Low-water vapor sensitive bubble-free polyurethane pouring sealant and preparation method thereof

Abstract

The invention relates to the field of polyurethane adhesives, and particularly discloses a low-water-vapor sensitive foamless polyurethane pouring sealant and a preparation method thereof. The polyurethane pouring sealant comprises a component A and a component B, wherein the component A comprises 35-80 parts by weight of polyol I, 0-20 parts by weight of a chain extender, 5-20 parts by weight of a flame retardant, 0.1-1 part by weight of an antioxidant, 0.1-1 part by weight of a defoaming agent and 0-1 part by weight of a catalyst; the component B comprises the following components in parts by weight: 20-70 parts of polyisocyanate, 10-40 parts of polyol II and 10-20 parts of a diluent; and the polyisocyanate is aliphatic isocyanate or alicyclic isocyanate. The polyurethane pouring sealant disclosed by the invention has good flame retardance, operability and mechanical property, no bubble is generated after curing, the air tightness of the electronic component is guaranteed, the safety of the electronic component in the use process is improved, and meanwhile, the service life of the electronic component is prolonged.

Description

Technical Field

[0001] The present application relates to the field of polyurethane adhesives, and more specifically, to a low-water vapor-sensitive, bubble-free polyurethane potting adhesive and a preparation method thereof. Background Art

[0002] Polyurethane potting glue, also known as PU potting glue, is a polymer material formed by the reaction of polyols of oligomers such as polyester, polyether and polydiolefin with diisocyanate, with diol or diamine as chain extender, and gradually polymerized. The modulus and hardness of this potting glue can be adjusted according to demand. It has moderate hardness, high elasticity, excellent impact resistance, wear resistance and low temperature resistance. It overcomes the shortcomings of traditional silicone potting glue, such as low strength, poor adhesion and insufficient tear resistance, and traditional epoxy potting glue, such as low elongation, poor moisture and heat resistance, and easy cracking under cold and hot shock. It is widely used in electronics, aerospace, automobile, shipbuilding and other fields.

[0003] In addition, polyurethane potting glue also has the characteristics of high transparency, excellent electrical insulation and flame retardancy, which make it an ideal material for potting and protecting electronic components. By using polyurethane potting glue, it can be ensured that the installed and adjusted electronic components and circuits are not affected by factors such as vibration, corrosion, moisture and dust, thereby improving the stability and reliability of the equipment. However, most of the key material components in polyurethane potting glue currently used in the field of electronic potting on the market are very sensitive to water, water vapor and high humidity. When these components come into contact with water vapor, chemical reactions are very likely to occur, affecting the curing effect, resulting in a large number of bubbles inside the colloid after curing, which not only affects the appearance, but also easily causes the airtightness to be damaged, and ultimately causes damage such as short circuits of electronic components due to moisture. Summary of the invention

[0004] In order to solve the above technical problems, the present application provides a low water vapor sensitivity and bubble-free polyurethane potting adhesive and a preparation method thereof.

[0005] In the first aspect, the present application provides a low vapor sensitivity and bubble-free polyurethane potting glue, which adopts the following technical scheme: a low vapor sensitivity and bubble-free polyurethane potting glue, the raw materials used include component A and component B, the component A includes the following ingredients: 35-80 weight parts of polyol I, 0-20 weight parts of chain extender, 5-20 weight parts of flame retardant, 0.1-1 weight part of antioxidant, 0.1-1 weight part of defoamer and 0-1 weight part of catalyst; the component B includes the following ingredients: 20-70 weight parts of polyisocyanate, 10-40 weight parts of polyol II and 10-20 weight parts of diluent; wherein the polyisocyanate is an aliphatic isocyanate or an alicyclic isocyanate.

[0006] Through the above technical scheme, the present application adopts aliphatic isocyanate or alicyclic isocyanate as the raw material of the curing agent in component B, which can solve the problem of foaming after curing while ensuring that the polyurethane potting glue has good flame retardancy, operability and mechanical properties, thereby obtaining an excellent bubble-free and smooth appearance, ensuring the airtightness of electronic components, improving the safety of electronic components during use, and at the same time increasing the service life of electronic components. Among them, compared with other types of polyisocyanates, such as aromatic isocyanates, etc., the aliphatic isocyanate or alicyclic isocyanate of the present application has a lower reactivity to water, and the NCO value is in the range of 10-25%, and the free isocyanate group is less, and it is not easy to react with water to produce chemical bubbles. It will be more likely to directly cure with component A first, so that the polyurethane potting glue of the present application is less sensitive to water vapor, and no foaming is generated after the colloid is cured, providing a safe and reliable material for electronic components.

[0007] In some preferred embodiments, the aliphatic isocyanate is one or more of hexamethylene diisocyanate, trimethyl-1,6-hexamethylene diisocyanate and 1,5-pentamethylene diisocyanate.

[0008] In some preferred embodiments, the alicyclic isocyanate is one or more of isophorone diisocyanate, dicyclohexylmethane diisocyanate, methylcyclohexyl diisocyanate and cyclohexyl dimethylene diisocyanate.

[0009] Preferably, the polyisocyanate is an alicyclic isocyanate.

[0010] Through the above technical solution, compared with aliphatic isocyanate, the alicyclic isocyanate used in the present application can introduce a rigid alicyclic structure, thereby further improving the hardness, strength and other mechanical properties of the polyurethane potting adhesive.

[0011] Preferably, the polyol I and the polyol II are both primary hydroxyl-terminated polyols with molecular weights between 300-6000.

[0012] In some preferred embodiments, the terminal primary hydroxyl group polyol is one or more of a bio-based polyol, a polyether polyol, a polyester polyol and a polymer polyol.

[0013] Through the above technical scheme, the present application adopts a polyol with terminal primary hydroxyl groups, which can react with polyisocyanate more stably than other polyols, helps to reduce gas generation, and further reduces the risk of bubble formation, so that the final polyurethane potting glue is free of bubbles after curing.

[0014] Optionally, the flame retardant is a commonly used flame retardant in the art. In some preferred embodiments, the flame retardant is a phosphate flame retardant.

[0015] In some preferred embodiments, the flame retardant is one or more of triethyl phosphate, dimethyl methyl phosphate, diethyl ethyl phosphate and tris(butoxyethyl) phosphate.

[0016] Optionally, the chain extender is a commonly used chain extender in the art. In some preferred embodiments, the chain extender is an amine chain extender.

[0017] In some preferred embodiments, the chain extender is one or more of 4,4'-bis-sec-butylaminodiphenylmethane, dimethylthiotoluenediamine, polyetheramine and 3,5-diethyltoluenediamine.

[0018] In some preferred embodiments, the antioxidant is octylated diphenylamine, 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid branched chain C 13 -C 15 One or more of alkyl esters, 3,5-di-tert-butyl-4-hydroxyphenylpropionate, and diphenyl isodecyl phosphite.

[0019] In some preferred embodiments, the defoamer is one or more of defoamer BYK-A530, defoamer BYK-A535, defoamer BYK-066N, defoamer BYK-024 and defoamer BYK-141.

[0020] In some preferred embodiments, the catalyst is one or more of organotin, organozinc and organobismuth.

[0021] In some preferred embodiments, the diluent is one or more of dioctyl terephthalate, diphenyl toluene phosphate and tricresyl phosphate.

[0022] In a second aspect, the present application provides a method for preparing the above-mentioned low water vapor sensitivity and bubble-free polyurethane potting glue, which adopts the following technical scheme: A method for preparing a low water vapor sensitive, bubble-free polyurethane potting adhesive comprises the following steps: S1. Preparation of component A Mix and stir all raw materials of component A under vacuum conditions for 25-35 minutes to obtain component A; S2. Preparation of component B Stirring and dehydrating polyol II and diluent under vacuum conditions at a temperature of 115-125° C. for 1.5-2.5 hours, then cooling to 35-45° C., adding polyisocyanate, reacting under vacuum conditions at a temperature of 75-85° C. for 2-4 hours, and then cooling to obtain component B; S3. Prepare potting glue After the A component and the B component are uniformly mixed in a weight ratio of 1: (0.8-1.2), the substrate is potted and then cured to obtain the polyurethane potting adhesive.

[0023] Wherein, the substrate is a substrate that has not been baked to remove water.

[0024] The curing is specifically curing at a temperature of 21-25° C. for 24-48 hours, or curing at a temperature of 78-82° C. for 1-2 hours.

[0025] Through the above technical scheme, the present application adopts a mixture of polyol I, chain extender, flame retardant, antioxidant, defoamer and catalyst in a suitable ratio to form component A, a mixture of polyisocyanate, polyol II and diluent in a suitable ratio to form component B, and then the component A and the component B are mixed and cured in a certain ratio to obtain a polyurethane potting adhesive, which can solve the problem of foaming of the polyurethane potting adhesive after curing while ensuring flame retardancy, operability, strength and other properties.

[0026] Furthermore, since the polyurethane potting adhesive of the present application is less sensitive to water vapor, when preparing the polyurethane potting adhesive, there is no need to dehydrate the raw materials of component A, and there is no need to bake and remove water from the potted electronic devices during potting. A bubble-free, smooth-looking polyurethane potting adhesive can be obtained, which simplifies the process flow and improves the convenience of operation.

[0027] In summary, this application has the following beneficial technical effects: 1. The present application optimizes the raw materials and ratio of component A and component B, and can solve the problem of foaming after curing while ensuring that the polyurethane potting adhesive has good flame retardancy, operability and mechanical properties, thereby obtaining an excellent bubble-free and smooth appearance, ensuring the air tightness of electronic components, improving the safety of electronic components during use, and at the same time increasing the service life of electronic components; 2. In the preparation of the polyurethane potting adhesive, the present application does not need to dehydrate the raw materials of component A, and does not need to bake and remove water from the encapsulated electronic devices during potting, thereby obtaining a bubble-free, smooth-looking polyurethane potting adhesive, thereby simplifying the process flow and improving the convenience of operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is an appearance diagram of the polyurethane potting adhesive prepared in Example 1; Figure 2 This is an appearance diagram of the polyurethane potting adhesive prepared in Example 2; Figure 3 This is an appearance diagram of the polyurethane potting adhesive prepared in Example 3; Figure 4 This is an appearance diagram of the polyurethane potting adhesive prepared in Example 4; Figure 5 This is an appearance diagram of the polyurethane potting adhesive prepared in Example 5; Figure 6 This is the appearance of the polyurethane potting glue prepared in Comparative Example 1; Figure 7 This is the appearance picture of the polyurethane potting glue prepared in comparative example 3. DETAILED DESCRIPTION

[0029] The following is combined with Figure 1-7 This application is described in further detail.

[0030] Unless otherwise specified, the raw materials used in this application are all commercially available products.

[0031] In some specific embodiments of the polyurethane potting adhesive, polyol I is one or more of a bio-based polyol with a terminal primary hydroxyl group, a terminal primary hydroxyl group polyether polyol, a terminal primary hydroxyl group polyester polyol and a terminal primary hydroxyl group polymer polyol with a molecular weight between 300 and 6000.

[0032] In some preferred embodiments of the polyurethane potting adhesive, the polyol I is one or more of polyether polyol EP-330NG, polytetramethylene glycol and polyethylene glycol.

[0033] Among them, the molecular weight of polyether polyol EP-330NG is 5000, the hydroxyl value is 32.5-35.5 mgKOH / g, the moisture content is ≤0.05%, the pH value is 5-7, the viscosity is 800-1000 mPa·s / 25°C, the potassium content is ≤3 mg / kg, and the color is ≤50 APHA; the functionality of polytetrahydrofuran polyol is 2, and the molecular weight is 650-1000; The functionality of polyethylene glycol is 2 and the molecular weight is 300.

[0034] In some specific embodiments of the polyurethane potting adhesive, the chain extender is one or more of 4,4'-bis-sec-butylaminodiphenylmethane, dimethylthiotoluenediamine, polyetheramine and 3,5-diethyltoluenediamine, wherein the polyetheramine is polyetheramine D4000.

[0035] In some specific embodiments of the polyurethane potting compound, the flame retardant is one or more of triethyl phosphate, dimethyl methyl phosphate, diethyl ethyl phosphate and tri(butoxyethyl) phosphate.

[0036] In some embodiments of the polyurethane potting adhesive, the antioxidant is octylated diphenylamine, 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid branched chain C 13 -C 15One or more of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid branched C13-C15 alkyl ester, 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid isooctyl ester and diphenyl isodecyl phosphite. Among them, 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid branched C13-C15 alkyl ester is 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid and the corresponding branched C 13 -C 15 The target ester compound is generated by reacting alcohol in the presence of a catalyst. The structure includes a 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid structure and a branched alkyl ester part, and the carbon chain length is between 13 and 15.

[0037] In some specific embodiments of the polyurethane potting adhesive, the defoamer is one or more of defoamer BYK-A530, defoamer BYK-A535, defoamer BYK-066N, defoamer BYK-024 and defoamer BYK-141.

[0038] In some specific embodiments of the polyurethane potting adhesive, the catalyst is one or more of organic tin, organic zinc and organic bismuth.

[0039] In some specific embodiments of the polyurethane potting adhesive, the aliphatic isocyanate is one or more of hexamethylene diisocyanate, trimethyl-1,6-hexamethylene diisocyanate and 1,5-pentamethylene diisocyanate.

[0040] In some specific embodiments of the polyurethane potting adhesive, the alicyclic isocyanate is one or more of isophorone diisocyanate, dicyclohexylmethane diisocyanate, methylcyclohexyl diisocyanate and cyclohexyl dimethylene diisocyanate.

[0041] In some specific embodiments of the polyurethane potting adhesive, the polyol II is one or more of a bio-based polyol with a terminal primary hydroxyl group, a terminal primary hydroxyl group polyether polyol, a terminal primary hydroxyl group polyester polyol and a terminal primary hydroxyl group polymer polyol with a molecular weight between 300 and 6000.

[0042] In some preferred embodiments of the polyurethane potting compound, the polyol II is polypropylene carbonate diol.

[0043] The functionality of polypropylene carbonate diol is 2 and the molecular weight is 2000.

[0044] In some specific embodiments of the polyurethane potting adhesive, the diluent is one or more of dioctyl terephthalate, diphenyl phosphate and tricresyl phosphate.

[0045] In some specific embodiments of the polyurethane potting glue, the above raw materials are used and the following steps are followed: S1, preparing component A, 35-80 parts by weight of polyol I, 0-20 parts by weight of chain extender, 5-20 parts by weight of flame retardant, 0.1-1 parts by weight of antioxidant, 0.1-1 parts by weight of defoamer and 0-1 parts by weight of catalyst are mixed and stirred for 25-35 minutes under vacuum conditions to obtain component A; S2, preparing component B, 10-40 parts by weight of polyol II and 10-20 parts by weight of diluent are mixed and stirred at a temperature of 115-125°C. Stir and dehydrate under vacuum conditions for 1.5-2.5 hours, then cool to 35-45°C, add 20-70 parts by weight of polyisocyanate, react under vacuum conditions at a temperature of 75-85°C for 2-4 hours, and then cool to obtain component B; S3, prepare a potting glue, mix component A and component B in a weight ratio of 1: (0.8-1.2), potting the substrate that has not been baked and dehydrated, and then cure it. The obtained polyurethane potting glue has no bubbles, a smooth appearance, and various properties such as flame retardancy, operability, and mechanical properties are at a better level.

[0046] Among them, the substrate of the present application can be an electronic device that needs to be encapsulated in the field. In the specific implementation of the present application, the PCB board is taken as an example for explanation. The specifications of the PCB board of the present application are: length × width × thickness = 25±0.5mm×25±0.5mm×1.5±0.2mm.

[0047] The curing conditions of the present application are specifically curing at a temperature of 21-25° C. for 24-48 hours, or curing at a temperature of 78-82° C. for 1-2 hours. In the specific implementation of the present application, room temperature curing is taken as an example for description.

[0048] In combination with the above content, the applicant further demonstrates the various properties of the polyurethane potting adhesive of the present application and its appearance after curing with the following Examples 1-7 and Comparative Examples 1-3.

[0049] Example 1 A method for preparing a low water vapor sensitive, bubble-free polyurethane potting adhesive comprises the following steps: S1. Preparation of component A 25 kg of polyether polyol EP-330NG, 50 kg of polytetrahydrofuran diol (M=1000), 5 kg of 4,4'-bis-sec-butylaminodiphenylmethane, 18.3 kg of triethyl phosphate, 1 kg of octylated diphenylamine, 0.7 kg of defoamer BYK-066N and 0.002 kg of bismuth neodecanoate were mixed and stirred under -0.095 MPa for 30 min to obtain component A; S2. Preparation of component B 35 kg of polypropylene carbonate diol and 20 kg of dioctyl terephthalate were stirred and dehydrated at 120° C. and -0.095 MPa for 2 hours, then cooled to 40° C., 35 kg of dicyclohexylmethane diisocyanate and 10 kg of isophorone diisocyanate were added, and reacted at 80° C. and -0.095 MPa for 3 hours, and the NCO% was measured to be 15%±0.5% by sampling, and then cooled to 40° C. to obtain component B; S3. Prepare potting glue After the component A and the component B are uniformly mixed in a weight ratio of 1:1, the PCB board which has not been baked to remove water is potted, and then cured at a temperature of 23° C. for 48 hours to obtain a polyurethane potting adhesive.

[0050] Example 2 A method for preparing a low water vapor sensitive, bubble-free polyurethane potting adhesive comprises the following steps: S1. Preparation of component A 10 kg of polyether polyol EP-330NG, 65 kg of polytetrahydrofuran diol (M=650), 10 kg of dimethylthiotoluenediamine, 13.3 kg of dimethyl methyl phosphate, 1 kg of octylated diphenylamine, 0.7 kg of defoamer BYK-066N and 0.002 kg of bismuth neodecanoate were mixed and stirred under a vacuum condition of -0.095 MPa for 30 min to obtain component A; S2. Preparation of component B 25 kg of polypropylene carbonate diol and 10 kg of toluene diphenyl phosphate were stirred and dehydrated at a temperature of 120° C. and -0.095 MPa for 2 hours, then cooled to 40° C., 10 kg of dicyclohexylmethane diisocyanate and 55 kg of isophorone diisocyanate were added, and reacted at a temperature of 80° C. and -0.095 MPa for 3 hours, and the NCO% was measured to be 20%±0.5% by sampling, and then cooled to 40° C. to obtain component B; S3. Prepare potting glue After the component A and the component B are uniformly mixed in a weight ratio of 1:1, the PCB board which has not been baked to remove water is potted, and then cured at a temperature of 23° C. for 48 hours to obtain a polyurethane potting adhesive.

[0051] Example 3 A method for preparing a low water vapor sensitive, bubble-free polyurethane potting adhesive comprises the following steps: S1. Preparation of component A 80 kg of polytetrahydrofuran diol (M=650), 5 kg of 3,5-diethyltoluenediamine, 13.3 kg of diethyl ethyl phosphate, 1 kg of octylated diphenylamine, 0.7 kg of defoamer BYK-066N and 0.008 kg of zinc isooctanoate were mixed and stirred at -0.095 MPa for 30 min to obtain component A; S2. Preparation of component B 40 kg of polypropylene carbonate diol and 20 kg of toluene diphenyl phosphate were stirred and dehydrated at 120° C. and -0.095 MPa for 2 hours, then cooled to 40° C., 20 kg of dicyclohexylmethane diisocyanate and 20 kg of isophorone diisocyanate were added, and reacted at 80° C. and -0.095 MPa for 3 hours, and the NCO% was measured to be 12%±0.5% by sampling, and then cooled to 40° C. to obtain component B; S3. Prepare potting glue After the component A and the component B are uniformly mixed in a weight ratio of 1:1, the PCB board which has not been baked to remove water is potted, and then cured at a temperature of 23° C. for 48 hours to obtain a polyurethane potting adhesive.

[0052] Example 4 A method for preparing a low water vapor sensitive, bubble-free polyurethane potting adhesive comprises the following steps: S1. Preparation of component A 60 kg of polyether polyol EP-330NG, 15 kg of polyethylene glycol, 10 kg of polyether amine D4000, 13.3 kg of triethyl phosphate, 0.5 kg of octylated diphenylamine, 0.5 kg of 3,5-di-tert-butyl-4-hydroxyphenylpropionate, 0.7 kg of defoamer BYK-066N and 0.002 kg of bismuth neodecanoate were mixed and stirred under a vacuum condition of -0.095 MPa for 30 min to obtain component A; S2. Preparation of component B 40 kg of polypropylene carbonate diol and 20 kg of toluene diphenyl phosphate were stirred and dehydrated at 120° C. and -0.095 MPa for 2 hours, then cooled to 40° C., 40 kg of dicyclohexylmethane diisocyanate were added, and reacted at 80° C. and -0.095 MPa for 3 hours. The NCO% was measured to be 13%±0.5% by sampling, and then cooled to 40° C. to obtain component B; S3. Prepare potting glue After the component A and the component B are uniformly mixed in a weight ratio of 1:1, the PCB board which has not been baked to remove water is potted, and then cured at a temperature of 23° C. for 48 hours to obtain a polyurethane potting adhesive.

[0053] Example 5 A method for preparing a low water vapor sensitive, bubble-free polyurethane potting adhesive comprises the following steps: S1. Preparation of component A 12 kg of polyether polyol EP-330NG, 55 kg of polytetrahydrofuran diol (M=1000), 18 kg of dimethylthiotoluenediamine, 13.3 kg of triethyl phosphate, 0.5 kg of octylated diphenylamine, 0.5 kg of 3,5-di-tert-butyl-4-hydroxyphenylpropionate isooctyl ester, 0.7 kg of defoamer BYK-066N, 0.002 kg of bismuth neodecanoate and 0.002 kg of isooctyl ester were mixed and stirred at -0.095 MPa for 30 min to obtain component A; S2. Preparation of component B 35 kg of polypropylene carbonate diol and 10 kg of toluene diphenyl phosphate were stirred and dehydrated at a temperature of 120° C. and -0.095 MPa for 2 hours, then cooled to 40° C., 35 kg of dicyclohexylmethane diisocyanate and 20 kg of isophorone diisocyanate were added, and reacted at a temperature of 80° C. and -0.095 MPa for 3 hours, and the NCO% was measured to be 18%±0.5% by sampling, and then cooled to 40° C. to obtain component B; S3. Prepare potting glue After the component A and the component B are uniformly mixed in a weight ratio of 1:1, the PCB board which has not been baked to remove water is potted, and then cured at a temperature of 23° C. for 48 hours to obtain a polyurethane potting adhesive.

[0054] Example 6 A method for preparing a low water vapor sensitive foam-free polyurethane potting adhesive, which is different from Example 1 in that: 35 kg of dicyclohexylmethane diisocyanate and 10 kg of isophorone diisocyanate in component B in step S2 are replaced by 45 kg of hexamethylene diisocyanate, and the rest is the same as Example 1.

[0055] Example 7 A method for preparing a low water vapor sensitive foam-free polyurethane potting adhesive, which is different from that of Example 1 in that: 35 kg of dicyclohexylmethane diisocyanate and 10 kg of isophorone diisocyanate in component B in step S2 are replaced by 30 kg of hexamethylene diisocyanate and 15 kg of trimethyl-1,6-hexamethylene diisocyanate, and the rest is the same as in Example 1.

[0056] Comparative Example 1 The difference from Example 4 is that the 40 kg of dicyclohexylmethane diisocyanate in component B in step S2 is completely replaced by aromatic isocyanate, specifically MDI-100LL of Wanhua Chemical, and the rest is the same as Example 4.

[0057] Comparative Example 2 The difference from Example 4 is that 40 kg of dicyclohexylmethane diisocyanate in component B in step S2 is replaced by 20 kg of MDI-100LL of Wanhua Chemical and 20 kg of isophorone diisocyanate, and the rest is the same as Example 4.

[0058] Comparative Example 3 The difference from Example 1 is that the 50 kg of polytetrahydrofuran diol in component A in step S1 is completely replaced by a polyol without terminal primary hydroxyl groups, specifically DL-1000 of Bluestar Dongda Chemical, and the rest is the same as Example 1.

[0059] Performance Testing The above-mentioned Examples 1-7 and Comparative Examples 1-3 were subjected to relevant performance tests, including viscosity test, operation time test, appearance test, hardness test, tensile strength test, shear strength test and flame retardant performance test; specifically: viscosity was tested in accordance with GB / T 2794-2013 standard; operation time was tested in accordance with GB / T 7123.1-2015 standard; appearance was visually inspected after curing; hardness was tested in accordance with GB / T 531.1-2008 standard; tensile strength was tested in accordance with GB / T 528-2009 standard; shear strength test was tested in accordance with GB / T 7124-2008 standard, and flame retardant performance was tested in accordance with ISO 9773-1998 standard. The test results are shown in Table 1.

[0060] According to the data in Table 1 and combined Figure 1-5 It can be seen that the polyurethane potting adhesive prepared in Examples 1-5 of the present application can still have good viscosity, operation time, hardness, tensile strength, shear strength, flame retardant properties, etc., without dehydrating the raw materials used in component A and without baking the PCB board for dehydration, and no bubbles are generated and the appearance is smooth. The difference between Example 6-7 and Example 1 is that aliphatic isocyanate is used instead of alicyclic isocyanate, and its appearance after curing is similar to that of Example 1 (the appearance diagram of Example 6-7 after curing is similar to that of Example 1, so it will not be repeated), and the hardness, tensile strength and shear strength are slightly worse than those of Example 1, which shows that the introduction of a rigid alicyclic structure can further improve the mechanical properties of the polyurethane potting adhesive.

[0061] The difference between Comparative Example 1-2 and Example 4 is that aromatic isocyanate is used to completely replace alicyclic isocyanate or is used in combination with alicyclic isocyanate. From the data in Table 1 and Figure 6It can be seen (the appearance of comparative example 2 after curing is similar to that of comparative example 1, so it will not be repeated), the tensile strength, shear strength and flame retardant properties of the polyurethane potting glue prepared in comparative example 1-2 are significantly worse than those of example 4, and a large number of bubbles are generated after curing. It can be seen that the use of aliphatic isocyanate or alicyclic isocyanate in the present application can reduce the sensitivity of the polyurethane potting glue to water vapor, so that the appearance of the polyurethane potting glue after curing can be smooth and free of bubbles, reducing the influence of bubbles on various properties of the polyurethane potting glue.

[0062] The difference between Comparative Example 3 and Example 1 is that the polyol part in component A adopts a polyol without terminal primary hydroxyl groups. From the data in Table 1 and Figure 7 It can be seen that the tensile strength, shear strength and flame retardant properties of the polyurethane potting glue prepared in Comparative Example 3 are significantly worse than those in Example 1, and a large number of bubbles are generated after curing. It can be seen that the polyurethane potting glue prepared by the polyol containing terminal primary hydroxyl groups in the present application is less sensitive to water vapor, so that the appearance of the polyurethane potting glue after curing can be smooth and free of bubbles, reducing the influence of bubbles on the various properties of the polyurethane potting glue.

[0063] The embodiments of this specific implementation method are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. Therefore, all equivalent changes made based on the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A low water vapor sensitive foam-free polyurethane potting glue, the raw materials used include component A and component B, characterized in that: The component A comprises the following ingredients: 35-80 parts by weight of polyol I, 0-20 parts by weight of chain extender, 5-20 parts by weight of flame retardant, 0.1-1 parts by weight of antioxidant, 0.1-1 parts by weight of defoamer and 0-1 parts by weight of catalyst; the component B comprises the following ingredients: 20-70 parts by weight of polyisocyanate, 10-40 parts by weight of polyol II and 10-20 parts by weight of diluent; wherein the polyisocyanate is aliphatic isocyanate or alicyclic isocyanate.

2. The low water vapor sensitivity and non-foaming polyurethane potting adhesive according to claim 1, characterized in that: The aliphatic isocyanate is one or more of hexamethylene diisocyanate, trimethyl-1,6-hexamethylene diisocyanate and 1,5-pentamethylene diisocyanate.

3. The low water vapor sensitivity and non-foaming polyurethane potting adhesive according to claim 1, characterized in that: The alicyclic isocyanate is one or more of isophorone diisocyanate, dicyclohexylmethane diisocyanate, methylcyclohexyl diisocyanate and cyclohexyl dimethylene diisocyanate.

4. The low water vapor sensitivity and non-foaming polyurethane potting adhesive according to claim 1, characterized in that: The polyisocyanate is an alicyclic isocyanate.

5. The low water vapor sensitivity and non-foaming polyurethane potting adhesive according to claim 1, characterized in that: The polyol I and the polyol II are both polyols with terminal primary hydroxyl groups and molecular weights between 300-6000.

6. The low water vapor sensitivity and non-foaming polyurethane potting adhesive according to claim 1, characterized in that: The flame retardant is one or more of triethyl phosphate, dimethyl methyl phosphate, diethyl ethyl phosphate and tri(butoxyethyl) phosphate.

7. The low water vapor sensitivity and non-foaming polyurethane potting adhesive according to claim 1, characterized in that: The chain extender is one or more of 4,4'-bis-sec-butylaminodiphenylmethane, dimethylthiotoluenediamine, polyetheramine and 3,5-diethyltoluenediamine.

8. The low water vapor sensitivity and non-foaming polyurethane potting adhesive according to claim 1, characterized in that: The antioxidant is octylated diphenylamine, 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid branched chain C 13 -C 15 One or more of alkyl esters, 3,5-di-tert-butyl-4-hydroxyphenylpropionate, and diphenyl isodecyl phosphite.

9. The low water vapor sensitivity and non-foaming polyurethane potting adhesive according to claim 1, characterized in that: The diluent is one or more of dioctyl terephthalate, diphenyl toluene phosphate and tricresyl phosphate.

10. A method for preparing the low water vapor sensitivity and bubble-free polyurethane potting adhesive according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Preparation of component A Mix and stir all raw materials of component A under vacuum conditions for 25-35 minutes to obtain component A; S2. Preparation of component B Stirring and dehydrating polyol II and diluent under vacuum conditions at a temperature of 115-125° C. for 1.5-2.5 hours, then cooling to 35-45° C., adding polyisocyanate, reacting under vacuum conditions at a temperature of 75-85° C. for 2-4 hours, and then cooling to obtain component B; S3. Preparation of potting glue After the component A and the component B are uniformly mixed in a weight ratio of 1: (0.8-1.2), the substrate is potted and then cured to obtain the polyurethane potting adhesive.

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