Pigment application coatings

Certain areas of pigment application in the printing ink industry challenge the performance of a pigment more severely than others. To be useful in inks for food cans, for instance, the inside coatings must be capable of being sterilized with steam without degradation. For bank notes, currency, and cheques, special security properties are needed. 

P.R.2 does not show perfect performance in special applications (Sec. 1.6.2.3) in prints, which is also true for a number of other members of this class. In this respect, P.R.2 is inferior to P.R.112. This may have a particular impact on marginal areas of pigment applicability. P.R.112 letterpress proof prints, for instance, tolerate mineral spirits and soap while P.R.2 prints only reach step 4 on the 5 step fastness scale. P.R.2 specimens are also sensitive to clear lacquer coatings and to sterilization. 

Special effect pigments suitable for outdoor applications must meet the highest standards for color fastness and weather resistance. These pigments are coated additionally with thin layers of transparent and colorless oxidic compounds. These layers increase the light resistance by reducing the photoactivity of the titanium dioxide surface. In addition, the interaction between pigment and binder is optimized. 

Applications of pigments for coatings, printing and information storage are widespread, but the fabrication of thin films of pigments is difficult because of their insoluble nature. Dyes, on the other hand, are easier to manipulate. Research at the Xerox Corporation has shown that Lewis acid complexes can be utilized to solubilize and lay down thin films of certain pigments. For example, the photosensitive perylene derivative shown below forms an adduct with AICI3 ... 

Figure 8. Aryloxyphosphazene elastomers (APN) offer excellent potential for applications such as A, closed cell foam thermal insulation with high fire retadancy and low smoke generation (32.34) B, pigmented APN coatings in aluminum substrates with low flanmablllty, low flame spread, and low smoke (35) C, APN Insulation and cable Jacketing (36) D, open cell APN comfort cushioning (37). Photograph courtesy of Firestone Tire and Rubber Company ( ).

Based on this comparison of TPO pretreatment processes, their quality control methods, including actual (a, b, c) or hypothetical (d, e) knowledge of their adhesion mechanisms and their benefits, it was concluded that the low viscosity olefinic polymers may be feasible to be incorporated in the production pigmented color coats. A rigorous evaluation is essential before their application can be adapted in the automotive manufacturing plants, and the benefits realized. 

J. T. Guthrie and L. Lin, Physical-chemical Aspects of Pigment Applications, Surface Coatings Reviews, Oil and Colour Chemists Association, London, 1994. 

Non-accelerated, neo-pentyl glycol/isophthalic resin suitable for formulating into easily pigmented gel coats specifically designed for brush application and offering chemical, heat and weather resistance. 

The International Cadmium Association (ICdA) in Brussels, Belgium, made an estimate of cadmium consumption for different end uses in 2001. Batteries account for 75%, pigments 12%, coatings and plating 8%, and stabihzers for plastics and similar purposes 4%. The remaining small amount of cadmium, 1%, is used in some very special applications such as nonferrous alloys and as cadmium telluride (CdTe) for electronic compounds. 

Massonnet, G., tnd W. Stoeddein. Identification of Organic Pigments in Coatings Applications to Red Automotive Topcoats. Part HI Raman Spectroscopy (NIR FT-Raman). Lausanne, Switzerlcind European Academy of Forensic Sciences, 1997. 

---