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Ceramics and enamels
When preparing solutions used in the ceramics and enamels industry, it may be necessary to include additives in order to obtain a fluid paste or a well-dispersed solution. So phosphates such as STPP (sodium tripolyphosphate) and SHMP (sodium hexametaphosphate) are used as dispersing agents.
Sodium fluoride (NaF) acts as a fluxing agent, i.e. it lowers the fusion temperature of some mixtures which in turn leads to a reduction in energy costs. Fluorine derivatives (NaF, SSF, PSF) are also used as enameling agents.
Porcelain
Phosphates of calcium (DCP and TCP) are used in the manufacture of high-quality porcelain (bone china).
They increase the translucent effects of this type of porcelain.
Paper
Many products are used in the paper pulp industry but few possess such a diverse range of uses as phosphates. The dispersing properties of phosphates make them extremely useful for limiting the caking of mineral fillers (*), pigments, resins (and other powdered solids) when in suspension. Accordingly, they play an important role in the preparation of coating compositions (**).
Other chemical, mechanical and de-inking properties are important in producing paper pulp (***), or virgin stock, made out of woods with a high resin content, a sort of "gum" sometimes appears around the fibers which can cause indentations on the sheet of paper. These are known as pitch spots. Adding selected phosphates can prevent this from occurring. The same applies during de-inking with stickies (****).
The main phosphates used are sodium tripolyphosphate (STPP), sodium hexametaphosphate (SHMP) and diammonium phosphate (DAP).
(*) Calcium carbonate and porcelain clay are the main mineral fillers used in the manufacture of certain types of paper. They can either be used in the thickness of the sheet to enhance the paper's optical properties (whiteness, opacity etc.) and mechanical properties (resistance, rigidity, etc.), or on the surface as a coating. Less frequently, titanium dioxide is used.
The difference between the mineral fillers and the pigments is linked, in particular, to the grade of the products, since the pigments are more delicate than the filler.
(**) Coating compositions are liquid mixtures made up primarily of polymer resins and minerals in the form of pigments. They are applied in thin layers to certain types of paper (magazines, for example) to enhance the surface (uniform thickness etc.), its optical properties, and its printing properties (whether it can be printed on). The type of composition coating depends on the paper's end use and the printing methods to be used.
(***) Paper pulp can fall into 2 categories: virgin stock and pulp made from recycled paper. Virgin stock can be obtained either through chemical processes (kraft cook, etc.), or mechanical processes (millstones, refiners etc.), and may be bleached or unbleached. Recycled pulp is made from paper placed in suspension and then treated to remove the printing inks (de-inking).
(****) Stickies are sticky particles found mainly in de-inked pulp. They may result from residues of glues or resins present in recycled magazines and newspapers, or may form during processing in the paper mill (precipitation of substances in solution following a change in operating conditions (pH, temperature etc.).
Flame retardants
Monoammonium phosphate (MAP) and diammonium phosphate (DAP) are often used as flame retardants to fireproof a variety of materials (particle boards, matches, textiles, etc.) and in the manufacture of fire extinguisher powder. DAP and ammonia polyphosphates are found in products used to fight forest fires.
Paint
Polyphosphates and, in particular, sodium hexametaphosphate (SHMP), are dispersing agents and can change the distribution of the ionic charges (positive - negative) in soluble compounds. This stabilizes the emulsion, which becomes more fluid. This property is very useful in the paint industry. Due to their chelating properties, phosphates are also used in corrosion inhibition through the chelation of iron ions.
Glass fiber
One specific grade of monoaluminium phosphate (MALP) is intended for use in the production of glass-fiber-based materials. This phosphate serves as a binding agent by replacing traditional organic compounds. MALP has the advantage that it does not form harmful and volatile organic compounds at high temperatures.
Antifreeze agents
Dipotassium phosphate (DKP) is frequently used in the manufacture of antifreeze, acting as an anti-corrosion agent in car radiators and other equipment. DKP helps to keep the pH stable at around 9, thereby reducing the risk of corrosion.
Polystyrene
Tricalcium phosphate (TCP) is one of the reactive substances used in the manufacture of expanded polystyrene. It acts as an anti-caking agent and prevents polymer droplets from joining together by coating them.
Latex
Sodium fluosilicate is used in producing latex foam for mattresses where it serves as an acidifying agent in gelling latex before it is vulcanized.
Tetrasodium pyrophosphate (TSPP) is also used as a dispersing agent in the manufacture of latex.
Plaster and cement
Calcium sulfate is used in the plaster industry on account of its low soluble P2O5 content (plaster sets more slowly), its whiteness, and the lack of heavy metals and toxic elements. In the cement industry, it is used as a "retarder"; for this application, it is also essential to limit the soluble P2O5 content in the calcium sulfate.
Other applications
Purified phosphoric acid is used in the purification of vegetable oils, the purification of activated carbon filters, the production of titanium dioxide and elsewhere. Phosphates are also used in many other applications such as textiles, manufacture of plaster boards, photography, drilling sludge, and stabilizing oxygenated water solutions. Fluorine derivatives (NaF, SSF and PSF) are used as insecticides (United States only). Sodium fluoride (NaF) is also one of the raw materials used in the manufacture of monofluorophosphate (MFP).
