Airtight coating and preparation method thereof

Abstract

The invention discloses an airtight coating. The airtight coating comprises a primer and a finish, the primer takes epoxy resin, an emulsifier, a primer curing agent and water as main raw materials; the finish paint takes epoxy resin, a diluent, silica powder, fumed silica, a coloring agent, a flatting agent, a defoaming agent and a finish paint curing agent as main raw materials, wherein the finish paint curing agent comprises an amine curing agent, an alcohol diluent and epoxy resin. According to the invention, the water-based emulsion type primer is adopted, and the modified main finish paint and the curing agent are combined, so that the obtained epoxy resin coating has the characteristics of good air tightness, high hardness, high elongation at break and the like, has good environmental benefits, and is suitable for the fields of controlled atmosphere insect prevention warehouses and the like; the preparation method is simple, convenient to operate, low in cost and suitable for popularization and application.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and particularly relates to an airtight coating and a preparation method thereof. Background Art

[0002] The airtightness of a warehouse is one of the important indicators for storing agricultural products. Epoxy resin is a polymer material with excellent properties such as high strength, high rigidity, and good chemical corrosion resistance; epoxy resin belongs to thermosetting resin. When it is mixed with a curing agent, a cross-linked structure is formed through ring-opening polymerization reaction. This cross-linked structure can endow epoxy resin with unique properties, including high strength, high rigidity, excellent chemical corrosion resistance, and relatively high heat resistance, etc. It was initially used in aerospace and military applications and is now widely used in fields such as coatings, composite materials, and electronic chemicals.

[0003] However, after epoxy resin is cured, its hardness is small, it is very easy to break during stretching, the elongation at break is extremely low, and the airtight performance is poor. In addition, using pure epoxy resin as the coating raw material, its cost is extremely high. Further exploring an epoxy resin-based coating system with low cost and good mechanical properties and airtight performance has important research and application significance. Summary of the Invention

[0004] The main purpose of the present invention is to provide an epoxy resin-based airtight coating aiming at the problems and deficiencies existing in the prior art, which can effectively solve the problems such as poor airtightness, small hardness, and low elongation at break of the coating; and the involved preparation method is relatively simple and has low cost, which is suitable for popularization and application.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] An airtight coating includes a primer and a topcoat. The primer uses epoxy resin, emulsifier, primer curing agent, and water as main raw materials; the topcoat uses epoxy resin, diluent, silica powder, fumed silica, leveling agent, defoaming agent, and topcoat curing agent as main raw materials, wherein the topcoat curing agent includes amine curing agent, alcohol diluent, and epoxy resin.

[0007] In the above solution, the epoxy resin (the epoxy resin introduced in the primer and topcoat) selects bisphenol A epoxy resin, and its epoxy equivalent is 184 - 190; specifically, NPEL-128 / E51 bisphenol A epoxy resin, etc. can be selected.

[0008] In the above solution, the primer includes a primer main paint and a primer curing agent. The components and their mass percentages in the primer main paint include: epoxy resin 40 - 60%, emulsifier 5 - 15%, water 30 - 45%; when curing, a curing agent is added, and the dosage of the primer curing agent accounts for 20 - 40% of the mass of the primer main paint.

[0009] In the above solution, the emulsifier can be selected from LZ4528 emulsifier, 4528 emulsifier, WH-W900 emulsifier, etc.

[0010] In the above solution, the primer curing agent is a low-molecular polyamide curing agent with an amine value of 380 - 450. Specifically, polyamide curing agent 651, etc. can be selected.

[0011] In the above solution, the topcoat includes a topcoat main paint and a topcoat curing agent. The components and their mass percentages in the topcoat main paint are as follows: epoxy resin 30 - 60%, diluent 5 - 12%, silicon micropowder 30 - 60%, fumed silica 0.1 - 0.4%, leveling agent 0.1 - 0.4%, defoaming agent 0.5 - 1.8%; The components and their mass percentages in the topcoat curing agent are as follows: amine curing agent 20 - 40%, alcohol diluent 50 - 70%, epoxy resin 3 - 15%.

[0012] Preferably, in the topcoat curing agent, the content of the amine curing agent is 30 - 35%; the content of the epoxy resin is 9 - 14%.

[0013] In the above solution, the diluent can be selected from alkyl (C12 - 14) glycidyl ether (AGE) or phenyl glycidyl ether (PGE), etc.

[0014] In the above solution, the epoxy resin is bisphenol A type epoxy resin with an epoxy equivalent of 184 - 190; specifically, NPEL-128 / E51, etc. can be selected.

[0015] Furthermore, the topcoat also contains a colorant, and its dosage accounts for 10 - 20% of the total mass of the topcoat main paint.

[0016] In the above solution, the colorant can be selected from conventional pigments such as inorganic pigments or organic pigments, or dye paints, etc.; among them, the inorganic pigments include one or more of titanium dioxide, carbon black, iron oxide, chromium oxide, etc.; the organic pigments include one or more of silicon fullerenes, safranine, phthalocyanine pigments, anthraquinone pigments, azo pigments, etc.

[0017] In the above solution, the particle size of the silicon micropowder is 300 - 3000 mesh.

[0018] Preferably, the silicon micropowder is obtained by compounding 400-mesh and 1250-mesh silicon micropowder according to a mass ratio of 1:0.1 - 0.2.

[0019] In the above solution, the fumed silica can be specifically selected as A200 fumed silica, etc.

[0020] In the above solution, the leveling agent can be selected from silicone leveling agents, specifically, silicone surface additives BYK-306 or BYK-307, etc.

[0021] In the above solution, the defoamer can be selected from silicone defoamers; specifically, silicone polymer defoamer BYK-A530, silicone defoamer BYK-A506, organically modified polysiloxane defoamer TEGO Airex 900, etc. can be selected. If the dosage of the defoamer is too small, the air bubbles in the epoxy resin cannot be completely removed. If the dosage is too large, cratering or oil bloom phenomenon will occur, and even the performance of the epoxy resin paint film will be reduced.

[0022] Preferably, the obtained defoamer is compounded from BYK-A530 and BYK-A506 in a mass ratio of 1:0.5 - 1.

[0023] In the above solution, the amine curing agent can be selected from one or more of 2-methylpentanediamine (DYTEK-A), isophorone diamine, 4,4'-methylenedianiline, 4,4'-diaminodiphenyl sulfone, etc.; the alcohol diluent can be selected from one or more of benzyl alcohol, polyols, etc.

[0024] In the above solution, the dosage of the topcoat curing agent accounts for 15 - 25% of the topcoat dosage.

[0025] In the above solution, the preparation method of the topcoat curing agent includes the following steps: Add the amine curing agent weighed according to the ratio to the reaction vessel, and dropwise add part of the alcohol diluent under stirring conditions (control the temperature below 30°C), and let it stand; After mixing and stirring the epoxy resin and the remaining alcohol diluent evenly, then drop it into the reaction vessel and react at 40 - 60°C (when the temperature is too high, by-products are likely to be produced, which is not conducive to the improvement of the topcoat performance; when the temperature is too low, the reaction is incomplete, which is not conducive to ensuring the improvement effect).

[0026] In the above solution, 30 - 60% of the dosage of the alcohol diluent is added to the amine curing agent first.

[0027] In the above solution, the standing time is 3 - 8 min.

[0028] In the above solution, the reaction time is 1 - 1.5 h.

[0029] The preparation method of the above airtight coating includes the following steps:

[0030] 1) Primer;

[0031] Add epoxy resin to the reactor with a stirring device, add an emulsifier under stirring conditions at room temperature, and carry out high-speed stirring; Dropwise add water and carry out high-speed dispersion stirring; Quickly add water and carry out homogenization and dispersion stirring to obtain the main primer paint. Before use, mix the main primer paint and the primer curing agent evenly to obtain the primer;

[0032] 2) Topcoat;

[0033] Epoxy resin is added to a reactor equipped with a stirring device, stirred at room temperature, and a diluent, silica powder, fumed silica, leveling agent, defoaming agent, and colorant are added in sequence, and then stirred at high speed at room temperature to obtain the main paint of the topcoat; before use, the main paint of the topcoat is mixed evenly with the topcoat curing agent to obtain the topcoat.

[0034] In the above solution, in step 1), the high-speed stirring rate is 1500 - 1800 r / min, and the time is 0.5 - 1.0 h; the high-speed stirring and dispersion rate is 1500 - 2000 r / min, and the time is 0.5 - 1.0 h; the homogenizing and dispersing stirring rate is 500 - 800 r / min, and the time is 0.5 - 1.0 h.

[0035] In the above solution, in step 2), during the feeding process, the stirring speed used is 300 - 500 r / min; the high-speed stirring rate is 1500 - 2000 r / min, and the time is 1.0 - 2.0 h.

[0036] During the preparation of the epoxy resin emulsion for the primer and topcoat, when high-speed stirring is required, the rotation speed is controlled above 1500 r / min to ensure a uniform dispersion effect, and further ensure the use performance and storage stability of the coating (it is not easy to delaminate during later storage), etc.

[0037] Applying the airtight coating prepared by the above solution to fields such as modified atmosphere insect-proof warehouses can exhibit good mechanical properties and airtight properties.

[0038] The principle of the present invention is as follows:

[0039] 1) Topcoat;

[0040] In the present invention, silica powder, defoaming agent, leveling agent, etc. are used to modify epoxy resin to prepare the main paint of the topcoat. Silica powder can reduce the reaction exothermic peak temperature, curing shrinkage rate, and linear expansion coefficient of the epoxy resin cured product, reduce internal stress, prevent the cured product from cracking, and improve the elongation at break and airtight properties of the coating; adding a defoaming agent can reduce the surface tension of the foam and effectively reduce the appearance of bubbles during the curing process of the coating; adding a leveling agent can increase the fluidity of the coating and prevent the appearance of shrinkage holes when the coating forms a film.

[0041] In addition, epoxy resin is used to modify the amine curing agent. The epoxy group breaks and reacts with the amino group of the amine curing agent, which can effectively increase the reaction activity of the curing agent, making it easier to polymerize with epoxy resin into a chain. The functional groups on the polymer molecular chain increase, which is beneficial to significantly improving the hardness, tensile strength, and other properties of the coating after curing and forming a film; at the same time, in cooperation with the main paint material of the topcoat, it significantly improves the airtight performance.

[0042] 2) Primer;

[0043] In the present invention, an emulsifier and water are added to epoxy resin, and high-speed stirring is carried out for dispersion and emulsification to prepare the main paint of the water-based primer. Its VOCs content is low, and it has significant economic and environmental benefits.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] 1) The airtightness coating described in the present invention includes a primer and a topcoat. The primer is a water-based coating with extremely low VOCs content, which is more environmentally friendly, safer for storage and transportation, and can be widely applied to various substrates; the topcoat uses a solvent-free coating with low VOCs content and high mechanical properties and airtightness after curing.

[0046] 2) The epoxy resin coating provided by the present invention has the characteristics of good airtightness, high hardness, high elongation at break, etc., and has good environmental benefits, and is applicable to fields such as modified atmosphere insect-proof warehouses.

[0047] 3) The preparation method of the epoxy resin-based coating described in the present invention is simple, easy to operate, and has low cost, and is suitable for popularization and application.

[0048] Description of the drawings

[0049] Figure 1 Synthesis schematic diagram of the topcoat modifier curing agent provided by one embodiment of the present invention;

[0050] Figure 2 FT-IR spectra of the topcoat curing agents obtained in Examples 1 to 3 of the present invention;

[0051] Figure 3 Schematic diagram of the structure of the mechanical property test samples of the topcoat coatings obtained in Examples 1 to 3 and Comparative Examples 1 to 2 of the present invention;

[0052] Figure 4 Maximum tensile strength test results of the topcoat coatings obtained in Examples 1 to 3 and Comparative Examples 1 to 2 of the present invention;

[0053] Figure 5 Elongation at break test results of the topcoat coatings obtained in Examples 1 to 3 and Comparative Examples 1 to 2 of the present invention;

[0054] Figure 6 Hardness test results of the topcoat coatings obtained in Examples 1 to 3 and Comparative Examples 1 to 2 of the present invention. Specific embodiments

[0055] The present invention will be further described in detail below in conjunction with embodiments, which is convenient for a clearer understanding of the present invention, but they do not constitute a limitation to the present invention.

[0056] In the following examples, those without special conditions specified are carried out according to conventional conditions or the conditions recommended by the manufacturer. Except as otherwise specified, the raw materials used in the following examples are all available from ordinary commercial sources.

[0057] In the following examples, the bisphenol A epoxy resin is NPEL-128 / E51 provided by Nan Ya Plastics Kunshan Co., Ltd., and its epoxy equivalent is 184-190.

[0058] In the following examples, the airtight coating includes a primer and a topcoat. The primer includes a primer main paint and a primer curing agent. The preparation method of the primer main paint includes the following steps:

[0059] Add 100.0 g of epoxy resin NPEL-128 / E51 to a reactor equipped with a stirring device, stir at room temperature and add 15.0 g of LZ4528 emulsifier, stir at high speed (1500 r / min) for 30-40 min; add 34.0 g of water dropwise, and disperse and stir at high speed (1500-2000 r / min, 30-50 min); quickly add 34.0 g of water, and homogenize and disperse and stir (500-800 r / min) for 30-60 min to obtain the primer main paint (epoxy resin emulsion); among them, the LZ4528 emulsifier is provided by Wuhan Longhua Zhengze Chemical Co., Ltd., with a viscosity of 3000-7000 mPa·S and an epoxy equivalent of 1600.

[0060] After testing, the viscosity of the obtained primer main paint (epoxy resin emulsion) is 33853 mPa·s; place the epoxy resin emulsion in an oven at 50 °C for 72 h, there is no obvious phase separation or precipitation, and the sample can be re-formed into an emulsion after shaking, proving that the thermal stability is qualified; place the epoxy resin emulsion in a centrifuge tube, adjust the centrifuge to more than 3000 r / min for 30 min, and there is no obvious phase separation or precipitation, proving that the centrifugal stability is qualified.

[0061] In addition, during the specific use of the primer, the primer main paint and the primer curing agent are mixed evenly and then cured at room temperature. Among them, the primer curing agent is 651 low molecular weight polyamide with an amine value of 400, provided by Guangzhou Jinyonggu New Materials Co., Ltd.; the dosage is 20-40% of the mass of the primer main paint.

[0062] Example 1

[0063] An airtight coating, wherein the preparation method of the topcoat (solvent-free epoxy resin coating) includes the following steps:

[0064] Preparation of the main paint of the topcoat: Add 167.2 g of EP128 epoxy resin to the stirring device reactor, stir at room temperature (300 - 500 r / min) and sequentially add 22.0 g of diluent (PGE), 158.36 g of silica powder (142 g of 400 - mesh silica powder and 16.36 g of 1250 - mesh silica powder), 0.84 g of fumed silica (A200), 2.8 g of defoamer (1.2 g of BYK - A 506 and 1.6 g of BYK - A530), 0.8 g of leveling agent (BYK - 306), 48.0 g of white dye paste (Kenying paint provided by Suzhou Jinhui New Type Coating Co., Ltd.; dye paint). After stirring evenly, stir at high speed (1500 - 2000 r / min) for 1.5 h, then cool to room temperature and discharge to obtain the main paint of the topcoat (epoxy resin emulsion), and its measured viscosity is 25557 mPa·S;

[0065] Preparation of the curing agent of the topcoat: Add 32.0 g of amine curing agent (DYTEK - A) to a three - necked flask, and drop 32.0 g of alcohol diluent (benzyl alcohol) into the three - necked flask under stirring conditions (control the temperature below 30 °C) for reaction; Mix 6.0 g of EP128 epoxy resin with 32.0 g of alcohol diluent (benzyl alcohol) and stir evenly, then drop it into the three - necked flask, react at 50 °C for 1.5 h, and then cool to room temperature to obtain the curing agent of the topcoat;

[0066] During the specific use of the topcoat, mix the main paint of the topcoat and the curing agent of the topcoat evenly, and then carry out room - temperature curing.

[0067] Example 2

[0068] An airtight coating, wherein the preparation method of the topcoat comprises the following steps:

[0069] Preparation of the main paint of the topcoat: The same as in Example 1;

[0070] Preparation of the curing agent of the topcoat: Add 32.0 g of amine curing agent (DYTEK - A) to a three - necked flask, and drop 29.5 g of diluent (benzyl alcohol) into the three - necked flask under stirring conditions (control the temperature below 30 °C) for reaction; Mix 9.0 g of EP128 epoxy resin with 29.5 g of diluent (benzyl alcohol) and stir evenly, then drop it into the three - necked flask, react at 50 °C for 1.0 h, and then cool to room temperature to obtain the curing agent of the topcoat;

[0071] During the specific use of the topcoat, mix the main paint of the topcoat and the curing agent of the topcoat evenly, and then carry out room - temperature curing.

[0072] Example 3

[0073] An airtight coating, wherein the preparation method of the topcoat comprises the following steps:

[0074] Preparation of the main topcoat paint: The same as in Example 1;

[0075] Preparation of the topcoat curing agent: Add 32.0 g of amine curing agent (DYTEK-A) to a three-necked flask, and drop 27.5 g of diluent (benzyl alcohol) into the three-necked flask under stirring conditions (controlling the temperature below 30 °C) for reaction; After mixing 12.0 g of EP128 epoxy resin and 27.5 g of diluent (benzyl alcohol) evenly by stirring, then drop it into the three-necked flask. After reacting at 50 °C for 1.0 h, cool it to room temperature to obtain the topcoat curing agent;

[0076] During the specific use of the topcoat, mix the main topcoat paint and the topcoat curing agent evenly, and then carry out room-temperature curing.

[0077] In Examples 1 to 3, the dosage ratio of the main topcoat paint remains unchanged, and by controlling the stirring time, the viscosities of the obtained epoxy resin emulsions are similar.

[0078] Comparative Example 1

[0079] An epoxy resin-based coating, the preparation method of its topcoat includes:

[0080] Main topcoat paint: EP128 epoxy resin;

[0081] Topcoat curing agent: Mix 32.0 g of amine curing agent (DYTEK-A) and 68.0 g of diluent (benzyl alcohol) evenly by stirring.

[0082] During the specific use of the topcoat, mix the main topcoat paint and the topcoat curing agent evenly, and then carry out room-temperature curing.

[0083] Comparative Example 2

[0084] An epoxy resin-based coating, its preparation method is substantially the same as that of Example 1, the difference being that the preparation method of the topcoat curing agent is the same as that of Comparative Example 1.

[0085] To test whether the EP128 epoxy resin in the topcoat curing agent provided by the present invention reacts completely, the FT-IR spectra of the topcoat curing agents described in Examples 1 to 3 (named D1 to 3 respectively) were tested. As Figure 2 shown, the absorption peak of the epoxy group of EP128 epoxy resin is around 910 cm -1 , and there is no absorption peak of the epoxy group in the FT-IR spectra of the curing agents D1 to 3, proving that the EP128 in the topcoat curing agents obtained in Examples 1 to 3 has all reacted completely.

[0086] Testing of the mechanical properties of the topcoat:

[0087] The topcoat main paints described in Examples 1 to 3, Comparative Example 1, and Comparative Example 2 were respectively mixed with their corresponding topcoat curing agents at mass ratios of 4:1, 2:1, and 4:1 and stirred evenly, and then poured into molds to prepare samples. A tensile testing machine was used to test the maximum tensile strength and elongation at break. The tensile sample model parameters were as Figure 3 ; and an LX-D Shore hardness tester was used to measure the hardness of the topcoat after curing.

[0088] The maximum tensile strength, elongation at break, and hardness were respectively as Figure 4 , Figure 5 and Figure 6 , where D1-3 were the samples obtained from the main paints and corresponding curing agents described in Examples 1 to 3, and D0-1 and D0-2 were the samples obtained from the main paints and curing agents described in Comparative Examples 1-2. When cured at 25°C for 12 h and 24 h, the elongation at break and hardness of the samples obtained from Examples 1 to 3 were better than those of the samples obtained from Comparative Examples 1 to 2, and increased with the increase in the dosage of EP128 epoxy resin in the modified curing agent; due to a secondary curing process between DYTEK-A and EP128 occurring in 7 to 14 days, when cured for 14 days, the hardness and tensile strength of the epoxy resin paint film increased.

[0089] Application Example

[0090] According to GB / T 25229-2010 "Airtightness Requirements for Grain Storage Bungalows", the airtightness coating of the present invention was subjected to an airtightness test. When applying the coating, the primer was first thinly applied, and the topcoat was applied after the primer had dried; the specific steps were as follows:

[0091] 1) A gypsum board was used to simulate the test wall, and a test environment was constructed with a test pressure of 500 Pa.

[0092] 2) Preparation of the primer: 100.0 g of EP128 epoxy resin was added to a reactor equipped with a stirring device, stirred at room temperature, and 15.0 g of LZ4528 emulsifier was added, and high-speed stirring (1500 r / min) was carried out for 30 to 40 min; 34.0 g of water was added dropwise, and high-speed dispersion stirring (1500 - 2000 r / min, 30 - 50 min) was carried out; 34.0 g of water was quickly added, and homogenizing dispersion stirring (500 - 800 r / min) was carried out for 30 to 60 min to obtain the primer main paint.

[0093] 20 g of the primer main paint was taken and mixed and stirred evenly with 10 g of 651 low molecular weight polyamide curing agent. Then it was evenly applied on one side of the gypsum board with a coating thickness of 0.05 - 0.1 mm, dried at room temperature, and after drying, the sampling, mixing, and coating operations were repeated. The primer was brushed three times, and the topcoat was applied after the primer had dried.

[0094] 3) Preparation of topcoat: The preparation methods of the topcoat main paint and the curing agent are the same as those in Example 2. Take 40 g of the topcoat main paint and mix it evenly with 10 g of the curing agent, and evenly apply it to one side of the gypsum board coated with the primer, with a coating thickness of 0.3 - 0.8 mm. After drying at room temperature, repeat the sampling and mixing and perform the coating operation, and brush the topcoat three times.

[0095] In summer, the temperature is relatively high, and the curing speed of the primer and the topcoat is fast, and it can be cured in 8 - 12 hours; in winter, the temperature is low, and the curing speed is slow, and heating can be used to assist curing.

[0096] Since the gypsum board has good air permeability, both the primer and the topcoat are brushed 3 times.

[0097] Application of comparative example

[0098] According to GB / T25229 - 2010 "Airtightness Requirements for Grain Storage Bungalows", the airtightness coating described in the present invention is subjected to an airtightness test. When brushing the coating, first thinly brush the primer, and then brush the topcoat after the primer is dry; the specific steps include:

[0099] 1) Use a gypsum board to simulate the test wall, construct a test environment, and the test pressure is 500 Pa;

[0100] 2) Preparation of primer: Take 20 g of epoxy resin EP128 and mix it evenly with 10 g of 651 low molecular weight polyamide curing agent, then evenly apply it to one side of the gypsum board, with a coating thickness of 0.05 - 0.1 mm, and dry it at room temperature. After drying, repeat the sampling and mixing and perform the coating operation. Brush the primer three times, and apply the topcoat after the primer is dry.

[0101] 3) Preparation of topcoat: The preparation methods of the topcoat main paint and the curing agent are the same as those in Comparative Example 1; take 40 g of epoxy resin EP128 and mix it evenly with 20 g of DYTEK - A curing agent, and evenly coat it on the side of the gypsum board coated with the primer, with a coating thickness of 0.3 - 0.8 mm. After drying at room temperature, repeat the sampling and mixing and perform the coating operation, and brush the topcoat three times.

[0102] Since the gypsum board has good air permeability, both the primer and the topcoat are brushed 3 times.

[0103] After the coating is completely cured, test the air leakage time of the gypsum board model coated with the coating. The airtightness level of the application example is grade one, and the airtight performance is significantly improved. The test results are shown in Table 1.

[0104] Table 1

[0105] Number Pressure difference change range (Pa) Pressure half-life (t) Air tightness level Application example 500～250 > 5 min First level Application comparative example 500～250 2 min < t < 4 min Third level

[0106] The present invention is not limited to the above embodiments. For those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications are also considered within the protection scope of the present invention. The content not described in detail in this specification belongs to the prior art well known to those skilled in the art.

Claims

1. An airtight coating, comprising a primer and a topcoat, characterized in that, the primer uses epoxy resin, emulsifier, primer curing agent and water as main raw materials; the topcoat uses epoxy resin, diluent, silica powder, fumed silica, leveling agent, defoaming agent and topcoat curing agent as main raw materials, wherein the topcoat curing agent includes amine curing agent, alcohol diluent and epoxy resin.

2. The airtight coating according to claim 1, characterized in that, the epoxy resin is bisphenol A epoxy resin with an epoxy equivalent of 184 - 190.

3. The airtight coating according to claim 1, characterized in that, the topcoat includes a topcoat main paint and a topcoat curing agent. The components and their mass percentages in the topcoat main paint are: epoxy resin 30 - 60%, diluent 5 - 12%, silica powder 30 - 60%, fumed silica 0.1 - 0.4%, leveling agent 0.1 - 0.4%, defoaming agent 0.5 - 1.8%; the components and their mass percentages in the topcoat curing agent are: amine curing agent 20 - 40%, alcohol diluent 50 - 70%, epoxy resin 3 - 15%.

4. The airtight coating according to claim 3, characterized in that, the diluent is alkyl glycidyl ether or phenyl glycidyl ether.

5. The airtight coating according to claim 3, characterized in that, the amine curing agent is one or more of 2 - methylpentamethylenediamine, isophorone diamine, 4,4'-methylenedianiline, 4,4'-diaminodiphenyl sulfone; the alcohol diluent is one or more of benzyl alcohol and polyol.

6. The airtight coating according to claim 3, characterized in that, the dosage of the topcoat curing agent accounts for 15 - 25% of the topcoat dosage.

7. The airtight coating according to claim 3, characterized in that, the preparation method of the topcoat curing agent includes the following steps: Add the amine curing agent weighed according to the ratio to the reaction vessel, dropwise add part of the alcohol diluent under stirring conditions below 30°C, and let it stand; Mix and stir the epoxy resin and the remaining alcohol diluent evenly and then drop them into the reaction vessel, and react at 40 - 60°C.

8. The airtight coating according to claim 1, characterized in that, the primer includes a primer main paint and a primer curing agent. The components and their mass percentages in the primer main paint are: epoxy resin 40 - 60%, emulsifier 5 - 15%, water 30 - 45%; When curing, add the curing agent, and the dosage of the primer curing agent accounts for 20 - 40% of the primer main paint quality.

9. The airtight coating according to claim 1, characterized in that, the primer curing agent is a low - molecular polyamide curing agent with an amine value of 380 - 450.

10. The preparation method of the airtight coating according to any one of claims 1 - 9, characterized in that, includes the following steps: 1) Primer; Add epoxy resin to a reactor with a stirring device, add an emulsifier under stirring conditions at room temperature, and carry out high - speed stirring; Dropwise add water and carry out high - speed dispersion stirring; Quickly add water and carry out homogenizing dispersion stirring to obtain the primer main paint. Before use, mix the primer main paint and the primer curing agent evenly to obtain the primer; 2) Topcoat; Epoxy resin is added to a reactor equipped with a stirring device, stirred at room temperature, and a diluent, silica powder, fumed silica, leveling agent, defoaming agent, and colorant are added in sequence, and then stirred at high speed at room temperature to obtain the main paint of the topcoat; before use, the main paint of the topcoat is mixed evenly with the topcoat curing agent to obtain the topcoat.

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