CN112516929A

CN112516929A - Microcapsule containing epoxy solution and preparation method thereof

Info

Publication number: CN112516929A
Application number: CN202011271902.0A
Authority: CN
Inventors: 张鹤; 肖楷彬
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2020-11-13
Filing date: 2020-11-13
Publication date: 2021-03-19
Anticipated expiration: 2040-11-13
Also published as: CN112516929B

Abstract

The invention discloses a microcapsule containing epoxy solution and a preparation method thereof, comprising the following steps: (1) continuously stirring or shaking the reaction solution I containing the shell-forming monomer A; the shell-forming monomer A is polyamine; (2) carrying out micro-dropletization treatment on a mixed solution containing an epoxy solution and a shell-forming monomer B, and enabling the micro-droplets to fall into a reaction solution I to form primary microcapsules; the shell-forming monomer B is a diisocyanate monomer/prepolymer; (3) heating the mixture obtained in the step (2) or the mixture of the nascent microcapsules and the reaction solution II obtained after the reaction solution of the mixture is replaced, reacting, and continuously stirring or shaking to obtain the nascent microcapsules; (4) and cleaning the primary microcapsule, and drying to obtain the finished microcapsule. The microcapsule has the advantages of extremely low impurity content, good drying and dispersion properties, stable quality, uniform, adjustable and controllable size, thin, uniform and compact capsule wall, good thermal stability and high core material content.

Description

Microcapsule containing epoxy solution and preparation method thereof

Technical Field

The invention belongs to the technical field of microencapsulation, and particularly relates to a method for preparing a microcapsule containing an epoxy solution.

Background

Microcapsules are tiny particles composed of a protective wall material and a functional core material protected by the wall material. The protection effect of the wall material can realize the isolation of the functional core material in the microcapsule from the external environment, and reduce the volatility of the core material, mask the smell, enhance the stability, protect the active ingredients, control the release and the like according to the actual requirements. The method for synthesizing the microcapsule with the specific function is a microencapsulation technology.

The epoxy resin refers to an organic compound having two or more epoxy groups in a molecule. The epoxy group has high activity, and can generate cross-linking reaction with various curing agents to form insoluble and infusible thermosetting high polymer. Because the epoxy resin has the advantages of wide formula selectivity, good mechanical property, strong adhesion, high chemical stability, excellent electrical property, convenient use and the like, the epoxy resin is widely applied to the fields of coatings, adhesives, electronic and electrical materials, engineering plastics, composite materials, building materials and the like.

In view of the wide application of epoxy resin, when the epoxy resin is encapsulated and protected by using microencapsulation technology, the formed microcapsule containing the epoxy resin has more application potential in various fields. Most simply, the epoxy resin monomer wrapped by the microencapsulation technology can be premixed with other curing agents to form a single-component premixing system convenient to use, so that the trouble of the original double-component system in the links of storage, transportation, on-site mixing, construction and the like is avoided. Meanwhile, the microcapsule-based premixing system can conveniently prepare the premixing resin sensitive to various external stimuli such as heat, mechanical force, light and the like through the design of the capsule wall, thereby realizing the controllable release under the external response and the curing of the premixing system. For example, by simple formulation calculations, a pre-applied glue for screw-hole fastening sealing can be formed using epoxy-containing microcapsules, amine-based curing agents and other fillers. The pre-applied glue can be conveniently applied to the surface of the bolt in advance and is broken due to the action of shearing force and extrusion force when being assembled with the screw hole, so that the chemical bonding of the bolt and the screw hole is realized, and the fastening degree, the fastening stability and the fastening tightness of the bolt are greatly improved.

The epoxy resin microcapsule is also widely applied to the self-repairing field. Since most of the currently developed explant type self-repairing systems take an epoxy resin matrix as a repairing object, the development of a homogeneous self-repairing system based on microencapsulated epoxy chemistry (namely, the epoxy resin matrix is repaired by using the epoxy chemistry) has extremely important practical significance. The synthesis and preparation of the high-quality epoxy resin-containing microcapsule can greatly promote the practical development of a homogeneous self-repairing system.

Because epoxy resin microcapsules have extremely wide potential application, researchers have successfully used different microencapsulation technologies to realize the encapsulation of epoxy resins, wherein the most widely used and mature microencapsulation technology is an emulsion method, namely epoxy resin solution is dispersed in aqueous solution under the action of shearing force to form stable emulsion, and then different technologies are adopted to form a capsule wall on the surface of stable micro-droplets, so that the encapsulation of epoxy resins is realized. The common shell-forming methods include an in-situ polymerization method (i.e., the polymer generated in the aqueous phase is precipitated on the interface of the epoxy resin micro-droplets) and an interfacial polymerization method (i.e., the shell-forming monomer in the aqueous phase and the shell-forming monomer in the epoxy resin micro-droplets diffuse to the interface and react to generate the polymer). However, the existing methods show certain limitations in encapsulating epoxy resins. Firstly, the prepared microcapsule containing epoxy resin has poor performance, and the problem that the microcapsule cannot be used due to the fact that core materials leak and are agglomerated in the processes of storage, transportation, use and the like due to the problems of microcapsule sealing performance, thermal stability and the like is caused. Particularly, when the microcapsule is small, the microcapsule is easy to agglomerate and block, and finally, the microcapsule with good dispersibility and free flow can not be obtained. Secondly, when the epoxy resin-containing microcapsules are prepared using the existing microencapsulation technology, impurities formed during the preparation process are difficult to separate from the microcapsules. On the one hand, the finally collected microcapsules contain certain impurities, so that the quality of the microcapsule product is reduced; on the other hand, the separation process is complex and time-consuming, so that part of the microcapsules are lost in the separation process, and the yield of the microcapsules is reduced.

Therefore, a need exists for a microcapsule with excellent comprehensive properties, such as good dispersibility, uniform and dense capsule wall, high core material content, low impurity content, good thermal stability, etc., through technical innovation of preparing a microcapsule containing an epoxy resin.

Disclosure of Invention

The invention aims to provide a novel method for preparing the microcapsule containing the epoxy solution, which can finish the microencapsulation of the epoxy solution and realize the preparation of the microcapsule containing the epoxy solution with good comprehensive performance.

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

a method for preparing microcapsules containing epoxy solution comprises the following steps:

(1) preparing a reaction solution I containing a shell-forming monomer A, and continuously stirring or shaking the reaction solution I; the shell-forming monomer A is polyamine;

(2) preparing a mixed solution of an epoxy solution and a shell-forming monomer B, carrying out micro-dropletization treatment on the mixed solution containing the epoxy solution, and enabling micro-droplets to fall into a reaction solution I to form primary microcapsules containing the epoxy solution, so as to obtain a mixture of the primary microcapsules and the reaction solution I; the shell-forming monomer B is a diisocyanate monomer/prepolymer;

(3) heating the mixture obtained in the step (2) or the mixture of the nascent microcapsules obtained after the reaction solution of the mixture is replaced and the reaction solution II for reaction, and continuously stirring or shaking to obtain the nascent microcapsules containing the epoxy solution;

(4) and cleaning the primary microcapsule containing the epoxy solution, and drying to obtain the finished microcapsule containing the epoxy solution.

Preferably, the reaction solution I and the reaction solution II are mixed by water, a surfactant and a shell-forming monomer A, which are the same or different; wherein the weight ratio of water, surfactant and shell-forming monomer A in each part of reaction solution is 50.0: 0.01-1.0: 0.5 to 25.0, more preferably 50.0: 0.05-0.5: 2.0 to 8.0.

Preferably, the shell-forming monomer A is any one or a mixture of more than two of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine with different molecular weights, polyether polyamine, aliphatic polyamine, polypropylene amine and aromatic polyamine.

Preferably, the surfactant is any one of an ionic surfactant and a nonionic surfactant or a mixed surfactant of two or more thereof capable of forming a stable oil-in-water emulsion.

Preferably, the reaction solution I in the step (1) is stirred by a mechanical stirrer at a speed of 80-300 r/min, or is stirred by a magnetic stirrer at a speed of 100-600 r/min, or is shaken by a shaking table at a speed of 50-200 r/min.

Preferably, the mixture in step (3) is stirred at a speed of 80-1000 r/min by using mechanical stirring, or is stirred at a speed of 200-1500 r/min by using a magnetic stirrer, or is shaken at a speed of 80-200 r/min by using a constant temperature water bath.

Preferably, the micro-droplet treatment in step (2) is performed by electrostatic spraying or high-pressure spraying.

Preferably, the temperature of the microdroplet treatment in step (2) is 20 ℃ to 60 ℃, more preferably 25 ℃ to 40 ℃.

Preferably, the reaction temperature in the step (3) is 60-100 ℃, more preferably 75-90 ℃, and the reaction time is 3-12 hours.

Preferably, the mass ratio of the epoxy solution to the diisocyanate monomer/prepolymer in the mixed solution in the step (2) is 70:30 to 97:3, and more preferably 85:15 to 97: 3.

Preferably, the epoxy solution consists of epoxy monomers diluted with a diluent.

Preferably, the epoxy monomer comprises any one or a mixture of more than two of glycidyl ether type epoxy resin monomers and glycidyl ester type epoxy resin monomers, wherein the glycidyl ether type epoxy resin comprises bisphenol A type epoxy resin, bisphenol F type epoxy resin, resorcinol type epoxy resin and hydroxymethyl bisphenol A type epoxy resin; the glycidyl ester type epoxy resin comprises diglycidyl phthalate, diglycidyl tetrahydrophthalate, diglycidyl hexahydrophthalate, diglycidyl 1, 2-epoxycyclohexane-4, 5-dicarboxylate and diglycidyl endomethyltetrahydrophthalate.

Preferably, the diisocyanate monomer/prepolymer comprises one or a mixture of two or more of hexamethylene diisocyanate, 4 '-dicyclohexylmethane diisocyanate, isophorone diisocyanate and toluene diisocyanate, or is a prepolymer which is miscible with epoxy solution and is formed by any one of hexamethylene diisocyanate, 4' -dicyclohexylmethane diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate or toluene diisocyanate.

Preferably, the diluent is a non-reactive diluent, a reactive diluent, or a mixture of any two or more thereof; wherein the non-reactive diluent comprises nonylphenol; the reactive diluent comprises any one or a mixture of more than two of n-butyl glycidyl ether, 2-ethylhexyl glycidyl ether, tert-butyl glycidyl ether, phenyl glycidyl ether, o-tolyl glycidyl ether, C12-C14 alkyl glycidyl ether, 1, 4-butanediol diglycidyl ether, polyethylene glycol diglycidyl ethers with different molecular weights and polypropylene glycol diglycidyl ethers with different molecular weights.

The method for replacing the reaction solution by the mixture in the step (3) comprises the following steps:

(31) standing the mixture of the nascent microcapsule containing the epoxy solution and the reaction solution I at room temperature for 2-20 minutes or centrifuging the mixture at a low speed of 100-300 r/min for 2-5 minutes to fully precipitate the nascent microcapsule;

(32) pouring out the supernatant in the mixture, and reserving the primary microcapsule;

(33) the reaction solution II was poured into the primary microcapsules described above.

The cleaning method in the step (4) can be a standing separation method or a suction filtration method.

Wherein, when the standing separation method is used, the specific process is as follows:

firstly, adding pure water into primary microcapsules, uniformly stirring the pure water, standing the microcapsules until the microcapsules are precipitated, removing supernatant, and repeatedly adding the pure water to wash the microcapsules for 3-6 times; and then, removing the clear supernatant, and putting the cleaned microcapsule into air or hot air until the moisture is completely volatilized to obtain a pure finished microcapsule.

When the suction filtration method is used, the specific process is as follows:

first, a buchner funnel holder (seal ring) for a buchner funnel was fixed to a filtration flask, and the filtration flask was connected to a vacuum pump with a vacuum tube (rubber tube). Next, a filter paper/filter cloth was placed in the buchner funnel, moistened with water and the vacuum pump was turned on, so that the filter paper/filter cloth was pressed against the buchner funnel bottom to prevent leakage. Subsequently, the mixture containing the as-made microcapsules was filtered by suction in a buchner funnel lined with filter paper/filter cloth. When the liquid in the mixture is quickly filtered, clear water is added to continue the suction filtration. Repeating the cleaning process of adding clear water and performing suction filtration for 3-6 times, and completely drying the mixture; finally, the cleaned microcapsule is put in air or hot air until the moisture is completely volatilized, and then the pure finished microcapsule is obtained.

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

(1) the method provided by the invention provides a method for preparing the microcapsule containing the epoxy solution, and the synthesized microcapsule containing the epoxy solution is dry, good in dispersity, stable in quality, uniform in size, adjustable and controllable, extremely low in impurity content, thin, uniform and compact in capsule wall, high in core material content and good in thermal stability.

(2) Compared with the traditional microencapsulation method which needs to form stable emulsion of epoxy solution firstly, the method has obvious advantages when coating the epoxy solution with higher viscosity, can expand the types of epoxy monomers which can be coated, and further expands the application range of the microcapsule containing the epoxy solution.

(3) The invention can prepare very small microcapsules by adjusting the spraying speed and/or the spraying voltage, and can expand the application field of the microcapsules containing the epoxy solution.

(4) The invention can rapidly produce the microcapsules containing epoxy solution with different components in large batch by improving the spray head and combining a plurality of spray heads (channels), thereby improving the production efficiency of enterprises and reducing the production cost of the microcapsules containing epoxy solution.

Drawings

FIG. 1 is a schematic view of an apparatus for preparing microcapsules containing an epoxy solution using electrostatic spraying as a micro-droplet formation apparatus and a microencapsulation principle; epoxy solution 1, shaking table 2 and metal plate 3. Wherein the epoxy solution mixed with the shell-forming monomer B is sprayed from a needle point in the form of independent micro-droplets under the action of an electrostatic field and falls into the reaction solution, the shell-forming monomer B in the micro-droplets and the shell-forming monomer A in the reaction solution I generate rapid interfacial polymerization reaction at the moment when the micro-droplets fall into the reaction solution, and the micro-droplets are wrapped by a macromolecular membrane formed at the interface of the micro-droplets and the reaction solution to form primary microcapsules. The nascent microcapsules in the reaction solution react for a certain time at a certain temperature to further thicken the capsule wall, and the final microcapsules with good performance are formed.

FIG. 2 is a schematic diagram of the construction of an apparatus for preparing microcapsules containing an epoxy solution using a high pressure spray as a micro-dripping apparatus according to the present invention; epoxy solution 1, reaction solution 4, high-pressure tank 5 and atomizing nozzle 6. Compared to fig. 1, the manner in which the micro-droplets are generated is substantially the same. The epoxy solution mixed with the shell-forming monomer B is stored in a high-pressure tank, when high-pressure gas enters the high-pressure tank to force the mixed solution to pass through an atomizing nozzle, the mixed solution is sprayed down from the nozzle in the form of independent micro-droplets and falls into the reaction solution to form primary microcapsules.

FIGS. 3(a-c) are external views of microcapsules containing epoxy solutions of about 200 microns, 100 microns, and 50 microns in size prepared in examples 2, 3, and 4 of the present invention after heat treatment in a vacuum oven at 100 deg.C for 4 hours. The heat stability and the capsule wall tightness of the microcapsules with different sizes are very good, and the microcapsules after heat treatment are well dispersed without the phenomena of leakage, agglomeration, caking and the like.

Fig. 4 is a Scanning Electron Microscope (SEM) image of microcapsules containing an epoxy solution prepared using the method of the present invention. Wherein, the graphs (a-c) are the global graphs of the microcapsules with the particle sizes of about 200 microns, 100 microns and 50 microns prepared in the examples 2, 3 and 4 respectively, and the microcapsules with uniform particle sizes and good dispersibility can be seen, and the microcapsules do not contain any impurities basically; FIG. d is a cross-sectional view of the wall of the microcapsule prepared in example 2, and it can be seen that the microcapsule has a perfect shell-core structure, the wall is thin and uniform, about 2 μm, and the wall is very dense.

FIG. 5 is a schematic diagram showing the preparation of microcapsules containing an amine-based curing agent used in example 22 of the present invention. The amine curing agent and the co-flow phase solution are respectively injected into the reaction solution through a T1 pipe and a T2 pipe of the T-shaped knot, and when the amine curing agent micro-droplets formed in the T-shaped knot flow into the reaction solution, the amine molecules on the surface of the micro-droplets and the shell-forming monomer (4, 4' -dicyclohexylmethane diisocyanate, HMDI) in the reaction solution undergo a rapid interfacial polymerization reaction, so that the micro-droplets are wrapped. The mixture is further heated to thicken the microcapsule wall to form the final microcapsules containing the amine-based curing agent.

FIG. 6(a) is the geometry of a Tapered Double Cantilever Beam (TDCB) sample for self-healing efficiency characterization in example 22 of the present invention, and FIG. 6(b) is a typical load-displacement curve before healing and after 48 hours of healing at room temperature (about 25 deg.C.) using the TDCB sample. FIG. 6(b) shows that the microcapsules containing the epoxy solution prepared by the method of the present invention can prepare self-repairing epoxy resin with self-repairing efficiency over 100%.

Detailed Description

The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.

Example 1

The embodiment discloses a preparation method of a microcapsule containing an epoxy solution, which comprises the following steps:

(1) preparing a reaction solution I, and continuously shaking the reaction solution I by using a shaking table in a room temperature environment;

the reaction solution I is formed by mixing water, sodium dodecyl sulfate serving as an ionic surfactant and diethylenetriamine serving as a shell-forming monomer A, wherein the weight ratio of the water to the sodium dodecyl sulfate to the diethylenetriamine in the reaction solution I is 50.0: 0.50: 6.0. 50.0mL of the prepared reaction solution I was placed in a room temperature environment and shaken by a shaker at a speed of 100 r/min.

(2) Preparing a mixed solution of an epoxy solution and a shell-forming monomer B, carrying out micro-droplet treatment on the mixed solution containing the epoxy solution by using an electrostatic spraying device at room temperature, and enabling micro-droplets to fall into a reaction solution I to form primary microcapsules containing the epoxy solution;

the mixed solution consists of an epoxy solution and a shell-forming monomer B, wherein the epoxy solution is formed by mixing 10 parts of n-butyl glycidyl ether serving as a reactive diluent and 90 parts of bisphenol F diglycidyl ether serving as an epoxy monomer, and the mixed solution is formed by mixing 90 parts of the epoxy solution and 10 parts of 4, 4' -dicyclohexylmethane diisocyanate serving as the shell-forming monomer B. The prepared mixed solution is subjected to micro-dropletization at room temperature by an electrostatic spraying device (figure 1) at a spraying speed of 10.0mL/h and under a voltage of 10.0kV, and the micro-droplets fall into the reaction solution I to form primary microcapsules containing the epoxy solution.

The mixed solution of the epoxy solution and the shell-forming monomer B (4, 4' -dicyclohexylmethane diisocyanate) is dripped into micro-droplets by micro-droplets and then falls into a reaction solution I, the shell-forming monomer B on the surface of the micro-droplets rapidly reacts with the shell-forming monomer A (diethylenetriamine) in the reaction solution I to form a polyurea thin-wall layer so as to wrap the epoxy solution in the polyurea thin-wall layer, and the primary microcapsule containing the epoxy solution is formed.

(3) The mixture of the primary microcapsules containing epoxy solution and reaction solution I obtained was heated to 90 ℃ and the mixture was stirred continuously at a speed of 200r/min using a mechanical stirrer and after 7 hours primary microcapsules containing epoxy solution were obtained.

When the mixture of the primary microcapsule containing the epoxy solution and the reaction solution I is heated, the shell-forming monomer A (diethylenetriamine) in the reaction solution I further diffuses through the polyurea thin-wall layer formed by the primary microcapsule and reacts with the shell-forming monomer B (4, 4' -dicyclohexylmethane diisocyanate) in the primary microcapsule in or near the inner wall of the thin-wall layer to continuously form polyurea, so that the capsule wall of the primary microcapsule is gradually thickened, and the primary microcapsule containing the epoxy solution is formed.

(4) And (3) washing the primary microcapsule containing the epoxy solution by using water, and drying to obtain the finished microcapsule containing the epoxy solution.

Firstly, adding pure water into primary microcapsules, uniformly stirring the pure water, standing the microcapsules until the microcapsules are precipitated, removing supernatant, and repeatedly adding the pure water to wash the microcapsules for 3-6 times; and removing the clear supernatant, and putting the cleaned microcapsule in air until the water is completely volatilized to obtain the pure finished microcapsule.

Example 2

The present embodiment is different from embodiment 1 in that: after forming primary microcapsules containing an epoxy solution in the reaction solution I, the mixture of the primary microcapsules and the reaction solution I is allowed to stand and primary microcapsules are separated, and then the reaction solution II is added to the primary microcapsules to carry out the next reaction. The method comprises the following specific steps:

(1) preparing a reaction solution I and a reaction solution II, and continuously shaking the reaction solution I by using a shaking table in a room temperature environment;

the reaction solution I is formed by mixing water, sodium dodecyl sulfate serving as an ionic surfactant and diethylenetriamine serving as a shell-forming monomer A, wherein the weight ratio of the water to the sodium dodecyl sulfate to the diethylenetriamine in each part of the reaction solution I is 50.0: 0.50: 6.0; the reaction solution II is formed by mixing water, sodium dodecyl sulfate serving as a surfactant and diethylenetriamine serving as a shell-forming monomer A, wherein the weight ratio of the water to the sodium dodecyl sulfate to the diethylenetriamine in each part of the reaction solution I is 50: 0.50: 3.0. 50.0mL of the prepared reaction solution I was placed in a room temperature environment and shaken by a shaker at a speed of 100 r/min.

(2) Preparing a mixed solution of an epoxy solution and a shell-forming monomer B, carrying out micro-dropletization treatment on the mixed solution containing the epoxy solution at the room temperature environment by using an electrostatic spraying device at the spraying rate of 10.0mL/h and under the voltage of 10.0kV, and enabling the micro-droplets to fall into a reaction solution I to form primary microcapsules containing the epoxy solution;

this step is the same as step (2) in example 1.

(3) Standing a mixture of the nascent microcapsule containing the epoxy solution and the reaction solution I, separating out the nascent microcapsule containing the epoxy solution, and then adding the reaction solution II into the nascent microcapsule;

the mode for replacing the reaction solution by the primary microcapsule containing the epoxy solution is as follows:

(31) standing the mixture of the nascent microcapsule containing the epoxy solution and the reaction solution I at room temperature for 5.0 minutes to fully precipitate the nascent microcapsule;

(33) 50.0mL of reaction solution II was poured into the primary microcapsules described above.

(4) Heating the mixture of the primary microcapsule containing the epoxy solution and the reaction solution II to 90 ℃, continuously stirring the mixture at the speed of 200r/min by using mechanical stirring, and obtaining the primary microcapsule containing the epoxy solution after 7 hours;

this step is the same as step (3) in example 1.

(5) And (3) washing the primary microcapsule containing the epoxy solution by using water, and drying to obtain the finished microcapsule containing the epoxy solution.

This step is the same as step (4) in example 1.

This example uses different reaction solutions at different stages of the preparation of the epoxy solution-containing microcapsules compared to example 1, allowing greater flexibility in the microencapsulation process and in the performance control of the finally prepared microcapsules.

FIG. 3(a) is a view showing the appearance of the microcapsule prepared in this example after being treated in vacuum at 100 ℃ for 4 hours; fig. 4(a) shows a scanning electron microscope picture of the microcapsule prepared in this example; fig. 4(d) shows a scanning electron microscope picture of a wall section of the microcapsule prepared in this example. The microcapsule has a size of about 200 microns, a perfect shell-core structure, and microcapsule core liquid accounting for about 85% of the mass of the microcapsule. The microcapsule has good dispersibility, good sealing performance and good thermal stability.

Example 3

The present embodiment is different from embodiment 2 only in that:

when the electrostatic spraying device is used for carrying out micro-droplet processing in the step (2), the spraying speed of the epoxy solution is changed from 10.0mL/h to 5.0mL/h, so that more tiny micro-droplets are generated, and therefore more tiny microcapsules are prepared.

FIG. 3(b) is a view showing the appearance of the microcapsule prepared in this example after being treated in vacuum at 100 ℃ for 4 hours; fig. 4(b) shows a scanning electron microscope picture of the microcapsule prepared in this example. The microcapsules are about 100 microns in size. The particle size of the microcapsules containing an epoxy solution prepared using the method of the present invention can be controlled by the injection rate.

Example 4

The present embodiment is different from embodiment 3 only in that:

when the electrostatic spraying device is used for carrying out micro-droplet processing in the step (2), the voltage of the device is changed from 10.0kV to 17.0kV so as to generate more tiny micro-droplets and prepare more tiny microcapsules.

FIG. 3(c) is a view showing the appearance of the microcapsule prepared in this example after being treated in vacuum at 100 ℃ for 4 hours; fig. 4(c) shows a scanning electron microscope picture of the microcapsule prepared in this example. The microcapsules are about 50 microns in size. The particle size of the microcapsules containing an epoxy solution prepared by the method of the present invention can also be controlled by the magnitude of the voltage.

Example 5

The present embodiment is different from embodiment 2 only in that:

when the electrostatic spraying device is used for carrying out micro-dripping treatment on the epoxy solution in the step (2), the epoxy solution is subjected to micro-dripping by using two sets of injection devices simultaneously so as to improve the micro-dripping efficiency of the epoxy solution and improve the preparation efficiency of the microcapsule containing the epoxy solution.

Example 6

The present embodiment is different from embodiment 2 only in that:

and (3) replacing the room temperature environment in the steps (1) and (2) with an environment of 40 ℃ to reduce the viscosity of the epoxy solution and facilitate the micro-dripping of the epoxy solution.

Example 7

The present embodiment is different from embodiment 2 only in that:

the micro-dripping of the mixed solution in the step (2) is completed by an electrostatic spraying device at a spraying rate of 10.0mL/h and a voltage of 10.0kV, and is replaced by a high-pressure spraying device shown in FIG. 2 at an air pressure of about 3.0MPa, so that the micro-dripping efficiency is further improved, and the preparation efficiency of the microcapsule containing the epoxy solution is improved. The content of impurities, dispersibility, appearance, wall structure, thermal stability, core content, and the like of the prepared microcapsule containing an epoxy solution were the same as those of the microcapsule prepared in example 2.

Example 8

The present embodiment is different from embodiment 2 only in that:

the surfactant in the reaction solution I was replaced by ionic sodium dodecylsulfate to nonionic polyethylene-maleic anhydride copolymer, and the content thereof was the same as that in example 2.

This example shows that the process of the present invention for preparing microcapsules containing an epoxy solution has a great flexibility in the choice of surfactant.

Example 9

The present embodiment is different from embodiment 2 only in that:

the weight ratio of water, sodium dodecyl sulfate and diethylenetriamine in the reaction solution I is 50.0: 0.50: 4.0.

the weight ratio of water, sodium dodecyl sulfate and diethylenetriamine in the reaction solution II is 50.0: 0.50: 2.0.

example 10

The present embodiment is different from embodiment 2 only in that:

the shell-forming monomer A in the reaction solution I was replaced by tetraethylenepentamine from diethylenetriamine, and the content thereof was the same as that in example 2.

Example 11

The present embodiment is different from embodiment 2 only in that:

the shell-forming monomer A in the reaction solution II was replaced with tetraethylenepentamine from diethylenetriamine, and its content was the same as that in example 2.

Example 12

The present embodiment is different from embodiment 2 only in that:

Examples 10 to 12 show that the components of reaction solution I and reaction solution II can be different, which provides greater flexibility in the use of the present invention for the preparation of microcapsules containing epoxy solutions, and that different reaction solution components can be selected according to the actual requirements.

Example 13

The present embodiment is different from embodiment 2 only in that:

the shell-forming monomer B in the mixed solution in the step (2) was replaced by isophorone diisocyanate from 4, 4' -dicyclohexylmethane diisocyanate, and the content thereof was the same as that in example 2.

This example shows that different diisocyanate monomers can be used as the shell-forming monomer B in the epoxy solution, and that the present invention provides greater flexibility in the preparation of microcapsules containing epoxy solutions, and that different diisocyanate monomers/prepolymers can be used depending on the actual requirements.

Example 14

The present embodiment is different from embodiment 2 only in that:

the proportion of the epoxy solution to the shell-forming monomer B in the mixed solution in the step (2) is 90 parts: 10 parts are changed to 95 parts: 5 parts of the raw materials.

The microcapsule containing the epoxy solution prepared in this example has the same impurity content, dispersibility, appearance, wall structure, thermal stability, etc. as those of the microcapsule prepared in example 2, but the core liquid content of the microcapsule is high, about 90% of the microcapsule mass.

Example 15

The present embodiment is different from embodiment 2 only in that:

the epoxy solution in the mixed solution in the step (2) is composed of 90 parts of bisphenol F diglycidyl ether and 10 parts of polypropylene glycol diglycidyl ether with molecular weight of 380.

Example 16

The present embodiment is different from embodiment 2 only in that:

and (3) the epoxy solution in the mixed solution in the step (2) consists of 90 parts of bisphenol F diglycidyl ether and 10 parts of non-reactive diluent nonyl phenol.

Example 17

The present embodiment is different from embodiment 2 only in that:

and (3) the epoxy solution in the mixed solution in the step (2) consists of 90 parts of tetrahydrophthalic acid diglycidyl ester and 10 parts of n-butyl glycidyl ether.

Examples 14-17 show that the present invention can prepare microcapsules containing different epoxy solutions, and the types of epoxy monomers, the types of diluents and the ratio of epoxy monomers to diluents in the epoxy solutions can be flexibly selected and adjusted according to actual needs, thus providing greater flexibility.

Example 18

The present embodiment is different from embodiment 2 only in that:

in the step (4), the heating at 90 ℃ was changed from 7 hours to 5 hours at 90 ℃.

Example 19

The present embodiment is different from embodiment 2 only in that:

in the step (4), the heating at 90 ℃ for 7 hours was changed to the heating at 80 ℃ for 7 hours.

Example 20

The present embodiment is different from embodiment 2 only in that:

the speed of mechanical stirring in the step (4) is changed from 200r/min to 800 r/min.

Example 21

The present embodiment is different from embodiment 2 only in that:

the mixing mode in the step (4) is changed from mechanical stirring to mixing in a constant temperature water bath box at the speed of 100 r/min.

Examples 8 to 21 all prepared microcapsules containing epoxy solution with low impurity content, good dispersibility, perfect shell-core structure, uniform and dense capsule wall thickness, excellent thermal stability, and high core material content. The above examples show very good flexibility of the process of the invention in the preparation of microcapsules containing epoxy solutions, which can be easily adjusted to different needs.

Example 22

This example illustrates the preparation of two-component self-healing epoxy resin using the microcapsules containing epoxy solution prepared in example 2 of the present invention and using microcapsules containing amine curing agent.

The microcapsules containing the epoxy solution used were prepared according to example 2.

The microcapsule containing the amine curing agent is prepared by the following specific steps:

a mixed amine curing agent comprising 25 parts of tetraethylenepentamine and 75 parts of polyether polyamine (trade name JEFFAMINE T403) was prepared, a cocurrent phase solution comprising n-hexadecane containing 1.0 wt% of a surfactant Arlacel P135 was prepared, and a reaction solution comprising 50.0mL of decalin as a solvent, 6.0g of a shell-forming monomer, 4' -dicyclohexylmethane diisocyanate, 0.50g of a surfactant Arlacel P135, and 0.50g of a catalyst triethylenediamine was prepared. As shown in fig. 5, the prepared mixed amine curing agent and the co-current phase solution were filled into syringes, and injected into the reaction solution at a rate of 0.01mL/min and 0.5mL/min by syringe pumps through T1 tube and T2 tube of the T-junction, respectively, to form nascent microcapsules containing the mixed amine curing agent. Wherein the T1 tube of the T-shaped knot is a Teflon tube with inner and outer diameters of 0.012 inch and 0.03 inch respectively, and the T2 tube is a Teflon tube with inner and outer diameters of 0.022 inch and 0.042 inch respectively. During the injection, the reaction solution was stirred gently continuously at 200rpm using a three-bladed propeller with a diameter of 60 mm. After the addition of 12.0mL of co-flow solution and the corresponding volume of mixed amine curing agent, the injection process was terminated and the mixture was allowed to react sequentially at 40 ℃ for 1 hour, 50 ℃ for 2 hours, and 60 ℃ for 2 hours with constant stirring to form the final microcapsules containing amine curing agent. And finally, rinsing the microcapsule 6-8 times by using pure cyclohexane, and drying for 5-10 minutes at room temperature to obtain the finished microcapsule containing the amine curing agent and with the diameter of about 200 micrometers.

0.5g of microcapsules containing the epoxy solution and 0.5g of microcapsules containing an amine-based curing agent were added to 9.0g of a premixed epoxy resin (Epolam 5015: Harden 5015 ═ 100: 30), stirred well and evacuated to eliminate bubbles. The mixture was poured into a mold of a TDCB sample and cured at room temperature and 35 ℃ for 24 hours each to obtain a TDCB sample.

The TDCB sample is snapped using a universal sample applicator, then repaired at room temperature (about 25 deg.C) for 48 hours and again snapped using a universal sample applicator. The load peak value of the load-displacement curve after the repair is compared with the load peak value of the load-displacement curve before the repair, namely the self-repairing efficiency.

FIG. 6(a) shows the geometry of a TDCB sample; fig. 6(b) shows load-displacement curves before and after the self-healing samples prepared in this example were repaired. The self-healing efficiency of this embodiment is about 110%.

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 method for preparing microcapsules containing epoxy solution is characterized by comprising the following steps:

(3) heating the mixture obtained in the step (2) or the mixture of the nascent microcapsules and the reaction solution II obtained after the reaction solution of the mixture is replaced, reacting, and continuously stirring or shaking to obtain the nascent microcapsules containing the epoxy solution;

2. The method of claim 1, wherein: the reaction solution I and the reaction solution II are formed by mixing water, a surfactant and a shell-forming monomer A in the same or different modes; wherein the weight ratio of water, surfactant and shell-forming monomer A in each part of reaction solution is 50.0: 0.01-1.0: 0.5 to 25.0, preferably 50.0: 0.05-0.5: 2.0 to 8.0.

3. The method of claim 2, wherein: the shell-forming monomer A is any one or a mixture of more than two of ethylenediamine, diethylenetriamine, triethylene tetramine, tetraethylenepentamine, polyethyleneimine with different molecular weights, polyether polyamine, aliphatic polyamine, polypropylene amine and aromatic polyamine.

4. The method of claim 3, wherein: the surfactant is one or more of ionic surfactant and nonionic surfactant capable of forming stable oil-in-water emulsion.

5. The method of claim 1, wherein: stirring the reaction solution I in the step (1) at a speed of 80-300 r/min by using a mechanical stirrer, or stirring the reaction solution I at a speed of 100-600 r/min by using a magnetic stirrer, or shaking the reaction solution I at a speed of 50-200 r/min by using a shaking table;

and (3) mechanically stirring the mixture in the step (3) at a speed of 80-1000 r/min, or stirring the mixture by using a magnetic stirrer at a speed of 200-1500 r/min, or shaking the mixture by using a constant-temperature water bath box at a speed of 80-200 r/min.

6. The method according to any one of claims 1 to 5, wherein: and (3) completing the micro-droplet treatment in the step (2) by using an electrostatic spraying or high-pressure spraying device.

7. The method of claim 6, wherein: the temperature of the micro-dropletization treatment in the step (2) is 20-60 ℃, preferably 25-40 ℃;

the reaction temperature in the step (3) is 60-100 ℃, preferably 75-90 ℃, and the reaction time is 3-12 hours.

8. The method according to any one of claims 1 to 5, wherein: the mass ratio of the epoxy solution to the diisocyanate monomer/prepolymer in the mixed solution in the step (2) is 70: 30-97: 3, preferably 85: 15-95: 5.

9. The method of claim 8, wherein: the epoxy solution is composed of epoxy monomers diluted by a diluent;

the epoxy monomer comprises any one or a mixture of more than two of glycidyl ether type epoxy resin monomers and glycidyl ester type epoxy resin monomers, wherein the glycidyl ether type epoxy resin comprises bisphenol A type epoxy resin, bisphenol F type epoxy resin, resorcinol type epoxy resin and hydroxymethyl bisphenol A type epoxy resin; the glycidyl ester type epoxy resin comprises diglycidyl phthalate, diglycidyl tetrahydrophthalate, diglycidyl hexahydrophthalate, diglycidyl 1, 2-epoxycyclohexane-4, 5-dicarboxylate and diglycidyl endomethyltetrahydrophthalate;

the diisocyanate monomer/prepolymer comprises one or a mixture of more than two of hexamethylene diisocyanate, 4 '-dicyclohexylmethane diisocyanate, isophorone diisocyanate and toluene diisocyanate, or a prepolymer which is generated by any one of hexamethylene diisocyanate, 4' -dicyclohexylmethane diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate or toluene diisocyanate and can be mutually soluble with epoxy solution;

the diluent is a non-reactive diluent, a reactive diluent or a mixture of any two or more of the non-reactive diluent and the reactive diluent; wherein the non-reactive diluent comprises nonylphenol; the reactive diluent comprises any one or a mixture of more than two of n-butyl glycidyl ether, 2-ethylhexyl glycidyl ether, tert-butyl glycidyl ether, phenyl glycidyl ether, o-tolyl glycidyl ether, C12-C14 alkyl glycidyl ether, 1, 4-butanediol diglycidyl ether, polyethylene glycol diglycidyl ethers with different molecular weights and polypropylene glycol diglycidyl ethers with different molecular weights.

10. Microcapsules containing an epoxy solution prepared by the process of any one of claims 1 to 9.