Patent GB-374914-A (GB)
Title: Process for making artificial resins and articles therefrom
IPC: C08G12/12
Filed: 1931-03-03
Abstract: Thiourea or a mixture of urea and thiourea is condensed with formaldehyde in a stronglyacid aqueous solution and without the application of heat, the proportion of thiourea or mixed urea and thiourea to less than 2, preferably 1\ba1/2\be, of formaldehyde. Mono- or di-methylolurea may replace part of the urea and formaldehyde.  The lower limit of acidity corresponds to a pH of 5, whilst the upper limit is determined by the prevention of the formation of methylene compounds incapable of undergoing further condensation; the acidity is preferably adjusted to a pH of 3. The synthetic resin solution obtained may be used,-together if desired with fillers, dyes or pigments, for impregnating paper or fabric in the form of sheets or endless bands, which are then superimposed--after the solution has been evaporated preferably without heating--and united under heat and pressure.  Laminated sheets so prepared are useful for the manufacture of tubes, gearing, toothed wheels, centrifugal pots for spinning machines, electric transformers, furniture, building materials, wall coverings and veneers.  The sheets may also be disintegrated and then moulded under high pressure.  For the manufacture of moulded objects, fibres are mixed with the resin solution, other fillers, dyes or pigments added if desired, the mixture allowed to remain at ordinary temperature until air-dry or nearly so, and then subjected to heat and pressure in a mould.  The resin solution may be used, with or without the addition of volatile solvents such as alcohol and softening agents such as ricinoleic acid, for impregnating electric coils, wood, and leather, or as a base for lacquers, or for coating metal or other surfaces; in each case, hardening of the resin is effected by heat treatment.  An example is given of the preparation of a resin by condensation of a mixture of urea and thiourea with formaldehyde in the presence of phosphoric acid and of its application to the impregnation of paper, linen and asbestos.  Specifications 171,369, [Class 140, Waterproof &c. fabrics], 248,477, 258,950, 266,028, [all in Class 2 (iii), Dyes &c.], and 344,872 are referred to.ALSO:For the manufacture of laminated sheets suitable for making centrifugal pots for spinning machines, thiourea or a mixture of urea and thiourea is condensed with formaldehyde in a strongly-acid aqueous solution and without the application of heat, the proportions of the reactants being 1 molecular proportion of thiourea or mixed urea and thiourea to less than 2, preferably 1 1/2 , of formaldehyde.  Mono- or di-methylolurea may replace part of the urea and formaldehyde.  The synthetic resin solution obtained is then used, together if desired with fillers, dyes or pigments, for impregnating paper or fabric sheets which are then superimposed-after the solution has been evaporated, preferably without heating-and united under heat and pressure.ALSO:Thiourea or a mixture of urea and thiourea is condensed with formaldehyde in a strongly acid aqueous solution and without the application of heat, the proportions of the reactants being 1 molecular proportion of thiourea or mixed urea and thiourea to less than 2, preferably 1 1/2 , of formaldehyde.  Mono- or dimethylolurea may replace part of the urea and formaldehyde. The synthetic resin solution obtained may be used, together if desired with fillers, dyes or pigments, for impregnating paper or fabric in the form of sheets or endless bands, which are then superimposed-after the solution has been evaporated preferably without heating-and united under heat and pressure.  Laminated sheets so prepared are useful for the manufacture of tubes, gearing, toothed wheels, centrifugal pots for spinning machines, electric transformers, furniture, building materials, wall coverings, and veneers.  The sheets may also be disintegrated and then moulded under high pressure.  For the manufacture of moulded objects, fibres are mixed with the resin solution, other fillers, dyes or pigments added if desired, the mixture allowed to remain at ordinary temperature until airdry or nearly so, and then subjected to heat and pressure in a mould.  An example is given of the preparation of a resin by condensation of a mixture of urea and thiourea with formaldehyde in the presence of phosphoric acid and of its application to the impregnation of paper, linen, and asbestos.  Specifications 171,369, [Class 140, Waterproof &c. fabrics], 248,477, 258,950, 266,028, [all in Class 2 (iii), Dyes &c.], and 344,872 are referred to.