| 摘要 |
The invention relates to compositions for defoaming aqueous media, comprising as defoamers urea derivatives of the formula IwhereR1-is a hydrocarbon radical, preferably having 4 to 30 carbon atoms or a hydrocarbon radical, preferably having 4 to 24 carbon atoms and one nitrogen atom or a hydrocarbon radical, preferably having 4 to 30 carbon atoms and one carbonyl group,R2-is a hydrogen atom or a hydrocarbon radical, preferably having 1 to 24 carbon atoms,R3-is a hydrogen atom or a hydrocarbon radical, preferably having 1 to 24 carbon atoms,R4-is an organic radical, preferably having 2 to 30 carbon atoms, andn-is from 0 to 5; in the form of solid particles, which are obtained by crystallization from a clear homogeneous melt dispersed in a carrier medium, and a process of preparation thereof.
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