A polyurethane potting compound, a method for preparing the polyurethane potting compound, and its applications.

Abstract

This invention discloses a polyurethane potting compound, a method for preparing the polyurethane potting compound, and its applications. The polyurethane potting compound is formed by mixing and curing component A and component B. Component A comprises the following raw materials: 5-20 parts by weight of castor oil, one or two of polycaprolactone polyol and polycarbonate diol with a total mass of 5-12 parts, 5-15 parts by weight of polytetrahydrofuran diol, 49-68 parts by weight of inorganic filler, and 6-15 parts by weight of additives. Component B is a curing agent, and its raw materials include: 40-80 parts by weight of polymethylene polyphenyl isocyanate and 20-60 parts by weight of carbodiimide-modified diphenylmethane diisocyanate. This invention can reduce the internal stress of the polyurethane potting compound.

Description

Technical Field

[0001] This invention relates to the packaging of electronic devices, and particularly to a polyurethane potting compound, a method for preparing the polyurethane potting compound, and its applications. Background Technology

[0002] Internal stress generated inside electronic devices and other electronic components due to thermal shock (thermal expansion and contraction) is the main cause of various defects such as encapsulation cracks and delamination. Therefore, reducing the internal stress of the potting compound can make electronic devices have high reliability.

[0003] Commonly available potting compounds include epoxy potting compounds, silicone potting compounds, and polyurethane potting compounds. Conventional epoxy potting compounds have high hardness, but under low-temperature conditions (-55℃), thermal shrinkage generates significant internal stress, leading to cracking. Chinese patent CN119799234A discloses a method of mixing a bridge shell toughening agent with terminal epoxy polybutadiene rubber and adding it to epoxy resin to form a special island structure. This reduces the internal stress of the epoxy potting compound and improves its resistance to thermal shock. However, its modification cost is too high, significantly increasing the potting cost of conventional products such as electronic devices. Furthermore, silicone potting compounds have low mechanical strength and poor adhesion, and their large volume expansion when heated (125℃) can cause deformation of the casing of electronic devices.

[0004] Polyurethane potting compounds possess excellent low-temperature resistance and impact resistance, and their hardness is adjustable with moderate bond strength, making them more suitable for potting electronic devices and other electronic components. However, polyurethane potting compounds exhibit higher internal stress under high-temperature conditions compared to epoxy potting compounds, and their long-term resistance to high temperatures and humidity is not very good, thus failing to fully meet the potting requirements of electronic devices and other electronic components.

[0005] The present invention mainly focuses on the rational design of key material types and their proportions in two-component polyurethane potting compounds, further reducing their internal stress under high and low temperature conditions, and providing a reliable material for potting electronic devices or electronic systems to meet their requirements in terms of resistance to thermal shock, high temperature and humidity, flame retardancy and environmental protection, and service life. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to provide a polyurethane potting compound, a method for preparing polyurethane potting compound and its application, to further reduce the internal stress of polyurethane potting compound under high and low temperature conditions, and to provide a reliable material for potting electronic devices to meet their requirements in terms of resistance to thermal shock, high temperature and humidity, flame retardancy and environmental protection, and service life.

[0007] As a first aspect of the present invention, the technical solution of the provided polyurethane potting compound is as follows:

[0008] A polyurethane potting compound, wherein: it is formed by mixing and curing component A and component B;

[0009] The raw materials of component A include: 5-20 parts by weight of castor oil, one or two of polycaprolactone polyol and polycarbonate diol with a total mass of 5-12, 5-15 parts by weight of polytetrahydrofuran diol, 49-68 parts by weight of inorganic filler, and 6-15 parts by weight of additives.

[0010] Component B is a curing agent, the raw materials of which include: 40-80 parts by weight of polymethylene polyphenyl isocyanate and 20-60 parts by weight of carbodiimide-modified diphenylmethane diisocyanate.

[0011] Preferably, the castor oil has a hydroxyl value of 162-168 mg KOH / g.

[0012] Preferably, the polycaprolactone polyol has a molecular weight of 500 to 4000 and a functionality of 2 or 3.

[0013] Preferably, the polycarbonate diol has a molecular weight of 500 to 3000.

[0014] Preferably, the polytetrahydrofuran diol has a molecular weight of 250 to 3000.

[0015] Preferably, the inorganic filler is selected from any one or more of calcium carbonate, silicon dioxide, aluminum hydroxide, and aluminum oxide.

[0016] Preferably, the additive is selected from any one or more of flame retardants, catalysts, antioxidants, coupling agents, dispersants, defoamers, anti-settling agents, and colorants.

[0017] As a second aspect of the present invention, the technical solution of the method for preparing polyurethane potting compound is as follows:

[0018] A method for preparing a polyurethane potting compound according to any one of the first aspects above includes: firstly mixing and preparing component A and component B separately, and then mixing and curing component A and component B to form a polyurethane potting compound.

[0019] As a third aspect of the present invention, the provided embodiment of the polyurethane potting compound is described in the form of reaction products as follows:

[0020] A polyurethane potting compound comprising three or four of the following structural formulas:

[0021] Glycerol-(-OOC-R2-O-CO-NH-)3

[0022] R1-NH-CO-O-(-CH2CH2CH2CH2O-) m-CO-NH-

[0023] R1-NH-CO-O-(CH2)6-O-(-CO-O-(CH2)6-O-) m -CO-NH-

[0024] R1-NH-CO-O-(-(CH2)5-CO) m -ORO-(CO-(CH2)5-) n -O-CO-NH-

[0025] Where R1 is a polymethylene polyphenyl group or a carbodiimide-modified diphenylmethane group, Glycerol is a glycerol skeleton, R2 is a long-chain alkyl group of castor oil, m and n represent the degree of polymerization, and R represents an aliphatic segment.

[0026] As a fourth aspect of the present invention, the provided embodiment of the electronic device is as follows:

[0027] An application of a polyurethane potting compound, wherein the polyurethane potting compound described in any one of the first or third aspects above is potted into an electronic device.

[0028] The beneficial effects of this invention are as follows:

[0029] 1. The two-component polyurethane potting compound of the present invention uses one or two of castor oil, polycaprolactone polyol and polycarbonate diol, and polytetrahydrofuran diol as the main polyol, and polymethylene polyphenyl isocyanate and carbodiimide modified diphenylmethane diisocyanate as the main curing agent. It not only has low viscosity and good fluidity, low internal stress after curing, and low water absorption, but also shows no cracking or delamination after 500 cycles of thermal shock (-55℃~125℃). It also has the characteristics of high temperature and high humidity resistance (electrical), and good flame retardancy, which can meet the needs of potting and protecting electronic devices or electronic systems.

[0030] 2. The curing temperature of the two-component polyurethane potting compound of the present invention is not high, and its preparation process is relatively simple, with clear steps and easy operation. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the embodiments of this invention will be described in detail below. However, the specific implementation of this invention is not limited thereto. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0032] As explained in the background section, existing polyurethane potting compounds have excessive internal stress at high temperatures, which can lead to defects in electronic devices after thermal shock tests. This manifests as cracking of the potting compound inside some products or delamination between the potting compound and the outer shell.

[0033] It is generally understood by those skilled in the art that low molecular weight polyester polyols (such as those with a molecular weight below 10,000) can increase the internal stress of the system. The main reason for this is related to their molecular structure characteristics and shrinkage behavior during the curing process, as follows:

[0034] (1) Due to the characteristics of molecular structure, low molecular weight polyester polyols contain more ester groups. These polar groups are prone to forming intramolecular hydrogen bonds during the curing process, which leads to enhanced interaction between molecular chain segments. When polyols react with isocyanates (one of the raw materials of the curing agent in component B of this invention) to form urethane structures, this hydrogen bonding effect will restrict the movement of chain segments, thereby generating greater stress during the curing process;

[0035] (2) Caused by shrinkage behavior during curing. Low molecular weight polyester polyols have shorter molecular chains and more significant volume shrinkage during curing. This shrinkage difference will cause local stress concentration. If other polymers (such as polyethers, one of the raw materials of component A of this invention, polytetrahydrofuran diol, is a polyether) are present in the system, the difference in thermal expansion coefficients between different components will exacerbate the formation of internal stress.

[0036] The above understanding is also confirmed in Chinese patent CN120349764A, which clearly states that adding low molecular weight polyester polyols can increase the internal stress of the system.

[0037] Furthermore, it is generally understood by those skilled in the art that when the raw materials of component A of the polyurethane potting compound include castor oil and polytetrahydrofuran diol, the polyurethane potting compound will have good low-temperature flexibility, which is also mentioned in Chinese patent CN110272709B. However, at high temperatures, the long-chain aliphatic groups in castor oil and the ether bonds in polytetrahydrofuran diol will move more violently, which will lead to greater internal stress in the polyurethane potting compound.

[0038] However, the molecular weights of polycaprolactone polyol and polycarbonate diol are generally less than 10,000. Therefore, for those skilled in the art, selecting one or two of castor oil, polycaprolactone polyol, and polycarbonate diol, or polytetrahydrofuran diol as the raw material for component A, and isocyanate as the raw material for component B, would subjectively be considered an infeasible approach. This is because, based on the above analysis, their combination would exacerbate the increase in internal stress of the polyurethane potting compound at high temperatures.

[0039] However, the inventors of this application were not influenced by the conventional knowledge of those skilled in the art. The inventors of this application noticed that if polycaprolactone polyol or polycarbonate diol is added to castor oil and polytetrahydrofuran diol, rigid ester groups or carbonate groups will be introduced, which can reduce the thermal motion of the overall molecular chain and help reduce the internal stress of polyurethane potting compound. To this end, the inventors repeatedly designed and verified the overall formula and proportion, and finally obtained the technical solution of this invention. It not only successfully reduced the internal stress of polyurethane potting compound at high temperature, so that electronic devices will not have defects such as potting compound cracking or delamination between potting compound and shell after thermal shock test, but also improved the long-term high temperature and high humidity resistance of potting compound by utilizing the hydrolysis resistance of carbonate groups or ether bonds.

[0040] Specifically, the polyurethane potting compound of the present invention is formed by mixing and curing component A and component B;

[0041] The raw materials of component A include: 5-20 parts by weight of castor oil, 5-12 parts by weight of one or two of polycaprolactone polyol and polycarbonate diol, 5-15 parts by weight of polytetrahydrofuran diol, 49-68 parts by weight of inorganic filler, and 6-15 parts by weight of additives.

[0042] Component B is a curing agent, and its raw materials include: 40-80 parts by weight of polymethylene polyphenyl isocyanate and 20-60 parts by weight of carbodiimide-modified diphenylmethane diisocyanate.

[0043] In embodiments of the present invention, the reaction product after curing the mixture of component A and component B includes three or four of the following structural formulas:

[0044] Glycerol-(-OOC-R2-O-CO-NH-)3 (Structural Formula 1)

[0045] R1-NH-CO-O-(-CH2CH2CH2CH2O-) m -CO-NH- (Structural Formula 2)

[0046] R1-NH-CO-O-(CH2)6-O-(-CO-O-(CH2)6-O-) m -CO-NH- (Structural Formula 3)

[0047] R1-NH-CO-O-(-(CH2)5-CO) m -ORO-(CO-(CH2)5-) n -O-CO-NH- (Structural Formula 4)

[0048] Where R1 is a polymethylene polyphenyl group or a carbodiimide-modified diphenylmethane group, Glycerol is a glycerol skeleton, R2 is a long-chain alkyl group of castor oil, m and n represent the degree of polymerization, and R represents an aliphatic segment.

[0049] In embodiments of the present invention, the cured polyurethane potting compound is opaque, highly cross-linked, and highly hydrophobic, exhibiting strong adhesion to civilian or military electronic devices. The cured product does not leave powdery residue when cut, has a Shore D hardness of 30 to 70, and a density of 1 g / cm³. 3 Up to 1.6 g / cm 3 .

[0050] As a specific example, the hydroxyl value of castor oil was selected to be 162-168 mg KOH / g.

[0051] As a specific embodiment, the molecular weight of the polycaprolactone polyol is selected to be between 500 and 4000, and the functionality is selected to be 2 or 3. Further, the molecular weight of the polycaprolactone polyol is preferably between 1000 and 2500.

[0052] As a specific embodiment, the molecular weight of the polycarbonate diol is selected to be between 500 and 3000. Further, the molecular weight of the polycarbonate diol is preferably between 500 and 1500. Further, the polycarbonate diol is obtained by copolymerization of 1,5-pentanediol and 1,6-hexanediol, and is purchased from Ube Chemicals.

[0053] As a specific example, the molecular weight of polytetrahydrofuran diol is selected to be between 250 and 3000. More specifically, the molecular weight of polytetrahydrofuran diol is preferably between 650 and 2000. Furthermore, the polytetrahydrofuran diol is purchased from Hyosung Chemical or Mitsubishi Chemical.

[0054] As a specific embodiment, the inorganic filler is selected from any one or more of calcium carbonate, silica, aluminum hydroxide, and alumina. Micron-sized silica, micron-sized aluminum hydroxide, and micron-sized alumina are preferred, with a particle size of 5-30 μm.

[0055] As a specific example, the additive is selected from any one or more of flame retardants, catalysts, antioxidants, coupling agents, dispersants, defoamers, anti-settling agents, and colorants.

[0056] As a specific example, the additives selected are flame retardants, coupling agents, dispersants, and defoamers.

[0057] As a specific embodiment, the flame retardant is one or more of ammonium polyphosphate powder flame retardants or liquid halogen-free phosphorus-containing flame retardants, preferably micron-sized ammonium polyphosphate with a particle size of 10-20 μm.

[0058] As a specific embodiment, the coupling agent is selected from any one or more of KH550, KH560, KH570, and KH580, with KH550 or KH560 being preferred.

[0059] As a specific embodiment, the dispersant is preferably either BYK W980 or BYK P104 from BYK Company.

[0060] As a specific embodiment, the defoamer is preferably either BYK A535 or BYK A530 from BYK Corporation.

[0061] The following examples illustrate how the present invention is implemented, and comparative examples verify the beneficial effects of the present invention:

[0062] Example 1

[0063] This embodiment provides a polyurethane potting compound, which is prepared by mixing component A and component B in a mass ratio of A:B of 5:1.

[0064] The raw materials for component A include: 12 parts by weight of castor oil, 9 parts by weight of polycaprolactone polyol PCL1000, 9 parts by weight of polytetrahydrofuran diol PTMEG1000, 47 parts by weight of aluminum hydroxide (particle size 20μm), 16 parts by weight of silica (particle size 5μm), 5 parts by weight of ammonium polyphosphate, 0.5 parts by weight of coupling agent KH550, 0.5 parts by weight of dispersant BYK W980, and 0.3 parts by weight of defoamer BYK A535;

[0065] Component B is a curing agent, and its raw materials include: 50 parts by weight of polymethylene polyphenyl isocyanate and 50 parts by weight of carbodiimide-modified diphenylmethane diisocyanate.

[0066] It should be noted that: PCL is the industry abbreviation for polycaprolactone polyol, and the value following it is the molecular weight; PTMEG is the industry abbreviation for polytetrahydrofuran diol, and the value following it is the molecular weight; other examples are the same and will not be repeated.

[0067] The preparation process of this two-component polyurethane potting compound is as follows:

[0068] Step 1: The liquid raw materials of component A, castor oil, polycaprolactone polyol and polytetrahydrofuran ether diol, are stirred and dehydrated in a reactor at 110℃ and -98Kpa for 1.5 hours. The water content is reduced to less than 0.05%, and the mixture is cooled to 60℃ for later use. The inorganic fillers, aluminum hydroxide and silicon dioxide, are baked in an oven at 110℃ for 2.5 hours. The water content is reduced to less than 0.2%, and the mixture is cooled to 60℃ for later use.

[0069] Step 2: Prepare component A and component B separately.

[0070] Method for preparing component A: The liquid component obtained in step one is put into a reaction vessel. After stirring is started, the inorganic fillers aluminum hydroxide and silicon dioxide from step one are added in sequence. The mixture is stirred for 3 hours at 80℃ and -98KPa. After cooling to 60℃, the auxiliary agents ammonium polyphosphate, coupling agent, dispersant and defoamer are added. Stirring is continued for 0.5 hours. The vacuum is turned off and the stirring is stopped. The material is discharged to obtain component A.

[0071] Method for preparing component B: The liquid raw materials for preparing component B, polymethylene polyphenyl isocyanate and carbodiimide modified diphenylmethane diisocyanate, are added to another reactor and stirred for 1.5 hours at 40℃ and -98KPa. The vacuum is then turned off and the stirring is stopped. Component B is then discharged.

[0072] Step 3: Mix component A and component B obtained in step 2 at a mass ratio of 5:1, cure at 25°C for 18 hours, and then heat to 60°C for 3 hours to cure. The resulting reaction product is polyurethane potting compound.

[0073] Example 2

[0074] This embodiment provides a polyurethane potting compound, which is prepared by mixing component A and component B in a mass ratio of A:B of 6:1.

[0075] The raw materials for component A include: 14 parts by weight of castor oil, 8 parts by weight of polycarbonate diol PCDL1000, 8 parts by weight of polytetrahydrofuran diol PTMEG2000, 51 parts by weight of aluminum hydroxide (particle size 15μm), 10 parts by weight of silica (particle size 3μm), 6 parts by weight of ammonium polyphosphate, 0.5 parts by weight of coupling agent KH560, 0.6 parts by weight of dispersant BYK W980, and 0.2 parts by weight of defoamer BYK A535;

[0076] Component B is a curing agent, and its raw materials include: 50 parts by weight of polymethylene polyphenyl isocyanate and 50 parts by weight of carbodiimide-modified diphenylmethane diisocyanate.

[0077] The preparation process of this two-component polyurethane potting compound is as follows:

[0078] Step 1: The liquid raw materials of component A, castor oil, polycarbonate glycol, and polytetrahydrofuran ether glycol, are stirred and dehydrated in a reactor at 110°C and -98 kPa for 1.5 hours. The water content is reduced to less than 0.05%, and the mixture is cooled to 60°C for later use. The inorganic fillers, aluminum hydroxide and silicon dioxide, are baked in an oven at 110°C for 2.5 hours. The water content is reduced to less than 0.2%, and the mixture is cooled to 60°C for later use.

[0079] Step 2: Prepare component A and component B separately.

[0080] Method for preparing component A: The liquid component obtained in step one is put into a reaction vessel. After stirring is started, the inorganic fillers aluminum hydroxide and silicon dioxide from step one are added in sequence. The mixture is stirred for 3 hours at 80℃ and -98KPa. After cooling to 60℃, the auxiliary agents ammonium polyphosphate, coupling agent, dispersant and defoamer are added. Stirring is continued for 0.5 hours. The vacuum is turned off and the stirring is stopped. The material is discharged to obtain component A.

[0081] Method for preparing component B: The liquid raw materials for preparing component B, polymethylene polyphenyl isocyanate and carbodiimide modified diphenylmethane diisocyanate, are added to another reactor and stirred for 1.5 hours at 40℃ and -98KPa. The vacuum is then turned off and the stirring is stopped. Component B is then discharged.

[0082] Step 3: Mix component A and component B obtained in step 2 at a mass ratio of 6:1, cure at 25°C for 18 hours, and then heat to 60°C for 3 hours to cure. The resulting reaction product is polyurethane potting compound.

[0083] Example 3

[0084] This embodiment provides a polyurethane potting compound, which is prepared by mixing component A and component B in a mass ratio of A:B of 6:1.

[0085] The raw materials for component A include: 16 parts by weight of castor oil, 7 parts by weight of polycaprolactone polyol PCL2000, 7 parts by weight of polytetrahydrofuran diol PTMEG1000, 55 parts by weight of aluminum hydroxide (particle size 15μm), 7 parts by weight of silica (particle size 3μm), 6 parts by weight of ammonium polyphosphate, 0.6 parts by weight of coupling agent KH560, 0.55 parts by weight of dispersant BYK W980, and 0.3 parts by weight of defoamer BYK A535;

[0086] Component B is a curing agent, comprising: 60 parts by weight of polymethylene polyphenyl isocyanate; and 40 parts by weight of carbodiimide-modified diphenylmethane diisocyanate.

[0087] The preparation process of this two-component polyurethane potting compound is as follows:

[0088] Step 1: The liquid raw materials of component A, castor oil, polycaprolactone polyol, and polytetrahydrofuran ether diol, are stirred and dehydrated in a reactor at 110°C and -98 kPa for 1.5 hours. The water content is reduced to less than 0.05%, and the mixture is cooled to 60°C for later use. The inorganic fillers, aluminum hydroxide and silicon dioxide, are baked in an oven at 110°C for 2.5 hours. The water content is reduced to less than 0.2%, and the mixture is cooled to 60°C for later use.

[0089] Step 2: Prepare component A and component B separately.

[0090] Method for preparing component A: The liquid component obtained in step one is put into a reaction vessel. After stirring is started, the inorganic fillers aluminum hydroxide and silicon dioxide from step one are added in sequence. The mixture is stirred for 3 hours at 80℃ and -98KPa. After cooling to 60℃, the auxiliary agents ammonium polyphosphate, coupling agent, dispersant and defoamer are added. Stirring is continued for 0.5 hours. The vacuum is turned off and the stirring is stopped. The material is discharged to obtain component A.

[0091] Method for preparing component B: The liquid raw materials for preparing component B, polymethylene polyphenyl isocyanate and carbodiimide modified diphenylmethane diisocyanate, are added to another reactor and stirred for 1.5 hours at 40℃ and -98KPa. The vacuum is then turned off and the stirring is stopped. Component B is then discharged.

[0092] Step 3: Mix component A and component B obtained in step 2 at a mass ratio of 6:1, cure at 25°C for 18 hours, and then heat to 60°C for 6 hours to cure. The resulting reaction product is polyurethane potting compound.

[0093] Example 4

[0094] This embodiment provides a polyurethane potting compound, which is prepared by mixing component A and component B in a mass ratio of A:B of 4:1.

[0095] The raw materials for component A include: 10 parts by weight of castor oil, 5 parts by weight of polycaprolactone polyol PCL2000, 5 parts by weight of polycarbonate diol PCDL1000, 10 parts by weight of polytetrahydrofuran diol PTMEG1000, 43 parts by weight of aluminum hydroxide (particle size 20μm), 20 parts by weight of silica (particle size 5μm), 5 parts by weight of ammonium polyphosphate, 0.6 parts by weight of coupling agent KH550, 0.6 parts by weight of dispersant BYK W980, and 0.2 parts by weight of defoamer BYK A535;

[0096] Component B is a curing agent, and its raw materials include: 40 parts by weight of polymethylene polyphenyl isocyanate and 60 parts by weight of carbodiimide-modified diphenylmethane diisocyanate.

[0097] The preparation process of this two-component polyurethane potting compound is as follows:

[0098] Step 1: The liquid raw materials of component A, castor oil, polycaprolactone polyol, polycarbonate diol, and polytetrahydrofuran ether diol, are stirred and dehydrated in a reactor at 110°C and -98 kPa for 1.5 hours. The water content is reduced to less than 0.05%, and the mixture is cooled to 60°C for later use. The inorganic fillers, aluminum hydroxide and silicon dioxide, are baked in an oven at 110°C for 2.5 hours. The water content is reduced to less than 0.2%, and the mixture is cooled to 60°C for later use.

[0099] Step 2: Prepare component A and component B separately.

[0100] Method for preparing component A: The liquid component obtained in step one is put into a reaction vessel. After stirring is started, the inorganic fillers aluminum hydroxide and silicon dioxide from step one are added in sequence. The mixture is stirred for 3 hours at 80℃ and -98KPa. After cooling to 60℃, the auxiliary agents ammonium polyphosphate, coupling agent, dispersant and defoamer are added. Stirring is continued for 0.5 hours. The vacuum is turned off and the stirring is stopped. The material is discharged to obtain component A.

[0101] Method for preparing component B: The liquid raw materials for preparing component B, polymethylene polyphenyl isocyanate and carbodiimide modified diphenylmethane diisocyanate, are added to another reactor and stirred for 1.5 hours at 40℃ and -98KPa. The vacuum is then turned off and the stirring is stopped. Component B is then discharged.

[0102] Step 3: Mix component A and component B obtained in step 2 at a mass ratio of 4:1, cure at 25°C for 12 hours, and then heat to 60°C for 6 hours to cure. The resulting reaction product is polyurethane potting compound.

[0103] Comparative Example 1

[0104] This comparative example provides a polyurethane potting compound, which is prepared by mixing component A and component B in a mass ratio of A:B of 5:1.

[0105] The raw materials for component A include: 20 parts by weight of castor oil, 10 parts by weight of polytetrahydrofuran diol PTMEG1000, 53 parts by weight of aluminum hydroxide (particle size 20μm), 8 parts by weight of silica (particle size 5μm), 5 parts by weight of ammonium polyphosphate, 0.4 parts by weight of coupling agent KH550, 0.6 parts by weight of dispersant BYK W980, and 0.2 parts by weight of defoamer BYK A535;

[0106] Component B is a curing agent, and its raw materials include: 70 parts by weight of polymethylene polyphenyl isocyanate and 30 parts by weight of carbodiimide-modified diphenylmethane diisocyanate.

[0107] The preparation process of this two-component polyurethane potting compound is as follows:

[0108] Step 1: The liquid raw materials castor oil and polytetrahydrofuran ether glycol of component A are stirred and dehydrated in a reactor at 110°C and -98 kPa for 1.5 hours. The water content is reduced to less than 0.05%, and the mixture is cooled to 60°C for later use. The inorganic fillers aluminum hydroxide and silicon dioxide are baked in an oven at 110°C for 2.5 hours. The water content is reduced to less than 0.2%, and the mixture is cooled to 60°C for later use.

[0109] Step 2: Prepare component A and component B separately.

[0110] Method for preparing component A: The liquid component obtained in step one is put into a reaction vessel. After stirring is started, the inorganic fillers aluminum hydroxide and silicon dioxide from step one are added in sequence. The mixture is stirred for 3 hours at 80℃ and -98KPa. After cooling to 60℃, the auxiliary agents ammonium polyphosphate, coupling agent, dispersant and defoamer are added. Stirring is continued for 0.5 hours. The vacuum is turned off and the stirring is stopped. The material is discharged to obtain component A.

[0111] Method for preparing component B: The liquid raw materials for preparing component B, polymethylene polyphenyl isocyanate and carbodiimide modified diphenylmethane diisocyanate, are added to another reactor and stirred for 1.5 hours at 40℃ and -98KPa. The vacuum is then turned off and the stirring is stopped. Component B is then discharged.

[0112] Step 3: Mix component A and component B obtained in step 2 at a mass ratio of 7:1, cure at 25°C for 12 hours, and then heat to 60°C for 6 hours to cure. The resulting reaction product is polyurethane potting compound.

[0113] After the polyurethane potting compounds of Examples 1-4 and Comparative Example 1 were placed at room temperature for 7 days, their performance parameters were tested using the following methods:

[0114] Mixed viscosity at 23℃: Refer to Method 1, Section 7.1 of GB / T 2794-2022 "Determination of Viscosity of Adhesives": Single-cylinder rotational viscometer method;

[0115] Thermal conductivity: Refer to ASTM D-5470-01, "Characteristic test for thermal conductivity of thin thermally conductive solid electrical insulating materials";

[0116] Volume shrinkage rate: Refer to national standard GB / T 24148.9-2014 "Plastics Unsaturated Polyester Resin (UP-R) Part 9: Determination of Total Volume Shrinkage Rate";

[0117] Water absorption rate: Refer to Method 1 in Section 6.3 of the national standard GB / T 1034-2008 "Determination of Water Absorption Rate of Plastics": Determination of water absorption at 23℃;

[0118] Flame retardancy: Refer to Test Method B—Vertical Burning Method in GB / T 2408-2021 "Determination of Burning Performance of Plastics";

[0119] Volume resistivity: Refer to the national standard GB / T 40719-2021 "Determination of volume and / or surface resistivity of vulcanized rubber or thermoplastic rubber";

[0120] Breakdown voltage: Refer to national standard GB / T 42125.10-2022 "Safety requirements for electrical equipment for measuring, controlling and laboratory use - Part 10: Particular requirements for equipment for measuring insulation resistance and testing dielectric strength";

[0121] Double 85 (energized) test 500H: According to the product's power-on requirements, continuously age for 500H under conditions of 85℃ temperature and 85%RH humidity. After the test, check whether the electrical performance is normal.

[0122] Thermal shock (-55℃~125℃) test cycle 500 times: High and low temperature shock test chamber program: -55℃ for 25min, 5min to 125℃, 125℃ for 25min, 5min to -55℃, 1 hour for one cycle, 500 cycles; after the test, check whether the electrical performance is normal.

[0123] The measured performance parameters are shown in Table 1:

[0124]

[0125] Table 1. Comparison of performance parameters of polyurethane potting compounds in Examples 1-4 and Comparative Example 1

[0126] Comparing Comparative Example 1 with Examples 1, 2, 3, and 4, it can be seen that when Comparative Example 1 does not add polycaprolactone polyol or polycarbonate diol, a small number of products will show cracks after the potting compound is poured into the electronic device and cured. Other examples have no defects, indicating that the greater the internal stress of the potting compound, the worse the reliability of the electronic device product.

[0127] Furthermore, a comparison of Comparative Example 1 and Examples 1, 2, 3, and 4 shows that when the water absorption rate of Comparative Example 1 is too high, the potting compound will exhibit poor pressure resistance after being cured in the electronic device and subjected to a double 85 (charged) test. Other examples are without defects, indicating that the higher the water absorption rate of the potting compound, the worse its resistance to high temperature and humidity (charged) will be.

[0128] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A polyurethane casting compound characterized in that: formed by mixing and curing the A component and the B component; the raw materials of the A component include: castor oil 5-20 parts by mass, one or both of polycaprolactone polyol and polycarbonate diol with a total of 5-12 parts by mass, polytetrahydrofuran diol 5-15 parts by mass, inorganic filler 49-68 parts by mass, additives 6-15 parts by mass; the B component is a curing agent, and its raw materials include: polymethylene polyphenyl isocyanate 40-80 parts by mass, carbodiimide modified diphenyl methane diisocyanate 20-60 parts by mass.

2. The polyurethane casting compound of claim 1, wherein: The castor oil has a hydroxyl value of 162-168 mgKOH / g.

3. The polyurethane casting compound of claim 1, wherein: The polycaprolactone polyol has a molecular weight of 500 to 4000 and a functionality of 2 or 3.

4. The polyurethane casting compound of claim 1 wherein: The polycarbonate diol has a molecular weight of 500 to 3000.

5. The polyurethane casting compound of claim 1 wherein: The polytetrahydrofuran diol has a molecular weight of 250 to 3000.

6. The polyurethane casting compound of claim 1 wherein: The inorganic filler is selected from any one or several of calcium carbonate, silicon dioxide, aluminum hydroxide, and aluminum oxide.

7. The polyurethane casting compound of claim 1 wherein: The additives are selected from any one or several of flame retardants, catalysts, antioxidants, coupling agents, dispersants, defoaming agents, anti-settling agents, and colorants.

8. Process for the production of the polyurethane casting compound according to any one of claims 1 to 7, characterized in that The A component and the B component are prepared separately, and then mixed and cured to form a polyurethane pouring sealant.

9. Use of a polyurethane casting compound, characterized in that: The polyurethane pouring sealant of any one of claims 1 to 7 is poured into an electronic device.

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