GB1207062A - An improved composite polyamide polyester, sheath-core filament and a method for manufacturing the same - Google Patents

Abstract

1,207,062. Sheath-core polyamide polyester filaments. TORAY INDUSTRIES Inc. 24 Jan., 1968 [27 Jan., 1967; 9 June, 1967; 13 Oct., 1967], No. 3844/68. Heading B5B. Composite sheath-core filaments in which the sheath component consists of an aliphatic polyamide and the core component consists of polyethylene terephthalate are characterized in that 20 to 60% by weight of the filament consists of the polyester and in that either the centre of the area of a cross-section of the core and the centre of the area of a cross-section of the composite filament coincide, or, if said centres of the areas do not coincide, then the distance between them divided by the " effective radius " of the cross-section of the composite filament is less than 0À2. The aliphatic polyamide may be poly-#-caproamide or polyhexamethylene adipamide. The filaments may be made by simultaneously extruding the molten polyester and the polyamide through the extrusion orifices of a pair of spinnerets arranged one above the other in such a manner that each orifice of the upper spinneret is above a corresponding orifice of the lower spinneret, the molten polyester being extruded through the orifice of the upper spinneret into the inlet portion of the corresponding orifice of the lower spinneret, which inlet portion has a greater cross-sectional area than the outlet portion of the orifice of the upper spinneret and is supplied with the molten polyamide in such a manner that the stream of molten polyester passing through the orifice of the lower spinneret is surrounded by a stream of the molten polyamide. The relative mean diameters of the corresponding spinneret orifices and the distance between their axes are such that the eccentricity of the filaments produced is less than 0À2. The rate of extrusion of the polyester is between 20 and 60% by weight of the combined rates of extrusion of the polyester and the polyamide. The aliphatic polyamide used may be poly-#-caproamide having a degree of polymerization of over 200 or polyhexamethylene adipamide having a degree of polymerization of over 90. The polyester used may have a degree of polymerization of over 90. When poly-#-caproamide is used as the aliphatic polyamide component, its birefringence may be maintained at a value below 2 Î 10<SP>-3</SP> and the composite filament may thereafter be stretched. The melt-spun composite filaments may be subjected to a stretching operation in which it is passed over and in contact with a heating member the surface temperature of which is maintained between a lower limit (TL) expressed by the equation: TL= -8+18À1 log 10 D +0À3##V, wherein TL>45‹ C., D=total denier of the unstretched multifilament yarn V=feeding speed of the unstretched multifilament yarn in metres per minute, and an upper limit (TH) expressed by the equation: TH= - 5+33À3 log 10 D + 0À3##V. The expression " effective radius " is defined as the radius of a circle circumscribing the cross-section of the composite filament.