Patent GB-262148-A (GB)
Title: Process for the production of varnish bases and masses insoluble in water
IPC: C08G12/42
Filed: 1926-11-29
Abstract: 262,148. Walter, G. Nov. 28, 1925, [Convention date]. Samples furnished. Condensation products of urea or thiourea with formaldehyde; methylol compounds of acid amides.-Condensation products are obtained by melting methylol compounds of urea, thiourea, or their homologues in the absence of water as a diluent and with the addition, to the solid or fused compound, (1) of alcohols or amides, particularly benzyl alcohol, urea, or thiourea, and/or (2) of acids or like substances; formaldehyde or its polymers may be added also. The specified substances may be added to the fused methylol compounds in such amounts that they act as solvents, and buffer compounds, such as sodium acetate, may be added also to regulate the acidity of the melt. It is preferred to heat the mixture to the reaction temperature as rapidly as possible, and the reaction may be carried out under pressure. The products may be used as varnishes or lacquers, with or without an additional solvent such as methyl or ethyl alcohol; alternatively, the products may be hardened by heat, with or without pressure. Filling or colouring materials, or plasticisers, may be incorporated with the masses. In one example, a mixture of dimethyl urea with 10 per cent by weight of thiourea is rapidly melted, a little chloracetic acid is added, and heating is continued until the mass becomes viscid; the mass is then heated under pressure to give a clear hard product. Alternatively, benzyl alcohol and/or acetamide. may be added prior to the gelatinization of the mass, and the mass may then be hardened by heat alone. If, however, the additions are sufficient in amount, and volatile solvents such as methyl alcohol are added also, stable lacquers may be obtained. In other examples, the initial materials of the first example are heated for some time at 120-160‹ C., with or without a subsequent addition of acetic acid. In a further example, dimethyl urea is rapidly fused, a little chloracetic acid is added, and the thickened mass heated in moulds under pressure. In the final example, dimethyl urea or a mixture thereof with thiourea is dissolved in acetic acid and benzyl alcohol and the solution is heated at 110- 140‹ C. to produce a gelatinous mass, which may then be hardened. Specification 284,272 is referred to. The Specification as open to inspection under Sect. 91 (3) (a) states that methylol compounds of acid amides, e.g. of acetamide, urea, or thiourea, are prepared by the interaction of non- aqueous formaldehyde with the acid amide in an organic solvent, such as methyl, ethyl, or benzyl alcohol; the presence of a base is necessary if the formaldehyde is not acid-free, and advantageous in any case as an accelerating agent. The product is precipitated by the addition of ether or carbon tetrachloride. According to the examples, (1) urea is added to a cold solution of paraformaldehyde in ethyl alcohol containing a little potassium hydroxide, when crystalline dimethylolurea separates out; (2) monomethylolurea is obtained by adding trioxymethylene to a solution of urea in methyl alcohol containing a little sodium hydroxide. The Specification includes also the following examples of the further treatment of the methylol compounds :-(1) Sodium acetate is added to fused monomethylolurea, and the mass further heated to a transparent gel; by the addition of the sodium acetate at the start, the fusion process may be carried out slowly and at a lower temperature; (2) a mixture of dimethylolurea. and monomethylolurea with a little paraformaldehyde and potassium acetate is fused for a short time and the melt heated after addition of acid: the product may be hardened directly in moulds, or be first poured into hot water or organic liquids and the washed product then hardened by heat or dissolved to form a varnish: (3) a mixture of dimethylolurea and thiourea with some sodium acetate and paraformaldehyde is melted and heated for a short time at a raised temrerature; the product is further treated as in the preceding example; by increasing the amount of paraformaldehyde, clear intermediate products are obtained which can be thinned in the cold for use as water varnishes; gaseous or dissolved formaldehyde may replace the paraformaldehyde, and other aldehydes or hexamethylenetetramine may be employed; (4) monomethylolurea and thiourea are fused with a little sodium acetate, and paraformaldehyde then added in portions, together with a little phosphoric acid; the product is hardened in moulds or it may be washed as in (2), rubbed into a powder, and pressed under heat; (5) dimethylolurea is fused with a little salt and sodium formate, further heated with a little formaldehyde and phosphoric acid, washed cold, and hardened. This subject-matter does not appear in the Specification as accepted.