Patent GB-878656-A (GB)
Title: Method of preparing synthetic resin-impregnated regenerated cellulose staple fibres
IPC: D01F11/02
Filed: 1958-02-10
Abstract: Regenerated cellulose staple fibres having synthetic resin incorporated therein are prepared by impregnating a tow (i.e. a mass of parallel continuous filaments having a total denier between 3,000 and 1,500,000, the denier of the individual filaments in the tow preferably being between 1 and 15) of regenerated cellulose fibres in the gel state, before they have ever been dried, with an aqueous liquid containing a resin precondensate, squeezing the tow until the liquid content of the fibres (based on their oven-dried weight) is reduced to less than their gel waterimbibition, (i.e. the percentage weight of water (based on the dry weight of the material) retained in the saturated material after centrifuging a 0,5 gram sample for 5 minutes at 1,000g), drying and curing the tow and then cutting it into staple fibres.  The regenerated cellulose fibres may be prepared by the cuprammonium or viscose process and are preferably made by spinning viscose into a bath containing, by weight, 7%-12% H2SO4, 14%-25%Na2SO4, 0%-8% ZnSO4, 0%-10%MgSO4, and surfaceactive agents to prevent spinnerette incrustation, at a temperature of 40 DEG -60 DEG C.  The tow may then be arranged in a zig-zag or plaited pattern on an endless-belt conveyer and subjected in succession to a regenerating treatment with a 1%-2% by weight solution of H2SO4 at 60 DEG -92 DEG C. for 3-15 minutes, a neutral or slightly alkaline (pH7,5-9,5) wash at 75 DEG -90 DEG C. for 3-15 minutes, a desulphurization treatment with a solution containing by weight, 0,1%-0,4%Na2S and 0%-0,4%Na2CO3 or NaOH at 55 DEG -70 DEG C. for 3-15 minutes, a sulphide wash with neutral water at 70 DEG -90 DEG C. for 3-15 minutes, an acid wash with a 0,2%-0,5% by weight solution of H2SO4 or HCl at 20 DEG -25 DEG C. for 3-15 minutes and another wash with neutral water at 60 DEG -85 DEG C. for 3-15 minutes to remove acid.  The tow is then impregnated with an aqueous liquid containing the resin precondensate, which may be an aminoplast, e.g. urea-formaldehyde, methylol ethylene urea, melamine-formaldehyde, dicyandiamideformaldehyde, guandine-formaldehyde and combinations of these and methylol amino-epihalohydrin compounds, a formaldehyde-acrolein or formaldehyde-acetone reaction product or a polyepoxy resin, in a monomeric or low polymer state with a molecular weight of 100-1,000, preferably in a concentration of 5%-15% by weight at 15 DEG -50 DEG C. for 1-20 minutes. The impregnating liquid may also contain 2%-20% (based on the weight of the resin precondensate) of a curing catalyst, wetting agents and 0,2%-4% by weight of a finishing agent to add lubricity, cohesion, water repellancy or scroop, e.g. polyglycol stearate, lauryl ketene dimer, silicone emulsions, stearamidomethyl pyridinium chloride or octadecyl pyridinium sulphate.  The tow, which may still be plaited or looped on the endless-belt conveyer during treatment with the resin precondensate solution, may be subjected to a series of impregnations, e.g. four, with the resin precondensate solution with squeezing between each impregnation.  After squeezing the liquid pick-up of the tow will normally be 70%-110% by weight, which is equivalent to a resin pick-up of 2%-10%, based on the weight of oven-dried tow, and the tow is then dried, preferably at 80 DEG -120 DEG C. for 10-45 minutes under a tension of 0,1-0,3 grams/denier or in a relaxed condition, and cured by heating at 125 DEG -180 DEG C. for 1-40 minutes in a relaxed condition by circulating hot air over, around and through the tow or by using dielectric heaters.  The tow is then cut into staple fibre.  Specifications 796,815 and 878,655 are referred to.