Dual self-repairing polyurethane coating and preparation method thereof

Abstract

The invention discloses a double self-repairing polyurethane coating containing a metal coordination bond and a Diels-Alder bond. The double self-repairing polyurethane coating is prepared from the following raw materials: polyol, an isocyanate derivative, a chain extender containing the metal coordination bond, metal salt and a binary chain extender containing the Diels-Alder bond. According to the double self-repairing polyurethane coating containing the metal coordination bond and the Diels-Alder bond, the repairing efficiency and the mechanical and chemical resistance can be improved.

Description

Technical Field

[0001] The invention relates to the field of self-repairing polyurethane, and in particular to a dual self-repairing polyurethane coating of Diels-Alder bonds and metal coordination bonds and a preparation method thereof. Background Art

[0002] When a polyurethane coating is damaged, the substrate will degrade due to corrosion or other destructive factors. Therefore, a coating that can efficiently self-repair after damage can extend the service life of the coating and improve the protection of the substrate.

[0003] Self-healing coatings can be prepared by adding microcapsule dispersions to polymers and have been used in the field of architectural coatings, but coatings containing microcapsules cannot repair repeated damage to the same area. In recent years, the focus has gradually shifted to intrinsic self-healing, that is, using dynamic covalent bonds (such as Diels-Alder reactions, disulfide bonds) or non-covalent interactions (such as hydrogen bonds, metal coordination interactions) for repeatable self-healing.

[0004] Patent CN108912371B uses polyisocyanate, polyol, furfurylamine, bismaleimide and graphene oxide as raw materials, and uses reversible DA reaction to obtain a polyurethane coating with both hydrophobicity and self-healing properties. Patent CN109337087B uses the coordination effect of ferrous ions and pyridine chain extenders to prepare elastomers with self-healing properties. Patent CN115819775B uses the coordination effect of monovalent silver ions with dicarboxyl and urea monomers to prepare polysiloxane elastomers with antibacterial self-healing properties. Patent CN115403934A uses reversible disulfide bonds and reversible coumarin cycloaddition to prepare a self-healing bio-based thermal conductive silicone elastomer. Patent CN113372529B uses three dynamic bonds: aromatic disulfide bonds, metal coordination bonds and hydrogen bonds to prepare polyphosphazene self-healing elastomers. Patent CN111471154B utilizes DA reaction and coumarin reversible cycloaddition to prepare a light or heat-induced self-healing elastomer.

[0005] At present, the research on self-repair is still mainly based on a single self-repair method, or combining hydrogen bonds with disulfide bonds or hydrogen bonds with metal coordination. The dual self-repair method combining metal coordination with DA reaction has not been reported. In addition, the self-repair effect brought by metal coordination is often used in the field of elastomers, but has not been reported in the field of coatings. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention designs and synthesizes a dual self-repairing structure containing metal coordination bonds and DA bonds to prepare a self-repairing coating with high self-repairing efficiency, high mechanical properties and high chemical resistance.

[0007] The technical solution of the present invention is as follows:

[0008] A dual self-repairing polyurethane coating containing metal coordination bonds and Diels-Alder bonds, comprising the following raw materials in parts by weight:

[0009]

[0010] The invention forms a double self-repairing polyurethane coating containing metal coordination and Diels-Alder bond through addition polymerization between raw materials.

[0011] As a preferred embodiment of the present invention, the polyols are selected from a mixture of one or more of hydroxy acrylic resins, polyester polyols, and polycarbonate polyols;

[0012] As a preferred embodiment of the present invention, the hydroxyl acrylic resin is selected from hydroxyl acrylic resins having a hydroxyl content of 2.5% to 4.5%, preferably ACR6780 and AC1100B;

[0013] The polyester polyol is selected from polycaprolactone and polyhexamethylene adipate with a molecular weight of 500 to 2000, preferably PCL210 and PCL220N;

[0014] The polycarbonate polyol is selected from polycarbonate diols with a molecular weight of 500 to 2000, preferably T5650J, T5651, and T5652.

[0015] As a preferred embodiment of the present invention, the isocyanate derivative is selected from HDI trimer, IPDI trimer, PDI trimer, H6XDI trimer, preferably at least one of HT-100, HT-600, HT-790, and IT-170B.

[0016] As a preferred embodiment of the present invention, the chain extender B coordinated with the metal ion is selected from at least one of pyrimidine type, thiazole type and pyridine type;

[0017] Wherein, the pyrimidine type is selected from 2,4-diaminopyrimidine, 2,5-diaminopyrimidine, 4,5-diaminopyrimidine, 4,6-diaminopyrimidine, 4-amino-2-mercaptopyrimidine, 2,4-dimercaptopyrimidine;

[0018] The thiazole type is selected from 2,4-diaminothiazole and 2-aminothiazol-4-ol;

[0019] The pyridine type is selected from 2,3-dihydroxypyridine, 2,4-dihydroxypyridine, 2,6-dihydroxypyridine, 3,4-dihydroxypyridine, 2-amino-3-hydroxypyridine, 2-amino-4-hydroxypyridine, 2-amino-6-hydroxypyridine, 3-amino-2-hydroxypyridine, 3-amino-4-hydroxypyridine, 3-amino-5-hydroxypyridine, 4-amino-2-hydroxypyridine, 4-amino-3-hydroxypyridine, 5-amino-2-hydroxypyridine, 2,3-diaminopyridine, 2,4-diaminopyridine, 2,5-diaminopyridine, 2,6-diaminopyridine, 3,4-diaminopyridine, and 2-aminopyrimidine-5-methanol.

[0020] As a preferred embodiment of the present invention, the metal salt, whose cation is a metal cation with a valence of +2 to +6, is selected from the group IIIB, IVB, VB, VIB, VIIB, VIII, IB, IIB elements of the fourth or fifth period of the periodic table, and at least one metal cation of the lanthanide metal elements, preferably ferrous ion, zinc ion, calcium ion, nickel ion; the anion is a counter anion with a valence of -1 to -3, including one or more of chlorine, iodine, bromine, fluorine, sulfuric acid, trifluoroacetic acid, nitric acid, phosphoric acid, phosphorous acid, acetic acid, silicic acid, octanoic acid, isooctanoic acid, cyclohexane acid, citric acid, methanesulfonic acid, acetylacetone copper, bis(trifluoromethanesulfonic acid)imide, trifluoromethanesulfonic acid, tetrafluoroboric acid, hexafluorosilicic acid, hexafluorophosphoric acid, ammonium sulfate hexahydrate, perchloric acid, ethylenediaminetetraacetic acid, acrylic acid or methacrylate.

[0021] As a preferred embodiment of the present invention, the binary chain extender A containing a Diels-Alder bond has the following structure:

[0022]

[0023] It can be prepared according to the following steps:

[0024] Equal amounts of N-(2-hydroxyethyl)maleimide and 2-thiophene methanol were stirred and reacted in toluene at 80°C for 24 hours, and the obtained precipitate was crushed, filtered, washed with ether, and dried to obtain a diol A containing a Diels-Alder bond;

[0025]

[0026] According to the present invention, the method for preparing the dual self-healing polyurethane coating containing metal coordination bonds and Diels-Alder bonds comprises the following steps:

[0027] (1) The isocyanate derivative reacts with the chain extender A to form a polyurethane prepolymer I;

[0028] (2) reacting the polyurethane prepolymer I with the chain extender B and the metal salt to generate the polyurethane prepolymer II;

[0029] (3) The polyurethane prepolymer II is mixed with a solvent, a polyol, and a catalyst to generate a dual self-healing polyurethane coating containing metal coordination bonds and Diels-Alder bonds.

[0030] As a preferred embodiment of the present invention, the solvent in step (3) is one or more mixed solvents selected from ethyl acetate, butyl acetate, xylene, trimethylbenzene, propylene glycol methyl ether acetate, propylene glycol methyl ether propionate, cyclohexanone, dimethyl carbonate, and sec-butyl acetate;

[0031] Preferably, the amount of solvent is such that the solid content of the coating is 40-80%, preferably 50-70%.

[0032] As a preferred embodiment of the present invention, the catalyst described in step (3) is one of dibutyltin dilaurate, dimethyltin diacetate, stannous octoate, lead octoate, bismuth isooctanoate, and pentafluorophenyl phosphate.

[0033] As a preferred embodiment of the present invention, the amount of catalyst added in step (3) is 10-1000ppm based on the mass of the coating.

[0034] Principle of the present invention:

[0035] The present invention combines the metal coordination self-repairing with the Diels-Alder bond self-repairing to synthesize a novel polyurethane coating containing a dual self-repairing structure of metal coordination and Diels-Alder bond, thereby improving the repair efficiency and mechanical and chemical resistance properties.

[0036] The beneficial effects of the present invention are as follows:

[0037] 1. The dual self-repairing polyurethane coating of the present invention combines metal coordination and Diels-Alder bond self-repair at the same time, and can achieve rapid repair under high temperature conditions with high repair efficiency.

[0038] 2. The double self-repairing polyurethane coating of the present invention has high strength, and the solvent wiping resistance after repair can reach more than 200 times, and the impact resistance can reach 100kgcm. DETAILED DESCRIPTION

[0039] The present invention is further described below by means of specific examples. The examples described in the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

[0040] The present invention prepares a two-component polyurethane coating tinplate sample according to the method of GB / T 1727-1992;

[0041] The present invention measures the impact resistance of the paint film of a two-component polyurethane coating based on the method of GB / T 1732-79 (88);

[0042] The present invention measures the solvent wiping resistance of a two-component polyurethane coating based on the method of GB / T 23989-2009;

[0043] The present invention measures the self-repairing performance of a two-component polyurethane coating based on the following method: a #0000 steel wire brush with a load of 500 g is slid back and forth on the surface of the paint film 5 times, the initial scratch damage area is S1, and then after heat treatment at 100°C for 2 hours, the scratch damage area after treatment is measured S2, and the self-repairing efficiency is calculated according to the formula 100%×(S1-S2) / S1;

[0044] The main raw materials used in the examples of the present invention are from the following sources. Other raw materials are common commercially available unless otherwise specified:

[0045] HT-100, Wanhua Chemical Group Co., Ltd.;

[0046] HT-600, Wanhua Chemical Group Co., Ltd.;

[0047] HT-790, Wanhua Chemical Group Co., Ltd.;

[0048] IT-170B, Wanhua Chemical Group Co., Ltd.;

[0049] ACR6780, Foshan Gaoming Tongde Chemical Co., Ltd.;

[0050] AC1100B, Foshan Gaoming Tongde Chemical Co., Ltd.;

[0051] T5651, Asahi Kasei Corporation, Japan.

[0052] Example 1

[0053] Preparation of chain extender A: N-(2-hydroxyethyl) maleimide (35 g, 248 mmol) and 2-thiophene methanol (28.31 g, 248 mmol) were stirred in 120 mL toluene at 80 ° C for 24 h, the obtained precipitate was crushed, filtered, washed with 50 mL of ether, and dried to obtain the product containing Diels-Alder bond diol. Nuclear magnetic characterization: 1H NMR (CDCl3, 400 MHz): δ5.78 (d, 2H), 4.64 (d, 1H), 3.79 (d, 1H), 3.61-3.67 (m, 6H), 3.54 (d, 1H), 3.06 (s, 2H);

[0054] Example 2

[0055] 50g HT-100 and 10g chain extender A were stirred and reacted at 70°C for 3h under nitrogen atmosphere to generate polyurethane prepolymer Ⅰ-a;

[0056] The polyurethane prepolymer Ⅰ-a was reacted with 6 g of 2,4-diaminopyrimidine and 5.53 g of ferrous chloride under a nitrogen atmosphere at 60°C for 4 h to generate a polyurethane prepolymer Ⅱ-a;

[0057] 49.34 g of polyurethane prepolymer II-a was mixed with 45.57 g of solvent (butyl acetate / xylene = 1 / 1), 25 g of polycarbonate T5651, and dibutyltin dilaurate (50 ppm) to generate a dual self-healing polyurethane coating containing metal coordination bonds and Diels-Alder bonds.

[0058] Example 3

[0059] 50g HT-600 and 5g chain extender A were stirred and reacted at 70°C for 3h under nitrogen atmosphere to generate polyurethane prepolymer Ⅰ-b;

[0060] The polyurethane prepolymer Ⅰ-b was reacted with 4 g of 2,4-dihydroxypyridine and 5.28 g of zinc acetate under a nitrogen atmosphere at 60°C for 3 h with stirring to generate a polyurethane prepolymer Ⅱ-b;

[0061] 40.6 g of polyurethane prepolymer II-b was mixed with 110.915 g of solvent (butyl acetate / xylene = 1 / 1), 100 g of hydroxypropyl resin AC1100B, and dibutyltin dilaurate (50 ppm) to generate a dual self-healing polyurethane coating containing metal coordination bonds and Diels-Alder bonds.

[0062] Example 4

[0063] 50g IT-170B and 2g chain extender A were stirred and reacted at 70°C for 3h under nitrogen atmosphere to generate polyurethane prepolymer Ⅰ-c;

[0064] The polyurethane prepolymer Ⅰ-c was reacted with 2 g of 2,4-diaminothiazole and 4.48 g of zinc cyclohexane under a nitrogen atmosphere at 60°C for 4 h to generate a polyurethane prepolymer Ⅱ-c;

[0065] 30.78 g of polyurethane prepolymer II-c was mixed with 23.68 g of solvent (butyl acetate / xylene = 1 / 1), 25 g of hydroxypropyl resin ACR6780, and bismuth isooctanoate (100 ppm) to generate a dual self-healing polyurethane coating containing metal coordination bonds and Diels-Alder bonds.

[0066] Comparative Example 1

[0067] 63 g of HT-100 was mixed with 135 g of solvent (butyl acetate / xylene=1 / 1), 165 g of polycarbonate T5651, and dibutyltin dilaurate (50 ppm) to form a polyurethane coating.

[0068] Comparative Example 2

[0069] 20.11 g of HT-600 was mixed with 80.17 g of butyl acetate / xylene = 1 / 1, 100 g of hydroxypropyl resin AC1100B, and a drying agent dibutyltin dilaurate (50 ppm) to produce a polyurethane coating.

[0070] Comparative Example 3

[0071] Referring to Example 3 of CN105949422B, prepare diol C containing Diels-Alder bonds.

[0072] Compared with Example 4, the difference is that the chain extender A is replaced by an equal mass of the diol C containing a Diels-Alder bond.

[0073]

Application example 1-6

[0074] The coating properties of Examples 2-4 and Comparative Examples 1-3 on tinplate were tested, including butanone wiping resistance, impact resistance (positive and negative impact) and self-repairing efficiency. The test results are shown in Table 1.

[0075] Table 1. Paint film performance test

[0076]

[0077] From the performance test in Table 1, we can see that:

[0078] The dual self-repairing polyurethane coating containing metal coordination bonds and Diels-Alder bonds of the present invention has high repair efficiency and good mechanical and chemical resistance properties.

[0079] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A dual self-healing polyurethane coating containing metal coordination bonds and Diels-Alder bonds, characterized in that: The invention comprises the following raw materials in parts by weight:

2. The polyurethane coating according to claim 1, characterized in that The polyols are selected from a mixture of one or more of hydroxy acrylic resins, polyester polyols, and polycarbonate polyols; Preferably, the hydroxy acrylic resin is selected from hydroxy acrylic resins having a hydroxy content of 2.5% to 4.5%, preferably ACR6780 and AC1100B; Preferably, the polyester polyol is selected from polycaprolactone and polyhexamethylene adipate with a molecular weight of 500 to 2000, preferably PCL210 and PCL220N; Preferably, the polycarbonate polyol is selected from polycarbonate diols with a molecular weight of 500 to 2000, preferably T5650J, T5651, and T5652.

3. The polyurethane coating according to claim 1, characterized in that The isocyanate derivative is selected from HDI trimer, IPDI trimer, PDI trimer, H6XDI trimer, and more preferably at least one of HT-100, HT-600, HT-790, and IT-170B.

4. The polyurethane coating according to claim 1, characterized in that The chain extender B coordinated with the metal ion is selected from at least one of pyrimidine type, thiazole type and pyridine type; Preferably, the pyrimidine type is selected from 2,4-diaminopyrimidine, 2,5-diaminopyrimidine, 4,5-diaminopyrimidine, 4,6-diaminopyrimidine, 4-amino-2-mercaptopyrimidine, 2,4-dimercaptopyrimidine; Preferably, the thiazole type is selected from 2,4-diaminothiazole and 2-aminothiazol-4-ol; Preferably, the pyridine type is selected from 2,3-dihydroxypyridine, 2,4-dihydroxypyridine, 2,6-dihydroxypyridine, 3,4-dihydroxypyridine, 2-amino-3-hydroxypyridine, 2-amino-4-hydroxypyridine, 2-amino-6-hydroxypyridine, 3-amino-2-hydroxypyridine, 3-amino-4-hydroxypyridine, 3-amino-5-hydroxypyridine, 4-amino-2-hydroxypyridine, 4-amino-3-hydroxypyridine, 5-amino-2-hydroxypyridine, 2,3-diaminopyridine, 2,4-diaminopyridine, 2,5-diaminopyridine, 2,6-diaminopyridine, 3,4-diaminopyridine, and 2-aminopyrimidine-5-methanol.

5. The polyurethane coating according to claim 1, characterized in that The metal salt has a cation with a valence of +2 to +6, selected from at least one metal cation of group IIIB, IVB, VB, VIB, VIIB, VIII, IB, and IIB elements of the fourth or fifth period of the periodic table, and lanthanide metal elements, preferably ferrous ion, zinc ion, calcium ion, and nickel ion; the anion is a counter anion with a valence of -1 to -3, including one or more of chlorine, iodine, bromine, fluorine, sulfuric acid, trifluoroacetic acid, nitric acid, phosphoric acid, phosphorous acid, acetic acid, silicic acid, octanoic acid, isooctanoic acid, cyclohexane acid, citric acid, methanesulfonic acid, acetylacetone copper, bis(trifluoromethanesulfonic acid)imide, trifluoromethanesulfonic acid, tetrafluoroboric acid, hexafluorosilicic acid, hexafluorophosphoric acid, ammonium sulfate hexahydrate, perchloric acid, ethylenediaminetetraacetic acid, acrylic acid, or methacrylate.

6. The polyurethane coating according to claim 1, characterized in that The binary chain extender A containing Diels-Alder bonds has the following structure:

7. The method for preparing a polyurethane coating according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) The isocyanate derivative reacts with the chain extender A to form a polyurethane prepolymer I; (2) reacting the polyurethane prepolymer I with the chain extender B and the metal salt to generate the polyurethane prepolymer II; (3) The polyurethane prepolymer II is mixed with a solvent, a polyol, and a catalyst to generate a dual self-healing polyurethane coating containing metal coordination bonds and Diels-Alder bonds.

8. The preparation method according to claim 7, characterized in that: The solvent in step (3) is one or more of ethyl acetate, butyl acetate, xylene, trimethylbenzene, propylene glycol methyl ether acetate, propylene glycol methyl ether propionate, cyclohexanone, dimethyl carbonate, and sec-butyl acetate.

9. The preparation method according to claim 7, characterized in that: The catalyst described in step (3) is at least one of dibutyltin dilaurate, dimethyltin diacetate, stannous octoate, lead octoate, bismuth isooctanoate, and pentafluorophenyl phosphate.

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