Patent GB-599668-A (GB)
Title: Improvements in or relating to the extrusion of thermoplastic compositions so as to obtain artificial filaments, films, foils, and like shaped articles
IPC: D01D5/08
Filed: 1940-02-27
Abstract: <PICT:0599668/IV/1> <PICT:0599668/IV/2> <PICT:0599668/IV/3> A thermoplastic composition is delivered to an extruding point by means of a feed-pump, at least the gland of which is surrounded by a non-solvent medium for the thermoplastic material of the composition at a temperature higher than the fusion point of the composition, and the fused composition is extruded to form artificial filaments, films, foils and similar articles. Preferably, the whole pump is immersed in the hot non-solvent medium which may be the same as that into which the thermoplastic composition is to be extruded.  The tendency for the fused thermoplastic composition to escape through the glands may be reduced by introducing non-solvent medium into the glands themselves, but at a pressure lower than the minimum pressure within the pump.  The thermoplastic material may be a cellulose ester or ether, mixed ester or esterether; a polyvinyl ester or ether; a polymerized ester of an unsaturated acid such as a polyacrylic or polymethacrylic ester; or a synthetic linear condensation polymer such as a polyamide obtained from an amino-carboxylic or sulphonic acid or from a diamine and a dicarboxylic or disulphonic acid.  The nonsolvent liquid may be a paraffin, arylated paraffin, acenaphthene, anthracene, benzene, diphenyl, toluene, a diphenyl methane or ethane, naphthalene, tetrahydronaphthalene, di-naphthyl, phenanthrene, isoamyl ether, dimethyl ether of triethylene glycol, anisol, ethyl naphthyl ether or diphenyl ether, or a halogen substitution derivative of a hydrocarbon or an ether.  Although liquid non-solvents are preferred, vapours or gaseous media may be used, e.g. nitrogen, hydrogen, carbon dioxide, or organic non-solvent vapours.  As shown in Fig. 2, pumps 1 are mounted inside a casing 2. The pump shafts protrude through the side of the casing so as to be driven by gearing.  The non-solvent liquid 6 in the casing is heated by an electric element 7.  Fused thermoplastic material is delivered through pipes 8 to each pump.  The pumps 1 discharge fused material down narrow tubes 11 surrounded by heating elements 12. The spinning nozzles 13 are heated by elements 14.  The extruded filaments 15 pass through a heated atmosphere and they may be stretched before collection.  The glands of the pumps are fed with heated non-solvent liquid through pipes 21.  As shown in Fig. 3, the pump 23 is immersed in non-solvent liquid in a casing 25 which also serves as a setting bath for the filaments 26.  The liquid is heated by pipes 28.  As shown in Fig. 4, the gland 20 of pump 1 is surrounded by casing 31 containing non-solvent liquid which enters by pipe 32 and leaves by pipe 33 and is heated by the electric element 34.  Non-solvent at a pressure lower than that of the fused material in the pump is admitted to the gland 20 by pipe 21. The pump may be made of or lined with iron, tin, silver, tantalum, aluminium, copper, chromium or stainless steel.  Heating of the thermoplastic material may be controlled by means of thermostats. The Provisional Specification refers to Specifications 182,154, [Class 102 (i)], and 529,510.