Gas adsorption filter

Abstract

To provide a geopolymer foam that can be used as a gas adsorption filter and has high gas adsorptivity.SOLUTION: A geopolymer foam for a gas adsorption filter contains a product from the reaction between aluminosilicate and alkali metal silicate, and aggregate, and has an open-cell structure made of multiple cells formed by foaming. The foam has a density of 100-500 kg / m3. When the foam is subjected to an air flow of 0.5 mm / s, the flow resistance is 0.02-3 Pa s / cm2.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to geopolymers foam.

Background Art

[0002] Geopolymer is an inorganic polymer produced by reacting aluminosilicate with alkali metal silicate. Geopolymer has attracted attention as an environmentally friendly material because the amount of carbon dioxide emitted from the production of raw materials to the production of products is small.

[0003] Geopolymer is an amorphous inorganic polymer, and its short-range order is similar to that of zeolite. Specifically, geopolymer has a tetrahedral structure formed from SiO4 and AlO4, and has exchangeable cations that compensate for the negative charge of AlO4 in the network formed by the tetrahedral structure. As a result, geopolymer has the property of adsorbing acidic gases such as sulfur oxides and nitrogen oxides, and harmful gases such as volatile organic hydrocarbons, without adding special adsorbing materials, etc., and thus is expected to be used for gas adsorption filter applications.

[0004] Also, when reacting aluminosilicate with alkali metal silicate, by adding a foaming agent or the like to the composition for forming geopolymer and reacting while foaming the composition, it is known that a geopolymer foam having a closed cell structure with a large number of bubbles can be obtained.

[0005] As a technology related to geopolymer foam, for example, Patent Document 1 describes a geopolymer composite having a particulate ceramic filler and a geopolymer binder constituting at least 2% by mass of the material in a composite article formed from a composite material. Further, this geopolymer composite is said to be usable for diesel particulate filters, catalytic converters, NOx adsorbents, catalyst carriers, honeycomb monoliths, etc.

[0006] In addition, Patent Document 2 describes an inorganic foam composition comprising 100 parts by weight of a main material composed of 20 to 65 parts by weight of an aqueous alkali metal silicate solution, 15 to 60 parts by weight of an inorganic solid component, and 0 to 65 parts by weight of a filler, 0.001 to 5 parts by weight of an anionic surfactant, and 2 to 30 parts by weight of a foaming agent. Since the inorganic foam (dipolymer foam) obtained from this inorganic foam composition has closed cells, it is said to be useful for sound absorbing materials, filters, and the like.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, in Patent Documents 1 and 2, there has been no sufficient study on using the dipolymer foam as a gas adsorption filter, the adsorption performance for gases such as acidic gases and toxic gases is insufficient, and it has been difficult to exhibit sufficient performance as a gas adsorption filter.

[0009] In view of the above circumstances, the present invention has been made, and an object thereof is to provide a dipolymer foam having high gas adsorption properties that can be used as a gas adsorption filter.

Means for Solving the Problems

[0010] In order to solve the above problems, the dipolymer foam of the present invention is characterized by the following. <1> It contains a reaction product of an aluminosilicate and an alkali metal silicate, and an aggregate, A dipolymer foam for a gas adsorption filter having a closed cell structure formed by a large number of cells formed by foaming, The density of the foam is 100 kg / m 3 or more and 500 kg / m 3 or less, and the flow resistance when air is flowing at 0.5 mm / s is 0.02 Pa·s / cm 2 or more and 3 Pa·s / cm 2 or less. <2>The average volume of the bubbles in the geopolimer foam is 0.5 mm 3 or more and 10 mm 3 or less, and the volume ratio of bubbles with a volume of 2 mm 3 or more is 20% or more and 90% or less. <3>The aggregate contains mica, and the average particle size of the mica is 80 μm or more and 200 μm or less.

Advantages of the Invention

[0011] The geopolimer foam of the present invention has high gas adsorption properties and can be used as a gas adsorption filter.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, an embodiment of the geopolimer foam of the present invention will be described.

[0013] The geopolimer foam of the present invention can be suitably used for gas adsorption filter applications. Gas adsorption filters can adsorb, for example, inorganic gases such as NOx (such as NO2), SOx (such as SO2), and volatile organic compounds such as toluene, xylene, and ethyl acetate.

[0014] The geopolimer foam of the present invention contains a reaction product of aluminosilicate and alkali metal silicate, and an aggregate.

[0015] (Aluminosilicate) Aluminosilicate (xM2O·yAl2O3·zSiO2·nH2O, where M is an alkali metal) reacts with an alkali metal silicate, which will be described later, in an aqueous solution (slurry). As a result, aluminum ions elute into the aqueous solution, and silicic acid monomers (silicic acid, Si(OH)4) are generated. The silicic acid monomers and cations thus generated polycondense to form a polymer network (dipolymer) with a tetrahedral structure of SiO4·AlO4.

[0016] The content of SiO2 (silicon dioxide) in the aluminosilicate is preferably 20% by mass or more and 80% by mass or less, and more preferably 30% by mass to 70% by mass or less. When the content of SiO2 is within this range, the produced dipolymer foam is likely to form a good continuous cell structure with a large number of cells, and the gas adsorption property can be stably enhanced. The content of SiO2 and the content of Al2O3, which will be described later, in the aluminosilicate can be determined by quantifying each element using a fluorescent X-ray analyzer (for example, EA6000V manufactured by Hitachi High-Technologies Corporation).

[0017] Also, the crystallinity of the aluminosilicate is preferably 20% or less, and more preferably 10% or less. When the crystallinity is within this range, when reacting with an alkali metal silicate in an aqueous solution, the alkali component derived from the alkali metal silicate makes it easier for aluminum ions to elute from the aluminosilicate source, and it also makes it easier for silicic acid monomers to be generated, and polycondensation proceeds stably. Therefore, it becomes easier to obtain a dipolymer foam having a good cell structure.

[0018] The crystallinity can be determined by X-ray diffraction. For example, using an X-ray analyzer having a two-dimensional detector (e.g., Rint2550 manufactured by Rigaku Corporation, etc.), setting the 2θ range to 10 to 40° at room temperature, and performing X-ray diffraction measurement on the aluminosilicate powder, the crystallinity can be measured. Note that the crystallinity can be determined by performing profile fitting on the diffraction pattern measured by X-ray diffraction and calculating the ratio of the peak area of the crystalline component to the total peak area ([peak area of the crystalline component] + [halo pattern area of the amorphous component]) from the obtained X-ray diffraction.

[0019] Suitable examples of aluminosilicates include industrial wastes such as fly ash, red mud, silica fume, and sewage sludge incineration ash; natural aluminosilicate minerals and their calcined products (e.g., metakaolin), and volcanic ash, etc. These substances can be commercially available ones, and one or a combination of two or more of these can be used. Further, the aluminosilicate is preferably in powder form. By appropriately pulverizing and classifying these substances and using a specific fraction, the aluminosilicate having a desired composition can be adjusted. Among them, the aluminosilicate is preferably an aluminosilicate mainly composed of metakaolin (chemical formula: Al2O3·2SiO2). Specifically, the proportion of metakaolin in the aluminosilicate is preferably 50% by mass or more, more preferably 60% by mass or more, further preferably 80% by mass or more, and particularly preferably 90% by mass or more. When the proportion of metakaolin in the aluminosilicate is within the above range, a good closed-cell structure due to a large number of bubbles is easily formed, and a diopolymer foam excellent in gas adsorption can be stably obtained.

[0020] In addition, these aluminosilicates preferably have an average particle size of 0.1 μm or more and 50 μm or less, and more preferably 0.3 μm or more and 30 μm or less. When the average particle size is within this range, the produced diopolymer foam forms a good closed-cell structure and is excellent in gas adsorption.

[0021] The average particle diameters of the aluminosilicate and the aggregate described later can be measured by the laser diffraction scattering method. Specifically, based on the volume-based particle size distribution measured by the laser diffraction scattering method, assuming the particle shape as a sphere, the volume-based particle size distribution is converted into a number-based particle size distribution to obtain the number-based particle size distribution. Then, the arithmetic mean particle diameter based on this number-based particle size distribution is obtained by arithmetically averaging the particle diameters, and this value is taken as the average particle diameter in the present invention. Note that the above average particle diameter means the diameter of a virtual sphere having the same volume as the particle.

[0022] The content of Al2O3 in the aluminosilicate is preferably 20% by mass or more, more preferably 30% by mass or more, based on the total mass of the aluminosilicate. In this case, it is easier to enhance the gas adsorption property of the geopolimer foam. Also, the content of Al2O3 in the aluminosilicate is preferably 80% by mass or less, more preferably 70% by mass or less, based on the total mass of the aluminosilicate. When the content of Al2O3 is within this range, it is easier to increase the strength of the geopolimer foam.

[0023] (Alkali metal silicate) When the alkali metal silicate is dissolved in water, a highly alkaline aqueous solution is formed. By reacting this aqueous solution with the aluminosilicate, cations such as Al can be eluted from the aluminosilicate, and silicic acid monomers can be generated. Also, the alkali metal silicate serves as a source of silicic acid monomers that form geopolymers by polycondensation.

[0024] Examples of the alkali metal silicate include one or more of potassium silicate, sodium silicate (water glass), lithium silicate, etc. Further, the alkali metal silicate can be preferably used, for example, as an aqueous solution (alkali metal silicate aqueous solution) in which these alkali metal silicates are dissolved in water. Among them, the alkali metal silicate is preferably potassium silicate. In addition, in order to adjust the hydrogen ion concentration of the aqueous solution to obtain an aqueous solution showing a desired alkalinity, alkali metal hydroxides such as potassium hydroxide and sodium hydroxide can be added to the alkali metal silicate aqueous solution.

[0025] In the alkali metal silicate aqueous solution, the molar ratio of silicon to the alkali metal is preferably 0.1 or more and 5 or less, and more preferably 0.3 or more and 3 or less. By setting the molar ratio within the above range, the strength of the geopolimer foam can be further increased.

[0026] Further, for example, the concentration of the alkali metal silicate in the alkali metal silicate aqueous solution is preferably 20% by mass or more and 80% by mass or less, preferably 25% by mass or more and 70% by mass or less, and more preferably 30% by mass or more and 60% by mass or less. When the concentration of the alkali metal silicate is within this range, the fluidity of the slurry obtained by mixing the aluminosilicate and the alkali metal silicate aqueous solution is increased, the foam molding property of the foaming composition can be improved, and a geopolimer foam excellent in strength with a good polymer network formed by a tetrahedral structure can be stably obtained. As a result, a geopolimer foam having a good closed cell structure and excellent gas adsorption properties can be stably obtained.

[0027] (Aggregate) The aggregate can exemplify one or more of mica, wollastonite, chalk, talc, molokite, cordierite, basalt, feldspar, zircon, graphite, and borax. The aggregate is preferably a powder, and the average particle size of the aggregate is preferably 50 μm or more and 300 μm or less. Among them, the aggregate is preferably an aggregate containing mica. The proportion of mica in the aggregate is preferably 50% by mass or more, more preferably 60% by mass or more, further preferably 80% by mass or more, and particularly preferably 90% by mass or more. Mica is a silicate mineral generally called muscovite, and is represented by the chemical composition of KAl2(AlSi3O 10 )(F,OH)2. In the present invention, the term "mica" includes sheet silicate (phyllosilicate) minerals that are physically and chemically similar.

[0028] The content of the aggregate in the geopololymer foam is preferably 5% by mass or more and 40% by mass or less, more preferably 10% by mass or more and 30% by mass or less, based on 100% by mass in total of aluminosilicate, alkali metal silicate, and the aggregate. When the content of the aggregate is within this range, a good polymer matrix structure is formed, and a geopololymer foam with improved strength due to the aggregate can be stably obtained.

[0029] Furthermore, when the aggregate contains mica, the average particle size of mica is preferably 80 μm or more and 200 μm. When the average particle size of mica contained in the aggregate is within this range, a good closed-cell structure is formed in the produced geopololymer foam, and an excessive increase in the viscosity of the foaming composition is suppressed, thereby suppressing the refinement of bubbles and increasing the ratio of bubbles having a volume equal to or more than a specific value in the foam. Therefore, a geopololymer foam excellent in gas adsorption property is obtained.

[0030] (Other materials) The geopololymer foam may contain other materials such as reactive materials and reinforcing fibers, if necessary.

[0031] Examples of the reactive material include one or more of clays such as bentonite, sepiolite, minogel, and attapulgite clay, cement binders, calcium aluminate cement, and organic polymer binders (such as cellulose binders). By adding the reactive material, the reaction (curing) time of the foaming composition can be adjusted.

[0032] The reinforcing fiber can be added for the purpose of improving the strength of the geopolimer foam and preventing cracks. Examples of the reinforcing fiber include vinylon fiber, polypropylene fiber, aramid fiber, acrylic fiber, rayon fiber, carbon fiber, glass fiber, potassium titanate whisker, alumina fiber, steel wool, slag wool, and the like. By adding the reinforcing fiber, the strength of the geopolimer foam can be increased.

[0033] The addition amount of other materials is not particularly limited as long as the intended object of the present invention can be achieved, but it is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, based on 100 parts by mass in total of aluminosilicate, alkali metal silicate, and aggregate.

[0034] (Geopolimer foam) The apparent density of the geopolimer foam of the present invention is 100 kg / m 3 or more and 500 kg / m 3 or less. If the apparent density of the geopolimer foam is too low, the flow resistance when permeating the fluid through the geopolimer foam becomes excessively low, making it difficult to enhance the adsorption performance. On the other hand, if the apparent density of the geopolimer foam is too high, the flow resistance when permeating the fluid through the geopolimer foam becomes excessively high, making it difficult to enhance the adsorption performance.

[0035] The flow resistance of the geopolimer foam of the present invention when flowing air at 0.5 mm / s is 0.02 Pa·s / cm 2 or more and 3 Pa·s / cm 2The following applies. When the flow resistance when air is flowing is within this range, a geopolimer foam excellent in gas adsorption performance is obtained. If the flow resistance of the geopolimer foam is too low when air at 0.5 mm / s is flowing, when the geopolimer foam is used as a gas adsorption filter, the fluid such as harmful gas passes through without colliding with the foam, and it becomes difficult to adsorb toxic gas etc. onto the geopolimer foam. From the above viewpoints, the flow resistance is 0.03 Pa·s / cm 2 or more, more preferably 0.1 Pa·s / cm 2 or more. On the other hand, when the flow resistance when air at 5 mm / s is flowing is too high, the resistance when allowing the fluid to permeate through the geopolimer foam increases, and it becomes difficult to efficiently adsorb harmful gas etc. From the above viewpoints, the flow resistance is more preferably 2 Pa·s / cm 2 or less. The method for measuring the flow resistance will be described in the examples below.

[0036] Also, in the geopolimer foam, the average volume of the bubbles in the foam is 0.5 mm 3 or more and 10 mm 3 or less, and the volume ratio of the bubbles with a volume of 2 mm 3 or more is preferably 20% or more and 90% or less. When the average volume of the bubbles and the volume ratio of the bubbles with a volume of 2 mm 3 or more are within this range, the flow resistance when air at 0.5 mm / s is flowing can be stably 0.02 Pa·s / cm 2 or more and 3 Pa·s / cm 2 or less, and a geopolimer foam having high gas adsorbability can be stably obtained.

[0037] From the viewpoint of further improving the strength of the geopolimer foam while forming a desired open-cell structure in the geopolimer foam, the average volume of the bubbles in the foam is more preferably 0.6 mm 3 or more and 5 mm 3 or less, and even more preferably 0.6 mm 3 or more and 3 mm 3 or less. Also, from the viewpoint of enhancing the gas adsorption performance of the geopolimer foam, the volume of 2 mm3 More preferably, the volume ratio of the above-mentioned bubbles is 25% or more and 85% or less, and even more preferably 30% or more and 80% or less.

[0038] Next, an embodiment of the method for producing the geopololymer foam of the present invention will be described. In the method for producing the geopololymer foam of the present invention, the description of the contents common to the above-described geopololymer foam of the present invention (such as aluminosilicate, alkali metal silicate, aggregate, etc.) can be appropriately referred to.

[0039] The geopololymer foam is preferably produced as follows.

[0040] A method for producing a geopololymer foam having a large number of bubbles communicating with the outside by foaming a foaming composition containing aluminosilicate, alkali metal silicate, aggregate, water, foaming agent and bubble communication agent, forming a large number of bubbles in the reaction product of aluminosilicate and alkali metal silicate, and communicating between the bubbles, The method for producing a geopololymer foam, wherein the aggregate contains mica and the average particle size of the mica is 80 μm or more and 200 μm or less.

[0041] Further, the method for producing a geopololymer foam preferably includes the following steps.

[0042] A first step of mixing a mixture A containing aluminosilicate, aggregate and bubble communication agent with an aqueous alkali silicate solution to obtain a slurry; A second step of adding a foaming agent to the slurry to obtain a foaming composition; and A third step of foaming the foaming composition to form a large number of bubbles in the reaction product of aluminosilicate and alkali silicate and communicate between the bubbles to obtain a geopololymer foam having a large number of bubbles communicating with the outside.

[0043] Hereinafter, each step will be described.

[0044] In the first step, a mixture A containing aluminosilicate, aggregate, and a bubble communication agent is mixed with an aqueous alkali silicate solution to obtain a slurry.

[0045] The mixing method of the materials in the first step is not particularly limited. Usually, at room temperature (25 °C), a known or conventional mixer etc. (for example, a mortar mixer, a tilting mixer, a truck mixer, a twin-shaft mixer, an omnimixer, a pan mixer, a planetary mixer, an Ehrlich mixer, etc.) can be used for mixing.

[0046] The order of charging each material into a mixer etc. is not particularly limited. The amount of water can be appropriately adjusted in consideration of the viscosity of the slurry or the foaming composition, the compressive strength of the obtained molded product, etc.

[0047] When mixing mixture A and an aqueous alkali silicate solution to form a slurry, it is preferably to add generally 30 parts by mass or more and 300 parts by mass or less of the aqueous alkali silicate solution, and preferably 50 parts by mass or more and 200 parts by mass or less, based on 100 parts by mass of mixture A. By setting the above range, while uniformly dispersing each component in the foaming composition, the strength of the obtained geopolimer foam can be increased. Also, from the same viewpoint, the amount of water in the foaming composition is preferably 20% by mass or more and 50% by mass or less, and more preferably 25% by mass or more and 45% by mass or less, based on 100% by mass of the foaming composition in the second step. Water may be added independently, or may be added as a solvent in the case of using water glass as the alkali metal silicate.

[0048] The viscosity of the slurry obtained by mixing mixture A and an aqueous alkali silicate solution, measured by the method described later, is preferably 1 Pa·s or more and 5 Pa·s or less, and more preferably 2 Pa·s or more and 4 Pa·s or less. By using an aggregate containing mica having the above average particle size and setting the slurry viscosity within the above range to adjust the viscosity relatively low, the ratio of bubbles having a volume of a specific value or more in the foam can be stably increased.

[0049] In the first step, the molar ratio Si / Al of Si to Al in the slurry is preferably 0.1 or more and 10 or less, more preferably 0.5 or more and 5 or less, and even more preferably 1 or more and 3 or less. When the molar ratio of Si / Al in the mixture is within this range, exchangeable cations can be appropriately present in the produced geopolimer foam, a good closed-cell structure can be formed, and a geopolimer foam with excellent gas adsorption performance can be stably obtained.

[0050] As the cell communication agent used in the first step, for example, microorganisms such as yeast and algae, proteins, surfactants, etc. can be used. Among them, the cell communication agent is preferably yeast (such as dry yeast). The addition amount of yeast is preferably 0.1 part by mass or more and 2 parts by mass or less, and more preferably 0.2 part by mass or more and 1 part by mass or less with respect to 100 parts by mass of the foaming composition adjusted in the second step. When the addition amount of yeast is within this range, a good closed-cell structure can be formed in the geopolimer foam, and a geopolimer foam having the desired flow resistance can be stably obtained.

[0051] In the second step, a foaming agent is added to the slurry obtained in the first step to obtain a foaming composition.

[0052] Examples of the foaming agent include hydrogen peroxide, sodium peroxide, potassium peroxide, sodium perborate, non-ferrous metal powder, etc. Examples of the non-ferrous metal powder include aluminum powder. Among these, it is preferable to use hydrogen peroxide solution and / or non-ferrous metal powder as the foaming agent, and it is more preferable to use hydrogen peroxide. Further, when hydrogen peroxide is used as the foaming agent, it is preferably used as hydrogen peroxide solution. In this case, from the viewpoint of stably foaming the foaming composition and easily obtaining a geopolimer foam having a good closed-cell structure, the concentration of hydrogen peroxide in the hydrogen peroxide solution is preferably 10% by mass or more and 50% by mass or less, and more preferably 20% by mass or more and 40% by mass or less.

[0053] The addition amount of the foaming agent is not particularly limited. For example, in the case of hydrogen peroxide, it is preferably 0.1% by mass or more and 5% by mass or less, more preferably 0.2% by mass or more and 3% by mass or less, and even more preferably 0.2% by mass or more and 2% by mass or less with respect to 100% by mass of the foamable composition. Thereby, the foamable composition foams sufficiently, and a diopolymer foam having an apparent density of 100 kg / m 3 or more and 500 kg / m 3 or less can be stably obtained.

[0054] In the third step, the foamable composition is foamed to form a large number of bubbles in the reaction product of aluminosilicate and alkali silicate, and the bubbles are made to communicate with each other. Thereby, a diopolymer foam having a large number of bubbles communicating with the outside is obtained.

[0055] In the third step, by adopting various molding methods, the foamable composition obtained in the second step can be molded into a desired shape suitable for a gas adsorption filter. As the molding method, there are a casting method in which the foamable composition is poured into a mold for molding, a dehydration molding method in which the foamable composition is dehydrated and molded by pressing the foamable composition or sucking the moisture of the foamable composition in the mold, and an extrusion molding method in which the foamable composition is extruded from a die provided on the downstream side of an extruder using an extruder and shaped while foaming the foamable composition, and the like can be adopted.

[0056] The conditions for foaming the foamable composition are appropriately set according to the physical properties of the desired diopolymer foam. For example, when the foamable composition is foamed by the casting method, the diopolymer foam can be obtained by reacting and foaming the foamable composition in a mold under the conditions of a temperature of 20 to 100°C and a holding time of 30 minutes to 24 hours.

[0057] As an example, when the casting method is adopted, in the third step, the bubbles formed by the foaming of the foamable composition grow and become larger during the period from about 30 minutes to 1 hour after the addition of the foaming agent. Also, while the bubbles are growing, the bubble communication agent forms communication holes that connect the bubbles by communicating the bubble walls between adjacent bubbles. The formation of the communication holes allows the bubbles inside the foam to communicate with the outside of the foam, forming an open-cell structure. Note that the geopolimer foam usually has mesopores derived from the geopolimer structure, and such mesopores are distinguishable from the numerous bubbles formed by the foaming agent.

[0058] In the method for producing a geopolimer foam according to the present invention, unlike physical foaming that forms bubbles by stirring or the like, since the bubbles are gradually grown and foamed by the addition of a foaming agent, it is difficult for the bubbles to be refined, and a foam having a relatively uniform cell structure with little variation in cell diameter can be obtained.

[0059] The geopolimer foam thus obtained contains a reaction product of an aluminosilicate and an alkali metal silicate and an aggregate, and has an open-cell structure formed by numerous bubbles formed by foaming. Also, the density of the foam is 100 to 500 kg / m 3 and the flow resistance when air is flowed at 0.5 mm / s is 0.2 to 3 Pa·s / cm 2 Therefore, the geopolimer foam has excellent gas adsorption properties and can be suitably used for gas adsorption filter applications.

[0060] The geopolimer foam and its production method of the present invention are not limited to the above embodiments.

Examples

[0061] Hereinafter, the geopolimer foam and its production method of the present invention will be described together with examples, but the geopolimer foam of the present invention is not limited to the following examples at all.

[0062] (Raw materials for geopolymer foam formation) Using the following raw materials, a geopolymer foam was produced. Aluminosilicate: Metakaolin (manufactured by Imerys: Argical M1200S, crystallinity 0%) Alkali metal silicate: Potassium silicate (manufactured by Nippon Chemical Industry Co., Ltd.: 2K potassium silicate) Aggregate: Mica (manufactured by Seishin Enterprise Co., Ltd.: CS-35, C100M, C60M) Bubble communication agent: Yeast (manufactured by Allinson: Dry yeast) Bubble nucleating agent: Talc (manufactured by Matsumura Sangyo Co., Ltd.: Hi-filler5000PJS) Foaming agent: Hydrogen peroxide solution (manufactured by Fujifilm Wako Pure Chemical Corporation: Hydrogen peroxide concentration 30% by mass) Potassium hydroxide (manufactured by Fujifilm Wako Pure Chemical Corporation: Special grade)

[0063] (Method for manufacturing geopolymer foam) First, aluminosilicate (metakaolin), aggregate (mica), and bubble communication agent (yeast) were mixed at the ratios shown in Table 1 to form mixture A. Also, potassium silicate, potassium hydroxide, and distilled water as needed were mixed to form an aqueous alkali metal silicate solution (concentration of alkali metal silicate: 36.5% by weight, molar ratio of silicic acid to potassium: 0.63).

[0064] Next, mixture A and the aqueous alkali metal silicate solution were mixed at the ratios shown in Table 1 and stirred at a stirring speed of 60 rpm to form a slurry with Si / Al = 2 and a viscosity of about 3 Pa·s.

[0065] Next, a foaming agent (hydrogen peroxide solution) was added to the slurry at the ratio shown in Table 1, and using a stirring paddle, it was stirred at a stirring speed of 60 rpm for 1 minute to form a foamable composition.

[0066] Thereafter, a foaming composition was injected into a mold (molding die) having a molding space with a diameter of 90 mm and a height of 60 mm, the mold was sealed, and the mold was held at a temperature of 60 °C for 1 hour to react and foam the foaming composition. At this time, the pressure inside the mold was atmospheric pressure. In this way, a geopolimer foam was formed. Thereafter, the mold was opened, and the formed geopolimer foam was taken out. Further, the taken-out geopolimer foam was dried by holding it at 60 °C for about 1 day.

[0067] (Measurement method) The average particle diameters of the aluminosilicate and the aggregate (mica) were measured using a HORIBA Laser Scattering Particle Size Distribution Partica LA-960 in accordance with JIS Z 8825:2013. Specifically, the volume-based particle size distribution of the measurement target was measured by the laser diffraction scattering method to obtain the number-based particle size distribution, and the arithmetic mean particle diameter based on the number-based particle size distribution was calculated by arithmetic averaging the particle diameters, and this value was adopted as the average particle diameter.

[0068] The viscosity of the slurry was measured using an ATAGO VISCO manufactured by ATAGO. Specifically, 10 mL of the slurry was placed in a 15 mL beaker, and the viscosity of the slurry when stirred at 60 rpm using an A3 spindle was measured.

[0069] The apparent density of the geopolimer foam was calculated by measuring the apparent volume and weight of a sample obtained by removing the skin portion (the portion molded adjacent to the mold) of the foam, and performing unit conversion by dividing the weight by the apparent volume.

[0070] The average volume of the bubbles in the geopolimer foam was measured as follows. First, an observation sample was cut out from near the center of the geopolimer foam. Next, the three-dimensional shape of the sample was measured using a Nikon X-ray CT three-dimensional measuring machine MCT225 to obtain 3D data on the bubble structure of the sample. Then, the 3D data was analyzed using VG-StudioMax manufactured by Volume Graphics to calculate the average volume of the bubbles in the geopolimer foam and the volume distribution of the bubbles. In the analysis, the influence of the through-holes was excluded and the volume of the bubbles was measured. Specifically, as an analysis condition, for a randomly selected 1 cm × 1 cm × 1 cm region, the merge threshold was set to 5%, and the through-holes with a volume less than 0.1 mm 3 were excluded from the measurement target, and then the volume distribution of the bubbles in the region was measured and the average volume of the bubbles was calculated. Also, from the obtained volume distribution of the bubbles, the volume ratio of the bubbles with a volume of 2 mm 3 or more was calculated.

[0071] The flow resistance of the geopolimer foam when air was flowing at 0.5 mm / s was measured as follows based on ISO 9053 (Method A) using a flow resistance measurement system (AirReSys) manufactured by Nippon Acoustic Engineering Co., Ltd. as the measuring device.

[0072] First, a cylindrical measurement sample with a diameter of 90 mm and a height of 40 mm without a skin portion on the upper and lower surfaces (bottom surface) in the column axis direction was prepared. Next, the measurement sample was placed in the sample holder (inner diameter 90 mm) of the measuring device so that the side surface of the cylindrical measurement sample (the surface excluding the bottom surface of the cylindrical measurement sample) faced the inner surface of the sample holder, and the resistance value when air was flowing at 0.5 mm / s was measured. The measured resistance value was divided by the thickness (length in the height direction) of the measurement sample used in the measurement to calculate the flow resistance (flow resistance per unit length) when air was flowing at 0.5 mm / s.

[0073] The gas adsorption performance of the geopolimer foam was carried out as follows using a "Catalyst Analyzer BEL-CAT (II)" manufactured by MicrotracBEL Corp. as the measuring device.

[0074] First, a cylindrical measurement sample with a diameter of 25 mm and a thickness of 10 mm without a skin portion was prepared. Next, a gas for measuring adsorption performance (helium gas containing 0.5 mass% nitrogen dioxide) was introduced into the column of the measuring device, and the flow rate of the gas for measuring adsorption performance in the column was adjusted to 500 ml / min. Next, the measurement sample was placed in the column of the measuring device (inner diameter 25 mm) so that the side surface of the cylindrical measurement sample faced the inner surface of the column, and the gas adsorption performance was measured until 60 minutes elapsed after the measurement sample was placed. Specifically, by the "electron ionization EI method (Electron Ionization)", the gas passing through the measurement sample was ionized and detected by a Faraday cup and a secondary electron multiplier tube. The adsorption amount of nitrogen dioxide was measured from the change in the ion current value of mass-to-charge ratio m / z = 30 over time, and the adsorption amount of nitrogen dioxide per 1 g of the diopolymer foam (mmol / g) was calculated. The measurement was performed at a temperature of 23°C, a relative humidity of 50%, and under 1 atm.

[0075] The adsorption efficiency after 10 minutes, 30 minutes, and 60 minutes elapsed after the measurement sample was placed was evaluated.

[0076] In addition, when the adsorption amount after 10 minutes elapsed after the measurement sample was placed is 0.6 mmol / g or more, when the diopolymer foam is placed in an environment where a specific gas exists, the adsorption performance is exhibited early, which is suitable for use as a gas adsorption filter.

[0077] Also, when the adsorption amount after 60 minutes elapsed after the measurement sample was placed is 2.0 mmol / g or more, when the diopolymer foam is placed in an environment where a specific gas exists, the specific gas can be efficiently adsorbed, which is suitable for use as a gas adsorption filter.

[0078] The compressive strength (maximum stress) of the geopolimer foam was measured as follows using "Autograph AG-500B" manufactured by Shimadzu Corporation as the measuring device. First, a cylindrical measurement sample with a diameter of 90 mm and a height of 50 mm without a skin portion on the upper and lower surfaces (bottom surface) in the column axis direction was placed in the measuring device, and a compressive load was applied to the measurement sample in the direction coinciding with the height direction of the measurement sample. The compression speed at this time was set to 1 mm / min. A compression test was conducted until the displacement of the measurement sample reached 4%, and the maximum stress (maximum point stress) in this measurement was obtained, and this value was taken as the compressive strength.

[0079] Since it becomes a geopolimer foam excellent in strength, the compressive strength is preferably 0.2 MPa or more, more preferably 0.3 MPa or more, and even more preferably 0.5 MPa or more. The upper limit of the compressive strength is not particularly limited, but is preferably approximately 5 MPa or less, more preferably 3 MPa or less, and even more preferably 2 MPa or less.

[0080] <Example 1> Mica with an average particle size of 112 μm was used as the aggregate, and 1.5 parts by mass of hydrogen peroxide solution and 0.3 parts by mass of yeast were added to 100 parts by mass of the slurry to obtain a geopolimer foam. This geopolimer foam has a density of 267 kg / m 3 and the proportion of bubbles with a bubble volume of 2 mm 3 or more is 46%, the average volume of the bubbles is 0.9 mm 3 and the air flow resistance is 1.1 Pa·s / cm 2 and it had good gas adsorption properties.

[0081] <Example 2> A geopolimer foam was obtained under the same conditions as in Example 1 except that the addition amount of yeast was changed to 0.5 parts by mass with respect to 100 parts by mass of the slurry. This geopolimer foam has a density of 280 kg / m 3 and the average volume of the bubbles is 0.6 mm 3 and the proportion of bubbles with a bubble volume of 2 mm 3 or more is 27%, and the air flow resistance is 2.1 Pa·s / cm2 and had good gas adsorption properties.

[0082] <Example 3> A diopolymer foam was obtained under the same conditions as in Example 1, except that the amount of hydrogen peroxide added was changed to 5.0 parts by mass and the amount of foaming agent added was changed to 3.0 parts by mass with respect to 100 parts by mass of the slurry. This diopolymer foam had a density of 170 kg / m 3 and an average bubble volume of 1.3 mm 3 and a proportion of bubbles with a bubble volume of 2 mm 3 or more was 75%, and the air flow resistance was 0.16 Pa·s / cm 2 and had good gas adsorption properties.

[0083] <Comparative Example 1> A diopolymer foam was obtained under the same conditions as in Example 1, except that mica with an average particle size of 68 μm was used. In this example, during production, the viscosity of the slurry increased and the bubbles in the diopolymer foam became finer. The flow resistance of the obtained diopolymer foam was 16 Pa·s / cm 2 and it had low gas adsorption properties.

[0084] <Comparative Example 2> A diopolymer foam was obtained under the same conditions as in Example 1, except that mica with an average particle size of 68 μm was used and the amount of yeast added was 0.3 parts by mass with respect to 100 parts by mass of the slurry. The flow resistance of the obtained diopolymer foam was 6.8 Pa·s / cm 2 and it had low gas adsorption properties.

[0085] <Comparative Example 3> A diopolymer foam was obtained under the same conditions as in Example 1, except that mica with an average particle size of 232 μm was used and the amount of yeast added was 0.3 parts by mass with respect to 100 parts by mass of the slurry. In this example, during production, the slurry viscosity increased and the bubbles in the diopolymer foam became finer. The flow resistance of the obtained diopolymer foam was 4.2 Pa·s / cm 2 and it had low gas adsorption properties.

[0086] <Comparative Example 4> A geopolimer foam was obtained under the same conditions as in Example 1, except that talc was used as a nucleating agent instead of yeast. In this example, a geopolimer foam having a cell structure with few through-holes was formed. The flow resistance of the obtained geopolimer foam exceeded the measurement limit of 460 Pa·s / cm 2 and had low gas adsorbability.

[0087] <Comparative Example 5> The same conditions as in Example 1 were used, except that the addition amount of hydrogen peroxide solution was 7.5 parts by mass with respect to 100 parts by mass of the slurry. In Comparative Example 5, the bubbles burst during foaming, and a geopolimer foam having sufficient strength could not be obtained. Also, the flow resistance of the obtained geopolimer foam was 0.008 Pa·s / cm 2 and had low gas adsorbability. Also, in Comparative Example 5, the gas adsorption amount tended to level off early.

[0088] <Comparative Example 6> A geopolimer foam was obtained under the same conditions as in Example 1, except that the addition amount of hydrogen peroxide solution was 0.5 parts by mass with respect to 100 parts by mass of the slurry. This geopolimer foam had a density of 578 kg / m 3 and no bubbles with a cell volume of 2 mm 3 or more were present. The flow resistance of the obtained geopolimer foam exceeded the measurement limit of 460 Pa·s / cm 2 and had low gas adsorbability.

[0089]

Table 1

Claims

1. A gas adsorption filter composed of a geopolimer foam having a continuous cell structure formed by a large number of cells formed by foaming, the filter containing a reaction product of an aluminosilicate and an alkali metal silicate and an aggregate. A gas adsorption filter composed of a geopolimer foam having a continuous cell structure formed by a large number of cells formed by foaming, the filter containing a reaction product of an aluminosilicate and an alkali metal silicate and an aggregate. The apparent density of the foam is 100 kg / m ３ or more and 500 kg / m ３ or less, and the flow resistance of the foam when air is flowing at 0.5 mm / s is 0.02 Pa·s / cm ２ or more and 3 Pa·s / cm ２ or less, a gas adsorption filter.

2. The average volume of the bubbles in the geopolymer foam is 0.5 mm ３ or more and 10 mm ３ or less, and the volume ratio of the bubbles with a volume of 2 mm ３ or more is 20% or more and 90% or less, The average volume of the cells is Using an X-ray CT three-dimensional measuring machine, the three-dimensional shape of a sample cut out from a geopolystyrene foam is measured to obtain 3D data regarding the bubble structure of the sample. For the obtained 3D data, with respect to a randomly selected region of 1 cm × 1 cm × 1 cm, pores with a volume of less than 0.1 mm ３ After performing a process of excluding communication pores with a volume of less than 0.1 mm from the measurement targets, the volume distribution of bubbles in the region is measured, and the gas adsorption filter according to claim 1, obtained by a method calculated from the volume distribution of the bubbles.

3. The gas adsorption filter according to claim 1 or 2, wherein the aggregate contains mica, and the average particle diameter of the mica is 80 μm or more and 200 μm or less.

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