Process for the production of electrically conductive polyolefin mouldings, and their application

Claim 1

A process for the manufacture of electrically conductive polyolefin moldings, which comprise (a) 100 parts by weight of a finely divided, partially crystalline polyolefin, which has a mean particle diameter of from 10 to 5,000nm and an intrinsic viscosity [η], measured in decahydronaphthalene at 135°C, of from 0.5 to 15 and b) from 0.01 to 30 parts by weight of an electrically conductive additive which has a maximum particle diameter of < 200µm and a mean particle diameter which is less than of the mean particle diameter of the polyolefin (a), and has a melting point or softening point which is at least 50°C higher than the melting point of the polyolefin (a), with or without (c) from 5 to 10 parts by weight of a fibrous additive which has a fiber diameter of <um and a maximum length-to-width ratio of 1,000:1, and has a melting point above that of the polyolefin (a), and with or without (d) conventional amounts of other conventional additives and auxiliaries, wherein, in a first process step (A) a finely divided molding material comprising the components (a) and (b), with or without (c) and'or (d), is produced by mixing the components (a) and (b), with or without (c) and/or (d), in a first stage (I), in a mixer (with or without the supply or removal of heat), during which first stage (I), in a first sub-stage (i.1), the mixture is brought, at a mixing intensity of from 100 to 500W/I of useful capacity, and within a period of from 2 to 50 minutes, from ambient temperature, which is below the crystallite melting point of the polyolefine (a) and is, in particular, room temperature, to the crystallite melting point of the polyolefin (a), and is immediately thereafter, in the course of a second sub- stage (1. 2), subjected to a mixing intensity which is from 0.3 to 0.8 times as great as the mixing intensity in the first sub-stage (1.1) and is brought, within a period of from 0.2 to 2G minutes, from the crystallite melting point of the polyolefin (a) to a temperature which is from 3 to 40°C above this, and, if appropriate, is immediately thereafter, in a third sub-stage (1.3), subjected to a mixing intensity which is from 0.5 to 1.0 times as great as the mixing intensity in the second substage (1.2) and is kept for a period of from 0.2 to 10 minutes at the temperature reached in sub-stage (1.2) and immediately thereafter, in a second stage (II), is discharged from the mixer within a period of from 0.5 to 30 seconds and is either brought, within 120 seconds, to a temperature below the crystallite melting point of the polyolefin (a), or is directly processed further in a second process step (B), in which the finely divided molding material obtained from the first process step (A) is molded at a temperature above the crystallite melting point of the polyolefin (a), by a continuous or discontinuous compression-molding process, under minimal shear, to give electrically conductive moldings having a specific conductivity of > 10' Q -1 cm -1 preferably of > 10 -3 Ω -1 cm -1 .