Patent GB-745000-A (GB)
Title: Process for the tanning of skins and hides
IPC: C14C3/18
Filed: 1953-04-17
Abstract: An artificial resin for tanning hides contains the residuee <FORM:0745000/IV(a)/1> basic groups of which have been reacted with an acid to form a salt.  The artificial resins according to the invention may be prepared by condensation of the following conpounds either as such (in which case the basic groups are subsequently neutralized) or in the form of their salts:-"guanidine, methyl guanidine, phenyl guanidine, diphenyl guanidine, methyl phenyl guanidine, amino guanidine, nitro guanidine, acetyl guanidine, guanyl-urea (dicyandiamidine) and dicyandiamide.  The condensation mixture may include as the second component:-formaldehyde (or substances giving off formaldehyde, such as para formaldehyde, trioxymethylene, hexamethylene tetramine, formaldehyde bisulphite, and methylal) acetaldehyde, butyraldehyde, crotonaldehyde, benzaldehyde, acetone, methyl ethyl ketone, vinyl ethyl ketone, ethyl propyl ketone, acetophenone, mesityloxide, phorone, or cyclohexanone and its homologues; and as a third component:-phenol and its homologues or substitution products such as cresols, pyrogallol, resorcinol or hydroquinone, halogen phenols; phenols containing carboxyl groups, such as salicylic acid; naphthols; wholly or partly etherified or esterified aromatic hydroxy compounds, such as phenoxy-acetic acid; urea, its substitution products or derivatives, such as alkyl ureas; thio urea; other amido-derivatives of carbonic acid such as urethane and guanidine, or its derivatives cyanamide or dicyandiamide; diamides of dicarboxylic acids; dihydrazides; compounds of the azine series, such as methyl diamino triazine, triamino triazine (melamine), and substances obtained therefrom by splitting off ammonia such as melam, melem, mellon, hydroxydiamino triazines (ammeline); corresponding compounds of the pyrimidine and quinazoline series, guanazol derivatives, and hydrazine derivatives of the heterocyclic series; paratoluene sulphonamide; phenyl hydrazine; and ketones with reactive methylene groups such as acetone and cyclohexanone.  Acids suitable for reaction with the guanidine residue are halogen halide, sulphuric, nitric and carboxylic acids, particularly low molecular weight fatty acids, acetates being referred to.  Condensation can be undertaken in neutral medium without any catalyst, or known catalysts such as acids or acid reacting salts can be added.  The salt forming component may be precondensed with a carbonyl compound, and the third component added thereto, or it may be added to a condensation mixture of the latter two components.  In example I the artificial resin is prepared from 1 mol. of dicyandiamide, 2 mols. of dicyandiamide hydrochloride, and 4 mols. of formaldehyde. This is typical of the resins used in the remainder of the examples.  After the resins have been incorporated in a hide or the like by tanning they may be made insoluble in situ by treating with alkaline media, e.g. with oxides or hydroxides of alkali or alkaline earth or earth metals; by formation of insoluble salts, e.g. with fatty acid salts, watersoluble salts of organic sulphuric acid esters, water-soluble salts of organic sulphonic acids and other anion active soap substitutes, watersoluble salts of tannins which contain acid groups, in particular sulphonic acid groups; by treatment with formaldehyde; by introduction of higher molecular weight organic radicals by acylation with alkyl or alkylbenzene sulphochlorides; or by reaction with isocyanates.