Progress of Plastic Flame Retardant Technology Cheng Zhiling Chen Wenjie (Resin Research Institute, Sinopec Corp., Zibo, Shandong 255400, China)
The field of plastic applications is expanding, but it is flammable and has a high calorific value, which is easy to ignite and brings unexpected dangers and losses to human beings. 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 varieties have risen sharply, growing at an annual rate of 6% to 8%. Among the many additives in the plastics industry, the consumption of flame retardants has leapt to the second place, becoming a large variety after plasticizers. The American Business Communications Corporation (BCC) expects an annual growth rate of 5.2% for flame retardants and $924 million for sales by the year 2000. Flame retardants are generally classified into additive and reactive types. Additive flame retardants are mostly used in thermoplastics. They 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 classified into inorganic flame retardants and organic flame retardants according to their chemical structure. The inorganic flame retardant mainly includes an antimony compound, an inorganic boron compound, an inorganic phosphorus-based flame retardant, an inorganic hydroxide, and the like. The organic flame retardant includes an organic halogen flame retardant and an organic phosphorus flame retardant.
1 Development of flame retardant technology
1.1 The development of 锑 flame retardant 锑 high product price, large amount of smoke, and antimony trioxide is an essential synergist for halogen flame retardant, so the fineness requirements of antimony trioxide particles are getting finer and finer. Not only can the dosage be greatly reduced, the flame retardancy is improved, and the amount of smoke is greatly reduced. 01微米。 The fineness is generally in the range of a few microns to 0. 01μm. For example, the average particle diameter of Patox developed by Seiko Co., Ltd. of Japan is from 0.01 to 0.02 μm. Guizhou Minjiang Fenghua Yupin Chemical Plant recently successfully developed ultra-fine and high-purity active cerium oxide with an average particle size of 0.22 μm and a content of 99.999%. Nya colADP480 developed by PolycomHuntsman Co., Ltd. is a bismuth pentoxide having a particle diameter of less than 0.1 μm. The addition of 1% can play a good flame retardant effect in PP, and does not affect 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 alternative products and reducing the amount of smoke are the hotspots of the development of antimony flame retardants.
1. 2 Development of bromine-based flame retardants Although the bromine-based flame retardants have a large amount of smoke, they are flame retardant, have a small amount of use, and have little effect on product performance, so they are still flame retardant for a long time to come. The main force of the agent. With the advancement of technology, the new development of the international bromine flame retardant is to continue to increase the bromine content and increase the molecular weight. For example, PB-68 of Ferro Company of the United States, the main component is brominated polystyrene, with a molecular weight of 15,000 and a bromine content of 68%. Polypentabromophenol acrylate developed by Bromine Chemical Company and Ameribrom, 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.
1. 3 Development of phosphorus-based flame retardants Phosphorus-based flame retardants are mostly liquids and are mainly used in plastics such as PU and PVC. The main disadvantage of small molecule phosphorus flame retardants is their high volatility and low heat resistance. At present, efforts are being made to develop large molecular weight compounds and oligomers. For example, GreatLake's Firemac ster836 is a halogenated phosphate containing phosphorus, bromine and chlorine. It has a very low viscosity and is particularly suitable for use in castables and PU soft foam plastics [ 1]. The multi-functionality of 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 plasticizing at low temperatures) are mainly used in PVC products, such as domestically produced 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.
1.4 Development of non-halogenated inorganic flame retardants Most organic flame retardants contain halogens, which generate large amounts of smoke during combustion and produce toxic gases. Therefore, the demand for non-halogenation of flame retardant materials has become more and more urgent in recent years. Some plastic products in some developed countries have begun to ban the use of halogen flame retardants. The German environmental group PAL stipulates that bromide and antimony oxide are banned in the outer casing of electronic equipment since 1995. Swedish TC095 stipulates that organic bromides and organic chlorides are banned in all electrical and electronic equipment over 25g plastic parts. Although halogen flame retardants still dominate the world, the trend of being gradually replaced by non-halogen flame retardants in the future has become clear. Inorganic flame retardants are an important component in non-halogen flame retardants. High performance non-halogenated inorganic flame retardants can be added to the polyolefin in large quantities without affecting the mechanical properties of the product.
1. 4. 1 new varieties of aluminum hydroxide
1 .4. 1. 1 Development of new heat-resistant varieties (1) Increasing the surface area of ​​aluminum hydroxide particles, that is, miniaturization and ultra-fine refinement, so that the partial pressure of water vapor on the surface of the particles is lowered, and the heat resistance of aluminum hydroxide can be improved, and The mechanical properties and flame retardant effect of the material are obviously enhanced. Tests have shown that in the same formulation, when the average particle size of aluminum hydroxide is 5 μm, the oxygen index is 28, and when the particle size is <1 μm, the oxygen index reaches 33 [2]. The new varieties Micral 1000 and Micral 1500 developed by Solem Company of the United States have a nominal particle size of 1.0 μm and 1.5 μm, respectively, and a narrow particle size distribution range, which can improve the injection molding and extrusion processing processes. There are five varieties of Hydrax series aluminum hydroxide from Climax, USA, which have a very narrow particle size distribution range.至0. 5。 Alcoa S-13 ultrafine aluminum hydroxide particle size of 0. 2 ~ 0. 5
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