Rigid polyurethane foam and heat insulation board using the foam

Abstract

To provide a rigid polyurethane foam having high fire retardancy such that foam after combustion is easily carbonized and a foam shape can be retained.SOLUTION: There is provided a rigid polyurethane foam obtained by reacting and curing a polyol component containing a polyol, a catalyst, a foaming agent and a flame retardant and a polyisocyanate component, wherein the polyol includes a terephthalic acid-based polyester polyol (A) and a sugar-based polyether polyol (B1) and / or an aromatic amine-based polyether polyol (B2), the catalyst is a trimerization catalyst containing a quaternary ammonium salt and a carboxylic acid alkali metal salt, the flame retardant contains a liquid phosphate ester and has an isocyanate index of more than 230 and less than 330 and a mass residual ratio of 25% or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a rigid polyurethane foam having excellent flame retardancy and a heat insulating board using the foam as a heat insulating material.

Background Art

[0002] Rigid polyurethane foam has excellent heat insulation properties and high mechanical strength, and thus is widely used as a heat insulating material for household and commercial refrigerators and freezers, bathtubs, vending machines, buildings, and various other equipment and structures in other fields. Among them, polyisocyanurate foam containing an isocyanurate ring formed from the trimerization reaction of isocyanate is known as a foam having excellent flame retardancy and high strength.

[0003] For example, Patent Document 1 discloses a polyisocyanurate foam that can improve poor dimensional stability such as foam shrinkage even when using a trimerization catalyst in which potassium acetate and potassium octylate are mixed at a specific ratio and using cyclopentane having low compatibility with polyol or the like as a foaming agent.

[0004] Further, Patent Document 2 discloses a rigid polyurethane foam having flame retardancy by containing 95 parts by weight or more of an aromatic polyester polyol based on 100 parts by weight of the total amount of polyol, a catalyst in which a trimerization catalyst and a tertiary amine are mixed at a specific ratio, and a specific amount of a high-boiling hydrophilic organic solvent having no active hydrogen group, with a small content of a flame retardant or without using a flame retardant.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in Patent Document 1 and Patent Document 2, the flame retardancy in the state where a facing material containing an aluminum foil layer or a steel plate is laminated on both sides of a rigid polyurethane foam is evaluated, and the flame retardancy of the rigid polyurethane foam alone is not evaluated.

[0007] In order to enhance the flame retardancy of a rigid polyurethane foam alone, it is required that the foam after combustion is a foam that is easily carbonized so that it does not burn and spread further. For example, the content of the trimerization catalyst can be increased to increase the ratio of the isocyanurate ring, but by doing so alone, the reaction proceeds rapidly, and appearance defects such as foaming defects and rough cell shapes are likely to occur.

[0008] Therefore, an object of the present invention is to provide a rigid polyurethane foam having a high flame retardancy such that the foam after combustion is easily carbonized and can retain the foam shape, and a heat insulation board using the foam.

Means for Solving the Problems

[0009] The present invention is (1) A rigid polyurethane foam obtained by reacting and curing a polyol component containing a polyol, a catalyst, a foaming agent, and a flame retardant with a polyisocyanate component, wherein the polyol contains a terephthalic acid-based polyester polyol (A) and a sugar-based polyether polyol (B1) and / or an aromatic amine-based polyether polyol (B2), the content ratio (A / (B1 + B2)) based on the mass of the polyester polyol (A) and the polyether polyols (B1, B2) is 60 or more and 90 or less / 10 or more and 40 or less, the catalyst is a trimerization catalyst containing a quaternary ammonium salt and an alkali metal carboxylate, the flame retardant contains a liquid phosphate ester, and the content is 30 parts by mass or more and 90 parts by mass or less with respect to 100 parts by mass of the total amount of the polyol, The isocyanate index is more than 230 and less than 330, characterized in that the mass retention rate measured by the method shown below is 25% or more. (Mass retention rate) Using a single piece of rigid polyurethane foam with a thickness of 25 mm, a length of 99 mm, and a width of 99 mm as a test piece, in accordance with ISO 5660-1, the heat release rate is 50 kW / m 2 in the heat release test (cone calorimeter test) carried out at, with a heating time of 5 minutes, the mass of the test piece after heating: X (g), the mass of the test piece before heating X 0 (g), the mass retention rate (%) is obtained by the following formula (1). Mass retention rate (%) = (X / X 0 ) × 100 ··· Formula (1) (2) The polyol is characterized by consisting of a terephthalic acid-based polyester polyol (A) and a sugar-based polyether polyol (B1) having a functional group number of 4 or more and 8 or less. (3) It may be a heat insulating board characterized by using the rigid polyurethane foam of (1) or (2) above as a heat insulating layer and having facing materials on the front and back surfaces of the heat insulating layer.

Effect of the Invention

[0010] According to the present invention, it is possible to provide a rigid polyurethane foam having high flame retardancy such that the foam after combustion is easily carbonized and can maintain the foam shape.

Mode for Carrying Out the Invention

[0011] The present invention is a rigid polyurethane foam obtained by reacting and curing a polyol component containing a polyol, a catalyst, a foaming agent, and a flame retardant, and a polyisocyanate component.

[0012] The polyol component includes, as a polyol, a terephthalic acid-based polyester polyol (A), and a sugar-based polyether polyol (B1) and / or an aromatic amine-based polyether polyol (B2).

[0013] The terephthalic acid-based polyester polyol (A) is a polyester polyol obtained from a terephthalic acid-based polyvalent carboxylic acid containing terephthalic acid, terephthalic anhydride or a derivative thereof alone or in combination of two or more, and a polyhydric alcohol. As the polyhydric alcohol, it has 2 to 8 hydroxyl groups, specifically, ethylene glycol, propylene glycol, glycerin, trimethylolpropane, pentaerythritol, sorbitol, sucrose, bisphenol A, etc. These can be used alone or in appropriate combination of two or more. As the polyvalent carboxylic acid, in addition to the terephthalic acid-based ones, aromatic polybasic acids such as orthophthalic acid, isophthalic acid, naphthalenedicarboxylic acid, trimellitic acid and their anhydrides may be included. However, the content ratio of the terephthalic acid-based in the polyvalent carboxylic acid is 50 mol% or more. Further, the terephthalic acid-based polyester polyol (A) includes a polyester polyol regenerated for use in polyurethane foam from polyethylene terephthalate (PET resin), which is a resin obtained by polycondensing terephthalic acid and ethylene glycol. As the PET resin, waste PET recovered after use such as in food bottles and fibers is used, and a polyurethane foam considering the global environment can be provided. Regarding the hydroxyl value and molecular weight of the terephthalic acid-based polyester polyol (A), there is no particular limitation, but the hydroxyl value is preferably 100 to 500 mgKOH / g and the molecular weight is preferably 200 to 600.

[0014] The sugar-based polyether polyol (B1) is a polyether polyol obtained by addition polymerization of one or more alkylene oxides to sugars such as sorbitol and sucrose. Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, etc. These sugar-based polyether polyols can be used alone or in appropriate combination of two or more. Regarding the hydroxyl value and molecular weight of such sugar-based polyether polyols (B1), there are no particular limitations, but a hydroxyl value of 300 to 700 mgKOH / g and a molecular weight of 500 to 800 are preferred. Also, in the sugar-based polyether polyol (B1), it is preferable to use those having a functional group number of 4 or more and 8 or less because the dimensional stability, which is the mechanical strength of the resulting rigid polyurethane foam, will be high.

[0015] The aromatic amine-based polyether polyol (B2) is a polyether polyol obtained by addition polymerization of one or more alkylene oxides to an amine having an aromatic ring. Examples of the amine having an aromatic ring include phenylenediamine, toluenediamine, diaminodiphenylmethane, Mannich condensates, etc., and examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, etc. These aromatic amine-based polyether polyols can be used alone or in appropriate combinations of two or more. Regarding the hydroxyl value and molecular weight of such aromatic amine-based polyether polyols (B2), there are no particular limitations, but a hydroxyl value of 200 to 600 mgKOH / g and a molecular weight of 400 to 700 are preferred.

[0016] In the polyester polyol (A) and polyether polyols (B1, B2), when using a plurality of polyols having different hydroxyl values, molecular weights, or functional group numbers, it is preferable that the average hydroxyl value, average molecular weight, or average functional group number is within the above ranges. The average hydroxyl value, average molecular weight, or average functional group number is a value obtained by averaging the hydroxyl value, molecular weight, or functional group number of each polyol according to the blending ratio.

[0017] In the present invention, the content ratio (A / (B1 + B2)) based on the masses of the polyester polyol (A) and the polyether polyols (B1, B2) is 60 or more and 90 or less / 10 or more and 40 or less, preferably 70 or more and 90 or less / 10 or more and 30 or less. If the content ratio of the polyester polyol (A) is less than 60 parts by mass, the foam after combustion is less likely to carbonize, and it is difficult to obtain high flame retardancy. Further, if the content ratio of the polyester polyol (A) exceeds 90 parts by mass, the foam is likely to shrink, and it is difficult to obtain a product suitable for actual use.

[0018] As the polyol, other polyols other than the polyester polyol (A) and the polyether polyols (B1, B2) may be included as long as the effects of the present invention are not inhibited. Examples of other polyols include aromatic polyester polyols, aromatic polyether polyols, aliphatic polyester polyols, aliphatic polyether polyols, amine-based polyether polyols, and polymer polyols.

[0019] The polyol component contains a quaternary ammonium salt and an alkali metal carboxylate as a trimerization catalyst. When a trimerization catalyst is included, the isocyanurate ring is more likely to be formed by the trimerization reaction (hereinafter also referred to as nurate formation) preferentially over the resinification reaction of a normal polyol and polyisocyanate or the foaming reaction of water and polyisocyanate. As a result, a rigid polyurethane foam with high flame retardancy can be obtained. When the trimerization catalyst is used alone as a quaternary ammonium salt, a rigid polyurethane foam with a good foam state can be obtained, but the trimerization reaction is slow, the formation of the isocyanurate ring does not proceed, and the foam after combustion is less likely to carbonize, making it difficult to obtain high flame retardancy. Further, since the alkali metal carboxylate tends to promote the curing reaction inside the foam, if the content is high, the foam may cure before expanding and may not expand. Thus, in order to take the balance of the reaction so as not to inhibit foaming while preferentially promoting the trimerization reaction, a quaternary ammonium salt and an alkali metal carboxylate are used in combination.

[0020] As the quaternary ammonium salt, tetramethylammonium salt, tetraethylammonium salt, tetraphenylammonium salt, etc. can be used. The content of the quaternary ammonium salt is preferably in the range of 0.1 part by mass or more and 0.8 part by mass or less with respect to 100 parts by mass of the total amount of the polyol. When the quaternary ammonium salt is less than 0.1 part by mass, sufficient nitration does not proceed and it is difficult to obtain high flame retardancy. When it exceeds 0.8 part by mass, the surface of the foam hardens quickly, inhibiting the growth of the foam and there is a risk that the foam will not expand.

[0021] As the alkali metal carboxylate, potassium acetate, sodium acetate, potassium 2-ethylhexanoate, sodium 2-ethylhexanoate, potassium octylate, potassium formate, sodium octylate, etc. can be used. In particular, alkali metal carboxylates such as potassium acetate and potassium octylate are preferred. The content of the alkali metal carboxylate is preferably in the range of 0.2 part by mass or more and 1.2 parts by mass or less with respect to 100 parts by mass of the total amount of the polyol. When the alkali metal carboxylate is less than 0.2 part by mass, sufficient nitration does not proceed and it is difficult to obtain high flame retardancy. When it exceeds 1.2 parts by mass, internal curing is fast and the foam hardens before it expands, and there is a risk that the foam will not expand.

[0022] Moreover, the total amount of the quaternary ammonium salt and the alkali metal carboxylate is preferably in the range of 0.3 part by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the total amount of the polyol.

[0023] The polyol component may contain catalysts that have been conventionally and generally used in addition to the quaternary ammonium salt and the alkali metal carboxylate. Examples of such catalysts include amine catalysts that promote resinification, such as N,N,N’,N’-tetramethylhexanediamine, N,N,N’,N’-tetramethylpropanediamine, N,N,N’,N’’,N’’-pentamethyldiethylenetriamine, N,N,N’,N’-tetramethylethylenediamine, N,N-dimethylbenzylamine, N-methylmorpholine, N-ethylmorpholine, triethylenediamine, N,N’,N’-trimethylaminoethylpiperazine, N,N-dimethylcyclohexylamine, N,N’,N’’-tris(3-dimethylaminopropyl)hexahydro-s-triazine, bis(dimethylaminoethyl)ether, N,N-aminoethoxyethanol, N,N-dimethylaminohexanol, tetramethylhexanediamine, 1-methylimidazole, 1-isobutyl-2-methylimidazole, etc. can be used. The content of the amine catalyst is preferably in the range of 0.01 part by mass or more and 1.0 part by mass or less with respect to 100 parts by mass of the total amount of the polyol.

[0024] The polyol component contains a foaming agent. For example, water, or hydrocarbons such as normal pentane, isopentane, cyclopentane, isobutane, hydrofluorocarbons such as HFC-365mfc, HFC-245fa, HFC-134a, hydrofluoroolefins such as 1-chloro-3,3,3,-trifluoropropene, 1,1,1,4,4,4-hexafluoro-2-butene, etc. can be mentioned, and these can be used alone or in appropriate combinations of two or more. Among them, the combination of water and cyclopentane is preferable.

[0025] When water is selected as the blowing agent, the water content is preferably in the range of 0.5 parts by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the total amount of the polyol. Since water generates heat by reacting with the isocyanate group and this heat promotes nuration, the calorific value is adjusted together with the density of the rigid polyurethane foam obtained depending on the water content. If the water content is less than 0.5 parts by mass, the heat generation by the reaction is low, so nuration does not proceed and it is difficult to obtain high flame retardancy. If it exceeds 3 parts by mass, there is a risk that nuration may be inhibited by the reaction between the polyisocyanate and water, and the foam may easily shrink.

[0026] The content of the blowing agent other than water is preferably in the range of 10 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the total amount of the polyol. The density of the rigid polyurethane foam obtained is adjusted depending on the content of the blowing agent, but if it is within this range, it is easy to obtain the desired density. Considering this point, the content of the blowing agent is more preferably 18 parts by mass or more and 30 parts by mass or less.

[0027] The polyol component contains a liquid phosphate ester as a flame retardant. Note that it only needs to be a liquid under the atmosphere of atmospheric pressure and normal temperature (25°C). In the present invention, examples of the phosphate ester include phosphate esters such as trimethyl phosphate and triethyl phosphate, condensed phosphate esters such as resorcinol polyphenyl phosphate, bisphenol A polycresyl phosphate, and aromatic condensed phosphate esters, or halogenated phosphate esters such as tris(chloroethyl) phosphate and tris(chloropropyl) phosphate.

[0028] The content of the phosphate ester is 30 parts by mass or more and 90 parts by mass or less, preferably 40 parts by mass or more and 80 parts by mass or less, with respect to 100 parts by mass of the total amount of the polyol. If the content of the phosphate ester is less than 30 parts by mass, it is difficult to obtain high flame retardancy. If it exceeds 90 parts by mass, the resin component in the foam decreases, the strength of the resin skeleton and resin film decreases, so the foam easily shrinks, and the gas of the blowing agent escapes, resulting in a high thermal conductivity, that is, a tendency to have poor heat insulation.

[0029] In the present invention, a solid flame retardant may be used as long as it does not inhibit the effects of the present invention. The solid flame retardant is a solid flame retardant under the atmosphere of atmospheric pressure and normal temperature (25°C), and examples thereof include red phosphorus, metal hydroxides, particularly aluminum hydroxide, magnesium hydroxide, zinc borate, ammonium polyphosphate, antimony oxide, and the like. The content of the solid flame retardant is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, based on 100 parts by mass of the total amount of the polyol.

[0030] In addition to the polyol, catalyst, foaming agent, and flame retardant, other additives may be added to the polyol component as necessary. Examples of other additives include additives generally used in the production of rigid polyurethane foam, such as foam stabilizers, crosslinking agents, plasticizers, fillers, antioxidants, defoaming agents, compatibilizers, colorants, stabilizers, and ultraviolet absorbers. The addition amount of other additives may be appropriately selected within a range that does not inhibit the effects of the present invention. Further, these additives may be added to the polyisocyanate component.

[0031] Examples of the foam stabilizer include conventionally generally used silicone-based compounds and fluorine-based compounds. The content of the foam stabilizer is preferably in the range of 0.5 part by mass or more and 5 parts by mass or less based on 100 parts by mass of the total amount of the polyol.

[0032] Examples of the crosslinking agent that can be used include alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, neopentyl glycol, tetramethylene ether glycol, glycerin, pentaerythritol, trimethylolpropane, monoethanolamine, diethanolamine, isopropanolamine, aminoethyl ethanolamine, sucrose, sorbitol, and glucose. In particular, among these, those having three or more functional groups are preferred.

[0033] The polyisocyanate component contains a polyisocyanate. The polyisocyanate can react with a polyol to form a urethane bond and can form an isocyanurate ring by a trimerization catalyst when mixed with the polyol component, and is not particularly limited. For example, aromatic isocyanates, aliphatic diisocyanates, alicyclic diisocyanates, isocyanate group-terminated prepolymers, etc. can be mentioned.

[0034] More specifically, examples of the polyisocyanate include aromatic isocyanates such as diphenylmethane diisocyanate, polymeric MDI (crude MDI), 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), and alicyclic diisocyanates such as isophorone diisocyanate, hydrogenated TDI, and hydrogenated MDI. These can be used alone or in combination of two or more.

[0035] The content of the polyisocyanate is such that the isocyanate index (= NCO groups of the polyisocyanate component / active hydrogen of the polyol component [equivalent ratio] × 100) is more than 230 and less than 330, preferably 250 or more and 300 or less, more preferably 250 or more and less than 300. If the isocyanate index is 230 or less, the content ratio of the isocyanurate ring formed by the trimerization reaction is small and flame retardancy cannot be obtained. If it is 330 or more, the unreacted isocyanate increases, making it prone to high brittleness, the cell shape becomes rough, and the thermal conductivity increases, that is, the heat insulation property tends to be poor.

[0036] To produce a rigid polyurethane foam by reacting and curing a polyol component containing the above polyol, catalyst, foaming agent, and flame retardant with a polyisocyanate component, generally used high-pressure and low-pressure rigid polyurethane foam machines are used, and a foaming method of continuously or discontinuously mixing the polyol component and the polyisocyanate component at a certain ratio can be used.

[0037] The rigid polyurethane foam of the present invention has high flame retardancy such that the foam after combustion is liable to carbonize and can retain its foam shape. Here, the ability to retain the foam shape can be evaluated from the mass retention rate (%) measured by the following method. In the present invention, a rigid polyurethane foam having a mass retention rate of 25% or more is judged to have high flame retardancy. More preferably, it is 30% or more. The mass retention rate is excellent in flame retardancy as it is higher, and there is no particular need to specify an upper limit value, but if forced to mention, it is about 60%.

[0038] 〔Flame retardancy: Mass retention rate〕 Using a single piece of rigid polyurethane foam with a thickness of 25 mm, a length of 99 mm, and a width of 99 mm as a test piece, in accordance with ISO5660-1, in the heat release test (cone calorimeter test) carried out at a heating intensity of 50 kW / m 2 , with a heating time of 5 minutes, measure the mass of the test piece after heating: X (g). When the mass of the test piece before heating is X 0 (g), the mass retention rate (%) is obtained by the following formula (1). Mass retention rate (%) = (X / X 0 ) × 100 ··· Formula (1)

[0039] Also, in the present invention, as an evaluation of flame retardancy, the maximum heat release rate (kW / m 2 ) in the following heat release test (cone calorimeter test) may be used. In the present invention, it is preferable that the maximum heat release rate is 150 kW / m 2 or less.

[0040] 〔Flame retardancy: Maximum heat release rate〕 Using a single piece of rigid polyurethane foam with a thickness of 25 mm, a length of 99 mm, and a width of 99 mm as a test piece, in accordance with ISO5660-1, in the heat release test (cone calorimeter test) carried out at a heating intensity of 50 kW / m 2 , measure the maximum heat release rate (kW / m 2 ) from the start of heating until 5 minutes have elapsed.

[0041] The rigid polyurethane foam of the present invention is excellent in heat insulation as well as flame retardancy. Generally, heat insulation is evaluated by the thermal conductivity: λ (W / (m·K)), and the smaller this value is, the better the heat insulation performance. In the present invention, a value of 0.024 (W / (m·K)) or less is preferable. The thermal conductivity can be measured by the heat flow meter method shown in JIS-A-1412, as described in the examples.

[0042] The present invention includes a heat insulation board having the above-mentioned rigid polyurethane foam as a heat insulation layer and facing materials on the front and back surfaces of the heat insulation layer. At this time, the thickness of the heat insulation layer is preferably 15 to 100 mm, and a heat insulation board excellent in flame retardancy and heat insulation can be obtained.

[0043] The facing material is not particularly limited, and for example, a laminated material obtained by laminating a synthetic resin film, a non-woven fabric, a metal vapor deposition film, etc. alone or in combination of a plurality can be used. Examples of the synthetic resin film include polyester films such as polyethylene film, polypropylene film, and polyethylene terephthalate film, polyvinyl chloride film, and other synthetic papers mixed with inorganic substances. In order to improve the adhesiveness with the rigid polyurethane foam which is the heat insulation layer, for example, corona treatment or the like may be performed. Examples of the non-woven fabric include those obtained by entangling one or more of synthetic fibers such as polyester fiber, nylon fiber, vinylon fiber, acrylic fiber, urethane fiber, and polyolefin fiber, natural fibers such as cotton, hemp, silk, and wool, and inorganic fibers such as glass fiber, carbon fiber, and metal fiber. Examples of the metal vapor deposition film include aluminum foil, copper foil, iron foil, lead foil, etc., and lightweight aluminum foil can be preferably used.

[0044] The heat-insulating board of the present invention can be used as a heat-insulating material for buildings such as wooden houses, concrete buildings, and steel-frame buildings. Further, since the heat-insulating board of the present invention uses a rigid polyurethane foam having high flame retardancy, it can be used in combination with various exterior wall materials and roof materials. Examples of the exterior wall materials and roof materials include wood-based, metal-based, ceramic-based materials, or heat-insulating panels having a heat-insulating material in a sandwich structure between a surface material and a back material. Note that the rigid polyurethane foam of the present invention can also be used as a heat-insulating material for such heat-insulating panels.

Examples

[0045] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

[0046] 〔Examples 1 to 13, Comparative Examples 1 to 10〕 As shown in Tables 1 and 2, a liquid obtained by blending a polyol component and a polyisocyanate component was stirred at 3000 revolutions per minute for 6 seconds using a hand mixer, and then freely foamed in a wooden box of 250 mm × 150 mm × 300 mm to obtain a rigid polyurethane foam. Note that the blending amounts in the table are shown in parts by mass.

[0047] Regarding the obtained rigid polyurethane foam, the foam state, density, dimensional stability, thermal conductivity, and flame retardancy (mass residue rate, maximum heat release rate) were measured and evaluated by the following methods, and the results are shown in Tables 1 and 2. Note that in Comparative Examples 2, 4, and 6, the foam state was poor and other measurements could not be performed.

[0048] Polyol component: Polyol 1 Terephthalic acid-based polyester polyol (hydroxyl value: 250 mgKOH / g, functionality: 2, "Maximol RFK-505" manufactured by Air Water Performance Chemical Co., Ltd.) Polyol 2 Sugar-based polyether polyol (sucrose initiator, hydroxyl value: 420 mgKOH / g, functionality: 8, "Sun Nix RP-410 A" manufactured by Sanyo Chemical Industries, Ltd.) Polyol 3 Sugar-based polyether polyol (sucrose initiator, hydroxyl value: 400 mgKOH / g, functionality: 4, "Actocol GR-35" manufactured by Mitsui Chemicals, Inc.) Polyol 4 Sugar-based polyether polyol (sorbitol initiator, hydroxyl value: 370 mgKOH / g, functionality: 3.8, "Actocol GR-17" manufactured by Mitsui Chemicals, Inc.) Polyol 5 Aromatic amine-based polyether polyol (toluenediamine initiator, hydroxyl value: 400mgKOH / g, functionality: 4, "Actocol RA-401" manufactured by Mitsui Chemicals, Inc.) Polyol 6 Phthalic anhydride-based polyester polyol (hydroxyl value: 315mgKOH / g, functionality: 2, "Maximol RDK-133" manufactured by Air Water Performance Chemicals, Inc.) Polyol 7 Aliphatic amine-based polyether polyol (ethylenediamine initiator, hydroxyl value: 750mgKOH / g, functionality: 4, "Excenol 750ED" manufactured by AGC, Inc.) Blowing agent: Blowing agent 1 Cyclopentane (manufactured by Maruzen Petrochemical Co., Ltd., trade name "Marucazol FH") Blowing agent 2 Water Catalyst: Catalyst 1 Quaternary ammonium salt (manufactured by Tosoh Corporation, "Toyocat TRX", quaternary ammonium salt / ethylene glycol / water = 65 / 30 / 5 (mass ratio)) Catalyst 2 Alkaline metal carboxylate (potassium octylate, "Dabco K-15" manufactured by Evonik Industries AG, potassium octylate / diethylene glycol = 75 / 25 (mass ratio)) Catalyst 3 Amine catalyst (N,N’,N’’-tris(3-dimethylaminopropyl)hexahydro-s-triazine: "Polycat 41" manufactured by Evonik Industries AG) Flame retardant: Tris(chloropropyl) phosphate (manufactured by Daihachi Chemical Industry Co., Ltd., trade name "TMC PP") Polyisocyanate component: Polymeric diphenylmethane diisocyanate (manufactured by Tosoh Corporation, trade name "MR-200")

[0049] 〔Foam state〕 The outer surface of the formed rigid polyurethane foam was visually observed and evaluated as follows. 〇: The foam is in good condition without shrinkage. △: There is some shrinkage in the foam, but the sample for measurement can be taken. ×: The foam has shrunk and it is impossible to take a sample for measurement, or the foam does not foam.

[0050] 〔Density (kg / m 3 )〕 The value was measured in accordance with JIS A9521. Using a test piece cut out to a size of 100 mm × 100 mm × 100 mm from the rigid polyurethane foam obtained by free foaming in a wooden box, the measurement was carried out.

[0051] 〔Dimensional stability〕 Using a test piece cut out to a size of 100 mm × 100 mm × 100 mm from the formed rigid polyurethane foam, when it was exposed to a cold and dark place at -20°C for 3 days, the volume change rate (vol.%) with respect to the test piece before exposure was measured and evaluated according to the following criteria. The volume change rate (vol.%) was obtained by the formula: (volume of the test piece after exposure / volume of the test piece before exposure - 1) × 100. A negative value indicates that the foam has shrunk. 〇: Those with 0 to less than -3 vol.%. △: Those with -3 to less than -5 vol.%. ×: -5 vol.% or less

[0052] 〔Thermal conductivity: λ (W / (m·K)〕 As shown in Tables 1 and 2, a liquid prepared by blending a polyol component and a polyisocyanate component was stirred at 3000 revolutions per minute for 6 seconds using a hand mixer, and then freely foamed on a metal plate maintained at 45°C. A test piece measuring 200 mm × 200 mm × 25 mm was cut out from the resulting rigid polyurethane foam and measured at an average temperature of 23°C using "Auto λHC-074" manufactured by Eihiro Seiki Co., Ltd. by the heat flow meter method shown in JIS-A-1412. In the present invention, the thermal conductivity may be 0.024 W / (m·K) or less.

[0053] [Flammability: Mass retention rate (%)] A test piece was cut out from the formed rigid polyurethane foam with a thickness of 25 mm, a length of 99 mm, and a width of 99 mm. In accordance with ISO5660-1, in the heat release test (cone calorimeter test) carried out at a heating intensity of 50 kW / m 2 , the heating time was set to 5 minutes, and the mass of the test piece after heating: X (g) was measured. When the mass of the test piece before heating was X 0 (g), the mass retention rate (%) was determined by the following formula (1). Mass retention rate (%) = (X / X 0 ) × 100 ··· Formula (1)

[0054] [Flammability: Maximum heat release rate (kW / m 2 )] A test piece was cut out from the formed rigid polyurethane foam with a thickness of 25 mm, a length of 99 mm, and a width of 99 mm. In accordance with ISO5660-1, in the heat release test (cone calorimeter test) carried out at a heating intensity of 50 kW / m 2 , the maximum heat release rate (kW / m 2 ) was measured from the start of heating until 5 minutes had elapsed.

[0055]

Table 1

[0056]

Table 2

[0057] From Table 1, Examples 1 to 13 are rigid polyurethane foams obtained by reacting and curing a polyol component containing a polyol, a catalyst, a foaming agent, and a flame retardant with a polyisocyanate component. The polyol contains a terephthalic acid-based polyester polyol (A) and a sugar-based polyether polyol (B1) or an aromatic amine-based polyether polyol (B2), and the content ratio (A / (B1 + B2)) based on the mass of the polyester polyol (A) and the polyether polyol (B1, B2) is 60 or more and 90 or less / 10 or more and 40 or less. The trimerization catalyst is a quaternary ammonium salt and an alkali metal carboxylate, the flame retardant is a liquid phosphate ester flame retardant, and its content is 30 parts by mass or more and 90 parts by mass or less based on 100 parts by mass of the total amount of the polyol. When the isocyanate index is more than 230 and less than 330, the resulting rigid polyurethane foam has a thermal conductivity of 0.024 W / (m·K) or less and excellent heat insulation properties, and a mass residue rate of 25% or more and is a foam that is easily carbonized, showing high flame retardancy.

[0058] In particular, Examples 1 to 10, 12, and 13 using a terephthalic acid-based polyester polyol (A) and a sugar-based polyether polyol (B1) as the polyol are preferred. Example 11 has a thermal conductivity of 0.024 W / (m·K) or less and excellent heat insulation properties, and a mass residue rate of 25% or more and shows high flame retardancy. However, since an aromatic amine-based polyether polyol (B2) is used, the amino group in the polyol acts as a catalyst, tending to inhibit nuration.

[0059] From Table 2, in Comparative Examples 1 to 10, when not satisfying any of the requirements of the present invention, the resulting rigid polyurethane foam had a mass residue rate of less than 25% and did not satisfy the flame retardancy, or had a high thermal conductivity and poor heat insulation properties. Further, in Comparative Examples 2, 4, and 6, the foam state was poor and no foam was obtained.

[0060] As described above, according to the present invention, it is possible to provide a rigid polyurethane foam having a high flame retardancy such that the foam after combustion is easily carbonized and can retain the foam shape.

Claims

1. A rigid polyurethane foam obtained by reacting and curing a polyol component containing a polyol, a catalyst, a blowing agent, and a flame retardant with a polyisocyanate component, wherein the polyol contains a terephthalic acid-based polyester polyol (A) and a sugar-based polyether polyol (B1) and / or an aromatic amine-based polyether polyol (B2), the content ratio (A / (B1 + B2)) based on the masses of the polyester polyol (A) and the polyether polyols (B1, B2) is 60 or more and 90 or less / 10 or more and 40 or less, the catalyst is a trimerization catalyst containing a quaternary ammonium salt and an alkali metal carboxylate, the flame retardant contains a liquid phosphate ester, and the content is 30 parts by mass or more and 90 parts by mass or less with respect to 100 parts by mass of the total amount of the polyol, the isocyanate index is more than 230 and less than 330, and a rigid polyurethane foam characterized in that the mass retention rate measured by the method shown below is 25% or more. (Mass retention rate) A single piece of rigid polyurethane foam with a thickness of 25 mm, a length of 99 mm, and a width of 99 mm was used as a test piece. In accordance with ISO 5660-1, in the heat release test (cone calorimeter test) carried out at a heating intensity of 50 kW / m ２ , the heating time was set to 5 minutes, and the mass of the test piece after heating: X (g) was measured. When the mass of the test piece before heating was X ０ (g), the mass retention rate (%) was determined by the following formula (1). Mass residual ratio (%) = (X / X ０ ) × 100... Equation (1)

2. The rigid polyurethane foam according to claim 1, wherein the polyol consists of a terephthalic acid-based polyester polyol (A) and a sugar-based polyether polyol (B1) having a functional group number of 4 or more and 8 or less.

3. A heat insulating board characterized by using the rigid polyurethane foam according to claim 1 or 2 as a heat insulating layer and having facing materials on the front and back surfaces of the heat insulating layer.

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