Study On Synthesis Of Cosmetic Grade Nanometer Titanium Dioxide By Microreaction Technology

Due to the damage to the ozone layer,the intensity of UV reaching the ground continues to increase.In order to prevent UV from causing damage to human skin,protective measures such as sunscreen clothing and sunscreen are receiving increasing attention.Among them,applying sunscreen is the most direct and effective protective measure.Nanometer TiO₂has characteristics such as high transparency,non-toxic,antibacterial,high UV absorption coefficient,and stability,and is often used as an additive in sunscreen.The crystal structure,particle size,and surface coating of TiO₂are important factors affecting its UV absorption ability.Therefore,in order to improve the sun protection factor of cosmetics and improve the feeling of use,the synthesis of rutile TiO₂with high whiteness,small particle size,and surface treatment is the focus of research.Aiming at the problem of large particle size of nano TiO₂particles,this topic utilizes the advantages of enhanced mixing in microchannel reactors to explore the effects of reactant type,molar ratio,concentration,liquid flow rate,and residence time on particle size.The experimental results show that:in the liquid-liquid precipitation method,the molar ratio of reactant TiCl₄to NH₄HCO₃was 1:6;The optimal process conditions were as follows:the concentration of TiCl₄solution was 0.5 mol/L,the flow rate was 20 m L/min,the concentration of NH₄HCO₃solution was 1.5 mol/L,and the flow rate was40 m L/min.The average particle size of the TiO₂obtained was 22.2±6.9 nm,and the purity was 99.8%.CFD calculations are used to simulate the mixing of two reaction fluids in a micro sieve device model,providing the possibility for the preparation of high yield nano TiO₂using micro reaction technology.The reaction generates amorphous TiO₂.In this topic,rutile TiO₂was finally obtained by changing the high-temperature calcination process at a crystallization temperature of 950℃.To reduce the photocatalytic activity of rutile TiO₂and improve its weather resistance,sodium silicate or aluminum sulfate is used to coat its surface with silicon dioxide or aluminum oxide.As an additive in cosmetics,it is necessary to improve the solvent shape and stability of TiO₂in organic solvents.In this paper,stearic acid is coated on its surface to improve its lipophilicity.