Low viscosity polyurethane pottant composition

Abstract

The polyurethane composition may include a reaction product of an isocyanate component containing one or more isocyanate compounds, an isocyanate-reactive component containing one or more polyether polyols, one or more aliphatic polyols, and one or more hollow particles present in at least one of the isocyanate component, the isocyanate-reactive component, or a third component. The method may include preparing the polyurethane composition by combining the isocyanate component and the isocyanate-reactive component to form a mixture and reacting the mixture to form the polyurethane composition. The method may include preparing a composite article, including disposing the polyurethane composition on a substrate and curing the composition to produce a composite article comprising the polyurethane article on the substrate.

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION Embodiments relate to low viscosity polyurethane compositions, methods for preparing same, and applications utilizing same. [Background technology]

[0002] Electric vehicles (EVs) operate on battery packs, with individual cells arranged in proximity in different patterns, along with cooling-related components and other parts. The battery's geometric shape and form can be cylindrical, rectangular / prismatic, and / or pouch-like. Pottant-like materials with different chemistries, including silicone, polyurethane, etc., can be used to connect these cells with surrounding components. The primary purpose of pottants and / or encapsulants in batteries is to provide insulation between battery cells during use (minimizing the effects of thermal events, including cascading damage between adjacent cells) and, in some cases, to increase the strength of the battery assembly to withstand stress and deformation as a structural element of the vehicle. Polyurethane-based foams are also used as pottants in some applications to reduce weight and improve efficiency and handling. However, there is often a tradeoff between the durability and heat resistance of such materials. Summary of the Invention

[0003] In one aspect, embodiments disclosed herein include a polyurethane composition comprising the reaction product of an isocyanate component containing one or more isocyanate compounds, an isocyanate-reactive component containing one or more polyether polyols, one or more aliphatic polyols, and one or more hollow particles present in at least one of the isocyanate component, the isocyanate-reactive component, or a third component.

[0004] In another aspect, embodiments disclosed herein include a method of preparing a polyurethane composition by combining an isocyanate component and an isocyanate-reactive component to form a mixture and reacting the mixture to form the polyurethane composition. The method can also include preparing a composite article, comprising disposing the polyurethane composition on a substrate and curing the composition to produce a composite article comprising the polyurethane article on the substrate. DETAILED DESCRIPTION OF THE INVENTION

[0005] Embodiments relate to polyurethane (PU) compositions for pottants and electronic materials that have low viscosity for increased flow and penetration during application and reduced swelling or bubble generation. The PU compositions can also produce materials with high strength, low density, and low thermal conductivity upon curing. In particular, the developed PU applications can exhibit reduced density without the need for the incorporation of chemical or physical blowing agents. Methods disclosed herein also include preparing and applying the PU compositions as pottants, encapsulants, or thermal barriers, particularly in electronic and / or automotive applications.

[0006] The PU compositions disclosed herein generally comprise two-component curable compositions, i.e., the product obtained from combining an isocyanate component ("A-side") and an isocyanate-reactive component ("B-side"). During application, the isocyanate and isocyanate-reactive component are mixed to initiate the curing reaction and form a polyurethane article or material. The PU compositions may also include one or more hollow particles added to the isocyanate and / or isocyanate-reactive component (or as a third component added during mixing) to reduce overall composition density and modify various mechanical properties.

[0007] The polyurethane compositions disclosed herein may include an isocyanate component containing one or more isocyanate compounds, such as polymeric isocyanates, aromatic isocyanates, or carbodiimide-modified isocyanates. The isocyanate compounds may be monomers, oligomers, prepolymers, or the like. The isocyanate component may include, for example, one or more isocyanate and / or polyisocyanate compounds. The isocyanate component may include isocyanate compounds having a nominal functionality greater than 1.5, greater than 2.0, or in the range of 1.5 to 4. The polyurethane compositions may include, in weight percent (wt%), 15 wt% to 80 wt%, 20 wt% to 80 wt%, or 25 wt% to 80 wt% of the isocyanate component.

[0008] The isocyanate component can include an isocyanate compound having a number average molecular weight of 150 g / mol to 750 g / mol. In some cases, the isocyanate compound can have a number average molecular weight as low as 150 g / mol, 200 g / mol, 250 g / mol, or 300 g / mol to as high as 350 g / mol, 400 g / mol, 450 g / mol, 500 g / mol, or 750 g / mol. Number average molecular weight values ​​reported herein are determined by end group analysis, gel permeation chromatography, and other methods known in the art. The isocyanate compound can be a monomer and / or polymer known in the art.

[0009] In some cases, the isocyanate component can include isocyanate compounds having an isocyanate content of 10% by weight or more, 20% by weight or more, or 30% by weight or more, or in the range of 10% to 50%.

[0010] The isocyanate component may include one or more of aliphatic polyisocyanates, cycloaliphatic polyisocyanates, araliphatic polyisocyanates, aromatic polyisocyanates, and the like. Examples of isocyanates include, but are not limited to, polymethylene polyphenylisocyanate, toluene 2,4- / 2,6-diisocyanate (TDI), methylenediphenyl diisocyanate (MDI, including its isomers), polymeric and prepolymeric MDI, triisocyanatononane (TIN), naphthyl diisocyanate (NDI), 4,4'-diisocyanatodicyclohexyl-methane, 3-isocyanatomethyl-3,3,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI), tetramethylene diisocyanate, hexamethylene diisocyanate, among others. diisocyanate (HDI), 2-methyl-pentamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate (THDI), dodecamethylene diisocyanate, 1,4-diisocyanatocyclohexane, 4,4'-diisocyanato-3,3'-dimethyl-dicyclohexylmethane, 4,4'-diisocyanato-2,2-dicyclohexylpropane, 3-isocyanatomethyl-1-methyl-1-isocyanatocyclohexane (MCI), 1,3-diisooctylcyanato-4-methylcyclohexane, 1,3-diisocyanato-2-methylcyclohexane, and combinations thereof. In addition to the isocyanates mentioned above, modified or partially modified polyisocyanates containing uretdione, isocyanurate, carbodiimide, uretonimine, allophanate, or biuret structures, among others, and combinations thereof, may also be utilized.For example, the isocyanate compound may include carbodiimide-modified MDI.

[0011] The isocyanate compound may include an isocyanate prepolymer resulting from the reaction of an isocyanate-reactive compound with a molar excess of an isocyanate compound or a polymeric isocyanate compound under conditions that do not cause gelation or solidification, and the isocyanate prepolymer may have a higher average isocyanate equivalent weight of greater than 400 g / eq. Formation of an isocyanate prepolymer is known in the art and may include reacting (1) at least one isocyanate compound with (2) at least one polyol compound. The isocyanate prepolymer may be described by its isocyanate index, which is defined as the ratio of isocyanate groups to isocyanate-reactive groups (e.g., OH groups) multiplied by 100. The isocyanate prepolymers disclosed herein can have an isocyanate index ranging from 30 to 400, 40 to 300, or 40 to 200, where the isocyanate index is defined as the equivalents of isocyanate divided by the total equivalents of isocyanate-reactive hydrogen-containing materials multiplied by 100.

[0012] Examples of commercially available isocyanates include, but are not limited to, polyisocyanates under the trade names VORANATE™, PAPI™, VORATRON™, VORAFORCE™, and ISONATE™, all of which are available from The Dow Chemical Company.

[0013] The isocyanate-reactive component can include a polyol blend containing one or more polyether polyols, polyester polyols, aliphatic polyols, polyol crosslinkers, and hollow particles, as well as other additives such as catalysts, surfactants, etc. The polyurethane composition can include a weight percent (wt%) range of 20 wt% to 85 wt%, 20 wt% to 80 wt%, or 25 wt% to 80 wt% of the isocyanate-reactive component.

[0014] The isocyanate-reactive component may comprise one or more polyether polyols prepared by polyaddition of alkylene oxides, such as propylene oxide and / or ethylene oxide, onto a polyhydroxy-functional starter compound in the presence of a catalyst known in the art. The polyether polyols may be prepared from a starter compound and one or more alkylene oxides, such as ethylene oxide, propylene oxide, and / or butylene oxide. Starter compounds may include, but are not limited to, molecules having 1 to 8 hydroxyl groups per molecule, such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, 1,4-butanediol, 1,6-hexanediol, triethanolamine, diethanolamine, diisopropanolamine, bisphenol A, glycerol, diglycerol, triglycerol, trimethylolpropane, di(trimethylolpropane)pentaerythritol, dipentaerythritol, tripentaerythritol, sugars and sugar alcohols such as sucrose and sorbitol. For purposes of this invention only, it is understood that polyether polyols may be blends of any of these polyether polyols with one or more starter compounds, and that polyether polyols may be one or more starter compounds themselves. Polyether polyols may also include polyols reacted with polyethers formed from copolymers of alkylene oxides, including block copolymers, and polyethers "capped" with hydroxyethyl and / or hydroxypropyl oligomers or polymers.

[0015] The polyether polyols may have a hydroxy functionality ranging from 1 to 8, or from 1.5 to 7. The polyether polyols may have a hydroxyl equivalent weight ranging from 30 Da to 4000 Da, or from 30 Da to 3000 Da, where hydroxyl equivalent weight is defined as the weight average molecular weight of the polyol divided by the average number of hydroxyl groups or average hydroxyl functionality of the molecule.

[0016] The isocyanate-reactive component can include at least one polyether polyol present in weight percent (wt%) from 40 wt% to 95 wt%, from 45 wt% to 95 wt%, or from 50 wt% to 90 wt%.

[0017] The isocyanate-reactive component may include one or more polyester polyols formed by the reaction of one or more carboxylic diacids with a polyol having an OH functionality of 2 to 4. Suitable carboxylic acids may include aromatic diacids or anhydrides, such as phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, methyl esters of phthalic acid, isophthalic acid, or terephthalic acid, dimethyl terephthalate, trimellitic anhydride, pyromellitic dianhydride, or mixtures thereof; and C4 to C12 aliphatic diacids. Suitable polyols for forming the polyester include one or more alkylene glycols or polyalkylene glycols having a hydroxy functionality of 2 to 4, such as ethylene glycol, 1,2- or 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, glycerin, and the like. Examples of polyester polyols include polyesters of phthalic anhydride and diethylene glycol, and polyesters of C4 to C12 diacids such as succinic acid or adipic acid and diethylene glycol.

[0018] The polyester polyols may have an average hydroxyl number (OH number) ranging from 100 mg KOH / g to 500 mg KOH / g, 150 mg KOH / g to 450 mg KOH / g, or 200 mg KOH / g to 450 mg KOH / g, as determined according to ASTM D4274-21. The isocyanate-reactive component may comprise one or more polyester polyols in weight percent (wt%) ranging from 10 wt% to 40 wt%, 15 wt% to 35 wt%, or 15 wt% to 30 wt%.

[0019] The isocyanate-reactive component can include one or more aliphatic polyols having at least two reactive hydroxyl groups. Aliphatic polyols include natural and synthetic polyester polyol derivatives, including products formed from the reaction of a polyol with one or more hydroxy fatty acids having 10 to 20 carbon atoms, including hydroxycapric acid, hydroxylauric acid, hydroxymyristic acid, hydroxypalmitic acid, hydroxymargaric acid, hydroxystearic acid, hydroxyeicosanoic acid, ricinoleic acid, and the like. For example, aliphatic polyols include triglycerides containing a fraction of hydroxy fatty acids, such as castor oil or its derivatives, and / or polyols made from epoxidized or hydroformylated natural oils, such as soybean oil and cashew nut shell liquid (i.e., CNSL). The aliphatic polyols can have a hydroxyl equivalent weight ranging from 30 Da to 2500 Da, or from 30 Da to 2000 Da.

[0020] The isocyanate-reactive component can include, in weight percent (wt%), 2 wt% to 25 wt%, 5 wt% to 25 wt%, or 5 wt% to 20 wt% of one or more aliphatic polyols.

[0021] The isocyanate-reactive component may include one or more polyol crosslinkers having a hydroxyl functionality of at least 3 and a weight average molecular weight of 800 g / mol or less. Suitable polyol crosslinkers may include glycerol, diglycerol, triglycerol, trimethylolpropane, di(trimethylolpropane), pentaerythritol, dipentaerythritol, tripentaerythritol, sorbitol, derivatives such as alkoxylates, or combinations thereof.

[0022] The isocyanate-reactive component may include, in weight percent (wt%), 1 wt% to 15 wt%, 1 wt% to 10 wt%, or 1 wt% to 5 wt% of one or more polyol crosslinkers.

[0023] The isocyanate-reactive component may include one or more silicone polyols having at least two reactive hydroxyl groups (e.g., diols, triols, polyols). The silicone polyol may include siloxane bonds (Si-O-Si) in its backbone, and may optionally further include divalent alkyl groups separating the siloxane units. Silicone polyols include HO-R 1 -Si(R 2 )2-[O-Si(R 2 )2] n -R 1 -OH, where each R 1 are independently a linking group having 0 to 18 carbon atoms, and each R 2 are independently a group having 2 to 18 carbon atoms, such as alkyl or hydroxyalkyl, where n is 10 to 20.

[0024] The isocyanate-reactive component can include one or more silicone polyols in weight percent (wt%) ranging from 10 wt% to 40 wt%, 15 wt% to 35 wt%, or 15 wt% to 30 wt%.

[0025] The isocyanate-reactive component may include one or more catalysts for enhancing polyurethane polymerization to produce the PU composition. Catalysts may be used individually or as catalyst packages containing multiple catalysts, such as gelling catalysts, blowing catalysts, and trimerization catalysts. Gelling catalysts and blowing catalysts may be distinguished by their tendency to favor either the urethane (gel) reaction in the case of gelling catalysts or the urea (blow) reaction in the case of blowing catalysts. A trimerization catalyst may be utilized to promote the isocyanurate-forming reaction in the composition. The catalyst package may also be added as a separate stream to the reaction mixture of the isocyanate and the isocyanate-reactive composition.

[0026] Gelling catalysts include organometallic compounds, cyclic tertiary amines and / or long-chain amines (e.g., containing several nitrogen atoms), and combinations thereof. Organometallic compounds include organotin compounds such as tin(II) salts of organic carboxylic acids, e.g., tin(II) diacetate, tin(II) dioctanoate, tin(II) diethylhexanoate, and tin(II) dilaurate, and dialkyltin(IV) salts of organic carboxylic acids, e.g., dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate, and dioctyltin diacetate. Bismuth salts of organic carboxylic acids can also be used as gelling catalysts, e.g., bismuth octanoate. Cyclic tertiary amines and / or long-chain amines include dimethylbenzylamine, triethylenediamine, and combinations thereof. Examples of commercially available gelling catalysts are POLYCAT® 8, DABCO® 33-LV, and DABCO® T-12 from Evonik, among other commercially available gelling catalysts.

[0027] The blowing catalyst may include bis-(2-dimethylaminoethyl)ether, pentamethyldiethylenetriamine, triethylamine, tributylamine, N,N-dimethylaminopropylamine, dimethylethanolamine, N,N,N',N'-tetra-methylethylenediamine, and combinations thereof, among others. One example of a commercially available blowing catalyst is POLYCAT® 5 from Evonik, among other commercially available blowing catalysts.

[0028] The trimerization catalyst may include any such catalyst known in the art. Examples of trimerization catalysts include, among others, N,N',N"-tris(3-dimethylaminopropyl)hexahydro-s-triazine; N,N-dimethylcyclohexylamine; 1,3,5-tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine; [2,4,6-tris(dimethylaminomethyl)phenol]; potassium acetate, potassium octanoate; tetraalkylammonium hydroxides such as tetramethylammonium hydroxide; alkali metal hydroxides such as sodium hydroxide; alkali metal alkoxides such as sodium methoxide and potassium isopropoxide; and alkali metal salts of long chain fatty acids having 10 carbon atoms to 20 carbon atoms, and combinations thereof. Some commercially available trimerization catalysts include, for example, DABCO® TMR-2, DABCO® TMR-20, DABCO® TMR-30, DABCO® TMR-7, DABCO® K, among other commercially available trimerization catalysts. 2097; DABCO® KI5, POLYCAT® 41, and POLYCAT® 46, each from Evonik.

[0029] Catalysts may include "latent catalysts" or "delayed catalysts," which are defined as catalytic compounds that have low catalytic activity or are relatively inactive at ambient temperatures and become more catalytically active upon heating, such as by dissociation, decoordination, ring-opening, ionization, or tautomerization, resulting in catalysis of at least one of the chemical reactions involved in making PU foam. Ambient temperatures may range from 15°C to 35°C, and room temperature is often about 23°C.

[0030] Latent / delayed catalysts may be gelling, blowing, and / or trimerization type catalysts, depending on their function in the foaming process. Latent catalysts are often a subset of tertiary amine gelling catalysts, including acid salts, phenol salts, or complexes of tertiary amine catalysts (e.g., delayed action tertiary amines based on 1,8-diazabicyclo[5.4.0]undec-7-ene), and the acid or phenol is often a carboxylic acid or phenolic species, such as, but not limited to, formic acid, acetic acid, propionic acid, 2-ethylhexanoic acid, phenoxyacetic acid, gluconic acid, tartaric acid, citric acid, phenol, nonylphenol, diisopropylphenol, and mixtures thereof. Some commercially available latent catalysts that can be used include, for example, DABCO® TMR-30, POLYCAT® SA2 LE, POLYCAT® SA-1 / 10, and DABCO® 8154 from Evonik; NIAX™ A-107, NIAX™ C-31, and NIAX™ C-225 from Momentive; and JEFFCAT™ ZF-54, JEFFCAT™ LED-204 from Huntsman Corporation; and mixtures thereof.

[0031] The catalyst or catalyst package may be present in the PU composition in weight percent (wt%) ranging from 0.1 wt% to 10 wt%, or from 1 wt% to 7 wt%. Optionally, the catalyst package may be added to the isocyanate-reactive components in an amount sufficient to provide a mixture having the corresponding weight percentages above.

[0032] The polyurethane composition may contain one or more hollow particles, which can modify physical properties, introduce void volume, and reduce overall density. The hollow particles and mixtures may be added to one or more of the isocyanate component and / or isocyanate-reactive component, or may be added as a third component during the combination of the isocyanate component and the isocyanate-reactive component. In some cases, hollow particles may be added to multiple components to improve viscosity matching and promote homogeneous mixing.

[0033] The hollow particles may include hollow shell particles or porous aerogels composed of glass, ceramic, silica, etc. The hollow particles may have different shapes and geometries, such as spheres, hemispheres, tubes, elongated, rectangular, oval, etc. The hollow particles may have densities ranging from 0.05 g / mL to 0.8 g / mL, or from 0.10 g / mL to 0.6 g / mL.

[0034] In some cases, the surface of the hollow particles can be modified to mediate interactions between the particle and the surrounding matrix and / or polymer phase, such as by adjusting its hydrophobicity or hydrophilicity. Surface modifications can include covalent and ionic chemistries to attach functional groups such as alkyl chains, siloxanes, hydroxyl groups, amines, thiols, isocyanates, epoxies, acrylates, aromatics, and the like. For example, the surface modification can involve the attachment of a compound of formula R (4-n) Si(OR 2 ) n where R is an alkyl or substituted alkyl group (e.g., substituted with the functional groups described above) having 1 to 20 carbon atoms, and n is an integer from 2 to 4. Examples of organosilanes include dimethoxydimethylsilane, dimethoxydiethylsilane, diethoxydimethylsilane; trimethoxymethylsilane, trimethoxyethylsilane, trimethoxypropylsilane, triethoxymethylsilane, triethoxyethylsilane, aminopropyltriethoxysilane, (3-glycidyloxypropyl)trimethoxysilane, methacryloxypropyltrimethoxylsilane, and vinyltriethoxysilane.

[0035] In some cases, the hollow particles may include glass particles having a density in the range of 0.1 g / mL to 0.6 g / mL and having an organosilane (e.g., epoxysilane) surface modification.

[0036] The polyurethane composition may include one or more hollow particles in weight percent (wt%) ranging from 0.5 wt% to 90 wt%, 1 wt% to 85 wt%, or 1 wt% to 70 wt%.

[0037] The polyurethane composition may include one or more flame retardants (also known as FRs or FR additives) to improve flame retardancy. Suitable flame retardants may include, for example, carbon black, aluminum hydroxide hydrate, silicates such as wollastonite, platinum and platinum compounds, carbonates such as calcium carbonate, red phosphorus, sodium citrate, and the like, among others. Alternatively, the flame retardant can be at least one of a halogen-based flame retardant, such as decabromodiphenyl oxide, octabromodiphenyl oxide, hexabromocyclododecane, decabromobiphenyl oxide, diphenyloxybenzene, ethylene bis-tetrabromophthalamide, pentabromoethylbenzene, pentabromobenzyl acrylate, tribromophenylmaleimide, tetrabromobisphenyl A, bis-(tribromophenoxy)ethane, bis-(pentabromophenoxy)ethane, polydibromophenylene oxide, tribromophenyl aryl ether, bis-dibromopropyl ether, tetrabromophthalic anhydride, dibromoneopentyl glycol, dibromoethyldibromocyclohexane, pentabromodiphenyl oxide, tribromostyrene, pentabromochlorocyclohexane, tetrabromoxylene, hexabromocyclododecane, brominated polystyrene, tetradecabromodiphenoxybenzene, trifluoropropene, and PVC. Alternatively, the flame retardant can be at least one of a phosphorus-based flame retardant, such as (2,3-dibromopropyl)-phosphate, phosphorus, cyclic phosphate, triaryl phosphate, bis-melaminium pentate, pentaerythritol bicyclic phosphate, dimethyl methyl phosphate, phosphine oxide diol, triphenyl phosphate, tris(2-chloroethyl) phosphate, trichloropropyl phosphate, triethyl phosphate, phosphate esters, such as tricresyl phosphate, trixylenyl phosphate, isodecyl diphenyl phosphate, ethylhexyl diphenyl phosphate, isopropylated triphenyl phosphate, t-butylated triphenyl phosphate, i-butylated triphenyl phosphate, and mixtures thereof.Alternatively, phosphate salts of various amines, such as ammonium polyphosphate, trioctyl, tributyl, or tris-butoxyethyl phosphate esters, and alkyl phosphate oligomers. Other flame retardants may include melamine and its derivatives, such as melamine salts, guanidine, dicyandiamide, ammonium sulfamate, alumina trihydrate, and magnesium hydroxide. FR additives may also include copolymer polyols, such as polyisocyanate polyaddition (PIPA) polyols or polyurea polyols, made by reacting low equivalent weight polyols (e.g., up to 80 hydroxyl equivalents) or polyamines with polyisocyanates in the presence of a base polyol continuous phase (e.g., a homopolymer or copolymer of propylene oxide and / or ethylene oxide having a hydroxyl equivalent weight of at least 200).

[0038] The amount of flame retardant can vary depending on factors such as the flame retardant selected and the intended use of the polyurethane composition to achieve a UL-94 vertical burn rating of V2 or higher, more preferably V1 or higher, and most preferably V0. Flame retardants and mixtures can be added to one or more of the isocyanate component and / or isocyanate-reactive components. The amount of flame retardant in the polyurethane composition can depend on the particular flame retardant used and, if present, can typically range up to 60% by weight, or from 5% to 60% by weight, based on the total weight of the polyurethane composition.

[0039] The PU composition may include one or more silicone or organic antifoam agents in a weight percent (wt%) range of 0.05 wt% to 5 wt%, 0.1 wt% to 1.5 wt%, or 0.1 wt% to 1 wt% of the polyurethane composition.

[0040] The polyurethane composition may include one or more fillers, including glass fiber, fiber, carbon fiber, silica, CaCO, kaolin, talc, alumina, alumina trihydrate (ATH), and the like. The one or more fillers may be added in a range of 0 wt% to 25 wt%, or 1 wt% to 20 wt% by weight of the composition. In some cases, the filler may be added to the isocyanate component and / or the isocyanate-reactive component in an amount sufficient to provide a mixture having the corresponding weight percentages described above.

[0041] The isocyanate-reactive component may also contain one or more additives, including blowing agents, surfactants, crosslinkers, plasticizers, smoke suppressants, fragrances, toughening agents, dyes, colorants, pigments, preservatives, odor maskers, physical blowing agents, chemical blowing agents, flame retardants, internal mold release agents, biocides, antioxidants, UV stabilizers, antistatic agents, thixotropic agents, adhesion promoters, cell openers, etc. When reacted in the presence of an amine catalyst and an isocyanate, additional amounts of epoxy resins can also be used to increase the thermoset glass transition temperature. Examples include DER383 and DER354 from Olin Corporation.

[0042] Although the formulation components are disclosed individually, it is contemplated that the component elements (e.g., isocyanates or compounds in the isocyanate-reactive component) may be included, excluded, or combined in any manner or subcombination, utilizing any of the above concentration ranges and nested subranges therein.

[0043] The PU compositions disclosed herein may have a flame retardancy of V2 or greater, or V1 or greater, for a vertical burn at 5 mm according to the UL94 standard.

[0044] The PU composition may have a thermal conductivity suitable for the intended application. In some cases, such as automotive applications, the thermal conductivity may be 0.2 W / mK or less, while in other applications the thermal conductivity may be higher, such as 0.5 W / mK, 0.4 W / mK, or 0.3 W / mK or less.

[0045] The PU composition may have a density in the range of less than 1 g / mL, or between 0.3 g / mL and 1.2 g / mL, or between 0.3 g / mL and 1.0 g / mL, according to ASTM D3574-17 Test A.

[0046] The PU composition may have a viscosity of less than 1500 cP at 6 seconds, less than 2500 cP at 2 minutes, and less than 3500 cP at 5 minutes upon mixing of the components.

[0047] Although the formulation components and properties are disclosed individually, it is contemplated that the component elements (e.g., isocyanates or compounds in the isocyanate-reactive component) may be included, excluded, or combined in any manner or subcombination using any of the above concentration ranges and nested subranges therein. Furthermore, the recited formulation properties may similarly be achieved by various combinations of the recited components within the recited ranges.

[0048] PU compositions can generally be formed by combining an isocyanate component and an isocyanate-reactive component (and an optional third component containing, for example, hollow particles) to form a mixture by a suitable method (e.g., static mixing, dynamic mixing, dynamic and static mixing, high-speed mixing, low-pressure mixing, overhead mixing with an impeller or paint mixer, impingement mixing, etc.), and reacting the mixture to form a PU article. The PU composition can be used in any suitable process for developing articles and composites, including molding, injection, vacuum infusion, etc. Methods can include applying the PU composition to a substrate by dispensing or coating using spin coating, brush coating, drop coating, spray coating, dip coating, roll coating, flow coating, slot coating, gravure coating, Mayer bar coating, etc. In some cases, methods can include combining an isocyanate component and an isocyanate-reactive component to form a mixture, applying the mixture to a substrate, and reacting the mixture to form a polyurethane article or composite (e.g., coating, encapsulant, pottant). The PU composition can be formed by dispensing, pouring, and / or spraying into and / or onto one or more specific locations of the battery pack or module using a process suitable for battery pack / module assembly to achieve complete (or partial) encapsulation of the battery cells.

[0049] The method may include preparing a polyurethane composition by combining an isocyanate component and an isocyanate-reactive component to form a mixture and reacting the mixture to form a polyurethane composition. The composite article may be prepared by disposing the composition on a substrate and curing the composition to produce a composite article comprising a polyurethane article on the substrate. In some cases, the substrate may define at least one gap, and disposing may include disposing the composition within the at least one gap such that the polyurethane article resides within the gap of the composite article. For example, the substrate may comprise a battery cell, surface, or component, and the composite article may comprise a battery pack and / or module. However, the polyurethane article may be used in other end-use applications, including as a pottant or encapsulant in end uses other than battery packs, such as for electrical circuitry, and for purposes other than a pottant and / or encapsulant.

[0050] The PU compositions disclosed herein can be used as pottants or thermal barriers for electrical, battery pack, and / or module-related applications. The pottants can coat and encapsulate (fully or partially) electrical connections and / or protect them from abusive environments such as heat, cold, fire, weather elements, dust (e.g., sand or dirt particles), physical shock or vibration, or other abusive elements. The amount of pottant used can range from a minimum amount sufficient to coat and protect the electrical connections to a maximum amount sufficient to fill voids in battery cells, junction boxes, and the like. The PU compositions can also be applied to stationary energy storage applications in personal and commercial environments. PU compositions can be formulated to meet the constraints for automotive and mobility solutions (e.g., EVs), but can be modified outside of those constraints for other related electrical and stationary energy storage applications. For example, stationary storage applications can be formulated with higher densities / weights (greater than 1 g / mL) and higher thermal conductivities (e.g., greater than 0.2 W / mK), where concerns about overall weight and lack of external cooling are not driving factors. [Example]

[0051] The following examples are provided to illustrate embodiments of the present invention, but are not intended to limit its scope. Table 1 provides the materials used in the following examples.

[0052] [Table 1]

[0053] Example 1: Properties of polyurethane compositions In this example, samples of the present invention containing a polyurethane composition were tested for physical properties compared to a comparative example containing no hollow particles. The sample formulations are shown in Table 2 (comparative) and Table 3 (inventive).

[0054] All amounts of isocyanate-reactive components from Tables 2 and 3 were weighed on an analytical balance according to the formulation requirements (polyol, additives, and catalyst), respectively, and mixed until dispersed using a DAC 600.1 FVZ-K speed mixer. Pre-blended batches were used within 2 hours of mixing; if used at a later date, they were pre-mixed in advance to avoid phase separation. When hollow particles were included, they were added to the isocyanate-reactive components and high-speed mixed before use in the formulation.

[0055] The corresponding isocyanate component was then added to the isocyanate-reactive component in the appropriate ratio, mixed at high speed, and placed in a rectangular metal mold at room temperature (20-25°C). The metal mold dimensions were 19 cm long and 12.5 cm wide (2 mm thick for mechanical properties, and 12.5 mm thick samples were further cut to 5 mm thick for 0.5 inch wide UL-94 vertical burn tests for flame retardancy (FR) performance measurements). Cured molded plaques of the PU pottant material samples were then tested to determine the pottant's mechanical properties.

[0056] After removal from the mold, the dimensions of the rectangular pottant sample are measured on a measuring scale and weighed on a weighing balance. The density of the sample is calculated as the weight of the sample / (length x width x height).

[0057] All pottant samples were removed from the mold after 30-60 minutes and post-cured at 60°C for 1 hour before being tested for mechanical and thermal properties to ensure cure similar to that used in EV batteries. Some of the pottant samples were found to break and / or shatter and / or snap during removal from the mold or during punching of the samples into dogbone shapes and were classified as "untestable" due to their brittleness.

[0058] [Table 2]

[0059] [Table 3]

[0060] The sample formulations were then tested for several physical characteristics (1) to (13), listed below. The test results for each formulation are shown in Tables 4 and 5.

[0061] UL94 Vertical Burn Test (1): Pottant material prepared in a metal mold at a thickness of 12.7 mm was then cut to a thickness of 5 mm at dimensions of 0.5 in. and 10 cm or greater using the procedure described above. Pre-fabricated pottant specimens (pottant alone) were tested to the standard UL94 vertical burn protocol and performance was classified into the appropriate category - V0 (best and desired performance), V1, V2, and Fail (Fail means the pottant specimen burns completely to the clamp during and / or after flame exposure).

[0062] Thermal Conductivity (2): Thermal conductivity was measured according to ISO 22007-2 on 2 mm thick pre-cured pottant samples using a Hot Disk AB TPS 2500S instrument equipped with a Kapton-insulated 5465 F1 sensor, with a heating power of 50 mW and a measurement time of 5 seconds and standard analysis using the isotropic (standard) module. Test pottant plaques were prepared at 2 mm thickness using the procedure described above.

[0063] Density (3): Calculated as the density (i.e., weight / volume) of the cured pottant plaque specimens, performed according to ASTM D3574-17 Test A. The weight of the plaque was measured in grams, and the height of the plaque was measured in cm. The width and thickness of the plaque were 12.5 cm and 0.2 cm, respectively. The density of the pottant specimens (g / cm 3 ):Weight of pottant sample x 1000 / (height x 12.5 x 0.2).

[0064] Viscosity (4-6): The flowability of the pottant material in an actual composite cell assembly was quantified using polyol + isocyanate reactive viscosity measurements on a TA Instruments AREG G2. A 50 mm cone-plate geometry made from stainless steel was used. The pre-blended polyol (with or without premixed air bubbles according to the formulation) was placed in a speed mixer cup (maximum 20 cups), and the appropriate amount and type of isocyanate was added to it (according to the formulation in Table 4). The formulation was mixed at 2100 rpm for 8-10 seconds, and the appropriate liquid volume was poured onto the AREG G2 rheometer plate (within 3-4 seconds after mixing was complete), the gap was set to 2 mm (excess was wiped off with a Q-tip), and the measurement was initiated as soon as possible (within 3-5 seconds after addition to the plate). The measurement temperature was set to 25°C ± 2°C, the oscillatory strain was 5%, and the angular frequency was 10 rad / s. The measurement lasted a minimum of 5 minutes. The viscosities of the reaction at the first data point (t=6 seconds), 2 minutes, and 5 minutes are reported in Tables 4 and 5.

[0065] Modulus of Elasticity (7), Ultimate Tensile Strength (8), Elongation at Break (9): Modulus of Elasticity (E), Elongation at Break (%), and Ultimate Tensile Strength (MPa) for the cured pottant plaque specimens prepared using the procedure described above were all obtained using an MTS machine according to ASTM DI708 standards. Microtensile specimens were punched into a dogbone shape from plaques formed in a 2 mm thick metal die. "N / A" specimens (C1-C2) could not be tested because they shattered during cutting of the dogbone shape from the 2 mm thick plaques due to their inherent brittleness.

[0066] Shear modulus at -30 °C (10), 25 °C (11), 50 °C (12), and 60 °C (13): Shear modulus in torsion mode (physical characteristics (10)–(13)) was obtained by dynamic mechanical analysis (DMA) according to ASTM D5279-21 in a TA Instruments Advanced Rheometric Expansion System (ARES-G2) equipped with liquid nitrogen environmental control and a torsion rectangular fixture. Rectangular specimens, 2 mm thick, were cut from pottant plaques prepared in metal molds (A and B) according to the procedure described above, measuring 45 mm in length and 12.8 mm in width. The specimen length was aligned axially with respect to the torsion axis, and DMA experiments were conducted in torsion mode. The temperature was increased from -70 °C to 150 °C at a ramp rate of 3 °C / min. The testing frequency was 1 Hz at a torsional strain of 0.05%, with the sample held taut by applying an axial tensile force of 0.098 N, with a data collection interval of 30 seconds per point. The output from the characterization was the storage modulus (G') in shear mode over the temperature range.

[0067] [Table 4]

[0068] [Table 5] * The "calculated" for sample I6 means that the value was extrapolated in the viscosity versus time curve measured using a rheometer (procedure described above) due to the absence of Isocyanate-3 incorporation (as with all other examples), so the reverse intercept was calculated.

[0069] The pottant formulations provided in Tables 4 and 5 were produced without the inclusion of chemical or physical blowing agents, resulting in no foaming action. For C1 and C2, the non-foaming liquid cured into a PU elastomer, but each failed the UL94 fire resistance (FR) test. For C3 and C6, the provision of the FR additive resulted in a V2 rating for C3 and a VO rating for C6 in the UL94 vertical burn test of a 5 mm thick pottant, but the thermal conductivity values ​​increased to 0.22 and 0.27, respectively. Samples C1-C3 and C6 had densities greater than 1 g / mL and thermal conductivities greater than 0.2 W / mK. Samples C4 and C5 incorporated hollow particles, and although these samples exhibited lower thermal conductivity (less than 0.2 W / mK) and density, the pottants failed the UL-94 vertical burn test and had high viscosities upon mixing (greater than 10,000 and 8,000 cP after 5 minutes, respectively). Therefore, C1-C6 were deemed unsuitable for EV battery pottant / encapsulant applications.

[0070] In contrast, the examples of the present invention, which combined polyol, liquid FR additive, and hollow particles, achieved the desired performance parameters. For I1-I6, all samples demonstrated UL-94 V0 performance while exhibiting low viscosity values, high mechanical strength, and softening points above 60°C, acceptable for flowability in pottant material applications. I1-I6 also demonstrated that isocyanate types 1, 2, and 3 can all be used individually (or in combination) to achieve pottant properties (1)-(14) with the performance required for I1-I6.

[0071] While the forgoing 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. 1. A polyurethane composition comprising: an isocyanate component comprising one or more isocyanate compounds; an isocyanate-reactive component, one or more polyether polyols, an isocyanate-reactive component comprising one or more aliphatic polyols; A polyurethane composition comprising the reaction product of one or more hollow particles present in at least one of the isocyanate component, the isocyanate-reactive component, or a third component.

2. 10. The composition of claim 1, further comprising an FR additive in a weight percentage of the composition ranging from 5% to 60% by weight.

3. The composition of claim 1 further comprising a polyol crosslinker.

4. The composition of any one of claims 1 to 3, wherein the polyurethane composition has a density in the range of 0.3 g / L to 1 g / L according to ASTM D3574-17.

5. The composition of any one of claims 1 to 4, wherein the hollow particles are present in a weight percent (wt%) range of 1 wt% to 70 wt% of the polyurethane composition.

6. The composition of any one of claims 1 to 5, wherein the polyurethane composition has a UL94 vertical burn performance of at least V2.

7. The composition of any one of claims 1 to 6, wherein the polyurethane composition has a viscosity of less than 3500 cP after 5 minutes of mixing at 25°C or above.

8. The composition of any one of claims 1 to 7, wherein the polyurethane composition has a viscosity of less than 1500 cP after 6 seconds of mixing at 25°C or above.

9. An article or composite prepared from the polyurethane composition of any one of claims 1 to 8.

10. 10. A method for preparing the polyurethane composition of claim 1, comprising: combining the isocyanate component and the isocyanate-reactive component to form a mixture; and reacting the mixture to form the polyurethane composition.

11. 1. A method of preparing a composite article, comprising: disposing the composition of any one of claims 1 to 8 on a substrate; and curing the composition to produce the composite article comprising a polyurethane article on the substrate.

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