KR20220120952A - Self healing microcapsules with multilayer shell structure and the method for manufacturing the same - Google Patents

Abstract

In the present specification, provided is a self-healing microcapsule with a core-shell structure comprising: a core including a self-healing polymer resin; and a first shell including a polymer of formaldehyde (F) and urea (U). When a capsule is destroyed by stimulation such as an external force or electric force (electric tree), the self-healing microcapsule can heal a damaged area by chemical bonding between an internal core material and a composition of an outer layer.

Description

Self-healing microcapsules having a multi-layered shell structure and manufacturing method thereof

Disclosed herein are self-healing microcapsules having a multi-layered shell structure and a method for manufacturing the same.

Microcapsule refers to micro-sized particles containing liquid, solid, and gaseous functional substances in the pores inside the capsule. Microcapsules are composed of a core material, which is a functional material contained in the capsule, and an outer wall (shell) surrounding the core material. It is used in various industries such as catalysts, pharmaceuticals, food industry, and insulators.

In particular, self-healing materials using microcapsules have been developed by American researchers. When the polymer matrix to which microcapsules are added is damaged by external force, the capsule wall material is broken around the damaged area and at the same time, the core material inside It flows out to the damaged area and crosslinks to restore the shape and function of the product.

Conventionally, a technique has been reported in which the inner core material contains two or more different microcapsules in the polymer matrix or is implemented by adding a catalyst for accelerating the crosslinking reaction, but this method occurs when the polymer matrix is destroyed by an external force. It has the disadvantage that the propagation of the cracks that are used has the disadvantage that the self-healing function must be destroyed only when all capsules containing different core materials are destroyed. In addition, according to the degree of the damaged microcapsules, the self-recovery efficiency is lowered at the same time.

When these microcapsules are introduced into materials and products that can be destroyed by mechanical or electrical shock, the stability and durability of the product can be significantly improved. The insulation function of the high voltage cable junction box damaged by the same electrical energy can be restored, so it is possible to prevent blackout accidents in advance, and it is very useful in the electrical field in that it can develop a cable covering material with long-term durability against mechanical shock or friction. It is expected as a useful material technology.

In embodiments of the present invention, it is an object to provide a method for optimizing self-healing efficiency (performance) as a microcapsule having one or more layers of wall material and a self-healing system using the same.

In addition, in embodiments of the present invention, when the material is damaged by various external stimuli, it can be restored (healed) by itself, and the self-healing efficiency can be adjusted by the surrounding temperature and time. would like to provide

In one embodiment according to the present invention to achieve the above object, a core comprising a self-healing polymer resin; and a first shell including a polymer of urea (U) and formaldehyde (F); and a core-shell structure comprising, it provides a self-healing microcapsule.

In an embodiment, the shell structure has a plurality of layer structures, and may further include a second shell including a polymer of melamine (M), urea (U), and formaldehyde (F).

In one embodiment, the outermost surface of the shell structure may be functionalized with an amine group.

In one embodiment, the amine group may be functionalized through a physical bond or a chemical bond.

In one embodiment, the outermost portion of the shell structure may be chemically bonded to the self-healing polymer resin.

In one embodiment, the diameter of the self-healing microcapsules may be in the range of 80 to 500㎛.

In one embodiment, according to energy dispersive x-ray (EDX) analysis, the surface of the self-healing microcapsule may be functionalized with at least 10% amine groups.

In another embodiment according to the present invention, a UF microcapsule having a core-shell structure including a core including a self-healing polymer resin and a first shell including a polymer of urea (U) and formaldehyde (F) is formed to do; and forming a second shell including a polymer of melamine (M), urea (U), and formaldehyde (F) on the first shell to prepare UF / MUF; Containing, self-healing microcapsules A manufacturing method is provided.

In one embodiment, the step of functionalizing the outermost surface of the shell structure with an amine group; may further include.

The microcapsule having self-healing properties according to an embodiment of the present invention releases a self-healing material (core material) when the shell is destroyed, and at this time, it reacts with the reactive composition present in the outermost layer of the capsule to restore the damaged portion It can be cured to recover the physical properties of the raw material. Accordingly, it can be used as an additive for various composite materials requiring self-healing properties, particularly composite materials requiring release of a core material.

In addition, according to the embodiment of the present invention, it is possible to easily optimize a specific size and/or a core material release amount of the microcapsule. Therefore, it is possible to provide a microcapsule having a self-healing property having a size (especially nano size) and/or a core material release amount suitable for a specific situation by using the same.

In addition, the self-healing microcapsule according to the embodiment of the present invention can be very usefully used as an industrial material or a bonding reinforcement for various structures.

1 schematically shows a method for manufacturing a microcapsule with a UF single outer wall in one embodiment of the present invention.
2 shows the structural formula of a melamine-urea-formaldehyde polymer, which is a component of the outer wall in the microcapsule in one embodiment of the present invention.
3 schematically shows a method for functionalizing the surface of the second shell of UF/MUF microcapsules with amine groups in one embodiment of the present invention.
Figure 4 schematically shows the amine functionalization of the surface of the UF / MUF microcapsules through chemical bonding in one embodiment of the present invention.
5a shows the SEM-EDX analysis result of the surface of UF/MUF microcapsules functionalized with amines by stirring for 1 hour in one embodiment of the present invention.
5b shows the SEM-EDX analysis result of the surface of UF/MUF microcapsules functionalized with amines by stirring for 3 hours in one embodiment of the present invention.
5c shows the results of SEM-EDX analysis of the surface of UF/MUF microcapsules functionalized with amines by stirring for 18 hours in one embodiment of the present invention.
Figure 6 shows a color change photograph after heat treatment (130 ℃ 5 hours) of each UF capsule and UF / MUF capsule in one embodiment of the present invention.
7 shows thermogravimetric analysis (TGA) results of UF capsules and UF/MUF capsules in one embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in more detail.

The embodiments of the present invention disclosed in the text are illustrated for the purpose of explanation only, and the embodiments of the present invention may be embodied in various forms and should not be construed as being limited to the embodiments described in the text. .

The present invention can make various changes and can have various forms, and the embodiments are not intended to limit the present invention to a specific disclosed form, and all changes, equivalents or substitutes included in the spirit and scope of the present invention should be understood as including

The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It is to be understood that this does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof.

self-healing microcapsules

In one embodiment according to the present invention to achieve the above object, a core comprising a self-healing polymer resin; and a first shell including a polymer of urea (U) and formaldehyde (F); and a core-shell structure comprising, it provides a self-healing microcapsule.

In an exemplary embodiment, the self-healing polymer resin may be a cross-linkable polymeric material. For example, it may be one or more selected from the group consisting of an epoxy resin, PDMS, dicyclopentadiene, and linseed oil.

In an exemplary embodiment, the shell structure has a plurality of layer structures, and may further include a second shell including a polymer of melamine (M), urea (U), and formaldehyde (F). When the multilayer shell structure further includes the second shell, it may have excellent thermal stability. For example, since melamine has a ring structure and can be cross-linked in a three-dimensional form, thermal properties may be remarkably increased, and excellent mechanical properties may be obtained due to the double-walled form.

On the other hand, in order to increase the stability of microcapsules, a capsule having a thick wall material must be formed. In the existing in-situ microcapsule manufacturing method using an emulsion, in order to increase the thickness of the wall material, even if the amount or ratio of the wall material is increased compared to the core material, the wall material is not thickened, and rather a capsule is not formed. That is, since there is an optimal ratio of the core material and the wall material for the formation of microcapsules, it is impossible to manufacture highly stable microcapsules with a thick wall material by the conventional method.

In the embodiment according to the present invention, it is possible to stably form microcapsules having thick wall materials by using the multiple in-situ polymerization method, as well as introducing an inorganic material layer to the outer walls of the organic-inorganic composite multi-layered outer wall type having higher stability Microcapsules may be made available.

In an exemplary embodiment, the outermost surface of the shell structure may be functionalized with an amine group. Through such functionalization of the amine group, interaction with the matrix may occur, thereby reducing the incompatibility between the interfaces. In addition, when the core material of the microcapsule containing epoxy flows out due to external stress, the epoxy can be cured only if there is a separate amine solution. self-curing may be possible.

In an exemplary embodiment, according to energy dispersive x-ray (EDX) analysis, the surface of the self-healing microcapsule may be functionalized with at least 10% amine groups. Specifically, it may be functionalized with 20% or more or 10 to 30% amine groups. If the surface of the self-healing microcapsule is highly functionalized with amines, the reaction rate and curing rate with the inner core material may be increased. .

In an exemplary embodiment, the amine group may be functionalized through a physical bond or a chemical bond. The physical bonding may be coating a solution containing an amine group, and the chemical bonding may be selecting a monomer material containing an amine functional group and bonding a portion capable of bonding to the outer capsule wall with a monomer containing an amine functional group.

In an exemplary embodiment, the outermost portion of the shell structure may be chemically bonded to the self-healing polymer resin. Specifically, the self-healing polymer resin may be cured by reacting with the outermost shell of the shell structure, which may be advantageous compared to a conventional self-healing capsule including two or more different types as an inner core material for curing. In particular, the wall material is composed of a single-layer (one-layer) or more complex multi-layered outer wall structure, and the outermost layer may be chemically bonded to the microcapsule core. When the capsule is destroyed by receiving a chemical bond, the inner core material and the composition of the outer layer can restore the damaged area.

In an exemplary embodiment, the diameter of the self-healing microcapsules may be in the range of 80 to 500 μm. When the diameter of the self-healing microcapsule is less than 80 μm, the content of the self-healing polymer resin, which is a core material located in the capsule, becomes small, so it may be disadvantageous, for example, in an epoxy/amine reaction that is cured by reacting in an equimolar ratio, and the size of the above-mentioned range , self-healing may be possible even if the crack (damage) is several micrometers in size.

How to make self-healing microcapsules

In another embodiment according to the present invention, a UF microcapsule having a core-shell structure including a core including a self-healing polymer resin and a first shell including a polymer of urea (U) and formaldehyde (F) is formed to do; and forming a second shell including a polymer of melamine (M), urea (U), and formaldehyde (F) on the first shell to prepare UF / MUF; Containing, self-healing microcapsules A manufacturing method is provided.

First, UF microcapsules having a core-shell structure including a core including a self-healing polymer resin and a first shell including a polymer of urea (U) and formaldehyde (F) may be formed.

Specifically, referring to FIG. 1 , first, an aqueous-based micelle is formed using a surfactant having both a hydrophilic group and a hydrophobic group. When urea is added thereto, it binds to a hydrophilic group to form an initial membrane. When a hydrophobic self-healing polymer resin is added here, it penetrates into the micelles and forms a core due to its hydrophobic properties. Thereafter, a first shell may be formed by adding formaldehyde to form UF microcapsules.

Next, a second shell including a polymer of melamine (M), urea (U), and formaldehyde (F) may be formed on the first shell. For example, the MUF polymer may have the structural formula of FIG. 2 .

Next, the outermost surface of the shell structure may be functionalized with an amine group.

Example

Hereinafter, the configuration and effect of the present invention will be described in more detail by way of examples. However, these examples are provided for the purpose of illustration only to help the understanding of the present invention, and the scope and scope of the present invention are not limited by the following examples.

Example 1: Preparation of microcapsules with UF wall material

UF microcapsules were prepared in an oil in water system using in-situ polymerization. After dissolving urea, a precursor that forms the shell in the UF capsule, resorcinol, which strengthens the outer wall of the capsule, ammonium chloride, which serves as a buffer for pH changes, and ethylene maleic anhydride (EMA) to stabilize the core emulsion in distilled water. The pH was adjusted using sodium hydroxide and hydrochloric acid.

The core was placed in the prepared solution and stirred for 30 minutes to stably form the emulsion, then formaldehyde was added and stirred at 60 °C for 4 hours. Thereafter, fractionation was performed using distilled water to remove the residue, filtered, and dried for 24 hours to obtain final UF microcapsules.

Example 2: Preparation of microcapsules with UF/MUF wall material

MUF wall material to which melamine, urea, and formaldehyde were applied as wall material precursors in an oil in water system using in-situ polymerization was formed in the UF capsule of Example 1.

First, the first solution and the second solution were prepared separately. The first solution was prepared by putting melamine and formaldehyde in distilled water and reacting at 70° C. for 30 minutes to prepare M-F prepolymer, and the second solution was urea in distilled water. was dissolved and prepared by mixing SLS (sodium lauryl sulfate) solution as an emulsifier and PVA (poly vinyl alcohol) as an emulsion stabilizer. was carried out and prepared.

After the removal of by-products, the first water washing was performed with ethanol, followed by natural drying for one day, and the second water washing with acetone was air-dried for one day to finally obtain UF/MUF capsules.

Example 3: Chemical Amine Functionalization of UF/MUF

The shell of the UF/MUF microcapsule of Example 2 was amine-functionalized through chemical bonding. After preparing a 1 wt% 3-aminopropyltriethoxy silane (KH550) solution (in water), 5 g of the synthesized microcapsules are dispersed in the prepared solution. At this time, after adjusting the pH to 7, the reaction was stirred and reacted at 500 rpm at 80 ° C. for 1 to 18 hours. When the reaction is complete, it is washed with distilled water 3 to 4 times, and when the filter is filtered, it is further washed with ethanol (and acetone) and dried.

Example 4: Physical Amine Functionalization of UF/MUF

For the physical amine functionalization of the capsule synthesized in Example 2, an amine composition was coated on the capsule wall material using a wet dipping method (filtering method), and the coating amount of the capsule wall material was varied by controlling the concentration of the coating composition. .

Experimental Example 1: Analysis of surface properties through SEM-EDX

The amount of functionalization according to the amine functionalization reaction time was quantitatively evaluated by analyzing SEM-EDX of the samples with different stirring times in the chemically amine-functionalized UF/MUF of Example 3. For quantification, the ratio of si contained in 3-aminopropyltriethoxy silane (KH550) used for amine functionalization was confirmed.

5A to 5C show the results of SEM-EDX analysis of the surface of UF/MUF microcapsules functionalized with amines by stirring for 1 hour, 3 hours, and 18 hours, respectively, in one embodiment of the present invention. Here, in the case of UF/MUF microcapsules functionalized with amines by stirring for 3 hours, it can be seen that the si ratio is distributed at about 24% on the surface.

Experimental Example 2: Thermal stability analysis

1) First, the microcapsules of Examples 1 and 2 were heat-treated at 130° C. for about 5 hours. As a result, as shown in FIG. 6 , the UF/MUF microcapsules of Example 2 maintained the same color as before heat treatment, but the UF microcapsules of Example 1 were discolored after heat treatment.

2) Next, the thermal stability of the microcapsules of Examples 1 and 2 and the microcapsule samples obtained by heat-treating Example 2 at 130° C. for about 4 hours were analyzed for thermal stability through TGA. The results are shown in FIG. 7, and it can be seen that the UF/MUF microcapsules of Example 2 have much superior thermal stability compared to the UF microcapsules of Example 1, and the stability is improved even after heat treatment at 130° C. for about 4 hours. You can check to keep it.

The embodiments of the present invention described above should not be construed as limiting the technical spirit of the present invention. The protection scope of the present invention is limited only by the matters described in the claims, and those skilled in the art can improve and change the technical idea of the present invention in various forms. Accordingly, such improvements and modifications will fall within the protection scope of the present invention as long as they are apparent to those of ordinary skill in the art.

Claims (9)

a core comprising a self-healing polymer resin; and
A self-healing microcapsule having a core-shell structure comprising; a first shell comprising a polymer of urea (U) and formaldehyde (F). According to claim 1,
The shell structure has a plurality of layer structures, and a second shell comprising a polymer of melamine (M), urea (U), and formaldehyde (F); further comprising, self-healing microcapsules. According to claim 1,
The outermost surface of the shell structure is functionalized with an amine group, self-healing microcapsules. 4. The method of claim 3,
The amine group is functionalized through a physical bond or a chemical bond, self-healing microcapsules. According to claim 1,
The outermost portion of the shell structure is capable of chemical bonding with the self-healing polymer resin, self-healing microcapsules. According to claim 1,
The self-healing microcapsule has a diameter in the range of 80 to 500 μm. According to claim 1,
According to EDX (Energy dispersive x-ray) analysis, the surface of the self-healing microcapsule is functionalized with at least 10% amine groups, the self-healing microcapsule. Forming a UF microcapsule having a core-shell structure including a core including a self-healing polymer resin and a first shell including a polymer of urea (U) and formaldehyde (F); and
Preparing a UF/MUF by forming a second shell including a polymer of melamine (M), urea (U), and formaldehyde (F) on the first shell; Way. 9. The method of claim 8,
Further comprising; functionalizing the outermost surface of the shell structure with an amine group; self-healing microcapsule manufacturing method.

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