Thermal interface material having a combination of filler and reduced squeeze force

Abstract

The thermally conductive composition may include a polymer matrix and a multimodal filler composition in the range of 60% to 95% by weight of the thermally conductive composition, the multimodal filler composition including: a first thermally conductive filler of aluminum trihydrate (ATH) having a D50 particle size in the range of 0.1 μm to 10 μm and a second thermally conductive filler of ATH having a D50 in the range of 10 μm to 100 μm, present in the range of 40% to 90% by weight of the multimodal filler composition in the range of 40% to 90% by weight of the multimodal filler composition; and 10% to 60% by weight of a third thermally conductive filler of alumina having a D50 in the range of 5 μm to 100 μm.

Description

[Technical Field]

[0001] Embodiments relate to thermally conductive compositions for use as gap fillers, adhesives, sealants, or pastes in applications requiring thermal management, such as electronics and automotive applications, and methods for using same.

[0002] Introduction Thermal interface materials, such as gap fillers and gels, are widely used for thermal management in electronics and automotive applications. For example, electric vehicle (EV) batteries are cooled by attaching one or more battery modules to a cooling plate that redirects heat. Efficient cooling requires consistent thermal contact between the battery module and the cooling plate, which often involves the use of thermal interface materials such as adhesives, sealants, and gap fillers. Thermal gap pads and dispensable gap fillers are two of the primary gap filler technologies. Of the two, dispensable gap fillers offer the advantages of more efficient heat transfer and less material waste compared to thermal pads, which may require trimming and customization during installation. It is desirable to have a thermal interface material composition with high thermal conductivity (>1.0 W / m·K), the ability to form a cured solid part without the application of heat, low density, and ease of processing. Another common challenge with thermal interface materials is the separation of the matrix phase and filler during storage. Therefore, there is a need to develop thermal interface materials with high thermal conductivity, low viscosity, and storage stability. Summary of the Invention

[0003] In one embodiment, a thermally conductive composition can include a polymer matrix and a multimodal filler composition in the range of 60% to 95% by weight of the thermally conductive composition, the multimodal filler composition including: a first thermally conductive filler of aluminum trihydrate (ATH) having a D50 particle size in the range of 0.1 μm to 10 μm and a second thermally conductive filler of ATH having a D50 in the range of 10 μm to 100 μm, present in the range of 40% to 90% by weight of the multimodal filler composition in the range of 40% to 90% by weight of the multimodal filler composition; and 10% to 60% by weight of a third thermally conductive filler of alumina having a D50 in the range of 5 μm to 100 μm.

[0004] In another aspect, a method of using a thermally conductive composition includes combining an isocyanate component comprising a blocked isocyanate prepolymer and an isocyanate-reactive component comprising one or more polyetheramines to form a thermally conductive composition, wherein the isocyanate component and / or the isocyanate-reactive component are in the range of 60% to 95% by weight of the thermally conductive composition on a weight percent (wt%) basis, a multimodal filler composition in the range of 40% to 90% by weight of the multimodal filler composition on a weight percent (wt%) basis. and forming a multi-modal filler composition comprising: a first thermally conductive filler of aluminum trihydrate (ATH) having a D50 particle size in the range of 0.1 μm to 10 μm, a second thermally conductive filler of ATH having a D50 in the range of 10 μm to 100 μm, and 10 wt% to 60 wt% on a weight percent basis of a third thermally conductive filler of alumina having a D50 in the range of 5 μm to 100 μm; and installing the thermally conductive composition between a heat source and a heat sink in an EV battery. DETAILED DESCRIPTION OF THE INVENTION

[0005] Embodiments disclosed herein relate to thermally conductive compositions for use in thermal management applications, including improving heat transfer in batteries, electronic devices, automotive applications, and the like. The thermally conductive composition may include a polymer matrix having a multimodal filler composition dispersed therein. In some aspects, the polymer matrix may be formed from the reaction of an isocyanate component and an isocyanate-reactive component, which are combined and applied in situ to cure at room temperature. The thermally conductive compositions disclosed herein may also include a multimodal filler composition in the isocyanate component and / or the isocyanate-reactive component to improve thermal conductivity and reduce squeeze forces during application. In some cases, the thermally conductive composition may be pre-cured and applied as a gap filler pad.

[0006] During the battery assembly process, the gap filler composition is applied to the substrate and the battery modules are assembled ("squeezed") onto the pre-dispensed gap filler.

[0007] The thermally conductive compositions disclosed herein may include multimodal fillers that improve thermal conductivity and reduce squeezing forces during preparation and application. Reducing the viscosity and squeezing forces of the components of the thermally conductive composition can be beneficial, for example, by reducing the force required to assemble the gap filler between a heat source and a heat sink, such as in EV battery applications.

[0008] Numerical ranges disclosed herein include all values ​​from the lower limit to the upper limit, inclusive, and all values ​​therebetween. Unless stated to the contrary, implicit from the context, or customary in the art, all parts and percentages are by weight and all testing methods are current as of the filing date of this disclosure.

[0009] As used herein, the term "average particle size" refers to the median particle size or diameter of a distribution of particles, as determined, for example, by a Multisizer 3 Coulter Counter (Beckman Coulter, Inc., Fullerton, CA) according to the procedure recommended by the manufacturer. Median particle size D 50 is defined as the size for which 50 cumulative percent of the distribution is smaller than a specified value, and D 90 is defined as the size at which 90% of the distributions are smaller than a specified value. 10 is defined as the size at which 10 cumulative percent of the distribution is smaller than a specified value. Particle size distribution can be determined by methods known in the art, such as ASTM B822-10 or ASTM B822-20 or ISO 13320, using an appropriate suspension medium or in the dry state. The average particle size can be estimated based on measuring the surface area according to 8-11 ASTM D4315, or by using sieves of various mesh sizes and calculating the average from the cumulative weight of each size group. These alternative methods give an estimate of the average particle size similar to that determined by laser diffraction. The span of the filler particle size distribution is determined by (D 90 -D 10 ) / D 50 It is defined as the width of the particle size distribution.

[0010] As disclosed herein, "room temperature" means a temperature range of 18°C ​​to 35°C.

[0011] As disclosed herein, "molecular weight" means number average molecular weight.

[0012] As disclosed herein, "thermally conductive filler" means a thermal conductivity value greater than 1 W / m·K as measured by ISO 22007-2 using a hot disc or by ASTM D-5470.

[0013] As disclosed herein, "thermally conductive composition" (including both cured and uncured compositions) means a composition having a thermal conductivity value greater than 1.0 W / m·K as measured by ISO 22007-2 using a hot disc or by ASTM D-5470.

[0014] As disclosed herein, "squeeze force" refers to the resistance of a thermally conductive composition or component to compression, measured in Newtons. Squeeze force is measured using a TA.XTplus texture analyzer equipped with a 50 kg load cell. After each sample was dispensed onto a flat aluminum substrate, an acrylic probe with a 40 mm diameter was lowered to pinch the test material against the flat substrate, achieving a standard gap thickness of 5.0 mm. Any excess overflow material was trimmed off with a flat-edged spatula. After trimming, the test was initiated, and the probe was moved at a rate of 1.0 mm / s to a final thickness of 0.3 mm while recording the force. The specific force value recorded at the 0.5 mm gap is reported as the "squeeze force."

[0015] Viscosity can be measured using a TA instruments ARES-G2, AR2000 model rheometer or an Anton Paar MCR rheometer using a parallel plate fixture using methods commonly known in the art.

[0016] Thermally conductive compositions for use in thermal management applications, including improving heat transfer in electronic devices, batteries, automotive applications, etc. The compositions described can be used as thermally conductive gap fillers or pre-cured thermal pads for applications requiring thermal management, such as electric vehicle batteries.

[0017] The thermally conductive composition may include a polymer matrix having a multimodal filler composition dispersed therein. The polymer matrix may be formed from any suitable polymeric material and may be a solid, semi-solid, grease, or other form suitable for application and use as a gap filler. Suitable polymer matrices may be formed from elastomeric materials, such as, for example, polyurethanes, polyureas, epoxies, acrylates, silicones, silane-modified polymers (SMPs), and the like. In one embodiment, the polymer matrix is ​​polyurethane.

[0018] In some cases, the thermally conductive compositions disclosed herein generally comprise a two-component curable composition, i.e., a polymer matrix resulting from combining an isocyanate component ("A-side") and an isocyanate-reactive component ("B-side"). During application, the A-side and B-side are mixed to initiate a curing reaction at room temperature to form the thermally conductive composition. The thermally conductive composition may also include one or more thermally conductive fillers in the A-side and / or B-side to enhance heat transport properties.

[0019] A.) Isocyanate component The isocyanate component (or A-side) may contain one or more blocked isocyanate prepolymers and other additives such as plasticizers and thermally conductive fillers.

[0020] Blocked Isocyanate Prepolymer The isocyanate component may include a blocked isocyanate prepolymer product produced by reacting an isocyanate-terminated prepolymer (including any residual monomeric diisocyanates) with one or more blocking agents. Reaction with the blocking agent can limit the presence of free isocyanate (e.g., to a concentration of less than 0.1% by weight) and minimize premature gelation and crosslinking of the prepolymer. In some cases, reaction of the isocyanate groups with the blocking agent reduces the free isocyanate content in the prepolymer to less than 0.1%, less than 0.01%, less than 0.001%, or 0% by weight.

[0021] The isocyanate-terminated prepolymer can be any prepolymer prepared by reacting one or more polyols with a stoichiometric excess of one or more polyisocyanates containing two or more isocyanate groups. The polyisocyanate can be aromatic, aliphatic, araliphatic, or cycloaliphatic polyisocyanate, or mixtures thereof. Suitable polyisocyanates include toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and the like. Examples of suitable polyisocyanates include tetramethylene-1,4-diisocyanate, cyclohexane-1,4-diisocyanate, hexahydrotolylene diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-diphenyl diisocyanate, and 3,3'-dimethyldiphenylpropane-4,4'-diisocyanate, isomers thereof, or mixtures thereof. Suitable polyisocyanates may have an average isocyanate functionality of 1.9 or greater, 2.0 or greater, 2.1 or greater, 2.2 or greater, and simultaneously 3.5 or less, 3.2 or less, 3.0 or less, or 2.8 or less. The isocyanate-terminated prepolymer may have an isocyanate (NCO) content by weight per ASTM D5155-19 of 1% or more, 2.7% or more, or 5% or more, and simultaneously 30% or less, 25% or less, or 20% or less.

[0022] The isocyanate used to prepare the isocyanate-terminated prepolymer can be any of the above-mentioned monomeric polyisocyanates, their isomers, their polymeric derivatives, or mixtures thereof. In some cases, the isocyanate is toluene diisocyanate (TDI), its polymeric derivatives, or mixtures thereof. The TDI used to prepare the isocyanate-terminated prepolymer can be, among others, the 2,4-isomer and 2,6-isomer of toluene diisocyanate. Toluene diisocyanate-based prepolymers can provide lower unblocking temperatures along with higher conversion and reaction rates. Mixtures of two or more polyisocyanates can also be used.

[0023] Polyols and polyol mixtures used to prepare isocyanate-terminated prepolymers include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, bis(hydroxymethyl)cyclohexane such as 1,4-bis(hydroxymethyl)cyclohexane, 2-methylpropane-1,3-diol, methylpentanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, polyether polyols, and the like. Isocyanate-terminated prepolymers can be prepared by suitable procedures, such as those described in U.S. Pat. Nos. 4,294,951, 4,555,562, and 4,182,825, and WO 2004 / 074343. Isocyanate prepolymers and / or blocked isocyanate prepolymers can be formed using catalysts, which in some embodiments can include amine-based catalysts and / or tin-based catalysts.

[0024] In some embodiments, blocked isocyanate prepolymers can be formed by mixing and reacting one or more of the isocyanate functional groups on an isocyanate prepolymer with one or more blocking agents. Blocking agents for reaction with the isocyanate-terminated prepolymer can include monophenols, alkylphenols such as nonylphenol, or alkenylphenols such as cardanol, or mixtures such as cashew nut shell liquid, as well as derivatives and mixtures of any of these. The blocking agent can be used in an amount such that the equivalent of the functional group on the blocking agent corresponds to the molar equivalent or excess equivalent of the isocyanate groups being blocked. In some embodiments, blocked isocyanate prepolymers are made from TDI using a PO polyol with a number average equivalent weight of 500 to 2500 Da and a functionality of 1.9 to 3.1, having 2 to 15% NCO, prior to blocking with a blocking agent such as cardanol.

[0025] The isocyanate component may comprise, on a weight percent (wt%) basis, 0.5 wt% to 10 wt%, 1 wt% to 8 wt%, or 1 wt% to 5 wt% of the blocked isocyanate prepolymer. The blocked isocyanate prepolymer composition may comprise, on a weight percent (wt%) basis, 50 wt% to 95 wt%, 75 wt% to 94 wt%, or 80 wt% to 92 wt% of a thermally conductive filler.

[0026] B.) Isocyanate-Reactive Components The isocyanate-reactive component (or B-side) may contain one or more isocyanate-reactive species containing one or more functional groups such as hydroxyl or amine, and one or more additives such as plasticizers and thermally conductive fillers.

[0027] Polyetheramine The isocyanate-reactive component may include one or more polyetheramines. The polyetheramines may include monoamines, diamines, and higher order amines (e.g., triamines, tetraamines, etc.). In some cases, the isocyanate-reactive component may include a mixture of high and low molecular weight polyetheramines, such as one or more polyetheramines having a molecular weight of 2000 or greater (high MW) and one or more polyetheramines having a molecular weight of 2000 or less (low MW). The high MW polyetheramines and low MW polyetheramines may independently be selected from polyetheramines having an amine functionality ranging from 1.5 to 4, 2 to 4, or 2.5 to 3.5. The molar ratio of high MW to low MW polyetheramines may be in the range of 10:1 to 1:10, 5:1 to 1:5, or 3:1 to 1:3.

[0028] Suitable polyetheramines include resins prepared from a suitable initiator to which a lower alkylene oxide, such as ethylene oxide, propylene oxide, butylene oxide, or a mixture thereof, is added, followed by aminating the resulting hydroxyl-terminated polyol. When two or more oxides are used, they may be present as a random mixture or as blocks of one or the other polyether. In the amination step, the terminal hydroxyl groups in the polyol may be primary or secondary hydroxyl groups. The reductive amination process is known and is described in U.S. Pat. No. 3,654,370. Polyetheramines may include commercially available amines such as the primary aliphatic JEFFAMINE™ series of polyetheramines, such as JEFFAMINE™ T-403, JEFFAMINE™ T-3000, and JEFFAMINE™ T-5000, available from Huntsman Corporation, or Baxxodur™ EC 3003 and Baxxodur™ EC311, available from BASF.

[0029] In some embodiments, the isocyanate-reactive component may include at least one polyetheramine present at 0.2 wt% to 10 wt%, 0.5 wt% to 8 wt%, or 0.5 wt% to 7 wt% of the isocyanate-reactive component on a weight percent (wt%) basis. In formulations containing a mixture of high MW and low MW polyetheramines, the wt% ranges may apply to each type of polyetheramine independently or as a combined total. The isocyanate-reactive component may also include a thermally conductive filler present at 50 wt% to 95 wt%, 75 wt% to 94 wt%, or 80 wt% to 92 wt% on a weight percent (wt%) basis.

[0030] The plasticizer may be mixed into either the blocked isocyanate component or the amine component in an amount of 0 to 20 weight percent, 2 to 12 weight percent, or 4 to 10 weight percent, based on the total weight of the two-component composition. Suitable plasticizers may be any common plasticizers useful in polyurethanes and known to those skilled in the art. The plasticizer may be present in an amount sufficient to disperse the prepolymer / amine or reduce the viscosity of the composition. One example of a suitable plasticizer may be a methyl ester derivative of soybean oil. Other plasticizers may also be used, such as phthalates, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB), or terephthalates. Still other useful plasticizers include glycol ether esters, partially hydrogenated terpenes commercially available as "HB-40" (Eastman, Kingsport, TN), chloroparaffins, alkyl naphthalenes, and the like.

[0031] The thermally conductive composition may also include a dispersing additive on the B-side to stabilize fillers and other ingredients in at least one of the blocked isocyanate prepolymer composition or the amine composition. The dispersing additive functions to stabilize particles through either steric, electrosteric, or electrostatic means and can be nonionic, anionic, cationic, or zwitterionic. The structure can be linear polymers and copolymers, head-to-tail modified polymers and copolymers, AB-block copolymers, ABA block copolymers, branched block copolymers, gradient copolymers, branched gradient copolymers, hyperbranched polymers and copolymers, including hyperbranched polyesters and copolymers, and star polymers and copolymers. BASF, Lubrizol, RT Vanderbilt, and BYK are all common manufacturers of dispersants. Trade names include the Lubrizol Solsperse series, Vanderbilt Darvan series, BASF Dispex series, BYK DisperByk series, and BYK LP-C 2XXXX series. Grades can include BYK DisperByk 162, 181, 182, 190, 193, 2200, and 2152; LP-C 22091, 22092, 22116, 22118, 22120, 22121, 22124, 22125, 22126, 22131, 22134, 22136, 22141, 22146, 22147, 22435; LP-N 22269; Solsperse 3000, and Darvan CN.

[0032] In some embodiments, the dispersing additive is a hyperbranched polyester containing amine groups sterically protected by polyester side chains. The dispersing additives disclosed herein may be present in the B-side of the composition in an amount of 0.01 wt.% to 2 wt.%, 0.1 wt.% to 1 wt.%, or 0.1 wt.% to 0.5 wt.%.

[0033] Multimodal filler composition The thermally conductive composition may also include one or more thermally conductive fillers on the A-side and / or B-side that, when combined, produce a multi-modal filler composition.

[0034] Thermally conductive fillers disclosed herein may include one or more of aluminum trihydrate (ATH), natural or synthetic aluminum oxide (alumina), and the like. Multimodal filler compositions may include one or more filler types and have three or more modes characterized by local maxima. The multimodal filler composition may include a first thermally conductive filler of ATH having a D50 particle size in the range of 0.1 μm to 10 μm and a second thermally conductive filler of ATH having a D50 in the range of 10 μm to 100 μm, present in a range of 40 wt% to 90 wt% of the multimodal filler composition on a weight percent (wt%) basis, and a third thermally conductive filler of alumina having a D50 in the range of 5 μm to 100 μm, present in a range of 10 wt% to 60 wt% on a weight percent basis.

[0035] In some cases, the first and second thermally conductive fillers may be provided as subcombinations before being mixed with the third thermally conductive filler and / or into the thermally conductive composition. Subcombinations can be produced by combining separate fractions, removing intervening fractions such as with a screen or particle sizer, or by various grinding and sizing techniques. Subcombinations may also be modified with various processing agents before being combined with the third thermally conductive filler and / or into the thermally conductive composition. Subcombinations of first and second thermally conductive fillers may have particle size distributions characterized by a span of (D90-D10) / D50) greater than 2, greater than 3, or greater than 4, or less than 10.

[0036] In one embodiment, the subcombination of the first thermally conductive filler and the second thermally conductive filler has a D 10 , D in the range of 5 to 50 microns 50 , and D in the range of 50 to 200 microns 90 The thermally conductive filler may also be pre-treated with a C5 to C20 silane treating agent to modify hydrophobicity and compatibility with the isocyanate component and / or isocyanate-reactive component, and to reduce viscosity / squeeze force.

[0037] The multimodal filler composition may include a mixture of ATH and alumina particles, where two or more of the modes are ATH or alumina. In a particular example, the multimodal filler composition may include a first thermally conductive filler of ATH having a D50 particle size in the range of 0.1 μm to 10 μm and a second thermally conductive filler of ATH having a D50 in the range of 10 μm to 100 μm, present in a range of 40 wt% to 90 wt% of the multimodal filler composition on a weight percent (wt%) basis, and 10 wt% to 60 wt% of a third thermally conductive filler of alumina having a D50 in the range of 5 μm to 100 μm.

[0038] The multimodal filler composition may comprise a mixture of an ATH filler, such as those described above, and an alumina filler, wherein the ATH filler is present in a weight percent (wt%) of at least 35%, at least 40%, or at least 45% of the multimodal filler composition on a weight percent basis. In some cases, the multimodal filler composition may comprise a bimodal ATH composition (which may be surface-modified) combined with a third thermally conductive filler of alumina and / or in a thermally conductive composition. The thermally conductive fillers of the present disclosure may be modified with a treating agent before being incorporated into the A-side and / or B-side of the thermally conductive composition. In some cases, modifying the thermally conductive filler before adding it to the A-side and / or B-side components can reduce the viscosity or crushing force of the composition, in addition to improving storage stability and handling.

[0039] The treating agents disclosed herein can be used to alter the hydrophobicity / hydrophilicity of the surface of the thermally conductive filler, improve the interaction between the filler and the polymer, and modify the viscosity and compressibility of the resulting thermally conductive composition. For example, the filler may be reacted with a treating agent such as a silane (a process also known as silanization), which can increase the compatibility of the filler with the isocyanate component and / or isocyanate-reactive component. In some cases, one or more of the first, second, or third thermally conductive fillers are hydrophobically modified with a treating agent.

[0040] Suitable treating agents may include fatty acids, silanating agents, titanates, zirconates, aluminates, or silazane compounds. In some embodiments, the silanating agent may contain at least one alkoxy group to facilitate surface treatment and / or chemical bonding to the filler. The silanating agent may also contain other groups, including, for example, alkyl, hydroxyl, vinyl, allyl, hydrosilyl (i.e., SiH), or other functional groups that may react with or be compatible or miscible with the formulation. The silanating agent may be a Si(OR) n (R') 4-n wherein n is an integer from 1 to 3, R is independently a C1 to C3 alkyl group, and R' is independently a C1 to C20 alkyl group, with at least one R' selected from C5 to C20.

[0041] The treating agent may be applied to the filler as a pre-treatment prior to introduction into the A-side and / or B-side. The concentration may vary depending on the nature of the treating agent and the thermally conductive filler type. The treating agents disclosed herein may be added to the filler as a pre-treatment on a weight percent (wt%) basis at 0.5% to 10%, 0.5% to 7.5%, or 0.5% to 5% by weight of the filler.

[0042] The multimodal filler compositions disclosed herein may be present on a weight percent (wt%) basis at 40 wt% to 98 wt%, 50 wt% to 95 wt%, 60 wt% to 95 wt%, 75 wt% to 95 wt%, or 80 wt% to 95 wt% of the total weight of the thermally conductive composition. The multimodal filler compositions may be loaded into the A-side and / or B-side in equal or different amounts that, when combined, result in a thermally conductive composition having a filler concentration within any of the above ranges.

[0043] The filler compositions disclosed herein may have a thermal conductivity of at least 1 W / m·K, at least 5 W / m·K, or at least 20 W / m·K, and may have a thermal conductivity of less than 1000 W / m·K, or less than 100 W / m·K. The fillers disclosed herein may have a low density to reduce the overall weight of the composition, reducing weight in automotive, EV, and other application areas. In one embodiment, the filler density is <6 gm / cc, <4 gm / cc, or <2.5 gm / cc, or greater than 1 gm / cc.

[0044] In some embodiments, one or more treating agents, such as a silanizing agent, may be added to the A-side and / or B-side to improve storage stability. The silanizing agents disclosed herein may be present on a weight percent (wt%) basis from 0.1 wt% to 10 wt%, 0.1 wt% to 7.5 wt%, or 0.1 wt% to 5 wt% of the total weight of the thermally conductive composition (regardless of whether present in or on the multimodal filler composition).

[0045] catalyst The thermally conductive composition may include one or more catalysts mixed with at least one of the isocyanate component or the isocyanate-reactive component to promote the reaction between the blocked isocyanate functional groups and the polyetheramine groups. The catalyst may be any one or any combination / mixture of two or more selected from carboxylate salts, tertiary amines, amidines, guanidines, and diazabicyclo compounds. Examples of suitable catalysts include bismuth octoate, bismuth neodecanoate, potassium acetate, potassium 2-ethylhexanoate, or mixtures thereof. The catalyst may include a sterically hindered tertiary amine, a long-chain tertiary amine (i.e., an amine substituent of at least six hydrocarbons), or a cyclic tertiary amine. Suitable tertiary amines include dimorpholinodialkyl ethers, di((dialkylmorpholino)alkyl)ethers such as (di-(2-(3,5-dimethyl-morpholino)ethyl)ether), triethylenediamine, N,N-dimethylcyclohexylamine, N,N-dimethylpiperazine, 4-methoxyethylmorpholine, N-methylmorpholine, N-ethylmorpholine, or mixtures thereof. In some embodiments, the amidine or guanidine is an N-hydrocarbyl-substituted amidine or guanidine, and in further embodiments, the amidine or guanidine is a cyclic amidine or cyclic guanidine. Suitable amidines or guanidines include 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5,7-triazabicyclo[4.4.0]dec-5-ene, diazabicyclo[5.4.0]undec-7-ene, and N-methyl-1,5,7-triazabicyclododecene. The catalyst may be present in the isocyanate-reactive component in a weight percent (wt%) range of 0.001 wt% to 5.0 wt%, 0.01 wt% to 2.0 wt%, or 0.02 wt% to 0.5 wt%.

[0046] The thermally conductive composition may also include one or more additives, such as moisture scavengers (e.g., zeolites, molecular sieves, p-toluenesulfonyl isocyanate), adhesion promoters, thixotropic agents, plasticizers, colorants such as dyes or pigments, antioxidants, wetting agents such as surfactants, filler dispersants, thickeners, compatibilizers, anti-settling agents, anti-syneresis agents, flame retardants, and / or filler treatments such as silanes and BYK surface treatments.

[0047] C. Preparation method Thermally conductive compositions can be prepared by incorporating the multimodal filler composition into a polymer matrix by any suitable method. For polyurea and polyurethane compositions, the thermally conductive compositions of the present disclosure can be prepared by mixing the isocyanate and isocyanate-reactive components in any order and curing the mixture. Suitable mixing techniques include the use of a Ross PD mixer (Charles Ross), a Myers mixer, a FlackTek Speedmixer, a butterfly mixer, or the like. The various components of the composition can also be mixed using a continuous process such as twin-screw extrusion. The various streams can be fed separately into the extruder or premixed in various combinations to form the blocked isocyanate composition and the isocyanate-reactive component. Such a process can be suitable for large-scale production.

[0048] Prior to combining to form the thermally conductive composition, the isocyanate component and / or isocyanate-reactive component may have a squeeze force of 200 N or less, 180 N or less, or 150 N or less. The isocyanate component and / or isocyanate-reactive component may have a squeeze force in the range of 35 N to 250 N, 50 N to 150 N, or 60 N to 150 N.

[0049] The thermally conductive composition may include an isocyanate component and / or an isocyanate-reactive component that exhibits storage stability characterized by minimal increase in viscosity or squeeze force over time until combined for future use. -1Less than 200 Pa.s for 1 second -1 less than 300 Pa.s or 1 sec -1 In some embodiments, the blocked isocyanate prepolymer composition and the amine composition may exhibit a viscosity change of <50% over 3 days, or a viscosity change of <20% after heating at 60° C. for 7 days.

[0050] The isocyanate-reactive component and the isocyanate component can be combined such that the molar ratio of blocked isocyanate groups to amine-reactive groups is in the range of 0.90:1.1 to 1.1:0.9, for example, 0.90:1.1, 0.95:1.05, 0.97:1.03, or 1: 1. At the same time, the volume ratio of isocyanate-reactive component to isocyanate component in the curable composition may be controlled within the range of 0.90:1.1 to 0.95:1.05, 0.97:1.03, or at a ratio of 1:1.

[0051] The mixture of isocyanate component and isocyanate-reactive component may be cured at a temperature (e.g., room temperature) of 0° C. to 60° C., 10° C. to 50° C., 15° C. to 45° C., or 18° C. to 35° C. The cured thermally conductive composition may have a hardness range as determined by ASTM D-2240-15 ranging from 40 to 90 Shore 00, 50 to 85 Shore 00, or 60 to 80 Shore 00.

[0052] The cured thermally conductive composition may have a thermal conductivity of >1.5 W / m·K, >2.0 W / m·K, >2.5 W / m·K, or >2.9 W / m·K, or <50 W / m·K. In some embodiments, the cured thermally conductive composition may have a density of 1 gm / cc to 4 gm / cc, 1.5 to 3.5 gm / cc, or 1.8 to 3.1 gm / cc.

[0053] The thermally conductive compositions disclosed herein can be useful as gap fillers for energy storage devices and in electronic vehicle battery thermal management. In some cases, the compositions may include gap fillers and pastes applied between a heat source and a heat sink to provide a thermally conductive interface, such as between a battery module and a cooling plate. Manual or automated dispensing tools can be used to apply the thermally conductive composition directly to the target surface, minimizing waste. In one embodiment, the thermally conductive composition can be prepared by combining an isocyanate component and an isocyanate-reactive component and applying the mixture to a cooling plate or heat sink using an automated mixing and dispensing system, followed by installation of a battery cell, module, or pack, or other heat source.

[0054] Additionally, the thermally conductive composition can be used to form pre-cured articles, such as thermal interface gap pads. In one example, the pre-cured article can be formed by curing the thermally conductive composition to a desired thickness, cutting the article to the desired shape, and then compressing it as needed to secure it in place. In some cases, the cured article can also help reduce vibration stresses for shock damping. [Example]

[0055] The following examples are presented to illustrate embodiments of the present invention, but are not intended to limit its scope. All parts and percentages are by weight unless otherwise indicated. Table 1 lists the materials used in the following examples.

[0056] [Table 1]

[0057] Sample formulations were prepared by mixing the individual components in a high-speed mixer. Part A and Part B of the formulation were prepared separately. To cure the two-component system, Part A and Part B were mixed in a 1:1 weight ratio and mixed using a high-speed mixer. The samples were allowed to cure at ambient conditions.

[0058] The squeeze force was measured using a texture analyzer equipped with a 50 kg load cell. After dispensing the gap filler onto a flat, sturdy aluminum substrate, a 40 mm diameter acrylic probe was lowered to clamp the test material against the flat substrate, resulting in a standard gap thickness of 5.0 mm. Any excess overflow material was trimmed off with a flat-edged spatula. After trimming, the test was initiated, and the probe was moved at a rate of 1.0 mm / s to a final thickness of 0.3 mm while recording the force. The specific force value recorded at a 0.5 mm gap is reported as the "squeeze force." A squeeze force of <150 N is desired.

[0059] Thermal conductivity was measured using a Hot Disk Thermal Constants Analyzer (TPS 2500S, Thermtest Instruments, Canada) according to ISO 22007-2. All measurements were performed with a thermal probe using a double-sided measurement with two 6 mm cups, with a heating power of 150 W and a measurement time of 5 seconds.

[0060] Viscosity was measured on a TA instruments DHR-2 rheometer equipped with a Peltier bottom plate and a 25 mm parallel plate fixture with a 0.45 mm gap.

[0061] Density was measured on the cured articles according to ASTM D 792.

[0062] Hardness was measured using a Shore 00 durometer according to ASTM D2240.

[0063] The results are summarized in Tables 2-4, where samples designated "C" indicate comparative samples and "I" indicates inventive samples according to the present disclosure.

[0064] [Table 2]

[0065] [Table 3]

[0066] [Table 4]

[0067] As shown in the results, C1, which contained only bimodal ATH filler (corresponding to the first and second fillers), exhibited a relatively high squeeze force. C2, which contained zinc oxide as an additional filler, produced a viscous sample with a squeeze force >400 N. Samples C3 and C4 contained a second filler, ATH, with an average particle size of less than 15 microns. Similar results were obtained for C5, which contained a second filler with an ATH filler with an average particle size >20 microns. In contrast, samples of the present invention, which contained alumina with a particle size of 5-100 microns as a filler, exhibited a low squeeze force of <150 N and high thermal conductivity.

[0068] The examples shown in Table 4 below include two-part curable compositions with the filler combinations disclosed above. Both Part A and Part B had low squeeze force and high thermal conductivity. Parts A and B could be mixed to form cured parts with a hardness range of 75-85 Shore 00 within seven days. The cured parts also had high thermal conductivity and low densities of 2.1-2.2 gm / cc.

[0069] [Table 5]

[0070] The examples shown in Table 5 below demonstrate that compositions with low viscosity, low compression force, and high thermal conductivity can be obtained by the addition of silanes and dispersing additives. Furthermore, the compositions were storage stable, as indicated by minimal separation of the liquid phase from the paste based on visual observation. The compositions also rapidly hardened to form a solid having a hardness of 75 Shore 00 within 5 days.

[0071] [Table 6]

[0072] While the foregoing is directed to exemplary embodiments, other and further embodiments may be devised without departing from the basic scope thereof, which scope is determined by the claims that follow.

Claims

1. a polymer matrix; 1. A thermally conductive composition comprising: a multimodal filler composition in the range of 60 wt. % to 95 wt. % of the thermally conductive composition, on a weight percent (wt. %) basis, comprising: a first thermally conductive filler of aluminum trihydrate (ATH) having a D50 particle size in the range of 0.1 μm to 10 μm and a second thermally conductive filler of ATH having a D50 in the range of 10 μm to 100 μm, present in the range of 40 wt. % to 90 wt. % of the multimodal filler composition on a weight percent (wt. %) basis; and 10 wt. % to 60 wt. % of a third thermally conductive filler of alumina having a D50 in the range of 5 μm to 100 μm.

2. the polymeric binder comprises an isocyanate component comprising a blocked isocyanate prepolymer; 10. The composition of claim 1 prepared by the reaction of an isocyanate-reactive component comprising one or more polyetheramines and one or more catalysts selected from the group consisting of carboxylate salts, tertiary amines, amidines, guanidines, and diazabicyclo compounds.

3. The composition of claim 1 , wherein the thermally conductive composition has a thermal conductivity of 1.5 W / m·K or greater.

4. 10. The composition of claim 1, wherein the isocyanate component and the isocyanate-reactive component each have a squeeze force of less than 150 N.

5. The isocyanate component and the isocyanate-reactive component each have a viscosity of 1 second as measured using a parallel plate rheometer. －１ 10. The composition of claim 1 having a viscosity of less than 300 Pa.s at 1000 Wt.

6. The first filler and the second filler have a D in the range of 0.1 to 10 microns. １０ , D in the range of 5 to 50 microns ５０ , and D in the range of 50 to 200 microns ９０ 2. The composition of claim 1, wherein the ATH is a combination of

7. 10. The composition of claim 1, wherein one or more of the first thermally conductive filler, the second thermally conductive filler, or the third thermally conductive filler are hydrophobically modified with a treating agent.

8. The composition of claim 1 , wherein the first thermally conductive filler and the second thermally conductive filler are pretreated with a silanizing agent.

9. The composition of claim 1 , wherein a silanizing agent is added to one or more of the isocyanate component and the isocyanate-reactive component.

10. 10. The composition of claim 1, wherein the isocyanate-reactive component comprises a highly branched polyester containing amine groups sterically protected by polyester side chains.

11. 11. A thermally conductive gap filler prepared by combining the isocyanate component and the isocyanate-reactive component and curing the resulting thermally conductive composition of any one of claims 1 to 10.

12. 1. A method of using a thermally conductive composition, comprising: combining an isocyanate component comprising a blocked isocyanate prepolymer and an isocyanate-reactive component comprising one or more polyetheramines to form the thermally conductive composition; forming a multimodal filler composition in the range of 60 wt% to 95 wt% of the thermally conductive composition on a weight percent (wt%) basis, the multimodal filler composition comprising: a first thermally conductive filler of aluminum trihydrate (ATH) having a D50 particle size in the range of 0.1 μm to 10 μm and a second thermally conductive filler of ATH having a D50 in the range of 10 μm to 100 μm, present in the range of 40 wt% to 90 wt% of the multimodal filler composition on a weight percent (wt%) basis; and 10 wt% to 60 wt% of a third thermally conductive filler of alumina having a D50 in the range of 5 μm to 100 μm; and installing the thermally conductive composition between a heat source and a heat sink within an EV battery.

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