Pipe manufactured from irradiated polyethylene containing carbon black

Claim 2

Pipe manufactured from polyethylene of density in the range 0.935 to 0.948 g/cm 3 having 1--3% by weight of carbon black blended therewith, said blend of polyethylene and carbon black having been irradiated while in the form of granules with irradiation selected from the group consisting of electron and gamma irradiation, said irradiation having been carried out in an inert atmosphere and being in an amount of less than 1.5 Mrad.

Claim 3

A process for the manufacture of pipe comprising feeding to an extruder a polyethylene of density in the range of 0.935 to 0.948 g/cm 3 having 1-3% by weight of carbon black blended therewith, the blend of polyethylene and carbon black being in the form of granules that have been irradiated with irradiation selected from the group consisting of electron and gamma irradiation, said irradiation having been carried out in an inert atmosphere and in an amount of less than 1.5 Mrad, extruding said polyethylene in the form of pipe and cooling the pipe so formed.

Claim 4

A process for the manufacture of pipe comprising feeding to an extruder a polyethylene of density in the range of 0.935 to 0.948 g/cm 3 having 1-3% by weight of carbon black blended therewith, the blend of polyethylene and carbon black being in the form of granules that have been irradiated with irradiation selected from the group consisting of electron and gamma irradiation, said irradiation having been carried out in an inert atmosphere and in an amount of less than 1.5 Mrad, extruding said polyethylene in the form of pipe and cooling the pipe so formed.

Claim 5

The pipe of Claim 1 or the process of Claim 2 in which said inert atmosphere was steam.

Claim 6

The pipe of Claim 1 or Claim 3 or the process of Claim 2 or Claim 3 in which temperature of irradiation was in the range between 80 0 C and the temperature of agglomeration of the granules of polyethylene.

Claim 7

The pipe of Claim 1 or Claim 3 or Claim 4 or the process of any one of Claims 2 to 4 in which the granules were subjected to steam before and after irradiation.

Claim 8

The pipe of Claim 1 or any one of Claims 3 to 5 or the process of any one of Claims 2 to 5 in which the amount of irradiation was in the range 0.05-0.75 Mrad.

Claim 9

The pipe of Claim 1 or any one of Claims 3 to 5 or the process of any one of Claims 2 to 5 in which the amount of irradiation was in the range 0.3-0.7 Mrad.

Claim 10

The pipe of Claim 1 or any one of Claims 3 to 7 or the process of any one of Claims 2 to 7 in which the polyethylene, before irradiation, had a melt index of less than 2.0.

Claim 11

The pipe of Claim 1 or any one of Claims 3 to 7 or the process of any one of Claims 2 to 7 in which the polyethylene, before irradiation, had a melt index of less than 0.4.

Claim 12

The pipe of Claim 1 or any one of Claims 3 to 9 or the process of any one of Claims 2 to 9 in which the polyethylene, before irradiation, had a density in the range 0.940-0.944.

Claim 13

The pipe of Claim 1 or any one of Claims 3 to 10 or the process of any one of Claims 2 to 10 in which the polyethylene is a copolymer of ethylene and a higher a-olefin having 4-10 carbon atoms.

Claim 14

The process of any one of Claims 2 to 11 in which (a) prior to irradiation the granules of polyethylene were subjected to an atmosphere of steam at a temperature of at least 80 0 C but less than the temperature of agglomeration of the granules for a minimum period of time inversely related to said temperature, said minimum period of time being in the range from 90 minutes when the temperature is 80 0 C to 20 minutes when the temperature is near that of agglomeration, and (b) after irradiation subjecting the irradiated granules of polyethylene to an atmosphere of steam at a temperature of at least 80°C but less than the temperature of agglomeration of the granules of irradiated polyethylene for a minimum period of time inversely related to said temperature, such that (a) when the irradiation is electron irradiation, the minimum period is in the range from 75 minutes when the temperature is 80°C to 30 minutes when the temperature is near that of agglomeration of the irradiated polymer, and (b) when the irradiation is gamma irradiation, the minimum period is in the range from 20 minutes when the temperature is 80°C to 10 minutes when the temperature is near that of agglomeration of the irradiated polymer.