Patent GB-936761-A (GB)
Title: Improvements in the treatment of cellulose products
IPC: D21H17/06
Filed: 1961-06-23
Abstract: A modification of the parent Specification, in which cellulose fibres are reacted with formaldehyde, comprises drying and heating the fibres after impregnation with an aqueous liquid containing zinc sulphate and formaldehyde, the molecular ratio of zinc sulphate to formaldehyde being at least 1:17, and the proportion of zinc sulphate carried by the fibres at the time of drying and heating being at least 0,003 gram molecules per 100 grams of cellulose.  The fibres may be of natural or regenerated cellulose, and may be in the form of staple fibre or continuous filaments of regenerated cellulose, optionally in "never-dried" state, paper or cardboard made from natural or regenerated cellulose, or woven, knitted or non-woven fabrics.  The fabrics may consist wholly of cellulose, or partly of fibres of other types, e.g. cellulose acetate, polyamides such as nylon, polyesters such as polyethylene terephthalate, or polyacrylonitrile.  Preferably, such fabrics contain at least 35% by weight of cellulose fibres.  The cellulose fibres may have been dyed before reaction with formaldehyde. Fabrics treated show improved crease-resistance, reduced water-imbibition and improved dimensional stability without loss of tensile and tear strengths. Impregnation of the cellulose fibres with the aqueous solution of zinc sulphate and formaldehyde, optionally containing other solvents, e.g. methanol or ethanol, is desirably followed by squeezing and centrifuging so that the amount of formaldehyde carried by the fibres is 0,5 to 6% based on dry weight of fibre, so that after drying, e.g. at 30 DEG -110\s2., and heating, e.g. at 110 DEG -180\s2., the fibres contain 0,1 to 3% by weight of formaldehyde chemically bound to the cellulose.  Following the heating stage, the treated fibres or fabrics may be washed with water, or water containing ammonia, urea or other substance which reacts with any unbound formaldehyde.  The pH of the treating solution may be at least 5.  In an example, never-dried viscose rayon staple fibre is soaked in an aqueous solution of zinc sulphate and formaldehyde with pH 5,5.  The fibres, after centrifuging to 140% liquid content, are dried at 80\s2. and heated at 155\s2. for 6 minutes.  Specification 878,655 also is referred to.ALSO:A modification of the parent Specification in which cellulose fibres are reacted with formaldehyde, comprises drying and heating the fibres after impregnation with an aqueous liquid containing zinc sulphate and formaldehyde, the molecular ratio of zinc sulphate to formaldehyde being at least 1:17, and the proportion of zinc sulphate carried by the fibres at the time of drying and heating being at least 0,003 gram molecules per 100 grams of cellulose.  The fibres may be of natural or regenerated cellulose, and may be in the form of staple fibre or continuous filaments of regenerated cellulose, optionally in "never-dried" state, paper or cardboard made from natural or regenerated cellulose, or woven, knitted or non-woven fabrics.  The fabrics may consist wholly of cellulose, or partly of fibres of other types, e.g. cellulose acetate, polyamides such as nylon, polyesters such as polyethylene terephthalate, or polyacrylonitrile.  Preferably, such fabrics contain at least 35% by weight of cellulose fibres.  The cellulose fibres may have been dyed before reaction with formaldehyde.  Fabrics treated show improved crease-resistance, reduced water-inhibition and improved dimensional stability without loss of tensile and tear strengths. Impregnation of the cellulose fibres with the aqueous solution of zinc sulphate and formaldehyde, optionally containing other solvents, e.g. methanol or ethanol, is desirably followed by squeezing and centrifuging so that the amount of formaldehyde carried by the fibres is 0,5 to 6% based on dry weight of fibre, so that after drying, e.g. at 30 DEG -110 DEG C. and heating, e.g. at 110 DEG -180 DEG C., the fibres contain 0,1 to 3% by weight of formaldehyde chemically bound to the cellulose.  Following the heating stage, the treated fibres or fabrics may be washed with water, or water containing ammonia, urea or other substance which reacts with any unbound formaldehyde.  The pH of the treating solution may be at least 5.  In an example, "never-dried" viscose rayon staple fibre is soaked in an aqueous solution of zinc sulphate and formaldehyde with pH5,5.  The fibres, after centrifuging to 140% liquid content, are dried at 80 DEG C. and heated at 155 DEG C. for 6 minutes. Specification 878,655 also is referred to.