GB855571A - Synthetic tanning agents - Google Patents

Abstract

Synthetic tanning agents are obtained by dispersing a condensation product of an aldehyde with a mono- or polyhydric phenol in a mixed condensation product of a polynuclear aromatic sulphonic acid, a halogenated phenol and an aldehyde. The dispersed phenolic resin may be the condensate of phenol itself, a cresol, a xylenol, a naphthol, 4, 41-dihydroxydiphenyl sulphone, 4, 41-dihydroxydiphenyl methane, 4, 41 dihydroxydiphenyl dimethyl methane, pyrocatechol, resorcinol, hydroquinone, o-chlorophenol, guaiacol, salicyclic acid, or salicyclic acid methyl ester with formaldehyde or a formaldehyde donating substance, acetaldehyde, crotonaldehyde, benzaldehyde or furfural; especially advantageous are the formaldehyde condensates of the phenol mixtures obtained from lignite pyrolysis. In the preparation of the dispersed resin urea, thiourea, melamine and dicyandiamide may partially replace the phenol. A minor amount of water solubilizing groups, especially sulphonic acid groups, may also be present in the dispersed resin. In the first of the ten examples an acid-catalysed phenol-formaldehyde resin is prepared, dehydrated and dispersed in a mixed condensate of a naphthalene sulphonation melt, o-chlorophenol and formaldehyde to give a clear syrup soluble in water. In another example, the phenolic resin is chlorinated before dispersion. In a further example, the dispersed resin is prepared under alkaline conditions from empyreumatic oil and formaldehyde, and added to the condensate of phenanthrene sulphonic acid, o-chlorophenol and formaldehyde. Other halogenated phenols used in the mixed condensation products used in the examples are p-chlorophenol and 6-chloro-o-cresol. Specifications 695,374, 747,675, 799,224 and 855,572 are referred to.