Crosslinkable silicone composition by polyaddition for the preparation of heat-conducting silicone elastomers

Abstract

This invention relates to organosilicon compositions crosslinked via a polyaddition reaction, intended for use in the production of thermally conductive elements. The organosilicon compositions comprise at least one organopolysiloxane A, each molecule having at least one C2-C bonded to silicon. 12 Alkenyl group; at least one organopolysiloxane B having at least two SiH units per molecule; at least one polyaddition catalyst C with a catalytically effective amount; and thermally conductive filler D, characterized in that the organopolysiloxane A has a linear structure, a viscosity of 50 mPa·s to 200 mPa·s at 25°C, and contains 130 ppm to 1000 ppm by mass of silicon-bonded OH groups.

Description

Technical Field

[0001] This invention relates to novel organosilicon compositions crosslinked by a polyaddition reaction, which are intended for the production of thermally conductive elements, particularly for use in the electronics and automotive industries, and especially for electric vehicles. Background Technology

[0002] Thermally conductive silicone elastomers are renowned for their excellent thermal conductivity, thermal resistance to heat and cold, and electrical insulation properties. They are particularly used in electrical and electronic applications and the automotive industry. Especially in the automotive sector, thermally conductive silicone elastomers are used in the batteries of electric vehicles and hybrid electric vehicles (EVs and HEVs) to dissipate heat from the individual cells of the battery packs and onboard electronics.

[0003] Formulations of thermally conductive organosilicones have been described in the prior art. As early as 1981, patent US 4,292,223 described a thermally conductive elastomer comprising organopolysiloxane, particulate filler, and viscosity modifier.

[0004] The amount of thermally conductive filler in silicone compositions is high, typically greater than 50% by weight, and sometimes even greater than 70% by weight. One of the difficulties in designing thermally conductive silicones lies in minimizing the impact of such a large amount of thermally conductive filler on the flowability of the composition. This is particularly critical for so-called “potting” compositions, which, despite containing a high concentration of thermally conductive filler, must have a low viscosity (typically less than 10,000 mPa·s).

[0005] Several solutions for controlling the viscosity of thermally conductive silicone compositions have been proposed in the prior art. One approach involves carefully selecting the type, shape, and size of the filler. For example, Elkem Silicones' application WO 2021 / 260279A1 proposes selecting certain fillers with specific sizes, where a certain ratio is maintained between large and small particles. Shin-Etsu Chemical's patent EP 1 788 031 B1 describes a thermally conductive silicone elastomer containing 10-2000 parts by weight of metallic silicon powder with an average particle size of less than 100 μm per 100 parts by weight of a thermally crosslinkable organopolysiloxane composition. Another approach involves changing the medium of the silicone formulation or adding a solvent. However, solvent evaporation generates volatile compounds associated with health and environmental risks. Finally, another approach involves treating the thermally conductive filler to improve its compatibility with the silicone matrix. For example, international patent application WO2023 / 283819 A1 filed by Dow Silicones and Dow Global Technologies describes a self-adhesive thermally conductive silicone composition, which specifically comprises a thermally conductive filler and a treatment agent, combined with an adhesion promoter containing both hydrogen atoms bonded to silicon atoms and at least one alkoxy group bonded to silicon atoms. However, the addition of the treatment agent to the formulation can negatively affect the mechanical properties of the silicone elastomer, and there is a phenomenon of the treatment agent leaching out of the silicone matrix. Summary of the Invention

[0006] The purpose of this invention is to provide a novel thermally conductive silicone composition that solves the problems mentioned above and simultaneously has a high thermally conductive filler content, good thermal conductivity, and low viscosity.

[0007] Overview of the Invention

[0008] The present invention aims to provide a crosslinkable organosilicon composition via a polyaddition reaction, comprising:

[0009] - At least one organopolysiloxane A, each molecule of which has at least one C2-C bonded to silicon. 12 alkenyl,

[0010] - At least one organopolysiloxane B, each molecule of which has at least two SiH units.

[0011] - A catalytically effective amount of at least one polyaddition catalyst C, and

[0012] - Thermally conductive filler D,

[0013] The organopolysiloxane A is characterized by having a linear structure, a viscosity of 50 mPa·s to 200 mPa·s at 25°C, and containing 130 ppm to 1000 ppm by mass of silicon-bonded OH groups.

[0014] Detailed description of the invention

[0015] Unless otherwise stated, all silicone oil viscosities considered in this disclosure correspond to 25. o The "Newtonian" dynamic viscosity under C is the dynamic viscosity measured by a Brinell viscometer in a manner known per se at a sufficiently low shear rate gradient that makes the measured viscosity independent of the velocity gradient.

[0016] In the following description of organopolysiloxane A, the following nomenclature is used to represent the silanoxy unit:

[0017] M: Silyoxyl unit R 1 3SiO 1 / 2 ,

[0018] M Vi Selected from YR 1 2SiO 1 / 2 and Y2R 1 SiO 1 / 2 YR Preferred 1 2SiO 1 / 2 The silyloxy unit,

[0019] D: Silyoxyl unit R 1 2SiO 2 / 2 ,

[0020] D Vi Selected from Y2SiO 2 / 2 and YR 1 SiO 2 / 2 YR Preferred 1 SiO 2 / 2 The silyloxy unit,

[0021] T: Silyoxyl unit R 1 SiO 3 / 2 ,

[0022] Q: SiO₂ unit 4 / 2 ,

[0023] Where Y and R 1 Make Y represent C2-C 12 Alkenyl, preferably vinyl; R 1It represents a monovalent hydrocarbon group 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.

[0024] As the terminal M and M Vi Examples of the unit may refer to trimethylsilyloxy, dimethylphenylsilyloxy, dimethylvinylsiloxy, or dimethylhexenylsiloxy.

[0025] As D and D Vi Examples of the unit may refer to dimethylsiloxy, methylphenylsiloxy, methylvinylsiloxy, methylbutenylsiloxy, methylhexenylsiloxy, methyldecenylsiloxy, or methyldecadienylsiloxy.

[0026] As an example of a T-unit, methylsiloxy can be mentioned.

[0027] Each molecule has at least one C2-C bonded to silicon. 12 The alkenyl-based organopolysiloxane A has a linear structure. "Linear structure" means a structure that contains no or substantially no T and / or Q siloxy units. The content of T and / or Q siloxy units is preferably less than or equal to 0.1% (mass % of T and / or Q units based on the total weight of organopolysiloxane A).

[0028] Organopolysiloxane A may have the following average general formula:

[0029] [YR 1 2SiO 1 / 2 ] a [R 1 2(OH)SiO 1 / 2 ] b [R 1 2SiO 2 / 2 ] c

[0030] in

[0031] - Y represents C2-C 12 Alkenyl, preferably vinyl;

[0032] - R 1 This indicates a monovalent hydrocarbon group 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

[0033] - a, b, and c such that a>0, b>0, a+b=2, c≥1, preferably c is 1-200, and the mass concentration of OH groups bonded to silicon is 130ppm to 1000ppm (based on the total weight of organopolysiloxane A in ppm mass).

[0034] It is understandable that in the above formula, if there are multiple R... 1 If the groups are the same as or different from each other, then they can be the same as or different from each other.

[0035] Optionally, although not represented in the general formula, organopolysiloxane A may contain a hydroxyl group (OH) carried by a silanoxy unit in the chain, and then have the formula R. 1 (OH)SiO 2 / 2 However, the content of these units is less than 0.1%, preferably 0%-0.01% (based on R based on the total weight of organopolysiloxane A). 1 (OH)SiO 2 / 2 (Unit mass %)

[0036] Preferably, the organopolysiloxane compound A has a mass content of 0.01%-10%, more preferably 0.1%-5% of alkenyl units (mass % of alkenyl units based on the total weight of organopolysiloxane A).

[0037] The organopolysiloxane A is an oil with a dynamic viscosity of 50 mPa·s to 200 mPa·s, preferably 80 mPa·s to 150 mPa·s, and more preferably 100 mPa·s to 130 mPa·s. This dynamic viscosity is measured at 25°C using a Brookfield viscometer in a manner known per se, at a sufficiently low shear rate gradient that makes the measured viscosity independent of the velocity gradient.

[0038] Organopolysiloxane A contains 130 ppm to 1000 ppm, preferably 150 ppm to 900 ppm, of silicon-bonded OH groups. The content of silicon-bonded OH groups in organopolysiloxane compound A is by mass (OH weight / sample weight). It can be measured by infrared spectroscopy after deuteration, as described in the following literature: Measurement of Trace Silanol in Siloxanes by IR Spectroscopy "Elmer D. Lipp," Applied Spectroscopy , vol. 45, no.3, 1991, pp. 477-483. For this purpose, the sample was analyzed using an IRTF (Fourier Transform Infrared) spectrophotometer.

[0039] According to one embodiment, organopolysiloxane A may have a residual acidity content. This residual acidity content may be greater than or equal to 5 ppm, preferably 6 ppm to 100 ppm, and more preferably 10 ppm to 100 ppm.

[0040] According to another embodiment, the organopolysiloxane A has no or minimal residual acidity. This residual acidity content can be strictly less than 5 ppm, preferably less than 4 ppm, and more preferably less than 3 ppm.

[0041] While not wishing to be bound by this theory, the inventors believe that the absence of significant residual acidity in organopolysiloxane A has the advantage of improving the stability of the organopolysiloxane over time, especially at high temperatures. Therefore, the crosslinkable organosilicon compositions according to the invention exhibit better stability over time and longer shelf life.

[0042] However, the inventors have discovered that the presence of residual acidity of 5 ppm or more, preferably 6 ppm to 100 ppm, in organopolysiloxane A can surprisingly reduce the viscosity of the crosslinkable organosilicon composition according to the invention via polyaddition and improve its thixotropic index.

[0043] In this paper, acidity is expressed in ppm (mg / kg HCl equivalent) of HCl (hydrochloric acid). Acidity content can be measured using a UV-Vis spectrophotometer by measuring the transmittance difference between the sample being analyzed and a standard obtained by adding a known amount of HCl.

[0044] The organopolysiloxane A according to the invention may be selected from commercially available compounds conforming to the stated specifications. Alternatively, it may be synthesized according to methods known in the art.

[0045] According to one embodiment, organopolysiloxane A is obtained by ring-opening polymerization (ROP) in the presence of a nucleophilic or electrophilic initiator. These synthetic methods are well known to those skilled in the art and are described, for example, in the following articles: Ring-Opening Polymerization (ROP) and Catalytic Rearrangement as a Way to Obtain Siloxane Mono- and Telechelics, as Well as Well-Organized Branching Centers: History and Prospects ”, Bezlepkina et al., Polymers 2022, 14,2408. These methods enable efficient control of the polymer molecular weight by selecting the amount of initiator and chain terminator. The synthesis of organopolysiloxane A according to the invention can be carried out by anionic polymerization or cationic polymerization. For anionic polymerization, the initiator can be selected from nucleophilic catalysts well known to those skilled in the art. For cationic polymerization, the initiator can be selected from acidic catalysts well known to those skilled in the art.

[0046] The use of chain-capping agents containing alkenyl (preferably vinyl) functional groups enables the synthesis of organopolysiloxanes having alkenyl (preferably vinyl) groups at the terminal positions. Therefore, the synthesis of organopolysiloxane A according to the invention can be achieved from a cyclic oligosiloxane (typically hexamethylcyclotrisiloxane (D3) or octamethylcyclotetrasiloxane (D4)) and an alkenylated (preferably vinylized) chain-capping agent (typically divinyldimethyldisiloxane (M... Vi 2)) This process can be carried out. The content of OH groups bonded to silicon can be controlled by adding a source of OH groups during synthesis. The source of these OH groups can be selected from: α,ω-dihydroxylated oligomeric organosiloxanes, α,ω-dihydroxylated polyorganosiloxanes, Silox, hydroxylated organosilicon resins, or water. The α,ω-dihydroxylated oligomeric and polyorganosiloxanes are preferably selected from those having low molecular weight, preferably less than 20,000 g / mol, more preferably less than 15,000 g / mol (weight-average molar mass), and / or low viscosity, preferably less than 1000 mPa·s.

[0047] "Silox" is understood to refer to a mixture of α,ω-dihydroxylated oligomeric and polyorganosiloxanes with cyclosiloxanes. These mixtures are derived from the direct synthesis (Rochow synthesis) of organochlorosilanes and the hydrolysis of the resulting chlorosilanes.

[0048] The organosilicon composition preferably contains 5%-50% by weight of organopolysiloxane A, and even more preferably 10%-40% by weight of organopolysiloxane A.

[0049] In the following description of organopolysiloxane B, the following nomenclature is used to represent the silanoxy unit:

[0050] M: Silyoxyl unit R 2 3SiO 1 / 2 ,

[0051] M': Silyoxyl unit R 2 2HSiO 1 / 2 ,

[0052] D: Silyoxyl unit R 2 2SiO 2 / 2 ,

[0053] D': Silyoxyl unit R 2 HSiO 2 / 2 ,

[0054] T: Silyoxyl unit R 2 SiO 3 / 2 ,

[0055] Q: SiO₂ unit 4 / 2 ,

[0056] Where R 2 This indicates a monovalent group having 1-12 carbon atoms.

[0057] Organopolysiloxane B is an organopolysiloxane having at least two SiH units per molecule. It is therefore an organohydrogen-based polysiloxane compound. Preferably, organopolysiloxane B contains at least three SiH units.

[0058] Organopolysiloxane B may advantageously be an organopolysiloxane containing at least two, preferably at least three, silanoxy units of the following formula: H d R 2 e SiO (4-d-e) / 2

[0059] Where R 2 This indicates a monovalent group with 1-12 carbon atoms, where d=1 or 2, e=0, 1 or 2, and d+e=1, 2 or 3;

[0060] And optionally, other units of the following formula: R 2 f SiO (4-f) / 2

[0061] Where R 2 It has the same meaning as above, and f = 0, 1, 2 or 3.

[0062] It should be understood that in the above formula, if multiple groups R exist... 2 If they are the same as or different from each other, then they can be the same as or different from each other.

[0063] Preferably, R 2 It can represent a monovalent group, selected from alkyl groups having 1-8 carbon atoms that are optionally substituted with at least one halogen atom such as chlorine or fluorine; cycloalkyl groups having 3-8 carbon atoms; and aryl groups having 6-12 carbon atoms. R 2 Advantageously selected from methyl, ethyl, propyl, 3,3,3-trifluoropropyl, xylyl, tolyl and phenyl.

[0064] The symbol d is preferably equal to 1.

[0065] The organopolysiloxane B may have a linear, branched, or cyclic structure. The degree of polymerization is preferably greater than or equal to 2. Typically, it is less than 5000. Preferably, the viscosity of the organopolysiloxane B is between 1 mPa·s and 5000 mPa·s, more preferably between 1 mPa·s and 2000 mPa·s, and even more preferably between 5 mPa·s and 1000 mPa·s.

[0066] When linear polymers are involved, they are essentially composed of D and / or D' siloxy units and M and / or M' terminal siloxy units. When cyclic polymers are involved, they are essentially composed of D and / or D' siloxy units. Examples of organohydrogen-based polysiloxanes that may be organopolysiloxane B according to the present invention are:

[0067] - Poly(dimethylsiloxane) with a hydrogen-dimethylsilyl terminus;

[0068] - Poly(dimethylsiloxane-co-methylhydrosiloxane) with a trimethylsilyl terminus;

[0069] - Poly(dimethylsiloxane-co-methylhydrosiloxane) with a dimethylsilyl end;

[0070] - Poly(methylhydrosiloxane) with a trimethylsilyl terminus; and

[0071] - Cyclic poly(methylhydrosiloxane).

[0072] When organopolysiloxane B has a branched structure, it is preferably selected from organosilicon resins of the following formula:

[0073] - M'Q, where the hydrogen atom bonded to the silicon atom is carried by the group M;

[0074] - MM'Q, where the hydrogen atoms bonded to silicon atoms are carried by a portion of the M unit;

[0075] - MD'Q, where the hydrogen atom bonded to the silicon atom is carried by the group D;

[0076] - MDD'Q, where the hydrogen atom bonded to the silicon atom is carried by a portion of the group D;

[0077] - MM'TQ, in which hydrogen atoms bonded to silicon atoms are carried by a portion of the M unit;

[0078] - MM'DD'Q, where the hydrogen atoms bonded to silicon atoms are carried by a portion of the M and D units;

[0079] - and its mixtures.

[0080] Preferably, the mass content of the silyl functional group Si-H in organopolysiloxane B is 0.2%-91%, more preferably 3%-80%, and even more preferably 15%-70%.

[0081] The organosilicon composition according to the invention preferably contains 0.1%-15% by weight, more preferably 0.5%-10% by weight, of organopolysiloxane B. The organosilicon composition according to the invention may contain one organopolysiloxane B or a mixture of multiple organopolysiloxane Bs, such as a mixture of dimethylsilyl-terminated poly(dimethylsiloxane) and organopolysiloxanes having at least three SiH units per molecule.

[0082] Advantageously, the molar ratio of the silyl functional group Si-H of organopolysiloxane B to the olefin functional group of organopolysiloxane A is between 0.2 and 10, preferably between 0.5 and 5.

[0083] The polyaddition catalyst C may be particularly selected from platinum and rhodium compounds, but may 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; nickel, cobalt, or iron complexes, such as those described in patent applications WO2016 / 071651, WO2016 / 071652, WO2016 / 071654, WO2018 / 115601, WO2019 / 008279, WO2019 / 138194, WO2023 / 031524, and WO2023 / 031525; or manganese complexes, such as those described in applications WO2023 / 139322 and WO2024 / 146993. 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 as 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, or complexes of platinum and vinylized organosiloxanes as described in patents US 3,419,593, US 3,715,334, US 3,377,432 and US 3,814,730, can be used.

[0084] Alternatively, a polyaddition photocatalyst can be used. This catalyst can be activated by irradiation, preferably by UV irradiation. Platinum-based photocatalysts can be selected, for example, from: bis(acetylacetone)platinum, trimethyl(acetylacetone)platinum, trimethyl(2,4-pentanedione)platinum, trimethyl(3,5-heptanedione)platinum, trimethyl(methylacetoacetate)platinum, bis(2,4-pentanedione)platinum, bis(2,4-hexanedione)platinum, bis(2,4-heptanedione)platinum, bis(3,5-heptanedione)platinum and bis(1-phenyl-1,3-butanedione)platinum.

[0085] Preferably, catalyst C is a platinum-derived compound. In this case, the amount of catalyst C by weight, based on platinum metal, is typically 2 ppm to 400 ppm, preferably 5 ppm to 200 ppm, based on the total weight of the organosilicon composition.

[0086] Preferably, catalyst C is Karstedt platinum.

[0087] The crosslinkable organosilicon composition according to the invention via polyaddition reaction is characterized in particular by comprising a thermally conductive filler D. This thermally conductive filler may consist of a single filler or a mixture of fillers with different chemical properties and / or different structures and / or different particle sizes. According to one embodiment of the invention, the thermally conductive filler D consists of a mixture of at least two or at least three fillers with different chemical properties and / or particle sizes. According to another embodiment of the invention, the thermally conductive filler D consists of a single filler.

[0088] In a crosslinkable organosilicon composition via a polyaddition reaction, the total weight of the thermally conductive filler D is preferably greater than 50% by weight, more preferably greater than 60% by weight, and even more preferably 70%-95% by weight, relative to the total weight of the crosslinkable organosilicon composition via a polyaddition reaction.

[0089] The thermally conductive filler D may comprise one or more fillers of different properties, which are known to those skilled in the art for their thermal conductivity, and are particularly selected from metals, alloys, metal oxides, metal hydroxides, metal nitrides, metal carbides, metal silicides, carbon, soft magnetic alloys, and ferrites. The thermal conductivity of these fillers is preferably greater than 10 W / mK, more preferably greater than 20 W / mK, and even more preferably greater than 50 W / mK. They may particularly be selected from alumina, aluminum trihydrate (ATH), aluminum, silicon dioxide, metallic silicon, 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 thermally conductive filler D may comprise thermally conductive fillers selected from alumina fillers, aluminum trihydrate (ATH) fillers, aluminum fillers, silica fillers, metallic silicon fillers, zinc oxide fillers, aluminum nitride fillers, boron nitride fillers, and mixtures thereof. More preferably, the thermally conductive filler D may comprise a thermally conductive filler selected from alumina filler, aluminum trihydrate (ATH) filler, zinc oxide filler, silica filler, and mixtures thereof.

[0090] The thermally conductive filler D can have any form known to those skilled in the art, such as spherical, needle-shaped, disc-shaped, rod-shaped, or irregularly shaped. Preferably, the thermally conductive filler has a spherical or irregular shape. When different thermally conductive fillers are used in the form of a mixture, they can have the same shape or different shapes.

[0091] The one or more thermally conductive fillers can be used as is, or they can be surface-treated. The purpose of such surface treatment is typically to improve the dispersibility of the filler in the organopolysiloxane composition and / or to improve the thermal stability of the composition. Furthermore, this heat treatment can improve the physical stability of the composition by preventing sedimentation, exudation, or increased viscosity.

[0092] The surface treatment may be a heat treatment, a chemical treatment, a physical treatment, or a combination thereof, particularly a combination of heat treatment and chemical treatment.

[0093] According to a preferred embodiment, the thermally conductive filler can be treated with organosilicon compounds commonly used for this purpose. The crosslinkable organosilicon compositions according to the invention, which are capable of being crosslinked via a polyaddition reaction, can therefore contain agents for treating the thermally conductive filler. These agents include:

[0094] - Organosiloxanes, especially methyl polysiloxanes such as hexamethyldisiloxane and octamethylcyclotetrasiloxane,

[0095] - Organosilazanes, especially methyl polysilazanes such as hexamethyldisilazane, divinyltetramethyldisilazane, and hexamethylcyclotrisilazane,

[0096] - Chlorosilanes such as dimethyldichlorosilane, trimethylchlorosilane, methylvinyldichlorosilane, and dimethylvinylchlorosilane,

[0097] - Alkoxysilanes such as methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, (C6-C 18 Alkyl)trimethoxysilanes such as octyltrimethoxysilane, vinyltrimethoxysilane, dimethylvinylethoxysilane, vinyltri(2-methoxyethoxy)silane, vinyltriacetoxysilane, allyltrimethoxysilane, butenyltrimethoxysilane, hexenyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, trimethylmethoxysilane, and trimethylethoxysilane.

[0098] More preferably, the thermally conductive filler can be made of alkoxysilane (especially (C6-C) 18 The filler is treated with alkyl (trimethoxysilane) or organosilazane (especially hexamethyldisilazane (HMDZ) and divinyltetramethyldisilazane) or mixtures thereof (especially mixtures of HMDZ and divinyltetramethyldisilazane). When treating thermally conductive fillers with chemical reagents (especially organosilazane), water can usually be added.

[0099] The crosslinkable organosilicon composition according to the invention preferably contains 0.05%-5% by weight, more preferably 0.1%-3% by weight, of a reagent for treating thermally conductive fillers relative to the total weight of the crosslinkable organosilicon composition according to the invention.

[0100] The heat treatment of the thermally conductive filler may involve subjecting the filler to a temperature of 70°C to 200°C for 1 to 4 hours.

[0101] According to one embodiment, the surface treatment can be performed before incorporating the thermally conductive filler into the silicone composition. According to another embodiment, the thermally conductive filler can be treated in situ during the preparation of the silicone composition.

[0102] The crosslinkable organosilicon compositions according to the present invention, which can be crosslinked via polyaddition, may also contain other compounds, particularly:

[0103] - At least one mineral filler, particularly silica, quartz or mixtures thereof;

[0104] - Crosslinking inhibitors;

[0105] - Non-reactive organopolysiloxanes that are liquid at ambient temperature;

[0106] - Coloring base;

[0107] - Optional, other fillers.

[0108] According to a preferred embodiment, the organosilicon composition comprises a mineral filler E, which is preferably pyrolytic silica or precipitated silica. The silica-type mineral filler preferably has a specific surface area of ​​at least 10 m² as measured by the BET method. 2 / g, especially 50m 2 / g to 400m 2 / g, preferably greater than 70m 2 / g, with an average primary particle size of less than 0.1 μm and a bulk density of less than 200 g / L. Most preferably, the mineral filler E has a specific surface area of ​​10 m² / L. 2 / g to 300m 2 Pyrolytic silicon dioxide between / g.

[0109] Preferred hydrophilic silica-type mineral fillers may be incorporated into the organosilicon composition as is, or optionally treated with a compatible agent. According to one variant, these silicas may optionally be treated with one or more organosilicon compounds commonly used for this purpose, such as organosilanes or organosilazanes. These compounds include methyl polysiloxanes such as hexamethyldisiloxane, octamethylcyclotetrasiloxane, methyl polysilazanes such as hexamethyldisilazane, hexamethylcyclotrisilazane, tetramethyldivinyldisilazane, chlorosilanes such as dimethyldichlorosilane, trimethylchlorosilane, methylvinyldichlorosilane, dimethylvinylchlorosilane, and alkoxysilanes such as dimethyldimethoxysilane, dimethylvinylethoxysilane, and trimethylmethoxysilane. These compounds may be used alone or as mixtures (see French patents FR 1 126 884, FR 1 136 885, FR 1 236 505 and British patent GB 1 024 234).

[0110] The silica can optionally be pre-dispersed in a silicone oil to obtain a suspension. Suspensions of treated (particularly treated with hexamethyldisilazane) pyrolytic silica in polysiloxane oils (especially vinyl polysiloxane oils) are particularly preferred.

[0111] Alternatively or as a supplement, the organosilicon composition according to the invention may also contain at least one other mineral filler, which is quartz. Ground natural quartz with an average particle size of less than 10 micrometers is preferred. The quartz may optionally be treated to improve its compatibility with organopolysiloxanes.

[0112] Other mineral fillers may be considered, especially compressive fillers, such as diatomaceous earth, calcium carbonate and / or kaolin.

[0113] According to one embodiment, the crosslinkable organosilicon composition according to the invention, which is capable of being crosslinked via a polyaddition reaction, may optionally contain a crosslinking inhibitor F. The inhibitor F functions to slow down the polyaddition reaction. The crosslinking inhibitor F may be selected from the following compounds:

[0114] - Advantageously, it is a cyclic organopolysiloxane substituted with at least one alkenyl group, with tetramethyltetravinylcyclotetrasiloxane being particularly preferred.

[0115] - Pyridine,

[0116] - Organic phosphites and phosphine,

[0117] - Unsaturated amides

[0118] - Alkylated maleate, and

[0119] - Alkynes, preferred formula (R) 1 (R) 2Alkynes of C(OH)-C=CH, wherein:

[0120] - R 1 It is a linear or branched alkyl group, or a phenyl group.

[0121] - R 2 It is a hydrogen atom, a linear or branched alkyl group, or a phenyl group.

[0122] - Group R 1 R 2 It may optionally form a ring with the carbon atom located at the α position relative to the triple bond; and

[0123] - R 1 and R 2 It contains a total of at least 5 carbon atoms, preferably 9-20.

[0124] The alkynyl alcohols are preferably selected from those with boiling points 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-pentadenylen-3-ol.

[0125] Preferably, the crosslinking inhibitor F is 1-ethynyl-1-cyclohexanol or tetramethyltetravinylcyclotetrasiloxane.

[0126] Depending on the method used to produce the silicone elastomer according to the invention, the presence of this inhibitor may be necessary or unnecessary. If desired, such crosslinking inhibitors may typically be present at a rate of up to 3000 ppm, preferably from 100 ppm to 2000 ppm, relative to the total weight of the crosslinkable silicone composition according to the invention via a polyaddition reaction.

[0127] According to one embodiment, the crosslinkable organosilicon composition according to the invention, which is capable of being crosslinked via a polyaddition reaction, may optionally include a nonreactive organopolysiloxane G that is liquid at ambient temperature. The role of this nonreactive organopolysiloxane, which is liquid at ambient temperature, is to reduce the overall viscosity of the composition. In this context, the term "nonreactive" is understood to mean that this organopolysiloxane does not participate in the polyaddition reaction that leads to crosslinking of the elastomer. Preferably, the nonreactive organopolysiloxane G, which is liquid at ambient temperature, is a linear diorganopolysiloxane, each end of its chain being capped with a trimethylsiloxy unit, wherein the organic group bonded to the silicon atom is selected from alkyl groups having 1-8 carbon atoms. It can typically be a trimethylsiloxy-capped polydimethylsiloxane. The nonreactive organopolysiloxane G, which is liquid at ambient temperature, preferably has a viscosity of 50 mPa·s to 1000 mPa·s, more preferably 50 mPa·s to 500 mPa·s, and more preferably 80 mPa·s to 200 mPa·s. The dynamic viscosity was measured at 25°C using a Brinell viscometer in a manner known per se, at a sufficiently low shear rate gradient that made the measured viscosity independent of the velocity gradient.

[0128] The crosslinkable organosilicon composition according to the invention comprises (by weight, relative to the total weight of the organosilicon composition) 0%-10%, preferably 0.1%-5%, of a nonreactive organopolysiloxane G that is liquid at ambient temperature.

[0129] According to one embodiment, the crosslinkable organosilicon composition according to the invention via a polyaddition reaction may optionally contain other additives conventionally used by those skilled in the art in this field, such as adhesion promoters, dyes, flame retardants, rheology modifiers such as thixotropic agents, etc.

[0130] According to one embodiment, the crosslinkable organosilicon composition according to the invention via polyaddition reaction may contain a low content of volatile organic compounds, typically less than 100 μg C / g, preferably less than 70 μg C / g, or less than 50 μg C / g. For this purpose, the organopolysiloxane compound used in the composition according to the invention is preferably selected from compounds that themselves contain a low content of volatile organic compounds.

[0131] According to one embodiment, the crosslinkable organosilicon composition by polyaddition reaction according to the present invention comprises (by weight, relative to the total weight of the organosilicon composition):

[0132] - 5%-50% of at least one organopolysiloxane A, each molecule of which has at least one C2-C bonded to silicon. 12 alkenyl,

[0133] - 0.1%-15% of at least one organopolysiloxane B, which has at least two SiH units per molecule.

[0134] - At least one polyaddition catalyst C, derived from platinum (by weight of metallic platinum), in the range of 2 ppm to 400 ppm, and

[0135] - 50%-95% thermally conductive filler D.

[0136] According to another embodiment, the crosslinkable organosilicon composition by polyaddition reaction according to the present invention comprises (by weight, relative to the total weight of the organosilicon composition):

[0137] - 10%-40% of at least one organopolysiloxane A, each molecule of which has at least one C2-C bonded to silicon. 12 alkenyl,

[0138] - 0.5%-10% of at least one organopolysiloxane B, which has at least two SiH units per molecule.

[0139] - At least one polyaddition catalyst C, derived from platinum (by weight of metallic platinum), in the range of 5 ppm to 200 ppm.

[0140] - 60%-95% thermally conductive filler D,

[0141] - 0%-5% mineral filler E,

[0142] - Crosslinking inhibitor F of 0ppm-3000ppm, and

[0143] - 0%-10% of non-reactive organopolysiloxane G, which is liquid at ambient temperature.

[0144] According to another embodiment, the crosslinkable organosilicon composition by polyaddition reaction according to the present invention comprises (by weight, relative to the total weight of the organosilicon composition):

[0145] - 10%-40% of at least one organopolysiloxane A, each molecule of which has at least one C2-C bonded to silicon. 12 alkenyl,

[0146] - 0.5%-10% of at least one organopolysiloxane B, which has at least two SiH units per molecule.

[0147] - At least one polyaddition catalyst C, derived from platinum (by weight of metallic platinum), in the range of 5 ppm to 200 ppm.

[0148] - 70%-95% thermally conductive filler D,

[0149] - 0.01%-1% mineral filler E,

[0150] - 100ppm-2000ppm of crosslinking inhibitor F, and

[0151] - 0%-10%, preferably 0.1%-5%, of a non-reactive organopolysiloxane G that is liquid at ambient temperature.

[0152] According to one embodiment, the organosilicon composition according to the invention can be prepared from a two-component (or multi-component) system, characterized in that it is presented as two (or more) separate portions intended to be mixed to form the organosilicon composition. In particular, in the case of the preferred organosilicon composition described above, the organosilicon composition can be prepared from a two-component system, characterized in that one portion contains catalyst C and does not contain organopolysiloxane B, while the other portion contains organopolysiloxane B and does not contain catalyst C. Other multi-component systems can be provided to improve shelf life and / or optimize the viscosity of each component. For example, the organosilicon composition according to the invention can be prepared from a three-component system, characterized in that it is presented as three separate portions intended to be mixed to form the organosilicon composition.

[0153] According to a preferred embodiment, the organosilicon composition according to the invention exists in two separate portions P1 and P2, said portions P1 and P2 being intended to be mixed to form the organosilicon composition, wherein portion P1 comprises:

[0154] - Each molecule has at least one C2-C bonded to silicon. 12 All or part of an alkenyl-based organopolysiloxane A

[0155] - Polyaddition catalyst C,

[0156] - All or part of the thermally conductive filler D, optionally having a reagent for treating the thermally conductive filler.

[0157] And part of P2 includes:

[0158] - Optionally, each molecule has at least one C2-C bonded to silicon. 12 A part of an alkenyl-based organopolysiloxane A.

[0159] - Organopolysiloxane B with at least two SiH units per molecule

[0160] - All or part of the thermally conductive filler D, optionally having a reagent for treating the thermally conductive filler.

[0161] - Optionally, crosslinking inhibitor F.

[0162] The thermally conductive filler D may be present in portions P1, P2, or both P1 and P2, with the same or different amounts between portions P1 and P2. Advantageously, the thermally conductive filler D may be present in portions P1 and P2 in equal amounts. Therefore, the total amount of the thermally conductive filler D remains constant in the crosslinkable organosilicon composition via polyaddition reaction, regardless of the mixing ratio of portions P1 and P2.

[0163] Each of P1 and P2 according to the invention can be obtained by mixing various components in a suitable apparatus known to those skilled in the art.

[0164] According to a particularly advantageous embodiment of the invention, portions of P1, P2, or both P1 and P2 can be obtained from an intermediate composition comprising a portion or all of organopolysiloxane A and a portion or all of thermally conductive filler D, and optionally, an agent for treating the thermally conductive filler.

[0165] Another object of the present invention is an organosilicon elastomer obtained or obtainable by crosslinking the organosilicon composition crosslinkable by polyaddition reaction as described above, a method for obtaining said elastomer, and the use of said elastomer.

[0166] The crosslinkable organosilicon composition described above via polyaddition reaction is particularly suitable for preparing organosilicon elastomers with thermal conductivity.

[0167] The present invention aims to provide a method for preparing a thermally conductive silicone elastomer, the method comprising the step of crosslinking a crosslinkable silicone composition by a polyaddition reaction to obtain the thermally conductive silicone elastomer.

[0168] Another object of the present invention is a method for preparing organosilicon elastomers, comprising the following steps:

[0169] a) Provides a two-component system comprising all the components of the organosilicon composition as defined above, which is crosslinkable via a polyaddition reaction;

[0170] b) Mixing the two components of the two-component system to obtain the crosslinkable organosilicon composition via polyaddition reaction; and

[0171] c) Crosslink the crosslinkable organosilicon composition via a polyaddition reaction to obtain the thermally conductive organosilicon elastomer.

[0172] The crosslinking step can have a variable duration depending on the silicone composition and temperature. Typically, a silicone elastomer with good properties is obtained within minutes or hours, depending on the concentrations of the inhibitors and catalysts in the silicone composition and the temperature. Mixing portions of this two-component (or multi-component) system can typically be carried out in a mixer (tilted blade mechanical stirrer, low-pressure dynamic mixer, or any other conventional stirring system) at temperatures close to ambient temperature (i.e., 10°C–40°C). Depending on the type of mixer and the applied shear, a temperature rise in the silicone composition is sometimes observed during this mixing. If it is desirable to accelerate the crosslinking of the silicone composition, mixing can be carried out at higher temperatures, advantageously between 40°C and 70°C.

[0173] The silicone elastomer is advantageously used as a thermally conductive material in various technical fields, particularly in the electronics, electrical applications, and automotive sectors. It can be advantageously used as a thermally conductive material for enrobage (i.e., potting), remplissage (i.e., gap-filler), or as a thermally conductive adhesive, especially for batteries, such as those in electric and hybrid vehicles, and can also be used to fix batteries. The invention also relates to a battery, preferably for electric or hybrid vehicles, comprising the thermally conductive silicone elastomer of the invention as a thermally conductive material for enrobage, remplage, or bonding. In the electronics field, the silicone elastomer according to the invention is advantageously used as a thermally conductive material in 5G devices.

[0174] Advantageously, the crosslinkable silicone composition according to the invention via polyaddition reaction, and portions P1 and P2 of the two-component system P serving as precursors to the crosslinkable silicone composition according to the invention, exhibit good processability. In particular, despite the presence of a high content of thermally conductive filler, the composition advantageously maintains sufficient flowability for easy handling, especially extrudability.

[0175] The crosslinkable organosilicon composition according to the invention via polyaddition reaction advantageously has a strength of less than 6000 mPa·s, preferably less than 5500 mPa·s, and more preferably 1000 mPa·s to 5000 mPa·s at 25°C for 10 s. -1 Viscosity at the shear rate.

[0176] Furthermore, the crosslinkable organosilicon composition according to the invention via polyaddition reaction advantageously has a thixotropic index of less than 3.00, preferably less than 2.50, and more preferably 0.50-2.00, which is defined as the thixotropic index at 25°C for 10 seconds. -1The viscosity at the shear rate and at 25°C in 1 s -1 The ratio of viscosity at the shear rate.

[0177] The organosilicon composition at 25°C and a shear rate of 10 s -1 (can be described as high shear) or 1s -1 Viscosities at low shear (which can be described as such) can be obtained according to methods known to those skilled in the art. In the embodiments herein, these viscosities are obtained using a Haake rheometer on a plate / plate apparatus. The diameter of the upper plate is 20 mm. The distance between the two plates is 0.500 mm.

[0178] The inventor's contribution lies in successfully identifying the desirable properties of organopolysiloxane A, thereby enabling the achievement of this technical effect.

[0179] The silicone elastomers that are the subject of this invention, obtained or obtainable by crosslinking the crosslinkable silicone composition via polyaddition reaction, advantageously have a thermal conductivity of 0.5 W / m·K to 7 W / m·K, preferably 0.9 W / m·K to 5 W / m·K, and even more preferably 1 W / m·K to 3 W / m·K. Detailed Implementation

[0180] Other details or advantages of the invention will become clearer from the following examples given by way of illustration only.

[0181] Example

[0182] The following examples of organosilicon compositions are obtained from the following raw materials:

[0183] A1-A14: Chain-end vinylized polydimethylsiloxane oils, the specifications of which are given in Tables 1 and 3.

[0184] B1: Has chain ends (α / The SiH-based dimethyl polysiloxane oil has a SiH vinyl content of 5.7% by weight and a viscosity of 8.5 mPa·s.

[0185] B2: Has both mid-chain and end-chain (α / Poly(methylhydro)(dimethyl)siloxane oil with SiH groups, SiH vinyl content of 7.3% by weight, viscosity = 30 mPa·s

[0186] C: Karstedt platinum catalyst, containing 10% by weight platinum metal.

[0187] D: ATH (aluminum trihydrate) powder;

[0188] E: Pyrolytic silica treated with hydrophobic coating has a specific surface area of ​​approximately 15-45 m². 2 / g;

[0189] F: Tetramethyltetravinylcyclotetrasiloxane

[0190] The following measurement scheme will be used for analysis:

[0191] Viscosity of silicone oil A The measurement was performed at 25°C and 500 rpm on a Brookfield rotational viscometer (rotor number 1).

[0192] Viscosity of organosilicon compositions Measurements were performed on a Haake rheometer at 25°C according to the following procedure: using rising and falling shear slopes, from 0s in 120 seconds. -1 By 20s -1 (Part 1), then from 20s in 120 seconds -1 to 0s -1 (Part 2). The recorded viscosity values ​​were obtained during Part 2 of the procedure (descent slope) at 10s. -1 and 1s -1 The viscosity value is specified below. The equipment used has a plate / plate geometry. The diameter of the upper plate is 20 mm. The distance between the two plates is 0.500 mm.

[0193] Thixotropic index (TI) At 25°C for 10 seconds -1 The viscosity at the shear rate and at 25°C in 1 s -1 The ratio of viscosity at the shear rate.

[0194] Determination of the content of OH groups bonded to silicon ([OH]) The content of OH groups bonded to silicon was measured by infrared spectroscopy according to the deuteration method described in the following literature: Measurement of Trace Silanol in Siloxanes by IR Spectroscopy Elmer D. Lipp, Applied Spectroscopy (vol. 45, no. 3, 1991, pp. 477-483). In practice, a calibration curve is constructed using a standard solution with a known OH group content. This is achieved by measuring 2726 cm⁻¹. -1 The OH group content of the sample is calculated from the optical density of the second derivative of the SiOD band.

[0195] Acidity measurement Measurements were performed using a UV-Vis spectrophotometer equipped with a tube holder accessory. Calibration was performed by adding a known stoichiometric amount of HCl to the reagent solvent of bromocresol purple in a butanol / toluene mixture. Results are expressed in ppm by mass of HCl equivalent.

[0196] Compositions 1-9 :

[0197] Compositions 1-9 were obtained by mixing 27.9% (by weight) of various end-vinylened polydimethylsiloxane oils A1-A9 with 72.10% (by weight) of thermally conductive filler D. Analytical results are given in Table 1.

[0198] [Table 1]

[0199]

[0200] At substantially equal oil viscosities, the use of oil A with an OH group content greater than 130 ppm advantageously enables a reduction in the overall viscosity of the composition and its thixotropic index.

[0201] Composition 10-14 :

[0202] The organosilicon compositions corresponding to portions P1 and P2 were prepared according to the following scheme: For portion P1: thermally conductive filler D, organosilicon oil A, and catalyst C were mixed according to the concentrations shown in Table 2 below. For portion P2: thermally conductive filler D, organosilicon oil A, organosilicon oils B1 and B2, and retarder F were mixed according to the concentrations shown in Table 2 below. The portions P1 and P2 thus obtained were mixed in a 1:1 ratio.

[0203] [Table 2]

[0204]

[0205] Thus, compositions of polydimethylsiloxane oils A10-A14 with various chain-end vinylizations were obtained, and the analytical results of a portion of P1 are given in Table 3:

[0206] [Table 3]

[0207]

[0208] For silica-free compositions, the use of oil A with an OH group content greater than 130 ppm advantageously reduces the overall viscosity and thixotropic index of the composition. Silica-containing compositions typically have higher viscosity than silica-free compositions. However, silica reduces sedimentation of the pre-crosslinked portion, thus improving shelf life.

Claims

1. A crosslinkable organosilicon composition via a polyaddition reaction, comprising: - At least one organopolysiloxane A, each molecule of which has at least one C2-C bonded to silicon. 12 alkenyl, - At least one organopolysiloxane B, each molecule of which has at least two SiH units. - A catalytically effective amount of at least one polyaddition catalyst C, and - Thermally conductive filler D, Its features Organopolysiloxane A has a linear structure, a viscosity of 50 mPa·s to 200 mPa·s at 25°C, and contains 130 ppm to 1000 ppm by mass of silicon-bonded OH groups.

2. The organosilicon composition according to claim 1, wherein the organopolysiloxane A has the following average general formula: [YR 1 2SiO 1 / 2 ] a [R 1 2(OH)SiO 1 / 2 ] b [R 1 2SiO 2 / 2 ] c in - Y represents C2-C 12 Alkenyl, preferably vinyl; - R 1 This indicates a monovalent hydrocarbon group 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 - a, b, and c such that a>0, b>0, a+b=2, c≥1, with c preferably being 1-200.

3. The organosilicon composition according to claim 1 or claim 2, wherein the organopolysiloxane A has a residual acidity content of greater than or equal to 5 ppm, preferably 6 ppm to 100 ppm and more preferably 10 ppm to 100 ppm.

4. The organosilicon composition according to claim 1 or claim 2, wherein the organopolysiloxane A has a residual acidity content of strictly less than 5 ppm, preferably less than 4 ppm and more preferably less than 3 ppm.

5. The organosilicon composition according to any one of claims 1-4, wherein the total weight of the thermally conductive filler D in the crosslinkable organosilicon composition via polyaddition reaction is greater than 50% by weight, more preferably greater than 60% by weight, and even more preferably 70%-95% by weight, relative to the total weight of the crosslinkable organosilicon composition via polyaddition reaction.

6. The organosilicon composition according to any one of claims 1-5, wherein the organosilicon composition further comprises a mineral filler E, preferably pyrolytic silica or precipitated silica.

7. The organosilicon composition according to any one of claims 1-6, wherein the organosilicon composition further comprises a non-reactive organopolysiloxane G that is liquid at ambient temperature.

8. The organosilicon composition according to any one of claims 1-7, wherein the crosslinkable organosilicon composition by polyaddition reaction comprises (by weight, relative to the total weight of the organosilicon composition): - 5%-50% of at least one organopolysiloxane A, each molecule of which has at least one C2-C bonded to silicon. 12 alkenyl, - 0.1%-15% of at least one organopolysiloxane B, which has at least two SiH units per molecule. - At least one polyaddition catalyst C, derived from platinum (by weight of metallic platinum), in the range of 2 ppm to 400 ppm, and - 50%-95% thermally conductive filler D.

9. The organosilicon composition according to any one of claims 1-8, wherein the crosslinkable organosilicon composition by polyaddition reaction comprises (by weight, relative to the total weight of the organosilicon composition): - 10%-40% of at least one organopolysiloxane A, each molecule of which has at least one C2-C bonded to silicon. 12 alkenyl, - 0.5%-10% of at least one organopolysiloxane B, which has at least two SiH units per molecule. - At least one polyaddition catalyst C, derived from platinum (by weight of metallic platinum), in the range of 5 ppm to 200 ppm. - 60%-95% thermally conductive filler D, - 0%-5% mineral filler E, - Crosslinking inhibitor F of 0ppm-3000ppm, and - 0%-10% of non-reactive organopolysiloxane G, which is liquid at ambient temperature.

10. The organosilicon composition according to any one of claims 1-9, wherein the organosilicon composition is prepared from a two-component system, characterized in that... One portion contains catalyst C and does not contain organopolysiloxane B, while the other portion contains organopolysiloxane B and does not contain catalyst C.

11. A method for preparing a thermally conductive silicone elastomer, comprising the following steps: The step involves crosslinking the crosslinkable organosilicon composition by polyaddition reaction according to any one of claims 1-10 to obtain the thermally conductive organosilicon elastomer.

12. A thermally conductive silicone elastomer obtained or obtainable by crosslinking a crosslinkable silicone composition by polyaddition reaction according to any one of claims 1-10.

13. Use of the thermally conductive silicone elastomer according to claim 12 as a thermally conductive material in the electronics, electrical, or automotive fields.

14. Use of the thermally conductive silicone elastomer according to claim 13 as a wrapper, filler or adhesive for thermally conductive materials.

15. A battery, preferably a battery for an electric vehicle or a hybrid vehicle, comprising the thermally conductive silicone elastomer of claim 12 as a wrapping thermally conductive material, a filling thermally conductive material, or an adhesive thermally conductive material.

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