High-strength degradable ultralow-temperature-resistant polyester adhesive and preparation method thereof

Abstract

The invention discloses a high-strength degradable ultralow-temperature-resistant polyester adhesive and a preparation method thereof, and relates to the technical field of preparation of special bonding materials. The preparation method comprises the following steps: sequentially adding monomer gamma-methyl-epsilon-caprolactone and monomer p-dioxanone under a solution polymerization condition by taking anilinopyridine amino-aluminum as a catalyst and alcohol small molecules as an initiator, and carrying out ring-opening polymerization reaction to obtain the polyester adhesive. The polyester adhesive shows excellent bonding performance, is suitable for bonding of various materials, does not generate embrittlement, separation or shrinkage phenomena in an extreme low-temperature environment of-196 DEG C, can be melted and reprocessed for multiple times, has good recycling value, can be completely degraded after the service life is over, and is environment-friendly and pollution-free. The problem that a traditional petroleum-based adhesive is unrecyclable or non-degradable is solved, and a more environment-friendly and more efficient technical scheme is provided for sustainable development.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of special adhesive materials, and particularly to a high-strength degradable ultra-low temperature resistant polyester adhesive and a preparation method thereof. Background Art

[0002] With the rapid development of fields such as aerospace, polar scientific research, superconducting technology, and deep-sea exploration, higher requirements are put forward for the bonding performance of materials in extremely low-temperature environments (such as liquid nitrogen temperature -196°C). However, traditional adhesives are prone to problems such as embrittlement, shrinkage failure, or interfacial debonding under low-temperature conditions, and it is difficult to meet the requirements of long-term stable service.

[0003] Currently, common low-temperature resistant materials on the market include polyurethane, acrylate, silicone rubber, and polyimide, etc. Although these materials have certain low-temperature resistance, the vast majority of commercial adhesives are non-degradable materials and cannot be recycled and reused. Therefore, after the end of their service life, these materials are usually disposed of by incineration or landfill, which not only causes serious waste of resources but also poses a major threat to the ecosystem, animal survival, and human health, and has become a global environmental problem.

[0004] In order to reduce the generation of plastic adhesive waste and alleviate its negative impact on the environment, it is urgent to develop a new type of adhesive that combines excellent low-temperature resistance and biodegradable characteristics to gradually replace the existing petroleum-based or non-biodegradable commercial adhesives and promote the process of sustainable development. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-strength degradable ultra-low temperature resistant polyester adhesive and a preparation method thereof to solve the problems existing in the above-mentioned prior art, ensure the excellent low-temperature resistance and biodegradable characteristics of the adhesive, realize the high performance of the polyester adhesive, and promote the development of degradable polyester adhesive materials.

[0006] To achieve the above purpose, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is to provide a polyester adhesive, and its general formula structure is as follows:

[0008]

[0009] Wherein, m = 150 - 400, n = 100 - 500.

[0010] Another technical solution of the present invention is to provide a preparation method of the above polyester adhesive, including the following steps:

[0011] Using aniline-based pyridine amino-aluminum as a catalyst and a small alcohol molecule as an initiator, ring-opening polymerization is carried out on γ-methyl-ε-caprolactone and p-dioxanone; after the reaction is completed, through precipitation, filtration and drying treatment, the polyester adhesive is obtained.

[0012] Further, in the preparation process of the present invention, first, γ-methyl-ε-caprolactone is mixed and reacted with the catalyst and the initiator, the reaction time is 20-60 min, after γ-methyl-ε-caprolactone completely reacts, p-dioxanone is added for ring-opening polymerization reaction, after the reaction is completed, through precipitation, filtration and drying treatment, the polyester adhesive is obtained.

[0013] In the ring-opening polymerization reaction, the monomer added first interacts with the initiator and the catalyst system first and starts to polymerize. First, γ-methyl-ε-caprolactone is added, and it will form an initial polymer chain segment under the action of the initiator and the catalyst. Then p-dioxanone is added, and it will continue to polymerize on the existing chain segment, and finally a triblock polyester adhesive is formed (the properties of the triblock polyester material can also be changed from hard plastic to soft rubber by controlling the feeding ratio of the monomers γ-methyl-ε-caprolactone and p-dioxanone). If the addition order is changed and p-dioxanone is added first to form an initial chain segment and then polymerized with the subsequent γ-methyl-ε-caprolactone, a polymer with a different structure will be obtained, and the structure of the polymer has a decisive influence on its properties.

[0014] Adding γ-methyl-ε-caprolactone first is to make the poly(γ-methyl-ε-caprolactone) chain segment located in the middle of the triblock polyester chain segment, and the poly(p-dioxanone) chain segment located at both ends of the triblock polyester chain segment. The soft segment (poly(γ-methyl-ε-caprolactone)) is an amorphous and highly flexible chain segment, while the hard segment (poly(p-dioxanone)) is a crystalline or rigid chain segment. When the hard segment is located at both ends of the molecular chain, it is easier to form physical cross-linking points (physical cross-linking network) through crystallization, and the soft segment is wrapped in the middle to form a continuous phase, endowing the material with high elasticity. When the hard segment is distributed at both ends, under the action of external force, the stress can be effectively transmitted through the hard segment and dispersed to the soft segment to avoid stress concentration. The soft segment acts as the middle phase to bear the main deformation, and the hard segment provides rigid support, forming a "rigid-flexible-rigid" gradient mechanical behavior.

[0015] The reaction formula of the present invention is as follows:

[0016]

[0017] The aniline-based pyridine amino-aluminum is the catalyst in Chinese Invention ZL202411185260.0, and its structure is:

[0018]

[0019] Further, the temperature of the ring-opening polymerization reaction is 25 to 100 °C, and the time is 20 to 1440 min.

[0020] Further, the small molecule alcohol is p-xylene glycol (BDM).

[0021] Further, the solvent used in the ring-opening polymerization reaction is toluene.

[0022] Further, the molar ratio of the catalyst, initiator, γ-methyl-ε-caprolactone and p-dioxanone is 1:1:(200 - 1000):(300 - 800).

[0023] Further, the precipitating agent used for precipitation is ethanol.

[0024] Under solution polymerization conditions, the present invention uses anilino-pyridine-amino-aluminum as a catalyst and a small molecule alcohol as an initiator, and sequentially adds the monomers γ-methyl-ε-caprolactone and p-dioxanone for ring-opening polymerization reaction. After the polymerization is completed, precipitation, filtration, and drying are carried out to obtain a triblock polyester adhesive. This polyester adhesive has a triblock structure, has excellent adhesive properties without adding any additives, can be used for bonding traditional metal materials, wood, glass, etc., and has cryogenic resistance, and can withstand ultra-low temperatures of -196 °C without embrittlement, detachment, or shrinkage. In addition, this adhesive is prepared by ring-opening polymerization of bio-based monomers, the reaction conditions are mild, and the material can be depolymerized and recycled for reuse after the end of its life.

[0025] Technical solution three of the present invention: Provide the polyester adhesive prepared by the above preparation method.

[0026] The polyester adhesive of the present invention is a triblock polyester adhesive, which has the characteristics of high strength, degradability, and can withstand ultra-low temperatures.

[0027] The triblock polymer of the polyester adhesive of the present invention has a number average molecular weight of 100.0 - 180.0 kDa, a molecular weight distribution of 1.3 - 1.6, and a melting temperature of 100 - 110 °C. The elongation at break of the polyester adhesive is 400 - 3000%, and the breaking strength is 1 - 51 MPa.

[0028] Technical solution four of the present invention: Provide the application of the above polyester adhesive in the fields of aerospace, automotive, medical, furniture manufacturing, or packaging.

[0029] The present invention discloses the following technical effects:

[0030] The present invention provides a polyester adhesive with high strength, degradability and ultra-low temperature resistance. The preparation method thereof adopts sequential feeding to carry out ring-opening polymerization of bio-based cyclic lactone monomers. The polyester adhesive exhibits excellent bonding performance, is applicable to the bonding of various materials, does not undergo embrittlement, detachment or shrinkage in an extreme low temperature environment of -196 °C, and moreover, the ester adhesive can be melt-reprocessed multiple times, has good recycling value, and can be completely degraded after the end of its service life, avoiding the problems of non-recyclability or non-degradability of traditional petroleum-based adhesives.

[0031] The polyester adhesive of the present invention provides a more environmentally friendly and efficient technical solution for sustainable development. Brief Description of the Drawings

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1 1H NMR spectrum of the polyester adhesive prepared in Example 1 of the present invention 1 ;

[0034] Figure 2 1H NMR spectrum of the polyester adhesive prepared in Example 2 of the present invention 1 ;

[0035] Figure 3 1H NMR spectrum of the polyester adhesive prepared in Example 3 of the present invention 1 ;

[0036] Figure 4 1H NMR spectrum of the polyester adhesive prepared in Example 4 of the present invention 1 ;

[0037] Figure 5 1H NMR spectrum of the polyester adhesive prepared in Example 5 of the present invention 1 ;

[0038] Figure 6 1H NMR spectrum of the polyester adhesive prepared in Example 6 of the present invention 1 ;

[0039] Figure 7 1H NMR comparison spectrum of the monomers collected after depolymerization of the polyester adhesive prepared in Example 1 of the present invention, monomer γ-methyl-ε-caprolactone and monomer p-dioxanone 1 ;

[0040] Figure 8 It is a physical diagram of the depolymerization device used in the depolymerization experiments of Examples 1-6 of the present invention;

[0041] Figure 9 It is the DSC curve of the polyester adhesive prepared in Example 1 of the present invention;

[0042] Figure 10 It is the stress-strain curve of the polyester adhesive prepared in Example 1 of the present invention;

[0043] Figure 11 It is a comparison chart of the bonding strengths of the polyester adhesives prepared in Examples 1-6 of the present invention and the commercial adhesive ethylene-vinyl acetate copolymer (EVA) to the metal steel material at room temperature and after being soaked in liquid nitrogen for 24 hours;

[0044] Figure 12 It is a physical diagram of the bonding effect of the polyester adhesive prepared in Example 1 of the present invention when bonding the steel material. Detailed implementation manners

[0045] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation to the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0046] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0047] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0048] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the present invention's specification, which are obvious to those skilled in the art. Other implementation manners obtained from the present invention's specification are also obvious to those skilled in the art. The present invention's specification and examples are only exemplary.

[0049] Regarding the terms "comprising", "including", "having", "containing", etc. used in this text, they are all open-ended terms, meaning including but not limited to.

[0050] Unless otherwise specified, the room temperature in the embodiments of the present invention refers to 25 ± 2°C.

[0051] In the process of preparing a high-strength degradable ultra-low temperature resistant polyester adhesive by ring-opening polymerization of γ-methyl-ε-caprolactone monomer and p-dioxanone monomer in the present invention, all operations sensitive to moisture and oxygen are carried out by professionals familiar with the technical field in an MBraun glove box or under nitrogen protection using standard Schlenk techniques. It should be noted that the aspects not described in detail in the present invention are all conventional operation means in the art and are not the focus of the present invention.

[0052] A series of tests were carried out on the prepared polyester adhesive in the present invention, and the specific methods and conditions are as follows:

[0053] 1. Nuclear magnetic resonance spectroscopy (NMR)

[0054] The structure of the polyester adhesive was determined using a Bruker-400 nuclear magnetic resonance spectrometer. Test temperature: 25°C; internal standard: TMS; solvent: deuterated chloroform; determination content: 1 H NMR.

[0055] 2. Gel permeation chromatography (GPC)

[0056] The molecular weight and molecular weight distribution index of the polyester adhesive were determined using a Waters gel permeation chromatograph. Solvent: dichloromethane (DCM); test temperature: 25°C; flow rate: 1.0 mL / min; standard sample: PL EasiCal PS-1.

[0057] 3. Differential scanning calorimetry (DSC)

[0058] The thermal properties of the polyester adhesive were determined using a differential scanning calorimeter from TA Instruments. First heating: heating at a rate of 5°C / min to 150°C, after holding for 5 min, starting to cool at a rate of 10°C / min until -70°C, and after holding for 5 min again, performing the second heating: heating at a rate of 5°C / min to 150°C.

[0059] 4. Mechanical property test

[0060] The mechanical properties of the polyester adhesive were tested using a universal tensile machine according to ASTM D882. Sample preparation: The polyester adhesive was hot-pressed into a sample sheet at 130°C and cut into tensile test strips with dimensions of 12 × 2 × 0.5 mm. Tensile rate: 50 mm / min.

[0061] 5. Bonding Performance Test

[0062] Samples were prepared according to GB / T 7124-2008, and metal materials were bonded using polyester adhesives for bonding performance testing. The shear strength of the materials at room temperature and after immersion in liquid nitrogen was measured.

[0063] 6. Biodegradability

[0064] Under the nitrogen atmosphere in a glove box, the generated triblock polyester (polyester adhesive) (0.5000 g) and anilinopyridine amino-aluminum (Al) (0.0013 mg) were added to a 50 ml round-bottom flask. After sealing the round-bottom flask with a glass stopper, it was taken out of the glove box, the glass stopper was quickly opened and connected to the depolymerization device, the vacuum pump and the circulating cooling water were turned on, and it was placed in a sand bath at 200 °C for reaction. After 60 min, the reaction was ended, the mass of the remaining substrate in the round-bottom flask was weighed, and the yield was calculated.

[0065] In the present invention, the structure of the polymer was determined by nuclear magnetic resonance spectroscopy, the molecular weight and molecular weight distribution index of the polymer were determined by gel permeation chromatography (GPC), the thermal properties of the polymer were determined by differential scanning calorimetry, and the mechanical properties and bonding properties of the polymer were determined by a universal tensile machine, which can comprehensively characterize the comprehensive properties of the polymer.

[0066] Example 1

[0067] (1) Under the nitrogen atmosphere in a glove box, γ-methyl-ε-caprolactone (0.52 g, 4 mmol), p-xylene glycol (1.4 mg, 0.01 mmol), anilinopyridine amino-aluminum (Al) (5 mg, 0.01 mmol) and toluene (1.48 ml, 2 M) were successively added to a pressure vessel. After sealing the pressure vessel, it was taken out of the glove box and placed in an oil bath at 100 °C for reaction. After 30 min of reaction (to completely react γ-methyl-ε-caprolactone and prevent the remaining γ-methyl-ε-caprolactone from undergoing random copolymerization with p-dioxanone), the pressure vessel was taken out of the oil bath and transferred back into the glove box and cooled to room temperature.

[0068] (2) Under the nitrogen atmosphere in the glove box, p-dioxanone (0.80 g, 8 mmol) was added to the pressure vessel that had been cooled to room temperature. After sealing the container again, it was taken out of the glove box and the reaction was allowed to continue at room temperature for 24 hours.

[0069] (3) After 24 hours of reaction, dichloromethane containing benzoic acid was added to the pressure vessel to quench the polymerization reaction and thus stop the reaction process.

[0070] (4) The polymer obtained from the reaction was dissolved in dichloromethane, and then the solution was poured into ethanol to precipitate the polymer. The precipitate was filtered and washed with cold methanol to remove any unreacted monomers. Finally, the washed product was placed in a vacuum oven and dried overnight until a constant weight was achieved, and a polyester adhesive was finally obtained.

[0071] The polyester adhesive prepared in Example 1 was subjected to NMR analysis, GPC analysis, DSC analysis, and mechanical property testing: NMR analysis showed that the ratio of the poly(p-dioxanone) segment to the poly(γ-methyl-ε-caprolactone) segment in the polymer was 0.62; the GPC analysis results showed that the number-average molecular weight of the polymer was 106.5 kDa and the molecular weight distribution was 1.33; DSC analysis showed that the glass transition temperature of the polymer was T g1 =-60 °C and T g2 =-14 °C, and the melting temperature was T m =105 °C; the test results of a universal tensile machine showed that the breaking strength of the polymer was 51.09 MPa and the elongation at break was 1113%. When using the polyester adhesive to bond steel metal materials, the shear strength was measured to be 3.7 MPa. After soaking in liquid nitrogen for one day, the shear strength was measured to be 3.8 MPa.

[0072] After the depolymerization experiment of the polyester adhesive prepared in Example 1, the monomer yield calculated was 92%.

[0073] Example 2

[0074] (1) Under the nitrogen atmosphere in a glove box, γ-methyl-ε-caprolactone (0.26 g, 2 mmol), p-xylene glycol (1.4 mg, 0.01 mmol), anilino-pyridylamino-aluminum (A1) (5 mg, 0.01 mmol), and toluene (0.74 ml, 2 M) were sequentially added to a pressure vessel. After sealing the pressure vessel, it was taken out of the glove box and placed in an oil bath at a temperature of 100 °C for reaction. After reacting for 20 min, the pressure vessel was taken out of the oil bath, transferred back into the glove box, and cooled to room temperature.

[0075] (2) Under the nitrogen atmosphere in the glove box, p-dioxanone (0.60 g, 6 mmol) was added to the pressure vessel that had been cooled to room temperature. After sealing the container again, it was taken out of the glove box and the reaction was continued at room temperature for 24 hours.

[0076] (3) After the reaction ended after 24 hours, dichloromethane containing benzoic acid was added to the pressure vessel to quench the polymerization reaction, thus stopping the reaction process.

[0077] (4) Dissolve the polymer obtained from the reaction in dichloromethane, and then pour the solution into cold methanol to precipitate the polymer. Filter the precipitate and wash it with ethanol to remove the unreacted monomers. Finally, place the washed product in a vacuum oven and dry it overnight until a constant weight is reached to obtain the polyester adhesive.

[0078] Perform nuclear magnetic resonance (NMR) analysis, gel permeation chromatography (GPC) analysis, differential scanning calorimetry (DSC) analysis, and mechanical property tests on the polyester adhesive prepared in Example 2: NMR analysis shows that the ratio of the poly(p-dioxanone) chain segment to the poly(γ-methyl-ε-caprolactone) chain segment in the polymer is 0.72; the GPC analysis results show that the number-average molecular weight of the polymer is 105.5 kDa and the molecular weight distribution is 1.61; DSC analysis shows that the glass transition temperatures of the polymer are T g1 =-57 °C and T g2 =-12 °C, and the melting temperature is T m =106 °C; the test results of a universal tensile machine show that the breaking strength of the polymer is 30.41 MPa and the elongation at break is 455%. When using the polyester adhesive to bond steel metal materials, the shear strength is measured to be 2.8 MPa. After soaking in liquid nitrogen for one day, the shear strength is measured to be 2.9 MPa.

[0079] After the depolymerization experiment of the polyester adhesive prepared in Example 2, the monomer yield calculated is 89%.

[0080] Example 3

[0081] (1) Under the nitrogen atmosphere in a glove box, add γ-methyl-ε-caprolactone (0.78 g, 6 mmol), p-xylene glycol (1.4 mg, 0.01 mmol), anilinopyridine amino-aluminum (A1) (5 mg, 0.01 mmol), and toluene (2.22 ml, 2 M) into a pressure vessel in sequence. After sealing the pressure vessel, take it out of the glove box and place it in an oil bath at 100 °C for reaction. After reacting for 30 min, take the pressure vessel out of the oil bath, transfer it back into the glove box, and let it cool to room temperature.

[0082] (2) Under the nitrogen atmosphere in the glove box, add p-dioxanone (0.80 g, 8 mmol) to the pressure vessel that has cooled to room temperature. After sealing the container again, take it out of the glove box and let the reaction proceed at room temperature for 24 hours.

[0083] (3) After the reaction ends after 24 hours, add dichloromethane containing benzoic acid to the pressure vessel to quench the polymerization reaction and stop the reaction process.

[0084] (4) The polymer obtained from the reaction was dissolved in dichloromethane, and then the solution was poured into ethanol to precipitate the polymer. The precipitate was filtered and washed with cold methanol to remove the unreacted monomers. Finally, the washed product was placed in a vacuum oven and dried overnight until a constant weight was achieved, and a polyester adhesive was finally obtained.

[0085] Nuclear magnetic resonance analysis, GPC analysis, DSC analysis, and mechanical property tests were carried out on the polyester adhesive prepared in Example 3: Nuclear magnetic resonance analysis showed that the ratio of the poly(p-dioxanone) chain segment to the poly(γ-methyl-ε-caprolactone) chain segment in the polymer was 0.51; the GPC analysis results showed that the number-average molecular weight of the polymer was 161.6 kDa and the molecular weight distribution was 1.56; DSC analysis showed that the glass transition temperature of the polymer was T g1 =-59 °C and T g2 =-13 °C, and the melting temperature was T m =104 °C; the test results of a universal tensile machine showed that the breaking strength of the polymer was 19.05 MPa and the elongation at break was 840%. When the polyester adhesive was used to bond steel metal materials, the shear strength was measured to be 2.6 MPa. After soaking in liquid nitrogen for one day, the shear strength was measured to be 2.8 MPa.

[0086] After the depolymerization experiment of the polyester adhesive prepared in Example 3, the monomer yield calculated was 86%.

[0087] Example 4

[0088] (1) Under the nitrogen atmosphere in a glove box, γ-methyl-ε-caprolactone (0.78 g, 6 mmol), p-xylene glycol (1.4 mg, 0.01 mmol), anilino-pyridine amino-aluminum (A1) (5 mg, 0.01 mmol), and toluene (2.22 ml, 2 M) were successively added to a pressure vessel. After sealing the pressure vessel, it was taken out of the glove box and placed in an oil bath at 100 °C for reaction. After reacting for 30 min, the pressure vessel was taken out of the oil bath and transferred back into the glove box and cooled to room temperature.

[0089] (2) Under the nitrogen atmosphere in the glove box, p-dioxanone (0.60 g, 6 mmol) was added to the pressure vessel that had been cooled to room temperature. After sealing the container again, it was taken out of the glove box and the reaction was allowed to continue at room temperature for 24 hours.

[0090] (3) After the reaction ended after 24 hours, dichloromethane containing benzoic acid was added to the pressure vessel to quench the polymerization reaction and thus stop the reaction process.

[0091] (4) Dissolve the polymer obtained from the reaction in dichloromethane, and then pour the solution into ethanol to precipitate the polymer. Filter the precipitate and wash it with cold methanol to remove the unreacted monomers. Finally, place the washed product in a vacuum oven and dry it overnight until a constant weight is reached to obtain the polyester adhesive.

[0092] Perform NMR analysis, GPC analysis, DSC analysis, and mechanical property tests on the polyester adhesive prepared in Example 4: NMR analysis shows that the ratio of the poly(p-dioxanone) segment to the poly(γ-methyl-ε-caprolactone) segment in the polymer is 0.42; the GPC analysis results show that the number-average molecular weight of the polymer is 137.4 kDa and the molecular weight distribution is 1.49; DSC analysis shows that the glass transition temperature of the polymer is T g1 =-60 °C and T g2 =-16 °C; the test results of the universal tensile machine show that the breaking strength of the polymer is 4.78 MPa and the elongation at break is 1144%. When using the polyester adhesive to bond steel metal materials, the shear strength is measured to be 2.2 MPa. After soaking in liquid nitrogen for one day, the shear strength is measured to be 2.3 MPa.

[0093] After the depolymerization experiment of the polyester adhesive prepared in Example 4, the monomer yield calculated is 84%.

[0094] Example 5

[0095] (1) Under the nitrogen atmosphere in the glove box, sequentially add γ-methyl-ε-caprolactone (0.78 g, 6 mmol), p-xylene glycol (1.4 mg, 0.01 mmol), anilinopyridine amino-aluminum (A1) (5 mg, 0.01 mmol), and toluene (2.22 ml, 2 M) into the pressure vessel. After sealing the pressure vessel, take it out of the glove box and place it in an oil bath at 100 °C for reaction. After reacting for 30 min, take the pressure vessel out of the oil bath, transfer it back into the glove box, and cool it to room temperature.

[0096] (2) Under the nitrogen atmosphere in the glove box, add p-dioxanone (0.40 g, 4 mmol) to the pressure vessel that has been cooled to room temperature. After sealing the container again, take it out of the glove box and let the reaction continue at room temperature for 24 hours.

[0097] (3) After the reaction ends after 24 hours, add dichloromethane containing benzoic acid to the pressure vessel to quench the polymerization reaction and thus stop the reaction process.

[0098] (4) Dissolve the polymer obtained from the reaction in dichloromethane, and then pour the solution into ethanol to precipitate the polymer. Filter the precipitate and wash it with cold methanol to remove the unreacted monomers. Finally, place the washed product in a vacuum oven and dry it overnight until a constant weight is reached to obtain the polyester adhesive.

[0099] Perform nuclear magnetic resonance (NMR) analysis, gel permeation chromatography (GPC) analysis, differential scanning calorimetry (DSC) analysis, and mechanical property tests on the polyester adhesive prepared in Example 5: NMR analysis shows that the ratio of the poly(p-dioxanone) segment to the poly(γ-methyl-ε-caprolactone) segment in the polymer is 0.32; the GPC analysis results show that the number-average molecular weight of the polymer is 113.3 kDa and the molecular weight distribution is 1.48; DSC analysis shows that the glass transition temperatures of the polymer are T g1 =-60 °C and T g2 =-15 °C; the test results of a universal tensile machine show that the breaking strength of the polymer is 2.25 MPa and the elongation at break is 1619%. When using the polyester adhesive to bond steel metal materials, the shear strength is measured to be 1.1 MPa. After soaking in liquid nitrogen for one day, the shear strength is measured to be 1.3 MPa.

[0100] After the depolymerization experiment of the polyester adhesive prepared in Example 5, the monomer yield calculated is 83%.

[0101] Example 6

[0102] (1) Under the nitrogen atmosphere in a glove box, γ-methyl-ε-caprolactone (1.30 g, 10 mmol), p-xylene glycol (1.4 mg, 0.01 mmol), anilino-pyridylamino-aluminum (A1) (5 mg, 0.01 mmol), and toluene (3.70 ml, 2 M) are successively added to a pressure vessel. After sealing the pressure vessel, take it out of the glove box and place it in an oil bath at 100 °C for reaction. After reacting for 60 min, take the pressure vessel out of the oil bath, transfer it back into the glove box, and let it cool to room temperature.

[0103] (2) Under the nitrogen atmosphere in the glove box, add p-dioxanone (0.40 g, 4 mmol) to the pressure vessel that has cooled to room temperature. After sealing the container again, take it out of the glove box and let the reaction proceed at room temperature for 24 hours.

[0104] (3) After the reaction ends after 24 hours, add dichloromethane containing benzoic acid to the pressure vessel to quench the polymerization reaction and thus stop the reaction process.

[0105] (4) The polymer obtained from the reaction was dissolved in dichloromethane, and then the solution was poured into ethanol to precipitate the polymer. The precipitate was filtered and washed with cold methanol to remove the unreacted monomers. Finally, the washed product was placed in a vacuum oven and dried overnight until a constant weight was achieved, and finally a polyester adhesive was obtained.

[0106] The polyester adhesive prepared in Example 6 was subjected to NMR analysis, GPC analysis, DSC analysis, and mechanical property testing: NMR analysis showed that the ratio of the poly(p-dioxanone) chain segment to the poly(γ-methyl-ε-caprolactone) chain segment in the polymer was 0.20; the GPC analysis results showed that the number-average molecular weight of the polymer was 163.5 kDa and the molecular weight distribution was 1.57; DSC analysis showed that the polymer T g1 = -60 °C and T g2 = -16 °C; the test results of the universal tensile machine showed that the breaking strength of the polymer was 0.97 MPa and the elongation at break was 3026%. When using the polyester adhesive to bond steel metal materials, the shear strength was measured to be 0.8 MPa. After soaking in liquid nitrogen for one day, the shear strength was measured to be 0.9 MPa.

[0107] After the depolymerization experiment of the polyester adhesive prepared in Example 6, the monomer yield calculated was 81%.

[0108] Figure 7 This is the comparison diagram of the 1H NMR spectra of the monomers collected after depolymerization of the polyester adhesive prepared in Example 1 of the present invention and the monomers γ-methyl-ε-caprolactone and p-dioxanone. 1 H NMR spectrum comparison diagram;

[0109] Figure 8 This is the physical diagram of the depolymerization device used in the depolymerization experiments of Examples 1-6 of the present invention;

[0110] Figure 9 This is the DSC curve of the polyester adhesive prepared in Example 1 of the present invention;

[0111] Figure 10 This is the stress-strain curve of the polyester adhesive prepared in Example 1 of the present invention;

[0112] Figure 11 This is the comparison diagram of the bonding strengths of the polyester adhesives prepared in Examples 1-6 of the present invention and the commercial adhesive ethylene-vinyl acetate copolymer (EVA) to metal steel materials at room temperature and after soaking in liquid nitrogen for 24 h;

[0113] Figure 12 This is the physical diagram of the bonding effect of the polyester adhesive prepared in Example 1 of the present invention when bonding steel materials.

[0114] Table 1 is the comparison table of the mechanical properties of the polyester adhesives prepared in Examples 1-6 of the present invention with the catalyst, initiator, and monomer feed ratios.

[0115] Table 1

[0116]

[0117] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A polyester adhesive, characterized in that, The general formula structure is as follows: Among them, m = 150 - 400, n = 100 - 500.

2. The preparation method of the polyester adhesive according to claim 1, characterized in that, It includes the following steps: Using aniline-based pyridine amino-aluminum (AI) as a catalyst and a small molecule alcohol as an initiator, ring-opening polymerization reaction is carried out with γ-methyl-ε-caprolactone and p-dioxanone; after the reaction is completed, through precipitation, filtration and drying treatment, the polyester adhesive is obtained.

3. The preparation method according to claim 2, characterized in that, It includes the following steps: First, γ-methyl-ε-caprolactone is mixed and reacted with the catalyst and the initiator, and then p-dioxanone is added for ring-opening polymerization reaction. After the reaction is completed, through precipitation, filtration and drying treatment, the polyester adhesive is obtained.

4. The preparation method according to claim 2, characterized in that, The temperature of the ring-opening polymerization reaction is 25 - 100 °C, and the time is 20 - 1440 min.

5. The preparation method according to claim 2, characterized in that, The small molecule alcohol is p-xylene glycol.

6. The preparation method according to claim 2, wherein, The solvent used in the ring-opening polymerization reaction is toluene.

7. The preparation method according to claim 2, wherein The molar ratio of the catalyst, initiator, γ-methyl-ε-caprolactone and p-dioxanone is 1∶1∶(200 - 1000)∶(300 - 800).

8. The preparation method according to claim 2, characterized in that, The precipitant used for precipitation is ethanol.

9. A polyester adhesive prepared by the preparation method according to any one of claims 1 - 8.

10. The application of the polyester adhesive according to claim 9 in the fields of aerospace, automotive, medical, furniture manufacturing or packaging.

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