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Polyurethane is the abbreviation of polyurethane. The English name is Polyurethane. It is an emerging organic polymer material. It is known as the fifth largest plastic and is widely used in many fields of the national economy because of its excellent performance. Applications include construction, automotive, light industry, textile, petrochemical, metallurgical, electronics, defense, medical, and machinery. With the internationalization, the deepening of globalization and the further development of China's largest polyurethane market in the world, many international polyester ester group companies have accelerated the process of achieving the standardization in China, and domestic enterprises have begun to take the country and the future. In the past five years, China's polyurethane I industry is still in a period of rapid growth.
Commonly used monomers such as toluene diisocyanate, diisocyanate diphenylmethane and the like. Polyols are classified into three categories, simple polyols (ethylene glycol, glycerol, etc.), polyester oligomers containing terminal hydroxyl groups, used to prepare polyester polyurethanes, polyether oligomers containing terminal hydroxyl groups, A polyether polyurethane is prepared. The polymerization method varies with the nature of the material. When synthesizing an elastomer, a low molecular diol is prepared, and then reacted with an arylene isocyanate to form an isocyanate-terminated prepolymer, and then extended with a butane diol to obtain a thermoplastic elastomer. The diamine is chain extended and further crosslinked to obtain a cast elastomer. The prepolymer is chain-extended with hydrazine or a diamine to obtain an elastic fiber. The prepolymer having a large amount of isocyanate is mixed with a catalyst and a foaming agent to directly obtain a rigid foam. If a monomer, a polyether, water, a catalyst, or the like is mixed, a flexible foam can be obtained in one step. The monomer and the polyol are reacted in a solution to obtain a coating, and the binder is mixed and reacted with a polyisocyanate monomer and a low molecular weight polyester or polyether.
MDI (4,4-diphenylmethane diisocyanate) is an important isocyanate product and a major raw material for polyurethane (PU) products. FU products have the dual advantages of plastics and rubber. They are the rapidly growing polymer synthetic materials in the world. They are widely used as adhesives for construction, automobiles, ships, shoes, tapes, aviation, electronics, fiberglass, metals, etc. It is one of the fastest growing polymer synthetic materials in the world and is a sunrise industry in the world today. At present, MDI production methods include phosgene method and non-phosgene method.
1, phosgene method. The condensation reaction of aniline with formaldehyde under acidic conditions is a technical route for the complete production of MDI in foreign countries. The reactants are neutralized with a base and then distilled to obtain diphenylmethanediamine (MDA). After dissolving JDA in a solvent, phosgenation reaction is carried out to prepare polyphenyl polyisocyanate 4,4-MDI, 2,2-MDI or mixed PMDI, and then subjected to distillation purification to obtain a pure MDIo liquid phase phosgene method. The main method of production at home and abroad.
Although the liquid phase phosgene method is mature, the phosgene used is volatile and highly toxic, and there are huge potential accidents, and there are technical requirements, environmental pollution, and ammonia sulfide generated in the reaction. Severe, and the yield and quality of pure MDI are also low, and the ammonia compound in the product is not easy to be separated. At present, Bayer, Huntsman, BASF and a few other multinational chemical giants and China have the core technology for the production of this product.
2, non-phosgene method. At present, the production of DI adopts the phosgene method, which uses highly toxic phosgene as a raw material, and produces hydrochloric acid by-product, which pollutes the environment and will eventually be eliminated. Non-phosgene method, less pollution, high yield, non-phosgene process for developing MDI has a good application prospect.
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