HARRY BURRELL
I/EC
Finishes Division, Interchemical Corp., P. O. 170 Evanston Sta., Cincinnati, Ohio
ANNUAL
REVIEW
PROTECTIVE COATINGS ONE item must be singled out as I F particularly significant from the considerable record of progress in coatings for 1956, most interested observers would agree that the final victory of alkyd-amine systems over nitrocellulose lacquers for automobile finishing deserves special comment. Chrysler, Ford, and Studebaker have used these synthetic enamels for several years ; General Motors continued to utilize nitrocellulose lacquers until this year. In spite of the advantages of easier touching u p and lower baking temperature, lacquers have at last succumbed to the superior gloss retention and mar-proofness of the enamels. Because of the popularity of the light bright colors, these finishes are being formulated much the same as the white appliance enamels which have been so successful for the past decade. T h e excellent color retention at high heat of these coconut alkyd-melamine resin blends has earned them the appellation of "O.B." (for overbake) enamels. Because the new car bodies can be and are baked at schedules of 30 minutes or more at 250° F., the finish is very hard and resists chalking, dulling, cracking, and moisture blistering for m a n y months. A low temperature catalyzed alkyd-amine touch-up enamel is being offered repair shops, but it is likely that many will prefer to continue to use air-drying color-matched lacquers for this work. In fact, one company introduced a line for color matching weathered paint. A more expensive but perhaps richer looking lacquer based on poly (methyl methacrylate) was used to finish certain types of Pontiacs. Here the low solids, multiple-coat jobs are warranted by the enhanced appearance. It is also 32 A
claimed that waxing of such finishes is unnecessary for 18 months. A comprehensive summary of the amounts of coatings and related materials consumed by the automotive industry was published for the first time. T h e quantities involved are truly tremendous; the annual volume would equal a 7-foot depth in the 22-acre lake at the new General Motors Technical Center. Another situation which made 1956 outstanding was the unusually large n u m b e r of testing instruments which were developed. A novel method of applying coatings was also introduced. This consists of immersing a heated object in a fluidized bed of solids, thus completely eliminating solvents. T w o improved spray guns were offered, one for automatic painting of curved surfaces and the other a low-air-volumc type for either suction or pressure feed. A quiet opcrating spray booth was developed, which is said to be virtually noiseless 10 feet away. Special air filters can be obtained which make water washing in spray booths unnecessary, while a newly engineered nonclogging disposal system incinerates varnish fumes. Interesting N e w Coatings
T h e excellent insulating characteristics of plastics sometimes lead to undesirable accumulation of static electricity. This can be overcome for vinyls and Teflon by two ingenious coating formulations. In the case of polyesters, a conducting coating can be applied by vacuum metalizing such a thin coating that it remains transparent. Conductive waxes were also marketed for application to floor surfaces. Maintenance engineers will be
INDUSTRIAL AND ENGINEERING CHEMISTRY
interested in a system for painting rusty woven wire fences quickly and evenly. T w o coatings were suggested for increasing the service life of black-top pavements, especially in areas subject to gasoline and oil spillage. Another finish was especially developed for plywood forms used in masonry construction. A waterproof, textured, masonry paint is available in an unusual color line for renovating old eroded exterior walls. Special abrasive-containing floor paints were also developed for nearly any surface where safety demands nonslip footing. T w o types of finishes normally used only industrially were m a d e available for amateur use: multicolored metalized alkyd enamels similar to automobile finishes and a catalyzed alkyd-amine varnish for extreme hardness, water, and alcohol resistance. Whether the usual doit-yourselfer will add catalyst in the correct proportions and be content to throw away the unused mixture (which will soon gel) remains to be seen. An unusual product is a latex paint containing a germicide claimed to have a 2-year effectiveness. Paints in stick form and also aerosol packaged are available for permanent marking and identification in various colors. Water-thinned paints continue to enjoy increasing sales, and acrylicbased products are moving rapidly into the exterior exposure market and are also gaining in wall paints. New developments include two specialties for application to concrete or other tanks to prevent leakage of petroleum products. T h e great success of thixotropic alkyds in the competitive oil paints has led to at least one manufacturer's marketing a jelled latex product. Packaging of water paints has been a problem which
prompted the introduction of two new types of containers : One has an "outward curl" construction; the other is solderless; both allow com plete internal enameled surfaces which are rust-resistant. Industrial Finishes
Epoxy resins continue to be used for difficult coating problems, and the emphasis in 1956 has been on low temperature curing systems. At least three companies announced their start in manufacturing such materials, touting their chemical resistance and adhesion to a variety of surfaces. A hammer finish of this type was also developed. Isocyanates received considerable publicity, but most companies seem to be cautiously continuing their research with these compounds with out being too anxious to commercial ize their work as yet. A solderable magnet wire enamel is being used, however, and a boat finish is avail able, while the price reduction an nounced in the late summer may encourage further usage. An outstanding development was ultragloss appliance top coats which can be flow-coated. This economical application method is becoming very popular; ability to use it for finish coats as well as primers has been a dis tinct step forward. Very careful ad justment of rheology is necessary to combine proper drainage with ade quate coverage, especially on sharp corners and edges. The perpetual demand for better heat resistance has led to several new coatings to meet these requirements. O n e is a low cost black containing pitch and silicone, while another supplier offers a variety of colors. Silicone has been successfully by passed in another case by using a polyester varnish for impregnating coils of electric motors designed for high temperature operation. Certain organosol coatings can be applied at extremely heavy film weights up to 60 mils thick. An other is available as a tough, abrasion-resistant wrinkle finish. Among the paints for application to special substrates were a silicone tie coat for heat-cleaned glass cloth, lacquers for cellulose butyrate and plastisols, an oil-resistant strippable coating for machinery, a sealer for porous brass castings, and a spe cial primer for solder. Surface preparation before paint-
Aluminum antirust applied by roller
paint
can
be
ing is often as important as the finish which goes on subsequently. Several items along these lines were notable in 1956, including a " H u r riclean gun" which dispenses steam and cleaning solution simultaneously, a degreasing gel which can be wiped off without harming paint, and a special detergent for removing buff ing compounds. For more difficult cleaning jobs a dustless sand blaster was invented which provides a suc tion housing around the area being cleaned. Silicon polishes have made automobile refinishing hazardous be cause they promote cratering and "fish eyes" ; three cleaners are cal culated to remove both silicons and waxes effectively. Another all-pur pose cleaner is claimed to remove paint, phosphate coatings, rust, oil, and grease in one operation. An other product is said to soften paint sufficiently so that it can be rinsed off with water without scraping. Raw Materials
The burgeoning water paint market has prompted the introduc tion of several new latexes, including a vinyl acetate terpolymer. T h e trend has been, however, toward much finer particle size which promotes better binding, film clarity, and gloss; both styrene-butadiene and poly (vinyl acetate) types are of fered. An aqueous nylon dispersion is new, but solids are only 10%. Four new thickeners were announced for both water and solvent systems, as well as an improved emulsifier for emulsion polymerization and a pack age-corrosion inhibitor. Λ'-Substituted acrylamides, aliène, and glycol dimethacrylate were among the vinyl monomers developed. The latter is recommended as a polymerizable hardener and dis-
Electrostatic flocker
persant for plastisols. Prepolymerized dialkyl phthalate is also useful here. New plants being built for acrylonitrile and methyl methacrylate will ensure their continued availability. A special grade of acrylic polymer suitable for the acrylic automobile paints was also made available and three high melting cyclopentadiene polymers were offered. Two nontoxic and one heat-resistant plasticizers were mentioned. Other additives included epoxy catalysts and defoamers. Recent progress in epoxidation chemistry has led to the development of such interesting intermediates as octylene and dodecene oxide, butadiene dioxide, diisobutylene oxide, and vinylcyclohexene dioxide. Three unusual polyglycols are polybutylene and polystyrene glycols and polyepichlorohydrin. Alpha - sulfonated fatty acids and naphthenic acids of high molecular weight were also synthesized commercially. The changing pattern of paint production in recent years has seriously reduced the demand for zinc pigments, and one manufacturer has abandoned the production of lithopone. Titanium dioxide, rather tight in the spring of 1956, was more available by year's end. Three new red pigments received attention. The first was a c a d m i u m mercury sulfide cheaper than the traditional pure cadmium compound and with cleaner hue and improved brilliance. The other two were organic pigments, one a heat-resistant maroon and the other a" lowcost, nonbleeding azo toner. A flocculation- and aromatic hydrocarbon—resistant phthalocyanine blue toner was also offered. And finally an exceptionally absorbant synthetic calcium silicate was marketed. VOL. 49, NO. 1
•
JANUARY 1957
33 A
