| 摘要 |
The present invention relates to a process where a wetting agent of solids, such as pigments, is to be changed from a first (e.g. aqueous) agent of a lower affinity to the solids to a second (e.g. oily) agent of a higher affinity to the solids. Solids, e.g. pigments, and agents are introduced into an extruder at a predetermined volume rate per time unit. The extruder includes an extruder barrel, with at least one screw which has screw threads over its length, a helical space between adjacent screw threads, and a drive for rotating the screw at a predetermined speed. The supply rate and the discharge speed of the extruder screw are selected in such a manner as to fill only part of the space between adjacent screw threads by solids and by the first and second agents, thereby retaining a free helical space to allow the first agent to segregate. At least one lateral opening is provided in the barrel for the first agent to escape.
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