Two component low density polyurethane potting formulations

Abstract

A two-component polyurethane-based potting formulation having good flame retardant properties is disclosed.

Description

Background Technology

[0001] With advancements in electric vehicle (EV) technology, the demand for lighter vehicles capable of longer ranges is increasing. This, in turn, requires each component manufacturer to minimize weight. Simultaneously, flame retardancy is also a crucial requirement for certain applications, such as battery potting materials. Automotive EV battery packs typically comprise multiple segments, or modules, each containing several lithium-ion batteries assembled within a frame. When a cell is damaged, thermal runaway can occur. For example, a short circuit can cause heat and pressure to accumulate within the cell. This heat and pressure can trigger further exothermic reactions in adjacent cells. If the heat does not dissipate quickly enough, it can lead to a battery fire. To prevent this, a thermal barrier needs to surround each cell to isolate the heat generated in the damaged cell, thus protecting adjacent cells. There is a need in the art for novel and alternative low-density potting materials that are lightweight and also meet applicable flame retardant standards. Summary of the Invention

[0002] This article describes a two-component potting compound comprising:

[0003] a) Isocyanate component, which contains isocyanate; and

[0004] b) Polyol components, which include:

[0005] i) Polyols with a viscosity of 5,000 cp or less at 25°C;

[0006] ii) Has 1 g / cm 3 Or lower density fillers; and

[0007] iii) 0.1% to 20% rheology modifier by weight of the potting compound.

[0008] Typically, uncured potting formulations are in the form of kits, in which the first and second components are not mixed before use.

[0009] A method for curing potting formulations is also described, which typically involves mixing an isocyanate component and a polyol component of the potting formulation and curing the mixture. Detailed Implementation

[0010] Filling formulations typically comprise an isocyanate component and a polyol component, usually in the form of a kit, with each component stored separately in the kit prior to use. It is also envisioned that one or more individual components may be offered or sold separately; for example, the polyol component may be offered without the isocyanate component, and vice versa. The ratio of the two components can vary over a wide range. In some embodiments, the filling formulation comprises 50%–80% of the polyol component by weight of the filling formulation. In another embodiment, the filling formulation comprises 20%–50% of the isocyanate component by weight of the filling formulation.

[0011] I. Isocyanate components

[0012] The isocyanate component of a two-component potting formulation is not limiting—any isocyanate component is contemplated. For example, the isocyanate may include any monomeric or polymeric isocyanate commonly used with polyurethane technology. In one embodiment, the isocyanate includes aromatic isocyanates, aliphatic isocyanates, or mixtures thereof. In another embodiment, the isocyanate includes isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), 4,4-diphenylmethane diisocyanate (MDI), or polymeric variants thereof, 4,4'-methylene diphenyl diisocyanate, or mixtures thereof. In yet another embodiment, the isocyanate includes polymeric 4,4-diphenylmethane diisocyanate (MDI), 4,4-diphenylmethane diisocyanate (MDI), tetramethylphenyl dimethyl diisocyanate (TMXDI), or 4,4'-methylene diphenyl diisocyanate.

[0013] Other suitable isocyanates include 4,4'-methylene-diphenyl diisocyanate; 2,2'-methylene-diphenyl diisocyanate; 2,4-methylene-diphenyl diisocyanate; toluene diisocyanate (TDI); toluene-2,4-diisocyanate; toluene-2,6-diisocyanate; naphthyl-1,5-diisocyanate; methoxyphenyl-2,4-diisocyanate; diphenylmethane-4,4'-diisocyanate; diphenylmethane-2,4'-diisocyanate; diphenylmethane-2,4'-diisocyanate. Isocyanates; 4,4'-biphenylene diisocyanate; 3,3'-dimethoxy-4,4'-biphenyl diisocyanate; 3,3'-dimethyl-4-4'-biphenyl diisocyanate; 3,3'-dimethyl-diphenylmethane-4,4'-diisocyanate; 4,4',4"-triphenylmethane triisocyanate; toluene-2,4,6-triisocyanate; 4,4-dimethyl-diphenylmethane-2,2,5,5'-tetraisocyanate; and mixtures thereof.

[0014] Any polymer of the monomeric isocyanate can also be used to manufacture isocyanate prepolymers, which in some embodiments may be used in combination with the monomeric isocyanate. Examples include any derivatives or polymers of the isocyanates described above. Other examples include polyisocyanates containing urethane, urea, biuret, carbodiimide, uretoneimine, ureocarbamate, or other groups formed by the reaction of the isocyanate group. The isocyanate component may also contain polymeric MDI (a mixture of MDI and poly-MDI, commonly referred to as "polymeric MDI"). Other examples include "liquid MDI" products, which are mixtures of MDI and poly-MDI derivatives having biuret, carbodiimide, uretoneimine, or ureocarbamate bonds.

[0015] The isocyanate component may comprise an isocyanate prepared by reacting a monomeric isocyanate or polymeric isocyanate with a polyol, or a diol or triol of lower molecular weight. For example, any of the polyols described below with respect to the polyol component may be used; or, for example, any of the polyols described in WO2016205252 (A1) (incorporated by reference).

[0016] II. polyol components

[0017] A. Polyols

[0018] The suitable first polyol for the polyol component can vary and can be any polyether polyol having a hydroxyl functionality of 2 to 7. Typically, the polyol component can comprise 20%-80% by weight, for example 25%-65%, 25%-50%, 25%-40%, or 25%-30% of a polyol. The polyol can be any glycerol-initiated propoxylated or ethoxylated polyol or any propoxylated or ethoxylated polyol prepared from alternative trifunctional and bifunctional starting materials. In some embodiments, the polyol can be a polyether polyol or a mixture of polyether polyols. In other embodiments, the first polyol can be a homopolymer or copolymer of propylene oxide, or a copolymer of propylene oxide with 70 wt% to 99 wt% propylene oxide and 1 wt% to 30 wt% ethylene oxide. If two or more polyether polyols are present, it is preferred that at least one of the polyols is a copolymer of such propylene oxide and ethylene oxide. In the case of copolymers, propylene oxide and ethylene oxide can be random copolymerized, block copolymerized, or both. In some embodiments, 50% or more of the hydroxyl groups in the polyether polyol or mixture of polyether polyols are primary hydroxyl groups, wherein the remainder of the hydroxyl groups are secondary hydroxyl groups. In another embodiment, 70% or more of the hydroxyl groups in the polyether polyol or mixture thereof may be primary hydroxyl groups.

[0019] In some embodiments, the polyol has a hydroxyl functionality ranging from 2 to 7. In another embodiment, the polyol has a viscosity of 5,000 cp or less, such as 4,000 cp or less, 3,000 cp or less, 2,000 cp or less, or 1,500 cp or less at room temperature (about 25°C).

[0020] B. Low-density filler

[0021] To maintain a low weight of the potting material, the formulation may include 0.1% to 50% low-density filler by weight of the potting formulation. The low-density filler may be present in the first component, the second component, or both. In one embodiment, the low-density filler is present in the polyol component. In another embodiment, the low-density filler is present in the polyol component but not in the isocyanate component. In some embodiments, the low-density filler has a concentration of less than 1 g / cm³. 3 The density of the filler.

[0022] In some embodiments, the potting formulation comprises 0.1% to 20% by weight of a low-density filler, which may be in any one or both components, such as in a polyol component. For example, in one embodiment, the formulation comprises 0.1% to 15%, for example, 0.1%-10%, by weight of the potting formulation. In another embodiment, the formulation comprises 1% to 10%, for example, 1%-8%, 2%-6%, 2%-5%, or 3%-5%, by weight of the potting formulation.

[0023] Various low-density fillers can be used. In some embodiments, the low-density filler includes hollow microspheres. Hollow microspheres can be hollow glass microspheres, hollow silica microspheres, silica aerogels, hollow phenolic resin microspheres or microballoons, or combinations thereof.

[0024] C. Rheology modifiers

[0025] One advantage of the described potting formulation is that the polyol component is thixotropic. The thixotropic properties on the polyol side allow low-density fillers to remain stable under storage conditions. It is also desirable to obtain formulations that flow easily under mixing or high-shear conditions. Such thixotropic properties can be achieved by using rheology modifiers.

[0026] In some embodiments, the potting formulation comprises 0.1%-20% rheology modifier by weight of the potting formulation. In another embodiment, the potting formulation comprises 0.5%-15% rheology modifier by weight of the potting formulation. In another embodiment, the potting formulation comprises 0.5%-10% rheology modifier by weight of the potting formulation. In another embodiment, the potting formulation comprises 0.5%-5% rheology modifier by weight of the potting formulation. In another embodiment, the potting formulation comprises 0.5%-2% rheology modifier by weight of the potting formulation. In another embodiment, the potting formulation comprises 0.5%-1.5% rheology modifier by weight of the potting formulation.

[0027] A variety of rheology modifiers can be used. In some embodiments, the rheology modifier is a urethane resin, such as ethoxylated hydrophobic urethane resin (HEUR), a sulfonate such as calcium sulfonate, a polyamide, or a modified urea such as alkylated or polyether alkyl urea. In one embodiment, the rheology modifier is a modified urea.

[0028] D. Crosslinking agents and other additives

[0029] In some embodiments, the polyol component comprises a crosslinking agent. The crosslinking agent can advantageously provide a high hard segment content and a high crosslinking density, which can improve the modulus after the potted formulation has fully cured. Any suitable crosslinking agent can be used, such as any short-chain diol, triol, or tetrafunctional polyol or polyamine. Non-limiting examples include glycerol and triethanolamine. When present in the polyol component, the crosslinking agent can be present in any suitable amount, for example, from 0.5% to 20% by weight of the polyol component, such as 0.5%-15%, 0.5%-10%, 1%-10%, 2%-10%, or 5%-10%.

[0030] In another embodiment, the polyol component may include a moisture scavenger. The potting formulation may contain 0.1-10% by weight, for example, 0.1%-5%, 0.1%-3%, or 0.1%-1.5% of the moisture scavenger based on the weight of the potting formulation. Various moisture scavengers are suitable. Examples include molecular sieves, vinylsilanes, oxazolidines, monofunctional isocyanates (e.g., pTSI), triethyl orthoformate, etc.

[0031] III. Other optional additives

[0032] A. Catalyst

[0033] Any component may contain a catalyst for catalyzing the reaction of the isocyanate with isocyanate reactive groups (including, for example, hydroxyl groups of a polyol, amine groups of a crosslinking agent, etc.). In one embodiment, the catalyst is present in the polyol component. In another embodiment, the catalyst is present in the polyol component but not in the isocyanate component.

[0034] The catalyst may include, for example, one or more latent room-temperature (25°C) organometallic catalysts. Latent room-temperature organometallic catalysts may contain tin, zinc, bismuth, or combinations thereof. For example, latent room-temperature organometallic catalysts may include one or more catalysts such as zinc alkanoate, bismuth alkanoate, dialkyltin alkanoate, dialkyltin thiolate, bis(alkyl-mercaptiacetic acid)dialkyltin, dialkyltin thioglycolate, or mixtures thereof. Specific examples include dioctyltin thiolate, dibutylmercaptidem, dibutyl thiolate, dibutyl thiolate, bis(dodecylthio)dimethyltinane, bis(2-ethylhexylmercaptiacetic acid)dimethyltin, dioctylcarboxylate, dioctyltin neodecanoate, and mixtures thereof.

[0035] Another type of catalyst that can be used in adhesive formulations is any catalyst that can be further thermally activated (referred to as a "thermosensitive catalyst") or otherwise catalyzes the reaction. In one embodiment, such a catalyst may include, for example, amine-based solid amine catalysts, such as cyclic amidine catalyst compounds, such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene, 2,4,6-tris-(dimethylaminomethyl)phenol, and mixtures thereof.

[0036] In another embodiment, the binder formulation may comprise a combination of a latent tin-containing catalyst and a thermosensitive amine-based catalyst. Both the tin-containing organocatalyst and the amine-based catalyst can be readily formulated into an isocyanate component, a polyol component, or both an isocyanate component and a polyol component.

[0037] In another embodiment, any non-tin-based organometallic catalyst exhibiting similar curing kinetics or catalytic characteristics to the tin-based catalysts described above can be used as a catalyst component in adhesive formulations. For example, available bismuth-based catalysts include bismuth(III)-neodecanate, and available zinc-based catalysts include zinc-neodecanate.

[0038] In yet another embodiment, non-tin-based or non-amine-based catalysts that can be used in adhesive formulations include carboxylic acid-terminated catalysts, such as DBU carboxylic acid-terminated catalysts. For example, DBU carboxylic acid-terminated catalysts may be TOYOCAT DB41 catalyst (a DBU carboxylic acid salt available from Tosoh Corporation), POLYCAT SA-102 / 10 (a DBU carboxylic acid salt available from Air Products), and mixtures thereof. Other available catalysts include acid-terminated amines, including, for example, catalysts based on tertiary amines and organic acids, such as TOYOCAT DB40, TOYOCAT DB60, and TOYOCAT DB70 available from Tosoh Corporation; amine catalysts based on 1H-1,2,4-triazoles, such as TOYOCAT DB30 available from Tosoh Corporation; and mixtures thereof. Any other known thermosensitive amine catalysts may also be used, including TOYOCAT F22 available from Tosoh Corporation; triethylenediamine (TEDA); and mixtures thereof. In one embodiment, the catalyst may be selected from tin catalysts, such as bis[isooctylthioacetic acid]di-n-octyltin; and amine catalysts, such as POLYCAT SA1 / 10 and TOYOCAT DB60; and mixtures thereof.

[0039] Typically, the amount of catalyst in an adhesive formulation can range from 0.005 wt% to 2.0 wt%; 0.01 wt% to 1.0 wt%; and 0.015 wt.% to 0.07 wt%, based on i) the total weight of the formulation or ii) the total weight of the first or second component of the formulation (i.e., the polyol or isocyanate component). In an illustrative embodiment, for example when a tin catalyst such as bis[isooctylthioacetic acid]di-n-octyltin is used in an adhesive formulation, the concentration of such catalyst in the formulation or any component can be from 0.005 wt% to 1.0 wt%; 0.02 wt% to 0.08 wt%; and 0.03 wt.% to 0.05 wt.%, based on the total weight of the formulation as a whole or any component thereof.

[0040] In another illustrative embodiment, when a thermosensitive amine catalyst such as POLYCAT SA 1 / 10 is used in an adhesive formulation, the concentration of such catalyst in the formulation may be from 0.01 wt% to 2.0 wt%; from 0.01 wt% to 1.0 wt%; and from 0.015 wt% to 0.025 wt%, based on the weight of the formulation as a whole or any component thereof.

[0041] In another illustrative embodiment, when a catalyst such as TOYOCAT DB60 is used in an adhesive formulation, the concentration of such catalyst in the formulation may be from 0.01 wt% to 2.0 wt%; from 0.01 wt% to 1.0 wt%; and from 0.045 wt% to 0.065 wt%, based on the weight of the formulation as a whole or any component thereof.

[0042] If the catalyst concentration is less than 0.005 wt% by weight of the formulation as a whole, the catalyst used may not be effectively active in the formulation, and the resulting formulation may have poor storage stability, meaning that any residual water present in the formulation may deactivate a small amount of catalyst. If the catalyst concentration exceeds 2.0 wt%, the reaction of the components present in the formulation may be too rapid, resulting in a short open time, i.e., an open time of, for example, less than 3 minutes. Furthermore, high catalyst levels in the formulation (e.g., greater than 2.0 wt%) may lead to increased processing and formulation costs of the resulting formulation.

[0043] B. Flame retardants

[0044] One or both components may contain a flame retardant. In some embodiments, the polyol component contains a flame retardant. Any suitable flame retardant may be used, such as halogenated phosphates, non-halogenated flame retardants, reactive flame retardants, or any combination thereof. Suitable halogenated phosphates include, for example, chlorinated or brominated organophosphates. Non-limiting examples include tris(1,3-dichloro-2-propyl) phosphate (TDCPP), tris(1-chloro-2-propyl) phosphate (TCPP), tris(2,3-dichloro-1-propyl) phosphate, and tris(2-chloroethyl) phosphate (TCEP). In one embodiment, the first halogenated phosphate is TCPP. Any suitable halogen-free phosphate may be used in combination with a halogenated organophosphate.

[0045] C. Plasticizers

[0046] Any component, and in some embodiments the polyol component, may contain a plasticizer. In one embodiment, the plasticizer may have a weight-average molecular weight of 2,000 g / mol or less, such as 1,000 g / mol or less, 800 g / mol or less, or 600 g / mol or less. The plasticizer will generally be liquid at a temperature of about 100°C. The plasticizer may be present in any suitable amount, for example, 1%-20% by weight of any component or alternatively by weight of the formulation.

[0047] Suitable plasticizers include any ester-based plasticizers, such as adipates, azelaates, citrates, benzoates, butyrates, phthalates, terephthalates, sebates, and trimellites. Examples include ester derivatives of acids and anhydrides such as adipic acid, azelaic acid, benzoic acid, citric acid, dimer acids, fumaric acid, isobutyric acid, isophthalic acid, lauric acid, linoleic acid, maleic acid, maleic anhydride, beeswax acid, myristic acid, oleic acid, palmitic acid, phosphoric acid, phthalic acid, ricinoleic acid, sebacic acid, stearic acid, succinic acid, 1,2-phthalic acid, and mixtures thereof. Also suitable are epoxidized oils, glycerol derivatives, paraffin derivatives, sulfonic acid derivatives, and mixtures thereof.

[0048] Specific examples of such plasticizers include diethylhexyl adipate, heptyl nonyl adipate, diisodecyl adipate, polyester adipate, dioctyl adipate, dimethyl azelaate, diethylene glycol dibenzoate and dipropylene glycol dibenzoate, polyethylene glycol dibenzoate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate benzoate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, methyl (or ethyl, or butyl) phthaloyl ethyl glycolate, and trimethyl citrate. Ethyl phthalate, dibutyl fumarate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, methyl laurate, methyl linoleate, di-n-butyl maleate, trioctyl trimellitate, heptylnonyl trimellitate, triisodecyl trimellitate, triisononyl trimellitate, isopropyl myristate, butyl oleate, methyl palmitate, tricresyl phosphate, tri(2-ethylhexyl) phosphate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diisobutyl phthalate bis-2-ethylhexyl phthalate, octyl decyl phthalate, diisodecyl phthalate, heptyl nonyl phthalate, diundecyl phthalate, ditridecyl phthalate, dicyclohexyl phthalate, diphenyl phthalate, butyl benzyl phthalate (such as n-butyl benzyl phthalate), isodecyl benzyl phthalate, alkyl (C7 / C9) benzyl phthalate, dimethoxyethyl phthalate, 7-(2, 6,6,8-Tetramethyl-4-oxa-3-oxo-nonyl)benzyl ester, di-2-ethylhexyl sebacate, butyl castor oil, dimethyl sebacate, methyl stearate, diethyl succinate, butylphenyl methyl 1,2-phthalic acid, epoxidized linseed oil, glyceryl triacetate, chlorinated paraffin having about 40% to about 70% Cl, o-, p-toluenesulfonamide, N-ethyl-p-toluenesulfonamide, N-cyclohexyl-p-toluenesulfonamide, sulfonamide-formaldehyde resin, and mixtures thereof.

[0049] Other suitable plasticizers known to those skilled in the art include castor oil, aromatic petroleum concentrates, partially hydrogenated terphenyl, silicone plasticizers (such as polydimethylsiloxane copolyesters, polydimethylsiloxane esters, silicone carboxylic esters), Guerbet esters, etc., alone or as a mixture with other plasticizers.

[0050] IV. Methods for curing potting compounds

[0051] Cured potting formulations are also disclosed, which are prepared by mixing the components of the described potting formulation and curing the mixture, for example, after application to a desired substrate (such as a battery module). Similarly, this disclosure covers a method for curing a potting formulation, the method comprising mixing an isocyanate component and a polyol component of the potting formulation and curing the mixture. In some embodiments, the first and second components of the potting formulation are mixed in a ratio ranging from 4:1 to 1:4, for example from 2:1 to 1:2 (by weight). In another embodiment, the first and second components of the potting formulation are mixed in a 1:1 ratio.

[0052] In one specific embodiment, the lightweight filler may optionally be dried, for example, at a temperature above 100°C (e.g., 110°C) to achieve the desired maximum moisture content. The isocyanate component and the polyol component can be prepared separately by mixing under an inert atmosphere (such as nitrogen) at maximum pressure (e.g., 80 mbar) for 30 min–1 h. To encapsulate the two components, the first and second components can be mixed under vacuum at the desired mass ratio for a sufficient amount of time. For testing methods, the density of each component can be measured using a density cup. Flame retardant properties can be evaluated according to the UL94 standard. Example

[0053] The following examples further illustrate this disclosure. The scope of this disclosure and the claims is not limited to the scope of the following examples.

[0054] I. Material

[0055] The raw materials described in Table 1 are used in the example.

[0056] Table 1.

[0057]

[0058] Optional: Water can be added as a foaming agent to the polyol side. Water can react with isocyanates to form CO2, which can produce foam-based potting compounds.

[0059] Table 2 below lists the proposed alternatives to the specific materials listed in Table 1.

[0060] Table 2.

[0061]

[0062] II. Examples of the present invention and comparative examples

[0063] The composition of the examples of the present invention and the comparative examples is shown in Table 3 below. The listed quantities are weight percentages of each material.

[0064] Table 3.

[0065]

[0066] III. Methods and Tests

[0067] First, the polyols and ANTIFLAME TCPP were dried under 3A molecular sieves for 3 days and then used in the formulation. Part B of the formulation (polyol blend) was prepared by adding all liquid components to a Max 300 cup (Flackteck). The contents were mixed for 2 min under 50 mbar vacuum in a Flackteck Speedmixer operating at 2000 rpm. The solid contents were then added to the cup and mixed for 2 min under non-vacuum conditions at 1200 rpm. The contents were then mixed again for 2 min under 50 mbar vacuum at 1200 rpm. The blended Part B was stored under nitrogen sealing before being mixed with Part A. For Example 2, Expancel 920 DE 40 d30 was first blended with TCPP to form a slurry, which was then added to the final blend.

[0068] To prepare the cured potting compound, parts A and B were mixed in a Max 100 cup at the given ratios shown in Table 2. The contents were then mixed for 2 min under a vacuum of 50 mbar in a Flackteck high-speed mixer operating at 1200 rpm. Immediately after mixing, the contents were poured into molds and allowed to cure at room temperature for 3 days.

[0069] Rheology: Rheological measurements were performed using a Discovery HR1 (TA Instruments) rheometer with a 25 mm aluminum parallel plate setup. Part B viscosity was measured over 120 s at 25°C with shear flow ramps from 0.01 / s to 100 / s. Viscosities at shear rates of 0.01 and 100 / s are reported in Table 4. For the mixed viscosity, the two parts were mixed using a high-speed mixer, and small samples were transferred to a 25 mm parallel plate, with viscosity measured at 25°C and a shear rate of 25 / s. To measure working time, viscosity measurements continued until a viscosity of 5000 cps was reached.

[0070] Flammability: Flammability testing was performed using the UL 94 standard for the safety of flammability of plastic materials for parts in devices and appliances testing. Five specimens (127 mm long, 13 mm wide, and 3 mm thick) were prepared for this test. Each specimen was cured for 3 days prior to the UL 94 test. A sample was rated V-0 if: (1) the flame duration of all five specimens did not exceed 10 seconds after each of the two 10-second flame applications; (2) the total flame duration of ten 10-second flame applications (2 applications for each of the five specimens) exceeded 50 seconds; (3) none of the five specimens burned to the retaining clips while flaming or glowing; (4) none of the five specimens dripped and ignited flaming particles from dry degreased cotton located 305 mm below the specimens; and (5) none of the five specimens continued to glow for more than 30 seconds after the second flame removal.

[0071] If the burning stops within 60 seconds after applying a flame for ten seconds twice to the test bar, the sample is given a V1 rating.

[0072] Compression: Perform compression testing according to ASTM D1621. Mix the material in a 300 mL-Max high-speed mixer cup, filling to a height of approximately 20 mm. Allow the material to solidify within the high-speed mixer cup into a solid “disc” approximately 150 mm in diameter. Grind the top and bottom surfaces of the “disc” to ensure they are parallel to each other. Extract individual test specimens from the “disc” using a 1-1 / 8” hole drill bit.

[0073] Each individual specimen was measured to record both its geometry and mass. INSTRON 5967 compression specimens equipped with 30 kN load cells and parallel compression plates were used. Tests were conducted at a rate of 1 / 10 x the measurement height of each specimen until 16% of the maximum compressive strain was reached. Transient force [F] and deflection [d] data were recorded at a sampling rate of 2.5 Hz during each test. Using the dimensions of the specimens recorded prior to testing, compressive engineering stress [s] and engineering strain [e] data were calculated using formulas known in the art.

[0074] Tensile testing: Tensile testing is performed according to ASTM D638 using specimens with dimensions of ISO 8256 Type 3 bars. The material is mixed in a Max high-speed mixer cup and poured into a rectangular mold to a height of approximately 2.5–3 mm. The material is allowed to fully cure, then trimmed and machined into ISO 8256 geometry using a router fixture.

[0075] Each individual specimen was measured to record both its geometry and mass. Specimens were tested under stress using an INSTRON 5969 equipped with a 10 kN load cell, mechanical grips, and a non-contact extensometer. Testing was conducted at a rate of 25 mm / min until failure. Transient force [F] and local deflection [d] data were recorded at a sampling rate of 50 Hz during each test. Using the dimensions of the specimens recorded prior to testing, engineering stress [s] and engineering strain [e] data were calculated using formulas known in the art.

[0076] Density: The density of the cured material was determined at room temperature using Archimedes' principle. The cured material was weighed in air and when immersed in water, and the difference was used to obtain the volume of water displaced (density of water = 1 g / cc). The density was then calculated by dividing the mass of the cured sample by the volume.

[0077] Thermal conductivity: Thermal conductivity was measured using a ThermTest Hot Disk TPS 2500 S according to ISO 22007-2:2022 Plastics—Determination of thermal conductivity and thermal diffusivity—Part 2: Transient plane heat source (hot disc) method. A Kapton 4922 sensor (14.61 mm radius) was used. This instrument measures the thermal diffusivity of materials. Thermal conductivity was calculated by multiplying the thermal diffusivity value obtained on the instrument by independently determined heat capacity and density. Each sample was measured in triplicate, and the average thermal conductivity value was reported.

[0078] IV. result

[0079] Table 4 shows the measurement characteristics of the examples of the present invention and the comparative examples.

[0080] Table 4.

[0081]

[0082] The viscosity of part B (polyol blend) was measured within a certain shear rate range. The low shear rate viscosity (1 / s) of the potting compound of Example 1 of the present invention was 4,280 cps, and the high shear rate viscosity (100 / s) was measured to be 850 cps. Similarly, the low shear rate viscosity (1 / s) of the potting compound of Example 2 of the present invention was 6,500 cps, and the high shear rate viscosity (100 / s) was measured to be 1,100 cps. High thixotropy, or "shear thinning," was observed in both cases. The high viscosity at low shear rates is due to the formation of a hydrogen bond network of the modified urea-based stabilizer used in the formulation. High viscosity at low or no shear allows low-density fillers to remain stable during storage. Hydrogen bonds break at high shear rates, resulting in low viscosity and high flowability. When parts A and B were mixed, the resulting initial viscosities for Examples 1 and 2 of the present invention were measured to be 1,040 and 1,100 cps, respectively. For Examples 1 and 2 of the present invention, the working time (defined as the time to reach a viscosity of 5,000 cps after mixing) was determined to be 11 and 12 minutes, respectively. The combination of low mixing viscosity and long working time makes this material suitable for pouring into battery packs and filling the small gaps between two cells.

[0083] Both potting formulations of this invention exhibited high flame retardancy (V0 rating) in UL94 testing. Furthermore, they both possess very high thermal resistivity, as indicated by their low thermal conductivity values. This combination of low thermal conductivity and high flame retardancy makes these materials suitable as thermal barriers to prevent the spread of thermal runaway reactions in lithium-ion battery packs.

[0084] The addition of low-density fillers allows the compositions of the present invention to have a lower density, compared to the significantly higher density of the comparative examples (1.2 g / cc).

[0085] During each test, the modulus was calculated at two different ranges within the stress-strain curve: 1) the initial slope (the linear portion within the first 1% strain), and 2) the second slope (the linear portion within approximately 10%–15% strain). Compressive strengths were also recorded at different compressive strain values ​​of 5%, 10%, and 15%. A summary table of the compression results is available in Table 5.

[0086] Table 5.

[0087]

[0088] Table 5 continues.

[0089]

[0090] During each test, the modulus was calculated within the initial linear portion of the stress-strain curve at approximately 0.5%–1.0% strain. The maximum tensile strength and elongation at break were also recorded for each test. A summary table of the compression results is available in Table 6.

[0091] Table 6.

[0092]

[0093] Table 6 continues.

[0094]

[0095] The features and advantages of this disclosure are apparent from the detailed description, and the claims cover all such features and advantages. Many variations will occur to those skilled in the art, and any variations equivalent to those described herein fall within the scope of this disclosure. Those skilled in the art will understand that the concepts upon which this disclosure is based can serve as the basis for designing other compositions and methods for carrying out the various purposes of this disclosure. Therefore, the claims should not be considered as limiting to the specification or examples.

Claims

1. A two-component filling formulation, the two-component filling formulation comprising: a) Isocyanate component, which contains isocyanate; b) Polyol components, which include: i) Polyols with a viscosity of 5,000 cp or less at 25°C; ii) Has 1 g / cm 3 Or lower density fillers; iii) 0.1% to 20% rheology modifier based on the weight of the potting compound; The uncured potting formulation is in the form of a kit, and the first and second components are not mixed in the kit before use.

2. The potting compound as described in claim 1, wherein, The polyol is a polyether polyol having a hydroxyl functionality in the range of 2 to 7.

3. The potting compound as described in claim 1, wherein, The low-density filler includes hollow glass microspheres, hollow silica microspheres, silica aerogels, hollow phenolic resin microspheres or microbeads, or combinations thereof.

4. The potting compound of claim 1, comprising 0.1% to 50% of the low-density filler by weight of the potting compound.

5. The potting compound of claim 1, comprising 0.1% to 20% of the low-density filler by weight of the potting compound.

6. The potting compound of claim 1, comprising 0.1% to 15% of the low-density filler by weight of the potting compound.

7. The potting compound of claim 1, comprising 0.1% to 10% of the low-density filler by weight of the potting compound.

8. The potting compound of claim 1, comprising 1% to 10% of the low-density filler by weight of the potting compound.

9. The potting compound of claim 1, comprising 1% to 8% of the low-density filler by weight of the potting compound.

10. The potting compound of claim 1, comprising 2% to 6% of the low-density filler by weight of the potting compound.

11. The potting compound of claim 1, comprising 2% to 5% of the low-density filler by weight of the potting compound.

12. The potting compound of claim 1, comprising 3% to 5% of the low-density filler by weight of the potting compound.

13. The potting formulation of claim 1, comprising 0.5% to 15% of the rheology modifier by weight of the potting formulation.

14. The potting formulation of claim 1, comprising 0.5% to 10% of the rheology modifier by weight of the potting formulation.

15. The potting formulation of claim 1, comprising 0.5% to 5% of the rheology modifier by weight of the potting formulation.

16. The potting formulation of claim 1, comprising 0.5% to 2% of the rheology modifier by weight of the potting formulation.

17. The potting formulation of claim 1, comprising 0.5% to 1.5% of the rheology modifier by weight of the potting formulation.

18. The potting compound as claimed in claim 1, wherein, The rheology modifier is a urethane resin, sulfonate, polyamide, or modified urea.

19. The potting compound as claimed in claim 1, wherein, The polyol component further comprises a crosslinking agent having at least two hydroxyl or amino functional groups that are reactive with the isocyanate.

20. The potting compound as claimed in claim 1, wherein, The polyol component further includes a moisture scavenger.

21. The potting formulation of claim 1, further comprising a catalyst capable of catalyzing the reaction of the isocyanate with the isocyanate reactive groups.

22. The potting compound of claim 1, further comprising a plasticizer.

23. A method for curing a potting compound as claimed in claim 1, the method comprising mixing the isocyanate component and the polyol component of the potting compound and curing the mixture.

Images