WO2015115668A1

WO2015115668A1 - Porous plate-shaped filler and thermal insulation film

Info

Publication number: WO2015115668A1
Application number: PCT/JP2015/053022
Authority: WO
Inventors: 博治小林
Original assignee: 日本碍子株式会社
Priority date: 2014-01-31
Filing date: 2015-01-28
Publication date: 2015-08-06

Abstract

Provided are a porous plate-shaped filler that can be used as a material for a thermal insulation film having exceptional thermal insulation performance, and a thermal insulation film. The porous plate-shaped filler (1) has a plate-like shape with an aspect ratio of 3 or higher and a minimum length is 0.5-50 μm, the overall porosity of the porous plate-shaped filler being 20-90%, and the porosity being lower on the periphery than in the center. Less of a matrix penetrates the filler, whereby the thermal conductivity can be lowered. Therefore, even a thin thermal insulation film has a greater thermal insulation effect than in the past.

Description

Porous plate filler and heat insulating film

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 insulation efficiency and flame retardancy by forming on the surface is desired. Patent Document 1 discloses an internal combustion engine including a structural member with improved heat insulation performance. In the internal combustion engine of Patent Document 1, 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. The heat insulating material is laminated in a state where each particle of spherical mesoporous silica (MSS) particles having an average particle diameter of 0.1 to 3 μm is closely packed via a bonding material. Innumerable mesopores having an average pore diameter of 1 to 10 nm are formed in the MSS particles. Thereby, heat insulation performance is demonstrated.

Patent Document 2 discloses that a porous plate-like filler having a plate shape with an aspect ratio of 3 or more, a minimum length of 0.1 to 50 μm, and a porosity of 20 to 99% is used for the heat insulating film. ing. In Patent Document 2, a porous coating filler is dispersed in an organic resin binder, an inorganic polymer binder, an organic-inorganic composite binder, or the like, so that the formed coating film (heat insulating film) exhibits heat insulating properties. Yes.

JP 2011-52630 A International Publication No. 2013/191263

However, when the particles and fillers described in Patent Documents 1 and 2 are used, matrix components such as binder penetrate into the pores of the above-mentioned particles and filler, and the heat insulating effect by the pores is weakened, and the heat conduction of the heat insulating film The rate was getting higher. For this reason, the filler and heat insulation film | membrane with a higher heat insulation effect are calculated | required.

An object of the present invention is to provide 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 present inventors have found that the above-mentioned problem can be solved by providing a layer different from the central portion on the outer peripheral portion of the porous plate-like filler. According to the present invention, the following porous plate filler and heat insulating film are provided.

[1] A plate shape with an aspect ratio of 3 or more, a minimum length of 0.5 to 50 μm, an overall porosity of 20 to 90%, and a lower porosity in the outer peripheral portion than in the central portion Plate-like filler.

[2] The porous plate filler according to [1], wherein the material types of the base material of the center portion and the outer peripheral portion are the same.

[3] The porous plate-like filler according to [1], wherein the material types of the base material of the central portion and the outer peripheral portion are different.

[4] The porous plate filler according to any one of [1] to [3], wherein the outer peripheral portion has a porosity of 10% or more lower than that of the central portion.

[5] The porous plate filler according to any one of [1] to [4], wherein the outer peripheral portion has an average pore diameter smaller than that of the central portion.

[6] The porous plate filler according to any one of [1] to [5], wherein an average pore diameter of the outer peripheral portion is 0.1 μm or less.

[7] The porous plate filler according to any one of [1] to [6], wherein the outer peripheral portion has a thickness of 1 μm or more.

[8] A heat insulating film containing the porous plate filler according to any one of [1] to [7].

[9] The heat insulation film according to [8], wherein the thermal conductivity is 1.5 W / (m · K) or less.

A porous plate with an aspect ratio of 3 or more, a minimum length of 0.5 to 50 μm, an overall porosity of 20 to 90%, and a lower porosity in the outer periphery than in the center. The filler is excellent in heat insulation performance. The heat insulation film | membrane of this invention contains said porous plate-shaped filler. Therefore, the heat insulating film of the present invention is less heat intruded into the filler by a matrix component such as a binder as compared with the case where a porous plate-like filler having the same porosity in the central portion and the outer peripheral portion is used. The conductivity can be lowered. For this reason, even if it is a thin heat insulation film | membrane, it is excellent in heat insulation performance and its heat insulation effect is higher than before.

It is a perspective view which shows typically one Embodiment of the porous plate-shaped filler of this invention. It is a figure explaining the outer peripheral part and center part of the porous plate-shaped filler of this invention. It is sectional drawing of the porous plate-shaped filler of other embodiment of this invention. It is sectional drawing which shows typically one Embodiment of the heat insulation film | membrane of this invention. 4 is a SEM photograph of the vicinity of the center of the porous plate filler in the heat insulating film of Example 1. 4 is a SEM photograph near the center of a porous plate-like filler in the heat insulating film of Comparative Example 1.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be added without departing from the scope of the invention.

[1] Porous plate filler:
FIG. 1A shows an embodiment of the porous plate filler 1. The 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 0.5 to 50 μm, an overall porosity of 20 to 90%, and an outer periphery from the central portion 4. Part 5 has a lower porosity. The porous plate-like filler 1 includes a base material and pores. A layer having a different base material from the central portion 4 of the porous plate-like filler 1 (when the materials are different) is the outer peripheral portion 5, and the outer peripheral portion 5 has a lower porosity than the central portion 4. In other words, when the materials are different, when the material type is specified from the central portion 4 toward the outer periphery, the changed portion to the outermost periphery is defined as the outer peripheral portion 5. When the porous plate-like filler 1 is formed of a single type of base material (when the material of the central portion 4 and the outer layer is the same type), it is similar to the outer shape of the porous plate-like filler 1 The area reduced 80% on the inner side is defined as the central part 4, and the other 20% on the other side is defined as the outer peripheral part 5 (FIG. 1B). The outer peripheral portion 5 has a lower porosity than the central portion 4, but depending on the manufacturing method, the material of the central portion 4 and the outer layer may be the same type or different types, with respect to the minimum length direction. The outer peripheral portion 5 in the vertical direction (left-right direction in the figure) may be thinner than 20% (FIG. 1C). Therefore, it is better to measure the porosity of the outer peripheral portion 5 in the minimum length direction.

In this specification, the aspect ratio is defined by 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 0.5 to 50 μm. And a plate-like material whose thickness (minimum length) is not constant are also included. Further, the porous plate-like filler 1 may have 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 aspect ratio, the longer the heat transfer path is refracted and the heat conductivity of the heat insulating film 3 becomes lower when the heat insulating film 3 is formed. 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 minimum length of the porous plate-like filler 1 is 0.5 to 50 μm, more preferably 0.5 to 20, further preferably 2 to 15 μm, and most preferably 5 to 15 μm. In the case of 0.5 to 50 μm, since the aspect ratio becomes large, it is easy to stack when the heat insulating film 3 is formed, and the thermal conductivity can be lowered. In the case of 5 to 50 μm, since the minimum length is large, the strength of the porous plate-like filler 1 can be made sufficient, which is suitable for handling and the yield is increased. By setting the minimum length to 0.5 μm or more, the strength of the porous plate-like filler 1 can be made sufficient, which is suitable for handling. Specifically, if the porous plate-like filler 1 is too thin, it may be difficult to maintain the shape of the porous plate-like filler 1 during the manufacturing process of the porous plate-like filler 1. However, by setting the minimum length to 0.5 μm or more, the strength to prevent the porous plate-like filler 1 from cracking in the process of making the porous plate-like filler 1 into a coating composition for forming a heat insulating film, etc. be able to. Further, when the heat insulating film 3 including the porous plate-like filler 1 is formed while ensuring a sufficient thickness for exhibiting heat insulating properties by setting the minimum length to 50 μm or less, the laminate can be formed well. can do. If the porous plate-like filler 1 is too thick, the number of layers of the porous plate-like filler 1 contained in the heat insulating film 3 is reduced when the heat insulating film 3 is formed, so that the heat transfer path becomes straight and shortens. It is easy and the heat conductivity of the heat insulation film 3 may become high.

The porous plate-like filler 1 preferably has an overall porosity of 20 to 90%. By setting the overall porosity to 90% or less, the strength can be ensured. In this specification, the porosity of the whole filler is obtained 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 overall porosity of the porous plate-like filler 1 is preferably 20 to 90%, more preferably 40 to 85%, and still more preferably 50 to 80%. If the porosity is too low, the thermal conductivity of the filler may be high, and if the porosity is too high, the strength of the filler may be weak.

In the porous plate-like filler 1, the porosity of the outer peripheral portion 5 is preferably lower than the porosity of the central portion 4, more preferably 10% or more, and particularly preferably 20% or more. In the present specification, the porosity of the central portion 4 and the outer peripheral portion 5 is measured using a microstructure image obtained by sampling a cross section parallel to the minimum length of the filler with an FIB and observing with a FE-SEM. This is done randomly with 10 fillers, and an average value is obtained, which is the respective porosity.

In the porous plate-like filler 1, the outer peripheral portion 5 is preferably smaller in average pore diameter than the central portion 4, and the outer peripheral portion 5 preferably has an average pore diameter of 0.1 μm or less. In the present specification, the pore diameters of the central portion 4 and the outer peripheral portion 5 are measured using a microstructure image obtained by sampling a cross section parallel to the minimum length of the filler with an FIB and observing with a FE-SEM. This is performed randomly with 10 fillers, and an average value is obtained to obtain the average pore diameter.

The thickness of the outer peripheral part 5 is preferably 1 μm or more. In addition, the thickness of the outer peripheral part 5 is the thickness t _{1 on} the upper side of the center part 4 or the thickness t ₂ on the lower side in the minimum length direction (see FIGS. 1B and 1C). The thickness of the outer peripheral portion 5 is more preferably 1 to 10 μm, still more preferably 1 to 7 μm. By setting it to 1 μm or more, it is possible to prevent the matrix 3 m from entering the central portion 4. Even if there are large pores in the outer peripheral portion 5, the matrix 3 m does not enter the central portion 4 by setting the thickness of the outer peripheral portion 5 to 1 μm or more. On the other hand, by setting the outer peripheral portion 5 to 10 μm or less, it is possible to prevent an increase in the low porosity portion, that is, the high thermal conductivity portion. That is, the heat insulation effect can be exhibited more by making the thickness of the outer peripheral part 5 into this range.

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

Hereinafter, the first embodiment and the second embodiment will be described as embodiments of the porous plate filler 1 in which the outer peripheral portion 5 has a lower porosity than the central portion 4.

[1-1] First embodiment:
As the first embodiment, it is preferable that the material types of the base material of the central portion 4 and the outer peripheral portion 5 of the porous plate filler 1 are the same. Even if the porous plate-like filler 1 contains an additive, it is included in the first embodiment as long as the material types of the base material of the central portion 4 and the outer peripheral portion 5 are the same. A material having a low thermal conductivity is used for the central portion 4 of the filler used as a heat insulating material. By using the same material for the outer peripheral portion 5, a filler having a low thermal conductivity can be obtained.

In addition, in order to confirm whether the material type of the base material is the same material type, element analysis (EDS) is performed in the FE-SEM observation of each of the central part 4 and the outer peripheral part 5, and the same kind of element is detected. The composition other than the pores is examined. For example, if Zr and O are mainly detected, it is determined that the material is Zr and O (zirconia). In this case, even if a small amount of Si is detected as an additive or impurity, if it is mostly Zr and O, it is determined that the material is Zr and O (zirconia).

When the central part 4 and the outer peripheral part 5 are formed of the same kind of material, it is preferable to use a material having a low thermal conductivity for both the central part 4 and the outer peripheral part 5, thereby reducing the thermal conductivity of the entire porous plate-like filler 1. Can be lowered. In the case where the central portion 4 and the outer peripheral portion 5 are formed of the same material, an inorganic material, an organic material, or a composite material of an inorganic material and an organic material may be used. Among them, zirconia, partially stabilized zirconia (for example, yttria partially stabilized zirconia), fully stabilized zirconia (for example, yttria fully stabilized zirconia), yttrium oxide, alumina, silica, titania, niobium oxide, strontium oxide, lanthanum oxide, Zirconium, yttria, aluminum, silicon, titanium, niobium, strontium, lanthanum, rare earth zirconate (eg lanthanum zirconate), rare earth silicate (eg yttrium silicate), niobate (eg strontium niobate), Smectite clay minerals such as mullite, mica, swellable mica, spinel, zircon, magnesia, ceria, silicon carbide, silicon nitride, aluminum nitride, strontium carbonate, montmorillonite, hydrotal It is preferably an inorganic material such as layered double hydroxide such as yttrium, zirconia, partially stabilized zirconia (eg, yttria partially stabilized zirconia), fully stabilized zirconia (eg, yttria fully stabilized zirconia), oxidation More preferred is a metal oxide such as yttrium, alumina, silica, titania, niobium oxide, strontium oxide, lanthanum oxide. These may be used alone or in combination of two or more. However, the material of the center part 4 and the outer peripheral part 5 is not limited to these.

[1-2] Second embodiment:
As the second embodiment, it is preferable that the material types of the base materials of the central portion 4 and the outer peripheral portion 5 of the porous plate-like filler 1 are different. The outer peripheral portion 5 is preferably made of a material that can be easily sintered at a low temperature. Sintering (densification) proceeds by using different materials that are easily sintered at a low temperature for the outer peripheral portion 5, and the porosity difference from the central portion 4 becomes large. When the central portion 4 and the outer peripheral portion 5 are formed of different materials, the same material as that of the first embodiment can be adopted as the central portion 4. Further, the same material as that of the first embodiment can be used for the outer peripheral portion 5, and in addition, a metal such as iron, silver, nickel, copper, titanium, chromium, manganese, cobalt, zinc, and molybdenum can be used. It can also be adopted. However, the material of the center part 4 and the outer peripheral part 5 is not limited to these.

[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 green sheet forming slurry and a peripheral portion forming slurry, a green sheet forming step for forming a green sheet, and a green A crushing step for crushing the sheet, an outer peripheral portion forming step for forming the outer peripheral portion 5 of the filler, and a firing step for firing the sheet to obtain the porous plate-like filler 1.

The slurry preparation step is a step of preparing a ceramic powder, a green sheet forming slurry containing a pore former, and a peripheral portion forming slurry. 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 said crushing process is a process of crushing a green sheet and obtaining a filler-like green sheet. The said outer peripheral part formation process is a process of forming the outer peripheral part 5 in the outer periphery of the formed filler-like green sheet, and obtaining a 2 layer structure green sheet. The firing step is a step of obtaining a porous plate-like filler 1 by firing a two-layer structure green sheet. In addition, the said crushing process may be after the said outer peripheral part formation process.

Since the manufacturing method of such a porous plate-like filler 1 includes the above steps, the porous plate-like filler 1 that can be used as a material of the heat insulating film 3 having excellent heat insulating performance can be manufactured. Hereinafter, each step will be described in detail.

[2-1] Slurry preparation process:
A green sheet forming slurry and an outer peripheral portion forming slurry are prepared by adding a pore former, a binder, a plasticizer, a solvent and the like to the ceramic powder and mixing them by a ball mill or the like.

Ceramic powders include zirconia powder, partially stabilized zirconia powder (eg, yttria partially stabilized zirconia powder), fully stabilized zirconia powder (eg, yttria fully stabilized zirconia powder), alumina powder, silica powder, titania powder, oxidation Lanthanum powder, yttria powder, rare earth zirconate powder (eg lanthanum zirconate powder), rare earth silicate powder (eg yttrium silicate powder), niobate powder (eg strontium niobate powder), mullite powder, spinel Powder, zircon particles, magnesia powder, yttria powder, ceria powder, silicon carbide powder, silicon nitride powder, aluminum nitride powder, and the like can be used. These may be used alone or in combination of two or more. Further, the powder is not limited to a dry powder, and a powder in a colloidal state (sol state) dispersed in water or an organic solvent may be used. As the pore former, latex particles, melamine resin particles, PMMA particles, polyethylene particles, polystyrene particles, carbon black particles, graphite, foamed resin, water absorbent resin, etc. can be used, and the shape is spherical, plate-like, fiber-like Etc. As the binder, polyvinyl butyral resin (PVB), polyvinyl alcohol resin, polyvinyl acetate resin, polyacrylic resin, or the like can be used. As the plasticizer, DBP (dibutyl phthalate), DOP (dioctyl phthalate), or the like can be used. As the solvent, xylene, 1-butanol and the like can be used.

In order to reduce the porosity of the outer peripheral portion 5, it is preferable that the outer peripheral portion forming slurry has a smaller amount of pore former than the green sheet forming slurry. Moreover, it is preferable to select a material that can be easily sintered at a low temperature as the ceramic powder used for the outer peripheral portion forming slurry. For example, silica, zinc oxide, and the like are preferably used, but are not limited thereto.

[2-2] Green sheet forming step:
The viscosity is adjusted to 100 to 10000 cps by subjecting the green sheet forming slurry to a vacuum defoaming treatment. Thereafter, a green sheet is formed by a doctor blade device so that the thickness after firing becomes 0.5 to 100 μm, and the outer shape is cut to a size of (0.5 to 200) mm × (0.5 to 200) mm. I do.

[2-3] Crushing step:
As a method for crushing the green sheet, for example, the green sheet 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 having a plate shape with an aspect ratio of 3 or more and a minimum length of 0.5 to 50 μm, it is preferable to use an airflow classifier to perform sizing (classification). The green sheet is crushed to obtain a filler-like green sheet.

[2-4] Outer peripheral part forming step:
Examples of the method for forming the outer peripheral portion 5 include dip molding, sputtering, plating, fluidized bed coating, rolling coating, and the like. Any method may be used, but dip molding will be described as an example.

The outer periphery 5 is formed by dipping the filler-like green sheet prepared in the crushing step on the outer periphery forming slurry prepared in the slurry preparation step. If the outer peripheral portion 5 is formed before firing, the pore-forming material is present and pores are not yet formed. Therefore, the outer peripheral portion forming slurry can be prevented from being immersed in the central portion 4 of the filler 1.

[2-5] Firing step:
The firing conditions of the two-layer structure green sheet to which the outer peripheral portion forming slurry is adhered can be appropriately set. For example, it is preferably 0.5 to 20 hours at 800 to 2300 ° C. in the air, more preferably 5 to 20 hours at 800 to 1800 ° C., and 5 to 20 hours at 800 to 1300 ° C. It is particularly preferred.

[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 insulating film 3 will be described with reference to FIG. FIG. 2 is a cross-sectional view parallel to the film thickness direction schematically showing one embodiment of the heat insulating film 3 of the present invention. The heat insulating film 3 is formed on the base material 8 and 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, but a larger number of stacked layers is preferable, and 5 or more is desirable. 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.

In the heat insulating film 3 of the present invention, it is preferable that the matrix 3m does not enter the pores of the porous plate-like filler 1. Since the matrix 3m having a high thermal conductivity enters the pores of the porous plate-like filler 1, the thermal conductivity of the porous plate-like filler 1 becomes high, and the heat conductivity of the heat insulating film 3 becomes high. It is. Since the porous plate-like filler 1 has a lower porosity in the outer peripheral portion 5 than in the central portion 4, the matrix 3 m is less likely to enter the pores, and the heat insulating performance of the heat insulating film 3 is improved.

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 material for forming the matrix 3m include silica, alumina, mullite, zirconia, titania, silicon nitride, silicon oxynitride, silicon carbide, silicon oxycarbide, calcium silicate, calcium aluminate, and calcium aluminosilicate. , Aluminum phosphate, potassium aluminosilicate, glass and the like. These are preferably amorphous from the viewpoint of low thermal conductivity. When the material of the matrix 3m is ceramic, the matrix 3m is preferably 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 a resin, examples of the matrix 3m include a silicone resin, a polyimide resin, a polyamide resin, an acrylic resin, and an epoxy resin.

The heat insulating film 3 preferably has a total 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 8 coat | covered with the heat insulation film | membrane 3. FIG. In addition, the thickness of the heat insulation film | membrane 3 can be suitably selected within the said range according to the use.

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

The heat insulating film 3 of the present invention is applied to a substrate 8 (for example, a surface constituting an engine combustion chamber, an inner wall of an automobile exhaust pipe, etc.) containing a porous plate filler 1 and dried. Can be formed. 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 8, the heat insulation film 3 formed in the shape of a thin plate independently is produced, and this heat insulation film | membrane 3 is produced. The target substrate 8 (a substrate different from the “temporary substrate”) may be bonded or bonded.

The coating composition may include the porous plate-like filler 1 and one or more selected from the group consisting of an inorganic binder, an inorganic polymer, an oxide sol, and water glass. Furthermore, the coating composition may contain a dense filler, a viscosity modifier, a solvent, a dispersant and the like.

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, geopolymer, sodium silicate and the like.

As the base material 8 for forming the heat insulating film 3, metal, ceramics, glass, plastic, wood, cloth, paper or the like can be used. In particular, examples where the substrate 8 is a metal include iron, iron alloy, stainless steel, aluminum, aluminum alloy, nickel alloy, cobalt alloy, tungsten alloy, and copper alloy.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1
Carbon black as a pore former, polyvinyl butyral resin (PVB) as a binder, dioctyl phthalate (DOP) as a plasticizer, and xylene and 1-butanol as solvents were added to zirconia powder as ceramic powder. This was made into the raw material composition. Specifically, two raw material compositions were prepared: a green sheet forming slurry and an outer peripheral portion forming slurry. The slurry for forming the green sheet was 6% by volume of zirconia powder, 6% by volume of carbon black, 7% by volume of binder, 4% by volume of plasticizer, and 77% by volume of solvent. The outer peripheral portion forming slurry was 9% by volume of zirconia powder, 3% by volume of carbon black, 7% by volume of binder, 4% by volume of plasticizer, and 77% by volume of solvent.

Next, these two raw material compositions (slurry) were mixed in a ball mill for 30 hours. Then, after performing each vacuum defoaming process, the viscosity was adjusted to 4 Pa.s. Thereafter, the slurry for forming a green sheet was applied in a film shape by a doctor blade device so that the thickness after firing was 8 μm, thereby forming a green sheet. The green sheet was cut to have a size of 50 mm long × 50 mm wide. Thereafter, this compact was pulverized using a dry bead mill. The crushed shaped body was dipped into the slurry for forming the outer peripheral portion to obtain a two-layer structure green sheet. This was degreased at 600 ° C. for 5 hours and then calcined at 1100 ° C. for 2 hours to obtain a porous plate filler 1.

The obtained porous platy filler 1 had a ZrO ₂ particle diameter of 50 nm, an average pore diameter of 0.13 μm, and an overall porosity of 62%. Moreover, when arbitrary 20 pieces were measured about the obtained porous plate-shaped filler 1, and the average was calculated | required, the aspect-ratio was 4, and minimum length was 10 micrometers. In Example 1, since the thickness after firing is 8 μm and the minimum length after forming the outer peripheral portion 5 is 10 μm, the thickness of the outer peripheral portion 5 is 1 μm (on the upper side of the central portion 4). Each of the thickness t ₁ and the lower thickness t ₂ is 1 μm) (see FIG. 1B).

Next, the matrix material (material that becomes the matrix 3 m) and the porous plate-like filler 1 were mixed at a volume ratio of 20:80 to prepare a coating composition. And this coating composition was apply | coated on the aluminum alloy which is the base material 8, and after heat-drying, it heat-processed at 200 degreeC for 2 hours, and formed the heat insulation film | membrane 3 (150 micrometers in thickness) on the base material 8. FIG.

(Thermal conductivity)
The thermal conductivity in the thickness direction of the heat insulating film 3 was measured with a laser flash two-layer model. Regarding thermal conductivity, 1.00 W / (m · K) or less is A and B is 1.01 to 1.59 W / (m · K) and B is 1.60 W / (m · K) or more. It is shown in Table 1 as C. In addition, the heat insulation film | membrane 3 was produced in the engine combustion chamber, and it was set as the criteria of judgment whether the heat insulation effect for improving a fuel consumption is exhibited.

(Presence or absence of matrix penetration)
The microstructure of the cross section in the film thickness direction of the heat insulating film 3 was sampled by FIB and observed by FE-SEM. FIG. 3A shows an SEM photograph of Example 1. The central part of the porous plate filler 1 was observed. Black matrix 3m was not observed in the pores of the filler. That is, the matrix 3 m did not enter the central portion of the porous plate filler 1.

(Comparative Example 1)
The green sheet-forming slurry was applied in a film form with a doctor blade device so that the thickness after firing was 10 μm, to form a green sheet. After performing the crushing step, the porous plate filler 1 was obtained by firing without performing the outer peripheral portion forming step. In Comparative Example 1, the outer peripheral portion 5 was not formed.

FIG. 3B shows an SEM photograph of Comparative Example 1. The central part of the porous plate filler 1 was observed. Unlike Example 1, in FIG. 3B of Comparative Example 1, black matrix 3m was observed in the pores of the filler. In other words, the matrix 3 m had entered the central portion of the porous plate filler 1.

(Example 2)
A slurry for forming the outer periphery was prepared with 12% by volume of zirconia powder, no carbon black added, 7% by volume of binder, 4% by volume of plasticizer, and 77% by volume of solvent. The same green sheet forming slurry as in Example 1 was used. Other than that, the porous plate-like filler 1 was produced in the same manner as in Example 1. The porosity of the entire porous plate-like filler 1 was 58%.

(Examples 3 and 4)
The ceramic powder of the outer periphery forming slurry was changed to SiO ₂ to prepare an outer periphery forming slurry. The outer peripheral portion forming step was performed before firing. In addition, the outer peripheral part forming slurry of Example 3 was added with 6% by volume of carbon black, and the outer peripheral part forming slurry of Example 4 was not added with carbon black. Otherwise, a porous plate-like filler 1 was prepared in the same manner as in Example 1. The overall porosity of the porous plate-like filler 1 was 58% in Example 3 and 52% in Example 4.

(Example 5)
The outer peripheral part 5 was formed by electroless Ni plating. Otherwise, a porous plate-like filler 1 was prepared in the same manner as in Example 1. The porosity of the whole porous plate-like filler 1 was 52%.

(Example 6)
The green sheet-forming slurry of Example 1 was applied in a film shape with a doctor blade device so that the thickness after firing was 35 μm, to form a green sheet. The outer peripheral portion 5 was formed using the outer peripheral portion forming slurry of Example 2. The overall porosity of the porous plate filler 1 was 63%.

(Example 7)
The molded body produced in Example 4 was fired at 1200 ° C. for 2 hours. The porosity of the entire porous plate-like filler 1 was 32%.

(Examples 8 to 17)
In the same manner as in Examples 3 and 4, porous plate filler 1 was produced. However, the thickness of the green sheet was changed. Further, the thickness of the outer peripheral portion 5 was changed by controlling the time for dipping the molded body obtained by cutting the green sheet into the slurry for forming the outer peripheral portion and the pulling speed of the molded body. Table 1 shows the aspect ratio, porosity, and the like of the porous plate-like filler 1.

The porous plate-like fillers 1 of Examples 1 to 17 in which the porosity of the outer peripheral portion 5 is smaller than that of the central portion 4 are less intruded into the pores of the matrix 3m when compared with the comparative example 1 when the heat insulating film 3 is formed. As a result, the thermal conductivity decreased. Comparing Example 4 with Examples 8 and 9, it can be seen that the thermal conductivity of the heat insulating film 3 decreases as the aspect ratio increases. Comparing Example 4 with Examples 10 to 12, it can be seen that the thermal conductivity of the heat insulating film 3 decreases as the minimum length decreases. Comparing Example 4 with Examples 13 to 15, it can be seen that the thermal conductivity of the heat insulating film 3 decreases as the porosity increases. Comparing Example 4 with Examples 16 and 17, it can be seen that the thermal conductivity of the heat insulating film 3 increases as the pore diameter of the outer peripheral portion 5 of the porous plate-like filler 1 increases.

The porous plate filler of the present invention can be used as a material for a heat insulating film having excellent 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, 4: central part, 5: outer peripheral part, 8: base material.

Claims

A porous plate with an aspect ratio of 3 or more, a minimum length of 0.5 to 50 μm, an overall porosity of 20 to 90%, and a lower porosity in the outer periphery than in the center. Filler.
The porous plate-like filler according to claim 1, wherein the base material of the central part and the outer peripheral part are the same.
The porous plate-like filler according to claim 1, wherein a material type of the base material of the central portion and the outer peripheral portion is different.
The porous plate-like filler according to any one of claims 1 to 3, wherein the outer peripheral portion has a porosity of 10% or more lower than that of the central portion.
The porous plate-like filler according to any one of claims 1 to 4, wherein the outer peripheral portion has an average pore diameter smaller than that of the central portion.
The porous plate filler according to any one of claims 1 to 5, wherein an average pore diameter of the outer peripheral portion is 0.1 µm or less.
The porous plate-like filler according to any one of claims 1 to 6, wherein the outer peripheral portion has a thickness of 1 µm or more.
A heat insulating film containing the porous plate-like filler according to any one of claims 1 to 7.
The heat insulating film according to claim 8, wherein the thermal conductivity is 1.5 W / (m · K) or less.