JP5294249B2 - Porous free-standing clay film and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous self-supporting clay film excellent in not only heat resistance but also thermal insulation properties and a method for producing the porous self-supporting clay film. <P>SOLUTION: The porous self-supporting clay film is based on clay, has such a structure that clay layered crystals are layered on one another, is used as a self-supporting film, has a void among the adjacent clay layered crystals, and has a hole which penetrates the clay layered crystals and reaches the surface of the clay film. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a porous self-supporting clay film excellent in heat resistance and heat insulation and a method for producing the same.

  In general, various production processes under high temperature conditions are used in many industrial fields. Therefore, various heat-resistant and heat-insulating host materials such as inorganic porous films such as alumina porous bodies and organic polymer films such as polyolefin porous films are used as membranes. Various chemical substances such as a catalyst, an enzyme, and an adsorbent are encapsulated in this membrane, and catalytic reaction, adsorption, separation reaction, and the like are performed. It is also used by wrapping around high temperature piping. However, although the inorganic porous membrane has high heat resistance, it is not flexible. On the other hand, the organic polymer membrane has excellent flexibility, but there is a membrane material that is inferior in heat resistance and has both flexibility and heat resistance. There was a problem of not doing.

From such a point of view, various studies have been made by paying attention to clay, which is an inorganic material, and the present inventors have made a clay thin film having a mechanical strength that can be used as a self-supporting film in which clay crystals are laminated and oriented (patented) Documents 1, 2) and a flexible clay film having a structure in which clay layered crystals are laminated and can be used as a self-supporting film have been developed (Patent Document 3).
JP 2005-104133 A JP 2006-77237 A JP 2006-188418 A

  The clay thin films described in Patent Documents 1 and 2 have excellent flexibility and mechanical strength, but are not porous and have no heat insulating properties. On the other hand, the clay film described in Patent Document 3 is a self-supporting film and is porous. However, the porous clay film is manufactured by a method in which the clay film is wet and foamed by rapid heating. However, the structure of the film is not uniform and significant warpage occurs, so it cannot be used as a heat insulating sheet material. there were.

  Therefore, the subject of this invention is providing the porous self-supporting clay film which is excellent not only in heat resistance but also in heat insulation, and its manufacturing method.

  Therefore, the present inventor has made various studies to overcome the above-described drawbacks of the porous clay film. First, as a result of examining the structure of this porous clay film, the clay film is heated to evaporate water to form a porous structure having voids between clay layers. The film itself has an extremely excellent gas barrier property. Therefore, it has been found that there is no escape space for excess moisture, and the membrane surface is destroyed as the moisture evaporates (foaming), resulting in non-uniform foaming and at the same time significant warping of the membrane. Therefore, as a result of further investigation, by performing fine hole processing on the clay film before foaming, the growth of voids at the processed hole position is suppressed, and excess gas is released from the processed part, so the foam size is reduced. As a result, it was found that a porous clay film with uniform voids inside the film can be obtained. Moreover, the obtained porous clay film was found to have a uniform shape, almost no warpage and the like, and excellent heat resistance and heat insulation performance, thereby completing the present invention.

That is, the present invention is composed of clay as a main component, has a structure in which clay layered crystals are laminated, can be used as a self-supporting film, has voids between clay layered crystals, and penetrates the clay layered crystals The present invention provides a porous self-supporting clay film characterized by having pores reaching the surface of the clay film.
Moreover, this invention provides the heat insulation sheet material which consists of the said porous self-supporting clay film.
Furthermore, the present invention is to disperse a raw material containing clay as a main component in water or a liquid containing water, obtain a uniform clay dispersion, and inject the dispersion into a container or apply it to the surface of an object, and then disperse the dispersion medium. The present invention provides a method for producing a porous self-supporting clay film, wherein a clay film is produced by removing the liquid, and the clay film is subjected to a fine hole forming process and then subjected to a heat treatment. .

  Since the porous self-supporting clay film of the present invention has uniform voids between the clay layered crystals, the thermal conductivity of the film plane is uniform, has excellent heat insulation, and can be used as a self-supporting film. Since it has strength and flexibility, and its film shape is uniform and does not warp, it is useful as a heat-resistant sheet material, particularly a heat-insulating sheet material. In particular, it is useful as a heat insulating sheet material that can be used by wrapping around high-temperature piping and heat utilization equipment in an industrial plant.

  The porous self-supporting clay film of the present invention is composed of clay as a main component, has a structure in which clay layered crystals are laminated, can be used as a self-supporting film, has voids between clay layered crystals, and the clay It has pores that penetrate the layered crystal and reach the surface of the clay film.

  The main component of the porous self-supporting clay film of the present invention is natural clay or synthetic clay. Examples of main constituents of the clay film include mica, vermiculite, montmorillonite, iron montmorillonite, beidellite, saponite, hectorite, stevensite, and nontronite. Examples of additives other than clay include a reinforcing material, a monomer that performs thermal polymerization, and a thermosetting polymer. Examples of the reinforcing material include mineral fiber, glass wool, carbon fiber, ceramic fiber, and vegetable fiber. The weight ratio of the additive to the total solid is preferably 30% or less, and the weight ratio of the reinforcing material to the total solid is preferably 30% or less. In the present invention, the content ratio of clay is preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more.

  The porous self-supporting clay film of the present invention has a structure in which clay layered crystals are laminated. Here, the clay layered crystal means that the clay crystal particles form a layer, and means that a layer is formed as shown in FIG. 1 of JP-A-2006-188418.

  The porous self-supporting clay film of the present invention can be used as a self-supporting film, that is, as a film itself without being supported on any solid.

  The porous self-supporting clay film of the present invention has voids between clay layered crystals. This void means having a layered void between layers of clay crystal particles as shown in FIG. 1 of JP-A-2006-188418. By having the voids, excellent heat insulating properties are imparted to the clay film of the present invention. Here, the thickness of the clay crystal particle layer and the gap thickness between the layers are both in the order of micrometers and nanometers and are highly oriented. The preferred layer thickness of the clay layered crystal is 0.1 to 5 nm, the major axis is 0.1 to 10 μm, and the aspect ratio is about 100 to 500. More preferably, the layer thickness of the clay layered crystal is about 0.5 to 5 nm, the major axis is 1 to 10 μm, and the aspect ratio is 200 to 400. The gap thickness between the layers is preferably 0.5 to 30 μm, more preferably 1 to 20 μm. It is a feature of the porous self-supporting clay film of the present invention that the voids between the layers are uniform throughout the clay film, and the homogeneity of the voids is achieved by forming the following through holes.

  The porous self-supporting clay film of the present invention has pores that penetrate the clay layered crystal and reach the surface of the clay film. This hole is perpendicular to the layer of clay crystal particles. Due to the presence of the through hole, the disadvantages in the step of forming the gap between the layers in the prior art are eliminated. In other words, the formation of voids between layers is performed by evaporating moisture present between the layers, but when there is no through hole, there is no escape space for excess moisture, so that the film surface is destroyed (for example, JP No. 2006-188418, as in the film surface structure of FIG. 1), the foam size becomes non-uniform, and the film is significantly warped. On the other hand, in the present invention, since the through holes are formed, moisture existing between the layers evaporates to form voids between the layers, and at the same time, excess water vapor escapes out of the film through the through holes. It becomes homogeneous and the shape of the membrane is also uniform.

  The through-holes preferably have a pore diameter of 1 mm or less, more preferably 0.1 mm or less, and particularly preferably 0.05 mm or less from the viewpoints of preventing the heat insulating property of the resulting porous self-supporting clay film from being deteriorated, maintaining mechanical strength, and preventing warpage. Also, the interval (pitch) between the through holes is preferably 1 to 3 mm, more preferably 1.5 to 3 mm, and particularly preferably 2 to 3 mm for the same reason. Further, it is preferable that the interval between the through holes is uniform for the same reason as described above. In addition, although this through-hole should just reach any one of the surface of this invention clay film, you may penetrate from the surface to the back surface.

  The porous self-supporting clay film of the present invention has mechanical strength and flexibility that can be used as a self-supporting film. The film thickness is preferably 5 to 3000 μm, more preferably 50 to 2000 μm, and particularly preferably 500 to 1500 μm. The porosity is preferably 20 to 80%, particularly preferably 20 to 70%. Moreover, heat resistance is 600 degreeC or more, and tensile strength is equivalent to a polypropylene, ie, 30-40 MPa. Regarding heat resistance, the porous self-supporting clay film of the present invention has a characteristic that no structural change occurs at 250 ° C. or more and 600 ° C. or less.

  The porous self-supporting clay film of the present invention has a thermal conductivity of 0.01 to 0.1 W / mK, more preferably 0.01 to 0.1 W / mK, and particularly 0.03 to 0.1 W / mK. Is preferred. This thermal conductivity is comparable to that of still air. Since it has such thermal conductivity, it is useful as a heat insulating sheet material that requires particularly excellent heat resistance.

  In the porous self-supporting clay film of the present invention, a raw material mainly composed of clay is dispersed in water or a liquid containing water to obtain a uniform clay dispersion, and this dispersion is poured into a container or applied to the surface of an object. After that, the liquid that is the dispersion medium is removed to produce a clay film, and the clay film is manufactured by subjecting it to a fine hole punching process, followed by heat treatment.

  The raw materials mainly composed of clay are the same as the constituent components of the above-mentioned clay film of the present invention. As a dispersion medium of these raw materials, water or a liquid containing water is used, and water, an aqueous alcohol solution, or the like can be given. The concentration of the clay dispersion is suitably 0.5 to 15% by weight, more preferably 1 to 10% by weight. At this time, if the concentration of the clay dispersion is too thin, there is a problem that it takes too long to dry. Further, when the concentration of the clay dispersion is too high, clay does not disperse well, so that there is a problem that the orientation of clay particles is poor and a uniform film cannot be formed.

  If necessary, a weighed solid or liquid additive is added to the clay dispersion to prepare a uniform dispersion. The additive is not particularly limited as long as it is a thermopolymerizable monomer or a thermosetting polymer. For example, one or more of epsilon-caprolactam and polyhydric phenol can be used. The weight ratio of the additive to the total solid is 30% or less, preferably 1 to 10%. At this time, if the ratio of the additive is too low, the effect of the addition does not appear, and if the ratio of the additive is too high, the distribution of the additive and the clay becomes uneven in the prepared film, and the resulting clay The uniformity of the film is lowered and the effect of addition is also diminished.

  If necessary, a weighed reinforcing material is added to the clay dispersion to prepare a uniform dispersion. As the reinforcing material, one or more of mineral fiber, glass wool, carbon fiber, ceramic fiber, and vegetable fiber resin can be used. The weight ratio of the reinforcing material to the total solid is 30% or less, preferably 1 to 10%. At this time, if the proportion of the reinforcing material is too low, the effect of addition does not appear, and if the proportion of the reinforcing material is too high, the distribution of the reinforcing material and the clay becomes uneven in the prepared film, and the resulting clay The uniformity of the film is lowered and the effect of addition is also diminished. Note that the order of addition of the reinforcing material and the additive is not determined first, and either may be added first.

  Next, after pouring this dispersion into a container or applying it to the surface of an object, the liquid as a dispersion medium is removed by drying to produce a clay film. As a method for producing a clay film, for example, a liquid which is a dispersion liquid is slowly evaporated to form a film. There is a method of applying a dispersion liquid on the surface of a support and drying and removing a liquid as a dispersion medium. As a method for drying and removing the liquid as a dispersion medium, for example, various solid-liquid separation methods such as centrifugation, filtration, vacuum drying, freeze vacuum drying, heat evaporation, or a combination of these methods can be used. It is. Among these methods, for example, when the dispersion is poured into a container and the heating evaporation method is used, the concentration of the clay is adjusted to 0.5 to 3% by weight, and the dispersion deaerated in advance is preferably a flat tray, preferably Is poured into a support such as a plastic or metal tray and kept in a horizontal state in a forced air oven at a temperature of 30 to 70 ° C, preferably 30 to 50 ° C. Dry for about 3 hours to half a day, preferably 3 to 5 hours to obtain a clay thin film.

  As another example, when the dispersion liquid is applied to an object and the heating evaporation method is used, the clay concentration is adjusted to 4 to 7% by weight, and the dispersion liquid that has been deaerated in advance is placed on a flat metal plate. To a thickness of 2 mm, and for 10 minutes to 2 hours, preferably 20 minutes to 1 hour under a temperature condition of 30 to 70 ° C., preferably 30 to 50 ° C. in a forced air oven. Dry to obtain a clay film.

  If the dispersion is not degassed in advance, there may be a problem that pores derived from bubbles are easily formed in the clay thin film. The drying conditions are set so as to be sufficient to dry and remove the liquid component. At this time, if the drying speed is too slow, there is a problem that it takes time to dry. Further, when the drying rate is too high, there is a problem that convection of the dispersion occurs and the uniformity of the clay film is lowered. The thickness of the clay film can be obtained by adjusting the amount of solid used in the dispersion liquid.

  In the present invention, the drying condition by the heat drying method is preferably about 30 to 70 ° C., more preferably about 30 to 50 ° C. for about 10 minutes to half a day in a forced air oven. More preferably, the drying is for about 10 minutes to 5 hours.

  When the clay film is used as a self-supporting film, the clay film is peeled off from the container or the object surface to obtain a clay self-supporting film. In the case where the clay thin film does not naturally peel from a support such as a container, the peeling is preferably promoted by evacuation to obtain a self-supporting film. Moreover, as another method of peeling, it is preferably dried under a temperature condition of about 110 to 200 ° C. to facilitate peeling and obtain a self-supporting film. At this time, if the temperature is too low, there is a problem that peeling does not easily occur. When the temperature is too high, there is a problem that the additive tends to deteriorate.

  In the present invention, fine drilling is performed on the clay film obtained here. The drilling process may be a process of penetrating the entire clay film, or may be penetrated about half from one side and about half from the other side. As described above, it is preferable to form holes with a hole diameter of 1 mm or less, further 0.1 mm or less, and particularly 0.05 mm or less at a predetermined interval. The interval between the holes is preferably 1 to 3 mm, more preferably 1.5 to 3 mm, and particularly preferably 2 to 3 mm. The hole pattern is not particularly limited as long as it is a uniform pattern such as a lattice shape, a concentric circle shape, a radial shape, or a turtle shell shape. It is easy to make a hole using a needle-shaped punch.

  Next, the clay film or the clay free-standing film is stored in a forced convection oven maintained at a temperature near room temperature and a relative humidity of 40 to 90%. At this time, as long as the above temperature and humidity conditions are obtained stably, it does not necessarily have to be in a forced convection oven. The clay stored under the above conditions contains moderate moisture, and this moisture becomes vapor during the heat treatment described later, resulting in voids in the film. At this time, when the relative humidity is lower than 5%, the water content of the clay is not sufficient, and as a result, the intended porous film cannot be obtained. Further, when the relative humidity is higher than 95%, there is a problem that the water content of the clay is excessive and a uniform porous film cannot be obtained. The storage time is desirably 10 seconds to 3 days.

  Next, the clay film or the clay self-supporting film is rapidly heated to vaporize water contained in the clay, and if necessary, a thermopolymerizable monomer is polymerized or a thermosetting resin is cured. As an apparatus used for this treatment, a hydraulic press capable of heating a ram, a microwave oven, and the like are conceivable, but this is not limited as long as the purpose of rapid heating is achieved. When the sample is slowly heated in a forced convection oven or the like, the temperature of the sample gradually increases, so that the internal moisture is dried up to a temperature of 200 ° C. or higher, or a thermosetting temperature, and as a result, voids are not generated. At this stage, in the present invention, since fine hole punching is performed, the evaporation of water (foam size) becomes uniform, and the shape of the film and the gap between layers become uniform.

The clay self-supporting film of the present invention can be easily cut into an arbitrary size and shape such as a circle, a square, and a rectangle with, for example, scissors and a cutter. The clay free-standing film of the present invention preferably has a thickness of less than 1 mm and an area of more than 1 cm ² . The clay film of the present invention has mechanical strength that can be used as a self-supporting film, has high flexibility, high heat resistance, is porous, is non-conductive to electricity, and has a thermal conductivity. It has a feature that it is low, can contain various chemical substances inside the film, and the film is uniform. Further, since the clay film of the present invention has a structure in which clay layered crystals are laminated, fine fibers such as glass wool and rock wool do not fall, and safety is also good.

  Therefore, the clay self-supporting film of the present invention is particularly useful as a heat-resistant insulating film and a heat-insulating sheet material in addition to a catalyst carrier and an enzyme carrier.

Next, the present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Example 1
(1) Manufacture of clay film As clay, 0.95 grams of natural montmorillonite (Kunipia P, manufactured by Kunimine Kogyo Co., Ltd.) is added to 60 cm ³ of distilled water, and sealed in a plastic sealed container made of Teflon (registered trademark). It was put together with the child and shaken vigorously to obtain a uniform dispersion. An aqueous solution containing 0.05 g of epsilon-caprolactam (manufactured by Wako Pure Chemical Industries, Ltd.) as an additive was added to this dispersion, and the resulting dispersion had a flat bottom and a round bottom. Yes, poured into a brass tray with a diameter of about 15 cm, the dispersion is allowed to stand horizontally, clay particles are slowly deposited, and the tray is kept horizontal in a forced air oven. It was dried for 5 hours under a temperature condition of 50 ° C. to obtain a uniform water-soluble polymer composite clay thin film having a thickness of about 30 μm. The produced clay thin film was peeled from the tray to obtain a clay film. The clay film is cut into 10 cm square, stored in an oven at a temperature of 20 ° C. and a relative humidity of 70% for 12 hours, then sandwiched between aluminum foils and heated at 250 ° C. for 30 minutes while being pressurized with a hydraulic press at 200 kN. Thus, a white porous clay film was obtained.

  Fine holes were processed on the entire surface of the clay film (t = 50 to 70 μm) at intervals of 0.5, 1, 2, 3, 4 mm, respectively, and the water content was adjusted to about 20% in a high humidity environment at 80 ° C. for 20 minutes. Thereafter, foaming was performed in a microwave oven (500 W for 2 minutes). About the obtained foamed film, the heat conductivity was measured with a HotDisk thermophysical property measuring apparatus (Kyoto Electronics Co., Ltd. TPA-501), and the appearance was evaluated by visual evaluation.

  The thermal conductivity and appearance evaluation results of the foamed film are shown in Table 1 and FIG. Table 2 shows the results of preliminary examination of humidification conditions using small pieces.

From Table 1 and FIG. 1, by performing hole processing on the clay film before foaming, the maximum blister size in the foaming process showed a tendency that the circle in contact with the processed hole became the upper limit size. In addition, as the drilling interval narrowed, the individual bubble size became constant and the warpage of the film also decreased.
From the results of thermal conductivity measurement, by performing hole machining at intervals of 2 mm or more, the thermal conductivity showed the same value as the unprocessed foam film.
Further, the moisture content of the clay film before the foaming treatment has a great influence on the foamed shape, and the condition that the moisture content is about 20% was suitable. However, when humidifying for a long time or when the film was in direct contact with water, the foaming was apt to be poor due to the weakening of the film.

It is a figure which shows the relationship between a hole process and the external appearance change of the obtained porous self-supporting clay film.

Claims (7)

It is composed of clay as a main component, has a structure in which clay layered crystals are laminated, can be used as a self-supporting film, has voids between clay layered crystals, penetrates the clay layered crystals, and is on the surface of the clay film A porous self-supporting clay film characterized by having reaching holes with a gap of 1 to 3 mm .   The porous self-supporting clay film according to claim 1, wherein the pore diameter of the holes penetrating the clay layered crystal and reaching the surface of the clay film is 1 mm or less. The porous self-supporting clay film according to claim 1 or 2, which has mechanical strength and flexibility usable as a self-supporting film. The porous self-supporting clay film according to any one of claims 1 to 3 , which has a thermal conductivity of 0.01 to 0.1 W / mK. The porous self-supporting clay film according to any one of claims 1 to 4 , wherein voids between the clay layered crystals are uniform throughout the clay film. The heat insulation sheet material which consists of a porous self-supporting clay film of any one of Claims 1-5 . Disperse the raw material containing clay as the main component in water or a liquid containing water to obtain a uniform clay dispersion, and then inject the dispersion into a container or apply it to the surface of the object, then remove the liquid as the dispersion medium. Then, a clay film is produced, and the clay film is finely perforated , stored at a temperature near room temperature and in a range of 40 to 90% relative humidity , and then heat-treated . 6. The method for producing a porous self-supporting clay film according to any one of 5 above.