A three-proofing adhesive including a dual-curing resin and a preparation method and application thereof

Abstract

The application belongs to the technical field of three-proofing glue and specifically relates to three-proofing glue comprising double-cured resin and a preparation method and application thereof. The three-proofing glue comprises, by mass fraction, 35-55 parts of siloxane-modified acrylate oligomer, 5-15 parts of di-functional group hydroxyl-containing polyurethane acrylate resin, 30-60 parts of active diluent and 1-5 parts of photoinitiator. The siloxane-modified acrylate oligomer is obtained by reacting side-chain fluorine-containing epoxy-terminated polysiloxane and acrylic acid to obtain prepolymer A and then reacting the prepolymer A with methyl orthosilicate. The three-proofing glue has excellent adhesion, neutral salt spray resistance, ammonium chloride solution resistance, sodium carbonate solution resistance and mixed gas resistance and can be used for protecting circuit boards and electronic equipment in a chemical plant environment.

Description

Technical Field

[0001] This invention belongs to the field of conformal adhesive technology, specifically relating to a conformal adhesive comprising a dual-curing resin, its preparation method, and its application. Background Technology

[0002] Conformal adhesive refers to a protective adhesive with outstanding "moisture-proof", "salt spray-proof", and "mildew-proof" properties. It is used to protect circuit boards and electronic components from the corrosion of harsh environments, thereby improving and extending the service life of products and ensuring the safety and reliability of products during use.

[0003] Conformal adhesives can be classified into thermosetting conformal adhesives, UV-curing conformal adhesives, and dual-curing conformal adhesives according to their curing methods. Thermosetting conformal adhesives use heating to accelerate curing, but the curing time is long. UV-curing conformal adhesives have a very fast curing speed, usually completed within a few seconds, but may result in incomplete curing for parts that are shaded from light. Dual-curing conformal adhesives have been extensively researched, particularly the UV-moisture dual-curing method, which first uses UV light to achieve rapid curing and then performs moisture curing, which can further improve the crosslinking density and therefore has broad application prospects.

[0004] Existing dual-curing conformal adhesives primarily focus on their resistance to damp heat, salt spray, yellowing, and thermal shock. For example, Chinese patent CN117567979B discloses a high-temperature resistant, thermally reversible, self-healing UV / moisture dual-curing conformal adhesive, comprising Y-type polyurethane modified acrylate oligomers, self-healing silicone modified acrylate oligomers, and acrylic reactive diluents. The Y-type polyurethane modified acrylate oligomers are prepared from diisocyanate, triisocyanate, polyol, functional acrylic derivatives, and furfural; the self-healing silicone modified acrylate oligomers are synthesized from bi-terminated epoxy silicone oil, N-carbamoyl maleimide, monoisocyanate monomers, and a catalyst. This high-temperature resistant, thermally reversible, self-healing UV / moisture dual-curing conformal adhesive exhibits excellent thermal stability and weather resistance. Simultaneously, the adhesive coating possesses thermally reversible self-healing properties, thus providing better protection for circuit boards and extending the lifespan of electronic components.

[0005] Chinese patent CN114574150B discloses a solvent-free UV / moisture dual-curing conformal adhesive. By weight, the preparation materials include: 40-60 parts of a self-made polyurethane acrylic prepolymer, 40-50 parts of an reactive diluent, 1-5 parts of a photoinitiator, 0.1-1 parts of a leveling agent, 0.1-1 parts of a defoamer, 0.1-1 parts of a dehydrating agent, and 0.001-0.01 parts of a catalyst. The self-made polyurethane acrylic prepolymer contains isocyanate groups, siloxane groups, and acrylic double bonds. This conformal adhesive can be UV-cured first, and then further moisture-cured through the isocyanate groups and siloxane groups, thus exhibiting better adhesion and salt spray resistance.

[0006] However, in chemical plant environments, electronic devices and circuit boards face challenges beyond just ordinary moisture, dust, and mechanical shocks. They also encounter more severe gas corrosion (such as sulfur dioxide and chlorine) and liquid corrosion (such as acid and alkali solutions). For the protection requirements of these specific environments, the conformal coatings of the above-mentioned technical solutions may not provide sufficient protection. Summary of the Invention

[0007] To address the above-mentioned problems, this invention provides a conformal adhesive comprising a dual-curing resin, its preparation method, and its application.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The first aspect of the present invention provides a conformal adhesive comprising a dual-curing resin, wherein the raw materials, by weight, include: 35-55 parts of siloxane-modified acrylate oligomer, 5-15 parts of difunctional hydroxyl-containing polyurethane acrylate resin, 30-60 parts of reactive diluent, and 1-5 parts of photoinitiator.

[0010] The siloxane-modified acrylate oligomer is obtained by reacting prepolymer A with fluorine-containing epoxy-terminated polysiloxane and acrylic acid, and then reacting prepolymer A with methyl orthosilicate.

[0011] Preferably, the mass ratio of the siloxane-modified acrylate oligomer, the difunctional hydroxyl-containing polyurethane acrylate resin, and the reactive diluent is (3.5-7):1:(4-6).

[0012] Preferably, the molar ratio of the fluorinated epoxy-terminated polysiloxane with side chains to acrylic acid is 1:(2-4), more preferably 1:3.

[0013] Preferably, the molar ratio of prepolymer A to methyl orthosilicate is 1:(1-1.5), more preferably 1:1.3.

[0014] Preferably, the preparation method of the siloxane-modified acrylate oligomer is as follows: under nitrogen protection, a polymerization inhibitor and tetramethylammonium chloride are added to a fluorine-containing epoxy-terminated polysiloxane, the mixture is stirred and heated to 50-70°C, acrylic acid is added dropwise, and the reaction is continued for 2-4 hours after the addition is completed to obtain prepolymer A; methyl orthosilicate and dibutyltin dilaurate are added to prepolymer A, the mixture is heated to 80-90°C, and the reaction is continued for 4-6 hours to obtain the siloxane-modified acrylate oligomer.

[0015] Preferably, the polymerization inhibitor is selected from at least one of hydroquinone, p-hydroxyanisole, and p-benzoquinone.

[0016] Preferably, the mass ratio of the polymerization inhibitor, tetramethylammonium chloride and acrylic acid is (0.02-0.04):(0.05-0.1):2.

[0017] Preferably, the mass ratio of dibutyltin dilaurate to prepolymer A is (0.2-

[0018] 0.5): 100.

[0019] Preferably, the fluorinated epoxy-terminated polysiloxane is obtained by reacting a fluorinated hydroxyl-terminated polysiloxane with a 3-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0020] Preferably, the molar ratio of the fluorinated hydroxyl-terminated polysiloxane with side chains to 3-(2,3-epoxypropoxy)propyltrimethoxysilane is (1-2):(2-5), more preferably 1.5:3.

[0021] Preferably, the preparation method of the side-chain fluorinated epoxy-terminated polysiloxane is as follows: the side-chain fluorinated hydroxyl-terminated polysiloxane and 3-(2,3-epoxypropoxy)propyltrimethoxysilane are mixed evenly, and an alkaline catalyst is added under nitrogen protection. The mixture is stirred and reacted at 40-50℃ for 1-3 hours. After the reaction is completed, the pH is adjusted to 7±0.2 with a neutralizing agent to obtain the side-chain fluorinated epoxy-terminated polysiloxane.

[0022] Preferably, the alkaline catalyst is a mixture of potassium hydroxide and ethanol in a mass ratio of (3-8):100.

[0023] Preferably, the mass ratio of the alkaline catalyst to the fluorinated hydroxyl-terminated polysiloxane is (1-3):100.

[0024] Preferably, the stirring speed during the preparation of fluorine-containing epoxy-terminated polysiloxanes is 300-500 rpm.

[0025] Preferably, the neutralizing agent is a mixture of phosphoric acid and ethanol in a mass ratio of (1-3):100.

[0026] Preferably, the fluorinated hydroxyl-terminated polysiloxane is obtained by reacting octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane and trifluoropropylmethylcyclotrisiloxane.

[0027] Preferably, the molar ratio of the octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane and trifluoropropylmethylcyclotrisiloxane is (1.5-3.5):(0.5-1.5):(2-5), and more preferably 2:1:3.

[0028] Preferably, the preparation method of the fluorinated hydroxyl-terminated polysiloxane is as follows: octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane, and trifluoropropylmethylcyclotrisiloxane are mixed evenly, stirred at 80-90°C for 20-40 min under nitrogen protection, the temperature is raised to 110-120°C, tetramethylammonium hydroxide aqueous solution and water are added, stirring is continued for 2-4 h, the temperature is raised to 140-150°C, and stirring is continued for 2-4 h to obtain the fluorinated hydroxyl-terminated polysiloxane.

[0029] Preferably, the stirring speed during the preparation of fluorinated hydroxyl-terminated polysiloxanes is 300-500 rpm.

[0030] Preferably, the mass concentration of the tetramethylammonium hydroxide aqueous solution is 20-30%.

[0031] Preferably, the mass ratio of the octamethylcyclotetrasiloxane, the tetramethylammonium hydroxide aqueous solution, and water is 100:(0.01-0.03):(0.2-0.5).

[0032] Preferably, the hydroxyl value of the difunctional hydroxyl-containing polyurethane acrylate resin is 80-100 mgKOH / g, preferably 96, and it was purchased from Kunshan Castel Polymer Materials Co., Ltd., trade name: 93726.

[0033] Preferably, the reactive diluent is selected from at least one of trimethylolpropane triacrylate, tetrahydrofurfuryl acrylate, tripropylene glycol diacrylate, isoborneol acrylate, isooctyl methacrylate, dipropylene glycol diacrylate, isoborneol acrylate, and isoborneol methacrylate.

[0034] More preferably, the reactive diluent is a mixture of trimethylolpropane triacrylate, tetrahydrofurfuryl acrylate, and tripropylene glycol diacrylate.

[0035] More preferably, the mass ratio of trimethylolpropane triacrylate, tetrahydrofurfuryl acrylate and dipropylene glycol diacrylate is (4-10):(2-6):1, more preferably 8:5:1.

[0036] Preferably, the photoinitiator is selected from at least one of 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylphenyl ketone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, methyl benzoylformate, isopropylthioxanthraphenone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0037] More preferably, the photoinitiator is a mixture of 2-hydroxy-2-methyl-1-phenylpropanone and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0038] More preferably, the mass ratio of 2-hydroxy-2-methyl-1-phenylpropanone to bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide is (1-3):(1-3), more preferably 1:1.

[0039] Preferably, the conformal adhesive comprising a dual-curing resin may further include additives commonly used in the art.

[0040] Preferably, the additives include, but are not limited to, adhesion promoters, leveling agents, defoamers, and polymerization inhibitors.

[0041] Preferably, the additive accounts for 1-10% of the total mass of the conformal coating.

[0042] The second aspect of the present invention provides a method for preparing the above-mentioned conformal adhesive including a dual-curing resin, comprising the following steps: mixing a siloxane-modified acrylate oligomer, a difunctional hydroxyl-containing polyurethane acrylate resin, an active diluent, and a photoinitiator in the dark until homogeneous.

[0043] The third aspect of the present invention provides the application of the above-mentioned conformal adhesive including dual-curing resin in the protection of circuit boards and electronic devices.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] This invention aims to address the severe gas and liquid corrosion faced by electronic devices and circuit boards in chemical plant environments. Existing conformal adhesives may not provide sufficient protection. To address this problem, the technical solution of this invention involves first reacting a fluorinated epoxy-terminated polysiloxane with acrylic acid to introduce fluorinated polysiloxane segments into the acrylate backbone. Then, it reacts with methyl orthosilicate to introduce alkoxysilanes into the acrylate side chains. The resulting siloxane-modified acrylate oligomer not only achieves UV protection... Dual curing via curing and moisture (the carbon-carbon double bonds in the siloxane-modified acrylate oligomer achieve UV curing under the action of a photoinitiator, while the polyalkoxy groups in the siloxane-modified acrylate oligomer achieve moisture curing through contact with moisture), and it is speculated that because the main chain of the siloxane-modified acrylate oligomer contains polysiloxane segments, as well as fluorinated side chains and alkoxy side chains, the three work together to give the conformal adhesive excellent adhesion and good corrosion resistance, and it can pass 168h of neutral salt spray and 5% sodium carbonate solution tests.

[0046] However, the inventors discovered that conformal coatings prepared using only siloxane-modified acrylate oligomers could not pass the 336-hour neutral salt spray test and the 168-hour 5% ammonium chloride solution test. To solve this technical problem, the inventors unexpectedly discovered through numerous inventive experiments that when a difunctional hydroxyl-containing polyurethane acrylic resin is compounded with siloxane-modified acrylate oligomers, the combined effect of the two allows the conformal coating to pass both the 336-hour neutral salt spray test and the 168-hour 5% ammonium chloride solution test. It is speculated that this is not only because additional functional groups are introduced into the conformal coating to form a more complex network structure, but also because the micro-phase separation formed after the two are mixed increases the tortuosity of the corrosive medium penetration path, enabling the conformal coating to pass both the 336-hour neutral salt spray test and the 168-hour 5% ammonium chloride solution test.

[0047] Meanwhile, the inventors also unexpectedly discovered that adding difunctional hydroxyl-containing polyurethane acrylate resin can improve the resistance of conformal coating to mixed gas corrosion. However, not all difunctional hydroxyl-containing polyurethane acrylate resins can produce conformal coatings that pass the 7-day mixed gas test. When the hydroxyl value of the difunctional hydroxyl-containing polyurethane acrylate resin is lower than 80 mg KOH / g or higher than 100 mg KOH / g, the resulting conformal coating will not pass the 7-day mixed gas test and the 336-hour neutral salt spray test, and the adhesion of the conformal coating will also decrease.

[0048] In addition, the inventors also discovered during the experiment that the mass ratio of siloxane-modified acrylate oligomer, difunctional hydroxyl-containing polyurethane acrylate resin, and reactive diluent is crucial to the balance between the adhesion, neutral salt spray resistance, acid and alkali solution resistance, and mixed gas resistance of the conformal adhesive. When the mass ratio of siloxane-modified acrylate, difunctional hydroxyl-containing polyurethane acrylate resin, and reactive diluent is not (3.5-7):1:

[0049] When the range of (4-6) is exceeded, it will lead to a decrease in the adhesion, resistance to neutral salt spray, resistance to acid solutions and resistance to mixed gases of the conformal coating. Detailed Implementation

[0050] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific implementation schemes are now described in detail.

[0051] The present invention will be further described below with reference to embodiments, but the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0052] Unless otherwise specified, all raw materials used in the following examples and comparative examples are commercially available or prepared by conventional methods in the art.

[0053] Example 1

[0054] A three-proof adhesive comprising a dual-curing resin, wherein, by weight, the raw materials consist of 35 parts of siloxane-modified acrylate oligomer, 5 parts of difunctional hydroxyl-containing polyurethane acrylate resin, 30 parts of reactive diluent, and 1 part of photoinitiator.

[0055] The preparation method of the siloxane-modified acrylate oligomer is as follows: under nitrogen protection, a polymerization inhibitor and tetramethylammonium chloride are added to a fluorine-containing epoxy-terminated polysiloxane, the mixture is stirred and heated to 60°C, acrylic acid is added dropwise, and the reaction is continued for 3 hours after the addition is completed to obtain prepolymer A; methyl orthosilicate and dibutyltin dilaurate are added to prepolymer A, the mixture is heated to 85°C, and the reaction is continued for 5 hours to obtain siloxane-modified acrylate.

[0056] The molar ratio of the fluorinated epoxy-terminated polysiloxane with side chains to acrylic acid is 1:3.

[0057] The molar ratio of prepolymer A to methyl orthosilicate is 1:1.3.

[0058] The polymerization inhibitor is hydroquinone.

[0059] The mass ratio of the polymerization inhibitor, tetramethylammonium chloride, and acrylic acid is 0.03:0.08:2.

[0060] The mass ratio of dibutyltin dilaurate to prepolymer A is 0.3:100.

[0061] The preparation method of the fluorinated epoxy-terminated polysiloxane is as follows: fluorinated hydroxyl-terminated polysiloxane and 3-(2,3-epoxypropoxy)propyltrimethoxysilane are mixed evenly, and an alkaline catalyst is added under nitrogen protection. The mixture is stirred and reacted at 45°C for 2 hours. After the reaction is completed, the pH is adjusted to 7±0.2 using a neutralizing agent to obtain the fluorinated epoxy-terminated polysiloxane.

[0062] The molar ratio of the fluorinated hydroxyl-terminated polysiloxane with side chains to 3-(2,3-epoxypropoxy)propyltrimethoxysilane (CAS No.: 2530-83-8) is 1.5:3.

[0063] The alkaline catalyst is composed of potassium hydroxide and ethanol in a mass ratio of 6:100.

[0064] The mass ratio of the alkaline catalyst to the fluorinated hydroxyl-terminated polysiloxane is 2:100.

[0065] The stirring speed during the preparation of fluorine-containing epoxy-terminated polysiloxanes is 400 rpm.

[0066] The neutralizing agent is a mixture of phosphoric acid and ethanol in a mass ratio of 2:100.

[0067] The preparation method of the fluorinated hydroxyl-terminated polysiloxane is as follows: octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane, and trifluoropropylmethylcyclotrisiloxane are mixed evenly, stirred at 85°C for 30 min under nitrogen protection, the temperature is raised to 110°C, tetramethylammonium hydroxide aqueous solution and water are added, stirring is continued for 3 h, the temperature is raised to 140°C, and stirring is continued for 3 h to obtain the fluorinated hydroxyl-terminated polysiloxane.

[0068] The molar ratio of the octamethylcyclotetrasiloxane (CAS No.: 556-67-2), hexamethylcyclotrisiloxane (CAS No.: 541-05-9), and trifluoropropylmethylcyclotrisiloxane (CAS No.: 2374-14-3) is 2:1:3.

[0069] The stirring speed during the preparation of fluorine-containing hydroxyl-terminated polysiloxanes is 400 rpm.

[0070] The mass concentration of the tetramethylammonium hydroxide aqueous solution is 25%.

[0071] The mass ratio of the octamethylcyclotetrasiloxane, the tetramethylammonium hydroxide aqueous solution, and water is 100:0.02:0.3.

[0072] The difunctional hydroxyl-containing polyurethane acrylate resin has a hydroxyl value of 96 mgKOH / g and was purchased from Kunshan Castel Polymer Materials Co., Ltd. Product name: 93726.

[0073] The reactive diluents are trimethylolpropane triacrylate (CAS No.: 15625-89-5), tetrahydrofurfuryl acrylate (CAS No.: 2399-48-6), and tripropylene glycol diacrylate (CAS No.:

[0074] A mixture of 42978-66-5.

[0075] The mass ratio of trimethylolpropane triacrylate, tetrahydrofurfuryl acrylate, and dipropylene glycol diacrylate is 8:5:1.

[0076] The photoinitiator is a mixture of 2-hydroxy-2-methyl-1-phenylpropanone (CAS No.: 7473-98-5) and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (CAS No.: 162881-26-7).

[0077] The mass ratio of 2-hydroxy-2-methyl-1-phenylpropanone to bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide is 1:1.

[0078] The preparation method of the above-mentioned conformal adhesive including dual-curing resin is as follows: siloxane-modified acrylate, difunctional hydroxyl-containing polyurethane acrylate resin, reactive diluent, and photoinitiator are stirred evenly in the dark to obtain the product.

[0079] Example 2

[0080] The difference from Example 1 is that the conformal adhesive comprising a dual-curing resin is composed of 55 parts of siloxane-modified acrylate oligomer, 15 parts of difunctional hydroxyl-containing polyurethane acrylate resin, 60 parts of reactive diluent, and 5 parts of photoinitiator; all other components are the same.

[0081] The preparation method of the above-mentioned conformal adhesive including the dual-curing resin is the same as in Example 1.

[0082] Example 3

[0083] The difference from Example 1 is that the conformal adhesive comprising a dual-curing resin is composed of 45 parts of siloxane-modified acrylate oligomer, 10 parts of difunctional hydroxyl-containing polyurethane acrylate resin, 45 parts of reactive diluent, and 3 parts of photoinitiator; all other components are the same.

[0084] The preparation method of the above-mentioned conformal adhesive including the dual-curing resin is the same as in Example 1.

[0085] Comparative Example 1

[0086] The difference from Example 3 is that the fluorinated hydroxyl-terminated polysiloxane with side chains was replaced with an equal molar amount of hydroxyl-terminated polysiloxane (molecular weight 2000 Da), purchased from Shenzhen Jipeng Silicon Fluorine Materials Co., Ltd.; all other aspects are the same.

[0087] Comparative Example 2

[0088] The difference from Example 3 is that the preparation method of the siloxane-modified acrylate oligomer is as follows: under nitrogen protection, a polymerization inhibitor and tetramethylammonium chloride are added to a fluorine-containing epoxy-terminated polysiloxane, the mixture is stirred and heated to 60°C, acrylic acid is added dropwise, and the reaction is continued for 3 hours after the addition is completed; the rest is the same.

[0089] Comparative Example 3

[0090] The difference from Example 3 is that the fluorinated epoxy-terminated polysiloxane with side chains is replaced with an equal molar amount of ethylene glycol diglycidyl ether (CAS No.: 2224-15-9); all other aspects are the same.

[0091] Comparative Example 4

[0092] The difference from Example 3 is that the difunctional hydroxyl-containing polyurethane acrylate resin is replaced with an equal mass of siloxane-modified acrylate oligomer; all other aspects are the same.

[0093] Comparative Example 5

[0094] The difference from Example 3 is that the difunctional hydroxyl-containing polyurethane acrylate resin has a hydroxyl value of 160 mg KOH / g and was purchased from Kunshan Castel Polymer Materials Co., Ltd., trade name: 93721; the rest are the same.

[0095] Comparative Example 6

[0096] The difference from Example 3 is that the difunctional hydroxyl-containing polyurethane acrylate resin has a hydroxyl value of 76 mgKOH / g and was purchased from Kunshan Castel Polymer Materials Co., Ltd., trade name: 93722; the rest are the same.

[0097] Comparative Example 7

[0098] The difference from Example 3 is that the difunctional hydroxyl-containing polyurethane acrylate resin was replaced with an equal mass of trifunctional aliphatic polyurethane acrylate, purchased from Guangdong Boxin New Material Technology Co., Ltd., model B-404; all other aspects are the same.

[0099] Comparative Example 8

[0100] The difference from Example 3 is that the three-proof glue including a dual-curing resin is composed of, by mass, 40 parts of a siloxane-modified acrylate oligomer, 20 parts of a difunctional hydroxyl-containing polyurethane acrylate resin, 40 parts of an active diluent, and 3 parts of a photoinitiator; the rest are the same.

[0101] Performance test:

[0102] The three-proof glues of Examples 1-3 and Comparative Examples 1-8 were respectively coated on the surface of a PCB substrate with a thickness of 40 μm, and were successively subjected to UV curing and moisture curing. The conditions for UV curing were: UV curing was carried out for 30 s under the condition of 1500 mJ / cm 2 using a high-pressure mercury lamp; the conditions for moisture curing were: curing for 72 h at 25 °C and 75% humidity under light-shielded conditions; the following tests were carried out after curing:

[0103] 1. Adhesion: Test standard: GB / T9286-2021;

[0104] 2. Neutral salt spray resistance: Test standard: GB / T2423.17-2008, the test time included 168 h and 336 h. If there were no phenomena such as bubbles, pinholes, blisters, cracks, microcracks, peeling, wrinkling, white spots, etc. on the glue film and no corrosion phenomenon was caused, it was recorded as qualified;

[0105] 3. Resistance to acid and alkali liquids: Test standard: GB / T1981.2-2009, the test solutions included 5% ammonium chloride solution and 5% sodium carbonate solution, the test time was 168 h. If there were no phenomena such as bubbles, pinholes, blisters, cracks, microcracks, peeling, wrinkling, white spots, etc. on the glue film and no corrosion phenomenon was caused, it was recorded as qualified;

[0106] 4. Resistance to mixed gas corrosion: Test standard GB / T2423.51-2020, the test method was Method 4, the test time was 14 d. If there were no phenomena such as bubbles, pinholes, blisters, cracks, microcracks, peeling, wrinkling, white spots, etc. on the glue film and no corrosion phenomenon was caused, it was recorded as qualified; the results are shown in Table 1:

[0107] Table 1 Performance test results of the three-proof glues of Examples 1-3 and Comparative Examples 1-7

[0108]

[0109] As can be seen from Table 1, the adhesion of the three-proof glues of Examples 1-3 can reach level 0, the neutral salt spray resistance can reach 336 h, the resistance to ammonium chloride solution and sodium carbonate solution can reach 168 h, and the resistance to mixed gases can reach 14 d;

[0110] Comparative Example 1 replaced the fluorine-containing hydroxyl-terminated polysiloxane with an equal molar amount of hydroxyl-terminated polysiloxane (molecular weight 2000 Da); the resulting conformal coating achieved an adhesion rating of 0, but its resistance to neutral salt spray could not reach 336 h, its resistance to ammonium chloride solution and sodium carbonate solution could not reach 168 h, and its resistance to mixed gases could not reach 14 d.

[0111] The siloxane-modified acrylate oligomer of Comparative Example 2 only has fluorinated side chains and no alkoxy side chains; the resulting conformal adhesive can only achieve Grade 1 adhesion, the neutral salt spray resistance cannot reach 336h, the resistance to ammonium chloride solution and sodium carbonate solution cannot reach 168h, and the resistance to mixed gases cannot reach 14d.

[0112] Comparative Example 3 replaced the fluorine-containing epoxy-terminated polysiloxane with an equal molar amount of ethylene glycol diglycidyl ether; the resulting conformal adhesive could achieve an adhesion grade of 0, but its resistance to neutral salt spray could not reach 168h, its resistance to ammonium chloride solution and sodium carbonate solution could not reach 168h, and its resistance to mixed gases could not reach 14d.

[0113] Comparative Example 4 replaced the difunctional hydroxyl-containing polyurethane acrylate resin with an equal mass of siloxane-modified acrylate oligomer; the resulting conformal adhesive achieved an adhesion grade of 0, a neutral salt spray resistance of 336h, and a sodium carbonate solution resistance of 168h, but its resistance to ammonium chloride solution could not reach 168h, and its resistance to mixed gases could not reach 14d.

[0114] Comparative Example 5: The hydroxyl value of the difunctional hydroxyl-containing polyurethane acrylate resin is 160. Although the obtained conformal coating can achieve an adhesion grade of 0, a neutral salt spray resistance of 336h, and a sodium carbonate solution resistance of 168h, it cannot achieve a resistance to ammonium chloride solution of 168h and a mixed gas resistance of 14d.

[0115] Comparative Example 6: The hydroxyl value of the difunctional hydroxyl-containing polyurethane acrylate resin was 76. Although the obtained three-proof adhesive had a resistance to ammonium chloride solution and sodium carbonate solution of 168h and a resistance to neutral salt spray of 168h, its adhesion could only reach level 1, its resistance to neutral salt spray could not reach 336h, and its resistance to mixed gases could not reach 14d.

[0116] Comparative Example 7 replaced the difunctional hydroxyl-containing polyurethane acrylate resin with an equal mass of trifunctional aliphatic polyurethane acrylate; the resulting conformal coating achieved a resistance to ammonium chloride solution and sodium carbonate solution of 168h and a resistance to neutral salt spray of 168h, but the adhesion could only reach level 2, the resistance to neutral salt spray could not reach 336h, and the resistance to mixed gases could not reach 14d.

[0117] In Comparative Example 8, the mass ratio of siloxane-modified acrylate, difunctional hydroxyl-containing polyurethane acrylate resin, and reactive diluent was not within the range of (3.5-7):1:(4-6). Although the obtained conformal coating achieved a sodium carbonate solution resistance of 168h and a neutral salt spray resistance of 168h, its adhesion could only reach level 1, its neutral salt spray resistance could not reach 336h, its ammonium chloride solution resistance could not reach 168h, and its mixed gas resistance could not reach 14d.

[0118] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A conformal adhesive comprising a dual-curing resin, characterized in that, By weight, the raw materials include: 35-55 parts of siloxane-modified acrylate oligomer, 5-15 parts of difunctional hydroxyl-containing polyurethane acrylate resin, 30-60 parts of reactive diluent, and 1-5 parts of photoinitiator. The siloxane-modified acrylate oligomer is obtained by reacting prepolymer A with fluorine-containing epoxy-terminated polysiloxane and acrylic acid, and then reacting prepolymer A with methyl orthosilicate. The mass ratio of the siloxane-modified acrylate oligomer, the difunctional hydroxyl-containing polyurethane acrylate resin, and the reactive diluent is (3.5-7):1:(4-6). The hydroxyl value of the difunctional hydroxyl-containing polyurethane acrylate resin is 80-100 mg KOH / g.

2. The conformal adhesive comprising a dual-curing resin according to claim 1, characterized in that, The molar ratio of the fluorinated epoxy-terminated polysiloxane with side chains to acrylic acid is 1:(2-4); the molar ratio of the prepolymer A to methyl orthosilicate is 1:(1-1.5).

3. The conformal adhesive comprising a dual-curing resin according to claim 2, characterized in that, The fluorinated epoxy-terminated polysiloxane is obtained by reacting a fluorinated hydroxyl-terminated polysiloxane with 3-(2,3-epoxypropoxy)propyltrimethoxysilane; the molar ratio of the fluorinated hydroxyl-terminated polysiloxane to 3-(2,3-epoxypropoxy)propyltrimethoxysilane is (1-2):(2-5).

4. The conformal adhesive comprising a dual-curing resin according to claim 3, characterized in that, The fluorinated hydroxyl-terminated polysiloxane with side chains is obtained by reacting octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane and trifluoropropylmethylcyclotrisiloxane; the molar ratio of octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane and trifluoropropylmethylcyclotrisiloxane is (1.5-3.5):(0.5-1.5):(2-5).

5. The conformal adhesive comprising a dual-curing resin according to claim 4, characterized in that, The active diluent is selected from at least one of trimethylolpropane triacrylate, tetrahydrofurfuryl acrylate, tripropylene glycol diacrylate, isoborneol acrylate, isooctyl methacrylate, dipropylene glycol diacrylate, isoborneol acrylate, and isoborneol methacrylate.

6. The conformal adhesive comprising a dual-curing resin according to claim 5, characterized in that, The photoinitiator is selected from at least one of 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylphenyl ketone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, methyl benzoylformate, isopropylthioxanthone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

7. The method for preparing the conformal adhesive comprising a dual-curing resin according to any one of claims 1-6, characterized in that, Includes the following steps: The product is obtained by mixing siloxane-modified acrylate oligomer, difunctional hydroxyl-containing polyurethane acrylate resin, reactive diluent, and photoinitiator in the dark until homogeneous.

8. The application of the conformal adhesive comprising a dual-curing resin as described in any one of claims 1-6 in the protection of circuit boards and electronic equipment.

Images