Preparation method of dual-cavity self-healing organic pigment microcapsule coating

Abstract

The present invention relates to the field of microcapsules, and discloses a method for preparing a dual-cavity self-healing organic pigment microcapsule coating. The present invention first uses a sol-gel method to make the surface of the hydrophobic organic pigment have hydrophilic groups, uses the hydrophilic groups to disperse a curing agent, and prepares a Pickering emulsion of modified organic pigment-dispersed curing agent particles, and then uses the modified organic pigment-dispersed curing agent particles as an emulsifier to prepare an emulsion loaded with a self-healing agent and a photocuring monomer, and obtains a dual-cavity self-healing organic pigment microcapsule coating after photocuring. The dual-cavity microcapsule of the present invention has dual chambers, which are respectively loaded with a self-healing agent and a curing agent. It can not only solve the problem of uneven distribution of the two microcapsules in the dual-microcapsule system, but also solve the problem of limited types of self-healing agents and self-healing conditions in the single-component self-healing system. In addition, since the outer microcapsule wall of the dual-cavity microcapsule is a modified organic pigment, its surface wettability is improved, so it is more practical.

Description

Technical Field

[0001] The present invention relates to the field of microcapsules, and in particular to a method for preparing a double-cavity self-healing organic pigment microcapsule coating. Background Art

[0002] Self-healing materials are an important component of smart biomimetic materials, capable of responding to external stimuli and damage. They hold broad application prospects in diverse fields, including automotive, aerospace, smart sensors, and architecture. Over the past decade, numerous approaches have been developed to achieve self-healing in materials. Generally speaking, these methods can be categorized as intrinsic approaches based on reversible bonds within the matrix itself and extrinsic approaches based on external healing agents stored within containers, such as microcapsules, hollow fibers, and microvessels. Microcapsules, among others, have been extensively studied because they can be conveniently and uniformly embedded within a polymer matrix.

[0003] Early self-healing systems based on exogenous microcapsules primarily consisted of microcapsules encapsulating a healing agent and a catalyst dispersed in a matrix. When the microcapsules rupture, the healing agent flows out and reacts with the catalyst to fill the cracks. However, the catalyst is easily deactivated during the dispersion process, causing some environmental pollution. To address this issue, researchers developed dual-microcapsule systems, encapsulating the two components in separate capsules. However, adding different types of microcapsules to the same matrix results in uneven distribution of the different components within the matrix, leading to uneven healing properties of the material. To address this issue, single-component self-healing systems have been developed. The healing agent encapsulated by the microcapsules is an active chemical component, such as isocyanate or drying oil, which can self-cure under specific conditions. However, the variety of active healing agents is still limited. Furthermore, such single-component self-healing systems typically require specific healing conditions (such as light, moisture, and oxygen), and their healing efficiency is significantly affected by these conditions.

[0004] On the other hand, organic pigments are rich in color and have strong hiding power, making them excellent coloring particles. However, organic pigments have low surface energy and are prone to agglomeration, so they need to be modified before use to improve their dispersibility. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing a dual-cavity self-healing organic pigment microcapsule coating. The coating of the present invention contains dual-cavity microcapsules, which have two chambers, an inner layer and an outer layer, and are respectively loaded with a self-healing agent located in the inner cavity and a curing agent located in the outer cavity, using organic pigments as carrier dispersants. This structural design can not only solve the problem of uneven distribution of the two microcapsules in the current dual-microcapsule system, but also solve the problem of limited types of self-healing agents that can self-cure and self-healing conditions in the current single-component self-healing system, and therefore has excellent self-healing performance. In addition, since the outer microcapsule wall of the dual-cavity microcapsule is a modified organic pigment, its surface wettability is improved, so its application in polymer-free coatings can increase practical effects.

[0006] The specific technical solution of the present invention is: a method for preparing a dual-cavity self-healing organic pigment microcapsule coating, comprising the following steps:

[0007] (1) A hydrophobic organic pigment and a cationic emulsifier are ball-milled in water, dispersed in ethanol after centrifugal washing, a dispersant and water are added, ultrasonic dispersion is performed, and a silane coupling agent is added to react to obtain a modified organic pigment coated with a silane coupling agent.

[0008] (2) taking a curing agent as an oil phase, a modified organic pigment and water as an aqueous phase, mixing the aqueous phase and the oil phase in a mass ratio of 1:0.1-10 and homogenizing to obtain a Pikering emulsion in which the modified organic pigment disperses the curing agent particles;

[0009] (3) The self-healing agent, the photocurable monomer and the photoinitiator are added to the Pickering emulsion, and the modified organic pigment dispersed curing agent particles are used as an emulsifier to stabilize the emulsified self-healing agent and the photocurable monomer, thereby obtaining a coated emulsion with the self-healing agent and the photocurable monomer as the core material. After ultraviolet irradiation, the photocurable monomer undergoes photocrosslinking and is converted into the inner layer microcapsule wall, thereby obtaining a double-cavity self-healing organic pigment microcapsule coating.

[0010] In step (1), the present invention firstly uses a sol-gel method to impart hydrophilic groups to the surface of a hydrophobic organic pigment to impart amphiphilicity, thereby enabling it to serve as a Pickering emulsifier. In step (2), the present invention uses the modified organic pigment to coat a curing agent to prepare a Pickering emulsion of modified organic pigment-dispersed curing agent particles. In step (3), the present invention uses the modified organic pigment-dispersed curing agent particles as a Pickering emulsifier to stabilize the emulsified self-healing agent and the photocurable monomer, thereby preparing an emulsion loaded with the self-healing agent and the photocurable monomer. The specific reaction process is as follows: Figure 1 Finally, the photocurable monomer is photo-crosslinked by light initiation and converted into the inner microcapsule wall. Since the organic pigment acts as the outer microcapsule wall to encapsulate the curing agent, the present invention successfully produces a double-cavity self-healing organic pigment microcapsule coating.

[0011] The dual-cavity microcapsules produced by the present invention have two chambers, an inner chamber and an outer chamber, each loaded with a self-healing agent in the inner chamber and a curing agent in the outer chamber. This structural design not only solves the problem of uneven distribution of the two microcapsules in current dual-microcapsule systems, but also addresses the limitations on the types of self-curing self-healing agents and self-healing conditions in current single-component self-healing systems, resulting in excellent self-healing performance. Furthermore, because the outer microcapsule wall of the dual-cavity microcapsules of the present invention is composed of a modified organic pigment, its surface wettability is improved, thus enhancing its practical application in polymer-free coatings.

[0012] Preferably, in step (1), the coverage rate of the silane coupling agent-modified organic pigment is 30-35%.

[0013] The coverage rate of modified organic pigments is crucial for their ability to act as Pickering emulsifiers for coating other substances. Solid particles with suitable surface wettability are crucial for preparing stable Pickering emulsions. However, organic pigment particles have low surface energy and strong hydrophobicity, making them unsuitable for direct use as Pickering emulsifiers. Therefore, after extensive research, the present inventors have discovered that within the aforementioned coverage rate range, modified organic pigments can serve as relatively ideal Pickering emulsifiers.

[0014] Preferably, in step (1), the mass ratio of the organic pigment to the silane coupling agent is 1:0.3-0.5; and the reaction conditions are: 25-50° C., 20-30 h.

[0015] The mass ratio of organic pigment to silane coupling agent and the reaction conditions largely determine the coverage rate of organic pigment by silane coupling agent. Under the above conditions, modified organic pigment with ideal coverage rate can be obtained.

[0016] Preferably, in step (1), the mass fraction of the cationic emulsifier to the organic pigment is 4-6%, and the ball milling time is 0.5-1.5 hours.

[0017] Preferably, in step (1), the organic pigment is one or more of Pigment Red 146, Pigment Yellow 74, Pigment Violet 19, Pigment Yellow 154, Pigment Red 122 and Pigment Orange 13; further preferably, it is one or more of Pigment Red 146, Pigment Yellow 74 and Pigment Orange 13.

[0018] Preferably, in step (1), the cationic emulsifier is selected from cetyltrimethylammonium bromide (CTAB).

[0019] Since the silane coupling agent carries a negative charge after hydrolysis, the organic pigment needs to be cationic modified to form a coating.

[0020] Preferably, in step (1), the dispersant is polyvinylpyrrolidone (PVP).

[0021] Preferably, in step (1), the silane coupling agent is γ-mercaptopropyltriethoxysilane (KH-580).

[0022] Preferably, in step (2), the mass ratio of the modified organic pigment to water is 1:60-80.

[0023] Preferably, in step (2), the mass ratio of the oil phase to the water phase is 1:6-9.

[0024] The oil-water ratio of the Pickering emulsion is a key factor in determining the size of the emulsion particles. In order to prepare an emulsion with nanometer-sized particles, the mass of the oil phase must be smaller than the mass of the water phase.

[0025] Preferably, in step (2), the curing agent is one or more of divinylbenzene, polyetheramine and methylimidazole, and more preferably divinylbenzene.

[0026] Preferably, in step (2), the homogenization treatment conditions are: 10000-20000 rpm, 5-20 min.

[0027] Preferably, in step (2), the particle size of the modified organic pigment-coated curing agent particles is 400-1900 nm, more preferably 400-600 nm.

[0028] Preferably, in step (3), the mass ratio of the oil phase to the Pickering emulsion is 1:6-9. The ratio of the self-healing agent, the photocurable monomer, and the photoinitiator is 70-90:10-30:0.2-0.5.

[0029] Preferably, in step (3), the self-healing agent is one or more of toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), and lysine diisocyanate (LDI); more preferably, isophorone diisocyanate (IPDI). The photocurable monomer is selected from hydroxyethyl methacrylate (HEMA). The photoinitiator is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO).

[0030] Preferably, in step (3), the UV curing conditions are: UV wavelength 365 nm, time 15-25 min.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The present invention first uses a sol-gel method to make the surface of a hydrophobic organic pigment have hydrophilic groups so that it can serve as a Pickering emulsifier, and then uses the hydrophilic groups to coat a curing agent to prepare a nano-scale Pickering emulsion containing modified organic pigment-dispersed curing agent particles. Then, the modified organic pigment-dispersed curing agent particles are used as an emulsifier to prepare an emulsion loaded with a self-healing agent and a photocurable monomer. After photocuring, a double-cavity self-healing organic pigment microcapsule coating is obtained.

[0033] (2) The dual-cavity microcapsule of the present invention has two chambers, each loaded with a self-healing agent and a curing agent. It can not only solve the problem of uneven distribution of the two microcapsules in the dual-microcapsule system, but also solve the problem of limited types of self-healing agents and self-healing conditions in the single-component self-healing system, thus having excellent self-healing properties.

[0034] (3) The outer microcapsule wall of the double-cavity microcapsule of the present invention is a modified organic pigment, and its surface wettability is improved, so its application in polymer-free coatings can increase practical effects.

[0035] (4) The dual-cavity self-healing organic pigment microcapsules of the present invention are applied to colored coatings, which not only have bright colors but also have excellent mechanical properties and can be used in fields such as construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the preparation process of the double-cavity self-healing organic pigment microcapsules of the present invention;

[0037] Figure 2 is a transmission electron microscope image of the double-cavity self-healing organic pigment microcapsule prepared in Example 1;

[0038] Figure 3 1 and 2 are stress-strain curves of the dual-cavity self-healing organic pigment microcapsule coatings prepared in Examples 1, 15-21. DETAILED DESCRIPTION

[0039] The present invention will be further described below with reference to the embodiments.

[0040] Overall embodiment

[0041] A method for preparing a dual-cavity self-healing organic pigment microcapsule coating, such as Figure 1 As shown, the following steps are included:

[0042] (1) A hydrophobic organic pigment and a cationic emulsifier are ball-milled in water for 0.5-1.5 hours, dispersed in ethanol after centrifugal washing, a dispersant and water are added, ultrasonic dispersion is performed, and a silane coupling agent is added and reacted at 25-50° C. for 20-30 hours to obtain a modified organic pigment coated with a silane coupling agent.

[0043] Preferably, the mass fraction of the cationic emulsifier to the organic pigment is 4-6%; the mass ratio of the organic pigment to the silane coupling agent is 1:0.3-0.5; the organic pigment is one or more of Pigment Red 146, Pigment Yellow 74, and Pigment Orange 13. The cationic emulsifier is selected from cetyltrimethylammonium bromide (CTAB). The dispersant is polyvinylpyrrolidone (PVP). The silane coupling agent is γ-mercaptopropyltriethoxysilane (KH-580).

[0044] (2) A curing agent is used as the oil phase, and a modified organic pigment and water are used as the aqueous phase. The aqueous phase and the oil phase are mixed in a mass ratio of 1:0.1-10 (preferably 1:6-9) and homogenized (10,000-20,000 rpm, 5-20 min); a Pickering emulsion containing modified organic pigment-coated curing agent particles (particle size of 400-1900 nm, more preferably 400-600 nm) is obtained.

[0045] Preferably, the mass ratio of the modified organic pigment to water is 1:60-80. The curing agent is one or more of divinylbenzene, polyetheramine, and methylimidazole, more preferably divinylbenzene.

[0046] (3) The self-healing agent, photocurable monomer and photoinitiator are added to the Pickering emulsion as the oil phase, and the modified organic pigment dispersed curing agent particles are used as the Pickering emulsifier to stabilize the emulsified self-healing agent and photocurable monomer to obtain an emulsion coated with the self-healing agent and photocurable monomer. After irradiation with ultraviolet light at a wavelength of 365 nm for 15-25 minutes, the photocurable monomer is cross-linked and converted into the inner layer of the microcapsule wall to obtain a double-cavity self-healing organic pigment microcapsule coating.

[0047] Preferably, the mass ratio of the oil phase to the dispersion is 1:6-9. The ratio of the self-healing agent, photocurable monomer, and photoinitiator is 70-90:10-30:0.2-0.5. The self-healing agent is one or more of toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), and lysine diisocyanate (LDI); more preferably, isophorone diisocyanate (IPDI); the photocurable monomer is selected from hydroxyethyl methacrylate (HEMA); and the photoinitiator is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO). Specific embodiments

[0049] Example 1

[0050] (1) 5 g of a hydrophobic organic pigment (Pigment Red 146) and 0.25 g of CTAB were ball-milled in 80 g of water for 1 h, washed three times by centrifugation, and dispersed in 200 mL of ethanol. 0.5 g of PVP and 4 g of water were added, and ultrasonic dispersion was performed. 1.5 g of silane coupling agent KH-580 was added and reacted at 25 °C for 20 h to obtain a modified organic pigment coated with a silane coupling agent.

[0051] (2) Taking curing agent divinylbenzene as the oil phase, taking modified organic pigment and water at a mass ratio of 1:80 as the aqueous phase, mixing the aqueous phase and the oil phase at a mass ratio of 9:1 and passing through a homogenizer (15000 rpm, 10 min) to prepare a Pickering emulsion in which modified organic pigment-dispersed curing agent particles are prepared.

[0052] (3) The self-healing agent isophorone diisocyanate, the photocuring monomer hydroxyethyl methacrylate (HEMA) and the photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) were mixed in a mass ratio of 80:20:0.3 and added to the Pickering emulsion as the oil phase. The modified organic pigment dispersed curing agent particles were used as a Pickering emulsifier to stabilize the emulsification of the self-healing agent and the photocuring monomer (the oil-water ratio was 1:6) to obtain an emulsion coated with the self-healing agent and the photocuring monomer. After being irradiated with ultraviolet light at a wavelength of 365 nm for 20 minutes, a double-cavity self-healing organic pigment microcapsule coating was obtained. Figure 2 This is a TEM image of the microcapsule prepared in Example 1. It can be seen from the image that the microcapsule has a double-cavity structure, which is loaded with a curing agent and a self-healing agent respectively.

[0053] Examples 2-14 and Comparative Examples 1-2

[0054] The differences between step (1) and step (2) of Examples 2-14 and Comparative Examples 1-2 and Example 1 are shown in Table 1.

[0055] Table 1

[0056]

[0057]

[0058] The data in the table above show that, by comparing Comparative Example 1 with Examples 1-3, the amount of silane coupling agent used affects the stability of the Pickering emulsion dispersed with the organic pigment. When the mass ratio of organic pigment to silane coupling agent is ≥1:0.3, the resulting Pickering emulsion has a smaller particle size and is more stable. Comparing Comparative Example 2 with Examples 1 and 7-9, it is found that when the oil-water ratio is 1:6-9, the emulsion particle size is within the range of 400-600 nm. The particle size of Comparative Example 2 is larger due to the lower oil-water ratio. Comparative Examples 10-14 show that when the pigments used are Pigment Red 146, Pigment Yellow 74, Pigment Orange 13, Pigment Red 122, and Pigment Violet 19, the Pickering emulsion has a smaller particle size and better stability.

[0059] Examples 15-21

[0060] The differences between step (3) of Examples 15-21 and Example 1 are shown in Table 2.

[0061] Table 2

[0062]

[0063]

[0064] Depend on Figure 3 As shown in Table 1, when the curing agent is divinylbenzene and the self-healing agent is isophorone diisocyanate (Example 1), the fracture growth rate of the prepared coating is 725.4% and the tensile strength is 1.9 MPa, which has the strongest mechanical properties (fracture growth rate and tensile strength are shown in Table 2). Figure 3 It can be seen from Example 1 and Examples 19-21 that as the proportion of the self-healing agent increases, the mechanical properties of the prepared coatings gradually increase; at the same time, as the proportion of the pigment dispersion decreases, the specific gravity of the curing agent decreases accordingly, and the gel fraction of the prepared coatings also gradually decreases.

[0065] Unless otherwise specified, the raw materials and equipment used in the present invention are commonly used in the art; the methods used in the present invention are conventional methods in the art unless otherwise specified.

[0066] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a dual-cavity self-healing organic pigment microcapsule coating, characterized in that include: (1) A hydrophobic organic pigment and hexadecyltrimethylammonium bromide are ball-milled in water for 0.5-1.5 hours, washed by centrifugation, and dispersed in ethanol. A dispersant and water are added, and ultrasonic dispersion is performed. A silane coupling agent, γ-mercaptopropyltriethoxysilane, is added, and the mixture is reacted at 25-50° C. for 20-30 hours to obtain a modified organic pigment coated with a silane coupling agent. The hexadecyltrimethylammonium bromide accounts for 4-6wt% of the organic pigment. The mass ratio of the organic pigment to the silane coupling agent is 1:0.3-0.

5. (2) taking a curing agent as an oil phase, a modified organic pigment and water as an aqueous phase, mixing the aqueous phase and the oil phase in a mass ratio of 6-9:1, and homogenizing to obtain a Pikering emulsion containing modified organic pigment-dispersed curing agent particles; the curing agent is one or more of polyetheramine and methylimidazole; (3) The self-healing agent isophorone diisocyanate, photocurable monomer and photoinitiator are added to the Pikering emulsion as the oil phase in a mass ratio of 1:6-9; the emulsification obtains a coated emulsion with the self-healing agent and the photocurable monomer as the core material, and the photocurable monomer is cross-linked and converted into the inner layer microcapsule wall by ultraviolet irradiation to obtain a double-cavity self-healing organic pigment microcapsule coating.

2. The preparation method according to claim 1, wherein: In step (1), the hydrophobic organic pigment is one or more of Pigment Red 146, Pigment Yellow 74, Pigment Violet 19, Pigment Yellow 154, Pigment Red 122 and Pigment Orange 13.

3. The preparation method according to claim 1, wherein: In step (1), the dispersant is polyvinyl pyrrolidone.

4. The preparation method according to claim 1, wherein: In step (2), the mass ratio of the modified organic pigment to water is in the range of 1:60-80.

5. The preparation method according to claim 1 or 4, wherein: In step (2), the homogenization conditions are: 10000-20000 rpm, 5-20 min.

6. The preparation method according to claim 1 or 4, wherein: In step (2), the particle size of the modified organic pigment-dispersed curing agent particles is 400-1900 nm.

7. The preparation method according to claim 1, wherein: In step (3), the mass ratio of the self-healing agent, the photocurable monomer and the photoinitiator is 70-90:10-30:0.2-0.

5.

8. The preparation method according to claim 1 or 7, wherein: In step (3), the photocurable monomer is selected from hydroxyethyl methacrylate.

9. The preparation method according to claim 1 or 7, wherein: In step (3), the photoinitiator is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

10. The preparation method according to claim 1 or 7, wherein: In step (3), the conditions of ultraviolet irradiation are: ultraviolet light wavelength 365 nm, time 15-25 min.

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