High-temperature-resistant contact and filling material and use thereof

Abstract

The invention relates to a high-temperature-resistant contact and filling material consisting of a component A and a component B. Component A comprises: a polyacrylate-based, silane-functionalised prepolymer or a mixture of silane-functionalised prepolymers having at least one polyacrylate-based, silane-functionalised prepolymer; a plasticiser in the form of a polyfunctional carboxylic acid ester; a wetting and dispersing additive having at least one amine value greater than >20 mg KOH / g, measured according to DIN 19645; a mixture of functionalised organosilanes; ZnO and a further thermally conductive filler or a mixture of multiple thermally conductive fillers. Component B comprises: a plasticiser in the form of a polyfunctional carboxylic acid ester; a wetting and dispersing additive having at least one amine value greater than >20 mg KOH / g, measured according to DIN 19645; a thermally conductive filler or a mixture of multiple thermally conductive fillers; water and an organometallic catalyst, an antioxidant or a mixture of multiple antioxidants. The mixing ratio by volume of component A to component B is between 1:1 and 10:1.

Description

[0001] 33502-P-EP NK 28.02.2023

[0002] High-temperature contact and filling material and its use

[0003] 5 Description

[0004] During operation of electronic and energy systems, heat is generated, which must be quickly and effectively dissipated from the heat-generating unit.

[0005] 10 must. An example of this is electromobility, where very high operating temperatures are achieved, particularly through the use of solid-state battery cells.

[0006] Solid-state battery cells are a new development in battery technology and, unlike currently available Li-ion and Li-polymer batteries, feature a solid electrolyte instead of a liquid electrolyte. The greatest advantage of this new technological development is the higher potential charge density that can be achieved with such batteries. This high charge density is partially compensated for by the currently comparatively low power density caused by the lower charge density of typical solid-state electrolytes, such as glass-ceramic electrolytes. Other technically significant advantages of solid-state batteries include the much lower flammability of these batteries and their more uniform behavior under extreme external conditions.

[0007] 25 temperatures, so the extremely complex thermal management of the battery, especially the cooling, can be designed more simply, and only a switchable heating device in conjunction with passive heat dissipation seems feasible. The possibility of operating the batteries at higher temperatures without risking short circuits, cell damage, and a battery fire that is difficult to extinguish places greater demands on the temperature resistance of the thermally conductive solutions used.

[0008] For heat dissipation and heat supply, thermal

[0009] 35 conductive contact and filler materials are used, which serve a dual role: They conduct heat and simultaneously connect the active components.

[0010] Contact and filler materials based on silane-functionalized prepolymers for use in thermal management are known from the literature (WO 2020 / 165288 A1, US 2015 / 166859, DE 2018 102 989 B4). However, due to the increasingly higher operating temperatures of electric vehicles, conventional contact and filler materials based on silane-functionalized prepolymers are unsuitable for this application due to their thermal instability. They decompose over time, thus preventing the desired function from being guaranteed over the entire operating life of such an electric vehicle.

[0011] For this reason, silicone-based contact and filler materials are used for applications involving very high operating temperatures. Silicone-based solutions offer outstanding temperature resistance, but are not universally applicable due to their negative effects on electronic circuits and connections. It is well known that silicone-based base oils contain small amounts of volatile silicone compounds, which can be released from the base oil into the ambient air. These volatile silicone compounds can be deposited on surfaces surrounding the active components. If subsequent painting or bonding processes are to be carried out on these contaminated surfaces, there is a risk that the adhesion of the paint or adhesive layers will be lost.If the volatile silicone compounds come into contact with electrical contacts, they are decomposed by sparking and form insulating oxide layers, which impairs or destroys the function of the contacts.

[0012] Since the demand for high-temperature-resistant contact and filling materials that do not have the above-mentioned disadvantages is increasing, the present invention is therefore based on the object of providing a high-temperature-resistant contact and filling material that has the desired properties for use at very high operating temperatures, but at the same time withstands the high heat transfer and has a viscosity suitable for this application. The object underlying the present invention was surprisingly achieved by a high-temperature-resistant contact and filling material with the features of claim 1. Advantageous developments of the inventive idea are the subject of subclaims. Further advantageous developments of the contact and filling material according to the invention can be found in the description and the examples.

[0013] For the purposes of the present invention, the term “prepolymer” refers to any polymer or oligomer which has been pre-extended by a specific pre-reaction and / or to which new functional groups have been introduced by a specific pre-reaction, which make the selected polymerization reaction possible in a further step.

[0014] For the purposes of the present invention, the term "silane-functionalized prepolymer" refers to alkoxysilane-functionalized oligomers, polymers, or prepolymers. Silane-modified prepolymers condense in the presence of water, splitting off the alkoxy groups, and form wide-meshed polymer networks. Due to the above definition of prepolymer, it is not important whether the prepolymer backbone already consists of a prepolymer (e.g., a polyurethane-based prepolymer) or whether it is a pure oligomer or polymer. Due to the specific pre-reaction of silane functionalization, all silane-modified polymers are simultaneously prepolymers according to the above definition.

[0015] Since there is no general consensus on the nomenclature and differentiation of different silane-modified prepolymers, all types of commercially or non-commercially producible silylated polymers and prepolymers are considered as silane-functionalized prepolymers in the sense of the present invention.

[0016] For the purposes of the present invention, the term "plasticizer" refers to low-viscosity additives that are unreactive to the chosen crosslinking chemistry and serve, on the one hand, to reduce the viscosity of the liquid components. After the matrix has cured, this plasticizer remains within the polymer network and reduces the mechanics of the resulting polymer, making it softer, more elastic, more flexible, and / or more extensible. This is because the typically very openly crosslinked polymer networks possess greater mobility due to the plasticizer they contain. Chemically speaking, the plasticizer is not covalently bound into the polymer matrix, but interacts with the polar groups of the polymer network via its polar groups, thus attaching itself between the polymer chains, giving them greater mobility and making the entire structure more flexible.Plasticizers tend to be low molecular weight, but polymeric plasticizers, such as those based on polypropylene glycol, can also be used. Typical examples of plasticizers are substances based on the chemistry of carboxylic acid esters, fatty oils, plastic resins, and camphor.

[0017] For the purposes of the present invention, the term "wetting and dispersing additives" refers to additives that have the property of mixing two incompatible substances. This is typically known from liquid-liquid systems, forming emulsions. However, it is also highly important for the formation of stable liquid-solid systems. By compatibilizing the interfacial tension and improving the wetting of the solid particles with the liquid medium, this dispersion is stabilized. These additives are used to wet the solids as effectively as possible, ideally completely, with the liquid phase. This also facilitates the shearing action required to separate the agglomerates into individual particles during production.Additionally, the wetting and dispersing additive remains on the particle surface and stabilizes it in the liquid phase, either creating a stable dispersion or at least preventing re-agglomeration and, consequently, rapid settling / sedimentation of these fillers as much as possible. Because the wetting and dispersing additives act as surfactants and some of these amphiphilic molecules or polymers are highly soluble in the liquid phase, particle stabilization is also explained by the pronounced steric effect of these chains around the particle surface. When these particles come close to each other, this creates a repulsive force, forcing the particles to always maintain a certain distance from each other, thus minimizing mechanical interaction (e.g., agglomeration, friction effects of the particles, which would lead to higher viscosity, etc.).This effect can occur either through steric repulsion or, in a similar way, through charges introduced via chemical functionalities (carboxylates, ammonium groups, etc.), which achieve the same effect through their electrostatic repulsion. Both modes of action can also be combined, thus achieving electrosteric stabilization of the particles. In general, it can be said that electrostatic and electrosteric repulsion work very well for relatively polar liquids, whereas steric repulsion alone is usually used for very nonpolar liquids.

[0018] The term “antioxidants” in the context of the present invention refers to chemical compounds that slow down or completely prevent the oxidation of other substances. They usually act as radical scavengers and thus inactivate degradation processes that are initiated by radicals and thus prevent the oxidative degradation of the organic compounds contained. They are added to the formulations in the adhesives sector in order to achieve greater stability of the cured polymers against harsh application conditions. These can be, for example, high temperatures in the presence of atmospheric oxygen, which lead to radical degradation cascades. Such radical degradation cascades are usually interrupted or significantly slowed down by antioxidants, as the contained antioxidant ions, for example,Sterically hindered phenol groups form very inert, stabilized radicals, thus preventing the further transfer of the radicals to other polymer groups. These are typically called primary antioxidants. Other types of antioxidants can also be reducing agents, for example, which are oxidized earlier than the substance to be protected and can also be used in combination. So-called secondary antioxidants can also be added and include, for example, phosphite compounds, which destroy peroxides and thus protect the polymer chain from oxidative attack, or thioester antioxidants or amine-based systems.

[0019] For the purposes of the present invention, the term “organosilanes” refers to chemical compounds that have a silyl group with at least one organic radical and one to three hydrolyzable substituents or hydroxyl groups. Hydrolyzable groups are, for example, alkoxy groups. They can be oligomeric ethylene glycol chains or acetoxy functions. Reactive silane groups are fully or partially hydrolyzed alkoxysilane groups, which then form silanol groups. There are many different types of such organosilanes, which differ primarily in the structure of the organic radical and are described by their chemical structure. Examples include hydroxysilanes, isocyanatosilanes, aminosilanes, thiosilanes, and vinylsilanes, each of which has an organic chain between the silyl group and at least one further functionality. There are, of course, organosilanes having more than one functionality, such asAminosilanes containing a secondary and a primary amino group or organoalkoxysilanes containing at least one hydroxyl group (OH), isocyanate group, amino group or vinyl group in the organic part.

[0020] With regard to the functionality(s) they contain, organosilanes can be divided into the following groups:

[0021] Without further functionality (organic chain) e.g. octyltrimethoxysilane, OCTMO;

[0022] Primary amine functionality e.g. 3-aminopropyltrimethoxysilane, AMMO;

[0023] - Secondary amino functionality e.g. N-(n-butyl)-3-aminopropyl- trimethoxysilane,

[0024] Diamino-functional, for example N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, DAMO;

[0025] Epoxy-functional e.g. 3-glycidyloxy-propyl-trimethoxysilane, GLYMO;

[0026] - Thiofunctional e.g. 3-mercaptopropyl-trimethoxysilane, MTMO;

[0027] - Methacrylic functional e.g. 3-methacryloxypropyltrimethoxysilane, MEMO;

[0028] - Vinyl functional e.g. B. vinyltrimethoxysilane, VTMO.

[0029] The chemically and commercially available compounds mentioned in the respective groups serve only as examples and the groups are not limited to them.

[0030] For the purposes of the present invention, the term "thermally conductive fillers" refers to chemical compounds that are added to formulations to ensure filling and are simultaneously thermally conductive. Typical thermally conductive fillers are:

[0031] - metals which are unsuitable for many applications due to their electrical conductivity;

[0032] - Aluminium oxideZ hydroxide, and

[0033] - Magnesium oxide / hydroxide and

[0034] Diamond, carbon nanotubes, aluminum nitride (AIN), boron nitride (BN) graphite.

[0035] For the purposes of the present invention, the term “catalyst” refers to chemical compounds that increase the rate of a reaction or reduce its activation energy by forming an intermediate between the catalyst and the reactants, without themselves being consumed in the reaction.

[0036] The high-temperature-resistant contact and filling material according to the invention comprises a component A and a component B, wherein component A has the following:

[0037] 1.A) a polyacrylate-based silane-functionalized prepolymer or a mixture of silane-functionalized prepolymers comprising at least one polyacrylate-based silane-functionalized prepolymer;

[0038] 2.A) a plasticizer which is a polyfunctional carboxylic acid ester;

[0039] 3.A) a wetting and dispersing additive having at least an amine number greater than >20 mg KOH / g measured according to DIN 19645;

[0040] 4.A) a mixture of functionalized organosilanes;

[0041] 5.A) ZnO and another thermally conductive filler or a mixture of several thermally conductive fillers; and wherein component B comprises: 1.B) a plasticizer which is a polyfunctional carboxylic acid ester;

[0042] 2.B) a wetting and dispersing additive having at least an amine number greater than >20 mg KOH / g measured according to DIN 19645;

[0043] 3.B) a thermally conductive filler or a mixture of several thermally conductive fillers;

[0044] 4.B) Water;

[0045] 5.B) an organometallic catalyst;

[0046] 6.B) an antioxidant or a mixture of several antioxidants; and wherein the mixing ratio by volume of component A to component B is 1:1 to 10:1.

[0047] The contact and filler material according to the invention surprisingly exhibits very high heat resistance. Surprisingly, it was found that the use of a combination of selected silane-modified prepolymers and antioxidants significantly improves the temperature resistance of this technology, making them suitable and recommendable for applications at higher temperatures. A suitable viscosity of the contact and filler material according to the invention was also surprisingly achieved. The polyacrylate-based silane-functionalized prepolymers of component A themselves have a very high viscosity, which is why there were concerns that the desired viscosity might not be achieved.Contrary to expectations, the contact and filler material according to the invention shows the desired properties, namely very good temperature resistance to be used at very high operating temperatures, very good heat transfer performance and a viscosity suitable for this application.

[0048] An advantageous development of the high-temperature-resistant contact and filler material provides that the mixture of silane-functionalized prepolymers additionally comprises at least one polyurethane- and / or polyol / diol-based silane-functionalized prepolymer. The generic term "silane-functionalized prepolymer" in the context of the present invention includes a compound of the following formula:

[0049] A in the above formula is a polymeric or prepolymer backbone, which is based on a polyol / diol (e.g. polyether polyol / diol, polypropylene glycol), a telechelic polyacrylate or can itself be prepolymers based on various technologies, e.g. a polyurethane-modified prepolymer, which is modified in a further reaction step with alkoxy-protected silane groups.

[0050] The substituents R 1 , R 2 and R 3 can be chemical groups in the sense of the present invention, where at least R 1 and R 2 an alkoxy group and R 3 is either an alkoxy group or an alkyl group.

[0051] For the purposes of the present invention, an alkyl group is understood to mean a C1-C10-alkyl group. For the purposes of the present invention, C1-C10-alkyl encompasses linear or branched saturated hydrocarbon groups having one to ten carbon atoms. These include, in particular, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, 2,2-dimethylpropyl, n-hexyl, isohexyl, 2-ethylhexyl, n-heptyl, isohexyl, n-octyl, isooctyl, n-nonyl, n-decyl, and the like.

[0052] For the purposes of the present invention, an alkoxy group is understood to be an O-C1-C2-alkyl group. C1-C10 alkyl is as defined above. A further advantageous development of the high-temperature-resistant contact and filler material provides that the alkoxy group is selected from: OCH3 and OCH2CH3, and the alkyl group is CH3.

[0053] A further particularly advantageous development of the high-temperature-resistant contact and filling material provides that the alkoxy group is OCH3 and the alkyl group is CH3.

[0054] A further advantageous development of the high-temperature-resistant material provides that a silane-functionalized prepolymer or a mixture of silane-functionalized prepolymers is selected from the following groups:

[0055] Group A

[0056] This group includes prepolymers based on a polyol / diol backbone and are known under the following chemical names: silyl-modified polymers (SMP), modified-silane polymers, MS polymers, silane-terminated polymers.

[0057] Commercially available prepolymers belonging to this group include:

[0058] Dimethoxysilane MS Polymer S (eg S303H) and high strength Dimethoxysilane MS Polymer SAX (eg SAX 350).

[0059] The most preferred prepolymer for the high temperature resistant contact and filler material is the formula A-1 : Group B

[0060] This group includes silane-functionalized prepolymers with telechelic polyacrylates as backbone.

[0061] Commercially available polymers belonging to this group include: Kaneka XMAP SA (e.g. Kaneka XMAP SA100).

[0062] The most preferred prepolymer for the high temperature resistant contact and filler material is the formula B-1 :

[0063] R 1 is H, C Ce-alkyl;

[0064] R 2 is H, C Ce-alkyl

[0065] - Group C

[0066] Group C includes prepolymers in which the polymer backbone itself consists of a PU prepolymer and thus contains urethane groups. The polyols used in the backbone can consist of polyether polyols, as shown, but other "polyols" are also possible.

[0067] These prepolymers are known under the following chemical names: silane-terminated polyurethane (SPU or STPU), silane-terminated PU, silane-modified PU.

[0068] Commercially available prepolymers belonging to this group include Polymer ST (e.g., Polymer ST 44) and Geniosil STP-E (e.g., Geniosil STP-E30). A further advantageous development of the high-temperature-resistant contact and filler material involves selecting one or more silane-functionalized prepolymers from the following group:

[0069] SAX 350, SAX 015 (Group A)

[0070] XMAP SA120S (Group B).

[0071] A further advantageous development of the high-temperature-resistant contact and filling material provides that the plasticizer is a multifunctional carboxylic acid ester.

[0072] A further advantageous development of the high-temperature-resistant contact and filling material provides that the plasticizer of component A is a trifunctional carboxylic acid ester.

[0073] A further advantageous development of the high-temperature-resistant contact and filling material provides that the plasticizer of component A is a triester of trimellitic acid.

[0074] A further advantageous development of the high-temperature-resistant contact and filling material provides that the plasticizer of component B comprises a trifunctional carboxylic acid ester.

[0075] For the purposes of the present invention, phthalic acid esters such as diethylhexyl phthalate or dioctyl phthalate can be used as plasticizers. Due to their potentially harmful effects on humans, phthalic acid esters are currently on the ECHA's candidate list of substances of very high concern (SVHC). Alkylsulfonic acid esters, citric acid-based plasticizers, e.g., triethyl citrate, or adipic acid-based plasticizers, e.g., diethylhexyl adipate or diethyl oxytyl adipate, can be used as replacements for the phthalic acid esters.

[0076] The selection of the appropriate plasticizer should be based on its function in the inventive high-temperature-resistant contact and filler material. It should be noted that these functions do not all coincide with the use of plasticizers in other formulations. In the inventive high-temperature-resistant contact and filler material, the plasticizer has the following functions:

[0077] Reduction of the viscosity of the liquid components

[0078] Typically, silyl-functionalized prepolymers are higher-viscosity raw materials, even when low-viscosity systems are typically selected for formulation. Nevertheless, the achievable filler content with the thermally conductive fillers is directly related to the mixed viscosity of the liquid components. For this reason alone, low-viscosity additives are necessary to reduce the mixed viscosity of the liquid components as much as possible in order to achieve the required filler content with the thermally conductive fillers without increasing the viscosity of the finished formulation too high for the application.

[0079] Increased flexibility in the cured material

[0080] Due to the very high filler content, the polymer network loses degrees of freedom, and the matrix, which is very flexible in the unfilled state with high elongation at break, becomes increasingly inflexible, and the elongation at break typically drops to very low values. The use of the plasticizer improves internal wetting of the filler, as the plasticizer molecules not only attach themselves between the polymer chains as defined above, but ideally also form a compatibility layer between the filler particles and the polymer chains, thus significantly increasing the degree of freedom of the polymer chains, which are severely restricted by the filler particles.

[0081] Typically, silane-functionalized prepolymers have a high molecular mass, usually due to the long (pre-)polymer backbone. This backbone strongly separates the crosslinking points from one another, creating a loose-meshed, flexible network suitable, for example, for flexible adhesives and / or sealants. As explained in the first point, the viscosity of these silane-functionalized prepolymers is extremely important for the application, so only low-viscosity types are fully suitable for this application. However, since a higher molecular weight backbone also results in an increase in the prepolymer's viscosity, low-molecular-weight silane-functionalized prepolymers are typically suitable for this application.These are naturally associated with a higher crosslinking density and, consequently, higher mechanical strength and lower flexibility, which is further amplified by the effect of the high filler content described in the above point. This is attempted to be compensated for by using plasticizers, exploiting the defined "plasticizing effect" between the cured prepolymers and the filler particles (see second point), but also by reducing the volume fraction of prepolymer used to a minimum. This can, of course, lead to the formation of an incomplete polymer network, in which not all polymer chains are fully crosslinked.This results in a more widely spanned polymer network, which at least partially eliminates the disadvantages of the low-molecular silane-functionalized prepolymers used and makes the network more flexible, lower-modulus, and more mechanically stable, as would also be possible with the use of long-chain, silane-functionalized prepolymers.

[0082] In view of the above statements, the following plasticizers have proven to be particularly suitable for the high-temperature-resistant contact and filling material according to the invention:

[0083] Oxsoft 3G8: CAS 94-28-0

[0084] - Triethylene glycol di-(2-ethylhexanoate) 2,2'-ethylenedioxydiethylbis(2-ethylhexanoate)

[0085] Cereplas L810TM: CAS 90218-76-1

[0086] 1,2,4-Benzenetricarboxylic acid, mixed decyl and octyl triester

[0087] Oxsoft TOTM LE: CAS 3319-31 -1

[0088] - Tris(2-ethylhexyl)benzene-1,2,4-tricarboxylate

[0089] - Trioctyl trimellitate.

[0090] A further advantageous development of the high-temperature-resistant contact and filler material provides for component A to contain an antioxidant or a mixture of several antioxidants. Examples can be found in the portfolios of typical antioxidant manufacturers, for example, ADK Stab® from Adeka Polymer Additives.

[0091] A further advantageous development of the high-temperature-resistant contact and filling material provides that the wetting and dispersing additive has at least functional aminic groups, which can also optionally contain acidic groups, such as carboxylate or phosphorus groups.

[0092] Particularly preferred are: Disperbyk 2157 or Byk W969.

[0093] The similarities between Disperbyk 2157 and Byk W969 lie in the shared amine groups, which are defined at least by the presence of an amine number according to DIN 16945 in the wetting and dispersing additive. Of course, other functional groups, such as phosphorus groups or carboxylate groups, which can also have a surface-active effect, can also be included. Optionally, the wetting and dispersing additives can also contain an acid number measured according to DIN EN ISO 2114.

[0094] Wetting and dispersing additives which have at least an amine number of >20 mg KOH / g and which can optionally also have an acid number are named as particularly relevant.

[0095] A further advantageous development of the high-temperature-resistant contact and filling material provides that component A comprises a mixture of functionalized organosilanes.

[0096] For the purposes of the present invention, mono- and multifunctional organosilanes are understood here. The multifunctional organosilanes, which exist as oligomers or precondensed silanes, can react more rapidly in oligomeric form due to their high functionality density, as well as increase the local crosslinking density of the curing polymer more significantly or enable better bonding of the adhesive to surfaces. Firstly, all of the organosilanes mentioned serve as crosslinkers. They are incorporated into the network of the silane-functionalized prepolymers and thus increase the crosslinking density of the prepolymer. The functional groups they contain are crucial for their function in a formulation.

[0097] A further advantageous development of the high-temperature-resistant contact and filling material provides for the use of the following organosilanes:

[0098] The following organosilanes are relevant in the formulations, including their functionality: a) amino-functionalized organosilanes

[0099] They generally accelerate the silane condensation reaction and, in addition to their general properties, are used as co-catalysts. Furthermore, similar to epoxy-functional organosilanes, they have an adhesion-enhancing effect on various substrates.

[0100] Another particularly advantageous development of the high-temperature-resistant contact and filling material provides that:

[0101] AMMO or

[0102] Oligomeric, precondensed silanes with amine groups, e.g., from the Dynasylan® SIVO series, can be used. b) vinyl-functional organosilanes

[0103] They primarily have a drying effect. The fillers and plasticizers used in the production process have a certain residual moisture or water content, which, although very low, negatively impacts the storage stability of the silane-functionalized prepolymers. This can lead to unwanted silane condensation over time, which can lead to a significant increase in viscosity and thus to a reduction in application properties. To dry the prepolymer, the vinyl-functional organosilanes are added to the formulation, thus drying the fillers and other formulation components in situ. The small proportion of unreactive vinyl-functional organosilanes remains in the formulation, thus enabling practical storage stability of the formulation without special equipment, such as production and overlay of the components under inert gas, or pre-drying of the fillers in special dryers.

[0104] Another particularly advantageous development of the high-temperature-resistant contact and filler material involves the use of VTMO. c) epoxy-functional organosilanes

[0105] In addition to the generally described properties, epoxysilanes have other interesting properties for which they are added to formulations. Firstly, epoxy- and amine-functional silanes can react with each other (in addition to silane condensation), thus creating cross-links. Furthermore, epoxysilanes are known for their good adhesion-enhancing properties on a wide range of different surface chemistries (from polymeric surfaces to metallic surfaces), thus helping to achieve a balanced product property profile.

[0106] A further particularly advantageous development of the high-temperature-resistant contact and filler material provides that the mixture of functionalized organosilanes comprises at least one amino-functionalized or one vinyl-functionalized or one epoxy-functionalized organosilane.

[0107] A further particularly advantageous development of the high-temperature-resistant contact and filler material provides that the mixture of functionalized organosilanes comprises at least two organosilanes selected from the group consisting of: an amino-functionalized, a vinyl-functionalized and an epoxy-functionalized organosilane.

[0108] A further particularly advantageous development of the high-temperature-resistant contact and filler material provides that the mixture of functionalized organosilanes comprises at least one amino-functionalized and one vinyl-functionalized organosilane. A further particularly advantageous development of the high-temperature-resistant contact and filler material provides that the mixture of functionalized organosilanes comprises one amino-functionalized, one vinyl-functionalized, and one epoxy-functionalized organosilane.

[0109] A further particularly advantageous development of the high-temperature-resistant contact and filling material provides that at least one of the functionalized organosilanes is an oligomeric silane.

[0110] Another particularly advantageous development of the high-temperature-resistant contact and filling material involves the use of GLYMO.

[0111] Another particularly advantageous development of the high-temperature-resistant contact and filling material requires the use of zinc oxide as a filler.

[0112] A further advantageous development of the high-temperature-resistant contact and filling material provides that, in addition to ZnO, a thermally conductive filler is used which is selected from the group consisting of: AI(OH)3, AI2O3.

[0113] A further advantageous development of the high-temperature-resistant contact and filling material provides that the total amount of fillers in components A and B is 80 to 95 wt.%, preferably 88 to 93 wt.%, even more preferably 88 to 90 wt.%, wherein the proportion of ZnO in the mixture of fillers is accordingly 10 to 30 wt.%, preferably 15 to 25 wt.%, even more preferably 15 to 20 wt.%.

[0114] A further advantageous development of the high-temperature-resistant contact and filling material provides that at least one of the thermally conductive fillers has a surface coating and / or surface functionalization which is preferably hydrophobic.

[0115] As is known, silane-functionalized prepolymers react in a condensation reaction in the presence of water. The water for this reaction is usually introduced primarily by the fillers. As described in detail above, these are at least partially coated with water on their surfaces due to atmospheric humidity. Furthermore, the filler particles retain water in pores and cracks through pore and capillary effects.

[0116] The fillers can be dried by adding vinyl-functional organosilanes, as provided in one embodiment of the present invention. In such a case, however, the required amount of vinyl-functional organosilane must be adjusted depending on the water content of the fillers. If the fillers are not sufficiently dried, the storage stability of the final formulated component is affected by a slow increase in viscosity of the liquid component, which occurs primarily due to the onset of slow condensation reactions of the polymers.

[0117] This can be circumvented by using partially hydrophobized fillers. Hydrophobization of fillers is a process used on a large scale industrially. Depending on the filler, fatty acids, organosilanes, organotitanates, functionalized, or unfunctionalized polymers are used for this purpose. Thus, both chemisorption and physisorption of these coating additives on the surface represent a practical option for surface functionalization.

[0118] This very thin coating makes the filler surfaces more hydrophobic, allowing only a much smaller amount of water from atmospheric moisture to adhere to the fillers, resulting in a lower residual moisture content. This means that, with an optimal selection of these coating agents, similar effects can be achieved to those achieved with the wetting and dispersing additives described above, which are not required in such cases.

[0119] A further advantageous development of the high-temperature-resistant contact and filling material provides that component B comprises a catalyst.

[0120] Another particularly advantageous development of the high-temperature-resistant contact and filler material provides for the catalyst to be an organometallic complex. All common organometallic catalysts available on the market are suitable. Tin complexes are mentioned as an example here, although this invention is not limited to them. The following are preferred as suitable catalysts: dibutyltin dilaurate (DBTL), dioctyltin dilaurate, its oxides such as dibutyltin oxide, dioctyltin oxide, or other tin complexes with additionally exchanged ligands, such as dioctyltin diacetylacetonate or dioctyltin / dibutyltin silane complexes.

[0121] Another particularly advantageous development of the high-temperature-resistant contact and filler material provides for the catalyst to be a co-catalyst base, such as amines, as proton acceptors. These are typically used as amino-functional organosilanes in the formulation and are summarized under the description of organosilanes.

[0122] Another particularly advantageous development of the high-temperature-resistant contact and filling material provides that the catalyst is an acid-catalyzed system.

[0123] Another particularly advantageous development of the high-temperature-resistant contact and filling material is that it is silicone-free.

[0124] This measure has the advantage of ensuring that no volatile silicone compounds are deposited on surfaces surrounding the active components. This prevents the adhesion of the paint or adhesive layers on the contaminated surfaces from being compromised, and it also protects the electrical contacts.

[0125] The invention is illustrated below by examples, but is not limited to these.

[0126] Example 1 - Preparation of component A and component B

[0127] The raw materials listed in Table 1 were weighed into a speed mixer cup and premixed for 30 seconds at a speed of 2000 rpm (revolutions per minute) to create a homogeneous composition. The composition was then degassed for 3 minutes at 900 rpm in a vacuum speed mixer. All of the above-mentioned compositions were prepared as described above.

[0128] As can be seen from Table 1, formulations F1 to F4 each lack one component compared to reference formulation F. Compositions F1 and F2 each use only one polymer (XMAP or SMP). Formulation F3 lacks ZnO, and formulation F4 lacks the antioxidant.

[0129] Table 1 - Component A

[0130] The raw materials listed in Table 2 were weighed into a speed mixer beaker and premixed for 30 seconds at a speed of 2000 rpm (revolutions per minute) to create a homogeneous composition. The composition was then degassed for 3 minutes at 900 rpm in a vacuum speed mixer. All of the above-mentioned compositions were prepared as described above.

[0131] Table 2 - Component B

[0132] The mixing ratio by volume of components A to B is 10: 1. Component B is a so-called booster component, which has two effects:

[0133] - Firstly, the homogeneous introduction of moisture into component A, so that it cures homogeneously. Without component B, component A would cure from the outside in when exposed to atmospheric moisture. Due to the very long diffusion paths that arise during a typical, large-area application within a module and the very small contact area of ​​component A alone with the ambient air, parts of the component would remain uncured for a very long time in the center of the large-area, high-temperature-resistant contact and filler material.

[0134] - On the other hand, the addition of the catalyst accelerates the condensation reaction of the silane functionalities.

[0135] Experiment 1 - Investigation of temperature stability using TGA measurements In a crucible, a small amount of the respective material, which had been cured for 7 days at RT, was heated at a heating rate of 10 K / min and the mass loss of the sample was determined over the temperature.

[0136] The individual mass loss was determined at 280°C, 340°C and 370°C.

[0137] Table 3

[0138] As can be seen from Table 3, formulation R performs better than formulations F2 and F4. In contrast, formulation F1 exhibits better thermal behavior than the reference formulation and would be preferable based on its thermal properties. However, due to the much higher viscosity of XMAP, this formulation is no longer suitable for application. The viscosity of the formulated component is too high, and no lower-viscosity prepolymers of this type are available on the market.

[0139] Furthermore, formulation F3 also shows slightly better values ​​than the reference formulation at temperatures of 280 °C and 370 °C. However, this formulation is also unusable due to poor application and settling behavior. As explained above, zinc oxide has no significant influence on temperature stability, but a significant impact on application and settling behavior.

[0140] In summary, the reference formulation R exhibits the best properties on average and is therefore preferred for this application. Experiment 2 - Investigation of the Mechanics

[0141] In a further experiment, the mechanics of the above-mentioned formulations were investigated after 7 days of room temperature curing and subsequent aging for 15 days at a constant temperature of 150°C. Tensile strength test specimens were prepared, cured, and measured according to DIN EN ISO 527, and the respective tensile strength and elongation at break were recorded. The measured values ​​after room temperature curing were then compared with the values ​​after aging at 150°C for 7 days, and the relative mechanics were calculated based on the initial values.

[0142] Table 4

[0143] Formulation F1 demonstrated the best thermal aging behavior and also the best values ​​for tensile strength and elongation at break after thermal aging. However, as already explained above, this formulation is unfortunately not applicable in this field due to its excessive viscosity.

[0144] Although formulation F2 is very good in terms of viscosity, it shows severe embrittlement and decomposition under temperature aging and must therefore be classified as unsuitable for this purpose.

[0145] The use of an antioxidant is essential, as demonstrated by the aging of formulation F3. Without an antioxidant, severe embrittlement and a loss of elongation at break occur, which is also of great importance for the application.

[0146] As in the TGA tests, it is shown that the use of zinc oxide has no influence on the aging behavior, but must be included in the formulation of sales products for better application and settling behavior.

Claims

Claims 1. High-temperature resistant contact and filling material consisting of a component A and a component B, wherein component A comprises: 1.A) a polyacrylate-based silane-functionalized prepolymer or a mixture of silane-functionalized prepolymers comprising at least one polyacrylate-based silane-functionalized prepolymer; 2.A) a plasticizer which is a polyfunctional carboxylic acid ester; 3.A) a wetting and dispersing additive having at least an amine number greater than >20 mg KOH / g measured according to DIN 19645; 4.A) a mixture of functionalized organosilanes; 5.A) ZnO and another thermally conductive filler or a mixture of several thermally conductive fillers; and wherein component B comprises: 1.B) a plasticizer which is a polyfunctional carboxylic acid ester; 2.B) a wetting and dispersing additive having at least an amine number greater than >20 mg KOH / g measured according to DIN 19645; 3.B) a thermally conductive filler or a mixture of several thermally conductive fillers; 4.B) Water; 5.B) an organometallic catalyst; 6. B) an antioxidant or a mixture of several antioxidants; and wherein the mixing ratio by volume of component A to component B is 1:1 to 10:

1.

2. High-temperature-resistant contact and filling material according to claim 1, characterized in that the mixture of silane-functionalized prepolymers additionally comprises at least one silane-functionalized prepolymer based on polyurethanes and / or polyol / diol.

3. High-temperature-resistant contact and filling material according to claim 1 or 2, characterized in that the plasticizer of component A is a trifunctional carboxylic acid ester.

4. High-temperature-resistant contact and filling material according to one of claims 1 to 3, characterized in that component A comprises an antioxidant or a mixture of several antioxidants.

5. High-temperature-resistant contact and filling material according to one of claims 1 to 4, characterized in that the mixture of functionalized organosilanes comprises at least one amino-functionalized or one vinyl-functionalized or one epoxy-functionalized organosilane.

6. Injectable thermal contact and filling material according to one of claims 1 to 4, characterized in that the mixture of functionalized organosilanes comprises at least two organosilanes selected from the group consisting of: an amino-functionalized, a vinyl-functionalized and an epoxy-functionalized organosilane.

7. Injectable contact and filling material according to one of claims 1 to 6, characterized in that at least one of the functionalized organosilanes is an oligomeric silane.

8. High-temperature-resistant contact and filling material according to one of claims 1 to 7, characterized in that the thermally conductive filler is selected from the group consisting of: Al(OH)3 and Al2O3.

9. High-temperature-resistant contact and filling material according to one of claims 1 to 8, characterized in that the mixture of thermally conductive fillers comprises Al(OH)3 and Al2O3.

10. High-temperature-resistant contact and filling material according to one of claims 1 to 9, characterized in that at least one of the thermally conductive fillers has a surface coating and / or surface functionalization.

11. High-temperature-resistant contact and filling material according to one of claims 1 to 10, characterized in that the total amount of fillers in components A and B is 80 to 95 wt.%, the proportion of ZnO in the mixture of fillers being 10 to 30 wt.%.

12. High-temperature-resistant contact and filling material according to one of claims 1 to 11, characterized in that the total amount of fillers in components A and B is 80 to 93 wt.%, the proportion of ZnO in the mixture of fillers being 15-25 wt.%.

13. High-temperature-resistant contact and filling material according to one of claims 1 to 12, characterized in that it comprises the following: 3 to 10 wt.% of the mixture of silane-functionalized prepolymers, wherein the silane-functionalized prepolymer based on polyacrylates accounts for up to 50 wt.%, 0.5 to 5% by weight of the antioxidant, 3 to 15 wt.% of the plasticizer, 0.2 to 2 wt.% of the wetting and dispersing additive, 0.5 to 5 wt.% of the organosilanes, and 78 to 93 wt.% of ZnO and the further thermally conductive filler or the mixture of several thermally conductive fillers, wherein the The proportion of ZnO in the mixture of fillers is up to 10-30 wt.%.

14. High-temperature-resistant contact and filling material according to one of claims 1 to 13, characterized in that it comprises the following: 5 to 9 wt.% of the mixture of silane-functionalized prepolymers, wherein the silane-functionalized prepolymer based on polyacrylates accounts for up to 50 wt.%, 0.5 to 1.5% by weight of the antioxidant, 3 to 5 wt.% of the plasticizer, 0.5 to 1.5 wt.% of the wetting and dispersing additive, 0.5 to 1.5 wt.% of the organosilanes, and 80 to 93 wt.% of ZnO and the further thermally conductive filler or the mixture of several thermally conductive fillers, wherein the proportion of ZnO in the mixture of fillers is up to 15-25 wt.%.

15. High-temperature-resistant contact and filling material according to one of claims 1 to 14, characterized in that it is silicone-free.

16. Use of the high-temperature-resistant contact and filling material according to one of claims 1 to 15 for electronic components subject to high thermal stress.

17. Use of the high-temperature-resistant contact and filling material according to one of claims 1 to 15 for battery systems with a complex accumulator structure.

Images