Roll-coat finish

Roll coating of paint is the final process in a coil coating line. Roll coating is an economical method to paint large areas of metal with a variety of finishes and to produce a uniform and high-quality coating. The reverse roll procedure for coils is used by the coil coating industry, and allows both sides of the coil to be painted simultaneously. 

Knedel micelles, 20 489 Knelson concentrator, 16 632 Knife coatings, 7 7-8, 10-11 method summarized, 7 5t Knife-over-roll chemical finishing,... 

PVC can be rigid or flexible, clear or opaque. It can be processed as a solution, paste, or powder extruded injection-, dip-, or rotomolded knife- or reverse-roll coated. It is easily printed and bonded by heat, radiofrequency welding, or solvent. This chapter reviews monomer synthesis, types of resin and their manufacturing methods, additives, compounding, and processing into the myriad finished products of the vinyl industry. 

Roll coating (Fig. 11-8) is the second most important method for application after spraying. The leather passes between two rolls (color print roll and transportation roU) by means of a transportation belt. The top roll transfers the relatively viscous color to the leather. The texture and the direction of rotation (synchronous or reverse) of the color print roU determine the amounts applied. Soft leathers can be processed on this machine only if the rolls turn in the same direction. Consequently, these types of leather can be roU coated only with finishes that do not require high amounts. 

Mastics are sprayed on a substrate in one or more coats, depending on the desired degree of fire resistance. The final coat of all fireproofing mastics should be rolled or brushed to provide a smooth surface finish. The material should be applied with a sufficient number of coats to prevent running or slumping and sufficient drying time should be allowed between coats. Mastics may also be hand-troweled, if permitted in the manufacturer s specifications. 

Polymer coatings on stiffer substrates can be measured by time-resolved techniques (Sinton et al. 1989). Often in these cases it is not convenient to measure a direct reflection from an uncoated part of the substrate at more or less the same time, and anyway the substrate may not be flat, but this may not matter if it can be assumed that either the thickness or the longitudinal velocity of the coating does not vary. The time interval between the echoes from the top and bottom surfaces of the coating can then be used to determine the unknown quantity. An example of the kind of signal that can be obtained is shown in Fig. 10.5. The specimen was a coating of PET (polyethylene terephthalate) 15 m thick on a stone-finish rolled steel substrate. Although there is some overlap of the two echoes, there is no difficulty in... 

Fig. 10.5. Signals reflected from the top and bottom surfaces of a 15 ym thick coating of polyethylene terephthalate on a stone-finish rolled steel substrate, using a short pulse of centre frequency 230 MHz and half-power bandwidth 110 MHz z = +40 (with the top surface of the polymer as datum) (Sinton etal. 1989).

Cold rolling of the powdered precursor NiAlj (10 to 20 fxm particle size), mixed with granules of Mond nickel (carbonyl nickel, which is very ductile) on stainless-steel or nickel foils, creates coatings of 20 to 30% coarse porosity (dp > 10 gm), which firmly adhere to the supporting foil (76). Due to the excessive sheer and stress exerted during rolling, the foils are deformed and must be shaped according to demands after this process has been finished. 

Secondary Treatments and Uses. Because hardboard products are utilized in a myriad of different ways, the variety of secondary treatments used by customers are practically unlimited. Hardboards are used in furniture, cabinets, paneling, doors, toys, and a host of other uses. Post-treatments may include cutting-to-size, finishing treatments with roll-applied patterns, melamine overlays, printed paper overlays, paints, and even some extremely durable and water-resistant coatings used in tub and shower linings or other uses where water contact is frequent and extreme. 

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