Coating systems

With the exception of neopentyl alcohol (mp 53°C), the amyl alcohols are clear, colorless Hquids under atmospheric conditions, with characteristic, slightly pungent and penetrating odors. They have relatively higher boiling poiats than ketonic or hydrocarbon counterparts and are considered iatermediate boiling solvents for coating systems (Table 1) (1—16). 

Fig. 2. Conventional thermally cured, organic solvent base coating system.

Fig. 3. Polymerization initiation and propagation by radiation-generated free radicals. A is the initiating radical produced by irradiating the Hquid coating. (1) represents the Hquid monomer—unsaturated polymer reactive coating system. R is functional. (2) is the growing polymer chain (free radical). The cured...

Polymers. The molecular weights of polymers used in high energy electron radiation-curable coating systems are ca 1,000—25,000 and the polymers usually contain acryUc, methacrylic, or fumaric vinyl unsaturation along or attached to the polymer backbone (4,48). Aromatic or aUphatic diisocyanates react with glycols or alcohol-terrninated polyether or polyester to form either isocyanate or hydroxyl functional polyurethane intermediates. The isocyanate functional polyurethane intermediates react with hydroxyl functional polyurethane and with acryUc or methacrylic acids to form reactive p olyurethanes. 

Examples of typical photoinitiator systems used to cure reactive coating systems are as follows (80,81). The reactive systems are primarily unsaturated acryUc acid esters of different alcohol and polymer stmctures. 

The majority of the commercial radiation-curable coating systems (high energy electron and light-cured coating systems) are clear or contain siflca... 

Printing Inks. Printing ink preparation is similar to many coating systems. The resin is dissolved in the solvent, followed by pigment dispersion to produce the ink. In most printing operations, the solvent must evaporate fast for best production speed. Alcohol—hydrocarbon solvent combinations are used with polyamide resins for some printing processes (see Inks). 

Fig. 1. An automatic spray-coating system, where air-automized electrostatic spray guns are mounted on reciprocators.

---