Melamine (Chemical formula: C3H6N6), commonly known as melamine, proteoglycan, IUPAC named "1,3,5-triazine-2,4,6-triamino", is a triazine nitrogen-containing heterocycle Organic compounds are used as chemical raw materials. It is a white monoclinic crystal, almost odorless, slightly soluble in water (3.1g/L at room temperature), soluble in methanol, formaldehyde, acetic acid, hot ethylene glycol, glycerin, pyridine, etc., insoluble in acetone, ethers, to the body Harmful, not for use in food processing or food additives. However, in recent days, Qinghai, Gansu, Jilin and other provinces have reappeared more than 500 times more milk than melamine. It is likely that the "Sanlu problem milk powder" that has not been completely destroyed will be processed and sold. Melamine (melamine) is a triazine nitrogen-containing heterocyclic organic compound, an important nitrogen heterocyclic organic chemical raw materials. Abbreviated as triamine, commonly known as melamine, proteoglycan, also known as 2,4,6-triamino-1,3,5-triazine, 1,3,5-triazine-2,4,6-triamine, 2 4,6-trisaminourea, melamine, cyanide triamide. More English name:1,3,5-Triazine-2,4,6-triamine; 2,4,6-Triamino-1,3,5-triazine; 2,4,6-Triamino-s-triazine; Aero ;Cyanuramide;Cyanuric triamide;Cyanurotriamide; Cyanurotriamine;DG 002(amine);Hicophor PR;Isomelamine;Melamine;NCI-C50715;Pluragard;Pluragard C 133;s-Triazine,2,4,6-triamino-;Teoharn;Theoharn;Virset 656-4; Chemical Formula (Molecular Formula) C3H6N6 Relative molecular mass 126.15 CAS registration number 108-78-1 EINECS accession number 203-615-4 (The diagram on the left shows the structure, and the diagram on the right shows the stick model.) The chemical nature is weakly alkaline (pH = 8), and melamine salt can be formed with hydrochloric acid, sulfuric acid, nitric acid, acetic acid, oxalic acid and the like. In the case of neutral or slightly alkaline, various methylol melamines are formed by condensation with formaldehyde, but in the slightly acidic state (pH 5.5 to 6.5), a polycondensation reaction of a hydroxymethyl derivative proceeds to produce a resin product. In the case of strong acid or alkali aqueous solution hydrolysis, amine groups are gradually replaced by hydroxyl, Mr. into cyanuric acid diamide, further hydrolysis to produce cyanuric acid monoamide, the final generation of cyanuric acid. The resulting tripolyamine gas is cooled and captured to obtain a crude product, which is then dissolved to remove impurities and recrystallized to obtain a finished product. Urea production of melamine consumes approximately 3,800 kg of urea per ton of product, and liquid ammonia is 500 kg. Most foreign melamine production processes are named after technology development companies such as BASF Process in Germany, Chemical Linz Process in Austria, Lurgi Process, Allied Signal Chemical in the United States. , Japan's Nissan Process, Stamka State, Netherlands? Both DSM method) and so on. These production processes vary in composition pressure and can be basically divided into three processes: high-pressure process, low-pressure process, and atmospheric process. At present, the world's advanced technology and strong competitiveness are mainly the Nissan method of Japan's Nissan and the Allied-Eurotechnica of Italy, the DSM low pressure method of the Netherlands and the BASF's atmospheric method of Germany. The melamine production enterprises in China mostly adopt the semi-dry atmospheric pressure process, which is based on urea as the raw material below 0.1 MPa. When the temperature is around 390°C, the melamine is synthesized using silica gel as a catalyst, and the melamine is crystallized in the desublimator. The crude product is dissolved. , Filtration, crystallization into finished products. The main purpose Melamine is a basic organic chemical intermediate product with a wide range of uses. Its main purpose is as a raw material for the production of melamine formaldehyde resin (MF). Melamine can also be used as flame retardants, water reducers, formaldehyde cleaners and so on. The hardness of the resin is higher than that of urea-formaldehyde resin. It is non-flammable, water-resistant, heat-resistant, weather-resistant, arc-resistant, chemical-resistant, has good insulation properties, gloss and mechanical strength. It is widely used in wood, plastics, coatings, papermaking, textiles. , leather, electrical, pharmaceutical and other industries. Its main uses are the following: (1) Decorative panels: can be made of fireproof, earthquake-resistant, heat-resistant laminates, bright color, strong and heat-resistant decorative panels, plywood for aircraft, ships and furniture, and fireproof, seismic, and heat-resistant housing decoration materials. (2) Coating: After being etherified with butanol and methanol, it can be used as a high-grade thermosetting coating and solid powder coating adhesive, and can be used to make metal coatings and high-grade amino resin decorative paints for vehicles and electrical appliances. (3) Moulding powder: It can be made into melamine plastics after mixing and granulating. It is non-toxic, anti-fouling, and can maintain good electrical properties when wet, and can be made into a white, beatable daily-use vessel. Sanitary ware and porcelain tableware, electrical equipment and other advanced insulation materials. (4) Paper: After being etherified with ether, it can be used as a paper treatment agent to produce high-quality paper such as anti-wrinkle, anti-shrinkage, non-corrupted banknotes and military maps. (5) Melamine formaldehyde resin mixed with other raw materials, can also produce fabric finishing agent, leather emollient, polishing agent and water repellent, rubber adhesive, combustion improver, high efficiency cement water reducer, steel desalination Agent and so on. (6) Agriculture: In agriculture, melamine is used to add fertilizers. Consumer Market China's melamine consumer market is mainly concentrated in wood processing, decorative panels, coatings, molding plastics, paper, textiles, leather and other industries, of which the wood processing industry accounts for 56% of total domestic consumption. In addition, about 50% of China's melamine is used for export, mainly exported to Japan, South Korea, Singapore, Spain, Germany, Indonesia, Italy and other countries. The market with large domestic demand is Guangdong, Guangxi, and South Jiangsu, and the annual demand is about 1.25 million tons. In the Guangdong-Guangzhou area, the market share of Shandong Haihua Kuixing Co., Ltd., Sichuan Chuanhua Group Co., Ltd. and Hefei Sifang Group Co., Ltd. accounted for about 65% of the total market usage. Market users in southern Jiangsu are mostly self-employed companies. Although the demand is large, the competition is fierce and the operating risks are high. The second is the Shanghai market. The annual demand is more than 10,000 tons. It is mainly used by Nanjing Jinxing, Petrochemical Industry Co., Ltd., Sichuan. Sichuan Chemical Group Corporation, Hefei Sifang Group Company. The annual demand of the North China market is about 12,000 tons, but there are numerous manufacturers in the region, prices are confusing, and competition is disorderly, so some manufacturers have limited supply to the region. The market demand in the northeast, Zhejiang, Chongqing, northwest, and Xiangxi increased continuously, and the prices were relatively stable. With the development of large-scale development in the western region, the amount of use in the future will continue to increase. The focus will be on construction, paint, coatings, etc. On the other hand, due to the poor overall economic level in the region, the demand is weak. The total global consumption of melamine increased by more than 5%, but the distribution was uneven across regions. In 2003, the global demand for melamine was about 1.1 million tons, mainly concentrated in Europe and the United States and Japan and other developed countries and regions, accounting for about 60% to 70% of the world's total consumption, mainly used for coatings, decorative paper or laminates, textiles or Paper, plastic and adhesive industries. Global consumption is expected to be about 1.2 million tons in 2004, an increase of about 8% over 2003. In recent years, China's melamine consumption has grown rapidly, and it has maintained a growth rate of 10% to 20%. With the continuous improvement of the overall level of economic development in China, people's demand for high-end building decorative materials is increasing. According to the data from the Flooring Committee of China Timber Distribution Association, the consumption of laminate flooring market in China has increased by about 30% year-on-year this year, and the state has officially implemented the mandatory standards for controlling free formaldehyde content in building materials since July 1, 2002. Stimulated the consumption of melamine in the production of laminate flooring. However, the demand growth in other areas is relatively slow. It is expected that the growth rate of melamine consumption in China in the next few years will remain at 10% to 20%. On September 12, 2008, the Ministry of Health issued the “Diagnosis and Treatment Program for Infants and Children with Urinary System Stones Associated with Eating Contaminated Sanlu Branded Infant Formulaâ€, which can be referred to by relevant parties. The program indicated that most of the stones involved the bilateral collecting system and bilateral ureters. This is different from the clinical manifestations of adult urinary stones. Multiple stones have a higher probability of affecting renal function. Since many children do not have the ability to complain about symptoms, parents need to strengthen the observation of related children, rely on abdominal ultrasound and (or) CT examination, can help determine early diagnosis. In terms of treatment, there is currently no specific antidote for the toxic effects of melamine. Clinically, it mainly depends on symptomatic and supportive treatment. If necessary, surgical intervention may be considered to relieve the risk of long-term damage to kidney function in children. Early diagnosis and early treatment are the key to early recovery of children. When melamine enters the human body, a substitution reaction (hydrolysis) occurs, cyanuric acid is generated, cyanuric acid and melamine form a large network structure, causing stones. Steven Sandrov, senior food safety official at the US Food and Drug Administration (FDA), said that the study found that only food containing both melamine and cyanuric acid poses a threat to the health of babies. It seems that although melamine and cyanuric acid together cause kidney stones, melamine is partially hydrolyzed into cyanuric acid in the strong acid environment of the stomach. Therefore, as long as melamine is contained, it is equivalent to a trimer. The danger of cyanic acid itself still stems from melamine. The melamine tolerant standard of melamine is a low-toxic chemical raw material. The results of animal experiments show that metabolism in animals is fast and does not persist, mainly affecting the urinary system. There is a clear dose-effect relationship between melamine doses and clinical disease. The maximum tolerated amount of melamine in infants is 15 mg/kg milk powder. Experts' risk assessment of contaminated infant formula milk powder shows that for a baby weighing 7 kg, assuming a daily intake of 150 grams of milk powder, the safe pre-value is a maximum tolerable dose of 15 mg/kg milk powder. According to the standards of the US Food and Drug Administration, the daily tolerable intake of melamine is 0.63 mg/kg body weight per day. The principle of false protein Due to the defect of China's method of estimating the protein content of food and feed industry, melamine is often added to foods or feeds by unscrupulous traders to improve the protein content index in food or feed testing. Therefore, melamine is also faked. People call it "protein essence." Proteins are mainly composed of amino acids. The average nitrogen content of protein is about 16%, while the nitrogen content of melamine is about 66%. The commonly used protein testing method “Kjeldahl method†estimates the protein content by measuring the nitrogen content multiplied by 6.25. Therefore, the addition of melamine will make the protein test content of the food high, thus making the inferior food and feed in the inspection agency. Only pass the simple test of crude protein. It has been estimated that increasing the test protein content in plant protein powders and feeds by one percentage point, the cost of using melamine is only 1/5 of the authentic protein material. Melamine as a white crystalline powder, has little smell and taste, so it is not easy to be Find. Milk powder incident: The protein content of each brand of milk powder is 15-20% (at the supermarket, it is also marked as 10-20% on the package), and the average nitrogen content in protein is 16%. The content of a qualified milk powder protein is 18%, and the nitrogen content is 2.88%. The nitrogen content of melamine is 66.6%, 151 times that of fresh milk and 23 times that of milk powder. Adding 0.1 grams of melamine per 100 grams of milk theoretically increases the protein by 0.625%. Slightly soluble means that 1 g (ml) of solute can be dissolved in 100 ml to 1000 ml of solvent, melamine is slightly soluble in water, and the solubility of milk in oil-in-water emulsion is not found. It should be better than the solubility of water. . Test program: In the national standards for the detection of existing powdered milk, the main tests are protein, fat, and bacteria. Melamine is a chemical raw material that is not allowed to be added to foods, so existing standards will not include the corresponding content. That is, there is no national standard for melamine detection. Therefore, Rheinland TÜ V Group refers to the FCC HPLC-UV quantification method, and also can use HPLC/MS detection method (laboratory method) for baby food, pet food, feed and raw materials (including Starch, rice protein, corn protein, wheat gluten, grain and oil, etc.) The inspection business carried out, the test results are authoritative. Another explanation for Sanlu milk powder false protein is that the company added urea, and the direct conversion of raw milk into milk powder is carried out at a high temperature. The high temperature causes urea to undergo a dehydration reaction and produce melamine. Therefore, the final milk powder is also produced. There is melamine. Melamine is added to milk and milk powder, mainly because it can impersonate proteins. Foods are tested for protein content as required. If the protein is not enough, it means that the milk is diluted with water, indicating that there are too many other things in the powder. However, proteins are too difficult to detect. Biochemists have come up with a lazy approach: Because proteins are nitrogenous, they can be extrapolated by measuring the amount of nitrogen in foods. Therefore, melamine added milk powder is difficult to detect its protein is not qualified, this is the melamine false protein. The determination of pure protein is faced with endless falsifications. The regular and strict nutrient measurement should be the actual protein content of samples waiting to be tested in milk powder. This is the determination of so-called pure protein (or true protein) in developed countries, and was adopted by China in advance. The daily standard test method for the food industry. The determination of pure protein in food or feed is also an international standard for the detection of nitrogen in milk (ISO 8968). In fact, it is the improvement of the Kjeldahl method, which has been applied for many years, including laboratories in China. The pure protein referred to in this Law is also calculated by measuring the amount of nitrogen in the food x 6.25. It is achieved by separating the non-protein nitrogen in the sample treatment solution and determining the true protein nitrogen remaining. In fact, as long as there is one more step, the sample treatment solution is first treated with trichloroacetic acid. Trichloroacetic acid allows proteins to form precipitates. After filtration, the precipitated nitrogen content is determined separately. The true content of the protein can be known, and if necessary, the nitrogen content of the protein imbibed in the filtrate can also be determined. If China adopts this as a standard, the imitation of pseudoproteins such as non-protein melamine in foods and feeds will be nothing. Ganoherb International Inc. , http://www.ganoherb.us
Physical properties Melamine traits are pure white monoclinic crystals, nonflammable, odorless, low toxicity, density 1.573G/cm3 (16°C). Atmospheric pressure melting point 354 °C, rapid decomposition will be heated; rapid heating sublimation, sublimation temperature of 300 °C. Solubility in water increases with increasing temperature and is approximately 3.3 g/L at 20°C, i.e. slightly soluble in cold water, soluble in hot water, very slightly soluble in hot ethanol, insoluble in ether, benzene and tetrachlorinated Carbon, soluble in methanol, formaldehyde, acetic acid, hot glycol, glycerol, pyridine, etc.
The synthesis process of melamine was first synthesized by Liebig in 1834. Early synthesis used dicyandiamide: calcium cyanoaminate (CaCN2) was prepared from calcium carbide (CaC2). After the hydrolysis of calcium cyanamide, it was dimerized to form dicyandiamide. Decomposition by heating to prepare melamine. At present, due to the high cost of calcium carbide, dicyandiamide has been eliminated. Compared with this method, the urea method has a low cost and is currently widely used. Urea is supported by ammonia gas and silica gel is used as a catalyst. It reacts at a boiling temperature of 380-400°C, first decomposes to generate cyanate, and further condenses to produce melamine. The reaction formula is: 6 CO(NH2)2→C3N6H6+6 NH3+3 CO2
Process classification According to different reaction conditions, melamine synthesis process can be divided into high pressure method (7-10MPa, 370-450 °C, liquid phase), low pressure method (0.5-1MPa, 380-440 °C, liquid phase) and atmospheric pressure method ( <0.3MPa, 390°C, gas phase) Three types.
Toxicity hazards Currently, melamine is considered to be slightly toxic and the oral lethal dose in rats is greater than 3 g/kg body weight. According to an experiment in 1945, a large dose of melamine was fed to rats, and no obvious poisoning was observed in rabbits and dogs. Long-term ingestion of melamine in animals can cause reproductive, urinary system damage, bladder, kidney stones, and can further induce bladder cancer. The third volume of the International Chemical Safety Handbook and the International Chemical Safety Card, co-edited by the International Chemical Safety Programme and the European Union Commission in 1994, also stated that long-term or repeated heavy ingestion of melamine may have an effect on the kidneys and bladder. Causes stone formation. However, a preliminary survey of pet food contamination incidents in the United States in 2007 found that wheat protein powders doped with ≤6.6% melamine were the cause of poisoning in pet foods, and a question mark was drawn on the slight toxicity mentioned above. However, for safety reasons, melamine-manufactured foodstuffs are generally marked as “cannot be put into microwave ovensâ€.
The effect of adding melamine to milk Milk powder is toxic because it contains melamine, which may be added directly to the milk powder or it may be added to raw milk.