Potting material for stabilizing battery cells in a battery module

Abstract

The present invention relates to a battery module in which an electrical cell is encapsulated in a potting material, and the potting material is obtained by mixing (a) one or more organic polyisocyanates, (b) one or more compounds having at least two isocyanate reactive hydrogen atoms, (c) one or more catalysts, (d) optional fillers and / or polyurethane additives to obtain a reaction mixture and then curing the reaction mixture, wherein the compound having at least two isocyanate reactive hydrogen atoms comprises at least one polyether polyol (b1) having a functionality of 1.8 to 3 and a hydroxyl value of less than 140 mg KOH / g, at least one polyether polyol (b2) having a functionality of more than 3 to 6 and a hydroxyl value of more than 180 mg KOH / g, and optionally at least one polyether polyol (b3) having a functionality of 1.8 to 3 and a hydroxyl value of more than 200 mg KOH / g, and optionally at least one chain extender (b4), and wherein the components for obtaining the reaction mixture are mixed with an isocyanate index of 100 to 200. The present invention also relates to a method for producing a battery module, wherein electrical cells are encapsulated in a potting material, and the potting material is obtained by inserting a reaction mixture according to the invention into the space between adjacent electrical cells in a battery case in which the electrical cells are arranged and then curing the reaction mixture.

Description

[0001] The present invention relates to a battery module in which an electrical cell is encapsulated in a potting material, and the potting material is obtained by mixing (a) one or more organic polyisocyanates, (b) one or more compounds having at least two isocyanate reactive hydrogen atoms, (c) one or more catalysts, (d) optional fillers and / or polyurethane additives to obtain a reaction mixture and then curing the reaction mixture, wherein the compound having at least two isocyanate reactive hydrogen atoms comprises at least one polyether polyol (b1) having a functionality of 1.8 to 3 and a hydroxyl value of less than 140 mg KOH / g, at least one polyether polyol (b2) having a functionality of more than 3 to 6 and a hydroxyl value of more than 180 mg KOH / g, and optionally at least one polyether polyol (b3) having a functionality of 1.8 to 3 and a hydroxyl value of more than 200 mg KOH / g, and optionally at least one chain extender (b4), and wherein the components for obtaining the reaction mixture are mixed with an isocyanate index of 100 to 200. The present invention also relates to a method for producing a battery module, wherein the battery cell is encapsulated in a potting material, and the potting material is obtained by inserting a reaction mixture according to the invention into the space between adjacent battery cells in a battery case in which the battery cells are arranged and then curing the reaction mixture.

[0002] The automotive industry is experiencing a very rapid shift from internal combustion engines to electric vehicles. Battery designs can vary considerably and are generally based on three types of battery cells: prismatic, pouch, or cylindrical cells. Particularly for cylindrical cells, the design from cell to cell assembly, but not limited to this, involves filling materials used to fill the cavities between cells, as described in the literature. The primary purpose of these filling materials is to mechanically stabilize the battery by reinforcing it, for example, by resisting mechanical stresses caused by temperature changes, vibrations during driving, and mechanical impacts in traffic accidents, and by maintaining contact between the cells and cooling devices.

[0003] The gap filler material must provide a given stiffness over a wide temperature range, from below -30°C in winter to above 70°C in summer, while still maintaining a certain level of flexibility to prevent crack formation.

[0004] EP 3753056 discloses a battery module comprising a polyurethane-based potting compound having a density of less than 0.5 g / cm³. 3The foam reacts with liquid flame retardants and additives such as chain extenders. The electrical cells embedded within this foam are described as cylinders. After complete curing, the potting compound can possess a degree of elasticity, thus cushioning impacts or vibrations to the battery module. The encapsulation of the battery cells ensures an appropriate level of protection, such as adequate structural stability and / or adequate flame retardancy, to help reduce the likelihood of uncontrolled fire from the battery module. However, the mechanical stability provided by the foam is often insufficient.

[0005] On the other hand, thermally conductive adhesives are known. These materials improve heat transfer from the battery cell to the cooling plate.

[0006] PCT / EP2023 / 074553 and CN111607351 disclose a thermally conductive adhesive for battery modules, which comprises an organic polyisocyanate, a polyether polyol, a chain extender, a flame retardant catalyst, and a thermally conductive filler.

[0007] Thermally conductive adhesives contain a large amount of inorganic fillers and do not exhibit excellent mechanical properties, such as stiffness and elasticity, over a wide temperature range.

[0008] The purpose of this invention is to provide a battery module in which electrical cells are encapsulated in a potting material, and the potting material has improved mechanical properties, such as elasticity and stiffness, in a temperature range of -35°C to 60°C.

[0009] The object of the present invention has been achieved by a battery module in which an electrical cell is encapsulated in a potting material, and the potting material is obtained by mixing (a) one or more organic polyisocyanates, (b) one or more compounds having at least two isocyanate reactive hydrogen atoms, (c) one or more catalysts, (d) optional fillers and / or polyurethane additives to obtain a reaction mixture and then curing the reaction mixture, wherein the compound having at least two isocyanate reactive hydrogen atoms comprises at least one polyether polyol (b1) having a functionality of 1.8 to 3 and a hydroxyl value of less than 140 mg KOH / g, at least one polyether polyol (b2) having a functionality of more than 3 to 6 and a hydroxyl value of more than 180 mg KOH / g, and optionally at least one polyether polyol (b3) having a functionality of 1.8 to 3 and a hydroxyl value of more than 200 mg KOH / g, and optionally at least one chain extender (b4), and wherein the components for obtaining the reaction mixture are mixed with an isocyanate index of 100 to 200.

[0010] The battery module according to the invention can be obtained by a method in which electrical cells are encapsulated in a potting material, and the potting material is obtained by inserting a reaction mixture according to the invention into the space between adjacent electrical cells in a battery case in which the electrical cells are arranged and then curing the reaction mixture. The battery module according to the invention comprises a plurality of electrical cells. In a preferred method, the cells are cylindrical. In a preferred embodiment, the outer surface of the cell is metal, preferably steel, and particularly preferably Hilumin. ® - Steel. Such battery modules can be applied to a range of mobile devices and are particularly suitable for electric vehicles such as electric cars. The cells of the battery module according to the invention are positioned within a potting material. In a preferred embodiment, the central portion of the cell may be inserted into a foam, such as polyurethane foam.

[0011] The battery case can be configured to provide protection against moisture, heat, cold, or any other potential factors that could damage the battery cells. In a preferred embodiment, the case includes a bottom, a top, and a wall extending between the bottom and the top. The bottom can be the positive or negative terminal of the battery cell, depending on the desired orientation. Preferably, the bottom of the battery cell is positioned within a potting compound. The potting compound occupies a portion of the internal volume of the battery case and extends substantially equal distances from the bottom to the top of the battery case at various points along the wall. Typically, the top of the potting compound is lower than the top of the battery cell. Alternatively, the top of the battery cell may be lower than the top of the potting compound. These spaces can be completely or partially filled, for example, in the lower portion, up to 50% of the battery cell height; or in the upper and lower portions, for example, up to 30% and 70% to 100% of the battery cell height, respectively. Preferably, the fill level between the battery cells is consistent throughout the battery module. When the cells are partially inserted into foam, the potting material according to the invention is able to flow around and adhere to the foam.

[0012] The size of the gap between adjacent electrical cells and / or the battery casing can be selected based on several variables, including but not limited to the size and / or weight of each electrical cell, the operating temperature of each electrical cell, the dimensions of each electrical cell, and the intended use of the battery module. In some examples, the size of the space between adjacent electrical cells can be a length from greater than 0 mm, about 0.25 mm, about 0.50 mm, about 0.75 mm to about 1.0 mm, about 1.5 mm, or about 2.0 mm, or between any pair of the foregoing values.

[0013] The battery module according to the invention can be used to power many applications, such as, but not limited to, household appliances, outdoor electrical equipment, or vehicles such as automobiles or boats.

[0014] In a preferred embodiment of the invention, the cured potting material has a tensile strength exceeding 15 MPa in a temperature range of -35°C to +60°C, an elongation at break exceeding 5% in a temperature range of -35°C to +25°C, and an elongation at break of at least 10% at 65°C. It also has an E modulus exceeding 1500 MPa at -35°C, and an E modulus exceeding 500 MPa, preferably exceeding 600 MPa, and more preferably exceeding 750 MPa, at both +25°C and +60°C. All measurements were performed according to ISO 527-3.

[0015] The potting material according to the invention is obtained by mixing (a) one or more organic polyisocyanates, (b) one or more compounds having at least two isocyanate reactive hydrogen atoms, (c) one or more catalysts, (d) optional fillers and / or polyurethane additives to obtain a reaction mixture and then curing the reaction mixture. The reaction mixture can flow through the gaps between adjacent cells and settle at a horizontal level around the cells, as well as in the gaps or spaces defined between the cells. For example, the reaction mixture can be poured into a battery case containing the cell arrangement. The liquid reaction mixture has sufficient fluidity before curing to allow the liquid potting composition to flow through the spaces defined by the gaps between adjacent cells and / or between the cells and the battery case, and to settle at a substantially horizontal level before its viscosity increases significantly due to the curing process.

[0016] According to the present invention, the polyisocyanate component (a) used in the production of the polyurethane of the present invention comprises any polyisocyanate known for the production of polyurethane. These polyisocyanates include aliphatic, alicyclic, and aromatic bifunctional or polyfunctional isocyanates known according to the art, and any desired mixtures thereof. Examples are diphenylmethane 2,2'-diisocyanate, diphenylmethane 2,4'-diisocyanate and diphenylmethane 4,4'-diisocyanate, a mixture of monomeric diphenylmethane diisocyanate and homologues of diphenylmethane diisocyanate having a larger ring number (polymer MDI), isophorone diisocyanate (IPDI) and its oligomers, toluene 2,4-diisocyanate and toluene 2,6-diisocyanate (TDI) and mixtures thereof, tetramethylene diisocyanate and its oligomers, hexamethylene diisocyanate (HDI) and its oligomers, pentane diisocyanate and its oligomers, naphthylene diisocyanate (NDI) and mixtures thereof.

[0017] Preferably, toluene 2,4-diisocyanate and / or 2,6-diisocyanate (TDI) or mixtures thereof, monomeric diphenylmethane diisocyanate and / or diphenylmethane diisocyanate homologues (polymer MDI) and mixtures thereof are used. Other possible isocyanates are described by way of example in the Polyurethanes Handbook, Carl Hanser Verlag, 2nd edition, 1994, chapters 3.2 and 3.3.2.

[0018] In a particularly preferred embodiment, the polyisocyanate (a) comprises at least one isocyanate selected from the group consisting of monomeric MDI, polymeric MDI, or modified MDI as an MDI-based prepolymer, or carbodiimide-modified MDI, or a mixture of at least two of these. At least 80% by weight, preferably at least 90% by weight, and more preferably 100% by weight of the isocyanate (a) comprises monomeric MDI, polymeric MDI, or modified MDI, or a mixture of at least two of these. Even more preferably, the polyisocyanate (a) does not contain polymeric MDI.

[0019] The polyisocyanate component (a) used can be used in the form of a polyisocyanate prepolymer. These polyisocyanate prepolymers can be obtained by reacting an excess of the above-mentioned polyisocyanate (component (a-1)) with a compound (b) (component (a-2)) having a group that is reactive to isocyanates, for example, at a temperature of 30°C to 100°C, preferably about 80°C.

[0020] Compounds (b) having isocyanate-reactive groups are known to those skilled in the art and are described by way of example in the Polyurethane Handbook, Carl Hansel, 2nd edition, 1994, Chapter 3.1. It is preferred to use polymer compounds having isocyanate-reactive groups as described below (b) as polymer compounds having isocyanate-reactive groups (a-2).

[0021] Compounds having isocyanate-reactive groups (b) may be used, wherein any compound known to have at least two isocyanate-reactive hydrogen atoms, such as those with a functionality of 2 to 8 and a number-average molar mass of 62 g / mol to 15,000 g / mol. By way of example, compounds selected from the group consisting of at least two isocyanate-reactive hydrogen atoms may be used as compounds having at least two isocyanate-reactive hydrogen atoms: polyether polyols, fatty acid-based polyols, polybutadiene-based polyols, polyester polyols and mixtures thereof, as well as chain extenders and crosslinking agents.

[0022] By way of example, polyether alcohols are produced from alkyl oxidases, such as propylene oxide and / or ethylene oxide, or from tetrahydrofuran and a starting compound exhibiting hydrogen activity containing 1 to 8, preferably 2 to 6, and more preferably 2 to 4, bound reactive hydrogen atoms, or a mixture of starting molecules containing 1.5 to 8, preferably 1.8 to 6, and more preferably 1.9 to 3.5 bound reactive hydrogen atoms, in the presence of a catalyst. As starting molecules, aliphatic alcohols, phenols, amines, carboxylic acids, water, or compounds based on natural substances, such as sucrose, can be used. If a mixture of starting molecules with different functionalities is used, partial functionality can be obtained. The effect on functionality, such as the effect of side reactions, is not considered in the nominal functionality. Examples of suitable catalysts are basic catalysts or bimetallic cyanide catalysts, as described by way of example in PCT / EP2005 / 010124, EP90444 or WO05 / 090440.

[0023] Polyester alcohols are generated, by way of example, from aliphatic or aromatic dicarboxylic acids and polyols, polysulfide polyols, polyesteramides, hydroxylated polyacetals and / or hydroxylated aliphatic polycarbonates, preferably in the presence of an esterification catalyst. Other possible polyols are mentioned, by way of example, in the Polyurethane Handbook, 2nd edition, 1993, edited by Guether Oertel, Carl Hansel Publishers, Munich, Chapter 3.1.

[0024] In a particularly preferred embodiment of the invention, component (b) comprises polyether alcohol, and more preferably does not comprise polyester alcohol.

[0025] According to the invention, the compound (b) having at least two isocyanate-reactive hydrogen atoms comprises at least one polyether polyol (b1) having a functionality of 1.8 to 3, preferably 2 or 3, and particularly preferably 2, and a hydroxyl value of less than 140 mg KOH / g, preferably from 20 mg KOH / g to 100 mg KOH / g, and particularly from 25 mg KOH / g to 50 mg KOH / g. Preferred starting molecules are selected from the group consisting of monoethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerol, and trimethylolpropane. Glycerol and / or propylene glycol are particularly preferred as starting molecules, and propylene glycol is most preferred. Ethylene glycol and / or propylene glycol are preferably used as epoxides. Preferably, based on the total amount of epoxide used to produce the polyether (b1), the polyether (b1) comprises at least 50% by weight, more preferably at least 60% by weight, and particularly preferably at least 70% by weight of propylene oxide.

[0026] According to the invention, the compound (b) having at least two isocyanate reactive hydrogen atoms comprises at least one polyether polyol (b2) having a functionality of more than 3 to 6, preferably 3.0 to 5, and particularly preferably 3.0 to 4.5, and a hydroxyl value of more than 180 mg KOH / g, preferably 200 mg KOH / g to 800 mg KOH / g, more preferably 300 mg KOH / g to 700 mg KOH / g, and particularly preferably 400 mg KOH / g to 600 mg KOH / g. Preferred starting molecules are selected from the group consisting of glycerol, pentanediol, diethylene glycol, trimethylene propane, sugar molecules (such as sucrose, cane sugar, sorbitol, or mannitol), and fatty acid methyl esters called biodiesel. Preferably, at least one polyether alcohol (b2) is produced from a mixture of starting molecules such as glycerol, biodiesel, and cane sugar. Examples of suitable epoxides are tetrahydrofuran, 1,3-epoxide, 1,2-epoxide or 2,3-epoxide, and preferably ethylene oxide and 1,2-epoxide. Preferably, based on the total amount of epoxide used to produce the polyether (b1), the polyether (b2) contains at least 50% by weight, more preferably at least 60% by weight, and particularly preferably at least 70% by weight of propylene oxide.

[0027] The polyether alcohol (b3) according to the invention has a functionality of 1.8 to 3, preferably 2, and a hydroxyl value of more than 200 mg KOH / g, preferably 210 mg KOH / g to 500 mg KOH / g, more preferably 220 mg KOH / g to 400 mg KOH / g. Preferred starting molecules are selected from the group consisting of water, monoethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerol, and trimethylolpropane. Particularly preferred starting molecules are glycerol and / or propylene glycol, and most preferably propylene glycol. Ethylene glycol and / or propylene glycol are preferably used as the epoxide. Preferably, based on the total amount of epoxide used to produce the polyether (b1), the polyether (b1) contains at least 50% by weight, more preferably at least 60% by weight, and particularly preferably at least 70% by weight of propylene oxide.

[0028] The chain extender (b4) used herein is a compound with a molar mass of less than 200 g / mol, preferably less than 150 g / mol, and more preferably 62 g / mol to 150 g / mol, having two isocyanate-reactive groups, such as -SH or NH2- groups, preferably OH- groups. According to the invention, if chain extenders (b4) are used, they are preferably used in amounts of 0.1% to 20% by weight, more preferably 1% to 10% by weight, and particularly preferably 1% to 5% by weight, each based on the total weight of component (b). Chain extenders known in polyurethane production can be used as chain extenders (b4). These chain extenders are preferably low molecular weight compounds having two functional groups reactive to isocyanates, such as monoethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentanediol, tetraethylene glycol, dipropylene glycol, cyclohexanediol, and chain extenders based on aliphatic or aromatic amines such as aliphatic or aromatic diamines, such as ethylenediamine, triethylenediamine, and / or diethyltoluenediamine (DETDA). Other possible low molecular weight chain extenders are mentioned by way of example in the Polyurethane Handbook, Carl Hansel, 2nd edition, 1994, Chapters 3.2 and 3.3.2. In a preferred embodiment, the chain extender (b4) is selected from the group consisting of monoethylene glycol, diethylene glycol, dipropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, or mixtures thereof.

[0029] In addition, a crosslinking agent may be added to the mixture. The crosslinking agent used in this invention is a compound with a molar mass of less than 200 g / mol, preferably less than 150 g / mol, having at least three groups reactive to isocyanates. Examples of crosslinking agents are glycerol, trimethylolpropane, pentaerythritol, and triethanolamine; in a preferred embodiment, glycerol is used as the crosslinking agent. Other possible low molecular weight crosslinking agents are mentioned by way of example in the *Polyurethane Handbook*, Carl Hansel, 2nd edition, 1994, chapters 3.2 and 3.3.2. According to the invention, if chain extenders and / or crosslinking agents are used, they are used in amounts of 0.1% to 10% by weight, preferably 0.5% to 10% by weight, and particularly preferably 1% to 5% by weight, each based on the total weight of component (b).

[0030] In a preferred embodiment, the amount of polyether alcohol (b1) is 15% to 60% by weight, preferably 20% to 50% by weight, and more preferably 25% to 40% by weight; the amount of polyether alcohol (b2) is 35% to 80% by weight, preferably 50% to 75% by weight; the amount of polyether polyol (b3) is 0% to 25% by weight, preferably 0% to 20% by weight; and the amount of chain extender (b4) is 0% to 20% by weight, more preferably 1% to 10% by weight, and particularly preferably 1% to 5% by weight, each based on the total weight of compound (b). The calculation of the ratio of compound (b) is irrelevant whether the compound is pre-reacted with isocyanate to form a prepolymer or whether the compound is added directly to the reaction mixture.

[0031] In a preferred embodiment, at least a portion of the polyether alcohol (b3) and / or chain extender (b4) is pre-reacted with the isocyanate to form an isocyanate prepolymer. Preferably, the isocyanate content of the isocyanate prepolymer is 15% to 30% by weight, more preferably 20% to 25% by weight.

[0032] In a preferred embodiment, based on the total amount of epoxide units in the polyether alcohols (b1), (b2), and (b3), the polyether alcohols (b1), (b2), and (b3), if present, contain more than 70% by weight, preferably more than 80% by weight, and particularly preferably more than 90% by weight of propylene glycol units. More preferably, the polyether polyols (b1), (b2), and (b3) and the chain extender (b4), if present, contain at least 50%, preferably at least 80%, and particularly preferably more than 95% secondary alcohol groups.

[0033] In a preferred embodiment of the invention, in addition to compounds (b1), (b2), (b3) and (b4), a total amount of compounds having at least two isocyanate reactive hydrogen atoms is added, which is less than 20% by weight, preferably less than 10% by weight and particularly preferably less than 5% by weight.

[0034] In particular, a compound is used as a catalyst (c) for the production of the polyurethane according to the invention, which strongly accelerates the reaction of the compound containing reactive hydrogen atoms, especially hydroxyl groups, of component (b) with the polyisocyanate (a).

[0035] The catalyst includes nitrogen-based catalysts. Examples include amidines such as 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tertiary amines such as triethylamine, tributylamine, dimethylbenzylamine, N-methyl-, N-ethyl-, N-cyclohexylmorpholine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethylbutyldiamine, N,N,N',N'-tetramethylhexanediamine, pentamethyldiethylenetriamine, tetramethyldiaminoethyl ether, bis(dimethylaminopropyl)urea, dimethylpiperazine, 1,2-dimethylimidazolium, 1-azabicyclo[3.3.0]octane and preferably 1,4-diazabicyclo[2.2.2]octane, and alkanolamine compounds such as triethanolamine, triisopropanolamine, N-methyl- and N-ethyldiethanolamine and dimethylethanolamine. In a preferred embodiment, the nitrogen-based catalyst is reactive to isocyanates. Preferred reactive catalysts are amine catalysts having -OH, -NH, or -NH2 functional groups, such as ethylenediamine, triethanolamine, diethanolamine, ethanolamine, and dimethylethanolamine. Such reactive catalysts, or "built-in catalysts," can be considered as compounds of both components (b) and (c) and can be used to replace non-reactive amine catalysts if emissions reduction is desired.

[0036] Also usable are organotransition metal compounds, preferably: organotin compounds, such as tin(II) salts of organocarboxylic acids, for example tin(II) acetate, tin(II) octoate, tin(II) ethylhexanoate, and tin(II) laurate; and dialkyltin(IV) salts of organocarboxylic acids, such as dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate, and dioctyltin diacetate; and bismuth carboxylate, such as bismuth(III) neodecanoate, bismuth 2-ethylhexanoate, and bismuth octoate, or mixtures thereof. Organotransition metal compounds can be used alone or preferably in combination with strongly basic amines.

[0037] In a preferred embodiment, catalyst (c) comprises a catalyst that catalyzes the trimerization of isocyanate by forming an isocyanurate structure, also known as an isocyanurate catalyst or trimerization catalyst. The following catalysts can be considered as catalysts for the trimerization reaction between excess -NCO groups: catalysts that form isocyanurate groups are, for example, ammonium salts or alkali metal salts, especially ammonium carboxylate or alkali metal carboxylate, particularly selected from the group consisting of potassium formate, potassium acetate, potassium 2-ethylhexanoate, potassium octanoate, potassium neodecanoate, potassium neopentanoate, potassium hexanoate, and potassium sorbate.

[0038] In a preferred embodiment, catalyst (c) contains at least one amine catalyst, such as triethylenediamine, and at least one organotransition metal catalyst, such as zinc neodecanoate and / or bismuth neodecanoate. Preferably, in addition to the amine catalyst and the organotransition metal catalyst, catalyst (c) also contains a trimerizing catalyst, such as potassium acetate.

[0039] If a catalyst (c) is used, it may be used as a catalyst or as a combination of catalysts, for example, at a concentration of 0.001 wt% to 5 wt%, particularly 0.01 wt% to 1 wt%, based on the weight of the components (b).

[0040] Optionally, fillers and / or polyurethane additives (d) may be added to the mixture of components (a) through (c). Any fillers and additives known for the production of polyurethanes may be used. Examples herein include surfactants, dyes, pigments, reinforcing fillers, liquid and solid flame retardants, water scavengers, hydrolytic stabilizers, and oxidative stabilizers. Such compounds are well known in the art and are disclosed, for example, in the Polyurethane Handbook, Carl Hansel, 2nd edition, 1994, chapters 3.4.4 and 3.4.6 through 3.4.11. In a preferred embodiment, the potting material according to the invention contains less than 30% by weight, more preferably less than 20% by weight, even more preferably less than 10% by weight, and particularly preferably less than 5% by weight of filler, each based on the total weight of the potting material.

[0041] In addition, a foaming agent known in the art may be added as an additive (d). However, it is preferable not to use a foaming agent, and more particularly not to add water. Thus, components (a) and (b) more preferably do not contain any foaming agent except for residual water present in industrially produced polyols. In a preferred embodiment, components (b) and (c) contain less than 0.2%, more preferably less than 0.1%, and particularly preferably less than 0.05% water, each based on the total weight of compounds (b) and (c).

[0042] A particularly preferred method is to reduce the residual water content by adding a water scavenger. Suitable water scavengers are, for example, zeolites. These water scavengers are used, for example, in amounts from 0.1% to 10% by weight, based on the total weight of compounds (b) having at least two isocyanate reactive hydrogen atoms.

[0043] As described above, without the use of a foaming agent, a dense polyurethane, rather than a polyurethane foam, is obtained as the product of this invention. In a preferred embodiment, the potting material according to the invention comprises less than 5% by volume, preferably less than 3% by volume, and particularly preferably less than 1% by volume of entrained air bubbles. This results in a preferred density of at least 900 g / cm³. 3 More preferably 950g / cm 3 Up to 1200g / cm 3 .

[0044] The starting components are typically mixed and reacted at temperatures ranging from 0°C to 100°C, preferably from 15°C to 60°C. Mixing can be performed using conventional PUR processing equipment. In a preferred embodiment, mixing is performed using either a low-pressure or high-pressure machine. Preferably, mixing is performed according to the following isocyanate index: 100 to 200, more preferably 103 to 200, even more preferably 105 to 160, and even more preferably 105 to 140, and particularly preferably 115 to 140. The isocyanate index is defined as the ratio of the number of NCO groups to the total number of reactive hydrogen atoms in the isocyanate, and an isocyanate index of 100 is associated with a 1:1 ratio of the number of NCO groups to the total number of reactive hydrogen atoms in the isocyanate.

[0045] In a preferred embodiment, a two-component method is used, wherein all starting materials (a) to (d) are present in either the isocyanate component (A) or the polyol component (B). Preferably, all isocyanate-reactive substances are added to the polyol component (B), while non-isocyanate-reactive starting materials may be added to either the isocyanate component (A) or the polyol component (B). The isocyanate component (A) and the polyol component (B) are mixed to form a reaction mixture. In a preferred embodiment, an isocyanate component (A) comprising a polyisocyanate (a) and a polyol component (B) comprising a compound (b) having at least two hydrogen atoms reactive to isocyanate groups, a catalyst (c), and fillers and / or polyurethane additives (d) are produced, and then the isocyanate component (A) and the polyol component (B) are mixed to obtain the reaction mixture.

[0046] To produce the battery module according to the invention, the reaction mixture according to the invention can flow through the gaps between adjacent cells and settle at a horizontal level around the cells and in the gaps or spaces defined between the cells. For example, the potting composition can be poured into a battery case containing the cells. Preferably, the liquid potting composition has sufficient fluidity before curing to allow it to flow through the spaces defined by the gaps between adjacent cells and / or between the cells and the battery case. In a preferred embodiment, the liquid reaction mixture has sufficient fluidity to settle at a substantially horizontal level before curing to form a potting material. In a particularly preferred embodiment, the theoretical viscosity of the reaction mixture at 40°C is less than 1000 MPa, more preferably less than 500 MPa, and particularly preferably less than 260 MPa. According to the invention, the theoretical viscosity η (mixture) of the reaction mixture is calculated from the viscosity η(B) of the polyol component (B) comprising components (b) to (d) and the viscosity η(A) of the isocyanate component (A) comprising component (a) according to the following formula:

[0047] ln(η(mixture)) = ln(η(A) * portions(A) / ( portions(A) + portions(B)) + ln(η(B) * portions(B) / ( portions(A) + portions(B))).

[0048] Part (A) represents the weight parts of polyisocyanate component (A), and part (B) represents the weight parts of polyol component (B). The viscosity of each of the polyisocyanate component (A) and polyol component (B) is at 50 s. -1 The shear rate and the cone-plate geometry at 40°C were measured.

[0049] In a preferred embodiment, the electrical unit is cleaned, for example, by laser cleaning or plasma treatment, before contact with the reaction mixture according to the invention. Furthermore, known adhesion promoters or known techniques for improving adhesion can be used.

[0050] The potting material according to the invention exhibits excellent mechanical properties, such as stiffness and elasticity, over a wide temperature range. This can be observed, for example, in climate change tests of more than 10 cycles between -40°C and +80°C, as disclosed in the Examples section.

[0051] The present invention will now be described with reference to the embodiments. Example

[0052] Raw materials:

[0053] Polyol 1: A polyalkylene glycol obtained by propoxylation and ethoxylation of glycerol, having an OH- count of 26 mg KOH / g and a propylene oxide content of 80% to 90% by weight based on the total weight of the epoxide.

[0054] Polyol 2: A polyalkylene glycol obtained by propoxylation of glycerol, having an OH- content of 42 mg KOH / g.

[0055] Polyol 3: A polyalkylene glycol obtained by propoxylation of glycerol, having an OH- content of 400 mg KOH / g.

[0056] Polyol 4: A polyalkylene glycol obtained by propoxylation of glycerol, having an OH- content of 805 mg KOH / g.

[0057] Polyol 5: A polyalkylene glycol obtained by propoxylation of a mixture of biodiesel, glycerol, and sucrose, having an OH- content of 420 mg KOH / g.

[0058] Additive 1: Water scavenger, K-Ca-Na-zeolite from castor oil (50% by weight each)

[0059] Additive 2: Defoamer polydimethylsiloxane

[0060] Catalyst 1: A solution of triethylenediamine (33 wt%) in dipropylene glycol (67 wt%)

[0061] Catalyst 2: Bismuth and zinc-based transition metal catalysts

[0062] Catalyst 3: A solution of potassium acetate (40 wt%) in ethylene glycol (60 wt%)

[0063] Isocyanate 1: An MDI-based prepolymer obtained by the reaction of MDI and polypropylene glycol, having an NCO content of 23% by weight.

[0064] Sample production

[0065] The sample was obtained by mixing the components according to Table 1 at room temperature and pouring the reaction mixture into a mold. Unless otherwise specified, all data are given in parts by weight.

[0066] Table 1

[0067]

[0068] Tensile strength, elongation at break and E modulus were determined according to ISO 527-3.

[0069] The cyclical climate change test is conducted as follows:

[0070] Fiberglass reinforced plastic (GFK) tubing (75mm inner diameter, 110mm height; degreased with isopropyl alcohol) is sealed on one side. Cylindrical battery cell (Hilumin) ® - A steel tube (45mm diameter, 100mm height; degreased with isopropanol) is placed in the middle of the GFK tube on the sealed side. The mixed reaction mixture (high-speed stirrer, 1600 rpm, under vacuum (<300 bar), 60 seconds; components at room temperature) is poured into the gap between the cell and the inner wall of the GFK tube, achieving a filling height accurate to 90mm. The composite material is cured under atmospheric conditions for at least 24 hours.

[0071] The following protocol was used to test the samples for approximately 14 days in climate change testing, during which cracks or detachment from the battery cells were not permitted in the materials:

[0072] 1) Cool the sample from room temperature to -40°C at a rate of 2 K / min.

[0073] 2)(C1) Keep the material at -40℃ for 10 hours.

[0074] 3)(C2) Then, the material is heated to +80°C over a period of one hour at a rate of 2K / min.

[0075] 4)(C3) Keep the material at +80℃ for 10 hours.

[0076] 5)(C4) Cool the material to -40°C over a period of one hour at a rate of 2 K / min.

[0077] 6) Repeat steps C1 to C4 for a total of 14 cycles. In the 15th cycle, cool the material from 80°C to room temperature at a rate of 2K / min. Then, complete the climate change test and visually inspect the sample for damage. For this purpose, the sealed bottom side is also opened.

[0078] It can be observed that the potting materials according to Examples 1 and 2 exhibit good mechanical properties, such as tensile strength and elongation at break, over a wide temperature range of -35°C to 60°C. Furthermore, the material according to Example 1 passed the cyclic climate change test.

Claims

1. A battery module, wherein electrical cells are encapsulated in a potting material and the potting material is prepared by mixing the following components: a) One or more organic polyisocyanates b) One or more compounds having at least two isocyanate reactive hydrogen atoms c) One or more catalysts d) Optional fillers and / or polyurethane additives to obtain the reaction mixture and to cure the reaction mixture to obtain... The compound having at least two isocyanate reactive hydrogen atoms comprises at least one polyether polyol (b1) having a functionality of 1.8 to 3 and a hydroxyl value of less than 140 mg KOH / g, at least one polyether polyol (b2) having a functionality of more than 3 to 6 and a hydroxyl value of more than 180 mg KOH / g, and optionally at least one polyether polyol (b3) having a functionality of 1.8 to 3 and a hydroxyl value of more than 200 mg KOH / g, and optionally at least one chain extender (b4). In addition to compounds (b1), (b2), (b3), and (b4), less than 20% by weight of compounds having at least two isocyanate-reactive hydrogen atoms were added, based on compound (b) having at least two isocyanate-reactive hydrogen atoms. When filler is added, the amount of filler material is less than 20% by weight based on the total weight of the potting material, and The components used to obtain the reaction mixture are mixed with an isocyanate index of 100 to 200.

2. The battery module according to claim 1, wherein, based on the total amount of epoxide units in the polyether alcohols (b1), (b2) and (b3), the polyether alcohols (b1), (b2) and (b3) contain more than 70% by weight of propylene glycol units.

3. The battery module according to claim 1 or 2, wherein the amount of polyether alcohol (b1) is 15% to 60% by weight, the amount of polyether alcohol (b2) is 35% to 80% by weight, the amount of polyether polyol (b3) is 0% to 25% by weight, and the amount of chain extender (b4) is 0% to 20% by weight, each based on the total weight of compound (b).

4. The battery module according to any one of claims 1 to 3, wherein the density of the potting material is at least 900 g / cm³. 3 (900kg / m 3 ).

5. The battery module according to any one of claims 1 to 4, wherein the components for obtaining the reaction mixture are mixed with an isocyanate index of 105 to 160.

6. The battery module according to any one of claims 1 to 5, wherein the catalyst (c) comprises an amine-based catalyst and a metal-based catalyst.

7. The battery module according to claim 6, wherein the catalyst (c) comprises a trimerizing catalyst.

8. The battery module according to any one of claims 1 to 7, wherein the isocyanate (a) comprises methylene diphenyl diisocyanate (MDI) or a prepolymer thereof.

9. The battery module according to any one of claims 1 to 8, wherein the potting material has an E modulus of more than 1500 MPa at -35°C and an E modulus of at least 500 MPa at 60°C, an elongation at break of at least 5% at -35°C and at least 10% at 60°C, and a tensile strength of at least 15 MPa at -35°C and at least 15 MPa at 60°C.

10. A method for producing a battery module, wherein battery cells are encapsulated in a potting material, the method comprising the following steps: A battery housing is provided, the battery housing having the electrical cells arranged within a defined space between adjacent electrical cells; Obtain the reaction mixture according to any one of claims 1 to 9; pour the reaction mixture into the battery and allow the reaction mixture to solidify.

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