Concentrate processing color compounding

The recent acquisition of Colortech by PPM, a German color compounder, presented an opportunity to eonduet a direct comparison of thermo-kinetic and conventional twin screw compounding technologies. The goal was to run identical color concentrate formulations on commercial scale processing equipment operated by individuals skilled in the art. Primary performance criteria were to include dispersion quality and color strength. Secondary characteristics such as melt index, ash content and product density were also evaluated. 

Dry coloring v. The process of combining colorants to molding compounds and resin pellets by tumble-blending them with dyes, pigments, or color concentrates. This process enables custom molders and extruders to carry a large inventory of uncolored compound, preparing smaller batches of colored compounds to customers specifications. 

Color Compound. A color compound is a system of colorants, additives, and resin that requires no letdown or addition of materials. It is ready to be processed into finished parts via molding or extrusion. A compoimd can be colored with dry pigment and dye or color concentrate. 

The complexers maybe tartrate, ethylenediaminetetraacetic acid (EDTA), tetrakis(2-hydroxypropyl)ethylenediamine, nittilotriacetic acid (NTA), or some other strong chelate. Numerous proprietary stabilizers, eg, sulfur compounds, nitrogen heterocycles, and cyanides (qv) are used (2,44). These formulated baths differ ia deposition rate, ease of waste treatment, stabiHty, bath life, copper color and ductiHty, operating temperature, and component concentration. Most have been developed for specific processes all deposit nearly pure copper metal. 

Dissimilatory sulfate reducers such as Desul-fovibrio derive their energy from the anaerobic oxidation of organic compounds such as lactic acid and acetic acid. Sulfate is reduced and large amounts of hydrogen sulfide are generated in this process. The black sediments of aquatic habitats that smell of sulfide are due to the activities of these bacteria. The black coloration is caused by the formation of metal sulfides, primarily iron sulfide. These bacteria are especially important in marine habitats because of the high concentrations of sulfate that exists there. 

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