Abstract: A process for producing a propylene-ethylene block copolymer by subjecting propylene and ethylene to three-step polymerization using a stereoregular polymerization catalyst, which comprises in the first step polymerizing propylene alone or a propylene/ethylene mixture so that the average ethylene/propylene reaction ratio is 6/94 or less, thereby polymerizing 60 to 95% by weight of the total polymerization amount, in the second step polymerizing a propylene/ethylene mixture so that the average ethylene/propylene reaction ratio is 25/75 to 67/33, thereby polymerizing 1 to 20% by weight of the total polymerization amount, and in the third step polymerizing a propylene/ethylene mixture so that the average ethylene/propylene reaction ratio is 76/24 to 89/11, thereby polymerizing 4 to 35% by weight of the total polymerization amount, wherein in the second and third steps, ethylene alone is supplied thereby gradually decreasing the amount of propylene in the polymerization system from the first step to the succeedin

Abstract: High impact polystyrene compositions are prepared by the intimate melt mixing of a styrene polymer and a particular AB two-block copolymer. The A block is a polymer of a monoalkenyl arene having a specified molecular weight range and the B block is a butadiene polymer block having a 1,2 vinyl content of greater than about 20 percent.

Abstract: High impact polystyrene compositions are prepared by the intimate melt mixing of a styrene polymer and a particular AB two-block copolymer. The A block is a polymer of a monoalkenyl arene having a specified molecular weight range and the B block is a butadiene polymer block having a 1,2, vinyl content of greater than about 20 percent.

Abstract: The invention pertains to a method for preparation of polymers, grafted polymers, and copolymers from olefins substituted by polar groups (ester, nitrile, or aryl) or from dienes, wherein the polymerization is initiated by the system formed by mixing of an organic amide of alkaline metal with an alkaline metal alkoxide. The organic amide is derived from primary or secondary amines or polyamines, or from tertiary polyamines containing at least one primary or secondary amino group. These amines contain N-C or N-Si bonds, 1-4000 C atoms and 1-1000 N atoms in a molecula, or have the molecular weight below 100,000. The alkoxides are derived from C.sub.3 -C.sub.16 alcohols. The polymerizations are carried out at -80.degree. to +80.degree. C. (advantageously at +20.degree. C.), at the monomer/organic amide molar ratio 5-1500, at the molar ratio alkoxide/amide 0.5-10, and in hydrocarbon or ether solvents.

Abstract: Copolymers of vinyl esters and crotonic acid are commonly prepared by polymerizing the monomers in bulk or in solution by means of a radical-forming initiator in the presence of a regulator. The polymers should be free from residual monomers and impurities as far as possible. This may be realized in that upon completion of the polymerization the unreacted monomers and other volatile impurities are removed from the reaction mixture by distillation. For this purpose, the use of an entrainer is advantageous. The copolymers are suitable as starting materials for adhesives and hair lacquers, hair setting lotions as well as hair sprays.

Abstract: Graft copolymers comprising a crosslinked, saturated, elastomeric grafting base and a hard shell are prepared by incorporating thermolabile comonomers, as copolymerized units, into the grafting base during the preparation of the latter, in particular at a conversion of from 50 to 90%. During the subsequent grafting of the shell, the conditions used are such that the thermolabile comonomers incorporated as copolymerized units into the grafting base decompose into free radicals. This gives graft copolymers having improved mechanical properties, which copolymers also prove advantageous for the preparation of mixtures with other thermoplastics compatible with the graft copolymers.