RU2303608C1 - Method of producing superhigh-molecular weight polyethylene - Google Patents

Abstract

FIELD: polymer production.

SUBSTANCE: superhigh-molecular weight polyethylene is obtained in suspension conditions at temperature between 40 and less than 70°C in hydrocarbon solvent medium using supported catalyst. The latter is prepared through interaction of compound Mg(C₆H₅)2_n*MgCl₂*mR₂O (R₂O is ether, R = i-Am, n-Bu) with silicon compound, which is a product prepared by reaction of compound R¹kSiCl_4-k with silicon tetraethoxide Si(OR)₄ (R¹ represents methyl or phenyl and k=0.1) at molar ratio R¹kSiCl_4-k/Si(OR)4 = 2-4 at 15-45°C and Si/Mg = 1-2.5. Loose weight of obtained polymer is higher than 0.35 g/cc.

EFFECT: increased yield of superhigh-molecular weight polyethylene with improved morphology.

1 tbl, 13 ex

Description

The present invention relates to a method for producing ultra-high molecular weight polyethylene (UHMWPE) by suspension polymerisation of ethylene in a hydrocarbon solvent using a supported Ziegler-type catalyst containing a titanium compound on a magnesium-containing support.

To obtain ultra-high molecular weight polyethylene by the suspension method, supported Ziegler-type catalysts containing titanium chlorides and magnesium chlorides obtained by various methods can be used. In this case, ethylene polymerization is carried out in the absence of hydrogen at polymerization temperatures of ≤70 ° C to obtain PE with a molecular weight of more than 1 · 10 ⁶ g / mol (the intrinsic viscosity determined in decalin at 135 ° C is more than 10 dl / g). The polymerization is carried out in the presence of cocatalyst - aluminum trialkyl. An important requirement for the catalyst for the synthesis of UHMWPE is the ability to obtain UHMWPE powder with an average particle size of less than 200 microns, a narrow particle size distribution and increased bulk density. For this, it is necessary to use supported catalysts having an average particle size of less than 10 microns, a narrow particle size distribution and low porosity.

UHMWPE can be obtained in the presence of a catalyst obtained by the method of [JP 59-53511, B01J 31/32, 1986]. This catalyst contains magnesium chloride as a carrier, obtained by reacting a solution of the compound MgCl ₂ · 3i-C ₈ H ₁₇ OH in a hydrocarbon diluent with TiCl ₄ in the presence of an electron-donor compound (ethyl benzoate, ethylanisate and others). The catalyst obtained in this way is characterized by a particle size of 5-10 μm, has a fairly high activity (up to 35 kg / g PE g Ti h atm C ₂ H ₄ ) and allows to obtain polyethylene powder with a narrow granulometry and high bulk density. The disadvantage of this catalyst is the use of low temperatures (up to -20 ° C) in its preparation, the use of large quantities of liquid TiCl ₄ as a reaction medium, and the release of a significant amount of hydrogen chloride during the synthesis of the catalyst.

Known supported catalyst for the polymerization of ethylene, obtained by the interaction of a magnesium-aluminum-alkyl compound of the composition RMgR '· nAlR ₃ "· mD with chlorocarbon and the subsequent interaction of the obtained solid product (carrier) with titanium halide [DE 3626060, B01J 31/32, 1987]. in this case, (n-Bu) Mg (i-Bu) or (n-Bu) Mg (Oct), which are soluble in hydrocarbons, are used as the organomagnesium compound RMgR ', and tret-BuCl is preferably used as the chlorohydrocarbon. the way is their lack A surprisingly high activity in suspension polymerization of ethylene and a large particle size (more than 10 microns).

The closest is the process of suspension polymerization of ethylene, including UHMWPE, in the presence of a supported catalyst containing a transition metal compound (TiCl ₄ , VOCl ₃ , VCl ₄ ) on a support of MgCl ₂ mR ₂ O composition obtained by the interaction of an organomagnesium compound (MOS) of Mg composition (C ₆ H ₅ ) ₂ · nMgCl ₂ · mR ₂ O (n = 0.37-0.7, m = 2, R ₂ 0 - ether with R = i-Am, n-Bu) with carbon tetrachloride [RF 2064836, B01J 31/38, 08/10/96]. The catalysts synthesized by this method have a controlled particle size in the region of 5-30 μm and a narrow particle size distribution. These catalysts make it possible to obtain polymers with a controlled particle size and a narrow particle size distribution and increased bulk density while maintaining high activity in the suspension polymerisation of ethylene, including UHMWPE, with an average particle size of less than 200 microns.

However, these catalysts have a number of significant disadvantages in the production of UHMWPE. The main disadvantages of these catalysts are:

1. The relatively low level of catalyst activity at polymerization temperatures of 50-65 ° C, which are necessary to obtain PE with a molecular weight of more than 1 million

2. The relatively low bulk density of UHMWPE obtained at polymerization temperatures of 50-65 ° C.

In the claimed invention, the task is to develop a method of producing ultra-high molecular weight UHMWPE polyethylene with high yield and high bulk density by the method of suspension polymerization through the use of special modifications of titanium-magnesium catalysts.

This problem is solved in that the ultra-high molecular weight UHMWPE polyethylene is obtained in suspension mode at a temperature of 40-70 ° C in a hydrocarbon solvent using a supported catalyst containing a titanium compound on a magnesium-containing support in combination with cocatalyst. The carrier is prepared by reacting a solution of an organomagnesium compound of the composition Mg (C ₆ H ₅ ) ₂ · nMgCl ₂ · mR ₂ O (n = 0.37-0.7, m = 2, R ₂ O — ether with R = i-Am, n-Bu) with a silicon compound, a product obtained by reacting a compound of the composition R ¹ _k SiCl _4-k with silicon tetraethoxide Si (OR) ₄ is used as a silicon compound, where: R ¹ = methyl or phenyl; k = 0.1, with a molar ratio of R ¹ _x SiCl _4-x / Si (OR) ₄ = 2-4 at a temperature of 15-45 ° C and with a ratio of Si / Mg = 1-2.5.

The proposed method provides for the production of polyethylene with high activity (100-1000 kg PE / g Ti hour) and with a high bulk density of 0.35-0.45 g / cm ³ .

The polymerization is carried out in suspension mode at a temperature of 40 - less than 70 ° C in a hydrocarbon solvent (e.g. hexane, heptane), ethylene pressure ≥1 bar in the presence of a cocatalyst - aluminum trialkyl (triisobutylaluminum or triethylaluminum).

The invention is illustrated by the following examples.

Example 1

(A) Preparation of a solution of an organomagnesium compound.

In a 1 liter glass reactor equipped with a stirrer and a thermostatic device, 29.2 g of powdered magnesium (1.2 mol) in 450 ml of chlorobenzene (4.4 mol), 203 ml of dibutyl ether (1.2 mol) and an activating agent, which is a solution of 0.05 g of iodine in 3 ml of butyl chloride. The reaction is carried out in an inert gas atmosphere (nitrogen, argon) at a temperature of from 80 to 100 ° C for 10 hours. At the end of the reaction, the resulting reaction mixture is settled and the liquid phase is separated from the precipitate. The liquid phase is a solution in chlorobenzene of an organomagnesium compound with the composition MgPh ₂ · 0.49 · MgCl ₂ · 2 (C ₄ H ₉ ) ₂ O with a concentration of 1.0 mol Mg / L.

(B) Carrier synthesis

200 ml of the resulting solution (0.2 mol Mg) is loaded into a stirred reactor and a solution of 123 ml of a mixture of SiCl ₄ with Si (OEt) _{4 is} dispensed into the reactor for 15 hours at a molar ratio of 3: 1 in 200 ml of decane ( Si / Mg = 1.8). Then the reaction mixture is heated to 60 ° C for 30 minutes and kept at this temperature for 1 hour. The mother liquor is removed and the precipitate formed is washed with heptane 4 times in 250 ml each at a temperature of 20 ° C. Obtain 33 g of powdered magnesium-containing media in the form of a suspension in heptane.

To the resulting suspension of a magnesium-containing support in 150 ml of heptane was added 22 ml of TiCl ₄ (TiCl ₄ / Mg = 1), the reaction mixture was heated to 70 ° C and kept under stirring for 2 hours, then the solid precipitate was settled and washed with heptane at a temperature of 60- 70 ° C 5 times in 200 ml. Get supported catalyst with a titanium content of 3 wt.%.

Ethylene is polymerized in a 0.8 L steel reactor equipped with a stirrer and a thermostatic jacket. Heptane (250 ml) and cocatalyst-triethylaluminium (AlEt ₃ ) with a concentration of 5 mmol / L are used as a solvent for polymerization. The polymerization is carried out at a temperature of 65 ° C, an ethylene pressure of 4 atm for 2 hours. The polymerization results are shown in the table.

Example 2

The catalyst was prepared under the conditions of Example 1 except that methyl trichlorosilane MeSiCl _{3 was} used instead of SiCl ₄ . The catalyst contains 2.9 wt.% Titanium. The polymerization of ethylene is carried out under the conditions of example 1. The polymerization results are shown in the table.

Example 3

The synthesis of the catalyst is carried out analogously to example 2. The polymerization of ethylene is carried out under the conditions of example 1 except that the polymerization temperature is 50 ° C. The polymerization results are shown in the table.

Example 4

The synthesis of the catalyst is carried out analogously to example 1 except that phenyltrichlorosilane PhSiCl _{3 is} used instead of SiCl ₄ . The polymerization of ethylene is carried out under the conditions of example 1 except that the polymerization temperature is 60 ° C, and triisobutylaluminum (TIBA) is used as a cocatalyst. The polymerization results are shown in the table.

Example 5

The synthesis of the catalyst is carried out analogously to example 2 except that the interaction of the organomagnesium compound with a mixture of MeSiCl ₃ / Si (OEt) ₄ (3: 1) is carried out at a temperature of 45 ° C. The catalyst contains 2.7 wt.% Titanium. The polymerization of ethylene is carried out under the conditions of example 1. The polymerization results are shown in the table.

Example 6

The synthesis of the catalyst is carried out analogously to example 2 except that the interaction of the organomagnesium compound with a mixture of MeSiCl ₃ / Si (OEt) ₄ (3: 1) is carried out at a ratio of Si / Mg = 1. The catalyst contains 2.4 wt.% Titanium. The polymerization of ethylene is carried out under the conditions of example 1 except that the polymerization temperature is 60 ° C. The polymerization results are shown in the table.

Example 7

The catalyst obtained in example 6 is used in the polymerization of ethylene under the conditions of example 1, except that the polymerization temperature is 40 ° C. The results are shown in the table.

Example 8

The synthesis of the catalyst is carried out analogously to example 2 except that the interaction of the organomagnesium compound with a mixture of MeSiCl ₃ / Si (OEt) ₄ (3: 1) is carried out at a ratio of Si / Mg = 2.5. The catalyst contains 2.4 wt.% Titanium. The polymerization of ethylene is carried out under the conditions of example 1. The polymerization results are shown in the table.

Example 9

The synthesis of the catalyst is carried out analogously to example 2 except that the interaction of the organomagnesium compound with a mixture of MeSiCl ₃ / Si (OEt) _{4 is} carried out at a ratio of MeSiCl ₃ / Si (OEt) ₄ equal to 2: 1. The catalyst contains 2.9 wt.% Titanium. The polymerization of ethylene is carried out under the conditions of example 1. The polymerization results are shown in the table.

Example 10

The synthesis of the catalyst is carried out analogously to example 2 except that the interaction of the organomagnesium compound with a mixture of MeSiCl ₃ / Si (OEt) _{4 is} carried out at a ratio of MeSiCl ₃ / Si (OEt) ₄ equal to 4: 1. The catalyst contains 2.4 wt.% Titanium. The polymerization of ethylene is carried out under the conditions of example 1. The polymerization results are shown in the table.

Example 11

The synthesis of the catalyst is carried out analogously to example 2, except that the support is additionally treated with diethylaluminium chloride at a molar ratio Al / Mg = 1.5 at a temperature of 40 ° C for 1 h, then the support is repeatedly washed with heptane and titanium tetrachloride is applied at a rate of 0.1 wt% titanium. The catalyst contains 0.16 wt.% Titanium. The polymerization of ethylene is carried out under the conditions of example 5 except that the ethylene pressure is 3 atm. The polymerization results are shown in the table.

Example 12. Comparative

The catalyst was prepared under the conditions of Example 1 except that PhSiCl _{3 was used} with Si / Mg = 1.8 to interact with the organomagnesium compound in the preparation of the support. The carrier is treated with titanium tetrachloride at 110 ° C. The catalyst contains 4.0 wt.% Titanium. The polymerization of ethylene is carried out under the conditions of example 3. The polymerization results are shown in the table.

Example 13. Comparative

The catalyst was prepared under the conditions of Example 1 except that, in accordance with the prototype [RF 2064836, B01J 31/38, 08/10/96], carbon tetrachloride was used at a ratio of CCl _{4 /} Mg = 1.6 to interact with the organomagnesium compound in the preparation of the support. The carrier is treated with titanium tetrachloride at 110 ° C. The catalyst contains 2.7 wt.% Titanium. The polymerization of ethylene is carried out under the conditions of example 1. The polymerization results are shown in the table.

From the presented examples it can be seen that the production of polyethylene using the titanium-magnesium catalyst proposed in the present invention allows to achieve high yields of polyethylene at polymerization temperatures of 40-65 ° C. UHMWPE obtained on these catalysts has an improved morphology (bulk density of PE> 0.35 g / cm ³ ). At the same time, when using prototype catalysts (carbon tetrachloride as a chlorinating agent; comparative example 13) or with PhSiCl ₃ as a chlorinating agent without the addition of tetraethoxysilane (comparative example 12), polymers with lower yields and lower bulk scales at polymerization temperatures of 50-60 ° C (compare experiments 4 and 12 and experiments 6 and 13, carried out under the same polymerization conditions).

Table No. of example Reagent for interaction with MOS

Si / Mg T ₁ ¹⁾ , ° C The content of Ti, wt.% AOS PC ₂ H _{4 atm} T ₂ ²⁾ , ° C Yield, kg PE / g cat

The bulk weight of PE, g / cm ³ Mv ³⁾ 10 ^-6 , g / mol one SiCl ₄ / Si (OEt) ₄ 3 1.8 fifteen 3.1 Tea four 65 8.6 278 0.4 1.7 2 MeSiCl ₃ / Si (OEt) ₄ 3 1.8 fifteen 3.1 Tea four 65 10.6 342 0.36 1.7 3 MeSiCl ₃ / Si (OEt) ₄ 3 1.8 fifteen 3.1 Tea four fifty 6.0 194 0.38 4.8 four PhSiCl ₃ / Si (OEt) ₄ 3 1.8 fifteen 3.1 Chiba four 60 8.4 271 0.35 3.4 5 MeSiCl ₃ / Si (OEt) ₄ four 1.8 45 2.7 Tea four 65 10.2 378 0.35 1.7 6 MeSiCl ₃ / Si (OEt) ₄ 3 1.0 fifteen 2.4 Tea four 60 11.3 471 0.38 2.5 7 MeSiCl ₃ / Si (OEt) ₄ 3 1.0 fifteen 2.4 Tea four 40 4.1 172 0.35 6.5 8 MeSiCl ₃ / Si (OEt) ₄ 3 2.5 fifteen 2.4 Tea four 60 6.0 250 0.36 2.8 9 MeSiCl ₃ / Si (OEt) ₄ 2 1.8 fifteen 2.9 Tea four 60 6.5 224 0.34 2.2 10 MeSiCl ₃ / Si (OEt) ₄ four 1.8 fifteen 2.4 Tea four 60 7.4 308 0.36 2.2 eleven MeSiCl ₃ / Si (OEt) ₄ 3 1.8 fifteen 0.16 Tea 3 60 1.8 1125 - 2.5 12 PhSiCl ₃ - 1.8 fifteen 4.0 Chiba four 60 2.8 70 0.30 4.8 13 CCl ₄ - - fifteen 2.7 Tea four 60 4.5 168 0.3 2.9 ^{1) the} temperature of the interaction of the MOC with the silicon compound or with CCl ₄
²⁾ polymerization temperature
³⁾ medium viscosity molecular weight calculated from the characteristic viscosity (η) determined in decalin at 135 ° C, according to the formula: Mv = 5.37 · 10 ⁴ η ^1.49

Claims (1)

A method of producing ultra-high molecular weight polyethylene in suspension in a hydrocarbon solvent using a supported catalyst containing a titanium compound on a magnesium-containing support, which is obtained by reacting a solution of an organomagnesium compound of the composition Mg (C ₆ H ₅ ) ₂ · nMgCl ₂ · mR ₂ O, where n = 0 , 37-0.7, m = 2, R ₂ O — ether with R = i-Am, n-Bu, with a silicon compound, characterized in that the product obtained by reacting a compound of the composition R ¹ _k is used as a silicon compound SiCl _4-k with silicon tetraethoxide Si (OR) ₄ , where R ¹ = methyl or phenyl; k = 0.1, with a molar ratio of R ¹ _x SiCl _4-x / Si (OR) ₄ = 2-4 at a temperature of 15-45 ° C and with a ratio of Si / Mg = 1-2.5, and the method is carried out in temperature range 40 - less than 70 ° С.