Polyurethane foaming potting material and preparation method and application thereof

Abstract

This invention relates to the field of polyurethane foam materials, specifically disclosing a polyurethane foam potting material, its preparation method, and its applications. The material comprises component A and component B, wherein component A is composed of grafted polyether polyol, flame-retardant filler, zinc stearate, water, a composite catalyst, ammonium bicarbonate, and polyethylene glycol; and component B is composed of isocyanate, triethyl phosphate, and coated molecular sieves. The mass ratio of component A to component B is 100:60~80. Compared with existing technologies, the polyurethane foam potting material prepared by this invention possesses excellent flame retardancy, heat insulation, and low water absorption properties, providing reliable protection for electronic components.

Description

Technical Field

[0001] This invention relates to the field of polyurethane foam materials technology, and in particular to a polyurethane foam potting material, its preparation method, and its application. Background Technology

[0002] Polyurethane foam is a porous polymer material made by chemically reacting isocyanates and polyols with foaming agents, catalysts, and other additives. Its core advantage lies in its exceptional designability; by precisely adjusting the raw material formulation and process parameters, its density, hardness, cell structure, and mechanical and thermal properties can be controlled. It is mainly divided into two types: flexible and rigid. Flexible polyurethane foam has an open-cell structure, is lightweight and soft, and possesses good resilience, breathability, and sound absorption. It is widely used in furniture fillings such as sofas and mattresses, car seats, clothing padding, packaging cushioning materials, and sound-absorbing cotton. Rigid polyurethane foam, on the other hand, is primarily closed-cell. Its superior thermal insulation properties, resulting from its low thermal conductivity gas, make it a widely used material, extensively used for building wall and roof insulation, cold storage panels, refrigerator and freezer insulation layers, and thermal insulation for industrial pipelines and equipment. In addition, there are semi-rigid foams used for energy-absorbing components in automotive interiors, self-skinning foams with a dense outer layer for steering wheels and shoe soles, and microporous elastomers for high-performance shoe midsoles, among other special categories. Its processing methods are flexible, including block foam cutting, molding, spraying, casting, and continuous sheet production. In summary, polyurethane foam materials, with their highly adjustable performance, lightweight, excellent thermal insulation, sound insulation, and cushioning properties, as well as diverse processing adaptability, have become an indispensable material in modern life and industry.

[0003] As a potting material, polyurethane can seal and protect the electronic components contained in a device, effectively preventing the intrusion of moisture, dust, and corrosive substances from the external environment. This places several performance requirements on polyurethane: firstly, it must have good flowability to facilitate the potting process; secondly, after curing, it must possess excellent mechanical properties, waterproof properties, adhesive properties, flame retardant properties, and electrical insulation properties to ensure reliable protection for electronic components; furthermore, it must not corrode components on the electronic circuit board.

[0004] CN113717347A discloses a polyurethane foam potting compound suitable for battery cells and its preparation method. The polyurethane foam potting compound composition for battery cells in this invention consists of a polyol component A and an isocyanate component B. The raw materials for polyol component A include special polyester polyols, vegetable oil-modified polyols, flame-retardant polyols, flame retardants, foaming agents, foam stabilizers, and delay catalysts; while the raw materials for isocyanate component B are small-molecule diols and isocyanates. This polyurethane foam potting compound for battery cells exhibits good flowability, excellent flame retardant properties, and superior resistance to environmental changes. Compared with traditional polyurethane potting compounds, it is lighter, reducing the weight of new energy vehicles. The invention also provides a corresponding preparation method, which involves first preparing polyol component A and isocyanate component B separately, then placing these two components into the hopper of a low-pressure casting machine, adjusting the proportions, and then injecting them into the gaps in the battery cell casing.

[0005] CN119307221A belongs to the field of polyurethane potting compound technology, specifically relating to a two-component hydrophobic and heat-resistant polyurethane potting compound and its preparation method. This potting compound is prepared by reacting component A and component B. Component A consists of the following raw materials in parts by weight: 17-33 parts of modified polyether polyol I, 15-27 parts of modified polyether polyol II, 18-30 parts of diisocyanate, and 20-34 parts of plasticizer; component B contains 47-64 parts of polyether polyol III, 36-53 parts of filler, and 0.15-0.35 parts of catalyst. By introducing siloxane-modified polyether polyols into the polyether polyol structure through acrylic bridging, siloxane-modified polyether polyols can be obtained. Introducing more side-ethyl, phenyl, and neopentyl structures into the polyether polyol can further improve the hydrophobic and heat-resistant properties of the raw material itself, thus giving the polyurethane potting compound strong hydrophobicity and heat resistance.

[0006] One of the core functions of polyurethane foam potting materials in the field of electronic equipment is to encapsulate and secure internal components (such as electronic modules, sensors, and circuit boards). These components may generate electrical sparks, short-circuit heat, or be exposed to environments containing flammable substances during operation, thus requiring flame retardancy. However, flame retardancy alone is insufficient to provide adequate protection for increasingly sophisticated electronic components, necessitating more versatile potting materials to meet these higher requirements. Summary of the Invention

[0007] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a polyurethane foam potting material, its preparation method and application.

[0008] Encapsulation materials are often exposed to heat generation from components or fluctuating ambient temperatures. Their heat resistance directly impacts their lifespan and protective effect. Insufficient heat resistance can lead to softening, degradation, or decreased mechanical properties (such as loss of elasticity or cracking), weakening the encapsulation of internal components and even causing a loss of insulation and shock absorption. Moisture is a major enemy of electronic devices and mechanical components; hydrophobicity effectively prevents moisture penetration, ensuring long-term stable operation. Therefore, this invention provides a flame-retardant, heat-resistant, and hydrophobic polyurethane foam encapsulation material. Boehmite is used as a flame-retardant filler, which dehydrates and absorbs heat at high temperatures, slowing the temperature rise. It transforms into dense α-Al₂O₃ at high temperatures, isolating oxygen and also serving as a reinforcing component, filling the pore walls after foaming and improving mechanical strength. Zinc and cerium form a bimetallic catalyst in coordination with acetylacetone, catalyzing the conversion of polyurea, a byproduct of polyurethane foaming, into nitrogen-based flame-retardant triazine rings, further enhancing flame retardancy. The grafted polyether polyol has hydrophobic groups grafted onto it, so the resulting foamed potting material is not easy to absorb water. Together with the dynamic migration of zinc stearate, it forms a dense hydrophobic barrier, thereby preventing water from entering the battery module.

[0009] The stearic acid coating forms a semi-permeable membrane barrier, allowing water molecules to slowly diffuse into the molecular sieve channels, ensuring that water is released as needed during the foaming process. The stearic acid in the coating can migrate to the cell walls, reducing surface tension and improving cell size uniformity. It also works synergistically with boehmite and zinc stearate to enhance cell wall toughness, resulting in better mechanical properties of the potting material.

[0010] To achieve the above objectives, the present invention provides a polyurethane foam potting material, comprising component A and component B, wherein component A is composed of the following raw materials in parts by weight: 50-70 parts grafted polyether polyol, 20-30 parts flame retardant filler, 5-8 parts zinc stearate, 0.5-1 parts water, 0.4-1 parts composite catalyst, 2-5 parts ammonium bicarbonate, and 4-10 parts polyethylene glycol; and component B is composed of the following raw materials in parts by weight: 60-80 parts isocyanate, 10-20 parts triethyl phosphate, and 2-4 parts coated molecular sieve, wherein the mass ratio of component A to component B is 100:60-80.

[0011] The method for preparing the grafted polyether polyol includes the following steps:

[0012] The polyether polyol is vacuum dehydrated and then mixed with modified monomers and catalysts. After the reaction is completed, it is post-treated to obtain the final product.

[0013] Furthermore, the modified monomer is one of 1,2-epoxyoctadecane, glycidyl oleate, or 4-tert-butylphenyl glycidyl ether.

[0014] Furthermore, the catalyst is one of boron trifluoride diethyl ether complex, tetrabutylammonium bromide, or triethylamine.

[0015] Furthermore, the flame-retardant filler is nano-boehmite.

[0016] Furthermore, the composite catalyst is obtained by mixing zinc chloride and cerium trichloride heptahydrate in ethanol, adding acetylacetone, heating and stirring, cooling and crystallizing, and then filtering and washing.

[0017] Furthermore, the isocyanate is polymeric MDI.

[0018] Furthermore, the coated molecular sieve is obtained by immersing 4A molecular sieve in a 10wt% stearic acid ethanol solution, followed by shaking and drying.

[0019] Preferably, the method for preparing the grafted polyether polyol includes the following steps:

[0020] The polyether polyol is vacuum dehydrated and then mixed with modified monomers and catalysts. The mixture is reacted at 80~110℃ and then post-treated to obtain the final product. The mass ratio of polyether polyol to modified monomers and catalysts is 100:12~20:3~5.

[0021] A method for preparing a polyurethane foam potting material includes the following steps, in parts by weight:

[0022] S1. After mixing the grafted polyether polyol with the flame retardant filler, vacuum dehydrate it and dry it until the moisture content is ≤0.03%. Then cool it down to 50~60℃, add zinc stearate and polyethylene glycol, disperse it evenly, add composite catalyst, ammonium bicarbonate and water, and stir evenly to obtain component A.

[0023] S2. After mixing polymeric MDI and triethyl phosphate at 50~60℃, add the coated molecular sieve and degas under vacuum to obtain component B.

[0024] S3. After mixing component A and component B, polyurethane foam potting material is obtained.

[0025] This invention also provides the application of the above-mentioned polyurethane foam potting material in batteries. Specifically, the freshly prepared polyurethane foam potting material is injected into the gaps in the casing containing the battery cells. After foaming, the gaps are filled, thus obtaining a fully potted battery module.

[0026] The beneficial effects of this invention are:

[0027] 1. This invention modifies polyether polyol by grafting hydrophobic groups, so the resulting foamed potting material does not easily absorb water, and together with the dynamic migration of zinc stearate, it forms a dense hydrophobic barrier, thereby preventing water from entering the battery module.

[0028] 2. This invention uses boehmite as a flame-retardant filler. It dehydrates and absorbs heat at high temperatures, slowing the temperature rise. At high temperatures, it transforms into dense α-Al₂O₃, isolating oxygen. It can also serve as a reinforcing component, filling the pore walls after foaming and improving mechanical strength. Zinc and cerium form a bimetallic catalyst under the coordination of acetylacetone, which catalyzes the polyurea byproduct produced during polyurethane foaming, converting it into a nitrogen-based flame-retardant triazine ring, thereby further enhancing flame retardancy. Detailed Implementation

[0029] Polyether polyol, model: 330N, Wanhua Chemical.

[0030] Polymer MDI, Model: PM500, Wanhua Chemical

[0031] Nano-boehmite, with an average particle size of 10~20nm, from Xuancheng Jingrui New Materials.

[0032] Polyethylene glycol, model: PEG400, Dow Chemical.

[0033] 4A molecular sieve, specifications: 1.7~2.5mm, Pingxiang Ruifu Balanced Environmental Protection New Materials.

[0034] Example 1

[0035] A method for preparing and applying a polyurethane foam potting material includes the following steps, in parts by weight:

[0036] S1. Mix 60 parts of grafted polyether polyol with 20 parts of nano boehmite and dehydrate under vacuum. Dry until the moisture content is ≤0.03% and then cool to 60℃. Add 8 parts of zinc stearate and 5 parts of polyethylene glycol. After dispersing evenly, add 0.5 parts of composite catalyst, 3 parts of ammonium bicarbonate and 0.6 parts of water. Stir evenly to obtain component A.

[0037] S2. Mix 70 parts of polymeric MDI and 12 parts of triethyl phosphate at 60°C, then add 4 parts of coated molecular sieve, and degas under vacuum to obtain component B.

[0038] S3. Mix component A and component B at a mass ratio of 100:70 to obtain polyurethane foam potting material; then inject it into the gaps in the housing containing the battery cells. After foaming, the gaps are filled, and the battery module with complete potting is obtained.

[0039] The method for preparing the grafted polyether polyol includes the following steps:

[0040] The polyether polyol was vacuum dehydrated and then reacted with a complex of 1,2-epoxyoctadecane and boron trifluoride diethyl ether at 80°C. After the reaction was completed, alkali was added for neutralization, followed by filtration and drying to obtain the final product. The mass ratio of the polyether polyol to the complex of 1,2-epoxyoctadecane and boron trifluoride diethyl ether was 100:15:5.

[0041] The composite catalyst was obtained by mixing 13.6 parts of zinc chloride and 7.45 parts of cerium trichloride heptahydrate in 200 parts of ethanol, adding 22 parts of acetylacetone, heating to 80°C and stirring for 3 hours, cooling and crystallizing, and then filtering and washing.

[0042] The coated molecular sieve was obtained by immersing 100 parts of 4A molecular sieve in 200 parts of 10wt% stearic acid ethanol solution, shaking for 30 minutes, and then drying.

[0043] Example 2

[0044] It is basically the same as Example 1, except that the grafted polyether polyol is different;

[0045] The method for preparing the grafted polyether polyol includes the following steps:

[0046] The polyether polyol was vacuum dehydrated and then reacted with glycidyl oleate and tetrabutylammonium bromide at 110°C. After the reaction was completed, the polyether polyol was washed with hot water at 80°C, the catalyst was removed by separation, and then the polyether polyol was dehydrated under reduced pressure to obtain the final product. The mass ratio of polyether polyol to glycidyl oleate and tetrabutylammonium bromide was 100:20:3.

[0047] Example 3

[0048] It is basically the same as Example 1, except that the grafted polyether polyol is different;

[0049] The method for preparing the grafted polyether polyol includes the following steps:

[0050] The polyether polyol was dehydrated under vacuum and then reacted with 4-tert-butylphenyl glycidyl ether and triethylamine at 110°C. After the reaction was completed, it was dehydrated under reduced pressure to obtain the product. The mass ratio of polyether polyol to 4-tert-butylphenyl glycidyl ether and triethylamine was 100:12:4.

[0051] Compare with Example 1

[0052] A method for preparing and applying a polyurethane foam potting material includes the following steps, in parts by weight:

[0053] S1. Mix 60 parts of polyether polyol with 20 parts of nano boehmite and dehydrate under vacuum. Dry until the moisture content is ≤0.03% and then cool to 60℃. Add 8 parts of zinc stearate and 5 parts of polyethylene glycol. After dispersing evenly, add 0.5 parts of composite catalyst, 3 parts of ammonium bicarbonate and 0.6 parts of water. Stir evenly to obtain component A.

[0054] S2. Mix 70 parts of polymeric MDI and 12 parts of triethyl phosphate at 60°C, then add 4 parts of coated molecular sieve, and degas under vacuum to obtain component B.

[0055] S3. Mix component A and component B at a mass ratio of 100:70 to obtain polyurethane foam potting material; then inject it into the gaps in the housing containing the battery cells. After foaming, the gaps are filled, and the battery module with complete potting is obtained.

[0056] The composite catalyst was obtained by mixing 13.6 parts of zinc chloride and 7.45 parts of cerium trichloride heptahydrate in 200 parts of ethanol, adding 22 parts of acetylacetone, heating to 80°C and stirring for 3 hours, cooling and crystallizing, and then filtering and washing.

[0057] The coated molecular sieve was obtained by immersing 100 parts of 4A molecular sieve in 200 parts of 10wt% stearic acid ethanol solution, shaking for 30 minutes, and then drying.

[0058] Compare with Example 2

[0059] A method for preparing and applying a polyurethane foam potting material includes the following steps, in parts by weight:

[0060] S1. Mix 60 parts of grafted polyether polyol with 20 parts of aluminum hydroxide and dehydrate under vacuum. Dry until the moisture content is ≤0.03% and then cool to 60℃. Add 8 parts of zinc stearate and 5 parts of polyethylene glycol. After dispersing evenly, add 0.5 parts of composite catalyst, 3 parts of ammonium bicarbonate and 0.6 parts of water. Stir evenly to obtain component A.

[0061] S2. Mix 70 parts of polymeric MDI and 12 parts of triethyl phosphate at 60°C, then add 4 parts of coated molecular sieve, and degas under vacuum to obtain component B.

[0062] S3. Mix component A and component B at a mass ratio of 100:70 to obtain polyurethane foam potting material; then inject it into the gaps in the housing containing the battery cells. After foaming, the gaps are filled, and the battery module with complete potting is obtained.

[0063] The method for preparing the grafted polyether polyol includes the following steps:

[0064] The polyether polyol was vacuum dehydrated and then reacted with a complex of 1,2-epoxyoctadecane and boron trifluoride diethyl ether at 80°C. After the reaction was completed, alkali was added for neutralization, followed by filtration and drying to obtain the final product. The mass ratio of the polyether polyol to the complex of 1,2-epoxyoctadecane and boron trifluoride diethyl ether was 100:15:5.

[0065] The composite catalyst was obtained by mixing 13.6 parts of zinc chloride and 7.45 parts of cerium trichloride heptahydrate in 200 parts of ethanol, adding 22 parts of acetylacetone, heating to 80°C and stirring for 3 hours, cooling and crystallizing, and then filtering and washing.

[0066] The coated molecular sieve was obtained by immersing 100 parts of 4A molecular sieve in 200 parts of 10wt% stearic acid ethanol solution, shaking for 30 minutes, and then drying.

[0067] Compare with Example 3

[0068] A method for preparing and applying a polyurethane foam potting material includes the following steps, in parts by weight:

[0069] S1. Mix 60 parts of grafted polyether polyol with 20 parts of nano boehmite and dehydrate under vacuum. Dry until the moisture content is ≤0.03% and then cool to 60℃. Add 8 parts of zinc stearate and 5 parts of polyethylene glycol. After dispersing evenly, add 3 parts of ammonium bicarbonate and 0.6 parts of water. Stir evenly to obtain component A.

[0070] S2. Mix 70 parts of polymeric MDI and 12 parts of triethyl phosphate at 60°C, then add 4 parts of coated molecular sieve, and degas under vacuum to obtain component B.

[0071] S3. Mix component A and component B at a mass ratio of 100:70 to obtain polyurethane foam potting material; then inject it into the gaps in the housing containing the battery cells. After foaming, the gaps are filled, and the battery module with complete potting is obtained.

[0072] The method for preparing the grafted polyether polyol includes the following steps:

[0073] The polyether polyol was vacuum dehydrated and then reacted with a complex of 1,2-epoxyoctadecane and boron trifluoride diethyl ether at 80°C. After the reaction was completed, alkali was added for neutralization, followed by filtration and drying to obtain the final product. The mass ratio of the polyether polyol to the complex of 1,2-epoxyoctadecane and boron trifluoride diethyl ether was 100:15:5.

[0074] The coated molecular sieve was obtained by immersing 100 parts of 4A molecular sieve in 200 parts of 10wt% stearic acid ethanol solution, shaking for 30 minutes, and then drying.

[0075] Test Example 1

[0076] The mechanical properties, flame retardancy, and heat resistance of the polyurethane foam potting materials prepared in the examples and control examples were tested. Tensile strength and elongation at break were tested according to GB / T 528-2009 standard, using type I specimens (25 mm in length) and a tensile rate of 100 mm / min. Flame retardancy was tested according to GB / T 2408-2021 standard using a horizontal and vertical combustion tester. The initial thermal decomposition temperature was determined using a differential scanning calorimeter.

[0077] Table 1

[0078] Experimental protocol Tensile strength / MPa Elongation at break / % Flame retardant rating Thermal decomposition temperature / °C Example 1 2.9 253.2 V-0 302.3 Example 2 2.8 248.1 V-0 300.1 Example 3 3.2 265.8 V-0 330.5 Compare with Example 1 2.5 220.3 V-1 298.6 Compare with Example 2 2.2 201.3 V-2 280.4 Compare with Example 3 2.4 210.6 V-2 250.3

[0079] As shown in Table 1, the polyurethane foam potting material prepared by this invention possesses good mechanical properties, flame retardancy, and heat resistance. A comparison with Comparative Examples 1 to 3 reveals that using boehmite as a flame-retardant filler allows for dehydration and heat absorption at high temperatures, delaying temperature rise. It transforms into dense α-Al₂O₃ at high temperatures, isolating oxygen and serving as a reinforcing component to fill the pore walls after foaming, thus improving mechanical strength. Compared to aluminum hydroxide, its performance improvement is significantly higher. Zinc-cerium, coordinated with acetylacetone, forms a bimetallic catalyst that catalyzes the polyurea byproduct generated during polyurethane foaming, converting it into a nitrogen-based flame-retardant triazine ring, thereby enhancing flame retardancy. The grafted polyether polyol, through modification and grafting of hydrophobic groups, results in a foam potting material that is less prone to water absorption. The modified monomer in Example 3 not only possesses hydrophobic groups but also rigid phenyl groups, resulting in a higher thermal decomposition temperature and better heat resistance.

[0080] Test Example 2

[0081] The water absorption of the polyurethane foam potting materials prepared in the examples and control examples was tested. The polyurethane potting compound was formed into cylinders with a bottom diameter and height of 5 cm, and their mass (m0) was recorded. These cylinders were then immersed in water at room temperature for 30 days. After removal and drying, their mass was measured and recorded as m1. The water absorption rate of the sample = (m1 - m0) / m0 * 100 (%).

[0082] Table 2

[0083] Experimental protocol Water absorption rate / % Example 1 1.48 Example 2 1.46 Example 3 1.51 Compare with Example 1 3.62 Compare with Example 2 1.68 Compare with Example 3 1.71

[0084] As shown in Table 2, the grafted polyether polyol in this invention, through modification, grafts hydrophobic groups, resulting in a foamed potting material that is less prone to water absorption. Together with the dynamic migration of zinc stearate, it forms a dense hydrophobic barrier, preventing moisture from entering the battery module. Therefore, the final foamed potting material has low water absorption, which provides excellent protection for electronic devices. The water absorption rates of Examples 1 and 2 are lower than those of Example 3. This may be because the modified monomers used in Examples 1 and 2 all have more hydrophobic long-chain alkyl groups, which are more hydrophobic than the phenyl and tert-butyl groups in Example 3, and therefore less prone to water absorption.

[0085] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A polyurethane foam potting material, characterized in that, The product comprises component A and component B. Component A consists of the following raw materials in parts by weight: 50-70 parts grafted polyether polyol, 20-30 parts flame retardant filler, 5-8 parts zinc stearate, 0.5-1 parts water, 0.4-1 parts composite catalyst, 2-5 parts ammonium bicarbonate, and 4-10 parts polyethylene glycol. Component B consists of the following raw materials in parts by weight: 60-80 parts isocyanate, 10-20 parts triethyl phosphate, and 2-4 parts coated molecular sieve. The ratio of component A to component B is 100:60-80. The method for preparing the grafted polyether polyol includes the following steps: The polyether polyol was vacuum dehydrated and then mixed with the modified monomer and catalyst I. The mixture was reacted at 80~110℃ and then post-treated to obtain the final product. The mass ratio of polyether polyol to modified monomer and catalyst I was 100:12~20:3~5. The modified monomer is one of 1,2-epoxyoctadecane, glycidyl oleate, or 4-tert-butylphenyl glycidyl ether. The catalyst I is one of boron trifluoride diethyl ether complex, tetrabutylammonium bromide or triethylamine; The flame-retardant filler is nano-boehmite; The composite catalyst is obtained by mixing zinc chloride and cerium trichloride heptahydrate in ethanol, adding acetylacetone, heating and stirring, cooling and crystallizing, and then filtering and washing.

2. The polyurethane foam potting material as described in claim 1, characterized in that, The isocyanate is polymeric MDI.

3. The polyurethane foam potting material as described in claim 1, characterized in that, The coated molecular sieve was obtained by immersing 4A molecular sieve in a 10wt% stearic acid ethanol solution, followed by shaking and drying.

4. A method for preparing the polyurethane foam potting material as described in any one of claims 1-3, characterized in that, The steps include the following, in parts by weight: S1. After mixing the grafted polyether polyol with the flame retardant filler, vacuum dehydrate it and dry it until the moisture content is ≤0.03%. Then cool it down to 50~60℃, add zinc stearate and polyethylene glycol, disperse it evenly, add composite catalyst, ammonium bicarbonate and water, and stir evenly to obtain component A. S2. Mix isocyanate and triethyl phosphate at 50~60℃, add to coated molecular sieve, and degas under vacuum to obtain component B; S3. After mixing component A and component B, polyurethane foam potting material is obtained.

5. The application of the polyurethane foam potting material as described in any one of claims 1 to 3 in batteries.