemental analysis (%, calculated): C 49.68 (49.78); H 6.14 (6.08). m/z: 530 (M ⁺ , 19.54%).

¹ HNMR (CDCl ₃ , TMS external standard, 90MHz), δ: 6.50(d,2H),6.00(d,2H),3.20-2.32(m,8H),1.92-1.52(m,8H),0.42(s ,6H), 0.32(s,6H). Similarly, meso-2 is obtained by hydrogenation of meso-1. mp 269-270°C. m/z: 530 (M ⁺ , 21%).

¹ HNMR (CDCl ₃ , TMS external standard, 90MHz), 6:6.74(d,2H),5.74(d,2H),3.26-2.26(m,8H),2.10-1.40(m,8H),0.36(s ,6H),0.30(s,6H).

Ethylene homopolymer

Using catalyst 22.0 μmole, MAO 5 m mole, Al/Zr molar ratio kept at 2500, polymerized at 60°C for 30 minutes, and other conditions were the same as those in Example 1 to obtain 3.09g of polymer, Hw 07,600, Tm131. 6°C, crystallinity 89.5%.

Embodiment 9-11, use catalyst 2 to complete polymerization result at different temperatures and list in table 2

Table 2. Ethylene polymerization of catalyst 2 at different temperatures example Catalyst (μmole) Al/Zr ratio time (minutes) temperature(℃) Polymer (g) Polymer Mw(10 ⁴ ) Tm(°C) Crystallinity (%) 91011 2.02.02.0 250025002500 303030 40200 5.705.431.4l 12.935.772.3 136.3 86.7

Example 12: 1,3-Tetramethyldisiloxane bridged bis(1-indenyl)titanium dichloride (catalyst 3)

To a suspension of 3,8g (11.38mmol) TiCl ₄ ·2THF and 50mLTHF, add dropwise a mixture of 4.139 (11.38mmO1) 1,3-bis(1-indenyl)tetramethyldisiloxane and 22.76mmoln-BuLi Dilithium salt solution prepared from alkane solution. Add completed, heated to reflux for 12h. After removing the solvent under reduced pressure, it was extracted with anhydrous ether. The extract was concentrated, and brown-black crystals were precipitated. Filtration afforded 0.8 g of 3 (14.66%). mp188-190°C. C ₂₂ H ₂₄ Cl ₂ OSi ₂ Ti elemental analysis (%, calculated value): C54.67 (55.12); H5.05 (5.05).

¹ HNMR (CDCl ₃ , TMS external standard, 400MHz), δ: 7.86(d, 8.0Hz, 2H, 7.61(d, 8.8Hz, 2H), 7.46(pseudo-t, 7.6Hz, 2H), 7.34(pseudo- t, 7.6Hz, 2H), 6.71(d, 2.8Hz, 2H), 5.88(d, 3.6Hz, 2H), 0.70(s, 6H), 0.39(s, 6H).

m/z: 478 (M ⁺ , 68.4%).

Example 13: 1,3-tetramethyldisiloxane bridged bis(1-tetrahydroindenyl)titanium dichloride (catalyst 4)

Add 0.55g 3, 100mg PtO2, 70mL CH ₂ Cl ₂ into a 100mL autoclave, fill with H ₂ to 7.1MPa, and stir at room temperature for 8h. Filter and remove the solvent to obtain the crude product. Recrystallized from CH ₂ Cl ₂ to obtain 40.49 g (88.18%) of dark red crystals. mp 133-4°C. C ₂₂ H ₃₂ Cl ₂ OSi ₂ Ti elemental analysis (%, calculated value): C54.16 (54.22); H6.77 (6.62).

¹ HNMR (CDCl ₃ , TMS external standard, 90MHz), δ: 6.60(d, 3.6Hz, 2H), 5.88(d, 3.6Hz, 2H), 3.22-2.34(m, 8H), 1.82-1.30(m, 8H), 0.30(s, 6H). 0.17(s,6H). m/z:486(M ⁺ ,7%)

Ethylene homopolymer

Catalyst 41.0 μmole, MAO 3 mmole, Al/Zr molar ratio kept at 3000, polymerized at 50°C for 30 minutes, and other conditions were the same as those in Example 1 to obtain 0.22 g of polymer with Mw of 5,500.

Examples 14-17, using Catalyst 4 to complete the polymerization at different temperatures, the results are listed in Table 3.

Table 3. Ethylene polymerization of catalyst 4 at different temperatures example Catalyst (μmole) Al/Zr ratio time (minutes) temperature(℃) Polymer (g) Polymer Mw(10 ⁴ ) Tm(°C) Crystallinity (%) 14151617 1.01.01.01.0 3000300030003000 30303030 4030200 0.511.101.720.64 1.564.164.7421.4 135.0 79.7

Example 18: Copolymerization of ethylene-hexene-1 with catalyst 1 Add 4.0ml of hexene, 2.5mmole of MAO and 1.0μmole of catalyst 1 in 100ml of toluene solvent, Al/Zr2500 and keep the temperature at 50°C. The polymerization time was 30 minutes, and 2.0 g of polymer was obtained. Mw measured by viscosity method was 106,000 g/mol, Tm measured by DSC was 121.6°C, crystallinity was 65.3%, and density was measured to be 0.9190 g/cm ³ .

Example 19: As a comparative example of Example 18, under the conditions of Example 18, 4.0 hexene, 2.5 mmole of MAO, and the catalyst Cp ₂ ZrCl ₂ , 1.0 μmole, Al/Zr2500, and a constant temperature of 50 ° C were sequentially added to the toluene solvent. The polymerization time was 20 minutes to obtain 0.67 g of polymer with Mw of 5,700, Tm of 111.2°C, crystallinity of 65.4%, and density of 0.9245.

Example 20-22 Same as Example 18, complete ethylene-hexene-1 copolymerization with catalyst 1 under different hexene-1 additions, the results are shown in Table 4.

Table 4. Catalyst 1 Ethylene-hexene-1 copolymerization example Catalyst Hl addition amount Polymer Polymer (μmole) (ml) (g) Mw Tm Crystallinity D(10 ⁴ ) (°C) (%) (g/cm ⁴ )20 1.0 0.8 3.0 26.5 129.5 80.121 1.0 1.2 2.6 18.7 127.5 70.5 0.921322 1.0 2.4 2.2 13.8 123.7 69.1 0.9198

Example 23: Ethylene-Octene-1 Copolymerization Using Catalyst 1

As in Example 18, octene-11.0me, MAO2.5mmole, and catalyst 11.0μmole were sequentially added to the toluene solvent, and the ethylene pressure was maintained at 0.1MPa at 50°C. Polymerize for 10 minutes to obtain 1.53 g of polymer, Mw 354,000, Tm 131.7°C, crystallinity 76.5%, and density 0.9231.

Examples 24-27, using different octene-1 additions to complete the copolymerization results are shown in Table 4, and the conditions are the same as Example 23.

^Table 5. ^Catalyst 1 Copolymerization example at different octene concentrations 24 2.0 1.01 23.1 128.3 85.0 4.2 0.920025 4.0 0.91 19.1 126.8 81.1 0.917326 6.0 0.53 11.8 125.4 84.4 0.919227 8.0 0.59 9.6 9.6 120.9

Claims (9)

1. metalloscene catalyst that is used for the synthetic macromolecule weight northylen, it is characterized in that described catalyzer comprises Primary Catalysts and two kinds of components of promotor, described Primary Catalysts is to contain the IV of silica support bridge linkage group or the cyclopentadienyl compound of V transiting metal group, has following structure:

Mt=titanium Ti or zirconium Zr or hafnium Hf or vanadium V or niobium Nb or tantalum Ta,

Y ₁, Y ₂Be respectively identical or different indenyl or tetrahydro indenyl or cyclopentadienyl or fluorenyl or have alkyl or the substituent above-mentioned group of silylation,

R ₁, R ₂, R ₃, R ₄Be respectively identical or different C ₁～C ₁₀Alkyl or alkoxyl group or aryl, described aryl is phenyl or substituted-phenyl or aralkyl or aryloxy,

X ₁And X ₂Be respectively identical or different halogen or alkyl or benzyl or alkoxyl group,

Described promotor is that organo-aluminium compound or positively charged ion generate agent.

2. a kind of metalloscene catalyst that is used for the synthetic macromolecule weight northylen according to claim 1 is characterized in that described R ₁, R ₂, R ₃, R ₄Be identical or different C ₁-C ₃Alkyl or alkoxyl group.

3, a kind of metalloscene catalyst that is used for the synthetic macromolecule weight northylen according to claim 1, it is characterized in that described catalyzer is 1,3-tetramethyl-two silica support bridging two (1-indenyl) zirconium dichloride or 1,3-tetramethyl-two silica support bridging two (1-tetrahydro indenyl) zirconium dichloride or 1,3-tetramethyl-two silica support bridging two (1-indenyl) titanium dichloride or 1,3-tetramethyl-two silica support bridging two (1-tetrahydro indenyl) titanium dichloride.

4, a kind of metalloscene catalyst that is used for the synthetic macromolecule weight northylen according to claim 1 is characterized in that described halogen is the chlorine element.

5, a kind of metalloscene catalyst that is used for the synthetic macromolecule weight northylen according to claim 1 is characterized in that described organo-aluminium compound is alumina alkane or alkylaluminium cpd.

6, a kind of metalloscene catalyst that is used for the synthetic macromolecule weight northylen according to claim 1 is characterized in that it is the ion-pair compound that contains four perfluorophenyl boron anions that described positively charged ion generates agent.

7, a kind of method for making that is used for the metalloscene catalyst of synthetic macromolecule weight northylen, it is characterized in that Primary Catalysts in the claim 1 is the mixture (I) and 1 by transition metal halide and tetrahydrofuran (THF) (THF), two lithium salts (II) of 3-two (1-indenyl)-two silica support react and form.

8, a kind of method for making that is used for the metalloscene catalyst of synthetic macromolecule weight northylen according to claim 7 is characterized in that described transition metal halide is a muriate.

9, a kind of method for making that is used for the metalloscene catalyst of synthetic macromolecule weight northylen according to claim 7, it is characterized in that described Primary Catalysts 1,3-tetramethyl-two silica support bridging two (1-tetrahydro indenyl) zirconium dichloride is by 1, zirconium dichloride is through hydrogenation for 3-tetramethyl-two silica support bridgings two (1-indenyl), and recrystallization makes.