Preparation of compositions a molded thermoplastic in a cylinder supplies at its upstream end by a load which is difficult to disperse and downstream by a load easy a mechanically

摘要

1537240 Mixing thermoplastics TBA INDUSTRIAL PRODUCTS Ltd 19 March 1976 [3 April 1975] 13619/75 Heading B1C In a process for producing a thermoplastic moulding composition (e.g. of the type described in Patent 1369589) a relatively difficultly dispersible particulate filler or fibrous reinforcing agent is fed to a screw mixer at an upstream location and a relatively easily mechanically degradable filler or reinforcing agent at a downstream location. Many examples of thermoplastics, fillers and reinforcing agents are given, the fillers and reinforcing agents being grouped according to their relative ease of dispersion and/or mechanical degradation. The mixer may have a single screw but is preferably a twin-screw extruder, the or each screw having a length/diameter ratio of at least 9:1 and preferably at least 15:1. The preferred length/diameter ratios for the zones between successive inlets (as shown in the Fig.) are given for various arrangements.