Method for forming heat insulating coating

Abstract

To provide hollow particles capable of further exhibiting heat insulating properties of a heat insulating coating film formed from a heat insulating coating material containing the hollow particles.SOLUTION: Since hollow particles 2 of the present invention have an average particle diameter of 10 to 200 nm, when the hollow particles are contained in a heat insulating coating material, a heat insulating coating film 1 in which the heat insulating coating material is transparent can be formed. Although the hollow particles 2 are hydrophilic because they are formed from siloxane bonds, they can be made compatible with an organic solvent-based heat insulating coating material because they are modified with a surface modifier. The hollow particles 2 having a hydrophilic siloxane bond as a base material have remarkable hydrophilicity when the heat insulating coating film is formed, and are excluded so that the concentration increases from the inside of the heat insulating coating film toward the surface layer, and an aggregate 3 of the hollow particles 2 in the order of μm is formed on the surface layer of the heat insulating coating film 1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to hollow particles, a thermal insulation paint containing hollow particles, and a thermal insulation coating film containing hollow particles. [Background technology]

[0002] As hollow particles and a heat insulating paint containing hollow particles, silica hollow particles and a heat insulating paint containing hollow silica particles are described in Patent Document 1. This heat insulating paint aims to improve heat insulating properties by uniformly dispersing the silica hollow particles in the paint. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-070458 A Summary of the Invention [Problem to be solved by the invention]

[0004] Heat insulation is effective by suppressing the transfer of heat. However, in a coating film formed from a conventional heat insulating paint containing hollow silica particles, although the hollow silica particles are uniformly dispersed in the coating film, most of the surface layer of the coating film is covered with a synthetic resin, and there is a problem that the suppression of the transfer of heat is insufficient, and the heat insulation may not be fully exhibited.

[0005] The present invention has been made in consideration of the above points, and has an object to provide hollow particles that can improve the heat insulating properties of a heat insulating coating film formed from a heat insulating paint containing hollow particles. [Means for solving the problem]

[0006] The hollow particles of the present invention are hollow particles having a siloxane bond as a main skeleton, The average particle size is 10 to 200 nm, and the particle is characterized by being modified with a surface modifier.

[0007] According to the hollow particles of the present invention, since the average particle diameter is 10 to 200 nm, when the hollow particles are contained in the heat insulating paint, the heat insulating paint can form a transparent heat insulating coating film. Although the hollow particles are hydrophilic because they are formed from siloxane bonds, they can be compatible with organic solvent-based heat insulating paint because they are modified by a surface modifier. When the heat insulating paint is formed into a film, the hollow particles having hydrophilic siloxane bonds as a base become significantly hydrophilic, and are rejected so that the concentration becomes higher from the inside of the heat insulating paint toward the surface layer, forming aggregates of hollow particles on the order of μm on the surface layer of the coating film. Therefore, the hollow particles can be used in the heat insulating paint to exhibit the heat insulating properties of the coating film.

[0008] Here, in the hollow particles, the surface modifier may be a compound having an organic compatible group and an inorganic bonding group.

[0009] According to this, in the hollow particles, the inorganic bonding group can be copolymerized with the main skeleton of the siloxane bond, and the organic compatible group can make the hollow particles appropriately compatible with the heat insulating coating material.

[0010] The hollow particles may contain 5 to 50 g of the surface modifier per 1 mol of Si in the siloxane bond.

[0011] According to this, when the insulating paint is formed, the hollow particles exhibit a balanced hydrophilicity, and are repelled so that their concentration increases from the inside of the insulating paint towards the surface. As the volatile components evaporate, hollow particle aggregates on the order of μm can be formed on the surface of the coating.

[0012] The heat insulating coating of the present invention may contain the above hollow particles in an amount of 5 to 30% by mass calculated as the non-volatile content.

[0013] According to the heat insulating coating of the present invention, an aggregate of hollow particles can be formed on the surface layer of the coating film.

[0014] The heat insulating coating of the present invention may comprise an aggregate of the above hollow particles on the surface layer of the coating.

[0015] The heat insulating coating of the present invention can reduce the hot / cold contact sensation caused by contact with human skin.

[0016] In the above heat insulating coating, the agglomerates may form an uneven shape on the order of μm on the surface layer of the coating.

[0017] This can further reduce the warm / cold contact sensation caused by contact with human skin. Effect of the Invention

[0018] According to the hollow particles of the present invention, when the hollow particles are contained in an organic solvent-based heat-insulating coating material, hollow particle aggregates are formed on the surface layer of the coating film formed from the heat-insulating coating material, thereby enabling the coating film to exhibit its heat insulating properties. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a cross-sectional image of a thermal barrier coating containing hollow particles according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a SEM (scanning electron microscope) photograph of a cross section of a thermal barrier coating of an example. [Diagram 3] FIG. 2 is a laser microscope photograph of the surface of a thermal barrier coating of an example. [Figure 4] FIG. 2 is a laser microscope photograph of the surface of a thermal barrier coating film of a comparative example. [Diagram 5] FIG. 1 is a diagram showing a laser microscope photograph of the surface of a coating film made of a metallic paint. [Figure 6] FIG. 2 is a view showing an SEM photograph of an aggregate of hollow particles in an example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the hollow particles 2 according to the present invention will be described. The hollow particles 2 of the embodiment have an average particle diameter of 10 to 200 nm and are modified with a surface modifier. The hollow particles 2 of the embodiment will be described in detail later, but are ultimately formed by coating calcium carbonate, which is dissolved to form hollow spaces, with alkoxysilane and a surface modifier to form a shell body of siloxane bonds that serves as the main skeleton of the hollow particles 2. The calcium carbonate with the shell body of siloxane bonds formed thereon is subjected to an acid treatment to dissolve only the calcium carbonate, thereby forming hollow particles 2 having a main skeleton of siloxane bonds modified with a surface modifier.

[0021] The calcium carbonate of the embodiment is calcium carbonate (calcite) having a rhombohedral structure with a particle size adjusted to a nano-order size. The average particle size of the calcium carbonate used in the embodiment (average value of 50 particle sizes measured from SEM (scanning electron microscope) photographs) is preferably 10 to 100 nm. This is because, when hollow particles 2 formed by coating calcium carbonate are mixed with a heat insulating paint, the heat insulating property and transparency of the heat insulating coating film 1 formed from the heat insulating paint can be improved. If the average particle size of calcium carbonate is less than 10 nm, the shell thickness of the hollow particles 2 becomes relatively thick, and the heat insulating performance may be deteriorated. On the other hand, if it exceeds 100 nm, the transparency of the heat insulating coating film 1 may be deteriorated. More preferably, the average particle size of calcium carbonate is 50 to 90 nm.

[0022] An alkoxysilane is a silane compound having an alkoxy group, which is hydrolyzed to produce silanol, and the silanol is condensed to produce a siloxane bond that forms the main skeleton of the hollow particle 2. In the hollow particle 2 of the embodiment, the alkoxysilane can be used without any particular limitation, and examples thereof include tetramethoxysilane (Si(OCH3)4), methyltrimethoxysilane (SiCH3(OCH3)3), dimethyldimethoxysilane (Si(CH3)2(OCH3)2), trimethylmethoxysilane (Si(CH3)3OCH3), ethyltrimethoxysilane (SiC2H5(OCH3)3), diethyldimethoxysilane (Si(C2H5)2(OCH3)2), triethylmethoxysilane (Si(C2H5)3OCH3), propyltrimethoxysilane (SiC3H7( OCH3)3), tetraethoxysilane (Si(OC2H5)4), methyltriethoxysilane (SiCH3(OC2H5)3), dimethyldiethoxysilane (Si(CH3)2(OC2H5)2), trimethylethoxysilane (Si(CH3)3OC2H5), ethyltriethoxysilane (SiC2H5(OC2H5)3), diethyldiethoxysilane (Si(C2H5)2(OC2H5)2), triethylethoxysilane (Si(C2H5)3OC2H5), propyltriethoxysilane (SiC3H7(OC2H5)3), or mixtures thereof.

[0023] The surface modifier is a compound having an organic compatible group and an inorganic bonding group, and the inorganic bonding group of the surface modifier is bonded to the hydrophilic siloxane bond main skeleton, thereby modifying the surface of the siloxane bond main skeleton with the organic compatible group. The siloxane bond hollow particles 2 whose surfaces are modified with organic compatible groups can be made compatible with the heat insulating coating by the organic compatible group. As the surface modifier having an organic compatible group and an inorganic bonding group, a silane coupling agent, a silicone surfactant, a modified silicone, etc. can be used.

[0024] In the silane coupling agent, the reactive functional group of the silane coupling agent becomes an organic compatible group, and the alkoxy group becomes an inorganic bonding group. The alkoxy group of the inorganic bonding group is hydrolyzed to generate silanol, and the silanol is condensed with the alkoxysilane that becomes the main skeleton of the hollow particle 2, so that the surface modifier is bonded to the siloxane bond that forms the hollow particle 2, and the reactive functional group of the organic compatible group modifies the surface of the hollow particle 2. The silane coupling agent can be one that contains an ethoxy group or a methoxy group as the alkoxy group of the inorganic bonding group, and can be one that contains a vinyl group, an epoxy group, a styryl group, a methacryl group, an acrylic group, an amino group, an isocyanate group, an isocyanurate group, a ureido group, a mercapto group, or a functional group consisting of these and an alkylene group as the reactive functional group of the organic compatible group.Specific examples of the silane coupling agent include vinyltrimethoxysilane and vinyltriethoxysilane containing a vinyl group, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane containing an epoxy group, p-styryltrimethoxysilane containing a styryl group, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane containing a methacryl group, 3-acryloxypropyltrimethoxysilane containing an acrylic group, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane containing an amino group. Examples of the silanes that can be used include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane containing an isocyanate group, tris-(trimethoxysilylpropyl)isocyanurate containing an isocyanurate group, 3-ureidopropyltrialkoxysilane containing a ureido group, 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane containing a mercapto group, and mixtures thereof.

[0025] Silicone surfactants are compounds composed of an organic group (organic compatible group) and a silicone chain (inorganic bonding group) that can condense with alkoxysilanes. Depending on the structure of the organic group, alkyl-modified silicone surfactants, polyether-modified silicone surfactants, polyether-alkyl co-modified silicone surfactants, etc. can be used.

[0026] Modified silicones are compounds composed of an organic modified group (organic compatible group) and a silicone chain (inorganic bonding group) that can condense with alkoxysilanes. Depending on the structure of the organic modified group, amino modified silicones, epoxy modified silicones, carbinol modified silicones, mercapto modified silicones, etc. can be used.

[0027] The surface modifier is preferably contained in an amount of 5 to 50 g per 1 mol of siloxane-bonded Si made of alkoxysilane. This is because the hollow particles 2 can be made compatible with the heat insulating paint, and the hollow particles 2 are expelled so that the concentration increases from the inside of the heat insulating paint toward the surface layer, and the hollow particles 2 can form aggregates 3 of the order of μm on the surface layer of the coating film when the heat insulating paint is formed. If the content of the surface modifier is less than 5 g per mol of siloxane-bonded Si, the hollow particles 2 are difficult to be dissolved in the heat insulating paint, and are expelled to the surface layer of the heat insulating paint when the heat insulating paint is formed, and irregular aggregates 3 of the hollow particles 2 are formed on the surface layer of the coating film, which makes the surface layer of the coating film rough and may cause the coating film to lose transparency. On the other hand, if the amount exceeds 50 g, the hollow particles 2 have most of their surfaces modified with organic compatible groups, are compatible with the heat insulating coating material, and are not excluded from the surface of the coating film, so that there is a risk that the heat insulating property cannot be improved. More preferably, the content of the surface modifier per mol of Si in the siloxane bond is 10 to 30 g, and even more preferably, it is 15 to 25 g.

[0028] The hollow particles 2 are formed by adding calcium carbonate, alkoxysilane, and a surface modifier to a mixture of water and alcohol that has been made alkaline with ammonia water, and mixing the mixture, so that the calcium carbonate is coated with the alkoxysilane and the surface modifier, forming a siloxane bond shell that serves as the main skeleton of the hollow particles 2. After the formation of the siloxane bond shell, the calcium carbonate is dissolved by acid treatment, and hollow particles 2 consisting of a siloxane bond shell are formed.

[0029] The specific surface area of ​​the hollow particles 2 is 50 to 400 m 2 / g. This is because the heat insulating properties of the heat insulating coating 1 containing the hollow particles 2 can be exhibited. 2 When the specific surface area of ​​the hollow particles 2 is less than 400 m / g, the heat insulating properties may not be sufficiently exhibited. 2 If the specific surface area exceeds 100 to 300 m / g, the thickness of the shell of the hollow particles 2 becomes relatively thin, and there is a risk that the hollow particles 2 may be damaged when the hollow particles 2 are mixed into the heat insulating coating material. 2 / g.

[0030] The average particle diameter of the hollow particles 2 is preferably 10 to 200 nm. This is because the heat insulating coating 1 containing the hollow particles 2 can be clear (transparent) while having heat insulating properties. If the average particle diameter of the hollow particles 2 is less than 10 nm, the shell of the hollow particles 2 becomes relatively thick, and the heat insulating properties may be poor. On the other hand, if it exceeds 200 nm, the transparency of the heat insulating coating 1 may be poor. More preferably, the average particle diameter of the hollow particles 2 is 50 to 150 nm.

[0031] Next, a description will be given of an embodiment of a heat insulating coating material containing hollow particles 2. The heat insulating coating material of the embodiment is a coating material that uses a synthetic resin diluted with an organic solvent as a binder and contains 5 to 30 mass % of hollow particles 2 calculated as non-volatile matter.

[0032] The hollow particles 2 are the hollow particles 2 described above, and are preferably contained in the heat insulating paint in an amount of 5 to 30% by mass, calculated as non-volatile content. This is because the heat insulating coating film 1 formed from the heat insulating paint can exhibit heat insulating properties. If the content of the hollow particles 2 in the heat insulating paint is less than 5% by mass, the aggregates 3 of the hollow particles 2 formed on the coating film surface layer may become discontinuous, and the heat insulating properties may be poor. On the other hand, if the content exceeds 30% by mass, the heat insulating effect may plateau, and it may be uneconomical. More preferably, the content of the hollow particles 2 in the heat insulating paint in an amount of 7 to 25% by mass, and even more preferably, 10 to 20% by mass, calculated as non-volatile content.

[0033] The heat insulating paint can be obtained by mixing hollow particles 2 and a thinner (thinner) with a base agent whose main binder is synthetic resin while stirring. Other additives such as viscosity regulators, defoamers, and UV absorbers can be added to the heat insulating paint, and the viscosity can be adjusted with a thinner as necessary. The heat insulating paint can also be used as a two-liquid (three-liquid) type consisting of a base agent whose main binder is synthetic resin, a hardener that hardens the base agent, and a thinner as necessary.

[0034] The hollow particles 2 mixed into the heat insulating paint are hydrophilic because they are formed from siloxane bonds, but because they are modified with a surface modifier, they can be made compatible with organic solvent-based heat insulating paints. When the heat insulating paint is applied to an object 6, the hollow particles 2 based on hydrophilic siloxane bonds become significantly hydrophilic as the heat insulating paint forms a film, and are expelled so that their concentration increases from the inside of the heat insulating paint toward the surface, forming aggregates 3 of the hollow particles 2 on the order of μm on the surface of the coating film. Therefore, the heat insulating coating film 1 formed from the heat insulating paint can exhibit heat insulating properties.

[0035] When the heat insulating paint containing hollow particles 2 is applied to an object 6 to be coated, a heat insulating coating film 1 having an aggregate 3 of hollow particles 2 on the surface layer is formed. When the object 6 to be coated is touched by human skin 7, the aggregate 3 of hollow particles 2 slows down the heat transfer caused by the temperature difference between the object 6 to be coated and the human body, thereby mitigating the contact thermal sensation that the person feels as if it is cold or hot.

[0036] The heat insulating paint containing the hollow particles 2 can be applied to building materials that come into direct contact with human skin 7, such as wood, glass, concrete, siding boards, plastic materials, and sanitary ware (wash basins, toilet bowls, and toilet seats), as well as to parts of automobiles that come into direct contact with people, such as the metal body, and interior plastic materials, such as the dashboard and steering wheel. EXAMPLES

[0037] The raw material blending amount (mass) of hollow particles 2 of the embodiment, the recipe for acid treatment, and the performance of hollow particles 2 are shown in Table 1. In the table, hollow particles A as hollow particles 2 and heat insulating paint A using hollow particles A, hollow particles B as hollow particles 2 and heat insulating paint B using hollow particles B, and hollow particles C as hollow particles C and heat insulating paint C using hollow particles C are examples, and hollow particles D as hollow particles and heat insulating paint D using hollow particles D are comparative examples. Hollow particles A to C are hollow particles 2 whose main skeleton is formed from alkoxysilane and a surface modifier and whose surface is modified. Hollow particle D is a hollow particle whose main skeleton is formed from alkoxysilane and whose surface is not modified.

[0038] [Table 1]

[0039] The calcium carbonate used had an average particle size of 80 nm (the average value of 50 particle sizes measured from SEM photographs). Tetraethoxysilane was used as the alkoxysilane, 3-aminopropyltriethoxysilane, a silane coupling agent, was used as surface modifier A, XIAMETER OFX-0203, a silicone surfactant (an alkyl-modified silicone surfactant manufactured by Dow-Toray Industries, Inc.), was used as surface modifier B, and KF-859, a modified silicone (an amino-modified silicone manufactured by Shin-Etsu Chemical Co., Ltd.), was used as surface modifier C.

[0040] Hollow particles A to C are formed through a reaction process and a dissolution process. In the reaction process, calcium carbonate is added and dispersed in a solvent consisting of ammonia water (25%), purified water, and methanol while stirring with an ultrasonic stirrer, and then alkoxysilane and a surface modifier are added to the solvent in which calcium carbonate is dispersed while stirring. By continuing the stirring, the calcium carbonate is covered with the alkoxysilane and the surface modifier, and a shell body consisting of a siloxane bond formed by condensation polymerization of the alkoxysilane and the surface modifier is formed. In the dissolution process, hydrochloric acid water is added to the solvent in which the calcium carbonate with the shell body formed is dispersed while stirring with a magnetic stirrer, and the calcium carbonate is dissolved, and the shell body of the siloxane bond with the surface modified, that is, hollow particles A to C as hollow particle 2, is obtained.

[0041] Hollow particles A to C contain 20.8 g of modifier per 1 mol of Si in the siloxane bond of alkoxysilane (tetraethoxysilane). Hollow particle D was produced in the same way as hollow particles A to C, but did not contain any modifier and formed a siloxane bond of alkoxysilane.

[0042] In the hollow particle A, the alkoxysilane and the ethoxysilane of the surface modifier 3-aminopropyltriethoxysilane undergo condensation polymerization to form a layer of siloxane bonds. The formed layer of siloxane bonds is hydrophilic, but the surface of hollow particle A is semi-hydrophilic because of the aminopropyl group of 3-aminopropyltriethoxysilane. In the hollow particle B, the alkoxysilane and the silicone chain of the surface modifier alkyl-modified silicone undergo condensation polymerization to form a layer of siloxane bonds. The formed layer of siloxane bonds is hydrophilic, but the surface of hollow particle B is semi-hydrophilic because of the alkyl-modified group of the alkyl-modified silicone. In the hollow particle C, the alkoxysilane and the silicone chain of the surface modifier amino-modified silicone undergo condensation polymerization to form a layer of siloxane bonds. The formed layer of siloxane bonds is hydrophilic, but the surface of hollow particle C is semi-hydrophilic because of the amino-modified group of the amino-modified silicone. Hollow particle D is hydrophilic because it is formed by condensation polymerization of only alkoxysilane.

[0043] Hollow particles A to D can be used for heat insulating paints by drying and removing volatiles. Figure 6 shows an SEM image of hollow particle A. The scale bar in Figure 6 is 500 nm.

[0044] Next, the heat insulating paint will be described. The heat insulating paints A to C of the examples contain hollow particles A to C of the examples, respectively, and are composed of a base agent with a synthetic resin as a binder, a hardener, and a thinner, and are mixed together to form a paint. The base agent, hardener, and thinner were each produced by mixing the raw materials with a dissolver mixer. The heat insulating paint D of the comparative example was produced in the same manner, using hollow particles D instead of hollow particles A to C. The raw material blend amounts (mass) of the heat insulating paints A to D and the performance of the heat insulating coating film formed from the heat insulating paints A to D are shown in Table 2. The raw material blend amounts are listed in terms of non-volatile content, excluding volatile content, and the volatile content (ester-based solvent) is added to the volatile content contained in the raw materials listed in terms of non-volatile content. The thermal conductivity was measured by a disk heat flow meter method (ASTM E 1530 JIS A 1412-2).

[0045] [Table 2]

[0046] Insulating paints A to D, the main binder resin is an acrylic polyol resin, and the hardener is an isocyanate, which becomes a urethane-modified acrylic resin when mixed. The average molecular weight of the acrylic polyol resin is 35,000, and the glass transition temperature (Tg) is -10°C. Silicone additives include viscosity adjusters, defoamers, and UV absorbers. The ester solvent is ethyl acetate and / or butyl acetate.

[0047] The heat insulating paints A to D are made by mixing the base agent, hardener, and thinner in a mass ratio of 100:25:75. The heat insulating paint forms a heat insulating coating film when applied to the object 6. In the examples, a wooden board (cedar board) was used as the object 6.

[0048] When the heat insulating paints A to C are formed, the aminopropyl groups, alkyl modified groups, and amino modified groups of the semi-hydrophilic hollow particles A to C blend with the paint, but because the siloxane bond layer is hydrophilic, they are gradually expelled from the surface of the coating film. Therefore, when the coating is formed, the hollow particles A to C are present in such a way that the concentration of the hollow particles A to C increases toward the surface of the coating film. On the surface of the coating film, the volatile components evaporate, and the hollow particles A to C aggregate to form aggregates 3 with an uneven shape on the order of μm. The uneven shape on the order of μm reduces the contact area between the coating film and the human skin 7, and an air layer is interposed in the uneven shape, suppressing heat transfer, and the heat insulating coating film 1 has excellent heat insulation properties (thermal conductivity). In addition, the transparency of the heat insulating coating film 1 was not hindered by the hollow particles A to C, and it remained transparent.

[0049] Figure 2 shows an SEM photograph of a cross section of a thermal insulation coating film 1 formed from thermal insulation paint A. From approximately the center of the upper part of Figure 2 to the lower right, it can be seen that agglomerates 3 of hollow particles 2 form an uneven shape on the order of μm. To be precise, the agglomerates 3 of hollow particles 2 form an uneven shape of 0.2 to 2 μm. The lower left side of the uneven shape is the thermal insulation coating film 1.

[0050] FIG. 3 shows a laser microscope photograph of a coating film formed from heat insulating paint A. The scale bar in FIG. 3 is 100 μm. FIG. 5 shows a laser microscope photograph of a coating film made of a metallic paint, and the scale bar in FIG. 5 is 100 μm. It can be confirmed that the coating film formed from heat insulating paint A containing semi-hydrophilic hollow particles A is smoother than the coating film formed from the metallic paint. In addition, the surface of the heat insulating coating film 1 formed from the heat insulating paint A was formed with an uneven shape on the order of μm, giving a smooth and dry feeling to the finger as skin 7. On the other hand, the surface of the coating film formed from the metallic paint was formed with vein-like unevenness, giving a moist feeling to the finger.

[0051] In the case of the heat insulating paint D, the siloxane layer of the hollow particles D is hydrophilic, so that the hollow particles D are expelled to the surface of the coating film when the coating film is formed. Therefore, the hollow particles D are present in a layer on the surface of the coating film, and shrink when the volatile components evaporate, forming a large (100 μm or more) uneven shape. Due to the large uneven shape, the coating film surface is rough, giving a rough feeling to the fingers. Because the coating film surface is rough, the area in contact with the skin 7 of the human body is small, and in the measurement method of the embodiment, the heat insulating paint D has better heat insulation (thermal conductivity) than the heat insulating paints A to C. A laser microscope photograph of the coating film formed from the heat insulating paint D is shown in FIG. 4. The scale bar in FIG. 4 is 200 μm. It can be confirmed that the coating film formed from the heat insulating paint B has an uneven shape of 100 μm or more.

[0052] The following can be understood from the results of the examples.

[0053] The heat insulating coating film 1 formed from the heat insulating paint of the embodiment may have a surface roughness (Ra) of 0.1 to 0.4. This allows the coating film to have excellent smoothness and heat insulating properties. More preferably, the surface roughness (Ra) of the heat insulating coating film 1 formed from the heat insulating paint is 0.2 to 0.3.

[0054] The heat insulating coating film 1 formed from the heat insulating paint of the embodiment may have a surface haze measurement value of 40 to 90%. This allows the coating film to have gloss. More preferably, the haze measurement value of the heat insulating coating film 1 formed from the heat insulating paint is 40 to 80%, and even more preferably, 50 to 70%.

[0055] The heat insulating coating film 1 formed from the heat insulating paint of the embodiment may have a thermal conductivity of 0.02 to 0.1 W / mK. This allows the coating film to have excellent heat insulating properties. More preferably, the heat insulating coating film 1 formed from the heat insulating paint has a thermal conductivity of 0.025 to 0.05 W / mK.

[0056] Other technical ideas that can be understood from the embodiments will be described below.

[0057] Hollow particles, characterized in that the alkoxysilane forming a siloxane bond is tetraethoxysilane, the surface modifier is 3-aminopropyltriethoxysilane, and the surface modifier is contained in an amount of 5 to 30 parts by mass per 100 parts by mass of the alkoxysilane. This makes it possible to make the hollow particles semi-hydrophilic, and when a heat insulating coating containing the hollow particles is formed into a film, the hollow particles are expelled so that the hydrophilicity is well balanced and the concentration increases from the inside of the heat insulating coating toward the surface layer, and the volatile components volatilize, forming aggregates 3 of hollow particles on the order of μm on the surface layer of the coating film. More preferably, the content of the surface modifier per 100 parts by mass of the alkoxysilane is 8 to 20 parts by mass.

[0058] A heat insulating paint characterized in that the glass transition temperature (Tg) of the synthetic resin used as a binder is −30 to 10° C. According to this, the heat insulating paint has a flexibility that enables the coating film formed from the heat insulating paint to follow the expansion and contraction of the base, and the appropriate flexibility reduces adhesion of dirt to the coating film, enabling the coating film to maintain its beautiful appearance. [Explanation of symbols]

[0059] 1...insulating coating film, 2...hollow particles, 3...aggregate, 6...coated object, 7...skin.

Claims

1. A method for forming a heat insulating coating film formed from a heat insulating paint, the method comprising the steps of: The hollow particles have an average particle diameter of 10 to 200 nm, have a main skeleton of a siloxane bond formed from tetraethoxysilane as an alkoxysilane, and are modified with 3-aminopropyltriethoxysilane as a surface modifier; The heat insulating coating composition has a binder resin as a main component that is an acrylic polyol resin, a curing agent that is an isocyanate, and contains 5 to 30 mass % of the hollow particles calculated as non-volatile matter, When the heat insulating coating film is formed from the heat insulating paint, the hollow particles are expelled from the inside of the heat insulating paint toward the surface layer so that the concentration of the hollow particles increases, and an aggregate of hollow particles is formed on the surface layer of the heat insulating coating film. A method for forming a heat insulating coating film.

2. 2. The method for forming a heat insulating coating according to claim 1, wherein the hollow particles contain 5 to 50 g of the surface modifier per 1 mol of Si in the siloxane bond.

3. 2. The method for forming a heat insulating coating according to claim 1, wherein the hollow particles contain 5 to 30 parts by mass of the surface modifier per 100 parts by mass of the alkoxysilane.

4. The method for forming a heat insulating coating film according to any one of claims 1 to 3, characterized in that the glass transition temperature (Tg) of the synthetic resin used as a binder for the heat insulating coating is -30 to 10°C.

5. 5. The method for forming a heat insulating coating according to claim 1, wherein the agglomerates form an uneven shape on the surface of the coating on the order of μm.

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