UV Absorber 326: A Key Additive for Enhanced Polymer Stability

Overview of UV Absorber 326

UV Absorber 326, as a light stabilizer, is a representative type of benzotriazole ultraviolet absorber. The advantages of UV Absorber 326 are stable performance, low toxicity, and strong UV absorption ability. It can be widely used in photosensitive materials such as color film, color film, color photo paper, polymer, external protective coatings, and many other fields. It can effectively absorb ultraviolet light with a wavelength of 270-380nm, and has a wide range of non food direct contact permits in polyolefins. It has low volatility at high temperatures and high resistance to thermal degradation. Therefore, it can reduce decomposition losses during polyolefin polymerization and film compression molding processes. UV protection is used in polyester resins, and the product will not form metal colored salts during the resin's heating process.

Figure 1 Characteristics of UV Absorber 326

Preparation of UV Absorber 326

Preparation of diazotization reaction: Weigh 6g of 98wt% H2SO4, 50ml of water, and 0.03mol of p-chloro-nitroaniline into the reaction kettle. When cooled to 5 ℃, slowly add 15g of 20wt% NaNO2 solution dropwise and continue stirring for 1 hour until the reaction is complete. Add residual nitrous acid from urea decomposition and filter to remove residue. Coupling reaction: Weigh 0.03 mol of 2-tert-butyl-p-cresol, 50 mL of water, and 0.1 g of sodium dodecylbenzenesulfonate into the reaction vessel, stir to form a uniform white emulsion. Adjust the pH to 7-9 and add the diazonium salt solution dropwise under weak alkaline conditions within 2 hours. After the reaction is complete, filter, wash, dry, and weigh. Glucose reduction reaction: Weigh 0.015mol of the product obtained from the diazo coupling reaction and add 10g of NaOH solution (20wt%) to the reaction kettle. When the temperature is 50 ℃, slowly add 100ml of 30wt% glucose solution dropwise and continue the reaction for 1 hour. After cooling, filter and dry to obtain the nitrogen oxide intermediate. Zinc powder reduction reaction: Add 17mL of chlorobenzene and 42g of 14wt% H2SO4 to the above nitrogen oxides, and heat to 90 ℃. Add 1.1g of zinc powder in batches within 2 hours, add activated carbon after the reaction is complete, stir for 0.5 hours, filter while hot, separate the filtrate, wash the oil layer with water until neutral, and evaporate the solvent to obtain UV Absorber 326. The analysis results show that the product yield is 90.9% and the purity is 99.3%.

Structure and Function of UV Absorber 326

The structure of UV Absorber 326 with X as a Cl substituent, tert butyl at the 3 '- position, and methyl at the 5' - position not only causes a red shift in the transmission spectrum, but also increases the molar extinction coefficient, resulting in improved UV absorption efficiency. Moreover, it exhibits a steep absorption edge at a wavelength of 400 nm and hardly absorbs visible light above 400 nm. Its impact on the color of polymer materials is smaller than that of hydroxyl benzophenone UV absorbers, making it highly effective in light colored transparent products.

The production method of UV Absorber 326

The synthesis of UV Absorber 326 generally adopts a multi-step method. Add 2-chloro-6-methyl-3-nitro-4-piperidinol to dichloromethane, followed by sodium mercaptoaldehyde, and stir the reaction at room temperature. After the reaction is complete, the product UV Absorber 326 is obtained through crystallization and filtration operations.

UV Absorber 326 Safety Information

UV Absorber 326 has low toxicity under normal usage conditions, but safety measures should still be taken when using it. Avoid inhaling dust, avoiding contact with skin, and avoiding ingestion. Appropriate protective measures should be worn during use, such as gloves, protective goggles, and respirators. If accidentally touched, it should be washed with soap and water in a timely manner. If there is any discomfort, seek medical attention as soon as possible. During storage, the product should be kept dry, cool, ventilated, and away from sources of fire and flammable materials.

Reference

[1] Jiang T, Mao Z, Qi Y, et al. The effect of two different UV absorbers combined with antioxidants on UV resistance of HDPE[J]. Polymers for Advanced Technologies, 2021, 32(12): 4915-4925.

[2] Gao Y, Gu Y, Wei Y. Determination of polymer additives–antioxidants and ultraviolet (UV) absorbers by high-performance liquid chromatography coupled with UV photodiode array detection in food simulants[J]. Journal of agricultural and food chemistry, 2011, 59(24): 12982-12989.

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