Step 1: add homemade 2-nitro-2′-hydroxy-5′-tert-octyl azobenzene (97.8%), 36.3 g (0.1021 mol), 10 g of sodium hydroxide, 250 ml of methanol and 50 ml of water to a 500 ml four-necked flask, control the reaction temperature at 64 and slowly add the reductant prepared according to Example 1 6.34 g, reflux reaction for 2 hours, the solution becomes light yellow is the end point of the reaction;
Step 2: slowly add 30% hydrochloric acid dropwise, neutralize the reaction solution PH is 6, produce a large number of yellow precipitate, filtration, respectively, washed twice with 50 ml of water, drying, to obtain the intermediate 2-(2 & prime;-hydroxy-5′-tert-octylphenyl)benzotriazole nitrogen oxides 31.6g, the yield was 93.2%;
Step 3: Take the 2-(2′-hydroxy-5′-tert-octylphenyl)benzotriazole nitrogen oxide 31.6 g (0.0977 mol) obtained from the previous step, 20 ml of 98% sulfuric acid, 120 ml of toluene and 60 ml of water, add it to 500 ml of four-necked flask, and control the reaction temperature at 64 and slowly add the Reducing agent 5.79 g, reflux reaction for 2 hours, the solution becomes light yellow-green is the end point of the reaction;
Step 4: the solution is first filtered to remove insoluble material, the filtrate is poured into 100 ml of water, cooling crystallization, filtration, respectively, washed twice with 50 ml of water, drying, to obtain the product ultraviolet absorber UV-32927.8g, yield of 86.1%, melting point of 103-105 .