Patent GB-664182-A (GB)
Title: Improvements in the treatment of textile materials
Filed: 1949-02-09
Abstract: Filaments or textile materials containing them having a basis of a polyurethane are treated by reacting them with formaldehyde or a substance yielding formaldehyde in alcoholic solution having a pH of at least 10.  The filaments may be made of a polyurethane obtainable by treatment of a di-isocyanate with a glycol.  The di-isocyanate may be a polymethylene di-isocyanate such as trimethylene, tetramethylene, pentamethylene, hexa - methylene, octamethylene or decamethylene di-isocyanate, a cyclo-alkylene di-isocyanate such as cyclopentylene-1.3-di-isocyanate, cyclohexylene-1.3-di-isocyanate, or cyclohexylene-1.4-di-isocyanate, an aromatic di-isocyanate such as ortho- or para-phenylene di-isocyanate, o  - o 1 - di - isocyano - 1 - 4 - xylene, 4,41 - di - isocyanodiphenyl, naphthylene - 1,4 - di - isocyanate, diphenyl - methane - 4,41 - di - isocyanate or o ,o 1 - di - isocyano - 4,41 - dimethyl diphenyl methane.  The glycol used for converting the isocyanates into polyurethanes may be ethylene glycol, diethylene glycol, triethylene glycol, or tri-, tetra-, penta-, hexa-, hepta-, octa-, nona-, or decamethylene glycol.  The formaldehyde may be applied to the filaments as an aqueous solution or as paraformaldehyde, hexamethylene tetramine, trioxane, methylal, or dimethylol urea.  The treating solution may be rendered alkaline by means of sodium hydroxide or other base having an ionization constant of the order of 10-6 or higher and the solution may contain a buffer substance such as trisodium phosphate.  The alcoholic medium may be anhydrous or aqueous and preferably, when the formaldehyde is used in the form of an aqueous solution of formaldehyde, the alcohol used is methyl alcohol.  The temperature of the treatment may be about 50 DEG  C. or higher.  When the material to be treated is in the form of filaments it is preferable that these should not have been completely cold-drawn before the treatment so that they may be further cold-drawn after the treatment without breakages.  It is said that modified polyurethane filaments may thus be produced having an elasticity of 10 to 400 per cent.  In an example a skein of 17 denier mono-filaments having a basis of a high molecular weight polymeric urethane formed by reacting 1,4-butane diol with tetramethylene di-isocyanate and having a melting-point of 203 DEG  C., is immersed for 1 hour at 60 DEG  C. in a medium having a pH of 11.1 and consisting of 4.5 parts by weight of formaldehyde (40 per cent by volume, aqueous), 0.01 part sodium hydroxide and 3.2 methyl alcohol. The treated skein is then washed thoroughly and dried.  The treated filaments have a melting-point of 270 DEG  C. and an elongation of 237 per cent.  The treatment is said to raise the melting-point, safe ironing temperature, moisture regain and elongation of the filaments. Specifications 615,884 and 620,116 are referred to.  The Specification as open to inspection under Sect. 91 comprises also the treatment of filaments having a basis of poly-carbamides and the carrying out of the treatment, whether the filaments be composed of polycarbamides or polyurethanes, in a solution of formaldehyde or a substance yielding formaldehyde, at a pH of less than 3.5 and preferably less than 1.5.  The necessary acidity may be achieved by the presence in the treatment media of any suitable acid with an ionization constant of the order of 10-6 upwards, e.g. hydrochloric, oxalic, acetic, phosphoric, or sulphuric acid.  The solution may contain a buffer substance such as ammonium chloride and the treating medium may be aqueous or alcoholic.  In an example, a yarn having a basis of a high molecular weight polyurethane formed by reacting 1,4-butane diol with tetramethylene di-isocyanate and having a melting-point of 203 DEG  C. is heated for 1 hour at 60 DEG  C. in a medium having a pH of 0.70 and consisting of 4.5 parts by weight of 40 per cent by volume aqueous formaldehyde, 0.12 parts by weight hydrochloric acid and 3.2 parts by weight of methyl alcohol.  The treated yarn is washed and soaked in water and dried at 105-110 DEG C.  Its melting-point is said to be increased to 300 DEG  C.  Other examples are given in which polyurethane yarns are treated in a similar manner in acid media, the acidifying substances being oxalic or phosphoric acid and ammonium chloride being present as a buffer substance.  It is stated that the treatments of the invention may also be applied to filaments made from filament-forming polyureas which may be prepared in a similar way to the polyurethanes, but using a diamine instead of a diol, for example ethylene diamine, tetramethylene diamine or paraphenylene diamine.  It is also stated that the treatments may be applied to interpolymers containing both the urethane and the urea residue, such as may be obtained, for example, by treatment with a di-isocyanate of a mixture of a diol and a diamine.  The invention is said to include the treatment of thin films and foils of polyurethanes or polyureas.  This subject-matter does not appear in the Specification as accepted.