Huls Aktiengesellschaft

Helmut Winzer

Salih Mumcu

Hans P Aurich

An improved process for preparing pulverulent coating compositions pigmented with titanium dioxide and based on polyamides having at least ten aliphatically bound carbon atoms per carbonamide group using the precipitation method. The titanium dioxide pigments used are without nucleating effects or only have weak nucleating effects on the polyamide precipitation. The pigments have nucleating effects less than or equal to 3.degree. C. where .DELTA.T=(T.sub.max p)-(T.sub.o). T.sub.max p is the maximum temperature at which precipitation takes place in a solution of polyamide having pigment therein and T.sub.o is the maximum temperature at which precipitation takes place in polyamide solution having no pigment therein.

Process for preparing polyamide based, titanium dioxide pigmented

The invention concerns an improved precipitation process in the manufacture of coating powders based on polyamides having at least ten aliphatically bound carbon atoms per carbonamide group. Rapid cooling takes place with stirring mainly by distilling the ethanol solvent until the temperature of precipitation is set in the range from 90.degree. to 113.degree. C. With the beginning of the saturation limit (about 125.degree. C.), the temperature difference between the coolant in the jacket and the solution inside is maintained at most at .+-.3.degree. C. The solution is maintained during the precipitation stage at constant temperature (isothermal procedure) by further distillation of the ethanol.

Growing community of inventors

Finnentrop, Germany

Helmut Winzer