Cationic silica sol and preparation process thereof

Abstract

The invention relates to the technical field of silica sol, and discloses cationic silica sol and a preparation process thereof.The cationic silica sol is obtained by adding silica sol with the positively charged surface and modified chitosan into a stirrer and stirring the silica sol and the modified chitosan. A silicon element and a sodium sulfonate group in the modified chitosan have a relatively good flame-retardant effect. The sulfur element in the contained sodium sulfonate can release sulfate or sulfur dioxide at a high temperature, and the substances can dilute oxygen in air to a certain extent and also have a flame-retardant effect; the silicon element contained in the flame-retardant material can form a vitreous substance on the surface of the material during combustion, so that substance transfer and energy transport between air and a base material are hindered, and the flame-retardant effect is achieved. A quaternary ammonium salt group in the modified chitosan has a relatively good antibacterial effect. A chitosan molecular structure in the modified chitosan has relatively good antibacterial and flame-retardant effects.

Description

Technical Field

[0001] The invention relates to the technical field of silica sol, in particular to a cationic silica sol and a preparation process thereof. Background Art

[0002] Silica sol is a colloidal solution formed by uniform dispersion of amorphous silica aggregate particles in water. It is a green and environmentally friendly inorganic nanomaterial. The hydroxyl groups on the surface of silica particles in silica sol are reactive. Modifiers with different structures can be selected to modify their surfaces, thereby expanding their application range and applying them to multiple fields. For example, patent CN113135573B discloses a zirconium-modified cationic silica sol and its preparation method. The silica sol obtained by the present invention has high stability and can be used in combination with a cationic system, but its flame retardant and antibacterial properties are not improved, which limits its application in the field of coatings. Summary of the invention

[0003] 1. Technical issues to be resolved

[0004] In view of the deficiencies of the prior art, the present invention provides a cationic silica sol and a preparation process thereof, which has good antibacterial and flame retardant effects.

[0005] (II) Technical solution

[0006] To achieve the above object, the present invention provides the following technical solutions: a cationic silica sol and a preparation process, comprising the following components by weight: 60-80 parts by weight of silica sol with positive surface charge, 5-7 parts by weight of modified chitosan;

[0007] The preparation method of the silica sol with positive surface charge is as follows:

[0008] In a high-pressure valve, nitrogen is introduced, silicate is added, (C6H5O)3SiCl is added, stirring is started, ammonia is introduced for reaction, the reaction is carried out at 60°C, the kettle pressure is controlled at 4-8Mpa, the reaction is carried out for 8-12 hours, the molar ratio is 5:1:75, and a reaction solution 1 is obtained, which is distilled for 2 hours, and silica sol (silicon dioxide content is 20-40%) is added to the reactor, and the reaction is carried out for 2-4 hours. At the same time, acid solution is added, and the volume ratio of silica sol to reaction solution 1 and acid solution is 125-130:0.5-5:1-15. After the addition is completed, stirring is continued for 3-5 minutes. After the addition is completed, a silica sol with a positively charged surface is obtained;

[0009] The acid solution is an inorganic acid or an organic acid; the inorganic acid is any one of hydrochloric acid, nitric acid, sulfuric acid, and boric acid; the organic acid is any one of acetic acid, citric acid, oxalic acid, and citric acid.

[0010] Preferably, the preparation method of the modified chitosan is:

[0011] S1. In a nitrogen atmosphere, hexamethyldisilazane and propenyl-1,3-sultone were added to a reaction kettle containing an isopropanol solvent, stirred evenly, and chloroplatinic acid catalyst was added thereto, reacted at 60-80° C. for 45-60 min, and then cooled to room temperature to obtain a tertiary aminosultone;

[0012] S2. 5-8 parts by weight of tertiary amino sultone and 13-15 parts by weight of ethylenediamine are added to N, N-dimethylformamide solvent, and then a 4-6% mass fraction of sodium hydroxide solution is added thereto, the temperature is raised to 70-90 ° C for reaction, and the solvent is removed by distillation under reduced pressure after the reaction, washed and dried to obtain an intermediate 1;

[0013] S3. 6-9 parts by weight of intermediate 1 and 8-13 parts by weight of 2-bromoethanol were added to an isopropanol solvent and the reaction was continued for 5-7 hours. After the reaction, the solvent was removed by rotary evaporation and recrystallized from ethanol to obtain intermediate 2.

[0014] S4. chitosan, chloromethylbenzoyl chloride and triethylamine catalyst were added to N, N-dimethylformamide, and the reaction was stirred at 50-65°C for 10-14h. After the reaction, distilled water was added to precipitate, the solvent was filtered, and the precipitate was washed with distilled water and acetone to obtain benzyl chloride chitosan;

[0015] S5. Add benzyl chloride chitosan and intermediate 2 to N,N-dimethylformamide solvent, stir evenly, and stir at 60-70°C for 4-6 hours. After the stirring, precipitate with deionized water, filter the solvent, wash with acetone, and dry to obtain modified chitosan.

[0016] Preferably, the mass ratio of hexamethyldisilazane, propenyl-1,3-sultone and chloroplatinic acid catalyst in S1 is 1:1.1-1.3:0.01-0.02.

[0017] Preferably, the reaction time in S2 is 6-8h.

[0018] Preferably, the reaction temperature in S3 is 65-85°C.

[0019] Preferably, the mass ratio of chitosan, chloromethylbenzoyl chloride and triethylamine catalyst in S4 is 0.4-0.6:1:0.02-0.024.

[0020] Preferably, the ratio of benzyl chloride chitosan to intermediate in S5 is 1:1.3-1.4.

[0021] Preferably, the preparation process of the cationic silica sol is: adding silica sol with positive charge on the surface and modified chitosan into a stirrer, stirring for 10-12 minutes, and obtaining the cationic silica sol after stirring.

[0022] (III) Beneficial technical effects

[0023] The invention adds silica sol with positive charge on the surface and modified chitosan into a stirrer, and stirs to obtain cationic silica sol.

[0024] The silicon-hydrogen bond in hexamethyldisilazane and the alkenyl group in allyl-1,3-sultone are subjected to addition reaction to introduce a tertiary amine group, thereby obtaining a tertiary amine sultone; the tertiary amine sultone is reacted with the amino group in ethylenediamine to obtain intermediate 1; the tertiary amine in intermediate 1 is reacted with the bromine group in 2-bromoethanol to introduce a hydroxyl group and generate a quaternary ammonium salt group, thereby obtaining intermediate 2; the chlorine in benzyl chloride chitosan is reacted with the hydroxyl group in intermediate 2 to obtain modified chitosan.

[0025] The silicon element and sodium sulfonate group in the modified chitosan have good flame retardant effect. The sulfur element in the sodium sulfonate will release sulfate or sulfur dioxide at high temperature. These substances can dilute the oxygen in the air to a certain extent and also have a flame retardant effect; the silicon element contained in it can form a glass-like substance on the surface of the material when burning, which hinders the material transfer and energy transport between the air and the substrate, and has a flame retardant effect. The quaternary ammonium salt group in the modified chitosan has a good antibacterial effect. The chitosan molecular structure in the modified chitosan itself has good antibacterial and flame retardant effects. DETAILED DESCRIPTION

[0026] Example 1

[0027] (1) In a high-pressure valve, nitrogen is introduced, silicate is added, (C6H5O)3SiCl is added, stirring is started, ammonia is introduced for reaction, the reaction is carried out at 60°C, the kettle pressure is controlled at 4 MPa, the reaction is carried out for 8 hours, the molar ratio is 5:1:75, a reaction solution 1 is obtained, distilled for 2 hours, silica sol (silicon dioxide content is 20%) is added to the reactor, the reaction is carried out for 2 hours, and acid solution is added at the same time, the volume ratio of silica sol to reaction solution 1 and acid solution is 125:0.5:1, and stirring is continued for 3 minutes after the addition is completed. After the addition is completed, a silica sol with a positively charged surface is obtained; the acid solution is hydrochloric acid;

[0028] (2) In a nitrogen atmosphere, hexamethyldisilazane and propenyl-1,3-sultone were added to a reaction kettle containing an isopropanol solvent, and the mixture was stirred evenly. A chloroplatinic acid catalyst was added thereto, wherein the mass ratio of hexamethyldisilazane, propenyl-1,3-sultone, and chloroplatinic acid catalyst was 1:1.1:0.01, and the mixture was reacted at 60° C. for 45 minutes. After the reaction was completed, the mixture was cooled to room temperature to obtain a tertiary aminosultone;

[0029] (3) adding 5 parts by weight of tertiary amino sulfonic acid lactone and 13 parts by weight of ethylenediamine to N,N-dimethylformamide solvent, and then adding 4% by weight sodium hydroxide solution thereto, heating to 70° C. to react for 6 hours, and after the reaction, removing the solvent by distillation under reduced pressure, washing and drying to obtain intermediate 1;

[0030] (4) adding 6 parts by weight of intermediate 1 and 8 parts by weight of 2-bromoethanol to isopropanol solvent, reacting at 65° C. for 5 h, and then removing the solvent by rotary evaporation, and recrystallizing from ethanol to obtain intermediate 2;

[0031] (5) adding chitosan, chloromethylbenzoyl chloride and triethylamine catalyst to N,N-dimethylformamide, wherein the mass ratio of chitosan, chloromethylbenzoyl chloride and triethylamine catalyst is 0.4:1:0.02, stirring and reacting at 50° C. for 10 hours, adding distilled water to precipitate after the reaction, filtering the solvent, washing and purifying with distilled water and acetone to obtain benzyl chloride chitosan;

[0032] (6) adding benzyl chloride chitosan and intermediate 2 to N,N-dimethylformamide solvent, wherein the ratio of benzyl chloride chitosan to intermediate is 1:1.3, stirring evenly, stirring at 60° C. for 4 h, after which the precipitate is precipitated with deionized water, the solvent is filtered, washed with acetone, and dried to obtain modified chitosan;

[0033] (7) 60 parts by weight of silica sol with a positive surface charge and 5 parts by weight of modified chitosan are added into a stirrer and stirred for 10 minutes to obtain cationic silica sol.

[0034] Example 2

[0035] (1) In a high-pressure valve, nitrogen is introduced, silicate is added, (C6H5O)3SiCl is added, stirring is started, ammonia is introduced for reaction, the reaction is carried out at 60°C, the kettle pressure is controlled at 8 MPa, the reaction is carried out for 12 hours, the molar ratio is 5:1:75, and a reaction solution 1 is obtained, which is distilled for 2 hours, and silica sol (silicon dioxide content is 40%) is added to the reactor, and the reaction is carried out for 4 hours. At the same time, an acid solution is added, and the volume ratio of the silica sol to the reaction solution 1 and the acid solution is 130:5:15. After the addition is completed, stirring is continued for 5 minutes. After the addition is completed, a silica sol with a positively charged surface is obtained; the acid solution is nitric acid;

[0036] (2) In a nitrogen atmosphere, hexamethyldisilazane and propenyl-1,3-sultone were added to a reaction kettle containing an isopropanol solvent, and the mixture was stirred evenly. A chloroplatinic acid catalyst was added thereto, wherein the mass ratio of hexamethyldisilazane, propenyl-1,3-sultone, and chloroplatinic acid catalyst was 1:1.3:0.02, and the mixture was reacted at 80° C. for 60 min. After the reaction was completed, the mixture was cooled to room temperature to obtain a tertiary aminosultone;

[0037] (3) adding 8 parts by weight of tertiary amino sulfonic acid lactone and 15 parts by weight of ethylenediamine to N,N-dimethylformamide solvent, and then adding 6% by weight sodium hydroxide solution thereto, heating to 90° C. to react for 8 hours, and after the reaction, removing the solvent by distillation under reduced pressure, washing and drying to obtain intermediate 1;

[0038] (4) adding 9 parts by weight of intermediate 1 and 13 parts by weight of 2-bromoethanol to isopropanol solvent, reacting at 85° C. for 7 h, and then removing the solvent by rotary evaporation, and recrystallizing from ethanol to obtain intermediate 2;

[0039] (5) adding chitosan, chloromethylbenzoyl chloride and triethylamine catalyst to N,N-dimethylformamide, wherein the mass ratio of chitosan, chloromethylbenzoyl chloride and triethylamine catalyst is 0.6:1:0.024, stirring and reacting at 65° C. for 14 h, adding distilled water to precipitate after the reaction, filtering the solvent, washing and purifying with distilled water and acetone to obtain benzyl chloride chitosan;

[0040] (6) adding benzyl chloride chitosan and intermediate 2 to N,N-dimethylformamide solvent, wherein the ratio of benzyl chloride chitosan to intermediate is 1:1.4, stirring evenly, stirring at 70° C. for 6 h, after which the precipitate is precipitated with deionized water, the solvent is filtered, washed with acetone, and dried to obtain modified chitosan;

[0041] (7) 80 parts by weight of silica sol with a positive surface charge and 7 parts by weight of modified chitosan are added into a stirrer and stirred for 12 minutes to obtain cationic silica sol.

[0042] Example 3

[0043] (1) In a high-pressure valve, nitrogen is introduced, silicate is added, (C6H5O)3SiCl is added, stirring is started, ammonia is introduced for reaction, the reaction is carried out at 60°C, the kettle pressure is controlled at 6 MPa, the reaction is carried out for 10 hours, the molar ratio is 5:1:75, and a reaction solution 1 is obtained, which is distilled for 2 hours, and silica sol (silicon dioxide content is 30%) is added to the reactor, and the reaction is carried out for 3 hours. At the same time, an acid solution is added, and the volume ratio of the silica sol to the reaction solution 1 and the acid solution is 130:2:4. After the addition is completed, stirring is continued for 4 minutes. After the addition is completed, a silica sol with a positively charged surface is obtained; the acid solution is citric acid;

[0044] (2) In a nitrogen atmosphere, hexamethyldisilazane and propenyl-1,3-sultone were added to a reaction kettle containing an isopropanol solvent, and the mixture was stirred evenly. A chloroplatinic acid catalyst was added thereto, wherein the mass ratio of hexamethyldisilazane, propenyl-1,3-sultone, and chloroplatinic acid catalyst was 1:1.2:0.015, and the mixture was reacted at 70° C. for 55 min. After the reaction was completed, the mixture was cooled to room temperature to obtain a tertiary aminosultone;

[0045] (3) adding 6 parts by weight of tertiary amino sulfonic acid lactone and 14 parts by weight of ethylenediamine to N,N-dimethylformamide solvent, and then adding 5% by weight sodium hydroxide solution thereto, heating to 80° C. to react for 7 hours, and after the reaction, removing the solvent by distillation under reduced pressure, washing and drying to obtain intermediate 1;

[0046] (4) adding 8 parts by weight of intermediate 1 and 10 parts by weight of 2-bromoethanol to isopropanol solvent, reacting at 75° C. for 6 h, and then removing the solvent by rotary evaporation, and recrystallizing from ethanol to obtain intermediate 2;

[0047] (5) adding chitosan, chloromethylbenzoyl chloride and triethylamine catalyst to N,N-dimethylformamide, wherein the mass ratio of chitosan, chloromethylbenzoyl chloride and triethylamine catalyst is 0.5:1:0.021, stirring and reacting at 55° C. for 12 h, adding distilled water to precipitate after the reaction, filtering the solvent, washing and purifying with distilled water and acetone to obtain benzyl chloride chitosan;

[0048] (6) adding benzyl chloride chitosan and intermediate 2 to N,N-dimethylformamide solvent, wherein the ratio of benzyl chloride chitosan to intermediate is 1:1.35, stirring evenly, stirring at 65° C. for 5 h, after which the precipitate is precipitated with deionized water, the solvent is filtered, washed with acetone, and dried to obtain modified chitosan;

[0049] (7) 70 parts by weight of silica sol with a positive surface charge and 6 parts by weight of modified chitosan were added into a stirrer and stirred for 11 minutes to obtain cationic silica sol.

[0050] Example 4

[0051] (1) In a high-pressure valve, nitrogen is introduced, silicate is added, (C6H5O)3SiCl is added, stirring is started, ammonia is introduced for reaction, the reaction is carried out at 60°C, the kettle pressure is controlled at 4 MPa, the reaction is carried out for 8 hours, the molar ratio is 5:1:75, a reaction solution 1 is obtained, distilled for 2 hours, silica sol (silicon dioxide content is 20%) is added to the reactor, the reaction is carried out for 2 hours, and acid solution is added at the same time, the volume ratio of silica sol to reaction solution 1 and acid solution is 125:0.5:1, and stirring is continued for 3 minutes after the addition is completed. After the addition is completed, a silica sol with a positively charged surface is obtained; the acid solution is hydrochloric acid;

[0052] (2) In a nitrogen atmosphere, hexamethyldisilazane and propenyl-1,3-sultone were added to a reaction kettle containing an isopropanol solvent, and the mixture was stirred evenly. A chloroplatinic acid catalyst was added thereto, wherein the mass ratio of hexamethyldisilazane, propenyl-1,3-sultone, and chloroplatinic acid catalyst was 1:1.1:0.01, and the mixture was reacted at 60° C. for 45 minutes. After the reaction was completed, the mixture was cooled to room temperature to obtain a tertiary aminosultone;

[0053] (3) adding 8 parts by weight of tertiary amino sulfonic acid lactone and 15 parts by weight of ethylenediamine to N,N-dimethylformamide solvent, and then adding 6% by weight sodium hydroxide solution thereto, heating to 90° C. to react for 8 hours, and after the reaction, removing the solvent by distillation under reduced pressure, washing and drying to obtain intermediate 1;

[0054] (4) adding 9 parts by weight of intermediate 1 and 13 parts by weight of 2-bromoethanol to isopropanol solvent, reacting at 85° C. for 7 h, and then removing the solvent by rotary evaporation, and recrystallizing from ethanol to obtain intermediate 2;

[0055] (5) adding chitosan, chloromethylbenzoyl chloride and triethylamine catalyst to N,N-dimethylformamide, wherein the mass ratio of chitosan, chloromethylbenzoyl chloride and triethylamine catalyst is 0.5:1:0.021, stirring and reacting at 55° C. for 12 h, adding distilled water to precipitate after the reaction, filtering the solvent, washing and purifying with distilled water and acetone to obtain benzyl chloride chitosan;

[0056] (6) adding benzyl chloride chitosan and intermediate 2 to N,N-dimethylformamide solvent, wherein the ratio of benzyl chloride chitosan to intermediate is 1:1.35, stirring evenly, stirring at 65° C. for 5 h, after which the precipitate is precipitated with deionized water, the solvent is filtered, washed with acetone, and dried to obtain modified chitosan;

[0057] (7) 70 parts by weight of silica sol with a positive surface charge and 6 parts by weight of modified chitosan were added into a stirrer and stirred for 11 minutes to obtain cationic silica sol.

[0058] Comparative Example 1

[0059] Compared with Example 4, this comparative example uses chitosan instead of modified chitosan.

[0060] Use an oxygen index tester to test the oxygen index of the material.

[0061] The combustion level of the material is tested using a horizontal vertical combustion tester.

[0062] Table 1: Flame retardancy tests.

[0063]

[0064]

[0065] It can be seen from Table 1 that Examples 1-4 of the present invention have better flame retardant effects than Comparative Example 1.

[0066] A Staphylococcus aureus liquid with a concentration of 2×108 CFU / mL was added as a test strain to a sterilized culture dish, and then a solid agar medium was added and dissolved, cooled to 45°C, and then poured into a culture dish, 20 mL was poured into each plate with an inner diameter of 10 cm, and then the cationic silica sol (with a diameter of 3 cm and a thickness of 1 mm) of the embodiment of the present invention and the comparative example was placed on the culture plate, and cultured in a constant temperature incubator for 12 hours at a temperature of 37°C. After culture, the diameter of the inhibition zone was measured. The test results are shown in Table 1.

[0067] Table 2: Antimicrobial testing.

[0068] project Diameter of inhibition zone (mm) Example 1 15.3 Example 2 16.2 Example 3 15.4 Example 4 15.9 Comparative Example 1 11.4

[0069] It can be seen from Table 2 that the cationic silica sol of Examples 1-4 of the present invention has better antibacterial effect than Comparative Example 1.

[0070] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A cationic silica sol and a preparation process, characterized in that: The invention comprises the following components by weight: 60-80 parts by weight of silica sol with positive charge on the surface and 5-7 parts by weight of modified chitosan; The preparation method of the silica sol with positive surface charge is as follows: In a high-pressure valve, nitrogen is introduced, silicate is added, (C6H5O)3SiCl is added, stirring is started, ammonia is introduced for reaction, the reaction is carried out at 60°C, the kettle pressure is controlled at 4-8Mpa, the reaction is carried out for 8-12 hours, the molar ratio is 5:1:75, and a reaction solution 1 is obtained, which is distilled for 2 hours, and silica sol (silicon dioxide content is 20-40%) is added to the reactor, and the reaction is carried out for 2-4 hours. At the same time, acid solution is added, and the volume ratio of silica sol to reaction solution 1 and acid solution is 125-130:0.5-5:1-15. After the addition is completed, stirring is continued for 3-5 minutes. After the addition is completed, a silica sol with a positively charged surface is obtained; The acid solution is an inorganic acid or an organic acid; the inorganic acid is any one of hydrochloric acid, nitric acid, sulfuric acid, and boric acid; the organic acid is any one of acetic acid, citric acid, oxalic acid, and citric acid.

2. The cationic silica sol according to claim 1, characterized in that The preparation method of the modified chitosan is: S1. In a nitrogen atmosphere, hexamethyldisilazane and propenyl-1,3-sultone were added to a reaction kettle containing an isopropanol solvent, stirred evenly, and chloroplatinic acid catalyst was added thereto, reacted at 60-80° C. for 45-60 min, and then cooled to room temperature to obtain a tertiary aminosultone; S2. 5-8 parts by weight of tertiary amino sultone and 13-15 parts by weight of ethylenediamine are added to N, N-dimethylformamide solvent, and then a 4-6% mass fraction of sodium hydroxide solution is added thereto, the temperature is raised to 70-90 ° C for reaction, and the solvent is removed by distillation under reduced pressure after the reaction, washed and dried to obtain an intermediate 1; S3. 6-9 parts by weight of intermediate 1 and 8-13 parts by weight of 2-bromoethanol were added to an isopropanol solvent and the reaction was continued for 5-7 hours. After the reaction, the solvent was removed by rotary evaporation and recrystallized from ethanol to obtain intermediate 2. S4. chitosan, chloromethylbenzoyl chloride and triethylamine catalyst were added to N, N-dimethylformamide, and the reaction was stirred at 50-65°C for 10-14h. After the reaction, distilled water was added to precipitate, the solvent was filtered, and the precipitate was washed with distilled water and acetone to obtain benzyl chloride chitosan; S5. Add benzyl chloride chitosan and intermediate 2 to N,N-dimethylformamide solvent, stir evenly, and stir at 60-70°C for 4-6 hours. After the stirring, precipitate with deionized water, filter the solvent, wash with acetone, and dry to obtain modified chitosan.

3. The cationic silica sol according to claim 1, characterized in that The mass ratio of hexamethyldisilazane, propenyl-1,3-sultone and chloroplatinic acid catalyst in S1 is 1:1.1-1.3:0.01-0.

02.

4. The cationic silica sol according to claim 1, characterized in that The reaction time in S2 is 6-8h.

5. The cationic silica sol according to claim 1, characterized in that: The reaction temperature in S3 is 65-85°C.

6. The cationic silica sol according to claim 1, characterized in that: The mass ratio of chitosan, chloromethylbenzoyl chloride and triethylamine catalyst in S4 is 0.4-0.6:1:0.02-0.

024.

7. The cationic silica sol according to claim 1, characterized in that: The ratio of benzyl chloride chitosan to intermediate in S5 is 1:1.3-1.

4.

8. A process for preparing the cationic silica sol according to any one of claims 1 to 7, characterized in that: The preparation process of the cationic silica sol is as follows: adding the silica sol with positive charge on the surface and the modified chitosan into a stirrer, stirring for 10-12 minutes, and obtaining the cationic silica sol after stirring.

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