A phenolic / polyurethane-isocyanate double-layer microcapsule and preparation and application thereof

Abstract

The application discloses a phenolic / polyurethane-isocyanate double-layer microcapsule and a preparation and application thereof, and belongs to the technical field of microcapsules. In view of the problems of low strength, poor heat resistance, aging performance and sealing performance of the existing isocyanate microcapsule wall material, which leads to rapid decay of the core material content, the application makes toluene diisocyanate and 1,4-butanediol interface polymerization to form a polyurethane-isocyanate microcapsule, and then uses an in-situ polymerization method to make phenolic resin and NL curing agent crosslinking reaction to coat the surface of the polyurethane-isocyanate microcapsule to form a phenolic / polyurethane-isocyanate double-layer microcapsule. The method has the characteristics of simplicity, stability, high efficiency and low cost, the prepared double-shell-layer phenolic / polyurethane-isocyanate microcapsule has improved mechanical properties, heat performance, aging performance and sealing performance compared with single-layer isocyanate microcapsules, and has excellent overall performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of microcapsules, and particularly relates to a phenolic / polyurethane-isocyanate double-layer microcapsule and preparation and application thereof. BACKGROUND

[0002] Metal materials such as steel are called the "skeleton of industry", and are an important material basis for the development of human society. Because of its good ductility, luster, excellent electrical conductivity and thermal conductivity and many other advantages, it is applied in various fields of the world, and the global demand for metal raw materials is increasing, from industrial and agricultural production to the development of national defense science and technology, which cannot be separated from the support of metal materials. However, metal materials are special and prone to corrosion damage, which seriously affects the service life of the materials, causes incalculable economic losses, and even endangers human life and safety. The corrosion loss is 10 times more than the loss caused by all kinds of natural disasters. These figures are enough to prove the great, deep and wide harm of corrosion to human beings, so we must control the occurrence of corrosion.

[0003] Among the methods of inhibiting corrosion, organic coatings can block the entry of corrosive ions and moisture into the metal, and are the most widely used protection means, accounting for about two-thirds of the protection cost. However, the coating is inevitably damaged by the environment and machinery during transportation and use, and the protective performance of the coating is also seriously harmed. The damage form may be local scratches or delamination, or stress-related macro cracks. The adhesion damage caused by environmental factors such as ultraviolet light, heat, oxygen, moisture and ions will also cause greater macro deterioration of the general protective performance and aesthetic performance of the coating. If not repaired in time and effectively, these damaged areas will quickly enter the corrosive medium, eventually leading to premature failure of the coating. Therefore, there is a great demand for a new generation of corrosion protection coatings that can intelligently respond to damage, have automatic repair function, and delay the corrosion of metal substrates. This emerging smart coating has self-repairing properties. Exogenous polymerizable repair agent microcapsules are added to the coating. When the coating is damaged, the microcapsules break under mechanical impact, release the repair agent, and then polymerize to form a protective film to repair the barrier performance of the coating.

[0004] Self-repairing microcapsules are usually micron-sized particles formed by coating the repair agent core material with a type of polymer material. The most commonly used anti-corrosion self-repairing microcapsules are isocyanate microcapsules, which can react with water in the environment to form a high polymer to repair the crack surface, so they can be used in anti-corrosion coatings as a single microcapsule system without the need to introduce additional initiators or curing agents. Isocyanate microcapsules are generally prepared by interfacial polymerization. In an oil-in-water emulsion system, isocyanate groups react with alcohols or amines to form isocyanate microcapsules.

[0005] The isocyanate microcapsules prepared at present have the characteristics of low wall material strength, poor heat resistance, poor aging performance and poor sealing performance, and cannot meet the harsh conditions required by industrial application, thereby limiting the engineering application. SUMMARY

[0006] In view of the low wall material strength of the existing isocyanate microcapsules, the microcapsules are easily broken and invalid in use. In addition, the existing isocyanate microcapsules have poor heat resistance, aging performance and sealing performance, resulting in rapid decay of the core material content. The present application provides a phenolic / polyurethane-isocyanate double-layer microcapsule and a preparation and application thereof.

[0007] In order to achieve the above-mentioned purpose, the following technical scheme is adopted in the present application:

[0008] A phenolic / polyurethane-isocyanate double-layer microcapsule, which is composed of a capsule wall and a capsule core, wherein the capsule wall is phenolic / polyurethane, and the capsule core is isophorone diisocyanate, and the weight ratio of the capsule wall to the capsule core is 1:1-3.

[0009] Further, the elastic modulus of the capsule wall is 5-9 GPa, and the hardness is 550-650 MPa; the particle size of the phenolic / polyurethane-isocyanate double-layer microcapsule is 20-150 μm; and the thickness of the capsule wall is 3-10 μm.

[0010] A self-repairing anticorrosive coating doped with the above-mentioned phenolic / polyurethane-isocyanate double-layer microcapsule, wherein the anticorrosive coating is coated on a steel plate to perform scratch corrosion experiment, the coating is scratched to the steel plate, and then the steel plate is immersed in 10 wt% NaCl brine, and the coating can realize rapid self-repairing, and the steel plate is still not corroded after being immersed for 7 days.

[0011] The above-mentioned phenolic / polyurethane-isocyanate double-layer microcapsule is applied in a coating.

[0012] A preparation method of a phenolic / polyurethane-isocyanate double-layer microcapsule, comprising the following steps:

[0013] Step (1), stirring deionized water and gum arabic at room temperature to form an aqueous phase;

[0014] Step (2), mixing and stirring toluene diisocyanate prepolymer L-75, isophorone diisocyanate and ethyl acetate to form an oil phase;

[0015] Step (3), under the condition of rapid stirring, the oil phase of step (2) is added dropwise into the aqueous phase of step (1), and then stirred and emulsified to form a stable oil-in-water emulsion;

[0016] Step (4), 1,4-butanediol is added dropwise to the oil-in-water emulsion of step (3), and the system temperature is raised to 50℃, and after a period of reaction, the stirring is stopped, and the product is filtered, washed with water, and dried to obtain polyurethane-isophorone diisocyanate microcapsules;

[0017] Step (5), dimethyl silicone oil and hydrophobic nanosilica are mixed and stirred uniformly by a high-speed emulsifier to form a continuous phase;

[0018] Step (6), alcohol-soluble phenolic resin, anhydrous ethanol, and NL curing agent are mixed and stirred to form a solution;

[0019] Step (7), the polyurethane-isophorone diisocyanate microcapsules of step (4) are added to the solution of step (6) to form a solid-liquid mixture;

[0020] Step (8), under the condition of stirring, the solid-liquid mixture of step (7) is added dropwise to the continuous phase of step (5), and after a period of reaction at room temperature, the stirring is stopped, and then centrifugation, washing, filtration, and drying are performed to obtain the final phenolic / polyurethane-isophorone diisocyanate microcapsules.

[0021] The mass ratio of deionized water to gum arabic in step (1) is 100:4-100:8; the mass ratio of isophorone diisocyanate, prepolymer L-75, and ethyl acetate in step (2) is 4:1:1; and the mass ratio of the oil phase to the water phase in step (3) is 1:3-1:5.

[0022] The stirring speed in step (1) is 400-800 r / min, and the stirring time is 3-5 h; the stirring speed in step (3) is 600-1000 r / min, and the emulsification time is 20-40 min.

[0023] The amount of 1,4-butanediol added in step (4) is 15%-25% of the amount of isophorone diisocyanate, and the system reaction time is 1-3 h.

[0024] The mass ratio of dimethyl silicone oil to hydrophobic nanosilica in step (5) is 100:2-100:4; the mass ratio of phenolic resin, anhydrous ethanol, and NL curing agent in step (6) is 100:200:15; the mass ratio of polyurethane-isophorone diisocyanate microcapsules to dimethyl silicone oil in step (5) in step (7) is 1:100-5:100, and the mass ratio to phenolic resin in step (6) is 2:1-1:2.

[0025] Further, the speed of the high-speed shearing machine in the step (5) is 10000-20000 r / min, and the stirring time is 1-3 min; the stirring speed in the step (8) is 400-700 r / min, and the reaction time is 6-12 h.

[0026] Compared with the prior art, the present application has the following advantages:

[0027] The present application makes toluene diisocyanate and 1,4-butanediol interface polymerization to form polyurethane-isocyanate microcapsule, and then uses in-situ polymerization method to make phenolic resin and NL curing agent crosslinking reaction to coat on the surface of the polyurethane-isocyanate microcapsule to form phenolic / polyurethane-isocyanate double-layer microcapsule. The method has the characteristics of simplicity, stability, high efficiency, low cost and high coating rate. The prepared double-shell layer phenolic / polyurethane-isophorone diisocyanate microcapsule has better mechanical properties, thermal properties, aging properties and sealing properties than single-layer isocyanate microcapsule, and the overall performance is excellent.

[0028] The phenolic / polyurethane-isocyanate microcapsule of the present application has good mechanical properties, compared with single-layer isocyanate microcapsule, the modulus is increased by more than 2 times, and the hardness is increased by more than 3 times. The heat resistance is improved, and the initial loss temperature of the microcapsule core material is increased by about 20℃. After aging at 200℃ for 8h, the core material loss is 10.98%, while the core material loss of single-layer isocyanate microcapsule can be nearly 20%. The microcapsule immersion experiment for 24h shows that the core material content of the phenolic / polyurethane-isocyanate microcapsule decreases from 55.76% to 41.11%, while the core material content of the single-layer isocyanate microcapsule decreases from 58.37% to 12.4%. The double-shell layer isocyanate microcapsule has better stability. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The process flow chart of the phenolic / polyurethane-isophorone diisocyanate microcapsule in the present application is shown in the figure;

[0030] Figure 2 The scanning electron microscope photo of the phenolic / polyurethane-isophorone diisocyanate microcapsule in the present application is shown in the figure;

[0031] Figure 3 The optical microscope photo of the phenolic / polyurethane-isophorone diisocyanate microcapsule in the present application is shown in the figure;

[0032] Figure 4 The scanning electron microscope photo of the double-shell wall material of the phenolic / polyurethane-isophorone diisocyanate microcapsule in the present application is shown in the figure;

[0033] Figure 5 The nanoindentation test comparison chart of the double-layer isocyanate microcapsule and the single-layer isocyanate microcapsule in the present application is shown in the figure;

[0034] Figure 6 Thermogravimetric analysis comparison chart of double-layer isocyanate microcapsules and single-layer isocyanate microcapsules in the present application;

[0035] Figure 7 Thermal aging comparison chart of double-layer isocyanate microcapsules and single-layer isocyanate microcapsules in the present application;

[0036] Figure 8 Water immersion stability comparison chart of double-layer isocyanate microcapsules and single-layer isocyanate microcapsules in the present application;

[0037] Figure 9 Scratch corrosion test result chart of coating without and with double-layer self-repairing microcapsules in the present application. DETAILED DESCRIPTION EMBODIMENT

[0038] A phenolic / polyurethane-isocyanate microcapsule and a synthesis method thereof, comprising the following steps:

[0039] (1) stirring deionized water and gum arabic at room temperature to form an aqueous phase;

[0040] (2) mixing and stirring toluene diisocyanate prepolymer L-75, isophorone diisocyanate, and ethyl acetate to form an oil phase;

[0041] (3) under the condition of rapid stirring, dropping the oil phase of step (2) into the aqueous phase of step (1) to form a stable oil-in-water emulsion after a period of stirring;

[0042] (4) dropping 1,4-butanediol into the emulsion of step (3) and increasing the system temperature to 50°C, stopping stirring after a period of reaction, and filtering, washing, and drying the product microcapsule to obtain a polyurethane-isophorone diisocyanate microcapsule;

[0043] (5) weighing dimethyl silicone oil and hydrophobic nanosilica, and mixing and stirring them with a high-speed shearing machine to form a continuous phase;

[0044] (6) mixing and stirring alcohol-soluble phenolic resin, anhydrous ethanol, and NL curing agent to form a solution;

[0045] (7) weighing the polyurethane-isophorone diisocyanate microcapsule in step (4) and adding it to the solution in step (6) to form a mixture;

[0046] (8) under the condition of stirring, dropping the solid-liquid mixture of step (7) into the continuous phase of step (5), and stopping stirring after a period of reaction at room temperature to obtain a microcapsule, which is then centrifuged, washed, filtered, and dried to obtain the final phenolic / polyurethane-isophorone diisocyanate microcapsule.

[0047] The mass ratio of deionized water to gum arabic in step (1) above is 100:4, the stirring speed is 400 r / min, and the stirring time is 5 h.

[0048] The mass ratio of isophorone diisocyanate, L-75, and ethyl acetate in step (2) above is 4:1:1, and the mass ratio of the oil phase of step (2) to the water phase of step (1) is 1:3.

[0049] The stirring speed in step (3) above is 600 r / min, and the emulsification time is 40 min.

[0050] The amount of 1,4-butanediol added in step (4) above is 15% of the amount of isophorone diisocyanate, and the system reaction time is 3 h.

[0051] The mass ratio of dimethyl silicone oil to hydrophobic nano-silicon dioxide in step (5) above is 100:2, and the mass ratio to the emulsion in step (3) is 100:1. The speed of the high-speed shearing machine is 20,000 r / min, and the stirring time is 1 min.

[0052] The mass ratio of phenolic resin, anhydrous ethanol, and NL curing agent in step (6) above is 100:200:15.

[0053] The mass ratio of polyurethane-isophorone diisocyanate microcapsules in step (7) to dimethyl silicone oil in step (5) is 1:100, and the mass ratio to phenolic resin in step (6) is 2:1.

[0054] The stirring speed in step (8) above is 400 r / min, and the reaction time is 12 h.

[0055] Nanoindentation analysis, thermal gravimetric analysis, aging analysis, and water immersion stability analysis are performed on the single-layer polyurethane-isophorone diisocyanate microcapsules of step (4) and the double-layer phenolic / polyurethane-isocyanate microcapsules of step (8).

[0056] The elastic modulus of the double-layer phenolic / polyurethane-isocyanate microcapsules is 5.44 GPa, the hardness is 618.06 MPa, the core material content is 55.76%, the initial loss temperature of the core material is 182.1°C, after 8 h of aging at 200°C, the core material loses 10.98%, and after 24 h of immersion in water, the core material content decays from 55.76% to 41.11%.

[0057] Correspondingly, the elastic modulus of the single-layer polyurethane-isophorone diisocyanate microcapsule is 2.48 GPa, the hardness is 172.85 MPa, the core material content is 58.37%, the initial loss temperature of the core material is 160.5°C, after aging at 200°C for 8h, the core material loss is 19.28%, and after soaking in water for 24h, the core material content decays from 58.37% to 12.4%. Example

[0058] In step (1) above, the mass ratio of deionized water to gum arabic is 100:8, the stirring speed is 800 r / min, and the stirring time is 3h.

[0059] In step (2) above, the mass ratio of the oil phase to the water phase of step (1) is 1:5.

[0060] In step (3) above, the stirring speed is 800 r / min, and the emulsification time is 20 min.

[0061] In step (4) above, the amount of 1,4-butanediol added is 25% of the amount of isophorone diisocyanate, and the system reaction time is 1h.

[0062] In step (5) above, the mass ratio of dimethyl silicone oil to hydrophobic nano-silicon dioxide is 100:2, and the mass ratio to the emulsion of step (3) is 100:15. The speed of the high-speed shearing machine is 20000 r / min, and the stirring time is 1 min.

[0063] In step (7) above, the mass ratio of polyurethane-isophorone diisocyanate microcapsule to dimethyl silicone oil of step (5) is 5:100, and the mass ratio to phenolic resin of step (6) is 1:2.

[0064] In step (8) above, the stirring speed is 700 r / min, and the reaction time is 6h.

[0065] The rest is the same as in Example 1. Example

[0066] In step (1) above, the mass ratio of deionized water to gum arabic is 100:4, the stirring speed is 400 r / min, and the stirring time is 5h.

[0067] In step (2) above, the mass ratio of the oil phase to the water phase of step (1) is 1:3.

[0068] In step (3) above, the stirring speed is 600 r / min, and the emulsification time is 40 min.

[0069] In step (4) above, the amount of 1,4-butanediol added is 15% of the amount of isophorone diisocyanate, and the system reaction time is 3h.

[0070] The mass ratio of dimethyl silicone oil to hydrophobic nano-silica in step (5) above was 100:2, the mass ratio to the emulsion in step (3) was 100:10, the rotation speed of the high-speed shearing machine was 20000 r / min, and the stirring time was 1 min.

[0071] The mass ratio of polyurethane-isophorone diisocyanate microcapsule to dimethyl silicone oil in step (5) above was 1:100, and the mass ratio to phenolic resin in step (6) was 2:1.

[0072] The stirring speed in step (8) above was 400 r / min, and the reaction time was 12 h.

[0073] The rest was the same as in Example 1. Example

[0074] The mass ratio of deionized water to gum arabic in step (1) above was 100:7, the stirring speed was 600 r / min, and the stirring time was 3.5 h.

[0075] The mass ratio of the oil phase in step (2) above to the water phase in step (1) was 1:4.

[0076] The stirring speed in step (3) above was 800 r / min, and the emulsification time was 20 min.

[0077] The amount of 1,4-butanediol added in step (4) above was 22% of the amount of isophorone diisocyanate, and the system reaction time was 1.5 h.

[0078] The mass ratio of dimethyl silicone oil to hydrophobic nano-silica in step (5) above was 100:3, the mass ratio to the emulsion in step (3) was 100:10, the rotation speed of the high-speed shearing machine was 12000 r / min, and the stirring time was 2 min.

[0079] The mass ratio of polyurethane-isophorone diisocyanate microcapsule to dimethyl silicone oil in step (5) above was 5:100, and the mass ratio to phenolic resin in step (6) was 1:1.

[0080] The stirring speed in step (8) above was 500 r / min, and the reaction time was 10 h.

[0081] The rest was the same as in Example 1. Example

[0082] The mass ratio of deionized water to gum arabic in step (1) above was 100:5, the stirring speed was 500 r / min, and the stirring time was 3 h.

[0083] The mass ratio of the oil phase in step (2) above to the water phase of step (1) is 1:3.

[0084] The stirring speed in step (3) above is 700 r / min, and the emulsification time is 35 min.

[0085] The ratio of the amount of 1,4-butanediol added in step (4) above to isophorone diisocyanate is 18%, and the system reaction time is 2 h.

[0086] The mass ratio of dimethyl silicone oil to hydrophobic nanosilica in step (5) above is 100:3, the mass ratio to the emulsion in step (3) is 100:1, the speed of the high-speed shearing machine is 20000 r / min, and the stirring time is 1 min.

[0087] The mass ratio of phenolic resin, anhydrous ethanol and NL curing agent in step (6) above is 100:200:15.

[0088] The mass ratio of polyurethane-isophorone diisocyanate microcapsules to dimethyl silicone oil in step (7) above is 4:100, and the mass ratio to phenolic resin in step (6) is 1:1.

[0089] The stirring speed in step (8) above is 600 r / min, and the reaction time is 10 h.

[0090] The rest is the same as in Example 1. Example

[0091] The mass ratio of deionized water to gum arabic in step (1) above is 100:5, the stirring speed is 800 r / min, and the stirring time is 3 h.

[0092] The mass ratio of the oil phase in step (2) above to the water phase of step (1) is 1:4.

[0093] The stirring speed in step (3) above is 900 r / min, and the emulsification time is 35 min.

[0094] The ratio of the amount of 1,4-butanediol added in step (4) above to isophorone diisocyanate is 21%, and the system reaction time is 2 h.

[0095] The mass ratio of dimethyl silicone oil to hydrophobic nanosilica in step (5) above is 100:3, and the speed of the high-speed shearing machine is 18000 r / min, and the stirring time is 2 min.

[0096] The mass ratio of the polyurethane-isophorone diisocyanate microcapsule in step (7) above to the dimethyl silicone oil in step (5) is 3:100, and the mass ratio to the phenolic resin in step (6) is 2:1.

[0097] The stirring speed in step (8) above is 500 r / min, and the reaction time is 8 h.

[0098] The rest is the same as in Example 1. Example

[0099] The mass ratio of deionized water to gum arabic in step (1) above is 100:4, the stirring speed is 500 r / min, and the stirring time is 4 h.

[0100] The mass ratio of the oil phase in step (2) above to the water phase in step (1) is 1:4.

[0101] The stirring speed in step (3) above is 600 r / min, and the emulsification time is 30 min.

[0102] The amount of 1,4-butanediol added in step (4) above is 25% of the amount of isophorone diisocyanate, and the system reaction time is 1.5 h.

[0103] The mass ratio of dimethyl silicone oil to hydrophobic nano-silica in step (5) above is 100:3, the speed of the high-speed shearing machine is 10,000 r / min, and the stirring time is 2 min.

[0104] The mass ratio of the polyurethane-isophorone diisocyanate microcapsule in step (7) above to the dimethyl silicone oil in step (5) is 2:100, and the mass ratio to the phenolic resin in step (6) is 1:1.

[0105] The stirring speed in step (8) above is 500 r / min, and the reaction time is 8 h.

[0106] The rest is the same as in Example 1.

[0107] The phenolic / polyurethane-isocyanate microcapsule prepared in this embodiment has a particle size of 20-150 μm.

[0108] The obtained phenolic / polyurethane-isocyanate microcapsules are mixed with epoxy resin E51 to prepare a self-repairing coating, which is coated on a Q235 carbon steel plate. The specific operation steps and parameters are as follows: 9-13 parts of curing agent diethylene triamine are mixed with 100 parts of epoxy E51, then vacuum filtration and defoaming are performed, the obtained phenolic / polyurethane-isocyanate microcapsules are added, and then curing is performed at room temperature for 24 h to obtain an epoxy resin coating doped with self-repairing microcapsules. The mass ratio of the phenolic / polyurethane-isocyanate microcapsules to the epoxy resin is 5:100-15:100.

[0109] The obtained epoxy resin coating doped with self-repairing microcapsules is subjected to scratch treatment with a scalpel to a carbon steel substrate, and is immersed in salt water for 7 days, and a blank test is performed for comparison. The results show that the carbon steel plate doped with phenolic / polyurethane-isocyanate self-repairing microcapsules is not corroded because the phenolic / polyurethane-isocyanate microcapsules are broken along the fracture surface and polymerize with water in the environment to repair the fracture surface. The blank sample without self-repairing microcapsules is corroded and rusted. It is proved that the phenolic / polyurethane-isocyanate microcapsules have good self-repairing effect.

[0110] In the embodiment, other resin materials can also be used to replace epoxy E51 to prepare different coating materials with self-repairing function.

[0111] The contents not described in detail in the specification of the present application belong to the prior art known to those skilled in the art. Although the above describes the specific embodiments of the present application in a descriptive manner, so as to facilitate those skilled in the art to understand the present application, it should be clear that the present application is not limited to the scope of the specific embodiments, and for those skilled in the art, it is obvious that various changes are within the spirit and scope of the present application defined and limited by the appended claims, and all the inventions utilizing the concept of the present application are included in the protection.

Claims

1. A process for the preparation of phenolic / polyurethane-isocyanate double-layer microcapsules, characterized by: The method comprises the following steps: Step (1), stirring deionized water and gum arabic at room temperature to form an aqueous phase; Step (2), mixing toluene diisocyanate prepolymer L-75, isophorone diisocyanate, and ethyl acetate to form an oil phase; Step (3), under the condition of rapid stirring, the oil phase of step (2) is added dropwise into the aqueous phase of step (1), and stirred to form a stable oil-in-water emulsion; Step (4), 1,4-butanediol is added dropwise into the oil-in-water emulsion of step (3), and the system temperature is raised to 50℃, and after a period of reaction, the stirring is stopped, and the product is filtered, washed with water, and dried to obtain polyurethane-isophorone diisocyanate microcapsules; Step (5), mixing dimethyl silicone oil and hydrophobic nano-silicon dioxide by a high-speed emulsifier to form a continuous phase; Step (6), mixing alcohol-soluble phenolic resin, anhydrous ethanol, and NL curing agent to form a solution; Step (7), adding the polyurethane-isophorone diisocyanate microcapsules of step (4) into the solution of step (6) to form a solid-liquid mixture; Step (8), under the condition of stirring, the solid-liquid mixture of step (7) is added dropwise into the continuous phase of step (5), and after a period of reaction at room temperature, the stirring is stopped, and then centrifugation, washing, filtration, and drying are performed to obtain the final phenolic / polyurethane-isophorone diisocyanate microcapsules; In step (5), the mass ratio of dimethyl silicone oil to hydrophobic nano-silicon dioxide is 100:2-100:4; in step (6), the mass ratio of phenolic resin, anhydrous ethanol, and NL curing agent is 100:200:15; in step (7), the mass ratio of polyurethane-isophorone diisocyanate microcapsules to dimethyl silicone oil in step (5) is 1:100-5:100, and the mass ratio to phenolic resin in step (6) is 2:1-1:

2.

2. A process for the preparation of a phenolic / polyurethane-isocyanate double layer microcapsule according to claim 1, characterized by: In step (1), the mass ratio of deionized water to gum arabic is 100:4-100:8; in step (2), the mass ratio of isophorone diisocyanate, prepolymer L-75, and ethyl acetate is 4:1:1; in step (3), the mass ratio of oil phase to aqueous phase is 1:3-1:

5.

3. A process for the preparation of a phenolic / polyurethane-isocyanate double layer microcapsule according to claim 1, characterized by: In step (1), the stirring speed is 400-800 r / min, and the stirring time is 3-5 h; in step (3), the stirring speed is 600-1000 r / min, and the emulsification time is 20-40 min.

4. The process for the preparation of phenolic / polyurethane-isocyanate double layer microcapsules according to claim 1, characterized by: In step (4), the amount of added 1,4-butanediol is 15%-25% of the amount of isophorone diisocyanate, and the system reaction time is 1-3 h.

5. The process for the preparation of phenolic / polyurethane-isocyanate double layer microcapsules according to claim 1, characterized by the fact that: In step (5), the rotation speed of the high-speed shearing machine is 10000-20000 r / min, and the stirring time is 1-3 min; in step (8), the stirring speed is 400-700 r / min, and the reaction time is 6-12 h.

6. A phenolic / polyurethane-isocyanate double-layer microcapsule prepared by the production method according to any one of claims 1 to 5, characterized in that: The phenolic / polyurethane-isocyanate double-layer microcapsules are composed of a capsule wall and a capsule core, the capsule wall is phenolic / polyurethane, and the capsule core is isophorone diisocyanate, and the weight ratio of the capsule wall to the capsule core is 1:1-3.

7. A phenolic / polyurethane-isocyanate bi-layer microcapsule according to claim 6, characterized in that: The elastic modulus of the capsule wall is 5-9 GPa, and the hardness is 550-650 MPa; the particle size of the phenolic / polyurethane-isocyanate double-layer microcapsule is 20-150 microns; and the thickness of the capsule wall is 3-10 microns.

8. A self-repairing anticorrosive coating of phenolic / polyurethane-isocyanate double-layer microcapsules prepared according to the method of any one of claims 1 to 5, characterized in that: The anti-corrosion coating is coated on a steel plate to perform scratch corrosion experiment, the coating is scratched to the steel plate, and the coating can realize rapid self-repairing when immersed in 10wt% NaCl brine, and the steel plate has not been corroded after being immersed for 7 days.

9. The phenolic / polyurethane-isocyanate double-layer microcapsule prepared by the preparation method of any one of claims 1-5 is applied in a coating.

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