A solventless epoxy coating

Abstract

The present application relates to the field of paint, especially to solventless epoxy paint. The solventless epoxy paint of the present application comprises an A component and a B component, the A component comprises bisphenol A type epoxy resin, reactive diluent, leveling agent, defoaming agent and anti-settling agent; the B component comprises a curing agent of oxalic acid modified isophorone diamine and mannich base modified diethylene triamine. After using the curing agent of the present application, the surface dry time and the real dry time are obviously improved, so that the paint can reach complete curing faster, thereby the subsequent processing or use can be carried out in advance, and the whole production process is accelerated.

Description

Technical Field

[0001] This invention relates to the field of coatings, and more particularly to solvent-free epoxy coatings. Background Technology

[0002] In the current field of coating technology, some curing agents have a relatively slow curing process. Under standard environmental conditions, it often takes several hours or even longer to reach a basic level of dryness. This significantly extends the coating application cycle, increases time and labor costs, reduces production efficiency, and fails to meet the requirements of modern industrial rapid production. For example, the waiting time is extended when applying multiple layers of coating, and in some industrial production lines with stringent efficiency requirements, it becomes a bottleneck factor limiting capacity expansion.

[0003] More seriously, existing coating curing agents produce coatings with extremely poor adhesion, making them prone to peeling. When the coating is applied to the substrate surface, under normal environmental stress, such as cyclical temperature changes and humidity fluctuations, microscopic observation and adhesion testing reveal a significant decrease in adhesion between the coating and the substrate after just a few weeks, resulting in large-scale peeling. In outdoor applications, such as decorative coatings on building facades and traffic signs, coating peeling not only severely affects aesthetics but also renders the coated object unprotected, accelerating substrate corrosion and damage. This shortens the coating's lifespan and increases maintenance and recoating costs.

[0004] In terms of hardness and wear resistance, the hardness of the cured coating is insufficient. When tested, the hardness value does not meet the standard, making it difficult to resist minor friction and scratches in daily use. It is prone to scratches and wear, causing the decorative and protective properties of the coating to decline rapidly. It cannot provide durable and reliable protection for the coated object, which greatly limits its application in fields with high wear resistance requirements.

[0005] In summary, existing coating curing agents are not performing well and cannot meet the increasingly diverse needs of various industries. There is an urgent need for a new type of high-performance coating curing agent to overcome these problems, thereby promoting the further development and application of coating technology. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a solvent-free epoxy coating that solves the technical problem that, under standard environmental conditions, it takes several hours or even longer to reach a basic degree of drying.

[0008] (II) Technical Solution

[0009] In a first aspect, the present invention provides a solvent-free epoxy coating, the coating comprising component A and component B, wherein component A comprises bisphenol A type epoxy resin, reactive diluent, leveling agent, defoamer and anti-settling agent;

[0010] Component B includes the curing agents oxalic acid-modified isophorone diamine and Mannich base-modified diethylenetriamine.

[0011] Optionally, component A includes the following raw materials in parts by weight: 40-50 parts of bisphenol A type epoxy resin, 5-10 parts of reactive diluent, 0.1-0.5 parts of leveling agent, 0.1-0.5 parts of defoamer, and 0.2-0.5 parts of anti-settling agent;

[0012] Component B comprises the following raw materials in parts by weight: curing agent oxalic acid modified isophorone diamine and Mannich base modified diethylenetriamine, totaling 60-70 parts by weight.

[0013] Optionally, component A includes the following raw materials in parts by weight: 42-48 parts of bisphenol A type epoxy resin, 7-9 parts of reactive diluent, 0.2-0.4 parts of leveling agent, 0.2-0.4 parts of defoamer, and 0.3-0.5 parts of anti-settling agent;

[0014] Component B comprises the following raw materials in parts by weight: curing agent oxalic acid modified isophorone diamine and Mannich base modified diethylenetriamine, totaling 62-70 parts by weight.

[0015] Optionally, component A includes the following raw materials in parts by weight: 45 parts of bisphenol A type epoxy resin, 8 parts of reactive diluent, 0.3 parts of leveling agent, 0.3 parts of defoamer, and 0.5 parts of anti-settling agent;

[0016] Component B comprises the following raw materials in parts by weight: 70 parts by weight of oxalic acid-modified isophorone diamine and Mannich base-modified diethylenetriamine curing agent.

[0017] Optionally, the curing agent comprises 30-35 parts of oxalic acid-modified isophorone diamine and 30-35 parts of Mannich base-modified diethylenetriamine.

[0018] Optionally, the bisphenol A type epoxy resin is one or two of bisphenol A type epoxy resin 128 and E51;

[0019] The active diluent is one or both of 1,4-butanediol diglycidyl ether and neopentyl glycol diglycidyl ether.

[0020] The defoamer is one or both of defoamer A530 and defoamer 088;

[0021] The leveling agent is one or more of the following: leveling agent BYK-320, leveling agent BYK-333, and leveling agent EFKA 3772;

[0022] The anti-settling agent is organic bentonite BS-1C.

[0023] Optionally, isophorone diamine and xylene solvent are added to a container and stirred. Then, oxalic acid is added, followed by toluenesulfonic acid catalyst. The reaction system is slowly heated to 100-180℃ and stirred at the reaction temperature for 4-12 hours. Samples are taken at regular intervals, and the changes in acid value or amine value are determined by acid-base titration. When the changes in acid value and amine value are not obvious, the reaction is complete. The solvent in the reaction system is removed by vacuum distillation, and finally dried at 40-60℃ for 12-24 hours to obtain the oxalic acid-modified isophorone diamine product.

[0024] Optionally, benzaldehyde, diethylenetriamine, and phenol are used as raw materials, and hydrochloric acid is used as a catalyst in an ethanol solution. The reaction is carried out at a temperature of 50℃-100℃ for 2-8 hours. After the reaction, the solvent is removed by vacuum distillation to obtain a crude product. The crude product can be dissolved in hot ethanol, filtered while hot to remove insoluble impurities, then cooled to crystallize, filtered, and dried to obtain the Mannich base-modified diethylenetriamine product.

[0025] (III) Beneficial Effects

[0026] After using the curing agent of this invention, the coating that may have taken several hours to dry to the surface may be able to reach the surface dry state within tens of minutes, which greatly improves the construction efficiency and reduces the waiting time. It is especially suitable for large-scale coating projects or production scenarios that require rapid turnover.

[0027] There is also a significant improvement in drying time, allowing the coating to fully cure faster, thus enabling subsequent processing or use earlier and accelerating the entire production process.

[0028] The curing agent of this invention can ensure that the coating can adhere firmly to various substrates, effectively prevent the coating from peeling and blistering under harsh conditions such as high temperature, humidity, and vibration, and reduce rework and repair costs caused by coating peeling.

[0029] In building exterior wall coatings, good adhesion allows the coating to remain stable over a long period of time under the influence of natural environmental factors such as wind, sun, and rain, making it less prone to peeling off. This avoids potential threats to pedestrian safety caused by coating peeling off and reduces the frequency and cost of building maintenance. Detailed Implementation

[0030] To better explain and facilitate understanding of the present invention, a detailed description of the invention will be provided through specific embodiments.

[0031] This invention provides a solvent-free epoxy coating, which includes component A and component B. Component A includes bisphenol A type epoxy resin, reactive diluent, leveling agent, defoamer and anti-settling agent.

[0032] Component B includes the curing agents oxalic acid-modified isophorone diamine and Mannich base-modified diethylenetriamine.

[0033] Mannich base-modified amines can rapidly cure bisphenol A type epoxy resins at lower temperatures. This is because the active groups (such as secondary amine groups) in the Mannich base can react quickly with the epoxy groups. In some winter construction projects or applications requiring high curing speed, using Mannich base-modified amine epoxy curing agents can effectively shorten the curing time. Due to the introduction of different groups (such as phenolic or ketone groups) into the molecular structure of Mannich base-modified amines, they can impart better flexibility to the cured epoxy resin compared to traditional amine curing agents. This allows the cured product to better resist external impacts and reduces the possibility of cracking.

[0034] The introduction of carboxylic acid groups can improve the compatibility between the curing agent and bisphenol A type epoxy resin. Bisphenol A type epoxy resin itself contains epoxy and hydroxyl groups. The carboxylic acid groups in the carboxylic acid-modified amine curing agent can interact with these groups in the bisphenol A type epoxy resin, resulting in a more uniform mixture and thus improving the curing effect. Bisphenol A type epoxy resin cured with carboxylic acid-modified amine curing agents exhibits excellent chemical corrosion resistance. The carboxylic acid groups can participate in the curing reaction, forming more stable chemical bonds and enhancing the resistance of the cured product to acids, alkalis, and other chemicals.

[0035] The active groups of the two curing agents can complement each other, reacting fully with the epoxy groups in bisphenol A epoxy resin. The secondary amine groups in the Mannich base-modified amine and the amine and carboxylic acid groups in the carboxylic acid-modified amine can all react with the epoxy groups, thereby improving the curing degree of the epoxy resin and giving the cured product better physical and chemical properties. When Mannich base-modified amine curing agents and carboxylic acid-modified amine curing agents are used together, the curing speed can be adjusted. The Mannich base-modified amine epoxy curing agent provides rapid curing, while the carboxylic acid-modified amine curing agent can slightly slow down the curing speed to some extent, avoiding problems such as internal stress caused by excessively rapid curing. In the curing process of some bisphenol A epoxy resin products, the combination of the two can make the curing process more stable, reducing product deformation and cracking.

[0036] Mannich base-modified amine curing agents impart flexibility to the cured product, while carboxylic acid-modified amine curing agents can increase the hardness and strength of the cured product to a certain extent. The combined use of both achieves a good balance between toughness and hardness in the cured product. The carboxylic acid groups in the carboxylic acid-modified amine curing agent can form weather-resistant chemical bonds during the curing reaction, while the flexibility of the Mannich base-modified amine curing agent also helps reduce damage to the cured product caused by environmental factors such as temperature changes, thus enabling the cured product to be better used in outdoor environments.

[0037] The bisphenol A type epoxy resin is one or more of the bisphenol A type epoxy resins 128 and E51 from Nan Ya Plastics, Taiwan.

[0038] The reactive diluent is one or both of 1,4-butanediol diglycidyl ether and neopentyl glycol diglycidyl ether from Wuxi Xinyehao Chemical Co., Ltd.; the reactive diluent has the effect of reducing the viscosity of the system and toughening it at the same time, which can improve the construction efficiency and coating toughness of solvent-free epoxy coatings.

[0039] The defoamer is one or both of BYK's A530 and 088;

[0040] The leveling agent is one or more of BYK-320 and BYK-333 from BYK Corporation and EFKA 3772 from EFKA Corporation;

[0041] The anti-settling agent is BS-1C organic bentonite from Zhejiang Fenghong Company.

[0042] Example 1

[0043] This embodiment provides a solvent-free epoxy coating comprising two components, A and B. Component A comprises the following raw materials in parts by weight: 45 parts of bisphenol A type epoxy resin 128, 8 parts of 1,4-butanediol diglycidyl ether, 0.3 parts of leveling agent BYK-320, 0.3 parts of defoamer A530, and 0.5 parts of BS-1C organic bentonite.

[0044] Component B comprises the following raw materials in parts by weight: 32 parts of curing agent oxalic acid modified isophorone diamine and 35 parts of Mannich base modified diethylenetriamine.

[0045] That is, component A includes the following components by mass percentage (as a percentage of component A): bisphenol A type epoxy resin 1288 2.9%, 1,4-butanediol diglycidyl ether 15%, leveling agent BYK-320 0.6%, defoamer A530 0.6%, BS-1C organic bentonite 0.9%;

[0046] Component B comprises the following components by mass percentage (as a percentage of Component B): 48% oxalic acid-modified isophorone diamine (curing agent) and 52% Mannich base-modified diethylenetriamine.

[0047] Preparation method of isophorone diamine modified with oxalic acid as a curing agent:

[0048] Isophorone diamine and xylene solvent were added to a container and stirred. Then, oxalic acid was slowly added at a molar ratio of 1:1.2. Toluenesulfonic acid catalyst, comprising 3% of the total mass, was then added. The reaction system was slowly heated to 150°C and stirred at the reaction temperature for 8 hours. Samples were taken at regular intervals, and the changes in acid value or amine value were determined by acid-base titration. When the changes in acid value and amine value were not significant, the reaction was considered complete. The solvent in the reaction system was removed by vacuum distillation, and the mixture was separated by cooling crystallization and filtration. Finally, it was dried at 50°C for 18 hours to obtain the oxalic acid-modified isophorone diamine product.

[0049] Preparation method of Mannich base-modified diethylenetriamine as a curing agent:

[0050] Using benzaldehyde, diethylenetriamine, and phenol as raw materials, and hydrochloric acid as a catalyst, benzaldehyde reacts with diethylenetriamine to form an imine intermediate, which then reacts with phenol. The molar ratio of benzaldehyde, diethylenetriamine, and phenol is 1.5:1:1. The reaction is carried out in an ethanol solution at 80°C for 6 hours. After the reaction, the solvent is removed by vacuum distillation to obtain a crude product. The crude product can be dissolved in hot ethanol, filtered while hot to remove insoluble impurities, then cooled to crystallize, filtered, and dried to obtain the Mannich base-modified diethylenetriamine product.

[0051] Example 2

[0052] This embodiment provides a solvent-free epoxy coating comprising two components, A and B. Component A comprises the following raw materials in parts by weight: 40 parts of bisphenol A type epoxy resin E51, 5 parts of neopentyl glycol diglycidyl ether, 0.1 parts of leveling agent BYK-333, 0.1 parts of defoamer 088, and 0.2 parts of BS-1C organic bentonite.

[0053] Component B comprises the following raw materials in parts by weight: 30 parts of curing agent oxalic acid modified isophorone diamine and 30 parts of Mannich base modified diethylenetriamine.

[0054] That is, component A includes the following components by mass percentage (as a percentage of component A): 8.1% bisphenol A type epoxy resin E518, 11.1% neopentyl glycol diglycidyl ether, 0.2% leveling agent BYK-333, 0.2% defoamer 088, and 0.4% BS-1C organic bentonite;

[0055] Component B comprises the following components by mass percentage (as a percentage of Component B): 50% oxalic acid modified isophorone diamine curing agent and 50% Mannich base modified diethylenetriamine.

[0056] The preparation methods for the curing agents oxalic acid-modified isophorone diamine and Mannich base-modified diethylenetriamine are the same as in Example 1.

[0057] Example 3

[0058] This embodiment provides a solvent-free epoxy coating comprising two components, A and B. Component A comprises the following raw materials in parts by weight: 50 parts of bisphenol A type epoxy resin 128, 10 parts of 1,4-butanediol diglycidyl ether, 0.5 parts of leveling agent EFKA 3772, 0.5 parts of defoamer A530, and 0.5 parts of BS-1C organic bentonite.

[0059] Component B comprises the following raw materials in parts by weight: 31 parts of curing agent oxalic acid modified isophorone diamine and 35 parts of Mannich base modified diethylenetriamine.

[0060] That is, component A includes the following components by mass percentage (as a percentage of component A): 1288 1.3% bisphenol A type epoxy resin, 16.3% 1,4-butanediol diglycidyl ether, 0.8% leveling agent EFKA 3772, 0.8% defoamer A530, and 0.8% BS-1C organic bentonite;

[0061] Component B comprises the following components by mass percentage (as a percentage of Component B): 47% oxalic acid modified isophorone diamine curing agent and 53% Mannich base modified diethylenetriamine.

[0062] The preparation methods for the curing agents oxalic acid-modified isophorone diamine and Mannich base-modified diethylenetriamine are the same as in Example 1.

[0063] Example 4

[0064] This embodiment provides a solvent-free epoxy coating comprising two components, A and B. Component A comprises the following raw materials in parts by weight: 42 parts of bisphenol A type epoxy resin E51, 7 parts of neopentyl glycol diglycidyl ether, 0.2 parts of leveling agent BYK-333, 0.2 parts of defoamer A530, and 0.3 parts of BS-1C organic bentonite.

[0065] Component B comprises the following raw materials in parts by weight: 32 parts of curing agent oxalic acid modified isophorone diamine and 33 parts of Mannich base modified diethylenetriamine.

[0066] That is, component A includes the following ingredients by mass percentage (as a percentage of component A): bisphenol A type epoxy resin E518 4.4%, neopentyl glycol diglycidyl ether 14.0%, leveling agent BYK-333 0.4%, defoamer A530 0.4%, BS-1C organic bentonite 0.8%;

[0067] Component B comprises the following components by mass percentage (as a percentage of Component B): 49% oxalic acid-modified isophorone diamine (curing agent) and 51% Mannich base-modified diethylenetriamine.

[0068] The preparation methods for the curing agents oxalic acid-modified isophorone diamine and Mannich base-modified diethylenetriamine are the same as in Example 1.

[0069] Example 5

[0070] This embodiment provides a solvent-free epoxy coating comprising two components, A and B. Component A comprises the following raw materials in parts by weight: 48 parts of bisphenol A type epoxy resin E51, 9 parts of 1,4-butanediol diglycidyl ether, 0.4 parts of leveling agent BYK-320, 0.4 parts of defoamer 088, and 0.5 parts of BS-1C organic bentonite.

[0071] Component B comprises the following raw materials in parts by weight: 35 parts of curing agent oxalic acid modified isophorone diamine and 31 parts of Mannich base modified diethylenetriamine.

[0072] That is, component A includes the following ingredients by mass percentage (as a percentage of component A): bisphenol A type epoxy resin E518 2.3%, 1,4-butanediol diglycidyl ether 15.4%, leveling agent BYK-320 0.7%, defoamer 088 0.7%, BS-1C organic bentonite 0.9%;

[0073] Component B comprises the following components by mass percentage (as a percentage of Component B): 53% oxalic acid-modified isophorone diamine (curing agent) and 47% Mannich base-modified diethylenetriamine.

[0074] The preparation methods for the curing agents oxalic acid-modified isophorone diamine and Mannich base-modified diethylenetriamine are the same as in Example 1.

[0075] Comparative Example 1

[0076] Component B is a curing agent, oxalic acid-modified isophorone diamine.

[0077] The rest is the same as in Example 1.

[0078] Comparative Example 2

[0079] Component B is Mannich base modified diethylenetriamine.

[0080] The rest is the same as in Example 1.

[0081] Comparative Example 3

[0082] Component B comprises the following ingredients by mass percentage (as a percentage of Component B): 25% oxalic acid-modified isophorone diamine (curing agent) and 75% Mannich base-modified diethylenetriamine.

[0083] The rest is the same as in Example 1.

[0084] Comparative Example 4

[0085] Component B comprises the following components by mass percentage (as a percentage of Component B): 80% oxalic acid-modified isophorone diamine (curing agent) and 20% Mannich base-modified diethylenetriamine.

[0086] The rest is the same as in Example 1.

[0087] The coating of the present invention was subjected to performance testing after complete curing. The main performance indicators and testing methods are shown in Table 1. The test results of Examples 1-5 and Comparative Examples 1-4 of the present invention are shown in Table 2.

[0088] Table 1. Main performance indicators and testing methods used in this invention.

[0089]

[0090] Table 2. Test results of Examples 1-5 and Comparative Examples 1-4 of the present invention.

[0091]

[0092]

[0093] In the test, "intact" was defined as "no blistering, no peeling, no rust spots, and no cracks in the coating".

[0094] In summary, due to the introduction of different functional groups (such as phenolic or ketone groups) into the molecular structure of Mannich base-modified amines, they can impart better flexibility to cured epoxy resins compared to traditional amine curing agents. This allows the cured product to better resist external impacts and reduces the likelihood of cracking. The carboxylic acid groups can participate in the curing reaction, forming more stable chemical bonds and enhancing the cured product's resistance to acids, alkalis, and other chemicals.

[0095] Different formulation ratios can lead to significant differences in the properties of the cured product. For example, if the proportion of Mannich base-modified amine epoxy curing agent is too high, the cured product may be too soft, while an excessively high proportion of carboxylic acid-modified amine curing agent may result in a slow curing speed. Therefore, Mannich base-modified amine epoxy curing agents offer rapid curing, while carboxylic acid-modified amine curing agents can, to some extent, moderate the curing speed and prevent problems such as internal stress caused by excessively rapid curing.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A solvent-free epoxy coating, characterized in that: The coating consists of component A and component B. Component A comprises the following raw materials in parts by weight: 40-50 parts of bisphenol A type epoxy resin, 5-10 parts of reactive diluent, 0.1-0.5 parts of leveling agent, 0.1-0.5 parts of defoamer, and 0.2-0.5 parts of anti-settling agent; Component B comprises the following raw materials in parts by weight: curing agent oxalic acid modified isophorone diamine and Mannich base modified diethylenetriamine, totaling 60-70 parts by weight; The curing agent comprises 30-35 parts of oxalic acid-modified isophorone diamine and 30-35 parts of Mannich base-modified diethylenetriamine; The preparation method of the oxalic acid modified isophorone diamine is as follows: Isophorone diamine and xylene solvent were added to a container and stirred. Then oxalic acid was added, followed by toluenesulfonic acid catalyst. The reaction system was slowly heated to 100-150℃ and stirred at the reaction temperature for 4-12 hours. Samples were taken at regular intervals, and the changes in acid value or amine value were determined by acid-base titration. When the changes in acid value and amine value were not obvious, the reaction was complete. The solvent in the reaction system was removed by vacuum distillation, and finally dried at 40-60℃ for 12-24 hours to obtain the oxalic acid-modified isophorone diamine product. The preparation method of the Mannich base-modified diethylenetriamine is as follows: Using benzaldehyde, diethylenetriamine, and phenol as raw materials, and hydrochloric acid as a catalyst, the reaction was carried out in an ethanol solution at a temperature of 50℃-100℃ for 2-8 hours. After the reaction, the solvent was removed by vacuum distillation to obtain a crude product. The crude product was then dissolved in ethanol, filtered to remove insoluble impurities, and then cooled to crystallize, filtered, and dried to obtain the Mannich base-modified diethylenetriamine product.

2. The solvent-free epoxy coating according to claim 1, characterized in that, Component A comprises the following raw materials in parts by weight: 42-48 parts of bisphenol A type epoxy resin, 7-9 parts of reactive diluent, 0.2-0.4 parts of leveling agent, 0.2-0.4 parts of defoamer, and 0.3-0.5 parts of anti-settling agent; Component B comprises the following raw materials in parts by weight: curing agent oxalic acid modified isophorone diamine and Mannich base modified diethylenetriamine, totaling 62-70 parts by weight.

3. The solvent-free epoxy coating according to claim 2, characterized in that, Component A comprises the following raw materials in parts by weight: 45 parts of bisphenol A type epoxy resin, 8 parts of reactive diluent, 0.3 parts of leveling agent, 0.3 parts of defoamer, and 0.5 parts of anti-settling agent; Component B comprises the following raw materials in parts by weight: 70 parts by weight of oxalic acid-modified isophorone diamine and Mannich base-modified diethylenetriamine curing agent.

4. The solvent-free epoxy coating according to claim 1, characterized in that, The bisphenol A type epoxy resin is one or both of bisphenol A type epoxy resin 128 and E51; The active diluent is one or both of 1,4-butanediol diglycidyl ether and neopentyl glycol diglycidyl ether. The defoamer is one or both of defoamer A530 and defoamer 088; The leveling agent is one or more of the following: leveling agent BYK-320, leveling agent BYK-333, and leveling agent EFKA 3772; The anti-settling agent is organic bentonite BS-1C.

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