WO1993007188A1

WO1993007188A1 - Activation of catalyst in ethylene polymerization at high temperatures

Info

Publication number: WO1993007188A1
Application number: PCT/CA1992/000419
Authority: WO
Inventors: Vaclav George Zboril; Stephen John Brown; Reginald Kurt Ungar
Original assignee: Du Pont Canada Inc.
Priority date: 1991-10-03
Filing date: 1992-09-25
Publication date: 1993-04-15
Also published as: TR28911A; EP0606285A1; CN1033812C; RU2119925C1; AU2585892A; IN178304B; GB9121019D0; CA2119737A1; CN1070919A; TW206242B; BR9206588A; JPH06511035A; CA2119737C; MY111171A; KR100245204B1; RU94021921A; MX9205650A

Abstract

A solution process for the preparation of high molecular weight polymers of alpha-olefins selected from the group consisting of homopolymers of ethylene and copolymers of ethylene and C3-C12 higher alpha-olefins, by polymerization of ethylene and/or mixtures of ethylene and C3-C12 higher alpha-olefins in the presence of a catalytic amount of a titanium-containing coordination catalyst in an inert solvent at a temperature in excess of 105 °C is disclosed. The improvement is characterized in that: (a) the catalyst is activated with a solution of alkoxyalkyl aluminum in inert solvent; and (b) the process is operated at least in part at a temperature of at least 180 °C. In an embodiment, the coordination catalyst is formed from a first component and a second component, the first component containing titanium and second component being selected from the group consisting of alkoxy aluminum alkyl and mixtures of alkyl aluminum and alkoxyalkyl aluminum. The aluminum alkyl is of the formula ARnX3-n and the alkoxy alkyl aluminum is of the formula AR'mOR'3-m, in which each of R, R' and R' may be the same or different and is alkyl or aryl of 1-20 carbon atoms, X is halogen, n is 1-3 and m is 0-2.

Description

ACTIVATION OP CATALYST IN ETHYLENE POLYMERIZATION AT HIGH TEMPERATURES

The present invention relates to a process and catalyst for the preparation of polymers of ethylene, especially homopolymers of ethylene and copolymers of ethylene and higher alpha-olefins. In particular, the invention relates to a solution polymerization process for the preparation of such polymers in which the process is operated at a temperature of at least 180°C, and the catalyst is activated with a alkoxy alkyl aluminum compound.

Polymers of ethylene, for example, homopolymers of ethylene and copolymers of ethylene and higher alpha- olefins, are used in large volumes for a wide variety of end-uses, for example, in the form of film, fibres, moulded or thermoformed articles, pipe coatings and the like.

There are two types of processes for the manufacture of polyethylene that involve the polymerization of monomers in an inert liquid medium in the presence of a coordination catalyst viz. those which operate at temperatures below the melting or solubilization temperature of the polymer and those which operate at temperatures above the melting or solubilization temperature of the polymer. The latter are referred to as "solution" processes, an example, of which is described in Canadian Patent 660,869 of A. . Anderson, E.L. Fallwell and J.M. Bruce, which issued 1963 April 9. In a solution process, the process is operated so that both the monomer and polymer are soluble in the reaction medium. Accurate control over the degree of polymerization, and hence the molecular weight of the polymer obtained, may be achieved by control of the reaction temperature. In solution polymerization processes, it is advantageous to operate the process at very high temperatures e.g..>250°C, and to use the heat of polymerization to flash off solvent from the polymer solution obtained.

While steps may be taken to remove catalyst from the polymer subsequent to the polymerization step in the process, it is preferred that a solution polymerization process be operated without catalyst removal steps. Thus, catalyst will remain in the polymer. Such catalyst, which may be referred to as "catalyst residue", may contribute to the colour of the polymer obtained and to degradation of the polymer during or subsequent to processing of the polymer. The amount of catalyst residue is related, at least in part, to the overall activity of the catalyst employed in' the polymerization step of the process as the higher the overall activity of the catalyst the less catalyst that is, in general, required to effect polymerization at an acceptable rate. Catalysts of relatively high overall activity are therefore preferred in solution polymerization processes. Two important factors in determining the overall activity of a catalyst are the instantaneous activity of the catalyst and the stability of the catalyst under the operating conditions, especially at the operating temperature. Many catalysts that are stated to be very active in low temperature polymerization processes also exhibit high instantaneous activity at the higher temperatures used in solution processes, but tend to decompose within a very short time in a solution process, with the result that the overall activity is disappointingly low. Such catalysts are of no commercial interest for solution processes. Other catalysts may exhibit acceptable overall activity at the' higher temperatures of a solution process but show tendencies to yield polymers of broad molecular weight distribution or of too low a molecular weight to be commercially useful for the manufacture of a wide range of useful products. Thus, the requirements for and the performance of a catalyst in a solution polymerization process are quite different from those of a catalyst in a low temperature polymerization process, as will be understood by those skilled in the art.

The preparation of polymers of ethylene in solution polymerization processes is described in published PCT patent application No. WO 91/17193 of D.J. Gillis, M.C. Hughson and V.G. Zboril, published 1991 November 14, and in the patent applications referred to therein.

Catalysts activated by siloxalanes are capable of polymerizing ethylene at very high temperatures. However, the siloxalane residues from such catalysts tend to significantly adversely affect the performance of adsorbers used to purify solvent in the associated solvent recovery and recycle sections of the polymerization process.

There is extensive prior art on the use of various electron donors as adjuncts to Ziegler-Natta catalysts in low (less than 90°C) temperature polymerization of ethylene and other alpha-olefins, to increase the activity and/or stereospecificity of the catalyst. Esters of aromatic acids e.g. toluic or benzoic acid, ethers and alcohols are frequently used for that purpose. However, most electron donors that are useful at low temperatures destroy catalyst activity as the polymerization temperature increases. As an example of the use of electron donors, U.S. Patent 4 097 659 of H.M.J.C. Creemers et al, issued 1978 June 27, discloses a low temperature polymerization process, operating in an inert solvent at temperatures in the range of 20- 100 ° C, in which the list of examples of activators includes dimethylmonobutoxy aluminum, monodecylpropoxy aluminum chloride^' and monobutyl monobutoxy aluminum hydride.

As exemplified hereinafter, substitution of even a part of trialkylaluminu with alkoxy alkylaluminum of the type used in U.S. Patent 4 097 659 results in a substantial decrease in catalyst activity even if the temperature is only 130°C i.e. in the lowest temperature range of operation of a solution polymerization process. Surprisingly, it has now been found that at higher temperatures this trend to decreased catalytic activity is reversed and alkoxyalkyl aluminum activated catalysts exhibit superior activity at temperatures above about 180°C.

Accordingly, the present invention provides in a solution process for the preparation of high molecular weight polymers of alpha-olefins selected from the group consisting of homopolymers of ethylene and copolymers of ethylene and C₃-C₁₂ higher alpha-olefins, by polymerization of ethylene and/or mixtures of ethylene and C-.-C._j2 higher alpha-olefins in the presence of a catalytic amount of a titanium-containing coordination catalyst in an inert solvent at a temperature in excess of 105 ° C, the improvement characterized in that:

(a) the catalyst is activated with a solution of alkoxyalkyl aluminum in inert solvent; and

(b) the process is operated at least in part at a temperature of at least 180°C. The present invention further provides a solution process for the preparation of high molecular weight polymers of alpha-olefins selected from the group consisting of homopolymers of ethylene and copolymers of ethylene and C₃-C₁₂ higher alpha-olefins, said process comprising feeding monomer selected from the group consisting of ethylene and mixtures of ethylene and at least one C₃-C₁₂ higher alpha-olefin, a coordination catalyst and inert hydrocarbon solvent to a reactor, polymerizing said monomer and recovering the polymer so obtained, characterized in that said monomer is polymerized at a temperature in the range of 180-320°C and said coordination catalyst having been formed from a first component and a second component, said first component containing titanium and second component being selected from the group consisting of alkoxy aluminum alkyl and mixtures of alkyl aluminum and alkoxyalkyl aluminum, said aluminum alkyl being of the formula AlR_nX₃._n and said alkoxy alkyl aluminum being of the formula AIR^OR"^, in which each R, R' and R" may be the same or different and is independently selected from alkyl or aryl of 1-20 carbon atoms, X is halogen, n is 1-3 and is 0-2.

In a preferred embodiment of the process of the invention, R is alkyl of 2-8 carbon atoms and n=3, and each of R' and R" is alkyl of 2-8 carbon atoms and m=2. In an embodiment of the process of the invention, the second component is in the form of a mixture of trialkyl aluminum and an alcohol in which the amount of alcohol is less than the stoichio etric amount to form dialkyl alkoxy aluminum, especially in which the trialkyl aluminum is A1R³ ₃ in which each R³ is an alkyl group having 1-10 carbon atoms and the alcohol is of the formula R⁴0H in which R is alkyl or aryl of 1-20 carbon atoms, especially alkyl of 1-16 carbon atoms.

In another embodiment of the process, the first component is formed from:

(i) a mixture of MgR¹ ₂ and A1R² ₃ in which each R¹ and R² are the same or different and each is independently selected from alkyl groups having 1-10 carbon atoms; (ii) a reactive chloride component; and (iϋ) titanium tetrachloride.

Alternatively, the first component may be formed by rapidly admixing a solution of a titanium tetrahalide, optionally containing vanadium oxytrihalide, and with organoaluminum compound e.g. trialkyl aluminum or dialkyl aluminum halide, at a temperature of less than 30°C, and heating the resultant admixture to a temperature of 150-300°C for a period of 5 seconds to 60 minutes.

In a further embodiment, the forming of the first and second catalyst components and the admixing thereof are carried out in-line at a temperature of less than 30"C.

The present invention is directed to a process for the preparation of high molecular weight polymers of alpha-olefins, such polymers being intended for fabrication into articles by extrusion, injection moulding, thermoforming, rotational moulding and the like. In particular, the polymers of alpha-olefins are homopolymers of ethylene and copolymers of ethylene and higher alpha-olefins i.e. alpha-olefins of the ethylene series, especially such higher alpha-olefins having 3 to 12 carbon atoms i.e. C₃-C₁₂ alpha-olefins, examples of which are 1-butene, 1-hexene and 1-octene. The preferred higher alpha-olefins have 4-10 carbon atoms. In addition cyclic endomethylenic dienes may be fed to the process with the ethylene or mixtures of ethylene and C₃-C₁₂ alpha-olefin. Such polymers are known.

In the process of the present invention, monomer, a coordination catalyst and inert hydrocarbon solvent, and optionally hydrogen, are fed to a reactor. The monomer may be ethylene or mixtures of ethylene and at least one C₃-C₁₂ higher alpha-olefin, preferably ethylene or mixtures of ethylene and at least one C₄-C₁₀ higher alpha-olefin; it will be understood that the alpha- olefins are hydrocarbons. The coordination catalyst is formed from two components viz. a first component and a second component. The first component contains titanium or admixtures thereof with other transition metals in lower than maximum valency, and is an organometallic component of the type, typically used in solution polymerization processes. The first component may be in a solid form. Examples of the first component have been given above.

The second component is a solution of an alkoxyalkyl aluminum or a mixture of aluminum alkyl and alkoxy alkyl aluminum in inert solvent; the ratio of aluminum alkyl to alkoxy aluminum alkyl in the mixture may be used in the control of the process. The aluminum alkyl is of the formula AlR_nX₃._n and the alkoxy aluminum alkyl is of the formula AIR^OR"^, in which each R, R' and R" is alkyl or aryl of 1-20 carbon atoms, X is halogen especially fluorine, chlorine or bromine, n is 1-3 and m is 2. The preferred halogen is chlorine.

The alkoxy aluminum alkyl may be prepared by admixing the corresponding alkyl aluminum with the corresponding alcohol, so as to form the alkoxy aluminum alkyl. Preferably, the alkyl aluminum is the same as the aluminum alkyl in the second component. In fact, the preferred method of forming the second component is to add the alcohol to the alkyl aluminum in less than the stoichiometric amount required to convert all of the alkyl aluminum to alkoxy aluminum alkyl. The mixing may be conveniently carried out in-line_. at a temperature of less than 30°C, permitting reaction to occur for some minimum time. This time depends on the type and reactivity of the components used to prepare a particular catalyst. As exemplified hereinafter, feeding the alcohol directly to the reactor in the ^' polymerization^' process is detrimental to the polymerization process.

The ratio of the alcohol to the alkyl aluminum used to achieve control of the polymerization process is in the range of 0.1-1 (alcohol:aluminum) .

The concentration of the components of the solutions used in the preparation of the catalyst is not critical and is primarily governed by practical considerations. Concentrations of as low as 25 ppm, on a weight basis, may be used but higher concentrations, for example 100 ppm and above, are preferred.

As exemplified hereinafter, the sequence of steps in the preparation of the catalyst is important in obtaining a catalyst with high activity. The coordination catalyst described herein is used in the process of the invention without separation of any of the components of the catalyst. In particular, neither liquid nor solid fractions are separated from the catalyst before it is fed to the reactor. In addition, the catalyst and its components are not slurries. All the components are easy-to-handle, storage stable liquids.

The solvent used in the preparation of the coordination catalyst is an inert hydrocarbon, in particular a hydrocarbon that is inert with respect to the coordination catalyst. Such solvents are known and include for example, hexane, heptane, octane, cyclohexane, methylcyclohexane and hydrogenated naphtha. The solvent used in the preparation of the catalyst is preferably the same as that fed to the reactor for the polymerization process.

The first component of the catalyst described herein may be used, according to the process of the present invention, over the wide range of temperatures that may be used in an alpha-olefin polymerization process operated under solution conditions. For example such polymerization temperatures may be in the range of 105-320°C and especially in the range of 105-310°C. However, as exemplified hereinafter, the activator is particularly effective at temperatures of at 180"C, and thus the process of the invention is operated, at least in part, at such elevated temperatures.

The pressures used in the process of.the present invention are those known for solution polymerization processes, for example, pressures in the range of about 4-20 MPa. In the process of the present invention, the alpha- olefin monomers are polymerized in the reactor in the presence of the catalyst. Pressure and temperature are controlled so that the polymer formed remains in solution.

Small amounts of hydrogen, for example 1-100 parts per million by weight, based on the total solution fed to the reactor may be added to the feed in order to improve control of the melt index and/or molecular weight distribution and thus aid in the production of a more uniform product, as is disclosed in Canadian Patent 703,704.

The solution passing from the polymerization reactor is normally treated to deactivate any catalyst remaining in the solution. A variety of catalyst deactivators are known, examples of which include fatty acids, alkaline earth metal salts of aliphatic carboxylic acids, alcohols and trialkanolamines, an example of which is triisopropanolamine. The hydrocarbon solvent used for the deactivator is preferably the same as the solvent used in the polymerization process. If a different solvent is used, it must be compatible with the solvent used in the polymerization mixture and not cause adverse effects on the solvent recovery system associated with the polymerization process.

After deactivation of the catalyst, the solution containing polymer may be passed through a bed of activated alumina or bauxite which removes part or all of the deactivated catalyst residues and/or other impurities. It is, however, preferred that the process be operated without removal of deactivated catalyst residues. The solvent may then be flashed off from the polymer, which subsequently may be extruded into water and cut into pellets or other suitable comminuted shapes. The recovered polymer may then be treated with saturated steam at atmospheric pressure to, for example, reduce the amount of volatile materials and improve polymer colour. The treatment may be carried out for about 1 to 16 hours, following which the polymer may be dried and cooled with a stream of air for 1 to 4 hours. Pigments, antioxidants, UV screeners, hindered a ine light stabilizers and other additives may be added to the polymer either before or after the polymer is initially formed into pellets or other comminuted shapes.

The antioxidant incorporated into polymer obtained from the process of the present invention may, in embodiments, be a single antioxidant e.g. a hindered phenolic antioxidant, or a mixture of antioxidants e.g. a hindered phenolic antioxidant combined with a secondary antioxidant e.g. a phosphite. Both types of antioxidant are known in the art. For example, the ratio of phenolic antioxidant to secondary antioxidant may be in the range of 0.1:1 to 5:1 with the total amount of antioxidant being in the range of 200 to 3000 ppm.

The process of the present invention may be used to prepare homopolymers of ethylene and copolymers of ethylene and higher alpha-olefins having densities in the range of, for example, about 0.900-0.970 g/cm³ and especially 0.915-0.965 g/cm³; the polymers of higher density, e.g. about 0.960 and above, being homopolymers. Such polymers may have a melt index, as measured by the method of ASTM D-1238, condition E, in the range of, for example, about 0.1-200, and especially in the range of about 0.1-120 dg/min. The polymers may be manufactured with narrow or broad molecular weight distribution. For^' example, the polymers may have a stress exponent, a measure of molecular weight distribution, in the range of about 1.1-2.5 and especially in the range of about 1.3-2.0. Stress exponent is determined by measuring the throughput of a melt indexer at two stresses (2160g and 6480g loading) using the procedures of the ASTM melt index test method, and the following formula: Stress exponent= 1 log(wt.extruded with 6480σ wt.)

0.477 (wt.extruded with 2160g wt.) Stress exponent values of less than about 1.40 indicate narrow molecular weight distribution while values above about 1.70 indicate broad molecular weight distribution. The polymers produced by the process of the present invention are capable of being fabricated into a wide variety of articles, as is known for homopolymers of ethylene and copolymers of ethylene and higher alpha- olefins. Unless otherwise noted, in the examples hereinafter the following procedures were used:

The reactor was a 81 mL free-volume (regular internal shape, with the approximate dimensions of 15 x 90 mm) pressure vessel fitted with six regularly spaced internal baffles. The vessel was fitted with a six blade turbine type impeller, a heating jacket, pressure and temperature controllers, three feed lines and a single outlet. The feed lines were located on the top of the vessel, each at a radial distance of 40 mm from the axis, while the outlet line was axial with the agitator drive shaft. The catalyst precursors and other reagents were prepared as solutions in cyclohexane which had been purified by passage through beds of activated alumina, molecular sieves and silica gel prior to being stripped with nitrogen.

Ethylene was metered into the reactor as a cyclohexane solution prepared by dissolving purified gaseous ethylene in purified solvent. The feed rates of the catalyst components were adjusted to produce the desired conditions in the reactor. The desired hold-up times in the catalyst lines were achieved by adjusting the length of the tubing through which the components were passed. The hold-up time in the reactor was held constant by adjusting the solvent flow to the reactor such that the total flow remained constant. The reactor pressure was maintained at 7.5 MPa and the temperature and flows were held constant during each experiment.

The initial (no conversion) monomer concentration in the reactor was 3-4 wt%. ^'A solution of deactivator viz. triisopropanolamine or nonanoic acid, in toluene or cyclohexane was injected into the reactor effluent at the reactor outlet line. The pressure of the stream was then reduced to about 110 kPa (Abs.) and the unreacted monomer was monitored by gas ehromatography. The catalyst activity was defined as Kp = (Q/(l-Q) ) (1/HUT) (1/catalyst concentration) Where Q is the fraction of ethylene (monomer) converted to polymer, HUT is the reactor hold-up time expressed in minutes and the catalyst concentration is the concentration in the reaction vessel expressed in mmol/1 and corrected for impurities. The catalyst concentration is based on the sum of the transition metals. The polymerization activity (Kp) was calculated.

The present invention is illustrated by the following examples. Unless stated to the contrary, in each example the solvent used was cyclohexane, the monomer was ethylene and the reactor hold-up time was held constant at 3.0 min.

Example I The catalyst was prepared by the in-line mixing at ambient temperature (approximately 30°C) of solutions of each of dibutyl magnesium, triethyl aluminum, tert butylchloride and titanium tetrachloride in cyclohexane, followed by the addition of further solution of triethyl aluminum in. cyclohexane. The concentrations and flows of each species were adjusted such that the following mole ratios were obtained: chlorine (from tert butyl chloride)/magnesium = 2.4; magnesium/titanium = 5.0; aluminum (first triethyl aluminum)/titanium = 0.9; aluminum (second triethyl aluminum)/titanium = 3.0.

The reactor polymerization was operated at a temperature of 230°C, as measured in the reactor. The solution passing from the reactor was deactivated and the polymer recovered, as described above. Catalyst activity (Kp) ^• was calculated and the results obtained are shown in Table 1. The ratios reported for Cl/Mg and Al²/Mg are the optimized ratios required in order to obtain maximum catalyst activity at the indicated ratios of Mg/Ti and Al¹/Mg. In Runs 2 and 3, the catalyst preparation was as above with the exception that one mole equivalent of tert butyl alcohol (per mole of Al²) was added to the second aliquot of triethyl aluminum (thus forming the alkoxide) .

TABLE I

Run RATIOS No. Cl/Mg Mg/Ti Al¹/ϊ-_g Al²/Mg Alcohol Temp Kp

1 2.4 5.0 0.9 3.0 none 230 13.9 2 2.2 5.0 0.9 6.0 t-butanol 230 31.7 3 2.4 5.0 0.9 3.0 t-butanol 230 4.8 4 2.3 5.0 0.9 3.0 phenol 230 30.4 5 2.2 5.0 0.9 3.0 ethanol 230 24.9 6 2.3 5.0 0.9 4.5 n-decanol 230 24.1 7 2.2 5.0 0.9 3.0 neopentyl 230 29.3 alcohol

2.3 5.0 0.9 6.0 t-butanol³ 230 2.7

Note:

1 ratio of triethyl aluminum to titanium at first addition. 2 ratio of triethyl aluminum or alkoxydiethyl aluminum to titanium at second addition.

Kp calculated polymerization rate constant.

1/mmol/min. 3. t-butanol added to the reactor rather than to the catalyst.

Runs 1, 2 and 3 illustrate that the ratios of the catalyst components for the alkoxide systems have significant effects on the increase in activity, which is expected to vary with the type and composition of the other catalyst components and the mode of operation of the process but nonetheless illustrates that increases in catalytic activity of greater than a factor of two are obtainable. Run 3 cf. Run 2 illustrates that catalyst activity is sensitive to ratios of components, which may be used in the control of the process.

Runs 4, 5, 6 and 7 illustrate the use of alcohols other than tert butanol.

Run 8 illustrates the detrimental effect of the addition of the alcohol directly to the reactor, rather ' than to the second triethyl aluminum stream. This indicates that prior formation the alkoxydialkyl aluminum species is necessary. Example II

As a comparison with other known activators for high temperature polymerization processes, the procedure of Example I was repeated using the activators and reaction temperatures indicated in Table II. The results obtained were as follows.

TABLE II

Run RATIOS

No. Cl/Mg Mg/Ti Al/Mg Al²/Mg Activator Temp Kp

This example shows the relative improvement in catalyst activity at the higher temperatures that is exhibited by t-butoxydiethyl aluminum compared with the other activators.

Example III

The catalyst was prepared from solutions of titanium tetrachloride, vanadium oxytrichlpride and diethylaluminum chloride in cyclohexane. The admixed solutions were heat treated at 205-210°C for 110-120 seconds by admixing with hot cyclohexane solvent. The activator was then added to activate the catalyst. The polymerization reactor was run at the temperature indicated in Table 3. The solution passing from the reactor was deactivated and the polymer recovered as described above. The catalyst activity was calculated. The results obtained were as follows; in each run, (moles Ti)/(moles V) = 1.

TABLE III

BUODEAL t-butoxydiethyl aluminum

DESI diethylaluminum ethyldimethylsiloxalane

DIBALO diisobutylaluminoxane

TEAL triethylaluminum

1 mole ratio of diethylaluminum chloride to the sum of the titanium and vanadium.

2 mole ratio of the activator to the sum of the titanium and vanadium.

This example illustrates improvements obtainable using t-butoxydiethyl aluminum as activator.

Example IV

In order to compare the use of alkoxydialkyl aluminum with other activators, the procedure of Example III was repeated using a reactor temperature of 130°C. The results were as follows. TABLE IV

Run RATIOS No . Al¹/ (Ti+V) Al²/ (Ti+V) Activator Temp Kp

30 1. 0 2.0 TEAL 130 231 31 1. 2 2.7 DESI 130 89 32 1. 1 2.0 DIBALO 130 292 33 1 . 0 3.5 BUODEAL 130 75

BUODEAL t-butoxydiethyl aluminum

DESI diethylaluminum ethyldimethylsiloxalane

DIBALO diisobutylaluminoxane

TEAL triethylaluminum

2 mole ratio of the activator to the sum of the titanium and vanadium. This example illustrates the poor low temperature activity of the catalyst when an alkoxydialkyl aluminum is used as the activator and hence the surprising good high temperature activity.

Claims

CLAIMS :

1. In a solution process for the preparation of high molecular weight polymers of alpha-olefins selected from the group consisting of homopolymers of ethylene and copolymers of ethylene and C₃-C₁₂ higher alpha- olefins, by polymerization of ethylene and/or mixtures of ethylene and C₃-C₁₂ higher alpha-olefins in the presence of a catalytic amount of a titanium-containing coordination catalyst in an inert solvent at a temperature in excess of 105°C, the improvement characterized in that:

(b) the process is operated at least in part at a temperature of at least 180°C.

2. A solution process for the preparation of high molecular weight polymers of alpha-olefins selected from the group consisting of homopolymers of ethylene and copolymers of ethylene and C₃-C₁₂ higher alpha-olefins, said process comprising feeding monomer selected from the group consisting of ethylene and mixtures of ethylene and at least one C₃-C₁₂ higher alpha-olefin, a coordination catalyst and inert hydrocarbon solvent to a reactor, polymerizing said monomer and recovering the polymer so obtained, characterized in that said monomer is polymerized at a temperature in the range of 180- 320°C and said coordination catalyst having been formed from a first component and a second component, said first component containing titanium and second component being selected from the group consisting of alkoxy aluminum alkyl and mixtures of alkyl aluminum and alkoxyalkyl aluminum, said aluminum alkyl being of the formula AlR_nX₃._n and said alkoxy alkyl aluminum being of the formula AlR'_mOR"₃__m, in which each R, ' and R" may be the same or.different and is independently selected from alkyl or aryl of 1-20 carbon atoms, X is halogen, n is 1-3 and is 0-2 .

3. The process of Claim 1 or Claim 2 in which R is alkyl of 2-8 carbon atoms and n=3, and each of R' and R" is alkyl of 2-8 carbon atoms and m=2.

4. The process of Claim 3 in which the first component is obtained by rapidly admixing a solution of a titanium tetrahalide, optionally containing vanadium oxytrihalide, and organoaluminum at a temperature of less than 30°C, and heating the resultant admixture to a temperature of 150-300°C for a period of 5 seconds to 60 minutes.

5. The process of Claim 3 in which the second component is in the form of a mixture of trialkyl aluminum and an alcohol in which the amount of alcohol is less than the stoichiometric amount to form dialkyl alkoxy aluminum.

6. The process of Claim 5 in which the trialkyl aluminum is A1R³ ₃ in which each R³ is an alkyl group having 1-10 carbon atoms and the alcohol is of the formula ROH in which R⁴ is alkyl or aryl of 1-20 carbon atoms.

7. The process of Claim 3 in which the first component is formed from:

(i) a mixture of MgR¹ ₂ and A1R² ₃ in which each R¹ and R² are the same or different and each is independently selected from alkyl groups having 1-10 carbon atoms^'; (ii) a reactive chloride component; and (iii) titanium tetrachloride.

8. The process of Claim 4 in which the organoaluminum compound is trialkyl aluminum or dialkyl aluminum halide.

9. The process of Claim 7 in which the halide is chloride.

10. The process of Claim 3 in which the forming of the first and second catalyst components and the admixing thereof are carried out in-line at a temperature of less than 30°C.

11. The process of any one of Claims 1-10 in which the coordination catalyst is used without separation of any components thereof.