GB568258A - Process for treating cellulose with formaldehyde - Google Patents

Abstract

Filaments, yarns, flocks, fabrics, films, or other structures made of natural or regenerated cellulose are rendered resistant to swelling by treating them with formaldehyde in the presence of large quantities of relatively concentrated solutions of strong acids which do not exert any parchmentizing effect under the conditions of the treatment, and continuing the treatment at least until the cellulose no longer dissolves in the usual cuprammonium solutions. The cellulosic materials may be impregnated with an aqueous solution of formaldehyde and then exposed to the action of the acid solution, with or without an intermediate drying step, or they may be treated with an aqueous solution containing formaldehyde and acid. Natural or artificial staple fibres in flock or yarn form may be treated with a mixture of formaldehyde and acid in a centrifuge. Fabrics may be treated while their dimensions are fixed by a stenter. They may be forwarded through the acid solution by means of rollers or selvedge clips or clamps. The treatment may be associated with the production of artificial filaments, e.g. formaldehyde may be added to the spinning solution and a relatively concentrated acid coagulating bath may be used, or the spinning solution may be extruded into an aqueous solution of formaldehyde and acid. The treatment may be applied at a later stage to the filaments, spun cakes or other packages. Instead of formaldehyde, trioxymethylene or hexamethylene tetramine may be used. The acid used may be sulphuric, hydrochloric, phosphoric, or trichloracetic acid, or a mixture of these. A solution of a strongly acid salt such as an alkali bisulphate may be used. With sulphuric acid, the concentration may correspond to 40-45 DEG Baum<\>ae, and with hydrochloric acid it may correspond to 17 DEG Baum<\>ae. The reaction period may vary from 1 minute to 1 hour at room temperature, and from 5-20 seconds at 70 DEG C. with sulphuric acid of 40 DEG Baum<\>ae. Examples describe the treatment of viscose cr<\>zepe de chine fabric, mercerised cotton voile, cotton batiste, staple fibre flock, viscose thread, mercerised cotton twist, and cuprammonium artificial silk in hanks. The treatment increases the affinity of the cellulosic materials for dyestuffs.