CHEMICALS
Molybdates: New Pigments for Primers Anticorrosive compounds are nontoxic, white, may be used in one-coat paints on food machinery Molybdates may find a place as corrosion-resisting pigments in paint. Initial studies at Battelle Memorial Institute show that the compounds generally equal, sometimes outperform red lead as inhibitive primers, according to Helmuth O. Schoen of the institute's polymer research division. Two big advantages: non toxicity and white color. "For many years, this field has been dominated by red lead, zinc chromate, and iron oxide," Mr. Schoen told the 38th Annual Meeting of the Federation of Societies for Paint Technology in Chicago. They have good hiding powers and corrosion-fighting ability, don't cost as much as molybdates. But, Mr. Schoen says, here's where molybdates' properties take over. Since they aren't toxic, molybdates could be used as primers for food processing machinery, food storage containers, water tanks, and the l i k e places where conventional materials can't be used, Mr. Schoen says. And
their white color may mean one-coat paints for metal surfaces that are both corrosion resistant and decorative. On a pound basis, molybdates are more expensive than commonly used materials. However, on a volume basis, the gap closes because of the lower density of molybdates, particularly when compared to red lead. Exposure Tests. An important property of inhibiting pigments is intermediate solubility. On this basis, Mr. Schoen and co-workers chose calcium molybdate ( C a M o 0 4 ) , normal zinc molybdate ( Z n M o 0 4 ) , and zinc polymolybdate (5 ZnO-7 M o 0 3 ) for their studies. These compounds are neither very soluble nor very insoluble in water. For the tests, the coatings chemists formulated all the primers with 25% excess free oil above the oil-absorbing capacity of the pigment plus extender. For the control primers, they used only linseed oil, diluted the ground paste with mineral spirits to an 80% solids
Water Soluble Resin Makes Paint Primer Workman uses standard spray gun to apply a water based primer coat to a truck body. The primer contains a new, water soluble, thermosetting resin—Cargill 750—developed by Cargill, Inc., of Minneapolis, Minn. After being applied and baked on, the primer is as hard as commercial epoxy primers, resists impact, water, and salt spray as well, Cargill says. Priced competitively, the primer eliminates odor and hazards of fire and toxicity, Cargill adds. 58
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content and a viscosity of about 25 sec. (No. 4 Ford c u p ) . Then they sprayed the various formulations on sets of four steel panels to a dry film thickness of about 2 mils. "On two panels, we sprayed the primers alone and scribed one of them. We coated the other two with primers plus blue automotive-type baking topcoats, and scribed one," Mr. Schoen told the meeting. Battelle also used controls pigmented with red lead, talc, and calcium carbonate. To test the performance of the materials, the Battelle chemists exposed sets of the panels in an accelerated weathering apparatus and at two outdoor locations: surburban Columbus, Ohio, and Battelle's research station near Daytona Beach, Fla. Zincs Are Best. When used as a primer alone, Mr. Schoen says, calcium molybdate shows better all-around performance than either of the zinc ones— although it isn't as good in the Florida exposure. And of the two zinc compounds, normal zinc molybdate stands up better than zinc polymolybdate, he finds. However, when you cover the molybdate primers with a topcoat, the zinc compounds are superior to the calcium molybdate—with normal zinc the best. Several of the unextended zinc molybdate coatings are really outstanding, Mr. Schoen says. After a year's exposure at the Columbus site, the scribe marks on these panels still look bright and shiny. "For an exposed steel surface to be rust-free after that length of time is unusual," he points out. Zinc molybdate in the accelerated weathering device after 2500 hr. also shows this effect. Generally, though, molybdates resist corrosion better when you extend them with calcium carbonate than when you don't use an extender at all, Mr. Schoen observes. Battelle also studied the effect of extenders, pigment particle size, vehicle, and composition of the pigments on the primers. Its findings: • Calcium carbonate is a better extender than talc for these compounds. • Fine molybdate particles combat corrosion more effectively than coarse material. • Linseed oil is a better vehicle than alkyd resin for molybdates in this system. • Increasing the zinc-to-molybdenum ratio from 1:1 to 1:1.4 lowers the corrosion resistance.
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BRIEFS Isophthaloyl chloride and terephthaloyl chloride are in semicommercial pro duction at Hooker Chemical's eastern chemical division plant, Niagara Falls, N.Y. The bifunctional acid chlorides are raw materials for synthetic fibers, intermediates in pigment, pharmaceu tical, adhesive, and rubber formula tions, Hooker says. Purity is 98% minimum. C1
Powdered molybdenum-tungsten al loy comes from Sylvania Electric Prod ucts, New York, N.Y. Each particle is a solid-solution, Sylvania says, thus elements won't segregate when the powders are processed into rod, wire, ingot, or sheet. C2
Increase the range, sensitivity and convenience of your present spectrophotometer simply and at reasonable cost with easyto-install Beckman "building block" accessories. You may select from a complete line of Beckman accessories that includes adapters for flame photometry analysis, diffuse reflectance measurement, energy recording, power regulation, fluorescence analysis, and photomultiplication. For specific accessory applications information contact your local Beckman laboratory apparatus dealer, or write us for Data File 13-47-03.
Beckman Scientific and Process Instruments Division Beckman Instruments, Fidlerton, California
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Inc.
Cleaner for cationic resins costs as little as 3 % of bed replacement price, according to its maker, Ionac Chemi cal, Birmingham, N.J. Permutit Cat ion Exchange Resin Cleaner 1112 forms soluble complexes with coat ings such as silt which can be re moved by backwashing and rinsing, the company says. The cleaner will remove iron, aluminum, carbonates, and other contaminating ions, and it regenerates the resin as it cleans, Ionac adds. C8
biphenyl are available in development quantities from K&K Laboratories, Jamaica, N.Y. The two are versatile chemical and pharmaceutical inter mediates, the company says. C3
Two-package system to produce rigid polyurethane foams comes from Pitts burgh Plate Glass, Pittsburgh, Pa. Selectrofoam 6504-6505 system will form open expansion foams with den sities of 1.6 lb. per cu. ft., molded foams with densities of 2.3 lb. per cu. ft., the company says. C9
Lauroyl peroxide is now available from Thompson Chemical, Pawtucket, R.I. The organic peroxide is a catalyst and activator for plastics and an interme diate and drying agent for oils and waxes, the company says. C4
Synthetic silica extender pigment has been introduced by J. M. Huber Corp., New York, N.Y. Added to latex and emulsion paints, Zeolex 80 coats or conditions titanium dioxide to reduce reagglomeration, thus increases hiding power, the company claims. C 10
Both o-amino biphenyl and o-nitro
build versatility with UV accessories
pended in a synthetic vehicle, Hoh man says. Vehicle evaporates and leaves a nonflammable, solid film use ful to 750° F., the company adds. C7
Two neutral
dyeing,
premetallized
dyes have been added to its line by Allied Chemical's National Aniline Division, New York, N.Y. Both Na tional Lanamid Scarlet G and Bor deaux BL are fast dyes for wool, nylon, and modified acrylics, the company says. C5
Line of synthetic enamels for poly styrene plastics has been developed by Cordon-Lacey Chemical Products, Maspeth, N.Y. The enamel builds and adheres well and dries quickly, the company says. Suggested uses: decorative coating or undercoat for sil ver and other metallic coatings. C 6
Lubricant for high temperatures and pressures is being manufactured by Hohman Plating and Mfg., Dayton, Ohio. Formulation is modified molyb denum disulfide plus additives sus
New mold release agent comes from Axel Plastics, Brooklyn, N.Y. The agent, called Mold Wiz Azn, is effi cient with "sticky" molds, such as those formed by glass fiber-epoxy combinations and isocyanate foams, the company says. C 11 Two new adhesives for plastics come from Adhesive Products, New York, N.Y. Plastix Wet Stick won't wrinkle thin plastics; Plastex Heat Seal will bond plastics to fibers or other plastics. Both are made from a latex polymer and applied in water base, but resist water and dry cleaning solvents after bonding, Adhesive Products says. C12
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Further useful information on keyed Chemical items mentioned is readily available . . .
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