Silicone potting compound compositions, methods thereof and uses

Abstract

This invention provides a silicone potting composition comprising: (A) a silicone polymer having two or more alkenyl groups per molecule; (B) a methyltrimethoxysilane oligomer; and (C) an inorganic filler. This silicone potting composition can be used as a thermally conductive encapsulant / sealant, exhibiting good anti-settling properties, good flowability and low viscosity, as well as good thermal conductivity due to high filler loading.

Description

Technical Field

[0001] This disclosure relates to a silicone potting compound composition, a method for preparing the silicone potting compound composition, and the use of the silicone potting compound composition. Background Technology

[0002] Thermally conductive potting compounds are critical materials for many applications, such as renewable energy, energy storage, energy vehicles, and 5G stations. Key requirements for thermally conductive potting compounds include: 1) high flowability or rheological control, which allows for easy and efficient manufacturing processes; 2) good thermal conductivity, necessary for thermal management in electronic devices with increased power density; 3) low density for weight reduction in total cost per unit; and 4) little or no filler settling or agglomeration, which provides lower cost of ownership and zero residual rigid packaging environmental waste. However, little or no filler settling contradicts other properties. High filler loading produces good thermal conductivity. High filler loading and low viscosity can easily lead to filler settling and further agglomeration.

[0003] Filler settling can result in soft or hard lumps at the bottom of encapsulant products. Soft lumps can be easily rehomogenized and accepted by the customer through remixing, while hard lumps with tight packing are almost impossible to rehomogenize. Therefore, filler settling or hard lumps are unnecessary or minimally necessary during the development of thermal encapsulant products. One approach is to introduce thixotropic agents to improve the thixotropic index.

[0004] Patent document 1 discloses a trimethoxy-terminated PDMS polymer used as a thixotropic agent in heat-sealing agent formulations to improve the anti-settling properties of fillers. This trimethoxy-terminated PDMS polymer has bistrimethoxy groups at both ends, which can form weak bonds with Al₂O₃ and aluminum hydroxide (ATH) fillers to construct a 3D network, thereby forming a gel-like product after 2 weeks of aging. This "gel-like" product can prevent long-term settling of the filler. However, thixotropic agents such as trimethoxy-terminated PDMS polymers significantly affect the viscosity of the product and reduce its flowability.

[0005] Patent Document 2 discloses a thixotropic silicone composition comprising fumed silica as a thixotropic agent, which has been shown to improve thixotropic properties and filler anti-settling properties in many silicone-based compositions. However, this fumed silica significantly increases the viscosity of the silicone-based composition.

[0006] Patent document 3 discloses a silicone composition for preparing, for example, cured automotive or electronic products, wherein the silicone composition contains a polyether as a thixotropic agent. This polyether improves the filler's anti-settling properties in the silicone composition. This polyether thixotropic agent readily forms small particles in the silicone product and is not easily stored.

[0007] [Existing Technical Documents]

[0008] Patent Document 1: Chinese Patent Publication No. CN115427508A (or PCT / CN2020 / 088737)

[0009] Patent Document 2: Japanese Patent Publication No. JP04778609B2

[0010] Patent Document 3: US Patent Publication No. US6448329B1 Summary of the Invention

[0011] The problem to be solved by the present invention

[0012] The problem this invention aims to solve is how to impart anti-settling properties to silicone potting compound compositions without significantly altering their viscosity, even in the presence of high filler loading. Therefore, an object of this invention is to provide a silicone potting compound composition exhibiting anti-settling properties, minimal viscosity variation, and high flowability.

[0013] Furthermore, another object of the present invention is to provide a method for preparing the silicone potting compound composition and the use of the silicone potting compound composition.

[0014] Methods for solving problems

[0015] As a result of ongoing research, the inventors have discovered a novel silicone potting compound composition comprising:

[0016] (A) Silicone polymers having two or more alkenyl groups per molecule;

[0017] (B) Methyltrimethoxysilane oligomers; and

[0018] (C) Inorganic fillers.

[0019] In some embodiments, the methyltrimethoxysilane oligomer is formed in situ by premixing methyltrimethoxysilane at a temperature below 60°C for at least 2 hours.

[0020] In some embodiments, the silicone potting compound composition further comprises at least one of the following groups:

[0021] (D) Polyorganohydrogen polysiloxanes with at least one Si-H bond per molecule;

[0022] (E) Hydrosilylation catalyst;

[0023] (F) Pigment;

[0024] (G) inhibitors; and

[0025] (H) Water.

[0026] In some embodiments, the amount of component (A) is from 5% to 80% by weight, based on the total weight of the silicone potting compound composition.

[0027] In some embodiments, the amount of component (B) is 0.1% to 1% by weight based on the total weight of the silicone potting compound composition.

[0028] In some embodiments, the amount of component (C) is 50% to 90% by weight based on the total weight of the silicone potting compound composition.

[0029] In some embodiments, component (C) is selected from Al2O3, aluminum hydroxide, quartz, or combinations thereof.

[0030] In some embodiments, based on the total weight of the silicone potting compound composition, the amount of component (D) is 0% to 1% by weight, the amount of component (E) is 0.01% to 0.5% by weight, the amount of component (F) is 0% to 10% by weight, the amount of component (G) is 0% to 0.3% by weight, and the amount of component (H) is 0% to 0.1% by weight.

[0031] In some implementations, components (B) and (C) are premixed before being mixed with component (A), provided that component (B) contains only methyltrimethoxysilane.

[0032] A second aspect of the present invention is a method for preparing the silicone potting compound composition, the method comprising:

[0033] (i) Mixing components (A), (B), and (C) at a temperature below 60°C for at least 2 hours to form a premix; and

[0034] (ii) Optionally, at least one of component (D), component (E), component (F), component (G) and component (H) is added to the premix.

[0035] In some implementations, the method further includes:

[0036] (i-1) In the presence of optional component (H), premix component (B) and component (C) and then mix them with component (A).

[0037] In some implementations, the method further includes:

[0038] (i-2) The premix is ​​maintained in a protective atmosphere at a temperature of 60°C to 120°C for 1 to 3 hours.

[0039] In some implementations, the method further includes:

[0040] (i-3) Cool the premix to a temperature below 60°C.

[0041] A third aspect of the invention is the use of the silicone potting compound composition in thermally conductive sealants.

[0042] Effects of the present invention

[0043] The present invention provides a silicone potting composition for use as a thermally conductive encapsulant / sealant, which exhibits good anti-settling properties, good flowability and low viscosity of less than 10,000 cPa·s, as well as good thermal conductivity due to high filler loading.

[0044] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and not intended to limit the invention as claimed. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the MTM reaction pathway during premixing and filler treatment according to this disclosure.

[0046] Figure 2 The results are LC-MS of MTM oligomers catalyzed by YF-14 (ATH / Al2O3) filler according to the present invention. Detailed Implementation

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. As disclosed herein, “and / or” means “and, or as an alternative” or “additionally or alternatively”. Unless otherwise specified, all scopes include the endpoints.

[0048] As used herein, the term “polymer” or “polymerization” in alternative contexts refers to a polymer prepared from one or more different monomers, such as copolymers, terpolymers, quaternary copolymers, pentomers, etc., and can be any of random polymers, block polymers, graft polymers, sequence polymers, or gradient polymers.

[0049] In this invention, unless otherwise stated, the singular forms of the articles “a” and “the / said” include plural references. In this invention, the terms “comprising,” “containing,” “including,” and variations thereof are open-ended claim language, i.e., allowing for additional elements.

[0050] According to the present invention, the silicone potting composition comprises, is substantially composed of, or is composed of: (A) a silicone polymer having two or more alkenyl groups per molecule; (B) a methyltrimethoxysilane oligomer; (C) an inorganic filler; (D) optionally, a polyorganohydrogen polysiloxane having at least one Si-H bond per molecule; (E) optionally, a hydrosilylation catalyst; (F) optionally, a pigment; (G) optionally, an inhibitor; and (H) optionally, water.

[0051] In some embodiments, component (B) comprises, is substantially composed of, or is composed of methyltrimethoxysilane (MTM), provided that component (B) and component (C) are premixed at a temperature below 60°C and optionally in the presence of component (H) for at least 2 hours prior to mixing with component (A). In some embodiments, component (B) comprises, is substantially composed of, or is composed of, a methyltrimethoxysilane oligomer or a combination of a methyltrimethoxysilane oligomer and methyltrimethoxysilane (MTM).

[0052] In some embodiments, the silicone potting compound composition is substantially free of any thixotropic agents, such as polyethers, trimethoxy-terminated PDMS polymers, and fumed silica.

[0053] Component (A)

[0054] In this invention, component (A) is known in the art and has two or more alkenyl (e.g., vinyl) groups per molecule; and examples include silicone polymers containing at least two alkenyl groups at the end or side groups. In some embodiments, examples include alkenyl-terminated polyorganosiloxanes (i.e., vinyl-terminated PDMS) of the following formula:

[0055]

[0056] Where R 3 and R 4 Selected from the group consisting of alkyl groups, phenyl groups, and vinyl groups, each having 1 to 6 carbon atoms, wherein at least 50% of the R groups are alkyl groups, phenyl groups, and vinyl groups. 4 The component is a methyl group. Preferably, the viscosity of component (A) is 0.1 Pa·s to 200 Pa·s, 1 Pa·s to 100 Pa·s, 5 Pa·s to 50 Pa·s, 8 Pa·s to 16 Pa·s, 8 Pa·s to 14 Pa·s, 8 Pa·s to 12 Pa·s, or 8 Pa·s to 10 Pa·s at 25°C.

[0057] In some embodiments of this disclosure, the alkenyl group contained in component (A) may contain 2 to 14 carbon atoms, 4 to 12 carbon atoms, or 6 to 10 carbon atoms; preferably, the alkenyl group is selected from the group consisting of vinyl, allyl, hexenyl, decenyl, and tetradecenyl, and most preferably, the alkenyl group is a vinyl group.

[0058] Particularly preferably, based on the total weight of the silicone potting compound composition, component (A) may be incorporated into the silicone potting compound composition in amounts of 5% to 80% by weight, 10% to 70% by weight, 20% to 60% by weight, 30% to 50% by weight, and 35% to 40% by weight.

[0059] Component (B)

[0060] In this invention, component (B) can be used as an anti-settling agent and treatment agent for inorganic fillers in silicone potting compositions containing methyltrimethoxysilane oligomers. In some embodiments, the methyltrimethoxysilane oligomer can be formed in situ by premixing methyltrimethoxysilane at a temperature below 60°C for at least 2 hours. In this invention, MTM can form oligomers with more trimethoxy groups than trimethoxy-terminated PDMS polymers, thereby helping the silicone potting product form a 3D network and form a gel-like product, such as... Figure 1 As shown, MTM tends to self-condense at lower temperatures to form oligomers catalyzed by, for example, ATH / Al2O3, but it tends to bond to the surface of inorganic fillers at higher temperatures. Extended premixing time helps MTM form more oligomers with more trimethoxy groups, which can contribute to the formation of a network and "gel"-like properties of the product. Simultaneously, the filler surface can have a larger polar surface area to interact with the MTM oligomers.

[0061] In some embodiments, component (B) consists of methyltrimethoxysilane, such that components (B) and (C) are premixed in the silicone potting compound composition before being mixed with component (A).

[0062] In some embodiments, component (B) comprises a methyltrimethoxysilane oligomer, such that components (A), (B), and (C) are mixed before optionally including other additives and heating the silicone potting compound composition.

[0063] Particularly preferably, based on the total weight of the silicone potting compound composition, component (B) may be incorporated into the silicone potting compound composition in an amount such as 0.1% to 1% by weight, 0.2% to 0.8% by weight, or 0.4% to 0.6% by weight, such as 0.5% by weight.

[0064] Component (C)

[0065] Component (C) is a thermally conductive filler. Component (C) may be thermally conductive and optionally electrically conductive. Alternatively, component (C) may be thermally conductive and optionally electrically insulating. Thermally conductive fillers are known in the art, see, for example, U.S. Patent No. 6,169,142. Component (C) may comprise metallic fillers, inorganic fillers, fusible fillers, or combinations thereof.

[0066] The amount of component (C) in the composition depends on various factors, including the silicone curing mechanism selected for the composition and the thermally conductive filler selected for component (C). In some embodiments, component (C) may be incorporated into the silicone potting compound composition in an amount of 50% to 90%, 60% to 80%, or 65% to 75%, such as 70%, based on the total weight of the silicone potting compound composition.

[0067] Metal fillers include metal particles and metal particles having layers on their surfaces. These layers can be, for example, metal nitride layers or metal oxide layers on the surface of the particles. Examples of suitable metal fillers are particles of metals selected from aluminum, copper, gold, nickel, tin, silver, and combinations thereof, and alternatively, aluminum. Examples of suitable metal fillers also include particles of the metals listed above having layers on their surfaces, selected from the group consisting of aluminum nitride, aluminum oxide, copper oxide, nickel oxide, silver oxide, and combinations thereof. For example, a metal filler may comprise aluminum particles having an aluminum oxide layer on their surface.

[0068] Examples of inorganic fillers include onyx; aluminum trihydrate, metal oxides such as aluminum oxide, beryllium oxide, magnesium oxide, and zinc oxide; nitrides such as aluminum nitride and boron nitride; carbides (such as silicon carbide and tungsten carbide); and combinations thereof. Barium titanate, carbon fiber, diamond, graphite, magnesium hydroxide, and combinations thereof are also included. In some embodiments, the inorganic filler comprises Al₂O₃, aluminum hydroxide, quartz, or combinations thereof.

[0069] The fusible filler may comprise Bi, Ga, In, Sn, or alloys thereof. Optionally, the fusible filler may also comprise Ag, Au, Cd, Cu, Pb, Sb, Zn, or combinations thereof. Examples of suitable fusible fillers include Ga-In-Bi-Sn alloys, Sn-In-Zn alloys, Sn-In-Ag alloys, Sn-Ag-Bi alloys, Sn-Bi-Cu-Ag alloys, Sn-Ag-Cu-Sb alloys, Sn-Ag-Cu alloys, Sn-Ag alloys, Sn-Ag-Cu-Zn alloys, and combinations thereof. The fusible filler may have a melting point in the range of 50°C to 250°C, or alternatively 150°C to 225°C. The fusible filler may be a eutectic alloy, an aeutectic alloy, or a pure metal. The fusible filler is commercially available.

[0070] There are no particular restrictions on the shape of the thermally conductive filler particles; however, round or spherical particles can prevent the viscosity from increasing to undesirable levels when there is a high filler content in the composition. The average particle size of the thermally conductive filler will depend on various factors, including the type of thermally conductive filler selected for component (C) and the exact amount added to the curable composition, as well as the thickness of the adhesive layer of the device in which the cured product of the composition will be used. In certain specific examples, the thermally conductive filler may have an average particle size in the range of 0.1 micrometers to 80 micrometers, alternatively 0.1 micrometers to 50 micrometers, and alternatively 0.1 micrometers to 10 micrometers.

[0071] Component (C) can be a single thermally conductive filler or a combination of two or more thermally conductive fillers that differ in at least one of the following properties: particle shape, average particle size, particle size distribution, and filler type. In some embodiments, a combination of metallic and inorganic fillers can be used, such as a combination of aluminum and alumina fillers; a combination of aluminum and zinc oxide fillers; or a combination of aluminum, alumina, and zinc oxide fillers. In other embodiments, it may be desirable to combine a first conductive filler with a larger average particle size with a second conductive filler with a smaller average particle size in a proportion conforming to the closest packing theory distribution curve. An example is combining two alumina formulations with different average particle sizes. In other embodiments, different thermally conductive filler materials with different particle sizes can be used, for example, a combination of alumina with a larger average particle size and zinc oxide with a smaller average particle size. Alternatively, it may be desirable to use a combination of metallic fillers, such as a first aluminum with a larger average particle size and a second aluminum with a smaller average particle size. Using a first filler with a larger average particle size and a second filler with an average particle size smaller than that of the first filler can improve filling efficiency, reduce viscosity, and enhance heat transfer.

[0072] Thermally conductive fillers are commercially available. For example, fusible fillers are available from Indium Corporation of America, Utica, NY, USA; Arconium, Providence, RI, USA; and AIM Solder, Cranston, RI, USA. Aluminum fillers are available, for example, from Toyal America, Inc., Naperville, III, USA; and Valimet Inc., Stockton, California, USA. Silver fillers are available from Metalor Technologies USA Corp., Attleboro, Massachusetts, USA. Zinc oxide, such as that under the trademark KADOX, is also available. ® and XX ® Zinc oxide is commercially available from Zinc Corporation of America, Monaca, Pa., USA. Additionally, CB-A20S and Al-43-Me are alumina fillers of different particle sizes available from Showa-Denko, while AA-04, AA-2, and AA 18 are alumina fillers available from Sumitomo Chemical Company. Boron nitride fillers are commercially available from Momentive Corporation (Cleveland, Ohio, USA).

[0073] In some preferred embodiments, (C) the thermally conductive filler comprises at least one of the following: (C1) spherical Al2O3 with an average particle size of 10 μm to 100 μm; and (C2) irregular Al2O3 with an average particle size of 0.1 μm to 5 μm. In some embodiments, (C) the thermally conductive filler comprises: (C1) spherical Al2O3 with an average particle size of 10 μm to 100 μm; (C2) irregular Al2O3 with an average particle size of 1 μm to 5 μm; and (C3) irregular Al2O3 with an average particle size of 0.1 μm to 0.7 μm.

[0074] Component (D)

[0075] In this invention, component (D) is used to adjust the crosslinking density and can be any polyorganohydrosiloxane having at least one silicon-bonded hydrogen atom per molecule (Si-H bond), and in some embodiments, having an average of at least two silicon-bonded hydrogen atoms per molecule. The remaining valence of the silicon atom is satisfied by a divalent oxygen atom or by a monovalent alkyl group (such as methyl, ethyl, propyl, isopropyl, butyl, hexyl, and phenyl groups) having 1 to 6 carbon atoms per group. The polyorganohydrosiloxane can be a homopolymer, copolymer, or mixture thereof. Preferably, the polyorganohydrosiloxane includes, but is not limited to, copolymers of trimethylsiloxy and methylhydrosiloxane, or copolymers of trimethylsiloxy, methylhydrosiloxane, and dimethylsiloxane. In embodiments of this invention, the polyorganohydrosiloxane has an average of at least three silicon-bonded hydrogen atoms per molecule. In embodiments of the invention, the viscosity of component (D) is 0.001 Pa·s to 0.5 Pa·s, 0.002 Pa·s to 0.3 Pa·s, 0.005 Pa·s to 0.1 Pa·s, 0.01 Pa·s to 0.08 Pa·s, 0.01 Pa·s to 0.06 Pa·s, 0.01 Pa·s to 0.04 Pa·s, or 0.01 Pa·s to 0.02 Pa·s at 25°C. In embodiments of the invention, component (D) comprises 0.01 wt% to 1.67 wt%, 0.02 wt% to 1.5 wt%, 0.05 wt% to 1.3 wt%, 0.1 wt% to 1.1 wt%, 0.2 wt% to 1.0 wt%, 0.4 wt% to 0.8 wt%, or 0.5 wt% to 0.6 wt% SiH. In an embodiment of the present invention, component (D) is a hydrogenated silicone oil with a viscosity of 0.02 Pa·s at 25°C and a SiH content of about 1.6% by weight.

[0076] In an embodiment of the present invention, the polyorganohydrosiloxane has the structural formula: R3-Si-(OSiR2). m -(OSiR1H) n -R3, wherein R1, R2, and R3 are independently selected from hydrocarbon groups, and have an average n = 1-5 and m = 1 to 20. In some embodiments, R1, R2, and R3 are independently selected from C1-C6 alkyl groups or C6-C20 aryl groups. In some embodiments, the average n = 1-3 and m = 1 to 10.

[0077] Particularly preferably, based on the total weight of the silicone potting compound composition, component (D) may be incorporated into the silicone potting compound composition in amounts of 0% to 1% by weight, 0.1% to 0.9% by weight, 0.2% to 0.8% by weight, 0.3% to 0.7% by weight, and 0.4% to 0.6% by weight.

[0078] Component (E)

[0079] In this invention, component (E) may be selected from the group consisting of platinum catalysts, palladium catalysts, rhodium catalysts, nickel catalysts, iridium catalysts, ruthenium catalysts, and mixtures thereof, preferably a platinum catalyst, which can efficiently promote the reaction of -SiH groups with vinyl / alkenyl groups. Particularly preferred are silicone compositions in which the catalyst is an organoplatinum compound. Particularly preferred are silicone compositions in which the catalyst is a functional organoplatinum compound selected from (n-diene)(α-aryl)platinum complex, (n-diene)(γ-aryl)-platinum complex, (n-diene)(γ-alkyl)-platinum complex, and mixtures thereof. Commercially available products may be used in this invention.

[0080] Particularly preferably, based on the total weight of the silicone potting compound composition, component (E) may be incorporated into the silicone potting compound composition in an amount such as 0.01% to 0.5% by weight, 0.05% to 0.4% by weight, or 0.1% to 0.3% by weight, such as 0.2% by weight.

[0081] Component (F)

[0082] In this invention, the silicone potting compound composition may optionally contain a pigment selected from the group consisting of carbon black, titanium dioxide, iron oxide red, and combinations thereof. In some embodiments of the invention, the pigment may be incorporated into the silicone potting compound composition in amounts of 0% to 10% by weight, 0.1% to 8% by weight, 1% to 6% by weight, 2% to 5% by weight, or 3% to 4% by weight, based on the total weight of the silicone potting compound composition.

[0083] Component (G)

[0084] In this invention, component (G) is an optional inhibitor for hydrosilylation, which can slow the reaction rate by inhibiting the hydrosilylation catalyst as needed, allowing mixing to be completed before the mixture begins to cure. Therefore, it should be understood that component (G) may need to be added if curing cannot proceed rapidly during or immediately after mixing, but may not be necessary if curing can proceed immediately after mixing. Determining whether component (G) needs to be added to the polysiloxane composite material is within the capabilities of those skilled in the art.

[0085] Examples of hydrosilylation catalyst inhibitors include methylvinylcyclosiloxane, tetravinyltetramethylcyclotetrasiloxane (vinyl D4), ethynylcyclohexanol (ECH), and mixtures thereof. Particularly preferably, the hydrosilylation catalyst inhibitor may be incorporated into the silicone potting compound composition in amounts such as 0.15% by weight, 0.05% by weight, 0.25% by weight, or 0.1% by weight, or 0.2% by weight, depending on the desired curing rate, based on the total weight of the silicone potting compound composition.

[0086] Component (H)

[0087] In this invention, component (H) can be used to premix component (B) before mixing component (B) with component (C), which can form more oligomers of component (B).

[0088] Particularly preferably, based on the total weight of the silicone potting compound composition, component (H) may be incorporated into the silicone potting compound composition in an amount such as 0.05% by weight, from 0.1% by weight, 0.02% by weight, or 0.04% by weight, or 0.06% by weight, such as 0.05% by weight.

[0089] Method for preparing silicone potting compound

[0090] In this invention, the silicone potting compound composition can be prepared by: i) mixing components (A), (B), and (C) at temperatures below 60°C, below 50°C, below 40°C, or in the range of 0°C to 59°C, in the range of room temperature to 45°C, or in the range of 30°C to 40°C for at least 2 hours, 2 hours to 48 hours, 3 hours to 36 hours, 4 hours to 24 hours, or 6 hours to 12 hours to form a premix; and (ii) optionally, adding at least one of components (D), (E), (F), (G), and (H) to the premix.

[0091] In some embodiments, step (i) includes (i-1) premixing components (B) and (C) in the presence of optional component (H) before mixing with component (A), in some embodiments at a temperature in the range of 60°C, 50°C, 40°C, 0°C to 59°C, 10°C to 50°C, 20°C to 40°C, or at room temperature.

[0092] In this invention, a premixing step of the silicone potting compound composition comprising inorganic fillers, MTM (oligomers), and alkenyl / vinyl-based polymers at a relatively low temperature (e.g., room temperature) prior to heating further improves anti-settling properties. In some embodiments, increasing the premixing time to at least 2 hours at a lower temperature can form a gel-like product and prevent sedimentation of the inorganic fillers.

[0093] In some embodiments, step (i) includes (i-2) maintaining the premix in a protective atmosphere, such as negative pressure, N2, etc., at a temperature of 60°C to 120°C, 70°C to 110°C, 80°C to 100°C, or 85°C to 95°C for 1 to 3 hours, 1.5 to 2.5 hours, or 1.8 to 2.3 hours.

[0094] In some embodiments, step (i) includes (i-3) cooling the premix to a temperature below 60°C, below 50°C, below 40°C, or in the range of 0°C to 59°C, in the range of room temperature to 45°C, or in the range of 30°C to 40°C.

[0095] Uses of silicone potting compound compositions

[0096] The present invention also includes thermally conductive sealants for electronic components prepared by the method of the present invention. The cured silicone potting compound compositions of the present invention can thermally connect heat sources and heat sinks in articles and act as thermal bridges between them.

[0097] [Example]

[0098] The following is a more detailed description of the invention with reference to embodiments. However, the invention is not limited to these embodiments. Unless otherwise specified, all parts and percentages are by weight.

[0099] [Viscosity]

[0100] Distributable viscosity was determined using an ARES-G2 rheometer equipped with a 25 mm parallel plate by a TA instrument, following the dynamic viscosity test method of ASTM D4440-15. Test conditions were based on strain scans at 25°C, strains from 0.1% to approximately 300%, and a frequency of 10 radians / second. Viscosities were measured using a Brinell viscometer: HBDVIII, Spindle 3 @ 1 RPM, 10 RPM, 50 RPM, with data collected for 1 minute.

[0101] [Thixotropic Index]

[0102] Thixotropic properties can be characterized by the thixotropic index, which is given by the following formula:

[0103]

[0104] Where η(A) is the viscosity at a lower shear rate, and η(B) is the viscosity at a higher shear rate. In this patent, we use parameters A = 1 rpm and B = 10 rpm.

[0105] [Anti-settlement performance]

[0106] The filler sedimentation score was used to measure the filler sedimentation status after aging in a 1L HDPE bottle by visual observation. Performance was rated as 1 - worst (sedimentation), 2 - poor, 3 - good, 4 - good, and 5 - best (no sedimentation). Since gel properties are highly correlated with filler sedimentation, gel properties were monitored after sample aging and ranked as gel, semi-gel, and no gel.

[0107] Table 1 below lists information about the raw materials used in the examples:

[0108] Table 1. Raw materials used in the examples

[0109]

[0110] Examples 1 to 2 (IE1 to IE2) of the present invention and Comparative Examples 1 to 5 (CE1 to CE5) of the present invention.

[0111] According to the process description listed in Table 2, samples IE1 to IE2 and CE1 to CE5 were prepared using a 10L Turello mixer in the SDC. Component A, along with components B1 and B2 (in any form), were loaded into the mixing vessel and then mixed at 0.4m... 3 Mix at 20 RPM for 5 min under a N2 protective atmosphere. Then, component C is gradually added and stirred at room temperature for 15 min to 2 h to form each mixture of IE 1 to IE 2 and CE 1 to CE 5. Samples of the mixtures are taken for viscosity testing.

[0112] The mixture was then heated to 120°C under vacuum and held for 1 to 3 hours. After cooling to 60°C, samples of the mixture were taken for basic property testing.

[0113] In CE 1 to CE 5, the PDMS polymer (if any) is added together with component A and mixed for 30 min to obtain the final product for testing.

[0114] Table 2: Formulations used in IE 1 to IE 2 and CE 1 to CE 5

[0115]

[0116] The viscosity and filler settling properties of IE 1 to IE 2 and CE 1 to CE 5 were monitored by aging time and summarized in Table 3.

[0117] Table 3: Viscosity and antisettling properties of IE 1 to IE 2 and CE 1 to CE 5

[0118]

[0119] As can be seen from Table 3, no anti-settling agent was added to CE1, which made component C (i.e., the filler) settle easily within 2 weeks without any gel-like appearance being observed; and its viscosity in CE1 was high because the filler was not treated with any anti-settling agent.

[0120] In CE2, the PDMS polymer is added after the base is heated, resulting in a lower viscosity and the formation of a gel-like appearance within 2 weeks, preventing filler sedimentation.

[0121] CE3 exhibits poor anti-settling properties, as it does not form a gel-like material and will settle upon aging because it does not contain MTM short-chain silanes, i.e., MTM, and only contains long-chain silanes.

[0122] Comparing IE1 and CE5, it was found that the formulations used were the same, with MTM used in both formulations. However, the premixing time was extended from 0.5 hours in CE5 to 2 hours in IE1. IE1 formed a gel-like appearance within 2 weeks and avoided long-term filler settling. In contrast, CE5 did not form a gel, and the filler settled after aging.

[0123] Comparing IE2 and CE4, both formulations use short-chain silanes (i.e., MTM) and long-chain silanes. IE2, with its longer premixing time, exhibits better anti-settling properties than CE4, which has a shorter premixing time. The longer premixing time in IE2 demonstrates better "gel" formation ability and anti-settling properties.

[0124] Examples 3 to 5 (IE3 to IE5) of the present invention and Comparative Example 6 (CE6)

[0125] According to the process description listed in Table 4, samples of IE3 to IE5 and CE6 were prepared using a 10L Turello mixer in the SDC. Component A, along with components B1 and B2 (in any form), were loaded into the mixing vessel and then mixed at 0.4m... 3 Mix at 20 RPM for 5 min under a N2 protective atmosphere. Then, gradually add component C and stir at room temperature for 15 min to 2 h to form each mixture of IE3 to IE5 and CE6. Samples of the mixtures were taken for viscosity testing.

[0126] The mixture was then heated to 120°C under vacuum and held for 1 to 3 hours. After cooling to 60°C, samples of the mixture were taken for basic property testing.

[0127] In IE3, 0.099% by weight of water is used for premixing with MTM to help form more MTM oligomers. In IE4, the water content is reduced from 0.99% to 0.33% compared to IE3. In IE5, no water is intentionally added, but the filler itself may contain 0.06% by weight of moisture, and the MTM content is reduced to 0.25%, with the premixing time at room temperature extended to 2 hours.

[0128] Table 4: Formulations used in IE3 to IE5 and CE6

[0129]

[0130] Viscosity, thixotropic index, and filler sedimentation properties of IE3 to IE5 and CE6 in fresh samples and 1-month aged samples were monitored and summarized in Table 5.

[0131] Table 5. Viscosity, thixotropic index, and anti-settling properties of fillers for IE3 to IE5 and CE6 .

[0132]

[0133] In CE6, the sample had low viscosity and poor anti-settling properties of the filler. The formed filler settled and formed hard clumps at the bottom of the bottle within one month.

[0134] IE3 exhibited very good anti-settling properties, with no sedimentation observed after aging for more than 6 months. The viscosity of IE3 is slightly higher than that of CE6.

[0135] IE4 exhibits excellent anti-settling properties, showing no sedimentation even after more than 6 months, and maintains low viscosity at high shear rates, similar to CE6, with an improved thixotropic index.

[0136] In IE5, although no additional water is used, the extended premixing time also improves anti-settling performance for more than 3 months. The extended premixing time is similar to that of IE1 to IE2.

[0137] like Figure 1As shown, MTM exhibits two reaction pathways when mixed with ATH / Al2O3 filler. In pathway 1, MTM hydrolyzes and then reacts with hydroxyl groups on the filler surface, which is the normal filler treatment process. In pathway 2, MTM hydrolyzes and self-condenses to form oligomers due to its high reactivity. DFT (density functional theory) calculations for both pathways were performed at room temperature, and the activation energy of pathway 2 (Ea = 26 kcal / mol) was lower than that of pathway 1 (Ea = 44 kcal / mol). Therefore, pathway 2 is advantageous during premixing at room temperature. If the premixing time is prolonged, the system will produce more MTM-based oligomers. Condensation is an endothermic reaction, which is a thermodynamically favorable process. Therefore, when the base is heated at 120 °C, MTM tends to react with the filler surface with increasing energy input. Although heating is thought to destroy the T-structure of MTM oligomers, the linear structure of MTM oligomers is stable with the removal of moisture from the system. If the method allows sufficient premixing time to form oligomers, the oligomers formed by MTM hydrolysis and self-condensation will have a structure similar to PDMS polymers, allowing them to act as PDMS polymers to form a "gel" appearance (as shown in IE1 to IE2). Meanwhile, MTM self-condensation consumes MTM, and when the substrate is heated, limited MTM is left for filler surface treatment. Therefore, IE1 to IE2 have less MTM monomer bound in the filler surface and leave more polar surface area to interact with the PDMS polymer to form a "gel." However, in CE5 to CE6, MTM is added just before substrate heating without sufficient premixing; it reacts directly with the filler surface, and the filler surface is well treated by components B1 and B2. There is insufficient polar filler surface area and no MTM oligomerization is induced, therefore no "gel" is formed.

[0138] like Figure 2 As shown, a simple experiment was conducted by blending YF-14 (ATH / Al2O3) packing material with MTM and mixing it in an open vial at room temperature for 2 hours. Another sample served as a baseline, containing MTM mixed only at room temperature for 2 hours. The components in both samples were characterized using liquid chromatography-mass spectrometry (LC-MS). No oligomers were found in the blank MTM sample, while some peaks were observed in the YF14 / MTM mixture sample. Possible structures were identified and are listed in Figure 3. The conclusion is that MTM can catalyze the formation of oligomers from YF-14 (ATH / Al2O3) packing material at room temperature. This is achieved by breaking the -Si-O-Al- bonds on the packing surface to form MeSi(OMe). 2+ cation.

Claims

1. A silicone potting compound composition, said silicone potting compound composition comprising: (A) Silicone polymers having two or more alkenyl groups per molecule; (B) Methyltrimethoxysilane oligomers; and (C) Inorganic fillers.

2. The silicone potting compound composition according to claim 1, wherein the methyltrimethoxysilane oligomer is formed in situ by premixing methyltrimethoxysilane at a temperature below 60°C for at least 2 hours.

3. The silicone potting compound composition of claim 1, wherein the silicone potting compound composition further comprises at least one of the following: (D) Polyorganohydrogen polysiloxanes with at least one Si-H bond per molecule; (E) Hydrosilylation catalyst; (F) Pigment; (G) inhibitors; and (H) Water.

4. The silicone potting compound composition according to claim 1, wherein the amount of component (A) is from 5% to 80% by weight based on the total weight of the silicone potting compound composition.

5. The silicone potting compound composition according to claim 1, wherein the amount of component (B) is from 0.1% to 1% by weight based on the total weight of the silicone potting compound composition.

6. The silicone potting composition according to claim 1, wherein the amount of component (C) is from 50% to 90% by weight based on the total weight of the silicone potting composition.

7. The silicone potting compound composition according to claim 1, wherein component (C) is selected from Al2O3, aluminum hydroxide, quartz, or combinations thereof.

8. The silicone potting composition according to claim 1, wherein, based on the total weight of the silicone potting composition, the amount of component (D) is 0% to 1% by weight, the amount of component (E) is 0.01% to 0.5% by weight, the amount of component (F) is 0% to 10% by weight, the amount of component (G) is 0% to 0.3% by weight, and the amount of component (H) is 0% to 0.1% by weight.

9. The silicone potting composition according to claim 1, wherein components (B) and (C) are premixed prior to mixing with component (A), provided that component (B) contains only methyltrimethoxysilane.

10. A method for preparing a silicone potting compound composition according to any one of claims 1 to 9, the method comprising: (i) Mix components (A), (B) and (C) at a temperature below 60°C for at least 2 hours to form a premix; as well as (ii) Optionally, at least one of component (D), component (E), component (F), component (G) and component (H) is added to the premix.

11. The method of claim 10, wherein the method further comprises: (i-1) In the presence of optional component (H), premix component (B) and component (C) and then mix them with component (A).

12. The method of claim 10, wherein the method further comprises: (i-2) The premix is ​​maintained in a protective atmosphere at a temperature of 60°C to 120°C for 1 to 3 hours.

13. The method of claim 10, wherein the method further comprises: (i-3) Cool the premix to a temperature below 60°C.

14. Use of the silicone potting compound composition according to any one of claims 1 to 9 in thermally conductive sealants.

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