Injectable thermal contact and filling material and its use for large-scale components

Abstract

The invention relates to an injectable thermal contact and filling material consisting of a component A and a component B. Component A comprises: a silane-functionalised prepolymer or a mixture of silane-functionalised prepolymers, with the silane-functionalised prepolymer being based on polyurethanes, polyol / diol or polyacrylates; 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. The mixing ratio by volume of component A to component B is between 1:1 and 10:1.

Description

[0001] Intuitable thermal contact and filling material and its use for large-area components

[0002] Description

[0003] During operation of electronic and energy systems, heat is generated which must be dissipated quickly and effectively from the heat-generating unit. To thermally contact the active components with the corresponding heat inputs or outputs, a fixed mechanical contact is traditionally created either by screwing, clamping or by soldering or welding. Mechanical fixing has the advantage that the connection can be undone. However, heat transfer between the active components only takes place via a few contact points. Since there is a layer of air in between, which is a very poor heat conductor, the generated heat is only incompletely dissipated. To improve heat transfer, thermally conductive materials are introduced into the joint between the active components, i.e. between the heat-generating and the heat-dissipating component.These materials have a dual role: they conduct heat and at the same time they connect the active components together.

[0004] Such thermally conductive materials are known from the state of the art in the form of thermal pastes. Thermal pastes are used in microelectronics to connect very small components.

[0005] Generally, such thermal pastes are applied to individual active components over small areas. They are bonded together by applying force to the components (compression).

[0006] In the electronics sector, the surfaces to be bonded are very small. At the same time, high-frequency switching intervals, high-speed integrated circuits or processors, etc., generate very high levels of heat, which must be dissipated through this small surface to avoid damage to the respective components and thus to the entire device. Therefore, when selecting a thermal contact and filler material in this field, the thermal conductivity properties are of primary importance due to the very high heat that must be dissipated through these very small surfaces.

[0007] One application of thermal pastes for connecting large-area components is described in DE 0 2018 102 989 B4. The document discloses a reactively curing thermal paste based on silane-functionalized prepolymers for use in the thermal management of modular accumulators comprising multiple interconnected battery cells, for example, in electric vehicles.

[0008] In a large-area application, such as in the batteries of electric vehicles, the thermal paste is applied to a carrier or a base plate before inserting the individual batteries or prefabricated battery modules comprising several battery cells and is pressed to a defined layer thickness when inserting the individual batteries or prefabricated battery modules.

[0009] The requirements for a thermal contact and filler material intended for large-area application are significantly more complex for the reasons described below.

[0010] The larger the surface to be joined, the greater the force required to bond the surfaces together. Due to the intrinsically high viscosity of such highly filled systems, such as the thermal pastes described above, a high force is required to compress the active component within an acceptable cycle time, which is of utmost importance in production. However, the cycle time cannot be arbitrarily accelerated by increasing the applied force.Even the individual accumulators or prefabricated battery modules comprising several battery cells intended for use in electric vehicles can only withstand a limited amount of force before they warp, suffer damage to the electrochemical structure or another defect, which can occur immediately or, as a result, significantly reduce the service life of the battery or accumulator and thus of the vehicle.

[0011] The described disadvantages of the process involving the compression of the active component can be circumvented by using a so-called injection process. In this process, the contact and filler material is not applied but injected. This significantly accelerates the assembly of, for example, a rechargeable battery comprising multiple battery cells during the production process, while simultaneously ensuring that the risk of damage to the battery cells is significantly reduced compared to the above-mentioned traditional process.

[0012] In order to apply the injection method, a defined gap must be ensured, both in terms of design and process, which is completely filled with a thermal contact and filler material, thereby ensuring excellent thermal conduction of the component to be joined. To completely fill the gap with the thermal contact and filler material, an injection from one or more injection points is necessary. This ensures that all the air present in the gap escapes. The injection method must be designed in such a way that no air pockets occur as a result of the injection. This can be achieved through flow simulation or through a suitable design of the injection method.This can be achieved either by adjusting the type and location of the injection holes or by deliberately changing the injection pressure at one or more of the injection holes. The injection process is complete when the thermal paste exits the air outlet hole, thus removing any air from the gap.

[0013] However, the requirements for the thermal contact and filler material suitable for the injection process are very high. Above all, the thermal contact and filler material must have an appropriate viscosity. If the viscosity is too high, as is the case with the thermal pastes known from DE 0 2018 102 989 B4 and other prior art thermal pastes, high backpressure is generated during injection, which requires powerful pumps and injection pressures. When applied to large-area applications, the demands on the injection pumps will be very high or sometimes impossible to implement.

[0014] Since the demand for thermally conductive contact and filling materials is increasing, especially for large-area applications, as new battery concepts, e.g. in e-mobility, are becoming increasingly dependent on functioning thermal management, the present invention is therefore based on the object of providing a thermal contact and filling material that has the desired properties in order to be used for large-volume and large-area applications in an injection process, but at the same time withstands the high heat transfer.

[0015] The problem underlying the present invention was surprisingly solved by an injectable thermal contact and filling material having the features of claim 1. Advantageous developments of the inventive concept are the subject of subclaims. Further advantageous developments of the injectable thermal contact and filling material according to the invention can be found in the description and the examples.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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 through the formation of emulsions. However, it is also highly important in 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. This creates a repulsive force when these particles come into close proximity, 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 the introduction of charges 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.

[0021] 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.

[0022] With regard to the functionality(s) they contain, organosilanes can be divided into the following groups:

[0023] - Without further functionality (organic chain) e.g. octyltrimethoxysilane, OCTMO;

[0024] Primary amine functionality e.g. 3-aminopropyltrimethoxysilane, AMMO;

[0025] - Secondary amino functionality e.g. N-(n-butyl)-3-aminopropyl-trimethoxysilane

[0026] Diamino-functional, for example N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, DAMO;

[0027] Epoxy-functional e.g. 3-glycidyloxy-propyl-trimethoxysilane, GLYMO;

[0028] - Thiofunctional e.g. 3-mercaptopropyl-trimethoxysilane, MTMO;

[0029] Methacrylic functional e.g. 3-methacryloxypropyltrimethoxysilane, MEMO;

[0030] - Vinyl functional e.g. vinyltrimethoxysilane, VTMO.

[0031] The chemically and commercially available compounds mentioned in the respective groups serve only as examples and the groups are not limited to them.

[0032] 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:

[0033] Metals that are unsuitable for many applications due to their electrical conductivity;

[0034] - Aluminium oxide / hydroxide, and magnesium oxide / hydroxide and

[0035] Diamond, carbon nanotubes, aluminum nitride (AIN), boron nitride (BN), graphite. 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 being consumed in the reaction.

[0036] The injectable thermal contact and filling material according to the invention comprises a component A and a component B, wherein component A comprises the following:

[0037] 1.A) a silane-functionalized prepolymer or a mixture of silane-functionalized prepolymers, wherein the silane-functionalized prepolymer is based on polyurethanes, polyol / diol or polyacrylates;

[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:

[0042] 1.B) a plasticizer which is a polyfunctional carboxylic acid ester;

[0043] 2.B) a wetting and dispersing additive having at least an amine number greater than >20 mg KOH / g measured according to DIN 19645;

[0044] 3.B) a thermally conductive filler or a mixture of several thermally conductive fillers;

[0045] 4.B) Water; and

[0046] 5.B) an organometallic catalyst; and wherein the mixing ratio by volume of component A to component B is 1:1 to 10:1.

[0047] The injectable thermal contact and filling material according to the invention surprisingly exhibits processing properties that are essential for use in the injection process. Surprisingly, it was found that the addition of zinc oxide to this mixture produces remarkable changes in processing properties, which are essential for injection applications.

[0048] It is well known among developers in the field that, to liquefy a thermally conductive composition, a formulation with larger particles is selected, as the surface area-to-volume ratio decreases with increasing particle size. Second, a nearly spherical particle size should be selected for the composition. This helps reduce viscosity, as the particles in a highly filled system can move past each other more like ball bearings rather than interlocking. However, such compositions typically have significant disadvantages in application and injection.The major disadvantage of such compositions is their high tendency to sediment, which severely impacts storage stability. The filler settles and separates during storage and transport, forming a dense bottom layer that cannot be fully re-agglomerated into suspension even with strong shear. Furthermore, such compositions have the disadvantage that the high pumping pressures required can lead to a separation of solid and liquid components during the injection process, making continuous and reproducible injection impossible.

[0049] To avoid these disadvantages, thixotropic agents are usually added to the composition to thicken the liquid phase through particle interactions or, for example, gel formation. However, the addition of a thixotropic agent no longer results in a self-flowing formulation that is as fluid and injectable as possible, but rather in a more viscous paste that prevents settling but is also unsuitable for injection.

[0050] Surprisingly, however, it was found that partially replacing the thermally conductive fillers with zinc oxide significantly improves the settling behavior of the fillers and their injectability without significantly affecting their viscosity. Since zinc oxide itself has a very high thermal conductivity, replacing it with zinc oxide is not associated with any decrease in thermal conductivity. Thus, an injectable thermal contact and filling material is provided that does not exhibit any of the aforementioned disadvantages and is suitable for large-scale applications.

[0051] An advantageous development of the injectable thermal contact and filling material provides for the use of a silane-functionalized prepolymer or a mixture of silane-functionalized prepolymers, wherein the silane-functionalized prepolymer is based on polyurethanes, polyol / diol or polyacrylates.

[0052] An advantageous further development of the injectable thermal contact and filling material provides that component A exclusively comprises a polyurethane-based silane-functionalized prepolymer.

[0053] The generic term silane-functionalized prepolymer in the sense of the present invention comprises a compound of the following formula:

[0054] A in the above formula is a polymeric or prepolymeric backbone, which serves as the basis

[0055] - a polyol / diol (e.g. polyether polyol / diol, polypropylene glycol),

[0056] - has a telechelic polyacrylate or - can itself be prepolymers based on different technologies, e.g. a polyurethane-modified prepolymer which is modified in a further reaction step with alkoxy-protected silane groups.

[0057] The substituents R 1 , R 2 and R3 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.

[0058] For the purposes of the present invention, an alkyl group is understood to mean a C1-C8-alkyl group. For the purposes of the present invention, C1-C8-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.

[0059] For the purposes of the present invention, an alkoxy group is understood to be an O-Cr-Cw-alkyl group. Cr-C alkyl is as defined above.

[0060] A further advantageous development of the injectable thermal contact and filling material provides that the alkoxy group is selected from: OCH3 and OCH2CH3 and the alkyl group is CH3.

[0061] A further particularly advantageous development of the injectable thermal contact and filling material provides that the alkoxy group is OCH3 and the alkyl group is CH3.

[0062] A further advantageous development of the injectable thermal contact and filling material provides that a silane-functionalized prepolymer or a mixture of silane-functionalized prepolymers is selected from the following groups:

[0063] - Group A This group includes prepolymers that are based on a backbone with polyol / diol and are known under the following chemical names: silyl-modified polymers (SMP), modified-silane polymers, MS polymers, silane-terminated polymers.

[0064] Commercially available prepolymers belonging to this group include:

[0065] Dimethoxysilane MS Polymer S (e.g. S303H) and high strength Dimethoxysilane MS Polymer SAX (e.g. SAX 350).

[0066] The most preferred prepolymer for the injectable thermal contact and filling material is the formula A-1:

[0067] - Group B

[0068] This group includes silane-functionalized prepolymers with telechelic polyacrylates as backbone.

[0069] Commercially available polymers belonging to this group include: Kaneka XMAP SA (e.g. Kaneka XMAP SA100).

[0070] The most preferred prepolymer for the injectable thermal contact and filling material is the formula B-1:

[0071] R 1 is H, CrCe-alkyl;

[0072] R 2 is H, C Cß-alkyl

[0073] - Group C

[0074] 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.

[0075] These prepolymers are known under the following chemical names: silane-terminated polyurethane (SPU or STPU), silane-terminated PU, silane-modified PU.

[0076] Commercially available prepolymers belonging to this group are, for example: Polymer ST (e.g. Polymer ST 44) and Geniosil STP-E (e.g. Geniosil STP-E30)

[0077] The most preferred prepolymer for the injectable thermal contact and filling material is the formula C-1: A further advantageous development of the injectable thermal contact and filling material provides that one or more silane-functionalized prepolymers are selected from the following group:

[0078] SAX 350 (Group A)

[0079] XMAP SA120S (Group B).

[0080] Polymer ST-61 LV (Group C).

[0081] A further particularly advantageous development of the injectable thermal contact and filling material provides that component A exclusively comprises a silane-functionalized prepolymer, which is a silane-functionalized prepolymer of group C, preferably ST-61 LV.

[0082] A further advantageous development of the injectable thermal contact and filling material provides that the plasticizer is a multifunctional carboxylic acid ester.

[0083] 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, such as triethyl citrate, or adipic acid-based plasticizers, such as diethylhexyl adipate or diethyl oxytyl adipate, can be used as replacements for the phthalic acid esters.

[0084] The selection of the appropriate plasticizer should be based on its function in the injectable thermal contact and filling material according to the invention. It should be noted that these functions do not all coincide with the use of plasticizers in other formulations. In the injectable thermal contact and filling material according to the invention, the plasticizer has the following functions:

[0085] Reducing the Viscosity of the Liquid Components: Silyl-functionalized prepolymers are typically 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 to achieve the required filler content with the thermally conductive fillers without increasing the viscosity of the finished formulation too high for the application.

[0086] Increased flexibility in the cured material

[0087] 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 and has a 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 that are severely restricted by the filler particles.

[0088] 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, lower 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, by 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.

[0089] In view of the above statements, the following plasticizers have proven to be particularly suitable for the injectable thermal contact and filling material according to the invention:

[0090] Oxsoft 3G8: GAS 94-28-0

[0091] - Triethylene glycol di-(2-ethylhexanoate) 2,2'-ethylenedioxydiethylbis(2-ethylhexanoate)

[0092] Cereplas L810TM: GAS 90218-76-1

[0093] 1,2,4-Benzenetricarboxylic acid, mixed decyl and octyl triester

[0094] Oxsoft TOTM LE: GAS 3319-31-1

[0095] - Tris(2-ethylhexyl)benzene-1,2,4-tricarboxylate

[0096] - Trioctyltrimel litate.

[0097] Di-, tri-, or polyfunctional carboxylic acid esters are most preferred. Another particularly advantageous development of the injectable thermal contact and filling material involves the use of Oxsoft 3G8 as a plasticizer.

[0098] A further advantageous development of the injectable thermal contact and filler material provides for the wetting and dispersing additive to contain at least functional amine groups, which may also optionally contain acidic groups, e.g., phosphorus groups or carboxylate groups. Particularly preferred are: Disperbyk 2157 or Byk W969.

[0099] 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, additional functional groups, such as phosphorus groups or carboxylate groups, which can also have a surface-active effect, can be optionally included. Optionally, the wetting and dispersing additives can also contain an acid number measured according to DIN EN ISO 2114.

[0100] 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.

[0101] A further advantageous development of the injectable thermal contact and filling material provides that component A comprises a mixture of functionalized organosilanes.

[0102] For the purposes of the present invention, this refers to mono- and multifunctional organosilanes. 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.

[0103] First, all of the organosilanes mentioned serve as crosslinkers. They are incorporated into the network of the silane-functionalized prepolymers, thereby increasing the crosslinking density of the prepolymer. The functional groups they contain are crucial for their function in a formulation.

[0104] A further advantageous development of the injectable thermal contact and filling material provides for the use of the following organosilanes: The following organosilanes are relevant in the formulations, including their functionality: a) amino-functionalized organosilanes

[0105] 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.

[0106] Another particularly advantageous development of the injectable thermal contact and filling material provides that:

[0107] - AMMO or

[0108] Oligomeric, precondensed silanes with amine groups, e.g., from the Dynasylan® SIVO series, can be used. b) vinyl-functional organosilanes

[0109] 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 blanketing of the components under inert gas, or pre-drying of the fillers in special dryers.

[0110] Another particularly advantageous development of the injectable thermal contact and filling material involves the use of VTMO. c) epoxy-functional organosilanes

[0111] 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.

[0112] A further particularly advantageous development of the injectable thermal contact and filling material provides that the mixture of functionalized organosilanes comprises at least one amino-functionalized or one vinyl-functionalized or one epoxy-functionalized organosilane.

[0113] A further particularly advantageous development of the injectable thermal contact and filling 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.

[0114] A further particularly advantageous development of the injectable thermal contact and filling material provides that the mixture of functionalized organosilanes comprises at least one amino-functionalized and one vinyl-functionalized organosilane.

[0115] A further particularly advantageous development of the injectable thermal contact and filling material provides that the mixture of functionalized organosilanes comprises an amino-functionalized, a vinyl-functionalized and an epoxy-functionalized organosilane.

[0116] Another particularly advantageous development of the injectable thermal contact and filling material provides for at least one of the functionalized organosilanes to be an oligomeric silane. Another particularly advantageous development of the injectable thermal contact and filling material provides for the use of GLYMO.

[0117] Another particularly advantageous development of the injectable thermal contact and filling material requires the use of zinc oxide as a filler.

[0118] A further advantageous development of the injectable thermal 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.

[0119] A further advantageous development of the injectable thermal 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.%.

[0120] A further advantageous development of the injectable thermal 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] A further advantageous development of the injectable thermal contact and filling material provides that component B comprises a catalyst.

[0126] A further particularly advantageous development of the injectable thermal contact and filler material provides that the catalyst is an organometallic complex. All common organometallic catalysts available on the market are suitable. Tin complexes are mentioned here as an example, although this invention is not limited to these. 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. A further particularly advantageous development of the injectable thermal contact and filler material provides that the catalyst can 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.

[0127] A further particularly advantageous development of the injectable thermal contact and filling material provides that the catalyst is an acid-catalyzed system.

[0128] Another particularly advantageous development of the injectable thermal contact and filling material is that it is silicone-free.

[0129] 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.

[0130] The invention is illustrated below by examples, but is not limited to these.

[0131] Example 1 - Preparation of component A and component B

[0132] 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.

[0133] As can be seen from Table 1, compositions F1 to F4 differ only in the type of fillers used. Compositions F1 and F2 contain the same fillers in the same amount, with V2 additionally containing fumed silica, a synthetically produced colloidal material with defined properties and particle size used as a filler. It consists entirely of amorphous silicon dioxide particles (SiO2) aggregated into larger units. Compositions F3 and F4, on the other hand, contain the same fillers in different amounts.

[0134] Table 1 - Component A

[0135] Table 2 - Component B

[0136] The raw materials listed in Table 2 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.

[0137]

[0138] The mixing ratio of components A to B is 10:1 by volume. Component B is a so-called booster component that has two effects:

[0139] 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 injectable thermal contact and filler material applied over a large area.

[0140] On the other hand, the addition of the catalyst accelerates the condensation reaction of the silane functionalities.

[0141] Experiment 1 - Investigation of settling behavior, viscosity and extrusion capability

[0142] The settling behavior was determined solely from the formulation of component A, as the sedimentation problem is considerably greater with component A, which is the reactive component. Therefore, component B was not described here. This would be unreactive and contains the required water and a catalyst for accelerated curing of the contact and filler material according to the invention. After preparing component A, either as a 100g or 500g batch, the viscosity of compositions F1 to F4 was measured immediately after preparation. The results are summarized in Table 2, lines 1 and 1:

[0143] Table 2 As can be seen, the compositions F1 and F3, which differ in the use of ZnO (see Table 1), show almost the same viscosity directly after preparation.

[0144] Compositions F1 to F4 were then transferred to the cartridges and stored upright at 60°C for one week. This quickly simulated aging and sedimentation processes during storage and transport. After one week at 60°C, the settling behavior of compositions F1 to F4 was determined by measuring the viscosity and density section by section in the cartridges of the respective compositions. For this purpose, the cartridges were divided into 5 volume sections and the corresponding samples were taken. It should be noted that "Sample 1" was taken directly from the upper part of the cartridge, "Sample 3" from the middle volume section, and "Sample 5" from the very bottom of the cartridge. Samples 2 and 4 are therefore intermediate measurements in the volume range above / below the middle of the respective cartridge.

[0145] The viscosity of the samples taken was measured on a plate-on-plate rheometer at a shear rate of 10 s-1. Due to the very high viscosity of the compositions, the density was measured in a small plastic cup with a capacity of approximately 2 ml. The volume of the cup was determined before measuring the density by completely filling it with water and reweighing it. After the cup was dried, it was filled with the respective component without any bubbles. Any excess material was removed flush with the cup rim. The filled cup was reweighed and the density was calculated from the mass of the component and the exact volume of the cup. The extrusion ability from the cartridge was also evaluated by squeezing the cartridge and recorded as an impression.

[0146] As can be seen from the results in Table 2, the viscosity development of composition V1 is comparable to the reference formulations F2 to F4. Settling behavior, associated with a viscosity increase of 20-30% in the lower volume section compared to the upper volume section, was observed for all formulations. This can also be correlated with a density increase in the lower part of the cartridge, although this increase is less pronounced. In formulation F4, the lower section was no longer easily measurable due to increased sedimentation, as bubble-free transfer to the measuring cup was impossible.

[0147] However, a significant difference in extrusion capability was observed between composition V1 and compositions V3 and V4, the latter two without ZnO addition. This clearly indicates the significantly improved injectability of composition V1, which is attributable to the addition of ZnO.

[0148] In direct comparison, compositions V3 and V4 appeared far too viscous and were very difficult to extrude. Even with composition V2, which is composition 1, to which 1.5% fumed silica was added to achieve a higher viscosity, extrusion properties were significantly improved, as was the case with the comparative formulations V3 and V4.

[0149] Experiment 2 - Investigation of injection ability

[0150] For this experiment, composition V1, which showed the best extrusion ability, was compared with composition F3, which does not contain ZnO.

[0151] Injection tests were conducted on a metal dummy with a screwed-on Plexiglas lid to capture the movement of the injection front on video and determine the injection time. The gap width was 1 mm, the injection volume was approximately 85 ml, and the dimensions of the injection cavity were 450 mm x 195 mm x 1 mm.

[0152] The Plexiglas lid was sealed with a gasket around the edge. The Plexiglas cover contains a hole for injection and a recess for the rubber seal to allow air to escape and excess injection material to be discharged from the opposite side of the injection volume after the test. The Plexiglas cover was divided into uniform injection areas of 1 / 3, 2 / 3, and the full injection length using two adhesive tapes, allowing for reproducible recording of intermediate injection times.

[0153] First, compositions V1 and V3, which consist exclusively of component A, were prepared as shown in Table 1. These were then transferred to a cartridge each containing component B at a ratio of 10:1, ensuring that no bubbles were formed, and then equipped with a static mixer (10-24T-MFHX). Compositions V1 + component B and V3 + component B were injected through a hole through the Plexiglas pane using a pneumatic cartridge gun. The pneumatic pressure was set to a maximum of 6 bar. The ambient and material temperatures were at laboratory temperature (approximately 23°C).

[0154] The results are summarized in Table 3:

[0155] Table 3

[0156] The injection of composition V3 + Component B was discontinued after 3:00 injection time. Due to the much higher viscosity and poorer flowability, complete injection with the cartridge gun was not achieved, as the maximum pneumatic pressure was insufficient for the injection. Furthermore, there was a risk of the Plexiglas plate bursting due to the pressure buildup. In contrast, the injectable thermal contact and filling material according to the invention (V1 + Component B) can be injected very quickly and easily.

Claims

Claims 1. Injectable thermal contact and filling material consisting of a component A and a component B, wherein component A comprises: 1.A) a silane-functionalized prepolymer or a mixture of silane-functionalized prepolymers, wherein the silane-functionalized prepolymer is based on polyurethanes, polyol / diol or polyacrylates; 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; and 5.B) an organometallic catalyst; and wherein the mixing ratio by volume of component A to component B is 1:1 to 10:

1.

2. Injectable thermal contact and filling material according to claim 1, characterized in that component A comprises exclusively a polyurethane-based silane-functionalized prepolymer.

3. Injectable thermal contact and filling material according to claim 1 or 2, characterized in that the plasticizer is a difunctional carboxylic acid ester.

4. Injectable thermal contact and filling material according to claim 3, characterized in that the plasticizer is a difunctional carboxylic acid ester based on a polyether alcohol.

5. 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 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. Injectable 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: AI(OH)3 and AI2O3.

9. Injectable thermal 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. Injectable thermal 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. Injectable thermal 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. Injectable thermal 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 88 to 93 wt.%, the proportion of ZnO in the mixture of fillers being 15-25 wt.%.

13. Injectable thermal contact and filling material according to one of claims 1 to 12, characterized in that it comprises: 1 to 10 wt.% of the mixture of silane-functionalized prepolymers, wherein the silane-functionalized prepolymer based on polyurethanes accounts for up to 50 wt.%, 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 80 to 95 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 10-30 wt.%.

14. Injectable thermal contact and filling material according to one of claims 1 to 13, characterized in that it comprises the following: 1 to 7 wt.% of the mixture of silane-functionalized prepolymers, wherein the silane-functionalized prepolymer based on polyurethanes accounts for up to 50 wt.%, 3 to 8 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 83 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. Injectable thermal contact and filling material according to one of claims 1 to 14, characterized in that it is silicone-free.

16. Use of the injectable thermal contact and filling material according to one of claims 1 to 15 in large-area electronic components.

17. Use of the injectable thermal contact and filling material according to one of claims 1 to 15 for battery systems with a complex accumulator structure.

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