| 摘要 |
The invention relates to methods for moulding melted polymers, mainly by extrusion, more specifically to polyolefin extrusion, in particular polyethylene which can be used for producing a polymeric profile, polymeric fibre, polymeric tube and a polymeric film obtainable by pipe ballooning. The inventive method for moulding a thermoplastic polymeric material consists in extruding the melted thermoplastic polymeric material containing elastomer additives through a device for moulding a thermoplastic polymeric material and in producing, during extrusion, a flexible coating at least on the part of the device surface contacting the melt. The inventive device for moulding a thermoplastic polymeric material consists of a body (1) provided with a unit for the fixation thereof to an extruder, a mounting pin (2), a container (3) which is fixed to the bearing body, a die (6), an annular plate (4) for mounting said die and screws (5) for fixing said plate (4) and the container (3) to the bearing body (1). The internal surface of the die (6) is provided with a coating (7) which can be embodied in the form of a catalytic coating or an oxide-containing coating for improving the elastomer adhesion to a metallic surface or a flexible coating. The composition of the thermoplastic polymeric material contains polyolefins and elastomeric additives and is characterised in that said elastomers are embodied in the form of block copolymers of rigid polymers (A) whose glass-transition temperature is greater than a room-temperature and less than the moulding temperature of said polyolephins and soft polymers (B) whose glass-transition temperature is less than a room-temperature. From the block copolymers are selected such copolymers which have a structure of a linear block copolymer A (BA)n, wherein n>0, or (BA)m, wherein m>1, or a graft-copolymer when at least two side segments of the rigid polymers are grafted to a soft polymer at the following component ratio: 0.001-10 % in weight of thermoplastic elastomers, the rest being a thermoplastic polymeric material. |
