Urea resin foam and heat insulation material for piping

Abstract

To provide a technique relating to an urea resin foam excellent in moisture absorption resistance.SOLUTION: There is provided an urea resin foam 100. The urea resin foam 100 has a core part 110 and a skin layer 120. The average cell diameter of the skin layer 120 is 70% or less of the average cell diameter of the core part 110.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a urea resin foam and a pipe insulating material. [Background technology]

[0002] Known examples of materials for insulating piping include a technique for covering piping with a glass wool sheet as disclosed in Patent Document 1, and a technique for covering piping with rigid urethane foam as disclosed in Patent Document 2. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP2002-181281 [Patent Document 2] JP 2002-168393 A Summary of the Invention [Problem to be solved by the invention]

[0004] When glass wool is used as a pipe insulation material, there is a problem that the insulation performance decreases with age due to insufficient moisture absorption resistance, and when rigid urethane foam is used, there is a problem that not only is moisture absorption resistance insufficient, but heat resistance is also insufficient.

[0005] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a technique relating to a urea resin foam having excellent moisture absorption resistance. [Means for solving the problem]

[0006] One embodiment of the present invention is a urea resin foam having a skin layer.

[0007] In the urea resin foam of the above embodiment, the average cell diameter of the skin layer may be 70% or less of the average cell diameter of the core portion of the urea resin foam, and the proportion of the surface where the skin layer is exposed to the total surface of the urea resin foam may be 80% or more.

[0008] Another aspect of the present invention is a pipe insulation material comprising the urea resin foam according to any one of the above aspects. Effect of the Invention

[0009] According to the present invention, a technique for a urea resin foam having excellent moisture absorption resistance can be provided. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic cross-sectional view of a urea resin foam according to an embodiment. [Diagram 2] 2(a) to (c) are schematic process diagrams illustrating a method for producing a urea resin foam according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present invention will be described in detail. In this specification, the expression "a to b" in the explanation of a numerical range means that the range is from a to b, unless otherwise specified.

[0012] (Urea resin foam) 1 is a schematic cross-sectional view of a urea resin foam 100 according to an embodiment. As shown in FIG. 1, the urea resin foam 100 according to the embodiment has a core portion 110 and a skin layer 120.

[0013] The average cell diameter in the core portion 110 is preferably 100 to 300 μm, more preferably 120 to 280 μm, and even more preferably 150 to 250 μm. The cells in the core portion 110 of the urea resin foam 100 are observed and measured using an optical microscope (for example, a digital microscope) equipped with an average cell diameter measuring function. Specifically, the test piece is taken out so that the flow direction of the foam when foamed in a mold (the direction in which the urea resin composition foams and expands, vertically upward from the bottom of the mold; hereafter, this direction will be referred to as the rise direction) corresponds to the thickness direction of the test piece. The surface of the taken-out test piece with the rise direction as the normal line is the CD surface. The surface perpendicular to the CD surface of the test piece is the MD surface. In the center portion in the rise direction, ten bubbles are randomly selected in the MD plane, and the lengths of their major axes are measured. The average is taken as the average cell diameter in the MD plane in the core portion 110 .

[0014] The skin layer 120 is a surface layer integrally formed on the surface of the urea resin foam 100. The skin layer 120 is a layer having a higher density than the core portion 110. The average cell diameter in the skin layer 120 is preferably 70% or less, more preferably 60% or less, and even more preferably 50% or less of the average cell diameter in the core portion 110 of the urea resin foam 100. This can suppress the water absorption of the urea resin foam 110. In addition, the strength and dimensional stability can be improved. The average cell diameter of the cells in the skin layer 120 of the urea resin foam 100 is observed and measured using an optical microscope with a length measurement function (for example, a digital microscope). Specifically, at a depth of 100 μm from the outermost surface in the rise direction of the above-mentioned test piece, 10 bubbles in the MD plane were randomly selected, the length of their major axes was measured, and the average was taken as the average cell diameter in the MD plane of the skin layer 120.

[0015] The urea resin foam 100 according to the embodiment includes the skin layer 120, which can prevent moisture from penetrating into the core 110, and thus can prevent a decrease in heat insulation. Furthermore, the urea resin foam 100 according to the embodiment includes the skin layer 120, which can improve the strength and dimensional stability.

[0016] The ratio of the exposed surface of the skin layer 120 to the entire surface of the urea resin foam 100, in other words, the ratio of the surface area of ​​the skin layer 120 covering the core portion 110 to the entire surface of the urea resin foam 100, is preferably 80% or more, more preferably 90% or more, even more preferably 95% or more, and most preferably 100%. The higher the ratio, the more the water absorption of the urea resin foam 110 can be suppressed while improving the strength and dimensional stability.

[0017] The urea resin foam 10 according to the embodiment is obtained by foaming and curing a urea resin composition, which will be described later, by a molding method.

[0018] (urea resin composition) The urea resin composition used to form the urea resin foam according to the embodiment will be described. The urea resin composition preferably contains a polyisocyanate compound (A), a polyamine compound (B), a trimerization catalyst, and a foaming agent, and further contains a foam stabilizer and a flame retardant. Each component of the urea resin composition will be described below.

[0019] (Polyisocyanate compound (A)) The polyisocyanate compound (A) is not particularly limited as long as it does not impair the effects of the present invention. Examples of the polyisocyanate compound (A) include monomeric polyisocyanates and polymeric polyisocyanates. The monomeric polyisocyanate is a compound having a plurality of isocyanate groups at the terminals of the monomer structure. The polymeric polyisocyanate is a compound having a plurality of isocyanate groups at the terminals of the polymer structure. These polyisocyanate compounds (A) can be used alone or in combination.

[0020] Examples of the monomeric polyisocyanate include bifunctional polyisocyanate compounds such as 2,4-toluene diisocyanate (2,4-TDI), 2,6-toluene diisocyanate (2,6-TDI), m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 2,2'-diphenylmethane diisocyanate (2,2'-MDI), hydrogenated MDI, xylylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, and 3,3'-dimethoxy-4,4'-biphenylene. Aromatic diisocyanates such as polymethylene polyphenyl polyisocyanate, 1,5-naphthalene diisocyanate, xylylene diisocyanate (XDI), hydrogenated XDI, tetramethyl xylene diisocyanate (TMXDI), etc.; alicyclic diisocyanates such as cyclohexane-1,4-diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, methylcyclohexane diisocyanate, etc.; alkylene diisocyanates such as butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, lysine diisocyanate, etc.; Examples of trifunctional or higher polyisocyanates include 1-methylbenzene-2,4,6-triisocyanate, 1,3,5-trimethylbenzene-2,4,6-triisocyanate, biphenyl-2,4,4'-triisocyanate, diphenylmethane-2,4,4'-triisocyanate, methyldiphenylmethane-4,6,4'-triisocyanate, 4,4'-dimethyldiphenylmethane-2,2',5,5'tetraisocyanate, triphenylmethane-4,4',4"-triisocyanate, polymeric MDI, lysine ester triisocyanate, 1,3,6-hexamethylene triisocyanate, 1,6,11-undecane triisocyanate, bicycloheptane triisocyanate, 1,8-diisocyanatomethyloctane, and the like. In addition, modified products and derivatives thereof may be included. Examples of modified products and derivatives thereof include isocyanurate compounds of diisocyanate compounds, adduct compounds of diisocyanate compounds, biuret compounds of diisocyanate compounds, allophanate compounds of diisocyanate compounds, and carbodiimide modified compounds of diisocyanate compounds. These polyisocyanate compounds may be used alone or in combination. Since the monomeric polyisocyanate compound forms the urea skeleton of the urea resin foam, it can be freely selected in consideration of the desired properties of the urea resin foam. Among these monomeric polyisocyanates, aromatic isocyanates are preferred in terms of excellent reactivity, MDI or modified or derivatives of MDI are more preferred, and monomeric MDI and crude MDI are even more preferred. In addition, among monomeric MDI and crude MDI having the same NCO%, crude MDI containing polynuclear compounds has excellent isocyanurate ratio and therefore excellent flame retardancy.

[0021] The polymeric polyisocyanate compound includes a prepolymer obtained by reacting an excess amount of a polyisocyanate compound (C) with an active hydrogen compound having two or more active hydrogen groups, such as a polyol compound or a polyamine compound (D). The polyamine compound (D) and the polyisocyanate compound (C) are raw materials for preparing the polymeric polyisocyanate, and are not included in the polyamine compound (B) and the polyisocyanate compound (A), which are raw materials for the urea resin composition according to the present embodiment. Here, the polyisocyanate compound (C) may be the same as or different from the polyisocyanate compound (A).

[0022] Examples of such polyol compounds include polyester polyols and polyether polyols. Examples of polyester polyols include those obtained by a condensation reaction between a polyhydric alcohol and a polycarboxylic acid. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, butanediol, butylene glycol, glycerin, and trimethylolpropane. Examples of polycarboxylic acids include Examples of the polyol include glutaric acid, adipic acid, maleic acid, phthalic acid, terephthalic acid, and isophthalic acid. These may be used alone or in combination. Further examples include polyester polyols obtained by ring-opening condensation of caprolactone, methyl valerolactone, and the like.

[0023] Examples of polyether polyols include those obtained by addition polymerization of oxides such as ethylene oxide, propylene oxide, trimethylene oxide, butylene oxide, etc., to polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, glycerin, trimethylolpropane, sorbitol, etc. These can be used alone or in combination.

[0024] The polyisocyanate compound (B) to be reacted with these polyol compounds is not particularly limited as long as it does not inhibit the effects of the present invention, and examples thereof include aliphatic or aromatic polyisocyanates, mixtures thereof, and modified polyisocyanates obtained by modifying them.

[0025] The polyamine compound (D) is not particularly limited as long as it does not impair the effects of the present invention. Examples of the polyamine compound (D) include aliphatic polyamines such as triethylenetetramine, aromatic polyamines such as metaphenylenediamine, and alicyclic polyamines such as isophoronediamine. Specifically, 4,4'-diamino-3,3'-dichlorodiphenylmethane, trimethylene-bis(4-aminobenzoate), 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, polytetramethylene oxide-di-p-aminobenzoate, 2,2',6,6'-tetraethyl-4,4'-methylenedianiline, 4,4'-methylenebis(2-isopropyl-6-methylaniline), 4,4'-methylenebis(2,6-diisopropylaniline), 4,4'-methylenebis(3-chloro-2,6-diethylaniline), 3,5-diethyltoluene-2,4-diamine, and dimethylthiotoluenediamine can be mentioned. These can be used alone or in combination. In addition, the polyamine compound (D) may be the same as or different from the polyamine compound (B) described later.

[0026] The NCO% of the polyisocyanate compound (A) is not limited as long as it does not impair the effects of the present invention, and can be, for example, 5 to 40%, preferably 10 to 35%, and more preferably 15 to 35%. When the NCO% of the polyisocyanate compound (A) is large, a urea resin foam having high shape retention during combustion, low thermal conductivity, and capable of suppressing deterioration over time in a humid and hot environment can be obtained. That is, a urea resin foam having excellent flame retardancy and shape retention during combustion, and capable of suppressing deterioration over time in a humid and hot environment can be obtained.

[0027] The NCO% (isocyanate content) of the polyisocyanate compound (A) is measured in accordance with Method A (toluene / dibutylamine, hydrochloric acid method) of JIS K1603-1:2007 "Plastics - Polyurethane raw material aromatic isocyanate test method Part 1: Determination of isocyanate group content".

[0028] The content of the polyisocyanate compound (A) in the urea resin composition can be 100 to 1000 parts by mass, assuming that the total content of the polyamine compound (B) in the urea resin composition is 100 parts by mass.

[0029] (Polyamine compound (B)) The polyamine compound (B) reacts with isocyanate to form a urea bond, which has the characteristics of excellent resistance to water, corrosion, and chemicals such as acids and alkalis.

[0030] The polyamine compound (B) is not particularly limited as long as it does not impair the effects of the present invention. Examples of the polyamine compound (B) include aliphatic polyamines such as triethylenetetramine, aromatic polyamines such as metaphenylenediamine, and alicyclic polyamines such as isophoronediamine. Specific examples include 4,4'-diamino-3,3'-dichlorodiphenylmethane, trimethylene-bis(4-aminobenzoate), 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, polytetramethylene oxide-di-p-aminobenzoate, 2,2',6,6'-tetraethyl-4,4'-methylenedianiline, 4,4'-methylenebis(2-isopropyl-6-methylaniline), 4,4'-methylene Examples of commercially available products include Iharacureamine MT, Iharacureamine M liquid, CUA-4, Curehard MED, Elasmer 250P, and Elasmer 1000P manufactured by Kumiai Chemical Industry Co., Ltd.; Lonzacure M-DEA, Lonzacure M-MIPA, Lonzacure M-DIPA, and Lonzacure M-CDEA manufactured by Lonza Japan Co., Ltd.; Ethacure 100, Ethacure 300, Ethacure 410, and Ethacure 420 manufactured by Albemarle Co., Ltd.; VERSALINK 740 manufactured by Evonik Nutrition & Care Co., Ltd.; and ANCAMINE 2049 manufactured by Evonik Co., Ltd. These may be used alone or in combination.

[0031] The amine value of the polyamine compound (B) is not particularly limited as long as it does not impair the effects of the present invention, and can be, for example, 50 to 1000 mgKOH / g, preferably 200 to 1000 mgKOH / g, more preferably 450 to 1000 mgKOH / g, and even more preferably 500 to 1000 mgKOH / g. When the amine value of the polyamine compound is within this range, a urea resin composition can be obtained that can provide a urea resin foam that has excellent flame retardancy and shape retention during combustion and can suppress deterioration over time in a moist and hot environment.

[0032] The amine value of the polyamine compound (B) can be measured by the method for measuring the total amine value described in JIS K1557-7:2011 "Plastics - Test methods for polyurethane raw material polyols - Part 7: Determination of basicity (indication of nitrogen content and total amine value)".

[0033] The content of the polyamine compound (B) in the urea resin composition is 2.0% by mass or more, preferably 5.0% by mass or more, and more preferably 8.0% by mass or more, when the total amount of the urea resin composition is 100% by mass. The upper limit of the content of the polyamine compound (B) can be, for example, 40.0% by mass or less, preferably 30.0% by mass or less, and more preferably 20.0% by mass or less. From another perspective, the content of the polyamine compound (B) can be blended so that the isocyanate index of the urea resin composition is 200 to 600, more preferably 200 to 500. Here, the isocyanate index refers to the ratio of the mole number of all active hydrogens in the resin composition, which is the total raw material blend, to the mole number of isocyanate groups in the polyisocyanate compound (A) multiplied by 100 (moles of NCO / moles of active hydrogen x 100). When the isocyanate index of the resin composition is within this range, a sufficient isocyanurate structure is formed, and the isocyanurate ratio can be made appropriate, so that the urea resin foam can have excellent flame retardancy.

[0034] In addition to the polyamine compound (B) described above, an active hydrogen compound can be added as long as it does not impair the effects of the present invention. Examples of the active hydrogen compound include alcohols such as primary alcohols, secondary alcohols, and tertiary alcohols, monools, polyol compounds, and thiol compounds. The alcohols and polyol compounds react with the polyisocyanate compound (A) to form urethane bonds and form part of the skeleton of the urea resin foam. However, since the urethane bond is more flammable than the urea bond, there is a risk that the flame retardancy of the urea resin foam may be reduced. For this reason, the content of the polyol compound can be 1 / 5 or less, preferably 1 / 10 or less, by mass ratio relative to the content of the polyamine compound (B), and more preferably no polyol compound is included.

[0035] (trimerization catalyst) The trimerization catalyst is not particularly limited as long as it does not impair the effects of the present invention. By using the trimerization catalyst, an isocyanurate structure can be formed in the urea resin foam when the urea resin foam is produced using the polyamine compound (B). Examples of the trimerization catalyst include metal oxides such as lithium oxide, sodium oxide, and potassium oxide; alkoxides such as sodium methoxy, sodium ethoxy, sodium propoxy, sodium butoxy, potassium methoxy, potassium ethoxy, potassium propoxy, and potassium butoxy; organic metal salts such as potassium acetate, potassium octylate, potassium caprylate, and iron oxalate; 2,4,6-tris(dimethylaminomethyl)phenol, N,N',N"-tris(dimethylaminopropyl)hexahydrotriazine, triethylenediamine, and 1,3,5-tris(dimethylaminopropyl)hexahydro-s-triazine. tertiary amines such as ethyleneimine derivatives; acetylacetone chelates of alkali metals, aluminum, and transition metals; quaternary ammonium salts; diazabicycloundecene (DBU), etc. These can be used alone or in combination. Of these, it is more preferable to use tertiary amines, organic metal salts, and diazabicycloundecene, and it is more preferable to use tertiary amines and diazabicycloundecene. By using these suitable trimerization catalysts, it is possible to obtain a urea resin foam that has excellent flame retardancy and shape retention during combustion and can suppress deterioration over time in a humid and hot environment.

[0036] The content of the trimerization catalyst in the urea resin composition can be 0.1 to 30 parts by mass, preferably 0.5 to 20 parts by mass, more preferably 1.5 to 20 parts by mass, and even more preferably 2.0 to 20 parts by mass, when the total content of the polyamine compound (B) in the urea resin composition is taken as 100 parts by mass. When the content of the trimerization catalyst is within this range, the isocyanuration is sufficient, and a urea resin foam having excellent flame retardancy and shape retention during combustion and capable of suppressing deterioration over time in a humid and hot environment can be obtained. In addition, the content of the trimerization catalyst contained in the urea resin foam can be 0.01 to 20% by mass, preferably 0.05 to 15% by mass, when the total mass of the urea resin foam is taken as 100% by mass.

[0037] The urea resin foam of the present embodiment preferably contains an isocyanurate structure, which is formed by trimerizing a polyisocyanate compound (A), which is a raw material of the urea resin composition, with a trimerization catalyst. The urea resin foam containing an isocyanurate structure can exhibit excellent flame retardancy and shape retention during combustion, and can also suppress deterioration over time of the urea resin foam in a humid and hot environment.

[0038] (foaming agent) The blowing agent is not particularly limited as long as it does not impair the effects of the present invention. Examples of the blowing agent include water, hydrocarbons (preferably C4 to C6), hydrofluoroolefins, and carbon dioxide gas. Specific examples include cyclopentane, HFO (1336mzz), and HFO (1233zd). These may be used alone or in combination.

[0039] The content of the foaming agent in the urea resin composition can be 1 to 80 parts by mass, preferably 5 to 70 parts by mass, when the total content of the polyamine compound (B) in the urea resin composition is taken as 100 parts by mass. When the content of the foaming agent is within this range, a urea resin foam can be obtained that has excellent flame retardancy and shape retention during combustion and can suppress deterioration over time in a humid and hot environment. In addition, the content of the foaming agent in the urea resin foam can be 1 to 60% by mass, preferably 3 to 55% by mass, when the total mass of the urea resin foam is taken as 100% by mass.

[0040] (Foam stabilizer) The foam stabilizer is not particularly limited as long as it does not impair the effects of the present invention. Examples of the foam stabilizer include silicone compounds and nonionic surfactants. These can be used alone or in combination.

[0041] The content of the foam stabilizer in the urea resin composition can be 0.1 to 40 parts by mass, where the total content of the polyamine compound (B) in the urea resin composition is taken as 100 parts by mass. The content of the foam stabilizer in the urea resin foam can be 0.1 to 20% by mass, and preferably 0.5 to 10% by mass, where the total mass of the urea resin foam is taken as 100% by mass.

[0042] (Flame retardant) The urea resin composition according to the present embodiment may contain a flame retardant. The flame retardant is not particularly limited as long as it does not impair the effects of the present invention, and examples thereof include red phosphorus, phosphoric acid ester, phosphate-containing flame retardant, bromine-containing flame retardant, boron-containing flame retardant, antimony-containing flame retardant, and metal hydroxide. These may be used alone or in combination. Among these, it is preferable to include at least one selected from red phosphorus or phosphate ester, phosphate-containing flame retardant, bromine-containing flame retardant, boron-containing flame retardant, antimony-containing flame retardant and metal hydroxide, more preferably to include red phosphorus, and more preferably to include at least one selected from phosphate ester, phosphate-containing flame retardant, bromine-containing flame retardant, boron-containing flame retardant, antimony-containing flame retardant and metal hydroxide in addition to red phosphorus, and particularly preferably to include red phosphorus and phosphate ester, and further to include at least one selected from chlorine-containing phosphate ester, phosphate-containing flame retardant, bromine-containing flame retardant, boron-containing flame retardant, antimony-containing flame retardant and metal hydroxide, and particularly preferably to include red phosphorus, phosphate ester and bromine-containing flame retardant. When the urea resin composition according to the present invention includes these flame retardants, it is possible to obtain a urea resin foam that has excellent flame retardancy and shape retention during combustion and can suppress deterioration over time in a moist and hot environment. In addition, it can include other flame retardants other than these flame retardants.

[0043] The phosphoric acid ester is not particularly limited as long as it does not impair the effects of the present invention. Examples of the phosphoric acid ester include aromatic phosphoric acid esters such as triphenyl phosphate, cresyl diphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, tris(t-butylated phenyl) phosphate, tris(i-propylated phenyl) phosphate, and 2-ethylhexyl diphenyl phosphate; 1,3-phenylenebis(diphenyl phosphate), 1,3-phenylenebis(diox Aromatic condensed phosphate esters such as resorcinol bis(diphenyl) phosphate, resorcinol bis(diphenyl) phosphate, and bisphenol A bis(diphenyl phosphate); Halogen-containing phosphate esters such as tris(dichloropropyl) phosphate, tris(β-chloropropyl) phosphate, and tris(chloroethyl) phosphate; Examples of the halogen-containing condensed phosphate esters include 2,2-bis(chloromethyl)trimethylene bis(bis(2-chloroethyl)phosphate) and polyoxyalkylene bisdichloroalkyl phosphate. These can be used alone or in combination.

[0044] The phosphate-containing flame retardant is not particularly limited as long as it does not impair the effects of the present invention. Examples of the phosphate-containing flame retardant include monophosphates such as ammonium salts such as ammonium phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate; Sodium salts such as monosodium phosphate, disodium phosphate, trisodium phosphate, monosodium phosphite, disodium phosphite, and sodium hypophosphite; Potassium salts such as monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, monopotassium phosphite, dipotassium phosphite, and potassium hypophosphite; Lithium salts such as lithium monophosphate, lithium diphosphate, lithium triphosphate, lithium monophosphite, lithium diphosphite, and lithium hypophosphite; barium salts such as barium dihydrogen phosphate, barium hydrogen phosphate, barium triphosphate, and barium hypophosphite; magnesium salts such as magnesium monohydrogen phosphate, magnesium hydrogen phosphate, magnesium trimagnesium phosphate, and magnesium hypophosphite; Calcium salts such as calcium dihydrogen phosphate, calcium hydrogen phosphate, tricalcium phosphate, calcium hypophosphite; Examples include zinc salts such as zinc phosphate, zinc phosphite, and zinc hypophosphite; and aluminum salts such as aluminum monophosphate, aluminum diphosphate, aluminum triphosphate, aluminum phosphite, and aluminum hypophosphite. Examples of polyphosphates include ammonium polyphosphate, piperazine polyphosphate, melamine polyphosphate, ammonium amide polyphosphate, aluminum polyphosphate, etc. These may be used alone or in combination.

[0045] The bromine-containing flame retardant is not particularly limited as long as it does not impair the effects of the present invention. Examples of the bromine-containing flame retardant include pentabromodiphenyl ether, octabromodiphenyl ether, decabromodiphenyl ether, tetrabromobisphenol A (TBBA), TBBA-epoxy oligomer, TBBA-polycarbonate oligomer, TBBA-bis(dibromopropyl ether), TBBA-bis(aryl ether), and other TBBA compounds. Polybenzene ring compounds such as bisphenylpentamethane, 1,2-bis(2,4,6-tribromophenoxy)ethane, 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine, 2,6-dibromophenol, and 2,4-dibromophenol; Brominated styrene compounds such as brominated polystyrene and polybrominated styrene; Phthalic acid compounds such as ethylene bis tetrabromophthalimide; Examples of the cyclic aliphatic compounds include hexabromocyclododecane, etc.; polyacrylic acid brominated aromatic ester compounds, such as poly(pentabromophenyl acrylate); etc. These can be used alone or in combination.

[0046] The boron-containing flame retardant is not particularly limited as long as it does not inhibit the effects of the present invention. Examples of the boron-containing flame retardant include borax; boron oxides such as diboron trioxide, boron trioxide, diboron dioxide, tetraboron trioxide, and tetraboron pentoxide; boric acid compounds such as boric acid, lithium borate, sodium borate, potassium borate, cesium borate, magnesium borate, calcium borate, barium borate, zirconium borate, zinc borate, aluminum borate, and ammonium borate.

[0047] The antimony-containing flame retardant is not particularly limited as long as it does not impair the effects of the present invention. Examples of the boron-containing flame retardant include antimony oxides such as antimony trioxide and antimony pentoxide; antimonate salts such as sodium antimonate and potassium antimonate; pyroantimonate salts such as sodium pyroantimonate and potassium pyroantimonate; and the like. These may be used alone or in combination.

[0048] The metal hydroxide is not particularly limited as long as it does not impair the effects of the present invention. Examples of the metal hydroxide include aluminum hydroxide and magnesium hydroxide. These can be used alone or in combination.

[0049] As the other flame retardant, a known flame retardant can be used. As the other flame retardant, for example, chlorine compounds such as chlorinated paraffin, nitrogen compounds such as hindered amines and melamine cyanurate, cellulose, etc. can be mentioned. These can be used alone or in combination.

[0050] The content of the flame retardant in the urea resin composition can be 10 to 300 parts by mass, preferably 30 to 250 parts by mass, and more preferably 50 to 150 parts by mass, when the total content of the polyamine compound (B) in the urea resin composition is taken as 100 parts by mass. When the content of the flame retardant is within this range, a urea resin foam having excellent flame retardancy can be obtained. In addition, the content of the flame retardant in the urea resin foam can be 1 to 60% by mass, and preferably 2 to 45% by mass, when the total mass of the urea resin foam is taken as 100% by mass.

[0051] The content of red phosphorus in the urea resin composition can be 100 parts by mass or less, preferably 5 to 40 parts by mass, and more preferably 25 to 40 parts by mass, when the total content of the polyamine compound (B) in the urea resin composition is 100 parts by mass. The content of red phosphorus contained in the urea resin foam can be 1 to 30% by mass, preferably 2 to 25% by mass, and more preferably 3 to 10% by mass, when the total mass of the urea resin foam is 100% by mass. When the content of red phosphorus is within this range, a urea resin foam with better flame retardancy can be obtained, and deterioration over time in a humid and hot environment can be suppressed. In particular, the ash content after thermal decomposition of the foam increases, and in the flame contact evaluation described later, a non-flammable carbonized layer is formed at the beginning of flame contact, thereby preventing combustion from progressing to the depth of the foam. The total content of the flame retardants selected from phosphoric acid esters, phosphate-containing flame retardants, bromine-containing flame retardants, boron-containing flame retardants, antimony-containing flame retardants, and metal hydroxides can be 10 to 200 parts by mass, assuming that the total content of the polyamine compound (B) in the urea resin composition is 100 parts by mass. The ratio (Fp / Ft) of the content of red phosphorus (Fp) in the urea resin composition to the total content (Ft) of the flame retardants selected from phosphoric acid esters, phosphate-containing flame retardants, bromine-containing flame retardants, boron-containing flame retardants, antimony-containing flame retardants, and metal hydroxides is not particularly limited, but can be, for example, 0.0 to 1, preferably 0.0 to 0.8, more preferably 0.09 to 0.73, and even more preferably 0.45 to 0.73. When the amount of the flame retardant is within the above range, a urea resin foam having excellent flame retardancy and shape retention during combustion and capable of suppressing deterioration over time in a humid and hot environment can be obtained.

[0052] (Other additives) In addition to the above-mentioned additives, other additives may be added to the urea resin composition according to the present embodiment, so long as the effects of the present invention are not impaired. Examples of other additives include resin (urea) catalysts, foaming catalysts, balance catalysts, antioxidants, ultraviolet absorbers, antibacterial agents, dispersants, and other known additives.

[0053] In the case of blending the content of a catalyst other than the trimerization catalyst (resinification catalyst, foaming catalyst, etc.) in the urea resin composition, the content of the catalyst other than the trimerization catalyst can be 1 to 10 parts by mass when the total content of the polyamine compounds in the urea resin composition is 100 parts by mass. Note that a compound having both the functions of a resinification catalyst and a foaming catalyst is blended as a resinification catalyst. In addition, the content of the catalyst other than the trimerization catalyst contained in the urea resin foam can be 0 to 20% by mass, and preferably 0.5 to 15% by mass, when the total mass of the urea resin foam is 100% by mass.

[0054] <density> The density of the urea resin foam is not particularly limited as long as it does not impair the effects of the present invention, but is preferably 10 to 200 kg / m 3 The thickness can be set to 10 to 100 kg / m 3 is preferable, and 10 to 80 kg / m 3 When the density of the urea resin foam is within this range, a urea resin foam having excellent thermal conductivity and excellent flame retardancy can be obtained. The density of the urea resin foam is measured according to JIS K7222:2005 "Foamed plastics and rubber - Determination of apparent density".

[0055] 2(a), a urea resin composition 20 is injected into a cavity in a mold (molding die) 10 through an injection port (not shown) of the mold 10. The molding shape of the mold 10 can be appropriately designed and modified depending on the structure and shape of the molded product to be formed from the urea resin foam. The urea resin composition 20 is prepared by mixing the polyisocyanate compound (A), the polyamine compound (B), the catalyst, the foaming agent, the foam stabilizer, the red phosphorus, other flame retardants, and other additives in advance. A known method can be used as the mixing method. Specifically, the raw materials other than the polyisocyanate (A) are mixed in a predetermined container with a mixer (e.g., a mixer equipped with a propeller-type stirring blade) (e.g., stirring at 2000 rpm for 5 minutes using the stirrer) to prepare a polyamine mixture. Next, the polyisocyanate (A) and the polyamine mixture are each cooled to a predetermined temperature (e.g., 20°C ± 2°C). Thereafter, the polyisocyanate (A) and the polyamine mixture are mixed (e.g., stirring at 3000 rpm for 2 seconds using the stirrer) to prepare the urea resin composition 20.

[0056] Next, as shown in FIG. 2(b), the urea resin composition 20 is foamed and cured in the cavity in the mold 10. The foaming and curing conditions are, for example, 30 to 70° C. and 1 to 30 minutes. In the foaming and curing process, a skin layer is formed on the surface portion of the urea resin foam produced from the urea resin composition 20 that contacts the inner wall of the mold 10. By controlling the foaming and curing conditions, the average cell diameter of the skin layer 120 described below can be adjusted to a desired value.

[0057] Next, as shown in Fig. 2(c), after foaming and curing are completed, the mold 10 shown in Fig. 2(b) is removed to obtain a urea resin foam 100 having a core portion 110 and a skin layer 120. Specifically, the urea resin foam 100 has a structure in which the skin layer 120 covers the core portion 110, and the skin layer 120 is exposed on the outermost surface of the urea resin foam 100.

[0058] (Insulation for piping) The pipe insulation material according to the embodiment includes the urea resin foam of the above-mentioned aspect. The shape of the pipe insulation material according to the embodiment is not particularly limited, but may be a cylindrical shape that can cover a predetermined outer peripheral surface of the pipe. In this case, it is preferable that a skin layer is formed on the outer peripheral surface (exposed surface) of the pipe insulation material. The urea resin foam of the above-mentioned embodiment has excellent moisture absorption resistance, strength and dimensional stability, and therefore when used as a material for a pipe insulating material, at least the following effects are achieved. -Prevents deterioration of insulation performance due to moisture absorption. - It is easier to maintain its shape when subjected to external impact during use. -Easily maintains its shape when used in high temperature environments.

[0059] The pipe insulation material according to the embodiment may be integrally molded using the urea resin foam of the above-mentioned aspect, or may be made into a plurality of parts using the urea resin foam of the above-mentioned aspect in accordance with the shape of the pipe to be insulated, and the parts may be fixed together using a known adhesive or the like. A facing material (aluminum foil or PVC film with aluminum vapor deposition) may be attached to the surface of the pipe insulating material of this embodiment. The method of attaching the facing material is not particularly limited, but examples include a method of attaching the facing material to the surface of the urea resin foam after molding the urea resin foam, and a method of setting the facing material in a mold when molding the urea resin foam and molding them together.

[0060] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various configurations other than those described above can also be adopted. EXAMPLES

[0061] EXAMPLES Hereinafter, the present invention will be described with reference to examples and comparative examples, but the present invention is not limited to these.

[0062] Example 1 A urea resin composition was prepared according to the urea formulation shown in Table 1. This urea resin composition was filled into a mold having an inner dimension of 300 mm×300 mm×t20 mm. After filling, foaming and curing were performed by molding at 55° C. for 5 minutes. The mold was then removed to obtain a urea resin foam having a skin layer. For the urea resin foam of Example 1, the average cell diameters of the core and at a depth of 100 μm from the surface were measured, and (average cell diameter at a depth of 100 μm from the surface) / (average cell diameter of the core)×100(%) was calculated. The obtained results are shown in Table 2.

[0063] Comparative Example 1 According to the urea formulation shown in Table 1, molding was carried out in the same manner as in Example 1, and then the foam was cut to a thickness of 20 mm and the skin layer was removed to obtain a urea resin foam. For the urea resin foam of Comparative Example 1, the average cell diameters of the core and the average cell diameter at a depth of 100 μm from the surface were measured, and the formula (average cell diameter at a depth of 100 μm from the surface) / (average cell diameter of the core)×100(%) was calculated. The results are shown in Table 2.

[0064] Comparative Example 2 A urethane resin composition was prepared according to the urethane formulation shown in Table 1. This urethane resin composition was filled into a mold having an inner dimension of 300 mm×300 mm×t20 mm. After filling, foaming and curing were carried out at 55° C. for 5 minutes, and the mold was removed to obtain a urethane resin foam having a skin layer. For the urethane resin foam of Comparative Example 2, the average cell diameters in the core and at a depth of 100 μm from the surface were measured, and (average cell diameter at a depth of 100 μm from the surface) / (average cell diameter in the core)×100(%) was calculated. The obtained results are shown in Table 2.

[0065] <Water absorption amount> The amount of water absorbed by each foam obtained is measured according to the following procedure in accordance with the water absorption test of JIS A 9511. Specifically, the foam is processed into a test piece of 20 mm x 20 mm x t20 mm. This test piece is immersed in water for 30 seconds, then removed into the air and left for 30 seconds, after which mass A is weighed. Meanwhile, the test piece is immersed in water for 24 hours, then removed into the air and left for 30 seconds, after which mass B is weighed. Surface area: 100 cm 2 The amount of water absorbed per unit is calculated using the following formula. (Water absorption amount) = 100 × [(mass B) - (mass A)] / 24 In the above formula, "24" is the total surface area of ​​the test piece (2 cm x 2 cm x 6 faces). The results obtained for water absorption are shown in Table 3.

[0066] <Compressive strength> The compressive strength of the test piece is measured using a force gauge. Specifically, the compressive strength is the strength when a circular terminal with a diameter of 1.6 cm sinks 6 mm. The results obtained for compressive strength are shown in Table 3.

[0067] <Dimensional stability> After measuring the thickness X of the test piece, the test piece is kept in an oven (120°C) for 7 days and then the thickness Y is measured. The dimensional stability (deformation rate) is calculated by the following formula. (Dimensional stability) = 100 x [(Thickness Y) - (Thickness X)] / (Thickness X) The results obtained regarding dimensional stability are shown in Table 3.

[0068] [Table 1]

[0069] [Table 2]

[0070] [Table 3] [Industrial Applicability]

[0071] The urea resin foam according to this embodiment has excellent moisture absorption resistance and is therefore applicable to applications as a thermal insulation material for pipes and the like. [Explanation of symbols]

[0072] 10 mold, 100 urea resin foam, 110 core, 120 skin layer

Claims

1. A urea resin foam having a skin layer.

2. The urea resin foam according to claim 1 , wherein the average cell diameter of the skin layer is 70% or less of the average cell diameter of the core portion of the urea resin foam.

3. 2. The urea resin foam according to claim 1, wherein a ratio of a surface where the skin layer is exposed to a total surface of the urea resin foam is 80% or more.

4. A pipe insulating material comprising the urea resin foam according to claim 1 .

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