Introduction

Benzotriazole ultraviolet absorbers are one of the main varieties of light stabilizers for polymer materials. UV-326 is a representative product of this kind of products, characterized by low toxicity and strong ability to absorb ultraviolet light. It can be widely used in polyolefin, polyester, ABS polymer materials and light-sensitive materials such as color film, color film, color photo paper, polymer, external protective coating and many other fields.

Picture 1 UV-326 powders

The ozone layer in the atmosphere can only shield ultraviolet light below 280 nm, while ultraviolet light above 280 nm is very harmful to human body. The chemical name is 2 - (2 ?- Hydroxy-3 ?- Tert butyl-5 ?- Ultraviolet absorber UV-326 of methylphenyl) - 5-chloro-benzotriazole. It can not only absorb 280~370 nm ultraviolet light. It has good stability and low toxicity. It's benzotriazole violet. The only additive among the external line absorbents approved by the US FDA for plastic products in contact with food can also be widely used in coatings, synthetic rubber, synthetic fibers, photosensitive materials, etc. Effectively improve the light resistance of these materials. The synthesis of such products is generally divided into three steps: diazotization, coupling and reduction. Reduction reaction is the key to the synthesis of such products. At present, the commonly used reduction methods at home and abroad mainly include zinc powder reduction method and hydrogenation reduction method. The zinc powder reduction method has low yield and high cost. The yield of hydrogenation reduction method is low and the operation is complex. Sodium hydrosulfite is the easiest to reduce azo group. It is a kind of reducing agent with mild conditions, fast reaction, high yield, pure product and cheap and easy to obtain in dilute alkali medium[1]

Synthesis of ultraviolet absorbent UV-326 by Rongalite Method

Ultraviolet absorbent UV-326 was synthesized by means of diazotization coupling and reduction with rongalite as reduction agent. The effects of components molar ratio temperature and the concentration of NaOH solution on the reaction yield and product quality were studied. The results showed the reasonable molar ratio for the coupling compound rongalite and NaOH was 1: 3.5: 10.5. the concentration of NaOH solution was 18％.reacted at 81 ℃ for 0.5 h in which the reaction yield was higher than 86％?with purity of 99.9% (by HPLC). The UV-Visible absorption capacity of this product was superior and had high transmittance at wavelengths of 440nm[2].

The synthesis and research of UV－326

The zinc one－step deoxidize way to synthesize the UV－326 were researched．The optimize condition were investigated．The mol ratio of coincidence substance and zinc and sodium hydroxide is 1∶1．5∶10，reaction temperature was 80℃，The yield was 90%．In the production process of UV-326, zinc and hydrochloric acid are used as reductants in the second step of reduction, and zinc is converted into zinc chloride after reaction. The original process is discharged in wastewater after centrifugation. Now it is improved to neutralize the centrifugal wastewater, add an appropriate amount of alkali to convert the zinc ion into zinc hydroxide precipitation, and then convert it into zinc powder, reducing the zinc ion degree in the wastewater and the COD concentration of the wastewater[1]. 

The application of slowing down the oxidation of the soybean oil

The ultraviolet absorber UV-326 was added into PET container for the purpose of slowing down the oxidation of the soybean oil. Peroxide value，acid value of soybean oil which was packed in PET bottles were studied with variation of temperature，light intensity and exposure time. Furthermore，studied on oil migration assay of PET container with 0.4%absorbent UV-326 was conducted. The results showed that the amount of absorber UV-326 in the migration equilibrium was 14.85mg/kg. The risk of UV absorbers in PET for packaging oil was low. Ultraviolet light was shield off by using PET bottles with 0.4%absorbent UV-326 and the degree of oxidation of soybean oil was reduced by using the PET bottles[3]. 

Reference

1 Lu Hua, Wang Haifeng. Improvement of the synthesis process of UV-326 [J]. Chemical Journal, 2016,30 (08): 18-19

2 Ding Zhuming. Production and Application of Ultraviolet Absorber UV-326 [J]. Plastic Additives, 2004 (04): 17-20

3 Li Wanzhen, Ma Lina, Sun He, Guan Zhong, Yu Dianyu. Effect of UV-365 light on acid value and peroxide value of different bottled soybean oil [J]. Food Industry Science and Technology, 2014, 35 (10): 324-328