Preparation method of non-animal-derived carboxyethyl chitosan

Abstract

The invention provides a preparation method of non-animal source carboxyethyl chitosan, and belongs to the technical field of chemical synthesis. Comprising the following steps: S1, uniformly mixing an ionic liquid and a deep eutectic solvent to prepare a reaction solvent; s2, adding the pretreated non-animal-derived chitosan into a reaction solvent, introducing carbon dioxide, adding acrylic acid, carrying out microwave heating and stirring reaction, cooling to room temperature after the reaction is finished, adding a precipitator, precipitating, filtering, washing a solid, purifying and drying to obtain non-animal-derived carboxyethyl chitosan; and S3, heating the liquid obtained after filtration in the step S2, carrying out reduced pressure recovery on the precipitant, enabling the obtained product reaction solvent to enter the step S1 for reuse, and enabling the recovered mixed solvent to enter the step S2 for reuse. According to the method, the reaction conditions are mild, the reaction time is short, a large amount of waste chemicals are not treated in the reaction process, the reaction solvent and the precipitant can be recycled, and the prepared non-animal-derived carboxyethyl chitosan is high in substitution degree and easy to realize industrial application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical synthesis, in particular to a preparation method of non-animal source carboxyethyl chitosan. BACKGROUND

[0002] Non-animal source chitosan (CS) is a natural nitrogen-containing polysaccharide, which has unique biocompatibility, non-toxicity and easy degradation, and is widely used in the fields of biological engineering and medicine. However, the water solubility of non-animal source chitosan is poor, which limits its application range. Through Michael addition reaction, a part of the amino groups of non-animal source chitosan can be modified to prepare non-animal source carboxyethyl chitosan (CEC), which retains a part of the amino groups and greatly improves the water solubility of non-animal source chitosan.

[0003] In the prior art, a large amount of alkali is consumed in the preparation process, the alkali consumption is huge, and the reaction needs to be switched between low temperature and high temperature for multiple times, which consumes a lot of energy. The single reaction time is long, and the reagent often needs to be added multiple times, so the production efficiency is low. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of non-animal source carboxyethyl chitosan, which uses ionic liquid and eutectic solvent composite solvent for the preparation of non-animal source carboxyethyl chitosan. The reaction conditions are mild, the reaction time is short, and there is no treatment of a large amount of waste chemicals in the reaction process. The reaction solvent and the precipitating agent can be reused. The substitution degree of the prepared non-animal source carboxyethyl chitosan is high, and it is easy to realize industrial application.

[0005] The technical scheme of the present application is as follows: The present application provides a preparation method of non-animal source carboxyethyl chitosan, comprising the following steps: S1. Mix the ionic liquid and the eutectic solvent uniformly to prepare a reaction solvent; S2. Add the pretreated non-animal source chitosan to the reaction solvent, pass in carbon dioxide gas, then add acrylic acid, and microwave heating and stirring reaction. After the reaction is completed, cool to room temperature, add methanol / ethanol mixed solvent to the system, precipitate, filter, wash the solid, purify, dry, and prepare non-animal source carboxyethyl chitosan; S3. Heat and reduce pressure to recover the mixed solvent from the liquid obtained after filtering in step S2, remove the carbon dioxide, and obtain the product reaction solvent, which is reused in step S1. The recovered mixed solvent is reused in step S2.

[0006] As a further improvement of the present application, the ionic liquid in step S1 is at least one of 1-ethyl-3-methylimidazolium hydroxide, 1-butyl-3-methylimidazolium hydroxide, and tetrabutylammonium hydroxide.

[0007] The anion of the basic ionic liquid selected by the application is hydroxyl, which can exchange protons with the amino group of the non-animal source chitosan, and significantly improve the nucleophilicity of the non-animal source chitosan.

[0008] As a further improvement of the application, the hydrogen bond acceptor of the eutectic solvent in step S1 is choline chloride, the hydrogen bond donor is at least one of urea, glycerol, ethylene glycol and acetic acid, and the molar ratio of the hydrogen bond acceptor and the hydrogen bond donor is 1:1-3.

[0009] The eutectic solvent selected by the application is weakly basic, and the Cl - The strong hydrogen bond formed between the -OH and -NH2 of the non-animal source chitosan and the Cl

[0010] As a further improvement of the application, the volume ratio of the ionic liquid and the eutectic solvent in step S1 is 1:1-3.

[0011] As a further improvement of the application, the aeration amount of the carbon dioxide gas in step S2 is 3-5 mL / min, and the aeration is 5-10 min per 100 mL of the reaction solvent.

[0012] As a further improvement of the application, the mass ratio of the pretreated non-animal source chitosan and acrylic acid in step S2 is 1:1.5-2.5.

[0013] The pretreatment method of the non-animal source chitosan: through acid deashing and alkali deproteinization, the pretreated non-animal source chitosan is obtained through acid-alkali cycle treatment.

[0014] As a further improvement of the application, the power of the microwave heating and stirring reaction in step S2 is 300-500 W, the heating temperature is 70-75℃, and the time is 3-5 h.

[0015] As a further improvement of the application, the volume ratio of methanol and ethanol in the methanol / ethanol mixed solvent in step S2 is 1:3-5.

[0016] As a further improvement of the application, the volume ratio of the reaction solvent and the methanol / ethanol mixed solvent in step S2 is 1:1-3.

[0017] As a further improvement of the application, the degree of substitution of the non-animal source carboxyethyl chitosan in step S3 is 0.8-0.9.

[0018] The application has the following beneficial effects: The present application selects ionic liquid and eutectic solvent as a mixed reaction solvent for preparing non-animal source carboxyethyl chitosan. The non-animal source chitosan has poor solubility in traditional solvents due to a large number of hydrogen bonds between molecules, and the amino groups are wrapped in dense molecular chains and are difficult to participate in the reaction. The anion of the ionic liquid or the hydrogen bond acceptor of the eutectic solvent can form strong hydrogen bonds with the hydroxyl (-OH) and amino (-NH2) of the non-animal source chitosan, competitively destroy the intermolecular hydrogen bond network, make the non-animal source chitosan molecular chain stretch, swell and even dissolve, weaken the intramolecular hydrogen bond of the non-animal source chitosan, reduce the rigidity of the molecular chain, and expose more active reaction sites, so as to facilitate the Michael addition reaction with acrylic acid. The cation of the ionic liquid can form an ion pair with the negative charge center of the transition state, reduce the energy of the transition state, and thus reduce the activation energy of the reaction, thereby accelerating the reaction process and reducing the reaction energy barrier, so that the reaction can still be carried out at a lower temperature, and the reaction time is significantly shortened, greatly improving the industrial application ability.

[0019] The present application introduces carbon dioxide into the reaction solvent, which can combine with the basic sites in the reaction system to form a carbonate or bicarbonate buffer pair, prevent the non-animal source chitosan from being degraded by alkali or the acrylic acid from being polymerized due to excessive basicity, is not easy to decompose and escape at a lower temperature, reduces the viscosity of the ionic liquid, improves the mass transfer efficiency, changes the solvent polarity, and may moderately improve the reaction rate, greatly improving the degree of substitution of the prepared non-animal source carboxyethyl chitosan. When heated and treated under reduced pressure in the later stage, the carbon dioxide will escape, so that the reaction solvent returns to the original state, facilitating the recycling and reuse of the solvent.

[0020] In the reaction process, the microwave heating treatment promotes the stretching of the non-animal source chitosan molecular chain, and accelerates the contact between the basic component and the amino group, so that the reaction efficiency is higher than that of traditional heating, and the reaction is more complete and faster.

[0021] After the reaction is completed, a methanol / ethanol mixed solvent is added, which can be well intermiscible with the reaction solvent, but the solubility of the generated non-animal source carboxyethyl chitosan in the methanol / ethanol mixed solvent is low, so that the prepared non-animal source carboxyethyl chitosan can be precipitated, greatly simplifying the separation step, and the methanol / ethanol mixed solvent removed under reduced pressure can be reused multiple times, greatly reducing the industrialization cost.

[0022] The present application uses ionic liquid and eutectic solvent complex solvent for the preparation of non-animal source carboxyethyl chitosan, which has mild reaction conditions and short reaction time, and no large amount of waste chemicals are treated during the reaction process. The reaction solvent and the precipitant can be reused, the degree of substitution of the prepared non-animal source carboxyethyl chitosan is high, and the industrial application is easy to realize. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0024] Embodiment 1

[0025] The embodiment provides a preparation method of non-animal source carboxyethyl chitosan, comprising the following steps: S1. uniformly mixing 100 mL of 1-butyl-3-methylimidazolium hydroxide and 100 mL of a deep eutectic solvent to prepare a reaction solvent; the hydrogen bond acceptor of the deep eutectic solvent is choline chloride, the hydrogen bond donor is urea, and the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:2; S2. adding 5 g of pretreated Pleurotus ostreatus chitosan into 100 mL of the reaction solvent, passing in carbon dioxide gas, the passing amount of the carbon dioxide gas is 3 mL / min, the carbon dioxide gas is passed in for 10 min, then 7.5 g of acrylic acid is added, 300 W microwave heating is performed until the temperature reaches 70 DEG C, stirring is performed for 3 h, after the reaction is completed, the system is cooled to room temperature, 100 mL of a methanol / ethanol mixed solvent is added into the system, the volume ratio of methanol to ethanol in the methanol / ethanol mixed solvent is 1:3, precipitation is performed for 1 h, filtration is performed, the solid is washed, purification is performed, drying is performed, and non-animal source carboxyethyl chitosan is prepared; The pretreatment method is: acid deashing, alkali deproteinization, and acid-alkali cycle treatment to obtain pretreated Pleurotus ostreatus chitosan.

[0026] S3. heating and reducing pressure recovery of the liquid obtained after filtration in step S2 to recover the mixed solvent and remove carbon dioxide, the obtained product reaction solvent is used repeatedly in step S1, and the recovered mixed solvent is used repeatedly in step S2.

[0027] Embodiment 2

[0028] The embodiment provides a preparation method of non-animal source carboxyethyl chitosan, comprising the following steps: S1. uniformly mixing 100 mL of 1-butyl-3-methylimidazolium hydroxide and 100 mL of a deep eutectic solvent to prepare a reaction solvent; the hydrogen bond acceptor of the deep eutectic solvent is choline chloride, the hydrogen bond donor is urea, and the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:2; S2. Add 5 g of pretreated Pleurotus ostreatus chitosan to 100 mL of reaction solvent, pass in carbon dioxide gas, the aeration amount of the carbon dioxide gas is 5 mL / min, pass in for 5 min, then add 12.5 g of acrylic acid, heat to 75℃ under 500W microwave, stir for 5h, after the reaction is completed, cool to room temperature, add 300 mL of methanol / ethanol mixed solvent to the system, the volume ratio of methanol and ethanol in the methanol / ethanol mixed solvent is 1:5, precipitate for 1h, filter, wash the solid, purify, dry, and prepare non-animal source carboxyethyl chitosan; The pretreatment method is: through acid deashing and alkali deproteinization, the pretreated Pleurotus ostreatus chitosan is obtained through acid-alkali cycle treatment.

[0029] S3. Heat and reduce the pressure of the liquid obtained after filtering in step S2 to recover the mixed solvent, remove the carbon dioxide, and the obtained product reaction solvent is used repeatedly in step S1, and the recovered mixed solvent is used repeatedly in step S2.

[0030] Example 3

[0031] The embodiment provides a preparation method of non-animal source carboxyethyl chitosan, which comprises the following steps: S1. Mix 100 mL of 1-ethyl-3-methylimidazole hydroxide and 200 mL of a eutectic solvent uniformly to prepare a reaction solvent; the hydrogen bond acceptor of the eutectic solvent is choline chloride, the hydrogen bond donor is ethylene glycol, and the molar ratio of the hydrogen bond acceptor and the hydrogen bond donor is 1:2; S2. Add 5 g of pretreated Pleurotus ostreatus chitosan to 100 mL of reaction solvent, pass in carbon dioxide gas, the aeration amount of the carbon dioxide gas is 4 mL / min, pass in for 7 min, then add 8 g of acrylic acid, heat to 72℃ under 400W microwave, stir for 4h, after the reaction is completed, cool to room temperature, add 200 mL of methanol / ethanol mixed solvent to the system, the volume ratio of methanol and ethanol in the methanol / ethanol mixed solvent is 1:4, precipitate for 1h, filter, wash the solid, purify, dry, and prepare non-animal source carboxyethyl chitosan; The pretreatment method is: through acid deashing and alkali deproteinization, the pretreated Pleurotus ostreatus chitosan is obtained through acid-alkali cycle treatment.

[0032] S3. Heat and reduce the pressure of the liquid obtained after filtering in step S2 to recover the mixed solvent, remove the carbon dioxide, and the obtained product reaction solvent is used repeatedly in step S1, and the recovered mixed solvent is used repeatedly in step S2.

[0033] Comparative Example 1 Compared with Example 3, the difference lies in that 1-ethyl-3-methylimidazole hydroxide is not added.

[0034] The embodiment provides a preparation method of non-animal source carboxyethyl chitosan, which comprises the following steps: S1. 5 g of pretreated Pleurotus ostreatus chitosan was added to 100 mL of a deep eutectic solvent, carbon dioxide gas was introduced, the amount of the carbon dioxide gas introduced was 4 mL / min, the introduction lasted for 7 min, then 8 g of acrylic acid was added, 400 W microwave heating was performed to 72 DEG C, stirring reaction was performed for 4 h, after the reaction was completed, cooling was performed to room temperature, 200 mL of a methanol / ethanol mixed solvent was added to the system, the volume ratio of methanol and ethanol in the methanol / ethanol mixed solvent was 1:4, precipitation was performed for 1 h, filtration was performed, the solid was washed, purification was performed, drying was performed, and non-animal source carboxyethyl chitosan was prepared; The pretreatment method is as follows: acid deashing, alkali deproteinization, and acid-alkali cycle treatment are performed to obtain pretreated Pleurotus ostreatus chitosan.

[0035] The hydrogen bond acceptor of the deep eutectic solvent is choline chloride, the hydrogen bond donor is ethylene glycol, and the molar ratio of the hydrogen bond acceptor and the hydrogen bond donor is 1:2; S2. The liquid obtained after filtration in step S1 was heated and reduced pressure recovery was performed to recover the mixed solvent, carbon dioxide was removed, the product deep eutectic solvent was used repeatedly in step S1, and the recovered mixed solvent was used repeatedly in step S1.

[0036] Comparative Example 2 Compared with Example 3, the difference is that no deep eutectic solvent is added.

[0037] The following steps are included: S1. 5 g of pretreated Pleurotus ostreatus chitosan was added to 100 mL of a deep eutectic solvent, carbon dioxide gas was introduced, the amount of the carbon dioxide gas introduced was 4 mL / min, the introduction lasted for 7 min, then 8 g of acrylic acid was added, 400 W microwave heating was performed to 72 DEG C, stirring reaction was performed for 4 h, after the reaction was completed, cooling was performed to room temperature, 200 mL of a methanol / ethanol mixed solvent was added to the system, the volume ratio of methanol and ethanol in the methanol / ethanol mixed solvent was 1:4, precipitation was performed for 1 h, filtration was performed, the solid was washed, purification was performed, drying was performed, and non-animal source carboxyethyl chitosan was prepared; The pretreatment method is as follows: acid deashing, alkali deproteinization, and acid-alkali cycle treatment are performed to obtain pretreated Pleurotus ostreatus chitosan.

[0038] S2. The liquid obtained after filtration in step S1 was heated and reduced pressure recovery was performed to recover the mixed solvent, carbon dioxide was removed, the product deep eutectic solvent was used repeatedly in step S1, and the recovered mixed solvent was used repeatedly in step S1.

[0039] Comparative Example 3 Compared with Example 3, the difference is that no carbon dioxide is introduced.

[0040] The following steps are included: S1. Mix 100 mL of 1-ethyl-3-methylimidazole hydroxide and 200 mL of a deep eutectic solvent uniformly to prepare a reaction solvent; the hydrogen bond acceptor of the deep eutectic solvent is choline chloride, the hydrogen bond donor is ethylene glycol, and the molar ratio of the hydrogen bond acceptor and the hydrogen bond donor is 1:2; S2. Add 5 g of pretreated Pleurotus ostreatus chitosan to 100 mL of the reaction solvent, then add 8 g of acrylic acid, heat to 72°C under microwave at 400 W, stir for 4 h, after the reaction is completed, cool to room temperature, add 200 mL of a methanol / ethanol mixed solvent to the system, the volume ratio of methanol and ethanol in the methanol / ethanol mixed solvent is 1:4, precipitate for 1 h, filter, wash the solid, purify, dry, and prepare non-animal source carboxyethyl chitosan; The pretreatment method is to obtain pretreated Pleurotus ostreatus chitosan through acid deashing and alkali deproteinization by acid-alkali circulation treatment.

[0041] S3. Heat and reduce the pressure to recover the mixed solvent from the liquid obtained after filtering in step S2, the obtained product reaction solvent is reused in step S1, and the recovered mixed solvent is reused in step S2.

[0042] Comparative Example 4 Compared with Example 3, the difference is that no microwave treatment is performed, and a traditional oil bath heating method is adopted.

[0043] Comprise the following steps: S1. Mix 100 mL of 1-ethyl-3-methylimidazole hydroxide and 200 mL of a deep eutectic solvent uniformly to prepare a reaction solvent; the hydrogen bond acceptor of the deep eutectic solvent is choline chloride, the hydrogen bond donor is ethylene glycol, and the molar ratio of the hydrogen bond acceptor and the hydrogen bond donor is 1:2; S2. Add 5 g of pretreated Pleurotus ostreatus chitosan to 100 mL of the reaction solvent, pass in carbon dioxide gas, the aeration amount of the carbon dioxide gas is 4 mL / min, pass in for 7 min, then add 8 g of acrylic acid, heat to 72°C under oil bath, stir for 4 h, after the reaction is completed, cool to room temperature, add 200 mL of a methanol / ethanol mixed solvent to the system, the volume ratio of methanol and ethanol in the methanol / ethanol mixed solvent is 1:4, precipitate for 1 h, filter, wash the solid, purify, dry, and prepare non-animal source carboxyethyl chitosan; The pretreatment method is to obtain pretreated Pleurotus ostreatus chitosan through acid deashing and alkali deproteinization by acid-alkali circulation treatment.

[0044] S3. Heat and reduce the pressure to recover the mixed solvent from the liquid obtained after filtering in step S2, remove carbon dioxide, the obtained product reaction solvent is reused in step S1, and the recovered mixed solvent is reused in step S2.

[0045] Comparative Example 5 The traditional preparation method is as follows: In a beaker containing 30 mL of distilled water, 8 g of acrylic acid is added and stirred. NaOH is weighed and added to a beaker containing 20 mL of water, stirred, and dissolved completely to obtain a NaOH solution. The NaOH solution is added to the acrylic acid aqueous solution under stirring within 30 min, and the pH value is adjusted to 6. 5 g of pretreated Pleurotus ostreatus chitosan is weighed and added to the reactor, and the above mixed solution is poured into it. The oil bath is heated to 90°C under stirring, and the reaction is carried out for 5 h. After the reaction is completed, the pH value of the reaction solution is adjusted to about 10 with an alkali solution, centrifuged, and the upper clear liquid is collected. Under magnetic stirring, three volumes of 95 wt% ethanol are added to the clear liquid for precipitation, washed, purified, dried, and non-animal source carboxyethyl chitosan is prepared.

[0046] Pretreatment method: through acid demineralization and alkali deproteinization, the pretreated Pleurotus ostreatus chitosan is obtained through acid-alkali cycle treatment.

[0047] Test Example 1 The non-animal source carboxyethyl chitosan prepared in Examples 1-3 and Comparative Examples 1-5 is tested for degree of substitution, and the results are shown in Table 1.

[0048] Table 1

[0049] As can be seen from the above table, the non-animal source carboxyethyl chitosan prepared by the method described in Examples 1-3 has a higher degree of substitution.

[0050] Test Example 2 0.15 g of non-animal source carboxyethyl chitosan prepared in Examples 1-3 and Comparative Example 5 and 0.35 g of sodium hyaluronate are dissolved in 100 mL of deionized water, 10 mL of glycerol, 5 mL of propylene glycol, and triethanol are added to adjust the pH value to 6-7. After stirring for 1 h, sterilization is performed to prepare a hydrogel. The hydrogel is tested according to the ISO10993-5 standard test method. The results are shown in Table 2.

[0051] Table 2

[0052] As can be seen from the above table, the non-animal source carboxyethyl chitosan prepared by the method described in Examples 1-3 has a lower cytotoxicity. Compared with Comparative Example 5, since no excessive chemical reagents are involved in the preparation of non-animal source carboxyethyl chitosan, the purity of the prepared non-animal source carboxyethyl chitosan is higher, and the cytotoxicity is lower.

[0053] The above merely provides the preferred embodiment of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a non-animal-derived carboxyethyl chitosan, characterized by, The method comprises the following steps: S1. mixing the ionic liquid and the eutectic solvent to prepare a reaction solvent; S2. adding the pretreated non-animal source chitosan into the reaction solvent, passing carbon dioxide gas, then adding acrylic acid, and then performing microwave heating and stirring reaction; after the reaction, cooling to room temperature, adding a methanol / ethanol mixed solvent into the system, precipitating, filtering, washing the solid, purifying, drying, and preparing the non-animal source carboxyethyl chitosan; S3. heating and reducing pressure to recover the mixed solvent from the liquid obtained after filtering in step S2, removing carbon dioxide, and obtaining the product reaction solvent for reuse in step S1, and the recovered mixed solvent for reuse in step S2.

2. The production method according to claim 1, characterized by, The ionic liquid in step S1 is at least one of 1-ethyl-3-methylimidazolium hydroxide, 1-butyl-3-methylimidazolium hydroxide, and tetrabutylammonium hydroxide.

3. The production method according to claim 1, characterized by, The hydrogen bond acceptor of the eutectic solvent in step S1 is choline chloride, and the hydrogen bond donor is at least one of urea, glycerol, ethylene glycol, and acetic acid, and the molar ratio of the hydrogen bond acceptor and the hydrogen bond donor is 1:1-3.

4. The method of claim 1, wherein, The volume ratio of the ionic liquid and the eutectic solvent in step S1 is 1:1-3.

5. The preparation method according to claim 1, characterized in that, The aeration amount of the carbon dioxide gas in step S2 is 3-5 mL / min, and the aeration is performed for 5-10 min per 100 mL of the reaction solvent.

6. The method of claim 1, wherein, The mass ratio of the pretreated non-animal source chitosan and the acrylic acid in step S2 is 1:1.5-2.

5.

7. The preparation method according to claim 1, characterized in that, The microwave heating and stirring reaction in step S2 is performed at a power of 300-500 W, a heating temperature of 70-75℃, and a time of 3-5 h.

8. The method of claim 1, wherein, The volume ratio of methanol and ethanol in the methanol / ethanol mixed solvent in step S2 is 1:3-5.

9. The method of claim 1, wherein, The volume ratio of the reaction solvent and the methanol / ethanol mixed solvent in step S2 is 1:1-3.

10. The method of claim 1, wherein, The degree of substitution of the non-animal source carboxyethyl chitosan in step S3 is 0.8-0.9.

Images