Excerpted from modern flame retardant materials and technology by Qian Lijun
Since the reform and opening-up in the 1980s, China’s economy has been developing vigorously, especially the manufacturing-based industrial economy has entered a stage of rapid development, one of the important signs is the rapid expansion of plastic production, sales, import and export volume. Plastic products are used in a variety of fields, including electronic appliances, building materials, automotive, high-speed rail and aircraft interior materials, etc. , however, the flammability of plastic materials determines the need for flame retardant treatment of plastic materials used in the above-mentioned fields. In addition, fires caused by inadequate fire retardant treatment of plastic materials also resulted in significant loss of life and property, an important event being the Beijing Television Cultural Center fire in 2009, because the external wall insulation material is not qualified to lead to the burning of the new landmark buildings, resulting in significant economic losses. Therefore, the fire-retardant material industry has received more and more attention in China. China’s fire control authorities have issued a series of mandatory regulations to curb the occurrence of major fire incidents, it has also promoted the rapid development of the market of flame retardants and flame retardant materials in China.
The manufacture of most flame retardants depends on natural resources. The following is a brief introduction to the distribution of flame retardants and the development of Chinese industry.
Present Situation and prospect of brominated flame retardants
Brominated flame retardants rely heavily on bromine resources. The world’s richest sources of bromine are in the Dead Sea region and the underground brine region of Arkansas State (figure 1-11) . China’s bromine resources are mainly distributed in the Laizhou Bay and the Bohai Bay region, laizhou Bay’s underground brine is the most concentrated source of bromine in China, but its abundance is still very low, only 200 ~ 300 mg/l, much lower than the 10,000 ~ 12,000 mg/l in the Dead Sea area.
But with these resources, China still has 19% of the world’s bromine production, which underpins a boom in China’s industrial production of brominated flame retardants. Relying on domestic bromine resources and imported bromine, China has formed a production base of brominated flame retardants centered in Binhai, Shandong Province, relying on imported resources and being close to the sales market, large-scale production of brominated flame retardants has also been formed in Jiangsu province.
Brominated flame retardants have been produced in China since the 1980s, and Chinese mainland has been able to produce almost all of them so far.
Including decabromodiphenyl ether and hexabromocyclododecane to be banned by the Stockholm convention; including reactive brominated flame retardants-tetrabromobisphenol A, 2,4,6-Tribromophenol; Products such as tri-(tribromophenoxy)-triazine (FR-245) , tetra-bromobisphenol a polycarbonate oligomers (BC-52/BC-58) , octabromodium ether, methyl octabromodium ether and tetrabromophenediol prepared from reactive flame retardants are also included They also include polymeric flame retardants-brominated epoxy resin (BEO) , brominated polystyrene (BPS) and brominated BS, but brominated SBS was not produced because of the DuPont patent (formerly Dow Chemical) .
Brominated flame retardants have stable application performance and good compatibility with polymers, and they still play an important role in the application market of organic flame retardants. At present, the price of bromine is high, the price of bromine flame retardant is high and will be maintained for a long time, which promotes the development of halogen-free flame retardant materials. Hexabromocyclododecane and polybrominated diphenyl ethers are banned as Persistent organic pollutant. However, due to the advantages of high molecular weight, relatively stable physical and chemical properties and good compatibility with polymer materials, brominated flame retardants can not be completely replaced by halogen-free flame retardants.
Present Situation and prospect of phosphorus-based flame retardants
(1) the situation of phosphate rock resources
China is the country with the second largest reserves of phosphate rock in the world. The phosphorus resources in China are mainly distributed in the southwest provinces of Yunnan, Guizhou, Sichuan, Hunan and Hubei, as shown in Figure 1-12. As the main raw material of halogen-free phosphorus flame retardants, the rich phosphate rock resources make the price of phosphorus flame retardants very competitive and the industry develops very fast.
(2) production of phosphorus-based flame retardants
Ammonium polyphosphate (APP) is the most widely used and basic flame retardant among the phosphorus-based flame retardants. The flame retardant agent is mainly used in flame retardant coatings, flame retardant polyolefins and other products. China currently produces about 30,000 tonnes a year. The major producers are Zhejiang Wansheng Co. , Ltd. , Hangzhou Jeers Chemical Co. , Ltd. , Zhejiang Xusen halogen-free smoke suppressant and Flame Retardant Co. , Ltd. , and Qingyuan Phosphorus Chemical Co. , Ltd. .
Phosphate esters are the largest class of phosphorus flame retardants. China’s annual production of phosphate esters is nearly 150,000 tons, the main producers are Jiangsu Yake Technology Co. , Ltd. and Zhejiang Wansheng Chemical Co. . Our main products include TCEP, TCPP, BDP, RDP, etc. .
Melamine polyphosphate (MPP) is a kind of flame retardant which can be used in engineering plastics such as flame retardant nylon. Major MPP producers include Shandong Weidong Chemical Co. , Ltd. , Sichuan Fine Chemical Research Institute, and Taizhou Baili Chemical Co. , Ltd. .
DOPO is a new type of flame retardant developed in the field of halogen-free flame retardants since 2000. It has been widely used in the epoxy industry. China’s two major producers are Shandong Weidong Chemical Co. , Ltd. and Jiangsu Hanfeng Industrial Co. , Ltd. . The research of the downstream phosphaphenanthrene derivatives is very prosperous at present, many new phosphaphenanthrene derivatives have entered the industrialization trial stage one after another. In addition to halogen free flame retardant epoxy, new phosphene derivatives are increasingly being used in flame retardant fabrics and engineering plastics.
Phosphazenes are also a class of phosphorus based flame retardants developed with the development of halogen free flame epoxy. The main product is hexaphenyloxy cyclotriphosphazene. Due to the low synthetic conversion rate of the product, the price of the product remains high, which limits the development of the product as a large industrial product.
(3) development prospect of phosphorus-based flame retardants
Phosphorus-based flame retardants have excellent flame retardancy, and have attracted much attention in the field of flame retardants. The structure diversity and composite application flexibility of phosphorus-based flame retardants are of great significance in developing new structural compounds and new high-efficiency composite flame retardants. At present, phosphorus-based flame retardants have been developed rapidly in China, and their research and production are active.
Present Situation and prospect of nitrogen-based flame retardants
(1) industrial situation of nitrogen-based flame retardants
Melamine cyanurate (MCA, fig. 1-13) , one of the nitrogen-based flame retardants, is very popular in the flame retardants market because of its low smoke, low toxicity and good thermal stability, especially its low price. China’s total MCA production in 2018 was 35,000 to 40,000 tons.
The other important nitrogen-based flame retardants are charring agents, including triazine and piperazine, which together with APP form intumescent flame retardants. The ratio of APP to intumescent flame retardants is about 1:3. At present, the formed industrial charring agent companies are pusaifu (Qingyuan) Phosphorus Chemical Co. , Ltd. , Hangzhou Jeers Chemical Co. , Ltd. . The main production of polyolefin intumescent flame retardant.
(2) development prospect of nitrogen-based flame retardants
The flame retardant efficiency of nitrogen-based flame retardants is not high when used alone, and a high amount of additives is often needed to achieve a satisfactory flame retardant effect. In order to overcome the shortcomings of flame retardants when used alone, they need to be combined with other flame retardants, in order to obtain better flame retardant effect. Therefore, the development trend of nitrogen-based flame retardants is as follows: designing and preparing new compound structures of nitrogen and phosphorus groups; The synthesis of triazine and piperazine charring agents with different substituents and their composite flame retardancy systems were developed.
Present Situation and prospect of magnesium flame retardant
(1) magnesium resources in China
China has the world’s largest reserves of magnesium, mainly in Liaoning province (figure 1-14) . Liaoning province has high-grade brucite MINERAL deposits, magnesite reserves account for more than 85% of China’s magnesite reserves, the main producers are KMT Industrial HK Limited Factory 2, Xingyang Mineral. Another source of magnesium comes from bittern. As a by product of the salt industry, Magnesium hydroxide is the main use of bittern. The main manufacturers are Gansu Kaimeite Materials Science and Technology Co. . , Ltd, ara@kmtindustrial. . Com
(2) magnesium flame retardants industry
At present, brucite powder is the main type of magnesium flame retardant in the market of China. Brucite powder can be produced by crushing brucite powder by physical method. The main costs of manufacturing brucite powder are electricity and freight. As a result of environmental protection action, the mining of brucite has been regulated, so that the price of brucite powder has significantly increased.
The conversion of magnesium flame retardants to bittern in salt making is mainly due to the chemical production of Magnesium hydroxide. It is possible to manufacture magnesium flame retardants in a recycling economy and pollution free manner by combining the production of sodium hydroxide and magnesium chloride with the production of Magnesium hydroxide. However, the cost and price of the Magnesium hydroxide products prepared by this method are high and the market competitiveness is insufficient. With China’s increasing pressure on resources and the environment, the current production of chemical Magnesium hydroxide is gradually starting up.
Present Situation and prospect of antimony-based flame retardant
China has the world’s largest antimony reserves. In China, antimony resources are mainly distributed in Guangxi, Hunan, Yunnan and Guizhou. China controls nearly half of the world’s antimony resources and produces 90 per cent of the world’s antimony.
Antimony is mainly used as flame retardant synergistic agent in the form of antimony oxide in all kinds of halogen-based flame retardants, and the most widely used in flame-retardant plastics.
Since the sharp rise in antimony prices in 2006, many manufacturers have taken measures to reduce the content of antimony oxide in brominated flame-retardant plastics or to develop alternatives. As the market share of halogen based flame retardants will remain stable, the proportion of demand for halogen based antimony trioxide products will remain stable.
At present, one of the important development trends of manufacturing products is light, thin and high performance. Therefore, although the application of flame retardant plastics will be more extensive, but the amount of plastic will be reduced, and the corresponding flame retardant products market will remain stable, but the demand for high-performance flame retardant varieties will continue to increase. This will promote our continuous efforts to develop high-performance flame retardant products. The demand for fire-proof and flame-retardant safety will also ensure the continuous development of flame-retardant products in electronic appliances, construction industry, electric vehicles, new energy materials, high-speed rail, aircraft and other fields. At present, the market of flame retardant in China is in a developing stage, and a large flame retardant enterprise group is being formed gradually.
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