Rigid Polyisocyanurate Foam

Abstract

To provide hard polyisocyanurate foam for back-filling injection that is excellent in mechanical strength and dimensional stability, storage stability, and also restrains an internal temperature rise, and has excellent fire retardancy and heat resistance, and also excellent in construction safety, when hydrofluoroolefin (HFO), hydrochlorofluoroolefin (HCFO) or the like is used as a foaming agent, and a two-component type premix composition suitably used for its manufacturing, and a back-filling injection construction method using them.SOLUTION: The present invention relates to a two-component type premix composition that is composed of liquid A containing a polyisocyanate compound and liquid B containing a polyol compound, a foaming agent, a silicone surface active agent and a carboxylate, in which the foaming agent contains at least one of HFO and HCFO, and an isocyanate index is 160 to 500, and hard polyisocyanurate foam for back-filling injection, and a back-filling injection construction method using them.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a backfill injection method for filling a cavity between a tunnel or underground structure and the natural ground behind it using a non-cement-based material. More specifically, the present invention relates to a rigid polyisocyanurate foam for backfill injection, a two-component premix composition suitable for producing the same, and a backfill injection method using the same. [Background technology]

[0002] Similar to rigid urethane foam, rigid polyisocyanurate foam is a resin foam obtained by mixing a polyisocyanate compound having two or more isocyanate groups and a polyol compound having two or more hydroxyl groups together with a blowing agent, a catalyst, etc., and simultaneously carrying out a foaming reaction and a resinification reaction. Polyisocyanate compounds undergo a trimerization reaction using a specific catalyst to produce isocyanurate rings. The bonds of these isocyanurate rings have higher thermal stability than urethane bonds, so rigid polyisocyanurate foams containing isocyanurate rings have excellent flame retardancy and heat resistance, as well as excellent strength properties such as compressive strength and flexural strength. For this reason, rigid polyisocyanurate foams have conventionally been widely used in civil engineering and construction applications, specifically as heat insulating materials, void filling materials, and the like.

[0003] Furthermore, among civil engineering and construction applications, hydrofluorocarbons (HFCs) have traditionally been used as foaming agents for rigid polyisocyanurate foams used as void fillers, particularly for backfill injection into tunnels, underground structures, etc., in order to suppress internal heat generation during injection into large cavities and to prevent volumetric shrinkage after foaming. However, although HFCs have an ozone depletion potential (ODP) of 0, their global warming potential (GWP) is high, for example, 794 for HFC-245fa and 1030 for HFC-365mfc, and as such they are designated as controlled greenhouse gases. In recent years, there has been a demand to reduce their use as a measure against global warming.

[0004] For this reason, it has been proposed to use water as a non-fluorocarbon type blowing agent (see, for example, Patent Document 1).

[0005] On the other hand, hydrofluoroolefins (HFOs) and hydrochlorofluoroolefins (HCFOs), which contain fluorine but have double bonds in the main chain, are attracting attention as new blowing agents that can be adapted to address environmental issues related to greenhouse gases. For example, Patent Document 2 describes a polyol premix for polyisocyanurate foam that uses 1-chloro-3,3,3-trifluoropropene (ODP: 0, GWP: 1), which is an HCFO, as a blowing agent. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-256054 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-196652 Summary of the Invention [Problem to be solved by the invention]

[0007] However, when water is used as the main component of the blowing agent as described in Patent Document 1, the injected rigid polyisocyanurate foam is likely to generate heat internally in the large cavity, and the temperature rises further due to the concurrent occurrence of an oxidation reaction and fluctuations in the internal pressure inside the foam, which can lead to carbonization and smoke generation, and ultimately to serious accidents such as fires inside the tunnel.

[0008] Furthermore, the polyol premix disclosed in Patent Document 2 only specifically uses, as the polyisocyanate to be reacted, polymeric MDI (polymethylene polyphenyl isocyanate) with an isocyanate index (Iso index) of 150. The reaction product, a polyisocyanurate foam with a relatively low isocyanate index, cannot be said to have sufficient flame retardancy and heat resistance for use in backfill injection.

[0009] Therefore, rigid polyisocyanurate foams for backfill injection are required to have superior flame retardancy and heat resistance, even when HFO, HCFO, etc. are used as blowing agents. Furthermore, it is desirable that the internal heat generation during injection into large cavities is suppressed to the same extent as when conventional HFCs are used, and that volumetric shrinkage after foaming can be suppressed, i.e., the dimensional stability is excellent. Furthermore, from the viewpoint of safety and durability in on-site construction, it is also necessary for the material to have predetermined strength characteristics, storage stability, and the like.

[0010] The present invention has been made to solve the above-mentioned problems, and has an object to provide a rigid polyisocyanurate foam for backfill injection that, when HFO, HCFO, or the like is used as a blowing agent, has excellent mechanical strength, dimensional stability, and storage stability, and further suppresses an increase in internal temperature, has excellent flame retardancy and heat resistance, and is also excellent in construction safety; a two-component premix composition that is suitably used for producing the same; and a backfill injection method using the same. [Means for solving the problem]

[0011] The present invention is based on the finding that, in rigid polyisocyanurate foams produced using HFO, HCFO, or the like as a blowing agent, the use of a carboxylate salt as a catalyst and a premix composition with a high isocyanate index improves storage stability and enables the production of good foams with excellent flame retardancy and heat resistance.

[0012] That is, the present invention provides the following [1] to [9]. [1] A two-component premix composition for producing rigid polyisocyanurate foam for backfill injection, comprising: a liquid A containing a polyisocyanate compound; and a liquid B containing a polyol compound, a blowing agent, a silicone surfactant, and a carboxylate salt, wherein the blowing agent contains at least one of hydrofluoroolefins and hydrochlorofluoroolefins, and the premix composition has an isocyanate index of 160 to 500. [2] The two-component premix composition according to the above [1], wherein the amount of the carboxylate is 2 to 30 parts by mass per 100 parts by mass of the polyol compound. [3] The two-component premix composition according to [1] or [2] above, wherein the amount of the carboxylate is 0.5 to 10 parts by mass per 100 parts by mass of the polyisocyanate compound. [4] The two-component premix composition according to any one of [1] to [3] above, wherein the carboxylate is one or more selected from potassium formate, potassium acetate, potassium n-octanoate, and potassium 2-ethylhexanoate.

[0013] [5] A rigid polyisocyanurate foam for backfill injection, which is produced by foaming a mixed liquid containing a polyisocyanate compound, a polyol compound, a blowing agent, a silicone surfactant, and a carboxylate salt, wherein the blowing agent contains at least one of hydrofluoroolefins and hydrochlorofluoroolefins, and has an isocyanate index of 160 to 500. [6] The rigid polyisocyanurate foam for backfilling injection according to [5] above, wherein the carboxylate is one or more selected from the group consisting of potassium formate, potassium acetate, potassium n-octanoate, and potassium 2-ethylhexanoate. [7] The rigid polyisocyanurate foam for backfill injection according to [5] or [6] above, which has an oxygen index of 23.0 or more as measured in accordance with JIS A 9511:2006R flammability test measurement method C. [8] The rigid polyisocyanurate foam for backfilling injection according to any one of the above [5] to [7], which has a compressive strength measured in accordance with JIS A 9511:2006R of 0.10 MPa or more and a flexural strength measured in accordance with JIS A 9511:2006R of 0.15 MPa or more.

[0014] [9] A backfill injection method for injecting a rigid polyisocyanurate foam into a cavity between a tunnel or underground structure and the natural ground behind it to foam and harden the foam, wherein the rigid polyisocyanurate foam comprises a mixed solution of liquid A containing a polyisocyanate compound and liquid B containing a polyol compound, a blowing agent, a silicone surfactant, and a carboxylate salt, the blowing agent comprising at least one of hydrofluoroolefin and hydrochlorofluoroolefin, and the isocyanate index of the mixed solution is 160 to 500. [Effects of the Invention]

[0015] According to the present invention, when HFO, HCFO, or the like is used as a blowing agent, it is possible to provide a rigid polyisocyanurate foam for backfill injection which has excellent mechanical strength and dimensional stability, as well as excellent flame retardancy and heat resistance, and is therefore excellent in construction safety. The present invention also provides a two-component premix composition that can be suitably used in the production of the rigid polyisocyanurate foam for backfill injection, and has excellent storage stability. Furthermore, by using the composition, it is possible to provide a backfill injection method using the rigid polyisocyanurate foam that is safer and more durable. DETAILED DESCRIPTION OF THE INVENTION

[0016] The two-component premix composition, the rigid polyisocyanurate foam for backfill injection, and the backfill injection method of the present invention will be described in detail below.

[0017] [Two-liquid premix composition] The two-component premix composition of the present invention is a premix composition for producing rigid polyisocyanurate foam for backfill injection. The premix composition comprises a component A containing a polyisocyanate compound and a component B containing a polyol compound, a blowing agent, a silicone surfactant, and a carboxylate salt, the blowing agent containing at least one of HFO and HCFO, and the premix composition has an isocyanate index of 160 to 500. The premix composition is a two-component type consisting of a premix of liquids A and B, and even when the blowing agent is HFO or HCFO, it can produce a rigid polyisocyanurate foam for backfill injection that is excellent in mechanical strength and dimensional stability, as well as in flame retardancy and heat resistance. Furthermore, because it is prepared as a two-component premix, it is also excellent in work efficiency and safety during on-site construction.

[0018] As mentioned above, "backfill injection" is a construction method in civil engineering and construction work that fills the cavity between a tunnel or underground structure and the natural ground behind it. In this specification, when referring specifically to this process or method, it will be referred to as the "backfill injection method."

[0019] The term "isocyanate index" used here refers to the number of moles of isocyanate groups of the polyisocyanate compound in solution A relative to 1 mole of hydroxyl groups of the polyol compound in solution B, expressed as a percentage [%]. The isocyanate index is also an indicator for distinguishing rigid polyisocyanurate foams from rigid polyurethane foams when evaluating flame retardancy and heat resistance. Specifically, in the flame retardancy and heat resistance evaluation by the Japan Urethane Industry Association, foams with an isocyanate index of 150 or more and containing a trimerization catalyst are defined as rigid polyisocyanurate foams, and all other foams are defined as rigid polyurethane foams.

[0020] In the present invention, for the backfilling injection, in order to obtain a rigid polyisocyanurate foam excellent in flame retardancy and heat resistance, the isocyanate index of the two-component premix composition is set to 160 to 500. The isocyanate index is preferably 200 to 400, more preferably 230 to 300. If the isocyanate index is less than 160, a rigid polyisocyanurate foam having sufficient flame retardancy and heat resistance cannot be obtained. On the other hand, when the isocyanate index exceeds 500, there is too little polyol compound, making it difficult to produce a rigid polyisocyanurate foam.

[0021] [[ID=⑧]]The A liquid is a liquid containing a polyisocyanate compound as a main component. In addition to the polyisocyanate compound, the A liquid may contain additives such as a solvent and a foam stabilizer as required. However, from the viewpoint of production efficiency and the like, the content of the polyisocyanate compound in the A liquid is preferably 70 to 100% by mass, more preferably 90 to 100% by mass, and still more preferably 95 to 100% by mass.

[0022] (Polyisocyanate compound) The polyisocyanate compound is an isocyanate compound having two or more isocyanate groups, and an isocyanurate ring is formed by its trimerization reaction. In addition, an isocyanate group that does not form an isocyanurate ring forms a urethane bond by an addition reaction with the polyol compound in the B liquid. Through these reactions, a rigid polyisocyanurate, which is a foam of a polyisocyanurate resin, is obtained.

[0023] The polyisocyanate compound may be either an aromatic polyisocyanate or an aliphatic polyisocyanate, and among these, it may be used alone or in combination of two or more. Examples of aromatic polyisocyanates specifically include monomeric MDI such as diphenyl ether-2,4'-diisocyanate, diphenyl ether-4,4'-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, 4,6-dimethyl-1,3-phenylene diisocyanate, 2,2'-diphenylmethane diisocyanate (2,2'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI), polymethylene polyphenyl polyisocyanate (crude MDI or polymeric MDI), 3,3'-dimethyl-4,4'-biphenylene diisocyanate, m-xylylene diisocyanate, and the like. The aliphatic polyisocyanate may be either an acyclic or alicyclic polyisocyanate. Specifically, examples include tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and the like. Among these, from the viewpoints of reactivity and mechanical strength of the produced rigid polyurethane foam, monomeric MDI such as 2,2'-MDI, 2,4'-MDI, 4,4'-MDI, crude MDI or polymeric MDI are preferred. Among them, from the viewpoint of cost, crude MDI or polymeric MDI is preferably used.

[0024] <Liquid B> Liquid B is a liquid mainly composed of a polyol compound, and further contains a foaming agent, a silicone surfactant, and a carboxylate. In addition to the polyol compound, foaming agent, silicone surfactant, and carboxylate, Liquid B may contain additives such as a solvent, an amine catalyst, a flame retardant, a non-silicone surfactant, a coloring agent, an antioxidant, etc. as required. However, from the viewpoint of production efficiency, etc., the content of the polyol compound in Liquid B, which is the main component, is preferably 30 to 90% by mass, more preferably 35 to 80% by mass, and even more preferably 40 to 65% by mass.

[0025] (Polyol compound) A polyol compound is an alcohol compound having two or more hydroxyl groups, and generates a urethane resin by addition reaction with an isocyanate compound. Examples of polyol compounds include polyester polyols and polyether polyols, and it is preferable to use any one selected from these, and one type may be used alone or two or more types may be used in combination. The molecular weight of the polyether polyol and polyester polyol is preferably 70 to 5,000, more preferably 100 to 3,000, from the viewpoint of obtaining a rigid polyisocyanurate foam having reactivity and sufficient mechanical strength.

[0026] Examples of polyester polyols include those obtained by polycondensation of polyhydric alcohols and polycarboxylic acids. Examples of the polyhydric alcohols include ethylene glycol, propanediol, butanediol, diethylene glycol, dipropylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, decamethylene glycol, neopentyl glycol, 3-methyl-1,5-pentanediol, glycerin, trimethylolpropane, pentaerythritol, sorbitol, and bisphenol A. Examples of the polycarboxylic acids include adipic acid, malonic acid, succinic acid, tartaric acid, pimelic acid, sebacic acid, oxalic acid, phthalic acid, terephthalic acid, orthophthalic acid, isophthalic acid, azelaic acid, trimellitic acid, glutaconic acid, α-hydromuconic acid, β-diethylsuccinic acid, hemimellitic acid, and 1,4-cyclohexanedicarboxylic acid. Further, examples of polyester polyols include those obtained by transesterifying polyalkylene terephthalates such as polyethylene terephthalate and polybutylene terephthalate with polyhydric diols. Examples of polyether polyols include those obtained by addition polymerization of alkylene oxides such as propylene oxide and ethylene oxide to polyhydric alcohols such as glycol, glycerin, sorbitol, and sugars, aromatic amines, aliphatic amines, and the like.

[0027] (foaming agent) The foaming agent vaporizes due to heat generated when the polyisocyanate compound and the polyol compound react to produce the polyurethane resin, and has the effect of foaming the polyurethane resin. The blowing agent includes HFO or HCFO. One of these may be used alone, or two or more may be used in combination. Compared to using only water as a blowing agent, HFOs and HCFOs can limit the internal heat generation of the foam during the exothermic reaction between polyisocyanate compounds and polyol compounds to temperatures below 180°C, thereby suppressing carbonization and smoke generation in the foam. Furthermore, from an environmental perspective, HFOs and HCFOs are blowing agents whose demand is expected to increase in the future as replacements for HFCs. Because HFOs and HCFOs are flame-retardant themselves, the formation of closed cells with these blowing agents allows for the production of rigid polyisocyanurate foams with even greater flame retardancy.

[0028] Specific examples of HFOs and HCFOs include trans-1,3,3,3-tetrafluoropropene (trans-HFO-1234ze), 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz), and trans-1-chloro-3,3,3-trifluoropropene (HCFO-1233zd). From the viewpoint of adequately foaming the polyisocyanurate resin, the foaming agent is added in an amount of preferably 3 to 40 parts by mass, more preferably 5 to 30 parts by mass, and even more preferably 7 to 20 parts by mass, per 100 parts by mass of the polyisocyanate compound in Liquid A.

[0029] The blowing agent may contain conventionally used HFCs or water. When the isocyanate groups of the polyisocyanate compound react with water to produce amino groups, carbon dioxide is generated, which also serves as a cause of foaming in the early stage of the polyurethane resin production reaction, so it is preferable that the blowing agent contain water. However, when the polyol compound contains a polyester polyol, the water content is preferably less than that of the other blowing agents, since there is a risk of hydrolyzing the polyester polyol depending on the storage conditions of Solution B. The blending amount of water is preferably 0.5 to 20 parts by mass, more preferably 1 to 18 parts by mass, and even more preferably 5 to 15 parts by mass per 100 parts by mass of the above blowing agents other than water.

[0030] (Silicone surfactant) The silicone surfactant acts as a foam stabilizer in the rigid isocyanurate foam and also contributes to dimensional stability. Known silicone surfactants can be used. For example, siloxane-polyalkylene oxide copolymers can be mentioned, which are commercially available. Among these, one type may be used alone, or two or more types may be used in combination. From the viewpoint of appropriately adjusting the bubbles in the rigid isocyanurate foam, the silicone surfactant is preferably added in an amount of 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, and even more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the polyisocyanate compound in Liquid A.

[0031] (Carboxylate) The carboxylate salt acts as a trimerization catalyst for polyisocyanate compounds to obtain rigid isocyanurate foams. Amine catalysts are also known as trimerization catalysts for polyisocyanate compounds. However, when an amine catalyst is used as the main trimerization catalyst in a premix composition containing a silicone surfactant and a polyol compound, the storage stability of the premix composition is poor. In contrast, by using a carboxylate as a trimerization catalyst, the storage stability of the premix composition can be improved.

[0032] The carboxylate salt is preferably an alkali metal salt or a quaternary ammonium salt of a carboxylic acid having 1 to 20 carbon atoms. Specific examples of the alkali metal salt include potassium formate, potassium acetate, potassium n-octanoate, potassium 2-ethylhexanoate, sodium 2-ethylhexanoate, potassium benzoate, sodium benzoate, potassium propionate, potassium caprate, and sodium N-(2-hydroxy-5-nonylphenol)methyl-N-methylglycinate. Examples of the quaternary ammonium salt include ammonium trimethylhydroxypropyl formate and N-(2-hydroxypropyl)-N-(2-hydroxyethyl)-N,N-dimethylammonium octanoate. One of these may be used alone, or two or more may be used in combination. Among these, potassium formate, potassium acetate, potassium n-octanoate, potassium 2-ethylhexanoate, or a quaternary ammonium salt of a carboxylic acid is preferred, with potassium n-octanoate or potassium 2-ethylhexanoate being more preferred.

[0033] From the viewpoint of sufficiently promoting the trimerization reaction of the polyisocyanate compound, the carboxylate is added in an amount of preferably 0.5 to 10 parts by mass, more preferably 1.0 to 5 parts by mass, and even more preferably 1.2 to 3 parts by mass, per 100 parts by mass of the polyisocyanate compound in Solution A. Furthermore, from the viewpoint of maintaining the storage stability of Solution B, the amount of carboxylate in Solution B relative to 100 parts by mass of the polyol compound is preferably 2 to 30 parts by mass, more preferably 3 to 25 parts by mass, and even more preferably 5 to 20 parts by mass.

[0034] (Other ingredients) Liquid B may contain, as needed, additives such as a solvent, an amine catalyst, a flame retardant, a non-silicone surfactant, a colorant, and an antioxidant. 〔solvent〕 The solvent is used as needed from the viewpoint of uniformly mixing the components, and may be a water-soluble organic solvent or a hydrophobic organic solvent as long as it does not interfere with the reactivity in the reaction for producing a rigid polyisocyanurate foam. Examples include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, and glycerin. These solvents may be contained in commercially available carboxylates, amine catalysts, silicone surfactants, etc.

[0035] [Amine catalyst] Although the carboxylate is the main catalyst of the trimerization catalyst, it is preferable to use an amine catalyst as a co-catalyst to promote the urethanization reaction. However, among amine catalysts, it is difficult to clearly distinguish between those that act as trimerization catalysts and those that act as urethanization catalysts, and when the blowing agent is an HFO or HCFO, many of them are reactive with these blowing agents. For this reason, the amount of amine catalyst in solution B is preferably smaller than that of carboxylate. Furthermore, since amine catalysts that have low reactivity with HFO or HCFO are expensive, it is preferable to use as little amine catalyst as possible from the viewpoint of cost.

[0036] Known amine catalysts can be used as such, and those that have excellent storage stability even when used together with blowing agents such as HFO and HCFO are preferred. Examples include bis(2-morpholinoethyl) ether, styrenated diphenylamine, N,N',N"-dimethylaminopropylhexahydro-s-triazine, and N,N,N',N'-tetramethylhexanediamine. Among these, one type may be used alone, or two or more types may be used in combination.

[0037] The amine catalyst is preferably added in an amount of 0.1 to 10 parts by mass, more preferably 0.1 to 8 parts by mass, and even more preferably 0.2 to 5 parts by mass, per 100 parts by mass of the polyisocyanate compound in the solution A. In addition, from the viewpoint of maintaining the storage stability of the liquid B, the amount of the amine catalyst blended in the liquid B relative to 100 parts by mass of the polyol compound is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, and even more preferably 3 to 10 parts by mass.

[0038] [Flame retardant] The rigid polyisocyanurate foam of the present invention has excellent flame retardancy even when no flame retardant is added, but a flame retardant may be added to further improve the flame retardancy. As the flame retardant, any known flame retardant used in the production of rigid polyisocyanurate foams can be used, and examples thereof include tricresyl phosphate, a non-halogen phosphate ester, and trischloropropyl phosphate, a halogen-containing phosphate ester.

[0039] [Non-silicone surfactants, colorants and antioxidants] The non-silicone surfactant, colorant and antioxidant are not particularly limited and may be any of those known in the production of rigid polyisocyanurate foams. The content of these additives can be adjusted appropriately depending on the desired physical properties of the resulting foam, within a range that does not affect the reactivity in the reaction for producing a rigid polyisocyanurate foam. The total content of the additives is preferably 0.5 to 30 parts by mass, more preferably 1 to 25 parts by mass, and even more preferably 5 to 20 parts by mass, per 100 parts by mass of the polyisocyanate compound in Solution A.

[0040] [Rigid polyisocyanurate foam for backfill injection] The rigid polyisocyanurate foam for backfill injection of the present invention is a rigid polyisocyanurate foam obtained by foaming a mixed liquid containing a polyisocyanate compound, a polyol compound, a blowing agent, a silicone surfactant, and a carboxylate salt, wherein the blowing agent contains at least one of HFO and HCFO, and the isocyanate index is 160 to 700. Such rigid polyisocyanurate foams have excellent mechanical strength and dimensional stability, as well as excellent flame retardancy and heat resistance, even when the blowing agent is HFO or HCFO.

[0041] The term "isocyanate index" used here refers to the number of moles of isocyanate groups in a polyisocyanate compound relative to 1 mole of hydroxyl groups in a polyol compound, expressed as a percentage [%]. Note that the meaning of the isocyanate index is the same as that described above in the explanation of the two-component premix composition, and therefore will not be explained here.

[0042] Rigid polyisocyanurate foam is made from a liquid mixture containing a polyisocyanate compound, a polyol compound, a foaming agent, a silicone surfactant, and a carboxylate salt. The method for producing a rigid polyisocyanurate foam is not particularly limited, and the raw material compositions may be mixed on-site. However, from the viewpoint of efficiency and safety of work during on-site construction, it is preferable to prepare a mixed liquid using the above-mentioned two-component premix composition of the present invention and foam it. The polyisocyanate compound, polyol compound, foaming agent, silicone surfactant, and carboxylate salt in the mixed liquid are the same as those described in the description of the two-component premix composition above, and therefore will not be described here.

[0043] The rigid polyisocyanurate foam preferably has an oxygen index of 23.0 or more as measured in accordance with the measuring method C of the flammability test of JIS A 9511:2006R. The "oxygen index" is an index of flammability, and as defined in JIS K 7201-2:2007, it is the minimum oxygen concentration of a mixed gas of oxygen and nitrogen at 23±2°C required to maintain flaming combustion of a sample under specified conditions, and is expressed as a volume fraction [%]. If the oxygen concentration is greater than about 21%, which is the oxygen concentration in air, it is usually difficult for the mixture to continue burning. In the present invention, from the viewpoint of obtaining a rigid polyisocyanurate foam having excellent flame retardancy for use in backfill injection, the oxygen index is preferably 23.0 or more. Measurement method C of the flammability test of JIS A 9511:2006R is based on JIS K 7201-2:2007, and in the present invention, it refers to a value measured on a test piece having a length of 150 mm, a width of 10 mm, and a thickness of 10 mm.

[0044] Furthermore, the rigid polyisocyanurate foam preferably has a compressive strength measured in accordance with JIS A 9511:2006R of 0.10 MPa or more and a flexural strength measured in accordance with JIS A 9511:2006R of 0.15 MPa or more. The compressive strength and flexural strength are indicators of mechanical strength. The compressive strength measured in accordance with JIS A 9511:2006R is measured based on JIS K 7220:2006. The bending strength measured in accordance with JIS A 9511:2006R is measured based on JIS K 7221-2:2006. In the present invention, from the viewpoint of obtaining a rigid polyisocyanurate foam having excellent mechanical strength suitable for backfill injection, the compressive strength is preferably 0.10 MPa or more, more preferably 0.14 MPa or more, and even more preferably 0.17 MPa or more. The higher the compressive strength, the better, and there is no particular upper limit. From the same viewpoint, the bending strength is preferably 0.15 MPa or more, more preferably 0.23 MPa or more, and even more preferably 0.28 MPa or more. The higher the bending strength, the better, and there is no particular upper limit.

[0045] [Backfill injection method] The backfill injection method of the present invention is a backfill injection method in which a rigid polyisocyanurate foam is foamed and cured by injecting it into a cavity between a tunnel or underground structure and the natural ground behind it. The rigid polyisocyanurate foam comprises a mixed solution of Liquid A containing a polyisocyanate compound and Liquid B containing a polyol compound, a blowing agent, a silicone surfactant, and a carboxylate salt, the blowing agent containing at least one of HFO and HCFO, and the mixed solution has an isocyanate index of 160 to 500. By using such a two-liquid mixture of liquids A and B, even when the blowing agent is HFO or HCFO, it is possible to perform backfill injection with a rigid polyisocyanurate foam that has excellent mechanical strength and dimensional stability, as well as excellent flame retardancy and heat resistance. In such a backfill injection method, the mixture of liquid A and liquid B reacts immediately after mixing, so it is preferable to prepare the mixture at the time of on-site construction. From the viewpoint of efficiency and safety during on-site construction, it is preferable to use the above-mentioned two-component premix composition of the present invention as the liquid A and liquid B used in this mixture. It is also preferable to use an injection machine that can mix the two liquids and inject them into the cavity during on-site construction. The components A and B and the isocyanate index are the same as those of the two-component premix composition. [Example]

[0046] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.

[0047] [Preparation of two-component premix composition] (Examples 1 to 3, Comparative Examples 1 to 3, and Reference Example 1) Liquids A and B of a two-liquid premix composition were prepared by mixing the raw material compounds of liquid B according to the formulations shown in Examples 1 to 3, Comparative Examples 1 to 3, and Reference Example 1 in Table 1 below. The compounds used to prepare liquids A and B are shown below. <Polyisocyanate compound (a)> 4,4'-Diphenylmethane diisocyanate; "Millionate (registered trademark) MR-200" manufactured by Tosoh Corporation <Polyol compound (b)> Polyether polyol: "Exenol 450SN" manufactured by Asahi Glass Co., Ltd. <Foaming agent> HCFO: trans-1-chloro-3,3,3-trifluoropropene; "Solstice (registered trademark) LBA", manufactured by Honeywell Japan Co., Ltd. HFO: (Z)-1,1,1,4,4,4-hexafluoro-2-butene; "Formacel 1100" manufactured by DuPont HFC(1): 1,1,1,3,3-pentafluoropropane; "HFC-245fa", manufactured by Central Glass Co., Ltd. HFC(2): 1,1,1,3,3-pentafluorobutane; "Solcan 365mfc", manufactured by Japan Solvay Co., Ltd. ·water <Carboxylate> (1) Potassium 2-ethylhexanoate: "DABCO (registered trademark) K-15" manufactured by Air Products Japan Co., Ltd.; 75% by weight diethylene glycol solution (2) Potassium octanoate; "NKC", manufactured by Katsuta Chemical Industry Co., Ltd., 50% by mass glycerin solution <Amine catalyst> (1) Bis(2-morpholinoethyl) ether; "JEFFCAT® DMDEE", manufactured by Huntsman Japan Co., Ltd. (2) N,N',N"-dimethylaminopropylhexahydro-s-triazine; "POLYCAT (registered trademark) 41", manufactured by Air Products Japan Co., Ltd. (3) N,N,N',N'-Tetramethylhexanediamine; "Kao Raiser No. 1", manufactured by Kao Corporation (4) Triethylenediamine; "DABCO (registered trademark) 33LV", manufactured by Air Products Japan Co., Ltd.; 33% by weight dipropylene glycol solution (5) Special amine: "U-CAT (registered trademark) 420A" manufactured by San-Apro Co., Ltd. <Silicone surfactant> (1) Polyether siloxane; "TEGOSTAB (registered trademark) B 8490", manufactured by Evonik Japan Co., Ltd. (2) Siloxane-polyalkylene oxide copolymer; "NIAX * (registered trademark) SILICONE L-6100NT, manufactured by Momentive Performance Materials Japan, LLC (3) "SRX 280A FLUID" manufactured by Dow Corning Toray Co., Ltd. (4) Polyalkylene oxide-methylsiloxane copolymer; "NIAX SILICONE L-6970" manufactured by Momentive Performance Materials Japan, LLC (5) Polyether-polydimethylsiloxane copolymer; "TEGOSTAB (registered trademark) B 8474", manufactured by Evonik Japan Co., Ltd. (6) Polyether-modified polysiloxane; "TEGOSTAB (registered trademark) B 8460", manufactured by Evonik Japan Co., Ltd. <Flame retardant> Trischloropropyl phosphate; "TMCPP", manufactured by Daihachi Chemical Industry Co., Ltd.

[0048] [Table 1]

[0049] [Evaluation by hand foaming] Liquids A and B prepared according to the formulations shown in Table 1 above were mixed in a descup to prepare a total of 150 g of foaming material. Approximately 100 g of this foaming material was packed into a wooden box with internal dimensions of 150 mm x 150 mm x 150 mm, and foamed and cured at 20°C. The hand foaming was evaluated for the following items, and the evaluation results are summarized in Tables 2 and 3.

[0050] <Each process time> The following time was measured from the time when mixing of the A and B liquids was started. (1) Melting time (MT): Time until mixing is completed (2) Cream time (CT): The time it takes for the dough to start to rise. (3) Gel time (GT): the time until gelation begins (4) Rise time (RT): The time until the expansion stops. The time required for each of these processes affects work efficiency during on-site construction, and a cream time (CT) of 7 to 17 seconds is considered to be good. Also, a rise time (RT) of 45 to 75 seconds is considered to be good. Furthermore, if the cream time (CT) and rise time (RT) are within the above ranges, rapid foaming and hardening allows for backfill injection in the lining concrete of tunnels and underground structures, while suppressing penetration into the ground at the backside and leakage of foaming raw material from cracks, and this is preferable because it minimizes loss of foaming raw material.

[0051] <Core density> After removing the wooden box, the foam was cut into a piece of approximately 100 mm x 100 mm x 100 mm, and the cut piece was measured with a vernier caliper to determine the volume. The mass was also measured, and the core density was calculated from the volume and mass. The core density is an index of the degree of foaming, and is between 27 and 33 kg / m 3 If it is within this range, it can be said to be good.

[0052] <Maximum heat generation temperature> The temperature at the center of the foam was measured, and the maximum temperature was taken as the maximum exothermic temperature. From the viewpoint of reducing the risk of smoke generation during on-site construction, it is considered preferable for the maximum heat generation temperature to be less than 180°C.

[0053] <Storage stability> Foams were prepared using each of the B liquids immediately after preparation and after storage for a predetermined period at room temperature (20°C), 40°C, and 50°C. The CT, GT, RT, and core density were measured in the same manner as above, and the appearance was visually observed to evaluate the change in storage stability due to storage conditions. The evaluation criteria for appearance are as follows: A: The bubble size is uniform. B: The cell size is non-uniform or the cells are broken. Alternatively, cell roughness (a phenomenon in which the cells on the surface of the foam become non-uniform and large) occurs. If the CT, RT and core density are all within the range of values ​​considered good even after a specified period of time has passed, and the appearance is rated as "A", then the storage stability can be said to be good. The evaluation results of storage stability are shown in Table 3.

[0054] [Evaluation using actual foaming equipment] A total of approximately 1 kg of liquids A and B prepared according to the formulation shown in Table 1 above was filled into a wooden box with internal dimensions of 150 mm width x 400 mm length x 500 mm height using an on-site injection machine (actual machine), and allowed to foam and harden at 20°C. However, for the evaluation of the maximum heat generation temperature and the state when watering, which will be described later, a wooden box with internal dimensions of 1m x 1m x 1m was filled with a total of approximately 36kg of liquid A and B (a total of approximately 27-30kg when watering), and the box was allowed to foam and harden at 20°C. The foaming was carried out using the actual machine and the following items were evaluated. The results are summarized in Table 2.

[0055] <Core density> The core density is an indicator of the degree of foaming, and is 27 to 33 kg / m 3 If it is within this range, it can be said to be good. After removing the wooden box, five samples of approximately 50 mm x 50 mm x 50 mm were cut out from the foam and measured with a vernier caliper to determine the volume. The mass of each sample was also measured, and the density was calculated from the volume and mass, and the average of these was taken as the core density.

[0056] <Compression strength> The compressive strength was measured for the five samples used in the above-mentioned core density measurement by a method in accordance with JIS A 9511:2006R (cited from JIS K 7220:2006), and the average value was used. <Bending strength> The bending strength was measured by a method according to the present invention for five samples of 120 mm x 25 mm x 20 mm cut out from the foam, and the average value was calculated.

[0057] <Dimensional stability> Dimensional stability was evaluated based on the measurement of dimensional change after 72 hours under high temperature (70°C), low temperature (-30°C), and moist heat (70°C, 95%RH) conditions in the directions parallel and perpendicular to the foaming direction according to the method of ASTM D2126-15. The evaluation criteria are as follows: A: Under all of the above conditions, the dimensional change rate is within ±1.0% in both the parallel and perpendicular directions. B: Under any one of the above conditions, the dimensional change rate is more than ±1.0% C: Under two or more of the above conditions, the dimensional change rate is more than ±1.0%

[0058] <Oxygen index> The oxygen index was measured on five 150mm x 10mm x 10mm samples cut out from the foam using a method in accordance with JIS A 9511:2006R flammability test measurement method C (cited in JIS K 7201-2:2007), and the average value was calculated.

[0059] <Maximum heat generation temperature> The central temperature of the foam (1 m x 1 m x 1 m) was measured, and the maximum temperature was taken as the maximum exothermic temperature. From the viewpoint of reducing the risk of smoke generation during on-site construction, it is considered preferable for the maximum heat generation temperature to be 180°C or less.

[0060] <Evaluation when watering (heat resistance)> During the production of the foam (1 m × 1 m × 1 m), the foam was hardened while spraying water in an amount of about 1% by mass relative to the total mass of the filled liquids A and B. The maximum exothermic temperature at this time was measured in the same manner as above. The resulting foam was then cut into approximately two equal parts in the height direction using a band saw, including the center, and the cross section of the foam was visually inspected for the degree (color and area) of "burnt" (burnt, dark brown discoloration). The heat resistance was evaluated based on the state of the burnt portion. The occurrence of scorching is an indicator of the heat resistance and risk of smoke generation when backfilling is performed in the presence of water such as groundwater. In an environment where water is present, the foam is more likely to reach high temperatures during foaming and hardening than when there is no contact with water. Even in such high-temperature conditions, if no scorching occurs, or if scorching occurs, the degree of scorching is small, it can be said to have excellent heat resistance and safety. The evaluation criteria for heat resistance are as follows: A: Almost no burnt condition is observed. Alternatively, discoloration is observed in approximately 1 / 4 or less of the cross-sectional area. B: Burns have occurred over approximately 1 / 4 of the cross-sectional area. C: The entire surface is burnt.

[0061] [Table 2]

[0062] [Table 3]

[0063] The symbol "-" in the GT column of Tables 2 and 3 indicates that the gelation onset could not be determined. The symbol "-" in the core density column of Comparative Example 1 in Table 3 indicates that the foam lost its shape and could not be cut out to the desired size, so the density was not measured.

[0064] As can be seen from the evaluation results shown in Tables 2 and 3, when the two-component premix composition of the present invention comprising the specified A and B components was used (Examples 1 to 3), even when the blowing agent was HFO or HCFO, it was found that rigid polyisocyanurate foams were obtained that had good foaming properties, excellent mechanical strength and dimensional stability for backfill injection, and excellent flame retardancy and heat resistance, and had properties comparable to those obtained when the blowing agent was HFC (Reference Example 1). On the other hand, when no carboxylate salt was blended in Solution B (Comparative Example 1), the storage stability was poor. Furthermore, when the isocyanate index was less than 160 (Comparative Example 2), the oxygen index was low, and the flame retardancy and heat resistance were poor. Furthermore, when only water was used as the blowing agent (Comparative Example 3), the foaming property was insufficient, the internal heat generation was large, and the heat resistance was poor.

Claims

1. A rigid polyisocyanurate foam obtained by foaming a mixture of liquids A and B of a two-component premix composition for producing a rigid polyisocyanurate foam for backfill injection, which is injected into a gap between a tunnel or underground structure and the natural ground behind the tunnel or underground structure, and foamed and cured, The two-component premix composition comprises a liquid A containing a polyisocyanate compound and a liquid B containing a polyol compound, a foaming agent, a silicone surfactant, and a carboxylate salt; The blowing agent includes at least one of hydrofluoroolefins and hydrochlorofluoroolefins, an isocyanate index of 160 to 500; the amount of the carboxylate is 2 to 30 parts by mass per 100 parts by mass of the polyol compound; Rigid polyisocyanurate foam.

2. The rigid polyisocyanurate foam according to claim 1, wherein the amount of the carboxylate is 0.5 to 10 parts by mass per 100 parts by mass of the polyisocyanate compound.

3. A rigid polyisocyanurate foam obtained by foaming a mixture of liquids A and B of a two-component premix composition for producing rigid polyisocyanurate foam for backfill injection, which is injected into the gap between a tunnel or underground structure and the ground behind it to foam and harden, The two-component premix composition comprises a liquid A containing a polyisocyanate compound and a liquid B containing a polyol compound, a foaming agent, a silicone surfactant, and a carboxylate salt; The blowing agent includes at least one of hydrofluoroolefins and hydrochlorofluoroolefins, an isocyanate index of 160 to 500; the amount of the carboxylate is 0.5 to 10 parts by mass per 100 parts by mass of the polyisocyanate compound; Rigid polyisocyanurate foam.

4. The rigid polyisocyanurate foam according to any one of claims 1 to 3, wherein the carboxylate is at least one selected from the group consisting of potassium formate, potassium acetate, potassium n-octanoate, and potassium 2-ethylhexanoate.

5. The rigid polyisocyanurate foam according to any one of claims 1 to 4, wherein the blowing agent contains water, and the blending amount of the water is 0.5 to 20 parts by mass per 100 parts by mass of the blowing agent other than water.

6. The rigid polyisocyanurate foam according to any one of claims 1 to 5, having an oxygen index of 23.0 or more as measured in accordance with measurement method C of the flammability test of JIS A 9511:2006R.

7. The rigid polyisocyanurate foam according to any one of claims 1 to 6, having a compressive strength measured in accordance with JIS A 9511:2006R of 0.10 MPa or more and a flexural strength measured in accordance with JIS A 9511:2006R of 0.15 MPa or more.

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