Toluene diisocyanate

colourless to light yellow liquid Toluene diisocyanate exists in two isomeric forms (2,4-toluene diisocyanate and 2,6-toluene diisocyanate), which have similar properties and effects. Toluene diisocyanate is produced commercially as an 80:20 (2,4-toluene diisocyanate:2,6-toluene diisocyanate) mixture of the two isomers. At room temperature, the mixture is a clear, pale yellow liquid with a sharp, pungent odor. It should be stored under refrigeration, away from light and moisture in a tightly cl

Preparation methods are amine phosgenation, nitro compound carbonylation and dimethyl carbonate method.
(1) amine phosgenation by nitration of toluene to produce dinitrotoluene, and then reduced to toluene diamine. Toluene diamine and phosgene reaction that TDI (mainly 2, 4-isomer). ① the atmospheric pressure method will be dissolved in diaminotoluene (105-110 ° C) dissolved in o-dichlorobenzene, dubbed 10% -20% of the solution; the photosol dissolved in o-dichlorobenzene, the content of 25% -50% The The two solutions were mixed in a mixer and heated to 80-200 ° C to react with toluene diisocyanate, hydrogen chloride and other by-products. The final reaction of phosgene, o-dichlorobenzene and the reaction product into the evaporation tower to separate part of the solvent, distilled o-dichlorobenzene and then as the recovery of phosgene absorbent. Evaporating the tower liquid into the pre-evaporator for flashing, distilling the toluene diisocyanate and o-dichlorobenzene into the distillation column, the top of the recovery of pure solvent, kettle liquid distillation toluene diisocyanate. ② pressure method The solvent used in this method is generally chlorobenzene. Liquid phosgene and 10% -20% of diaminotoluene chlorobenzene solution 80-120 ° C MPa pressure, the reaction in the circulating pipeline, the pipeline in the cycle ratio of 10-40. The reaction crude product enters the reactor through a buffer and the reactor is heated with a heater. Recovery of hydrogen chloride from the top of the reactor is carried out by by-product hydrochloric acid, which contains a small amount of phosgene condensed by the condenser into the phosgene tank. The reaction crude product enters the evaporation column to vaporize the phosgene at a pressure of 0.1-0.5 MPa. The kettle is toluene diisocyanate, chlorobenzene and other by-products, further distilled and refined to recover chlorobenzene to give toluene diisocyanate. Raw material ratio: phosgene / diaminotoluene (ratio of matter) 3: 6 (non-cyclic process). Consumption of fixed amount (kg / t): atmospheric pressure diaminotoluene 1280 (atmospheric pressure method), 905 (pressure method); phosgene 1250 (atmospheric pressure method), 2260 (pressure method); o-dichlorobenzene 3- 10 (normal pressure method); chlorobenzene 218 (pressurized method).
(2) nitro compound carbonylation method This method from the aromatic nitro compounds, the use of chromium, rhodium, palladium and other carbonylation catalyst at 60-150 ℃, 686-981MPa pressure, with the direct reaction of CO to toluene diisocyanate Acid esters.
(3) Dimethyl carbonate method This method is a new method for the production of toluene diisocyanate with phthalic acid instead of phosgene, which has been developed since the 20th century, since the 1980s, the methylation of dimethyl carbonate. With a simple equipment, pollution-free, without phosgene and many other ills. With the continuous development of dimethyl carbonate, the scale of production continues to expand, the price will gradually decrease. I believe that the environmental issues are increasingly valued today, the law will be more viable.

1. Occupational asthma is the principal cause of work-related respiratory disease in the industrial world. Toluene-2,4-diisocyanate (TDI) is one of the most common respiratory sensitizers leading to occupational asthma.
2. TDI (toluene diisocyanate) is an important basic raw materials of polyurethane. TDI is a mixture of 2,4-TDI and 2,6-TDI two kinds of isomers, including 3 kinds of commonly used grades: TDI-80/20, TDI-100 and TDI-65/35. Mainly used in the production of flexible polyurethane foam and polyurethane elastomer coatings, adhesives, etc..