JP7503891B2 - Insulation - Google Patents

Description

The present invention relates to an insulating material for protecting parts of automobiles and the like from heat, and in particular to an insulating material that has high heat resistance capable of withstanding high heat and can be applied to areas around high-temperature heat sources such as floor tunnels around exhaust pipes located under the floor of vehicles such as automobiles, and engine rooms.

In recent years, as the fuel efficiency of automobiles has accelerated with the primary goal of improving fuel efficiency from an environmental perspective, such as curbing global warming and protecting the global environment, there has been active research into making vehicles lighter and more compact. As car bodies become more compact and slimmer, the arrangement of vehicle parts becomes denser and vehicle parts come closer to heat sources, making protection of parts from heat a very important issue. Therefore, in order to ensure space-saving installation of parts and not restrict the freedom of spatial design, there is a demand for the development of insulation materials to protect parts from high heat.

Here, conventionally, urethane foam (urethane foam) has been known as a heat insulating material used in vehicles such as automobiles. However, because urethane foam is weak against high heat and has low flame retardancy, it cannot be applied to high heat areas such as the engine room, around the exhaust pipe, or around the brake carrier, and it has been difficult to use it to protect the parts in those areas.

Foamed silicone (silicone foam, silicone foam) made from silicone as a base material is known as a material with better heat resistance than foamed urethane. The curing reaction types of this silicone include a condensation reaction type that cures by reacting with moisture in the air, an addition reaction type that allows curing in a short time when heated, and a UV reaction type that accelerates curing when exposed to ultraviolet light. Considering the working environment, workability, productivity, etc. when applied to thermal protection of automotive parts, addition reaction type silicone is preferable because it cures in an extremely short time, does not produce by-products due to decomposition of organic peroxides, and does not shrink when cured.

On the other hand, methods for foaming silicone include, for example, a heat foaming type, as shown in Patent Document 1, in which a thermal decomposition type foaming agent is added to a silicone rubber compound, and nitrogen gas is generated by the decomposition of the foaming agent by heating to form foamed silicone, and a self-foaming reaction type, as shown in Patent Document 2, in which silicone is foamed and hardened while generating hydrogen through a dehydrogenation reaction caused by the reaction of a silanol group-containing siloxane with a hydrogen siloxane.

In the method of foaming by adding a foaming agent, for example, azo compounds and nitrile compounds such as azodicarbonamide and azoisobutyronitrile, which have been widely used as foaming agents in the past, are highly poisonous to platinum catalysts and cause silicone to harden poorly, so they are considered unsuitable for foaming addition reaction type silicones that are cured by addition reaction with platinum catalysts. In particular, the method of foaming by heating using these foaming agents requires high heating to decompose the foaming agent, and there are also problems with the toxicity of the foaming agent decomposition products, the odor, and other working environment issues, as well as foam decomposition residues.

In contrast, the method of foaming using hydrogen gas, which is a by-product during curing, allows for foaming and curing without the need for high-temperature heating, and does not cause problems with the toxicity, odor, and residue of foam decomposition products, or the catalytic poisoning of the foaming agent. Therefore, Patent Document 3 discloses a method for producing silicone foam in which a liquid silicone composition that foams through a dehydrogenation reaction is mixed in a certain way and spray-coated.

Japanese Patent Application Laid-Open No. 5-059207 Japanese Patent Application Laid-Open No. 5-031814 Japanese Patent Application Laid-Open No. 8-156003

However, this type of self-foaming silicone foam uses a catalyst to promote the chemical reaction of condensation reaction and progress the curing, while also causing a chemical reaction of dehydrogenation to cause foaming with the hydrogen gas produced by the reaction. Therefore, the foaming and curing properties are easily affected by coating conditions such as temperature, humidity, application area, and application amount. In particular, when the silicone is a liquid composition, the foaming property changes depending on the curing speed, making it difficult to control the bubbles. For this reason, conventional silicone foams are unable to achieve stable high foaming properties, which limits the application area, application amount, application conditions, etc. In other words, because stable high foaming properties cannot be obtained, it is not possible to obtain a practical insulating effect to protect surrounding parts from high heat sources, even if it is applied to areas with severe thermal environments such as engine rooms, around exhaust pipes, and around brake carriers.

Therefore, the present invention was made to solve these problems, and the objective of the present invention is to provide an insulating material that can improve foaming properties.

The heat insulating material of the invention of claim 1 is a mixture of an organopolysiloxane containing an alkenyl group bonded to a silicon atom, an organopolysiloxane containing a hydroxyl group bonded to a silicon atom, an organohydrogenpolysiloxane containing a hydrogen atom bonded to a silicon atom, a platinum group metal catalyst, and an inorganic filler having a median diameter in the range of 10 μm to 150 μm, and is cured by an addition reaction of the alkenyl group of the organopolysiloxane and the hydrosilyl group of the organohydrogenpolysiloxane by the mixture, and is foamed by a dehydration condensation reaction of the hydroxyl group of the organopolysiloxane and the hydrosilyl group of the organohydrogenpolysiloxane.

Here, the organopolysiloxane containing an alkenyl group bonded to the silicon atom is one in which an organic functional group is bonded to the siloxane bond (Si-O bond) in the main chain, and contains an alkenyl group as the organic functional group. This organopolysiloxane contains at least two alkenyl groups bonded to silicon atoms in one molecule to ensure curability.
The organopolysiloxane containing hydroxyl groups (silicon atoms) bonded thereto has an organic functional group bonded to the siloxane bond (Si-O bond) in the main chain, and contains a hydroxyl group (OH group) as the organic functional group. In order to ensure foaming properties, this organopolysiloxane contains at least two hydroxyl groups bonded to silicon atoms, i.e., silanol groups (Si-OH groups), per molecule.
Alternatively, organopolysiloxanes containing both alkenyl groups and hydroxyl groups bonded to silicon atoms may be used.

The above organohydrogenpolysiloxane is a compound in which an organic functional group is bonded to the siloxane bond (Si-O bond) in the main chain, and contains a hydrogen atom bonded to a silicon atom, i.e., a hydrosilyl group (Si-H group). In order to ensure curability and foamability, this organohydrogenpolysiloxane contains at least three hydrogen atoms bonded to silicon atoms in each molecule.

The platinum group metal catalyst may be any metal capable of catalytically acting in the addition reaction and dehydrogenative condensation reaction. Examples of such metal catalysts that can be used include fine particles of platinum adsorbed onto a carrier such as silica, alumina, or silica gel, platinum black, platinic chloride, chloroplatinic acid, complex salts of chloroplatinic acid with olefins or vinylsiloxanes, alcohols of chloroplatinate, palladium, and rhodium.

As the inorganic filler, metal hydroxides such as aluminum hydroxide and magnesium hydroxide, calcium carbonate, diatomaceous earth, iron oxide, titanium oxide, aluminum oxide, aluminum silicate, zinc oxide, calcium silicate, titanium dioxide, ferric oxide, talc, bentonite, etc., having a median diameter in the range of 10 μm or more and 150 μm or less, preferably 20 μm or more and 150 μm or less, can be used.

According to the definition of terms in the text and explanation of JIS Z 8901 "Test Powders and Test Particles", the median diameter is the particle diameter (diameter) when the number (or mass) of particles larger than a certain particle diameter accounts for 50% of the total powder in the particle size distribution of the powder, that is, the particle diameter of 50% oversize, and is usually called the median diameter or 50% particle diameter and expressed as _D50 . By definition, the size of the particle group is expressed by the average particle diameter and the median diameter, but here, it is the value measured by the display of the product description and the laser diffraction/scattering method. And, this "median diameter measured by the laser diffraction/scattering method" refers to the particle diameter (D50) where the cumulative weight part is 50% in the particle size distribution obtained by the laser diffraction/scattering method using a laser diffraction type particle size distribution measuring device. The numerical values of the above particle diameters are approximate rather than strict, and are of course approximate values including errors due to measurement, etc., and do not deny errors of several tens of percent. From the viewpoint of this error, the difference from the average particle size is also small as the distribution approaches normal, so that the average particle size is approximately equal to the median size, and it can also be considered that the average particle size is equal to the median size.

The inorganic filler of the heat insulating material of the invention according to claim 1 is aluminum hydroxide (Al(OH)3) which is an aluminum hydrate.
Alternatively, the inorganic filler of the heat insulating material of the invention of claim 1 is calcium carbonate (CaCO3), preferably ground calcium carbonate.

The heat insulating material of the invention of claim 2 is a silicone foamed and cured product obtained by foaming and curing by mixing a base material containing an organopolysiloxane containing an alkenyl group bonded to a silicon atom, an organopolysiloxane containing a hydroxyl group bonded to a silicon atom, and a platinum group metal catalyst with a curing agent containing an organohydrogenpolysiloxane containing a hydrogen atom bonded to a silicon atom, and the silicone foamed and cured product contains an inorganic filler with a median diameter in the range of 10 μm or more and 150 μm or less.

Here, the organopolysiloxane containing an alkenyl group bonded to the silicon atom is one in which an organic functional group is bonded to the siloxane bond (Si-O bond) in the main chain, and contains an alkenyl group as the organic functional group. This organopolysiloxane contains at least two alkenyl groups bonded to silicon atoms in one molecule to ensure curability.
The organopolysiloxane containing hydroxyl groups (silicon atoms) bonded thereto has an organic functional group bonded to the siloxane bond (Si-O bond) in the main chain, and contains a hydroxyl group (OH group) as the organic functional group. In order to ensure foaming properties, this organopolysiloxane contains at least two hydroxyl groups bonded to silicon atoms, i.e., silanol groups (Si-OH groups), per molecule.
Alternatively, organopolysiloxanes containing both alkenyl groups and hydroxyl groups bonded to silicon atoms may be used.

The above organohydrogenpolysiloxane is a compound in which an organic functional group is bonded to the siloxane bond (Si-O bond) in the main chain, and contains a hydrogen atom bonded to a silicon atom, i.e., a hydrosilyl group (Si-H group). In order to ensure curability and foamability, this organohydrogenpolysiloxane contains at least three hydrogen atoms bonded to silicon atoms in each molecule.

The platinum group metal catalyst may be any metal that has catalytic function for addition reactions and dehydrogenation condensation reactions, and examples of such metals that can be used include fine particles of platinum adsorbed onto a carrier such as silica, alumina, or silica gel, platinum black, platinic chloride, chloroplatinic acid, complex salts of chloroplatinic acid with olefins or vinylsiloxanes, alcohols of chloroplatinate, palladium, and rhodium.

As the inorganic filler, metal hydroxides such as aluminum hydroxide and magnesium hydroxide, calcium carbonate, diatomaceous earth, iron oxide, titanium oxide, aluminum oxide, aluminum silicate, zinc oxide, calcium silicate, titanium dioxide, ferric oxide, talc, bentonite, etc., having a median diameter in the range of 10 μm or more and 150 μm or less, preferably 20 μm or more and 150 μm or less, can be used.

The inorganic filler of the heat insulating material according to the invention is aluminum hydroxide (Al(OH) ₃ ) which is an aluminum hydrate.
Alternatively, the inorganic filler of the heat insulating material according to the invention is calcium carbonate (CaCO ₃ ), preferably ground calcium carbonate.

The heat insulating material of the invention according to claim 3 further contains, in the mixed material before foaming and curing, a reinforcing filler having a median diameter in the range of 10 nm or more and 1,000 nm or less, preferably 10 nm or more and 100 nm or less.
As the reinforcing filler, carbon black, silica, fumed titanium dioxide, etc. can be used, with silica and/or carbon black being preferred.
As the silica, there can be used dry silica such as fumed silica and aerosolized silica, wet silica such as precipitated silica and calcined silica, crystalline silica (quartz powder), and the like.
Examples of the carbon black that can be used include acetylene black, conductive furnace black (CF), super conductive furnace (SCF), extra conductive furnace black (XCF), conductive channel black (CC), furnace black that has been heat-treated at a high temperature of about 1500° C., and channel black.

The insulating material of the invention of claim 4 contains at least one hydroxyl group-containing compound selected from the group consisting of water, alcohol, silanol group-containing organosilane, and silanol group-containing siloxane in the mixed material before foaming and curing, and the compound containing a hydroxyl group is added to enhance the stability of foaming and expansion.

The heat insulating material according to the invention of claim 1 is produced by mixing an organopolysiloxane containing an alkenyl group bonded to a silicon atom, an organopolysiloxane containing a hydroxyl group bonded to a silicon atom, an organohydrogenpolysiloxane containing a hydrogen atom bonded to a silicon atom, a platinum group metal catalyst, and an inorganic filler having a median diameter in the range of 10 μm or more and 150 μm or less, and then foaming and curing the mixture.

The heat insulating material of the invention of claim 1 is cured into a rubber-like state by an addition reaction between the alkenyl groups of the organopolysiloxane and the hydrosilyl groups of the organohydrogenpolysiloxane, and is foamed by a dehydrogenation condensation reaction between the hydroxyl groups of the organopolysiloxane and the hydrosilyl groups of the organohydrogenpolysiloxane, so it has heat insulating properties, and because the base material is silicone, it has heat resistance.

The inventors conducted intensive experimental research into technology that can enhance foaming properties in order to obtain a silicone foam cured product that can exert a practical heat insulating effect for protecting components surrounding high heat sources in locations with severe thermal environments, such as engine compartments, areas around exhaust pipes, and areas around brake calipers. As a result, they discovered that by mixing an inorganic filler with a median diameter of 10 μm or more and 150 μm or less with an organopolysiloxane containing an alkenyl group bonded to a silicon atom, an organopolysiloxane containing a hydroxyl group bonded to a silicon atom, an organohydrogenpolysiloxane (organosilane) containing a hydrogen atom bonded to a silicon atom, and a platinum group metal catalyst, foaming properties are improved compared to those without the inorganic filler, and the present invention was completed based on these findings.

Here, even if an inorganic filler having a median diameter of less than 10 μm is mixed, the silicone hardening is inhibited and the foaming property is inhibited, and the foaming property is not improved, whereas if an inorganic filler having a median diameter of more than 150 μm is mixed, clogging of the application nozzle occurs during application, which reduces the application workability and makes the product less practical.
By mixing an inorganic filler having a median diameter in the range of 10 μm or more and 150 μm or less with an organopolysiloxane containing an alkenyl group bonded to a silicon atom, an organopolysiloxane containing a hydroxy group bonded to a silicon atom, an organohydrogenpolysiloxane (organosilane) containing a hydrogen atom bonded to a silicon atom, and a platinum group metal catalyst, a heat insulating material is obtained with improved foaming properties without impairing curing properties, and this heat insulating material also ensures practical coating workability.

According to the heat insulating material of the invention , the inorganic filler is aluminum hydroxide , so that the flame retardancy is improved, strength is maintained even under more severe thermal environmental conditions, and safety is also high.
According to the heat insulating material of the present invention , the inorganic filler is calcium carbonate, so that the heat resistance is improved and the material is less susceptible to deterioration due to heat. Therefore , the material exhibits high strength even in a high temperature environment and is less susceptible to cracks.

The heat insulating material according to the invention of claim 2 is a silicone foamed and cured product obtained by foaming and curing by mixing a base material containing an organopolysiloxane containing an alkenyl group bonded to a silicon atom, an organopolysiloxane containing a hydroxyl group bonded to a silicon atom, and a platinum group metal catalyst with a curing agent containing an organohydrogenpolysiloxane containing a hydrogen atom bonded to a silicon atom, and the silicone foamed and cured product contains an inorganic filler with a median diameter in the range of 10 μm or more and 150 μm or less.

The insulating material of the invention of claim 2 hardens into a rubber-like state through an addition reaction between the alkenyl groups of the organopolysiloxane and the hydrosilyl groups of the organohydrogenpolysiloxane, and foams through a dehydrogenation condensation reaction between the hydroxyl groups of the organopolysiloxane and the hydrosilyl groups of the organohydrogenpolysiloxane, so has insulating properties, and because the base material is silicone, it has heat resistance.
In particular, it is formed by mixing a base resin with a curing agent, which causes foaming and hardening, and the hardening speed can be easily adjusted.

The inventors conducted intensive experimental research into technology that can enhance foamability in order to obtain a silicone foam cured product that can exert a practical heat insulating effect for protecting components surrounding high heat sources in locations with severe thermal environments such as the engine room, the area around the exhaust pipe, and the area around the brake carrier pan. As a result, they discovered that by mixing an inorganic filler with a median diameter of 10 μm or more and 150 μm or less with an organopolysiloxane containing an alkenyl group bonded to a silicon atom, an organopolysiloxane containing a hydroxyl group bonded to a silicon atom, an organohydrogenpolysiloxane (organosilane) containing a hydrogen atom bonded to a silicon atom, and a platinum group metal catalyst, foamability is improved compared to when no inorganic filler is mixed in, and the present invention was completed based on these findings.

Here, even if an inorganic filler having a median diameter of less than 10 μm is mixed, the silicone hardening is inhibited and the foaming property is inhibited, and the foaming property is not improved, whereas if an inorganic filler having a median diameter of more than 150 μm is mixed, clogging of the application nozzle occurs during application, which reduces the application workability and makes the product less practical.
By mixing an inorganic filler having a median diameter in the range of 10 μm or more and 150 μm or less with an organopolysiloxane containing an alkenyl group bonded to a silicon atom, an organopolysiloxane containing a hydroxy group bonded to a silicon atom, an organohydrogenpolysiloxane (organosilane) containing a hydrogen atom bonded to a silicon atom, and a platinum group metal catalyst, a heat insulating material is obtained with improved foaming properties without impairing curability, and this heat insulating material also ensures practical application workability.

According to the heat insulating material of the present invention , the inorganic filler is aluminum hydroxide , so that the flame retardancy is improved, strength is maintained even under more severe thermal environmental conditions, and safety is also high.
According to the heat insulating material of the present invention , the inorganic filler is calcium carbonate, so that the heat resistance is improved and the material is less susceptible to deterioration due to heat. Therefore , the material exhibits high strength even in a high temperature environment and is less susceptible to cracks.

According to the heat insulating material of the invention of claim 3 , the mixed material before foaming and curing contains a reinforcing filler having a median diameter in the range of 10 nm or more and 1,000 nm or less, preferably 10 nm or more and 100 nm or less. Therefore, in addition to the effects described in claim 1 or 2 , the strength is improved and cracks and the like are less likely to occur even in areas with severe thermal environments, such as an engine room, around an exhaust pipe, or around a brake caliper.

According to the heat insulating material of the invention of claim 4 , the mixed material before foaming and curing contains at least one of water, alcohol, silanol group-containing organosilane, and silanol group-containing siloxane as a hydroxy group-containing compound, so that in addition to the effects of any one of claims 1 to 3 , the stability of the foaming and curing can be improved.

Hereinafter, an embodiment of the present invention will be described.
In the embodiments, the numerical values in the same column in Tables 1 to 3 indicate the magnitude of the quantity, and since there is basically no difference in the materials, duplicated explanations will be omitted here.

First, a heat insulating material according to an embodiment of the present invention will be described.
The heat insulating material of the present embodiment is produced from a silicone compound (silicone composition) obtained by mixing an alkenyl group-containing organopolysiloxane, a hydroxyl group-containing (silanol group-containing) organopolysiloxane, an organohydrogenpolysiloxane containing hydrogen atoms bonded to silicon atoms, a platinum group metal catalyst, and an inorganic filler having a median diameter in the range of 10 μm or more and 150 μm or less.

Here, the organopolysiloxane that is the base polymer is generally a mixture of two or more types of organopolysiloxanes, namely, alkenyl-group-containing organopolysiloxanes having at least two alkenyl groups bonded to silicon atoms in one molecule and organopolysiloxanes having at least two hydroxyl groups bonded to silicon atoms, i.e., at least two silanol groups, in one molecule, but it is also possible to use one type of organopolysiloxane having at least two alkenyl groups bonded to silicon atoms in one molecule and at least two hydroxyl groups bonded to silicon atoms in one molecule.

The alkenyl-containing organopolysiloxane has at least two alkenyl groups bonded to silicon atoms in one molecule, and is, for example, represented by the following composition formula (1).
R ¹ _a SiO _(4-a)/2 ... (1)
Here, R ¹ in the composition formula (1) is an organic functional group bonded to a silicon atom, and is preferably a monovalent hydrocarbon group having 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, and even more preferably 1 to 6 carbon atoms. Specific examples of R ¹ in the composition formula (1) include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, and hexyl groups, alkenyl groups such as vinyl, allyl, butenyl, pentenyl, and hexenyl groups, cycloalkyl groups such as cyclohexyl and cyclohexenyl groups, aryl groups such as phenyl, tolyl, and xylyl groups, aralkyl groups such as benzyl and phenylethyl groups, and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms or the like, such as substituted monovalent hydrocarbon groups such as chloromethyl and 3,3,3-trifluoropropyl groups. The multiple substituents may be different or the same. It is essential that the silicon-bonded substituents contain two or more alkenyl groups in one molecule, and other than the alkenyl groups, methyl or phenyl groups are preferred. The alkenyl groups bonded to silicon atoms are preferably vinyl groups, and the alkenyl groups may be at the molecular chain terminals or side chains, but it is preferred that one is present at each of the terminals. The average degree of polymerization is not particularly limited, but in the above average composition formula (1), a is preferably a positive number of 1.9 to 2.4, more preferably a positive number of 1.95 to 2.05.

The alkenyl-containing organopolysiloxane is preferably linear, consisting of only _{R3SiO1 /2} units and _R2SiO units, but may also contain a partially branched structure of RSiO3 _/2 units and SiO4 _/2 units in addition to these units. An example of a linear alkenyl-containing organopolysiloxane is an organopolysiloxane whose main chain is made up of repeated diorganopolysiloxane units (D units) and whose molecular chain ends are blocked with triorganosiloxy groups (M units). Such an alkenyl-containing organopolysiloxane can be obtained by a known production method, for example, by equilibrating an organocyclopolysiloxane with a compound having _{R3SiO1 /2} units as terminal groups in the presence of an alkali or acid catalyst.
From the viewpoints of mechanical strength, uniform foaming, and workability of the heat insulating material made from the silicone foam cured product, the alkenyl group-containing organopolysiloxane preferably has a viscosity at 25° C. of 10 to 1,000,000 cSt, more preferably 100 to 500,000 cSt, and even more preferably 400 to 200,000 cSt.

By using such an alkenyl-containing organopolysiloxane having at least two alkenyl groups per molecule, the alkenyl groups undergo an addition reaction with the hydrosilyl groups (Si-H groups) of the organohydrogenpolysiloxane to form crosslinks, and the silicone resin hardens into a rubber-like state. The alkenyl-containing organopolysiloxane used can harden as long as it contains two or more alkenyl groups per molecule that become crosslinking points when hardened, and may be a single compound or a mixture of multiple types.

The hydroxyl-containing organopolysiloxane has at least two hydroxyl groups (OH groups) bonded to silicon atoms in one molecule, i.e., at least two silanol groups (Si-OH groups) in one molecule. Typically, an organopolysiloxane that is liquid at room temperature (25° C.) and has, for example, at least two units represented by the following composition formula (2) in one molecule is used.
^R2a (OH) _{bSiO [4-(a+b)]/2 ...} (2)
Here, R ² in the composition formula (2) is an unsubstituted or substituted monovalent hydrocarbon group that does not have an aliphatic unsaturated bond, for example, an alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, or a propyl group, a cycloalkyl group having 6 to 10 carbon atoms such as a cyclohexyl group, an aryl group having 6 to 10 carbon atoms such as a phenyl group or a tolyl group, an aralkyl group having 7 to 12 carbon atoms such as a benzyl group, a 2-phenylethyl group, or a 2-phenylpropyl group, or a group in which at least a part of the hydrogen atoms of these groups is substituted with a halogen atom or the like, for example, a 3,3,3-trifluoropropyl group. Among these, a methyl group, a phenyl group, and a 3,3,3-trifluoropropyl group are preferred, and a methyl group is particularly preferred. In the composition formula (2), a and b are integers of 0 to 2 and b is an integer of 1 to 3, provided that a+b is 1 to 3. The unit having a Si-OH group shown in the composition formula (2) may be present at the end of the molecular chain or may be present in the middle of the molecular chain. The molecular structure may be linear, branched, cyclic, network, etc., but linear ones are usually used. Furthermore, this hydroxyl-containing organopolysiloxane may contain any other organosiloxane unit, so long as it has at least two units of the above composition formula (2) in one molecule. If the viscosity of this hydroxyl-containing organopolysiloxane is too low, the resulting heat insulating material (cured silicone foam) becomes brittle, and if the viscosity is too high, the workability decreases. Therefore, it is preferable that the viscosity of this hydroxyl-containing organopolysiloxane is 50 to 1,000,000 cSt at 25°C. More preferably, it is 100 to 100,000 cSt, and even more preferably, it is 500 to 100,000 cSt.

Representative examples of this hydroxyl-containing organopolysiloxane are those represented by the following formulas (3) and (4).
HO( ^{R3R4SiO )} _LH ... (3)
^R53SiO ( _R3R4SiO ⁾ _M [ ^R3Si ( ^OH )O] _NSi ( ^R5 ) ₃ ... (4)
In formulas (3) and (4), ^R3 and ^R4 may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups containing no aliphatic unsaturated bonds, and R5 is independently an unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bonds, and is the same as the examples of ^R2 in formula (2) above. In formulas (3) and (4), ^L is preferably an integer of 20 to 3,000, more preferably 200 to 2,000, M is preferably an integer of 2 to 20, and N is preferably an integer of 3 to 20.
Among these, a hydroxyl-containing organopolysiloxane that is preferably used is, for example, a dimethylorganopolysiloxane having silanol groups at both ends.

By using such an organopolysiloxane having at least two silanol groups (Si-OH groups) in one molecule, the silanol groups (Si-OH groups) undergo a dehydrogenation reaction with the hydrosilyl groups (Si-H groups) of the organohydrogenpolysiloxane, causing the silicone resin to foam and become a sponge-like cured product. The silanol-containing organopolysiloxane used can foam if it contains two or more silanol groups in one molecule, but it may be a single compound or a mixture of two or more types.

On the other hand, the organohydrogenpolysiloxane containing hydrogen atoms bonded to silicon atoms is one that contains at least two hydrogen atoms bonded to silicon atoms in one molecule, i.e., one that has at least three hydrosilyl groups (Si-H groups) in one molecule. For example, an organopolysiloxane having at least three units represented by the following composition formula (5) in one molecule is used.
^R6bHcSiO _(4-bc )/2 ... _{( 5} )
Here, R ⁶ in the above formula (5) is preferably a monovalent hydrocarbon group (excluding aliphatic unsaturated hydrocarbon groups) having 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms, such as an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, or a hexyl group, or an unsubstituted or substituted monovalent hydrocarbon group such as a cyclohexyl group, a cyclohexenyl group, a phenyl group, or a 3,3,3-trifluoropropyl group. Among these, a methyl group or a phenyl group is preferable. In the above formula (5), b is preferably 0≦b≦2, more preferably 0.7≦b≦2.1, and even more preferably 0.8≦b≦2; c is preferably 0<c≦3, more preferably 0.18≦c≦1.0, and even more preferably 0.2≦c≦1.0; and b+c is preferably 0<b+c<4, more preferably 0.8≦b+c≦3.0, and even more preferably 1.0≦b+c≦2.5. Preferably, d and e are numbers which respectively satisfy 0.002≦e≦1.0, 1.8<d<2.2, and 1.8<d+e≦3.0.

Examples of organohydrogenpolysiloxanes include those represented by the following formulas (6) and (7).
^R7 [( ^R8 ) _2SiO ] _{L (} ^R7HSiO ) _MSi ( ^R8 ) ^2R7 ... (6)
[( ^R9 ) _2SiO ] _L ( ^R9HSiO ) _M ... (7)
Here, in the above formula (5), R ⁷ is independently a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group having no aliphatic unsaturated bonds, and R ⁸ is independently a substituted or unsubstituted monovalent hydrocarbon group having no aliphatic unsaturated bonds. Examples include the same groups as those exemplified as R ² in the above formula (2). In formula (5), L is an integer of 0 to 100, and M is an integer of 2 to 100. In addition, in formula (6), L is an integer of 0 to 20, M is an integer of 2 to 20, and R ⁹ is the same as above.

Examples of organohydrogenpolysiloxanes include copolymers composed of ( _CH3 ) _{2HSiO1 /2} units and SiO4 _/2 units, and copolymers composed of ( _CH3 ) _{2HSiO1 /2} units, SiO4 _/2 units, and ( _C6H5 ) _{SiO3 /2} units. Specific examples of the copolymer that can be used include dimethylsiloxane-methylhydrogensiloxane copolymers capped at both ends with trimethylsiloxy groups, methylhydrogenpolysiloxane capped at both ends with trimethylsiloxy groups, dimethylpolysiloxane capped at both ends with dimethylhydrogensiloxy groups, methylhydrogensiloxane-diphenylsiloxane copolymers capped at both ends with trimethylsiloxy groups, methylhydrogensiloxane-diphenylsiloxane-dimethylsiloxane copolymers capped at both ends with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymers capped at both ends with dimethylhydrogensiloxane, cyclic methylhydrogenpolysiloxane, cyclic methylhydrogensiloxane-dimethylsiloxane copolymers, and cyclic methylhydrogensiloxane-diphenylsiloxane-dimethylsiloxane copolymers.

The molecular structure of this organohydrogenpolysiloxane may be any of linear, cyclic, branched, and three-dimensional mesh structures, but linear and cyclic structures are preferred. In this case, the number of silicon atoms in one molecule, or the degree of polymerization, is preferably 2 to 300, more preferably 4 to 200, and is liquid at room temperature (25°C). Its weight average molecular weight (polystyrene equivalent by GPC) is preferably 500 to 20,000, more preferably 800 to 5,000. The hydrogen atoms bonded to the silicon atoms may be at the molecular chain terminals or side chains, or may be at both. The viscosity of this organohydrogenpolysiloxane is not particularly limited, but the viscosity at 25°C is preferably 1 to 200,000 cSt, more preferably 1 to 30,000 cSt, 1 to 10,000 cSt, and even more preferably 1 to 1,500 cSt.

Such organohydrogenpolysiloxanes can be produced by known production methods, for example, by equilibrating tetramethylcyclotetrasiloxane and/or octamethylcyclotetrasiloxane with a compound having terminal ( _CH3 ) _{3SiO1 /2} units and/or H( _CH3 )2SiO1 _/2 units (e.g., hexamethyldisiloxane and 1,1-dihydro-2,2',3,3'-tetramethyldisiloxane units) in the presence of a catalyst such as sulfuric acid, trifluoromethanesulfonic acid, or methanesulfonic acid at about -10 to +40°C.

This organohydrogenpolysiloxane has at least three hydrogen atoms bonded to silicon atoms (Si-H bonds) in one molecule, and acts as a crosslinking agent for the organopolysiloxane described above. The hydrosilyl groups (Si-H groups) of the organohydrogenpolysiloxane undergo an addition reaction (hydrosilation) with the alkenyl groups of the organopolysiloxane, causing the silicone resin to harden into a rubber-like form. The hydrosilyl groups (Si-H groups) of the organohydrogenpolysiloxane undergo a dehydrogenation reaction with the hydroxyl groups (silanol groups) of the organopolysiloxane, generating hydrogen gas, i.e., foaming, and the silicone resin becomes a sponge-like hardened product.

The amount of organohydrogenpolysiloxane to be used should be sufficient to achieve sufficient curing and foaming, but if the amount is too large, unreacted hydrosilyl groups (Si-H groups) will remain, which may cause the resulting silicone foamed cured product, i.e., the insulating material, to become brittle and may reduce the physical properties of the insulating material, such as distortion and heat resistance. The number of hydrogen atoms bonded to silicon atoms in the organohydrogenpolysiloxane is preferably 1 to 50 times the molar equivalent of the total amount of hydroxyl groups contained in the organopolysiloxane and the hydroxyl group-containing compound described below, and alkenyl groups in the organopolysiloxane, and is more preferably 3 to 40 times the molar equivalent.

The platinum group metal catalyst also acts as a catalyst to promote the addition reaction (hydrosilation) between the alkenyl groups in the organopolysiloxane and the hydrosilyl groups (Si-H groups) in the organohydrogensiloxane, and the dehydrogenation condensation reaction between the hydroxyl groups (silanol groups) in the organopolysiloxane and the hydrosilyl groups (Si-H groups) in the organohydrogensiloxane.

Such platinum group metal catalysts include platinum-based, palladium-based, and rhodium-based catalysts, with platinum-based catalysts being preferred. Examples of platinum-based catalysts include platinum group metals such as platinum _, rhodium, ruthenium _{, and palladium , platinum black ,} platinum chloride (e.g., _{H2PtCl4.nH2O , H2PtCl6.nH2O , NaHPtCl6.nH2O , KHPtCl6.nH2O , Na2PtCl6.nH2O} , K2PtCl4.nH2O, PtCl4.nH2O _{, PtCl2 , Na2HP ...} O (wherein n is an integer of 0 to 6, preferably 0 or 6), platinum group metal compounds such as chloroplatinic acid and alcohol-modified chloroplatinic acid, or complexes thereof, for example, complexes of platinum and olefins, complexes of platinum and vinyl group-containing silanes (vinylsiloxanes) or siloxanes (for example, vinylsiloxane complexes such as divinyltetramethyldisiloxane and 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane), phosphite complexes of platinum, phosphine complexes of platinum, etc. are preferably used. Examples of the complexes include platinum black, chloroplatinic acid, alcohol-modified chloroplatinic acid, and complexes of chloroplatinic acid with olefins, aldehydes, vinylsiloxanes, or acetylene alcohols. Among these, from the viewpoint of providing stability before curing and an appropriate foaming rate, preferred are chloroplatinic acid, platinic chloride, complexes of platinum and olefin compounds, platinum complexes of vinylsiloxanes, complexes of chloroplatinic acid hexahydrate and olefins or divinyldimethylpolysiloxanes, alcohol solutions of chloroplatinic acid hexahydrate, etc. Fine particle platinum metal adsorbed on a carrier such as silica, alumina, or silica gel may also be used.

The amount of platinum group metal catalyst can be appropriately set depending on the curing speed, etc., but if it is too much, the pot life (creaming time) will be too short, workability will be significantly reduced, and heat resistance will also be reduced. On the other hand, if it is too little, the catalytic effect will not be obtained and sufficient foaming and curing will not occur. For this reason, for example, the amount of platinum group metal catalyst is preferably 0.1 to 300 ppm, calculated as the amount of platinum metal, based on the total weight of siloxane in the material to be mixed. More preferably, it is 1 to 500 ppm, and even more preferably, it is 5 to 100 ppm.
By using such platinum group metals as catalysts, it is possible to shorten the curing time and increase the expansion ratio. In addition, it is easy to make the silicone foam cured product flame retardant and highly heat resistant.

In the present embodiment, aluminum hydroxide or calcium carbonate having a median diameter in the range of 10 μm or more and less than 150 μm is used as the inorganic filler having a median diameter in the range of 10 μm or more and less than 150 μm.
The aluminum hydroxide (Al(OH) ₃ ) to be used preferably has a specific surface area measured by the BET method of 1 to 250 m ² /g and a DOP oil absorption of 50 to 100 ml/100 g. If the specific surface area is within this range, curing inhibition is unlikely to occur, and suitable foaming and curing properties can be obtained. Surface-treated aluminum hydroxide may be used, and may be hydrophobized with a surface treatment agent such as organopolysiloxane, osilazanes such as hexamethyldisilazane, or silanes, or the hydrophobization treatment may be carried out when the materials are mixed.

As calcium carbonate, known heavy, precipitated, colloidal, etc., can be used, but heavy calcium carbonate is preferred. In addition, calcium carbonate may be surface-treated with, for example, organochlorosilane, organopolysiloxane, partial hydrolysis condensate of hexaorganosilazane tetraalkoxysilane, etc. In addition, the surface treatment of calcium carbonate may be performed, for example, by mixing diorganopolysiloxane, calcium carbonate, and a predetermined hydrolysis condensate, heating the mixture, and then mixing the remaining components. In particular, with calcium carbonate that has been surface-treated in this way, the dehydrogenation condensation reaction between the alkali component contained in the calcium carbonate powder and the organohydrogenpolysiloxane is reduced, and more stable foaming and curing properties can be ensured. However, when the present invention is implemented, by specifying the particle size of calcium carbonate to a predetermined particle size, the reaction between the alkali component contained in the calcium carbonate powder and the organohydrogenpolysiloxane is suppressed, and stable foaming and curing properties can be ensured, even when calcium carbonate that has not been surface-treated is used.

If the amount of inorganic filler such as aluminum hydroxide or calcium carbonate is too small, the foaming effect is not improved, while if the amount is too large, the coating workability is reduced. Therefore, if the amount is preferably 10 parts by mass or more per 100 parts by mass of the total amount of polysiloxane components, a practical foaming effect is obtained. More preferably, it is 20 parts by mass or more, and even more preferably, it is 40 parts by mass or more. Also, if the amount is preferably 150 parts by mass or less, the specific gravity of the insulating material is small and the light weight is good. More preferably, it is 130 parts by mass or less, and even more preferably, it is 120 parts by mass or less.

Furthermore, by using such inorganic fillers such as aluminum hydroxide or calcium carbonate, whose particle size is in the range of 10 μm or more and 150 μm or less as a median diameter as a cumulative average diameter ( _D50 ) on a volume basis measured by a laser diffraction method, it is possible to improve the foaming properties without causing poor curing of the silicone, and also to ensure ease of application.

In addition, when carrying out the present invention, it is also possible to mix a hydroxyl group-containing compound to ensure stable foaming, if necessary. The hydroxyl group-containing compound is a source of hydroxyl groups for appropriate expansion and foaming, and for example, water, alcohol, silanol group-containing organosilane, silanol group-containing organosiloxane, etc. are used. These may be used alone or in combination of two or more. In this case, for example, a monohydric or polyhydric alcohol having 1 to 12 carbon atoms is used as the alcohol, and particularly preferred ones are methanol, ethanol, propanol, isopropyl alcohol, butanol, lauryl alcohol, octyl alcohol, n-propyl alcohol, etc. In addition, for example, trimethylhydroxysilane, dimethylsilanediol, diphenylsilanediol, dimethylphenylsilanol, trimethylsilanol, etc. can be used as the silanol group-containing organosilane. Furthermore, the silanol group-containing organosiloxane preferably has a viscosity of 1 to 50 cSt, more preferably 1 to 30 cSt at 25° C. As the silanol group-containing organosiloxane, organohydroxysiloxanes and the like can be used.
If the amount of this hydroxy group-containing compound is too large, the size of the expanded cells will become non-uniform and the physical strength will decrease, so the compounded amount is, for example, 0.1 to 5 parts by mass, and preferably 0.2 to 3 parts by mass, per 100 parts by mass of the total organopolysiloxane.

Furthermore, when carrying out the present invention, a reinforcing filler is blended in order to increase strength, if necessary.
Examples of the reinforcing filler include silica, carbon black, etc. These may be used alone or in combination of two or more.

As the silica, dry fine silica such as fumed silica and aerosol silica, wet silica such as precipitated silica (precipitated silica), crystalline silica, etc. can be used, and one type may be used alone or two or more types may be used in combination. In addition, it may be hydrophilic silica or hydrophobic silica (surface hydrophobized with an organic silicon compound, etc.). That is, the hydrophobic silica may be surface-treated (hydrophobized) with halogenated silane, silazane such as hexamethyldisilazane, low molecular weight siloxane, organopolysiloxane, organopolysilazane, chlorosilane, alkoxysilane, etc. In this way, hydrophobic silica whose surface has been hydrophobized in advance may be used, but the hydrophobization of silica may also be performed by mixing untreated silica with a surface treatment agent during mixing.

The silica used preferably has a BET specific surface area of 50 m ² /g to 1000 m ² /g, more preferably 100 m ² /g to 500 m ² /g. If the specific surface area is within this range, sufficient reinforcing properties can be obtained, and a viscosity suitable for coating can be obtained. Such silica is blended, for example, in an amount of 1 to 50 parts by mass, preferably 2 to 4 parts by mass, more preferably 2.5 to 30 parts by mass, per 100 parts by mass of the total amount of the organopolysiloxane components. If the amount is within this range, a sufficiently high strength that is less likely to cause cracks can be imparted without reducing application workability or foaming properties.

Carbon black generally includes furnace black, channel black, acetylene black, thermal black, etc., depending on the manufacturing method, but acetylene black, which has a low content of sulfur and amines that inhibit curing and has developed secondary pores, and ketjen black, which has a large specific surface area and is highly effective in imparting dispersibility and flame retardancy, are preferably used. It is preferable to use carbon black with a BET specific surface area of 10 _m2 /g or more.
Such carbon black is blended, for example, in an amount of 0.03 to 10 parts by mass, preferably 0.05 to 1 part by mass, and more preferably 0.05 to 0.5 parts by mass, per 100 parts by mass of the total amount of organopolysiloxane. Within this range, it is possible to impart sufficiently high strength that is less susceptible to cracking, without deteriorating coating workability or rubber physical properties.
Furthermore, by blending such carbon black, it is possible to impart coloring and electrical conductivity, and further to improve heat resistance and flame retardancy.

Such reinforcing fillers, when the particle diameter is in the range of 10 nm or more and 1000 nm or less as the median diameter as the cumulative average diameter ( _D50 ) based on the volume by the laser diffraction method, can be obtained at low cost, have good dispersibility, and have a sufficient reinforcing effect. In the case of wet silica, the primary particles are very small and actually aggregate to form secondary aggregates, so the particle diameter of these secondary aggregates is usually taken as the median diameter (average particle diameter) of the wet silica.

In addition, when implementing the present invention, it is possible to incorporate additives that control the reaction speed of foaming and curing, for example, curing inhibitors (curing retarders) such as acetylene alcohol, polymethylvinyl cyclic compounds, and hydroperoxy group-containing organic compounds to extend the pot life (time until foaming and curing), curing accelerators that shorten the foaming and curing time, and adhesion improvers such as epoxy group-containing polysiloxane compounds and ester siloxane compounds, as necessary.

Such a silicone compound of an alkenyl group-containing organopolysiloxane, a hydroxyl group (silanol group)-containing organopolysiloxane, a hydrosilyl group-containing organohydrogenpolysiloxane, a platinum group metal catalyst, and aluminum hydroxide or calcium carbonate as an inorganic filler having a median diameter in the range of 10 μm or more and 150 μm or less is prepared by uniformly mixing and stirring the materials using a known mixing and dispersion or mixing stirrer such as a planetary mixer, grain mill, kneader, attritor, roll, or dissolver. The silicone compound (silicone composition) before curing exhibits appropriate fluidity and is applied to the desired coating area by a conventionally known coating method such as airless spray coating, air spray coating, brush coating, roller coating, immersion coating, etc., and after coating, it foams and hardens at room temperature, or foams and hardens by heating at a predetermined temperature, becoming an insulating material consisting of a sponge-like silicone foamed and hardened body having rubber elasticity. The silicone compound before curing can be molded using known molding equipment such as injection molding or casting, and after molding, it foams and hardens at room temperature, or when heated to a specified temperature, forming an insulating material made of a sponge-like silicone foamed and hardened body with rubber elasticity.

That is, the heat insulating material of the present embodiment can be obtained by mixing an alkenyl group-containing organopolysiloxane, a hydroxyl group (silanol group)-containing organopolysiloxane, a hydrosilyl group-containing organohydrogenpolysiloxane, a platinum group metal catalyst, and aluminum hydroxide or calcium carbonate as an inorganic filler having a median diameter in the range of 10 μm or more and 150 μm or less.
When an alkenyl group-containing organopolysiloxane, a hydroxyl group (silanol group)-containing organopolysiloxane, a hydrosilyl group-containing organohydrogenpolysiloxane, a platinum group metal catalyst, and aluminum hydroxide or calcium carbonate as an inorganic filler having a median diameter in the range of 10 μm to 150 μm are mixed, an addition reaction between the alkenyl group of the organopolysiloxane and the hydrosilyl group (Si-H group) of the organohydrogenpolysiloxane occurs to produce a white polymer. The silicone compound is cured by crosslinking due to an addition reaction between alkenyl groups and hydrosilyl groups (Si-H groups) promoted by the platinum group metal catalyst, and the dehydration condensation reaction between the hydroxyl groups (silanol groups) of the organopolysiloxane and the hydrosilyl groups (Si-H groups) of the organohydrogenpolysiloxane is promoted by the platinum group metal catalyst. Hydrogen gas is generated by the dehydrogenation condensation reaction, causing the silicone compound to foam, resulting in a foamed and cured silicone product.

In particular, in this embodiment, from the viewpoint of storage stability and controllability of the curing speed, a two-liquid type is used in which a main agent (main agent) contains at least an alkenyl group-containing organopolysiloxane, a hydroxyl group (silanol group)-containing organopolysiloxane, and a platinum group metal catalyst, and a curing agent contains at least a hydrosilyl group-containing organohydrogenpolysiloxane, and the main agent and the curing agent are mixed to foam and harden. Inorganic fillers with a median diameter in the range of 10 μm or more and 150 μm or less may be mixed when the main agent and the curing agent are mixed, or may be contained in the main agent or the curing agent in advance. The above-mentioned reinforcing fillers and hydroxyl group-containing compounds such as water and alcohol may also be mixed when the main agent and the curing agent are mixed, or may be contained in the main agent or the curing agent in advance. In any case, it is sufficient that the above materials are uniformly mixed and dispersed before foaming and hardening are started. The foaming and hardening process usually proceeds even if the material is left at room temperature after mixing, but to make the foaming and hardening occur in a short time, it may be heated to, for example, 30 to 180°C, preferably 80 to 150°C. Such two-liquid addition reaction types have excellent storage stability and the hardening speed can be easily adjusted by temperature, resulting in good work efficiency.

Here, as the base agent containing at least an alkenyl group-containing organopolysiloxane, a hydroxyl group (silanol group)-containing organopolysiloxane, and a platinum group metal catalyst, and the curing agent containing at least a hydrosilyl group-containing organohydrogenpolysiloxane, commercially available liquid silicones such as TB5277 manufactured by Threebond Co., Ltd., SEF-10 manufactured by Toray Dow Corning Silicone Co., Ltd., and KE-521AB, KE-524AB, X-31-1075AB, X-32-1576AB, and X-32-1703AB manufactured by Shin-Etsu Chemical Co., Ltd. can be used. Such liquids have good penetration into fine details, and can ensure high adhesion, cohesion, and adhesion to painted surfaces even if the painted surface has irregularities or curves. In addition, in such two-liquid addition curing types that use a platinum group metal as a catalyst, the base agent and curing agent are mixed in a ratio of, for example, 1:1, but this is not a limitation when implementing the present invention.

In this manner, when an organopolysiloxane containing alkenyl groups bonded to silicon atoms, an organopolysiloxane containing hydroxyl groups bonded to silicon atoms, an organohydrogenpolysiloxane containing hydrogen atoms bonded to silicon atoms, a platinum group metal catalyst, and an inorganic filler having a median diameter in the range of 10 μm or more and 150 μm or less are mixed, the compound foams and cures at room temperature or under heat to become a heat insulating material made of a silicone foam cured product.
In particular, the heat insulating material of the present embodiment is a silicone base material that is foamed and cured by mixing a main agent that contains at least an organopolysiloxane containing alkenyl groups bonded to silicon atoms, an organopolysiloxane containing hydroxyl groups bonded to silicon atoms, and a platinum group metal catalyst, with a curing agent that contains at least an organohydrogenpolysiloxane that contains hydrogen atoms bonded to silicon atoms, and contains an inorganic filler with a median diameter in the range of 10 μm or more and 150 μm or less.

The insulating material of the present embodiment thus obtained has stable electrical properties, weather resistance, water resistance (waterproofing), cold resistance, and heat resistance because its base material is silicone resin (silicone rubber). In particular, it has higher heat resistance than organic materials such as general organic rubber, and has high heat resistance that does not melt even when placed around a high-temperature heat source such as an automobile exhaust pipe, and can handle temperature ranges that are difficult for organic materials to handle. In addition, it is foamed by a dehydrogenation condensation reaction and has many bubbles and air layers, so it has insulating properties. In particular, it exhibits high insulating properties due to the low thermal conductivity of silicone resin and the insulating structure with many bubbles and voids. In addition, the foaming ratio of the silicone compound is increased by blending an inorganic filler with a median diameter in the range of 10 μm or more and 150 μm or less, and high foaming is possible, so it can exhibit better insulating properties. Since it is foamed, it is also lightweight. Furthermore, the silicone base material has a low crosslink density and contains organic components, so that it has good adhesion, adhesion, and adhesion to, for example, the surface of a car body made of metal such as a steel plate, and even after curing, it has good adhesion, adhesion, and adhesion to the painted surface just by applying it to the painted area. In addition, the two-liquid addition curing type is easy to apply to curved surfaces or areas with complex surface shapes. Furthermore, since the silicone base material has rubber properties, it can ensure elasticity and flexibility that can follow the thermal expansion and contraction of the application area, and cracks are unlikely to occur even when the application area expands due to thermal load. Furthermore, since the silicone cures by addition reaction, cracks and bulges are unlikely to occur in the silicone foam cured body due to curing without shrinkage, and the curing speed can be controlled, making it highly efficient to apply. In addition, since it is a silicone foam cured body, it has high sound and vibration absorption and impact resistance due to the foam and rubber properties, and also has vibration damping and soundproofing effects.

According to the heat insulating material of the present embodiment, the alkenyl group-containing organopolysiloxane, the hydroxyl group (silanol group)-containing organopolysiloxane, the hydrosilyl group-containing organohydrogenpolysiloxane, and the platinum group metal catalyst are mixed with an inorganic filler such as aluminum hydroxide or calcium carbonate having a median diameter of 10 μm or more and 150 μm or less, thereby improving the foaming property of the silicone (siloxane component). That is, the foaming ratio of the silanol is improved compared to the case where an inorganic filler of a predetermined particle size is not mixed. The reason for this is not necessarily clear, but it is thought that the hardening and foaming speed of the compound are balanced by mixing an inorganic filler such as aluminum hydroxide or calcium carbonate having a median diameter of 10 μm or more and 150 μm or less. That is, the hardening and viscosity characteristics of the silicone during foaming caused by the dehydrogenation condensation reaction of the siloxane component are suitable for foaming, and the silicone has hardness and viscosity characteristics that make it difficult for the foaming gas to escape, that is, the silicone thickens, and therefore a large amount of the foamed gas is retained, improving the foaming property of the silicone.It is also considered that the dispersibility of the silicone component (siloxane component) is improved by mixing an inorganic filler such as aluminum hydroxide or calcium carbonate with a median diameter in the range of 10 μm or more and 150 μm or less, and the reactivity of the dehydrogenation condensation is improved.
In particular, when an inorganic filler such as aluminum hydroxide or calcium carbonate with an excessively small median diameter is mixed, curing is inhibited; therefore, by specifying the median diameter of the inorganic filler such as aluminum hydroxide or calcium carbonate to a predetermined particle size, the foamability of the silicone is improved without curing inhibition caused by poisoning of the platinum group metal catalyst or reaction between the inorganic filler and the siloxane component.

That is, if the median particle diameter of the inorganic filler such as aluminum hydroxide or calcium carbonate is too small, the foaming and curing of the silicone is inhibited, the size of the foamed cells becomes non-uniform, and the foamed cells become too large. This is presumably because, as the particle diameter of the inorganic filler becomes smaller, the specific surface area becomes larger, and, for example, the inorganic filler and the impurities contained therein react significantly with the silicone material or the platinum group metal catalyst. On the other hand, if the particle diameter of the inorganic filler is too large, the workability, for example, when the compound is applied with an applicator during construction, the application nozzle becomes clogged, and the application workability decreases. In addition, there is a risk of reducing the adhesion, adhesion, and adhesion to the painted area. If the particle diameter of the inorganic filler is within the range of 10 μm or more and 150 μm or less in median diameter, the foaming property is improved without impairing the curing property, the size of the foamed cells is less varied, the foamed cells are approximately uniform and fine, and the application workability can be ensured. Furthermore, the adhesion, adhesion, and adhesion to the painted area are not reduced. And because the silicone foaming ratio can be increased in this way, the desired foaming properties can be ensured stably even if the coating conditions, such as temperature and humidity environment, application area, and application amount, vary, making it possible to achieve a high level of heat insulation.

In this way, an insulating material made of a silicone foamed cured product with improved foamability is obtained by mixing an inorganic filler with a median diameter in the range of 10 μm or more and 150 μm or less with an alkenyl group-containing organopolysiloxane, a hydroxyl group (silanol group)-containing organopolysiloxane, a hydrosilyl group-containing organohydrogenpolysiloxane, and a platinum group metal catalyst. The improved foamability of the insulating material made of the silicone foamed cured product thus obtained allows for weight reduction and improved insulation. In addition, the improved foamability allows for uniform and fine cells to be formed with little variation in the diameter of the foamed cells, even without injecting gas for foaming control, and the dimensions are also uniform with little variation.

In this way, the insulating material of the present embodiment, which is made by mixing an alkenyl group-containing organopolysiloxane, a hydroxyl group (silanol group)-containing organopolysiloxane, a hydrosilyl group-containing organohydrogenpolysiloxane, and a platinum group metal catalyst with an inorganic filler having a median diameter in the range of 10 μm or more and 150 μm or less, and then foaming and curing it, has improved foamability without impairing curing properties. Therefore, even when applied to high-heat areas such as a floor tunnel around the exhaust pipe under the floor of an automobile, the engine room of a vehicle, and around the brake carrier of a vehicle, i.e., even when painted around a high-temperature heat source, the desired foamability is stably exhibited, and a practical insulating effect can be obtained. In particular, due to the improved elasticity and flexibility of silicone due to its improved rubber properties and foaming properties, even when applied to uneven areas, curved surfaces, or areas with complex surface shapes, or when the painted area expands due to heat, cracks (cracking), destruction, peeling, etc. are unlikely to occur, and high insulation properties can be maintained, making it applicable to a wide range of high-heat areas. In other words, there are no restrictions on painting conditions such as the painting location and application amount, making it suitable for protecting parts around high-temperature heat sources over a wide range and for insulation measures. Furthermore, since silicone has excellent heat resistance, it is possible to exert insulation properties by painting directly on the painted surface of the desired painted area, and since it enables an insulation structure that does not create gaps in the painted surface, it is possible to obtain a high insulation effect, save space in the application space, and do not restrict the design freedom.

In particular, when the inorganic filler is aluminum hydroxide, the high flame retardancy of the aluminum hydroxide improves the flame retardancy of the insulating material made of the silicone foam cured body, allowing it to maintain high strength even under more severe thermal environmental conditions, and also improving safety. This allows the range of application of the insulating material to be broadened, and it is also effective as an insulating measure for, for example, floor tunnels that house exhaust pipes that become extremely hot because high-temperature exhaust gas from the engine flows through them, engine rooms in high-temperature environments, and around brake calipers.

Furthermore, when the inorganic filler is calcium carbonate, preferably heavy calcium carbonate, the heat resistance of the heat insulating material made of the silicone foam cured product is improved and thermal deterioration is less likely to occur, so that the heat insulating material can exhibit high strength even in high-temperature environments. This allows the range of application of the heat insulating material to be expanded, and is effective as a heat insulating measure for, for example, a floor tunnel containing an exhaust pipe that becomes quite hot because high-temperature exhaust gas from the engine flows through it, an engine room in a high-temperature environment, the periphery of a brake caliper, etc.
In particular, when calcium carbonate powder contains an alkaline component as an impurity, the alkaline component reacts with the organohydrogenpolysiloxane, inhibiting the foaming and curing properties. Alternatively, the amount of poisoning of the platinum group metal catalyst increases. In particular, in the case of calcium carbonate that has not been surface-treated, it is difficult to obtain sufficient foaming and curing properties. However, when heavy calcium carbonate having a particle size in the range of 10 μm or more and 150 μm or less is mixed, poor curing does not occur and foaming properties can be improved even when calcium carbonate that has not been surface-treated is used.

Next, examples of the heat insulating material according to the embodiment of the present invention will be specifically described.
The heat insulating material according to the present embodiment is manufactured by mixing an alkenyl group-containing organopolysiloxane, a hydroxyl group (silanol group)-containing organopolysiloxane, a hydrosilyl group-containing organohydrogenpolysiloxane, a platinum group metal catalyst, and an inorganic filler having a median diameter in the range of 10 μm to 150 μm. Specifically, in the present embodiment, the heat insulating material was manufactured by mixing a two-liquid addition reaction type liquid silicone ("KE-521-A/B" manufactured by Shin-Etsu Chemical Co., Ltd.) and aluminum hydroxide or calcium carbonate as an inorganic filler. Here, "KE-521-A" manufactured by Shin-Etsu Chemical Co., Ltd. contains as the main component an alkenyl group-containing organopolysiloxane, a hydroxyl group (silanol group)-containing organopolysiloxane, a platinum group metal catalyst, an alcohol as a hydroxy-containing compound, and crystalline silica (content 5-10% by mass) and carbon black (content 1-5% by mass) as reinforcing fillers. "KE-521-B" manufactured by Shin-Etsu Chemical Co., Ltd. contains as the curing agent a hydrosilyl group-containing organohydrogenpolysiloxane and crystalline silica (content 20-25% by mass) as a reinforcing filler.
The composition of materials used to prepare the thermal insulation materials according to Examples 1 to 8 is shown in the upper part of Tables 1 and 2. For comparison, the thermal insulation materials according to Comparative Examples 1 to 3 were also prepared with the composition shown in Table 3.

Specifically, in Example 1, the main component of the first liquid ("KE-521A" manufactured by Shin-Etsu Chemical Co., Ltd.) containing an alkenyl group-containing organopolysiloxane, a hydroxyl group (silanol group)-containing organopolysiloxane, a platinum group metal catalyst, alcohol, crystalline silica, and carbon black, the hardener of the second liquid ("KE-521B" manufactured by Shin-Etsu Chemical Co., Ltd.) containing a hydrosilyl group-containing organohydrogenpolysiloxane and crystalline silica, and aluminum hydroxide with an average particle size (≒ median diameter) of 23 μm as an inorganic filler ("Fine/Fine Aluminum Hydroxide" manufactured by Nippon Light Metal Co., Ltd.) were mixed in the amounts shown in Table 1. B303') was mixed, and the compound (silicone composition) was applied to a steel plate in a thickness of 10 mm, and after leaving it at room temperature (23°C), it was heated at 150°C for 20 minutes to obtain an insulating material made of a silicone foamed and cured body that had foamed and cured on the steel plate.

In Example 2, aluminum hydroxide (Standard Aluminum Hydroxide B53, manufactured by Nippon Light Metals Co., Ltd.) with an average particle size (≒ median diameter) of 55 μm, which is larger than that in Example 1, was used as the inorganic filler. The other conditions were the same as in Example 1.

In Example 3, aluminum hydroxide ("Standard Aluminum Hydroxide B53" manufactured by Nippon Light Metals Co., Ltd.) with the same average particle size (≒ median diameter) of 55 μm as in Example 2 was used as the inorganic filler, but the amount of filler was less than that in Example 2. Also, the same two-liquid addition reaction type liquid silicone as in Example 2 was used, but the amount of filler was more than that in Example 2.

In Example 4, aluminum hydroxide ("Standard Aluminum Hydroxide B53" manufactured by Nippon Light Metals Co., Ltd.) with the same average particle size (≒ median diameter) of 55 μm as in Examples 2 and 3 was used as the inorganic filler, but the amount of filler was greater than in Example 2. Also, the same two-liquid addition reaction type liquid silicone as in Example 2 was used, but the amount of filler was less than in Example 2.

In Example 5, aluminum hydroxide ("Standard Aluminum Hydroxide B53" manufactured by Nippon Light Metals Co., Ltd.) with an average particle size (≒ median diameter) of 55 μm, the same as in Examples 2 to 4, is used as the inorganic filler, but the amount of filler is even greater than in Example 4. Also, the same two-liquid addition reaction type liquid silicone is used as in Examples 1 to 4, but the amount of filler is even less than in Example 4.

In Example 6, the first liquid base agent ("KE-521A" manufactured by Shin-Etsu Chemical Co., Ltd.) containing alkenyl group-containing organopolysiloxane, hydroxyl group (silanol group)-containing organopolysiloxane, platinum group metal catalyst, alcohol, crystalline silica, and carbon black, the second liquid curing agent ("KE-521B" manufactured by Shin-Etsu Chemical Co., Ltd.) containing hydrosilyl group-containing organohydrogenpolysiloxane and crystalline silica, and calcium carbonate ("Takehara Heavy Carbon" manufactured by Takehara Chemical Co., Ltd.) with an average particle size (≒ median diameter) of 20 μm as an inorganic filler were mixed according to the compounding amounts shown in Table 2, and the compound (silicone composition) was applied to a steel plate to a thickness of 10 mm, left at room temperature (23°C), and then heated at 150°C for 20 minutes to obtain an insulating material made of a silicone foam cured body that was foamed and cured on the steel plate.

In Example 7, calcium carbonate (LW3000, manufactured by Shimizu Kogyo Co., Ltd.) with an average particle size (≒ median diameter) of 28 μm, which is larger than that in Example 6, was used as the inorganic filler. The other conditions were the same as in Example 6.

In Example 8, calcium carbonate (LW3000, manufactured by Shimizu Kogyo Co., Ltd.) with an average particle size (≒ median diameter) of 45 μm, which is larger than that in Example 7, was used as the inorganic filler. The other conditions were the same as in Examples 6 and 7.

On the other hand, in Comparative Example 1, an insulating material made of a silicone foam cured body was produced without mixing aluminum hydroxide or calcium carbonate as an inorganic filler as in Example 1. That is, in Comparative Example 1, only the main component of the first liquid ("KE-521A" manufactured by Shin-Etsu Chemical Co., Ltd.) containing an alkenyl group-containing organopolysiloxane, a hydroxyl group (silanol group)-containing organopolysiloxane, a platinum group metal catalyst, alcohol, crystalline silica, and carbon black, and the hardener of the second liquid ("KE-521B" manufactured by Shin-Etsu Chemical Co., Ltd.) containing a hydrosilyl group-containing organohydrogenpolysiloxane and crystalline silica were mixed, and the compound (silicone composition) was applied to a steel plate in a thickness of 10 mm, left at room temperature (23°C), and then heated at 150°C for 20 minutes to obtain an insulating material made of a silicone foam cured body that had foamed and cured on the steel plate.

In Comparative Example 2, aluminum hydroxide was mixed as an inorganic filler with the above-mentioned base agent and hardener, but the aluminum hydroxide used had an average particle size (≒median diameter) of 7.7 μm, which is smaller than that used in Examples 1 to 5 ("Fine/Micrograin Aluminum Hydroxide B103" manufactured by Nippon Light Metals Co., Ltd.). The other conditions were the same as those in Example 1.

Furthermore, in Comparative Example 3, calcium carbonate was mixed as an inorganic filler with the above-mentioned base agent and hardener, but the calcium carbonate used had an average particle size (≒ median size) of 4.4 μm ("NN500" manufactured by Nitto Funka Kogyo Co., Ltd.), which is smaller than those used in Examples 6 to 8. The other conditions were the same as those in Example 6.

Here, evaluation tests were carried out on the heat insulating materials made of the silicone foam cured products according to Examples 1 to 8 and the heat insulating materials made of the silicone foam cured products according to Comparative Examples 1 to 3 to assess their curability, light weight, and foamability.

Curability was evaluated based on whether the resulting insulation material was sticky when touched with the finger. Insulation materials that did not feel sticky when touched with the finger (no stickiness) were judged to have good curability and were rated as ○, while insulation materials that felt sticky (sticky) were judged to have insufficient curability and were rated as ×.

Regarding lightness, the volume and weight of the obtained insulation material were measured, and the specific gravity was calculated from the measured values. Insulation materials made of silicone foam cured body with a specific gravity of 1.0 or less were judged to be suitable for practical use and rated as ○, those with a specific gravity of more than 1.0 and less than 1.075 were judged to be at a level that can withstand practical use and rated as △, and those with a specific gravity of more than 1.075 were judged to be unsuitable for practical use and rated as ×.

The foaming property was evaluated by comparing with the foaming ratio of the silicone foam cured body of Comparative Example 1. Specifically, the volume and weight of the liquid compound before foaming and curing were measured, and the specific gravity (liquid specific gravity) of the compound before foaming and curing was calculated from the measured values. Then, the foaming ratio A of the heat insulating material was calculated from the liquid specific gravity of the compound before foaming and curing and the specific gravity of the foam cured body after foaming and curing, that is, the specific gravity of the heat insulating material (cured specific gravity). That is, the actual foaming ratio A of the heat insulating material was calculated from the specific gravity before foaming and curing and the specific gravity after foaming and curing. Next, in order to compare with the foaming ratio of the heat insulating material of Comparative Example 1, the foaming ratio B was calculated in terms of the amount of silicone resin corresponding to the two-liquid addition reaction type silicone (100 parts by mass) of Comparative Example 1 from the actual foaming ratio A according to the following formula (1).
Expansion ratio B=expansion ratio A×(100÷amount of two-component addition reaction type silicone (parts by mass)) (1)
The expansion ratio B calculated according to formula (1) is calculated based on the two-liquid addition reaction type silicone resin.
When the expansion ratio B calculated according to the above formula (1) was lower than the expansion ratio A of Comparative Example 1 (in Comparative Example 1, the expansion ratio A=expansion ratio B), it was judged that the expandability was decreased by mixing the inorganic filler and was evaluated as X, and when it was higher than the expansion ratio A of Comparative Example 1, it was judged that the expandability was improved and was evaluated as O.

The results of the evaluation tests on the hardening, light weight, and foaming properties of the insulating materials of Examples 1 to 8 and Comparative Examples 1 to 3 are shown in the lower part of Tables 1, 2, and 3.

As shown in Tables 1 and 2, the heat insulating materials made of the silicone cured foams according to Examples 1 to 5 are prepared by mixing a first liquid base agent ("KE-521A" manufactured by Shin-Etsu Chemical Co., Ltd.) containing an alkenyl group-containing organopolysiloxane, a hydroxyl group (silanol group)-containing organopolysiloxane, a platinum group metal catalyst, alcohol, crystalline silica, and carbon black, a second liquid curing agent ("KE-521B" manufactured by Shin-Etsu Chemical Co., Ltd.) containing a hydrosilyl group-containing organohydrogenpolysiloxane and crystalline silica, and aluminum hydroxide having an average particle size (≒ median diameter) of 23 μm to 55 μm as an inorganic filler, and The insulating materials made of silicone cured foam according to Examples 6 to 8, which are a mixture of a first liquid base agent ("KE-521A" manufactured by Shin-Etsu Chemical Co., Ltd.) containing organopolysiloxane, hydroxyl group (silanol group)-containing organopolysiloxane, platinum group metal catalyst, alcohol, crystalline silica, and carbon black, a second liquid curing agent ("KE-521B" manufactured by Shin-Etsu Chemical Co., Ltd.) containing hydrosilyl group-containing organohydrogenpolysiloxane and crystalline silica, and calcium carbonate with an average particle size (≒ median diameter) of 20 μm to 45 μm as an inorganic filler, were not sticky when touched with the fingers and showed good curing properties.

In addition, in terms of light weight, the insulating materials of Examples 1 to 4 and Examples 6 to 8 exhibited good light weight with a specific gravity of 1.0 or less, and the insulating material of Example 5 exhibited a specific gravity of 1.075 or less, exhibiting light weight sufficient for practical use.
As for the foaming property, the foaming ratio B in terms of silicone resin in the heat insulating materials of Examples 1 to 8, which were prepared by mixing a two-liquid addition reaction type silicone consisting of a first liquid base and a second liquid curing agent with an inorganic filler of a predetermined particle size, was higher than the foaming ratios A and B of the heat insulating material of Comparative Example 1, which was prepared without mixing an inorganic filler with a two-liquid addition reaction type silicone consisting of a first liquid base and a second liquid curing agent. That is, in the heat insulating materials of Examples 1 to 8, the foaming ratio of silicone was increased by mixing an inorganic filler of a predetermined particle size. The heat insulating materials of Examples 1 to 8 had a large number of closed bubbles, and the closed bubble ratio was also higher than that of the heat insulating material of Comparative Example 1.
In Examples 1 to 5, the larger the particle size of the inorganic filler such as aluminum hydroxide or calcium carbonate is within the range of 10 μm or more and 150 μm or less, and the greater the blending amount, the higher the expansion ratio.

In contrast, as shown in Table 3, the insulation material of Comparative Example 1, which was made without mixing inorganic fillers into a two-liquid addition reaction type silicone consisting of a first liquid base agent and a second liquid curing agent, has expansion ratios A and B smaller than the expansion ratio B of the insulation materials of Examples 1 to 8, and is inferior in expandability to the insulation materials of Examples 1 to 8.

In addition, in the insulating material of Comparative Example 2, in which aluminum hydroxide was mixed as an inorganic filler into a two-liquid addition reaction type silicone consisting of a first liquid base agent and a second liquid curing agent, and the average particle size (≒ median diameter) was 7.7 μm, the expansion ratio B was lower than the expansion ratios A and B of Comparative Example 1, and the expansion ratio of the silicone was reduced. In other words, in Comparative Example 2, the mixing of aluminum hydroxide with an average particle size (≒ median diameter) of 7.7 μm reduced the expansion ratio of the silicone.

Furthermore, in the insulation material of Comparative Example 3, in which calcium carbonate was mixed as an inorganic filler into a two-liquid addition reaction type silicone consisting of a first liquid base agent and a second liquid curing agent, and the average particle size (≒ median diameter) was 4.4 μm, the curing was impaired, and the expansion ratio B was also lower than the expansion ratios A and B of Comparative Example 1, resulting in poor foaming and curing properties. In other words, in Comparative Example 3, the mixing of calcium carbonate with an average particle size (≒ median diameter) of 4.4 μm inhibited the curing of the silicone, lowered the expansion ratio of the silicone, and made it impossible to function as an insulation material.

Thus, in the insulating materials of Examples 1 to 8, the expansion ratio B is all higher than the expansion ratios A and B of Comparative Example 1, which shows that the silicone expansion ratio was increased by mixing aluminum hydroxide or calcium carbonate having an average particle size (≒ median diameter) of 10 μm or more with an organopolysiloxane containing an alkenyl group bonded to a silicon atom, an organopolysiloxane containing a hydroxyl group bonded to a silicon atom, an organohydrogenpolysiloxane having a hydrogen atom bonded to a silicon atom, and a platinum group metal catalyst. In particular, a comparison of Examples 1 to 8 with Comparative Examples 2 to 3 shows that aluminum hydroxide or calcium carbonate as inorganic fillers mixed with organopolysiloxanes containing alkenyl groups bonded to silicon atoms, organopolysiloxanes containing hydroxyl groups bonded to silicon atoms, organohydrogenpolysiloxanes having hydrogen atoms bonded to silicon atoms, and platinum group metal catalysts can improve the foamability of silicone without impairing curability, so long as their average particle size (≒median diameter) is 10 μm or more. That is, in the heat insulating materials of Examples 1 to 8, the foamability is improved without impeding the curing of silicone.
Therefore, according to the heat insulating materials of Examples 1 to 8, the foaming property of the silicone is improved, and thus the heat insulating property can be improved.

Here, according to the experimental research of the present inventors, if the median diameter of inorganic fillers such as aluminum hydroxide or calcium carbonate mixed with organopolysiloxanes containing alkenyl groups bonded to silicon atoms, organopolysiloxanes containing hydroxyl groups bonded to silicon atoms, organohydrogenpolysiloxanes having hydrogen atoms bonded to silicon atoms, and platinum group metal catalysts is less than 10 μm, the curing of silicone is easily inhibited and the expansion ratio of silicone cannot be effectively increased, and it has been confirmed that if the median diameter of inorganic fillers such as aluminum hydroxide or calcium carbonate mixed with organopolysiloxanes containing alkenyl groups bonded to silicon atoms, organopolysiloxanes containing hydroxyl groups bonded to silicon atoms, organohydrogenpolysiloxanes having hydrogen atoms bonded to silicon atoms, and platinum group metal catalysts is 10 μm or more, a practical effect of improving the expansion ratio of silicone can be obtained.

On the other hand, it has been confirmed that the curing of the silicone is easily inhibited, making it impossible to effectively increase the foaming ratio of the silicone, and that when the median diameter of inorganic fillers such as aluminum hydroxide or calcium carbonate mixed with organopolysiloxanes containing alkenyl groups bonded to silicon atoms, organopolysiloxanes containing hydroxyl groups bonded to silicon atoms, organohydrogenpolysiloxanes having hydrogen atoms bonded to silicon atoms, and platinum group metal catalysts exceeds 150 μm, clogging of the applicator is likely to occur during application, and applicability is reduced.

Therefore, by making the median diameter of the inorganic filler such as aluminum hydroxide or calcium carbonate to be mixed with the organopolysiloxane containing an alkenyl group bonded to a silicon atom, the organopolysiloxane containing a hydroxyl group bonded to a silicon atom, the organohydrogenpolysiloxane having a hydrogen atom bonded to a silicon atom, and the platinum group metal catalyst 10 μm or more and 150 μm or less, it is possible to effectively increase the foaming ratio without impairing the curing property of the silicone while ensuring the coatability. More preferably, the median diameter of the inorganic filler is 15 μm or more and 145 μm or less, and even more preferably, 20 μm or more and 140 μm or less.

By mixing an inorganic filler such as aluminum hydroxide or calcium carbonate having a median diameter of 10 μm or more and 150 μm or less with an organopolysiloxane containing an alkenyl group bonded to a silicon atom, an organopolysiloxane containing a hydroxyl group bonded to a silicon atom, an organohydrogenpolysiloxane having a hydrogen atom bonded to a silicon atom, and a platinum group metal catalyst, the silicone can be foamed at a high rate, and the desired foaming properties can be obtained stably, thereby improving the insulating effect of the silicone. Therefore, for example, even when applied to a part in a severe thermal environment such as an automobile exhaust pipe, a practical insulating effect that protects parts from high heat can be obtained.

In particular, the insulating materials of Examples 1 to 8 are blended with silica and carbon black as reinforcing fillers, which gives them high strength, and the silicone resin base material gives them heat resistance, so they exhibit strength that is less likely to crack even when applied to high-heat areas. Furthermore, when aluminum hydroxide of a specified particle size is mixed in as the inorganic filler, high flame retardancy is imparted, strength is maintained even under more severe thermal conditions, and safety is also high. Furthermore, when calcium carbonate of a specified particle size is mixed in as the inorganic filler, heat resistance is improved and the material is less likely to deteriorate due to heat, so that high strength is exhibited even in higher temperature environments and cracks are less likely to occur.

According to the experimental research of the present inventors, the blending amount of inorganic filler such as aluminum hydroxide or calcium carbonate of a predetermined particle size is preferably 1 part by mass or more per 100 parts by mass of the total amount of the first liquid base agent containing an alkenyl group-containing organopolysiloxane, a hydroxyl group (silanol group)-containing organopolysiloxane, a platinum group metal catalyst, alcohol, crystalline silica, and carbon black ("KE-521A" manufactured by Shin-Etsu Chemical Co., Ltd.), and the second liquid curing agent containing a hydrosilyl group-containing organohydrogenpolysiloxane and crystalline silica ("KE-521B" manufactured by Shin-Etsu Chemical Co., Ltd.), to obtain a practical improvement effect on foamability. More preferably, it is 5 parts by mass or more, and even more preferably, it is 40 parts by mass or more. Also, if it is preferably 125 parts by mass or less, the specific gravity of the obtained insulating material is small and the light weight is good. More preferably, it is 120 parts by mass or less, and even more preferably, it is 100 parts by mass or less. The amount of inorganic filler such as aluminum hydroxide or calcium carbonate of a specified particle size is, for example, within the range of 70 to 190 parts by mass, preferably 75 to 160 parts by mass, and more preferably 80 to 150 parts by mass, per 100 parts by mass of the total amount of the alkenyl group-containing organopolysiloxane, the hydroxyl group (silanol group)-containing organopolysiloxane, and the hydrosilyl group-containing organohydrogenpolysiloxane.

As described above, the heat insulating material according to the above embodiment is formed by mixing and foaming and curing an organopolysiloxane containing an alkenyl group bonded to a silicon atom, an organopolysiloxane containing a hydroxyl group bonded to a silicon atom, an organohydrogenpolysiloxane containing a hydrogen atom bonded to a silicon atom, a platinum group metal catalyst, and an inorganic filler having a median diameter in the range of 10 μm or more and 150 μm or less, more preferably 15 μm or more and 145 μm or less, and even more preferably 20 μm or more and 140 μm or less.

In addition, since the above embodiment is a method of foaming and curing silicone by mixing the first liquid base agent and the second liquid curing agent, it can also be considered as an invention of a heat insulating material containing an inorganic filler with a median diameter in the range of 10 μm or more and 150 μm or less, more preferably 15 μm or more and 145 μm or less, and even more preferably 20 μm or more and 140 μm or less in a silicone foam cured body obtained by foaming and curing by mixing a base agent containing an organopolysiloxane containing an alkenyl group bonded to a silicon atom, an organopolysiloxane containing a hydroxyl group bonded to a silicon atom, and a platinum group metal catalyst, and a curing agent containing an organohydrogenpolysiloxane containing a hydrogen atom bonded to a silicon atom.

According to the heat insulating material of this embodiment, the base material for forming it contains an organopolysiloxane containing at least two alkenyl groups bonded to silicon atoms per molecule, and the curing agent mixed with the base material contains an organohydrogenpolysiloxane containing at least three hydrogen atoms bonded to silicon atoms per molecule, i.e., silanol groups (Si-H groups). Therefore, the addition reaction between the alkenyl groups of the organopolysiloxane and the hydrosilyl groups (Si-H groups) of the organohydrogenpolysiloxane is promoted by the platinum group metal catalyst contained in the base material, and the material hardens through crosslinking caused by the addition reaction of the alkenyl groups and the silanol groups (Si-H groups). In addition, the base resin contains an organopolysiloxane containing at least two hydroxyl groups (OH groups) bonded to silicon atoms, i.e., hydrosilyl groups (SH groups), per molecule, and the curing agent contains an organohydrogenpolysiloxane containing at least three hydrogen atoms bonded to silicon atoms, i.e., silanol groups (Si-H groups), per molecule. Therefore, the dehydration condensation reaction of the hydroxyl groups (OH groups) of the organopolysiloxane and the silanol groups (Si-H groups) of the organohydrogenpolysiloxane is promoted by the platinum group metal catalyst contained in the base resin, and foaming occurs due to the generation of hydrogen gas by the dehydrogenation condensation reaction.
Therefore, the heat insulating material of the present embodiment is obtained by mixing a base material containing an organopolysiloxane containing an alkenyl group bonded to a silicon atom, an organopolysiloxane containing a hydroxyl group bonded to a silicon atom, and a platinum group metal catalyst with a curing agent containing an organohydrogenpolysiloxane containing a hydrogen atom bonded to a silicon atom, and the compound is cured by an addition reaction and foamed by a dehydrogenation condensation reaction.

In the heat insulating material of this embodiment, the silicone hardens into a rubber-like (elastomer-like) state through an addition reaction between the alkenyl groups of the organopolysiloxane and the hydrosilyl groups (Si-H groups) of the organohydrogenpolysiloxane, and foams through a dehydrogenation condensation reaction between the hydroxyl groups (silanol groups) of the organopolysiloxane and the hydrosilyl groups (Si-H groups) of the organohydrogenpolysiloxane. Therefore, the heat insulating material has heat resistance because the base material is silicone.
In particular, it is a two-liquid addition reaction type silicone consisting of a first liquid base agent and a second liquid curing agent that is foamed and cured, making it easy to control the curing speed.

And, according to the heat insulating material of this embodiment, an organopolysiloxane containing an alkenyl group bonded to a silicon atom, an organopolysiloxane containing a hydroxyl group bonded to a silicon atom, an organohydrogenpolysiloxane (organosilane) containing a hydrogen atom bonded to a silicon atom, and a platinum group metal catalyst are mixed with an inorganic filler such as aluminum hydroxide or calcium carbonate having a median diameter in the range of 10 μm or more and 150 μm or less, and foamed and cured, thereby improving the foaming property of the silicone. Therefore, the desired foaming property can be obtained stably, and the heat insulating property can be improved. Therefore, even when placed in a severe heat environment such as an engine room, around an exhaust pipe, or around a brake carrier, a practical heat insulating effect can be obtained, and the temperature rise of surrounding parts of a high heat source can be effectively prevented, and the protection effect of the parts from high heat can be high. In addition, the improved foaming property can also improve the light weight.

In particular, in the insulating material according to this embodiment, the particle size of the inorganic filler, such as aluminum hydroxide or calcium carbonate, contained therein is set within a predetermined range, which prevents poor curing and improves the expansion ratio of the silicone, making it possible to achieve high expansion without injecting gas for expansion control, i.e., without the need for a gas injection device. Therefore, an insulating material with good physical properties such as expandability and insulation can be obtained through a simple process.

Here, when the inorganic filler is aluminum hydroxide, the flame retardancy is improved, strength is maintained even under more severe thermal environmental conditions, and safety is also high. In addition, by using aluminum hydroxide of a specified particle size, it is difficult to react with organosiloxanes and platinum group metal catalysts, and the foaming and curing stability is high.

Furthermore, when the inorganic filler is calcium carbonate, the heat resistance is improved and the product is less susceptible to heat deterioration, so it can demonstrate high strength even in high-temperature environments and is less susceptible to cracking. In addition, by using calcium carbonate of a specified particle size, calcium carbonate and by-products contained in the product are less likely to react with organosiloxanes and platinum group metal catalysts, and the foaming and hardening is highly stable.

In addition, if a reinforcing filler such as silica or carbon black is further mixed into the mixed material (compound) before foaming and hardening, the strength can be improved at low cost, and the strength is strong enough to prevent cracks even when applied to areas with severe thermal environments such as the engine room, around the exhaust pipe, and around the brake carrier.

In addition, if the mixed material (compound) before foaming and curing further contains one or more hydroxy-containing compounds selected from the group consisting of water, alcohol, silanol-containing organosilane, and silanol-containing siloxane, the stability of the foaming can be further improved.

The above embodiment can also be considered as an invention of a method for producing a heat insulating material by mixing an organopolysiloxane containing an alkenyl group bonded to a silicon atom, an organopolysiloxane containing a hydroxyl group bonded to a silicon atom, an organohydrogenpolysiloxane containing a hydrogen atom bonded to a silicon atom, a platinum group metal catalyst, and an inorganic filler having a median diameter in the range of 10 μm or more and 150 μm or less.

In carrying out the present invention, the other configurations, components, materials, blending, shape, size, manufacturing method, etc. of the heat insulating material are not limited to the present embodiment. In addition, the numerical values given in the embodiment of the present invention do not all indicate critical values, and some numerical values indicate appropriate values suitable for carrying out the invention, so even if the numerical values are slightly changed, the implementation is not denied.
Furthermore, as described above, the insulating material can be applied as an insulating material to protect components around high-temperature heat sources in a vehicle, that is, to areas around high heat sources such as the engine room, the area around the exhaust pipe, and the area around the brake carrier pan, to reduce heat movement and heat transfer. However, the material is not limited to vehicle components and can also be used for parts for ships, aircraft, and spacecraft, as well as home appliances, electrical equipment, office equipment parts, AV equipment parts, precision equipment, construction equipment, and the like. Furthermore, the material can also be used, for example, as a component part of industrial furnaces and the like, where high heat resistance is required.

Claims (4)

A heat insulating material characterized by being produced by mixing and foaming and curing an organopolysiloxane containing an alkenyl group bonded to a silicon atom, an organopolysiloxane containing a hydroxyl group bonded to a silicon atom, an organohydrogenpolysiloxane containing a hydrogen atom bonded to a silicon atom, a platinum group metal catalyst, and aluminum hydroxide or calcium carbonate as an inorganic filler having a median diameter in the range of 10 μm or more and 150 μm or less. A heat insulating material comprising aluminum hydroxide or calcium carbonate as an inorganic filler having a median diameter in the range of 10 μm or more and 150 μm or less, in a silicone foamed and cured product obtained by foaming and curing by mixing a base material comprising an organopolysiloxane containing an alkenyl group bonded to a silicon atom, an organopolysiloxane containing a hydroxyl group bonded to a silicon atom, and a platinum group metal catalyst, with a curing agent comprising an organohydrogenpolysiloxane containing a hydrogen atom bonded to a silicon atom . 3. The heat insulating material according to claim 1, wherein the mixed material before foaming and curing further contains a reinforcing filler having a median diameter in the range of 10 nm or more and 1000 nm or less. The heat insulating material according to any one of claims 1 to 3, characterized in that the mixed material before foaming and curing contains at least one of water, alcohol, silanol group-containing organosilane, and silanol group-containing siloxane as a hydroxyl group-containing compound.