GB1593934A - Catalyst system for olefinic polymerisation - Google Patents

Description

(54) CATALYST SYSTEM FOR OLEFINIC POLYMERIZATION (71) We, EXXON RESEARCH AND ENGINEERING COMPANY, a Corporation duly organised and existing under the laws of the State of Delaware, United States of America, of Linden, New Jersey, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to catalyst systems for the conventional alpha-olefin type polymerization at significantly improved polymerization activity, wherein the resultant polymers have a high degree of isotactic stereoregularity.

An object of the present invention is to provide improved catalyst systems having a major increase in polymerization activity while being able to control over a wide range the polymer crystallinity, e.g. isotacticity, wherein the catalyst system includes a transition metal compound, a dialkylmagnesium compound, and a di- or tri-halide of aluminium.

It is well known in the art to use an alkyl metal compound of Groups I-III in combination with a transition metal compound of Groups IVA-VIII as a catalyst system for olefinic polymerization. Although nearly all of the alkyl metal compounds are effective for the polymerization of ethylene, only a few are effective for the preparation of isotactic polymers of propylene and higher alpha olefins and only Et2AlCl and AlEt3 have any important commercial utility.

A major cost involved in the polymerization of the alpha olefins is the cost of the catalyst components. The cost of the manufacture of the polymer can be effectively reduced by the use of catalyst systems having a higher polymerization activity. A further concern is the ability to produce polymers having a minimum amount of catalyst residues thereby eliminating a costly de-ashing operation. A still further concern is the ability to produce polymers having a high degree of isotactic stereoregularity thereby enabling the manufacturer to eliminate the costly operation involving the removal and separation of atactic polymer from the isotactic polymer. The improved catalyst system of the present invention provides a means for the manufacturer to obtain these desirable realizations.

According to this invention a catalyst composition suitable for use in alpha-olefin polymerization comprises a mixture of (a) Group IVA, VA, VIA, VIIA or VIII transition metal chloride or bromide, (b) an aluminium halide of the formula AIX3, R"AlX2, R"AlXY, or a mixture thereof, wherein X is chlorine or bromine, Y is chlorine, bromine or an anion incapable of initiating olefinic polymerization, and R" is an alkyl, cycloalkyl, branched alkyl, naphthenic or aralkyl group, and (c) a dialkylmagnesium compound having the formula: R R'Mg wherein R and R' can be the same or different and are acyclic alkyl groups in which the magnesium atom is attached to a secondary or tertiary carbon atom, wherein the molar ratio of the aluminium halide to the di-alkyl magnesium compound is between 0.5:1 and 2:1 and the molar ratio of the aluminium halide or the dialkyl magnesium compound to the transition metal chloride or bromide is less than 20:1. Regarding component (a) the metal groups refer to the table given in the 'Notes on the Use of the Classification Key of Abridgments of Patent Specifications'.

The transition metal catalyst compound is a Group IVA-VIII transition metal halide, wherein the halide is chloride or bromide and the transition metal halide may be in the form of solid crystalline compounds, solid solutions or compositions with other metal salts or supported on the surface of a wide range of solid supports. For highest stereospecificity it is desirable to have the transition metal halide or its support composition, in the layer lattice structure with very small crystallites, high surface area, or sufficierit defects or foreign components to facilitate high dispersion during polymerization. The transition metal halide may also contain various additives such as Lewis bases, pi bases, polymers, or organic or inorganic modifiers. Vanadium and titanium halides such as VCl3, VBr3, TiCl3, Tics, TiBr3 or TiBr4 are preferred, most preferably TiCl3 or TiCl4 and mixtures thereof. The most preferred TiCl3 compounds are those which contain TiCl4 edge sites on the layer lattice support such as alpha, delta, or gamma TiCl3 or various structures and modifications of TiCl3 on MgCl2. The most preferred TICS, compounds are those supported on chloride layer lattice compounds such as MgCl2. By chloride layer lattice compounds we mean those compounds having layer structures in which the anion layers are predominantly chlorides.

Minor amounts of other anions may be also present such as other halides, pseudohalides, alkoxides, hydroxides, oxides, or carboxylates. Mixed salts or double salts such as K2TiCl6 or MgTiCl6 can be employed alone or in combination with electron dondor compounds.

Other supports besides MgCl2 which are useful are hydroxychlorides, oxides, or other inorganic or organic supports. The most preferred crystal structure of TiCl3 is delta or pseudo delta, the latter being a mixture of alpha and gamma crystallites. The TiCl3-type catalysts may be prepared from TiCl4 by any one of the reduction and crystallization procedures known in the art (H2, metal, metal hydrides, metal alkyls, etc.). "Low aluminum" containing TiCl3 refers to TiCl3 catalysts which have low Al content because of the method of formation or because a major portion of the aluminum was removed in subsequent reactions.

For the alkyl metal cocatalysts of this invention, the most preferred transition metal compounds contain TiCl4 supported on MgCl2 and, optionally, one or more Lewis bases.

Regarding component (b), i.e. the aluminum, R" may be a C, to C20 alkyl group and when Y is an anion which cannot initiate polymerization of olefinic monomers, it may be an alkoxide, phenoxide, thioalkoxide or carboxylate. Typical examples of component (b) are ethyl aluminum dichloride, aluminum trichloride, ethyl aluminum dibromide, ethyl chloroaluminum bromide, octyl aluminum dichloride, butyl aluminum dichloride, benzyl aluminum dichloride, ethyl chloroaluminum butoxide, and mixtures thereof. Mixtures of metal halide compounds can be readily employed.

The C2-C4 alkyl aluminum dihalides are most preferred for high stereospecificity and the monoalkylaluminum dichlorides are most preferred.

Examples of the dialkylmagnesium compound (component (c)) are (s-Bu)2Mg, (t-Bu)2Mg, and (iPr)2Mg. Mixtures of diorganomagnesium compounds can be readily employed. The most preferred secondary or tertiary alkyl groups are tertiary and sec-butyl.

Additionally, Lewis bases can be employed in the combination with the Al metal halide, the dialkylmagnesium compound and the Group IVA-VIII transition metal compound provided they are not added in an amount which causes excessive cleavage of metal carbon bonds or loss of active sites. Suitable Lewis bases are defined as tertiary amines, esters, phosphines, phosphines oxides, phosphates (alkyl + aryl) phosphites, hexaalkyl phosphoric triamides, dimethyl sulfoxide, dimethyl formamide, secondary amines, dialkyl ethers, epoxides, saturated and unsaturated heterocycles, cyclic ethers or mixtures thereof. Typical examples are diethyl ether, tri-ethyl amine, ethyl benzoate, diisopentyl ether or tetra-hydrofuran.

The molar ratio of the aluminium halide to the alkylmagnesium compound is critical and is 0.5:1 to 2:1, more preferably about 1:1. The number of moles of Lewis base can vary widely but is preferably equal to or less than the sum of the moles of the metal halide compound and the diorganomagnesium compound. The molar ratio of the aluminium halide or the dialkylmagnesium compound to the transition metal compound is less than 20:1 and more preferably less than 10:1.

Also, additional dialkyl aluminum halide type cocatalyst can be employed for further modification of polymerization activity. Diethyl aluminum chloride is a typical, but a non-limiting example.

The catalyst system of the invention enables the process for making alpha olefin polymers having a high degree of isotactic stereoregularity to be carried out at a temperature of 25 to 1500C., more preferably 40 to 800C. at pressures of 1 atm to 50 atm. The reaction time for polymerization is 0.1 to 10 hours, more preferably 0.5 to 3 hours. Due to the high catalyst activity, shorter times and temperatures below 80"C can be readily employed.

The reaction solvent for the system can be any inert paraffinic, naphthenic or aromatic hydrocarbon such as benzene, toluene, xylene, propane, butane, pentane, hexane, heptane, cyclohexane, and mixtures thereof. Preferably, excess liquid monomer is used as solvent. Gas phase polymerizations may also be carried out with or without minor amounts of solvent.

Typical, but non-limiting examples of C2-C20 alphaolefinic monomers employed in the present invention for the manufacture of homo-, co- and terpolymers are ethylene, propylene, butene-1, pentene-1, hexene-1, octadecene-1, 3-methylbutene-1, styrene, vinylidene norbornene, 1,5-hexadiene and the like and mixtures thereof. Isotactic polymerization of propylene and higher olefins is espcially preferred.

The aluminium halide and dialkylmagnesium compound can be added separately to the reactor containing the transition metal compound but are preferably premixed before addition to the reactor. Employing either the aluminium halide or the dialkylmagnesium compound alone with the transition metal compound does not provide the improved catalyst efficiency and stererospecificity as envisioned in this application. In order to attain this, it is necessary to employ both the aluminium halide and dialkylmagnesium compound in combination with the transition metal compound in the critical proportions as previously defined. The concentration of the transition metal compound in the monomer plus any solvent present in the polymerisation zone is 0.001 to 5mM, preferably less than 0.1 mM, wherein mM represents millimolar i.e. millimoles per litre of liquid monomer plus solvent if present.

Example 1 Polymerizations were carried out in a 1 liter baffled resin flask fitted with an efficient reflux condenser and a high speed stirrer. In a standard procedure for propylene polymerizations, 475 ml n-heptane ( < 1 ppm water) containing 10 mmole Et2AlCl (1.20 g), or the mixture of cocatalysts, was charged to the reactor under dry N2 heated to reaction temperature (65"C) and saturated with pure propylene at 765 mm pressure. The TiCl3 (1.00 g) (6.5 mmole) was charged to a catalyst tube containing a stopcock and a rubber septum cap. Polymerization started when the TiCl3 was rinsed into the reactor with 25 ml n-heptane from a syringe. Propylene feed rate was adjusted to maintain an exit gas rate of 200-500 cc/min at a pressure of 765 mm. After one hour at temperature and pressure, the reactor slurry was poured into one liter isopropyl alcohol, stirred 2-4 hours, filtered, washed with alcohol and vacuum dried.

The TiCl3 was prepared by reduction of TiCl4 with Et2AlCl followed by treatment with diisopentyl ether and TiCl4 under controlled conditions, yielding a high surface area delta TiCl3 having a low aluminum content.

The sec-butyl magnesium in Runs B, D and E was obtained from Orgmet and contained 72% non-volatile material in excess of the s-Bu2Mg determined by titration. IR, NMR and GC analyses showed the presence of butoxide groups and 0.07 mole diethyl ether per s-Bu2Mg. A second sample of (s-Bu)2Mg was used in Runs G and I. It was substantially pure s-Bu2Mg but contained 0.33 mole diethyl ether per s-Bu2Mg.

TABLE I g Mmoles Rate Run TiCl3 EtAlCl2 (s-Bu)2Mg Et2AlCl gig/h % HI A(Control) l(a) 0 0 10 33 95.2 B 1(a) 5 5 0 152 52.6 C(Control) l(b) 0 0 10 85 96.3 D 0.2(b) 0.4 0.2 1.6 123 88.0 E 0.2(b) 2 2 0 210 49.2 F(Control) l(c) 0 0 5 8 79.5 G 1(C) 2.5 2.5 0 36 57.6 H(Control) l(d) 0 0 10 20 91.7 I 0.2(d) 1 1 0 200 57.4 (a) and (b) were different preparations of low aluminium TiCl3 catalyst.

(c) Stauffer HA grade TiCl3 (hydrogen-reduced, dry ball milled).

(d) Stauffer AA grade TiCl3.0.33 AlCl3 (aluminium-reduced, dry ball milled).

Comparaison of runs B, D, E, G and I with their respective control runs A, C, F and H shows that each type of TiCl3 catalyst the novel cocatalyst combination gave 2-10 times higher activity than the customary Et2AlCl cocatalyst.

The percent heptane insolubles (% HI) decreased substantially using the new cocatalysts.

Thus, these high activity catalysts are attractive for making low crystallinity homopolymers of propylene and higher alpha olefins. They are particularly attractive for making thermoelastic polymers and amorphous copolymers and terpolymers for elastomers.

Example 2 A titanium catalyst containing MgCl2 was prepared by dry ball milling 4 days a mixture of anhydrous MgCl2 (1 mole), TiCl4 (1 mole) and #-TiCl3 (0.1 mole). Propylene was polymerized using the conditions in Example 1, Run B and the quantities shown in Table 2.

Activity with the cocatalyst of this invention (Run L) was intermediate between those of the AlEt3 and AlEt2Cl controls (Runs J and K), but the stereospecificity as shown by % HI was much higher than the controls. The large increase in % HI obtained with this MgCl2-containing catalyst is in contrast to the results in Example 1 using TiCl3 catalysts in which activity increased sharply but % HI decreased.

TABLE II Alkyl Rate Run Catalyst Metals g/g Cat/hr % HI J(Control) 1 10 AlEt3 79 54.4 K(Control) 1 10 AlEt2Cl 18 35.8 L 0.2 1 AlEtCl2 + 42 81.0 1 (s-Bu)2Mg Example 3 A titanium catalyst was prepared by dry ball milling 4 days a mixture of 5 MgCl2, 1 TiCl4 and 1 ethyl benzoate, heating a slurry of the solids in neat TiCl4 2 hours at 80 C, washing with n-heptane and vacuum drying. The catalyst contained 3.78% Ti.

Propylene was polymerized following the procedure of Example 1, Run B. As shown in Table III, all the control runs (M through S) gave substantially lower activity and/or % HI than the AlEtCl2 + S-Bu2Mg combination (Run T) or AlCl3 + Bu2Mg (Run U).

If the new cocatalysts simply reacted as the separate alkyl metals compounds, the results should have been like Runs M + Q. If the new cocatalysts simply reacted according to the equation: AlRCl2 + R2Mg < AlR2Cl + RMgCl, then the results should have been like Runs N + P. However, the results in Run T and U are dramatically better, showing a remarkable synergism.

TABLE III Mmoles Mmoles Time Rate Run Catalyst Al Cpd Mg Cpd Hrs. g/g Cat/hr % HI M(Control) 0.2 1 AlEtCl2 --- 0.5 0 - N(Control) 0.2 1 AlEt2Cl --- 1 47 61.1 O(Control) 0.2 1 AllEt3 --- 1 326 82.6 P(Control) 0.2 --- 0.83 s-Bu MgCl 0.25 0 - Q(Control) 0.2 --- 0.83 (s-Bu)2Mg 0.25 0 - R(Control) 0.2 1 AlEt3 0.83 (s-Bu)2mg 0.25 6 -- S(Control) 0.2 1 AlEt2Cl 0.83 (s-Bu)2Mg 1 165 80.5 T 0.2 1 AlEtCl2 0.83 (s-Bu)2Mg 1 367 91.9 U 0.2 1 AlCl3 0.83 (s-Bu)2Mg 1 220 88.9 fital A much smaller synergistic effect was obtained by combining AlEt2Cl + Bu2Mg (Run S), but the results were poorer than those obtained with AlEt3. Combining Bu2Mg with AlEt3 (Run R) destroyed the activity shown by AlEt3 alone (Run O). Thus, the outstanding results were obtained only when R2Mg was combined with RAlCl2 or Ail3.

Example 4 The procedure of Example 3 was followed using 0.2 g of the MgCl2-containing catalyst together with (s-Bu)2Mg and various aluminum compounds.

TABLE IV Mmoles Mmoles Time Rate Run Al Cpd (s-Bu)2Mg Hrs. g/g Cat/hr % HI V 0.4 AlEtCl2 0.33 1 60 94.5 W 1 AlEtCl2 0.41 1 64 76.6 X 0.5 AlEtCl2 0.83 1 260 87.2 Y 0.5 AICl3 0.83 2 136 90.7 Z 1 AlEtCl2 + 1 AlEt2Cl 0.83 1 404 86.9 AA 1 AlEtBr2 0.83 1 220 88.9 BB 1 AlC8H17Cl2 0.83 1 425 88.0 CC 0.63 EtClAlN(iPr)2 0.53 1 6 - DD 1 Br2AlN(iPr)2 0.83 1 16 - Comparison of Runs V, W and X shows that the highest % HI is obtained at approximately equimolar amounts of RAlCl2 and R2Mg (Run V), that a large excess of RAlCl2 is undesirable (Run W) and that a small excess of R2Mg increases activity (Run X).

Activity also increased upon addition of AlEt2Cl to the AlEtCl2-(s-Bu)2Mg system (Run Z). The remainder of the experiments show that the dibromide may be used in place of dichloride (Run AA), that long chain alkyl aluminum compounds are very effective (Run BB), but that dialkyl amide groups on the aluminum compound destroy catalyst activity (Runs CC and DD).

Example 5 The procedure of Example 3, Run T was followed except that Lewis bases were also added to the AlEtCl2-(s-Bu)2Mg cocatalysts.

Addition of Lewis bases causes a decrease in catalyst activity until it becomes zero at a mole ratio of one strong base per mole of RAlCl2 + R2Mg.

TABLE V Rate Run Mmoles Base/(sec Bu)2Mg Time, Hrs g/g Cat/hr % HI EE 0.24 COOEt(a) 0.5 174 94.3 FF 0.5 Et3N(b) 1 62 85.5 GG 2 Diisopentyl ether 1 127 78.8 HH 2 Tetrahydrofuran(c) 1 0 - (a) Added to the (s-Bu)2Mg (b) Premixed total catalyst in 100 ml n-heptane at 65"C, 5 min. before adding Et3N (c) Added to premixed AlEtC12-(s-Bu)2Mg As shown in Run EE, small quantities of Lewis base are effective in improving isotacticity (94.3% HI vs. 91.9 in Run T) while maintaining high activity (nearly 9 times the conventional AlEt2Cl/TiCl3-0.33 AICl3 catalyst, Run H).

Example 6 The procedure of Example III, Run T was followed except that xylene diluent was used for polymerization instead of n-heptane. Activity was 676 g/g Cat/hr and the polymer gate 90.9% heptane insolubles.

Example 7 The procedure of Example 3, Run T was followed except that polymerization was carried out at 50"C and 80"C. Both polymerization rate and % HI decreased with increasing temperature, with the largest decrease taking place above 65"C.

TABLE VI Polymer Time, Run Temp, "C Hours Rate % HI II 50 1 474 90.4 T 65 1 367 91.9 JJ 80 0.5 148 74.6 Example 8 Propylene was polymerized at 690 kPa pressure in a stirred autoclave at 50"C, 1 hour. A second preparation of MgCl-containing TiCl4 catalyst (2.68% Ti) made as in Example 3 except that TiCl4-ethylbenzoate complex was preformed, was used in combination with AlRCl2-R2Mg. High stereospecificity was obtained at high rates and catalyst efficiencies.

TABLE VII g Mmoles Mmoles Run Cat AlEtCl2 (s-Bu2)Mg Rate % HI KK 0.10 0.5 0.5 1672 88.8 LL 0.10 0.25 0.25 696 95.0 Example 9 The procedure of Example 5, Run EE was followed except that the catalyst of Example 8 was used, 0.5 mmole diethyl ether was used in place of ethylbenzoate, and Lithium Corporation (n + s Bu)2Mg in hexane was used in place of (s-Bu)2Mg. Rate was 327 g/g Cater and % HI = 91.8.

Example 10 The procedure of Example 9 was followed except that a new pure sample of (sec-Bu)2Mg was used with 0.33 mole diethyl ether. Rate was 268 g/g Cat/hr and % HI = 92.2 Example 11 A catalyst was prepared by dry ball milling 4 days a mixture of 10 MgCl2, 2 Tics, 2 ethylbenzoate and 1 Mg powder, heating the solids in neat TiCl4 2 hours at 80"C, washing with n-heptane and vacuum drying (Ti = 2.16%).

Propylene was polymerized 1 hour at 650C and atmospheric pressure using 0.20 g of this catalyst under the conditions of Example 3, Run T except only 0.4 mmole (s-Bu)2Mg and 0.4 mmole AlEtCl2. Rate was 240 g/g Cat/hr and % HI = 93.9.

Example 12 A catalyst was prepared by dry ball milling for 1 day a mixture of 5 MgCl2 and 1 ethylbenzoate, adding 1 TiC14 and milling an additional 3 days, then treating the solids with neat TiC14 2 hours at 80"C, washing with n-heptane and vacuum drying (3.44 % Ti).

Propylene was polymerized following the procedure of Example 3, Run T, except that 1 mmole (s-Bu)2Mg was used instead of 0.83 mmole. Rate was 298 g/g Cat/hr and % HI = 89.

Example 13 Following the procedure in Example 8, two catalysts were made at different Mg/Ti ratios.

Catalyst A was made with 1 MgCl2 + 1 TiCl4-ethylbenzoate and B (2.10% Ti) was made with 10 MgC12 + 1 TiCl4-ethylbenzoate complex. Propylene was polymerized following the procedure of Example 3, Run T (Tabel 8).

TABLE VIII g Mmoles Mmoles Run Cat AlEtCl2 (s-Bu)2Mg Rate % HI MM 0.107A 2 1.66 60 72.0 NN 0.316B 0.25 0.25 512 60.4 00(a) 0.316B 0.25 0.25 124 84.2 (a) Added 0.25 mmole triethylamine to the alkyl metal cocatalysts.

Claims (15)

WHAT WE CLAIM IS:

1. A catalyst composition suitable for use in an alpha-olefin polymerization which comprises a mixture of: (a) Group IVA, VA, VIA, VIIA or VIII transition metal chloride or bromide, (b) an aluminium halide of the formula AIR3, R"AIX2, R"A1XY, or a mixture thereof, wherein X is chlorine or bromine, Y is chlorine, bromine or an anion incapable of initating olefinic polymerization, and R" is an alkyl, cycloalkyl, branched alkyl, naphthenic or aralkyl group, and (c) a dialkylmagnesium compound having the formula: R R'Mg wherein R and R' can be the same or different and are acyclic alkyl groups in which the magnesium atom is attached to a secondary or tertiary carbon atom, wherein the molar ratio of the aluminum halide to the dialkyl magnesium compound is between 0.5:1 and 2:1 and the molar ratio of the aluminium halide or the dialkyl magnesium compound to the transition metal chloride or bromide is less than 20:1.

2. A composition according to claim 1, wherein said anion is an alkoxide, phenoxide, thioalkoxide or carboxylate.

3. A composition according to any one of the preceding claims wherein the transition metal of the transition metal halide is trivalent titanium, trivalent vanadium or tetravalent titanium.

4. A composition according to any one of the preceding claims wherein the transition metal chloride is TiCI4.

5. A composition according to anyone of the preceding wherein the transition metal halide is supported on a support.

6. A composition according to claim 5 wherein said support is MgCl2.

7. A composition according to claims 4 and 5 wherein the TiCI4 is supported on a chloride lattice compound (as herein before defined).

8. A composition according to any one of the preceding claims wherein the aluminium halide is EtAICI,.

9. A composition according to anyone of the preceding claims wherein the dialkylmagnesium compound is (s-Bu)2Mg.

10. A composition according to any one of the preceding claims which includes a Lewis base (as hereinbefore defined).

11. A composition according to any one of the preceding claims which includes a dialkyl aluminium halide.

12. A catalyst composition according to claim 1 substantially as hereinbefore described with reference to the Examples.

13. A process for the polymerisation of a C2 to C20 alpha olefin or a mixture thereof to a solid homo-, co- or terpolymer in which said olefin is polymerized at a temperature of 25"C to 1500C, a pressure of 1 atm to 50 atm., for 0.1 to 10 hrs in the presence of a catalyst composition according to any one of the preceding claims wherein the concentration of transition metal compound in monomer plus any solvent present is 0.001 to 5mM.

14. A catalyst composition according to claim 1 substantially as hereinbefore described with reference to the Examples.

15. A process for the polymerisation of a C2 to C20 alpha olefin or a mixture thereof according to claim 13 substantially as hereinbefore described with reference to the Examples.