Melamine stereoscopic model Appearance and properties: white, monoclinic crystal
Odor: Almost no taste Melting point (℃):> 300 (sublimation)
Relative vapor density (air = 1): 4.34
Saturated vapor pressure (kPa): 6.66
Soluble: insoluble in cold water, soluble in hot water, soluble in methanol, formaldehyde, acetic acid, hot ethylene glycol, glycerol, pyridine, etc., slightly soluble in ethylene glycol, glycerol, ethanol, insoluble in ether, benzene, Carbon, acetone, ethers.
Chemical structure is not flammable, stable at room temperature. Aqueous solution was weakly alkaline (pH = 8), and hydrochloric acid, sulfuric acid, nitric acid, acetic acid, oxalic acid and so can form melamine salt. In the case of neutral or slightly alkaline, and formaldehyde condensation of a variety of hydroxymethyl melamine, but slightly acidic (pH 5.5 ~ 6.5) and hydroxymethyl derivatives of polycondensation reaction to produce resin products. In the case of strong acid or strong alkali hydrolysis, the amine group is gradually replaced by hydroxyl, first into cyanuric acid diamide, further hydrolysis of cyanuric acid amide, and finally the formation of cyanuric acid.
Melamine is thought to be mild in toxicity, and the median lethal dose of oral administration in rats is greater than 3 g / kg body weight. Long-term intake of melamine animals can cause reproductive, urinary system damage, bladder, kidney stones, and can further induce bladder cancer. General adult body will discharge most of the melamine, but if combined with cyanuric acid, will form insoluble cyanuric acid melamine, causing severe kidney stones. The International Chemical Safety Manual, Volume III and International Chemical Safety Cards, compiled by the International Program on Chemicals Security and the European Commission in 1994, also show that long-term or repeated intake of melamine may have an effect on the kidneys and the bladder, Resulting in stones.  Melamine formation of the mechanism of the formation of kidney stones is not very clear, there are studies that melamine often mixed with a similar structure of cyanuric acid, into the human body into the kidney cells, melamine and cyanuric acid will form a crystalline deposition, resulting in Kidney stones and block the renal tubules, and may lead to renal failure.
Melamine - synthesis
Melamine was first synthesized in 1834, early synthesis of dicyandiamide method: Calcium cyanide calcium [Ca (CN) 2] was prepared from calcium carbide (CaC2), and melamine was hydrolyzed to form dicyandiamide and then heated Preparation of melamine by decomposition. Synthesis method Because of the high cost of calcium carbide in dicyandiamide, dicyandiamide (98%) 1180kg per ton of product consumes 10kg of liquid ammonia, so the dicyandiamide method has been eliminated. Compared with the method, the cost of urea method is low, and the industrial synthesis mainly uses urea as raw material. Under the condition of heating and certain pressure, urea is used as carrier and silica gel as catalyst, and the reaction is carried out at the temperature of 380-400 ℃. Cyanic acid, and further condensation to produce melamine. The resulting triamine gas is collected by cooling to obtain a crude product which is then dissolved and removed to remove the impurities and recrystallize the product. Urea production of melamine per ton of product consumption of about 3800kg of urea, liquid ammonia 500kg. 6 (NH2) 2CO → C3H6N6 + 6 NH3 + 3 CO2 ↑
(7-1MPa, 370-450 ℃, liquid phase), low pressure method (0.5-1MPa, 380-440 ℃, liquid phase) and atmospheric pressure method (low pressure method (0.5-1MPa, 380-440 ℃, liquid phase) and atmospheric pressure method <0.3MPa, 390 ℃, gas phase) three categories. Melamine production process are mostly named after the technology development company, such as Germany BASF, Austria Linz chemical method, Lu Qi law, the United States combined signal chemical company chemical method. The world's advanced technology, strong competitiveness of the main Nissan Nissan Nissan Nissan and Italy Allied-Eurotechnica high pressure method, the Netherlands DSM low pressure method and the German BASF atmospheric pressure method. China's melamine production enterprises to use semi-dry atmospheric pressure process.
Melamine - main use
Decorative panels: can be made of fire, earthquake, heat-resistant laminate, bright color, strong heat-resistant decorative panels, aircraft, ships and furniture, panels and fire, earthquake, heat-resistant housing decoration materials. The following are the same as the "
Paint: With butanol, methanol etherification, as a high-level thermosetting coating, solid powder coating adhesive agent, can be made of metal coatings and vehicles, electrical appliances with high-grade amino resin decorative paint. The following are the same as the "
Molded powder: made by mixing, granulation and other processes can be made of melamine plastic, non-toxic, anti-fouling, wet can still maintain good electrical performance, can be made of white, resistant to beat the daily utensils, sanitary ware and Imitation porcelain tableware, electrical equipment and other high-level insulation materials.
Paper: etherified with ether can be used as a paper treatment agent, the production of anti-wrinkle, anti-shrink, do not rotten banknotes and military maps and other advanced paper.
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