Light metal alloy-containing thermal conductive paste

Abstract

The present invention relates to a crosslinkable thermally conductive silicone composition (Y), which comprises the following: 5 to 60 volume % of a crosslinkable silicone composition (S), and 40 to 95% by volume of at least one thermally conductive filler (Z) having a thermal conductivity of at least 5 W / mK, provided that The crosslinkable thermally conductive silicone composition (Y) has a thermal conductivity of at least 0.6 W / mK, At least 20% by volume of metallic light metal alloy particles present as thermally conductive filler (Z) have the following characteristics: a) their median particle size x50 is in the range of 30-150 μm; b) they are produced via a melting process in the final production step and have a predominantly rounded surface profile; c) Their distribution span SPAN ((x90-x10) / x50) must be at least 0.40 The present invention relates to a crosslinkable thermally conductive silicone composition (Y) and its preparation and use.

Description

[Technical field]

[0001] The present invention relates to a thermally conductive silicone composition, and to its preparation and use. [Background technology]

[0002] Thermally conductive silicone compositions are widely used in thermal management in the automotive and electronics industries. Examples of important display forms include thermally conductive adhesives, thermally conductive pads, gap fillers and encapsulation compounds. Among the applications mentioned, gap fillers for lithium-ion batteries in electric vehicles are by far the most used in terms of quantity. Gap fillers are thermally conductive elastomers that completely and persistently fill the voids caused by manufacturing tolerances, build height differences or different expansion coefficients, and minimize the thermal resistance between, for example, electronic components and cooling jackets or heat sinks.

[0003] The art includes various thermally conductive fillers that are added to silicones to increase thermal conductivity. However, these have significant drawbacks. Ceramic fillers, such as aluminum oxide, have very high densities and therefore add very significant weight to the part. They are also relatively expensive. Many thermally conductive metal fillers, such as finely divided copper and silver particles, are also unsuitable for gap fillers due to their high density and cost.

[0004] Many of the additional fillers with high thermal conductivity, such as carbon nanotubes, boron nitride and aluminum nitride, can only be used to a limited extent, or in small amounts, or in specific applications, due to their relatively high cost.

[0005] The prior art includes various thermally conductive silicone compositions that contain metal particles as thermally conductive fillers.The use of chemically pure metal particles is often disadvantageous.Metal particles, for example, based on copper, silver or gold, have high thermal conductivity, but significantly increase the weight and cost of parts.Aluminum particles have low density and high thermal conductivity, but their high electrical conductivity makes them unsuitable for many applications, for example, electronics or electromobility.Chemically pure silicon particles are electrically insulating, but are very brittle, have high Mohs hardness, and are therefore very abrasive.

[0006] The use of alloys allows for the integration of advantageous properties of different metals and the production of new compounds with improved properties.

[0007] The advantageous properties of light metals, especially metal alloys based on aluminum and silicon, are described, for example, in US2001051673, US4292223, CN109749427, CN109749292.

[0008] However, prior art metal alloy particles are unsuitable for use as gap fillers in lithium ion batteries for electric vehicles.

[0009] US2001051673 describes the advantageous properties of alloy particles having an average particle size of 0.5-20 μm. However, the use of such finely divided metal particles is disadvantageous because such small particles have a relatively low minimum ignition energy and therefore pose a risk of dust explosion, requiring complex and costly safety measures in industrial processing. Also, gap fillers containing such finely divided alloy particles do not achieve the required fire properties according to UL94V-0.

[0010] It has also been found that gap fillers containing alloy particles having a relatively narrow particle size distribution do not achieve the required fire properties per UL94 V0.

[0011] The disadvantage of ground alloy particles is that such particles have a high surface area and bind a very large amount of polymer. This increases the viscosity of the silicone composition very significantly. It is only possible to produce mixtures with relatively low filler levels and low thermal conductivity. At higher filler levels, the composition becomes very hard and can no longer be processed by conventional methods, for example with a dispenser. It has also been found that silicone compositions containing ground alloy particles are relatively flammable. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] US Patent Application Publication No. 2001 / 051673 [Patent Document 2] U.S. Pat. No. 4,292,223 [Patent Document 3] China Patent Publication No. 109749427 [Patent Document 4] China Patent Application Publication No. 109749292 Summary of the Invention [Problem to be solved by the invention]

[0013] It was therefore an object of the present invention to provide a thermally conductive silicone elastomer composition which does not exhibit the above-mentioned drawbacks of the prior art and which combines the properties of low density, low cost and high thermal conductivity. [Means for solving the problem]

[0014] This object is achieved by the crosslinkable heat-conductive silicone composition (Y) according to the invention, which contains relatively large light metal alloy particles having an average particle size of 25 to 150 μm, a predominantly rounded surface shape and at the same time a particularly large or wide particle distribution range. Quite surprisingly, it has been found in experiments that these silicone compositions (Y) according to the invention have a clearly reduced flammability.

[0015] In the context of the present invention, light metal alloy particles with a "predominantly rounded surface shape" are understood to mean those having a spherical to elliptical, irregular or nodular shape and at the same time having a smooth and curved surface. Figures 1a-1c show, by way of example, the inventive predominantly rounded surface shape of these light metal alloy particles. The inventive light metal alloy particles with a predominantly rounded surface shape are produced by a melting process. In other words, the inventive light metal alloy particles must be obtained by solidification from the melt at the final stage of production and not by mechanical comminution of a solid material. This can be done, for example, by plasma rounding or by atomization of the melt. Here, atomization is the preferred process.

[0016] Non-inventive light metal alloy particle shapes are shown by way of example in Figures 2a and 2b with angular and pointed particle surfaces, which are produced by crushing or grinding or grinding methods.

[0017] Thus, the metallic light metal alloy particles of the present invention are neither angular nor sharp-edged, but the inclusion of such particles as impurities does not prevent the inventive action of the present invention.

[0018] The present invention relates to a crosslinkable thermally conductive silicone composition (Y), which comprises the following: 5 to 60 volume % of a crosslinkable silicone composition (S), and 40 to 95% by volume of at least one thermally conductive filler (Z) having a thermal conductivity of at least 5 W / mK, provided that The crosslinkable thermally conductive silicone composition (Y) has a thermal conductivity of at least 0.6 W / mK, At least 20% by volume of metallic light metal alloy particles present as thermally conductive filler (Z) have the following characteristics: a) their median particle size x50 is in the range of 25 to 150 μm; b) they are produced via a melting process in the final manufacturing step and have a predominantly rounded surface profile; c) providing a crosslinkable thermally conductive silicone composition (Y) in which the distribution range SPAN ((x90-x10) / x50) is at least 0.40;

[0019] In the context of the present invention, the terms "heat-conducting" and "thermally conductive" are equivalent.

[0020] In the context of the present invention, a thermally conductive filler (Z) is understood to mean any filler having a thermal conductivity of at least 5 W / mK.

[0021] In the context of the present invention, thermally conductive silicone compositions (Y) are understood to mean silicone compositions which are characterized in that they have a thermal conductivity of at least 0.6 W / mK, which is clearly greater than the thermal conductivity of polydimethylsiloxanes without fillers and additives, typically about 0.2 W / mK.

[0022] In the context of the present invention, all parameters describing particle size (parameter: median particle size x 50) or particle size distribution (parameter: distribution range SPAN) are based on volume-based distribution. The mentioned indices can be determined by dynamic image analysis, for example according to ISO 13322-2 and ISO 9276-6, for example using a Camsizer X2 from Retsch Technology.

[0023] In order to avoid excessive page count in the description of the present invention, only preferred embodiments of individual features are detailed in the text.

[0024] However, the expert reader will explicitly understand that this disclosure methodology also expressly discloses and explicitly desires any combination of different levels of preference. [Brief description of the drawings]

[0025] [Figure 1a] These light metal alloy particles exhibit the predominantly rounded surface shape of the present invention. [Figure 1b] These light metal alloy particles exhibit the predominantly rounded surface shape of the present invention. [Figure 1c] These light metal alloy particles exhibit the predominantly rounded surface shape of the present invention. [Figure 2a] 1 shows a non-inventive light metal alloy particle shape having angular particle surfaces. [Figure 2b] 1 shows a non-inventive light metal alloy particle shape having a pointed particle surface. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] <Crosslinkable Silicone Composition (S)> As crosslinkable silicone composition (S) it is possible to use silicones known to the skilled person from the prior art, such as addition-crosslinking, peroxide-crosslinking, condensation-crosslinking or radiation-crosslinking compositions (S). It is preferred to use addition-crosslinking or peroxide-crosslinking silicone compositions (S).

[0027] Peroxide crosslinking silicone compositions (S) have been known to those skilled in the art for a long time.In the simplest case, they comprise at least one organopolysiloxane with at least two crosslinkable groups per molecule, for example methyl or vinyl groups, and at least one suitable organic peroxide catalyst.When the composition of the present invention is crosslinked by free radicals, the crosslinking agent used is an organic peroxide that functions as a source of free radicals. Examples of organic peroxides are acyl peroxides such as dibenzoyl peroxide, bis(4-chlorobenzoyl)peroxide, bis(2,4-dichlorobenzoyl)peroxide and bis(4-methylbenzoyl)peroxide, alkyl and aryl peroxides such as di-tert-butylperoxide, 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, dicumyl peroxide and 1,3-bis(tert-butylperoxyisopropyl)benzene, perketals such as 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, peresters such as diacetylperoxydicarbonate, tert-butylperbenzoate, tert-butylperoxy-isopropylcarbonate, tert-butylperoxyisononanoate, dicyclohexylperoxydicarbonate and 2,5-dimethylhexane, 2,5-diperbenzoate.

[0028] One type of organic peroxide can be used. It is also possible to use a mixture of at least two different types of organic peroxide.

[0029] It is particularly preferred to use addition-crosslinking silicone compositions (S).

[0030] The addition-crosslinking silicone compositions (S) used according to the invention are known in the prior art and in the simplest case comprise: (A) at least one linear compound having a group having an aliphatic carbon-carbon multiple bond; (B) at least one linear organopolysiloxane having Si-bonded hydrogen atoms; Or, instead of (A) and (B): (C) at least one linear organopolysiloxane having an aliphatic carbon-carbon multiple bond and a SiC-bonded group having a Si-bonded hydrogen atom, and (D) at least one hydrosilylation catalyst.

[0031] The addition-crosslinking silicone composition (S) can be a one-component silicone composition or a two-component silicone composition.

[0032] In a two-component silicone composition (S), the two components of the addition-crosslinked silicone composition (S) of the present invention can generally contain any of the components in any combination, provided that one component does not simultaneously contain a siloxane having an aliphatic multiple bond, a siloxane having Si-bonded hydrogen, and a catalyst, i.e., does not essentially simultaneously contain components (A), (B) and (D), or (C) and (D).

[0033] As is well known, the compounds (A) and (B) or (C) used in the addition crosslinking silicone composition (S) of the present invention are selected so that they can crosslink.For example, compound (A) has at least two aliphatically unsaturated groups, and (B) has at least three Si-bonded hydrogen atoms, or compound (A) has at least three aliphatically unsaturated groups, and siloxane (B) has at least two Si-bonded hydrogen atoms, or instead of compounds (A) and (B), siloxane (C) is used, which has aliphatically unsaturated groups and Si-bonded hydrogen atoms in the above ratio.Also possible is a mixture of (A), (B) and (C) which has aliphatically unsaturated groups and Si-bonded hydrogen atoms in the above ratio.

[0034] The addition-crosslinking silicone composition (S) of the present invention typically contains 30 to 99.0 wt%, preferably 40 to 95 wt%, more preferably 50 to 90 wt% of (A). The addition-crosslinking silicone composition (S) of the present invention typically contains 1 to 70 wt%, preferably 3 to 50 wt%, more preferably 8 to 40 wt% of (B). When the addition-crosslinking silicone composition of the present invention contains component (C), typically at least 30 wt%, preferably at least 45 wt%, more preferably at least 58 wt% of (C) is present, based on the total amount of the addition-crosslinking silicone composition (S) of the present invention.

[0035] The compound (A) used according to the present invention may preferably comprise a silicon-free organic compound having at least two aliphatically unsaturated groups, and an organosilicon compound having at least two aliphatically unsaturated groups, or a mixture thereof.

[0036] Examples of the silicon-free organic compound (A) are 1,3,5-trivinylcyclohexane, 2,3-dimethyl-1,3-butadiene, 7-methyl-3-methylene-1,6-octadiene, 2-methyl-1,3-butadiene, 1,5-hexadiene, 1,7-octadiene, 4,7-methylene-4,7,8,9-tetrahydroindene, methylcyclopentadiene, 5-vinyl-2-norbornene, bicyclo [2.2.1]Hepta-2,5-diene, 1,3-diisopropenylbenzene, polybutadiene containing vinyl groups, 1,4-divinylcyclohexane, 1,3,5-triallylbenzene, 1,3,5-trivinylbenzene, 1,2,4-trivinylcyclohexane, 1,3,5-triisopropenylbenzene, 1,4-divinylbenzene, 3-methyl-1,5-heptadiene, 3-phenyl-1,5 -hexadiene, 3-vinyl-1,5-hexadiene and 4,5-dimethyl-4,5-diethyl-1,7-octadiene, N,N'-methylenebisacrylamide, 1,1,1-tris(hydroxymethyl)propane triacrylate, 1,1,1-tris(hydroxymethyl)propane trimethacrylate, tripropylene glycol diacrylate, diallyl ether, diallylamine, diallyl carbonate, N,N'-diallyl urea, triallylamine, tris(2-methylallyl)amine, 2,4,6-triallyloxy-1,3,5-triazine, triallyl-s-triazine-2,4,6(1H,3H,5H)-trione, diallyl malonate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, poly(propylene glycol) methacrylate.

[0037] The addition-crosslinking silicone composition (S) of the present invention preferably contains as component (A) at least one aliphatically unsaturated organosilicon compound, and it is possible to use any of the aliphatically unsaturated organosilicon compounds that have been used up to now in addition-crosslinking compositions, such as silicone block copolymers having urea segments, silicone block copolymers having amide segments and / or imide segments and / or esteramide segments and / or polystyrene segments and / or silarylene segments and / or carborane segments, and silicone graft copolymers having ether groups.

[0038] The organosilicon compounds (A) used having SiC-bonded groups with aliphatic carbon-carbon multiple bonds are preferably linear or branched organosiloxanes composed of units of the general formula (I). R 4 a R 5 b SiO (4-a-b) / 2 (I) [In the formula, R 4 are independently the same or different and are organic or inorganic groups that do not contain aliphatic carbon-carbon multiple bonds; R 5 are independently the same or different and are monovalent substituted or unsubstituted SiC-bonded hydrocarbyl groups having at least one aliphatic carbon-carbon multiple bond; a is 0, 1, 2 or 3; b is 0, 1 or 2; However, the sum of a+b is 3 or less, and there are at least two R 5 There is a group.

[0039] R 4 The groups can be monovalent or polyvalent groups, and polyvalent groups, such as divalent, trivalent and tetravalent groups, can connect multiple, such as 2, 3 or 4, siloxy units of formula (I) together.

[0040] R 4Further examples of the monovalent groups -F, -Cl, -Br, -OR 6 , -CN, -SCN, -NCO and SiC-bonded substituted or unsubstituted hydrocarbyl groups (which may be interrupted by oxygen atoms or C(O)- groups), and divalent groups bonded to Si at either end as in formula (I). 4 When the group contains a SiC-substituted hydrocarbyl group, preferred substituents are halogen atoms, phosphorus-containing groups, cyano groups, -OR 6 , -NR 6 -, -NR 6 2, -NR 6 -C(O)-NR 6 2. -C(O)-NR 6 2. -C(O)R 6 , -C(O)OR 6 , -SO2-Ph and -C6F5, where R 6 are independently the same or different and are a hydrogen atom or a monovalent hydrocarbyl group having 1 to 20 carbon atoms, and Ph is a phenyl group.

[0041] R 4 Examples of groups are alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobulyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl groups such as n-hexyl, heptyl groups such as n-heptyl, octyl groups such as n-octyl, and isooctyl groups such as 2,2,4-trimethylpentyl, nonyl groups such as n-nonyl, decyl groups such as n-decyl, cycloalkyl groups, such as cyclopentyl, cyclohexyl, cycloheptyl and methylcyclohexyl; aryl groups, such as phenyl, naphthyl, anthryl and phenanthryl; alkaryl groups, such as o-, m-, p-tolyl, xylyl and ethylphenyl; and aralkyl groups, such as benzyl, α- and β-phenylethyl.

[0042] replacement R 4Examples of groups include haloalkyl groups, such as 3,3,3-trifluoro-n-propyl, 2,2,2,2',2',2'-hexafluoroisopropyl, and heptafluoroisopropyl groups, and haloaryl groups, such as o-, m-, and p-chlorophenyl groups, -(CH)-N(R 6 )C(O)NR 6 2, -(CH2) o -C(O)NR 6 2, -(CH2) o -C(O)R 6 , -(CH2) o -C(O)OR 6 , -(CH2) o -C(O)NR 6 2. -(CH2)-C(O)-(CH2) p C(O)CH3, -(CH2)-O-CO-R 6 , -(CH2)-NR 6 -(CH2) p -NR 6 2, -(CH2) o -O-(CH2) p CH(OH)CH2OH, -(CH2) o (OCH2CH2) p OR 6 , -(CH2) o -SO2-Ph and -(CH2) o -O-C6F5, where R 6 and Ph meet the definition given above, and o and p are the same or different integers from 0 to 10.

[0043] R as a divalent group bonded to Si at either end as in formula (I) 4 The example of R is different from R in that there is an additional bond due to the replacement of a hydrogen atom. 4 From the monovalent examples given above for the radicals, examples of such radicals are -(CH2)-, -CH(CH3)-, -C(CH3)2-, CH(CH3)-CH2-, -CH4-, -CH(Ph)-CH2-, -C(CF3)2-, -(CH2) o -C6H4-(CH2) o -, -(CH2) o -C6H4-C6H4-(CH2) o-, -(CH2O) p , (CH2CH2O) o , -(CH2) o -O x -C6H4-SO2-C6H4-O x -(CH2) o -, where x is 0 or 1, and Ph, o and p have the definitions given above.

[0044] R 4 The group is preferably a monovalent SiC-bonded, optionally substituted hydrocarbyl group which contains no aliphatic carbon-carbon multiple bonds and has 1 to 18 carbon atoms, more preferably a monovalent SiC-bonded hydrocarbyl group which contains no aliphatic carbon-carbon multiple bonds and has 1 to 6 carbon atoms, in particular a methyl group or a phenyl group.

[0045] R 5 The group can be any group that will undergo an addition reaction (hydrosilylation) with a SiH functional compound.

[0046] R 5 When the group contains a SiC-substituted hydrocarbyl group, preferred substituents are halogen atoms, cyano groups and -OR 6 where R 6 has the definition given above.

[0047] R 5 The group preferably includes an alkenyl group or an alkynyl group having 2 to 16 carbon atoms, such as a vinyl group, an allyl group, a methallyl group, a 1-propenyl group, a 5-hexenyl group, an ethynyl group, a butadienyl group, a hexadienyl group, a cyclopentenyl group, a cyclopentadienyl group, a cyclohexenyl group, a vinylcyclohexylethyl group, a divinylcyclohexylethyl group, a norbornenyl group, a vinylphenyl group, or a styryl group, and it is particularly preferred to use a vinyl group, an allyl group, or a hexenyl group.

[0048] The molecular weight of component (A) can be within a wide range, e.g., 10 2 ~10 6For example, component (A) can be a relatively low molecular weight alkenyl-functional oligosiloxane (e.g., 1,2-divinyltetramethyldisiloxane), but with Si-bonded vinyl groups in the chain or terminal positions, e.g., 10 5 It may also be a polymeric polydimethylsiloxane having a molecular weight (number average determined by NMR) of g / mol. Also, the structure of the molecules forming component (A) is not fixed, more specifically the structure of the polymeric, i.e. oligomeric or polymeric siloxanes may be linear, cyclic, branched or resinous and network-like. Linear and cyclic polysiloxanes are preferably of the formula R 4 3SiO 1 / 2 , R 5 R 4 2SiO 1 / 2 , R 5 R 4 SiO 1 / 2 and R 4 2SiO 2 / 2 It is composed of units of R 4 and R 5 has the definition given above. The branched and network-like polysiloxanes further comprise trifunctional and / or tetrafunctional units and have the formula R 4 SiO 3 / 2 , R 5 SiO 3 / 2 and SiO 4 / 2 Of course, it is also possible to use mixtures of different siloxanes which meet the criteria of component (A).

[0049] Particular preference is given to using as component (A) vinyl-functional, essentially linear polydiorganosiloxanes which in each case have a viscosity at 25°C of 10 to 100,000 mPa·s, more preferably 15 to 20,000 mPa·s and particularly preferably 20 to 2,000 mPa·s.

[0050] As organosilicon compound (B), any hydrogen-functional organosilicon compound that has heretofore been used in addition crosslinking compositions can be used.

[0051] The organopolysiloxane (B) having Si-bonding atoms used is preferably a linear, cyclic or branched organopolysiloxane composed of units of the general formula (III). R 4 c H d SiO (4-c-d) / 2 (III) [In the formula, R 4 has the definition given above, c is 0, 1, 2 or 3; d is 0, 1 or 2; provided that the sum of c+d is 3 or less and there are at least two Si-bonded hydrogen atoms per molecule.] Preferably, there is at least one organopolysiloxane (B) having at least three, more preferably at least four, Si-bonded hydrogen atoms per molecule.

[0052] The organopolysiloxane (B) used in accordance with the present invention preferably contains from 0.01 to 1.7 weight percent (wt%) of Si-bonded hydrogen, based on the total weight of the organopolysiloxane (B), preferably from 0.02 to 0.8 wt%, more preferably from 0.03 to 0.3 wt%.

[0053] The molecular weight of component (B) may likewise be within a wide range, e.g. 2 ~10 6 For example, component (B) can be a relatively low molecular weight SiH-functional oligosiloxane (e.g., tetramethyldisiloxane), but also a polymeric polydimethylsiloxane with SiH groups in the chain or terminal positions, or a silicone resin with SiH groups.

[0054] Also, the structure of the molecules forming component (B) is not fixed, more specifically, the structure of the polymeric, i.e. oligomeric or polymeric, SiH-containing siloxanes can be linear, cyclic, branched or resinous and network-like. Linear and cyclic polysiloxanes (B) are preferably of the formula R 4 3SiO 1 / 2, H.R. 4 2SiO 1 / 2 , H.R. 4 SiO 2 / 2 and R 4 2SiO 2 / 2 It is composed of units of R 4 has the definition given above. The branched and network-like polysiloxanes further comprise trifunctional and / or tetrafunctional units and have the formula R 4 SiO 3 / 2 , HSiO 3 / 2 and SiO 4 / 2 In the formula R 4 has the definition given above.

[0055] Of course, it is also possible to use mixtures of different siloxanes that meet the criteria of component (B). Particularly preferred is the use of low molecular weight SiH-functional compounds such as tetrakis(dimethylsiloxy)silane and tetramethylcyclotetrasiloxane, and higher molecular weight SiH-containing siloxanes such as poly(hydromethyl)siloxane and poly(dimethylhydromethyl)siloxane, or similar SiH-containing compounds in which some of the methyl groups have been replaced by 3,3,3-trifluoropropyl or phenyl groups.

[0056] Particular preference is given to using as component (B) essentially linear, SiH-containing poly(hydromethyl)siloxanes and poly(dimethylhydromethyl)siloxanes, which may be hydrodimethylsiloxy-terminated, having in each case a viscosity in the range from 1 to 100,000 mPa·s, preferably in the range from 2 to 1,000 mPa·s, more preferably in the range from 3 to 750 mPa·s and particularly preferably in the range from 5 to 500 mPa·s at 25°C, and also to using hydrodimethylsiloxy-terminated polydimethylsiloxanes having in each case a viscosity in the range from 10 to 100,000 mPa·s, more preferably in the range from 15 to 20,000 mPa·s and particularly preferably in the range from 20 to 2,000 mPa·s at 25°C, and mixtures thereof.

[0057] Component (B) is preferably present in the crosslinkable silicone composition (S) of the present invention in an amount such that the molar ratio of SiH groups to aliphatically unsaturated groups from (A) is from 0.1 to 10, more preferably between 0.5 and 5.0, and especially between 0.5 and 3.

[0058] Components (A) and (B) used in accordance with the present invention are either commercially available products or can be prepared by standard chemical methods.

[0059] Instead of components (A) and (B), the silicone composition (S) of the present invention may contain an organopolysiloxane (C) that simultaneously contains aliphatic carbon-carbon multiple bonds and Si-bonded hydrogen atoms. It is also possible for the silicone composition (S) of the present invention to contain all three components (A), (B) and (C).

[0060] If siloxanes (C) are used, these are preferably those composed of units of the general formulae (IV), (V) and (VI). R 4 f SiO 4 / 2 (IV) R 4 g R 5 SiO 3-g / 2 (V) R 4 h HSiO 3-h / 2 (VI) [In the formula, R 4 and R 5 has the definition given above, f is 0, 1, 2 or 3; g is 0, 1, or 2; h is 0, 1 or 2; However, there are at least two R 5 group and at least two Si-bonded hydrogen atoms are present.

[0061] Examples of organopolysiloxanes (C) include SO 4 / 2 Units, R 4 3SiO 1 / 2Units, R 4 2R 5 SiO 1 / 2 Units and R 4 2HSiO 1 / 2 These resins are composed of R units and are called MP resins. 4 SiO 3 / 2 Units and R 4 The linear organopolysiloxane may further contain 2SiO units, and the linear organopolysiloxane may further contain R 4 2R 5 SiO 1 / 2 Units, R 4 2SiO units and R 4 It consists essentially of HSiO units, and R 4 and R 5 is as defined above.

[0062] The organopolysiloxane (C) in any case has an average viscosity of preferably 0.01 to 500,000 Pa·s, more preferably 0.1 to 100,000 Pa·s at 25° C. The organopolysiloxane (C) can be prepared by standard chemical methods.

[0063] As hydrosilylation catalyst (D), any of the heat curing catalysts or UV curing catalysts known from the prior art can be used. Component (D) can be a platinum group metal, such as platinum, rhodium, ruthenium, palladium, osmium or iridium, an organometallic compound or a combination thereof. Examples of component (D) are compounds such as hexachloroplatinic (IV) acid, platinum dichloride, platinum acetylacetonate, and complexes of said compounds encapsulated in a matrix or core / shell type structure. Platinum complexes with low molecular weight organopolysiloxanes include 1,3-diethenyl-1,1,3,3-tetramethyldisiloxane complexes with platinum. Further examples are platinum-phosphite complexes or platinum-phosphine complexes. For light or UV curable compositions, it is possible to use, for example, alkyl-platinum complexes, such as derivatives of cyclopentadienyltrimethylplatinum(IV), cyclooctadienyldimethylplatinum(II), or diketonato complexes, such as bisacetylacetonatoplatinum(II), to initiate the addition reaction using light. These compounds may be encapsulated in a resin matrix.

[0064] The concentration of component (D) is sufficient to catalyze the hydrosilylation reaction of components (A), (B) and (C) upon contact to generate the heat required herein in the method described. The amount of component (D) can be between 0.1 and 1000 parts per million (ppm), 0.5 and 100 ppm or 1 and 25 ppm of platinum group metal according to the total weight of the components. If the platinum group metal component is less than 1 ppm, the cure rate may be slow. The use of more than 100 ppm of platinum group metal is uneconomical or reduces the storage stability of the silicone composition.

[0065] The addition-crosslinking silicone composition (S) may optionally contain all further additives that have been used up to now for the preparation of addition-crosslinking compositions. Examples of positively reinforcing fillers (E) that are not included in the definition of the thermally conductive filler (Z) that can be used as a component in the addition-crosslinking silicone composition (Y) of the present invention are fillers having a viscosity of at least 50 m. 2Fumed or precipitated silica having a BET specific surface area of ​​at least 50 m / g, and carbon black and activated carbon, such as furnace black and acetylene black. 2 Fumed and precipitated silicas having a BET specific surface area of ​​100 / g are preferred.

[0066] The silica fillers (E) mentioned may be hydrophilic or may be hydrophobized by known methods. Preferred fillers (E) have a carbon content of at least 0.01% by weight and up to 20% by weight, preferably between 0.1% by weight and 10% by weight, more preferably between 0.5% by weight and 6% by weight, as a result of a surface treatment.

[0067] In the addition-crosslinking silicone composition (S) of the present invention, component (E) is preferably used in the form of a single finely divided filler or, equally preferably, as a mixture of several of them. The content of the positively reinforcing filler in the crosslinkable silicone composition (S) of the present invention is in the range of 0% to 50% by weight, preferably 0% to 30% by weight, more preferably 0% to 10% by weight.

[0068] The crosslinkable addition-crosslinking silicone composition (S) is more preferably characterized in that the filler (E) has been surface-treated, the surface treatment being achieved by methods known in the prior art for hydrophobizing finely divided fillers.

[0069] The addition crosslinking silicone composition (S) of the present invention may contain alkyltrialkoxysilanes (F) as further additives in order to reduce its viscosity. If they are present, they are preferably present in an amount of 0.1 to 8% by weight, preferably 0.2 to 6% by weight, based on the total mass of the silicone composition (S), the alkyl groups can be saturated or unsaturated, linear or branched alkyl groups having 2 to 20, preferably 8 to 18, carbon atoms, and the alkoxy groups can have 1 to 5 carbon atoms. Examples of alkoxy groups include methoxy, ethoxy, propoxy and butoxy groups, with methoxy and ethoxy groups being particularly preferred. Preferred for (F) are n-octyltrimethoxysilane, n-decyltrimethoxysilane, n-dodecyltrimethoxysilane, n-hexadecyltrimethoxysilane and n-octadecyltrimethoxysilane.

[0070] The addition-crosslinking silicone composition (S) of the invention may optionally contain further additives as constituents, in a proportion of up to 70% by weight, preferably up to 42% by weight, based in each case on the addition-crosslinking silicone composition (S) of the invention, which are different from the thermally conductive filler (Z) of the invention and from the additives (E) and (F). These additives may be, for example, inert fillers, resinous polyorganosiloxanes other than the siloxanes (A), (B) and (C), non-reinforcing fillers, fungicides, fragrances, rheological additives, corrosion inhibitors, antioxidants, light stabilizers, retarders and compositions for influencing electrical properties, dispersing aids, solvents, adhesion promoters, pigments, dyes, plasticizers, organic polymers, heat stabilizers, etc.

[0071] <Thermal conductive filler (Z)> The crosslinkable thermally conductive silicone composition (Y) of the present invention contains at least one thermally conductive filler (Z) having a thermal conductivity of at least 5 W / mK, with the proviso that the crosslinkable thermally conductive silicone composition (Y) contains at least 20 vol.-% of light metal alloy particles as thermally conductive filler (Z), which must still satisfy at least the further specific characteristics a) to c), and the total amount of thermally conductive filler (Z) is at least 40 vol.-%.

[0072] a) The median particle size x50 of these metallic light metal alloy particles (Z) of the present invention is in the range of 25 to 150 μm, preferably in the range of 30 to 140 μm, more preferably in the range of 40 to 130 μm, and particularly preferably in the range of 50 to 125 μm.

[0073] b) The metallic light metal alloy particles (Z) of the present invention are produced via a melting process in the final production step and therefore have a predominantly rounded surface shape.

[0074] c) The particle size distribution span (SPAN) is defined as SPAN=(x90-x10) / x50. The SPAN of the metal-light metal alloy particles (Z) of the present invention is at least 0.4, preferably at least 0.5, more preferably at least 0.6, particularly preferably at least 0.7. In a preferred embodiment, the SPAN is between 0.7 and 2.5, in particular between 0.75 and 2.

[0075] Here, it is not important whether a single fraction of light metal alloy particles (Z) having a SPAN within the scope of the present invention is used, or whether two or more fractions of light metal alloy particles are mixed, thereby achieving the particle size distribution range of the present invention according to characteristic c) of the light metal alloy particles (Z) of the present invention. If two or more fractions of light metal alloy particles are mixed, this may precede the mixing with one or more components of the composition of the present invention, or the fractions of light metal alloy particles may also be mixed separately from each other with one or more components of the composition of the present invention. The order of addition here does not matter.

[0076] Preferably, no more than four fractions of light metal alloy particles are mixed to achieve the distribution range of the present invention, preferably no more than three fractions of light metal alloy particles are mixed to achieve the distribution range of the present invention, more preferably no more than two fractions of the light metal alloy particles of the present invention are used to achieve the distribution range of the present invention, and particularly preferably only a single light metal alloy powder of the present invention is used.

[0077] Metal light metal aluminum has several very advantageous properties for use as thermally conductive filler (Z). For example, the very high thermal conductivity of light metal alloy particles (Z) based on aluminum, silicon or magnesium improves the thermal conductivity of the thermally conductive silicone composition (Y) produced therefrom. The low density of light metal alloy particles (Z) reduces the weight of the compositions and components produced therefrom, which helps to save costs. Further properties such as electrical conductivity, Mohs hardness and brittleness can be controlled and optimized in a targeted manner within the wide range required by the application through the combination of different alloy metals and the ratio of the alloy components, thus, for example, producing electrically dissipative or electrically insulating silicone compositions, or, for example, reducing the abrasiveness of the particles.

[0078] The light metal alloy of the present invention contains as main constituent at least 60% by weight, preferably at least 70% by weight, more preferably at least 80% by weight, in particular at least 90% by weight of a light metal or light metalloid selected from B, C, S, P, Be, Mg, Ca, Al and Si.

[0079] Preferred light metal alloys contain as main constituents at least 60% by weight, preferably at least 70% by weight, more preferably at least 80% by weight, in particular at least 90% by weight of a light metal or light metalloid selected from Al, Ca, Mg and Si, with Al and Si being particularly preferred as main constituents.

[0080] In particularly preferred embodiments, the light metal alloy is essentially free of heavy metals.

[0081] It is known to those skilled in the art that metallic light metal alloy particles are flammable under certain conditions and that dust is an explosion hazard. Those skilled in the art also recognize that the dust formation, flammability and explosion hazards associated with metal powders increase significantly with decreasing particle size. Therefore, very small light metal alloy particles less than 25 μm are unsuitable as fillers for many applications, for example, gap fillers in lithium ion batteries. Such particles have a low minimum ignition energy, making them dangerous to handle and requiring complex and costly safety precautions in industrial processing. It has also been found that compositions containing very small light metal alloy particles less than 25 μm are relatively highly flammable and do not meet the UL94V-0 flammability class for gap fillers in lithium ion batteries.

[0082] The light metal alloy particles of the invention preferably contain a particle fraction with a diameter of less than or equal to 20 μm, more preferably less than 15% by weight and particularly preferably less than 10% by weight, in each case based on the total amount of the light metal alloy particles.

[0083] The light metal alloy particles of the invention preferably contain less than 15% by weight, more preferably less than 10% by weight and particularly preferably less than 5% by weight of particle fractions with a diameter of 10 μm or less, in each case based on the total amount of the light metal alloy particles.

[0084] In a particularly preferred embodiment, no light metal alloy particles having an average diameter of 20 μm or less, more preferably 10 μm or less, especially 5 μm or less, are intentionally added.

[0085] Larger light metal alloy particles having an average particle size greater than 25 μm have a relatively high minimum ignition energy and are therefore safer and easier to process in industrial processes. Nevertheless, compositions containing non-inventive milled angular light metal alloy particles greater than 25 μm were found to be relatively highly flammable and did not meet the UL94V-0 flammability class for gap fillers in lithium ion batteries.

[0086] Light metal alloy particles having an average particle size of more than 150 μm are unsuitable for many applications of thermally conductive silicone compositions, for example because they often do not fit into the fine gaps that the gap filler must fill. Moreover, quite unexpectedly, it has been found that even such large light metal alloy particles exhibit relatively high flammability.

[0087] Quite surprisingly, it has been found that the crosslinkable silicone composition (Y) of the present invention is both thermally conductive and low flammable when it contains the metallic light metal alloy particles of the present invention which simultaneously satisfy characteristics a) to c) in the minimum required amount.

[0088] The crosslinkable silicone composition (Y) of the present invention contains at least 20% by volume, preferably at least 25% by volume, more preferably at least 30% by volume, and particularly preferably at least 35% by volume of such metal light metal alloy particles (Z). If the silicone composition (Y) contains a smaller amount of metal light metal alloy particles (Z), the desired beneficial effects of the metal light metal alloy particles, such as low density and high thermal conductivity, are no longer sufficiently provided.

[0089] The prior art includes various methods for producing fine metal particles. The light metal alloy particles (Z) of the present invention are produced from a molten state, and as a result have a relatively smooth surface and are essentially free of cracks, sharp edges and sharp corners. In this way, they differ from conventional crushed particles that are converted into a final form, for example, by crushing, grinding or milling. Here, it is not important whether the particles are crushed at low temperature in a first method step, for example, by grinding, and then converted into a molten form by heating above their melting point, for example, by heat treatment in a high temperature range, for example, by plasma, or whether a melt is first produced and then crushed, for example, by atomization. The light metal alloy particles of the present invention are preferably converted into the solid form of the present invention by spraying or atomizing the light metal alloy melt, followed by cooling.

[0090] Suitable methods for producing the light metal alloy particles (Z) of the present invention are known to those skilled in the art and are described, for example, in Chapter 2.2 of "Pulvermetallurgie" Technologien und Werkstoffe [Powder Metallurgy]: Technologies and Materials, 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 methods for producing the light metal alloy particles (Z) of the present invention are inert gas atomization, also called gas atomization, pressurized water atomization, also called liquid atomization or water atomization, or melt spinning, also called centrifugal atomization or rotary atomization.

[0091] The described method allows the production of metal light metal alloy particles with very different particle size ranges, in particular with an average particle size range of several micrometers to several millimeters. It is also possible to produce metal light metal alloy particles with very different particle morphologies, for example with "sputtered" morphologies, i.e. with very irregular, nodular, elliptical or spherical morphologies, and with a very variable range of particle size distributions. Regardless of particle shape, these particles produced by the melting process have the relatively smooth surface of the invention and are essentially free of cracks, sharp edges and sharp corners.

[0092] Quite surprisingly, it has been found that the advantageous properties of the present invention, in particular the relatively low flammability, are only exhibited by light metal alloy particles which are produced by a melting process and therefore exhibit a predominantly rounded surface shape and at the same time fulfil the characteristics a) to c) of the present invention.

[0093] The method for producing the metal light metal alloy particles (Z) of the present invention should preferably be carried out in such a way that the particles are obtained with a predominantly rounded surface shape according to the present invention, thus fulfilling the characteristics a) to c), and are essentially free of angular or sharp particles. The solidified particles can be separated by size in a subsequent method step by standard methods, for example by classification by sieving, or by sieving. These methods make it possible to separate weak agglomerates and combined particles, but do not essentially destroy the particles. What is meant by "predominantly rounded" and "essentially free" is that the presence of such particles is permitted within the range of impurities in the particles (Z) of the present invention and does not interfere with the effect of the present invention.

[0094] In addition to these metal light metal alloy particles (Z), the crosslinkable silicone composition (Y) of the present invention may contain an additional thermally conductive filler (Z) having a thermal conductivity of more than 5 W / mK. Examples of such additional thermally conductive fillers (Z) are magnesium oxide, metallic aluminum powder, metallic silicon powder, metallic silver powder, zinc oxide, boron nitride, aluminum carbide, aluminum nitride, aluminum hydroxide, aluminum oxide, graphite, etc. Preferred additional fillers are aluminum powder, magnesium oxide, aluminum hydroxide, zinc oxide and aluminum oxide. Particularly preferred fillers are zinc oxide, aluminum hydroxide and aluminum oxide, with aluminum hydroxide being particularly preferred. The shape of the additional filler is essentially not limited. The particles can be, for example, spherical, elliptical, needle-like, tubular, platelet, fibrous or irregularly shaped. They are preferably spherical, elliptical or irregularly shaped. The average diameter of the further thermally conductive filler (Z) is preferably in the range of 0.01 to 150 μm, preferably in the range of 0.1 to 100 μm, more preferably in the range of 0.2 to 80 μm, in particular in the range of 0.4 to 60 μm.

[0095] Fillers with very high densities increase the weight of the components very significantly, which is disadvantageous, for example, in the use in aircraft and electric vehicles. The further thermally conductive filler (Z) preferably has a density of 5.0 g / cm 3 Less than 3.8 g / cm 3 Less than or equal to 3.0 g / cm 3 It has the following density:

[0096] The crosslinkable silicone composition (Y) of the present invention preferably has a crosslinking ratio of less than 16% by weight, preferably less than 14% by weight, more preferably less than 12% by weight, of 5.0 g / cm 3 In a particularly preferred embodiment, the crosslinkable silicone composition (Y) of the present invention contains a further thermally conductive filler (Z) having a density of more than 5.0 g / cm 3 The thermally conductive filler (Z) does not include a further thermally conductive filler (Z) having a density greater than

[0097] The crosslinkable silicone composition (Y) of the present invention has a crosslinking coefficient of 3.0 g / cm 3, preferably less than 35% by weight, more preferably less than 30% by weight, more preferably less than 25% by weight, and particularly preferably less than 20% by weight. 3 In a particularly preferred embodiment, the crosslinkable silicone composition (Y) of the present invention contains a further thermally conductive filler (Z) having a density of more than 3.0 g / cm 3 The thermally conductive filler (Z) does not include a further thermally conductive filler (Z) having a density greater than

[0098] A preferred crosslinkable silicone composition (Y) of the present invention contains, as the thermally conductive filler (Z), the metal light metal alloy particles of the present invention, either as the only thermally conductive filler (Z) or in combination with up to two further thermally conductive fillers (Z). Up to 5% of impurities are not considered as further fillers (Z) here.

[0099] When the preferred compositions of the present invention contain the metal-light metal alloy particles (Z) of the present invention as the only thermally conductive filler (Z) having a thermal conductivity of more than 5 W / mK, it is preferred to add a rheology modifier or thickener that prevents the filler from settling. Suitable rheology modifiers are known to those skilled in the art, and fumed silica, e.g., component (E), is preferred.

[0100] The total amount of the thermally conductive filler (Z) in the crosslinkable thermally conductive silicone composition (Y) of the present invention is 40 to 95% by volume, preferably 50 to 90% by volume, and more preferably 60 to 88% by volume. If the silicone composition (Y) contains a smaller amount of the thermally conductive filler (Z), the thermal conductivity is insufficient, and if the silicone composition (Y) contains a larger amount of the thermally conductive filler (Z), the composition (Y) has a high viscosity or is even brittle, making it difficult to process.

[0101] The non-crosslinked thermally conductive silicone composition (Y) of the present invention has a thermal conductivity of at least 0.6 W / mK, preferably at least 0.8 W / mK, more preferably at least 1.2 W / mK, especially at least 1.5 W / mK.

[0102] The viscosity of the non-crosslinked heat conductive silicone composition (Y) of the present invention can vary within a very wide range and can be adapted to the requirements of the application. The viscosity of the non-crosslinked heat conductive silicone composition (Y) of the present invention is preferably adjusted by the content of heat conductive filler (Z) and / or the composition of silicone composition (Z) by standard methods from the art. These are known to those skilled in the art. It is preferable to adjust the viscosity through the selection and combination of components (A), (B) and (C) and the optional addition of rheology modifiers and / or active fillers (E) and / or alkyltrialkoxysilanes (F).

[0103] The dynamic viscosity of the non-crosslinked, thermally conductive silicone composition (Y) of the present invention was measured at a shear rate of D = 10 s -1and at 25° C., it is preferably in the range of 100 to 1,000,000 mPa·s, preferably in the range of 1,000 to 750,000 mPa·s, more preferably in the range of 2,000 to 500,000 mPa·s, and particularly preferably 250,000 mPa·s or less.

[0104] The density of the uncrosslinked silicone composition (Y) of the present invention is 3.5 g / cm 3 less than 3.0 g / cm 3 less than 2.6 g / cm 3 Less than 2.3g / cm 3 is less than.

[0105] The present invention further provides a method for preparing the crosslinkable silicone composition (Y) of the present invention by mixing the individual components.

[0106] The components can be mixed by conventional continuous and batchwise prior art methods. Suitable mixing equipment is any of the known equipment. Examples of these are single- or double-shaft continuous mixers, twin rollers, Ross mixers, Hobart mixers, dental mixers, planetary mixers, kneaders and Henschel mixers or similar mixers. Mixing in a planetary mixer, kneader or continuous mixer is preferred. The crosslinkable silicone composition (Y) may optionally be heated in the course of mixing and is preferably mixed within a temperature range of 15 to 40°C. The procedure for producing the preferred addition-crosslinking silicone composition (S) is also known to the skilled person. In principle, the components can be added in any order. For example, components e) and optionally g) can be premixed and then mixed with components a) and / or b). Here, it is also possible, optionally, to heat and / or evacuate the mixture. It is preferred to mix at least a portion of a) with the alkoxysilane g) and then mix in the thermally conductive filler (Z). The production is preferably carried out without active heating.

[0107] In a preferred embodiment, light metal alloy particles having an average diameter of 20 mm or more, more preferably 10 mm or more, especially light metal alloy particles having an average diameter of 5 mm or less are not intentionally added, as this is associated with certain safety risks in industrial production.

[0108] The crosslinkable silicone composition (Y) of the present invention can be provided as a one-component, two-component or multi-component mixture. Examples are two-component heat-curable compositions (Y) or one-component UV-crosslinkable compositions (Y), which have likewise been known to those skilled in the art for a long time.

[0109] The crosslinkable silicone composition (Y) of the present invention has very good processing properties in terms of flowability, gap-filling properties and layer thickness control, and can be applied precisely.

[0110] The temperature conditions for curing the silicone composition (Y), preferably curable via a hydrosilylation reaction, are not limited and are typically in the range of 20 to 180°C, preferably in the range of 20 to 150°C, and preferably in the range of 20 to 80°C.

[0111] The present invention further provides a silicone product obtained by dispensing or applying the crosslinkable silicone composition and then crosslinking / curing. The cured silicone product (e.g., a thermally conductive element) exhibits excellent thermal conductivity and precise layer thickness.

[0112] The hardness of the crosslinked thermally conductive silicone composition (Y) of the present invention can vary within a very wide range and can be adapted to the requirements of the application. For example, for applications as a gap filler, it is preferable to use a relatively soft and flexible product, and for applications as a thermally conductive adhesive, it is preferable to use a relatively hard and rigid product. The hardness of the crosslinked thermally conductive silicone composition (Y) of the present invention is preferably adjusted by the composition of the silicone composition (S) by standard methods from the prior art. These are known to those skilled in the art. It is preferable to adjust the hardness through the selection and combination of components (A), (B) and (C) and the optional addition of reinforcing filler (E).

[0113] The hardness of the cured silicone product is preferably in the range of Shore 00 2 to Shore A 100, and more preferably in the range of Shore 00 10 to Shore A 85. When used as a gap filler, the hardness of the crosslinked thermally conductive silicone composition of the present invention is particularly preferably in the range of Shore 00 15 to Shore A 65.

[0114] The crosslinked silicone product has a thermal conductivity of at least 0.6 W / mK, preferably at least 0.8 W / mK, more preferably at least 1.2 W / mK, especially at least 1.5 W / mK.

[0115] The present invention further provides the use of the crosslinkable silicone compositions as gap fillers (=thermally conductive elements), thermally conductive pads, thermally conductive adhesives and encapsulation compounds.They are particularly suitable for use as gap fillers for lithium-ion batteries in electric vehicles and as encapsulation compounds for electronic components, such as electronic components in electric vehicles.

[0116] The density of the crosslinked silicone product of the present invention is 3.5 g / cm 3 less than 3.0 g / cm 3 More preferably less than 2.6 g / cm 3 Less than 2.3g / cm 3 is less than.

[0117] The crosslinked silicone products of the present invention preferably meet the UL94V-0 flammability class.

[0118] In a preferred embodiment, the crosslinked silicone product of the present invention has a density of 2.5 g / cm 3 The dynamic viscosity of the uncrosslinked silicone composition of the present invention is less than 1.0 mmHg at a shear rate of D=10 s -1 and less than 500,000 mPa·s, in particular less than 250,000, at 25°C.

[0119] In a particularly preferred embodiment, the silicone product of the present invention has a density of 2.3 g / cm 3 the thermal conductivity is greater than 1.8 W / mK, preferably greater than 3.0 W / mK, and the flammability satisfies UL94V-0, provided that the dynamic viscosity of the uncrosslinked silicone composition of the present invention is less than 1.0 mmHg at a shear rate of D=10 s -1 and at 25° C., less than 500,000 mPa·s, in particular less than 250,000.

[0120] <Test Method> <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, Lindenstraße 13 / 1, 72141 Waldorf-Heslach, Germany), which determines the thermal resistance of a sample between two test cylinders with a constant heat flow. The layer thickness of the sample is used to calculate the effective thermal conductivity.

[0121] For the measurements, the sample is applied using a stencil, the measuring cylinder is manually narrowed to a thickness of 1.9-2.0 mm, then excess material is removed. The thermal conductivity is measured at a constant gap of 1.8-1.6-1.4-1.2-1.0 mm. The evaluation is performed by the integrated reporter position. After validity tests (linear coefficient of determination >0.998), the thermal conductivity lambda is reported as the effective thermal conductivity in W / (m*K).

[0122] <Measurement of dynamic viscosity> The dynamic viscosity was measured according to DIN EN ISO 3219:1994 and DIN 53019 using an Anton Paar MCR 302 rheometer with the following parameters: measurement type: T / D, temperature: 25.0°C, measuring element: PP25, measuring gap: 0.50 mm, shear rate: 0.1-10 s -1 The viscosity was measured using a flow curve with a time of 120 seconds and 30 measurements. Viscosity reported in Pa s is D = 10 s -1 is the interpolated value at shear rates of

[0123] <Density measurement> The density of the uncrosslinked thermally conductive silicone composition was confirmed according to ISO 1183, and the density of the crosslinked thermally conductive silicone composition was confirmed according to ISO 1184.

[0124] <Particle size and shape analysis> Using a Camsizer X2 manufactured by Retsch Technology (measurement principle: dynamic image analysis), the particle size (median particle size x 50) and particle size distribution (parameter: distribution range SPAN) were analyzed according to ISO 13322-2 and ISO 9276-6 (analysis method: dry measurement of powders and granules, measurement range: 0.8 μm to 30 mm, compressed air dispersion by X-Jet, dispersion pressure = 0.3 bar). The evaluation was based on volume and x c min It was based on the model.

[0125] The following examples illustrate the basic feasibility of carrying out the invention, but are not intended to limit the invention to the content disclosed therein.

[0126] In the following examples, all figures relating to parts and percentages are by weight unless otherwise indicated. Unless otherwise indicated, the following examples are carried out at ambient pressure, i.e., about 1000 hPa, at room temperature, i.e., about 20° C., or at a temperature established by combining the reactants at room temperature without further heating or cooling. EXAMPLES

[0127] <Summary of the alloy particles and light metal alloy particle mixtures of the present invention and non-present invention used> The light metal alloys listed in Table 1 are used in the inventive and non-inventive examples.

[0128] [Table 1]

[0129] Table 2 shows the properties of the inventive (Examples 1-7) and non-inventive (Comparative Examples V1-V8) light metal alloy particles that were used in the crosslinkable thermally conductive silicone composition.

[0130] Examples 1 to 6 use light metal alloy particles according to the invention which have been obtained by inert gas atomization and therefore have a predominantly rounded surface shape and further have a relatively broad particle size distribution according to the invention and therefore satisfy all of the features a) to c) of the invention.

[0131] The non-inventive comparative examples V1 to V4 use non-inventive light metal alloy particles which are obtained by inert gas atomization and therefore have a predominantly rounded but relatively narrow non-inventive particle size distribution and do not fulfil feature c) of the invention.

[0132] The non-inventive comparative examples V5 to V7 use non-inventive light metal alloy particles which have a relatively broad particle size distribution but which have been obtained by a grinding process and are therefore inherently angular and have sharp edges and do not satisfy feature b) of the invention.

[0133] [Example 7: Production of light metal alloy particle mixture 7] 100 g of the non-invention light metal alloy particles of Comparative Example V2, 200 g of the non-invention light metal alloy particles of Comparative Example V3, 400 g of the non-invention light metal alloy particles of Alloy A having a x50 of 103.5 μm and a SPAN of 0.31, produced by inert gas atomization and therefore essentially rounded, 200 g of the non-invention light metal alloy particles of Alloy A having a x50 of 134.2 μm and a SPAN of 0.24, produced by inert gas atomization and therefore essentially rounded, and 100 g of the non-invention light metal alloy particles from Comparative Example V4 are mixed homogeneously in a standard commercially available RW28 laboratory stirring system (IKA®-Werke GmbH & CO.KG, 79219 Staufen, Germany). This provides a light metal alloy particle mixture of the present invention having a x50 of 106.9 μm and a SPAN of 0.77, being essentially rounded and satisfying characteristics a) to c) of the present invention.

[0134] Comparative Example V8: Production of Light Metal Alloy Particle Mixture V8 (Non-Invention) 300 g of non-invention light metal alloy particles of alloy A, having a x50 of 134.2 μm and a SPAN of 0.24, produced by inert gas atomization and therefore essentially rounded, and 600 g of non-invention light metal alloy particles from comparative example V4 are mixed homogeneously in a standard commercial RW28 laboratory stirring system (IKA®-Werke GmbH & CO.KG, 79219 Staufen, Germany). This gives a non-invention light metal alloy particle mixture having a x50 of 153.1 μm and a SPAN of 0.42, being essentially rounded, not satisfying feature a) of the invention.

[0135] <abbreviation> Example: V Comparative example PS particle shape r Predominantly rounded surface shape e Angular I. The present invention NI Non-invention nd undecided

[0136] [Table 2]

[0137] <General method 1 (GM1) for producing a molded silicone body containing crosslinked thermally conductive light metal alloy particles (inventive examples 8 to 14, non-inventive examples V9 to V20)> <Step 1: Preparation of addition-crosslinkable thermally conductive light metal alloy particle-containing silicone composition> 24.5 g of vinyldimethylsiloxy-terminated polydimethylsiloxane with a viscosity of 1000 mPa·s, 16.3 g of hydrodimethylsiloxy-terminated polydimethylsiloxane with a viscosity of 1000 mPa·s, and 1.0 g of a copolymer composed of dimethylsiloxy, methylhydrosiloxy and trimethylsiloxy units, with a viscosity of 200 mPa·s and a content of Si-bonded hydrogen of 0.18 wt.% were homogenized for 25 seconds at a speed of 2350 rpm using a SpeedMixer DAC 400 FVZ (Hauschild & Co KG, 1 Vaterkamp, ​​59075 Hamm, Germany). Afterwards, the light metal alloy particles were added in each case in the ratios given in Table 3 and mixed for 25 seconds at 2350 rpm using the SpeedMixer. The silicone composition containing the light metal alloy particles was stirred with a spatula to incorporate the light metal alloy particle residue from the edge of the container. It was then homogenized for an additional 25 seconds at 2350 rpm using a SpeedMixer and cooled to room temperature.

[0138] For crosslinking, 4.18 g of ELASTOSIL® CAT PT (available from Wacker Chemie AG, Hanns-Seidel-Platz 4, 81737 Munich, Germany) were added, corresponding to a mixing ratio of 1 part catalyst solution to 10 parts silicone composition, without counting the proportion of thermally conductive filler (Z). The mixture was mixed three times for 10 seconds at 2350 rpm in a SpeedMixer, stirring the sample each time with a spatula between the mixing operations. The result was a reactive, pasty mass that could only be stored for a few hours and was directly processed further.

[0139] <Step 2: Production of a cross-linked thermally conductive light metal particle-containing molded silicone body> Compacts having dimensions of 207 mm x 207 mm x 2 mm were prepared by standard prior art methods in a stainless steel mold at 165°C and 380 N / cm 2 The material was then compression vulcanized at 200°C for 5 minutes. The vulcanizate was then heat-treated at 200°C for 4 hours. A homogeneous and elastic molding was obtained.

[0140] [Example 15 Flammability Test] Flammability is tested in a simplified test based on UL 94V, a standard from Underwriters Laboratories for testing vertical flames that allows the classification of plastics according to their flame retardancy. This method is the most common test for the classification of flame-retardant plastics.

[0141] Test specimens 5 inches (127 mm) long and 0.5 inches (12.7 mm) wide were punched out from the silicone molded bodies of the invention according to Examples 8-14 and the non-invention silicone molded bodies according to Comparative Examples V9-V13 and V18-V20. The plaque is fixed in a vertical position at its top end over a length of 1 / 4 inch. A piece of absorbent cotton is placed 12 inches (305 mm) below the test plaque. The burner is adjusted so that a blue flame 3 / 4 inches long is produced. The flame is directed at the bottom edge of the plastic plaque from a distance of 3 / 8 inch (9.5 mm). After 10 seconds of contact, the flame is removed. The afterflame time (total afterflame time and afterglow time) of the test specimen is recorded. The sample should be extinguished immediately after the flame is removed and burn for an additional 4 seconds or less. The test is performed on five different specimens and the average afterflame time is determined. The results can be found in Table 3.

[0142] In the non-inventive comparative experiments V14 to V16, which contained 62.5 vol. % of non-inventive light metal alloy particles according to comparative examples V5 to V7, respectively (more specifically not satisfying feature b)), a silicone composition with a very high viscosity was formed which could not be pressed to obtain a suitable molded silicone body.

[0143] [Table 3]

[0144] Comparative Examples V9-V13 and V17-V19, which contain non-invention light metal alloy particles or mixtures according to Comparative Examples V1-V8 that do not meet one or more of the features a)-c), show relatively high flammability in flammability tests. The flammability of non-invention comparative sample V19, which contains light metal alloy particles with an average particle size of less than 20 μm, was particularly pronounced. The sample continued to burn after the flame was removed until the compact had completely burned.

[0145] Quite unexpectedly, it was found that light metal alloy particles simultaneously satisfying characteristics a) to c) exhibit the inventive advantage of reduced flammability. It was also found, quite surprisingly, in inventive example 14 that a mixture of a plurality of non-inventive light metal alloy particles can produce an inventive light metal alloy particle mixture having the inventive advantageous property of low flammability, provided that the resulting mixture satisfies characteristics a) to c). In contrast, the non-inventive light metal alloy particle mixture from comparative example V8 does not satisfy characteristics a) to c) and does not exhibit the inventive advantage.

[0146] [Example 16 UL94V complete combustion test] The molded silicone bodies of the present invention from inventive examples 11A and 12 and the non-inventive molded silicone bodies from non-inventive comparative examples V10, V11 and V18 were subjected to the UL94V complete flammability test and classified as V-0, V-1 or V-2. For many industrial applications, especially for use as gap fillers in electric vehicles, a classification of V-0 is necessary. The results are shown in Table 4.

[0147] [Table 4]

[0148] Example 17: Preparation of a crosslinked thermally conductive molded silicone body containing an in situ mixture of two light metal alloy particles (invention) According to the general method GM1, 187.55 g of the aluminum powder of the present invention from Example 1 (37.6 vol. % based on the total amount of the thermally conductive silicone composition) produced by separately having the crosslinkable thermally conductive silicone composition of the present invention as the light metal alloy particles and 183.95 g of non-invention light metal alloy particles (36.8 vol. % based on the total amount of the thermally conductive silicone composition) having a x50 of 104.9 mm and a SPAN of 0.36, and thus essentially rounded, produced by inert gas atomization, are mixed in situ to form the light metal alloy particle mixture of the present invention.

[0149] The result was a powder containing 74.4% by volume of the light metal alloy particles of the present invention and a shear rate of D=10 s -1 and a dynamic viscosity of 61,500 mPa s at 25°C. The thermal conductivity was 5.14 W / mK and the density was 2.22 g / cm 3 The mass of the present invention has good processability, high thermal conductivity and low density, making it very suitable for use as a gap filler. The crosslinked silicone molding of the present invention was produced using the general method GM1. The afterflame time according to Example 15 was 0.9 seconds. Example 16 resulted in a UL94 V0 classification.

[0150] Comparative Example V20: Preparation of a crosslinked molded silicone body containing an in situ mixture of two types of light metal alloy particles (non-invention) A crosslinked silicone molding was produced according to invention example 17, except that 19.0 vol. % of the light metal alloy particles from example 1 was used, and 18.6 vol. % of a non-invention aluminum powder having a x50 of 105.8 mm and a SPAN of 0.35, produced by inert gas atomization, and therefore essentially rounded.

[0151] The non-inventive molded silicone body has a non-inventive total content of thermally conductive filler (Z) of 37.6% by volume and has a thermal conductivity of 0.48 W / mK. Example 16 resulted in a UL94V-1 classification. This composition is unsuitable for use as a gap filler.

[0152] [Example 18 Two-component gap filler (the present invention)] [Production of Component A] In a commercially available Labotop planetary mixer (PC Laborsystem GmbH, Miesplatz 6, 4312 Magden, Switzerland) equipped with two bar stirrers and a stripper, 115.4 g of vinyl dimethylsiloxy-terminated polydimethylsiloxane having a viscosity of 120 mPa·s and 1.1 g of WACKER(R) CATALYST EP (available from Wacker Chemie AG, Hans-Zeidler-Platz 4, 81737 Munich, Germany) were mixed at room temperature and a stirrer speed of 300 rpm for 5 minutes. 308.5 g of BAK-5 spherical aluminum oxide (available from Shanghai Bestry Performance Materials Co., Ltd., Room 209, Yunchuang Space, 325 Yunqiao Road, Pudong, Shanghai) was added and homogeneously incorporated at 300 rpm for 10 minutes under a slightly reduced pressure (950 mbar). Subsequently, a total of 658.29 g of the light metal alloy particles of the present invention having a diameter of 79.2 mm x 50 and a SPAN of 1.61 and produced by inert gas atomization and thus essentially rounded were added in two portions (first portion: 438.86 g, second portion: 219.53 g), and after each addition, the mixture was mixed at 300 rpm for 10 minutes under a slightly reduced pressure (950 mbar). The resulting paste-like mass was further homogenized at 300 rpm for 10 minutes under a slightly reduced pressure (950 mbar). Component A of the present invention having a content of 55.5% by volume of the light metal alloy particles of the present invention and a total content of 73.1% by volume of the thermal conductivity filler was obtained. The paste-like composition has a density of 2.43 g / cm 3 , a shear rate D = 10 s -1 and a dynamic viscosity of 53200 mPa·s at 25°C, and a thermal conductivity of 3.4 W / mK, and is thus very well suited for use as a gap filler.

[0153] [Production of Component B] In a commercially available Labotop planetary mixer (PC Laborsystem GmbH, Meispracherstrasse 6, 4312 Magden, Switzerland) equipped with two bar agitators and strippers, 106.5 g of vinyldimethylsiloxy-terminated polydimethylsiloxane with a viscosity of 120 mPa·s and 9.0 g of a copolymer composed of dimethylsiloxy, methylhydrosiloxy and trimethylsiloxy units with a viscosity of 200 mPa·s and a Si-bonded hydrogen content of 0.18 wt% were mixed at room temperature and a stirring speed of 300 rpm for 5 min. 306.0 g of BAK-5 spherical aluminum oxide (available from Shanghai Bestry Performance Materials Co., Ltd. Room 209, Yunchuang Space, 325 Yunqiao Road, Pudong, Shanghai) was added and homogeneously incorporated at 300 rpm for 10 min under a slight reduced pressure (950 mbar). Subsequently, a total of 652.83 g of the aluminum powder of the present invention, having a x50 of 78.8 mm and a SPAN of 1.64, produced by inert gas atomization and therefore essentially rounded, was added in two portions (first portion: 435.22 g, second portion: 217.61 g), mixing for 10 minutes at 300 rpm under a slight vacuum (950 mbar) after each addition. The resulting pasty mass was homogenized for another 10 minutes at 300 rpm under a slight vacuum (950 mbar). An inventive B component was obtained with a content of light metal alloy particles of the present invention of 55.5% by volume and a total content of thermally conductive fillers of 73.1% by volume. The pasty composition had a mass of 2.43 g / cm 3 density, shear rate D=10s -1 and a dynamic viscosity of 39500 mPa·s at 25° C., and a thermal conductivity of 3.5 W / mK, and is therefore very well suited for use as a gap filler.

[0154] <Production of Molded Product> The crosslinked test specimens of the present invention were prepared by intimately mixing 1 part by weight of the A component of the present invention with 1 part by weight of the B component of the present invention and vulcanizing according to general method GM1. The resulting molding has a Shore A hardness of 1.8. Example 16 resulted in a UL94V-0 classification. This composition is very well suited for use as a gap filler.

Claims

1. A crosslinkable thermally conductive silicone composition (Y) comprising: 5 to 60 volume percent of a crosslinkable silicone composition (S), and % of at least one thermally conductive filler (Z) having a thermal conductivity of at least 5 W / mK, The crosslinkable thermally conductive silicone composition (Y) has a thermal conductivity of at least 0.6 W / mK; At least 20% by volume of metallic light metal alloy particles present as thermally conductive filler (Z) have the following characteristics: a) their median particle size x50 is in the range of 25 to 150 μm; b) they are produced via a melting process in the final production step and have a predominantly rounded surface profile; c) A crosslinkable thermally conductive silicone composition (Y), whose distribution range SPAN ((x90-x10) / x50) is at least 0.

40.

2. The crosslinkable silicone composition (Y) according to claim 1, which is an addition-crosslinking silicone composition.

3. 3. The crosslinkable silicone composition (Y) according to claim 1 or 2, characterized in that the thermally conductive filler (Z) contains at least 25 volume % of metallic light metal alloy particles.

4. 4. A crosslinkable silicone composition (Y) according to claim 1, characterized in that in addition to the metallic light metal alloy particles it contains only one or two further thermally conductive fillers (Z).

5. 5.0 g / cm ３ 5. The crosslinkable silicone composition (Y) according to claim 1, characterized in that less than 16% by weight of a further thermally conductive filler (Z) is present, the filler having a density of more than 16% by weight.

6. 6. A crosslinkable silicone composition (Y) according to any one of claims 1 to 5, characterized in that the median particle size x50 of the metallic light metal alloy particles is in the range of 40 to 130 μm.

7. The crosslinkable silicone composition (Y) according to any one of claims 1 to 6, characterized in that the metallic light metal alloy particles comprise a particle fraction having a diameter of 20 μm or less that is less than 20% by weight, based on the total amount of the light metal alloy particles.

8. The crosslinkable silicone composition (Y) according to any one of claims 1 to 7, characterized in that it has a thermal conductivity of at least 0.8 W / mK.

9. In both cases, the shear rate D = 10 s －１ and a dynamic viscosity at 25° C. of 1,000 to 750,000 mPa·s.

10. A method for producing the crosslinkable silicone composition of the present invention according to any one of claims 1 to 9 by mixing the individual components.

11. A silicone product obtainable by dispensing or applying the crosslinkable silicone composition of the present invention according to any one of claims 1 to 9, followed by curing.

12. Use of the crosslinkable silicone composition according to any of claims 1 to 9 as gap fillers (=thermally conductive elements), thermally conductive pads, thermally conductive adhesives and encapsulating compounds.

13. 13. The use according to claim 12 as a gap filler for lithium ion batteries in electric vehicles.

14. 13. The use according to claim 12 as an encapsulation compound in an electric vehicle.

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