阅读说明：本技术 一种光/热协同修复型水性聚氨酯涂层材料及其制备方法 (Light/heat synergistic repair type waterborne polyurethane coating material and preparation method thereof ) 是由 程新峰 李君君 李奇洋 秦佳乐 桂源 李政隆 郭戈 刘光印 于 2020-04-14 设计创作，主要内容包括：本发明公开了一种光/热协同修复型水性聚氨酯涂层材料的制备方法,将亲水性扩链剂、马来酰亚胺封端剂引入到聚氨酯中得到聚氨酯预聚体,进而加入含二硫键的双呋喃环扩链剂,中和、乳化得到改性的水性聚氨酯乳液,即可；及依该方法得到的产品。该方法简单,绿色环保,实用性强,制得材料具有优异力学性能和自修复功能,材料裂隙通过加热或紫外光照即可实现高效自我修复,可延长材料的使用寿命,具有良好的应用前景。(The invention discloses a preparation method of a light/heat synergistic repair type waterborne polyurethane coating material, which comprises the steps of introducing a hydrophilic chain extender and a maleimide end-capping reagent into polyurethane to obtain a polyurethane prepolymer, further adding a disulfide bond-containing difuran ring chain extender, and neutralizing and emulsifying to obtain a modified waterborne polyurethane emulsion; and the product obtained by the method. The method is simple, environment-friendly and strong in practicability, the prepared material has excellent mechanical properties and a self-repairing function, the material crack can be efficiently self-repaired by heating or ultraviolet irradiation, the service life of the material can be prolonged, and the method has a good application prospect.)

1. A preparation method of a light/heat synergistic repair type waterborne polyurethane coating material is characterized in that a hydrophilic chain extender and a maleimide end-capping reagent are introduced into polyurethane to obtain a polyurethane prepolymer, and then a disulfide bond-containing difuran ring chain extender is added to neutralize and emulsify to obtain a modified waterborne polyurethane emulsion.

2. The preparation method of the light/heat synergistic repair type waterborne polyurethane coating material as claimed in claim 1, wherein the hydrophilic chain extender is a micromolecular diol containing hydrophilic carboxyl, and the polyurethane is a prepolymer of diisocyanate and polymer diol.

3. The preparation method of the light/heat synergistic repair type aqueous polyurethane coating material according to claim 2, characterized by comprising the following steps:

(1) mixing 10-20 parts by weight of polymer diol which is heated, dried and dewatered, and 4.15-7.15 parts by weight of diisocyanate, stirring, adding 0.0076-0.087 part by weight of catalyst, and carrying out prepolymerization at 60-100 ℃ for 2-3 h in an inert atmosphere to obtain a polyurethane prepolymer I;

(2) carrying out further catalytic reaction on the polyurethane prepolymer I obtained in the step (1), 0.68-1.87 parts of hydrophilic chain extender and 0.92-4.36 parts of maleimide-terminated end-capping agent at 60-120 ℃ in an inert atmosphere for 2-8 h to obtain a maleimide-terminated polyurethane prepolymer II;

(3) diluting the polyurethane prepolymer II obtained in the step (2) with a diluent, adding 0.78-4.18 parts of a disulfide bond-containing bis-furan ring chain extender, carrying out secondary chain extension reaction for 2-6 hours at 60-90 ℃ in an inert atmosphere to obtain modified polyurethane, cooling to 30-40 ℃, adding a neutralizing agent for neutralization reaction, adding deionized water for dispersion and emulsification, and removing the diluent under reduced pressure to obtain a modified aqueous polyurethane emulsion.

4. The preparation method of the light/heat synergistic repairing type waterborne polyurethane coating material as claimed in claim 3, wherein in the step (1), the temperature for heating, drying and water removal is 80-120 ℃, the time is 2-3 h, and the vacuum degree is less than 1 kPa;

the polymer diol comprises one or more of polyethylene glycol, polypropylene glycol, polytetrahydrofuran diol, polycarbonate diol, poly adipic acid-1, 4-butanediol diol, polybutylene terephthalate, polycaprolactone diol and polydimethylsiloxane diol;

the diisocyanate comprises one or more of isophorone diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, 1, 4-cyclohexane diisocyanate and dicyclohexylmethane-4, 4' -diisocyanate;

the catalyst comprises one or two of dibutyltin dilaurate, tetramethylbutanediamine, triethylenediamine and stannous octoate.

5. The preparation method of the light/heat synergistic repair type aqueous polyurethane coating material according to claim 3, wherein in the step (2), the hydrophilic small molecule chain extender comprises one or two of dimethylolpropionic acid and dimethylolbutyric acid;

the maleimide-based end-capping reagent comprises one or two of N-hydroxyethyl maleimide, N-aminoethyl maleimide, 3-maleimide propionic acid and 4-maleimide butyric acid.

6. The preparation method of the light/heat synergistic repairing type aqueous polyurethane coating material according to claim 3, wherein in the step (3), the diluent comprises one or more of acetone, butanone and tetrahydrofuran;

the disulfide bond-containing difuranic ring chain extender is difurfuryl disulfide which is an additive for food;

the neutralizing agent comprises one or more of triethylamine, tripropylamine, sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium acetate, sodium pyrophosphate, sodium carbonate, ammonia water, diethanolamine and triethanolamine.

7. The preparation method of the light/heat synergistic repairing type waterborne polyurethane coating material as claimed in claim 3, wherein the inert atmosphere comprises one of nitrogen and argon.

8. An aqueous polyurethane coating material obtainable by the process according to any one of claims 1 to 7.

Technical Field

The invention belongs to the technical field of high polymer materials, and particularly relates to a light/heat synergistic repair type waterborne polyurethane coating material and a preparation method thereof.

Background

In recent years, energy saving and emission reduction and environmental protection have become the focus of global attention. Because the traditional solvent-based paint is easy to volatilize and has a large smell, air pollution is easy to cause, and the volatilized solvent has high toxicity and is gradually limited to use. As a typical representative of energy-saving and environment-friendly coatings, water-based coatings are widely applied due to the fact that the water-based coatings have no solvent or contain a small amount of solvent, no pollution, no volatilization and high environmental protection and economic benefits (Advanced Functional Materials 2017,27, 1604261). The waterborne polyurethane coating has the advantages of excellent mechanical property, good weather resistance, chemical corrosion resistance, high temperature resistance, wear resistance and the like, is safe to use and free of pollution, and is widely applied to the fields of public infrastructure, furniture, automobiles, adhesives, paper, electronics and the like (Progress in Organic Coatings 2018,121, 73-79; European Polymer Journal 2019,112, 636-. However, when the waterborne polyurethane is used as a protective coating material, the performance is reduced and the service life is influenced due to the fact that the waterborne polyurethane is difficult to avoid being damaged by various machines. Therefore, in order to comply with the green environmental protection concept, the development of the waterborne polyurethane protective coating material with the self-repairing property has become a necessary choice for the industry development (ACS Omega2019,4, 1703-.

At present, a great deal of research reports about self-repairing type waterborne polyurethane coatings exist at home and abroad, and the self-repairing type waterborne polyurethane coatings are mainly divided into two types of external self-repairing and intrinsic self-repairing. Wherein, the exogenous self-repairing (such as microcapsule and micro-vascular method) has the problem that the material loses the self-repairing capability after the repairing agent is consumed. And the intrinsic self-repairing type waterborne polyurethane material capable of realizing multiple repairing functions is paid much attention by researchers. The self-repairing material has a reversible covalent bond or non-covalent bond chemical structure, can initiate the breakage and recombination of an internal reversible structure under external stimulation (light, heat, pH and the like), and drives local molecular chains to flow, thereby achieving the effect of repairing microscopic molecules and macroscopic damage. Reversible structures commonly used in self-repairing waterborne polyurethanes include reversible covalent bonds (e.g., Diels-Alder bonds, S-S bonds, imine bonds, etc.), hydrogen bonds, pi-pi stacking or coordination, etc., which theoretically allow for unlimited repair possibilities of damaged materials (Progress in Organic Coatings 2019,130, 31-43; ACS Sustainable Chemistry & Engineering 2018,6, 14490-. At present, self-repairing high polymer materials face the irreconcilable contradiction between the repairing efficiency and the mechanical strength, and a single repairing mechanism is not enough to meet the dual requirements on the performance maintenance and the self-repairing capability of the self-repairing materials. Among a plurality of reversible covalent bonds, the Diels-Alder (D-A) bond and the disulfide bond have the advantages of simple dynamic exchange reaction condition, mild repair condition and the like, so that the Diels-Alder bond and the disulfide bond are simultaneously introduced into polyurethane, a waterborne polyurethane material with excellent repair performance is hopeful to be prepared, and the high-efficiency self-repair of the material can be realized by utilizing the light/heat synergistic effect, so that the service life and the safety of the material are improved, the material cost is reduced, and the resources are saved.

CN106632957A discloses a method for synthesizing waterborne polyurethane with self-repairing performance and preparing dispersion liquid thereof, wherein dihydric alcohol containing Diels-Alder dynamic bonds is introduced into the waterborne polyurethane through chain extension to prepare a waterborne polyurethane material for realizing self-repairing of cracks and damages by utilizing the breakage and recombination of thermally reversible D-A bonds. However, the preparation method is complex, a micromolecule diol chain extender containing a D-A bond needs to be synthesized firstly, and only one repair mode based on the D-A bond thermoreversible action exists. CN110028648A provides a self-repairing aqueous polyurethane obtained by mixing an aqueous polyurethane prepolymer emulsion containing a furan ring side group or a terminal group with a bismaleimide crosslinking agent and heating for reaction. The preparation condition is mild, the operation is simple, but a toxic small-molecule bismaleimide cross-linking agent is introduced, and only one D-A bond-based thermally reversible repair mode is provided. In another study, a highly flexible PPG prepolymer is used as a matrix material, and dynamic covalent bonds Diels-Alder (D-A) bonds and disulfide bonds are simultaneously introduced into polyurethane molecules to prepare a polyurethane elastomer PUSSDA (high molecular journal 2019,50,527-534) capable of self-repairing at room temperature. The PU-SSDA is repaired at room temperature for 60min, the repairing efficiency is as high as 93%, the repairing efficiency is still kept above 90% after 4 times of circulation, and the material can be reprocessed by means of hot pressing at 120 ℃. The self-repairing polyurethane material is prepared by a solvent-free method, but glycol molecules containing D-A bonds and S-S bonds need to be synthesized firstly, the preparation process is complex, the viscosity of the three-dimensional cross-linked material is high, and the self-repairing polyurethane material is difficult to construct if being used as a coating material.

At present, research on self-repair by simultaneously introducing a D-A bond and a disulfide bond on a main chain of waterborne polyurethane through a Diels-Alder addition reaction and further utilizing a retro-DA reaction and a disulfide bond photo-reversible exchange reaction is not reported.

Disclosure of Invention

The first purpose of the present invention is to solve the above problems and provide a preparation method of a self-repairing aqueous polyurethane coating material, wherein an aqueous polyurethane emulsion containing a maleimide end-capping group is mixed with a common food additive "difurfuryl disulfide", and a Diels-Alder addition reaction is used to prepare an aqueous polyurethane material with light/heat synergistic repair and excellent mechanical properties.

The second object of the present invention is to provide an aqueous polyurethane coating material obtained by the above method.

The purpose of the invention is realized by the following technical scheme:

a preparation method of a light/heat synergistic repair type waterborne polyurethane coating material comprises the steps of introducing a hydrophilic chain extender and a maleimide end-capping reagent into polyurethane to obtain a polyurethane prepolymer, further adding a disulfide bond-containing difuran ring chain extender, and neutralizing and emulsifying to obtain a modified waterborne polyurethane emulsion.

Preferably, the hydrophilic chain extender is a micromolecular diol containing a hydrophilic group, and the polyurethane is a prepolymer of diisocyanate and polymer diol.

Further, the method comprises the following steps:

(1) mixing 10-20 parts by weight of polymer diol which is heated, dried and dewatered, and 4.15-7.15 parts by weight of diisocyanate, stirring, adding 0.0076-0.087 part by weight of catalyst, and carrying out prepolymerization at 60-100 ℃ for 2-3 h in an inert atmosphere to obtain a polyurethane prepolymer I;

(2) carrying out further catalytic reaction on the polyurethane prepolymer I obtained in the step (1), 0.68-1.87 parts of hydrophilic chain extender and 0.92-4.36 parts of maleimide-terminated end-capping agent at 60-120 ℃ in an inert atmosphere for 2-8 h to obtain a maleimide-terminated polyurethane prepolymer II;

(3) diluting the polyurethane prepolymer II obtained in the step (2) with a diluent, adding 0.78-4.18 parts of a disulfide bond-containing bis-furan ring chain extender, carrying out secondary chain extension reaction for 2-6 hours at 60-90 ℃ in an inert atmosphere to obtain modified polyurethane, cooling to 30-40 ℃, adding a neutralizing agent for neutralization reaction, adding deionized water for dispersion and emulsification, and removing the diluent under reduced pressure to obtain a modified aqueous polyurethane emulsion.

Preferably, in the step (1), the temperature for heating, drying and dewatering is 80-120 ℃, the time is 2-3 h, and the vacuum degree is less than 1 kPa;

the polymer diol comprises one or more of polyethylene glycol, polypropylene glycol, polytetrahydrofuran diol, polycarbonate diol, poly adipic acid-1, 4-butanediol diol, polybutylene terephthalate, polycaprolactone diol and polydimethylsiloxane diol;

the diisocyanate comprises one or more of isophorone diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, 1, 4-cyclohexane diisocyanate and dicyclohexylmethane-4, 4' -diisocyanate;

the catalyst comprises one or two of dibutyltin dilaurate, tetramethylbutanediamine, triethylenediamine and stannous octoate.

Preferably, in the step (2), the hydrophilic small molecule chain extender comprises one or two of dimethylolpropionic acid and dimethylolbutyric acid;

the maleimide-based end-capping reagent comprises one or two of N-hydroxyethyl maleimide, N-aminoethyl maleimide, 3-maleimide propionic acid and 4-maleimide butyric acid, and the structural formula is

Preferably, in the step (3), the diluent comprises one or more of acetone, butanone and tetrahydrofuran;

the disulfide bond-containing difuranic ring chain extender is difurfuryl disulfide which is an additive for food and has a structural formula

The neutralizing agent comprises one or more of triethylamine, tripropylamine, sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium acetate, sodium pyrophosphate, sodium carbonate, ammonia water, diethanolamine and triethanolamine.

Preferably, the inert atmosphere comprises one of nitrogen and argon.

The waterborne polyurethane coating material obtained by any one of the methods.

According to the invention, macromolecule dihydric alcohol and diisocyanate react to generate a prepolymer I, and the prepolymer I is further reacted with a hydrophilic micromolecule chain extender and a maleimide-terminated end-capping agent to obtain a maleimide-terminated prepolymer II; then adding a difurfuryl disulfide serving as a difuranfunctional reagent containing a disulfide bond, and performing secondary chain extension by utilizing Diels-Alder addition reaction between a furan ring and maleimide; and then adding a neutralizing agent for neutralization, adding water for emulsification to obtain the aqueous polyurethane emulsion with the main chain containing a thermoreversible D-A bond and a photoreversible S-S bond, and curing to form a film to obtain the aqueous polyurethane coating material with the light/heat synergistic repair characteristic. The preparation method disclosed by the invention is simple in preparation process, environment-friendly and strong in practicability, the prepared material has excellent mechanical properties and a self-repairing function, the material crack can be efficiently self-repaired by heating or ultraviolet irradiation, the service life of the material can be prolonged, and the application prospect is good.

The invention has the following beneficial effects:

the preparation method of the light/heat synergistic repair type waterborne polyurethane coating material and the obtained product have the following advantages:

(1) the light/heat synergistic repair type waterborne polyurethane coating disclosed by the invention combines the self-repair advantages of Diels-Alder bonds and disulfide bonds, adopts non-contact light and heat for repair, is easy to control, and can complete self-repair at normal temperature; in addition, the heat treatment can promote the reversible exchange and the synergy of the D-A bond and the disulfide bond, and the film has better repairing effect;

(2) the light/heat synergistic repair type waterborne polyurethane coating disclosed by the invention is mild in reaction condition and simple in process, is prepared by adopting industrial organic intermediates of hydroxyl (or carboxyl) maleimide and common food additive difurfuryl disulfide, and is prepared by taking convenient and easily-obtained polyurethane industrial monomers such as diisocyanate, polymer dihydric alcohol, dimethylolpropionic acid, triethylamine and the like as raw materials, is easy to realize industrial production, and is high in added value of obtained products;

(3) the coating material prepared by the invention has higher mechanical strength and self-repairing function, can meet the mechanical index requirements of various support coating materials, can improve the service life and safety of the coating, is green and environment-friendly, has good application prospect, and can be applied to flexible substrate materials, wearable electronic skin equipment, biomedical materials, anti-scratch self-repairing function coating materials, leather finishing agents and other intelligent protective coatings.

Drawings

FIG. 1 is a schematic flow chart of the preparation of an aqueous polyurethane emulsion in example 1.

FIG. 2 is an infrared spectrum of the aqueous polyurethane emulsion containing D-A bonds and disulfide bonds prepared in example 1.

FIG. 3 is a particle size distribution and a transmission electron micrograph of the aqueous polyurethane emulsion obtained in example 1.

FIG. 4 is an optical microscope photograph of the coating layer after the aqueous polyurethane emulsion prepared in example 2 is cured into a film before and after ultraviolet irradiation or heat treatment for repair.

FIG. 5 is a stress-strain curve diagram of the coating after the aqueous polyurethane emulsion prepared in example 2 is cured into a film, and the coating is repaired by heating or ultraviolet.

Detailed Description

The following description of the preferred embodiments of the present invention is provided for the purpose of illustration and description, and is in no way intended to limit the invention.

The raw materials in the following examples are all commercially available products.