Organopolysiloxane foam containing ceramic microspheres

Abstract

A thermally insulating, compressible, and flame resistant foam material comprising a polyorganosiloxane foam, a flame retardant, and micron-sized hollow ceramic particles. The foam material is useful for providing thermal insulation, flame resistance, and compressibility for applications such as lithium ion batteries.

Description

[Technical Field]

[0001] This invention relates to an organopolysiloxane foam containing micron-sized ceramic particles. [Background technology]

[0002] Rechargeable batteries, such as lithium-ion batteries (LiBs), are commonly used in a variety of applications, including electric vehicles (EVs) and grid energy storage systems. While LiBs possess desirable characteristics such as high energy density and stability, their practical use is currently limited due to safety concerns. Firstly, LiB cell failures can be caused by manufacturing defects, internal short circuits, overheating, overcharging, or mechanical shocks. Secondly, heat generated from a failed cell can propagate, potentially causing thermal runaway in adjacent cells. The rapid pressure increases resulting from these thermal events increase the risk of fire and explosion.

[0003] Thermal runaway can be mitigated by placing thermal barriers that provide insulation and flame resistance between cells in a LiB module. Commonly used thermal barriers such as aerogel, ceramic fiber, and mica board offer such properties, but aerogel and ceramic fiber have poor mechanical elasticity, while mica board has poor compressibility. On the other hand, blown silicone foam provides adequate compressibility and is suitable for low and medium energy density batteries, but it has the problem of insufficient insulation to prevent thermal runaway in very high energy density battery packs. Therefore, in the field of thermal barriers for rechargeable batteries, it is desirable to create barriers that provide insulation, flame resistance, and satisfactory compressibility. [Overview of the project]

[0004] The present invention relates to a thermally insulating, compressible, and flame-resistant foamed material comprising, based on the weight of the foamed material, 35 to 95 weight percent of polyorganosiloxane foam, 1 to 30 weight percent of flame retardant, and 1 to 35 weight percent of hollow ceramic particles having a volume-average particle size in the range of 25 μm to 300 μm, with a concentration of 0.10 to 0.90 g / cm³. 3 The present invention addresses the needs in the art by providing a foamed material having a density in the range of [value missing]. The foamed material of the present invention is useful in lithium-ion batteries to provide one or more spacers that are thermally insulating, flame-resistant, and compressible. [Modes for carrying out the invention]

[0005] The present invention relates to a thermally insulating, compressible, and flame-resistant foamed material comprising, based on the volume of the article, 35 to 95 weight percent of polyorganosiloxane foam, 1 to 30 weight percent of flame retardant, and 1 to 35 weight percent of hollow ceramic particles having a volume-average particle size in the range of 25 μm to 300 μm, with a concentration of 0.10 to 0.90 g / cm³. 3 We address the needs in this field by providing foamed materials having densities within a certain range.

[0006] The polyorganosiloxane foam material of the present invention can be prepared by modifying a method such as that described in U.S. Patent No. 5,358,975. For example, a polydimethylsiloxane (a) functionalized with at least two, preferably at least three Si-H groups is brought into contact with one or more hydroxyl-containing compounds (b), which are preferably water, alcohol, diol, polyol, or compounds containing at least one silanol group, a divinyl-functionalized polydimethylsiloxane (c), a hydrosilylation catalyst, such as a platinum-based catalyst (d), a flame retardant (e), and hollow ceramic particles (f) to form a crosslinked network of a thermally insulating, compressible, and flame-resistant foam material having -Si-CH2-CH2-Si groups and -Si-OR groups (wherein R is H, or a structural unit of alcohol, diol, polyol, or silanol (i.e., a reaction product)). The total of components (a), (b), and (c) ranges from 35 or 40 weight percent to 80 or 70 weight percent of the polyorganosiloxane foam.

[0007] It may be advantageous to prepare the foaming material using the following two-part approach. Specifically, in a first container, a first portion of divinyl-functionalized polydimethylsiloxane, a first portion of a flame retardant, a hydrosilylation catalyst, a hydroxyl-containing compound, and a first portion of hollow ceramic particles are blended to form Part A composition. In a second container, the remaining portion of divinyl-functionalized polydimethylsiloxane, a polymer resin blend which is a mixture of divinyl-functionalized polydimethylsiloxane and a crosslinked organopolysiloxane resin, the remaining portion of a flame retardant, polydimethylsiloxane functionalized with at least three Si-H groups, and the remaining portion of hollow ceramic particles are blended to form Part B composition. Parts A and B are then combined and mixed, and then injected between two release film sheets to form the foaming material of the present invention.

[0008] Flame retardants are metal hydroxides, carbonates, hydroxide-carbonates, or hydrates that release CO2, water, or both when heated. Examples of flame retardants include Al(OH)3, Mg(OH)2, Ca(OH)2MgCO3·3H2O (neskehonite), Mg5(CO3)4(OH)2·4H2O (hydromagnesite), MgCa(CO3)2 (huntite), AlO(OH) (boehmite), NaHCO3, and hydrated MgSO4 (epsomite). Polyorganosiloxane foam materials contain flame retardants ranging from 1, 2, or 3 weight percent to 30, 20, or 15 weight percent, based on the weight of the foam material.

[0009] The composition further comprises hollow, air-filled, or inert gas-filled ceramic particles ranging from 1 or 5 or 10 weight percent to 35 or 30-25 weight percent. As used herein, “ceramic” refers to crystalline or semi-crystalline inorganic oxides, nitrides, carbides, oxynitrides, or oxycarbides of metals such as aluminum (e.g., crystalline or semi-crystalline Al2O3), silicon (e.g., crystalline or semi-crystalline SiO2), or calcium (e.g., crystalline or semi-crystalline CaO), or combinations thereof. Crystallinity can be measured by X-ray powder diffraction. As used herein, the term “semi-crystalline” refers to ceramic materials having amorphous and crystalline regions. The hollow ceramic particles have average volume particle sizes ranging from 25 μm, or 50 μm, or 70 μm to 300 μm, or 200 μm, or 150 μm, as measured using a dynamic light scattering analyzer such as a Beckman Coulter LS 130 Particle Size Analyzer. The resulting article has a concentration of 0.10 or 0.15 g / cm³. 3 From 0.90 or 0.50 g / cm³ 3 It has a density in the range up to [a certain value].

[0010] In another aspect, the present invention provides a composition comprising, based on the weight of the composition: a) 2 to 50 weight percent of a polysiloxane functionalized with at least two Si—H groups and having a degree of polymerization in the range of 5 to 1000; b) 1 to 50 weight percent of water, an alcohol, a diol, a polyol, or a compound containing one or more silanol groups; c) 10 to 90 weight percent of a polysiloxane functionalized with at least one ethylenically unsaturated group and having a degree of polymerization in the range of 20 to 2000, (the total concentration of components a, b, and c ranges from 35 to 95 weight percent based on the weight of the composition) d) a catalytic amount of a hydrosilylation catalyst; e) 1 to 30 weight percent of a flame retardant; and f) 1 to 35 weight percent of hollow ceramic particles having a volume average particle size in the range of 25 μm to 300 μm.

[0011] In yet another aspect, the present invention provides a battery module comprising a shell containing an array of spatially separated battery cells and a polyorganosiloxane foam material contacting adjacent battery cells. The polyorganosiloxane foam can contact the battery cells by filling the space between adjacent battery cells with the foam and / or by coating the battery cells with the foam. The battery module may further comprise an end plate at an inner edge of the shell that directly or indirectly contacts the battery cell closest to the edge. The foam material can also be inserted into cavities between adjacent battery cells and between the cells and the end plate, or a foam precursor can be applied over the cells and within the cavities and then cured to form the foam material.

[0012] The foam material of the present invention has been found to provide the desired properties of thermal insulation, flame resistance, and compressibility in LiB thermal barrier applications.

[0013] In the following examples, ViMe2SiO 1 / 2 / (CH3)3Si - O 1 / 2 / SiO 4 / 2 The M of the resin w and M nThis was determined by gel permeation chromatography using a GPC column packed with 5mm diameter divinylbenzene crosslinked polystyrene bead pore type Mixed-C (Polymer Laboratory). THF was used as the mobile phase, and detection was performed using a refractive index detector.

[0014] Example 1 - Preparation of foamed organopolysiloxane article containing ceramic particles Using a Flacktek Speed ​​Mixer, dimethylvinylsiloxy-terminated polydimethylsiloxane (polymer 1, 11.3pbw) with a viscosity of approximately 40,000 mPa·s, 1) dimethylvinylsiloxy-terminated polydimethylsiloxane with a viscosity of approximately 1,900 mPa·s and approximately 0.22 wt% Vi, and 2) ViMe2SiO5 in a ratio of 5:40:55. 1 / 2 :(CH3)3Si-O 1 / 2 :SiO 4 / 2 Structural unit ratio, 5000 M n , and 21,400 M w ViMe2SiO 1 / 2 / (CH3)3Si-O 1 / 2 / SiO 4 / 2 The first component (Part A) was prepared by mixing a 64:36 w / w blend with resin (polymer-resin blend, 64.9 pbw) and Micral 855 aluminum hydroxide (15.2 pbw). The contents were stirred at 2000 rpm for 30 seconds, then a complex of Pt(0) and divinyltetramethyldisiloxane (0.93 pbw, 0.62 wt% Pt), 1,4-butanediol (2.6 pbw), and benzyl alcohol (3.3 pbw) were added to the mixture, and the contents were stirred at 2000 rpm for 30 seconds. Finally, Elminas Spheres HCMS-W150 hollow ceramic particles (average volume particle size of 100 μm; 20 pbw) were added to the mixture, and the contents were stirred at 2000 rpm for 30 seconds.

[0015] A second composition (Part B) was similarly prepared by mixing Polymer 1 (8.9 pbw), a polymer resin blend (51 pbw), and Hymod M855 aluminum hydroxide (26.4 pbw). The contents were stirred at 2000 rpm for 30 seconds, and then linear organohydrogenpolysiloxane having a viscosity of 30 mPa·s and a SiH content of 1.6 wt% (6.7 pbw), and polydimethyl organohydrogensiloxane having a viscosity of 5 mPa·s and a SiH content of 0.7 wt% (5.1 pbw) were added to the mixture, and the contents were stirred at 2000 rpm for 30 seconds. Next, Elminas Spherers HCMS-W150 hollow ceramic particles (20 pbw) were added to the mixture, and the contents were stirred at 2000 rpm for 30 seconds.

[0016] Next, equal amounts of parts A and B were mixed, and the mixture was poured between two release film sheets (matte Mylar film). The initial (pre-foaming) thickness was controlled to 0.045 inches using a nip roller. The sample was cured at 70°C for 5 minutes, then at 100°C for 15 minutes to produce a foam sheet for further testing. (Density = 0.31 g / cm³) 3 )

[0017] Example 2 - Preparation of foamed organopolysiloxane article containing ceramic particles The process for preparing the foamed article in Example 1 was substantially the same as the process for preparing the foamed article in Example 1, except that Elminas Spheres HCMS THERMO-W75 hollow ceramic particles (average volume particle size of 80 μm, 20 pbw) were used in Parts A and B. (Density = 0.31 g / cm³) 3 )

[0018] Example 3 - Preparation of foamed organopolysiloxane article containing ceramic particles The process for preparing the foamed article in Example 1 was substantially the same as the process for preparing the foamed article in Example 1, except that Elminas Spheres-W300 hollow ceramic particles (average volume particle size of 180 μm, 20 pbw) were used in Parts A and B. (Density = 0.34 g / cm³) 3 )

[0019] Heat insulation and flammability The foam prepared as described in the examples was tested for heat insulation and flammability using a hot plate placed on a hydraulic press. The hot plate was set to 600 °C, and an insulator was placed on the surface. Four thermocouples (type K) were fixed onto an aluminum heat sink (4 inches × 4 inches × 0.47 inches) using Kapton tape. Next, the sample (4 inches × 4 inches) was placed and fixed onto the heat sink using Kapton tape. An additional thermocouple (type K) was attached to the sample surface using Kapton tape. The insulator was removed from the hot surface, and the sample attached to the heat sink was quickly placed on the hot surface with the sample surface facing the hot plate surface and the Al heat sink facing the opposite side. The pressure was rapidly increased to 355 kPa. The interface temperature between the hot plate surface and the sample surface, and the interface temperature between the sample surface and the heat sink were recorded using a data logger. When the time reached 300 seconds, the pressure was released and the test was terminated. If the temperature of the sample surface was less than 300 °C, it was considered acceptable. If there was no observable flame throughout the test, it was considered to have acceptable flame resistance.

[0020] Hardness The hardness was measured using a Shore 00 durometer. The test specimen was placed on a hard and flat surface. Next, the indenter of the Shore 00 durometer was pressed against the specimen to ensure that the indenter was parallel to the surface. The hardness was read while in firm contact with the specimen. If the hardness was less than 80, it was considered acceptable.

[0021] Compressive force Compressive force was measured using a TA.HDplus texture analyzer equipped with a 100 kg load cell, a 40 mm diameter aluminum probe, and a flat heavy-duty aluminum substrate. A silicone foam sample was cut into a circle using a 1-inch diameter die cutter and placed between the substrate and the probe. The probe was initially set to the same height as the sample thickness and lowered at a rate of 1 mm / second until the pressure reached its peak. The sample thickness and pressure were recorded as a compressive force curve. The pressure at 30% of the original sample thickness was recorded. Compressive forces below 500 kPa were considered acceptable.

[0022] foam density The foam density was calculated based on the average thickness and weight of two 1-inch diameter foam samples.

[0023] The properties of the ceramic-filled organopolysiloxane article were compared with a commercially available organopolysiloxane article (COHRlastic Silicone Foam, available from Stockwell Elastomerics) that is structurally similar to the foam in the example, except that it does not contain hollow ceramic particles.

[0024] Table 1 summarizes the performance characteristics of the foams from Examples 1-3 and a commercially available comparative foam. Density is g / cm³. 3 The measurements were taken using the following method. Hardness was measured in Shore 00 units. Compressive force (force) was measured in kPa at 30% compression. The temperature at 600°C (T after 300 seconds) refers to the surface temperature of the sample after 300 seconds, and flammability refers to the observability of the flame during the adiabatic test.

[0025] [Table 1]

[0026] Table 1 shows that the foam of the present invention passes all tests, while commercially available examples fail the thermal insulation test. Surprisingly, hollow ceramic particles were found to reduce the surface temperature in 300 seconds without adversely affecting other important properties of the foam. Furthermore, hollow ceramic particle sizes in the range of 50 μm to 150 μm were found to be particularly effective in reducing the surface temperature. This disclosure includes the following aspects: [Aspect 1] A foamed material that is heat insulating, compressible, and flame-resistant, comprising, based on the volume of the foamed material, 35 to 95 weight percent of polyorganosiloxane foam, 1 to 30 weight percent of flame retardant, and 1 to 35 weight percent of hollow ceramic particles having a volume-average particle size in the range of 25 μm to 300 μm. It contains 0.10-0.90 g / cm³ 3 A foamed material having a density in the range of [value]. [Aspect 2] The foaming material according to embodiment 1, wherein the foaming material comprises 50 to 80 weight percent of the polyorganosiloxane foam and 2 to 20 weight percent of the flame retardant. [Aspect 3] The aforementioned flame retardant is Al(OH) 3 Mg(OH) 2 MgCO 3 ·3H 2 O or Mg 5 (CO 3 ) 4 (OH) 2 ·4H 2 O, MgCa(CO) 3 ) 2 AlO(OH), NaHCO 3 , or hydrated MgSO 4 The foamed material according to embodiment 2, or a combination thereof. [Aspect 4] 0.15~0.50 g / cm³ 3 A foamed material according to any one of embodiments 1 to 3, having a density in the range of [value]. [Aspect 5] The foamed material according to embodiment 4, wherein the hollow ceramic particles have an average volume particle size in the range of 25 μm to 200 μm due to dynamic light scattering. [Aspect 6] The foamed material according to embodiment 4, wherein the hollow ceramic particles have an average volume particle size in the range of 50 μm to 150 μm due to dynamic light scattering. [Aspect 7] The hollow ceramic particles are crystalline or semicrystalline Al 2 O 3 Particles, crystalline or semi-crystalline SiO 2 The foaming material according to embodiment 5 or 6, which is a particle, a crystalline or semi-crystalline CaO particle, or a crystalline or semi-crystalline Al / Mg / Ca silicate.

Claims

1. A foamed material that is heat insulating, compressible, and flame-resistant, comprising, based on the volume of the foamed material, 35 to 95 weight percent of polyorganosiloxane foam, 1 to 30 weight percent of flame retardant, and 1 to 35 weight percent of hollow ceramic particles having a volume-average particle size in the range of 25 μm to 300 μm. Includes, The foaming material is 0.15 to 0.50 g / cm³. ３ It has a density in the range, The hollow ceramic particles have an average volume particle size in the range of 25 μm to 200 μm due to dynamic light scattering. The foamed material wherein the hollow ceramic particles are crystalline or semi-crystalline Al₂O₃ particles, crystalline or semi-crystalline SiO₂ particles, crystalline or semi-crystalline CaO particles, or crystalline or semi-crystalline Al / Mg / Ca silicate.

2. The foaming material according to claim 1, wherein the foaming material comprises 50 to 80 weight percent of the polyorganosiloxane foam and 2 to 20 weight percent of the flame retardant.

3. The flame retardant is Al(OH) ３ , Mg(OH) ２ , MgCO ３ ·3H ２ O, or Mg ５ (CO ３ ) ４ (OH) ２ ·4H ２ O, MgCa(CO ３ ) ２ , AlO(OH), NaHCO ３ , or hydrated MgSO ４ , or a combination thereof, the foamed material according to claim 2.

4. The foamed material according to claim 1, wherein the hollow ceramic particles have an average volume particle size in the range of 50 μm to 150 μm due to dynamic light scattering.

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