Method for manufacturing urethane-based aerogel, urethane-based aerogel, and composite material

Abstract

To provide a method for producing a urethane-based aerogel with low shrinkage rate of the solvent-containing gel during the drying process, a novel urethane-based aerogel with high strength, and a composite material containing a urethane-based aerogel. [Solution] A method for producing a urethane-based aerogel, comprising step A of mixing an isocyanate-terminated prepolymer obtained by reacting a first polyol with a polyisocyanate, a second polyol, and an organic solvent to obtain a solvent-containing gel, and step B of drying the solvent-containing gel.

Description

[Technical Field]

[0001] This disclosure relates to a method for manufacturing urethane-based aerogels, urethane-based aerogels, and composite materials. [Background technology]

[0002] Thermal insulation materials are essential for effectively utilizing thermal energy and promoting energy conservation. Various types of insulation materials, such as foamed insulation materials, fiber insulation materials, and vacuum insulation materials, are used, mainly in automobiles and housing.

[0003] In recent years, aerogels have attracted attention as materials with excellent heat insulation properties. Aerogels are a general term for low-density, highly porosity dry gel bodies formed by the aggregation of dense primary particles into secondary particles that are further linked together in a bead-like structure. They are porous materials obtained by drying solvent-containing gels. Silica-based aerogels are known as examples of aerogels. However, silica-based aerogels are extremely brittle and difficult to handle on their own. Therefore, in order to improve their strength, organic aerogels using organic compounds are being developed.

[0004] For example, Patent Document 1 discloses a porous gel containing, in a reacted form, (a1) at least one polyfunctional aromatic isocyanate, (a2) at least one polyfunctional aromatic amine selected from 4,4'-diaminodiphenylmethane, 2,4'-diaminodiphenylmethane, 2,2'-diaminodiphenylmethane and oligomeric diaminodiphenylmethane, and (a3) ​​at least one polyalkylene polyamine containing a total of at least three primary and secondary amino groups and having a weight-average molecular weight of at least 500 g / mol, wherein component (a3) ​​is present in an amount of 0.1% to 5% by weight based on the total weight of components (a1) to (a3). Patent Document 2 discloses a polyamide dry gel obtained by drying a polyamide wet gel. Patent Document 3 discloses an organic aerogel based on polyurethane, polyisocyanurate, or polyurea, having a thermal conductivity in the range of 13 mW / (m·K) to 30 mW / (m·K) measured in accordance with DIN 12667, and a compressive strength exceeding 0.20 N / mm 2 of an organic porous material, which is an organic aerogel.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the production method of an organic aerogel, since a plurality of raw materials are used, a plurality of reactions occur during gelation. Therefore, compared with the production method of a silica - based aerogel using a single raw material, the production method of an organic aerogel tends to be difficult to control the reactions during gelation. Also, in the production method of an organic aerogel, an organic solvent is used, but because the affinity between the organic compound as a raw material and the organic solvent is high, when drying the solvent - containing gel, the solvent - containing gel tends to shrink.

[0007] This disclosure has been made in view of the above - described situation. The problem to be solved by one embodiment of this disclosure is to provide a method for producing a urethane - based aerogel in which the shrinkage rate of the solvent - containing gel in the drying process is small. The problem to be solved by another embodiment of this disclosure is to provide a novel urethane - based aerogel having high strength and a composite material containing the above urethane - based aerogel. [Means for solving the problem]

[0008] The following are examples of specific means for solving the problem: <1> A method for producing a urethane-based aerogel, comprising: step A, mixing an isocyanate-terminated prepolymer obtained by reacting a first polyol with a polyisocyanate, a second polyol, and an organic solvent to obtain a solvent-containing gel; and step B, drying the solvent-containing gel. <2> The above organic solvent is at least one selected from N,N-dimethylformamide and dimethyl sulfoxide. <1> A method for producing urethane-based aerogel as described above. <3> In step A described above, a catalyst is further mixed to obtain a solvent-containing gel. <1> or <2> A method for producing urethane-based aerogel as described above. <4> The catalyst described above is at least one selected from the group consisting of organotin compounds, organoiron compounds, and organobismuth compounds. <3> A method for producing urethane-based aerogel as described above. <5> The catalyst described above is at least one selected from the group consisting of organoiron compounds and organobismuth compounds. <3> A method for producing urethane-based aerogel as described above. <6> In step B above, the solvent-containing gel is dried at a temperature in the range of 40°C to 80°C. <1> ~ <5> A method for manufacturing urethane-based aerogel as described in any one of the following. <7> A urethane-based aerogel having a specific gravity of 0.200 or less, an average pore size of 100 nm or less, and made using two or more polyols as raw materials. <8> A porous substrate having voids that communicate internally, and the voids of the porous substrate filled <7> A composite material containing the urethane-based aerogel described in [reference]. [Effects of the Invention]

[0009] According to one embodiment of the present disclosure, a method for producing a urethane-based aerogel with a low shrinkage rate of the solvent-containing gel during the drying process is provided. Other embodiments of the present disclosure provide a novel urethane-based aerogel having high strength, and a composite material containing the urethane-based aerogel. [Modes for carrying out the invention]

[0010] The following describes in detail the method for manufacturing the urethane-based aerogel, the urethane-based aerogel, and the composite material of this disclosure. The descriptions of the requirements below may be based on representative embodiments relating to this disclosure, but this disclosure is not limited to such embodiments and can be implemented with appropriate modifications within the scope of the purpose of this disclosure.

[0011] In this disclosure, numerical ranges indicated using "~" mean a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. In addition, in numerical ranges described in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples.

[0012] In this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In this disclosure, the amount of each component in a composition means the total amount of any multiple substances present in the composition, unless otherwise specified, if there are multiple substances corresponding to each component in the composition.

[0013] In this disclosure, "mass%" and "weight%" are synonymous, and "parts of mass" and "parts of weight" are synonymous.

[0014] In this disclosure, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, as long as their intended purpose is achieved.

[0015] In this disclosure, "polyol" means a compound having two or more hydroxyl groups in its molecule, "diol" means a polyol having two hydroxyl groups, and "triol" means a polyol having three hydroxyl groups. In this disclosure, "polyisocyanate" means a compound having two or more isocyanate groups in its molecule.

[0016] [Manufacturing method for urethane-based aerogel] The method for producing a urethane-based aerogel according to the present disclosure includes step A, which involves mixing an isocyanate-terminated prepolymer (hereinafter also simply referred to as "prepolymer") obtained by reacting a first polyol with a polyisocyanate, a second polyol, and an organic solvent to obtain a solvent-containing gel, and step B, which involves drying the solvent-containing gel.

[0017] The method for producing urethane-based aerogels described herein exhibits a low shrinkage rate of the solvent-containing gel during the drying process. While the reason for this effect is not clear, the inventors speculate as follows. However, these speculations are not intended to limit the interpretation of the method for producing urethane-based aerogels described herein, but rather to illustrate the case as an example.

[0018] According to the method for producing urethane-based aerogels of this disclosure, the reaction between the polyol and isocyanate can be well controlled by reacting an isocyanate-terminated prepolymer, which is obtained by reacting a first polyol with an isocyanate beforehand, with a second polyol. Since a solvent-containing gel with a strong structure is formed by a two-step reaction—the reaction between the first polyol and the isocyanate, and the reaction between the isocyanate-terminated prepolymer and the second polyol—it is presumed that shrinkage of the solvent-containing gel during the drying process is less likely to occur.

[0019] The following describes in detail each step of the manufacturing method for the urethane-based aerogel described herein.

[0020] The method for producing the urethane-based aerogel described herein may include steps other than steps A and B (so-called other steps). Other processes include, for example, a prepolymer preparation process.

[0021] <Prepolymer preparation process> The prepolymer preparation step involves preparing an isocyanate-terminated prepolymer by reacting a first polyol with a polyisocyanate.

[0022] The prepolymer preparation step may be a step of preparing a commercially available prepolymer, or it may be a step of synthesizing a prepolymer. If the prepolymer preparation step is a step for synthesizing the prepolymer, the method for synthesizing the prepolymer is not particularly limited other than reacting the first polyol with the polyisocyanate, and conventionally known methods can be applied. For example, the prepolymer can be synthesized by charging the polyisocyanate and organic solvent into a reactor, stirring the contents of the reactor under a nitrogen atmosphere, and then adding the first polyol dropwise to allow the reaction to proceed.

[0023] (Prepolymer) The isocyanate-terminated prepolymer in this disclosure is a compound that is a reaction product of a first polyol and a polyisocyanate, and has an isocyanate group at the end of the molecule. That is, the isocyanate-terminated prepolymer in this disclosure is a compound that includes a polymerization chain containing structural units derived from the first polyol and structural units derived from the polyisocyanate, and has an isocyanate group as the terminal group of the polymerization chain.

[0024] The isocyanate content (NCO content) of the prepolymer is not particularly limited, but for example, from the viewpoint of storage stability, it is preferably in the range of 5% to 40% by mass, more preferably in the range of 10% to 40% by mass, and even more preferably in the range of 10% to 30% by mass, relative to the total mass of the prepolymer.

[0025] The isocyanate group content of the prepolymer was measured according to the method compliant with JIS K 1603-1:2007.

[0026] The number-average molecular weight (Mn) of the prepolymer is not particularly limited, but from the viewpoint of handling and storage, it is preferably in the range of 500 to 10000, more preferably in the range of 750 to 5000, and even more preferably in the range of 1000 to 3000.

[0027] The number-average molecular weight of the prepolymer was determined as a standard styrene equivalent value using the GPC method under the following conditions.

[0028] -conditions- Measurement device: High-speed GPC [Model number: HLC-8320GPC, manufactured by Tosoh Corporation] Detector: Differential refractometer (RI) Column: TSKgel® SuperMultiporeHZ-N [Column size: 4.6mmφ x 15cm, manufactured by Tosoh Corporation] Column temperature: 40℃ Eluent: Tetrahydrofuran Sample solution injection volume: 15 μL Flow rate: 1.0mL / min

[0029] (First polyol) The type of the first polyol is not particularly limited. The first polyol may be, for example, a polyol having two hydroxyl groups in its molecule (i.e., a diol), or a polyol having two or more hydroxyl groups in its molecule. However, from the viewpoint of ease of handling, it is preferable that it be at least one of a diol and a triol, and more preferably a diol.

[0030] Examples of the first polyol include aliphatic polyols, aromatic polyols, alicyclic polyols, polyester polyols, polyether polyols, and polymer polyols. Among these, at least one selected from the group consisting of aliphatic polyols and aromatic polyols is preferred as the first polyol from the viewpoint of ease of reaction control.

[0031] Examples of aliphatic polyols include ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, and tetraethylene glycol.

[0032] Examples of aromatic polyols include aromatic polyols having phenolic hydroxyl groups such as catechol, resorcinol, hydroquinone, bisphenol A, bisphenol F, and 1,1,1-tris(4-hydroxyphenyl)ethane, and aromatic polyols having alcoholic hydroxyl groups such as benzenedimethanol and benzenediethanol. Examples of aromatic polyols include polycarbonate polyols having an aromatic skeleton, polyester polyols having an aromatic skeleton, polyether polyols having an aromatic skeleton, castor oil-based modified polyols having an aromatic skeleton, and polymeric aromatic polyols such as phenol novolac and cresol novolac. It is preferable that the aromatic polyol is an aromatic polyol having phenolic hydroxyl groups. Furthermore, it is preferable that the aromatic polyol is a compound containing multiple benzene rings having phenolic hydroxyl groups. A phenolic hydroxyl group refers to a hydroxyl group directly bonded to an aromatic ring.

[0033] Examples of alicyclic polyols include cyclohexanediol, isophoronediol, dicyclohexylmethanediol, and dimethyldicyclohexylmethanediol.

[0034] Examples of polyester polyols include polymers obtained by dehydration condensation of polybasic acids (e.g., adipic acid, azelaic acid, sebacic acid, terephthalic acid, isophthalic acid, and succinic acid) and polyhydric alcohols (e.g., ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, diethylene glycol, 1,6-hexane glycol, and neopentyl glycol), polymers obtained by ring-opening polymerization of lactones (e.g., ε-caprolactone and α-methyl-ε-caprolactone), and condensates of hydroxycarboxylic acids (e.g., castor oil) and polyhydric alcohols.

[0035] Examples of polyether polyols include compounds obtained by adding an alkylene oxide (e.g., ethylene oxide and propylene oxide) to a polyhydric alcohol.

[0036] Examples of polymer polyols include polymers obtained by graft polymerization of ethylenically unsaturated compounds such as acrylonitrile and styrene onto polyols such as aliphatic polyols, aromatic polyols, and alicyclic polyols.

[0037] The first polyol may be one type or two or more types.

[0038] When the prepolymer preparation step is a step for synthesizing a prepolymer, the amount of the first polyol used is not particularly limited, but for example, from the viewpoint of reaction control, it is preferably in the range of 1 to 100 parts by mass, more preferably in the range of 10 to 75 parts by mass, and even more preferably in the range of 20 to 50 parts by mass, per 100 parts by mass of polyisocyanate.

[0039] (Polyisocyanate) The type of polyisocyanate is not particularly limited. Examples of polyisocyanates include aliphatic polyisocyanate compounds, alicyclic polyisocyanate compounds, and aromatic polyisocyanate compounds. Modified polyisocyanates, obtained by modifying the above-mentioned polyisocyanate compounds, are also examples of polyisocyanates.

[0040] Examples of aliphatic polyisocyanate compounds include hexamethylene diisocyanate (HDI), pentamethylene diisocyanate (PDI), tetramethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate.

[0041] Examples of alicyclic polyisocyanate compounds include isophorone diisocyanate (IPDI), hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0042] Examples of aromatic polyisocyanate compounds include tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), diphenylmethane diisocyanate (MDI), and polymeric MDI.

[0043] The polyisocyanate reacted with the first polyol may be one type or two or more types.

[0044] (organic solvent) If the prepolymer preparation step is a step in synthesizing the prepolymer, the type of organic solvent used is the same as the organic solvent used in the "sol solution preparation step" described later, so the explanation is omitted here.

[0045] In the process of synthesizing the prepolymer, one organic solvent may be used alone, or two or more may be used in combination.

[0046] The amount of organic solvent used is not particularly limited and can be set appropriately according to the amount of the first polyol and polyisocyanate used.

[0047] [Process A] Step A is a step in which an isocyanate-terminated prepolymer obtained by reacting a first polyol with a polyisocyanate, a second polyol, and an organic solvent are mixed to obtain a solvent-containing gel.

[0048] Process A may consist of two or more processes. For example, step A may include a sol solution preparation step of mixing an isocyanate-terminated prepolymer obtained by reacting a first polyol with a polyisocyanate, a second polyol, and an organic solvent to prepare a sol solution, and a solvent-containing gel preparation step of gelling the sol solution to prepare a solvent-containing gel.

[0049] <Solu solution preparation process> The sol solution preparation step involves mixing an isocyanate-terminated prepolymer obtained by reacting a first polyol with a polyisocyanate, a second polyol, and an organic solvent to prepare a sol solution.

[0050] (Second polyol) The type of the second polyol is not particularly limited. Examples of the second polyol include those similar to the first polyol. From the viewpoint of ease of synthesis, the second polyol is preferably at least one selected from the group consisting of aliphatic polyols and aromatic polyols. Furthermore, from the viewpoint of ease of handling, the second polyol is preferably at least one of a diol and a triol, and more preferably a diol.

[0051] The first polyol and the second polyol may be the same or different, but it is preferable that they be different, for example, from the viewpoint of synthesizing a flexible urethane-based aerogel.

[0052] The second polyol may be one kind or two or more kinds.

[0053] The amount of the second polyol used is not particularly limited. For example, from the viewpoint of ease of synthesis, it is preferably in the range of 1 to 100 parts by mass, more preferably in the range of 5 to 75 parts by mass, based on 100 parts by mass of the polyisocyanate.

[0054] (Organic solvent) The organic solvent is not particularly limited. For example, from the viewpoint of solubility, it is preferably a polar solvent. Examples of the polar solvent include amide solvents such as N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, and N,N-diethylacetamide; pyrrolidone solvents such as N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, and N-vinyl-2-pyrrolidone; sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide; phenol solvents such as phenol, o-cresol, m-cresol, p-cresol, halogenated phenol, and catechol; ether solvents such as tetrahydrofuran and dioxane; ketone solvents such as acetone; alcohol solvents such as methanol, ethanol, and butanol; and cellosolve solvents such as butyl cellosolve. Among the polar solvents, an aprotic solvent is more preferable as the organic solvent.

[0055] The solubility parameter of the organic solvent is not particularly limited. For example, in the Hansen solubility parameter (HSP value), the value of the dispersion term δd is preferably 10 MPa 1 / 2 ~25 MPa 1 / 2 and more preferably 12 MPa 1 / 2 ~21 MPa 1 / 2 and even more preferably 15 MPa 1 / 2 ~19 MPa 1 / 2 Also, the value of the polar term δp is preferably 5 MPa 1 / 2 ~25 MPa 1 / 2 and more preferably 10 MPa 1 / 2 ~23 MPa 1 / 2It is more preferable that it be 12 MPa 1 / 2 ~20MPa 1 / 2 It is even more preferable that the hydrogen bonding term δh is 5 MPa. 1 / 2 ~25MPa 1 / 2 Preferably, it is 10 MPa 1 / 2 ~23 MPa 1 / 2 It is more preferable that it be 12 MPa 1 / 2 ~20MPa 1 / 2 It is even more preferable that this be the case.

[0056] The values ​​for the dispersion term δd, the polarity term δp, and the hydrogen bonding term δh are described in "ACS Applied Materials & Interfaces, 2017, 9(21), 18222-18230, Superinsulating Polyisocyanate Based Aerogels: A Targeted Search for the Optimum Solvent System," and their contents are incorporated herein by reference.

[0057] The organic solvent preferably contains at least one selected from the group consisting of N,N-dimethylformamide, dimethyl sulfoxide, and tetrahydrofuran, more preferably at least one selected from the group consisting of N,N-dimethylformamide, dimethyl sulfoxide, and tetrahydrofuran, even more preferably at least one selected from the group consisting of N,N-dimethylformamide and dimethyl sulfoxide, and particularly preferably N,N-dimethylformamide. By using these organic solvents, finer particles can be formed.

[0058] Furthermore, N,N-dimethylformamide has a dispersion term δd value of 17.4 MPa. 1 / 2 The value of the polarity term δp is 13.7 MPa. 1 / 2 The hydrogen bonding term δh is 11.3 MPa. 1 / 2 Dimethyl sulfoxide has a dispersion term δd value of 18.4 MPa.1 / 2 The value of the polarity term δp is 16.4 MPa. 1 / 2 The hydrogen bonding term δh is 10.2 MPa. 1 / 2 For tetrahydrofuran, the value of the dispersion term δd is 16.8 MPa. 1 / 2 The value of the polarity term δp is 5.7 MPa. 1 / 2 The hydrogen bonding term δh is 8.0 MPa. 1 / 2 That is the case. When N,N-dimethylformamide and dimethyl sulfoxide, which have high values ​​for the polar term δp and hydrogen bonding term δh, are used, the formation of aerogel-forming particles improves, and thus the thermal insulation tends to be higher.

[0059] In step A (including the sol solution preparation step), one organic solvent may be used alone, or two or more may be used in combination.

[0060] The amount of organic solvent used is not particularly limited and can be appropriately set according to the amount of the essential components, the prepolymer and the second polyol, and the optional component, the catalyst. The amount of organic solvent used is preferably such that, from the viewpoint of gelation rate and particle formation, the resin concentration calculated by the following formula is in the range of 1% by mass or more and 30% by mass or less, more preferably in the range of 5% by mass or more and 25% by mass or less, and even more preferably in the range of 10% by mass or more and 20% by mass or less. Resin concentration = (Amount of prepolymer + Amount of second polyol) / (Amount of prepolymer solution + Amount of second polyol + Amount of catalyst + Amount of organic solvent) × 100

[0061] In step A (including the sol solution preparation step), it is preferable to further mix in a catalyst to obtain a solvent-containing gel. Further mixing in the catalyst promotes gelation, making it easier to obtain a solvent-containing gel. Furthermore, when mixing in a catalyst, the prepolymer, second polyol, organic solvent, and catalyst may be mixed together, or the prepolymer, second polyol, and organic solvent may be mixed first, and then the catalyst may be added and mixed further.

[0062] The type of catalyst is not particularly limited. Examples of catalysts include amine catalysts and metal catalysts. From the viewpoint of reactivity, for example, a metal catalyst is preferred.

[0063] Examples of amine catalysts include triethylamine, triethylenediamine, N-ethylmorpholine, N-(N',N'-2-dimethylaminoethyl)morpholine, N,N,N',N'',N''-pentamethyldipropylenetriamine, N,N,N',N'-tetramethylhexamethylenediamine, N,N-dimethylcyclohexylamine, N-(2-dimethylaminoethyl)-N'-methylpiperazine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'',N''-pentamethyldiethylenetriamine, bis(2-dimethylaminomethyl) ether, N-(2-hydroxyethyl)-N'-methylpiperazine, N,N-dimethylaminoethanol, N,N-dimethylaminoethoxyethanol, N,N,N'-trimethylaminoethylethanolamine, and 1,8-diazabicyclo(5,4,0)-undecene-7.

[0064] Examples of metal catalysts include organotin compounds, organoiron compounds, organobismuth compounds, organolead compounds, and organozinc compounds. The catalyst is preferably at least one selected from the group consisting of organotin compounds, organoiron compounds, and organobismuth compounds, for example, from the viewpoint of reaction rate during gelation. Furthermore, the catalyst is more preferably at least one selected from the group consisting of organoiron compounds and organobismuth compounds, for example, from the viewpoint of obtaining an aerogel with lower thermal conductivity.

[0065] Examples of organotin compounds include dibutyltin dilaurate and dioctyltin dilaurate. Examples of organoiron compounds include iron(III) acetylacetonate. Examples of organobismuth compounds include bismuth acetylacetonate and bismuth carboxylic acid.

[0066] When a catalyst is used in step A (including the sol solution preparation step), one type of catalyst may be used alone, or two or more types may be used in combination.

[0067] A commercially available catalyst can be used. Examples of commercially available catalysts include "Dibutyltin Dilaurate" manufactured by Tokyo Chemical Industries, Ltd., "Iron(III) Acetylacetonate" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., and "TIB KAT 716 (component: Bismuth Acetylacetonate)" manufactured by TIB Chemicals. Please note that "TIB KAT" is a registered trademark.

[0068] When a catalyst is used in step A (including the sol solution preparation step), the amount of catalyst used is not particularly limited, as long as it is sufficient to adequately gel the sol solution. The amount of catalyst used is preferably 0.002 parts by mass or more, and more preferably 0.01 parts by mass or more, per 100 parts by mass of prepolymer. Furthermore, from the viewpoint of suppressing gel solidification, the amount of catalyst used is preferably 0.2 parts by mass or less, and more preferably 0.1 parts by mass or less. In one embodiment, the amount of catalyst used may be in the range of 0.002 parts by mass or more and 0.2 parts by mass or in the range of 0.01 parts by mass or more and 0.1 parts by mass or less, per 100 parts by mass of prepolymer.

[0069] <Solvent-containing gel preparation process> The solvent-containing gel preparation process is a process of preparing a solvent-containing gel by gelling a sol solution.

[0070] The method for gelling the sol solution is not particularly limited; for example, the sol solution can be left to stand in a container. The standing of the sol solution is usually carried out at room temperature, but it may also be carried out in a heated environment.

[0071] When a sol solution contains a catalyst, its gelation is promoted, allowing the sol solution to be efficiently converted into a solvent-containing gel.

[0072] [Process B] Step B is a step of drying the solvent-containing gel. By drying the solvent-containing gel, a urethane-based aerogel can be obtained.

[0073] Process B may consist of two or more processes. For example, step B may include a solvent replacement step of replacing the solvent contained in the solvent-containing gel with a low-boiling point solvent, and a drying step of drying the solvent-containing gel after solvent replacement.

[0074] <Solvent replacement process> The solvent replacement step is a process in which the solvent contained in the solvent-containing gel is replaced with a low-boiling point solvent in order to suppress the shrinkage of the solvent-containing gel during the drying process.

[0075] As a low-boiling point solvent, for example, a solvent with a boiling point in the range of 50°C to 100°C is preferred. Specific examples of low-boiling point solvents include tetrahydrofuran, ethanol, n-butanol, 2-butanol, hexane, heptane, acetone, isopropanol, and 2,3-dihydrodecafluoropentane.

[0076] In step B (including the solvent substitution step), a single low-boiling point solvent may be used, or two or more may be used in combination.

[0077] The solvent replacement step may be performed once or multiple times. For example, from the viewpoint of improving work efficiency, reducing costs, and reducing environmental impact, it is preferable to perform the solvent replacement step once. If the solvent replacement step is performed multiple times, the type of solvent may be changed each time.

[0078] The amount of low-boiling point solvent used in each solvent replacement step is preferably, for example, 1 to 100 times the volume of the solvent-containing gel.

[0079] The solvent replacement method may be total replacement, partial replacement, or cyclic replacement. For example, from the viewpoint of improving workability, total replacement is preferred as the solvent replacement method.

[0080] <Drying process> The drying process involves drying the solvent-containing gel after solvent replacement. By performing the drying process, the solvent-containing gel after solvent replacement can be converted into a urethane-based aerogel.

[0081] The drying method is not particularly limited and examples include supercritical drying and atmospheric pressure drying. Among these, supercritical drying is preferred from the viewpoint of suppressing shrinkage.

[0082] When the drying method is supercritical drying, carbon dioxide is preferred as the supercritical fluid. When the supercritical fluid is carbon dioxide, the drying temperature is preferably above the temperature at which carbon dioxide becomes supercritical (i.e., the critical temperature), for example, preferably 40°C or higher, and more preferably 45°C or higher. Furthermore, from the viewpoint of suppressing shrinkage of the solvent-containing gel, the drying temperature is preferably 80°C or lower, and more preferably 75°C or lower. In one embodiment, the drying temperature may be in the range of 40°C to 80°C, or in the range of 45°C to 75°C.

[0083] When the supercritical fluid is carbon dioxide, the drying pressure is preferably equal to or greater than the pressure at which carbon dioxide becomes supercritical (i.e., the critical pressure), for example, preferably 10 MPa or higher, and more preferably 12 MPa or higher. Furthermore, the drying pressure is preferably 20 MPa or less, more preferably 18 MPa or less, and even more preferably 15 MPa or less. In one embodiment, the drying pressure may be in the range of 10 MPa to 20 MPa, 10 MPa to 18 MPa, 10 MPa to 15 MPa, 12 MPa to 20 MPa, 12 MPa to 18 MPa, or 12 MPa to 15 MPa.

[0084] The drying time is not particularly limited and can be set appropriately depending on the temperature and pressure during drying, for example.

[0085] [Urethane-based aerogel] The urethane-based aerogel of this disclosure has a specific gravity of 0.200 or less, an average pore diameter of 100 nm or less, and is an aerogel made using two or more polyols as raw materials. The urethane-based aerogel disclosed herein is a novel urethane-based aerogel with high strength (so-called gel strength). The strength of the urethane-based aerogel disclosed herein tends to be higher than that of conventional silica-based aerogels.

[0086] The specific gravity of the urethane-based aerogel of this disclosure is preferably 0.200 or less, more preferably 0.175 or less, and more preferably 0.150 or less, from the viewpoint of thermal conductivity. The lower limit of the specific gravity of the urethane-based aerogel of this disclosure is not particularly limited, but is preferably 0.100 or higher, for example, from the viewpoint of thermal conductivity. In one embodiment, the specific gravity of the urethane-based aerogel of this disclosure may be in the range of 0.100 to 0.200, in the range of 0.100 to 0.175, or in the range of 0.100 to 0.150.

[0087] In this disclosure, the specific gravity of the urethane-based aerogel is the value measured using a hydrometer with a urethane-based aerogel sample measuring 50 mm in diameter and 5 mm in thickness. For example, the MD-200S (model number), an electronic hydrometer manufactured by Alpha Mirage Co., Ltd., can be suitably used as the hydrometer. However, the hydrometer is not limited to this.

[0088] From the viewpoint of thermal conductivity, the average pore diameter of the urethane-based aerogel of this disclosure is 100 nm or less, preferably 85 nm or less, and more preferably 70 nm or less. The lower limit of the average pore diameter of the urethane-based aerogel of this disclosure is not particularly limited, but for example, from the viewpoint of thermal conductivity, it is preferably 1 nm or more, preferably 5 nm or more, and preferably 10 nm or more. In one embodiment, the average pore size of the urethane-based aerogel of the present disclosure may be in the range of 1 nm to 100 nm, in the range of 5 nm to 85 nm, or in the range of 10 nm to 70 nm.

[0089] In this disclosure, the average pore size of the urethane-based aerogel is a value measured by the nitrogen gas adsorption method in accordance with JIS Z 8831-2:2010 "Pore size distribution and pore characteristics of powders (solids) Part 2: Measurement method of mesopores and macropores by gas adsorption". As the measuring device, for example, the Belsorp II mini (model number), a pore distribution measuring device manufactured by Microtrac-Bel, can be suitably used. However, the measuring device is not limited to this.

[0090] As for embodiments of the urethane-based aerogel of this disclosure, for example, from the viewpoint of suitability as a thermal insulation material, an embodiment in which the specific gravity is in the range of 0.100 to 0.200 and the average pore diameter is in the range of 1 nm to 100 nm is preferred, an embodiment in which the specific gravity is in the range of 0.100 to 0.150 and the average pore diameter is in the range of 5 nm to 85 nm is more preferred, and an embodiment in which the specific gravity is in the range of 0.100 to 0.150 and the average pore diameter is in the range of 10 nm to 70 nm is even more preferred.

[0091] The pore size volume distribution [dVp / dlog] of the urethane-based aerogel of this disclosure is not particularly limited, but for example, from the viewpoint of thermal conductivity, it is preferably in the range of 1.0 to 15.0, more preferably in the range of 1.5 to 12.5, and even more preferably in the range of 1.9 to 10.0.

[0092] In this disclosure, the pore size volume distribution [dVp / dlog] of the urethane-based aerogel is a value measured by the nitrogen gas adsorption method in accordance with JIS Z 8831-2:2010 "Pore size distribution and pore characteristics of powders (solids) Part 2: Measurement method for mesopores and macropores by gas adsorption". As the measuring device, for example, the Belsorp II mini (model number), a pore distribution measuring device manufactured by Microtrac-Bel, can be suitably used. However, the measuring device is not limited to this.

[0093] The isocyanate index (INDEX) of the urethane-based aerogel of this disclosure is not particularly limited, but is preferably 80 to 120, and more preferably 90 to 110.

[0094] In this disclosure, the isocyanate index is expressed as a percentage of the equivalent ratio of the isocyanate groups of the polyisocyanate to the hydroxyl groups of the polyol, and is calculated by the following formula. Isocyanate Index = (NCO equivalent of isocyanate / hydroxyl group equivalent of polyol) × 100

[0095] The urethane-based aerogel of this disclosure is an aerogel made using two or more polyols as raw materials. The types of polyols used as raw materials are not particularly limited as long as there are two or more. The urethane-based aerogel of this disclosure may be an aerogel made using two polyols as raw materials, or it may be an aerogel made using three or more polyols as raw materials. The polyol used as a raw material for the urethane-based aerogel of this disclosure is the same as the polyol described in the section "Method for producing the urethane-based aerogel of this disclosure" above, and the preferred embodiment is also the same; therefore, a detailed explanation is omitted here.

[0096] The method for producing the urethane-based aerogel described herein is not particularly limited. The urethane-based aerogel of this disclosure can be suitably manufactured, for example, by the method for manufacturing the urethane-based aerogel of this disclosure described above.

[0097] [Composite material] The composite material of this disclosure includes a porous substrate having voids communicating internally, and a urethane-based aerogel of this disclosure filled in the voids of the porous substrate. Because the composite material of this disclosure contains the urethane-based aerogel of this disclosure, it tends to have higher strength compared to a composite material containing a silica-based aerogel, which is a common type of aerogel in the conventional sense. Furthermore, because the composite material of this disclosure contains the urethane-based aerogel of this disclosure, it tends to be less prone to powder shedding compared to a composite material containing a silica-based aerogel. In addition, because the composite material of this disclosure contains the urethane-based aerogel of this disclosure, it has low thermal conductivity and can be suitably used, for example, as an insulating material.

[0098] (Porous base material) Porous substrates have voids that communicate with each other internally. The pore size (so-called pore diameter) of the porous substrate is not particularly limited. The pore size may be micropores, mesopores, or macropores.

[0099] Examples of porous substrates include fibrous substrates (e.g., woven and nonwoven fabrics) and foams. Among these, foams are preferred as the porous substrate, for example, because they have high retention capabilities for the urethane-based aerogel filled in the voids.

[0100] Examples of fibers constituting the fibrous base material include organic fibers, inorganic fibers, and metallic fibers. Examples of organic fibers include fibers composed of organic materials such as polyolefins (olefin resins), polyesters, polyvinyl chlorides, acrylic resins, polyimides, and polyamides. Examples of inorganic fibers include fibers composed of inorganic materials such as glass, carbon, silica, rock wool, and ceramics. Examples of metallic fibers include fibers composed of metals such as stainless steel and aluminum.

[0101] Examples of materials for the foam include resins. Examples of resins that make up the foam include polyolefins, polystyrenes, polyesters, polyethers, acrylic resins, polyamides, polyurethanes, polycarbonates, polyvinyl chlorides, melamine resins, and fluororesins. The foam may consist of one type of resin or two or more types. The resin that makes up the foam is preferably polyolefin or melamine resin, and more preferably melamine resin.

[0102] The thermal conductivity of the porous substrate is not particularly limited and can be set appropriately depending on the application of the composite material. From the viewpoint of suitability as a thermal insulation material, for example, the thermal conductivity of the porous substrate is preferably 0.050 W / (m·K) or less, and more preferably 0.040 W / (m·K) or less. Furthermore, the thermal conductivity of the porous substrate may be, for example, 0.010 W / (m·K) or higher. In one embodiment, the thermal conductivity of the porous substrate may be in the range of 0.010 W / (m·K) or more and 0.050 W / (m·K) or less, or in the range of 0.020 W / (m·K) or more and 0.040 W / (m·K) or less.

[0103] In this disclosure, the thermal conductivity of the porous substrate is a value measured by a method conforming to JIS A 1412-2:1999 "Method for measuring thermal resistance and thermal conductivity of thermal insulating materials". As a measuring device, for example, the HC-074 F200 (model number), a thermal conductivity measuring device manufactured by Eiko Seiki Co., Ltd., can be suitably used. However, the measuring device is not limited to this.

[0104] The density of the porous substrate is not particularly limited and can be set appropriately depending on the application of the composite material. Porous substrates tend to have lower thermal conductivity and higher insulation properties as their density decreases. Therefore, from the viewpoint of suitability as an insulating material, the density of the porous substrate is considered to be 0.3 g / cm³. 3 Preferably, it is 0.2 g / cm³. 3 It is more preferable that the following is the case: 0.15 g / cm³ 3 The following is even more preferable: Furthermore, the density of the porous substrate is, for example, 0.005 g / cm³. 3 That's fine too. In one embodiment, the density of the porous substrate is 0.005 g / cm³. 3 More than 0.3g / cm 3 The following range is also acceptable: 0.01 g / cm³ 3 More than 0.2g / cm 3 The following range is also acceptable: 0.02 g / cm³ 3 More than 0.15g / cm 3 The following range is also acceptable.

[0105] In this disclosure, the density of the porous substrate is a value measured by a method in accordance with JIS K 7222:2005 "Foamed plastics and rubber - Method for determining apparent density".

[0106] The thickness of the porous substrate is not particularly limited and can be set as appropriate depending on the application of the composite material. From the viewpoint of handling, ease of manufacturing, and thermal insulation of the composite material, the thickness of the porous substrate is preferably in the range of 0.1 mm to 10 mm, more preferably in the range of 0.2 mm to 7 mm, and even more preferably in the range of 0.5 mm to 5 mm.

[0107] In this disclosure, the thickness of the porous substrate refers to the average thickness of the porous substrate. The average thickness of the porous substrate was determined by the following method: The thickness was measured at 10 randomly selected points along the thickness direction of the porous substrate. The arithmetic mean of the measured values ​​was calculated, and this value was taken as the average thickness of the porous substrate.

[0108] Since the composite material of this disclosure contains the urethane-based aerogel of this disclosure in the interconnected voids inside the porous substrate, the thickness of the composite material of this disclosure can be considered to be equivalent to the thickness of the porous substrate.

[0109] The shape of the porous substrate is not particularly limited and can be set as appropriate depending on the application of the composite material.

[0110] (Urethane-based aerogel) In the composite material of this disclosure, the urethane-based aerogel of this disclosure is filled into interconnected voids within a porous substrate. Details of the urethane-based aerogel of this disclosure have been previously described and will therefore not be explained here.

[0111] <<Physical Properties of Composite Materials>> The thermal conductivity of the composite material of this disclosure is not particularly limited and can be set as appropriate depending on the application. From the viewpoint of suitability as an insulating material, the thermal conductivity of the composite material of this disclosure is preferably 0.0350 W / (m·K) or less, more preferably 0.0300 W / (m·K) or less, and even more preferably 0.0280 W / (m·K) or less. Furthermore, the thermal conductivity of the composite material of this disclosure may be, for example, 0.0100 W / (m·K) or higher. In one embodiment, the thermal conductivity of the composite material of the present disclosure may be in the range of 0.0100 W / (m·K) or more and 0.0350 W / (m·K) or less, in the range of 0.0120 W / (m·K) or more and 0.0300 W / (m·K) or less, or in the range of 0.0140 W / (m·K) or more and 0.0280 W / (m·K) or less.

[0112] In this disclosure, the thermal conductivity of the composite material is a value measured by a method conforming to JIS A 1412-2:1999 "Method for measuring thermal resistance and thermal conductivity of thermal insulating materials". As a measuring device, for example, the HC-074 F200 (model number), a thermal conductivity measuring device manufactured by Eiko Seiki Co., Ltd., can be suitably used. However, the measuring device is not limited to this.

[0113] The density of the composite material disclosed herein is not particularly limited and can be set as appropriate depending on the application. Composite materials tend to have lower thermal conductivity and higher thermal insulation properties as their density decreases. Therefore, from the viewpoint of suitability as a thermal insulation material, the density of the composite material disclosed herein is 0.25 g / cm³. 3 Preferably, it is 0.20 g / cm³. 3 It is more preferable that the following is the case: 0.19 g / cm³ 3 The following is even more preferable: Furthermore, the density of the composite material disclosed herein is, for example, 0.10 g / cm³. 3 That's fine too. In one embodiment, the density of the composite material of this disclosure is 0.10 g / cm³. 3 More than 0.25g / cm 3 The following range is also acceptable: 0.12 g / cm³ 3 More than 0.20g / cm 3 The following range is also acceptable: 0.14 g / cm³ 3 More than 0.19g / cm 3 The following range is also acceptable.

[0114] In this disclosure, the density of the composite material is a value measured by a method in accordance with JIS K 7222:2005 "Foamed plastics and rubber - Method for determining apparent density".

[0115] The average pore diameter of the composite material of this disclosure is not particularly limited and can be set as appropriate depending on the application. From the viewpoint of suitability as a thermal insulation material, for example, the average pore diameter of the composite material of this disclosure is preferably 100 nm or less, more preferably 85 nm or less, and even more preferably 70 nm or less. Also from a similar viewpoint, the average pore diameter of the composite material of this disclosure is preferably 1 nm or more, more preferably 2 nm or more, and even more preferably 10 nm or more. In one embodiment, the average pore diameter of the composite material of this disclosure may be in the range of 1 nm to 100 nm, 2 nm to 100 nm, 10 nm to 100 nm, 20 nm to 100 nm, 30 nm to 85 nm, or 40 nm to 70 nm.

[0116] In this disclosure, the average pore size of the composite material is a value measured by the nitrogen gas adsorption method in accordance with JIS Z 8831-2:2010 "Pore size distribution and pore characteristics of powders (solids) Part 2: Measurement method for mesopores and macropores by gas adsorption". As a measuring device, for example, the Belsorp II mini (model number), a pore distribution measuring device manufactured by Microtrac-Bel, can be suitably used. However, the measuring device is not limited to this.

[0117] <<Applications of Composite Materials>> The composite material of this disclosure has higher strength, is less prone to powder shedding, and tends to exhibit thermal conductivity equivalent to that of conventional aerogel composite materials, such as silica-based aerogel composite materials. Therefore, applications of the composite material of this disclosure include: wall materials, floor materials, or ceiling materials for buildings; insulation materials used by wrapping them around plant piping; insulation materials used by attaching them to thermoelectric elements to prevent heat diffusion or improve power generation efficiency; insulation materials used by assembling them in the housings of various batteries to stabilize battery performance; insulation materials used in cooler boxes or warmer boxes for keeping food, medical products, pharmaceuticals, etc. cold or warm; insulation materials used in freezers, refrigerators, etc.; interior materials for vehicles such as automobiles, railway cars, aircraft, and ships (e.g., ceiling materials installed inside the roofs of vehicles); and insulation materials used in clothing, gloves, shoes, etc.

[0118] [Manufacturing method for composite materials] The composite material of this disclosure can be manufactured, for example, by carrying out the following steps. (1) A sol solution preparation step, in which an isocyanate-terminated prepolymer obtained by reacting a first polyol with a polyisocyanate, a second polyol, and an organic solvent are mixed to prepare a sol solution. (2) Sol solution filling process: Filling the voids of the porous substrate with a sol solution. (3) Solvent-containing gel preparation step: preparing a solvent-containing gel by gelling the sol solution. (4) Solvent replacement step: Replacing the solvent contained in the solvent-containing gel with a low-boiling point solvent. (5) Drying step to dry the solvent-containing gel after solvent replacement.

[0119] The above process may be carried out continuously or intermittently, or multiple processes may be carried out simultaneously.

[0120] The following describes each step in order.

[0121] <Solu solution preparation process> The sol solution preparation step involves mixing an isocyanate-terminated prepolymer obtained by reacting a first polyol with a polyisocyanate, a second polyol, and an organic solvent to prepare a sol solution. The sol solution preparation step in the method for producing the composite material of this disclosure is the same as the sol solution preparation step in the method for producing the urethane-based aerogel of this disclosure, and the preferred embodiments are also the same; therefore, a detailed explanation is omitted here.

[0122] In addition, in the method for producing the composite material of this disclosure, a step of preparing a prepolymer before the sol solution preparation step may be performed, similar to the method for producing the urethane-based aerogel of this disclosure.

[0123] <Solus solution filling process> The sol solution filling process is a process of filling the voids in a porous substrate with a sol solution. The sol solution filling process can be carried out, for example, by impregnating a porous substrate with a sol solution. The impregnation time should be adjusted as appropriate to allow sufficient time for the sol solution to fill the voids in the porous substrate. Vibration of the sol solution may be applied to promote the filling of the voids in the porous substrate.

[0124] <Solvent-containing gel preparation process> The solvent-containing gel preparation step is a step of preparing a solvent-containing gel by gelling a sol solution, that is, a step of obtaining a porous substrate (hereinafter also referred to as a "gel composite") in which the voids are filled with a solvent-containing gel by gelling a sol solution that has been filled into the voids of a porous substrate.

[0125] The method for gelling a sol solution filled into the voids of a porous substrate is not particularly limited, and one example is to allow the porous substrate filled with the sol solution to stand.

[0126] When the sol solution contains a catalyst, the gelation of the sol solution is promoted, allowing the sol solution packed into the voids of a porous substrate to be efficiently converted into a solvent-containing gel.

[0127] <Solvent replacement process> The solvent replacement step is a process in which the solvent contained in the solvent-containing gel is replaced with a low-boiling point solvent in order to suppress the shrinkage of the solvent-containing gel during the drying process.

[0128] The low-boiling point solvent used in the solvent substitution step in the method for producing the composite material of this disclosure is the same as the low-boiling point solvent used in the solvent substitution step in the method for producing the urethane-based aerogel of this disclosure, and therefore its explanation is omitted here. In the solvent substitution step, one low-boiling point solvent may be used alone, or two or more may be used in combination.

[0129] The solvent replacement step may be performed once or multiple times. For example, from the viewpoint of improving work efficiency, reducing costs, and reducing environmental impact, it is preferable to perform the solvent replacement step once. If the solvent replacement step is performed multiple times, the type of solvent may be changed each time.

[0130] The amount of low-boiling point solvent used in each solvent replacement step is preferably, for example, between 1 and 100 times the volume of the gel complex.

[0131] The solvent replacement method may be total replacement, partial replacement, or cyclic replacement. For example, from the viewpoint of improving workability, total replacement is preferred as the solvent replacement method.

[0132] <Drying process> The drying process involves drying the solvent-containing gel after solvent replacement. By performing the drying process, the solvent-containing gel that has filled the voids of the porous substrate after solvent replacement can be converted into a urethane-based aerogel.

[0133] The drying method and preferred embodiment of the drying step in the manufacturing method of the composite material of this disclosure are the same as the drying method and preferred embodiment of the drying step in the manufacturing method of the urethane-based aerogel of this disclosure, and therefore, a description is omitted here. [Examples]

[0134] The method for producing the urethane-based aerogel, the urethane-based aerogel, and the composite material described herein will be further explained in detail below with reference to examples. This disclosure is not limited to the following examples unless it exceeds the spirit of the disclosure.

[0135] Details of each component used in this embodiment are as follows. <Polyisocyanate> • Polyisocyanate 1 (Polymeric MDI) [Product name: Millionate MR-200, manufactured by Tosoh Corporation] <Polyol> • Polyol 1 (aliphatic diol) [Product name: tetraethylene glycol, manufactured by Tokyo Chemical Industry Co., Ltd.] • Polyol 2 (aromatic diol) [Product name: Bisphenol A, manufactured by Tokyo Chemical Industry Co., Ltd.] • Polyol 3 (aromatic triol) [Trade name: 1,1,1-tris(4-hydroxyphenyl)ethane, manufactured by Sigma-Aldrich] <Catalyst> • Catalyst 1 (Tin catalyst) [Product name: Dibutyltin dilaurate, manufactured by Tokyo Chemical Industry Co., Ltd.] • Catalyst 2 (iron catalyst) [Product name: Iron(III) acetylacetonate, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.] • Catalyst 3 (Bismuth catalyst) [Product name: TIB KAT 716 (Component: Bismuth acetylacetonate), manufactured by TIB Chemicals] <organic solvents> • Organic solvent 1 (DMF) [Product name: N,N-dimethylformamide, manufactured by Ando Parachemy Co., Ltd.]

[0136] [Aerogel manufacturing] <Example 1> (1) Synthesis of prepolymer 1 100 parts by mass of polyisocyanate 1 (polymeric MDI) and 135 parts by mass of organic solvent 1 (DMF) were charged into a flask while flowing nitrogen gas through a three-way stopcock. Next, the contents of the flask were stirred while flowing nitrogen gas into the flask, and while continuing this stirring, 35 parts by mass of polyol 1 (aliphatic diol) was added dropwise as the first polyol, taking care to control the heat of reaction. After the dropwise addition, the contents of the flask were reacted while stirring for 1 hour to obtain a solution of prepolymer 1, which is an isocyanate group-terminated prepolymer (concentration of prepolymer 1: 50% by mass).

[0137] A portion of the obtained prepolymer 1 solution was sampled, and the isocyanate content (NCO content) of prepolymer 1 was measured according to the method in accordance with JIS K 1603-1:2007, confirming that it was 20.4% by mass. Furthermore, the number-average molecular weight (Mn) of prepolymer 1 was determined as a standard styrene equivalent value by the GPC method under the following conditions, confirming that it was 1400.

[0138] -conditions- Measurement device: High-speed GPC [Model number: HLC-8320GPC, manufactured by Tosoh Corporation] Detector: Differential refractometer (RI) Column: TSKgel® SuperMultiporeHZ-N [Column size: 4.6mmφ x 15cm, manufactured by Tosoh Corporation] Column temperature: 40℃ Eluent: Tetrahydrofuran Sample solution injection volume: 15 μL Flow rate: 1.0mL / min

[0139] (2) Preparation of solvent-containing gel (Step A) To 100 parts by mass of the solution of prepolymer 1 (isocyanate-terminated prepolymer) in the flask, 20 parts by mass of polyol 2 (aromatic diol) and 346 parts by mass of organic solvent 1 (DMF) were added as the second polyol. Next, the contents of the flask were stirred, and while continuing this stirring, 0.005 parts by mass of catalyst 1 (tin catalyst) was added to the flask to form a sol solution [sol solution preparation step]. Next, the sol solution was poured into an aluminum container (diameter: 50 mm) to a height of 5 mm, and then allowed to stand to gel, thereby obtaining a 5 mm thick solvent-containing gel [solvent-containing gel preparation step].

[0140] (3) Drying of the solvent-containing gel (Step B) The obtained solvent-containing gel was immersed in tetrahydrofuran (THF). The THF in which the solvent-containing gel was immersed was repeatedly replaced while stirring, and solvent replacement was carried out for 24 hours [solvent replacement step]. Next, the solvent-containing gel after solvent replacement was impregnated in carbon dioxide at a temperature of 50°C and a pressure of 14 MPa, and supercritical drying was performed for 24 hours to obtain the aerogel of Example 1 [drying step].

[0141] <Example 2> The aerogel of Example 2 was obtained in the same manner as in Example 1, except that the carbon dioxide conditions in the "drying step" of "(3) Drying of solvent-containing gel (step B)" were changed from "temperature 50°C and pressure 14 MPa" to "temperature 70°C and pressure 14 MPa".

[0142] <Example 3> The aerogel of Example 3 was obtained in the same manner as in Example 2, except that the second polyol used in the "sol solution preparation step" of "(2) Preparation of solvent-containing gel (step A)" was changed from "polyol 2 (aromatic diol)" to "polyol 3 (aromatic triol)".

[0143] <Example 4> The aerogel of Example 4 was obtained in the same manner as in Example 1, except that the type of catalyst used in the "sol solution preparation step" of "(2) Preparation of solvent-containing gel (Step A)" was changed from "Catalyst 1 (tin catalyst)" to "Catalyst 2 (iron catalyst)".

[0144] <Example 5> The aerogel of Example 5 was obtained in the same manner as in Example 1, except that the type of catalyst used in the "sol solution preparation step" of "(2) Preparation of solvent-containing gel (Step A)" was changed from "Catalyst 1 (tin catalyst)" to "Catalyst 3 (bismuth catalyst)".

[0145] <Comparative Example 1> In a flask, while flowing nitrogen gas through a three-way stopcock, 100 parts by mass of polyisocyanate 1 (polymeric MDI), 35 parts by mass of polyol 1 (aliphatic diol), 50 parts by mass of polyol 2 (aromatic diol), and 1040 parts by mass of organic solvent 1 (DMF) were charged. Next, the contents of the flask were stirred, and while continuing this stirring, 0.001 parts by mass of catalyst 1 (tin catalyst) were added to the flask. After the addition, the contents of the flask were reacted while stirring for 1 hour to obtain a sol solution. Next, the sol solution was poured into an aluminum container (diameter: 50 mm) to a height of 5 mm, and then allowed to stand to gel, obtaining a 5 mm thick solvent-containing gel. The obtained solvent-containing gel was immersed in tetrahydrofuran. The tetrahydrofuran in which the solvent-containing gel was immersed was repeatedly replaced while stirring, and solvent replacement was carried out for 24 hours. Next, the solvent-containing gel after solvent replacement was impregnated in carbon dioxide at a temperature of 50°C and a pressure of 14 MPa, and supercritical drying was performed for 24 hours to obtain the aerogel of Comparative Example 1.

[0146] [Preparation of solvent-containing gels] <Reference example 1> A sol solution was prepared by mixing tetramethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) as the main component with 1 mole of the main component, 45 moles of methanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 25 moles of ion-exchanged water (electrical resistivity: 1 × 10¹⁰ Ω·cm or higher), and 0.01 mole of catalyst (25% by mass aqueous ammonia, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). The sol solution was then poured into an aluminum container (diameter: 50 mm) to a height of 5 mm, and allowed to stand to gel, thereby obtaining a 5 mm thick solvent-containing gel. The obtained solvent-containing gel was used as the solvent-containing gel for Reference Example 1.

[0147] [evaluation] The aerogels and their manufacturing methods obtained from Examples 1-5 and Comparative Example 1 were evaluated as follows. The results are shown in Tables 1 and 2. Furthermore, for the solvent-containing gel of Reference Example 1 obtained above, only "4. Solvent-containing gel strength" was evaluated from the following evaluation items.

[0148] 1. Specific gravity The specific gravity of the aerogel was measured. An electronic hydrometer, model MD-200S, manufactured by Alpha Mirage Co., Ltd., was used for the measurement.

[0149] 2. Contraction rate The shrinkage rate (in %) of the solvent-containing gel during the drying process was determined. The shrinkage rate of the solvent-containing gel was measured using the volume V1 (in mm³) of the solvent-containing gel measured before the drying process (specifically, after step A2 and before step B1). 3 ) and the volume V2 (unit: mm³) of the aerogel measured after the drying process (i.e., after process B2) 3 The following formula was used to calculate the value from the above. The size of the solvent-containing gel before the drying process was 50 mm in diameter and 5 mm in thickness, so V1 is 25 mm × 25 mm × 3.14 × 5 mm = 9812.5 mm 3 That is the case. Shrinkage rate of solvent-containing gel = (V1 - V2) / V1 × 100

[0150] 3. Average pore diameter and pore diameter volume distribution The average pore size (in nm) and pore size volume distribution [dVp / dlog] of the aerogel were measured. The average pore size and pore size volume distribution of the aerogel were measured using the nitrogen gas adsorption method in accordance with JIS Z 8831-2:2010 "Pore size distribution and pore characteristics of powders (solids) Part 2: Measurement method for mesopores and macropores by gas adsorption". The measurement device used was the Belsorp II mini (model number) pore distribution analyzer manufactured by Microtrac-Bel.

[0151] 4. Solvent-containing gel strength The strength (unit: kPa) of the solvent-containing gel was measured. Since a higher strength of the solvent-containing gel tends to correlate with a higher strength of the resulting aerogel, measuring the strength of the solvent-containing gel allows for indirect evaluation of the aerogel's strength. To measure the strength of the solvent-containing gel, a Shimadzu Autograph AG-X10kN (model number) was used as the measuring device, and an aerogel with a diameter of 50 mm and a thickness of 5 mm was used as the measurement sample. The measurement sample was compressed using the Autograph at a compression rate of 1 mm / min. The sample was compressed until it broke, and the maximum compressive load at that time was defined as the gel strength.

[0152] [Table 1]

[0153] [Table 2]

[0154] In Table 1, a "-" in the "Formulation of Solvent-containing Gel" column indicates that the ingredient corresponding to that column is not used. The "resin concentration" listed in Table 1 refers to the total concentration of prepolymers and polyols contained in the solvent-containing gel, and is the value calculated according to the following formula, rounded to two decimal places. The resin concentration listed in Table 1 = (amount of prepolymer + amount of polyol) / (amount of prepolymer solution + amount of polyol + amount of catalyst + amount of organic solvent) × 100

[0155] The "resin concentration" listed in Table 2 refers to the total concentration of polyisocyanates and polyols contained in the solvent-containing gel, and is the value calculated according to the following formula, rounded to two decimal places. The resin concentration listed in Table 2 = (amount of polyisocyanate + amount of polyol) / (amount of polyisocyanate + amount of polyol + amount of catalyst + amount of organic solvent) × 100

[0156] In Tables 1 and 2, "Condition 1" and "Condition 2" in the column for carbon dioxide conditions refer to "using carbon dioxide at a temperature of 50°C and a pressure of 14 MPa" and "using carbon dioxide at a temperature of 70°C and a pressure of 14 MPa," respectively.

[0157] As shown in Tables 1 and 2, it was found that Examples 1 to 5 had a smaller shrinkage rate of the solvent-containing gel during the drying process compared to Comparative Example 1. The strength of the solvent-containing gels in Examples 1 to 5 was found to be higher than that of the solvent-containing gel in Comparative Example 1. Furthermore, although not shown in the table, the strength of the solvent-containing gel in Reference Example 1 was 50 kPa, indicating that the strength of the solvent-containing gels in Examples 1 to 5 is significantly higher than that of silica-based aerogels. These results suggest that Examples 1 to 5 represent novel urethane-based aerogels with high gel strength.

[0158] [Manufacturing of composite materials] <Example C1> (1) Sol solution preparation process A sol solution was prepared by the method described in Example 1.

[0159] (2) Sol solution filling process Porous substrate [Product name: Basotect (registered trademark) TG, melamine resin foam, density: 0.100 g / cm³] 3 The porous substrate (manufactured by BASF) was cut and placed in a separable flask. Next, the sol solution prepared above was added to the separable flask containing the cut porous substrate until the porous substrate was completely immersed.

[0160] (3) Solvent-containing gel preparation process A porous substrate immersed in a sol solution was left to stand under normal pressure for 3 hours. During this time, the sol solution gelled, yielding a porous substrate filled with solvent-containing gel.

[0161] (4) Solvent replacement step After immersing a porous substrate filled with a solvent-containing gel in THF, the THF was repeatedly replaced while stirring, and solvent replacement was carried out for 24 hours.

[0162] (5) Drying process The porous substrate, after solvent replacement, was impregnated in carbon dioxide at a temperature of 50°C and a pressure of 14 MPa, and supercritical drying was performed for 72 hours to obtain the composite material of Example C1.

[0163] <Example C2> In the "(2) Sol Solution Filling Process," the porous substrate is changed from "melamine resin foam" to "olefin resin foam [product name: FOLEC(registered trademark) OPN, density: 0.100 g / cm³]." 3 The composite material of Example C2 was obtained in the same manner as in Example C1, except that the material was changed to [manufactured by Inoac Corporation].

[0164] <Example C3> The composite material of Example C3 was obtained in the same manner as in Example 1, except that in the "(1) Sol solution preparation step," the sol solution was prepared by the method described in Example 3.

[0165] <Comparative Example C1> In the "(1) Sol solution preparation step," the sol solution was prepared by the method described in Comparative Example 1, except that the composite material of Comparative Example C1 was obtained in the same manner as in Example 1.

[0166] <Comparative Example C2> A composite material of Comparative Example C2 was obtained in the same manner as in Example 1, except that the sol solution was prepared by the following method in the "(1) Sol Solution Preparation Step". "Using tetramethoxysilane [manufactured by Shin-Etsu Chemical Co., Ltd.] as the main component, a sol solution was prepared by mixing 45 moles of methanol [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.], 25 moles of ion-exchanged water [electrical resistivity: 1 × 10¹⁰ Ω·cm or higher], and 0.01 moles of catalyst [25% by mass aqueous ammonia, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.] with 1 mole of the main component."

[0167] [evaluation] The composite materials obtained from Examples C1 to C3 and Comparative Example C1 were evaluated as follows. The results are shown in Table 3. Furthermore, for the composite material of Comparative Example C2 obtained above, only "4. Powder shedding properties" was evaluated from the following evaluation items.

[0168] 1. Density Density of composite materials (unit: g / cm³) 3 The density of the composite material was measured according to the method specified in JIS K 7222:2005 "Foamed plastics and rubber - Method for determining apparent density".

[0169] 2.Average pore diameter The average pore size (in nm) of the urethane-based aerogel in the composite material was measured. The average pore size of the urethane-based aerogel in the composite material was measured by the nitrogen gas adsorption method in accordance with JIS Z 8831-2:2010 "Pore size distribution and pore characteristics of powders (solids) Part 2: Measurement method of mesopores and macropores by gas adsorption". The measurement device used was the Belsorp II mini (model number), a pore distribution analyzer manufactured by Microtrac-Bel.

[0170] 3. Thermal conductivity The thermal conductivity of composite materials and porous substrates was measured. Both the thermal conductivity of composite materials and porous substrates were measured using methods compliant with JIS A 1412-2:1999, "Method for measuring thermal resistance and thermal conductivity of thermal insulating materials." The measuring device used was the HC-074 F200 (model number), a thermal conductivity measuring device manufactured by Eiko Seiki Co., Ltd.

[0171] 4. Powder shedding properties The powder shedding properties of the composite material were evaluated. A compression test was performed on the composite material in accordance with JIS K 6254:2016 "Vulcanized rubber and thermoplastic rubber - Method for determining stress-strain properties," involving 1000 cycles of 25% compression. The mass loss rate (in %) after the compression test was determined. The mass loss rate after the compression test was calculated using the following formula, based on the mass W1 (in g) of the composite material measured before the compression test and the mass W2 (in g) of the composite material measured after the compression test. Furthermore, the calculated value was evaluated according to the following evaluation criteria. Furthermore, a smaller mass loss rate after the compression test indicates that powder is less likely to fall off, while a larger rate indicates that powder is more likely to fall off. Mass reduction rate after compression test = (W1 - W2) / W1 × 100

[0172] -Evaluation Criteria- A: The mass loss rate was less than 5%. B: The mass reduction rate was between 5% and less than 10%. C: The mass reduction rate was 10% or more.

[0173] [Table 3]

[0174] As shown in Table 3, Examples C1 to C3 were found to be composite materials with lower thermal conductivity compared to Comparative Example C1. Although not shown in the table, the evaluation result for the powder shedding properties of Comparative Example C2 was B (mass loss rate: 5%), indicating that Example C3, a composite material containing urethane-based aerogel, is less prone to powder shedding compared to Comparative Example C2, a composite material containing silica-based aerogel. Furthermore, since all composite materials of Examples C1 to C3 contain the urethane-based aerogel of the examples, they can be said to have higher strength compared to composite materials containing general silica-based aerogel.

Claims

1. Step A involves mixing an isocyanate-terminated prepolymer obtained by reacting a first polyol with a polyisocyanate, a second polyol, and an organic solvent to obtain a solvent-containing gel. Step B involves drying the solvent-containing gel, A method for producing urethane-based aerogels, including [the specified ingredient].

2. A urethane-based aerogel having a specific gravity of 0.200 or less, an average pore size of 100 nm or less, and made using two or more polyols as raw materials.

3. A porous substrate having voids that communicate with each other, The urethane-based aerogel according to claim 2 is filled in the voids of the porous substrate, A composite material that includes [this material].

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