Preparation method of silica sol with high storage stability and silica sol with high storage stability

Abstract

The invention provides a preparation method of silica sol with high storage stability and the silica sol with high storage stability, the preparation method comprises the following steps: (1) uniformly mixing methyltrimethoxysilane, tetraethyl orthosilicate and a silane coupling agent to obtain a solution A; (2) adding the solution A into an alcohol-water mixed solvent to obtain a mixed solution B; (3) carrying out synergistic hydrolysis and polycondensation on methyltrimethoxysilane, tetraethyl orthosilicate and a silane coupling agent in the mixed solution B to form an oligomer, so as to obtain a solution C; (4) adding benzotriazole into the solution C, and reacting until the solution is clear and transparent; and (5) aging the product obtained in the step (4) to obtain the silica sol with high storage stability. A silica sol synthesis process is simplified by adopting one-step co-hydrolysis of a silane coupling agent and a precursor, and the stability of the silica sol is improved by synergistically loading benzotriazole and the silane coupling agent.

Description

Technical Field

[0001] The invention relates to the technical field of silica sol, and in particular to a preparation method of silica sol with high storage stability and the silica sol with high storage stability. Background Art

[0002] Sol-gel technology has the characteristics of low synthesis energy consumption, controllable composition and mild synthesis temperature, which makes it widely used in the preparation of corrosion-resistant coatings for metal materials. Siloxane materials have gradually replaced traditional chromium materials with their excellent film-forming properties, low toxicity and green environmental protection.

[0003] Compared with traditional organic coatings, the corrosion-resistant coating prepared with silica sol as the film-forming material has obvious improvements in water resistance, heat resistance and mechanical properties. The storage stability of silica sol is an important factor limiting its large-scale application.

[0004] At present, a large number of research works have been carried out on improving the storage stability of silica sol. For example, the patent application with publication number CN118790998A provides a method for improving the long-term stability of silica sol by modifying the silica sol. The commercial silica sol is modified by hydroxylation and amino. After modification, it is washed with toluene and ethanol, and then vacuum dried to obtain modified silica gel. The silica gel is dispersed in a certain amount of ethanol, aldehyde compounds are added, and the modified silica sol is obtained by stirring and dispersing at a certain temperature.

[0005] The patent application with publication number CN114874645A provides a method for preparing high-stability silica sol using tetraethyl orthosilicate as a precursor and fluorinated silane as a modifier, wherein the precursor, modifier, ethanol and silane coupling agent are stirred and mixed under sealed conditions to prepare high-stability silica sol. The existing technology mainly uses modifiers to modify silica sol to improve the storage stability of silica sol.

[0006] It can be seen from the above-mentioned patent documents that some methods have problems such as complicated preparation process, and the modifiers and solvents are not environmentally friendly, which to a certain extent limits their large-scale application. Summary of the invention

[0007] Based on the above technical problems existing in the prior art, the present invention provides a method for preparing a silica sol with high storage stability and a silica sol with high storage stability, which simplifies the silica sol synthesis process by one-step co-hydrolysis of a silane coupling agent and a precursor, and improves the stability of the silica sol by synergistically loading benzotriazole and a silane coupling agent.

[0008] The present invention provides a method for preparing a silica sol with high storage stability, comprising the following steps:

[0009] (1) Methyltrimethoxysilane (CAS: 1185-55-3), tetraethyl orthosilicate (CAS: 78-10-4) and a silane coupling agent are uniformly mixed to obtain a solution A; the silane coupling agent is at least one of 3-(methacryloyloxy)propyltrimethoxysilane (KH570, CAS: 2530-85-0) and 3-(2,3-epoxypropyloxy)propyltrimethoxysilane (KH560, CAS: 2530-83-8);

[0010] (2) adding solution A to an alcohol-water mixed solvent to obtain a mixed solution B;

[0011] (3) methyltrimethoxysilane, tetraethyl orthosilicate and silane coupling agent in the mixed solution B are synergistically hydrolyzed and polycondensed to form oligomers to obtain solution C;

[0012] (4) Add benzotriazole (CAS: 95-14-7) to solution C and react until the solution becomes clear and transparent;

[0013] (5) The product obtained in step (4) is aged to obtain the silica sol with high storage stability.

[0014] Principle description:

[0015] By optimizing the stoichiometry of silane, reaction temperature, and pH value of the reaction system during the synthesis of silica sol, the silane coupling agent and the polysilane precursor are co-hydrolyzed and polycondensed to form oligomers in one step, simplifying the synthesis process of silica sol. In addition, by introducing benzotriazole into the sol system, the corrosion resistance of the silica sol is improved while the steric hindrance between the silane colloidal particles is enhanced, and a silica sol with excellent storage stability is prepared.

[0016] Preferably, in step (1), the molar ratio of methyltrimethoxysilane, tetraethyl orthosilicate and silane coupling agent is 1:1:2-3.

[0017] Preferably, in step (2), the molar ratio of alcohol to water in the alcohol-water mixed solvent is 1:1; and the alcohol in the alcohol-water mixed solvent is at least one of ethanol and isopropanol.

[0018] Preferably, in step (2), the ratio of the total molar number of each substance in solution A to the molar number of water in the alcohol-water mixed solvent is 1:4.

[0019] Preferably, in step (3), the pH of the mixed solution B is adjusted to 3-4, and the mixed solution B after the pH adjustment is reacted at 60-80° C. for 6-10 hours, and the reaction time is preferably 6 hours.

[0020] Preferably, in step (4), the molar ratio of the silane coupling agent to benzotriazole is 7 to 10:1.

[0021] Preferably, in step (5), the aging time is not less than 24 hours. Aging means standing at room temperature. During the aging process, the colloidal particles further aggregate and gradually reach a stable state.

[0022] The present invention also provides a silica sol with high storage stability prepared by the above preparation method.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. Silane material is an environmentally friendly raw material with great prospects in the current corrosion protection field. The present invention uses silane as a sol precursor and anhydrous ethanol and other alcohols as solvents, which effectively avoids the problem of using toluene and fluorine-containing modifiers in the existing technology for improving the stability of silica sol, so that the silica sol prepared by the present invention has good environmental performance.

[0025] 2. The present invention can not only achieve long-term stable storage of silica sol but also improve the corrosion resistance of silica sol by synergistically loading silane coupling agent and benzotriazole.

[0026] 3. The present invention synthesizes silica sol by one-step co-hydrolysis of silane raw materials and silane coupling agents, avoiding the process of step-by-step hydrolysis required in the existing process, greatly simplifying the synthesis process of silica sol, improving production efficiency, and facilitating large-scale production of silica sol. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The particle size distribution and actual photo of the silica sol prepared in Example 1. DETAILED DESCRIPTION

[0028] Example 1

[0029] A method for preparing a silica sol with high storage stability comprises the following steps:

[0030] (1) 0.01 mol of methyltrimethoxysilane, 0.01 mol of tetraethyl orthosilicate and 0.02 mol of KH560 were mixed to obtain solution A;

[0031] (2) Mix 0.16 mol of anhydrous ethanol and 0.16 mol of distilled water to prepare an alcohol-water mixed solvent;

[0032] (3) adding solution A to the above alcohol-water mixed solvent to obtain a mixed solution B, and adjusting the pH value of the system to 3 using phosphoric acid;

[0033] (4) The pH-adjusted mixed solution B was transferred to a three-necked flask and stirred at 80°C for 6 h;

[0034] (5) adding 0.002 mol of benzotriazole to the product obtained in step (4), and continuing the reaction for 2 h until the solution becomes clear and transparent;

[0035] (6) The product obtained in step (5) was aged for 24 hours to obtain silica sol. The particle size distribution and actual photo of the silica sol are shown in Figure 1 .

[0036] The above steps (1) to (3) are all carried out at room temperature, and the stirring speed during mixing is 300 r / min.

[0037] In steps (4) and (5), the reaction stirring rate is 600 r / min.

[0038] The silica sol prepared by the method can be stably stored at room temperature for more than one year.

[0039] Example 2

[0040] A method for preparing a silica sol with high storage stability comprises the following steps:

[0041] (1) 0.01 mol of methyltrimethoxysilane, 0.01 mol of tetraethyl orthosilicate and 0.03 mol of KH560 were mixed to obtain solution A;

[0042] (2) Mix 0.2 mol of anhydrous ethanol and 0.2 mol of distilled water to prepare an alcohol-water mixed solvent;

[0043] (3) adding solution A to the above alcohol-water mixed solvent to obtain a mixed solution B, and adjusting the pH value of the system to 3 using phosphoric acid;

[0044] (4) The pH-adjusted mixed solution B was transferred to a three-necked flask and stirred at 80°C for 6 h;

[0045] (5) adding 0.003 mol of benzotriazole to the product obtained in step (4), and continuing the reaction for 2 h until the solution becomes clear and transparent;

[0046] (6) The product obtained in step (5) is aged for 24 hours to obtain silica sol.

[0047] The above steps (1) to (3) are all carried out at room temperature, and the stirring speed during mixing is 300 r / min.

[0048] In steps (4) and (5), the reaction stirring rate is 600 r / min.

[0049] The silica sol prepared by the method can be stably stored at room temperature for more than one year.

[0050] Example 3

[0051] A method for preparing a silica sol with high storage stability comprises the following steps:

[0052] (1) 0.01 mol of methyltrimethoxysilane, 0.01 mol of tetraethyl orthosilicate and 0.02 mol of KH570 were mixed to obtain solution A;

[0053] (2) taking 0.16 mol of isopropanol and 0.16 mol of distilled water and mixing them evenly to prepare an alcohol-water mixed solvent;

[0054] (3) adding solution A to the above alcohol-water mixed solvent to obtain a mixed solution B, and adjusting the pH value of the system to 4 using phosphoric acid;

[0055] (4) The pH-adjusted mixed solution B was transferred to a three-necked flask and stirred at 60°C for 6 h;

[0056] (5) adding 0.0025 mol of benzotriazole to the product obtained in step (4), and continuing the reaction for 2 h until the solution becomes clear and transparent;

[0057] (6) The product obtained in step (5) is aged for 24 hours to obtain silica sol.

[0058] The above steps (1) to (3) are all carried out at room temperature, and the stirring speed during mixing is 200 r / min.

[0059] In steps (4) and (5), the reaction stirring rate is 500 r / min.

[0060] The silica sol prepared by the method can be stably stored at room temperature for more than one year.

[0061] Example 4

[0062] A method for preparing a silica sol with high storage stability comprises the following steps:

[0063] (1) 0.035 mol of methyltrimethoxysilane, 0.035 mol of tetraethyl orthosilicate and 0.07 mol of KH560 were mixed to obtain solution A;

[0064] (2) Mix 0.56 mol of anhydrous ethanol and 0.56 mol of distilled water to prepare an alcohol-water mixed solvent;

[0065] (3) adding solution A to the above alcohol-water mixed solvent to obtain a mixed solution B, and adjusting the pH value of the system to 3 with nitric acid;

[0066] (4) Transfer the pH-adjusted mixed solution B to a three-necked flask and stir the reaction at 70°C for 6 h;

[0067] (5) adding 0.01 mol of benzotriazole to the product obtained in step (4), and continuing the reaction for 2 h until the solution becomes clear and transparent;

[0068] (6) The product obtained in step (5) is aged for 24 hours to obtain silica sol.

[0069] The above steps (1) to (3) are all carried out at room temperature, and the stirring speed during mixing is 300 r / min.

[0070] In steps (4) and (5), the reaction stirring rate is 600 r / min.

[0071] The silica sol prepared by the method can be stably stored at room temperature for more than one year.

[0072] Example 5

[0073] A method for preparing a silica sol with high storage stability comprises the following steps:

[0074] (1) 0.01 mol of methyltrimethoxysilane, 0.01 mol of tetraethyl orthosilicate and 0.02 mol of KH560 were mixed to obtain solution A;

[0075] (2) Mix 0.16 mol of anhydrous ethanol and 0.16 mol of distilled water to prepare an alcohol-water mixed solvent;

[0076] (3) adding solution A to the alcohol-water mixed solvent to obtain a mixed solution B, and adjusting the pH value of the system to 4 with nitric acid;

[0077] (4) The pH-adjusted mixed solution B was transferred to a three-necked flask and stirred at 80°C for 6 h;

[0078] (5) adding 0.002 mol of benzotriazole to the product obtained in step (4), and continuing the reaction for 2 h until the solution becomes clear and transparent;

[0079] (6) The product obtained in step (5) is aged for 24 hours to obtain silica sol.

[0080] The above steps (1) to (3) are all carried out at room temperature, and the stirring speed during mixing is 300 r / min.

[0081] In steps (4) and (5), the reaction stirring rate is 600 r / min.

[0082] The silica sol prepared by the method can be stably stored at room temperature for more than one year.

[0083] Comparative Example 1

[0084] The "pH value is 3" in step (3) of Example 4 was replaced by "pH value is 8", and the remaining steps were the same as Example 4. The obtained silica sol could only be stored at room temperature for 7 days before gelling occurred.

[0085] Comparative Example 2

[0086] In step (1) of Example 4, "KH560" was replaced by "3-aminopropyltriethoxysilane (KH550, CAS: 919-30-2)", and the remaining steps were the same as those of Example 4. The prepared silica sol showed gelation after 2 days.

[0087] Comparative Example 3

[0088] Referring to the method described in patent application CN1831069A, 0.025 mol 3-glycidyloxypropyltrimethoxysilane (GPTS), 0.075 mol isopropanol and 0.075 mol distilled water were mixed evenly, and nitric acid solution was slowly added dropwise to adjust the pH value of the solution to 4. After reflux reaction for 30 minutes, 0.025 mol methoxytrimethoxysilane (MTMS) and 0.075 mol isopropanol were added to the system, and the pH value of the system was adjusted to 4 again. At the same time, the amount of water was satisfied (GPTS+MTMS): water = 1:2, and the reflux reaction was continued for 4 hours to prepare silica sol. The maximum storage time of the silica sol was about 4 days.

[0089] Comparative Example 4

[0090] According to the method described in patent application CN114874645A, 0.25g of fluorine-containing epoxy resin was dissolved in 60ml of anhydrous ethanol, 5ml of ammonia water was added, and solution A was obtained by stirring at room temperature; 2.6ml of tetraethyl orthosilicate was added to 5ml of anhydrous ethanol, and solution B was obtained by stirring at room temperature; solution B was added drop by drop to solution A which was continuously stirred, and after the addition was completed, the solution was sealed and stirred for 4h, and then allowed to stand overnight, and then a certain amount of anhydrous ethanol and water were added to adjust the solid content to 1wt% to 2wt%, and solution C was obtained. 2.4ml of KH550 was dissolved in 5ml of anhydrous ethanol, and solution C was added drop by drop, sealed and stirred for 4h, and allowed to stand overnight to prepare silica sol. The silica sol showed a milky white precipitate after standing at room temperature for 30 days.

[0091] Test Example 1

[0092] Storage stability test of silica sol: The silica sol was left to stand at room temperature, and the state of the sol system, viscosity and gelation time were observed. The test results are shown in Table 1.

[0093] Table 1

[0094]

[0095] It can be seen that the silica sol prepared in the embodiment of the present invention has good stability and can be stored stably for a long time.

Claims

1. A method for preparing a silica sol with high storage stability, characterized in that: The following steps are involved: (1) mixing methyltrimethoxysilane, tetraethyl orthosilicate and a silane coupling agent to obtain a solution A; The silane coupling agent is at least one of 3-(methacryloyloxy)propyltrimethoxysilane and 3-(2,3-epoxypropyloxy)propyltrimethoxysilane; (2) adding solution A to an alcohol-water mixed solvent to obtain a mixed solution B; (3) methyltrimethoxysilane, tetraethyl orthosilicate and silane coupling agent in the mixed solution B are synergistically hydrolyzed and polycondensed to form oligomers to obtain solution C; (4) adding benzotriazole to solution C and reacting until the solution becomes clear and transparent; (5) The product obtained in step (4) is aged to obtain the silica sol with high storage stability.

2. The method for preparing the silica sol with high storage stability according to claim 1, characterized in that: In step (1), the molar ratio of methyltrimethoxysilane, tetraethyl orthosilicate and silane coupling agent is 1:1:2-3.

3. The method for preparing the silica sol with high storage stability according to claim 1, characterized in that: In step (2), the molar ratio of alcohol to water in the alcohol-water mixed solvent is 1:1; In the alcohol-water mixed solvent, the alcohol is at least one of ethanol and isopropanol.

4. The method for preparing the silica sol with high storage stability according to claim 1, characterized in that: In step (2), the ratio of the total molar number of each substance in solution A to the molar number of water in the alcohol-water mixed solvent is 1:

4.

5. The method for preparing a silica sol with high storage stability according to claim 1, characterized in that: In step (3), the pH of the mixed solution B is adjusted to 3-4, and the mixed solution B after the pH adjustment is reacted at 60-80° C. for 6-10 hours;.

6. The method for preparing a silica sol with high storage stability according to claim 1, characterized in that: In step (4), the molar ratio of the silane coupling agent to benzotriazole is 7 to 10:

1.

7. The method for preparing a silica sol with high storage stability according to claim 1, characterized in that: In step (5), the aging time is not less than 24 hours.

8. Silica sol with high storage stability prepared by the preparation method according to any one of claims 1 to 7.

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