A water-based high-temperature resistant insulating coating and its preparation method and application

Abstract

The present invention discloses a water-based, high-temperature-resistant insulating coating, its preparation method, and application. The raw materials for the preparation include the following components, by weight: 45-50 parts of a phenol-modified water-based epoxy resin emulsion, 15-20 parts of a bisphenol A epoxy resin emulsion, 4-5 parts of an amino resin, 0.5-1 parts of a catalyst, 2-3 parts of a blocked isocyanate, and 10-25 parts of water. The coating of the present invention can achieve good insulating properties at a relatively low film thickness, has minimal effect on the material's dimensions after spraying, and does not affect subsequent assembly. The coating of the present invention also has good adhesion and excellent high-temperature and weather resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and in particular relates to a water-based high-temperature resistant insulating coating and a preparation method and application thereof. Background Art

[0002] In daily life, people often encounter the need to insulate items they use. For example, in the 3C consumer electronics sector, the internal shielding covers, circuit boards, and components of mobile phones must not interfere with other components during use. Therefore, surface insulation treatment to block the outward spread of electromagnetic fields is particularly important. Currently, there are two common insulation solutions on the market: coating and spraying insulating coatings. Coating is a complex process with low production efficiency and is time-consuming and labor-intensive. Spraying coatings to achieve insulation has become a trend, replacing coatings. Currently, most commercially available insulating coatings are oil-based with VOC contents exceeding 550g / L, which does not meet the national green environmental protection requirements. Insulation performance is primarily dependent on high film thickness. At low film thicknesses (around 30μm), the tested breakdown voltage is generally between 500-1000kV, resulting in mediocre insulation performance. This makes it unsuitable for the smaller spray-coated products used in 3C information appliances. Moreover, its adhesion and high-temperature and high-humidity resistance cannot be combined with insulation performance. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology, provide a water-based high-temperature resistant insulating coating and its preparation method and application, and at the same time improve the insulation performance, adhesion performance and high-temperature and high-humidity resistance at low film thickness.

[0004] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0005] A water-based high-temperature resistant insulating coating, wherein the raw materials for its preparation include the following components in parts by weight: 45-50 parts of phenol-modified water-based epoxy resin emulsion, 15-20 parts of bisphenol A epoxy resin emulsion, 4-5 parts of amino resin, 0.5-1 part of catalyst, 2-3 parts of blocked isocyanate, and 10-25 parts of water;

[0006] The epoxy equivalent of the phenol-modified waterborne epoxy resin emulsion is 180-220 g / Eq, and the epoxy equivalent of the bisphenol A epoxy resin emulsion is 520-600 g / Eq;

[0007] The amino resin is a melamine cross-linking agent, and the catalyst is an acid catalyst.

[0008] As a further improvement, the composition further comprises: 0.5-1 parts of a defoaming agent, 1-2 parts of a wetting agent, 3-5 parts of a film-forming aid, 1-2 parts of a thickener, and 0.1-0.2 parts of a pH regulator.

[0009] As a further improvement, the phenol-modified waterborne epoxy resin emulsion uses a non-ionic emulsifier.

[0010] As a further improvement, the phenol-modified waterborne epoxy resin emulsion uses E-pos2209 produced by QR-Polymers, and the bisphenol A epoxy resin emulsion uses E-pos 1011W55 produced by QR-Polymers.

[0011] As a further improvement, the amino resin adopts allnex 303LF.

[0012] As a further improvement, the blocked isocyanate is a blocked aliphatic isocyanate, and BAYHYDUR BL 2867 from Covestro is used.

[0013] As a further improvement, the pH adjuster is an amine neutralizer.

[0014] The present invention also provides a method for preparing the water-based high-temperature resistant insulating coating, which comprises stirring and mixing the components uniformly to prepare the water-based high-temperature resistant insulating coating.

[0015] The present invention also provides an application of the water-based high-temperature resistant insulating coating, which is applied to the surface of a product material with a film thickness of 25-30 μm and cured to form an insulating layer.

[0016] As a further improvement, the curing temperature is 155-165°C.

[0017] The present invention achieves the effect of simultaneously improving the insulation performance, adhesion performance and high temperature and humidity resistance at low film thickness by compounding two different epoxy resin emulsions (phenol-modified epoxy resin emulsion and bisphenol A epoxy resin emulsion) and strictly controlling the ratio of the two, and by adding an amino resin and controlling its dosage, achieving synergistic effects.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The coating of the present invention can achieve good insulation performance at a relatively low film thickness (the breakdown voltage can reach 3KV when the film thickness is about 30μm), which can be achieved by spraying once. After spraying, the size of the material itself is slightly affected and does not affect subsequent assembly. At the same film thickness, the insulation performance is significantly improved compared with similar products on the market;

[0020] 2. The coating of the present invention has good adhesion, and is resistant to high temperatures and weathering. The paint film has good adhesion after being heated at 170 degrees for 2 hours and subjected to high temperature and high humidity for 1000 hours.

[0021] 3. The coating of the present invention is a water-based coating, which adopts a water-based PU system, with a VOC of less than 300g / L, which is lower than the national standard and meets environmental protection requirements. The product is easy to construct and does not require the addition of other curing agents and additives. It can be sprayed after stirring evenly and can meet performance test requirements after baking for 30 minutes, with high production efficiency. DETAILED DESCRIPTION

[0022] To facilitate understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0023] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0024] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0025] In some specific embodiments, the water-based high-temperature resistant insulating coating of the present invention is prepared by raw materials including the following components in parts by weight: 45-50 parts of phenol-modified water-based epoxy resin emulsion (epoxy resin 1), 15-20 parts of bisphenol A epoxy resin emulsion (epoxy resin 2), 0.5-1 parts of defoaming agent, 1-2 parts of wetting agent, 4-5 parts of amino resin, 0.5-1 parts of catalyst, 2-3 parts of blocked isocyanate, 3-5 parts of film-forming aid, 1-2 parts of thickener, 10-25 parts of water, and 0.1-0.2 parts of pH regulator.

[0026] In some specific embodiments, the phenol-modified water-based epoxy resin emulsion particle size used in the present invention is below 2 μm, and the product of preparation has good performance in terms of heat resistance, solvent resistance, chemical resistance, etc., and good storage stability, uniform particle size, and viscosity between 50-10000mPa.s, which is easy to construct. The phenol-modified water-based epoxy resin emulsion epoxide equivalent (solid state) 180-220g / Eq used, solid content 55 ± 1.5%, is conducive to one-time spraying to required film thickness. The phenol-modified water-based epoxy resin emulsion used, its emulsifier is nonionic. Specifically, the E-pos2209 produced by QR-Polymers company can be selected for use.

[0027] In some specific embodiments, the modified bisphenol A epoxy resin emulsion (formed by condensation of bisphenol A and epichlorohydrin under alkaline conditions) used in the present invention has excellent adhesion to multiple substrates, good corrosion resistance and chemical resistance, an epoxy equivalent (solid state) of 520-600 g / Eq, and a high solid content of 51-55%, which is conducive to spraying to the required film thickness in one time. Specifically, E-pos 1011W55 produced by QR-Polymers can be used.

[0028] The resin in the present invention is compounded with two epoxy resin emulsions. Epoxy resin one is a phenol-modified epoxy resin emulsion. The phenol-modified epoxy resin makes the paint film more rigid, has enhanced arc resistance, and improves insulation. Compared with ionic emulsifiers, non-ionic emulsifiers are not easily affected by electrolytes, so they have better stability and are not easy to conduct electricity, which is also beneficial to improving insulation performance. Epoxy resin two is a bisphenol A type epoxy resin, which has excellent adhesion to multiple substrates, good corrosion resistance and chemical resistance. By strictly controlling the ratio of the two, the two work synergistically to achieve the effect of simultaneously improving the insulation performance, adhesion performance and high temperature and high humidity resistance at low film thickness. When too much epoxy resin 1 is added to the formula, the insulation is better, but due to the strong rigidity of the paint film, the paint is prone to chipping at the 100-grid line and the adhesion is poor. In addition, the epoxy equivalent of epoxy resin 1 is low, the degree of cross-linking of the paint film is insufficient, and the water boiling and high temperature and high humidity tests are poor. When too much epoxy resin 2 is added to the formula, the insulation decreases, the rigidity of the paint film is weak and the hardness deteriorates, but due to its high epoxy equivalent, the degree of cross-linking of the paint film is high and the adhesion performance is better.

[0029] In some specific embodiments, the defoaming agent used in the present invention is one or more of polyether siloxane copolymer and polydimethylsiloxane, specifically one or more of Tego810 and Tego902W from Tego and BYK024 from BYK.

[0030] In some specific embodiments, the wetting agent used in the present invention is a siloxane-based twin structure surfactant, which has substrate wettability, anti-cratering performance and a certain degree of defoaming performance, good compatibility, and is suitable for a variety of coatings and applications. Specifically, Evonik Twin 4100.

[0031] In some specific embodiments, the amino resin used in the present invention is a melamine crosslinker containing a solid content of more than 98%, a high degree of methyl etherification and a high monomer content. Although it is insoluble in water, it has excellent compatibility with water-soluble polymer base resins. Specifically, allnex can be used. 303LF.

[0032] The curing mechanism of the present invention is that the functional groups in the amino resin and blocked isocyanate cross-link with the main resin at high temperature to form a dense paint film. This reaction only occurs at relatively high temperatures. Therefore, mixing them during the preparation of the coating will not affect the storage stability of the paint and also reduces the number of operating steps during construction.

[0033] The curing of the present invention adopts high-temperature baking. When the amino resin in the formula is excessive, the appearance of the paint film is poor. At the same time, the paint film is too hard and brittle due to excessive cross-linking, and the paint is easy to break at the adhesion line in the 100-grid test; insufficient addition will lead to insufficient cross-linking and poor adhesion performance. At the same time, because the paint film is not dense enough, the breakdown voltage is low, the insulation is poor, and the paint film hardness is not ideal.

[0034] In some specific embodiments, the catalyst used in the present invention is an acid catalyst, for example, a 40% p-toluenesulfonic acid dissolved in isopropyl alcohol solution, which can play a stable and effective catalytic role in most water-based thermosetting coating formulations. It is particularly recommended for accelerating the curing of high-etherification melamine formaldehyde crosslinking systems, which can reduce the temperature and shorten the baking time. 4040.

[0035] In some specific embodiments, the blocked isocyanate used in the present invention is a blocked aliphatic isocyanate, does not contain an organic solvent, and is dispersed in an aqueous solution at a concentration of approximately 38%, specifically BAYHYDUR BL 2867 from Covestro.

[0036] In some specific embodiments, the film-forming aid used in the present invention is an alcohol ether solvent, which is used to improve the leveling of the paint film, solve the problem of gun clogging during paint spraying, and improve the workability, specifically BCS.

[0037] In some specific embodiments, the thickener used in the present invention is a polyurethane thickener, which is used to provide thixotropy to the coating and prevent the wet film of the coating from sagging, specifically Evonik's Tego3060.

[0038] In some specific embodiments, the pH adjuster used in the present invention is an amine neutralizer, which mainly adjusts the pH of the coating to a weakly alkaline range, is beneficial to the storage of water-based coatings, improves activation and anti-sedimentation, etc., specifically DMEA.

[0039] The present invention provides an environmentally friendly water-based paint with a VOC content of less than 300g / L and a breakdown voltage of up to 3KV when the film thickness is about 30μm. This film thickness does not require multiple recoatings, the spraying area is small, and can be obtained by one spraying, which saves time and has little impact on the size of the product itself and will not affect subsequent assembly. It can be applied to internal components of 3C products, which is consistent with the characteristics of small size and high insulation requirements of 3C information appliances, while meeting the requirements of good adhesion, high temperature resistance and high temperature and high humidity resistance tests.

[0040] In some specific embodiments, the method for preparing the coating of the present invention comprises the following steps:

[0041] Under stirring, adding the defoaming agent to the phenol-modified waterborne epoxy resin emulsion and the bisphenol A epoxy resin emulsion, and stirring and mixing;

[0042] Keep stirring, add wetting agent, amino resin, catalyst and blocked isocyanate, and stir to mix;

[0043] Keep stirring and add film-forming aid;

[0044] Then add thickener, deionized water and pH adjuster and filter to obtain the product.

[0045] Examples and Comparative Examples:

[0046] The weight parts of each component in each embodiment and comparative example are shown in Table 1.

[0047] Table 1

[0048]

[0049]

[0050] Preparation methods of Examples and Comparative Examples:

[0051] S1. Add the phenol-modified waterborne epoxy resin emulsion and bisphenol A epoxy resin emulsion in the components into a dispersion container;

[0052] S2. Add defoamer at a high speed of 1000-1500 rpm, adding slowly and stirring for 8-10 minutes;

[0053] S3, then add the wetting agent, amino resin, catalyst and blocked isocyanate at 600-800 rpm, stir for 5-8 minutes, and pay attention to scraping the edges;

[0054] S4. Add the film-forming aid at 600-800 rpm. Note that it should be added slowly and preferably on the surface of the coating, not near the dispersant shaft or the wall.

[0055] S5. Add thickener, deionized water, and pH regulator. Mix the deionized water and pH regulator in advance and let them stand at room temperature for more than 5 minutes before adding them; adjust the pH with the pH regulator and adjust the viscosity with deionized water and thickener (control the temperature at 5-35°C throughout the process);

[0056] S6. Filter the package with a 250-350 mesh filter to obtain the water-based high-temperature resistant insulating coating.

[0057] Construction method:

[0058] The water-based high-temperature resistant insulating coatings prepared in Examples 1 to 5 and Comparative Examples 1-3 were adjusted to a viscosity suitable for construction by adding water, and were applied to the surface of the material by spraying with a film thickness of 25-30 μm. The dry film with the final effect was obtained after baking at 160° C. for 30 minutes.

[0059] The performance test items are shown in Table 2:

[0060] Table 2

[0061]

[0062]

[0063] High temperature resistance test: test after heating at 170 degrees for 2 hours. The results are shown in Table 3:

[0064] Table 3

[0065]

[0066]

[0067] As can be seen from the table above, Comparative Example 1 exhibits poor adhesion and poor results in the water boiling and high-temperature, high-humidity tests due to an excessively high ratio of epoxy resin 1 to epoxy resin 2. Comparative Example 2 exhibits poor insulation and hardness due to an insufficient ratio of epoxy resin 1 to epoxy resin 2. Comparative Example 3 exhibits poor adhesion, insulation, water boiling, and high-temperature, high-humidity tests. Comparative Example 4 exhibits poor appearance, adhesion, water boiling, and high-temperature, high-humidity tests due to an excessive amount of amino resin. However, the insulation performance is not significantly affected. The synergistic effect of these components simultaneously improves insulation performance, adhesion, and high-temperature, high-humidity resistance at low film thicknesses.

[0068] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any form. Therefore, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical solution of the present invention and are based on the technical essence of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A water-based high-temperature resistant insulating coating, characterized in that: The raw materials for its preparation include the following components in parts by weight: 45-50 parts of phenol-modified waterborne epoxy resin emulsion, 15-20 parts of bisphenol A epoxy resin emulsion, 4-5 parts of amino resin, 0.5-1 part of catalyst, 2-3 parts of blocked isocyanate, and 10-25 parts of water; The phenol-modified waterborne epoxy resin emulsion adopts E-pos 2209 produced by QR-Polymers, with an epoxy equivalent weight of 180-220 g / Eq; the bisphenol A epoxy resin emulsion adopts E-pos1011W55 produced by QR-Polymers, with an epoxy equivalent weight of 520-600 g / Eq; The amino resin is a melamine cross-linking agent, and the catalyst is an acid catalyst.

2. The water-based high-temperature resistant insulating coating according to claim 1, characterized in that: Also includes: 0.5-1 parts of defoaming agent, 1-2 parts of wetting agent, 3-5 parts of film-forming aid, 1-2 parts of thickener, and 0.1-0.2 parts of pH regulator.

3. The water-based high-temperature resistant insulating coating according to claim 1 or 2, characterized in that: The amino resin used is CYMEL® 303 LF produced by allnex.

4. The water-based high-temperature resistant insulating coating according to claim 1 or 2, characterized in that: The blocked isocyanate is a blocked aliphatic isocyanate, and is BAYHYDUR BL 2867 from Covestro.

5. The water-based high-temperature resistant insulating coating according to claim 2, characterized in that: The pH adjuster is an amine neutralizer.

6. A method for preparing the water-based high-temperature resistant insulating coating according to any one of claims 1 to 5, characterized in that: The components are stirred and mixed evenly to prepare the water-based high-temperature resistant insulating coating.

7. An application of the water-based high-temperature resistant insulating coating according to any one of claims 1 to 5, characterized in that: The water-based high-temperature resistant insulating coating is applied to the surface of the product material with a film thickness of 25-30 μm, and is cured to form an insulating layer.

8. The use according to claim 7, characterized in that The curing temperature is 155-165°C.

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