JP2024050899A - Coating Method - Google Patents

Abstract

[Problem] To provide a method for forming a coating which provides excellent curing of the coating and can stably ensure coating performance regardless of the coating environment, and furthermore, the formed coating exhibits excellent foaming properties when the temperature rises due to a fire or the like, and can maintain the heat-resistant protective performance of the substrate. [Solution] A method for forming a coating by applying a coating material to a substrate under high humidity conditions, the coating material is a coating material which forms a carbonized heat insulating layer when the temperature of the coating rises to 200°C or higher, the coating material contains a polyol compound, a polyisocyanate compound, a heat resistance imparting powder, and a water absorbing agent, and the mixing ratio of the polyol compound and the polyisocyanate compound is 1.2 to 3.5 in terms of NCO/OH equivalent ratio. [Selected Drawing] None

Description

The present invention relates to a novel coating material and a coating formation method.

A variety of coating materials have been proposed to protect substrates such as steel, concrete, wood, and synthetic resin from fire, by foaming when the temperature rises during a fire or other event, forming a carbonized insulating layer. Known coating materials include synthetic resins mixed with foaming agents, carbonizing agents, and flame retardants. The heat-resistant protective performance of such coating materials is often determined by the coating thickness, and in order to obtain the desired heat-resistant protective performance, it is important to apply the coating uniformly at the specified thickness, and in particular, the selection of the synthetic resin is important.

For example, a coating material for thick coating has been developed that contains a composition of a polyol compound and a polyisocyanate compound, and also contains a flame retardant, a foaming agent, and a carbonizing agent (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 5-70540

However, in the case of the above-mentioned Patent Document 1, the expansion ratio of the coating when the temperature rises is low compared to coating materials using acrylic resin or epoxy resin as a synthetic resin, and furthermore, problems such as incineration and shrinkage of the carbonized insulation layer (foamed layer) occur, and there is still room for improvement in order to obtain the desired heat-resistant protective performance. In addition, it is necessary to respond to changes in the painting environment due to recent climate change and sudden weather changes. However, depending on the painting environment, the hardening of the coating may be poor, and it may be difficult to obtain the coating performance and sufficient heat-resistant protective performance. The present invention has been made in consideration of such problems, and aims to provide a coating material that has excellent hardening of the coating regardless of the painting environment, can stably ensure the coating performance, and can form a stable carbonized insulation layer when the temperature rises, thereby ensuring excellent heat-resistant protective performance.

In order to solve these problems, the inventors discovered that a coating material, the coating of which forms a carbonized insulation layer due to a temperature rise caused by a fire or the like, contains a polyol compound and a polyisocyanate compound in a specific mixing ratio, and further contains a heat resistance imparting powder and a water absorbing agent, which results in excellent hardening of the coating and stable coating performance regardless of the coating environment, and furthermore, the coating thus formed exhibits excellent foaming properties when the temperature rises due to a fire or the like, forms a carbonized insulation layer, and is able to maintain the heat-resistant protective performance of the substrate, thus completing the present invention.

That is, the present invention has the following features.
1. A coating forming method for forming a coating by applying a coating material to a substrate, comprising the steps of:
The coating material is a coating material that forms a carbonized heat insulating layer when its coating is heated to 200° C. or higher, the coating material includes a polyol compound, a polyisocyanate compound, a heat resistance imparting powder, and a water absorbing agent, and the mixing ratio of the polyol compound to the polyisocyanate compound is 1.2 to 3.5 in terms of NCO/OH equivalent ratio,
The coating material is applied in one or more steps under high humidity conditions of 70% Rh or higher, and the dry film thickness per step is 300 μm or more.
2. The method for forming a coating film according to 1., wherein the coating material comprises a base agent containing a polyol compound, a heat resistance imparting powder, and a water absorbing agent, and a curing agent containing a polyisocyanate compound.
3. The method for forming a coating film according to 1. or 2., wherein the water absorbing agent is contained in an amount of 0.5 to 50 parts by weight per 100 parts by weight of the solid content of the polyol compound.
4. The coating forming method according to any one of 1. to 3., wherein the heat resistance imparting powder contains at least one selected from a foaming agent, a carbonizing agent, a flame retardant, and a filler.

The present invention is a coating material whose coating forms a carbonized insulation layer as the temperature rises. The coating material contains a polyol compound, a polyisocyanate compound, a heat resistance imparting powder, and a water absorbent. The mixing ratio of the polyol compound and the polyisocyanate compound is an NCO/OH equivalent ratio of 1 or more, so that the coating has excellent curing properties (curing speed, coating hardness, etc.) regardless of the painting environment, and the coating performance can be stably ensured. Furthermore, when the temperature rises due to a fire or the like, the coating has excellent foaming properties, and the carbonized insulation layer is inhibited from being incinerated or contracted, forming a stable carbonized insulation layer, thereby enhancing the heat resistance protection of the substrate.

The present invention will be described in detail below based on its embodiments.

(Coating material)
The coating material of the present invention is characterized in that the coating forms a carbonized heat insulating layer due to a temperature rise (heating) caused by a fire, etc., and contains a polyol compound, a polyisocyanate compound, a heat resistance imparting powder, and a water absorbing agent. Specifically, the coating formed by the coating material of the present invention has excellent foaming properties when the temperature rises to 200°C or higher (more preferably 250°C or higher), and can improve the heat resistance protection performance of the substrate by forming a carbonized heat insulating layer.

The coating material of the present invention contains, as the film-forming component (A), a polyol compound (A1) and a polyisocyanate compound (A2) as essential components. The polyol compound (A1) and the polyisocyanate compound (A2) are components that react to form a coating.

In the present invention, it is preferable to include polyether polyol (a1) as the polyol compound (A1). The molecular weight of polyether polyol (a1) is preferably 1000 or more (more preferably 3000 to 20000, even more preferably 5000 to 18000, particularly preferably 6000 to 15000, and most preferably 6500 to 12000). By including such polyether polyol (a1) as the polyol compound (A1), the coating exhibits excellent foaming properties due to the temperature rise of the coating (preferably the coating surface temperature is 200°C or more, more preferably 250°C or more), and the heat-resistant protection performance of the substrate can be improved. In addition, the molecular weight of the polyol compound (A1) in the present invention is a number average molecular weight (Mn), which is a so-called polystyrene-equivalent molecular weight obtained by gel permeation chromatography using a polystyrene polymer as a reference.

The polyether polyol (a1) is obtained by addition polymerization of polyhydric alcohols such as trimethylolpropane, glycerin, hexanetriol, pentaerythritol derivatives, sorbitol, and neopentyl glycol with alkylene oxides such as ethylene oxide and propylene oxide. In the present invention, a polymer obtained by addition polymerization of the above polyhydric alcohols with ethylene oxide and/or propylene oxide is preferred, and one having ethylene oxide and/or propylene oxide added to the terminal is more preferred. Furthermore, it is preferable that the above polyether polyol contains a polyether polyol having three or more functional groups having active hydrogen atoms (functional group number 3 or more). In this case, the curing property is excellent and a coating can be stably formed, so that the effect of the present invention is easily obtained. A hydroxyl group is preferred as the functional group having an active hydrogen atom.

Such polyether polyol (a1) preferably has a hydroxyl value (solid content) of 3 to 150 mgKOH/g (more preferably 5 to 100 mgKOH/g, even more preferably 7 to 40 mgKOH/g, and most preferably 10 to 30 mgKOH/g). By using such a polyol compound (a1), it is possible to achieve even better foaming properties and improve the heat-resistant protection performance of the substrate. In the present invention, the hydroxyl value is a value (mgKOH/g) expressed by the number of mg of potassium hydroxide equivalent to the moles of hydroxyl groups contained in 1 g of solid content, and "α to β" is synonymous with "α or more and β or less".

The content of the polyether polyol (a1) is preferably 50% by weight or more and 100% by weight or less (more preferably 60 to 99% by weight, and even more preferably 70 to 98% by weight) based on the total amount of the polyol compound (A1).

In the present invention, it is preferable that the polyol compound (A1) contains a fluorine-containing polyol (a2). This allows the coating to have excellent foaming properties due to a temperature rise (preferably a coating surface temperature of 200°C or higher, more preferably 250°C or higher), and also allows a stable carbonized insulation layer to be formed by suppressing incineration and shrinkage of the carbonized insulation layer, thereby improving the heat resistance protection of the substrate.

Such fluorine-containing polyol (a2) is not particularly limited, but may be obtained by copolymerizing, for example, a fluorine-containing monomer such as a fluoroolefin monomer or a fluoroalkyl group-containing acrylic monomer with a hydroxyl group-containing vinyl monomer and, if necessary, other polymerizable monomers. Examples of the fluoroolefin monomer include perfluoroolefins such as tetrafluoroethylene, chlorotrifluoroethylene, and hexafluoropropylene, vinyl fluoride, and vinylidene fluoride. Examples of the fluoroalkyl group-containing acrylic monomer include perfluoromethyl methacrylate, perfluoroisononylmethyl methacrylate, 2-perfluorooctylethyl acrylate, 2-perfluorooctylethyl methacrylate, and trifluoroethyl acrylate. These may be used alone or in combination of two or more. In the present invention, it is preferable to use one or more selected from tetrafluoroethylene and chlorotrifluoroethylene, and more preferably chlorotrifluoroethylene.

Examples of hydroxyl group-containing vinyl monomers include hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, and hydroxypentyl vinyl ether; hydroxyallyl ethers such as ethylene glycol monoallyl ether, diethylene glycol monoallyl ether, and triethylene glycol monoallyl ether; and hydroxyl group-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 4-hydroxyethyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. One or more of these can be used.

Other polymerizable monomers include, for example, (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate, and cyclohexyl (meth)acrylate; dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, dimethylamino (meth)acrylate, aminoethyl (meth)acrylate, and diethylaminoethyl (meth)acrylate. Amino group-containing monomers such as ethyl (meth)acrylate; carboxyl group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, maleic acid or its monoalkyl ester, itaconic acid or its monoalkyl ester, and fumaric acid or its monoalkyl ester; amide-containing monomers such as (meth)acrylamide and ethyl (meth)acrylamide; nitrile group-containing monomers such as (meth)acrylonitrile; epoxy group-containing monomers such as glycidyl (meth)acrylate; aromatic vinyl monomers such as styrene, methylstyrene, chlorostyrene, and vinyltoluene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl pivalate; olefin-based monomers such as ethylene and propylene, and the like can be used alone or in combination as necessary.

As for such a fluorine-containing polyol (a2), the fluorine content in the solid content of the fluorine-containing polyol (a2) is preferably 10 to 50% by weight (more preferably 15 to 40% by weight, and even more preferably 20 to 35% by weight). In addition, the hydroxyl value (solid content) is preferably 5 to 100 mg KOH/g (more preferably 10 to 80 mg KOH/g). Furthermore, the molecular weight [number average molecular weight (Mn)] is preferably 5,000 to 100,000 (more preferably 8,000 to 60,000). By including such a fluorine-containing polyol (a2), when the temperature rises due to a fire or the like, the coating exhibits excellent foaming properties and forms a carbonized insulation layer, and incineration and shrinkage can be suppressed even in a high-temperature atmosphere, thereby improving the heat-resistant protection performance of the substrate.

The content of the fluorine-containing polyol (a2) is preferably 0.1 to 30% by weight (more preferably 0.5 to 20% by weight, and even more preferably 1 to 10% by weight) in terms of solid content relative to the total amount of the polyol compound (A1). By satisfying this range, the heat resistance protection performance of the substrate can be improved and sufficient adhesion with the topcoat material can be ensured.

In addition to the above-mentioned components (a1) and (a2), examples of the polyol compound (A1) of the present invention include polyester polyols, acrylic polyols, epoxy-containing polyols, silicone-containing polyols, castor oil, castor oil-modified polyols, polycarbonate polyols, polylactone polyols, polybutadiene polyols, polypentadiene polyols, etc., and one or more selected from these can be used.

The polyol compound (A1) is preferably liquid at 20°C, and each of the polyol compounds preferably has a viscosity of 0.05 to 10 Pa·s (more preferably 0.1 to 5.0 Pa·s). This makes it easier to achieve the effects of the present invention. The viscosity of the polyol component is the viscosity at 20 rpm (guideline value at the fifth revolution) measured with a BH type viscometer at a temperature of 20°C.

Examples of the polyisocyanate compound (A2) of the present invention include toluene diisocyanate (TDI), 4,4-diphenylmethane diisocyanate (pure-MDI), polymeric MDI, xylylene diisocyanate (XDI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), hydrogenated XDI, hydrogenated MDI, etc., or derivatives thereof which have been allophanated, biurated, dimerized (uretdione), trimerized (isocyanurated), adducted, or carbodiimided; and blocked isocyanates which have been blocked with alcohols, phenols, ε-caprolactam, oximes, active methylene compounds, etc., and one or more selected from these can be used.

In the present invention, the polyisocyanate compound (A2) preferably contains hexamethylene diisocyanate (HMDI) and/or its derivatives (hereinafter also referred to as "HMDIs"). The content of the HMDIs is preferably 90% by weight or more (more preferably 95% by weight or more) based on the total amount of the polyisocyanate compound (A2). In addition, an embodiment in which the polyisocyanate compound (A2) consists only of HMDIs is also suitable. In addition, as the derivative, a biuret and/or an isocyanurate is suitable. In such a case, the formed coating has excellent curing properties, exhibits better foaming properties when the temperature rises, and can enhance the heat resistance protection of the substrate.

In the present invention, it is preferable that the polyisocyanate compound (A2) contains an isocyanate group content of 10% by weight or more (preferably 15% by weight or more and 30% by weight or less) in the solid content. In such a case, the formed coating can exhibit excellent curing effect, and a stable coating can be formed. In the present invention, the isocyanate group content is defined as the content (weight %) of isocyanate groups contained in the solid content of the polyisocyanate compound, and is a value obtained by back titration with hydrochloric acid after neutralizing the isocyanate groups with an excess amine.

The present invention is characterized in that the mixing ratio of the polyol compound (A1) and the polyisocyanate compound (A2) is 1 or more (preferably 1.2 to 3.5, more preferably 1.5 to 3.0) in terms of NCO/OH equivalent ratio. In such a case, regardless of the coating environment, a coating with excellent curing properties and a uniform coating with the desired thickness can be formed. In addition, when the coating material is applied in layers, the coating has excellent adhesion between layers and can stably form a thick film. Furthermore, the formed coating has excellent foaming properties in the event of a temperature rise due to a fire or the like, and can form a stable carbonized insulation layer to improve the heat-resistant protection performance of the substrate. Furthermore, the formed coating has excellent durability (e.g., waterproofness, water permeability resistance, crack resistance, base following ability, etc.), can maintain the initial appearance (beauty) for a long period of time, and can fully exert the effects of the present invention in the event of a temperature rise due to a fire or the like.

In the present invention, a curing catalyst that promotes the reaction between the polyol compound (A1) and the polyisocyanate compound (A2) can be used in combination. A curing catalyst is a substance that promotes the reaction and curing of isocyanate groups. Examples of the curing catalyst include various types of amine catalysts, organometallic catalysts, and inorganic catalysts. Examples of amine catalysts include ethylenediamine, triethylenediamine, triethylamine, ethanolamine, diethanolamine, and hexamethylenediamine, or their derivatives or mixtures with solvents. Examples of organometallic catalysts include organometallic compounds such as dibutyltin dilaurate and dibutyltin diacetate; and organometallic salts such as potassium acetate, zinc stearate, calcium stearate, lead stearate, aluminum stearate, and tin octylate. Examples of inorganic catalysts include tin chloride. These can be used alone or in combination, and can also be used in a mixture with a solvent. In the present invention, it is particularly preferable to include an organometallic catalyst. In this case, the curing is accelerated and the curability of the film-forming component (A) is increased, thereby enhancing the effects of the present invention. The content of the curing catalyst is preferably 0.01 to 3 parts by weight (more preferably 0.05 to 2.5 parts by weight) per 100 parts by weight of the solid content of the polyol compound (A1).

The cured coating formed from the coating component (A) has an exothermic peak in differential thermal analysis (DTA), and the exothermic peak preferably has a maximum value in the temperature range of 200 to 400°C (more preferably 250 to 380°C). In such a case, when the temperature rises due to a fire or the like, the foaming property is further improved, and it is possible to form an excellent carbonized insulating layer, thereby improving the heat-resistant protection of the substrate.

The mechanism of action is not limited, but for example, the cured coating of the coating-forming component (A) begins to soften with an increase in temperature, and then the decomposition reaction of urethane bonds and the like proceeds. When the exothermic peak of the cured coating of the coating-forming component (A) has a maximum value in the above temperature range, the decomposition does not proceed much and the coating is in a softened state, and the foaming and carbonization reactions can proceed efficiently, so that the foaming property is improved and a carbonized insulation layer can be formed stably. In particular, in the present invention, the coating-forming component (A) contains a fluorine-containing polyol (a2) as the polyol compound (A), so that the exothermic peak of the cured coating can be shifted to a higher temperature side. This enhances the flame retardancy of the cured coating and suppresses decomposition at temperatures below 200°C, and it is believed that the effects of the present invention can be fully exerted.

In the present invention, the differential thermal analysis of the cured coating of the coating-forming component (A) is performed by measuring the cured coating containing the polyol compound (A1) and the polyisocyanate compound (A2) as a sample. The differential thermal analysis is performed using a differential thermal analyzer (for example, "Differential Thermobalance Thermo plus EVO2 TG-DTA Series" manufactured by Rigaku Corporation, etc.), in which 3±1 mg of the sample is placed in a platinum sample pan, α-alumina is used as the standard substance, and the temperature is increased from 100 to 900°C at a heating rate of 20°C/min.

In the coating material of the present invention, the heat resistance imparting powder (B) is a component that forms a carbonized heat insulating layer by interacting with the above-mentioned coating-forming component (A) when the temperature rises during a fire or the like (for example, at least one of a dehydration and cooling effect, a non-flammable gas generating effect, a carbonization promotion effect, a carbonized heat insulating layer forming effect, etc.). The heat resistance imparting powder (B) preferably contains, for example, one or more selected from a foaming agent (b1), a carbonizing agent (b2), a flame retardant (b3), and a filler (b4), etc.

The foaming agent (b1) imparts a foaming action to the coating due to a temperature rise during a fire or the like, and specifically imparts a foaming action when the temperature of the coating surface preferably reaches 200°C or higher. Examples of the foaming agent (b1) include melamine and its derivatives, dicyandiamide and its derivatives, azobistetrazole and its derivatives, azodicarbonamide, urea, and thiourea. These can be used alone or in combination of two or more. The content of the foaming agent (b1) is preferably 10 to 200 parts by weight (more preferably 20 to 150 parts by weight) per 100 parts by weight of the solid content of the polyol compound (A1).

The carbonizing agent (b2) is a dehydrating carbonizing agent that forms a carbonized heat insulating layer by carbonizing the film forming component (A) and dehydrating the film when the temperature rises during a fire or the like. Examples of the carbonizing agent (b2) include pentaerythritol, dipentaerythritol, trimethylolpropane, starch, casein, tris(2-hydroxyethyl)isocyanurate, etc., and the like. These can be used alone or in combination of two or more. In the present invention, pentaerythritol and dipentaerythritol are particularly preferred because they have excellent dehydrating cooling effects and carbonized heat insulating layer forming effects. The content of the carbonizing agent (b2) is preferably 10 to 200 parts by weight (more preferably 20 to 120 parts by weight) per 100 parts by weight of the solid content of the polyol compound (A1).

Examples of the flame retardant (b3) include organic phosphorus compounds such as tricresyl phosphate and diphenyl cresyl phosphate; chlorine compounds such as chlorinated polyphenyl, chlorinated polyethylene, diphenyl chloride, triphenyl chloride, chlorinated paraffin, pentachlorinated fatty acid ester, perchloropentacyclodecane, chlorinated naphthalene, and tetrachlorophthalic anhydride; antimony compounds such as antimony trioxide and antimony pentachloride; phosphorus compounds such as phosphorus trichloride, phosphorus pentachloride, ammonium phosphate, ammonium polyphosphate, melamine phosphate, melamine polyphosphate, melam polyphosphate, melem polyphosphate, boron phosphate, boron polyphosphate, aluminum phosphate, and aluminum polyphosphate; and inorganic compounds such as zinc borate and sodium borate. These can be used alone or in combination of two or more. In the present invention, the flame retardant (b3) preferably contains at least one phosphorus compound selected from, for example, melamine polyphosphate, melam polyphosphate, a melamine-melam-melem double salt, or a complex compound of a melamine-melam-melem double salt of polyphosphate and dimelam pyrosulfate, and further preferably contains these in combination with ammonium polyphosphate. The content of the flame retardant (b3) is preferably 30 to 800 parts by weight (more preferably 50 to 500 parts by weight) per 100 parts by weight of the solid content of the polyol compound (A1).

Examples of fillers (b4) include talc, calcium carbonate, sodium carbonate, aluminum oxide, titanium oxide, zinc oxide, silica, clay, siliceous silica, mica, silica sand, silica powder, quartz powder, barium sulfate, and the like. These can be used alone or in combination of two or more. The content of filler (b4) is preferably 3 to 200 parts by weight (more preferably 5 to 150 parts by weight) per 100 parts by weight of the solid content of the polyol compound (A1).

In addition to the above components, the present invention may also contain metal hydrate (b5), fibers (b6), and the like. The metal hydrate (b5) exhibits endothermic properties due to a dehydration reaction or the like when the temperature rises, and is different from the filler (b4). Examples of such metal hydrate (b5) include aluminum hydroxide and magnesium hydroxide. These may be used alone or in combination of two or more. The average particle size of the metal hydrate (b5) is preferably 0.1 to 20 μm (more preferably 0.2 to 15 μm, even more preferably 0.3 to 8 μm, and most preferably 0.4 to 3 μm). The content of the metal hydrate (b5) is preferably 0.1 to 50 parts by weight (more preferably 0.2 to 30 parts by weight) per 100 parts by weight of the solid content of the polyol compound (A1).

In the present invention, it is preferable to use the filler (b4) and the metal hydrate (b5) in combination. In this case, the content of the metal hydrate (b5) is preferably 0.1 to 20% by weight (more preferably 0.3 to 15% by weight, and even more preferably 0.5 to 10% by weight) relative to the filler (b4). In this case, the foamability, particularly the shrinkage of the carbonized insulation layer at high temperatures, can be suppressed, and a stable carbonized insulation layer can be formed, thereby enhancing the effects of the present invention. The average particle size is measured by a laser diffraction particle size distribution analyzer.

Fiber (b6) can improve the coating thickness and suppress cracking of the coating. In addition, fiber (b6) can prevent the coating from sagging during a temperature rise due to a fire or the like, and can increase the thermal conductivity inside the coating. As a result, it shows excellent foaming properties, forms a uniform carbonized insulation layer, and can improve the heat-resistant protection performance of the substrate. Examples of such fibers (b6) include organic fibers such as acrylic fibers, acetate fibers, aramid fibers, cuprammonium fibers (cupra), nylon fibers, novoloid fibers, pulp fibers, viscose rayon, vinylidene fibers, polyester fibers, polyethylene fibers, polyvinyl chloride fibers, polychlar fibers, boronosic fibers, polypropylene fibers, and cellulose fibers, and inorganic fibers such as carbon fibers, rock wool fibers, glass fibers, silica fibers, alumina fibers, silica-alumina fibers, slag wool fibers, ceramic fibers, carbon fibers, and silicon carbide fibers. These can be used alone or in combination of two or more.

In the present invention, it is preferable that the fiber (b6) contains inorganic fibers, and among them, artificial mineral fibers such as rock wool fibers, slag wool fibers, glass fibers, and ceramic fibers are preferable. This can further suppress cracking of the coating. Furthermore, in the event of a temperature rise due to a fire or the like, it is possible to make it difficult for the coating to sag, and to further increase the thermal conductivity inside the coating. As a result, it is possible to form a carbonized insulation layer that exhibits uniform and excellent foaming properties all the way to the inside (core) of the coating, and has a more uniform and excellent strength, and to further improve the heat resistance protection performance of the substrate.

The size (fiber length and fiber diameter) of the fiber (b6) may be set according to the performance of the coating material, the application substrate, the specifications of the applicator, etc., and the average fiber length is preferably within the range of 10 to 1000 μm (more preferably 15 to 800 μm, even more preferably 20 to 600 μm), and the average fiber diameter is preferably within the range of 0.5 to 10 μm (more preferably 1 to 8 μm). The aspect ratio (fiber length/fiber diameter) is preferably 3 to 300 (more preferably 5 to 200). If the above range is satisfied, the coating can be applied thicker, cracks in the formed coating are less likely to occur, and sagging of the coating is less likely to occur in the event of a temperature rise due to a fire, etc., and a stable carbonized insulation layer can be formed. The content of the fiber (b6) is preferably 0.5 to 30 parts by weight (more preferably 1 to 25 parts by weight, even more preferably 2 to 20 parts by weight) relative to 100 parts by weight of the solid content of the polyol compound (A1).

The coating material of the present invention is characterized by containing a water absorbing agent (C). The water absorbing agent (C) imparts the function of absorbing moisture in the coating material and/or in the air. The moisture in the coating material and/or in the air easily reacts with the polyisocyanate compound (A2). Therefore, the coating material is easily affected by the moisture in the air during the coating method and coating environment, particularly when the coating material is spray-coated or coated (film-formed) under high humidity (even in rainy weather or under high temperature and humidity), and the reaction between the polyisocyanate compound (A2) and the polyol compound (A1) is inhibited, and the curing property (curing speed, coating strength, etc.) and adhesion to the substrate are reduced, and as a result, sufficient heat resistance protection may not be obtained. In the present invention, by blending the water absorbing agent (C), the coating material or the moisture in the air is absorbed, and the curing property and adhesion to the substrate can be sufficiently secured regardless of the coating method and coating environment, and a thick film can be stably formed.

The water absorbing agent (C) is not particularly limited as long as it has the above-mentioned effect, but for example, a water binding agent (c1) and a dehydrating agent (c2) can be used. These can be used alone or in combination of two or more. The water absorbing agent (C) can be in any form, such as pellets, powder, liquid, or paste. In the present invention, pellets and powder are preferred.

The water binding agent (c1) has the effect of removing water from the coating material and/or the air by reacting with water. Examples of such water binding agents include alkyl orthoformates such as methyl orthoformate, ethyl orthoformate, trimethyl orthoformate, triethyl orthoformate, and tributyl orthoformate; trialkyl orthoacetates such as trimethyl orthoacetate, triethyl orthoacetate, and tributyl orthoacetate; trialkyl orthoborates such as trimethyl orthoborate, triethyl orthoborate, and tributyl orthoborate; monoisocyanate compounds such as phenyl isocyanate, p-chlorophenyl isocyanate, benzene Examples of such compounds include monoisocyanate compounds such as toluenesulfonyl isocyanate, p-toluenesulfonyl isocyanate, and isocyanate ethyl methacrylate; alkoxysilanes such as tetraethoxysilane, tetrabutoxysilane, tetraphenoxysilane, tetrakis(2-ethoxybutoxy)silane, methyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, trimethylethoxysilane, and diphenyldiethoxysilane; and acid anhydrides such as maleic anhydride and phthalic anhydride.

The dehydrating agent (c2) has the function of removing water from the coating material and/or the air by absorbing water as crystal water, adsorbed water, etc. (water adsorption). Furthermore, the dehydrating agent can improve heat resistance protection because it can dehydrate adsorbed water when the temperature rises (at high temperatures). Examples of such dehydrating agents include silica gel, synthetic zeolite, natural zeolite, synthetic clay, activated alumina, calcium oxide, magnesium sulfate, sodium sulfate, hemihydrate gypsum, anhydrous gypsum, crystalline gypsum, cement, activated carbon, partially cross-linked acrylic acid polymer (polymer water absorbent), etc.

In the present invention, the dehydrating agent (c2) is preferred as the water absorbing agent (C). Among them, porous inorganic particles such as silica gel, synthetic zeolite, natural zeolite, and activated alumina are preferred, and the form thereof is preferably in powder form. In particular, powdered synthetic zeolite is preferred in the present invention. Synthetic zeolites include A-type, X-type, Y-type, L-type, mordenite type, and chabazide type, and A-type zeolite is preferred in the present invention. The average pore size of the porous inorganic particles may be larger than the molecular diameter of water molecules (about 2.3 to 3.9 Å), and is preferably 2.3 to 30 Å (more preferably 2.5 to 10 Å, even more preferably 3 to 8 Å, and particularly preferably 3.5 to 5 Å). In this case, the water adsorption is excellent, and the curing property of the above-mentioned (A) component is excellent, and the curing speed and coating hardness can be increased. In addition, it has excellent adhesion to the substrate, can form a uniform coating, and can fully maintain the heat-resistant protective performance of the substrate without inhibiting the foaming properties of the coating (does not adsorb non-flammable gases, etc.) in the event of a temperature rise due to a fire, etc. The average pore size of the porous inorganic particles can be measured, for example, by nitrogen adsorption measurement.

When the water-absorbing agent (C) is in powder form, its average particle size is preferably 30 to 500 μm (more preferably 40 to 400 μm, and even more preferably 50 to 300 μm).

The content of the water absorbent (C) is preferably 0.5 to 50 parts by weight (more preferably 1 to 50 parts by weight, and even more preferably 1.5 to 30 parts by weight) per 100 parts by weight of the solid content of the polyol compound (A1).

The coating material of the present invention preferably further contains a high-boiling compound (D). The high-boiling compound (D) is a high-boiling liquid compound that is liquid at 20°C and has a boiling point of 100°C or higher (more preferably 150°C or higher, and even more preferably 200°C or higher). By containing such a high-boiling compound (D), the dispersion stability of the heat resistance imparting component (B) and the like can be improved. In addition, a good coating with excellent adhesion is formed, and in particular, the elasticity of the coating is improved, preventing cracking of the coating. Furthermore, when the coating is exposed to high temperatures due to a fire or the like, it contributes to moderate softening of the coating, further increasing the foaming property, suppressing the falling off (peeling) of the formed carbonized insulation layer, and improving the heat resistance protection performance of the substrate.

The high-boiling point compound (D) is not particularly limited as long as it satisfies the above conditions, and examples thereof include phthalate ester compounds such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, dihexyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate, diisodecyl phthalate, diundecyl phthalate, and butyl benzyl phthalate; diethyl adipate, dibutyl adipate, diisobutyl adipate, dihexyl adipate, di-2-ethylhexyl adipate, dioctyl adipate, diisononyl adipate, diisodecyl adipate, bis(butyl diglycol adipate), diethyl sebacate, dibutyl sebacate ... aliphatic dibasic acid ester compounds such as dihexyl hexyl and di-2-ethylhexyl sebacate; adipic acid polyesters such as 1,3-butylene glycol adipic acid polyester and 1,2-propylene glycol adipic acid polyester; maleic acid ester compounds such as dimethyl maleate, diethyl maleate, dibutyl maleate, dihexyl maleate, di-2-ethylhexyl maleate, diisononyl maleate, and diisodecyl maleate; phosphate ester compounds such as triethyl phosphate, tributyl phosphate, tri-2-ethylhexyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, and 2-ethylhexyl diphenyl phosphate;

Trimellitic acid ester compounds such as tris-2-ethylhexyl trimellitate; ricinoleic acid ester compounds such as methyl acetyl risinolate; epoxy ester compounds such as di-2-ethylhexyl epoxyhexahydrophthalate, diepoxystearyl epoxyhexahydrophthalate, epoxidized fatty acid butyl, epoxidized fatty acid 2-ethylhexyl, epoxidized soybean oil, and epoxidized linseed oil; benzoic acid ester compounds such as benzoic acid glycol ester; aromatic hydrocarbon compounds such as 1-phenyl-1-xylylethane and 1-phenyl-1-ethylphenylethane; lactones such as γ-butyrolactone; and mixtures of petroleum resins (polymers of aromatic hydrocarbon fractions having 8 to 10 carbon atoms) and styrylxylene. These can be used alone or in combination of two or more.

In the present invention, the high-boiling point compound (D) preferably includes one or more compounds selected from phthalate ester compounds, aliphatic dibasic acid ester compounds, and phosphate ester compounds, and more preferably includes one or more compounds selected from phthalate ester compounds and aliphatic dibasic acid ester compounds having an alkyl group with 4 to 11 carbon atoms (more preferably 5 to 10, and even more preferably 6 to 9). Specific examples of suitable compounds include diisononyl phthalate and diisononyl adipate.

The content of the high boiling point compound (D) is preferably 5 to 150 parts by weight (more preferably 8 to 100 parts by weight, and even more preferably 10 to 80 parts by weight) per 100 parts by weight of the solid content of the polyol compound (A1). When the above range is satisfied, the dispersibility of the powder components is increased, the coating properties are excellent, and when the temperature rises due to a fire or the like, the coating has excellent foaming properties and can fully demonstrate the effect of maintaining the heat-resistant protective performance of the substrate. Furthermore, excellent suitability for topcoat materials can be obtained.

Other additives may be used as long as they do not significantly impair the effects of the present invention, and examples of such additives include pigments, wetting agents, plasticizers, lubricants, preservatives, antifungal agents, anti-algae agents, antibacterial agents, thickeners, leveling agents, dispersants, defoamers, crosslinking agents, silane coupling agents, UV absorbers, light stabilizers, antioxidants, halogen scavengers, dilution solvents, etc.

Examples of the antioxidant include phosphorus-based, sulfur-based, and hindered phenol-based antioxidants. These can be used alone or in combination of two or more. By including such an antioxidant, deterioration of the coating can be suppressed not only under normal conditions but also when the temperature rises due to a fire or the like, and the properties of the carbonized insulation layer formed by the temperature rise can be improved.

The coating material of the present invention preferably has a heating residue of 70 to 98% by weight (more preferably 75 to 95% by weight, and even more preferably 80 to 93% by weight). When the heating residue of the coating material satisfies the above range, it is possible to obtain excellent thick coating properties and good coating workability. This allows sufficient heat resistance protection to be exhibited. The heating residue of the coating material is a value measured by the method of JIS K 5601-1-2, the heating temperature being 105°C, and the heating time being 60 minutes).

In the present invention, the viscosity of the coating material is preferably 5 to 70 Pa·s (more preferably 7 to 60 Pa·s, even more preferably 10 to 50 Pa·s, and particularly preferably 15 to 40 Pa·s). When the viscosity of the coating material satisfies the above range, the coating material has excellent workability and thick coating properties, and a uniform coating can be formed. As a result, sufficient heat resistance protection can be obtained. The viscosity of the coating material is the viscosity at 20 rpm (guideline value at the fifth revolution) measured with a BH type viscometer at a temperature of 23°C immediately after preparation of the coating material (after mixing the base agent and hardener in the case of a two-component type).

In the present invention, by applying a coating material that satisfies the above heating residue and viscosity range to form a coating, it is possible to form a thick coating, which exhibits good adhesion to the substrate and can be stably formed as a uniform coating. Furthermore, when the temperature rises due to a fire or the like, the formed coating exhibits excellent foaming properties, forms a carbonized insulating layer, and can maintain the heat-resistant protective performance of the substrate.

The coating material of the present invention is preferably a two-liquid coating material having a base agent containing the polyol compound (A1) and a curing agent containing the polyisocyanate compound (A2). That is, during distribution, the base agent and the curing agent are stored in separate packages, and are mixed when used (applied). In this case, the heat resistance imparting powder (B) and the water absorbing agent (C), (and if necessary, the high boiling point compound (D), curing catalyst, and additives) may be mixed into at least one of the base agent and the curing agent, but in the present invention, it is preferable to mix them into the base agent. Also, each component can be added when mixing the base agent and the curing agent.

The coating material of the present invention is suitable as a foamable fireproof coating material to be applied to the surface coating of structures such as buildings and civil engineering structures. Specifically, it can be applied to various substrates such as walls, pillars, floors, beams, roofs, stairs, ceilings, and doors. Examples of substrates that can be applied include concrete, mortar, siding boards, extruded boards, gypsum boards, perlite boards, bricks, plastics, wood, metals, steel frames (steel materials), glass, and porcelain tiles. These substrates may already have a coating formed on their surface, may have been subjected to some kind of surface treatment (rust prevention treatment, fire retardant treatment, etc.), or may have wallpaper applied to them.

When applying the coating material of the present invention to a substrate, application tools such as a spray, roller, brush, trowel, etc. can be used. In particular, the coating material of the present invention is particularly suitable for spray coating because it can suppress the reaction between moisture in the air and the polyisocyanate compound (A2) during application.

(Method of forming coating)
The coating formation method of the present invention involves applying the coating material to a substrate to form a coating. The coating method is not particularly limited, and various methods such as brush coating, roller coating, and spray coating (air spray, airless spray) can be used for coating.

The coating material of the present invention is also suitable for spray coating (air spray, airless spray). The coating material of the present invention contains the water absorbent (C) and can suppress the reaction between moisture in the air and the polyisocyanate compound (A2). Therefore, even if the coating material is atomized during spray coating, good curing properties can be ensured and a thick film can be efficiently formed. The coating material can be applied at temperatures of -10 to 45°C, and good coating workability and curing properties can be obtained even at high temperatures of 30°C or higher (even 35°C or higher). Furthermore, although the humidity during coating is not particularly limited, good coating workability, curing properties, and adhesion to the substrate can be obtained even under high humidity conditions (including rainy weather) of humidity 70% Rh or higher (even 80% Rh or higher). As a result, a coating with excellent heat resistance protection can be formed. Furthermore, even if the curing (drying) environment of the coating material after coating is high and humid, good curing properties and adhesion to the substrate can be obtained, and a coating with excellent heat resistance protection can be formed.

When the coating material of the present invention is applied to a substrate, it may be applied in one or several steps by the above method, but it is preferable to apply the coating so that the dry film thickness per step is preferably 300 μm or more (more preferably 400 to 8000 μm). Even when the coating material of the present invention is applied so that the dry film thickness per step exceeds 1000 μm, it is possible to obtain excellent curing properties and adhesion to the substrate, and to form a coating with excellent heat resistance protection. In addition, the coating thickness finally formed may be appropriately set depending on the desired functionality, application site, etc., but is preferably about 0.4 to 8 mm. In addition, the coating material of the present invention has excellent curing properties because the coating is formed by the reaction of the polyol compound (A1) and the polyisocyanate compound (A2) in the presence of the above component (C), and the coating is preferably dried at room temperature, and the interval between the next step is preferably 2 hours or more (more preferably 3 hours or more and up to 30 days).

(Undercoat material)
In addition, in the present invention, if necessary, before applying the coating material, the substrate can be subjected to surface treatment or a primer can be applied. This can improve adhesion to the substrate and corrosion resistance (rust resistance), etc. Surface treatment of the substrate can be performed, for example, by surface treatment with a solvent or acid, or scraping with a disk sander, wire foil, scraper, wire brush, sandpaper, etc.

As the undercoat material, for example, a sealer, a primer, a base conditioner, a surfacer, a putty, etc., as well as a flat-type paint can be applied. These may be either clear type or colored type. They may also be either water-based or solvent-based, and can be appropriately selected depending on the part to be painted, etc., and one or more types can be used. As the undercoat material, for example, it is preferable to include a resin component such as an acrylic resin, a urethane resin, an epoxy resin, etc., and in addition to the above-mentioned resin components, various additives can be blended to an extent that does not affect the effect of the present invention. Examples of such additives include anti-rust pigments, body pigments, coloring pigments, plasticizers, preservatives, anti-mold agents, anti-algae agents, defoamers, leveling agents, pigment dispersants, anti-settling agents, anti-sagging agents, antioxidants, catalysts, crosslinking agents, etc.

The undercoat material can be applied using various methods such as brush coating, roller coating, spray coating, etc. The amount of application is preferably 30 to 500 g/m ² (more preferably 50 to 300 g/m ² ). The number of coats of the undercoat material may be appropriately set depending on the surface condition of the substrate, etc., but is preferably 1 to 2 coats.

(Finishing materials)
In the present invention, a finishing material layer can be laminated on the coating material layer (coating) formed by the above coating material. Such a finishing material layer is not particularly limited as long as it does not inhibit the above coating material layer from foaming and forming a carbonized insulation layer when the temperature rises due to a fire or the like, and any known finishing material can be laminated. Such a finishing material layer can be laminated by applying a topcoat material or by attaching various sheet materials.

As the above-mentioned topcoat material, any of clear type or colored type, glossy type or matte type, hard type or elastic type, thin type or thick type, etc. can be used. In addition, either water-based or solvent-based may be used, and can be appropriately selected according to the desired purpose. In addition, it is preferable that the topcoat material of the present invention contains a resin component. Examples of the form of such a resin include solvent-soluble resin, non-water-dispersed resin, solventless resin, water-dispersed resin, water-soluble resin, etc. Examples of the type of resin include acrylic resin, urethane resin, epoxy resin, vinyl chloride resin, vinyl acetate resin, acrylic silicone resin, fluororesin, silicon resin, polyvinyl alcohol, cellulose derivatives, etc., or composites thereof. These can be used alone or in combination of two or more. In particular, in the present invention, it is preferable to include one or more types selected from urethane resin, epoxy resin, acrylic resin, and acrylic silicone resin.

Furthermore, the resin component may have crosslinking reactivity. When the resin component is a crosslinking reaction type resin, the water resistance, durability, and adhesion of the formed coating are improved, and the occurrence of swelling and peeling of the coating due to rainfall, condensation, etc. and the decrease in heat resistance can be suppressed. Such a crosslinking reaction type resin may be either one that causes a crosslinking reaction by itself or one that causes a crosslinking reaction by a crosslinking agent that is mixed separately. Such crosslinking reactivity can be imparted by combining reactive functional groups such as, for example, a hydroxyl group and an isocyanate group, a carbonyl group and a hydrazide group, an epoxy group and an amino group, an aldo group and a semicarbazide group, a keto group and a semicarbazide group, alkoxyl groups, a carboxyl group and a metal ion, a carboxyl group and a carbodiimide group, a carboxyl group and an epoxy group, a carboxyl group and an aziridine group, or a carboxyl group and an oxazoline group. Among these, it is preferable to include one or more crosslinking reaction type resins selected from a hydroxyl group-isocyanate group, a carbonyl group and a hydrazide group, and an epoxy group and an amino group.

As components other than the resin component of the above-mentioned topcoat material, for example, color pigments, extender pigments, aggregates, etc. can be mixed. By appropriately blending such components, it is possible to express the desired color and texture. There are no particular restrictions on the amount of color pigments, extender pigments, aggregates, etc. mixed, so long as it does not impair the effects of the above-mentioned coating material (foamability, heat-resistant protection, etc.), but it is preferably 1 to 2000 parts by weight (more preferably 5 to 1000 parts by weight) per 100 parts by weight of the solid content of the resin component.

In the present invention, it is particularly preferable to use pigments that are infrared reflective and/or infrared transparent as the color pigments and extender pigments. This can further enhance the effects of heat resistance protection, etc.

Examples of pigments having infrared reflectivity include aluminum flakes, titanium oxide, barium sulfate, zinc oxide, iron oxide, calcium carbonate, silicon oxide, magnesium oxide, zirconium oxide, yttrium oxide, indium oxide, alumina, iron-chromium composite oxide, manganese-bismuth composite oxide, manganese-yttrium composite oxide, black iron oxide, iron-manganese composite oxide, iron-copper-manganese composite oxide, iron-chromium-cobalt composite oxide, copper-chromium composite oxide, copper-manganese-chromium composite oxide, etc., and one or more of these can be used.

Examples of pigments that are infrared transparent include perylene pigments, azo pigments, yellow lead, titanium red, cadmium red, quinacridone red, isoindolinone, benzimidazolone, phthalocyanine green, phthalocyanine blue, cobalt blue, indanthrene blue, ultramarine, and Prussian blue, and one or more of these can be used.

Furthermore, the topcoat material can also contain various additives that can be used in regular paints. Examples of such additives include thickeners, film-forming agents, leveling agents, wetting agents, plasticizers, antifreeze agents, pH adjusters, preservatives, antifungal agents, anti-algae agents, antibacterial agents, dispersants, defoamers, adsorbents, UV absorbers, light stabilizers, antioxidants, fibers, anti-pollution agents, hydrophilizing agents, water repellents, coupling agents, catalysts, etc.

In the coating method of the present invention, the topcoat material can be applied by layering, or two or more types of topcoat materials can be layered. When two or more types of topcoat materials are layered, it is preferable that the first topcoat material (intermediate coat material) contains one or more resin components selected from urethane resin, epoxy resin, acrylic resin, and acrylic silicone resin (particularly preferably urethane resin, epoxy resin, etc.). This can further increase the adhesion between the layers of the coating material and the topcoat material. Furthermore, a topcoat material coating with excellent coating properties can be formed.

The topcoat material may be applied by a known application method, for example, by using various methods such as brush coating, roller coating, and spray coating. The amount of coating is preferably 30 to 5000 g/m ² (more preferably 50 to 3000 g/m ² ). The number of coats of the topcoat material may be appropriately set depending on the surface condition of the substrate, but is preferably 1 to 2 times. In addition, drying may be preferably performed at room temperature.

Examples of the sheet material include decorative films, decorative sheets, sheet building materials, wallpaper, etc. The thickness of the sheet is preferably 0.01 to 30 mm (more preferably 0.05 to 20 mm). These may be attached via a known adhesive (pressure-sensitive adhesive) or the like.

The following examples will clarify the features of the present invention. However, the present invention is not limited to these examples.

The following ingredients were used:

Polyol compound (A1)
(a1-1) Polyether polyol (number average molecular weight 7000, number of functional groups 3, hydroxyl value 24 mgKOH/g)
(a1-2) Polyether polyol (number average molecular weight 5100, functional group number 3, hydroxyl value 33 mgKOH/g)
(a1-3) Polyether polyol (number average molecular weight 4000, functional group number 3, hydroxyl value 43 mgKOH/g)
(a2) Fluorine-containing polyol (chlorotrifluoroethylene-vinyl ether-hydroxyalkyl vinyl ether copolymer, fluorine content 27% by weight, hydroxyl value (solid content) 52 mg KOH/g, solid content 60% by weight, containing aromatic hydrocarbon solvent)

Polyisocyanate compound (A2)
(A2) Biuret type hexamethylene diisocyanate (NCO content 23.5%)

Fire resistance imparting component (B)
(b1) Foaming agent: melamine (b2) Carbonizing agent: pentaerythritol (b3-1) Flame retardant: ammonium polyphosphate (b3-2) Flame retardant: melamine-melam-melem double salt polyphosphate (b4) Filler: titanium oxide (b5) Metal hydrate: aluminum hydroxide (average particle size: 1 μm)
(b6) Fiber: Rock wool fiber (average fiber length 125 μm, average fiber diameter 4.5 μm)
Water absorbing agent (C)
(C1) Powdered synthetic zeolite (average particle size 150 μm or less, A type, average pore size 4 Å)
(C2) Powdered synthetic zeolite (average particle size 150 μm or less, X-type, average pore size 9 Å)
(C3) Synthetic silica gel (average particle size 40 μm, A type, average pore size 24 Å)
High boiling point compound (D)
(D1) Diisononyl phthalate (boiling point 420°C)
・Curing catalyst: organometallic catalyst ・Additive 1: dispersant, defoamer, thickener, etc. ・Additive 2: dilution solvent, etc.

(Examples 1 to 14, Comparative Examples 1 to 3)
<Production of Coating Material>
According to the formulation shown in Table 1, the (A1), (B), (C), (D) components and others (curing catalyst, additives 1 and 2) were mixed in a conventional manner to prepare a base resin. Next, the (A2) component (curing agent) was mixed in such that the NCO/OH equivalent ratio was shown in Table 1, to obtain a coating material.

<Preparation of test specimen>
A coating material was sprayed onto the entire surface of a steel plate (length 150 mm x width 70 mm x thickness 1.6 mm) that had previously been painted with an anti-rust coating under the following coating environment so that the dry film thickness was 1.5 mm. After curing (step intervals as described below), the same coating material was sprayed onto the entire surface of the steel plate so that the dry film thickness was 1.5 mm. The resulting plate was then cured (for 24 hours or 7 days) to prepare a test specimen.
・Painting environment (painting and curing conditions)
[1] Room temperature (25°C, 60% Rh, process interval 16 hours)
[2] High temperature and high humidity (30°C, 90% Rh, 16 hour interval)
[3] High temperature and high humidity (30°C, 90% Rh, 3 hour interval)

<Curability evaluation>
(Coating hardness)
The hardness of the coating was measured using an A-type durometer (rubber hardness tester, manufactured by Asker Corporation). The evaluation criteria are as follows:
A: Hardness 80 or more B: Hardness over 70 and below 80 C: Hardness over 55 and below 70 D: Hardness 55 or less (interlayer adhesion)
After 7 days of curing, cross-cuts were made in the coating of the test specimen with a cutter knife, and tape was applied to the cross-cut areas and then peeled off to evaluate adhesion. The evaluation criteria were a four-level evaluation (excellent: A>B>C>D: poor), with "A" being no abnormality and "D" being interlayer peeling.
It is as follows.

<Heat resistance evaluation>
A coating material was sprayed onto the entire surface of a steel plate (length 150 mm x width 70 mm x thickness 1.6 mm) that had previously been anti-rust painted, under application condition [2], so that the dry film thickness was 1.5 mm, and after curing for 16 hours, the same coating material was sprayed onto the plate so that the dry film thickness was 1.5 mm, and after curing for 7 days, the plate was used as a test specimen, and the following evaluations were carried out. The results are shown in Table 1.
<Heat resistance evaluation>
According to the ISO 5660-1 cone calorimeter method, the expansion ratio and the steel plate backside temperature were measured when radiant heat of 50 kW/ ^m2 was radiated to the surface of the test specimen for 30 minutes using an electric heater (CONEIII, manufactured by Toyo Seiki Co., Ltd.), and the denseness and incinerability were evaluated. The evaluation criteria are as follows.
(Expansion Ratio)
AA: Expansion ratio over 35 times A: Expansion ratio over 25 times and less than 35 times B: Expansion ratio over 20 times and less than 25 times C: Expansion ratio over 15 times and less than 20 times D: Expansion ratio less than 15 times (reverse surface temperature)
AA: Less than 430°C A: 430°C or more and less than 470°C B: 470°C or more and less than 500°C C: 500°C or more and less than 550°C D: More than 550°C (Density evaluation)
The test specimen for which the expansion ratio was measured was cut, and the denseness of the carbonized insulation layer in the cross section was visually confirmed. The evaluation criteria were a four-level evaluation (excellent: A>B>C>D: poor), with "A" being high denseness and "D" being low denseness.
(Ashing property evaluation)
In the heat resistance evaluation 2, the cross section of the carbonized heat insulating layer formed after 30 minutes of radiation heat was checked, and the proportion of the ashed (white) portion was calculated. The evaluation criteria were a four-level evaluation (excellent: A>B>C>D: poor), with "A" being a less ashed portion and "D" being an advanced ashed portion.

Claims (4)

A coating forming method for forming a coating by applying a coating material to a substrate, comprising the steps of:
The coating material is a coating material that forms a carbonized heat insulating layer when its coating is heated to 200° C. or higher, the coating material includes a polyol compound, a polyisocyanate compound, a heat resistance imparting powder, and a water absorbing agent, and the mixing ratio of the polyol compound to the polyisocyanate compound is 1.2 to 3.5 in terms of NCO/OH equivalent ratio,
The coating material is applied in one or more steps under high humidity conditions of 70% Rh or higher, and the dry film thickness per step is 300 μm or more. 2. The method for forming a coating film according to claim 1, wherein the coating material comprises a base agent containing a polyol compound, a heat resistance imparting powder, and a water absorbing agent, and a curing agent containing a polyisocyanate compound. 3. The method for forming a coating film according to claim 1, wherein the water absorbing agent is contained in an amount of 0.5 to 50 parts by weight based on 100 parts by weight of the solid content of the polyol compound. 4. The method for forming a coating film according to claim 1, wherein the heat resistance imparting powder contains at least one selected from the group consisting of a foaming agent, a carbonizing agent, a flame retardant, and a filler.