CN110684238B

CN110684238B - Microcapsule capable of being self-repaired repeatedly at room temperature, preparation method and application

Info

Publication number: CN110684238B
Application number: CN201910822900.7A
Authority: CN
Inventors: 许一婷; 王宏超; 戴李宗; 杨杰; 曹莹; 张丹丹; 张加甜; 陈国荣
Original assignee: Xiamen University; Jinyoung Xiamen Advanced Materials Technology Co Ltd
Current assignee: Xiamen University; Jinyoung Xiamen Advanced Materials Technology Co Ltd
Priority date: 2019-09-02
Filing date: 2019-09-02
Publication date: 2020-10-09
Anticipated expiration: 2039-09-02
Also published as: WO2021043123A1; CN110684238A

Abstract

The invention discloses a microcapsule capable of self-repairing for multiple times at room temperature, a preparation method and application thereof. By utilizing the characteristics of the microcapsule and the properties of the reversible borate ester bond, the invention effectively improves the performance of the high polymer material, achieves the effects of quickly repairing and repeatedly repairing microcracks for many times, prevents the microcracks from diffusing to cause macroscopic damage of the material, greatly prolongs the service life of the material, and is further widely applied to the fields of automobile finish, automobile primer, intelligent household paint, intelligent household parts, electronic and electric sealant and the like.

Description

Microcapsule capable of being self-repaired repeatedly at room temperature, preparation method and application

Technical Field

The invention belongs to the field of room temperature self-repairing materials, and particularly relates to a microcapsule capable of self-repairing for multiple times at room temperature, a preparation method and application.

Background

Due to its excellent properties, polymer materials have become an indispensable material in the fields of life industry, military and the like. However, since the strength of the polymer material is relatively low compared to metal ceramics and other materials, how to prolong the service life of the polymer material becomes a concern. The preparation of self-repairable materials is an effective way to prolong the service life of the materials, and has been receiving more and more attention.

The microcapsule added in the material is a common method for preparing the self-repairable material, and can quickly generate the repairing effect. In the research work of the microcapsule, Wang Wei and the like (micro-crack self-repairing microcapsule and a preparation method thereof, Chinese patent, publication No. CN102702838A) prepare the microcapsule which takes isocyanate derivatives as a capsule core, takes urea-formaldehyde resin containing a chain extender as a capsule wall, can realize the function of completely automatically repairing without adding extra repairing catalyst or initiator, and solve the problem of small contact probability between the capsule core material and the catalyst or initiator after flowing into a crack. High macro and the like (a method for preparing a self-repairing material based on a mercapto-alkene click addition reaction, Chinese patent, publication No. CN109081919A) sequentially and uniformly mixing polysulfide rubber, an acrylate monomer, an initiator or a catalyst and a self-repairing accelerator to obtain a prepolymer, and curing in a curing mode corresponding to the initiator or the catalyst to obtain the self-repairing material. However, the microcapsule can only be repaired once, and cannot achieve the aim of repeatedly repairing materials.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, provides a microcapsule capable of self-repairing for many times at room temperature, a preparation method and application thereof, and solves the problems in the background technology.

One of the technical schemes adopted by the invention for solving the technical problems is as follows: a microcapsule capable of self-repairing for multiple times at room temperature is provided, which comprises a first microcapsule and a second microcapsule;

the capsule wall of the first microcapsule is urea resin, the capsule core is dipropyl thiopropyl ether borate methyl dimethoxy siloxane, a catalyst and an adhesion promoter, and the mass ratio of the dipropyl thiopropyl ether borate methyl dimethoxy siloxane to the catalyst to the adhesion promoter is 1: 0.005-0.015: 0.002 to 0.005;

the capsule wall of the second microcapsule is urea-formaldehyde resin, and the capsule core is dihydroxy polydimethylsiloxane, a catalyst and an adhesion promoter, wherein the mass ratio of the dihydroxy polydimethylsiloxane to the catalyst to the adhesion promoter is 1: 0.005-0.015: 0.002 to 0.005;

the mass ratio of the capsule wall to the capsule core of the first microcapsule to the second microcapsule is 1: 2.5 to 5.

The catalyst comprises dibutyltin dilaurate, and the adhesion promoter is methacryloxypropyltriethoxysilane or bis [3- (trimethoxysilyl) propyl ] amine.

The second technical scheme adopted by the invention for solving the technical problems is as follows: the preparation method of the microcapsule capable of self-repairing for multiple times at room temperature comprises the following steps:

one) preparation of reversible boronic ester bond siloxane coupling agents: reacting boric acid with 3-allyloxy-1, 2-propanediol and performing thiol-ene click chemical reaction to obtain dipropylthiopropylether borate methyldimethoxysiloxane; the double propyl thiopropyl ether borate methyldimethoxysiloxane has a reversible covalent bond, can perform bond exchange with a non-covalent bond under a certain condition, and can be used for preparing a multi-time self-repairing material, so that the quick repair and the multi-time repeated repair of microcracks can be realized, the macroscopic damage of the material caused by the diffusion of the microcracks can be prevented, and the service life of the material can be prolonged.

The synthetic route of the dipropylthiopropyl ether borate methyldimethoxysiloxane is as follows:

1) adding boric acid and a first solvent into a round-bottom flask, and regulating with KOH_pAnd H is about 9-11, 3-allyloxy-1, 2-propylene glycol is added, stirring is carried out at the temperature of 20-40 ℃ for reaction for 4-8H, stirring is carried out at the temperature of 100-140 ℃, the first solvent is removed through evaporation, and finally drying is carried out at the temperature of 100-140 ℃ under vacuum, so that the bis (allyloxy) methyl borate is obtained.

2) Dissolving the bis (allyloxy) methyl borate and mercaptopropyl methyldimethoxysilane obtained in the step 1) in a second solvent under the protection of nitrogen, adding a photoinitiator 2-hydroxy-2-methyl propiophenone, stirring and reacting for 0.5-1.5 h under the ultraviolet light of 365nm at room temperature, and drying in vacuum at room temperature to obtain the dipropyl thiopropyl ether borate methyl dimethoxysiloxane.

II) assembling and mixing the microcapsules: preparing a first microcapsule with a capsule wall made of urea-formaldehyde resin, a capsule core made of dipropyl thiopropyl ether borate methyl dimethoxy siloxane, a catalyst and an adhesion promoter through in-situ polymerization of an oil-in-water emulsion, and a second microcapsule with a capsule wall made of urea-formaldehyde resin and a capsule core made of dihydroxy polydimethylsiloxane, a catalyst and an adhesion promoter.

1) Adding an emulsifier and distilled water into a round-bottom flask, adding urea, ammonium chloride and resorcinol, uniformly stirring, adding the dipropyl thiopropyl ether borate methyl dimethoxysiloxane or dihydroxy polydimethylsiloxane obtained in the step 1, a catalyst dibutyltin dilaurate and a corresponding adhesion promoter, adjusting the pH to be 3-4 by using formic acid, adjusting the rotation speed to be 500-2000 rpm, shearing and emulsifying for 5-20 min to adjust the size of the microcapsule, adding an antifoaming agent n-octanol to remove surface bubbles, adding 37 wt% of formaldehyde solution, heating to 60 ℃ at the speed of 1 ℃/min, keeping the rotation speed for reacting for 1-3 h, adding 5-20 wt% of urea, keeping the rotation speed for reacting for 2-4 h, centrifugally separating, washing with distilled water for multiple times, and drying in normal-temperature air for 24-48 h after suction filtration to obtain a first microcapsule;

2) replacing the dipropylthiopropyl ether borate methyldimethoxysiloxane in the step 1) with dihydroxy polydimethylsiloxane to prepare a second microcapsule;

3) physically mixing the first microcapsule obtained in the step 1) with the second microcapsule obtained in the step 2).

In a preferred embodiment of the present invention, the first solvent is deionized water.

In a preferred embodiment of the present invention, the second solvent is chloroform or n-hexane.

In a preferred embodiment of the present invention, the emulsifier is sodium dodecylbenzene sulfonate, sodium dodecyl sulfate or OP-10. The concentration of the emulsifier is 0.3 wt% -1.0 wt%.

In a preferred embodiment of the present invention, the adhesion promoter is methacryloxypropyltriethoxysilane or bis [3- (trimethoxysilyl) propyl ] amine.

In a preferred embodiment of the present invention, the boric acid and 3-allyloxy-1, 2-propanediol are present in a mass ratio of 2: 8-9, wherein the mass ratio of the bis (allyloxy) methyl borate to the mercaptopropyl-methyldimethoxysilane to the 2-hydroxy-2-methyl propiophenone is 6: 7-8: 0.1 to 0.3.

In a preferred embodiment of the present invention, the mass ratio of the capsule wall to the capsule core is 1: 2.5 to 5.

In a preferred embodiment of the present invention, the mass ratio of urea, ammonium chloride, resorcinol and 37 wt% formaldehyde solution is 1: 0.1: 0.1: 3 to 5.

In a preferred embodiment of the present invention, the mass ratio of the dihydroxy polydimethylsiloxane, the dibutyltin dilaurate and the adhesion promoter is 1: 0.005-0.015: 0.002 to 0.005.

In a preferred embodiment of the present invention, the first microcapsule and the second microcapsule are used in combination in a mass ratio of 1: 10 to 20.

The third technical scheme adopted by the invention for solving the technical problems is as follows: an application of the microcapsule able to self-repair many times at room temp in high-molecular material, such as resin paint. And dispersing and mixing the microcapsules capable of self-repairing for multiple times at room temperature, matrix resin and other components in a dispersion machine for 1-4 hours to obtain the self-repairing resin coating. The resin coating is selected from epoxy resin coating, polyurethane resin coating, phenolic resin coating and the like. The preparation steps of the self-repairing epoxy resin coating are as follows:

weighing a certain amount of epoxy resin, adding 15-35 wt% of a third solvent, stirring for 25-50 min, adding 10-20 wt% of microcapsules capable of self-repairing repeatedly at room temperature, and stirring for 30-90 min to obtain a component A. Weighing a certain amount of curing agent, adding 15-35 wt% of third solvent, and stirring for 10-30 min to obtain a component B. And mixing the component A and the component B, and stirring for 20-60 min to obtain the self-repairing epoxy resin coating.

The epoxy resin is a commercial epoxy resin, i.e. a compound containing two or more epoxy groups in a molecule, such as glycidyl ether, glycidyl amine, glycidyl ester and the like; the glycidyl ether includes bisphenol A type, bisphenol F type, bisphenol S type, etc.; the glycidyl amine includes aniline glycidyl amine, diaminodiphenylmethane tetraglycidyl amine, etc.; examples of the glycidyl ester include diglycidyl terephthalate and the like.

The third solvent is n-butanol and/or butyl acetate.

The microcapsules capable of self-repairing for multiple times at room temperature are a first microcapsule and a second microcapsule, and the mass ratio of the first microcapsule to the second microcapsule is 1: 10 to 20.

The curing agent is amine or anhydride compound used in combination with epoxy resin, such as 4, 4' -diaminodiphenylmethane, ethylenediamine, diethylenetriamine, m-phenylenediamine, etc.; acid anhydrides such as phthalic anhydride, pyromellitic anhydride, methylcyclohexene tetracarboxylic anhydride, and the like.

The mass ratio of the component A to the component B is 2-4: 1.

the microcapsule capable of self-repairing for multiple times at room temperature can also be applied to the fields of automobile finish, automobile primer, intelligent household paint, intelligent household parts, electronic and electrical sealants and the like.

The invention provides a microcapsule which is prepared by adopting an oil-in-water emulsion in-situ polymerization method, wherein a siloxane coupling agent containing a reversible boric acid ester bond is used as a capsule core, a urea-formaldehyde resin is used as a capsule wall, and the microcapsule, which is prepared by adopting dihydroxy polydimethylsiloxane, an adhesion promoter and a catalyst as the capsule core and the urea-formaldehyde resin as the capsule wall, can be self-repaired for multiple times at room temperature. The microcapsule core substance capable of self-repairing for multiple times at room temperature comprises a siloxane coupling agent containing reversible boric acid ester bonds, dihydroxy polydimethylsiloxane, a catalyst and an adhesion promoter, and is different from the reported microcapsules, siloxane coupling agent and polydimethylsiloxane. By utilizing the characteristics of the microcapsule and the property of the reversible borate bond, the prepared self-repairing material can be repeatedly repaired for many times, and the service life of the material is greatly prolonged. The urea-formaldehyde resin capsule wall has high chemical stability, better mechanical property and good film forming property, and has little influence on the mechanical property of the self-repairing material. When the self-repairing material is subjected to external force to generate micro-cracks and/or cracks, the microcapsules are broken, the capsule core substances flow out to be mutually contacted and mixed, the dihydroxy polydimethylsiloxane is crosslinked and cured under the action of a siloxane coupling agent containing reversible boric acid ester bonds and a catalyst at room temperature, the micro-cracks and/or cracks are quickly repaired, the material is prevented from being macroscopically damaged due to further diffusion, the chemical property of the cured silicon rubber is stable, and the silicon rubber has good adhesion with a high polymer matrix under the action of an adhesion promoter. When the silicon rubber formed by curing is damaged by external force, the boric acid bonds and glycol bonds can be reversibly generated at two ends of the generated microcracks and/or cracks under the action of water in the air, the boric acid bonds and glycol bonds at two ends of the silicon rubber can react again at room temperature to generate boric acid ester bonds, the microcracks and/or cracks can be repaired repeatedly under the action of the exchange of the boric acid ester bonds of the reversible bonds and the movement of molecular chain segments, and the like, when the microcracks and/or cracks are generated in the silicon rubber area of the repaired self-repairing material under the action of external force again, the microcracks and/or cracks can be repaired repeatedly, the microcracks and/or cracks generated in the non-silicon rubber repairing area are cracked through microcapsules, the capsule core substances are mixed and cured into the silicon rubber to achieve the self-repairing effect, the two synergistic effect enables the material to be repeatedly self, greatly prolonging the service life of the material.

Compared with the prior art, the invention has the following beneficial effects:

(1) the microcapsule prepared by the invention can be uniformly dispersed in a high polymer material, the performance of repeated self-repairing at room temperature is introduced on the premise of ensuring the mechanical property of the high polymer material, and the chemical properties of the capsule wall and the capsule core material of the microcapsule are stable.

(2) The dipropylthiopropylether borate methyldimethoxysiloxane, the dihydroxypolydimethylsiloxane, the catalyst and the adhesion promoter are respectively encapsulated in the two microcapsules, and are mixed and added into the resin matrix, the capsule core substances can be stably stored under the protection of the capsule wall, and when the material has micro cracks and/or cracks, the capsule core substances are mutually contacted and cured at room temperature when the microcapsules are broken, so that the premature curing of the capsule core substances or the reaction with the resin matrix is prevented.

(3) When the self-repairing material receives external force to generate micro cracks and/or cracks, the microcapsules are broken, and the dihydroxy polydimethylsiloxane, the dipropyl thiopropyl ether borate methyl dimethoxyl siloxane, the catalyst and the adhesion promoter in the microcapsules are contacted with each other, mixed and cured to form the silicon rubber so as to repair the micro cracks and/or cracks. When the self-repairing material receives the external force again, microcracks and/or cracks are generated in the silicon rubber area, the borate bonds leaked from the two ends can be reversibly changed into borate bonds and glycol bonds under the action of water in the air, the borate bonds and the glycol bonds react at room temperature to generate the borate bonds again, a large amount of borate ester can carry out reversible bond exchange and reversible equilibrium conversion, the molecular chain segment continuously moves, and the effect of repairing the material is achieved through the reversible covalent bonds. When micro cracks and/or cracks are generated in the area except the silicon rubber, the self-repairing is carried out through a microcapsule mechanism. The two self-repairing modes are mutually cooperated, so that the prepared material can achieve the effect of self-repairing for many times at room temperature.

Drawings

FIG. 1 shows NMR hydrogen spectra and NMR boron spectra of bis (allyloxy) methyl borate, wherein a is NMR hydrogen spectra and b is NMR boron spectra.

FIG. 2 shows optical and scanning electron micrographs of microcapsules of dihydroxypolydimethylsiloxane, catalyst and adhesion promoter in which a, b, c are optical images (50 μm scale) and d is a scanning electron micrograph (500X, 10 μm scale).

Detailed Description

Example 1

(1) Preparation of microcapsule capable of self-repairing repeatedly at room temperature

To a round bottom flask was added 2g of boric acid and 20mL of deionized water, adjusted to pH 10 with KOH, added 8.55g of 3-allyloxy-1, 2-propanediol, reacted at 30 ℃ with stirring for 6h, evaporated to remove water at 110 ℃ with stirring, and finally dried at 110 ℃ under vacuum to give bis (allyloxy) methyl borate. Weighing 6g of bis (allyloxy) methyl borate and 7.98g of mercaptopropyl-methyldimethoxysilane, dissolving in 100mL under the protection of nitrogen, adding 0.2g of 2-hydroxy-2-methyl propiophenone, stirring and reacting for 1h under the ultraviolet light of 365nm at room temperature, and drying in vacuum at room temperature to obtain the dipropyl thiopropyl ether borate methyl dimethoxy siloxane. Adding 0.625g of sodium dodecyl benzene sulfonate and 62.5mL of distilled water into a round-bottom flask, adding 1.25g of urea, 0.125g of ammonium chloride and 0.125g of resorcinol, uniformly stirring, adding 8g of dipropyl thiopropyl ether borate methyl dimethoxysiloxane or 8g of dihydroxy polydimethylsiloxane, 0.05g of dibutyltin dilaurate and 0.024g of bis [3- (trimethoxysilyl) propyl ] amine, adjusting the pH to 3.5 by formic acid, adjusting the rotation speed to 1000rpm, shearing and emulsifying for 15min, adding 2 drops of n-octanol, adding 4g of 37 wt% formaldehyde solution, heating to 60 ℃ at the speed of 1 ℃/min, keeping the rotation speed for reacting for 1 hour, adding 0.125g of urea, continuing to keep the rotation speed for reaction for 3 hours, centrifugally separating, washing with distilled water for multiple times, performing suction filtration, and drying in normal-temperature air for 36 hours to obtain the microcapsule capable of self-repairing for multiple times at room temperature.

(2) Preparation of epoxy resin coating

Weighing 50g of epoxy resin, adding 7g of n-butanol and 3g of butyl acetate, stirring for 30min, adding 7g of second microcapsule with a core made of dihydroxy polydimethylsiloxane, a catalyst and an adhesion promoter and 0.7g of first microcapsule with a core made of dipropylthiopropyl ether borate methyldimethoxysiloxane, and stirring for 30min to obtain the component A. 15g of curing agent was weighed, 2.1g of n-butanol and 0.9g of butyl acetate were added, and stirring was carried out for 30min to obtain component B. And mixing the component A and the component B, and stirring for 30min to obtain the self-repairing epoxy resin coating.

In example 1, the nmr hydrogen spectrum and nmr boron spectrum of the synthesized bis (allyloxy) methyl borate are shown in fig. 1, and the optical image and sem image of the prepared second microcapsule with a core of dihydroxy polydimethylsiloxane, catalyst and adhesion promoter are shown in fig. 2.

Examples 2 to 5

(1) The same as in example 1.

(2) The same process as in example 1 was used, except that the amounts of the microcapsules capable of self-repairing at room temperature were changed to 5g, 5.5g, 6g, and 6.5g of the second microcapsules having a core made of dihydroxypolydimethylsiloxane, a catalyst, and an adhesion promoter, and to 0.5g, 0.55g, 0.6g, and 0.65g of the first microcapsules having a core made of dipropylene thiopropyl ether borate methyldimethoxysiloxane (in terms of mass%, the microcapsules capable of self-repairing at room temperature were 11%, 12%, 13%, and 14%, respectively), to obtain a self-repairing epoxy resin coating.

50g of epoxy resin is weighed, 7g of n-butanol and 3g of butyl acetate are added, and the mixture is stirred for 30min to obtain a component A. 15g of curing agent was weighed, 2.1g of n-butanol and 0.9g of butyl acetate were added, and stirring was carried out for 30min to obtain component B. And mixing the component A and the component B, and stirring for 30min to obtain the control group epoxy resin coating.

Example 6

(1) The same as in example 1.

(2) Weighing 50g of polyurethane resin, adding 20g of butyl acetate, 6.5g of a second microcapsule with a capsule core made of dihydroxy polydimethylsiloxane, a catalyst and an adhesion promoter and 0.65g of a first microcapsule with a capsule core made of dipropyl thiopropyl ether borate methyl dimethoxysiloxane, stirring for 1 hour, adding 25g of polyisocyanate curing agent, and stirring for 1 hour to obtain the self-repairing polyurethane resin coating.

Example 7

(1) The same as in example 1.

(2) Weighing 50g of phenolic resin, 5.5g of second microcapsule with a capsule core made of dihydroxy polydimethylsiloxane, a catalyst and an adhesion promoter, 0.55g of first microcapsule with a capsule core made of dipropyl thiopropyl ether borate methyl dimethoxysiloxane, 10g of butanol and 15g of xylene, stirring for 1h, adding 5g of polyamide curing agent, and stirring for 30min to obtain the self-repairing phenolic resin coating.

Example 8

(1) The same as in example 1.

(2) Weighing 50g of waterborne polyurethane resin commercial automobile finish, 6g of a second microcapsule with a capsule core of dihydroxy polydimethylsiloxane, a catalyst and an adhesion promoter and 0.6g of a first microcapsule with a capsule core of dipropyl thiopropyl ether borate methyl dimethoxysiloxane, adding 15g of deionized water and 5g of a cross-linking agent, and dispersing and mixing in a dispersion machine for 3 hours to obtain the self-repairing automobile finish.

The hydrogen nuclear magnetic resonance spectrum and the boron nuclear magnetic resonance spectrum of the bis (allyloxy) methyl borate are shown in figure 1.

The optical and scanning electron micrographs of the second microcapsules with the core of dihydroxy polydimethylsiloxane, catalyst and adhesion promoter are shown in figure 2.

Self-repairing performance test:

the experimental epoxy resin paint containing the microcapsules prepared in example 1 and the control group common epoxy resin paint were coated on a Q235 steel plate, respectively, and after complete curing, the coatings were crossed, and left in an atmospheric environment for three days to perform a neutral salt spray resistance test. The experimental result shows that the neutral salt fog resistant time of the epoxy resin coating of the control group is 300 hours, and the neutral salt fog resistant time of the self-repairing epoxy resin coating of 11%, 12%, 13%, 14% and 15% respectively in the experimental group is 650, 660, 680, 700 and 720 hours.

And marking a fork on the self-repairing epoxy resin coating of the experimental group, placing the coating in an atmospheric environment for three days, then marking the fork at the coating marking fork again, placing the coating in the atmospheric environment for three days, and carrying out a neutral salt spray resistance test. The experimental results show that the neutral salt spray resistance of the self-repairing epoxy resin coating with the microcapsule contents of 11%, 12%, 13%, 14% and 15% in the experimental group is 630, 640, 660, 680 and 700 hours respectively.

By analogy, a fork is drawn at the same place on the self-repairing epoxy resin coating of the experimental group, the epoxy resin coating is placed for three days in an atmospheric environment, and after three times of circulation, a neutral salt spray resistance test is performed. The experimental results show that the neutral salt spray resistance of the self-repairing epoxy resin coating with the microcapsule contents of 11%, 12%, 13%, 14% and 15% in the experimental group is 620, 630, 650, 670 and 690 hours respectively.

The above description is only a preferred embodiment of the present invention, and therefore should not be taken as limiting the scope of the invention, which is defined by the appended claims and their equivalents.

Claims

1. A microcapsule capable of self-repairing for many times at room temperature is characterized in that: comprises a first microcapsule and a second microcapsule;

the capsule wall of the first microcapsule is urea resin, the capsule core is dipropyl thiopropyl ether borate methyl dimethoxy siloxane, a catalyst and an adhesion promoter, and the mass ratio of the dipropyl thiopropyl ether borate methyl dimethoxy siloxane to the catalyst to the adhesion promoter is 1: 0.005-0.015: 0.002 to 0.005; the catalyst is dibutyltin dilaurate, and the adhesion promoter is methacryloxypropyltriethoxysilane or bis [3- (trimethoxysilyl) propyl ] amine;

2. A preparation method of microcapsules capable of self-repairing for many times at room temperature is characterized by comprising the following steps:

one) preparation of reversible boronic ester bond siloxane coupling agents: reacting boric acid with 3-allyloxy-1, 2-propanediol and performing thiol-ene click chemical reaction to obtain dipropylthiopropylether borate methyldimethoxysiloxane;

3. The method for preparing the microcapsule capable of self-repairing repeatedly at room temperature according to claim 2, wherein the step one) of preparing the siloxane coupling agent with reversible borate bonds is as follows:

4. the method for preparing the microcapsule capable of self-repairing repeatedly at room temperature as claimed in claim 2, wherein the step one) of preparing the siloxane coupling agent with reversible borate bonds comprises the following steps:

1) mixing boric acid and a first solvent, adjusting the pH value to be about 9-11 by using KOH, adding 3-allyloxy-1, 2-propylene glycol, stirring and reacting for 4-8 h at the temperature of 20-40 ℃, stirring and evaporating at the temperature of 100-140 ℃ to remove the first solvent, and finally drying at the temperature of 100-140 ℃ in vacuum to obtain bis (allyloxy) methyl borate;

5. The method for preparing microcapsules capable of self-repairing repeatedly at room temperature according to claim 4, wherein the method comprises the following steps: the first solvent is deionized water, and the second solvent is chloroform or n-hexane.

6. The method for preparing microcapsules capable of self-repairing repeatedly at room temperature according to claim 4, wherein the method comprises the following steps: the mass ratio of the boric acid to the 3-allyloxy-1, 2-propanediol is 2: 8-9, wherein the mass ratio of the bis (allyloxy) methyl borate to the mercaptopropyl-methyldimethoxysilane to the 2-hydroxy-2-methyl propiophenone is 6: 7-8: 0.1 to 0.3.

7. The method for preparing microcapsules capable of self-repairing many times at room temperature according to claim 2, wherein the assembling and mixing of the microcapsules in the second step) comprises the following steps:

1) mixing an emulsifier, distilled water, urea, ammonium chloride and resorcinol, stirring uniformly, adding the dipropylthiopropylether borate methyl dimethoxysiloxane prepared in the step one), a catalyst dibutyltin dilaurate and a corresponding adhesion promoter, adjusting the pH to 3-4 by formic acid, adjusting the rotation speed to 500-2000 rpm, shearing and emulsifying for 5-20 min to adjust the size of the microcapsule, adding a defoaming agent n-octanol to remove surface bubbles, adding 37 wt% of formaldehyde solution, heating to 60 ℃ at the speed of 1 ℃/min, keeping the rotation speed for reaction for 1-3 h, adding 5 wt% -20 wt% of urea, keeping the rotation speed for heat preservation reaction for 2-4 h, performing centrifugal separation, washing with distilled water for multiple times, performing suction filtration, and drying in normal-temperature air for 24-48 h to obtain a first microcapsule;

8. The method for preparing microcapsules capable of self-repairing repeatedly at room temperature according to claim 7, wherein the method comprises the following steps: the emulsifier is sodium dodecyl benzene sulfonate, sodium dodecyl sulfate or OP-10, and the concentration of the emulsifier is 0.3-1.0 wt%.

9. The method for preparing microcapsules capable of self-repairing repeatedly at room temperature according to claim 7, wherein the method comprises the following steps: the mass ratio of the urea to the ammonium chloride to the resorcinol to the 37 wt% formaldehyde solution is 1: 0.1: 0.1: 3 to 5.