Patent GB-439270-A (GB)
Title: Artificial masses and processes for their production
IPC: C08G12/00
Filed: 1935-02-18
Abstract: Water-soluble hard resins are manufactured by first preparing a water-soluble soft resin by condensing urea and hexamethylenetetramine (preferably in the proportion of 6 molecules of urea for every 8 methylene groups), in the presence or absence of water or other solvent, by heating to temperatures such that vigorous evolution of ammonia occurs, heating the product with water if the initial condensation has been effected in the absence of water, eliminating any water present in the soft resin, and finally converting the latter into a water-soluble hard resin by splitting off water therefrom, either by heating to 110--130 DEG  C. or by treating with a dehydrating agent.  When working in aqueous solution the hexamethylenetetramine may be replaced by formaldehyde and ammonia in the molecular proportion of 6 : 4.  The initial condensation is advantageously carried out in the presence of very small quantities of acids or salts, e.g. hydrochloric, nitric, sulphuric or phosphoric acid, acetic, formic or other organic acids, or ammonium, urea or metal salts thereof. Before converting the water-soluble soft resin into the water-soluble hard resin it is preferably first purified by treatment with an organic solvent, e.g. alcohol, acetylene tetrachloride, hydrogenated derivatives of naphthalene, or mixtures of benzene and methyl ethyl ketone.  By the use of a solvent which is also a dehydrating agent, e.g. alcohol, the dehydration proceeds simultaneously with the purification.  The water-soluble hard resins may be employed as vulcanization accelerators or as manures.  They may also be converted into insoluble masses by hardening with formaldehyde, preferably 3 molecular proportions to every 6 of urea originally employed, in a weakly acid solution, advantageously at a temperature which is gradually raised from 60 to about 130 DEG  C.  Preferably the amount of acid employed in the initial condensation is just sufficient for the hardening process to be carried out without further addition of acid, since any surplus has to be neutralized.  The hardening process may be interrupted before the attainment of the final insoluble state, the mass, which is still brittle, being pulverized and employed for moulding in the hot press, alone or mixed with filling materials.  Solutions of the intermediate products may be used for the production of insoluble resins inside porous or fibrous materials or on foundations of all kinds for varnish coatings.  Filling or colouring matter may be added to the masses at any stage.  In examples: (1) urea and hexamethylenetetramine are boiled with water, the solution is concentrated, the product agitated with acetylene tetrachloride or tetrahydronaphthalene and then heated to 110--130 DEG  C.; the resulting resin is pulverized and dissolved in water, the solution is filtered, concentrated, heated with formaldehyde, and then cast by heating to 60 DEG  C. after adding formic acid, yielding a glass-clear shaped article; (2) urea and hexamethylenetetramine are fused together, the product is boiled with water, the solution is concentrated and the product is treated with alcohol, cleansed of water-insoluble constituents and then hardened; (3) urea and hexamethylenetetramine are boiled with water with the addition of urea nitrate, the mass is concentrated, the product heated to 115--120 DEG  C and then dissolved in water, the solution is filtered and concentrated and then cast with the addition of formaldehyde by heating to 60--135 DEG  C.; (4) urea and hexamethylenetetramine are fused with ammonium chloride and the product is worked up as in (2); (5) urea and hexamethylenetetramine are refluxed in n-propyl alcohol with the addition of urea nitrate and the solution is cooled to separate the resin which is dissolved in water, the solution is concentrated and the product heated to 120--130 DEG  C. and further worked up as in (3).ALSO:As vulcanization accelerators may be employed water-soluble hard synthetic resins prepared by first preparing a water-soluble soft resin by condensing urea and hexamethylenetetramine in the presence or absence of water or other solvent, by heating to temperatures such that vigorous evolution of ammonia occurs, heating the product with water if the initial condensation has been effected in the absence of water, eliminating any water present in the soft resin, and finally converting the latter into a water-soluble hard resin by splitting of water therefrom, either by heating to 110-130 DEG  C. or by treating with a dehydrating agent.