GB1034177A - Production of high tenacity viscose rayon - Google Patents

Abstract

1,034,177. Producing high tenacity viscose rayon. COURTAULDS NORTH AMERICA Inc. April 29, 1963 [April 30, 1962], No. 16656/63. Heading B5B. High tenacity viscose rayon filaments are produced by extruding viscose into an acid bath containing a small proportion of formaldehyde to form filaments, removing the filaments from the bath and stretching them, at a stretch ratio of 1À5 to 3À5 while not more than 20% regenerated, in an atmosphere of steam, preferably saturated and at a temperature between 90‹ and 110‹ C. The viscose is preferably made from pulp of D.P. over 600, the alkali cellulose made from the pulp is preferably not aged and the viscose is preferably spun without substantial ageing. It may contain 2 to 7% of cellulose and 2 to 9% NaOH. It may have a salt (NaCl) figure of 12 to 23, a gamma number of not less than 60, normally 73 to 90, or higher, and a ball fall viscosity of 30 to 400 seconds. The spinning bath normally contains 3 to 9% by weight of sulphuric acid and 4 to 18% of sodium sulphate, preferably about twice the sodium hydroxide content of the viscose. Zinc sulphate is preferably omitted or maintained at a concentration below about 0À2%. The formaldehyde content of the spinning bath is normally about 0À5 to 2À0%, preferably about 0À5 to 1À0%, its function being to retard regeneration. The temperature of the spinning bath will normally be about 20‹ to 35‹ C. and the residence time of the filaments in the bath normally about 1 to 4 seconds. Upon emerging from the steam stretching zone the filaments may be about 90% regenerated and may be immediately cut up into staple fibres. Regeneration may be completed by sluice acid (1% H 2 SO 4 ) used to wash the staple fibres out of the cutter.