Degradable water-based bio-based adhesive and preparation method thereof
Polyurethane is generated by reacting polyether glycol with lysine diisocyanate, and polybutylene succinate is generated by reacting dimethyl succinate with 1,4-butanediol. This forms a copolymer of polyurethane and polybutylene succinate, which solves the problems of environmental pollution and poor bonding effect of existing adhesives and achieves high bonding strength and biodegradability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-02
- Publication Date
- 2026-03-10
AI Technical Summary
Existing adhesives contain harmful substances during the preparation process, and bio-based adhesives have a loose molecular structure and weak cohesion, resulting in poor flowability and adhesion, which affects the environment and performance.
Polyurethane is generated by reacting polyether glycol with lysine diisocyanate, and polybutylene succinate is generated by reacting dimethyl succinate with 1,4-butanediol. Polyurethane and polybutylene succinate copolymer are formed, and tannic acid, filler and antioxidant are added. Organic bismuth catalyst and reaction conditions are used in the preparation process to form a cross-linked network to improve the adhesion strength and biodegradability.
It achieves high bonding strength and good biodegradability, reduces the environmental pollution caused by the adhesive, and improves the adhesive's antioxidant properties and resilience.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of adhesive technology, specifically to a biodegradable water-based bio-based adhesive and its preparation method. Background Technology
[0002] Adhesives are substances that firmly bond similar or dissimilar materials through physical or chemical action to achieve functions such as bonding, sealing, and repair. Most current adhesive products are mainly made by polyvinyl alcohol and formaldehyde through a condensation reaction in an acidic medium, followed by amination. The manufacturing process contains unreacted harmful substances such as benzene and formaldehyde, thus posing a significant environmental hazard.
[0003] Although environmentally friendly bio-based adhesives have emerged, common bio-based adhesives such as starch and soy protein have loose molecular structures and weak cohesion. They are also prone to clumping after long-term storage, which affects solubility and dispersibility, resulting in poor flowability and adhesion. Summary of the Invention
[0004] To address the above problems, the present invention provides a biodegradable water-based bio-based adhesive and its preparation method.
[0005] The technical solution of the present invention is: a biodegradable water-based bio-based adhesive, comprising the following components by weight: 30-40 parts of polyether glycol, 40-50 parts of lysine diisocyanate, 1-5 parts of dibutyltin dilaurate, 40-60 parts of dimethyl succinate, 0.5-2 parts of organic bismuth catalyst, 40-60 parts of 1,4-butanediol, 1-3 parts of tetrabutyl titanate, 5-10 parts of dimethylolpropionic acid, 20-30 parts of tannic acid, 6-10 parts of filler, 3-6 parts of antioxidant, 30-50 parts of acetone, and 20-30 parts of deionized water.
[0006] Note: The adhesives described above are produced by reacting polyether glycol with lysine diisocyanate to generate polyurethane, and dimethyl succinate can react with 1,4-butanediol to generate polybutylene succinate, forming a polyurethane-polybutylene succinate copolymer. This gives the adhesive high bonding strength while also providing good biodegradability, thus reducing the adhesive's environmental pollution.
[0007] Furthermore, the organic bismuth catalyst is bismuth laurylate or bismuth isooctanoate.
[0008] Note: The above-mentioned organic bismuth catalyst can reduce the formation of side reactions to avoid abnormal increase in binder viscosity and bubble problems, and has low toxicity and good biocompatibility.
[0009] Furthermore, the filler is nano-silica or nano-titanium dioxide.
[0010] Note: The filler described above can form a cross-linked network with polyurethane molecular chains to improve the resilience and impact resistance of the adhesive.
[0011] Furthermore, the antioxidant is antioxidant 1726 or antioxidant 5057.
[0012] Note: The antioxidants mentioned above can improve the antioxidant properties of the adhesive and prevent it from failing due to oxidation during use.
[0013] Furthermore, the water content of the polyether diol is ≤0.05%.
[0014] Note: Limiting the water content of polyether glycol can reduce the formation of side reactions and prevent abnormal increases in adhesive viscosity.
[0015] On the other hand, the present invention also provides a method for preparing a biodegradable water-based bio-based adhesive, comprising the following steps: S1. According to the stated weight proportions, polyether glycol, lysine diisocyanate and dibutyltin dilaurate are placed into a reaction vessel and stirred for 5-10 minutes. Then, the reaction vessel is kept at 80-90°C for 3-4 hours to obtain the prepolymer. S2. After the prepolymer is cooled to 40~50℃, dimethyl succinate and organic bismuth catalyst are added to the prepolymer and kept at 120~140℃ for 3~4h to obtain the intermediate. S3. After the intermediate is cooled to 70~80℃, add the intermediate, 1,4-butanediol and tetrabutyl titanate into the polycondensation reactor. Then, evacuate the polycondensation reactor and keep it at 230~240℃ for 2~3 hours to obtain the polycondensate. S4. After the condensate is cooled to 50~60℃, dimethylolpropionic acid is added to the condensate and kept at this temperature for 1~1.5h to obtain the first mixture. S5. Dilute the viscosity of the first mixture to ≤2000 cP using acetone, and then adjust the pH of the first mixture to 7.5~8.5 using triethylamine to obtain the second mixture; S6. Add the second mixture, tannic acid, filler and antioxidant to deionized water, shear and disperse, and remove acetone by vacuum distillation to obtain water-based bio-based adhesive.
[0016] Explanation: The above preparation method generates a polyurethane prepolymer by reacting polyether glycol with lysine diisocyanate, and then grafts dimethyl succinate onto the polyurethane molecular chain by reacting the polyurethane prepolymer with dimethyl succinate. Subsequently, dimethyl succinate is converted into polybutylene succinate by reacting dimethyl succinate with 1,4-butanediol, thus generating a copolymer of polyurethane and polybutylene succinate. Tannic acid, fillers, and antioxidants are added to form an adhesive, giving the adhesive good biodegradability and bonding strength.
[0017] Furthermore, in step S1, during the heat preservation process, nitrogen gas is introduced into the reactor 2 to 4 times, each time until the pressure inside the reactor reaches 0.2 to 0.3 MPa, and the pressure is maintained for 2 to 3 minutes before being released.
[0018] Note: Repeated nitrogen purging can reduce the oxygen content in the reactor, preventing the prepolymer from deteriorating due to oxidation.
[0019] Furthermore, in step S3, after the vacuuming is completed, the vacuum degree inside the polycondensation reactor reaches 50~200 Pa.
[0020] Note: Limiting the vacuum level of the polycondensation reactor can prevent the intermediates from turning yellow due to temperature rise, and promptly remove small molecule byproducts to ensure the viscosity of the intermediates.
[0021] Furthermore, in step S6, the shear rate during shear dispersion is 2000~3000 rpm.
[0022] Note: Limiting the shear rate ensures uniform dispersion of the adhesive components and guarantees the adhesive's performance.
[0023] The beneficial effects of this invention are: (1) The adhesive of the present invention uses polyether glycol and lysine diisocyanate to generate polyurethane, and dimethyl succinate can react with 1,4-butanediol to generate polybutylene succinate, forming a polyurethane-polybutylene succinate copolymer, which makes the adhesive have high bonding strength and good biodegradability, so as to reduce the pollution of the adhesive to the environment.
[0024] (2) The preparation method of the present invention generates a polyurethane prepolymer by reacting polyether glycol with lysine diisocyanate, grafts dimethyl succinate onto the polyurethane molecular chain, and then reacts dimethyl succinate with 1,4-butanediol to convert dimethyl succinate into polybutylene succinate, thereby generating a copolymer of polyurethane and polybutylene succinate. Tannic acid, filler and antioxidant are added to make an adhesive, so that the adhesive has good biodegradability and bonding strength. Detailed Implementation
[0025] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.
[0026] Example 1: A biodegradable water-based bio-based adhesive, comprising the following components by weight: 35 parts polyether glycol, 45 parts lysine diisocyanate, 3 parts dibutyltin dilaurate, 50 parts dimethyl succinate, 1 part organic bismuth catalyst, 50 parts 1,4-butanediol, 2 parts tetrabutyl titanate, 8 parts dimethylolpropionic acid, 25 parts tannic acid, 8 parts filler, 4 parts antioxidant, and 25 parts deionized water; wherein the organic bismuth catalyst is bismuth laurate, the filler is nano-silica, and the antioxidant is antioxidant 1726; The preparation method of the above-mentioned water-based bio-based adhesive includes the following steps: S1. According to the stated weight proportions, polyether glycol, lysine diisocyanate and dibutyltin dilaurate are placed in a reaction vessel and stirred for 8 minutes. Then, the reaction vessel is kept at 85°C for 3.5 hours to obtain a prepolymer. The water content of the polyether glycol is 0.02%. During the heat preservation process, nitrogen gas is introduced into the reaction vessel three times, each time until the pressure inside the reaction vessel reaches 0.25 MPa. The pressure is maintained for 2.5 minutes and then released. S2. After the prepolymer is cooled to 45°C, dimethyl succinate and an organic bismuth catalyst are added to the prepolymer and kept at 130°C for 3.5 hours to obtain the intermediate. S3. After the intermediate is cooled to 75°C, the intermediate, 1,4-butanediol and tetrabutyl titanate are added to the polycondensation reactor. Then, the polycondensation reactor is evacuated until the vacuum degree inside the polycondensation reactor reaches 100Pa. The polycondensation reactor is then kept at 235°C for 2.5 hours to obtain the polycondensate. S4. After the condensate is cooled to 55°C, dimethylolpropionic acid is added to the condensate and kept at this temperature for 1.2 hours to obtain the first mixture. S5. The viscosity of the first mixture is diluted to 1800 cP using acetone, and then the pH of the first mixture is adjusted to 8 using triethylamine to obtain the second mixture. S6. The second mixture, tannic acid, filler and antioxidant are added to deionized water, sheared and dispersed, and acetone is removed by vacuum distillation to obtain an aqueous bio-based adhesive; wherein the shear rate during shear dispersion is 2500 rpm.
[0027] Example 2: This example is basically the same as Example 1, except that the water-based bio-based adhesive includes the following components: 30 parts polyether glycol, 40 parts lysine diisocyanate, 1 part dibutyltin dilaurate, 40 parts dimethyl succinate, 0.5 parts organic bismuth catalyst, 40 parts 1,4-butanediol, 1 part tetrabutyl titanate, 5 parts dimethylolpropionic acid, 20 parts tannic acid, 6 parts filler, 3 parts antioxidant, and 20 parts deionized water.
[0028] Example 3: This example is basically the same as Example 1, except that the water-based bio-based adhesive includes the following components: 40 parts polyether glycol, 50 parts lysine diisocyanate, 5 parts dibutyltin dilaurate, 60 parts dimethyl succinate, 2 parts organic bismuth catalyst, 60 parts 1,4-butanediol, 3 parts tetrabutyl titanate, 10 parts dimethylolpropionic acid, 30 parts tannic acid, 10 parts filler, 6 parts antioxidant, and 30 parts deionized water.
[0029] Example 4: This example is basically the same as Example 1, except that nitrogen gas is introduced into the reactor twice during the heat preservation process.
[0030] Example 5: This example is basically the same as Example 1, except that nitrogen gas is introduced into the reactor four times during the heat preservation process.
[0031] Example 6: This example is basically the same as Example 1, except that the pressure inside the reactor is increased to 0.2 MPa each time.
[0032] Example 7: This example is basically the same as Example 1, except that the pressure inside the reactor is increased to 0.3 MPa each time.
[0033] Example 8: This example is basically the same as Example 1, except that after the prepolymer is cooled to 40°C, dimethyl succinate and an organic bismuth catalyst are added to the prepolymer.
[0034] Example 9: This example is basically the same as Example 1, except that after the prepolymer is cooled to 50°C, dimethyl succinate and an organic bismuth catalyst are added to the prepolymer.
[0035] Example 10: This example is basically the same as Example 1, except that the intermediate is obtained by keeping it at 120°C for 3 hours.
[0036] Example 11: This example is basically the same as Example 1, except that the intermediate is obtained by keeping it at 140°C for 4 hours.
[0037] Example 12: This example is basically the same as Example 1, except that after the intermediate is cooled to 70°C, the intermediate, 1,4-butanediol and tetrabutyl titanate are added to the polycondensation reactor.
[0038] Example 13: This example is basically the same as Example 1, except that after the intermediate is cooled to 80°C, the intermediate, 1,4-butanediol and tetrabutyl titanate are added to the polycondensation reactor.
[0039] Example 14: This example is basically the same as Example 1, except that the polycondensation reactor is kept at 230°C for 2 hours to obtain the polycondensate.
[0040] Example 15: This example is basically the same as Example 1, except that the polycondensation kettle is kept at 240°C for 3 hours to obtain the polycondensate.
[0041] Example 16: This example is basically the same as Example 1, except that after the condensation polymer is cooled to 50°C, dimethylolpropionic acid is added to the condensation polymer.
[0042] Example 17: This example is basically the same as Example 1, except that after the condensation polymer is cooled to 60°C, dimethylolpropionic acid is added to the condensation polymer.
[0043] Example 18: This example is basically the same as Example 1, except that triethylamine is used to adjust the pH of the first mixture to 7.5.
[0044] Example 19: This example is basically the same as Example 1, except that triethylamine is used to adjust the pH of the first mixture to 8.5.
[0045] Comparative Example 1: Referring to Example 1, dimethyl succinate and 1,4-butanediol were removed, and polybutylene succinate was directly added to the aqueous bio-based adhesive.
[0046] Comparative Example 2: Referring to Example 1, nitrogen was not introduced into the reactor.
[0047] Comparative Example 3: Referring to Example 1, dimethyl succinate and an organic bismuth catalyst were added directly to the prepolymer without waiting for it to cool down.
[0048] Comparative Example 4: Referring to Example 1, without waiting for the intermediate to cool down, the intermediate, 1,4-butanediol and tetrabutyl titanate were directly added to the polycondensation reactor.
[0049] Comparative Example 5: Referring to Example 1, dimethylolpropionic acid was added directly to the condensate without waiting for it to cool down.
[0050] Experimental Example: To investigate the influence of preparation parameters of each embodiment on adhesive performance, leather samples of the same size were bonded together and cured at 60°C for 8 hours. The cured samples were then subjected to a 180° peel strength test. Subsequently, the samples were treated at 80°C for 36 hours, and the 180° peel strength of each sample was tested again. The peel strength reduction rate was calculated. The specific investigation is as follows: Experiment Example 1: Investigating the effect of adhesive composition on adhesive properties Using Examples 1, 2, and 3, as well as Comparative Example 1, as experimental comparisons, the adhesive properties under different compositions are shown in Table 1 below: Table 1 Adhesive properties under different compositions
[0051] As shown in Table 1, compared with Examples 1, 2, and 3, Example 1 has the highest adhesive peel strength and the lowest peel strength reduction rate, indicating that the adhesive in Example 1 has the highest adhesive strength and the best high temperature resistance. Therefore, the adhesive component selected in Example 1 is the best.
[0052] Compared with Comparative Example 1, Example 1: After removing dimethyl succinate and 1,4-butanediol, and directly adding polybutylene succinate to the water-based bio-based adhesive, the adhesive strength and high-temperature resistance of the adhesive decreased significantly. This may be because the directly added polybutylene succinate failed to be effectively compatible with polyurethane. Therefore, the adhesive components selected in Example 1 are optimal.
[0053] Experiment Example 2: Investigating the effect of nitrogen purging parameters on adhesive properties Using Examples 1, 4, 5, 6, and 7, as well as Comparative Example 2, as experimental comparisons, the adhesive performance under different nitrogen filling parameters is shown in Table 2 below: Table 2 Adhesive performance under different nitrogen filling parameters
[0054] As shown in Table 2, compared with Examples 1, 4, and 5, the adhesive peel strength gradually increases and the peel strength reduction rate gradually decreases with the increase of nitrogen purging times, until the adhesive peel strength of Example 1 reaches the highest and the peel strength reduction rate is the lowest. With the continued increase of nitrogen purging times, the adhesive peel strength and peel strength reduction rate begin to show no significant change. Therefore, from the perspective of time cost, the number of nitrogen purging times selected in Example 1 is optimal.
[0055] Compared with Examples 1, 6, and 7, Example 1 showed the highest adhesive peel strength and the lowest peel strength reduction rate, indicating that the adhesive in Example 1 had the highest adhesive strength and the best high-temperature resistance. This may be because the oxygen content in the reactor was lower and there were fewer side reactions under the reactor pressure in Example 1. Therefore, the reactor pressure selected in Example 1 was the optimal one.
[0056] Compared with Comparative Example 2, in Example 1, the adhesive strength and high-temperature resistance of the adhesive decreased significantly after nitrogen was not introduced into the reactor. This may be because the lack of nitrogen introduction into the reactor resulted in a higher oxygen content and a lower polyurethane conversion rate. Therefore, the nitrogen introduction method selected in Example 1 was the optimal one.
[0057] Experiment Example 3: Investigating the effect of intermediate preparation parameters on adhesive properties Using Examples 1, 8, 9, 10, 11 and Comparative Example 3 as experimental comparisons, the adhesive properties under different intermediate preparation parameters are shown in Table 3 below: Table 3 Adhesive properties under different intermediate preparation parameters
[0058] As shown in Table 3, compared with Examples 1, 8, and 9, the adhesive of Example 1 has the highest peel strength and the lowest peel strength reduction rate, indicating that the adhesive of Example 1 has the highest adhesive strength and the best high temperature resistance. This may be because the dimethyl succinate added at the selected temperature in Example 1 can be fully mixed with the prepolymer, so the selected dimethyl succinate added temperature in Example 1 is the optimal.
[0059] Compared with Examples 1, 10, and 11, the adhesive of Example 1 has the highest peel strength and the lowest peel strength reduction rate, indicating that the adhesive of Example 1 has the highest adhesive strength and the best high temperature resistance. This may be because the dimethyl succinate can fully react with the prepolymer at the intermediate preparation temperature selected in Example 1. Therefore, the intermediate preparation temperature selected in Example 1 is the optimal.
[0060] Compared with Comparative Example 3, in Example 1, the adhesive strength and high-temperature resistance of the adhesive decreased significantly after dimethyl succinate and organic bismuth catalyst were added directly to the prepolymer without waiting for it to cool down. This may be because the prepolymer was oxidized at high temperature without waiting for it to cool down, which affected its viscosity. As a result, dimethyl succinate could not be fully mixed with the prepolymer. Therefore, the dimethyl succinate addition method selected in Example 1 was the optimal one.
[0061] Experiment Example 4: Investigating the Influence of Condensation Polymer Preparation Parameters on Adhesive Properties Using Examples 1, 12, 13, 14, 15 and Comparative Example 4 as experimental comparisons, the adhesive properties under different condensation polymer preparation parameters are shown in Table 4 below: Table 4 Adhesive properties under different condensation polymer preparation parameters
[0062] As shown in Table 4, compared with Examples 1, 12, and 13, the adhesive of Example 1 has the highest peel strength and the lowest peel strength reduction rate, indicating that the adhesive of Example 1 has the highest adhesive strength and the best high temperature resistance. This may be because at the 1,4-butanediol addition temperature selected in Example 1, 1,4-butanediol can fully react with dimethyl succinate. Therefore, the 1,4-butanediol addition temperature selected in Example 1 is the optimal one.
[0063] Compared with Examples 1, 14, and 15, the adhesive of Example 1 has the highest peel strength and the lowest peel strength reduction rate, indicating that the adhesive of Example 1 has the highest adhesive strength and the best high temperature resistance. This may be because at the condensation preparation temperature selected in Example 1, 1,4-butanediol can fully react with dimethyl succinate, thus the condensation preparation temperature selected in Example 1 is the optimal one.
[0064] Compared with Comparative Example 4, Example 1: Without waiting for the intermediate to cool down, the intermediate, 1,4-butanediol and tetrabutyl titanate were directly added to the polycondensation reactor. The adhesive strength and high temperature resistance of the adhesive decreased significantly. This may be because not waiting for the intermediate to cool down affected the catalytic effect of tetrabutyl titanate, resulting in 1,4-butanediol not being able to react fully with dimethyl succinate. Therefore, the method of adding 1,4-butanediol selected in Example 1 is the optimal one.
[0065] Experiment Example 5: Investigating the effects of temperature and pH on the properties of the first mixture. Using Examples 1, 16, 17, 18, and 19, as well as Comparative Example 5, as experimental comparisons, the adhesive properties of the first mixture at different temperatures and pH values are shown in Table 5 below: Table 5 Adhesive properties of the first mixture at different temperatures and pH values.
[0066] As shown in Table 5, compared with Examples 1, 16, and 17, the adhesive of Example 1 has the highest peel strength and the lowest peel strength reduction rate, indicating that the adhesive of Example 1 has the highest adhesive strength and the best high temperature resistance. This may be because at the first mixing temperature of Example 1, dimethylolpropionic acid can fully react with the condensation polymer, improving the hydrophilicity of the adhesive. Therefore, the first mixing temperature selected in Example 1 is the optimal one.
[0067] Compared with Examples 1, 18, and 19: The adhesive of Example 1 has the highest peel strength and the lowest peel strength reduction rate, indicating that the adhesive of Example 1 has the highest adhesive strength and the best high temperature resistance. This may be because the second mixture has the best dispersibility at the first mixture pH value of Example 1. Therefore, the first mixture selected in Example 1 has the optimal pH value.
[0068] Compared with Comparative Example 5, in Example 1, dimethylolpropionic acid was added directly to the condensate without waiting for it to cool down, resulting in a significant decrease in the adhesive strength and high-temperature resistance of the adhesive. This may be because dimethylolpropionic acid cannot fully react with the condensate after it has cooled down. Therefore, the method of adding dimethylolpropionic acid selected in Example 1 is the optimal one.
Claims
1. A degradable waterborne bio-based adhesive, characterized in that, By weight parts, including the following ingredients: polyether glycol 30~40 parts, lysine diisocyanate 40~50 parts, dibutyl tin dilaurate 1~5 parts, dimethyl succinate 40~60 parts, bismuth organic catalyst 0.5~2 parts, 1,4-butanediol 40~60 parts, tetrabutyl titanate 1~3 parts, dimethylol propionic acid 5~10 parts, tannic acid 20~30 parts, filler 6~10 parts, antioxidant 3~6 parts, deionized water 20~30 parts.
2. The degradable waterborne bio-based adhesive of claim 1, wherein, The bismuth organic catalyst is bismuth laurate or bismuth iso-octoate.
3. The degradable waterborne bio-based adhesive of claim 1, wherein, The filler is nano-silicon dioxide or nano-titanium dioxide.
4. The degradable waterborne bio-based adhesive of claim 1, wherein, The antioxidant is antioxidant 1726 or antioxidant 5057.
5. The degradable waterborne bio-based adhesive of claim 1, wherein, The polyether glycol contains water content ≤0.05%.
6. A method for preparing a biodegradable aqueous bio-based adhesive according to any one of claims 1 to 5, characterized in that, Including the following steps: S1, according to the weight parts, polyether glycol, lysine diisocyanate and dibutyl tin dilaurate are put into the reaction kettle, stirred for 5~10 min, then the reaction kettle is incubated at 80~90℃ for 3~4h, and the prepolymer is obtained; S2, after the prepolymer is cooled to 40~50℃, dimethyl succinate and bismuth organic catalyst are added to the prepolymer, and incubated at 120~140℃ for 3~4h, and the intermediate is obtained; S3, after the intermediate is cooled to 70~80℃, the intermediate, 1,4-butanediol and tetrabutyl titanate are added to the polycondensation kettle, then the polycondensation kettle is vacuumed, and the polycondensation kettle is incubated at 230~240℃ for 2~3h, and the polycondensate is obtained; S4, after the polycondensate is cooled to 50~60℃, then dimethylol propionic acid is added to the polycondensate, and incubated for 1~1.5h, and the first mixture is obtained; S5, the viscosity of the first mixture is diluted to ≤2000cP using acetone, then the pH value of the first mixture is adjusted to 7.5~8.5 using triethylamine, and the second mixture is obtained; S6, the second mixture, tannic acid, filler and antioxidant are added to deionized water, sheared and dispersed, then acetone is removed by vacuum distillation, and the water-based bio-based adhesive is obtained.
7. A process for the preparation of a degradable waterborne bio-based adhesive according to claim 6, characterized in that, In step S1, during the incubation process, the reaction kettle is filled with nitrogen 2~4 times, each time the pressure in the reaction kettle reaches 0.2~0.3MPa, and the pressure is released after 2~3min.
8. The method for preparing a biodegradable aqueous bio-based adhesive according to claim 6, characterized in that, In step S3, after the vacuum is completed, the vacuum degree in the polycondensation kettle reaches 50~200Pa.
9. The method for preparing a biodegradable aqueous bio-based adhesive according to claim 6, characterized in that, In step S6, the shearing rate is 2000~3000rpm during shearing and dispersion.