Preparation for providing a thermally conductive adhesive formulation for bonding battery cells

Abstract

The present invention relates to the technical fields of electric batteries and adhesive formulations for fitting the latter in vehicles. It relates to a preparation for providing a thermally conductive adhesive formulation, to a process for producing the preparation, to a structure consisting of at least one battery cell, an adhesive layer and a heat sink, and to a method for producing the structure of the invention.

Description

[0001] PREPARATION FOR PROVIDING A THERMALLY CONDUCTIVE ADHESIVE FORMULATION FOR BONDING BATTERY CELLS

[0002] The present invention relates to the technical fields of electric batteries and adhesive formulations for fitting the latter in vehicles. It relates to a preparation for providing a thermally conductive adhesive formulation, to a process for producing the preparation, to a structure consisting of at least one battery cell, an adhesive layer and a heat sink, and to a method for producing the structure of the invention.

[0003] BACKGROUND OF THE INVENTION

[0004] Batteries for electric cars consist of many individual battery cells in which the electrochemical reaction for the generation and storage of electricity takes place. The battery cells are first connected in series to what are known as battery modules; these battery modules are then assembled into what is known as a battery pack. To regulate the temperature of the individual modules, they are often arranged on a cooling plate that can be actively cooled / heated. For efficient temperature regulation, the heat transfer between the cooling plate and battery modules must be maximized. For this reason, the battery modules are normally bonded to the cooling plate with a thermally conductive adhesive (also termed gap filler). Appropriate adhesives usually consist of a curing agent component (based for example on polyurethanes or silyl- modified polymers) that contains high concentrations of a thermally conductive filler (for example AI2O3 or AI(OH)s). Filler concentrations of up to 90% by weight are not uncommon. During battery production, the adhesive is usually applied to the cooling plate in paste form, after which the battery module is mounted. It is important here that the adhesive can be easily applied despite the high filler content; on the other hand, it is important in order to avoid the formation of thermal bridges that the adhesive spreads into a completely sealed layer when the module is attached. In order to satisfy these requirements, dispersing additives are often employed in such highly-filled adhesives to control the flow properties of the system. However, the dispersing additives available to date have not been optimized for the application described above, consequently there is still great interest in tailored additives for thermally conductive adhesives.

[0005] OBJECT OF THE INVENTION

[0006] The object of the present invention was therefore to meet the requirements outlined in the introduction. It was also the object of the present invention to overcome the disadvantages of the prior art.

[0007] One object was therefore to provide a preparation for providing a thermal conductive adhesive formulation, for example one based on polyurethanes or sily l-modified polymers, that can be highly filled with thermally conductive solids such as AI2O3 or AI(OH)3.

[0008] SUMMARY OF THE INVENTION

[0009] The objects of the present invention are achieved by the inventive preparation for providing a thermally conductive adhesive formulation, comprising

[0010] I) at least one component selected from the group consisting of isocyanate and polymer;

[0011] II) at least one filler; and III) at least one dispersing aid obtained (or obtainable) from the reaction of at least one amino-functional polymer with at least one polyester.

[0012] The preparation of the invention and the adhesive formulations provided therewith show high stability. They also show no precipitates, inhomogeneities or other optical shortcomings that can result in inhomogeneous applications. They can advantageously be applied easily, for example as pastes.

[0013] In addition, the (thermally conductive) fillers are better distributed in the preparation of the invention and the adhesive formulations of the invention than in the solutions proposed in the prior art. This advantageously achieves improved thermal conductivity in the adhesive formulation and in the adhesive layers produced therefrom (with for example the same amount of filler).

[0014] BRIEF DESCRIPTION OF THE FIGURES

[0015] Figure 1 shows the shear rate-dependent viscosities of the experimental formulations #1 , #2 and #3. In the figure, experiment #1 is shown with a solid line, experiment #2 with a dashed line, and experiment #3 with a dotted line.

[0016] Figure 2 shows the shear rate-dependent viscosities of the experimental formulations #4, #5 and #6. In the figure, experiment #4 is shown with a solid line, experiment #5 with a dashed line, and experiment #6 with a dotted line.

[0017] Figure 3 shows the shear rate-dependent viscosities of the experimental formulations #7, #8, and #9. In the figure, experiment #7 is shown with a solid line, experiment #8 with a dashed line, and #9 with a dotted line.

[0018] Figure 4 (schematic, not to scale) shows the structure of the invention comprising eight battery cells (3), an adhesive layer (2) and a heat sink (1). The adhesive layer (2) is arranged between the battery cells (3) and the heat sink (1).

[0019] DESCRIPTION OF THE INVENTION

[0020] Percentages in the description and in the claims are percentages by weight (abbreviated as % by weight), unless otherwise specified. Concentrations in the description and in the claims refer to the total mass or the total volume of the solutions or dispersions or compositions concerned, unless otherwise specified. The terms “preparation” and “composition” are for the purposes of the present invention to be understood as synonymous.

[0021] The various details and embodiments described hereinbelow can be combined with one another where this is technically possible and nothing to the contrary is specified. The term “aliphatic” encompasses for the purposes of the present invention cyclic and acyclic (non- cyclic), saturated and unsaturated carbon compounds, aromatic compounds being expressly not included under this term (cf. Compendium of Technical Terminology, Gold Book, International Union of Pure and Applied Chemistry, 2014, version 2.3.3, p. 57).

[0022] The term “alkyl” encompasses for the purposes of the present invention branched and unbranched alkyl groups including cyclic and / or acyclic structural elements, where cyclic structural elements comprise by definition at least three carbon atoms. C1-CX alkyl in the description and in the claims refers to alkyl groups comprising 1 to X carbon atoms (X is a natural number). For example, C1 -C8 alkyl includes methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, tert-pentyl, neopentyl, hexyl, heptyl and octyl.

[0023] Where more than one radical needs to be selected for a compound named in the claims or in the description, said radicals are unless otherwise specified selected independently of one another, irrespective of whether selection is from one or more than one list. They may, if the lists provide for this, therefore be the same or different.

[0024] Where the term “at least one” is stated in the description and in the claims, this means that one or more than one, for example two or three, of the named elements may be selected. The same applies to higher numbers such as two or three.

[0025] The preparation of the invention for providing a thermally conductive adhesive formulation comprises

[0026] I) at least one component selected from the group consisting of isocyanate and polymer;

[0027] II) at least one filler; and

[0028] III) at least one dispersing aid obtained from the reaction of at least one amino-functional polymer with at least one polyester.

[0029] The at least one component is selected from the group consisting of isocyanate and polymer. This component is referred to herein as “component I”.

[0030] Suitable isocyanates have at least 2 NCO groups (“isocyanate groups”) and are selected from the group comprising aliphatic, cycloaliphatic, araliphatic or aromatic isocyanates. Preferred aromatic isocyanates are selected from the group comprising toluene 2,4-diisocyanate, diphenylmethane 4,4'-diisocyanate (4,4'-MDI), diphenylmethane 2,4'-diisocyanate (2,4'-MDI), diphenylmethane 2,2'-diisocyanate (2,2'-MDI), urethane-modified liquid diphenylmethane 4,4'-diisocyanate, urethane-modified liquid diphenylmethane 2,4'-diisocyanate, urethane-modified liquid diphenylmethane 2,2'-diisocyanate, higher polycyclic homologues of diphenylmethane diisocyanate (also termed oligomeric, polymeric or technical MDI), naphthylene 1 ,2-diisocyanate, naphthylene 1 ,5-diisocyanate and mixtures of these substances, particular preference being given to MDI and / or polymeric MDI. Suitable aliphatic or cycloaliphatic isocyanates are selected from the group comprising tri-, tetra-, penta-, hexa-, hepta- and / or octamethylene diisocyanate, 2-methylpentamethylene-1 ,5-diisocyanate, 2- ethylbutylene 1 ,4-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 1 ,3-bis(isocyanatomethyl)cyclohexane (HXDI), cyclohexane 1 ,4-diisocyanate, 1- methylcyclohexane 2,4-diisocyanate, 1 -methylcyclohexane 2,6-diisocyanate, dicyclohexylmethane 4,4'- diisocyanate, dicyclohexylmethane 2,4'-diisocyanate, dicyclohexylmethane 2,2'-diisocyanate and mixtures of the above.

[0031] The at least one polymer (of component I) is preferably selected from the group consisting of polyols, polyethers, polyurethane prepolymers and sily l-modified polymers.

[0032] Polyols are preferably selected from the group consisting of polyester polyols, polyether polyols and polycarbonate polyols and mixtures of the above. For example, the polyol contains 2 to 6, preferably 2 to 4, (NCO-reactive) OH functions.

[0033] Suitable polyethers are known to those skilled in the art. They are preferably produced by addition reactions of alkylene oxides, such as ethylene oxide or propylene oxide, to a starter having at least two active hydrogen atoms. Examples of such starters are polyhydric alcohols (for example ethylene glycol, propylene glycol, glycerol, trimethylolpropane or pentaerythritol), aliphatic amines (for example ethylenediamine), aromatic amines (for example toluenediamine) and alkanolamines (for example ethanolamine and diethanolamine) and sugars (for example sorbitol, glucose and sucrose). The addition reaction can take place according to a method in “Polyurethane Handbook” (1985) by Gunter Oertel, Hanser Verlag Deutschland, pp. 42 to 53.

[0034] Suitable polyester polyols are likewise known to those skilled in the art. They are preferably prepared by reacting at least one dibasic acid with at least one polyhydric alcohol. The at least one dibasic acid is preferably selected from the group consisting of adipic acid, maleic acid, phthalic acid and terephthalic acid. As the polyhydric alcohol, preference is given to using glycols preferably selected from the group consisting of ethylene glycol, propanediol, butanediol, hexanediol, neopentyl glycol and cyclohexane-1 ,4- dimethanol.

[0035] Suitable polymer polyols are likewise known to those skilled in the art. They are preferably accessible by reacting the polyether polyols described above with ethy lenically unsaturated monomers, for example butadiene, acrylonitrile or styrene, in the presence of a free-radical initiator.

[0036] Suitable polycarbonate polyols are likewise known to those skilled in the art. They are preferably prepared by reacting a polyhydric alcohol (usually a glycol preferably selected from the group consisting of ethylene glycol, propanediol, butanediol, hexanediol, neopentyl glycol and cyclohexane-1 ,4- dimethanol) with at least one carbonic ester (preferably dimethyl carbonate or diphenyl carbonate) and then removing the excess carbonic ester and the liberated monoalcohols to expose the terminal OH groups. Alternatively, polycarbonate polyols are obtainable by directly reacting diols with carbon dioxide in the presence of a suitable catalyst.

[0037] Suitable polyether polyols preferably have a mass-weighted average molecular weight (Mw) of 750 to 6000 g / mol. The mass-weighted average molecular weight (Mw) can preferably be determined here by gel-permeation chromatography (GPC) using an SDV 1000 / 10 000 A column combination (length: 65 cm) at a temperature of 30°C with THF as mobile phase and a flow rate of 1 ml / min, a sample concentration of 10 g / l and an Rl detector calibrated against polypropylene glycol as standard.

[0038] Suitable polyester polyols preferably have a mass-weighted average molecular weight (Mw) of 100 to 2500 g / mol, it being possible to determine the molecular weight by GPC as described above.

[0039] Preferably, the polyols have an OH value in the range from 20 to 1000 mg KOH / g. Polyether polyols used with preference have an OH value in the range from 20 to 800 mg KOH / g. Polyester polyols used with preference have an OH value in the range from 40 to 1000 mg KOH / g. Suitable methods for determining the hydroxyl value are in particular those according to DGF C-V 17a (53) and Ph. Eur. 2.5.3 Method A.

[0040] Suitable polyurethane prepolymers are likewise known to those skilled in the art. They are obtainable preferably by reacting at least one isocyanate with a substoichiometric amount of at least one polyol. The reaction is preferably carried out at a temperature of 30 to 100°C. The corresponding polyurethane prepolymers have at least two reactive NCO groups.

[0041] Silyl-modified polymers are known to those skilled in the art and are generally formed from three structural units: a polymer backbone, at least two linking groups and at least two condensable alkoxysilyl groups that are each connected to the polymer backbone via one of said linking groups. The polymer backbone is here preferably selected from the group consisting of polyether polyols (preferably based on polyethylene and polypropylene oxide), polyesters, polycarbonates, poly acrylates, polyolefins, polyurethanes and mixtures of the above. Particular preference is given here to polyether polyols. Preferred linking groups are selected from alkanediyl groups, carbamate groups, urethane groups, and urea groups. The condensable alkoxysilyl groups are preferably selected from dimethoxysilyl group, trimethoxysilyl group, diethoxysilyl group or triethoxysilyl group.

[0042] The preparation of the invention contains the at least one component I preferably in an amount of 1 to 49 percent by weight, more preferably 5 to 29 percent by weight, even more preferably 10 to 19 percent by weight, based on the total mass of the preparation. If more than one component I is used, their total mass is preferably within one of the ranges defined above.

[0043] The preparation of the invention contains at least one filler. The filler serves in particular to ensure that the adhesive layer produced from the preparation of the invention or from an adhesive formulation described hereinbelow has adequate thermal conductivity after being applied. Those skilled in the art are aware of numerous fillers that may be used for this purpose. The filler is preferably selected from the group consisting of metallic fillers, ceramic fillers, carbon-based fillers and mixtures of the above. Preferred metallic fillers are selected from the group consisting of silver and copper. Preferred carbonbased fillers are selected from the group consisting of graphite and carbon black. Preferred ceramic fillers are selected from the group consisting of aluminium oxide, aluminium hydroxide, aluminium oxide hydroxide and boron nitride. Ceramic fillers are preferred, since they permit good thermal conductivity but have low electrical conductivity. This prevents the risk of a short circuit and damage to the battery. Particularly preferably, the at least one filler is selected from the group consisting of aluminium oxide, aluminium hydroxide and aluminium oxide hydroxide. Most preferably, the at least one filler is aluminium oxide or aluminium hydroxide.

[0044] It is preferable that the at least one filler is present in the form of particles. A bi- or polymodal particle size distribution is preferred. Preferably, the at least one filler has a particle size (dgo) of from 0.5 to 500 pm, preferably from 1 to 250 pm, more preferably from 5 to 150 pm. The particle size can be determined by laser diffraction, for example with a Mastersizer 3000 from Malvern.

[0045] The preparation of the invention contains the at least one filler preferably in an amount of 50 to 99 percent by weight, more preferably 70 to 95 percent by weight, even more preferably 80 to 90 percent by weight, based on the total mass of the preparation. If more than one filler is used, their total mass is preferably within one of the ranges defined above. Lower proportions of the at least one filler can sometimes result in the thermal conductivity of the adhesive layer produced being too low and amounts that are too high can potentially result in the adhesion of the layer being too low.

[0046] The at least one dispersing aid is obtained or is obtainable from the reaction of at least one aminofunctional polymer with at least one polyester. The reaction results in the formation of amide bonds between the reactants. This dispersing aid thus obtained is referred to herein as dispersing aid product. The product mixture that results from the reaction is complex and not definitively analysable.

[0047] Amino-functional polymers are known to those skilled in the art. Preferably, the at least one aminofunctional polymer is selected from the group consisting of polylysine, polyamidoamine, polyallylamine, poly(N-alkyl)allylamine, polyvinylamine, polyethyleneimine and polypropyleneimine, the at least one amino-functional polymer being in particular a polyethyleneimine.

[0048] The at least one amino-functional polymer preferably has a mass-weighted average molecular weight (Mw) in the range from 400 to 100 000 g / mol, preferably from 600 to 50 000 g / mol.

[0049] Preferably, the at least one polyester has a mass-weighted average molecular weight (Mw) in the range from 100 to 5000 g / mol, preferably from 200 to 3000 g / mol. Mass-weighted average molecular weights (Mw) can preferably be determined by gel-permeation chromatography (GPC) using an SDV 1000 / 10 000 A column combination (length: 65 cm) at a temperature of 30°C with THF as mobile phase and a flow rate of 1 ml / min, a sample concentration of 10 g / l and an Rl detector calibrated against polypropylene glycol as standard.

[0050] The at least one polyester is not limited further. It has been found to be advantageous when the at least one polyester is not aromatic (i.e. it does not contain any aromatic groups such as phenyl groups). More advantageously, the at least one polyester is not unsaturated (i.e. it contains no unsaturated groups such as phenyl groups or vinyl groups).

[0051] It is preferable that the at least one polyester was obtained by ring-opening polymerization of at least one lactone with at least one starter compound, where the at least one starter compound is preferably selected from the group consisting of R1-CH2-OH and R2-COOH, where R1is a monovalent aliphatic saturated or unsaturated hydrocarbon radical having 3 to 39, preferably having 4 to 21 , more preferably having 5 to 17, carbon atoms; and where R2is a monovalent aliphatic saturated or unsaturated hydrocarbon radical having 3 to 39, preferably having 4 to 21 , more preferably having 5 to 17, carbon atoms.

[0052] The at least one starter compound is used to cleave the ester bond of the at least one lactone. The cleavage of the ester bond can be promoted by addition of an acid or base, typically in a substoichiometric (for example catalytic) amount. Suitable acids and bases are known to those skilled in the art. The cleavage of the ester bond results in initiation of the ring-opening polymerization. The at least one starter compound is preferably used in a molar ratio of from 1 :1 to 1 :30, more preferably from 1 :2 to 1 :20, based on the at least one lactone.

[0053] The reaction of the at least one polyester with the at least one amino-functional polymer is preferably carried out at a temperature of 60 to 250°C, more preferably 100 to 230°C.

[0054] The duration of the reaction of the at least one polyester with the at least one amino-functional polymer is not specified more precisely and the course of said reaction can be monitored by means known to those skilled in the art (for example chromatographic or spectroscopic monitoring of the decrease in the reactants employed).

[0055] The reaction of the at least one amino-functional polymer with the at least one polyester can take place either completely or partially, preference being given to a partial reaction (that is to say, not all amino functions of the polymer react). Preferably, the at least one lactone is selected from the group consisting of p-propiolactone, p- butyrolactone, 3, 6-dimethyl-1 ,4-dioxane-2, 5-dione, 5-valerolactone, e-caprolactone, y-caprolactone, 4- methylcaprolactone, 2-methylcaprolactone, 5-hydroxydodecanoic acid lactone, 12-hydroxydodecanoic acid lactone and 12-hydroxy-9-octadecenoic acid lactone. More preferably, the at least one lactone is preferably selected from the group consisting of 5-valerolactone and e-caprolactone.

[0056] The preparation preferably contains the at least one dispersing aid product in an amount of 0.1 to 10.0 percent by weight, more preferably 0.5 to 5.0 percent by weight, even more preferably 1 .0 to 3.0 percent by weight, based on the total mass of the preparation. If more than one dispersing aid product is used, their total mass is preferably within one of the ranges defined above.

[0057] The present invention also relates to the use of the dispersing aid product for improving the rheological properties and / or the stability of a polymer dispersion or adhesive formulation. In particular, the use of the dispersing aid product makes it possible to improve the rheological properties of an adhesive formulation capable of producing a thermally conductive adhesive layer. The adhesive formulation preferably contains a filler from the group mentioned above in one of the amounts mentioned herein.

[0058] The present invention is also directed to a process for producing the preparation of the invention comprising the process steps of:

[0059] M1) providing the at least one component selected from the group consisting of isocyanate and polymer (component I);

[0060] M2) providing the at least one filler;

[0061] M3) providing the at least one dispersing aid product; and

[0062] M4) mixing the at least one component I, the at least one filler and the at least one dispersing aid product; such that the preparation is obtained.

[0063] The process of the invention comprises the abovementioned process steps, for example in the stated sequence. The sequence of process steps M1 to M3 can be varied as desired. Process step M4 follows on from process steps M1 to M3. The process according to the invention optionally comprises further process steps that can be executed before, during or after process steps M1 to M4.

[0064] The mixing in process step M4 can be effected by customary methods by those skilled in the art. For example, the component I, the at least one filler and the at least one dispersing aid product can be mixed in a suitable container using a stirrer.

[0065] The temperature in process step M4 is preferably in the range from 5 to 60°C, more preferably in the range from 10 to 50°C.

[0066] The present invention is also directed to a kit of parts for providing a thermally conductive polyurethane- based adhesive formulation comprising part 1 and part 2, where: part 1 comprises 1-1) at least one polyol;

[0067] 1-2) at least one filler;

[0068] 1-3) at least one dispersing aid product; and part 2 comprises

[0069] 2-1) at least one component selected from the group consisting of isocyanate and polyurethane prepolymer;

[0070] 2-2) at least one filler;

[0071] 2-3) at least one dispersing aid product.

[0072] A kit of parts is sometimes referred to in the art also as a multicomponent formulation or multicomponent system, for example as a 2K formulation.

[0073] The term polyurethane is known to those skilled in the art and describes the product obtained by reacting at least one isocyanate with at least one polyol, both as described above. In addition to polyurethanes, other chemical groups, for example uretdiones, carbodiimides, isocyanurates, allophanes, biurets, urea groups and / or uretonimines, may also be formed in the reaction. In the context of the present invention, the term polyurethane therefore also includes reaction products formed from polyols and isocyanates which may additionally include the aforementioned groups.

[0074] The thermally conductive polyurethane-based adhesive formulation can be obtained by mixing part 1 and part 2. The mixing may take place at room temperature and standard methods may be used for this. The individual constituents correspond to those described hereinabove. The amounts of the individual components in part 1 and part 2 are preferably selected such that they are, after mixing, present in the amounts described above for the preparation of the invention. The two parts 1 and 2 are preferably provided in a ratio such that the NCO index of a mixture obtained from part 1 and part 2 is in the range from 90 to 200%, preferably in the range from 95 to 175%, even more preferably in the range from 97 to 159%. The term NCO index is known to those skilled in the art and describes the molar amount of all NCO groups present in part 2 relative to all isocyanate-reactive groups (for example hydroxy groups) present in part 1 . At an NCO index of 100%, the number of NCO groups in part 2 is exactly the same as the number of all isocyanate-reactive groups present in part 1 , an NCO index > 100% indicates that NCO groups are present in excess, and an NCO index < 100% indicates that they are present substoichiometrically. If it is to be used, the optional catalyst described below is preferably added to part 1 .

[0075] The proportions of the individual components in the adhesive formulations correspond to those in the preparation of the invention, wherein they are correspondingly reduced by the proportion added to the adhesive formulation (components not yet present in the preparation). The invention is also directed to a thermally conductive polyurethane-based adhesive formulation comprising (or consisting of) P1) at least one polyol;

[0076] P2) at least one filler preferably selected from the group consisting of aluminium oxide, aluminium hydroxide and aluminium oxide hydroxide, wherein the adhesive formulation contains the at least one filler preferably in an amount of from 50 to 99 percent by weight, more preferably 70 to 95 percent by weight, even more preferably 80 to 90 percent by weight, based on the total mass of the adhesive formulation;

[0077] P3) at least one dispersing aid product;

[0078] P4) at least one component selected from the group consisting of isocyanate and polyurethane prepolymer; and

[0079] P5) optionally at least one catalyst.

[0080] The thermally conductive polyurethane-based adhesive formulation can be obtained by mixing the aforementioned P1 to P4 and optionally P5.

[0081] The optional at least one catalyst mediates the reaction of the at least one polyol and the at least one component I. Those skilled in the art are aware of suitable catalysts. Preferred catalysts are selected from the group of gel catalysts that catalyse the polyurethane reaction between isocyanate and polyol. These may be selected from the class of amine catalysts, for example triethylamine, dimethylcyclohexylamine, tetramethylethylenediamine, tetramethylhexanediamine, pentamethyldiethylenetriamine, pentamethyldipropylenetriamine, triethylenediamine, dimethylpiperazine, 1 ,2-dimethylimidazole, N- ethylmorpholine, tris(dimethylaminopropyl)hexahydro-1 ,3,5-triazine, dimethylaminoethanol, dimethylaminoethoxyethanol, tetramethylguanidine and 1 ,8-diazabicyclo[5.4.0]undec-7-ene. In addition, amine catalysts may be selected from the class of what are known as emission-free catalysts, which are characterized in that they have a catalytically active nitrogen atom and an NCO-reactive group, for example an OH group. Appropriate emission-free amine catalysts are marketed for example under the Dabco NE product series from Evonik. In addition, the catalysts may be selected from the class of metal catalysts, for example tin-, zinc-, bismuth-, iron-, copper- or zirconium-based catalysts. Metal catalysts may here be used in the form of salts, for example, or as organically modified catalysts, for example tin laurate, tin octanoate, tin neodecanoate or bismuth neodecanoate.

[0082] The present invention also relates to a thermally conductive silyl-modified-polymer-based adhesive formulation comprising (or consisting of)

[0083] 51) at least one silyl-modified polymer;

[0084] 52) at least one filler preferably selected from the group consisting of aluminium oxide, aluminium hydroxide and aluminium oxide hydroxide, wherein the adhesive formulation contains the at least one filler preferably in an amount of from 50 to 99 percent by weight, more preferably 70 to 95 percent by weight, even more preferably 80 to 90 percent by weight, based on the total mass of the adhesive formulation; 53) at least one dispersing aid;

[0085] 54) optionally at least one plasticizer;

[0086] 55) optionally at least one adhesion promoter;

[0087] 56) optionally at least one desiccant; and

[0088] 57) optionally at least one catalyst for crosslinking the silyl-modified polyether.

[0089] The thermally conductive silyl-modified-polymer-based adhesive formulation comprises at least one plasticizer. Plasticizers are known to those skilled in the art. The at least one plasticizer can be used to regulate the viscosity of the formulation and can in addition have an influence on the mechanical properties, for example tensile strength or elongation, of the cured adhesive layer. Appropriate plasticizers may be for example from the group of the phthalates, for example dibutyl phthalate, diisononyl phthalate (DINP), di-2-ethylhexyl phthalate, and diisodecyl phthalate (DIDP), terephthalates, for example bis(2-ethylhexyl)benzene-1 ,4-dicarboxylate, phthalate-free plasticizers, for example diisononyl cyclohexane-1 ,2-dicarboxylate (DINCH), aliphatic carboxylates, for example dioctyl adipate, dioctyl sebacate and acetyltributyl citrate, unsaturated fatty acid esters, for example butyl oleate, phenyl alkylsulfonates, phosphate compounds, for example tricresyl phosphate or tributyl phosphate, chloroparaffins, hydrocarbon oils and epoxidized plasticizers such as epoxidized soybean oil. In addition, the plasticizers may be selected from the group of polymeric plasticizers, for example vinyl polymers, esters of polyalkylene glycols and polyester-based plasticizers, preferably based on dibasic acids and dihydric alcohols.

[0090] Preferably, the thermally conductive silyl-modified-polymer-based adhesive formulation contains the at least one plasticizer in an amount of 5 to 100 percent by weight, more preferably 10 to 75 percent by weight, even more preferably 15 to 50 percent by weight, based on the total mass of the thermally conductive silyl-modified-polymer-based adhesive formulation.

[0091] Optionally, the thermally conductive silyl-modified-polymer-based adhesive formulation comprises at least one adhesion promoter. Adhesion promoters are known to those skilled in the art and are preferably selected from the group of silane coupling agents, such as silanes containing amino groups, for example y-aminopropyltrimethoxysilane, y-aminopropyltriethoxysilane, y-aminopropylmethyldimethoxysilane, N-p- aminoethyl-y-aminopropyltrimethoxysilane, N-p-aminoethyl-y-aminopropylmethyldimethoxysilane, N-p- aminoethyl-y-aminopropyltriethoxysilane and y-ureidopropyltrimethoxysilane, silanes containing isocyanate groups, for example y-isocyanatopropyltrimethoxysilane, y-isocyanatopropyltriethoxysilane, a- isocyanatomethyltrimethoxysilane and a-isocyanatomethyldimethoxymethylsilane, silanes containing mercapto groups, for example y-mercaptopropyltrimethoxysilane and y-mercaptopropyltriethoxysilane, silanes containing epoxy groups, for example y-glycidoxypropyltrimethoxysilane, y- glycidoxypropyltriethoxysilane and y-glycidoxypropylmethyldimethoxysilane, and carboxysilanes, for example p-carboxyethyltriethoxysilane, unsaturated silanes bearing vinyl groups, and halogen-modified silanes. Preferably, the thermally conductive silyl-modified-polymer-based adhesive formulation contains the at least one optional adhesion promoter in an amount of 0.05 to 20 percent by weight, more preferably 0.1 to 15 percent by weight, even more preferably 0.5 to 10 percent by weight, based on the total mass of the thermally conductive silyl-modified-polymer-based adhesive formulation.

[0092] Optionally, the thermally conductive silyl-modified-polymer-based adhesive formulation comprises at least one desiccant. Desiccants are known to those skilled in the art. The at least one optional desiccant is preferably selected from the group consisting of pulverulent desiccants, in particular zeolites, molecular sieves, silica gel or activated aluminium oxide, and trialkoxysilanes, in particular vinyltrialkoxysilanes, such as vinyltrimethoxysilanes and vinyltriethoxysilanes.

[0093] Preferably, the thermally conductive silyl-modified-polymer-based adhesive formulation contains the at least one optional desiccant in an amount of 0.05 to 20 percent by weight, more preferably 0.1 to 15 percent by weight, even more preferably 0.5 to 10 percent by weight, based on the total mass of the thermally conductive silyl-modified-polymer-based adhesive formulation.

[0094] Optionally, the thermally conductive silyl-modified-polymer-based adhesive formulation comprises at least one catalyst for crosslinking the sily l-modified polymer. Such catalysts are known to those skilled in the art. The at least one optional catalyst for crosslinking the sily l-modified polyether is preferably selected from the group consisting of amine catalysts, in particular 1 ,8-diazabicyclo[5.4.0]undec-7-ene, 1 ,5,7- triazacyclo[4.4.0]dec-5-ene and 1 ,1 ,3,3-tetramethylguanidine, metal catalysts, in particular ones based on bismuth, for example bismuth neodecanoate, on tin, for example dibutyltin dilaurate, dibutyltin dimaleate, dibutyltin dioctanoate, dibutyltin bis(2-ethylhexanoate), dibutyltin diacetate, dibutyltin oxide and dioctyltin dilaurate, on titanium, for example tetrabutyl titanate, tetrapropyl titanate and tetrakis(acetylacetonato)titanium, on zinc, for example zinc acetate or zinc ricinoleate, on aluminium and on zirconium, organophosphates, organic sulfonic acids and inorganic acids.

[0095] Preferably, the thermally conductive silyl-modified-polyether-based adhesive formulation contains the at least one optional catalyst for crosslinking the sily l-modified polyether in an amount of 0.02 to 5 percent by weight, more preferably 0.05 to 3 percent by weight, even more preferably 0.1 to 2 percent by weight, based on the total mass of the thermally conductive silyl-modified-polymer-based adhesive formulation.

[0096] The present invention also relates to a structure comprising (or consisting of) at least one battery cell (1), an adhesive layer (2) and a heat sink (3), wherein the adhesive layer has been produced by applying the adhesive formulation of the invention, in particular the thermally conductive silyl-modified-polymer-based adhesive formulation or the thermally conductive polyurethane-based adhesive formulation, between the at least one battery cell (1) and the heat sink (3).

[0097] A battery cell is the basic functional unit of a battery and consists of an array of electrodes with active materials, electrolyte, containers, connectors, and usually separators. Typically, the structure of the invention comprises a plurality of battery cells that form a battery. The at least one battery cell or the totality of the battery cells is preferably designed such that they (arranged side-by-side in the case of the totality of the battery cells) can be fitted to the heat sink.

[0098] A preferred heat sink is a cooling plate. Such cooling plates are known to those skilled in the art. The heat sink can be actively heated or cooled and is provided with the appropriate devices.

[0099] The adhesive layer is preferably designed such that it comprises the entire contact surface between the heat sink and the at least one battery cell. This ensures the best possible dissipation of heat from the at least one battery cell.

[0100] Also part of the present invention is a method for producing the inventive structure, comprising the process steps of

[0101] Q-A) providing a heat sink;

[0102] Q-B) providing at least one battery cell; and

[0103] Q-C) applying the adhesive formulation of the invention, more particularly the thermally conductive silyl- modified-polymer-based adhesive formulation or the thermally conductive polyurethane-based adhesive formulation, between the heat sink and the at least one battery cell; such that the structure is obtained.

[0104] The method of the invention comprises the abovementioned process steps, preferably in the stated sequence. Process steps Q-A and Q-B can also be executed in different sequence. The process according to the invention optionally comprises further process steps that can be executed before, during or after process steps Q-A to Q-C.

[0105] Optionally, the method of the invention is supplemented by process step Q-D, which is executed after process step Q-C:

[0106] Q-D) curing of the adhesive layer.

[0107] Curing can be effected by customary processes. For example, the structure of the invention can be exposed to elevated temperatures, for example in an oven. Curing, especially at elevated temperatures, also allows evaporable fractions to be removed from the adhesive layer.

[0108] The present invention is elucidated more particularly with reference to the examples that follow, without limiting the subject matter.

[0109] EXAMPLES

[0110] Commercial products are used as per the technical information sheets available at the time of filing of this application, unless otherwise stated.

[0111] Materials Voranol CP 3322: Polyether triol, OH value = 56 mg KOH / g from Dow

[0112] Suprasec 6506: Polymeric MDI from Huntsman

[0113] Martinal TM-3810: Pulverulent aluminium oxide having a bimodal particle size distribution (5 pm / 75 pm) from Huber

[0114] MS Polymer SAX 530: Methoxysilyl-terminated polyether from Kaneka

[0115] Dispersant 1 : Dispersing aid product obtained by reaction of a polyethyleneimine (Mw = 2000 g / mol) with a lauric-acid-started e-caprolactone - 8-valerolactone copolyester (Mw = 2300 g / mol) in a mass ratio of 1 :17, dissolved in xylene (30 wt.-%).

[0116] Dispersant 2: hyperbranched polyester from Merck, dissolved in xylene (30 wt.-%).

[0117] Polycat SA 2 LE: Polyurethane catalyst from Evonik

[0118] MS Polymer SAX 015: Reactive plasticizer from Kaneka

[0119] Dynasylan VTMO: Vinyltrimethoxysilane from Evonik (desiccant)

[0120] Dynasylan DAMO: 2-Aminoethyl-3-aminopropyltrimethoxysilane from Evonik (adhesion promoter) Kosmos T 12: Dibutyltin laurate-based catalyst from Evonik (catalyst for crosslinking the silyl-modified polyether)

[0121] Dispersion experiments

[0122] All dispersion experiments were carried out using a SpeedMixer (model DAC 400.1 FVZ from Hauschild). For this purpose, all components were weighed into a 25 ml plastic beaker and homogenized at 2750 rpm for 1 min. The visual appearance of the filled systems was then evaluated. The viscosity profile of the samples was determined by shear rate-dependent viscosity measurements. These were performed using a model MCR 702 rheometer from Anton-Paar with plate-plate geometry. All viscosity measurements were performed at a temperature of 25°C and in a shear rate range of 1-10 s-1.

[0123] Example 1 - Dispersion experiments in polyurethane systems

[0124] To test the effectiveness of the dispersing additives of the invention in polyurethane-based systems, dispersion experiments were carried out in both polyol and isocyanate components. Tables 1 and 2 give an overview of the composition of the respective experiments. In all cases, the samples were homogenized and evaluated according to the procedure described above. Optical appearance and the viscosity of the samples at a shear rate of 0.1 s-1are also noted in the tables. Figures 1 and 2 in addition show the shear rate-dependent viscosity profile of the samples. For these experiments a dispersant according to the invention (dispersant 1) as well as a non-inventive dispersant, based on a polyester, (dispersant 2) were used.

[0125] Table 1 : Overview of dispersion experiments in polyol

[0126] Experiment #1 Experiment #2 Experiment #3

[0127] Comparative experiment Inventive Comparative experiment

[0128] Voranol CP 3322 13 g 13 g 13 g Martinal TM-3810 87 g 87 g 87 g

[0129] Dispersant 1 3 g

[0130] Dispersant 2 3 g

[0131] Optical appearance inhomogeneous / lumpy homogeneous / creamy inhomogeneous / lumpy

[0132] Viscosity at 1 s'11.4 1064.8 1051.3 106

[0133] Table 2: Overview of dispersion experiments in isocyanate

[0134] Experiment #4 Experiment #5 Experiment #6

[0135] Comparative experiment Inventive Comparative experiment

[0136] Suprasec 6506 16 g 16 g 16 g

[0137] Martinal TM-3810 84 g 84 g 84 g

[0138] Dispersant 1 3 g

[0139] Dispersant 2 3 g

[0140] Optical appearance inhomogeneous / lumpy homogeneous / creamy inhomogeneous / lumpy

[0141] Viscosity at 1 s'14.0 1061 .9 1054.2 106

[0142] As is clear from these experiments, the preparations of the invention have good stability. Thus, in all cases, a significant lowering of the viscosity of the preparations of the invention is observed (experiments #2 and #5) compared with the comparative formulations without dispersant (experiments #1 and #4). The comparative formulations comprising a non-inventive dispersant exhibit a substantially higher viscosity (experiments #3 and #6). In addition, the preparations according to the invention have a markedly improved optical appearance.

[0143] 2 - Dispersion experiments in methoxvsilvl-terminated polvethers

[0144] Preparations with silyl-modified polyether systems were also tested. Table 3 gives an overview of the composition of these experiments. The samples were again homogenized and evaluated according to the procedure described above. Optical appearance and the viscosity of the samples at a shear rate of 0.1 s-1are likewise noted in Table 3. The shear rate-dependent viscosity profile of the samples is shown in Figure 3.

[0145] The good stability of the preparation of the invention (experiment #8) compared with a comparative formulations (experiments #7 and #9) is clear from these experiments too. Thus, the preparation of the invention shows a significant lowering in viscosity compared with the comparative formulations. In addition, the preparation of the invention had a markedly better optical appearance than the comparative experiments.

[0146] Table 3: Overview of dispersion experiments in MS Polymer SAX 530

[0147] Experiment #7 Experiment #8 Experiment #9

[0148] Comparative experiment Inventive Comparative experiment MS Polymer SAX 530 13 g 13 g 13 g Martinal TM-3810 87 g 87 g 87 g Dispersant 1 3 g Dispersant 2 3 g Optical appearance inhomogeneous / lumpy homogeneous / creamy inhomogeneous / lumpy

[0149] Viscosity at 0.1 s'15.3 1062.1 1064.7 106

[0150] Example 3 - Production of a highly-filled, thermally conductive polyurethane-based adhesive

[0151] In addition to the dispersion experiments of polyurethane systems described in Example 1 , polyurethane- based adhesive formulations were also produced to further demonstrate the effectiveness of the present invention. Table 4 gives an overview of the composition of these experiments.

[0152] Table 4: Overview of PU-based adhesive formulations

[0153] Experiment #10 Experiment #11 Experiment #12

[0154] Comparative Comparative

[0155] Inventive experiment experiment

[0156] Component A: Voranol CP 13 g 10 g 13 g

[0157] 3322 Martinal TM- 87 g 87 g 87 g

[0158] 3810 Dispersant 1 3 g

[0159] Dispersant 2 3g

[0160] Component B: Suprasec 6506 17 g 14 g 17 g

[0161] Martinal TM- 83 g 83 g 83 g

[0162] 3810 Dispersant 1 3 g

[0163] Dispersant 2 3g

[0164] Component A 100 g 100 g 100 g

[0165] Component B 42.1 g 46.98 g 47.8 g

[0166] Inhomogeneous Homogeneous, Inhomogeneous

[0167] Optical coating with smooth and coating with appearance imperfections creamy imperfections

[0168] Spreadability poor good poor

[0169] For these experiments, components A and B were first dispersed separately on the SpeedMixer according to the procedure described above, then the two filled components were mixed in the ratio described in Table 4 and homogenized again in the SpeedMixer for 1 min at 2750 rpm. The adhesive formulation thus obtained was spread onto a metal plate (thickness approx. 1 cm) and cured in the oven at 80°C for 5 minutes. In all cases, solid, well-cured adhesive formulations were obtained. The adhesive formulation of the invention (experiment #11) exhibited no change in curing properties when compared to the comparative examples. However, it was noticeable that the adhesive formulation of the invention could be spread significantly more easily on the metal plates, affording in these cases homogeneous, smooth adhesive layers that were free of defects. In the case of the comparative coatings (experiments #10 and #12), the application of the formulation onto the plate was significantly more difficult on account of the high viscosity, and inhomogeneous layers having many imperfections and defects were obtained. Such inhomogeneities result in undesirable thermal bridges, which in turn reduces the dissipation of heat from the battery cell. The consequence of this can be a shortening of the battery cell life.

[0170] Example 4 - Production of a highly-filled, heat-conducting adhesive from methoxysilyl-terminated polyethers

[0171] In addition, adhesive formulations based on a methoxysilyl-terminated polyether (a silyl-modified polymer) were produced in order to further demonstrate the effectiveness of the dispersing additives of the invention. Table 5 gives an overview of the composition of these experiments.

[0172] Table 5: Overview of silyl-terminated polyether-based adhesive formulations

[0173] Experiment #13 Experiment #14 Experiment #13

[0174] Comparative Inventive Comparative

[0175] MS Polymer SAX 12 g 10 g 12 g

[0176] 530

[0177] MS Polymer SAX

[0178] „„ „4s394g

[0179] 015

[0180] Martinal TM-3810 84 g 84 g 84 g

[0181] Dynasylan VTMO 1 g 1 g 1 g

[0182] Dynasylan DAMO 0.5 g 0.5 g 0.5 g

[0183] Kosmos T 12 0.3 g 0.3 g 0.3 g

[0184] Dispersant 1 3 g

[0185] Dispersant 2 3 g

[0186] Inhomogeneous coating Homogeneous, smooth Inhomogeneous coating

[0187] Optical appearance with imperfections and creamy with imperfections

[0188] Spreadability poor good poor

[0189] For these experiments, all components were dispersed with the SpeedMixer according to the procedure described above. The adhesive formulation thus obtained was spread onto a metal plate (thickness approx. 1 cm) and then cured overnight at room temperature. In all cases, solid, well-cured adhesive layers were obtained. The adhesive formulation of the invention (experiment #14) exhibited no change in curing properties. However, it was noticeable that the adhesive formulation of the invention could be spread significantly more easily on the metal plates, affording in these cases homogeneous, smooth adhesive layers that were free of defects. In the case of the comparative coatings (experiments # 13 and #15), the application of the formulations onto the plate was difficult on account of the high viscosity, and an inhomogeneous coatings having many imperfections and defects were obtained. Such inhomogeneities result in undesirable thermal bridges, which in turn reduces the dissipation of heat from the battery cell. The consequence of this can be a shortening of the battery cell life.

Claims

CLAIMS1 . Preparation for providing a thermally conductive adhesive formulation, comprisingI) at least one component selected from the group consisting of isocyanate and polymer;II) at least one filler; andIII) at least one dispersing aid obtained from the reaction of at least one amino-functional polymer with at least one polyester.

2. Preparation according to Claim 1 , characterized in that the at least one amino-functional polymer has a mass-weighted average molecular weight (Mw) in the range from 400 to 100 000 g / mol, preferably from 600 to 50 000 g / mol.

3. Preparation according to either of the preceding claims 1 or 2, characterized in that the at least one polyester has a mass-weighted average molecular weight (Mw) in the range from 100 to 5000 g / mol, preferably from 200 to 2000 g / mol.

4. Preparation according to any of the preceding claims, characterized in that the at least one polyester was obtained by ring-opening polymerization of at least one lactone with at least one starter compound, where the at least one starter compound is preferably selected from the group consisting of R1-CH2- OH and R2-COOH, where R1is a monovalent aliphatic saturated or unsaturated hydrocarbon radical having 3 to 39, preferably having 4 to 21 , more preferably having 5 to 17, carbon atoms, and where R2is a monovalent aliphatic saturated or unsaturated hydrocarbon radical having 3 to 39, preferably having 4 to 21 , more preferably having 5 to 17, carbon atoms.

5. Preparation according to any of the preceding claims, characterized in that the at least one aminofunctional polymer is selected from the group consisting of polylysine, polyamidoamine, polyallylamine, poly(N-alkyl)allylamine, polyvinylamine, polyethyleneimine and polypropyleneimine, the at least one amino-functional polymer being in particular a polyethyleneimine.

6. Preparation according to any of the preceding claims, characterized in that the at least one polymer is selected from the group consisting of polyol, polyether, polyurethane prepolymer, polymeric isocyanate, polyurethane and silyl-modified polyether.

7. Preparation according to any of the preceding claims, characterized in that the at least one filler is selected from the group consisting of aluminium oxide, aluminium hydroxide and aluminium oxide hydroxide.

8. Preparation according to any of the preceding claims, characterized in that the preparation contains the at least one filler in an amount of 50 to 99 percent by weight, preferably 70 to 95 percent by weight, more preferably 80 to 90 percent by weight, based on the total mass of the preparation.

9. Use of a dispersing aid as defined in any of the preceding Claims 1 to 5 for improving the rheological properties and / or the stability of a polymer dispersion or adhesive formulation.

10. Process for producing the preparation according to any of Claims 1 to 8, comprising the process steps of:M1) providing the at least one component selected from the group consisting of polymer, isocyanate and oligomeric isocyanate;M2) providing the at least one filler;M3) providing the at least one dispersing aid obtained from the reaction of at least one aminofunctional polymer with at least one polyester; andM4) mixing the at least one component, the at least one filler and the at least one dispersing aid obtained from the reaction of at least one amino-functional polymer with at least one polyester; such that the preparation is obtained.

11. Kit of parts for providing a thermally conductive polyurethane-based adhesive formulation comprising part 1 and part 2, where: part 1 comprises1-1) at least one polyol;1-2) at least one filler;1-3) at least one dispersing aid obtained from the reaction of at least one amino-functional polymer with at least one polyester; and part 2 comprises2-1) at least one component selected from the group consisting of isocyanate, oligomeric isocyanate and polymeric isocyanate;2-2) at least one filler;2-3) at least one dispersing aid obtained from the reaction of at least one amino-functional polymer with at least one polyester.

12. Thermally conductive polyurethane-based adhesive formulation comprisingP1) at least one polyol;P2) at least one filler preferably selected from the group consisting of aluminium oxide, aluminium hydroxide and aluminium oxide hydroxide, wherein the adhesive formulation contains the at least one filler preferably in an amount of from 50 to 99 percent by weight, more preferably 70 to 95 percent by weight, even more preferably 80 to 90 percent by weight, based on the total mass of the adhesive formulation;P3) at least one dispersing aid obtained from the reaction of at least one amino-functional polymer with at least one polyester;P4) at least one component selected from the group consisting of isocyanate, oligomeric isocyanate and polymeric isocyanate; andP5) optionally at least one catalyst.

13. Thermally conductive silyl-modified-polyether-based adhesive formulation comprising51) at least one silyl-modified polyether;52) at least one filler preferably selected from the group consisting of aluminium oxide, aluminium hydroxide and aluminium oxide hydroxide, wherein the adhesive formulation contains the at least one filler preferably in an amount of from 50 to 99 percent by weight, more preferably 70 to95 percent by weight, even more preferably 80 to 90 percent by weight, based on the total mass of the adhesive formulation;53) at least one dispersing aid obtained from the reaction of at least one amino-functional polymer with at least one polyester;54) at least one plasticizer;55) optionally at least one tackifier;56) optionally at least one desiccant; and57) optionally at least one catalyst for crosslinking the silyl-modified polyether.

14. Structure comprising at least one battery cell (1), an adhesive layer (2) and a heat sink (3), characterized in that the adhesive layer (2) has been produced by applying the adhesive formulation according to either of Claims 12 or 13 between the at least one battery cell (1) and the heat sink (3).

15. Method for producing the structure according to Claim 14, comprising the process steps ofQ-A) providing a heat sink;Q-B) providing at least one battery cell; andQ-C) applying the adhesive formulation according to either of Claims 12 or 13 between the heat sink and the at least one battery cell; such that the structure is obtained.

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