GB2054616A - Propylene polymerization process and product - Google Patents

Abstract

Improved catalyst productivity rates are obtained in a propylene polymerization process conducted at sufficient pressure to maintain propylene in the liquid phase, by carrying out the polymerization at a temperature of 115 to 165 DEG F in the presence of small amounts of ethylene and of a catalyst system containing a trialkylaluminum component and a magnesium halide-supported titanium tri- or tetrahalide catalyst component. The polymer produced by the process exhibits improved physical and mechanical properties.

Description

SPECIFICATION Propylene polymerization process and product The continuous polymerization of propylene under sufficient pressure to maintain at least a portion of the propylene in the liquid phase ("liquid pool") is well known in the art. In the past the conventional catalyst system used in such polymerization has been an unmodified or an electron donor-modified titanium halide component, activated with an organoaluminum cocatalyst. Typical examples of conventional propylene polymerization catalyst systems include cocrystallized titanium trichloride-aluminum trichloride catalysts of the general formula n.Ti Cl3.AICI3 activated with diethyl aluminum chloride of triethylaluminum.The co-crystallized titanium/aluminum trichloride can have been subjected to a modification treatment with a suitable electron donor compound to increase its activity or steresospecificity. Such compounds include phosphorous compounds, esters of inorganic and organic acid ethers and numerous other compounds.

Recently new catalysts have been developed which are far more active than the aforementioned conventional catalysts in the polymerization of alpha-olefins. Briefly described, these catalysts are comprised of a titanium halide catalyst component supported on magnesium dihalide and an alkylaluminum compound, which can be present as a complex with an electron donor compound. These catalyst components have been described in the patent literature, e.g.

in U.S. Patents No. 3,830,787, No. 3,953,414, No. 4,051,313, No. 4,115,319 and No.

4,149,990.

In the polymerization of propylene in the presence of liquid monomer, it is known that the efficiency (productivity) of the above catalyst systems is increased by an increase in temperatures up to level in the vicinity of about 1 55 F or slightly higher, where maximum productivities are obtained. Typically, a raise in temperature from about 1 25 F to about 1 55 F results in almost a doubling of the catalyst efficiency, regardless of the particular selection of catalyst system. Further increases in temperature cause a rapid decline in productivity from the maximum values.

Thus for any catalyst system used in the liquid propylene polymerization there is a maximum productivity level that can be achieved, and this maximum productivity level is achieved at a relatively high temperature and pressure (to assure liquid phase at the temperature). These optimum operating conditions contribute to the overall cost of the process in the form of utilities needed for increased preheat, cooling and compression requirements.

It is therefore an object of the present invention to provide a process for the polymerization of propylene wherein the temperatures (and pressures) can be maintained at lower levels, while achieving significantly better catalyst productivities.

Another object is to significantly improve catalyst productivities at any predetermined polymerization temperature.

A further object of the present invention is to provide a novel propylene polymer which exhibits improved processability when extruded or injection molded as compared to conventional propylene polymers.

Still another object of the present invention is to provide a novel polypropylene which can be processed at lower extrusion or molding temperatures and/or lower extrusion or molding pressures than conventional polypropylene resins of the same meltflows.

DESCRIPTION OF THE DRAWING The Figures show by comparison the improved results obtained by this invention. In Fig. 1, the improvement in catalyst efficiency is shown, while the improvement in polymer impact properties is illustrated in Fig. 2.

THE INVENTION In accordance with the present invention there is provided in a continuous process for the catalytic polymerization of propylene at elevated temperatures and sufficient pressures to maintain propylene in liquid phase in the polymerization zone the improvement of increasing the productivity rate of the catalyst composition to a value higher than the optimum productivity rate defined hereinafter.The improvement comprises: (i) in a prior step determining the optimum productivity rate of the catalyst composition defined below in the homopolymerization of propylene; (ii) introducing ethylene with the propylene feed into the reaction zone in amounts from about 0.3 to about 2 weight percent based on the weight of the propylene feed stream; (iii) polymerizing the mixture of ethylene and propylene at a temperature in the range from about 1 1 5 F to about 1 65 F in the presence of a catalyst composition containing the components (a) an aluminum trialkyl or an aluminum trialkyl at least partially complexed with an electron donor compound, and (b) titanium tri- or tetrahalide supported on magnesium dihalide, or a complex of a titanium tri- or tetrahalide with an electron donor compound supported on magnesium dihalide.

The determination set forth in step (i) is obtained by operating the liquid pool reactor with propylene monomer only, i.e. homopolymerization, at temperatures between 115"F and 165"F and measuring the resulting productivity at each temperature. This establishes the catalyst productivity vs. temperature performance which are needed for step (i).

It was unexpectedy found that the introduction of small amounts of ethylene with the propylene feed and using the above-described catalyst system caused a dramatic and completely unexpected increase in the catalyst productivity. It was further found that the increase in productivity was not dependent on the particular level of ethylene concentration in the total feed, but that any level within the range of from about 0.3 to about 2 wt %, preferably from about 0.5 to about 1.7 wt %, would result in about the same improvement. In addition, and most significant, was the discovery that with ethylene present in the monomer feed, the effect of temperature on catalyst productivity appeared to have been eradicated, i.e., the increased catalyst productivity remained substantially constant over a broad temperature range.

These findings are in direct contradiction to what occurs in the same process, with ethylene addition to the propylene feed but with conventional unsupported titanium catalyst systems.

There, the temperature is the main factor affecting the productivity and although at lower than optimum temperatures the presence of ethylene sometimes appears to increase the productivity to a slight degree, e.g. up to 10% or less, there has been no instance where the presence of ethylene in the propylene feed has resulted in better productivities compared to those obtained in the absence of ethylene in the feed and at the optimum polymerization temperature (i.e.

155-160 F) for obtaining maximum productivity. In fact, with some conventional catalysts there is commonly seen a detrimental effect of ethylene feed incorporation at temperatures above about 140"F, resulting in productivities that are lower than those obtained in the absence of ethylene and at the optimum polymerization temperature.

The catalyst components used in the process of the invention can be any one of the recently developed, high activity magnesium halide supported catalyst components and organoaluminum cocatalyst components disclosed e.g. in U.S. Patents No. 3,830,787, No. 3,953,414, No.

4,051,313, No. 4,115,319 and No. 4,149,990, hereby incorporated in this application by reference.

Typically, such a catalyst composition is a two component composition where the components are introduced separately into the polymerization reactor. Component (a) of such a composition is advantageously selected from trialkyl aluminums containing from 1 to 8 carbon atoms in the alkyl group, such as triethyl aluminum, trimethyl aluminum, tri-n-butyl aluminum, triisobutyl aluminum, triisohexyl aluminum, tri-n-octyl aluminum and triisooctyl aluminum. Most preferably the trialkyl aluminum is complexed with an electron donor prior to introduction into the polymerization reactor. Best results are achieved when esters of carboxylic acids or diamines, particularly esters of aromatic acids are used as the electron donors.

Some typical examples of such compounds are methyl- and ethylbenzoate, methyl- and ethylp-methoxybenzoate, diethylcarbonate, ethylacetate, dimethylmaleate, triethylborate, ethyl-o-chlorobenzoate, ethylnaphthenate, methyl-p-toluate, ethyltoluate, ethyl-p-butoxy benzoate, ethylcyclohexanoate, ethylpivalate, N,N,N',N'-tetramethylenediamine, 1 ,2,4,-trimethylpiperazine, 2,5dimethylpiperazine and the like. The molar ratio of aluminum alkyl to electron donor can range between 1 and 100, preferably between 2 and 5. Solutions of the electron donor and the trialkylaluminum compound in a hydrocarbon such as hexane or heptane are preferably prereacted for a certain period of time generally less than 1 hour prior to feeding the mixture into the polymerization reaction zone.

The other component of the catalyst composition is either a titanium tri- or tetrahalide supported on magnesium dihalide, or a complex of a titanium tri- or tetrahalide with an electron donor compound supported on magnesium dihalide. The halogen in the respective halides can be chlorine, bromine or iodine, the preferred halogen being chlorine. The electron donor, if it is used in forming a complex, is suitably selected from the esters of inorganic and organic oxygenated acids and the polyamines. Examples of such compounds are the esters of aromatic carboxylic acids, such as benzoic acid, p-methoxybenzoic acid and p-toluic acids and particularly the alkyl esters of said acids; the-alkylene diamines, e.g. N',N",N"', N""-tetramethylethylenediamine. The magnesium to electron donor molar ratio are equal to or higher then 1 and preferably between 2 and 10. Generally the titanium content expressed as titanium metal ranges between 0.1 and 20 wt % in the supported catalyst component and preferably between 1 and 3 wt %.

The preparation of such supported catalyst components have been described in the prior art and are commercially available.

The catalyst components (a) and (b) are fed to the reaction zone in amounts such that the Al/Ti molar ratio is maintained in the broad range between about 1 and about 10,000 and preferably between about 10 and 200.

It is essential that the polymerization process used in this invention is one wherein the propylene functions as the liquid diluent as well as feed to the reaction, except for small quantities of inert hydrocarbons, e.g. hexane, mineral oil, petrolatum, etc., that may be used for the introduction of the catalyst components into the reaction zone. The reaction conditions used in the process of this invention generally include polymerization temperatures in the range from about 11 5,F to about 165"F and preferably in the range from about 125"F to about 155"F.

The pressure should be sufficiently elevated to maintain at least a portion of the propylene in the liquid phase. Suitably pressure of 200 psig and higher are used, e.g. up to about 500 psig.

Total solids in the reaction zone, in accordance with this system, are ordinarily in the order of from 1 5 to 50%, although obviously lower or higher, for example up to 60% polymer solids can be achieved. In order, however, to efficiently handle the slurry, it is preferred to keep the polymerization to the percent solids above indicated. The reaction is continuous and monomer feed (i.e. propylene and ethylene) and catalyst components are continuously fed to the reactor and a slurry of polymer product and liquid propylene is withdrawn, preferably through a cyclic discharge valve which simulates continuous operation. If desired, various modifiers such as hydrogen may be added to alter the properties of the polymer product. Such modifiers are well known in the art and need not be discussed in any further detail since they form no part of this invention.

The withdrawn polymer slurry is let down in pressure to, for example, 50 psig or less in a low pressure zone (meaning a zone maintained at a pressure lower than that in the polymerization reaction) where due to the drop in pressure and the volatile nature of the polymerization ingredients, there is a flashing of these volatiles from the solid polymer. This flashing, which can be aided by heating, results in a polymer powder which is substantially dry and which by this term is to be understood to be a polymer containing 5% or less volatiles. The unreacted monomer stream is taken overhead from this low pressure flashing zone and at least a portion thereof is compressed and condensed and returned to the reactor. The polymer is usually passed to a final drying zone to remove residual volatiles.

Alternately the liquid polymerization medium can be filtered or centrifuged under pressure and the liquid propylene can be returned (after suitable purge) to the reactor, thus saving energy in the form of recompression. This method has the advantage that certain soluble impurities (the aluminum alkyls and organic esters) are removed from the polymer. This in turn leads to a polymer product with lower residual residue content.

Because of the generally high productivity of the supported catalyst system expressed in terms of pounds of polymer produced per pound of titanium metal, which productivity has been further enhanced by the present invention, there is no need to remove catalyst residues from the polymer in a deashing step as is the case with conventional catalyst.

The polymer products provided in accordance with this invention have a meltflow range between about 0.1 and about 10 g/ 1 Omin., ratio of weight-average molecular weight to number-average molecular weight of above about 6.5, ethylene content between about 0.3 and about 5 wt %, Ti content not exceeding about 3ppm, Mg content not exceeding about 40 ppm, CI content not exceeding about 100ppm and total ash content not exceeding about 400ppm.

Compared to conventional random copolymers of same ethylene contents, the polymers of this invention exhibit about a 20 to 30 percent improvement in impact strength. Further advantages of the polymers of this invention compared to conventional polymers includ wider processability range, lower processing energy requirements, superior ability to fill thin sections and multiple cavity molds, better draw-down, easier drawability and higher processing speed in the continuous filament and staple fiber production.

For example, based on spiral meltflow measurements it was found that polymers of this invention having meltflows (ASTM-1238) in the range of about 2-10g/10min. can be processed at 50-30"F lower molding temperatures, or 350-150 psi lower molding pressures than conventional polymers of same meltflows (ASTM-1238).

It is believed that the molecular weight distribution, Mw/Mn is the property that best relates to the improvements in impact strength as well as polymer rheological properties and processability. Typically, polymerization with a conventional catalyst system would result in a polymer product having a Mw/Mn ratio of at most 6.5 and generally below 6, while the polymers of this invention have Mw/Mn ratios of at least 6.5 e.g. between about 6.5 and about 10.

Various additivies can, if desired, be incorporated into the polypropylene resin, such as fibers, fillers, anti-oxidants, metal deactivating agents, heat and light stabilizers, dyes, pigments, lubricants and the like.

The polymers can be used with advantage in the manufacture of fibers, filaments and films by extrusion, of rigid articles by injection molding; and of bottles by blow molding techniques.

The following examples further illustrate the advantages obtained by the invention. EXAMPLES 1-10 The experiments were conducted in large scale continuous pilot plant operations, wherein monomer and catalyst components were continuously charged to a stirred reactor, the monomer feed rate corresponding to 2 hours residence time in the reactor. The organoaluminum compound of the catalyst system was a hexane solution of triisobutyl aluminum (TIBA) which has been treated prior to introduction into the reactor with a hexane solution of methyl-p-toluate (MPT), an electron donor compound. The solid supported titanium halide catalyst component was a commercially available catalyst (FT-1) obtained from Montedison, S.p.A., Milan, Italy.

The supported catalyst component contained about 1.5 wt % titanium, 20.3 wt % magnesium, 60.0 wt % chlorine and 9.6 wt % hydrocarbon volatiles. Ethylbenzoate had been used in the manufacture of the supported catalyst component. The two catalyst components were added at rates directly proportional to the polymer production rates and in amounts sufficient to maintain a polymer solids concentration in the reactor slurry at a nominal value of about 40%. The catalyst productivity (Ib polymer/lb of Ti metal) was calculated in each case from the polymer slurry withdrawal rate, solids content in the slurry and the titanium catalyst component addition rate. The pertinent operating conditions and results are shown in Table 1.

In Table 2 the same data are presented in somewhat different form. The average productivity of the catalyst at 1 55 F and 0% ethylene addition is the base value (100% efficiency) in the comparison of the data. The average catalyst efficiencies of the experiments at each of the other temperatures have been obtained by expressing the observed productivities in percent of that of the average base productivities.

The data are also depicted in Fig. 1.

TABLE 1 EXAMPLE REACTOR REACTOR ETHYLENE TIBA/MPT Al/Ti PRODUCTIVITY % POLYMER NO. TEMP.- F PRESS.-PSIG -WT% MOLAR RATIO MOLAR RATIO 1000lbs/lb Ti ETHYLENE Comp. 1 155 442 0 2.8 152 376 0 Ex. 2 155 445 0.9 2.8 152 411 1.5 Ex. 3 155 452 1.8 2.8 152 449 3.0 Comp. 4 155 438 0 2.8 40 394 0 Ex. 5 155 456 1.4 2.8 40 513 2.7 Comp. 6 130 340 0 2.8 75 268 0 Ex. 7 130 348 1.1 2.8 75 498 2.4 Ex. 8 130 346 1.1 2.8 150 551 2.4 Comp. 9 125 320 0 2.8 150 215 0 Ex. 10 125 327 1.6 2.1 150 433 3.7 TABLE 2 CAT.

TEMP. EFF.

EX. NO ETHYLENE - % Comp. 1 and 4 (avg.) No 155 100 Ex. 2, 3 and 5 (avg.) Yes 155 119 Comp. 6 No 130 70 Ex. 7 and 8 (avg.) Yes 130 136 Comp. 9 No 125 56 Ex. 10 Yes 125 112 "Catalyst efficiency low due to low TIBA/MPT ratio (2.1 vs. 2.8 in all other experiments) As seen from the data plotted in Fig. 1, the effect of small amounts of ethylene in the propylene feed dramatically increases the catalyst efficiency (productivity) over and above that obtained at the optimum temperature when no ethylene was added. Also, the effect of temperature appears to have been eradicated, that is, the improved productivity rate is substantially constant over the rather wide temperature range of from 125"F to 155"F.

COMPARATIVE EXAMPLES 11-16 The polymerization procedure described before was followed except that the catalyst systems were two similar performing conventional non-supported electron donor promoted titanium trichloride catalysts with diethyl aluminum chloride as cocatalysts. The pertinent data from the experiments are listed in Table 3 and Table 4. As seen from the data, the productivity rates with ethylene present were in all cases inferior to that obtained at about optimum temperature conditions (155"F) in the absence of ethylene, and the polymerization temperature had an appreciable effect upon the productivity rates.

TABLE 3 EXAMPLE REACTOR REACTOR ETHYLENE Al/Ti PRODUCTIVITY % POLYMER NO. TEMP.- F PRESS.-PSIG -WT% MOLAR RATIO LBS/LB CAT. ETHYLENE Comp. 11 (1) 155 440 0 3.0 1160 0 Comp. 12 (1) 150 419 0.9 3.0 1125 3.8 Comp. 13 (1) 140 376 0.9 3.0 1118 3.6 Comp. 14 (1) 130 345 1.4 3.0 937 4.5 Comp. 15 (2) 150 432 0 3.0 1023 0 Comp. 16 (2) 150 440 1.0 3.0 1115 2.7 (1) Toho S- 13 catalyst, electron donor modified 3.TiCl3.AlCl3 (2) Mixture of Toyo Stauffer catalysts I (electron donor modified 3.TiCl3.AlCl3) and S (unmodified 3.TiCl3.AlCl3) TABLE 4 CAT.

TEMP. EFF.

EX. NO. ETHYLENE - F Comp. 11 No 155 100 Comp. 12 Yes 150 97 Comp. 13 Yes 140 96 Comp. 14 Yes 130 81 Comp. 15 No 150 88 Comp. 16 Yes 150 96 COMPARATIVE EXAMPLES 17-19 In this set of experiments a conventional unpromoted TiC13.AIC13 catalyst (Stauffer AA) was used under the conditions shown in Table 5. As seen from Table 6 no improvements over the optimum productivity were obtained in this set of experiments.

TABLE 5 EXAMPLE REACTOR REACTOR ETHYLENE Al/Ti PRODUCTIVITY % POLYMER NO. TEMP.- F PRESS.-PSIG -WT% MOLAR RATIO LBS/LB CAT. ETHYLENE Comp. 17 155 440 0 3.65 1275 0 Comp. 18 140 366 0 3.65 890 0 Comp. 19 140 372 0.9 3.65 1015 3.3 TABLE 6 CAT.

TEMP. EFF.

EX. NO. ETHYLENE - F % Comp. 17 No 155 100 Comp. 18 No 140 70 Comp. 19 Yes 140 80 COMPARATIVE EXAMPLES 20-22 The catalyst used in this set of experiments was a phosphorus oxytrichloride modified 3TiCI3.AICI3 catalyst with diethylaluminum chloride as cocatalyst. Again, no improvement over the optimum productivity rates was obtained with this conventional catalyst as shown by the data in Tables 7 and 8.

TABLE 7 EXAMPLE REACTOR REACTOR ETHYLENE Al/Ti PRODUCTIVITY % POLYMER NO. TEMP.- F PRESS.-PSIG -WT% MOLAR RATIO LBS/LB CAT. ETHYLENE Comp. 20 155 440 0 3.0 1480 0 Comp. 21 130 360 1.3 3.0 796 2.5 Comp. 22 130 360 1.3 3.0 664 4.0 TABLE 8 CAT.

TEMP. EFF.

EX. NO ETHYLENE - % Comp. 20 No 155 100 Comp. 21 and 22 (avg.) Yes 130 49 EXAMPLE 23 The polymer product from a continuous polymerization run conducted essentially according to the technique described in Examples 1-10 was subjected to a detailed analysis. The results are shown in Table 9 together with pertinent operating conditions.

As indicated in Table 9, standard ASTM test methods were used to determine the majority of the properties of the polymer products.

The Mw/Mn ratio was determined by liquid chromatography using o-dichlorobenzene as solvent.

The contents of Ti, Mg and Al were determined by atomic absorption analysis of polymer ash dissolved in hydrochloric acid.

and the chlorine content by colorimetric determination of combusted polymer sample using a Parr oxygen bomb.

TABLE 9 EXAMPLE NO. 23 Catalyst FT- 1 Trialkyl aluminum Triethyl Trialkyl aluminum/MPTmol ratio 3.1 Al/Ti-mol ratio 150 Reactor Temperature F 130 Reactor Pressure-psig 350 Residence Time-hrs. 1.7 Productivity kg/gTi 565 Additives: BHT-ppm 1200 Irganox 1010-ppm 500 Calcium stearate-ppm 1000 Hydrotalcite-ppm 1000 Polymer Properties:: Dimer-trimer content-g/kg polymer 3 Isotactic Index-% 69.0 Melt Flow g/10min. (1) 2.7 Density gm/cc (2) 0.8971 Mn 47,000 Mw 329,000 Mw/Mn 7.0 Tensile Strength @ Yield-psi (3) 3270 @ Break-psi (3) > 3390 Elongation at Break-% (3) > 577 Flex Modulus psiX105(4) 1.25 Tensile Moduluspsi x 105 (3) 1.30 HDT-at 66 psi C (5) 72.8 Hardness (Rockwell) (6) 54.9 LTB- C (7) - 9.0 Izod Impact ft Ibs/in (8) 2.0 Polymer Impurities: Ash-ppm 380 Mg-ppm 29 Ti-ppm 2 Cl-ppm 84 Al-ppm 169 (1) ASTM D1238 Cond. L (2) ASTM D1505 (3) ASTM D638 (4) ASTM D790 (5) ASTM D648 (6) ASTM D785 (7) ASTM D746 (8) ASTM D256 EXAMPLES 24-31 The following Table 10 shows the substantial improvement in impact strength obtained with the polymers of this invention (Examples 24-26) compared to conventional polymers (Comp.

Examples 27-31).

TABLE 10 Polymerized Impact Strength, EX. NO C2-, wt % inches(1) 24 1.7 37 25 2.4 33 26 3.6 76 Comp. 27 2.2 15 Comp. 28 2.4 27 Comp. 29 4.0 62 Comp. 30 4.0 66 Comp. 31 4.4 77 '1'ASTM D2463, bottle drop impact strength at 40 F, F50.

The impact improvement is depicted graphically in Fig. 2, which is based on the data of Table 10.

Claims (25)

1. A random propylene/ethylene copolymer having a meltflow range between 0.1 and 10 g/10 min., a ratio of weight-average molecular weight to number-average molecular weight (Mw/Mn) above 6.5/1, a polymerized ethylene content of between 0.3 and 5 wt %, a Ti content not exceeding 2 ppm, an Mg content not exceeding 40 ppm, a Cl content not exceeding 100 ppm and a total ash content not exceeding 400 ppm.

2. A random propylene/ethylene copolymer according to claim 1 substantially as described with reference to any one of Examples 23 to 26.

3. A process for the preparation of a random ethylene/propylene copolymer as claimed in claim 1, which process comprises continuously feeding catalyst components and a mixture of propylene and ethylene to a polymerization reactor, the mixture containing from 0.3 to 2 weight percent ethylene based on the weight of the propylene, at a temperature between 115"F and 165"F and at a sufficiently elevated pressure to maintain at least a portion of the propylene in the liquid phase, withdrawing product in a substantially continuous fashion as a slurry in liquid propylene, wherein the catalyst components comprise:: (a) an aluminum trialkyl or an aluminum trialkyl at least partially complexed with an electron donor compound, and (b) a titanium tri- or tetrahalide supported on magnesium dihalide, or a complex of a titanium tri- or tetrahalide with an electron donor compound supported on magnesium dihalide.

4. A process according to claim 3, wherein the alkyl group of the aluminum trialkyl of catalyst component (a) contains from 1 to 8 carbon atoms.

5. A process according to claim 3, wherein the aluminum trialkyl of catalyst component (a) is triisobutyl aluminum.

6. A process according to claim 3, wherein the aluminum trialkyl of catalyst component (a) is triethyl aluminum.

7. A process according to any one of claims 3 to 6, wherein the electron donor compound of catalyst component (a) is an ester of a carboxylic acid or a diamine.

8. A process according to claim 7, wherein the electron donor is an ester of an aromatic acid.

9. A process according to claim 8, wherein the ester is methyl-p-toluate.

10. A process according to any one of claims 3 to 9, wherein the molar ratio of trialkyl aluminum to electron donor in catalyst component (a) is from 1:1 to 100:1.

11. A process according to claim 10, wherein the molar ratio is between 2:1 and 5:1.

1 2. A process according to any one of claims 3 to 11, wherein component (a) has been prepared by prereacting the aluminum trialkyl with the electron donor for less than one hour prior to polymerization.

1 3. A process according to any one of claims 3 to 12, wherein the titanium tri- or tetrahalide of catalyst component (b) is a titanium trichloride or titanium tetrachloride.

14. A process according to any one of claims 3 to 1 3 wherein the magnesium dihalide of catalyst component (b) is magnesium dichloride.

15. A process according to any one of claims 3 to 14, wherein the electron donor compound of catalyst component (b) is a polyamine or an ester of an inorganic or an organic oxygenated acid.

1 6. A process according to claim 15, wherein said electron donor is an ester of an aromatic carboxylic acid.

1 7. A process according to claim 16, wherein the ester is ethylbenzoate.

18. A process according to any one of claims 3 to 1 7, wherein the magnesium to electron donor molar ratio of catalyst component (b) is at least 1:1.

19. A process according to claim 18, wherein said molar ratio is between 2:1 and 10:1.

20. A process according to any one of claims 3 to 18, wherein the titanium content of catalyst component (b) expressed as titanium metal is from 0.1 to 20 weight percent, based on the weight of the supported catalyst component (b).

21. A process according to claim 20, wherein the titanium content is between 1 and 3 weight percent.

22. A process according to any one of claims 3 to 21, wherein catalyst components (a) and (b) are fed to the reaction zone in a molar ratio Al/Ti f between 1:1 and 10,000:1.

23. A process according to claim 22, wherein said Al/Ti molar ratio is between 10:1 and 200:1.

24. A process according to claim 3 substantially as described with reference to any one of Examples 2,3,5,7,8 and 10.

25. Shaped articles of a copolymer as claimed in claim 1 or 2.