Patent GB-627483-A (GB)
Title: Improvements in or relating to relatively thermoset laminated members
IPC: B32B27/00
Filed: 1945-09-07
Abstract: Phenol, arylamine and formaldehyde condensation products are produced by reaction in the presence of a basic catalyst of a phenol, 20-300 per cent of the weight of phenol of an arylamine and from 0.8-1.5 mols. of formaldehyde for each mol. of phenol and arylamine. Suitable phenols are phenol, cresols, cresylic acid and xylenols. Specified arylamines are aniline, diphenylamine, toluidines, naphthylamine and m-phenylene diamine. An aqueous solution of formaldehyde, paraformaldehyde or hexamethylenetetramine may be used. Suitable basic catalysts are aqueous ammonia, hexamethylene tetramine, diamines and alkali and alkaline earth oxides and hydroxides, e.g. lime.  Solutions of A-stage reaction products in alcohol, acetone, motor benzol, benzene or mixtures thereof to which is added up to 30 per cent by weight of the condensation product of a thermoplastic polymer may be used to impregnate fibrous materials or fabrics for the manufacture of laminates (see Group VIII).  The thermoset laminates produced may be reformed on application of heat and low pressures, e.g. less than 100 lbs./sq. inch, and formed into complex shapes in wooden forms, plaster moulds or in low m.p. metal dies.  Specified moulded articles are aircraft parts, e.g. wing tips, aileron tabs, fairings and guard members.  Specified thermoplastic polymers are polyvinyl acetates, butyrates, acetatebutyrates, butyrals and formals, ethyl cellulose and cellulose acetate. Plasticizers, e.g. diamyl and dioctyl phthalates, tricresyl phosphate and glycolates, may also be added. If desired the fabric may be impregnated with the thermoplastic polymer and then treated with a solution of the arylamine-phenol-formaldehyde condensation products, the solvent removed by heat-treatment and the laminates moulded into flat sheets in multiple platen moulds.ALSO:Thermoset laminates capable of being reformed on application of heat and pressure into complex three dimensional shapes are made from superposed sheets of stretchable fibrous material or fabric impregnated with at least half its weight of a resin composed of up to 30 per cent of a thermoplastic polymer and the balance being essentially a phenol, arylamine and formaldehyde condensation product isee Group VIII). The condensation product is obtained by reaction in the presence of a basic catalyst of a phenol 20-30 per cent of the weight of phenol of an arylamine and from 0.8-1.5 mols of formaldehyde for each mol of phenol and arylamine (see Group IV(a)).  The sheets of laminate are heated to a temperature of 150-200 DEG  C and post-formed by application of low pressures e.g. less than 100 lb./sq. in., into complex three dimensional shapes, using wooden forms, plaster moulds or in low m.p. metal dies, and cooled whilst restrained in the mould. The product retains its shape and the resin exhibits thermoset properties.  The sheets of laminate may be heated by infra-red lamps, high frequency electric fields or by placing them between heated platens.  The process is particularly applicable to the manufacture of moulded aircraft parts e.g. wing tips, aileron tabs, fairings and guard members.