JP7732044B2 - Rigid Polyisocyanurate Foam - Google Patents

Description

Article 30, paragraph 2 of the Patent Act applies. Sales will begin on June 21, 2016 to the destinations listed in the attached table.

The present invention relates to a backfill injection method that uses a non-cementitious material to fill voids between tunnels or underground structures and the natural ground behind them. More specifically, the present invention relates to a rigid polyisocyanurate foam for backfill injection, a two-component premix composition suitable for use in producing the same, and a backfill injection method that uses the same.

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.

Furthermore, among civil engineering and construction applications, in particular, in rigid polyisocyanurate foams for use as void fillers, particularly for backfill injection into tunnels, underground structures, etc., hydrofluorocarbons (HFCs) have traditionally been used as blowing agents 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, they have high global warming potentials (GWP), for example, 794 for HFC-245fa and 1030 for HFC-365mfc, and are designated as controlled greenhouse gases. In recent years, there has been a demand for their reduction in order to combat global warming.

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

On the other hand, hydrofluoroolefins (HFOs) and hydrochlorofluoroolefins (HCFOs) that contain double bonds in the main chain have attracted attention as new blowing agents that contain fluorine but 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.

Japanese Patent Application Laid-Open No. 2002-256054 Japanese Patent Application Laid-Open No. 2016-196652

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 prone to internal heat generation in the large cavity, and the temperature rises further due to the accompanying oxidation reaction and fluctuations in the internal pressure inside the foam, resulting in carbonization and smoke emission, which could ultimately lead to serious accidents such as fires inside the tunnel.

Furthermore, the polyol premix described in Patent Document 2 only discloses one that uses polymeric MDI (polymethylene polyphenyl isocyanate) with an isocyanate index (Iso index) of 150 as the polyisocyanate to be reacted. The polyisocyanurate foam that is the reaction product of this, which has a relatively low isocyanate index, cannot be said to have sufficient flame retardancy and heat resistance for use in backfill injection.

Therefore, rigid polyisocyanurate foams for backfill injection are required to have superior flame retardancy and heat resistance, even when HFOs, HCFOs, 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 volume shrinkage after foaming can be suppressed, i.e., that 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.

The present invention was made to solve the above-mentioned problems, and aims to provide a rigid polyisocyanurate foam for backfill injection that, when HFOs, HCFOs, etc. are used as blowing agents, has excellent mechanical strength, dimensional stability, and storage stability, and also suppresses internal temperature rise, has excellent flame retardancy and heat resistance, and is safe to install; a two-component premix composition that is suitable for use in producing the same; and a backfill injection method using the same.

The present invention is based on the discovery that, in rigid polyisocyanurate foams produced using HFOs, HCFOs, etc. as blowing agents, the use of a carboxylate salt as a catalyst and a premix composition with a high isocyanate index improves storage stability and produces good foams with excellent flame retardancy and heat resistance.

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 hydrofluoroolefin and hydrochlorofluoroolefin, and the premix composition has an isocyanate index of 160 to 500.
[2] The two-component premix composition according to [1] above, 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 salt 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.

[5] A rigid polyisocyanurate foam for backfill injection, 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 hydrofluoroolefins and hydrochlorofluoroolefins, and the isocyanate index is 160 to 500.
[6] The rigid polyisocyanurate foam for backfilling injection according to the above [5], wherein the carboxylate is one or more selected from potassium formate, potassium acetate, potassium n-octanoate, and potassium 2-ethylhexanoate.
[7] The rigid polyisocyanurate foam for backfill injection described in [5] or [6] above, having an oxygen index of 23.0 or more measured in accordance with the measurement method C of the flammability test of JIS A 9511:2006R.
[8] The compressive strength measured in accordance with JIS A 9511:2006R is 0.10 MPa or more, and the flexural strength measured in accordance with JIS A 9511:2006R is 0.15 MPa or more. [5] - [7] The rigid polyisocyanurate foam for backfill injection according to any one of the above.

[9] A backfill injection method in which rigid polyisocyanurate foam is foamed and hardened by injecting it into a cavity between a tunnel or underground structure and the natural ground behind it, wherein the rigid polyisocyanurate foam comprises a mixed liquid 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 contains one or more of hydrofluoroolefins and hydrochlorofluoroolefins, and the mixed liquid has an isocyanate index of 160 to 500.

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.

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

[Two-component 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 an HFO and an 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 an HFO or HCFO, it is possible to obtain 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.

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

The term "isocyanate index" used herein 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 index 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.

In the present invention, in order to obtain a rigid polyisocyanurate foam excellent in flame retardancy and heat resistance for backfill injection, the isocyanate index of the two-component premix composition is set to 160 to 500. The isocyanate index is preferably 200 to 400, and more preferably 230 to 300.
If the isocyanate index is less than 160, it is impossible to obtain a rigid polyisocyanurate foam having sufficient flame retardancy and heat resistance. On the other hand, if the isocyanate index is more than 500, the amount of polyol compound is too small, making it difficult to produce a rigid polyisocyanurate foam.

<Liquid A>
Liquid A is a liquid containing a polyisocyanate compound as a main component.
In addition to the polyisocyanate compound, Liquid A may contain additives such as a solvent and a foam stabilizer, if necessary. However, from the viewpoint of production efficiency, the content of the polyisocyanate compound in Liquid A is preferably 70 to 100% by mass, more preferably 90 to 100% by mass, and even more preferably 95 to 100% by mass.

(Polyisocyanate compound)
The polyisocyanate compound is an isocyanate compound having two or more isocyanate groups, and generates an isocyanurate ring by a trimerization reaction. Furthermore, the isocyanurate groups that do not constitute an isocyanurate ring undergo an addition reaction with the polyol compound in liquid B to form a urethane bond. These reactions produce a rigid polyisocyanurate, which is a foam of the polyisocyanurate resin.

The polyisocyanate compound may be either an aromatic polyisocyanate or an aliphatic polyisocyanate, and one of these may be used alone or two or more of them may be used in combination.
Specific examples of aromatic polyisocyanates include 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, monomeric MDI such as 2,2'-diphenylmethane diisocyanate (2,2'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), and 4,4'-diphenylmethane diisocyanate (4,4'-MDI), polymethylene polyphenyl polyisocyanate (crude MDI or polymeric MDI), 3,3'-dimethyl-4,4'-biphenylene diisocyanate, and m-xylylene diisocyanate.
The aliphatic polyisocyanate may be either an acyclic or alicyclic polyisocyanate, and specific examples thereof include tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate.
Among these, from the viewpoints of reactivity and the mechanical strength of the rigid polyurethane foam to be produced, monomeric MDI such as 2,2'-MDI, 2,4'-MDI, and 4,4'-MDI, crude MDI, and polymeric MDI are preferred, and among these, crude MDI and polymeric MDI are preferably used from the viewpoint of cost.

<Liquid B>
Liquid B is a liquid containing a polyol compound as a main component, and further containing a blowing agent, a silicone surfactant, and a carboxylate salt. Liquid B may contain, as necessary, additives such as a solvent, an amine catalyst, a flame retardant, a non-silicone surfactant, a colorant, and an antioxidant in addition to the polyol compound, the blowing agent, the silicone surfactant, and the carboxylate salt.
However, from the viewpoint of production efficiency and the like, the content of the polyol compound in the main component, Solution B, is preferably 30 to 90 mass %, more preferably 35 to 80 mass %, and even more preferably 40 to 65 mass %.

(Polyol Compound)
The 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 the polyol compound 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.

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.

(Blowing 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 of them may be used in combination.
Compared to using only water as a blowing agent, HFOs and HCFOs can suppress the internal heat generation of the foam to a temperature of 180°C or less in the exothermic reaction between a polyisocyanate compound and a polyol compound, thereby suppressing carbonization and smoke generation of the foam. Furthermore, from the perspective of environmental concerns, HFOs and HCFOs are blowing agents whose demand is expected to increase in the future as an alternative to HFCs. Since 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 superior flame retardancy.

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 Solution A.

The blowing agent may contain a conventionally used HFC or water. When the isocyanate group of the polyisocyanate compound reacts with water to produce an amino group, carbon dioxide is generated, which also serves as a cause of foaming in the initial stage of the polyurethane resin production reaction, so it is preferable that water be contained as the blowing agent.
However, when the polyol compound contains a polyester polyol, the water content is preferably smaller 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 blend 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-mentioned blowing agents other than water.

(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 added in an amount of preferably 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 Solution A.

(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.

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. These salts may be used alone or in combination. Of these, potassium formate, potassium acetate, potassium n-octanoate, potassium 2-ethylhexanoate, or a quaternary ammonium salt of a carboxylic acid are preferred, with potassium n-octanoate or potassium 2-ethylhexanoate being more preferred.

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.
From the viewpoint of maintaining the storage stability of Solution B, the amount of the 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.

(Other ingredients)
Liquid B may contain, as necessary, 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.

[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 blended in solution B is preferably smaller than that of carboxylate. Furthermore, since amine catalysts that have low reactivity with HFOs or HCFOs are expensive, it is preferable to use as little amine catalyst as possible from the viewpoint of cost.

Known amine catalysts can be used as such, and those with excellent storage stability, even when used in combination with blowing agents such as HFOs and HCFOs, are preferred. Examples include bis(2-morpholinoethyl) ether, styrenated diphenylamine, N,N',N"-dimethylaminopropylhexahydro-s-triazine, and N,N,N',N'-tetramethylhexanediamine. These catalysts may be used alone or in combination of two or more.

The amine catalyst is added in an amount of preferably 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 Solution A.
From the viewpoint of maintaining the storage stability of Solution B, the amount of the amine catalyst blended in Solution 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.

[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.

[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 appropriately adjusted 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.

[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 an HFO or HCFO.

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

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 respective 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 the mixture.
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, description thereof will be omitted here.

The rigid polyisocyanurate foam preferably has an oxygen index of 23.0 or more as measured in accordance with the measurement 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, 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 of 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, the value is measured on a test piece having a length of 150 mm, a width of 10 mm, and a thickness of 10 mm.

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 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.

[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 liquid 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 liquid has an isocyanate index of 160 to 500.
By using such a two-liquid mixture of liquids A and B, even when the foaming agent is an 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 mixed solution of components A and B reacts immediately after mixing, so it is preferable to prepare the mixed solution at the time of on-site construction. From the viewpoint of efficiency and safety during on-site construction, it is preferable to use the two-component premix composition of the present invention described above as the components A and B used in this mixed solution. It is also preferable to use an injection machine that can mix the two components 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.

The present invention will be described in detail below using examples, but the present invention is not limited thereto.

[Preparation of two-component premix composition]
(Examples 1 to 3, Comparative Examples 1 to 3, and Reference Example 1)
Liquids A and B of two-liquid premix compositions 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; "Solkane 365mfc" manufactured by Nippon Solvay K.K. Water <Carboxylate>
(1) Potassium 2-ethylhexanoate; "DABCO (registered trademark) K-15" manufactured by Air Products Japan Co., Ltd.; 75% by mass 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 (registered trademark) 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 mass 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-methyl siloxane copolymer; "NIAX SILICONE L-6970" manufactured by Momentive Performance Materials Japan LLC (5) Polyether-polydimethyl siloxane 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.

[Evaluation by hand foaming]
A total of 150 g of foaming raw material was prepared by mixing the liquids A and B prepared according to the formulations shown in Table 1 in a descup. Approximately 100 g of this foaming raw material was filled into a wooden box with inner 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. The evaluation results are summarized in Tables 2 and 3.

<Each process time>
The following time was measured from the time when mixing of the A and B solutions was started.
(1) Mixing time (MT: melting time): time until mixing is complete; (2) Cream time (CT: cream time): time until expansion begins; (3) Gel time (GT: gel time): time until gelation begins; (4) Rise time (RT: rise time): time until expansion stops. These process times affect work efficiency during on-site construction, and a cream time (CT) of 7 to 17 seconds can be considered good. A rise time (RT) of 45 to 75 seconds can also be considered 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 lining concrete for tunnels, underground structures, etc., 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.

<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 foamability, and a value within the range of 27 to 33 kg/ ^m3 is considered to be good.

<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 can be said that a maximum heat generation temperature of less than 180°C is preferable.

<Storage stability>
Foams were prepared using each of the B solutions 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 were as follows:
A: The bubble size is uniform.
B: The cell size is non-uniform or the cells are broken, or 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 evaluated as "A", then the storage stability can be said to be good.
The evaluation results of storage stability are shown in Table 3.

[Evaluation using actual foaming equipment]
A total of about 1 kg of liquids A and B prepared according to the blending compositions shown in Table 1 above was filled into a wooden box with inner dimensions of 150 mm width × 400 mm length × 500 mm height using an injection machine (actual machine) for on-site application, and foamed and cured at 20°C.
However, in 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 1 m x 1 m x 1 m was filled with a total of approximately 36 kg of liquid A and liquid B (a total of approximately 27 to 30 kg when watering), and the liquid was allowed to foam and harden at 20°C.
The foaming was carried out using the actual machine and the following evaluation items were carried out. The evaluation results are summarized in Table 2.

<Core density>
The core density is an index of the degree of foaming property, and if it is within the range of 27 to 33 kg/ ^m3 , 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. The average value of these was used as the core density.

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

<Dimensional stability>
The dimensional stability was evaluated based on the measurement values of the dimensional change rate after 72 hours in the directions parallel and perpendicular to the foaming direction under high temperature (70°C), low temperature (-30°C), and wet heat (70°C, 95% RH) conditions in accordance with ASTM D2126-15. The evaluation criteria were 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 exceeds ±1.0%. C: Under two or more of the above conditions, the dimensional change rate exceeds ±1.0%.

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

<Maximum heat generation temperature>
The temperature at the center 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 that the maximum heat generation temperature is 180°C or less.

<Evaluation during watering (heat resistance)>
During the production of a foam (1 m × 1 m × 1 m), the foam was hardened by spraying with a spray bottle about 1% by mass of water 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). 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 scorching is observed. Alternatively, coloring is observed in approximately 1/4 or less of the cross-sectional area.
B: Burns occurred over about 1/4 or more of the cross-sectional area.
C: The entire surface is burnt.

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

As can be seen from the evaluation results shown in Tables 2 and 3, when the two-component premix composition of the present invention consisting of the specified A and B components was used (Examples 1 to 3), even when the blowing agent was an 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 an 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 (7)

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. 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. 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 0.5 to 10 parts by mass per 100 parts by mass of the polyisocyanate compound;
Rigid polyisocyanurate foam. The rigid polyisocyanurate foam according to any one of claims 1 to 3, wherein the carboxylate is one or more selected from potassium formate, potassium acetate, potassium n-octanoate, and potassium 2-ethylhexanoate. The rigid polyisocyanurate foam according to any one of claims 1 to 4, wherein the blowing agent contains water, and the amount of water blended is 0.5 to 20 parts by mass per 100 parts by mass of the blowing agent other than water. The rigid polyisocyanurate foam according to any one of claims 1 to 5, having an oxygen index of 23.0 or greater as measured in accordance with JIS A 9511:2006R, flammability test, measurement method C. 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.