Defoamers for aqueous media

A urea derivative in the form of solid particles of the formula I

• where
• is an organic radical of the formula:
• where R5 is a hydrocarbon radical having 1 to 18 carbon atoms,
• R2—is a hydrogen atom or a hydrocarbon radical,
• R3—is a hydrogen atom or a hydrocarbon radical,
• R4—is an organic radical, and
• n—is from 0 to 5.

A process for preparing a dispersion of urea derivatives in the form of solid particle of the formula I

• where
• R1—is a hydrocarbon radical, a hydrocarbon radical having one nitrogen atom, or a hydrocarbon radical having one carbonyl group,
• R2—hydrogen hydrocarbon radical,
• R3—is a hydrogen atom or a hydrocarbon radical,
• R4—is an organic radical, and
• n—is from 0 to 5;
• in carrier medium comprising a mixture of at least two compounds selected from the group consisting of organic oil, a mineral oil, a siloxane and an organomodified siloxane which comprises the steps of
• (a) heating the urea derivative solution in a first carrier media above the melting points of said urea derivatives to form a homogeneous solution;
• (b) mixing the homogeneous solution of step (a) with a second carrier media having a temperature of less than 25° C., and
• (c) dispersing the solid particles of the urea derivatives obtained in the carrier medium.