Heat-reflection heat-insulation polyurethane microporous foam and preparation method thereof

Abstract

According to the heat-reflection heat-insulation polyurethane microporous foam and the preparation method thereof provided by the invention, the flame retardant, the heat-reflection nanoparticles and the hollow heat-insulation filler are introduced into the formula, and a self-skinning forming process is adopted; the prepared heat-reflection heat-insulation polyurethane microporous foam is very excellent in the aspects of heat conductivity, compression heat conductivity, flame retardant property, compression strength and the like. The heat-reflection heat-insulation polyurethane microporous foam provided by the invention is used for filling battery cell gaps in a power battery pack, has the effects of reducing heat diffusion and prolonging the occurrence time of thermal runaway of the battery pack, does not cause strong extrusion on battery cells, and does not damage the service life of the battery cells.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane microporous elastomers, and particularly relates to a heat-reflective and heat-insulating polyurethane microporous foam and a preparation method thereof. Background Art

[0002] With the continuous growth of the ownership of electric vehicles in China, the frequency of electric vehicle fire accidents has also been increasing year by year, seriously endangering the life and property safety of vehicle occupants. The ignition source of electric vehicles mainly comes from the lithium-ion power batteries they carry. Adverse conditions such as overcharging, extrusion, collision, wading, and manufacturing process defects may all lead to thermal runaway of lithium-ion batteries, and then cause electric vehicle fires or even explosions.

[0003] The common structures of power battery systems from small to large are battery cells, modules, and battery packs. When a single battery cell undergoes thermal runaway, according to the principle of heat transfer, the generated heat will be transferred to adjacent battery cells. When the temperature rises to a certain value, adjacent battery cells will also start thermal runaway, and finally it will be transmitted to the entire power battery pack. This process is similar to the domino effect. The Safety Requirements for Power Batteries for Electric Vehicles in China (GB 38031-2020) stipulate that the battery pack or system should provide a thermal event alarm signal 5 minutes before thermal diffusion caused by a single battery thermal runaway leads to danger in the passenger compartment. With the increasing attention to electric vehicle fire accidents, this time will be further extended.

[0004] Battery manufacturers generally adopt fireproof and heat-insulating materials that can reduce the rate of heat diffusion between battery cells to extend the thermal runaway time of the battery pack. In addition to having good flame retardancy and heat insulation performance, this fireproof and heat-insulating material should also have a certain degree of resilience to fix the battery cells and play a buffering role. Currently, the commercially available fireproof and heat-insulating materials between battery cells are mainly silica aerogel pads and polysiloxane foams. Silica aerogel pads have the advantages of low thermal conductivity (<0.03 W / (m·K), 25 °C) and high flame retardancy, but their compression and rebound performance is poor, which is likely to cause strong extrusion to the battery cells and affect the battery cell life; secondly, the relatively high production cost also limits the popularization of silica aerogel pads. Polysiloxane foams have excellent compression and resilience and relatively high heat resistance, but their thermal conductivity is relatively high (>0.1 W / (m·K), 25 °C) and they are also limited by production costs. In addition, most of the current material design ideas are to reduce the heat conduction effect by reducing the thermal conductivity, ignoring the role of thermal radiation in heat diffusion. Summary of the Invention

[0005] To this end, the present invention provides a heat-reflective and heat-insulating polyurethane microcellular foam and a preparation method thereof. By introducing a flame retardant, heat-reflective nanoparticles, and hollow heat-insulating fillers into the formulation and adopting a self-skinning molding process, the polyurethane microcellular foam can have high heat reflectivity, low thermal conductivity, and excellent flame retardancy. Combining with the excellent compression resilience and low cost of the polyurethane microcellular elastomer itself, the existing deficiencies of the above two fireproof and heat-insulating materials between the two types of battery cells are solved.

[0006] The technical solution adopted by the present invention is as follows:

[0007] On the one hand, the present invention provides a heat-reflective and heat-insulating polyurethane microcellular foam, which is prepared by reacting component A and component B according to a mass ratio of 1:0.2 - 0.5.

[0008] Furthermore, component A includes the following raw materials in parts by mass: 100 parts of polyol, 1 - 10 parts of cross-linking agent, 0.1 - 1 part of catalyst, 0.5 - 1.5 parts of foaming agent, 0.5 - 1.5 parts of foam stabilizer, 1 - 5 parts of antioxidant, 10 - 30 parts of flame retardant, 10 - 20 parts of hollow heat-insulating filler, 5 - 15 parts of heat-reflective nanoparticles; component B is a prepolymer of diisocyanate.

[0009] Furthermore, the polyol in component A includes at least one of polyether polyol and polyester polyol, preferably a polyether polyol with a molecular weight of 2000 - 6000 and a functionality of 3;

[0010] The cross-linking agent includes at least one of ethylene glycol, butanediol, diethylene glycol, dipropylene glycol, diethanolamine, triethanolamine, glycerol, trimethylolpropane, and pentaerythritol;

[0011] The catalyst includes a blowing catalyst and a gelling catalyst. Preferably, the catalyst is an amine catalyst; the foaming agent is water;

[0012] The foam stabilizer is a block copolymer of dimethylsiloxane and polyether, preferably a block copolymer of dimethylsiloxane and polyether suitable for polyurethane microcellular elastomers, such as Dow DC3042, DC3043, DC5179, etc.;

[0013] The antioxidant includes at least one of 1135, 1010, and 1076; the flame retardant includes phosphorus-containing polyol, phosphate flame retardant, inorganic flame retardant, and expanded graphite. Furthermore, the mass ratio of phosphorus-containing polyol, phosphate flame retardant, inorganic flame retardant, and expanded graphite is 5 - 15:3 - 10:3 - 10:5 - 15;

[0014] Further, the phosphorus-containing polyol has a molecular weight of 100 to 1000 and a functionality of 2; the phosphate flame retardant includes at least one of tris(1-chloro-2-propyl) phosphate, dimethyl methylphosphonate, trimethyl phosphate, triethyl phosphate, and triphenyl phosphate; the inorganic flame retardant includes at least one of ammonium polyphosphate, antimony trioxide, zinc borate, and aluminum hydroxide; the expanded graphite has a particle size of 100 to 300 mesh, preferably 300 mesh.

[0015] The hollow heat-insulating filler includes at least one of hollow glass microspheres, hollow ceramic microspheres, and closed-cell expanded perlite, preferably hollow glass microspheres with a particle size of 10 to 30 μm; the heat-reflective nanoparticles include at least one of nano-titanium dioxide, nano-tin oxide, and nano-zirconium oxide.

[0016] Further, the component B includes at least one of toluene diisocyanate prepolymer and diphenylmethane diisocyanate prepolymer; preferably, a toluene diisocyanate prepolymer or a diphenylmethane diisocyanate prepolymer with a viscosity of 50 to 1000 mPa·s at 25°C and an NCO mass content of 15 to 30%.

[0017] On the other hand, the present invention provides a method for preparing the above-mentioned heat-reflective heat-insulating polyurethane microcellular foam, including the following operating steps:

[0018] 1) Measure the dosage of the blowing agent when the foam produces a self-skinning effect.

[0019] 2) Mix the raw materials in component A, stir well until uniform, and then seal and store.

[0020] 3) Inject the uniformly stirred component A and component B into the material tanks of the casting machine respectively, inject the mixture into the mold according to a ratio of 1:0.2 to 0.5, the mold temperature is 40 to 60°C, and after demolding for 3 to 10 minutes, a heat-reflective heat-insulating polyurethane microcellular foam with a specific thickness is obtained.

[0021] In step 1) of the present invention, by exploring the dosage of the blowing agent within the above 0.5 to 1.5 parts by mass before sample making on the machine, the free foam density is determined, so that the foam can produce a self-skinning effect under overfilling conditions.

[0022] In step 3), the specific thickness range is 2 to 10 mm, preferably 5 mm.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] The heat-reflective and heat-insulating polyurethane microcellular foam provided by the present invention is added with a flame retardant, a hollow heat-insulating filler, and heat-reflective nanoparticles, and combined with the self-skinning molding process, so that the skin of the microcellular foam has excellent heat-reflective and heat-insulating effects. At the same time, the polyurethane microcellular foam also has good compression and tensile strengths and can maintain excellent heat-insulating performance whether in the normal state or in the compressed state. Detailed implementation manners

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present invention.

[0026] Raw materials and equipment:

[0027] The cross-linking agent is glycerol, commercially available;

[0028] The polyether polyol is Wanhua Chemical F3135, with a hydroxyl value of 32.5 - 35.5 mg KOH / g and a functionality of 3;

[0029] Catalysts: Evonik A1 and A33, with a mass ratio of 0.05:0.3;

[0030] Foam stabilizer: Dow DC3043;

[0031] Antioxidant: Rianlon 1135;

[0032] Flame retardant: Flame-retardant polyether from Wanhua Chemical FR-312, tris(1-chloro-2-propyl) phosphate, ammonium polyphosphate, expanded graphite (particle size of 300 mesh);

[0033] Hollow heat-insulating filler: Shenglaite hollow glass microspheres CQ242, with a particle size of 30 μm;

[0034] Heat-reflective particles: Rutile-type nano-titanium dioxide, with a particle size of 100 nm;

[0035] Component B: Liquid derivative of diphenylmethane diisocyanate, 8019, with a viscosity of 150 mPa·s at 25°C and an NCO mass content of 26 - 27%;

[0036] Cell opener: Wanhua Chemical WH001;

[0037] Unless otherwise specifically stated, all other various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchase or can be prepared by existing methods.

[0038] Example 1

[0039] Component A includes 100 parts of polyether polyol, 3 parts of crosslinking agent, 0.35 part of catalyst, 1 part of foaming agent, 0.5 part of foam stabilizer, 2 parts of antioxidant, 30 parts of flame retardant, 10 parts of hollow heat-insulating filler, and 5 parts of heat-reflective nanoparticles.

[0040] Mix the raw materials in Component A, stir well, and store them sealed. After fully mixing Component A and Component B with a mass ratio of 34.9% of Component A, inject them into a square mold with a depth of 5 mm. Set the mold temperature at 50 °C, and after demolding in 10 minutes, a heat-reflective and heat-insulating polyurethane microcellular foam with a thickness of 5 mm is obtained.

[0041] Example 2

[0042] Component A includes 100 parts of polyether polyol, 3 parts of crosslinking agent, 0.35 part of catalyst, 1.5 parts of foaming agent, 0.5 part of foam stabilizer, 2 parts of antioxidant, 20 parts of flame retardant, 15 parts of hollow heat-insulating filler, and 10 parts of heat-reflective nanoparticles.

[0043] Mix the raw materials in Component A, stir well, and store them sealed. After fully mixing Component A and Component B with a mass ratio of 34.8% of Component A, inject them into a square mold with a depth of 5 mm. Set the mold temperature at 50 °C, and after demolding in 10 minutes, a heat-reflective and heat-insulating polyurethane microcellular foam with a thickness of 5 mm is obtained.

[0044] Example 3

[0045] Component A includes 100 parts of polyether polyol, 3 parts of crosslinking agent, 0.35 part of catalyst, 0.5 part of foaming agent, 0.5 part of foam stabilizer, 2 parts of antioxidant, 20 parts of flame retardant, 10 parts of hollow heat-insulating filler, and 5 parts of heat-reflective nanoparticles.

[0046] Mix the raw materials in Component A, stir well, and store them sealed. After fully mixing Component A and Component B with a mass ratio of 35.4% of Component A, inject them into a square mold with a depth of 5 mm. Set the mold temperature at 50 °C, and after demolding in 10 minutes, a heat-reflective and heat-insulating polyurethane microcellular foam with a thickness of 5 mm is obtained.

[0047] Comparative Example 1

[0048] Component A includes 100 parts of polyether polyol, 3 parts of crosslinking agent, 0.35 part of catalyst, 1 part of foaming agent, 0.5 part of foam stabilizer, 2 parts of antioxidant, 30 parts of flame retardant, 15 parts of hollow heat-insulating filler, 10 parts of heat-reflective nanoparticles, and 3 parts of cell-opening agent. The purpose of adding the cell-opening agent is to make the surface of the foam without skinning.

[0049] Mix the raw materials in Component A, stir well, and store them sealed.

[0050] Component A and component B (32.15% by mass of component A) were fully mixed and injected into a square mold with a depth of 5 mm. The mold temperature was set at 50° C. After demolding for 10 minutes, a polyurethane microporous foam with a thickness of 5 mm was obtained.

[0051] Comparative Example 2

[0052] Component A includes 100 parts of polyether polyol, 3 parts of cross-linking agent, 0.35 parts of catalyst, 1 part of foaming agent, 0.5 parts of foam stabilizer, 2 parts of antioxidant, 30 parts of flame retardant, 15 parts of hollow thermal insulation filler, and 10 parts of heat-reflecting nanoparticles.

[0053] Add all raw materials in component A into the reactor, stir thoroughly, and seal for storage.

[0054] Component A and component B (32.7% by mass of component A) were fully mixed and injected into a square mold with a depth of 10 mm. The mold temperature was set at 50°C. After demolding for 10 minutes, a polyurethane microporous foam with a thickness of 10 mm was obtained. The foam was cut and peeled with a foam cutter, leaving only the middle 5 mm thick part.

[0055] Comparative Example 3

[0056] Component A includes 100 parts of polyether polyol, 3 parts of cross-linking agent, 0.35 parts of catalyst, 1 part of foaming agent, 0.5 parts of foam stabilizer, 2 parts of antioxidant, 30 parts of flame retardant and 25 parts of hollow heat-insulating filler.

[0057] Mix all the raw materials in component A, stir thoroughly, and seal for storage.

[0058] Component A and component B (32.7% by mass of component A) were fully mixed and injected into a square mold with a depth of 5 mm. The mold temperature was set at 50° C. After demolding for 10 minutes, a polyurethane microporous foam with a thickness of 5 mm was obtained.

[0059] Comparative Example 4

[0060] Component A includes 100 parts of polyether polyol, 3 parts of cross-linking agent, 0.35 parts of catalyst, 1 part of foaming agent, 0.5 parts of foam stabilizer, 2 parts of antioxidant and 30 parts of flame retardant.

[0061] Mix all the raw materials in component A, stir thoroughly, and seal for storage.

[0062] Component A and component B (32.15% by mass of component A) were fully mixed and injected into a square mold with a depth of 5 mm. The mold temperature was set at 50° C. After demolding for 10 minutes, a polyurethane microporous foam with a thickness of 5 mm was obtained.

[0063] Comparative Example 5

[0064] Component A includes 100 parts of polyether polyol, 3 parts of crosslinking agent, 0.35 part of catalyst, 2 parts of foaming agent, 0.5 part of foam stabilizer, 2 parts of antioxidant, 20 parts of flame retardant, 15 parts of hollow heat insulation filler, and 10 parts of heat-reflective nanoparticles.

[0065] Mix the raw materials in Component A, stir well, and store them sealed.

[0066] Fully mix Component A and Component B with a mass ratio of 34.67% of Component A, and then inject the mixture into a square mold with a depth of 5 mm. Set the mold temperature at 50 °C, and demold after 10 minutes to obtain a polyurethane microcellular foam with a thickness of 5 mm.

[0067] The raw material components and dosages of Examples 1 to 3 and Comparative Examples 1 to 5 are shown in Table 1 (unit: parts by mass):

[0068] Table 1 Raw material components and dosages of each example and comparative example

[0069]

[0070]

[0071] Take 10 sample pieces of polyurethane microcellular foam prepared from Examples 1 to 3 and Comparative Examples 1 to 5 for testing. The testing methods are as follows:

[0072] 1) Density test:

[0073] Refer to ASTM D1056.

[0074] 2) Thermal conductivity test:

[0075] Refer to ASTM D5470, 25 °C.

[0076] 3) Total afterflame time test for vertical burning:

[0077] Refer to UL94-2016. For the vertical burning test, record 5 groups of combustion, with two ignitions for each group, and test the total afterflame time of the foam material after each flame application.

[0078] 4) Compressive strength test:

[0079] Refer to ASTM D1056, 50% deformation.

[0080] 5) Compressive permanent deformation test:

[0081] Refer to ASTM D1056, place at 70 °C for 22 h, 50% compressive deformation.

[0082] 6) Tensile strength test:

[0083] Refer to ASTM D412.

[0084] 7) Elongation at break test:

[0085] Refer to ASTM D412.

[0086] 8) Tear strength test:

[0087] Refer to ASTM D624.

[0088] 9) Heat insulation performance test:

[0089] Place the foam on a 300 °C flat heating table and use an infrared thermometer gun to measure the temperature of the cold surface of the foam after 10 min.

[0090] The average value of the test results is shown in Table 2:

[0091] Table 2 Test results of each example and comparative example

[0092]

[0093] The test results show that the addition of heat insulation fillers can significantly reduce the thermal conductivity of the foam; compared with single flame retardants and heat insulation fillers, the use of heat reflection nanoparticles not only enhances the heat reflection performance of the foam, specifically manifested as a further increase in the temperature difference between the hot and cold surfaces of the foam, but also the compression thermal conductivity of the foam is more excellent. Moreover, the test results also reveal the positive effect of the self-skinning process of the foam on the heat insulation performance. Comparative Examples 1 and 2 reveal that during the chemical foaming process, the fillers will move towards the growth direction of the pores, and the pressure in the middle of the foam is higher than that on the upper and lower surfaces during the skinning process, which will promote the aggregation of the fillers towards the foam skin, resulting in a significantly higher filler content in the skin than in the interior of the foam. Therefore, the foam skin can play a role in enhancing heat reflection. Therefore, adding heat insulation fillers and heat reflection nanoparticles and combining with the self-skinning process can make the prepared polyurethane microcellular foam have excellent thermal conductivity and heat reflection performance while retaining the elasticity and compression performance of polyurethane itself, and at the same time, the compression and tensile strengths are also improved.

[0094] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A heat-reflective and heat-insulating polyurethane microcellular foam, characterized in that, the heat-reflective and heat-insulating polyurethane microcellular foam is prepared by reacting component A and component B in a mass ratio of 1: 0.2-0.5; wherein, component A comprises the following raw materials in parts by mass: 100 parts of polyol, 1-10 parts of crosslinking agent, 0.1-1 part of catalyst, 0.5-1.5 parts of foaming agent, 0.5-1.5 parts of foam stabilizer, 1-5 parts of antioxidant, 10-30 parts of flame retardant, 10-20 parts of hollow heat-insulating filler, 5-15 parts of heat-reflective nanoparticles; component B is a prepolymer of diisocyanate.

2. The heat-reflective and heat-insulating polyurethane microcellular foam according to claim 1, characterized in that, the polyol comprises at least one of polyether polyol or polyester polyol; preferably, a polyether polyol with a molecular weight of 2000-6000 and a functionality of 3.

3. The heat-reflective and heat-insulating polyurethane microcellular foam according to claim 1, characterized in that, the crosslinking agent comprises at least one of ethylene glycol, butanediol, diethylene glycol, dipropylene glycol, diethanolamine, triethanolamine, glycerol, trimethylolpropane, pentaerythritol.

4. The heat-reflective and heat-insulating polyurethane microcellular foam according to claim 1, characterized in that, the catalyst comprises a blowing catalyst and a gelling catalyst, preferably an amine catalyst; and / or: the foaming agent is water; and / or: the foam stabilizer is a block copolymer of dimethyl silicone and polyether, preferably Dow Corning DC3042, DC3043, DC5179; and / or: the antioxidant comprises at least one of 1135, 1010, 1076.

5. The heat-reflective and heat-insulating polyurethane microcellular foam according to claim 1, characterized in that, the flame retardant comprises phosphorus-containing polyol, phosphate ester flame retardant, inorganic flame retardant, expanded graphite; preferably, the mass ratio of phosphorus-containing polyol, phosphate ester flame retardant, inorganic flame retardant, expanded graphite is 5-15: 3-10: 3-10: 5-15; preferably, the molecular weight of the phosphorus-containing polyol is 100-1000 and the functionality is 2 or more; and / or: the phosphate ester flame retardant comprises at least one of tris(1-chloro-2-propyl) phosphate, dimethyl methylphosphonate, trimethyl phosphate, triethyl phosphate, triphenyl phosphate; and / or: the inorganic flame retardant comprises at least one of ammonium polyphosphate, antimony trioxide, zinc borate, aluminum hydroxide; and / or: the particle size of the expanded graphite is 100-300 mesh.

6. The heat-reflective and heat-insulating polyurethane microcellular foam according to claim 1, characterized in that, the hollow heat-insulating filler comprises at least one of hollow glass microspheres, hollow ceramic microspheres, closed-cell expanded perlite, preferably hollow glass microspheres with a particle size of 10-30 μm.

7. The heat-reflective and heat-insulating polyurethane microcellular foam according to claim 1, characterized in that, the heat-reflective nanoparticles comprise at least one of nano-titanium dioxide, nano-tin oxide, nano-zirconium oxide.

8. The heat-reflective and heat-insulating polyurethane microcellular foam according to any one of claims 1-7, characterized in that, The component B includes at least one of toluene diisocyanate prepolymer and diphenylmethane diisocyanate prepolymer; preferably, a toluene diisocyanate prepolymer or a diphenylmethane diisocyanate prepolymer with a viscosity of 50-1000 mPa·s at 25°C and an NCO mass content of 15-30%.

9. The preparation method of the heat-reflective and heat-insulating polyurethane microcellular foam according to any one of claims 1-8, characterized in that, it includes the following operating steps: 1) Calculate the dosage of the foaming agent when the foam produces a self-skinning effect; 2) Mix the raw materials in component A, stir well until uniform, and then store them sealed; 3) Inject the uniformly stirred component A and component B into the material tanks of the casting machine respectively. After adjusting the mixing ratio of the two, inject the mixture into the mold, and after demolding, obtain a heat-reflective and heat-insulating polyurethane microcellular foam with a specific thickness.

10. The preparation method according to claim 9, characterized in that, in step 3), the mold temperature is 40-60°C, and the specific thickness is 2-10 mm.

Images