Preparation method of polyurethane-hydrogen bond organic framework composite adhesive

Abstract

The invention relates to a preparation method of a polyurethane-hydrogen bond organic framework composite adhesive. According to the method, HOFs are uniformly dispersed in a polyurethane solution, and then the adhesive of polyurethane and HOFs is formed through a solvent evaporation method. According to the composite adhesive obtained by the invention, the cohesive force of polyurethane is enhanced by introducing HOFs, the toughness of the adhesive is improved, and the adhesive can be circularly adhered and used. Compared with a single polyurethane adhesive, the toughness of the obtained composite adhesive is improved by 2.9 times.

Description

Technical Field

[0001] The invention belongs to the technical field of adhesive preparation, and particularly relates to a method for preparing a high-toughness polyurethane adhesive. Background Art

[0002] With the booming development of the global adhesive market, my country has become a major adhesive producer and consumer in the world. In particular, with the rapid development of emerging industries such as aerospace, wearable devices, and artificial intelligence, the demand for adhesives has grown strongly. There is an urgent need to develop adhesives that can be firmly adhered to both rigid and flexible substrates and can adapt to the deformation of the substrate. High toughness and recyclable adhesives. At present, polyurethane materials have received widespread attention in the field of adhesives because of their adjustable structure and composition, excellent mechanical properties, and low price. By adjusting the structure of polyurethane, introducing covalent or non-covalent effects into it to enhance the cohesion of polyurethane is an effective method to improve its bonding strength. Wang et al. (D. Wang, X. Ge, H. Nie, Z. Yao, J. Zhang, Demulsification-induced fast solidification: a novel strategy for the preparation of polymer films, Chem. Commun., 2019, 55, 9192.) reported a polyurethane-acrylic adhesive with a bonding strength greater than 1 MPa with metal zinc. Wang et al. (D.Wang, J.Li, Y.Wang, AOOmoniyi, Z.Fu, J.Zhang, Z.Su, Water-based polyurethane adhesive films with enhanced bonding strength capable of in situ and high-efficient deposition on metal surface, Chem.Eng.J., 2022, 431, 134055.) reported a metal ion coordinated polyurethane adhesive, the bonding strength of which with metal zinc was 2.57 ± 0.63MPa, while the bonding strength of pure polyurethane adhesive with metal zinc was less than 2MPa, achieving a significant improvement in performance. Although covalent or non-covalent effects are introduced into polyurethane, the bonding strength is improved. However, the deformation of these adhesives during stretching is less than 500%, indicating that their toughness is poor, which greatly limits their adhesion ability during substrate deformation. Therefore, when subjected to external force, the adhesive is difficult to resist the deformation caused by the external force, and it is easy to debond, and the adhesive after debonding is difficult to recycle. Moreover, the above adhesive preparation process is to form an electrolytic cell with metal and polyurethane emulsion, and then after power is applied, the adhesive is prepared on the surface of the anode metal. This method limits the use of the adhesive to the bonding of conductive metal materials, and it is difficult to adhere to the surface of non-conductive substrates, thereby limiting the expansion of its application field. Designing and synthesizing new polyurethane adhesives is the key to achieving high-strength adhesion with a variety of substrates and recyclability.

[0003] Hydrogen-bonded organic frameworks (HOFs) are porous crystalline supramolecular materials that are self-assembled by organic building blocks through hydrogen bonding. Due to their advantages such as adjustable composition, stable structure, rich functional groups and good solution processability, they show great application prospects in the field of high-toughness adhesives. When HOFs are introduced into polyurethane adhesives, the functional groups on the surface of HOFs can form hydrogen bonds with polyurethane, enhancing the interfacial compatibility between HOFs and polyurethane. The amorphous phase of polyurethane and the crystal structure of HOFs can form a soft-hard multi-level structure. Under the action of external force, the soft-hard multi-level structure forms a graded energy dissipation, which is beneficial to enhance the cohesion of the adhesive and improve the toughness of the adhesive. A large number of functional groups in HOFs and polyurethane can form non-covalent interactions such as hydrogen bonding, coordination, and hydrophobic-hydrophobic interactions with different substrates, which increases the adhesion between the polyurethane-hydrogen-bonded organic framework composite adhesive and the substrate. Moreover, after the adhesive and the substrate are disassembled, these non-covalent interactions are conducive to the re-adhesion of the two.

[0004] At present, there are few reports on adhesives involving polyurethane and HOFs composites used in the bonding field. Developing polyurethane and HOFs adhesives with high toughness, excellent bonding performance, stable recycling, wide substrate adhesion range, simple preparation, and low cost has become an urgent problem to be solved in expanding its bonding applications. Summary of the invention

[0005] The present invention mainly aims at the problem of poor toughness of current adhesives, and provides a method for preparing a polyurethane-hydrogen bond organic framework composite adhesive. The method evenly disperses HOFs in a polyurethane solution, and then forms an adhesive of "polyurethane and HOFs" by a solvent volatilization method. In the composite adhesive obtained by the present invention, the introduction of HOFs enhances the cohesive force of the polyurethane, improves the toughness of the adhesive, and can be used for cyclic bonding. Compared with a single polyurethane adhesive, the toughness of the composite adhesive obtained by the present invention is increased by 2.9 times.

[0006] The technical solution of the present invention is:

[0007] A method for preparing a polyurethane-hydrogen bond organic framework composite adhesive, the method comprising the following steps:

[0008] At 25 to 90° C., a polyol is dissolved in a first organic solvent under a nitrogen atmosphere, and then a diisocyanate is added to the solution; after stirring for 0.1 to 2 hours, a catalyst dibutyltin dilaurate is added; after continuing to stir for 1 to 12 hours, a chain extender is added; finally, stirring for 1 to 12 hours to obtain a polyurethane solution; then, a HOFs dispersion is added to the polyurethane solution, and stirred for 5 to 36 hours to obtain a dispersion of polyurethane and HOFs; the obtained dispersion is poured into a polytetrafluoroethylene mold, and after drying at 25 to 100° C. for 3 to 36 hours, it is taken out from the mold to obtain a polyurethane-hydrogen bond organic framework composite adhesive;

[0009] The molar ratio of polyol, diisocyanate and chain extender is 1:(1-8):(0.1-8); 0.1-20 mmol of polyol and 0.01-0.50 mL of dibutyltin dilaurate are added to every 20 mL of the first solvent; the mass of HOFs is 0.01-50 wt% of the total mass of polyol, diisocyanate, chain extender and catalyst;

[0010] The solvent of the HOFs dispersion is also the first organic solvent; the concentration is 1 mg / mL to 200 mg / mL;

[0011] The polyol is any one or more of polybutylene adipate diol, hydroxyl-terminated polydimethylsiloxane, and polycaprolactone diol.

[0012] The diisocyanate is isophorone diisocyanate, toluene diisocyanate or hexamethylene diisocyanate.

[0013] The first organic solvent is acetone or tetrahydrofuran.

[0014] The volume of the first organic solvent is 5 to 500 mL.

[0015] The chain extender is any one of 1,4-butanediol, 1,6-hexanediol, ethylenediamine and 1,6-hexanediamine.

[0016] The volume of the dibutyltin dilaurate is 0.01-10 mL.

[0017] The preparation method of HOFs comprises the following steps:

[0018] The building block is dissolved in N,N-dimethylformamide, heated at 25 to 150° C. for 5 to 60 minutes to obtain a solution, cooled to room temperature, and then a second organic solvent is added. After stirring for 0.1 to 24 hours, the synthesized solid is centrifuged, washed, and dried to obtain HOFs;

[0019] The mass ratio of the building block, N,N-dimethylformamide, and the second organic solvent is 0.2:(1-100):(10-1000); the second organic solvent is any one or more of ethanol, water, and ethyl acetate;

[0020] The building blocks are 1,3,6,8-tetracarboxypyrene, 1,3,6,8-tetra(4-carboxyphenyl)pyrene, 1,3,6,8-tetra(6-carboxy-2-naphthyl)pyrene, 4,4',4",4"'-(pyrene-1,3,6,8-tetrayl)tetra(2-fluorobenzoic acid), 4,4',4",4"'-(pyrene-1,3,6,8-tetrayl)tetra(2-aminobenzoic acid) or 4,4',4",4"'-(pyrene-1,3,6,8-tetrayl)tetra(2-methylbenzoic acid)aldehyde;

[0021] The polyurethane-hydrogen bond organic framework composite adhesive obtained by the method is used as a high-toughness adhesive.

[0022] The method specifically comprises the following steps: placing a polyurethane-hydrogen bond organic framework composite adhesive between two substrates, pressing for 1 to 60 minutes at a continuous pressure of 0.01 to 10 MPa and a temperature of 70 to 150° C., so as to bond the two substrates together.

[0023] The two substrates are the same or different, and the substrate of a single substrate is metal, stainless steel, glass, polyethylene terephthalate or wood;

[0024] The essential features of the present invention are:

[0025] The present invention evenly disperses HOFs in a polyurethane solution, and prepares a polyurethane and HOFs composite adhesive by a solvent volatilization method; in the composite adhesive, the functional groups on the surface of HOFs can form hydrogen bonds with polyurethane, thereby enhancing the interface compatibility between HOFs and polyurethane. The amorphous phase of polyurethane and the crystal structure of HOFs can form a soft-hard multi-level structure, and under the action of external force, the soft-hard multi-level structure forms a graded energy dissipation, thereby enhancing the cohesion of the composite adhesive, thereby enhancing the toughness. A large number of functional groups in HOFs and polyurethane form non-covalent interactions such as hydrogen bonds, coordination, and hydrophobic-hydrophobic interactions with different substrates, thereby increasing the adhesion of the polyurethane-hydrogen bond organic framework composite adhesive to a variety of substrates. Moreover, after the adhesive and the substrate are debonded, these non-covalent interactions are conducive to the re-adhesion of the two, and the above synergistic effects further improve the bonding performance and recycling performance of the adhesive, which is superior to many existing adhesives.

[0026] The beneficial effects of the present invention are:

[0027] (1) The present invention provides a method for preparing an adhesive by compounding polyurethane and HOFs. The clear structures of polyurethane and HOFs provide an ideal platform for understanding the relationship between adhesive structure and bonding performance.

[0028] (2) The adhesive prepared by combining the polyurethane and HOFs provided by the present invention benefits from the hydrogen bonding effect formed between the polyurethane and HOFs and the crystal structure of the HOFs, and has a bonding strength with the zinc substrate of 1.17±0.12MPa. Compared with the single polyurethane adhesive (0.29±0.06MPa), the bonding strength of the composite adhesive is increased by 4 times.

[0029] (3) The adhesive prepared by the composite of polyurethane and HOFs provided by the present invention has bonding strengths of 1.65±0.29MPa, 1.99±0.26MPa and 2.61±0.51MPa with copper, aluminum and stainless steel respectively. The composite adhesive can be bonded not only with metals but also with glass (1.23±0.10MPa), polyethylene terephthalate (1.53±0.20MPa) and wood (4.35±0.34MPa).

[0030] (4) The adhesive prepared by combining polyurethane and HOFs provided by the present invention can be bonded not only to the same substrate but also to different substrates. The bonding strength with metal copper and zinc is 1.13±0.09MPa.

[0031] (5) The adhesive prepared by the composite of the polyurethane and HOFs provided by the present invention was bonded to copper and then subjected to a tensile test. The composite adhesive after the tensile test was then bonded to copper again. After five repeated bonding-tensile tests, the fifth bonding strength was 1.75±0.20 MPa, which was similar to the first bonding strength (1.65±0.29 MPa).

[0032] (6) The adhesive prepared by combining polyurethane and HOFs provided by the present invention has a toughness of 80.52±11.46 MJ m -3 , compared with the single polyurethane adhesive (27.48±3.84MJ m -3 ), the toughness of the composite adhesive increased by 2.9 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the bonding between adhesive and substrate.

[0034] Figure 2 It is the bonding strength between adhesive and different substrates.

[0035] Figure 3 The bonding strength of the polyurethane-hydrogen bond organic framework composite adhesive of Example 3 and metal copper after repeated bonding for 5 times.

[0036] Figure 4 It is the toughness of the polyurethane adhesive in the comparative example and the polyurethane-hydrogen bond organic framework composite adhesive in Example 4. DETAILED DESCRIPTION

[0037] In order to further understand the method of the present invention, the following examples are specifically described in conjunction with the accompanying drawings. The following examples are only specific preparation methods of the present invention, and do not limit the scope of the present invention.

[0038] Comparative Example 1 Preparation of polyurethane adhesive

[0039] At 60°C, hydroxy-terminated polydimethylsiloxane (0.089 g, 1.2 mmol) and polycaprolactone diol (0.916 g, 0.9 mmol) were dissolved in tetrahydrofuran (20 mL) under a nitrogen atmosphere, and then isophorone diisocyanate (0.6 g, 2.7 mmol) was added to the solution; after stirring for 0.1 hour, dibutyltin dilaurate (0.05 mL) was added; after continuing to stir for 3 hours, 1,4-butanediol (0.054 g, 0.6 mmol) was added; finally, stirring was performed for 2 hours to obtain a polyurethane solution; the obtained polyurethane solution was poured into a rectangular polytetrafluoroethylene mold, and after drying at 60°C for 36 hours, it was taken out from the mold to obtain a polyurethane adhesive.

[0040] Example 1 Preparation of polyurethane-hydrogen bond organic framework composite adhesive

[0041] At 60°C, hydroxy-terminated polydimethylsiloxane (0.089 g, 1.2 mmol) and polycaprolactone diol (0.916 g, 0.9 mmol) were dissolved in tetrahydrofuran (20 mL) under a nitrogen atmosphere, and then isophorone diisocyanate (0.6 g, 2.7 mmol) was added to the solution; after stirring for 0.1 hour, dibutyltin dilaurate (0.05 mL) was added; after continuing to stir for 3 hours, 1,4-butanediol (0.054 g, 0.6 mmol) was added; finally, the mixture was stirred for 2 hours to obtain a polyurethane solution;

[0042] 1,3,6,8-Tetrakis(4-carboxyphenyl)pyrene (0.21 g) was dissolved in N,N-dimethylformamide (31.5 mL) and heated at 25 °C for 60 min to obtain a clear solution. After cooling to room temperature, water (210 g) and ethanol (174 g) were added. After stirring for 1 hour, the synthesized solid was centrifuged, washed, and dried to obtain HOFs.

[0043] HOFs (0.016 g) were dispersed in tetrahydrofuran (1 mL) to obtain a HOFs dispersion; these HOFs dispersions were added to all the polyurethane solutions obtained above, and stirred for 36 hours to obtain a dispersion of polyurethane and HOFs; the obtained dispersion was poured into a rectangular polytetrafluoroethylene mold, and after drying at 60° C. for 36 hours, it was taken out from the mold to obtain a polyurethane-hydrogen bond organic framework composite adhesive.

[0044] Example 2 Adhesion Performance Test

[0045] The polyurethane adhesive prepared in Comparative Example 1 and the polyurethane-hydrogen bond organic framework composite adhesive prepared in Example 1 were tested for their bonding properties. Figure 1 In the bonding method shown, the two adhesives are placed between two zinc substrates respectively, and pressed for 1 min at a continuous pressure of 0.5 MPa and a temperature of 120°C to bond the two substrates together, and the bonding strength is obtained by the tensile lap shear test method.

[0046] Figure 2 The bonding strength between polyurethane adhesive and zinc substrate was 0.29±0.06MPa, which was lower than the bonding strength between polyurethane-hydrogen bond organic framework composite adhesive and zinc substrate, which was 1.17±0.12MPa. The bonding strengths of polyurethane-hydrogen bond organic framework composite adhesive on copper, aluminum, stainless steel, glass, polyethylene terephthalate, and wood were 1.65±0.29MPa, 1.99±0.26MPa, 2.61±0.51MPa, 1.23±0.10MPa, 1.53±0.20MPa, and 4.35±0.34MPa, respectively. The bonding strength between polyurethane-hydrogen bond organic framework composite adhesive and copper and zinc was 1.13±0.09MPa.

[0047] Example 3 Repeated Adhesion Performance Test

[0048] The polyurethane-hydrogen bond organic framework composite adhesive prepared in Example 1 was subjected to repeated bonding performance tests.

[0049] Figure 3 In the process, the polyurethane-hydrogen bond organic framework composite adhesive was bonded to metal copper and then subjected to a tensile lap shear test. Then, the polyurethane-hydrogen bond organic framework composite adhesive was bonded to metal copper again after being disassembled after the tensile test. After 5 repeated bonding-tensile tests, the fifth bonding strength was 1.75±0.20MPa, which was similar to the first bonding strength.

[0050] Example 4 Toughness Test

[0051] The polyurethane-hydrogen bond organic framework composite adhesive prepared in Example 1 was subjected to a tensile stress-strain test, and the toughness was obtained by calculating the area under the stress-strain curve.

[0052] Figure 4 The toughness of the polyurethane-hydrogen bond organic framework composite adhesive prepared in this example is 80.52±11.46 MJ m -3 , which is greater than the toughness of polyurethane adhesive 27.48±3.84MJ m -3 .

[0053] Example 5

[0054] At 60°C, hydroxy-terminated polydimethylsiloxane (0.89 g, 12 mmol) and polycaprolactone diol (9.16 g, 9 mmol) were dissolved in tetrahydrofuran (50 mL) under a nitrogen atmosphere, and then isophorone diisocyanate (6 g, 27 mmol) was added to the solution; after stirring for 0.1 hour, dibutyltin dilaurate (0.5 mL) was added; after continuing to stir for 3 hours, 1,4-butanediol (0.54 g, 6 mmol) was added; finally, the mixture was stirred for 2 hours to obtain a polyurethane solution;

[0055] 1,3,6,8-Tetracarboxypyrene (0.2 g) was dissolved in N,N-dimethylformamide (10 mL) and heated at 25 °C for 60 min to obtain a clear solution. After cooling to room temperature, water (200 g) and ethanol (200 g) were added. After stirring for 1 hour, the synthesized solid was centrifuged, washed, and dried to obtain HOFs.

[0056] HOFs (0.16 g) were dispersed in tetrahydrofuran (3 mL) to obtain a HOFs dispersion; these HOFs dispersions were added to all the polyurethane solutions obtained above, and stirred for 36 hours to obtain a dispersion of polyurethane and HOFs; the obtained dispersion was poured into a rectangular polytetrafluoroethylene mold, and after drying at 60° C. for 36 hours, it was taken out from the mold to obtain a polyurethane-hydrogen bond organic framework composite adhesive.

[0057] Example 6

[0058] At 60°C, hydroxy-terminated polydimethylsiloxane (0.89 g, 12 mmol) and polycaprolactone diol (9.16 g, 9 mmol) were dissolved in acetone (50 mL) under a nitrogen atmosphere, and then hexamethylene diisocyanate (4.5 g, 27 mmol) was added to the solution; after stirring for 0.1 hour, dibutyltin dilaurate (0.5 mL) was added; after continuing to stir for 3 hours, 1,4-butanediol (0.54 g, 6 mmol) was added; and finally, the mixture was stirred for 2 hours to obtain a polyurethane solution;

[0059] 1,3,6,8-Tetrakis(6-carboxy-2-naphthyl)pyrene (0.4 g) was dissolved in N,N-dimethylformamide (20 mL) and heated at 25 °C for 60 min to obtain a clear solution. After cooling to room temperature, water (300 g) and ethanol (300 g) were added. After stirring for 1 hour, the synthesized solid was centrifuged, washed, and dried to obtain HOFs.

[0060] HOFs (0.32 g) were dispersed in acetone (5 mL) to obtain a HOFs dispersion; these HOFs dispersions were added to all the polyurethane solutions obtained above, and stirred for 36 hours to obtain a dispersion of polyurethane and HOFs; the obtained dispersion was poured into a rectangular polytetrafluoroethylene mold, and after drying at 60° C. for 36 hours, it was taken out from the mold to obtain a polyurethane-hydrogen bond organic framework composite adhesive.

[0061] Matters not covered by the present invention are known technologies.

Claims

1. A method for preparing a polyurethane-hydrogen bond organic framework composite adhesive, characterized in that: The method comprises the following steps: At 25 to 90° C., a polyol is dissolved in a first organic solvent under a nitrogen atmosphere, and then a diisocyanate is added to the solution; after stirring for 0.1 to 2 hours, a catalyst dibutyltin dilaurate is added; after continuing to stir for 1 to 12 hours, a chain extender is added; finally, stirring for 1 to 12 hours, a polyurethane solution is obtained; then, a HOFs dispersion is added to the polyurethane solution, and stirred for 5 to 36 hours to obtain a dispersion of polyurethane and HOFs; the obtained dispersion is poured into a polytetrafluoroethylene mold, and after drying, a polyurethane-hydrogen bond organic framework composite adhesive is obtained; The molar ratio of the polyol, diisocyanate and chain extender is 1:(1-8):(0.1-8); 0.1-20 mmol of the polyol and 0.01-0.50 mL of dibutyltin dilaurate are added to every 20 mL of the first solvent; The mass of HOFs is 0.01 to 50 wt% of the total mass of polyol, diisocyanate, chain extender and catalyst; The solvent of the HOFs dispersion is also the first organic solvent.

2. The method for preparing the polyurethane-hydrogen bond organic framework composite adhesive according to claim 1, characterized in that: The concentration of the HOFs dispersion is 1 mg / mL to 200 mg / mL.

3. The method for preparing the polyurethane-hydrogen bond organic framework composite adhesive according to claim 1, characterized in that the dispersion is dried at 25-100°C for 3-36 hours.

4. The method for preparing the polyurethane-hydrogen bond organic framework composite adhesive according to claim 1, characterized in that: The polyol is any one or more of polybutylene adipate diol, hydroxyl-terminated polydimethylsiloxane, and polycaprolactone diol; The diisocyanate is isophorone diisocyanate, toluene diisocyanate or hexamethylene diisocyanate.

5. The method for preparing the polyurethane-hydrogen bond organic framework composite adhesive according to claim 1, characterized in that: The first organic solvent is acetone or tetrahydrofuran.

6. The method for preparing the polyurethane-hydrogen bond organic framework composite adhesive according to claim 1, characterized in that: The chain extender is 1,4-butanediol, 1,6-hexanediol, ethylenediamine or 1,6-hexanediamine.

7. The method for preparing the polyurethane-hydrogen bond organic framework composite adhesive according to claim 1, characterized in that: The preparation method of HOFs comprises the following steps: The building block is dissolved in N,N-dimethylformamide, heated at 25 to 150° C. for 5 to 60 minutes to obtain a solution, cooled to room temperature, and then a second organic solvent is added. After stirring for 0.1 to 24 hours, the synthesized solid is centrifuged, washed, and dried to obtain HOFs; The mass ratio of the building block, N,N-dimethylformamide, and the second organic solvent is 0.2:(1-100):(10-1000); the second organic solvent is any one or more of ethanol, water, and ethyl acetate; The building blocks are 1,3,6,8-tetracarboxypyrene, 1,3,6,8-tetra(4-carboxyphenyl)pyrene, 1,3,6,8-tetra(6-carboxy-2-naphthyl)pyrene, 4,4',4",4"'-(pyrene-1,3,6,8-tetrayl)tetra(2-fluorobenzoic acid), 4,4',4",4"'-(pyrene-1,3,6,8-tetrayl)tetra(2-aminobenzoic acid) or 4,4',4",4"'-(pyrene-1,3,6,8-tetrayl)tetra(2-methylbenzoic acid)aldehyde.

8. The use of the polyurethane-hydrogen bond organic framework composite adhesive obtained by the method according to claim 1, characterized in that it is used as a high-toughness adhesive; Specifically, the method comprises the following steps: placing a polyurethane-hydrogen bond organic framework composite adhesive between two substrates, pressing the two substrates together at a continuous pressure of 0.01 to 10 MPa and a temperature of 70 to 150° C. for 1 to 60 minutes to bond the two substrates together; The two substrates are the same or different, and the substrate of a single substrate is metal, stainless steel, glass, polyethylene terephthalate or wood.

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