GB1242229A - Manufacture of polypivalolactone fibres - Google Patents

Abstract

1,242,229. Polypivalolactone fibres. KANEGAFUCHI BOSEKI K.K. 31 July, 1968 [31 July, 1967], No. 36566/68. Heading B5B A polypivalolactone fibre having an intrinsic viscosity # f of at least 1À0 and an elongation at break of at least 200% and enhanced heatsettability is made by melt-spinning a polymer consisting substantially of polypivalolactone having an intrinsic viscosity # p of at least 1À1 at an extrusion temperature from 240‹ to 310‹ C. through an orifice of a spinneret, and applying to the extruded polymer, while the latter is still in the molten or plasticized state, a high draw-down such that the deformation ratio A takes a value which satisfies the following two equations: to make the degree of orientation R of the resulting undrawn filament at least 0À87. Intrinsic viscosity is determined at 30‹ C. in a solvent consisting of a 6 : 4 by weight mixture of phenol and orthochlorophenol. A copolymer made by copolymerizing pivalolactone with up to 25 mole per cent of another lactone, e.g. #-propiolactone or α,α-diethyl propiolactone may be used. The undrawn filament may be elasticized either by heat-treatment or by swelling treatment while avoiding substantial drawing of the undrawn filament until it has a degree of orientation R of at least 0À9, a degree of crystallinity of at least 55%, a long period D of at least 80 Š and an average length L a of the amorphous part of at least 40 Š and a structure coefficient of less than 1À70. The filament may, however, be drawn up to 1À5 times its original length in the take-up step or in the heattreatment step. Preferably, heat-treatment is effected for a sufficient period of time for the resulting filament to retain a tensile strength of at least 15 g/d, a tensile recovery of at least 96% at 5% elongation at room temperature, at least 85% at 50% elongation at room temperature, of at least 90% at 5% elongation at 120‹ C., and of at least 80% at 50% elongation at 120‹ C., a work recovery at 50% elongation of at least 40% at room temperature and at least 35% at 120‹ C. and a fatigue resistivity enough to withstand at least ten 50% elongation-relaxation cycles at 120‹ C. Such heat-treatment may consist of steam heat-treatment or wet heat-treatment at 100‹ to 150‹ C., especially 120‹ to 150‹ C. Alternatively, such heat-treatment may consist of a dry heat-treatment at 175‹ to 210‹ C. for a length of time in the range satisfying the two equations: # # exp (16À2828 - 0À089456#) and # # exp (0 002003#<SP>2</SP> - 0 8662# + 95À1964) where # represents the duration of the heat treatment in minutes and # represents the temperature of the heat treatment. Swelling treatment preferably utilizes a swelling bath prepared by dissolving or dispersing at least one organic compound active to said polypivalolactone and comprising phenol, its derivatives, chlorinated hydrocarbons, e.g. monochlorobenzene, dichlorobenzene, trichlorobenzene and tetrachlorobenzene halogenated fatty acids, acid amides, e.g. dimethylformamide and dimethylacetamide, dimethyl sulphoxide or nitrobenzene in at least one liquid medium inert to said polypivalolactone and comprising water, alcohol glycerine or acetone; in a concentration suitably of at least 1À0% by weight. A 75-85% by weight solution of phenol, a 90-95% by weight solution of metacresol, and a 10-30 g/l. solution of chlorophenol, all used at room temperature, are especially mentioned. Alternatively, swelling treatment may utilize an aqueous solution of at least one inorganic compound active to said polypivalolaotone and selected from chlorides of the metals of Group II of the Periodic Table, thiocyanates and inorganic acids. Those specified include zinc chloride, calcium chloride and magnesium chloride; calcium, potassium and ammonium thiocyanates; and sulphuric, hydrochloric and nitric acids. Fibres so made may show a knot strength not smaller than their tensile strength, and intrinsic viscosities of 1 to 5, especially 1À3 to 3À5.