Mica powder for in-situ constructed silicon elastomer coated cosmetics and preparation method of mica powder

Abstract

The method comprises the following steps: firstly, immobilizing vinyl active groups on the surface of mica through silanization treatment, and then by taking silanized mica as a substrate, carrying out a hydrosilylation reaction between alkenyl-terminated silicone oil and hydrogen-containing polysiloxane under the catalysis of platinum, so as to obtain the mica powder for in-situ construction of silicon elastomer coated cosmetics. A silicon elastomer coating layer with a three-dimensional network structure is constructed and chemically bonded on the surface of mica in situ. The process is carried out under mild conditions, and the stability of the coating layer is ensured through chemical bonding. The surface of the obtained composite powder is changed from hydrophilic to super-hydrophobic, and the composite powder has excellent compatibility and dispersion stability with common oil phases of cosmetics such as silicone oil, esters and the like. Meanwhile, the surface silicon elastomer layer endows the powder with a unique skin feeling of smoothness, freshness and no dry feeling, and the application performance of the powder in high-end cosmetics is remarkably improved. The invention provides a new solution for developing high-performance cosmetic powder raw materials.

Description

Technical Field

[0001] This invention belongs to the field of cosmetic raw material preparation technology, specifically relating to an in-situ constructed silicon elastomer-coated mica powder for cosmetics and its preparation method. Background Technology

[0002] Mica is a commonly used powder ingredient in cosmetics. Due to its flaky structure and unique luster, it is widely used to give makeup products a pearlescent effect and improve the texture of the application. However, mica's surface is rich in hydroxyl groups, exhibiting strong hydrophilicity. This makes it poorly compatible with the hydrophobic oils commonly used in cosmetic formulations, easily leading to powder agglomeration and uneven dispersion, which in turn affects the stability of the product and the final makeup effect.

[0003] Currently, surface treatment methods for mica mainly include physical coating and surface chemical modification. For example, Chinese patent CN102007188B discloses a method for forming a coating layer on the surface of mica by high-temperature sintering of organosilicon resin. Although this method can improve water resistance, the high-temperature process may damage the crystal integrity of mica, and its improvement on skin feel is limited. Chinese patent CN104606072A uses dimethyl silicone oil for surface treatment, which is simple but has weak adhesion, and the coating layer is prone to falling off during mechanical shearing or storage.

[0004] Existing technologies generally suffer from the following problems: First, physical adsorption coatings have weak bonding with the mica surface and are easily desorbed in the presence of surfactants or solvents; second, traditional processes make it difficult to precisely control the structure and thickness of the coating layer, limiting its application in functional high-end cosmetics; third, there are no reports of achieving a fundamental breakthrough in powder performance by constructing a chemically bonded three-dimensional network structure of silicon elastomers in situ on the mica surface.

[0005] Silicon elastomers possess excellent flexibility, breathability, and a silky feel against the skin. If a stable silicon elastomer layer can be chemically constructed on the surface of mica, the compatibility issue with oil-based systems can be effectively resolved, significantly improving the user experience. Therefore, developing a technology to achieve a strong bond between mica and silicon elastomers under mild conditions is of great significance for promoting the functionalization and differentiation of high-end cosmetics. Summary of the Invention

[0006] To address the aforementioned issues, this invention discloses an in-situ constructed silicon elastomer-coated mica powder for cosmetics and its preparation method. The resulting composite powder surface changes from hydrophilic to superhydrophobic, exhibiting excellent compatibility and dispersion stability. Simultaneously, the surface silicon elastomer layer imparts a smooth, refreshing, and non-drying unique skin feel to the powder, significantly enhancing its application performance in high-end cosmetics.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: A method for preparing mica powder for cosmetics by in-situ construction of silicon elastomers includes the following steps: S1, Silanization treatment on mica surface S11. Disperse the dried mica powder in a solvent and stir thoroughly to form a uniformly dispersed suspension slurry; Furthermore, in step S11, the mica powder is one or more combinations of muscovite powder, sericite powder, or synthetic mica powder.

[0008] Furthermore, in step S11, the solvent is selected from one or more combinations of ethanol, isopropanol, isododecane, and isohexadecane, and the mass-volume ratio of mica powder to solvent is 1:5 to 1:20.

[0009] S12. Under stirring conditions, add a silane coupling agent containing unsaturated hydrocarbon groups and a pH adjuster to control the pH of the reaction system to 4.0–6.5. React at 50℃–80℃ for 2–5 hours to allow the mica surface to be grafted with vinyl active groups through dehydration condensation.

[0010] Furthermore, in step S12, the silane coupling agent containing unsaturated hydrocarbon groups is one or more combinations of vinyltrimethoxysilane and vinyltriethoxysilane.

[0011] Furthermore, in step S12, the pH adjuster is one or more combinations of acetic acid, citric acid, hydrochloric acid, and phosphoric acid.

[0012] S13. After the reaction is complete, the mica powder is separated, washed and dried to obtain surface-functionalized mica powder.

[0013] S2, In-situ construction of silicon elastomers on mica surfaces.

[0014] S21. The silanized mica powder obtained in step S13 is redispersed in the solvent and stirred thoroughly to form a uniformly dispersed suspension slurry.

[0015] S22. Add terminal alkenyl silicone oil, hydrogen-containing polysiloxane and platinum catalyst sequentially to the slurry obtained in step S21, and react at 60℃–90℃ for 2–6 hours under an inert atmosphere to form a chemically bonded three-dimensional silicon elastomer network structure on the mica surface through hydrosilylation reaction.

[0016] Furthermore, in step S22, the terminal alkenyl silicone oil is a terminal vinyl polydimethylsiloxane with a viscosity of 100 mPa·s to 10,000 mPa·s at 25°C.

[0017] Furthermore, in step S22, the hydrogen-containing polysiloxane is a hydrogen-containing methyl polysiloxane or a hydrogen-containing terminal polydimethylsiloxane, and its active hydrogen content is 0.05% to 1.5%.

[0018] Furthermore, in step S22, the platinum catalyst, calculated as platinum metal, is added in an amount of 5 ppm to 100 ppm of the total mass of the terminal alkenyl silicone oil and the hydrogen-containing polysiloxane.

[0019] Furthermore, in step S22, during the hydrosilylation reaction, the molar ratio of Si-H bonds to Si-Vi bonds is controlled to be (0.8–2.0):1.

[0020] S3. Purification and post-treatment of composite powder of mica coated with silicon elastomer.

[0021] S31. The slurry obtained in step S22 is separated by centrifugation or filtration to obtain a solid semi-finished cake. S32. Add solvent to the cake obtained in step S31 and wash it to remove unreacted substances and catalyst residues to obtain the cake product. S33. The cake obtained in step S32 is vacuum dried, crushed and dispersed and sieved to obtain a composite powder with good flowability.

[0022] The beneficial effects of this invention are as follows: 1. The prepared composite powder has a significant improvement in skin feel. Due to the low coefficient of friction and elasticity of the surface silicon elastomer layer, it is smooth and uniform when applied, and after film formation, it presents a comfortable touch that is dry but not drying. 2. By utilizing the surface energy matching principle, the silicon elastomer coating transforms mica from hydrophilic to hydrophobic, greatly improving its compatibility with cosmetic oil-phase systems, effectively preventing aggregation, and enhancing dispersion stability. 3. The silicon elastomer is firmly bonded to the mica surface through Si-O-Si covalent bonds, resulting in high bonding strength and resistance to mechanical shearing and temperature changes. The stability of the coating layer is significantly better than that of physical adsorption treatment methods. Attached Figure Description

[0023] Figure 1 Scanning electron microscope image of the complex in Example 1.

[0024] Figure 2 Scanning electron microscope image of the complex in Example 2.

[0025] Figure 3 Scanning electron microscope image of the complex in Example 3.

[0026] Figure 4 Scanning electron microscope images of the comparative complexes.

[0027] Figure 5 Examples 1-3 and comparative contact angle diagrams. Detailed Implementation

[0028] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Example

[0029] A method for preparing mica powder for cosmetics by in-situ construction of silicon elastomers includes the following steps: (1) Silanization of mica surface: 100 g of dry mica powder was dispersed in 1000 mL of isopropanol and dispersed for 30 minutes under mechanical stirring. 1% acetic acid aqueous solution was added dropwise to adjust the pH to 5.0. 5 g of vinyltrimethoxysilane was slowly added and the temperature was raised to 65 °C for 3 hours. After the reaction was completed, the mixture was filtered, washed 3 times with ethanol, and dried under vacuum at 80 °C for 4 hours to obtain silanized mica.

[0030] (2) In-situ construction of silicon projectile: The above-mentioned silanized mica was dispersed in 800 mL of isododecane, and 30 g of vinyl-terminated polydimethylsiloxane (viscosity 1000 mPa·s), 3 g of hydrogen-terminated polydimethylsiloxane (hydrogen content 0.8%) and platinum catalyst (20 ppm platinum) were added in sequence. Under nitrogen protection, the reaction was carried out at 75 °C for 4 hours, and the molar ratio of Si-H to Si-Vi was controlled to be about 1.2:1.

[0031] (3) Purification and post-treatment: After cooling the reaction solution, centrifuge to separate it, wash with ethanol 3–5 times until the washing solution is clear, vacuum dry at 80℃ for 6 hours, crush and disperse and sieve to obtain white composite powder. Example

[0032] An in-situ constructed silicon elastomer-coated mica powder for cosmetics and its preparation method include the following steps: (1) Silanization of mica surface: 100 g of dry sericite powder was dispersed in 1500 mL of ethanol and dispersed for 30 minutes under mechanical stirring. The pH was adjusted to 4.0 with citric acid, and 15 g of vinyltriethoxysilane was added. The reaction was carried out at 50 °C for 5 hours. The post-treatment was the same as in Example 1.

[0033] (2) In-situ construction of silicon elastomer: silanized mica powder was redispersed in isododecane, and 10 g of vinyl-terminated polydimethylsiloxane (viscosity 100 mPa·s), 0.5 g of hydrogen-containing polysiloxane (hydrogen content 1.5%) and platinum catalyst (100 ppm) were added. The reaction was carried out at 60 °C for 6 hours under nitrogen atmosphere. The molar ratio of Si-H to Si-Vi was about 0.8:1.

[0034] (3) Post-processing: The product was collected by filtration, washed with isopropanol, dried under vacuum at 80°C for 6 hours, and sieved to obtain silicon elastomer coated sericite powder. Example

[0035] An in-situ constructed silicon elastomer-coated mica powder for cosmetics and its preparation method include the following steps: (1) Silanization of mica surface: 100 g of dry synthetic mica powder was dispersed in 500 mL of isododecane and dispersed for 40 minutes under mechanical stirring. The pH was adjusted to 6.5 with dilute hydrochloric acid, and 2 g of vinyltrimethoxysilane was added. The reaction was carried out at 80 °C for 2 hours. The post-treatment was the same as in Example 1.

[0036] (2) In-situ construction of silicon elastomer: Silanized mica powder was dispersed in isopropanol, and 60 g of vinyl-terminated polydimethylsiloxane (viscosity 10,000 mPa·s), 10 g of hydrogen-containing polysiloxane (hydrogen content 0.05%) and platinum catalyst (5 ppm) were added. The reaction was carried out at 90 °C for 2 hours under nitrogen atmosphere. The molar ratio of Si-H to Si-Vi was about 2.0:1.

[0037] (3) Post-processing: After the reaction solution is cooled, it is centrifuged, washed with ethanol, dried under vacuum at 100°C for 4 hours, and sieved to obtain silicon elastomer-coated synthetic mica powder.

[0038] Comparative Example 30 g of vinyl-terminated polydimethylsiloxane, 3 g of hydrogen-containing polysiloxane and platinum catalyst were mixed in isododecane and reacted at 75°C for 4 hours to generate a silicon elastomer. Then 100 g of untreated muscovite was added and the mixture was stirred for another 2 hours. The post-treatment was the same as in Example 1 to obtain a physically mixed powder.

[0039] Composite Powder Performance Testing Human skin feel test: The examples and comparative examples were randomly numbered, and 10 volunteers were selected to be tested separately. They used their index fingers to take an appropriate amount of sample powder and spread it for 5cm length 10cm above their wrists. The application feeling was evaluated. Easy application and smooth skin feel indicate that the powder has a good skin feel. The test results are shown in Table 1.

[0040] Table 1. Record of Complex Human Skin Feel Test

[0041] Friction coefficient test: Apply 0.3-0.5g of powder to the artificial leather (evenly spread) and place it on the friction coefficient meter for testing. The smaller the friction coefficient, the smoother the powder feels to the skin. The test results are shown in Table 2.

[0042] Table 2 Friction Coefficient Test Record Table

[0043] The test results of the friction coefficient meter show that Example 1 has the smoothest skin feel, followed by Example 3 and Example 2, while the comparative example has the worst skin feel, which is the same as the human skin feel test.

[0044] Compatibility test: 0.5g of the test sample was added to 10g of commonly used cosmetic oil esters of different polarities (cyclopentamethoxysiloxane, caprylic / capric triglyceride, squalane), and the mixture was vortexed for 1 minute. The initial dispersion state was then observed. The test results are shown in Table 3.

[0045] Table 3. Record of Composite Compatibility Test

[0046] Excellent compatibility with silicone oils: All examples exhibited optimal dispersibility in cyclopentamethoxysiloxane. This is because the present invention, through surface silicon elastomerization, transforms the powder from hydrophilic to hydrophobic-oleophilic (especially silicone-loving oil), whose surface properties and refractive index are highly compatible with silicone oils, thus forming a homogeneous dispersion system. Examples 1 and 3 also showed good to excellent compatibility in moderately polar ester and hydrocarbon oils such as caprylic / capric triglycerides and squalane. This demonstrates the universality of the surface modification method provided by the present invention, which can significantly improve the performance of powders in various cosmetic oil phases. Comparative examples (physical mixing): Due to the ineffective modification of the mica surface, dispersion with the oil phase was difficult.

[0047] Hydrophobicity test: Using a contact angle meter, the test powder is pressed into a dense thin sheet on a tablet press. In an aqueous environment, the static contact angle of water droplets on the powder surface is measured. The larger the contact angle, the stronger the hydrophobicity of the powder surface and the better the compatibility with the organic phase. The test results are shown in Table 4.

[0048] Table 4. Record of Contact Angle Test of Composite Material

[0049] The water contact angles of the powder surfaces in Examples 1-3 are all greater than 135°, exhibiting superhydrophobicity, proving that their surfaces have been successfully transformed from hydrophilic mica to hydrophobic organosilicon materials. The comparative examples, however, retain their hydrophilic nature.

[0050] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing mica powder for cosmetics by in-situ construction of silicon elastomers, characterized in that, Includes the following steps: S1, Silanization treatment of mica surface S11. Disperse the dried mica powder in a solvent and stir thoroughly to form a uniformly dispersed suspension slurry; S12. Under stirring conditions, add a silane coupling agent containing unsaturated hydrocarbon groups and a pH adjuster to control the pH of the reaction system to 4.0–6.5, and react at 50℃–80℃ for 2–5 hours to allow the mica surface to be grafted with vinyl active groups through dehydration condensation. S13. After the reaction is complete, the mica powder is separated, washed and dried to obtain surface-functionalized mica powder. S2, In-situ construction of silicon projectiles on mica surface S21. The silanized mica powder obtained in step S13 is redispersed in a solvent and stirred thoroughly to form a uniformly dispersed suspension slurry. S22. Add terminal alkenyl silicone oil, hydrogen-containing polysiloxane and platinum catalyst sequentially to the slurry obtained in step S21, and react at 60℃–90℃ for 2–6 hours under an inert atmosphere to form a chemically bonded three-dimensional silicon elastomer network structure on the mica surface through hydrosilylation reaction. S3. Purification and post-treatment of composite powders of silicon elastomer-coated mica S31. The slurry obtained in step S22 is separated by centrifugation or filtration to obtain a solid semi-finished cake. S32. Add solvent to the cake obtained in step S31 and wash it to remove unreacted substances and catalyst residues to obtain the cake product. S33. The cake obtained in step S32 is vacuum dried, crushed and dispersed and sieved to obtain a composite powder with good flowability.

2. The method for preparing mica powder for cosmetics by in-situ construction of silicon elastomers according to claim 1, characterized in that, In step S11, the mica powder is one or more of muscovite powder, sericite powder, or synthetic mica powder.

3. The method for preparing mica powder for cosmetics by in-situ construction of silicon elastomers according to claim 1, characterized in that, In step S11, the solvent is selected from one or more combinations of ethanol, isopropanol, isododecane, and isohexadecane, and the mass-volume ratio of mica powder to solvent is 1:5 to 1:

20.

4. The method for preparing mica powder for cosmetics by in-situ construction of silicon elastomers according to claim 1, characterized in that, In step S12, the silane coupling agent containing unsaturated hydrocarbon groups is one or more combinations of vinyltrimethoxysilane and vinyltriethoxysilane.

5. The method for preparing mica powder for cosmetics by in-situ construction of silicon elastomers according to claim 1, characterized in that, In step S12, the pH adjuster is one or more combinations of acetic acid, citric acid, hydrochloric acid, and phosphoric acid.

6. The method for preparing mica powder for cosmetics by in-situ construction of silicon elastomers according to claim 1, characterized in that, In step S22, the terminal alkenyl silicone oil is a terminal vinyl polydimethylsiloxane with a viscosity of 100 mPa·s to 10,000 mPa·s at 25°C.

7. The method for preparing mica powder for cosmetics by in-situ construction of silicon elastomers according to claim 1, characterized in that, In step S22, the hydrogen-containing polysiloxane is a hydrogen-containing methyl polysiloxane or a hydrogen-containing terminal polydimethylsiloxane, and its active hydrogen content is 0.05% to 1.5%.

8. The method for preparing mica powder for cosmetics by in-situ construction of silicon elastomers according to claim 1, characterized in that, In step S22, during the hydrosilylation reaction, the molar ratio of Si-H bonds to Si-Vi bonds is controlled to be (0.8–2.0):

1.

9. A method for preparing mica powder for cosmetics by in-situ construction of silicon elastomers according to claim 1, characterized in that, In step S22, the platinum catalyst, calculated as platinum metal, is added in an amount of 5 ppm to 100 ppm of the total mass of the terminal alkenyl silicone oil and the hydrogen-containing polysiloxane.

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