Polyurethane prepolymer based on supramolecular weaving crosslinking, composition and preparation method thereof

Abstract

The invention relates to the technical field of polyurethane synthesis, and discloses a polyurethane prepolymer and composition based on supramolecular weaving crosslinking and a preparation method of the polyurethane prepolymer, and a cross-linking agent in the polyurethane prepolymer comprises a compound as shown in a formula I and organic copper salt; the molar ratio of the compound as shown in the formula I to the organic copper salt is 1: (1.8-3); the organic copper salt is selected from copper tetraacetonitrile tetrafluoroborate and / or copper tetraacetonitrile hexafluorophosphate. According to the invention, the dynamic nature of a mechanical interlocking supramolecular structure is utilized, and a polymer with a topological structure is woven through an ectopic ring-opening polymerization strategy. The woven polymer can be used as a cross-linking agent of a polyurethane composition, can endow the polyurethane composition with relatively high mechanical property and good tensile property at the same time, and greatly improves the tensile toughness of polyurethane. # imgabs0 #

Description

Technical Field

[0001] The invention relates to the technical field of polyurethane synthesis, and in particular to a polyurethane prepolymer and a composition based on supramolecular braiding and cross-linking, and a preparation method thereof. Background Art

[0002] As a material adhesive, polyurethane compositions have the advantages of adjustable hardness, low temperature resistance, good flexibility, and high bonding strength. They can bond a variety of materials such as metals and non-metals, and have broad application prospects in the fields of construction, electronic materials, and decoration. In the prior art, in order to adjust the mechanical properties of polyurethane, the structure of the polyurethane composition is often adjusted by adding a multifunctional cross-linking agent or changing the ratio of soft and hard segments, and auxiliary agents and fillers are used to adjust the mechanical properties to meet actual application needs.

[0003] However, conventional polyurethane compositions with high hard segment content have high mechanical strength but poor tensile properties, and exhibit brittle fracture with low elongation at break when the polyurethane composition is destroyed. Conversely, polyurethane compositions with high soft segment content are elastomers with excellent tensile properties, but their tensile strength is low. The method of adjusting the microscopic network-like molecular structure and its phase separation state through soft and hard segments cannot simultaneously take into account high mechanical properties and excellent tensile properties.

[0004] In order to obtain a polyurethane with both mechanical strength and tensile toughness, invention CN111909337A discloses a mechanically interlocking crosslinking agent, which is formed by a rotaxane composed of a long-chain axis molecule and at least one cyclic molecule encapsulating the axis molecule. This mechanically interlocking rotaxane structure is used in a polyurethane composition to simultaneously take into account the high mechanical properties and excellent tensile properties of the polyurethane adhesive.

[0005] CN101633629A synthesizes a polyurethane prepolymer with double bonds at the end through allyl alcohol ether and isocyanate, and then carries out free radical solution polymerization with olefin monomers under the action of an initiator to construct a new type of polyurethane crosslinking agent. By adjusting the proportion of the components, adhesives with different strengths and flexibility can be obtained.

[0006] In the early research process, the inventors found that 4,4'-(1,10-phenanthroline-2,9-diyl)bisphenol has dynamic characteristics and woven crosslinking effects, and can be used as a crosslinker in polyurethane to make the polymer have good self-healing and processability. (Robust and Dynamic Polymer Networks Enabled by Woven Crosslinks, G Li, J Zhao, Z Zhang, X Zhao, L Cheng, Y Liu, Z Guo, W Yu, X Yan Angewandte Chemie, 2022) However, the effect of improving the toughness of polyurethane is still insufficient. How to give the polyurethane composition good mechanical strength and higher and better toughness requires further research. Summary of the invention

[0007] The present invention aims to solve the problem that mechanical strength and toughness of a polyurethane composition cannot be taken into account at the same time, and provides a cross-linking agent with a woven structure. The cross-linking agent is used to prepare a polyurethane polymer and can significantly improve the elongation at break of the material. While ensuring the mechanical strength, the toughness is greatly improved, thus breaking through some limitations of the polyurethane composition in application.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] A polyurethane prepolymer based on supramolecular braiding cross-linking, wherein the cross-linking agent in the polyurethane prepolymer comprises a compound represented by formula I and an organic copper salt; the molar ratio of the compound represented by formula I to the organic copper salt is 1:1.8-3;

[0010]

[0011] The organic copper salt is selected from tetraethyl copper cyanide tetrafluoroborate and / or tetraethyl copper cyanide hexafluorophosphate.

[0012] The present invention unexpectedly discovered during research that the compound shown in Formula I also has the structure of biphenyl and o-phenanthroline, and can coordinate with organic metal components to form a supramolecular woven structure. When used as a crosslinking agent for polyurethane, the toughness of the polyurethane composition can be greatly improved, and the elongation at break is greatly improved, and the effect is far superior to 4,4'-(1,10-phenanthroline-2,9-diyl)bisphenol with a similar structure.

[0013] For example, when the organic metal salt is copper tetraethyl cyanide tetrafluoroborate, the coordination structure formed by the compound shown in Formula I and copper tetraethyl cyanide tetrafluoroborate is as follows: Such a structure is used as a supramolecular cross-linking node during the polyurethane polymerization process.

[0014]

[0015] The method for preparing the compound with the structure shown in Formula I comprises the steps of:

[0016] Step 1, reflux reaction of 4,7-dihalo-1,10-phenanthroline and 4-[(tetrahydropyran-2-yl)oxy]phenylboronic acid in the presence of a catalyst to obtain an intermediate product as shown in formula II;

[0017]

[0018] Step 2: reacting the intermediate product represented by formula II with methanol in a solution to obtain the compound represented by formula I.

[0019] The reaction formula is as follows:

[0020]

[0021] The structural formula of the 4,7-dihalo-1,10-phenanthroline is shown in Formula III:

[0022]

[0023] wherein X is selected from F, Cl, Br or I;

[0024] In step 1, the molar ratio of 4,7-dihalo-1,10-phenanthroline to 4-[(tetrahydropyran-2-yl)oxy]phenylboronic acid is 1:1.8-4;

[0025] In step 1, the catalyst is tricyclohexylphosphine, tri(dibenzylideneacetone)dipalladium and potassium phosphate, the molar ratio of the three is 1:0.2-0.7:20-35, and the molar ratio of the total catalyst amount to 4,7-dihalo-1,10-phenanthroline is 1:4-6;

[0026] In step 1, the reaction temperature is 70-120° C., and the reaction time is 15-30 hours; the reaction solvent is selected from a combination of 1,4-dioxane, toluene, N,N-dimethylformamide, dimethyl sulfoxide and water;

[0027] In step 2, the weight ratio of the intermediate product represented by formula II to methanol is 1:0.5-3;

[0028] Preferably, step 2 further comprises an acidifying agent, wherein the acidifying agent is a combined solvent of hydrogen chloride and 1,4-dioxane in a molar ratio of 1:0.1-10;

[0029] Preferably, the polyurethane prepolymer comprises raw material components: polyether diol, zinc ethylhexanoate, triethanolamine, isophorone isocyanate, a compound as shown in formula I, an organic copper salt, polymethylene polyisocyanate, butanone oxime and a solvent;

[0030] The solvent includes any one or more of common solvents such as ethyl acetate and N,N-dimethylformamide.

[0031] Further preferably, the polyurethane prepolymer comprises the following components in parts by weight: 20 to 40 parts of polyether diol, 0.0005 to 0.006 parts of zinc ethylhexanoate, 0.0005 to 0.006 parts of triethanolamine, 3 to 15 parts of isophorone isocyanate, 0.3 to 1.3 parts of the compound shown in formula I, 0.3 to 1.3 parts of copper acetonitrile, 1 to 5 parts of polymethylene polyisocyanate, 1 to 5 parts of butanone oxime and 5 to 18 parts of solvent;

[0032] Preferably, the polymethylene polyisocyanate is Wanhua Chemical PM200.

[0033] The present invention also provides a method for preparing the polyurethane prepolymer based on supramolecular braiding and cross-linking, comprising the steps of:

[0034] Step 1, reacting raw materials including polyether diol, zinc ethylhexanoate, triethanolamine, isophorone isocyanate, and solvent at 60 to 90° C. for 0.5 to 3 hours;

[0035] Step 2, adding the compound shown in formula I, organic copper salt and solvent to the reaction solution of step 1 and reacting at 60-90° C. for 0.5-3 hours;

[0036] Step 3, adding polymethylene polyisocyanate and solvent to the reaction solution of step 2 and reacting at 60-90° C. for 0.5-3 hours;

[0037] Step 4, measuring the isocyanate content in the reaction solution, adding butanone oxime and a solvent to react at 60 to 90° C. for 0.5 to 3 hours to obtain the polyurethane prepolymer.

[0038] The invention also provides a polyurethane composition, comprising the polyurethane prepolymer.

[0039] Preferably, the polyurethane composition is a delayed curing polyurethane, comprising the following components in parts by weight: 60 to 80 parts of polyurethane prepolymer, 3 to 10 parts of epoxy resin, and 10 to 25 parts of polyether amine;

[0040] Or it includes the following components in parts by weight: 25-40 parts of polyurethane prepolymer, 5-25 parts of epoxy resin, 5-15 parts of liquid rubber with core-shell structure, 10-20 parts of nitrile rubber toughening agent, 1-5 parts of water absorbent, 15-30 parts of filler, 1-5 parts of curing agent and 0.1-1 parts of curing accelerator;

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) Compared with the conventional covalent cross-linking agents, such as 1,3-butanediol, 1,4-butanediol, trimethylolpropane, and propylene glycol, the present invention utilizes the dynamics of the mechanically interlocked supramolecular structure to realize a polymer with a braided topological structure through an ectopic ring-opening polymerization strategy. The braided polymer can be used as a cross-linking agent for a polyurethane composition, and can simultaneously impart high mechanical properties and good tensile properties to the polyurethane composition.

[0043] (2) Compared with 4,4'-(1,10-phenanthroline-2,9-diyl)bisphenol with N-ortho phenyl substitution structure, 4,4'-(1,10-phenanthroline-4,7-diyl)bisphenol with N-para phenyl substitution structure in the present invention has significant differences and can greatly improve the tensile toughness of polyurethane. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is the H NMR spectrum of 4,4'-(1,10-phenanthroline-4,7-diyl)bisphenol prepared in Example 1.

[0045] Figure 2 This is the H NMR spectrum of 4,4'-(1,10-phenanthroline-2,9-diyl)bisphenol prepared in Comparative Example 1. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with embodiment. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Those skilled in the art can make modifications or equivalent substitutions based on the understanding of the technical scheme of the present invention without departing from the spirit and scope of the technical scheme of the present invention, and all should be included in the protection scope of the present invention.

[0047] The raw materials used in the following specific embodiments are all purchased from market reagent companies or chemical dealers.

[0048] Example 1

[0049] The synthesis of braided structure compound I comprises the steps:

[0050] Step 1: Add 0.45 g of 4,7-dichloro-1,10-phenanthroline, 0.82 g of 4-[(tetrahydropyran-2-yl)oxy]phenylboronic acid, 0.07 g of tricyclohexylphosphine, 0.1 g of tri(dibenzylideneacetone)dipalladium(0) and 1.58 g of potassium phosphate into a three-necked flask, fully remove the oxygen in the flask, then fill it with nitrogen, add 10 ml of deoxygenated 1,4-dioxane and 5 ml of water into the three-necked flask, and then heat and reflux at 95°C for azeotropic stirring for 20 hours. The reaction solution is cooled to room temperature, the reaction solution is washed twice with a saturated sodium chloride solution, the organic phase is dried with anhydrous magnesium sulfate and then rotary evaporated to obtain a crude product, and the crude product is recrystallized and purified with a mixed solution of dichloromethane and petroleum ether to obtain an intermediate product of formula II

[0051] Step 2: Dissolve the aforementioned 0.7 g of the intermediate product of formula II in 40 ml of methanol, add 1.3 ml of dry hydrogen chloride / 1.4-dioxane mixed solution (wherein the molar concentration of hydrogen chloride is 4 mol / ml), and stir the mixture at room temperature for 6 hours. Filter the reaction solution, wash with 15 ml of chloroform, and add 0.4 g of potassium carbonate, 2.5 ml of chloroform, and 0.25 ml of methanol to the obtained solid. Then the mixture is spin-dried and separated by a chromatographic column (methanol / chloroform) to obtain a compound shown in formula I (hereinafter referred to as cross-linking agent A).

[0052] The reaction equation is as follows:

[0053]

[0054] like Figure 1 As shown, the 600 MHz H NMR spectrum test results of the compound represented by the product formula I are δ (ppm): 9.89 (s, 2H), 9.10 (s, 2H), 7.94 (s, 2H), 7.67 (s, 2H), 7.43 (d, J = 8.5 Hz, 4H), 6.99 (d, J = 6.4 Hz, 4H), the test conditions are room temperature, and the test solvent is deuterated dimethyl sulfoxide.

[0055] Comparative Example 1

[0056] Synthesis process of 4,4'-(1,10-phenanthroline-2,9-diyl)bisphenol:

[0057] Step 1: Add 500 mg of 2,9-dichloro-1,10-phenanthroline, 1114 mg of 4-[(tetrahydropyran-2-yl)oxy]phenylboronic acid, 700 mg of tetrakis(triphenylphosphine)palladium(0) and 15000 mg of sodium carbonate into a three-necked flask, fully remove the oxygen in the flask, then fill it with nitrogen, add 180 ml of oxygen-free toluene and 80 ml of oxygen-free water into the three-necked flask, and then heat and reflux at 80°C for azeotropic stirring for 20 hours. Then the reaction solution is cooled to room temperature, the reaction solution is washed twice with a saturated sodium chloride solution, the organic phase is dried with anhydrous magnesium sulfate and then rotary evaporated to obtain a crude product, and the crude product is recrystallized and purified with a mixed solution of dichloromethane and petroleum ether to obtain an intermediate product.

[0058] Step 2: Dissolve the aforementioned 1.4 g intermediate product in 80 ml methanol, add 2.6 ml dry hydrogen chloride 1.4-dioxane solution (4 mol / ml), and stir the mixture at room temperature for 6 hours. Filter the reaction solution, wash with 30 ml chloroform, and add 0.7 g potassium carbonate, 5 ml chloroform, and 0.5 ml methanol to the obtained solid. Then the mixture is spin-dried and separated by a chromatographic column (methanol / chloroform) to obtain 4,4'-(1,10-phenanthroline-2,9-diyl)bisphenol (hereinafter referred to as crosslinker B).

[0059] The reaction formula is as follows:

[0060]

[0061] The 600MHz H NMR spectrum test results of the prepared 4,4'-(1,10-phenanthroline-2,9-diyl)bisphenol are as follows: Figure 2 As shown, specifically δ (ppm): 9.89 (s, 2H), 8.47 (d, J = 8.4 Hz, 2H), 8.37 (d, J = 8.4 Hz, 4H), 8.27 (d, J = 8.4 Hz, 2H), 7.91 (s, 2H), 7.00 (d, J = 8.5 Hz, 4H), the test conditions were room temperature, and the test solvent was deuterated dimethyl sulfoxide.

[0062] Example 2

[0063] The crosslinking agent A prepared in Example 1 is used to prepare a polyurethane prepolymer, including the following steps:

[0064] Step 1: Add 300 g of polyether diol (DL-3000D) with a molecular weight of 3000D into a 500 ml glass reactor, heat to 108°C, vacuum dehydrate, keep warm for 1 hour, then cool to 35°C, seal and set aside.

[0065] Step 2: 8 grams of dehydrated polyether diol (DL-3000D), 0.001 grams of zinc ethylhexanoate, 0.001 grams of triethanolamine and 2 milliliters of ethyl acetate were added to the reactor as solvents, stirred for 10 minutes, 1.36 grams of isophorone polyisocyanate were added to the reactor under stirring, the temperature was raised to 85°C for insulation reaction, the reaction time was 1.2 hours, and the temperature was lowered to room temperature. 0.13 grams of crosslinking agent A and 2 grams of DMF (N, N-dimethylformamide) were added to the reactor, 0.03 grams of tetrafluoroborate tetraethyl cyanide copper were added under stirring and nitrogen protection, the mixture was stirred at room temperature for 20 minutes, the temperature was raised to 80°C for insulation reaction, the reaction time was 50 minutes, and the temperature was lowered to room temperature.

[0066] Step 3: Add a mixed solution of 0.55 g of polymethylene polyisocyanate (Wanhua Chemical Pm 200) and 5 g of ethyl acetate into the reactor, heat to 65°C for reaction under stirring, the reaction time is 50 minutes, cool to room temperature, and obtain a polyurethane prepolymer. The mass fraction of -NCO groups in the polyurethane prepolymer is detected to be 2.63%.

[0067] Step 4: Add a mixed solution of 0.61 g of butanone oxime and 5 g of ethyl acetate into the reactor, heat it to 75° C. for reaction under stirring, the reaction time is 2 hours, cool it to room temperature, remove the solvent, and obtain a room temperature stable polyurethane prepolymer A1.

[0068] The viscosity of the polyurethane prepolymer A1 based on the braided structure crosslinker A was measured at 33670 cps at room temperature (25°C).

[0069] Comparative Example 2

[0070] The crosslinking agent B prepared in Comparative Example 1 is used to prepare a polyurethane prepolymer, including the following steps:

[0071] Step 1: Add 300 g of polyether diol (DL-3000D) with a molecular weight of 3000D into a 500 ml glass reactor, heat to 108°C, vacuum dehydrate, keep warm for 1 hour, then cool to 35°C, seal and set aside.

[0072] Step 2: 8 grams of dehydrated polyether diol (DL-3000D), 0.001 grams of zinc ethylhexanoate, 0.001 grams of triethanolamine and 2 milliliters of ethyl acetate were added to the reactor as solvents, stirred for 10 minutes, 1.36 grams of isophorone polyisocyanate were added to the reactor under stirring, the temperature was raised to 85°C for insulation reaction, the reaction time was 1.2 hours, and the temperature was lowered to room temperature. 0.13 grams of crosslinking agent B and 2 grams of DMF (N, N-dimethylformamide) were added to the reactor, 0.03 grams of tetrafluoroborate tetraethyl cyanide copper were added under stirring and nitrogen protection, the mixture was stirred at room temperature for 20 minutes, the temperature was raised to 80°C for insulation reaction, the reaction time was 50 minutes, and the temperature was lowered to room temperature.

[0073] Step 3: Add a mixed solution of 0.55 g of polymethylene polyisocyanate (Wanhua Chemical Pm 200) and 5 g of ethyl acetate into the reactor, heat to 65° C. for reaction under stirring, the reaction time is 50 minutes, cool to room temperature, and obtain a polyurethane prepolymer. The mass fraction of -NCO groups in the polyurethane prepolymer is detected to be 2.56%.

[0074] Step 4: Add a mixed solution of 0.61 g of butanone oxime and 5 g of ethyl acetate into the reactor, heat it to 75°C for reaction under stirring, the reaction time is 2 hours, cool it to room temperature, remove the solvent, and obtain a room temperature stable polyurethane prepolymer B1.

[0075] The viscosity of the polyurethane prepolymer B1 based on the braided structure crosslinking agent B was measured at room temperature (25° C.) to be 37,800 cps.

[0076] Comparative Example 3

[0077] The process of preparing polyurethane prepolymer based on covalently cross-linked pentaerythritol is carried out according to the following process route:

[0078] Step 1: Add 300 g of polyether diol (DL-3000D) with a molecular weight of 3000D into a 500 ml glass reactor, heat to 108°C, vacuum dehydrate, keep warm for 1 hour, then cool to 35°C, seal and set aside.

[0079] Step 2: Add 8 grams of dehydrated polyether diol (DL-3000D), 0.001 grams of zinc ethylhexanoate, 0.001 grams of triethanolamine and 2 milliliters of ethyl acetate as solvent into the reactor, stir for 10 minutes, add 1.36 grams of isophorone polyisocyanate into the reactor under stirring, heat to 85°C for insulation reaction, the reaction time is 1.2 hours, and the temperature is lowered to room temperature. Add 0.06 grams of pentaerythritol and 2 grams of DMF (N, N-dimethylformamide) mixed solution into the reactor, stir the mixture at room temperature for 20 minutes under stirring and nitrogen protection, heat to 80°C for insulation reaction, the reaction time is 50 minutes, and the temperature is lowered to room temperature.

[0080] Step 3: Add a mixed solution of 0.55 g of polymethylene polyisocyanate (Wanhua Chemical Pm 200) and 5 g of ethyl acetate into the reactor, heat to 65° C. for reaction under stirring, the reaction time is 50 minutes, cool to room temperature, and obtain a polyurethane prepolymer. The mass fraction of -NCO groups in the polyurethane prepolymer is detected to be 2.60%.

[0081] Step 4: Add a mixed solution of 0.61 g of butanone oxime and 5 g of ethyl acetate into the reactor, heat it to 75°C for reaction under stirring, the reaction time is 2 hours, cool it to room temperature, remove the solvent, and obtain a room temperature stable polyurethane prepolymer C1.

[0082] The viscosity of the pentaerythritol polyurethane prepolymer C1 measured at room temperature (25° C.) was 40,300 cps.

[0083] Application Example 1

[0084] A polyurethane preparation process, which mainly explores the properties of polyurethane bulk materials:

[0085] According to the mass fractions of the raw materials in Table 1, epoxy resin and polyetheramine D900 were added to the polyurethane prepolymers A1, B1 and C1, mixed and stirred at 30-40°C, 15 Hz revolution and 10 Hz rotation, and vacuum degassed for 5-15 minutes to obtain delayed-curing polyurethanes D1, D2 and D3.

[0086] Application Example 2

[0087] A preparation process of a polyurethane composition, which mainly explores the performance of the adhesive after the polyurethane is mixed with other powder materials:

[0088] According to the mass fractions of the raw materials in Table 1, epoxy resin, liquid rubber with a core-shell structure, nitrile rubber toughening agent, and diluent were added to polyurethane prepolymers A1, B1, and C1, and the materials were placed in a dynamic mixer, mixed and stirred at 30° C. to 40° C., revolution 15 Hz, and rotation 30 Hz, and vacuum degassing was performed for 8 to 25 minutes to obtain an epoxy resin primary mixture; then, a water absorbent, a filler, a heat-activated latent curing agent, and a curing accelerator were added to the epoxy resin primary mixture, mixed and stirred at 30° C. to 40° C., revolution 15 Hz, and rotation 10 Hz, and vacuum degassing was performed for 8 to 25 minutes to obtain delayed-curing polyurethane compositions D4, D5, and D6.

[0089] The epoxy resin used in the above application examples 1-2 is E51 liquid epoxy resin; the liquid rubber with core-shell structure is MX154 core-shell rubber particles / epoxy resin (wherein the mass fraction of core-shell particles is 40%); the nitrile rubber toughening agent is liquid nitrile rubber modified by CTBN2050 epoxy resin; the water absorbent is 4A molecular sieve; the filler is fumed silica; the curing agent is Dyhard 100S dicyandiamide curing agent; and the curing accelerator is UR700, all of which are purchased from the market.

[0090] The performance of polyurethane and its compositions D1-D6 were tested at room temperature, and the test method was based on the national standard GBT228-2002 tensile specimen. Specifically, the test substrate was wiped clean with acetone. The aforementioned delayed curing polyurethane composition was evenly applied to the mold, and then the mold was kept at 160°C for 1 hour, and then the molded test strips were taken out for testing. The tensile strength and elongation at break were tested three times, and the results are summarized in Table 1.

[0091] Table 1 Raw material composition and performance measurement results of polyurethane and polyurethane composition of application examples

[0092]

[0093] From the results in Table 1, it can be seen that D1 and D4 are polyurethane compositions prepared using the mechanical interlocking braided structure crosslinker A of the present invention. Compared with the traditional pentaerythritol crosslinkers of D3 and D6, their elongation at break is greatly improved, and the bulk polyurethane is increased to 3 times. The elongation of the polyurethane composition (57.39%) is increased by 462% compared with the covalent structure (10.21%), and the effect is very obvious.

[0094] Compared with the crosslinker B studied earlier by the applicant, although the structure is similar, the effect is very different due to the different substitution positions of the phenol structure. The elongation of the composition obtained by the dynamically coordinated crosslinker B (20.03%) is only increased by 96.2% compared with the covalent structure (10.21%).

Claims

1. A polyurethane prepolymer based on supramolecular braiding and cross-linking, characterized in that: The crosslinking agent in the polyurethane prepolymer includes a compound represented by formula I and an organic copper salt; the molar ratio of the compound represented by formula I to the organic copper salt is 1:1.8-3; The organic copper salt is selected from tetraethyl copper cyanide tetrafluoroborate and / or tetraethyl copper cyanide hexafluorophosphate.

2. The polyurethane prepolymer based on supramolecular braiding and cross-linking according to claim 1, characterized in that: The method for preparing the compound shown in formula I comprises the steps of: Step 1, reflux reaction of 4,7-dihalo-1,10-phenanthroline and 4-[(tetrahydropyran-2-yl)oxy]phenylboronic acid in the presence of a catalyst to obtain an intermediate product as shown in formula II; Step 2: reacting the intermediate product represented by formula II with methanol in a solution to obtain the compound represented by formula I.

3. The polyurethane prepolymer based on supramolecular braiding and cross-linking according to claim 2, characterized in that: The structure of the 4,7-dihalo-1,10-phenanthroline is shown in Formula III: wherein X is selected from F, Cl, Br or I.

4. The polyurethane prepolymer based on supramolecular braiding and cross-linking according to claim 2, characterized in that: In step 1, the molar ratio of 4,7-dihalo-1,10-phenanthroline to 4-[(tetrahydropyran-2-yl)oxy]phenylboronic acid is 1:1.8-4; And / or, in step 1, the catalyst is tricyclohexylphosphine, tri(dibenzylideneacetone)dipalladium and potassium phosphate, the molar ratio of the three is 1:0.2-0.7:20-35, and the molar ratio of the total catalyst amount to 4,7-dihalo-1,10-phenanthroline is 1:4-6; And / or, in step 1, the reaction temperature is 70-120° C., the reaction time is 15-30 h; the reaction solvent is selected from a combination of any one of 1,4-dioxane, toluene, N,N-dimethylformamide, dimethyl sulfoxide and water.

5. The polyurethane prepolymer based on supramolecular braiding and cross-linking according to claim 2, characterized in that: In step 2, the weight ratio of the intermediate product represented by formula II to methanol is 1:0.5-3; And / or, step 2 further comprises an acidifying agent, wherein the acidifying agent is a combined solvent of hydrogen chloride and 1,4-dioxane in a molar ratio of 1:0.1-10.

6. The polyurethane prepolymer based on supramolecular braiding and cross-linking according to claim 1, characterized in that: The polyurethane prepolymer comprises the following components in parts by weight: 20-40 parts of polyether diol, 0.0005-0.006 parts of zinc ethylhexanoate, 0.0005-0.006 parts of triethanolamine, 3-15 parts of isophorone isocyanate, 0.3-1.3 parts of a compound as shown in formula I, 0.3-1.3 parts of an organic copper salt, 1-5 parts of polymethylene polyisocyanate, 1-5 parts of butanone oxime and 5-18 parts of a solvent.

7. The method for preparing a polyurethane prepolymer based on supramolecular braiding and cross-linking according to claim 6, characterized in that: Includes steps: Step 1, reacting raw materials including polyether diol, zinc ethylhexanoate, triethanolamine, isophorone isocyanate, and solvent at 60 to 90° C. for 0.5 to 3 hours; Step 2, adding the compound shown in formula I, copper acetonitrile and solvent to the reaction solution of step 1 and reacting at 60-90° C. for 0.5-3 hours; Step 3, adding polymethylene polyisocyanate and solvent to the reaction solution of step 2 and reacting at 60-90° C. for 0.5-3 hours; Step 4, measuring the isocyanate content in the reaction solution, adding butanone oxime and a solvent to react at 60 to 90° C. for 0.5 to 3 hours to obtain the polyurethane prepolymer.

8. A polyurethane composition, characterized in that The invention comprises a polyurethane prepolymer as described in any one of claims 1 to 7.

9. The polyurethane composition according to claim 8, characterized in that The polyurethane composition comprises the following components in parts by weight: 60 to 80 parts of the polyurethane prepolymer according to any one of claims 1 to 7, 3 to 10 parts of epoxy resin, and 10 to 25 parts of polyether amine.

10. The polyurethane composition according to claim 8, characterized in that The polyurethane composition comprises the following components in parts by weight: 25 to 40 parts of the polyurethane prepolymer according to any one of claims 1 to 7, 5 to 25 parts of epoxy resin, 5 to 15 parts of liquid rubber with a core-shell structure, 10 to 20 parts of a nitrile rubber toughening agent, 1 to 5 parts of a water absorbent, 15 to 30 parts of a filler, 1 to 5 parts of a curing agent and 0.1 to 1 part of a curing accelerator.

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