Urethane resin composition, polyurethane foam, method for producing polyurethane foam, and structure

Abstract

This urethane resin composition contains a polyol compound, a polyisocyanate compound, a catalyst, a foaming agent, and mica.

Description

Urethane resin composition, polyurethane foam, method for producing polyurethane foam, and composite

[0001] The present invention relates to a urethane resin composition, a polyurethane foam and a method for producing the same, and a structure including the polyurethane foam.

[0002] Structural materials and walls of buildings, which are important structural elements, require fire resistance to protect the structural materials in the event of a fire and to prevent the spread of fire between fire compartments. Therefore, fire-resistant materials are sometimes used for structural materials and walls. Conventionally, a widely known fire-resistant material is a fire-resistant sheet obtained by previously molding a fire-resistant resin composition containing thermally expandable graphite into a sheet shape.

[0003] Furthermore, polyurethane foams are widely used to improve thermal insulation inside buildings. Various methods have been studied to impart self-extinguishing properties to polyurethane foams to prevent the spread of fire in the event of a fire. For example, Patent Document 1 discloses blending a flame retardant such as a phosphate ester or red phosphorus into a urethane resin composition for forming polyurethane foam.

[0004] International Publication No. 2014 / 112394

[0005] Conventional fire-resistant sheets are attached to structural materials, for example, by wrapping them around them. However, if the structural material has corners or other complexities, the workability of attaching them to the structural material may be reduced. Polyurethane foam, on the other hand, can be formed by spraying or other methods, improving workability. However, there have been few studies on polyurethane foam to make it fire-resistant, taking into account its behavior during a fire. Generally, when heated at temperatures around 800 to 1000°C, almost no residue remains.

[0006] Therefore, an object of the present invention is to provide a urethane resin composition capable of forming a polyurethane foam having a high volume retention rate after combustion at high temperatures.

[0007] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by incorporating mica into a urethane resin composition, and have thus completed the present invention. Specifically, the present invention provides the following [1] to

[10] . [1] A urethane resin composition comprising a polyol compound, a polyisocyanate compound, a catalyst, a blowing agent, and mica. [2] The urethane resin composition according to [1] above, having an isocyanate index of 200 or more. [3] The urethane resin composition according to [1] or [2] above, wherein the catalyst comprises a trimerization catalyst. [4] The urethane resin composition according to [3] above, wherein the trimerization catalyst comprises at least one selected from the group consisting of a nitrogen-containing aromatic compound, an alkali metal carboxylate salt, a tertiary ammonium salt, and a quaternary ammonium salt. [5] A polyurethane foam obtained by foaming and curing the urethane resin composition according to any one of [1] to [4] above. [6] The polyurethane foam according to [5] above, wherein the polyurethane foam has a volume retention rate of more than 20% after heating from 600°C to 800°C over 6 minutes and maintaining the temperature at 800°C for 14 minutes. [7] A structure comprising an object to be treated and the polyurethane foam according to [5] or [6] above, covering the object to be treated. [8] The structure according to [7] above, wherein the object to be treated is either a structural material or a wall of a building. [9] A method for producing a polyurethane foam, comprising coating an object to be treated with the urethane resin composition according to any one of claims [1] to [4].

[10] A method for producing a polyurethane foam according to [9] above, comprising coating the object to be treated with the urethane resin composition by spraying.

[0008] According to the present invention, it is possible to provide a urethane resin composition capable of forming a polyurethane foam having a high volume retention rate after combustion at high temperatures.

[0009] The present invention will be described below with reference to embodiments. The urethane resin composition of the present invention contains a polyol compound, a polyisocyanate compound, a catalyst, a blowing agent, and mica. Each component will be described in detail below.

[0010] [Polyol Compound] The polyol compound used in the present invention is not particularly limited, and examples thereof include polyether polyols, polyester polyols, polylactone polyols, polycarbonate polyols, and polymer polyols. The polyol compound preferably contains at least one selected from polyester polyols and polyether polyols, and from the viewpoint of improving the flame retardancy of the polyurethane foam, it preferably contains a polyester polyol. Furthermore, from the viewpoint of improving flame retardancy, a halogen-containing polyol or a phosphorus-containing polyol may be used. From the viewpoint of improving flame retardancy, the content of the polyester polyol is preferably 20 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 80 parts by mass or more, and particularly preferably 100 parts by mass, per 100 parts by mass of the polyol compound.

[0011] The average hydroxyl value of the polyol compound used in the present invention is not particularly limited, but is preferably 100 to 500 mgKOH / g, more preferably 150 to 450 mgKOH / g, and even more preferably 180 to 400 mgKOH / g. When one type of polyol compound is used, the average hydroxyl value is the hydroxyl value of that one type of polyol compound. When two or more types of polyol compounds are used, the average hydroxyl value is the average value of the hydroxyl groups in accordance with the blending ratio of the two or more types of polyol compounds. For example, when two types of polyol compounds (d1) and (d2) are used as the polyol compounds, the hydroxyl value of the polyol compound (d1) is X １ , the blending ratio is m １ , the hydroxyl value of the polyol compound (d2) is X ２ , the blending ratio is m ２ Then, the average hydroxyl value is expressed by the following formula: Average hydroxyl value (mgKOH / g) = X １ × (m １ / (m １ +m ２ )) + X ２ × (m ２ / (m １ +m ２)) The hydroxyl value is a value measured in accordance with JIS K1557-1:2007.

[0012] The polyester polyol may be either a polyester polyol having an aromatic ring or an aliphatic polyester polyol. However, from the viewpoint of the flame retardancy of the resulting polyurethane foam, it is preferable to use a polyester polyol having an aromatic ring. From the viewpoint of improving the flame retardancy of the polyurethane foam formed from this composition, the urethane resin composition of the present invention preferably contains 50 to 100 parts by mass, more preferably 70 to 100 parts by mass, and even more preferably 85 to 100 parts by mass of the polyester polyol having an aromatic ring per 100 parts by mass of the polyol compound. The polyester polyol having an aromatic ring is preferably a condensate of an aromatic dicarboxylic acid such as o-phthalic acid (phthalic acid), m-phthalic acid (isophthalic acid), p-phthalic acid (terephthalic acid), or naphthalenedicarboxylic acid with a glycol. In particular, from the viewpoint of improving the flame retardancy of the polyurethane foam, the polyester polyol preferably contains a phthalic acid-based polyester polyol, which is a condensate of phthalic acid and a glycol, and more preferably a p-phthalic acid-based polyester polyol, which is a condensate of p-phthalic acid and a glycol. The glycol is not particularly limited, but it is preferable to use low molecular weight aliphatic glycols known as constituent components of polyester polyols, such as ethylene glycol, propylene glycol, and diethylene glycol.

[0013] Examples of polyether polyols include polyoxyalkylene polyols obtained by ring-opening addition polymerization of alkylene oxide with an initiator having two or more active hydrogen atoms. Specific examples of the initiator include aliphatic polyhydric alcohols, such as glycols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 1,6-hexanediol, neopentyl glycol, cyclohexylene glycol, and cyclohexanedimethanol, triols such as trimethylolpropane and glycerin, tetrafunctional alcohols such as pentaerythritol, and highly functional alcohols such as sucrose and sorbitol. Examples of initiators include aliphatic amines, such as alkylenediamines (e.g., ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, neopentyldiamine), alkanolamines (e.g., monoethanolamine, diethanolamine), and aromatic amines (e.g., aniline, tolylenediamine, xylylenediamine, diphenylmethanediamine, Mannich condensation products). Among these, polyether polyols produced using initiators with aromatic rings are polyether polyols with aromatic rings, and for example, polyether polyols produced using aromatic amines as initiators are polyether polyols with aromatic rings. Among polyether polyols with aromatic rings, tolylenediamine-based polyether polyols, Mannich-based polyether polyols, and the like can be suitably used.

[0014] The tolylenediamine-based polyether polyol is a tolylenediamine-based polyether polyol produced using tolylenediamine as an initiator. The Mannich-based polyether polyol is obtained by utilizing the Mannich reaction and is a Mannich condensation product having two or more hydroxyl groups in the molecule, or a polyether polyol obtained by adding an alkylene oxide to such a Mannich condensation product. More specifically, it is a Mannich condensation product obtained by the Mannich reaction of at least one of phenol and its alkyl-substituted derivatives, formaldehyde, and an alkanolamine, or a polyether polyol obtained by ring-opening addition polymerization of this compound with at least one of ethylene oxide and propylene oxide.

[0015] Examples of polylactone polyols include polypropiolactone glycol, polycaprolactone glycol, and polyvalerolactone glycol. Examples of polycarbonate polyols include polyols obtained by dealcoholization of a hydroxyl group-containing compound such as ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, octanediol, or nonanediol with ethylene carbonate, propylene carbonate, or the like.

[0016] Examples of polymer polyols include polymers obtained by graft polymerizing an ethylenically unsaturated compound such as acrylonitrile, styrene, methyl acrylate, or methacrylate with an aromatic polyol, alicyclic polyol, aliphatic polyol, or polyester polyol, polybutadiene polyol, or hydrogenated products thereof.

[0017] The polyol content in the urethane resin composition of the present invention is preferably 8 to 60% by mass, more preferably 10 to 50% by mass, and even more preferably 15 to 40% by mass. When the polyol content is within the above range, polyurethane foam can be appropriately formed.

[0018] [Polyisocyanate Compound] Examples of polyisocyanate compounds include aromatic polyisocyanates, alicyclic polyisocyanates, and aliphatic polyisocyanates. Examples of aromatic polyisocyanates include phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanates such as 4,4'-diphenylmethane diisocyanate, dimethyldiphenylmethane diisocyanate, triphenylmethane triisocyanate, naphthalene diisocyanate, and polymethylene polyphenyl polyisocyanate (polymeric MDI).

[0019] Examples of alicyclic polyisocyanates include cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and dimethyldicyclohexylmethane diisocyanate. Examples of aliphatic polyisocyanates include methylene diisocyanate, ethylene diisocyanate, propylene diisocyanate, tetramethylene diisocyanate, and hexamethylene diisocyanate.

[0020] Among these, from the viewpoints of reactivity and availability, aromatic polyisocyanates are preferred, and diphenylmethane diisocyanate, polymeric MDI, or a mixture thereof is more preferred. The polyisocyanates may be used alone or in combination of two or more.

[0021] The content of the isocyanate compound in the urethane resin composition may be adjusted so that the isocyanate index is, for example, 115 or more. If the isocyanate index is equal to or greater than the above lower limit, the amount of the polyisocyanate compound relative to the polyol compound becomes excessive, making it easier to form isocyanurate bonds due to the trimerization of the polyisocyanate compound. As a result, an isocyanurate foam can be appropriately formed, and the residual rate and shape retention of the foam after high-temperature heating can be easily improved. From the viewpoint of further improving the residual rate and shape retention of the foam after high-temperature heating, the isocyanate index may be 180 or more, preferably 200 or more, more preferably 250 or more, even more preferably 300 or more, and even more preferably 350 or more. Furthermore, the isocyanate index may be, for example, 1000 or less, preferably 800 or less, more preferably 600 or less, and even more preferably 550 or less. If the isocyanate index is equal to or less than the above upper limit, performance commensurate with the production cost can be obtained.

[0022] The isocyanate index can be calculated by the following method: Isocyanate index = number of equivalents of polyisocyanate compound ÷ (number of equivalents of polyol compound + number of equivalents of water) × 100 Here, each number of equivalents can be calculated as follows: Number of equivalents of polyisocyanate compound = amount of polyisocyanate compound used (g) × NCO content (mass%) / molecular weight of NCO (mol) × 100 Number of equivalents of polyol compound = OHV × amount of polyol compound used (g) ÷ molecular weight of KOH (mmol), where OHV is the hydroxyl value (mgKOH / g) of the polyol compound. Number of equivalents of water = amount of water used (g) / molecular weight of water (mol) × number of OH groups in water In the above formulas, the molecular weight of NCO is 42 (mol), the molecular weight of KOH is 56,100 (mmol), the molecular weight of water is 18 (mol), and the number of OH groups in water is 2.

[0023] [Catalyst] (Trimerization Catalyst) The catalyst preferably contains at least a trimerization catalyst. The trimerization catalyst reacts with isocyanate groups contained in a polyisocyanate compound to cause trimerization, thereby promoting the formation of isocyanurate rings. By containing a trimerization catalyst, the urethane resin composition undergoes isocyanuration, making it possible to easily form an isocyanurate foam. By forming an isocyanurate foam, it becomes easier to improve the residue retention rate and shape retention after high-temperature heating. Examples of trimerization catalysts include nitrogen-containing aromatic compounds, alkali metal carboxylates, tertiary ammonium salts, and quaternary ammonium salts. These may be used alone or in combination of two or more. Among these, it is preferable to use at least one of alkali metal carboxylates and quaternary ammonium salts as the trimerization catalyst, and it is also preferable to use both of these.

[0024] Examples of the nitrogen-containing aromatic compound used in the trimerization catalyst include tris(dimethylaminomethyl)phenol, 2,4-bis(dimethylaminomethyl)phenol, 2,4,6-tris(dialkylaminoalkyl)hexahydro-S-triazine, etc. Examples of the alkali metal carboxylate include potassium organic acids, preferably potassium octylate such as potassium 2-ethylhexanoate, potassium acetate, potassium propionate, potassium butanoate, potassium benzoate, and other potassium carboxylates having 2 to 8 carbon atoms.

[0025] Examples of tertiary ammonium salts include triethylammonium salts and triphenylammonium salts. Examples of quaternary ammonium salts include tetramethylammonium salts, tetraethylammonium salts, tetraphenylammonium salts, triethylmethylammonium salts, hydroxybutyltrimethylammonium salts, and hydroxypropyltrimethylammonium salts. The ammonium salt is, for example, an ammonium salt of a carboxylic acid. Examples of the carboxylic acid in the ammonium salt include saturated fatty acids having 1 to 10 carbon atoms, preferably 2 to 8 carbon atoms. The saturated fatty acid may have a hydrocarbon group that is linear or branched, but preferably branched. Specific examples of the carboxylic acid include 2-ethylhexanoic acid, 2,2-dimethylpropanoic acid, acetic acid, and formic acid.

[0026] The content of the trimerization catalyst is preferably 0.1 to 20 parts by mass, more preferably 1 to 18 parts by mass, and even more preferably 5 to 15 parts by mass, relative to 100 parts by mass of the polyol. When the content of the trimerization catalyst is within this range, the trimerization reaction can be appropriately carried out at a rate commensurate with the amount of catalyst, and isocyanurate rings can be appropriately formed. This makes it easier to increase the residue rate and shape retention after high-temperature heating.

[0027] (Resinification catalyst) A resinification catalyst may be used as the catalyst. The resinification catalyst is a catalyst that promotes the reaction between a polyol compound and a polyisocyanate compound. Use of the resinification catalyst allows polyurethane to be appropriately produced at a good reaction rate, making it easier to appropriately form a polyurethane foam, for example, by spraying. The catalyst preferably contains a resinification catalyst in addition to a trimerization catalyst. Use of both the trimerization catalyst and the resinification catalyst as catalysts allows both the urethanization reaction and the trimerization reaction to proceed appropriately, making it easier to appropriately form an isocyanurate foam, for example, by spraying.

[0028] Resinification catalysts include amine catalysts such as imidazole compounds and piperazine compounds, and metal catalysts. Examples of imidazole compounds include tertiary amines in which the secondary amine at the 1-position of the imidazole ring is substituted with an alkyl group, alkenyl group, or the like. Specific examples include N-methylimidazole, 1,2-dimethylimidazole, 1-ethyl-2-methylimidazole, 1-methyl-2-ethylimidazole, 1,2-diethylimidazole, and 1-isobutyl-2-methylimidazole. Other examples include imidazole compounds in which the secondary amine in the imidazole ring is substituted with a cyanoethyl group. Examples of piperazine compounds include tertiary amines such as N-methyl-N',N'-dimethylaminoethylpiperazine and trimethylaminoethylpiperazine. Examples of the amine catalyst include, in addition to imidazole compounds and piperazine compounds, various tertiary amines such as pentamethyldiethylenetriamine, triethylamine, N-methylmorpholinebis(2-dimethylaminoethyl)ether, N,N,N',N",N"-pentamethyldiethylenetriamine, N,N,N'-trimethylaminoethyl-ethanolamine, bis(2-dimethylaminoethyl)ether, N,N-dimethylcyclohexylamine, diazabicycloundecene, triethylenediamine, tetramethylhexamethylenediamine, and tripropylamine.

[0029] Examples of metal catalysts used as resinification catalysts include metal salts of lead, tin, bismuth, copper, zinc, cobalt, nickel, etc., and preferably organic acid metal salts of lead, tin, bismuth, copper, zinc, cobalt, nickel, etc. More preferred are organic acid tin salts such as dibutyltin dilaurate, dioctyltin dilaurate, and dioctyltin versatate, and organic acid bismuth salts such as bismuth trioctate and bismuth tris(2-ethylhexanoate), and among these, organic acid bismuth salts are preferred. The resinification catalysts may be used alone or in combination of two or more. The resinification catalyst is preferably at least one selected from amine catalysts and metal catalysts, and among these, amine catalysts are more preferred, and imidazole compounds are even more preferred.

[0030] The content of the resinification catalyst in the urethane resin composition is preferably 0.1 to 15 parts by mass, more preferably 1 to 10 parts by mass, and even more preferably 2 to 8 parts by mass, relative to 100 parts by mass of the polyol. When the content of the resinification catalyst is within this range, the reaction between the polyol and the isocyanate tends to proceed appropriately.

[0031] The total content of the catalyst in the urethane resin composition is not particularly limited, but is preferably 0.1 to 30 parts by mass, more preferably 3 to 25 parts by mass, and even more preferably 6 to 20 parts by mass, relative to 100 parts by mass of the polyol. When the total content of the catalyst is within this range, the reaction between the polyol and the isocyanate and the trimerization reaction tend to proceed appropriately.

[0032] [Blowing Agent] The blowing agent promotes the foaming of the urethane resin composition. Examples of the blowing agent include low-boiling hydrocarbons such as water, propane, butane, pentane, hexane, heptane, cyclopropane, cyclobutane, cyclopentane, cyclohexane, and cycloheptane; chlorinated aliphatic hydrocarbon compounds such as dichloroethane, propyl chloride, isopropyl chloride, butyl chloride, isobutyl chloride, pentyl chloride, and isopentyl chloride; organic physical blowing agents such as hydrofluoroolefins (hereinafter sometimes referred to as "HFOs") and ether compounds such as diisopropyl ether, or mixtures of these compounds; and inorganic physical blowing agents such as nitrogen gas, oxygen gas, argon gas, and carbon dioxide gas. Among the above-mentioned blowing agents, it is preferable to use hydrofluoroolefins (HFOs), which have high stability as blowing agents, are less likely to reduce catalytic activity, and have a low environmental impact.

[0033] Suitable HFOs include fluoroalkenes having about 3 to 6 carbon atoms. The HFO may be a hydrochlorofluoroolefin having a chlorine atom, and therefore may be a chlorofluoroalkene having about 3 to 6 carbon atoms. Examples of HFOs include trifluoropropene, tetrafluoropropenes such as HFO-1234, pentafluoropropenes such as HFO-1225, chlorodifluoropropene, chlorotrifluoropropenes such as HFO-1233, and chlorotetrafluoropropene. More specifically, 3,3,3-trifluoropropene (HFO-1243zf), trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)), cis-1,3,3,3-tetrafluoropropene (HFO-1234ze(Z)), 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1,1,3,3-tetrafluoropropene, cis-1,3,3,3-tetrafluoropropene (HFO-1234ze(Z)), trans-1,2,3,3,3-tetrafluoropropene 1,1,3,3,3-pentafluoropropene (HFO-1225ye(E)), cis-1,2,3,3,3-pentafluoropropene (HFO-1225ye(Z)), 1,1,3,3,3-pentafluoropropene (HFO-1225zc), 1,1,2,3,3-pentafluoropropene (HFO-1225yc), trans-1-chloro-3,3,3-trifluoropropene (HFO-1233zd(E)), 1,1,1,4,4,4-hexafluorobut-2-ene (HFO-1336mzz), and the like. Of these, HFO-1233zd(E) is preferred.

[0034] The amount of foaming agent in the urethane resin composition is not particularly limited, and is preferably 10 to 100 parts by mass, more preferably 20 to 80 parts by mass, and even more preferably 25 to 65 parts by mass, per 100 parts by mass of polyol. When the content of the foaming agent is equal to or greater than the above-mentioned lower limit, foaming is promoted, foamability is improved, the density of the polyurethane foam is reduced, and good heat insulating performance can be imparted. When the content of the foaming agent is equal to or less than the above-mentioned upper limit, excessive foaming can be suppressed.

[0035] The blowing agents may be used alone or in combination of two or more. In the urethane resin composition of the present invention, it is preferable to use the above-mentioned HFO in combination with another blowing agent. For example, an HFO may be used in combination with water, oxygen gas, or carbon dioxide gas, which are easy to handle. Water is particularly preferable from the viewpoint of adjusting the isocyanate index and ease of handling. The content of the HFO is preferably 8 to 95 parts by mass, more preferably 15 to 75 parts by mass, and even more preferably 20 to 60 parts by mass, per 100 parts by mass of the polyol. The content of water is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 5 parts by mass, and even more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the polyol.

[0036] [Mica] The urethane resin composition of the present invention contains mica, a type of clay mineral. By including mica in the urethane resin composition, polyurethane foams formed from the urethane resin composition exhibit a high residue retention rate and shape retention after high-temperature heating. Although the mechanism behind this is unclear, it is presumed that mica melts and bonds to each other when heated, for example, at 800 to 1000°C, thereby retaining the shape of the residue, thereby ensuring a high residue retention rate and shape retention. Examples of mica include, but are not limited to, muscovite, phlogopite, and margarite.

[0037] The average particle size of the mica is not particularly limited, but is, for example, 1 to 100 μm, preferably 5 to 50 μm, more preferably 10 to 40 μm, and even more preferably 12 to 30 μm. When the particle size of the mica is within the above range, it is easy to increase the residue remaining rate and shape retention after high-temperature heating. The average particle size is the volume average diameter measured by laser diffraction / scattering method. The shape of the mica is not particularly limited, but is, for example, flaky.

[0038] The mica content in the urethane resin composition may be, for example, 1 to 30% by mass, based on the total amount of the urethane resin composition. By setting the mica content at or above the lower limit, it becomes easier to increase the residue remaining rate and shape retention after high-temperature heating. Furthermore, by setting the mica content at or below the upper limit, it becomes possible to contain a certain amount of components such as polyol compounds and polyisocyanate compounds in the urethane resin composition, and to appropriately form a foam. From the viewpoint of increasing the residue remaining rate and shape retention after high-temperature heating, the mica content is preferably 3 to 25% by mass, more preferably 4 to 22% by mass, and even more preferably 8 to 20% by mass.

[0039] The content of mica is not particularly limited, but is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 50 parts by mass or more, and even more preferably 80 parts by mass or more, based on 100 parts by mass of polyol compound. Increasing the amount of mica makes it easier to impart high fire resistance. On the other hand, setting the amount of mica to a certain level or less prevents the viscosity from increasing, making it easier to improve the workability of the urethane resin composition. Since the fire resistance improves as the content of mica increases, the upper limit of the content of mica is not particularly limited, and is, for example, 200 parts by mass.

[0040] [Phosphate Ester] The urethane resin composition may contain a phosphate ester. It is preferable to use a phosphate ester that is liquid at room temperature (23°C) and normal pressure (1 atmosphere). The use of a phosphate ester reduces the viscosity of the urethane resin composition and the polyol liquid agent described below, making it easier to handle. In addition, the phosphate ester is also a flame retardant, and it is easier to improve the flame retardancy of the polyurethane foam.

[0041] Examples of the phosphate ester that can be used include monophosphate esters and condensed phosphate esters. Monophosphate esters are phosphate esters having one phosphorus atom in the molecule. Examples of the monophosphate ester include trialkyl phosphates such as trimethyl phosphate, triethyl phosphate, tributyl phosphate, and tri(2-ethylhexyl)phosphate; halogen-containing phosphate esters such as tris(β-chloropropyl)phosphate; trialkoxy phosphates such as tributoxyethyl phosphate; aromatic ring-containing phosphate esters such as tricresyl phosphate, trixylenyl phosphate, tris(isopropylphenyl)phosphate, cresyl diphenyl phosphate, and diphenyl(2-ethylhexyl)phosphate; and acidic phosphate esters such as monoisodecyl phosphate and diisodecyl phosphate.

[0042] Examples of condensed phosphate esters include aromatic condensed phosphate esters such as trialkyl polyphosphate, resorcinol polyphenyl phosphate, bisphenol A polycresyl phosphate, and bisphenol A polyphenyl phosphate. Commercially available condensed phosphate esters include "CR-733S," "CR-741," and "CR747" manufactured by Daihachi Chemical Industry Co., Ltd., and "ADEKA STAB PFR" and "FP-600" manufactured by ADEKA Corporation.

[0043] The phosphate ester may be used singly or in combination of two or more of the above. Among these, monophosphate esters are preferred, and halogen-containing phosphate esters such as tris(β-chloropropyl)phosphate are more preferred, from the viewpoint of facilitating low viscosity and improving the flame retardancy of polyurethane foams. The content of the phosphate ester in the urethane resin composition is, for example, 5 to 100 parts by mass, preferably 15 to 90 parts by mass, more preferably 20 to 75 parts by mass, and even more preferably 30 to 60 parts by mass, per 100 parts by mass of polyol.

[0044] [Foam stabilizer] The urethane resin composition may contain a foam stabilizer. By containing a foam stabilizer, the foamability of the polyurethane foam can be improved, and for example, foaming can be appropriately promoted when spraying by spraying. Specific examples of foam stabilizers include surfactants, more specifically polyoxyalkylene foam stabilizers such as polyoxyalkylene alkyl ethers, and silicone foam stabilizers such as organopolysiloxanes. The foam stabilizer used in the present invention is not particularly limited, but silicone foam stabilizers are preferred from the viewpoint of foamability. One type of foam stabilizer may be used alone, or two or more types may be used in combination.

[0045] The content of the foam stabilizer in the urethane resin composition of the present invention is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 5 parts by mass, and even more preferably 0.5 to 3 parts by mass, per 100 parts by mass of polyol. When the content of the foam stabilizer is at least the above-mentioned lower limit, the urethane resin composition becomes easier to foam, making it possible to obtain a homogeneous polyurethane foam. Furthermore, when the content of the foam stabilizer is at most the above-mentioned upper limit, an optimal balance between production costs and the obtained effects is achieved.

[0046] [Other Components] In addition to the above, the urethane resin composition of the present invention may contain at least one of a flame retardant other than phosphate ester, a filler other than mica, etc. Examples of flame retardants other than phosphate ester include solid flame retardants that are solid at room temperature (23°C) and normal pressure (1 atmosphere). Examples of flame retardants other than phosphate ester include red phosphorus-based flame retardants, phosphate-containing flame retardants, bromine-containing flame retardants, boron-containing flame retardants, antimony-containing flame retardants, metal hydroxides, etc.

[0047] The red phosphorus-based flame retardant may be red phosphorus alone, red phosphorus coated with a resin, metal hydroxide, metal oxide, or the like, or red phosphorus mixed with a resin, metal hydroxide, metal oxide, or the like. Examples of phosphate-containing flame retardants include phosphates formed from salts of various phosphoric acids, such as phosphoric acid, phosphorous acid, hypophosphorous acid, monophosphoric acid, pyrophosphoric acid, and polyphosphoric acid, with at least one metal or compound selected from metals in Groups IA to IVB of the Periodic Table, ammonia, aliphatic amines, aromatic amines, and heterocyclic compounds containing nitrogen in the ring. Specific examples include aluminum phosphate, aluminum phosphite, ammonium polyphosphate, and aluminum polyphosphate.

[0048] Bromine-containing flame retardants include monomeric organic bromine compounds such as hexabromobenzene, pentabromotoluene, hexabromobiphenyl, decabromobiphenyl, decabromodiphenyl ether, octabromodiphenyl ether, hexabromodiphenyl ether, bis(pentabromophenoxy)ethane, ethylenebis(pentabromophenyl), ethylenebis(tetrabromophthalimide), and tetrabromobisphenol A, as well as polymeric organic bromine compounds. Boron-containing flame retardants include borax, boron oxide, boric acid, and borates such as zinc borate. Antimony-containing flame retardants include antimony oxides such as antimony trioxide and antimony pentoxide, antimonates, and pyroantimonates. Metal hydroxides include magnesium hydroxide, aluminum hydroxide, iron hydroxide, nickel hydroxide, zirconium hydroxide, titanium hydroxide, zinc hydroxide, copper hydroxide, vanadium hydroxide, and tin hydroxide. The above flame retardants other than phosphate esters may be used alone or in combination of two or more.

[0049] Examples of fillers other than mica include calcium sulfate, barium sulfate, calcium silicate, wollastonite, sepiolite, montmorillonite, saponite, stevensite, hectorite, activated clay, glass beads, aluminum nitride, boron nitride, silicon nitride, various metal powders, magnesium sulfate, lead zirconate titanate, molybdenum sulfide, silicon carbide, various magnetic powders, fly ash, etc. The fillers other than mica may be used alone or in combination of two or more.

[0050] In addition to the above, the urethane resin composition may contain, as necessary, one or more selected from phenol-based, amine-based, sulfur-based, and other antioxidants, heat stabilizers, metal inhibitors (metal deactivators), antistatic agents, crosslinking agents, lubricants, softeners, pigments, dyes, tackifiers, and the like, within the scope of the object of the present invention.

[0051] The urethane resin composition of the present invention may be a one-component type, or may be divided into two or more components and mixed for use. When divided into two or more components, it is preferable to divide it into at least a polyol liquid containing a polyol compound and an isocyanate liquid containing a polyisocyanate compound. The urethane resin composition is preferably a two-component type. In a two-component type, it is preferable to comprise a polyol liquid and a polyisocyanate liquid. In a two-component type, various components such as a catalyst, a blowing agent, and mica may be contained in either the polyol liquid or the polyisocyanate liquid, but from the viewpoint of storage stability, it is preferable to contain them in the polyol liquid. In addition, it is preferable to contain components other than the catalyst, blowing agent, and mica, such as a phosphate ester, a foam stabilizer, a flame retardant, a filler, and other components, in the polyol liquid.

[0052] The urethane resin composition of the present invention can be produced by mixing the components constituting the urethane resin composition. Furthermore, in the case of a two-component type, it can be obtained by mixing a polyol liquid and a polyisocyanate liquid. When each of these liquids contains two or more components, it can be obtained by mixing the components constituting each liquid.

[0053] <Polyurethane Foam> The polyurethane foam of the present invention is obtained by foaming and curing the above-described urethane resin composition. The method for foaming and curing the urethane resin composition may be a known method. For example, in the case of a two-component type, the polyurethane foam can be obtained by mixing a polyol liquid agent and a polyisocyanate liquid agent prepared in advance as described above, and foaming and curing the resulting urethane resin composition. The polyurethane foam is preferably an isocyanurate foam isocyanurated with an excess amount of a polyisocyanate compound as described above.

[0054] The polyurethane foam obtained by foaming and curing the urethane resin composition of the present invention preferably has a thermal conductivity of 0.010 to 0.050 W / (m·K), more preferably 0.015 to 0.04 W / (m·K), and even more preferably 0.018 to 0.03 W / (m·K). Having a thermal conductivity of the polyurethane foam below the upper limit above provides excellent heat insulation. This, combined with the increased residue retention and shape retention after high-temperature heating, as described above, facilitates excellent fire resistance. Furthermore, having a thermal conductivity above the lower limit above prevents excessive foaming and also facilitates increased mechanical strength. Thermal conductivity can be measured using the method described in the Examples section below.

[0055] The polyurethane foam obtained by foaming and curing the urethane resin composition of the present invention has a volume retention rate, for example, of more than 20%, preferably 40% or more, more preferably 50% or more, and even more preferably 70% or more, after heating from 600°C to 800°C over 6 minutes and maintaining the temperature at 800°C for 14 minutes. By ensuring that the volume retention rate is at least a certain level as described above, the polyurethane foam of the present invention is likely to have good fire resistance in the event of a fire. The volume retention rate may be 100% or less, but may be 97% or less in practical use. The volume retention rate can be measured by the method described in the Examples below.

[0056] It is preferable to use a polyurethane foam by covering an object to be treated. The polyurethane foam can provide heat insulation by covering the object to be treated. Furthermore, as described above, the polyurethane foam has a high residue remaining rate and shape retention after high-temperature heating. Therefore, the polyurethane foam can be used as a fire-resistant material (e.g., a fire-resistant coating material) that suppresses heating and combustion of the object to be treated in the event of a fire. In this specification, an object to be treated that is covered with a polyurethane foam may be simply referred to as a "structure." In other words, in the present invention, the structure comprises an object to be treated and a polyurethane foam covered on the object to be treated.

[0057] Examples of materials that can be used as the substrate include wood, metal materials such as steel, concrete, brick, concrete block, stone, mortar, gypsum board, cement board, and fiberboard. Among these, metal materials such as steel and wood are preferred, with steel being more preferred. The shape of the substrate is not particularly limited, and may be a flat plate, or may have a cross-sectional shape such as an H-shape, Z-shape, L-shape, cylindrical shape, round shape, or a polygonal shape such as a triangle, square, or pentagon, or may have any other shape. Even if the surface of the substrate has a complex shape, it can be appropriately covered with polyurethane foam by forming the polyurethane foam by spraying.

[0058] The object to be protected is a component that needs to be protected in the event of a fire, and examples thereof include architectural components constituting a building and civil engineering components constituting a civil engineering structure. Examples of architectural components include structural materials for buildings and walls, with structural materials for buildings being preferred. Structural materials for buildings are components that form the framework of a building and bear the forces acting on the building, such as the weight and load of the components that make up the building. Examples of structural materials include wooden columns, beams, girders, and braces, as well as steel frames and reinforcing bars, with steel frames and reinforcing bars being preferred. Walls are not particularly limited, but may be made of gypsum board, concrete, mortar, plywood, medium-density fiberboard (MDF), wood cement boards, wood wool cement boards, decorative boards, etc.

[0059] In the event of a fire, structural materials of a building are heated and lose strength, or burn, causing the building to collapse. However, by coating these surfaces with the polyurethane foam of the present invention, the heating and burning of these structural materials in the event of a fire can be suppressed, thereby preventing the collapse of the building. Furthermore, by coating the surface of a wall with the polyurethane foam of the present invention, the heating and burning of the polyurethane foam-coated wall can be suppressed, and the spread of fire can be prevented in the event of a fire. Therefore, a wall coated with the polyurethane foam of the present invention is also preferably used as a wall for defining a fire compartment.

[0060] Examples of civil engineering materials include reinforcing bars, steel frames, concrete, mortar, and stone, with reinforcing bars and steel frames being preferred. More specifically, examples of civil engineering materials include reinforcing bars used in tunnels. Civil engineering materials such as reinforcing bars and steel frames are preferably materials that bear the forces acting on civil engineering structures, such as the weights and loads of the components that make up the civil engineering structure. For example, by covering reinforcing bars used in tunnels with the polyurethane foam of the present invention, heating of the reinforcing bars in the event of a fire can be suppressed, thereby preventing the collapse of the tunnel wall.

[0061] Although not particularly limited, polyurethane foams are preferably obtained by applying a urethane resin composition to an object to be treated, laminating the composition on the object, and allowing it to cure and foam. The method for applying the urethane resin composition to an object to be treated is not particularly limited, but spraying is preferred. Spraying allows building components and civil engineering components to be coated on-site. The spraying method is not particularly limited, but can be carried out, for example, using a spray foaming machine. Spraying can be carried out by adjusting the temperature of a polyol liquid agent and an isocyanate liquid agent contained in separate containers in the spray foaming machine, causing them to collide and mix at the tip of a spray gun attached to the spray foaming machine, and then atomizing the mixed liquid using air pressure. Spray foaming machines are well known, and commercially available products can be used, such as Graco's "A-25" and "H-40." Furthermore, the temperature settings and pressures of each liquid agent can be appropriately set in accordance with general polyurethane foam spraying conditions.

[0062] The urethane resin composition (i.e., polyurethane foam) may be coated on an object by means other than coating. For example, a polyurethane foam previously molded into a predetermined shape such as a sheet may be coated on the object. The method for obtaining a polyurethane foam molded into a predetermined shape such as a sheet is not particularly limited. For example, the polyurethane foam may be obtained by coating the composition on a support such as a release sheet, foaming and curing the polyurethane foam on the support, and then removing the polyurethane foam from the support. Alternatively, the polyurethane foam may be obtained by casting the urethane resin composition into a molding die such as a metal mold, curing and foaming the cast urethane resin composition, and then demolding the mold.

[0063] Polyurethane foam can also be used as the core material of a panel with double-sided non-combustible facings. A panel with double-sided non-combustible facings has a pair of opposing facings and a core material placed between them. The thickness of the core material is preferably 50 to 300 mm, more preferably 60 to 290 mm, and even more preferably 70 to 280 mm. By keeping the thickness of the core material within the above ranges, it is possible to achieve high fire resistance and heat insulation properties and lightweight construction.

[0064] The facing material is a non-combustible facing material. Examples of non-combustible facing materials include calcium silicate board, gypsum board, FRP, and metal plate, and metal plate is preferred. Therefore, the facing material is preferably a metal facing material. Using a metal plate as the facing material can improve fire resistance. The metal facing material is not particularly limited, but various steel plates such as galvanized steel plate, Galvalume steel plate (registered trademark), stainless steel plate, and aluminum steel plate can be used. In other words, it is more preferable that the panel with double-sided non-combustible facing material is a panel with double-sided steel plate. The facing material is bonded to both the front and back surfaces of the core material. Layers other than the core material and non-combustible facing material (hereinafter also referred to as optional layers), such as paper sheets, aluminum plates, aluminum craft sheets, polyethylene laminate sheets, and cross-laminated sheets, may be present between the facing material and the core material.

[0065] In addition, to further improve fire resistance, an inorganic core material may be combined with the core material. Examples of inorganic core materials include core materials containing mineral fibers such as rock wool, glass wool, long glass fibers, special-purpose glass microfibers, ceramic wool, alkaline earth silicate wool (AES), refractory ceramic fibers (RCF), alumina fibers, potassium titanate whiskers, and silicon carbide whiskers, as well as calcium silicate boards and ALC panels. The inorganic core material may be laminated on only one side of the core material, or on both sides of the core material, resulting in a configuration with three or more layers in total. Furthermore, two or more layers of inorganic core material may be laminated on at least one side of the core material.

[0066] The thickness of each face material is preferably 0.1 to 5 mm, more preferably 0.2 to 3 mm, and even more preferably 0.3 to 1 mm. Having a face material thickness equal to or greater than the above-mentioned lower limit can provide high fire resistance. Furthermore, having a face material thickness equal to or less than the above-mentioned upper limit can reduce the weight of the panel with double-sided non-combustible face materials.

[0067] In a panel with double-sided non-combustible facings, surfaces (side surfaces) other than the surfaces constituting the front and back surfaces of the core material, which are covered by other materials, may also be appropriately covered with a facing material. The material of the facing material covering the side surfaces is not particularly limited, and may be metal, a resin such as FRP, or other non-combustible facing materials. The metal facing material may be various steel plates, as with the metal facing material. Furthermore, the resin facing material is not particularly limited, and may be formed from, for example, FRP. A panel with double-sided non-combustible facings is generally approximately rectangular and has four sides, but all four sides may be covered with a facing material, or only two opposing sides may be covered with a facing material.

[0068] A plurality of panels with non-combustible facings on both sides may be connected together for use. When a plurality of panels are connected, it is preferable that the side surfaces of the panels with non-combustible facings on both sides are connected together. When the side surfaces are connected together, the surface material of the side surfaces of the panels may be formed with irregularities or the like, and the panels may be connected by fitting or the like.

[0069] The double-sided non-combustible facing panel may be installed in a partition section of a building for the purpose of separating the sections. Examples of partition sections of a building to which the double-sided non-combustible facing panel may be installed include walls, partitions, floors, ceilings, and roofs, preferably walls and partitions, and more preferably fire-resistant exterior walls and fire-resistant partitions. Furthermore, the fire-resistant exterior walls and fire-resistant partitions are preferably used as fire-resistant exterior walls and fire-resistant partitions for refrigerator compartments, and particularly preferably as fire-resistant partitions for refrigerator compartments. The fire-resistant partition may be used as a fire-resistant partition between a refrigerator compartment and a room-temperature compartment, or as a fire-resistant partition between refrigerator compartments, or as a fire-resistant partition between a refrigerator compartment and a freezer compartment.

[0070] A panel with non-flammable facings on both sides can be manufactured by filling a urethane resin composition between the facings, foaming and curing the urethane resin composition to form a polyurethane foam, and integrating the polyurethane foam with the facings.

[0071] For example, a laminated structure of a panel with double-sided non-combustible panels can be produced by supplying a urethane resin composition onto one face material, placing the other face material at a predetermined distance from the first face material so as to cover the top of the supplied urethane resin composition, and foaming the urethane resin composition to form a polyurethane foam. In this method, panels with double-sided non-combustible panels can be produced continuously. Specifically, in a production line, a urethane resin composition is discharged from a discharge head installed on the production line onto one of the conveyed face materials, while the other face material is supplied to cover the top of the discharged urethane resin composition. The urethane resin composition is then foamed and cured between the double-sided faces flowing on the production line to form a polyurethane foam between the two face materials.

[0072] Alternatively, a panel with double-sided non-combustible facings may be manufactured using a mold. Specifically, facings are set at a predetermined interval inside a mold such as a press, a urethane resin composition is poured into the mold, and the urethane resin composition is foamed and cured between the facings to form a polyurethane foam between the two facings. A facing material for covering the side surfaces may also be set inside the mold as appropriate to provide a facing material for covering the side surfaces. The facing material, polyurethane foam, and facing material laminate obtained by each of the above methods may be used as a panel with double-sided non-combustible facings as is, or may be cut appropriately as needed for use.

[0073] Furthermore, the double-sided non-combustible facing panel of the present invention may be manufactured by combining a pre-fabricated core material with a facing material. For example, a facing material may be attached to a pre-fabricated core material to form a double-sided non-combustible facing panel. In this case, the core material may be obtained, for example, by foaming and curing a urethane resin composition on any of the above-mentioned layers to form a polyurethane foam, and then cutting the polyurethane foam into the desired shape. Alternatively, the urethane resin composition may be injected into a mold or the like, foamed and cured inside the mold, and then released from the mold to obtain a core material having the desired shape.

[0074] Furthermore, when a panel with double-sided non-combustible face materials has face materials covering both sides of the opposing core material in addition to face materials covering the front and back of the core material, a rectangular frame-shaped member consisting of a pair of face materials and a pair of face materials constituting the sides can be obtained by bending metal material or joining appropriate non-combustible face materials, and then inserting a core material into the rectangular frame-shaped member to obtain a panel with double-sided non-combustible face materials.Alternatively, a panel with double-sided non-combustible face materials can be obtained by fitting a core material between two U-shaped face materials.

[0075] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0076] The evaluation methods for each example and comparative example are as follows. [Volume Residual Ratio and Shape Retention of Residue] A polyurethane foam was cut into a size of 50 mm x 50 mm and 20 mm thick so as to include the gap between the second and third layers, and placed on a thin steel plate. The cut pieces were then placed in an electric furnace heated to 600°C. After the foam was placed in the electric furnace, the temperature of the electric furnace was increased from 600°C to 800°C over 6 minutes and maintained at 800°C for 14 minutes. The heated residue was then removed from the electric furnace. The volume residual ratio was determined by calculating the ratio of the volume of the residue after removal from the electric furnace to the volume of the polyurethane foam before placement in the electric furnace. A volume residual ratio of more than 50% was evaluated as "A," a volume residual ratio of more than 20% but not more than 50% was evaluated as "B," and a volume residual ratio of 20% or less was evaluated as "C."

[0077] Regarding the shape retention of the residue, when the residue removed from the electric furnace was picked up by hand from both sides and lifted, those that could be lifted with almost no change in shape were rated as "AA", those that had some damage but did not change shape significantly were rated as "A", those that retained their shape but fell apart when picked up by hand and could not be lifted were rated as "B", and those that did not retain their shape at all were rated as "C".

[0078] [Thermal Conductivity] The obtained polyurethane foam was cut into a piece of 200 mm x 200 mm and 25 mm thick, including the space between the second and third layers, and the thermal conductivity was measured using a thermal conductivity measuring device manufactured by Eiko Seiki Co., Ltd. (product name "HC-047").

[0079] The components used in each example and comparative example are as follows: (Polyol compound) p-phthalic acid polyester polyol, manufactured by Kawasaki Chemical Industries, Ltd., product name: Maximol RFK-087, hydroxyl value = 200 mg KOH / g (Isocyanate compound) Polymeric MDI, manufactured by Tosoh Corporation, product name: Millionate MR-200 (Foam stabilizer) Silicone-based foam stabilizer, manufactured by Dow Toray Industries, Inc., product name: SH193

[0080] (Catalysts) Trimerization catalyst 1: manufactured by Toei Chemical Industry Co., Ltd., product name: potassium hexoate, potassium 2-ethylhexanoate (concentration: 75% by mass); Trimerization catalyst 2: manufactured by Tosoh Corporation, product name: TOYOCAT-TRX, quaternary ammonium salt (concentration: 60 to 70% by mass); Resinization catalyst 1: manufactured by Tosoh Corporation, product name: TOYOCAT-DM70, 1,2-dimethylimidazole (concentration: 65 to 75% by mass); Resinization catalyst 2: manufactured by Shepherd Chemical Company, product name: BiCAT8210, bismuth tris(2-ethylhexanoate) (concentration: 80 to 90% by mass); (Flame retardant) Phosphate ester: tris(β-chloropropyl)phosphate, manufactured by Daihachi Chemical Industry Co., Ltd., product name: TMCPP

[0081] (Clay minerals) Mica 1: manufactured by Osaka Mica Co., Ltd., product name: H-2000, average particle size 12.5 μm Mica 2: manufactured by Yamaguchi Mica Co., Ltd., product name: A-21S, average particle size 23 μm Mica 3: manufactured by Yamaguchi Mica Co., Ltd., product name: TM-10, average particle size 11 μm Sepiolite: manufactured by Omi Mining Co., Ltd., product name: Miraclay P-300, average particle size 5 μm Montmorillonite: manufactured by Kunimine Kogyo Co., Ltd., product name: Kunipia F Saponite: manufactured by Kunimine Kogyo Co., Ltd., product name: Sumecton-SA Stevensite: manufactured by Kunimine Kogyo Co., Ltd., product name: Sumecton-ST Hectorite: manufactured by Kunimine Kogyo Co., Ltd., product name: Sumecton-SWN

[0082] (Blowing agent) Water Hydrofluoroolefin (HFO): trans-1-chloro-3,3,3-trifluoropropene (manufactured by Honeywell Japan, product name: Soltis LBA)

[0083] [Examples 1 to 10, Comparative Examples 1 to 6] A polyol premix liquid (polyol liquid) was prepared by previously mixing raw materials other than the polyisocyanate compound according to the formulations in Tables 1 and 2. Using a spray foaming machine ("H-40" manufactured by Graco), the polyol premix liquid and the polyisocyanate compound as the isocyanate liquid were mixed, and the urethane resin composition was sprayed from a spray gun to a thickness of 10 mm for the first layer, 20 mm for the second layer, and 20 mm for the third layer, followed by foaming and curing to obtain a polyurethane foam with a thickness of 50 mm.

[0084] *In Tables 1 and 2, the amount of catalyst blended is the amount in the product.

[0085] As shown in each of the above examples, polyurethane foams obtained by foaming and curing urethane resin compositions containing a polyol compound, a polyisocyanate compound, a catalyst, a blowing agent, and mica had low thermal conductivity and good volume retention and residue retention after high-temperature heating. Therefore, the urethane resin compositions of each example can be suitably used as fire-resistant materials that can adequately prevent objects from overheating or burning in the event of a fire. In contrast, the polyurethane foams obtained by foaming and curing the urethane resin compositions of each comparative example did not contain a clay mineral, and even if they did contain mica, they had insufficient volume retention and residue retention after high-temperature heating, making it difficult to adequately prevent objects from overheating or burning in the event of a fire.

Claims

1. A urethane resin composition comprising a polyol compound, a polyisocyanate compound, a catalyst, a blowing agent, and mica.

2. The urethane resin composition according to claim 1, which has an isocyanate index of 200 or more.

3. The urethane resin composition according to claim 1 or 2, wherein the catalyst comprises a trimerization catalyst.

4. The urethane resin composition according to claim 3, wherein the trimerization catalyst comprises at least one selected from the group consisting of nitrogen-containing aromatic compounds, alkali metal carboxylates, tertiary ammonium salts, and quaternary ammonium salts.

5. A polyurethane foam obtained by foaming and curing the urethane resin composition according to any one of claims 1 to 4.

6. The polyurethane foam according to claim 5, wherein the volume retention rate after the polyurethane foam is heated from 600°C to 800°C over 6 minutes and maintained at 800°C for 14 minutes is more than 20%.

7. A structure comprising an object to be treated and the polyurethane foam according to claim 5 or 6 covering the object to be treated.

8. The structure according to claim 7, wherein the object to be treated is either a structural member or a wall of a building.

9. A method for producing a polyurethane foam, which comprises coating an object with the urethane resin composition according to any one of claims 1 to 4.

10. The method for producing a polyurethane foam according to claim 9, wherein the urethane resin composition is applied to the object by spraying.

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