GB2058095A - Olefin polymerization and catalyst composition for use therein - Google Patents

Abstract

Polymerization of olefins is carried out in the presence of a two-component catalyst comprising a component A obtained by the reaction of an organic hydroxy compound with an organo- magnesium compound and a titanium tetrahalide and a component B comprising metallic hydride or an organo- metallic compound, e.g., an organo- aluminum compound.

Description

SPECIFICATION Olefin polymerization and catalyst composition for use therein This invention relates to an olefin polymerization process and catalysts therefor. In another aspect, this invention relates to an olefin polymerization catalyst comprising a catalyst component A formed by the reaction of an organic hydroxy compound with an organomagnesium compound and a titanium tetrahalide then combining the catalysts thus formed with a cocatalyst component B. In accordance with another aspect, this invention relates to a process for the polymerization of a-olefins using a two-component catalyst system formed as set forth herein. In another aspect, this invention relates to a process for forming a titanium-containing catalyst component which can be used with an organometallic cocatalyst to form a catalyst system useful for the polymerization of a-olefins.In accordance with a further aspect, this invention relates to a process for forming the catalysts comprising a titanium-containing component A and an organometallic component B.

It is known to polymerize ct-olefins and mixtures thereof according to the low pressure process of Ziegler.

In this process, the catalysts used are prepared from mixtures of compounds of elements of subgroups IV-VI of the Periodic Table and the organometallic compounds of the elements of Groups I-Ill of the Periodic Table.

The polymerization is generally carried out in suspension, in solution or even in a gaseous phase.

The activity of an olefin polymerization catalyst is one important factor in a continuous search for a catalyst useful for the polymerization of cr-olefins. It is also desirable that the process used in forming the catalysts be such as to allow ease in preparation and to allow control over the final catalysts formed.

In accordance with the invention, an olefin polymerization catalyst is formed upon mixing A) an organo-titanium complex obtained by reacting an organic hydroxy compound containing from 1-12 carbon atoms and from 1 to 6 hydroxyl groups per molecule, a titanium tetrahalide and an organomagnesium compound of the formula MgR2, wherein each R is a C1-C12 hydrocarbyl group; and B) a metallic hydride or organometallic compound of a metal from Group IA, IIA or IIIA of the Periodic Table.

In a specific embodiment of this invention, catalyst component A is formed by the reaction of an organic hydroxy compound with one of an organomagnesium compound and a titanium tetrahalide and then further contact of the product thus formed with the other of organomagnesium and titanium tetrahalide to form a titanium-containing catalyst component. The resulting titanium catalyst component can be combined with a cocatalyst component B comprising a metallic hydride or an organometallic compound, for example, an organoaluminum compound.

As set forth above, this invention pertains to a catalyst comprising a titanium compound A which is used in conjuction with an organometallic compound B as cocatalyst to form a catalyst system useful in the polymerization of a 1-olefin or admixture of 1-olefins. More preferably, the catalyst system is employed in the production of normally solid ethylene polymers or ethylene copolymerized with at least one aliphatic 1-olefin containing from 3 to about 10 carbon atoms or a conjugated acyclic diolefin containing 4 or 5 carbon atoms. In such polymers, the ethylene content can range from about 80 to 100 mole percent. The polymers can be usefully employed in the production of films, fibers, injection molded articles, blow molded articles, and the like by utilizing conventional plastics fabrication equipment.

Catalyst A can be formed in several ways, designated for convenience as catalyst A-1 or catalyst A-2.

Catalyst A-l can be prepared by reacting an organo-magnesium compound with an alcohol to first form an intermediate compound.

The organomagnesium compounds can be represented by the formula MgR2 where R is the same or different hydrocarbyl group selected from alkyl, aryl, cycloalkyl, alkaryl, aralkyl and alkyl groups containing from 1 to 12 carbon atoms. Exemplary organomagnesium compounds include dimethylmagnesium, diethylmagnesium, diphenylmagnesium, sec-butyl-n-butylmagnesium and the like.

The alcohols generally used to react with the organomagnesium compound to form the intermediate compounds are monohydric alcohols. The preferred alcohols can be expressed as R'OH wherein R' is a hydrocarbyl group having from 1 to 12 carbon atoms. Exemplary compounds include methanol, ethanol, n-butanol, 2-ethylhexanol-1, 2,3-dimethyl-butanol-2, 2-methyl-1-butanol, dodecanol-1 and the like.

The amount of alcohol reacted with the organomagnesium compound will range from about 1 to about 4 mols preferably 1 to 2 mols of alcohol per mol of organomagnesium compound.

The organomagnesium compound can be contacted with the alcohol in a hydrocarbon solution, for example, a paraffin, cycloparaffin, or aromatic hydrocarbon containing from about 4 to 12 carbon atoms per molecule which is inert in the process. Exemplary hydrocarbons include n-butane, n-pentane, nhexane, isooctane, benzene, toluene and the like. Generally, any well-known inert hydrocarbon diluent can be used.

Preferred organomagnesium compounds are dialkylmagnesium compounds in which the alkyl group contains from 1 to about 6 carbon atoms. Preferred R'OH compounds are acyclic alcohols containing from 1 to about 6 carbon atoms. The intermediate compounds formed are comprised of RMgOR' or Mg(OR')2 or mixtures thereof, and by-product RH. These intermediate compounds can form a precipitate or be partially, if not entirely, soluble in hydrocarbon solvents.

The product mixture obtained from reaction of the organomagnesium compound and alcohol can be treated in situ with a hydrocarbon solution of a titanium tetrahalide, generally titanium tetrachloride because of its availability and relatively low cost, for a time and at a temperature sufficient to produce an active 1-olefin polymerization catalyst component. The product is isolated, washed with a dry hydrocarbon such as n-hexane to remove unreacted titanium tetrahalide and dried to obtain catalyst A-1 in the form of a particulate solid. Alternatively, the precipitate can be separated from the reaction mixture and treated with the titanium tetrahalide to form catalyst A-l as before.

Catalyst A-2 can be prepared by reacting a titanium tetrahalide, generally titanium tetrachloride usually contained in a hydrocarbon such as n-hexane with an organic hydroxy compound containing from 1 to about 12 carbon atoms to form an intermediate compound. The hydroxy compound can contain from 1 to about 6 hydroxyl groups per molecule.

The hydroxy compounds are selected from the group consisting of saturated acyclyic and alicyclic alcohols, aromatic alcohols, glycols, simple sugars, and phenols. Examples of specific compounds include methanol, butanol-1, hexanol-1, 2-methyl-butanol-4, 2-ethyl-hexanol-4, dodecanol-1, pentaerythritol, dipentaerythritol, cyclohexanol, 1,2-ethanediol, 1,4-butanediol, 1,7-heptanediol, 1,2,3-propanetriol, diethylene glycol, triethylene glycol, dipropylene glycol, 1,2,6-hexanetriol, erythritol, xylitol, sorbital, d-xylose, d-glucose, d-fructose, benzyl alcohol, 2-phenylethanol, diphenylcarbinol, phenol, o-cresol, catechol, pyrogallol, and the like as well as mixtures thereof.

The mole ratio of titanium tetrahalide to hydroxy compound can vary from about 1:1 to about 1:4. The intermediate compound formed can be represented as TiXn(OR")4n where n is an integer of 0 to 3 and R" is the residue of the hydroxy compound selected. The product still in admixture with the hydrocarbon solvent employed is contacted with MgR2, generally under refluxing conditions, to produce the final product, which after isolation, purification by washing with a dry hydrocarbon, and drying, constitutes catalyst A-2.

In the preparation of catalyst A-l and catalyst A-2, the reaction mixture can be stirred or agitated to improve contact of the reactants. Although the reaction can take place at room temperature, if desired, better results generally happen by mixing the reactants in a refluxing reaction mixture.

Contacting of the intermediate product formed in the production of catalyst A with the titanium tetrahalide can be carried out generally at temperatures ranging from about 0 C to about 1 50"C, with the decomposition temperature of the titanium tetrahalide determining the upper treating temperature limit. The length of the contacting period can vary widely and generally ranges from about 0.05 to about 20 hours.

The mole ratio of titanium tetrahalide to dihydro-carbylmagnesium compound can range from about 50:1 to about 0.5:1, preferably from about 10:1 to about 1:1.

Regardless of its manner of preparation, each catalyst A is used in combination with an organometallic compound cocatalyst B selected from a hydride of the metals of Groups IA, IIA, and IIIA of the Periodic Table, or an organic compound of the metals to give the catalyst system employed in the polymerization process.

Generally, the cocatalyst is an organoaluminum compound represented by the formula AlR"'bY3 b in which R"' is the same or different hydrocarbon radical selected from alkyl, cycloalkyl, aryl, alkaryl, and the like having from 1 to about 12 carbon atoms, Y is a monovalent radical selected from among the halogens and hydrogen, and b is an integer of0 to 3. Examples of specific compounds include trimethylaluminum, triethylaluminum, tridodecylaluminum, tricyclohexylaluminum, triphenylaluminum, tribenzylaluminum, diethylaluminum chloride, diisobutylaluminum hydride, ethylaluminum dibromide, and the like including mixtures thereof.

The amount of cocatalyst employed with the catalyst during polymerization can vary rather widely from about 0.005 mmole to about 10 mmole per liter of reactor contents. However, particularly good results are obtained at a more preferred range from about 0.01 mmole to about 2.5 mmole per liter of reactor contents.

This corresponds approximately to a weight ratio of cocatalyst to catalyst broadly ranging from about 0.01:1 to about 250:1.

The polymerization process can be effected in a batchwise or in a continuous fashion by employing any conventional mode of contact between the catalyst system and the monomer or monomers. Thus the monomer can be polymerized by contact with the catalyst system in solution, in suspension, or in gaseous phase at temperatures ranging from about 20"-200"C and pressures ranging from about atmospheric to about 1,000 psia (0.1-6.9 MPa). The polymerization process can be conducted batchwise such as in a stirred reactor or in continuous fashion such as in a loop reactor under turbulent flow conditions sufficient to maintain the catalyst in suspension.

It is especially convenient when producing ethylene polymers to conduct the polymerization in the presence of a dry hydrocarbon diluent inert in the process such as isobutane, n-heptane, methylcyclohexane, benzene, and the like at a reactor temperature ranging from about 60 to about 11 OOC and a reactor pressure ranging from about 250 to about 600 psia (1.7-4.1 MPa). In such a process, particle form polymerization, the polymer is produced as discrete solid particles suspended in the reaction medium. The polymer can be recovered, can be treated to deactivate or remove catalyst residues, can be stabilized with an antioxidant system, and can be dried, all as is known in the art to obtain the final product. Molecular weight control agents such as hydrogen can be employed in the reactor as known in the art to adjust the molecular weight of the polymer, if desired.

EXAMPLE 1 CatalystA- 1 preparation To a 10 or. pop bottle in a dry box was charged the specified quantity of sec-buty!-n-butyl mag nesiu m contained as a 0.56 molar solution in Iso par E (Exxon Co., Houston, TX, high purity isoparaffinic material) and the specified quantity of the indicated organic hydroxy compound (2-methyl-l-butanol). The bottle was capped. A gelatinous precipitate which initially formed mostly dissolved as the bottle was rotated overnight on a roller mill. The next day, in a dry box, the contents of the bottle and about 200 ml of dry n-hexane were placed in a 500 ml round bottom flask equipped for stirring and refluxing and to it was charged in 2 unequal portions (minor portion first) the indicated quantity of titanium tetrachloride. A brown gelatinous precipitate formed.The mixture was refluxed for about 1 hour, cooled, the precipitate washed several times with n-pentane, and dried over a warm water bath to produce a brown, powdery solid. The details are given in Table 1.

EXAMPLE 2 CataXystA-2 preparation A series of catalysts was prepared by charging to a 500 ml round bottom flask equipped for. refluxing and stirring under a dry nitrogen purge a designated amount of the specified organic hydroxy compound as a slurry or dissolved in about 200 ml of dry n-hexane. To the contents was charged the specified quantity of titanium tetrachloride. (On occasion, the reverse charging technique was employed with similar results.) The flask and contents were heated about 30 minutes at reflux temperature (about 68"C) and cooled to room temperature (about 23"C). Then the specified quantity of sec-butyl-n-butylmagnesium contained as a 0.56 molar solution in Isopar E was added dropwise.The mixture was refluxed for about 30 to 60 minutes, cooled to room temperature, and the precipitate was washed with several portions of a dry hydrocarbon such as n-pentane or n-hexane. The product was dried over a warm water bath to produce a powdery solid. The details are given in Table 1.

TABLE I Catalyst preparation Mole Ratios Catalyst Cat. Cat. TiCl4 Hydroxy compound MgR2 TiCl4 MgR2 TiCl4 Yield No. Type g Moles g Moles Name g Moles HyCa HyCa MgR2 g Color 1 A-1 65.6 0.346 4.9 0.055 2-methyl-1-butanol 7.76 0.056 6.3:1 1.0:1 6.2:1 11.3 brown 2 A-2 10.4 0.054 2.5 0.054 ethanol 3.88 0.28 1.0:1 0.52:1 1.9:1 12.1 brown 3 A-2 10.4 0.054 4.8 0.054 2-methyl-1-butanol 3.88 0.028 1.0:1 0.52:1 1.9:1 9.4 brown 4 A-2 10.4 0.054 1.8 0.029 ethylene glycol 3.80 0.027 1.9:1 0.91:1 2.0:1 12.3 brown 5 A-2 11.2 0.059 2.0 0.015 pentaerythritol 4.03 0.029 3.9:1 1.9:1 2.0:1 14.4 brown 6 A-2 8.5 0.045 2.0 0.011 i-glucose 3.10 0.022 4.1:1 2:1 1.1:1 10.3 brown 7 A-2 15.4 0.081 7.6 0.081 phenol 4.89 0.035 1.0:1 0.43:1 2.3::1 21.0 brown a - Hydroxy compound EXAMPLE 3 Ethylene polymerization Ethylene was polymerized in a particle form process generally in the absence of any molecular weight control agent by employing a dry, stirred, stainless steel reactor of 1 gallon (3.8 liter) capacity. The reactor was conditioned for each run by adding to it about 3 liters of dry n-heptane, closing the port, and heating reactor and contents at 175"C for 30 minutes. The reactor was drained, residual heptane purged with dry nitrogen, the reactor closed, and cooled to room temperature under nitrogen pressure. The cool reactor was purged with dry isobutane vapor and 3 ml of cocatalyst solution containing 15 wt. % triethylaluminum (TEA) in dry n-heptane (2.8 mmoles TEA) was charged to it.The catalyst was added, the reactor closed, about 2 liters of dry isobutane charged or as indicated and the reactor and contents were heated to about 80"C. (One run was made at 100 C.) Ethylene was then charged, partial pressure of 0.69 MPa (115 psia), or as indicated, and additional ethylene was supplied to the reactor on demand from a reservoir to maintain the desired pressure.

Each run was terminated by flashing ethylene and isobutane and hydrogen, if present, from the reactor.

The polymer was recovered, dried, and weighed to determine the yield.

Calculated productivity of each catalyst in terms of kilograms polyethylene per gram catalyst per hour was obtained by dividing the weight of polymer in grams by the weight of catalyst in grams employed in each run.

The quantity of each catalyst employed and results obtained are shown in Table 2.

TABLE 2 Ethylene polymerization 1 hour at 80"C Catalyst Run Polymer Productivity No. g No. g kg/g 1 0.0335 A 730 (1370)a 21.8 (40.9)a 1 0.0118 B 117 9.92 2 0.0120 C 509 42.2 3 0.0153 D 527 344b 4 0.0190 E 315 16.6 5 0.0261 F 403 (604)C 15.4 (23.2)C 5 0.0177 G 488 27.6 6 0.0237 H 514 21.7 7d 0.0296 1 688 23.2 7e 0.0112 J 284 25.4 Notes: (a) Run time of 32 minutes. Values in parentheses normalized to 60 minutes based on a linear response. Bulk density of product was about 23.7 Ibs. per cubic foot (0.38 g/cc).

(b) Bulk density of product was about 21.8 Ibs. per cubic foot.

(c) Run time of 40 minutes. Values in parentheses normalized to 60 minutes based on a linear response.

(d) Used 1.2 liters isobutane in reactor.

(e) Used 1.2 liters isobutane in reactor, ethylene partial pressure of 1.38 MPa (215 psia), hydrogen partial pressure of 0.41 MPa (75 psia); melt index of product =0.26, HLMI/MI = 35. ASTM D 1238-65T condition E for melt index and condition F for high load melt index.

The data presented in Table 2 indicate that active ethylene polymerization catalysts have been prepared according to this invention. Calculated productivities ranged from about 10 kg polyethylene per gram catalyst per hour for run B to about 42 kg polyethylene per gram catalyst per hour for run C. Most of the calculated productivities ranged from about 22 to about 34 kg polyethylene per gram catalyst per hour. The run J polymer had a melt index of 0.26 which is in a desirable range for injection molded articles, for example. The ratio of high load melt index to melt index of 35 for this polymer is believed to indicate that it has relatively narrow molecular weight distribution. This value is more or less typical of polymers made with titanium-containing catalysts. The bulk density values for the polymers produced in runs A and D are generally typical for polyethylenes made in the slurry process with titanium-containing catalysts.

Claims (18)

1. A catalyst composition for the polymerisation of olefins comprising: A) an organo-titanium complex obtained by reacting an organic hydroxy compound containing from 1-12 carbon atoms and from 1 to 6 hydroxyl groups per molecule, a titanium tetrahalide and an organomagnesium compound of the formula MgR2, where each R is a C1-C12 hydrocarbyl group; and B) a metallic hydride or organometallic compound of metal from Group IA, IIA or IIIA of the Periodic Table.

2. A catalyst composition according to claim 1, wherein titanium tetrahalide used in the preparation of component A is titanium tetrachloride.

3. A composition according to claim 1 or 2, wherein component B is an organoaluminum compound.

4. A composition according to claim 3, wherein component B is triethylaluminum.

5. A composition according to any one of claims 1 -4, wherein, in component A, the mole ratio oftitanium tetrahalide to the organomagnesium compound is from 50:1 to 0.5:1, the mole ratio of titanium tetrahalide to hydroxy compound is from 1:1 to 1:4 and the mole ratio of organomagnesium compound to hydroxy compound is 1:1 to 1:4.

6. A composition according to any one of claims 1-5, wherein the organomagnesium compound is a di(C1-C6)alkyl magnesium.

7. A composition according to claim 6, wherein the organomagnesium compound is sec-butyl-n-butyl magnesium.

8. A composition according to any one of claims 1-7, wherein component A is obtained by reacting the organic hydroxy compound with the organomagnesium compound and then adding the titanium tetrahalide.

9. A composition according to claim 8, wherein the organic hydroxy compound is a monohydric alcohol of the formula R'OH, where R' is C1-C12 hydrocarbyl.

10. A composition according to claim 9, wherein R' is an acyclic hydrocarbyl group of 1-6 carbon atoms.

11. A composition according to claim 10, wherein the organic hydroxy compound is 2-methyl-butanol-1.

12. A composition according to any one of claims 1-7, wherein component A is obtained by reacting the organic hydroxy compound with the titanium tetrahalide, and then adding the organomagnesium compound.

13. A composition according to claim 12, wherein the organic hydroxy compound is ethanol, 2-methyl-1 -butanol, ethylene glycol, pentaerythritol, d-glucose or phenol.

14. A process for the preparation of a catalyst composition as claimed in any on of claims 1-7 which comprises a) reacting the organic hydroxy compound with the organomagnesium compound; b) reacting the product of step a) with the titanium tetrahalide; and c) mixing the product of step b) with the metallic hydride or organometallic compound of a metal from Group IA, IIA or IIIA of the Periodic Table.

15. A process for the preparation of a catalyst composition as claimed in any one of claims 1-7, which comprises a) reacting the organic hydroxy compound with the titanium tetrahalide; b) reacting the product of step a) with the organomagnesium compound; and c) mixing the product of step b) with the metallic hydride or organometallic compound of a metal from Group IA, IlA or IIIA of the Periodic Table.

16. A catalyst com position accordi ng to claim 1, substantially as hereinbefore described in Example 1 or 2.

17. A process which comprises polymerising one or more 1-olefins in the presence of a polymerisation catalyst, wherein the catalyst used is a composition as claimed in any one of claims 1-13 or 16.

18. A process according to claim 17, wherein the olefin is or comprises ethylene in an amount of from 80-100 molar percent.