Synthesis
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Melamine was first synthesized by Liebig in 1834, and the early synthesis used the dicyandiamide method: calcium cyanamide (CaCN2) was prepared from calcium carbide (CaC2), and calcium cyanamide was hydrolyzed and dimerized to produce dicyandiamide, and then heated to decomposition to prepare melamine.
The dicyandiamide method has been eliminated because of the high cost of calcium carbide. Industrial synthesis mainly uses urea as raw material, under heating and certain pressure conditions:
6 (NH2)2CO → C3H6N6 + 6 NH3 + 3 CO2
According to the different reaction conditions, melamine synthesis process can be divided into high-pressure method (7-10MPa, 370-450℃, liquid phase), low-pressure method (0.5-1MPa, 380-440℃, liquid phase). 440℃, liquid phase) and atmospheric pressure method (<0.3MPa, 390℃, gas phase) three categories.
Physical properties
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Melting point 345°C (decomposition), density 1.573 g/cm3 (16°C). Slightly soluble in water and hot ethanol. Industry melamine by dicyanamide (acyl) amine and ammonia in high temperature reaction or by urea directly in the high temperature and high pressure, the latter low cost, more used, melamine and formaldehyde condensation can be produced melamine formaldehyde resin, in addition to melamine is also used as a synthesis of pharmaceutical intermediates.
Chemical structure formula
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C3H6N6
ProductsIntroductionThe melamine is a kind of important organic chemical intermediate products, mainly used to make melamine resin, which has excellent water resistance, heat resistance, arc resistance, excellent flame retardant. Uses: It can be used in the production of decorative boards, used in amino plastics, adhesives, coatings, coin paper enhancers, textile auxiliaries and so on.
Chemical properties
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Melamine is weakly alkaline (pKb=8), and can react with a variety of acids to form melamine salts. When hydrolyzed by strong acid or strong alkali aqueous solution, the amine group is gradually replaced by the hydroxyl group, Mr. into melamine diamide, and further hydrolyzed to produce melamine monoamide, and finally to produce cyanuric acid.
Main uses
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(1) Decorative panels: can be made into fireproof, earthquake-resistant, heat-resistant laminates, brightly colored, strong and heat-resistant decorative panels for aircraft, ships and furniture veneer panels and fireproof, earthquake-resistant, heat-resistant decorative materials for the house.
(2) Coatings: etherified with butanol and methanol, it can be used as advanced thermosetting coatings, adhesives for solid powder coatings, and can be used to make metal coatings and decorative paints of high-grade amino resins for vehicles and electrical appliances.
(3) molding powder: after mixing, granulation and other processes can be made of honey amine plastic, nondegree, anti-dirt, moisture can still maintain good electrical properties, can be made of white, drop-resistant daily utensils, sanitary ware and imitation ceramic tableware, electrical equipment and other high-grade insulating materials.
(4) paper: ether etherification can be used as a paper treatment agent, the production of wrinkle-resistant, shrinkage-resistant, non-corrosive banknotes and military maps and other high-grade paper.
(5) Melamine-formaldehyde dendrimer mixed with other raw materials can also produce fabric finishing agent, leather tanning and wetting agent, varnish and water-resistant agent, rubber adhesive, combustion-aiding agent, high-efficiency cement water-reducing agent, steel desalination agent and so on.
Biological toxicity
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Melamine is currently considered to be mildly toxic, with an oral LD50 greater than 3 g/kg body weight in rats. An experiment in 1945 reported that no significant toxicity was observed after feeding large doses of melamine to rats, rabbits, and dogs. Long-term ingestion of melamine by animals can cause reproductive and urinary damage, bladder and kidney stones, and can further induce bladder cancer. However, the preliminary findings of the 2007 U.S. pet food contamination incident concluded that wheat protein powder adulterated with ≤6.6% melamine was the cause of the poisoning caused by the pet food, putting a question mark on the above conclusion of mild toxicity. However, for safety reasons, the general use of melamine manufactured utensils will be labeled "not for use in microwave ovens.
CAS No.: 108-78-1
Principle of fake protein:
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The biggest characteristic of melamine is that it has high nitrogen content (66%), coupled with its simple production process and low cost, it gives a great deal of interest to the adulterators and counterfeiters to drive, and it is estimated by some people that to make the increase of protein by one percentage point in plant protein powder and feed, it is necessary to use melamine. It has been estimated that to increase the protein in vegetable protein powder and feed by one percentage point, the cost of melamine is only 1/5 of the real protein raw material, so "increasing" the apparent protein content of the product is the main reason for adding melamine, and melamine, as a kind of white crystalline powder, has no smell and taste, and it is not easy to be detected after adulteration, etc. It has also become the auxiliary reason for adulteration and counterfeiting to take chances.
Melamine is a white crystalline powder with no odor or taste.
In 1994, the International Chemical Safety Handbook, Volume III, and the International Chemical Safety Card, jointly compiled by the International Organization for Standardization and the European Commission, only stated that the long-term or repeated intake of large quantities of melamine may have an effect on the kidneys and bladder, leading to the production of stones.
Related cases of illness
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Xinhua Beijing, September 11, 2008 (Reporter Zhou Tingyu Zhang Honghe Zhu Xudong Zhu Guoliang) China's Ministry of Health pointed out on the evening of the 11th, the recent report of Gansu and other places in a number of infants and young children urinary stone cases, the investigation found that most of the children have to consume the history of the Sanlu brand of infant formula, after the investigation of the relevant departments
Xinhua News, Beijing, Sept. 11 (Xinhua Zhou Tingyu) -- Shijiazhuang Sanlu Group Co. released a product recall statement on the evening of Sept. 11, saying that the company's self-inspection found that part of the batches of Sanlu infant formula that were shipped out before Aug. 6, 2008 were contaminated with melamine, and that about 700 tons of the product were on the market.
China's health ministry reminded the public to stop using the milk powder immediately, and that infants and children who have already consumed the milk powder should seek medical attention if they have any abnormal symptoms such as difficulty in urinating.
In addition, Jiangsu, Shaanxi, Hubei and other medical institutions have also been admitted to a number of cases of infants with urinary stones, infants are in the breastfeeding period, have taken or are still taking the same brand of milk powder. After careful treatment, most of the children have recovered from the hospital.
According to the Nanjing Children's Hospital, which has been treating the children's deputy director Huang Songming introduced, after investigation, the hospital found that these children are more or less fed the same brand of milk powder, because some of the children fed the brand of milk powder cross-phenomenon, the hospital can not be concluded that this brand of milk powder and kidney stones have a direct relationship.
Nanjing University School of Medicine doctoral tutor, Nanjing Gulou Hospital, Professor Sun Xizhao, Department of Urology Surgery, received 10 cases of urinary stone samples sent to the Nanjing Children's Hospital, the test found that the mix of these 10 cases of stones is China has never been found, the onset of the disease for the infants who are still breastfeeding.
According to doctors, urinary stones are rare in infants, and it is very rare for so many infants to have double kidney stones in a short period of time.
What tripped Sanlu up this time was a term that was unfamiliar in the past: melamine. According to a professional website, it is an important nitrogen heterocyclic organic chemical raw materials, mainly used in the production of melamine-formaldehyde resin, widely used in wood processing, plastics, coatings, papermaking, textiles, leather, electrical, pharmaceutical and other industries, and is now an important urea post-processing products. In addition melamine can also be used as a flame retardant, water reducer, formaldehyde cleaner and so on. According to the Ministry of Health, Sanlu brand infant formula may have been contaminated with melamine, which can cause stones in the human urinary system. It is speculated that this is likely to be caused by contamination of the production environment or faulty process control in production.