What is polymeric MDI? Is it poisonous? Is there any excessive injury?

MDI is a mixture of diphenylmethane diisocyanate (pure MDI), pure MDI and polyphenyl polymethylene polyisocyanate (polymeric MDI) in a certain proportion, and the general name of modified products of pure MDI and polymeric MDI. It is the most important raw material for producing polyurethane, and a small amount of MDI is used in other aspects besides polyurethane. Polyurethane has both the elasticity of rubber and the strength and excellent processability of plastic, especially in heat insulation, sound insulation, wear resistance, oil resistance and elasticity. It is the sixth largest plastic after polyethylene, polyvinyl chloride, polypropylene, polystyrene and ABS, and is widely used in national defense, aerospace, light industry, chemical industry, petroleum, textile, transportation, automobile, medical treatment and other fields. MDI and TDI are substitutes for each other, and they are both raw materials for producing polyurethane. At present, MDI is a little expensive, but its toxicity is lower than TDI, and the polyurethane products formed by MDI have relatively good moldability. Chemical name: diphenylmethane diisocyanate product classification: pure MDI, polymeric MDI, liquefied MDI, modified MDI, etc. Physical properties: pure MDI: white to yellowish crystal at room temperature, storage temperature below 5 degrees, shelf life of three months, and packaging is generally 250 kg nitrogen-filled iron drum (shelf life of nitrogen-filled tank car 10 day). Polymerized MDI: brown transparent liquid, stored at room temperature, with a shelf life of two years. Generally, the package is a 250kg iron drum filled with nitrogen. Existing technology: At present, the popular MDI production methods in the world basically use aniline as raw material, which is reduced by phosgene method to form crude MDI, and then separated into pure MDI and polymeric MDI by fractionation device. Latest technology: Due to the great harm of phosgene, many factories are actively developing new synthetic processes to replace phosgene production, such as dimethyl carbonate method. But at present, these methods are only successful in small-scale workshops and cannot be applied to large-scale production at all. Main suppliers: European and American enterprises: BASF, Bayer, Huntsman, Dow, Japanese and Korean enterprises: Japanese Polyurethane, Mitsui and Kumho Mitsui, and domestic enterprises: yantai wanhua Application fields: pure MDI: slurry, sole stock solution, spandex, TPU, polyurea spraying, etc. Polymerized MDI: rigid foam, case MDI sales method: pure MDI: middlemen (few), downstream factory polymerized MDI: middlemen (miscellaneous). MDI customers develop hard foam compound factory and downstream factory: pure MDI: slurry, sole stock solution, spandex, TPU polymerization MDI: middleman: compound factory: hard foam downstream: refrigerator freezer factory, container, refrigerated truck, solar water heater and electric water heater, disinfection cabinet, imitation wood furniture, PU board, etc. Case: MDI of adhesives, sealants and coatings in aerosol (pharmaceutical industry) means MDI = meter dose inhaler, which means quantitative inhalation. MDI health assessment method is a system that WHO uses all indicators suggested by diseases that are most harmful to human death to measure (determine, according to the actual detection status of the subjects), with a full score of 100, which corresponds to WHO's definition of health and carries out comprehensive evaluation. Its criteria are: a score of 85 or above is a healthy state, a score of 70 or below () is a disease state, and 70 ~ 85 is a third-level sub-health state. Many scholars use this method to quantitatively study the sub-health state.