As plastic applications continue to expand, they are flammable and generate heat and are easily ignited, presenting unexpected dangers and losses to humans. Therefore, from the late 1960s, people began to pay attention to and emphasize the flame retardancy of natural and synthetic materials. Flame retardants began to emerge as an important class of additives in the chemical fiber and plastics industries.
Since the 1970s, foreign flame retardants have developed rapidly, and consumption and variety have risen sharply, growing at a rate of about 6 to 8% per year. The consumption of flame retardants in the plastics industry has jumped to the second place, becoming the second largest plasticizer. The American Business Communications Corporation (BCC) expects an annual growth rate of 5.2% for flame retardants, and global sales in 2006 will exceed $1 billion. Flame retardants are generally divided into additive and reactive types: additive flame retardants are mostly used in thermoplastics, and are the most widely used flame retardants in the world, accounting for 90% of the total flame retardant production. Reactive flame retardants are mostly used in thermosetting plastics; flame retardants can be divided into inorganic flame retardants and organic flame retardants according to chemical structure. Inorganic flame retardants mainly include antimony compounds, inorganic boron compounds, inorganic phosphorus flame retardants, Inorganic hydroxides and the like, the organic flame retardant includes an organic halogen-based flame retardant and an organic phosphorus-based flame retardant.
é”‘Flame retardant é”‘ product has high price and large amount of smoke, and antimony trioxide is an essential synergist for halogen flame retardant. Therefore, the fineness of antimony trioxide granules is getting finer and finer, which can not only be greatly reduced. The amount of use, the improvement of flame retardancy, and the amount of smoke is also greatly reduced. The fineness is generally several micrometers to 0.01 Î¼m, and the average particle diameter of Patox developed by Seiko Co., Ltd. of Japan is 0.01 to 0.02 Î¼m. The ultra-fine and high-purity active cerium oxide developed by Guizhou Lijiang Fenghua Yupin Chemical Plant has an average particle size of 0.02Î¼m and a content of 99.999%. NyacoIaDP480 developed by PolycomHuntsman Company is a tantalum pentoxide with a particle size of less than 0.1 Î¼m. The addition of 1% can play a good flame retardant effect in PP without affecting the impact strength and transparency of PP. In addition, the use of antimony trioxide and aluminum hydroxide, zinc borate, fluoroborate and the like can not only reduce the amount of antimony trioxide but also greatly reduce the amount of smoke. In short, ultra-fine refinement, seeking surrogate supplies and reducing the amount of smoke are the hotspots of the development of antimony flame retardants.
Although the bromine-based flame retardant bromine-based flame retardant has a large amount of smoke, it is limited by the European Union due to environmental protection problems. However, due to its good flame retardant performance, low dosage and little impact on product performance, it is still resistant for a long time in the future. The main force of the fuel. With the advancement of technology, the new development of bromine-based flame retardants in the world is to continue to increase bromine content and increase molecular weight. For example, the main component of PB-68 of Ferro Company of the United States is brominated polystyrene, with a molecular weight of 15000 and a bromine content of 68%. The polypentabromophenol acrylate developed by Bromine Chemical Fast Company and ameribrom Company respectively has a bromine content of 70.5% and a molecular weight of 30,000 to 80,000. These flame retardants are especially suitable for all kinds of engineering plastics, and are much better than many small molecule flame retardants in terms of mobility, compatibility, thermal stability and flame retardancy, and may become future replacement products.
Phosphorus-based flame retardants Phosphorus-based flame retardants are mostly liquids and are mainly used in plastics such as PU and PVC. The main disadvantages of small-molecule phosphorus-based flame retardants are high volatility and low heat resistance. At present, efforts are being made to develop large molecular weight compounds and oligomers, such as GreatLake's Firemacster 836, which is a halogenated phosphate containing phosphorus, bromine and chlorine. It has a very low viscosity and is especially suitable for use in castables and PU soft foam plastics. Multifunctionalization with flame retardant and plasticizing, flame retardant and cross-linking is another major aspect of the development of phosphorus-based flame retardants. Flame-retardant plasticizers, especially at low temperatures, are mainly used in PVC products, such as domestic Production of dicumyl phosphate. Flame-retardant cross-linking agents are some reactive phosphorus-containing polyols, which can be used not only as a reactive flame retardant for PU but also as a bromine-based flame retardant in epoxy resins, which can greatly reduce bromine flame retardant. The amount of the agent.
Phosphorus-based flame retardants will continue to be low-toxic in the future, not only to address the toxicity of the product itself, but also to consider the toxicity of combustion decomposition products and the environmental pollution of waste products, and even to consider the toxicity during production, sale, storage and transportation. problem.
Non-halogenated inorganic flame retardants Most organic flame retardants contain halogens, which generate toxic gases when burned. Therefore, in recent years, non-halogenation requirements for flame retardant materials have become more and more urgent. Some plastic products in developed countries have begun to ban the use of halogen flame retardants. The EU's â€œtwo directivesâ€ on environmental protection have made clear restrictions. Prior to the German environmental group PaL, in 1995, bromide and antimony oxide were banned in the outer casing of electronic equipment. Sweden TC095 stipulates that organic bromides and organic chlorides are banned in all electrical and electronic equipment over 25 grams of plastic parts. Although halogen flame retardants are still dominant in the world, the trend of being replaced by non-halogen flame retardants has become clear. Inorganic flame retardants are an important component in non-halogen flame retardants, and high performance non-halogenated inorganic flame retardants can be added to polyolefins in large quantities without affecting the mechanical properties of the products.
New varieties of new aluminum hydroxide varieties are developed, including: (1) increasing the surface area of â€‹â€‹aluminum hydroxide particles, that is, miniaturization and ultra-fine refinement, reducing the partial pressure of water vapor on the surface of the particles, improving the heat resistance of aluminum hydroxide and making the material mechanics The performance and flame retardant effect are obviously enhanced. Some experiments show that the average particle size of aluminum hydroxide is 5Î¼m, the oxygen index is 28, the particle size is <1Î¼m, and the oxygen index reaches 33. The new variety Micrai1000 developed by American SOLEM company Micrai 1500, nominal particle size of 1.0Î¼m, 1.5Î¼m, and a narrow particle size distribution range can improve injection molding and extrusion processing. There are five varieties of Hydrax series aluminum hydroxide from Climax, USA, which have a very narrow particle size distribution range. Alcoa's S-13 ultrafine aluminum hydroxide has a particle size between 0.2 and 0.5 Î¼m, has a tight particle size distribution range and low silicon content, and can also be mixed with larger particle size aluminum hydroxide to increase packing density and reduce Viscosity. (2) Aluminium hydroxide reacts with a substance with a high thermal decomposition temperature to synthesize a new product having a thermal decomposition temperature between the two, such as a eutectic of aluminum hydroxide and sodium carbonate, which liberates water at 300-350 Â° C and Carbon dioxide, which has strong inhibitory effect on hydrogen chloride and smoke, is an excellent flame retardant for PVC and polyolefin. (3) Reducing the content of ionic insolubles, especially sodium oxide, in aluminum hydroxide, so that the mass fraction is less than 0.2%. For example, the high-purity aluminum hydroxide slag of the Japan Light Metal Co., Ltd. has a content of aluminum hydroxide greater than 99.9%. The new variety developed by sOLEM has low sodium content, high specific surface area and excellent electrical properties. It can be used at 290 Â°C.
A new type of aluminum hydroxide with improved surface is generally surface treated with a silane coupling agent, a titanate coupling agent and stearic acid (salt). This aspect has just started in China, and a new special function hydrogen peroxide has been further developed abroad. Development of aluminum surface modifiers. Solem's new silane treatment and organosilicone-coated aluminum hydroxide can be processed well in PP and PE by 60-70%, and the physical properties and flame retardancy are improved.
Add a new variety of inorganic synergists. A small amount of flame retardant synergist can significantly improve the performance of aluminum hydroxide filler materials, such as inhibiting dripping and improving mechanical properties. A wide range of inorganic flame retardant synergists with aluminum hydroxide, mainly metal oxides with zinc borate, phosphorus compounds (red phosphorus, phosphate), silicon compounds, metal nitrates (copper nitrate) , silver nitrate), ammonium polyphosphate, and the like.
The second is a new variety of magnesium hydroxide, including: (1) Many people think that magnesium hydroxide can be used as a substitute for aluminum hydroxide, but due to the physical crystal water inside the magnesium hydroxide, strong polarity, etc. The olefin has poor compatibility. Although the mechanical properties of the coupling agent are improved after coupling, it is not obvious, and the large amount of filled magnesium hydroxide is not mature in the polyolefin.
However, when the low addition amount (<30%) of magnesium hydroxide is used together with aluminum hydroxide, the carbonization of the material can be improved, and when W[Mg(OH)2]:W[aI(OH)3]=1:1, There is the best synergy in PE. (2) Morton International Industrial Chemicals and Additives Co., Ltd. coats Versamag 702 magnesium hydroxide with proprietary fatty acids to improve the rheology and physical properties of the filled polymer. The filler fluidity is still good when added at 50-60%. There is also a magnesium hydroxide solid solution Finemagsn prepared by controlling the growth of micron-sized crystals. The structure is characterized in that high concentration of divalent metal ions are mainly distributed near the crystal surface and have high acid and water resistance, so that the formulation is added. The amount is lower than ordinary high purity magnesium hydroxide.
The research on intumescent flame retardant intumescent flame retardant polymer opens up a new way for polymer flame retardant technology. Intumescent flame retardant polymer basically overcomes the shortcomings of traditional flame retardant technology, and has the following advantages: high flame retardancy, No droplets, good resistance to long-term or repeated exposure to flame; no halogen, no bismuth oxide; low smoke, less toxic, non-corrosive gases. Main components of intumescent flame retardant: (1) Acid source, generally refers to inorganic acid or a salt capable of generating acid in situ during combustion and heating, such as phosphoric acid, sulfuric acid, boric acid and phosphate; (2) carbon source, Generally referred to as a multi-carbon polyol compound, such as pentaerythritol, ethylene glycol, and phenolic resin; (3) a foaming source, a nitrogen-containing multi-carbon compound such as urea, dicyandiamide, polyamide, urea-formaldehyde resin, and the like. The research on intumescent flame retardants is mainly carried out on PP, and the inflated flame retardants which have been commercialized are mostly used in PP and polyurethane. For example, Montefluos's SpinflamMF82, which is a synergistic component of phosphorus and nitrogen, contains no halogen and cerium oxide, and contains 21% phosphorus and 18% nitrogen. Its flame retardant PP flame retardant dosage is 24%, the oxygen index is 37, and the flexural modulus is increased by 30-40%. In addition, there are GreatLake's NH-1197, NH-1151 and so on. It was not until the early 1990s that someone committed to the flame retardant research of intumescent flame retardant PE and achieved some good results.
Smoke elimination technology is the first factor in the fire and the most likely to cause death and delay in the fire. According to statistics, 80% of the deaths in the fire are caused by asphyxiation, so the contemporary "flame retardant" is "smooth suppression" In a similar way, and for some high polymers such as PVC, "smoke suppression" is more important than "flame retardant". Halogen-containing high-polymer and halogen-based flame retardants and antimony compounds are the main sources of smoke. Therefore, in addition to the non-halogenation of flame retardants, which is the main way to reduce the amount of smoke, the addition of smoke-free polymers to PVC is added. The combination of the agent and antimony trioxide is another measure to solve the problem of smoking. Molybdenum compounds have hitherto been considered to be the best smoke suppressant. For example, Kemad911a developed by Shemlnwilliams is a complex containing a small amount of zinc and molybdenum. Adding 4% to PVC can reduce the amount of smoke by 1/3. Due to the high price of molybdenum compound, compounding with zinc borate, ferrocene, aluminum hydroxide and silicon and a small amount of molybdenum compound is a realistic way to solve the problem of smoke elimination. For example, Moly-FR-201 developed by Climax is molybdenum. The composite of ammonium acid and aluminum hydroxide can reduce the amount of smoke added by 5 to 10 parts of PVC by 43%.
Flame-retardant microencapsulation technology micro-encapsulation technology can prevent flame retardant migration, improve flame retardant efficiency, improve thermal stability, change dosage form and many other advantages, compound and synergize between components and manufacture multifunctional flame retardant materials Also very beneficial. At present, China is exploring. For example, Hunan Plastics Research Institute has developed microencapsulated red phosphorus masterbatch, which has been successfully applied in PE, PP, PS and aBS resins. The microencapsulated dibromophenyl phosphate and microencapsulated chloro wax-70 developed by Anhui Research Institute of Chemical Industry have also achieved good results.
Cross-linking technology cross-linking polymers have much better flame retardancy than linear polymers. Therefore, adding a small amount of cross-linking agent to the thermoplastic processing to make the polymer into a partial network structure can not only improve the flame retardant. The dispersibility is also conducive to the formation of charcoal in the condensed phase during the combustion of the polymer, effectively improving the flame retardant performance and increasing the physical and mechanical properties, weather resistance and heat resistance of the product, such as adding a small amount of season in the soft PVC. The ammonium salt is heated to form a crosslinked flame retardant material.
It is also possible to add a metal oxide and a crosslinking agent by a radiation method, or to transfer a high polymer.
The direct generation of flame retardant monomer technology directly makes the monomer flame retardant before the polymerization reaction, so that the formed polymer becomes a flame retardant material,
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