Epoxy composite microsphere with core-shell structure as well as preparation method and application of epoxy composite microsphere

Abstract

The invention discloses an epoxy composite microsphere with a core-shell structure, the composite microsphere comprises a shell layer and an inner core, the shell layer is composed of modified nano SiO2, the mass fraction of the shell layer is 10-30% of the total mass of the composite microsphere, and the thickness of the shell layer is 0.8-1.2 [mu] m; the inner core is composed of an epoxy resin matrix and an organic dye, and the diameter of the inner core is 10-20 [mu] m; the mass of the organic dye accounts for 1-5% of the mass of the epoxy resin matrix, the modified nano SiO2 group is obtained through modification by using a surface modifier, and the surface modifier is any one of dodecyl trimethoxy silane, mercaptopropyl trimethoxy silane or dimethyldichlorosilane. According to the structure disclosed by the invention, through encapsulation of a core-shell structure, a high-dispersity and high-stability platform is provided for the organic dye, and the application prospect of the organic dye in water-based paint is effectively improved.

Description

Technical Field

[0001] The present invention relates to a preparation technology of polymer composite microspheres, in particular to epoxy composite microspheres with a core-shell structure and a preparation method thereof. Background Art

[0002] As material performance requirements increase, the demand for functional coatings and optical materials with improved UV shielding, light stability, and color retention continues to grow. Organic dyes are widely used in the industrial market due to their superior color richness and high color rendering, accounting for approximately a quarter of total pigment production. However, organic dyes generally suffer from poor light stability and are easily photodegraded by UV light and oxygen, resulting in color fading and performance degradation in the coating.

[0003] To reduce direct exposure of organic dyes to light and oxygen, core-shell encapsulation strategies are an effective way to improve their photostability. Polymers provide a suitable matrix for organic dyes, maintaining good dispersion. The dense shell formed by inorganic nanoparticles effectively blocks oxygen diffusion, providing a stable environment for the core dye.

[0004] Traditionally, the core-shell structure of inorganic nanoparticle-coated polymer microspheres is prepared by first preparing the polymer microspheres and then coating them with an inorganic shell. This two-step preparation method is complex and inefficient, making it unsuitable for large-scale industrial production.

[0005] The Pickering emulsion method is an emulsion system stabilized by solid particles, with good interfacial stability and controllable particle size. By selectively adsorbing inorganic nanoparticles at the oil-water interface, self-assembly of the microsphere core and shell can be effectively achieved. For example, patent application number CN107497378A discloses a one-step method for preparing polyvinyl alcohol / silica composite microspheres with a core-shell structure. The Pickering emulsion method is used to achieve nucleation of silica colloidal particles at the droplet interface, and the core polyvinyl alcohol is coated to obtain a core-shell composite microsphere.

[0006] CN114874642A provides an oxygen-deficient microsphere with a UV-shielding shell structure. The oxygen-deficient microsphere consists of a shell and a core. The shell is composed of SiO2 and a UV-shielding functional material in a mass ratio of 1:(0.05-0.1), with a shell thickness of 10-30 nm. The core is composed of a resin matrix, an oxygen-deficient functional filler, and dye molecules, with a core diameter of 200-500 μm. The mass of the dye molecules is 0.1-0.5% of the mass of the resin matrix, and the mass of the oxygen-deficient functional filler is 0.1-1% of the mass of the resin matrix. This structure, through the construction of the oxygen-deficient shell and the combination of the oxygen-deficient functional filler in the core, provides an oxygen-deficient environment for organic dyes to shield against UV radiation, effectively ensuring the photostability of the organic dyes during application.

[0007] Although significant progress has been made in the preparation technology of core-shell microspheres, the following technical bottlenecks still exist in practical applications: (1) the uniformity and thickness of the shell layer are difficult to control in terms of the stability and shielding properties of the microspheres; (2) the dispersion state and aggregation effect of the dye in the core directly affect the color development and photostability of the composite microspheres; (3) the stability of the organic dye cannot be affected during the synthesis of the composite microspheres. Therefore, there is an urgent need for a core-shell microsphere encapsulated organic dye that can be prepared in an integrated manner with good oxygen barrier properties, structural stability, and good dispersion to address the limitations of organic dyes in applications. Summary of the Invention

[0008] Purpose of the invention: To address the problems that organic dyes are prone to photooxidation / photoaging during application and are difficult to disperse in water-based coatings, the present invention provides a core-shell epoxy composite microsphere and its preparation method and application. The shell layer encapsulates and protects the organic dye, significantly improving its photostability and dispersibility.

[0009] In order to solve the above technical problems, the present invention discloses a core-shell structured epoxy composite microsphere, which includes a shell layer and an inner core. The shell layer is composed of modified nano-SiO2, the mass fraction of which accounts for 10 to 30% of the total mass of the composite microsphere, and the shell layer thickness is 0.8 to 1.2 μm; the inner core is composed of an epoxy resin matrix and an organic dye, and the inner core diameter is 10 to 20 μm; the mass of the organic dye accounts for 1 to 5% of the mass of the epoxy resin matrix, and the modified nano-SiO2 group is obtained by modifying with a surface modifier, and the surface modifier is any one of dodecyltrimethoxysilane, mercaptopropyltrimethoxysilane or dimethyldichlorosilane.

[0010] Wherein, the average particle size of the modified nano-SiO2 in the shell layer is 25 to 35 nm.

[0011] The epoxy resin matrix is any one of bisphenol A epoxy resin, bisphenol F epoxy resin, epoxy linoleic acid resin, epoxy silane resin and epoxy novolac resin.

[0012] The organic dye is a combination of any one or more of azo dyes, anthraquinone dyes, phthalocyanine dyes, aniline dyes and pyrrole dyes; wherein the azo dye is any one of methyl orange and Congo red, the anthraquinone dye is any one of alizarin red and anthraquinone blue, the phthalocyanine dye is any one of zinc phthalocyanine and phthalocyanine green, the aniline dye is any one of aniline black and aniline yellow, and the pyrrole dye is any one of chlorophyll and pyrrole red.

[0013] The present invention further provides a method for preparing the composite microspheres, comprising the following steps:

[0014] (1) adding the surface modifier to an ethanol / water mixed solution for hydrolysis, then adding it to the nano-SiO2 dispersion, reacting in a water bath at 50-70°C for 6-18 hours to obtain modified nano-SiO2;

[0015] (2) Weighing a certain amount of modified nano-SiO2 obtained in step (1) into the aqueous phase, uniformly dispersing it by ultrasonication, adding epoxy resin to the aqueous phase at 60-80°C and emulsifying at high speed to form an emulsion system;

[0016] (3) adding the organic dye to the curing agent, ultrasonically dispersing the mixture, and then adding the mixture to the emulsion system obtained in step (2) to complete the curing reaction and obtain core-shell epoxy composite microspheres containing the organic dye.

[0017] The curing agent includes at least one of a water-soluble amine curing agent, a water-soluble acid anhydride curing agent, and a water-soluble amide curing agent; wherein the water-soluble amine curing agent is any one of m-phenylenediamine, ethylenediamine, and diethylenetriamine; the water-soluble acid anhydride curing agent is any one of maleic anhydride and phthalic anhydride; and the water-soluble amide curing agent is any one of urea and dicyandiamide.

[0018] Preferably, the amount of surface modifier used is 1 to 10% of the mass of nano-SiO2; the amount of modified SiO2 added is 0.5 to 1.5% of the mass of the water phase; the amount of epoxy resin used is 3 to 8% of the mass of the water phase; the amount of the curing agent used is 10 to 30% of the mass of the epoxy resin; and the amount of organic dye added is 1 to 5% of the mass of the epoxy resin.

[0019] In step (2), the emulsification speed is 1000-2000 rpm, and the emulsification time is 0.5-1.5 h to obtain an emulsion system.

[0020] Preferably, in step (3), the curing speed is 800-1200 rpm, the curing temperature is 60-80° C., and the curing time is 1.5-3 h.

[0021] Beneficial Effects: The composite microspheres of the present invention exhibit a good particle size distribution, providing excellent oxygen and UV shielding properties for the organic dyes contained within, facilitating the dispersion of organic dyes in water-based coatings and finding wide application in the field. The structure of the present invention effectively inhibits the photodegradation rate of organic dyes. Through core-shell encapsulation, the structure of the present invention provides a highly dispersible and stable platform for organic dyes, effectively enhancing their application prospects in water-based coatings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of scanning electron microscopy of chlorophyll / epoxy@SiO2 microspheres prepared in Example 1;

[0023] Figure 2 : is the particle size distribution diagram of chlorophyll / epoxy@SiO2 microspheres prepared in Example 1;

[0024] Figure 3 The scanning electron microscope image and element distribution diagram of the cross section of the chlorophyll / epoxy@SiO2 microspheres prepared in Example 1;

[0025] Figure 4 This is an SEM image of the dispersion effect of chlorophyll / epoxy@SiO2 microspheres in the polyurethane coating in Example 7. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more apparent, but the present invention is not limited to the following embodiments.

[0027] Example 1

[0028] DTMS was selected as the surface modifier of nano-SiO2. 0.25 g DTMS was added to a 25 / 5 ml ethanol / water mixed solution for hydrolysis. 5 g nano-SiO2 was added to a 70 / 10 ml ethanol / water mixed solution. After ultrasonic dispersion, the hydrolyzed DTMS solution was added dropwise to the SiO2 dispersion. The mixture was reacted at 60°C for 15 h and centrifuged and dried to obtain DTMS-modified nano-SiO2.

[0029] Weigh 0.5g of modified SiO2 and add it to 100g of deionized water, place it in a 70℃ water bath and stir, add 5g of epoxy resin DGEBA, and stir at 1500rpm for 1h to form an emulsion; weigh 0.1g of chlorophyll and 1.0g of curing agent m-phenylenediamine, stir evenly, add it to the emulsion system, and cure it at 70℃ and 1000rpm for 2h to obtain chlorophyll / epoxy composite microspheres with core-shell structure.

[0030] Example 2

[0031] DTMS was selected as the surface modifier of nano-SiO2. 0.45 g DTMS was added to a 25 / 5 ml ethanol / water mixed solution for hydrolysis. 5 g nano-SiO2 was added to a 70 / 10 ml ethanol / water mixed solution. After ultrasonic dispersion, the hydrolyzed DTMS solution was added dropwise to the SiO2 dispersion. The mixture was reacted at 70°C for 18 h and centrifuged and dried to obtain DTMS-modified nano-SiO2.

[0032] Weigh 0.5g of modified SiO2 and add it to 100g of deionized water, place it in a 70℃ water bath and stir, add 5g of epoxy resin DGEBA, and stir at 1000rpm for 1.5h to form an emulsion; weigh 0.1g of chlorophyll and 1.0g of curing agent m-phenylenediamine, stir evenly, add to the emulsion system, and cure at 70℃ at 1200rpm for 2.5h to obtain chlorophyll / epoxy composite microspheres with core-shell structure.

[0033] Example 3

[0034] DTMS was selected as the surface modifier of nano-SiO2. 0.45 g DTMS was added to a 25 / 5 ml ethanol / water mixed solution for hydrolysis. 5 g nano-SiO2 was added to a 70 / 10 ml ethanol / water mixed solution. After ultrasonic dispersion, the hydrolyzed DTMS solution was added dropwise to the SiO2 dispersion. The mixture was reacted at 70°C for 18 h and centrifuged and dried to obtain DTMS-modified nano-SiO2.

[0035] Weigh 1.0g of modified SiO2 and add it to 100g of deionized water, place it in a 70℃ water bath and stir, add 5g of epoxy resin DGEBA, and stir at 1000rpm for 1.5h to form an emulsion; weigh 0.1g of chlorophyll and 1.0g of curing agent m-phenylenediamine, stir evenly, add it to the emulsion system, and cure it at 70℃ and 1200rpm for 2.5h to obtain chlorophyll / epoxy composite microspheres with core-shell structure.

[0036] Example 4

[0037] DTMS was selected as the surface modifier of nano-SiO2. 0.45 g DTMS was added to a 25 / 5 ml ethanol / water mixed solution for hydrolysis. 5 g nano-SiO2 was added to a 70 / 10 ml ethanol / water mixed solution. After ultrasonic dispersion, the hydrolyzed DTMS solution was added dropwise to the SiO2 dispersion. The mixture was reacted at 70°C for 18 h and centrifuged and dried to obtain DTMS-modified nano-SiO2.

[0038] Weigh 1.5g of modified SiO2 and add it to 100g of deionized water, place it in a 70℃ water bath and stir, add 5g of epoxy resin DGEBA, and stir at 1000rpm for 1.5h to form an emulsion; weigh 0.1g of chlorophyll and 1.0g of curing agent m-phenylenediamine, stir evenly, add it to the emulsion system, and cure it at 70℃ and 1200rpm for 2.5h to obtain chlorophyll / epoxy composite microspheres with core-shell structure.

[0039] Example 5

[0040] MPTMS was selected as the surface modifier of nano-SiO2. 0.45 g of MPTMS was added to a 25 / 5 ml ethanol / water mixed solution for hydrolysis. 5 g of nano-SiO2 was added to a 70 / 10 ml ethanol / water mixed solution. After ultrasonic dispersion, the hydrolyzed DTMS solution was added dropwise to the SiO2 dispersion. The mixture was reacted at 70°C for 6 h and centrifuged and dried to obtain DTMS-modified nano-SiO2.

[0041] Weigh 1.5g of modified SiO2 and add it to 100g of deionized water, place it in a 60℃ water bath and stir, add 5g of epoxy resin DGEBA, and stir at 1000rpm for 1.5h to form an emulsion; weigh 0.05g of chlorophyll and 0.5g of curing agent diethylenetriamine, stir evenly, add it to the emulsion system, and cure it at 80℃ and 800rpm for 1.5h to obtain chlorophyll / epoxy composite microspheres with core-shell structure.

[0042] Example 6

[0043] DMCS was selected as the surface modifier of nano-SiO2. 0.45g DMCS was added to a 25 / 5ml ethanol / water mixed solution for hydrolysis. 5g nano-SiO2 was added to a 70 / 10ml ethanol / water mixed solution. After ultrasonic dispersion, the hydrolyzed DTMS solution was added dropwise to the SiO2 dispersion. The mixture was reacted at 50°C for 18h and centrifuged and dried to obtain DTMS-modified nano-SiO2.

[0044] Weigh 1.5g of modified SiO2 and add it to 100g of deionized water, place it in an 80℃ water bath and stir, add 5g of epoxy resin DGEBA, and stir at 1000rpm for 0.5h to form an emulsion; weigh 0.25g of zinc phthalocyanine and 1.5g of curing agent triethylenetetramine, stir evenly, add to the emulsion system, and cure at 60℃ and 1200rpm for 3h to obtain chlorophyll / epoxy composite microspheres with core-shell structure.

[0045] Example 7

[0046] MPTMS was selected as the surface modifier of nano-SiO2. 0.1g MPTMS was added to a 25 / 5ml ethanol / water mixed solution for hydrolysis. 5g nano-SiO2 was added to a 70 / 10ml ethanol / water mixed solution. After ultrasonic dispersion, the hydrolyzed DTMS solution was added dropwise to the SiO2 dispersion. The mixture was reacted at 60°C for 18h and centrifuged and dried to obtain DTMS-modified nano-SiO2.

[0047] Weigh 0.5g of modified SiO2 and add it to 100g of deionized water, place it in a 60℃ water bath and stir, add 5g of epoxy resin DGEBA, and stir at 1500rpm for 1.5h to form an emulsion; weigh 0.05g of perylene black and 1.5g of curing agent diethylenetriamine, stir evenly, add to the emulsion system, and cure at 80℃ and 800rpm for 3h to obtain chlorophyll / epoxy composite microspheres with core-shell structure.

[0048] Example 8

[0049] DMCS was selected as the surface modifier of nano-SiO2, and 0.15g MPTMS was added to a 25 / 5ml ethanol / water mixed solution for hydrolysis; 5g nano-SiO2 was added to a 70 / 10ml ethanol / water mixed solution, and after ultrasonic dispersion, the hydrolyzed DTMS solution was added dropwise to the SiO2 dispersion, reacted at 50°C for 6h, and centrifuged and dried to obtain DTMS-modified nano-SiO2.

[0050] Weigh 0.5g of modified SiO2 and add it to 100g of deionized water, place it in an 80℃ water bath and stir, add 5g of epoxy resin DGEBA, and stir at 1000rpm for 0.5h to form an emulsion; weigh 0.25g of chlorophyll and 0.5g of curing agent triethylenetetramine, stir evenly, add it to the emulsion system, and cure it at 60℃ and 1200rpm for 1.5h to obtain chlorophyll / epoxy composite microspheres with core-shell structure.

[0051] Example 9

[0052] Add 0.5 g of the chlorophyll / epoxy composite microspheres obtained in Example 4 to 5 g of the polyurethane resin solution and stir at 1000 rpm for 30 minutes until uniformly dispersed. The resin dispersion was coated onto a tinplate substrate to a film thickness of 1000 μm to obtain a chlorophyll / epoxy composite microsphere-polyurethane coating.

[0053] Comparative Example 1

[0054] Pure chlorophyll, at the same chlorophyll content as the chlorophyll composite epoxy microspheres in Example 4, was added to 5 g of a polyurethane resin solution and stirred at 1000 rpm for 30 minutes until uniformly dispersed. The resin dispersion was then coated onto a tinplate substrate to a film thickness of 1000 μm to obtain a chlorophyll-polyurethane coating.

[0055] Figures 1-4 Tables 1 and 2 show the characterization results of the prepared microspheres, where L represents the brightness of the object, a * Indicates the red and green color of the object, b * It indicates the yellow-blueness of an object, and ΔE indicates the color difference.

[0056] Table 1

[0057]

[0058]

[0059] Table 2

[0060]

[0061] in, Figure 1 This is a scanning electron microscope image of the chlorophyll / epoxy@SiO2 composite microspheres prepared in Example 4. Clearly spherical particles can be seen, and the surface of the microspheres is coated with nanoparticles to form a dense and rough shell; Figure 2 Figures (a) and (b) show that the amount of DTMS added has a certain effect on the particle size of the microspheres. Increasing the amount of DTMS is beneficial for obtaining microspheres with smaller particle sizes. Figures (b) and (d) show that the amount of modified SiO2 added is changed. The increase in SiO2 content is more conducive to the stability of the oil-water interface, thereby obtaining composite microspheres with smaller and more uniform particle sizes, which is beneficial for the dispersion of the microspheres in the coating system. Figure 3 The scanning electron microscope image and Si element distribution diagram of the cross section of the chlorophyll / epoxy@SiO2 microspheres prepared in Example 4 show that the outer layer of the microspheres has obvious Si element distribution, and the shell thickness is about 1 μm.

[0062] Table 1 shows the colorimetric changes of chlorophyll during UV aging in Comparative Example 1. The color difference ΔE of the coating after aging for 2 and 4 hours was 11.4 and 15.8, respectively. After aging for more than 4 hours, the ΔE change at each time point was less than 1, indicating that the chlorophyll photoaging was essentially complete before this time.

[0063] Table 2 shows the changes in colorimetric parameters of the chlorophyll / epoxy@SiO2 microspheres prepared in Example 9 during UV aging. Compared to the color difference of the untreated chlorophyll coating after 4 hours, the core-shell encapsulated chlorophyll microspheres required at least 56 hours of UV irradiation to achieve the same color difference, indicating that encapsulation of the core-shell epoxy / SiO2 microspheres effectively improves the photostability of the core organic dye.

[0064] Figure 4 This is a scanning electron microscope image of a cross section of the chlorophyll / epoxy composite microsphere-polyurethane coating in Example 9. The composite microspheres are uniformly dispersed in the coating as single particles, showing good dispersion and uniformity.

[0065] The present invention provides a method and concept for preparing a core-shell epoxy composite microparticle. There are numerous methods and approaches for implementing this technical solution. The foregoing merely represents a preferred embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also within the scope of protection of the present invention. Any components not specified in this embodiment may be implemented using existing technologies.

Claims

1. A core-shell epoxy composite microsphere, characterized in that: The composite microspheres include a shell layer and an inner core, wherein the shell layer is composed of modified nano-SiO2, the mass fraction of which accounts for 10-30% of the total mass of the composite microspheres, and the shell layer thickness is 0.8-1.2 μm; the inner core is composed of an epoxy resin matrix and an organic dye, and the inner core diameter is 10-20 μm; the mass of the organic dye accounts for 1-5% of the mass of the epoxy resin matrix, and the modified nano-SiO2 group is obtained by modifying with a surface modifier, and the surface modifier is any one of dodecyltrimethoxysilane, mercaptopropyltrimethoxysilane or dimethyldichlorosilane.

2. The composite microsphere according to claim 1, characterized in that The average particle size of the modified nano-SiO2 in the shell layer is 25-35 nm.

3. The composite microsphere according to claim 1, characterized in that The epoxy resin matrix is any one of bisphenol A epoxy resin, bisphenol F epoxy resin, epoxy linoleic acid resin, epoxy silane resin and epoxy novolac resin.

4. The composite microsphere according to claim 1, characterized in that The organic dye is a combination of any one or more of azo dyes, anthraquinone dyes, phthalocyanine dyes, aniline dyes and pyrrole dyes; wherein the azo dye is any one of methyl orange and Congo red, the anthraquinone dye is any one of alizarin red and anthraquinone blue, the phthalocyanine dye is any one of zinc phthalocyanine and phthalocyanine green, the aniline dye is any one of aniline black and aniline yellow, and the pyrrole dye is any one of chlorophyll and pyrrole red.

5. The method for preparing the composite microspheres according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) The surface modifier is added to an ethanol / water mixed solution for hydrolysis, and then added to the nano-SiO2 dispersion, and reacted in a 50-70°C water bath for 6-18 hours to obtain modified nano-SiO2; (2) Weigh a certain amount of modified nano-SiO2 obtained in step (1) into the aqueous phase, disperse it evenly with ultrasound, then add epoxy resin to the aqueous phase at 60-80°C and emulsify at high speed to form an emulsion system; (3) Adding the organic dye to the curing agent, ultrasonically dispersing it, and then adding it to the emulsion system obtained in step (2) to complete the curing reaction and obtain core-shell structured epoxy composite microspheres containing the organic dye.

6. The preparation method according to claim 5, characterized in that The curing agent includes at least one of a water-soluble amine curing agent, a water-soluble acid anhydride curing agent, and a water-soluble amide curing agent; wherein the water-soluble amine curing agent is any one of m-phenylenediamine, ethylenediamine, and diethylenetriamine; the water-soluble acid anhydride curing agent is any one of maleic anhydride and phthalic anhydride; and the water-soluble amide curing agent is any one of urea and dicyandiamide.

7. The method according to claim 5, characterized in that The amount of surface modifier used is 1-10% of the mass of nano-SiO2; the amount of modified SiO2 added is 0.5-1.5% of the mass of the water phase; the amount of epoxy resin used is 3-8% of the mass of the water phase; the amount of the curing agent used is 10-30% of the mass of the epoxy resin; and the amount of organic dye added is 1-5% of the mass of the epoxy resin.

8. The method according to claim 5, characterized in that In step (2), the emulsification speed is 1000-2000 rpm, and the emulsification time is 0.5-1.5 h to obtain an emulsion system.

9. The method according to claim 5, characterized in that In step (3), the curing speed is 800-1200 rpm, the curing temperature is 60-80°C, and the curing time is 1.5-3h.

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