Production enamels

A large volume of alkyds is used in pigmented undercoat and topcoat enamels for mass-produced metal products. Enamels that require forced drying by heat (baking) are preferred. Alkyd-amino resin blends are used mainly for the quality finishes required in the appliance, metal furniture, and automotive fields. 

Most of the acid-grade spar used for HF production ia the United States is imported. More than two-thkds of the fluorspar consumed ia the United States goes iato production of HF nearly 30% is consumed as a flux ia steelmaking and the remainder is consumed ia glass manufacture, enamels, welding rod coatings, and other end uses or products (see Fluorine compounds, inorganic-calcium). 

Types of internal enamel for food containers include oleoresins, vinyl, acryflc, phenoHc, and epoxy—phenoHc. Historically can lacquers were based on oleoresinous products. PhenoHc resins have limited flexibiHty and high bake requirements, but are used on three-piece cans where flexibiHty is not required. Vinyl coatings are based on copolymers of vinyl chloride and vinyl acetate dissolved in ketonic solvents. These can be blended with alkyd, epoxy, and phenoHc resins to enhance performance. FlexibiHty allows them to be used for caps and closures as weU as drawn cans. Their principal disadvantage is high sensitivity to heat and retorting processes this restricts their appHcation to cans which are hot filled, and to beer and beverage products. 

Polyimides (PI) were among the eadiest candidates in the field of thermally stable polymers. In addition to high temperature property retention, these materials also exhibit chemical resistance and relative ease of synthesis and use. This has led to numerous innovations in the chemistry of synthesis and cure mechanisms, stmcture variations, and ultimately products and appHcations. Polyimides (qv) are available as films, fibers, enamels or varnishes, adhesives, matrix resins for composites, and mol ding powders. They are used in numerous commercial and military aircraft as stmctural composites, eg, over a ton of polyimide film is presently used on the NASA shuttle orbiter. Work continues on these materials, including the more recent electronic apphcations. 

Finishes for aluminum products can be both decorative and useful. Processes in use include anodic oxidation, chemical conversion coating, electrochemical graining, electroplating (qv), thin film deposition, porcelain enameling, and painting. Some alloys respond better than others to such treatments. 

Porcelain enameling requires the use of frits and melting temperatures of 550 °C or below. Enamels are appHed over chemical conversion coatings that are compatible with the frit. AHoy selection is important to obtain good spall resistance. Alloys 1100, 3003, and 6061 are employed most extensively among wrought products and alloy 356 for castings. 

Another large appHcation is as an ingredient in the production of charcoal briquettes. The amount of sodium nitrate used in charcoal briquette manufacture depends on the type and amount of wood and coal used. Typically charcoal briquettes contain up to almost 3% sodium nitrate. Sodium nitrate is also used in the manufacture of enamels and porcelain as an oxidizing and fluxing agent. In porcelain—enamel frits used for metal coating, the amount of sodium nitrate in a batch varies with the various metal bases to be coated, typically from about 3.8 to 7.8 wt %. 

The demand for pipe-coating enamels tends to fluctuate, depending on the success of oil and gas exploration. In the United Kingdom plastic-coated pipes are used on shore. Most production is exported for use in the Middle and Far Eastern regions. 

Table 11 Hsts the types and appHcations of special pigment-grade carbon blacks. Included in this Hst are thermal black and lampblack. Over 40 special black grades have been developed based on the furnace process having a broad range of surface areas, from 20 m /g to over 1500 m /g. The lower surface area products are used in printing inks and tinting. The high area, more expensive products find use in high color enamels and lacquers.

Branched-chain acids have a wide variety of industrial uses as paint driers (7), vinyl stabilizers (8), and cosmetic products (9). Cobalt and manganese salts of 2-ethyIhexanoic acid and neodecanoic acid are used as driers for paint, varnishes, and enamels litbium, magnesium, calcium, and aluminum salts of 2-ethyIhexanoic acid are used in the formation of greases and lubricants (see Driers and metallic soaps). Derivatives of isostearic acid have been used as pour point depressants in two-cycle engine oils, as textile lubricants, and in cosmetic formulations. Further industrial appHcations can be found (10). 

Cobalt(II) phosphate octahydrate [10294-50-5], Co2(P0272 8H20, is a red to purple amorphous powder. The product is obtained by reaction of an alkaline phosphate and solutions of cobalt salts. The material is insoluble in water or alkaU, but dissolves in mineral acids. The phosphate is used in glazes, enamels, pigments (qv) and plastic resins, and in certain steel (qv) phosphating operations (see Enamels,PORCELAIN ORVITREOUS). 

Any product that depends on aesthetics for consideration for purchase and use will be improved by the use of color. Hence, many ceramic products, such as tile, sanitary ware, porcelain enameled appHances, tableware, and some stmctural clay products and glasses, contain colorants. 

For both economic and technical reasons, the most effective way to impart color to a ceramic product is to apply a ceramic coating that contains the colorant. The most common coatings, gla2es and porcelain enamels, are vitreous in nature. Hence, most appHcations for ceramic colorants involve the coloring of a vitreous material. 

Only synthetically prepared Ti02 can be used as a color additive. It is permitted ia foods to 1% and is used to color such products as confectionary paimed goods, cheeses, and icings. It is also widely used ia tableted dmg products and ia numerous cosmetics such as Upsticks, nail enamels, face powder, eye makeup, and rouges, ia amounts consistent with good manufactuting practice (42). 

Fluorides. Most woddwide reductions in dental decay can be ascribed to fluoride incorporation into drinking water, dentifrices, and mouth rinses. Numerous mechanisms have been described by which fluoride exerts a beneficial effect. Fluoride either reacts with tooth enamel to reduce its susceptibihty to dissolution in bacterial acids or interferes with the production of acid by bacterial within dental plaque. The multiple modes of action with fluoride may account for its remarkable effectiveness at concentrations far below those necessary with most therapeutic materials. Fluoride release from restorative dental materials foUow the same basic pattern. Fluoride is released in an initial short burst after placement of the material, and decreases rapidly to a low level of constant release. The constant low level release has been postulated to provide tooth protection by incorporation into tooth mineral. 

---