Flame retardants aluminum hydroxides

The aluminum containing compound having the largest worldwide market, estimated to be over 30 x 10 t in 1990, is metal grade alumina. Second, is aluminum hydroxide. In 1990 the market for Al(OH)2 should approach or exceed 3.5 million metric tons which is equivalent to 2.3 million tons on an alumina basis. The spHt between additive and feedstock appHcations for Al(OH)2 (16) is roughly 50 50. Additive appHcations include those as flame retardants (qv) in products such as carpets, and to enhance the properties of paper (qv), plastic, polymer, and mbber products. Significant quantities are also used in pharmaceuticals (qv), cosmetics (qv), adhesives (qv), poHshes (qv), dentifrices (qv), and glass (qv). 

Hitachi Cable Ltd. (35) has claimed that dehydrogenation catalysts, exemplified by chromium oxide—zinc oxide, iron oxide, zinc oxide, and aluminum oxide—manganese oxide inhibit drip and reduce flammability of a polyolefin mainly flame retarded with ATH or magnesium hydroxide. Proprietary grades of ATH and Mg(OH)2 are on the market which contain small amounts of other metal oxides to increase char, possibly by this mechanism. 

Flame retardant - [ALUMENUMCOMPOUNDS - ALUMINUM SULFATE AND ALUMS] (Vol 2) - [AMMONIUMCOMPOUNDS](Vol2) - [VINYL POLYMERS - VINYL CHLORIDE POLYMERS] (Vol24) -ethyleneimines [IMINES, CYCLIC] (Vol 14) -filler for [LEAD COMPOUNDS - LEAD SALTS] (Vol 15) -iron compounds as [IRON COMPOUNDS] (Vol 14) -magnesium hydroxide as filler [MAGNESIUMCOMPOUNDS] (Vol 15)... 

By reacting aluminum hydroxide with oxalic acid, basic aluminum oxalate can be produced, which is thermally stable to 330°C, losing 51% of its mass on decomposition at temperatures above 450°C. It is reported to have a flame-retarding and smoke-suppressing action similar to ATH, but because of its increased thermal stability, it can be used in polyamides and thermoplastic polyesters. However, unlike magnesium hydroxide, in these polymers it does not cause hydrolytic degradation.2... 

These are a series of magnesium aluminum hydroxycarbonates with varying magnesium to aluminum ratios between 1.5 and 3.0g-atoms of magnesium to 1 g-atom of aluminum. They have layers of magnesium hydroxide interspersed with aluminum cations and carbonate anions. They show similar flame-retardant activity and thermal stability to ATH, but their higher cost currently limits their potential use. 

Stinson, J.M. and Horn, W.E. Flame retardant performance of a modified aluminum hydroxide with increased thermal stability, Proceedings from Society of Plastics Engineers 52nd Annual Technical Conference (ANTEC 94), Part 3, Newtown, CT, U.S.A, May 1-5, 1994, pp. 2829-2833. 

Kirschbaum, G.S., Aluminum hydroxide for non-halogen compounds-well known- and still ever young, Proceedings from Flame Retardants 94, British Plastics Federation, London, Interscience Communication Ltd., London, U.K., 1994, p. 169. 

Additive flame-retardants may be more easily incorporated in polyurethane formulation. Several class of compounds have been used to improve flame retardancy of PU foams such compounds are halogen- (very often chloroalkyl-phosphate) or phosphorous-based compounds, although also other substances, like as EG, melamine, aluminum trihydrate and magnesium hydroxide, may be used. 

The afterglow of open-cell foams (punking) can be suppressed by the addition of flame-retardants such as boron trioxide or aluminum hydroxide. Hybrid foams with good mechanical properties and low combustibility can be produced from PF resins and polyisocyanates.104... 

Flame-retardants are used as additives in the preparation of fire retardant paints. They are decomposed by heat to produce nonflammable components, which are able to blanket the flames. Both inorganic and organic types of flame-retardants are available in the market. The most widely used inorganic flame-retardants are aluminum trihydroxide, magnesium hydroxide, boric acid, and their derivatives. These substances have a flame-retardant action mainly because of their endothermic decomposition reaction and their dilution effect. The disadvantage of these solids is that they are effective in very high filler loads (normally above 60 percent). 

The effect of the amount of melamine on the flame retardance of the resulting foams was studied in detail by Shell (131) and Dow Chemical (133). A combined use of ammonium sulfate and aluminum hydroxide was proposed by Toyo Rubber Chemical Industries Corp. (136). Recently, blends of ammonium sulfate and weakly basic organic compounds, e.g., sodium carboxylates, were patented (158, 165). 

Zinc borate is an inorganic flame retardant which can be used by itself or in combination with aluminum hydroxide or magnesium hydroxide with which it forms synergistic mixtures of high performance flame retardants. It is frequently used as a surface coating on these two fillers. It reduces smoke emission and promotes char formation. 

Fillers such as magnesium hydroxide and aluminum trihydroxide are used as flame retardants because their decomposition product - water -is an active ingredient in flame retardancy. These fillers are discussed in detail in Chapter 12. 

Special considerations presence of zinc, copper, iron and nickel compounds accelerated dehydrochlorination combination of basic magnesium carbonate and aluminum hydroxide is used as flame retardant and smoke supressant chlorinated polyethylene adsorbs on the surface of titanium dioxide forming a layer 1-20 nm thick depending on the aciii/base interaction parameter of titanium dioxide ... 

Flame retardant polyurethanes are mostly manufactured with compounds of phosphorus, such as ammonium phosphate or polyphosphate. Aluminum hydroxide alone or in combination with melamine is an alternate approach. In intumescent applications, graphite is frequently used. Calcium carbonate is useful as a flame retarding additive, in combination with other flame retarding materials, because of its large endothennic peak found in DTA curves. ... 

Manufacturers of various fillers continue studies on altemative systems. Most antimony oxide used as a fire retardant can be replaced by a combination of zinc borate without the loss of other properties (in some cases improvements are reported). Another option is to use the same filler systems which are used in polyethylene insulated cables and wires. These are based on magnesium hydroxide and aluminum hydroxide. These systems pcrfoim as flame retardants but require a high filler concentration which affects jacket resistance and mechanical performance. Recently, new coated grades have been developed which can be used at up to 65 wt% without the loss of properties or productivity (extrusion rates 2,500 m/min of cable are possible). ... 

In both Europe and the United States, aluminum trihydrate, or ATH [Al(OH)3)], has by far the largest share of the mineral flame-retardant market however, magnesium hydroxide presently has the highest growth rate. To date, most of the research using magnesium hydroxide has focused on thermoplastics, including ethylene-vinyl acetate copolymer (EVA), polypropylene, acrylonitrile-butadiene-styrene (ABS) copolymer, and modified polyphenylene oxide (Hornsby and Watson, 1986). 

The flame-retardant effect of magnesium hydroxide and ATH is based on the endothermic decomposition to magnesium or aluminum oxide, see reactions (11.1) and (11.2). This decomposition effectively acts as a heat sink cooling the surface of the polymer. 

Alfrimal. [Ali a Calcit Fullstoff GmbH] Aluminum hydroxide flame retardant... 

Aluminum trihydrate, magnesium hydroxide, calcium and zinc molybdates, antimony pentoxide, and zinc borate are examples of inorganic compounds used as flame retardants in the manufacture of household furniture, upholstery, wall coverings, draperies, and carpets (National Research Council (NRC), 2000). Antimony trioxide is sometimes used in combination... 

Western-world bauxite production in 1988 totaled about 90 x 10 t, approximately 90% of which was refined to aluminum hydroxide by the Bayer process. Most of the hydroxide was then calcined to alumina and consumed in making aluminum metal. The balance, which constituted about 2.3 x 10 t in 1988 (Table 2), was consumed in production of abrasives (qv) adhesives (qv) calcium aluminate cement used in binding ceramics (qv) and refractories (qv) catalysts used in petrochemical processes and automobile catalytic converter systems (see Petroleum Exhaust control, automotive) ceramics that insulate electronic components such as semiconductors and spark plugs chemicals such as alum, aluminum halides, and zeoHte countertop materials for kitchens and baths cultured marble fire-retardant filler for acryhc and plastic materials used in automobile seats, carpet backing, and insulation wrap for wire and cable (see Flame retardants) paper (qv) cosmetics (qv) toothpaste manufacture refractory linings for furnaces and kilns and separation systems that remove impurities from Hquids and gases. 

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