Filled low density organopolysiloxane foams

Abstract

The present invention provides a composition comprising a polyorganosiloxane foam having 30 to 50 weight percent of a filler dispersed therein, the foam having a density of 0.20 g / cm 3 ~0.60g / cm 3 The compositions of the present invention are useful as thermal barriers for battery modules.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to low density organopolysiloxane foams having relatively high filler contents. [Background technology]

[0002] Polyorganosiloxane (PDMS) foams offer lower density and higher compressibility than their rigid counterparts. Filled PDMS foams offer additional benefits, such as flame retardancy, targeted (high or low) thermal conductivity, and more robust mechanical properties. Filled foams can be used as thermal barriers for rechargeable batteries, such as lithium-ion batteries (LiBs), which are commonly used in various applications, including electric vehicles (EVs). While LiBs have desirable properties, such as high energy density and cycling stability, safety concerns currently limit their practical use. First, LiB cell failure can be caused by manufacturing defects, internal short circuits, overheating, overcharging, or mechanical shock. Second, heat generated from a failed cell can propagate, potentially causing thermal runaway in adjacent cells. The rapid pressure buildup resulting from these thermal events increases the risk of fire and explosion.

[0003] Thermal events can be mitigated by placing a thermal barrier between cells in a battery module that provides thermal insulation and flame resistance. Commonly used thermal barriers, such as aerogel, ceramic fiber, and mica board, offer such properties, but aerogel and ceramic fiber have poor mechanical resilience, while mica board is not compressible. Silicone blown foam, on the other hand, offers adequate compressibility and is therefore suitable for low- and medium-energy density batteries, but suffers from insufficient insulation to prevent thermal events in very high-energy density battery packs. Adding filler particles to the foam overcomes this problem, but the presence of filler at useful levels nevertheless disadvantageously increases the density of the foam.

[0004] Therefore, it would be advantageous in the field of thermal barriers to find a low density insulating barrier that has desirable thermal properties, flame retardancy, and other mechanical properties such as a high modulus of elasticity and greater mechanical strength. Summary of the Invention

[0005] In one aspect, the present invention provides a composition for forming a polyorganosiloxane foam, wherein the polyorganosiloxane foam is dispersed with 30 to 50 weight percent, based on the weight of the composition, of one or more fillers selected from the group consisting of metals, metal oxides, metal hydroxides, metal acetates, metal carbides, metal oxycarbides, metal carbonates and bicarbonates, metal hydroxycarbonates, metal nitrides, metal nitrates, metal sulfates, metal chlorides, metal silicides, and metal silicates, and the foam has a density of 0.20 g / cm. 3 ~0.60g / cm 3 wherein the foam comprises Si-O-R' and Si-X-R" groups in a ratio of Si-O-R':Si-XR" in the range of 0.4:1 to 7:1, where each X is independently O or CHCH, O-R' is the remainder of the blowing agent, and XR" is the remainder of the vinyl- or OH-substituted polyorganosiloxane.

[0006] The present invention addresses a need in the art by providing a method for preparing polyorganosiloxane foams having relatively low densities and relatively high filler contents. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram of a battery module including polyorganosiloxane foam material. DETAILED DESCRIPTION OF THE INVENTION

[0008] In one aspect, the present invention provides a composition comprising a polyorganosiloxane foam, the polyorganosiloxane foam having dispersed therein 30 to 50 weight percent, based on the weight of the composition, of one or more fillers selected from the group consisting of metals, metal oxides, metal hydroxides, metal carbides, metal oxycarbides, metal acetates, metal carbonates and bicarbonates, metal hydroxycarbonates, metal nitrides, metal nitrates, metal sulfates, metal chlorides, metal silicides, and metal silicates, the foam having a density of 0.20 g / cm 3 ~0.60g / cm 3 and wherein the foam comprises Si-O-R' and Si-X-R" groups in a ratio of Si-O-R':Si-XR" in the range of 0.4:1 to 7:1, where each X is independently O or CH2CH2, O-R' is the remainder of the blowing agent, and XR" is the remainder of the vinyl- or OH-substituted polyorganosiloxane.

[0009] The term "blow- ing agent balance" refers to a blowing agent and a copolymer having a degree of polymerization in the range of 5 to 200 and a D in the range of 60 to 100 mole percent. H The term "blowing agent" refers to the repeating units resulting from the reaction of the first polyorganosiloxane with the Si-H groups from the second polyorganosiloxane. The blowing agent may be a C1-C8 alcohol, a C1-C8 diol, benzyl alcohol, or HO-CH2CHRO. z—H, or water, where R is H, methyl, or ethyl, and z is 2 to 5. Examples of blowing agents include benzyl alcohol, ethanol, propanol, and 1,4-butanediol.

[0010] The first polyorganosiloxane has the structure I:

[0011] [ka] In the formula, m is 0 to 80, and n is 5 to 200 or up to 100, provided that the ratio of m:n is in the range of 0:100 to 40:60, preferably up to 36:64. H The concentration is in the range of 60 or 64 mole percent to 100 mole percent. The first polyorganosiloxane has a weighted average D H It is understood that the polyorganosiloxane may be one or more polyorganosiloxanes having a concentration of D and D H It is further understood that the groups may be distributed in a random, block, or alternating manner.

[0012] Thus, the remainder of the blowing agent is reacted with the following reaction:

[0013] [ka] where R—Si—H is the first organopolysiloxane and R′—OH is the blowing agent.

[0014] Similarly, the remainder of the vinyl-substituted polyorganosiloxane results from the reaction of the Si-H groups of the first polyorganosiloxane with a second polyorganosiloxane functionalized with one or more vinyl groups, the second polyorganosiloxane having a degree of polymerization ranging from 50 or 100 to 2000 or 1000.

[0015] Thus, the remainder of the vinyl-substituted polyorganosiloxane is reacted with the following reaction:

[0016] [ka] where =-R'' is a vinyl-substituted second polyorganosiloxane.

[0017] The remainder of the OH-substituted polyorganosiloxane can be prepared by the following reaction:

[0018] [ka] where HO-R'' is an OH-substituted second polyorganosiloxane.

[0019] Polyorganosiloxane foam: 0.20 g / cm 3 or 0.25g / cm 3 to 0.60 g / cm 3 or 0.52 g / cm 3 or 0.40 g / cm 3 The Si-O-R':Si-X-R" ratio, preferably the Si-O-R':Si-CHCH-R" ratio, ranges from 0.4:1 or 0.6:1 or 0.8:1 or 1:1 to 7:1 or 5:1 or 3:1. As used herein, the term "Si-O-R':Si-X-R" ratio refers to the Si-O-R':Si-X-R" ratio, as described in the Examples section. 13 It refers to the ratio determined by the area under the curve measured by C NMR spectroscopy.

[0020] The fillers are metals, metal oxides, metal hydroxides, metal acetates, metal carbides, metal oxycarbides, metal carbonates and bicarbonates, metal hydroxycarbonates, metal nitrides, metal nitrates, metal sulfates, metal chlorides, metal silicides, and metal silicates, as well as hydrates and mixtures thereof. The fillers are typically in the form of particles having an average volume particle size ranging from 0.1 μm or 0.5 μm or 1 μm to 1000 μm or 500 μm or 200 μm or 100 μm or 50 μm, as determined using a dynamic light scattering analyzer such as a Beckman Coulter LS 130 particle size analyzer.

[0021] Examples of suitable fillers include aluminum trihydroxide, hydromagnesium, sodium hydroxide, nesquehonite, boehmite, hunt's stone, magnesium hydroxide, silica, ground quartz, alumina, calcium sulfate, copper acetate, magnesium chloride, sodium sulfate, aluminosilicates, boron nitride, aluminum nitride, mica, wollastonite, calcium silicate, basalt, clays including calcined clay, zeolites, hollow fillers such as hollow glass spheres and hollow ceramics, expanded perlite, calcium carbonate, cesium oxide, iron oxide, titanium oxide, zinc oxide, and glass fibers, as well as hydrates of these fillers.

[0022] To achieve desired properties such as improved fire resistance and mechanical strength at high temperatures, it may be desirable to use a high-loading filler combination. A particularly desirable filler combination is aluminum trihydroxide and wollastonite. The filler concentration, based on the weight of the composition, ranges from 30, preferably 35, to 50, preferably 45, weight percent.

[0023] The composition is advantageously prepared in a two-part system. More specifically, to prevent premature reaction between the first polyorganosiloxane and the second polyorganosiloxane and the blowing agent, the catalyst, preferably a Pt catalyst, is separated from the first polyorganosiloxane. In one preferred method of preparing the composition of the present invention, a first portion of the second polyorganosiloxane, the catalyst, and the blowing agent are mixed in a first chamber. Then, while further mixing, a first portion of the filler is added to the contents of the first chamber. In a second container, the first polyorganosiloxane is mixed with a second portion of the second polyorganosiloxane, followed by the addition of a second portion of the filler and further mixing. To facilitate mixing of the two parts, it is advantageous to include a filler in each chamber. Then, each of the two parts is dispensed onto the desired substrate or target area through a dispenser, typically a double-pack cartridge equipped with a static mixer. After the first polyorganosiloxane contacts the second polyorganosiloxane and the blowing agent, reaction and accompanying foaming resulting from the release of hydrogen begins. The foam is advantageously cured at elevated temperatures, preferably at least 80°C or at least 100°C, preferably up to 200°C or up to 150°C.

[0024] The foams are useful as barrier materials for battery module applications. Thus, in another aspect, the invention is a battery module comprising a shell containing an array of spatially separated battery cells and a composition of the invention in contact with adjacent battery cells.

[0025] FIG. 1 illustrates this embodiment of the present invention. The battery module includes a shell (20) containing an array of spatially separated battery cells (30 and 30a) and a barrier material (40) that contacts adjacent battery cells (30 and 30a) and thereby forms an insulating barrier between the battery cells (30 and 30a). In this embodiment, the barrier material is disposed between adjacent battery cells (30 and 30a); in another embodiment, the barrier material covers the battery cells. The battery module may further include end plates (50) on the inner edge of the shell that are in direct contact with the battery cells (not shown) or indirect contact with the battery cells (30a) through the barrier material (40). The barrier material can be inserted into the spaces between adjacent battery cells and between the cells and the end plates, or a foam precursor can be applied over the cells and into the spaces between the battery cells and then cured to form the barrier material. Examples of suitable battery cell designs include cylindrical cells, pouch cells, and prismatic cells. [Example]

[0026] In the following examples, pbw refers to parts by weight. All ingredients were mixed using a Flacktex speed mixer at 2000 rpm.

[0027] Comparative Intermediate Example 1 - Preparation of a Filler-Free Two-Part Composition 1) a dimethylvinylsiloxy-terminated polydimethylsiloxane with a viscosity of approximately 1,900 mPa·s and 0.22 wt% vinyl groups, and 2) a 5:40:55 ViMe2SiO 1 / 2 :(CH3)3Si-O 1 / 2 :SiO 4 / 2 Structural unit ratio: 5000 m n , and 21,400 M w ViMe2SiO with 1 / 2 / (CH3)3Si-O 1 / 2 / SiO 4 / 2The first component (Part A) was prepared by mixing a 64:36 (w / w) blend of a) dimethylvinylsiloxy-endcapped polydimethylsiloxane (Polymer 1, 13.63 pbw) with b) dimethylvinylsiloxy-endcapped polydimethylsiloxane having a viscosity of 40,000 mPa·s (Polymer 1, 13.63 pbw) for 30 seconds. Pt(0) divinyltetramethyldisiloxane complex (1.13 pbw, 0.62 pbw Pt), 1,4-butanediol (3.14 pbw), and benzyl alcohol (4 pbw) were added to the mixture, and mixing was continued for an additional 30 seconds.

[0028] The second component (Part B) was prepared by mixing the polymer-resin blend (64.36 pbw) with Polymer 1 (11.23 pbw) for 30 seconds. H 79.31 M linear organohydrogenpolysiloxane (polymer 2, 17.95 pbw), and MD 3.2 D H 5.8 M of polydimethylorganohydrogensiloxane (Polymer 3, 6.46 pbw) was added to the mixture and mixing was continued for an additional 30 seconds.

[0029] Comparative Intermediate Example 2 - Filler and Si-H:Vinyl Ratio of 6.23:1 and D of 31.8% H Preparation of Two-Part Compositions with Mole Percentages The first component (Part A) was prepared by mixing the polymer-resin blend (45.53 pbw), Polymer 1 (7.94 pbw), and Micral 855 aluminum hydroxide (10.68 pbw) for 30 seconds. Then, Pt(0) divinyltetramethyldisiloxane complex (0.66 pbw, 0.62 wt% Pt), 1,4-butanediol (1.82 pbw), and benzyl alcohol (2.33 pbw) were added to the mixture, and mixing was continued for 30 seconds. Imerys Nyad G wollastonite (31.03 pbw) was added to the mixture, and mixing was continued for another 30 seconds.

[0030] Polymer Resin Blend (48.27 pbw), Polymer 1 (3.91 pbw), and Hymod M855 aluminum hydroxide (10.41 pbw) were mixed for 30 seconds, then Polymer 3 (2.02 pbw) and MD 8.7 D H 3.7 Part B was prepared by adding M linear organohydrogenpolysiloxane (Polymer 4, 33.72 pbw). Mixing was continued for 30 seconds, after which Imerys Nyad G wollastonite (31.03 pbw) was added to the mixture and mixing was continued for an additional 30 seconds.

[0031] Comparative Intermediate Example 3 - Filler and Si-H:Vinyl Ratio of 1.48:1 and 21.5% D H Preparation of a two-part composition having:

[0032] The first component (Part A) was prepared by mixing the polymer-resin blend (18.75 pbw) with dimethylvinylsiloxy-endcapped polydimethylsiloxane (Polymer 5, 50.9 pbw) having a viscosity of approximately 2,200 mPa·s for 30 seconds. Pt(0) divinyltetramethyldisiloxane complex (0.64 pbw, 0.62 pbw Pt) and benzyl alcohol (7.72 pbw) were added to the mixture. The contents were mixed for 30 seconds, after which Imerys Nyad G wollastonite (14.39 pbw) and Minusil 5 silica (5 μm, 7.6 pbw) were added to the mixture, and mixing was continued for an additional 30 seconds.

[0033] Part B was prepared by mixing Polymer Resin Blend (18.75 pbw) and Polymer 5 (47.58 pbw) for 30 seconds. Polymer 4 (6.68 pbw) and MD 60 D H 7M linear organohydrogenpolysiloxane (Polymer 6, 5 wt%) was added to the mixture and the contents were mixed at 2000 rpm for 30 seconds. Imerys Nyad G wollastonite (14.39 wt%) and Minusil 5 silica (5 μm, 7.6 wt%) were then added to the mixture and mixing was continued for an additional 30 seconds.

[0034] Intermediate Example 1 - Filler and Si-H:Vinyl Ratio of 1.94:1 and D of 90.6% H Preparation of a two-part composition having The first component (Part A) was prepared by mixing the polymer-resin blend (45.53 pbw), Polymer 1 (7.94 pbw), and Micral 855 aluminum hydroxide (10.68 pbw) for 30 seconds. Then, Pt(0) divinyltetramethyldisiloxane complex (0.66 pbw, 0.62 pbw Pt), 1,4-butanediol (1.82 pbw), and benzyl alcohol (2.33 pbw) were added to the mixture, and mixing was continued for 30 seconds. Imerys Nyad G wollastonite (31.03 pbw) was added to the mixture, and mixing was continued for another 30 seconds.

[0035] A second composition (Part B) was prepared by mixing polymer resin blend (48.27 pbw), Polymer 1 (3.91 pbw), and Hymod M855 aluminum hydroxide (11.59 pbw) for 30 seconds. Polymer 2 (2.93 pbw) and Polymer 3 (2.25 pbw) were then added to the mixture, and the contents were mixed for 30 seconds. Imerys Nyad G wollastonite (31.03 pbw) was added to the mixture, and mixing was continued for an additional 30 seconds.

[0036] Table 1 summarizes the formulations of Parts A and B in pbw. PRB refers to polymer-resin blend, P1-P6 refer to Polymers 1-6, BDO refers to 1,4-butanediol, BzOH refers to benzyl alcohol, Pt refers to Pt(0) complex, F1 refers to Micral 855 ATH filler, F2 refers to Hymod M855-SP filler, F3 refers to Nyad G wollastonite filler, and F4 refers to Minusil 5 silica.

[0037] [Table 1]

[0038] Table 2 shows the additional Part A and Part B formulations used to prepare the compositions of the present invention. F5 refers to Mica WG-325 Muscovite mica.

[0039] [Table 2]

[0040] Foam sheet manufacturing All foam sheets were manufactured using the following procedure: Parts A and B were thoroughly mixed for 15 seconds. The mixture was then poured between two matte mylar film sheets. Nip rollers were used to control the initial (pre-foaming) thickness at 0.045". The samples were then transferred to an oven set at 120°C. After 2 minutes, the release film sheet was removed and the samples were allowed to cure continuously at 120°C. Foam density was calculated based on the average thickness and weight of two 1-inch (2.54 cm) diameter foam samples.

[0041] 13 Calculation of Si-O-R':Si-X-R" ratios by C NMR spectroscopy Crosslinked silicone foam samples were cryogenically ground using liquid nitrogen in a SPEX SamplePrep 6875 Freezer / Mill. The resulting powder was 13 The samples were packed into a 4 mm zirconia rotor for C NMR (ssC NMR) spectroscopy. ssC NMR experiments were performed using a Bruker AVIII 400 MHz spectrometer equipped with a 4-mm CP / MAS probe. All experiments were performed at room temperature (approximately 20 °C) without further heating or cooling of the sample. The spinning speed was fixed at 13,000 Hz. Spectra were acquired using a standard hpdec pulse sequence with a 60 s recycle delay time and 4096 scans. All spectra were acquired using Bruker Topspin 3.2 software and processed using MestReNova 12.004 software. 13The Si-CH peak in the C spectrum was adjusted to 1.25 ppm. For the Si-CHCH-Si groups (Si-X-R" groups), the peak at 9 ppm was integrated, and for the Si-O-CH- groups (Si-O-R' groups), the peaks between 58 ppm and 67 ppm were integrated. To account for each vinyl group, the area under the peak at 9 ppm was divided by 2. The ratios of resonances associated with Si-O-R' to those associated with Si-X-R" groups were 0.5:1 and 2:1 for the foams formed from the compositions of Example 1 and Example 3, respectively. Table 3 shows the calculated D H Mole Percent D H %=D H m / (D H m +D n ), D for the blend of Parts A and B (i.e., pre-foam) when mixed H The ratio of vinyl groups to vinyl groups (D H : vinyl), filler concentration (filler%), g / cm 3 The figures show the foam density (Density) and foam uniformity (Foam). U indicates a uniform foam and NU indicates a non-uniform foam.

[0042] [Table 3]

[0043] Table 3 shows the D H : vinyl group ratio and D H By adjusting the concentration, the polyorganosiloxane composition can be made to be less than 0.6 g / cm 3 The data show that foams with densities of 1000 to 15000 and filler concentrations of greater than 30% can be obtained. The data also suggest that low density, high filler concentration foams are feasible with a variety of filler materials. Surprisingly, the foam without filler (Comparative Example 1) was found to be non-uniform, resulting in poor thickness control and poor compressibility.

[0044] A relatively high ratio of Si-H groups to vinyl or SiOH groups, combined with a relatively high concentration of Si-H groups in the first polyorganosiloxane, results in more H gas generation, resulting in greater expansion and, therefore, lower foam density, with a corresponding decrease in crosslink density. Surprisingly, a high concentration of filler contributes to the production of a uniform foam despite the increased H gas generation.

Claims

1. 1. A composition for forming a polyorganosiloxane foam, the polyorganosiloxane foam having dispersed therein 30 to 50 weight percent, based on the weight of the composition, of one or more fillers selected from the group consisting of metals, metal oxides, metal hydroxides, metal acetates, metal carbides, metal oxycarbides, metal carbonates, metal bicarbonates, metal hydroxycarbonates, metal nitrides, metal nitrates, metal sulfates, metal chlorides, metal silicides, and metal silicates, the foam having a density of 0.20 g / cm. ３ ~0.60 g / cm ３ wherein the foam comprises Si—O—R′ and Si—X—R″ groups in a ratio of SiOR′:SiX—R″ ranging from 0.4:1 to 7:1, where each X is independently O or CH ２ CH ２ wherein OR' is the remainder of a blowing agent and XR" is the remainder of a vinyl- or OH-substituted polyorganosiloxane), compositions.

2. the filler is one or more fillers selected from the group consisting of aluminum trihydroxide, hydromagnesium, sodium hydroxide, nesquehonite, boehmite, hunt's stone, magnesium hydroxide, silica, crushed quartz, alumina, calcium sulfate, copper acetate, magnesium chloride, sodium sulfate, aluminosilicates, boron nitride, aluminum nitride, mica, wollastonite, calcium silicate, basalt, clays including calcined clays, zeolites, hollow fillers such as hollow glass spheres and hollow ceramics, expanded perlite, calcium carbonate, cesium oxide, iron oxide, titanium oxide, zinc oxide, and glass fiber; and each X is selected from the group consisting of CH ２ CH ２ 2. The composition of claim 1, wherein:

3. The foam has a density of 0.25 g / cm ３ ~0.52 g / cm ３ 3. The composition of claim 2, wherein the foam has a density in the range of from 0.6:1 to 5:1, and the foam comprises Si—O—R′ and Si—X—R″ groups in a ratio of Si—O—R′:Si—X—R″ in the range of from 0.6:1 to 5:

1.

4. The foam has a density of 0.25 g / cm ３ ~0.40 g / cm ３ 3. The composition of claim 2, wherein the foam has a density in the range of from about 0.8:1 to about 5:1, and the foam comprises Si—O—R′ and Si—X—R″ groups in a ratio of Si—O—R′:Si—X—R″ in the range of from about 0.8:1 to about 5:

1.

5. 5. The composition of claim 4, wherein the filler is wollastonite or aluminum hydroxide or a combination thereof, the remainder of the blowing agent is benzyl alcohol, ethanol, propanol, or 1,4-butanediol, or any combination thereof, and the foam comprises Si—O—R′ and Si—X—R″ groups in a ratio of Si—O—R′:Si—X—R″ in the range of 1:1 to 3:

1.

6. 10. The composition of claim 1, wherein the filler is one or more fillers selected from the group consisting of aluminum trihydroxide, hydromagnesium, stearate, nesquehonite, boehmite, hunt's stone, magnesium hydroxide, silica, crushed quartz, alumina, calcium sulfate, copper acetate, magnesium chloride, sodium sulfate, aluminosilicates, boron nitride, aluminum nitride, mica, wollastonite, calcium silicate, basalt, clays including calcined clays, zeolites, hollow fillers such as hollow glass spheres and hollow ceramics, expanded perlite, calcium carbonate, cesium oxide, iron oxide, titanium oxide, zinc oxide, and glass fiber; and each X is O.

7. A battery module comprising a shell containing an array of spatially separated battery cells, and the composition of any one of claims 1 to 6 in contact with adjacent battery cells.

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