Cassella Aktiengesellschaft

Hoechst Aktiengesellschaft

Karlfried Keller

Manfred Schon

Werner Lotz

Hans Honel

Walter Michel

Hermann Becker

Frank Forster

An improved process for tanning leather by treating animal skins with a water-soluble melamine-formaldehyde resin in the presence of an acid catalyst towards the end is improved by using a melamine-formaldehyde resin which is at least partially etherified with a glycol ether, alkyl glycol ether, or both.

Processing for tanning leather

Use of a resin mixture of, or of a mixed resin from, a melamine-formaldehyde resin and an anionically modified melamine-formaldehyde resin for tanning leather. The anionic modification of the melamine-formaldehyde resin is obtained by preparing the resin in the presence of alkali metal sulfite, alkali metal hydrogensulfite or alkali metal sulfamate. By partial modification it is possible to obtain a mixed resin, while mixing a modified with an unmodified resin gives a resin mixture.

Process for tanning leather

This invention relates to a process for the manufacture of methanol-etherified methylolmelamines which are largely monomeric containing more than 5 mols of formaldehyde and more than 4 mols of methyl-etherified methylol groups, per mol of melamine, and having a viscosity of less than 20 pascal-seconds at 25.degree. C. and a solids content of at least 95%, comprising (a) methylolating melamine with formaldehyde at a molar melamine:formaldehyde ratio of 1:6.5 to 1:8 for 11/2 to 5 hours at 50.degree. C. to 85.degree. C., with the formaldehyde source being an aqueous solution of formalin containing 30 to 50% by weight of formaldehyde and having a pH of 6.7 to 7.3, and (b) etherifying the resulting suspension of methylolmelamine with 15 to 30 mols of methanol per mol of melamine at temperatures of 30.degree. C. to 60.degree. C. in the presence of a strong acid.

Preparation of methoxy-methyl melamines

A process for the preparation of a substantially monomeric methylolmelamine etherified by methanol which contains per mol of melamine, more than 5 mols of formaldehyde and more than 4 mols of methyl-etherified methylol groups which has a viscosity of less than 10 Pa.s at 25.degree. C. at a solids content of at least 95%, said process comprising reacting melamine and formaldehyde in a molar ratio of from 1 : 6.2 to 1 : 8, at a temperature of from 40 to 60.degree. C., in the presence of a basic catalyst in a reaction mixture which contains from 10 to 40% by weight of water and from 40 to 20% by weight of methanol thereby producing a suspension of methylolmelamine, and then etherifying the methylol melamine in the presence of from 15 to 30 mols of methanol per mol of melamine, at a temperature of from 25 to 50.degree. C., in the presence of a strong acid.

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Frankfurt am Main, Germany

Karlfried Keller