| 摘要 |
1529944 Screw mixers IMPERIAL CHEMICAL INDUSTRIES Ltd 16 Jan 1976 [7 Feb 1975] 5284/75 Heading B1C [Also in Division B5] An inlet 4, into for an additive to molten polymer being delivered by a rotating screw, 3 through an extruder barrel 2, is of an axial length at least equal to that of the screw diameter and comprises a land 6 along the length of one side of the inlet 4 towards which the screw rotates, so that the additive is drawn into a rolling bank of the polymer which is formed along the land 6, from polymer which it draws off from the screw 3. The land 6 enables a higher concentration of additive to be incorporated, and effects a degree of mixing which minimises the amount required by the screw downstream of the inlet 4 i.e. to avoid breakage of glass fibre additive. On the side opposite the land 6, the inlet 4 comprises a step 7 sloping down to and around the screw and widening to the downstream end of the inlet 4 to merge with and restrain the polymer roll into a tapering scallop shaped groove 8 in the barrel wall extending downstream of the inlet 4. Spiral rotation of the polymer along the length of the step 6 to be drawn into the scallop 8, is enhanced by tapering of the width of land 6 in the downstream direction. The land 6 may be horizontal, but may be downwardly inclined along its length, and inclined inwardly towards the screw axis. The inlet 4 may be open to atmosphere, connected to vacuum, or supplied with gases such as nitrogen and an evacuation port may be provided downstream of the inlet 4. The examples relate to polypropylene polymer with the additive comprising chopped glass strand, titanium dioxide, or talc. The additive may also comprise pigment, and various other polymers are specified.
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