GB2051832A - Titanium trichloride catalyst and process for its preparation - Google Patents

Abstract

A storage stable component of an olefin polymerisation catalyst is obtained when an aluminum-reduced titanium trichloride catalyst which has been modified by treatment with an electron donor is heated at a temperature and for a period of time sufficient to drive the reaction to completion e.g. at 40 DEG to 110 DEG C for 10 mins to 12 hours. In some instances this will involve the removal of by-product which has been formed during the modification. The component corresponds to the formula (3 TiCl3. AlCl3)1-x (3 TiCl3AlCl2XR)x where X is O, S, Se or Te, R is an organic group and X is positive and less than or equal to 1.

Description

SPECIFICATION Titanium trichloride catalyst and process for its pre paration The preparation of aluminum-reduced titanium trichloride catalysts is well known, and such catalysts are widely employed in the production of polyolefins, such as polyethylene and polyp ropylene. The preparation of such catalysts and their use in polymerization reactions is discussed in a number of patents, for example, in U. S. Patents Nos.

3,121,063,3,475,394, 4,154,702,3,642,746 and 3,647,772, and in British Patent No. 1,310,547.

It is also known that the performance of such catalysts can be improved by treatment with electron donor substances. Details of such treatment and examples of electron donors which have been employed are disclosed in, among others, U. S. Patents Nos. 3,186,977,4,110,248,4,1 4,111,836, 4,115,319, 4,126,576,4,127,504, 4,127,505,4,142,991, and British Patent No. 1,310,547.

However, the treatment of aluminum-reduced titanium trichloride catalysts with electron donors containing an OR radical, illustratively with various ethers, may result in the generation of by-products which adversely affect the catalysts. For example, they can generate undesirable pressures in the ship ping container. In other instances the by-products which are formed may be toxic. This introduces an element of hazard which it is clearly desirable to avoid.

In accordance with the present invention it has been found that the presence of the undesirable and potentially hazardous by products can be eliminated by heat treating the modified aluminum-reduced titanium trichloride catalyst, and thereafter removing such substances by volatilization or extraction with a suitable solvent. This heat treatment is most advantageously effected after modification of the catalyst by the particular selected electron donor has taken place but can also be effected while the modification or activation treatment is being carried out.

Broadly, the modified catalyst is placed in a suitable vessel and the heat treatment is carried out at a temperature and for a time sufficient to drive the reaction to completion. In some instances this will involve removal of a gas formed in modification.

The temperature used in carrying out the heat treatment can be varied over the range of from about 40 to about 110 . The preferred range is from about 800 to about 100 , with a temperature of about 90 being the most advantageous.

The time of treatment can likewise be varied and will of course be related to the particulartemperature at which the heat treatment is carried out. Thus, the time of treatment can be from about 10 minutes to about 300 minutes, with a preferred range of from about 60 to 120 minutes. In the usual practice of the present invention, the time will be about 80 minutes.

The heat treatment resulting in the elimination of the by products can be effected at above or below ambient pressure, illustratively from about 0.001 to about 2 atmospheres, but it is preferred to carry out the heat treatment at atmospheric pressure.

The heat treatment of the modified aluminumreduced titanium trichloride catalyst in accordance with the present invention results in the production of a new and advantageous catalyst composition.

When the base aluminum-reduced titanium trichloride is treated with a small quantity of an electron donor containing the group -OR and activated by milling at a temperature of about-10 C to about 40"C, the following reaction will occur: 3 TiCI3, AICI3 t x ROR' 3 (1-x) (3TiC13, AICI3) x (3TiCl3, AICI3, ROR') (I) On heating the above product, the electron donor modified aluminum-reduced titanium trichloride, according to the procedure disclosed in the instant application, the following reaction takes place:: (1-x) (3TiC13, AICI3) x (3TiCl3, AICI3, ROR') o (1-x) (3TiCl3, AICI3) x (3TiCl3, AICI2 (OR')) + RCI.

In the above equations, x is a positive number equal to or less than, one.

The product obtained after completion of the above reaction is a new catalytic agent of a composition hitherto unknown. This catalyst has a high catalyst efficiency (CE) expressed as the weight of polymer produced in grams per gram of modified TiCI3 catalyst. The polymer which is produced using the new and improved catalyst of the present invention has improved isotacticity, that is, has a higher heptane insoluble (HI) content.

The starting catalyst employed in the practice of the present invention can be aluminum-reduced, activated (AA-TiCI3) or aluminum-reduced, unactivated (A-TiCI3) titanium trichloride. Optionally, extra aluminum chloride, titanium tetrachloride, or titanium trichloride may be added.

The particular electron donor compounds which are employed as modifying agents in the activation of the catalysts with which the present invention is concerned are compounds of the following general formula R1-X-R2 where X is O, S, Se or Te, and wherein R1 and R2 are the same or are different, and are alkyl, cycloalkyl, aryl, or substituted derivatives thereof or a grouping of the formula

FrIEPELV X L(T () S ze op TE a"8 P3 is alkyl, cyc- loalky, aryl, or substituted derivatives thereof.

The sole limitation on R1 and R2 is that the compounds RtCI and/or R2CI, should be readily removable from the reaction product or their presence should be innocuous.

Examples of the modifier R' -X-R2 in the case where X is oxygen are organic oxygen-containing compounds such as the aliphatic ethers, aromatic ethers, aliphatic carboxylic acid esters and anhydrides, aromatic carboxylic acid esters and anhydrides acid esters and an hydrides, and unsaturated carboxylic acid esters and anhydrides. Specific examples of illustrative compounds are (C2H5)30, C6Hs.O.CH3, C6H5CH2.O.CH3 (CH3.CH (OC2Hs)2" (CH3)2.C(OC2Hs)2, CH(OC2Hs)3 CH3CO.OC2Hs, CsHs.CO.OC2Hsl C6H50.CO.OC2HS C,H,O.CO.OC,H, C,H,O.CO.OC,Hr and (CH3CO)20.

Special instances are compounds where R' and RZ are part of a heterocyclic system as, for example, in tetrahydrofuran ory- butyrolactone.

Hydrogen in the foregoing examples can be substituted by the any one or more of the following groupings, for example, - Cl, -Br, - CH2Cl, - O.C3Hs, -Ch2.OCh3, -) .CO.CH3 and -CO.CH3.

As earlier noted, there are certain art recognized problems associated with such modified catalysts.

Among these problems are a lack of storage stability and a potential hazard arising from the generation of volatile or toxic substances. This is known to arise according to the following reaction:

which has been discussed in the text "Fridel - Crafts and Related Reactions, Edited by George A. Olah; 1963, published by Interscience Publishers, New York, pages 572 and 585.

It has most suprisingly been found that the above problems can be overcome without loss of catalytic activity and efficiency by subjecting the electron donor modified aluminum-reduced titanium trichloride catalyst to a heat treatment at a temperature and for a period of time sufficientto effect the elimi nation of the RC1 generated in accordance with reac tion Ill.

The A-or the AA-TiCI3 is mixed with the electron donor compound in an inert atmosphere and the mixture is heated to effect reaction. The heating according to the present invention can be done simultaneously with ball milling for activation or further activation of the catalyst, orthe mixture can be heated after activation.

Gas products which are volatile can be removed by evaporation at elevated or at reduced pressure.

Other products can also be removed by solvent extraction followed by filtration or can be left in the catalyst mixture if innocuous.

Other operations can be carried out after the heat treatment. For example, a low temperature milling or a grinding step may be run to adjust catalyst particle size. These subsequent steps could include the addition of further modifiers, especially to improve efficiency further and control particle size.

The following Examples which illustrate certain preferred embodiments of the present invention are intended only to illustrate the invention and are not to be construed in any limiting sense.

EXAMPLE I 7.6 kg of crystalline titanium trichloride compound of the approximate formula TiCI30.33 AICI3 (AA-TiCI3 manufactured by Purechem Co.) are put in a vibrat ory ball mill having a 40 liter inner volume and con taining 144 kg of steel balls of 1 inch diameter, under a nitrogen atmopshere. Anisole, in an amount of 12% wt. based on the amount of TiCI30.33 AICI3 is dispersed onto the catalyst over a period of 1 hour, while the mixture is being milled at 1 0 C for 4 hours art a speed of 1500 rpm.

A sample of the catalyst was tested in the liquid propylene polymerization test as follows: 0.0259 of the modified TiCl3catalyst and 1.2 ml of a 0.66 M DEAC solution in n-heptane (DEAC/Ti (moles) = 3.0) are charged into a 1 liter stainless steel autoclave equipped with an agitator. 0.027 moles of H3 is then charged followed by the addition of 2509 of liquid propylene. The polymerization is carried out at 75"C for 2 hours after which the unreacted propylene is vented off. The polymer thus obtained weighs 1339 and the catalyst productivity is 25579 PP/g Cat.

A fraction of the polymer is extracted with boiling n-heptane for 16 hours in a Soxhlet Extractor and the n-heptane insoluble fraction is dried. The weight percent of the n-heptane insoluble polymer is 93.5.

EXAMPLE II An anisole modified titanium trichloride is prepared using the same conditions and quantities recited in EXAMPLE I, except that the milling is carried out at 409C. A sample of the co-pulverised mixturn thus prepared, tested underthe same polymerization conditions as in EXAMPLE I, gave a productivity of 27009 PP/g Cat and an ll of 95.6%.

EXAMPLE Ill An anisole modified titanium trichloride is prepared using the same condition and quantities recited in EXAMPLE I, except that the amount of anisole used was 9% wt. based on the amount of TiCI3 0.33 AlCI3. A sample of the co-pulverised mixturn thus prepared, when tested landed the same polymerization conditions as described in EXAMPLE I, gave a productivity of 25009 PP/g Cat and an II of 93.3%.

EXAMPLE IV A sample of the anisole modified titanium trichloride prepared using the same conditions and quantities recited in EXAMPLE II was extracted with n-hexane using 10 ml of n-hexane per gram of catalyst and then dried under nitrogen. A sample of the thus treated catalyst was tested under the same polymerization conditions as in EXAMPLE I. The following results were obtained: CATALYST EFFICIENCY gPPIgCat 11% Before solvent extraction 2692 95.7 After solvent extraction 2846 96.0 EXAMPLE V HEAT TREATMENT OF THE MODIFIED CATALYST 100 g of an anisole modified titanium trichloride catalyst prepared as described in EXAMPLE II was placed in a sealed glass tube and treated at 85"C and the gas evolved was monitored. Gas evolution was completed after 4 hours of heating. A sample of the heat treated catalyst was tested under the same polymerization conditions as in EXAMPLE I. The results obtained were as follows: CATALYST EFFICIENCY g PPlg Cat 11% Before heating 2385 95.5 After heating 2385 95.2 Samples of the modified catalyst were similarly heat treated at 90"C and 110 C. At these temperatures, the gas evolution was completed after 3 hours and 0.5 hours respectively.

Claims (12)

1. A catalyst comprising (3TiCl3, AICI3)1-3 (3TiCl3, AICI(XR)), where xis a positive number less than, or equal to, one, X is O, S, Se orTe and R is an organic grouping.

2. A catalyst according to claim 1 where R is alkyl, cyloalkyl, aryl, or a substituted derivative of any of these or a grouping of the formula

wherein R' is alkyl, cycloalkyl, aryl or a substituted derivative of any of these.

3. A catalyst according to claim 1 or 2 wherein X is 0 and R is aryl or substituted aryl.

4. A catalyst according to claim 1, 2 or3 where R is phenyl.

5. A catalyst according to claim 1 substantially as described in Example V.

6. A process for providing a storage stable olefin polymerization catalyst which comprises heating an aluminum-reduced titanium trichloride catalyst which has been activated by treatment with an electron donor compound of the formula R1-X-R2 wherein X is O, S, Se or Te, and wherein R1 and R2 are the same or different, and are alkyl, cycloalkyl, aryl, or a substituted derivative of any of these or a grouping ofthe formula

wherein X is O, S, Se orTe and R' is alkyl, cycloalkyl, aryl, or a substituted derivative of any of these.

7. A process according to claim 6 wherein the electron donor compound is an organic ether or ester.

8. A process according to claim 6 wherein the electron donor compound is anisole.

9. A process according to any one of claims 6 to 8 wherein the temperature is from 40 to 110"C and the period of heating is from 10 minutes to 12 hours.

10. A process according to claim 9 wherein the temperature is from 80 to 100"C and the period of heating is from 20 minutes to 3 hours.

11. A process according to claim 9 wherein the temperature is 90 and the period of heating is two hours.

12. A process for preparing an olefin polymer which comprises polymerising an olefin, optionally mixed with one or more ethylenically unsaturated monomer copolymerisable therewith, in the pres ence of a catalyst as claimed in any one of claims 1 to 5 or when prepared by a process as claimed in any one of claims 6 to 11.