Organopolysiloxane foam having expanded perlite

Abstract

A heat-insulating, compressible, and flame-retardant foamed material is provided. The foamed material includes a polyorganosiloxane foam, a flame retardant, and expanded perlite. The foamed material is useful for providing heat insulation, flame resistance, and compressibility for applications such as lithium-ion batteries.

Description

Technical Field

[0001] The present invention relates to an organopolysiloxane foam containing expanded perlite.

[0002] Rechargeable batteries such as lithium-ion batteries (LiB) are commonly used in various applications including electric vehicles (EV) and grid energy storage systems. LiB has desirable characteristics such as high energy density and stability, but its practicality is currently limited due to safety concerns. First, the failure of a LiB cell can be caused by manufacturing defects, internal short circuits, overheating, overcharging, or mechanical shock. Second, the heat generated from a failed cell can propagate, thereby causing thermal runaway in adjacent cells. The rapid pressure increase resulting from these thermal events increases the risk of fire and explosion.

[0003] Thermal runaway can be mitigated by placing a thermal barrier that provides heat insulation and flame resistance between cells in a LiB module. Commonly used thermal barriers such as aerogels, ceramic fibers, and mica boards provide such characteristics, but aerogels and ceramic fibers lack mechanical elasticity, while mica boards lack compressibility. On the other hand, silicone blown foams are suitable for batteries with low and medium energy densities because they provide appropriate compressibility, but they have a problem of insufficient heat insulation to prevent thermal runaway in battery packs with very high energy densities. Therefore, in the field of thermal barriers for rechargeable batteries, it is desirable to create a barrier that provides heat insulation, flame resistance, and satisfactory compressibility.

Summary of the Invention

[0004] The present invention relates to a foam material having heat insulation, compressibility, and flame resistance, which comprises, based on the weight of the foam material, 35 to 95 weight percent of a polyorganosiloxane foam, 1 to 30 weight percent of a flame retardant, and 1 to 15 weight percent of expanded perlite, and has a density in the range of 0.10 to 0.90 g / cm 3 to address the needs in the art. The foam material of the present invention is useful for providing one or more spacers that are heat-insulating, flame-resistant, and compressible in a rechargeable battery module.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The present invention relates to a foam material having heat insulation, compressibility, and flame resistance, which comprises, based on the weight of the foam material, 35 to 95 weight percent of a polyorganosiloxane foam, 1 to 30 weight percent of a flame retardant, and 1 to 15 weight percent of expanded perlite, and has a density in the range of 0.10 to 0.90 g / cm 3 The foam material is as described above.

[0006] The polyorganosiloxane foam material of the present invention can be prepared by modifying the method as described in U.S. Patent No. 5,358,975. For example, polydimethylsiloxane (a) functionalized with at least two, preferably at least three Si-H groups is advantageously contacted with one or more hydroxyl-containing compounds (b) which are water, alcohol, diol, polyol, or a compound containing at least one silanol group, divinyl-functionalized polydimethylsiloxane (c), a hydrosilylation catalyst such as a platinum-based catalyst (d), a flame retardant (e), and expanded perlite particles (f) to form a crosslinked network of a heat-insulating, compressible, and flame-resistant foam material having -Si-CH2-CH2-Si- groups and -Si-O-R groups (wherein R is H, or a structural unit of alcohol, diol, polyol, or silanol, i.e., the 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 foam material using a two - part approach as follows. That is, 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 expanded perlite particles are blended to form a 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 cross - linked organopolysiloxane resin, the remaining portion of the flame retardant, a polydimethylsiloxane functionalized with at least three Si - H groups, and the remaining portion of expanded perlite particles are blended to form a Part B composition. Then, Part A and B are combined, mixed, and then injected between two release film sheets to form the foam material of the present invention.

[0008] The flame retardant is a metal hydroxide, carbonate, hydroxide - carbonate, or hydrate that releases CO2 or water or both upon heating. Examples of flame retardants include Al(OH)3, Mg(OH)2, Ca(OH)2MgCO3·3H2O (nesquehonite), Mg5(CO3)4(OH)2·4H2O (hydromagnesite), MgCa(CO3)2 (huntite), AlO(OH) (boehmite), NaHCO3, and hydrated MgSO4 (epsomite). The polyorganosiloxane foam material contains from 1 or 2 or 3 weight percent to 30 or 20 or 15 weight percent of the flame retardant based on the weight of the foam material.

[0009] The foam material further comprises from 1 or 2 to 15 or 10 weight percent of expanded perlite. Expanded perlite can be formed by rapidly heating perlite ore to a temperature in the range of 750 °C to 1000 °C. The resulting expanded particles generally have a density of 0.03 - 0.20 g / cm 3It has a dry bulk density in the range of. The average volume particle size is typically in the range of 0.1 μm to 1000 μm using a dynamic light scattering analyzer such as a Beckman Coulter LS 130 Particle Size Analyzer.

[0010] The resulting barrier material has a density in the range from 0.10 g / cm 3 or 0.15 g / cm 3 to 0.90 g / cm 3 or 0.50 g / cm 3 up to.

[0011] In another aspect, the present invention provides, 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, alcohol, diol, 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 is in the range of 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 expanded perlite particles.

[0012] In yet another aspect, the present invention is a battery module comprising a shell containing an array of spatially separated battery cells and a polyorganosiloxane foam material in contact with adjacent battery cells. The polyorganosiloxane foam can contact the battery cells by filling the space between adjacent battery cells with the foam and / or coating the battery cells with the foam. The battery module may further comprise an end plate at the 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 the cavities between adjacent battery cells and between the cells and the end plate, or a foam precursor can be applied onto the cells and into the cavities and then cured to form the foam material.

[0013] The foam material of the present invention has been found to provide desired properties of heat insulation, flame resistance, and compressibility in battery thermal barrier applications.

[0014] In the following examples, ViMe2SiO 1 / 2 / (CH3)3Si-O 1 / 2 / SiO 4 / 2 The M w and M n were determined by gel permeation chromatography using a gpc column filled with divinylbenzene cross-linked polystyrene bead pore type Mixed-C (Polymer Laboratory) with a size of 5 mm in diameter. Tetrahydrofuran was used as the mobile phase, and detection was performed with a refractive index detector.

[0015] Example 1 - Preparation of a Foamed Organopolysiloxane Article with Expanded Perlite Particles Using a Flacktek Speed Mixer, dimethylvinylsiloxy-terminated polydimethylsiloxane (Polymer 1, 11.0 pbw) having a viscosity of about 40,000 mPas, 1) dimethylvinylsiloxy-terminated polydimethylsiloxane having a viscosity of about 1,900 mPa·s and about 0.22 wt% of Vi, and 2) a ViMe2SiO 1 / 2 :(CH3)3Si-O 1 / 2 :SiO 4 / 2 structural unit ratio, M of 5000 n and M of 21,400 w having a ViMe2SiO 1 / 2 / (CH3)3Si-O 1 / 2 / SiO 4 / 2The first component (Part A) was prepared by mixing together a 64:36 w / w blend with resin (polymer-resin blend, 62.9 pbw), and Micral 855 aluminum hydroxide (14.7 pbw). The contents were stirred at 2000 rpm for 30 seconds, and then a complex of Pt(0) with divinyltetramethyldisiloxane (0.9 pbw, 0.62 wt% Pt), 1,4-butanediol (2.5 pbw), and benzyl alcohol (3.2 pbw) were added to the mixture, and the contents were stirred at 2000 rpm for 30 seconds. Finally, Omyasphere TP-312 FQ expanded perlite particles (average volume particle size of 63 μm; 4.8 pbw) were added to the mixture, and the contents were stirred at 2000 rpm for 30 seconds.

[0016] The second composition (Part B) was similarly prepared by mixing together Polymer 1 (8.6 pbw), a polymer resin blend (49.5 pbw), and Hymod M855 aluminum hydroxide (25.6 pbw). The contents were stirred at 2000 rpm for 30 seconds, and then a linear organohydrogenpolysiloxane having a viscosity of 30 mPa·s and an SiH content of 1.6 wt% (6.5 pbw), and a polydimethyloorganohydrogensiloxane having a viscosity of 5 mPa·s and an SiH content of 0.7 wt% (4.9 pbw) were added to the mixture, and the contents were stirred at 2000 rpm for 30 seconds. Then, Omyasphere TP-312 FQ expanded perlite particles (average volume average particle size of 63 μm, 4.8 pbw) were added to the mixture, and the contents were stirred at 2000 rpm for 30 seconds.

[0017] Next, equal amounts of Part A and B were mixed, and the mixture was poured between two release film sheets (matte Mylar film). The initial (pre-foam) thickness was controlled to 0.045 inches using a nip roller. The sample was cured at 70 °C for 5 minutes and then at 100 °C for 15 minutes to produce a foam sheet for further testing. (Density = 0.29 g / cm 3 )

[0018] Example 2 - Preparation of a Foamed Organopolysiloxane Article with Expanded Perlite Particles A part and B part were processed in substantially the same manner as the process for preparing the foamed article of Example 1, except that Omyasphere 235 T-FQ expanded perlite particles (average volume average particle size of 124 μm, 4.8 pbw) were used. (Density = 0.31 g / cm 3 )

[0019] Example 3 - Preparation of a Foamed Organopolysiloxane Article with Expanded Perlite Particles A part and B part were processed in substantially the same manner as the process for preparing the foamed article of Example 1, except that Omyasphere 235 T-FQ expanded perlite particles (9.1 pbw) were used. (Density = 0.35 g / cm 3 )

[0020] Comparative Example 2 - Preparation of a Foamed Organopolysiloxane Article with Hollow Glass Beads A part and B part were processed in substantially the same manner as the process for preparing the foamed article of Example 1, except that 3M iM16K hollow glass beads (average volume average particle size of 20 μm, 20 pbw) were used. (Density = 0.28 g / cm 3 ) The amount of beads was selected to give a filling volume similar to that of the expanded perlite of Example 1.

[0021] Thermal Insulation and Combustibility The foam prepared as described in the examples was tested for heat insulation and flammability using a hot plate installed 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 on 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 on 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 high-temperature surface, and the sample attached to the heat sink was quickly placed on the high-temperature 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.

[0022] Hardness The hardness was measured using a Shore 00 durometer. The test piece was placed on a hard and flat surface. Next, the indenter of the Shore 00 durometer was pressed against the test piece so that the indenter was surely parallel to the surface. The hardness was read while in firm contact with the test piece. If the hardness was less than 80, it was considered acceptable.

[0023] Compressive force The compressive force was measured using a TA.HDplus texture analyzer equipped with a 100 kg load cell, an aluminum probe with a diameter of 40 mm, and a flat heavy-duty aluminum substrate. A silicone foam sample was cut into a circular shape using a 1-inch diameter die cut and placed between the substrate and the probe. First, the probe was set at the same height as the sample thickness and lowered at a speed of 1 mm / second until the pressure reached the peak point. The sample thickness and pressure were recorded as a compressive force curve. The pressure at 30% of the original sample thickness was recorded. If the compressive force was less than 500 kPa, it was considered acceptable.

[0024] Density of the foam The foam density was calculated based on the average thickness and weight of two 1-inch diameter foam samples.

[0025] The properties of the expanded perlite-filled organopolysiloxane articles were compared with two other foams, namely Comparative Example 1 and Comparative Example 2. Comparative Example 1 was a commercially available organopolysiloxane article (COHRlastic Silicone Foam available from Stockwell Elastomerics), which had a structure similar to the foam of the examples except that it did not contain expanded perlite. Comparative Example 2 was a foam containing 3M Glass Bubbles iM16K hollow glass microspheres.

[0026] Table 1 is an overview of the performance characteristics of the foams of Examples 1 to 3, the commercially available comparative foams, and the foam containing hollow glass microspheres. The density was measured in g / cm 3 and the hardness was measured in Shore 00 units. The compressive force (force) was measured in kPa at 30% compression. The temperature at 600 °C (T after 300 s) refers to the surface temperature of the sample after 300 s, and the flammability refers to the observability of the flame during the heat insulation test.

[0027] TP-312-FQ refers to Omyasphere TP-312-FQ expanded perlite, 235T-FQ refers to Omyasphere 235-T-FQ expanded perlite, and iM16K refers to 3M Glass Bubbles iM16K hollow glass microspheres.

[0028]

Table 1

[0029] Table 1 shows that all the expanded perlite-containing foams of the present invention pass all the tests, while the sample without expanded perlite (Comparative Example 1) fails the heat insulation test, and the sample containing the hollow glass microsphere filler (Comparative Example 2) fails the compressive force test.

Claims

Claim 1 A heat-insulating, compressible and flame-resistant foam material, comprising 35 to 95 weight percent of a polyorganosiloxane foam, 1 to 30 weight percent of a flame retardant, and 1 to 15 weight percent of expanded perlite, based on the weight of the foam material, and having a density in the range of 0.10 to 0.90 g / cm ３ of the foam material. Claim 2 The foaming material according to claim 1, comprising 50 to 80% by weight of the polyorganosiloxane foam, 2 to 20% by weight of the flame retardant, and 2 to 10% by weight of expanded perlite. Claim 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. Claim 4 A foamed material according to any one of claims 1 to 3, having a density in the range of 0.15 to 0.50 g / cm ３ .

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