JP2016047791A - Layering double hydroxide oriented dense sheet and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably and efficiently provide and manufacture a layering double hydroxide oriented dense sheet having not only a high level density but also a high level orientation property in a sheet thickness direction.SOLUTION: There is provided a layering double hydroxide oriented dense sheet which is a sheet consisting of layering double hydroxide having 90% or more of relative density and represented by the general formula: MM(OH)AmHO, where Mis a bivalent cation, Mis a trivalent cation, Ais n valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, and having a ratio of integrated intensity of a peak of a (110) face to integrated intensity of a peak of a (003) face, (110)/(003), when X ray diffraction is conducted on a sheet face of the oriented dense sheet of 0.7 or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a layered double hydroxide oriented dense plate and a method for producing the same.

  Layered Double Hydroxide (hereinafter referred to as LDH) typified by hydrotalcite is a group of substances having anions that can be exchanged between hydroxide layers. It is utilized as a catalyst, an adsorbent, or a dispersant in a polymer for improving heat resistance. In recent years, it has attracted attention as a material that conducts hydroxide ions, and addition to an electrolyte of an alkaline fuel cell or a catalyst layer of a zinc-air cell is also being studied. For example, Patent Document 1 (International Publication No. 2010/109670) proposes using a layered double hydroxide film as an alkaline electrolyte film of a direct alcohol fuel cell.

  When considering a catalyst or the like which is a conventional application field, since a high specific surface area is necessary, synthesis and use in a powder form is sufficient. On the other hand, when considering application to an electrolyte utilizing hydroxide ion conductivity such as an alkaline fuel cell, the denseness is important in order to prevent mixing of the fuel gas and obtain a sufficient electromotive force.

  However, although layered double hydroxides have recently attracted attention as hydroxide ion conductors, they are hydroxides and cannot be densified by firing, and most of them are synthesized as powders. Therefore, the current situation is that the evaluation of the electrolyte of the alkaline fuel cell so far is carried out with a green compact obtained by solidifying the powder. In fact, the alkaline electrolyte membrane disclosed in Patent Document 1 is also only a compacted body obtained by forming hydrotalcite powder into a pellet shape with a cold press. Therefore, a simple method for stably obtaining a layered double hydroxide represented by hydrotalcite in a form having sufficient density is desired.

  In this regard, Patent Document 2 (International Publication No. 2013/073292) and Patent Document 3 (International Publication No. 2013/118561) have an inorganic solid having a relative density of 90% or more and made of a layered double hydroxide. It has been proposed to use the electrolyte body for a zinc-air secondary battery, a nickel zinc secondary battery, or the like.

International Publication No. 2010/109670 International Publication No. 2013/073292 International Publication No. 2013/118561

  The present inventors have now found that it is possible to stably and efficiently provide and produce a layered double hydroxide oriented dense plate having not only high density but also high orientation in the thickness direction. did.

  Accordingly, an object of the present invention is to stably and efficiently provide and manufacture a layered double hydroxide-oriented dense plate having not only high-density properties but also high-level orientation properties in the plate thickness direction. is there.

According to one embodiment of the present invention, it has a relative density of 90% or more, and has the general formula: M ²⁺ _1-x M ³⁺ _x (OH) ₂ A ^n- _{x / n} · mH ₂ O (wherein M ²⁺ is a divalent ^{cation, M 3+} is a trivalent ^{cation, a n-n-valent} anion, n represents an integer of 1 or more, x is in the a) 0.1 to 0.4 It is a layered double hydroxide oriented dense plate which is a plate made of the layered double hydroxide shown,
When the X-ray diffraction is performed on the plate surface of the oriented dense plate, the ratio (110) / (003) of the (110) plane peak integrated intensity to the (003) plane peak integrated intensity is 0.00. A layered double hydroxide oriented dense plate that is 7 or more is provided.

According to another aspect of the present invention, there is provided a method for producing a layered double hydroxide oriented dense plate,
(A) the general ^{_{formula: M 2+ 1-x M 3+}} x (OH) 2 A n- x / n · mH 2 O
^{(Wherein, M 2+} is a divalent ^{cation, M 3+} is a trivalent ^{cation, A n-n-valent} anion, n represents an integer of 1 or more, x is 0.1 to 0.4 A step of preparing a raw material powder comprising plate-like particles of a layered double hydroxide represented by:
(B) orienting the raw material powder by a technique using a shearing force to produce a plurality of oriented sheets in which the (003) faces of the plate-like particles are oriented parallel to the sheet surface;
(C) laminating the plurality of oriented sheets to obtain an oriented laminate;
(D) firing the oriented laminate to obtain an oriented fired body;
(E) subjecting the oriented fired body to hydrothermal treatment to regenerate the layered double hydroxide, thereby obtaining a layered double hydroxide oriented regenerated body;
(F) drying the layered double hydroxide regenerator to obtain a layered double hydroxide dense body;
And after the laminating step (c) and before, during or after any of the firing step (d), the regeneration step (e) and the drying step (f) The oriented laminated body, the oriented fired body, the layered double hydroxide oriented regenerated body, or the layered double hydroxide dense body is cut perpendicularly to the plane derived from the sheet surface, and (003) ) Further comprising a step (g) of obtaining a plate whose surface is oriented perpendicular to the plate surface, and as a result, a layered double hydroxide oriented dense plate is obtained as a final product. The

It is a perspective view which shows typically an example of the layered double hydroxide orientation dense board of this invention. It is a schematic diagram which shows a layered double hydroxide (LDH) plate-like particle. It is a process flowchart which shows an example of the manufacturing method of a layered double hydroxide oriented dense board. 3 is an XRD profile obtained for samples 1 and 7 in Example 3. 4 is a profile of wide-angle X-ray diffraction measurement obtained for Samples 1 and 7 in Example 4.

Layered Double Hydroxide Oriented Dense Plate The layered double hydroxide oriented dense plate (hereinafter referred to as LDH oriented dense plate) of the present invention has a general formula: M ²⁺ _1-x M ³⁺ _x (OH) ₂ A ⁿ⁻ _{x / n} · _mH in 2 O ^{(wherein, M 2+} is a divalent ^{cation, M 3+} is a trivalent ^{cation, a n-n-valent} anion, n represents an integer of 1 or more, x is 0.1 Is a plate made of a layered double hydroxide (hereinafter referred to as LDH). The LDH oriented dense plate has a relative density of 90% or more, and therefore has a high degree of denseness. In addition, the LDH oriented dense plate has a ratio of the integrated intensity of the peak of the (110) plane to the integrated intensity of the peak of the (003) plane (110) when the plate surface of the oriented dense plate is subjected to X-ray diffraction. ) / (003) is 0.7 or more. This means that the oriented dense plate has a high degree of orientation in the thickness direction. That is, the layered double hydroxide (LDH) is composed of an aggregate of a plurality of plate-like particles (that is, LDH plate-like particles) having a layered structure as shown in FIG. The c-axis direction (00l) plane (l is 3 and 6) to which the plane belongs is a plane parallel to the layered structure of the LDH plate-like particles. Therefore, as shown in FIG. 1, when the LDH plate-like particles 1 are oriented in a substantially vertical direction (that is, a substantially plate thickness direction) with respect to the plate surface of the LDH-oriented dense plate 10, the LDH layered structure also has a substantially vertical direction. As a result, when the separator layer surface is measured by the X-ray diffraction method, the peak of the (00l) plane (l is 3 and 6) appears smaller than the non-oriented state (in some cases, substantially Does not appear in). In particular, the peak of the (003) plane tends to be stronger than the peak of the (006) plane when it exists, so it is easier to evaluate the presence or absence of the vertical orientation than the peak of the (006) plane. I can say that. On the other hand, the peak on the (110) plane tends to appear rather strongly when the LDH plate-like particles are oriented in a substantially vertical direction (ie, substantially in the plate thickness direction) (this is similar to the LDH-oriented dense plate in FIG. 4 described later). It is better understood by comparing the corresponding XRD profile of Sample 1 with the XRD profile of Sample 7, which is an unoriented sample). Therefore, the larger the value of the ratio (110) / (003) of the (110) plane peak integrated intensity to the (003) plane peak integrated intensity, the higher the (003) plane plate surface direction (ie, the plate thickness direction). It can be said to mean a high degree of orientation. That is, according to the present invention, it is possible to provide an LDH oriented dense plate having not only high density but also high orientation in the thickness direction.

  The high degree of orientation in the plate thickness direction is a very advantageous property for LDH-oriented dense plates. This is because the LDH-oriented dense plate has a much higher hydroxide ion conductivity in the direction in which the LDH plate-like particles are oriented (that is, the direction parallel to the LDH layer) than the conductivity in the direction perpendicular thereto. This is because there is conductivity anisotropy. In fact, the present inventors have found that in an LDH oriented bulk body, the conductivity (S / cm) in the orientation direction is an order of magnitude higher than the conductivity (S / cm) in the direction perpendicular to the orientation direction. It has gained. That is, the orientation in the thickness direction of the LDH oriented dense plate of the present invention maximizes or significantly brings out the conductivity anisotropy that the LDH oriented body can have in the thickness direction, and as a result, in the thickness direction. Can be maximized or significantly increased. An LDH-oriented dense plate having such an orientation is easy to conduct hydroxide ions in the thickness direction. In addition, since it is densified, it is extremely suitable for a hydroxide ion conductive separator in which high conductivity in the thickness direction and high density are desired. For example, the LDH-oriented dense plate of the present invention has a conductivity in the direction perpendicular to the plate surface of the oriented dense plate of 0.5 mS / cm or more when measured by the 4-terminal method at 30 ° C. and a relative humidity of 90%. More preferably, it is 0.75 mS / cm or more, More preferably, it is 1.0 mS / cm or more, Most preferably, it is 2.0 mS / cm or more. The higher the conductivity, the better. The upper limit value should not be particularly limited, but typically can be 20 mS / cm or less.

  The LDH oriented dense plate of the present invention performs wide-angle X-ray diffraction in-plane measurement on the plane of the oriented dense plate at an incident angle of 0.24 ° and a diffraction angle of 2θχ = 11.2 °. In this case, it is preferable that the peak of the (003) plane is observed at an in-plane rotation angle φ with a period of 180 °. As described above, the LDH-oriented dense plate has the (003) plane oriented in the direction perpendicular to the plate surface, but not only that, but also in the in-plane direction of the plate surface as shown in FIG. It is preferable. This unique orientation state can also be expressed as a state where the (003) planes of the plate-like particles are aligned in one direction in the in-plane direction of the plate and are standing in the vertical direction of the plate surface. This orientation state can be confirmed by observing the peak of the (003) plane at an in-plane rotation angle φ with a period of 180 ° by the above-described in-plane measurement (this will be described later). This can be better understood by comparing the XRD profile of sample 1 corresponding to the LDH-oriented dense plate in FIG. 5 with the XRD profile of sample 7 which is a non-oriented sample). That is, since the (003) plane is aligned in one direction in the in-plane direction of the plate, when the sample is rotated in the in-plane direction during the in-plane measurement, a peak of the (003) plane occurs every 180 °. Maximize. By providing such a specific orientation, the conductivity in the in-plane direction of the plate surface can be improved, and this can be bypassed. As a result, the conductivity in the direction perpendicular to the plate surface is improved. Furthermore, due to the unique anisotropy that the conductivity is high not only in the vertical direction of the plate surface but also in one predetermined direction in the plate surface direction (that is, the conductivity is high in two directions), the LDH-oriented dense plate is newly developed. Can be expected. The LDH-oriented dense plate is obtained when the in-plane measurement of the wide-angle X-ray diffraction method is performed on the plate surface of the oriented dense plate at an incident angle of 0.24 ° and a diffraction angle of 2θχ = 11.2 °. The half width of the (003) plane peak is preferably 50 ° or less, more preferably 40 ° or less, still more preferably 35 ° or less, and particularly preferably 30 ° or less. It can be said that the smaller the half width is, the stronger the in-plane orientation of the (003) plane is, and it is possible to exhibit the above-described specific anisotropy to a higher degree. More precisely, the in-plane measurement uses a fully automatic horizontal multipurpose X-ray diffractometer (manufactured by Rigaku Corporation, SmartLab (rotating anti-cathode type)), output: 45 kV, 200 mA, scan method: φ continuous scan (φ = 0 to 360 °), incident angle: 0.24 °, diffraction angle: 2θχ = 11.2 ° ((003) peak), measurement step: 1 °, scan speed: 100 ° / min. Can do. The slit system used for this measurement is 1) 0.5 ° incidence vertical divergence prevention solar slit, 2) 0.1 mm height from the upstream side (X-ray incident side) to the downstream side (detector side). A 10 mm wide slit, 3) sample, 4) 20 mm wide slit, 5) 0.5 ° light receiving vertical divergence preventing solar slit, and 6) 20 mm wide slit may be arranged in this order.

The LDH-oriented dense plate of the present invention has a general formula: M ²⁺ _1−x M ³⁺ _x (OH) ₂ A ⁿ⁻ _{x / n} · mH ₂ O (where M ²⁺ is a divalent cation, M ³⁺ is a trivalent ^{cation, a n-n-valent} anion, n represents an integer of 1 or more, x is made of a layered double hydroxide (LDH) represented by a is) 0.1 to 0.4 Preferably, it consists essentially of (or consists only of) the LDH. In the above general formula, M ²⁺ may be any divalent cation, and preferred examples include Mg ²⁺ , Ca ²⁺ and Zn ²⁺ , and more preferably Mg ²⁺ . M ³⁺ may be any trivalent cation, but preferred examples include Al ³⁺ or Cr ³⁺ , and more preferred is Al ³⁺ . A ^n- may be any anion, preferred examples OH ^- and _CO ^{3 2-} and the like. Accordingly, the general ^formula, the ^{M 2+} is ^{Mg 2+,} include ^{M 3+} is ^{Al 3+, A n-is} OH ^- and / or preferably comprises _CO ^{3 2-} and. n is an integer of 1 or more, preferably 1 or 2. x is 0.1 to 0.4, preferably 0.2 to 0.35. m is an arbitrary real number.

  The LDH oriented dense plate of the present invention has a very high relative density, preferably 90% or more, more preferably 94% or more. Such an LDH-oriented dense plate with a very high relative density has sufficient airtightness (gas tightness) and liquid tightness. That is, the LDH oriented dense plate can be densified to such an extent that it does not have air permeability and water permeability. In addition, this oriented dense plate also has the property of conducting hydroxide ions as an inherent property of LDH. For this reason, in applications such as alkaline fuel cells, improvement in power generation performance can be expected while suppressing gas leaks derived from porosity. In addition, it can be expected to be applied to a separator that can prevent the extension of zinc dendrite and the intrusion of carbon dioxide, which has been a great technical barrier for the secondary battery of a zinc-air battery using an electrolytic solution. Similarly, it is expected to be applied to a nickel-zinc battery in which the progress of zinc dendrite is a major barrier to practical use. In view of these uses, the LDH-oriented dense plate of the present invention preferably contains substantially no cracks, and more preferably does not contain cracks.

The LDH-oriented dense plate of the present invention preferably has a thickness of 1-1000 μm, more preferably 2-1000 μm, further preferably 2-500 μm, particularly preferably 3-250 μm, most preferably. Is 5 to 100 μm. The preferred size of the oriented dense plate is 5 mm × 5 mm or more, more preferably 10 mm × 10 mm to 200 mm × 200 mm, and still more preferably 20 mm × 20 mm to 100 mm × 100 mm. Expressed another way, preferred size of the LDH orientation dense plate is at 25 mm ² or more, more preferably 100～40000Mm ^2, more preferably from 400~10000mm ^2.

  The LDH oriented dense plate of the present invention is preferably composed of LDH particles in which no clear endothermic peak is observed below 300 ° C. in differential thermal analysis. That is, a clear endothermic peak observed mainly in the vicinity of 200 ° C. in differential thermal analysis is said to be due to desorption of interlayer water, and there is a large structural change such as a sudden change in interlayer distance. This is because the possibility that the stable temperature region is narrow is estimated.

  The LDH-oriented dense plate of the present invention has a linear transmittance at 600 nm of 20 when both surfaces thereof are polished with a polishing cloth having a particle size of # 8000 defined in JIS R 6001 (1998) to a thickness of 1 mm. % Or more is preferable, more preferably 30% or more, and still more preferably 40% or more.

Production Method The LDH-oriented dense plate of the present invention may be produced by any method, but one embodiment of a preferred production method will be described below. In this manufacturing method, as shown in FIG. 3, for example, (a) a raw material powder containing LDH plate-like particles is prepared, and (b) the raw material powder is oriented by a technique using shearing force. Then, a plurality of oriented sheets in which the (003) plane of the plate-like particles are oriented in parallel with the sheet surface are prepared, (c) these oriented sheets are laminated, and (d) the obtained oriented laminate is obtained. And (e) subjecting the obtained oriented fired body to hydrothermal treatment to regenerate LDH, and (f) drying the obtained LDH regenerated body to obtain an LDH dense body. And after the lamination step (c) and before, during or after any step of the firing step (d), the regeneration step (e) and the drying step (f), an oriented laminate, an oriented fired body, Step (g) of obtaining a plate in which the (003) plane of the plate-like particles is oriented perpendicular to the plate surface by cutting the LDH oriented regenerator or the LDH dense body perpendicular to the surface derived from the sheet surface As a result, an LDH-oriented dense plate is obtained as a final product. According to this method, it is possible to stably and efficiently manufacture an LDH-oriented dense plate having not only high-density properties but also high-level orientation properties in the plate thickness direction.

(A) preparation step general ^{_{formula: M 2+ 1-x M 3+}} x (OH) 2 A n- x / n · mH 2 O ( ^{wherein, M 2+} is a divalent ^{cation, M 3+} is a trivalent cation an ^{ion, a n-n-valent} anion, n represents an integer of 1 or more, x is prepared a raw material powder comprising platy particles of LDH represented by a is) 0.1 to 0.4 To do. In the above general formula, M ²⁺ may be any divalent cation, and preferred examples include Mg ²⁺ , Ca ²⁺ and Zn ²⁺ , and more preferably Mg ²⁺ . M ³⁺ may be any trivalent cation, but preferred examples include Al ³⁺ or Cr ³⁺ , and more preferred is Al ³⁺ . A ^n- may be any anion, preferred examples OH ^- and _CO ^{3 2-} and the like. Accordingly, the general formula is at least ^{M 2+} is ^{Mg 2+,} include ^{M 3+} is ^{Al 3+, A n-is} OH ^- and / or _CO preferably contains ^{3 2-.} n is an integer of 1 or more, preferably 1 or 2. x is 0.1 to 0.4, preferably 0.2 to 0.35. m is an arbitrary real number. Such a raw material powder may be a commercially available LDH product, or a raw material produced by a known method such as a liquid phase synthesis method using nitrate or chloride. The particle size of the raw material powder is not limited as long as a desired LDH-oriented dense plate is obtained, but the volume-based D50 average particle size is preferably 0.1 to 1.0 μm, more preferably 0.3 to 0.00. 8 μm.

If desired, the raw material powder may be calcined before the alignment step. By performing calcination, generation of cracks during firing can be effectively suppressed. In this case, the calcination temperature is preferably 800 ° C. or less, more preferably 400 to 800 ° C., and further preferably 500 to 750 ° C. It is preferable that the maximum temperature of the calcination temperature is a temperature at which the raw material particle size does not change greatly and the crystal structure does not change to MgAl ₂ O ₄ spinel and MgO. By doing so, regeneration to LDH can be desirably performed in a later regeneration step. Although the minimum temperature of the calcination temperature is not particularly limited, if it is 400 ° C. or higher, thermal decomposition of LDH (that is, gas generation associated with dehydration and CO ₂ desorption) occurs, and thus gas generation during firing is significantly reduced. The generation of cracks can be more effectively suppressed.

(B) Orientation process The raw material powder is oriented by a technique using a shearing force to produce a plurality of oriented sheets in which the (003) planes of the plate-like particles are oriented parallel to the sheet surface. Orientation by a technique using shearing force is preferably performed by slurrying the raw material powder and subjecting it to tape molding or extrusion molding. A particularly preferred orientation method is tape molding, and a typical tape molding method includes a doctor blade method. In any of the methods exemplified above, the orientation method using the shearing force is made into a slurry by appropriately adding additives such as a binder, a plasticizer, a dispersant, and a dispersion medium to the plate-like zinc oxide powder. It is preferable to discharge and form the sheet on the substrate by passing through a thin discharge port. The slit width of the discharge port is preferably 10 to 400 μm. In addition, it is preferable to make the quantity of a dispersion medium into the quantity from which a slurry viscosity will be 4000-100000 cP, More preferably, it is 5000-60000 cP. The thickness of the alignment sheet is preferably 1 to 300 μm, more preferably 5 to 200 μm, and still more preferably 10 to 100 μm.

(C) Lamination process A plurality of oriented sheets are laminated to obtain an oriented laminate having a desired thickness. The number of the oriented sheets to be laminated, that is, the number of layers of the laminated body may be a number that gives a thickness sufficient to secure the area of the oriented dense plate to be finally obtained, for example, 100 layers or more, 500 layers As described above, it may be 800 layers or more, or 1000 layers or more.

The oriented laminate is preferably pressed at a molding pressure of 50 to 1000 kgf / cm ² before firing. By sufficiently pressing the alignment sheet in this way, it is possible to improve the denseness while having high orientation derived from the alignment sheet. This press can be preferably performed by warm isostatic pressing at a pressure of 50 to 2000 kgf / cm ² in 50 to 95 ° C. warm water by packaging the precursor laminate with a vacuum pack or the like. In addition, when using extrusion molding, the sheet-shaped molded body is integrated and laminated in the mold after passing through a narrow discharge port in the mold due to the design of the flow path in the mold. The molded body may be discharged. The obtained molded body is preferably degreased according to known conditions.

(D) Firing step The oriented laminate is fired to obtain an oriented fired body. A preferable firing temperature for obtaining the oriented fired body is 400 to 850 ° C, more preferably 700 to 800 ° C. It is preferable to hold | maintain for 1 hour or more with the calcination temperature in this range, and a more preferable holding time is 3 to 10 hours. Further, in order to prevent moisture and carbon dioxide from being released due to rapid temperature rise and cracking the molded body, the temperature rise for reaching the firing temperature is preferably performed at a rate of 100 ° C./h or less. Preferably it is 5-75 degreeC / h, More preferably, it is 10-50 degreeC / h. Therefore, it is preferable to secure a total firing time from temperature increase to temperature decrease (100 ° C. or lower) of 20 hours or more, more preferably 30 to 70 hours, and further preferably 35 to 65 hours.

(E) Regeneration process The alignment fired body is subjected to a hydrothermal treatment to regenerate LDH, thereby obtaining an LDH alignment regenerated body. That is, the alignment fired body obtained in the above step is retained in or directly above the aqueous solution containing the n-valent anion (A ⁿ⁻ ) and regenerated to LDH, thereby being rich in moisture. Get. That is, the LDH alignment regenerator obtained by this manufacturing method necessarily contains excess moisture. The anion contained in the aqueous solution may be the same kind of anion as that contained in the raw material powder, or may be a different kind of anion. It is preferable that the oxide fired body is held in an aqueous solution or immediately above the aqueous solution by a hydrothermal synthesis method in a sealed container, and an example of such a sealed container is a sealed container made of Teflon (registered trademark). More preferably, it is a closed container provided with a jacket made of stainless steel or the like on the outside thereof. The hydrothermal treatment is preferably performed by maintaining at least one surface of the fired oxide body in contact with the aqueous solution. The hydrothermal treatment is preferably performed at 20 to 200 ° C, more preferably 50 to 180 ° C, and even more preferably 100 to 150 ° C. It is preferable that the oxide sintered body is held at such LDH temperature for 1 hour or more, more preferably 2 to 50 hours, and further preferably 5 to 20 hours. With such a holding time, it is possible to avoid or reduce the occurrence of a heterogeneous phase by sufficiently promoting the regeneration to LDH. The holding time is not particularly problematic if it is too long, but it may be set in a timely manner with emphasis on efficiency.

  In the case of assuming carbon dioxide (carbonate ion) in the air as an anion species of an aqueous solution containing an n-valent anion used for regeneration to LDH, ion-exchanged water can be used. In the hydrothermal treatment in the sealed container, the fired oxide body may be submerged in the aqueous solution, or the treatment may be performed in a state where at least one surface is in contact with the aqueous solution using a jig. When the treatment is carried out in a state where at least one surface is in contact with the aqueous solution, the amount of excess water is small compared to complete submersion, and the subsequent steps may be completed in a short time. However, if the amount of the aqueous solution is too small, cracks are likely to occur. Therefore, it is preferable to use moisture equal to or greater than the weight of the fired body.

(F) Drying process The LDH reproduction body obtained at the said process is dried and an LDH dense body is obtained. That is, since the LDH regenerated body obtained in the above step is rich in water, excess water is removed by drying. Thus, the LDH dense body of the present invention is obtained. The step of removing excess water is preferably performed in an environment of 300 ° C. or lower and an estimated relative humidity of 25% or higher at the maximum temperature of the removal step. In order to prevent rapid evaporation of moisture from the LDH solidified body, when dehydrating at a temperature higher than room temperature, it is preferable to re-enclose in the sealed container used in the regeneration process to LDH. The preferable temperature in that case is 50-250 degreeC, More preferably, it is 100-200 degreeC. Moreover, the more preferable relative humidity at the time of spin-drying | dehydration is 25 to 70%, More preferably, it is 40 to 60%. Dehydration may be performed at room temperature (for example, 20 to 30 ° C.), and there is no problem as long as the relative humidity is within a range of 40 to 70% in a normal indoor environment.

(G) Cutting step After the lamination step (c) and before, during or after any step of the firing step (d), the regeneration step (e) and the drying step (f), A fired body, an LDH oriented regenerator, or an LDH oriented dense plate is cut perpendicularly to the plane derived from the sheet surface to obtain a plate in which the (003) plane of the plate-like particles is oriented perpendicular to the plate surface. . As a result, the LDH-oriented dense plate of the present invention is obtained as the final product. The oriented dense plate preferably has a thickness of 0.001 to 1 mm, more preferably 0.002 to 1 mm, still more preferably 0.002 to 0.5 mm, and particularly preferably 0.003 to 3. It is 0.25 mm, and most preferably 0.005 to 0.1 mm. The preferred size of the oriented dense plate is 5 mm × 5 mm or more, more preferably 10 mm × 10 mm to 200 mm × 200 mm, and still more preferably 20 mm × 20 mm to 100 mm × 100 mm. Expressed another way, preferred size of the LDH orientation dense plate is at 25 mm ² or more, more preferably 100～40000Mm ^2, more preferably from 400~10000mm ^2.

(H) Polishing Step If desired, the LDH oriented dense plate obtained as the final result may be further polished. By polishing, not only the surface is flattened but also the LDH oriented dense plate can be processed to a desired thickness. When the strength of the DH-oriented dense plate is insufficient, the surface of the LDH-oriented dense plate may be polished after the LDH-oriented dense plate is bonded to the porous substrate. In any case, a thin LDH-oriented dense film may be obtained by polishing the LDH-oriented dense plate.

Example 1 Production of LDH Oriented Dense Plates Samples 1 to 7 which are dense plates of hydrotalcite which is a kind of LDH were produced according to various conditions shown in Table 1. The specific production procedure for each sample is as follows.

(Sample 1-Tape molding)
(A) Preparation of raw material powder Hydrotalcite powder (DHT-6, manufactured by Kyowa Chemical Industry Co., Ltd.), which is commercially available LDH, was prepared as the raw material powder. The composition of this raw material powder was Mg ²⁺ _0.75 Al ³⁺ _0.25 (OH) ₂ CO ₃ ^n- _{0.25 / n} · mH ₂ O.

(B) Production of sheet compact 100 parts by weight of dispersion medium (xylene: butanol = 1: 1) and 7 parts by weight of binder (polyvinyl butyral: BM-2 manufactured by Sekisui Chemical Co., Ltd.) with respect to 100 parts by weight of the raw material powder , 3.5 parts by weight of a plasticizer (DOP: manufactured by Kurokin Kasei Co., Ltd.) and 2 parts by weight of a dispersant (Reodol SP-O30 manufactured by Kao Corporation) are mixed, and the mixture is stirred under reduced pressure to remove bubbles. Thus, a slurry was obtained. It was 30000 cP when the viscosity of the obtained slurry was measured. This slurry was molded into a sheet shape on a PET film using a tape molding machine so that the film thickness after drying was 25 μm to obtain a sheet molded body.

(C) Lamination | stacking of sheet molded object The obtained sheet molded object was cut out to 25 mm x 25 mm, and 1000 layers were laminated | stacked this. The obtained laminate was pressure-bonded by a warm isostatic press under the conditions of holding at 80 ° C., 300 kg / cm ² for 20 minutes to obtain a laminate having a size of 25 mm × 25 mm × 25 mm.

(D) Firing The laminated body thus obtained was placed in an alumina sheath and fired in an air atmosphere with the lid opened. This firing is performed at a rate of 30 ° C./h or less in order to prevent the binder and hydrotalcite powder from being thermally decomposed by rapid temperature rise and releasing moisture and carbon dioxide to crack the molded body. , Kept at 750 ° C. for 5 hours, and then cooled.

(E) Regeneration The fired body thus obtained is sealed in a Teflon (registered trademark) sealed container with a stainless steel jacket on the outside together with ion-exchanged water in the atmosphere, and hydrothermally treated at 100 ° C. for 5 hours. A sample was obtained. Since the sample cooled to room temperature contained excess moisture, the moisture on the surface was gently wiped off with a filter paper or the like.

(F) Natural dehydration (drying)
The sample thus obtained was naturally dehydrated (dried) in a room at 20 to 30 ° C. and a relative humidity of about 40 to 60% to obtain a dried product.

(G) Cutting process Sample 1 was obtained by cutting a 20 mm × 20 mm × 1 mm thick plate from the dried body thus obtained so that the plate surface was perpendicular to the stacking surface when the sheets were stacked.

(Sample 2-Tape molding)
Sample 2 was prepared in the same manner as Sample 1, except that the amount of dispersion medium added was 120 parts in the preparation of the sheet molded body (step (b)), and the viscosity of the slurry was 10000 cP.

(Sample 3-Tape molding)
Sample 3 was prepared in the same manner as Sample 1, except that the amount of dispersion medium added was 150 parts in the preparation of the sheet compact (step (b)), and the viscosity of the slurry was 2000 cP.

(Sample 4-Tape molding)
As the raw material powder prepared in step (a), the same procedure as in Sample 1 was used, except that a powder obtained by calcining hydrotalcite powder (DHT-6, manufactured by Kyowa Chemical Industry Co., Ltd.) at 600 ° C. for 20 hours was used. Sample 4 was prepared.

(Sample 5-Uniaxial press molding / comparison)
i) Instead of producing and laminating a sheet compact (steps (b) and (c)), the raw material powder is filled into a 30 mm diameter mold and uniaxial press molding is performed at a molding pressure of 300 kgf / cm ² ( 20 mm × 20 mm × from the dried body so that the plate surface is parallel to the uniaxial press surface in the cutting process (step (g)) Sample 5 was produced in the same manner as Sample 1 except that a 1 mm thick plate was cut out.

(Sample 6—uniaxial press molding / comparison)
Sample 6 was produced in the same manner as Sample 5, except that uniaxial press molding was performed at a molding pressure of 500 kgf / cm ² .

(Sample 7-CIP molding / comparison)
i) Preparation of sheet compact and lamination (steps (b) and (c)) Instead of placing the raw material powder in a rubber container and vacuum-sealing, cold isotropy at a molding pressure of 500 kgf / cm ² A press-molded body was obtained by molding by pressure and pressure (CIP) (instead of the laminate), and ii) 20 mm × 20 mm in any direction from the dried body in the cutting process (step (g)) × Sample 7 (non-oriented sample) was prepared in the same manner as Sample 1 except that a 1 mm thick plate was cut out.

Example 2 : Measurement of relative density The density was determined by calculating the density from the dimensions and weights of the samples 1 to 7 prepared in Example 1, and dividing this density by the theoretical density. In calculating the theoretical density, the JCPDS card No. 1 was used as the hydrotalcite theoretical density of Mg / Al = 3. 2.06 g / cm ³ described in 22-22700 is used as the theoretical density of hydrotalcite with Mg / Al = 2. 2.09 g / cm ³ described in 70-2151 was used. The results were as shown in Tables 1 and 2.

Example 3 : Evaluation of orientation degree of (003) plane in the direction perpendicular to the plate surface X-ray diffraction was performed on the plate surfaces of the plate-like samples of Samples 1 to 7 prepared in Example 1. The XRD profile performed on samples 1 and 7 is shown in FIG. In sample 7, a peak group consisting of almost the same peak intensity as that of the card information was recognized, and it was considered that the sample was in a non-oriented state as intended. On the other hand, since the peak intensity of the (003) plane on the plate surface is weak in the sample 1, in the sample 1, the (003) plane is aligned in the direction perpendicular to the plate surface (that is, the orientation) ). Here, as an index of the degree of orientation, a ratio (110) / (003) of the integrated intensity of the peak of the (110) plane which is a plane perpendicular to the (003) plane to the integrated intensity of the peak of the (003) plane. Using. It can be said that as this value is larger, the (003) plane is oriented in the direction perpendicular to the plate surface. Tables 1 and 2 show the (110) / (003) ratio obtained for Samples 1-7.

Example 4 : Evaluation of degree of orientation in the in-plane direction of the (003) plane In order to examine the degree of orientation in the in-plane direction of the (003) plane of the samples 1 to 7 produced in Example 1, wide-angle X-ray diffraction Measurement by the method (In-Plane method) was performed. This measurement uses a fully automatic horizontal multi-purpose X-ray diffractometer (manufactured by Rigaku Corporation, SmartLab (rotating anti-cathode type)), output: 45 kV, 200 mA, scan method: φ continuous scan (φ = 0 to 360 °), Measurement was performed under conditions of incident angle: 0.24 °, diffraction angle: 2θχ = 11.2 ° ((003) peak), measurement step: 1 °, scan speed: 100 ° / min. In addition, the slit system used for this measurement is 1) 0.5 ° incidence vertical divergence prevention solar slit from the upstream side (X-ray incident side) to the downstream side (detector side), and 2) 0.1 mm height. A length x 10 mm width slit, 3) sample, 4) 20 mm width slit, 5) 0.5 ° light receiving vertical divergence prevention solar slit, and 6) 20 mm width slit were arranged in this order.

  FIG. 5 shows a profile of the wide-angle X-ray diffraction measurement performed on Samples 1 and 7. In FIG. 5, since the peak of the (003) plane was observed in Sample 1 with an in-plane rotation angle φ of a period of 180 °, the (003) plane was not only observed in the vertical direction of the plate surface confirmed in Example 3. ) Orientation was also observed in the in-plane direction of the plate surface. On the other hand, no peak is confirmed for sample 7, and it is considered that the (003) plane is not oriented in the in-plane direction of the plate surface. Here, the half width of the peak was used as an index of the in-plane orientation degree of the (003) plane. It can be said that the smaller the half width, the stronger the in-plane orientation of the (003) plane. Tables 1 and 2 show the half widths obtained for samples 1 to 7.

Example 5 : Measurement of conductivity The conductivity of Samples 1 to 7 was measured by the 4-terminal method. In addition, since a certain amount of thickness is required for the sample in the four-terminal method, the sample was newly cut out for measurement of conductivity from the dried body before the plate cutting process step (g) of each sample. Samples 1 to 4 are 20 mm × 20 mm × thickness so that the plate surface is perpendicular to the laminated surface and samples 5 to 7 are parallel to the uniaxial press surface. Cut into a 10 mm plate shape, the conductivity in the direction perpendicular to the plate surface (pressed surface or uniaxial press surface direction) was measured.

  A current introduction terminal was formed of carbon cloth carrying Pt on the plate surface of each sample and foamed nickel, and a voltage terminal was formed near the center of the sample with a Pt line. The measurement was performed by DC method and AC impedance method using Solartron 1287 and 1260. The measurement was carried out in a constant temperature and humidity chamber in an environment with a temperature of 30 to 85 ° C. and a relative humidity of 90%. In the DC method, the voltage was swept at −0.3 to 0.3 V, and in the AC impedance method, the AC voltage amplitude was 100 mV, and the measurement frequency range was 0.1 to 1 MHz. The same conductivity was measured for both DC and AC impedance methods. The measurement results at a temperature of 30 ° C. are shown in Tables 1 and 2. Under the slurry conditions, in Sample 1 which was tape-molded with the slurry having the smallest number of dispersion medium and the highest viscosity, a very high conductivity of 8.3 mS / cm was realized. Moreover, it turned out that the activation energy exists in the range of 0.2-0.4 eV from the measurement which changed the temperature of 30-85 degreeC.

Claims (16)

It has a relative density of 90% or more and has a general formula: M ²⁺ _1-x M ³⁺ _x (OH) ₂ A ⁿ⁻ _{x / n} · mH ₂ O (wherein M ²⁺ is a divalent cation, M ³⁺ is a trivalent ^{cation, a n-n-valent} anion, n represents an integer of 1 or more, x is composed of layered double hydroxide represented by a is) 0.1 to 0.4 It is a layered double hydroxide oriented dense plate that is a plate,
When the X-ray diffraction is performed on the plate surface of the oriented dense plate, the ratio (110) / (003) of the (110) plane peak integrated intensity to the (003) plane peak integrated intensity is 0.00. 7. A layered double hydroxide oriented dense plate, which is 7 or more.   When the in-plane measurement of the wide-angle X-ray diffraction method is performed at an incident angle of 0.24 ° and a diffraction angle of 2θχ = 11.2 ° on the plate surface of the dense dense plate, the (003) plane. The layered double hydroxide oriented dense plate according to claim 1, wherein a peak of is observed at an in-plane rotation angle φ and a period of 180 °.   When the in-plane measurement of the wide-angle X-ray diffraction method is performed at an incident angle of 0.24 ° and a diffraction angle of 2θχ = 11.2 ° on the plate surface of the dense dense plate, the (003) plane. The layered double hydroxide oriented dense plate according to claim 1 or 2, wherein the half-value width of the peak is 50 ° or less.   The conductivity in the direction perpendicular to the plate surface of the oriented dense plate is 0.5 mS / cm or more when measured by a four-terminal method at 30 ° C and a relative humidity of 90%. The layered double hydroxide-oriented dense plate described in the item. Among the general ^formula, the ^{M 2+} is ^{Mg 2+,} include ^{M 3+} is ^{Al 3+, A n-is} OH ^- and / or _CO containing ^{3 2-,} according to any one of claims 1-4 Layered double hydroxide oriented dense plate.   The layered double hydroxide oriented dense plate according to any one of claims 1 to 5, wherein the oriented dense plate has a thickness of 1 to 1000 µm.   The layered double hydroxide oriented dense plate according to any one of claims 1 to 6, which does not contain cracks.   The layered double hydroxide oriented dense plate according to any one of claims 1 to 7, substantially consisting of only the layered double hydroxide. A method for producing a layered double hydroxide oriented dense plate,
(A) the general _{^{formula: M 2+ 1-x M 3+}} x (OH) 2 A n- x / n · mH 2 O
^{(Wherein, M 2+} is a divalent ^{cation, M 3+} is a trivalent ^{cation, A n-n-valent} anion, n represents an integer of 1 or more, x is 0.1 to 0.4 A step of preparing a raw material powder comprising plate-like particles of a layered double hydroxide represented by:
(B) orienting the raw material powder by a technique using a shearing force to produce a plurality of oriented sheets in which the (003) faces of the plate-like particles are oriented parallel to the sheet surface;
(C) laminating the plurality of oriented sheets to obtain an oriented laminate;
(D) firing the oriented laminate to obtain an oriented fired body;
(E) subjecting the oriented fired body to hydrothermal treatment to regenerate the layered double hydroxide, thereby obtaining a layered double hydroxide oriented regenerated body;
(F) drying the layered double hydroxide regenerator to obtain a layered double hydroxide dense body;
And after the laminating step (c) and before, during or after any of the firing step (d), the regeneration step (e) and the drying step (f) The oriented laminated body, the oriented fired body, the layered double hydroxide oriented regenerated body, or the layered double hydroxide dense body is cut perpendicularly to the plane derived from the sheet surface, and (003) ) The method further comprises the step (g) of obtaining a plate whose surface is oriented perpendicularly to the plate surface, and as a result, a layered double hydroxide oriented dense plate is obtained as the final product.   The method according to claim 9, wherein the orientation by the technique using the shearing force is performed by slurrying the raw material powder and subjecting it to tape molding or extrusion molding.   The method according to claim 9 or 10, wherein the alignment sheet has a thickness of 1 to 300 µm.   The method according to any one of claims 9 to 11, wherein the oriented dense plate has a thickness of 0.001 to 1 mm. The method according to any one of claims 9 to 12, wherein the oriented laminate is pressed at a molding pressure of 50 to 1000 kgf / cm ² before the firing.   The method according to any one of claims 9 to 13, wherein the baking is performed at a temperature of 700 to 800C.   The method according to any one of claims 9 to 14, wherein the hydrothermal treatment is performed at 20 to 200 ° C.   The method according to any one of claims 9 to 15, further comprising a step of calcining the raw material powder at 800 ° C or lower before the alignment step.

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