Preparation,Surface Modification And UV Resistance Of Silica Microspheres Based On Cheap Silicon Source

As a common cosmetic filler,SiO₂ microspheres have the advantages of strong fluidity,high mechanical strength,stable properties and easy surface modification.In industry sector,TEOS is mainly used as a raw material for the production of SiO₂ microspheres.The cheaper and environment-friendly sodium silicate has not been widely used because of the high degree of agglomeration of the product.Organic UV absorbers commonly used in cosmetics have shortcomings such as irritation to the skin and easy migration,while inorganic UV absorbers have the defects of poor skin feeling and high hiding power.In this paper,highly dispersed SiO₂microspheres were synthesized from sodium silicate as a silicon source,and then the surface was modified to obtain an anti-UV composite functional material with the advantages of organic and inorganic ultraviolet absorbents,and evaluated its application performance in cosmetics.（1）Taking water glass as the silicon source and PEG as the structure guide,the highly dispersed SiO₂ microspheres are prepared by ultrasonic auxiliary means,and the particle size and specific surface area are effectively regulated by adjusting the reaction temperature,p H value and PEG molecular weight;the PEG will be embedded in the SiO₂ microsphere during the synthesis process,thereby bringing a certain number of alcohol hydroxyl groups to its surface.When the reaction temperature was 40°C,the p H was 3.5,and the PEG molecular weight was 2000,the synthetic SiO₂ microspheres had the best dispersion,with an average particle size of 6.34μm,a specific surface area of 135.44 m²·g^-1,a surface silicon hydroxyl content of 5.21×10^-4 mol·g^-1,and an alcohol hydroxyl content of 1.95×10^-4 mol·g^-1.（2）In this paper,the silicon hydroxyl group and the alcohol hydroxyl group on the surface of the silica microsphere were grafted and modified,and the anti-ultraviolet functional group was introduced.The use of A-143 as a surface modifier grafted 4-hydroxybenzophenone to the silicon hydroxyl group on the surface of the SiO₂ microspheres,and the use of IPDI 4-hydroxybenzophenone grafted to the alcohol hydroxyl group on the surface of the SiO₂microsphere.The silicon hydroxyl modified SiO₂ microspheres had excellent UVB absorption performance,with Abs values of 1.52 at 291 nm,the alcohol hydroxyl modified SiO₂microspheres exhibited excellent UVA absorption performance,with Abs values of 1.29 at 341nm,and the composite modified SiO2 microspheres had both UVA and UVB absorption capacity,with Abs values of 1.51 and 1.19 at 291 and 341 nm,respectively.（3）Sunscreen prepared with composite modified SiO₂ microspheres as UV absorbers,when the amount of microspheres is 10 wt%,its UV absorption performance is similar to that of commercially available SPF10 sunscreen;Compared with organic UV absorbers,the UV absorption functional groups on the surface of the modified microspheres are firmly connected to the main body and will not migrate to the sunscreen system and thus irritate the skin;compared with inorganic UV absorbers,the composite modified SiO₂ microspheres have stronger UV absorption performance,and the sunscreen formulated has a better skin feeling and a richer color mixing space.The process of synthesizing SiO₂ microspheres with water glass as a silicon source is low cost,simple to operate and green environmental protection;the composite modified SiO₂microspheres obtained by surface modification avoid the defects of traditional ultraviolet absorbers and are expected to become a new type of ultraviolet absorber for cosmetics.