Method for preparing 2,2'-(4,4'-distyryl)bisbenzoxazole fine product

Abstract

The invention discloses a method for preparing a refined 2,2'-(4,4'-distyryl)bisbenzoxazole, which is realized through condensation reaction, vulcanization reaction, crude product refining, solid-liquid separation and other steps, and the crude product The refined medium and crude product is refined and desulfurized under the action of 30% NaOH solution, the desulfurization rate is high, the product OB-1 has a purity of over 99%, the yield is high, the quality is good, the color is bright, and the performance is greatly improved. The desulfurization detergent is made of 30% After the %NaOH solution replaces the traditional xylene, the production safety factor is high, the operation is safe, and the cost is reduced. The invention can be used to prepare the fluorescent whitening agent OB-1 used as ingredients for materials such as plastics, paints and road marking paints.

Description

technical field [0001] The invention belongs to the field of preparation of chemical raw materials, in particular to a method for preparing a fluorescent whitening agent, in particular to a method for preparing 2,2'-(4,4'-distyryl)bisbenzoxazole Methods. Background technique [0002] 2,2'-(4,4'-distyryl)bisbenzoxazole is a fluorescent whitening agent OB-1, with stable performance, good high temperature resistance, light resistance, chlorine bleaching resistance and migration resistance , Widely used as a mixing raw material for plastics, paints, road marking paints, etc., to play a role in whitening. At present, there are three ways to produce OB-1: sulfur process, sodium tert-butoxide process, and oxazole aldehyde process. Among them, the sulfur method production process is accepted by domestic and foreign manufacturers due to its relatively mature production technology and better product quality. [0003] In the existing technology, 2-(p-toluene) benzoxazole is generate...

AI Technical Summary

Problems solved by technology

[0004] 1. Due to the existence of a small amount of sulfur in OB-1 after refining and recrystallization, the appearance of the product is dark, no light, the crystal particle size is uneven, and the purity of OB-1 in the product is low

[0005] 2. A large amount of xylene desulfurization is required for the secondary washing of crude products, resulting in increased consumption of organic solvents and equipment investment, high industrial production costs, and at the same time, the remaining sulfur cannot be completely removed during washing, and the xylene detergent used Toxic, can cause injury to the operator

[0006] 3. Most of the sulfur remaining in the crude product will be left in the activated carbon during the refining process, while the refined filtration is high-temperature filtration, and the ignition point of sulfur is low. In the process of recycling carbon after filtration, the sulfur remaining in the activated carbon will spontaneously ignite. There are security risks

In the production of this method, 2-(p-methylbenzene) benzoxazole is excessive. Due to the high reaction temperature, the reaction is an instantaneous reaction. In order to avoid the reaction being too violent and dangerous, sulfur can only be added in batches in stages. This method is effective Reduce the amount of sulfur, but the reaction temperature is high, the yield of 2-(p-methylbenzene) benzoxazole and the target product OB-1 is affected; the product produced by this method needs to be washed and desulfurized with a large amount of xylene , not only increases the production cost, but also endangers the health of the operator; xylene cannot completely wash away the sulfur in the product, and a small amount of sulfur is mixed in the product, and the appearance of the product OB-1 is poor, and the content and purity are low

In addition, compared with sulfur, the cost of raw materials for the production of 2-(p-methylbenzene) benzoxazole is relatively high. Since 2-(p-methylbenzene) benzoxazole is in excess, after folding out the product, Need to crystallize and separate unreacted 2-(p-methylbenzene)benzoxazole, the later separation process is more complicated, which increases energy consumption and production cost

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