JP4332605B2 - Humidity conditioning material and method for producing the same - Google Patents

Description

  The present invention relates to calcium silicate hydrate produced by the pozzolanic reaction of natural zeolite (hydration reaction of aluminosilicate with calcium ions such as cement and lime). In particular, the present invention relates to a highly functional and easily recyclable humidity control material that can provide a comfortable and safe indoor environment that is resource-saving, energy-saving, and a method for manufacturing the same.

  Japan's climate is subject to drastic changes in humidity and temperature, bringing high temperature and high humidity in summer, low temperature drying or low temperature and high humidity in winter, and recent architectural design is based on high airtightness and high heat insulation simply for the purpose of energy saving. In addition, mold and ticks are likely to occur when the humidity is high due to the sealed space, and health problems such as allergies and sick houses caused by volatile organic chemicals from interior building materials are becoming problems. Also, from the viewpoint of global environmental problems, CO2 reduction, the construction of a recycling society, etc. are required, and the high humidity environment promotes the decay of building materials, especially wood, leading to an increase in construction waste. Providing a comfortable and safe living environment and extending the life of buildings are important issues.

  As countermeasure technologies, the introduction of a forced ventilation system, the use of moisture-permeable materials, and regulatory measures based on the establishment of indoor environmental standards have been taken. Forced ventilation, including adjustment of humidity in the indoor space and formalin In order to reduce volatile organic chemicals, the equipment and running costs are high and insufficient, and it leads to an increase in energy consumption, so it is not a fundamental problem solving means from the viewpoint of global environmental problems.

  Under such circumstances, it has been advocated to use materials that have an autonomous humidity control function (humidity control materials) as interior building materials that absorb moisture when the relative humidity of the indoor space is high and release moisture when the relative humidity is low. In addition to the earth walls that have been used for Japanese architecture, diatomaceous earth, charcoal, and other materials have been reviewed as interior finishing materials and under-floor conditioning materials.

  However, conventional materials have low humidity control performance per weight and area, so the construction cost is high and design flexibility is limited. There is a need for wet materials.

  The mechanism of the humidity control function utilizes the capillary condensation action. In “Non-patent Document 1,” the pore diameter of the material corresponding to the humidity control action at a relative humidity of 40 to 70% that humans feel comfortable is approximately 2 From 6 to 6 nanometers, and the water vapor adsorption characteristics of various materials are reported and described.

  In addition, “Non-patent Document 2” outlines the criteria and problems of evaluation as a humidity control material, and it is preferable to use a material that has a large capacity of pores that contribute to humidity control and has high responsiveness to humidity. Has been.

  According to these documents, the humidity control material has many nano-level pores that exhibit a high humidity control function in the range of relative humidity of 40 to 70%, in particular, pores having a diameter of 2 to 6 nanometers. It can be understood that how to obtain the material is a fundamental technical problem.

  Conventionally, a painted wall material mainly made of natural minerals such as diatomaceous earth. Panel made by hydrothermal curing reaction using diatomaceous earth and slaked lime as main ingredients. Also, zonotlite (Ca6 (Si6O17) (OH) 2)), diatomaceous earth, fiber, which is a kind of calcium silicate hydrate crystal obtained by synthesizing a slurry of lime and silica sand by high-temperature hydrothermal treatment at 200 ° C or higher Various humidity control materials are manufactured, such as a calcite plate manufactured by papermaking press molding of materials (including inorganic fibers) and the like, and then drying.

  Humidity control boards and tiles that use pores generated by calcining water in the crystal structure of clay minerals such as allophane and sepiolite. Furthermore, although it is not a clay mineral, the humidity control material etc. which utilized the porosity and pore of siliceous shale represented by the Wakkanai shale are known.

  In particular, as in the case of using the zeolite as in the present invention, as described in “Patent Document 1” “Environmental Conditioning Material and Method for Producing the Same”, the water in the crystal pores of the zeolite does not lose its ion adsorption / exchange function. There is a humidity control material that uses zeolitic tuff preliminarily calcined at a temperature, mixes fiber materials, and is molded and cured by a dehydration press.

  Since these materials are basically simply a natural humidity control material supported by fibers or organic / inorganic binders, the humidity control function is based on the performance of the main material and the blending ratio of other materials. Depending on the type and strength, it depends on auxiliary materials such as fibers and binders.

  In addition, as described in “Patent Document 2”, “Humidity control building material and humidity control material”, a method of obtaining a humidity control material by using an aluminum sludge fired material and cement as raw materials has been proposed. The expressed pores are formed by dehydration of aluminum hydroxide, and the crystal, texture, formation method, and the like are also different from the present invention.

Journal of Clay Science, Sinji Tomura, Clay Science 10, 195-203 (1997) Building Materials Testing Center, Building Materials Testing Information 05, 4, P26-29 Takashi Iwasaki et al., Properties of mordenite tuff from the Aiko Plateau deposit, Aoba-ku, Sendai, Tohoku Industrial Technology Laboratory Report, No. 23, 1990, p18 Terao, et al., Characteristics and utilization of zeolitic tuff in Kawanishi area, Fukui city, 1998 Fukui Industrial Technology Center research report No15, p45-49 Urabe Kazunori et al., Thermal contraction and control of tobermorite, Cement Technology Annual Report 37, Showa 58 JP-A-6-24813 JP 2003-176128 A

  Since organic materials such as paper, wood, and charcoal used as building materials with humidity control function burn, there is a disadvantage that if you try to secure humidity control performance with inorganic non-combustible building materials, you have to use it as a soil wall. However, in addition to performance uncertainty due to soil quality, cost and workability, in order to obtain a large amount of pore capacity, the thickness and weight hinder the diversity of architectural design, and the response to humidity changes is low There is a problem.

  Moreover, since diatomaceous earth used as a typical humidity conditioning material is mainly made of natural raw materials, there are large variations in quality such as the raw material production area, mining place, pore distribution and quantity. In addition, the humidity control performance in the high humidity region is high, but the performance is low in the medium humidity region (relative humidity 40 to 70%) that humans feel comfortable. In addition to having a small cation exchange capacity, When the required strength is ensured by the addition, performance deterioration and performance fluctuation due to the additive blending conditions of the binder cannot be avoided.

  On the other hand, the calcite plate, which is used as a heat insulating material and is said to have an excellent humidity control function, is manufactured by papermaking press molding a mixed slurry of xonotlite crystals and fibers obtained by hydrothermal reaction of lime and silica sand. However, in order to increase the material strength, it is necessary to use various fibers and organic binders. In addition to the deterioration in performance, it is difficult to recycle with asbestos or similar substances.

  In the method described in “Patent Document 1” using zeolite as a raw material, since the main material is zeolite itself, a change in its purity directly leads to a change in performance, and a gel-like shape with low crystallinity due to the hydration reaction of cement. Because it is hardened with calcium silicate hydrate (hereinafter referred to as CSH), it has a large shrinkage and expansion rate due to changes in humidity, and increases the amount of cement to improve and stabilize humidity conditioning performance. It was difficult.

  In addition, as shown in the example of “Patent Document 2”, the method of using cement as an inorganic binder for the one obtained by firing aluminum sludge once at 300 to 900 ° C. requires much energy for production. In addition, there is a problem in recyclability as a valuable resource after disposal.

  In this way, the existing humidity control material that has the function of adsorbing and exchanging harmful volatile substances in addition to the humidity control function is not only high performance and stability, but also the efficiency of the manufacturing stage, cutting and use・ There are problems in the environment and safety at each stage of disposal, etc., and in terms of usefulness from the viewpoint of recycling, and there has been no material that can satisfy these issues comprehensively at a high level.

  Naturally, natural zeolitic tuff is mostly produced by diagenesis of acidic volcanic rocks such as rhyolite and pearlite in a high temperature and high pressure alkaline water environment. Many of these include crystals of clinobutyrolite, mordenite, or both as zeolite crystal minerals. Moreover, there are many glassy things which are not crystallized, and it is known that even in the same deposit, performance such as ion exchange capacity varies depending on purity and composition.

  The crystals of mordenite contained in typical zeolitic tuff are fibers having a length of several tens of microns and a width of about 0.2 to 0.5 microns, as is apparent from “Non-patent Document 3”, “Non-patent Document 4”, and the like. The crystal structure has about 7 angstroms of pores in the lengthwise direction, and has ion adsorption sites consisting of aluminum and oxygen tetrahedrons on the side. Water holes and metal ions are adsorbed in the pores, which show properties such as cation exchange capacity and moisture absorption capacity, and are used for soil improvement materials and underfloor moisture absorbents.

  In the present invention, in order to achieve high reactivity due to the mechanochemical effect, ultra-fine pulverization is performed as a mechanical treatment, so that a high level of pozzolanic reaction with calcium ions is performed on both raw materials that are mostly zeolitic and those that are not. Since the amount of calcium silicate hydrate with high crystallinity is high and constant, the problem is solved that the content of zeolite causes fluctuations in performance as a humidity control material. Therefore, it is possible to obtain a humidity control material that is high and has little performance variation.

  In particular, the crystals of mordenite are fibrous with a length of 10 microns or more, so if the fine tuff containing this is pulverized to 10 microns or less, the zeolite crystals will be damaged and the surface will have increased crystal lattice defects. Because it is activated by the effect, the pozzolanic reaction with calcium ions progresses further with an increase in surface area.

  Furthermore, the reaction proceeds from the inside of the pores, which are the main ion exchange sites of the zeolite crystal, and as a result, the reaction rate is extremely high and the reaction proceeds even under low temperature and low pressure conditions.

  The hydration reaction between silica and calcium proceeds even at normal temperature and pressure, as represented by cement hydration. However, it is said that it takes about 3 years for Portland cement to complete the reaction, and about 4 weeks for the reaction rate to reach about 80%. The reaction product is also low in crystallinity and gelled C—S—H, and has a large shrinkage on drying, so that cracks are likely to occur in the drying and firing processes.

  Regarding the composition and thermal shrinkage of tobermorite, there is a study of “Non-patent Document 5”, and it is reported that the heat loss of tobermorite is reduced when a large amount of Si in the crystal structure is substituted with Al.

  In addition, the product calcium silicate hydrate becomes dense when the production rate is slow, and as a result, the formation of nano-level crystal gaps is small. In the present invention, however, the mechano- CSH, which is a calcium silicate hydrate with good crystallinity that has a composition of 0.8 to 1.33 CaO · SiO 2 · XH 2 O by chemical effect and hydrothermal treatment at 180 ° C. or less using steam curing or autoclave. I) and plate-like tobermorite are rapidly generated, resulting in a porous cured body with many nano-level pores that are optimal as humidity control materials in a short time even under low-temperature and low-pressure conditions, and dehydration by drying and firing. Shrinkage due to can also be reduced.

  Furthermore, this hardened body becomes a hardened body having high cation adsorption capacity because the ion adsorption sites are increased by substituting silicon in the crystal structure of calcium silicate hydrate and entering aluminum.

In addition, when silicic plant ash is used as a pozzolanic material, the silicic acid content in the plant is amorphous, so it is highly reactive with calcium ions. In addition to the increase in non-surface area, the formation of pores similar to activated carbon and the characteristics of surface functional groups result in a cured product having a high adsorption ability for hydrophobic substances such as organic solvents.

  If the pozzolanic reaction-cured product is heat-dried or calcined at a low temperature as a process, free water and pore water between crystal grains are removed by drying at 110 ° C., and pores are formed. The humidity control function is exhibited by the capillary condensation action corresponding to the pore diameter. If the crystal structure is decomposed and sintered at a higher temperature in the range up to the temperature at which the sintering starts, water bonded to hydrogen between the crystal layers and the surface of the gaps disappears and a humidity control material is obtained.

  According to the present invention, unlike the prior art, by utilizing the mechanochemical effect by ultra-fine grinding treatment, the high reactivity of silicic acid in plant ash, etc., by significantly increasing the rate and rate of pozzolanic reaction with calcium ions To produce crystals such as CSH (I) and tobermorite, which have many pore-sized mesopores that contribute to the humidity control function in the middle humidity range, at a temperature and pressure lower than the conventional production conditions, and dry or calcinate them. Thus, there is an advantage that a humidity control material having high humidity control / ion adsorption function and cation exchange ability and having stable performance without being affected by variations in the quality of natural zeolite.

  In addition, the feature of the production technique of the present invention is different from the conventional one in which pre-calcined zeolite or aluminum sludge having a large particle diameter or zonotlite particles synthesized by slurry hydrothermal method are supported on other materials. Since the molded body is cured by hydrothermal treatment and then dried or fired, a humidity control material with little dimensional change due to humidity change is obtained, and less energy is required for production. It is a highly functional and multifunctional material that also has functions, and has the advantage that recycling after disposal can be used as a soil improvement material, environmental purification material, etc. by simple processing of the degree of pulverization.

  As the zeolitic tuff used as a siliceous starting material, a clinoptilolite system has an ion exchange / adsorption function as well, but this may be used, but a mordenite system is desirable. In addition, since a large amount of crystal components such as quartz and feldspar affects the reaction rate, a raw material with a small amount of these is preferable.

  Although it is necessary to control the reaction by adjusting the degree of grinding and hydrothermal treatment conditions, the grinding treatment conditions are such that the average particle size at which the fibrous morphology collapses is 10 microns or less, and in particular, ultrafine grinding is performed so that the number of submicron level particles increases. To do.

  The raw material for siliceous plant ash is Susuki, straw, and other rice plants, but rice husk ash containing residual carbon is the best for securing large quantities.

  The blending ratio of silicate mineral raw materials such as zeolite and calcium-based raw materials such as cement takes into account the balance between the types and amounts of other raw materials, the degree of grinding, processing time, manufacturing efficiency, and performance. However, as unreacted calcium increases, the size and performance fluctuate with time and aging. Therefore, the blending ratio is sufficient so as not to generate excess free calcium so as not to be affected.

  Further, as the calcareous raw material, Portland cement, quick lime, slaked lime, or a mixture of at least one of them is used, and an autoclave treatment at 180 ° C. and 10 atm is desirable.

  Control of dehydration shrinkage is important in the drying or firing process of the cured product, and in order to prevent cracking, it is best to control by mixing inorganic fiber materials and coarse particles, and the construction method is nailing or screwing In such a case, it may be adjusted according to the type and blending amount of the fiber material. Further, the drying / calcination treatment temperature of the cured body is preferably 415 ° C., which is the dehydration decomposition temperature of calcium hydroxide, and the dehydration of tobermorite is almost completed at about 400 ° C. The treatment conditions below this are desirable.

Further, for improving the color tone and increasing the number of colors, white Portland and colored pigments may be used. When carbonized plant ash is blended, the surface carbon may be removed after curing by heat treatment or the like.

  In order to confirm the effectiveness of finely pulverized zeolitic tuff, a fly ash having almost the same chemical composition as that of the fly ash was used, and a reaction experiment with ordinary Portland cement was conducted under the composition and treatment conditions shown in Table 1 to control humidity. The (water vapor adsorption characteristics) were compared.

  Zeolite tuff, a pozzolanic material blended in Portland cement, is finely ground with a hammer mill to an average particle size of 7 microns. According to XRD analysis, the mineral composition is mordenite, amorphous, feldspar / quartz. Contains trace amounts of kaolin and the like. Fly ash is discharged from a thermal power plant and has an average particle size of 20 microns, an amorphous mineral composition, mullite, cristobalite, and the like.

  Further, after the compound was filled into a mold, the cured product obtained by hydrothermal treatment conditions of steam curing at 60 ° C. for 2 hours and autoclave curing at 180 ° C. for 4 hours was wet-cured for 4 weeks. Then, it dried at 110 degreeC and measured the water vapor | steam adsorption isotherm.

  From Fig. 1, the zeolitic tuff pulverized product has a higher maximum moisture absorption and higher moisture absorption / release performance against changes in the middle humidity range than the similar pozzolanic material fly ash. The effectiveness of the finely pulverized product was confirmed.

  Moreover, as a result of identifying the mineral composition by X-ray diffraction analysis and observing them with an electron microscope, the fly ash is mostly C—S—H, which is a gel-like calcium silicate hydrate, even in steam curing. Tobermorite strip-like crystals could not be confirmed even in the oclave-treated product, but in the case of zeolitic tuff, there were many strip-like tobermorite crystals and it was confirmed that the reactivity with calcium was high. In addition, a difference in reactivity was also confirmed by comparing the amount of CSH (I) crystals produced in the steam-cured product.

  Furthermore, Table 2 shows the results of measuring the cation exchange capacity of the main raw material zeolitic tuff and the above test specimen.

  From this, it was confirmed that when finely pulverized zeolitic tuff is blended, it exceeds 50 meq / 100 g, which is a standard certified as a soil improvement material, and a very high performance can be obtained compared to fly ash.

  In order to confirm the effect of the mixing conditions of zeolitic tuff and calcium-based raw materials, the pulverization degree of zeolitic tuff on the reactivity with calcium ions and the humidity control function, in an autoclave after steam curing treatment at 60 ° C for 2 hours A test body obtained by wet curing the cured body obtained by treating at 180 ° C. for 4 hours for another 2 weeks was dried at 110 ° C., and the relative humidity ranged from 43% to 69% (medium humidity) in accordance with the JIS standard desiccator method. Area). Further, the total pore volume, the average pore diameter, and the specific surface area as an index of the adsorption capacity, which are comparative standards for humidity control performance, are also measured by the BET method, and the results compared with the conventional commercial products are shown in Table 3.

  From these results, the humidity control material of the present invention exceeds the commercial products in all items such as the total pore volume, the moisture absorption performance and the moisture release performance, which are performance indicators, and the pulverization degree of the zeolite tuff from the results of No10 It was proved that the higher the humidity, the higher the humidity control performance. Moreover, in the measurement result by BET method, it has also confirmed that it exceeded a commercial item by obtaining the hardening body from which an average pore radius becomes 10 nanometers or less.

  In order to confirm the effect of the difference between the calcareous raw material and the pozzolanic substance on the humidity control function, reaction experiments and evaluation tests were conducted under the same conditions as in Example 4 using slaked lime as the lime-based raw material and rice husk charcoal as the pozzolanic substance. went.

  As a result, in order to produce tobermorite, the total pore volume of 0.50 cm3 / g, an average pore radius of 9.3 nm, and a humidity control performance of 8.5 mg / g.

In the measurement result of the water vapor adsorption isotherm in Example 1, the solid line is a finely pulverized zeolite tuff, and the broken line is a fly ash, and shows a comparison of moisture absorption and desorption characteristics depending on the type of pozzolanic material and hydrothermal treatment conditions. ing.

Claims (2)

A blend comprising 100 parts by weight of zeolitic tuff finely pulverized to an average particle size of 10 microns or less and 100 to 150 parts by weight of Portland cement, quick lime, slaked lime or at least one mixture thereof as a lime-based raw material. A humidity control material obtained by heat-dehydrating a cured product of calcium silicate hydrate containing CSH (I) or tobermorite crystals produced by hydrothermal reaction, and having an average pore radius of 10 nanometers or less inside A humidity control material, wherein the pores are formed to be 0.18 cm ³ or more per gram. To 100 parts by weight of zeolitic tuff finely pulverized to an average particle size of 10 microns or less, 100 to 150 parts by weight of Portland cement, or quick lime or slaked lime with the same amount of calcium released by hydration as water is added. Step of compounding, step of reactive hardening of calcium silicate hydrate containing CSH (I) or tobermorite crystals by hydrothermal treatment at 180 ° C for 4 hours, heat dehydration at a temperature of 110 ° C to 400 ° C A method for producing a humidity control material, comprising a step.

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