JP2014219082A - Heat insulation material, heat insulation structure, and heat insulation structure manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat insulation material having excellent heat resistance, heat insulation property and flexibility.SOLUTION: A heat insulation material includes a cap sheet made of a polyimide precursor sheet 1 having plural protrusion parts 2 on its surface. The heat insulation material includes a cap sheet made of a polyimide sheet obtained by hardening the polyimide precursor sheet 1 having the plural protrusion parts 2 on its surface. Or, the heat insulation material has plural air bubble chambers on a surface by further laminating a back sheet on any cap sheet described above, and tightly closing the plural protrusion parts 2 provided on the cap sheet.

Description

  The present invention relates to a heat insulating material, a heat insulating structure, and a method for manufacturing the heat insulating structure.

  A polyethylene bubble sheet in which a large number of sealed air chambers are formed by laminating a cap sheet having a large number of convex portions (caps) on the surface and a flat back sheet using low density polyethylene as a cushioning material ( Buffer packaging materials) and heat insulation materials are widely used in industrial and consumer fields.

  The polyethylene bubble sheet is generally used for extruding two polyethylene melt sheets (a melt sheet for forming a cap sheet and a melt sheet for a back sheet) by using an extruder and two dies, and for vacuum forming. The cap sheet forming molten sheet is formed into a cap sheet by a vacuum forming roll having a large number of dents and vacuum suction means, and the back sheet molten sheet is bonded to the bottom surface of the cap sheet as a back sheet and pressed. The air bubble sheet manufactured by completely integrating with a roll is manufactured by peeling from a vacuum forming roll (see, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2009-160857)).

The polyethylene air bubble sheet is usually used by being wound around an object. Generally, since the heat resistance temperature of low density polyethylene is as low as about 70 to 90 ° C., for example, the outer surface of a pipe through which high temperature fluid circulates. In the case of being wound around and used as a heat insulating material, a bubble sheet having higher heat resistance is required.
In particular, when used in a variety of factories or power plants where the generation and mixing of impurities are highly restricted, such as semiconductor manufacturing equipment, and pipes through which high-temperature fluid circulates frequently, melting during use, There has been a demand for a bubble sheet having a high degree of heat resistance in which decomposition is highly suppressed.

JP 2009-160857 A

  As a resin excellent in heat resistance, a polyimide resin having a decomposition temperature as high as about 500 to 600 ° C. is known, but the polyimide resin is a highly crystalline, infusible and insoluble resin, Since it is difficult to melt the polyimide resin or dissolve it in an organic solvent and then process it into a sheet or form a convex part (cap), use it as a material for forming a bubble sheet. I could not.

  Under such circumstances, the present invention aims to provide a heat insulating material capable of exhibiting excellent heat resistance, heat insulating properties and flexibility, and to provide a heat insulating structure and a method for manufacturing the heat insulating structure. It is.

  As a result of intensive studies by the present inventors, a polyimide precursor sheet is formed in advance, and by pressing the polyimide precursor sheet, a convex portion (cap) can be formed on the surface. The polyimide precursor sheet having a plurality of convex portions formed thereon is cured to find that a polyimide sheet having convex portions on the surface can be easily formed, and the present invention is completed based on such knowledge. It came to.

That is, the present invention
(1) A heat insulating material comprising a cap sheet made of a polyimide precursor sheet having a plurality of convex portions on the surface (hereinafter referred to as the heat insulating material I of the present invention as appropriate),
(2) A heat insulating material including a cap sheet made of a polyimide sheet obtained by curing a polyimide precursor sheet having a plurality of convex portions on the surface (hereinafter referred to as the heat insulating material II of the present invention as appropriate). ),
(3) The heat insulating material according to (1) or (2), wherein the height of the convex portion is 1 mm to 25 mm,
(4) The heat insulating material according to any one of (1) to (3), wherein the cap sheet has a thickness of 0.01 to 0.20 mm.
(5) A back sheet is further laminated on the cap sheet according to any one of the above (1) to (4), and a plurality of convex portions provided on the cap sheet are sealed, so that a plurality of surfaces are sealed. A heat insulating material comprising a bubble chamber (hereinafter referred to as the heat insulating material III of the present invention as appropriate),
(6) The heat insulating structure according to any one of the above (1) to (5), wherein a plurality of the heat insulating materials are stacked on the object to be heat-insulated, and (7) on the object to be heat-insulated After arranging a plurality of heat insulating materials including a cap sheet made of a polyimide precursor sheet having a plurality of convex portions on the surface,
A method for producing a heat insulating structure, wherein the polyimide precursor sheet is cured using heat radiated from the object to be insulated;
Is to provide.

  ADVANTAGE OF THE INVENTION According to this invention, while providing the heat insulating material which can exhibit the outstanding heat resistance, heat insulation, and a softness | flexibility, the manufacturing method of a heat insulation structure and a heat insulation structure can be provided.

It is a figure which shows one example of the heat insulating material which concerns on this invention. It is a schematic diagram explaining the manufacturing process of the heat insulating material which concerns on this invention. It is a figure which shows the usage example of the heat insulating material which concerns on this invention. It is a figure which shows one example of the heat insulating material which concerns on this invention. It is a figure which shows the example of 1 form of the heat insulation structure which concerns on this invention. It is a figure which shows the example of arrangement | positioning form of the heat insulating material which comprises the heat insulation structure which concerns on this invention.

First, the heat insulating material of the present invention will be described.
The heat insulating material of the present invention includes the heat insulating material I of the present invention to the heat insulating material III of the present invention.
The heat insulating material I of the present invention includes a cap sheet made of a polyimide precursor sheet having a plurality of convex portions on the surface.
The heat insulating material II of the present invention includes a cap sheet made of a polyimide sheet obtained by curing a polyimide precursor sheet having a plurality of convex portions on the surface.
In the heat insulating material III of the present invention, a back sheet is further laminated on the cap sheet constituting the heat insulating material I of the present invention or the heat insulating material II of the present invention, and a plurality of convex portions provided on the cap sheet are sealed. Thus, a plurality of bubble chambers are provided on the surface.
In the heat insulating material I of the present invention and the heat insulating material II of the present invention, the cap sheet constituting the heat insulating material is composed of a polyimide precursor sheet having a plurality of convex portions on the surface, or the sheet is cured. It is different only in whether it consists of what is made. Moreover, the heat insulating material III of this invention contains the cap sheet which comprises the heat insulating material I of this invention or the heat insulating material II of this invention as an essential structural material.
For this reason, after demonstrating the heat insulating material I of this invention below, the heat insulating material II of this invention and the heat insulating material III of this invention shall be demonstrated sequentially.

  The heat insulating material I of the present invention includes a cap sheet made of a polyimide precursor sheet having a plurality of convex portions on the surface.

1A is a top view of an embodiment of the heat insulating material I of the present invention, FIG. 1B is a cross-sectional view taken along line AA ′ of FIG. 1A, and FIG. It is a fragmentary perspective view in one example of a heat insulating material I of this invention.
As illustrated in FIGS. 1A to 1C, the heat insulating material I of the present invention has a cap sheet made of a polyimide precursor sheet 1 having a plurality of convex portions (caps) 2 on the surface. Is.

  In the heat insulating material I of the present invention, the shape of the convex portion provided on the polyimide precursor sheet is not particularly limited, and examples thereof include a cylindrical shape (as illustrated in FIG. 1), a prismatic shape, a conical shape, and the like. Preferably, it is cylindrical.

  In the heat insulating material I of the present invention, the height of the convex portion provided on the polyimide precursor sheet is preferably 1 mm to 25 mm, more preferably 2 to 10 mm, and further preferably 3 to 7 mm.

In the heat insulating material I of the present invention, when the height of the convex portion provided on the polyimide precursor sheet is within the above range, when one or a plurality of layers are stacked on the surface of the object to be insulated, An air layer suitable for heat insulation can be formed between the object to be insulated.
When the height of the convex portion is less than 1 mm, it becomes easy to form an air layer suitable for heat insulation, but the number of layers for obtaining necessary heat insulation increases, and the construction cost increases. When the height of the convex part exceeds 25 mm, the height of the air layer becomes too high, and convection is likely to occur, which tends to cause a decrease in heat insulation.

  In addition, as shown with the symbol h in FIG.1 (b), in this application document, the height of the said convex part is from the lowest part of the convex part including the thickness of a sheet | seat made from a polyimide precursor to the uppermost part (top part). It means distance.

  In the heat insulating material I of this invention, when a convex part is a cylindrical shape, 1-25 mm is preferable, as for the internal diameter of a convex part, 5-15 mm is more preferable, and 7-10 mm is further more preferable.

In the heat insulating material I of the present invention, the convex portion provided on the polyimide precursor sheet has an inner diameter within the above range, so that even if the surface of the object to be insulated has a curved surface shape, the convex portion is buckled. It can arrange | position, making it closely_contact | adhere to the surface of a to-be-insulated object (following the surface shape of to-be-insulated object), etc., without producing etc.
In addition, because the inner diameter of the protrusions provided on the polyimide precursor sheet is within the above range, even if some of the protrusions are damaged, etc., sufficient heat insulation is exhibited by the other protrusions. can do.

In the heat insulating material I of the present invention, when the convex portion has a cylindrical shape, as the convex portion, the distance between adjacent convex portions (length (pitch) L shown in FIG. 1 (a)),
What is 2-50 mm is preferable, what is 6-30 mm is more preferable, and what is 8-15 mm is further more preferable.

  In the heat insulating material I of this invention, when a convex part is a cylindrical shape, as a convex part, the width | variety of the clearance gap between adjacent convex parts (width D shown to Fig.1 (a)) is 1-25 mm Are preferable, those having 1 to 15 mm are more preferable, and those having 1 to 5 mm are more preferable.

  In the heat insulating material I of this invention, appropriate heat insulation can be ensured by the distance between adjacent convex parts and the width | variety of a clearance gap being in the said range.

In the heat insulating material I of the present invention, the cap sheet preferably has a thickness of 0.01 to 0.20 mm, more preferably 0.02 to 0.10 mm, and 0.04 to 0.08 mm. More preferred.
When the average thickness of the polyimide precursor sheet is within the above range, sufficient strength and heat insulation can be imparted.
In addition, in this application document, the average thickness of a cap sheet means the arithmetic mean value when the thickness of five places is measured using a micrometer.

  Next, a method for producing a polyimide precursor and a polyimide precursor sheet will be described.

  In the present application documents, the polyimide precursor constituting the polyimide precursor sheet is formed by condensing an aromatic tetracarboxylic acid and an aromatic diamine, and has a desired physical property by thermosetting. The non-reacted aromatic tetracarboxylic acid and aromatic diamine, and those having a polyamide / imide structure or imide structure in part are included.

  Specific examples of the aromatic tetracarboxylic acids constituting the polyamic acid include pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,3 ′, 3,4′-biphenyltetracarboxylic acid. 3,3 ′, 4,4′-benzophenone tetracarboxylic acid, 2,3,6,7-naphthalene tetracarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) propane or pyridine-2,3 , 5,6-tetracarboxylic acid, an acid anhydride of each of the above aromatic tetracarboxylic acids, a kind selected from aromatic tetracarboxylic acids derived from the ester compounds or halides of each of the above aromatic tetracarboxylic acids, etc. The above is mentioned.

  Specific examples of the aromatic diamine constituting the polyamic acid include paraphenylene diamine, metaphenylene diamine, benzidine, paraxylylene diamine, 4,4′-diaminodiniphenyl ether, 3,4′-diaminodiphenyl ether, 4 , 4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 1,5-diaminonaphthalene, 3,3'-dimethoxybenzidine, 1,4-bis One or more selected from (3-methyl-5-aminophenyl) benzene or derivatives thereof may be mentioned.

  Suitable combinations of aromatic tetracarboxylic acids and aromatic diamines constituting the polyamic acid include a combination of pyromellitic dianhydride and 4,4′-diaminodiphenyl ether, pyromellitic dianhydride and 4, Combination of 4′-diaminodiphenyl ether and paraphenylenediamine, combination of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether, 3,3 ′, 4,4 Mention may be made of combinations of '-biphenyltetracarboxylic dianhydride with 4,4'-diaminodiphenyl ether and paraphenylenediamine.

  The polyamic acid can be prepared by stirring or mixing aromatic tetracarboxylic acids and aromatic diamines in an organic solvent.

  Specifically, the organic solvent used in the preparation of the polyamic acid is at least one selected from organic polar amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methyl-2-pyrrolidone. Further, one or more organic solvents selected from benzene, toluene and xylene may be used in combination.

  In the case of preparing an organic solvent solution by mixing an aromatic tetracarboxylic acid and an aromatic diamine in an organic solvent, the order of mixing the organic solvent, the aromatic tetracarboxylic acid and the aromatic diamine is not particularly limited, It is preferable to prepare by mixing aromatic tetracarboxylic acids after mixing aromatic diamines with an organic solvent.

  Aromatic tetracarboxylic acids and aromatic diamines are preferably added and mixed in an organic solvent at a ratio in which the respective molar numbers are approximately equal to prepare an organic solvent solution. The amount may be excessive in the range of 10 mol% or less, or may be excessive in the range of 5 mol% or less.

When the polyamic acid is prepared, the organic solvent solution obtained by mixing aromatic tetracarboxylic acids and aromatic diamines in an organic solvent preferably has a solid content concentration of 5 to 40% by mass, and 10 to 30% by mass. % Is more preferable.
In addition, when the polyamic acid is prepared, the organic solvent solution preferably has a viscosity measured by a Brookfield viscometer of 10 to 2000 Pa · s, more preferably 100 to 1000 Pa · s, and an organic solvent. When the viscosity of the solution is within the above range, stable liquid feeding is possible and film formation can be easily performed.

The organic solvent solution can be prepared, for example, by adding aromatic tetracarboxylic acids and aromatic diamines to the organic solvent at a liquid temperature of 0 to 80 ° C. and stirring and mixing for 10 minutes to 30 hours. However, the liquid temperature may be raised or lowered within the above temperature range, or may be continuously stirred and mixed within the above time or may be divided and stirred and mixed.
It is preferable that the inside of the reaction system is appropriately degassed during the stirring and mixing.
Moreover, you may control reaction by adding a small amount of terminal blockers to the said organic solvent solution.

After completion of the stirring and mixing, a polyamic acid-containing liquid can be obtained by appropriately drying and adjusting the amount of the organic solvent.
The obtained polyamic acid-containing liquid preferably has a solid content concentration of 2 to 20% by mass, more preferably 7 to 15% by mass.

  In the heat insulating material I of the present invention, a commercially available product can be used as the polyamic acid. Specifically, for example, Ube Industries 'polyimide varnish U-varnish, Toray Industries' semicofine, Unitika ( Uimide varnish manufactured by Co., Ltd. can be mentioned.

  Moreover, a functional filler (for example, carbon black, spherical silica, etc.) may be added to the polyamic acid to increase the conductivity of the polyimide precursor sheet or increase the strength.

  As a method for producing the heat insulating material I of the present invention, a polyimide precursor sheet provided with a plurality of convex portions on the surface by pressing a flat polyimide precursor sheet to provide a plurality of convex portions on the surface. The method of forming the cap sheet | seat which consists of can be mentioned.

  Examples of a method for producing a flat polyimide precursor sheet include a method in which the above-described polyamic acid is poured or coated on a flat support, stretched with a bar coater, and then appropriately dried. .

  For example, as shown in FIG. 2, a resin film B2 such as a polyphenylene sulfide (PPS) film is pasted on a flat plate B1 made of stainless steel or the like to form a flat support, and the polyamic acid is formed on the support. After pouring or applying PA, a flat polyimide precursor sheet can be produced by stretching the bar coater C at both ends with spacers Sp interposed therebetween and appropriately drying.

The thickness of the spacer Sp can be appropriately selected according to the thickness of the polyimide precursor sheet to be obtained.
Moreover, when performing the said drying process after extending the said polyamic acid PA, it can dry-process by processing for 1 to 48 hours, for example on the temperature conditions of 25-100 degreeC.

  Examples of a method of providing a plurality of convex portions on the surface by pressing a flat polyimide precursor sheet include a press working method and an embossing method.

For example, a sheet made of a flat polyimide precursor cut into a predetermined shape is inserted into a mold consisting of a pair of upper mold and lower mold having a molding surface shape corresponding to the surface shape to be caught, and the polyimide precursor A polyimide precursor sheet having a plurality of convex portions on the surface can be produced by pressing under a temperature condition lower than the thermosetting temperature.
Since the polyimide precursor sheet constituting the heat insulating material I of the present invention has a plurality of convex portions on the surface, at least one of the pair of upper molds or lower molds corresponds to the convex shape. A plurality of convex portions or concave portions are formed.
Moreover, the said press work can be implemented by well-known methods, such as an air press.

Further, for example, a flat polyimide precursor sheet cut into a predetermined shape is inserted between a pair of rollers having a surface shape corresponding to the surface shape to be obtained, and the temperature is lower than the thermosetting temperature of the polyimide precursor. By pressure-molding under conditions, a polyimide precursor sheet having a plurality of convex portions on the surface can be produced.
Since the polyimide precursor sheet constituting the heat insulating material I of the present invention has a plurality of convex portions on the surface, at least one of the pair of rollers has a plurality of convex portions corresponding to the convex shape. Or the recessed part is formed.

  When the polyimide precursor sheet constituting the heat insulating material I of the present invention is produced by pressing a flat polyimide precursor sheet, the atmospheric temperature during the pressing process is less than the thermosetting temperature of the polyimide precursor. It is temperature, it is suitable that it is 50-250 degreeC, and it is more suitable that it is 100-200 degreeC.

  When the polyimide precursor sheet constituting the heat insulating material I of the present invention is produced by pressing a flat polyimide precursor sheet, the pressing time during the press molding is preferably 10 seconds or less.

When the polyimide precursor sheet is produced by pressing a flat polyimide precursor sheet, the press-molded product is taken out from the press mold after pressing.
In the case of pressing while heating the mold, the press-molded product can be taken out after being cooled by natural cooling while being sandwiched in the mold until the temperature of the mold becomes less than 50 ° C.

  Thus, the cap sheet which consists of a sheet | seat made from a polyimide precursor which comprises the heat insulating material I of this invention and was equipped with the some convex part on the surface can be produced.

As described above, polyimide resin is a highly crystalline, infusible and insoluble resin, so it can be processed into a sheet or formed into a cap after the polyimide resin is melted or dissolved in an organic solvent. It is difficult to perform processing such as.
However, according to the study by the present inventors, a convex portion can be easily formed on the surface by forming a polyimide precursor sheet in advance and pressing the polyimide precursor sheet. It has been found that by curing a polyimide precursor sheet having a plurality of convex portions, a cap sheet made of a polyimide sheet having convex portions on the surface can be easily formed. It came to complete.

Since the heat insulating material I of the present invention includes a cap sheet made of a polyimide precursor sheet having a plurality of convex portions (caps) on the surface, the heat insulating material I is disposed in a single layer or multiple layers on the object to be heat-insulated. In addition, a desired air layer can be formed to exhibit excellent heat insulation.
For example, as shown in FIG. 3, two layers of a cap sheet made of a polyimide precursor sheet 1 having a plurality of convex portions on the surface are laminated on the pipe P, which is an object to be insulated, as the heat insulating material I of the present invention. The air chamber S1 formed by the convex portion 2 and the air chamber S2 formed between the two adjacent convex portions 2 on the object to be insulated P, By forming the air chamber, excellent heat insulation can be exhibited.

  Further, since the heat insulating material I of the present invention is composed of a polyimide precursor sheet, it exhibits superior flexibility as compared to a polyimide sheet, and the object to be heat-insulated has a curved shape. However, it can arrange | position, making it closely_contact | adhere to the surface of a to-be-insulated object (following the surface shape of to-be-insulated object), without producing a buckling etc. to a convex part.

  Furthermore, since the cap sheet is made of a polyimide precursor sheet, the heat insulating material I of the present invention is a polyimide that forms a sheet when heat is radiated from the surface of the object to be heat-insulated during use of the object to be heat-insulated. Since the precursor undergoes thermosetting and is converted into polyimide, high heat resistance can be exhibited after disposition even if it is not disposed after being cured.

Next, the heat insulating material II of the present invention will be described.
The heat insulating material II of the present invention includes a cap sheet made of a polyimide sheet obtained by curing a polyimide precursor sheet having a plurality of convex portions on the surface.

In the heat insulating material II of the present invention, the details of the polyimide precursor sheet having a plurality of convex portions on the surface are as described in the description of the heat insulating material I of the present invention.
The heat insulating material II of the present invention comprises a polyimide sheet obtained by curing the polyimide precursor sheet constituting the heat insulating material I of the present invention. For this reason, the shape and size of the projections provided on the surface of the polyimide sheet, the details of the distance between the projections and the width of the gap, the shape and size of the projections provided on the surface of the polyimide precursor sheet, This is the same as the distance between the convex portions and the width of the gap.

In the heat insulating material II of the present invention, the polyimide sheet preferably has a thickness of 0.01 to 0.20 mm, more preferably 0.02 to 0.10 mm, and 0.04 to 0.00. What is 08 mm is more preferable.
When the average thickness of the polyimide sheet is within the above range, sufficient strength and heat insulation can be imparted.
In addition, in this application document, the average thickness of a sheet | seat made from a polyimide means the arithmetic mean value when measuring the thickness of five places using a micrometer.

  In the heat insulating material II of the present invention, the polyimide sheet constituting the cap sheet can be produced by producing a polyimide precursor sheet having a plurality of convex portions on the surface by the above-described method and then curing the sheet. it can.

  The curing treatment of the polyimide precursor sheet can be performed by heating the polyimide precursor sheet to a temperature equal to or higher than the thermosetting temperature of the polyimide precursor, and may be performed by heating to a temperature of 380 to 450 ° C. preferable.

  The treatment time at the time of the thermosetting treatment is not particularly limited as long as it is a time sufficient for the polyimide precursor to be cured, but usually 1 to 5 minutes is appropriate, and it is 1 to 2 minutes. More appropriate.

  Thus, the polyimide sheet | seat which comprises the heat insulating material II of this invention and was equipped with the some convex part on the surface can be produced.

  Since the heat insulating material II of the present invention is made of a polyimide sheet having a plurality of convex portions (caps) on the surface, it is desirable to arrange a single layer or multiple layers on the object to be insulated. An air layer can be formed to exhibit excellent heat insulation.

  Moreover, since the heat insulating material II of this invention consists of a sheet | seat made from a polyimide, it can exhibit high heat resistance.

Next, the heat insulating material III of the present invention will be described.
In the heat insulating material III of the present invention, a back sheet is further laminated on the cap sheet constituting the heat insulating material I of the present invention or the heat insulating material II of the present invention, and a plurality of convex portions provided on the cap sheet are sealed. Thus, a plurality of bubble chambers are provided on the surface.

4A is a top view of one embodiment of the heat insulating material III of the present invention described above, FIG. 4B is a cross-sectional view taken along the line BB ′ of FIG. 4A, and FIG. ) Is a partial perspective view of one embodiment of the heat insulating material III of the present invention described above.
As illustrated in FIGS. 4A to 4C, the heat insulating material III of the present invention is a cap sheet made of a polyimide precursor sheet or a polyimide sheet 11 having a plurality of convex portions 12 on the surface. On the other hand, the back sheet 13 is laminated, and the plurality of convex portions 12 provided on the cap sheet are sealed, whereby a plurality of convex bubble chambers R are provided on the surface.

  In the heat insulating material III of the present invention, the details of the form of the polyimide precursor sheet or the polyimide sheet constituting the cap sheet and the manufacturing method thereof are as described above.

In the heat insulating material III of the present invention, examples of the backsheet include a polyimide precursor backsheet, a polyimide backsheet, a metal backsheet, or a polyimide precursor backsheet formed by depositing metal on the surface.
The back sheet may be one having convex portions or concave portions formed on the surface, but is preferably flat.

The back sheet preferably has a thickness of 0.01 to 0.20 mm, more preferably 0.02 to 0.10 mm, and still more preferably 0.04 to 0.08 mm.
When the average thickness of the back sheet is within the above range, sufficient strength and heat insulation can be imparted.
In addition, in this application document, the average thickness of a backsheet means the arithmetic mean value when the thickness of five places is measured using a micrometer.

  When the back sheet is a flat polyimide precursor back sheet, the flat polyimide precursor back sheet can be produced by the same method as the above-described flat polyimide precursor sheet.

  When the back sheet is a metal back sheet, examples of the metal back sheet include an aluminum back sheet, a stainless steel back sheet, and the like.

  Specific examples of the aluminum back sheet include aluminum foil.

When the back sheet is a polyimide precursor back sheet obtained by vapor-depositing metal on the surface, the polyimide precursor back sheet obtained by vapor-depositing metal on the surface includes the above-described flat polyimide precursor back sheet. The thing formed by vapor-depositing various metals can be mentioned.
Examples of the metal deposited on the polyimide precursor backsheet include aluminum.

  Examples of the method for depositing metal on the polyimide precursor backsheet include known methods such as chemical vapor deposition (CVD) and physical vapor deposition (PVD).

  In the heat insulating material III of the present invention, as a method of laminating the back sheet on the polyimide precursor sheet constituting the heat insulating material I of the present invention or the polyimide sheet (cap sheet) constituting the heat insulating material II of the present invention, For example, the method of adhering using an adhesive etc. can be mentioned.

Moreover, when laminating a polyimide precursor backsheet on the polyimide precursor sheet constituting the heat insulating material I of the present invention, they are laminated and integrated by combining them with various organic solvents and drying them. A method can be mentioned.
In this case, examples of the compatible organic solvent include one or more selected from organic polar amide solvents such as N-methyl-pyrrolidone, N, N-dimethylformamide, and N, N-dimethylacetamide.
The polyimide precursor sheet and the polyimide precursor backsheet constituting the heat insulating material I of the present invention are overlapped, and an organic solvent having the above compatibility is applied between them, preferably at 25 to 100 ° C. Both can be laminated and integrated by drying for 1 to 48 hours.

  After laminating a polyimide back sheet to the polyimide precursor sheet constituting the heat insulating material I of the present invention, the sheet is further subjected to curing treatment, or to the polyimide precursor sheet constituting the heat insulating material II of the present invention. After laminating the polyimide precursor backsheet, further heat treatment can be performed to obtain a heat immobilization material that is entirely imidized, and for the polyimide precursor sheet constituting the heat insulation material I of the present invention. After the polyimide precursor backsheet is laminated, a further heat treatment can be applied to obtain a heat-insulating material that is entirely imidized.

The said hardening process can be performed by heating to the temperature more than the thermosetting temperature of a polyimide precursor, and it is preferable to carry out by heating to the temperature of 380-450 degreeC.
The treatment time at the time of the thermosetting treatment is not particularly limited as long as it is a time sufficient for the polyimide precursor to be cured, but usually 1 to 5 minutes is appropriate, and it is 1 to 2 minutes. More appropriate.

  The heat insulating material III of the present invention includes the polyimide precursor sheet constituting the heat insulating material I of the present invention or the polyimide sheet constituting the heat insulating material II of the present invention. The same effects as those of the heat insulating material II of the present invention can be exhibited.

  Further, the heat insulating material III of the present invention has a back sheet laminated to the polyimide precursor sheet constituting the heat insulating material I of the present invention or the polyimide sheet (cap sheet) constituting the heat insulating material II of the present invention, Since the plurality of convex portions provided on the polyimide precursor sheet or the polyimide sheet are sealed, the surface is provided with a plurality of convex bubble chambers. A high air layer can be formed.

  Furthermore, in the heat insulating material III of the present invention, when the back sheet is a metal back sheet or a polyimide precursor back sheet obtained by vapor-depositing metal on the surface, the heat reflection effect (heat shielding effect) by the metal More excellent heat insulation can be exhibited.

Next, the heat insulation structure of this invention is demonstrated.
The heat insulating structure of the present invention is characterized in that a plurality of the heat insulating materials of the present invention are arranged on an object to be heat-insulated.

  In the heat insulating structure of the present invention, the method of laminating and arranging the heat insulating material of the present invention on the object to be heat-insulated is not particularly limited, and a plurality of long heat insulating materials of the present invention are wound on the object to be heat-insulated. And a method of fixing with a heat resistant tape or the like, a method of winding the heat insulating material of the present invention one layer at a time and fixing with a heat resistant tape or the like.

For example, as shown in FIG. 5, the heat insulating structure of the present invention is formed by stacking a total of three layers by winding the heat insulating material of the present invention made of the sheet laminate 21 one by one and fixing it with heat-resistant tape or the like. Can be mentioned.
In the heat insulating structure of the present invention, the number of laminated heat insulating materials of the present invention varies depending on the surface temperature of the object to be heat-insulated, but is preferably 2 to 20 layers, and more preferably 5 to 10 layers.
When the number of laminated layers is less than two layers, it is difficult to obtain desired heat insulation performance. When the number of laminated layers exceeds 20 layers, the construction cost increases, making it difficult to put to practical use.

Since the heat insulating structure of the present invention is formed by laminating a polyimide precursor sheet or a polyimide sheet including a plurality of convex portions (caps) on the surface as a cap sheet, When laminated on an object, a desired air layer can be formed to exhibit excellent heat insulation.
For example, as shown in FIG. 5, when the laminated integrated product 21 of the cap sheet and the back sheet is arranged in three layers as the heat insulating material III of the present invention on the pipe P which is a heat insulating object, By forming the air chamber S1 formed by the protrusions 22 and the air chamber S2 formed between the adjacent protrusions 22 on the heat insulator P, excellent heat insulation can be exhibited.

  In the heat insulating structure of the present invention, among the plurality of heat insulating materials to be stacked, at least a part of the adjacent heat insulating materials may be stacked and disposed so that the convex portions face each other.

  For example, as shown in a cross-sectional view in FIG. 6, in the heat insulating structure of the present invention, among the plurality of heat insulating materials to be laminated, at least a part of the adjacent heat insulating materials is such that the convex portions 32 face each other. It may be a layered arrangement.

  Thus, in the heat insulating structure of the present invention, at least a part of the adjacent heat insulating materials is laminated and disposed so that the convex portions face each other, so that the height of the air layer shown in FIG. Heat insulation can be controlled by adjusting H appropriately.

  The heat insulating structure of the present invention is a heat insulating structure in which a plurality of the heat insulating materials of the present invention are stacked on an object to be heat-insulated, and each layer is formed from the innermost layer toward the outermost layer. The curability of the cap sheet may tend to be reduced.

  In the heat insulating structure of the present invention, the curability tends to be reduced, among the cap sheets forming each layer of the heat insulating structure, the hardness of the cap sheet constituting the heat insulating material forming the innermost layer is the highest, and the outermost layer is It means that the hardness of the cap sheet constituting the heat insulating material is the lowest and the hardness of the cap sheet constituting the adjacent heat insulating material is the same or lower from the innermost layer toward the outermost layer.

  Since the degree of curability of the heat insulating material forming each layer from the innermost layer toward the outermost layer tends to be reduced, the polyimide precursor has a lower thermal conductivity than polyimide, so the whole is polyimide. Compared with the case where the heat insulating material which consists of these is laminated | stacked, the heat insulation effect excellent in the heat insulation structure can be provided.

As a method for producing a heat insulating structure in which the curability of the heat insulating material forming each layer from the innermost layer toward the outermost layer tends to be reduced, for example, a plurality of convex portions are provided on the surface of the object to be heat-insulated. An example is a method in which a plurality of heat insulating materials including a cap sheet made of a polyimide precursor sheet are stacked and then the polyimide precursor sheet is cured using heat radiated from the object to be insulated.
The heat insulating material including a cap sheet made of a polyimide precursor sheet having a plurality of convex portions on the surface is further backed against a cap sheet made of a polyimide precursor sheet having a plurality of convex portions on the surface. Sheets are stacked, and a plurality of convex portions provided on the cap sheet are sealed to include a plurality of bubble chambers on the surface.

  Thus, the heat insulation containing the cap sheet which consists of a sheet | seat made from a polyimide is carried out by arranging and laminating | stacking multiple heat insulating materials containing the cap sheet which consists of a sheet | seat made from a polyimide precursor provided with the some convex part on the surface to be insulated Compared to the case where a plurality of materials are arranged in multiple layers, it exhibits excellent flexibility, and even if the object to be insulated has a curved surface shape, it is in close contact with the surface of the object to be insulated (insulated (Following the surface shape of the object).

  Moreover, it replaced with the cap sheet | seat which consists of a polyimide sheet | seat which heat-cured previously, and arrange | positioned multiple heat insulation materials containing the cap sheet | seat consisting of a polyimide precursor sheet | seat, and arrange | positioned in the innermost layer using the waste heat of a to-be-insulated object. By curing the heat insulating material, energy required for curing can be suppressed, and a heat insulating structure can be manufactured under high energy efficiency.

  Furthermore, by curing the heat insulating material using the exhaust heat of the object to be insulated, it is possible to produce a heat insulating structure in which the curability of the heat insulating material forming each layer from the innermost layer toward the outermost layer tends to be reduced. In addition, as described above, the heat insulating structure obtained has a structure in which the curability tends to decrease from the innermost layer to the outermost layer, so that more excellent heat insulating properties can be imparted.

  EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated further in detail, this invention is not restrict | limited by these examples.

Example 1
(1) Preparation of polyimide precursor organic solvent solution N-methyl-2-pyrrolidone was added to the polyimide varnish (solid content concentration 18% by mass) so that the solid content concentration was 13% by mass, and a magnetic stirrer was used. After mixing for 10 minutes, a polyimide precursor organic solvent solution was prepared by vacuum degassing.

(2) Production of flat polyimide precursor sheet As shown in FIG. 2, a PPS film B2 having a thickness of 0.1 mm is pasted on a flat plate B1 made of stainless steel having a thickness of 0.2 mm, and a flat support. After pouring the polyimide precursor organic solvent solution onto this support, it was stretched with a bar coater C through spacers Sp each having a thickness of 0.5 mm at both ends, and then dried in a draft for 24 hours. Then, a flat polyimide precursor sheet having a thickness of 0.08 mm was produced by further drying in an oven at 60 ° C. for 24 hours.
The thermosetting temperature of the polyimide precursor which comprises the said flat polyimide precursor sheet | seat is 400 degreeC.

(3) Preparation of polyimide precursor sheet having a plurality of convex portions on the surface The flat polyimide precursor sheet obtained in the above (2) is a plurality of cylindrical sheets having an inner diameter of 10 mm and a height of 3.5 mm. While being inserted into a mold composed of a pair of an upper mold and a lower mold heated to 180 ° C. provided with a molding surface shape capable of forming a convex portion, while applying a pressure of 5 MPa (gauge pressure) with an air press A polyimide precursor having a thickness of 0.08 mm and having a plurality of convex portions on the surface after being pressed for 5 seconds and allowed to cool until the temperature of the mold reaches 50 ° C. or less. A sheet made was produced.

(4) Preparation of polyimide sheet having a plurality of protrusions on the surface The polyimide precursor sheet having a plurality of protrusions on the surface obtained in (3) above was heated at 400 ° C. for 1 hour. The surface has a plurality of cylindrical convex portions having an inner diameter of 10 mm and a height of 3.5 mm, the distance between the convex portions is 13 mm, and the width of the gap between the convex portions is 3 mm. The thickness was 0.08 mm, and a polyimide sheet having a plurality of convex portions on the surface was obtained.

  The thermal conductivity of the obtained polyimide sheet was measured at 25 ° C. by a heat flow meter method using HC-110 manufactured by Eihiro Seiki Co., Ltd. The results are shown in Table 1.

Moreover, after winding the obtained polyimide sheet around a rod having a diameter of 5 mm, the flexibility of the sheet was evaluated based on the following criteria by visually checking the degree of breakage of the sheet. The results are shown in Table 1.
○: Almost no change before and after winding.
(Triangle | delta): After winding, a part is missing and a crack is seen.
X: After winding, it is completely broken and damaged.

Furthermore, after heating the obtained polyimide sheet at 300 ° C. for 1 hour, the heat resistance was evaluated according to the following criteria by visually confirming the change in shape before and after heating. The results are shown in Table 1.
○: Almost no change in shape before and after heating.
Δ: Some change in shape and shrinkage are observed after heating.
X: The shape before a heating is hardly maintained after a heating.

(Example 2)
A flat polyimide precursor sheet having a thickness of 0.2 mm was prepared in Example 1 (2), and a polyimide precursor having a plurality of convex portions on the surface having a thickness of 0.2 mm in Example 1 (3). Except for producing the sheet, the surface has a plurality of cylindrical convex portions having an inner diameter of 10 mm and a height of 3.5 mm in the same manner as in Example 1, and the distance between the convex portions is 13 mm. A polyimide sheet having a gap width of 3 mm and a thickness of 0.2 mm and having a plurality of convex portions on the surface was prepared.
The thermal conductivity, flexibility, and heat resistance of the obtained polyimide sheet were evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 3
A flat polyimide precursor sheet having a thickness of 0.05 mm was prepared in Example 1 (2), and a polyimide precursor sheet having a plurality of convex portions on the surface having a thickness of 0.05 mm in Example 1 (3). Except for producing the sheet, the surface has a plurality of cylindrical convex portions having an inner diameter of 10 mm and a height of 3.5 mm in the same manner as in Example 1, and the distance between the convex portions is 13 mm. A polyimide sheet having a gap width of 3 mm and a thickness of 0.05 mm and having a plurality of convex portions on the surface was prepared.
The thermal conductivity, flexibility, and heat resistance of the obtained polyimide sheet were evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 4
A flat polyimide precursor sheet having a thickness of 0.08 mm was prepared in Example 1 (2), and a plurality of cylindrical convex portions having an inner diameter of 1 mm and a height of 3.5 mm were formed on the surface in Example 1 (3). A polyimide having a plurality of convex portions on a surface having a thickness of 0.08 mm, which can be formed and is inserted into a mold composed of a pair of an upper mold and a lower mold heated to 180 ° C. and having a corresponding molding surface shape Except for producing the precursor sheet, the surface has a plurality of cylindrical protrusions having an inner diameter of 1 mm and a height of 3.5 mm, and the distance between the protrusions is 4 mm. A polyimide sheet having a width of 3 mm between the portions and a thickness of 0.08 mm and having a plurality of convex portions on the surface was prepared.
The thermal conductivity, flexibility, and heat resistance of the obtained polyimide sheet were evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Example 5)
A flat polyimide precursor sheet having a thickness of 0.08 mm was prepared in Example 1 (2), and a plurality of cylindrical convex portions having an inner diameter of 10 mm and a height of 10 mm were formed on the surface in Example 1 (3). Obtained polyimide precursor having a corresponding molding surface shape, charged in a molding die consisting of a pair of an upper die and a lower die heated to 180 ° C., and having a plurality of convex portions on a surface having a thickness of 0.08 mm Except for producing the sheet, the surface has a plurality of cylindrical protrusions having an inner diameter of 10 mm and a height of 10 mm, the distance between the protrusions is 13 mm, and the gap between the protrusions is the same as in Example 1. A polyimide sheet having a width of 3 mm and a thickness of 0.08 mm and having a plurality of convex portions on the surface was prepared.
The thermal conductivity, flexibility, and heat resistance of the obtained polyimide sheet were evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
As a sheet according to Comparative Example 1, a low density polyethylene sheet (# 38 manufactured by Kawakami Sangyo Co., Ltd.) having the same shape as the polyimide sheet obtained in Example 1 was prepared, and the thermal conductivity of the polyethylene sheet was prepared. The flexibility and heat resistance were evaluated in the same manner as in Example 1. The results are shown in Table 1.

  From Table 1, the heat insulating materials obtained in Examples 1 to 5 are made of a polyimide sheet obtained by curing a polyimide precursor sheet having a plurality of convex portions on the surface, and thus heat conduction. It can be seen that it has a low rate and high heat insulating properties, and also has excellent flexibility and heat resistance.

  On the other hand, it can be seen from Table 1 that the heat insulating material obtained in Comparative Example 1 is inferior in heat resistance because it is made of a polyethylene sheet.

(Example 6)
A flat polyimide precursor sheet having a thickness of 0.05 to 0.20 mm was prepared in Example 1 (2), and a plurality of protrusions were formed on the surface of 0.05 to 0.20 mm in Example 1 (3). Except that a polyimide precursor sheet provided with a portion was prepared, the surface had a plurality of cylindrical convex portions having an inner diameter of 10 mm and a height of 2.0 mm in the same manner as in Example 1, and between the convex portions. A polyimide sheet having a distance of 13 mm, a width of the gap between the convex portions of 3 mm, and a thickness of 0.05 to 0.20 mm and having a plurality of convex portions on the surface was prepared.
The thermal conductivity at 25 ° C. of a polyimide precursor sheet (thickness 0.05 mm, 0.08 mm, 0.20 mm) having a plurality of protrusions on the surface was determined as HC-110 manufactured by Eihiro Seiki Co., Ltd. And the thermal conductivity at 300 ° C. of the polyimide precursor sheet was determined.
Specifically, the thermal conductivity at 300 ° C. was measured from the thermal conductivity at 25 ° C., 40 ° C., 55 ° C., and 70 ° C. measured by a heat flow meter method using HC-110 manufactured by Eihiro Seiki Co., Ltd. Based on the Fricke equation, a relational expression (approximate expression) between the cube of the absolute temperature and the thermal conductivity was created and calculated based on the approximate expression. The results are shown in Table 2.

(Example 7)
A flat polyimide precursor sheet having a thickness of 0.05 to 0.20 mm was prepared in Example 1 (2), and a plurality of protrusions were formed on the surface of 0.05 to 0.20 mm in Example 1 (3). Except that a polyimide precursor sheet provided with a portion was prepared, the surface had a plurality of cylindrical convex portions having an inner diameter of 10 mm and a height of 2.5 mm in the same manner as in Example 1, and between the convex portions. A polyimide sheet having a distance of 13 mm, a width of the gap between the convex portions of 3 mm, and a thickness of 0.05 to 0.20 mm and having a plurality of convex portions on the surface was prepared.
The thermal conductivity at 25 ° C. of a polyimide precursor sheet (thickness 0.05 mm, 0.08 mm, 0.20 mm) having a plurality of protrusions on the surface was determined as HC-110 manufactured by Eihiro Seiki Co., Ltd. And the thermal conductivity at 300 ° C. of the polyimide precursor sheet was determined.
Specifically, the thermal conductivity at 300 ° C. was measured from the thermal conductivity at 25 ° C., 40 ° C., 55 ° C., and 70 ° C. measured by a heat flow meter method using HC-110 manufactured by Eihiro Seiki Co., Ltd. A relational expression (approximate expression) between the cube of the absolute temperature and the thermal conductivity was created based on Fricke's expression, and the calculation was made based on the approximate expression. The results are shown in Table 2.

(Example 8)
A flat polyimide precursor sheet having a thickness of 0.05 to 0.20 mm was prepared in Example 1 (2), and a plurality of protrusions were formed on the surface of 0.05 to 0.20 mm in Example 1 (3). Except that a polyimide precursor sheet provided with a portion was prepared, the surface had a plurality of cylindrical convex portions with an inner diameter of 10 mm and a height of 3.0 mm in the same manner as in Example 1, and between the convex portions. A polyimide sheet having a distance of 13 mm, a width of the gap between the convex portions of 3 mm, and a thickness of 0.05 to 0.20 mm and having a plurality of convex portions on the surface was prepared.
The thermal conductivity at 25 ° C. of a polyimide precursor sheet (thickness 0.05 mm, 0.08 mm, 0.20 mm) having a plurality of protrusions on the surface was determined as HC-110 manufactured by Eihiro Seiki Co., Ltd. And the thermal conductivity at 300 ° C. of the polyimide precursor sheet was determined.
Specifically, the thermal conductivity at 300 ° C. was measured from the thermal conductivity at 25 ° C., 40 ° C., 55 ° C., and 70 ° C. measured by a heat flow meter method using HC-110 manufactured by Eihiro Seiki Co., Ltd. A relational expression (approximate expression) between the cube of the absolute temperature and the thermal conductivity was created based on Fricke's expression, and the calculation was made based on the approximate expression. The results are shown in Table 2.

  From Table 2, it can be seen that the polyimide precursor sheet can exhibit excellent heat insulation properties even if the height of the convex portion and the thickness of the sheet are different.

Example 9
(1) Preparation of polyimide precursor organic solvent solution N-methyl-2-pyrrolidone was added to the polyimide varnish (solid content concentration 18% by mass) so that the solid content concentration was 13% by mass, and a magnetic stirrer was used. After mixing for 10 minutes, a polyimide precursor organic solvent solution was prepared by vacuum degassing.

(2) Production of flat polyimide precursor sheet As shown in FIG. 2, a PPS film B2 having a thickness of 0.1 mm is pasted on a flat plate B1 made of stainless steel having a thickness of 0.2 mm, and a flat support. After pouring the polyimide precursor organic solvent solution onto this support, it was stretched with a bar coater C through spacers Sp each having a thickness of 0.5 mm at both ends, and then dried in a draft for 24 hours. Then, a plurality of flat polyimide precursor sheets having a thickness of 0.08 mm were produced by further drying in an oven at 60 ° C. for 24 hours.
The thermosetting temperature of the polyimide precursor which comprises the said flat polyimide precursor sheet | seat is 400 degreeC.

(3) Production of polyimide precursor sheet having a plurality of protrusions on the surface One of the flat polyimide precursor sheets obtained in (2) above had an inner diameter of 10 mm and a height of 2.0-3. It is inserted into a mold composed of a pair of an upper mold and a lower mold heated to 180 ° C. and provided with a molding surface shape capable of forming a plurality of cylindrical projections of 0.0 mm, and is 5 MPa (gauge) by an air press. Pressure) is applied for 5 seconds, allowed to cool until the temperature of the mold reaches 50 ° C. or lower, and then taken out from the mold to obtain a polyimide precursor having a plurality of convex portions on the surface. A sheet was obtained.

(4) Sheet lamination and integration After applying N-methyl-2-pyrrolidone to the flat part of the polyimide precursor sheet having a plurality of convex parts on the surface obtained in (3) above, On the other hand, after laminating the flat polyimide precursor sheet obtained in the above (2), pressing it lightly and pasting both together, drying both in an oven at 100 ° C. for 3 hours, Stacked and integrated.

(5) Production of polyimide sheet having a plurality of convex portions on the surface The whole of the two sheets obtained in the above (4) is imidized by heating at 400 ° C. for 1 hour. The surface has a plurality of cylindrical convex portions having an inner diameter of 10 mm and a height of 2.0 to 3.0 mm, the distance between the convex portions is 13 mm, the width of the gap between the convex portions is 3 mm, and the thickness is 0.08 mm, and a polyimide sheet having a plurality of convex portions on the surface was obtained.
While measuring the thermal conductivity at 25 ° C. of the polyimide sheet (thickness 2.0 mm, 2.5 mm, 3.0 mm) using HC-110 manufactured by Eihiro Seiki Co., Ltd., The thermal conductivity at 300 ° C. of the polyimide sheet (thickness 2.0 mm, 2.5 mm, 3.0 mm) was determined.
Specifically, the thermal conductivity at 300 ° C. was measured from the thermal conductivity at 25 ° C., 40 ° C., 55 ° C., and 70 ° C. measured by a heat flow meter method using HC-110 manufactured by Eihiro Seiki Co., Ltd. A relational expression (approximate expression) between the cube of the absolute temperature and the thermal conductivity was created based on Fricke's expression, and the calculation was made based on the approximate expression. The results are shown in Table 3.

  From Table 3, it can be seen that the polyimide laminated sheet obtained in Example 9 can exhibit excellent heat insulation properties even if the heights of the convex portions are different.

  ADVANTAGE OF THE INVENTION According to this invention, while providing the heat insulating material which can exhibit the outstanding heat resistance, heat insulation, and a softness | flexibility, the manufacturing method of a heat insulation structure and a heat insulation structure can be provided.

DESCRIPTION OF SYMBOLS 1 Polyimide precursor sheet provided with a plurality of protrusions on the surface or polyimide sheet provided with a plurality of protrusions on the surface 2 Convex part 3 Back sheet P Insulation object h Height R Bubble chamber Sp Spacer

Claims (7)

  A heat insulating material comprising a cap sheet made of a polyimide precursor sheet having a plurality of convex portions on a surface thereof.   A heat insulating material comprising a cap sheet made of a polyimide sheet obtained by curing a polyimide precursor sheet having a plurality of convex portions on the surface.   The heat insulating material according to claim 1 or 2, wherein a height of the convex portion is 1 mm to 25 mm.   The heat insulating material according to any one of claims 1 to 3, wherein the cap sheet has a thickness of 0.01 to 0.20 mm.   A back sheet is further laminated on the cap sheet according to any one of claims 1 to 4, and a plurality of convex portions provided on the cap sheet are sealed, so that a plurality of bubble chambers are formed on the surface. A heat insulating material characterized by comprising.   A heat insulating structure in which a plurality of the heat insulating materials according to any one of claims 1 to 5 are arranged on an object to be heat-insulated. On the object to be insulated, after arranging a plurality of heat insulating materials including a cap sheet made of a polyimide precursor sheet having a plurality of convex portions on the surface,
A method for producing a heat insulating structure, comprising: curing a polyimide precursor sheet using heat radiated from the object to be insulated.

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