GB1583883A - Process for the preparation of olefin polymerisation catalysts - Google Patents

Description

(54) PROCESS FOR THE PREPARATION OF OLEFIN POLYMERISATION CATALYSTS (71) We, PHILLIPS PETROLEUM COMPANY, a corporation organised and existing under the laws of the State of Delaware, United States of America, of Bartlesville, Oklahoma, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to titanium trihalide catalyst systems produced by reduction of a titanium tetrahalide with a magnesium reducing agent.

It is known to reduce titanium tetrahalide with a true Grignard reagent, that is, a compound or mixture of compounds produced by reacting magnesium and an organic halide in the presence of an ether. Such a compound is conventionally expressed as RMgX. It is also known to produce what is termed in the art a "solventless" Grignard, which is produced by reacting magnesium metal with an organic halide in the presence of a solvent which is designated as a non-solvating solvent (i.e. an inert or non-complexing diluent) such as a hydrocarbon as distinguished from an ether.

True Grignard reagents as a practical matter present serious problems as reducing agents in the production of high activity catalysts in view of the difficulty in removing the large amounts of remaining ether and the remaining complexed ether which can reduce the effectiveness of such Grignard reagents used in preparing olefin polymerization catalyst systems.

In certain olefin polymerizations, it is necessary to tailor the catalyst to give the type of polymer desired. Particularly in the polymerization of propylene, it is desirable to cause the polymerization to take place in such a manner as to give a stereospecific polymer.

In accordance with the present invention a new technique is provided for the preparation of improved titanium trihalide olefin polymerisation catalyst systems.

In accordance with thc present invention a process for the preparation of olefin polymer isation catalysts is provided which comprises reducing a titanium tetrahalide by reaction with a magnesium reducing agent obtained by reacting magnesium metal with an organic hydrocarbyl halide, and activating the reduced product obtained by adding thereto an organoaluminum compounds wherein the magnesium reducing agent is prcpared and reacted with the titanium tetrahalide by adding the magnesium, the organic hydrocarbyl halide and the titanium tetrahalide substantially simultaneously, as hereinafter defined, to a reaction vessel and intensively milling the reactants therein.

By 'substantially simultaneously' is meant that three reactants are added to the reaction vessel each in a single increment, as opposed to dropwise, either at the same time, or in such rapid succession that no substantial reaction takes place between any two of the three reactants before the addition of the third in particular that there is no contact between the titanium tetrahalide and an already reacted magnesium metal-organic halide mixture, the reaction between thc three reactants not substantially commencing until the milling operation. The term 'substantially simultaneous' therefore does not preclude the possibility of having the magnesium metal and organic halide already mixed together (but not reacted) prior to introduction into the mill. By intensive milling we mean conditions such as to break up agglomerates present or forming in the reaction mixture with concomitant generation of heat by the milling operation.

The milling is carried out in the absence of any ether or other complexing compound or compound capable of reacting with the magnesium reducing agent and more preferably in the complete absence of any extraneous compound or diluents i.e. cven without an inert hyd rocarbon diluent, although once the reaction is complete an inert diluent or solvent can be added to facilitate subsequent handling. An inert non-complexing hydrocarbon diluent can be present, however, if desired during the milling process. Suitable hydrocarbon diluents include pentane, hexane, cyclohexane, heptane, and other inert hydrocarbon diluents normally used as diluents in olefin polymerisation. In accordance with this invention the reactants are milled under intensive conditions preferably for a time within the range of 0.1 to 200, more preferably 5 to 100, and most preferably 15 to 75 hours. The milling can be carried out in any conventional mill utilised for preparing catalysts such as a ball mill, a rod mill, a pebble mill, or a vibratory ball mill, the milling times can be about one-tenth of those set out hereinabove.

The term 'means capable of intensive mixing' as used herein is also intended to encompass high speed shearing means, colloid mills and means to pass the components through an orifice of a homogenizing valve at high pressure, for instance 1,000 psig or greater. All of these produce intensive mixing conditions where heat is generated and agglomerates are broken up and are to be included within the general term 'milling'.

The milling temperature is generally whatever is produced by the intensive milling which will generally be above 40 , preferably from 40"C to 1 100C, more preferably from 50 to 60"C. With a vibratory ball mill some cooling may be necessary and it is possible to cool enough to maintain the temperature at about room temperature.

After the milling is complete, the product is recovered and used with the activator compound to form the complete polymerisation catalyst system. Preferably the activator compound is used in conjunction with an adjuvant such as ethyl anisate.

Since in the preferred embodiment, no liquid diluent of any kind is utilised, that is, neither an ether nor an inert non-solvating hydrocarbon, it is frequently desirable simply to utilise the monomer to be polymerised as the vehicle to transfer the catalyst to the reactor. This is particularly desirable when using an easily liquefied monomer such as propylene.

Preferably the milled product is washed with an inert liquid, such as a non-reactive hydrocarbon, before transfer to remove any unreacted TiCL. Suitable wash liquids include, pentane, hexane, cyclohexane and heptane.

The organic hydrocarbyl halide used in the procedures of this invention is a saturated or unsaturated hydrocarbyl halide preferably having the formula RX in which X represents a halogen, preferably chlorine or bromine, and R is selected from alkynyl, alkenyl, alkyl, aryl, cycloalkenyl and cycloalkyl radicals and combinations thereof, such as arylalkyl, containing from 1 to 12 carbon atoms per molecule. The organic halide can also be a polyhalogenated hydrocarbyl halide of the formula R' X2 where X is a halogen atom as before and R' is a saturated divalent aliphatic hydrocarbyl radical, containing from 2 to 10 carbon atoms per molecule. Exemplary compounds include 1,2-dibromoethane, 1,4-dichlorobutane, cyclohexyl chloride, bromobenzene and 1,10-dibromodecane. An alkyl halide is presently preferred, however, containing from 1 to 12 carbon atoms. Representative alkyl halides include methyl chloride, n-butyl bromide, n-pentyl chloride and n-dodecyl chloride. A primary alkyl halide such as n-pentyl chloride is most preferred.

The magnesium is in the form of the free metal, preferably in the form of a powder.

The magnesium metal and the organic hydrocarbyl halide are preferably reacted in stoichiometric amounts, although this can vary from 0.25:1 to 1:0.25 gram atoms Mg:moles of organic hydrocarbyl halide.

A typical analysis of the magnesium reducing agent used in this invention using n-pentyl chloride added to magnesium in the absence of any diluent is: Compound Weight per cent Hydrocarbon soluble components Di-n-pentylmagnesium 25.0 Decane 8.2 Di-n-decylmagnesium 1.1 Magnesium n-pentoxide 0.6 Hydrocarbon Insoluble Components Magnesium chloride 55.2 Magnesium 4.9 Chloromagnesium hydride 2.3 n-Pentylmagnesium chloride 2.0 Magnesium n-pentoxide 0.7 This is shown for illustrative purposes and is not intended to limit the scope of the invention. Substantial variation in the exact analysis from that shown is obtained if a different halogen is used or if a different organo radical is substituted for the n-pentyl. However, in all cases there is present a substantial amount (at least 10 weight per cent) each of the dior ganomagnesium and the magnesium chloride. It is the reaction mixture that is the magnesium reducing agent as defined herein.

The titanium tetrahalide is preferably titanium tetrachloride, titanium tetrabromide, or titanium tetraiodide, most preferably titanium tetrachloride.

The preferred organoaluminum compounds used to activate the titanium containing component are trialkylaluminum compounds of formula A1R"3, dialkylaluminum-com- pounds of formula R"2AlZ, alkyl aluminum compounds of the formula R"AlZ2 and dialkyl aluminum alkoxides of formula R"2AlOR" wherein each R" may be the same or different and represents an alkyl group containing from 1 to 12 carbon atoms per molecule and Z represents either a hydrogen atom or a halogen atom, preferably chlorine or bromine. Most preferred are the trialkylaluminum compounds. When used the R"A1Z2 compounds are preferably dichlorides or dibromides. Examples of suitable compounds include trimethylaluminum, triethylaluminum, tri-n-dodecylaluminum, dimethylethylaluminum, dimethylaluminum bromide, diethylaluminum chloride, ethylaluminum dichloride, ethylaluminum dihydride, diisobutylaluminum bromide, d-n-dodecylaluminum chloride, ethyl-t-butylaluminum chloride, diisobutylaluminum hydride, dimethylaluminum butoxide, diethylaluminum ethoxide, di-n-dodecylaluminum n-propoxide, and ethylmethylaluminum ethoxide and mixtures thereof. Triethylaluminum is preferred. It is also within the scope of this invention to use an organoaluminum monohalide (previously described) in combination with additional magnesium reducing agent (previously described) as the activator component of the polymerisation catalyst system.

In addition to the magnesium reduced titanium catalyst component and activator it is preferred to use one or more adjuvants which are polar organic compounds, i.e. electron donor compounds (Lewis bases).

These adjuvants are added to the catalyst system after formation of the magnesium reducing agent and after reaction thereof with the titanium tetrahalide. The adjuvants may be incorporated into the catalyst system by premixing with the activator.

Suitable electron donors for this purpose are described in U.S. Patent 3,642,746. They include amides, amines, aldehydes, arsines, alcoholates, esters, ethers, ketones, nitriles, phosphines, phosphites, phosphoramides, stibines, sulfones and sulfoxides. Exemplary compounds include triethylamine, acetamide, benzaldehyde, sodium ethoxide, ethyl acetate, diethyl ether, acetone, benzonitrile, triphenyl phosphine; triphenyl phosphite, hexamethyl phosphoric triamide, triethyl stibine, trioctyl arsine, dimethyl sulfone and dibutyl sulfoxide.

Presently preferred adjuvants, when premixed with the organoaluminum compounds, are the lower alkyl esters (i.e. 1 to 4 carbon atoms per molecule) of benzoic acid which may be additionally substituted in the para position to the carboxyl group with a monovalent radical selected from the group consisting of -F, -Cl, -Br, -I, -OH, -OR"', -COOR"', -SH, -NH, -NR"'2, -NHCOR"', -NO2, -CN, -CHO, -COOR', -CONH2, -CONR2"', -SO2R"', and -CF3. The R"' group is a 1-4 carbon atom alkyl radical. Examples of suitable compounds include ethyl anisate (p-methoxybenzoate), ethyl benzoate, methyl benzoate, ethyl p-dimethylaminobenzoate, ethyl p-fluorobenzoate, isopropyl p-diethylaminobenzoate, butyl p-fluorobenzoate, n-propyl p-cyanobenzoate, ethyl p-trifluoromethylbenzoate, methyl p-hydroxybenzoate, methyl p-acetylbenzoate, methyl p-nitrobenzoate, ethyl p-mercaptobenzoate and mixtures thereof. Particularly preferred esters are ethyl anisate and ethyl benzoate. Triphenyl phosphite, triethylamine and dimethylaniline are preferred for mixing with the other components as they are contacted. As noted hereinabove another adjuvant such as ethyl anisate or ethyl benzoate may already be mixed with the organoaluminum compound.

If one or more adjuvants are used with the titanium tetrahalide component, the molar ratio of titanium tetrahalide compound to adjuvant (or adjuvants) is generally in the range of 1:1 to 200:1.

If one or more adjuvants are used with the organoaluminum compound or compounds in the activator component, the molar ratio of organoaluminum compound(s) component to adjuvant (or adjuvants) is generally in the range of 1:1 to 350:1. However, in no instance should the total adjuvant from all sources exceed a 1:1 mole ratio of adjuvant to aluminum.

The atom ratio of aluminum to titanium in the catalyst systems of the invention preferably ranges from 20:1 to 450:1, more preferably from 40:1 to 150:1, and the atomic ratio of Al:Mg is preferably from 0.5:1 to 2:1.

The catalysts of this invention are suitable for the polymerisation of aliphatic mono 1-olefins containing 2 to 8 carbon atoms per molecule and particularly the stero-specific polymerisation of propylene.

The conditions suitable for carrying out the polymerisation reaction are similar to other related processes in which a catalyst system comprising reduced titanium is employed. The process is conveniently carried out in liquid phase in the presence or absence of an inert hydrocarbon diluent, e.g. n-heptane, n-pentane, isobutane, cyclohexane, etc., but it is not limited to liquid phase conditions. If no added diluent is used, the process can be carried out in liquid monomer which is preferred.

The polymerisation temperature employed depends on the monomer employed and the mode of reaction selected but generally falls within the range of 60-212"F (15.5-100"C). In the liquid phase polymerisation of propylene, for example, a temperature in the range of 75 to 200"F (24-93 C) can be employed. Any convenient pressure is used. However, in liquid phase operation, sufficient pressure is employed to maintain the reactants in liquid phase within the reaction zone.

As is known in the art, control of the molecular weight of the polymer is readily achieved by the presence of small amounts of hydrogen during the polymerization.

The polymers prepared with the catalysts of this invention are normally solid resinous materials which can be extruded, molded, etc., into useful articles including film, fibers, containers and the like.

Example I A Norton grinding jar, size 00, located in a dry box was charged in the order named with 6.1 g (0.247 gram atoms) magnesium power (50 mesh), 30.4 ml (0.25 moles) n-pentyl chloride (or molar equivalent of another alkyl halide, when another halide was used), electron donor compound, if used, 27.4 ml (0.25 moles) titanium tetrachloride, and 50 ml dry n-heptane, if used. The closed jar was removed from the dry box and rotated at 150 rpm for 65 hours. The operation was conducted in a room maintained at about 25 C. The jar was then returned to the dry box and the contents processed. If n-heptane ws not used during milling, the pasty contents of the jar were washed onto a filter with dry n-heptane and filtered.

The purple solid was washed again with dry n-heptane and dried under vacuum. If n-heptane was present during milling, the contents of the jar were filtered, the solid washed with dry n-heptane and dried under vacuum.

The activator compound used was triethylaluminum (TEA) premixed with ethyl anisate (EA) adjuvant with a variable molar ratio as shown in the Table. As noted in the Table, another electron donor compound was used on occasion.

A 1 liter, stirred reactor purged with dry nitrogen was charged under a propylene flush, in the order named. with activator compound, titanium catalyst component, adjuvant (if any in addition to that in the activator. if any. 0.5 liter hydrogen -(STP) and about 200 g liquid propylene. Sufficient liquid propylene was added as required during the reaction to maintain the vessel in the liquid full state. The vessel and its contents were heated to the specified temperature. After one hour. the contents were removed, the polymer washed with methanol and dried under vacuum.

The reaction temperature used. or adjuvants employed, and the results obtained are given in Table I. Productivity is given in terms of grams polymer per gram component per hour, where the component is shown as Ti. Xylene solubles are determined according to established practice known in the art by separating xylene-soluble material from the total polymer or aliquot thereof and calculating the weight % thus separated. In each run 9.8 mmoles triethyl aluminum was used.

Table I Polymerization of Propylene Ti Activator Productivity Catalyst Molar Adjuvant or g/g Component/Hr. Xylene Run Component Ratio Coactivator M o l a r Ratios Reactor Temp. Component Solubles, No. mmoles TEA/EA Type Mmoles Al/Ti Al/Adjuvant F C Ti Wt.% Notes 1 0.108 3.5 none 90 - 170 77 18240 9.1 1 2 .108 3.5 none 90 - 170 77 9630 15.8 1 3 .146 3.0 none 67 - 170 77 11550 10.7 2 4 .111 3.0 none 88 - 170 77 12240 9.8 3 5 .146 3.5 9DEAC 0.5 67 19.6 170 77 19980 13.9 4 9 .112 3.0 none 87 - 170 77 12190 8.2 6 10 .152 2.7 none 64 - 180 82 7260 7.2 6 11 .171 3.0 TPP 0.03 57 327 170 77 13290 10.3 7 12 .105 3.5 none 93 - 175 79 14900 10.0 13 .125 3.0 none 78 - 175 79 14550 10.0 14 .125 3.0 none 78 - 175 79 16230 12.5 15 .125 2.7 none 78 - 175 79 9420 7.6 16 .120 2.5 none 82 - 175 79 6420 8.4 17 .113 2.7 9DEAC 0.75 87 13 175 79 10000 8.0 4 18 .130 2.7 9DEAC 1.25 75 7.8 175 79 13530 6.8 4 19 .116 3.5 none 84 - 175 79 18600 13.1 8 20 .146 3.0 none 67 - 175 79 10940 8.5 8 21 .126 2.7 none 78 - 175 79 9080 8.6 8 22 .103 2.5 none 95 - 175 79 8740 8.8 8 23 .126 2.7 9DEAC 0.75 78 13 175 79 9050 8.7 8 24 .067 2.7 9DEAC 1.00 145 9.8 175 79 11080 12.4 8 25 .101 2.7 9DEAC 1.25 97 7.8 175 79 12050 11.5 8 NOTES: 1. Mixture of n-C5H11Cl/n-C5H11I = 4 used in magnesium reducing agent preparation.

2. Used n-C5H11Br as the alkyl halide in magnesium reducing agent preparation.

3. Used N-C3H7Cl as the alkyl halide in magnesium reducing agent preparation.

4. DEAC is diethylaluminum chloride.

6. Titanium catalyst component milled in the presence of n-heptane diluent.

7. TPP is triphenyl phosphite.

8. Tritanium catalyst component milled in the absence of a diluent for 65 hours. 50 ml dry n-hexane added and mixture milled an additional 24 hours. The titanium catalyst component was recovered by filtration and dried under a vacuum.

9. Coactivator.

Inspection of the data presented in Table I reveals that active catalyst systems are prepared in the practice of this invention. Runs 1 and 12 are representative of the results obtained by preparing a catalyst system according to the preferred embodiment 1, with no diluent even during milling. Runs 2 and 3 illustrate that alkyl halides other than n-pentyl chloride can be used in preparing the magnesium reducing agent. The effect of DEAC as a coactivator for improving productivity of the total catalyst system is shown in run 5. Run 11 shows an active catalyst system with TPP as an adjuvant. The effect on productivity of the ratio of TEA/ EA in the activator compound is shown in runs 12-16. The results suggest that a ratio below about 2.7 adversely affects productivity although, perhaps, less xylene soluble polymer is produced.

Runs 17 and 18 compared to run 15 again show that DEAC included as part of the activator compound system improves productivity compared to a run made in the absence of DEAC.

This is again illustrated in runs 23-25 compared to run 21 in which the titanium catalyst component was prepared by additionally milling a previously prepared titanium catalyst component with n-hexane. Runs 19-22 (hexane milling) compared to runs 12-16 (no hexane) at similar TEA/EA activator compound ratios show some data scattering with a suggestion that hexane washing may be desirable in some instances, i.e. at an activator compound ratio (TEA/EA) of about 3.5, to improve catalyst productivity.

Example II The effect of aging on catalyst productivity and xylene solubles was determined by preparing a titanium catalyst component sample according to the procedure and component amounts of Example I by milling together for 65 hours, in the absence of diluent, n-pentyl chloride, magnesium powder and titanium tetrachloride. The procedure of the first Example was also followed in recovering and drying the milled product.

The product was used with an activator compound consisting of premixed triethylaluminum activator compound and ethyl anisate adjuvant to polymerize propylene in the manner described in the first Example. In each instance, a reactor temperature of 1700 F (77 C) was used. Also in each instance 9.8 mmoles of triethylaluminum was used and the TEA/EA ratio was 3.5. The results are presented in Table II.

Table II Polymerization of Propylene Ti Productivity Catalyst g/g Component/Hr.

Run Component Component Xylene Aging Time, No. (mmoles) Ti Solubles, Wt. % Days 1 0.143 15100 11.4 < 1 2 .122 16650 14.2 7 3 .124 13520 12.2 14 4 .079 13220 12.1 21 5 .092 14160 11.3 28 6 .123 15730 12.7 35 Inspection of the results of Table II shows that a titanium catalyst component prepared according to this invention can be stored over a period of weeks and utilized with an activator compound to prepare polypropylene at high rates.

Claims (22)

WHAT WE CLAIM IS:

1. A process for the preparation of olefin polymerisation catalysts which comprises reducing a titanium tetrahalide by reaction with a magnesium reducing agent obtained by reacting magnesium metal with an organic hydrocarbyl halide, and activating the reduced product obtained by adding thereto an organoaluminum compound, wherein the magnesium reducing agent is prepared and reacted with the titanium tetrahalide by adding the magnesium, the organic hydrocarbyl halide and the titanium tetrahalide substantially simultaneously, as hereinbefore defined. to a reaction vessel and intensively milling the reactants therein in the absence of any ether or other compound capable of forming a complex with or reacting with the magnesium reducing agent.

2. A process according to claim I wherein the three reactants are brought together and milled in the complete absence of any extraneous compound or diluent.

3. A process according to claim 1 or 2. wherein the milling is performed at a temperature in the range 40-110"C.

4. A process according to claim 1. 2 or 3, wherein the milling is performed in a ball mill.

5. A process according to any one of the preceding claims, wherein the hydrocarbyl halide and magnesium metal are reacted at a ratio gm. atoms Mg:moles of hydrocarbyl halide in the range 0.25:1 to 1:0.25.

6. A process according to any one of the preceding claims, wherein the hydrocarbyl halide is of the formula RX wherein X represents chlorine or bromine and R is an alkynyl, alkenyl, alkyl, aryl, cycloalkenyl, or cycloalkyl radical having from 1 to 12 carbon atoms.

7. A process according to any one of the preceding claims, wherein the organoaluminum compound is of the formula AIR3", R"2AIZ, R"AIZ2 or R"2AIOR" wherein R" is an alkyl radical having from 1 to 12 carbon atoms and Z is H or halogen.

8. A process according to any one of the preceding claims, wherein the titanium tetrahalide is titanium tetrachloride.

9. A process according to any one of the preceding claims, wherein the specified reactants are mixed in such quantities as to provide, in the final product, an atomic ratio of aluminum to titanium within the range 40:1 to 150:1, and an atomic ratio of aluminum to magnesium within the range 0.5:1 to 2:1.

10. A process according to any one of the preceding claims, wherein the hydrocarbyl halide is n-pentylchloride.

11. A process according to any one of the preceding claims, wherein the organoaluminum compound is triethylaluminum.

12. A process according to any one of the preceding claims, wherein there is incorporated into the catalyst mixture a Lewis base in such an amount as to provide a molar ratio of organoaluminum compound to Lewis base in the range 1:1 to 350:1 and a molar ratio of titanium tetrahalide to Lewis base in the range 1:1 to 200: 1, the Lewis base being incorporated into the catalyst mixture together with the organoaluminum compound.

13. A process according to claim 12, wherein the Lewis base is a C1-C4 alkyl benzoate optionally containing a para-substituent selected from halogen, OH, OR"', OOCR"', SH.

NH -NR"' 2. -NHCOR" ,NO2, CN, CHO, COR"', COOR"', CONH2, CONR"'2, SO2Rand CF3, where R"' is C1-C4 alkyl.

14. A process according to claim 12, wherein theLewis base is triphenyl phosphite, triethylamine. dimethyl aniline, ethyl anisate, ethyl benzoate or a mixture of two or more thereof.

15. A process according to claim 1, substantially as hereinbefore described in I or II.

16. An olefin polymerisation catalyst, when prepared by a process claimed in any one of the preceding claims.

17. A process for the preparation of olefin polymers. which comprises polymerising a 1-olefin or 1-olefin mixture in the presence of a catalyst according to claim 16.

18. A process according to claim 17, wherein said olefin is or comprises propylene.

19. A process according to claim 17 or 18. wherein the polymerisation is carried out in the presence of an inert hydrocarbon diluent.

20. A process according to claim 17. 18 or 19, wherein the polymerisation is effected at a terilperature in the range 15.5-100"C.

21. A process according to claim 17. substantially as hereinbefore described in Examples I - II.

22. Olefin polymers when prepared by a process claimed in any one of claims 17-21.