CN115368528A - Potting adhesives for polyurethane (meth)acrylate and low temperature printed circuit boards - Google Patents

Abstract

The invention discloses a potting glue for polyurethane (meth)acrylate and low-temperature printed circuit boards. The polyurethane (meth)acrylate is obtained by addition reaction of hydroxy olefins containing carbon-carbon double bonds with different reactivity and isocyanate. In the invention, after compounding polyurethane (meth)acrylate, monomer and photoinitiator, a fast-curing glue that can be used for printed circuit board (PCB board) detection is prepared. The molecular structure of the UV curable polyurethane (meth)acrylate resin synthesized by the present invention contains two kinds of carbon-carbon double bonds (C=C) with different reactivity. Under the action of photoinitiator, the polyurethane (meth)acrylate (Meth) acrylate double bond and vinyl double bond successively undergo free radical polymerization reaction, the heat release is moderate during the polymerization reaction, and the cured test block has good transparency and high hardness, especially suitable for metallographic cold mounting PCB board packaging and testing purposes .

Description

Potting adhesives for polyurethane (meth)acrylate and low temperature printed circuit boards

technical field

The invention belongs to the field of organic polymer encapsulation materials, and specifically relates to a UV-curable polyurethane (meth)acrylate and its synthesis method and the application of UV-curable glue in the field of metallographic cold mounting, specifically polyurethane (meth)acrylate ) Potting glue for acrylate and low temperature printed circuit boards.

Background technique

By detecting the quality of the microscopic circuit of the PCB board, evaluating the rationality of the process parameters set in the PCB board manufacturing process, and deciding whether to correct or adjust the process parameters. Therefore, there is a need for a fast and efficient curing molding method to more conveniently obtain samples that can be used for microstructure testing. Among the currently used PCB board sample preparation methods, the UV curing sample preparation strategy is more effective than the traditional two-component epoxy resin (which can be shortened to 2h) and unsaturated polyester resin (which can shorten the curing cycle to 1-2 hours). 2h) products, UV curing products have short curing time, high reaction efficiency (15-20min), and are relatively more convenient to use. At present, not all UV curing systems can be applied to cold packaging for PCB inspection. The main reasons are as follows: 1) The sample size of the packaged PCB board is large (about 30mm in diameter), and the height is 30-35mm (about 20g in dosage). Usually, the curing depth of UV-curable glue is usually ≤2mm, and it is difficult to cure a sample block with a thickness of 30-35mm; 2) UV-curable glue reacts quickly in a short period of time during the polymerization process, resulting in concentrated heat release (heat release per unit time) ) is large, and in severe cases, small molecule monomers will "vaporize" and produce a large number of bubbles inside the cured sample block, and sometimes cause the problem of "core burning" of the UV-cured sample block. Therefore, effectively reducing the concentrated heat release of glue during the UV curing process is of great significance for reducing sample defects and promoting UV-cured PCB board cold packaging glue.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a polyurethane (meth)acrylate and a potting glue for low-temperature printed circuit boards, specifically polyurethane (meth)acrylate and its preparation method, and a low-temperature ultraviolet printed circuit board Board with potting glue.

For realizing one of above-mentioned object of the invention, the technical scheme of polyurethane (meth)acrylate is as follows:

Polyurethane (meth) acrylate is characterized in that formula (I):

中的任意一种，其中，5≤m≤10、5≤n≤10；where _R1 is

Any one of them, wherein, 5≤m≤10, 5≤n≤10;

中的任意一种或至少两种的混合物； _R2 is

Any one or a mixture of at least two of them;

R ₃ is H or CH ₃ ;

R ₄ is H or CH ₃ .

For realizing two of above-mentioned invention objects, the technical scheme of the preparation method of polyurethane (meth)acrylate is as follows:

The preparation method of polyurethane (meth)acrylate, the steps are as follows:

1) Feed polyester or polyether diol and diisocyanate in a molar ratio of 1:2, and add 0.01% dibutyltin dilaurate catalyst in the mass of the above-mentioned materials participating in the reaction; then heat to 60°C under nitrogen protection and stirring -90℃, then react for 2-8h,

Wherein, the polyester or polyether glycol is polytetrahydrofuran glycol, polyethylene adipate glycol, polyethylene succinate glycol, polycarbonate glycol, At least one of polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol copolymer,

The diisocyanate is 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, 1,3-m-xylylene diisocyanate, hexamethylene Methyl diisocyanate, dicyclohexylmethane diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate or 1,3-cyclohexyl dimethylene diisocyanate at least one of the

2) Add a hydroxyl compound in an equimolar amount to the diisocyanate, and add a polymerization inhibitor of 0.01-0.05% by weight of all the above-mentioned materials; then, under nitrogen protection and reaction conditions of 60-90°C, react until the isocyanate group completely disappears , that is;

Wherein, the hydroxyl compound is 2-hydroxy-2-methyl-5 (-isopropenyl) methyl cyclohexyl acrylate, 2-hydroxy-2-methyl-5 (-vinyl) methyl cyclohexyl acrylate, 2-Hydroxy-5(-isopropenyl)cyclohexyl acrylate, 2-hydroxy-5(-vinyl)cyclohexyl acrylate, 2-hydroxy-2-methyl-5(-isopropenyl)cyclo Hexyl acrylate, 2-hydroxy-2-methyl-5(-vinyl)cyclohexyl acrylate, 2-hydroxy-5(-isopropenyl)cyclohexyl acrylate, 2-hydroxy-5(-vinyl) At least one of cyclohexyl acrylate.

Preferably, the polymerization inhibitor is hydroquinone, p-hydroxyanisole, p-benzoquinone, p-tert-butylcatechol, phenothiazine, p-tert-butylhydroquinone, 6-tert-butyl-2 , One or more mixtures of 4-dimethylphenol and p-methylhydroquinone.

In order to achieve the third purpose of the above invention, the technical scheme of the potting glue for low-temperature ultraviolet printed circuit boards is as follows:

Potting glue for low-temperature printed circuit boards, including the following components in parts by mass:

(Meth)acrylate monomer: 70-89.5 parts;

Polyurethane (meth)acrylate: 10-30 parts;

0.5-3.0 parts of photoinitiator;

After the above components are mixed evenly under the condition of avoiding light, the low-temperature printed circuit board potting glue is obtained.

Preferably, the monofunctional (meth)acrylate is isobornyl acrylate, isobornyl methacrylate, o-phenylphenoxyethyl acrylate, o-phenylphenoxyethyl methacrylate, trifluoroacrylate Any one or at least two of ethyl ester, trifluoroethyl methacrylate, hexafluorobutyl acrylate, hexafluorobutyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate a mixture of species;

The photoinitiator is benzoin dimethyl ether, isopropylthioxanthone, benzophenone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-1-[4-(2-hydroxyethoxy )phenyl]-2-methyl-1-propanone, 2-benzyl-2-dimethylamino-1-(4-morpholinephenyl) butanone, 2,2-dimethyl-α-hydroxyl Oxidation of acetophenone, α,α'-ethoxyacetophenone, ethyl 4-(N,N-dimethylamino)benzoate, phenylbis(2,4,6-trimethylbenzoyl) Phosphine, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, methyl phthaloylformate, methyl phthaloylbenzoate or 2,4,6-trimethylbenzoylbenzene Any one or a mixture of at least two of ethyl phosphonates.

When using the potting glue for low-temperature printed circuit boards, the cured thickness of the ultraviolet light-curable glue is not greater than 35mm, and the power of the ultraviolet light lamp is 45-2000W.

Compared with the prior art, the beneficial effects of the present invention are: 1. The main resin of the glue can be graded and polymerized (the highly active acrylate or methacrylate double bond first undergoes a polymerization reaction, and the low-reactivity vinyl double bond post-bond polymerization), effectively controlling the reaction rate and avoiding the concentrated heat release of the polymerization system. 2. There are many kinds of diols of polyurethane (meth)acrylate, and polyester/polyether diols with different structures and molecular weights can be screened according to the needs, and the reaction speed, hardness and grinding performance can be adjusted. 3. The substituent of the double bond can be adjusted by adjusting the type of R ₃ and R ₄ (hydrogen atom or methyl group), which can further adjust the activity of the double bond, thereby adjusting the polymerization reaction speed and the performance of the cured rubber block.

The molecular structure of the UV-curable polyurethane (meth)acrylate synthesized by the present invention contains two kinds of different carbon-carbon double bonds (C=C) of reactivity, and under the photoinitiator effect, in the polyurethane (meth)acrylate ( The meth)acrylate double bond and the vinyl double bond undergo free radical polymerization successively. During the polymerization reaction, the heat release is moderate, and the cured test block has good transparency and high hardness, and is especially suitable for metallographic cold mounting PCB board packaging and testing purposes.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Description of drawings

The accompanying drawings are used to provide a further understanding of the technical solution of the present invention, and constitute a part of the description, and are used together with the specific embodiments of the application to explain the technical solution of the present invention, and do not constitute a limitation to the technical solution of the present invention.

The infrared spectrum of the polyurethane acrylate resin that Fig. 1. embodiment 1 obtains.

Fig. 2. The reaction time-glue block temperature curve of the UV-curable glue prepared by resin obtained in Example 1.

The infrared spectrum of the polyurethane methacrylate resin that Fig. 3. embodiment 2 obtains.

Fig. 4. The reaction time-glue block temperature curve of the UV-curable glue prepared by resin obtained in Example 2.

Fig. 5. The reaction time-glue block temperature curve of the UV-curable glue prepared by resin obtained in Example 3.

Fig. 6. The reaction time-glue block temperature curve of the UV-curable glue prepared by resin obtained in Example 4.

Fig. 7. The reaction time-glue block temperature curve of the UV-curable glue prepared by resin obtained in Example 5.

Figure 8. The reaction time-glue block temperature curve of the UV-curable glue prepared by resin obtained in Example 6.

Detailed ways

The invention will now be described in more detail, wherein preferred embodiments of the invention are shown, it being understood that those skilled in the art may modify the invention described herein and still achieve the beneficial effects of the invention. Therefore, the following description should be understood as the broad knowledge of those skilled in the art, but not as a limitation of the present invention.

Example 1

1) Add 30.00g (0.02mol) of polytetrahydrofuran diol, 8.89g (0.04mol) of isophorone diisocyanate, and 0.039g of dibutyltin dilaurate (catalyst) into a 100ml reaction flask. Under the condition of nitrogen protection and stirring, the above mixture was reacted at 60° C. for 8 h.

2) Add 8.40 g (0.04 mol) of methyl 2-hydroxy-2-methyl-5(-vinyl)cyclohexylacrylate, and then add 4.7 mg (0.01%) of hydroquinone. Under the protection of nitrogen and under the reaction conditions of 60°C, react for 24 hours until the isocyanate group disappears completely, and the target product is obtained. The chemical structure of the product obtained in Example 1 was determined with an infrared spectrometer, and the results are shown in Figure 1. The absorption peak that occurs at ^3337cm of the product is the characteristic peak of -NH in the polyurethane group, and the absorption peak that occurs at ^1733cm is the characteristic stretching vibration absorption peak of C=C; in the raw material, isophorone diisocyanate (IPDI )'s -NCO characteristic absorption peak should appear at 2270cm ^-1 , and the absorption peak here has disappeared after the reaction, indicating that -NCO and -OH have completely reacted, indicating that the target product was successfully synthesized.

27 parts of the product of Example 1, 45 parts of isobornyl acrylate, 25 parts of phenoxyethyl methacrylate, 2.0 parts of photoinitiator benzoin dimethyl ether, 2,4,6-trimethylbenzoyl diphenyl 1.0 parts of phosphine oxide.

The above components are weighed according to the mass composition, mixed, and left to defoam. Pour it into a polyethylene mold with a diameter of 30mm and a height of 35mm, and control the actual height of poured glue to 30mm. Under the irradiation of a 2000W mercury lamp (wavelength 350-450nm), measure the temperature at the center of the glue block with a thermocouple, and measure the surface temperature of the glue with a hand-held infrared thermometer. During the curing reaction process of the tested glue, the reaction time and the temperature change curve of the center of the glue block are shown in Figure 2. Among them, the illustration is a photo of curing after the temperature of the center of the UV-curable glue is tested by a thermocouple. It can be seen from the photos that after the glue is cured, there are no bubbles inside the glue block, and it is clear and transparent.

It can be seen from Figure 2 that the temperature of the glue block reaches the highest peak (121.7°C) around 139s. During the curing process tested by a hand-held infrared thermometer, the highest temperature on the surface of the rubber block was 97.5°C, indicating that the potting glue of the present invention is cured in stages. The "vaporization" of small monomer molecules produces bubbles and "core burning" problems caused by concentrated heat release, and also reduces the thermal shrinkage of the rubber block during the curing process.

After irradiating with ultraviolet light for 5 minutes, the rubber block was taken out, and the hardness of the rubber block was tested to reach 80D (Shore hardness).

Example 2

1) Add 30.00g (0.03mol) of polyethylene adipate diol, 10.10g (0.06mol) of hexamethylene diisocyanate, and 0.04g of dibutyltin dilaurate (catalyst) to a 100ml reaction flask middle. Under the condition of nitrogen protection and stirring, the above mixture was reacted at 90° C. for 2 h.

2) Add 12.01 g (0.06 mol) of 2-hydroxy-2-methyl-5(-vinyl) cyclohexyl acrylate, and add 26.5 mg of p-hydroxyanisole. Under nitrogen protection and reaction conditions of 90°C, react for 10 h until the isocyanate group disappears completely, and the target product is obtained.

The chemical structure of the product obtained in Example 2 was determined with an infrared spectrometer, and the results are shown in Figure 3. The absorption peak that product occurs at 3337cm ^-1 is the characteristic peak of -NH in the polyurethane group, and the absorption peak that occurs at 1739cm ^-1 is the characteristic stretching vibration absorption peak of C=C; Simultaneously, isophorone diisocyanate (IPDI )'s -NCO characteristic absorption peak appeared at 2270cm ^-1 , and the absorption peak here disappeared after the reaction, indicating that -NCO and -OH were completely reacted, indicating that the target product was successfully synthesized.

10.0 parts of the product of Example 2, 19.5 parts of hexafluorobutyl methacrylate, 60.0 parts of isobornyl methacrylate, 10.0 parts of o-phenylphenoxyethyl acrylate, phenyl bis(2,4,6-tri 0.5 part of methylbenzoyl) phosphine oxide.

The above components are weighed, mixed, and left to defoam. Then, pour it into a polyethylene mold with a diameter of 30mm and a height of 35mm, and control the actual height of the poured glue not to exceed 35mm. Under the irradiation of a 1000W mercury lamp (wavelength 350-450nm), measure the temperature at the center of the glue block with a thermocouple, and measure the surface temperature of the glue with a hand-held infrared thermometer. During the curing reaction of the tested glue, the change curve of the reaction time and the temperature of the center of the glue block is shown in Figure 4.

It can be seen from Figure 4 that the temperature of the glue block reaches the highest peak (117.3°C) around 174s. During the curing process with a hand-held infrared thermometer, the highest temperature on the surface of the rubber block was 97.7°C, which showed that the center temperature and surface temperature of the rubber block on the packaged PCB board were relatively low, which not only solved the problem of thermal deformation of the PCB board, but also avoided Problems such as "bubbles" and "core burnt" occur due to excessive local temperature of the rubber block.

After irradiating with ultraviolet light for 20 minutes, the rubber block was taken out, and the hardness of the tested rubber block reached 80D (Shore hardness).

The excellent hardness of the rubber block indicates that during the graded curing process of the rubber block, the double bond reacts and converts into a saturated carbon-carbon single bond, which improves the crosslinking density and hardness of the rubber block. It is very beneficial to the subsequent grinding, polishing and observation of the glue block, that is, the construction performance of the glue block does not change after the glue is graded and cured.

Example 3

1) Add 30.0g (0.02mol) of polybutylene adipate diol, 10.49g (0.04mol) of dicyclohexylmethane diisocyanate, and 0.045g of dibutyltin dilaurate (catalyst) into a 100ml reaction flask . Under the condition of nitrogen protection and stirring, the above mixture was reacted at 80° C. for 4 h.

2) Add 9.12 g (0.04 mol) of 2-hydroxy-5 (-isopropenyl) cyclohexyl acrylate, and add 14.9 mg of p-tert-butylcatechol. Under the protection of nitrogen and under the reaction conditions of 80°C, react for 12 hours until the isocyanate group disappears completely, and the target product is obtained.

30 parts of the product of Example 3, 40 parts of isobornyl methacrylate, 20 parts of o-phenylphenoxyethyl methacrylate, 9 parts of trifluoroethyl acrylate, 2,4,6-trimethylbenzoyl 0.5 parts of ethyl phenylphosphonate, 0.5 parts of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

The above components are weighed according to the mass composition, mixed, and left to defoam. Pour it into a polyethylene mold with a diameter of 30mm and a height of 35mm, and control the actual height of the poured glue not to exceed 30mm. Under the irradiation of 45W LED lamp tubes (five 9W LED lamp tubes with a wavelength of 350-400nm), measure the temperature at the center of the glue block with a thermocouple, and measure the surface temperature of the glue with a hand-held infrared thermometer. During the curing reaction of the tested glue, the change curve of the reaction time and the temperature of the center of the glue block is shown in Figure 5.

It can be seen from Figure 5 that the temperature of the glue block reaches the highest peak at about 207.1s, 107.4°C. During the curing process, the highest temperature on the surface of the rubber block was 90.0°C using a hand-held infrared thermometer.

The rubber block was taken out after being irradiated with ultraviolet light for 20 minutes, and the hardness of the tested rubber block reached 81D (Shore hardness).

Example 4

1) 20.0g (0.02mol) polytetrahydrofuran diol, 10.0g (0.01mol) polycarbonate diol (T5651, Asahi Kasei Fine Chemical Co., Ltd.), 13.34g (0.06mol) isophorone diisocyanate, 0.043 g dibutyltin dilaurate (catalyst) is added in the 100ml reaction bottle. Under the condition of nitrogen protection and stirring, the above mixture was reacted at 70°C for 8h.

2) Add 14.29g (0.06mol) of methyl 2-hydroxy-2-methyl-5(-isopropenyl)cyclohexylacrylate, and add 23.0mg of p-tert-butylhydroquinone. Under the protection of nitrogen and under the reaction conditions of 70°C, react for 24 hours until the isocyanate group disappears completely, and the target product is obtained.

23.5 parts of the product of Example 4, 47.0 parts of phenoxyethyl methacrylate, 25 parts of o-phenylphenoxyethyl methacrylate, 3.0 parts of hexafluorobutyl methacrylate, 2,2-dimethyl 1.0 parts of -α-hydroxyacetophenone, 0.5 parts of ethyl 2,4,6-trimethylbenzoylphenylphosphonate.

The above components are weighed according to the mass composition, mixed, and left to defoam. Pour it into a polyethylene mold with a diameter of 30mm and a height of 35mm, and control the actual height of the poured glue not to exceed 30mm. Under the irradiation of 90W LED lamp tubes (10 9W LED lamp tubes with a wavelength of 350-400nm), measure the temperature at the center of the glue block with a thermocouple, and measure the surface temperature of the glue with a hand-held infrared thermometer. During the curing reaction of the tested glue, the curve of the reaction time and the temperature of the center of the glue block is shown in Figure 6. It can be seen from Figure 6 that the temperature of the glue block reaches the highest peak (106.5°C) around 165s. During the curing process, the highest temperature on the surface of the rubber block was 90.3°C using a hand-held infrared thermometer.

The rubber block was taken out after being irradiated with ultraviolet light for 20 minutes, and the hardness of the tested rubber block reached 83D (Shore hardness).

Example 5

1) 10.0g (0.01mol) polyethylene succinate diol, 10.00g (0.02mol) polytetrahydrofuran ether diol, 10.49g (0.04mol) dicyclohexylmethane diisocyanate, 4.45g ( 0.02mol) isophorone diisocyanate, 0.04g dibutyltin dilaurate (catalyst) was added in the 100ml reaction bottle. Under the condition of nitrogen protection and stirring, the above mixture was reacted at 80° C. for 4 h.

2) 5.89g (0.03mol) 2-hydroxy-2-methyl-5 (-vinyl) cyclohexyl acrylate, 7.14g (0.03mol) 2-hydroxy-5 (-isopropenyl) cyclohexyl methacrylate Esters, add 14.39mg p-hydroxyanisole, 4.8mg (0.01%) p-benzoquinone. Under the protection of nitrogen and under the reaction conditions of 80°C, the reaction was carried out for 16 hours until the isocyanate group disappeared completely, and the target product was obtained.

25 parts of the product of embodiment 5, 15 parts of phenoxyethyl methacrylate, 25 parts of isobornyl acrylate, 15 parts of isobornyl methacrylate, 18 parts of trifluoroethyl methacrylate, phenyl bis( 1.5 parts of 2,4,6-trimethylbenzoyl)phosphine oxide, and 0.5 parts of benzoin dimethyl ether.

The above components are weighed according to the mass composition, mixed, and left to defoam. Pour it into a polyethylene mold with a diameter of 30mm and a height of 35mm, and control the actual height of the poured glue not to exceed 30mm. Under the irradiation of 180W LED lamp tubes (20 9W LED lamp tubes with a wavelength of 350-400nm), measure the surface temperature of the glue with a hand-held infrared thermometer. The highest surface temperature of the glue during curing was 87.1°C. It can be seen from Figure 7 that the temperature of the glue block reaches the highest peak (109.5°C) around 187s.

The rubber block was taken out after being irradiated with ultraviolet light for 20 minutes, and the hardness of the tested rubber block reached 82D (Shore hardness).

Example 6

1) 10.0g (0.01mol) polyethylene succinate diol, 10.00g (0.02mol) polytetrahydrofuran ether diol, 10.49g (0.04mol) dicyclohexylmethane diisocyanate, 4.45g ( 0.02mol) isophorone diisocyanate, 0.04g dibutyltin dilaurate (catalyst) was added in the 100ml reaction bottle. Under the condition of nitrogen protection and stirring, the above mixture was reacted at 80° C. for 4 h.

2) 7.85g (0.04mol) 2-hydroxy-2-methyl-5 (-vinyl) cyclohexyl acrylate methyl ester, 4.75g (0.02mol) 2-hydroxy-5 (-isopropenyl) cyclohexyl acrylate Add methyl esters, 4.7mg p-methylhydroquinone, 4.7mg p-hydroxyanisole, and 4.7mg hydroquinone into a round bottom flask. Under the protection of nitrogen and under the reaction conditions of 90°C, react for 8 hours until the isocyanate group disappears completely, and the target product is obtained.

30 parts of the product of Example 6, 20 parts of phenoxyethyl methacrylate, 40 parts of isobornyl methacrylate, 7 parts of trifluoroethyl acrylate, phenyl bis(2,4,6-trimethyl 2.0 parts of benzoyl)phosphine oxide, 1.0 parts of 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone.

The above components are weighed according to the mass composition, mixed, and left to defoam. Slowly pour it into a polyethylene mold with a diameter of 30mm and a height of 35mm, and control the actual height of the poured glue not to exceed 30mm. Under the irradiation of 90W LED lamp tubes (10 9W LED lamp tubes with a wavelength of 350-400nm), measure the surface temperature of the glue with a hand-held infrared thermometer. The highest surface temperature of the glue during curing is 91.3°C. It can be seen from Figure 8 that the temperature of the glue block reaches the highest peak (113.6°C) around 202s.

The rubber block was taken out after being irradiated with ultraviolet light for 25 minutes, and the hardness of the tested rubber block reached 82D (Shore hardness).

Because contain two kinds of carbon-carbon double bonds of different reactivity in the molecular structure of graded curing polyurethane (meth)acrylate resin of the present invention, promptly contain two pairs of (meth)acrylate double bonds of high reactivity and low reaction simultaneously Active vinyl double bonds, under the action of photoinitiators, the two double bonds undergo free radical polymerization according to different reactivity, which artificially prolongs the curing reaction cycle, that is, (meth) in polyurethane (meth)acrylate Acrylate double bonds and vinyl double bonds undergo free radical polymerization successively, which slows down the concentrated exothermic heat of the polymerization system, reduces the internal temperature of the cured rubber block, and avoids "vaporization" to generate a large number of bubbles inside the cured sample block, sometimes It can also cause "core burning" of UV-cured samples. Moreover, since the synthesized polyurethane (meth)acrylate resin has four functionalities, it can be cured in stages, and the cured rubber block has good transparency and high hardness.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be carried out to the technical solutions of the present invention. These equivalent transformations All belong to the protection scope of the present invention. In addition, it should be noted that the various specific technical features described in the above specific implementation manners may be combined in any suitable manner if there is no contradiction. In order to avoid unnecessary repetition, various possible combinations are not further described in the present invention. In addition, various combinations of different embodiments of the present invention can also be combined arbitrarily, as long as they do not violate the idea of the present invention, they should also be regarded as the disclosed content of the present invention.

Claims (5)

1. A urethane (meth) acrylate having a structural formula of formula (I):

wherein R is ₁ Is composed of

M is more than or equal to 5 and less than or equal to 10, n is more than or equal to 5 and less than or equal to 10;

R ₂ is composed of

Any one or a mixture of at least two of them;

R ₃ is H or CH ₃ ；

R ₄ Is H or CH ₃ 。

2. A method for producing a urethane (meth) acrylate according to claim 1, characterized by comprising the steps of:

1) Feeding polyester or polyether diol and diisocyanate according to a molar ratio of 1; then heating to 60-90 ℃ under the protection of nitrogen and stirring, then reacting for 2-8h,

wherein the polyester or polyether diol is at least one of polytetrahydrofuran diol, polyethylene glycol adipate diol, polyethylene glycol succinate diol, polycarbonate diol, polyethylene glycol, polypropylene glycol and polyethylene glycol-polypropylene glycol copolymer,

the diisocyanate is at least one of 2, 4-toluene diisocyanate, 2, 6-toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, 1, 3-m-xylylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, 2, 4-trimethylhexamethylene diisocyanate, 2, 4-trimethylhexamethylene diisocyanate or 1, 3-cyclohexyldimethylene diisocyanate,

2) Adding a material hydroxyl compound with the same molar weight as the diisocyanate, and adding a polymerization inhibitor accounting for 0.01-0.05% of the mass of all the materials participating in the reaction; then under the protection of nitrogen and the reaction condition of 60-90 ℃, reacting until isocyanate groups completely disappear, thus obtaining the isocyanate-terminated polyurethane;

wherein the hydroxyl compound is at least one of 2-hydroxy-2-methyl-5 (-isopropenyl) cyclohexyl methyl acrylate, 2-hydroxy-2-methyl-5 (-vinyl) cyclohexyl methyl acrylate, 2-hydroxy-5 (-isopropenyl) cyclohexyl methyl acrylate, 2-hydroxy-5 (-vinyl) cyclohexyl methyl acrylate, 2-hydroxy-2-methyl-5 (-isopropenyl) cyclohexyl acrylate, 2-hydroxy-2-methyl-5 (-vinyl) cyclohexyl acrylate, 2-hydroxy-5 (-isopropenyl) cyclohexyl acrylate, and 2-hydroxy-5 (-vinyl) cyclohexyl acrylate.

3. The method according to claim 2, wherein the polymerization inhibitor is one or more selected from the group consisting of hydroquinone, p-hydroxyanisole, p-benzoquinone, p-tert-butylcatechol, phenothiazine, p-tert-butylhydroquinone, 6-tert-butyl-2, 4-dimethylphenol, and p-methylhydroquinone.

4. The potting glue for the low-temperature printed circuit board is characterized by comprising the following components in parts by mass:

(meth) acrylic acid ester: 70-89.5 parts;

the urethane (meth) acrylate according to claim 1: 10-30 parts;

0.5-3.0 parts of photoinitiator;

the components are uniformly mixed under the condition of keeping out of the sun to obtain the potting adhesive for the low-temperature printed circuit board.

5. The potting adhesive for a low-temperature printed circuit board according to claim 4, wherein the (meth) acrylate is any one of isobornyl acrylate, isobornyl methacrylate, o-phenylphenoxyethyl acrylate, o-phenylphenoxyethyl methacrylate, trifluoroethyl acrylate, trifluoroethyl methacrylate, hexafluorobutyl acrylate, hexafluorobutyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate or a mixture of at least two thereof;

the photoinitiator is any one or a mixture of at least two of benzoin dimethyl ether, isopropyl thioxanthone, benzophenone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-1- [4- (2-hydroxyethoxy) phenyl ] -2-methyl-1-acetone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone, 2-dimethyl-alpha-hydroxyacetophenone, alpha' -ethoxyacetophenone, ethyl 4- (N, N-dimethylamino) benzoate, phenyl bis (2, 4, 6-trimethylbenzoyl) phosphine oxide, 2,4, 6-trimethylbenzoyl diphenylphosphine oxide, methyl o-benzoylformate, methyl o-benzoylbenzoate or ethyl 2,4, 6-trimethylbenzoyl phenylphosphonate.

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