A cross-scale thermal response self-repairing polyurethane material, a preparation method and application thereof

Abstract

The present application relates to a kind of cross-scale thermal response self-repairing polyurethane material and its preparation method and application, belong to self-repairing polyurethane material field.The polyurethane material main chain is introduced pyridyl group and metal salt forms reversible coordination bond, realize molecular scale self-repairing, preferred double-metallic synergic system can enhance the dynamic nature of coordination bond;Side chain is designed as furan-maleimide structure based on Diels-Alder reaction, give it thermal response macroscopic self-repairing performance, introduce methyl substituted furan group to improve steric hindrance, can expand high-temperature application scene.The polyurethane material has thermal response and double self-repairing mechanism of metal coordination, is suitable for high temperature, high ionic concentration and other harsh working conditions under the polymer protection and repair application.

Description

TECHNICAL FIELD

[0001] The present application relates to a cross-scale thermal response self-repairing polyurethane material, a preparation method and application thereof, and belongs to the field of self-repairing polyurethane materials. BACKGROUND

[0002] Under the industrial and mining environment, especially under the working condition of high temperature and high ion concentration of ore pulp, the steel lining polyurethane composite pipe faces severe service challenges. Typical damage mechanisms include:

[0003] High temperature damage: the friction generates heat during ore pulp transportation, combined with the high temperature (60-120℃) of the environment, which leads to the hydrolysis and oxidation fracture of the polyurethane molecular chain, and the difference in thermal expansion coefficient between different materials leads to the delamination of the interface between steel and polyurethane. For example, the surface temperature of the pipeline in the copper mine in Chile is as high as 90℃, and the traditional polyurethane layer cracks in 3 months.

[0004] Ion erosion: high concentration of Fe 3+ , Ca 2+ , Cl - , SO4 2- , etc. in the ore pulp penetrates into the material, causing swelling or destruction of the coordination structure of the polyurethane, seriously affecting the stability of the material. For example, the Cl - concentration in the iron ore pulp in Australia is more than 5000ppm, and the pH fluctuation range is 2-11, which accelerates the aging and degradation of the material.

[0005] Mechanical wear: the ore pulp carries high-hardness particles (such as quartz sand with Mohs hardness of 7), which continuously erodes the surface of the material during transportation, easily forming microcracks as the corrosion starting point.

[0006] There are currently some researches on self-repairing polyurethane materials. For example, patent CN202211525743.1 uses acylhydrazone bond and DA bond to prepare a double-crosslinking self-repairing polyurethane, which has mild preparation conditions and high self-repairing efficiency. Patent CN202510124437.4 proposes a self-repairing polyurethane film containing disulfide bond and DA bond, which has good self-repairing ability under mild conditions and good mechanical properties. CN106750145B discloses a self-repairing and force-responsive polyurethane material and a preparation method thereof, which has excellent mechanical properties and mild self-repairing conditions, high repair efficiency, but the lower repair speed (heating to 60℃ and lasting for 24h) limits its application in instant repair scenarios.

[0007] Most of the self-healing polyurethane materials currently have good self-healing ability, but they all do not have outstanding high temperature resistance and ion corrosion resistance, and it is difficult to meet the requirements of industrial and mining environment on self-healing polyurethane materials. Under this background, it is of great significance to develop self-healing polyurethane materials for high temperature and high ion concentration ore pulp working conditions, which can effectively improve the service life and safety of the pipeline and meet the requirements of long-term stability of materials under harsh working conditions. SUMMARY

[0008] In order to overcome the defects in the prior art, the application provides a cross-scale thermal response self-healing polyurethane material and a preparation method and application thereof.

[0009] In a first aspect of the application, a cross-scale thermal response self-healing polyurethane material is disclosed, which is synthesized by using isocyanate and polyol to form a polyurethane backbone, one end of the polyurethane backbone is a coordination bond formed by a pyridine group and a metal salt, and the other end is a methoxy inert end cap; the furan-maleimide module based on Diels-Alder reaction is a side chain hanging structure, and a methyl-substituted furan is introduced as a steric hindering group.

[0010] In a second aspect of the application, a preparation method of the cross-scale thermal response self-healing polyurethane material is provided, which comprises the following steps:

[0011] S01: ternary alcohol, furan carboxylic acid derivative and anhydrous methyl formamide are mixed in a molar ratio of 1 :(0.3~0.35):(140~180), concentrated sulfuric acid is added dropwise, the molar ratio of ternary alcohol to concentrated sulfuric acid is 1 :(0.03~0.06); keep stirring, reflux heating at 75~85℃ for 6~8h, column chromatography separation to obtain monomer A;

[0012] The furan group is added before polymerization to avoid excessive crosslinking of the polyurethane chain after polymerization caused by the use of ternary alcohol, and to ensure the orderly arrangement of the DA group in the side chain;

[0013] S02: linear diol, isocyanate, monomer A, chain extender and catalyst are added to anhydrous dimethyl formamide, heated to 70~75℃ and reacted for 1~2h; the temperature is reduced to below 40℃, stirring is kept and 1~3wt% of ethylene glycol methyl ether is slowly added, and the reaction is continued for 6~8h to obtain a single-side inert end-capped polyurethane prepolymer;

[0014] S03: pyridine acetic acid, N,N'-dicyclohexyl carbodiimide, 4-dimethylamino pyridine and anhydrous dimethyl formamide are mixed in a molar ratio of 1 :(0.01~0.05):(0.01~0.05):(10~20) to obtain a mixed solution; 8~10wt% of the mixed solution is added to the single-side inert end-capped polyurethane prepolymer, and the reaction is carried out at room temperature under nitrogen protection for 15~24h to obtain an asymmetric end-capped polyurethane prepolymer;

[0015] S04: 10-15wt% of maleimide derivative is dissolved in anhydrous dimethylformamide and added dropwise to the above asymmetric end-capped polyurethane prepolymer, stirred at 50-60℃ for 12-24h to obtain a thermal-responsive self-healing polyurethane containing Diels-Alder structure;

[0016] S05: 3-6wt% of metal salt solution is added dropwise to the above thermal-responsive self-healing polyurethane containing Diels-Alder structure, stirred at room temperature for 8-12h, after cooling to room temperature, 4-6 times the mass of the mixture of anhydrous ethanol is added to induce precipitation, stand for 10-20min, decant the solvent, repeat 2-3 times, vacuum drying to obtain a cross-scale thermal-responsive self-healing polyurethane material for industrial and mining environments.

[0017] In the present application, one end is capped with pyridine to form a coordination bond with metal ions. Only the metal coordination module is introduced at one end of the main chain to avoid excessive metal coordination bonds in the chain segment at the molecular scale from hindering the DA reaction and rearranging, resulting in a decrease in the reversibility of the DA reaction and a decrease in the repair ability of the thermal-triggered DA module. The inert end capping at the other end can avoid excessive crosslinking of the polyurethane and avoid affecting the side chain DA module. The single-sided end group structure separates the two repair mechanisms to avoid coupling interference (antagonism) around the chain skeleton. Under the high-temperature working conditions of the ore slurry, the single-sided metal coordination group can provide sufficient real-time and rapid repair, and the cross-scale self-healing system dominated by the deep repair of the DA reaction under high temperature is more compatible with the high-temperature working conditions of the ore slurry.

[0018] The monosubstituted furan carboxylic acid in the present application is first reacted with a triol to realize functionalization and protection of the hydroxyl groups in the triol, that is, a methyl-substituted furan group is introduced on one hydroxyl group of the triol under controllable conditions to ensure the orderly arrangement of the furan-maleimide module in the subsequent synthesis, effectively avoiding the random participation of the triol in crosslinking during the synthesis of the main chain.

[0019] In a preferred embodiment, the molar ratio of the linear diol, isocyanate, monomer A, chain extender, catalyst, and anhydrous dimethylformamide is 1: (1.4-1.7): (0.3-0.5): (0.2-0.4): (0.01-0.05): (140-190).

[0020] The triol is one or more of trimethylol ethane, trimethylol propane, trimethylol hexane, 1,2,4-butanetriol, 1,2,6-hexanetriol, and glycerol; the linear diol is one or more of polypropylene glycol, polycaprolactone diol, and polycarbonate diol.

[0021] The isocyanate is one or more of isophorone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, p-phenylene diisocyanate, L-lysine diisocyanate; the chain extender is one or more of 1,4-butanediol, 1,6-hexanediol, diethylene glycol, p-xylylene glycol and cyclohexanedimethanol; and the catalyst is one or more of dibutyltin dilaurate, stannous octoate, lead octoate, dibutyltin oxide and triethylenediamine.

[0022] The furan carboxylic acid derivative is one or more of 2-furan carboxylic acid, 3-methyl furan-2-carboxylic acid and 5-methyl furan-2-carboxylic acid.

[0023] The maleimide derivative is one or more of N-(2-hydroxyethyl) maleimide, N-methyl maleimide, N-ethyl maleimide, N-phenyl maleimide, N-benzyl maleimide and 4,4'-bismaleimido diphenylmethane.

[0024] The metal salt is one or more of Fe 3+ , Zn 2+ , Cu 2+ , Co 2+ , Ag + and Ac - , Cl - , NO3 - .

[0025] Preferably, the metal salt is formed by mixing Zn(Ac)2 and FeCl3 in equimolar amounts.

[0026] The third aspect of the present application discloses the polymer protection and repair application of the aforementioned cross-scale thermal response self-repairing polyurethane material for industrial and mining environments under high-temperature and high-ionic-concentration ore pulp working conditions.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] 1. The cross-scale thermal response self-repairing polyurethane material for industrial and mining environments has the cross-scale self-repairing characteristics of repairing surface / interface damage by metal coordination at the microscale and repairing bulk material cracks by DA covalent bond at the macroscale. At the microcrack stage of the material, metal coordination responds preferentially and can be repaired quickly at room temperature; at the macrocrack stage, high temperature triggers the reconstruction of the DA network to achieve deep repair.

[0029] 2. The cross-scale thermal response self-healing polyurethane material for industrial and mining environments provided by the present application introduces metal coordination groups on one side of the main chain, avoiding excessive cross-linking of polyurethane during synthesis; preferably Fe 3+ / Zn 2+ A bimetallic synergistic system, which makes the metal coordination bond have high strength and high reversibility. Under the condition of high ion concentration in industrial and mining environments, ion response self-healing can also convert destructive metal ions (such as Fe 3+ ) into repair media, and cooperatively improve the repair efficiency.

[0030] 3. The cross-scale thermal response self-healing polyurethane material for industrial and mining environments provided by the present application designs DA covalent bond in the side chain, reducing the influence on the mechanical properties of polyurethane; introduces methyl-substituted furan as a steric hindrance group, which can increase the DA reverse reaction repair threshold to 150℃, which matches the high temperature working condition (80~120℃) of industrial and mining environments; the introduction of methyl helps to maintain the geometric configuration of metal ions and pyridine groups, thereby prolonging the existence time of metal coordination bond, making the end metal coordination repair more durable. If a larger substituent such as phenyl is introduced, it will cause uneven spatial distribution of furan groups, resulting in uneven grafting of maleimide modules, affecting the normal DA reaction, and it is difficult to achieve deep repair under high temperature working conditions. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a comparison chart of constant potential impedance modulus values of each example / contrast example before and after self-healing. DETAILED DESCRIPTION

[0032] The present application will be further described in detail through specific examples.

[0033] Example 1

[0034] S01: Mix glycerol, 5-methylfuran-2-carboxylic acid and anhydrous methyl formamide according to the molar ratio of 1:0.3:165, drop 98% concentrated sulfuric acid into it, the molar ratio of glycerol to H2SO4 in concentrated sulfuric acid is 1:0.04; keep stirring and heat at 80℃ for 6h, column chromatography separation to obtain monomer A;

[0035] S02: Polypropylene glycol, isophorone diisocyanate, monomer A, 1,6-hexanediol, dibutyltin dilaurate were added into anhydrous dimethylformamide, heated to 70°C for 1 h; the temperature was reduced to 30°C, the stirring was maintained and 1 wt% (referring to the mass ratio of ethylene glycol methyl ether to the mixture consisting of polypropylene glycol, isophorone diisocyanate, monomer A, 1,6-hexanediol, dibutyltin dilaurate, anhydrous dimethylformamide) of ethylene glycol methyl ether was slowly added dropwise, and the reaction was continued for 6 h to obtain a single-sided inert end-capped polyurethane prepolymer; wherein the molar ratio of polypropylene glycol, isophorone diisocyanate, monomer A, 1,6-hexanediol, dibutyltin dilaurate to anhydrous dimethylformamide was 1:1.5:0.3:0.2:0.02:140;

[0036] S03: Pyridine acetic acid, N,N'-dicyclohexyl carbodiimide, 4-dimethylamino pyridine were mixed with anhydrous dimethylformamide at a molar ratio of 1:0.02:0.03:15 to obtain a mixed solution; 8 wt% of the mixed solution was added to the single-sided inert end-capped polyurethane prepolymer (wherein 8 wt% refers to the mass ratio of the mixed solution to the single-sided inert end-capped polyurethane prepolymer), and the reaction was carried out at room temperature under nitrogen protection for 15 h to obtain an asymmetric end-capped polyurethane prepolymer;

[0037] S04: 10 wt% of N-(2-hydroxyethyl) maleimide was dissolved in anhydrous dimethylformamide and added dropwise to the above asymmetric end-capped polyurethane prepolymer, and the reaction was carried out at 55°C for 12 h to obtain a thermal response self-repairing polyurethane containing a Diels-Alder structure; 10 wt% refers to the mass ratio of the maleimide derivative to the asymmetric end-capped polyurethane;

[0038] S05: 4 wt% of a metal salt solution (wherein 4 wt% refers to the mass ratio of the metal salt to the single-sided inert end-capped polyurethane prepolymer, and the metal salt was obtained by mixing Zn(Ac)2 and FeCl3 in equimolar amounts) was added dropwise to the above thermal response self-repairing polyurethane containing a Diels-Alder structure to obtain a mixture, which was stirred at room temperature for 8 h, and then precipitated by adding anhydrous ethanol in an amount of 4.5 times the mass of the mixture, and the mixture was allowed to stand for 18 min. The solvent was decanted and removed, and the operation was repeated twice, and the vacuum-dried product was a cross-scale thermal response self-repairing polyurethane material for industrial and mining environments.

[0039] Example 2

[0040] S01: Trimethylolpropane, 5-methylfuran-2-carboxylic acid, and anhydrous methylformamide were mixed at a molar ratio of 1:0.35:155, and 98% concentrated sulfuric acid was added dropwise; the molar ratio of glycerol to H2SO4 in concentrated sulfuric acid was 1:0.04; the stirring was maintained and the reaction was carried out at 80°C under reflux for 6 h; column chromatography was used to separate monomer A;

[0041] S02: Poly (caprolactone) diol, hexamethylene diisocyanate, monomer A, 1,4-butanediol, triethylenediamine were added into anhydrous dimethylformamide, heated to 75°C for 1 h; the temperature was reduced to 30°C, the stirring was maintained and 3wt% of ethylene glycol methyl ether was slowly added dropwise, and the reaction was continued for 6h to obtain a single-sided inert end-capped polyurethane prepolymer; wherein the molar ratio of poly (caprolactone) diol, hexamethylene diisocyanate, monomer A, 1,4-butanediol, triethylenediamine and anhydrous dimethylformamide was 1:1.6:0.4:0.2:0.05:190.

[0042] S03: Pyridine acetic acid, N,N'-dicyclohexyl carbodiimide, 4-dimethylamino pyridine were mixed with anhydrous dimethylformamide in a molar ratio of 1:0.05:0.05:20 to obtain a mixed solution; 10wt% of the mixed solution was added to the single-sided inert end-capped polyurethane prepolymer, and the reaction was carried out at room temperature under nitrogen protection for 24h to obtain an asymmetric end-capped polyurethane prepolymer;

[0043] S04: 15wt% of N-methyl maleimide was dissolved in anhydrous dimethylformamide and added dropwise to the above asymmetric end-capped polyurethane prepolymer, and the reaction was carried out at 50°C for 24h to obtain a thermal response self-repairing polyurethane containing Diels-Alder structure;

[0044] S05: 6wt% of a metal salt solution (the metal salt was prepared by mixing Zn(Ac)2 and FeCl3 in equal molar amounts) was added dropwise to the above thermal response self-repairing polyurethane containing Diels-Alder structure, and the reaction was carried out at room temperature for 12h; after cooling to room temperature, 5 times the mass of anhydrous ethanol was added to induce precipitation, and the precipitation was allowed to stand for 15 min; the solvent was decanted and removed, and the operation was repeated 3 times, and vacuum drying was carried out to obtain a cross-scale thermal response self-repairing polyurethane material for industrial and mining environments.

[0045] Example 3

[0046] S01: Glycerol, 5-methylfuran-2-carboxylic acid and anhydrous methylformamide were mixed in a molar ratio of 1:0.35:165, and 98% concentrated sulfuric acid was added dropwise; the molar ratio of glycerol to H2SO4 in concentrated sulfuric acid was 1:0.04; the stirring was maintained and the heating was carried out at 80°C for 6h; column chromatography was used to separate monomer A;

[0047] S02: polycarbonate diol, isophorone diisocyanate, monomer A, 1,6-hexanediol, dibutyl tin dilaurate were added into dry dimethylformamide, heated to 70°C for 1 h; the temperature was reduced to 30°C, kept stirring and 2wt% of ethylene glycol methyl ether was added dropwise slowly, the reaction was continued for 6h, to obtain a single-sided inert end-capped polyurethane prepolymer; wherein the molar ratio of polycarbonate diol, isophorone diisocyanate, monomer A, 1,6-hexanediol, dibutyl tin dilaurate to dry dimethylformamide was 1 : 1.5 : 0.4 : 0.3 : 0.04 : 150.

[0048] S03: pyridine acetic acid, N,N'-dicyclohexyl carbodiimide, 4-dimethylamino pyridine were mixed with dry dimethylformamide in a molar ratio of 1 : 0.03 : 0.04 : 18 to obtain a mixed solution; 9wt% of the mixed solution was added into the single-sided inert end-capped polyurethane prepolymer, stirred at room temperature for 20h under nitrogen protection to obtain an asymmetric end-capped polyurethane prepolymer;

[0049] S04: 10wt% of N-(2-hydroxyethyl) maleimide was dissolved in dry dimethylformamide and added dropwise into the above asymmetric end-capped polyurethane prepolymer, stirred at 60°C for 20h to obtain a thermal response self-repairing polyurethane containing Diels-Alder structure;

[0050] S05: 5wt% of a metal salt solution (the metal salt was obtained by mixing Zn(Ac)2 and FeCl3 in equimolar amount) was added dropwise into the above thermal response self-repairing polyurethane containing Diels-Alder structure, stirred at room temperature for 8h, after cooling to room temperature, 4 times the mass of the mixture of anhydrous ethanol was added to induce precipitation, and the mixture was allowed to stand for 20 min, the solvent was decanted and removed, the operation was repeated for 3 times, and vacuum drying was performed to obtain a cross-scale thermal response self-repairing polyurethane material for industrial and mining environment.

[0051] Comparative Example 1

[0052] In this comparative example, compared with Example 3, the 5-methyl furan-2-carboxylic acid in step S01 was replaced by furan carboxylic acid (without methyl introduction).

[0053] Comparative Example 2

[0054] In this comparative example, compared with Example 3, the 5-methyl furan-2-carboxylic acid in step S01 was replaced by 1-benzofuran-5-carboxylic acid (a phenyl group was introduced).

[0055] Comparative Example 3

[0056] In this comparative example, compared with Example 3, no functional protection was performed on the hydroxyl groups in the triols, and the specific steps were as follows:

[0057] S01: polycarbonate diol, isophorone diisocyanate, glycerol, 1,6-hexanediol, dibutyltin dilaurate were added into anhydrous dimethylformamide, heated to 70 °C for 1 h; the temperature was reduced to 30 °C, the stirring was maintained and 2 wt% of ethylene glycol methyl ether was slowly added dropwise, the reaction was continued for 6 h to obtain a single-sided inert end-capped polyurethane prepolymer; wherein the molar ratio of polycarbonate diol, isophorone diisocyanate, glycerol, 1,6-hexanediol, dibutyltin dilaurate to anhydrous dimethylformamide was 1:1.5:0.4:0.3:0.04:150.

[0058] S02: pyridine acetic acid, N,N'-dicyclohexyl carbodiimide, 4-dimethylamino pyridine were mixed with anhydrous dimethylformamide in a molar ratio of 1:0.03:0.04:18 to obtain a mixed solution; 9 wt% of the mixed solution was added to the single-sided inert end-capped polyurethane prepolymer, and the reaction was stirred at room temperature under nitrogen protection for 20 h to obtain an asymmetrically end-capped polyurethane prepolymer;

[0059] S03: 5-methyl furan carboxylic acid was added to the above asymmetrically end-capped polyurethane prepolymer in the same amount as in Example 3, 98% concentrated sulfuric acid was added dropwise, and the molar ratio of glycerol in S01 to H2SO4 in concentrated sulfuric acid was 1:0.04; the stirring was maintained and heated at 80 °C for 6 h, then 10 wt% of N-(2-hydroxyethyl) maleimide was dissolved in anhydrous dimethylformamide and added dropwise, and the reaction was stirred at 60 °C for 20 h to obtain a thermal response self-repairing polyurethane containing a Diels-Alder structure;

[0060] S04: 5 wt% of a metal salt solution (the metal salt was obtained by mixing Zn(Ac)2 and FeCl3 in equal molar amounts) was added dropwise to the above thermal response self-repairing polyurethane containing a Diels-Alder structure, and the stirring was continued at room temperature for 8 h; after cooling to room temperature, anhydrous ethanol was added to induce precipitation, the mixture was allowed to stand for 20 min, the solvent was decanted, and the above steps were repeated three times to obtain a cross-scale thermal response self-repairing polyurethane material for industrial and mining environments.

[0061] Comparative Example 4

[0062] In this comparative example, compared with Example 3, the metal-ligand module was designed as a main chain embedded structure, and dihydroxy pyridine was introduced to add a pyridine group to the main chain, and the 1,6-hexanediol chain extender was omitted; twice the amount of ethylene glycol methyl ether was added to obtain a polyurethane prepolymer inertly end-capped on both sides of the main chain, and the specific steps were as follows:

[0063] S01: Glycerol, 5-methylfuran-2-carboxylic acid and anhydrous methyl formamide were mixed in a molar ratio of 1 : 0.35 : 165, 98% concentrated sulfuric acid was added dropwise, the molar ratio of glycerol to H2SO4 in concentrated sulfuric acid was 1 : 0.04; keep stirring, heat at 80°C reflux for 6h, column chromatography separation to obtain monomer A;

[0064] S02: Polycarbonate diol, isophorone diisocyanate, monomer A, 2,3-dihydroxypyridine, dibutyltin dilaurate were added to anhydrous dimethylformamide, heated to 70°C for 1h; the temperature was reduced to 30°C, keep stirring and slowly add 4wt% ethylene glycol methyl ether dropwise, continue to react for 6h to obtain methoxy inert end-capped polyurethane prepolymer; the molar ratio of polycarbonate diol, isophorone diisocyanate, monomer A, 2,3-dihydroxypyridine, dibutyltin dilaurate to anhydrous dimethylformamide was 1 : 1.5 : 0.4 : 0.3 : 0.04 : 150.

[0065] S03: 10wt% N-(2-hydroxyethyl) maleimide was dissolved in anhydrous dimethylformamide and added dropwise to the above inert end-capped polyurethane prepolymer, stirred at 60°C for 20h to obtain a Diels-Alder structure containing thermal response self-repairing polyurethane;

[0066] S04: 5wt% metal salt solution (metal salt is made by mixing Zn(Ac)2 and FeCl3 in equimolar amount) was added dropwise to the above Diels-Alder structure containing thermal response self-repairing polyurethane, stirred at room temperature for 8h, cooled to room temperature, then 4 times the mass of anhydrous ethanol was added to induce precipitation, and the mixture was allowed to stand for 20 min, the solvent was decanted, and the above steps were repeated 3 times, and vacuum drying to obtain a cross-scale thermal response self-repairing polyurethane material for industrial and mining environment.

[0067] Comparative Example 5

[0068] This comparative example omits the metal-ligand module, i.e. omits the S03, S05 steps in Example 3, and adds twice the amount of ethylene glycol methyl ether to obtain a polyurethane prepolymer inertly capped on both sides of the main chain, the specific steps are as follows:

[0069] S01: Glycerol, 5-methylfuran-2-carboxylic acid and anhydrous methyl formamide were mixed in a molar ratio of 1 : 0.35 : 165, 98% concentrated sulfuric acid was added dropwise, the molar ratio of glycerol to H2SO4 in concentrated sulfuric acid was 1 : 0.04; keep stirring, heat at 80°C reflux for 6h, column chromatography separation to obtain monomer A;

[0070] S02: polycarbonate diol, isophorone diisocyanate, monomer A, 1,6-hexanediol, dibutyltin dilaurate were added into anhydrous dimethylformamide, heated to 70°C for 1 h; the temperature was reduced to 30°C, stirring was maintained and 4 wt% of ethylene glycol methyl ether was slowly added dropwise, and the reaction was continued for 6 h to obtain a methoxy inert end-capped polyurethane prepolymer; wherein the molar ratio of polycarbonate diol, isophorone diisocyanate, monomer A, 2,3-dihydroxypyridine, dibutyltin dilaurate to anhydrous dimethylformamide was 1:1.5:0.4:0.3:0.04:150.

[0071] S03: 10 wt% of N-(2-hydroxyethyl)maleimide was dissolved in anhydrous dimethylformamide and added dropwise into the above inert end-capped polyurethane prepolymer, and stirred at 60°C for 20 h. After cooling to room temperature, 4 times the mass of the mixture of anhydrous ethanol was added to induce precipitation, and the precipitate was allowed to stand for 20 min. The solvent was decanted and removed, and the process was repeated 3 times. Vacuum drying was performed to obtain a thermal response self-repairing polyurethane material for industrial and mining environments.

[0072] Comparative Example 6

[0073] The present comparative example omits the DA side chain, i.e. omits the S01, S04 steps in Example 3, and omits monomer A. The specific steps are as follows:

[0074] S01: polycarbonate diol, isophorone diisocyanate, 1,6-hexanediol, dibutyltin dilaurate were added into anhydrous dimethylformamide, heated to 70°C for 1 h; the temperature was reduced to 30°C, stirring was maintained and 2 wt% of ethylene glycol methyl ether was slowly added dropwise, and the reaction was continued for 6 h to obtain a single-sided inert end-capped polyurethane prepolymer; wherein the molar ratio of polycarbonate diol, isophorone diisocyanate, 1,6-hexanediol, dibutyltin dilaurate to anhydrous dimethylformamide was 1:1.5:0.7:0.04:150.

[0075] S02: pyridine acetic acid, N,N'-dicyclohexyl carbodiimide, 4-dimethylamino pyridine and anhydrous dimethylformamide were mixed in a molar ratio of 1:0.03:0.04:18 to obtain a mixed solution; 9 wt% of the mixed solution was added into the single-sided inert end-capped polyurethane prepolymer, and stirred at room temperature for 20 h under nitrogen protection to obtain an asymmetric end-capped polyurethane prepolymer;

[0076] S03: To the above thermal-responsive self-healing polyurethane containing Diels-Alder structure, 5wt% of metal salt solution (metal salt is mixed by equimolar amount of Zn(Ac)2 and FeCl3) is added dropwise, stirred at room temperature for 8h, after cooling to room temperature, 4 times the mass of the mixture of anhydrous ethanol is added to induce precipitation, and the precipitate is allowed to stand for 20 min, the solvent is decanted and removed, and the process is repeated 3 times, and vacuum drying is performed to obtain a cross-scale thermal-responsive self-healing polyurethane material for industrial and mining environments.

[0077] The present application uses the bending method to manufacture micro-cracks on the steel sample plate coated with self-healing polyurethane according to ISO 1519, and bends 180° on a mandrel with a diameter of 20 mm, randomly selects a 1cm 2 region as a reference.

[0078] Verification condition 1: The pretreated sample plate is stored at 100℃ for 2h, and the number of cracks in the reference area is recorded; the peel strength of the coating in the reference area before and after verification is recorded according to ISO 8510-2.

[0079] Verification condition 2: Use 5wt% FeCl3 solution as simulated ore slurry, immerse the pretreated sample plate in the simulated ore slurry, heat to 100℃ and store for 2h, record the number of cracks in the reference area; record the peel strength of the coating in the reference area before and after verification according to ISO 8510-2.

[0080] The present application calculates the three times crack recovery rate and peel strength recovery rate, and takes the average value as the performance reference, the crack healing rate = (1- the number of cracks after verification / the number of cracks before verification) x 100%; the peel strength recovery rate = (the peel strength after verification / the peel strength before verification) x 100%.

[0081] The present application tests the constant potential impedance as the self-repairing performance reference of the polyurethane coating under the ore slurry condition, and records the impedance modulus value of each example before and after verification condition 2, wherein the constant potential refers to the open circuit potential (OCP) of electrochemical test.

[0082] Table 1 Performance comparison of examples and comparative examples

[0083]

[0084] Comparative example 1 does not introduce methyl to improve steric hindrance in the DA module, and the reversible temperature of the DA module is low, i.e. the temperature required to trigger self-repairing is low (50~70℃), and compared with the examples, although comparative example 1 has certain self-repairing effect, its low reversible temperature is difficult to meet the high temperature demand under the ore slurry conveying condition.

[0085] The DA module of Comparative Example 2 replaces the methyl group with a phenyl group, the furan group is unevenly distributed in space, the maleimide module is unevenly grafted, and the activation energy of the DA module is greater, resulting in a decrease in the rate of the DA forward addition reaction, and the DA module needs a higher temperature to trigger the reverse reaction, and the temperature in the ore slurry working condition (80-120°C) is difficult to trigger the repair process of the DA module; the introduction of the phenyl group increases the local rigidity of the segment, and the recombination rate of the metal-ligand bond in the repair process decreases, the dynamic reversibility and stability of the metal coordination module decrease, and finally the synergistic repair efficiency of the coating decreases, so the repair capacity of Comparative Example 2 in the simulated ore slurry at 100°C is significantly lower than that of the examples.

[0086] Comparative Example 3 does not protect the hydroxyl group, the main chain is excessively cross-linked during the synthesis of the polyurethane, and a large number of DA side chain sites are occupied, making it difficult to introduce the DA module, and the single-sided end metal coordination module has a smaller influence, so the self-repairing performance of the material is greatly reduced but not failed.

[0087] Comparative Example 4 introduces more metal coordination modules into the main chain, and too many metal coordination bonds hinder the approach and rearrangement of the DA reaction segments at the molecular scale, resulting in a decrease in the reversibility of the DA reaction and a decrease in the repair capacity of the thermally triggered DA module, but the more metal coordination bonds make the material have a higher repair effect than Comparative Example 3.

[0088] Comparative Example 5 only retains the DA module, and the absence of the metal coordination module makes it difficult to achieve the effect of repairing micro surface / interface damage in the examples, so its crack healing rate is much lower than that of the examples.

[0089] Comparative Example 6 only retains the metal coordination module, and compared with Comparative Example 3, the polyurethane segment movement is not restricted by the excessive cross-linking of the main chain after the introduction of the metal coordination module, and the metal coordination self-repairing capacity is complete, so the self-repairing capacity is slightly higher than that of Comparative Example 3.

[0090] The Fe 3+ in the examples in verification condition 2 is introduced into the coating after the coating is damaged, and the repair capacity of the coating after the damage is higher than that in verification condition 1, which proves that the cross-scale self-repairing polyurethane designed in the application can convert the destructive Fe 3+ in the ore slurry into a repair medium (pyridine-Fe 3+ coordination bond).

[0091] Figure 1 In the constant potential impedance test, the impedance modulus is derived from the inherent impedance of the polyurethane, and before repair, the samples of each example are flat and have no cracks, so each group has a similar impedance modulus, and after repair, the impedance modulus of each comparative example is significantly lower than that of the examples, which directly reflects the repair effect of each example and comparative example, and has a similar trend to the data in Table 1.

[0092] The above merely describes preferred embodiments of the present application, and is not intended to limit the present application in any form. Although the present application has been disclosed with the preferred embodiments as above, it is not intended to limit the present application. Any person skilled in the art, without departing from the technical solution of the present application, can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application, as long as it does not deviate from the technical solution of the present application, still belongs to the scope of the technical solution of the present application.

Claims

1. A cross-scale thermally responsive self-healing polyurethane material, characterized in that, The polyurethane main chain is synthesized using isocyanate and polyol, one end of the polyurethane main chain is a coordination bond formed by a pyridine group and a metal salt, and the other end is a methoxy inert end cap; the furan-maleimide module based on the Diels-Alder reaction is a side chain hanging structure, and a methyl-substituted furan is introduced as a steric hindering group; The preparation method of the cross-scale thermal response self-repairing polyurethane material comprises the following steps: S01: ternary alcohol, monosubstituted furan carboxylic acid and anhydrous dimethylformamide are mixed in a molar ratio of 1 :(0.3-0.35):(140-180), concentrated sulfuric acid is added dropwise, the molar ratio of ternary alcohol to concentrated sulfuric acid is 1 :(0.03-0.06), stirring is maintained, 75-85 DEG C reflux heating is carried out for 6-8 hours, and column chromatography separation is carried out to obtain monomer A; the monosubstituted furan carboxylic acid is one or both of 3-methyl furan-2-carboxylic acid and 5-methyl furan-2-carboxylic acid; S02: linear dihydric alcohol, isocyanate, monomer A, chain extender, catalyst are added to anhydrous dimethylformamide, heated to 70-75 DEG C and reacted for 1-2 hours; the temperature is reduced to below 40 DEG C, stirring is maintained, and 1-3 wt% of ethylene glycol methyl ether is slowly added, and the reaction is continuously carried out for 6-8 hours to obtain a single-side inert end-capped polyurethane prepolymer; S03: pyridine acetic acid, N,N'-dicyclohexyl carbodiimide, 4-dimethylamino pyridine and anhydrous dimethylformamide are mixed in a molar ratio of 1 :(0.01-0.05):(0.01-0.05):(10-20) to obtain a mixed solution; 8-10 wt% of the mixed solution is added to the single-side inert end-capped polyurethane prepolymer, and stirring reaction is carried out at room temperature for 15-24 hours under nitrogen protection to obtain an asymmetric end-capped polyurethane prepolymer; S04: 10-15 wt% of maleimide derivative is dissolved in anhydrous dimethylformamide and added dropwise to the asymmetric end-capped polyurethane prepolymer, and stirring reaction is carried out at 50-60 DEG C for 12-24 hours to obtain a thermal response self-repairing polyurethane containing Diels-Alder structure; S05: 3-6 wt% of a metal salt solution is added dropwise to the thermal response self-repairing polyurethane containing Diels-Alder structure, and stirring is carried out at room temperature for 8-12 hours; after cooling to room temperature, 4-6 times the mass of the mixture of anhydrous ethanol is added to induce precipitation, the precipitation is allowed to stand for 10-20 minutes, the solvent is decanted and removed, the operation is repeated 2-3 times, and vacuum drying is carried out to obtain a cross-scale thermal response self-repairing polyurethane material for industrial and mining environments.

2. The method for preparing a multi-scale thermally responsive self-healing polyurethane material according to claim 1, characterized in that, The molar ratio of the linear dihydric alcohol, isocyanate, monomer A, chain extender, catalyst and anhydrous dimethylformamide is 1 :(1.4-1.7):(0.3-0.5):(0.2-0.4):(0.01-0.05):(140-190).

3. The method for preparing a multi-scale thermally responsive self-healing polyurethane material according to claim 1, characterized in that, The ternary alcohol is one or more of trimethylol ethane, trimethylol propane, trimethylol hexane, 1,2,4-butanetriol and 1,2,6-hexanetriol; and the linear dihydric alcohol is one or more of polypropylene glycol, polycaprolactone diol and polycarbonate diol.

4. The method for preparing a multi-scale thermally responsive self-healing polyurethane material according to claim 1, characterized in that, The isocyanate is one or more of isophorone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, p-phenylene diisocyanate, L-lysine diisocyanate; the chain extender is one or more of 1,4-butanediol, 1,6-hexanediol, diethylene glycol, p-xylylene glycol and cyclohexanedimethanol; the catalyst is one or more of dibutyl tin dilaurate, stannous octoate, lead octoate, dibutyl tin oxide and triethylenediamine.

5. The method for preparing a multi-scale thermally responsive self-healing polyurethane material according to claim 1, characterized in that, The maleimide derivative is one or more of N-(2-hydroxyethyl)maleimide, N-methylmaleimide, N-ethylmaleimide, N-phenylmaleimide, N-benzylmaleimide and 4,4'-bismaleimidodiphenylmethane.

6. The method for preparing a multi-scale thermally responsive self-healing polyurethane material according to claim 1, characterized in that, The metal salt is one or more of Fe 3+ , Zn 2+ , Cu 2+ , Co 2+ , Ag + and Ac - , Cl - , NO3 - .

7. The method for preparing a multi-scale thermally responsive self-healing polyurethane material according to claim 6, characterized in that, The metal salt is formed by mixing Zn(Ac)2 and FeCl3 in equimolar amounts.

8. The cross-scale thermal response self-repairing polyurethane material according to claim 1 is applied to polymer protection and repair under high-temperature and high-ionic-concentration ore pulp working conditions.

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