Method for combined production of TDI and stabilized tar and utilization method of stabilized tar

Abstract

The invention discloses a method for combined production of TDI and stabilized tar and a utilization method of the stabilized tar. The method for combined production of TDI and stabilized tar comprises the following steps: 1) carrying out phosgenation reaction on amine in the presence of an inert solvent to generate crude TDI, wherein the amine is a mixture of toluenediamine and cyclic polyamine; and 2) removing phosgene and an inert solvent from the crude TDI, and further performing rectification separation to respectively obtain the product TDI and the stabilized tar. According to the invention, the cyclic polyamine and toluenediamine are mixed and fed to produce TDI and co-produce the stabilized tar at the same time, so that the tar can be used as a raw material of an adhesive for resource reutilization favourably, the process is simple and safe, and the waste utilization rate is high.

Description

technical field [0001] The invention relates to a co-production method, in particular to a method for TDI co-production of stabilized tar and a utilization method of the stabilized tar. Background technique [0002] TDI (toluene diisocyanate) is an important raw material for polyurethane production, mainly used for raw materials and intermediates of polyurethane soft foam, hard foam, adhesives, coatings, sealants and a series of elastomers. At the end of the TDI synthesis process, TDI is usually separated from the product mixture by rectification. The high-boiling distillation residue discharged after the bottom fraction of the rectification tower is dried is commonly known as liquid tar. Liquid tar contains 30-70% TDI, and other substances are mainly CDI and UTI. The formation reaction is as follows: [0003] MTDA+TDI→urea [0004] MTDA+carbamoyl chloride→urea [0005] TDI+urea→urea [0006] Urea / urea+phosgene→CDI [0007] CDI+TDI→UTI [0008] The traditional technolo...

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Problems solved by technology

[0008] The traditional technology treats the liquid tar produced in the TDI synthesis process through a disc dryer to recover TDI and directly incinerates the remaining tar residue, but the accompanying disadvantages are: (1) need to add expensive disc dryer equipment and high-temperature incinerator ( 1000°C or higher); (2) The tar is partially cracked during the drying process, producing by-products, which affects the quality of TDI products; (3) The high-temperature combustion process produces a large amount of carbon emissions, and at the same time generates secondary pollutants, including nitrogen oxides (NO x ), sulfur oxides (SO x ), dioxins, etc., and other equipment is required to remove them

Among them, it is a well-known technology to hydrolyze TDI tar residue foam to prepare TDA by adding ammonia water, alkaline aqueous solution of alkaline earth metal hydroxide, or acidic aqueous solution of inorganic and organic acids. However, due to the special physical and chemical properties of tar, both Insoluble in water and organic solvents, the hydrolysis reaction speed is extremely slow at normal temperature and pressure, the yield is extremely low, and the treatment process is complicated, resulting in a large amount of difficult-to-treat wastewater

[0010] Patent CN106753180A mixes and modifies liquid tar and polymeric MDI to prepare adhesives, avoiding the drying and incineration process of TDI tar, but the molecular weight of CDI and UTI in liquid tar is relatively large, the product has poor stability and is prone to polymerization , increasing the blending process and safety risks

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