Patent GB-425037-A (GB)
Title: Improvements in and relating to improving the properties of synthetic tanning agents
IPC: C14C3/20
Filed: 1933-08-28
Abstract: Tanning-agents are obtained by combining urea-formaldehyde condensation products in an acid medium with crystalline, water-soluble sulphonated condensation products obtained from ketones and phenols unsubstituted in p-position to the hydroxy group, such as the sulphonated condensation products of phenol or o- or m-cresol with acetone, methylethyl ketone, diethyl ketone, methylpropyl ketone, acetophenone, cyclohexanone, or methylcyclohexanones.  The reaction may be effected by warming the two condensation products together, or by producing the urea-formaldehyde product in the presence of the sulphonated phenol-ketone product, or by warming the sulphonated phenol-ketone product with a methylolurea.  The acidity of the reaction medium may be derived solely from the sulphonated condensation product, or a small proportion of an inorganic or organic acid, such as acetic, formic or glycollic acid, may be added to the medium.  The products may be used alone or with suitable non-tanning additions, e.g. oxalic acid, or with other tanning agents, particularly vegetable tanning agents such as sumac or gall nut extract, mineral tanning agents such as chromium salts, or other synthetic tanning agents.  They may be used for removing the green shade of chrome leather and for tanning reptile hides.  In the examples: (1) 4 : 4<1>-dioxydiphenyldimethylmethane-3 : 3<1>-disulphonic acid dissolved in aqueous urea solution is warmed with a solution of formaldehyde; (2) 4 : 4<1>-dioxydiphenylmethyl-ethylmethane-3 : 3<1>-disulphonic acid is treated as in example 1; (3) 4 : 4<1>-dioxydiphenyl-diethylmethane-3 : 3<1>-disulphonic acid or 4 : 4<1>-dioxydiphenylmethylpropylmethane - 3 : 3<1> - disulphonic acid is treated as in example 1; (4) 4 : 4<1> - dioxydiphenylmethylphenylmethane - 3 : 3<1>-disulphonic acid is treated as in example 1; (5) 4 : 4<1>-dioxydiphenylethylphenylmethane - 3 : 3<1>-disulphonic acid is treated as in example 1; (6) di-(4<1>-oxy-3<1>-sulphophenyl)-1 : 1-cyclohexane is treated as in example 1; (7) 4 : 4<1>-dioxy-3 : 3<1>-dimethyldiphenyldimethylmethane-5 : 5<1>-disulphonic acid, 4 : 4<1>-dioxy-3 : 3<1>--dimethyldiphenylmethylphenylmethane-5 : 5<1>-disulphonic acid, or di-(4<1>-oxy-3<1>-methyl-5<1>-sulphophenyl)-1; (8) urea and formaldehyde are condensed in aqueous caustic soda, and the neutralized solution is added to a solution of 4 : 4<1>-dioxydiphenyldimethylmethane-3 : 3<1>-disulphonic acid; (9) a solution of dimethylolurea is added to a warmed solution of 4 : 4<1>-dioxydiphenyldimethylmethane - 3 : 3<1> - disulphonic acid. Specifications 8511/12, 111,141, 305,013, [all in Class 2 (iii)], and 388,475 are referred to.  The Provisional Specification states that condensation products of thiourea or of urea-thiourea mixtures with formaldehyde may be used in place of urea-formaldehyde condensation products.  It refers to salicylic acid as a phenol from which the phenol-ketone condensation products may be derived, and includes an example in which 4 : 4<1>-dioxy-2 : 2<1>-dimethyldiphenyldimethylmethane-3 : 3<1>-disulphonic acid is treated as in example 1.  Sulphonated phenol-ketone condensation products.  4 : 4<1> - Dioxydiphenylmethylethyl - methane-3 : 3<1>-disulphonic acid is prepared by condensing phenol with methylethyl ketone in the presence of gaseous hydrochloric acid, and sulphonating the 4 : 4<1>-dioxydiphenylmethylethylmethane so obtained.  4 : 4<1>-Dioxydiphenyldiethylmethane - 3 : 3<1> - disulphonic acid and 4 : 4<1>-dioxydiphenylmethylpropylmethane-3 : 3<1>-disulphonic acid are obtained similarly from phenol and diethyl ketone or methylpropyl ketone respectively.  4 : 4<1> - Dioxydiphenylmethylphenylmethane-3 : 3<1>-disulphonic acid, 4 : 4<1>-dioxydiphenylethylphenylmethane-3 : 3<1>-disulphonic acid, and di-(4<1>-oxy-3<1>-sulphophenyl) - 1 : 1 - cyclohexane are prepared by sulphonating the condensation products of phenol with acetophenone, propiophenone, and cyclohexanone respectively.  4 : 4<1>-Dioxy-3 : 3<1>-dimethyldiphenyldimethylmethane-5 : 5<1>-disulphonic acid, 4 : 4<1>-dioxy-3 : 3<1>-dimethyldiphenylmethylphenylmethane-5 : 5<1>-disulphonic acid and di-(4<1>-oxy-3<1>-methyl-5<1>-sulphophenyl)-1 : 1-cyclohexane are prepared by sulphonating the condensation products of o-cresol with acetone, acetophenone and cyclohexanone respectively.