Abstract: The invention provides a process for the preparation of but-1-ene homopolymers or copolymers of but-1-ene containing up to 15% by weight of at least one other .alpha.-olefin by the stereo-specific polymerization, using a Ziegler-Natta catalyst, of but-1-ene in a homogeneous reaction mixture. By employing a homogeneous reaction mixture comprising at least 70% by weight of but-1-ene and from 1 to 30% by weight of an inert hydrocarbon solvent which is capable of dissolving at least 100 g/l of an isotactic polybutene it is possible to employ reaction temperatures of from 35.degree. to 55.degree. C., thereby improving the quality of the resulting but-1-ene polymer while avoiding precipitation of polymer during the course of the reaction.

Abstract: Photodegradable polyolefin compositions are described which comprise from 5 to 500 ppm of iron in the form of an alkali metal, preferably potassium, trioxalatoferrate and from 5 .times. 10.sup.-.sup.5 to 5 .times. 10.sup.-.sup.3 mol per 100 g of polyolefin of a photosensitizing organic compound having a triplet energy of at least 30 Kcal/mol, such as certain aromatic ketones or aldehydes, certain organic nitro derivatives or dyestuffs, or certain aromatic hydrocarbons.

Abstract: Modified copolymers which have viscosities which vary very markedly with changes in temperature are obtained by malaxating a statistical copolymer of ethylene and maleic anhydride containing between 0.5 and 20% by weight of units derived from maleic anhydride and having a melt index of between 0.1 and 500 dg/min, in the molten state with at least one chemical reagent containing at least two reactive groups which are amine or alcoholic --OH groups but at most primary or secondary amine group and at least one alcoholic --OH group.

Abstract: A method for the polymerization or copolymerization of ethylene comprising polymerizing the ethylene at a pressure greater than 500 bars, at a temperature in the range 160.degree. to 280.degree.C and under conditions in which polymerization takes place in a single liquid phase, in the presence of a catalyst system comprisingA. an alkylsiloxalane derivative of the formula, ##EQU1## and B. a halogenated titanium compound of the titanium trichloride type, the Al/Ti ratio between the constituents being between 1 and 10.