Surface Modification Technology of Titanium Dioxide Powder for Cosmetics——Organic Surface Modification Technology


INTRODUCTION: The use of surface-modified titanium dioxide powders in the field of fine chemicals, cosmetics, is becoming more widespread. Modification of the surface of titanium dioxide powder by various inorganic and organic surface treatments can greatly improve the weather resistance, skin feel, water repellency, oleophobicity, or hydrophilicity and lipophilicity of titanium dioxide powder. Wait. In view of this, it is necessary to analyze and summarize the surface modification technology of titanium dioxide powder for cosmetics, and it is also useful for research and development, production and application.


There are many types of surface treatment agents, and the treatment agents are classified into organic surface treatment agents and inorganic surface treatment agents according to chemical properties. Inorganic surface treatment agents are generally used, such as hydrated silica, hydrated alumina, and the like. The effect of the inorganic surface treatment is generally to shield the photocatalytic activity of the titanium dioxide powder, and to improve durability and optical superiority. The organic surface treatment agent includes an aluminate coupling agent, stearic acid, a titanate coupling agent, a stearate, a silane coupling agent, a perfluorophosphate, and the like. The purpose of the surface treatment of the organic substance is to enhance the wet dispersibility, skin feel, water repellency, oleophobicity, or hydrophilicity, lipophilicity and the like in the cosmetic system of the titanium dioxide powder. The silicon-aluminum composite and single-aluminum coating in the previous article "Surface modification technology of titanium dioxide powder for cosmetics - inorganic surface modification technology" is not enough, and some surface modification of organic matter is required.


First, the common surface modification technology of titanium dioxide
1, silane coupling agent treatment


a. Triethoxy octylsilane surface treatment


Triethoxyoctylsilane is one of the silane coupling agents commonly used in titanium dioxide for cosmetics. Triethoxyoctylsilane is a very easy-to-react surface treatment agent. In the case of water, Si-O bonds can be rapidly The hydrolysis reaction forms a silanol. This reaction is particularly suitable for the treatment of metal oxides. Upon completion of the reaction, all of the ethoxy groups are replaced and the octylsilane crosslinks on the surface of the pigment to form a very stable surface coating, even at low pH.


The silane-treated pigments are well dispersed in cyclopentasiloxane, they have very low surface tension and good hydrophobicity. However, sometimes the wettability is poor in ordinary organic carriers, and the treatment with triethoxyoctylsilane not only provides the best water repellency, but also makes it easy to disperse in the ester due to the lipophilic octyl group. , minerals and silicone oils. It achieves a higher level of pigment loading than methylsiloxane treated surface pigments. The triethoxyoctylsilane treated pigment has stable physicochemical properties, and is stable even at pH = 3, without residual methanol. Since there is no Si-H bond, there is no danger of releasing hydrogen.


b. Polydimethylsilane surface treatment


Polydimethylsilane is a kind of dimethyldichlorosilane as the main raw material, which is separated or rectified on the basis of the hydrolyzate obtained by the hydrolysis synthesis process, or after the hydrolyzate is cracked or based on DMC. The compound obtained after separation and rectification. It is widely used in cosmetics and body care products and has good compatibility with most alcohols and other cosmetic solvents. Therefore, polydimethylsiloxane is harmless to the human body and does not harm the skin. Polydimethylsiloxane chemical state dimethyl silicone oil, colorless or light yellow liquid, odorless, high transparency, heat resistance, cold resistance, viscosity change with temperature, water resistance, surface tension, heat conduction Sexual, non-toxic and tasteless, physiologically inert, and good chemical stability. In addition to direct use, polydimethylsiloxane is easy to be impregnated, sprayed, and improved in efficiency in order to disperse the methyl silicone oil. It can also be used in three types: solution type, lipid type and emulsion type. It and its derivatives are high-quality raw materials for cosmetics, with good skin care functions, and are synthetic fats in cosmetic raw materials. Non-toxic, non-irritating to the skin and mucous membranes, but irritating to the eyes, generally recognized as safe. The titanium dioxide treated with polydimethylsiloxane disperses well in silicone oil, leaving skin smooth, fresh, breathable and long-lasting.


c. Fluorosilane surface treatment


The fluorosilane surface-treated titanium dioxide pigment not only has hydrophobic properties, but also has low surface tension, and the fluorosilane surface-treated pigment also has oleophobicity. These characteristics can be directly measured by the "bead effect" amount of the surface of the powder cake being greater than 135 degrees. In addition, since the fluorosilane is chemically bonded to the surface of the pigment, it provides a stable environment and prevents surface treatment from being removed.


Fluorosilane surface treatment (0.08-2%) prevents pigments from accumulating in fine lines and wrinkles, and also helps pigments spread well and conform to the skin surface. The skin-friendly properties of fluorosilane surface treatment pigments make these treated pigments durable even in the presence of sebum and water. Through the repulsion of sebum and pigment on the surface of the skin, the residue of the oil is reduced, and the phenomenon of darkening of the color is less observed than other surface treatments.


The fluorosilane treatment material can be used for long-lasting liquid foundations, wet and dry foundations, and pressed powders, as well as for improving water repellency and durability in mascara. Using this surface treatment can give the product a better lasting effect and oil control effect. Unlike early fluorine treatment, the new fluorosilane surface treatment does not release the risk of potentially irritating perfluorooctanoic acid PFOA, so it is safer.


2, titanate surface treatment


Surface treatment of isopropoxytitanyl triisostearate. Since the O-Ti bond in the isopropoxy titanyl triisostearate is easily reacted with the hydroxyl group, the isopropoxy group is easily substituted, and thus the isopropoxy titanyl triisostearate is used for all the pigments. It exhibits excellent activity and forms a uniform coating of lipophilic isostearic acid groups. There are a large number of fatty acid ester groups on the treated surface, so the titanate-treated pigments are easily wetted and dispersed in organic media such as esters, mineral oil and petrolatum. The oil absorption is greatly reduced, and the loading of the pigment in the formulation is increased.


The unique properties of titanate treatment can be best achieved by dispersing surface treated titanium dioxide in esters: compared to untreated or polymethylsiloxane or silane treated titanium dioxide, after triisostearic acid The viscosity of the propionate is greatly reduced after treatment.


Pigments and powders treated with isopropoxy titanyl stearate can be dispersed in a variety of esters, natural oils and hydrocarbons at a solids content of more than 70%. Optimizing the amount of solids in the dispersion will maximize the properties of the pigment.


Since the pigment treated with triisostearate is very easy to disperse and has a very good affinity for the skin, it can be used to develop dry (non-greasy) cream powder products, one-step makeup products, New liquid foundation, blush, eye shadow and sunscreen formulations can be developed.


3. Lauroyl lysine surface treatment


Surfactants and conditioners are amino acid derivatives made from natural coconut oil fatty acids. It is most commonly used as a hair and skin conditioner and can be added to the product to help the solvent colloidalize to improve the texture of the product. Laurelyl lysine can be used not only in combination with hair skin conditioning or cream gel products, but also in eye shadow and powder products. Studies have shown that the lysine component of lauroyl lysine is helpful in treating (not healing) cold sores because it inhibits the replication of herpesviruses. The lauryl lysine wet-precipitation coating imparts a good smoothness and excellent skin affinity to the powder.


4. Stearic acid surface treatment


Stearic acid is suitable for use in a variety of cosmetics, as a base, especially suitable for creams and lotions; stearyl stearyl alcohol is most often derived from stearic acid, or animal fat, although it can also come from cocoa or shea butter. Its emollient, softening and properties make it a good ingredient for beauty products. Coating the surface of titanium dioxide with stearic acid can improve the adaptability of the product.


Second, the envelope example
The organic coating of titanium dioxide may be composite coated or separately coated, and various products may be available depending on the type of coating and the amount of coating. A brief introduction to a surface treatment example is now available.


1 Kg of single aluminum-coated titanium oxide, 10 g of fluorosilane was dissolved in 70 g of ethanol to prepare a treatment liquid. Under high-speed stirring, the treatment liquid is sprayed into the single aluminum-coated titanium dioxide, heated at 80 ° C, stirred at a high speed, and the treatment liquid and the powder are thoroughly mixed, and then heat-treated at 120 ° C, and after being pulverized by air flow, 1% fluorosilane treatment is obtained. Titanium dioxide. After surface treatment, a cosmetic titanium dioxide pigment powder which is hydrophobic, oleophobic, silky, skin-friendly and spreadable is obtained.






Process chart for organic surface modification of cosmetics


Third, summary
Due to the untreated, the stability of the formulation and the stability of the dispersion will be somewhat deficient, and the chemical properties will be insufficient. After the treatment, the titanium dioxide powder can greatly improve the above defects, and the performance and the like are improved. It can improve the wettability of titanium dioxide powder in liquid, improve coating, skin feel and contamination, and also improve the stability of the formulation.


With the continuous development of fine chemicals science and technology, and the increasing demand for cosmetics performance by consumers, organic surface treatment technology will have further development, and new progress will be made in the selection, dosage and treatment of modified treatment agents.