Preparation method of phenolic chitosan quaternary ammonium salt antibacterial agent

Abstract

The invention discloses a preparation method of a phenolic chitosan quaternary ammonium salt antibacterial agent, which comprises the following steps: alkalizing chitosan at low temperature, then carrying out substitution reaction on the alkalized chitosan and a carboxylic acid derivative, and introducing a reactive carboxyl group on the hydroxyl of the chitosan to obtain O-carboxylated chitosan, so as to provide reactive sites for subsequent secondary modification; the preparation method comprises the following steps: preparing O-carboxylated chitosan, introducing a quaternary ammonium salt group on an amino group of the O-carboxylated chitosan through a ring-opening reaction so as to improve the antibacterial property and water solubility of the chitosan, and finally reacting with a phenolic derivative to obtain the phenolic chitosan quaternary ammonium salt antibacterial agent. According to the preparation method of the phenolic chitosan quaternary ammonium salt antibacterial agent, industrial production is easy, and the prepared phenolic chitosan quaternary ammonium salt antibacterial agent has good antibacterial performance and free radical scavenging capacity and also has good water solubility.

Description

Technical Field

[0001] The invention relates to the technical field of chitosan quaternary ammonium salt preparation, and in particular to a method for preparing a phenol-based chitosan quaternary ammonium salt antibacterial agent. Background Art

[0002] The use of antimicrobial agents can effectively reduce exogenous infections caused by bacteria. Commonly used antimicrobial agents include three categories: natural antimicrobial agents, inorganic antimicrobial agents, and organic antimicrobial agents. However, long-term use of a single type of antimicrobial agent will produce serious drug resistance, so the preparation of new antimicrobial agents is very necessary.

[0003] Chitosan is widely present in nature and is composed of (1-4)-2-amino-2-deoxy- β -High molecular weight cationic polysaccharide composed of glucan is the deacetylation product of chitin. Chitosan itself has certain antibacterial activity and is widely used in the fields of medicine, cosmetics, food, pesticides, daily chemicals, etc. However, chitosan has poor water solubility, and the antibacterial properties of unmodified chitosan are not significant. Although the research on chitosan-based antibacterial agents has made significant progress, there are still few commercially available products, mainly limited by high production costs, single performance, etc. For example, although the common quaternized chitosan has significantly improved antibacterial properties compared to chitosan, its ability to scavenge free radicals is limited. During use, it is often necessary to add free radical scavengers, which not only increases the cost of use, but also needs to consider the stability of the compounded product. Compared with chitosan, phenolic acid-modified chitosan has significantly improved free radical scavenging ability, but its antibacterial effect is limited, and the introduction of phenolic acid also has a certain effect on the solubility of chitosan in water. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing a phenolic chitosan quaternary ammonium salt antibacterial agent, which is easy to industrialize and produce. The prepared phenolic chitosan quaternary ammonium salt antibacterial agent has good antibacterial performance and free radical scavenging ability, and has good water solubility.

[0005] In order to achieve the above object, the solution of the present invention is: A method for preparing a phenolic chitosan quaternary ammonium salt antibacterial agent comprises the following steps: Step 1, first dispersing chitosan in an isopropanol solution to obtain a chitosan dispersion; Step 2, then slowly adding sodium hydroxide solution to the chitosan dispersion and alkalizing at -20°C for 6 to 24 hours; Step 3: Then, at room temperature, the carboxylic acid derivatives are added in batches to the alkalized chitosan dispersion, and then the reaction temperature is increased to 60-100 °C, and the reaction is carried out at a constant temperature for 6-24 hours. After the reaction is completed, the product is filtered, washed with anhydrous ethanol for multiple times, and dried to obtain O - Carboxylated chitosan; Step 4, then O -Carboxylated chitosan was dissolved in deionized water, and the amino groups of chitosan were further quaternized to obtain O - Carboxylated chitosan quaternary ammonium salt; Step 5, then dissolving the phenol derivative in anhydrous ethanol, lowering the system temperature to 0°C, adding EDC (ethyl-(3-dimethylaminopropyl)carbodiimide) and NHS to obtain an ethanol solution of the phenol derivative; Step 6, then O - Dissolve the carboxylated chitosan quaternary ammonium salt in deionized water, and slowly add the ethanol solution of the phenolic derivative into O -In an aqueous solution of carboxylated chitosan quaternary ammonium salt, the reaction temperature is increased to 20-60 °C, and the reaction is carried out at a constant temperature for 6-24 hours. After the reaction is completed, the crude product is successively ultrafiltered, concentrated, and freeze-dried to obtain a phenolic chitosan quaternary ammonium salt antibacterial agent; The O - carboxylated chitosan quaternary ammonium salt is selected from O -Carboxymethyl- N , N , N -Trimethyl chitosan quaternary ammonium salt, O -Carboxymethyl- N , N , N -Triethyl chitosan quaternary ammonium salt, O -Carboxymethyl- N , N -Dimethyl- N -Dodecyl chitosan quaternary ammonium salt, O -Carboxymethyl- N -Biguanide chitosan hydrochloride, O -Carboxymethyl- N -(2-Hydroxypropyltrimethylammonium chloride)chitosan, O -Carboxymethyl- N -Sulfopropyl chitosan, O -Carboxyethyl- N -Carboxybenzyl- N ', N '-Dimethyl- N '-Dodecyl chitosan or O -Carboxybenzyl- N -Sulfopropyl chitosan; In step 5, the phenol derivative is selected from p-aminophenol, 2-aminophenol, 2-amino-resorcinol, 2-(3,4-dihydroxyphenyl)ethylamine, 4-amino-resorcinol or 4-amino-3,5-dichlorophenol.

[0006] In step 1, the mass fraction of the chitosan dispersion is 1% to 10%.

[0007] In step 2, the mass ratio of sodium hydroxide in the sodium hydroxide solution to chitosan in the chitosan dispersion is 1-5:1.

[0008] In step 3, the carboxylic acid derivative is selected from chloroacetic acid, chloropropionic acid, p-chloromethylbenzoic acid, bromoacetic acid or bromopropionic acid, and the mass ratio of the carboxylic acid derivative to the chitosan in the alkalized chitosan dispersion is 1-5:1.

[0009] In step 4, the quaternization reaction process is a well-known quaternization reaction process.

[0010] In step 5, the molar ratio of the phenolic derivative, the EDC and NHS is 1:1:1.

[0011] In step 6, the phenolic derivative and the O -The molar dosage ratio of carboxylated chitosan quaternary ammonium salt is 1~5:1.

[0012] After adopting the above technical scheme, the present invention provides a method for preparing a phenolic chitosan quaternary ammonium salt antibacterial agent, wherein chitosan is first alkalized at low temperature, and then subjected to a substitution reaction with a carboxylic acid derivative to introduce a reactive carboxyl group on the hydroxyl group of chitosan to obtain O -Carboxylation of chitosan provides reactive sites for subsequent secondary modification, and then reacts with chitosan through ring-opening reaction. O -Introducing quaternary ammonium salt groups on the amino groups of carboxylated chitosan, thereby improving the antibacterial property and water solubility of chitosan, and finally reacting with phenolic derivatives to obtain phenolic chitosan quaternary ammonium salt antibacterial agent. The core improvement of the present invention is that a small molecule derivative containing amino and phenolic structures is grafted into chitosan quaternary ammonium salt through a mild EDC / NHS reaction, so that the prepared chitosan derivative has not only antibacterial activity but also excellent antioxidant properties.

[0013] The phenolic chitosan quaternary ammonium salt antibacterial agent synthesized by the preparation method of the invention has good water solubility, excellent antibacterial activity and free radical scavenging ability, and has better performance than single chitosan and chitosan quaternary ammonium salt. The preparation method is simple, the raw material source is convenient, and it is easy to industrialize production. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The synthetic route schematic diagram of Example 1; Figure 2 The synthetic route schematic diagram of Example 1; Figure 3 The synthetic route schematic diagram of Example 1; Figure 4 Schematic diagram of the synthesis route of Example 1. DETAILED DESCRIPTION

[0015] In order to further explain the technical solution of the present invention, the present invention is described in detail below through specific embodiments.

[0016] 1. Preparation of phenolic chitosan quaternary ammonium salt antibacterial agent Example 1 A method for preparing a phenolic chitosan quaternary ammonium salt antibacterial agent, wherein the synthetic route is as follows: Figure 1 As shown, the following steps are included: Step 1: Disperse 1.0 kg of chitosan in 30 kg of isopropanol solution to obtain a chitosan dispersion, and put it into a reactor; Step 2, then dissolving 3 kg of sodium hydroxide in 10 kg of deionized water to obtain a sodium hydroxide solution, and then slowly adding the sodium hydroxide solution to the chitosan dispersion, and alkalizing at -20°C for 12 h; Step 3: Then, at room temperature, 3 kg of chloroacetic acid was added in batches to the alkalized chitosan dispersion, and then the reaction temperature was raised to 60°C and the reaction was carried out at a constant temperature for 6 hours. After the reaction was completed, the product was filtered, washed with anhydrous ethanol for multiple times, and dried to obtain O - carboxymethyl chitosan; Step 4, then weigh 2.2 kg O -Carboxymethyl chitosan was dissolved in 100 kg of deionized water, then 7.6 kg of 2,3-epoxypropyltrimethylammonium chloride was dissolved in 15 kg of deionized water, and then the aqueous solution of 2,3-epoxypropyltrimethylammonium chloride was slowly added dropwise to O -carboxymethyl chitosan aqueous solution, raise the reaction temperature to 85 ° C, keep constant temperature reaction for 12 h, after the reaction is completed, transfer the crude product to an ultrafiltration device, ultrafiltration to remove 2,3-epoxypropyltrimethylammonium chloride that does not participate in the reaction, and then concentrate and freeze-dry to obtain O -Carboxymethyl- N -(2-Hydroxypropyltrimethylammonium chloride)chitosan( O -carboxymethyl chitosan quaternary ammonium salt); Step 5, then dissolve 3.8 kg of 2-(3,4-dihydroxyphenyl)ethylamine (dopamine hydrochloride) in 50 kg of anhydrous ethanol, lower the system temperature to 0 ° C, add 4.8 kg of EDC and 2.9 kg of NHS, and obtain an ethanol solution of dopamine hydrochloride after complete dissolution; Step 6, then 2.3 kg O -Carboxymethyl chitosan quaternary ammonium salt was dissolved in 100 kg of deionized water, and the ethanol solution of dopamine hydrochloride was slowly added to the O -carboxymethyl chitosan quaternary ammonium salt aqueous solution, raise the reaction temperature to 25 ℃, and react at constant temperature for 24 hours. After the reaction is completed, the crude product is transferred to an ultrafiltration device for ultrafiltration, and then concentrated and freeze-dried to obtain a phenolic chitosan quaternary ammonium salt antibacterial agent with the following structure:

[0017] Example 2 A method for preparing a phenolic chitosan quaternary ammonium salt antibacterial agent, wherein the synthetic route is as follows: Figure 2 As shown, the following steps are included: Step 1, first disperse 1.0 kg of chitosan in 40 kg of isopropanol solution to obtain a chitosan dispersion, and put it into a reactor; Step 2, then dissolving 4 kg of sodium hydroxide in 13 kg of deionized water to obtain a sodium hydroxide solution, and then slowly adding the sodium hydroxide solution to the chitosan dispersion, and alkalizing at -20°C for 16 hours; Step 3: Then, at room temperature, 5 kg of p-chloromethylbenzoic acid was added to the alkalized chitosan dispersion in batches, and then the reaction temperature was raised to 80°C and the reaction was carried out at a constant temperature for 10 h. After the reaction was completed, the product was filtered, washed with anhydrous ethanol for multiple times, and dried to obtain O - carboxybenzyl chitosan; Step 4, then weigh 3.1 kg O -Carboxybenzyl chitosan was dissolved in 15 kg formic acid, 30 kg of 37% formaldehyde solution and 45 kg of deionized water were added, the reaction temperature was raised to 75 °C, and the reaction was carried out at a constant temperature for 120 h. After the reaction was completed, the pH was adjusted with a 50% sodium hydroxide solution until a large amount of precipitation was produced, and then the deionized water was washed several times until neutral, and the intermediate was obtained by vacuum drying. Then the intermediate was dissolved in 100 kg of N- 15 kg of iodomethane was added to methyl pyrrolidone, and the mixture was reacted at 45 °C in the dark for 120 h. The crude product was transferred to an ultrafiltration device and dialyzed with 1% sodium chloride solution and deionized water in turn. After concentration and freeze-drying, the product was obtained. O -Carboxybenzyl- N , N , N -Trimethyl chitosan ( O -carboxybenzyl chitosan quaternary ammonium salt); Step 5, then dissolve 5.7 kg of 2-(3,4-dihydroxyphenyl)ethylamine (dopamine hydrochloride) in 50 kg of anhydrous ethanol, lower the system temperature to 0 ° C, add 5.8 kg of EDC and 3.5 kg of NHS, and obtain an ethanol solution of dopamine hydrochloride after complete dissolution; Step 6, then 3.1 kg O -Carboxybenzyl chitosan quaternary ammonium salt was dissolved in 100 kg of deionized water, and the ethanol solution of dopamine hydrochloride was slowly added to the O -carboxybenzyl chitosan quaternary ammonium salt aqueous solution, raise the reaction temperature to 30 ℃, and react at constant temperature for 18 hours. After the reaction is completed, the crude product is transferred to an ultrafiltration device for ultrafiltration, and then concentrated and freeze-dried to obtain a phenolic chitosan quaternary ammonium salt antibacterial agent with the following structure:

[0018] Example 3 A method for preparing a phenolic chitosan quaternary ammonium salt antibacterial agent, wherein the synthetic route is as follows: Figure 3 As shown, the following steps are included: Step 1: Disperse 1.0 kg of chitosan in 35 kg of isopropanol solution to obtain a chitosan dispersion, and put it into a reactor; Step 2, then dissolving 5 kg of sodium hydroxide in 15 kg of deionized water to obtain a sodium hydroxide solution, and then slowly adding the sodium hydroxide solution to the chitosan dispersion, and alkalizing at -20°C for 12 h; Step 3: Then, at room temperature, 4 kg of chloropropionic acid was added in batches to the alkalized chitosan dispersion, and then the reaction temperature was raised to 80°C and the reaction was carried out at a constant temperature for 12 h. After the reaction was completed, the product was filtered, washed with anhydrous ethanol for multiple times, and dried to obtain O - carboxyethyl chitosan; Step 4, then weigh 2.5 kg O -Carboxyethyl chitosan was dispersed in 30 kg N -methyl pyrrolidone, then slowly add 3.8 kg of p-chloromethylbenzoyl chloride, raise the reaction temperature to 30 ° C, and react at constant temperature for 12 h. After the reaction is completed, filter it, wash the filter cake with anhydrous ethanol for several times, and dry it to obtain the intermediate. Then weigh 4.0 kg of the intermediate and dissolve it in 50 kg of N -Methylpyrrolidone, add 4.2 kg N , N -dimethyldodecylamine, raise the reaction temperature to 85 °C, keep the reaction at constant temperature for 12 h, filter after the reaction, wash the filter cake with anhydrous ethanol several times, and dry to obtain O -Carboxyethyl- N -Carboxybenzyl-N ', N '-Dimethyl- N '-Dodecyl chitosan ( O -carboxyethyl chitosan quaternary ammonium salt); Step 5, then dissolving 1.6 kg of p-aminophenol in 30 kg of anhydrous ethanol, lowering the system temperature to 0°C, adding 2.9 kg of EDC and 1.7 kg of NHS, and obtaining an ethanol solution of p-aminophenol after complete dissolution; Step 6, then 3.1 kg O -Carboxyethyl chitosan quaternary ammonium salt was dissolved in 100 kg of deionized water, and the ethanol solution of p-aminophenol was slowly added to the O -carboxyethyl chitosan quaternary ammonium salt aqueous solution, raise the reaction temperature to 35 ℃, and react at constant temperature for 24 hours. After the reaction is completed, the crude product is transferred to an ultrafiltration device for ultrafiltration, and then concentrated and freeze-dried to obtain a phenolic chitosan quaternary ammonium salt antibacterial agent with the following structure:

[0019] Example 4 A method for preparing a phenolic chitosan quaternary ammonium salt antibacterial agent, wherein the synthetic route is as follows: Figure 4 As shown, the following steps are included: Step 1: Disperse 1.0 kg of chitosan in 35 kg of isopropanol solution to obtain a chitosan dispersion, and put it into a reactor; Step 2, then dissolving 3 kg of sodium hydroxide in 15 kg of deionized water to obtain a sodium hydroxide solution, and then slowly adding the sodium hydroxide solution to the chitosan dispersion, and alkalizing at -20°C for 18 hours; Step 3: Then, at room temperature, 4.5 kg of p-chloromethylbenzoic acid was added to the alkalized chitosan dispersion in batches, and then the reaction temperature was raised to 85°C and the reaction was carried out at a constant temperature for 12 h. After the reaction was completed, the product was filtered, washed with anhydrous ethanol for multiple times, and dried to obtain O - carboxybenzyl chitosan; Step 4, then weigh 3.1 kg O -Carboxybenzyl chitosan was dissolved in 100 kg of deionized water, and then 4.9 kg of 1,3-propane sultone was slowly added dropwise to O -carboxybenzyl chitosan aqueous solution, raise the reaction temperature to 75 ° C, keep constant temperature reaction for 24 hours, after the reaction is completed, transfer the crude product to an ultrafiltration device, ultrafiltration to remove 1,3-propane sultone that does not participate in the reaction, and then concentrate and freeze-dry to obtain O -Carboxybenzyl- N -Sulfopropyl chitosan ( O-carboxybenzyl chitosan quaternary ammonium salt); Step 5, then dissolving 6.5 kg of 4-amino-resorcinol in 60 kg of anhydrous ethanol, lowering the system temperature to 0°C, adding 7.7 kg of EDC and 4.6 kg of NHS, and obtaining an ethanol solution of 4-amino-resorcinol after complete dissolution; Step 6, then 4.4 kg O -Carboxybenzyl chitosan quaternary ammonium salt was dissolved in 120 kg of deionized water, and the ethanol solution of 4-amino-resorcinol was slowly added to O -carboxybenzyl chitosan quaternary ammonium salt aqueous solution, raise the reaction temperature to 25 ℃, and react at constant temperature for 24 hours. After the reaction is completed, the crude product is transferred to an ultrafiltration device for ultrafiltration, and then concentrated and freeze-dried to obtain a phenolic chitosan quaternary ammonium salt antibacterial agent with the following structure:

[0020] Comparative Example First, 1.0 kg of chitosan was weighed and dissolved in 100 kg of acetic acid aqueous solution with a volume fraction of 2%, and then 4.7 kg of 2,3-epoxypropyltrimethylammonium chloride was dissolved in 10 kg of water. The aqueous solution of 2,3-epoxypropyltrimethylammonium chloride was added to the acetic acid solution of chitosan by a peristaltic pump, and the temperature of the reaction system was raised to 85 ° C. The reaction was kept at a constant temperature for 12 h. After the reaction was completed, it was transferred to an ultrafiltration device for ultrafiltration, and then concentrated and freeze-dried to obtain N -Chitosan quaternary ammonium salt, the structure is as follows:

[0021] 2. Antibacterial performance test of phenolic chitosan quaternary ammonium salt antibacterial agent The plate count method was used to N -Chitosan quaternary ammonium salt, obtained in Example 1 O -Carboxymethyl chitosan, O -The antibacterial properties of carboxymethyl chitosan quaternary ammonium salt and the phenolic chitosan quaternary ammonium salt antibacterial agent obtained in each example were tested.

[0022] Specifically, each of the above chitosan derivatives was first dissolved in deionized water to obtain a corresponding solution with a concentration of 1.0 mg / mL, which was sterilized for use. The test bacteria were activated and diluted to a certain concentration, and then 0.5 mL of the diluted bacterial solution was fully mixed with the sterilized chitosan derivative solution. At this time, the concentration of the chitosan derivative in each solution was 0.5 mg / mL, and then incubated in a 37°C constant temperature shaker for 10 min, and then an appropriate amount was evenly spread on the LB agar medium, placed in a 37°C incubator for 18~24 h, and sterilized deionized water was added as the control group. The antibacterial rate was calculated using the following formula, and the results are shown in Table 1.

[0023]

[0024] Table 1 N -Chitosan quaternary ammonium salt, O -Carboxymethyl chitosan, O - Antibacterial effect of carboxymethyl chitosan quaternary ammonium salt and phenolic chitosan quaternary ammonium salt prepared in each example

[0025] The results in Table 1 show that the antibacterial rate of the phenolic chitosan quaternary ammonium salt antibacterial agent prepared by the present invention against Staphylococcus aureus and Escherichia coli can reach more than 90%, and the antibacterial effect is better than O -Carboxymethyl chitosan, N -Chitosan quaternary ammonium salt, O - Antibacterial effect of carboxymethyl chitosan quaternary ammonium salt. When the concentration of antibacterial components is 0.5 mg / mL, O -The antibacterial rates of carboxymethyl chitosan quaternary ammonium salt against Staphylococcus aureus and Escherichia coli were 67.3% and 54.3%, respectively; N -Chitosan quaternary ammonium salt and O -The inhibition rates of carboxymethyl chitosan quaternary ammonium salt against Escherichia coli and Staphylococcus aureus are similar.

[0026] 3. Free Radical Scavenging Ability Test of Phenolic Chitosan Quaternary Ammonium Salt Antibacterial Agent The absorbance method was used to N -Chitosan quaternary ammonium salt, obtained in Example 1 O -Carboxymethyl chitosan, O - The scavenging ability of carboxymethyl chitosan quaternary ammonium salt and the phenolic chitosan quaternary ammonium salt antibacterial agent prepared in each embodiment on DPPH free radicals was tested. First, DPPH was dissolved in anhydrous ethanol to obtain a 180 µmol / L DPPH-ethanol solution; then, each of the above chitosan derivatives was dissolved in deionized water to obtain a corresponding chitosan solution with a concentration of 1.0 mg / mL, and then 0.5 mL of DPPH-ethanol solution was mixed with 0.5 mL of chitosan solution, and after mixing evenly, the final concentration of the sample was 0.5 mg / mL. Finally, the mixture was incubated at room temperature in the dark for 20 min, and its absorption value at 520 nm was tested. The mixed solution of 0.5 mL of deionized water and 0.5 mL of DPPH-ethanol solution was used as the blank group, and the mixed solution of 0.5 mL of anhydrous ethanol and 0.5 mL of DPPH-ethanol solution was used as the control group. The DPPH free radical scavenging rate was calculated according to the following formula, and the results are shown in Table 2.

[0027]

[0028] Table 2 N -Chitosan quaternary ammonium salt, O -Carboxymethyl chitosan, O -Carboxymethyl chitosan quaternary ammonium salt and phenolic chitosan quaternary ammonium salt antibacterial agent prepared in each embodiment have DPPH free radical scavenging ability

[0029] The results in Table 2 show that 0.5 mg / mL N -Chitosan quaternary ammonium salt, O -Carboxymethyl chitosan and O -The scavenging ability of carboxymethyl chitosan quaternary ammonium salt on DPPH free radicals is weak and basically consistent, and its scavenging rate on DPPH free radicals is only 15%. After the introduction of phenolic groups, its scavenging ability on DPPH free radicals has been greatly improved. The scavenging ability of 0.5 mg / mL phenolic chitosan quaternary ammonium salt on DPPH free radicals exceeds 90%.

[0030] The above results show that the phenolic chitosan quaternary ammonium salt antibacterial agent synthesized by the preparation method of the present invention has excellent antibacterial activity and free radical scavenging ability, and its performance is better than that of chitosan quaternary ammonium salt.

[0031] The above embodiments and drawings do not limit the product form and style of the present invention. Any appropriate changes or modifications made by ordinary technicians in the relevant technical field should be deemed to be within the patent scope of the present invention.

Claims

1. A method for preparing a phenolic chitosan quaternary ammonium salt antibacterial agent, characterized in that: The following steps are involved: Step 1, first dispersing chitosan in an isopropanol solution to obtain a chitosan dispersion; Step 2, then slowly adding sodium hydroxide solution to the chitosan dispersion and alkalizing at -20°C for 6 to 24 hours; Step 3: Then, at room temperature, the carboxylic acid derivatives are added in batches to the alkalized chitosan dispersion, and then the reaction temperature is increased to 60-100 °C, and the reaction is carried out at a constant temperature for 6-24 hours. After the reaction is completed, the product is filtered, washed with anhydrous ethanol for multiple times, and dried to obtain O - Carboxylated chitosan; Step 4, then O -Carboxylated chitosan was dissolved in deionized water, and the amino groups of chitosan were further quaternized to obtain O - Carboxylated chitosan quaternary ammonium salt; Step 5, then dissolving the phenol derivative in anhydrous ethanol, lowering the system temperature to 0°C, adding EDC and NHS to obtain an ethanol solution of the phenol derivative; Step 6, then O - Dissolve the carboxylated chitosan quaternary ammonium salt in deionized water, and slowly add the ethanol solution of the phenolic derivative into O -In an aqueous solution of carboxylated chitosan quaternary ammonium salt, the reaction temperature is increased to 20-60 °C, and the reaction is carried out at a constant temperature for 6-24 hours. After the reaction is completed, the crude product is successively ultrafiltered, concentrated, and freeze-dried to obtain a phenolic chitosan quaternary ammonium salt antibacterial agent; The result obtained in step 4 O - carboxylated chitosan quaternary ammonium salt is selected from O -Carboxymethyl- N , N , N -Trimethyl chitosan quaternary ammonium salt, O -Carboxymethyl- N , N , N -Triethyl chitosan quaternary ammonium salt, O -Carboxymethyl- N , N -Dimethyl- N -Dodecyl chitosan quaternary ammonium salt, O -Carboxymethyl- N -Biguanide chitosan hydrochloride, O -Carboxymethyl- N -(2-Hydroxypropyltrimethylammonium chloride)chitosan, O -Carboxymethyl- N -Sulfopropyl chitosan, O -Carboxyethyl- N -Carboxybenzyl- N ', N '-Dimethyl- N '-Dodecyl chitosan or O -Carboxybenzyl- N -Sulfopropyl chitosan; In step 5, the phenol derivative is selected from p-aminophenol, 2-aminophenol, 2-amino-resorcinol, 2-(3,4-dihydroxyphenyl)ethylamine, 4-amino-resorcinol or 4-amino-3,5-dichlorophenol.

2. The method for preparing a phenolic chitosan quaternary ammonium salt antibacterial agent according to claim 1, wherein: In step 1, the mass fraction of the chitosan dispersion is 1% to 10%.

3. The method for preparing a phenolic chitosan quaternary ammonium salt antibacterial agent according to claim 1, characterized in that: In step 2, the mass ratio of sodium hydroxide in the sodium hydroxide solution to chitosan in the chitosan dispersion is 1-5:

1.

4. The method for preparing a phenolic chitosan quaternary ammonium salt antibacterial agent according to claim 1, wherein: In step 3, the carboxylic acid derivative is selected from chloroacetic acid, chloropropionic acid, p-chloromethylbenzoic acid, bromoacetic acid or bromopropionic acid, and the mass ratio of the carboxylic acid derivative to the chitosan in the alkalized chitosan dispersion is 1-5:

1.

5. The method for preparing a phenolic chitosan quaternary ammonium salt antibacterial agent according to claim 1, characterized in that: In step 5, the molar ratio of the phenol derivative, the EDC and NHS is 1:1:

1.

6. The method for preparing a phenolic chitosan quaternary ammonium salt antibacterial agent according to claim 1, characterized in that: In step 6, the phenolic derivative and the O -The molar dosage ratio of carboxylated chitosan quaternary ammonium salt is 1~5:1.

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