Organopolysiloxane composition containing expanded perlite

Abstract

The present invention relates to a composition comprising a reactive polysiloxane and a hydroxyl-containing precursor, a flame retardant, and expanded perlite. This composition is useful in the preparation of a heat-insulating, compressible, and flame-retardant foamed material that is useful for providing heat insulation, flame retardancy, and compressibility for applications such as lithium-ion batteries.

Description

Technical Field

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

Background Art

[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 currently its practicality is 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 disposing 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 there is a problem that the heat insulation is insufficient to prevent thermal runaway of battery packs with very high energy densities. Therefore, in the field of thermal barriers for rechargeable batteries, it is desirable to produce a barrier that provides heat insulation, flame resistance, and satisfactory compressibility.

Summary of the Invention

[0004] The present invention addresses the needs in the art by providing 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 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 15 weight percent of expanded perlite.

[0005] The composition of the present invention is useful in providing a foamed material as a compressible, heat-insulating, and flame-retardant spacer in a rechargeable battery module.

DETAILED DESCRIPTION OF THE INVENTION

[0006] The present invention is 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 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 15 weight percent of expanded perlite.

[0007] The polysiloxane (a) functionalized with at least two, preferably at least three Si-H groups has a degree of polymerization in the range from 5 to 1000 or 500 or 200. The hydroxyl-containing compound (b) is preferably benzyl alcohol or a C2-C8-alkyl diol. The polysiloxane (c) functionalized with at least one, preferably at least two ethylenically unsaturated groups has a degree of polymerization in the range from 20 or 100 or 200 or 300 to 2000 or 1500 or 1000. The total weight percentages of components a, b, and c range from 35 or 50 weight percent to 95 weight percent based on the weight of the composition.

[0008] The polysiloxane functionalized with at least one ethylenically unsaturated group is preferably functionalized with two C2-C8-alkenyl groups, more preferably two vinyl groups or two allyl groups. The polysiloxane functionalized with at least one ethylenically unsaturated group is most preferably a polydimethylsiloxane functionalized with two vinyl groups. The polydimethylsiloxane functionalized with two vinyl groups is advantageously designed to have a viscosity in the range of 10,000 to 50,000 mPa·s. This viscosity is conveniently achieved by combining divinyl-functionalized polydimethylsiloxanes of different degrees of polymerization, i.e., by a bimodal distribution of divinyl-functionalized polydimethylsiloxane.

[0009] The hydrosilylation catalyst is preferably a platinum-based catalyst such as chloroplatinic acid, and they are used in a catalytic amount, typically in the range of 0.5 ppm to 200 ppm of Pt based on the weight of the composition.

[0010] The composition also includes a flame retardant from 1 or 2 or 3 weight percent to 30 or 20 or 15 weight percent, and 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)2, MgCO3·3H2O (nesquehonite), Mg5(CO3)4(OH)2·4H2O (hydromagnesite), MgCa(CO3)2 (huntite), AlO(OH) (boehmite), NaHCO3, and hydrated MgSO4 (epsomite).

[0011] The composition further includes expanded perlite from 1 or 2 weight percent to 15 or 10 weight percent. Expanded perlite can be formed by rapidly heating perlite ore to a temperature in the range of 750°C to 1000°C. The resulting foamed particles generally have a dry density in the range of 0.03 - 0.20 g / cm 3 and 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 distribution analyzer. The resulting article has a density in the range of 0.10 or 0.15 g / cm 3 to 0.90 or 0.50 g / cm 3

[0012] The composition is useful, for example, in preparing polyorganosiloxane foam articles substantially as described in U.S. Patent No. 5,358,975. A polysiloxane functionalized with at least three Si-H groups is preferably contacted, in the presence of a platinum-based catalyst, with a) an alcohol, diol, polyol, or silanol, and b) a divinyl-functionalized polydimethylsiloxane to form a cross-linked network of organopolysiloxane having -Si-CH2-CH2-Si groups and -Si-O-R groups, where R is a structural unit (i.e., the reactive product) of an alcohol, diol, polyol, or silanol.

[0013] ​It can be advantageous to prepare the foam material using a two-component approach, where in a first container, a first portion of a divinyl-functionalized polydimethylsiloxane, a first portion of a flame retardant, a platinum-based catalyst, a hydroxyl-containing compound, and a first portion of expanded perlite are blended to form a part A composition. In a second container, the remaining portion of the divinyl-functionalized polydimethylsiloxane, a polymer resin blend that is a mixture of a divinyl-functionalized polydimethylsiloxane and a crosslinked organopolysiloxane resin, the remaining portion of the flame retardant, a polydimethylsiloxane functionalized with at least three Si-H groups, and the remaining portion of the expanded perlite are blended to form a part B composition. The part A and B are then combined, mixed, and then injected between two release film sheets to form the foam material of the present invention.

[0014] Accordingly, in another aspect, the present invention is a foam material having heat insulation, compressibility, and flame retardancy, 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 35 weight percent of expanded perlite, and the foam material has a density in the range of 0.10 to 0.90 g / cm 3 .

[0015] 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 covering the battery cells with the foam. The battery module may further comprise end plates at the inner edge of the shell that contact directly or indirectly the battery cells 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 plates, or a foam precursor can be applied onto the cells and into the cavities and then cured to form the foam material.

[0016] The foam material of the present invention has been found to provide the desired properties of heat insulation, flame retardancy, and compressibility in battery thermal barrier applications.

[0017] 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.

[0018] Example 1 - Preparation of a Foamed Organopolysiloxane Article Containing Expanded Perlite Particles Using a Flacktek high-speed mixer, dimethylvinylsiloxy terminated polydimethylsiloxane (Polymer 1, 11.0 pbw) having a viscosity of about 40,000 mPas, and 1) dimethylvinylsiloxy terminated polydimethylsiloxane having a viscosity of about 1,900 mPa·s and about 0.22 wt% Vi, and 2) ViMe2SiO 1 / 2 :(CH3)3Si-O 1 / 2 :SiO 4 / 2 with a structural unit ratio of 5:40:55, an M n of 5000, and an M w of 21,400, and having 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, after which a complex of Pt(0) and 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 mean particle size of 63 μm; 4.8 pbw) were added to the mixture, and the contents were stirred at 2000 rpm for 30 seconds.

[0019] 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, after which a linear organohydrogenpolysiloxane having a viscosity of 30 mPa·s and an SiH content of 1.6 wt% (6.5 pbw) and a polydimethyorganohydrogensiloxane 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 mean particle size of 63 μm, 4.8 pbw) were added to the mixture, and the contents were stirred at 2000 rpm for 30 seconds.

[0020] 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 nip rollers. 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 )

[0021] Example 2 - Preparation of a Foamed Organopolysiloxane Article Containing Expanded Perlite Particles The process for preparing the foamed article of Example 1 was carried out in substantially the same manner, except that Omyasphere 235 T-FQ expanded perlite particles (average volume average particle size of 124 μm, 4.8 pbw) were used in Parts A and B. (Density = 0.31 g / cm 3 )

[0022] Example 3 - Preparation of a Foamed Organopolysiloxane Article Containing Expanded Perlite Particles The process for preparing the foamed article of Example 1 was carried out in substantially the same manner, except that Omyasphere 235 T-FQ expanded perlite particles (9.1 pbw) were used in Parts A and B. (Density = 0.35 g / cm 3 )

[0023] Comparative Example 2 - Preparation of a Foamed Organopolysiloxane Article Using Hollow Glass Beads The process for preparing the foamed article of Example 1 was carried out in substantially the same manner, except that 3M iM16K hollow glass beads (average volume average particle size of 20 μm, 20 pbw) were used in Parts A and B. (Density = 0.28 g / cm 3 ). The amount of beads was selected to give a filler volume similar to that of the expanded perlite of Example 1.

[0024] Thermal Insulation and Combustibility 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.

[0025] 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 ensuring that the indenter was parallel to the surface. The hardness was read while in firm contact with the specimen. A hardness less than 80 was considered acceptable.

[0026] Compressive force The 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 circularly cut 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 rate 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. A compressive force less than 500 kPa was considered acceptable.

[0027] Density of the foam The foam density was calculated based on the average thickness and weight of two 1-inch diameter foam samples.

[0028] The properties of the organopolysiloxane article filled with expanded perlite were compared with two other foams: Comparative Example 1 (a commercially available organopolysiloxane article (COHRlastic silicone foam available from Stockwell Elastomerics), which has the same structure as the foam of the example except that it does not contain expanded perlite) and Comparative Example 2 (a foam containing 3M Glass Bubbles iM16K hollow glass microspheres).

[0029] Table 1 is an overview of the performance characteristics of the foams of Examples 1 to 3, the commercially available comparative foams, and the foams containing hollow glass microspheres. The density was measured in g / cm 3 . 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 seconds) refers to the surface temperature of the sample after 300 seconds, and the flammability refers to the observability of the flame during the heat insulation test.

[0030] 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 iM316K hollow glass microspheres.

[0031]

Table 1

[0032] Table 1 shows that all the expanded perlite-containing foams of the present invention pass all the tests, but 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

1. 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; f) 1 to 15 weight percent of expanded perlite.

2. The polysiloxane functionalized with at least two Si-H groups is functionalized with at least three Si-H groups, the total concentration of components a, b, and c is in the range of 50 to 80 weight percent based on the weight of the composition, the concentration of the flame retardant is in the range of 2 to 20 weight percent based on the weight of the composition, and the concentration of expanded perlite is in the range of 2 to 10 weight percent based on the weight of the composition. The composition according to Claim 1.

3. The polysiloxane functionalized with at least one ethylenically unsaturated group is a divinyl-functionalized polydimethylsiloxane having a degree of polymerization in the range of 100 to 1000. The composition according to Claim 2.

4. The flame retardant is Al(OH) ３ , Mg(OH) ２ , MgCO ３ ·3H ２ O, Mg ５ (CO ３ ) ４ (OH) ２ ·4H ２ O, MgCa(CO ３ ) ２ , AlO(OH), NaHCO ３ , and hydrated MgSO ４ The composition according to claim 3, which is one or more flame retardants selected from the group consisting of

5. The divinyl-functionalized polydimethylsiloxane has a bimodal distribution of divinyl-functionalized polydimethylsiloxane having an overall viscosity in the range of 10,000 to 50,000 mPa·s. The composition according to any one of Claims 1 to 4.

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