Polyacrylic acid-nano lignin composite hydrogel as well as preparation method and application thereof

Abstract

The invention provides polyacrylic acid-nano lignin composite hydrogel as well as a preparation method and application thereof, nano modified lignin with double bonds is taken as a cross-linking point, and the hydrogel is obtained by initiating polymerization of acrylic acid and / or alkyl acrylic acid, an acrylic acid hydroxyl ester compound and a hydroxyimide acrylate compound through ultraviolet light. The prepared hydrogel has better tensile strength and elongation at break, and can be used for a biological hydrogel adhesive.

Description

Technical Field

[0001] The present invention belongs to the technical field of binder materials, and particularly relates to a polyacrylic acid-nano lignin composite hydrogel, a preparation method thereof, and an application thereof. Background Art

[0002] Compared with traditional wound suture methods such as surgical sutures, medical adhesives are convenient to use, can shorten the operation time, reduce tissue damage, promote wound healing, reduce scar formation, and provide better liquid / gas sealing. Medical adhesives are widely used in the closure of soft tissue wounds, especially narrow and small wounds. Polyacrylic acid adhesives are a common type of medical adhesives, which mainly utilize the formation of hydrogen bonds between carboxyl groups and human skin to produce adhesion.

[0003] Patent CN 114887110 A discloses a hemostatic material capable of quickly stopping bleeding. The first component includes a chitosan component and a polyacrylic acid hydrogel component, and the polyacrylic acid hydrogel component is also grafted with N-hydroxysuccinimide. The second component includes dialdehyde polysaccharide. The hemostatic material is formed by in-situ crosslinking through a Schiff base reaction after mixing the first component and the second component, and the hydrogel has hemostatic and adhesive effects.

[0004] Patent CN 114874479 A discloses a preparation method of a sponge-like macroporous hydrogel. Acrylic acid, double-bonded dopamine and deionized water are mixed, an initiator and a crosslinking agent are added, and after stirring evenly, then Ti 3 C 2 MXene is added. After mixing and degassing, the reaction is carried out at room temperature to obtain a sponge-like macroporous hydrogel for chronic wound repair.

[0005] The toughness and strength of conventional single-network hydrogels are usually poor, which limits the practical application of hydrogels. Currently, strategies for preparing double-network hydrogels or nano-reinforcement are commonly used to enhance the mechanical properties of hydrogels. Patent CN113174062 A discloses a preparation method of a double-network polyvinyl alcohol-polyacrylic acid hydrogel. The first network is formed by crosslinking acrylic acid through a crosslinking agent, and then the second network is prepared by repeatedly freezing and thawing to form a PVA physical gel. After testing, the double-network hydrogel has high strength and high toughness, and its mechanical properties are significantly better than those of single-network hydrogels. Patent CN 106519152 A provides a composite hydrogel reinforced by nanoparticles formed by self-assembly of PAA-b-PS block copolymers, and the hydrogel has excellent compressive strength.

[0006] Lignin is the world's most abundant renewable and biodegradable natural resource after cellulose, and currently only 5% is used in additives, dispersants, adhesives, and surfactants. Existing studies have shown that micro-nano lignin has antibacterial and non-cytotoxic properties, making it a potential alternative product to inorganic nanoparticles and applicable in the biomedical field. Additionally, lignin has numerous functional groups such as hydroxyl, methoxy, carbonyl, and carboxyl groups, which can be further functionalized and modified to expand its application scope. Summary of the Invention

[0007] The present invention provides a polyacrylic acid-nano lignin composite hydrogel. Enzymatically hydrolyzed lignin is acrylated through acryloyl double bonds as crosslinking points to crosslink polyacrylic acid for copolymerization to prepare a hydrogel material, which can be used as a biological hydrogel adhesive.

[0008] One object of the present invention is to provide a polyacrylic acid-nano lignin composite hydrogel, including the reaction product of nano-modified lignin, acrylic acid, and / or its derivative monomers. Among them, the nano-modified lignin is nano-acrylated lignin, and the acrylic acid and / or its derivative monomers include acrylic acid and / or alkyl acrylic acid, acrylic acid hydroxy esters, and hydroxyimide acrylate compounds.

[0009] According to the present invention, in the polyacrylic acid-nano lignin composite hydrogel:

[0010] The particle size of the nano-modified lignin is 10 - 1000 nm, for example, it can be any value among 10, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 850, 900, 950, 1000 nm or the value within any two numerical ranges. Preferably, the particle size of the nano-modified lignin is 50 - 300 nm;

[0011] The nano-modified lignin is obtained by reacting enzymatically hydrolyzed lignin, triethanolamine, and acryloyl chloride. Among them, triethanolamine is used as an acid-binding agent to promote the reaction between enzymatically hydrolyzed lignin and acryloyl chloride, enabling enzymatically hydrolyzed lignin to be acrylated through acryloyl double bonds and copolymerize with acrylic acid and / or its derivatives as chemical crosslinking points;

[0012] The acrylic acid and / or alkyl acrylic acid can be selected from acrylic acid or alkyl-substituted acrylic acid compounds commonly used in the art. Among them, the alkyl acrylic acid is selected from at least one of methacrylic acid and ethyl acrylic acid;

[0013] The acrylic acid hydroxy esters can be selected from acrylic acid hydroxy esters commonly used in the art. Preferably, the acrylic acid hydroxy esters are selected from at least one of 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, hydroxyethyl acrylate, and hydroxypropyl acrylate;

[0014] The described hydroxyimide acrylate compounds are selected from N-hydroxysuccinimide acrylate.

[0015] The second object of the present invention is to provide a method for preparing the above-mentioned polyacrylic acid-nano lignin composite hydrogel, which includes: mixing a nano-modified lignin dispersion liquid, acrylic acid and / or its derivative monomer solution, and then subjecting it to ultraviolet light-initiated polymerization to obtain the polyacrylic acid-nano lignin composite hydrogel.

[0016] According to the present invention, the described preparation method specifically includes the following steps:

[0017] (1) Add acrylic acid and / or alkyl acrylic acid, acrylic acid hydroxy ester compounds, and hydroxyimide acrylate compounds into water and mix evenly;

[0018] (2) Add a nano-acrylated lignin dispersion liquid, and after dispersing evenly, obtain a mixed reaction system;

[0019] (3) Add a photoinitiator and initiate polymerization with ultraviolet light to obtain the polyacrylic acid-nano lignin composite hydrogel.

[0020] According to the present invention, in the method for preparing the polyacrylic acid-nano lignin composite hydrogel:

[0021] In the described mixed reaction system, the contents of each reaction monomer can be adjusted within a relatively wide range. Specifically, in the described mixed reaction system, the content of acrylic acid and / or alkyl acrylic acid is 20-50 wt%, preferably 25-35 wt%; the content of acrylic acid hydroxy ester compounds is 1-20 wt%, preferably 2-10 wt%; the content of hydroxyimide acrylate compounds is 1-20 wt%, preferably 5-15 wt%; the content of nano-acrylated lignin is 0.1-5 wt%, preferably 0.1-1 wt%;

[0022] The described photoinitiator can be selected from commonly used photoinitiators in the art. For example, the described photoinitiator is selected from at least one of lithium phenyl-2,4,6-trimethylbenzoylphosphonate, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, and ketoglutaric acid;

[0023] In the nano acrylated lignin dispersion liquid, the concentration of nano acrylated lignin can be adjusted within a relatively wide range. Specifically, the concentration of the nano acrylated lignin dispersion liquid is 0.1-20 wt%, for example, it can be any value among 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 wt% or a value between any two numerical ranges. Preferably, the concentration of the nano acrylated lignin dispersion liquid is 0.5-5 wt%.

[0024] The dosage of the photoinitiator can adopt the conventional dosage in the art. Specifically, the dosage of the photoinitiator is 0.01-5 wt% of the total amount of nano modified lignin, acrylic acid and / or its derivative monomers. For example, it can be any value among 0.01, 0.05, 0.1, 0.2, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 wt% or a value between any two numerical ranges. Preferably, the dosage of the photoinitiator is 0.1-2 wt% of the total amount of nano modified lignin, acrylic acid and / or its derivative monomers;

[0025] The ultraviolet light-induced polymerization can be completed under the ultraviolet irradiator and irradiation conditions common in the art. For example, the time of the ultraviolet light-induced polymerization is 20-40 min.

[0026] According to the present invention, the preparation method of the nano acrylated lignin dispersion liquid includes: under the stirring action, adding an alkaline solution to the acrylated lignin solution to adjust the pH value of the solution to alkaline, and then adding an acidic solution to adjust the pH value of the solution to acidic to obtain the nano acrylated lignin dispersion liquid.

[0027] According to the specific implementation manner of the present invention, the preparation method of the nano acrylated lignin dispersion liquid specifically includes the following steps:

[0028] (a) Adding enzymatically hydrolyzed lignin to an organic solvent and stirring to dissolve;

[0029] (b) Adding triethanolamine and acryloyl chloride for reaction;

[0030] (c) Precipitating and filtering the reaction product to obtain acrylated lignin;

[0031] (d) Adding acrylated lignin to water, and under the stirring action, adding an alkaline solution to adjust the pH value of the solution to alkaline;

[0032] (e) Then adding an acidic solution to adjust the pH value of the solution to acidic to obtain the nano acrylated lignin dispersion liquid.

[0033] According to the specific embodiments of the present invention, in the preparation method of the nano-acrylated lignin dispersion:

[0034] The organic solvent is selected from at least one of dimethyl sulfoxide, tetrahydrofuran, N,N-dimethylformamide, and dioxane;

[0035] Based on the volume of the organic solvent, 1 to 10 g of enzymatically hydrolyzed lignin is added per 100 mL of the organic solvent; preferably, based on the volume of the organic solvent, 5 to 10 g of enzymatically hydrolyzed lignin is added per 100 mL of the organic solvent;

[0036] Based on the molar amount, the amount of acryloyl chloride used is 5 to 25 mol%, preferably 10 to 20 mol%, of the molar content of hydroxyl groups in the enzymatically hydrolyzed lignin;

[0037] The molar ratio of triethanolamine to acryloyl chloride is (1.1 to 1.3):1, and for example, it can be 1.1:1, 1.12:1, 1.13:1, 1.14:1, 1.15:1, 1.16:1, 1.17:1, 1.18:1, 1.19:1, 1.2:1, 1.21:1, 1.22:1, 1.23:1, 1.24:1, 1.25:1, 1.26:1, 1.27:1, 1.28:1, 1.29:1, or 1.3:1;

[0038] The basic solution can be selected from common inorganic basic compound solutions. For example, the basic solution is selected from at least one of sodium hydroxide solution and potassium hydroxide solution;

[0039] The acidic solution can be selected from common inorganic acidic compound solutions. For example, the acidic solution is selected from at least one of hydrochloric acid solution, sulfuric acid solution, and nitric acid solution.

[0040] According to the specific embodiments of the present invention, in the preparation method of the nano-acrylated lignin dispersion:

[0041] The reaction conditions in step (b) are: under the condition of a protective gas, react in the dark at 0 to 10 °C for 24 to 48 h;

[0042] The precipitation conditions in step (c) are: add anhydrous ether for precipitation. Among them, the amount of anhydrous ether added is not particularly limited. Specifically, after most of the solvent in the reaction system is removed first, a large amount of anhydrous ether can be added to precipitate acrylated lignin from the solution;

[0043] In step (d), an alkaline solution is added to adjust the pH value of the solution to above 10. The concentration of the alkaline solution used is not particularly limited and can be selected within a relatively wide range as long as it can adjust the pH value of the solution to above 10;

[0044] In step (e), an acidic solution is added to adjust the pH value of the solution to 2.5 - 3.5. The concentration of the acidic solution used is not particularly limited and can be selected within a relatively wide range as long as it can adjust the pH value of the solution to 2.5 - 3.5.

[0045] The polyacrylic acid - lignin composite hydrogel provided by the present invention can be prepared according to the following steps:

[0046] Preparation of acrylated lignin: A certain amount of enzymatically hydrolyzed lignin powder is added to organic solvent A and stirred thoroughly until completely dissolved. Below 10°C, a certain amount of triethanolamine is added, nitrogen is introduced to fill the reactor, and a certain amount of acryloyl chloride is added with a syringe. The reaction is carried out under light - shielding conditions for 24 - 48 hours, and the whole reaction is carried out under nitrogen protection. After the reaction is completed, the reaction mixture is rotary evaporated to remove most of the solvent, and then a large amount of anhydrous ether is added for precipitation and filtration to obtain a dark - brown powder, which is acryloyl double - bonded lignin.

[0047] Preparation of nano - acrylated lignin: Weigh a certain amount of modified lignin powder, add deionized water, and under stirring, adjust the pH value to above 10 with an alkaline solution to completely dissolve the powder. Then adjust the pH value to 2.5 - 3.5 with an acidic solution to form a modified lignin nano - dispersion.

[0048] Preparation of polyacrylic acid - lignin composite hydrogel:

[0049] Mix acrylic acid, 2 - hydroxyethyl methacrylate, acrylic acid - N - hydroxysuccinimide, and deionized water evenly. Add a certain amount of nano - acrylated lignin dispersion, and ultrasonicate for 5 - 10 min to evenly disperse the nano - lignin in the reaction system. Add a certain amount of photo - initiator, and ultrasonicate for 10 - 20 min under light - shielding conditions to mix evenly. Pour the reaction mixture into an appropriate mold or glass bottle, and initiate polymerization with ultraviolet light for 20 - 40 min to obtain the polyacrylic acid - lignin composite hydrogel.

[0050] The third object of the present invention is to provide the application of the above polyacrylic acid - nano - lignin composite hydrogel or the polyacrylic acid - nano - lignin composite hydrogel obtained by the above preparation method in a biological adhesive.

[0051] The present invention uses nano-modified lignin with double bonds as cross-linking points, and polymerizes acrylic acid and / or alkyl acrylic acid, acrylic acid hydroxy esters, and hydroxyimide acrylate compounds through ultraviolet light initiation to obtain a transparent hydrogel material. The prepared hydrogel has better tensile strength and elongation at break.

[0052] The beneficial effects of the present invention are as follows: The lignin molecular skeleton contains a large number of phenolic hydroxyl groups and alcoholic hydroxyl groups. By reacting with acryloyl chloride, polymerizable double bonds can be introduced onto the lignin molecule. Enzymatic lignin can be dissolved under alkaline conditions and form a nano-dispersion under acidic conditions. The aqueous solution of acrylic acid has a strong acidity. The double-bond functionalized nano-enzymatic lignin can maintain a stable dispersion state in the reaction system and form a polyacrylic acid-based hydrogel as a cross-linking point. Moreover, the nano-materials filled in the hydrogel system can also enhance the mechanical properties of the material. Specific embodiments

[0053] The following specifically describes the present invention in combination with specific embodiments. It is necessary to point out here that the following embodiments are only used for further illustration of the present invention and cannot be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the protection scope of the present invention.

[0054] For the raw materials used in the examples and comparative examples, if not specifically defined, they are all disclosed in the prior art. For example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0055] Example 1

[0056] Preparation of acrylated lignin

[0057] Add 5 g of enzymatic lignin powder (hydroxyl content 0.11 g / g) to 100 ml of dimethyl sulfoxide, and stir well until completely dissolved. Below 10 °C, add 0.72 g of triethanolamine, fill the reactor with nitrogen, add 0.5 ml of acryloyl chloride with a syringe, and react in the dark for 24 hours. The whole reaction is carried out under nitrogen protection. After the reaction is completed, rotate and evaporate the reaction mixture to remove most of the solvent, then add a large amount of anhydrous ether to precipitate and filter to obtain a dark brown powder, which is acryloyl double-bonded lignin.

[0058] Preparation of nano acrylated lignin

[0059] Weigh 1 g of modified lignin powder, add 19 g of deionized water, and under stirring, adjust the pH value to above 10 with 20 wt% NaOH aqueous solution to completely dissolve the powder. Then adjust the pH value to about 3 with 20 wt% HCl aqueous solution to form a modified lignin nano-dispersion, where the particle size of the modified lignin nano-ions is 100 - 300 nm.

[0060] Preparation of Polyacrylic Acid-Lignin Composite Hydrogel

[0061] Step 1: Mix 5 g of acrylic acid, 1 g of 2-hydroxyethyl methacrylate, 1.7 g of acrylic acid-hydroxysuccinimide and 6.6 g of deionized water evenly.

[0062] Step 2: Add 2.7 g of 5 wt% nanoacrylated lignin dispersion, and ultrasonicate for 10 min to evenly disperse the nano lignin in the reaction system.

[0063] Step 3: Add 0.02 g of ketoglutaric acid, and ultrasonicate in the dark for 15 min to mix evenly.

[0064] Step 4: Pour the reaction mixture into a polytetrafluoroethylene mold, and initiate polymerization with ultraviolet light for 40 min to obtain the polyacrylic acid-lignin composite hydrogel.

[0065] Example 2

[0066] Preparation of Polyacrylic Acid-Lignin Composite Hydrogel

[0067] Step 1: Mix 5 g of acrylic acid, 1.5 g of 2-hydroxyethyl methacrylate, 1.5 g of acrylic acid-hydroxysuccinimide and 9 g of deionized water evenly.

[0068] Step 2: Add 1.9 g of 5 wt% nanoacrylated lignin dispersion (the nanoacrylated lignin dispersion is the same as that in Example 1), and ultrasonicate for 8 min to evenly disperse the nano lignin in the reaction system.

[0069] Step 3: Add 0.08 g of 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, and ultrasonicate in the dark for 20 min to mix evenly.

[0070] Step 4: Pour the reaction mixture into a polytetrafluoroethylene mold, and initiate polymerization with ultraviolet light for 30 min to obtain the polyacrylic acid-lignin composite hydrogel.

[0071] Example 3

[0072] Preparation of Polyacrylic Acid-Lignin Composite Hydrogel

[0073] Step 1: Mix 5 g of acrylic acid, 0.42 g of 2-hydroxyethyl methacrylate, 1.68 g of acrylic acid-hydroxysuccinimide and 7.9 g of deionized water evenly.

[0074] Step 2: Add 0.56 g of 5 wt% nanoacrylated lignin dispersion (the nanoacrylated lignin dispersion is the same as that in Example 1), and ultrasonicate for 8 min to evenly disperse the nano lignin in the reaction system.

[0075] Step 3: Add 0.05 g of lithium phenyl-2,4,6-trimethylbenzoylphosphonate, and ultrasonically mix evenly for 20 min in the dark.

[0076] Step 4: Pour the reaction mixture into a polytetrafluoroethylene mold, and initiate polymerization with ultraviolet light for 20 min to obtain a polyacrylic acid-lignin composite hydrogel.

[0077] Comparative Example 1

[0078] Preparation of polyacrylic acid hydrogel

[0079] Step 1: Mix 5 g of acrylic acid, 1 g of 2-hydroxyethyl methacrylate, 1.7 g of acrylic acid-hydroxysuccinimide, and 9.3 g of deionized water evenly.

[0080] Step 2: Add 0.02 g of ketoglutaric acid, and ultrasonically mix evenly for 15 min in the dark.

[0081] Step 3: Pour the reaction mixture into a polytetrafluoroethylene mold, and initiate polymerization with ultraviolet light for 40 min to obtain a polyacrylic acid-lignin composite hydrogel.

[0082] Comparative Example 2

[0083] Preparation of nano-lignin dispersion

[0084] Weigh 1 g of lignin powder, add 19 g of deionized water, and under stirring, adjust the pH value to above 10 with 20 wt% NaOH aqueous solution to completely dissolve the powder. Then adjust the pH value to about 3 with 20 wt% HCl aqueous solution to form a modified nano-lignin dispersion.

[0085] Preparation of polyacrylic acid-lignin composite hydrogel

[0086] Step 1: Mix 5 g of acrylic acid, 1 g of 2-hydroxyethyl methacrylate, 1.7 g of acrylic acid-hydroxysuccinimide, and 6.6 g of deionized water evenly.

[0087] Step 2: Add 2.7 g of 5 wt% nano-lignin dispersion, and ultrasonically mix for 10 min to evenly disperse the nano-lignin in the reaction system.

[0088] Step 3: Add 0.02 g of ketoglutaric acid, and ultrasonically mix evenly for 15 min in the dark.

[0089] Step 4: Pour the reaction mixture into a polytetrafluoroethylene mold, and initiate polymerization with ultraviolet light for 40 min to obtain a polyacrylic acid-lignin composite hydrogel.

[0090] Test Example

[0091] The tensile strength and elongation at break of the polyacrylic acid-lignin composite hydrogel and polyacrylic acid hydrogel in the examples and comparative examples were tested using an XLW(EC) intelligent electronic tensile tester, and the test standard was GB / T 33428-2016. The results are shown in Table 1 below.

[0092] Table 1. Tensile strength of hydrogels obtained in Examples 1-3 and Comparative Examples 1-2

[0093]

[0094] As can be seen from the results in Table 1, the tensile strength of the polyacrylic acid-nano lignin hydrogels obtained in Examples 1-3 of the present invention is significantly higher than that of the polyacrylic acid hydrogel (Comparative Example 1), and higher than that of the polyacrylic acid hydrogel reinforced only by nano lignin filling (Comparative Example 2), indicating that the nano acryloylated lignin in the hydrogel prepared by the preparation method provided by the present invention not only plays a role in nano filling, but can also serve as a crosslinking point to increase the crosslinking degree, thereby improving the mechanical properties of the hydrogel material to a greater extent.

Claims

1. A polyacrylic acid-nano lignin composite hydrogel, comprising the reaction product of nano-modified lignin, acrylic acid and / or its derivative monomers, wherein: The nano-modified lignin is nano-acrylated lignin, and the acrylic acid and / or its derivative monomers include acrylic acid and / or alkyl acrylic acid, acrylic acid hydroxy ester compounds, and hydroxyimide acrylic acid ester compounds.

2. The composite hydrogel according to claim 1, characterized in that The particle size of the nano-modified lignin is 10 to 1000 nm, preferably 50 to 300 nm; and / or, The nano-modified lignin is obtained by the reaction of enzymatic lignin, triethanolamine and acryloyl chloride; and / or, The alkyl acrylic acid is selected from at least one of methacrylic acid and ethacrylic acid; and / or, The hydroxy acrylate compound is at least one selected from hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, and hydroxypropyl acrylate; and / or, The hydroxyimide acrylate compound is selected from N-hydroxysuccinimide acrylate.

3. A method for preparing the polyacrylic acid-nano lignin composite hydrogel according to claim 1 or 2, comprising: The nano-modified lignin dispersion and acrylic acid and / or its derivative monomer solution are mixed and then polymerized by ultraviolet light to obtain the polyacrylic acid-nano-lignin composite hydrogel.

4. The preparation method according to claim 3, characterized in that: The preparation method specifically comprises the following steps: (1) adding acrylic acid and / or alkyl acrylic acid, hydroxy acrylate compounds, and hydroxyimide acrylate compounds into water and mixing them evenly; (2) adding nano-acrylated lignin dispersion and dispersing the dispersion evenly to obtain a mixed reaction system; (3) adding a photoinitiator and initiating polymerization with ultraviolet light to obtain the polyacrylic acid-nano lignin composite hydrogel.

5. The preparation method according to claim 4, characterized in that: In the mixed reaction system, the content of acrylic acid and / or alkyl acrylic acid is 20-50wt%, preferably 25-35wt%; the content of hydroxy acrylate compounds is 1-20wt%, preferably 2-10wt%; the content of hydroxy imide acrylate compounds is 1-20wt%, preferably 5-15wt%; the content of nano-acrylated lignin is 0.1-5wt%, preferably 0.1-1wt%; and / or, The photoinitiator is selected from at least one of phenyl-2,4,6-trimethylbenzoylphosphonic acid lithium, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, and ketoglutaric acid; and / or, The concentration of the nano-acrylated lignin dispersion is 0.1-20 wt%, preferably 0.5-5 wt%; and / or, The amount of the photoinitiator is 0.01-5 wt %, preferably 0.1-2 wt % of the total amount of the nano-modified lignin, acrylic acid and / or its derivative monomers; and / or, The ultraviolet light initiated polymerization time is 20 to 40 minutes.

6. The preparation method according to claim 4, characterized in that: The preparation method of the nano-acrylated lignin dispersion comprises: adding an alkaline solution to the acrylated lignin solution under stirring to adjust the pH value of the solution to alkaline, and then adding an acidic solution to adjust the pH value of the solution to acidic, to obtain the nano-acrylated lignin dispersion.

7. The preparation method according to claim 6, characterized in that: The preparation method of the nano-acrylated lignin dispersion specifically comprises the following steps: (a) adding enzymatically degraded lignin into an organic solvent and stirring to dissolve; (b) adding triethanolamine and acryloyl chloride to react; (c) precipitating and filtering the reaction product to obtain acryloyl lignin; (d) adding acryloyl lignin to water, and adding an alkaline solution to adjust the pH value of the solution to alkaline under stirring; (e) then adding an acidic solution to adjust the pH value of the solution to acidic, thereby obtaining a nano-acrylated lignin dispersion.

8. The preparation method according to claim 7, characterized in that: The organic solvent is selected from at least one of dimethyl sulfoxide, tetrahydrofuran, N,N-dimethylformamide and dioxane; and / or, Calculated by volume of the organic solvent, 1 to 10 g of enzymatically hydrolyzed lignin is added per 100 mL of organic solvent; preferably, calculated by volume of the organic solvent, 5 to 10 g of enzymatically hydrolyzed lignin is added per 100 mL of organic solvent; and / or, In terms of molar amount, the amount of acryloyl chloride used is 5 to 25 mol%, preferably 10 to 20 mol%, of the molar content of hydroxyl groups in the enzymatically hydrolyzed lignin; and / or, The molar ratio of triethanolamine to acryloyl chloride is (1.1-1.3):1; and / or, The alkaline solution is selected from at least one of a sodium hydroxide solution and a potassium hydroxide solution; and / or, The acidic solution is selected from at least one of hydrochloric acid solution, sulfuric acid solution and nitric acid solution.

9. The preparation method according to claim 7, characterized in that: The reaction conditions in step (b) are: reacting at 0-10° C. in the dark for 24-48 hours under protective gas conditions; and / or, The precipitation conditions in step (c) are: adding anhydrous ether for precipitation; and / or, In step (d), an alkaline solution is added to adjust the pH value of the solution to above 10; and / or, In the step (e), an acidic solution is added to adjust the pH value of the solution to 2.5 to 3.

5.

10. Use of the polyacrylic acid-nano lignin composite hydrogel according to claim 1 or 2 or the polyacrylic acid-nano lignin composite hydrogel obtained by the preparation method of any one of claims 3 to 9 in a bioadhesive.

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