Preparation method of degradable composite adhesive

Abstract

The invention discloses a preparation method of a degradable composite adhesive. The preparation method comprises the following steps: (1) preparing an ester A and an ester B; (2) putting the ester A and the ester B into a reaction kettle to prepare the degradable polyester polyol, (3) preparing a main agent of the degradable composite adhesive by utilizing degradable polyester polyol, poly (diethylene glycol adipate) and poly (butylene adipate); and (4) diluting the prepared degradable composite adhesive main agent and the curing agent in proportion, and uniformly mixing to obtain the degradable composite adhesive. The prepared degradable composite adhesive contains a main chain structure similar to PBAT, PLA and PHA, and the high polarity of carbonate bonds enables the binding force between the degradable composite adhesive and degradable film materials PBAT, PLA and PHA films to be good, so that the peel strength of the degradable composite adhesive is high, and the purposes of degrading under natural or compost conditions, reducing the preparation difficulty of the degradable composite adhesive and improving the performance of the degradable composite adhesive are achieved.

Description

Technical Field

[0001] The invention relates to the production, preparation and application field of adhesive materials, and in particular to a method for preparing a degradable composite adhesive. Background Art

[0002] With the rapid development of global industrialization and consumer trends, traditional composite adhesives are widely used in a wide range of fields, including packaging, building materials, and automotive manufacturing, and were once indispensable for their adhesive properties. However, these materials, often based on petroleum-based polymers, have a stable chemical structure and are extremely difficult to decompose in the natural environment. This leads to the continuous accumulation of waste, rapidly saturating landfills, and the release of harmful gases during incineration, exacerbating the greenhouse effect and air pollution. Furthermore, the market demand for biodegradable composite adhesives among packaging composite manufacturers is growing, leading to a trend towards developing biodegradable composite adhesives that meet the needs of packaging materials.

[0003] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention proposes a method for preparing a degradable composite rubber, so as to achieve the purpose of achieving degradation under natural or composting conditions, reducing the difficulty of preparing the degradable composite rubber and improving the performance of the degradable composite rubber.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A method for preparing a degradable composite adhesive comprises the following steps:

[0007] (1) preparing ester A and ester B;

[0008] The esterified product A is obtained by adding PBAT and diol into a reaction kettle and reacting in a condensing total reflux device;

[0009] The reaction of the esterified product A is as follows:

[0010]

[0011] The esterified product B is prepared by placing DMC, ethylene glycol, butanediol, diethylene glycol, and a catalyst into a reactor for reaction, distilling off the methanol component of the ester exchange product and excess alcohols, and collecting the substrate small molecule esterification product, thereby obtaining the esterified product B;

[0012] The reaction of the esterified product B is as follows:

[0013]

[0014] (2) Ester A and ester B are put into a reactor to prepare degradable polyester polyol.

[0015]

[0016] (3) Preparation of degradable composite adhesive main agent using degradable polyester polyol, polydiethylene glycol adipate and polybutylene adipate:

[0017]

[0018] (4) The prepared degradable composite adhesive main agent and curing agent are diluted in proportion and then mixed evenly to obtain the degradable composite adhesive.

[0019] The degradable composite adhesive prepared by the above steps of the present invention contains a main chain structure similar to PBAT, PLA, and PHA, and the high polarity of the carbonate bond makes the degradable composite adhesive have good bonding strength with the degradable film materials PBAT, PLA, and PHA film, and has high peel strength, thereby achieving the purpose of achieving degradation under natural or composting conditions, reducing the difficulty of preparing the degradable composite adhesive, and improving the performance of the degradable composite adhesive.

[0020] It is further worth noting that the raw materials for making the ester A are PBAT and diol.

[0021] The ratio of PBAT to diol is: PBAT: diol = 1:2-6;

[0022] The PBAT is a commercially available finished particle or recycled material;

[0023] The diol is a mixture of ethylene glycol and any one of propylene glycol, butylene glycol, and diethylene glycol, and the ratio of ethylene glycol to other alcohols is ≥9:1;

[0024] The reaction temperature for preparing the esterified product A is 160-220° C., and the reaction time is 3-7 hours.

[0025] It is further worth noting that the raw materials for producing the ester B are DMC, ethylene glycol, butanediol, and diethylene glycol, and the ratio of DMC, ethylene glycol, butanediol, and diethylene glycol is: 1:0.3-0.6:0.1-0.3:0.5-0.8.

[0026] It is further worth noting that the preparation process of the ester B is as follows:

[0027] Prepare the raw materials DMC, ethylene glycol, butanediol, and diethylene glycol according to the ratio, and at the same time, add 0.05-0.5% of the catalyst based on the total amount of the above raw materials into a reactor. Stir and react for a period of time at a certain temperature, and evaporate the ester exchange product methanol component and excess alcohols. Finally, collect the substrate small molecule esterification product, which is esterification product B.

[0028] It is further worth noting that the catalyst A is an organic catalyst of a metal such as zinc, tin, titanium, or antimony;

[0029] The reaction temperature of the esterification product B is 150-210° C., and the reaction time is 5-12 hours.

[0030] It is further worth noting that the step (2) of preparing the degradable polyester polyol is as follows: prepare ester A and ester B according to a ratio of 1:1-1:5, and prepare catalyst B according to 0.03-0.1% of the total mass of the raw materials of ester A and ester B; then put the ester A, ester B and catalyst B into a reactor, first carry out an ester exchange reaction at 160-200°C for 2-5h, remove excess alcohol small molecules, and then react at a temperature of 180-230°C and a vacuum degree of 0-0.1MPa for 5-10h to obtain polyester polyol.

[0031] The polyester polyol has a molecular weight of 1800-2200 and an acid value of ≤1.0 and is an amorphous viscous liquid.

[0032] It is further worth noting that the preparation process of the degradation composite adhesive main agent in step (3) is as follows: prepare degradable polyester polyol, poly(ethylene glycol adipate) and poly(butylene adipate) in a ratio of 1:0.3-0.6:0.1-0.2; then put the above raw materials into a reactor for dehydration; then add 0.01-0.05% of the total mass of catalyst C and 8-12% of the total mass of isocyanate to the reactor and react; then cool to a suitable temperature and add 0.1-1% of the total mass of the raw materials as a chain extender for chain extension and viscosity increase; finally, add 20-40% of the total mass of the raw materials as a mixed solvent to the mixed raw materials and stir at high speed until all the raw materials are dissolved, thereby obtaining the degradation composite adhesive main agent, and the molecular weight of the degradation composite adhesive main agent is 15000-25000.

[0033] It is further worth noting that the isocyanate is a mixture obtained by mixing TDI, MDI, HDI, and IPDI in a ratio of 3:2:2:1;

[0034] The catalyst C is an organic bismuth compound;

[0035] The chain extender is a mixture of one or more of ethylene glycol, ethylenediamine, butanediol, and ethanolamine;

[0036] The mixed solvent is a mixture of ethyl acetate, methyl acetate, butyl acetate and acetone.

[0037] It is further worth noting that in step (4), the degradable composite adhesive main agent and the curing agent are mixed in a ratio of 10:2-5.

[0038] It is further worth noting that the curing agent is TMP-TDI.

[0039] The present invention has the following advantages:

[0040] 1. The degradable composite adhesive prepared by the present invention contains a main chain structure similar to PBAT, PLA, and PHA, and the high polarity of the carbonate bond makes the degradable composite adhesive have good bonding with the degradable film materials PBAT, PLA, and PHA film, and has high peel strength, thereby achieving the purpose of achieving degradation under natural or composting conditions, reducing the difficulty of preparing the degradable composite adhesive, and improving the performance of the degradable composite adhesive. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present invention are described clearly and completely below.

[0042] The present invention provides a method for preparing a degradable composite adhesive. The degradable composite adhesive prepared according to the method contains a main chain structure similar to that of PBAT, PLA, and PHA, and the high polarity of the carbonate bond ensures that the degradable composite adhesive has good bonding strength with the degradable film materials PBAT, PLA, and PHA films, resulting in high peel strength, thereby achieving the purpose of achieving degradation under natural or composting conditions, reducing the difficulty of preparing the degradable composite adhesive, and improving the performance of the degradable composite adhesive.

[0043] The present invention will be further described in detail below with reference to examples and specific implementation methods.

[0044] A method for preparing a degradable composite adhesive comprises the following steps:

[0045] (1) preparing ester A and ester B;

[0046] (1-1) The raw materials for producing the esterified product A are PBAT and diol, and the ratio of PBAT and diol is:

[0047] PBAT: diol = 1: 2-6;

[0048] The PBAT is a commercially available finished particle or recycled material; the diol is a mixture of ethylene glycol and any one of propylene glycol, butylene glycol, and diethylene glycol, and the ratio of ethylene glycol to other alcohols is ≥9:1;

[0049] The specific synthesis method of the esterified product A is to put the PBAT and diol distributed according to the ratio into a reactor [the reaction temperature should be 160-220°C, the reaction time is 3-7h], and then use a condensing total reflux device to react to obtain the product;

[0050] The reaction of the esterified product A is as follows:

[0051]

[0052] (1-2) The raw materials for producing the ester B are DMC, ethylene glycol, butanediol, and diethylene glycol, and the ratio of DMC, ethylene glycol, butanediol, and diethylene glycol is: 1:0.3-0.6:0.1-0.3:0.5-0.8;

[0053] The specific synthesis method of the esterification product B is as follows: prepare the raw materials DMC, ethylene glycol, butanediol, and diethylene glycol according to the ratio, and at the same time, add 0.05-0.5% of the catalyst based on the total amount of the above raw materials, put DMC, ethylene glycol, butanediol, diethylene glycol and catalyst A [the catalyst A is an organic catalyst of metal such as zinc, tin, titanium, or antimony] into a reactor, react at a reaction temperature of 150-210°C for 5-12 hours, and evaporate the ester exchange product methanol component and excess alcohols, and finally collect the substrate small molecule esterification product, which is the esterification product B.

[0054] The reaction of the esterified product B is as follows:

[0055]

[0056] (2) Esterification product A and esterification product B are put into a reactor to prepare a degradable polyester polyol; specifically:

[0057] Ester A and ester B are prepared in a ratio of 1:1-1:5, and catalyst B is prepared in an amount of 0.03-0.1% by weight of the total raw material mass of ester A and ester B. Ester A, ester B and catalyst B are then put into a reactor, and an ester exchange reaction is first carried out at 160-200° C. for 2-5 hours to remove excess alcohol small molecules. The reaction is then carried out at a temperature of 180-230° C. and a vacuum degree of 0-0.1 MPa for 5-10 hours to obtain a polyester polyol having a molecular weight of 1800-2200 and an acid value of ≤1.0, and being an amorphous viscous liquid.

[0058]

[0059] (3) Degradable polyester polyol, polydiethylene glycol adipate, and polybutylene adipate are used to prepare the main agent of the degradable composite adhesive; the details are as follows:

[0060] Prepare degradable polyester polyol, poly(ethylene glycol adipate), and poly(butylene adipate) in a ratio of 1:0.3-0.6:0.1-0.2; then put the above raw materials into a reactor for dehydration; then add 0.01-0.05% of the total mass of catalyst C and 8-12% of the total mass of isocyanate to the reactor and react; then cool to a suitable temperature and add 0.1-1% of the total mass of the raw materials to extend the chain and increase viscosity; finally, add 20-40% of the total mass of the raw materials to the mixed raw materials. The raw materials are stirred at high speed until all the raw materials are dissolved [wherein the isocyanate is a mixture of TDI, MDI, HDI, and IPDI mixed in a ratio of 3:2:2:1; the catalyst C is an organic bismuth compound; the chain extender is a mixture of one or more of ethylene glycol, ethylenediamine, butanediol, and ethanolamine; and the mixed solvent is a mixture of ethyl acetate, methyl acetate, butyl acetate, and acetone] to obtain a degradable composite adhesive main agent having a molecular weight of 15,000-25,000.

[0061]

[0062] (4) The prepared degradable composite adhesive main agent and curing agent [the curing agent is TMP-TDI] are mixed evenly according to a ratio of 10:2-5 to obtain the degradable composite adhesive.

[0063] According to the above steps, the following degradation composite adhesives with different ratios were prepared, and the corresponding tests and comparisons were performed, as follows:

[0064] Example 1:

[0065] (1) PBAT, ethylene glycol and butanediol were added into a reactor at a ratio of 1:3:0.2, and reacted at 195°C for 5 hours. The esterification product was collected as ester A;

[0066] DMC, ethylene glycol, butanediol, and diethylene glycol were added to a reactor at a ratio of 1:0.4:0.1:0.6, and 0.1% zinc acetate and antimony acetate catalysts were added. The mixture was stirred at 180°C for 6 hours, and the esterification product was collected as ester B.

[0067] (2) Ester A, ester B, and organic titanium catalyst were added to a reactor in a ratio of 1:3:0.002, and transesterification was carried out at 200°C for 4 hours to remove excess alcohol small molecules; then the reaction was carried out at a temperature of 220°C and a vacuum degree of 1000 Pa for 6 hours to obtain a polyester polyol with an acid value of 0.25 and a molecular weight of 2124;

[0068] (3) Degradable polyester polyol, poly(ethylene glycol adipate) and poly(butylene adipate) were added into a reactor at a ratio of 1:0.5:0.1, dehydrated at 75°C and 3000Pa for 2h, and 10% of the total mass of the raw materials in the form of mixed isocyanate and 0.03% of the catalyst were added. The reaction was carried out at a temperature of 83°C for 2.5h. After the reaction was completed, the reactor temperature was lowered to 40°C, and the chain extender ethylenediamine was added and stirred for 10min. A mixed solvent of 30% of ethyl acetate and methyl acetate was added to the obtained product, and the product was stirred at high speed for 1h to completely dissolve it, thereby obtaining the main agent of the degradable composite adhesive.

[0069] (4) The ratio of the main agent of the degradation composite adhesive and the curing agent is 10:3, and a certain amount of solvent is diluted to a mixed solution with a solid content of 30%. The adhesive is applied on the PLA and PHA film using a coating machine. After drying in the air duct for 30 seconds, the composite film is rolled up and aged in a drying room at 45°C for 48 hours. Samples are taken for 180° peel strength and degradation tests.

[0070] Example 2:

[0071] (1) PBAT, ethylene glycol, and butanediol were added into a reactor at a ratio of 1:5:0.3 and reacted at 195°C for 4 hours to obtain ester A;

[0072] DMC, ethylene glycol, butanediol, and diethylene glycol were added into a reactor at a ratio of 1:0.5:0.2:0.5, and 0.3% of tetrabutyl titanate and stannous octoate catalyst were added. The mixture was stirred and reacted at 170°C for 8 hours to obtain ester B.

[0073] (2) Ester A, ester B, and tetrabutyl titanate catalyst were added to a reactor at a ratio of 1:4:0.003, and transesterification was carried out at 200°C for 3 hours to remove excess alcohol small molecules. The reaction was then continued at a temperature of 215°C and a vacuum degree of 800 Pa for 8 hours to obtain a polyester polyol with an acid value of 0.1 and a molecular weight of 2036.

[0074] (3) Degradable polyester polyol, poly(ethylene glycol adipate) and poly(butylene adipate) were added into a reactor at a ratio of 1:0.3:0.2, dehydrated at 90°C and 3000Pa for 0.5h, and 12% of the total mass of the raw materials in the form of mixed isocyanate and 0.05% of the catalyst were added. The reaction was carried out at a temperature of 80°C for 3h. After the reaction, the reactor temperature was lowered to 65°C, and the chain extender butanediol was added and stirred for 25min. A mixed solvent of 30% ethyl acetate and acetone was added to the obtained product, and the product was stirred at high speed for 0.5h to completely dissolve it, thereby obtaining the main agent of the degradable composite adhesive.

[0075] (4) According to the ratio of 10:3 of the main agent and curing agent of the degradation composite adhesive, a mixed solution was diluted with a certain amount of solvent to a solid content of 30%. The adhesive was applied on the PLA and PHA film materials using a coating machine. After drying in the air duct for 30 seconds, the composite was rolled up with the PBAT film and aged in a drying room at 45°C for 48 hours. The 180° peel strength and degradation tests were carried out.

[0076] Example 3:

[0077] (1) PBAT, ethylene glycol, and butanediol were added into a reactor at a ratio of 1:2:0.1 and reacted at 215°C for 3 hours to obtain ester A;

[0078] DMC, ethylene glycol, butanediol, and diethylene glycol were added into a reactor at a ratio of 1:0.3:0.3:0.6, and 0.08% antimony trioxide and zinc acetate catalyst were added. The mixture was stirred and reacted at 180°C for 6 hours to obtain ester B.

[0079] (2) Ester A, ester B, and tetrabutyl titanate catalyst were added to a reactor at a ratio of 1:1:0.005, and the ester exchange reaction was carried out at 190°C for 3.5 hours to remove excess alcohol small molecules. The reaction was then carried out at a temperature of 220°C and a vacuum degree of 2000 Pa for 7 hours to obtain a polyester polyol with an acid value of 0.43 and a molecular weight of 2096;

[0080] (3) Degradable polyester polyol, poly(ethylene glycol adipate) and poly(butylene adipate) were added into a reactor at a ratio of 1:0.4:0.1, dehydrated at 75°C and 3000Pa for 1 hour, and 9% of the total mass of the raw materials and 0.04% of the catalyst were added. The reaction was carried out at a temperature of 95°C for 2 hours. After the reaction, the reactor temperature was lowered to 50°C, and a mixture of chain extender ethylenediamine and butanediol was added and stirred for 30 minutes. A mixed solvent of 30% ethyl acetate and acetone was added to the obtained product, and the product was stirred at high speed for 1 hour to completely dissolve it, thereby obtaining the main agent of the degradable composite adhesive.

[0081] (4) According to the ratio of 10:3 of the main agent and curing agent of the degradation composite adhesive, a mixed solution was diluted with a certain amount of solvent to a solid content of 30%. The adhesive was applied on the PLA and PHA film materials using a coating machine. After drying in the air duct for 30 seconds, the composite was rolled up with the PBAT film and aged in a drying room at 45°C for 48 hours. The 180° peel strength and degradation tests were carried out.

[0082] Comparative Example 1:

[0083] Polyethylene glycol adipate and polybutylene adipate were added into the reactor at a ratio of 2:1, dehydrated at 80°C and 3000Pa for 1 hour, 12% of the total mass of the raw materials in the form of mixed isocyanate and 0.05% of the catalyst were added, and the reaction was carried out at a temperature of 85°C for 2 hours. After the reaction, the reactor temperature was lowered to 40°C, and the chain extender ethylenediamine was added and stirred for 15 minutes. A mixed solvent of 30% ethyl acetate and methyl acetate was added to the obtained product, and the product was stirred at high speed for 1.5 hours to completely dissolve it to obtain the main agent of the degradable composite adhesive.

[0084] According to the ratio of composite adhesive main agent and curing agent of 10:3, a mixed solution was diluted with a certain amount of solvent to a solid content of 30%. The glue was applied on PLA and PHA film materials using a coater. After drying in the air duct for 30 seconds, it was composited and rolled with PBAT film and aged in a drying room at 45°C for 48 hours. The 180° peel strength and degradation tests were carried out.

[0085] Comparative Example 2:

[0086] PBAT, ethylene glycol, and butanediol were added into a reactor at a ratio of 1:2:0.1 and reacted at 215°C for 3 hours to obtain ester A.

[0087] DMC, ethylene glycol, butanediol, and diethylene glycol were added into a reactor at a ratio of 1:0.3:0.3:0.6, and 0.08% antimony trioxide and zinc acetate catalyst were added. The mixture was stirred and reacted at 180°C for 6 hours to obtain ester B.

[0088] A single degradable polyester polyol was put into a reactor, dehydrated at 75°C and 3000Pa for 1.5 hours, 12% of the total mass of the raw materials was added with a mixed isocyanate and 0.04% of the catalyst, and reacted at 80°C for 2 hours. After the reaction, the reactor temperature was lowered to 40°C, and the chain extender ethylenediamine was added and stirred for 30 minutes. A mixed solvent of 30% ethyl acetate and methyl acetate was added to the obtained product, and stirred at high speed for 2 hours to completely dissolve it to obtain the main agent of the degradable composite adhesive.

[0089] According to the ratio of 10:3 of the main agent of the degradation composite adhesive and the curing agent, a mixed solution was diluted with a certain amount of solvent to a solid content of 30%. The adhesive was applied on PLA and PHA film materials using a coater. After drying in the air duct for 30 seconds, it was composited and rolled with the PBAT film and aged in a drying room at 45°C for 48 hours. The 180° peel strength and degradation tests were then carried out.

[0090] The above five groups of products were tested, and the test data are as follows:

[0091]

[0092] It can be clearly seen from the table above that the composite film material has been tested by double 85 aging and the 180° peel force test is still high, indicating that it has a relatively stable molecular chain structure and the composite adhesive can maintain good product stability during normal use; through composting degradation experiment evaluation, its 6-month biodegradation rate can reach more than 98%, meeting the degradation needs of flexible packaging and in line with the sustainable development strategy.

[0093] The degradable composite adhesive prepared by the present invention was tested in terms of viscosity, peeling rate, aging test, and compost degradation test. It can be seen that the above data all show that the degradable composite adhesive of the present invention has excellent performance, and the degradable polyester polyol in the degradable composite adhesive has the effect of inducing the degradation of other non-degradable polyester polyols under composting conditions.

[0094] The biodegradable composite adhesive produced by the method provided herein can degrade under natural or composting conditions. It boasts the advantages of simple preparation, abundant and inexpensive raw material sources, outstanding product performance, and controllable degradation. Using finished PBAT particles or recycled materials significantly reduces raw material costs, shortens reaction time, reduces energy consumption, and enables the reuse of waste materials. It is primarily used to compound biodegradable film materials such as PBAT, PLA, and PHA in lightweight packaging, achieving a green transformation of the composite adhesive industry.

[0095] The above is only a preferred embodiment of the method for preparing a degradable composite adhesive disclosed in the present invention. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the creative concept of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a degradable composite adhesive, characterized in that: The following steps are included: (1) preparing ester A and ester B; The esterified product A is obtained by adding PBAT and diol into a reaction kettle and reacting in a condensing total reflux device; The reaction of the esterified product A is as follows: The esterified product B is prepared by placing DMC, ethylene glycol, butanediol, diethylene glycol, and a catalyst into a reactor for reaction, distilling off the methanol component of the ester exchange product and excess alcohols, and collecting the substrate small molecule esterification product, thereby obtaining the esterified product B; The reaction of the esterified product B is as follows: (2) Ester A and ester B are put into the reactor to prepare the degradable polyester polyol. (3) Preparation of degradable composite adhesive main agent using degradable polyester polyol, polydiethylene glycol adipate and polybutylene adipate: (4) The prepared degradable composite adhesive main agent and curing agent are diluted in proportion and then mixed evenly to obtain the degradable composite adhesive.

2. The method for preparing a degradable composite adhesive according to claim 1, wherein: The raw materials for making the esterified product A are PBAT and diol. The ratio of PBAT to diol is: PBAT: diol = 1:2-6; The PBAT is a commercially available finished particle or recycled material; The diol is a mixture of ethylene glycol and any one of propylene glycol, butylene glycol, and diethylene glycol, and the ratio of ethylene glycol to other alcohols is ≥9:1; The reaction temperature for preparing the esterified product A is 160-220° C., and the reaction time is 3-7 hours.

3. The method for preparing a degradable composite adhesive according to claim 1, wherein: The raw materials for producing the ester B are DMC, ethylene glycol, butanediol, and diethylene glycol, and the ratio of DMC, ethylene glycol, butanediol, and diethylene glycol is 1:0.3-0.6:0.1-0.3:0.5-0.

8.

4. The method for preparing a degradable composite adhesive according to claim 3, characterized in that: The preparation process of the esterified product B is as follows: Prepare the raw materials DMC, ethylene glycol, butanediol, and diethylene glycol according to the ratio, and at the same time, add 0.05-0.5% of the catalyst based on the total amount of the above raw materials into a reactor. Stir and react for a period of time at a certain temperature, and evaporate the ester exchange product methanol component and excess alcohols. Finally, collect the substrate small molecule esterification product, which is esterification product B.

5. The method for preparing a degradable composite adhesive according to claim 4, characterized in that: The catalyst A is an organic catalyst of a metal such as zinc, tin, titanium, or antimony; The reaction temperature of the esterification product B is 150-210° C., and the reaction time is 5-12 hours.

6. The method for preparing a degradable composite adhesive according to claim 1, characterized in that: Step (2) preparing the degradable polyester polyol is specifically as follows: preparing ester A and ester B according to a ratio of 1:1-1:5, and preparing catalyst B according to 0.03-0.1% of the total mass of the raw materials of ester A and ester B; then putting the ester A, ester B and catalyst B into a reactor, first performing an ester exchange reaction at 160-200°C for 2-5 hours, removing excess alcohol small molecules, and then reacting at a temperature of 180-230°C and a vacuum degree of 0-0.1MPa for 5-10 hours to obtain polyester polyol. The polyester polyol has a molecular weight of 1800-2200 and an acid value of ≤1.0 and is an amorphous viscous liquid.

7. The method for preparing a degradable composite adhesive according to claim 1, characterized in that: The preparation process of the degradation composite adhesive main agent in step (3) is as follows: prepare degradable polyester polyol, poly(ethylene glycol adipate) and poly(butylene adipate) in a ratio of 1:0.3-0.6:0.1-0.2; then put the above raw materials into a reactor for dehydration; then add 0.01-0.05% of the total mass of catalyst C and 8-12% of the total mass of isocyanate into the reactor and react; then cool to a suitable temperature and add 0.1-1% of the total mass of the raw materials as a chain extender for chain extension and viscosity increase; finally, add 20-40% of the total mass of the raw materials as a mixed solvent to the mixed raw materials and stir at high speed until all the raw materials are dissolved, thereby obtaining the degradation composite adhesive main agent, wherein the molecular weight of the degradation composite adhesive main agent is 15000-25000.

8. The method for preparing a degradable composite adhesive according to claim 7, characterized in that: The isocyanate is a mixture of TDI, MDI, HDI, and IPDI in a ratio of 3:2:2:1; The catalyst C is an organic bismuth compound; The chain extender is a mixture of one or more of ethylene glycol, ethylenediamine, butanediol, and ethanolamine; The mixed solvent is a mixture of ethyl acetate, methyl acetate, butyl acetate and acetone.

9. The method for preparing a degradable composite adhesive according to claim 1, characterized in that: In the step (4), the degradable composite adhesive main agent and the curing agent are mixed in a ratio of 10:2-5.

10. The method for preparing a degradable composite adhesive according to claim 9, characterized in that: The curing agent is TMP-TDI.

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