2870 



Chapter 23 



DOCTOR BLADE 



OFFSET ROLL 



METERING ROLL 



DOCTOR BLADE 



BOARD 



•PRESSURE ROLL 



Figure 23-96. — Precision roll coater. (Drawing from Suchsland and Woodson 1985. 



chemical resistance, weatherability, and strength. Most commonly used 

 are acrylic, alkyd, and polyester resins. 



• Pigments provide color in coatings; they may be organic or inorganic. 



• Solvents, which maintain the coating in a liquid state and control its 

 viscosity, evaporate soon after application (with heat input) so that the 

 coating can solidify. Usually they are organic compounds such as toluol 

 or xylene, both of which have high rates of evaporation and require 

 incineration to avoid air pollution; other organics with slower evapora- 

 tion rates and not requiring incineration include butyl acetate, butyl 

 cellusolve, and cellusolve acetate. Water is a cheap and safe solvent but 

 water-borne finishes lack the water resistance obtainable with organic 

 solvents. 



Two alternatives to solvent-borne finishes are plasticized vinyl films, usually 

 6 mil (0.006 inch) thick and embossed with a cloth- weave pattern, and printed 

 paper overlays laminated to the substrate with a water-based adhesive. 



Interior wall paneling and decorative board. — With the layout dia- 

 grammed in figure 23-97, alternative coating machines provide flexibility to 

 finish either grooved wood-grain printed interior paneling or decorative board. 

 Boards fed into the line by a vacuum feeding device are brush cleaned before 

 application of fill coat by two reverse roll coaters (fig. 23-98) each followed by 

 a hot-air dryer and a chrome-plated polished roll rotating opposite to the board 

 feed, thereby forcing the fill coat into surface pores and wiping the excess. The 

 dried fill coat is abrasive buffed with 320-400 grit paper. If panels are grooved, 

 the grooves are spray painted a dark color. 



The ground coat, next applied, is background for the printed pattern. For 

 grooved panels it is applied by precision roll coater to top surfaces, but not to 

 grooves. Decorative panels, which do not have grooves, are curtain coated (fig. 

 23-99) to form smooth films over entire top surfaces. 



