WO2013081115A1 - 多孔質セラミックス及びその製造方法 - Google Patents
多孔質セラミックス及びその製造方法 Download PDFInfo
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- WO2013081115A1 WO2013081115A1 PCT/JP2012/081108 JP2012081108W WO2013081115A1 WO 2013081115 A1 WO2013081115 A1 WO 2013081115A1 JP 2012081108 W JP2012081108 W JP 2012081108W WO 2013081115 A1 WO2013081115 A1 WO 2013081115A1
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B33/00—Clay-wares
- C04B33/02—Preparing or treating the raw materials individually or as batches
- C04B33/04—Clay; Kaolin
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
- C04B38/02—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof by adding chemical blowing agents
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/009—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone characterised by the material treated
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/53—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone involving the removal of at least part of the materials of the treated article, e.g. etching, drying of hardened concrete
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/80—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only ceramics
- C04B41/91—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only ceramics involving the removal of part of the materials of the treated articles, e.g. etching
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00241—Physical properties of the materials not provided for elsewhere in C04B2111/00
- C04B2111/00284—Materials permeable to liquids
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
- C04B2235/60—Aspects relating to the preparation, properties or mechanical treatment of green bodies or pre-forms
- C04B2235/602—Making the green bodies or pre-forms by moulding
Definitions
- the present invention relates to a porous ceramic and a manufacturing method thereof.
- This application claims priority based on Japanese Patent Application No. 2011-262017 filed in Japan on November 30, 2011, the contents of which are incorporated herein by reference.
- porous ceramics are used for fireproof heat insulating materials, water purification materials, humidity control materials, volatile organic compound (VOC) adsorbing materials, and the like.
- VOC volatile organic compound
- Examples of the structure of such porous ceramics include a closed cell type, a lattice structure type, an aggregate type, a type having minute crack pores, a type having continuous through pores, and the like, and is selected according to the application.
- Known lattice-structured porous ceramics are those obtained by injecting and filling a ceramic composition into the pores of a urethane foam resin, and then decomposing and sintering the resin component.
- Known aggregate-type porous ceramics have pores in the gaps between the aggregates of elementary particles in the composition.
- the independent pore-type porous ceramics those in which pores are generated by a high-temperature decomposition volatile component in the composition in the firing step are known.
- porous ceramics having minute crack pores those obtained by sintering a composition obtained by mixing a raw material such as clay that shrinks when heated and slag that expands when heated are known.
- porous ceramics having continuous through pores those obtained by adding an alkali solution to metal aluminum in a water-containing composition to generate hydrogen and sintering it are known.
- porous ceramics have been used as building materials such as road surface materials for paved roads, rooftop materials and wall materials for buildings, and greening bases. Porous ceramics used as building materials are required to have water permeability (high water permeability) and appropriate water retention.
- a porous ceramic sintered body obtained by mixing and sintering diatomaceous earth, clay, and organic sludge has been proposed (for example, Patent Document 1).
- water permeability and water retention are achieved by micrometer-order pores derived from diatomaceous earth that are maintained by preventing clay from entering the pores of diatomite, and artificially formed millimeter-order pores. It is intended to increase.
- porous ceramic of the present invention is that a mixture containing clay is molded and sintered to obtain a porous ceramic sintered body, and the surface of the porous ceramic sintered body is ground.
- the surface portion of the porous ceramic sintered body is removed by grinding. It is characterized by.
- the mixture preferably contains a foaming agent.
- a mixture containing clay is formed and sintered to obtain a porous ceramic sintered body, and the surface of the porous ceramic sintered body is ground. It is characterized by.
- the mixture preferably contains a foaming agent.
- porous ceramic of the present invention it is possible to suppress a decrease in water permeability over a long period of time.
- porous ceramics One aspect of the porous ceramics of the present invention is a mixture in which a clay-containing mixture is molded and sintered to obtain a porous ceramic sintered body, and the surface of the porous ceramic sintered body is subjected to grinding. .
- Porous ceramics are those in which pores are formed.
- the size of the pores formed in the porous ceramics can be determined in consideration of the application.
- the pore size may be a nanometer order pore having a pore diameter of 10 to 1000 nm, or a micrometer order having a pore diameter of more than 1 ⁇ m and less than 1000 ⁇ m.
- the pores may be pores in the order of millimeters having a pore diameter of more than 1 mm and not more than 300 mm, or these pores may be mixed.
- the pore diameter refers to the length in the long side direction of the pores.
- the term “pore diameter” refers to the major diameter of the pores.
- the pore diameter can be adjusted by combining the types of raw materials and the firing conditions.
- the pore diameter of a millimeter order pore is a value measured by cutting a porous ceramic and using a scale.
- the pore diameter of nanometer order and micrometer order pores is a value measured by cutting a porous ceramic and
- the pores formed in the porous ceramic may be independent from each other or may be communication holes communicating with each other.
- the porous ceramic preferably has a communication hole from the viewpoint of improving heat insulation, sound absorption, water retention, water permeability or air permeability. More preferably, the communication hole is formed through the porous ceramic.
- the volume ratio (porosity) of the pores in the porous ceramics is determined according to the application, and for example, the porosity represented by [(pore volume) / (porous ceramic volume)] ⁇ 100 is preferable. Is 20 to 85% by volume, more preferably 40 to 80% by volume, and still more preferably 60 to 70% by volume. If the porosity is equal to or higher than the lower limit, various properties such as water permeability, water retention, soundproofing, and heat insulating properties can be further increased. If the porosity is equal to or lower than the upper limit, the strength of the porous ceramic can be further increased. For example, the saturated moisture content of the porous ceramic is preferably 20% or more, more preferably 30% or more, and further preferably 40% or more.
- the upper limit is preferably as high as possible, but if it is too high, the strength may be insufficient depending on the application. Therefore, it is preferably 100% or less, more preferably 80% or less. If the saturated moisture content is less than 20%, even if the porosity is high, the water retention tends to be low, and the cooling effect (suppression of temperature rise) caused by vaporizing the greening base and the retained water, etc. As a purpose (for example, a road surface material, a ceiling material, a wall material, etc.), there is a possibility that a sufficient effect cannot be obtained.
- the porous ceramic preferably has a specific gravity represented by [mass of the porous ceramic in an absolutely dry state (g)] / [volume of the porous ceramic (cm 3 )], preferably 0.4 to 1.3 g / cm 3. More preferably, it is 0.45 to 1.1 g / cm 3 , and further preferably 0.55 to 0.85 g / cm 3 . If the specific gravity is not less than the above lower limit value, the strength of the porous ceramic can be further increased, and if it is not more than the above upper limit value, various characteristics can be further enhanced.
- the shape of the porous ceramics can be determined in consideration of the use and the like, and examples thereof include a plate-like plate-like object, a columnar object such as a columnar shape or a prismatic shape (block shape), and the like. Among them, the effects of the present invention are remarkable in plate-like objects and prismatic objects suitable as building materials such as road surface materials, ceiling materials, and wall materials.
- the size of the porous ceramics can be determined in consideration of the application and the like. For example, in the case of a plate-like material, the length is 5 to 100 cm ⁇ width 5 to 100 cm ⁇ thickness 1 to 10 cm.
- One aspect of the method for producing porous ceramics of the present invention includes a step of obtaining a mixture containing clay (mixing step), a step of forming a mixture to obtain a molded body (molding step), and sintering the molded body. It comprises a step of obtaining a porous ceramic sintered body (firing step) and a step of grinding the surface of the porous ceramic sintered body (grinding step).
- a mixing process is a process of mixing clay and arbitrary components as needed, and obtaining a mixture.
- ⁇ Clay ⁇ Clay is a mineral material that exhibits clay-like properties that are commonly used as ceramic raw materials. However, the clay in one embodiment of the present invention does not include diatomaceous earth.
- the clay known ones conventionally used for ceramic sintered bodies can be used.
- the clay is composed of a mineral composition such as quartz, feldspar, clay, etc., and the constituent mineral is mainly kaolinite, and halloysite. , Montmorillonite and illite are preferred.
- those containing coarse quartz grains having a particle diameter of 500 ⁇ m or more are more preferable from the viewpoint of suppressing the progress of cracks during sintering and preventing damage to the porous ceramics.
- the coarse quartz particles preferably have a particle diameter of 5 mm or less.
- examples of such clays include cocoon clay. The clay is blended alone or in combination of two or more.
- the blending amount of the clay in the mixture is appropriately determined in consideration of the use of the porous ceramics and the like, and is preferably 5 to 60% by mass, more preferably 10 to 50% by mass, for example. If it is less than the lower limit, the porous ceramics may become brittle, and if it exceeds the upper limit, the formability may be impaired.
- the optional component examples include a foaming agent, organic sludge, diatomaceous earth, filler, various additives, and the like. Among them, a foaming agent and organic sludge are preferable, and a foaming agent is more preferable.
- a foaming agent or organic sludge as an optional component, the porosity of the porous ceramic can be increased, and various characteristics of the porous ceramic can be more easily exhibited.
- a foaming agent foams at the time of baking For example, well-known foaming agents for ceramics, such as calcium carbonate, silicon carbide, magnesium carbonate, and slag, can be used. Of these foaming agents, slag is preferred.
- the slag is not particularly limited. For example, it is generated when blast furnace slag generated during metal refining, municipal waste melting slag generated when melting municipal waste, sewage sludge melting slag generated when sewage sludge is melted, cast iron such as ductile cast iron, etc. Examples thereof include glassy slag such as cast iron slag. Among these, cast iron slag is more preferable.
- cast iron slag Since cast iron slag has a stable composition, a stable foamed state can be obtained, and the foaming rate is about 1.5 to 2 times that of other slags. By using cast iron slag, large pores on the order of millimeters can be formed in the porous ceramics.
- the blending amount of the foaming agent in the mixture is appropriately determined in consideration of the application of the porous ceramics, and is preferably 10 to 80% by mass, more preferably 30 to 70% by mass, for example. If the amount is less than the above lower limit value, the porosity may be too low and various characteristics of the porous ceramic may not be sufficiently exhibited. If the value exceeds the above upper limit value, the formability may be impaired.
- Organic sludge is sludge containing organic substances as the main component.
- organic sludge pores of nanometer order to micrometer order are formed in the porous ceramics.
- the activated sludge is obtained by being discharged from a wastewater treatment facility using the activated sludge method through a coagulation and dehydration process. By using such organic sludge, desired pores can be easily formed.
- activated sludge derived from wastewater treatment, which has been positioned as waste can be recycled as a raw material.
- the water content of the organic sludge is preferably 60 to 90% by mass, more preferably 65 to 85% by mass. If it is in the said range, while being able to obtain a homogeneous mixture by a mixing process, favorable moldability can be maintained also in continuous molding.
- the organic sludge content of the organic sludge is not particularly limited.
- the organic sludge content (organic content) in the solid content of the organic sludge is preferably 70% by mass or more, and more preferably 80% by mass or more. 100 mass% may be sufficient as content of the organic substance in solid content of organic sludge as an upper limit. The higher the organic content, the easier the formation of pores.
- the organic content is a value obtained from the following formula (1) by measuring the ash content (mass%) of the sludge after drying at a carbonization temperature of 700 ° C. according to JIS M8812-1993.
- the blending amount of the organic sludge in the mixture is appropriately determined in consideration of the use of the porous ceramics, and is, for example, preferably 1 to 60% by mass, more preferably 3 to 40% by mass. If it is in the said range, a mixture is equipped with moderate fluidity
- Diatomaceous earth is a deposit made of diatom remains and is porous with pores on the order of micrometers.
- Diatomaceous earth is not particularly limited, and those conventionally used for refractory bricks, filter media and the like can be used. For example, it is not necessary to separate and refine clay minerals (montmorillonite, etc.), quartz, feldspar, etc., which are narrow, and the amount of the mixture can be adjusted after recognizing these contents. Further, the diatomaceous earth may be one obtained by pulverizing tiles, seven wheels and the like manufactured using diatomaceous earth.
- the moisture content of the diatomaceous earth is not particularly limited, and for example, the moisture content in a natural dry state is preferably 20 to 60% by mass, more preferably 30 to 50% by mass, and further preferably 35 to 45% by mass. If it is within the above range, it is because a mixture with good moldability can be obtained by removing the coarse particles in the narrow material during mixing while recognizing the moisture content.
- the moisture content is a value obtained by drying the sample (200 ° C., 12 minutes) using an infrared moisture meter having the following specifications, which is a weight loss method, and calculating the following equation (2).
- Measurement method Drying loss method (mass measurement method by heat drying) Minimum display: moisture content; 0.1% by mass Measurement range: Moisture content; 0.0 to 100% by mass Drying temperature: 0-200 ° C Measurement accuracy: sample weight 5g or more, moisture content ⁇ 0.1% by mass Heat source: infrared lamp; 185W
- Moisture content (mass%) [(m 1 -m 2 ) / (m 1 -m 0 )] ⁇ 100 (2) m 1 : between the mass of the container before drying and the mass of the sample before drying total weight (g) m 2: the total mass of the mass of the sample after drying and the mass of the container after drying (g) m 0: after drying of the container of the mass (g)
- the blending amount of diatomaceous earth in the mixture is appropriately determined in consideration of the porosity required for the porous ceramics, and is, for example, 55% by mass or less.
- the blending amount of diatomaceous earth in the mixture is preferably 0 to 40 parts by mass, more preferably 0 to 20 parts by mass, and still more preferably 0 to 15 parts by mass.
- the filler examples include particles of high melting point glass having a melting temperature of 900 ° C. or higher, carbon fiber, rock wool, and the like.
- the high melting point glass particles are partially melted and fused with each other, or function as a binder for clay or diatomaceous earth.
- the strength of the porous ceramic can be increased.
- Carbon fiber and rock wool can be taken into the porous ceramics to increase the strength of the porous ceramics.
- high melting point glass particles are preferable. By using the high melting point glass particles, the strength of the porous ceramics can be further increased, and in particular, the bending strength of the porous ceramics can be increased.
- the high melting point glass has a melting temperature of 900 ° C. or higher, preferably a melting temperature of 1000 ° C. or higher, more preferably a melting temperature of 1200 ° C. or higher. If it is more than the said lower limit, the particle
- the material of the high melting point glass is not particularly limited, but alkali-free glass, aluminosilicate glass, borosilicate glass, and quartz glass are preferable, and borosilicate glass is particularly preferable. With such a material, the strength of the porous ceramic can be sufficiently increased.
- the alkali-free glass is a glass that does not substantially contain an alkali metal element such as sodium, potassium, or lithium. “Substantially not contained” means that the content of the alkali metal element in the glass composition is 0.1% by mass or less in terms of oxide.
- the content of the alkali metal element in the glass composition is preferably 0 to 0.1% by mass, more preferably 0 to 0.01% by mass in terms of oxide.
- Aluminosilicate glass is an oxide glass mainly composed of aluminum and silicon.
- Borosilicate glass is an oxide glass mainly composed of boron and silicon. Quartz glass refers to glass made from quartz and having high silicon oxide purity. Examples of such high melting point glass include AN100 (trade name, non-alkali borosilicate glass, manufactured by Asahi Glass Co., Ltd.).
- the high melting point glass is, for example, a liquid crystal display such as a liquid crystal television, a panel such as a plasma display, a cover glass for EL, a cover glass for a solid-state image sensor represented by a CCD, a glass for an optical filter such as a hand pass filter, a chip Used in various products such as glass for glass substrates, flasks and beakers for on-glass use.
- a liquid crystal display such as a liquid crystal television
- a panel such as a plasma display
- a cover glass for EL a cover glass for a solid-state image sensor represented by a CCD
- a glass for an optical filter such as a hand pass filter
- a chip Used in various products such as glass for glass substrates, flasks and beakers for on-glass use.
- waste glass discharged in the manufacturing process of the above products, or a panel recovered from a discarded liquid crystal television or the like can be used.
- a panel for a flat display such as a liquid crystal television generates a large amount of waste glass when the flat display is manufactured as the size of the panel increases. Waste can be reduced by making the waste glass of the flat display panel into particles of high melting point glass. For this reason, it is preferable to use the waste glass of the panel for flat displays as a high melting glass particle from a viewpoint of reducing environmental load.
- the waste glass of the flat display panel can be used as a high-melting glass having a stable quality without special purification because the purity of the glass composition is high.
- the particle diameter of the high melting point glass particles is not particularly limited, but is preferably 0.3 to 5 mm.
- the particle diameter is less than 0.3 mm, the porosity of the porous ceramic is decreased or the specific gravity is increased. Various properties may be impaired due to the decrease in porosity, and the mass of porous ceramics may be significantly increased due to an increase in specific gravity. If the particle diameter is more than 5 mm, the moldability may be impaired in the molding step described later.
- the particle diameter of the high melting point glass is more preferably more than 0.6 mm and 1.2 mm or less from the viewpoint of productivity of porous ceramics and further improvement of strength.
- carbon fiber various carbon fibers such as polyacrylonitrile (PAN), pitch, rayon, or cellulose can be used.
- PAN polyacrylonitrile
- pitch rayon
- rayon rayon
- the length of the carbon fiber can be determined in consideration of the shape of the porous ceramics and the like, and for a plate-like material, for example, 1 mm to 10 cm is preferable, and 5 to 25 mm is more preferable. If it is less than the lower limit, the strength of the porous ceramics may not be sufficiently increased, and if it exceeds the upper limit, productivity may be impaired or the appearance of the porous ceramics may be impaired.
- the thickness of the carbon fiber can be determined in consideration of the shape of the porous ceramics and the like. For a plate-like material, the thickness is preferably 1 to 1000 ⁇ m, and more preferably 5 to 100 ⁇ m. If it is less than the lower limit, the strength of the porous ceramics may not be sufficiently increased, and if it exceeds the upper limit, productivity may be impaired or the appearance of the porous ceramics may be impaired.
- Rock wool is an artificial mineral fiber that is produced by mixing lime, etc., with basalt, iron slag, etc., and melting at high temperatures.
- the length of the rock wool can be determined in consideration of the shape of the porous ceramics and the like, and if it is a plate-like material, for example, it is preferably 1 mm to 10 cm, more preferably 5 to 25 mm. If it is less than the lower limit, the strength of the porous ceramics may not be sufficiently increased, and if it exceeds the upper limit, productivity may be impaired or the appearance of the porous ceramics may be impaired.
- the thickness of the rock wool can be determined in consideration of the shape of the porous ceramics and the like, and is preferably 1 to 100 ⁇ m, and more preferably 3 to 30 ⁇ m for a plate-like material. If it is less than the lower limit, the strength of the porous ceramics may not be sufficiently increased, and if it exceeds the upper limit, productivity may be impaired or the appearance of the porous ceramics may be impaired.
- the blending amount of the filler in the mixture is appropriately determined in consideration of the type of filler and the use of the porous ceramics, and is, for example, 5 to 35% by mass. If the amount is less than the lower limit, it is difficult to obtain the effect of blending the filler, and if it exceeds the upper limit, the porosity and the saturated water content are lowered, and various properties may not be sufficiently exhibited.
- the blending amount of the filler in the mixture can be determined in consideration of the strength required for the porous ceramic sintered body. For example, when using high melting point glass particles as the filler, the total amount of raw materials other than the filler is 100 parts by mass. The amount is preferably 10 to 40 parts by mass, and more preferably 15 to 40 parts by mass.
- the strength of the porous ceramic sintered body may not be sufficiently improved, and if it exceeds the upper limit, the moldability may be impaired.
- the blending amount of the filler in the mixture is preferably 0.01 to 20 parts by mass, and 0.01 to 10 parts by mass with respect to 100 parts by mass of the raw material when, for example, a fibrous filler such as carbon fiber is used as the filler. Is more preferably 0.05 to 5 parts by mass, and particularly preferably 0.1 to 2 parts by mass. If it is less than the said lower limit, there exists a possibility that the intensity
- additives examples include naphthalene-based fluidizing agents such as Mighty 2000WH (trade name, manufactured by Kao Corporation), melamine-based fluidizing agents such as Melment F-10 (trade name, manufactured by Showa Denko KK), and the like.
- Polycarboxylic acid-based fluidizing agents such as Darex Super 100pH (trade name, manufactured by Grace Chemicals Co., Ltd.); antibacterial agents such as silver, copper and zinc; adsorbents such as zeolite and apatite, metallic aluminum and the like .
- blend a deodorizer examples of the deodorant include ammonium chloride and zinc chloride.
- the additive may be added in an amount that does not impair the object of the present invention in consideration of the intended effect of the additive.
- ammonium chloride or zinc chloride it is preferably 0.05 to 5% by mass with respect to the organic sludge and preferably 0.005 to 1% by mass in the mixture.
- These arbitrary components may be used individually by 1 type, and may be used in combination of 2 or more type.
- the composition of the mixture can be determined in consideration of the use of porous ceramics, for example, a mixture of clay and diatomaceous earth, a mixture of clay and at least one of a foaming agent and organic sludge, clay, diatomaceous earth, and a foaming agent. And a mixture of at least one of organic sludge, a mixture of these and a filler, and the like.
- the water content of the mixture is not particularly limited, but is preferably 25 to 45% by mass, and more preferably 25 to 30% by mass. If it is in the said range, a mixture will have moderate fluidity
- the mixing method in a mixing process is not specifically limited, For example, the method of throwing clay and an arbitrary component as needed into a mixing apparatus and mixing this is mentioned.
- the order in which the raw materials are charged is appropriately determined according to the composition.
- the raw materials may be charged into a mixing apparatus in a lump and mixed.
- diatomaceous earth and organic sludge may be mixed, and then clay and other raw materials may be sequentially introduced into the mixing apparatus and mixed.
- the mixing device is not particularly limited, and a conventionally known mixing device can be used.
- a kneader such as a mix muller (manufactured by Shinto Kogyo Co., Ltd.), a kneader (manufactured by Moriyama Co., Ltd.), a mixer ( (Nippon Ceramic Science Co., Ltd.)
- the mixing time in the mixing step is set to a time for the mixture to be in a plastic state in consideration of the mixing ratio of each raw material, for example, 15 to 45 minutes.
- the temperature condition in the mixing step is appropriately determined in consideration of the blending ratio of each raw material, and is set to 10 to 80 ° C., for example.
- the forming step is a step of forming the mixture obtained in the mixing step into an arbitrary shape.
- the molding method is appropriately determined according to the shape of the porous ceramics. For example, a method of continuously obtaining a molded body having an arbitrary shape using a molding apparatus, or a mold having an arbitrary shape is obtained by filling a mixture with an arbitrary shape. The method and the method of extending
- molding apparatus can be determined according to the shape of the desired porous ceramics.
- a vacuum clay molding machine a flat plate press molding machine, a flat plate extrusion molding machine, etc. are mentioned, and among these, a vacuum clay molding machine is preferable.
- the pores can be well controlled by removing air in the molded body using a vacuum kneading machine.
- the size of the compact can be determined in consideration of the desired size of the porous ceramic.
- the firing step is a step of firing the formed body obtained in the forming step to obtain a porous ceramic sintered body.
- Examples of the firing step include a method of drying the formed body (drying operation), firing the dried formed body (firing operation), and sintering clay to obtain a porous ceramic sintered body.
- the drying operation is not particularly limited, and a known method can be used.
- the molded body may be naturally dried, or may be dried by treating in a hot air drying oven at 50 to 220 ° C. for an arbitrary time.
- the moisture content of the dried molded object is not specifically limited, For example, less than 5 mass% is preferable and less than 1 mass% is more preferable.
- the lower limit of the moisture content of the dried molded body is not particularly limited, and may be 0% by mass.
- the firing method is not particularly limited, and a known method can be used. Examples thereof include a method of firing at an arbitrary temperature using a continuous sintering furnace such as a roller hearth kiln or a batch sintering furnace such as a shuttle kiln. Among them, it is preferable to use a continuous sintering furnace for firing from the viewpoint of productivity.
- a deodorizing apparatus When organic sludge etc. are mix
- the firing temperature is determined in consideration of the type of optional component, the blending ratio of raw materials, and the like. For example, when a filler, diatomaceous earth, clay, slag, organic sludge is included as a composition example, the firing temperature is such that the filler partially melts, the diatomaceous earth or clay is sintered, and the organic matter contained in the organic sludge is thermally decomposed. It is assumed that the slag expands by volatilizing and reducing the weight.
- the firing temperature when firing the molded body of the above composition example is preferably, for example, 950 to 1200 ° C., more preferably 1000 to 1100 ° C.
- the firing operation before the firing temperature is reached, water is first evaporated from the molded body, the foaming agent is foamed, and then the organic matter of the organic sludge is thermally decomposed and reduced in weight.
- the temperature rise heat curve, temperature gradient
- rapid evaporation of water or rapid volatilization of organic substances can be suppressed, and damage to the molded body can be prevented.
- the porous ceramic sintered body may be damaged such as cracking or crushing, but cooling can be achieved by adjusting the temperature gradient in the firing operation. Can be prevented from being damaged.
- the firing time can be determined in consideration of the firing temperature, the water content of the mixture, etc., and the residence time in the state of being at the firing temperature is preferably 4 to 10 minutes, more preferably 6.5 to 7. 5 minutes. If the residence time is within the above range, the porous ceramic sintered body can be satisfactorily sintered while preventing damage to the porous ceramic sintered body.
- the grinding process is a process of grinding the surface of the porous ceramic sintered body obtained in the firing process. By passing through this step, the porous ceramics obtained can be prevented from decreasing in water permeability over a long period of time.
- Examples of the grinding method include a method of grinding the surface of the porous ceramic sintered body with a cutting machine such as a vertical milling machine PV series (Amitech Co., Ltd.), a grinder, a sandpaper, or the like.
- the surface to be ground can be determined in consideration of the use and usage of the porous ceramics. For example, when producing plate-like porous ceramics, it is preferable to grind both surfaces or one surface in the thickness direction of the plate-like porous ceramic sintered body. Normally, when a plate-like porous ceramic is used as a building material, it is constructed so that one surface in the thickness direction is desired outdoors. Since the surface subjected to the grinding process is prevented from being reduced in water permeability over a long period of time, the surface subjected to the grinding process is a desired surface outdoors.
- the degree of grinding is determined in consideration of the properties and size of the porous ceramic sintered body, for example, a depth of about 0.5 to 5 mm from the surface of the porous ceramic sintered body. If it is less than the lower limit, it is difficult to obtain the effect of grinding, and if it exceeds the upper limit, the strength of the obtained porous ceramics may be lowered.
- a reduction in water permeability can be suppressed over a long period by grinding the surface of the porous ceramic sintered body.
- the reason why the reduction in water permeability can be suppressed by grinding the surface is unknown, but is presumed as follows.
- the surface of the porous ceramic sintered body rapidly rises in temperature during the firing operation, and due to vitrification, the pores are blocked, the pore diameter is small, or there are many pores not communicating with the pores formed inside. It is estimated that When such a porous ceramic sintered body is used as a building material, pores formed on the surface are considered to be blocked in a short time by invading fine particles. For this reason, it is thought that porous ceramics can maintain water permeability over a long period of time by removing the surface layer having a structure that is easily clogged with fine particles.
- the raw materials used in the examples are as follows.
- Organic sludge As organic sludge, the activated sludge discharged
- the activated sludge had an organic content (based on solid content) of 83% by mass and a water content of 85% by mass.
- Sakaime clay produced in Gifu Prefecture or Aichi Prefecture
- Cast iron slag was used as a foaming agent.
- the cast iron slag is a ductile iron slag SiO 2, Al 2 O 3, CaO, Fe 2 O 3, FeO, MgO, MnO, K 2 O, the Na 2 O as main components.
- Example 1 Slag, organic sludge, clay and water were mixed with a mix muller (manufactured by Shinto Kogyo Co., Ltd.) with the composition shown in Table 1 to obtain a plastic mixture (mixing step). Subsequently, the obtained mixture was extrusion-molded with a vacuum clay molding machine (manufactured by Takahama Kogyo Co., Ltd.) to obtain a strip-shaped primary molded body having a width of 60 cm and a thickness of 2 cm. The primary molded body was cut at an arbitrary pitch and width to obtain a substantially square flat plate-shaped molded body having a thickness of 2 cm (molding step).
- a mix muller manufactured by Shinto Kogyo Co., Ltd.
- Table 1 plastic mixture
- the obtained mixture was extrusion-molded with a vacuum clay molding machine (manufactured by Takahama Kogyo Co., Ltd.) to obtain a strip-shaped primary molded body having a width of 60 cm and
- the obtained molded body was dried with a hot air dryer (180 ° C., 0.5 hour) to a moisture content of 1% by mass or less, and then using a continuous sintering furnace, the firing temperature was 1050 ° C. at the firing temperature. Firing was performed under firing conditions of a residence time of 7 minutes (firing step).
- a roller hearth kiln (effective length of the sintering furnace: total length 15 m, the sintering furnace was divided into zones 1 to 10 each having a length of 1.5 m) was used.
- Example 1 A porous ceramic was obtained in the same manner as in Example 1 except that the porous ceramic sintered body was not ground. About the obtained porous ceramics, specific gravity, saturation water content, and water transmission rate were measured, and the results are shown in Table 1.
- a cylinder made of vinyl chloride having a diameter of 50 mm is set up on the surface of the porous ceramic of each example (the surface subjected to grinding in Example 1), and this is put on a waterproof putty (bathroom putty, manufactured by Toyo Materan Co., Ltd.). Fixed. The porous ceramic was immersed in water for 60 minutes, then removed from the water and placed in a vat. 200 mL of water was poured into the cylinder, and the time taken for the water level of the poured water to drop by 50 mL was measured (initial water permeability time).
- a clay suspension in which 0.01 g of clay (average particle size 4 ⁇ m) is suspended in 100 mL of water is poured into the cylinder, and the total amount of clay suspension It was allowed to stand until it penetrated into the porous ceramics (deterioration treatment).
- the clay used in this test has a particle size equivalent to that of yellow sand, and 0.01 g of clay with respect to the area surrounded by the cylinder corresponds to the amount of yellow sand fall (5 g / m 2 ) for one year.
- the porous ceramics infiltrated with 100 mL of the clay suspension is a model that has been used outdoors for 1 year (in the table, described as equivalent to 1 year).
- 200 mL of water was newly poured into the cylinder, and the time taken for the water level of the poured water to drop by 50 mL was measured (water permeability time corresponding to the passage of one year).
- the deterioration treatment and the work of pouring 200 mL of water into the cylinder and measuring the water permeation time were repeated. Based on the measured water permeation time, the water permeation speed is obtained by the following equation (4), and the results are shown in Table 1.
- FIG. 1 is a plan view photograph of a porous ceramics 1 formed with a surface (ground surface) 10 that has been subjected to a grinding process and a surface (non-ground surface) 20 that has not been subjected to a grinding process
- FIG. 1 is a perspective photograph of a ceramic material 1.
- reference numeral 2 indicates a boundary between the ground surface 10 and the non-ground surface 20. As shown in FIGS. 1 and 2, the ground surface 10 was formed with large irregularities compared to the non-ground surface 20.
- FIG. 3 is a graph showing the transition of the water transmission rate in Example 1 and Comparative Example 1, with the water transmission rate on the vertical axis and the elapsed equivalent years on the horizontal axis.
- Example 1 to which the present invention was applied had a faster water permeation rate over the course of 10 years from the beginning than Comparative Example 1 in which grinding was not performed.
- the water permeation rate corresponding to the passage of 10 years was 83.4% of the initial water permeation rate
- Comparative Example 1 the water permeation rate corresponding to the passage of 10 years was the initial water permeation rate. It was 18.1% of the speed. From the above results, it was found that the porous ceramics to which the present invention was applied can suppress a decrease in water permeability over a long period of time.
- porous ceramics of the present invention a decrease in water permeability can be suppressed over a long period of time, which is extremely useful industrially.
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Abstract
Description
本願は、2011年11月30日に、日本に出願された特願2011-262017号に基づき優先権を主張し、その内容をここに援用する。
アグリゲート型の多孔質セラミックスとしては、組成物中の素粒子の骨材の間隙を気孔としたものが知られている。
独立気孔型の多孔質セラミックスとしては、焼成工程において、組成物中の高温分解揮発成分により気孔を生成させたものが知られている。
微小な亀裂孔隙を有する多孔質セラミックスとしては、加熱時に収縮する粘土類等の原料と、加熱時に膨張するスラグ類とを混合した組成物を焼結し得られるものが知られている。
また、連続貫通気孔を有する多孔質セラミックスとしては、含水組成物内に、金属アルミニウムにアルカリ溶液を加えて水素を発生させ、これを焼結して得られるものが知られている。
このような多孔質セラミックスとして、例えば、珪藻土と粘土と有機汚泥とを混合し、焼結した多孔質セラミックス焼結体が提案されている(例えば、特許文献1)。特許文献1の発明によれば、珪藻土の気孔に粘土が入り込むのを防いで維持した珪藻土由来のマイクロメートルオーダーの気孔と、人工的に形成されたミリメートルオーダーの気孔とにより、透水性及び保水性を高めることが図られている。
そこで、本発明は、長期間にわたって、透水性の低下を抑制できる多孔質セラミックスを目的とする。
本発明の多孔質セラミックスの一態様は、粘土を含む混合物を成形し、焼結して多孔質セラミックス焼結体を得、前記多孔質セラミックス焼結体の表面に研削加工を施したものである。
多孔質セラミックスに形成されている気孔の大きさは、用途を勘案して決定でき、例えば、孔径10~1000nmのナノメートルオーダーの気孔であってもよいし、孔径1μm超1000μm以下のマイクロメートルオーダーの気孔であってもよいし、孔径1mm超300mm以下のミリメートルオーダーの気孔であってもよいし、これらの気孔が混在していてもよい。気孔の孔径とは、気孔の長辺方向の長さをいい、以下、単に孔径という場合には、気孔の長径を指す。気孔の孔径は、原料の種類や、焼成条件を組み合わせることにより調節できる。ミリメートルオーダーの気孔の孔径は、多孔質セラミックスを切断し、スケールを用いて測定される値である。ナノメートルオーダー及びマイクロメートルオーダーの気孔の孔径は、多孔質セラミックスを切断し、電子顕微鏡を用いて測定される値である。
多孔質セラミックスの飽和含水率は、例えば、20%以上が好ましく、30%以上がより好ましく、40%以上がさらに好ましい。上限は高い程よいが、高すぎると用途によっては強度が不足することもあるため、100%以下が好ましく、80%以下がより好ましい。飽和含水率が20%未満であると、気孔率が高いものであっても、保水性が低くなる傾向にあり、緑化基盤や保水した水を気化させて生じる冷却効果(温度上昇の抑制)等を目的とする用途(例えば、路面材、天井材、壁材等)としては、十分な効果が得られないおそれがある。
多孔質セラミックスは、[絶乾状態の多孔質セラミックスの質量(g)]/[多孔質セラミックスの体積(cm3)]で表される比重が、好ましくは0.4~1.3g/cm3、より好ましくは0.45~1.1g/cm3、さらに好ましくは0.55~0.85g/cm3とされる。比重が上記下限値以上であれば、多孔質セラミックスの強度をより高められ、上記上限値以下であれば、諸特性をより高められる。
多孔質セラミックスの大きさは、用途等を勘案して決定でき、例えば、板状物であれば、長さ5~100cm×幅5~100cm×厚み1~10cmとされる。
本発明の多孔質セラミックスの製造方法の一態様は、粘土を含む混合物を得る工程(混合工程)と、混合物を成形して成形体を得る工程(成形工程)と、成形体を焼結して多孔質セラミックス焼結体を得る工程(焼成工程)と、多孔質セラミックス焼結体の表面に研削加工を施す工程(研削工程)とを備えるものである。
混合工程は、粘土と、必要に応じて任意成分とを混合し、混合物を得る工程である。
≪粘土≫
粘土は、一般に窯業原料として用いられる粘土状の性状を示す鉱物材料である。ただし、本発明の一態様における粘土には、珪藻土が含まれない。
粘土としては、従来、セラミックス焼結体に用いられる公知のものを用いることができ、例えば、石英、長石、粘土系等の鉱物組成で構成され、構成鉱物としては、カオリナイトを主とし、ハロイサイト、モンモリロナイト、イライトを含むものが好ましい。中でも、焼結時のクラックの進展を抑え、多孔質セラミックスの破損を防ぐ観点から粒子径が500μm以上の石英の粗粒を含むものがより好ましい。前記石英の粗粒は、粒子径が5mm以下であることが好ましい。このような粘土としては、例えば、蛙目粘土等が挙げられる。粘土は、1種単独で又は2種以上を適宜組み合わせて配合される。
任意成分としては、発泡剤、有機汚泥、珪藻土、フィラー、各種添加剤等が挙げられ、中でも、発泡剤、有機汚泥が好ましく、発泡剤がより好ましい。任意成分として発泡剤や有機汚泥を用いることで、多孔質セラミックスの気孔率を高め、多孔質セラミックスの諸特性をより発揮しやすくできる。
スラグとしては特に限定されず、例えば、金属精錬時に発生する高炉スラグ、都市ゴミの溶融時に発生する都市ゴミ溶融スラグ、下水汚泥の溶融時に発生する下水汚泥溶融スラグ、ダクタイル鋳鉄等の鋳鉄時に発生する鋳鉄スラグ等のガラス質スラグ等が挙げられる。これらの中でも、鋳鉄スラグがより好ましい。鋳鉄スラグは、組成が安定しているため安定した発泡状態が得られると共に、他のスラグに比べ1.5~2倍程度の発泡率である。鋳鉄スラグを用いることで、多孔質セラミックスにミリメートルオーダーの大きな気孔を形成できる。
珪藻土は、特に限定されず、従来、耐火煉瓦、濾過材等に使用されていたものと同様のものを用いることができる。例えば、狭雑している粘土鉱物(モンモリロナイト等)や石英、長石等を分別精製する必要はなく、これらの含有率を認識した上で、混合物への配合量を調整することができる。また、珪藻土は、珪藻土を用いて製造された瓦、七輪等が粉砕されたものであってもよい。
珪藻土の含水率は特に限定されず、例えば、自然乾燥状態での含水率が20~60質量%が好ましく、30~50質量%が好ましく、35~45質量%がさらに好ましい。上記範囲内であれば、含水率を認識しながら、混合の際に狭雑物中の粗粒子分を除去して使用することで、成形性が良好な混合物を得られるためである。
含水率は、乾燥減量方式である下記仕様の赤外線水分計を用い試料を乾燥(200℃、12分間)し、下記(2)式により求めた値である。
測定方式:乾燥減量法(加熱乾燥による質量測定方式)
最小表示:含水率;0.1質量%
測定範囲:含水率;0.0~100質量%
乾燥温度:0~200℃
測定精度:試料質量5g以上で、含水率±0.1質量%
熱源:赤外線ランプ;185W
珪藻土を含む混合物の成形体を焼成すると、200℃前後にて体積変化が起こり、焼成時又は焼成後の冷却時に割れや表面欠損が生じるおそれある。このため、混合物には、珪藻土を配合しないことが好ましい。「珪藻土を配合しない」とは、混合物全体に対して、珪藻土の配合量が、0~1質量%であり、0~0.1質量%が好ましく、0~0.01質量%がより好ましい。
フィラーの中でも、高融点ガラスの粒子が好ましい。高融点ガラスの粒子を用いることで、多孔質セラミックスの強度をより高められ、特に多孔質セラミックスの曲げ強度を高められる。
このような材質であれば、多孔質セラミックスの強度を十分に高められる。
アルミノケイ酸ガラスは、アルミニウムと珪素とを主成分とする酸化物ガラスである。
ホウケイ酸ガラスは、ホウ素と珪素とを主成分とする酸化物ガラスである。
石英ガラスは、石英から作製されるガラスで、酸化珪素の純度が高いものをいう。
このような高融点ガラスとしては、AN100(商品名、無アルカリホウケイ酸ガラス、旭硝子株式会社製)等が挙げられる。
高融点ガラスの粒子には、上記の製品の製造工程で排出される廃ガラスや、廃棄された液晶テレビ等から回収されるパネルを用いることができる。
高融点ガラスの粒子径は、多孔質セラミックスの生産性とさらなる強度の向上の観点から、0.6mm超1.2mm以下がより好ましい。
炭素繊維の太さは、多孔質セラミックスの形状等を勘案して決定でき、板状物であれば、例えば、1~1000μmが好ましく、5~100μmがより好ましい。上記下限値未満であると、多孔質セラミックスの強度を十分に高められないおそれがあり、上記上限値超であると、生産性が損なわれたり、多孔質セラミックスの外観が損なわれるおそれがある。
ロックウールの長さは、多孔質セラミックスの形状等を勘案して決定でき、板状物であれば、例えば、1mm~10cmが好ましく、5~25mmがより好ましい。上記下限値未満であると、多孔質セラミックスの強度を十分に高められないおそれがあり、上記上限値超であると、生産性が損なわれたり、多孔質セラミックスの外観が損なわれるおそれがある。
ロックウールの太さは、多孔質セラミックスの形状等を勘案して決定でき、板状物であれば、例えば、1~100μmが好ましく、3~30μmがより好ましい。上記下限値未満であると、多孔質セラミックスの強度を十分に高められないおそれがあり、上記上限値超であると、生産性が損なわれたり、多孔質セラミックスの外観が損なわれるおそれがある。
混合物中のフィラーの配合量は、多孔質セラミックス焼結体に求める強度等を勘案して決定でき、例えば、フィラーとして高融点ガラスの粒子を用いる場合、フィラー以外の原料の合計100質量部に対し、10~40質量部が好ましく、15~40質量部がより好ましい。上記下限値未満であると、多孔質セラミックス焼結体の強度を十分に向上できないおそれがあり、上記上限値超であると、成形性が損なわれるおそれがある。
また、混合物中のフィラーの配合量は、例えば、フィラーとして炭素繊維などの繊維状フィラーを用いる場合、原料100質量部に対し、0.01~20質量部が好ましく、0.01~10質量部がより好ましく、0.05~5質量部がさらに好ましく、0.1~2質量部が特に好ましい。上記下限値未満では、多孔質セラミックス焼結体の強度を十分に向上できないおそれがあり、上記上限値超では、成形性が損なわれるおそれがある。
また、有機汚泥から悪臭が生じる場合には、消臭剤を配合するとよい。消臭剤としては、例えば、塩化アンモニウム、塩化亜鉛等が挙げられる。このような成分の消臭剤を用いた場合には硫化水素等の臭いの成分を中和し、無臭化することができる。
添加剤の配合量は、本発明の目的を損なわない範囲で、添加剤の目的とする効果を勘案し添加すればよい。例えば、塩化アンモニウム、塩化亜鉛を消臭剤として用いた場合には、有機汚泥に対し0.05~5質量%とし、混合物中に0.005~1質量%とすることが好ましい。
各原料の投入順序は、組成に応じて適宜決定され、例えば、各原料を混合装置に一括で仕込み、混合してもよい。また、例えば、珪藻土を配合する場合、珪藻土と有機汚泥とを混合し、次いで、粘土他の原料を混合装置に順じ投入し、混合してもよい。
成形工程は、混合工程で得られた混合物を任意の形状に成形する工程である。
成形方法は、多孔質セラミックスの形状に応じて適宜決定され、例えば、成形装置を用いて任意の形状の成形体を連続的に得る方法、混合物を任意の形状の型に充填し成形体を得る方法、混合物を延伸又は圧延し、これを任意の形状に切断して成形体を得る方法が挙げられる。
例えば、板状又は角柱状の多孔質セラミックスを得る場合、真空土練成形機、平板プレス成形機及び平板押出成形機等が挙げられ、中でも真空土練成形機が好ましい。真空土練成形機を用いて成形体中の空気を除去することで、気孔を良好に制御できる。
成形体の大きさは、所望する多孔質セラミックスの大きさを勘案して決定できる。
焼成工程は、成形工程で得られた成形体を焼成して多孔質セラミックス焼結体を得る工程である。
焼成工程は、例えば、成形体を乾燥し(乾燥操作)、乾燥した成形体を焼成し(焼成操作)、粘土を焼結して多孔質セラミックス焼結体を得る方法が挙げられる。
乾燥操作は、特に限定されず、公知の方法を用いることができる。例えば、成形体を自然乾燥してもよいし、50~220℃の熱風乾燥炉で任意の時間処理することで乾燥してもよい。乾燥した成形体の含水率は、特に限定されないが、例えば、5質量%未満が好ましく、1質量%未満がより好ましい。乾燥後の成形体の含水率の下限値は、特に限定されず、0質量%であってもよい。
焼成の方法は特に限定されず、公知の方法を用いることができる。例えば、ローラーハースキルン等の連続式焼結炉、シャトルキルン等の回分式焼結炉を用い、任意の温度で焼成する方法が挙げられる。中でも、焼成には、生産性の観点から連続式焼結炉を用いることが好ましい。
混合物に有機汚泥等を配合し、焼成時に臭いが発生する場合、焼成装置には、脱臭装置を取り付けるとよい。脱臭装置としては、スクラバー脱臭装置やオゾン脱臭装置や光触媒等を用いた触媒脱臭装置等を挙げることができる。
例えば、組成例としてフィラー、珪藻土、粘土、スラグ、有機汚泥が含まれる場合、焼成温度は、フィラーが部分的に溶融し、珪藻土又は粘土が焼結され、有機汚泥に含まれる有機物が熱分解により揮発して減量し、スラグが膨張する条件とされる。前記組成例の成形体を焼成する場合の焼成温度は、例えば、950~1200℃が好ましく、1000~1100℃がより好ましい。有機物の多くは、700℃前後より分解が始まり、950℃において有機汚泥特有の臭いは、臭気成分が熱分解され解消されると共に、有機汚泥中の有機物の大部分が揮発して減量する。また、スラグの多くは800~950℃で結晶化により膨張する。有機物の減量、スラグの膨張により、気孔が形成される。
加えて、フィラーは、その溶融温度以上で部分的に溶融し、フィラー同士が融着したり、珪藻土又は粘土へ融着してバインダーとして機能する。こうしてフィラー同士が融着したり、フィラーがバインダーとして機能することで、多孔質セラミックスは、その骨格が補強され、諸特性を維持したまま、強度が向上したものとなる。
焼成温度が1200℃を超えると、多孔質セラミッス焼結体の組織全体のガラス化が進み、焼成中に成形体が破損したり、気孔が閉塞するおそれがある。
また、焼成温度に達した後の急激な冷却の際にも、多孔質セラミックス焼結体に割れや粉砕等の破損が生じることがあるが、焼成操作での温度勾配を調整することにより、冷却の際の破損を防ぐことができる。
研削工程は、焼成工程で得られた多孔質セラミックス焼結体の表面に研削加工を施す工程である。本工程を経ることで、得られる多孔質セラミックスは、長期間にわたって、透水性の低下が抑制される。
研削加工を施す方法としては、例えば、バーチカルミーリングマシーンPVシリーズ(アミテック株式会社製)等の切削機、グラインダー、サンドペーパー等で、多孔質セラミックス焼結体の表面を研削する方法が挙げられる。
例えば、板状の多孔質セラミックスを製造する場合、板状の多孔質セラミックス焼結体の厚さ方向の両面又は一方の面に研削加工を施すことが好ましい。通常、板状の多孔質セラミックスは、建築材料として用いられる場合、厚さ方向の一方の面が屋外に望むように施工される。研削加工が施された面は、長期間にわたって透水性の低下が抑制されるため、研削加工された面が屋外に望む面とされる。
表面に研削加工が施されることで、透水性の低下を抑制できる理由は不明であるが、以下のように推測される。多孔質セラミックス焼結体の表面は、焼成操作において温度が速く上昇し、ガラス化等によって、気孔が閉塞されたり、開孔径が小さかったり、内部に形成された気孔に連通していない気孔が多くなっていると推測される。このような多孔質セラミックス焼結体を建築材料として用いると、表面に形成された気孔は、侵入した微粒子により短期間に閉塞されると考えられる。
このため、微粒子により閉塞されやすい構造の表層が除去されることで、多孔質セラミックスは長期間にわたって透水性を維持できると考えられる。
実施例に用いた原料は、次の通りである。
<有機汚泥>
有機汚泥としては、染色工場(小松精練株式会社)の活性汚泥法による排水処理設備から凝集及び脱水工程を経て排出された活性汚泥を用いた。この活性汚泥の有機物含有量(対固形分)は83質量%、含水率は85質量%であった。
<粘土>
粘土としては、蛙目粘土(岐阜県産又は愛知県産)を用いた。
<スラグ>
発泡剤として、鋳鉄スラグを用いた。この鋳鉄スラグは、SiO2、Al2O3、CaO、Fe2O3、FeO、MgO、MnO、K2O、Na2Oを主成分とするダクタイル鋳鉄スラグである。
表1に示す組成でスラグ、有機汚泥、粘土及び水をミックスマラー(新東工業株式会社製)で混合し、可塑状態の混合物を得た(混合工程)。
次いで、得られた混合物を真空土練成形機(高浜工業株式会社製)で押し出し成形し、幅60cm、厚み2cmの帯状の一次成形体を得た。この一次成形体を任意のピッチと幅で切断して、厚み2cmの略正方形の平板状の成形体を得た(成形工程)。
得られた成形体を熱風乾燥機で乾燥(180℃、0.5時間)し、含水率1質量%以下とした後、連続式焼結炉を用いて、焼成温度1050℃、焼成温度での滞留時間7分間の焼成条件にて焼成した(焼成工程)。連続式焼結炉としては、ローラーハースキルン(焼結炉の有効長:全長15m、焼結炉を各1.5mのゾーン1~10に分割)を用いた。
焼成後、多孔質セラミックス焼結体の4つの側面に沿って側端を切除して、幅15cm×長さ15cm×厚み3.5cmの多孔質セラミックス焼結体とした。
得られた多孔質セラミックス焼結体の厚さ方向の一方の面の全体に、グラインダーで研削加工を施して、多孔質セラミックスを得た。研削加工においては、表面から2mmの深さまで研削した。
得られた多孔質セラミックスについて、比重、飽和含水率及び透水速度を測定し、その結果を表1に示す。
多孔質セラミックス焼結体に研削加工を施さなかった以外は、実施例1と同様にして多孔質セラミックスを得た。得られた多孔質セラミックスについて、比重、飽和含水率及び透水速度を測定し、その結果を表1に示す。
<比重>
ノギスを用いて、各例の多孔質セラミックスの長さ、幅、厚みを測定して体積(cm3)を求め、その多孔質セラミックスの絶乾状態の質量(g)を測定した。[絶乾状態の多孔質セラミックスの質量(g)]/[多孔質セラミックスの体積(cm3)]の式より、比重を求めた。
比重を測定した多孔質セラミックス(N=5)を水に60分間浸漬した後、表面を上にして、多孔質セラミックスを傾けずに水から取り出し(傾けた際に多孔質セラミックスから水が流れ出すことを防ぐため)、多孔質セラミックスの表面に付着している余剰水分を布で拭き、直ちに質量を測定(飽和状態質量)し、下記(3)式により求めた。
各例の多孔質セラミックスの表面(実施例1については、研削加工が施された面)にφ50mmの塩化ビニル製の円筒を立て、これを防水パテ(浴室パテ、トーヨーマテラン株式会社製)で固定した。多孔質セラミックスを水に60分間浸漬した後、水から取り出して、バット内においた。円筒内に水200mLを注ぎ入れ、注ぎ入れた水の水位が50mL分下がる時間を測定した(初期の透水時間)。
円筒内の水200mLの全てが多孔質セラミックスに浸透した後、粘土(平均粒径4μm)0.01gを水100mLに懸濁した粘土懸濁液を円筒内に注ぎ入れ、粘土懸濁液の全量が多孔質セラミックスに浸透するまで静置した(劣化処理)。本試験に用いた粘土は、黄砂と同等の粒径であり、円筒で囲われた領域に対する粘土0.01gは、1年間の黄砂降下量(5g/m2)に相当する。即ち、粘土懸濁液100mLを浸透させた多孔質セラミックスは、1年間、屋外で使用されたモデルである(表中、1年経過相当と記載)。
次いで、新たに水200mLを円筒内に注ぎ入れ、注ぎ入れた水の水位が50mL分下がる時間を測定した(1年経過相当の透水時間)。
この後、劣化処理と、水200mLを円筒内に注ぎ入れ透水時間を測定する作業とを繰り返した。測定した透水時間に基づき、下記(4)式で透水速度を求め、それらの結果を表1に示す。
図1~2に示すように、研削面10は、非研削面20に比べて大きい凹凸が形成されたものであった。
表1及び図3に示すように、本発明を適用した実施例1は、研削加工を施していない比較例1に比べ、初期から10年経過相当にわたって、速い透水速度であった。
加えて、実施例1は、10年経過相当における透水速度が、初期の透水速度の83.4%であったのに対し、比較例1は、10年経過相当における透水速度が、初期の透水速度の18.1%であった。
以上の結果から、本発明を適用した多孔質セラミックスは、長期間にわたって、透水性の低下を抑制できることが判った。
Claims (4)
- 粘土を含む混合物を成形し、焼結した多孔質セラミックス焼結体において、前記多孔質セラミックス焼結体の表面部分が研削加工により取り除かれたことを特徴とする多孔質セラミックス。
- 前記混合物は、発泡剤を含むことを特徴とする請求項1に記載の多孔質セラミックス。
- 粘土を含む混合物を成形し、焼結して多孔質セラミックス焼結体を得、前記多孔質セラミックス焼結体の表面に研削加工を施すことを特徴とする多孔質セラミックスの製造方法。
- 前記混合物は、発泡剤を含むことを特徴とする請求項3に記載の多孔質セラミックスの製造方法。
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JP2014221703A (ja) * | 2013-05-14 | 2014-11-27 | 小松精練株式会社 | 多孔質セラミックス焼成体 |
JP2015161158A (ja) * | 2014-02-28 | 2015-09-07 | 小松精練株式会社 | 排水構造 |
JP2016043038A (ja) * | 2014-08-22 | 2016-04-04 | 小松精練株式会社 | 脱臭装置および脱臭方法 |
JP6340126B1 (ja) * | 2017-10-03 | 2018-06-06 | 東京窯業株式会社 | ガス吹き用ノズルの製造方法およびガス吹き用ノズル |
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WO2016099234A1 (es) * | 2014-12-16 | 2016-06-23 | G-Cover De México, S.A. De C.V. | Recubrimiento ignífugo, aislante, ecológico e inhibidor de la corrosión |
RU2664288C1 (ru) * | 2017-08-01 | 2018-08-16 | Федеральное государственное бюджетное образовательное учреждение высшего образования "Тульский государственный университет" (ТулГУ) | Керамическая масса |
KR102156665B1 (ko) * | 2020-01-31 | 2020-09-16 | 문준희 | 다공성 세라믹 성형체의 제조방법 |
KR102398304B1 (ko) * | 2021-09-24 | 2022-05-17 | 주식회사 넷폼알앤디 | 퍼티재를 활용한 크랙보수층을 포함하는 콘크리트 구조물의 도장방법 |
KR102398289B1 (ko) * | 2021-09-24 | 2022-05-18 | 주식회사 넷폼알앤디 | 퍼티재를 활용한 콘크리트 구조물의 크랙보수층 |
KR102398296B1 (ko) * | 2021-09-24 | 2022-05-17 | 주식회사 넷폼알앤디 | 퍼티재를 활용한 콘크리트 구조물의 크랙보수층을 포함하는 유기계 방수층 |
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JP2015161158A (ja) * | 2014-02-28 | 2015-09-07 | 小松精練株式会社 | 排水構造 |
JP2016043038A (ja) * | 2014-08-22 | 2016-04-04 | 小松精練株式会社 | 脱臭装置および脱臭方法 |
JP6340126B1 (ja) * | 2017-10-03 | 2018-06-06 | 東京窯業株式会社 | ガス吹き用ノズルの製造方法およびガス吹き用ノズル |
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