Thermally Conductive Organosilicon Composition

Abstract

The present invention relates to an organopolysiloxane composition comprising an organopolysiloxane having at least two alkenyl groups per molecule, an organopolysiloxane having at least two SiH units per molecule, a hydrosilylation catalyst, and a thermally conductive filler, the thermally conductive filler comprising at least 40% by weight of metal silicon and a specific particle size distribution. The present invention also relates to an organosilicon elastomer obtainable by crosslinking and / or curing the composition, and to its use as a coating or filling thermally conductive material particularly for the automotive field, especially for the field of electric vehicles.

Description

Technical Field

[0001] The present invention relates to novel organopolysiloxane compositions crosslinked by polyaddition, which are intended for the production of heat-conducting elements especially for the automotive field, in particular for the field of electric vehicles. Background Art

[0002] Thermally conductive silicone elastomers are known for their significant heat transfer, thermal resistance to heat and cold, and electrical insulation properties. They are particularly used in electrical and electronic applications and in the automotive field. Especially in the automotive field, thermally conductive silicone elastomers are used at the batteries of electric vehicles and hybrid vehicles (abbreviated as "EV" and "HEV" in English terms) to discharge heat from in-vehicle electronics and battery cells of battery packs.

[0003] Formulations of thermally conductive silicones have been described in the prior art. As early as 1981, patent US 4,292,223 described a thermally conductive elastomer comprising an organopolysiloxane, a particulate filler, and a viscosity modifier. The particulate filler comprises silica and a thermally conductive metal powder. However, the weight content of the metal powder is only 0.5:1 to 2.5:1 based on the mass ratio of powder / polymer, and the maximum thermal conductivity obtained is only 11.7×10 -4 cal / s.cm.°C, i.e., 0.5 W / m.K, which is insufficient for the required applications. Currently, it is desired to obtain a thermal conductivity greater than 2.0 W / m.K, preferably at least 3.0 W / m.K.

[0004] Traditionally, powders of metal oxides have been used to improve the thermal conductivity of elastomers, such as aluminum trihydrate (ATH), alumina, and / or magnesia (see, for example, patent application US 2019 / 0161666). However, adding these thermally conductive fillers at very high concentrations results in an increase in the density of the elastomer. For the target application fields (such as automotive), the density of the elastomer material is a very important property. It is desired to obtain a thermally conductive elastomer material with a density preferably less than 4 g / cm 3 and more preferably less than 3 g / cm 3 and even more preferably less than 2.5 g / cm 3 and still more preferably less than 2 g / cm 3 of the thermally conductive elastomer material.

[0005] Patent application JP 2000-063670 describes a thermally conductive silicone elastomer containing metallic silicon as a thermal conductive filler. Patent EP 1,788,031 also describes the use of metallic silicon powder in a silicone elastomer as a thermal conductive filler for obtaining high thermal conductivity and good storage stability. However, the maximum thermal conductivity obtained in this literature is between 0.6 W / m·K and 1.0 W / m·K. Similarly, patent application JP 2007-311628 describes a thermally conductive elastomeric film in which metallic silicon powder is used as a thermal conductive filler and an electrical insulator. Preferably, the metallic silicon powder has a particle size of less than 20 μm. Patent application KR20120086249 describes a method for preparing a thermally conductive silicone elastomer that contains a thermal conductive filler in powder form and a hollow organic resin filler. According to this literature, it is preferred to use a thermal conductive powder having particles with a diameter of 3 - 15 μm. It is stated that the obtained silicone elastomer can have a thermal conductivity of 0.15 W / m·K to 3.0 W / m·K. However, in the examples, the thermal conductivity does not exceed 0.41 W / m·K.

[0006] In another technical field, patent JP524573 describes thermally conductive hot melt tapes and rollers that use a silicone elastomer layer containing metallic silicon powder. The obtained thermal conductivity is 2 W / m·K.

[0007] There is a desire to provide a thermally conductive silicone elastomer that simultaneously has a high thermal conductivity, preferably greater than 2.0 W / m·K or 3.0 W / m·K, and a low density, preferably less than 3 g / cm 3 or less than 2 g / cm 3 Moreover, it is also necessary that the consistency of this silicone elastomer is such that it can be implemented and applied in the required technical fields. This is because the inventors have found that if the filler is not properly selected, the composition may become powdery and the preparation of the elastomer becomes impossible. Summary of the Invention

[0008] The object of the present invention is to provide a novel thermally conductive organopolysiloxane composition that solves the above-mentioned problems and simultaneously has high thermal conductivity, low density, and good processing properties.

[0009] Overview of the Invention

[0010] The subject of the present invention is an organopolysiloxane composition X, which comprises:

[0011] - at least one organopolysiloxane A having at least two C2 - C6 alkenyl groups bonded to silicon per molecule,

[0012] - at least one organopolysiloxane B having at least two SiH units per molecule,

[0013] - a catalytically effective amount of at least one hydrosilylation catalyst C, and

[0014] - a heat-conducting filler D,

[0015] characterized in that

[0016] the heat-conducting filler D contains at least 40% by weight of metallic silicon,

[0017] the heat-conducting filler D contains 3% - 22% of particles with a diameter less than or equal to 2 μm, and the size distribution of the particles is such that the ratio d90 / d10 of the filler is greater than or equal to 20.

[0018] Another subject of the present invention relates to a two-component system P, which is a precursor of the organopolysiloxane composition X as defined above and contains the components A, B, C, and D as defined above. The two-component system P is characterized in that it is in the form of two separate parts P1 and P2, and the two parts P1 and P2 are intended to be mixed to form the organopolysiloxane composition X, and one of the parts P1 or P2 contains the catalyst C and does not contain the organopolysiloxane B, while the other part P1 or P2 contains the organopolysiloxane B and does not contain the catalyst C.

[0019] Another subject of the present invention relates to an organosilicon elastomer obtainable by crosslinking and / or curing the organopolysiloxane composition X as defined above, and to the use of this organosilicon elastomer as a coating or filling heat-conducting material especially for the automotive field, particularly for the field of electric vehicles.

[0020] Another subject of the present invention relates to a method for preparing an organosilicon elastomer, comprising the following steps:

[0021] a) providing a two-component system P containing all the components of the organopolysiloxane composition X as defined above;

[0022] b) mixing the two parts of the two-component system P to obtain the organopolysiloxane composition X; and

[0023] c) crosslinking and / or curing the organopolysiloxane composition X to obtain the organosilicon elastomer.

[0024] Finally, the subject of the present invention relates to an intermediate composition, which comprises:

[0025] - at least one organopolysiloxane A having at least two C2 - C6 alkenyl groups bonded to silicon per molecule, and

[0026] - a heat-conducting filler D,

[0027] characterized in that

[0028] The heat-conductive filler D contains at least 40% by weight of metallic silicon,

[0029] the heat-conductive filler D contains 3%-22% of particles with a diameter less than or equal to 2 μm, and the size distribution of the particles is such that the ratio d90 / d10 of the filler is greater than or equal to 20.

[0030] Detailed description of the invention

[0031] Unless otherwise indicated, all viscosities of the organosilicon oils considered in this disclosure correspond to the "Newtonian" dynamic viscosity measured at 25 °C, i.e., the dynamic viscosity measured in a manner known per se using a Brookfield viscometer at a sufficiently low shear velocity gradient such that the measured viscosity is independent of the velocity gradient.

[0032] The organopolysiloxane composition X according to the invention comprises at least the following components A, B, C and D:

[0033] - an organopolysiloxane A having at least two C2-C6 alkenyl groups bonded to silicon per molecule,

[0034] - an organopolysiloxane B having at least two SiH units per molecule,

[0035] - a hydrosilylation catalyst C, and

[0036] - a heat-conductive filler D.

[0037] The organopolysiloxane A having at least two C2-C6 alkenyl groups bonded to silicon per molecule can in particular be formed from the following units:

[0038] - at least two siloxy units of the following formula: Y a R 1 b SiO (4-a-b) / 2

[0039] where:

[0040] Y is a C2-C6 alkenyl group, preferably vinyl,

[0041] R 1 is a monovalent hydrocarbon radical having 1-12 carbon atoms, preferably selected from alkyl groups having 1-8 carbon atoms such as methyl, ethyl, propyl, cycloalkyl groups having 3-8 carbon atoms and aryl groups having 6-12 carbon atoms, and

[0042] a = 1 or 2, b = 0, 1 or 2 and a + b = 1, 2 or 3; and

[0043] - optionally, a unit of the following formula: R 1 c SiO(4-c) / 2

[0044] wherein R 1 has the same meaning as described above and c = 0, 1, 2 or 3.

[0045] It should be understood that in the above formula, if there are multiple groups R 1 , they may be the same or different from each other.

[0046] These organopolysiloxanes A may have a linear structure and are substantially formed by the following units: siloxane units "D", selected from siloxane units Y2SiO 2 / 2 , YR 1 SiO 2 / 2 and R 1 2SiO 2 / 2 and terminal siloxane units "M", selected from siloxane units YR 1 2SiO 1 / 2 , Y2R 1 SiO 1 / 2 and R 1 3SiO 1 / 2 . The symbols Y and R 1 are as described above.

[0047] As examples of the terminal unit "M", mention may be made of trimethylsiloxy, dimethylphenylsiloxy, dimethylvinylsiloxy or dimethylhexenylsiloxy groups.

[0048] As examples of the unit "D", mention may be made of dimethylsiloxy, methylphenylsiloxy, methylvinylsiloxy, methylbutenylsiloxy, methylhexenylsiloxy, methyldecenylsiloxy or methyldecadienylsiloxy groups.

[0049] Examples of linear organopolysiloxanes that can be organopolysiloxanes A according to the present invention are:

[0050] - Poly(dimethylsiloxane) having dimethylvinylsilyl terminals;

[0051] - Poly(dimethylsiloxane-co-methylphenylsiloxane) having dimethylvinylsilyl terminals;

[0052] - Poly(dimethylsiloxane-co-methylvinylsiloxane) having dimethylvinylsilyl terminals;

[0053] - Poly(dimethylsiloxane-co-methylvinylsiloxane) having trimethylsilyl terminals; and

[0054] - Cyclic poly(methylvinylsiloxane).

[0055] In the most preferred form, the organopolysiloxane A contains terminal dimethylethenylsilyl units, and more preferably, the organopolysiloxane A is a poly(dimethylsiloxane) having dimethylethenylsilyl termini.

[0056] The organosilicone oil generally has a viscosity of 1 mPa·s to 2,000,000 mPa·s. Preferably, the organopolysiloxane A is an oil having a dynamic viscosity of 20 mPa·s to 100,000 mPa·s, preferably 20 mPa·s to 80,000 mPa·s at 25 °C and more preferably 100 mPa·s to 50,000 mPa·s.

[0057] Optionally, the organopolysiloxane A may further contain siloxy units "T" (R 1 SiO 3 / 2 ) and / or siloxy units "Q" (SiO 4 / 2 ). The symbol R 1 is as described above. In this case, the organopolysiloxane A has a branched structure. Examples of branched organopolysiloxanes that can be the organopolysiloxane A according to the present invention are:

[0058] - Poly(dimethylsiloxane)(methylsiloxane) having trimethylsilyl and dimethylethenylsilyl termini, composed of trimethylsiloxy "M", dimethylethenoxysiloxy "M", dimethylsiloxy "D" and methylsiloxy "T" units;

[0059] - A resin composed of trimethylsiloxy "M", dimethylethenoxysiloxy "M" and "Q" units; and

[0060] - A resin composed of trimethylsiloxy "M", methylethenoxysiloxy "D" and "Q" units.

[0061] However, according to one embodiment, the organopolysiloxane composition X does not contain a resin or a branched organopolysiloxane containing C2-C6 alkenyl units.

[0062] Preferably, the organopolysiloxane compound A has an alkenyl unit mass content of 0.001% - 30%, preferably 0.01% - 10%, preferably 0.02 - 5%.

[0063] The organopolysiloxane composition X preferably contains 5% - 30% of the organopolysiloxane A, more preferably 8% - 15% of the organopolysiloxane A, by weight, based on the total weight of the organopolysiloxane composition X.

[0064] The organopolysiloxane composition X may comprise a single organopolysiloxane A or a mixture of a plurality of organopolysiloxanes A having, for example, different viscosities and / or different structures.

[0065] The organohydrogenpolysiloxane B is an organohydrogenpolysiloxane compound containing at least two, and preferably at least three, hydridosilyl functional groups or Si-H units per molecule. The organopolysiloxane composition X may comprise a single organohydrogenpolysiloxane B or a mixture of a plurality of organohydrogenpolysiloxanes B having, for example, different viscosities and / or different structures.

[0066] The organohydrogenpolysiloxane B may advantageously be an organopolysiloxane comprising at least two, preferably at least three, siloxane units of the following formula: H d R 2 e SiO (4-d-e) / 2

[0067] wherein:

[0068] - the group R 2 , which may be the same or different, represents a monovalent group having 1 to 12 carbon atoms,

[0069] - d = 1 or 2, e = 0, 1 or 2 and d + e = 1, 2 or 3;

[0070] and optionally, other units of the following formula: R 2 f SiO (4-f) / 2

[0071] where R 2 has the same meaning as defined above, and f = 0, 1, 2 or 3.

[0072] It should be understood that in the above formulae, if there are a plurality of groups R 2 , they may be the same or different from each other. Preferably, R 2 may represent a monovalent group selected from alkyl groups having 1 to 8 carbon atoms optionally substituted with at least one halogen atom such as chlorine or fluorine; cycloalkyl groups having 3 to 8 carbon atoms; and aryl groups having 6 to 12 carbon atoms. R 2 may advantageously be selected from methyl, ethyl, propyl, 3,3,3-trifluoropropyl, dimethylphenyl, tolyl and phenyl.

[0073] In the above formula, the symbol d is preferably equal to 1.

[0074] The organohydrogenpolysiloxane B may have a linear, branched or cyclic structure. The degree of polymerization is preferably greater than or equal to 2. Usually, it is less than 5000.

[0075] When it comes to linear polymers, they are basically composed of siloxy units selected from the following formula D:R 2 2SiO 2 / 2 or D’:R 2 HSiO 2 / 2 and terminal siloxy units selected from the following formula M:R 2 3SiO 1 / 2 or M’:R 2 2HSiO 1 / 2 where R 2 has the same meaning as described above.

[0076] Examples of organohydrogenpolysiloxanes that can be organohydrogenpolysiloxanes B containing at least two hydrogen atoms bonded to silicon atoms according to the present invention are:

[0077] - Poly(dimethylsiloxane) with hydrogen-based dimethylsilyl terminals;

[0078] - Poly(dimethylsiloxane-co-methylhydrogensiloxane) with trimethylsilyl terminals;

[0079] - Poly(dimethylsiloxane-co-methylhydrogensiloxane) with hydrogen-based dimethylsilyl terminals;

[0080] - Poly(methylhydrogensiloxane) with trimethylsilyl terminals; and

[0081] - Cyclic poly(methylhydrogensiloxane).

[0082] When the organohydrogenpolysiloxane B has a branched structure, it is preferably selected from organosilicon resins of the following formula:

[0083] - M’Q, where the hydrogen atom bonded to the silicon atom is carried by the group M,

[0084] - MM’Q, where the hydrogen atom bonded to the silicon atom is carried by a part of the M unit,

[0085] - MD’Q, where the hydrogen atom bonded to the silicon atom is carried by the group D,

[0086] - MDD’Q, where the hydrogen atom bonded to the silicon atom is carried by a part of the group D,

[0087] - MM’TQ, where the hydrogen atom bonded to the silicon atom is carried by a part of the M unit,

[0088] - MM’DD’Q, where the hydrogen atom bonded to the silicon atom is carried by a part of the M and D units,

[0089] - And their mixtures,

[0090] wherein M, M’, D and D’ are as defined above, T: a siloxy unit of formula R 2 3SiO 1 / 2 and Q: a siloxy unit of formula SiO 4 / 2 wherein R 2 has the same meaning as defined above.

[0091] Preferably, the mass content of the hydrosilyl group Si-H in the organohydrogenpolysiloxane compound B is 0.2% - 91%, more preferably 3% - 80%, and still more preferably 15% - 70%.

[0092] Considering the entire organopolysiloxane composition X, the molar ratio of the hydrosilyl group Si-H to the olefin functional group can advantageously be between 0.2 and 20, preferably between 0.5 and 15, more preferably between 0.5 and 10, and even more preferably between 0.5 and 5.

[0093] Preferably, the viscosity of the organohydrogenpolysiloxane B is 1 mPa·s - 5000 mPa·s, more preferably 1 mPa·s - 2000 mPa·s, and still more preferably 5 mPa·s - 1000 mPa·s.

[0094] The organopolysiloxane composition X preferably contains 0.1% - 10% and more preferably 0.5 - 5% by weight of the organohydrogenpolysiloxane B, based on the total weight of the organopolysiloxane composition X.

[0095] The hydrosilylation catalyst C can be particularly selected from compounds of platinum and rhodium, but can also be selected from silicon compounds such as those described in patent applications WO2015 / 004396 and WO2015 / 004397; germanium compounds such as those described in patent application WO2016 / 075414; or complexes of nickel, cobalt or iron such as those described in patent applications WO2016 / 071651, WO2016 / 071652 and WO2016 / 071654. The catalyst C is preferably a compound derived from at least one metal belonging to the platinum group. These catalysts are well-known. In particular, complexes of platinum and organic products described in patents US 3,159,601, US 3,159,602, US 3,220,972 and European patents EP 0.057.459, EP 0.188.978 and EP 0.190.530 can be used, or complexes of platinum and vinylated organosiloxanes described in patents US 3,419,593, US 3,715,334, US 3,377,432 and US 3,814,730.

[0096] Preferably, catalyst C is a compound derived from platinum. In this case, the weight dosage of catalyst C calculated based on the weight of platinum metal is generally 2 ppm - 400 ppm by mass, preferably 5 ppm - 200 ppm, based on the total weight of composition X.

[0097] Preferably, catalyst C is Karstedt platinum catalyst.

[0098] The organopolysiloxane composition X according to the present invention is characterized in that it contains a heat-conducting filler D. The heat-conducting filler can be composed of a single filler or a mixture of fillers having different chemical properties and / or different structures and / or different particle sizes. According to a preferred embodiment of the present invention, the heat-conducting filler D is composed of a mixture of at least two fillers or at least three fillers having different chemical properties and / or particle sizes. According to another preferred embodiment of the present invention, the heat-conducting filler D is composed of a single filler.

[0099] The total weight of the heat-conducting filler D in the organopolysiloxane composition X is preferably greater than 70% by weight, more preferably greater than 75% by weight, and still more preferably between 80% by weight and 95% by weight, based on the total weight of the organopolysiloxane composition X. According to a particularly advantageous embodiment of the present invention, the total weight of the heat-conducting filler D in the organopolysiloxane composition X is greater than or equal to 85%. Such a particularly high content of the heat-conducting filler enables a very high thermal conductivity to be obtained.

[0100] The heat-conducting filler D contains at least 40% by weight, preferably at least 50% by weight, more preferably at least 60% by weight, more preferably at least 70% by weight, and still more preferably at least 80% by weight of metal silicon.

[0101] According to the first embodiment, the heat-conducting filler D contains 60% to 99.99% by weight, preferably 65% to 99.95% by weight, more preferably 70% to 99.99% by weight, even more preferably 70% - 99% by weight, more preferably 75% - 97% by weight, and more preferably 80% - 95% by weight of metal silicon.

[0102] In addition to this metallic silicon, the heat-conducting filler D may further comprise one or more other fillers of different natures, which other fillers are known to those skilled in the art by reason of their heat-conducting properties and are especially selected from metals, alloys, metal oxides, metal hydroxides, metal nitrides, metal carbides, metal silicides, carbon, soft magnetic alloys and ferrites. The thermal conductivities of these fillers are preferably greater than 10 W / m.K, more preferably greater than 20 W / m.K and even more preferably greater than 50 W / m.K. They may especially be selected from alumina, aluminum trihydroxide (ATH), aluminum, silicon carbide, silicon nitride, magnesium oxide, magnesium carbonate, boron nitride, zinc oxide, aluminum nitride, and carbon such as carbon black, diamond, carbon nanotubes, graphite and graphene. Preferably, the heat-conducting filler D may further comprise, in addition to the metallic silicon, a heat-conducting filler selected from alumina fillers, aluminum trihydroxide (ATH) fillers, aluminum fillers, silica fillers, zinc oxide fillers, aluminum nitride fillers, boron nitride fillers and mixtures thereof. More preferably, the heat-conducting filler D may further comprise, in addition to the metallic silicon, a heat-conducting filler selected from alumina fillers, aluminum trihydroxide (ATH) fillers, zinc oxide fillers, silica fillers and mixtures thereof. The heat-conducting filler D may comprise 0.01% to 60% by weight, preferably 0.05% to 50% by weight, more preferably 0.1% to 40% by weight, more preferably 1% to 30% by weight, more preferably 3% to 25% by weight, more preferably 5% to 20% by weight of a heat-conducting filler other than metallic silicon.

[0103] According to another embodiment, the heat-conducting filler D comprises 100% by weight of metallic silicon, i.e., the heat-conducting filler D consists of metallic silicon, excluding any other heat-conducting filler of a different chemical nature. Thus, preferably:

[0104] - The organopolysiloxane composition X does not contain alumina, and / or

[0105] - The organopolysiloxane composition X does not contain aluminum trihydroxide (ATH), and / or

[0106] - The organopolysiloxane composition X does not contain zinc oxide, and / or

[0107] - The organopolysiloxane composition X does not contain silica.

[0108] The heat-conducting filler D according to the invention has certain granulométrie characteristics.

[0109] On the one hand, the heat-conducting filler D comprises 3% - 22% (by volume) of particles having a diameter less than or equal to 2 μm (micrometers). More preferably, the heat-conducting filler D comprises 3% - 20% (by volume) of particles having a diameter less than or equal to 2 μm (micrometers). Even more preferably, the heat-conducting filler D comprises 6% - 18% (by volume) of particles having a diameter less than or equal to 2 μm.

[0110] On the other hand, the particle size distribution is such that the ratio d90 / d10 of the filler is greater than or equal to 20. More preferably, the particle size distribution is such that the ratio d90 / d10 of the filler is greater than or equal to 30. Advantageously, the ratio d90 / d10 of the filler is less than 200, preferably less than 100.

[0111] In this text, the particle size of the filler is measured by laser diffraction. The content of particles with a diameter less than or equal to 2 μm is a volume content, obtained by summing the volumes of all particles with a diameter less than or equal to 2 μm measured by laser diffraction. "d90" corresponds to the characteristic diameter corresponding to 90% of the volume cumulative frequency of the particle size distribution of the filler. "d10" corresponds to the characteristic diameter corresponding to 10% of the volume cumulative frequency of the particle size distribution of the filler.

[0112] The one or more thermally conductive fillers may have a specific surface area of at least 0.1 m 2 / g measured according to the BET method. Typically, the specific surface area is less than or equal to 3000 m 2 / g. Preferably, the one or more thermally conductive fillers may have a specific surface area of 0.1 m 2 / g to 100 m 2 / g, or even 0.1 m 2 / g to 10 m 2 / g measured according to the BET method.

[0113] The thermally conductive filler D may have any form known to those skilled in the art, such as spherical, needle-shaped, disk-shaped, rod-shaped or irregular. Preferably, the thermally conductive filler has a spherical or irregular shape. When different thermally conductive fillers are used in a mixture, they may have the same shape or different shapes.

[0114] Regarding the metal silicon thermally conductive filler, it can be obtained by any method known to those skilled in the art. According to the first embodiment, the metal silicon thermally conductive filler is a powder obtained by chemically reducing silicon dioxide and then grinding it in a crusher or an industrial mill. According to the second embodiment, the metal silicon thermally conductive filler is a powder obtained from the fragments of metal silicon wafers and chips in the semiconductor industry that have been finely cut or ground. According to the third embodiment, the metal silicon thermally conductive filler is a spherical powder obtained by high-temperature melting of metal silicon, atomizing the molten silicon, and then cooling or solidifying the resulting spherical particles. The metal silicon can be single-crystalline or polycrystalline. The metal silicon thermally conductive filler can be classified according to methods known to those skilled in the art, such as by dry classification or wet classification, or by a series of multiple classification steps of the same or different types.

[0115] The metal silicon thermal conductivity filler typically has a purity greater than 50%, or greater than 80%, or greater than 95% (by weight). However, it is known that the surface of the metal silicon filler can be covered with a silica layer. The appearance of this silica layer can be natural or generated by certain treatments. It can advantageously impart better thermal stability to the filler.

[0116] The one or more metal silicon thermal conductivity fillers can be used as such, or they can be surface-treated. The purpose of the surface treatment typically lies in improving the dispersibility of the filler in the organopolysiloxane composition and / or improving the thermal stability of the composition. In addition, the heat treatment can improve the physical stability of the composition by preventing phenomena such as sedimentation or exudation or an increase in viscosity.

[0117] The surface treatment can be a heat treatment, a chemical treatment, a physical treatment, or a combination thereof, especially a combination of chemical treatments.

[0118] According to a preferred embodiment, the metal silicon thermal conductivity filler can be treated with organosilicon compounds commonly used for this purpose. The organopolysiloxane composition X according to the present invention can thus contain a reagent E for treating the thermal conductivity filler. These reagents include:

[0119] - Organosiloxanes, especially methylpolysiloxanes such as hexamethyldisiloxane and octamethylcyclotetrasiloxane,

[0120] - Organosilazanes, especially methylpolysilazanes such as hexamethyldisilazane, divinyltetramethyldisilazane, and hexamethylcyclotrisilazane,

[0121] - Chlorosilanes such as dimethyldichlorosilane, trimethylchlorosilane, methylvinyldichlorosilane, and dimethyvinylchlorosilane,

[0122] - Alkoxysilanes such as methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, octyltrimethoxysilane, vinyltrimethoxysilane, dimethyvinyl ethoxysilane, vinyltris(2-methoxyethoxy)silane, vinyltriacetoxysilane, allyltrimethoxysilane, butenyltrimethoxysilane, hexenyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, trimethylmethoxysilane, and trimethylethoxysilane.

[0123] More preferably, the metal silicon heat conductive filler can be treated with an alkoxysilane (especially octyltrimethoxysilane) or with an organosilazane (especially hexamethyldisilazane (HMDZ) and divinyltetramethyldisilazane) or a mixture thereof (especially a mixture of HMDZ and divinyltetramethyldisilazane). When treating the heat conductive filler with a chemical reagent (especially with an organosilazane), water can usually be added.

[0124] The organopolysiloxane composition X preferably contains 0.1% to 5% by weight, more preferably 1% to 3% by weight, based on the total weight of the organopolysiloxane composition X, of the reagent E for treating the heat conductive filler.

[0125] The heat treatment of the metal silicon heat conductive filler can involve subjecting the filler to a temperature of 100°C to 200°C for a time of 1 hour to 4 hours.

[0126] Physical treatment means adding a physical treatment agent to the heat conductive filler, which interacts with the filler substantially physically rather than chemically, for example through ionic interactions or through hydrogen bonds. The physical treatment agent can usually be an organopolysiloxane containing OH in the group.

[0127] According to one embodiment, the surface treatment can be carried out before combining the heat conductive filler into the organopolysiloxane composition. According to an alternative embodiment, the heat conductive filler can be treated in situ during the preparation of the organopolysiloxane composition.

[0128] In addition to the components A, B, C, and D already mentioned above, the organopolysiloxane composition X according to the present invention can optionally contain other components.

[0129] According to one embodiment, the organopolysiloxane composition X according to the present invention can optionally contain a filler E that is not a heat conductive filler.

[0130] According to one embodiment, the organopolysiloxane composition X according to the present invention can optionally contain a crosslinking inhibitor F. The function of the inhibitor F is to slow down the hydrosilylation reaction. The crosslinking inhibitor F can be selected from the following compounds:

[0131] - Advantageously cyclic and organopolysiloxanes substituted by at least one alkenyl group, particularly preferably tetramethylethylenetetrasiloxane,

[0132] - Pyridine,

[0133] - Organic phosphites and phosphines,

[0134] - Unsaturated amides,

[0135] - Alkylated maleates, and

[0136] - Alkynols.

[0137] Preferably, the crosslinking inhibitor F is an acetylenic alcohol of the formula (R 1 )(R 2 )C(OH)-C≡CH, where

[0138] -R 1 is a linear or branched alkyl group, or a phenyl group,

[0139] -R 2 is a hydrogen atom, a linear or branched alkyl group, or a phenyl group,

[0140] -The group R 1 、R 2 may optionally form a ring with the carbon atom located at the α-position relative to the triple bond; and

[0141] -R 1 and R 2 The total number of carbon atoms contained in is at least 5, preferably 9-20.

[0142] The alcohol is preferably selected from those having a boiling point greater than 250 °C. As examples, the following commercially available products may be mentioned: 1-ethynyl-1-cyclohexanol, 3-methyl-1-dodecyn-3-ol, 3,7,11-trimethyl-1-dodecyn-3-ol, 1,1-diphenyl-2-propyn-1-ol, 3-ethyl-6-ethyl-1-nonyn-3-ol, and 3-methyl-1-pentadecyn-3-ol. Preferably, the crosslinking inhibitor F is 1-ethynyl-1-cyclohexanol.

[0143] According to the method for producing the silicone elastomer according to the present invention, the presence of this inhibitor may or may not be necessary. If required, such a crosslinking inhibitor may typically be present in a proportion of up to 3000 ppm, preferably 100 ppm to 2000 ppm, based on the total weight of the organopolysiloxane composition X.

[0144] According to one embodiment, the organopolysiloxane composition X according to the present invention may optionally contain other additives conventionally used by those skilled in the art in this technical field, such as adhesion promoters, colorants, flame retardants, rheological agents such as thixotropic agents, etc.

[0145] According to one embodiment, the organopolysiloxane composition X according to the present invention may contain a low ratio of volatile organic compounds, typically less than 100 μgC / g, preferably less than 70 μgC / g, or less than 50 μgC / g. For this purpose, the organopolysiloxane compounds used in the composition of the present invention may preferably be selected from compounds that themselves contain a low ratio of volatile organic compounds.

[0146] According to a preferred embodiment, the organopolysiloxane composition X according to the present invention comprises:

[0147] -5% - 30%, preferably 8% - 15%, of an organopolysiloxane A having at least two C2 - C6 alkenyl groups bonded to silicon per molecule,

[0148] -0.1% - 10%, preferably 0.5% - 5%, of an organopolysiloxane B having at least two SiH units per molecule,

[0149] -2 ppm - 400 ppm, preferably 5 ppm - 200 ppm, of a hydrosilylation catalyst C,

[0150] -70% - 95%, preferably 80% - 95%, of a heat - conducting filler D,

[0151] -0.1% - 5%, preferably 1% - 3%, of a reagent E for treating the heat - conducting filler,

[0152] -100 ppm - 3000 ppm, preferably 100 ppm - 2000 ppm, of a cross - linking inhibitor F.

[0153] The percentages and ppm are mass percentages and ppm. The weight amount of catalyst C is calculated based on the weight of platinum metal.

[0154] Another subject of the present invention is an organosilicon elastomer obtainable or obtained by cross - linking and / or curing the organopolysiloxane composition X as defined above, a method for obtaining said elastomer, and an intermediate composition used in said obtaining method.

[0155] The organopolysiloxane composition X as defined above is particularly suitable for preparing an organosilicon elastomer having heat - conducting properties.

[0156] According to one embodiment, the elastomer is prepared from a two - component system P comprising all the components of the organopolysiloxane composition X.

[0157] More particularly, another subject of the present invention is a two - component system P which is a precursor of the organopolysiloxane composition X as defined above and comprises at least components A, B, C, and D. The two - component system P is characterized in that it is in the form of two separate parts P1 and P2, the two parts P1 and P2 being intended to be mixed to form the organopolysiloxane composition X, and one of the parts P1 or P2 contains catalyst C and does not contain organopolysiloxane B, while the other part P1 or P2 contains organopolysiloxane B and does not contain catalyst C.

[0158] Another subject of the present invention is a method for preparing an organosilicon elastomer, comprising the following steps:

[0159] a) providing a two - component system P comprising all the components of the organopolysiloxane composition X as defined above;

[0160] b) Mix the two parts of the two-component system P to obtain the organopolysiloxane composition X; and

[0161] c) Crosslink and / or cure the organopolysiloxane composition X to obtain the silicone elastomer.

[0162] According to a preferred embodiment, part P1 comprises:

[0163] - Part or all of an organopolysiloxane A having at least two C2-C6 alkenyl groups bonded to silicon per molecule,

[0164] - A hydrosilylation catalyst C,

[0165] - Part or all of a heat-conductive filler D,

[0166] - Optionally, a reagent E for treating the heat-conductive filler,

[0167] And part P2 comprises:

[0168] - Optionally, part of an organopolysiloxane A having at least two C2-C6 alkenyl groups bonded to silicon per molecule,

[0169] - An organopolysiloxane B having at least two SiH units per molecule,

[0170] - Part or all of a heat-conductive filler D,

[0171] - Optionally, a reagent E for treating the heat-conductive filler,

[0172] - Optionally, a crosslinking inhibitor F.

[0173] The heat-conductive filler D may be present in part P1, part P2 or both part P1 and P2, with the same or different amounts between part P1 and P2. The heat-conductive filler D may advantageously be present in part P1 and part P2 in the same amount. Thus, the total amount of the heat-conductive filler D remains constant in the organopolysiloxane composition X, regardless of the mixing ratio of part P1 and P2.

[0174] Each of part P1 and P2 according to the present invention can be obtained by mixing various components in a suitable apparatus known to those skilled in the art.

[0175] According to a particularly advantageous embodiment of the present invention, part P1, part P2 or both part P1 and P2 can be obtained from an intermediate composition comprising part or all of an organopolysiloxane A and part or all of a heat-conductive filler D, and optionally, a reagent E for treating the heat-conductive filler.

[0176] Another subject of the present invention is an intermediate composition comprising:

[0177] - at least one organopolysiloxane A having at least two C2-C6 alkenyl groups bonded to silicon per molecule, and

[0178] - a heat-conductive filler D,

[0179] characterized in that

[0180] the heat-conductive filler D comprises at least 40% by weight of metallic silicon,

[0181] the heat-conductive filler D comprises 3% - 22% of particles having a diameter less than or equal to 2 μm, and the size distribution of the particles is such that the ratio d90 / d10 of the filler is greater than or equal to 20.

[0182] The organopolysiloxane A and the heat-conductive filler D are preferably as described above.

[0183] The total weight of the heat-conductive filler D in the intermediate composition is advantageously greater than 70% by weight, more preferably greater than 75% by weight, and even more preferably greater than 80% by weight, and still more preferably between 85% by weight and 98% by weight, based on the total weight of the intermediate composition. This intermediate composition, which is particularly rich in the heat-conductive filler D, can be diluted with other components to easily obtain the organopolysiloxane composition X or the precursor parts P1 and / or P2. The intermediate composition according to the present invention can be obtained by at least mixing the organopolysiloxane A and the heat-conductive filler D by means of devices known to those skilled in the art (such as a Z-arm mixer or a butterfly mixer). The heat-conductive filler D can optionally be surface-treated, and the treatment can be a heat treatment, a chemical treatment, or a combination of a heat treatment and a chemical treatment. The intermediate composition can optionally contain the reagent E for treating the heat-conductive filler as described above. The heat-conductive filler can be heat-treated before being mixed into the intermediate composition. Additionally, optionally, after mixing the organopolysiloxane A, the heat-conductive filler D, and optionally the reagent E for treating the heat-conductive filler, the intermediate composition can be heat-treated.

[0184] The organopolysiloxane composition X and the parts P1 and P2 of the two-component precursor system P of the organopolysiloxane composition X advantageously have good processing properties. The reason is that, despite the very high content of the heat-conductive filler, the composition is advantageously paste-like rather than powdery, and thus is easy to handle, especially by extrusion. The contribution of the present inventors lies in successfully determining the good characteristics of the heat-conductive filler that allow this technical result to be achieved.

[0185] The silicone elastomer which is the subject of the present invention and which is obtained or obtainable by crosslinking and / or curing the organopolysiloxane composition X advantageously has a thermal conductivity of greater than or equal to 1 W / m.K, preferably greater than or equal to 1.5 W / m.K, more preferably greater than or equal to 2 W / m.K, more preferably greater than or equal to 3 W / m.K and even more preferably between 3 W / m.K and 7 W / m.K.

[0186] Moreover, the silicone elastomer advantageously has a density of less than or equal to 4 g / cm 3 , preferably less than or equal to 3 g / cm 3 , more preferably less than 2 g / cm 3 .

[0187] Advantageously, the silicone elastomer according to the invention can be easily recycled after use. This is because such an elastomer preferably contains a very high content of elemental silicon, especially when the thermally conductive filler itself contains a very high content of metallurgical silicon. The used silicone elastomer can be advantageously recycled using a combustion furnace.

[0188] The silicone elastomer can advantageously be used as a thermally conductive material in various technical fields, especially in the electronics field, electrical applications and the automotive field. The silicone elastomer can advantageously be used as a coating (i.e., the English term is "potting") or filling (i.e., the English term is "gap filler") thermally conductive material, especially for batteries, such as the batteries of electric vehicles and hybrid vehicles, and can also be used for fixing batteries. In the electronics field, the silicone elastomer according to the invention can advantageously be used as a thermally conductive material in 5G devices. Detailed Description

[0189] Examples

[0190] The following exemplified organopolysiloxane compositions are obtained from the following raw materials:

[0191] A: Chain-end vinylated organopolysiloxane oil with a vinyl content of 1.2% by weight and a viscosity = 100 mPa.s

[0192] B1: Hydrogen-based dimethylpolysiloxane oil with chain-end (α / ω)SiH groups, SiH vinyl content of 5.7% by weight and a viscosity = 8.5 mPa.s

[0193] B2: Poly(methylhydrogen)(dimethyl)siloxane oil with chain-middle and chain-end (α / ω)SiH groups, SiH vinyl content of 7.3% by weight and a viscosity = 30 mPa.s

[0194] C: Karstedt platinum catalyst containing 10% by weight of platinum metal

[0195] D1: Silicon powder (purity > 99%), d10 = 42.3 μm, d50 = 70 μm, d90 = 112 μm, d100 = 200 μm

[0196] D2: Silicon powder (purity > 99%), d10 = 15 μm, d50 = 31.6 μm, d90 = 54 μm, d100 = 100 μm

[0197] D3: Silicon powder (purity > 99%), d10 = 6.4 μm, d50 = 10.4 μm, d90 = 16.4 μm, d100 = 30 μm

[0198] D4: Silicon powder (purity > 99%), d10 = 2 μm, d50 = 10.7 μm, d90 = 26 μm, d100 = 60 μm

[0199] D5: Silicon powder (purity > 99%), d10 = 0.9 μm, d50 = 2.7 μm, d90 = 5.3 μm, d100 = 10 μm

[0200] D6: Silicon powder (purity > 99%), d10 = 4.0 μm, d50 = 10 μm, d90 = 25

[0201] D7: Alumina powder, d10 = 1 μm, d50 = 5.7 μm, d90 = 12.3 μm

[0202] D8: Alumina powder, d10 = 18 μm, d50 = 46 μm, d90 = 73 μm

[0203] D9: Alumina powder, d10 = 0.3 μm, d50 = 2.4 μm, d90 = 18 μm

[0204] D10: Zinc oxide powder, d10 = 0.2 μm, d50 = 1.5 μm, d90 = 5 μm

[0205] E1: Octyltrimethoxysilane

[0206] F: 1-Ethynyl-1-cyclohexanol (ECH)

[0207] In the following examples, the particle size of the filler was measured by laser diffraction method:

[0208] - "d10" corresponds to the characteristic diameter corresponding to 10% of the volume cumulative frequency of the particle size distribution of the filler.

[0209] - "d50" corresponds to the characteristic diameter corresponding to 50% of the volume cumulative frequency of the particle size distribution of the filler.

[0210] - "d90" corresponds to the characteristic diameter corresponding to 90% of the volume cumulative frequency of the particle size distribution of the filler.

[0211] - "d100" corresponds to the characteristic diameter corresponding to 100% of the volume cumulative frequency of the particle size distribution of the filler.

[0212] - The content of particles with a diameter less than or equal to 2 μm is the volume content, obtained by summing the volumes of all particles with a diameter less than or equal to 2 μm measured by laser diffraction.

[0213] Examples 1 to 17 :

[0214] The silicone compositions corresponding to parts P1 and P2 are prepared according to the following scheme:

[0215] For part P1: The thermal conductive filler D, silicone oil A, and catalyst C are mixed in a Speed Mixer at 1800 revolutions per minute at the concentrations shown in Table 1 below. The concentration of the thermal conductive filler is 85%.

[0216] For part P2: The thermal conductive filler D, silicone oil A, silicone oils B1 and B2, and 1-ethynyl-1-cyclohexanol F are mixed in a Speed Mixer at 1800 revolutions per minute at the concentrations shown in Table 1 below. The concentration of the thermal conductive filler is 85%.

[0217] [Table 1]

[0218] Examples 1 to 17 are achieved by following the above production scheme and changing the thermal conductive filler D as described in Tables 2 and 3 below.

[0219] The processing performance of the resulting compositions is visually evaluated and classified as follows:

[0220] "--" = very poor - powdery appearance

[0221] "-" = poor - appearance of chips and aggregates

[0222] "+" = good - pasty appearance

[0223] "++" = very good - pasty and smooth appearance.

[0224] The results are shown in Tables 2 and 3 below.

[0225] [Table 2]

[0226]

[0227] [Table 3]

[0228]

[0229] Examples 18 to 22

[0230] Examples 18 to 22 were achieved by mixing 85% of the thermal conductive filler D with 15% of the organosilicone oil A using a Speed Mixer (stirring at 1800 revolutions per minute for 2 x 2 minutes), and changing the thermal conductive filler D as shown in Table 4 below. As described above, the processability of the resulting composition was visually evaluated. The thermal conductivity and density of the elastomeric material that could be obtained from the exemplified compositions were estimated by calculation.

[0231] [Table 4]

[0232]

[0233] Example 23

[0234] Step 1: Preparation of the intermediate composition

[0235] 89% of the thermal conductive filler D, 9% of the organosilicone oil A, and 2% of octyltrimethoxysilane E1 (by mass percentage) were mixed in a Z-arm mixer for 30 minutes. The resulting composition was heat-treated at 150 °C for 2 hours.

[0236] The thermal conductive filler D consisted of 60% by weight of filler D2 and 40% by weight of filler D5. The characteristics of the filler were as follows:

[0237] - Proportion of particles with a diameter less than or equal to 2 μm = 13.7%

[0238] - d90 / d10 = 32.

[0239] Step 2: Production of parts P1 and P2

[0240] For part P1: The paste formulation obtained in step 1 was diluted with organosilicone oil A and catalyst C at the concentrations shown in Table 5 below. The concentration of the thermal conductive filler was 85%.

[0241] For part P2: The paste formulation obtained in step 1 was diluted with organosilicone oil A, organosilicone oils B1 and B2, and 1-ethynyl-1-cyclohexanol F at the concentrations shown in Table 5 below. The concentration of the thermal conductive filler was 85%.

[0242] These diluted formulations were obtained by mixing in a Speed Mixer at 1800 revolutions per minute.

[0243] Parts P1 and P2 had very good processability.

[0244] Step 3: Preparation of the thermally conductive silicone composition and the thermally conductive silicone elastomer

[0245] Mix the portions P1 and P2 obtained in Step 2 in a 1:1 ratio in a Speed Mixer. Degas the obtained mixture under reduced pressure and then pour it into a mold. Then place the mixture in the mold in a hot press at a pressure of 2 bar and a temperature of 100 °C for 30 minutes.

[0246] [Table 5]

[0247]

[0248] Measure the thermal conductivity of the elastomer by the transient plane heat source method (TPS method) (Determination of thermal conductivity and heat effusivity. Part 2: Transient plane heat source (hot disk) method) as described in ISO standard 22007-2, with the aid of the device Hot Disk TPS 2200. The thermal conductivity of the elastomer is 3.42 W / m.K. The density of the elastomer is 1.94 g / cm 3 .

Claims

1. An organopolysiloxane composition X, comprising: - at least one organopolysiloxane A having at least two C2-C6 alkenyl groups bonded to silicon per molecule, - at least one organopolysiloxane B having at least two SiH units per molecule, - a catalytically effective amount of at least one hydrosilylation catalyst C, and - a thermally conductive filler D, characterized in that the thermally conductive filler D contains at least 40% by weight of metallic silicon, the thermally conductive filler D contains 3% - 22% of particles with a diameter less than or equal to 2 µm, and the size distribution of the particles is such that the ratio d90 / d10 of the filler is greater than or equal to 20 and less than 200.

2. The organopolysiloxane composition X according to claim 1, characterized in that, The total weight of the thermally conductive filler D in the organopolysiloxane composition X is 80% - 95%.

3. The organopolysiloxane composition X according to claim 1 or 2, characterized in that, The thermally conductive filler D contains 3% - 20% of particles with a diameter less than or equal to 2 µm.

4. The organopolysiloxane composition X according to claim 1 or 2, characterized in that, The size distribution of the particles is such that the ratio d90 / d10 of the filler is greater than or equal to 30.

5. The organopolysiloxane composition X according to claim 1 or 2, characterized in that, The thermally conductive filler D contains at least 70% by weight of metallic silicon.

6. The organopolysiloxane composition X according to claim 1 or 2, characterized in that, The thermally conductive filler D contains 100% by weight of metallic silicon.

7. The organopolysiloxane composition X according to claim 1 or 2, characterized in that, In addition to metallic silicon, the thermally conductive filler D further contains a thermally conductive filler selected from alumina filler, aluminum trihydrate filler, aluminum filler, silica filler, zinc oxide filler, aluminum nitride filler, boron nitride filler, and mixtures thereof.

8. The organopolysiloxane composition X according to claim 1 or 2, characterized in that, The organopolysiloxane composition X comprises: - 5% - 30% of an organopolysiloxane A having at least two C2-C6 alkenyl groups bonded to silicon per molecule, - 0.1% - 10% of an organopolysiloxane B having at least two SiH units per molecule, - 2 ppm - 400 ppm of a hydrosilylation catalyst C, - 70% - 95% of a thermally conductive filler D, - 0.1% - 5% of a reagent E for treating the thermally conductive filler, - 100 ppm - 3000 ppm of a crosslinking inhibitor F.

9. A two-component system P, which is a precursor of the organopolysiloxane composition X defined in any one of claims 1 - 8 and contains components A, B, C, and D defined in any one of claims 1 - 8. The two-component system P is characterized in that it is in the form of two separate parts P1 and P2, and the two parts P1 and P2 are intended to be mixed to form the organopolysiloxane composition X. One of the parts P1 or P2 contains the catalyst C and does not contain the organopolysiloxane B, while the other part P1 or P2 contains the organopolysiloxane B and does not contain the catalyst C.

10. An organosilicon elastomer obtainable by crosslinking and / or curing the organopolysiloxane composition X defined in any one of claims 1 - 8.

11. A method for preparing an organosilicon elastomer, comprising the following steps: a) providing a two-component system P containing all the components of the organopolysiloxane composition X defined in any one of claims 1 - 8; b) mixing the two parts of the two-component system P to obtain the organopolysiloxane composition X; and c) crosslinking and / or curing the organopolysiloxane composition X to obtain the organosilicon elastomer.

12. Use of the organosilicon elastomer defined in claim 10 as a coating or filling thermally conductive material.

13. Intermediate composition, comprising: - at least one organopolysiloxane A having at least two C2-C6 alkenyl groups bonded to silicon per molecule, and - a thermally conductive filler D, characterized in that the thermally conductive filler D contains at least 40% by weight of metallic silicon, the thermally conductive filler D contains 3% - 22% of particles having a diameter less than or equal to 2 µm, and the size distribution of the particles is such that the ratio d90 / d10 of the filler is greater than or equal to 20 and less than 200.

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