What are the flame retardants

With the development of China's synthetic material industry and the continuous expansion of application fields, flame retardants have broad market prospects in various fields, such as chemical building materials, electronic appliances, transportation, aerospace, daily furniture, interior decoration, clothing, food, housing and transportation, etc. In addition, the fields of coal field, oil field and forest fire extinguishing also promote the rapid development of flame retardant and fire extinguishing agent production in China. In China, flame retardant has become the second largest polymer material modification additive after plasticizer. At present, the production capacity is about 200000 t / A, the annual production is between 150000-170000 T, and the annual consumption is about 200000 t. The insufficient parts are mainly imported from the United States and Israel, and the main imported varieties are organic bromine and halogen phosphorus flame retardants. There are more than 60 flame retardants factories in China, which can produce more than 50 kinds of products, mainly brominated phosphorus series. Brominated flame retardants are the most important series, accounting for about 30% of China's organic flame retardants.


The variety and consumption of flame retardants in China are mainly organic flame retardants, while the production and consumption of inorganic flame retardants are still small. However, in recent years, the development momentum is good and the market potential is large. Halogenated flame retardants, which are the most commonly used flame retardants, have incomparable high efficiency compared with other flame retardants, but their harm to the environment and people can not be ignored. Environmental protection is the focus of the development and application of additives, so the product structure of flame retardants has been adjusted at home and abroad, and the development of high efficiency and environmental friendly flame retardants has been increased.


1. Application and production status of environmental friendly flame retardant


With the increasing awareness of environmental protection, safety and health, countries around the world began to take environmental flame retardants as the focus of research and development and application, and have achieved certain results. According to the effective elements, flame retardants can be divided into phosphorus, chlorine, bromine, antimony, aluminum and boron based flame retardants. According to the effective elements of flame retardants, the flame retardants are divided into halogen-free flame retardants, brominated flame retardants, halogen phosphorus synergistic flame retardants and other flame retardants.


1.1 halogen free flame retardant


Halogen free, low smoke, low toxic environmental flame retardant has been the goal of people's pursuit. In recent years, some flame retardant suppliers and applicators in the world have shown high enthusiasm for halogen-free flame retardant, and have invested a lot in the development of halogen-free flame retardant and flame retardant materials. According to the analysis, the main types of halogen-free flame retardants are phosphorus flame retardants and inorganic hydrates. The former mainly includes red phosphorus flame retardant, inorganic phosphorus ammonium polyphosphate (APP), ammonium dihydrogen phosphate, diammonium dihydrogen phosphate, phosphate ester, etc., and organic phosphorus non halogen phosphate ester, etc. The latter mainly includes magnesium hydroxide, aluminum hydroxide and modified materials such as hydrotalcite. Ammonium polyphosphate and hydrotalcite are representative products of this series with environmental protection and good market prospect. The following is an analysis of these two products.


1.1.1 ammonium polyphosphate


Ammonium polyphosphate (APP) is a long chain inorganic polymer containing phosphorus and nitrogen. Its molecular formula is: (nh4p03) n. Because of its good chemical stability, small hygroscopicity, good dispersibility, small specific gravity and low toxicity, it has been widely used in plastics, rubber and fibers as flame retardants in recent years; it can also be used in the preparation of intumescent fire retardant coatings for ships, trains, cables and high-rise buildings; it can also be used in the production of dry powder fire extinguishing agents for coal fields, oil wells and forests In addition, it can be used as fertilizer. The polymerization degree of ammonium polyphosphate is the key to the quality of its flame retardant products. The higher the polymerization degree is, the better the flame retardant and fireproof effect is. There are products with polymerization degree more than 100 in China, while it is common for app (ammonium polyphosphate) to have polymerization degree more than 500 abroad. The research and development of ammonium polyphosphate in China began in 1978. After more than 20 years of development, the production of ammonium polyphosphate in China has a certain foundation and basically meets the needs of the domestic market. In 2005, China's output of ammonium polyphosphate exceeded 20000 tons, and a small amount of it was exported in addition to meeting domestic demand. The production capacity of ammonium polyphosphate in China is mainly concentrated in southwest, East China and south central region, with the largest output in southwest region, followed by East China and south central region. Ammonium polyphosphate is rarely produced in North China, Northeast China and Northwest China. The scale of domestic ammonium polyphosphate production plant is small. The largest production plants are Guizhou Zunyi Xinyuan phosphating Co., Ltd. and Shifang Changfeng Chemical Co., Ltd. with the scale of 3000t / A, and Rongtai plant has reached 3000t / A. The second is Shanghai Xinhua flame retardant factory, with a production scale of 2000 t / A. The general plant scale is 400-1000t / A, and the minimum production scale is only 300t / A. With the continuous expansion of consumption market of ammonium polyphosphate, its output will continue to increase.


1.1.2 hydrotalcite


In the application of inorganic flame retardants, anionic layered functional materials have developed rapidly as flame retardants. It is a kind of inorganic compound with special structure. M2 + is a divalent ion, generally magnesium, m3 + is a trivalent metal ion, and an - is an anion. This material is called LDHs for short. Hydrotalcite has been widely used as inorganic functional materials in catalysis, ion exchange, adsorption, medicine and other fields due to its unique layered structure, laminar composition and adjustable modification of interlayer anions. As a halogen-free high smoke suppression flame retardant, hydrotalcite can be widely used in plastics, rubber, coatings and other fields. The development of MgO based anionic layered functional materials in China started in the late 1990s. Although the development history is short, it develops rapidly. In 1999, Beijing University of Chemical Technology cooperated with Yixing Chemical plant to build a 500t / a hydrotalcite production line in Yixing, Jiangsu Province, becoming the first hydrotalcite production plant in China, and forming a complete set of production technology with independent intellectual property rights. On this basis, in 2000, relying on China's advantage of marine chemical brine resources, a 1000t / a hydrotalcite production line was established in Dalian, which laid the foundation for further construction of more large-scale production facilities. From the current situation of magnesium resources in China and the urgent demand and great potential of new flame retardant market, it is not difficult to judge that the time is ripe for the rapid development of magnesium based anionic layered functional materials in China. In the next five years, magnesium based anionic layered functional materials will enter the peak period of development as substitutes for brominated flame retardants in China.


1.2 Australian flame retardant


Brominated flame retardants have been produced and used for more than 30 years. At present, there are about 70 kinds of brominated flame retardants, the most important of which are decabromodiphenyl ether (DBDPO), tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCD). The production of the first two products accounts for about 50% of brominated flame retardants. Some traditional brominated flame retardants are under the pressure of increasingly stringent environmental requirements, forcing users to find substitutes for brominated flame retardants, and promoting the emergence of new flame retardant systems. The shrinking market of traditional brominated flame retardants such as polybrominated diphenyl ethers provides market space for brominated epoxy resin, decabromodiphenylethane and other environmentally friendly brominated flame retardants.


1.2.1 decabromodiphenylethane


Decabromodiphenylethane (dbpe) was first developed by American albertale company. Its relative molecular weight, thermal stability and bromine content are similar to those of DBDPO, but it is not a flame retardant of polybrominated diphenyl ether system. PBDD and pbdf are not produced in the combustion process. It also complies with German regulations on dioxin and the regulations of US Environmental Protection Agency. Moreover, the heat resistance, light resistance and impermeability of decabromodiphenylethane are better than those of decabromodiphenyl ether. The flame retardant plastics can be recycled, which is a characteristic that many brominated flame retardants do not have. At present, the product has been used in a variety of engineering plastics, such as ABS, PBT, PA and hips.


The production technology of decabromodiphenylethane in China was successfully tested in industrial scale at the end of 2004 and put into the market in 2005. The main manufacturers are Shandong Weidong Chemical Co., Ltd. (5000t / a), Shandong Weifang Dacheng Salt Chemical Co., Ltd., Shouguang Ocean Chemical Co., Ltd., Jiangsu Shuangling Chemical Group Co., Ltd., Jinan Taixing Fine Chemical Co., Ltd., Suzhou Jinghua Chemical Co., Ltd., Laizhou Laiyu Chemical Co., Ltd., etc., with a total production capacity of about 11000t / A. Decabromodiphenylethane has a broad prospect in flame retardant market at home and abroad because of its excellent properties and properties.


1.2.2 brominated epoxy resin


Brominated epoxy resin is widely used in the flame retardant treatment of engineering plastics such as PBT, pet, ABS, nylon-66, thermoplastic plastics and PC / ABS plastic alloy due to its excellent melt flow rate, high flame retardant efficiency, excellent thermal stability and light stability, as well as good physical and mechanical properties and frost resistance. Brominated epoxy resins can be divided into low, medium and high molecular weight according to their relative molecular weight. They can also be divided into EP type and EC type according to their end group structure. They can be used in different plastic materials.


In recent years, brominated epoxy resin has developed rapidly in China, especially for its low bromine content, low molecular weight and only used as insulating and potting materials. At present, brominated epoxy resin technology in our country can produce products matching with flame retardant polymer according to the relative molecular weight of flame retardant polymer, so as to achieve the best flame retardant effect and excellent flame retardant performance. The main manufacturers are Dongying Guangrao Haifeng Salt Chemical Co., Ltd. (1000t / a), Jinan Taixing Fine Chemical Co., Ltd., Laizhou Laiyu Chemical Co., Ltd., etc., with a total production capacity of about 3500t / A. Among brominated flame retardants, brominated epoxy resin, as a new type of flame retardant, has been paid more and more attention in domestic and foreign markets.


1.2.3 brominated polystyrene


Brominated polystyrene (BPS) is a brominated organic flame retardant, which has good mechanical, physical and chemical properties such as high flame retardancy, thermal stability and light stability. It is widely used in engineering plastics such as polybutylene terephthalate, polyethylene terephthalate, polyphenylene oxide, nylon-66, etc. The main production plants are Shandong Dongying Wanda Group Co., Ltd., Shandong Shouguang Marine Chemical Co., Ltd., Jiangsu Zhangjiagang Xinyi Chemical Co., Ltd., etc., with a total production capacity of about 1000t / A, and basically no industrial scale production. With the rapid development of domestic engineering plastics industry, the demand for brominated polystyrene will be greatly increased, and the market prospect is broad.


1.3 halogen phosphorus flame retardant


The characteristic of this kind of flame retardant is that there are bromine and phosphorus or bromine, phosphorus and nitrogen atoms in the molecule at the same time. In terms of flame retardancy, they have synergistic effect; the bromine content in the molecule is low, the combustion process is accompanied by less smoke, and the harmful gas volatiles are less; a certain degree of bromine content can improve the disadvantages of general phosphate flame retardants, such as high volatility, poor migration resistance and poor thermal aging resistance. The main products include dibromooctanediol (dbnpg), dibromooctanediol phosphate and dibromooctanediol phosphate cyanamide salts. Halogen phosphorus flame retardants complement each other by using different mechanisms to achieve synergistic effect.