High-stability UV moisture dual-curing conformal coating and preparation method thereof

Abstract

The invention belongs to the technical field of paint surface coatings, and particularly relates to a high-stability UV moisture dual-curing three-proofing paint and a preparation method thereof.The high-stability UV moisture dual-curing three-proofing paint is prepared from, by weight, 25.5%-77.9% of 3, 3, 5-trimethyl cyclohexyl acrylate, 20%-54% of polyurethane acrylate with isocyanate groups, 1%-8.5% of auxiliary stable cross-linking agent, 0.1%-5% of dehydrating agent and 1%-7% of photoinitiator; the weight ratio of the polyurethane acrylate to the 3, 3, 5-trimethyl cyclohexyl acrylate to the auxiliary stable cross-linking agent is 1: (1.10 to 1.40): (0.05 to 0.30); the auxiliary stabilizing cross-linking agent is selected from trimethylolpropane triacrylate and / or trimethylolpropane trimethacrylate. On the basis of UV (ultraviolet) and moisture dual-curing performance, the high-stability UV curing adhesive has relatively high stability and can resist acid and alkali environments.

Description

Technical Field

[0001] The invention belongs to the technical field of paint coatings, and particularly relates to a highly stable UV moisture dual-curing conformal coating and a preparation method thereof. Background Art

[0002] Currently, most traditional UV conformal coatings use IBOA (isobornyl acrylate) as a monomer. Studies have shown that IBOA itself carries a considerable risk of allergic reactions. To prevent skin sensitization caused by contact with IBOA and to meet diverse market demands, it is necessary to develop a sustainable, biofriendly, IBOA-free UV conformal coating system.

[0003] In the prior art, there is a UV conformal paint with dual UV and moisture curing properties. Since the circuit board has an uneven surface, most of the surface of the conformal paint sprayed on the circuit board has been cured after UV light irradiation, while the shadow area needs to go through a moisture curing process to achieve surface dryness; the UV conformal paint with dual UV and moisture curing properties can be quickly cured by ultraviolet irradiation, and at the same time, it can be cured by moisture in areas where light cannot directly reach. The first step of the moisture curing process is mainly the reaction of the isocyanate group -N=C=O in the resin with the water molecules in the environment to generate unstable carbamic acid. The second step, The unstable carbamate intermediate immediately decomposes, releasing carbon dioxide and forming a primary amine and a hydroxyl group. In the third step, the newly formed primary amine is highly reactive and quickly reacts with another isocyanate group on a neighboring resin molecule to form a stable urea bond. This ultimately leads to the formation of stable urea bonds between the resin molecules, building a three-dimensional cross-linked network structure. UV curing provides high hardness and rapid surface drying, while moisture curing is relatively slow, working from the surface to the inside, effectively curing areas that UV light cannot reach (shadowed areas, deep layers of thick films). Both curing methods ensure uniformity and durability of the coating, and the formula does not contain ingredients that may cause allergic reactions. However, this dual-curing UV conformal coating has poor stability and is not suitable for use in acidic and alkaline environments.

[0004] It should be noted that this part of the present invention only provides background technology related to the present invention and does not necessarily constitute prior art or public known technology. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of poor stability and acid and alkali resistance of UV conformal coatings in the prior art, and to provide a highly stable UV moisture dual-curing conformal coating and a preparation method thereof. The coating has both UV and moisture dual-curing properties and high stability, and can resist acid and alkali environments.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a highly stable UV moisture dual-curing conformal coating, comprising the following raw material components in weight percentage: based on the total amount of raw materials, 25.5-77.9 wt% of 3,3,5-trimethylcyclohexyl acrylate, 20-54 wt% of polyurethane acrylate with an isocyanate group, 1-8.5 wt% of an auxiliary stabilizing crosslinker, 0.1-5 wt% of a dehydrating agent, and 1-7 wt% of a photoinitiator; the weight ratio of the polyurethane acrylate to the 3,3,5-trimethylcyclohexyl acrylate to the auxiliary stabilizing crosslinker is 1:(1.10-1.40):(0.05-0.30); the auxiliary stabilizing crosslinker is selected from trimethylolpropane triacrylate and / or trimethylolpropane trimethacrylate.

[0007] In the present invention, the content of isocyanate groups in the polyurethane acrylate is preferably 10% to 18% by mass.

[0008] In some preferred embodiments of the present invention, the content of 3,3,5-trimethylcyclohexyl acrylate is 30-75 wt %, and / or the weight ratio of polyurethane acrylate, 3,3,5-trimethylcyclohexyl acrylate and auxiliary stabilizing crosslinker is 1: (1.135-1.298): (0.142-0.230).

[0009] In some preferred embodiments of the present invention, the molecular weight of the polyurethane acrylate is 600-3500 g / mol and its functionality is 0.7-1.2.

[0010] In some preferred embodiments of the present invention, the dehydrating agent is selected from p-toluenesulfonyl isocyanate and / or N,N-dicyclohexylcarbodiimide, and the photoinitiator is selected from 1-hydroxy-cyclohexyl-phenyl ketone and / or 2,4,6 (trimethylbenzoyl) diphenylphosphine oxide.

[0011] In some preferred embodiments of the present invention, the raw material components of the highly stable UV moisture dual-curing conformal coating further include a free radical inhibitor and / or a catalytic moisture curing agent. When the free radical inhibitor and the catalytic moisture curing agent are contained, the weight ratio of the free radical inhibitor, the catalytic moisture curing agent to the polyurethane acrylate is (1-4): (5-25):1000.

[0012] In some preferred embodiments of the present invention, the catalytic moisture curing agent is selected from 、 、 At least one of .

[0013] In some preferred embodiments of the present invention, the free radical inhibitor is selected from 、 、 、 At least one of the following, wherein R and R1 are each independently selected from an alkyl group having 4 to 10 carbon atoms.

[0014] In some preferred embodiments of the present invention, the raw material components of the highly stable UV moisture dual-curing conformal coating further include: 0.01-0.03 wt% of a fluorescent brightener and 0-2 wt% of an adhesion promoter, based on the total amount of raw materials.

[0015] Further preferably, the fluorescent whitening agent is selected from at least one of 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene, 1,4-2(benzoxazolyl-2-yl)naphthalene, 4,4-bis(2-benzoxazolyl)stilbene, and 4,4-bis(2-dimethoxystyryl)biphenyl; and the adhesion promoter is selected from alkyl acrylate phosphate and / or methacryloxysilane.

[0016] In a second aspect, the present invention provides a method for preparing a highly stable UV moisture dual curing conformal coating, which is used to prepare the highly stable UV moisture dual curing conformal coating described in the first aspect, and the preparation method comprises the following steps: S1. Mix the required amounts of 3,3,5-trimethylcyclohexyl acrylate, auxiliary stabilizing crosslinking agent, polyurethane acrylate, and dehydrating agent to obtain a primary mixed solution; S2. Introducing a photoinitiator into the primary mixed solution for secondary mixing to obtain a secondary mixed solution.

[0017] In some preferred embodiments of the present invention, the preparation method further comprises: A free radical inhibitor and / or a fluorescent whitening agent are also introduced in the secondary mixing in S2; Then, a catalytic moisture curing agent and / or an adhesion promoter is introduced into the obtained secondary mixed liquid for a third mixing.

[0018] In some preferred embodiments of the present invention, the conditions for the primary mixing include: a stirring speed of 1700-2300 rpm, and a stirring time of 100-150 s.

[0019] In some preferred embodiments of the present invention, the conditions for the secondary mixing include: a stirring speed of 2000-2500 rpm, a total stirring time of 150-200 s; and a stirring frequency of 1-3 times.

[0020] In some preferred embodiments of the present invention, the conditions for the three mixing steps include: a stirring speed of 1500-2000 rpm, and a stirring time of 100-150 s.

[0021] Beneficial effects: The present invention adopts the above technical solution, especially adds a specific appropriate amount of 3,3,5-trimethylcyclohexyl acrylate and an auxiliary stabilizing crosslinking agent to a polyurethane acrylate with an isocyanate group that can be dual-cured by UV and moisture. The isocyanate reactive group in the polyurethane acrylate reacts with the acrylate group at the end of the chain in 3,3,5-trimethylcyclohexyl acrylate and the three acrylate groups in the auxiliary stabilizing crosslinking agent. Specifically, the three acrylate groups contained in the auxiliary stabilizing crosslinking agent are like three hands, which can simultaneously grasp different molecular chains during curing (while ordinary monofunctional auxiliary agents can only extend the chain, and bifunctional auxiliary agents can only form linear crosslinks). During the curing process, the double bond in the acrylate group opens and undergoes free radical polymerization reaction with the carbon-carbon double bond on the acrylate group at the end of the chain in the polyurethane acrylate and 3,3,5-trimethylcyclohexyl acrylate to form a covalent bond connection, thereby generating a three-dimensional network structure, increasing the crosslinking density and making the structure denser. This structure not only reduces the free volume between polymer chains but also increases the tortuosity of the permeation path, thereby hindering the diffusion of permeants (water molecules, oxygen, and salt ions). These microscopic changes work synergistically, resulting in a significantly enhanced barrier capability of the conformal coating against permeants such as water vapor and salt spray ions. Specifically, during the UV curing stage, a highly cross-linked, rigid polyacrylate network is rapidly constructed, slowing the migration of isocyanate groups in the polyurethane acrylate and the permeation of water vapor. This supports the dense skeleton structure throughout the moisture curing process. During the moisture curing process, the reactivity generated by the dense skeleton rapidly reacts with adjacent isocyanate groups in the polyurethane acrylate to form stable urea bonds, resulting in a more robust, tightly cross-linked structure and ensuring uniform and complete curing of the entire coating. This effectively improves the weathering and abrasion resistance of the UV conformal coating, allowing the conformal coating to possess both UV and moisture curing properties while also possessing high stability and resistance to acidic and alkaline environments. The present invention also incorporates a dehydrating agent to enhance curing efficiency and protective properties. Among them, when exposed to ultraviolet light, the photoinitiator will absorb light energy and convert into free radicals, which will further trigger the polymerization reaction of polyurethane acrylate and 3,3,5-trimethylcyclohexyl acrylate. At the same time, the auxiliary stabilizing cross-linker can form more stable chemical bonds between these molecules, connecting them into a stable network structure, improving the strength and hardness of the UV three-proof paint, and enabling it to better resist erosion and damage from the external environment.

[0022] The present invention also controls the appropriate weight ratio of polyurethane acrylate, 3,3,5-trimethylcyclohexyl acrylate, and auxiliary stabilizing crosslinking agent, and balances the amount of the auxiliary stabilizing crosslinking agent, thereby obtaining a network skeleton structure with appropriate tight crosslinking, improving the deep moisture curing efficiency and curing effect, and improving the stability and acid and alkali resistance of the three-proof paint, avoiding the situation where too little auxiliary stabilizing crosslinking agent causes insufficient skeleton support, and too much auxiliary stabilizing crosslinking agent causes the network to be too dense and may excessively hinder moisture diffusion, thereby affecting the deep curing efficiency.

[0023] This invention has developed a highly stable, UV-moisture-resistant dual-curing conformal coating with improved performance and wider application, aiming to promote the upgrading and transformation of related industries and enhance their overall competitiveness and sustainable development. Furthermore, the preparation method is simple, convenient, and highly practical. The resulting conformal coating poses no risk of human sensitization and exhibits excellent resistance to moisture, salt spray, and mildew. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 This is a comparison of the appearance of the three-proof paint obtained in Example 1 of the present invention before and after the alkali resistance test.

[0026] Figure 2 This is a comparison of the appearance of the conformal coating obtained in Example 1 of the present invention before and after the acid resistance test.

[0027] Figure 3 This is a comparison of the appearance of the three-proof paint obtained in Example 2 of the present invention before and after the alkali resistance test.

[0028] Figure 4 This is a comparison of the appearance of the conformal coating obtained in Example 2 of the present invention before and after the acid resistance test.

[0029] Figure 5 This is a comparison of the appearance of the conformal coating obtained in Example 3 of the present invention before and after the alkali resistance test.

[0030] Figure 6 This is a comparison of the appearance of the conformal coating obtained in Example 3 of the present invention before and after the acid resistance test.

[0031] Figure 7 This is a comparison of the appearance of the conformal coating obtained in Example 4 of the present invention before and after the alkali resistance test.

[0032] Figure 8 This is a comparison of the appearance of the conformal coating obtained in Example 4 of the present invention before and after the acid resistance test.

[0033] Figure 9 This is a comparison of the appearance of the conformal coating obtained in Example 5 of the present invention before and after the alkali resistance test.

[0034] Figure 10 This is a comparison of the appearance of the conformal coating obtained in Example 5 of the present invention before and after the acid resistance test.

[0035] Figure 11 This is a comparison of the appearance of the three-proof paint obtained in Comparative Example 1 of the present invention before and after the alkali resistance test.

[0036] Figure 12 This is a comparison of the appearance of the three-proof paint obtained in Comparative Example 1 of the present invention before and after the acid resistance test.

[0037] Figure 13 This is a comparison of the appearance of the three-proof paint obtained in Comparative Example 2 of the present invention before and after the alkali resistance test.

[0038] Figure 14 This is a comparison of the appearance of the three-proof paint obtained in Comparative Example 2 of the present invention before and after the acid resistance test.

[0039] Figure 15 This is a comparison of the appearance of the three-proof paint obtained in Comparative Example 3 of the present invention before and after the alkali resistance test.

[0040] Figure 16 This is a comparison of the appearance of the three-proof paint obtained in Comparative Example 3 of the present invention before and after the acid resistance test.

[0041] Figure 17 This is a comparison of the appearance of the three-proof paint obtained in Comparative Example 4 of the present invention before and after the alkali resistance test.

[0042] Figure 18 This is a comparison of the appearance of the three-proof paint obtained in Comparative Example 4 of the present invention before and after the acid resistance test.

[0043] Figure 19 This is a comparison of the appearance of the three-proof paint obtained in Comparative Example 5 of the present invention before and after the alkali resistance test.

[0044] Figure 20 This is a comparison of the appearance of the three-proof paint obtained in Comparative Example 5 of the present invention before and after the acid resistance test.

[0045] Figure 21 This is a comparison of the appearance of the three-proof paint obtained in Comparative Example 6 of the present invention before and after the acid resistance test.

[0046] Figure 22This is a comparison of the appearance of the three-proof paint obtained in Comparative Example 7 of the present invention before and after the acid resistance test.

[0047] Figure 23 This is a comparison of the appearance of the three-proof paint obtained in Comparative Example 8 of the present invention before and after the acid resistance test. DETAILED DESCRIPTION

[0048] In the present invention, unless otherwise specified, directional words such as "up, down, left, right" are generally understood in conjunction with the directions shown in the drawings and actual applications.

[0049] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0050] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0051] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein. The terms "optional" and "optional" both mean that a range may or may not be included (or may or may not be present).

[0052] In a first aspect, the present invention provides a highly stable UV moisture dual-curing conformal coating, comprising the following raw material components in weight percentage: based on the total amount of raw materials, 25.5-77.9 wt% of 3,3,5-trimethylcyclohexyl acrylate, 20-54 wt% of polyurethane acrylate with an isocyanate group, 1-8.5 wt%, preferably 1-2.5 wt% of an auxiliary stabilizing crosslinking agent, 0.1-5 wt% of a dehydrating agent, 1-7 wt% photoinitiator; and the weight ratio of polyurethane acrylate, 3,3,5-trimethylcyclohexyl acrylate and auxiliary stabilizing crosslinker is 1: (1.10-1.40): (0.05-0.30), preferably 1: (1.20-1.40): (0.05-0.20), further preferably 1: (1.25-1.40): (0.05-0.20); the auxiliary stabilizing crosslinker is selected from trimethylolpropane triacrylate and / or trimethylolpropane trimethacrylate.

[0053] In the present invention, the polyurethane acrylate preferably contains 10% to 18% isocyanate groups by weight. This optimal content of isocyanate groups in the polyurethane acrylate facilitates the reaction between the polyurethane acrylate, 3,3,5-trimethylcyclohexyl acrylate, and the auxiliary stabilizing crosslinker, forming a more stable chemical bond. This creates a more robust network structure that is more conducive to moisture curing, further promoting moisture curing, and further improving the strength and hardness of the UV conformal coating, while also making it more resistant to erosion and damage from the external environment.

[0054] The isocyanate group content of the present invention is measured by back titration.

[0055] In some preferred embodiments of the present invention, the content of 3,3,5-trimethylcyclohexyl acrylate is 30-75 wt %.

[0056] Preferably, the weight ratio of polyurethane acrylate, 3,3,5-trimethylcyclohexyl acrylate, and auxiliary stabilizing crosslinker is 1:(1.135-1.298):(0.142-0.230), more preferably 1:(1.135-1.160):(0.142-0.230). Using this preferred ratio of polyurethane acrylate, 3,3,5-trimethylcyclohexyl acrylate, and auxiliary stabilizing crosslinker further enhances the protective performance of the UV-moisture dual-cure conformal coating.

[0057] In some preferred embodiments of the present invention, the molecular weight of the polyurethane acrylate is between 600 and 3500 g / mol, preferably between 1000 and 5500 g / mol, and its functionality is between 0.7 and 1.2. Using this preferred embodiment, the polyurethane acrylate exhibits higher reactivity and crosslinking density, forming a more compact three-dimensional network structure, thereby improving the resin's mechanical strength, chemical resistance, heat resistance, and other properties. Furthermore, the oxygen barrier is lower, further contributing to improved curing efficiency. However, if the molecular weight and / or functional groups of the polyurethane acrylate are too large, the viscosity increases dramatically, processing performance deteriorates, and heat and chemical resistance decreases. Polyurethane acrylate resins can be purchased commercially, for example, from Changxing Materials Industry Co., Ltd. or Arkema Group (Sartomer); they can also be prepared using existing methods.

[0058] The polyurethane acrylate of the present invention is preferably an aliphatic polyurethane acrylate with an isocyanate group, which has excellent weather resistance and is not prone to yellowing. The polyurethane acrylate of the present invention can be purchased commercially or prepared.

[0059] In some preferred embodiments of the present invention, the dehydrating agent is selected from p-toluenesulfonyl isocyanate and / or N,N-dicyclohexylcarbodiimide.

[0060] Preferably, the photoinitiator is selected from 1-hydroxy-cyclohexyl-phenylmethanone and / or 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide.

[0061] In some preferred embodiments of the present invention, the raw material components of the highly stable UV moisture dual-curing conformal coating further include a free radical inhibitor and / or a catalytic moisture curing agent.

[0062] Preferably, when a free radical inhibitor and a catalytic moisture curing agent are present, the weight ratio of the free radical inhibitor, the catalytic moisture curing agent, and the polyurethane acrylate is (1-4): (5-25): 1000. Using an appropriately proportioned free radical inhibitor and catalytic moisture curing agent facilitates moisture curing.

[0063] In some preferred embodiments of the present invention, the catalytic moisture curing agent is selected from (dimorpholinyl diethyl ether), (N,N-dimethyl-p-toluidine).

[0064] In some preferred embodiments of the present invention, the free radical inhibitor is selected from (2,6-di-tert-butyl-4-methylphenol), (3,5-di-tert-butyl-4-hydroxyphenylpropionic acid C7-C9 mixed esters), (Octamine (CAS: 37338-62-8)), (such as C 20 H 27 N), wherein R and R1 are each independently selected from an alkyl group having 4 to 10 carbon atoms. The alkyl group having 4 to 10 carbon atoms can be, for example, C4H9, C8H 17 Or other alkyl chains.

[0065] In some embodiments, the radical inhibitor is selected from C 25 H 42 O3(CAS:125643-61-0), C 33 H 52 O2(CAS 7786-17-6), C 25 H 44 OS2 (CAS: 110553-27-0), Octamine (CAS: 37338-62-8), C 20 H 27 N (CAS: 68411-46-1).

[0066] In some preferred embodiments of the present invention, the raw material components of the highly stable UV-moisture dual-cure conformal coating further include: 0.01-0.03 wt% of a fluorescent brightener and 0-2 wt%, preferably 0.5-2 wt%, of an adhesion promoter, based on the total raw material volume. This preferred solution further improves the adhesion of the UV-moisture dual-cure conformal coating to substrates and facilitates identification.

[0067] Further preferably, the fluorescent whitening agent is selected from 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene (C 26 H 26 N2O2S), 1,4-2 (benzoxazolyl-2-yl) naphthalene (C 24 H 14 O2N2), 4,4-bis(2-benzoxazolyl)stilbene (C 28 H 18 N2O2), 4.4-bis(2-dimethoxyphenyl)biphenyl (C 30 H 26 O2) at least one.

[0068] Preferably, the adhesion promoter is selected from alkyl acrylate phosphates and / or methacryloxysilanes.

[0069] In a second aspect, the present invention provides a method for preparing a highly stable UV moisture dual curing conformal coating, which is used to prepare the highly stable UV moisture dual curing conformal coating described in the first aspect, and the preparation method comprises the following steps: S1. Mix the required amounts of 3,3,5-trimethylcyclohexyl acrylate, auxiliary stabilizing crosslinking agent, polyurethane acrylate, and dehydrating agent to obtain a primary mixed solution; S2. Introducing a photoinitiator into the primary mixed solution for secondary mixing to obtain a secondary mixed solution.

[0070] In some preferred embodiments of the present invention, the preparation method further comprises: A free radical inhibitor and / or a fluorescent whitening agent are also introduced in the secondary mixing in S2; Then, a catalytic moisture curing agent and / or an adhesion promoter is introduced into the obtained secondary mixed liquid for a third mixing.

[0071] Compared with a method of mixing all raw materials together, the present invention adopts the above-mentioned specific mixing steps, which can make the reaction more complete and help improve the stability of the UV conformal paint.

[0072] In some preferred embodiments of the present invention, the conditions for the primary mixing include: a stirring speed of 1700-2300 rpm, and a stirring time of 100-150 s.

[0073] In some preferred embodiments of the present invention, the secondary mixing conditions include: a stirring speed of 2000-2500 rpm, a total stirring time of 150-200 s. The secondary mixing can be stirred multiple times, illustratively 1-3 times, and the total stirring time satisfies the aforementioned range.

[0074] In some preferred embodiments of the present invention, the conditions for the three mixing steps include: a stirring speed of 1500-2000 rpm, and a stirring time of 100-150 s.

[0075] By adopting the above-mentioned mixing conditions of the present invention, the components can be mixed more evenly, which is more conducive to improving the curing efficiency of the UV moisture dual-curing conformal coating.

[0076] The embodiments of the present invention are described in detail below, which are exemplary and only used to explain the present invention, and are not to be construed as limiting the present invention.

[0077] Example 1 A conformal coating has a raw material formula as shown in Table 1. The polyurethane acrylate has a molecular weight of 1000-3500 g / mol, a functionality of 0.8-1.2, and an isocyanate group content of 15% by mass. It was purchased from Changxing Materials Industry Co., Ltd. under model number 6133N-15 (see the company's product brochure).

[0078] The weight ratio of polyurethane acrylate to 3,3,5-trimethylcyclohexyl acrylate and auxiliary stabilizing crosslinker (trimethylolpropane triacrylate) was calculated to be 1:1.291:0.05. The weight ratio of free radical inhibitor, catalytic moisture curing agent to polyurethane acrylate was 1.25:7.5:1000.

[0079] Table 1

[0080] The preparation process comprises the following steps: 1. Mix TMCHA, polyurethane acrylate, trimethylolpropane triacrylate and p-toluenesulfonyl isocyanate once in a mixer (mixing speed 2000 rpm, 100 s).

[0081] 2. Add photoinitiator 184, BHT, and UV-OB to the mixture obtained in step 1 and mix twice under a mixer (mixing speed 2000 rpm, mixing for a total of 150 seconds).

[0082] 3. Add DMDEE to the mixture obtained in step 2 and mix once under a mixer (mixing speed 2000 rpm, 150 s).

[0083] Example 2 The method of Example 1 was followed, except that the amounts of polyurethane acrylate and the auxiliary stabilizing crosslinking agent were adjusted so that the weight ratio of polyurethane acrylate to the auxiliary stabilizing crosslinking agent was 1:0.25, and the total content of polyurethane acrylate and the auxiliary stabilizing crosslinking agent remained unchanged.

[0084] Example 3 The method of Example 1 was used, except that the amounts of polyurethane acrylate and 3,3,5-trimethylcyclohexyl acrylate were adjusted so that the weight ratio of polyurethane acrylate to 3,3,5-trimethylcyclohexyl acrylate was 1:1.17.

[0085] Example 4 The method of Example 1 was used, except that the polyurethane acrylate had a molecular weight of 600-1300 g / mol, a functionality of 1-2, and an isocyanate group content of 10% by mass. It was purchased from Changxing Materials Industry Co., Ltd. under the model number 6133N-10.

[0086] Example 5 The method of Example 1 was used, except that the dehydrating agent was N,N-dicyclohexylcarbodiimide, and the amount used remained unchanged.

[0087] Comparative Example 1 The method of Example 1 was used, except that 3,3,5-trimethylcyclohexyl acrylate was replaced by isobornyl acrylate, and the amount used remained unchanged.

[0088] Comparative Example 2 The method of Example 1 was followed, except that no auxiliary stabilizing cross-linking agent was added and the amount used remained unchanged.

[0089] Comparative Example 3 The method of Example 1 was used, except that the amounts of polyurethane acrylate and 3,3,5-trimethylcyclohexyl acrylate were adjusted so that the weight ratio of polyurethane acrylate to 3,3,5-trimethylcyclohexyl acrylate was 1:1.42, but the total amount of the two remained unchanged.

[0090] Comparative Example 4 The method of Example 1 was followed, except that the amount of the auxiliary stabilizing crosslinking agent was adjusted so that the weight ratio of the polyurethane acrylate to the auxiliary stabilizing crosslinking agent was 1:0.40.

[0091] Comparative Example 5 The method of Example 1 was followed, except that no dehydrating agent was added.

[0092] Comparative Example 6 The method of Example 1 was followed, except that the auxiliary stabilizing cross-linking agent was replaced with tris(2-hydroxyethyl)isocyanurate triacrylate (THEICTA) in the same amount.

[0093] Comparative Example 7 The method of Example 1 was followed, except that the auxiliary stabilizing cross-linking agent was replaced with pentaerythritol triacrylate (PET3A) in the same amount.

[0094] Comparative Example 8 The method of Example 1 was referred to, except that the polyurethane acrylate was replaced by polyurethane acrylate without isocyanate group, which was purchased from Changxing Materials Industry Co., Ltd., model number 61329.

[0095] Test Case The performance of the three-proof coatings obtained in the above examples and comparative examples was tested. The results are shown in Table 2. The appearance pictures of the acid and alkali resistance test samples of Examples 1-5 are shown in Table 2. Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 、 Figure 8 、 Figure 9 、 Figure 10The pictures of the acid and alkali resistance test samples of comparative examples 1-5 are as follows: Figure 11 、 Figure 12 、 Figure 13 、 Figure 14 、 Figure 15 、 Figure 16 、 Figure 17 、 Figure 18 、 Figure 19 、 Figure 20 ; Comparative Examples 6-8 of the acid resistance test sample appearance pictures taken as Figure 21 、 Figure 22 、 Figure 23 .

[0096] Among them, the adhesion grade is tested and characterized according to GB / T 9286-2021, and the water vapor transmission rate is tested according to GB / T 1037-2021.

[0097] Acid and alkali resistance tests were conducted in accordance with GB / T1981.2-2009. The test solution used for the acid test was a 5wt% hydrochloric acid aqueous solution, and for the alkali test was a 5wt% sodium hydroxide aqueous solution. The test duration was 168 hours, and the test temperature was 22-24°C. Acid and alkali resistance was classified as either acceptable or unacceptable based on appearance. Acceptable means the uniformly distributed conformal coating showed no blistering, stickiness, white spots, cracks, or wrinkling, and the metal substrate beneath the conformal coating showed no obvious corrosion. Unacceptable means at least one of the following conditions was observed: blistering, stickiness, white spots, cracks, flaking, or wrinkling on the uniformly distributed conformal coating, or visible corrosion on the metal substrate beneath the conformal coating. As can be seen from the accompanying figures of the comparative examples, Comparative Example 1 exhibited visible corrosion on the metal substrate beneath the conformal coating, which was deemed unqualified. Comparative Example 2 exhibited significant peeling on the metal substrate beneath the conformal coating, which was deemed unqualified. Comparative Example 3 exhibited edge peeling and surface tackiness, which were deemed unqualified. Comparative Example 4 exhibited edge peeling, which was deemed unqualified. Comparative Example 5 exhibited bulging and peeling (at black spots) along the edges of the conformal coating, which were deemed unqualified. The conformal coating materials in Comparative Examples 6 and 7, after replacing the crosslinking agent with other crosslinkers, were difficult to spread evenly and smoothly on the substrate, exhibiting craters and wrinkling, and were deemed unqualified. Comparative Example 8 employed a polyurethane acrylic resin without isocyanate groups. The conformal coating prepared with this polyurethane acrylic resin lacked moisture curing properties, was relatively soft, and exhibited poor barrier properties (poor water permeability data). In the acid resistance test, it easily deformed upon contact with other test specimens, and was deemed unqualified.

[0098] Table 2

[0099] It can be seen from the above results that, compared with the comparative example, the embodiment of the present invention has both UV and moisture dual curing properties and higher stability, and can resist acid and alkali environments.

[0100] Furthermore, according to Examples 1 and 2-5, it can be seen that the preferred solution of the present invention is more conducive to improving stability and acid and alkali resistance.

[0101] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A highly stable UV moisture dual curing conformal coating, characterized in that: The invention comprises the following raw material components in weight percentage: based on the total amount of raw materials, 25.5-77.9 wt% of 3,3,5-trimethylcyclohexyl acrylate, 20-54 wt% of polyurethane acrylate with an isocyanate group, 1-8.5 wt% of an auxiliary stabilizing crosslinking agent, 0.1-5 wt% of a dehydrating agent, and 1-7 wt% of a photoinitiator; The weight ratio of polyurethane acrylate, 3,3,5-trimethylcyclohexyl acrylate and auxiliary stabilizing crosslinking agent is 1: (1.10-1.40): (0.05-0.30); the auxiliary stabilizing crosslinking agent is selected from trimethylolpropane triacrylate and / or trimethylolpropane trimethacrylate.

2. The highly stable UV moisture dual curing conformal coating according to claim 1, characterized in that: The content of 3,3,5-trimethylcyclohexyl acrylate is 30-75 wt%, and / or the weight ratio of polyurethane acrylate, 3,3,5-trimethylcyclohexyl acrylate and auxiliary stabilizing crosslinker is 1: (1.135-1.298): (0.142-0.230).

3. The highly stable UV moisture dual curing conformal coating according to claim 1, characterized in that: The isocyanate group content of the polyurethane acrylate is 10% to 18% by mass; and / or, The molecular weight of polyurethane acrylates is between 600 and 3500 g / mol and their functionality is between 0.7 and 1.

2.

4. The highly stable UV moisture dual curing conformal coating according to claim 1, characterized in that: The dehydrating agent is selected from p-toluenesulfonyl isocyanate and / or N,N-dicyclohexylcarbodiimide, and the photoinitiator is selected from 1-hydroxy-cyclohexyl-phenyl ketone and / or 2,4,6 (trimethylbenzoyl) diphenylphosphine oxide.

5. The highly stable UV moisture dual curing conformal coating according to claim 1, characterized in that: The raw material components of the highly stable UV moisture dual-curing conformal coating further include a free radical inhibitor and / or a catalytic moisture curing agent. When the free radical inhibitor and the catalytic moisture curing agent are contained, the weight ratio of the free radical inhibitor, the catalytic moisture curing agent to the polyurethane acrylate is (1-4): (5-25):1000.

6. The highly stable UV moisture dual curing conformal coating according to claim 5, characterized in that: Catalytic moisture curing agent is selected from and / or ; The free radical inhibitor is selected from 、 、 、 At least one of the following, wherein R and R1 are each independently selected from an alkyl group having 4 to 10 carbon atoms.

7. The highly stable UV moisture dual curing conformal coating according to claim 1, characterized in that: The raw material components of the highly stable UV moisture dual-curing conformal coating further include: 0.01-0.03 wt% of a fluorescent brightener and 0-2 wt% of an adhesion promoter, based on the total amount of raw materials; wherein the fluorescent brightener is selected from at least one of 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene, 1,4-2(benzoxazolyl-2-yl)naphthalene, 4,4-bis(2-benzoxazolyl)stilbene, and 4,4-bis(2-dimethoxystyryl)biphenyl; and the adhesion promoter is selected from alkyl acrylate phosphate and / or methacryloxysilane.

8. A method for preparing a highly stable UV moisture dual curing conformal coating, characterized in that: The method is used to prepare a highly stable UV moisture dual-curing conformal coating as claimed in any one of claims 1 to 7, and the preparation method comprises the following steps: S1. Mix the required amounts of 3,3,5-trimethylcyclohexyl acrylate, auxiliary stabilizing crosslinking agent, polyurethane acrylate, and dehydrating agent to obtain a primary mixed solution; S2. Introducing a photoinitiator into the primary mixed solution for secondary mixing to obtain a secondary mixed solution.

9. The method for preparing a highly stable UV moisture dual-curing conformal coating according to claim 8, wherein: The preparation method further comprises: A free radical inhibitor and / or a fluorescent whitening agent are also introduced in the secondary mixing in S2; Then, a catalytic moisture curing agent and / or an adhesion promoter is introduced into the obtained secondary mixed liquid for a third mixing.

10. The method for preparing a highly stable UV moisture dual-curing conformal coating according to claim 9, characterized in that: The conditions for primary mixing include: stirring speed of 1700-2300 rpm, stirring time of 100-150 s; The conditions for secondary mixing included: stirring speed of 2000-2500 rpm and total stirring time of 150-200 s; The conditions for the three-step mixing include: a stirring speed of 1500-2000 rpm and a stirring time of 100-150 s.

Images