Process for the polymerization of α-olefins

Claim 1

In a process for the continuous polymerization of at least one α-olefin monomer having from 2 to 8 carbon atoms per molecule wherein monomer feed and catalyst components are fed continuously to the reactor and product is withdrawn in a substantially continuous fashion as a slurry in liquid monomer, said slurry having a solids content between about 15 and about 50 percent by weight, the improvement which comprises: polymerizing the α-olefin monomer at a temperature between about 125° F and about 175° F and at a pressure of at least 150 psi and sufficient to maintain monomer in the liquid phase in the presence of a catalyst system comprising: (1) between about 0.02 and about 0.3 percent by weight based on the α-olefin monomer feed rate of a modified titanium trichloride component obtained by agitating in the presence of a liquid aromatic hydrocarbon diluent at a temperature of from about 140° F to about 176° F a titanium trichloride of the formula n·TiCl 3 ·AlCl 3 , where n has a value between about 1 and about 5, with sufficient phosphorus oxitrichloride to provide a titanium to phosphorus mole ratio of about 3:1 to about 10:1 in the modified component, separating said component from the diluent and drying said component; (2) an organoaluminum compound selected from aluminum trialkyls or dialkyl aluminum halides or mixtures thereof in amounts from about 1.9 moles to about 4 moles per mole of titanium chloride, and (3) between about 40 and about 150 ppm by weight based on the α-olefin monomer feed rate of a trialkyltrithiophosphite, wherein each of the alkyl groups contain from 1 to 20 carbon atoms.