Defoamer formulations

Abstract

The invention relates to defoamer formulations which comprise (A) siloxane-based antifoam agents and (B) polysiloxane copolymers which are obtainable by reacting, in a first step, organopolysiloxanes (1) which comprise at least one Si-bound hydrogen atom, preferably at least two Si-bound hydrogen atoms, per molecule, with the substantially linear oligomer or polymer compounds (2) of the general formula R<1>-(A-CnH2n)m-A<1>-H (I), wherein R<1> represents a monovalent optionally substituted hydrocarbon group to which Si-H groups can be attached in a hydrosilylation reaction, preferably a hydrocarbon group comprising an aliphatic C-C multiple bond, A represents a divalent, polar organic group selected from the group comprising -O-, -C(O)-O-, -O-C(O)-, -O-C(O)-O-, -C(O)-NH-, -NH-C(O)-, a urethane group and a urea group, preferably an oxygen atom -O-, A<1> represents a divalent, polar organic group selected from the group comprising -O-, -NH- and -NR'- (whereby R' represents a monovalent hydrocarbon group with 1 to 18 carbon atoms), n is an integer from 1 to 20 and m is a positive integer, and, in a second step, reacting the intermediate products (4) so obtained which comprise H-A<1> groups with organic compounds (5) having at least two isocyanate groups per molecule, with the proviso that the water content of the compounds (1) and (2) used for producing the polysiloxane copolymers is less than 2000 % ppm, based on the total weight of compounds (1) and (2) .

Description

technical field [0001] The present invention relates to defoamer formulations comprising (A) silicone-based antifoams and (B) polysiloxane copolymers, and their use in defoaming aqueous media, especially those obtained in pulp production . Background technique [0002] In many liquid systems, especially in aqueous systems containing desired surface-active substances or other undesired components, if these systems are more or less intensively exposed to gaseous Problems due to foaming can then arise during stirring, during distillation, washing or coloring operations, or, for example, during dispersion processes. [0003] This foam can be controlled by mechanical means or by adding defoamers. Antifoams based on silicones have proven to be particularly suitable for this. [0004] Silicone defoamers are prepared, for example, according to DD-A 056 762 by heating hydrophilic silicon dioxide in polydimethylsiloxane. This process is very expensive and inconvenient, and, among ...

AI Technical Summary

Problems solved by technology

However, in the presence of water, this antifoam formulation becomes less active

[0009] Antifoam formulations prepared according to prior art are either not always sufficiently active or are not stable to hydrolysis

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