Patent GB-576363-A (GB)
Title: Improvements in or relating to the production of derivatives of synthetic linear polyamides
IPC: C08G69/50
Filed: 1943-06-02
Abstract: N-methylol polyamides are prepared by reacting formaldehyde, paraformaldehyde or trioxanes with a linear polyamide containing hydrogen-bearing amide groups, the polyamide being in solution in an oxygen-containing acid which is free from formaldehyde-reactive groups, and isolating the product by precipitation with a non-solvent prior to the gelation of the solution.  The polyamides are generally of the class described in Specifications 461,236 and 461,237, but the term includes polyesteramides and interpolymers.  Reaction is preferably effected at a temperature between 30 DEG  C. and 80 DEG C. and 5-60 minutes is a suitable reaction time.  Preferably, 20-60 per cent of the amide groups are converted to N-methylol amide groups.  The Specification contains a list of materials from which the polyamide may be prepared. Suitable acids are formic, acetic, propionic, butyric, phosphoric or mono-, di- or trichloracetic. Mixtures of acids and anhydrides may be used.  Diluents and other solvents such as water, hydrocarbons, e.g. benzene or toluene, chlorinated hydrocarbons, e.g. chloroform, or esters such as methyl or ethyl formate or acetate may be present during the reaction. These added materials may retard gelation and permit a higher degree of substitution.  Suitable precipitants for the reaction products are methyl formate, or acetone and water, or ammonium hydroxide. Strong alkali should be avoided.  The N-methylol polyamides are soluble in aqueous ethanol, methanol, normal or iso-propanol, isobutanol, in ethylene glycol, in pyridine-water mixtures or in mixtures of alcohols with aromatic hydrocarbons or with chlorinated hydrocarbons, e.g. chloroform.  Shaped articles may be formed from the solutions by known methods.  The products may be insolubilised by heating, e.g. for one hour at 80 DEG  C. or by treatment at room temperature with acidic or basic catalysts.  The products may be mixed with pigments, dyes, cellulose derivatives, resins, e.g. phenol-or sulphonamide-formaldehyde resins, plasticisers such as 1,12-di-(hydroxyphenyl) octadecane, methyl 10-phenylolstearate or amylbenzenesulphonamide.  The products may be used, e.g. for coating, impregnating or adhesive compositions, for films or for electrical insulation.  Examples describe (1) commercial formaldehyde was stirred at 60 DEG  C. on a water bath with a formic acid solution of polyhexamethylene adipamide. After 10 minutes, the solution was poured into acetone containing sufficient ammonium hydroxide to neutralise the formic acid.  The product was a soft fluffy precipitate soluble in aqueous ethanol, from which solution film could be cast.  Heating at 85 DEG  C. or 90 DEG  C. converted the film into an insoluble one with higher melting point not capable of being cold drawn.  (2) Similar to (1), the precipitant used being aqueous acetone.  (3) The product was precipitated in granular form with methyl formate.  (4) Paraformaldehyde, water, formic acid and polyhexamethylene adipamide was heated in a closed vessel to 130 DEG C. and cooled and the product precipitated by addition of methyl formate. Specification 576,362 also is referred to.