Overview[1]
UV absorber UVA is a light stabilizer. It is a kind of substance that can absorb the ultraviolet part of sunlight or fluorescence source without changing its structure. It can convert high-energy ultraviolet light energy into heat energy or release non-destructive longer light waves, thereby protecting materials added with ultraviolet absorbers from ultraviolet damage. It is mainly used as a light stabilizer for plastics, rubber, coatings, dyes, etc. to prevent their photodecomposition when exposed to sunlight for a long time. Generally, the requirements are light color, good miscibility, heat resistance and chemical stability, low volatility, etc. When used as food packaging materials, it also needs to be non-toxic and non-migrating. Various substances have different sensitive wavelengths to ultraviolet rays, and the range of light waves that various ultraviolet absorbers can absorb are also different. Only by appropriate selection can a satisfactory light stabilization effect be achieved. Ultraviolet absorber UVA is one of them.
Features[1]
Ultraviolet plastic deodorant absorber UVA is a broad-band oil-soluble ultraviolet absorber. This product has strong absorption of ultraviolet rays in the entire UVA band (320-nm), with a maximum absorption peak of 354nm. It is currently one of the best UV absorbers in the UVA band. Compared with UV1789 (avobenzone), it has better photostability. Avobenzone is limited by its own structure, and its UV absorption performance will be greatly reduced under UV irradiation. Therefore, MC80 (octyl p-methoxycinnamate) and HMS (homosalate) have to be used during the application process. protection. The molecular structure of the ultraviolet absorber UVA has good resonance and hydrogen ion transfer effects. The molecular structure will not be destroyed when the absorber absorbs the outer rays of the purple plastic antistatic agent, so it can provide long-term protection.
Preparation[2]
1) Preparation of 2-(4-N, N-diethylamino-2-hydroxybenzoyl)benzoic acid
In a nitrogen atmosphere, 99g (0.60mol) 3-diethylaminophenol, 93.2g (0.63mol) phthalic anhydride and 460ml toluene were introduced into a 500ml tetrahydrofuran equipped with a Teflon stirrer, thermometer and reflux condenser. neck flask and heat to reflux temperature. After 2 hours of reaction, a total of 300 g of toluene was distilled off within 30 minutes, and the mixture was stirred under reflux for 3 hours. The mixture was cooled to room temperature and filtered with suction. The filter cake was washed with 90 ml of toluene and 2×90 ml of hexanol in sequence. The hexanol-moistened acid can be used directly in the second step. Yield: 169 g (90%) pink 2-(diethylamino-2-hydroxybenzoyl)benzoic acid.
2) Preparation of n-hexyl 2-(4-N, N-diethylamino-2-hydroxybenzoyl)benzoate (UV absorber UVA)
Put 313g (1.0mol) hexanol-moistened 2-(4-diethylamino-2-hydroxybenzoyl)benzoic acid (based on 100%) and 750ml n-hexanol into an anchor stirrer. In a 1 liter shallow flange flask with nitrogen line, thermocouple and water trap, mix with 53g (519mmol) 96% strength sulfuric acid and heat to an internal temperature of 105-110°C. After heating, the water formed by the reaction is azeotropically distilled off at an internal temperature of 105-110° C. and a pressure of approximately 200 mbar over a period of 6-8 hours. After cooling to approximately 70° C., the mixture is mixed with 830 ml of water and neutralized with a 25% strength NaOH solution at a temperature of 52-58° C. The aqueous phase was separated and the organic phase was extracted with 500 ml of water (temperature: 52-58°C). The aqueous phase was separated, the organic phase was cooled to 20°C and awaited crystallization of the ester. After holding for 1 hour to allow the in situ seed material to mature, the mixture was cooled to 0-5°C at 5 K/h, stirred at this temperature for 2 hours and filtered under suction. The filter cake was washed with 2×85 ml cold hexanol. The crude hexanol-moistened pink product UV absorber UVA (407 g) was thoroughly blotted dry and purified by adsorption on activated carbon.
Main reference materials
[1] Concise Dictionary of Fine Chemicals
[2] CN03811000.8 Method for preparing 2-(4-N, N-dialkylamino-2-hydroxybenzoyl) benzoate
