Aluminum-containing thermal paste

Abstract

The present invention provides a crosslinkable thermally conductive silicone composition (Y), comprising: 5 to 50 volume % of a crosslinkable silicone composition (S), and 50 to 95% by volume 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 aluminum particles present as thermally conductive filler (Z) have the following characteristics: a) their median diameter x50 is in the range of 30 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 cross-linkable thermally conductive silicone composition (Y) in which the distribution range SPAN ((x90-x10) / x50) is at least 0.40. and its manufacture and use.

Description

[Technical Field]

[0001] The present invention relates to thermally conductive silicone compositions, and to their preparation and use. [Background technology]

[0002] Thermally conductive silicone compositions are widely used for 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 dominate in quantity. Gap fillers are thermally conductive elastomers that completely and persistently fill voids caused by manufacturing tolerances, differences in build height, or different expansion coefficients, thereby minimizing 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 silicone to increase thermal conductivity. However, these have significant drawbacks. Ceramic fillers, such as aluminum oxide, have very high densities and therefore significantly increase the weight of the component. They are also relatively expensive. Many thermally conductive metal fillers, such as finely divided copper and silver particles, are similarly 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 containing aluminum particles as a thermally conductive filler. These are relatively lightweight and inexpensive. Aluminum, being a semiconductor, also has very low electrical conductivity. However, the aluminum particles of the prior art are unsuitable for use as a gap filler in lithium-ion batteries for electric vehicles.

[0006] Prior art applications have used very finely divided aluminum particles with an average particle size of less than 20 μm. The use of aluminum particles smaller than 20 μm is disadvantageous because such particles have a relatively low minimum ignition energy, thus presenting a risk of dust explosion and requiring complex and costly safety measures in industrial processing. Furthermore, gap fillers containing such finely divided aluminum particles do not achieve the required fire properties required for UL94V-0 compliance.

[0007] Another drawback of very fine aluminum particles or crushed aluminum particles is that such particles have a relatively high surface area and can bind a very large amount of polymer.This significantly increases the viscosity of silicone composition, and therefore can only produce a mixture with a relatively low filler level and low thermal conductivity.At higher filler levels, the composition becomes very hard and can no longer be processed by conventional methods, such as dispensers.It has also been found that silicone compositions containing crushed aluminum particles are relatively flammable.

[0008] Numerous patents disclose the use of finely divided aluminum particles in thermally conductive silicone compositions, such as US2007167564, US2002014692, US2003049466, US2018022977, JP2014037460, WO21079714, US2011163460, US2016208156, JP2010013521, JP2014037460, US2016060462, and US2016068732. These documents do not disclose the shape of the particles, and only provide very broad definitions of the average particle size. Specific examples disclose the use of very fine aluminum particles of less than 20 μm.

[0009] However, the use of very small aluminum particles (less than 20 μm) has significant drawbacks. They have a relatively low minimum ignition energy, and therefore pose a risk of dust explosions, requiring complex and costly safety measures during industrial processing. Furthermore, silicone compositions containing such finely divided aluminum particles do not achieve the required fire resistance according to the UL94V-0 standard, making them unsuitable for use as gap fillers in lithium-ion batteries. A further drawback is that such finely divided aluminum particles have a large surface area, binding a very large amount of polymer. This significantly increases the viscosity of the silicone composition. It is only possible to produce mixtures with relatively low filler levels and low thermal conductivity.

[0010] US2017002248 claims a thermal interface material with a high thermal conductivity exceeding 6 W / mK and a low secant modulus of elasticity. A wide selection of possible matrix materials is identified (thermoplastics, thermosets, polymers). A wide selection of possible thermally conductive fillers is disclosed, such as ceramics containing metal oxides, metal nitrides, or metallic aluminum, without further specification of shape and size. The examples disclose the combination of an addition-crosslinked silicone composition, silicone oil, and mineral oil as matrix materials, and only aluminum oxide and metallic aluminum as fillers, by mixing three different sizes of aluminum oxide and four different sizes of aluminum (Al-1: 150 μm, Al-2: 80 μm, Al-3: 5 μm, Al-4: 50 μm), all of which are spherical. Here, the content of aluminum particles exceeds 42% by weight, and the content of aluminum oxide particles exceeds 37% by weight. The proportion of small aluminum particles less than 20 μm (particles of Example Al-3) added, based on the total amount of aluminum particles, exceeds 20% in all cases. The addition and content of very small aluminum particles less than 20 μm is related to the aforementioned drawbacks. The use of such a large amount of aluminum oxide also makes the production of such thermal interface materials very expensive and leads to their relatively high density exceeding 2.69 g / ml. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] US Patent Application Publication No. 2007 / 167564 [Patent Document 2] US Patent Application Publication No. 2002 / 014692 [Patent Document 3] US Patent Application Publication No. 2003 / 049466 [Patent Document 4] US Patent Application Publication No. 2018 / 022977 [Patent Document 5] Japanese Patent Application Laid-Open No. 2014-037460 [Patent Document 6] International Publication No. 2021 / 079714 [Patent Document 7] US Patent Application Publication No. 2011 / 163460 [Patent Document 8] US Patent Application Publication No. 2016 / 208156 [Patent Document 9] Japanese Patent Application Laid-Open No. 2010-013521 [Patent Document 10] Japanese Patent Application Laid-Open No. 2014-037460 [Patent Document 11] US Patent Application Publication No. 2016 / 060462 [Patent Document 12] US Patent Application Publication No. 2016 / 068732 [Patent Document 13] US Patent Application Publication No. 2017 / 002248 Summary of the Invention [Problem to be solved by the invention]

[0012] It was therefore an object of the present invention to provide a thermally conductive silicone elastomer composition that does not exhibit the above-mentioned drawbacks of the prior art and that combines the properties of low density, low cost and high thermal conductivity. [Means for solving the problem]

[0013] The goal is to μ This is achieved by the crosslinkable thermally conductive silicone composition (Y) of the present invention, which contains relatively large aluminum particles, mainly of rounded surface shape, having an average particle size of 100 μm and at the same time having a particularly large or wide particle distribution range. Quite surprisingly, it has been found in experiments that these silicone compositions (Y) of the present invention have clearly reduced flammability.

[0014] In the context of the present invention, aluminum particles having a "predominantly rounded surface shape" are understood to mean those having a spherical to ellipsoidal, irregular, or nodular shape, and simultaneously having a smooth and curved surface. Figures 1a to 1c show, by way of example, the predominantly rounded surface shape of these aluminum particles according to the present invention. The predominantly rounded surface shape of the aluminum particles according to the present invention is produced by a melting process. In other words, the aluminum particles according to the present invention must be obtained at the final stage of production by solidification from the melt, and not by mechanical crushing 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.

[0015] Non-inventive aluminum particle shapes are shown by way of example in Figures 2a and 2b, which have angular and pointed particles, which are produced by crushing or grinding or abrasive processes.

[0016] Thus, the metallic aluminum particles of the present invention have a predominantly rounded surface shape, and are neither angular nor sharp, although they may contain such particles to the extent of impurities without any interference with the operation of the present invention.

[0017] Accordingly, the present invention provides a crosslinkable thermally conductive silicone composition (Y), comprising: 5 to 50% by volume of a crosslinkable silicone composition (S), and 50 to 95% by volume 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 aluminum particles present as thermally conductive filler (Z) have the following characteristics: a) their median diameter x50 is in the range of 30 to 150 μm; b) they are produced via a melting process in the final manufacturing step and have a predominantly rounded surface profile; c) their distribution range SPAN ((x90-x10) / x50) is at least 0.40.

[0018] In the context of the present invention, the terms "heat-conducting" and "thermally conductive" are equivalent.

[0019] Thermally conductive filler (Z) in the context of the present invention is understood to mean any filler having a thermal conductivity of at least 5 W / mK.

[0020] Thermally conductive silicone compositions (Y) in the context of the present invention are understood to mean silicone compositions characterized in that they have a thermal conductivity of at least 0.6 W / mK, which clearly exceeds that of polydimethylsiloxane without fillers and additives, typically about 0.2 W / mK.

[0021] In the context of the present invention, all parameters describing particle size (parameter: median diameter x 50) or particle size distribution (parameter: distribution range SPAN) are based on volume-based distribution. The mentioned indices can be measured, for example, by dynamic image analysis according to ISO 13322-2 and ISO 9276-6, using, for example, a Camsizer X2 from Retsch Technology.

[0022] In order to avoid generating an excessive number of pages in the description of the present invention, only preferred embodiments of individual features are detailed in the description.

[0023] However, any combination of different levels of preference is also expressly disclosed and as expressly desired, as the expert reader will expressly understand this disclosure method. [Brief explanation of the drawings]

[0024]

Figure 1a

Figure 1b

Figure 1c

Figure 2a

Figure 2b

[0025] <Crosslinkable Silicone Composition (S)> As the crosslinkable silicone composition (S), silicones known to those skilled in the art from the prior art can be used, such as addition-crosslinked, peroxide-crosslinked, condensation-crosslinked or radiation-crosslinked silicone compositions (S). It is preferred to use addition-crosslinked or peroxide-crosslinked silicone compositions (S).

[0026] Peroxide-crosslinked 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 having at least two crosslinkable groups per molecule, such as 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 free radical source. 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-butylperoxyisopropylcarbonate, tert-butylperoxyisononanoate, dicyclohexylperoxydicarbonate and 2,5-dimethylhexane, 2,5-diperbenzoate.

[0027] One type of organic peroxide can be used, or a mixture of at least two different types of organic peroxides can be used.

[0028] It is particularly preferred to use an addition-crosslinking silicone composition (S).

[0029] 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 with 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.

[0030] The addition-crosslinking silicone composition (S) can be a one-component silicone composition or a two-component silicone composition.

[0031] In two-component silicone compositions (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).

[0032] 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 crosslinking is possible. For example, compound (A) has at least two aliphatic unsaturated groups and (B) has at least three Si-bonded hydrogen atoms, or compound (A) has at least three aliphatic unsaturated groups and siloxane (B) has at least two Si-bonded hydrogen atoms, or siloxane (C) having aliphatic unsaturated groups and Si-bonded hydrogen atoms in the above-mentioned ratio is used instead of compounds (A) and (B). Also possible are mixtures of (A), (B), and (C) having aliphatic unsaturated groups and Si-bonded hydrogen atoms in the above-mentioned ratios.

[0033] The addition-crosslinking silicone composition (S) of the present invention typically contains 30 to 99.0 wt%, preferably 40 to 95 wt%, and 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%, and 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%, and 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.

[0034] The compound (A) used in accordance with 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.

[0035] 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.

[0036] The addition-crosslinking silicone composition (S) of the present invention preferably contains, as component (A), at least one aliphatically unsaturated organosilicon compound, and any of the aliphatically unsaturated organosilicon compounds that have been used to date in addition-crosslinking compositions can be used, 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.

[0037] The organosilicon compounds (A) used, which have 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 and b is 3 or less, and there are at least two R 5 There is a group.]

[0038] 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.

[0039] 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 Si-bonded divalent groups at either end as in formula (I). 4 When the group contains a SiC-bonded 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.

[0040] R 4 Examples of groups are alkyl groups, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl groups, hexyl groups, such as n-hexyl groups, heptyl groups, such as n-heptyl groups, octyl groups, such as n-octyl groups, and isooctyl groups, such as 2,2,4-trimethylpentyl groups, nonyl groups, such as n-nonyl groups, decyl groups, such as n-decyl groups, 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.

[0041] 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, haloaryl groups such as o-, m-, and p-chlorophenyl, and -(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 conform to the definition given above, and o and p are the same or different integers from 0 to 10.

[0042] R as a divalent group bonded to Si at either end as in formula (I) 4 The examples of R are different in that there is an additional bond due to the replacement of a hydrogen atom. 4 The monovalent examples given above for the radicals are derived from the examples of such radicals, -(CH2)-, -CH(CH3)-, -C(CH3)2-, CH(CH3)-CH2-, -C6H4-, -CH(Ph)-CH2-, -C(CF3)2-, -(CH2) o -C6H4-(CH2) o -, -(CH2) o -C6H4-C6H4-(CH2) o-, -(CHO) 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.

[0043] R 4 The group is preferably a monovalent SiC-bonded, optionally substituted hydrocarbyl group having from 1 to 18 carbon atoms and containing no aliphatic carbon-carbon multiple bonds, more preferably a monovalent SiC-bonded hydrocarbyl group having from 1 to 6 carbon atoms and containing no aliphatic carbon-carbon multiple bonds, especially a methyl group or a phenyl group.

[0044] R 5 The group can be any group that will undergo an addition reaction (hydrosilylation) with a SiH functional compound.

[0045] R 5 When the group contains a SiC-bonded substituted hydrocarbyl group, preferred substituents are halogen atoms, cyano groups and -OR 6 where R 6 has the definition given above.

[0046] R 5 The group preferably includes alkenyl and alkynyl groups having 2 to 16 carbon atoms, such as vinyl, allyl, methallyl, 1-propenyl, 5-hexenyl, ethynyl, butadienyl, hexadienyl, cyclopentenyl, cyclopentadienyl, cyclohexenyl, vinylcyclohexylethyl, divinylcyclohexylethyl, norbornenyl, vinylphenyl, and styryl groups, with vinyl, allyl, and hexenyl groups being particularly preferred.

[0047] 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 as measured by NMR) of 10 ... 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 that meet the criteria of component (A).

[0048] 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.

[0049] As organosilicon compound (B), any hydrogen-functional organosilicon compound that has been used to date in addition-crosslinking compositions can be used.

[0050] 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, and more preferably at least four, Si-bonded hydrogen atoms per molecule.

[0051] The organopolysiloxane (B) used in accordance with the present invention preferably contains Si-bonded hydrogen in the range of 0.01 to 1.7 weight percent (wt%), preferably in the range of 0.02 to 0.8 wt%, more preferably in the range of 0.03 to 0.3 wt%, based on the total weight of the organopolysiloxane (B).

[0052] The molecular weight of component (B) may likewise be within a wide range, e.g., 10 2 ~10 6 For example, component (B) can be a relatively low molecular weight SiH-functional oligosiloxane (e.g., tetramethyldisiloxane), but it can also be a polymeric polydimethylsiloxane with SiH groups in the chain or terminal positions, or a silicone resin with SiH groups.

[0053] Furthermore, 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 wherein R 4 has the definition given above.

[0054] It is, of course, 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.

[0055] Particular preference is given to using as component (B) SiH-containing essentially linear poly(hydromethyl)siloxanes and poly(dimethylhydromethyl)siloxanes, optionally hydrodimethylsiloxy-terminated, having a viscosity in each case in the range of 1 to 100,000 mPa·s, preferably in the range of 2 to 1,000 mPa·s, more preferably in the range of 3 to 750 mPa·s, and particularly preferably in the range of 5 to 500 mPa·s, at 25°C; and also to using hydrodimethylsiloxy-terminated polydimethylsiloxanes having a viscosity in each case in the range of 10 to 100,000 mPa·s, more preferably in the range of 15 to 20,000 mPa·s, and particularly preferably in the range of 20 to 2,000 mPa·s, at 25°C, and mixtures thereof.

[0056] 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 aliphatic unsaturated groups from (A) is between 0.1 and 10, more preferably between 0.5 and 5.0, and especially between 0.5 and 3.

[0057] Components (A) and (B) used in accordance with the present invention are commercially available products or can be prepared by standard chemical methods.

[0058] 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. The silicone composition (S) of the present invention may also contain all three components (A), (B), and (C).

[0059] When 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 per molecule. 5 group and at least two Si-bonded hydrogen atoms are present.]

[0060] Examples of organopolysiloxane (C) include SO 4 / 2 Units, R 4 3SiO 1 / 2Units, R 4 2nd Round 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 R 2SiO units. 4 2nd Round 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.

[0061] In either case, the organopolysiloxane (C) preferably has an average viscosity of 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.

[0062] As the hydrosilylation catalyst (D), any of the thermal 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) include compounds such as hexachloroplatinic acid (IV), platinum dichloride, platinum acetylacetonate, and complexes of these compounds encapsulated in a matrix or core / shell 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) or 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.

[0063] 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 described method. 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 based on the total weight of the components. If the platinum group metal component is less than 1 ppm, the cure rate may be slow. Use of more than 100 ppm of platinum group metal is uneconomical or reduces the storage stability of the silicone composition.

[0064] The addition-crosslinked silicone composition (S) may optionally contain all further additives that have been used up to now for the preparation of addition-crosslinked 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-crosslinked silicone composition (Y) of the present invention include fillers having a viscosity of at least 50 mPa. 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 ​​1 / g are preferred.

[0065] The silica filler (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% and 10% by weight, more preferably between 0.5% and 6% by weight, as a result of a surface treatment.

[0066] 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 thereof. 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, and more preferably 0% to 10% by weight.

[0067] The crosslinkable addition-crosslinking silicone composition (S) is more preferably characterized in that the filler (E) has been surface-treated, which is achieved by methods known in the prior art for hydrophobizing finely divided fillers (E).

[0068] The addition-crosslinking silicone composition (S) of the present invention may contain an alkyltrialkoxysilane (F) as a further additive to reduce its viscosity. If present, it is present in an amount of preferably 0.1 to 8 wt. %, preferably 0.2 to 6 wt. %, based on the total mass of the silicone composition (S). The alkyl group can be a saturated or unsaturated, linear or branched alkyl group having 2 to 20, preferably 8 to 18, carbon atoms, and the alkoxy group 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.

[0069] The addition-crosslinking silicone composition (S) of the present invention may optionally contain further additives as constituents, in a proportion of up to 70% by weight, preferably up to 42% by weight, in each case based on the addition-crosslinking silicone composition (S) of the present invention, which are different from the thermally conductive filler (Z) of the present invention and 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, adhesion promoters, pigments, dyes, plasticizers, organic polymers, heat stabilizers, etc.

[0070] <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% by volume of metallic aluminum particles as the thermally conductive filler (Z), which must still satisfy at least further specific characteristics a) to c), and the total amount of thermally conductive filler (Z) is at least 50% by volume.

[0071] a) The median diameter x50 of these metallic aluminum particles (Z) of the present invention is in the range of 20 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.

[0072] b) The metallic aluminum 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.

[0073] c) The particle size distribution range (SPAN) is defined as SPAN = (x90 - x10) / x50. The SPAN of the aluminum metal particles (Z) of the present invention is at least 0.4, preferably at least 0.5, more preferably at least 0.6, and particularly preferably at least 0.7. In a preferred embodiment, the SPAN is between 0.7 and 2.5, particularly between 0.75 and 2.

[0074] Here, it is not important whether a single fraction of aluminum particles (Z) having a SPAN within the scope of the present invention is used, or whether two or more fractions of aluminum particles are mixed, thereby achieving the particle size distribution range of the present invention according to feature c) of the aluminum particles (Z) of the present invention. When two or more fractions of aluminum particles are mixed, this may precede mixing with one or more components of the composition of the present invention, or the fractions of aluminum particles may also be mixed with one or more components of the composition of the present invention separately from each other. The order of addition here does not matter.

[0075] Preferably, no more than four fractions of aluminum particles are mixed to achieve the distribution range of the present invention, preferably no more than three fractions of aluminum particles are mixed to achieve the distribution range of the present invention, more preferably no more than two fractions of aluminum particles of the present invention are used to achieve the distribution range of the present invention, and particularly preferably only a single aluminum powder of the present invention is used.

[0076] Metallic aluminum has several highly advantageous properties for use as a thermally conductive filler (Z). For example, the very high thermal conductivity of aluminum particles (Z) improves the thermal conductivity of the thermally conductive silicone composition (Y) produced therefrom. The low density of aluminum particles (Z) reduces the weight of the composition and the components produced therefrom, helping to save costs. If required by the application, electrical conductivity can be reduced by prior art processes, for example, by surface oxidation. The low Mohs hardness of aluminum particles (Z) reduces wear during processing. It is clear to those skilled in the art that the aforementioned advantages are lost in whole or in part as the purity of aluminum decreases. The purity, and therefore the aluminum content, of the aluminum particles (Z) of the present invention is at least 80%, preferably at least 90%, and more preferably at least 95%.

[0077] Those skilled in the art are aware that metallic aluminum particles are flammable under certain conditions, and that the dust poses an explosion risk. They also recognize that the risks of dust formation, flammability, and explosion associated with metal powders increase significantly with decreasing particle size. Therefore, very small aluminum particles less than 20 μm in size are unsuitable as fillers for many applications, such as 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 during industrial processing. It has also been found that compositions containing very small aluminum particles less than 20 μm are relatively highly flammable and do not meet the UL94V-0 standard flammability class for gap fillers in lithium-ion batteries.

[0078] The aluminum particles (Z) of the present invention preferably account for less than 20% by weight, more preferably less than 15% by weight, particularly preferably less than 10% by weight, based on the total amount of aluminum particles in each case. μ It contains a particle fraction with a diameter of less than 1 m.

[0079] The aluminum particles (Z) of the present invention preferably account for less than 15% by weight, more preferably less than 10% by weight, particularly preferably less than 5% by weight, based on the total amount of aluminum particles in any case. μ It contains a particle fraction with a diameter of less than 1 m.

[0080] The aluminum particles (Z) of the present invention preferably contain not more than 1.5% by weight, more preferably not more than 1% by weight, and particularly preferably not more than 0.5% by weight of aluminum particles smaller than 2 μm, in each case based on the total amount of aluminum particles. Particularly preferred aluminum particles are essentially free of particle fractions smaller than 2 μm.

[0081] In a particularly preferred embodiment, 20 μ m or less, preferably 10 μ Aluminum particles with an average diameter of less than 5 m, especially μ Aluminum particles smaller than m shall not be intentionally added.

[0082] Larger aluminum particles having an average particle size greater than 20 μm have a relatively high minimum ignition energy and are therefore safer and easier to process in industrial processes. Nevertheless, compositions containing non-inventive crushed angular aluminum particles greater than 20 μm were found to be relatively highly flammable and did not meet the UL94V-0 standard flammability class for gap fillers in lithium-ion batteries.

[0083] Aluminum particles with an average particle size greater than 150 μm are unsuitable for many applications of thermally conductive silicone compositions, for example, because they often cannot fit into the minute gaps that the gap filler must fill. Furthermore, quite unexpectedly, it has been discovered that even such large aluminum particles exhibit relatively high flammability.

[0084] Quite surprisingly, it has been found that the crosslinkable silicone composition (Y) of the present invention is both thermally conductive and low inflammable when it contains the metallic aluminum particles (Z) of the present invention that simultaneously satisfy characteristics a) to c) in the minimum amount required.

[0085] 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 metallic aluminum particles (Z). If the silicone composition (Y) contains a smaller amount of metallic aluminum particles (Z), the desired beneficial effects of metallic aluminum, such as low density and high thermal conductivity, are no longer sufficiently provided.

[0086] The prior art includes various methods for producing fine metal particles. The aluminum particles (Z) of the present invention are preferably 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. As such, they differ from conventional crushed particles that are converted into a final form, for example, by crushing, grinding, or milling. It is immaterial whether the particles are crushed at a 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 an aluminum melt is first generated and then crushed, for example, by atomization. The aluminum particles of the present invention are preferably converted into the solid form of the present invention by spraying or atomizing the aluminum melt and then cooling it.

[0087] Suitable methods for producing the aluminum particles (Z) of the present invention are known to those skilled in the art and are described, for example, in "Pulvermetallurgie", Chapter 2.2, 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 aluminum particles (Z) of the present invention are inert gas atomization, also known as gas atomization, pressurized water atomization, also known as liquid atomization or water atomization, or melt spinning, also known as centrifugal atomization or rotary atomization.

[0088] The described method allows the production of metallic aluminum particles with a very different particle size range, in particular an average particle size range of several micrometers to several millimeters. It is also possible to produce metallic aluminum particles with very different particle morphologies, for example "sputtered" morphologies, i.e., very irregular, nodular, ellipsoidal, or spherical morphologies, and with a very variable particle size distribution. Regardless of particle shape, these particles produced by the melting process have the relatively smooth surface of the present invention and are essentially free of cracks, sharp edges, and sharp corners.

[0089] Quite surprisingly, it has been found that the advantageous properties of the present invention, in particular the relatively low flammability, are only exhibited by aluminum particles which are produced by a melting process and therefore exhibit a predominantly rounded surface shape, while at the same time fulfilling the characteristics a) to c) of the present invention.

[0090] The method for producing the aluminum metal particles (Z) of the present invention is preferably carried out in such a way that the particles are obtained with a predominantly rounded surface shape according to the present invention, thus satisfying characteristics a) to c), and essentially free of angular or sharp particles. The agglomerated particles can be separated by size in a subsequent process step by standard methods, for example, by sieving or by sieving. These methods allow for the separation of agglomerates and combined particles, but do not essentially destroy the particles.

[0091] What is meant by "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 effects of the present invention.

[0092] In addition to these metallic aluminum particles (Z), the crosslinkable silicone composition (Y) of the present invention may contain an additional thermally conductive filler (Z) having a thermal conductivity of greater than 5 W / mK. Examples of such additional thermally conductive fillers (Z) include magnesium oxide, metallic silicon powder, metallic silver powder, zinc oxide, boron nitride, aluminum carbide, aluminum nitride, aluminum hydroxide, aluminum oxide, and graphite. Preferred additional fillers are aluminum powder, magnesium oxide, aluminum hydroxide, zinc oxide, and aluminum oxide. Particularly preferred fillers are zinc oxide, metallic silicon powder, aluminum hydroxide, and aluminum oxide, with metallic silicon powder and aluminum hydroxide being particularly preferred. The shape of the additional filler is essentially unlimited. The particles may be, for example, spherical, ellipsoidal, acicular, tubular, platelet-like, fibrous, or irregularly shaped. They are preferably spherical, ellipsoidal, 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.

[0093] Fillers with very high densities increase the weight of the component very significantly, which is disadvantageous for use in, for example, aircraft and electric vehicles. The further thermally conductive filler (Z) is preferably 6.0 g / cm 3 Below 4.5, preferably g / cm 3 Below 3.0, preferably g / cm 3 It has the following density:

[0094] The crosslinkable silicone composition (Y) of the present invention preferably contains 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 greater than 5.0 g / cm 3 The composition does not contain any further thermally conductive filler (Z) having a density greater than

[0095] The crosslinkable silicone composition (Y) of the present invention preferably contains less than 35% by weight, preferably less than 30% by weight, more preferably less than 25% by weight, and particularly preferably less than 20% by weight of 3.0 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 greater than 3.0 g / cm 3 The composition does not contain any further thermally conductive filler (Z) having a density greater than

[0096] Preferred crosslinkable silicone compositions (Y) of the present invention contain the metallic aluminum particles of the present invention as the thermally conductive filler (Z), either as the sole thermally conductive filler (Z) or in combination with up to two additional thermally conductive fillers (Z). Up to 5% of impurities are not considered additional fillers (Z) herein.

[0097] When the preferred compositions of the present invention contain the inventive metal aluminum particles (Z) as the only thermally conductive filler (Z) having a thermal conductivity of more than 5 W / mK, it is preferable to add a rheology modifier or thickener to prevent the filler from settling. Suitable rheology modifiers are known to those skilled in the art, and fumed silica, for example, component (E), is preferred.

[0098] The total amount of thermally conductive filler (Z) in the crosslinkable thermally conductive silicone composition (Y) of the present invention is 50 to 95% by volume, preferably 60 to 90% by volume, and more preferably 65 to 88% by volume. If silicone composition (Y) contains a smaller amount of thermally conductive filler (Z), the thermal conductivity will be insufficient. If silicone composition (Y) contains a larger amount of thermally conductive filler (Z), composition (Y) will have a high viscosity or will be brittle, making it difficult to process.

[0099] 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, and especially at least 1.5 W / mK.

[0100] The viscosity of the non-crosslinked thermally conductive silicone composition (Y) of the present invention can be varied within a very wide range and adapted to the requirements of the application. The viscosity of the non-crosslinked thermally conductive silicone composition (Y) of the present invention is preferably adjusted by the content of the thermally conductive filler (Z) and / or the composition of the silicone composition (Z) using standard methods known to those skilled in the art. The viscosity is preferably adjusted through the selection and combination of components (A), (B), and (C) and the optional addition of a rheology modifier and / or an active filler (E) and / or an alkyltrialkoxysilane (F).

[0101] 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 250,000 mPa·s or less.

[0102] The density of the uncrosslinked silicone composition (Y) of the present invention is 3.5 g / cm 3 Less than 3.0, preferably g / cm 3 less than 2.6, more preferably g / cm 3 Less than, especially 2.3 g / cm 3 is less than.

[0103] The silicone composition of the present invention is primarily free of volatile organic solvents, as these can form flammable vapors and / or cause undesirable shrinkage during or after crosslinking. By "primarily free," it is meant that there are no intentionally added solvents; instead, solvents may only be present in small amounts of less than 0.1 wt. % as impurities in the components of the silicone composition of the present invention.

[0104] The present invention further provides a method for producing the crosslinkable silicone composition (Y) of the present invention by mixing the individual components.

[0105] The components can be mixed by conventional continuous and batch methods of the prior art. Suitable mixing equipment is any known device. Examples of these are single- or double-screw continuous mixers, twin roller mixers, 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) is preferably mixed at a temperature within the range of 15 to 40°C, optionally heated during the mixing process. Procedures for preparing preferred addition-crosslinked silicone compositions (S) are also known to those skilled in the art. In principle, the components can be added in any order. For example, component e) and optionally g) can be premixed and then mixed with component a) and / or b). Optionally, the mixture can be heated and / or evacuated. Preferably, at least a portion of a) is mixed with alkoxysilane g), and then the thermally conductive filler (Z) is mixed in. The preparation is preferably carried out without active heating.

[0106] In a preferred embodiment, 20 μ m or more, more preferably 10 μ Aluminum particles with an average diameter of 5 m or more, especially μ Aluminum particles smaller than 1 m are not intentionally added, as this is associated with certain safety risks in industrial production.

[0107] 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.

[0108] The crosslinkable silicone composition (Y) of the present invention has very good processing properties in terms of flowability, gap filling ability and layer thickness control, and can be applied precisely.

[0109] The temperature conditions for curing the silicone composition (Y), which is 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.

[0110] The present invention further provides a silicone product obtained by blending or applying the crosslinkable silicone composition and then crosslinking / curing the composition. The cured silicone product (e.g., a thermally conductive element) exhibits excellent thermal conductivity and precise layer thickness.

[0111] 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, while 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) using standard methods from the prior art, which 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 a reinforcing filler (E).

[0112] 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.

[0113] 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.

[0114] The present invention further provides the use of the crosslinkable silicone composition as a gap filler (=thermally conductive element), a thermally conductive pad, a thermally conductive adhesive and an encapsulating compound, which are particularly suitable for use as a gap filler for lithium-ion batteries in electric vehicles and as an encapsulating compound for electronic components, such as electronic components in electric vehicles.

[0115] The density of the crosslinked silicone product of the present invention is 3.5 g / cm 3 Less than 3.0, preferably g / cm 3 less than 2.6 g / cm 3 Less than 2.3 g / cm 3 is less than.

[0116] The crosslinked silicone products of the present invention preferably meet the UL94V-0 standard flammability class.

[0117] In a preferred embodiment, the crosslinked silicone product of the present invention has a density of 2.5 g / cm 3 The uncrosslinked silicone composition of the present invention has a dynamic viscosity of less than 1000 kJ / cm2 at a shear rate of D = 10 s, a thermal conductivity of more than 1.8 W / mK, and flammability that satisfies the UL94V-0 standard. -1 and less than 500,000 mPa·s, in particular less than 250,000 at 25°C.

[0118] In a particularly preferred embodiment, the density of the silicone product of the present invention is 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 the UL94V-0 standard, provided that the dynamic viscosity of the uncrosslinked silicone composition of the present invention is less than 1.0 W / mK 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.

[0119] <Test Method> <Measurement of thermal conductivity lambda> Thermal conductivity is measured according to the ASTM D5470-12 standard using a TIM Tester (Steinbeis Transferzentrum Waermemanagement in der Elektronik, Lindenstraße 13 / 1, 72141 Walldorf-Höslach, Germany). This measures 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.

[0120] For measurement, the sample is applied using a stencil, the measuring cylinder is manually narrowed to a thickness of 1.9-2.0 mm, and then excess material is removed. Thermal conductivity is measured at a fixed gap of 1.8-1.6-1.4-1.2-1.0 mm. Evaluation is performed by integrated reporter position. After validity testing (linear determination coefficient >0.998), the thermal conductivity lambda is reported as the effective thermal conductivity in W / (m*K).

[0121] <Measurement of dynamic viscosity> Dynamic viscosity was measured in accordance with 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 to 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

[0122] <Density measurement> The density of the uncrosslinked thermally conductive silicone composition was confirmed in accordance with ISO 1183, and the density of the crosslinked thermally conductive silicone composition was confirmed in accordance with ISO 1184.

[0123] <Particle size and particle shape analysis> Using a Camsizer X2 manufactured by Retsch Technology (measurement principle: dynamic image analysis), particle size (median diameter x 50) and particle size distribution (parameter: distribution range SPAN) were analyzed in accordance with 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.

[0124] 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.

[0125] In the following examples, all parts and percentages are by weight unless otherwise specified. Unless otherwise specified, the following examples are carried out at ambient atmospheric 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. [Example]

[0126] <Summary of the aluminum powder of the present invention, aluminum powder not of the present invention, and aluminum powder mixture used> Table 1 summarizes the properties of the aluminum powders of the present invention and of the aluminum powders not of the present invention used in the examples.

[0127] Inventive Examples 1 to 6 and 8 use aluminum powder of the present invention which has been obtained by inert gas atomization and therefore has a predominantly rounded surface shape, and further has a relatively broad particle size distribution of the present invention.

[0128] The non-inventive comparative examples V1 to V4 use non-inventive aluminum powders that are obtained by inert gas atomization and therefore have primarily rounded, but relatively narrow, non-inventive particle size distributions and do not satisfy feature c) of the invention.

[0129] The non-inventive comparative examples V5 to V7 use non-inventive aluminum powders which have a relatively broad particle size distribution but which have been obtained by a milling process and are therefore inherently angular and have sharp edges, and which do not satisfy feature b) of the invention.

[0130] The non-inventive comparative examples V9 and V10 use non-inventive aluminum powder which is obtained by inert gas atomization and is therefore mainly rounded, and which also has a relatively wide particle size distribution, but the particle size is relatively small and does not satisfy feature a) of the invention.

[0131] Example 7: Production of Aluminum Powder Mixture 7 (Invention) 100 g of the non-inventive aluminum powder from Comparative Example V2, 200 g of the non-inventive aluminum powder from Comparative Example V3, 400 g of the non-inventive aluminum powder having a x50 of 106.2 μm and a SPAN of 0.37, produced by inert gas atomization and therefore essentially rounded, 200 g of the non-inventive aluminum powder having a x50 of 133.5 μm and a SPAN of 0.27, produced by inert gas atomization and therefore essentially rounded, and 100 g of the non-inventive aluminum powder from Comparative Example V4 are homogeneously mixed using a standard commercially available RW 28 laboratory stirring system (IKA®-Werke GmbH & CO.KG, 79219 Staufen, Germany). This results in an inventive aluminum powder mixture having a x50 of 107.4 μm and a SPAN of 0.75, which is essentially rounded and satisfies Features a) to c) of the present invention.

[0132] Comparative Example V8: Preparation of Aluminum Powder Mixture V8 (Not According to the Invention) 300 g of a non-inventive aluminum powder having a x50 of 133.5 μm and a SPAN of 0.27, produced by inert gas atomization and therefore essentially rounded, and 600 g of the non-inventive aluminum powder from Comparative Example V4 are homogeneously mixed using a standard commercially available RW 28 laboratory stirring system (IKA®-Werke GmbH & CO.KG, 79219 Staufen, Germany), resulting in a non-inventive aluminum powder mixture having a x50 of 155.0 μm and a SPAN of 0.41, which does not satisfy feature a) of the present invention.

[0133] Abbreviation Example: Example V Comparative example PS particle shape r Mainly rounded surface shape e Angular I. The present invention NI Not an invention nd undecided

[0134] [Table 1]

[0135] <General Method 1 (GM1) of Producing a Silicone Molded Body Containing Crosslinked Thermally Conductive Aluminum Powder (Inventive Examples 9 to 16, Non-Inventive Examples V11 to V23)> <Step 1: Preparation of Addition-Crosslinkable Thermally Conductive Aluminum Powder-Containing Silicone Composition> 24.5 g of a vinyldimethylsiloxy-terminated polydimethylsiloxane with a viscosity of 1000 mPa·s, 16.3 g of a 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 silicon-bonded hydrogen content of 0.18 wt% were homogenized for 25 seconds at 2350 rpm using a SpeedMixer DAC 400 FVZ (Hauschild & Co. KG, 1, Vaterkamp, ​​59075 Hamm, Germany). Aluminum powder was then added in each case in the proportions specified in Table 2, and the mixture was mixed for 25 seconds at 2350 rpm using the SpeedMixer. The aluminum particle-containing silicone composition was stirred with a spatula to incorporate any remaining aluminum powder from the edge of the container. The mixture was then homogenized for an additional 25 seconds at 2350 rpm using a SpeedMixer and cooled to room temperature.

[0136] 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 taking into account the proportion of thermally conductive filler (Z). The mixture was mixed in a SpeedMixer at 2350 rpm for 10 seconds three times, stirring the sample with a spatula between each mixing operation. The result was a reactive, paste-like mass that could only be stored for a few hours and was directly processed further.

[0137] <Step 2: Manufacturing of a molded silicone body containing cross-linked thermally conductive aluminum powder> 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 vulcanizate was then heat-treated at 200°C for 4 hours. The result was a homogeneous, elastic molded body.

[0138] [Example 17 Flammability Test] Flammability is tested in a simplified test based on the UL 94V standard, a standard from Underwriters Laboratories for testing vertical flames that allows plastics to be classified according to their flame retardancy. This method is the most common test for classifying flame-retardant plastics.

[0139] Test specimens measuring 5 inches (127 mm) in length and 0.5 inches (12.7 mm) in width were punched out from the silicone molded articles of the present invention according to Examples 9-16 and the silicone molded articles not of the present invention according to Comparative Examples V11-V15 and V19-V21. The plaques were fixed in a vertical position at their top end over a length of 1 / 4 inch. A piece of absorbent cotton was placed 12 inches (305 mm) below the test plaque. The burner was adjusted to produce a 3 / 4 inch long blue flame. The flame was 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 was removed. The afterflame time (total afterflame time and afterglow time) of the test specimen was recorded. The specimen should be extinguished immediately after the flame was removed and continue to burn for an additional 4 seconds or less. Tests were performed on five different specimens, and the afterflame time was averaged. The results can be found in Table 2.

[0140] In the non-inventive comparative experiments V16 to V18, which each contained 62.5% by volume of non-inventive aluminum particles according to comparative examples V5 to V7 (more particularly not meeting feature b)), very high viscosity silicone compositions were formed which could not be pressed to obtain suitable molded silicone bodies.

[0141] [Table 2] TIFF0007739451000003.tif68165

[0142] In the flammability tests, comparative examples V11 to V15 and V19 to V23 containing non-inventive aluminum powders or non-inventive aluminum powder mixtures according to comparative examples V1 to V10, which do not satisfy one or more of characteristics a) to c), were found to exhibit relatively high flammability. Particularly notable was the flammability of non-inventive comparative sample V21, which contained aluminum powder with an average particle size of less than 20 μm. The sample continued to burn after the flame was removed until the compacts were completely combusted.

[0143] Quite unexpectedly, it was found that aluminum powders simultaneously satisfying characteristics a) to c) exhibit the inventive advantage of reduced flammability. Also, in Inventive Example 15, it was quite surprisingly found that blending multiple non-inventive aluminum powders can produce an inventive aluminum powder mixture having the inventive advantageous property of low flammability, provided that the resulting mixture satisfies characteristics a) to c). In contrast, the non-inventive aluminum powder mixture from Comparative Example V8 does not satisfy characteristics a) to c) and does not exhibit the inventive advantage.

[0144] [Example 18 Complete Combustion Test Based on UL94V Standard] The molded silicone bodies of the present invention from Examples 12 and 13 and the non-inventive molded silicone bodies of the non-inventive comparative examples V11, V12, and V20 were subjected to a complete flammability test in accordance with the UL94V standard and were classified as V-0, V-1, or V-2. For many industrial applications, particularly for use as gap fillers in electric vehicles, a V-0 classification is required. The results are shown in Table 3.

[0145] [Table 3]

[0146] Example 19: Preparation of a crosslinked, thermally conductive molded silicone body containing an in-situ mixture of two aluminum powders (invention) In accordance with General Method GM1, a crosslinkable thermally conductive silicone composition of the present invention was produced by mixing in situ 191.0 g (37.6 vol. %, based on the total amount of the thermally conductive silicone composition) of the aluminum powder of the present invention from Example 1 and 187.4 g (36.8 vol. %, based on the total amount of the thermally conductive silicone composition) of aluminum powder not of the present invention, which had a x50 of 106.2 mm and a SPAN of 0.37 and was therefore essentially rounded, with the aluminum powders being mixed together.

[0147] The resultant product had a content of aluminum particles of the present invention of 74.4% by volume and a shear rate of D=10 s -1 The reactive silicone composition of the present invention had a dynamic viscosity of 58,600 mPa·s at 25°C. Its thermal conductivity was 4.65 W / mK and its density was 2.19 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. General method GM1 was used to produce a crosslinked silicone molding of the present invention. Example 17 had an afterflame time of 2.1 seconds. Example 18 resulted in a UL94 V0 classification.

[0148] Comparative Example V24: Preparation of a crosslinked molded silicone body containing an in-situ mixture of two aluminum powders (not according to the invention). A crosslinked silicone molded body was produced according to Inventive Example 19, except that 19.0 vol. % of the aluminum powder from Inventive Example 1 was used, and 18.6 vol. % of a non-inventive aluminum powder having a x50 of 106.2 mm and a SPAN of 0.37, which was produced by inert gas atomization and therefore essentially rounded.

[0149] The non-inventive molded silicone body has a total non-inventive content of 37.6% by volume of the heat-conductive filler (Z) and has a thermal conductivity of 0.45 W / mK. Example 18 resulted in the UL94V-1 standard classification. This composition is not suitable for use as a gap filler.

[0150] [Example 20 Two-component gap filler (the present invention)] In a commercially available Labotop planetary mixer (PC Laborsystem GmbH, Miesprachstrasse 6, 4312 Magden, Switzerland) equipped with two bar stirrers and a stripper, 115.4 g of vinyl dimethyl siloxy terminated polydimethyl siloxane 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 slightly reduced pressure (950 mbar). Subsequently, a total of 670.7 g of the aluminum powder of the present invention having an x50 of 79.5 mm and a SPAN of 1.62 and produced by the inert gas atomization method and thus essentially rounded was added in two portions (first portion: 447.1 g, second portion: 223.6 g), and mixed at 300 rpm for 10 minutes under slightly reduced pressure (950 mbar) after each addition. The resulting paste-like mass was further homogenized at 300 rpm for 10 minutes under slightly reduced pressure (950 mbar). An A component of the present invention having a content of 55.5% by volume of the aluminum particles of the present invention and a total content of 73.1% by volume of the heat-conductive filler was obtained. This paste-like composition has a density of 2.46 g / cm 3 and a shear rate D = 10 s -1and has a dynamic viscosity of 57800 mPa·s at 25°C and a thermal conductivity of 3.2 W / mK, and is thus very well suited for use as a gap filler.

[0151] <Production of Component B> In a commercially available Labotop planetary mixer (PC Laborsystem GmbH, Miesplatzstrasse 6, 4312 Magden, Switzerland) equipped with two bar stirrers and a stripper, 106.5 g of vinyl dimethylsiloxy terminated polydimethylsiloxane having a viscosity of 120 mPa·s and 9.0 g of a copolymer composed of dimethylsiloxy units, methylhydroxysiloxy units and trimethylsiloxy units and having 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 minutes. 306.0 g of BAK-5 spherical aluminum oxide (available for purchase 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 slight vacuum (950 mbar). Subsequently, a total of 665.2 g of the aluminum powder of the present invention having a diameter of 79.5 µm x 50 and a SPAN of 1.62 and produced by an inert gas atomization method and thus essentially spherical was added in two portions (first portion: 443.5 g, second portion: 221.7 g), and after each addition, it was mixed at 300 rpm for 10 minutes under a slight vacuum (950 mbar). The resulting paste-like mass was further homogenized at 300 rpm for 10 minutes under a slight vacuum (950 mbar). Component B of the present invention having a content of 55.5 vol% of the aluminum particles of the present invention and a total content of 73.1 vol% of the thermal conductive filler was obtained. This paste-like composition has a density of 2.46 g / cm <> 3 of density, shear rate D = 10 s -1 and has a dynamic viscosity of 42800 mPa·s at 25°C and a thermal conductivity of 3.5 W / mK, and is thus very well suited for use as a gap filler.

[0152] <Production of Molded Product> Crosslinked test specimens of the present invention were prepared by uniformly mixing 1 part by weight of component A of the present invention with 1 part by weight of component B of the present invention and vulcanizing according to general method GM1. The resulting molded article had a Shore A hardness of 1.6. Example 18 achieved 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 50% by volume of a crosslinkable silicone composition (S), and 50 to 95% by volume 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 aluminum particles present as thermally conductive filler (Z) have the following characteristics: a) their median diameter x50 is in the range of 30 to 150 μm; b) they are produced via a melting process in the final manufacturing step and have a rounded surface profile; c) their distribution span SPAN ((x90-x10) / x50) is at least 0.40; Fulfilling that, The aluminum particles (Z) contain 1.5% by weight or less of aluminum particles smaller than 2 μm, The remainder of the thermally conductive filler (Z) is selected from aluminum powder, magnesium oxide, aluminum hydroxide, zinc oxide, and aluminum oxide. Crosslinkable thermally conductive silicone composition (Y).

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, wherein the thermally conductive filler (Z) contains at least 25% by volume of metallic aluminum particles.

4. The crosslinkable silicone composition (Y) according to any one of claims 1 to 3, characterized in that it contains, in addition to the metallic aluminum particles, one or two additional thermally conductive fillers (Z).

5. 5.0 g / cm ３ 5. A crosslinkable silicone composition (Y) according to any one of claims 1 to 4, characterized in that less than 16% by weight of a further thermally conductive filler (Z) having a greater density is present.

6. 6. The crosslinkable silicone composition (Y) according to claim 1, wherein the median diameter x50 of the metallic aluminum particles is in the range of 40 to 130 μm.

7. 7. The crosslinkable silicone composition (Y) according to claim 1, wherein the metallic aluminum 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 aluminum 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 The crosslinkable silicone composition (Y) according to any one of claims 1 to 8, characterized in that it has a dynamic viscosity of 1,000 to 750,000 mPa·s at 25°C.

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 one of claims 1 to 9 as a gap filler (=thermally conductive element), a thermally conductive pad, a thermally conductive adhesive and an encapsulating compound.

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

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

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