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

Abstract

This invention discloses a high-strength, biodegradable, ultra-low temperature resistant polyester adhesive and its preparation method, belonging to the field of special adhesive material preparation technology. Under solution polymerization conditions, using aniline-pyridine amino-aluminum as a catalyst and small alcohol molecules as initiators, the monomers γ-methyl-ε-caprolactone and p-dioxanone are sequentially added to carry out a ring-opening polymerization reaction to obtain the polyester adhesive. This polyester adhesive exhibits excellent bonding properties, is suitable for bonding various materials, and does not experience embrittlement, detachment, or shrinkage under extreme low-temperature conditions of -196℃. Furthermore, this ester adhesive can be repeatedly melted and reprocessed, possessing good recycling value. It is completely degradable at the end of its service life, avoiding the problems of traditional petroleum-based adhesives being non-recyclable or non-degradable, providing a more environmentally friendly and efficient technical solution for sustainable development.

Description

Technical Field

[0001] This invention relates to the field of special adhesive material preparation technology, and in particular to a high-strength, biodegradable, ultra-low temperature resistant polyester adhesive and its preparation method. Background Technology

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

[0003] Currently, common low-temperature resistant materials on the market include polyurethane, acrylate, silicone rubber, and polyimide. Although these materials possess certain low-temperature resistance, the vast majority of commercially available adhesives are non-degradable and cannot be recycled or reused. Therefore, at the end of their service life, these materials are typically disposed of through incineration or landfill, which not only causes serious resource waste but also poses a significant threat to ecosystems, animal survival, and human health, becoming a global environmental problem.

[0004] To reduce the generation of plastic adhesive waste and mitigate its negative environmental impact, there is an urgent need to develop a new type of adhesive that combines excellent low-temperature resistance and biodegradability to gradually replace existing petroleum-based or non-biodegradable commercial adhesives and promote sustainable development. Summary of the Invention

[0005] The purpose of this invention is to provide a high-strength, biodegradable, ultra-low temperature resistant polyester adhesive and its preparation method, so as to solve the problems existing in the prior art, ensure the excellent low-temperature resistance and biodegradability of the adhesive, realize the high performance of polyester adhesive, and promote the development of biodegradable polyester adhesive materials.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] One of the technical solutions of this invention is to provide a polyester adhesive, the general formula of which is shown below:

[0008]

[0009] Where m = 150–400, n = 100–500.

[0010] The second technical solution of the present invention is to provide a method for preparing the above-mentioned polyester adhesive, comprising the following steps:

[0011] Using phenylaminopyridine amino-aluminum as a catalyst and small alcohol molecules as initiators, a ring-opening polymerization reaction was carried out with γ-methyl-ε-caprolactone and p-dioxanone. After the reaction was completed, the polyester adhesive was obtained by precipitation, filtration and drying.

[0012] Furthermore, in the preparation process of the present invention, γ-methyl-ε-caprolactone is first mixed with the catalyst and the initiator for a reaction time of 20-60 min. After the γ-methyl-ε-caprolactone has completely reacted, p-dioxanone is added to carry out a ring-opening polymerization reaction. After the reaction is completed, the polyester adhesive is obtained by precipitation, filtration and drying.

[0013] In ring-opening polymerization, the monomer added first interacts with the initiator and catalyst system and begins polymerization. When γ-methyl-ε-caprolactone is added first, it forms initial polymer segments under the action of the initiator and catalyst. Then, p-dioxanone is added, and polymerization continues based on the existing segments, ultimately forming a triblock polyester adhesive (the properties of the triblock polyester material can also be changed from rigid plastic to soft rubber by controlling the feed ratio of γ-methyl-ε-caprolactone and p-dioxanone). If the order of addition is changed, with the initial segments formed by adding p-dioxanone first polymerizing with the subsequent γ-methyl-ε-caprolactone, polymers with different structures will be obtained, and the structure of the polymer has a decisive influence on its properties.

[0014] The addition of γ-methyl-ε-caprolactone (γ-methyl-ε-caprolactone) first positions the polyγ-methyl-ε-caprolactone (PME) segments in the middle of the triblock polyester chain, while the polydioxanone (PDE) segments are located at both ends. The soft segments (PME) are amorphous and highly flexible, while the hard segments (PDE) are crystalline or rigid. When the hard segments are located at both ends of the molecular chain, they are more likely to form physical cross-linking points (physical cross-linking networks) through crystallization, while the soft segments are encapsulated in the middle to form a continuous phase, imparting high elasticity to the material. When the hard segments are distributed at both ends, stress under external force can be effectively transferred through the hard segments and dispersed to the soft segments, avoiding stress concentration. The soft segments, as the intermediate phase, bear the main deformation, while the hard segments provide rigid support, forming a gradient mechanical behavior of "rigid-flexible-rigid".

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

[0016]

[0017] The aniline-pyridine-aluminum catalyst described in Chinese invention ZL202411185260.0 has the following structure:

[0018]

[0019] Furthermore, the ring-opening polymerization reaction is carried out at a temperature of 25–100°C for a time of 20–1440 min.

[0020] Furthermore, the alcohol molecule is terephthalic acid (BDM).

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

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

[0023] Furthermore, the precipitant used for the precipitation is ethanol.

[0024] This invention involves ring-opening polymerization of γ-methyl-ε-caprolactone and p-dioxanone monomers under solution polymerization conditions, using aniline-pyridine amino-aluminum as a catalyst and small alcohol molecules as initiators. After polymerization, the monomers are precipitated, filtered, and dried to obtain a triblock polyester adhesive. This polyester adhesive has a triblock structure and exhibits excellent bonding properties without the need for any additives. It can be used to bond traditional metal materials, wood, glass, etc., and possesses ultra-low temperature resistance, able to withstand temperatures as low as -196°C without becoming brittle, detaching, or shrinking. Furthermore, this adhesive is prepared through the ring-opening polymerization of bio-based monomers under mild reaction conditions, and the material can be depolymerized and recycled for reuse after its lifespan ends.

[0025] The third technical solution of the present invention is to provide a polyester adhesive prepared by the above preparation method.

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

[0027] The present invention relates to a triblock polymer polyester adhesive with a number-average molecular weight of 100.0–180.0 kDa, a molecular weight distribution of 1.3–1.6, and a melt temperature of 100–110°C. The polyester adhesive has an elongation at break of 400–3000% and a tensile strength of 1–51 MPa.

[0028] The fourth technical solution of the present invention is to provide the application of the above-mentioned polyester adhesive in the fields of aerospace, automotive, medical, furniture manufacturing or packaging.

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

[0030] This invention provides a high-strength, biodegradable, and ultra-low temperature resistant polyester adhesive, prepared by sequential feeding ring-opening polymerization of bio-based cyclic lactone monomers. This polyester adhesive exhibits excellent bonding properties, is suitable for bonding various materials, and does not experience embrittlement, detachment, or shrinkage at extreme low temperatures of -196°C. Furthermore, this ester adhesive can be repeatedly melted and reprocessed, possessing good recycling value, and is completely biodegradable at the end of its service life, avoiding the problems of traditional petroleum-based adhesives being non-recyclable or non-degradable.

[0031] The polyester adhesive of this invention provides a more environmentally friendly and efficient technical solution for sustainable development. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

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

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

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

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

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

[0039] Figure 7 The monomers collected after depolymerization of the polyester adhesive prepared in Example 1 of this invention, along with monomers γ-methyl-ε-caprolactone and p-dioxanone, are... 1 H NMR spectrum comparison diagram;

[0040] Figure 8 These are physical images of the depolymerization apparatus used in the depolymerization experiments of Examples 1-6 of the present invention;

[0041] Figure 9 The DSC curve of the polyester adhesive prepared in Example 1 of this invention;

[0042] Figure 10 The stress-strain curve of the polyester adhesive prepared in Example 1 of this invention;

[0043] Figure 11 The image shows a comparison of the bonding strength of the polyester adhesive prepared in Examples 1-6 of this invention and the commercial adhesive ethylene-vinyl acetate copolymer (EVA) to metal steel materials at room temperature and after being immersed in liquid nitrogen for 24 hours.

[0044] Figure 12 This is a photograph of the bonding effect of the polyester adhesive prepared in Example 1 of the present invention on steel materials. Detailed Implementation

[0045] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0046] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0047] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0048] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0049] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

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

[0051] In the preparation of a high-strength, biodegradable, ultra-low temperature resistant polyester adhesive by ring-opening polymerization of γ-methyl-ε-caprolactone monomer and p-dioxanone monomer, all moisture- and oxygen-sensitive operations are performed by personnel skilled in the art under nitrogen protection in an MBraun glove box or using standard Schlenk techniques. It should be noted that any aspects not described in detail herein are conventional practices in the field and are not the focus of this invention.

[0052] The prepared polyester adhesive was subjected to a series of tests, 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℃; internal standard: TMS; solvent: deuterated chloroform; determination details: 1 H NMR.

[0055] 2. Gel permeation chromatography (GPC)

[0056] The molecular weight and molecular weight distribution index of polyester adhesives were determined using a Waters gel permeation chromatography system. Solvent: dichloromethane (DCM); Test temperature: 25℃; 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: The temperature was increased to 150°C at a rate of 5°C / min, held for 5 minutes, then decreased at a rate of 10°C / min until -70°C was reached. After holding for another 5 minutes, a second heating was performed: the temperature was increased to 150°C at a rate of 5°C / min.

[0059] 4. Mechanical property testing

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

[0061] 5. Adhesion performance test

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

[0063] 6. Biodegradability

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

[0065] This invention uses nuclear magnetic resonance spectroscopy to determine the structure of polymers, gel permeation chromatography (GPC) to determine the molecular weight and molecular weight distribution index of polymers, differential scanning calorimetry to determine the thermal properties of polymers, and a universal tensile testing machine to determine the mechanical and adhesive properties of polymers, thus comprehensively characterizing the overall performance of the polymer.

[0066] Example 1

[0067] (1) Under a nitrogen atmosphere in a glove box, γ-methyl-ε-caprolactone (0.52 g, 4 mmol), terephthalic acid (1.4 mg, 0.01 mmol), anilinepyridineaminoaluminum (Al) (5 mg, 0.01 mmol), and toluene (1.48 ml, 2 M) were sequentially added to a pressure vessel. After sealing the pressure vessel, it was removed from the glove box and placed in an oil bath at 100 °C for reaction. After reacting for 30 min (to ensure complete reaction of γ-methyl-ε-caprolactone and prevent random copolymerization of the remaining γ-methyl-ε-caprolactone with p-dioxanone), the pressure vessel was removed from the oil bath, transferred back to the glove box, and allowed to cool to room temperature.

[0068] (2) Under the nitrogen atmosphere of the glove box, add p-dioxanone (0.80 g, 8 mmol) to the pressure vessel that has been cooled to room temperature. After sealing the container again, remove it from the glove box and let the reaction continue at room temperature for 24 hours.

[0069] (3) After the reaction has been completed for 24 hours, dichloromethane containing benzoic acid is 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 then washed with cold methanol to remove any unreacted monomers. Finally, the washed product was placed in a vacuum oven and dried overnight until constant weight was reached, thus obtaining the polyester adhesive.

[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 poly(p-dioxanone) segments to poly(γ-methyl-ε-caprolactone) segments was 0.62. GPC analysis showed that the polymer's number-average molecular weight was 106.5 kDa and its molecular weight distribution was 1.33. DSC analysis showed that the polymer's glass transition temperature was T. g1 = -60℃ and T g2 = -14℃, melting temperature is T m =105℃; universal tensile testing showed that the polymer's tensile strength was 51.09 MPa and its elongation at break was 1113%. Using polyester adhesive to bond steel materials, the shear strength was measured to be 3.7 MPa. After immersion in liquid nitrogen for one day, the shear strength was measured to be 3.8 MPa.

[0072] The polyester adhesive prepared in Example 1 was subjected to a depolymerization experiment, and the calculated monomer yield was 92%.

[0073] Example 2

[0074] (1) Under a nitrogen atmosphere in a glove box, γ-methyl-ε-caprolactone (0.26 g, 2 mmol), terephthalic acid (1.4 mg, 0.01 mmol), anilinepyridineaminoaluminum (Al) (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 removed from the glove box and placed in an oil bath at 100 °C for reaction. After reacting for 20 min, the pressure vessel was removed from the oil bath, transferred back to the glove box, and allowed to cool to room temperature.

[0075] (2) Under the nitrogen atmosphere of the glove box, add p-dioxanone (0.60 g, 6 mmol) to the pressure vessel that has been cooled to room temperature. After sealing the container again, remove it from the glove box and let the reaction continue for 24 hours at room temperature.

[0076] (3) After the reaction has been completed for 24 hours, dichloromethane containing benzoic acid is added to the pressure vessel to quench the polymerization reaction and thus stop the reaction process.

[0077] (4) The polymer obtained from the reaction was dissolved in dichloromethane, and then the solution was poured into cold methanol to precipitate the polymer. The precipitate was filtered and then washed with ethanol to remove unreacted monomers. Finally, the washed product was placed in a vacuum oven and dried overnight until constant weight was reached, thus obtaining the polyester adhesive.

[0078] The polyester adhesive prepared in Example 2 was subjected to NMR analysis, GPC analysis, DSC analysis, and mechanical property testing. NMR analysis showed that the ratio of poly(p-dioxanone) segments to poly(γ-methyl-ε-caprolactone) segments was 0.72. GPC analysis showed that the polymer's number-average molecular weight was 105.5 kDa and its molecular weight distribution was 1.61. DSC analysis showed that the polymer's glass transition temperature was T. g1 = -57℃ and T g2 = -12℃, melting temperature is T m =106℃; Universal tensile testing showed that the polymer's tensile strength was 30.41 MPa and its elongation at break was 455%. Using polyester adhesive to bond steel materials, the shear strength was measured to be 2.8 MPa. After immersion in liquid nitrogen for one day, the shear strength was measured to be 2.9 MPa.

[0079] The polyester adhesive prepared in Example 2 was subjected to a depolymerization experiment, and the calculated monomer yield was 89%.

[0080] Example 3

[0081] (1) Under a nitrogen atmosphere in a glove box, γ-methyl-ε-caprolactone (0.78 g, 6 mmol), terephthalic acid (1.4 mg, 0.01 mmol), anilinepyridineaminoaluminum (Al) (5 mg, 0.01 mmol), and toluene (2.22 ml, 2 M) were sequentially added to a pressure vessel. After sealing the pressure vessel, it was removed from the glove box and placed in an oil bath at 100 °C for reaction. After reacting for 30 min, the pressure vessel was removed from the oil bath, transferred back to the glove box, and allowed to cool to room temperature.

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

[0083] (3) After the reaction has been completed for 24 hours, dichloromethane containing benzoic acid is added to the pressure vessel to quench the polymerization reaction and thus 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 then washed with cold methanol to remove unreacted monomers. Finally, the washed product was placed in a vacuum oven and dried overnight until constant weight was reached, thus obtaining the polyester adhesive.

[0085] The polyester adhesive prepared in Example 3 was subjected to NMR analysis, GPC analysis, DSC analysis, and mechanical property testing. NMR analysis showed that the ratio of poly(p-dioxanone) segments to poly(γ-methyl-ε-caprolactone) segments was 0.51. GPC analysis showed that the polymer's number-average molecular weight was 161.6 kDa, and its molecular weight distribution was 1.56. DSC analysis showed that the polymer's glass transition temperature was T. g1 = -59℃ and T g2 = -13℃, melting temperature is T m =104℃; Universal tensile testing showed that the polymer's tensile strength was 19.05 MPa and its elongation at break was 840%. Using polyester adhesive to bond steel materials, the shear strength was measured to be 2.6 MPa. After immersion in liquid nitrogen for one day, the shear strength was measured to be 2.8 MPa.

[0086] The polyester adhesive prepared in Example 3 was subjected to a depolymerization experiment, and the calculated monomer yield was 86%.

[0087] Example 4

[0088] (1) Under a nitrogen atmosphere in a glove box, γ-methyl-ε-caprolactone (0.78 g, 6 mmol), terephthalic acid (1.4 mg, 0.01 mmol), anilinepyridineaminoaluminum (Al) (5 mg, 0.01 mmol), and toluene (2.22 ml, 2 M) were sequentially added to a pressure vessel. After sealing the pressure vessel, it was removed from the glove box and placed in an oil bath at 100 °C for reaction. After reacting for 30 min, the pressure vessel was removed from the oil bath, transferred back to the glove box, and allowed to cool to room temperature.

[0089] (2) Under the nitrogen atmosphere of the glove box, add p-dioxanone (0.60 g, 6 mmol) to the pressure vessel that has been cooled to room temperature. After sealing the container again, remove it from the glove box and let the reaction continue at room temperature for 24 hours.

[0090] (3) After the reaction has been completed for 24 hours, dichloromethane containing benzoic acid is added to the pressure vessel to quench the polymerization reaction and thus stop the reaction process.

[0091] (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 then washed with cold methanol to remove unreacted monomers. Finally, the washed product was placed in a vacuum oven and dried overnight until constant weight was reached, thus obtaining the polyester adhesive.

[0092] The polyester adhesive prepared in Example 4 was subjected to NMR analysis, GPC analysis, DSC analysis, and mechanical property testing. NMR analysis showed that the ratio of poly(p-dioxanone) segments to poly(γ-methyl-ε-caprolactone) segments was 0.42. GPC analysis showed that the polymer's number-average molecular weight was 137.4 kDa, and its molecular weight distribution was 1.49. DSC analysis showed that the polymer's glass transition temperature was T. g1 = -60℃ and T g2 = -16℃; Universal tensile testing showed that the polymer's tensile strength was 4.78 MPa and its elongation at break was 1144%. Using polyester adhesive to bond steel materials, the shear strength was measured to be 2.2 MPa. After immersion in liquid nitrogen for one day, the shear strength was measured to be 2.3 MPa.

[0093] The polyester adhesive prepared in Example 4 was subjected to a depolymerization experiment, and the calculated monomer yield was 84%.

[0094] Example 5

[0095] (1) Under a nitrogen atmosphere in a glove box, γ-methyl-ε-caprolactone (0.78 g, 6 mmol), terephthalic acid (1.4 mg, 0.01 mmol), anilinepyridineaminoaluminum (Al) (5 mg, 0.01 mmol), and toluene (2.22 ml, 2 M) were sequentially added to a pressure vessel. After sealing the pressure vessel, it was removed from the glove box and placed in an oil bath at 100 °C for reaction. After reacting for 30 min, the pressure vessel was removed from the oil bath, transferred back to the glove box, and allowed to cool to room temperature.

[0096] (2) Under the nitrogen atmosphere of 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, remove it from the glove box and let the reaction continue at room temperature for 24 hours.

[0097] (3) After the reaction has been completed for 24 hours, dichloromethane containing benzoic acid is added to the pressure vessel to quench the polymerization reaction and thus stop the reaction process.

[0098] (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 then washed with cold methanol to remove unreacted monomers. Finally, the washed product was placed in a vacuum oven and dried overnight until constant weight was reached, thus obtaining the polyester adhesive.

[0099] The polyester adhesive prepared in Example 5 was subjected to NMR analysis, GPC analysis, DSC analysis, and mechanical property testing. NMR analysis showed that the ratio of poly(p-dioxanone) segments to poly(γ-methyl-ε-caprolactone) segments was 0.32. GPC analysis showed that the polymer had a number-average molecular weight of 113.3 kDa and a molecular weight distribution of 1.48. DSC analysis showed that the polymer's glass transition temperature was T. g1 = -60℃ and T g2 = -15℃; Universal tensile testing showed that the polymer's tensile strength was 2.25 MPa and its elongation at break was 1619%. Using polyester adhesive to bond steel materials, the shear strength was measured to be 1.1 MPa. After immersion in liquid nitrogen for one day, the shear strength was measured to be 1.3 MPa.

[0100] The polyester adhesive prepared in Example 5 was subjected to a depolymerization experiment, and the calculated monomer yield was 83%.

[0101] Example 6

[0102] (1) Under a nitrogen atmosphere in a glove box, γ-methyl-ε-caprolactone (1.30 g, 10 mmol), terephthalic acid (1.4 mg, 0.01 mmol), anilinepyridineaminoaluminum (Al) (5 mg, 0.01 mmol), and toluene (3.70 ml, 2 M) were sequentially added to a pressure vessel. After sealing the pressure vessel, it was removed from the glove box and placed in an oil bath at 100 °C for reaction. After reacting for 60 min, the pressure vessel was removed from the oil bath, transferred back to the glove box, and allowed to cool to room temperature.

[0103] (2) Under the nitrogen atmosphere of 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, remove it from the glove box and let the reaction continue at room temperature for 24 hours.

[0104] (3) After the reaction has been completed for 24 hours, dichloromethane containing benzoic acid is added 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 then washed with cold methanol to remove unreacted monomers. Finally, the washed product was placed in a vacuum oven and dried overnight until constant weight was reached, thus obtaining the polyester adhesive.

[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 poly(p-dioxanone) segments to poly(γ-methyl-ε-caprolactone) segments was 0.20. GPC analysis showed that the polymer had a number-average molecular weight of 163.5 kDa and a molecular weight distribution of 1.57. DSC analysis showed that the polymer T... g1 = -60℃ and T g2 = -16℃; Universal tensile testing showed that the polymer's tensile strength was 0.97 MPa and its elongation at break was 3026%. Using polyester adhesive to bond steel materials, the shear strength was measured to be 0.8 MPa. After immersion in liquid nitrogen for one day, the shear strength was measured to be 0.9 MPa.

[0107] The polyester adhesive prepared in Example 6 was subjected to a depolymerization experiment, and the calculated monomer yield was 81%.

[0108] Figure 7 The monomers collected after depolymerization of the polyester adhesive prepared in Example 1 of this invention, along with monomers γ-methyl-ε-caprolactone and p-dioxanone, are... 1 H NMR spectrum comparison diagram;

[0109] Figure 8 These are physical images of the depolymerization apparatus used in the depolymerization experiments of Examples 1-6 of the present invention;

[0110] Figure 9 The DSC curve of the polyester adhesive prepared in Example 1 of this invention;

[0111] Figure 10 The stress-strain curve of the polyester adhesive prepared in Example 1 of this invention;

[0112] Figure 11 The image shows a comparison of the bonding strength of the polyester adhesive prepared in Examples 1-6 of this invention and the commercial adhesive ethylene-vinyl acetate copolymer (EVA) to metal steel materials at room temperature and after being immersed in liquid nitrogen for 24 hours.

[0113] Figure 12 This is a photograph of the bonding effect of the polyester adhesive prepared in Example 1 of the present invention on steel materials.

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

[0115] Table 1

[0116]

[0117] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A polyester adhesive, characterized in that, The reaction formula is shown below: Where m = 150~400, n = 100~500.

2. The method for preparing the polyester adhesive as described in claim 1, characterized in that, Includes the following steps: Using phenylaminopyridine amino-aluminum as a catalyst and small alcohol molecules as initiators, a ring-opening polymerization reaction was carried out with γ-methyl-ε-caprolactone and p-dioxanone. After the reaction was completed, the polyester adhesive was obtained by precipitation, filtration and drying.

3. The preparation method according to claim 2, characterized in that, Includes the following steps: First, γ-methyl-ε-caprolactone is mixed with the catalyst and the initiator for reaction. Then, p-dioxanone is added to carry out a ring-opening polymerization reaction. After the reaction is completed, the polyester adhesive is obtained by precipitation, filtration and drying.

4. The preparation method according to claim 2, characterized in that, The ring-opening polymerization reaction is carried out at a temperature of 25–100°C for a time of 20–1440 min.

5. The preparation method according to claim 2, characterized in that, The alcohol molecule is terephthalic acid.

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

7. The preparation method according to claim 2, characterized in that, 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. The polyester adhesive prepared by the preparation method according to any one of claims 2-8.

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

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