master batch techniques known by a person skilled in the art compounds having anti microbial activity may also be added to the powder coating compositions the cross linking reaction may be additionally accelerated by the presence in the powder coating composition according to the invention of catalysts known from thermal cross linking such catalysts are for example tin salts phosphides amines and amides they may be used for example in quantities of 0 to 5 wt based on the total weight of the powder coating composition the powder coating composition of this invention may contain transparent color imparting and or special effect imparting pigments and or fillers extenders suitable color imparting pigments are any conventional coating pigments of an organic or inorganic nature examples of inorganic or organic color imparting pigments are titanium dioxide micronized titanium dioxide carbon black azopigments and phthalocyanine pigments examples of special effect imparting pigments are metal pigments for example made from aluminum copper or other metals interference pigments such as metal oxide coated metal pigments and coated mica examples of usable extenders are silicon dioxide aluminum silicate barium sulfate and calcium carbonate the constituents are used in conventional amounts known to the person skilled in the art for example 0 05 to 30 wt based on the total weight of each powder coating base preferably 0 1 to 20 wt the powder coating composition according to this invention may be prepared by conventional manufacturing techniques used in the powder coating industry such as extrusion and or grinding processes known by a person skilled in the art for example the ingredients can be blended together by dry blending methods and can be heated to a temperature to melt the mixture and then the mixture is extruded the.