GB2125053A

GB2125053A - Process for polymerizing ethylene

Info

Publication number: GB2125053A
Application number: GB08319780A
Authority: GB
Inventors: Takefumi Yano; Tokuji Inoue; Shigeru Ikai; Yoshiyuki Kai
Original assignee: Ube Industries Ltd
Current assignee: Ube Corp
Priority date: 1982-07-28
Filing date: 1983-07-22
Publication date: 1984-02-29
Also published as: GB8319780D0; FR2531090B1; JPH0153889B2; GB2125053B; KR900004669B1; CA1233948A; FR2531090A1; KR840005466A; JPS5922909A

Abstract

Ethylene or a mixture of ethylene with an alpha -olefin having at least 3 carbon atoms is polymerized in the presence of a catalyst formed from (A) a solid catalyst component and (B) an organic aluminum compound of the formula: R<5>nAlH3-n wherein R5 is C1-6 alkyl and n is 1 or 2. The solid catalyst component is prepared by (1) reacting an aluminum halide with a silicon compound of the formula: R<1>ISi(OR<2>)4-I wherein R<1> and R<2> independently signify C1-8 alkyl, phenyl or C7-10 aralkyl and I is 0, 1, 2 or 3, (2) reacting the obtained product with a Grignard compound of the formula: R<3>MgX<1> wherein R<3> is C1-8 alkyl, phenyl or C7-10 aralkyl and X<1> is halogen, to form a carrier, and then, (3) contacting the carrier with a titanium compound of the formula: (R<4>O)mTiX<2>4-m wherein R<4> is C1-8 alkyl, phenyl or C7-10 aralkyl, X<2> is halogen and m is 0, 1, 2 or 3.

Description

SPECIFICATION Process for polymerizing ethylene Background of the invention (1 ) Field of the invention This invention relates to a process for the polymerization of ethylene. More particularly, it relates to a process for the polymerization of ethylene or a mixture of ethylene with an a-olefin having at least three carbon atoms using a Ziegler type catalyst having an enhanced activity.

(2) Description of the prior art The applicant proposed a process for the polymerization of ethylene using a Ziegler type catalyst which is prepared from (A) a solid catalyst component and (B) a dialkyl aluminum hydride, the solid catalyst component being prepared by reacting an aluminum halide with a tetraalkoxysaline, reacting the obtained reaction product with a Grignard compound to prepare a carrier, and then, contacting the carrier with a titanium tetrahalide (see U.S. Patent No. 4,306,046).

Summary of the invention It is a primary object of the present invention to provide a process for the polymerization of ethylene in which the amount of an ethylene polymer prepared per unit amount of the solid catalyst component is enhanced as compared with the amount of an ethylene polymer prepared by the process of the above-mentioned prior art.

In accordance with the present invention, there is provided a process for the polymerization of ethylene, which comprises polymerizing ethylene or a mixture of ethylene with an a-olefin having at least 3 carbon atoms in the presence of a catalyst obtained from (A) a solid catalyst component and (B) an organic aluminum compound represented by the following formula (I): RnAIH3~n (I) wherein R5 is an alkyl group having 1 to 6 carbon atoms and n is 1 or 2, said solid catalyst component being obtained by (1) reacting an aluminum halide with a silicon compound represented by the following formula (ill):: R',Si(OR2)4~l (II) wherein R' and R2 independently signify an alkyl group having 1 to 8 carbon atoms, a phenol group or an aralkyl group having 7 to 10 carbon atoms, and I is 0, 1, 2 or 3, (2) reacting the reaction product with a Grignard compound represented by the following formula (III): R3MgX1 (III) wherein R3 is an alkyl group having 1 to 8 carbon atoms, a phenyl group or an aralkyl group having 7 to 10 carbon atoms, and X' is a halogen atom, to form a carrier, and then, (3) contacting the carrier with a titanium compound represented by the following formula (IV): (R40)mTX42m (IV) wherein R4 is an alkyl group having 1 to 8 carbon atoms, a phenyl group or an aralkyl group having 7 to 10 carbon atoms, X2 iS a halogen atom, and m is 0, 1, 2 or 3.

Description of the preferred embodiments According to the present invention, an ethylene polymer is obtained in an extremely high yield based on the solid catalyst component. For example, when ethylene is polymerized at an ethylene partial pressure of 7 kg/cm2 and a polymerization temperature of 900C for one hour, the yield of polyethylene reaches about 140 kg per gram of the solid catalyst component. Furthermore, the ethylene polymer possesses a large bulk density.

In the present invention, the preparation of the solid catalyst component (A) is carried out in an atmosphere of an inert gas such as nitrogen or argon. It is preferable that the starting materials used for the preparation of the solid catalyst component be substantially anhydrous.

As examples of the aluminum halide used in the present invention, aluminum chloride, aluminum bromide and aluminum iodide can be mentioned. Of these, aluminum chloride is preferable.

As examples of the silicon compound represented by the formula (II), there can be mentioned tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, tetrapentoxysilane, methyltrimethoxysilane, methyltriethoxysilane, m ethyltri-n-butoxysilane, methyltri-isopentoxysilane, methyltri-n-hexoxysilane, methyltriisoctoxysilane ethyltriethoxysilane, ethyltriisopropoxysilane, ethyltriisopentoxysilane, n-butyl triethoxysilane, isobutyltriethoxysila ne, isopentyltriethoxysilane, isopentyltri-n-butoxysilane, dimethyldiethoxysilane, dimethyldi-n-butoxysilane, dimethyldiisopentoxysilane, diethyldiethoxysilane, diethyldiisopentoxysilane, di-n-butyldiethoxysilane, diisobutyldiisopentoxysilane, trimethylmethoxysilane, trimethylethoxysilane, trimethylisobutoxysilane, triethylisopropoxysilane, tri-n-propylethoxysilane, tri-n-butylethoxysilane, triisopentylethoxysilane, phenyltriethoxysilane, phenyltriisobutoxysilane, phenyltriisopentoxysilane, diphenyldiethoxysilane, diphenyldiisopentoxysilane, diphenyldioctoxysilane, triphenylmethoxysilane, triphenylethoxysilane, triphenylisopentoxysilane, trimethylphenoxysilane, triethylphenoxysilane, dimethyldiphenoxysilane, benzyltriethoxysilane, dibenzyldiethoxysilane and methyl-tris(benzyloxy)silane.

It is preferable that the aluminum halide be used for the reaction in an amount of from 0.25 to 10 moles, more preferably from 0.5 to 2 moles, per mole of the silicon compound.

The reaction of the aluminum halide with the silicon compound is ordinarily carried out by stirring both the compounds in an inert organic solvent at a temperature of from --500C to 1 000C for from 0.1 to 2 hours. The reaction proceeds with generation of heat, and the reaction product is obtained in the form of a solution in the inert organic solvent. The reaction product may be used as it is in the form of the solution in the inert organic solvent for the reaction with a Grignard compound.

As the Grignard compound represented by the formula (III), an alkyl magnesium chloride, i.e., the compound of the formula (III) in which Xa is a chlorine atom, is preferably used. As specific examples, methyl magnesium chloride, ethyl magnesium cloride, n-butyl magnesium chloride, n-hexyl magnesium chloride, phenyl magnesium chloride, and benzyl magnesium chloride can be mentioned.

It is preferable that the Grignard compound be used in an amount of from 0.05 to 4 moles, more preferably from 1.5 to 2 moles, per mole of the silicon compound used for the preparation of the above-mentioned reaction product.

The method in which the reaction product of the aluminum halide with the organic silicon compound is reacted with the Grignard compound is not particularly critical, but it is preferable that the reaction be effected by gradually adding a solution of the Grignard compound in an ether or an ether/aromatic hydrocarbon mixed solvent to a solution of the above-mentioned reaction product in an inert organic solvent or by adding the solution of the above-mentioned reaction product to the solution of the Grignard compound. A compound represented by the following formula: R6-0-R7 wherein each of Re and R7 is an alkyl group having 2 to 8 carbon atoms, is preferably used as the ether in which the Grignard compound is dissolved. As examples of the ether, diethyl ether, diisopropyl ether, di-n-butyl ether and diisoamyl ether can be mentioned.

The reaction is carried out ordinarily at a temperature of from -50 to 1000C and preferably at a temperature of from -20 to 250C. The reaction time is not particularly critical, but ordinarily, the reaction is conducted for not less than 5 minutes. As the reaction proceeds, the formed carrier is precipitated. The thus obtained carrier in the form of the as-obtained reaction mixture may be used for the contact with the titanium compound of the formula (IV). However, it is preferable that the carrier be separated from the reaction mixture in advance, washed with an inert organic solvent and then contacted with the titanium compound of the formula (IV).

As specific examples of the titanium compound of the formula (IV), there can be mentioned titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, methoxytrichlorotitanium, dimethoxydichlorotitanium, trimethoxychlorotitanium, ethoxytrichlorotitanium, diethoxydichlorotitanium, propoxytrichlorotitanium, dipropoxydichlorotitanium, butoxytrichlorotitanium, dibutoxydichlorotitanium, phenoxytrichlorotitanium, diphenoxydichlorotitanium, methoxytribromotitanium, phenoxytribromotitanium, methoxytriiodotitanium, phenoxytriiodotitanium, benzyloxytrichlorotitanium, bis(benzyloxy)dichlorotitanium, tris(benzyloxy)chlorotitanium, benzyloxytribromotitanium, and benzyloxytriiodotitanium.It is preferable that the titanium compound be used in an amount of at least 1 mole, more preferably from 2 to 100 moles, per mole of the Grignard compound used for the preparation of the carrier.

The contact treatment of the carrier with the titanium compound of the formula (IV) may be effected either in the presence or absence of an inert organic solvent. The contact temperature is in the range of from 20 to 2000 C, preferably from 60 to 1400C. The contact time is not particularly critical, but is ordinarily in the range of from 0.5 to 3 hours. The contact treatment with the titanium compound may be conducted at least one time. In the present invention, the solid catalyst component obtained by conducting the contact treatment two times exhibits a highest activity for the polymerization of ethylene.

The solid catalyst component (A) is recovered from the mixture by filtration, decantation or other conventional means, and then washed with an inert organic solvent. The titanium content in the solid catalyst component (A) is in the range of from 0.5 to 10% by weight.

As specific examples of the inert organic solvent used in the respective stages in the preparation of the solid catalyst component, there can be mentioned aliphatic hydrocarbons such as hexane and heptane; aromatic hydrocarbons such as benzene, toluene and xylene; and halogenated products of these hydrocarbons.

In the present invention, ethylene or a mixture of ethylene with an a-olefin having at least 3 carbon atoms is polymerized in the presence of catalyst obtained from the solid catalyst component and the aluminum compound.

As specific examples of the aluminum compound, there can be mentioned diethyl aluminum hydride, diisobutyl aluminum hydride and dihexyl aluminum hydride. The aluminum compound is ordinarily used in an amount of 1 to 1,000 moles per gram-atom of titanium in the solid catalyst component.

The polymerization reaction may be effected either by a medium or low pressure polymerization process or a high pressure polymerization process. The medium or low pressure polymerization process may be carried out in the liquid phase or gaseous phase.

When the polymerization reaction is carried out in the liquid phase, for example, aliphatic hydrocarbons such as n-butane, n-propane, n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and cyclopentane; and aromatic hydrocarbons such as benzene and toluene are used as the polymerization medium. The concentration of the catalyst in the polymerization medium is not particularly critical, but ordinarily, the concentration is such that the amount of the solid catalyst component is within the range of from 0.0005 to 10 mg-atom, as titanium metal per liter of the polymerization medium and the amount of the organic aluminum compound is in the range of from 0.001 to 1,000 millimoles per liter of the polymerization medium.

In the present invention, ethylene is homopolymerized or is copolymerized with an a-olefin having at least 3 carbon atoms, such as propylene, 1-butene, 4-methyl-1-pentene or 1-hexene.

The polymerization reaction is carried out in a substantially water-free and oxygen-free state in a manner similar to that in the conventional polymerization of ethylene using an ordinary Ziegler catalyst.

The polymerization temperature is ordinarily from 30 to 3000 C, and the polymerization pressure is ordinarily from 1 to 3000 kg/cm2.

The molecular weight of the resulting ethylene polymer can easily be controlled by adding hydrogen to the polymerization system.

The present invention will now be described in detail with reference to the following Examples. In the Examples, the "polymerization activity" indicates the yield (kg) of the polymer per gram of the solid catalyst component (A) used for the polymerization and per hour of the polymerization time. "M.l." indicates the melt flow index as measured at 1900C under a load of 2.16 kg/cm2 according to ASTM D-1 238. Incidentally, in each example, the preparation of the solid catalyst component (A) was carried out in an atmosphere of dry nitrogen gas.

Example 1 (1) Preparation of solid catalyst component (A) To 2.0 g of anhydrous aluminum' chloride was added 30 ml of toluene. 13.5 ml of a solution of 3.50 ml of phenyltriethoxysilane in toluene was dropped into the mixture with stirring at 250C over a period of 30 minutes. The mixture was heated to 600C and maintained at that temperature for one hour to effect reaction.

The reaction mixture was cooled to from -11 1 to 700. 1 6.8 ml of a solution of 27 millimoles of n-butyl magnesium chloride in diisoamyl ether was dropped into the reaction mixture over a period of 45 minutes. Then, the reaction mixture was heated to 300C, and maintained at this temperature for 60 minutes to effect reaction. The precipitated carrier was separated by filtration and washed three times with 30 ml of toluene for each time.

The carrier was suspended in 30 ml of toluene. Then, 1 5.0 ml of titanium tetrachloride was added to the suspension whereby the solid carrier was contacted with titanium tetrachloride with stirring of 900C for 60 minutes. At the same temperature, the thus obtained solid catalyst component was recovered by filtration and washed five times with 30 ml of toluene for each time and then five times with 30 mi of n-heptane for each time.

To the solid catalyst component (having a titanium content of 5.92% by weight) was added 80 ml of n-heptane to prepare a slurry of the solid catalyst component.

(2) Polymerization A glass ampoule containing the suspension of the solid catalyst component (4.0 mg as the solid catalyst component) sealed therein was attached to a 2-liter inner volume autoclave provided with a stirrer. Then, air in the autoclave was replaced by nitrogen.

One liter of n-hexane and then 12 ml of n-hexane containing diisobutyl aluminum hydride in an amount of 222 moles per gram-atom of titanium in the solid catalyst component were introduced into the autoclave. The content in the autoclave was heated to 900C whereby the inner pressure reached 0.9 kg/cm2 (all pressures hereinafter used mean "gauge pressure").

Ethylene was introduced into the autoclave until the total pressure reached 7.9 kg/cm2. Stirring was then initiated and the glass ampoule was broken to initiate the polymerization of ethylene. The polymerization was carried out at 900C for 60 minutes while continuously supplying ethylene so as to maintain the total pressure at 7.9 kg/cm2.

After the polymerization, unreacted ethylene was discharged. The polymer thus produced was recovered by filtration and then dried at 50 C under reduced pressure for 20 hours to obtain 420 g of white polyethylene. The polymerization activity was 125, the density of the polyethylene was 0.951 g/cm3 and the bulk density thereof was 0.37 g/cm3.

Examples 2 and 3 The procedures of Example 1 were repeated in the same manner except that the amount (moles per gram-atom of titanium in the solid catalyst component) of diisobutyl aluminum hydride was varied as shown in Table 1. The results are shown in Table 1.

Table 1 (i~C4HgJ2AlH Polymerization Bulk density (mole ratio) activity ,g/cm3J Example 2 50 109 0.38 Example 3 100 118 0.38 Examples 4 through 6 The procedures of Example 1 were repeated in the same manner except that the amount of diisobutyl aluminum hydride was varied to 200 moles per gram-atom of titanium in the solid catalyst component and prior to introduction of ethylene, hydrogen was introduced into the autoclave so that the pressure was elevated to a level shown in Table 2. The results are shown in Table 2.

Table 2 Hydrogen Bulk pressure Polymerization density M l.

(kg/cm2) activity (g/cm3) (g/10 min) Example 4 1 96 0.38 0.5 Example 5 3 82 0.37 2.1 Example 6 5 77 0.37 3.2 Examples 7 through 10 The procedures of Example 1 were repeated in the same manner except that 1 5 millimoles of a silicon comopund shown in Table 3 was used instead of phenyltriethoxysilane. The titanium content in the solid catalyst component and the polymerization results are shown in Table 3.

Table 3 Titanium content Bulk Silicon (% by Polymerization density compound weight) activity (g/cm3) Example 7 tetraethoxy- 5.83 115 0.38 silane Example 8 methyltri- 6.02 120 0.37 ethoxysilane Example 9 dimethyldi-n- 5.95 127 0.36 butoxysilane Example 10 tetraisopent- 5.76 123 0.38 oxysilane Examples 11 and 12 The procedures of Example 1 were repeated in the same manner except that a titanium compound shown in Table 4 was used instead of titanium tetrachloride. The titanium content in the solid catalyst component and the polymerization results are shown in Table 4.

Table 4 Titanium Bulk Titanium content Polymerization density compound (% by weight) activity (g/cm3) Example 11 n-butoxytri- 5.80 112 0.37 chlorotitanium Example 12 phenoxytri- 5.91 110 0.37 chlorotitanium Example 13 In 30 ml of toluene was suspended 3.43 g of the solid catalyst component obtained in (1) of Example 1. Then, 1 5 ml of titanium tetrachloride was added to the suspension with stirring whereby the reaction was carried out at 90"C for 1 hour. At the same temperature, the solid was recovered by filtration and then washed five times with 30 ml of n-heptane for each time to obtain a solid catalyst component having a titanium content of 5.519/0 by weight. Then, 80 ml of n-heptane was added to the solid catalyst component to prepare a slurry.

By using 3.6 mg of this solid catalyst component, ethylene was polymerized in the same manner as described in (2) of Example 1 . The polymerization activity was 140, and the bulk density of the polyethylene was 0.38 g/cm3.

Example 14 A glass ampoule containing the slurry of 2.50 mg of the solid catalyst component prepared in (1) of Example 1 was attached to a 2 liter inner volume autoclave provided with a stirrer. Then, air in the autoclave was replaced by nitrogen.

Then, 1.0 ml of an n-heptane solution containing 0.630 millimole of diisobutyl aluminum hydride was introduced into the autoclave and then hydrogen was introduced into the autoclave until the hydrogen pressure reached 5 kg/cm2. Then, 200 ml of liquid 1-butene and 1 ,000 ml of n-butane were supplied under pressure into the autoclave. Then, the content of the autoclave was heated to 660C whereby the pressure in the autoclave reached 1 7.7 kg/cm2. Ethylene was introduced into the autoclave until the total pressure reached 28 kg/cm2. Stirring was initiated and the glass ampoule was broken whereby ethylene was copolymerized with 1-butene at 660C for 60 minutes. During the polymerization, ethylene was continuously supplied into the autoclave to maintain the total pressure at 28 kg/cm2.

After the polymerization, the unreacted monomers and n-butane were discharged, and 245.5 g of a white ethylene/butene-1 copolymer was recovered.

The density of the copolymer was 0.925 g/cm3, M.l. of the copolymer was 2.4 g/1 0 min and the bulk density of the copolymer was 0.36 g/cm3. The polymerization activity was 98.2.

Claims

1. A process for the polymerization of ethylene, which comprises polymerizing ethylene or a mixture of ethylene with an a-olefin having at least 3 carbon atoms in the presence of a catalyst obtained from (A) a solid catalyst component and (B) an organic aluminum compound represented by the following formula (I): Rn5AIH3~n (I) wherein R5 is an alkyl group having 1 to 6 carbon atoms, and n is 1 or 2, said solid catalyst component being obtained by (1) reacting an aluminum halide with a silicon compound represented by the following formula (ill):: R'gSi(OR2)4~l (II) wherein R1 and R2 independently signify an alkyl group having 1 to 8 carbon atoms, a phenyl group or an aralkyl group having 7 to 10 carbon atoms, and I is 0, 1,2 or 3, (2) reacting the reaction product with a Grignard compound represented by the following formua (III): R3MgX' (III) wherein R3 is an alkyl group having 1 to 8 carbon atoms, a phenyl group or an aralkyl group having 7 to 10 carbon atoms, and X1 is a halogen atom, to form a carrier, and then, (3) contacting the carrier with a titanium compound represented by the following formula (IV):: (R40)mTX42m (IV) wherein R4 is an alkyl group having 1 to 8 carbon atoms, a phenyl group or an aralkyl group having 7 to 10 carbon atoms, X2 iS a halogen atom, and m is 0, 1,2 or 3.

2. A process according to claim 1, wherein said reaction of an aluminum halide with the organic silicon compound of the formula (II) is carried out by using from 0.25 to 10 moles, per mole of the silicon compound, of an aluminum halide in an inert organic solvent at a temperature of from -50 to 10000 for 0.1 to2 hours.

3. A process according to claim 1, wherein said aluminum halide is aluminum chloride.

4. A process according to claim 1, wherein said organic silicon compound of the formula (II) is methyltriethoxysilane, dimethyldiethoxysilane, tetraethoxysilane, phenyltriethoxysilane, tetraisopentoxysilane, or phenyltripentoxysilane.

5. A process according to claim 1, wherein the reaction product of an aluminum halide with the silicon compound of the formula (II) is reacted with from 0.05 to 4 moles of the Grignard compound of the formula (III), per mole of the silicon compound used for the preparation of said reaction product, in a manner such that a solution of said reaction product in an inert organic solvent and a solution of the Grignard compound in an ether or a mixed solvent of an ether and an aromatic organic solvent are gradually incorporated with each other, said ether being represented by the formula: R6-0-R7 wherein R6 and R7 independently signify an alkyl group having 2 to 8 carbon atoms.

6. A process according to claim 1, wherein said Grignaid compound of the formula (III) is an alkyl magnesium chloride.

7. A process according to claim 1, wherein the carrier, prepared by the reaction of the reaction product of an aluminum halide and the silicon compound of the formula (II) with the Grignard compound of the formula (III) is washed with an inert organic solvent prior to said contact treatment with the titanium compound of the formula (IV).

8. A process according to claim 1, wherein said carrier is contacted with at least one mole of the titanium compound per mole of the Grignard compound used for the preparation of said carrier.

9. A process according to claim 1, wherein the amount of said organic aluminum compound (B) is in the range of from 1 to 1,000 moles per gram-atom of titanium contained in the solid catalyst component (A).

10. A process according to claim 1, wherein said organic aluminum compound (B) is diisobutyl aluminum hydride.

11. A process according to claim 1, wherein ethylene or a mixture of ethylene with a mixture of ethylene with an a-olefin having at least 3 carbon atoms is polymerized under a pressure of from 1 to 3000 kg/cm2 at a temperature of from 30 to 3000C in a substantially water-free and oxygen-free state.

1 2. A process according to claim 1, wherein the polymerization is carried out in a liquid phase using a liquid hydrocarbon polymerization medium, and using the catalyst in an amount such that the amount of the solid catalyst component (A) is in the range of from 0.0005 to 10 mg-atom, as titanium atom, per liter of the polymerization medium and the amount of the organic aluminum compound (B) is in the range of from 0.001 to 1,000 millimoles per liter of the polymerization medium.