A high thermal conductivity intrinsic flame-retardant polyurethane potting compound and its preparation method

Abstract

This invention provides a high thermal conductivity intrinsically flame-retardant polyurethane potting compound and its preparation method. The polyurethane potting compound comprises component A and component B. Component A, by mass parts, includes the following raw materials: 5-10 parts of hyperbranched flame-retardant monomer, 30-50 parts of fatty diacid-based polyester polyol, 30-50 parts of modified thermally conductive filler, 0.05-0.2 parts of catalyst, and 0.5-0.8 parts of defoamer. Component B includes the following raw materials: 50-100 parts of polyisocyanate, 0.5-0.8 parts of defoamer, and 2-5 parts of molecular sieve. The high thermal conductivity intrinsically flame-retardant polyurethane potting compound provided by this invention possesses high thermal conductivity, high intrinsic flame-retardant properties, and excellent mechanical properties, and can be applied to the potting of power batteries.

Description

Technical Field

[0001] This invention belongs to the technical field of polyurethane adhesive materials, specifically relating to a high thermal conductivity intrinsic flame-retardant polyurethane potting compound and its preparation method. Background Technology

[0002] With the miniaturization and integration of electronic components, the heat generated per unit area of ​​electronic devices has increased dramatically. Excessive heat accumulation can lead to fires, making potting materials with excellent thermal conductivity and flame retardancy increasingly important in the electronics industry. Potting involves manually or automatically injecting liquid adhesive into the device, which then cures at room temperature or under heating conditions to become a high-performance insulating material. Potting compounds improve the impact resistance of electronic devices. Common potting compounds include epoxy resin, silicone, and polyurethane. Among them, polyurethane has excellent adhesion, water resistance, cold and UV resistance, acid and alkali resistance, moisture resistance, environmental friendliness, and high cost-effectiveness. It effectively overcomes the brittleness of epoxy resin and the low strength and poor adhesion of silicone resin, making it a more ideal potting and protective material for electronic components. However, the thermal conductivity of polyurethane itself is only 0.18-0.20 W·m. -1 ·K -1 Its limiting oxygen index is only 18%. Therefore, it is necessary to modify polyurethane to improve its thermal conductivity and flame retardant properties.

[0003] Chinese patent CN107216846B discloses a method for preparing and using a low-viscosity, flame-retardant, thermally conductive, solvent-free polyurethane electronic potting compound. The electronic potting compound comprises component A and component B. Component A is prepared through the following process: 100 parts by weight of castor oil, 5-15 parts by flame retardant, 1-5 parts by weight of high thermal conductivity insulating composite powder, and 0.05-0.3 parts by weight of defoamer are added to a reaction vessel, mixed evenly, and then vacuum dehydrated. A catalyst is then added... Component A is obtained by mixing 0.05-0.3 parts of the agent evenly; Component B is liquefied diphenylmethylene diisocyanate; wherein, the flame retardant is a mixture of dibromoneopentyl glycol and resorcinol bis(diphenyl phosphate) in a mass ratio of 1:3-5; the high thermal conductivity insulating composite powder is a mixture of nano-silicon carbide, nano-aluminum carbide, nano-boron carbide, nano-zinc oxide, and nano-alumina in a mass ratio of 3:(1-1.5):(1-1.4):(1-1.5):(3-4.5). This patent improves the flame retardant performance of potting compound by adding flame retardant. However, the flame retardant does not bind to the polyurethane matrix and is prone to migration and loss, which may cause the flame retardant performance of the material to decrease with the extension of service time.

[0004] Chinese patent CN116410690A discloses a polyurethane potting compound and its preparation method. The raw material formulation of this polyurethane potting compound consists of component A and component B in a mass ratio of 2-5:1. Component A comprises the following raw materials in parts by mass: 30-45 parts vegetable oil-based polyol, 20-40 parts flame retardant, 30-40 parts powder filler, 0.5-3 parts dehydrating agent, 0.1-1 part colorant, 0.3-1 part anti-settling agent, 0.05-0.3 parts defoamer, 0.2-1.0 parts catalyst, and 0.1-0.3 parts antioxidant. Component B comprises the following raw materials in parts by mass: polyisocyanate and / or plasticizer. The flame retardant in this patent is not integrated with the polyurethane matrix, and its excessive addition can negatively impact other properties of the polyurethane potting compound. Furthermore, this patent does not perform thermal conductivity modification, resulting in poor thermal conductivity of the polyurethane potting compound, making it unsuitable for potting electronic products such as power batteries.

[0005] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0006] The purpose of this invention is to provide a high thermal conductivity intrinsic flame-retardant polyurethane potting compound and its preparation method, in order to solve the problems of easy migration of current additive flame retardants and their inability to be used for potting power batteries due to poor thermal conductivity. The polyurethane potting compound provided by this invention has excellent thermal conductivity and stable and long-lasting flame-retardant properties, and can be used to pot power batteries for new energy vehicles.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A high thermal conductivity intrinsic flame-retardant polyurethane potting compound, comprising component A and component B, wherein component A comprises the following raw materials in parts by mass:

[0009] 5-10 parts of hyperbranched flame retardant monomer, 30-50 parts of fatty dicarboxylic acid-based polyester polyol, 30-50 parts of modified thermally conductive filler, 0.05-0.2 parts of catalyst and 0.5-0.8 parts of defoamer;

[0010] The B component includes the following raw materials:

[0011] 50-100 parts of polyisocyanate, 0.5-0.8 parts of defoamer, and 2-5 parts of molecular sieve.

[0012] In an optional embodiment of the present invention, the mass ratio of component A to component B is (4-5):1.

[0013] In an optional embodiment of the present invention, the hyperbranched flame retardant monomer comprises the following raw materials by mass:

[0014] 20-30 parts of dimethyl methylphosphonate, 20-30 parts of triethanolamine, and 0.5-1 parts of sodium hydroxide.

[0015] In an optional embodiment of the present invention, the modified thermally conductive filler is a hexyltrimethoxysilane-modified thermally conductive filler.

[0016] In an optional embodiment of the present invention, the thermally conductive filler is at least one of silicon carbide, alumina, and boron nitride;

[0017] The fatty dicarboxylic acid-based polyester polyol is at least one of polybutylene adipate, polyhexylene adipate, and polybutylene sebacate.

[0018] The catalyst is at least one of stannous octoate, dibutyltin dilaurate, dimorpholine diethyl ether, and dimethyl maleate.

[0019] In an optional embodiment of the present invention, the polyisocyanate is at least one selected from toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and phenyl diisocyanate.

[0020] The defoamer is at least one of BYK-1790, BYK-A525 and BYK-A535;

[0021] The molecular sieve is at least one of 3A, 4A and 5A.

[0022] This invention also provides a method for preparing the high thermal conductivity intrinsic flame-retardant polyurethane potting compound as described above, the method comprising the following steps:

[0023] Step 1: Mix hyperbranched flame retardant monomer and fatty diacid-based polyester polyol according to the formula, remove moisture, cool and then add modified thermally conductive filler, catalyst and defoamer, and disperse evenly to obtain component A.

[0024] Step 2: Mix polyisocyanate, defoamer and molecular sieve according to the formula, and disperse evenly to obtain component B;

[0025] Step 3: Mix component A and component B, degas and cure to obtain a high thermal conductivity intrinsic flame retardant polyurethane potting compound.

[0026] In an optional embodiment of the present invention, in step one, the hyperbranched flame-retardant monomer is prepared by the following steps:

[0027] Mix dimethyl methylphosphonate, triethanolamine and sodium hydroxide according to the specified ratio, stir and heat to 140-170℃, maintain the temperature for 12-24 hours, and then perform vacuum distillation at 90-110℃ and a vacuum degree of 0.09-0.1MPa. The product obtained is the hyperbranched flame retardant monomer.

[0028] In an optional embodiment of the present invention, in step one, the modified thermally conductive filler is prepared using the following steps:

[0029] Disperse 5-10 parts of thermally conductive filler into a mixed solution of 80-150 parts of ethanol and water, add 10-20 parts of n-hexyltrimethoxysilane, hydrolyze at a temperature of 65-80℃, and then obtain the modified thermally conductive filler by centrifugation, washing and freeze drying.

[0030] In an optional embodiment of the present invention, in step one, the specific operation of removing moisture is to remove moisture from the mixture under conditions of a temperature of 110-130℃ and a vacuum degree of 0.085-0.095MPa.

[0031] In step three, the specific operation of degassing is to degas the mixture under a vacuum of 0.09-0.1 MPa.

[0032] Beneficial effects:

[0033] In the high thermal conductivity intrinsic flame-retardant polyurethane potting compound of this invention, hyperbranched flame-retardant monomers can be grafted into polyurethane segments to form an intrinsic flame-retardant system. This avoids the problem of flame-retardant performance degradation caused by easy migration in additive flame retardants, and is beneficial for achieving stable and long-lasting flame-retardant performance. Simultaneously, hyperbranched monomers have numerous active sites, which can increase the crosslinking density of polyurethane molecules, thereby enhancing their mechanical properties. The addition of hyperbranched monomers can effectively solve the loss of mechanical properties caused by the addition of ordinary flame retardants. Furthermore, hyperbranched flame-retardant monomers can suppress smoke generation through free radical capture in the gas phase and char-promoting effects in the condensed phase.

[0034] The high thermal conductivity intrinsic flame retardant polyurethane potting compound provided by this invention has high thermal conductivity, high intrinsic flame retardancy, and excellent mechanical properties, and can be used for potting power batteries.

[0035] The preparation method of the high thermal conductivity intrinsic flame-retardant polyurethane potting compound provided by the present invention is simple, low-cost, highly operable, and suitable for industrial production. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0037] The present invention will now be described in detail with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0038] To address the problems of easy migration of additive flame retardants and their unsuitability for potting power batteries due to poor thermal conductivity, this invention provides a high thermal conductivity intrinsic flame-retardant polyurethane potting compound. The polyurethane potting compound provided by this invention has excellent thermal conductivity and stable and long-lasting flame retardant properties, as well as excellent mechanical properties, and can be used to pot power batteries for new energy vehicles.

[0039] The high thermal conductivity intrinsic flame-retardant polyurethane potting compound provided by this invention comprises component A and component B. Component A, by mass parts, comprises the following raw materials:

[0040] 5-10 parts of hyperbranched flame retardant monomer (e.g., 5, 6, 7, 8, 9, 10 parts, or any range between two endpoints), 30-50 parts of fatty dicarboxylic acid-based polyester polyol (e.g., 30, 35, 40, 45, 50 parts, or any range between two endpoints), 30-50 parts of modified thermally conductive filler (e.g., 30, 35, 40, 45, 50 parts, or any range between two endpoints), 0.05-0.2 parts of catalyst (e.g., 0.05, 0.1, 0.15, 0.2 parts, or any range between two endpoints), and 0.5-0.8 parts of defoamer (e.g., 0.5, 0.6, 0.7, 0.8 parts, or any range between two endpoints);

[0041] Material B comprises the following raw materials:

[0042] 50-100 parts of polyisocyanate (e.g., 50, 60, 70, 80, 90, 100 parts, or any range between two endpoints), 0.5-0.8 parts of defoamer (e.g., 0.5, 0.6, 0.7, 0.8 parts, or any range between two endpoints), and 2-5 parts of molecular sieve (e.g., 2, 3, 4, 5 parts, or any range between two endpoints).

[0043] It should be noted that the molecular sieve is used as a water-absorbing agent.

[0044] In a specific embodiment of the present invention, the mass ratio of component A to component B is (4-5):1 (e.g., 4:1, 4.5:1, 5:1, and any range between the two endpoints).

[0045] In a specific embodiment of the present invention, the hyperbranched flame retardant monomer comprises the following raw materials by mass:

[0046] 20-30 parts of dimethyl methylphosphonate (e.g., 20, 22, 25, 28, 30 parts, or any range between two endpoints), 20-30 parts of triethanolamine (e.g., 20, 22, 25, 28, 30 parts, or any range between two endpoints), and 0.5-1 part of sodium hydroxide (e.g., 0.5, 0.6, 0.7, 0.8, 0.9, 1 part, or any range between two endpoints).

[0047] In a specific embodiment of the present invention, the modified thermally conductive filler is a hexyltrimethoxysilane-modified thermally conductive filler. Hexyltrimethoxysilane is a non-polar modifier, which can effectively avoid the interaction between fillers caused by the use of polar modifiers, thereby greatly improving the stability of polyurethane potting compound.

[0048] In a specific embodiment of the present invention, the thermally conductive filler is at least one of silicon carbide, alumina, and boron nitride. Preferably, the thermally conductive filler is nanoscale silicon carbide, micron-scale alumina, or micron-scale boron nitride, wherein the particle size of the nanoscale silicon carbide is 50-500 nm, and the particle size of the micron-scale alumina and micron-scale boron nitride is 5-40 μm.

[0049] In a specific embodiment of the present invention, the fatty dicarboxylic acid-based polyester polyol is at least one of polybutylene adipate, polyhexane adipate, and polybutylene sebacate.

[0050] The catalyst is at least one of stannous octoate, dibutyltin dilaurate, dimorpholine diethyl ether, and dimethyl maleate.

[0051] The polyisocyanate is at least one of toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and phenyl diisocyanate.

[0052] The defoamer is at least one of BYK-1790, BYK-A525 and BYK-A535.

[0053] The molecular sieve has at least one of the following specifications: 3A, 4A, and 5A.

[0054] It should be noted that the defoamer in component A and component B may be the same or different, and may be independently selected from at least one of BYK-1790, BYK-A525 and BYK-A535.

[0055] This invention also provides a method for preparing the high thermal conductivity intrinsic flame-retardant polyurethane potting compound as described above, the method comprising the following steps:

[0056] Step 1: Mix hyperbranched flame retardant monomer and fatty diacid-based polyester polyol according to the formula, remove moisture, cool and then add modified thermally conductive filler, catalyst and defoamer, and disperse evenly to obtain component A.

[0057] In a specific embodiment of the present invention, the hyperbranched flame-retardant monomer is prepared by the following steps:

[0058] By mass, 20-30 parts of dimethyl methylphosphonate, 20-30 parts of triethanolamine, and 0.5-1 parts of sodium hydroxide are mixed in a flask. The mixture is then stirred and heated to 140-170°C (e.g., 140°C, 150°C, 160°C, 170°C, and any range between the two endpoints) and held at this temperature for 12-24 hours (e.g., 12 hours, 16 hours, 20 hours, 24 hours, and any range between the two endpoints). Vacuum distillation is then performed at a temperature of 90-110°C (e.g., 90°C, 100°C, 110°C, and any range between the two endpoints) and a vacuum degree of 0.09-0.1 MPa (e.g., 0.09 MPa, 0.1 MPa, and any range between the two endpoints). The resulting product is the hyperbranched flame retardant monomer.

[0059] This invention prepares a hyperbranched flame-retardant monomer via transesterification. This monomer can be grafted into polyurethane segments to form an intrinsic flame-retardant system, avoiding the flame-retardant performance degradation caused by easy migration in additive flame retardants and thus achieving stable and durable flame-retardant performance. Simultaneously, the hyperbranched monomer possesses numerous active sites, increasing the crosslinking density of polyurethane molecules and enhancing its mechanical properties. The addition of the hyperbranched monomer effectively addresses the loss of mechanical properties caused by the addition of ordinary flame retardants. Furthermore, the hyperbranched flame-retardant monomer can suppress smoke generation through free radical capture in the gas phase and char-promoting effects in the condensed phase.

[0060] In a specific embodiment of the present invention, the modified thermally conductive filler (i.e., the surface-activated thermally conductive filler) is prepared by the following steps:

[0061] Disperse 5-10 parts (e.g., 5, 6, 7, 8, 9, 10 parts, or any range between two endpoints) of thermally conductive filler into a mixed solution of 80-150 parts (e.g., 80, 90, 100, 110, 120, 130, 140, 150 parts, or any range between two endpoints) of ethanol and water. Add 10-20 parts (e.g., 10, 12, 15, 18, 20 parts, or any range between two endpoints) of n-hexyltrimethoxysilane. Hydrolyze the solution at a temperature of 65-80℃ (e.g., 65℃, 70℃, 75℃, 80℃, or any range between two endpoints). Then, centrifuge, wash, and freeze-dry the solution sequentially to obtain the modified thermally conductive filler. In the mixture of ethanol and water, the mass ratio of ethanol to water is (0.8-1.2):1 (e.g., 0.8:1, 0.9:1, 1:1, 1.2:1, and any range between the two endpoints); the freeze-drying time is 12-24h (e.g., 12h, 16h, 20h, 24h, and any range between the two endpoints).

[0062] This invention uses a silane hydrolysis reaction to activate the surface of the thermally conductive filler, which can prevent two-phase separation between the thermally conductive filler and the polyurethane matrix.

[0063] In a specific embodiment of the present invention, the specific operation for removing moisture is to remove moisture from the mixture under the conditions of a temperature of 110-130℃ (e.g., 110℃, 120℃, 130℃ and any range between two endpoints) and a vacuum of 0.085-0.095MPa (e.g., 0.085MPa, 0.09MPa, 0.095MPa, 0.1MPa and any range between two endpoints).

[0064] Step 2: Mix polyisocyanate, defoamer and molecular sieve according to the formula, and disperse evenly to obtain component B.

[0065] Step 3: Mix component A and component B, degas and cure to obtain a high thermal conductivity intrinsic flame retardant polyurethane potting compound.

[0066] In a specific embodiment of the present invention, the degassing operation involves degassing the mixture under a vacuum of 0.09-0.1 MPa (e.g., 0.09 MPa, 0.1 MPa, and any interval between two endpoints).

[0067] The following detailed description of the high thermal conductivity intrinsic flame-retardant polyurethane potting compound and its preparation method is provided through specific embodiments.

[0068] Example 1

[0069] This embodiment provides a high thermal conductivity intrinsically flame-retardant polyurethane potting compound and its preparation method, which includes the following steps:

[0070] (1) Preparation of hyperbranched flame retardant monomer: 25 parts by mass of dimethyl methylphosphonate, 24 parts by mass of triethanolamine and 1 part by mass of sodium hydroxide were mixed in a flask. The mixture was then stirred and heated to 160°C and kept at that temperature for 18 hours. After vacuum distillation at 100°C with a vacuum degree of 0.1 MPa, the product obtained was the hyperbranched flame retardant monomer.

[0071] (2) Preparation of modified thermally conductive filler (alumina): 8 parts by mass of alumina were dispersed in a mixed solution of 120 parts of ethanol / water, wherein the mass ratio of ethanol to water was 1.2:1. 15 parts of n-hexyltrimethoxysilane were added and kept at 70°C until hydrolysis was complete. After centrifugation, washing and freeze drying for 12 hours, surface-activated alumina was obtained, which is the modified thermally conductive filler.

[0072] (3) Preparation of component A: By mass, 8 parts of hyperbranched flame retardant monomer and 40 parts of polybutylene adipate were mixed and the water was removed at 120°C under a vacuum of 0.09 MPa. After cooling to room temperature, 40 parts of surface-activated alumina, 0.1 parts of catalyst dibutyltin dilaurate and 0.75 parts of defoamer BYK-A525 were added and dispersed evenly to obtain component A, which was then sealed and stored for later use.

[0073] (4) Preparation of component B: 80 parts by mass of polymethylene polyphenyl polyisocyanate, 0.65 parts of defoamer BYK-1790 and 4 parts of 4A molecular sieve are dispersed at room temperature and mixed evenly to obtain component B, which is then sealed and stored for later use.

[0074] (5) Preparation of polyurethane potting compound: Mix component A and component B at a mass ratio of 4.5:1, maintain a vacuum of 0.1MPa to degas the potting compound, and obtain a high thermal conductivity intrinsic flame retardant polyurethane potting compound after curing.

[0075] Example 2

[0076] This embodiment provides a high thermal conductivity intrinsically flame-retardant polyurethane potting compound and its preparation method, which includes the following steps:

[0077] (1) Preparation of hyperbranched flame retardant monomer: 20 parts by mass of dimethyl methylphosphonate, 20 parts by mass of triethanolamine and 0.5 parts by mass of sodium hydroxide are mixed in a flask. The mixture is then stirred and heated to 140°C and kept at that temperature for 12 hours. After vacuum distillation at 90°C with a vacuum degree of 0.1 MPa, the product obtained is the hyperbranched flame retardant monomer.

[0078] (2) Preparation of modified thermally conductive filler (silicon carbide): 5 parts by mass of silicon carbide were dispersed in a mixed solution of 80 parts of ethanol / water, wherein the mass ratio of ethanol to water was 1.2:1. 10 parts of n-hexyltrimethoxysilane were added and kept at 65°C until hydrolysis was complete. After centrifugation, washing and freeze drying for 12 hours, surface-activated silicon carbide was obtained, which is the modified thermally conductive filler.

[0079] (3) Preparation of component A: By mass, 5 parts of hyperbranched flame retardant monomer and 30 parts of polyhexyl adipate were mixed and the water was removed at 110°C under a vacuum of 0.09 MPa. After cooling to room temperature, 30 parts of surface-activated silicon carbide, 0.05 parts of catalyst stannous octoate and 0.5 parts of defoamer BYK-A535 were added and dispersed evenly to obtain component A, which was then sealed and stored for later use.

[0080] (4) Preparation of component B: 50 parts by mass of diphenylmethane diisocyanate, 0.5 parts of defoamer BYK-1790 and 2 parts of 3A molecular sieve are dispersed at room temperature and mixed evenly to obtain component B, which is then sealed and stored for later use.

[0081] (5) Preparation of polyurethane potting compound: Mix component A and component B at a mass ratio of 4:1, maintain a vacuum of 0.1 MPa to degas the potting compound, and obtain a high thermal conductivity intrinsic flame retardant polyurethane potting compound after curing.

[0082] Example 3

[0083] This embodiment provides a high thermal conductivity intrinsically flame-retardant polyurethane potting compound and its preparation method, which includes the following steps:

[0084] (1) Preparation of hyperbranched flame retardant monomer: 30 parts by mass of dimethyl methylphosphonate, 30 parts by mass of triethanolamine and 1 part by mass of sodium hydroxide are mixed in a flask. The mixture is then stirred and heated to 170°C and kept for 24 hours. After vacuum distillation at 110°C with a vacuum degree of 0.1 MPa, the product obtained is the hyperbranched flame retardant monomer.

[0085] (2) Preparation of modified thermally conductive filler (boron nitride): 10 parts by mass of boron nitride were dispersed in a mixed solution of 150 parts of ethanol / water, wherein the mass ratio of ethanol to water was 1.2:1. 20 parts of n-hexyltrimethoxysilane were added and kept at 80°C until hydrolysis was complete. After centrifugation, washing and freeze drying for 24 hours, surface-activated boron nitride was obtained, which is the modified thermally conductive filler.

[0086] (3) Preparation of component A: By mass, 10 parts of hyperbranched flame retardant monomer and 50 parts of polybutylene sebacate were mixed and the water was removed at 130°C under a vacuum of 0.09 MPa. After cooling to room temperature, 50 parts of surface-activated boron nitride, 0.2 parts of catalyst bismorpholine diethyl ether and 0.8 parts of defoamer BYK-1790 were added and dispersed evenly to obtain component A, which was then sealed and stored for later use.

[0087] (4) Preparation of component B: By mass, 100 parts of isophorone diisocyanate, 0.8 parts of defoamer BYK-A535 and 5 parts of 5A molecular sieve are dispersed at room temperature and mixed evenly to obtain component B, which is then sealed and stored for later use.

[0088] (5) Preparation of polyurethane potting compound: Mix component A and component B at a mass ratio of 5:1, maintain a vacuum of 0.1 MPa to degas the potting compound, and obtain a high thermal conductivity intrinsic flame retardant polyurethane potting compound after curing.

[0089] Comparative Example 1

[0090] This comparative example is the same as Example 1 except that hyperbranched flame retardant monomers are not added (i.e., step (1) is omitted, and the addition of hyperbranched flame retardant monomers is omitted in step (3)).

[0091] Comparative Example 2

[0092] This comparative example is the same as Example 1 except that triethanolamine is not added (i.e., the addition of triethanolamine is omitted in step (1)).

[0093] Comparative Example 3

[0094] This comparative example is the same as Example 1 except that n-hexyltrimethoxysilane is not added (i.e., step (2) is omitted, and the surface-activated alumina is replaced with ordinary alumina in step (3)).

[0095] The polyurethane potting compounds prepared in Examples 1-3 and Comparative Examples 1-3 were placed at room temperature for 72 hours, and their properties were tested. The measured performance parameters are shown in Table 1. The tensile strength and elongation at break of the polyurethane potting compounds were measured according to GB / T528-1998 standard, with type I specimens (25 mm in length) and a tensile rate of 100 mm / min. The thermal conductivity of the polyurethane potting compounds was tested according to GB / T10294-2008 standard. The vertical burning test (i.e., flame retardancy rating) of polyurethane potting compound was conducted according to GB / T 2408-2021 standard; the limiting oxygen index of polyurethane potting compound was conducted according to GB / T2406-1993 standard; the Shore D hardness of polyurethane potting compound was conducted according to GB / T 531-1999 standard; the volume resistivity of polyurethane potting compound was conducted according to GB / T 1410-2006 standard; the storage stability of the sample was determined by observing whether the polyurethane potting compound separated into layers or settled at the bottom after 30 days at 30℃.

[0096] Table 1 Performance parameters of the polyurethane potting compounds obtained in Examples 1-3 and Comparative Examples 1-3

[0097]

[0098]

[0099] As shown in Table 1, the addition of dimethyl methylphosphonate can improve the limiting oxygen index of the polyurethane potting compound. Furthermore, the hyperbranched flame-retardant monomer obtained through transesterification can significantly improve the flame-retardant properties of the polyurethane potting compound. In addition, the addition of the hyperbranched flame-retardant monomer can also improve the tensile strength of the polyurethane potting compound, indicating that the hyperbranched monomer prepared in this invention can both improve mechanical properties and impart intrinsic flame-retardant characteristics. Moreover, the thermally conductive filler modified by silane surface activation can be uniformly dispersed in the polyurethane matrix, contributing to increased storage stability and thermal conductivity. The high thermal conductivity intrinsically flame-retardant polyurethane potting compound of this invention also possesses reasonable hardness and volume resistivity.

[0100] In summary, this invention prepares hyperbranched flame-retardant monomers and surface-activated modified thermally conductive fillers, endowing polyurethane potting compounds with intrinsic flame-retardant properties and high thermal conductivity. The high thermal conductivity intrinsically flame-retardant polyurethane potting compound obtained by this invention, due to its excellent performance in various aspects, can be applied to the potting of power batteries for new energy vehicles.

[0101] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high thermal conductivity intrinsically flame-retardant polyurethane potting compound, characterized in that, The polyurethane potting compound comprises component A and component B; The preparation method of the intrinsically flame-retardant polyurethane potting compound with high thermal conductivity includes the following steps: Step 1: Mix hyperbranched flame retardant monomer and fatty diacid-based polyester polyol according to the formula, remove moisture, cool and then add modified thermally conductive filler, catalyst and defoamer, and disperse evenly to obtain component A. Step 2: Mix polyisocyanate, defoamer and molecular sieve according to the formula, and disperse evenly to obtain component B; Step 3: Mix component A and component B, degas and cure to obtain a high thermal conductivity intrinsic flame retardant polyurethane potting compound; By mass, component A comprises the following raw materials: 5-10 parts of hyperbranched flame retardant monomer, 30-50 parts of fatty dicarboxylic acid-based polyester polyol, 30-50 parts of modified thermally conductive filler, 0.05-0.2 parts of catalyst and 0.5-0.8 parts of defoamer; By mass, the hyperbranched flame retardant monomer comprises the following raw materials: 20-30 parts of dimethyl methylphosphonate, 20-30 parts of triethanolamine, and 0.5-1 parts of sodium hydroxide; The modified thermally conductive filler is a hexyltrimethoxysilane-modified thermally conductive filler; The B component includes the following raw materials: 50-100 parts polyisocyanate, 0.5-0.8 parts defoamer, and 2-5 parts molecular sieve; The modified thermally conductive filler is prepared by the following steps: 5-10 parts of thermally conductive filler are dispersed in a mixed solution of 80-150 parts of ethanol and water, 10-20 parts of n-hexyltrimethoxysilane are added, hydrolyzed at a temperature of 65-80°C, and then centrifuged, washed and freeze-dried to obtain the modified thermally conductive filler. In step one, the hyperbranched flame retardant monomer is prepared by the following steps: dimethyl methylphosphonate, triethanolamine and sodium hydroxide are mixed in proportion, stirred and heated to 140-170℃, and kept at a constant temperature for 12-24h. Then, vacuum distillation is carried out at a temperature of 90-110℃ and a vacuum degree of 0.09-0.1MPa. The product obtained is the hyperbranched flame retardant monomer. In step one, the specific operation for removing moisture is to remove moisture from the mixture under conditions of a temperature of 110-130℃ and a vacuum degree of 0.085-0.095MPa; In step three, the specific operation of degassing is to degas the mixture under a vacuum of 0.09-0.1 MPa.

2. The preparation method of the high thermal conductivity intrinsic flame-retardant polyurethane potting compound as described in claim 1, characterized in that, The mass ratio of component A to component B is (4-5):

1.

3. The preparation method of the high thermal conductivity intrinsic flame-retardant polyurethane potting compound as described in claim 1, characterized in that, The thermally conductive filler is at least one of silicon carbide, aluminum oxide, and boron nitride. The fatty dicarboxylic acid-based polyester polyol is at least one of polybutylene adipate, polyhexyl adipate, and polybutylene sebacate. The catalyst is at least one of stannous octoate, dibutyltin dilaurate, dimorpholine diethyl ether, and dimethyl maleate.

4. The preparation method of the high thermal conductivity intrinsic flame-retardant polyurethane potting compound as described in claim 1, characterized in that, The polyisocyanate is at least one of toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and phenyl diisocyanate; The defoamer is at least one of BYK-1790, BYK-A525 and BYK-A535; The molecular sieve is at least one of 3A, 4A and 5A.

5. A high thermal conductivity intrinsically flame-retardant polyurethane potting compound, characterized in that, The high thermal conductivity intrinsic flame-retardant polyurethane potting compound is prepared using the method described in any one of claims 1-4.

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