Process for the production of polyethylene materials

Claim 2

A process for producing a polyethylene material of great mechanical strength and high elastic modulus, which comprises; (a) polymerizing ethylene at a temperature between -20° C. and 110° C. in the presence of a catalyst comprising (1) a solid component containing magnesium and vanadium and (2) an organometallic compound to produce particulate polyethylene having an intrinsic viscosity in the range of from 5 to 50 dl/g at 135° C. in decalin; and (b) drawing the resulting particulate polyethylene, without melting or dissolution, at a temperature lower than the melting point thereof.

Claim 3

The process of claim 1 wherein said polyethylene material has an elastic modulus greater than 120 GPa and a tensile strength more than 2 GPa.

Claim 4

The process of claim 1 wherein said particulate polyethylene has a melting point higher than 38° C.

Claim 5

The process of claim 1 wherein said drawing comprises extrusion and stretching.

Claim 6

The process of claim 1 wherein said drawing comprises compression, rolling and stretching.

Claim 7

A process for producing a polyethylene material of great mechanical strength and high elastic modulus, which comprises; (a) polymerizing ethylene in a first reaction stage in a reactor at a temperature in the range of from 0° C. to 90° C. in the presence of a catalyst comprising (1) a solid component containing magnesium and titanium and (2) an organometallic compound, in the absence of hydrogen or in the presence of hydrogen at reduced concentration, to from 50-99.5 parts by weight of an ethylene homopolymer having an intrinsic viscosity in the range of from 12 to 50 dl/g at 135° C. in decalin; (b) introducing a fresh feed of ethylene into said reactor and polymerizing the fresh feed of ethylene in a second reaction stage at a temperature in the range of from 40° C. to 100° C. in the presence of hydrogen at increased concentration to from 50-0.5 parts by weight of an ethylene polymer having an intrinsic viscosity in the range of from 0.1 to 4.9 dl/g at 135° C. in decalin; and (c) drawing particular polyethylene of ultrahigh molecular weight which results from the above two stages of polymerization, without melting or dissolution, at a temperature lower than the melting point thereof, said particular polyethylene having an intrinsic viscosity in the range of 5 to 50 dl/g at 135° C. in decalin.

Claim 8

A process for producing a polyethylene material of great mechanical strength and high elastic modulus, which comprises; (a) polymerizing ethylene in a first reaction stage in a reactor at a temperature in the range of from 0° C. to 90° C. in the presence of a catalyst comprising (1) a solid component containing magnesium and titanium and (2) an organometallic compound, in the absence of hydrogen or in the presence of hydrogen at reduced concentration, to from 50-99.5 parts by weight of an ethylene homopolymer having an intrinsic viscosity in the range of from 12 to 50 dl/g at 135° C. in decalin; (b) introducing a fresh feed of ethylene into said reactor and polymerizing the fresh feed of ethylene in a second reaction stage at a temperature in the range of from 40° C. to 100° C. in the presence of hydrogen at increased concentration to from 50-0.5 parts by weight of an ethylene polymer having an intrinsic viscosity in the range of from 0.1 to 4.9 dl/g at 135° C. in decalin; and (c) drawing particular polyethylene of ultrahigh molecular weight which results from the above two stages of polymerization, without melting or dissolution, at a temperature lower than the melting point thereof, said particular polyethylene having an intrinsic viscosity in the range of 5 to 50 dl/g at 135° C. in decalin.

Claim 9

The process of claim 6 wherein said polyethylene material has an elastic modulus greater than 120 GPa and a tensile strength more than 3 GPa.

Claim 10

The process of claim 6 wherein said particulate polyethylene has an intrinsic viscosity in the range of 5-30 dl/g at 135° C. in decalin.

Claim 11

The process of claim 6 wherein said drawing comprises extrusion and stretching.

Claim 12

The process of claim 6 wherein said ethylene polymers are formed in amounts of 70-99 parts by weight in the first reaction stage and of 30-1 parts by weight in the second reaction stage.