Cationic silica sol and preparation process thereof

Abstract

The application relates to the technical field of silica sol, and discloses a cationic silica sol and a preparation process; the positively-charged silica sol and modified chitosan are added into a stirrer, stirred, and the cationic silica sol is obtained after the stirring is completed. The silicon element and the sodium sulfonate group in the modified chitosan have good flame-retardant effects. The sulfur element in the sodium sulfonate can release sulfate or sulfur dioxide at high temperatures, the substances can dilute oxygen in air to a certain extent, and the sodium sulfonate also has a flame-retardant effect; the silicon element can form a glass-like substance on the surface of the material during combustion, hinders the material transmission and energy transportation of air and the base material, and has a flame-retardant effect. The quaternary ammonium salt group in the modified chitosan has good antibacterial effect. The chitosan molecular structure in the modified chitosan has good antibacterial and flame-retardant effects.

Description

Technical Field

[0001] This invention relates to the field of silica sol technology, specifically to a cationic silica sol and its preparation process. Background Technology

[0002] Silica sol is a colloidal solution formed by the uniform dispersion of amorphous silica aggregates in water. It is a green and environmentally friendly inorganic nanomaterial. The hydroxyl groups on the surface of the silica particles in silica sol are reactive, and surface modification can be performed using modifiers with different structures, thereby expanding its application range to multiple fields. For example, patent CN113135573B discloses a zirconium-modified cationic silica sol and its preparation method. The silica sol obtained by this invention has high stability and can be used in combination with cationic systems. However, its flame retardant and antibacterial properties have not been improved, limiting its application in the coatings field. Summary of the Invention

[0003] (a) Technical problems to be solved

[0004] To address the shortcomings of existing technologies, this invention provides a cationic silica sol and its preparation process, which exhibits good antibacterial and flame-retardant effects.

[0005] (II) Technical Solution

[0006] To achieve the above objectives, the present invention provides the following technical solution: a cationic silica sol and its preparation process, comprising the following weight components: 60-80 parts by weight of positively charged silica sol and 5-7 parts by weight of modified chitosan;

[0007] The method for preparing the positively charged silica sol is as follows:

[0008] Nitrogen gas is introduced into a high-pressure valve, followed by the addition of silicate ester and (C6H5O)3SiCl. Stirring is started, and ammonia gas is introduced to react at 60°C. The reactor pressure is controlled at 4-8 MPa, and the reaction is carried out for 8-12 hours. The molar ratio is 5:1:75, resulting in reaction solution 1. After distillation for 2 hours, silica sol (silica content of 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. The volume ratio of silica sol to reaction solution 1 to acid solution is 125-130:0.5-5:1-15. After the addition is complete, stirring is continued for 3-5 minutes. After the reaction 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 modified chitosan is prepared by:

[0011] S1. In a nitrogen atmosphere, hexamethyldisilazane and propenyl-1,3-sulfonate lactone were added to a reaction vessel containing isopropanol solvent, stirred until homogeneous, and chloroplatinic acid catalyst was added. The reaction was carried out at 60-80℃ for 45-60 min. After the reaction was completed, the mixture was cooled to room temperature to obtain tertiary aminosulfonate lactone.

[0012] S2. Add 5-8 parts by weight of tertiary aminosulfonyl lactone and 13-15 parts by weight of ethylenediamine to N,N-dimethylformamide solvent, and then continue to add sodium hydroxide solution with a mass fraction of 4-6%. Heat to 70-90℃ to carry out the reaction. After the reaction, remove the solvent by vacuum distillation, wash and dry to obtain intermediate 1.

[0013] S3. Add 6-9 parts by weight of intermediate 1 and 8-13 parts by weight of 2-bromoethanol to isopropanol solvent, react for 5-7 hours, remove the solvent by rotary evaporation after reaction, recrystallize the ethanol to obtain intermediate 2.

[0014] S4. Add chitosan, chloromethylbenzoyl chloride and triethylamine catalyst to N,N-dimethylformamide, stir the reaction at 50-65℃ for 10-14h, add distilled water to precipitate the precipitate, filter the solvent, wash and purify 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, stir at 60-70℃ for 4-6 hours, after which deionized water precipitates out the precipitate, filter the solvent, wash with acetone, and dry to obtain modified chitosan.

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

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

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

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

[0021] Preferably, the preparation process of the cationic silica sol is as follows: positively charged silica sol and modified chitosan are added to a stirrer and stirred for 10-12 minutes to obtain cationic silica sol.

[0022] (III) Beneficial Technical Effects

[0023] This invention involves adding positively charged silica sol and modified chitosan to a stirrer, stirring, and then obtaining a cationic silica sol.

[0024] The silane-hydrogen bond in hexamethyldisilazane and the alkenyl group in propenyl-1,3-sulfonate lactone are added to introduce a tertiary amine group, thus obtaining tertiary amine sulfonate lactone; the tertiary amine sulfonate lactone 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 a quaternary ammonium salt group is generated to obtain intermediate 2; the chlorine in benzyl chloride chitosan is reacted with the hydroxyl group in intermediate 2 to obtain modified chitosan.

[0025] The silicon and sodium sulfonate groups in modified chitosan exhibit good flame-retardant properties. The sulfur in the sodium sulfonate releases sulfates or sulfur dioxide at high temperatures, which can dilute oxygen in the air and thus contribute to flame retardancy. The silicon in the modified chitosan forms a glassy substance on the material surface during combustion, hindering the transfer of matter and energy between the air and the substrate, thereby also contributing to flame retardancy. The quaternary ammonium groups in modified chitosan also demonstrate good antibacterial effects. The chitosan molecular structure itself possesses excellent antibacterial and flame-retardant properties. Detailed Implementation

[0026] Example 1

[0027] (1) Nitrogen gas was introduced into a high-pressure valve, silicate ester was added, (C6H5O)3SiCl was added, stirring was started, ammonia gas was introduced to react, the reaction was carried out at 60°C, the pressure of the reactor was controlled at 4 MPa, the reaction was carried out for 8 hours, the molar ratio was 5:1:75, and reaction solution 1 was obtained. After distillation for 2 hours, silica sol (silica content of 20%) was added to the reactor, and the reaction was carried out for 2 hours. At the same time, acid solution was added. The volume ratio of silica sol to reaction solution 1 to acid solution was 125:0.5:1. After the addition was completed, stirring was continued for 3 minutes. After the reaction was completed, silica sol with positive surface charge was obtained. The acid solution was hydrochloric acid.

[0028] (2) In a nitrogen atmosphere, hexamethyldisilazane and propenyl-1,3-sulfonate lactone were added to a reaction vessel containing isopropanol solvent and stirred until homogeneous. Chloroplatinic acid catalyst was then added to the vessel, wherein the mass ratio of hexamethyldisilazane, propenyl-1,3-sulfonate lactone and chloroplatinic acid catalyst was 1:1.1:0.01. The reaction was carried out at 60°C for 45 min. After the reaction was completed, the mixture was cooled to room temperature to obtain tertiary aminosulfonate lactone.

[0029] (3) Add 5 parts by weight of tertiary aminosulfonyl lactone and 13 parts by weight of ethylenediamine to N,N-dimethylformamide solvent, and then continue to add sodium hydroxide solution with a mass fraction of 4%. Heat to 70°C and react for 6 hours. After the reaction, remove the solvent by vacuum distillation, wash and dry to obtain intermediate 1.

[0030] (4) Add 6 parts by weight of intermediate 1 and 8 parts by weight of 2-bromoethanol to isopropanol solvent, react at 65°C for 5 h, remove the solvent by rotary evaporation after the reaction, recrystallize the ethanol to obtain intermediate 2.

[0031] (5) Chitosan, chloromethylbenzoyl chloride and triethylamine catalyst were added to N,N-dimethylformamide, wherein the mass ratio of chitosan, chloromethylbenzoyl chloride and triethylamine catalyst was 0.4:1:0.02. The mixture was stirred at 50°C for 10 h. After the reaction, distilled water was added to precipitate the precipitate. The solvent was filtered, and the mixture was washed with distilled water and acetone to obtain benzyl chloride chitosan.

[0032] (6) Add benzyl chloride chitosan and intermediate 2 to N,N-dimethylformamide solvent, wherein benzyl chloride chitosan and intermediate 1:1.3, stir evenly, stir at 60℃ for 4h, after which deionized water precipitates out the precipitate, filter the solvent, wash with acetone, and dry to obtain modified chitosan.

[0033] (7) Add 60 parts by weight of positively charged silica sol and 5 parts by weight of modified chitosan to a stirrer and stir for 10 minutes to obtain cationic silica sol.

[0034] Example 2

[0035] (1) Nitrogen gas was introduced into a high-pressure valve, silicate ester was added, (C6H5O)3SiCl was added, stirring was started, ammonia gas was introduced to react, the reaction was carried out at 60°C, the pressure of the reactor was controlled at 8 MPa, the reaction was carried out for 12 hours, the molar ratio was 5:1:75, and reaction solution 1 was obtained. After distillation for 2 hours, silica sol (silica content of 40%) was added to the reactor, the reaction was carried out for 4 hours, and acid solution was added at the same time. The volume ratio of silica sol to reaction solution 1 to acid solution was 130:5:15. After the addition was completed, stirring was continued for 5 minutes. After the reaction was completed, silica sol with positive surface charge was obtained. The acid solution was nitric acid.

[0036] (2) In a nitrogen atmosphere, hexamethyldisilazane and propenyl-1,3-sulfonate lactone were added to a reaction vessel containing isopropanol solvent and stirred until homogeneous. Chloroplatinic acid catalyst was then added to the vessel, wherein the mass ratio of hexamethyldisilazane, propenyl-1,3-sulfonate lactone and chloroplatinic acid catalyst was 1:1.3:0.02. The reaction was carried out at 80°C for 60 min. After the reaction was completed, the mixture was cooled to room temperature to obtain tertiary aminosulfonate lactone.

[0037] (3) Add 8 parts by weight of tertiary aminosulfonyl lactone and 15 parts by weight of ethylenediamine to N,N-dimethylformamide solvent, and then continue to add sodium hydroxide solution with a mass fraction of 6%. Heat to 90℃ and react for 8 hours. After the reaction, remove the solvent by vacuum distillation, wash and dry to obtain intermediate 1.

[0038] (4) Add 9 parts by weight of intermediate 1 and 13 parts by weight of 2-bromoethanol to isopropanol solvent, react at 85°C for 7 h, remove the solvent by rotary evaporation after the reaction, recrystallize the ethanol to obtain intermediate 2.

[0039] (5) Chitosan, chloromethylbenzoyl chloride and triethylamine catalyst were added to N,N-dimethylformamide, wherein the mass ratio of chitosan, chloromethylbenzoyl chloride and triethylamine catalyst was 0.6:1:0.024. The mixture was stirred at 65°C for 14 h. After the reaction, distilled water was added to precipitate the precipitate. The solvent was filtered, and the mixture was washed with distilled water and acetone to obtain benzyl chloride chitosan.

[0040] (6) Add benzyl chloride chitosan and intermediate 2 to N,N-dimethylformamide solvent, wherein benzyl chloride chitosan and intermediate 1:1.4, stir evenly, stir at 70℃ for 6h, after which deionized water precipitates out the precipitate, filter the solvent, wash with acetone, and dry to obtain modified chitosan.

[0041] (7) Add 80 parts by weight of positively charged silica sol and 7 parts by weight of modified chitosan to a stirrer and stir for 12 minutes to obtain cationic silica sol.

[0042] Example 3

[0043] (1) Nitrogen gas was introduced into a high-pressure valve, silicate ester was added, (C6H5O)3SiCl was added, stirring was started, ammonia gas was introduced to react, the reaction was carried out at 60°C, the pressure of the reactor was controlled at 6 MPa, the reaction was carried out for 10 hours, the molar ratio was 5:1:75, and reaction solution 1 was obtained. After distillation for 2 hours, silica sol (silica content of 30%) was added to the reactor, the reaction was carried out for 3 hours, and acid solution was added at the same time. The volume ratio of silica sol to reaction solution 1 to acid solution was 130:2:4. After the addition was completed, stirring was continued for 4 minutes. After the reaction was completed, silica sol with positive surface charge was obtained; the acid solution was citric acid.

[0044] (2) In a nitrogen atmosphere, hexamethyldisilazane and propenyl-1,3-sulfonate lactone were added to a reaction vessel containing isopropanol solvent and stirred until homogeneous. Chloroplatinic acid catalyst was then added to the vessel, wherein the mass ratio of hexamethyldisilazane, propenyl-1,3-sulfonate lactone and chloroplatinic acid catalyst was 1:1.2:0.015. The reaction was carried out at 70°C for 55 min. After the reaction was completed, the mixture was cooled to room temperature to obtain tertiary aminosulfonate lactone.

[0045] (3) Add 6 parts by weight of tertiary aminosulfonyl lactone and 14 parts by weight of ethylenediamine to N,N-dimethylformamide solvent, and then continue to add 5% sodium hydroxide solution. Heat to 80℃ and react for 7h. After the reaction, remove the solvent by vacuum distillation, wash and dry to obtain intermediate 1.

[0046] (4) Add 8 parts by weight of intermediate 1 and 10 parts by weight of 2-bromoethanol to isopropanol solvent, react at 75°C for 6 hours, remove the solvent by rotary evaporation after the reaction, and recrystallize the ethanol to obtain intermediate 2.

[0047] (5) Chitosan, chloromethylbenzoyl chloride and triethylamine catalyst were added to N,N-dimethylformamide, wherein the mass ratio of chitosan, chloromethylbenzoyl chloride and triethylamine catalyst was 0.5:1:0.021. The mixture was stirred at 55°C for 12 h. After the reaction, distilled water was added to precipitate the precipitate. The solvent was filtered, and the mixture was washed with distilled water and acetone to obtain benzyl chloride chitosan.

[0048] (6) Add benzyl chloride chitosan and intermediate 2 to N,N-dimethylformamide solvent, wherein benzyl chloride chitosan and intermediate 1 are in a ratio of 1.35. Stir evenly and stir at 65°C for 5 hours. After stirring, deionized water precipitates out the precipitate, filter the solvent, wash with acetone, and dry to obtain modified chitosan.

[0049] (7) Add 70 parts by weight of positively charged silica sol and 6 parts by weight of modified chitosan to a stirrer and stir for 11 minutes to obtain cationic silica sol.

[0050] Example 4

[0051] (1) Nitrogen gas was introduced into a high-pressure valve, silicate ester was added, (C6H5O)3SiCl was added, stirring was started, ammonia gas was introduced to react, the reaction was carried out at 60°C, the pressure of the reactor was controlled at 4 MPa, the reaction was carried out for 8 hours, the molar ratio was 5:1:75, and reaction solution 1 was obtained. After distillation for 2 hours, silica sol (silica content of 20%) was added to the reactor, and the reaction was carried out for 2 hours. At the same time, acid solution was added. The volume ratio of silica sol to reaction solution 1 to acid solution was 125:0.5:1. After the addition was completed, stirring was continued for 3 minutes. After the reaction was completed, silica sol with positive surface charge was obtained. The acid solution was hydrochloric acid.

[0052] (2) In a nitrogen atmosphere, hexamethyldisilazane and propenyl-1,3-sulfonate lactone were added to a reaction vessel containing isopropanol solvent and stirred until homogeneous. Chloroplatinic acid catalyst was then added to the vessel, wherein the mass ratio of hexamethyldisilazane, propenyl-1,3-sulfonate lactone and chloroplatinic acid catalyst was 1:1.1:0.01. The reaction was carried out at 60°C for 45 min. After the reaction was completed, the mixture was cooled to room temperature to obtain tertiary aminosulfonate lactone.

[0053] (3) Add 8 parts by weight of tertiary aminosulfonyl lactone and 15 parts by weight of ethylenediamine to N,N-dimethylformamide solvent, and then continue to add sodium hydroxide solution with a mass fraction of 6%. Heat to 90℃ and react for 8 hours. After the reaction, remove the solvent by vacuum distillation, wash and dry to obtain intermediate 1.

[0054] (4) Add 9 parts by weight of intermediate 1 and 13 parts by weight of 2-bromoethanol to isopropanol solvent, react at 85°C for 7 h, remove the solvent by rotary evaporation after the reaction, recrystallize the ethanol to obtain intermediate 2.

[0055] (5) Chitosan, chloromethylbenzoyl chloride and triethylamine catalyst were added to N,N-dimethylformamide, wherein the mass ratio of chitosan, chloromethylbenzoyl chloride and triethylamine catalyst was 0.5:1:0.021. The mixture was stirred at 55°C for 12 h. After the reaction, distilled water was added to precipitate the precipitate. The solvent was filtered, and the mixture was washed with distilled water and acetone to obtain benzyl chloride chitosan.

[0056] (6) Add benzyl chloride chitosan and intermediate 2 to N,N-dimethylformamide solvent, wherein benzyl chloride chitosan and intermediate 1 are in a ratio of 1.35. Stir evenly and stir at 65°C for 5 hours. After stirring, deionized water precipitates out the precipitate, filter the solvent, wash with acetone, and dry to obtain modified chitosan.

[0057] (7) Add 70 parts by weight of positively charged silica sol and 6 parts by weight of modified chitosan to a stirrer and stir for 11 minutes to obtain cationic silica sol.

[0058] Comparative Example 1

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

[0060] The oxygen index of the material was tested using an oxygen index meter.

[0061] The flammability rating of materials is tested using a horizontal and vertical combustion tester.

[0062] Table 1: Flame retardancy test.

[0063]

[0064]

[0065] As shown in Table 1, Examples 1-4 of the present invention have better flame retardant effects compared with Comparative Example 1.

[0066] Staphylococcus aureus bacterial suspension with a concentration of 2×10⁸ CFU / mL was added to sterilized petri dishes as the test strain. Solid agar medium was then added to dissolve the bacteria, and the mixture was cooled to 45°C. The solution was then poured into petri dishes, with 20 mL poured into each 10 cm inner diameter dish. The cationic silica sol (3 cm in diameter and 1 mm thick) from the embodiments and comparative examples of this invention was then placed on the culture medium plates. The plates were incubated at 37°C for 12 hours. The diameter of the inhibition zone was measured after incubation. The test results are shown in Table 1.

[0067] Table 2: Antibacterial test.

[0068] project Diameter of the 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] As shown in Table 2, the cationic silica sol of the present invention, Examples 1-4, has a better antibacterial effect than Comparative Example 1.

[0070] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A process for the preparation of a cationic silica sol, characterized in that, The preparation method of the surface positive silicon sol comprises the following steps: The preparation method of the surface positive silicon sol comprises the following steps: The preparation method of the surface positive silicon sol comprises the following steps: The acid liquid is inorganic acid or 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 and oxalic acid; The preparation method of the modified chitosan comprises the following steps: S1. In a nitrogen atmosphere, a reaction kettle containing isopropyl alcohol solvent is added with hexamethyldisilazane and propenyl-1,3-sulfolactone, and stirred uniformly, and then chloroplatinic acid catalyst is continuously added, and reaction is carried out at 60-80 DEG C for 45-60 min, and then cooled to room temperature to obtain a tertiary amine group sulfolactone; S2. 5-8 parts by weight of the tertiary amine group sulfolactone and 13-15 parts by weight of ethylenediamine are added into N,N-dimethylformamide solvent, and then a sodium hydroxide solution with a mass fraction of 4-6% is continuously added, and then reaction is carried out by heating to 70-90 DEG C, and then the solvent is removed by distillation under reduced pressure after reaction, and then washed and dried to obtain an intermediate 1; S3. 6-9 parts by weight of the intermediate 1 and 8-13 parts by weight of 2-bromoethanol are added into isopropyl alcohol solvent, and reaction is carried out for 5-7 h, and then the solvent is removed by rotary evaporation after reaction, and then ethanol recrystallization is carried out to obtain an intermediate 2; S4. Chitosan, chloromethyl benzoyl chloride and triethylamine catalyst are added into N,N-dimethylformamide, and then stirred and reacted at 50-65 DEG C for 10-14 h, and then distilled water is added to precipitate, and then the solvent is filtered, and then distilled water and acetone are used for washing and purification to obtain benzyl chloro chitosan; S5. The benzyl chloro chitosan and the intermediate 2 are added into N,N-dimethylformamide solvent, and then stirred uniformly, and then stirred at 60-70 DEG C for 4-6 h, and then deionized water is used for precipitating after reaction, and then the solvent is filtered, and then acetone is used for washing, and then dried to obtain the modified chitosan.

2. The process for preparing a cationic silica sol according to claim 1, characterized in that, The mass ratio of the hexamethyldisilazane, the propenyl-1,3-sulfolactone and the chloroplatinic acid catalyst in S1 is 1:1.1-1.3:0.01-0.

02.

3. The process for preparing a cationic silica sol according to claim 1, characterized in that, The reaction time in S2 is 6-8 h.

4. The process for preparing a cationic silica sol according to claim 1, characterized in that, The reaction temperature in S3 is 65-85 DEG C.

5. The process for preparing a cationic silica sol according to claim 1, characterized in that, The mass ratio of the chitosan, the chloromethyl benzoyl chloride and the triethylamine catalyst in S4 is 0.4-0.6:1:0.02-0.

024.

6. The process for preparing a cationic silica sol according to claim 1, characterized in that, The ratio of benzylchloride chitosan and intermediate in S5 is 1:1.3-1.4.

Images