Coating method of fire-resistant material

Abstract

To provide a coating method of a fire-resistant material which can prevent contamination of the fire-resistant material in an immersion tank even when the coating is formed by a dip coat.SOLUTION: A coating method of a fire-resistant material includes: an immersion step in which an object to be coated (a coated object) 10 is immersed in a fire-resistant material 21 containing a resin and a heat expansion component and placed in an immersion tank 20. An inner surface 20A of the immersion tank 20 are at least partially provided with predetermined spaces D1 to D7 formed between the inner surface 20A and an outer surface of at least parts of the immersed coated object 10 and has a shape corresponding to that of the coated object 10.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for coating a refractory material on a structural material of a building or the like.

Background Art

[0002] Structural materials of buildings, which are important elements in terms of structure, may be coated with refractory materials to protect them from fire. The structural materials of buildings are generally formed of steel materials. Further, the refractory material can expand during a fire to form a heat insulating layer, and can protect the structural material of the building from flames and heat during a fire. Conventionally, as the refractory material, a refractory sheet obtained by previously molding a refractory resin composition containing thermally expandable graphite into a sheet shape is known.

[0003] Also, as the refractory material, a refractory paint is known. As the refractory paint, for example, as disclosed in Patent Document 1, those containing a foaming agent, a carbonizing agent, an inorganic powder, and a binder are known. The refractory paint is generally applied to a structural material or the like after being diluted with an organic solvent for construction.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, the refractory sheet is generally wound around and attached to the structural material of the building at the construction site. However, if the shape of the structural material is complicated, the workability when attaching it to the structural material may decrease.

[0006] On the one hand, refractory coatings can be applied relatively easily even when the shape of the structural material is complex. However, dripping may occur when applying to structural materials, etc., and the drying time and curing time after application take more than a certain time, and the workability is not good. Furthermore, in order for the refractory material to exhibit sufficient refractory performance, a certain thickness or more is required. However, when trying to increase the thickness of the refractory coating, dripping is more likely to occur, and the drying time and curing time are even more necessary, and the workability is likely to decrease.

[0007] Therefore, the present inventors have considered coating the surface of a structural material with a refractory material by dip coating. Dip coating is generally performed by immersing an object to be coated in an immersion tank in which a large amount of coating liquid is stored. However, when immersing a structural material such as steel in a refractory material, the refractory material in the immersion tank is contaminated, resulting in a large amount of raw material loss, and there is also a problem that a refractory material of good quality cannot be stably obtained.

[0008] Therefore, an object of the present invention is to provide a coating method for a refractory material that can prevent the refractory material in the immersion tank from being contaminated and can control the thickness even when formed by dip coating.

Means for Solving the Problems

[0009] The present invention provides the following [1] to [9]. [1] A coating method for a refractory material, comprising a dipping step of immersing an object to be coated in a refractory material containing a resin and a thermally expandable component and placed inside an immersion tank, wherein at least a part of the inner surface of the immersion tank is provided with a predetermined interval with respect to at least a part of the outer surface of the immersed object to be coated, and has a shape corresponding to the object to be coated. [2] The coating method according to [1] above, wherein a coating film of the refractory material having a thickness corresponding to the predetermined interval is formed on at least a part of the outer surface of the object to be coated. [3] The coating method according to [1] above, wherein a coating film of the refractory material is formed on at least a part of the outer surface of the workpiece to be coated, the coating film having a thickness smaller than the distance between the outer surface in the dipping step and the inner surface of the dipping tank. [4] A coating film of the refractory material having a thickness corresponding to the predetermined distance is formed on a part of the outer surface of the workpiece to be coated, and The coating method according to [1] above, wherein a coating film of the refractory material is formed on another part of the outer surface of the workpiece to be coated, the coating film having a thickness smaller than the distance between the outer surface in the dipping step and the inner surface of the dipping tank. [5] The coating method according to any one of [1] to [4] above, wherein the dipping step includes a first dipping step of dipping the heated workpiece to be coated into the refractory material so that a part of the outer surface of the workpiece to be coated is coated. [6] The dipping step includes a second dipping step of dipping the heated workpiece to be coated into the refractory material so that a part of the outer surface of the workpiece to be coated different from the above-mentioned part is coated, The coating method according to [5] above, wherein the second dipping step is performed after the first dipping step. [7] The coating method according to any one of [1] to [6] above, wherein the refractory material further includes a plasticizer. [8] The coating method according to [7] above, wherein the resin is a plastisol dispersed in a sol state in the plasticizer. [9] The coating method according to any one of [1] to [8] above, including a heating step of heating the workpiece to be coated, and dipping the heated workpiece to be coated into the refractory material.

Advantages of the Invention

[0010] According to the present invention, there is provided a coating method for a refractory material capable of preventing contamination of the refractory material in the dipping tank even when a refractory material is formed by dip coating.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0012] Hereinafter, the present invention will be described with reference to embodiments. The method for coating a refractory material of the present invention coats an object to be coated with a refractory material as a coating agent by dip coating.

[0013] (Refractory material) Hereinafter, first, one embodiment of the refractory material used in the present invention will be described in detail. The refractory material according to one embodiment of the present invention is a resin composition containing a resin, a plasticizer, and a thermally expandable component.

[0014] <Resin> The resin used in the refractory material (refractory coating agent) includes a thermoplastic resin. By including a thermoplastic resin as the resin, the refractory material is gently softened when heated, and voids are formed during softening. The plasticizer enters the voids, and thereby the refractory material gradually loses fluidity and changes to a gel state. Therefore, for example, by dip coating the refractory material on a heated object to be coated, a coating film having a certain film thickness can be formed.

[0015] The refractory material of the present invention is a plastisol in which a resin such as a thermoplastic resin exists as particles and is dispersed in a sol state in a plasticizer. By being a plastisol, the refractory material can be easily applied to the object to be coated. Further, in the refractory material, since the thermoplastic resin exists as particles in a sol state, when softened by heating, the plasticizer easily enters the voids, and the workability is easily improved. Furthermore, after the particulate thermoplastic resin is gelled, by further advancing the molten state by heating, the particle shape disappears and it integrates with the plasticizer. Therefore, upon cooling after heating, the refractory material becomes a solid-state (also referred to as "quasi-cured") coating film, and the mechanical strength and the like in the coating film are excellent. Note that after coating the object to be coated, the refractory material needs to be heated for a certain period of time to be quasi-cured. However, since the heating time can be shortened even when the coating film is thick, the workability is good.

[0016] Specific resins used for the refractory material include thermoplastic resins such as polyvinyl chloride-based resins and acrylic resins. These resins can form a sol state in the refractory material, and at the same time, the plasticizer can enter by heating and can be easily gelled, so the workability is further improved more easily. Among these, polyvinyl chloride-based resins are preferred.

[0017] The polyvinyl chloride-based resin (PVC) may be a homopolymer obtained by polymerizing vinyl chloride alone, or may be a copolymer of vinyl chloride as a main component and a monomer copolymerizable therewith. By using a copolymer, it becomes possible to adjust the glass transition temperature and lower the heating temperature described later. Examples of monomers copolymerizable with vinyl chloride include olefin compounds such as ethylene and propylene, vinyl esters such as vinyl acetate and vinyl propionate, unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid, unsaturated monocarboxylic acid esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, N,N-dimethylaminoethyl methacrylate, unsaturated amides such as acrylamide and methacrylamide, unsaturated nitriles such as acrylonitrile and methacrylonitrile, unsaturated dicarboxylic acids such as maleic acid and fumaric acid, their esters and their anhydrides, N-substituted maleimides, vinyl ethers such as vinyl methyl ether and vinyl ethyl ether, vinylidene compounds such as vinylidene chloride, and the like. The monomers copolymerizable with vinyl chloride may be used alone or in combination of two or more. The polyvinyl chloride-based resin preferably contains 80% by mass or more, more preferably 90% by mass or more, of the structural units derived from vinyl chloride.

[0018] The polyvinyl chloride-based resin is preferably a so-called paste PVC dispersed in a sol state in a plasticizer. Examples of commercially available polyvinyl chloride-based resins used for paste PVC include the Leuron Paste (registered trademark) series manufactured by Tosoh Corporation, the ZEST (registered trademark) series of Shin Daiichi Vinyl Co., Ltd., and the Kanevynil (registered trademark) paste series manufactured by Kaneka Corporation.

[0019] The acrylic resin is preferably a (meth)acrylic polymer. The (meth)acrylic polymer is a polymer obtained by polymerizing a monomer having a (meth)acryloyl group (also referred to as a “(meth)acrylic monomer”) or a monomer containing acrylonitrile, and may be a homopolymer obtained by polymerizing one of the (meth)acrylic monomers and acrylonitrile alone, or a copolymer obtained by polymerizing two or more of these monomers. The (meth)acrylic polymer is preferably a polymer obtained by polymerizing a monomer containing a (meth)acrylic monomer.

[0020] Examples of the (meth)acrylic monomer include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and n-octyl (meth)acrylate; cyclic alkyl (meth)acrylates such as cyclohexyl (meth)acrylate; carboxyl group-containing monomers such as methacrylic acid, acrylic acid, 2-succinoyloxyethyl-2-methacryloyloxyethyl succinate of methacrylic acid, 2-maleinoyloxyethyl-2-methacryloyloxyethyl maleate of methacrylic acid, 2-phthaloyloxyethyl-2-methacryloyloxyethyl phthalate of methacrylic acid, and 2-hexahydrophthaloyloxyethyl-2-methacryloyloxyethyl hexahydrophthalate of methacrylic acid; phosphate group-containing (meth)acrylates such as 2-(meth)acryloyloxyethyl acid phosphate; hydroxyl group-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate; carbonyl group-containing (meth)acrylates such as acetoacetoxyethyl (meth)acrylate; amino group-containing (meth)acrylates such as N-dimethylaminoethyl (meth)acrylate and N-diethylaminoethyl (meth)acrylate; acrylamide derivatives such as acrylamidodiacetone acrylamide, N-methylolacrylamide, N-methoxymethylacrylamide, N-ethoxymethylacrylamide, and N-butoxymethylacrylamide; and polyfunctional (meth)acrylates such as (poly)ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate. Among these, the (meth)acrylic monomer preferably contains at least one of alkyl (meth)acrylate, methacrylic acid, and acrylic acid.

[0021] (Meta)acrylic polymers may be polymers of the above-mentioned (meta)acrylic monomers or polymers of (meta)acrylic monomers and acrylonitrile. However, they may also be polymers of at least one of acrylonitrile and (meta)acrylic monomers and monomers other than acrylonitrile and (meta)acrylic monomers. Examples of monomers other than acrylonitrile and (meta)acrylic monomers include styrene derivatives such as styrene, α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, etc., polyfunctional monomers such as divinylbenzene, divinylnaphthalene, divinyl ether, etc., maleic acid derivatives such as itaconic acid, crotonic acid, maleic acid, maleic acid ester, maleic anhydride, etc., fumaric acid derivatives such as fumaric acid, fumaric acid ester, etc., and triaryl isocyanurate.

[0022] (Meta)acrylic polymers preferably have either constituent units derived from (meta)acrylic monomers or constituent units derived from acrylonitrile as the main component, and more preferably have constituent units derived from (meta)acrylic monomers as the main component. Here, the main component means that it is contained in the (meta)acrylic polymer in an amount of 50% by mass or more, preferably 70% by mass or more.

[0023] The acrylic resin is preferably an acrylic sol dispersed in a sol state in a plasticizer. The structure of the particles of the acrylic resin in the acrylic sol is not particularly limited, and examples include a single structure, a core-shell structure of two or more layers, or a gradient structure in which the composition continuously changes from the central part to the outer part of the polymer particles. Among these, a core-shell structure with different compositions for each layer is preferred. By adopting a core-shell structure, the dispersibility in the plasticizer can be enhanced, and the gelling temperature can be appropriately adjusted. Examples of commercially available acrylic resins used in acrylic sols include the Dianal LP series manufactured by Mitsubishi Chemical Corporation.

[0024] The content of the thermoplastic resin in the refractory material is preferably 10 to 60% by mass, more preferably 20 to 50% by mass, and still more preferably 25 to 45% by mass based on the total amount of the refractory material. If the content of the thermoplastic resin is at least the above lower limit, the refractory material will gel appropriately upon heating and is also likely to undergo pseudo-curing. On the other hand, if it is at most the above upper limit, it becomes easier to contain a certain amount or more of components other than the resin, such as plasticizers and thermally expandable components, in the refractory material.

[0025] Also, the resin contained in the refractory material may consist of a thermoplastic resin, but as long as the effects of the present invention are achieved, it may contain resins other than thermoplastic resins. Examples of resins other than thermoplastic resins include thermosetting resins and photocurable resins. In the refractory material, the content of the resin other than the thermoplastic resin may be, for example, 50 parts by mass or less, preferably 30 parts by mass or less, and still more preferably 20 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin. Note that it is preferable that the refractory material does not contain a resin other than the thermoplastic resin, and the content of the resin other than the thermoplastic resin may be 0 parts by mass or more. The resin other than the thermoplastic resin may be contained as a sol in the plasticizer in the refractory material, or may be contained in other forms.

[0026] <Plasticizer> The plasticizer contained in the refractory material can be appropriately selected and used from known ones. Specifically, examples include phthalate plasticizers, aliphatic ester plasticizers, trimellitate plasticizers, and phosphate plasticizers. Note that plasticizers are usually liquids at room temperature (23°C).

[0027] Examples of phthalate plasticizers include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, di-2-ethylhexyl phthalate, di-n-octyl phthalate, diisononyl phthalate, diisodecyl phthalate, butyl benzyl phthalate, and the like. Examples of aliphatic ester plasticizers include adipic acid ester plasticizers such as dimethyl adipate, dibutyl adipate, diisobutyl adipate, dihexyl adipate, di-2-ethylhexyl adipate, diisononyl adipate, di-n-octyl adipate, di-n-decyl adipate, diisodecyl adipate, bis[2-(2-butoxyethoxy)ethyl] adipate, and bis(2-butoxyethyl) adipate, and aliphatic ester plasticizers other than adipic acid ester plasticizers such as di-2-ethylhexyl azelate, dibutyl sebacate, di-2-ethylhexyl sebacate, diethyl succinate, methyl acetyl ricinoleate, and glyceryl triacetate.

[0028] Examples of trimellitic acid ester plasticizers include tri-2-ethylhexyl trimellitate, tri-n-octyl trimellitate, tridecyl trimellitate, triisodecyl trimellitate, di-n-octyl-n-decyl trimellitate, and the like. Examples of phosphate plasticizers include trimethyl phosphate, triethyl phosphate, tributyl phosphate, tri-2-ethylhexyl phosphate, tributoxyethyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl phenyl phosphate, and the like.

[0029] Among the above, phthalate plasticizers and aliphatic ester plasticizers are preferred as plasticizers, and among them, phthalate plasticizers and adipic acid ester plasticizers are more preferred. Also, from the viewpoint of reducing environmental impact, plasticizers other than phthalate plasticizers are preferred, and particularly adipic acid ester plasticizers are preferred. The plasticizer may be used alone or in combination of two or more of the above-mentioned ones.

[0030] The content of the plasticizer in the refractory is preferably 40 to 240 parts by mass, more preferably 60 to 180 parts by mass, and still more preferably 70 to 150 parts by mass with respect to 100 parts by mass of the resin contained in the refractory. When the content of the plasticizer is 40 parts by mass or more, the resin, especially the thermoplastic resin, is easily dispersed in the plasticizer in a sol state, and is easily gelled and pseudo-cured by heating, making it easier to further improve workability. Also, it becomes easier to impart a certain degree of flexibility to the coating film formed from the refractory. On the other hand, when the content of the plasticizer is 240 parts by mass or less, it is possible to prevent the viscosity during coating from becoming low, making it easier to form a coating film with a large film thickness. Also, it becomes easier to suppress the occurrence of dripping after coating, and furthermore, it becomes easier to impart a certain degree of mechanical strength to the coating film.

[0031] <Thermal expansion component> As the thermal expansion component contained in the refractory, thermally expandable layered inorganic substances, foaming agents, etc. can be used. The thermally expandable layered inorganic substance is a conventionally known substance that expands upon heating, and examples thereof include vermiculite, thermally expandable graphite, etc., and thermally expandable graphite is particularly preferred. As the thermally expandable layered inorganic substance, particulate or flaky ones may be used. Since the thermally expandable layered inorganic substance expands upon heating to form voids with a large volume, the coating film formed from the refractory can form a heat-insulating layer with excellent heat-insulating performance during a fire.

[0032] Thermally expandable graphite is obtained by treating powders such as natural flake graphite, pyrolytic graphite, and kish graphite with an inorganic acid and a strong oxidizing agent to form a graphite intercalation compound, and is a kind of crystalline compound that maintains the layered structure of carbon. Examples of the inorganic acid include concentrated sulfuric acid, nitric acid, and selenic acid. Examples of the strong oxidizing agent include concentrated nitric acid, persulfate, perchloric acid, perchlorate, permanganate, dichromate, dichromate, and hydrogen peroxide. The thermally expandable graphite obtained by the acid treatment as described above may be further neutralized with ammonia, lower aliphatic amines, alkali metal compounds, alkaline earth metal compounds, etc.

[0033] The particle size of the thermally expandable graphite is preferably 20 to 200 mesh. When the particle size of the expandable graphite is within the above range, it is easy to expand and create a large volume of voids, so the fire resistance is improved. Also, the dispersibility in the resin is improved. The average aspect ratio of the thermally expandable graphite is preferably 2 or more, more preferably 5 or more, and still more preferably 10 or more. The upper limit of the average aspect ratio of the thermally expandable graphite is not particularly limited, but from the viewpoint of preventing cracking of the thermally expandable graphite, it is preferably 1,000 or less. When the average aspect ratio of the thermally expandable graphite is 2 or more, it is easy to expand and create a large volume of voids, so the flame retardancy is improved. The average aspect ratio of the thermally expandable graphite is the average value of the values obtained by measuring the maximum dimension (major axis) and the minimum dimension (minor axis) for each of 10 thermally expandable graphites and dividing the maximum dimension (major axis) by the minimum dimension (minor axis). The major axis and minor axis of the thermally expandable graphite can be measured using, for example, a field emission scanning electron microscope (FE-SEM).

[0034] The foaming agent used for the thermally expandable component is a foaming agent that foams upon heating, and is preferably a nitrogen-containing compound-based foaming agent. When the nitrogen-containing compound-based foaming agent is heated, it thermally decomposes, sublimates, or vaporizes at a certain temperature or higher, generating gases such as nitrogen and ammonia. Therefore, a coating film formed of a refractory material containing a nitrogen-containing compound-based foaming agent is likely to form a heat-insulating layer with excellent heat-insulating performance during a fire.

[0035] Examples of nitrogen-containing compound blowing agents include phosphate compounds such as ammonium phosphate, ammonium polyphosphate, melamine phosphate, and melamine polyphosphate; melamine compounds such as melamine, methylol melamine, melamine cyanurate, and melamine-formaldehyde resin; azo dicarboxylic acid metal salts such as azodicarbonamide and barium azodicarboxylate; azo compounds such as azobisisobutyronitrile; nitroso compounds such as N,N'-dinitrosopentamethylenetetramine; hydrazine derivatives such as hydrazodicarbonamide, 4,4'-oxybis(benzenesulfonyl hydrazide), and toluenesulfonyl hydrazide; semicarbazide compounds such as toluenesulfonyl semicarbazide, etc. Among these, from the viewpoint of foaming temperature, etc., phosphate compounds and melamine compounds are preferred. By using these blowing agents, it becomes easier to form a heat-insulating layer with good heat-insulating performance in the coating film. In addition, the phosphate compound acts as a catalyst to promote the polymerization of the charring agent described later by heating during a fire, and the phosphate compound itself can form an inorganic phosphate film, enhancing the fire resistance and heat-insulating performance of the coating film. Among the nitrogen-containing compound blowing agents, ammonium polyphosphate and melamine are preferred. The thermally expandable component may be used alone or in combination of two or more.

[0036] The content of the thermally expandable component in the refractory is preferably 10 to 140 parts by mass, more preferably 20 to 100 parts by mass, and still more preferably 30 to 80 parts by mass with respect to 100 parts by mass of the resin contained in the refractory. When the content of the thermally expandable component is 10 parts by mass or more, the coating film formed by the refractory can expand appropriately by heating during a fire, and a heat-insulating layer with excellent heat-insulating performance can be formed. Also, by setting it to 140 parts by mass or less, the ratio of the resin and plasticizer in the refractory can be kept above a certain level, so that the viscosity of the refractory can be adjusted appropriately, and gelation and pseudo-curing can be carried out appropriately when heated. Furthermore, it becomes easier to improve the mechanical strength of the coating film, etc.

[0037] <Carbonizing agent> The refractory material of the present invention may contain a carbonizing agent. When the coating film is heated by a fire and the heat-insulating layer is formed by the above-described thermally expandable component, the carbonizing agent can form a carbonized layer to improve the heat-insulating performance of the heat-insulating layer. The carbonizing agent can be preferably used when a foaming agent, particularly a nitrogen-containing compound-based foaming agent, is used as the above-described thermally expandable component. The carbonizing agent may polymerize upon heating during a fire to form a carbonized layer.

[0038] When the refractory material contains a carbonizing agent, it preferably further contains an acidic component that reacts with the carbonizing agent upon heating to promote polymerization. The acidic component may be an acidic substance that exhibits acidity at normal temperature, or may be a substance that generates an acidic substance by decomposition or the like upon heating. As the acidic component, phosphates, particularly polyphosphates, are preferred. In particular, phosphate-based compounds that can also be used as the above-described foaming agent are preferred, and ammonium polyphosphate is more preferred. That is, when the refractory material contains a carbonizing agent, it preferably contains the above-described phosphate-based compound that also functions as a foaming agent. In addition, when the refractory material contains a carbonizing agent, from the viewpoint of sufficiently promoting foaming during a fire to form a heat-insulating layer having excellent heat-insulating properties, in addition to phosphates, it preferably further contains a foaming agent other than phosphates, and more preferably further contains a melamine-based compound.

[0039] As the carbonizing agent, polyhydric alcohols are preferred, and among them, polyhydric alcohols having three or more hydroxyl groups are more preferred. By using a polyhydric alcohol, particularly a polyhydric alcohol having three or more hydroxyl groups, as the carbonizing agent, a carbonized layer can be appropriately formed by the carbonizing agent. Specific examples of the polyhydric alcohol used as the carbonizing agent include polyhydric alkanols such as pentaerythritol, dipentaerythritol, pentaerythritol, dipentaerythritol, tripentaerythritol, trimethylolpropane, ditrimethylolpropane, and tritrimethylolpropane, or their dimers to tetramers, and polysaccharides such as cellulose.

[0040] The content of the carbonizing agent in the refractory material is preferably 2 to 40 parts by mass, more preferably 4 to 25 parts by mass, and still more preferably 6 to 20 parts by mass with respect to 100 parts by mass of the resin contained in the refractory material. When the content of the carbonizing agent is 2 parts by mass or more, it becomes easier to improve the heat insulation property by the carbonized layer formed by the carbonizing agent. Further, when the content is 40 parts by mass or less, it becomes easier to exhibit an effect commensurate with the content.

[0041] When the refractory material contains a carbonizing agent, as described above, it is preferably contains both a phosphate compound such as ammonium polyphosphate and a melamine compound. When the refractory material contains both a phosphate compound and a melamine compound, the content of the phosphate compound is preferably 5 to 80 parts by mass, more preferably 15 to 65 parts by mass, and still more preferably 25 to 55 parts by mass with respect to 100 parts by mass of the resin contained in the refractory material. Further, the content of the melamine compound is preferably 2 to 25 parts by mass, more preferably 4 to 20 parts by mass, and still more preferably 6 to 15 parts by mass with respect to 100 parts by mass of the resin contained in the refractory material. In addition, when containing both a phosphate compound and a melamine compound, the mass ratio of the content of the melamine compound to the content of the phosphate compound (melamine compound / phosphate compound) is, for example, 1 / 20 to 1, but the content of the phosphate compound is preferably more than the content of the melamine compound, and the above mass ratio is preferably 1 / 15 to 9 / 10, and more preferably 1 / 8 to 1 / 2.

[0042] <Flame retardant> The refractory material may further contain a flame retardant. Examples of the flame retardant include those other than the above-described thermally expandable components, and specifically include phosphate-containing flame retardants, boron-containing flame retardants, metal hydroxide-based flame retardants, halogen-based flame retardants, and other metal-containing compounds.

[0043] Examples of the phosphate-containing flame retardant include phosphates composed of salts of phosphoric acids and at least one selected from metals of Groups IA to IVB of the periodic table. The phosphoric acids are not particularly limited, and may be monophosphoric acids such as phosphoric acid, phosphorous acid, hypophosphorous acid, etc., or may be pyrophosphoric acid, polyphosphoric acid, etc. Examples of the metals of Groups IA to IVB of the periodic table include lithium, sodium, calcium, barium, iron (II), iron (III), aluminum, etc. In addition, the above-mentioned phosphate-containing flame retardant may be subjected to known water resistance improvement treatments such as treatment with a silane coupling agent and coating with a melamine resin.

[0044] Specific examples of the phosphate-containing flame retardant include, for example, monophosphates, pyrophosphates, polyphosphates, etc. The monophosphates are not particularly limited, and examples include sodium salts such as sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium phosphite, disodium phosphite, sodium hypophosphite, etc., potassium salts such as potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium phosphite, dipotassium phosphite, potassium hypophosphite, etc., lithium salts such as lithium dihydrogen phosphate, dilithium hydrogen phosphate, trilithium phosphate, lithium phosphite, dilithium phosphite, lithium hypophosphite, etc., barium salts such as barium dihydrogen phosphate, barium hydrogen phosphate, tribarium phosphate, barium hypophosphite, etc., magnesium salts such as magnesium hydrogen phosphate, magnesium hydrogen phosphate, trimagnesium phosphate, magnesium hypophosphite, etc., calcium salts such as calcium dihydrogen phosphate, calcium hydrogen phosphate, tricalcium phosphate, calcium hypophosphite, etc., zinc salts such as zinc phosphate, zinc phosphite, zinc hypophosphite, etc., and aluminum salts such as aluminum phosphite. The polyphosphates are not particularly limited, and examples include aluminum polyphosphate. As the phosphate-containing flame retardant used in the present invention, aluminum salts such as aluminum phosphite are preferred.

[0045] Examples of the boron-containing flame retardant used in the present invention include borax, boron oxide, boric acid, borate, etc. Examples of boron oxide include diboron trioxide, boron trioxide, diboron dioxide, tetraboron trioxide, tetraboron pentoxide, etc. Examples of borates include borates of alkali metals, alkaline earth metals, elements of Group 4, Group 12, or Group 13 of the periodic table, etc. Specifically, alkali metal borates such as lithium borate, sodium borate, potassium borate, cesium borate, etc., alkaline earth metal borates such as magnesium borate, calcium borate, barium borate, etc., zirconium borate, zinc borate, aluminum borate, etc. The boron-containing flame retardant used in the present invention is preferably a borate, and more preferably zinc borate.

[0046] Examples of the metal hydroxide-based flame retardant include metal hydroxides such as magnesium hydroxide, calcium hydroxide, aluminum hydroxide, iron hydroxide, nickel hydroxide, zirconium hydroxide, titanium hydroxide, zinc hydroxide, copper hydroxide, vanadium hydroxide, tin hydroxide, etc. As the metal hydroxide, aluminum hydroxide is preferred.

[0047] Examples of halogen-based flame retardants include chlorine-based flame retardants and bromine-based flame retardants, with bromine-based flame retardants being preferred. The bromine-based flame retardants are not particularly limited as long as they are compounds containing bromine in their molecular structures, and examples thereof include aromatic brominated compounds. Specific examples of aromatic brominated compounds include, for example, monomeric organic bromine compounds such as hexabromobenzene, pentabromotoluene, hexabromobiphenyl, decabromobiphenyl, hexabromocyclodecane, decabromodiphenyl ether, octabromodiphenyl ether, hexabromodiphenyl ether, bis(pentabromophenoxy)ethane, ethylene bis(pentabromophenyl), ethylene bis(tetrabromophthalimide), tetrabromobisphenol A, etc., brominated polycarbonates such as polycarbonate oligomers produced from brominated bisphenol A, copolymers of the above polycarbonate oligomer and bisphenol A, diepoxy compounds produced by the reaction of brominated bisphenol A and epichlorohydrin, brominated epoxy compounds such as monoepoxy compounds obtained by the reaction of brominated phenols and epichlorohydrin, poly(brominated benzyl acrylate), brominated polyphenylene ether, brominated bisphenol A, condensates of cyanuric chloride and brominated phenol, brominated polystyrenes such as brominated (polystyrene), poly(brominated styrene), crosslinked brominated polystyrene, and halogenated bromine compound polymers such as crosslinked or non-crosslinked brominated poly(α-methylstyrene).

[0048] Examples of metal-containing compounds other than the above compounds include metal oxides such as aluminum oxide, titanium oxide, calcium oxide, magnesium oxide, iron oxide, tin oxide, antimony oxide, titanium oxide, metal carbonates such as calcium carbonate, magnesium carbonate, zinc carbonate, barium carbonate, and metal sulfates such as calcium sulfate, barium sulfate, magnesium sulfate, etc. Among these, metal oxides and metal carbonates are preferred, and titanium oxide and calcium carbonate are more preferred. The flame retardant may be used alone or in combination of two or more of the above-mentioned ones.

[0049] The content of the flame retardant in the refractory material is preferably 5 to 120 parts by mass, more preferably 10 to 100 parts by mass, and even more preferably 20 to 70 parts by mass with respect to 100 parts by mass of the resin contained in the refractory material. When the content of the flame retardant is 5 parts by mass or more, the flame retardancy of the coating film formed by the refractory material with the flame retardant can be improved. Also, when it is 120 parts by mass or less, other components such as resin, plasticizer, and thermal expansion component can be contained in the refractory material in a sufficient proportion.

[0050] <Other additives> The refractory material of the present invention can contain additional components other than the above as necessary, as long as the object of the present invention is not impaired. The type of this additional component is not particularly limited, and various additives can be used. Such additives include, for example, inorganic fillers, lubricants, shrinkage preventers, crystal nucleating agents, coloring agents (pigments, dyes, etc.), ultraviolet absorbers, antioxidants, anti-aging agents, flame retardant aids, antistatic agents, surfactants, vulcanizing agents, dispersants, and surface treatment agents other than the above-mentioned flame retardants and thermal expansion components. The addition amount of the additive can be appropriately selected as long as the object of the present invention is not impaired. These additives may be used alone or in combination of two or more.

[0051] The refractory material of the present invention is preferably substantially solvent-free. Note that substantially solvent-free means that the refractory material does not contain organic solvents and water, or even if it contains them, the amount is trace. Specifically, the total content of water and solvent in the refractory material is preferably 3% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, and still more preferably 0.1% by mass or less with respect to the total amount of the refractory material. Since the refractory material is substantially solvent-free, it does not need to be dried after coating, so the workability is improved, and it is also easy to reduce the environmental load.

[0052] (Manufacturing method of refractory material) The refractory material of the present invention can be obtained by mixing the components constituting the refractory material. For example, a resin, a thermally expandable component, and further a carbonizing agent, a flame retardant, and other additives that are blended as required can be added to a plasticizer and mixed. The refractory material is a plastisol as described above. Therefore, the mixing of the components may be performed by stirring with a known mixer so that the thermoplastic resin can be dispersed in the plasticizer in a sol state. In addition, components other than the thermoplastic resin, for example, a thermally expandable component, a carbonizing agent, a flame retardant, a resin other than the thermoplastic resin, and other additives may be dispersed in the plasticizer or dissolved by the above mixing.

[0053] (Coating method) Hereinafter, the coating method of the refractory material will be described in detail. The coating method of the refractory material of the present invention includes an immersion step of immersing an object to be coated in the refractory material placed inside an immersion tank. At least a part of the inner surface of the immersion tank used in the immersion step is provided with a predetermined interval with respect to at least a part of the outer surface of the immersed object to be coated and has a shape corresponding to the object to be coated. In the present invention, since the shape of the inner surface of the immersion tank has a shape corresponding to the object to be coated, the amount of the refractory material filled inside the immersion tank can be reduced while it is a dip coat. When the refractory material filled in the immersion tank comes into contact with the object to be coated, impurities (for example, those that adhere to the object to be coated with a pseudo-cured product and remain in the immersion tank without completely adhering) may be mixed in. In addition, the refractory material may be heated when the heated object to be coated is immersed, and impurities may be generated by heating and cause contamination. When the contamination progresses, for example, the viscosity of the plastisol changes due to impurities such as pseudo-cured products, making it difficult to control the thickness of the coating film. In the present invention, as described above, by reducing the amount of refractory material filled inside the dipping tank, after the object to be coated is dipped, the amount of refractory material remaining in the dipping tank can be reduced, or the dipping tank can be made free of refractory material remaining therein. Therefore, generation of contaminated refractory material can be suppressed, raw material loss can be reduced, and a coating film of refractory material with good quality can be obtained with high production efficiency.

[0054] Hereinafter, a preferred embodiment in the case where the object to be coated is an H-shaped steel in the coating method of the present invention will be described in detail below as a first embodiment with reference to the drawings.

[0055] <First Embodiment> As shown in Fig. 1(A), an object to be coated 10 made of an H-shaped steel has a plate-shaped web 11 and plate-shaped flanges 12 and 13 respectively connected to both ends of the web 11. In the H-shaped steel, the web 11 is thinner than the flanges 12 and 13. The thickness of each of the flanges 12 and 13 is not particularly limited, but for example, it is 2 to 40 mm, preferably 3 to 23 mm, more preferably 5 to 20 mm. Also, the thickness of the web 11 is not particularly limited, but for example, it is 1 to 20 mm, preferably 2 to 16 mm, more preferably 4 to 12 mm.

[0056] In this specification, the surfaces perpendicular to the thickness direction of the plate-shaped web 11 are defined as surfaces 11A and 11B, the surfaces perpendicular to the thickness direction of the flange 12 are defined as surfaces 12A and 12B respectively, and the surfaces perpendicular to the thickness direction of the flange 13 are defined as surfaces 13A and 13B for explanation. Further, the end faces at one end of the H shape of the H-shaped steel are defined as one end faces 12C and 13C respectively, and the end faces at the other end are defined as other end faces 12D and 13D respectively for explanation. The surfaces 11A, 11B, 12A, 12B, 13A, 13B, one end faces 12C, 13C, and other end faces 12D, 13D each constitute the outer surface of the object to be coated 10 on which the refractory material 21 is coated.

[0057] The coating method of the present invention preferably includes a heating step before the dipping step and a secondary heating step after the dipping step. Also in this embodiment, the heating step, the dipping step, and the secondary heating step may be performed in this order. Hereinafter, each step will be described in detail.

[0058] (Heating Step) The heating step is a step of heating the workpiece 10 before dipping. The workpiece 10 may be heated to a temperature higher than the temperature of the refractory material 21 during dipping. For example, it may be heated to about 45 to 180°C, preferably 60 to 150°C, and more preferably 80 to 140°C. Note that these heating temperatures are the temperatures of the workpiece 10 when it is immersed in the refractory material 21. Also, dipping may be performed two or more times on the same workpiece. However, a heating step may be included between each dipping step (for example, the first and second dipping steps described later) so that the above temperature is reached at each dipping. The method of heating the workpiece 10 is not particularly limited. The workpiece 10 may be heated by putting it into a heating oven, or may be heated by hot air, an infrared heater, or the like.

[0059] (Dipping Step) In this embodiment, the workpiece 10 heated as described above is immersed in the refractory material 21 filled inside the dipping tank 20 as shown in FIGS. 1(A) and (B), so that the refractory material 21 is coated on the workpiece 10, and the coating films 11X, 12X, and 13X of the refractory material 11 are formed. The coating films 11X, 12X, and 13X are coating films formed on the web 11, the flange 12, and the flange 13, respectively (see FIG. 1(C)). The coating film is used as a refractory material to protect the workpiece from fire or the like. In the present invention, by using dip coating by dipping, the outer surface of the workpiece 10 can be appropriately coated with high workability without dripping or the like.

[0060] In the coating method of the present invention, the thermal energy of the heated workpiece 10 is transferred to the refractory material existing around the workpiece, and the refractory material 21 is heated. As a result, the refractory material 21 loses its fluidity and gels to form the coating films 11X, 12X, and 13X. Therefore, the greater the transferred thermal energy, the greater the thickness of the coating films 11X, 12X, and 13X. Thus, the thickness of the coating films 11X, 12X, and 13X can be adjusted by adjusting the heating temperature of the workpiece 10. Further, since the heat capacity of the workpiece 10 varies depending on its shape, size, etc., the thermal energy transferred to the refractory material 21 can result in different thicknesses of the obtained coating film depending on the position where the refractory material 21 is coated and the coating method, even when the workpiece 10 is heated to the same temperature.

[0061] For example, even when the workpiece 10 is heated to the same temperature, the greater the thickness of the workpiece 10, the greater its heat capacity, and thereby the greater the heat transfer to the coated refractory material 21, and a coating film with a large thickness can be formed. Also, when coating only one side of a plate-shaped workpiece 10 (e.g., the web 11), the thermal energy accumulated in the workpiece 10 is concentrated and transferred to the refractory material 21 on one side, and a coating film with a relatively large thickness can be formed. On the other hand, when coating both sides (e.g., both sides of the flanges 12 and 13), the thermal energy accumulated in the workpiece 10 is dispersed and transferred to the refractory materials 21 on both sides, and a coating film with a relatively small thickness can be formed. In contrast, in the present embodiment, as will be described later, the intervals D1 to D7 are adjusted to a size equal to or less than the thickness of the coating film that can be formed by the above thermal energy. Therefore, the coating films 11X, 12X, and 13X formed on the workpiece 10 can be prevented from having their thicknesses fluctuating due to the coating position, coating method, temperature change of the workpiece 10, etc.

[0062] The temperature of the refractory material 21 before dipping (i.e., the temperature of the refractory material 21 inside the dipping tank 20) may be near room temperature, for example, about 0 to 50°C, preferably 10 to 40°C, and more preferably 20 to 30°C. By being coated at a temperature near room temperature, the refractory material 21 can be easily maintained in a sol state with fluidity before adhering to the workpiece 10, so that the workpiece 10 can be coated with high workability, and for example, it is also possible to coat the workpiece 10 without gaps and with a uniform thickness.

[0063] In the dipping process of this embodiment, a first dipping process in which a part of the workpiece 10 is dipped in the refractory material 21 so that a part of the outer surface of the workpiece 10 is coated, and after the first dipping process, the outer surface of the workpiece 10 coated in the first dipping process and another part of the outer surface are coated. It is advisable to perform a second dipping process in which the workpiece 10 is dipped in the refractory material 21. In the first and second dipping processes, the workpiece 10 is preferably heated as described above. Specifically, the workpiece 10, which is an H-shaped steel, may be dipped and coated in the refractory material 21 inside the dipping tank 20 by half in each of the first dipping process and the second dipping process.

[0064] That is, in the first dipping process, as shown in FIG. 1(B), the workpiece 10 is placed into the refractory material 21 inside the dipping tank 20 from one end surface 12C, 13C side of the flange, and the flanges 12, 13 are dipped from the one end surface 12C, 13C over the central part which is the connection part with the web 11 and coated with the refractory material 21. At this time, both surfaces 12A, 12B, 13A, 13B of the flanges 12, 13 will be coated. Also, one surface 11A of the web 11 will also be dipped and coated.

[0065] On one hand, the internal shape of the dipping tank 30 has a shape that conforms to the shape of the workpiece 10 to be dipped, as shown in Fig. 1(A). Specifically, it may be composed of a cavity having recesses 32 and 33 that conform to the shapes of the flanges 12 and 13, and a connecting portion 31 that conforms to the shape of the web 11 and connects the upper ends of the recesses 32 and 33 between the recesses 32 and 33. Also, the dipping tank 20 includes a sheet-like member 25 and a base member 26 that supports the sheet-like member 25. The sheet-like member 25 constitutes the inner surface 20A of the dipping tank 20. Therefore, the above-described recesses 32 and 33 and the connecting portion 31 are formed inside it. The sheet-like member 25 may be composed of a sheet that has high mold release properties with respect to the refractory material 21 and has flexibility. For example, it may be composed of a known mold release sheet such as a silicone sheet or a fluororesin sheet. The sheet-like member 25 is used as a mold release sheet for releasing the workpiece 10 having a coating film formed thereon from the dipping tank 20, as will be described later.

[0066] The base member 26 is composed of four members and includes central portions 26A and 26B where the connecting portion 31 is provided upward, and both side portions 26C and 26D provided on both sides of the central portions 26A and 26B. The portion corresponding to the recess 32 is formed by the central portion 26A and the side portion 26C, and the portion corresponding to the recess 33 is formed by the central portion 26B and the side portion 26D. A clearance 27 is provided between each of the side portion 26C, the central portion 26A, the central portion 26B, and the side portion 26D, and the central portions 26A and 26B are displaceable in the left-right direction in Fig. 1. Although not shown, a sponge or the like may be appropriately inserted into the clearance 27.

[0067] The internal shape of the immersion tank 20 (i.e., the shape of the cavity) should have a size slightly larger than that of the workpiece 10 so that a predetermined interval is formed between the inner surface 20A of the immersion tank 20 and the outer surface of the immersed workpiece 10, as shown in FIG. 1(B). That is, as shown in FIG. 1(B), the intervals D1 and D2 between the surfaces 12A and 12B of the flange 12, which are the surfaces to be coated, and the side surface of the recess 32, the interval D3 between one end surface 12C and the bottom surface of the recess 32, the intervals D4 and D5 between the surfaces 13A and 13B of the flange 13 and the side surface of the recess 33, the interval D6 between one end surface 13C and the bottom surface of the recess 33, and the interval D7 between the surface 11A of the web 11 and the upper surface of the connecting portion 31 should be predetermined intervals.

[0068] Here, it is preferable that the intervals D1 to D7 are the same as each other, but they may be different from each other. Also, in this embodiment, the intervals D1 to D7 are sized corresponding to the thickness of the coating films 11X, 12X, and 13X to be formed, but are preferably 0.3 to 10 mm, more preferably 0.8 to 8 mm, and even more preferably 1 to 6 mm. Note that the workpiece 10 may be suspended from a support member (not shown) or placed on the inner surface 20A of the immersion tank 20 so that the intervals D1 to D7 are within the above ranges.

[0069] In this embodiment, in the first immersion step, the heated workpiece 10 is immersed in the refractory material 21, and the thermal energy of the workpiece 10 is transferred to the refractory material 21 to form a coating film of a certain thickness. However, the above intervals D1 to D7 are sized to be less than or equal to the thickness of the coating film that can be formed by thermal energy. Thereby, the coating films 11X, 12X, and 13X are all formed by the inner surface 20A of the immersion tank 20. Therefore, coating films 11X, 12X, and 13X having a thickness corresponding to the intervals D1 to D7 are formed on the outer surface of the workpiece 10. That is, for example, if the interval D7 is 5 mm, the thickness of the coating film 11X formed on the surface 11A of the web 11 is also approximately 5 mm. Thus, in this embodiment, the inside of the immersion tank 20 where the workpiece 10 and the refractory material 21 are arranged is slightly larger than the workpiece 10 by the thickness of the coating film to be formed.

[0070] The coated object 10 with the films 11X, 12X, and 13X formed thereon may be removed from the dipping tank 20. At this time, in the support member 26, as shown in FIG. 1(C), the central portions 26A and 26B may be displaced so as to be separated from the outer portions 26C and 26D, respectively. When the central portions 26A and 26B are displaced, the recesses 32 and 33 formed by the sheet-like member 25 are partially not supported by the support member 26, so that the recesses 32 and 33 formed by the sheet-like member 25 can be easily deformed. Therefore, the coated object 10 with the films 11X, 12X, and 13X formed thereon can be easily demolded from the dipping tank 20 constituting the mold by deforming the recesses 32 and 33 and removed from the dipping tank 20.

[0071] In this embodiment, the refractory material 21 inside the dipping tank 20 only needs to be filled inside the dipping tank 20 up to the height position H (see FIG. 1(B)) at which the coated object 10 can coat the outer surfaces of half of the one end surfaces 12C and 13C sides of the flanges 12 and 13 and one surface 11A of the web 11 when the coated object 10 is placed inside the dipping tank 20. Therefore, the refractory material 21 does not need to be filled up to the height position H before the coated object 10 is dipped, and may be filled up to a position lower than the height position H as shown in FIG. 1(A). The refractory material 21 filled in this way, as shown in FIG. 1(B), when the coated object 10 is placed inside the dipping tank 20, is pushed aside by the coated object 10 and reaches the height position H so that the outer surfaces of the one end surfaces 12C and 13C sides of the flanges 12 and 13 and the surface 11A of the web 11 can be coated. Also, generally all of the refractory material 21 inside the dipping tank 20 may be coated on the coated object 10, and when removed from the coated object 10, as shown in FIG. 1(C), there may be no refractory material 21 remaining inside the dipping tank 20.

[0072] In the above description, the first immersion process has been typically described and illustrated in FIG. 1. However, the second immersion process is performed in the same manner as the first immersion process. In the second immersion process, half of the other end surfaces 12D and 13D of the flanges 12 and 13, and the surface 11B of the web 11 are coated with the refractory material 21. Then, as shown in FIG. 1(D), the entire coated object 10 will be coated.

[0073] (Secondary heating process) The secondary heating process is a process of further heating the coated object 10 (hereinafter also referred to as "secondary heating") after the above immersion process. The refractory material 21 on the coated object 10 is heated, so that the thermoplastic resin further melts, the particle shape disappears, and it integrates with the plasticizer. Therefore, the refractory material 21 becomes a pseudo-cured solid coating film after cooling after secondary heating, and the obtained coating films 11X, 12X, and 13X have excellent mechanical strength and the like. In secondary heating, the refractory material 21 may be heated to about 80 to 180 °C, preferably 100 to 150 °C. Also, secondary heating is preferably performed until the particle shape of the thermoplastic resin in the refractory material 21 disappears. There is no limit to the heating time, but for example, it may be performed for about 1 to 60 minutes, preferably 2 to 30 minutes. The method of further heating the refractory material 21 on the coated object 10 is not particularly limited. The coated object with the refractory material coated may be put into a heating oven for heating, or it may be heated by hot air, an infrared heater, or the like.

[0074] The thickness of the coating film formed by the above coating method is preferably 0.3 to 10 mm, more preferably 0.8 to 8 mm, and even more preferably 1 to 6 mm. When the thickness of the coating film is 0.3 mm or more, appropriate fire resistance can be imparted by the coating film. Also, when it is 10 mm or less, it is possible to prevent the coating film from becoming thicker than necessary, and a coating film can be formed with high workability.

[0075] In the dipping method according to the above-described first embodiment, since substantially all of the refractory material 21 inside the dipping tank 20 is coated on the workpiece 10 to be coated, it is possible to suppress the generation of the contaminated refractory material 21. Also, since the thicknesses of the coating films 11X, 12X, and 13X are determined by the distance between the outer surface of the workpiece 10 to be coated and the inner surface 20A of the dipping tank 20, the thickness of the coating film can be freely designed. Therefore, for example, by making the distances D1 to D7 between the outer surface of the workpiece 10 to be coated and the inner surface 20A of the dipping tank 20 constant, it is also possible to form a uniform coating film.

[0076] In this embodiment, the dipping tank 20 is configured with a sheet-like member 25 provided on a base member 26, and the refractory material 21 is filled on the sheet-like member 25. However, as long as the workpiece 10 with the coating film formed thereon can be demolded, the sheet-like member 25 may be omitted. Further, a sheet or a film may be provided on the sheet-like member 25, and two or more sheet-like members may be provided, or another configuration may be adopted. By further providing a sheet or a film, it becomes easier to smooth the surface of the coating film.

[0077] <Second Embodiment> In the first embodiment described above, the dipping tank 20 is used as a mold for shaping the surface of the coating film by its inner surface 20A. However, it is not necessary for all surfaces of the coating film to be shaped by the inner surface 20A of the dipping tank 20. A part of the coating film may be shaped by the inner surface 20A of the dipping tank 20, and the dipping tank 20 may be used as a semi-mold in which a part of the coating film is not shaped by the inner surface 20A of the dipping tank 20. The form in which the dipping tank 20 is used as a semi-mold will be described below as a second embodiment by taking the case where the workpiece 10 is of the H type as an example. In the following description after the second embodiment, the description of the same configuration as that of the first embodiment will be omitted.

[0078] Also in the second embodiment, the dipping process includes the first and second dipping processes. In each dipping process, as in the first embodiment, one surface of the web 11 and half of the flanges 12 and 13 are dipped into the refractory material 21 (see Fig. 2(B)). On the other hand, as shown in Fig. 2(A), the internal shape of the dipping tank 30 has a shape adapted to the shape of the workpiece 10 to be coated, similar to the first embodiment, and has recesses 32 and 33 and a connecting portion 31.

[0079] However, in the second embodiment, the dipping tank 20 is not provided with a sheet-like member, and the recesses 32 and 33 and the connecting portion 31 are formed in the base member 26. In this embodiment, as will be described later, the inner surfaces of the recesses 32 and 33 are not used as a mold for forming the coating film, and since it is not necessary to release the flanges 12 and 13 from the recesses 32 and 33, it is not necessary to provide a sheet-like member which is a release sheet.

[0080] The internal shape of the dipping tank 20 may have a shape slightly larger than the workpiece 10 to be coated so that a predetermined interval is formed between the inner surface 20A of the dipping tank 20 and the outer surface of the dipped workpiece 10 as shown in Fig. 2(B). That is, as shown in Fig. 2(B), there may be intervals D1 to D7 between the outer surface of the workpiece 10 and the inner surface 20A of the dipping tank 20, similar to the second embodiment. Here, the upper surface of the connecting portion 31 is used as a mold, similar to the first embodiment, and the coating film 11X may be formed by the upper surface of the connecting portion 31. Therefore, a coating film 11X having a thickness corresponding to the interval D7 between the surface 11A of the web 11 and the upper surface of the connecting portion 31 (i.e., the inner surface 20A of the dipping tank 20) is formed. Therefore, the thickness of the interval D7 is preferably a size corresponding to the coating film 11X, preferably 0.3 to 10 mm, more preferably 0.8 to 8 mm, and even more preferably 1 to 6 mm.

[0081] On the other hand, the inner surfaces of the recesses 32 and 33 are not used as a molding die, and coating films 12X and 12Y smaller than the intervals D1 to D6 between the surfaces 12A, 12B, 13A, and 13B of the flanges 12 and 13 and the inner surface 20A of the recesses 32 and 33 (immersion tank 20) are formed. That is, the intervals D1 to D6 are larger than the thicknesses of the coating films 12X and 12Y. Specifically, it is preferably 0.5 mm or more, more preferably 1 mm or more, and even more preferably 1.5 mm or more.

[0082] Also, in the present embodiment, by making the intervals D1 to D6 below a certain level, the amount of the refractory material 21 to be put into the immersion tank 20 can be appropriately suppressed. From such a viewpoint, the intervals D1 to D6 are preferably 20 mm or less, more preferably 12 mm or less, and even more preferably 10 mm or less. The intervals D1 to D6 may be the same as or different from each other.

[0083] Also in the present embodiment, in the first and second immersion steps, the heated workpiece 10 is immersed in the refractory material 21, and by being immersed, heat energy is transferred to the refractory material 21, and the refractory material 21 is gelled to form a coating film of a certain thickness. Also, as described above, the intervals D1 to D6 between the outer surfaces of the flanges 12 and 13 and the inner surface 20A of the immersion tank 20 are larger than the thickness of the coating film that can be formed by heat energy. Therefore, the coating films 12X and 13X formed on the outer surfaces of the flanges 12 and 13 become coating films of a certain thickness formed by the above gelation, and the surfaces of the coating films 12X and 13X are surfaces that are not formed by the inner surface of the immersion tank 20. And the thicknesses of the coating films 12X and 13X are smaller than the intervals D1 to D6. On the other hand, the interval D7 is sized to be equal to or less than the thickness of the coating film that can be formed by heat energy. Therefore, the coating film 11X on the outer surface of the web 11 is formed by the inner surface (upper surface of the connecting portion 31) of the immersion tank 20 and has a thickness corresponding to the interval D7. That is, in the present embodiment, inside the dipping tank 20 where the workpiece 10 and the refractory material 21 are arranged, a part thereof (i.e., the part where the web 11 is arranged) is slightly larger than the workpiece 10 by the thickness of the coating film 11X to be formed. Also, another part thereof (the part where the flanges 12 and 13 are arranged) is also slightly larger than the workpiece 10, and the size thereof is larger than the thickness of the coating films 12X and 13X to be formed.

[0084] The workpiece 10 with the coating films 11X, 12X, and 13X formed thereon may be removed from the dipping tank 20. In the present embodiment, the coating films 12X and 13X are not formed by the inner surface 20A of the dipping tank 20, and a liquid refractory material 21 exists between the coating films 12X and 13X and the inner surface 20A of the dipping tank 20. Therefore, the workpiece 10 with the coating films 11X, 12X, and 13X formed thereon can be easily removed from the dipping tank 20 by pulling it upward from the dipping tank 20. Also, not all of the refractory material 21 inside the dipping tank 20 is coated on the workpiece 10. When the workpiece 10 is removed, as shown in FIG. 2(C), a part of the refractory material 21 remains inside the dipping tank 20. The remaining refractory material 21 inside the dipping tank 20 may be used in the next dipping process. The remaining refractory material 21 can be, for example, mixed with virgin refractory material and used to minimize the contamination of the refractory material 21 due to repeated use.

[0085] In the above description, the first dipping process has been typically described and illustrated in FIG. 2. However, in the present embodiment, the second dipping process is performed in the same manner as the first dipping process. In the second dipping process, it is preferable that half of the other end surfaces 12D and 13D sides of the flanges 12 and 13, and the surface 11B of the web 11 are coated with the refractory material 21.

[0086] As described above, in this embodiment, since the gaps D1 to D6 are larger than the coating films 12X and 13X, even if the position where the workpiece 10 is immersed is slightly deviated from the designed position, the coating films 12X and 13X having a certain thickness can be formed. Therefore, since the workpiece 10 does not need to be immersed after being aligned with high precision, workability is improved. Further, in this embodiment, since the coating films 12X and 13X are formed by the same coating method (double-sided coating) for members (flanges 12 and 13) having the same thickness, their thicknesses are substantially uniform. Therefore, by making the size of the interval D7 match the thickness of the coating films 12X and 13X, the thicknesses of the coating films 11X, 12X, and 13X formed on the entire workpiece 10 can be made substantially uniform.

[0087] Note that, in the second embodiment described above, the coating film 11X on the outer surface of the web 11 is formed by the inner surface 20A of the immersion tank 20, has a thickness corresponding to the interval D7, and the coating films 12X and 13X on the outer surfaces of the flanges 12 and 13 are not formed by the inner surface 20A of the immersion tank 20, and the thicknesses of the coating films 12X and 13X are smaller than the intervals D1 to D6. However, in the second embodiment, as long as a coating film having a thickness corresponding to the interval between the outer surface and the inner surface 20A is formed on a part of the outer surface of the workpiece 10, and a coating film smaller than the interval between the outer surface and the inner surface 20X is formed on another part of the outer surface of the workpiece 10, any aspect may be adopted.

[0088] Furthermore, in this embodiment, the dipping tank 20 was used as a semi-molding die for molding the coating film 11X formed on the web 11 with the inner surface 20A (the upper surface of the connecting portion 31). However, the coating film 11X may not be molded by the inner surface 20A, and the dipping tank 20 may not be used as a molding die. That is, in this embodiment, a refractory coating film smaller than the distance D7 between the surface of the web 11 and the inner surface 20A (the upper surface of the connecting portion 31) of the dipping tank 20 may be formed on the surface of the web 11. In this case, the distance D7 is larger than the thickness of the coating film 11X. Specifically, similar to the distances D1 to D6, it is preferably 20 mm or less, more preferably 12 mm or less, and even more preferably 10 mm or less. The lower limit may be the same as that of the distances D1 to D6 above.

[0089] Also, the workpiece 10 to be coated of the present invention is not limited to H-shaped steel and can be applied to various types of steel materials. It can be applied to steel materials of any shape such as round steel, square steel, L-shaped steel, angle steel, and U-shaped steel. Even if the workpiece 10 to be coated is a steel material other than H-shaped steel, a coating film may be formed by the methods of the first and second embodiments.

[0090] <The Third Embodiment> FIG. 3 shows a coating method when the workpiece 10 to be coated is round steel. Hereinafter, the coating method when the workpiece 10 to be coated is round steel will be described as the third embodiment. Also in the fourth embodiment, similar to the first and second embodiments, the dipping tank 20 is preferably provided with a distance D8 between the inner surface 20A of the dipping tank 20 and the outer surface of the workpiece 10 to be dipped, and has a shape corresponding to the workpiece 10 to be coated. Further, the dipping process includes the first and second dipping processes, and the workpiece 10 to be coated is preferably dipped and coated in the refractory material 21 in two halves. Therefore, the inner surface 20A of the dipping tank 20 preferably has a semi-circular cross section corresponding to the outer surface of the round steel to be dipped.

[0091] In this embodiment, the interval D8 is preferably not greater than the thickness of the coating film that can be formed by thermal energy. As a result, the coating film 10X formed on the workpiece 10 is shaped by the inner surface 20A of the dipping tank 20. Therefore, a coating film 10X having a thickness corresponding to the interval D8 is formed on the outer surface of the workpiece 10. That is, for example, if the interval D8 is 5 mm, the thickness of the coating film 10X formed on the surface of the workpiece 10 is also approximately 5 mm. Note that the specific preferred range of the interval D8 is the same as the intervals D1 to D7 described in the first embodiment, and thus the description thereof is omitted.

[0092] In the first dipping step, as shown in FIGS. 3(B) and 3(C), a semi-annular coating film 10X is formed on the outer surface of the workpiece 10 dipped in the dipping tank 20. Further, in the second dipping step, the outer surface of the workpiece 10 on which the coating film 10X has not been formed in the first dipping step is coated by dipping, and a semi-annular coating film is similarly formed. As a result, as shown in FIG. 3(D), the workpiece 10 made of round steel is coated with the coating film 10X over the entire circumference.

[0093] However, the interval D8 may be larger than the thickness of the film that can be formed by thermal energy. That is, a coating film 10X having a thickness smaller than the interval D8 may be formed on the outer surface 10A of the workpiece 10. In the case of round steel, thermal energy is evenly transferred to the surrounding refractory material 21. Therefore, even if the interval D8 is made larger than the thickness of the formed coating film 10X, a coating film 10X having a uniform thickness can be formed on the outer surface 10A of the workpiece 10.

[0094] <Fourth Embodiment> FIG. 4 shows a coating method in the case where the workpiece 10 is square steel. Hereinafter, the coating method in the case where the workpiece 10 is square steel will be described as the fourth embodiment. Also in the fourth embodiment, the immersion tank 20 preferably has a shape corresponding to the workpiece to be coated such that an interval D9 is provided between the inner surface 20A of the immersion tank 20 and the outer surface of the immersed workpiece 10, similar to the first to third embodiments. Further, the immersion process preferably includes the first and second immersion processes, and the workpiece 10 is preferably immersed and coated in the refractory material 21 in two halves. Therefore, the inner surface 20A of the immersion tank 20 is preferably rectangular corresponding to the outer surface of the square steel. However, since the corners of the square steel are generally formed by curved surfaces, the corners of the bottom surface 20E of the immersion tank 20 are also preferably formed by curved surfaces in accordance with the corners 10E of the workpiece 10 to be coated.

[0095] In this embodiment, in the first immersion process, as shown in FIGS. 4(B) and 4(C), a coating film 10X having a U-shaped cross section is formed on the outer surface of the workpiece 10 immersed in the immersion tank 20. Also, the corner 10Y of the coating film 10X formed on the corner 10E having a curved surface is also curved. Further, in the second immersion process, the outer surface of the workpiece 10 on which the coating film 10X was not formed in the first immersion process is similarly coated by immersion, and the workpiece 10 made of square steel is coated over the entire circumference (see FIG. 4(D)).

[0096] Also in this embodiment, the interval D9 is preferably not greater than the thickness of the film that can be formed by thermal energy. Thereby, the coating film 10X is formed by the inner surface 20A of the immersion tank 20, and thus, a coating film 10X having a thickness corresponding to the interval D9 is formed on the outer surface of the workpiece 10 to be coated. That is, for example, if the interval D9 is 5 mm, the thickness of the coating film 10X formed on the surface of the workpiece 10 to be coated is also approximately 5 mm. The specific preferred range of the interval D9 is the same as the intervals D1 to D7 described in the first embodiment, and thus the description thereof is omitted.

[0097] However, also in this embodiment, the interval D9 may be larger than the thickness of the coating film that can be formed by thermal energy. That is, a coating film 10X having a thickness smaller than the interval D9 may be formed on the outer surface 10A of the workpiece 10. However, in the case of square steel, the refractory material 21 that contacts the corner portion 10E receives less thermal energy transferred than the refractory material 21 that contacts the other portions. Therefore, when the interval D9 is increased, the thickness of the coating film 10X at the corner portion 10E becomes thinner as shown in FIG. 5. Thus, in this embodiment, it is preferable that a coating film 10X having a thickness corresponding to the interval D9 is formed on the outer surface of the workpiece 10 as shown in FIG. 4.

[0098] <Modification example> In addition, in each of the above embodiments, although the coating film is formed on the entire outer surface of the workpiece 10, it is not necessary to form the coating film on all the outer surfaces, and the coating film may not be formed on some of the outer surfaces. For example, in the case of H-shaped steel, the coating film may not be formed on the outer surface 12A of the flange 12. In such a case, as shown in a modification example (see FIG. 6) of the first embodiment, when the workpiece 10 is immersed in the refractory material 21, the surface 12A of the flange 12 is brought into close contact with the inner surface 20A (the side surface of the concave portion 32) of the immersion tank 20, and the other configurations may be the same as those described in the first embodiment. In this modification example, since the surface 12A of the flange 12 is in close contact with the inner surface 20A of the immersion tank 20, the refractory material 21 filled inside the immersion tank 20 is prevented from entering between the surface 12A and the inner surface 20A of the immersion tank 20, and a workpiece 10 on which the coating film is not formed on the surface 12A can be obtained. Note that, also in the second embodiment, similar to the first embodiment, the surface 12A may be brought into close contact with the inner surface 20A of the immersion tank 20 so that the coating film is not formed on the surface 12A. Also in other embodiments, the workpiece 10 may have an outer surface on which the coating film is not formed.

[0099] In each of the above embodiments, the immersion process includes the first and second immersion processes, and the number of immersions is shown as two times. However, the second immersion process may be omitted, and the number of immersions may be one time. Also, the number of immersions in the immersion process may be three or more. The immersion process may include a third immersion process in addition to the first and second immersion processes, or may include even more immersion processes. Also, in each of the above embodiments, the inner surface 20A of the immersion tank 20 has a corresponding shape with respect to the entire outer surface of the work piece 10 to be coated. However, it is not necessary for the inner surface 20A to have a corresponding shape with respect to the entire outer surface of the work piece 10 to be coated, and it may not have a corresponding shape with respect to some of the outer surfaces.

[0100] In each of the above embodiments, the case where the refractory material contains a resin containing a thermoplastic resin, a plasticizer, and a thermally expandable component and is a plastisol has been described. However, the refractory material is not necessarily limited to the above configuration, and as long as it contains a resin and a thermally expandable component, refractory materials with other configurations may be used. In that case, in each of the above embodiments, the heating process and the secondary heating process may be omitted, or the steps of the heating process and the secondary heating process may be appropriately added according to the type of resin and the properties of the refractory material.

[0101] In the above description, an example where the work piece to be coated is a steel material has been described. However, the work piece to be coated may be other than a steel material, and examples include wood, metal materials other than steel, concrete, bricks, concrete blocks, stones, etc. However, the work piece to be coated is preferably a metal material such as a steel material, and more preferably a steel material. Metal materials such as steel materials are easy to heat and hardly deform even when heated. Therefore, for example, by coating a refractory material on a heated metal material, it becomes easy to form a thick coating film without deforming the work piece to be coated.

[0102] The use of the work piece to be coated is not particularly limited, but it is preferably a member that needs to be protected in case of a fire. Specifically, examples include structural materials of buildings and bodies of various vehicles. That is, the refractory material of the present invention is preferably used for structural materials of buildings and bodies of vehicles. Note that the structural material is a member that forms the framework in a building and is a member that bears the forces applied to the building such as the weight and load of the members constituting the building.

[0103] The structural materials of building materials will be heated during a fire, resulting in a decrease in strength, or will burn, causing the building to collapse. However, by forming and coating a coating film on these surfaces by the coating method of the present invention, a heat insulation layer will be formed on these surfaces when a fire occurs. Therefore, heating and combustion are suppressed, and the collapse of the building can be prevented. In addition, the formation of the coating film on the workpiece described above may be carried out at the construction site when the workpiece is a building, but it is preferably carried out in a factory or the like. When the workpiece is a building, it is advisable to transport the coated workpiece coated in the factory to the construction site.

[0104] Also, by forming and coating a coating film on the surface of the members constituting the vehicle body by the coating method of the present invention, when a fire occurs in a part of the vehicle, the spread of the fire to the whole vehicle can be prevented. Therefore, in a vehicle equipped with a battery such as a lithium-ion battery (LIB), even when the battery undergoes thermal runaway and catches fire due to an internal short circuit or the like, the spread of the fire to the whole vehicle can be prevented. In addition, the vehicle may be a vehicle such as an automobile, a train, a steam locomotive, a railway vehicle such as a train, a civil engineering heavy machine such as a forklift or an excavator, a cart, an amusement park vehicle, or a vehicle other than a ship or an airplane. Among these, an automobile is preferred. Also, the refractory material is preferably used for underbody coat applications. Therefore, the workpiece is preferably the underbody of an automobile.

Explanation of symbols

[0105] 10 Workpiece 11 Web 12, 13 Flange 10X, 11X, 12X, 13X Coating film 11A, 11B, 12A, 12B, 13A, 13B Surfaces (outer surfaces of the workpiece) 12C, 13C One end face 12D, 14D The other end face 20 Immersion tank 20A Inner surface of the immersion tank 21 Refractory material D1 to D9 at a predetermined interval

Claims

1. A coating method for a refractory material, comprising a dipping step of dipping an object to be coated into the refractory material containing a resin and a thermally expandable component and placed inside a dipping tank, wherein at least a part of the inner surface of the dipping tank is provided with a predetermined interval with respect to at least a part of the outer surface of the dipped object to be coated, and has a shape corresponding to the object to be coated.

2. The coating method according to claim 1, wherein a coating film of the refractory material having a thickness corresponding to the predetermined interval is formed on at least a part of the outer surface of the object to be coated.

3. The coating method according to claim 1, wherein a coating film of the refractory material smaller than the interval between the outer surface and the inner surface of the dipping tank in the dipping step is formed on at least a part of the outer surface of the object to be coated.

4. A coating film of the refractory material having a thickness corresponding to the predetermined interval is formed on a part of the outer surface of the object to be coated, and a coating film of the refractory material smaller than the interval between the outer surface and the inner surface of the dipping tank in the dipping step is formed on another part of the outer surface of the object to be coated. The coating method according to claim 1.

5. The coating method according to claim 1, wherein the dipping step includes a first dipping step of dipping the heated object to be coated into the refractory material so that a part of the outer surface of the object to be coated is coated.

6. The dipping step includes a second dipping step of dipping the heated object to be coated into the refractory material so that a part different from a part of the outer surface of the object to be coated is coated, and the second dipping step is performed after the first dipping step. The coating method according to claim 5.

7. The coating method according to claim 1, wherein the refractory material further contains a plasticizer.

8. The coating method according to claim 7, wherein the resin is a plastisol dispersed in a sol state in the plasticizer.

9. including a heating step of heating the object to be coated, The coating method according to any one of claims 1 to 8, wherein the heated object to be coated is immersed in the refractory material.

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