Abstract: A novel process for polymerizng ethylene or a mixture of ethylene and another olefin is provided. In this process a novel catalyst having a very high activity per solid component of catalyst is used. Said catalyst is prepared by reacting a specific hydrocarbon-soluble organoaluminum-magnesium complex containing alkoxy, aryloxy, siloxy or siloxane groups, with one or more kinds of a titanium or vanadium compound having at least one halogen atom, and subsequently reacting the thus obtained hydrocarbon-insoluble reaction product (A) with a specified organoaluminum compound (B).

Abstract: A novel process for polymerizing ethylene or a mixture of ethylene and another olefin is provided. In this process a novel catalyst having a very high activity per solid component of catalyst is used. Said catalyst is prepared by reacting a specific hydrocarbon-soluble organoaluminum-magnesium complex containing alkoxy, aryloxy, siloxy or siloxane groups, with one or more kinds of a titanium or vanadium compound having at least one halogen atom, and subsequently reacting the thus obtained hydrocarbon-insoluble reaction product (A) with a specified organoaluminum compound (B).

Abstract: Polyethylene or copolymers of ethylene with another .alpha.-olefin can be produced by the use of a novel polymerization catalyst obtained by using, in combination, (A) a specified, hydrocarbon-insoluble solid component prepared by reacting (i) a specific, hydrocarbon-soluble organoaluminum-magnesium complex (Al.sub.n Mg.sub.m R.sub.n(3.sub.-.sub..alpha.).sup.1 -R.sub.2m.sup.2 H.sub.n, wherein R.sup.1 and R.sup.2 are hydrocarbon radicals) with (ii) a titanium or vanadium compound containing halogen atom(s), and (B) an organoaluminum compound. This catalyst exhibits a surprisingly high activity per the unit amount of the solid component.

Abstract: A process for polymerizing ethylene or a mixture of ethylene and another olefin is proposed in which the polymerization can be carried out with an extremely high efficiency by using a catalyst prepared by reacting (A) a hydrocarbon-insoluble reaction product (obtained by reacting (i) a specified organomagnesium-containing hydrocarbon-soluble complex, or reaction product of (i), with (ii) a specified siloxane compound and with (iii) at least one kind of titanium or vanadium compound containing at least one halogen atom), with (B) a specified organoaluminum compound. Resultant polymers have a high molecular weight and a high rigidity and molecular weight and molecular weight distribution thereof can be easily controlled.

Abstract: A thermoplastic composite composition comprisingI. about 95 to about 30 percent by weight of a thermoplastic material andIi. about 5 to about 70 percent by weight of a polyolefin composition comprisingA. about 15 to about 60 percent by weight of a polyolefin andB. about 85 to about 40 percent by weight of at least one reactive inorganic filler,Said reactive inorganic filler having been prepared by effecting reaction betweenA. an inorganic material substantially comprising at least one compound selected from the group consisting of metal carbonates, metal hydroxides and metal oxides, said metal being selected from the group consisting of beryllium, magnesium, calcium, strontium, barium, zinc, cadmium and aluminum, said compound having a number average particle diameter of from about 0.01 .mu.. to about 50 .mu.. and a maximum particle diameter of about 100 .mu.., andB.