Modified acrylate prepolymer, ultraviolet-moisture dual-curing coating adhesive and preparation method and application thereof

Abstract

The invention belongs to the technical field of adhesives, and particularly relates to a modified acrylate prepolymer, an ultraviolet-moisture dual-curing coating adhesive and a preparation method and application of the ultraviolet-moisture dual-curing coating adhesive. The modified acrylate prepolymer is successfully prepared by innovatively combining the polyisocyanate, the caprolactone modified acrylate, the polymerization inhibitor, the phosphate stabilizer and the catalyst, and the ultraviolet-moisture dual-curing coating adhesive is prepared on the basis of the modified acrylate prepolymer. Due to the adoption of the caprolactone modified acrylate, the irritation of the acrylate is reduced, the self-polymerization risk is effectively reduced by virtue of the high-boiling-point characteristic of the caprolactone modified acrylate, and the obtained prepolymer shows excellent mechanical property and flame retardance. The further developed ultraviolet-moisture dual-curing coating glue successfully solves the problems of weak adhesiveness and flammability of the traditional coating glue, the adhesive force is remarkably improved, and the overall strength of the material is enhanced. In addition, the preparation process of the prepolymer is simple and easy to implement, and industrial production is facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of adhesives. More specifically, it relates to a modified acrylate prepolymer, an ultraviolet-moisture dual-curing coating adhesive, and its preparation method and application. Background Art

[0002] The coating adhesive is a protective material coated on the printed circuit board of the soldered and plugged components, which can enhance the moisture-proof and anti-fouling capabilities of electronic components, improve the insulation performance of the circuit board, and also play a role in shielding and eliminating electromagnetic interference and preventing circuit short circuits, improving the working stability of the instrument and extending its service life.

[0003] Currently, coating adhesives are mainly divided into types such as ultraviolet light curing, moisture curing, and ultraviolet-moisture dual curing. Among them, the ultraviolet-moisture dual-curing type has the widest application range. This type combines the advantages of rapid ultraviolet curing, makes up for the deficiencies of ultraviolet curing in insufficient depth and difficult curing in shadow areas, and also absorbs the characteristics of high bonding strength and good weather resistance brought by moisture curing, and alleviates the problems of curing speed affected by environmental conditions and storage stability to a certain extent. Nevertheless, there are still some areas for improvement in ultraviolet-moisture dual-curing coating adhesives, such as weak substrate adhesion, flammability, insufficient hardness, poor flexibility and weather resistance, etc. To address these challenges, Chinese Patent Application CN112552866A successfully prepared an environmentally friendly three-proof adhesive with smooth surface drying, non-sticky hands, excellent toughness, and an adhesion level of 5B through self-preparation of two modified acrylates. However, during the preparation process of self-made acrylate, hydroxyacrylate is extremely prone to self-polymerization during the process of reducing water content under vacuum. If the large amount of heat released during the self-polymerization process cannot be quickly dissipated, and if the reaction conditions cannot be properly controlled, it is extremely easy to trigger an explosion accident. This not only increases the production difficulty but also poses a huge safety risk. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the safety risks existing in the preparation process of the adhesive prepolymer in the prior art, as well as the defects and deficiencies of the coating adhesive being flammable and having poor weather resistance, and to provide a modified acrylate prepolymer.

[0005] Another object of the present invention is to provide a preparation method of the above-mentioned modified acrylate prepolymer.

[0006] Another object of the present invention is to provide an ultraviolet-moisture dual-curing coating adhesive.

[0007] Another object of the present invention is to provide a preparation method of the above-mentioned ultraviolet-moisture dual-curing coating adhesive.

[0008] Another object of the present invention is to provide the application of the above-mentioned modified acrylate prepolymer or the above-mentioned UV-moisture dual-curing coating adhesive in the coating protection of printed circuit boards.

[0009] The above object of the present invention is achieved by the following technical solutions:

[0010] The present invention protects a modified acrylate prepolymer, which comprises the following components in parts by weight:

[0011] 50-70 parts of polyisocyanate;

[0012] 30-50 parts of caprolactone-modified acrylate;

[0013] 0.01-1 part of polymerization inhibitor;

[0014] 0.1-1 part of phosphate stabilizer;

[0015] 0.05-0.2 part of catalyst;

[0016] Wherein, the NCO content of the modified acrylate prepolymer is 7%-9%.

[0017] The present invention has successfully prepared a modified acrylate prepolymer. Among them, polyisocyanate is used as a crosslinking agent, which can react with the hydroxyl groups or other active functional groups in caprolactone-modified acrylate to form a crosslinked network structure. This crosslinked structure can significantly improve the strength, hardness and wear resistance of the prepolymer. In addition, compared with the commonly used hydroxy acrylate (hydroxyethyl acrylate), the introduction of caprolactone-modified acrylate not only significantly reduces the potential irritation to the skin (such as reducing the risk of skin problems such as dermatitis or rash), but also has a higher boiling point, showing unique performance advantages. Specifically, the boiling point of caprolactone-modified acrylate FA2D is as high as 458.5 °C at normal temperature and pressure, which is much higher than the boiling point of hydroxyethyl acrylate of 92 °C under the same conditions. This high boiling point characteristic makes it more convenient to handle moisture during the production process. Due to the higher boiling point of caprolactone-modified acrylate, it is less likely to volatilize during vacuum dehydration, and together with the polymerization inhibitor, it further effectively reduces the risk of self-polymerization. At the same time, the addition of phosphate stabilizer not only significantly enhances the stability of the prepolymer, but also greatly improves its flame retardant performance, making the final product safer and more reliable. In addition, by precisely controlling the NCO content of the modified acrylate prepolymer, the problems of prolonged moisture curing time caused by low NCO content (NCO content < 7%) and the decline of electrical insulation performance and storage stability caused by high NCO content (NCO content > 9%) are effectively avoided.

[0018] Preferably, the viscosity of the modified acrylate prepolymer is 10,000 to 20,000 cP. The achievement of this viscosity range is affected by raw material usage (especially the moisture content), synthesis temperature control, and the feeding process. The prepolymer within this viscosity range not only meets the usage requirements but also ensures that the polymerization reaction proceeds fully and smoothly.

[0019] Furthermore, the polyisocyanate includes one or more of aliphatic polyisocyanate, alicyclic polyisocyanate, and aromatic polyisocyanate.

[0020] Preferably, the polyisocyanate is an aliphatic polyisocyanate.

[0021] More preferably, the aliphatic polyisocyanate includes one or more of Desmodur N3300, Desmodur N3600, HT-100, and HT-600.

[0022] Furthermore, the structure of the caprolactone-modified acrylate is

[0023]

[0024] The n is any integer from 1 to 3. Within this numerical range, the prepared coating adhesive exhibits good flexibility and hardness characteristics, and the larger the n value, the better the flexibility performance of the coating adhesive.

[0025] Furthermore, the inhibitor includes one or more of hydroquinone, p-methoxyphenol, and p-benzoquinone.

[0026] Furthermore, the phosphate stabilizers include one or more of triphenyl phosphite, tridecyl phosphite, and tris(trimethylsilyl) phosphate.

[0027] Furthermore, the catalyst includes one or more of organic bismuth catalysts, organic zinc catalysts, and zinc-bismuth composite catalysts.

[0028] Preferably, the catalyst is an organic bismuth catalyst. Compared with tin catalysts, organic bismuth catalysts exhibit significant environmental friendliness and human health safety. Due to their non-toxic or low-toxic characteristics, the potential threats to the environment and human body are extremely small. In addition, organic bismuth catalysts have higher hydrolysis stability, which helps to reduce the interference of water molecules on the catalyst, thereby reducing unnecessary side reactions between water and -NCO groups. More importantly, organic bismuth catalysts show excellent selectivity for -NCO groups, can more efficiently catalyze the reaction of -NCO groups with hydroxyl groups to form urethane bonds, effectively reduce the generation of by-products such as carbon dioxide, and maximize the avoidance of other side reactions of -NCO groups, thus ensuring the high efficiency and purity of the reaction.

[0029] More preferably, the organobismuth catalyst is Bi1610 and / or Bi2010.

[0030] The present invention protects a method for preparing the above-mentioned modified acrylate prepolymer, which includes the following steps:

[0031] Under the atmosphere of a protective gas, polyisocyanate, inhibitor, phosphate stabilizer, and catalyst are melted and mixed evenly, and then ε-caprolactone-modified acrylate is added, and the mixture is fully reacted at 60-70 °C to obtain the modified acrylate prepolymer.

[0032] The preparation process of the modified acrylate prepolymer of the present invention is simple, easy to control, and conducive to industrial production.

[0033] Furthermore, the protective gas includes one or more of nitrogen, argon, and helium.

[0034] Furthermore, the melting temperature is 60-70 °C.

[0035] Furthermore, the full reaction is carried out until the NCO content is 7%-9%. The prepolymer within this range can enable the coating adhesive to smoothly carry out the moisture curing reaction; at the same time, this prepolymer also has good storage stability, and the prepared coating adhesive shows a faster curing speed during the photocuring process.

[0036] Furthermore, as a preferred method, the test method for the NCO content is titration test by the dibutylamine method.

[0037] Furthermore, in the titration test by the dibutylamine method, dibutylamine reacts with the isocyanate group in the sample. After the reaction is completed, a standard hydrochloric acid solution is used to titrate the excess dibutylamine, and the isocyanate group content in the sample is determined by calculating the amount of hydrochloric acid consumed.

[0038] Furthermore, the time for the full reaction is 2-4 h.

[0039] Furthermore, the cooling is to cool to room temperature.

[0040] The present invention protects an ultraviolet-moisture dual-curing coating adhesive, which includes the following components by weight:

[0041] 10-30 parts of the above-mentioned modified acrylate prepolymer;

[0042] 10-30 parts of ultraviolet-moisture dual-curing acrylate prepolymer;

[0043] 5-50 parts of diluent;

[0044] 1-5 parts of photoinitiator;

[0045] 1-5 parts of dehydrating agent;

[0046] Coupling agent: 0.1 - 1 part;

[0047] Defoaming agent: 0.1 - 1 part;

[0048] Polymerization inhibitor: 0.01 - 0.1 part;

[0049] Other additives: 0.05 - 2 parts;

[0050] Among them, the NCO content of the ultraviolet - moisture dual - curing acrylate prepolymer is 10% - 16%.

[0051] The present invention relates to an ultraviolet - moisture dual - curing coating glue, which incorporates a modified acrylate prepolymer containing isocyanate trimer (the structure is shown in Formula I). This trimer not only constructs a stable three - dimensional network framework due to its rich nitrogen element, but also complements the phosphate stabilizer in the modified acrylate prepolymer, significantly enhancing the self - extinguishing flame - retardant performance of the coating glue, effectively solving the problems of poor adhesion and flammability of traditional ultraviolet - curable coating glue. Further, after curing, this trimer forms a stable nitrogen - containing six - membered ring structure, which endows the coating with excellent abrasion resistance and corrosion resistance, enabling it to effectively resist the erosion of chemicals and ensuring the long - term durability of the coating. At the same time, in this application, by skillfully incorporating a modified acrylate prepolymer with a low NCO content (NCO content is 7% - 9%) and an ultraviolet - moisture dual - curing acrylate prepolymer with a high NCO content (NCO content is 10% - 16%), the problems of slow curing speed and insufficient strength caused by the soft texture of the modified acrylate prepolymer material with a low NCO content when used alone are effectively avoided. At the same time, the problems of insufficient toughness, easy cracking, and decreased storage stability caused by the high hardness of the ultraviolet - moisture dual - curing acrylate prepolymer with a high NCO content when used alone are also solved, achieving an excellent balance in the core performance indicators such as hardness and curing speed of the coating glue. This coating glue can be quickly cured under ultraviolet light irradiation. At the same time, its ability of secondary moisture curing ensures that full curing can be achieved even in shadow areas where it is difficult to directly receive light, thereby further enhancing the adhesion and overall structural strength.

[0052]

[0053] Further, the ultraviolet - moisture dual - curing acrylate prepolymer is commercially available BASF LR9000 (NCO content is 15.5%) and / or Allnex ZHANXIN EBECRYL 4150 (EB4150) (NCO content is 12.8% ± 1%). These two prepolymers are prepared by mature preparation methods, have excellent storage stability, and their NCO contents are not less than 10%, belonging to the category of high NCO content, which helps to ensure the efficiency of the curing process and improve product performance.

[0054] Preferably, the ultraviolet-moisture dual-curing acrylate prepolymer is EB4150.

[0055] More preferably, the viscosity of the EB4150 is 7500 to 12500 cP.

[0056] Furthermore, the diluent is an acrylate active diluent.

[0057] Preferably, the diluent includes one or more of isobornyl methacrylate, tetrahydrofurfuryl acrylate, 2-phenoxyethyl acrylate, trimethylolpropane triacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, tricyclodecane dimethanol diacrylate, neopentyl glycol diacrylate.

[0058] Furthermore, the photoinitiator includes one or more of α-hydroxyalkyl phenyl ketone photoinitiators, acylphosphine oxide photoinitiators, benzoin and derivative photoinitiators, benzil and derivative photoinitiators.

[0059] Even further, the photoinitiator includes one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, (2,4,6-trimethylbenzoyl) diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoyl phenylphosphinate, 1-hydroxycyclohexyl phenyl ketone, bis(2,4,6-trimethylbenzoyl) phenylphosphine oxide, benzoin dimethyl ether.

[0060] Preferably, the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0061] More preferably, the 2-hydroxy-2-methyl-1-phenyl-1-propanone is photoinitiator 1173.

[0062] Furthermore, the dehydrating agent includes one or more of p-toluenesulfonyl isocyanate, p-toluenesulfonyl chloride, chloral.

[0063] Furthermore, the coupling agent is a silane coupling agent.

[0064] Even further, the coupling agent includes one or more of γ-glycidoxypropyltrimethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, aminoethylaminopropyltrimethoxysilane.

[0065] Preferably, the coupling agent is γ-(methacryloyloxy)propyltrimethoxysilane.

[0066] More preferably, the γ-(methacryloyloxy)propyltrimethoxysilane includes one or more of KH540, KH570, and KH560.

[0067] Furthermore, the defoaming agent includes Airex 920, AIRex 978, one or more of Airex 923.

[0068] Furthermore, the other additives include a fluorescent brightening agent and / or a leveling agent.

[0069] Even further, the fluorescent brightening agent is fluorescent brightening agent OB and / or fluorescent brightening agent OB-1.

[0070] Even further, the leveling agent includes Glide 432, Glide 496, one or more of Glide 4168.

[0071] Preferably, the viscosity of the ultraviolet-moisture dual-curing coating adhesive is 200 to 1000 cP. Within this viscosity range, the coating adhesive exhibits good fluidity, facilitating construction operations; at the same time, it can effectively reduce the generation of bubbles and defects, ensuring the coating quality; in addition, it can improve the thickness uniformity of the coating, enhancing the protection effect; and moreover, the coating adhesive with this viscosity is suitable for electronic component circuit boards of various materials, which is conducive to the wide application and promotion of the coating adhesive.

[0072] More preferably, the viscosity of the ultraviolet-moisture dual-curing coating adhesive is 220 to 500 cP.

[0073] The present invention protects the preparation method of the above-mentioned ultraviolet-moisture dual-curing coating adhesive, including the following steps:

[0074] S1. Under the atmosphere of a protective gas, the diluent, inhibitor, coupling agent, defoaming agent, dehydrating agent, and other additives are mixed evenly under vacuum to obtain a mixture;

[0075] S2. The aforementioned modified acrylate prepolymer and ultraviolet-moisture dual-curing modified acrylate prepolymer are added to the mixture obtained in step S1, and they are mixed evenly under normal temperature and vacuum conditions to obtain the ultraviolet-moisture dual-curing coating adhesive.

[0076] The present invention prepares the ultraviolet-moisture dual-curing coating adhesive by a stepwise method, effectively avoiding the side reaction between the moisture in the raw materials and the -NCO groups in the prepolymer, thereby ensuring the high stability and overall performance of the coating adhesive.

[0077] Further, in step S1, the diluent is a dehydrated diluent.

[0078] Further, the qualified standard for the dehydration treatment is that the water content is < 300 ppm.

[0079] Further, in steps S1 and S2, the mixing is performed by stirring and mixing.

[0080] Further, in steps S1 and S2, the mixing time is 0.5 - 1 h.

[0081] Preferably, in step S2, the mass ratio of the modified acrylate prepolymer to the UV - moisture dual - curing acrylate prepolymer is 1:(0.8 - 2). Within this ratio range, it can ensure that the two can be fully mixed and uniformly fused.

[0082] The present invention protects the application of the above - mentioned modified acrylate prepolymer or the above - mentioned UV - moisture dual - curing coating adhesive in the coating protection of electronic circuit boards.

[0083] Compared with the prior art, the present invention has the following beneficial effects:

[0084] By innovatively combining polyisocyanate, caprolactone - modified acrylate, inhibitor, phosphate stabilizer and catalyst, the present invention successfully prepares a modified acrylate prepolymer, and on this basis, prepares a UV - moisture dual - curing coating adhesive. The use of caprolactone - modified acrylate not only reduces the irritation of acrylate, but also effectively reduces the self - polymerization risk due to its high boiling point characteristics. The obtained prepolymer exhibits excellent mechanical properties and flame retardancy. The further developed UV - moisture dual - curing coating adhesive successfully solves the problems of weak adhesion and flammability of traditional coating adhesives, significantly improves the adhesion and enhances the overall strength of the material. In addition, the preparation process of the prepolymer is simple and easy to implement, which is conducive to industrial production. Specific Embodiments

[0085] The following specific examples are used to further illustrate the present invention, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field.

[0086] Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0087] Aliphatic polyisocyanate: Desmodur N3300 is purchased from Covestro AG;

[0088] Phosphate stabilizer: Triphenyl phosphite is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0089] Organic bismuth catalyst: Bi1610 was purchased from Umicore (Beijing) Heavy Machinery Co., Ltd.;

[0090] Caprolactone-modified acrylate: FA2D was purchased from Daicel Corporation;

[0091] Hydroxy acrylate: 2-Hydroxyethyl acrylate was purchased from Guangzhou Songda New Materials Technology Co., Ltd.

[0092] Coupling agent: KH570 was purchased from Jiangxi Chenguang New Materials Co., Ltd.;

[0093] Leveling agent: Glide 432 was purchased from Degussa TEGO Additives;

[0094] Defoaming agent: Airex 920 was purchased from Degussa TEGO Additives;

[0095] Fluorescent brightening agent: Fluorescent brightening agent OB-1 was purchased from Dongguan Dingyuan Titanium Industry Co., Ltd.;

[0096] Photoinitiator: Photoinitiator 1173 was purchased from Tianjin Jiuri New Materials Co., Ltd.;

[0097] Dehydrating agent: p-Toluenesulfonyl isocyanate TI was purchased from Jining Huakai Resin Co., Ltd.;

[0098] UV-moisture dual-curing acrylate prepolymer: EB4150 was purchased from Axalta Coating Systems.

[0099] Example 1 Preparation of a modified acrylate prepolymer and a UV-moisture dual-curing coating adhesive

[0100] 1. Preparation of a modified acrylate prepolymer

[0101] 62 parts of aliphatic polyisocyanate - Desmodur N3300 (low-viscosity HDI trimer), 0.05 part of inhibitor - p-Methoxyphenol, 0.5 part of phosphate stabilizer - Triphenyl phosphite, and 0.1 part of organic bismuth catalyst - Bi1610 were added to a four-necked flask equipped with a stirrer, a thermometer, a dropping funnel, and a device for filling with dry inert gas, and stirred until the inhibitor was completely dissolved. Under a nitrogen atmosphere, the temperature was raised to 65 °C, and 38 parts of caprolactone-modified acrylate - FA2D with qualified moisture content was slowly added dropwise, and the temperature was maintained at 65 °C. The reaction was carried out for 3 h until the NCO content reached 8%, then the reaction was stopped, cooled, and the product was discharged and sealed for use, obtaining a modified acrylate prepolymer with a viscosity of 17500 cP.

[0102] 2. Preparation of a UV-moisture dual-curing coating adhesive

[0103] S1. Add 26 parts of diluent-dehydrated isobornyl methacrylate, 20 parts of tetrahydrofurfuryl acrylate, 0.05 part of inhibitor-p-hydroxyanisole, 0.8 part of coupling agent-KH570, 0.3 part of leveling agent- Glide 432, 0.3 part of defoaming agent- Airex 920, 0.05 part of fluorescent brightening agent-OB-1, 5 parts of photoinitiator-photoinitiator 1173, and 2.5 parts of dehydrating agent-p-toluenesulfonyl isocyanate into a dynamic mixer. Pressurize with nitrogen and stir under normal temperature and vacuum for 0.5 h to obtain a mixed system;

[0104] S2. Add 20 parts of the modified acrylate prepolymer obtained in step 1 and 25 parts of the ultraviolet-moisture dual-curing acrylate prepolymer-EB4150 (NCO content is 12.8% ± 1%, viscosity is 11500 cP) to the mixed system obtained in step S1. Stir under vacuum and normal temperature conditions for 0.5 h and mix evenly to obtain an ultraviolet-moisture dual-curing coating adhesive with a viscosity of 260 cP.

[0105] Example 2 Preparation of a modified acrylate prepolymer and an ultraviolet-moisture dual-curing coating adhesive

[0106] The difference from Example 1 is that in the preparation of the modified acrylate prepolymer, the reaction is stopped when the NCO content of the self-made modified acrylate prepolymer reaches 8% is changed to the reaction is stopped when the NCO content reaches 7%; in step S1 of the preparation of the ultraviolet-moisture dual-curing coating adhesive, the number of parts of isobornyl methacrylate is changed from 26 parts to 30 parts; 20 parts of tetrahydrofurfuryl acrylate are replaced with 16 parts of dipropylene glycol diacrylate.

[0107] Other steps and conditions are the same as those in Example 1.

[0108] Example 3 Preparation of a modified acrylate prepolymer and an ultraviolet-moisture dual-curing coating adhesive

[0109] The difference from Example 1 is that in the preparation of the modified acrylate prepolymer, the reaction is stopped when the NCO content of the self-made modified acrylate prepolymer reaches 8% is changed to the reaction is stopped when the NCO content reaches 9%; in step S1 of the preparation of the ultraviolet-moisture dual-curing coating adhesive, the number of parts of isobornyl methacrylate is changed from 26 parts to 46 parts; tetrahydrofurfuryl acrylate is not added; in step S2, the number of parts of the modified acrylate prepolymer is changed from 20 parts to 25 parts, and the number of parts of the ultraviolet-moisture dual-curing acrylate prepolymer is changed from 25 parts to 20 parts.

[0110] Other steps and conditions are the same as those in Example 1.

[0111] Example 4 Preparation of a Modified Acrylate Prepolymer and an UV-Moisture Dual-Curing Coating Adhesive

[0112] The difference from Example 1 is that in step S1 of the preparation of the UV-moisture dual-curing coating adhesive, the amount of isobornyl methacrylate is changed from 26 parts to 40 parts; 20 parts of tetrahydrofurfuryl acrylate are replaced with 6 parts of trimethylolpropane triacrylate; in step S2, the amount of the modified acrylate prepolymer is changed from 20 parts to 15 parts, and the amount of the UV-moisture dual-curing acrylate prepolymer is changed from 25 parts to 30 parts.

[0113] Other steps and conditions are the same as those in Example 1.

[0114] Comparative Example 1 Preparation of a Modified Acrylate Prepolymer and an UV-Moisture Dual-Curing Coating Adhesive

[0115] The difference from Example 1 is that in the preparation of the modified acrylate prepolymer, the caprolactone-modified acrylate is replaced with an equal amount of hydroxyacrylate - 2-hydroxyethyl acrylate.

[0116] Other steps and conditions are the same as those in Example 1.

[0117] Comparative Example 2 Preparation of an UV-Moisture Dual-Curing Coating Adhesive

[0118] The difference from Example 1 is that in step S2 of the preparation of the UV-moisture dual-curing coating adhesive, the UV-moisture dual-curing acrylate prepolymer is not added, and the amount of the modified acrylate prepolymer is changed from 20 parts to 45 parts.

[0119] Other steps and conditions are the same as those in Example 1.

[0120] Comparative Example 3 Preparation of a Modified Acrylate Prepolymer and an UV-Moisture Dual-Curing Coating Adhesive

[0121] The difference from Example 1 is that in step S2 of the preparation of the UV-moisture dual-curing coating adhesive, the modified acrylate prepolymer is not added, and the amount of the UV-moisture dual-curing acrylate prepolymer is changed from 25 parts to 45 parts.

[0122] Other steps and conditions are the same as those in Example 1.

[0123] Comparative Example 4 Preparation of a Modified Acrylate Prepolymer and an UV-Moisture Dual-Curing Coating Adhesive

[0124] The difference from Example 1 is that in the preparation of the modified acrylate prepolymer, the reaction is stopped when the NCO content of the self-made modified acrylate prepolymer reaches 8% is changed to the reaction is stopped when the NCO content reaches 6%.

[0125] Other steps and conditions are the same as those in Example 1.

[0126] Comparative Example 5 Preparation of a Modified Acrylate Prepolymer and an Ultraviolet-Moisture Dual-Curing Coating Adhesive

[0127] The difference from Example 1 is that in the preparation of the modified acrylate prepolymer, the reaction is stopped when the NCO content of the self-made modified acrylate prepolymer reaches 10% instead of 8%.

[0128] Other steps and conditions are the same as those in Example 1.

[0129] Experimental Example Physical and Chemical Property Tests of the Ultraviolet-Moisture Dual-Curing Coating Adhesive

[0130] 1. Experimental Method

[0131] (1) Light surface drying time: A 0.1-mm-thick adhesive film is scraped on a printed circuit board (PCB), and irradiated with a high-pressure mercury lamp with an illumination intensity of 120 mW / cm 2 , and the surface drying time of the adhesive layer is measured; Evaluation method: The surface is dry and completely hardened, and there are no fingerprints when touched, which is considered surface dry.

[0132] (2) Adhesion test: The test is carried out according to the standard of GB / T 9286-1988. The adhesion grade is divided into 6 levels from 0 to 5, where 0 indicates the best adhesion and 5 indicates the worst adhesion. The specific operation is to scrape a 0.1-mm-thick adhesive film on a printed circuit board (PCB), and irradiate it with a high-pressure mercury lamp with an illumination intensity of 120 mW / cm 2 , cure for 15 s. After the sample is photocured, it is placed in a thermostatic and humid test chamber (23 ± 2°C, 50 ± 5% RH) for one week of curing. Then, a crosshatch cutter is used to make scratches with a spacing of 2 mm horizontally and vertically, intersecting 100 squares. A 3M test tape is used for peeling test, and three different positions are tested to calculate the integrity of the adhesive film in the grid.

[0133] (3) Hardness test: The test is carried out using a Shore D hardness tester according to the provisions of GB / T 531.1-2008 - "Test Method for Indentation Hardness of Vulcanized Rubber or Thermoplastic Rubber - Part 1: Shore Hardness".

[0134] (4) Thermal shock test: -40 to 120°C, cycle 500 times, 1 h each time. Observe whether there are any cracks, peeling or blistering phenomena on the specimen.

[0135] (5) High temperature and high humidity test: 85°C, 85% RH for 500 h. Observe whether there are any cracks, peeling or blistering phenomena on the specimen.

[0136] (6) Pure moisture curing: In the dark, place the sample rubber in a constant temperature and humidity (23 ± 2°C, 50 ± 5% RH) chamber and let it stand still. To ensure darkness, cover the constant temperature and humidity chamber with black cloth for light shielding treatment, and then check the surface dryness of curing according to the set target time.

[0137] (7) Flame retardancy rating test (UL 94 vertical burning test): Spray coatings with nearly the same thickness on FR-4 substrates, cure them, and then test. Five parallel samples are tested in each group of experiments. Its flame retardancy rating is divided into three levels: V-0, V-1, and V-2, where V-0 is the highest flame retardancy level and V-2 is the lowest flame retardancy level.

[0138] (8) Dielectric strength: Test according to ASTM D149-2009 standard.

[0139] (9) Volume resistivity: Test according to ASTM D257-2014 standard.

[0140] (10) Storage stability: Test the viscosity value of the coating glue on the 1st of each month. If the test value exceeds 1.5 times the upper limit of the viscosity value (1000 cP), it is determined that the storage stability of the coating glue is unqualified.

[0141] 2. Experimental results

[0142] Table 1 Statistical table of physical and chemical property test results of ultraviolet-moisture dual-curing coating glue

[0143]

[0144]

[0145] From the data in Table 1, it can be concluded that the ultraviolet-moisture dual-curing coating glues prepared in Examples 1 to 4 comprehensively exhibit many excellent characteristics, which together constitute the expected factory quality standards. Specifically, these coating glues have a fast curing speed and good surface dryness, and can achieve an ideal curing effect in a short time (light surface dry time < 15 s); they have high hardness (65 - 75 Shore D) and good weather resistance (no abnormalities in thermal shock test and high temperature and high humidity test); they have strong adhesion, reaching the 0-level standard, indicating a very firm bond with the substrate; at the same time, they also meet the UL94 V-0 flame retardancy rating requirements; they have excellent electrical insulation performance, specifically manifested as dielectric strength > 22 KV / mm and volume resistivity > 9×10 14Ω·cm. These two indicators are important bases for measuring the quality of electrical insulation. The larger the indicator value, the stronger the ability to prevent current leakage and short - circuit phenomena; the storage stability ≥ 9 months. Therefore, only the UV - moisture dual - curing coating adhesive that meets the above characteristics simultaneously can be regarded as a qualified product for leaving the factory. They are suitable for coating the protective layer of PCB circuit boards and play an excellent protective role in the assembly - line production of printed circuit boards.

[0146] It can be seen from the comparison between Example 1 and Comparative Example 1 that Comparative Example 1 used hydroxyacrylate to replace caprolactone - modified acrylate. This change significantly accelerated the curing speed and improved the hardness. However, due to the excessive hardness (>75 Shore D), the toughness of the material was insufficient. Therefore, in the thermal shock test and high - temperature and high - humidity test, partial cracking occurred in this material.

[0147] It can be seen from the comparison between Example 1 and Comparative Example 2 that when using the self - made modified acrylate prepolymer to replace the commercially available UV - moisture dual - curing acrylate prepolymer, due to the relatively low NCO content of the self - made modified acrylate prepolymer and the relatively soft texture of the material itself, this directly led to a slowdown in the curing speed, and the curing time was extended by 21 h. In addition, a series of performance problems were also caused: insufficient strength and electrical insulation performance, specifically manifested as a decrease in hardness, making the surface of the product prone to scratch damage; a slight decrease in dielectric strength and volume resistivity; and at the same time, the adhesion grade was also reduced to level 1, failing to meet the expected factory quality requirements.

[0148] It can be seen from the comparison between Example 1 and Comparative Example 3 that when using the commercially available UV - moisture dual - curing acrylate prepolymer to replace the self - made modified acrylate prepolymer, although the commercially available UV - moisture dual - curing acrylate prepolymer usually has a high NCO content and relatively high hardness, thus improving in terms of hardness, this high hardness sacrifices its toughness, resulting in local cracking of the material in the thermal shock test and high - temperature and high - humidity test. In addition, both the dielectric strength and the volume resistivity decreased significantly, and the flame - retardant grade also dropped to level 1. Moreover, the relatively high NCO content of the commercially available UV - moisture dual - curing acrylate prepolymer used led to an accelerated reaction rate with water vapor after the coating adhesive was unsealed, which in turn had an adverse effect on its storage stability, resulting in its storage stability being only maintained for 5 months. Since the preparation process of the commercially available prepolymer is mature, the coating adhesive obtained in Comparative Example 3 is slightly better than the coating adhesive in Comparative Example 5 in terms of stability, but the overall storage stability is still poor and fails to meet the factory quality standard.

[0149] Comparing Example 1 with Comparative Example 4, it can be seen that when the NCO content of the self-made modified acrylate prepolymer is lower than 7% (6%), due to the moisture curing process initiated by the reaction of -NCO groups in the prepolymer with water molecules, the reduction of the prepolymer NCO content results in an extension of the moisture curing time by 14 h, thereby significantly reducing the moisture curing rate.

[0150] Comparing Example 1 with Comparative Example 5, it can be seen that when the NCO content of the self-made modified acrylate prepolymer is greater than 9% (10%), both its dielectric strength and volume resistivity decrease. In addition, the storage validity period of the coating glue is significantly shortened, from the storage stability period of 11 months in Example 1 to 4 months in Comparative Example 5, and the reduction amplitude of the stability period exceeds 60%, which significantly indicates a substantial reduction in its storage stability.

[0151] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A modified acrylate prepolymer, characterized in that: By weight, it includes the following components: 50-70 parts of polyisocyanate; 30-50 parts of caprolactone modified acrylate; Inhibitor 0.01 to 1 part; Phosphate stabilizer 0.1-1 part; Catalyst 0.05-0.2 parts; Wherein, the NCO content of the modified acrylate prepolymer is 7% to 9%.

2. The modified acrylate prepolymer according to claim 1, characterized in that: The viscosity of the modified acrylate prepolymer is 10000-20000 cP.

3. The modified acrylate prepolymer according to claim 1, characterized in that: The structure of the caprolactone-modified acrylate is The n is any integer from 1 to 3.

4. The modified acrylate prepolymer according to claim 1, characterized in that: The phosphate stabilizer includes one or more of triphenyl phosphite, tridecyl phosphite, and tris(trimethylsilyl)phosphate.

5. The method for preparing the modified acrylate prepolymer according to any one of claims 1 to 4, characterized in that: The following steps are involved: In a protective gas atmosphere, polyisocyanate, polymerization inhibitor, phosphate stabilizer and catalyst are melted and mixed, and then caprolactone modified acrylate is added and fully reacted at 60-70° C. to obtain a modified acrylate prepolymer.

6. A UV-moisture dual-curing coating adhesive, characterized in that: By weight, Includes the following components: 10 to 30 parts of the modified acrylate prepolymer according to any one of claims 1 to 4; 10-30 parts of UV-moisture dual-curing acrylate prepolymer; 5 to 50 parts of diluent; 1 to 8 parts of photoinitiator; 1 to 5 parts of dehydrating agent; Coupling agent 0.1-1 part; Defoaming agent 0.1-1 part; Inhibitor 0.01-0.1 part; Other additives 0.05-2 parts; Wherein, the NCO content of the UV-moisture dual-curing acrylate prepolymer is 10% to 16%.

7. The UV-moisture dual-curing coating adhesive according to claim 6, characterized in that: The diluent is an acrylate reactive diluent.

8. The UV-moisture dual-curing coating adhesive according to claim 6, characterized in that: The photoinitiator includes one or more of α-hydroxyalkyl phenone photoinitiators, acylphosphine oxide photoinitiators, benzoin and derivative photoinitiators, and benzil and derivative photoinitiators.

9. The method for preparing the UV-moisture dual-curing coating adhesive according to any one of claims 6 to 8, characterized in that: The following steps are involved: S1. Under a protective gas atmosphere, the diluent, inhibitor, coupling agent, defoamer, dehydrating agent, and other additives are mixed at room temperature and vacuum to obtain a mixture; S2. Add the modified acrylate prepolymer according to any one of claims 1 to 4 and the UV-moisture dual-curing modified acrylate prepolymer to the mixture obtained in step S1, and mix them at room temperature and vacuum conditions to obtain a UV-moisture dual-curing coating adhesive.

10. Use of the modified acrylate prepolymer according to any one of claims 1 to 4 or the UV-moisture dual-curing coating adhesive according to any one of claims 6 to 8 in coating protection of electronic circuit boards.

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