CN111790325B

CN111790325B - Double-shell self-repairing microcapsule and preparation method and application thereof

Info

Publication number: CN111790325B
Application number: CN202010690443.3A
Authority: CN
Inventors: 杨晶磊; 郭晔
Original assignee: Hong Kong University of Science and Technology HKUST
Current assignee: Hong Kong University of Science and Technology HKUST
Priority date: 2020-07-17
Filing date: 2020-07-17
Publication date: 2022-09-09
Anticipated expiration: 2040-07-17
Also published as: WO2022011814A1; CN111790325A

Abstract

The invention provides a double-shell self-repairing microcapsule and a preparation method and application thereof. The double-shell microcapsule comprises a core material, a first wall material layer wrapping the core material and a second wall material layer wrapping the first wall material. The double-shell microcapsule provided by the invention has two wall material layers, is high in mechanical strength, is a single-component repair system, and can be used for intelligently repairing damage by breaking and releasing the isocyanate core material to react and cure with moisture in the air after the coating is damaged, and meanwhile, in a high-humidity environment, the isocyanate core material in the microcapsule can absorb the moisture slowly permeating into the coating, so that the waterproof performance in the coating material is enhanced.

Description

Double-shell self-repairing microcapsule and preparation method and application thereof

Technical Field

The invention belongs to the technical field of coatings, and particularly relates to a double-shell self-repairing microcapsule as well as a preparation method and application thereof.

Background

The metal corrosion is a difficult problem which puzzles people for a long time and often involves very large economic cost and labor cost, and according to the American society of metals, the average loss of corrosion in recent years in British reaches 100 hundred million pounds, which accounts for 3.5 percent of GDP; the Germany loss is about 450 hundred million Euros and accounts for 3.0% of GDP, and the U.S. annual corrosion loss is more than 3000 hundred million dollars and accounts for 4.2% of GDP. The loss of China is about 3-5% of GDP, the total amount of the GDP in the whole country in 2018 is 11.94 trillion dollars, in other words, about 3582 and 5970 billion dollars of metal are corroded, about one third of the metal can be avoided by an effective anticorrosion means, and the anticorrosion product has a huge market share and a great development prospect.

Anticorrosive and antirust coatings are one of the most convenient methods for anticorrosive protection applications. The anticorrosive paint is a paint which is widely applied in modern industries, transportation, energy, ocean engineering and other departments. According to the corrosion resistance degree and the use requirement of a coating film layer, the coating is generally divided into a conventional type and a heavy-duty type. At present, the anticorrosive paint in China is mainly applied to the industries of chemical industry and petroleum industry, railways, highway bridges, metallurgical industry, electric power and energy industry, machinery and textile industry, industrial product field, automobiles, ships, containers, naval equipment and the like.

However, the painted structure is inevitably subjected to accidents such as collision, scraping, even low-speed impact and the like during transportation, assembly and service processes or during use after the installed structure is coated, so that microcracks which are difficult to detect are generated on the painted surface. During subsequent service, the presence of microcracks can lead to unnoticed corrosion of the underlying structure until very severe rust generation or structural failure. In order to solve the problem, coating materials with self-repairing function, such as intrinsic self-repairing materials, PET or PVC-based photo-curing and thermosetting self-repairing coating materials, appear on the market, after being damaged by external force, the coating can automatically recover to the state before being damaged under the action of self elasticity or chemical bonds, in addition, a double-capsule repairing system formed by respectively preparing epoxy resin and other high polymer materials and catalysts into microcapsules is also provided, and after being damaged by external force, the resin and the catalysts are respectively released, and the crosslinking reaction and curing are carried out at cracks, so that the repairing purpose is achieved.

However, the intrinsic self-repairing material can only repair some very fine scratches through the interaction of the elasticity or chemical bonds of the material, and cannot repair large-area coating damage caused by scratching, and the repair action is usually caused by external force intervention such as heating or illumination, and cannot adapt to complex and diversified use environments. In addition, in the actual damage process of the two microcapsules, the resin repair base material is released at the damaged part, and the catalyst reaches the optimal reaction ratio, so that a good repair effect can be realized.

In the synthesis process of microcapsules with double shells of traditional polyurethane/polyurea and polyurea-formaldehyde, the microcapsules are usually cleaned after the reaction for forming the first shell is finished, an emulsifier and a shell forming agent in a reaction solution are removed, and side reaction with the raw materials of the next layer of wall material is avoided.

Disclosure of Invention

The invention aims to provide a double-shell self-repairing microcapsule as well as a preparation method and application thereof. When the double-shell microcapsule is lost to generate scratches or cracks, the microcapsule is broken to release the isocyanate core material, and the isocyanate core material reacts with moisture in the air to be cured, so that the self-repairing process can be realized without intervention of external factors, the service lives of a coating and protected equipment can be effectively prolonged, the maintenance cost is reduced, and the double-shell microcapsule has good economic benefit.

The technical scheme adopted by the invention is as follows:

in a first aspect of the present invention, there is provided:

a double-shell microcapsule comprises a core material, a first wall material layer wrapping the core material and a second wall material layer wrapping the first wall material.

Preferably, the mass fraction of the core material is 20% to 70%, the mass fraction of the first wall material layer is 10% to 30%, and the mass fraction of the second wall material layer is 20% to 50% based on the mass of the double-shell microcapsule.

Preferably, the particle size of the double-shell microcapsule is 5 to 200 μm. The appearance of the double-shell microcapsule is spherical.

Preferably, the core material is at least one selected from isocyanates containing two or more isocyanate groups, the first wall material layer is at least one selected from polyurethane layers and polyurea layers, and the second wall material layer is a polyurea resin layer.

Preferably, the core material is at least one selected from isophorone diisocyanate, 4' -dicyclohexylmethane diisocyanate, and lysine diisocyanate.

Preferably, the polyurethane layer includes an oil-soluble polyurethane precursor and a water-soluble polyurethane precursor, and the polyurea layer includes an oil-soluble polyurea precursor and a water-soluble polyurea precursor.

Preferably, the mass ratio of the oil-soluble polyurethane precursor to the water-soluble polyurethane precursor in the polyurethane layer is 1: (1-2), wherein the mass ratio of the oil-soluble polyurea precursor to the water-soluble polyurea precursor in the polyurea layer is 1: (1-2).

Preferably, the oil-soluble polyurethane precursor is at least one selected from hexamethylene diisocyanate, diphenylmethane diisocyanate, trimer of hexamethylene diisocyanate and a diphenylmethane diisocyanate prepolymer; the oil-soluble polyurea precursor is at least one selected from hexamethylene diisocyanate, diphenylmethane diisocyanate, trimer of hexamethylene diisocyanate and prepolymer of diphenylmethane diisocyanate.

Preferably, the diphenylmethane diisocyanate prepolymer is at least one selected from the group consisting of hensmei Suprasec2644, Suprasec2244 and Suprasec 2344.

Preferably, the trimer of hexamethylene diisocyanate is at least one selected from the group consisting of Desmodur N3390, Wanhua WANNATE HT-100.

Preferably, the water-soluble polyurethane precursor is at least one selected from water-soluble compounds containing two or more hydroxyl groups, and the water-soluble polyurea precursor is at least one selected from water-soluble compounds containing two or more amine groups.

Preferably, the water-soluble polyurethane precursor is at least one selected from the group consisting of 1, 4-dibutanol, 1, 6-hexanediol, glycerol, 1, 3-propanediol and polypropylene glycol.

Preferably, the water-soluble polyurea precursor is at least one selected from the group consisting of triethylene tetramine, tetraethylene pentamine, and polyethylene imine having a molecular weight of 200-.

Preferably, the crosslinking degree of the polyurea resin layer is 5% to 20%; the functionality of the polyurea-formaldehyde resin is 2.0-2.5.

In a second aspect of the present invention, there is provided:

a preparation method of double-shell microcapsules comprises the following steps:

(1) adding a core material and an oil-soluble precursor mixed solution into an emulsifier solution, and stirring for reaction to obtain an oil-in-water emulsion;

(2) adding a water-soluble precursor and a modified coupling agent mixed solution into the oil-in-water emulsion, and stirring for reaction to obtain a single-shell microcapsule; the water-soluble precursor and the oil-soluble precursor undergo interfacial polymerization on the surface of the core material to form a first wall material layer.

(3) Adding the single-shell microcapsule and the urea-formaldehyde prepolymer into the mixed solution of the dispersant and the urea-formaldehyde resin modifier, adjusting the pH value, and stirring for reaction to obtain the double-shell microcapsule.

Preferably, when the oil-soluble precursor in the step (1) is an oil-soluble polyurethane precursor, the water-soluble precursor in the step (2) is a water-soluble polyurethane precursor. The subsequent reactant can be directly added for reaction without cleaning.

Preferably, when the oil-soluble precursor in step (1) is an oil-soluble polyurea precursor, the water-soluble precursor in step (2) is a water-soluble polyurea precursor, and the step (2) further includes a step of washing with water after the stirring reaction. The step of centrifugal washing is adopted, the residual water-soluble polyurea precursor in the solution can be washed away, and the subsequent reactant is added.

Preferably, the emulsifier in step (1) is at least one selected from the group consisting of gum arabic, polyvinyl alcohol 1788, polyvinyl alcohol 2488, polyvinyl alcohol 124, sodium dodecylsulfate, sodium dodecylbenzenesulfonate, and polyoxyethylene octylphenol ether-10.

Preferably, in the step (2), the modifying coupling agent is at least one selected from sorbitol, mannitol and triethanolamine.

Preferably, the dispersant in the step (3) is at least one selected from the group consisting of an ethylene-maleic anhydride copolymer, a styrene-maleic anhydride copolymer, and polyvinyl alcohol.

Preferably, the urea resin modifier in the step (3) is at least one selected from the group consisting of bisphenol a, resorcinol, catechol, hydroquinone, phloroglucinol, pyrogallol and anthratriphenol. The urea-formaldehyde resin obtained by directly polymerizing urea and formaldehyde has low crosslinking degree, so that the product is soft, poor in solvent resistance and low in mechanical strength, and the urea-formaldehyde resin modifier is added to improve the crosslinking degree and functionality of the urea-formaldehyde resin, so that the surface micro-nano structure of the double-shell microcapsule is regulated and controlled, and the strength of the wall material of the urea-formaldehyde resin polymer layer is enhanced.

Preferably, the mass ratio of urea to formaldehyde in the urea-formaldehyde prepolymer in the step (3) is (1-10): (1.5 to 65).

Preferably, the preparation method of the urea-formaldehyde prepolymer in the step (3) comprises the following steps: mixing urea and formaldehyde, adjusting the pH value to 7.5-9.0, stirring at the rotation speed of 100-600 rpm, and reacting at 50-80 ℃ for 30-90 min to obtain the urea-formaldehyde prepolymer.

Preferably, in the step (1), the mass fraction of the emulsifier is 0.35-5.0% of the mass of the oil-in-water emulsion.

Preferably, in the step (2), the mass fraction of the modified coupling agent is 0.10 to 1.0 percent based on the mass of the single-shell microcapsule.

Preferably, in the step (3), the mass fraction of the dispersant is 0.5 to 2.0 percent and the mass fraction of the urea-formaldehyde resin modifier is 5.0 to 30 percent based on the mass of the double-shell microcapsule.

Preferably, the reaction temperature of the stirring reaction in the step (1) is 30 to 70 ℃, the stirring speed is 200 to 2000rpm, and the stirring time is 5 to 60 min.

Preferably, the reaction temperature of the stirring reaction in the step (2) is 40 to 70 ℃, the stirring speed is 200 to 1200rpm, and the stirring time is 60 to 150 min.

Preferably, the reaction temperature of the stirring reaction in the step (3) is 45 to 70 ℃, the stirring speed is 100 to 600rpm, and the stirring time is 30 to 300 min.

Preferably, the pH value in the step (3) is 2.5-3.5.

In a third aspect of the present invention, there is provided:

the application of the double-shell microcapsule in preparing coating and/or adhesive is disclosed, wherein the double-shell microcapsule is prepared by the double-shell microcapsule or the preparation method of the double-shell microcapsule.

The invention has the beneficial effects that:

1. the double-shell microcapsule provided by the invention has two wall material layers, is high in mechanical strength, is a single-component repair system, and can be used for intelligently repairing damage by releasing the isocyanate core material through the rupture of the microcapsule to react and cure with moisture in the air after the coating is damaged, and meanwhile, in a high-humidity environment, the isocyanate core material in the microcapsule can absorb the moisture slowly permeating into the coating, so that the waterproof performance in the coating material is enhanced.

2. The double-shell microcapsule of the invention has the appearance of a standard round sphere, shows single round sphere dispersion, has good dispersibility, and has good high temperature resistance and solvent resistance stability.

3. The double-shell microcapsule has good high temperature resistance and solvent resistance, the core material of the microcapsule volatilizes when the temperature is raised to more than 150 ℃, and the core material loss rate of the microcapsule phase change material is only 5-10% after the microcapsule phase change material is continuously soaked in solvents such as water, normal hexane, dimethylbenzene and ethyl acetate for 20 days.

4. The invention discloses a preparation method of double-shell microcapsules, which belongs to continuous synthesis, and can realize that the raw material of a second wall material layer is directly added into a reaction solution to carry out the reaction of an outer wall material after a first wall material layer is synthesized by introducing a certain modified coupling agent, an intermediate cleaning process is not needed, the production process is simple, and the product quality and the production efficiency are improved.

5. In the preparation method of the double-shell microcapsule, the modified coupling agent is introduced, so that the mechanical strength of the first wall material layer can be enhanced on the premise of not increasing the thickness of the wall material, the compactness of the microcapsule is improved, the microcapsule has higher core material rate, and the functionality of the surface of the shell of the first wall material layer can be increased, so that the coupling effect is realized in the subsequent reaction process of the second wall material layer, and the effective and sufficient coupling of the first wall material layer and the second wall material layer is realized.

Drawings

FIG. 1 is a schematic structural diagram of a double-shell microcapsule of the present invention.

FIG. 2 is an electron microscope scan of the double-shell microcapsules prepared in example 1.

FIG. 3 is an electron micrograph of the double-shell microcapsule prepared in example 2.

FIG. 4 is an electron microscope scan of the double shell microcapsules prepared in example 3.

FIG. 5 is an electron microscope scan of a double-shell microcapsule prepared in a comparative example.

Fig. 6 is a thermogravimetric analysis curve of the double-shell microcapsule prepared in example 1.

Fig. 7 is a thermogravimetric analysis curve of the double-shell microcapsule prepared in example 2.

FIG. 8 is a thermogravimetric analysis curve of the double-shell microcapsule prepared in example 3.

Fig. 9 is a thermogravimetric analysis curve of the double-shell microcapsule prepared by the comparative example.

FIG. 10 is a graph of core loss after 20 days of immersion of the double-shell microcapsules prepared in example 1 in different solvents.

FIG. 11 is a test chart of rust inhibitive performance of the coating prepared from the double-shell microcapsule of example 1 and the control coating, wherein a is a test chart of rust inhibitive performance of the coating prepared from the double-shell microcapsule of example 1, and b is a test chart of rust inhibitive performance of the control coating.

FIG. 12 is a test chart of rust inhibitive performance of the coating prepared from the double-shell microcapsule of example 3 and the control coating, wherein a is a test chart of rust inhibitive performance of the coating prepared from the double-shell microcapsule of example 3, and b is a test chart of rust inhibitive performance of the control coating.

Detailed Description

In order to make the objects, technical solutions and technical effects of the present invention more clear, the present invention will be described in further detail with reference to specific embodiments. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

The structure of the double-shell microcapsule of the invention is schematically shown in figure 1.

Description of the reagents:

hensmei Suprasec2644, manufacturer: hensmei; NCO: 20.1% ± 0.5%; viscosity (@25 ℃): 850 mPa.s-1150 mPa.s; average functionality: 2.0.

example 1: a double-shell microcapsule and a preparation method thereof are disclosed:

(1) adding 100g of water and 3g of Arabic gum into a beaker, keeping the temperature at 40 ℃, and stirring at 500rpm for 10min to obtain an emulsifier solution;

(2) adding 14g of 4,4' -dicyclohexylmethane diisocyanate and 1g of Hensmei Suprasec2644 into a beaker, and uniformly stirring at room temperature of 500rpm to obtain an oil phase;

(3) adding the oil phase into an emulsifier solution, stirring at 1200rpm for 20min at 40 ℃, adding 3g of 1, 4-butanediol, 1g of glycerol and 0.5g of sorbitol, adjusting the stirring speed to 500rpm, heating to 60 ℃, reacting for 100min to obtain a single-shell microcapsule, and cooling the reaction system to below 30 ℃;

(4) dissolving 3g of resorcinol and 3g of polyethylene-maleic anhydride copolymer in 100g of water, uniformly mixing, and adding into the single-shell microcapsule;

(5) mixing 8g of urea with 20g of formaldehyde solution with the mass fraction of 37%, stirring at 400rpm, adjusting the pH to 8.5, reacting at 65 ℃ for 50min to form a urea-formaldehyde prepolymer, adding the urea-formaldehyde prepolymer into the single-shell microcapsule obtained in the step (4), adjusting the pH to 3.0, heating to 52 ℃, reacting for 150min, and washing, filtering and drying the product after the reaction is finished to obtain the double-shell microcapsule.

Example 2: a double-shell microcapsule and a preparation method thereof are as follows:

(1) adding 100g of water and 2g of polyvinyl alcohol 1788 into a beaker, keeping the temperature at 45 ℃, and stirring at 500rpm for 10min to obtain an emulsifier solution;

(2) adding 13g of 4,4' -dicyclohexylmethane diisocyanate into a beaker, heating at 40 ℃, adding 2g of hexamethylene diisocyanate, and uniformly stirring at 500rpm to obtain an oil phase;

(3) adding the oil phase into an emulsifier solution, stirring at the temperature of 45 ℃ and 1000rpm for 15min, adding 6g of tetraethylenepentamine and 1g of polyethyleneimine with the molecular weight of 1800, adjusting the stirring speed to 400rpm, heating to 65 ℃ for reaction for 70min, centrifuging the obtained product, washing with water for 5 times, and removing amines and the emulsifier in the solution for later use to obtain a single-shell microcapsule;

(4) mixing 5g of urea with 13g of formaldehyde solution with the mass fraction of 37%, stirring at 500rpm, adjusting the pH value to 8.2, and reacting at 75 ℃ for 45min to obtain urea-formaldehyde oligomer;

(5) dissolving 1.5g of polyethylene-maleic anhydride copolymer and 1g of styrene-maleic anhydride copolymer in 120g of water, adding 3.5g of resorcinol, adding the urea-formaldehyde oligomer obtained in the step (4), adjusting the pH to 2.9, then adding the single-shell microcapsule obtained in the step (3), heating to 58 ℃, reacting for 120min, and washing, filtering and drying the product after the reaction is finished to obtain the double-shell microcapsule.

Example 3: a double-shell microcapsule and a preparation method thereof are disclosed:

(1) adding 200g of water, 1.5g of polyvinyl alcohol 1788 and 0.5g of polyoxyethylene octyl phenol ether-10 into a beaker, and stirring at constant temperature of 40 ℃ and 500rpm for 60min to obtain an emulsifier solution;

(2) adding 26g of 4,4' -dicyclohexylmethane diisocyanate, 2g of Hensmei Suprasec2644 and 2g of Wanhua HT-10 into a beaker, and uniformly stirring at room temperature and 500rpm to obtain an oil phase;

(3) adding the oil phase into an emulsifier solution, stirring at 1200rpm for 20min at 40 ℃, adding 4g of 1, 3-propylene glycol, 1g of triethanolamine and 0.6g of sorbitol, adjusting the stirring speed to 500rpm, heating to 60 ℃, reacting for 100min to obtain a single-shell microcapsule, and cooling the reaction system to below 30 ℃;

(4) dissolving 4g of resorcinol and 2.5g of polyethylene-maleic anhydride copolymer in 200g of water, uniformly mixing, and adding into the solution in the step (3);

(5) mixing 7.5g of urea with 19g of formaldehyde solution with the mass fraction of 37%, stirring at 400rpm, adjusting the pH to 8.5, reacting at 65 ℃ for 50min to form a urea-formaldehyde prepolymer, adding the urea-formaldehyde prepolymer into the solution obtained in the step (4), adjusting the pH to 3.2, heating to 56 ℃, reacting for 150min, and washing, filtering and drying the product after the reaction is finished to obtain the double-shell microcapsule.

Comparative example: a microcapsule and a preparation method thereof:

(2) 26g of 4,4' -dicyclohexylmethane diisocyanate, 2g of Hensmei Suprasec2644 and 2g of Wanhua HT-10 are added into a beaker, and stirred uniformly at room temperature of 500rpm to obtain an oil phase;

(3) adding the oil phase into an emulsifier solution, stirring at 1200rpm for 20min at 40 ℃, adding 6g of 1, 3-propylene glycol, adjusting the stirring speed to 500rpm, heating to 60 ℃, reacting for 100min to obtain single-shell microcapsules, and cooling a reaction system to below 30 ℃;

(5) mixing 7.5g of urea with 19g of formaldehyde solution with the mass fraction of 37%, stirring at 400rpm, adjusting the pH to 8.5, reacting at 65 ℃ for 50min to form a urea-formaldehyde prepolymer, adding the urea-formaldehyde prepolymer into the solution obtained in the step (4), adjusting the pH to 3.2, heating to 56 ℃, reacting for 300min, and washing, filtering and drying the product after the reaction is finished to obtain the microcapsule.

Test example:

the microcapsules prepared in examples 1 to 3 and comparative example were subjected to electron microscope scanning, and the results are shown in fig. 2 to 5.

As shown in FIG. 2, the double-shell microcapsule prepared in example 1 is regular round and spherical, has good dispersibility and no adhesion, and has a particle size of 10 μm to 50 μm; as shown in FIG. 3, the double-shell microcapsule prepared in example 2 is spherical, has good dispersibility, mostly has no adhesion, and has a particle size of 5-60 μm; as shown in fig. 4, the double-shell microcapsule prepared in example 3 is in a regular spherical shape, has good dispersibility, and is free from adhesion; as shown in FIG. 5, the microcapsules prepared in the comparative example have serious adhesion, and a product with the dispersibility similar to that of example 3 cannot be obtained after the reaction time is 300min, and the bonding caused by the overflow of the microcapsule core material can be obviously seen in the circle marked part in the figure. The double-shell microcapsule prepared by the invention has good sphericity and dispersity, no adhesion and uniform particle size.

The thermal weight loss analysis was performed on the microcapsules prepared in examples 1 to 3 and comparative example, the used test instrument was a TA-Q50 thermogravimetric analyzer, the test temperature range was 25 ℃ to 800 ℃, the temperature rise rate was 10 ℃/min, and the results are shown in fig. 6 to 9.

As shown in fig. 6 to 9, the content of the phase change material core material in the double-shell microcapsule prepared in example 1 is about 47.8%, and the loss of the double-shell microcapsule core material begins after the double-shell microcapsule core material is heated to about 150 ℃; as shown in fig. 7, the content of the phase change material core material in the double-shell microcapsule prepared in example 2 is about 39%, the core material of the double-shell microcapsule begins to lose when heated to about 150 ℃, and only 5% of the mass of the core material is lost when the temperature is raised to 219 ℃; as shown in fig. 8, the content of the phase change material core material in the double-shell microcapsule prepared in example 3 is about 64%, the core material of the double-shell microcapsule starts to lose when heated to about 150 ℃, and only 5% of the mass of the core material is lost when the temperature is raised to 210 ℃; as shown in fig. 9, the phase change material core material content of the microcapsule prepared in the comparative example was about 28%, the core material had lost 5% of its mass when heated to 194 ℃, and mass loss began to occur when heated to 100 ℃. Therefore, the double-shell microcapsule phase change material prepared by the invention has high core material content, microcapsules with the same quality contain more repairing core materials, the high-temperature resistance is good, and the core materials of the microcapsules volatilize when the temperature is raised to more than 150 ℃.

The microcapsules prepared in example 1 were immersed in 4 different solvents, i.e., water, n-hexane, xylene, and ethyl acetate, at room temperature for 20 days, and the core loss rate was measured, and the results are shown in fig. 10.

As can be seen from fig. 10, the double-shell microcapsule of the present invention has good solvent resistance, and after being continuously soaked in solvents such as water, n-hexane, xylene, and ethyl acetate for 20 days, the core loss rate of the microcapsule phase change material is only 5% to 10%, which proves that the self-repairing microcapsule has good solvent resistance, and the microcapsule is not damaged by soaking in the solvent in the coating during the process of being doped into the coating to be coated.

Application example 1: the self-repairing antirust coating and the preparation method thereof are as follows:

10g of the double-shell microcapsule prepared in example 1 and 90g of a commercially available waterborne alkyd resin finish are added into a plastic cup, mechanically stirred at 500rpm for 10min, placed into a spray gun and sprayed on the surface of an iron plate, the iron plate is placed at room temperature for 6h, the surface of the coating is dried, then the coating is sprayed again, the spraying is totally carried out for 3 to 4 times, the thickness of the coating is 100 to 150 mu m, after the coating is completely cured, a cross mark is marked on the surface by a blade, and the coating is immersed in a 10% sodium chloride solution for 35 days, and the result is shown in fig. 11 (a). The same spraying and soaking operations were carried out without adding microcapsules on a commercially available water-based alkyd top coat as a control, and the results are shown in fig. 11 (b).

As can be seen from FIG. 11, the self-repairing antirust coating prepared by applying the double-shell microcapsule of the present invention has no corrosion and damage after being soaked in 10% sodium chloride solution for 35 days, and can still provide good protection for equipment, while the control group has severe corrosion of the coating scratch, and the coating surface is cracked by bubbling.

Application example 2: the self-repairing antirust coating and the preparation method thereof are as follows:

a component A and a component B of a commercially available epoxy resin paint are mixed according to the product specification to obtain 90g of epoxy paint, 10g of double-shell microcapsule prepared in example 3 is added, mechanical stirring is carried out at 600rpm for 10min, the mixture is brushed on the surface of an iron plate, the thickness of the coating is 100 microns +/-20 microns, after the coating is completely cured, a blade is used for scratching a line-shaped scratch on the surface, a neutral salt spray test is carried out according to GBT 1771-2007, and the result is shown in figure 12(a) after a 1000-hour salt spray performance test. Commercially available epoxy paint A and B were mixed according to the product specifications to give 90g of epoxy paint, and the same brushing and salt spray test operations were carried out as a control, and the results are shown in FIG. 12 (B).

As can be seen from FIG. 12, after the neutral salt spray performance test of 1000h, the self-repairing antirust coating prepared by applying the double-shell microcapsule of the invention has no corrosion and damage, and can still provide good protection for equipment, while the control group coating has severe foaming and shedding.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims

1. A double-shell microcapsule, characterized in that: the composite material comprises a core material, a first wall material layer wrapping the core material and a second wall material layer wrapping the first wall material layer; the core material is isocyanate containing more than two isocyanate groups, the first wall material layer is a polyurethane layer, and the second wall material layer is a polyurea resin layer; the cross-linking degree of the polyurea resin layer is 5-20%; the functionality of the urea-formaldehyde resin is 2.0-2.5;

the preparation method of the double-shell microcapsule comprises the following steps:

(2) adding a water-soluble precursor and a modified coupling agent mixed solution into the oil-in-water emulsion, and stirring for reaction to obtain a single-shell microcapsule; carrying out interfacial polymerization reaction on the water-soluble precursor and the oil-soluble precursor on the surface of the core material to form a first wall material layer;

(3) adding a single-shell microcapsule and a urea-formaldehyde prepolymer into a mixed solution of a dispersing agent and a urea-formaldehyde resin modifier, adjusting the pH, and stirring for reaction to obtain the double-shell microcapsule;

the modified coupling agent is at least one selected from sorbitol, mannitol and triethanolamine.

2. A double-shell microcapsule according to claim 1, characterized in that: based on the mass of the double-shell microcapsule, the mass fraction of the core material is 20-70%, the mass fraction of the first wall material layer is 10-30%, and the mass fraction of the second wall material layer is 20-50%.

3. A double-shell microcapsule according to claim 2, characterized in that: the polyurethane layer comprises an oil-soluble polyurethane precursor and a water-soluble polyurethane precursor.

4. A double-shell microcapsule according to claim 3, characterized in that: the oil-soluble polyurethane precursor is at least one of hexamethylene diisocyanate, diphenylmethane diisocyanate, trimer of hexamethylene diisocyanate and prepolymer of diphenylmethane diisocyanate.

5. A double-shell microcapsule according to claim 3, characterized in that: the water-soluble polyurethane precursor is a water-soluble compound containing more than two hydroxyl groups.

6. A preparation method of double-shell microcapsules is characterized in that: the method comprises the following steps:

(2) adding a water-soluble precursor and a modified coupling agent mixed solution into the oil-in-water emulsion, and stirring for reaction to obtain a single-shell microcapsule;

(3) adding a single-shell microcapsule and a urea-formaldehyde prepolymer into a mixed solution of a dispersing agent and a urea-formaldehyde resin modifier, adjusting the pH, and stirring for reaction to obtain the double-shell microcapsule according to any one of claims 1-5;

in the step (2), the modified coupling agent is at least one selected from sorbitol, mannitol and triethanolamine.

7. A process for the preparation of double-shell microcapsules according to claim 6, characterized in that: and (2) when the oil-soluble precursor in the step (1) is an oil-soluble polyurethane precursor, the water-soluble precursor in the step (2) is a water-soluble polyurethane precursor.

8. The application of double-shell microcapsule in preparing paint and/or adhesive is characterized by that: the double-shell microcapsule is the double-shell microcapsule described in any one of claims 1 to 5, or is prepared by the preparation method of the double-shell microcapsule described in any one of claims 6 to 7.