Thermally conductive polyurethane adhesive composition for electric vehicle batteries

Abstract

The present invention relates to a thermally conductive polyurethane adhesive composition for use in an electric vehicle battery, in particular to a thermally conductive polyurethane adhesive composition having excellent mechanical properties, excellent flame retardancy, high thermal conductivity and high cycle efficiency, to an article comprising the adhesive composition, and to a method for manufacturing the same.

Description

[0001] This invention relates to a thermally conductive polyurethane adhesive composition for use in electric vehicle batteries, and more particularly to a thermally conductive polyurethane adhesive composition having excellent mechanical properties, excellent flame retardancy, high thermal conductivity and high cycle rate, articles comprising said adhesive composition, and a method for manufacturing the same.

[0002] Electric vehicles (EVs) have advantages over internal combustion engine vehicles in terms of reducing CO2 emissions, pollution, and greener energy consumption. Currently, battery thermal management limits energy density, which in turn limits the driving range of EVs. Concerns about driving range are a key factor hindering consumer adoption of EVs.

[0003] In electric vehicles, batteries are typically thermally managed or cooled by cooling units. Thermal interface materials (TIMs) facilitate efficient heat transfer between the battery and the cooling unit. TIMs come in various forms, with effective physical bridging of the battery and cooling unit surfaces and good thermal conductivity being key criteria, regardless of the TIM's properties. TIMs can take the form of thermally conductive grease, putty, gaskets, gap fillers, and phase change materials, each with its own set of performance characteristics, advantages, and disadvantages.

[0004] Thermally conductive adhesives (TCAs) are TIMs and offer advantages over the aforementioned technologies because they attempt to combine the mechanical strength of structural adhesives (including the strength that remains ideally maintained under fluctuations in temperature, humidity, and vibration levels) with the thermal properties of TIMs. Typical additional requirements for these materials in battery applications include excellent flame retardancy and electrical isolation.

[0005] Automotive or battery manufacturers' dispensing and assembly processes typically require a range of specific properties, such as low abrasiveness of single-component materials, good dispensing properties of pre-cured materials, and excellent cycle-time performance / cycle rate, to achieve assembly efficiency. Cycle time refers to the time required to dispense the adhesive, assemble the component, and then remove the assembled component from the production line. TCA influences this cycle time through a trade-off between: the compressive strength of the pre-cured material, which needs to be low within a given time window to clamp the battery assembly and cooling plate together without damage; and the build-up strength of the cured 2K mixture, which needs to provide structural integrity for the newly assembled component as it leaves the production line.

[0006] Developing a TCA that simultaneously meets all of the above characteristics is challenging. It is particularly advantageous to develop a TCA that meets the above characteristics while providing low energy, room temperature curing, and eliminating the need for UV curing or additional time-consuming or expensive steps.

[0007] To achieve high thermal conductivity (i.e., exceeding 1 W / mK), fillers with high thermal conductivity (i.e., exceeding 80 W / mK) can be used, but they have disadvantages such as being expensive, abrasive, and / or conductive. Inexpensive, less abrasive, and electrically insulating fillers typically have lower thermal conductivity (i.e., less than 50 W / mK), thus requiring high filler loadings to achieve thermal conductivity exceeding 1 W / mK. These high filler loadings often result in low application rates, high compressive forces, high density, and generally poor aging performance.

[0008] To achieve good cycle time performance, careful control of TCA reactivity and prudent selection of filler packs and polyols are necessary to minimize compressive forces. If the material cures too quickly, the battery components cannot be properly assembled on fragile parts with the required minimum force, for example, less than 0.5 MPa at a 0.8 mm gap 15 minutes after applying the adhesive composition. If the adhesive cures too slowly, the battery components will not have the required structural strength to be removed intact from the assembly line within a given time window, for example, greater than 0.25 MPa at 60 minutes after application.

[0009] Efforts have been made to develop thermally conductive adhesive compositions for assembling electric vehicle batteries.

[0010] For example, WO2019120924A1 discloses a two-component adhesive composition for electric vehicles, comprising a first component (A) and a separate second component (B), wherein component (A) comprises a-1) at least one polyol with a molecular weight Mn of 700 to 12000 g / mol; a-2) a chain extender with a molecular weight Mn of 60 to 600 g / mol; a-3) at least one thermally conductive filler A1 with a thermal conductivity not exceeding 50 W / m·K, such as alumina and aluminum hydroxide; and a-4) at least one thermally conductive filler A2 with a thermal conductivity of at least 80 W / m·K, such as graphite and boron nitride; and wherein component (B) comprises at least one NCO-terminated compound.

[0011] CN111995979A discloses a fast-curing polyurethane thermally conductive structural adhesive composition comprising component (A) and component (B), wherein component (A) consists of polyether glycol, chain extender, thermally conductive filler, flame retardant, dehydrating agent, and catalyst; and component (B) consists of polyether glycol, 4,4'-diphenylmethane diisocyanate (MDI), thermally conductive filler, and flame retardant. This adhesive is used for assembling batteries for electric vehicles.

[0012] US20220209324A1 discloses a thermal interface composition for a battery-powered vehicle comprising: a) a urethane-based binder component comprising at least one non-reactive polyurethane prepolymer, and b) aluminum trioxide, wherein the at least one non-reactive polyurethane prepolymer: i) is a reaction product of at least one polyisocyanate and at least one aliphatic monool; ii) is substantially free of residual isocyanate groups; and iii) has an average molecular weight of 2,000-50,000 g / mol, and wherein, if a polyol-based material is present in the composition, the content level of the polyol-based material is less than the total content level of the urethane-based binder component.

[0013] CN111019587A discloses a two-component polyurethane adhesive composition for battery-powered vehicles, comprising component (A) and component (B), wherein component (A) comprises a hydrophobic polyol, a polyester polyol, a surface-modified thermally conductive filler, an additional filler, and a catalyst; and component (B) comprises a polyisocyanate, a polyisocyanate trimer, a surface-modified thermally conductive filler, and a dispersant.

[0014] CN111808570A also discloses a two-component polyurethane adhesive composition for battery-powered vehicles, comprising component (A) and component (B), wherein component (A) comprises hydroxyl-terminated polybutadiene polyol, flame-retardant polyester polyol, aromatic polyether polyol, chain extender, filler, silane coupling agent, and catalyst; and component B comprises polyurethane prepolymer, dehydrating agent, filler, and dispersant.

[0015] Therefore, there is a strong need to develop high-performance, low-density / lightweight polyurethane-based TCA that can meet the combined criteria of high thermal conductivity, excellent flame retardancy, low compressibility, good sizing properties, high cycle rate, good mechanical properties, and good aging performance.

[0016] These objectives are achieved through this invention. One aspect of this invention relates to a thermally conductive adhesive composition comprising: (a) At least one polyol (A) having an average hydroxyl functionality of at least 2.0 and a weight-average molecular weight greater than 3000 g / mol. (b) At least one polyol (B) having an average hydroxyl functionality of at least 2.0 and a weight-average molecular weight of not more than 3000 g / mol. (c) At least one chain extender, (d) At least one catalyst, (e) at least one reaction retarder, (f) at least one isocyanate-terminated compound, (g) at least one type of aluminum oxide, and (h) At least one aluminum hydroxide.

[0017] Unless otherwise stated, "molecular weight" refers to weight-average molecular weight. According to the present invention, the number-average molecular weight Mn and the weight-average molecular weight Mw are determined by gel permeation chromatography (GPC, also known as SEC) using styrene standards at 23°C, in accordance with DIN EN ISO 16014-5:2012-10.

[0018] Polyol (A) Polyols are understood to be compounds containing more than one hydroxyl group (-OH) in their molecules. Polyols may also have other functional groups on their molecules. The term "polyol" includes a single polyol or a mixture of two or more polyols. The polyol (A) in the thermally conductive adhesive composition has an average hydroxyl functionality of at least 2.0, preferably 2.0 to 3.5, more preferably 2.0 to 3.0, and a weight-average molecular weight greater than 3000 g / mol, preferably greater than 4000 g / mol, more preferably 4000 to 6000 g / mol. Average hydroxyl functionality refers to the average number of reactive hydroxyl groups contained in a polyol molecule. When the -OH functionality and molecular weight of the polyol (A) are within the respective ranges, this polyol (A) can impart sufficient flexibility to the cured adhesive, which is necessary for battery assemblies bonded by the adhesive, for example, considering impact resistance.

[0019] Suitable polyols (A) with this type of -OH functionality and molecular weight include reaction products of low molecular weight polyols with epoxides, i.e., so-called polyether polyols. The epoxides preferably contain 2 to 4 carbon atoms. Some reaction products of this type include, for example, ethylene glycol, propylene glycol, isobutanediol, hexanediol, or 4,4'-dihydroxydiphenylpropane with ethylene oxide, propylene oxide, or butane oxide, or mixtures thereof. It is also suitable to react polyols such as glycerol, trimethylolethane or trimethylolpropane, pentaerythritol, or sugar alcohols, or mixtures thereof, with the aforementioned epoxides to form polyether polyols. Thus, depending on the desired molecular weight, products can be obtained by adding only a few moles of ethylene oxide and / or propylene oxide per mole of low molecular weight polyol, or by adding more than one hundred moles of ethylene oxide and / or propylene oxide. Other polyether polyols can be obtained by, for example, condensation of glycerol or pentaerythritol while eliminating water. Some suitable polyols include those that can be obtained by the polymerization of tetrahydrofuran.

[0020] Polyethers are prepared in a known manner by reacting a starting compound containing active hydrogen atoms with an epoxide, such as ethylene oxide, propylene oxide, butane oxide, styrene oxide, tetrahydrofuran, or epichlorohydrin, or a mixture of two or more of these.

[0021] Suitable starting compounds are, for example, water, ethylene glycol, 1,2- or 1,3-propanediol, 1,4- or 1,3-butanediol, hexane-1,6-diol, octane-1,8-diol, neopentyl glycol, 1,4-hydroxymethylcyclohexane, 2-methylpropane-1,3-diol, glycerol, trimethylolpropane, hexane-1,2,6-triol, butane-1,2,4-triol, trimethylolethane, pentaerythritol, and mannitol. Sorbitol, methyl glycosides, sugars, phenol, isononylphenol, resorcinol, hydroquinone, 1,2,2- or 1,1,2-tris(hydroxyphenyl)ethane, ammonia, methylamine, ethylenediamine, tetramethylenediamine or hexamethylenediamine, triethanolamine, aniline, phenylenediamine, 2,4- and 2,6-diaminotoluene, and polyphenyl polymethylene polyamines obtainable by aniline / formaldehyde condensation, or mixtures of two or more of these.

[0022] Some suitable polyols (A) include glycol EO / PO (ethylene oxide / propylene oxide) block copolymers, EO-terminated polypropylene glycol, or alkoxylated bisphenol A.

[0023] Some suitable polyols (A) include polyether polyols modified with vinyl polymers. These polyols can be obtained, for example, by polymerizing styrene or acrylonitrile or mixtures thereof in the presence of polyether polyols.

[0024] Some suitable polyols (A) include polyester polyols. For example, polyester polyols obtained by reacting a low molecular weight alcohol with caprolactone can be used, said low molecular weight alcohol being more particularly ethylene glycol, diethylene glycol, neopentyl glycol, hexanediol, butanediol, propylene glycol, glycerol, or trimethylolpropane. Other suitable polyols for producing polyester polyols are 1,4-hydroxymethylcyclohexane, 2-methylpropane-1,3-diol, butane-1,2,4-triol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol, and polybutanediol.

[0025] Some suitable polyols (A) include polyester polyols obtained by polycondensation. Therefore, diols and / or triols can be condensed with less than stoichiometric amounts of dicarboxylic acids and / or tricarboxylic acids or their reactive derivatives to form polyester polyols. Suitable dicarboxylic acids are, for example, adipic acid or succinic acid and their higher homologues containing up to 16 carbon atoms, unsaturated dicarboxylic acids such as maleic acid or fumaric acid, cyclohexanedicarboxylic acid (CHDA), and aromatic dicarboxylic acids, more particularly isophthalic acids, such as phthalic acid, isophthalic acid, or terephthalic acid. Citric acid and trimellitic acid are also suitable tricarboxylic acids, for example. The mentioned acids can be used alone or as a mixture of two or more. A polyester polyol with a residual OH group content, formed by reacting at least one of the mentioned dicarboxylic acids with glycerol, is suitable. Suitable alcohols include, but are not limited to, propylene glycol, butanediol, pentanediol, hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, cyclohexanediol (CHDM), 2-methyl-1,3-propanediol (MPDiol), or neopentyl glycol or its isomers or derivatives, or mixtures of two or more thereof. High molecular weight polyester polyols may be used in the second synthetic stage and include, for example, the reaction products of polyols, preferably diols (optionally with a small amount of triols), and polycarboxylic acids, preferably dicarboxylic acids. Instead of free polycarboxylic acids, (if possible) the corresponding polycarboxylic anhydrides or corresponding polycarboxylic acid esters with alcohols preferably containing 1 to 3 carbon atoms may also be used. Polycarboxylic acids may be aliphatic, alicyclic, aromatic, or heterocyclic, or a combination of both. They may optionally be substituted, for example, by alkyl, alkenyl, ether, or halogen groups. Suitable polycarboxylic acids are, for example, succinic acid, adipic acid, octanoic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, methylenetetrahydrophthalic anhydride, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dimer fatty acids, or trimer fatty acids, or mixtures of two or more of these. A small amount of monofunctional fatty acids may optionally be present in the reaction mixture.

[0026] Polyester polyols may optionally contain a small amount of terminal carboxyl groups. Polyesters obtained from lactones, such as those based on ε-caprolactone (also known as "polycaprolactone"), or hydroxycarboxylic acids such as ω-hydroxyhexanoic acid may also be used.

[0027] Alternatively, oleochemically derived polyester polyols can be used. Oleochemically derived polyester polyols can be obtained, for example, by completely ring-opening an epoxidized triglyceride containing at least a portion of an olefinically unsaturated fatty acid mixture with one or more alcohols containing 1 to 12 carbon atoms, followed by partial transesterification of the triglyceride derivative to form an alkyl ester polyol having 1 to 12 carbon atoms in the alkyl group.

[0028] Some suitable polyols (A) include C36 dimer diols and their derivatives. Some suitable polyols include castor oil and its derivatives. Some suitable polyols include fatty polyols, such as hydroxylated products of unsaturated or polyunsaturated natural oils, hydrogenated products of unsaturated and polyunsaturated polyhydroxy natural oils, polyhydroxy esters of alkyl hydroxy fatty acids, polymerized natural oils, soybean polyols, and alkyl hydroxylated amides of fatty acids. Some suitable polyols include hydroxyl-functionalized polybutadiene. Some suitable polyols include polyisobutylene polyols. Some suitable polyols include polyacetal polyols. Polyacetal polyols are understood to be compounds that can be obtained by reacting a diol (e.g., diethylene glycol or hexanediol or mixtures thereof) with formaldehyde. Polyacetal polyols can also be obtained by the polymerization of cyclic acetals. Some suitable polyols include polycarbonate polyols. Polycarbonate polyols can be obtained, for example, by reacting a diol (e.g., propylene glycol, butane-1,4-diol or hexane-1,6-diol, diethylene glycol, triethylene glycol or tetraethylene glycol or a mixture of two or more thereof) with a diaryl carbonate (e.g., diphenyl carbonate) or phosgene. Some suitable polyols include polyamide polyols.

[0029] Some suitable polyols (A) include polyacrylates containing OH groups. These polyacrylates can be obtained, for example, by polymerizing olefinically unsaturated monomers with OH groups. Such monomers can be obtained, for example, by esterification of olefinically unsaturated carboxylic acids with diols, typically in slight excess. Suitable olefinically unsaturated carboxylic acids for this purpose are, for example, acrylic acid, methacrylic acid, crotonic acid, or maleic acid. The corresponding OH-functionalized esters are, for example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, or 3-hydroxypropyl methacrylate, or mixtures of two or more of these.

[0030] In one embodiment, the polyol (A) is selected from polyether polyols, polyester polyols, and combinations thereof. In a preferred embodiment, the polyol (A) is one or more polyether polyols, more preferably polypropylene glycol. Polyether polyols with an average hydroxyl functionality of at least 2.0 and a weight-average molecular weight greater than 3000 g / mol are commercially available, such as Voranol 4000LM and Voranol EP1900 from Dow.

[0031] In another embodiment of the invention, the polyol (A) is present in the adhesive composition in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, based on the total weight of the adhesive composition. When the adhesive composition is in a two-component or multi-component form, the polyol (A) is present in one component in an amount of 1 to 40% by weight, preferably 1% to 20% by weight, based on the total weight of the components in the adhesive composition.

[0032] Polyol (B) The polyol (B) in the thermally conductive adhesive composition has an average hydroxyl functionality of at least 2.0, preferably at least 2.5, more preferably greater than 3.0 to 5.0, and a weight-average molecular weight of not more than 3000 g / mol, preferably 500 to 2500 g / mol. When the OH functionality and molecular weight of the polyol (B) are within the corresponding ranges, the cured adhesive exhibits improved adhesive strength, which is crucial for battery assembly in electric vehicles.

[0033] Suitable polyols (B) with this type of -OH functionality and molecular weight include reaction products of low molecular weight polyols with epoxides, i.e., so-called polyether polyols. The epoxides preferably contain 2 to 4 carbon atoms. Some reaction products of this type include, for example, ethylene glycol, propylene glycol, isobutanediol, hexanediol, or 4,4'-dihydroxydiphenylpropane with ethylene oxide, propylene oxide, or butane oxide, or mixtures thereof. It is also suitable to react polyols such as glycerol, trimethylolethane or trimethylolpropane, pentaerythritol, or sugar alcohols, or mixtures thereof, with the aforementioned epoxides to form polyether polyols. Therefore, depending on the desired molecular weight, products can be obtained by adding only a few moles of ethylene oxide and / or propylene oxide per mole of low molecular weight polyol, or by adding more than one hundred moles of ethylene oxide and / or propylene oxide. Other polyether polyols can be obtained by, for example, condensation of glycerol or pentaerythritol while eliminating water. Some suitable polyols include those that can be obtained by the polymerization of tetrahydrofuran.

[0034] Polyethers are prepared in a known manner by reacting a starting compound containing active hydrogen atoms with an epoxide, such as ethylene oxide, propylene oxide, butane oxide, styrene oxide, tetrahydrofuran, or epichlorohydrin, or a mixture of two or more of these.

[0035] Suitable starting compounds are, for example, water, ethylene glycol, 1,2- or 1,3-propanediol, 1,4- or 1,3-butanediol, hexane-1,6-diol, octane-1,8-diol, neopentyl glycol, 1,4-hydroxymethylcyclohexane, 2-methylpropane-1,3-diol, glycerol, trimethylolpropane, hexane-1,2,6-triol, butane-1,2,4-triol, trimethylolethane, pentaerythritol, and mannitol. Sorbitol, methyl glycosides, sugars, phenol, isononylphenol, resorcinol, hydroquinone, 1,2,2- or 1,1,2-tris(hydroxyphenyl)ethane, ammonia, methylamine, ethylenediamine, tetramethylenediamine or hexamethylenediamine, triethanolamine, aniline, phenylenediamine, 2,4- and 2,6-diaminotoluene, and polyphenyl polymethylene polyamines obtainable by aniline / formaldehyde condensation, or mixtures of two or more of these.

[0036] Some suitable polyols (B) include glycol EO / PO (ethylene oxide / propylene oxide) block copolymers, EO-terminated polypropylene glycol, or alkoxylated bisphenol A.

[0037] Some suitable polyols (B) include polyether polyols modified with vinyl polymers. These polyols can be obtained, for example, by polymerizing styrene or acrylonitrile or mixtures thereof in the presence of polyether polyols.

[0038] Some suitable polyols (B) include polyester polyols. For example, polyester polyols obtained by reacting a low molecular weight alcohol with caprolactone can be used, said low molecular weight alcohol being more particularly ethylene glycol, diethylene glycol, neopentyl glycol, hexanediol, butanediol, propylene glycol, glycerol, or trimethylolpropane. Other suitable polyols for producing polyester polyols are 1,4-hydroxymethylcyclohexane, 2-methylpropane-1,3-diol, butane-1,2,4-triol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol, and polybutanediol.

[0039] Some suitable polyols (B) include polyester polyols obtained by polycondensation. Therefore, diols and / or triols can be condensed with less than stoichiometric amounts of dicarboxylic acids and / or tricarboxylic acids or their reactive derivatives to form polyester polyols. Suitable dicarboxylic acids are, for example, adipic acid or succinic acid and their higher homologues containing up to 16 carbon atoms, unsaturated dicarboxylic acids such as maleic acid or fumaric acid, cyclohexanedicarboxylic acid (CHDA), and aromatic dicarboxylic acids, more particularly isophthalic acids, such as phthalic acid, isophthalic acid, or terephthalic acid. Citric acid and trimellitic acid are also suitable tricarboxylic acids, for example. The mentioned acids can be used alone or as a mixture of two or more. A polyester polyol with a residual OH group content, formed by reacting at least one of the mentioned dicarboxylic acids with glycerol, is suitable. Suitable alcohols include, but are not limited to, propylene glycol, butanediol, pentanediol, hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, cyclohexanediol (CHDM), 2-methyl-1,3-propanediol (MPDiol), or neopentyl glycol or its isomers or derivatives, or mixtures of two or more thereof. High molecular weight polyester polyols may be used in the second synthetic stage and include, for example, the reaction products of polyols, preferably diols (optionally with a small amount of triols), and polycarboxylic acids, preferably dicarboxylic acids. Instead of free polycarboxylic acids, (if possible) the corresponding polycarboxylic anhydrides or corresponding polycarboxylic acid esters with alcohols preferably containing 1 to 3 carbon atoms may also be used. Polycarboxylic acids may be aliphatic, alicyclic, aromatic, or heterocyclic, or a combination of both. They may optionally be substituted, for example, by alkyl, alkenyl, ether, or halogen groups. Suitable polycarboxylic acids are, for example, succinic acid, adipic acid, octanoic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, methylenetetrahydrophthalic anhydride, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dimer fatty acids, or trimer fatty acids, or mixtures of two or more of these. A small amount of monofunctional fatty acids may optionally be present in the reaction mixture.

[0040] Polyester polyols may optionally contain a small amount of terminal carboxyl groups. Polyesters obtained from lactones, such as those based on ε-caprolactone (also known as "polycaprolactone"), or hydroxycarboxylic acids such as ω-hydroxyhexanoic acid may also be used.

[0041] Alternatively, oleochemically derived polyester polyols can be used. Oleochemically derived polyester polyols can be obtained, for example, by completely ring-opening an epoxidized triglyceride containing at least a portion of an olefinically unsaturated fatty acid mixture with one or more alcohols containing 1 to 12 carbon atoms, followed by partial transesterification of the triglyceride derivative to form an alkyl ester polyol having 1 to 12 carbon atoms in the alkyl group.

[0042] Some suitable polyols (B) include C36 dimer diols and their derivatives. Some suitable polyols include castor oil and its derivatives. Some suitable polyols include fatty polyols, such as hydroxylated products of unsaturated or polyunsaturated natural oils, hydrogenated products of unsaturated and polyunsaturated polyhydroxy natural oils, polyhydroxy esters of alkyl hydroxy fatty acids, polymerized natural oils, soybean polyols, and alkyl hydroxylated amides of fatty acids. Some suitable polyols include hydroxyl-functionalized polybutadiene. Some suitable polyols include polyisobutylene polyols. Some suitable polyols include polyacetal polyols. Polyacetal polyols are understood to be compounds that can be obtained by reacting a diol (e.g., diethylene glycol or hexanediol or mixtures thereof) with formaldehyde. Polyacetal polyols can also be obtained by the polymerization of cyclic acetals. Some suitable polyols include polycarbonate polyols. Polycarbonate polyols can be obtained, for example, by reacting a diol (e.g., propylene glycol, butane-1,4-diol or hexane-1,6-diol, diethylene glycol, triethylene glycol or tetraethylene glycol or a mixture of two or more thereof) with a diaryl carbonate (e.g., diphenyl carbonate) or phosgene. Some suitable polyols include polyamide polyols.

[0043] Some suitable polyols (B) include polyacrylates containing OH groups. These polyacrylates can be obtained, for example, by polymerizing olefinically unsaturated monomers with OH groups. Such monomers can be obtained, for example, by esterification of olefinically unsaturated carboxylic acids with diols, typically in slight excess. Suitable olefinically unsaturated carboxylic acids for this purpose are, for example, acrylic acid, methacrylic acid, crotonic acid, or maleic acid. The corresponding OH-functionalized esters are, for example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, or 3-hydroxypropyl methacrylate, or mixtures of two or more of these.

[0044] In one embodiment, the polyol (B) is selected from polyether polyols, polyester polyols, and combinations thereof. In a preferred embodiment, the polyol (B) is a polyether polyol and / or polyester polyol based on castor oil or soybean oil. Such polyether and / or polyester polyols are preferably reaction products of castor oil and ketone raisins, particularly those marketed by Covestro under the trade name Desmophen 1150 and by BASF under the trade name Sovermol 805.

[0045] In one embodiment of the invention, the polyol (B) is present in the adhesive composition in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, based on the total weight of the adhesive composition. When the adhesive composition is in a two-component or multi-component form, the polyol (B) is present in one component in an amount of 1 to 20% by weight, preferably 1% to 10% by weight, based on the total weight of the components in the adhesive composition.

[0046] Chain extender The adhesive composition according to the invention further comprises a chain extender. Typically, the chain extender is a low molecular weight molecule used to modify the backbone of a given polymer. Preferably, the molecular weight M of the chain extender is... n The concentration is 60 to 600 g / mol, more preferably 60 to 500 g / mol. In a preferred embodiment, the chain extender is a diol, particularly a straight-chain or branched diol having 9 or fewer carbon atoms. In a particularly preferred embodiment, the chain extender is selected from 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, neopentyl glycol, polybutanediol, cyclohexane-1,2-diol, cyclohexane-1,4-diol, 1,4-bis(hydroxymethyl)cyclohexane, dimer diols (e.g., from Croda's Pripol series), and mixtures thereof. In a preferred embodiment, the chain extender is 1,3-butanediol or 1,4-butanediol.

[0047] The chain extender is present in the adhesive composition in an amount of 0.1 to 10% by weight, preferably 0.2 to 5% by weight, based on the total weight of the adhesive composition. It has been found that the mechanical properties of the adhesive composition can be adjusted as needed by varying the amount of chain extender in component A.

[0048] In another embodiment, the weight ratio of polyols (A) and (B) to chain extender in the adhesive composition is 50:1 to 4:1, preferably 20:1 to 5:1.

[0049] catalyst The adhesive composition according to the invention further comprises one or more catalysts selected from tertiary amine compounds, organometallic compounds, and mixtures thereof. As catalysts, commonly known organometallic compounds in polyurethane chemistry can be used, such as iron or, in particular, tin compounds. Examples include 1,3-dicarbonyl compounds of iron, such as iron(III)-acetylacetonate, organotin compounds of tin, particularly divalent and tetravalent tin, especially Sn(II)-carboxylates or dialkyl-Sn(IV)-dicarboxylates or corresponding dialkoxylates, such as dibutyltin dilaurate, dibutyltin diacetate, dioctyltin diacetate, dibutyltin maleate, and tin(II) octoate. In particular, tertiary amines or amidines can be used as catalysts, optionally in combination with the aforementioned tin compounds. As amines, acyclic and, in particular, cyclic compounds can be used. Examples include tetramethylbutanediamine, bis(dimethylaminoethyl) ether, 1,4-diazabicyclooctane (DABCO), 1,8-diazabicyclo(5.4.0)undecene, 2,2'-dimorpholinodiethyl ether, dimethylpiperazine, or mixtures of the above amines. A preferred embodiment of the adhesive composition according to the invention comprises a tin compound, particularly dibutyltin dilaurate, as a catalyst, such as those sold under the trade name TINSTAB BL277.

[0050] The catalyst is present in the adhesive composition in an amount of 0.001 to 1% by weight, preferably 0.01 to 0.5% by weight, based on the total weight of the adhesive composition.

[0051] Reaction inhibitors The adhesive composition according to the invention further comprises one or more reaction retarders. In the context of this invention, a reaction retarder is understood to be a substance capable of slowing down the reaction between OH groups and NCO groups. For this purpose, thiols, such as alkyl thiols and / or acidic compounds, are suitable.

[0052] Examples of acidic compounds are organic or inorganic carboxylic acids, acyl chlorides, acidic inorganic salts, or other acidic organic compounds. Organic acids used as reaction retarders according to the invention are, for example, acids with a pKa range of 2.8 to 4.5, such as phthalic acid, isophthalic acid, terephthalic acid, ascorbic acid, benzoic acid, o-hydroxybenzoic acid, p-hydroxybenzoic acid, 2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, salicylic acid, adipic acid, succinic acid, malic acid, acetylsalicylic acid, alanine, β-alanine, 4-aminobutyric acid, glycine, lactic acid, sarcosine, and serine. However, formic acid, acetic acid, monochloroacetic acid or dichloroacetic acid, 2,4- or 2,6-dichlorophenylacetic acid; phosphoric acid, hydrogen phosphate; polymeric cation exchangers having carboxyl or orthophosphate groups; and lithium chloride, 4-toluenesulfonyl isocyanate, or acyl chlorides of the aforementioned carboxylic acids may also be used. The above-mentioned acidic compounds can be used alone or in combination.

[0053] Examples of thiols include, but are not limited to, isooctyl 3-mercaptopropionate, dodecyl 3-mercaptopropionate, trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetra(3-mercaptopropionate), dipentaerythritol hexa(3-mercaptopropionate), tris[2-(3-mercaptopropionyloxy)ethyl]isocyanurate, tetraethylene glycol bis(3-mercaptopropionate), 1,10-decanedithiol, ethylene glycol bis(3-mercaptopropionate), 1,2-ethylenedithiol, 1,3-propanedithiol, 1,4-butanedithiol, 1,6-hexanedithiol, 1,8-octanedithiol, and 2-mercaptoethanol, having n=2 to 40 carbon atoms. Monofunctional aliphatic straight-chain and branched thiols, 1,8-dimercapto-3,6-dioxaoctane, n-dodecyl thiols, n-octyl thiols, pentaerythritol tetra(3-mercaptobutyrate), 1,4-bis(3-mercaptobutyryloxy)butane, 1,3,5-tris(3-mercaptobutoxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, tert-dodecyl thiols, ethanethiol, isopropanethiol, dipentene dithiol, methanethiol, n-propanethiol, sec-butanethiol, tert-nonylthiol, tert-dodecyl thiols, tert-thiol blends, tert-butanethiol, grapefruit thiol Mercaptan), thioglycolic acid, thiolactic acid, 3-mercaptopropionic acid, ammonium thioglycolate, monoethanolamine thioglycolate, sodium thioglycolate, potassium thioglycolate, 2-ethylhexyl thioglycolate, isooctyl thioglycolate, isothiazyl thioglycolate, glycerol thioglycolate, glycerol dimercaptoacetate, pentaerythritol tetramercaptoacetate, butyl 3-mercaptopropionate, 2-ethylhexyl 3-mercaptopropionate, 3-mercaptopropionate The following thiols are mentioned: isotridecyl ester, octadecyl 3-mercaptopropionate, ethoxylated trimethylolpropane tris(3-mercaptopropionate) having n=1 to 10,000 ethylene oxide repeating units, monoethanolamine thiolactic acid, thiodiglycolic acid, diammonium dithioglycolic acid, di(2-ethylhexyl) thiodiglycolic acid, methylene bis(butyl thioglycolic acid), thiodipropionate, dithiobis(stearylpropionate), thioglycerol, and dithioglycerol. These thiols can be used alone or in combination.

[0054] In a preferred embodiment, the reaction retarder is a monofunctional aliphatic straight-chain and branched thiol, particularly n-dodecyl mercaptan.

[0055] Based on the total weight of the adhesive composition, the reaction retarder is present in the adhesive composition in an amount of 0.001 to 2% by weight, preferably 0.01 to 1% by weight.

[0056] In a preferred embodiment, the weight ratio of the reaction retarder to the catalyst in the adhesive composition is in the range of greater than 1 to less than 2, particularly 1.2 to 1.8. When the above weight ratio is within this range, a good balance between the build-up strength and compressive force of the cured adhesive can be obtained, thereby enabling a high cycle rate of the battery assembly bonded by the adhesive composition.

[0057] Isocyanate-terminated compounds The isocyanate-terminated compound can be any compound having an average of two, three, or more isocyanate groups. As used herein, the term "isocyanate-terminated compound" includes diisocyanates, polymeric isocyanates, and isocyanate-terminated oligomers and polymers. Such isocyanate-terminated compounds can be used alone or in combination. In one embodiment, the isocyanate-terminated compound is selected from aromatic polyisocyanates, alicyclic polyisocyanates, aliphatic polyisocyanates, and mixtures thereof, and preferably one or more aliphatic polyisocyanates. The isocyanate-terminated compound preferably has an NCO content of 20% to 30%. The viscosity of the isocyanate-terminated compound preferably does not exceed 5000 mPa·s.

[0058] Some advantageous isocyanate-terminated compounds have the general formula O=C=NXN=C=O, where X is aliphatic, alicyclic, or aryl, preferably an aliphatic or alicyclic group containing 4 to 18 carbon atoms.

[0059] Some suitable isocyanates include 1,5-naphthalene diisocyanate, diphenylmethane diisocyanate (MDI) (including 2,2'-, 2,4'-, and 4,4'- isomers), polymeric MDI, hydrogenated MDI (HMDI), phenyl dimethyl diisocyanate (XDI), tetramethylphenyl diisocyanate (TMXDI), di and tetraalkylene diphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, isomers of toluene diisocyanate (TDI), 1-methyl-2,4-diisocyanatocyclohexane, 1,6-diisocyanatocyclohexane, 1,6-diisocyanatocyclohexane, 1,6 - Diisocyanate-2,4,4-trimethylhexane, 1-isocyanate-methyl-3-isocyanate-1,5,5-trimethylcyclohexane (IPDI), chlorinated and brominated diisocyanates, phosphorus-containing diisocyanates, 4,4'-diisocyanate-phenylperfluoroethane, tetramethoxybutane-1,4-diisocyanate, butane-1,4-diisocyanate, hexane-1,6-diisocyanate (HDI), dicyclohexylmethane diisocyanate, cyclohexane-1,4-diisocyanate, ethylene diisocyanate, phthalate-bis-isocyanate ethyl ester; diisocyanates containing reactive halogen atoms, such as 1-chloromethylphenyl-2,4-diisocyanate, 1-bromomethylphenyl-2,6-diisocyanate, or 3,3-bis-chloromethyl ether 4,4'-diphenyl diisocyanate. Aromatic polyisocyanates are preferred, with diphenylmethane diisocyanate (MDI) and its isomers and polymeric MDI (pMDI) being more preferred, as part or all of the polyisocyanates used to synthesize prepolymers.

[0060] Some suitable isocyanates include isocyanate-functionalized prepolymers. Such prepolymers are formed by reacting an excess of polyisocyanate with a polyol, polyamine, polythiol, or a combination thereof. "Excess" is understood to mean that, during the reaction forming the prepolymer, the equivalent number of isocyanate functional groups from the polyisocyanate compound is greater than the equivalent number of hydroxyl functional groups from the polyol. In this disclosure, it should be understood that the terms polyisocyanate prepolymer or prepolymer or isocyanate-functionalized prepolymer apply to any compound prepared according to the foregoing description, i.e., as long as the compound is prepared with at least a stoichiometric excess of isocyanate groups relative to the isocyanate reactive groups, it will be referred to herein as a polyisocyanate prepolymer or prepolymer or isocyanate-functionalized prepolymer.

[0061] Sulfur-containing polyisocyanates are obtained, for example, by reacting 2 moles of hexamethylene diisocyanate with 1 mole of thiodiethylene glycol or dihydroxydihexyl sulfide. Other suitable diisocyanates are, for example, trimethylhexamethylene diisocyanate, 1,4-diisocyanate butane, 1,12-diisocyanate dodecane, and dimer fatty acid diisocyanates. Suitable diisocyanates are tetramethylene diisocyanate, hexamethylene diisocyanate, undecane diisocyanate, dodecane diisocyanate, 2,2,4-trimethylhexane-2,3,3-trimethylhexamethylene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, 1,3- and 1,4-tetramethylxylene diisocyanate, isophorone diisocyanate, 4,4-dicyclohexylmethane diisocyanate, tetramethylphenyl dimethyl diisocyanate (TMXDI), and lysine ester diisocyanate.

[0062] Aliphatic polyisocyanates with two or more isocyanate functional groups, formed by biuret bonds, diuret bonds, urethane bonds and / or trimerization reactions, are suitable.

[0063] Suitable at least trifunctional isocyanates are polyisocyanates formed by the trimerization or oligomerization of diisocyanates or by the reaction of diisocyanates with polyfunctional compounds containing hydroxyl or amino groups. Isocyanates suitable for producing trimers are the aforementioned diisocyanates, preferably trimers of HDI, MDI, TDI, or IPDI.

[0064] End-capped, reversibly blocked polyisocyanates, such as 1,3,5-tris-[6-(1-methylpropanediaminooxycarbonylamino)hexyl]-2,4,6-trioxahexahydro-1,3,5-triazine, are also suitable. Polymeric isocyanates, for example, formed as residues in diisocyanate distillation, are also suitable. Isocyanate-terminated compounds include single compounds or mixtures of two or more compounds.

[0065] In a preferred embodiment, the isocyanate-terminated compound is selected from HDI, IPDI, oligomers thereof, and combinations thereof, particularly combinations of HDI trimers and IPDI. The specially selected isocyanate-terminated compound may contribute to improving the lap shear strength and tensile strength of the cured product.

[0066] Based on the total weight of the adhesive composition, the isocyanate-terminated compound is present in the adhesive composition in an amount of 1 to 20% by weight, preferably 1 to 10% by weight. When the isocyanate-terminated compound is included in a two-component adhesive composition, the amount of the isocyanate-terminated compound is 5 to 30% by weight, preferably 15 to 20% by weight, based on the total weight of the component.

[0067] The ratio of isocyanate groups in the isocyanate-terminated compound to the OH groups in the polyol is generally within the equivalence range, and it is preferable if there is a slight excess of isocyanate groups on the surface relative to moisture. According to the invention, the NCO / OH ratio is between 0.90:1 and 1.5:1, particularly between 1.0:1 and 1.3:1.

[0068] Alumina According to the present invention, the thermally conductive adhesive composition comprises at least one type of alumina as a thermally conductive filler. The thermally conductive filler provides thermal conductivity to the cured adhesive, preventing battery overheating. The average particle size D50 of the alumina can be from 0.1 μm to 100 μm, preferably from 0.5 μm to 50 μm. Alumina can be used alone or as a mixture of two or more types of alumina with different particle sizes.

[0069] In this invention, there are no particular limitations on the shape of the alumina filler. The shape can be regular or irregular, including but not limited to polygons, cubes, ellipses, spheres, needles, sheets, plates, or any combination thereof. Preferably, the alumina is spherical. The alumina can be surface-modified or non-surface-modified.

[0070] Examples of commercially available alumina include, for example, AX1 M from NIPPON STEEL Chemical & Material Co., Ltd.; NASSR-05 from Bestry Performance Materials Co., Ltd.; DAW-01 from Denka Corporation; BAK 10 from Bestry Performance Materials Co., Ltd.; BA 7 from Bestry Performance Materials Co., Ltd.; and BAK 5 from Bestry Performance Materials Co., Ltd.

[0071] Alumina is present in an amount of 10 to 60% by weight, preferably 20 to 50% by weight, based on the total weight of the thermally conductive adhesive composition.

[0072] aluminum hydroxide According to the present invention, the thermally conductive adhesive composition further comprises at least one aluminum hydroxide as a thermally conductive filler and a flame retardant. In addition to its thermal conductivity, aluminum hydroxide inhibits or delays the spread of fire by suppressing chemical reactions in the flame or forming a protective layer on the surface of the adhesive material. The average particle size D50 of the aluminum hydroxide can be from 1 μm to 200 μm, preferably from 30 μm to 150 μm. Aluminum hydroxide can be used alone or in a mixture of two or more types of aluminum hydroxide with different particle sizes.

[0073] In this invention, there are no particular limitations on the shape of the aluminum hydroxide filler. The shape can be regular or irregular, including but not limited to polygons, cubes, ellipses, spheres, needles, sheets, plates, or any combination thereof. Preferably, the aluminum hydroxide is spherical. The aluminum hydroxide can be surface-modified or non-surface-modified.

[0074] Examples of commercially available aluminum hydroxide include, for example, the Martinal series of products from Huber Advanced Materials.

[0075] Aluminum hydroxide is present in an amount of 10 to 60% by weight, based on the total weight of the thermally conductive adhesive composition. Preferably, aluminum hydroxide is present in an amount of 30 to 50% by weight to improve the flame retardancy of the cured adhesive.

[0076] Based on the total weight of the thermally conductive adhesive composition, the total content of alumina and aluminum hydroxide is preferably from 50% to 98% by weight, more preferably from 70% to 95% by weight, to achieve a good balance between the viscosity of the adhesive composition and the thermal conductivity of the cured adhesive.

[0077] additive The compositions according to the invention may further comprise additives. Preferably, the additives are selected such that they do not react or undergo side reactions with isocyanates, at least during the crosslinking reaction. Preferably, the one or more additives are selected from: plasticizers, additional fillers, pigments, rheology modifiers, desiccants, additional flame retardants, dehydrating agents, antisettling agents, and defoamers. In a preferred embodiment, the amount of additives present in the adhesive composition is 0 to 10% by weight, preferably 0.1 to 5% by weight, based on the total weight of the adhesive composition. In another embodiment, the adhesive composition according to the invention is substantially free of plasticizers, or even free of plasticizers such as phthalates, because plasticizers may leach from the adhesive composition during storage or application. "Substantially free" should be understood to mean that each component is present in an amount of less than 2% by weight, more preferably less than 1% by weight, even more preferably less than 0.5% by weight, and particularly less than 0.1% by weight, based on the total weight of the adhesive composition. In yet another embodiment, the adhesive composition according to the invention is substantially free of phosphorus compounds as flame retardants, or even free of phosphorus compounds, because they may be incompatible with other components in the adhesive composition.

[0078] One-component, two-component or multi-component thermally conductive adhesive compositions The thermally conductive adhesive composition according to this application may be in the form of a one-component, two-component, or multi-component composition. In one embodiment, the thermally conductive adhesive composition may be preserved and stored as a single component when the reactants are inert under storage conditions, for example by blocking the reactive groups of certain reactants.

[0079] When the thermally conductive adhesive composition is a two-component adhesive composition, it consists of the following: Component (A), which comprises: (a) At least one polyol (A) having an average hydroxyl functionality of at least 2.0 and a weight-average molecular weight greater than 3000 g / mol. (b) At least one polyol (B) having an average hydroxyl functionality of at least 2.0 and a weight-average molecular weight of not more than 3000 g / mol. (c) At least one chain extender, (d) at least one catalyst, and (e) at least one reaction retardant, and Component (B), which comprises: (f) at least one isocyanate-terminated compound, Component (A) and / or component (B) further include: (g) at least one type of aluminum oxide, and (h) At least one aluminum hydroxide.

[0080] If necessary, some components, such as fillers or other additives, can be retained in one or more components other than components (A) and (B), forming a multi-component thermally conductive adhesive composition.

[0081] In a preferred embodiment, the two-component adhesive composition comprises the following: Based on the weight of component (A), component (A) comprises: (a) 1 to 40% by weight, preferably 1% to 20% by weight, of at least one polyol (A) having an average hydroxyl functionality of at least 2.0 and a weight-average molecular weight greater than 3000 g / mol. (b) 1 to 20% by weight, preferably 1% to 10% by weight, of at least one polyol (B) having an average hydroxyl functionality of at least 2.0 and a weight-average molecular weight of not more than 3000 g / mol. (c) 0.1 to 10% by weight, preferably 0.2 to 5% by weight, of at least one chain extender. (d) 0.001 to 1% by weight, preferably 0.01 to 0.5% by weight, of at least one catalyst, and (e) 0.001 to 2% by weight, preferably 0.01 to 1% by weight, at least one reaction retarder. (g) 10 to 60% by weight, preferably 20 to 50% by weight, of at least one type of alumina, and (h) 10 to 60% by weight, preferably 20 to 50% by weight, of at least one aluminum hydroxide, and Based on the weight of component (B), component (B) comprises: (f) 5 to 30% by weight, preferably 15 to 20% by weight, of at least one isocyanate-terminated compound. (g) 10 to 60% by weight, preferably 20 to 50% by weight, of at least one type of alumina, and (h) 10 to 60% by weight, preferably 20 to 50% by weight of at least one aluminum hydroxide.

[0082] Another object of the present invention is a cured adhesive product obtainable by curing the adhesive composition according to the invention. The curing of the adhesive composition of the invention can be carried out by common methods well known to those skilled in the art, such as low-energy and room-temperature curing, radiation treatment such as UV light treatment, exposure to moisture, induction, and / or heating.

[0083] For processability in industrial applications, the adhesive composition needs to have a viscosity that allows for easy and precise application. Therefore, an embodiment is preferred in which the viscosity of the adhesive composition according to the invention does not exceed 10,000 Pas, preferably not more than 1,000 Pas, particularly 30 to 1,000 Pas, at 2.4 s using a HAAKE rotational rheometer with parallel plates (20 mm in diameter). -1 The shear rate was measured at 20°C. Furthermore, the density of the adhesive composition according to the invention is 2 to 3 g / mL, preferably 2.1 to 2.6 g / mL.

[0084] The adhesive composition of the present invention is thermally conductive. In a preferred embodiment, the adhesive composition exhibits a thermal conductivity of at least 0.8 W / mK, preferably from 1.0 to 3.0 W / mK, as measured at 25°C according to ISO 22007-2. Surprisingly, it has been found that a favorable balance between thermal conductivity and adhesiveness can be achieved if the thermal conductivity of the adhesive composition is selected within the above range. Furthermore, the thermal conductivity within the above range makes the adhesive composition particularly suitable for use in components of energy storage devices such as batteries.

[0085] Typically, the high thermal conductivity of adhesive compositions is achieved at the expense of other adhesive properties such as flame retardancy, adhesion, and mechanical properties. Surprisingly, the cured adhesive compositions of the present invention not only exhibit excellent thermal conductivity but also favorable mechanical properties and a high cycle rate.

[0086] The cured adhesive product according to the invention exhibits a tensile strength of at least 0.5 MPa, preferably at least 1.0 MPa, measured at 23°C according to DIN EN ISO 527-2. The cured adhesive product according to the invention exhibits an lap shear strength of at least 2.0 MPa, preferably at least 3.0 MPa, measured at 23°C according to DIN EN ISO 4587-03. The cured adhesive product according to the invention exhibits an elongation at break of at least 10%, preferably at least 15%, measured at 23°C according to DIN EN ISO 527-2.

[0087] In addition, the cured adhesive product has excellent flame retardancy and exhibits no burning drips (V0 rating) at a thickness of 1 mm in the UL 94 fire test.

[0088] According to DIN EN ISO 4587-03, cured adhesive products exhibit a build-up strength of 0.25 to 1.0 MPa after curing at room temperature for 60 minutes. If the material cures too slowly and exhibits low build-up strength, the bonded workpiece, such as a battery, will not have the required structural strength to be completely removed from the assembly line within a given time window.

[0089] When the thermally conductive adhesive composition is a two-component composition as described above, component (A) has a compressive force of 0.1 to 0.5 MPa, preferably 0.2 to 0.4 MPa, when compressed to a thickness of 0.5 mm by an indenter moving at 1 mm / s. Compressive force is defined as the force measured at a given thickness when a fixed-area indenter moves at a specific speed to compress the test material to this specified thickness. After the mixed adhesive composition is cured at room temperature (23°C) for 10 minutes, when compressed to a thickness of 0.5 mm by an indenter moving at 1 mm / s, the mixed adhesive composition has a compressive force of 0.1 to 0.5 MPa, preferably 0.2 to 0.4 MPa, at that thickness. If the adhesive cures too quickly and exhibits high compressive force shortly after curing, the bonded workpiece, such as a battery, will not be able to be properly assembled on the fragile cured adhesive with the required minimum force within a sufficiently wide time window, meaning that the cycle rate achieved using this adhesive will be very low. Therefore, by combining the above-mentioned curing and mechanical properties, a sufficient cycle rate can be achieved in the manufacturing process using this adhesive composition.

[0090] The adhesive composition of the present invention is particularly suitable for assembling energy storage devices such as batteries. Therefore, it is important that the cured adhesive composition does not exhibit any significant conductivity. In a preferred embodiment, the cured adhesive composition thus has a high volume resistivity, preferably greater than 10⁻⁶. 9 m, especially greater than 10 10 m, determined according to DIN EN 62631-3-1.

[0091] To produce the adhesive composition according to the invention, polyols (A) and (B) are optionally mixed under heating, followed by optionally dissolving the solid components in the mixture. Additives are then mixed and dispersed. In this context, the moisture content should be kept low, for example, by reducing water through molecular sieves. Inert additives may also be partially mixed into the polyisocyanate compound. For application, the polyol components and isocyanate components are mixed together in a manner known per se, and the mixture is applied together to the substrate to be bonded.

[0092] Another object of the present invention is a method for manufacturing articles using the adhesive composition according to the present invention. The method according to the present invention comprises the following steps: i) Apply the adhesive composition according to the invention to the surface of the first substrate to be bonded; ii) Bringing the surface of the first substrate to be bonded, treated with the adhesive composition, into contact with the second substrate to be bonded; and iii) Curing the adhesive composition to obtain the desired article.

[0093] In a preferred embodiment, the contact between the first substrate to be bonded and the second substrate to be bonded is achieved by applying pressure.

[0094] The method according to the invention is particularly suitable for manufacturing temperature-sensitive devices. In a preferred embodiment, the adhesive composition is thus applied to the surface of a first substrate at a temperature of 20°C to 100°C, preferably 23°C to 70°C.

[0095] Another objective is an article obtainable by the manufacturing method according to the invention. Preferably, the article according to the invention comprises a cured adhesive composition according to the invention.

[0096] The adhesive composition according to the invention can be applied to various technical fields and is particularly suitable for manufacturing heat-sensitive objects, especially objects that generate heat. Therefore, another object of the invention is the use of the adhesive composition in the following areas: pipes, preferably cooling coils; electronic components, preferably light-emitting devices, computer devices, mobile phones, tablets, touch screens, energy storage devices, automotive technology, hi-fi systems and audio systems; joints between heat pipes and water tanks in solar heating; fuel cells and wind turbines; manufacturing of computer chips; lighting devices; batteries; housings; coolers; heat exchangers; wires; cables; heating wires; household appliances, such as refrigerators and dishwashers; air conditioners; accumulators; transformers; lasers; functional clothing; car seats; medical devices; fireproofing; electric motors; aircraft and trains.

[0097] The present invention will be described in more detail through the following embodiments, which should not be construed as limiting the concept of the invention.

[0098] Example The following materials are used in the examples.

[0099] Polyol (A) is an ethylene glycol-terminated polyethylene glycol / polypropylene glycol polyol with a Mw of approximately 4000 g / mol and an OH functionality of approximately 2.0. It was purchased from Dow under the trade name Voranol EP 1900.

[0100] Polyol (B) is a castor oil-based polyether / polyester polyol with a molecular weight of approximately 1000 g / mol and an OH functionality of approximately 3.5. It was purchased from BASF under the trade name Sovermol 805.

[0101] PPG-2000 is a polyether polyol with a molecular weight of approximately 2000 g / mol and an OH functionality of approximately 2.0. It was purchased from Covestro under the trade name ArcolPPG-2000.

[0102] Krasol LBH P 2000 is a polybutadiene polyol with a molecular weight of approximately 2100 g / mol and an OH functionality of approximately 1.9. It was purchased from Cray Valley.

[0103] The chain extender was 1,3-butanediol, purchased from Sigma-Aldrich.

[0104] The alumina filler is a commercially available mixture of alumina with D50 particle sizes of approximately 10 μm and approximately 2 μm, respectively.

[0105] Aluminum hydroxide filler is a commercially available product with a D50 particle size of approximately 100-90 μm.

[0106] The catalyst was dibutyltin dilaurate, purchased from Akcros under the trade name TINSTAB BL 277.

[0107] The reaction retardant was n-dodecyl mercaptan, purchased from Sigma-Aldrich.

[0108] Polyisocyanate 1 is a mixture of HDI trimer and IPDI, and is available from Covestro.

[0109] Polyisocyanate 2 is an HDI trimer and is available from Covestro.

[0110] The additive is a mixture of dehydrating agents, antisettling agents and adhesion promoters commonly used in the art.

[0111] Two-component polyurethane adhesive compositions were prepared as Examples (Ex.) and Comparative Examples (CEx.). Component A of the composition was formulated by thoroughly mixing all components except the thermally conductive filler and flame retardant using a Speed ​​Mixer DAC 400 (from FlackTek Inc.) according to the components and amounts in Tables 1 and 2. The thermally conductive filler and flame retardant were added to the mixture and thoroughly mixed until completely dissolved to obtain Component A.

[0112] Component B of the composition contains a polyisocyanate and the same filler / flame retardant package as component A, as shown in Table 3. Component B was thoroughly mixed using a Speed ​​Mixer DAC400 (from FlackTek Inc.). Components A and B were mixed together at a 2:1 weight ratio before application to the substrate. Different combinations of two-component adhesive formulations are shown in Table 4.

[0113] Table 1. Formulation of component A of the adhesive composition according to the present invention (in grams)

[0114] Table 2. Formulation (in grams) of component A in adhesive compositions not according to the invention.

[0115] Table 3. Formulation (in grams) of component B of the adhesive composition according to the present invention.

[0116] Table 4. Formulations of the two-component adhesive compositions according to the present invention (by weight)

[0117] Performance evaluation Flame retardancy To obtain samples for flame retardancy testing, a two-component adhesive composition was mixed and applied to achieve a thickness of 1 mm. The material was cured for 7 days under ambient pressure and temperature, and then 1 mm thick specimens measuring 125 × 13 mm were cut out.

[0118] The flammability rating of the 1 mm thick sample was evaluated according to the UL 94 fire resistance test, and the results are shown in Table 5.

[0119] Table 5. Test results of flammability rating

[0120] thermal conductivity To obtain samples for thermal conductivity testing, a two-component adhesive composition was mixed and applied to achieve a thickness of 1 mm. The material was cured for 7 days under ambient pressure and temperature, and then 1 mm thick circular specimens with a diameter of 30 mm were cut out.

[0121] Thermal conductivity was tested according to ASTM D5470. The test results are shown in Table 6.

[0122] Table 6. Test results of thermal conductivity

[0123] Lap shear strength, tensile strength and elongation at break To obtain samples for tensile strength and elongation testing, a two-component adhesive composition was mixed and cured for 7 days under ambient pressure and temperature. The samples were then cut into 5A test specimens. The test results are shown in Table 7.

[0124] The lap shear strength was tested according to ISO 4587-03. Tensile strength and elongation at break were tested according to ISO 527-2. The settling strength was tested according to ISO 4587-03. The test results are shown in Table 7.

[0125] Table 7. Test results of mechanical strength properties

[0126] Establish strength To obtain samples for testing build-up strength, a two-component adhesive composition was mixed and applied to an e-coated steel substrate to prepare lap shear specimens with an overlap of 15 × 25 mm and a gap of 1 mm. The specimens were cured under ambient pressure and temperature for 1 hour, and then the lap shear strength of the specimens was measured. The build-up strength was tested according to ISO 4587-03. The test results are shown in Table 8.

[0127] Table 8. Test results for establishing strength

[0128] Compression To measure the initial compressive force of component A (compression force A (MPa), @ 0.5 mm), an amount of material sufficient to cover a diameter of 40 mm and a height of 5 mm was deposited on the lower plate and pressed from 5 mm to 0.3 mm by an upper indenter (40 mm diameter) at a speed of 1 mm / s. The force corresponding to a thickness of 0.5 mm was recorded as the compressive force. To obtain the cured compressive force (compression force 2K (MPa, 10 min RT), @ 0.5 mm), the mixed adhesive composition was applied and measured as described above after a 10-minute curing time. The test results are shown in Table 9.

[0129] Table 9. Test results of initial and cured compressive forces

[0130] As can be seen from Tables 5 to 9, the adhesive composition according to the present invention achieves the expected performance in terms of flame retardancy, thermal conductivity, mechanical strength and cycle rate after curing.

[0131] However, Comparative Example 1, which did not contain aluminum hydroxide, exhibited poor flame retardancy. Comparative Example 2, which did not contain polyol (B) with an average hydroxyl functionality of at least 3.0 and a weight-average molecular weight of no more than 3000 g / mol, exhibited poor lap shear strength and tensile strength. Comparative Examples 3 and 5, which contained a lower molecular weight polyol instead of polyol (A), exhibited poor elongation at break. Comparative Example 4, which contained a lower molecular weight and higher functionality polyol instead of polyol (A), also exhibited poor elongation at break. Furthermore, Comparative Example 5, which contained a lower molecular weight polyol instead of polyol (A), could not achieve a good cycle rate in manufacturing because the compressive force increased rapidly during curing.

Claims

1. A thermally conductive adhesive composition comprising: (a) At least one polyol (A) having an average hydroxyl functionality of at least 2.0 and a weight-average molecular weight greater than 3000 g / mol. (b) At least one polyol (B) having an average hydroxyl functionality of at least 2.0 and a weight-average molecular weight of not more than 3000 g / mol. (c) At least one chain extender, (d) At least one catalyst, (e) at least one reaction retarder, (f) at least one isocyanate-terminated compound, (g) at least one type of aluminum oxide, and (h) At least one aluminum hydroxide.

2. The adhesive composition according to claim 1, wherein the polyol (A) is a polyether polyol, preferably having a weight-average molecular weight greater than 4000 g / mol.

3. The adhesive composition according to claim 1 or 2, wherein the polyol (B) is a polyether polyol and / or polyester polyol based on castor oil or soybean oil, preferably having a weight-average molecular weight of not more than 3000 g / mol.

4. The adhesive composition according to any one of claims 1 to 3, wherein the isocyanate-terminated compound is selected from aromatic polyisocyanates, alicyclic polyisocyanates, aliphatic polyisocyanates and mixtures thereof, and preferably one or more aliphatic polyisocyanates.

5. The adhesive composition according to any one of claims 1 to 4, wherein the chain extender is selected from 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, neopentanediol, polybutanediol, cyclohexane-1,2-diol, cyclohexane-1,4-diol, 1,4-bis(hydroxymethyl)cyclohexane, and mixtures thereof.

6. The adhesive composition according to any one of claims 1 to 5, wherein the catalyst is selected from tertiary amine compounds, organometallic compounds, and mixtures thereof.

7. The adhesive composition according to any one of claims 1 to 6, wherein the reaction retarder is selected from alkyl thiols, organic carboxylic acids, inorganic carboxylic acids, acyl chlorides, inorganic acid salts, and mixtures thereof.

8. The adhesive composition according to any one of claims 1 to 9, wherein the adhesive composition is a one-component, two-component, or multi-component adhesive composition, and preferably a two-component adhesive composition.

9. The adhesive composition according to any one of claims 1 to 8, wherein the adhesive composition is a two-component adhesive composition comprising: Component (A), which comprises: (a) At least one polyol (A) having an average hydroxyl functionality of at least 2.0 and a weight-average molecular weight greater than 3000 g / mol. (b) At least one polyol (B) having an average hydroxyl functionality of at least 2.0 and a weight-average molecular weight of not more than 3000 g / mol. (c) At least one chain extender, (d) at least one catalyst, and (e) at least one reaction retardant, and Component (B), which comprises: (f) at least one isocyanate-terminated compound, Component (A) and / or component (B) further include: (g) at least one type of aluminum oxide, and (h) At least one aluminum hydroxide.

10. A method of manufacturing the adhesive composition according to claim 9, comprising: a) Provide component (A) and component (B); as well as b) Mix component A and component B to obtain the adhesive composition.

11. A cured adhesive product, which can be obtained by curing an adhesive composition according to any one of claims 1 to 9.

12. An article comprising an adhesive composition according to any one of claims 1 to 9 or a cured adhesive product according to claim 11.

13. A method for manufacturing an article comprising at least two bonded substrates, comprising: i) Applying the adhesive composition according to any one of claims 1 to 9 to the surface of the first substrate to be bonded; and ii) Bring the surface of the first substrate containing the adhesive composition to be bonded into contact with the second substrate to be bonded.

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