Abstract: A polypropylene molding composition with a good hardness and good impact strength at low temperatures is formed by two-stage polymerization of propylene and ethylene in liquid propylene in the presence of a special supported catalyst.

Abstract: During the recovery of the unreacted propylene from the mother liquor obtained in the polymerization of liquid propylene, the major part of the propylene is evaporated in a first evaporation step at a low temperature and the remaining part is evaporated in a second evaporator at a high temperature. In this way an early agglomerization of the atactic and/or low-molecular weight polymer dissolved in the mother liquor and fouling of the heat exchanger tubes and/or of the column trays is avoided.

Abstract: In polyolefins, the content of titanium and light metal halides and aluminum compounds emanating from the catalyst system can be considerably reduced by treatment with a higher, preferably branched, aliphatic monocarboxylic acid having 6 to 10 carbon atoms.

Abstract: A polypropylene molding composition of polypropylene, ethylene-propylene copolymer and polyethylene having a high hardness and increased impact strength and homogeneity after processing is obtained by way of a continuous three-stage polymerization, when the melt viscosities of the polymer mixtures obtained in the individual stages are in a determined ratio of one to the other.

Abstract: A polypropylene having a strongly reduced melting temperature and improved optical properties is obtained by copolymerization of propylene with small quantities of ethylene and butene-(1).

Abstract: A catalyst of high activity and stereospecificity in .alpha.-olefin polymerization is obtained when titanium trichloride, prepared by reduction with aluminum alkyl halides, is treated first with an ether and then, without separation of the ether, with an aluminum alkyl halide in the presence of a small amount of a cyclopolyene and/or an olefin.

Abstract: A catalyst of high activity and stereospecificity in .alpha.-olefin polymerization is obtained when titanium trichloride, prepared from titanium tetrachloride by reduction with an aluminum alkyl halide, is thermally treated, first with an ether in the presence of a cyclopolyene and the solid reaction product is then treated with an aluminum alkyl halide in the presence of a small amount of a cyclopolyene and/or an olefin. With the catalyst obtained high space-time yields of .alpha.-olefin polymers and copolymers can be produced.

Abstract: A catalyst of high activity and stereospecificity in .alpha.-olefin polymerization is obtained by subjecting titanium trichloride, prepared from titanium tetrachloride by reduction with aluminum alkyl halides, to two thermal treatments, the second one being carried out in the presence of an dialkyl ether and a cyclopolyene, and/or after-treating the solid reaction product with an aluminum alkyl halide, optionally in the presence of a small amount of a cyclopolyene and/or an olefin.

Abstract: A catalyst of high activity and stereospecificity in .alpha.-olefin polymerization is obtained by subjecting titanium trichloride, obtained by reduction of titanium tetrachloride with aluminum alkyl halides, to two thermal treatments, the second thermal treatment being carried out in the presence of a dialkyl ether.

Abstract: A polypropylene molding composition having an excellent impact strength at a temperature down to -60.degree. C and simultaneously a good hardness contains from 70 to 90% by weight of a polypropylene, 2 to 10% by weight of an ethylene propylene copolymer and 8 to 25% by weight of a polyethylene and is distinguished by a melt index MFI 230/5 lower than that of the polypropylene contained therein and simultaneously higher by the coefficient 1.3 to 7.0 than that of a polypropylene prepared in the presence of the same catalyst as the molding composition and having the same RSV.