JPWO2015087888A1 - Porous plate filler and heat insulating film - Google Patents

Abstract

Provided are a porous plate-like filler that can be used as a material for a heat insulating film excellent in heat insulating performance, and a heat insulating film. The porous plate-like filler 1 has a plate shape with an aspect ratio of 3 or more, a minimum length of 0.1 to 50 μm, a porosity of 20 to 90%, a tetravalent atom and a part of Zr. The ZrO 2 porous plate-like filler 1 is substituted and has a molar ratio of O and Zr in the range of 2 <O / Zr <2.4. By replacing a part of Zr of the ZrO2 particles constituting the porous plate-like filler 1 with other atoms (Ti, Si, Ce, Hf), the crystal structure becomes complicated and phonons are easily scattered.

Description

  The present invention relates to a porous plate-like filler and a heat insulating film containing the porous plate-like filler.

  A heat insulating film for improving heat insulating efficiency and flame retardancy is desired by forming on the surface. Patent Document 1 discloses a coating film having a high surface hardness and capable of preventing scratches. The coating film is formed by dispersing hollow particles made of silica shells in a binder. The wear resistance of the hollow particles made of silica shell and the high hardness can improve the wear resistance of the substrate on which the coating film is formed. Moreover, flame retardance can be improved by the heat insulation of the hollow particle which consists of silica shells.

  Patent Document 2 discloses an internal combustion engine including a structural member with improved heat insulation performance. In the internal combustion engine of Patent Document 2, a heat insulating material is disposed adjacent to the inner wall of the exhaust passage, and high-temperature working gas (exhaust gas) flows along a flow path formed by the heat insulating material. In the heat insulating material, each particle of spherical mesoporous silica (MSS) particles having an average particle size of 0.1 to 3 μm is laminated in a state where the particles are closely packed with each other through a bonding material. Innumerable mesopores having an average pore diameter of 1 to 10 nm are formed in the MSS particles.

In Patent Document 3, Ln _1-x Ta _x O _{1.5 + x} or Ln _1-x Nb _x O _{1.5 + x} (Ln is one or two kinds selected from the group consisting of Sc, Y and a lanthanoid element) The compounds represented by the above elements) and satisfying 0.13 ≦ x ≦ 0.24 are disclosed.

JP 2008-200902 A JP 2011-52630 A JP 2009-221551A

  In Patent Document 1, hollow particles made of silica shells having an outer diameter of about 30 to 300 nm are dispersed in an organic resin binder, an inorganic polymer binder, or an organic-inorganic composite binder, so that the formed coating film has a heat insulating property. Demonstrating. Further, in Patent Document 2, the MSS (spherical mesoporous silica) particles having mesopores having an average particle diameter of 0.1 to 3 μm and an average pore diameter of 1 to 10 nm are stacked in a dense state. Therefore, in patent document 2, the heat insulation performance is obtained. The compound of Patent Document 3 has a low thermal conductivity as compared with conventional rare earth stabilized zirconia due to disorder of oxygen defects.

  However, even with the materials described in Patent Documents 1 to 3, the heat insulation performance of the heat insulation film obtained using this material is not sufficient, and further development of a material for the heat insulation film having excellent heat insulation performance has been eagerly desired. It was. That is, even if it is the material described in patent documents 1-3, the heat conductivity of the heat insulation film obtained using this material was not sufficiently low.

  The subject of this invention is providing the porous plate-shaped filler which can be used as a material of the heat insulation film | membrane excellent in the heat insulation performance, and a heat insulation film | membrane.

The inventors of the present invention have found that the heat insulating properties of the ZrO ₂ porous plate-like filler having a predetermined shape and a part of Zr substituted with another predetermined atom are improved as compared with the prior art. According to the present invention, the following porous plate-like filler and heat insulating film are provided.

[1] A plate having an aspect ratio of 3 or more, a minimum length of 0.1 to 50 μm, a porosity of 20 to 90%, a part of Zr is substituted with tetravalent atoms, and O and A ZrO ₂ porous plate-like filler having a Zr molar ratio in the range of 2 <O / Zr <2.4 and a single phase.

[2] The composition formula is Zr _1-x O ₂ A _x (A is at least one selected from the group consisting of Ti, Si, Ce, and Hf), and 0 <x <0.18 1] The ZrO ₂ -based porous plate filler described in 1].

[3] The ZrO ₂ porous plate filler according to [1] or [2], wherein the thermal conductivity is 1 W / (m · K) or less.

[4] The ZrO ₂ porous plate filler according to any one of [1] to [3], wherein the heat capacity is 250 to 2500 kJ / (m ³ · K).

[5] The ZrO ₂ porous plate filler according to any one of the above [1] to [4], which has pores having an average pore diameter of 10 to 500 nm.

[6] A heat insulating film containing the ZrO ₂ -based porous plate filler according to any one of [1] to [5].

The ZrO ₂ porous plate-like filler of the present invention is one in which a part of Zr of ZrO ₂ particles is substituted with other atoms. Substitution of a part of Zr with other atoms complicates the crystal structure, and phonons are easily scattered, resulting in a decrease in thermal conductivity. Further, since the plate has an aspect ratio of 3 or more, the minimum length is 0.1 to 50 μm, and the porosity is 20 to 90%, the ZrO ₂ porous plate filler of the present invention has a heat insulation performance. It can be used as a material for a heat insulating film excellent in the above.

Insulation film of the present invention comprises a ZrO ₂ based porous plate-like filler of the present invention. Therefore, the heat insulating film of the present invention is excellent in heat insulating performance.

One embodiment of the ZrO ₂ porous plate-like filler of the present invention is a perspective view schematically showing. It is sectional drawing which shows typically one Embodiment of the heat insulation film | membrane of this invention.

  Embodiments of the present invention will be described below. The present invention is not limited to the following embodiments, and appropriate modifications and improvements are added to the following embodiments on the basis of ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that what has been described also falls within the scope of the invention.

[1] Porous plate filler:
FIG. 1 shows an embodiment of a ZrO ₂ -based porous plate filler 1. The ZrO ₂ -based porous plate-like filler 1 of the present invention has a plate shape with an aspect ratio of 3 or more, a minimum length of 0.1 to 50 μm, a porosity of 20 to 90%, and a tetravalent atom. And Zr is partially substituted, and the molar ratio of O and Zr is in the range of 2 <O / Zr <2.4, which is a single phase. The ZrO ₂ system refers to one in which a part of Zr of ZrO ₂ is substituted with another atom. When a part of Zr of ZrO ₂ particles constituting the porous plate-like filler 1 is replaced with other atoms, the crystal structure becomes complicated and phonons are easily scattered. Therefore, the ZrO ₂ -based porous plate-like filler 1 of the present invention (hereinafter also simply referred to as a porous plate-like filler) is more than ZrO ₂ particles in which a part of Zr having a low thermal conductivity is not substituted with other atoms. However, the thermal conductivity is lower. Therefore, it is suitable as a heat insulating material.

  In this specification, the aspect ratio is defined as the maximum length / minimum length of the porous plate-like filler 1. Here, the maximum length is the maximum length when the particles (porous plate filler 1) are sandwiched between a pair of parallel surfaces. Similarly, the minimum length is the minimum length when the particles are sandwiched between a pair of parallel surfaces, and corresponds to a so-called thickness in the case of a flat plate shape. The plate shape of the porous plate filler 1 is not only flat plate (flat and uncurved plate) but also curved as long as the aspect ratio is 3 or more and the minimum length is 0.1 to 50 μm. And a plate-like material whose thickness (minimum length) is not constant are also included. Further, the shape may be a fiber shape, a needle shape, a lump shape, or the like. Among these, it is preferable that the porous plate-like filler 1 has a flat plate shape. Further, the surface shape of the plate may be any shape such as a square, a square, a triangle, a hexagon, and a circle. That is, the porous plate-like filler 1 may have any shape as long as it is flat.

  The aspect ratio of the porous plate filler 1 is preferably 3 or more. The larger the heat insulation film 3 is, the larger the heat insulation path is refracted and lengthened, and the heat conductivity of the heat insulation film 3 is lowered. However, when the aspect ratio is too large, handling in manufacturing becomes difficult, and the yield may be deteriorated. For example, if the minimum length is shortened to increase the aspect ratio, the strength may not be sufficient. On the other hand, if the maximum length is increased, the porous plate-like filler 1 becomes large and may be damaged. Therefore, the aspect ratio is more preferably 3 to 50, further preferably 3.5 to 40, and most preferably 4 to 30.

The porous plate-like filler 1 preferably has a porosity of 20 to 90%, more preferably 40 to 85%, and still more preferably 50 to 80%. By setting the porosity to 20% or more, the thermal conductivity of the porous plate-like filler 1 can be lowered, and by setting the porosity to 90% or less, the strength can be ensured. In the present specification, the porosity is determined by the following formula.
Porosity (%) = (1− (apparent particle density ÷ true density)) × 100
In the above formula, the apparent particle density is measured by an immersion method using mercury. The true density is measured by a pycnometer method after sufficiently pulverizing the porous plate filler 1.

  The porous plate-like filler 1 preferably has an average pore diameter of 10 to 500 nm, more preferably 10 to 300 nm, and particularly preferably 10 to 100 nm. The average pore diameter is preferably smaller as the thermal conductivity is lower, but the production cost may be increased. On the other hand, if it exceeds 500 nm, the thermal conductivity may be too high. Here, in this specification, the “average pore diameter of the porous plate-like filler” is a gas adsorption method in the range of 0.1 to 100 nm, and a mercury porosimeter (mercury intrusion method) in the range of 100 nm to 500 μm. It is a measured value.

  By including such a porous plate-like filler 1 in the heat insulating film 3 as described later, the heat insulating effect can be improved.

The ZrO ₂ particles constituting the porous plate-like filler 1 preferably have an average particle diameter of 10 nm to 1 μm, more preferably 10 nm to 500 nm, and particularly preferably 10 nm to 100 nm. The average particle size is preferably as the average particle size is small because the thermal conductivity is low, but if it is less than 10 nm, the production cost may be high. On the other hand, if it exceeds 1 μm, the thermal conductivity may increase. The average particle diameter of the ZrO ₂ particles observes the microstructure of the porous plate-like filler (FE-SEM), measuring the size of a grain particles in the image processing, be determined as 10 Mean value it can.

  The minimum length of the porous platy filler 1 is 0.1 to 50 μm, more preferably 0.5 to 20 μm, still more preferably 2 to 15 μm, and most preferably 2 to 10 μm. If the minimum length of the porous plate-like filler 1 is shorter than 0.1 μm, it is difficult to maintain the shape of the porous plate-like filler 1 during the manufacturing process, and the minimum length of the porous plate-like filler 1 is longer than 50 μm. When the heat insulating film 3 is included, the number of laminated porous plate-like fillers 1 is reduced. Therefore, the heat transfer path is shortened by being close to a straight line, and the heat conductivity of the heat insulating film 3 is increased. Moreover, when the minimum length of the porous plate-like filler 1 is short, the heat insulating film 3 can be made thin. That is, even if it is the thin heat insulation film 3, the heat insulation effect can be improved.

  The porous plate-like filler 1 preferably has a thermal conductivity of 1 W / (m · K) or less. The thermal conductivity is more preferably 0.7 W / (m · K) or less, further preferably 0.5 W / (m · K) or less, and most preferably 0.3 W / (m · K) or less. When the porous plate-like filler 1 having such a thermal conductivity is included in the heat insulating film 3, the heat insulating effect can be improved.

  The “thermal conductivity of the porous plate filler” is a value calculated as follows. First, the density of the porous plate filler 1 is measured with a mercury porosimeter. Next, the specific heat of the porous plate filler 1 is measured by DSC method. Next, the thermal diffusivity of the porous plate filler 1 is measured by an optical alternating current method. Thereafter, the thermal conductivity of the porous plate filler 1 is calculated from the relational expression of thermal diffusivity × specific heat × density = thermal conductivity.

The porous plate-like filler 1 preferably has a heat capacity of 250 to 2500 kJ / (m ³ · K). The heat capacity is more preferably 250 to 2300 kJ / (m ³ · K), and further preferably 250 to 2000 kJ / (m ³ · K). When the porous plate-like filler 1 having a heat capacity in such a range is included in the heat insulating film 3, the heat insulating effect can be improved. Although the heat capacity varies depending on the porosity, the ZrO ₂ porous plate-like filler 1 has a porosity of about 2500 kJ / (m ³ · K) when the porosity is 20% and 250 kJ / (when the porosity is 90%. the m ³ · K) degree. In this specification, since the heat capacity is generally discussed per unit volume called volume specific heat, the unit is kJ / (m ³ · K).

  “The heat capacity of the porous plate filler” is a value calculated as follows. Specific heat is measured by the DSC method, and the product of specific heat and density (apparent particle density) is defined as the heat capacity of the porous plate-like filler 1. The apparent particle density is measured by an immersion method using mercury.

Hereinafter, embodiments of the ZrO ₂ -based porous plate filler 1 in which a part of Zr is substituted with other atoms will be further described. The ZrO ₂ porous plate-like filler 1 of the present invention has a molar ratio of O and Zr in the range of 2 <O / Zr <2.4 because part of Zr is substituted with other atoms. It is preferable. More preferably, 2.01 <O / Zr <2.3, and still more preferably 2.02 <O / Zr <2.25. When a part of Zr is substituted with another atom, Zr in the crystal decreases, and the molar ratio O / Zr of O and Zr deviates from 2. As a result, the crystal structure becomes complicated, phonons are easily scattered, and the thermal conductivity is lowered. By 2 <O / Zr, the effect of lowering the thermal conductivity is easily obtained. On the other hand, by setting O / Zr <2.4, it is possible to further reduce the thermal conductivity while taking advantage of the low thermal conductivity of ZrO ₂ .

Specifically, the ZrO ₂ -based porous plate-like filler 1 has a composition formula of Zr _1-x O ₂ A _x (A is at least one selected from the group consisting of Ti, Si, Ce, and Hf). Yes, 0 <x <0.18. A (hereinafter also referred to as a substituted atom) is an atom that can be easily substituted with Zr, is a tetravalent atom having the same valence as Zr, and does not generate oxygen defects in the crystal. A may be one type or two or more types. When A is 2 or more types (A1, A2,...), The sum of the respective ratios x1, x2,... Is x (x = x1 + x2 +...). By introducing an atom as described above as a substitution atom into ZrO ₂ , the substitution between the Zr atom and the substitution atom occurs, and O / Zr becomes larger than 2. As a result, disorder of the crystal structure occurs and phonons are easily scattered. If too many substitution atoms are added, the crystal structure is too disordered, a heterogeneous phase having a high thermal conductivity is generated, and the thermal conductivity may be increased.

The content ratio of the substituted atoms is preferably 0 <x <0.18, more preferably 0.005 <x <0.13, and particularly preferably 0.01 <x <0.11. preferable. By being in the above range, there is an advantage that the thermal conductivity can be further reduced while maintaining the characteristics of ZrO ₂ . There exists a possibility that the reduction effect of thermal conductivity may be inadequate that the content rate of a substituted atom is less than the said lower limit. If it exceeds the above upper limit value, there is a possibility that problems may occur in the material properties such as heat resistance and strength of ZrO ₂ .

  In addition, the ratio of Zr, O, and a substituted atom is measured by chemical analysis (JIS R1603), and O / Zr (molar ratio) is calculated from the result.

The substitution atoms are dissolved in the ZrO ₂ particles. Thus, when a substituted atom dissolves in ZrO ₂ particles, the thermal conductivity can be further lowered.

The "substituted atoms is dissolved in ZrO ₂ in particles" that part of the elements constituting the substituted atom ZrO ₂ in the particle is in a state that is present in the crystal structure of ZrO ₂ particles means. For example, it means that Ti of TiO ₂ as a substitution atom is substituted at the Zr site in the crystal structure of the ZrO ₂ particle. Such a state can be confirmed by conducting a chemical analysis of the porous plate-like filler 1 to identify constituent elements and analyzing the crystal structure by X-ray diffraction.

  When there are two kinds of substituent atoms, the value of these volume ratios is preferably 1/9 to 9. If the value of the ratio is outside the above range, the effect of adding both may not be recognized.

The ZrO ₂ -based porous plate filler 1 means that the porous plate filler 1 has a single crystal structure. For example, it means a state where only ZrO ₂ is detected when X-ray analysis is performed, and TiO ₂ as an additive (described later) is not detected. That is, it is a state where an additive below the limit that can be replaced is added. Since it is composed of only Zr _(1-x) O _(2-x) A _x having a low thermal conductivity without a crystal such as TiO ₂ having a high thermal conductivity when it is a single phase, the thermal conductivity is Lower.

An additive comprising a substitution atoms is added to ZrO _2, by heat treatment, can be introduced substitutions atoms in ZrO _2. Examples of the additive containing a substituent atom include TiO ₂ , SiO ₂ , CeO ₂ , and HfO ₂ . The diameter of the additive is preferably smaller than the diameter of the ZrO ₂ particles. In this way, there is an advantage that tends to maintain the characteristics of ZrO _2. The “additive diameter” can also be referred to as the average particle diameter of the additive. The “diameter of ZrO ₂ particles” can also be referred to as an average particle diameter of ZrO ₂ particles.

The additive preferably has an average particle size of 0.1 to 300 nm, more preferably 0.1 to 100 nm, and particularly preferably 0.1 to 50 nm. The average particle diameter is preferably as small as possible, but if it is less than 0.1 nm, the production cost may increase. On the other hand, if it exceeds 300 nm, there is a possibility that the reaction may be insufficient due to insufficient contact between ZrO ₂ and the additive during firing. In addition, there is a risk that defects may occur in material properties such as heat resistance and strength of ZrO ₂ . That is, there is a possibility that the heat resistance is lowered or the strength is lowered. The “average particle diameter of the additive” is a value measured in the same manner as the average particle diameter of the ZrO ₂ particles described above.

[2] Method for producing porous plate filler:
One embodiment of the method for producing the porous plate-like filler 1 of the present invention includes a slurry preparing step for preparing a slurry for forming a green sheet, a green sheet forming step for forming a green sheet, and a fired body for producing a fired body. A production step and a crushing step of crushing the fired body to obtain the porous plate-like filler 1. The slurry preparation step is a step of preparing a slurry for forming a green sheet containing ZrO ₂ particles, an additive containing a substituent atom, and a pore former. The green sheet forming step is a step of forming a green sheet by forming a slurry for forming a green sheet into a film shape. The fired body preparation step is a step of baking the formed green sheet to produce a film-like fired body. The crushing step is a step of obtaining the porous plate filler 1 by crushing the fired body.

  Since the manufacturing method of such a porous plate-shaped filler 1 has said each process, the porous plate-shaped filler 1 which can be used as a material of the heat insulation film excellent in heat insulation performance can be manufactured.

[2-1] Slurry preparation process:
Green ZrO ₂ particles and substituted atoms contained in the sheet-forming slurry is the same as the porous plate ZrO ₂ particles and substituted atoms of the filler of the present invention described above.

  The pore former is not particularly limited as long as it is a material that disappears and forms a plurality of pores in the fired body manufacturing step. Examples of the pore former include carbon black, latex particles, melamine resin particles, polymethyl methacrylate (PMMA) particles, polyethylene particles, polystyrene particles, foamed resins, water absorbent resins and the like. Among these, carbon black is preferable because of the advantage that the particle size is small and small pores are easily formed in the porous plate-like filler 1.

The green sheet forming slurry may contain other components such as a binder, a plasticizer, and a solvent in addition to the ZrO ₂ particles, the additive containing a substituent atom, and the pore former. In order to replace a part of Zr with a substituent atom, the additive containing a substituent atom preferably has poor crystallinity, for example, amorphous TiO ₂ is preferably used, but is not limited thereto. It is not a thing.

  Examples of the binder include polyvinyl butyral resin (PVB), polyvinyl alcohol resin / polyvinyl acetate resin / polyacrylic resin, and the like. Examples of the plasticizer include dibutyl phthalate (DBP) and dioctyl phthalate (DOP). Examples of the solvent include xylene and 1-butanol.

The content ratio of ZrO ₂ particles in the green sheet forming slurry is preferably 5 to 20% by volume.

  It is preferable that the content rate of the additive (all the sum total when introduce | transducing two or more) in the slurry for green sheet formation is 0.1-5 volume%.

  The content of the pore former in the green sheet forming slurry is preferably 2 to 20% by volume.

  The content ratio of “other components” in the slurry for forming a green sheet is preferably 70 to 90% by volume.

  The viscosity of the slurry for forming a green sheet is preferably 0.1 to 10 Pa · s. In addition, the method of performing a vacuum defoaming process is mentioned to make such a viscosity.

[2-2] Green sheet forming step:
The green sheet is preferably in the form of a film having a thickness after firing of 10 to 50 μm.

  As a method of forming the green sheet forming slurry into a film shape, a conventionally known method can be adopted. For example, a method using a doctor blade device can be adopted.

[2-3] Firing body manufacturing process:
The firing conditions of the green sheet can be appropriately set. For example, it is preferably 0.5 to 20 hours at 800 to 2300 ° C. in the air, and 5 to 20 hours at 800 to 1800 ° C. Is more preferable, and it is particularly preferable that the temperature is 800 to 1300 ° C. for 5 to 20 hours.

[2-4] Crushing step:
As a method for crushing the fired body, for example, the fired body can be crushed at room temperature using a dry bead mill, a roller mill or the like. In particular, in order to obtain a porous particle “a plate having an aspect ratio of 3 or more and a minimum length of 0.1 to 50 μm”, it is preferable to use an airflow classifier to perform sizing (classification).

[3] Thermal insulation film:
The heat insulating film 3 of the present invention includes the porous plate-like filler 1 of the present invention as a material. Such a heat insulating film 3 is excellent in heat insulating performance.

  The heat insulation film | membrane 3 is demonstrated using FIG. FIG. 2 is a cross-sectional view parallel to the film thickness direction schematically showing one embodiment of the heat insulating film of the present invention. The heat insulating film 3 includes the porous plate-like filler 1 according to an embodiment of the present invention and a matrix 3m in which the porous plate-like filler 1 is dispersed. That is, the porous plate-like filler 1 is disposed in a dispersed manner in the matrix 3m for bonding the porous plate-like filler 1. The matrix 3m is a component that exists around the porous plate-like filler 1 and between these particles, and is a component that binds between these particles.

  In the heat insulating film 3 of the present invention, the porous plate-like filler 1 is preferably arranged (laminated) in layers. The term “layered arrangement” as used herein refers to a matrix in which a number of porous plate-like fillers 1 are oriented in a direction in which the minimum length of the porous plate-like filler 1 is parallel to the thickness direction of the heat insulating film 3. It says that it exists in 3m. At this time, the position (position of the center of gravity) of the porous plate filler 1 is regularly and periodically arranged in the X, Y, and Z directions of the heat insulating film 3 (where the Z direction is the thickness (film thickness) direction). It is not necessary to be arranged in the space, and there is no problem even if they are present at random. There is no problem as long as the number of stacked layers is 1 or more. By laminating the porous plate-like filler 1 in the heat insulating film 3, the heat transfer path is refracted and lengthened, and the heat insulating effect can be improved. In particular, as shown in FIG. 2, the position of the porous plate-like filler 1 is not aligned in the Z direction (which is shifted alternately), because the heat transfer path is refracted and becomes longer, preferable.

  As shown in FIG. 2, the matrix 3m portion having a high thermal conductivity is the main heat transfer path, but the heat insulating film 3 of the present invention includes the porous plate-like filler 1, and the heat transfer path transfers heat. There are many detours in the direction (thickness direction) that you do not want. That is, since the length of the heat transfer path is increased, the thermal conductivity can be lowered. Further, since the bonding area between the porous plate-like fillers 1 through the matrix 3m is wider than that of the spherical filler, the strength of the entire heat insulating film is increased, and erosion and peeling are less likely to occur.

  The heat insulating film 3 of the present invention preferably contains at least one of ceramics, glass, and resin as the matrix 3m. From the viewpoint of good heat resistance, the matrix 3m is more preferably ceramics or glass. More specifically, examples of the matrix material include silica, alumina, mullite, zirconia, titania, silicon nitride, silicon oxynitride, silicon carbide, silicon oxycarbide, calcium silicate, calcium aluminate, Calcium aluminosilicate, aluminum phosphate, aluminosilicate, potassium aluminosilicate, glass and the like can be mentioned. These are preferably amorphous from the viewpoint of low thermal conductivity. Or when the material of the matrix 3m is ceramics, it is desirable to be an aggregate of fine particles having a particle size of 500 nm or less. By making an aggregate of fine particles having a particle diameter of 500 nm or less into the matrix 3 m, the thermal conductivity can be further lowered. Moreover, when the material used as the matrix 3m is resin, a silicone resin, a polyimide resin, a polyamide resin, an acrylic resin, an epoxy resin, etc. can be mentioned.

  The heat insulating film 3 preferably has an overall porosity of 10 to 90%, and the matrix 3m has a porosity of 0 to 70%.

  The heat insulating film 3 preferably has a thickness of 0.1 to 5 mm. By setting it as such thickness, the heat insulation effect can be acquired, without having a bad influence on the characteristic of the base material coat | covered with the heat insulation film | membrane 3. In addition, the thickness of the heat insulation film | membrane 3 can be suitably selected within the said range according to the use.

Insulation film 3 is preferably heat capacity is 1500kJ / ^(m 3 · K) or less, more preferably 1300kJ / ^(m 3 · K) or ^{less, 1000kJ / (m 3 · K} ) that less is Is more preferable, and most preferably 500 kJ / (m ³ · K) or less. When the heat insulating film 3 is formed in the engine combustion chamber with such a low heat capacity, for example, the gas temperature in the engine combustion chamber is easily lowered after the fuel is exhausted. Thereby, problems such as abnormal combustion of the engine can be suppressed.

  The heat insulating film 3 preferably has a thermal conductivity of 1.5 W / (m · K) or less, more preferably 1 W / (m · K) or less, and particularly preferably 0.5 W / (m · K) or less. . Thus, heat transfer can be suppressed by having low thermal conductivity.

  The heat insulating film of the present invention can be used, for example, as a heat insulating film formed on the “surface constituting the engine combustion chamber”. The heat insulating film 3 of the present invention can be used as a heat insulating film formed on an “inner wall of an automobile exhaust pipe” or a heat insulating film when it is desired to block heat from a heat generating portion.

  The heat insulating film of the present invention can be formed by applying a coating composition on a substrate and drying it. It can also be formed by heat treatment after drying. At this time, the heat insulating film 3 can be laminated by repeatedly performing application and drying or heat treatment to form a thick heat insulating film 3 (a laminated body of heat insulating films). Or after forming the heat insulation film | membrane 3 on the temporary base material 8, by removing this temporary base material, the heat insulation film 3 formed in the shape of a thin plate independently is produced, and this heat insulation film | membrane 3 is You may adhere | attach or join to the target base material (base material different from a "temporary base material").

  As the substrate, metal, ceramics, glass, plastic, wood, cloth, paper, or the like can be used. In particular, examples where the substrate is a metal include iron, iron alloy, stainless steel, aluminum, aluminum alloy, nickel alloy, cobalt alloy, tungsten alloy, and copper alloy.

  The coating composition uses the porous plate-like filler 1 and one or more selected from the group consisting of an inorganic binder, an inorganic polymer, an organic-inorganic hybrid material, an oxide sol, and water glass. Can do. Furthermore, a dense filler, a viscosity modifier, a solvent, a dispersant, and the like may be included.

  Specific materials included in the coating composition include cement, bentonite, aluminum phosphate, silica sol, alumina sol, boehmite sol, zirconia sol, titania sol, tetramethyl orthosilicate, tetraethyl orthosilicate, polysilazane, polycarbosilane, polyvinyl silane, Polymethylsilane, polysiloxane, polysilsesquioxane silicone, geopolymer, sodium silicate and the like. In the case of organic-inorganic hybrid materials, acrylic-silica hybrid materials, epoxy-silica hybrid materials, phenol-silica hybrid materials, polycarbonate-silica hybrid materials, nylon-silica hybrid materials, nylon-clay hybrid materials An acrylic-alumina hybrid material, an acrylic-calcium silicate hydrate hybrid material, and the like are desirable.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

Example 1
ZrO ₂ raw material (ZrO ₂ particles) zirconia powder, TiO ₂ as an additive containing a substituent atom, carbon black as a pore former, polyvinyl butyral resin (PVB) as a binder, dioctyl phthalate (DOP) as a plasticizer, And xylene and 1-butanol were added as a solvent. This was made into the raw material composition. The addition amount (preparation amount) of each component in the raw material composition was 0.99 mol of zirconia powder and 0.01 mol of TiO ₂ (total of Zr and Ti was 1 mol. The actual substitution ratio will be described later. (Table 1 shows the formulation and Table 2 shows the analysis results.) Furthermore, they were 6% by volume of carbon black, 9% by volume of binder, 4% by volume of plasticizer, and 74.3% by volume of solvent with respect to the total of ZrO ₂ particles and substituted atoms.

  Next, this raw material composition was mixed in a ball mill for 30 hours to prepare a slurry for forming a green sheet (coating composition). Thereafter, the slurry was vacuum defoamed, and the viscosity was adjusted to 4 Pa · s. Thereafter, the slurry was applied in the form of a film so that the thickness after firing was 10 μm by a doctor blade device to form a green sheet. The green sheet was cut to have a size of 50 mm long × 50 mm wide. Thereafter, the compact was degreased at 600 ° C. for 5 hours and then fired at 1100 ° C. for 2 hours to obtain a thin plate-like fired body. Thereafter, the obtained fired body was crushed using a dry bead mill to obtain a porous plate filler 1.

Next, in the obtained porous plate-like filler 1, the diameter of the ZrO ₂ particles was 50 nm. The porous plate-like filler 1 had an average pore diameter of 0.13 μm and a porosity of 60%. The porous plate-like filler 1 had a thermal conductivity of 0.15 W / (m · K). The “thermal conductivity of the porous plate filler” is a value obtained by measuring the thermal conductivity of the fired body (before pulverization). Further, when 20 arbitrary porous plate-like fillers 1 were measured, the aspect ratio was 4 and the minimum length was 10 μm.

In addition, the porosity was calculated | required by the following formula.
Porosity (%) = (1− (apparent particle density ÷ true density)) × 100
In the above formula, the apparent particle density was measured by an immersion method using mercury. The true density was measured by a pycnometer method after sufficiently pulverizing the porous plate-like filler.

  Moreover, the particle diameter observed the fine structure (FE-SEM) of the porous plate-shaped filler, measured the magnitude | size of one particle by image processing, and calculated | required the average value of ten pieces.

The proportion of atoms contained in the porous plate filler 1 was measured by chemical analysis (JIS R1603). From the result, O / Zr (molar ratio) was calculated and obtained. Table 2 _shows x of _{Zr 1-x} O 2 _{A x,} the O / Zr. In addition, when there was one kind of substituent atom, it was set as the substituted atom A1 and the addition amount was expressed as x1 (in this case, A1 and x1 correspond to A and x of Zr _1-x O ₂ A _x ). When there are two kinds of substituent atoms, the substituent atoms are A1 and A2, and the respective addition amounts are x1 and x2 (in this case, A1 and A2 correspond to A of Zr _1-x O ₂ A _x , and x1 + x2 is Zr _1-x corresponds to _x of O ₂ A _x ). Moreover, it was confirmed by X-ray analysis whether it is a single phase (whether a different phase such as TiO ₂ exists).

[Thermal conductivity]
The thermal conductivity of the porous plate filler 1 was measured as follows. First, the porous plate filler 1 and the same material separately molded into 0.5 mm × 5 mm × 30 mm are fired, the thermal diffusivity is measured by the optical alternating current method, and the specific heat is measured by the DSC method. The product of the diffusivity, specific heat, and density (apparent particle density) was defined as the thermal conductivity of the porous plate filler 1. The apparent particle density was measured by an immersion method using mercury.

[Heat capacity]
The heat capacity of the porous plate filler 1 was measured as follows. First, the same material as the porous plate filler 1 is separately molded into 0.5 mm × 5 mm × 30 mm, fired, the specific heat is measured by DSC method, and the product of specific heat and density (apparent particle density) is porous. The heat capacity of the plate filler 1 was used. The apparent particle density was measured by an immersion method using mercury.

  Next, the polysiloxane used as the matrix 3m and the porous plate-like filler 1 were mixed at a volume ratio of 20:80. And this composition was apply | coated on the aluminum alloy which is a base material, and after drying, it heat-processed at 200 degreeC for 2 hours, and formed the heat insulation film 3 (150 micrometers in thickness) on a base material.

  The heat conductivity and heat capacity of the heat insulating film 3 were measured in the same manner as the method for measuring the heat conductivity and heat capacity of the porous plate filler 1.

(Comparative Example 1)
The porous plate filler 1 was produced by firing in the air atmosphere without adding the additive. Others were the same as in Example 1. The porosity of the porous plate filler 1 was 60%.

(Examples 2-7, Comparative Example 2)
As shown in Table 2, the porous plate-like filler 1 was produced as in Example 1 by changing the additive and the amount of addition. The amount of ZrO _{2 and} the amount of additive were determined so that the sum of the substitution atoms (Ti, Si, Ce, Hf) and Zr of the additive was 1 mol. The analysis results are shown in Table 3. The porosity of the porous plate-like filler 1 of Examples 2 to 7 and Comparative Example 2 was 60%.

(Examples 8 to 17)
The addition amount (preparation amount) of each component in the raw material composition was 0.9 mol of zirconia powder and 0.1 mol of TiO ₂ (total of Zr and Ti was 1 mol). And the porous plate-like filler 1 of Table 1 having the values of the aspect ratio, minimum length, porosity, average pore diameter, and average particle diameter after firing was prepared. Others were the same as in Example 3. The analysis results are shown in Table 3.

  Porous materials of Examples 1 to 17 in which a part of Zr is substituted with Ti, Si, Ce, and Hf, the molar ratio of O and Zr is in the range of 2 <O / Zr <2.4, and is a single phase The plate-like filler 1 has a lower thermal conductivity and a larger heat capacity than Comparative Example 1. Similarly, in the heat insulating film 3 using the porous plate-like filler 1, the thermal conductivity was lowered and the heat capacity was increased. In Comparative Example 2, the result was not good because the amount of the additive added was large and a different phase was generated.

In Examples 1 to 3, a part of Zr was substituted with Ti. When the amount of TiO ₂ added was large and the molar ratio of O and Zr was large, the thermal conductivity of the porous plate-like filler 1 was lowered and the heat capacity was increased. Also in the heat insulating film 3 using this porous plate-like filler 1, the thermal conductivity was lowered and the heat capacity was increased. Further, Example 7 is substituted with two kinds of atoms. When Example 3 and Example 7 were compared, the thermal conductivity of the porous plate-like filler 1 was lowered when Ti and Si were substituted rather than being substituted with Ti alone. The thermal conductivity of the heat insulating film 3 using the porous plate filler 1 was also lowered.

  When Example 8 and Example 3 are compared, Example 8 has a larger aspect ratio of the porous plate-like filler 1. For this reason, the heat conductivity of the heat insulating film 3 of Example 8 was lower than that of the heat insulating film 3 of Example 3. When Example 9 and Example 3 are compared, Example 9 has a larger aspect ratio of the porous plate-like filler 1 and a shorter minimum length. For this reason, the heat conductivity of the heat insulating film 3 of Example 9 was lower than that of Example 3. When Example 10 and Example 3 are compared, Example 10 has a shorter minimum length of the porous plate filler 1. For this reason, the heat conductivity of the heat insulating film 3 of Example 10 was lower than that of Example 3. Further, when Example 11 and Example 3 are compared, Example 11 has a shorter minimum length of porous plate filler 1. For this reason, the heat conductivity of the heat insulating film 3 of Example 11 was lower than that of Example 3.

  The porous plate-like filler of Example 12 has a minimum length longer than that of Example 3. For this reason, the heat insulating film 3 of Example 12 had higher thermal conductivity than Example 3.

  When Example 13 is compared with Example 3, Example 13 has a lower porosity of porous plate-like filler 1, a smaller average pore diameter, and a higher thermal conductivity. For this reason, the heat insulating film 3 of Example 13 had higher thermal conductivity than the heat insulating film 3 of Example 3. On the other hand, when Example 14 and Example 3 are compared, the porosity of the porous plate-like filler 1 of Example 14 is high, the average pore diameter is large, and the thermal conductivity is low. For this reason, the heat insulating film 3 of Example 14 had lower thermal conductivity than the heat insulating film 3 of Example 3. The porous plate-like filler 1 of Example 15 has a higher porosity, a larger average pore diameter, and a lower thermal conductivity than the porous plate-like filler 1 of Example 14. For this reason, the heat insulating film 3 of Example 15 was lower in thermal conductivity than the heat insulating film 3 of Example 14.

  Comparing Example 16 and Example 3, Example 16 has a smaller average particle diameter of the porous plate filler 1 and a lower thermal conductivity. For this reason, the heat insulation film 3 of Example 16 had lower thermal conductivity than the heat insulation film 3 of Example 3. On the other hand, when Example 17 and Example 3 are compared, Example 17 has a larger average particle diameter of the porous plate-like filler 1 and higher thermal conductivity. For this reason, the heat insulating film 3 of Example 17 had higher thermal conductivity than the heat insulating film 3 of Example 3.

  The porous plate-like filler of the present invention can be used as a material for a heat insulating film excellent in heat insulating performance. The heat insulating film of the present invention can be used, for example, as a heat insulating film formed on the “surface constituting the engine combustion chamber”.

1: porous plate-like filler, 3: heat insulation film, 3m: matrix, 8: substrate.

Claims (6)

The plate has an aspect ratio of 3 or more, the minimum length is 0.1 to 50 μm, the porosity is 20 to 90%, a part of Zr is substituted with tetravalent atoms, and the moles of O and Zr A ZrO ₂ -based porous plate filler having a ratio of 2 <O / Zr <2.4 and a single phase. The composition formula is Zr _1-x O ₂ A _x (A is at least one selected from the group consisting of Ti, Si, Ce, and Hf), and 0 <x <0.18. ZrO ₂ -based porous plate filler. The ZrO ₂ porous plate filler according to claim 1 or 2, wherein the thermal conductivity is 1 W / (m · K) or less. The ZrO ₂ porous plate filler according to any one of claims 1 to ³ , wherein the heat capacity is 250 to 2500 kJ / (m ³ · K). The ZrO ₂ porous plate filler according to any one of claims 1 to 4, which has pores having an average pore diameter of 10 to 500 nm. Insulation film containing ZrO ₂ based porous plate-like filler according to any one of claims 1 to 5.

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