Heat-insulating silicone composition and method for producing heat-insulating cured product using the composition

Abstract

Provided is a heat-insulating silicone composition having low adhesiveness and improved softness at high temperatures. The composition includes: (A) an organopolysiloxane containing alkenyl groups bonded to at least two silicon atoms within one molecule; (B) an organohydrogenpolysiloxane containing 0.0001 to 0.005 mol / g of hydrogen atoms bonded to silicon atoms; (C) an organic-resin hollow filler; and (D) an addition reaction catalyst. Relative to 100 parts by mass of the total amount of the components (A) and (B), the content of the component (C) is 5 to 25 parts by mass, and the content of the component (D) is 0.05 to 1.8 parts by mass, and the molar ratio [Si-H groups / alkenyl groups] of the total amount of the Si-H groups contained in the entirety of the heat-insulating silicone composition to that of the alkenyl groups bonded to the silicon atoms in the component (A) is 0.5 to 1.0.

Description

HEAT-INSULATING SILICONE COMPOSITION AND METHOD FOR PRODUCING HEAT-INSULATING CURED PRODUCT USING THE COMPOSITIONTechnical Field

[0001] The present invention relates to a heat-insulating silicone composition and a method for producing a heat- insulating cured product using the composition.Background Art

[0002] A silicone rubber adhesive composition is used as a protective agent for adhesion-fixing, heat resistance, weather resistance, electrical insulation, and the like, in components such as various electrical and electronic components, automobile components, and various computer-related components in a PC and a mobile device.

[0003] PTL 1 discloses a low-specific gravity silicone rubber adhesive composition that is a low-specific gravity adhesive having cushioning properties and heat insulating properties. The adhesive is obtained by adding an adhesion aid to a silicone rubber composition containing a hollow filler formed of an organic resin.Citation ListPatent Literature

[0004] PTL 1: Japanese Patent No. 5115716Summary of Invention Technical Problem

[0005] For example, a member such as a battery casing may expand in a high-temperature use environment or the like. A cured product of the silicone rubber adhesive composition of PTL 1 has high adhesiveness. Therefore, when the cured product is disposed around an expandable member, the cured product may confine the expansion force and break the member.

[0006] The present invention provides a heat-insulating silicone composition having low adhesiveness and improved softness at high temperatures, and a method for producing a heat-insulating cured product using the heat-insulatingsilicone composition.Solution to Problem

[0007] The heat-insulating silicone composition of the present invention includes: a component (A) that is an organopolysiloxane containing alkenyl groups bonded to at least two silicon atoms within one molecule; a component (B) that is an organohydrogenpolysiloxane containing 0.0001 mol / g or more and 0.005 mol / g or less of hydrogen atoms bonded to silicon atoms; a component (C) that is a hollow filler formed of an organic resin; and a component (D) that is an addition reaction catalyst.

[0008] When the total amount of the component (A) and the component (B) is 100 parts by mass, the content of the component (C) may be 5 parts by mass or more and 25 parts by mass or less, the content of the component (D) may be 0.05 parts by mass or more and 1.8 parts by mass or less, and the molar ratio [Si-H groups / alkenyl groups] of the total amount of the Si-H groups contained in the entirety of the heat-insulating silicone composition to the total amount of the alkenyl groups bonded to the silicon atoms in the component (A) may be 0.5 or more and 1.0 or less.The molar ratio [Si-H groups / alkenyl groups] may preferably be 0.5 or more and 0.9 or less.

[0009] An inorganic substance may adhere to at least a part of the surface of the component (C).In the component (C), the inorganic substance may be subjected to a compatibility-imparting surface treatment or a dispersibility-imparting surface treatment.The component (C) may have a true density of 0.2 g / cm3or less.The component (C) may have an average particle diameter of 150 pm or less, and more preferably 30 pm or more and 80 pmor less.

[0010] The heat-insulating silicone composition may further include a component (E) that is a silicone resin having at least one alkenyl group in the molecule with a number-average molecular weight of 1,000 or more and 10,000 or less, preferably 1,400 or more and 4,000 or less, and more preferably 1,400 or more and 2,500 or less.

[0011] The heat-insulating silicone composition preferably does not include silica.

[0012] The heat-insulating silicone composition preferably does not include an adhesion aid.

[0013] The uncured heat-insulating silicone composition may have a viscosity at 25°C of 10,000 mPa-s or less, and more preferably 1,000 mPa-s or more and 4,000 mPa-s or less. In the case where the heat-insulating silicone composition is a two- component mixture type including a first liquid and a second liquid, the viscosity at 25°C of each of the first liquid and the second liquid may be 10,000 mPa-s or less, and more preferably 1,000 mPa-s or more and 4,000 mPa-s or less. When the first liquid and the second liquid are mixed, the viscosity at 25°C before the start of curing or at the initial stage of curing may be 10,000 mPa-s or less, and more preferably 1,000 mPa-s or more and 4,000 mPa-s or less.(Measurement method)The viscosity at 25°C of the heat-insulating silicone composition is measured in accordance with JIS K 7117—2. For example, the uncured heat-insulating silicone composition is placed between a cone that has a diameter of 25 mm and rotates at an angle of 1° or 2° and a fixed flat plate to measure its viscosity using a viscometer at a shear rate of 10 (1 / s) with a gap of 0.106 mm.

[0014] A heat-insulating cured product obtained by curing the heat-insulating silicone composition may have a thermal conductivity of 0.2 W / mK or less, preferably 0.1 W / mK or more and 0.18 W / mK or less, and more preferably 0.12 W / mK or moreand 0.15 W / mK or less. (Measurement method)The thermal conductivity at 25°C of the heat-insulating cured product is measured in accordance with ISO 22007-2. For example, the heat-insulating silicone composition is cured at 100°C for 30 minutes to produce test pieces with a diameter of 40 mm and a height of 10 mm, and then, a sensor is sandwiched between the resulting two test pieces to measure its thermal conductivity.

[0015] A heat-insulating cured product obtained by curing the heat-insulating silicone composition may have a hardness (in terms of needle penetration) of 10 or more and 40 or less. (Measurement method)The needle penetration at 23°C of the heat-insulating cured product is measured in accordance with ASTM D 2240. For example, the needle penetration of a heat-insulating cured product obtained by curing the heat-insulating composition at 100°C for 30 minutes is measured in a 60 mL container. The "needle penetration" is indicated by the length of the portion of a steel standard needle that has penetrated into a sample at a constant temperature. The penetration length at a load of 100 g for 5 seconds is measured, and the measured needle penetration depth is expressed with increments of 1 / 10 mm.

[0016] A heat-insulating cured product obtained by curing the heat-insulating silicone composition may have a specific gravity of 0.7 or less.

[0017] A heat-insulating cured product obtained by curing the heat-insulating silicone composition may have a density of 0.5 g / cc or more and 0.68 g / cc or less, and preferably 0.52 g / cc or more and 0.67 g / cc or less. (Measurement method)The density at 23°C of the heat-insulating cured product is measured in accordance with JIS K 6249. For example, the density of a test piece obtained by curing the heat-insulating silicone composition at 100°C for 30 minutes is measured by anunderwater displacement method.

[0018] A heat-insulating cured product obtained by curing the heat-insulating silicone composition may have a tensile strength of 50 kPa or more and 400 kPa or less.(Measurement method)The tensile strength at 25°C of the heat-insulating cured product is measured in accordance with JIS K 6251. For example, a 2mm-thick sheet obtained by curing the heat- insulating silicone composition at 100°C for 30 minutes is punched in a dumbbell No. 3 shape, and the break strength and elongation when pulling is performed at a tensile speed of 500 mm / min are measured using a tensile tester.

[0019] In the heat-insulating silicone composition, the floatability of the component (C) relative to the other components may be 40% or more and 70% or less, and preferably 40% or more and 65% or less.(Measurement method)The floatability of the filler is determined from the interface position between the liquid phase (silicone phase) and the filler phase (component (C) phase) after the uncured heat-insulating silicone composition has been left to stand for a certain period of time. For example, the material (a first liquid or a second liquid when the composition is distributed into the first and second liquids) is poured in a 50 mL container with a diameter of 35 mm and a height of 78 mm to a filling height of 55 mm from the bottom, and stored under conditions with a high temperature for a prescribed period of time (for example, 50°C for one week). After that, the interface position between the silicone phase and the filler phase is measured by a ruler or the like. The floatability of the filler component is determined from the interface position and the filling amount of the filler component. A volume fraction of the blended amount of the component (C) relative to the blended amount of the other components in the first liquid or the second liquid is calculated. For example, assumethat the volume fraction, i.e., the component (C) : the liquid phase of the other components is 4:6. Then, the theoretical height HO of the liquid phase is obtained by multiplying the volume fraction (= 6 / 10) of the liquid phase by the filing height (= 55 mm). The height Hl of the liquid phase after storage at a high temperature for a prescribed period of time is measured by a ruler. For example, assume a case where the measured height Hl (interface position) is 16.5 mm (the component (C) : the liquid phase of other components is 7:3).The floatability can be expressed by H1 / H0 x 100 (in the above example, H1 / H0 x 100 = 16.5 / 33 x 100 = 50%).

[0020] The strength of the component (C) may be 2 N or less. (Measurement method)The strength of the filler component (component (C)) floating on the surface of a sample after floatability evaluation test is measured. For example, a maximum load value when a spherical compression jig with a diameter of 12.7 mm is pressed against a sample at a compression speed of 240 mm / min so that it penetrates the sample is measured using a compression tester.

[0021] When a heat-insulating cured product obtained by curing the heat-insulating silicone composition is heated at 190 to 210°C for 1 to 2.5 hours, the volume change rate may be a volume shrinkage by 15% or more and 34% or less (a volume change rate of -34% or more and -15% or less) after heating as compared to before heating. (Measurement method)The volume change rate of a sample heated for a prescribed time (for example, 2 hours) using a heating device (for example, an oven) at a prescribed temperature (for example, 200°C) is measured. For example, the weight and density of a test piece with a diameter of 40 mm and a height of 10 mm obtained by curing the heat-insulating silicone composition at 100°C for 30 minutes are measured to calculatethe volume (before heating shrinkage). The weight and density of the test piece that has been heated in an oven at 200°C for 2 hours and then cooled to room temperature are measured to calculate the volume (after heating shrinkage). The volume change rate is calculated from the difference between the volume before heating and that after heating.Volume change rate = {(volume after heating shrinkage) - (volume before heating shrinkage)} / (volume before heating shrinkage) x 100

[0022] A method for producing a heat-insulating cured product obtained by curing the above-described heat-insulating silicone composition, includes: a step of potting the heat-insulating silicone composition on a substrate (a step of filling and applying) to form a potted layer; and a step of curing the potted layer at a temperature of 5°C or higher and 100°C or lower, and more preferably 15°C or higher and 50°C or lower.

[0023] (Operation and effect)(1) Although adhesiveness is generated by an interaction between an Si-H group and a functional group (a -OH group or the like) on the surface of an adherend, the amount of the organohydrogenpolysiloxane (i.e. the density of an Si-H group) of the present composition is small, and thus, the adhesiveness is lower than that of the composition disclosed in PTL 1.(2) Although curing is achieved when the Si-H group and an Si-alkenyl group are bonded and crosslinked to each other by an addition reaction, the Si-H amount of the present composition is small, and thus, the crosslinking density is low, and a cured product obtained after curing has a low hardness and is soft.(3) The heat-insulating silicone composition has the lower adhesiveness and improved softness as compared to the composition of PTL 1, and a cured product thereof shrinks at acertain temperature or higher.(4) When a silicone resin is blended, a heat-insulating cured product obtained by curing the heat-insulating silicone composition can have reduced brittleness.(5) When silica is not blended, the heat-insulating silicone composition can have reduced viscosity.(6) The lower viscosity thereof can improve workability, operability, and potting properties.(7) The present composition at least functions as a potting agent and has hardness and adhesiveness to some extent. A cured product of the present composition can be satisfactorily peeled at a certain temperature or higher, and thus reworking and maintenance properties are excellent.(8) A known battery cell of an electric vehicle is covered with a heat insulating material having strong adhesion force in order to prevent the spread of fire at damage and explosion. However, this firm adhesion complicates recycling and increases the environmental load. According to the present invention, there can be provided a heat insulating material that exerts a controlled adhesion force to the skin of a battery cell in order to improve recycling properties. The weakened adhesion force facilitates disassembling work and improves resource recovery. The present invention contributing to a reduction in environmental load is an innovative technology that enhances the sustainability of electric vehicle batteries.Description of Embodiments

[0024] Hereinafter, a heat-insulating silicone composition and a method for producing a heat-insulating cured product using the heat-insulating silicone composition according to the present invention will be described in detail.

[0025] (Heat-insulating silicone composition)The heat-insulating silicone composition is a composition for forming a heat-insulating cured product. Examples of the heat-insulating silicone composition include configurationsapplied as a potting agent for, for example, a certain substrate such as a substrate of an electrical apparatus or an electronic apparatus, a circuit chip, an on-board component, a battery component, and the like.

[0026] Temperatures and procedures for curing the heat- insulating silicone composition are not particularly limited, and can be appropriately selected depending on use applications or the like of an obtained cured product.

[0027] Respective components of the heat-insulating silicone composition when the curing method of the heat- insulating silicone composition according to the present invention is an addition reaction will be described hereinafter in detail.

[0028] Component (A): OrganopolysiloxaneThe component (A) is the main agent of the heat- insulating silicone composition and is an organopolysiloxane containing alkenyl groups bonded to at least two silicon atoms within one molecule.The molar ratio [Si-H groups / alkenyl groups] of the total amount of the Si-H groups contained in the entirety of the heat-insulating silicone composition to the total amount of the alkenyl groups bonded to the silicon atoms in the component (A) is 0.5 or more and 1.0 or less.

[0029] The viscosity and the degree of polymerization of the component (A) are not particularly limited, and may be selected according to the required mixed viscosity and the like of the heat-insulating silicone composition. For example, the viscosity at 25°C thereof may be 10 mPa-s or more and 30,000 mPa-s or less.As the organopolysiloxane, one type thereof may be used alone, or two or more types thereof may be used in combination as appropriate. The organopolysiloxane is the main component of the heat-insulating silicone composition and has, on average, at least two alkenyl groups bonded to silicon atoms within one molecule, preferably 2 to 50 alkenyl groups, andmore preferably 2 to 20 alkenyl groups.

[0030] The molecular structure of the component (A) is not specifically limited, and may be, for example, a linear structure, a partially branched linear structure, a branched chain structure, a cyclic structure, or a branched cyclic structure. Among these, the component (A) is preferably a substantially linear organopolysiloxane. Specifically, the component (A) can be a linear diorganopolysiloxane in which the molecular chain is mainly composed of a diorganosiloxane repeat unit and in which both terminals of the molecular chain are blocked with a triorganosiloxy group. Some or all of the molecular chain terminals, or some of the side chains, may be a silanol group.

[0031] The positions of the alkenyl groups bonded to the silicon atoms in the component (A) are not particularly limited, and the component (A) may be an organopolysiloxane having an alkenyl group bonded to a silicon atom at both molecular chain terminals.The organopolysiloxane having one alkenyl group at each terminal of the molecular chain has an advantage in that the content of the alkenyl groups serving as the reaction point of the cross-linking reaction is small and the softness of the cured product obtained by curing the heat-insulating silicone composition is enhanced.An organopolysiloxane having an alkenyl group in the side chains of the molecular chain, in addition to having alkenyl groups at both terminals, can enhance the cross-linking density and the hardness of the cured product obtained by curing the heat-insulating silicone composition.The number of alkenyl groups within one molecule of the component (A) can be appropriately determined in accordance with the required hardness of the cured product, the molecular weight of the component (A), and the like. The number of alkynyl groups within one molecule may be two or more, more preferably two or more and five or less, and most preferablytwo (having one alkynyl group at each terminal of the molecular chain).

[0032] The alkenyl group may be bonded to the silicon atom at the molecular chain terminal, to the silicon atom at a non- terminal molecular chain site (in the middle of the molecular chain), or to both.The component (A) may be a polymer composed of a single type of siloxane unit or a copolymer composed of two or more types of siloxane units.

[0033] The viscosity of the component (A) at 25°C is 10 mPa-s or more and 30,000 mPa-s or less, preferably 50 mPa-s or more and 1,000 mPa-s or less, and more preferably 100 mPa-s or more and 500 mPa-s or less.

[0034] In order to adjust the viscosity (mixed viscosity) of the heat-insulating silicone composition before curing, two or more types of organopolysiloxanes having an alkenyl group and having different viscosities can also be used in combination .

[0035] Specifically, the component (A) is represented by the following general formula (1) as an average composition formula:R1aS10(4-a) / 2 ... (1)(In the formula (1), Rxs are the same as or different from each other and each are an unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms, a is 1.7 to 2.1, preferably 1.8 to 2.5, and more preferably 1.95 to 2.05.).

[0036] In one embodiment, at least two or more of the monovalent hydrocarbon groups represented by the aforementioned R1are selected from alkenyl groups such as a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, an isobutenyl group, a hexenyl group, and a cyclohexenyl group. Groups other than these groups are substituted or unsubstituted monovalent hydrocarbon groups having 1 to 18 carbon atoms. Specifically, the aforementionedR1is selected from the group consisting of an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert- butyl group, a pentyl group, a neopentyl group, a hexyl group, a 2-ethylhexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, and a dodecyl group; a cycloalkyl group such as a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group; an aryl group such as a phenyl group, a tolyl group, a xylyl group, a biphenyl group, and a naphthyl group; an aralkyl group such as a benzyl group, a phenylethyl group, a phenylpropyl group, and a methylbenzyl group; and a halogen-substituted or cyano-substituted alkyl group in which a part or all of hydrogen atoms in the above-described hydrocarbon groups have been substituted with a halogen atom, a cyano group, or the like, such as a chloromethyl group, a 2- bromoethyl group, a 3,3,3-trifluoropropyl group, a 3- chloropropyl group, and a cyanoethyl group.

[0037] Examples of R1s to be selected preferably include, as the two or more alkenyl groups required, a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a 2- methyl-l-propenyl group, a 2-methylallyl group, and a 2- butenyl group. A vinyl group is particularly preferable. Preferable examples of R1other than the alkenyl group include a methyl group and a phenyl group, with a methyl group being particularly preferable. In addition, it is preferable that 70 moll or more of Rxs be a methyl group, in consideration of physical properties and economic efficiency of the cured product, and normally, it is preferable that 80 moll or more of Rxs be a methyl group.

[0038] Specific examples of the molecular structure of the component (A) include a dimethylpolysiloxane with both molecular chain terminals blocked with a dimethylvinylsiloxy group, a dimethylsiloxane-methylphenylsiloxane copolymer with both molecular chain terminals blocked with a dimethylvinylsiloxy group, a dimethylsiloxane-methylvinylsiloxane copolymer with both molecular chain terminals blocked with a dimethylvinylsiloxy group, a dimethylsiloxane-methylvinylsi1oxane -methylphyenylsiloxane copolymer with both molecular chain terminals blocked with a dimethylvinylsiloxy group, a dimethylsiloxane- methylvinylsiloxane copolymer with both molecular chain terminals blocked with a trimethylsiloxy group, an organopolysiloxane composed of a siloxane unit represented by the formula: (CH3)2ViSiOi / 2, a siloxane unit represented by the formula: (CH3)3S1O1 / 2, and a siloxane unit represented by the formula: S1O4 / 2 (Vi in the formula represents a vinyl group), an organopolysiloxane in which part or all of the methyl groups in the above-mentioned organopolysiloxanes are substituted by an alkyl group such as an ethyl group or a propyl group, an aryl group such as a phenyl group or a tolyl group, and a halogenated alkyl group such as a 3,3,3- trifluoropropyl group, and mixtures of two or more of these organopolysiloxanes. From the viewpoint of enhancing elongation at the time of breakage of the cured product due to increased molecular chain length, a linear diorganopolysiloxane with one vinyl group at each molecular chain terminal is preferable.

[0032] These diorganopolysiloxanes may be commercially available or prepared by methods known to those skilled in the art.

[0040] Component (B): OrganohydrogenpolysiloxaneThe component (B) is an organohydrogenpolysiloxane containing 0.0001 mol / g or more and 0.005 mol / g or less of hydrogen atoms bonded to silicon atoms.The component (B) is an organohydrogenpolysiloxane containing two or more hydrogen atoms bonded to silicon atoms within one molecule, and is a crosslinked component for forming a cured product by an addition-curing reaction between the Si-H group and the alkenyl group.

[0041] The organohydrogenpolysiloxane as the component (B)is represented by the following average composition formula(2):[Chemical formula 2](In the formula (2), R2s are each independently a hydrogen atom, a hydroxyl group, or a substituted or unsubstitutedmonovalent hydrocarbon group having 1 to 12 carbon atoms, provided that the component (B) contains two or more hydrogen atoms bonded to silicon atoms within one molecule, a is an integer of 2 or more, b is an integer of 1 or more, c is an integer of 0 or more, and d is an integer of 0 or more, and the value of a + b + c + d is not particularly limited as long as the viscosity of the component (B) satisfies a viscosity range to be described later, and may be 5 or more and 600 or less, but may be 10 or more and 400 or less.).

[0042] The viscosity at 25°C of the component (B) may be 1 mPa-s or more and 3,000 mPa-s, and preferably 10 mPa-s or more and 1,000 mPa-s or less.

[0043] When the R2s bonded to silicon atoms in the component (B) are other monovalent hydrocarbon groups, specific examples of the monovalent hydrocarbon groups include an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, a neopentyl group, a hexyl group, a 2-ethylhexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, and a dodecyl group; a cycloalkyl group such as a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group; an aryl group such as a phenyl group, a tolyl group, a xylyl group, a biphenyl group, and a naphthyl group; an aralkyl group such as a benzyl group, a phenylethyl group, a phenylpropyl group, and a methylbenzylgroup; and a substituted hydrocarbon group in which a part or all of hydrogen atoms in the above-described hydrocarbon groups have been substituted with a halogen atom, a cyano group, or the like, such as a chloromethyl group, a 2- bromoethyl group, a 3,3,3-trifluoropropyl group, a 3- chloropropyl group, a chlorophenyl group, a dibromophenyl group, a tetrachlorophenyl group, a difluorophenyl group, a 0- cyanoethyl group, a y-cyanopropyl group, and a 0-cyanopropyl group. Particularly preferred monovalent hydrocarbon groups are a methyl group and a phenyl group.

[0044] The component (B) can further include those having an -SiOH group at one portion of the molecular chain terminals. In such a case, the proportion of the number of silicon atoms having an OH group to the total number of terminal silicon atoms of the entire organohydrogenpolysiloxanes in the component (B) is less than 5%, preferably less than 2%. When the proportion satisfies the above-mentioned condition, addition reaction proceeds sufficiently, and a cured film with sufficient qualities can be obtained.

[0045] The hydrogen content (H content) of the component(B) is 0.0001 mol / g or more and 0.005 mol / g or less, preferably 0.0002 mol / g or more and 0.005 mol / g or less, more preferably 0.0003 mol / g or more and 0.005 mol / g or less, and even more preferably 0.0004 mol / g or more and 0.005 mol / g or less.

[0046] The component (B) may function as a cross-linking agent. The cross-linking agent is preferably an organohydrogenpolysiloxane having 5 or more hydrosilyl groups, and may be one having 10 or more and 18 or less hydrosilyl groups. The organohydrogenpolysiloxane that is the cross- linking agent has at least two hydrosilyl groups present in its side chain. The number of hydrosilyl groups at a molecular chain terminal may be zero or more and two or less, and is, from an economic perspective, preferably two. The molecularstructure of the organohydrogenpolysiloxane may be any of linear, cyclic, branched, and three-dimensional network structures. The position of the silicon atom to which a hydrogen atom is bonded is not particularly limited, and may be at a molecular chain terminal, at a non-terminal molecular chain site (in the middle of the molecular chain), or in a side chain. Other conditions, the type of the organic group other than a hydrosilyl group, the bonding position, the degree of polymerization, the structure, and the like in the organohydrogenpolysiloxane serving as the cross-linking agent are not particularly limited. Two or more types of organohydrogenpolysiloxanes may be used in combination.

[0047] The content of the component (B) is, for example,30 parts by mass or more and 35 parts by mass or less relative to 100 parts by mass of the total of the component (A) and the component (B).

[0048] The hydrosilyl group in the component (B) may be present at the molecular chain terminals, may be present in side chains, or may be present both at the molecular chain terminals and in the side chains. It is preferable to use a mixture of an organohydrogenpolysiloxane having one hydrosilyl group only at each molecular chain terminal and an organohydrogenpolysiloxane having hydrosilyl groups only in the side chain of the molecular chain.

[0049] From the viewpoint of improving heat resistance, the component (B) may include an organohydrogenpolysiloxane having at least one aromatic group within the molecule. For economic reasons, the aromatic group is more preferably a phenyl group. An aromatic group-containing organohydrogenpolysiloxane and an aromatic group-free organohydrogenpolysiloxane may be used in combination.

[0050] Component (C): Hollow filler formed of organic resinThe component (C) is a hollow filler formed of an organic resin.The organic resin for the hollow filler formed of an organic resin may be selected from the group consisting of various polymers such as, for example, a polymer of vinylidene chloride, a polymer of acrylonitrile, a polymer of methacrylonitrile, a polymer of an acrylic acid ester, and a polymer of a methacrylic acid ester; and a copolymer of two or more selected from these monomer units.

[0051] The average particle diameter of the hollow filler formed of an organic resin may be 15 pm or more and 150 pm or less, preferably 20 pm or more and 100 pm or less, and more preferably 20 pm or more and 80 pm or less. An average particle diameter is a value measured as a cumulative weight- average value (D50) or a median diameter, measured by a laser diffraction method using a particle size distribution measuring device.

[0052] The component (C), or the component (C) with an attached inorganic substance, has a true specific gravity of 0.1 or more and 0.3 or less, preferably 0.11 or more and 0.25 or less, more preferably 0.12 or more and 0.20 or less, and still more preferably 0.12 or more and 0.18 or less. Controlling the specific gravity of the filler can suppress separation (floating) of the filler in the composition (the first liquid or the second liquid).

[0053] The content of the component (C) is 5 parts by mass or more and 25 parts by mass or less, or 7 parts by mass or more and 22 parts by mass or less, preferably 8 parts by mass or more and 20 parts by mass or less, more preferably 8 parts by mass or more and 16 parts by mass or less, still more preferably 8 parts by mass or more and 14 parts by mass or less, relative to 100 parts by mass of the total amount of the component (A) and the component (B).

[0054] The component (C) may have an inorganic substance that adhere to at least a part of its surface. Examples of the inorganic substance include calcium carbonate, zinc oxide, hydroxyapatite, and hydrous magnesium silicate.

[0055] In the component (C), the inorganic substance may be subjected to a compatibility-imparting surface treatment or a dispersibility-imparting surface treatment. The compatibility-imparting surface treatment or dispersibility- imparting surface treatment may be performed using an organic substance such as fatty acids and resin acids.

[0056] Coating the hollow filler made of an organic resin with an inorganic substance can suppress separation (floating) of the filler in the heat-insulating silicone composition (the first liquid or the second liquid). The low-viscosity first liquid or the second liquid of the heat-insulating silicone composition suppresses floating of the filler by setting the specific gravity of the filler and performing a surface treatment since the filler is likely to float during storage.

[0057] Component (D): Addition reaction catalyst)The addition reaction catalyst of the component (D) is a catalyst that promotes an addition-curing reaction between an alkenyl group bonded to a silicon atom in the component (A) described above and a hydrogen atom bonded to a silicon atom in the component (B) described above, and is a catalyst known to those skilled in the art. Examples of the component (D) include a platinum group metal such as platinum, rhodium, palladium, osmium, iridium, and ruthenium, and catalysts in which any of the aforementioned metals is supported by a particulate carrying material (for example, activated carbon, aluminum oxide, and silicon oxide).Furthermore, specific examples of the component (D) include a platinum halide, a platinum-olefin complex, a platinum-alcohol complex, a platinum-alcoholate complex, a platinum-vinylsiloxane complex, dicyclopentadiene-platinum dichloride, cyclooctadiene-platinum dichloride, and cyclopentadiene-platinum dichloride.

[0058] In addition, from an economic viewpoint, a metal compound catalyst other than platinum group metals as described above may be used as the component (D). Examples ofthe iron catalyst for hydrosilylation include an iron-carbonyl complex catalyst, an iron catalyst having a cyclopentadienyl group as a ligand, an iron catalyst having a terpyridine-based ligand or a combination of a terpyridine-based ligand and a bistrimethylsilylmethyl group, an iron catalyst having a bisiminopyridine ligand, an iron catalyst having a bisiminoquinoline ligand, an iron catalyst having an aryl group as a ligand, an iron catalyst having a cyclic or acyclic olefin group with an unsaturated group, and an iron catalyst having a cyclic or acyclic olefinyl group with an unsaturated group. Other examples of the catalyst for hydrosilylation include a cobalt catalyst, a vanadium catalyst, a ruthenium catalyst, an iridium catalyst, a samarium catalyst, a nickel catalyst, and a manganese catalyst.

[0059] The blending amount of the component (D) is, in terms of the concentration of the catalyst metal element, in the range of preferably 0.5 ppm or more and 1,000 ppm or less, more preferably 1 ppm or more and 500 ppm or less, and still more preferably 1 ppm or more and 100 ppm or less relative to the total mass of the heat-insulating silicone composition, although an effective amount thereof according to the curing temperature and curing time desired depending on the use applications is used. If the blending amount is less than 0.5 ppm, the addition reaction becomes remarkably slow. If the blending amount exceeds 1,000 ppm, it is not economically preferable because of cost increase.

[0060] The content of the component (D) may be 0.05 parts by mass or more and 1.8 parts by mass or less, preferably 0.08 parts by mass or more and 1.6 parts by mass or less, relative to 100 parts by mass of the total amount of the component (A) and the component (B).

[0061] Component (E): Silicone resinThe component (E) is a silicone resin having at least one alkenyl group in the molecule with a number-average molecular weight of 1,000 or more.The silicone resin may be a modified silicone resin, and may be a mixture of a resin containing no alkenyl group and an alkenyl group-containing organopolysiloxane.

[0062] Examples of the silicone resin include a methyl silicone resin and a methyl phenyl silicone resin. Examples of a modified silicone resin include an alkyd-modifled silicone resin, an epoxy-modifled silicone resin, an acryl-modifled silicone resin, and a polyester-modifled silicone resin.

[0063] The component (E2) may be the same as the organopolysiloxane containing alkenyl groups of the component (A).

[0064] SilicaThe heat-insulating silicone composition preferably does not include silica (silicon dioxide).

[0065] Adhesion aidThe heat-insulating silicone composition preferably does not include an adhesion aid.The adhesion aid that should preferably not be included is an organosilicon compound or an organosiloxane having an organic functional group in its molecule, or those having a silyl group containing an alkoxy group bonded to a silicon atom. The organic functional group contained in the adhesion aid that should preferably not be included is a silicon atom- bonded alkoxy group. Examples of such a silicon atom-bonded alkoxy group include a methoxy group, an ethoxy group, and a propoxy group. Examples of the silyl group containing an alkoxy group bonded to a silicon atom include an alkyldialkoxysilyl group such as a methyldimethoxysilyl group, an ethyldimethoxysilyl group, a methyldiethoxysilyl group, and an ethyldiethoxysilyl group. In this case, the silyl group may be bonded to the silicon atom via another group such as an alkylene group.Examples of organic groups that may be included as groups other than the above-mentioned groups include an alkenyl group such as a vinyl group, a (meth)acryl group, a hydrosilylgroup, an isocyanate group, an epoxy group, an alkyl group, and an aryl group. It is preferable not to include organosilicon compounds or organosiloxanes having at least one organic group (e.g., an epoxy group, an alkyl group, an aryl group, etc.) and at least two or more silicon atom-bonded alkoxy groups.

[0066] When an epoxy group is included as the other organic groups, the epoxy group may be a linear or branched alkyl group having 1 to 20 carbon atoms or an epoxy group having an aromatic ring, and those containing 2 to 3 epoxy groups in one molecule are mentioned as the adhesion aid that should preferably not be included. Examples of the epoxy group-containing group include a glycidoxyalkyl group such as a glycidoxypropyl group and a group bonded to a silicon atom in the form of an epoxy-containing cyclohexylalkyl group such as a 2,3-epoxycyclohexylethyl group and a 3,4- epoxycyclohexylethyl group.Specific examples of the adhesion aid that should preferably not be included include vinyltrimethoxysilane, tetraethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3- glycidoxypropyltriethoxysilane, an oligomer of 3- glycidoxypropyltrimethoxysilane, an oligomer of 3- glycidoxypropyltriethoxysilane, a methacryloxysilane such as 3-methacryloxypropyltrimethoxysilane and 3- methacryloxypropyltriethoxysilane, 3- trimethoxysilylpropylsuccinic anhydride, and a furandione such as dihydro-3- (3- (triethoxysilyl)propyl)-2,5-furandione.

[0067] In the heat-insulating silicone composition of the present invention, as an additional optional component other than the aforementioned components (A) to (E), a conventionally known additive for use in a silicone rubber or gel can be used as long as the object of the present invention is not impaired. Examples of such additives include a cross- linking agent, an organosilicon compound or an organosiloxane (also referred to as a silane coupling agent) that producessilanols by hydrolysis, a reaction rate regulator, a condensation catalyst, a pigment, a dye, a curing inhibitor, a heat-resistance imparting agent, a flame retardant, an antistatic agent, a conductivity imparting agent, an airtightness improving agent, a radiation shielding agent, an electromagnetic wave shielding agent, a preservative, a stabilizer, an organic solvent, a plasticizer, a fungicide, an organopolysiloxane that contains one hydrogen atom or alkenyl group bonded to a silicon atom within one molecule and that contains no other functional groups, and a non-functional organopolysiloxane that contains neither a silicon atom-bonded hydrogen atom nor a silicon atom-bonded alkenyl group. As these optional components, one type thereof may be used alone, or two or more types thereof may be used in combination as appropriate.

[0068] Component (F): Reaction rate regulatorThe reaction rate regulator is, for example, one having a capability of regulating the curing rate of the addition reaction, and examples thereof include acetylenic compounds, hydrazines, triazoles, phosphines, and mercaptans. Any curing inhibitor conventionally known in the art as a compound having a curing inhibiting effect can be used as the reaction rate regulator. Examples of such compounds include a phosphorus- containing compound such as triphenylphosphine, a nitrogen- containing compound such as tributylamine, tetramethylethylenediamine, and benzotriazole, a sulfur- containing compound, an acetylenic compound, a compound containing two or more alkenyl groups, a hydroperoxy compound, a maleic acid derivative, a silane having an amino group, and a silicone compound having an amino group.In particular, in the present invention, it is preferable that the effect on the fluidity be small and the curing proceed at room temperature. In such a case, examples of the reaction rate regulator include various "ene-yne" systems such as 3-methyl-3-penten-l-yne and 3,5-dimethyl-3-hexen-l-ynehaving low viscosities (e.g., viscosity of 100 mPa-s or less); an acetylenic alcohol such as 3,5-dimethyl-l-hexin-3-ol, 1- ethynyl-l-cyclohexanol, and 2-phenyl-3-butyn-2-ol; well known dialkyl-, dialkenyl-, and dialkoxyalkyl- fumarates and maleates; and those containing a cyclovinylsiloxane.

[0069] Component (G): PigmentExamples of the pigment include titanium oxide, alumina silicic acid, iron oxide, zinc oxide, calcium carbonate, carbon black, a rare earth oxide, chromium oxide, a cobalt pigment, ultramarine blue, cerium silanolate, aluminum oxide, aluminum hydroxide, titanium yellow, barium sulfate, precipitated barium sulfate, and mixtures thereof.Under normal circumstances, the blending amount of the pigment is preferably in the range of 0.001% to 5% relative to the total mass of the heat-insulating silicone composition. However, an effective amount thereof according to the curing temperature and curing time desired depending on the use applications is used. The amount of the pigment is preferably in the range of 0.01% or more and 2% or less, and more preferably 0.05% or more and 1% or less. If the amount is less than 0.001%, the resulting composition is insufficiently colored, and thus it becomes difficult to visually distinguish the first liquid from the second liquid. On the other hand, if the amount exceeds 5%, there will be a cost increase, which is not economically preferable.

[0070] Component (I): DispersantA dispersant may be used for the purpose of highly dispersing the component (C) in the system and suppressing re- aggregation. The dispersant is preferably an organopolysiloxane having an organic functional group in its molecule, or those having a silyl group containing an alkoxy group bonded to a silicon atom. Examples of the organic functional groups include a carboxyl group, an amino group, an alkyl group, a hydrosilyl group, an isocyanate group, an epoxy group, an aryl group, a polyether group, a polyglucosidegroup, a methoxy group, an ethoxy group, and a propoxy group. Examples of the more preferred dispersant include an organopolysiloxane having at least one organic group at its terminal or in a side chain, where the organic group is one selected from the group consisting of a carboxyl group, an amino group, an epoxy group, a polyether group, and the like group. Examples of the silyl group containing an alkoxy group bonded to a silicon atom include an alkyldialkoxysilyl group such as a methyldimethoxysilyl group, an ethyldimethoxysilyl group, a methyldiethoxysilyl group, and an ethyldiethoxysilyl group. In this case, the silyl group may be bonded to the silicon atom via another group such as an alkylene group. Furthermore, examples of the more specific dispersant may include a carboxyl-modifled organopolysiloxane, a non-reactive amino-modifled organopolysiloxane, and an epoxy-modifled organopolysiloxane. As a commercially available carboxyl- modified organopolysiloxane, WACKER M 642 manufactured by Wacker Chemie AG may be adopted. As a commercially available non-reactive amino-modifled organopolysiloxane, WACKER FINISH WT 1270 manufactured by Wacker Chemie AG may be adopted. As a commercially available epoxy-modifled organopolysiloxane, WACKER SILICON FLUID 22254 VP manufactured by Wacker Chemie AG may be adopted.

[0071] As the dispersant other than the organosilicon compound or the organopolysiloxane, a titanate-based coupling agent having a hydrophobic group such as an alkyl group is preferable, and for example, triisostearoyloxyisopropoxytitanium is preferable.

[0072] Using a dispersant having an organic functional group can assist the dispersion of the component (C) by the interaction of the organic function group with the hydrophilic group on the surface of the component (C), thereby reducing the viscosity of the uncured heat-insulating silicone composition and suppressing re-aggregation of the component (C) during storage. As a result, flotation of the component(C) can be suppressed and the strength of the floating matter can be reduced, thereby facilitating re-stirring.

[0073] The content of the dispersant may be 0.05 parts by mass or more and 2 parts by mass or less, preferably 0.08 parts by mass or more and 1.0 parts by mass or less, and more preferably 0.1 parts by mass or more and 0.5 parts by mass or less, relative to 100 parts by mass of the total amount of the component (A) and the component (B).

[0074] The heat-insulating silicone composition of the present invention may contain any one or more selected from the group consisting of octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), tetradecamethylcycloheptasiloxane (D7), and hexadecamethylcyclooctasiloxane (D8).The total content of (D4), (D5), (D6), (D7), and (D8) may be less than 0.1 parts by mass (i.e., less than 1,000 ppm) relative to 100 parts by mass of the total amount of the component (A) and the component (B).When the total content of (D4) to (D8) contained in the heat-insulating silicone composition falls within the aforementioned range, the flashing point of the whole composition may be increased, and safety during storage may be improved. Furthermore, the cured product obtained by curing the composition can be provided in a manner wherein the cured product is unlikely to cause a contact failure with an electronic part and the like.A heat-insulating silicone composition containing (D4) to (D8) in an amount of less than 0.1 parts by mass as the total content of (D4) to (D8) relative to 100 parts by mass of the total amount of the components (A) and (B) can be produced by using the component (A) in which the total content xA of (D4) to (D8) is less than 0.1 parts by mass, and the component (B) in which the total content xB of (D4) to (D8) is less than 0.1 parts by mass such that the total content xA + xB is less than0.1 parts by mass.The respective contents of (D4) to (D8) are measured by gas chromatography. The measurement condition of gas chromatography may be appropriately selected in accordance with a conventionally known method.

[0075] Two-component type:In the present embodiment, a two-component heat- insulating silicone composition may be used in which a first liquid and a second liquid are mixed to start curing.The first liquid contains the components (A), (C) and (D), for example. The first liquid may further contain a reaction rate regulator, a pigment, and a dispersant. Each of the components (A), (C), and (D), the reaction rate regulator, and a pigment in the first liquid may be a single type or two or more types thereof.The second liquid contains the components (A), (B), (C), and (E). Each of the components (A), (B), (C) and (E) in the second liquid may be a single type or two or more types thereof. The second liquid may further contain a dispersant.Both the first liquid and the second liquid do not contain silica and an adhesion aid.

[0076] First liquid:The first liquid may contain, relative to 100 parts by mass of the total blending amount thereof, the component (A) in an amount of 80 parts by mass or more and 96 parts by mass or less, the component (C) in an amount of 5 parts by mass or more and 15 parts by mass or less, the component (D) in an amount of 0.1 parts by mass or more and 0.5 parts by mass or less, the reaction rate regulator (F) in an amount of 0.1 parts by mass or less, the pigment (G) in an amount of 0.2 parts by mass or less, and the dispersant (I) in an amount of 0.5 parts by mass orless.

[0077] Second liquid:The second liquid may contain, relative to 100 parts by mass of the total blending amount thereof, the component (A) in an amount of 24 parts by mass or more and 36 parts by mass or less, the component (B) in an amount of 55 parts by mass or more and 65 parts by mass or less, the component (C) in an amount of 8 parts by mass or more and 10 parts by mass or less, the component (E) in an amount of 0 parts by mass or more and 2.5 parts by mass or less, and the dispersant (I) in an amount of 0.5 parts by mass or less.

[0078] The two-component heat-insulating silicone composition includes, relative to 100 parts by mass of the total blending amount thereof, the first liquid in an amount of 40 parts by mass or more and 60 parts by mass or less, and the second liquid in an amount of 60 parts by mass or more and 40 parts by mass or less.

[0079] Method for producing heat-insulating cured product:A method for producing a heat-insulating cured product obtained by curing the heat-insulating silicone composition of the present invention includes: a step of mixing the first liquid and the second liquid to produce the heat-insulating silicone composition; a step of potting the heat-insulating silicone composition onto a substrate (a step of filling and applying) to form a potted layer; and a step of curing the potted layer at a temperature of 5°C or higher and 100°C or lower, and more preferably 15°C or higher and 50°C or lower, for a predetermined period of time.The curing temperature condition is preferably room temperature curing. Rapid curing may be performed at atemperature higher than room temperature. However, it is preferable to set the curing temperature at which the component (C) does not cause deformation such as shrinkage.The curing time depends on the curing temperature, and can be shortened when the curing temperature is high.

[0080] Substrate:Examples of the substrate include various substrates for use in various electric and electronic components, automotive components, various computer-related components such as PCs and portable terminals, a battery unit, an electric device, and an electronic device.The electric device and the electronic device are not particularly limited, and examples thereof include a mobile phone, a smart phone, a tablet PC, a smart watch, a computer, a semiconductor package substrate, an electronic circuit substrate, an LED package substrate, a sensor substrate, an imaging device substrate, a liquid crystal substrate, and an organic EL substrate.

[0081] The heat-insulating silicone composition can be potted and cured in gaps between a plurality of substrates.The heat-insulating silicone composition can be potted and cured in gaps between components of the substrate.

[0082] Examples:In the following, examples of the two-component mixture type will be described. However, the present invention is not limited to the following examples. Table 1 shows various conditions of respective components of the first liquid. Table 2 shows various conditions of respective components of the second liquid.

[0083] Table 1:

[0085] Table 3 shows the blending proportions of respective components of the first liquid in each of Examples 1 to 15, and Table 4 shows the blending proportions of respective components of the second liquid. Table 5 shows the blending proportions of respective components when the first liquid and the second liquid of each of Examples 1 to 15 are mixed. Table 6 shows evaluation results of Examples 1 to 15. The numerical values of the blending proportions are indicated in terms of part by mass. The hollow filler formed of an organic resin is a polymer mainly composed of acrylonitrile, methyl methacrylate, and methacrylonitrile.

[0086] Table 3

[0090] Comparative Example:Table 7 shows the blending proportions of respective components of the first liquid in each of Comparative Examples 1 to 6, and Table 8 shows the blending proportions of respective components of the second liquid. Table 9 shows the blending proportions of respective components when the first liquid and the second liquid of each of Comparative Examples 1 to 6 are mixed. Table 10 shows evaluation results of Comparative Examples 1 to 6. The numerical values of the blending proportions are indicated in terms of part by mass.

[0091] Table 7:

[0092] Table 8:

[0093] Table 9:

[0094] Table 10:

[0095] Production method:The heat-insulating silicone composition was produced by mixing the first liquid and the second liquid shown in each of Examples and Comparative Examples.For example, the equivalent of 40 wt% of the liquid material in the composition (the first liquid or the second liquid) and the total amount of the filler were placed in a planetary centrifugal mixer, and mixed at a revolution rate of 660 rpm and a rotation rate of 220 rpm for 2 minutes. After that, the remaining liquid material (60 wt%) was fed thereto, and mixed at the same speed as above for 2 minutes.Subsequently, the first liquid and the second liquid were mixed at a mass ratio of 1:1.Subsequently, various evaluations were performed on the mixture before (in an uncured state) and after curing. The evaluation method (measurement method) of each evaluation will be described below.

[0096] Theoretical specific gravity:The theoretical specific gravity is calculated from the specific gravity of each component and the blending proportion thereof.

[0097] Molar ratio:The molar ratio [Si-H groups / alkenyl groups] is a molar ratio of the total amount of the Si-H groups contained in the entirety of the heat-insulating silicone composition to the total amount of the alkenyl groups bonded to the silicon atoms in the component (A).

[0098] Thermal conductivity:The thermal conductivity at 25°C of the heat-insulating cured product was measured in accordance with ISO 22007-2. The heat-insulating silicone composition was cured at 100°C for 30 minutes to produce test pieces with a diameter of 40 mm and a height of 10 mm, and then, a sensor was sandwiched between the resulting two test pieces to measure the thermal conductivity (W / mK) using a TPS-500 measuring instrument (manufactured by Hot Disk).

[0099] Needle penetration:The needle penetration at 23°C of the heat-insulating cured product was measured in accordance with ASTM D 2240. The needle penetration of a heat-insulating cured product obtained by curing the heat-insulating silicone composition at 100°C for 30 minutes was measured in a 60 mL container using an automatic needle penetration / consistency measuring instrument (PENETROMETER RPM-101). The "needle penetration" was indicated by the length of the portion of a steel standard needle that has penetrated into a sample at a constant temperature. Thepenetration length at a load of 100 g for 5 seconds was measured, and the obtained needle penetration depth was expressed with increments of 1 / 10 mm.

[0100] Density:The density at 23°C of the heat-insulating cured product was measured in accordance with JIS K 6249. The density (g / cc) of a test piece obtained by curing the heat-insulating silicone composition at 100°C for 30 minutes was measured by an underwater displacement method using a densimeter (AUTOMATIC DENSIMETER, MODEL DSG-1).The difference (!) from the theoretical specific gravity was calculated.

[0101] Viscosity:The viscosity at 25°C of the heat-insulating silicone composition was measured in accordance with JIS K 7117—2. The uncured heat-insulating silicone composition was placed between a cone with a diameter of 25 mm which rotated at an angle of 1° or 2° and a fixed flat plate to measure the viscosity using a Physica MR 301 viscometer (manufactured by Anton Paar) at a shear rate of 10 (1 / s) with a gap of 0.106 mm .In Table 6, "1st Liquid (D = 10)" indicates the viscosity at a shear rate of 10 (1 / s) in the first liquid, "2nd Liquid (D = 10)" indicates the viscosity at a shear rate of 10 (1 / s) in the second liquid, and "Mixture (D = 10)" indicates the viscosity at a shear rate of 10 (1 / s) in a mixture of the first liquid and the second liquid.

[0102] Tensile strength:The tensile strength at 25°C of the heat-insulating cured product was measured in accordance with JIS K 6251. A 2mm- thick sheet obtained by curing the heat-insulating silicone composition at 100°C for 30 minutes was punched in a dumbbell No. 3 shape, and the break strength (kPa) and elongation (displacement!) when pulling was performed at a tensile speed of 500 mm / min were measured using a tensile tester (AutographAGS-X manufactured by Shimadzu Corporation).

[0103] Floatability:The equivalent of 40 wt% of the liquid material of the first liquid or the second liquid and the total amount of the filler were placed in a planetary centrifugal mixer, and mixed at a revolution rate of 660 rpm and a rotation rate of 220 rpm for 2 minutes. After that, the remaining liquid material (60 wt%) was fed thereto, and mixed at the same speed as above for 2 minutes.After that, the floatability of the filler was determined from the interface position between the liquid phase (silicone phase) and the filler phase (component (C) phase) after the uncured heat-insulating silicone composition had been left to stand for a certain period of time. The material (the first liquid or the second liquid) was poured in a 50 mL container with a diameter of 35 mm and a height of 78 mm to a filling height of 55 mm from the bottom, and stored under conditions with a high temperature for a prescribed period of time (for example, 50°C for one week). After that, the interface position between the silicone phase and the filler phase was measured by a ruler or the like. The floatability of the filler component was determined from the interface position and the filling amount of the filler component.The volume fraction of the blended amount of the component (C) relative to the blended amount of the other components in the heat-insulating silicone composition (the first liquid or the second liquid) was calculated.Theoretical height HO of liquid phase = volume fraction (for example, 6 / 10) of liquid phase x filling height (= 55 mm) The height Hl of the liquid phase after storage at a high temperature for a prescribed period of time was measured by a ruler.Floatability (%) = H1 / H0 x 100In Table 6, "Liquid phase height: 1st liquid" and "Difference from theoretical value of liquid phase height: 1stliquid" indicate the evaluation results of the first liquid, and "Liquid phase height: 2nd liquid" and "Difference from theoretical value of liquid phase height: 2nd liquid" indicate the evaluation results of the second liquid.

[0104] Strength of floating matter:The strength of the filler component (component (C)) floating on the surface of a sample after floatability evaluation test was measured. The maximum load value (N) when a spherical compression jig with a diameter of 12.7 mm was pressed against a sample at a compression speed of 240 mm / min so that it penetrated the sample was measured using a compression tester (Autograph AGS-X manufactured by Shimadzu Corporation) .In Table 6, "Test force: 1st liquid" indicates the strength result in the first liquid, and "Test force: 2nd liquid" indicates the strength result in the second liquid.

[0105] Volume change rate:The weight and density of a test piece with a diameter of 40 mm and a height of 10 mm obtained by curing the heat- insulating silicone composition at 100°C for 30 minutes were measured to calculate the volume (before heating shrinkage). The weight and density of the test piece that had been heated in an oven at 200°C for 2 hours and then cooled to room temperature were measured to calculate the volume (after heating shrinkage). The volume change rate (%) was calculated from the difference between the volume before heating and that after heating.Volume change rate = {(volume after heating shrinkage) - (volume before heating shrinkage)} / (volume before heating shrinkage) x 100

[0106] Evaluation of Examples:In Example 1 in which the polymer viscosity and the molar ratio (Si-H groups / alkenyl groups) were adjusted, hardness, viscosity, floatability, and floating matter strength werebetter than those in Comparative Examples, and the volume change rate (shrinking properties) was also larger.In Example 2 in which the silicone resin (component (E)) of Example 1 was not included and the amount of the component (A) was increased instead, the tensile strength and displacement improved.In Example 3 in which a silicone resin different from the silicone resin used in Example 1 was used, the tensile strength and displacement improved.In Example 4 in which a silicone resin different from the silicone resin used in Example 1 was used, the tensile displacement improved.In Example 5 in which the amounts of the component (B) and the component (C) were increased from those in Example 1 and the amount of the component (A) was decreased from that in Example 1, the viscosity increased.In Example 6 in which the filler of Examples 1 to 5 was replaced with a filler (component (C)) that had a comparable particle diameter and a comparable specific gravity but was subjected to a surface hydrophobicity-imparting treatment (fatty acid treatment), the viscosity decreased, and as a result the filler became likely to float.In Example 7 in which the amounts of the component (B) and the component (C) of Example 1 were increased and the amount of the component (A) of Example 1 was decreased, the viscosity increased.In Example 8 in which the filler of Examples 1 to 5 was replaced with a different filler (talc surface treatment), the thermal conductivity increased and the viscosity decreased.In Example 9 in which the filler of Examples 1 to 5 was replaced with a resin filler with a large particle diameter and a large amount of attached inorganic substance, the thermal conductivity increased and the viscosity decreased.In Example 10 in which the filler of Example 1 was replaced with a resin filler with a smaller particle diameterand an identical specific gravity, the tensile displacement improved.In Example 11 in which the filler of Example 1 was replaced with a resin filler with a comparable particle diameter and a lower specific gravity, the viscosity decreased, and as a result the filler became likely to float.In Example 12 in which the filler of Example 1 was replaced with a resin filler with a comparable particle diameter and a lower specific gravity, the viscosity decreased.In Example 13 in which the silicone resin (component (E)) of Example 11 was not included, and the amount of the component (A) was increased instead, the strength of the floating matter decreased.Example 14 is the same as Example 13 except for the addition of carboxyl-modifled silicone oil. Because of this addition, the viscosity decreased, and the strength of the floating matter decreased.Example 15 is the same as Example 13 except for the addition of non-reactive modified silicone oil. Because of this addition, the viscosity decreased, and the strength of the floating matter decreased.

[0107] Evaluation of Comparative Examples:In Comparative Example 1, the difference from the theoretical specific gravity was as large as 3% or more. The tensile strength and displacement were small, and the softness was low. The strength of the floating matter after storage was high, and re-stirring was difficult.In Comparative Example 2 in which the molar ratio (Si-H groups / alkenyl groups) was increased from that in Example 1, the needle penetration was low.In Comparative Example 3 in which the molar ratio (Si-H groups / alkenyl groups) was increased from that Example 1, the needle penetration was low.In Comparative Example 4 in which the component (B) inExample 1 was changed to an organohydrogenpolysiloxane containing greater than 0.005 mol / g of hydrogen atoms bonded to silicone atoms and, the molar ratio of the hydrogen atoms bonded to silicone atoms to alkenyl groups bonded to silicone atoms (Si-H groups / alkenyl groups) was changed to 2 or more and an adhesion aid was added to the composition in Example 1, the hardness increased, and the elongation deteriorated.In Comparative Example 5 in which the molar ratio (Si-H groups / alkenyl groups) of Example 1 was decreased, the needle penetration was high.In Comparative Example 6 in which the filler of Example 1 was changed to a resin filler with a high specific gravity and a smaller particle diameter, the hardness and the viscosity increased.

Claims

Claims

1. A heat-insulating silicone composition comprising: a component (A) that is an organopolysiloxane containing alkenyl groups bonded to at least two silicon atoms within one molecule; a component (B) that is an organohydrogenpolysiloxane containing 0.0001 mol / g or more and 0.005 mol / g or less of hydrogen atoms bonded to silicon atoms; a component (C) that is a hollow filler formed of an organic resin; and a component (D) that is an addition reaction catalyst, wherein relative to 100 parts by mass of a total amount of the component (A) and the component (B), a content of the component (C) is 5 parts by mass or more and 25 parts by mass or less, a content of the component (D) is 0.05 parts by mass or more and 1.8 parts by mass or less, and a molar ratio [Si-H groups / alkenyl groups] of a total amount of Si-H groups contained in an entirety of the heat- insulating silicone composition to a total amount of alkenyl groups bonded to silicon atoms in the component (A) is 0.5 or more and 1.0 or less.

2. The heat-insulating silicone composition according to claim 1, further comprising a component (E) that is a silicone resin having at least one alkenyl group in the molecule with a number-average molecular weight of 1,000 or more and 10,000 or less.

3. The heat-insulating silicone composition according to claim 1, wherein the component (C) has a true density of 0.2 g / cm3or less and / or the component (C) has an average particle diameter of 150 pm or less.

4. The heat-insulating silicone composition accordingto claim 1, having a viscosity at 25°C of 10,000 mPa-s or less measured in accordance with JIS K 7177-2.

5. The heat-insulating silicone composition according to claim 1, wherein a heat-insulating cured product obtained by curing the heat-insulating silicone composition has a hardness in terms of needle penetration of 10 or more and 40 or less.

6. The heat-insulating silicone composition according to claim 1, wherein a heat-insulating cured product obtained by curing the heat-insulating silicone composition, when heated at 190 to 210°C for 1 to 2.5 hours, has a volume shrinkage by 15% or more and 34% or less after heating as compared to before heating.

7. A method for producing a heat-insulating cured product obtained by curing the heat-insulating silicone composition according to any one of claims 1 to 6, including: a step of potting the heat-insulating silicone composition on a substrate (a step of filling and applying) to form a potted layer; and a step of curing the potted layer at a temperature of 5°C or higher and 100°C or lower, and more preferably 15°C or higher and 50°C or lower.

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