MXPA98004682A - Process for ethylene polymerization and heteroge catalytic system - Google Patents

Abstract

Novel catalyst systems are described comprising nickel diimine dihalide complexes which can be used with methylaluminoxane in a thick mixture polymerization process to polymerize ethylene and, optionally a high molecular weight alpha-olefin comonomer, to produce high weight polymers molecul

Description

PROCESS FOR ETHYLENE POLYMERIZATION AND HETEROGENEO CATALYST SYSTEM Field of Invention This invention relates to the homopolymerization of mono-1-olefin monomers, such as ethylene, and copolymerization of the mono-1-olefin monomer, such as ethylene, with at least one higher alpha-olefin comonomer.

BACKGROUND OF THE INVENTION It is well known that mono-1-olefins, such as ethylene, can be polymerized with catalyst systems using transition metals such as titanium, vanadium, chromium, nickel and / or other metals, supported or unsupported such as alumina, silica, titania, and other refractory metals. The supported polymerization catalyst systems are often used with a cocatalyst, such as alkyl boron and / or aluminum alkyl. Organometallic catalyst systems, that is, Ziegler-Natta type catalyst systems are usually not REF: 27707 supported and are frequently used with a cocatalyst, such as methylaluminioxane.

It is also well known that, since no polymer production process is easy, the polymerization, thick-mix, or cycle processes are relatively much more commercially desirable than other polymerization processes. Additionally, the type of polymerization process used can have an effect on the resulting polymer. For example, high reactor temperatures may result in low catalytic activity and productivity, or as a low molecular weight polymeric product. The high pressures of the reactor can also reduce the amount of desirable branching in the resulting polymer.

Many of the polymeric products are made in thick mixing processes, especially those polymeric products made using supported chromium catalyst systems, have a wider molecular weight distribution and, therefore, the polymeric product is much easier to process in the Final product. Polymers made by other processes, such as, for example, high temperatures and / or pressure solution processes, can produce polymers having a narrow molecular weight distribution; These polymers can be much more difficult to process in a manufacturing article.

Unfortunately, many homogeneous organometallic catalyst systems have low activity, high consumption of very expensive cocatalysts, such as methylaluminoxane (MAO), and can produce low molecular weight polymers with a narrow molecular weight distribution. Additionally, although it is thought that MAO may be necessary to produce a polymer with desirable characteristics, an excess of MAO may result in a decrease in activity in the catalyst system. Additionally, these types of homogeneous catalyst systems are preferably used only in a solution or a gas phase polymerization process.

Deactivation of the Invention.

It is desirable to provide catalyst systems that are relatively simple to make, that have increased activity and increased productivity. It is also desirable to provide catalyst systems that have a reduced consumption of cocatalysts. It is also desirable provide ethylene homopolymers and copolymers of ethylene and higher alpha-olefins that can be easily processed, as indicated by the increase in branching and in a wide molecular weight distribution. It is also desirable to provide ethylene homopolymers and copolymers of ethylene and higher alpha-olefins having an increased molecular weight.

In accordance with the present invention there is provided the catalyst system which is useful for the polymerization of olefins and the process for making said catalyst system, wherein said catalyst system comprises a complex of nickel diimide diimide and methylaluminoxane.

According to another embodiment of the present invention, the thick mixture polymerization process comprising contacting in an ethylene reaction zone, and optionally one or more alpha-olefins, with a catalyst system comprising a nickel dihalide is provided. Diimine complex in the presence of a methylaluminoxane.

In accordance with yet another embodiment of the present invention, ethylene homopolymers and copolymers of ethylene and higher alpha-olefins which can be characterized with a high molecular weight, branched and with a wide molecular weight distribution, are provided.

Description of the Preferred Modalities.

Catalyst System The catalysts of this invention can be complexed as nickel diimide dihalide complexes, having a general formula as presented below in Compound I. wherein X is halogen; R may be the same or different and is selected from the group consisting of a branched and / or linear alkyl or aromatic groups from about 1 to 8 carbon atoms per alkyl group; Y R 'may be the same or different and is selected from the group consisting of hydrogen and / or linear, branched, cyclic, in-connection, aromatic aliphatic hydrocarbons, having from about 1 to 70 carbon atoms per radical group.

The halogen of the nickel diimide dihalide complex is selected from the group consisting of fluorine, chlorine, bromine, iodine, and mixtures thereof. Preferably, the halogen is selected from the group consisting of chlorine and / or bromine for high catalytic activity and productivity. More preferably, the halide is bromine for better activity and productivity of the catalyst system.

The substituents R on the aromatic rings of the nickel diimide dihalide complex can be the same or different, and are selected from the group consisting of linear or branched, aliphatic or aromatic groups having from about 1 to about 8 carbon atoms per alkyl group. Although hydrogen can be used, hydrogen can inhibit the synthesis of the ligand. The R groups can have more than about 8 carbon atoms per group and can result in a catalyst system with low activity and / or productivity. Although it is not desirable to be bound in theory, it is believed that the substituent groups can cause steric hindrances in the catalyst system, whereby the activity and / or productivity in the catalyst system can be decreased. Exemplary alkyl substituents are selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, phenyl groups, and mixtures of two or more thereof. Preferably, the substituent R is a kind of electron donor, selected from the group consisting of linear or branched aliphatic groups having from about 1 to about 5 carbon atoms per group. More preferably, the R groups are both the same and are selected from the group consisting of methyl and isopropyl, due to their commercial availability and ease of synthesis of the ligand.

The group R can be in any position, that is, from 2 to 6, in the aromatic ring. Preferably, the group R, which may be the same or different, is either of the two in position 2 and / or 6, due to the ease of synthesis. More preferably, for better activity and productivity catalytic, both R groups are the same and are in positions 2 and 6 in the aromatic ring.

The substituents R 'may be the same or different and are selected from the group consisting of hydrogen and branched, linear, cyclic, aromatic or aliphatic radicals having from about 1 to about 70 carbon atoms per radical. Additionally, the substituents R 'can be linked, or bonded, through the carbon-carbon bridge between the two nitrogen atoms. Although the link is not desirable in theory, it is believed that radicals having more than 70 carbon atoms can help the steric difficulty of the catalytic system and hinder productivity and catalytic activity. Preferably, the substituent group R 'is selected from the group consisting of hydrogen and branched, linear, cyclic, aromatic or aliphatic radicals having from about 1 to about 20 carbon atoms per radical, due to its commercial availability and ease of synthesis of the ligand. More preferably, the substituent groups R 'are the same or linked through the carbon-carbon bridge between the nitrogen atoms, and the substituent R' is selected from the group consisting of of hydrogen and branched, linear, cyclic, aromatic or aliphatic radicals having from about 1 to about 12 carbon atoms per radical, for the reasons given above. Exemplary R 'substituents include, but are not limited to, hydrogen, methyl, ethyl, propyl, phenyl, taken together with acenaphyl or cyclobutadienyl. Preferably, the substituents R 'are identical and are selected from the group consisting of hydrogen, methyl and acenaphthyl for better results in the productivity and activity of the catalyst system.

The new catalyst systems described in this invention can be prepared in accordance with any manner known in the art. In general, the diimine ligands are contacted with a nickel halide to form a nickel diimide dihalide complex. Usually, to facilitate the preparation of the catalyst system, the diimine ligand is prepared first. The process of catalytic preparation may vary, depending on the substituents on the diimine ligand. For example, to prepare a specific diimine ligand, wherein R 'is hydrogen, a mixture of three components is prepared. A molar excess of double aniline, which contains the desirable R substituents (RnC6H (7.n) N, where n is equal to 1.2), is contacted with a dialdehyde, such as, for example, glyoxal (CHOCHO), in the presence of a compound capable of being a solvent for both organic and aqueous compounds. Exemplary compounds for both organic and aqueous compounds include, but are not limited to, methanol, ethanol, and / or tetrahydrofuran (THF). The mixture can be contacted, preferably at reflux, under any atmosphere to form the desired ligand. Preferably, the mixture is refluxed for at least 10, preferably 20 minutes, cooled and the desired ligand can be recovered. Generally, after refluxing and cooling, the ligand can be recovered in a crystalline form.

To prepare another specific diimine ligand wherein the R 'group is any other hydrogen, a similar procedure can be used. For example, a molar excess of at least twice aniline or a substituted aniline can be combined with a compound capable of dissolving both organic and aqueous compounds and a very small amount of formic acid. Therefore, about one molar equivalent of an alfadicetone (R'COCOR ') can be added to the mixture. The mixture can be stirred, under atmospheric conditions of temperature and pressure until the reaction is completed and the desired ligand is formed. Preferably, the water is absent from the reaction mixture. Generally, the reaction is completed in about 18, preferably 24 hours. A crystalline ligand product can be recovered in accordance with any method known in the art.

The complex nickel diimide dihalide catalyst system can be prepared, again by any method known in the art. For example, approximate molar equivalents of a diimine ligand and a nickel dihalide can be contacted in the presence of any compound that can dissolve the diimine ligand and the nickel dihalide, either partially or completely. The contact conditions can be any desirable condition for nickel diimide dihalide forming effects. Preferably, for best results in the products, the diimine ligand / nickel dihalide blends are contacted at room temperature under a dry atmosphere for any amount of time sufficient to form the nickel diimide dihalide compound. The complete formation of the nickel diimide dihalide complex is evident by a color change. Generally enough, contact times of around 8, preferably 12 hours. Usually, as a result of the preparation process, the resulting nickel diimine halide comprises from about 3 to about 20, preferably from about 5 to about 15, percent by weight of nickel, based on the total mass of nickel diimide dihalide. The presence of oxygen is not intended to be detrimental to this aspect of the preparation process.

After the formation of the nickel diimide dihalide, the nickel diimide dihalide can be recovered by any method known in the art, such as, for example, evaporation and / or vacuum filtration of the solvent. Additionally, if desired, the nickel diimide dihalide can be further purified by washing. An exemplary wash compound may be heptane. The catalyst system of nickel dihalide diimide can be recovered and used as a solid heterogeneous catalyst system.

Reagents, Polymer Products and Polymerization.

The polymers produced in accordance with the process of this invention may be homopolymers of ethylene or copolymers of ethylene and a higher alpha-olefin. If the reaction product is a copolymer, the ethylene can be polymerized with a comonomer which is a higher alpha-olefin having from 3 to about 8 carbon atoms per molecule. Exemplary comonomers include, but are not limited to, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, and mixtures thereof. Preferably, the comonomer is 1-hexane and / or 4-methyl-1-pentene, in order to obtain the maximum hardness of the polymer product.

If a comonomer is used, the comonomer may be added to the polymerization reactor, or reaction zone, in an amount within a range of about 1 to about 20 weight percent, preferably within 7 to about 18 weight percent. percent by weight, based on the weight of the ethylene monomer. More preferably, a copolymer is present near the reaction zone within a range of about 10 to about 16 weight percent, in order to produce a polymer having the most desired physical properties.

The polymerization of the monomer and comonomer can be carried out under thick mixture polymerization conditions, also known as thick circuit / mixture or particle form, wherein the temperature is taken care of under the temperature at which the polymers swell significantly. The thick mixture polymerization process is much easier to operate and maintain than other polymerization processes; A polymeric product produced by a thick mixing process can be recovered much easier. Such polymerization techniques are well known in the art and were described, for example in Nor ood, US Pat. No. 3,248,179, the disclosure which is incorporated herein by reference.

The thick mixing process is generally carried out in an inert diluent (medium), such as, for example, a paraffin, cycloparaffin, and / or aromatic hydrocarbon. Preferably, the inert diluent is an alkane having at least about 12 carbon atoms per molecule, for better operation of the reactor and polymer product. Exemplary diluents include, but are not limited to, propane, n-butane, isobutane, n-pentane, 2-methylbutane (isopentane), and mixtures thereof. Isobutane is the most preferred diluent due to the low cost and ease of use.

The temperature of the reactor. Polymerization, or reaction zone, where isobutane is used as the reactor diluent, in accordance with this invention, is critical and can be cared for within a range of from about 10 ° to about 90 ° C (50 ° -200 ° C). ° F) and preferably within a range of about 10 ° to about 38 ° C (50 ° -100 ° F). More preferably, the temperature of the reaction zone is within the range of 21 ° to 32 ° C (70 ° -90 ° F) for better activity and catalytic productivity. Reaction temperatures below about 10 ° C may be ineffective for polymerization.

The pressures in the thick mixing process can vary from about 100 to about 1000 psia (0.76 - 7.6 MPa), preferably from about 200 (1.52 MPa) to about 700 psia (5.32 MPa). More preferably, the reaction zone is maintained at a pressure within the range of 300 (2.28 MPa) to 600 psia (4.56 MPa) for better reactor operating parameters and for a better resulting polymer product. The catalyst system is kept in suspension and it is contacted with the monomer and comonomer (s) with sufficient pressure to maintain the medium and at least a minor portion of the monomer and comonomer (s) in the liquid phase. The medium and temperature are thus selected in such a way that the polymer or copolymer is produced as solid particles and are recovered in this form. The concentrations in the catalyst system in the reactor can be such that the catalyst system contains ranges from 0.001 to about 1 weight percent based on the weight of the reactor contents.

The catalyst system and the melaluminioxane (MAO) can be added to the reactor in any order for polymerization purposes. For example, the catalyst system can be added, then some reactor diluent, such as an isobutane, followed by the MAO, therefore more diluent and finally, ethylene. However, as previously stated, this order of addition can be varied, depending on the availability in equipment and / or desired polymer product properties. Preferably, the catalyst system and the MAO do not make contact prior to the addition to the polymerization reactor due to the possibility of a decrease in the catalytic activity.

The amount of catalyst system and MAO added to the reactor may vary. Generally, a molar excess of MAO occurs, in relation to the nickel compound. Preferably, the molar ratio of aluminum for nickel (Al: Ni) is less than about 750: 1, more preferably within a range of about 50: 1 to about 600: 1. More preferably, the molar ratio of aluminum to nickel is within the range of a ratio of 100: 1 to 300: 1 for better activity and productivity of the catalyst system.

The two preferred methods for the polymerization of the thick mixing process are those which employ a loop reactor of the type described in Norod and those which use a plurality of stirred reactors either in series, parallel or combinations thereof where the conditions of reaction can be the same or different in different reactors. For example, in a series of reactors, a chromium catalyst system that is not subject to the reduction step can be used either before or after the use of the reactor of the catalyst system of this invention.

The polymers produced according to this invention generally have a heterogeneity index (Hl), which is a ratio of the weight average molecular weight (Mw) and the numerical average molecular weight (Mn) (also expressed as (Mw / Mn). polymers produced in accordance with this invention, usually have an Hl within a range of about 2 to about 10 and preferably within a range of about 2 to about 8. More preferably, as an indicator of good and easy processability , the polymers produced in accordance with this invention have an Hl within the range of 4.5 to 8.

The copolymers produced according to this invention comprise a significant amount of a short chain branched. This branched short chain is evidence that these comonomers are incorporated into the polymer. Usually, the copolymers produced in accordance with this invention comprise up to about 200, and generally from about 100 to about 200, short chain branched per 10,000 carbon atoms of polymer column.

A further understanding of this invention and these advantages are provided by the following examples.

Examples The following examples illustrate various aspects of the invention. The data is included for each example about the polymerization conditions, as well as the resulting polymer. All chemical handling, including reactions, preparation and storage, are performed under a dry, inert atmosphere (usually nitrogen). Unless otherwise indicated, the polymerization reference scales were completed in a 2.6 liter autoclave reactor and the desirable temperature using an isobutane suspension (1.2 liters). The reactor was heated to 120 ° C and purged with nitrogen for about 20 minutes. The reactor was then cooled to the desired polymerization temperature and pressurized with isobutane for about 400 psig (3.04 MPa). A known amount (mass) of a complex nickel diimine halide catalyst was again charged to the reactor against a countercurrent of isobutane and the stirrer was set at 490 rpm. If hydrogen was charged to the reactor, the addition of hydrogen was followed by isobutane. The desired amount of methylaluminoxane (MAO) (10% by weight in toluene) was charged directly to the reactor via syringe. After the complete volume of isobutane was added, ethylene was added to bring the total reactor pressure up to 550 psig (4.18 MPa). The ethylene was fed as required and the finished polymerization reaction when the ethylene flow to the reactor ceased.

Several nickel halide di- aral catalyst systems were prepared and used to polymerize ethylene in the following examples. The abbreviation for each one of the catalytic systems used are the following: [(iPr2Ph) 2DABMe2] NiCl2- N, N'-bis (2,6-diisopropylphenyl) -2,3-butanediimine nickel (II) chloride. [(iPr2Ph) 2DABH2] NiBr2- N, N'-bis (2,6-diisopropylphenyl) ethylene glycine nickel (II) bromide. [(iPr2Ph) 2DABMe2] NiCl2- N, N'-bis (2,6-diisopropylphenyl) -2,3-butanediimine nickel (II) chloride. [(iPr2Ph) 2DABH2] NiBr2- N, N'-bis (2,6-diisopropylphenyl) ethylene glycine nickel (II) bromide.

[(Me2Ph) 2DABMe2] NiCl2- N, N'-bis (2,6-dimethylphenyl) -2, 3- - •• - ^ butanediimine nickel (II) chloride. J- [(Me2Ph) 2DABH2] NiBr2- - N, N'-bis (2,6-dimethylphenyl) ethylene glycine nickel (II) bromide.

[(Me2Ph) 2DABMe2] NiBr2- N, β-bis (2,6-dimethylphenyl) -2, 3-butanediimine nickel (II) bromide. [(iPr2Ph) 2DABMe2] NiBr2- N, N'-bis (2,6-diisopropylphenyl) -2, 3-butanediimine nickel (II) bromide.

[(Me2Ph) 2DABMe2] NiBr2- N, N'-bis (2,6-dimethylphenyl) -2, 3-butanediimine nickel (II) bromide. [(iPr2Ph) 2DABAn] NiCl2- N, N'-bis (2,6-diisopropylphenyl) acenaphthylenediimine nickel (II) chloride. [(iPr2Ph) 2DABAn] NiBr2- N, N'-bis (2,6-diisopropylphenyl) acenaphthylenediimine nickel (II) bromide. [(iPr2Ph) 2DABMe2] NiBr2- N, N'-bis (2,6-diisopropylphenyl) -2, 3-butanediimine nickel (II) bromide [(Me2PH) 2DABH2] NiCl2- N, N'-bis (2,6-dimethylphenyl) ethylene glycol nickel (II) chloride [(Me2Ph) 2DABH2] NiBr2- N, '-bis (2,6-dimethylphenyl) ethylenediimine nickel (II) bromide.

[(Me2Ph) 2DABH2] NIC12- N, N'-bis (2,6-dimethylphenyl) ethylenediimine nickel (II) chloride.

[(Me2Ph) 2DABMe2] NiCl2- N, N'-bis (2,6-dimethylphenyl) -2,3-butanediimine nickel (II) chloride. [(iPr2Ph) 2DABAn] NiBr2- N, N'-bis (2,6-diisopropylphenyl) acenaphthylendiimide nickel (II) bromide.

[(Me2Ph) 2DABH2] NiCl2- N, N'-bis (2,6-dimethylphenyl) ethylenediimine nickel (II) chloride.

[(Me2Ph) 2DABH2] NiCl2- N, N'-bis (2,6-dimethylphenyl) ethylenediimine nickel (II) chloride.

[(Me2Ph) 2DABH2] NiBr2- N, N'-bis (2,6-dimethylphenyl) ethylene glycol nickel (II) bromide. [(iPr2Ph) 2DABAn] NiCl2- N, N'-bis (2,6-diisopropylphenyl) acenaphthylenediimine nickel (II) chloride.

[(Me2Ph) 2DABH2] NiCl2- N, N'-bis (2,6-dimethylphenyl) ethylenediimine nickel (II) chloride. [(iPr2Ph) 2DABMe2] NiCl2- N, N'-bis (2,6-diisopropylphenyl) -2,3-butanediimine nickel (II) chloride.

[(Me2Ph) 2DABH2] NiCl2- N, N'-bis (2,6-dimethylphenyl) ethylenediimine nickel (II) chloride.

In general, the catalyst systems used for the polymerization in the Examples were prepared as described in this application.

The density of the polymer was determined in grams per cubic centimeter (g / cc) in a compression mold sample, cooled to about 15 ° C per hour, and conditioned for about 40 hours at room temperature in accordance with ASTM D1505 and ASTM D1928, procedure C. The high rate of fusion loading (HLMI, g / 10 minutes) was determined in accordance with ASTM D1238 at 190 ° C with 21,600 grams of weight. The melt index (MI, g / 10 minutes) was determined in accordance with ASTM D1238 at 190 ° C with 2,160 grams of weight. The analyzes by size exclusion chromatography (SEC) were executed at 140 ° C in a Waters, model 150 GPC with a refractive index detector. A solution concentration of 0.17 to 0.65 weight percent in 1, 2, 4-trichlorobenzene was found to give reasonable elution times.

Example 1 This example shows that the high activity and productivity in the catalyst system can be maintained at commercial reactor temperatures and at low levels of MAO, based on the amount of nickel in the catalyst system.

The polymerizations of the following Runs were carried out as described above, with a reactor pressure of 550 psig of ethylene in a thick mixture of isobutane. MAO was added in a solution of 10% by weight of the weight in toluene. 5 ml of MAO was added in each Run unless otherwise indicated. The results of the polymerization are listed below in Table 1.

TABLE 1 (a) 2 mL of charged MAO (b) 3 mL of MAO loaded (c) 1 mL of MAO loaded The data in table 1 show that the nickel-diimine halide catalytic systems can effectively polymerize ethylene with low Al: Ni molar ratios, ie, less than about 300. Catalytic productivities, with those lower molar ratios Al: Ni , they can be very high, usually higher than 10,000 grams of polymer per gram of nickel. It can also be noted that the reactor temperatures are within the commercially acceptable ranges, that is, between 60 and 80 ° C.

Example 2 This example shows that a high branching of the polymer can be retained with high pressure and reactor temperatures, as well as low Al: Ni molar ratios. The branched numbers in Table 2 were determined in accordance with the IR and ASTM procedures. Again, all the following polymerizations were carried out as is described above, with a reactor pressure of 550 psig of ethylene in a thick mixture of isobutane. MAO was added in a solution of 10% by weight by weight in toluene. 5 ml of MAO was added in each Run, unless otherwise indicated. The polymerization catalyst systems and the results are listed below in Table 2. c-n ro o in Table 2 t o The extension of the branching determined by the IR and ASTM methods is presented in Table 2. The high eleven Table 3 The data in Table 3 show that MAO that is not modified can be used as a cocatalyst with nickel diimine halide complexes for a Effective polymerization under commercial conditions using high pressures and temperatures.

Example 4 This example shows that the polymers have a wide molecular weight distribution and can be produced with the inventive catalyst system with the inventive polymerization process. Several catalytic nickel-diimine halide catalytic systems are used to polymerize ethylene. All the runs were executed at 550 psig and at temperatures of 80 ° C (Cours 401-404) or at 60 ° C (Cours 405-416). The amount of MAO in toluene solution added was 5 ml for all the runs, except Corrida 406, which had 3 ml added, Corrida 407 which had 1 ml added and Corrida 408 which had 2 ml added. The results are given in Table 4.

Table 4 The data in Table 4 show that a relatively wide molecular weight distribution, as evidenced by the heterogeneity index (Hl), which is a Mw / Mn ratio, can be achieved by an ethylene polymer produced with a system of nickel diimine halide catalyst as a reactor of high pressures and temperatures, or as low molar radii Al: Ni.

This invention is described in detail for purposes of illustration, it is not limiting, therefore it tries to cover all changes and modifications within the spirit and scope of it.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following is claimed as property.

Claims (22)

Claims

1. An ethylene polymerization process characterized in that it comprises contacting in a reaction zone under polymerization reactor conditions of thickened mixture or suspension: a) ethylene and b) a heterogeneous catalyst system comprising methylaluminoxane and one or more nickel halide complexes diimine

2. The process according to claim 1, characterized in that a comonomer which is an alpha-olefin has from about 3 to about 10 carbon atoms per molecule and is also polymerized.

3. The process according to claim 2, characterized in that the comonomer is propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-penten, or a mixture thereof.

4. A process according to any one of the preceding claims, characterized in that the nickel diimine halide complex is represented by the formula: wherein X is halogen; R may be the same or different and is selected from the group consisting of branched and / or linear alkyl or aromatic groups or aromatic groups having from about 1 to 8 carbon atoms per alkyl group; Y R 'can be the same or different and is selected from the group consisting of hydrogen and linear, branched, cyclic, in connection, aromatic, and / or aliphatic hydrocarbons, having from about 1 to 70 carbon atoms per radical group.

5. The process according to claim 4, characterized in that the halogen is the same or different than chlorine or bromine.

6. The process according to any one of claims 4 or 5, characterized in that the substituent R is a linear or branched aliphatic group having about 1 to about 5 carbon atoms per group.

7. The process according to claim 6, characterized in that the substituent R is the same or different than the methyl groups, or isopropyl groups.

8. The process according to any one of claims 4-7, characterized in that the substituent R 'is hydrogen or a branched, linear, cyclic, aromatic or aliphatic branched radical having from about 1 to about 12 carbon atoms per radical.

9. The process according to claim 8, characterized in that the substituent R 'is the same or different as hydrogen or a methyl, ethyl, propyl, phenyl, acenaphthyl, or cyclobutadienyl group.

10. The process according to any one of the preceding claims, characterized in that the nickel diimine halide complexes and methylaluminoxane are present in the reactor in amounts to have a molar ratio of aluminum to nickel of less than about 750: 1.

11. The process according to claim 10, characterized in that the molar ratio of aluminum to nickel is within the range of about 50: 1 to about 600: 1.

12. The process according to any of the preceding claims, characterized in that the polymerization conditions of the thick mixture comprise a temperature in the range of about 10 ° to about 90 ° C and a pressure in the range of about 100 up to around 1000 psia (0.76 - 7.6 MPa).

13. The process according to any of the preceding claims, characterized in that the polymerization of the thick mixture is carried out in a diluent comprising isobutane.

14. A heterogeneous catalytic composition characterized in that it comprises: a) nickel diimine halide complexes that have the formula wherein X is halogen; R may be the same or different and is selected from the group consisting of aromatic or branched and / or linear alkyl groups having from about 1 to 5 carbon atoms per alkyl group; Y R 'can be the same or different and is selected from the group consisting of hydrogen and / or linear, branched, cyclic, in-connection, aromatic, aliphatic hydrocarbons, having from about 1 to 12 carbon atoms per radical group and b) methylaluminoxane,

15. The composition according to claim 14, characterized in that said halogen is the same or different than chlorine or bromine.

16. The composition according to any one of claims 14 or 15, characterized in that the substituent R is selected from the group consisting of branched or linear aliphatic groups having from about 1 to about 5 carbon atoms per group.

17. The composition according to claim 16, characterized in that the substituent R is the same or different than methyl groups or isopropyl groups.

18. The composition according to any of claims 14-17, characterized in that the substituent R 'is hydrogen or a branched, linear, cyclic, aromatic or aliphatic radical having from about 1 to about 12 carbon atoms per radical.

19. The composition according to claim 18, characterized in that the substituent R 'is hydrogen or a methyl, ethyl, propyl, phenyl, acenaphthyl or cyclobutadienyl group.

20. The composition according to any one of claims 14-19, characterized in that the nickel diimine and methylaluminoxane halide complexes are present in an amount to have a molar ratio of nickel to aluminum of less than about 750: 1.

21. The composition according to claim 20, characterized in that the molar ratio of nickel to aluminum is within the range of about 50: 1 to about 600: 1.

22. An ethylene polymer, characterized in that it comprises from 100 to 200 short chain branches per 10,000 carbon atoms in the main column of the polymer and wherein the polymer has an index of heterogeneity in the range of about 4 to about 10. Summarize the Invention. Novel catalyst systems are described comprising nickel diimine dihalide complexes which can be used with methylaluminoxane in a thick mixture polymerization process to polymerize ethylene and, optionally a high molecular weight alpha-olefin comonomer, to produce high weight polymers molecular.