NON-CATALYTIC DURABLE PRESS PROCESS FOR TREATING CELLULOSIC MATERIAL USING FORMALDEHYDE VAPOR AND POST-HEATING

1390473 Treating cellulosic fabrics COTTON Inc 12 June 1973 [13 July 1972] 27951/ 73 Heading D1P The dimensional stability, wrinkle resistance, smooth drying characteristics and total shape retentivity of a cellulosic fibre-containing fabric are improved by a non-catalytic process which comprises (a) applying to the fabric a catalyst-free aqueous solution of a non-polymeric nitrogen containing compound which has at least one active hydrogen atom and is capable of reacting with formaldehyde, (b) exposing the impregnated fabric to formaldehyde vapour in the absence of a catalyst until a water-insoluble condensate is affixed on the fabric without effecting any substantial cross-linking with the cellulosic fibre, and (c) post-heating the fabric in an inert gaseous atmosphere in the absence of a catalyst at a temperature of from 100- 180‹C, preferably 140-160‹C, for from 1-20, preferably 3-10 minutes to cross-link the fabric and further polymerise the condensate. The non-polymeric compound is preferably urea or a substituted urea, but may alternatively be thiourea, melamine, a carboxylic amide, a sulphonamide or a carbamate. It is preferably applied at an alkaline pH to leave from 0.5-25 preferably from 2.5-15% by weight of the nitrogen compound on the fabric. The contacting with formaldehyde may be effected with an atmosphere containing from 1-100 preferably from 30-95 volume percent formaldehyde, at a temperature of from 100-160‹C, preferably from 105-120‹C for 0.1-60, preferably from 1-5 minutes. The formaldehyde vapour may be in admixture with air or steam. The postheating step may follow the formaldehyde vapour treatment step immediately or after an indefinite delay during which the fabric may be stored or used in garment manufacture. Alternatively the fabric may be formed into a garment prior to step (b). The fabric is preferably not washed between steps (b) and (c). The impregnated fabric may be conditioned to a moisture content of from 2-100%, preferably from 5-15% by weight of the dry fabric prior to exposure to the formaldehyde vapours. A soft film-forming polymer dispersion, e.g. a polyurethane latex, an acrylic emulsion, polyethylene, acrylonitrile-butadiene copolymers, and deacetylated copolymers of ethylene and vinyl acetate may be applied to the fabric prior to exposure to the formaldehyde vapours. The formaldehyde vapour may be generated by heating a suspension of paraformaldehyde in mineral oil, and is provided in at least sufficient amount to