Aminosiloxanes of high purity

An aminoalkyl-functional polysiloxane of general formula (I), wherein the polysiloxane has a Hazen number <100 and has a NH2-functionality of >1.96,

• wherein R1 is a group is independently selected from the group consisting of a monovalent C1-C20 alkyl, arylalkyl, alkylaryl, and aryl group, each of them being linear or branched, each R2 group is independently selected from the group consisting of linear or branched divalent optionally substituted organic radicals with 3 to 7 carbon atoms which can be interrupted by —O—, —NH—, and n is an integer of 0 to 7,
• wherein the polysiloxane is made by a process comprising the steps of:
• i) reacting an aminoalkyl-functional polysiloxane having a NH2-functionality >0 and <1.96 and/or color according to Hazen number of >100 with a stoichiometric excess, related to the content of NH2 groups, of an acid with a pKa ≦5.5 and a stoichiometric excess water, related to the acid,
• ii) removing the volatile compounds present in the product of step i) by distillation, optionally with the use of an inert carrier gas, at temperatures of 40 to 250° C. at 0.1 to 1030 mbar,
• iii) neutralizing the resulting devolatilized higher boiling product of step ii) with at least one base, and
• iv) depolymerizing the product of step iii) in the presence of at least one base and isolating the product by distillation at temperatures of 60° C. to 250° C. at 0.1 to 1030 mbar.

A process for purifying an aminoalkyl-functional polysiloxane of general formula (I),

• wherein R1 is a group is independently selected from the group consisting of a monovalent C1-C20 alkyl, arylalkyl, alkylaryl, and aryl group, each of them being linear or branched, each R2 group is independently selected from the group consisting of linear or branched divalent optionally substituted organic radicals with 3 to 7 carbon atoms which can be interrupted by —O—, —NH—, and n is an integer of 0 to 7,
• comprising the steps of:
• i) reacting a composition comprising
• (A) at least one aminoalkyl-functional polysiloxane of general formula (I), and
• (B) at least one compound which differs from (A) and is obtained by the hydrosilylation of at least one olefinic amine and at least one hydridosiloxane in the presence of a platinum catalyst,
• wherein the NH2-functionality of the composition is >0, but <1.96,
• with a stoichiometric excess of at least one acid having a pKa ≦5.5 and a stoichiometric excess water, the stoichiometric excess acid referring to the NH2-functionality of the composition comprising (A) and (B), and the stoichiometric excess of water referring to the acid,
• ii) removing the volatile compounds present in the product of step i) by distillation, optionally with the use of an inert carrier gas, at temperatures of 40 to 250° C. at 0.1 to 1030 mbar,
• iii) neutralizing the resulting devolatilized higher boiling product of step ii) with at least one base, and
• iv) depolymerizing the product of step iii) in the presence of at least one base and isolating the product by distillation at temperatures of 60° C. to 250° C. at 0.1 to 1030 mbar.