Patent GB-618195-A (GB)
Title: Improvements in the preparation of solutions or dispersions of linear super polyamides and the treatment of fibrous materials therewith
IPC: D01F6/60
Filed: 1946-11-01
Abstract: A solution of a synthetic linear polyamide in hydrochloric, sulphuric, nitric or phosphoric acid is concentrated by dissolving therein a salt of one of those acids until the mixture separates into two layers, and isolating the layer containing the higher concentration of polyamide.  The salt need not be one of the acid in which the polyamide is dissolved.  Mixtures of salts or mixed salts may be employed.  Usually the amount of salt added is the minimum necessary for separation into two layers, but excess may be added, in which case the final polyamide concentration is higher, but may be so high that the layer containing the higher polyamide concentration is not homogeneous and may even show gel formation.  Suitable salts are those of alkali metals, ammonium, alkaline earth metals or zinc or magnesium.  Solutions prepared according to the invention are commonly more concentrated than may be prepared by direct solution of the polyamide in the acid.  They also show less tendency to degradation.  Fibrous or other materials, e.g. textiles or paper (see Group VIII) may be treated with the solutions and then with water to precipitate the polyamide on the fibres.  They may be used for glazing fabrics or in dyeing or producing coloured pattern effects on fabrics.  The solutions may be coagulated in aqueous, aqueous alkaline or alkaline media in the form of threads or films.  A number of examples are given employing a polyamide from hexamethylene diamine and adipic acid prepared by the method of Specification 474,999.  In a typical example 10 grams of this polyamide were dissolved in 100 ccs. of 45 per cent by weight aqueous sulphuric acid.  7 grams of sodium chloride were dissolved in the solution which separated into 42.7 ccs. of a solution containing 21.3 grams of polyamide for 100 ccs. and very little salt and 68.1 ccs. of a solution containing substantially all the salt and only 0.7 grams of polyamide.  Other salts used in the examples are sodium sulphate (anhydrous), zinc sulphate (heptahydrate), ammonium sulphate, magnesium sulphate (heptahydrate), zinc chloride, potassium nitrate, ammonium nitrate, tri-sodium phosphate, ammonium dihydrogen phosphate, and a mixture of ammonium and sodium sulphate.  The use of all the acids referred to is exemplified.  In another example the polyamide from hexamethylene diammonium adipate and aminostearic acid described in Specification 559,514 is employed.  Other polyamides are also mentioned.  Specifications 461,236, 461,237, 487,734, 491,111, 567,043, and U.S.A. Specification 2,130,948 also are referred to.ALSO:A solution of a synthetic linear polyamide in hydrochloric, sulphuric, nitric or phosphoric acid is concentrated by dissolving therein a salt of one of those acids until the mixture separates into two layers, and isolating the layer containing the higher concentration of polyamide.  Solutions prepared according to the invention are commonly more concentrated than may be prepared by direct solution of the polyamide in the acid.  They also show less tendency to degradation.  Fibrous or other materials, e.g. textiles or paper (see Group VIII) may be treated with the solutions and then with water to precipitate the polyamide on the fibres.  The solution may be used for glazing fabrics or in dyeing or producing coloured pattern effects on fabrics.  The solutions may be coagulated in aqueous, aqueous alkaline or alkaline media.