Crosslinkable compositions based on silane-crosslinked organic polymers with high thermal conductivity

Abstract

The present invention provides a compound of formula (I): Y-[(CR 1 2) b -SiR a (OR 2 ) 3-a ] x wherein Y is an x-valent organic polymer group bonded via nitrogen, oxygen, sulfur, or carbon; R may be the same or different and is a monovalent hydrocarbon group which may be substituted; R 1 are the same or different and are hydrogen atoms or monovalent optionally substituted hydrocarbon groups which can be bonded to a carbon atom via nitrogen, phosphorus, oxygen, sulfur or a carbonyl group; R 2 may be the same or different and are hydrogen atoms or monovalent optionally substituted hydrocarbon groups, x is an integer of 1 to 10, a may be the same or different and are 0, 1 or 2, and b may be the same or different and are integers of 1 to 10. and 100 to 1900 parts by weight of at least one filler (B), wherein at least 30% by weight of all fillers (B) consist of metal silicon particles (B1).

Description

[Technical Field]

[0001] The present invention relates to a crosslinkable composition with high thermal conductivity based on a silane-crosslinked polymer, a process for its preparation and its use. [Background technology]

[0002] Thermally conductive compositions are widely used for thermal management in the automotive and electronics industries. Important formulations include, for example, thermally conductive adhesives and potting compounds. Another important application is known as a gap filler, particularly for lithium-ion batteries. Gap fillers are thermally conductive elastomers that completely and permanently fill gaps and voids within the respective components, minimizing the thermal resistance, for example, between electronic components and cooling housings or heat sinks.

[0003] Silicone elastomers are often used as binders for thermally conductive compositions. They have the advantage of being relatively heat-resistant and able to withstand the thermal stresses to which thermally conductive compositions are often exposed in their final applications. Various curing mechanisms, such as silane condensation, hydrosilylation, or peroxide crosslinking, are known, allowing the composition to be applied in liquid or paste form and subsequently cured to obtain a material with the desired elastomeric properties. Corresponding systems are described, for example, in US2016122611 or WO2022 / 161634.

[0004] However, in many applications, silicone is undesirable, because the polydimethylsiloxane chain present in silicone is highly surface active, and can dramatically reduce the adhesion of components or further coating materials.In particular, when applying paint or varnish coatings, even the smallest traces of polydimethylsiloxane are enough to cause a large amount of paint or varnish defects.In addition, shorter polydimethylsiloxane chains have a certain volatility, and therefore can also disperse over long distances through ventilation or air conditioning systems in building complexes, so there are strict restrictions on the entire substance group in many manufacturing sectors, especially in the automotive industry.

[0005] An alternative technology to silicone-based products could be the use of binders based on what are known as hybrid polymers, that is, polymers with an organic backbone bearing reactive and crosslinkable alkoxysilyl groups.

[0006] Polymer systems containing reactive alkoxysilyl groups have been known for a long time. Upon contact with water or atmospheric moisture, these alkoxysilane-terminated polymers can condense with each other, even at room temperature, with the elimination of alkoxy groups.

[0007] One of the most important established uses of such materials is the production of adhesives and sealants for use in construction. Thus, in the cured state, adhesives and sealants based on alkoxysilane crosslinked polymers not only exhibit good adhesive properties to virtually all inorganic substrates used in the construction sector, but also very good mechanical properties.

[0008] A further advantage of silane crosslinking systems over many other products that are curable at room temperature (eg isocyanate crosslinking systems) is the toxicological safety of the prepolymer.

[0009] In addition to "one-component" products that react and cure with atmospheric moisture and / or traces of water in the substrate to which they are applied, there are also "two-component" systems. These cure as soon as the two components are mixed; one component of the system usually contains a silane-crosslinked polymer, and the second component is water available in a suitable form. The latter can be dissolved, emulsified, absorbed onto the surface of a suitable filler (e.g., zeolite), or chemically reversibly bonded.

[0010] Silane crosslinked polymers have been known to those skilled in the art for decades and are available from numerous manufacturers.

[0011] A first specific variant of this technology consists of the use of what are known as α-silane-terminated prepolymers. These have reactive alkoxysilyl groups linked to adjacent urethane units by methylene spacers. This class of compounds is highly reactive and does not require either tin catalysts or strong acids or bases to achieve high cure rates upon contact with air. Commercially available α-silane-terminated prepolymers are Geniosil® STP-E10 or -E30 from Wacker Chemie AG.

[0012] A second particular variant of the adhesive based on silane crosslinked polymers is described, for example, in US2014155545A, which corresponds to EP2744842A, and which contains a phenyl silicone resin in addition to the silane crosslinked polymer. The corresponding resin additive also results in a product that exhibits significantly higher hardness when fully cured.

[0013] A third particular variant of the sealants based on silane crosslinked polymers that is of particular interest is described, for example, in US 2017198101A, which corresponds to EP 3149095A: In addition to the conventional, preferably linear, silane crosslinked polymers that contain crosslinkable silane functional groups at both chain ends, products with reactive silane groups at only one chain end are also described.

[0014] Despite their widespread use as conventional adhesives and sealants, particularly in the construction sector, there have been only a few isolated accounts of systems based on silane-crosslinked polymers with high thermal conductivity. One of these rare references can be found in Example 5 of US 2022119593A, which corresponds to EP 3924428A. This uses a specific filler mixture of spherical aluminum oxide particles, calcined aluminum oxide particles, and zinc oxide. The filler content is very high, at 90%. Because silane-terminated polymers themselves have very low thermal conductivities of only 0.15-0.20 W / mK, the specific filler mixture with such a high content is essential to achieve high thermal conductivity.

[0015] The two-component system described in Example 5 of US 2022119593A, which corresponds to EP 3924428A, has a thermal conductivity of 2.8-2.9 W / mK. This is quite substantial. However, for many applications, such as high-performance batteries, even higher thermal conductivities would be desirable. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] US Patent Application Publication No. 2016 / 122611 [Patent Document 2] International Publication No. 2022 / 161634 [Patent Document 3] European Patent Application Publication No. 2744842 [Patent Document 4] U.S. Patent Application Publication No. 2014 / 155545 [Patent Document 5] European Patent Application Publication No. 3149095 [Patent Document 6] U.S. Patent Application Publication No. 2017 / 198101 [Patent Document 7] European Patent Application Publication No. 3924428 [Patent Document 8] U.S. Patent Application Publication No. 2022 / 119593 Summary of the Invention [Problem to be solved by the invention]

[0017] The object of the present invention was therefore to develop compositions based on silane-crosslinked polymers with an organic, i.e. non-polysiloxane-containing backbone, which have a further improved thermal conductivity compared to the prior art. [Means for solving the problem]

[0018] This object has surprisingly been achieved by the present invention.

[0019] The present invention provides a crosslinkable thermally conductive composition (M), 100 parts by weight of at least one compound (A) of the following formula: Y-[(CR 1 2) b -SiR a (OR 2 ) 3-a ] x (I) [In the formula, Y is an x-valent organic polymeric group attached through nitrogen, oxygen, sulfur, or carbon; R may be the same or different and is a monovalent optionally substituted hydrocarbon group; R 1 are the same or different and are hydrogen atoms or monovalent optionally substituted hydrocarbon radicals which can be bonded to a carbon atom via nitrogen, phosphorus, oxygen, sulfur or a carbonyl group; R 2 may be the same or different and are a hydrogen atom or a monovalent optionally substituted hydrocarbon group, x is an integer of 1 to 10, preferably 1, 2, or 3, and more preferably 1 or 2; a may be the same or different and is 0, 1 or 2, preferably 0 or 1; b may be the same or different and is an integer of 1 to 10, preferably 1, 3 or 4, more preferably 1 or 3, and particularly 1.] 100 to 1900 parts by weight of at least one filler (B); wherein at least 30% by weight of all fillers (B) consist of metal silicon particles (B1).

[0020] In the context of the present invention, the terms heat-conducting, thermoconductive and thermally conductive are synonymous. DETAILED DESCRIPTION OF THE INVENTION

[0021] In order to avoid generating an excessive number of pages in the description of the present invention, only preferred embodiments of individual features are identified below.

[0022] However, the expert reader should clearly understand this type of disclosure to mean that all combinations of different preference levels are also specifically disclosed and specifically desired.

[0023] The present invention is based on the surprising discovery that the silicon particles (B1) of the present invention can significantly improve the thermal conductivity of crosslinkable compositions (M) compared to the values ​​achieved in the prior art. At the same time, their low density makes it possible to provide thermally conductive compositions (M) with relatively low density.

[0024] Compound (A) Examples of radicals R in formula (I) are alkyl radicals such as methyl, ethyl, n-propyl, isopropyl, 1-n-butyl, 2-n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, and tert-pentyl radicals, hexyl radicals such as n-hexyl radical, heptyl radicals such as n-heptyl radical, octyl radicals such as n-octyl radical, isooctyl radical, and 2,2,4-trimethylpentyl radical, nonyl radicals such as n-nonyl radical, decyl radicals such as n-decyl radical, dodecyl radicals such as n- dodecyl, octadecyl, such as n-octadecyl; cycloalkyl groups, such as cyclopentyl, cyclohexyl, cycloheptyl, and methylcyclohexyl; alkenyl groups, such as vinyl, 1-propenyl, and 2-propenyl; aryl groups, such as phenyl, naphthyl, anthryl, and phenanthryl; alkaryl groups, such as o-, m-, and p-tolyl, xylyl, and ethylphenyl; and aralkyl groups, such as benzyl and α- and β-phenylethyl.

[0025] Examples of substituted groups R are haloalkyl groups such as 3,3,3-trifluoro-n-propyl, 2,2,2,2',2',2'-hexafluoroisopropyl, and heptafluoroisopropyl, and haloaryl groups such as o-, m-, and p-chlorophenyl.

[0026] The group R is preferably a monovalent hydrocarbon group having 1 to 6 carbon atoms which may be substituted with a halogen atom, more preferably an alkyl group having 1 or 2 carbon atoms, and particularly a methyl group.

[0027] base R 1 Examples of are hydrogen atoms, groups specified for R, and optionally substituted hydrocarbon groups bonded to a carbon atom through nitrogen, phosphorus, oxygen, sulfur, carbon, or a carbonyl group.

[0028] base R 1 is preferably a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and particularly preferably a hydrogen atom.

[0029] base R 2 Examples of are those given for a hydrogen atom and for the group R.

[0030] base R 2 is preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms which may be substituted with a halogen atom, and particularly a methyl group or an ethyl group.

[0031] For the purposes of the present invention, the polymer on which the organic polymer group Y is based is to be understood as meaning any polymer in which at least 50%, preferably at least 70%, more preferably at least 90% of all bonds in the main chain are carbon-carbon, carbon-nitrogen or carbon-oxygen bonds. Particularly preferably, all bonds in the main chain of the polymer group Y consist of carbon-carbon, carbon-nitrogen or carbon-oxygen bonds.

[0032] Silicones having a backbone consisting essentially of silicon-oxygen bonds, ie to the extent of at least 50% of all bonds, are not polymers on which the polymeric group Y is based.

[0033] Examples of polymeric groups Y are polyester groups, polyether groups, polyurethane groups, polyalkylene groups, and polyacrylate groups.

[0034] The polymer group Y is preferably an organic polymer group containing polyoxyalkylene as the polymer chain, such as polyoxyethylene, polyoxypropylene, polyoxybutylene, polyoxytetramethylene, polyoxyethylene-polyoxypropylene copolymers and polyoxypropylene-polyoxybutylene copolymers, hydrocarbon polymers such as polyisobutylene and copolymers of polyisobutylene and isoprene, polychloroprene, polyisoprene, polyurethane, polyester, polyacrylate, polymethacrylate, acrylate, vinyl polymer or polycarbonate, and preferably -OC(=O)-NH-, -NH-C(=O)O-, -NH-C(=O)-NH-, -NR'-C(=O)-NH-, NH-C(=O)-NR'-, -NH-C(=O)-, -C(=O)-NH-, -C(=O)-O-, -OC(=O)-, OC(=O)-O-, -SC(=O)-NH-, -NH-C(=O)-S-, -C(=O)-S-, -SC(=O)-, -SC(=O)-S-, -C(=O)-, -S-, -O-, -NR'-, -[(CR 1 2) b -SiR a (OR 2 ) 3-a ] group, where R' may be the same or different and are as defined for R, or a CH(COOR")-CH-COOR" group, where R" may be the same or different and are as defined for R.

[0035] The group R' is preferably a -CH(COOR")-CH-COOR" group or an optionally substituted hydrocarbon group having 1 to 20 carbon atoms, more preferably a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms and optionally substituted with a halogen atom.

[0036] Examples of radicals R' are cyclohexyl, cyclopentyl, n- and isopropyl, n-, iso- and t-butyl radicals, the various stereoisomers of pentyl, hexyl or heptyl radicals, and also the phenyl radical.

[0037] The group R" is preferably an alkyl group having 1 to 10 carbon atoms, more preferably a methyl group, an ethyl group or a propyl group.

[0038] Component (A) may be attached in the described manner to any position in the polymer, for example, at the chain and / or terminal positions. 1 2) b -SiR a (OR 2 ) 3-a ] group.

[0039] More preferably, the group Y in formula (I) is an organic polymeric group having a valence of x attached through nitrogen, oxygen, sulfur or carbon, including polyurethane or polyoxyalkylene as the polymer chain, and in particular a terminally attached -[(CR 1 2) b -SiR a (OR 2 ) 3-a ] groups or terminally attached -[(CR 1 2) b -SiR a (OR 2 ) 3-a A polyoxyalkylene group having a ] group (wherein the groups and subscripts are as defined above). The group Y is preferably linear or has 1 to 3 branch points. The group Y is more preferably linear.

[0040] The polyurethane group Y preferably has a chain terminated via -NH-C(=O)O-, -NH-C(=O)-NH-, -NR'-C(=O)-NH- or -NH-C(=O)-NR'-, in particular via -OC(=O)-NH- or -NH-C(=O)-NR'-, -[(CR 1 2) b -SiR a (OR 2 ) 3-a] group, where all groups and indices are as defined above. The polyurethane group Y can preferably be formed from linear or branched polyoxyalkylenes, in particular from polypropylene glycols, and diisocyanates or polyisocyanates. The group Y preferably has an average molar mass M of 400 to 30,000 g / mol, preferably 3,000 to 20,000 g / mol. n (number average). Examples of suitable methods for preparing the corresponding component (A) and of the component (A) itself are described, inter alia, in EP1093482B1 (paragraphs

[0014] to

[0023] ,

[0039] to

[0055] , and Example 1 and Comparative Example 1), which corresponds to US6884852B, or in EP1641854B1 (paragraphs

[0014] to

[0035] , Examples 4 and 6, and Comparative Examples 1 and 2), which correspond to US2007167598A, and are included in the disclosure content of the present application.

[0041] number average molar mass M n is determined in the context of the present invention by size exclusion chromatography (SEC) on a Styragel HR3-HR4-HR5-HR5 column set from Waters USA in THF at a flow rate of 1.2 ml / min at 60° C. against polystyrene standards with an injection volume of 100 μl and detection by RI (refractive index detector).

[0042] The polyoxyalkylene group Y is preferably a linear or branched polyoxyalkylene group, more preferably a polyoxypropylene group, and the chain end thereof is preferably connected via —OC(═O)—NH— or O— to —[(CR 1 2) b -SiR a (OR 2 ) 3-a ] group, where the groups and subscripts are as defined above. Preferably, at least 85%, more preferably at least 90%, especially at least 95% of all chain ends are bonded to -[(CR 1 2) b -SiR a (OR 2) 3-a The polyoxyalkylene group Y preferably has an average molar mass M of 400 to 30,000 g / mol, preferably 3,000 to 20,000 g / mol. n Examples of suitable methods for preparing the corresponding component (A) and of the component (A) itself are described, inter alia, in EP1535940B1 (paragraphs

[0005] to

[0025] and Examples 1 to 3 and Comparative Examples 1 to 4), which corresponds to US2005119436A, or in EP1896523B1 (paragraphs

[0008] to

[0047] ), which corresponds to US2010016537A, and these are included in the disclosure content of the present application.

[0043] In a particular embodiment of the present invention, compound (A) has the formula -[(CR 1 2) b -SiR a (OR 2 ) 3-a

[0033] The groups and subscripts are as defined above. In other words, they are compounds (A) of formula (I) where x is 1. In this case, the other chain end is preferably terminated with a hydroxyl group, an aryl group having 6 to 20 carbon atoms, or an alkyl group having 1 to 20 carbon atoms, with the latter being particularly preferred.

[0044] More preferably, in this particular embodiment of the invention, compound (A) has one chain end terminated by a branched, unbranched or cyclic alkyl group having from 1 to 20 carbon atoms and a group of formula -[(CR 1 2) b -SiR a (OR 2 ) 3-a and a second chain end having a reactive silyl group of formula (I).

[0045] The end groups of the compounds (A) used according to the invention are preferably of the general formula: NH-C(=O)-NR'-(CR 12) b -SiR a (OR 2 ) 3-a (II) OC(=O)-NH-(CR 1 2) b -SiR a (OR 2 ) 3-a (III) O-(CR 1 2) b -SiR a (OR 2 ) 3-a (IV) wherein the groups and indices are as defined above.

[0046] When the compounds (A) are polyurethanes, which are preferred, they have one or more of the following end groups: NH-C(=O)-NR'-(CH2)3-Si(OCH3)3, NH-C(=O)-NR'-(CH2)3-Si(OC2H5)3, -OC(=O)-NH-(CH2)3-Si(OCH3)3 or -OC(=O)-NH-(CH2)3-Si(OC2H5)3 where R' is as defined above.

[0047] When the compounds (A) are polypropylene glycols, which are particularly preferred, they preferably have one or more of the following end groups: -O-(CH2)3-Si(CH3)(OCH3)2, -O-(CH2)3-Si(OCH3)3, -OC(=O)-NH-(CH2)3-Si(OC2H5)3, -OC(=O)-NH-CH2-Si(CH3)(OC2H5)2, -OC(=O)-NH-CH2-Si(OCH3)3, -OC(=O)-NH-CH2-Si(CH3)(OCH3)2 or -OC(=O)-NH-(CH2)3-Si(OCH3)3 The latter two end groups are particularly preferred.

[0048] Average molecular weight M of compound (A) n is preferably at least 200 g / mol, more preferably at least 1000 g / mol, in particular at least 3000 g / mol, preferably at most 30000 g / mol, more preferably at most 20000 g / mol, in particular at most 13000 g / mol.

[0049] When the group Y is a polyurethane or polyether, which is preferred, the average molecular weight M of the compound (A) n is preferably obtained by adding the above-mentioned preferred molar mass of the group Y and the mass of the respective binder and / or end group.

[0050] The viscosity of compound (A), in each case measured at 20°C, is preferably at least 0.1 Pa·s, more preferably at least 0.5 Pa·s, particularly preferably at least 1 Pa·s, and preferably at most 100 Pa·s, more preferably at most 10 Pa·s, particularly preferably at most 5 Pa·s.

[0051] The viscosity of the polymer (A) used according to the invention is determined in the context of the present invention using a DV 3P rotational viscometer from A. Paar (Brookfield Systems) using spindle 5 at 2.5 rpm after thermal equilibration at 20°C according to ISO 2555.

[0052] The compounds (A) used according to the invention are commercially available products or can be prepared by standard chemical methods.

[0053] Polymer (A) can be prepared by known methods such as addition reactions, e.g., hydrosilylation, Michael addition, Diels-Alder addition, or the reaction between an isocyanate-functional compound and a compound having an isocyanate-reactive group.

[0054] Component (A) used according to the present invention may comprise only one compound of formula (I) or a mixture of different compounds of formula (I). Component (A) may comprise only compounds of formula (I) in which more than 90%, preferably more than 95%, more preferably more than 98% of all silyl groups bonded to group Y are identical. However, in this case, it is also possible to use component (A) which, at least in part, comprises compounds of formula (I) in which different silyl groups are bonded to group Y. Finally, it is also possible to use as component (A) a mixture of different compounds of formula (I) in which there are a total of at least two different types of silyl groups bonded to group Y, but in which all silyl groups bonded to a specific group Y are identical.

[0055] Filler (B) Preferably, at least 30% by weight, more preferably at least 40% by weight, particularly preferably at least 60% by weight of all fillers (B) consist of metal silicon particles (B1).

[0056] If filler (B) does not consist solely of silicon metal particles (B1), it is preferred that it contains an additional thermally conductive filler (B2) consisting of a material with a thermal conductivity of at least 5 W / mK.In total, filler (B) preferably comprises at least 60% by weight, more preferably at least 70% by weight, particularly preferably at least 80% by weight of filler (B1), and if present, (B2).In a particularly preferred embodiment of the present invention, filler (B) consists solely of filler (B1), and if present, (B2).

[0057] The median diameter x50 of the metal silicon particles (B1) of the present invention is in the range of 0.5 to 250 μm, preferably 10 to 200 μm, preferably 20 to 180 μm, more preferably 30 to 160 μm, and particularly preferably 35 to 150 μm.

[0058] Particularly preferably, the silicon particles (B1) having the above-mentioned preferred or more preferred median diameter x50 further have a width / length ratio (aspect ratio w / l) of at least 0.76.

[0059] The silicon particles (B1) are preferably produced from the molten state.

[0060] More preferably, the silicon particles (B1) are brought into solid particle form from a silicon melt by spraying or atomizing and subsequent cooling.

[0061] The thermally conductive composition (M) of the present invention preferably contains at least 27% by weight, more preferably at least 36% by weight, and particularly preferably at least 54% by weight of metal silicon particles (B1). If the content of metal silicon particles (B1) in the composition (M) is too low, the desired beneficial effects of this component, such as low density and high thermal conductivity, can no longer be achieved to the desired extent.

[0062] The silicon metal particles (B1) of the present invention can have any regular or irregular shape.For example, the particles can be spherical, round, elliptical, cylindrical, fibrous, square, sharp-edged, potato-shaped, nodular, or "sputtered" shape.The silicon metal particles (B1) of the present invention are preferably mainly elliptical, potato-shaped, round, or spherical.The silicon particles (B1) preferably have a width / length ratio (aspect ratio w / l) of at least 0.76, more preferably at least 0.77, and particularly preferably at least 0.78.Even more preferred are silicon particles (B1) with a width / length ratio of at least 0.79.

[0063] The particle size distribution width (span) is defined as Span = (x90 - x10) / x50, where x90, x50, and x10 represent the 90th, 50th, and 10th percentiles. The distribution width of the metal silicon particles (B1) of the present invention is not limited in principle. The metal silicon particles (B1) of the present invention preferably have a span greater than 0.28, more preferably greater than 0.30, and particularly preferably greater than 0.35. In a preferred embodiment, the span is between 0.40 and 2.5, preferably between 0.41 and 2.2, and particularly preferably between 0.5 and 2.0.

[0064] In the silicon particles (B1) of the present invention, in order to achieve the particle size distribution width of the present invention, it is not important whether to use one silicon particle (B1) whose span is within the scope of the present invention, or to mix two or more silicon particles.When two or more fractions of silicon particles are mixed, this can be done before mixing with one or more components of the composition of the present invention, or the fractions of silicon particles can also be mixed separately with one or more components of the composition of the present invention.The order of addition is not important.

[0065] Preferably, up to four fractions of silicon particles (B1) are mixed, preferably up to three fractions of silicon particles (B1) are mixed, more preferably up to two fractions of silicon particles (B1) of the present invention are used, and particularly preferably, only a single silicon powder (B1) of the present invention is used.

[0066] A disadvantage of silicon particles having an average particle size greater than 250 μm is that such large silicon particles often do not fit into minute gaps between parts, for example, that are to be filled with the gap filler.

[0067] The disadvantage of very fine silicon particles or pulverized silicon particles is that these particles have a relatively large surface area and can combine a large amount of polymer.This greatly increases the viscosity of composition, resulting in the mixture having a relatively low filler content, and therefore having a lower thermal conductivity.If the content of fine silicon particles as filler is high, composition becomes very hard, and can no longer be processed by traditional process, such as dispenser.

[0068] Furthermore, under certain conditions, silicon metal particles are flammable, and their dust poses an explosion hazard. The risk of dust formation, flammability, and explosion hazard of metal powders increases significantly with decreasing particle size. The low minimum ignition energy of fine silicon metal particles makes their handling more dangerous, requiring cumbersome and expensive safety measures when working in industry.

[0069] In a preferred embodiment, the silicon particles (B1) of the present invention contain 1.5% by weight or less, preferably 1% by weight or less, more preferably 0.5% by weight or less of silicon particles with a maximum diameter of 2 μm, based on the total amount of silicon particles (B1) in each case.Particularly preferred silicon particles (B1) do not essentially contain the fraction of particles less than 2 μm.The term "essentially do not contain" is understood to mean that the existence of such particles is acceptable to the extent that they are the "impurities" of particles (B1) of the present invention and do not interfere with the effect of the present invention.

[0070] The term "maximum diameter" refers to the longest possible distance between two particle surfaces within a particle.

[0071] The silicon particles (B1) of the present invention preferably contain a fraction of particles with a diameter of 20 μm or less, which fraction is in each case less than 20% by weight, preferably less than 15% by weight, more preferably less than 10% by weight, relative to the total amount of silicon particles (B1).

[0072] Silicon metal has many highly advantageous properties for use as a thermally conductive filler (B1). For example, the very high thermal conductivity of the silicon particles (B1) improves the thermal conductivity of the thermally conductive composition (M) produced therefrom. The low density of the silicon particles (B1) reduces the weight of the composition and the parts produced therefrom, helping to reduce costs. The low electrical conductivity makes it possible to produce electrically insulating parts and improves dielectric strength. The low Mohs hardness of the silicon particles (B1) reduces wear during processing. Since the above-mentioned advantages are completely or partially lost with a decrease in silicon purity, the purity of the silicon particles (B1) of the present invention, and therefore the silicon content, is at least 80% by weight, preferably at least 90% by weight, and more preferably at least 95% by weight.

[0073] Various methods for producing finely divided metal particles having a "sputtered", "nodular", "ellipsoidal", "potato-shaped", "round" or "spherical" shape are known in the prior art. The silicon particles (B1) of the present invention are preferably produced from a molten state in the final production step, and as a result have a smooth surface and a rounded surface shape, and are essentially free of fracture sites, sharp edges and sharp corners. This distinguishes them from conventional crushed particles that are formed into their final shape by, for example, crushing, milling or grinding. Here, it is not important whether the particles are powdered at a low temperature in the first process step, for example by grinding, and then heated above their melting point, for example by heat treatment in a high temperature range, for example by plasma, to form a molten form, or whether a silicon melt is first generated and then powdered, for example by atomization. The silicon particles of the present invention are preferably formed into the solid particle shape of the present invention by spraying or atomizing a silicon melt and then cooling it.

[0074] Suitable processes for producing silicon particles (B1) of the present invention are known to those skilled in the art, and are described, for example, in "Pulvermetallurgie Technologien und Werkstoffe" [Powder Metallurgy: Technology and Materials], Chapter 2.2, Schatt, Werner, Wieters, Klaus-Peter, Kieback, Bernd, pp.5-48, ISBN 978-3-540-681112-0, e-book: https: / / doi.org / 10.1007 / 978-3-540-68112-0_2.Preferred processes for producing silicon particles (B1) of the present invention are inert gas spraying, also known as gas atomization, pressurized water spraying, also known as liquid atomization or water atomization process, or melt spinning, also known as centrifugal atomization or rotary atomization.

[0075] The described process makes it possible to produce silicon metal particles with a wide range of particle sizes, particularly with an average particle size ranging from a few micrometers to a few millimeters. In addition, the silicon metal particles can be produced with widely varying particle shapes and highly variable particle size distributions, for example, "sputtered," i.e., highly irregular, nodular, oval, potato-shaped, round, or spherical.

[0076] The process for producing the silicon metal particles (B1) of the present invention should preferably be carried out so that the particles are obtained in a preferred predominantly nodular, "sputtered", ellipsoidal, potato-shaped, round or spherical shape, and are essentially free of sharp edges or pointed particles.

[0077] More preferably, the manufacturing process for the silicon metal particles (B1) of the present invention should be carried out so that the particles are obtained in their preferred, primarily elliptical, potato-shaped, round, or spherical shape, characterized by a width / length ratio (aspect ratio w / l) of preferably at least 0.76, preferably at least 0.77, more preferably at least 0.78, and particularly at least 0.79, and the particles are essentially free of "sputtered," nodular, sharp-edged, or pointed particles. In a subsequent process step, the solidified particles can be separated by size by commonly used processes, such as classification, sieving, or sorting. These processes allow for the removal of agglomerates and particles stuck together, but do not essentially destroy the particles. "Predominantly rounded" and "essentially free" are understood to mean that the presence of such particles is tolerated to the extent that it constitutes an "impurity" of the particles (B1) of the present invention at a content of 10% by weight or less, preferably 5% by weight or less, and does not interfere with the effect of the present invention.

[0078] The composition (M) of the present invention may contain, as filler (B), not only silicon metal particles (B1), but also a further thermally conductive filler (B2) consisting of a material having a thermal conductivity of at least 5 W / mK, and any further optional fillers (B3). The filler (B) here is any inorganic material that is solid, crystalline or amorphous at temperatures below 200°C.

[0079] The filler used in addition to metal silicon particles (B1) is preferably thermally conductive filler (B2).Examples of thermally conductive filler (B2) include magnesium oxide, metallic aluminum powder, metallic silver powder, zinc oxide, boron nitride, silicon carbide, aluminum nitride, aluminum hydroxide, aluminum oxide, graphite, etc.Preferred thermally conductive filler (B2) is aluminum powder, magnesium oxide, aluminum hydroxide, zinc oxide, and aluminum oxide.Particularly preferred thermally conductive filler (B2) is aluminum hydroxide, aluminum oxide, and zinc oxide.

[0080] Examples of optional further fillers (B3) are non-reinforcing fillers, i.e. preferably 50 ml 2 Fillers with a BET specific surface area of ​​up to 50 m / g, such as quartz, diatomaceous earth, calcium silicate, zirconium silicate, talc, kaolin, zeolites, barium sulfate, calcium carbonate, gypsum or glass powder, reinforcing fillers, i.e. 2 Fillers having a BET specific surface area of ​​more than 1 / g, such as fumed silica, precipitated silica, precipitated chalk, carbon black, such as furnace black and acetylene black, or graphite, which have a large BET specific surface area, hollow spherical fillers, such as ceramic microspheres, glass beads, or fibrous fillers. The mentioned fillers can be hydrophobized, for example, by treatment with organosilanes or organosiloxanes or stearic acid, or by etherification of hydroxyl groups to alkoxy groups.

[0081] The shape of the further fillers (B2) and / or (B3) is in principle not limited. The particles can be, for example, spherical, ellipsoidal, acicular, tubular, tabular, fibrous, "sputtered", nodular or irregularly shaped. They are preferably predominantly round, spherical, ellipsoidal, potato-shaped or irregularly shaped. The median diameter of the further fillers (B2) and / or (B3) is preferably in the range of 0.01 to 250 μm, more preferably in the range of 0.1 to 200 μm, particularly preferably in the range of 0.2 to 180 μm, in particular in the range of 0.4 to 150 μm.

[0082] A very high density filler (B) would increase the weight of the component very significantly, which is disadvantageous for use in, for example, aircraft and electric vehicles. Therefore, it is preferable to use a filler (B2) and / or (B3) having a density of 5.0 g / cm 3 or more. 3 or less, preferably 4.0 g / cm 3 or less, more preferably 3.0 g / cm 3 Materials having the following densities are preferred:

[0083] The composition (M) of the present invention preferably contains 24% by weight or less, more preferably 10% by weight or less, and more preferably 5.0 g / cm3 and particularly preferably contains no fillers (B2) and / or (B3) having a density above 1000 .mu.m.

[0084] In many applications, it is undesirable for a thermally conductive composition to have electrical conductivity, as this may lead to, for example, short circuits. The composition (M) of the present invention preferably has a resistance of at least 1 Ω·mm 2 The filler (B) contains only a filler having a specific resistance of 1 / m.

[0085] The total amount of filler (B) in the thermally conductive composition (M) of the present invention is 100 to 1900 parts by weight of (B) per 100 parts by weight of (A), preferably 150 to 1850 parts by weight of (B) per 100 parts by weight of (A), and more preferably 200 to 1800 parts by weight of (B) per 100 parts by weight of (A).

[0086] Preferably, at least 90% by weight, more preferably at least 95% by weight, particularly preferably at least 98% by weight of all fillers used in the inventive composition (M) are thermally conductive fillers (B1) and optionally (B2). In a particularly advantageous embodiment of the present invention, the inventive composition (M) comprises only thermally conductive fillers (B1) and optionally (B2).

[0087] In addition to the components (A) and (B) used, the composition (M) produced according to the present invention may also contain any further substances previously used in crosslinkable compositions and different from components (A) and (B), such as those selected from the group consisting of nitrogen-containing organosilicon compounds (C), non-reactive plasticizers (D), silicone resins (E), catalysts (F), adhesion promoters (G), water scavengers (H), additives (I), and aggregates (J).

[0088] Ingredients (C) The optional component (C) is preferably an organosilicon compound comprising units of the formula: D e Si(OR 4 ) d R 3 c O (4-c-d-e) / 2(V), [In the formula, R 3 are the same or different monovalent, optionally substituted, SiC-bonded nitrogen-free organic groups, R 4 may be the same or different and are a hydrogen atom or an optionally substituted hydrocarbon group, D may be the same or different and are monovalent SiC-bonding groups having at least one nitrogen atom that is not bonded to a carbonyl group (C=O); c is 0, 1, 2 or 3, preferably 0 or 1; d is 0, 1, 2 or 3, preferably 1, 2 or 3, more preferably 2 or 3; e is 0, 1, 2, 3 or 4, preferably 1; provided that the sum of c+d+e is 4 or less and at least one group D is present per molecule.

[0089] The organosilicon compound (C) optionally used according to the present invention can be either a silane, i.e. a compound of formula (V) in which c+d+e=4, or a siloxane, i.e. a compound containing units of formula (V) in which c+d+e≦3, although silanes are preferred.

[0090] base R 3 The example given for R is:

[0091] base R 3 is preferably a hydrocarbon group having 1 to 18 carbon atoms which may be substituted with a halogen atom, more preferably a hydrocarbon group having 1 to 5 carbon atoms, and particularly a methyl group.

[0092] optionally substituted hydrocarbon group R 4 The examples are given for the group R.

[0093] base R 4is preferably a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms which may be substituted with a halogen atom, more preferably a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, particularly a methyl group or an ethyl group.

[0094] Examples of the group D are groups of the formula H2N(CH2)3-, H2N(CH2)2NH(CH2)3-, H2N(CH2)2NH(CH2)2NH(CH2)3-, H3CNH(CH2)3-, C2H5NH(CH2)3-, C3H7NH(CH2)3-, C4H9NH(CH2)3-, C5H 11 NH(CH2)3-, CH 13 NH(CH2)3-, C7H 15 NH(CH2)3-, H2N(CH2)4-, H2N-CH2-CH(CH3)-CH2-, H2N(CH2)5-, cyclo-C5H9NH(CH2)3-, cyclo-C6H 11 NH(CH2)3-, phenyl-NH(CH2)3-, (CH3)2N(CH2)3-, (C2H5)2N(CH2)3-, (C3H7)2N(CH2)3-, (C4H9)2N(CH2)3-, (C5H 11 )2N(CH2)3-, (C6H 13 )2N(CH2)3-, (C7H 15 )2N(CH2)3-, H2N(CH2)-, H2N(CH2)2NH(CH2)-, H2N(CH2)2NH(CH2)2NH(CH2)-, H3CNH(CH2)-, C2H5NH(CH2)-, C3H7NH(CH2)-, C4H9NH(CH2)-, C5H 11 NH(CH2)-, CH 13 NH(CH2)-, C7H 15 NH(CH2)-, cyclo-C5H9NH(CH2)-, cyclo-C6H 11 NH(CH2)-, phenyl-NH(CH2)-, (CH3)2N(CH2)-, (C2H5)2N(CH2)-, (C3H7)2N(CH2)-, (C4H9)2N(CH2)-, (C5H 11 )2N(CH2)-, (C6H 13 )2N(CH2)-, (C7H 15)2N(CH2)-, (CHO)3Si(CH2)3NH(CH2)3-, (CHO)3Si(CH2)3NH(CH2)3-, (CHO)2(CH3)Si(CH2)3NH(CH2)3-, (CHO)2(CH3)Si(CH2)3NH(CH2)3-, and (CHO)2(CH3)Si(CH2)3NH(CH2)3- groups, as well as reaction products of the above primary amino groups with compounds containing double bonds or epoxide groups reactive towards primary amino groups.

[0095] The group D is preferably H2N(CH2)3-, H2N(CH2)2NH(CH2)3- or cyclo-CH 11 It is the NH(CH2)3- group.

[0096] Examples of silanes of formula (V) which may optionally be used in accordance with the present invention are HN(CH)-Si(OCH, HN(CH)-Si(OCH), HN(CH)-Si(OCH, HN(CH)-Si(OCH), HN(CH)-Si(OCH), HN(CH)-NH(CH)-Si(OCH), HN(CH)-NH(CH)-Si(OCH), HN(CH)-NH( CH2)3-Si(OCH3)2CH3, H2N(CH2)2NH(CH2)3-Si(OC2H5)2CH3, H2N(CH2)2NH(CH2)3-Si(OH)3, H2N(CH2)2NH(CH2 )3-Si(OH)2CH3, H2N(CH2)2NH(CH2)2NH(CH2)3-Si(OCH3)3, H2N(CH2)2N(CH2)2NH(CH2)3-Si(OC2H5)3, Cyclo-C6H 11 NH(CH2)3-Si(OCH3)3, cyclo-CH 11 NH(CH2)3-Si(OC2H5)3, cyclo-C6H 11 NH(CH2)3-Si(OCH3)2CH3, cyclo-C6H 11 NH(CH2)3-Si(OC2H5)2CH3, cyclo-C6H 11 NH(CH2)3-Si(OH)3, cyclo-CH 11NH(CH2)3-Si(OH)2CH3, phenyl-NH(CH2)3-Si(OCH3)3, phenyl-NH(CH2)3-Si(OC2H5)3, phenyl-NH(CH2)3-Si(OCH3)2CH3, phenyl-NH(CH2)3-Si(OC2H5)2CH3, phenyl-NH(CH2)3-Si(OH)3, phenyl-NH(CH2)3-Si(OH)2CH3, HN((CH2)3-Si(OCH3)3)2, HN((CH2)3-Si(OC2H5)3)2, HN((CH2)3-Si(OCH3)2CH3)2, HN((CH2)3-Si(OC2H5)2CH3)2, cyclo-C6H 11 NH(CH2)-Si(OCH3)3, cyclo-CH 11 NH(CH2)-Si(OC2H5)3, cyclo-C6H 11 NH(CH2)-Si(OCH3)2CH3, cyclo-C6H 11 NH(CH2)-Si(OC2H5)2CH3, cyclo-C6H 11 NH(CH2)-Si(OH)3, cyclo-CH 11 NH(CH2)-Si(OH)2CH3, phenyl-NH(CH2)-Si(OCH3)3, phenyl-NH(CH2)-Si(OC2H5)3, phenyl-NH(CH2)-Si(OCH3)2CH3, phenyl-NH(CH2)-Si(OC2H5)2CH3, phenyl-NH(CH2)-Si(OH)3 and phenyl-NH(CH2)-Si(OH)2CH3 and partial hydrolysates thereof, preferably H2N(CH2)2NH(CH2)3-Si(OCH3)3, H2N(CH2)2NH(CH2)3-Si(OC2H5)3, H2N(CH2)2NH(CH2)3-Si(OCH3)2CH3, cyclo-CH 11 NH(CH2)3-Si(OCH3)3, cyclo-CH 11 NH(CH2)3-Si(OC2H5)3 and cyclo-CH 11 NH(CH2)3-Si(OCH3)2CH3 and its partial hydrolysates, particularly preferred are H2N(CH2)2NH(CH2)3-Si(OCH3)3, H2N(CH2)2NH(CH2)3-Si(OCH3)2CH3, cyclo-CH 11 NH(CH2)3-Si(OCH3)3, cyclo-CH11 NH(CH2)3-Si(OCH3)2CH3 and its partial hydrolysates.

[0097] The organosilicon compound (C) optionally used according to the present invention may also play the role of a curing catalyst or co-catalyst in the composition (M) of the present invention.

[0098] In addition, the organosilicon compound (C) optionally used in accordance with the present invention may act as an adhesion promoter and / or a water scavenger.

[0099] The organosilicon compounds (C) optionally used in accordance with the present invention are commercially available products or can be prepared by standard chemical methods.

[0100] When the composition (M) of the present invention contains the component (C), the amount contained is preferably 0.1 to 25 parts by weight, more preferably 0.2 to 20 parts by weight, and particularly preferably 0.5 to 15 parts by weight, based on 100 parts by weight of the component (A). The composition (M) of the present invention preferably contains the component (C).

[0101] Ingredients (D) The optional non-reactive plasticizer (D) can be any non-reactive plasticizer used to date in crosslinkable organopolysiloxane compositions.

[0102] The non-reactive plasticizer (D) is preferably an organic compound selected from the group of substances consisting of: fully esterified aromatic or aliphatic carboxylic acids, fully esterified derivatives of phosphoric acid, fully esterified derivatives of sulfonic acids, branched or unbranched saturated hydrocarbons, Polystyrene, Polybutadiene, Polyisobutylene, Polyester or Polyether.

[0103] The non-reactive plasticizer (D) optionally used in accordance with the present invention is preferably one that does not react with water or any of the components (A) and (B) at temperatures below 80°C, is liquid at 20°C and 1013 hPa, and has a boiling point above 250°C at 1013 hPa.

[0104] Examples of the carboxylic acid ester (D) are phthalic acid esters such as dioctyl phthalate, diisooctyl phthalate, diisononyl phthalate, diisodecyl phthalate, and diundecyl phthalate, perhydrogenated phthalic acid esters such as diisononyl cyclohexane-1,2-dicarboxylate and dioctyl cyclohexane-1,2-dicarboxylate, adipic acid esters such as dioctyl adipate, benzoic acid esters, esters of trimellitic acid, glycol esters, and esters of saturated alkanediols such as 2,2,4-trimethylpentane-1,3-diol monoisobutyrate and 2,2,4-trimethylpentane-1,3-diol diisobutyrate.

[0105] Examples of polyethers (D) are polyethylene glycols, polyTHF and polypropylene glycols, preferably with an average molar mass Mn of 200 to 20000 g / mol.

[0106] The plasticizers (D) used preferably have a molar mass or, in the case of polymeric plasticizers, an average molar mass M of at least 200 g / mol, more preferably more than 500 g / mol, in particular more than 900 g / mol. n They preferably have a molar mass or average molar mass M of at most 20000 g / mol, more preferably at most 10000 g / mol, in particular at most 8000 g / mol. n It has.

[0107] When a non-reactive plasticizer (D) is used according to the present invention, the amount contained is preferably 5 to 300 parts by weight, more preferably 10 to 200 parts by weight, and particularly 20 to 150 parts by weight, based on 100 parts by weight of component (A). Preferably, no plasticizer (D) is used in the composition (M) of the present invention.

[0108] Ingredient (E) The silicone resin (E) optionally used according to the invention particularly preferably has the formula PhSiO 2 to an extent of at least 50% by weight, preferably to an extent of at least 70% by weight and in particular to an extent of at least 90% by weight, in each case based on the total number of units. 3 / 2 , PhSi(OR 5 )O 2 / 2 , PhSi(OR 5 )2O 1 / 2 , MeSiO 3 / 2 , MeSi(OR 5 )O 2 / 2 and / or MeSi(OR 5 )2O 1 / 2 where Ph is a phenyl group, Me is a methyl group, and R 5 is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms which may be substituted with a halogen atom, preferably an unsubstituted alkyl group having 1 to 4 carbon atoms. These resins preferably consist of three units having the above-mentioned PhSi functional group to an extent of at least 30% by weight, more preferably to an extent of at least 40% by weight.

[0109] The silicone resin (E) optionally used according to the invention particularly preferably has the formula PhSiO 2 to an extent of at least 50% by weight, preferably to an extent of at least 70% by weight and in particular to an extent of at least 90% by weight. 3 / 2 , PhSi(OR 5 )O 2 / 2 and / or PhSi(OR 5 )2O 1 / 2 and T units, all variables are as defined above.

[0110] The silicone resin (E) optionally used according to the invention preferably has an average molar mass (number average) M of at least 400 g / mol, more preferably at least 600 g / mol. n The average molar mass M of the silicone resin (E) n is preferably at most 400000 g / mol, more preferably at most 10000 g / mol, in particular at most 3000 g / mol.

[0111] The silicone resin (E) optionally used according to the invention can be either solid or liquid at 23°C and 1000 hPa, with liquid silicone resins (E) being preferred. The silicone resin (E) preferably has a viscosity of 10 to 100,000 mPa·s, preferably 50 to 50,000 mPa·s, in particular 100 to 20,000 mPa·s, in each case at 25°C.

[0112] The silicone resin (E) can be used either in pure form or in the form of a mixture in a suitable solvent, although its use in pure form is preferred.

[0113] Examples of phenylsilicone resins that can be used as component (E) are commercially available products such as various SILRES® types from Wacker Chemie AG, such as SILRES® IC368, SILRES® IC678 or SILRES® IC231 and SILRES® SY231.

[0114] If a resin (E) is used in the composition of the present invention (M), it is preferably present in an amount of at least 1 part by weight, more preferably at least 5 parts by weight, in particular at least 10 parts by weight, preferably at most 1000 parts by weight, more preferably at most 500 parts by weight, in particular at most 300 parts by weight, in each case based on 100 parts by weight of component (A).

[0115] Ingredient (F) The catalyst (F) optionally used in the composition (M) of the present invention can be any catalyst currently known for compositions that cure by silane condensation.

[0116] Examples of metal-containing curing catalysts (F) are organic titanium or tin compounds, such as titanate esters, e.g., tetrabutyl titanate, tetrapropyl titanate, tetraisopropyl titanate, and titanium tetraacetylacetonate, tin compounds, e.g., dibutyltin dilaurate, dibutyltin maleate, dibutyltin diacetate, dibutyltin dioctanoate, dibutyltin acetylacetonate, dibutyltin oxide, and the corresponding dioctyltin compounds.

[0117] Examples of metal-free curing catalysts (F) are basic compounds such as triethylamine, tributylamine, 1,4-diazabicyclo[2.2.2]octane, 1,5-diazabicyclo[4.3.0]non-5-ene, 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,1,2,2-tetramethylguanidine, 1,1,2,3-tetramethylguanidine, N,N-bis(N,N-dimethyl-2-aminoethyl)methylamine, N,N-dimethylcyclohexylamine, N,N-dimethylphenylamine, and N-ethylmorpholinine.

[0118] Acidic compounds may be used as catalysts (F), such as phosphoric acid and its partially esterified derivatives, toluenesulfonic acid, sulfuric acid, nitric acid or organic carboxylic acids, such as acetic acid and benzoic acid.

[0119] When catalyst (F) is used according to the present invention, the amount contained is preferably 0.01 to 20 parts by weight, more preferably 0.05 to 5 parts by weight, based on 100 parts by weight of component (A) in any case.

[0120] In one embodiment of the present invention, the optionally used catalyst (F) is a metal-containing curing catalyst, preferably a tin-containing catalyst. This embodiment of the present invention is particularly preferred when component (A) consists entirely or at least partly, i.e., to the extent of at least 90% by weight, preferably to the extent of at least 95% by weight, of compounds of formula (I) in which b is not equal to 1.

[0121] In the composition (M) of the invention, component (A) is completely or at least partially, i.e. to the extent of at least 10% by weight, preferably to the extent of at least 20% by weight, b is equal to 1 and R 1 consists of a compound of formula (I) where is defined as a hydrogen atom, the metal-containing catalyst (F), in particular the tin-containing catalyst, can preferably be omitted.

[0122] Ingredients (G) The adhesion promoter (G) optionally used in accordance with the present invention can be any adhesion promoter described to date for systems cured by silane condensation.

[0123] Examples of adhesion promoters (G) are epoxy silanes, for example glycidoxypropyltrimethoxysilane, glycidoxypropylmethyldimethoxysilane, glycidoxypropyltriethoxysilane or glycidoxypropylmethyldiethoxysilane, 2-(3-triethoxysilylpropyl)maleic anhydride, N-(3-trimethoxysilylpropyl)urea, N-(3-triethoxysilylpropyl)urea, N-(trimethoxysilylmethyl)urea, N-(methyldimethoxysilylmethyl)urea, N-(3-triethoxysilylmethyl)urea, N-(3-methyldiethoxysilylmethyl)urea, O-methylcarbamatomethylmethyldimethoxysilane, O-methylcarbamatomethyltrimethysilane, Examples of acryloyloxymethylsilane include acryloyloxymethyl methyldiethoxysilane, O-ethylcarbamatomethyl methyldiethoxysilane, O-ethylcarbamatomethyl triethoxysilane, 3-methacryloyloxypropyl trimethoxysilane, methacryloyloxymethyl trimethoxysilane, methacryloyloxymethyl methyldimethoxysilane, methacryloyloxymethyl triethoxysilane, methacryloyloxymethyl methyldiethoxysilane, 3-acryloyloxypropyl trimethoxysilane, acryloyloxymethyl trimethoxysilane, acryloyloxymethyl methyldimethoxysilane, acryloyloxymethyl triethoxysilane, acryloyloxymethyl methyldiethoxysilane, and partial condensates thereof.

[0124] When the composition (M) of the present invention contains an adhesion promoter (G), the amount contained is preferably 0.5 to 30 parts by weight, more preferably 1 to 10 parts by weight, based on 100 parts by weight of the crosslinkable composition (M) in any case.

[0125] Ingredients (H) The water scavenger (H) optionally used in accordance with the present invention can be any of the water scavenger described for systems cured by silane condensation.

[0126] Examples of water scavengers (H) are silanes such as vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenylmethyldimethoxysilane, tetraethoxysilane, O-methylcarbamatomethylmethyldimethoxysilane, O-methylcarbamatomethyltrimethoxysilane, O-ethylcarbamatomethylmethyldiethoxysilane, O-ethylcarbamatomethyltriethoxysilane, and / or partial condensates thereof and orthoesters such as 1,1,1-trimethoxyethane, 1,1,1-triethoxyethane, trimethoxymethane and triethoxymethane, with vinyltrimethoxysilane being preferred.

[0127] When the composition (M) of the present invention contains a water scavenger (H), the amount contained is preferably 0.5 to 30 parts by weight, more preferably 1 to 10 parts by weight, based on 100 parts by weight of the crosslinkable composition (M). The composition of the present invention preferably contains a water scavenger (H), more preferably vinyltrimethoxysilane and / or phenyltrimethoxysilane.

[0128] Component (I) The additive (I) optionally used according to the invention can be any additive known to date that is typical for silane crosslinking systems.

[0129] The additives (I) optionally used according to the invention are compounds different from the components mentioned so far, preferably antioxidants, UV stabilizers, such as so-called HALS compounds, fungicides, defoamers commercially available from, for example, Byk (Wesel, Germany), wetting agents commercially available from, for example, Byk (Wesel, Germany), or pigments.

[0130] When additive (I) is used for the production of composition (M) according to the present invention, which constitutes a preferred embodiment, the amount contained is preferably 0.01 to 30 parts by weight, more preferably 0.1 to 10 parts by weight, based in each case on 100 parts by weight of component (A).

[0131] Ingredients (J) The additional material (J) optionally used according to the invention is preferably a tetraalkoxysilane, such as tetraethoxysilane and / or a partial condensate thereof, a reactive plasticizer, a rheological additive, a flame retardant or an organic solvent.

[0132] Preferred reactive plasticizers (J) are compounds containing an alkyl chain with 6 to 40 carbon atoms and having a group reactive with compound (A). Examples are isooctyltrimethoxysilane, isooctyltriethoxysilane, N-octyltrimethoxysilane, N-octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, tetradecyltrimethoxysilane, tetradecyltriethoxysilane, hexadecyltrimethoxysilane and hexadecyltriethoxysilane.

[0133] The flame retardant (J) used can be any flame retardant typical of adhesive and sealant systems, preferably halogenated compounds and (partial) esters of phosphoric acid and its derivatives, in particular (partial) esters of phosphoric acid.

[0134] Examples of organic solvents (J) are low molecular weight ethers, esters, ketones, aromatic and aliphatic and optionally halogen-containing hydrocarbons and alcohols, the latter being preferred.

[0135] Preferably, no organic solvent (J) is added to the composition (M) of the present invention.

[0136] If one or more components (J) are used in the preparation of composition (M) according to the invention, the amount present is preferably 0.5 to 200 parts by weight, more preferably 1 to 100 parts by weight, in particular 2 to 70 parts by weight, in each case based on 100 parts by weight of component (A).

[0137] In a preferred embodiment, the composition (M) of the invention comprises: (A) 100 parts by weight of a compound of formula (I), (B1) 100 to 1900 parts by weight of filler (B1), (B2) 0 to 1000 parts by weight of a filler (B2), (B3) 0 to 500 parts by weight of a filler (B3), (C) 0.1 to 50 parts by weight of an organosilicon compound containing a unit of general formula (V), optionally (D) a non-reactive plasticizer; optionally (E) a silicone resin; optionally (F) a catalyst; optionally (G) an adhesion promoter; optionally (H) a water scavenger; optionally (I) an additive, and Optionally (J) aggregates.

[0138] In a more preferred embodiment, the composition (M) of the invention comprises: (A) 100 parts by weight of a compound of formula (I), (B1) 200 to 1500 parts by weight of filler (B1), (B2) 10 to 500 parts by weight of filler (B2), (B3) 0 to 200 parts by weight of a filler (B3), (C) 0.5 to 30 parts by weight of an organosilicon compound containing a unit of general formula (V), optionally (D) a non-reactive plasticizer; optionally (E) a silicone resin; optionally (F) a catalyst; (G) 0.5 to 30 parts by weight of a water scavenger, optionally (G) an adhesion promoter; optionally (H) a water scavenger; optionally (I) an additive, and Optionally (J) aggregates.

[0139] In a particularly preferred embodiment, the composition (M) of the invention comprises: (A) 100 parts by weight of a compound of formula (I), (B1) 300 to 1200 parts by weight of filler (B1), (B2) 50 to 400 parts by weight of filler (B2), (B3) 0 to 50 parts by weight of a filler (B3), (C) 0.5 to 30 parts by weight of an organosilicon compound containing a unit of general formula (V), optionally (D) a non-reactive plasticizer; optionally (E) a silicone resin; optionally (F) a catalyst; (G) 0.5 to 30 parts by weight of vinyltrimethoxysilane and / or phenyltrimethoxysilane, optionally (G) an adhesion promoter; optionally (H) a water scavenger; optionally (I) an additive, and Optionally (J) aggregates.

[0140] Composition (M) of the present invention preferably does not contain any components other than components (A) to (J). The components used according to the present invention can in each case be a single type of such component or a mixture of at least two specific types of components.

[0141] The thermally conductive composition (M) of the present invention preferably has a thermal conductivity of at least 1.0 W / mK, more preferably at least 2.0 W / mK, and particularly preferably at least 3.5 W / mK.

[0142] The viscosity (M) of the compositions of the invention can be varied over very wide ranges and can be adapted to the requirements of the use.

[0143] The density (M) of the composition of the present invention is preferably 4.5 g / cm 3 less than 4.0 g / cm 3 less than 3.3 g / cm 3 is less than.

[0144] The present invention further provides a process for preparing the composition (M) of the present invention by mixing the individual components by conventional continuous or discontinuous mixing processes of the prior art. Suitable mixing devices are all known devices. Examples include single- or double-screw continuous mixers, double rollers, Ross mixers, Hobart mixers, dental mixers, planetary mixers, kneaders, and Henschel mixers or similar mixers.

[0145] The composition (M) of the present invention is preferably prepared with the exclusion of water.

[0146] The composition (M) of the present invention is a one-component crosslinkable composition, depending on the application requirements in a particular case. However, the composition (M) produced according to the present invention may also be part of a two-component crosslinkable system, in which an OH-containing compound, such as water, is added to the second component.

[0147] The composition (M) of the present invention can be stored with the exclusion of water and can crosslink on the entry of water.

[0148] Therefore, the present invention further provides a silicone molded article obtainable by filling or applying the crosslinkable composition (M) and then crosslinking / curing it.

[0149] The normal water content of air is often sufficient for crosslinking the composition (M) of the present invention. The composition (M) of the present invention is preferably crosslinked at room temperature. If desired, they may also be crosslinked at temperatures higher or lower than room temperature, for example, from -5°C to 15°C or from 30°C to 50°C, and / or using a water concentration that exceeds the normal water content of air.

[0150] The moulded articles produced according to the invention preferably have an elongation at break of at least 100%, more preferably at least 200%, measured in each case according to DIN EN 53504-S1.

[0151] The molded article produced according to the present invention may be any molded article, such as a seal, a molded article, an extruded profile, a coating, an impregnation, a potting, a lens, a prism, a polygonal structure, a laminate layer or an adhesive layer.

[0152] The present invention further provides the use of the thermally conductive composition (M) of the present invention as a thermally conductive paste, gap filler, thermally conductive pad, thermally conductive adhesive, and potting compound.

[0153] The thermally conductive composition (M) of the present invention is ideal for this, as it allows very good dissipation of heat from heat generating or heat dissipating elements in electrical and / or electronic devices.

[0154] For this purpose, the thermally conductive composition (M) of the present invention is applied to a heat generating element or a heat radiating element, or the thermally conductive composition (M) of the present invention, which has already been crosslinked or cured, is introduced between the heat generating element and / or the heat radiating element as a molded article, for example as a thermally conductive pad.

[0155] Typical heat generating elements are found in electrical and electronic equipment and electronic devices, such as power supply transistors, power modules, transistors, thermocouples, and temperature sensors, and heat generating electronic components, such as integrated circuit components, such as CPUs and batteries, in power supply units. In the automotive industry, heat generating elements are particularly found near lithium-ion batteries, charging infrastructure, and control devices and sensors. Suitable heat dissipators include heat distributors and heat sinks, as well as heat dissipation components such as cooling fins. Introducing the thermally conductive composition (M) between the heat generating element and the heat dissipation element can efficiently transfer heat from the heat generating element to the heat dissipation element. This allows for effective cooling of the heat generating element.

[0156] The thermally conductive composition (M) of the present invention is particularly suitable for use as a gap filler for lithium ion batteries in electric vehicles and as a potting compound for, for example, electronic components in electric vehicles. [Example]

[0157] The following examples illustrate how the present invention may be practiced, but are not intended to limit the invention to the specifics disclosed therein.

[0158] Unless otherwise specified, all work steps in the following examples are carried out at ambient pressure, i.e., 1013 hPa, at room temperature, i.e., 23°C, or at the temperature established when the reactants are mixed at room temperature without additional heating or cooling. Crosslinking of composition (M) is carried out at a relative humidity of 50%. Additionally, all parts and percentages listed are by weight unless otherwise specified.

[0159] Measurement of thermal conductivity lambda The thermal conductivity is determined according to ASTM D5470-12 using a TIM Tester (Steinbeis Transferzentrum Waermemanagement in der Elektronik, Lindenstr. 13 / 1, 72141 Walddorfhäeslach, Germany). The thermal resistance of a sample placed between two test cylinders is determined by constant heat flow. The effective thermal conductivity of the sample is calculated over the sample layer thickness.

[0160] For the measurements, the sample is applied using a stencil and the measuring cylinder is manually adjusted to a thickness of 1.9-2.0 mm, after which excess material is removed. Thermal conductivity measurements are carried out at constant gaps of 1.8-1.6-1.4-1.2-1.0 mm. Evaluation is carried out via the integrated report generation function. After validity tests (linear determination coefficient >0.998), the thermal conductivity is calculated as the effective thermal conductivity λ in W / (mK). eff Display as.

[0161] Particle size / shape analysis Analysis of particle size (median diameter × 50), particle size distribution (parameters: standard deviation sigma and distribution width span), and particle shape (parameter: aspect ratio w / l) was performed using a Camsizer X2 (measurement principle: dynamic image analysis) manufactured by Retsch Technology in accordance with ISO 13322-2 and ISO 9276-6 (analysis type: dry measurement of powders and granules; measurement range: 0.8 μm to 30 mm; compressed air dispersion with X-Jet; dispersion pressure = 0.3 bar). c min The evaluation was carried out on a volume basis according to the model.

[0162] [Example 1] Preparation of a mixture of silane-terminated polypropylene glycols as component (A) In a 2000 ml three-necked flask equipped with a thermometer, reflux condenser, stirrer and heating means, first a solution of 18000 g / mol of 1,000 ml of ammonium hydroxide with a number-average molar mass M n400.0 g (22.2 mmol) of hydroxy-terminated polypropylene glycol (commercially available under the name Acclaim® 18200 from Covestro AG, Leverkusen, Germany) having the formula (I) is added and dried at 80° C. and 1 mbar for 2 hours with stirring. The vacuum is then released with nitrogen. The entire following reaction is carried out under a nitrogen inert gas atmosphere.

[0163] To perform silane termination, 27.4 g (133.2 mmol) of 3-isocyanatopropyltrimethoxysilane (available commercially under the name Geniosil® GF40 from Wacker Chemie AG, Munich, Germany) is first added dropwise to the dry polyether at 80 °C, followed by the addition of 0.31 g of Borchi catalyst 315 (a bismuth neodecanoate-containing catalyst from Borchers) using an Eppendorf pipette. Immediately after adding the catalyst, the reaction mixture is heated to 82–83 °C. It is then stirred at a temperature of 80 °C.

[0164] After 60 minutes, the average molar mass M of 5000 g / mol n 484 g (96.8 mmol) of monohydroxy-monobutoxy-terminated polypropylene glycol having the formula (commercially available under the name Preminol® S1005 from AGC Chemicals Europe, LTD, Amsterdam, The Netherlands) is added at a constant temperature. The mixture is then stirred for an additional 60 minutes at 80° C. The reaction mixture is then cooled to room temperature, and a sample is taken and examined by IR analysis for any residual isocyanatosilane that may still be present. The sample is free of isocyanate.

[0165] [Example 2] Preparation of silane-terminated polypropylene glycol as component (A) A 2000 ml four-neck flask equipped with a dropping funnel, reflux condenser, thermometer, stirrer, and heating means is initially charged with 1080 g (270 mmol) of a doubly hydroxy-terminated polypropylene glycol having a number average molecular weight of 4000 g / mol (commercially available under the name Acclaim® 4200 from Covestro AG, Leverkusen, Germany) and dried at 80° C. and 1 mbar for 2 hours while stirring. The vacuum is then released with nitrogen. The entire following reaction is carried out under a nitrogen inert gas atmosphere.

[0166] To perform the silane termination, 91.4 g (567 mmol) of α-isocyanatomethylmethyldimethoxysilane (commercially available under the name Geniosil® XL42 from Wacker Chemie AG, Munich, Germany) is added dropwise to the dry polyether over 15 minutes with stirring at 80°C. The temperature remains at 80°C. Then, 0.17 g of Borchi catalyst 315 (a bismuth neodecanoate-containing catalyst from Borchers) is added using an Eppendorf pipette. This corresponds to a value of 150 ppm of catalyst based on the total weight of the reaction mixture. A slight increase in the temperature of the reaction mixture occurs (<5°C). The mixture is then stirred at 80°C for 2 hours. After this time, a small isocyanate peak is still present in the IR spectrum of the reaction mass.

[0167] Then, the average molar mass M of 350 g / mol n 18.9 g (54 mmol) of monohydroxy-monomethoxy-terminated polyethylene glycol (commercially available under the name PEG350M from Clariant, Gendorf, Germany) having the formula: is added at a constant temperature. The mixture is then stirred for an additional 15 minutes at 80° C. The reaction mixture is then cooled to room temperature and a sample is taken and examined by IR analysis for any residual isocyanatosilane that may still be present. The sample is isocyanate-free.

[0168] [Example 3a] Preparation of thermally conductive composition (M) of the present invention In a laboratory planetary mixer manufactured by PC-Laborsystem, equipped with two cross-arm mixers, terminated at one end, the mixture was heated to an average molar mass (M n 34 g of polypropylene glycol silane (commercially available under the name Geniosil® XM25 from Wacker Chemie AG, Munich, Germany) having terminal groups of the formula -OC(═O)-NH-(CH2)3-Si(OCH3)3 is homogenized with 4.8 g of vinyltrimethoxysilane and 1.0 g of a stabilizer mixture (a mixture of 20% Irganox® 1135 (CAS number 125643-61-0), 40% Tinuvin® 571 (CAS number 23328-53-2), and 40% Tinuvin® 765 (CAS number 41556-26-7) (commercially available under the name Tinuvin® B75 from BASF SE, Germany) at about 25° C. for 2 minutes at 200 rpm.

[0169] 136 g of primary circular silicon particles with a median diameter x50 of 49.1 μm, a distribution width span of 0.96 (x10 = 21.8 μm, x90 = 69.0 μm), and an aspect ratio w / l of 0.86, 136 g of primary circular silicon particles with a median diameter x50 of 82.9 μm, a distribution width span of 0.85 (x10 = 55.7 μm, x90 = 125.8 μm), and an aspect ratio w / l of 0.83, and 87 g of zinc oxide (commercially available from USZinc (Houston, USA) under the name Zinc Oxide Grade AZO 66) are continuously stirred at 600 rpm for 1 minute. Finally, 1.2 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane is added and mixed at 200 rpm for 1 minute. Finally, the mixture is homogenized and stirred at 100 mbar pressure for 2 minutes at 600 rpm and 1 minute at 200 rpm, avoiding air bubbles.

[0170] The prepared composition is transferred to an airtight closable container and is suitable for use, inter alia, as a thermally conductive adhesive, gap filler, potting compound, or, in the cured state, as a thermally conductive pad.

[0171] [Example 3b] Preparation of thermally conductive composition (M) of the present invention The procedure was the same as in Example 3a, except that as component (A), 34 g of Geniosil® XM25 was replaced with the same amount of the mixture of silane-terminated polypropylene glycols prepared in Example 1.

[0172] Again, the prepared composition is transferred to an airtight closable container and is suitable for use as, inter alia, a thermally conductive adhesive, gap filler, potting compound, or, in the cured state, as a thermally conductive pad.

[0173] [Example 3c] Preparation of thermally conductive composition (M) of the present invention The procedure was the same as in Example 3a, except that as component (A), 34 g of Geniosil® XM25 was replaced with the same amount of silane-terminated polypropylene glycol prepared in Example 2.

[0174] Again, the prepared composition is transferred to an airtight closable container and is suitable for use as, inter alia, a thermally conductive adhesive, gap filler, potting compound, or, in the cured state, as a thermally conductive pad.

[0175] [Comparative Example 1a] Preparation of a non-inventive moisture-curable composition In a PC-Laborsystem laboratory planetary mixer equipped with two cross-arm mixers, 95.8 g of Geniosil® XM25 are homogenized at 200 rpm for 2 minutes at about 25° C. with 2.0 g of vinyltrimethoxysilane, 1.0 g of a stabilizer mixture (a mixture of 20% Irganox® 1135 (CAS number 125643-61-0), 40% Tinuvin® 571 (CAS number 23328-53-2) and 40% Tinuvin® 765 (CAS number 41556-26-7), commercially available from BASF SE (Germany) under the name Tinuvin® B75), 1.0 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and 0.2 g of dioctyltin dilaurate.

[0176] The prepared composition is transferred into an airtight closable container.

[0177] [Comparative Example 1b] Preparation of a non-invention moisture-curable composition The procedure was the same as in Comparative Example 1a, except that as component (A), the mixture of the same amounts of silane-terminated polypropylene glycol prepared in Example 1 was used instead of Geniosil® SX25.

[0178] Again, the prepared composition is transferred into an airtight closable container.

[0179] [Comparative Example 1c] Preparation of a non-inventive moisture-curable composition The procedure was the same as in Comparative Example 1a, except that as component (A), the same amount of silane-terminated polypropylene glycol prepared in Example 2 was used instead of Geniosil® SX25.

[0180] [Comparative Example 2a] Preparation of a non-invention thermally conductive composition In a PC-Laborsystem laboratory planetary mixer equipped with two cross-arm mixers, 34 g of Geniosil® XM25 are homogenized with 4.8 g of vinyltrimethoxysilane and 1.0 g of a stabilizer mixture (a mixture of 20% Irganox® 1135 (CAS number 125643-61-0), 40% Tinuvin® 571 (CAS number 23328-53-2) and 40% Tinuvin® 765 (CAS number 41556-26-7), commercially available from BASF SE (Germany) under the name Tinuvin® B75) for 2 minutes at 200 rpm at about 25°C.

[0181] 136 g of primarily circular aluminum oxide particles with a median diameter x 50 μm (commercially available from Showa Denko, Tokyo, under the name Alunabeads™ CB A50), 136 g of calcined aluminum oxide with a median diameter x 50 μm (commercially available from Almatis, Ludwigshafen, Germany, under the name Allumina CL 3000 SG), and 87 g of zinc oxide (commercially available from USZinc, Houston, USA, under the name Zinc Oxide Grade AZO 66) were continuously mixed at 600 rpm for 1 minute. Finally, 1.2 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane was added and mixed at 200 rpm for 1 minute. Finally, the mixture was homogenized and stirred at 100 mbar pressure for 2 minutes at 600 rpm and 1 minute at 200 rpm, avoiding air bubbles.

[0182] The prepared composition is transferred into an airtight closable container.

[0183] [Comparative Example 2b] Preparation of non-invention thermally conductive composition (M) The procedure was the same as in Comparative Example 2a, except that as component (A), 34 g of Geniosil® SX25 was replaced with the same amount of the mixture of silane-terminated polypropylene glycols prepared in Example 1.

[0184] Again, the prepared composition is transferred into an airtight closable container.

[0185] [Comparative Example 2c] Preparation of non-invention thermally conductive composition (M) The procedure was the same as in Comparative Example 2a, except that as component (A), the same amount of silane-terminated polypropylene glycol prepared in Example 2 was used instead of 34 g of Geniosil® SX25.

[0186] Again, the prepared composition is transferred into an airtight closable container.

[0187] [Example 4] Measurement of thermal conductivity The thermal conductivities of the compositions (M) prepared in Examples 3a to 3c and Comparative Examples 1a to 1c and 2a to 2c were measured as described above. The results are shown in Table 1.

[0188] [Table 1]

[0189] Example 5: Characterization of samples from Examples 3b and 3c Skin Formation Time (SFT) To determine the skin formation time, the crosslinkable compositions obtained in the examples are applied to a PE film in a layer 2 mm thick and stored under standard climatic conditions (23°C and 50% relative humidity). During curing, the formation of a skin is checked every 5 minutes. This is done by carefully placing a dry laboratory spatula on the surface of the sample and pulling upwards. If the sample sticks to the spatula, a skin has not yet formed. If no sample sticks to the spatula, a skin has formed and the time is recorded. The results are shown in Table 2.

[0190] Mechanical properties Each composition was spread to a depth of 2 mm onto a ground Teflon panel and allowed to cure for 2 weeks at 23°C and 50% relative humidity.

[0191] The Shore A hardness is determined in accordance with DIN EN 53505.

[0192] The tensile strength is determined in accordance with DIN EN 53504-S1.

[0193] The elongation at break is determined in accordance with DIN EN 53504-S1.

[0194] The results are shown in Table 2.

[0195] [Table 2]

Claims

1. A crosslinkable thermally conductive composition (M), 100 parts by weight of at least one compound (A) of the following formula: Y-[(CR １ ２ ) ｂ -SiR ａ (OR ２ ) ３－ａ ] ｘ (I) [In the formula, Y is an x-valent organic polymeric group attached through nitrogen, oxygen, sulfur, or carbon; R may be the same or different and is a monovalent optionally substituted hydrocarbon group; R １ are the same or different and are hydrogen atoms or monovalent optionally substituted hydrocarbon radicals which can be bonded to a carbon atom via nitrogen, phosphorus, oxygen, sulfur or a carbonyl group; R ２ may be the same or different and are a hydrogen atom or a monovalent optionally substituted hydrocarbon group, x is an integer from 1 to 10; a may be the same or different and is 0, 1 or 2; b may be the same or different and is an integer from 1 to 10. 100 to 1900 parts by weight of at least one filler (B); wherein at least 30% by weight of all fillers (B) consist of metal silicon particles (B1).

2. 2. The crosslinkable thermally conductive composition (M) according to claim 1, wherein at least 40% by weight of all fillers (B) consists of metal silicon particles (B1).

3. 3. A crosslinkable thermally conductive composition (M) according to claim 1, wherein the filler (B) comprises at least one further thermally conductive filler (B2) consisting of a material having a thermal conductivity of at least 5 W / mK.

4. 4. A crosslinkable thermally conductive composition (M) according to claim 3, wherein at least 60% by weight of the filler (B) consists of metal silicon particles (B1) and further fillers (B2).

5. The crosslinkable thermally conductive composition (M) according to any one of claims 1 to 4, wherein the silicon particles (B1) comprise a fraction of particles having a diameter of 20 µm or less, which fraction is less than 20 wt%, based on the total amount of the silicon particles (B1).

6. A process for producing a crosslinkable thermally conductive composition (M) according to any one of claims 1 to 5, wherein the individual components are mixed continuously or discontinuously.

7. 7. The process of claim 6, wherein the preparation is carried out with the exclusion of moisture.

8. A silicone molded article obtainable by filling or applying the crosslinkable thermally conductive composition (M) according to any one of claims 1 to 5, followed by crosslinking / curing.

9. Use of the crosslinkable thermally conductive composition (M) according to any one of claims 1 to 5 as a thermally conductive paste, gap filler, thermally conductive adhesive, and potting compound.

10. Use of the silicone molded article according to claim 8 as a heat conduction pad.

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