Hybrid self-healing microcapsules for waterborne coatings and methods of making the same

Abstract

The application belongs to the technical field of metal corrosion prevention, and relates to a hybrid self-repairing microcapsule for water-based paint and a preparation method thereof. The hybrid self-repairing microcapsule for water-based paint prepared by the application mainly comprises: a capsule core, which is vegetable oil; a capsule wall, which is wrapped outside the capsule core and is a composite hybrid material; and the composite hybrid material has two layers, an inner layer of urea-formaldehyde resin and an outer layer of polydopamine modified graphite phase carbon nitride. The hybrid self-repairing microcapsule has strong capsule wall stability and mechanical strength, can realize the self-healing ability of the water-based coating, and improves the overall corrosion prevention performance of the metal component.

Description

Technical Field

[0001] This invention belongs to the field of metal corrosion protection technology, specifically relating to a hybrid self-healing microcapsule for water-based coatings and its preparation method. Background Technology

[0002] Metal corrosion not only causes enormous losses to the national economy but also leads to safety accidents such as component failure and engineering collapses. Currently, one of the most effective solutions is to coat metal surfaces with organic anti-corrosion coatings. With increasing environmental awareness, green and environmentally friendly water-based coatings are gradually replacing traditional solvent-based coatings and have become a research hotspot in the coating industry. However, water-based coatings are prone to defects such as pores and cracks during curing and use, which greatly limits their application range.

[0003] In recent years, the effective improvement of coating protective performance through coating self-healing technology has attracted widespread attention, and self-healing microcapsules are one of the core technologies of coating self-healing. Most common self-healing microcapsules are single-walled microcapsules, which have unstable mechanical properties; some disclosed double-walled microcapsules have outer walls made of inorganic materials, which have poor compatibility with water-based resins and are difficult to use in water-based coatings. Therefore, there are currently few methods for preparing self-healing microcapsules that simultaneously possess strong wall stability and mechanical strength and are suitable for water-based coatings. Summary of the Invention

[0004] To address the above problems, the present invention aims to provide a hybrid self-healing microcapsule for water-based coatings and its preparation method. This hybrid self-healing microcapsule possesses strong capsule wall stability and mechanical strength, enabling the self-healing ability of water-based coatings and improving the overall corrosion resistance of metal components.

[0005] A hybrid self-healing microcapsule for water-based coatings mainly comprises:

[0006] The core of the capsule is made of vegetable oil;

[0007] The capsule wall, which surrounds the outer periphery of the capsule core, is a composite hybrid material;

[0008] The composite hybrid material consists of two layers: an inner layer of urea-formaldehyde resin and an outer layer of polydopamine-modified graphitic carbon nitride.

[0009] Furthermore, the hybrid self-healing microcapsules have a particle size of 0.5 micrometers to 100 micrometers.

[0010] A method for preparing hybrid self-healing microcapsules for water-based coatings includes the following steps, in parts by mass:

[0011] Step 1: Add 1-10 parts of urea, 0.1-1 parts of ammonium chloride, and 0.1-1 parts of resorcinol to 100 parts of an emulsifier aqueous solution with a mass fraction of 0.1 wt.%~5 wt.%. Stir well and then add an acid regulator to adjust the pH value to obtain a mixed solution.

[0012] Step 2: Add 1-20 parts of vegetable oil to the mixture from Step 1 for emulsification; add 1-20 parts of formaldehyde solution for heat preservation reaction; after the reaction is completed, wash, centrifuge, dry, and grind to obtain solid powder A;

[0013] Step 3: Take 1-10 parts of graphitic carbon nitride and ultrasonically disperse it in 100-500 parts of deionized water. Then add 0.1-2 parts of dopamine hydrochloride and 50-200 parts of buffer solution and keep it at a warm temperature for reaction. After the reaction is completed, wash, centrifuge, dry and grind to obtain solid powder B.

[0014] Step 4: Add 1-10 parts of solid powder A, 1-10 parts of solid powder B and 1-5 parts of silane coupling agent to 50-200 parts of deionized water for a heat-preserving reaction; after the reaction is completed, wash, centrifuge, dry and grind to obtain a hybrid self-healing microcapsule with polydopamine-modified graphite phase carbon nitride-modified urea-formaldehyde resin as the capsule wall and vegetable oil as the capsule core.

[0015] Furthermore, in step 1, the emulsifier is sodium dodecylbenzenesulfonate and / or polyvinyl alcohol.

[0016] Furthermore, in step 1, the acid regulator is a 1 mol / L hydrochloric acid aqueous solution with a pH value of 3.0~5.0.

[0017] Furthermore, the vegetable oil in step 2 is any one or a combination of tung oil, linseed oil, perilla oil, soybean oil, coconut oil, corn oil, and castor oil.

[0018] Furthermore, in step 2, the emulsification stirring rate is 800~1200 rpm, and the time is 1~5 h; the heat preservation reaction temperature is 50~70℃, and the time is 3~6 h.

[0019] Furthermore, in step 3, the graphitic carbon nitride is nanoscale graphitic carbon nitride sheet; the buffer solution is an aqueous solution of tris(hydroxymethyl)aminomethane hydrochloride (Tris solution).

[0020] Furthermore, in step 3, the heat preservation reaction temperature is 30~50℃, and the time is 12~30 h.

[0021] Furthermore, in step 4, the silane coupling agent is any one or a combination of two or more of KH-550, KH-560, and KH-570.

[0022] Furthermore, in step 4, the heat preservation reaction temperature is 40~60℃, and the time is 1~3h.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0024] (1) The core of the hybrid self-healing microcapsule for water-based coatings in this invention is vegetable oil. When the microcapsule ruptures, the vegetable oil flows out and fills the pores and cracks, thus achieving self-repair of the coating. The inner wall is urea-formaldehyde resin, which has a dense structure and excellent encapsulation properties. The outer wall is polydopamine-modified graphite phase carbon nitride. Graphite phase carbon nitride can give the microcapsule strong wall stability and mechanical strength, while polydopamine can improve the compatibility and dispersibility between the microcapsule and the water-based resin, enabling the microcapsule to be better applied in water-based coatings.

[0025] (2) The solvents used in the hybrid self-healing microcapsules for water-based coatings prepared by the present invention are all water and do not involve organic solvents. The manufacturing process is green and environmentally friendly. Detailed Implementation

[0026] The technical solution of the present invention will be further described and illustrated below with reference to specific embodiments, but it is not limited to these embodiments.

[0027] A hybrid self-healing microcapsule for water-based coatings mainly comprises:

[0028] The core of the capsule is made of vegetable oil;

[0029] The capsule wall, which surrounds the outer periphery of the capsule core, is a composite hybrid material;

[0030] The composite hybrid material consists of two layers: an inner layer of urea-formaldehyde resin and an outer layer of polydopamine-modified graphitic carbon nitride.

[0031] Furthermore, the hybrid self-healing microcapsules have a particle size of 0.5 micrometers to 100 micrometers.

[0032] A method for preparing hybrid self-healing microcapsules for water-based coatings includes the following steps, in parts by mass:

[0033] Step 1: Add 1-10 parts of urea, 0.1-1 parts of ammonium chloride, and 0.1-1 parts of resorcinol to 100 parts of an emulsifier aqueous solution with a mass fraction of 0.1 wt.%~5 wt.%. After stirring evenly, add 1 mol / L hydrochloric acid aqueous solution to adjust the pH value to 3.0-5.0 to obtain a mixed solution.

[0034] Step 2: Add 1-20 parts of vegetable oil to the mixture from Step 1 for emulsification. The emulsification stirring rate is 800-1200 rpm, and the time is 1-5 h. Add 1-20 parts of formaldehyde solution for heat preservation reaction at 50-70℃ for 3-6 h. After the reaction is completed, wash, centrifuge, dry, and grind to obtain solid powder A.

[0035] Step 3: Take 1-10 parts of nano-sized graphitic carbon nitride sheets and ultrasonically disperse them in 100-500 parts of deionized water. Then add 0.1-2 parts of dopamine hydrochloride and 50-200 parts of tris(hydroxymethyl)aminomethane hydrochloride aqueous solution (Tris solution) and carry out the reaction at a temperature of 30-50℃ for 12-30 h. After the reaction is completed, wash, centrifuge, dry and grind to obtain solid powder B.

[0036] Step 4: Add 1-10 parts of solid powder A, 1-10 parts of solid powder B, and 1-5 parts of silane coupling agent to 50-200 parts of deionized water for a heat-preserving reaction at 40-60℃ for 1-3 hours. After the reaction is completed, wash, centrifuge, dry, and grind to obtain a hybrid self-healing microcapsule with a polydopamine-modified graphite phase carbon nitride-modified urea-formaldehyde resin as the capsule wall and a vegetable oil as the core.

[0037] Furthermore, in step 1, the emulsifier is sodium dodecylbenzenesulfonate and / or polyvinyl alcohol.

[0038] Furthermore, the vegetable oil in step 2 is any one or a combination of tung oil, linseed oil, perilla oil, soybean oil, coconut oil, corn oil, and castor oil.

[0039] Furthermore, in step 4, the silane coupling agent is any one or a combination of two or more of KH-550, KH-560, and KH-570.

[0040] Example 1.

[0041] (1) Take 0.1 parts sodium dodecylbenzenesulfonate and 0.05 parts polyvinyl alcohol and add them to 100 parts deionized water. After stirring evenly, add 3 parts urea, 0.4 parts ammonium chloride and 0.4 parts meta-diphenol. Then adjust the pH of the above mixture to 4 with 1 mol / L hydrochloric acid aqueous solution.

[0042] (2) Add 5 parts of tung oil to the mixture in step (1) and stir and emulsify at a stirring rate of 900 rpm for 4 hours; add 8 parts of formaldehyde solution (37 wt.%), heat to 55 ℃ and keep warm for 6 hours; after cooling, wash, centrifuge and dry to obtain solid powder A.

[0043] (3) Take 1 part of nano-scale graphite phase carbon nitride sheet and ultrasonically disperse it in 500 parts of deionized water. Then add 1 part of dopamine hydrochloride, stir evenly, and then add 80 parts of Tris solution. Heat to 40 ℃ and keep warm for 24 h. After cooling, wash, centrifuge, dry and grind to obtain solid powder B.

[0044] (4) Add 2 parts of solid powder A, 2 parts of solid powder B and 1 part of KH-550 to 100 parts of deionized water, heat to 50 ℃ and keep warm for 2 h; after cooling, wash, centrifuge, dry and grind to obtain hybrid self-healing microcapsules.

[0045] Example 2.

[0046] (1) Take 0.1 parts of sodium dodecylbenzenesulfonate and 0.2 parts of polyvinyl alcohol and add them to 100 parts of deionized water. After stirring evenly, add 2 parts of urea, 0.2 parts of ammonium chloride and 0.2 parts of meta-diphenol. Then adjust the pH of the above mixture to 3.5 with 1 mol / L hydrochloric acid aqueous solution.

[0047] (2) Add 10 parts of tung oil to the mixture in step (1) and stir and emulsify at a stirring rate of 1000 rpm for 4 hours; add 8 parts of formaldehyde solution (37 wt.%), heat to 60 ℃ and keep warm for 6 hours; after cooling, wash, centrifuge and dry to obtain solid powder A.

[0048] (3) Take 2 parts of nano-scale graphite phase carbon nitride sheet and ultrasonically disperse it in 500 parts of deionized water. Then add 2 parts of dopamine hydrochloride, stir evenly, and then add 120 parts of Tris solution. Heat to 45 ℃ and keep warm for 24 h. After cooling, wash, centrifuge, dry and grind to obtain solid powder B.

[0049] (4) Add 5 parts of solid powder A, 5 parts of solid powder B and 1 part of KH-560 to 100 parts of deionized water, heat to 50 ℃ and keep warm for 1 h; after cooling, wash, centrifuge, dry and grind to obtain hybrid self-healing microcapsules.

[0050] Preparation of hybrid self-healing microcapsule modified waterborne anticorrosive coating: Take 2 parts of the hybrid self-healing microcapsules from Example 2 as fillers, add them to a mixture of 20 parts of deionized water and 100 parts of waterborne epoxy resin (EPIKOTE 3520-WY-55A), and disperse by ball milling for 2 h. Then, take 50 parts of waterborne curing agent (EPIKURE8537-MY-60) and add it to the above resin mixture. After mixing evenly, the hybrid self-healing microcapsule modified waterborne anticorrosive coating can be obtained.

[0051] Example 3.

[0052] (1) Take 0.1 parts sodium dodecylbenzenesulfonate and 0.1 parts polyvinyl alcohol and add them to 100 parts deionized water. After stirring evenly, add 2 parts urea, 0.15 parts ammonium chloride and 0.15 parts meta-diphenol. Then adjust the pH of the above mixture to 3.5 with 1 mol / L hydrochloric acid aqueous solution.

[0053] (2) Add 5 parts of castor oil to the mixture in step (1) and stir emulsify at a stirring rate of 1000 rpm for 3 h; add 4 parts of formaldehyde solution (37 wt.%), heat to 60 ℃ and keep warm for 5 h; after cooling, wash, centrifuge and dry to obtain solid powder A.

[0054] (3) Take 1 part of nano-scale graphite phase carbon nitride sheet and ultrasonically disperse it in 400 parts of deionized water. Then add 1 part of dopamine hydrochloride, stir evenly, and then add 100 parts of Tris solution. Heat to 40℃ and keep warm for 20 h. After cooling, wash, centrifuge, dry and grind to obtain solid powder B.

[0055] (4) Add 5 parts of solid powder A, 8 parts of solid powder B and 2 parts of KH-570 to 100 parts of deionized water, heat to 50 ℃ and keep warm for 2 h; after cooling, wash, centrifuge, dry and grind to obtain hybrid self-healing microcapsules.

[0056] Preparation of hybrid self-healing microcapsule modified waterborne anticorrosive coating: Take 1 part of the hybrid self-healing microcapsule from Example 3 as a filler and add it to a mixture of 20 parts of deionized water and 100 parts of waterborne epoxy resin (EPIKOTE 3520-WY-55A). After ball milling and dispersion for 4 h, take 50 parts of waterborne curing agent (EPIKURE8537-MY-60) and add it to the above resin mixture. After mixing evenly, the hybrid self-healing microcapsule modified waterborne anticorrosive coating can be obtained.

[0057] Comparative Example 1.

[0058] (1) Take 0.1 parts of sodium dodecylbenzenesulfonate and 0.2 parts of polyvinyl alcohol and add them to 100 parts of deionized water. After stirring evenly, add 2 parts of urea, 0.2 parts of ammonium chloride and 0.2 parts of meta-diphenol. Then adjust the pH of the above mixture to 3.5 with 1 mol / L hydrochloric acid aqueous solution.

[0059] (2) Add 10 parts of tung oil to the mixture in step (1) and stir and emulsify at a stirring rate of 1000 rpm for 4 hours; add 8 parts of formaldehyde solution (37 wt.%), heat to 60 ℃ and keep warm for 6 hours; after cooling, wash, centrifuge and dry to obtain single-walled microcapsules.

[0060] Preparation of single-walled microcapsule modified waterborne anticorrosive coating: Take 2 parts of the single-walled microcapsules from Comparative Example 1 as fillers, add them to a mixture of 20 parts of deionized water and 100 parts of waterborne epoxy resin (EPIKOTE 3520-WY-55A), and disperse by ball milling for 2 h. Then, take 50 parts of waterborne curing agent (EPIKURE8537-MY-60) and add it to the above resin mixture. After mixing evenly, the single-walled microcapsule modified waterborne anticorrosive coating can be obtained.

[0061] Comparative Example 2.

[0062] (1) Take 0.1 parts sodium dodecylbenzenesulfonate and 0.1 parts polyvinyl alcohol and add them to 100 parts deionized water. After stirring evenly, add 2 parts urea, 0.15 parts ammonium chloride and 0.15 parts meta-diphenol. Then adjust the pH of the above mixture to 3.5 with 1 mol / L hydrochloric acid aqueous solution.

[0063] (2) Add 5 parts of castor oil to the mixture in step (1) and stir emulsify at a stirring rate of 1000 rpm for 3 h; add 4 parts of formaldehyde solution (37 wt.%), heat to 60 ℃ and keep warm for 5 h; after cooling, wash, centrifuge and dry to obtain single-walled microcapsules.

[0064] Preparation of single-walled microcapsule modified waterborne anticorrosive coating: Take 1 part of the single-walled microcapsule from Comparative Example 2 as a filler, add it to a mixture of 20 parts of deionized water and 100 parts of waterborne epoxy resin (EPIKOTE 3520-WY-55A), and disperse by ball milling for 4 h. Then, take 50 parts of waterborne curing agent (EPIKURE8537-MY-60) and add it to the above resin mixture. After mixing evenly, the single-walled microcapsule modified waterborne anticorrosive coating can be obtained.

[0065] The hybrid self-healing microcapsules prepared in Examples 1-3 above were placed together with the single-walled microcapsules in Comparative Examples 1 and 2 for 2 months. The change in the core mass fraction was compared to illustrate the stability of the hybrid self-healing microcapsules. 1 wt.% of the microcapsules were added to deionized water, stirred evenly, and left for 1 h. The sedimentation before and after the addition was observed to illustrate the dispersibility and compatibility of the hybrid self-healing microcapsules in water. The results are shown in Table 1.

[0066] Table 1. Results of microcapsule performance tests.

[0067]

[0068] As shown in Table 1, the hybrid self-healing microcapsules prepared by the present invention showed a smaller change in core mass fraction after 2 months than the comparative example, indicating that the microcapsules in the examples had better performance stability. When 1 wt.% of the microcapsules were added to deionized water and stirred evenly, the microcapsules in both the examples and the comparative example were uniformly dispersed, and some sedimentation occurred after 1 h. This indicates that although the outer wall of the hybrid self-healing microcapsules prepared by the present invention is made of inorganic material, its dispersibility in water is comparable to that of single-walled microcapsules (urea-formaldehyde resin microcapsules) due to polydopamine modification.

Claims

1. A hybrid self-healing microcapsule for use in waterborne coatings, characterized in that, Mainly includes: The core of the capsule is made of vegetable oil; The capsule wall, which surrounds the outer periphery of the capsule core, is a composite hybrid material; The composite hybrid material consists of two layers: an inner layer of urea-formaldehyde resin and an outer layer of polydopamine-modified graphitic carbon nitride. The method for preparing the hybrid self-healing microcapsules for water-based coatings includes the following steps, in parts by mass: Step 1: Add 1-10 parts of urea, 0.1-1 parts of ammonium chloride, and 0.1-1 parts of resorcinol to 100 parts of an emulsifier aqueous solution with a mass fraction of 0.1 wt.%~5 wt.%. Stir well and then add an acid regulator to adjust the pH value to obtain a mixed solution. Step 2: Add 1-20 parts of vegetable oil to the mixture from Step 1 for emulsification; add 1-20 parts of formaldehyde solution for heat preservation reaction; After the reaction is complete, solid powder A is obtained by washing, centrifugation, drying, and grinding. Step 3: Take 1-10 parts of graphitic carbon nitride and ultrasonically disperse it in 100-500 parts of deionized water, then add 0.1-2 parts of dopamine hydrochloride and 50-200 parts of buffer solution and keep it at a warm temperature for reaction; After the reaction is complete, solid powder B is obtained by washing, centrifugation, drying, and grinding. Step 4: Add 1-10 parts of solid powder A, 1-10 parts of solid powder B and 1-5 parts of silane coupling agent to 50-200 parts of deionized water and carry out the reaction at a constant temperature. After the reaction was completed, the capsules were washed, centrifuged, dried and ground to obtain hybrid self-healing microcapsules with polydopamine-modified graphite phase carbon nitride-modified urea-formaldehyde resin as the capsule wall and vegetable oil as the capsule core.

2. Hybrid self-healing microcapsules for use in waterborne coatings according to claim 1, characterized in that, The particle size of the hybrid self-healing microcapsules ranges from 0.5 micrometers to 100 micrometers.

3. The hybrid self-healing microcapsule for water-based paints according to claim 1, characterized in that, In step 1, the emulsifier is sodium dodecylbenzenesulfonate and / or polyvinyl alcohol.

4. The hybrid self-healing microcapsule for water-based paints according to claim 1, characterized in that, In step 1, the acid regulator is a 1 mol / L hydrochloric acid aqueous solution with a pH value of 3.0~5.

0.

5. The hybrid self-healing microcapsule for water-based paints according to claim 1, characterized in that, The vegetable oil in step 2 is any one or a combination of tung oil, linseed oil, perilla oil, soybean oil, coconut oil, corn oil, and castor oil.

6. The hybrid self-healing microcapsule for water-based paints according to claim 1, characterized in that, In step 2, the emulsification stirring rate is 800~1200 rpm, and the time is 1~5 h; the heat preservation reaction temperature is 50~70℃, and the time is 3~6 h.

7. The hybrid self-healing microcapsule for water-based paints according to claim 1, characterized in that, In step 3, the heat preservation reaction temperature is 30~50℃ and the time is 12~30 h.

8. The hybrid self-healing microcapsule for water-based paints according to claim 1, characterized in that, In step 4, the silane coupling agent is any one or a combination of two or more of KH-550, KH-560, and KH-570.

9. The hybrid self-healing microcapsule for water-based paints according to claim 1, characterized in that, In step 4, the heat preservation reaction temperature is 40~60℃, and the time is 1~3h.

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