GB2109800A - Benzoate ester-titanium halide coordination complex catalysts for the preparation of homopolymers and copolymers of alpha monoolefins - Google Patents

Abstract

A process for the preparation of homopolymers and copolymers of alpha monoolefins by means of a catalyst system characterized by high activity, high polymer production rates, low residual chloride in the polymer, and polymer morphological properties which allow the use of high reactor temperatures, and comprising (1) a coordination complex formed between a titanium halide of the formula TiCl3 &cirf& m AlCl3 where m is a number from 0 to 0.5, and a benzoic acid ester of the formula <IMAGE> where R<1> is an alkyl radical or an aromatic or aliphatic radical, and (2) an appropriate conventional aluminium alkyl, the titanium halide and the ester having been milled together before use.

Description

SPECIFICATION Benzoate ester-titanium halide coordination complex catalysts for the preparation of homopolymers and copolymers of alpha monoolefins The present invention relates to a catalyst system and to a process for the preparation of homopolymers and copolymers of alpha monoolefins at from 20 to 1 600 C, preferably from 50 to 1200 C, and under a pressure of from 0.1 to 10, preferably from 2 to 7, megapascals (MPa), by means of a catalyst system comprising (1) a coordination complex formed between a titanium halide of the formula TiCl3.m AICI3 where m is a number from 0 to 0.5, preferably from 0.1 to 0.4, and an ester, and (2) an aluminum-alkyl of the formula

where X and Y are each an alkyl radical of not more than 8, preferably not more than 2, carbon atoms, and Z is a halogen or an alkyl radical of not more than 8, preferably not more than 2, carbon atoms, with the proviso that (I) the molar ratio of titanium halide:ester is from 2:1 to 10:1, preferably from 3:1 to 4.5:1 (it) the molar ratio of titanium halide: aluminum-alkyl is from 1:1 to 1:20, preferably from 1:2 to 1:15 and (III) the titanium halide and the ester have been milled together before use.

Processes of this type are known. Their special feature relative to comparable processes is in the specific nature of the catalyst system used, typical examples being given in U.S. Patent Nos.

4,120,823,4,154,699, and 4,154,700. U.S. Patent No. 4,154,699 and German Laid Open Application DAS 2,841,645 broadly disclose the use of a wide variety of acid esters in polyolefin catalyst but do not disclose the specific utility of benzoic acid ester coordination complexing agents nor do they suggest that benzoics acid esters are far superior to the other acid esters disclosed therein. The laid open application specifically discloses only ethylphenylacetate and neither the application nor the patent recognize the special advantages of benzoic acid esters; namely, high productivity, high production rates, and other advantages discussed below.

Benzoic acid esters have been used in supported polyolefin catalyst systems (British Patent No.

1,527,736, German Laid Open Application Nos. 2,829,162, 2,904,598, 2,905,455, and others).

However, these systems are distinguishable from the catalyst system of the present invention because the present system utilizes dry milling of the catalyst, a simple preparation procedure, and eliminates extraneous support materials from the polymer.

The specific modifications of the catalyst system are made in order to achieve particular objectives, for example the following: (a) Catalyst systems which on polymerization of alpha monoolefins, especially propylene, give polymers with a relatively high proportion of stereoregular (=isotactic) polymer.

(b) Catalyst systems which can give an increased yield of polymer, namely systems of increased productivity (systems where the amount of polymer formed per unit weight of catalyst system is increased). The catalysts of the present invention provide increased productivity and production rates, when compared to catalyst with phenylacetic acid ester and tributyl phosphine modifiers. This provides great economy both in catalyst usage and other production costs.

(c) Catalyst systems which introduce less halogen into the polymer, which is achievable by increasing the yield according to (b) and/or by employing a titanium halide which contains very little halogen. The catalysts of the present invention help to provide easier and more complete dehalogenation at high production rates of the polymer produced than tributyl phosphine or phenylacetic acid ester-complexed catalysts.

(d) Catalyst systems which retain a constant or relatively constant activity maximum during storage over a very long time and also a high, relatively constant average activity, both of which are of substantial importance for the catalyst field.

(e) Catalyst systems which make it possible, by increasing the polymerization temperature, to increase the conversion without a significant reduction in the stereoregularity of the polymers, an effect which is generally desirable, especially in gas phase polymerization, because at higher temperatures polymerization rates are increased, reactor production rate is therefore higher, and removal of heat of polymerization is facilitated giving, in general, smoother operation. In addition, less chain transfer agent is required at the higher temperatures to maintain the same average molecular weight. In contrast to the present catalyst system, most catalyst systems exhibit a pronounced decrease in stereospecificity and, therefore, in polymer physical properties as temperature is increased.This diminution of physical properties precludes operating at the higher temperatures with these alternate catalyst systems. Also, with our catalysts, there is a more uniform temperature profile in the polymerization reactor, which, in turn, allows the use of higher overall reactor temperatures because there are less hot spots which could cause a reduction in stereospecificity.

(f) Catalyst systems by means of which-especially at relatively high polymerization temperatures-the morphological properties of the polymers can be influenced in a particular way, for example, in giving a uniform particle size and/or reducing the proportion of fines and/or giving a high bulk density. The benzoic acid ester-titanium halide coordination, complex catalysts have a significantly lower percentage of fines than tributyl phosphine or phenylacetic acid ester-complexed catalysts thereby allowing more uniform dispersion of the catalyst in the reactor which ih turn leads to more uniform reaction temperatures, the advantages of which are discussed above. These factors may, for example, be significant in respect of technical control of the polymerization system, of working of the polymers and/or processability of the polymers.

(g) Catalyst systems which are simple and safe to prepare and easy to handle; for example, systems which can be prepared in (inert) hydrocarbon auxiliary media.

(h) Catalyst systems which make it possible, where the polymerization is carried out in the presence of a molecular weight regulator, especially hydrogen, to manage with relatively small amounts of regulator. Less hydrogen is necessary when the catalyst of the present invention is used than when tributyl phosphine or phenylacetic acid esters catalysts are used. This can be sigr:ificant, for example, in respect to the thermodynamics of the process.

(i) Catalyst systems which are tailored for specific polymerization processes, for example, catalysts which are suited either to the specific perculiarities of suspension polymerization or to the specific peculiarities of dry phase polymerization.

(j) Catalyst systems which give polymers having a pattern of properties which makes them particularly suitable for one or another field of use.

Experience to data has shown that amongst the various objectives there are some which can only be achieved by special embodiments of the catalyst system if other objectives are lowered. Under these circumstances it is, in general, desirable to find embodiments which not only achieve the particular objectives but also demand minimum lowering of other desirable objectives. The use of benzoic acid ester-titanium halide coordination complexes allows the attainment of high productivity and high production rates without sacrificing the other objectives.

Accordingly, the present invention relates to a process for the preparation of homopolymers and copolymers of alpha monoolefins at from 20 to 1 600 C, preferably from 50 to 1 200C, and under pressures of from 0.1 to 10, preferably from 2 to 7 megapascals (MPa) by means of a catalyst system comprising (1) a coordination complex formed between a titanium halide of the formula TiCI3. m AICI3 where m is a number from 0 to 0.5, preferably from 0.1 to 0.4, and a benzoic acid ester of the formula

where R' is an alkyl radical, preferably C1-C8, or an aromatic or aliphatic radical, preferably ethyl, butyl, or benzyl, and (2) an aluminum-alkyl of the formula,

where X and Y are each an alkyl radical of not more than 8, preferably not more than 2, carbon atoms, and Z is a halogen or an alkyl radical of not more than 8, preferably not more than 2, carbon atoms, with the proviso that (I) the molar ratio of titanium halide:ester is from 2:1 to 10:1, preferably from 3:1 to 4.5:1 (it) the molar ratio of titanium halide:aluminum-alkyl is from 1:1 to 1:20, preferably from 1:2 to 1: :1 5 and (III) the titanium halide and the ester have been milled together before use.

The polymerization process as such can-taking into account its characterizing feature-be carried out in virtually all relevant conventional technological embodiments, i.e. as a batchwise, cyclic or continuous process, which may, for example, be a suspension polymerization process, solution polymerization process, or gas phase polymerization process. The technological embodiments mentioned are well know from the literature and from industrial practice and do not require more detailed comments.

For completeness, it should be mentioned that in the process according to the invention, the molecular weights of the polymers can be regulated by the relevant conventional measures, e.g. by means of regulators, especially hydrogen. Further, it is to be noted that in the process according to the invention, the components of the catalyst system can be introduced into the polymerization space in various ways, for example (i) by introducing the coordination complex obtained by milling the titanium halide (1) and the ester (2), as one component, and the aluminum-alkyl (3) as a further component, all at the same place, or (ii) by introducing the complex obtained by milling (1) and (2), on the one hand, and (3), on the other hand, at different places which is in particular advantageous in gas phase polymerization processes and provides significant advantages in terms of higher production rates because there are fewer hot spots and the overall stability is better. Finally it is pointed out that the advantageous features of the process according to the invention in general manifest themselves particularly if the process is carried out as a gas phase polymerization (typical examples of such polymerization processes being given in German Published Applications DAS 1,217,071, 1,520,307 and 1,520,373).

One of the features of the process according to the invention is that the titanium halide and the ester have been milled together to form a stable coordination complex before use. This milling can again be carried out by relevant conventional methods, most simply by conjointly treating the two components in a vibratory mill, especially a vibratory ball mill, for a period up to 50 hours at from 0 to 1 0O0C, with a milling acceleration of from 30 to 80 m.sec-2, in the absence of a diluent. However, milling can also be carried out by special methods, for example, those described in U.S. Patent Nos.

4,120,823,4,154,699, and 4,1 54,700, referred to above.

Regarding the materials used in the catalyst system, the following details should be noted: The titanium halide employed can be a titanium halide, for example, a reaction product obtained on reducing a titanium tetrahalide with hydrogen, aluminum or an aluminum-organic compound.

Compounds which have proved very suitable are, for example, trichlorides of the formula TiCI3, as obtained by reducing titanium tetrachloride with hydrogen, and especially co-crystals, as obtained by co-crystallizing TiCI3 and AlCI3 or reducing TiCI4 with aluminum or with mixtures of aluminum and titanium. Co-crystals of the formula TiCI3.1/3AICI3 are particularly suitable. The appropriate titanium halides are commercially available and hence do not require further comment.

Suitable benzoic acid esters having the formula shown are again the relevant conventional compounds of this formula, e.g. those where R1 is methyl, ethyl, n-propyl, n-butyl, i-propyl, i-butyl, tert.butyl, n-propoxy, or n-butoxy. Typical examples of very suitable esters are ethyl, butyl, and benzyl benzoates, especially butyl benzoate.

Suitable aluminum-alkyls of the stated formula are again the relevant conventional compounds of this formula. These are so well known from the literature and from industrial practice that they do not require more detailed discussions here. Particularly important examples are triethylaluminum and diethyl-aluminum chloride.

The catalysts may also be advantageously used with the unhindered phenolic compounds disclosed in our copending application No. entitled "Polyolefin Polymerization Catalysts Containing Sterically Unhindered Phenolic Compounds", or the hindered phenolic compounds disclosed in German Laid Open Application DAS 2,841,645 and represented by the following formula::

wherein R2 is a C1-C6-alkyl radical, preferably C3-C4-alkyl, R3 is a hydrogen atom or a C1-C6-alkyl radical, preferably C3-C4-alkyl, R4 is a hydrogen atom or a saturated hydrocarbon radical of not more than 30, preferably not more than 24, carbon atoms which may contain up to a total of 6, preferably up to a total of 4, ether groups and/or ester groups, R5 is a C2-C24-alkyl radical, preferably C4C18-alkyl and n is an integer from 1 to 6, preferably from 1 to 4, with the proviso that the molar ratio of aluminum-alkyl:phenolic compound is from 1:1 to 40:1, preferably from 3:1 to 25:1.

Preferably, the aluminum-alkyl and the phenolic compound are pre-mixed and then added to the other components. This provides significant advantages in the catalyst productivity and in operability, i.e. simplification of metering and storage, and allows sufficient time for all alkyl-phenolic reactions to be completed before the material enters the reactor.

The process according to the invention makes it possible to prepare homopolymers and copolymers of alpha monoolefins in an advantageous manner, particularly suitable polymerizable alpha monoolefins being ethylene, propylene, butene-1, and 4-methylpentene-1 and copolymers thereof with ethylene. The advantages hereinbefore discussed are attained with the use of the catalysts described above, i.e., a productivity of at least 5,000 kilograms of polypropylene per kilogram of titanium per megapascal monomer pressure at a production rate of at least 1.5 metric tons of polymer per day per cubic meter of reactor space per megapascal monomer pressure. Significantly different values can be expected for other polymers, i.e., the productivity for the polyethylene should be much higher.

In addition to the aforementioned advantages, the catalysts of the present invention allow the production of polypropylene and random copolymers of ethylene and propylene which have a very low amount of extractable material when extracted with xylene and hexane according to standard Food and Drug Administration procedures. Also, the catalyst of the present invention produce random copolymers of propylene and ethylene with lower melting points. Finaliy, polymers produced with the catalysts of the present invention exhibit, on the average, better tensile, flex mbdulus, deflection temperature, and hardness properties as a direct consequence of their higher crystallinity.

Example 1 In a 1 liter autoclave reactor equipped with a stirrer and means of heating and cooling are added: a) 5.3 ml of 41.2% diethylaluminum chloride (DEAC) solution, b) 0.4738 grams of a titanium chloride-ester coordination complex obtained by milling TiC13.1/3 AICI3 and butyl benzoate in a 3.8/1 mole ratio.

Polymerization is carried out at 650C for 2 hours at a maintained propylene pressure above atmospheric of 300 kilopascals while the reactants and products are stirred at 500 rpm. The reactor is then vented and the material is exposed to the air overnight. In this way, 60.8 grams of polypropylene is obtained or 659 grams of polypropylene (PP)/gram titanium (Ti). The material had a heptane insoluble portion of 94.8%.

Under similar conditions, catalyst prepared by milling aluminum reduced, activated titanium trichloride (TiCI3.AA) with ethyl phenyl acetate provides 550-600 grams PP/g Ti with 95.8% heptane insolubles. A tributyl phosphine-TiCI3.AA complexed catalyst yields 618 PP/g Ti with 96.3% heptane insolubles.

Example 2 To the autoclave of the preceding example is added the following: a) 6.4 ml of a solution obtained by dissolving 8.0 grams of Organox 1076 (octadecyl -3, 5-ditert butyl-4-hydroxyl-hydrocinnamate) with 136 ml of 25.2% DEAC.

b) 0.3371 grams of ball milled TiCl3.AA/butyl benzoate coordination complex catalyst in a 3.8/l mole ratio.

Polymerization is carried out at 650C for 2 hours at a maintained propylene pressure of 300 kilopascals above atmospheric. The reactor is vented and the contents exposed to air overnight. A yield of 54.9 grams of polypropylene or 836 grams of PP/gTi is obtained wiht 96.2% heptane insolubles.

In a similar fashion, a catalyst prepared from ethyl phenyl acetate provides 739 g PP/g Ti with a 96.1% heptane insoluble portion.

Example 3 In a 2 liter autoclave equipped with a stirrer and means of heating and cooling are placed: a) 15.0 grams granular ethylene/butene copolymer of known composition (less than 6% butene 1) b) 8.5 ml of 24.7% triethyl aluminum c) 0.4635 grams of TiCI3.AA/butyl benzoate coordination complex catalyst prepared in a 3.8/1 mole ratio.

Polymerization is carried out by maintaining a pressure above atmospheric of 1 60 kilopascals of a blend of 91% (wt) ethylene and 9% butene-1 and stirring at 500 rpm. The temperature of reaction is kept at 70-960C for 4 hours. The reactor is vented and 240.7 grams of polymer is obtained of which 225.7 are synthesized or 2500 g polymer/g Ti. The material has a density of 0.9250 g/cc, 6.1% butene-1 by 13C NMR analysis and a melting point range of 111.4--127.50C.

Example 4 In a 2 liter autoclave with stirrer and means of heating and cooling are placed: a) 10.0 grams of a copolymer containing 4 methyl-1 -pentene (4.5% wt) and ethylene.

b) 10.0 ml of 24.9% triethyl aluminum c) 0.38 grams of a coordination complex prepared by milling TiCI3.AA and butyl benzoate at a 3.8/1 mole ratio.

Polymerization is carried out by charging the reactor with 400 kilopascals of H2 above atmospheric and heating to 600 C. Ethylene saturated with 4-methyl-I -pentene (prepared by bubbling ethylene into 20 ml of 4-methyl-1-pentene at ambient temperature) is charged into the reactor and the pressure of the reactor maintained at 400 kilopascals above atmospheric. Polymerization is allowed to proceed for 3 hours at a temperature less than 1 000C. The reactor is vented and 149.9 grams of polymer are recovered, 139.9 being synthesized or 1 890 polymer/g Ti.The material has a melting point of 1 19.9--131.20C, a density of 0.9348 g/cc and contains 7.5% (wt) 4-methyl-l-pentene by carbon 3 nuclear magnetic resonance spectroscopy.

Example 5 In a similar manner to the preceding example: a) 1 5.0 grams of copolymer of 1-hexene and ethylene b) 12 ml of triethyl aluminum c) 0.38 grams of butyl benzoate-titanium halide coordination complex catalyst are charged in a 2 liter reactor.

Polymerization is carried out without H2 at 80-980C for 5 hours at 400 kilopascals above atmospheric pressure of ethylene saturated with 1-hexane (26 ml total taken up). The reactor is vented and 157.7 grams of polymer recovered of which 142.7 g are synthesized or 1930 g polymer/g Ti. The product has a melting point of 112.5-1 29.00 C, a density of 0.9297 g/cc and contains 6.396 (wt) hexene-1 by carbon-13 nuclear magnetic resonance spectroscopy.

Example 6 In a liter autoclave equipped with stirrer and means of heating and cooling were placed: a)4methyl-1-pentene, 131 ml,87.0g b) DEAC 25.2%, 5.0 ml c) Butyl benzoate-TiCI3.AA coordination complex, as above, 0.1385 g d) H2 to pressure reactor to 100 kilopascals above atmospheric.

Polymerization was carried out at 700C for 45 min. The reactor was vented and the polymer allowed to air dry overnight to yield 61.7 g of poly-4-methyl-1-pentene or 2288 g polymer/gTi.

In an analogous manner, when ethyl phenyl acetate was used, the productivity was 241 8 g/Q Ti.

Tributyl phosphine TiCI3.AA produced 1690 g/g Ti, and TiCI3.AA alone yielded 1990 g/g Ti.

Example 7 A copolymer of ethylene and butene-l was prepared as follows. In a stirred two-liter glass reactor, 0.9119 9 of Irganox 1076 was dissolved in 1300 ml of pure, dry nitrogen-purged nhaptane. 1 5.5 ml of a 25% solution of diethylaluminum chloride (DEAC) in heptane was injected and allowed to react for 15 minutes at 6O0C. Then 0.7845 g of a ball-milled coordination complex was added. The complex had been prepared from aluminum-reduced, activated titanium trichloride and butyl benzoate in a mole ratio of 3.8/1. A mixture of 80 mol % ethylene and 20 mol % butene-1 was bubbled through the catalyst slurry at the rate of about one standard liter per minute for three hours at 600C.Polymerization was terminated by turning off the monomer feed and adding 100 ml of methanol slowly enough (dropwise) to prevent excessively rapid gas evolution. The polymer slurry was precipitated into 5 liters of methanol containing 10 ml of concentrated hydrochloric acid and stirred for five minutes. The polymer was isolated by vacuum filtration and dried in a vacuum oven at 900 C. The yield was 108.9 g, representing a catalyst productivity of 711 g/g Ti. The product was pressed into sheets and found to have a density of 0.8987. Analysis by carbon-13 nuclear magnetic resonance spectroscopy showed that 1 2.8 mol % of butene-1 had been incorporated into the copolymer in a random fashion.

Example 8 A two-liter reactor was charged with 1300 ml of pure, dry n-heptane and 0.9857 g of Irganox 1076. The solution was heated to 600C while passing nitrogen through it, and 1 6.8 ml of a 25% solution of DEAC in heptane was injected. The mixture was stirred for 1 5 minutes, then 0.888 g of a ball-milled coordination complex was added. The catalyst had been prepared from TiCl3.AA and butyl benzoate in the mole ratio of 3.8/1. Then ethylene and butene-1 were fed at a mass-flow ratio of 80/20; i.e. a mole ratio of 89/1 1, at a flow rate of about one standard liter per minute, for three hours at 600 C.

The polymer yield was 73.7 g, representing a catalyst productivity of 425 g/g Ti. The copolymer was pressed into plaques, and the density was determined to be 0.9147. Carbon-13 nuclear magnetic resonance spectroscopy showed the presence of 21.7 ethyl branches per 1000 carbon atoms, indicating that 4.5 mol % of butene-l had been incorporated into the copolymer. The latter melted over a range of 113-1 28.50C.

Example 9 25 ml of butyl benzoate was added to a slurry of TiCI3.AA 225 ml of dry, nitrogen-purged nheptane at 21-250C, with stirring, over a 30 minute period. The temperature was raised to a maximum of 690C and held, with intermittent heating, at 65+1 OC, under a slow stream of ultra high purity nitrogen. The effluent gas was tested for HCl evolution with moist pH paper (positive; ph approximately 1). The heat was turned off after 4.5 hours at 64-690C, and the product was left under a slow stream of nitrogen over the weekend. Then the heptane was distilled off, with a slow stream of nitrogen flowing through the flask, up to a maximum pot temperature of 1030C. In the end, some fumes were observed in the receiver. A solid precipitate was found in the distillate.This procedure gave the catalyst mixture the same thermal history it would have received in a typical catalyst milling.

The finely divided solid obtained as a residue after distillation of the diludnt was tested as a polymerization catalyst for propylene. The catalyst system was modified with Irganox 1076 (0.5 mole) prereacted with DEAC (7 moles, per mole of Ti) for 1 5 minutes at 600 C. Propylene was polymerized for 3 hours at 740C in heptane slurries. The results were as follows: Productivity, Heptane Catalyst sample g PP/g Ti insolubles, % Stauffer TiCI3.AA* 256 94.6 (not ball-milled) 254 95.2 Modified catalyst 214 94.5 (not ball-milled) 207 94.7 *Propylene polymerized for 3 hours at 60 C in heptane slurries (duplicate determinations) with DEAC/Ti mole ratio of 4/1.

The productivity of this catalyst is much lower than that of the other catalysts tested in the preceding examples. Thus, milling the ester and titanium halide to form a coordination complex is necessary to achieve the advantages of the present invention.

Example 10 1.0383 g of Irganox 1076 was dissolved in 20 ml of pure, dry, deoxygenated n-heptane. Then 1 7.7 ml of a 25% solution of diethylaluminum chloride (DEAC) was injected under a nitrogen atmosphere and allowed to react for 15 minutes. Then 0.9501 g of a ball-milled coordination catalyst was added which had been prepared from TiCI3.AA and butyl benzoate in a mole ratio of 3.8/1. The resulting slurry was ultrasonically dispersed for 40 minutes. It was then transferred to a stirred polymerization reactor containing 1 300 ml of pure, dry, deoxygenated n-heptane. Gaseous propylene at atmospheric pressure was bubbled through the slurry and polymerized for three hours at 740 C. The reaction was terminated by dropwise addition of 100 ml of methanol.The polymer was precipitated in five liters of methanol containing 10 ml of concentrated hydrochloric acid, washed, filtered, and dried.

The yield was 100.6 g, representing a catalyst productivity of 543 g PP/g Ti. This was 47.4% higher than the productivity obtained in comparison Example 11. The heptane insoluble fraction was 97.9%.

Example 11 1.2923 g of Irganox 1076 was dissolved in 20 ml of pure, dry, deoxygenated n-heptane. Then 22.0 ml of a 25% solution of diethylaluminum chloride (DEAC) was injected under a nitrogen atmosphere and allowed to react for 1 5 minutes. Then 1.2184 g of a ball-miiled coordination complex was added which had been prepared from TiCI3.AA and ethyl phenylacetate in a mole ratio of 3/1. The resulting slurry was ultrasonically dispersed for 40 min. It was then transferred to a two-liter stirred polymerization reactor containing 1 300 ml of pure, dry deoxygenated n-heptane. Gaseous propylene at atmospheric pressure was bubbled through the slurry and polymerized for three hours at 740 C. The reaction was terminated by dropwise addition of 100 ml of methanol.The polymer, including the fraction soluble in the reaction medium, was precipitated in five liters of methanol containing 10 ml of concentrated hydrochloric acid, washed, collected on a filter, and dried in a vacuum oven. The polymer yield was 84.8 g, representing a catalyst productivity of 368 g PP/g Ti. The heptane insoluble fraction was 98.5%. Thus, butyl benzoate performed better than ethylphenylacetate.

Example 12 Three different catalysts were evaluated by polymerizing propylene in a continuous pilot plant reactor at the conditions shown in Table No. 1 below. The catalysts comprised aluminum activated titanium trichloride coordination complexes and diethylaluminum chloride which were added separately to the reactor. A different complexing agent was used in each of the catalyst samples. In Sample No. 1, the aluminum activated titanium trichloride was complexed with ethylphenylacetate, in Sample No. 2, it was complexed with tributylphosphine, and in Sample No. 3, it was complexed with butyl benzoate. The aluminum activated titanium trichloride coordination complex of the catalyst was milled in accordance with the milling procedures set forth in previous examples for each of the different types of complexing agent.

Table 1 Catalyst 1 2 3 React. temp. (OC) 77 82 79 React. pressure MPa (megapascals) 3.13 3.13 2.78 Production rate (tons per cubic meter/day) 3.88 2.73 4.42 In each case, the reactor was run to maximize the production rate therein. It can be seen that the butyl benzoate-containlng catalyst No. 3 allowed the attainment of the highest rate in the reactor.

Example 13 A tributylphosphine-containing catalyst was compared with a butyl benzoate-containing catalyst in a large scale commercial reactor in the same manner as in the previous example. Again, the reactor was run so that the maximum production rate could be achieved. It can be seen by reviewing Table 2 that the butyl benzoate catalyst (Catalyst No. 2) allows the attainment of a higher production rate than the tributylphosphine catalyst (Catalyst No. 1).

In the case of butyl benzoate-containing catalyst, the achievable polymerization rate was limited by the capacity of the cooling system to remove heat of polymerization. As demonstrated in Example 12, this limitation is not caused by catalyst limitations, but rather by equipment capacity in use at the time the data were obtained.

Table 2 Catalyst 1 2 React. temp. (OC) 85 69 React. pressure MPa 2.87 2.93 Production rate (tons per cubic meter/day) 2.66 3.30* *Limited by capacity of cooling system to remove heat of polymerization.

Example 14 A butyl benzoate catalyst as described above was prepared in a vibratory ball mill and milling temperatures ranging from about -1 OOC to 800 C. Activated titanium trichloride was premilled for 8 hours and then 0.263 mols per mol of titanium trichloride of butyl benzoate was added thereto over a four hour period with maximum cooling. The internal temperature was then adjusted to 600C and milling was continued for 24 hours.Catalyst samples were taken at two or four hour intervals and tested by laboratory polymerizations of propylene in heptane slurry for three hours at 740The productivity of the catalyst after the 24 hours milling cycle was 403 grams of the polypropylene per gram of titanium and the heptane insolubles content of the polymer produced was 97.7 percent.The particle size distribution of the polymer is shown in Table 3 below: Table 3 Particle size, microns: Milling cyc/e > 1700, 600- 250- 150- 75- 45 hours, 60 OC %(wt) 1700 600 250 150 75 < 45 2 14.5 41.5 26.9 7.8 6.8 1.6 0.9 4 8.2 35.8 33.2 10.5 8.7 2.5 1.1 6 42.2 39.2 12.1 3.6 2.4 0.2 0.3 8 18.3 49.9 22.9 5.3 3.1 0.25 0.25 12 33.8 54.7 6.5 3.5 1.5 0 0 16 46.0 40.0 11.3 2.1 0.6 0 0 20 51.9 34.8 10.7 2.1 0.5 0 0 24* 4.8 41.9 37.9 8.8 4.2 1.1 1.3 *Catalyst postmilled for 30 minutes.

It can be seen that the morphological properties of the polymer are excellent. The particle size distribution is extremely narrow in that 79.8 percent by weight of the particles are in two size distribution ranges (260--600 microns and 6001700 microns). Furthermore, the total fines content, the amount of particles or the size below 250 microns, is only 15.4 percent by weight.

Example 15 Dechlorination of polypropylene powder is an important problem. Residual chloride levels of polymer made with butyl benzoate catalysts are about half the levels experienced with ethyiphenylacetate catalysts and also less than those experienced with tributyl phosphine catalysts.

The three types of catalysts were compared by polymerizing propylene in a continuous pilot plant reactor under conditions substantially similar to those in Example 12. The catalysts were compared at comparable production rates as measured by space-time-yield because the higher throughput catalyst, butyl benzoate catalyst, is inherently harder to dechlorinate if for no other reason than the reduced residence time of the polymer in the dechlorination unit. The results of the experiments which show that butyl benzoate catalysts allows the attainment of lower residual chloride levels in a polymer are shown in Table 4 below: Table 4 Tributyl phosphine Ethylphenylacetate Butyl benzoate prod. rate chloride prod. rate chloride prod. rate chloride (T/D/m3)* PPM (T/D/m3)* PPM (T/D/m3)* PPM - 3.16 78 3.22 54 - 2.91 87 2.86 23 - 2.67 39 2.72-2.78 19 - 2.60 29 - 2.32 49 2.47 46 2.40-2.42 14-19 2.10 42 - - - *Metric tons/per day/per cubic meter of reactor volume.

Claims (10)

Claims

1. A catalyst system for the preparation of homopolymers and copolymers of alpha monoolefins and characterized by high catalyst activity, high polymer production rates, low residual halide in the polymer, and polymer morphological properties which allow the use of high reactor temperatures, and comprising (1) a coordination complex formed between a titanium halide of the formula TlCl3.m AICI3 where m is a number from 0 to 0.5, and a benzoic acid ester of the formula

where R1 is an alkyl or an aromatic or aliphatic radical, and (2) an aluminum-alkyl of the formula

where X and Y are each an alkyl radical of not more than 8 carbon atoms, and Z is a halogen or an alkyl radical of not more than 8 carbon atoms, with the proviso that (I) the molar ratio of titanium halide:ester is made from 2::1 to 10:1, (it) the molar ratio of titanium halide:aluminum-alkyl is from 1:1 to 1:20, and (III) the titanium halide and the ester have been milled together before use.

2. A catalyst system as claimed in claim 1, wherein the activity of the catalyst is at least 5000 kilograms of polypropylene per kilograms of titanium per megapascal monomer pressure and the polymer production rate is at least 4 metric tons per day per cubic meter of reactor space per megapascal monomer pressure.

3. A catalyst system as claimed in claim 1 or 2, wherein the benzoic acid ester is selected from ethyl benzoate, butyl benzoate and benzyl benzoate.

4. A catalyst system as claimed in claim 1, 2 or 3, wherein the aluminum-alkyl is diethylaluminum chloride.

5. A catalyst system as claimed in any preceding claim additionally including a phenolic compound of the formula:

wherein R2 is a C1-C6-alkyl radical, R3 is a hydrogen atom or a CCf-alkyl radical, R4 is a hydrogen atom or a saturated hydrocarbon radical of not more than 30 carbon atoms which may contain up to a total of 6, ether groups and/or ester groups, R5 is a C2C24-alkyl radical, and n is an integer from 1 to 6, with the proviso that the molar ratio of aluminum-alkyi:phenolic compound is from 1:1 to 40:1.

6. A catalyst system as claimed in any preceding claim wherein the aluminum-alkyl and the phenolic compound are premixed and then added to the other components.

7. A catalyst system for the preparation of homopolymers and copolymers of alpha monoolefins as claimed in any preceding claim, substantially as hereinbefore described and exemplified.

8. A process for the preparation of homopolymers and copolymers of alpha monoolefins at from 20 to 1 600C and under pressures of from 0.1 to 10 megapascals by means of a catalyst system as claimed in any one of claims 1 to 7.

9. A process as claimed in claim 8, substantially as hereinbefore described and exemplified.

10. In a process for the preparation of homopolymers and copolymers of alpha olefins at from 20 to 1 600C under pressures of from 0.1 to 10 megapascals, by means of catalyst system comprising (1) a coordination complex formed between a titanium halide of the formula TiCI3. m AICI3 where m is a number from 0 to 0.5, and an ester of a total of 2 to 34 carbon atoms, which has the general formula R8-OO-R7 or

where R6 is (I) an alkyl radical of 1 to 16 carbon atoms or (II) a phenylalkyl radical of a total of 7 to 23 carbon atoms, up to 5 hydrogen atoms of the phenyl radical being unsubstituted or substituted by an alkyl radical of 1 to 5 carbon atoms, and R7 Is (I) a hydrogen atom, (II) an alkyl radical of 1 to 1 8 carbon atoms, (III) a phenyl-alkyl radical of-a total of 7 to 23 carbon atoms, up to 5 hydrogen atoms of the phenyl radical being unsubstituted or substituted by an alkyl radical of 1 to 5 carbon atoms, (IV) a phenyl radical, or (V) an alkylphenyl radical of a total of 7 to 23 carbon atoms, up to 5 hydrogen atoms of the phenyl radical being unsubstituted or substituted by an alkyl radical of 1 to 5 carbon atoms, individual radicals R7 being identical or different when more than one is present, and (2) an aluminum-alkyl of the formula

where X and Y are each an alkyl radical of not more than 8 carbon atoms, and Z is a halogen or an alkyl radical of not more than 8 carbon atoms, with the proviso that (I) the molar ratio of titanium halide:ester is from 2: :1 to 10:1, (11) the molar ratio of titanium halide:aluminum-alkyI is from 1:1 to 1:20, and (III) the titanium halide and the ester have been milled together before use, the improvement which comprises using as the ester a benzoic acid ester of the formula

where R' is an alkyl radical or an aromatic or aliphatic radical, whereby the improved catalyst is characterized by high activity, high polymer production rates, low residual halide in the polymer, and polymer morphological properties which allow the use of high reactor temperatures.