A hydrophilically modified silicone elastomer having moisturizing properties and a method of making the same

Abstract

The application relates to the field of daily chemical personal care, in particular to a hydrophilic modified organic silicone elastomer with moisturizing performance and a preparation method thereof, which comprises the following components: a polysiloxane containing at least three Si-H units in the molecule; a divinyl-terminated polysiloxane; a hyaluronic acid-modified monovinyl polysiloxane; a polyethylene glycol-modified vinyl polysiloxane; a carrier fluid; and a platinum metal catalyst for silicon hydrogen addition. The organic silicone elastomer is hydrophilically modified by introducing hyaluronic acid fragments and polyethylene glycol segments, the moisturizing performance of the organic silicone elastomer is improved, the organic silicone elastomer can effectively enhance the moisturizing feeling of skin in cosmetic application, and dryness and tightness are reduced. The modified elastomer has good self-emulsifying properties, can easily form a stable gel system in a water-based or water-containing formula, simplifies the emulsification process, and improves the applicability and stability of the formula.

Description

TECHNICAL FIELD

[0001] The technical scheme mainly relates to the field of daily chemical personal care, and particularly relates to a hydrophilic modified silicone elastomer with moisturizing performance and a preparation method thereof. BACKGROUND

[0002] The silicone elastomer is an excellent skin feel adjusting and viscosity adjusting cosmetic ingredient, has unique silky and powdery feel, and thus is favored by many formulators, and is applied to personal care products. As a silicone polymer with a crosslinked three-dimensional network space, the silicone elastomer can impart skin smoothness to skin care products, can effectively arrange hair, improve wet and dry combing properties of hair, and has thickening, oil reduction and other effects. However, when applied to water-based cosmetic formulations, the unmodified silicone elastomer has poor film forming effect, and the compatibility with other ingredients is also not ideal, and an emulsifier often needs to be added in the formulation, and the silicone elastomer has poor compatibility with skin sebum in actual use, lacks moisturizing effect, and the skin is prone to mud and tightness. One of the common reasons is that the compatibility of the silicone elastomer with various personal care product ingredients, active ingredients and health care active ingredients is limited, and thus how to improve the existing silicone elastomer and improve the compatibility between the silicone elastomer and the formulation components and the moisturizing feel of the skin has become one of the directions of modification of the silicone elastomer. SUMMARY

[0003] The purpose of the present application is to provide a hydrophilic modified silicone elastomer with moisturizing performance and a preparation method thereof. The silicone elastomer is hydrophilically modified by introducing a hyaluronic acid fragment and a polyethylene glycol segment, the moisturizing performance of the silicone elastomer is improved, the moisturizing feel of the skin can be effectively enhanced in cosmetic applications, and the dryness and tightness phenomenon is reduced. The modified elastomer has good self-emulsifying properties, can easily form a stable gel system in a water-based or water-containing formulation, simplifies the emulsification process, and improves the applicability and stability of the formulation.

[0004] In order to solve the above technical problems, the following technical scheme is adopted: a hydrophilic modified silicone elastomer with moisturizing performance is provided, which comprises the following components: a polysiloxane containing at least 3 Si-H units in the molecule; a divinyl-terminated polysiloxane; a hyaluronic acid modified monovinyl polysiloxane; a polyethylene glycol modified vinyl polysiloxane; a carrier fluid; and a platinum metal catalyst for silicon hydrogen addition.

[0005] Further, the weight percentage of each component is: 2-6% polysiloxane containing at least 3 Si-H units in the molecule; 0.2-1.2% hyaluronic acid modified monovinyl polysiloxane; 0.2-1.2% polyethylene glycol modified vinyl polysiloxane; 8-18% divinyl terminated polysiloxane; 75-90% carrier fluid; 0.05-0.1% platinum gold catalyst.

[0006] Further, the polysiloxane containing at least 3 Si-H units in the molecule is a polysiloxane containing at least 3 Si-H groups in the side chain, the ratio of the amount of D linkages to D' linkages in the chain is 5-20, the weight percentage of H in the Si-H group in the molecule is 0.05%-0.5%, and the molecular weight is 1000-20000.

[0007] Further, the divinyl terminated polysiloxane has a vinyl content of 0.15%-5% and a polymerization degree of 10-500, and a molecular weight of 1000-20000.

[0008] Further, the hyaluronic acid modified monovinyl polysiloxane is prepared by the following method: reacting unmodified low molecular weight hyaluronic acid with dimethyl vinyl ethoxy silane under the action of an organic titanium catalyst to form a monovinyl modified hyaluronic acid derivative.

[0009] Further, the polyethylene glycol modified vinyl polysiloxane is a monovinyl polysiloxane, wherein the vinyl content is 0.1%-0.6% and the polyethylene glycol repeating unit is 8-25.

[0010] Further, the carrier fluid is selected from one or more of low viscosity polydimethylsiloxane, decamethylcyclopentasiloxane, isomeric alkanes or natural oils with a viscosity of 1-50 mPa·s.

[0011] Further, the catalyst used for the hydrosilylation is chloroplatinic acid or Karstedt platinum gold catalyst, and the use concentration is 0.5-10 ppm.

[0012] The application also provides a preparation method of a hydrophilically modified silicone elastomer with moisturizing properties, comprising the following steps:

[0013] (1) Put the polysiloxane containing at least 3 Si-H units in the molecule, the hyaluronic acid modified monovinyl polysiloxane, the polyethylene glycol modified vinyl polysiloxane, part of the carrier fluid and the catalyst used for the hydrosilylation into a clean stirred tank, and pass N2 throughout the whole process and stir to react;

[0014] (2) After the reaction in step (1) is completed, add the divinyl terminated polysiloxane and the remaining carrier fluid into the stirred tank and continue the constant temperature reaction.

[0015] (3) After the reaction is completed, cooling to a certain temperature, continue to stir, get silicone elastomer.

[0016] Further, in step (1), the partial carrier fluid accounts for 30%-70% of the total carrier fluid, the stirring speed is 10-80 rpm / min, the reaction temperature is 50-120℃, and the reaction time is 0.5-1.5h; in step (2), the time for continuing constant temperature reaction is 2-5h; in step (3), the gel is cooled to 25-35℃, and the stirring time is 0.5-1h.

[0017] The beneficial effects of the present application are as follows:

[0018] (1) The present application improves the moisturizing performance of the silicone elastomer by introducing hyaluronic acid fragments and polyethylene glycol segments for hydrophilic modification, which can effectively enhance the moisturizing feeling of the skin and reduce dryness and tightness in cosmetic applications. The modified elastomer has good self-emulsifying properties, can easily form a stable gel system in water-based or water-containing formulations, simplifies the emulsification process, and improves the applicability and stability of the formulation.

[0019] (2) The silicone elastomer of the present application exhibits excellent compatibility and can be well compatible with various common cosmetic ingredients such as esters, fatty alcohols, silicone oils and some sunscreens, etc., avoiding the problems of separation and layering of traditional silicone elastomers, which helps to improve the overall stability and use experience of the final product.

[0020] (3) The present application further improves the absorption performance of the elastomer by optimizing the crosslinking degree and preparation process, making it easier to spread and absorb on the skin, with a smooth and silky skin feel without greasiness. The material preparation process is simple, the conditions are mild, and it is easy to scale up production, providing a new material basis for developing more functional and comfortable personal care products. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the following examples are used to further illustrate the present application. However, it should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the scope of the present application. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present application.

[0022] The following is further illustrated by specific examples:

[0023] Example 1:

[0024] A hydrophilic modified silicone elastomer with moisturizing properties is prepared by the catalysis of platinum catalyst from the following components by mass percentage: 3.75% hydrogen-containing silicone oil, 0.5% hyaluronic acid modified vinyl silicone oil, 0.5% polyethylene glycol modified silicone oil, 83.98% polydimethylsiloxane (5cst), 11.25% double-end vinyl silicone oil and 0.02% platinum catalyst. The specific preparation method is as follows: hydrogen-containing silicone oil, hyaluronic acid modified vinyl silicone oil, polyethylene glycol modified silicone oil, half of the required polydimethylsiloxane (5cst) and platinum catalyst are weighed in a stirred tank, and the reaction is carried out at 30 rpm / min and 80°C for 45 min. After the reaction is completed, double-end vinyl silicone oil and the remaining polydimethylsiloxane (5cst) are added, and the stirring speed is increased to 50 rpm / min, and the reaction is continued at 80°C for 2.5 h. After the reaction is completed, the temperature of the stirred tank is reduced to 35°C, and the stirring is continued for 30 min to obtain a silicone elastomer gel. The whole reaction is carried out under N2 protection.

[0025] Example 2:

[0026] A hydrophilic modified silicone elastomer with moisturizing properties is prepared by the catalysis of platinum catalyst from the following components by mass percentage: 3.75% hydrogen-containing silicone oil, 0.5% hyaluronic acid modified vinyl silicone oil, 0.5% polyethylene glycol modified silicone oil, 83.98% polydimethylsiloxane (5cst), 11.25% double-end vinyl silicone oil and 0.02% platinum catalyst. The specific preparation method is as follows: hydrogen-containing silicone oil, hyaluronic acid modified vinyl silicone oil, polyethylene glycol modified silicone oil, half of the required polydimethylsiloxane (5cst) and platinum catalyst are weighed in a stirred tank, and the reaction is carried out at 30 rpm / min and 80°C for 45 min. After the reaction is completed, double-end vinyl silicone oil and the remaining polydimethylsiloxane (5cst) are added, and the stirring speed is increased to 50 rpm / min, and the reaction is continued at 80°C for 2.5 h. After the reaction is completed, the temperature of the stirred tank is reduced to 35°C, and the stirring is continued for 30 min to obtain a silicone elastomer gel. The whole reaction is carried out under N2 protection.

[0027] Example 3:

[0028] A hydrophilic modified silicone elastomer with moisturizing properties is prepared by the catalysis of platinum catalyst from the following components by mass percentage: 3.75% hydrogen-containing silicone oil, 0.5% hyaluronic acid modified vinyl silicone oil, 0.8% polyethylene glycol modified silicone oil, 83.98% polydimethylsiloxane (5 cst), 10.95% double-end vinyl silicone oil and 0.02% platinum catalyst. The specific preparation method is as follows: hydrogen-containing silicone oil, hyaluronic acid modified vinyl silicone oil, polyethylene glycol modified silicone oil, half of the required polydimethylsiloxane (5 cst) and platinum catalyst are weighed in a stirred tank, and the reaction is carried out at 30 rpm / min and 80°C for 45 min. After the reaction is completed, double-end vinyl silicone oil and the remaining polydimethylsiloxane (5 cst) are added, and the stirring speed is increased to 50 rpm / min, and the reaction is continued at 80°C for 2.5 h. After the reaction is completed, the temperature of the stirred tank is reduced to 35°C, and the stirring is continued for 30 min to obtain a silicone elastomer gel. The whole reaction is carried out under N2 protection.

[0029] Example 4:

[0030] A hydrophilic modified silicone elastomer with moisturizing properties is prepared by the catalysis of platinum catalyst from the following components by mass percentage: 3.75% hydrogen-containing silicone oil, 0.5% hyaluronic acid modified vinyl silicone oil, 0.8% polyethylene glycol modified silicone oil, 83.98% polydimethylsiloxane (5 cst), 10.95% double-end vinyl silicone oil and 0.02% platinum catalyst. The specific preparation method is as follows: hydrogen-containing silicone oil, hyaluronic acid modified vinyl silicone oil, polyethylene glycol modified silicone oil, half of the required polydimethylsiloxane (5 cst) and platinum catalyst are weighed in a stirred tank, and the reaction is carried out at 30 rpm / min and 80°C for 45 min. After the reaction is completed, double-end vinyl silicone oil and the remaining polydimethylsiloxane (5 cst) are added, and the stirring speed is increased to 50 rpm / min, and the reaction is continued at 80°C for 2.5 h. After the reaction is completed, the temperature of the stirred tank is reduced to 35°C, and the stirring is continued for 30 min to obtain a silicone elastomer gel. The whole reaction is carried out under N2 protection.

[0031] Example 5:

[0032] A hydrophilic modified silicone elastomer with moisturizing properties is prepared from the following components by mass percentage under the catalysis of platinum catalyst: 3.75% hydrogen-containing silicone oil, 0.5% hyaluronic acid modified vinyl silicone oil, 0.5% polyethylene glycol modified silicone oil, 82.48% polydimethylsiloxane (5cst), 12.75% double-end vinyl silicone oil and 0.02% platinum catalyst. The specific preparation method is as follows: the hydrogen-containing silicone oil, hyaluronic acid modified vinyl silicone oil, polyethylene glycol modified silicone oil, half of the required polydimethylsiloxane (5cst) and platinum catalyst are weighed in a stirred tank, and the reaction is carried out at 30 rpm / min and 80°C for 45 min. After the reaction is completed, the double-end vinyl silicone oil and the remaining polydimethylsiloxane (5cst) are added, and the stirring speed is increased to 50 rpm / min, and the reaction is continued at 80°C for 2.5 h. After the reaction is completed, the temperature of the stirred tank is reduced to 35°C, and the stirring is continued for 30 min to obtain the silicone elastomer gel. The whole reaction is carried out under N2 protection.

[0033] Example 6:

[0034] A hydrophilic modified silicone elastomer with moisturizing properties is prepared from the following components by mass percentage under the catalysis of platinum catalyst: 3.75% hydrogen-containing silicone oil, 0.5% hyaluronic acid modified vinyl silicone oil, 0.5% polyethylene glycol modified silicone oil, 82.48% polydimethylsiloxane (5cst), 12.75% double-end vinyl silicone oil and 0.02% platinum catalyst. The specific preparation method is as follows: the hydrogen-containing silicone oil, hyaluronic acid modified vinyl silicone oil, polyethylene glycol modified silicone oil, half of the required polydimethylsiloxane (5cst) and platinum catalyst are weighed in a stirred tank, and the reaction is carried out at 30 rpm / min and 80°C for 45 min. After the reaction is completed, the double-end vinyl silicone oil and the remaining polydimethylsiloxane (5cst) are added, and the stirring speed is increased to 50 rpm / min, and the reaction is continued at 80°C for 2.5 h. After the reaction is completed, the temperature of the stirred tank is reduced to 35°C, and the stirring is continued for 30 min to obtain the silicone elastomer gel. The whole reaction is carried out under N2 protection.

[0035] Comparative Example 1:

[0036] A hydrophilic modified silicone elastomer with moisturizing properties is prepared by the catalysis of platinum catalysts from the following components by mass percentage: 3.75% hydrogen-containing silicone oil, 0.5% polyethylene glycol modified silicone oil, 83.98% polydimethylsiloxane (5cst), 11.75% double-end vinyl silicone oil and 0.02% platinum catalyst. The specific preparation method is as follows: hydrogen-containing silicone oil, hyaluronic acid modified vinyl silicone oil, polyethylene glycol modified silicone oil, half of the required polydimethylsiloxane (5cst) and platinum catalyst are weighed in a stirred tank, and the reaction is carried out at 30 rpm / min and 80°C for 45 min. After the reaction is completed, double-end vinyl silicone oil and the remaining polydimethylsiloxane (5cst) are added, and the stirring speed is increased to 50 rpm / min, and the reaction is continued at 80°C for 2.5 h. After the reaction is completed, the temperature of the stirred tank is reduced to 35°C, and the stirring is continued for 30 min to obtain the silicone elastomer gel. The whole reaction is carried out under N2 protection.

[0037] Comparative Example 2:

[0038] A hydrophilic modified silicone elastomer with moisturizing properties is prepared by the catalysis of platinum catalysts from the following components by mass percentage: 3.75% hydrogen-containing silicone oil, 0.5% polyethylene glycol modified silicone oil, 83.98% polydimethylsiloxane (5cst), 11.75% double-end vinyl silicone oil and 0.02% platinum catalyst. The specific preparation method is as follows: hydrogen-containing silicone oil, hyaluronic acid modified vinyl silicone oil, polyethylene glycol modified silicone oil, half of the required polydimethylsiloxane (5cst) and platinum catalyst are weighed in a stirred tank, and the reaction is carried out at 30 rpm / min and 80°C for 45 min. After the reaction is completed, double-end vinyl silicone oil and the remaining polydimethylsiloxane (5cst) are added, and the stirring speed is increased to 50 rpm / min, and the reaction is continued at 80°C for 2.5 h. After the reaction is completed, the temperature of the stirred tank is reduced to 35°C, and the stirring is continued for 30 min to obtain the silicone elastomer gel. The whole reaction is carried out under N2 protection.

[0039] Comparative Example 3:

[0040] A hydrophilic modified silicone elastomer with moisturizing property is prepared by using the following components by mass percentage under the catalysis of platinum catalyst: 3.75% hydrogen-containing silicone oil, 83.98% polydimethylsiloxane (5cst), 12.25% double-end vinyl silicone oil and 0.02% platinum catalyst. The specific preparation method is as follows: the hydrogen-containing silicone oil, hyaluronic acid modified vinyl silicone oil, polyethylene glycol modified silicone oil, half of the required polydimethylsiloxane (5cst) and platinum catalyst are weighed in a stirred tank, and the reaction is carried out at 30 rpm / min and 80°C for 45 min. After the reaction is completed, the double-end vinyl silicone oil and the remaining polydimethylsiloxane (5cst) are added, and the stirring speed is increased to 50 rpm / min, and the reaction is continued at 80°C for 2.5 h. After the reaction is completed, the temperature of the stirred tank is reduced to 35°C, and the stirring is continued for 30 min to obtain the silicone elastomer gel. The whole reaction is carried out under N2 protection.

[0041] The stability and application performance of the above examples and comparative examples are investigated, and the results are shown in Table 1.

[0042] Table 1 is the stability investigation result table of Examples 1 to 6 and Comparative Examples 1 to 3.

[0043]

[0044] According to the stability test results, the stability of the prepared series of silicone elastomers is good, and no oil separation, caking and other phenomena occur during the test, and the uniform viscous gel state is always maintained. And by comparing Example 1 with Example 5 and Example 6, it can be found that although the crosslinking degree of the elastomer gel is improved, the stability is still well guaranteed, that is, the preparation process of the silicone elastomer has good stability.

[0045] Application performance evaluation:

[0046] 1. Compatibility test.

[0047] The common daily chemical formula raw materials with different properties and the silicone elastomer of the application are mixed according to the proportions of 1:9 and 1:3, and the compatibility of the common cosmetic ingredients is observed after standing for 24H, and the results are shown in Table 2.

[0048] Table 2 is the compatibility test result table of the daily chemical formula raw materials with different properties and the silicone elastomers prepared in Examples 1 to 3.

[0049]

[0050] Note: compatible is C, partially compatible is PC, and incompatible is NC

[0051] From the results, it can be seen that the introduction of the polyethylene glycol segment significantly improves the compatibility of the silicone elastomer gel with some cosmetic ingredients, which also ensures the stability of the subsequent formulation.

[0052] 2. Moisturizing test.

[0053] The moisturizing performance of a product is usually tested by measuring the water loss rate on the surface of the skin. The transepidermal water loss measuring instrument is a fully portable instrument that can be used to measure the (transepidermal water loss) value and evaporation rate. In this test, 15 volunteers were selected, and three 3*3 square centimeter areas on the inner side of the arm were selected as the test area in a test room with constant temperature of 20°C and constant humidity of 50%. After washing with clean water and standing for 30 minutes, the initial value was measured. Then 0.2g of the elastomer gel sample was evenly applied to the test area, and after 30 minutes, the measurement was taken again. The moisture increase rate can be represented by the ratio of the difference between the before and after test results to the value before the sample was applied. The final results are shown in the table.

[0054] Table 3 is the moisturizing test results table of Example 1, Example 2, Example 4, Comparative Example 1 and Comparative Example 3.

[0055]

[0056] As can be seen from the table, the introduction of the hyaluronic acid segment significantly increases the moisture (Example 1 vs. Comparative Example 1), indicating that the introduction of hyaluronic acid indeed improves the moisturizing performance of the silicone elastomer. In addition, comparing Example 1 and Example 2, it can be seen that appropriately increasing the proportion of hyaluronic acid segment introduction can enhance the moisturizing performance of the prepared silicone elastomer to some extent.

[0057] 3. Absorption performance and skin feel test.

[0058] In order to test the improvement of the absorption performance of the prepared silicone elastomer after adjusting the process, Example 1, Example 5 and Example 6 were applied to an essence, and the formula is shown in Table 4.

[0059] Table 4 is the formula composition table of the silicone elastomer prepared by Example 1, Example 5 and Example 6 applied to an essence.

[0060]

[0061] To ensure the accuracy of the experimental results, the prepared formulations were respectively assigned to 15 test volunteers, about 0.025 g of the sample of the formulation was weighed, a region of the same size was drawn on the arm, and the sample was evenly applied in the region by drawing circles, until the resistance to application became large, the number of circles at this time was recorded as a reference value for the speed of absorption. The evaluation criteria are: the fewer the number of circles, the faster the sample absorbs; the more the number of circles, the slower the sample absorbs. The test is as follows: with formulation 1 as the standard, 11 people think that formulation 2 absorbs faster, and 8 people think that formulation 3 absorbs faster. It is shown that after the crosslinking degree is improved, the absorption of the elastomer sample is improved, but it is not the case that the higher the crosslinking degree, the better. It is shown that only a proper crosslinking degree can obtain a better absorption performance.

[0062] The above merely describes specific embodiments of the present application, but the technical features of the present application are not limited thereto. Any simple change, equivalent replacement or modification, etc. made on the basis of the present application to solve basically the same technical problem and realize basically the same technical effect, all fall within the protection scope of the present application.

Claims

1. A hydrophilically modified silicone elastomer having a moisturizing property, characterized in that, characterized in that, The following components are included, each component being present in a weight percentage of: Polysiloxane containing at least 3 Si-H units in the molecule 2-6%; Hyaluronic acid modified monovinyl polysiloxane 2-1.2%; Polyethylene glycol modified vinyl polysiloxane 2-1.2%; Bisvinyl terminated polysiloxane 8-18%; Carrier fluid 75-90%; Platinum metal catalyst for hydrosilylation 0.05-0.1%; The sum of the weight percentages of the components is 100%. The bisvinyl terminated polysiloxane has a vinyl content of 0.15-5% and a degree of polymerization of 10-500 and a molecular weight of 1000-20000. The polyethylene glycol modified vinyl polysiloxane is a monovinyl polysiloxane having a vinyl content of 0.1-0.6% and 8-25 polyethylene glycol repeat units.

2. The hydrophilically modified silicone elastomer with moisturizing properties according to claim 1, characterized in that: The polysiloxane containing at least 3 Si-H units in the molecule is a polysiloxane having at least 3 Si-H groups in the side chain, the ratio of the amount of D and D' segments in the segment is 5-20, the weight percentage of H in the Si-H group in the molecule is 0.05-0.5%, and the molecular weight is 1000-20000.

3. The hydrophilically modified silicone elastomer with moisturizing properties according to claim 1, characterized in that: The hyaluronic acid modified monovinyl polysiloxane is prepared by reacting unmodified low molecular weight hyaluronic acid with dimethyl vinyl ethoxy silane in the presence of an organic titanium catalyst to form a monovinyl modified hyaluronic acid derivative.

4. The hydrophilically modified silicone elastomer with moisturizing properties according to claim 1, characterized in that: The carrier fluid is selected from one or more of low viscosity polydimethylsiloxane having a viscosity of 1-50 mPa・s, decamethylcyclopentasiloxane, isomeric alkanes, or natural oils.

5. The hydrophilically modified silicone elastomer with moisturizing properties according to claim 1, characterized in that: The catalyst for hydrosilylation is chloroplatinic acid or Karstedt platinum catalyst, and the use concentration is 0.5-10 ppm.

6. A process for producing a hydrophilically modified silicone elastomer having a moisturizing property according to any one of claims 1 to 5, characterized by, The following steps are included: (1) Put the polysiloxane containing at least 3 Si-H units in the molecule, hyaluronic acid modified monovinyl polysiloxane, polyethylene glycol modified vinyl polysiloxane, part of the carrier fluid, and platinum metal catalyst for hydrosilylation into a clean stirred tank, and pass N2 throughout the whole process, and stir to react; (2) After the reaction in step (1) is completed, add bisvinyl terminated polysiloxane and the remaining carrier fluid into the stirred tank, and continue to react at a constant temperature; (3) After the reaction is completed, cool to a certain temperature, continue to stir, and obtain the silicone elastomer.

7. The method for preparing the hydrophilically modified silicone elastomer with moisturizing properties according to claim 6, characterized in that: In step (1), the part of the carrier fluid accounts for 30-70% of the total carrier fluid, the stirring speed is 10-80 rpm / min, the reaction temperature is 50-120℃, and the reaction time is 0.5-1.5 h. The constant temperature reaction in step (2) is continued for 2-5 hours; The gel in step (3) is cooled to 25-35 DEG C and stirred for 0.5-1 hour.

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