Patent GB-584561-A (GB)
Title: Improvements in or relating to synthetic linear polyamides
IPC: C08G69/50
Filed: 1945-01-01
Abstract: Polyamides of the general type described in Specifications 461,236 and 461,237 are converted into N-methylol polyamides in the presence of a basic liquid reaction medium by heating with formaldehyde.  The dibasic carboxylic acids, diamines, monoaminomonocarboxylic acids and monoaminomonohydric alcohols used in making the initial polyamides include those in which the chain separating the functional groups is interrupted by one or more heterogeneous atoms, such as oxygen, sulphur or a tertiary nitrogen atom.  The polyamides may be prepared from a dibasic acid, such as glutaric, adipic, pimelic, suberic, azelaic, sebacic, carbonic, 1 : 2-cyclohexanediacetic, p-phenylenediacetic, or diglycollic, and a diamine such as ethylene diamine, tetramethylene diamine, pentamethylene diamine, hexamethylene diamine, octamethylene diamine, decamethylene diamine, m-phenylene diamine, p-xylene diamine, b : b 1-diaminodiethyl sulphide, or triglycol diamine, or from primary monoaminomonocarboxylic acids, such as 6-amino caproic, 7-amino heptoic, 12-amino stearic and 4-amino-cyclohexylcarboxylic acids. Primary monoaminomonohydric alcohols, such as ethanolamine and 4-aminobutyl alcohol may also be employed.  The term formaldehyde includes formaldehyde-liberating materials, such as paraformaldehyde, trioxane and various polyoxymethylenes and the amount of formaldehyde used may be as little as 5 per cent, but preferably from 50-200 per cent of the weight of polyamide.  The reaction medium consists of either an inert organic liquid which will not hydrolyse the polyamides such as dimethyl formamide, chloroform, dioxane, methylene dichloride, ethylene dichloride, dioxalane, benzene, toluene, xylene, chlorobenzene and carbon tetrachloride, containing in solution or suspension a basic material, particularly one having alkali or alkaline earth cations, or an inert liquid organic base which provides an aqueous solution having a pH of at least 8.5, such as pyridine, quinoline, dimethyl aniline and triethylamine.  A mixture of such an inert liquid organic base with an inert organic liquid may also be employed.  The preferred method for carrying out the process is to mix approximately equal parts of fibre-forming polyamide and formaldehyde in a pressure vessel with several parts of basic catalyst, preferably 0.1-10 per cent by weight of the polyamide, in the case of inorganic bases.  The closed vessel is heated with stirring and shaking preferably at a temperature of 130-140 DEG  C. When a solution of N-methylol polyamide in aqueous ethanol is warmed to 60 DEG  C. and cast on to a glass plate and heated at 100 DEG  C. for an hour, a clear tough film is formed which is insoluble in ethanol but soluble in cresol.  If maleic acid is added to the solution before casting, the resulting film is insoluble in both cresol and ethanol.  The maleic acid-treated solution is also suitable for bonding plywood.  The N-methylol polyamides produced by this process can be used for manufacturing films, fibres, bristles, tubes, ribbons and sheets, extended with carbon black, wood flour, ground leather, clay and mica, or plasticised.  They can be mixed with various resins, e.g. urea formaldehyde, or pigments, natural or synthetic rubber, cellulose derivatives or other modifying agents, and can be used alone or in admixtures as coating compositions and particularly adhesives, when small amounts of acids such as formic, adipic, maleic, oxalic, phosphoric and p-toluene sulphonic are added, followed by heat or pressure treatment.  Specification 576,363 also is referred to.