Patent GB-722774-A (GB)
Title: Aqueous dispersions of n-alkoxymethyl polyamides and their application
IPC: B44C1/16
Filed: 1952-11-13
Abstract: Filaments, fabrics, stockings or films made of wool, cotton, rayon, nylon, acrylonitrile polymers, ethylene polymers, polyethylene terephthalate, leather or combinations thereof are treated with an aqueous dispersion comprising (1) 1-50 per cent based on the weight of the dispersion of an N-alkoxymethyl polyhexamethylene adipamide; (2) a dispersing agent; and (3) a water-soluble salt derived from a nitrogen-containing base and an acid having an ionization constant for the first or only hydrogen of at least 1 X 10-5 at 25 DEG  C., said salt being decomposed on heating to a temperature of less than 170 DEG  C. to yield an acidic residue which effects curing of the polyamide.  The treatment results in improved properties such as increased abrasion resistance, increased snag resistance, anti-static properties, dye-fastness, shrink resistance, dimensional stability, increased water absorption, a better hand, a delustering effect, a reduction in fabric slippage and increased tensile strength.  The dispersion contains at least 50 per cent water and may also contain water-miscible or water-immiscible liquids, e.g. the C1-C4 alcohols, benzyl alcohol, furfuryl alcohol, acetone or phenols.  The size of the particles is 0.1 microns or less to 10 microns.  The dispersing agent may be anionic, cationic or non-ionic and there are specified the sodium salts of long-chain alkyl sulphates, the sodium or triethanolamine salts of sulphated secondary alcohols and the sodium salts of branched-chain alkyl sulphonates.  Suitable water-soluble salts are the ammonium, alkyl amine, pyridine and morpholine salts of lactic, citric, chloracetic, itaconic, malonic, mesaconic, diglycollic, tartaric, maleic, hydroxyacetic, oxalic, glutaric, adipic, malic, fumaric, phthalic, salicylic, formic, phosphoric, sulphuric or hydrochloric acids.  The dispersion may contain diethanolamine to effect plasticization and prevent over-curing. The dispersion may also contain urea to produce thickening, pigments, dyes, delustering agents, anti-static agents, flame-retarding agents, water-repellants, anti-oxidants, heat-stabilizers, e.g. sodium phenyl phosphinate, plasticizers, e.g. N-ethyl toluene sulphonamide, temporary plasticizers, e.g. diethylene glycol, fillers, or dimensional stabilizers, e.g. urea- or melamine-formaldehyde resins. Co-dispersions may be prepared with unmodified polyamides, natural or synthetic rubber, natural resins or ethylene polymers.  After treating the fabric with the dispersion, the fabric is heated to decompose the salt and effect curing of the modified polyamide. Loadings of from 0.2 to 15 per cent of modified polyamide, based on the weight of the fabric, are generally employed.  The fabric may be pre-treated with a cation-active agent, e.g. stearyl dimethyl benzyl ammonium chloride to improve the hand of the finished fabric.  In examples, (2) unsized cotton broadcloth is passed through an aqueous dispersion of N-methoxymethyl polyhexamethylene adipamide containing sodium dodecyl sulphate and ammonium citrate.  The fabric is then squeezed between rubber rolls and heated to 120 DEG  C. for 20 minutes to cure the polyamide; (3) unsized cotton broadcloth is first pretreated by immersion in a bath of a 0.25 per cent solution of cetyl dimethyl benzyl ammonium chloride followed by passage between padding rolls and drying at 80 DEG  C. The fabric is then immersed in a dispersion similar to that of example (2), passed through squeeze rolls and heated to 140 DEG  C. for 5 minutes; (4) nylon taffeta or marquisette is immersed in a dispersion similar to that of example (2), passed through rubber wringer rolls and then cured at 120 DEG C. for 5 minutes.ALSO:An aqueous dispersion comprises (1) 1-50 per cent based on the weight of the dispersion of an N-alkoxymethyl polyhexamethylene adipamide; (2) a dispersing agent; and (3) a water-soluble salt derived from a nitrogen-containing base and an acid having an ionisation constant for the first or only hydrogen of at least 1 X 10-5 at 25 DEG  C., said salt being decomposed on heating to a temperature of less than 170 DEG  C. to yield an acidic residue which effects curing of the polyamide.  The dispersion has a pH of 7.5-11.5 and the size of the dispersed particles is preferably from 0.1 microns or less to 10 microns.  It is preferably made by injecting a solution of the polyamide into water whilst providing a shearing action or turbulent flow, e.g. by using a colloid mill, an orifice or a Venturi tube.  Suitable solvents are the C1-C4 alcohols, phenols and mixtures thereof with water.  The stability of the alcoholic solutions is improved by the addition of benzyl or furfuryl alcohol.  When the dispersion is made by diluting alcoholic solutions the tendency of the alcohol to dissolve the polyamide may be counteracted by adding acetone.  The dispersion may be prepared directly from the mixture resulting from the reaction of polyhexamethylene adipamide with formaldehyde and alcohol.  The dispersing agent may be anionic, cationic or non-ionic and suitable agents are the sodium salts of long chain alkyl sulphates, the sodium or triethanolamine salts of sulphated secondary alcohols and the p sodium salts of branched-chain alkyl sulphonates.  Suitable water-soluble salts are the ammonium, alkyl amine, pyridine and morpholine salts of lactic, citric, chloracetic, itaconic malonic, mesaconic, diglycollic, tartaric, maleic, hydroxyacetic, oxalic, glutaric, adipic, malic, fumaric, phthalic, salicylic, formic, phosphoric, sulphuric or hydrochloric acids.  The dispersion may contain diethanolamine to prevent over-curing and to effect plasticization.  The dispersion may also contain urea to produce thickening, pigments, dyes, delustring agents, anti-static agents, flame-retarding agents, water-repellants, anti-oxidants, heat stabilizers, e.g. sodium phenyl phosphinate, plasticizers, e.g. N-ethyl toluene sulphonamide, temporary plasticizers, e.g. diethylene glycol, fillers, or dimensional stabilizers, e.g. urea- or melamineformaldehyde resins.  Co-dispersions may be prepared with unmodified polyamides, natural or synthetic rubber, natural resins or ethylene polymers.  The dispersions may be used for treating textiles (see Group IV (c)) in which case the impregnated textile is heated to effect liberation of the acid and curing of the modified polyamide. The dispersions may also be employed in the preparation of adhesives; binders; coatings for paper, furniture or bowling pins; impregnated articles; films; and leather-like products.  In examples, (1) a solution of N-methoxymethyl polyhexamethylene adipamide and sodium decyl sulphate in aqueous methanol is injected through an orifice into a stream of water passing through a Venturi whilst maintaining a pH of 10.5 by adding sodium hydroxide.  The resultant dispersion is heated to 60 DEG  C. and circulated to a vacuum chamber where methanol is distilled off.  The dispersion is recirculated to the Venturi until the solids content is raised to 20 DEG  C.  Diammonium citrate is then added, the pH adjusted to 9.5-10.5 by ammonia and ammonium citrate added; (2)-(4) textiles are treated with the dispersion of example (1); (5) cowhide leather is sprayed with a mixture of polymer dispersion and casein dispersion containing a red pigment; (6) the dispersion of example (1) diluted to 10 per cent solids is cast onto a glass surface and dried at 80  DEG C. to produce a 0.001 inch thick film suitable for use as an interliner in laminating textile fabrics, paper, wood and metal surfaces. The film is cured at 110 DEG  C.ALSO:A dispersion of N-methoxymethyl-polyhexamethylene adipamide is produced from a solution of 10 parts of the modified polyamide and 0.7 parts of sodium dodecyl sulphate in 90 parts of 60 per cent aqueous methanol by injecting the solution at 4 litres per hour through an orifice plate having eight 0.007 inch holes into a stream of water passing through a venturi.  The water is maintained at pH 105 by the addition of sodium hydroxide.  The water flows at a rate of 66 gallons per minute through the venturi at such a rate that the Reynolds number at the point of mixing is about 110,000.  The dispersion so produced is heated to 60 DEG C. and circulated to a vacuum chamber, maintained at 100 mm. pressure, where the methanol is distilled off.  The essentially methanol free dispersion is recirculated to the venturi dispersing section until the solids content of the dispersion is raised to 20 per cent.  The dispersion has an average particle diameter of 0.5 micron and contains less than 2 per cent. methanol.