Phosphatizing finish

One of the best finishes for firearm steel is phosphatizing (Parkerizing) but few manufacturers offer this finish other than if required for military or police markets. The process deposits a crystalline layer of phosphates on the metal surface by immersion in a bath of iron, zinc, or manganese dioxide and phosphoric acid. Of these, a manganese phosphate finish is preferred for military use. 

Uses Film-former, corrosion inhibitor depositing a hard, dear, glossy dry finish on bare metal surls. and all types of conversion coatings, bik. oxide, antique/oxidized and phosphate finishes E-Tec 521 [Electrochem. Prods.]... 

Alkyd resin Nonoxynol-9 phosphate finishes, fabrics industrial Epoxy-novolac finishes, fibers Epoxy resin finishes, floors... 

Ammonium Phosphates. Monoammonium Phosphate [7722-76-1], NH4H2PO4, and diammonium phosphate [7783-28-0], (NH4)2HP04 (or mixtures of the two), have long been used for low cost flame retarding and afterglow prevention of paper, textiles, disposable nonwoven cellulosic fabrics, and wood products (42-44). Ammonium phosphate finishes are resistant to dry-cleaning solvents but not to water. 

Acrylates are primarily used to prepare emulsion and solution polymers. The emulsion polymerization process provides high yields of polymers in a form suitable for a variety of appHcations. Acrylate polymer emulsions were first used as coatings for leather in the eady 1930s and have found wide utiHty as coatings, finishes, and binders for leather, textiles, and paper. Acrylate emulsions are used in the preparation of both interior and exterior paints, door poHshes, and adhesives. Solution polymers of acrylates, frequentiy with minor concentrations of other monomers, are employed in the preparation of industrial coatings. Polymers of acryHc acid can be used as superabsorbents in disposable diapers, as well as in formulation of superior, reduced-phosphate-level detergents. 

The routes by which mineral phosphates are processed into finished fertilizers are outlined in Eigure 7. World and U.S. trends in the types of products produced are shown in Eigures 8 and 9, respectively. Most notable in both instances is the large, steady increase in the importance of monoammonium and diammonium phosphates as finished phosphate fertilizers at the expense of ordinary superphosphate, and to some extent at the expense of triple superphosphate. In the United States, about 65% of the total phosphate appHed is now in the form of granular ammonium phosphates, and additional amounts of ammonium phosphates are appHed as integral parts of granulated mixtures and fluid fertilizers. 

Eig. 7. Routes for making finished fertilizer from mineral phosphate. Consumption data are for year ending June 30, 1990 (5). includes quantities appHed... 

An improved version of the THPC—amide process, developed in 1972, is based on a finish containing THPC, cyanamide, and disodium phosphate [13708-85-5] Na2HP04. It has the advantage of removing the mutagenicaHy suspect TMM from the finish while retaining many of its attributes (81). 

THPC—Amide—PoIy(vinyI bromide) Finish. A flame retardant based on THPC—amide plus poly(vinyl bromide) [25951-54-6] (143) has been reported suitable for use on 35/65, and perhaps on 50/50, polyester—cotton blends. It is appUed by the pad-dry-cure process, with curing at 150°C for about 3 min. A typical formulation contains 20% THPC, 3% disodium hydrogen phosphate, 6% urea, 3% trimethylolglycouril [496-46-8] and 12% poly(vinyl bromide) soUds. Approximately 20% add-on is required to impart flame retardancy to a 168 g/m 35/65 polyester—cotton fabric. Treated fabrics passed the FF 3-71 test. However, as far as can be determined, poly(vinyl bromide) is no longer commercially available. 

Raw Materials. PVC is inherently a hard and brittle material and very sensitive to heat it thus must be modified with a variety of plasticizers, stabilizers, and other processing aids to form heat-stable flexible or semiflexible products or with lesser amounts of these processing aids for the manufacture of rigid products (see Vinyl polymers, vinyl chloride polymers). Plasticizer levels used to produce the desired softness and flexibihty in a finished product vary between 25 parts per hundred (pph) parts of PVC for flooring products to about 80—100 pph for apparel products (245). Numerous plasticizers (qv) are commercially available for PVC, although dioctyl phthalate (DOP) is by far the most widely used in industrial appHcations due to its excellent properties and low cost. For example, phosphates provide improved flame resistance, adipate esters enhance low temperature flexibihty, polymeric plasticizers such as glycol adipates and azelates improve the migration resistance, and phthalate esters provide compatibiUty and flexibihty (245). 

G. Lorin, Phosphating of Metals, Finishing Pubhcations Ltd., Middlesex, U.K., 1974. 

The rate of stripping or the stripabiUty on cataly2ed urethane and epoxy resin finishes can be increased by adding formic acid, acetic acid, and phenol. Sodium hydroxide, potassium hydroxide, and trisodium phosphate [10101-89-0] may be added to the formula to increase the stripabiUty on enamel and latex paints. Other activators include oleic acid [112-80-17, trichloroacetic acid [76-85-9], ammonia, triethanolamine [102-71-6], and monoethyl amine. Methylene chloride-type removers are unique in their abiUty to accept cosolvents and activators that allow the solution to be neutral, alkaline, or acidic. This abihty gready expands the number of coatings that can be removed with methylene chloride removers. 

Formulas for representative floor poHshes are Hsted in References 3, 12, 13, and 25. An aqueous formula may contain 0—12 wt % polymer, 0—12 wt % resin, 0—6 wt % wax, 0.3—1.5 wt % tris(butoxyethyl)phosphate, 1—6 wt % glycol ether, and 0—1 wt % zinc, with water filling the rest. Water-clear floor finishes contain Htfle or no wax, whereas buffable products contain relatively large amounts of wax. Sealers contain Htfle wax and relatively large amounts of emulsion polymers (28). For industrial use, sealers are appHed to porous substrates to fiH the pores and prevent poHshes that are used as topcoats from soaking into the floor. 

Fluorides and dust are emitted to the air from the fertilizer plant. All aspects of phosphate rock processing and finished product handling generate dust, from grinders and pulverizers, pneumatic conveyors, and screens. The mixer/reactors and dens produce fumes that contain silicon tetrafluoride and hydrogen fluoride. A sulfuric acid plant has two principal air emissions sulfur dioxide and acid mist. If pyrite ore is roasted, there will also be particulates in air emissions that may contain heavy metals such as cadmium, mercury, and lead. 

The cleanliness of the surface produced by emulsifiable cleaners is rarely of a very high standard, and additional cleaning may well be necessary before further finishing operations. Success has been achieved, however, in the use of these products prior to some immersion phosphating operations, where the crystal growth can be quite refined due to the absence of the passivation effect often encountered with some heavy-duty alkali cleaners. The supplier of the phosphating solution should be asked to advise on the suitability of any particular cleaning/pretreatment combination. 

Care must be taken here not to confuse acid cleaners with the high-strength, phosphoric acid-based chemical polishes and chemical brighteners, which are used specifically to obtain the surface finish which such materials produce. Also in the category of acid cleaners could be considered the lightweight alkali-metal phosphating cleaner-coater solutions, but a discussion on such materials is best left to specialist publications on metal pretreatment chemicals. 

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