Composition and process for waterproofing leather

A composition for treatment of leather comprising

• (A) a polydiorganosiloxane that may have some degree of branching and which has carboxylic side groups and/or epoxide side groups;
• (B) at least one polymer dispersion that contains 2 to 35 weight % of carboxylic groups;
• (C) optionally one or more emulsifiers;
• (D) optionally one or more plasticizers or organic solvents;
• and
• (E) optionally water;
• wherein the polydiorganosiloxane has units of the general formula (I)
• R1aR2bQcSiO((4-a-b-c)/2) (I)
• wherein the substituents R1 are hydrogen atoms or identical or different C1- to C18-hydrocarbon radicals which are optionally substituted by fluorine, chlorine or bromine atoms or cyano groups and are optionally interrupted by the groups —O— or —S— or additional polyoxyalkylene groups, R2 are C1- to C12-alkoxy radicals or hydroxyl radicals, and the substituents Q are identical or different monovalent groups of the formula (II)
• —CR32—CHR3—R4—Z (II)
• wherein Z is a carboxyl group or an epoxide group;
• wherein the substituents R3 are hydrogen atoms or identical or different monovalent C1- to C10-hydrocarbon radicals which are optionally substituted by fluorine, chlorine or bromine atoms;
• wherein the substituent R4 is a divalent C1- to C18-hydrocarbon radical which is optionally substituted by fluorine, chlorine or bromine atoms or cyano groups and optionally interrupted by the groups —O— or —S— or additional polyoxyalkylene groups;
• wherein a has the values 0, 1, 2 or 3 and b has the values 0, 1, 2 or 3 and c has the values 0, 1, 2 or 3 and the sum of a+b+c is not more than 3;
• with the proviso that, if Z represents a carboxy group, at least 0.1 mol % of units according to formula (I) are present in the polydiorganosiloxane, and a has the value 0 or 1, b has the value 0, 1, 2 or 3, c has the value 0 or 1, and R1, R2, R3 are as above defined and the sum of a+b+c is not more than 3 and the sum of a+c is not more than 1.