CA1105175A - Preparation of hydrocarbon solutions of ethylene polymers - Google Patents

Abstract

PREPARATION OF HYDROCARBON SOLUTIONS OF ETHYLENE POLYMERS

ABSTRACT OF THE DISCLOSURE

A process is provided for the direct preparation of a hot hydrocarbon solution of an ethylene polymer having an inherent vis-cosity of at least 3.5. The solution is prepared by polymerizing ethylene in the hydrocarbon at a temperature of at least 130°C in the presence of a polymerization initiator prepared by reacting an aluminum alkyl with a supported, chemically-modified, transition metal chloride compound prepared by a multistep process in which:
1. A finely-divided polymer such as polyethylene is sus-pended in an alkanol solution of a magnesium compound, e.g., a solution of magnesium chloride in methanol, 2. The alkanol is vaporized to deposit magnesium compound-alkanol complex on the support, 3. The product of Step (2) is suspended in a liquid hydro-carbon and reacted with an aluminum alkyl compound such as diethyl aluminum chloride, and 4. The product of Step (3) is reacted with a transition metal chloride compound such as titanium tetrachloride.

Description

British Patent 1,372,116 Gulf Research and Development Co., published October 30, 1974 on an appli.cation filed October 27, 1972 describes the preparation of fibre-like materials suitable for use in manufacture of waterlaid ~heets. Such products are prepared from high molecular weight eth~lene polymers and are referred to as fibrils. In the preparation of such fibrils the high molecular wei~ht ethylene polymer, having an inherent viscosity of at least 3.5, is dissolved in a hydrocarbon at a temperature of at least about 130C and is the starting material from which such fibrils are prepared.
The preparation of such ethylene polymer solutions presents technical problems. By reason of the very high molecular weight of the ethylene polymers employed in the process, such polymer solutions have high viscosities, even at low concentrations of the ethylene polymer.
The hi~h viscosities of such polymer solutions makes it difficult to provide adequate stirrin~ to dissolve all of the ethylene polymer par-ticles. This presents serious problems in that it also has been observed that the quality of the ultimately-obtained fibrils is adversely affected, if undissolved polymer solids are present in the ethylene polymer solution employed in the process.
The preparation of such ethylene polymer solutions is costly and energy-lntensive in that very large quantities of the hydrocarbon solvent are required to dissolve the ethylene polymer. Typically, 96 parts by ~eight of hydrocarbon solvent are required to dissolve four parts by weight of the ethylene polymer. In the preparation of the fibrils, the heated polymer solution is subsequently cooled to precipi-tate the ethyle~e pol~mer therefro~. Upon recycling, the hydr~carbon then must be reheated In vie~ of 2:he considerations noted above, it would appear to be desirable to prepare a hot hydrocarbon solution of an ethylene polymer ~y polymerizin~ ethylene in the hydrocarbon solvent. Such an approach would reduce the total energy requirement for preparing the ultimately-desired fibrils~ in that the ethylene polymer would not be cooled and . - .- : . . . : . :
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reheated. Moreover, the heat of p~lymeriZE~tl.On of th~ ethylene would provide ~ substantlal portion of the energy required to prepare the hot ethylene polymer solution. It h~s not been possible up t~ this time to directly Frepare such hot solution~ of ethylene polymers of high mole-cular weight by direc~ polyme~izatiDn of ethylene in a hydrocarbon s~lvent. The difficulty that has been presented i~ the well-recognized fact that the molecular weight of an ethylene polymer decreases as the temperature employed ~n the polymerization is increased. With ~resently known catalysts, it has not been po~sible to prepare ethylene polyme-rs having an inherent viscosity of at least 3.5 in a hydrocarbon ~olvent by carrying out the polymeri~ation at temperatures above 100C.
The present invention provides a yroces~ for preparing hot hydrocarbon solutions of ethylene polymers having an inherent viscosity of at least 3.5. The invention is based upon the observation that, when ethylene is polymerized in a hydrocarbon solution in the presence o a special type of polymeri~ation initiator, it is possible to prepare ethylene polymers having an inherent viscosity of at least 3.5, even when the polymerization is carried out at a temperature of at least about 130C.
Thus according to the present invention there is provided a process for preparing a hot hydrocarbon solution of an ethylene polymer having an inherent viscosity of at least 3.5, which consists essentially of contacting ethylene wi~h a polymerization initiator in a high boiling liquid hydrocarbon at a tamperature of at least a~out 130C; said liquid hydro-car~on having a boiling point range such that its vapor pressure at 130C is not higher than 5 atmospheres; said poly-merization initiator having been prepared by reacting an aluminum alkyl selected from the group consisting of dialkyl : aluminum hydrides, dialkyl aluminum halides, and trialkyl aluminums with a supported, chemically-modified transition -.

metal chloride product prepared by a process which consists essentially of the sequential steps of:
~a) Suspending a finely-divided polymer in a 1-4 carbon atom alkanol solution of a m~gnesium compound, (b3 Vaporizing the alkanol from khe suspension of Step (a) to deposit the magnesium compound, ~ogether w~th the quanti~y of alkanol which forms a complex therewith, on ~he surface of ~he finely-divided polymer, (c) Suspending the product of Step (b) in a liqtlid hydrocarbon and - adding thereto an aluminum alkyl compound; and (d) Adding a transition metal chloride compound to the suspension of Step (c);
the polymer employed in Step (a) beinB selected from the group con-sisting of organic thermoplastic polymers and thermoset polymers~
the particles of said pol~mer having at least one dim~nsion not exceeding 600 microns, the magnesium compou~d eMployed in Step (a) having the structure:
' MgX2' nH20 where X is Cl, F, Br, I9 N03, OC~3, OCOC~3, and n is not greater tha~ 6; the magnesiu~ compound employed i~ Step (a) constituting 5-25 weight X of the combined welght of the finely-divided polymer and the magn2sium compound; the alumlnum alkyl compound employed in Step (c) being selec~ed from the group consisting of dialkyl aluminum hydride~, dialkyl aluminum halides, and trialkyl alumlnums; : :
the quantity oE the alumlnum alkyl employ~d in Step (c) being not in exce~s af the quantity tha~ will react wi~h the magnesium compound-alkanol comple~ carried on the polymeric suppor~; the transition metal chloride employed in Step (d) being selected from ~he group cons.!s~ing of titanium tetrachlorlde and vanadium oxy-trichloride; and the quantity of the transition metal chlo~ide compound employed i~ Step (d) bei~g at least molarly equivalent to the quantity of the alum~num alkyl compound employed ln Step (c).

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-' - : . : ' ' .. - ., Hoe hydrocarbon solutions of an ethylene polymer havin~ an inherent viscosity of at least 3.5 are prepared by contactlng ethylene with a special type of polymerization initiator in a high-boiling liquid hydrocarbon at a temperature of at least about 130C. The poly~eri zation initiator employed in the procelss is the reaction product of (1) an aluminum alkyl selected from the group consisting of dialkyl aluminum hydride!s, dialkyl aluminum halides, and trialkyl aluminums and (2~ a supported, chemically-modified transition metal chloride product pre-pared by a multistep proces~s subsequently described.

- 3b -- . -The special polymerization initiators employed in the process of the present invention are described in the copending Canadian Patent application o~ Fa;indar K. Kochhar and Robert J.
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Rowatt, Serial No. ~ 3~, filed on May 3, 1977, and assigned to the Assignee of this application-The ~luminum alkyl employed in the preparation ~f the special polymerization lnitiator may be either a dialkyl aluminum hydride, a dialkyl aluminum halide, or a trialkyl aluminum. Typical exa~pl~s of suitable alkyl aluminums include triethyl aluminu~, triisobutyl aluminum, 1~ diethyl aluminum hydride, and diethyl aluminum chloride. Such alkyl aluminums should be of the purity and quality conventionally employed in the preparation of Ziegler-type polymerization initiatorq.
The supported, chemically-modified transition metal chloride product employed as the second component in the preparation of the special polymerization initiators of the invention ls prepared by a multistep process.
In the first step of the preparation of the ~upported, chemically-modified, transition metal chloride compound, a finely-divided polymeric support is suspended in an alkanol solution of a particular class of magnesium compounds. The polymeric support may be either an organic therm~set polymer, or preferably an organic thermo-plastic p~lymer. Thè polymeric support should be i~ a finely-divided particulate form which has at least one dimension not e~ceeding about 600 microns and preferably having one dimension falling within the r~nge of abou~ 1 t~ 200 microns. The polymeric ~upport may be of any desired shape such as sp~res, rods, or c~linders. Suita~le polymeric materials include poly (triallylisocyanurate), polye~hylene, polypropylene, po:Ly (3-methylbutene), poly ~4-methylpentene), polyamides, polyesber~, polyacrylamides, polyacrylonitriles, polycarkonates, 30 and cellulose. ~le essentially any po~ymer not soluble in an alkanol can be employed ~ 4 , ~ . - - : - , . .
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for this purpose, it is preferred to employ an ethylene polymer, parti-cularly an ethylene polymer having an inherent viscosity of at leasL
3.5.
The alkanol solution of a magnesium compound employed in the treatment of the polymeric support in the first step of the preparation will be an alkanol solution of a magnesium compound having the struc~
ture:

MgX2 . nH20 where X is an anion which imparts solubility of at least 1% in a lower alkanol (C4 or less), and n is not greater than 6. Thus, X can represent Cl, F, Br, I, N03, OCOCH3, or OCOH.
Magnesium compounds found to be par-ticularly suitable in the practice of the invention include magnesium chloride, magnesium methoxide, magnesium nitrate, and magnesium acetate. The alkanol in which the magnesium com-pound will be dissolved will be an alcohol containing 1-4 carbon atoms such as methanol, isopropanol, butanol and the like. The alkanol solu-tion should contain a relatively high concentration of the magnesium com-pound, e.g., desirably at least 5% by weight, by reason of the fact t~at the alkanol subsequently will be removed from the process by vapori-zation.
In carrying out the first step of the process, the polymeric support wlll be suspended in a sufficient quantity of the alkanol solu-tion of the magnesium compound so that the magnesium compound contained therein will constitute 1-60 weight % and preferably 5-25 weight % of the combined weight of the polymeric support and~the magnesium compound.
The polymeric carrier should be stirred with the alkanol solution of tXe magnesium compound to the extent required to thoroughly wet and impregnate the polymeric carrier with the alkanol solution.
In the second step of~the process, the alkanol is vaporized : .
from the suspension of the polymeric carrier in the alkanol solution so as to deposit the magnesium~compound uniformly ovér the polymeric , ~ - 5 -carrier. The magLIesium compou~d is deposLted on the carrier in the form of a complex with the alkanol. The precise structure of the com-plex has not been established, but it i9 believed to contain l-~ mols of alkanol per mol oE magnesium compound. It is observed, however, that the magnesium compound-alkanol complex is in a highly active stake particularly suitable for use in the preparation of the chemically-modified, transition metal chloride compolmds in the subsequent steps of the process. To the extent that is practically feasible, all of the alkanol, except that complexed with the magnesium compound, should be removed as any excess alkanol will react with and consume the aluminum alkyl compound employed in the next step of the process.
The alkanol can be removed by simply distilling or evaporating the alkanol from the suspension of the polymeric carrier in the alkanol solution. When this technique is employed, the distillation or evapora-tion is preferably carried out under reduced pressure. Care should be exercised to remove the alkanol solution at moderate temperatures not exceeding 150C and preferably not exceeding 75C. Frequently the dis-tlllation or evaporation of the alkanol will be accelerated by passing an inert sweep gas such as nitrogen or argon over the surface of the alkanol solution. When a sweep gas is employed, it should be free of water, oxygen and other compounds recognized as having a deleterious effect upon Ziegler-type catalysts.
While a simple evaporation or distillation as described above can be used to remove the alkanol, somewhat better results are obtained if at least the final portions of the alkanol are removed by codistilla-t~on with an inert hydrocarbon. In this procedure, after a portion of the alkanol is removed as described previously, a liquid hydrocarbon such as heptane, or the like, will be added to the reaction vessel. The hydrocarbon then will be distilled from the system under atmospheric or preferably reduced pressure. So long as any free, uncomplexed alkanol remains in the system, the distillate being removed from the system will be a mixture of the hydrocarbon and alkanol. When the final traces , , .

of the uncomplexed alkanol are removed from the system, the vapor tem-perature oE the distillate will rise to the boiling point o~ the hydro-carbon at the prevailing pressure employed in the distillation. Thus, the observed boiling point of the distlllate serves as a criterion for determining when the removal of the alkanol is completed.
The hydrocarbon employed for removal of the alkanol may be of any of the hydrocarbon types conventionally employed in the prepara-tion of Ziegler-type catalysts. Predominantly aliphatic hydrocarbons such as heptanes and octanes are preferred. The hydrocarbon employed should be purified in a manner so as to remove therefrom molsture and other materials kno~l to have a deleterious effect upon the activity of Ziegler-type catalysts.
In the next step of the process, the polymeric carrier with the magnesium compound deposited thereon will be suspended in a liquid hydrocarbon of the type previously described. Normally, such a slurry already will have been prepared, particularly where the Einal traces of the alkanol are removed by codistillation as described above. A suit able aluminum alky compound such as diethyl aluminum chloride then will be added to the slurry. The aluminum alkyl reacts with the ~agnesium compound-alkanol complex carried on the polymeric support. The mechanism by which the two components reac~t and the structure of the resulting reaction product have not been fully established. The evidence tha, a chemical reaction takes place is that a gas, possibly an alkane, is Eormed when the aluminum alkyl is added to the reaction mixture. The reaction product formed in this step of the process is firmly bonded to the polymeric support.
The aluminum alkyl employed in the step of the process de--:
; scribed immediately above may be a dialkyl halide, a dialkyl aluminum hydride, or a trialkyl aluminum, with the dialkyl aluminum~halides being preferred. Typical examples of~ suitable alkyl aluminums include tri-ethyl aluminum, triisobutyl~aluminum, diethyl aluminum hydride and diethyl aluminum chloride.

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~ t~ 5 The alum:Lnum alkyl should be employed -In a quantity such that all of the aluminum alkyl added to the reaction mixture will react with the magnesium compound-alkanol complex carried on the polymeric support and so that the reaction system, after complet:Lon of thls step of the process, contains little or no unreacted aluminum alkyl in the hydro-carbon phase of the reaction mixture. If an excess of the aluminum alkyl is employed, the remaining free, unreacted aluminum alkyl will react with the transition metal chloride employed in the next step of the process to form a more conventional Ziegler-type catalyst as a coproduct. The presence of such conventional ~legler-type catalyst will tend to mlnl-mize the advantages obtalned wlth the present invention.
The precise quantity of the aluminum alkyl to be employed will be somewhat dependent upon the completeness with whlch uncomplexed alkanol is removed from earlier steps of the process. This results from the fact that any free, uncomplexed alkanol present in the reactlon system will react wlth the aluminum alkyl compound. Ordinarlly, the applicant prefers to employ approxlmately 0.1 - 2.0 mols and preferably about 0.25 -0.5 mol of the aluminum alkyl for each mol of the magnesium compound present in the reaction system. If desired or believed to be necessaryl 20 the presence of unreacted aluminum alkyl can be determined either quali-tatively or quantitively by removing a sample from the reaction system;
filtering the solids from the slurry and measuring the concentration (if any) of the aluminum alkyl present in the hydrocarbon filtrate. Ana lytical methods for measuring the concentration of aluminum alkyls in hydrocarbons are known in the art.
The use of less than the stoichiometrically required quantity of the alkyl aluminum has no serious effect upon the quality of the ultimate product. If the supported reaction product contains unreacted magnesium compound~ the unreacted magnesium compound will react with the transition metal chloride in the next step of the process to provide a reaction product which will be converted into a slightly different polymerlzation catalyst in subsequent processing steps.

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In the next step of the proeess, a trans1tion metal ehloride of the group consis~ing of tltanium tetrachloride and vanadiuTn oxytri--chloride is added to tile reaction mixt~lre of the previous step, ~7hich contains as the active reactant ~he reaction product formed between the supported magnesi~lm compound-alkanol complex and the aluminum alkyl.
The transition metal chloride reacts with the previously prepared reaction product and is reduced to a lower valence state. This supported, chemically-modified, transition metal chloride compound is the ulti-mately desired catalyst component and is insoluble in the hydrocarbon reaction medium. The structure of product has not been established, but probably is complex. Virtually all of the titanium becomes bound to the polymeric support, probably by reason of formation of a chemical or physical complex with the magnesium compound.
In this step of the process, from about l to 2 mols of the transition metal chloride will be employed for each mol of aluminum alkyl employed in the previous step of the process. Not more than 2 mols of the transition metal chloride compound can be reduced by l mol of the previously-prepared reaction product, and any quantity of transition metal chloride added in excess of this quantity serves principally to drive the reaction to completion in the shortest possible period of time.
As the supported, chemically-modified, transition metal chloride product is insoluble in the hydrocarbon medium, it can be recovered by filtration and stored for future use if desired. If the product is recovered in this manner for storage, the hydrocarbon filtrate containing . .
unconsumed transition metal chloride can be recovered and reused in the subsequent production of additional product. The recovered solid reaction product should be washed with hydrocarbon to free it from any occluded unreacted transition metal chloride compound.
It is frequently desirable, however, to use the supported, chemically-modified, transition metal chloride product shortly after it is prepared. In such situations, it is usually desirable to employ the ~ product in the slurry in which it is prepared. In such situations, it '~ ,: . . . :, ' .

is desirable to re~ove any unreacted transition metal clllo~ide from the system. Such removal can be effected by si~ply distilling the h~drocarbon from the slurry at either atmospheric or reduced pressure.
The unreacted transition metal chloride codistills with the hydrocarbon.
The distillation is continued until the distillate gives a negative test for chloride.
To p~epare the special polymerization initiator used for the polymerlzation of ethylene; the supported, chemically-modified transl-tion me~al chloride product ls reacted with an aluminum alkyl compound in a hydrocarbon medium, preferably the same hydrocarbon that will be used in the subsequent polymeriæation. The reaction is carried out in amanner generally equivalent to that employed to prepare more conven-tional Ziegler-type catalystsO The supported, chemically-modified transition metal chloride product is employed in the same molar propor-tions as conventional transition metal chlorides are employed in their reactions with aluminum alkyls. Typically, the two components are employed in proportions to provide an Al/Ti atomic ratio of about 0.5 ~ 1, or preferably 1.0 - 5.0:1. While dialkyl aluminum hydrides and dialkyl aluminum halides csn be employed for this purpose~ the trialkyl aluminums and particularly triethyl aluminum and triisobutyl aluminum are the preferred aluminum alkyls to be employed in the prepara-tion of such polymerization initiators.
The special polymerization initiators prepared as described --~ above have a nu~ber of features which make them particularly effective `~ and desirable for use in the polymerization bf ethylene by the method of the present invention. Initially, it will be noted that the magnesiu~
, ~ compo~md, the transition metal compound, and the aluminum alkyl compounds are employed in the precise quantities* required in the final polymeri-zation initlator. Thus~ no expenslve compounds are employed in excess *The transition metal chloride may be employed in slight excess of that stoichiometrically required for reasons previously discussed.
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of their actual need. The polymerization initiators have high pro-ductivity rates and provide low production costs for the ethylene polym~rs produced. In addition, by reason of the high catalyst productivities, the finished polymers contain very low co~centrations of metallic catalyst residues so that, for most purposes, they need not be removed from the polymers. Yet another advantage of the polymerization initiators is that they have a specific gravity substantially the same as the hydro-carbon solvent employed in the ethylene polymerization process. Thus, a uniform dispersion of the polymerization catalyst in the polymerizatlon solvent is more easily obtained than is the case with more conventional Ziegler-type catalysts.
The polymerization of ethylene is carried out by suspending the special polymerization initiator in an appropriate hi~h-boiling liquid hydrocarbon, heating the hydrocarbon to the desired reaction temperature, and feeding polymerization-grade ethylene to the reaction zone. If the polymerization is carried out batchwise, the polymerization is continued until the concentration of the ethylene polymer reaches the desired level. Ordinarily, the polymerization is carried to the point at which the ethylene polymer reaches a concentration of at least 3 weight %, and preferably 4-7 weight %. Ordinarily, the polymerization cannot be carried beyond the point at which the ethylene polymer con-stitutes more than about 7 weight % of the reaction mixture. This pro-~ -cess limitation is~set by the practical consideration that higher solids solutions are too viscous for easy handling; the high viscosity resulting ; from the very high molecular weight of the ethylene polymer~produced in ~the process. It is preferred to carry out the polymerization by a con-tinuous process with ethylene, the~special polymerization initiator, and .
the hydrocarbon being continuously fed to the reaction zone wi-th a polymer solution being continuously withdrawn from the reaction zone.

The feed rate and the~withdrawal rate are selected 90 that the residence time of ethylene in the reaction zone is such~that the polymer solution being withdrawn from the reactor has an ethylene polymer content within the desired range previously noted.

The hydrocarbon employed in the process should have a boiling point range such that its v~por press~lre at 130C is not higher than 5 atmospheres and preEerably less than 2 atmospheres. It is preferred to employ a predominantly aliphatic hydrocarbon mixture such as kerosene, but the hydrocarbon employed may contain modest percentages of aromatic and cycloaliphatic hydrocarbons without adversely affecting the process.
The hydrocarbon employed should be carefully dried, as it is well-known that water acts to poison or deactivate Ziegler-type polymeri-zation initiators. Depending upon the source oE the hydrocar~on, additional treatments may be required to remove organic compounds containing nitrogen, oxygen, or sulEur atoms, as it is known that such compounds also tend to deactivate Ziegler-type polymerization initiators.
The polymerization initiator should be employed in the process at a concentration within the range of 0.01 to 4 grams per liter of reactor volume. The polymerization will be carried out at a temperature of at least about 130C, and no advantages are obtained by carrying out the polymerization at a temperature above about 150C.
`~ The polymerization normally will be carried out at a superatmospheric pressure of at least about 2 and preferably at least about 30 atmospheres

2~ to maintain a sufficient concentration of ethylene in the reaction medium to provide reasonable rates of poly~erization.
The polymeri~ation temperature, the concentration of polymeri-zation initiator, and concentration of ethylene (controlled by the ethylene partial pressure) are maintained in appropriate ~alance to produce an ethylene polymer having inherent viscosity of at least 3.5.
Methods for determining the inherent viscosities of ethylene polymers are set forth in the art, e.g., see British Patent 1,372,116. The most unexpected and unique characteristic of the process of the invention i5 that ethylene polymers of such high inherent viscosity can be produced at the high temperatures employed in this process. It is well recognized in the art that increasing the polymeri~ation temperature in a process ' , .

ordinarily reduces the molecular weight and tlle inherent-visco~ity oE
the ethylene polymers produced. Moreover, most Ziegler-type catalysts are deactivated at the temperature employed in the process o~ the present invention.
The process of the invention provides very high yields of polymer based on the polymeriza-tion initiator employed. Typically the process provides minimum yields of the order of about 1200 grams of polymer per gram oE titanium per hour. As a result of the high yield, the polymers produced contain a sufficiently low level of catalyst resi-dues that no post polymerization treatment is required to remove such residues.
While the process of the invention is designed principally to produce homopolymers of ethylene, it is also possible to produce copolymers of ethylene with C3 and higher monoolefins, such as propylene and butylene. It is preferred, however, to limit the concentration of any higher olefin comonomer in the monomer mixture to a level not more than about 25 mol % of the ethylene employed in the process. Minor concentrations of hydrogen can be employed in the process to modify the molecular weight of the ethylene polymers produced in the process.
The following examples are set forth to illustrate more clearly the principle and practice of this invention to those skilled in the art.
Examples 1-3 -Three polymerization initiators were prepared for use in the polymerization of ethylene by the process of this invention.
Part A
Preparation of Support A ~-liter reaction vessel fitted with a stirrer, a reflux condenser, a dropping funnel9 and heating and cooling means; was charged with a methanolic solution of magnesium chloride prepared by dissolving 75 grams of magnesium chloride in l liter of methanol. Six hundred ~ ~5~ 5 seventy grams o~ a Einely-divided powder of high density yolyethylene having an average part-icle diameter o~ less tharL 40 microns was slurried in the methanolic solu~ion of magnesium chloride. The slurry was heated to a temperature of 55C over a period of 30 minutes and stirring at this temperature was continued for another 30 minutes. This pres-sure then was reduced to about 10 mm of ~lg to remove methanol f~oM the system. Heating was continued for two hou-rs under these conditions to assure removal of all methanol which did not form a complex with the magnesium chloride deposited on the polyethylene support. The powder was removed from the reaction vessel and ground to pass through a 40-mesh U.S. screen.
Part B

Preparation of Chemically-Modified Transition Metal Chloride Compound The magnesium chloride treated polyethylene powder prepared as described above in the amount of 200 grams, an appropriate quantity of heptane, and an appropriate quantity of diethyl aluminum chloride, was charged to a 4-liter reactor equipped as described above. This reaction mixture was stirred for one hour while maintaining the temperature at 25C. Evolution of a gas was noted. At this point in the reaction, it is believed that the charged diethyl aluminum chloride has been chemi-cally bonded to the polymeric support or one of the chemicals carried thereon. The reaction mixture then was heated to 80C and an appropriate quantity of TiC14 was added to the reaction mixture from the dropping funnel over a period of one hour. The reaction mixture then was stirred for an additional 16-20 hours, while maintainin~ the temperature at 80C
to assure complete reaction between the TiC14 and the components carried on the support. Prior to the addition of the TiC14, the solids present in the slurry were light yellow in color, but the color changed to a purple-red shortly after the addition of the TiC14. The liquid present in the slurry was removed by decantation, and the solids were washed with several aliquots of heptane until the heptane gave no test for the presence of chlorides. The solids then were recovered and dried under vacuum at ambient temperature.

~ t~ 5 Part C
_ation of Polymeri~at:ion Initiator _ __ _.___ Two parts of a product prepared in Part B were s~lspended in 500 parts of heptane. Thirty-six parts of triethyl aluminum (added as a 25% solution heptane) then were added over a period of 10 minutes with stirring. This dispersion of polymer:i~ation initiator wa~ stored under rigorously anhydrous conditions for use in the polymerization of ethylene.
In all of the procedures described above, care was exercised to carry out all reactions under rigorously anhydrous conditions. All reactants employed were purified grades and contained no identifiable concentrations of water or reactive hydrogen compounds known to have a deleterious effect upon ~iegler-type polymerization reactions.
In Table I, Section A shows the proportions of reactants employed in the reactions of Part B above. Section B of Table I sets forth the chemical analysis of each chemically-modified transition metal chloride compound prepared in Part B above.
TABLE I
Section A

Preparation of Thermically-Modified Transition Metal Chloride Compound Example Catalyst Heptane DEAC (l) TiC14 No. Support~ gms ml gms gms - - _ 1 200~ 400 72 ~63 2 200300 36 345 ~

3 200300 36 345 Section B

_Catalyst Analysis - Total Example Magnesium Aluminum Chlorine Titanium Inorganic 30 No ~ wt % wt % wt % wt % wt %
.__ 1 1.7 0.3 9.7 2.0 13.7 2 2.0 4.1 15.9 2.6 24.6 3 1.7 2.7 15.1 2.8 22.3 :

:` -' 15 -, Example 4 _ Sixty-seven grams of part-Lculate high density polyethylene, having a particle size less than 40 microns, was suspended in 100 ml of methanol containing 7.5 grams of dissolved magnesium chloride in a 1-liter reaction vessel equipped as described in Example 1. Two hundred fifty ml of heptane then was added to the reactor and the reaction mixture was heated to take off an overhead fraction having a boiling point of 59-60C. After about 175 ml of distillate was recovered, the temperature of the distillate rose to the atmospheric boiling point of heptane.

The reactor was cooled to room temperature and 70 ml of a hep-tane solution containing 12.7 grams of diethyl aluminum chloride was added to the reactor dropwise over a period of 15 minutes. A colorless gas was liberated and vented during this addition. Thereafter, the reaction mixture was heated to 80C and 138 grams of TiCl~ was added dropwise to the reaction system. At the start of tha addition of the TiC14 the reaction mixture was a straw yellow in color, but about 15 minutes after the addition of the TiC14 had been completed, the solids in the reaction system changed to a purple-red color. Heating was con-tinued with stirring for another 16 hours. Thereaf-ter the reactor was cooled and the catalyst solids were recovered by filtration. The re-covered solids were washed with aliquots of dry heptane un-til the wash heptane gave a negative test for soluble chlorides.
A total of 0.2 gram of catalyst component described in the paragraph above was suspended in 50 ml of heptane having dissolved therein 0.36 gram of triethyl aluminum.

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A five-gallon sti~red rPactor was charged with 12.3 kg. of kerosene (Gulfsol 20) and a slurry of 2 grams of the catalyst of E~ample 2 in 40 ml of heptane. The reactor was heated to a temperature of 145C
over a period of about one hour with a bleed in the reactor being opened periodically to vent the minor amount of heptane charged to the reactor.
Polymerization grade ethylene then was fed to the reactor until the reactor pressure increased to 200 psig. Controls then were set to feed the ethylene to the reactor at a rate of 0.3 pound per hour. Ethylene 10 gas was fed to the reactor over a period of 3.5 hours. After the feed of ethylene was cut off 7 stirring was continued for an additional hour at 145C to convert the remainin~ ethylene to polymer. The final reaction product consisted o a hydrocarbon solution containing 3 wei~ht % of ethylene polymer.
The polymer solution was cooled to room temperature to precipi--tate the ethylene polymer therefrom. The recovered polymer solids were washed with several aliquots of heptane and dried overnight in a vacuum oven at a temperature of about 50C. The inherent v~scosity of the recovered polymer, measured by the method as set forth in British 20 patent l,372,116, was greater -than 3.5. The polymer's high load melt index, determined by AS~M 1238-70 (Condition F), was less than 0.02.

Example 6 was repeated and the hot polymer solution was employed directly to prepare fibrils by the method of British patent 1,372,116.
The recovered fibrils were of better quality than a control lot of fibrils prepared from a 3% solution of ethylene polymer having a substan-tially identical inherent viscosity which was dissolved in the same kerosene employed in Example 5.
As the two poIymers employed had substantially identical inherent viscosities and were employed in the same concentration in the sa~e kerosene solvent, it is believed that the improved quality oE the /`ac~ R~k - , . . ; ~ - , .

fibrils resulted by reason of the fact that, in the preparation of the control hydrocarbon solution, m:inor quantities of the ethylene polymer were not completely dissolved and gave rise to imperfections in the final fibrils.

Three additional solutions of h:igh molecular weight ethylene polymer were prepared by the method descr:ibed in E~ample 5, except that the polymeri7ation initiator employed was, respectively, the poly-merization initiator prepared ln Examples 1, 3, and 4. In each in~tance, the polymerization ran smoothly and provided an ethylene polymer having an inherent viscosity in excess oE 3.5, as determined by the method setforth in British patent 1,372,116.

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Claims (8)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for preparing a hot hydrocarbon solution of an ethylene polymer having an inherent viscosity of at least 3.5, which con-sists essentially of contacting ethylene with a polymerization initiator in a high boiling liquid hydrocarbon at a temperature of at least about 130°C; said liquid hydrocarbon having a boiling point range such that its vapor pressure at 130°C is not higher than 5 atmospheres; said polymerization initiator having been prepared by reacting an aluminum alkyl selected from the group consisting of dialkyl aluminum hydrides, dialkyl aluminum halides, and trialkyl aluminums with a supported, chemically-modified transition metal chloride product prepared by a process which consists essentially of the sequential steps of:
(a) Suspending a finely-divided polymer in a 1-4 carbon atom alkanol solution of a magnesium compound, (b) Vaporizing the alkanol from the suspension of Step (a) to deposit the magnesium compound, together with the quantity of alkanol which forms a complex therewith, on the surface of the finely-divided polymer, (c) Suspending the product of Step (b) in a liquid hydrocarbon and adding thereto an aluminum alkyl compound; and (d) Adding a transition metal chloride compound to the suspension of Step (c);
the polymer employed in Step (a) being selected from the group con-sisting of organic thermoplastic polymers and thermoset polymers, the particles of said polymer having at least one dimension not exceeding 600 microns; the magnesium compound employed in Step (a) having the structure:
MgX2. nH20 where X is C1 F, Br, I, N03, 0CH3, 0C0CH3, and n is not greater than 6; the magnesium compound employed in Step (a) constituting 5-25 weight % of the combined weight of the finely-divided polymer and the magnesium compound; the aluminum alkyl compound employed in Step (c) being selected from the group consisting of dialkyl aluminum hydrides, dialkyl aluminum halides, and trialkyl aluminums;
the quantity of the aluminum alkyl employed in Step (c) being not in excess of the quantity that will react with the magnesium compound-alkanol complex carried on the polymeric support; the transition metal chloride employed in Step (d) being selected from the group consisting of titanium tetrachloride and vanadium oxy-trichloride; and the quantity of the transition metal chloride compound employed in Step (d) being at least molarly equivalent to the quantity of the aluminum alkyl compound employed in Step (c).

2. The process of Claim 1 in which the alkanol is vaporized in Step (b) by being distilled directly from the suspension.

3. The process of claim 1 in which a hydrocarbon is added to the suspension formed in Step (a) and the alkanol is vaporized in Step (b) by being distilled from the suspension with the hydrocarbon.

4. The process of claim 1 in which said magnesium compound is selected from the group consisting of magnesium chloride, magnesium methoxide, magnesium acetate and magnesium nitrate.

5. The process of claim 1 in which said support is an organic thermo-plastic polymer.

6. The process of claim 5 in which the organic thermoplastic polymer is an ethylene polymer.

7. The process of claim 6 in which the ethylene is contacted with the polymerization initiator at a temperature of about 145°C.

8. The process of claim 7 in which hydrocarbon solvent employed in kerosene.