Moisture-resistant and heat-resistant polyurethane foam potting adhesive and application thereof

Abstract

The application provides a moisture and heat resistant polyurethane foam potting adhesive for cylindrical battery packs and application, the polyurethane foam potting adhesive comprises two components A and B, the A component comprises antioxidant BHT-X grafted polymethylene polyphenyl isocyanate, polymethylene polyphenyl isocyanate and other isocyanate components, and the B component comprises polyether polyol, polyester polyol, catalyst, crosslinking agent, chain extender, foam stabilizer, foaming agent, flame retardant and stabilizer.The moisture and heat resistant polyurethane foam potting adhesive provided by the application can avoid performance loss caused by the migration of small molecule antioxidants in a humid and hot environment, and simultaneously has the advantages of good workability, excellent fluidity, low thermal conductivity, UL94-V0 level flame retardancy, high strength and high toughness and the like.The application also discloses an operation system for cylindrical battery potting, which can realize more uniform, complete filling, bonding and fixing of cylindrical battery packs.

Description

Technical Field

[0001] This invention belongs to the field of electronic potting compounds, specifically relating to a moisture- and heat-resistant polyurethane foam potting compound for filling gaps in cylindrical battery packs and its application. Background Technology

[0002] The development of new energy vehicles is progressing rapidly, but pain points such as range, charging efficiency, cost, and safety still need to be addressed. Compared to prismatic and blade batteries, large cylindrical batteries have advantages such as high energy density, fast charging, high safety, and long lifespan, which are well-suited to the future passenger vehicle demand for long range and ultra-fast charging, making them the optimal solution for future mid-to-high-end electric vehicles. However, after cylindrical batteries are arranged into battery packs, a large number of gaps are formed in the middle. If conventional potting compounds are used, it will result in a large overall weight and high cost of the battery pack. Therefore, low-density polyurethane foam potting compounds have become a new option. Currently, existing polyurethane foam potting compounds have achieved properties such as good flowability, low thermal conductivity, and flame retardancy. However, polyurethane foam potting compounds typically have a service life of over several decades after potting, and there is currently limited research on their weather resistance.

[0003] CN 116874730A discloses a foamed polyurethane for power batteries, which is composed of a mixture of component A and component B. By weight, component A contains 51-63 parts of isocyanate-terminated polyurethane prepolymer, 60-85 parts of organic solvent, 4.5-7.5 parts of stabilizer, 1.5-3 parts of chain extender, 12-22 parts of flame retardant, 2-4.5 parts of dehydrating agent, 1.5-3.5 parts of anti-aging agent, 1.3-2.5 parts of catalyst, 2.5-4.5 parts of coupling agent, and 2-3.5 parts of butyltin mercaptan. Component B contains 45-62 parts of oligomeric diol, 3.5-9 parts of chain extender, 15-27 parts of thermally conductive filler, and 12-15 parts of flame retardant. The polyurethane foam formulation disclosed in this invention exhibits good hydrolysis resistance under normal temperature water bath testing conditions and good aging resistance under ultraviolet light aging testing conditions. However, it does not cover high temperature and high humidity testing conditions. Since the antioxidant 2,6-di-tert-butyl-4-cresol (BHT) in this invention is a small molecule, it is easy to migrate to the outer layer of the foam under high temperature and high humidity conditions, leading to performance degradation or aging and cracking.

[0004] Therefore, it is of great significance to develop a polyurethane foam potting compound that can uniformly distribute and lock small antioxidant molecules inside the foam to improve the product's aging resistance, while also possessing advantages such as good workability, excellent flowability, low thermal conductivity, UL94-V0 flame retardancy, high strength and high toughness. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of poor resistance to moisture and heat, easy migration of antioxidants, and poor flowability of polyurethane foam in the prior art. It provides a moisture-resistant polyurethane foam potting compound and operating system for cylindrical battery packs. The polyurethane foam potting compound has a longer milky whitening time and a shorter molding time, which can combine workability and production efficiency.

[0006] The technical solution of this invention is as follows:

[0007] On one hand, the present invention provides a moisture- and heat-resistant polyurethane foam potting compound for cylindrical battery packs, wherein the polyurethane foam comprises component A and component B;

[0008] Component A includes:

[0009] a1) Polymethylene polyphenyl isocyanate grafted with antioxidant BHT-X, wherein BHT-X is one or a mixture of two of BHT-OH and BHT-COOH;

[0010] a2) One or more mixtures of polymethylene polyphenyl isocyanate, polymethylene polyphenyl isocyanate prepolymerized from polymer polyol, toluene diisocyanate, and terephthalic diisocyanate;

[0011] The mass ratio of a1) to a2) is 0 to 2, excluding 0; for example, the mass ratio is 0.5, 1, 1.5;

[0012] Component B includes:

[0013] b1) Polyether polyol A: 0-60 parts by weight;

[0014] b2) Polyether polyol B: 0-55 parts by weight;

[0015] b3) Polyester polyol: 0-30 parts by weight;

[0016] b4) Catalyst: 0.1-0.6 parts by mass;

[0017] b5) Crosslinking agent: 0-3 parts by weight;

[0018] b6) Chain extender: 0-3 parts by weight;

[0019] b7) Foaming agent: 0-3 parts by weight;

[0020] b8) Foaming agent: 0.1-0.5 parts by weight;

[0021] b9) Flame retardant: 0-15 parts by weight;

[0022] b10) Stabilizer: 0-3 parts by weight;

[0023] Where b1), b2), and b3) are not all 0 at the same time.

[0024] In this mixture, component A and component B are mixed at a molar ratio of -NCO group to active hydrogen of 1.05 to 2.

[0025] The antioxidant BHT-X in component A is BHT-OH (3,5-di-tert-butyl-4-hydroxybenzyl alcohol) or BHT-COOH (3,5-di-tert-butyl-4-hydroxybenzoic acid);

[0026] The polymethylene polyphenyl isocyanate can be Wanhua Chemical PM200 or BASF M10, etc.

[0027] The reaction process of BHT-X grafted polymethylene polyphenyl isocyanate is as follows:

[0028] The molar ratio of BHT-X to polymethylene polyphenyl isocyanate was set at (1-5:100). The mixture was placed in a three-necked flask and stirred at 60℃-80℃ for 2-3 hours. After the reaction was complete, BHT-X-grafted polymethylene polyphenyl isocyanate was obtained. The reaction process of antioxidants BHT-OH and BHT-COOH with polymethylene polyphenyl isocyanate is as follows:

[0029]

[0030] To reduce the viscosity of component A, improve the flowability of the system during foaming, and ensure the strength and toughness of the foam after foaming, antioxidant BHT-X grafted modified polymethylene polyphenyl isocyanate can be compounded with polymethylene polyphenyl isocyanate, polymethylene polyphenyl isocyanate prepolymerized from polymer polyol, toluene diisocyanate, terephthalic diisocyanate, etc. After compounding, the mass concentration of -NCO in component A system is 18-30%, and the viscosity of component A system is 100-2000 cps.

[0031] Component B is an isocyanate reactive component.

[0032] b1) The polyether polyol A is one or more of glycerol-based polyoxypropylene polyol, sucrose-based polyoxypropylene polyol, or diethylene glycol-based polyoxypropylene, with a hydroxyl value of 200-760 mgKOH / g, preferably 300-600 mgKOH / g; and an average molecular weight of 200-1000, preferably 250-550; for example R2303, etc.

[0033] The b2) polyether polyol B is a glycerol polyoxypropylene oxide ethylene oxide polyol, with a PO content of 40-80 wt% in its molecular structure, a hydroxyl value of 20-300 mgKOH / g, preferably 50-200 mgKOH / g, and a molecular weight of 2000-4000, preferably 3000-4000; for example F3156D, etc.

[0034] The polyester polyol mentioned in b3) is an aromatic polyester polyol with a hydroxyl value of 300-500 mgKOH / g. For example, PS3152 (Stepan); the aromatic polyester polyol has good compatibility with the system, and because it contains benzene rings, it can enhance the temperature resistance and strength of the foamed material.

[0035] The catalyst described in b4) is a physical blend of two or more catalysts selected from the following: modified tertiary amine delayed gel catalyst, N,N-dimethylcyclohexylamine, triethylenediamine solution, pentamethyldiethylenetriamine, potassium acetate solution, and trimethylhydroxyethylpropanediamine. The modified tertiary amine delayed gel catalyst is selected from delayed catalysts such as A300 (Shanghai Yexing) and ECOADD 8301 (Shanghai Yexing). To ensure the fluidity of the liquid in the early stage and the gelation and surface drying speed in the later stage of foam material foaming, i.e., to balance the operation time and production efficiency in the production process, the delayed gel catalyst needs to be used in combination with a conventional catalyst.

[0036] The crosslinking agent (b5) is selected from polyols with trifunctionality or above, such as polyether polyols with glycerol, triethanolamine or sorbitol as initiators; the crosslinking agent has a large hydroxyl value, generally above 1000 mg KOH / g. A small amount of crosslinking agent can significantly increase the amount of isocyanate, which can further increase the crosslinking density of the foam material. At the same time, after the isocyanate reacts, it forms hard segment molecular chains, which improves the hardness and strength of the foam material.

[0037] The chain extender (b6) is selected from difunctional small molecule polyols, such as diethylene glycol, 1,4-butanediol, 1,2-propanediol, neopentyl glycol, etc.; the chain extender is connected to isocyanate groups at both ends, which act as flexible segments between hard molecular chains and reduce the brittleness of the foam material.

[0038] The foam stabilizer mentioned in b7) is a polyether-modified silicone oil, which is a polyether side chain grafted onto the polysiloxane main chain to play the roles of emulsification, nucleation and foam stabilization. Wanhua Chemical's 8180 and Evonik's B8404 can be selected.

[0039] The foaming agent described in b8) is water, which can react with isocyanate groups to generate carbamate and CO2;

[0040] The flame retardant mentioned in b9) is one or more of the following liquid flame retardants: tri(2-1-chloropropyl) phosphate, dimethyl methyl phosphate, diethyl ethyl phosphate, dimethyl propyl dimethyl ester, etc.

[0041] The b10) stabilizer is selected from monomeric carbodiimide or polycarbodiimide.

[0042] Unlike prismatic or blade batteries that transfer heat to heat sinks via thermally conductive adhesive, the new generation of large cylindrical batteries features a serpentine cooling band. Coolant flows within this band to actively cool the cylindrical cells. The cooling band adheres closely to the sides of the cylindrical cells and weaves around them, further minimizing the gaps between the cells. Traditional potting methods, such as first placing the battery pack in position and then applying foam potting compound to fill the gaps, cannot effectively pot the new generation of large cylindrical batteries with cooling bands. The cooling band restricts the flow of the foam, resulting in many gaps remaining unfilled. To address the shortcomings of traditional potting methods…

[0043] On the other hand, the present invention provides a method for potting cylindrical battery packs, the method comprising the following steps:

[0044] 1) First, mix component A and component B according to the ratio of isocyanate molar amount to active hydrogen molar amount of (1.05-2):1 to obtain a mixture of components A and B, wherein the active hydrogen is a hydrogen atom that can react with isocyanate;

[0045] 2) Pour the mixture of components A and B into the battery compartment at a temperature of 25–45°C;

[0046] 3) Place the battery pack into the battery compartment until the mixture of components A and B is fully foamed.

[0047] In embodiments of the present invention, the density of the foamed and cured foam material is 100-400 kg / m³. 3 Preferred weight: 100-300 kg / m 3 ;

[0048] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0049] 1) Grafting the small molecule antioxidant BHT-X onto polymethylene polyphenyl isocyanate prevents its migration under high temperature and high humidity conditions, which would lead to a decrease in foam performance.

[0050] 2) Polyurethane foam potting compound has good workability and fluidity, which can achieve uniform and complete filling, bonding and fixing of cylindrical battery packs;

[0051] 3) The foaming agent of the polyurethane foam potting compound is water, and it does not use flammable and explosive foaming agents such as cyclopentane and n-pentane. At the same time, it meets the UL94-V0 flame retardant level and has good safety when used as a battery potting compound.

[0052] 4) Compared with traditional filling operations, the cylindrical battery potting system can achieve more uniform and complete filling of cylindrical battery packs, and play a better role in bonding, fixing, shock absorption and heat insulation. Attached Figure Description

[0053] Figure 1 The foam core of the cylindrical battery is removed after the cylindrical battery pack is filled. Detailed Implementation

[0054] The present invention will be further described below through specific embodiments.

[0055] Raw material information:

[0056] Polymethylene polyphenyl isocyanate: PM200

[0057] BHT-OH (3,5-di-tert-butyl-4-hydroxybenzyl alcohol): Merck Chemicals

[0058] BHT-COOH (3,5-di-tert-butyl-4-hydroxybenzoic acid)

[0059] Homemade antioxidant BHT-X grafted polymethylene polyphenyl isocyanate A1: 2g of BHT-OH and 100g of PM200 were mixed and placed in a three-necked flask. The mixture was stirred at 80°C for 3 hours to obtain a brownish-yellow liquid with a viscosity of 260 cps and an isocyanate content of 29.1%.

[0060] Homemade antioxidant BHT-X grafted polymethylene polyphenyl isocyanate A2: 4g of BHT-OH and 100g of PM200 were mixed and placed in a three-necked flask. The mixture was stirred at 80°C for 3 hours to obtain a brownish-yellow liquid with a viscosity of 370 cps and an isocyanate content of 28.2%.

[0061] Homemade antioxidant BHT-X grafted polymethylene polyphenyl isocyanate A3: 6g of BHT-OH and 100g of PM200 were mixed and placed in a three-necked flask. The mixture was stirred at 80°C for 3 hours to obtain a brownish-yellow liquid with a viscosity of 630 cps and an isocyanate content of 27.3%.

[0062] Homemade antioxidant BHT-X grafted polymethylene polyphenyl isocyanate B1: 2g of BHT-COOH and 100g of PM200 were mixed and placed in a three-necked flask. The mixture was stirred at 80°C for 3 hours to obtain a brownish-yellow liquid with a viscosity of 230 cps and an isocyanate content of 29.2%.

[0063] Homemade antioxidant BHT-X grafted with polymethylene polyphenyl isocyanate B2: 4g of BHT-COOH and 100g of PM200 were mixed and placed in a three-necked flask. The mixture was stirred at 80°C for 3 hours to obtain a brownish-yellow liquid with a viscosity of 310 cps and an isocyanate content of 28.4%.

[0064] Homemade antioxidant BHT-X grafted with polymethylene polyphenyl isocyanate B3: 6g of BHT-COOH and 100g of PM200 were mixed and placed in a three-necked flask. The mixture was stirred at 80°C for 3 hours to obtain a brownish-yellow liquid with a viscosity of 560 cps and an isocyanate content of 27.6%.

[0065] Polyether polyol A: R2303, Wanhua Chemical;

[0066] Polyether polyol B: F3156D, Wanhua Chemical;

[0067] Polyester polyol: PS3152, Nanjing Jinling Stepan Company;

[0068] Catalyst 1: Modified tertiary amine catalyst 8301v, Shanghai Yexing Industrial Co., Ltd.

[0069] Catalyst 2: Dimethylcycloamine PC-8, Wanhua Chemical;

[0070] Catalyst 3: 33% potassium acetate solution, Aladdin;

[0071] Crosslinking agents: glycerin, Inokai;

[0072] Chain extender: 1,4-Butanediol, Inokai;

[0073] Foaming agent: B 8404, Evonik Industries;

[0074] Foaming agent: pure water

[0075] Flame retardant 1: TCPP, Taian Dino Chemical New Materials;

[0076] Flame retardant 2: DMMP, Qingdao Lianmei Chemical Co., Ltd.

[0077] Stabilizer: Polycarbodiimide, Shanghai Langyi Functional Materials.

[0078] The foam material formulation is shown in Table 1:

[0079]

[0080]

[0081] Test method for resistance to damp heat aging: 100g each of component A and component B, both at 23±1℃, were poured into a plastic cup. The speed of the high-speed disperser was adjusted to 2000rpm / min, and the mixture of components A and B was stirred for 30s. The mixture was then allowed to stand until foaming was complete. The cured foam was cut into 30mm×30mm×5mm cubes and 150mm×25mm×10mm strips using a vertical cutter for testing foam density, compressive strength, tensile properties, and flame retardant properties. The foam was placed in an aging chamber at 85℃ / 80% relative humidity, and the change in tensile strength was continuously tracked to characterize its resistance to damp heat. The test data are shown in Table 2. Comparative Example 1 cracked after 12 weeks and could not be tested further. The foam prepared by the comparative example and the example with added antioxidants did not crack.

[0082] Table 2:

[0083]

[0084] As shown in the table above, the foam prepared in Comparative Example 1 without antioxidants cracked after aging in week 12. The foams prepared in Comparative Examples 2 and 3, where antioxidants were directly added to component B, experienced a 23-38% performance decrease in week 12. The moisture-heat resistant polyurethane foam prepared in this invention experienced a 10-20% performance decrease in week 12, and its performance remained stable throughout the aging process. Therefore, the polyurethane foam material prepared in this invention, with antioxidant grafted onto the polymethylene polyphenyl isocyanate of component A, exhibits superior moisture-heat aging resistance compared to foam materials prepared without antioxidants or with antioxidants directly added to component B. Furthermore, the formulation proposed in this invention uses all-water foaming, does not contain flammable and explosive foaming agents such as cyclopentane, and has a UL94-V0 flame retardant rating, making it a battery encapsulation foam with excellent safety.

[0085] Cylindrical battery pack potting simulation test:

[0086] According to the types and quantities of raw materials in the examples in Table 2, the A and B components, which were mixed uniformly at 23°C, were poured into a plastic cup. The speed of the high-speed disperser was adjusted to 2000 rpm / min, and the mixture of A and B components was stirred for 30 seconds. Then, the mixture of A and B components was poured into the battery compartment at 45°C, and the battery pack was placed into the battery compartment as soon as possible. Waiting for foaming to complete was allowed. To observe the flowability of the foam material between the battery pack gaps, the cover was not applied temporarily. After the cylindrical battery pack was filled, the foam body of the cylindrical battery was removed. Figure 1 It can be seen that the polyurethane foam potting compound formulation disclosed in this invention has good fluidity and workability, and the proposed cylindrical battery potting system can ensure that the gaps between cylindrical batteries are uniformly filled, thereby achieving battery bonding, fixation, shock absorption, and heat insulation.

[0087] Through the above specific embodiments, those skilled in the art can easily implement the present invention. However, the present invention is not limited to the above specific embodiments. Any improvements to the present invention, equivalent substitutions of raw materials for the products of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A moisture- and heat-resistant polyurethane foam potting compound, wherein the polyurethane foam comprises component A and component B; Component A includes: a1) Polymethylene polyphenyl isocyanate grafted with antioxidant BHT-X, wherein BHT-X is one or a mixture of two of BHT-OH and BHT-COOH; a2) One or more mixtures of polymethylene polyphenyl isocyanate, polymethylene polyphenyl isocyanate prepolymerized from polymer polyol, toluene diisocyanate, and terephthalic diisocyanate; The mass ratio of a1) to a2) is 0 to 2, excluding 0; Component B includes: b1) Polyether polyol A: 0-60 parts by weight; b2) Polyether polyol B: 0-55 parts by weight; b3) Polyester polyol: 0-30 parts by weight; b4) Catalyst: 0.1-0.6 parts by mass; b5) Crosslinking agent: 0-3 parts by weight; b6) Chain extender: 0-3 parts by weight; b7) Foaming agent: 0-3 parts by weight; b8) Foaming agent: 0.1-0.5 parts by weight; b9) Flame retardant: 0-15 parts by weight; b10) Stabilizer: 0-3 parts by weight; Where b1), b2), and b3) are not all 0 at the same time.

2. The moisture- and heat-resistant polyurethane foam potting compound material as described in claim 1, characterized in that, Component A and Component B are mixed at a molar ratio of -NCO group to active hydrogen of 1.05 to 2; and / or, the polymethylene polyphenyl isocyanate can be Wanhua Chemical PM200 or BASF M10.

3. The moisture- and heat-resistant polyurethane foam potting compound material as described in claim 1 or 2, characterized in that, The reaction process of BHT-X grafted polymethylene polyphenyl isocyanate is as follows: the molar ratio of BHT-X to polymethylene polyphenyl isocyanate is (1-5:100), the two are mixed and placed in a three-necked flask, and stirred at 60℃~80℃ for 2~3h. After the reaction is completed, BHT-X grafted polymethylene polyphenyl isocyanate is obtained.

4. The moisture- and heat-resistant polyurethane foam potting compound material according to any one of claims 1-3, characterized in that, The b1) polyether polyol A is one or more of glycerol-based polyoxypropylene polyol, sucrose-based polyoxypropylene polyol, or diethylene glycol-based polyoxypropylene, with a hydroxyl value of 200-760 mgKOH / g, preferably 300-600 mgKOH / g; and an average molecular weight of 200-1000, preferably 250-550; and / or, the b2) polyether polyol B is glycerol polyoxypropylene ethylene oxide polyol, with a PO content of 40-80 wt% in the molecular structure, a hydroxyl value of 20-300 mgKOH / g, preferably 50-200 mgKOH / g, and a molecular weight of 2000-4000, preferably 3000-4000.

5. The moisture- and heat-resistant polyurethane foam potting compound material according to any one of claims 1-4, characterized in that, The b3) polyester polyol is an aromatic polyester polyol with a hydroxyl value of 300-500 mg KOH / g; and / or, the b4) catalyst is composed of two or more catalysts selected from modified tertiary amine delayed gel catalyst, N,N-dimethylcyclohexylamine, triethylenediamine solution, pentamethyldiethylenetriamine, potassium acetate solution, and trimethylhydroxyethylpropanediamine through physical blending. Preferably, the modified tertiary amine delayed gel catalyst is selected from A300 (Shanghai Yexing) and ECOADD 8301 (Shanghai Yexing).

6. The moisture- and heat-resistant polyurethane foam potting compound material according to any one of claims 1-5, characterized in that, The crosslinking agent (b5) is selected from polyols with 3 or higher functionality, such as polyether polyols with glycerol, triethanolamine or sorbitol as initiators; and / or the chain extender (b6) is selected from small molecule polyols with 2 functionality, such as diethylene glycol, 1,4-butanediol, 1,2-propanediol, neopentyl glycol.

7. The moisture- and heat-resistant polyurethane foam potting compound material according to any one of claims 1-6, characterized in that, The foaming agent b7) is a polyether-modified silicone oil, such as Wanhua Chemical's 8180 or Evonik's B8404; and / or, the foaming agent b8) is water.

8. The moisture- and heat-resistant polyurethane foam potting compound material according to any one of claims 1-7, characterized in that, The flame retardant b9) is one or more of the liquid flame retardants such as tris(2-1-chloropropyl) phosphate, dimethyl methyl phosphate, diethyl ethyl phosphate, and dimethylpropyl dimethyl phosphate; and / or, the stabilizer b10) is selected from monomeric carbodiimide or polycarbodiimide.

9. The application of the moisture- and heat-resistant polyurethane foam potting compound material as described in any one of claims 1-7 in the potting of cylindrical battery packs, wherein the application comprises the following steps: 1) First, mix component A and component B according to the ratio of isocyanate molar amount to active hydrogen molar amount of (1.05-2):1 to obtain a mixture of components A and B, wherein the active hydrogen is a hydrogen atom that can react with isocyanate; 2) Pour the mixture of components A and B into the battery compartment at a temperature of 25–45°C; 3) Place the battery pack into the battery compartment until the mixture of components A and B is fully foamed.

10. The application as described in claim 9, characterized in that, The density of the fully foamed material is 100-400 kg / m³. 3 Preferred weight: 100-300 kg / m 3 .

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