JP4331576B2 - Manufacturing method of inorganic fiber mat for vacuum heat insulating material - Google Patents

Description

  The present invention relates to a method for producing an inorganic fiber mat for a vacuum heat insulating material.

  Conventionally, as a heat insulating core material for a vacuum heat insulating material, an inorganic fiber mat (hereinafter, glass fiber will be described as a representative example) such as glass wool or rock wool having a high heat insulating effect has been widely adopted. Patent Document 1 discloses that when the glass fiber mat is used as a core material and an inside of a vacuum heat insulating material is filled with the glass fiber mat, an organic binder is added to the glass fiber mat so that the core material can be easily filled. And Patent Document 2.

  The content described in the above-mentioned patent document is that after obtaining a mat-like material by fiberizing and depositing (cotton collecting) an inorganic material melted by a centrifugal method or a flame method, the glass fiber mat is then applied to the mat-like material. A glass fiber mat (core material) is formed by spraying a binder, heating and pressurizing to form.

  However, the mat-like material obtained by the above-described centrifugal method or the like is drawn with relatively long fibers and deposited in a curved state, so that the fibers are entangled and oriented three-dimensionally. Further, when a glass fiber mat is obtained by applying a binder to this mat-like material and pressing and heating to form a glass fiber mat, the fibers are fixed as they are in the above state. When the heat insulating casing is filled with what is inserted and made into a vacuum heat insulating material, there is a problem that the heat insulating property is inferior because the fibers are not oriented perpendicular to the heat transfer direction.

  Further, the vacuum heat insulating material obtained by the above method has a problem that the surface is not smooth, and when the heat insulating material is filled in the heat insulating housing, the inner wall of the housing and the heat insulating material are caused by surface irregularities of the heat insulating material. There was a problem that a gap was formed between the two, and the heat insulating property of the heat insulating material was poor. On the other hand, a method for orienting the fibers perpendicular to the heat transfer direction is described in Patent Document 3, but this method is a method in which a fiber having a length of 1 mm or less is dispersed in water to make paper, which is troublesome. There was a problem such as.

In addition, in Patent Document 4, as a method for producing an inorganic fiber board, an aggregate of inorganic fibers provided with an adhesive is collected, a dimension slightly thicker than the thickness of the inorganic fiber board as a finished product, and a little more than the above thickness. After compression to a pre-selected thickness between thin dimensions, between the endless steel belt without holes and the perforated endless belt facing it, to the thickness of the finished inorganic fiberboard It is described that hot air is blown from the perforated endless belt side and heated and cured at the same time, and an aggregate of inorganic fibers having an average fiber diameter in the range of 5 to 10 μm has a density of 48 kg / m ^{3 to} 300 kg / In the range of m ³ , it is described that at least one surface is compressed and molded into a flat plate having a smooth surface and bonded with a cured adhesive.

  As a result, the necessary compressive load to be applied to the inorganic fiber web during compression and heat curing in the molding chamber can be reduced, and the tension acting on the endless conveyor in the molding process can be reduced and the driving power can be reduced. It is described that the apparatus can be operated continuously for a long time, and the production efficiency can be improved and the production cost can be reduced.

Japanese Patent Laid-Open No. 60-14695 JP 2001-108186 A Japanese Patent Laid-Open No. 9-4785 JP 2003-62847 A

  However, the invention of Patent Document 4 manufactures a so-called ordinary inorganic fiber board obtained by compressing an aggregate of inorganic fibers to retain the shape by heating and curing the adhesive. In order to obtain an inorganic fiber board by heating and curing the adhesive to maintain the shape, it is necessary to increase the amount of binder attached. Since the inorganic fiber board has strong bonding between fibers and becomes rigid per se, when it is used as a vacuum heat insulating material, due to uneven adhesion of the organic binder, compression in a rigid place is not possible during decompression. There are not only the problem that the surface is not smooth and the heat insulation performance is inferior due to a mixture of sufficient parts and parts that are sufficiently compressed in non-rigid parts. Therefore, there is a problem that the heat insulation performance is inferior due to the generated gas.

  The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is a glass for a vacuum heat insulating material excellent in heat insulating properties in which the fiber orientation is perpendicular to the heat transfer direction and the surface is smooth. Provides a fiber mat (hereinafter sometimes referred to as “core material for vacuum heat insulating material” or “core material”), and it is possible to easily obtain a vacuum heat insulating material by using an ordinary glass fiber mat manufacturing facility. It is providing the manufacturing method of the core material for a vacuum heat insulating material.

The above object is achieved by the present invention described below. That is, the present invention provides an inorganic fiber mat formed by collecting inorganic fibers to which an uncured thermosetting organic binder is attached in an amount of 0.5 to 3.0% by mass in a solid content, and has a density of 50 to 1,000 kg / m. Formed by heating while pressing so that the density is 50 to 150 kg / m ³ between the first step of pressing using a pair of rollers to be ³ and the upper and lower conveyors in the hot-air passing oven The second step to be performed and the third step to pressurize so as to have a density of 50 to 1,000 kg / m ³ using a pair of rollers after the second step are continuously performed in the order described herein. A method for producing an inorganic fiber mat for a vacuum heat insulating material is provided, wherein an inorganic fiber mat having a density of 20 to 60 kg / m ³ and a thickness of 1.2 times or more the thickness of the second step is obtained. .

In the above-described present invention, before Symbol first step, a density of 100 to 300 / m ³ and so as to pressurizing it; be the second step of the pressure-time heating 30 seconds to 200 seconds; And pressing in the third step so that the density is 100 to 300 kg / m ³ ; after the inorganic fiber mat imparts an uncured thermosetting organic binder to the inorganic fiber, the inorganic fiber is accumulated. It is preferable to use a mat.

  According to the present invention as described above, the core material for vacuum heat insulating material excellent in heat insulating properties whose fiber orientation is perpendicular to the heat transfer direction and whose surface is smooth can be provided with a simple apparatus with high productivity. By using this core material, a vacuum heat insulating material excellent in heat insulating performance can be easily obtained with good workability.

  Next, the present invention will be described in more detail with reference to preferred embodiments. The vacuum heat insulating material referred to in the present invention covers a core material made of a glass fiber mat with a gas barrier outer covering material such as an aluminum vapor-deposited polyethylene film, and the inside of the outer covering material is in a vacuum (reduced pressure) state (for example, about 1 to 10 Pa). ).

  In the vacuum heat insulating material, the core material for the vacuum heat insulating material made of the glass fiber mat is simply covered with the covering material, and therefore all the glass fibers in the core material are horizontal in the plane direction of the vacuum heat insulating material. Therefore, the heat insulating property was insufficient. For the same reason, the surface of the jacket material is inferior when used as a vacuum heat insulating material, and in a case where various heat insulating properties such as a refrigerator and a personal computer are required, in the casing in which the heat insulating material is stored. A space was created on the inner surface of the housing, which also caused poor heat insulation. Furthermore, when manufacturing a vacuum heat insulating material, workability is inferior when a bulky glass fiber mat is inserted into a bag made of a jacket material.

  The present invention solves the above-mentioned problems, and by manufacturing a vacuum heat insulating core material made of a glass fiber mat by a specific method, the glass fibers in the core material are substantially in the plane direction of the vacuum heat insulating material. Therefore, it is intended to provide a core material for a vacuum heat insulating material that is horizontally aligned and has a smooth surface when it is made into a vacuum heat insulating material, and has good workability.

The glass fiber mat that constitutes the core material for vacuum heat insulating material and before the pressurizing-heating / pressurizing treatment described below is known per se, and the glass fiber is matted with a suitable uncured thermosetting organic binder. It is formed by molding. Such glass fiber mats are known to have various densities, but in the present invention, the average diameter of the glass fibers is 1 to 5 μm, and the glass fiber mat before the pressure-heating and pressure treatment is used. It is preferable that the density is 3 kg / m ³ or more and the thickness of one mat is 30 to 500 mm.

When the average diameter of the glass fiber is more than 5 μm, the effect of the present invention cannot be sufficiently obtained in that the thermal performance of the obtained vacuum heat insulating material is lowered, while the thickness is less than 1 μm. This glass fiber is difficult to manufacture. Further, if the density of the glass fiber mat before the pressure-heat pressure treatment is less than 3 kg / m ³ , the handling property during the pressure-heat pressure treatment is inferior. Further, if the thickness of one of the mats is less than 30 mm, the productivity of the core material for vacuum heat insulating material is inferior, and it is not preferable in that many mats are required. On the other hand, the thickness is 500 mm. If it exceeds, it is difficult to introduce the mat into equipment such as a roller conveyor after pressurization or heating / pressurization.

  Further, the organic binder itself used in the present invention may be an organic binder used in a conventionally known glass fiber mat, and preferably an aqueous solution of a phenol resin precursor which is a thermosetting resin can be used. These organic binders require a solid content of the organic binder to be in the range of 0.5 to 3.0% by mass with respect to the total amount of glass fibers containing the solid content of the organic binder, 1.5 mass% is preferable. When the amount of the organic binder used is less than 0.5% by mass, the glass fiber mat is bulky and the mat has flexibility, so that it is difficult to fill the core material made of the mat into the jacket material. The handling property is inferior. On the other hand, if the amount used exceeds 3.0% by mass, the binder is heated and cured in the second step to be described later, but the bonding between the fibers becomes stronger. The surface smoothness of the resulting vacuum insulation core material and vacuum insulation material is inferior, and gas is likely to be generated in the vacuum insulation material due to the adhesion of excess binder, resulting in poor insulation performance. Absent.

  In the present invention, the glass fiber mat containing the organic binder is subjected to pressure-heating / pressure treatment. That is, in the present invention, it is important to pressurize, heat, and pressurize with a specific pressure while the organic binder is adhered to the glass fiber mat in an uncured state. On the other hand, when the pressure is applied only after the organic binder is cured, the surface smoothness of the vacuum heat insulating material formed by filling the obtained core material for vacuum heat insulating material cannot be sufficiently obtained.

(First step)
The core material for a vacuum heat insulating material of the present invention is a method in which glass fibers are continuously deposited on a belt conveyor while continuously melt-spinning, and a continuous uncured thermosetting organic binder is applied. As a process, as shown in FIG. 1, this glass fiber mat is pressurized using a pair of rollers from the point of productivity so that a density may be set to 50-1,000 kg / m < ³ >. Further, in the first step, it is preferable that the density of the glass fiber mat is 100 to 300 kg / m ³ .

The purpose of pressurization in the first step is to compensate for the lack of pressing force of the glass fiber mat between the belt conveyors in the oven in the next second step. In order to continuously produce the core material, if the pressing ability of the oven that is normally used is low, or if you do not want to apply a load to the oven, pressing at low pressure in the oven will provide sufficient smoothness as a vacuum heat insulating material. I can't get it. When the glass fiber mat is pressed and compressed at a low pressure, the surface smoothness of the core material obtained can be improved by slowing the production rate. However, the smoothness is insufficient and the productivity is inferior when time is required. Although it is conceivable to lengthen the oven in order to increase productivity, there is a problem that the equipment cost increases when the oven is lengthened. In the present invention, the glass fiber mat is compressed to an appropriate density (50 to 1,000 kg / m ³ ) in advance by a pair of rolls before the second step to be described later. The shortage of the pressing force in the oven in the two steps can be compensated, and an increase in the equipment cost of the oven can be suppressed.

When the density is less than 50 kg / m ³ , the compression of the glass fiber mat is insufficient, and it is difficult to arrange the glass fibers horizontally in the plane direction of the mat even when heated and pressurized in the second step. On the other hand, if it exceeds 1,000 kg / m ³ , the glass fibers constituting the mat are broken, which is not preferable.

(Second step)
The pressure glass fiber mat obtained as described above is used in the second step so that the density is 50 to 150 kg / m ³ , preferably ³⁰ to 200 seconds, and preferably the clearance (mat thickness) is 5 to 30 mm. In this way, pressurization and heating can be performed simultaneously, and it is performed between the upper and lower conveyors in the hot air passage type oven as shown in FIG. The length of the conveyor is preferably 10 to 30 m, although it depends on the line speed. When the length of the conveyor is less than 10 m, pressurization and heating become insufficient, and it is impossible to obtain a core material for vacuum heat insulating material that gives a smooth vacuum heat insulating material. On the other hand, when the length of the conveyor exceeds 30 m Since the apparatus becomes large, it is not preferable.

In this second step, the uncured thermosetting resin is heat-cured to form a vacuum heat insulating core material. When the density is less than 50 kg / m ³ , it is difficult to make the orientation of the glass fibers coincide with the mat and the horizontal plane. On the other hand, when the density exceeds 150 kg / m ³ , the surface of the vacuum heat insulating material is easily smoothed. It is necessary to install additional equipment to put a load on the oven and to increase the pressure.

  The pressing time is preferably 30 to 200 seconds, and most preferably 60 to 150 seconds. Moreover, generally heating temperature is the temperature more than the temperature which an organic binder hardens | cures, and the range of 160-280 degreeC is specifically preferable. This temperature is not the temperature of the conveyor itself, but the temperature in the glass fiber mat. Therefore, the pressurizing / heating treatment can be performed by raising the temperature in the oven to an appropriate temperature. When the pressurization / heating is less than 30 seconds or 160 ° C. or less, the orientation of the glass fibers is not uniform, and the binding of the glass fibers by the binder is insufficient. On the other hand, if the pressurization / heating exceeds 200 seconds or exceeds 280 ° C., the production rate may decrease or the binder may deteriorate.

In the present invention, it is possible to obtain a core material having sufficient smoothness as a vacuum heat insulating material in the first step and the second step. It is preferable to pressurize again so that the density of the fiber mat is 50 to 1,000 kg / m ³ . More preferably, the pressing is performed so that the density of the glass fiber mat is 100 to 300 kg / m ³ . This pressurization method may be any pressurization method, but as shown in FIG. 1, it is preferable to use a pair of rollers from the viewpoint of productivity. The purpose of the pressurization in the third step is the same as that in the first step. In addition, the orientation of the glass fibers in the glass fiber mat treated in the second step is aligned and the surface smoothness of the mat is improved. It is to improve. When the density is less than 50 kg / m ³ , the above-mentioned purpose is not achieved. On the other hand, when the density exceeds 1,000 kg / m ³ , the glass fibers constituting the mat may be broken.

As described above, the core material for vacuum heat insulating material that has been subjected to pressure-pressurization and heat treatment is substantially pressurized with respect to the planar direction of the core material. Level and a moderate amount of binder attached, when released from the pressure after the second or third step, the thickness increases to a thickness of 15 to 100 mm, a density of 20 to 60 kg / m ³ , A core material for a vacuum heat insulating material having a thickness of 1.2 times or more, more preferably 2.0 times or more the thickness of the mat is obtained. If the value is less than 1.2 times, it is a rigid core material, and since the surface smoothness is inferior, the heat insulating performance of the vacuum heat insulating material is inferior. The glass fibers constituting the core material by such pressurization-pressurization / heating-pressurization treatment are not only substantially horizontal to the plane direction but also improve the surface smoothness of the core material. In addition, the above-described state is maintained by thermosetting the organic binder. As a result, a vacuum heat insulating material excellent in heat insulating properties, surface smoothness and workability can be obtained by using the glass fiber mat subjected to pressure and heat treatment as a core material for a vacuum heat insulating material.

  When the vacuum heat insulating material obtained by the present invention is used as a vacuum heat insulating material, for example, the core obtained by the present invention is covered with a gas barrier outer covering material, Is obtained by degassing. Examples of gas barrier coating materials include polyester, polyethylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polypropylene, and other resin films, kraft paper laminated with the above film, the above film laminated with aluminum foil, and the above film Those obtained by vapor-depositing aluminum are preferably used.

  Moreover, the manufacturing method itself of a vacuum heat insulating material may be a known method. As an example, an upper mold and a lower mold are used, and a mold having an exhaust port exhausted by a vacuum pump is prepared in either one of the molds, and an inner surface of a cavity formed by the upper mold and the lower mold is prepared. One is a gas barrier sheath material having an exhaust and sealing tube, for example, an aluminum-deposited high-density polyethylene film, and the vacuum insulation core material of the present invention is placed between them, and then the mold is closed and The peripheral portions of the two jacket materials are fused and deaerated through the tube, so that the internal pressure of the gas barrier jacket material is 10.0 Pa or less. The tube is then sealed and demolded to obtain a vacuum heat insulating material. The size and thickness of the obtained vacuum heat insulating material can be arbitrarily changed depending on the application.

  Further, when the vacuum heat insulating material is manufactured, the vacuum heat insulating core material of the present invention is pressure-molded to a certain range of density, so that the workability at the time of covering with the jacket material is good. Further, by using the core material obtained by the present invention, since the glass fibers of the core material are arranged in the plane direction of the core material, the heat insulating property of the vacuum heat insulating material is remarkably improved. For the same reason, since the surface of the vacuum heat insulating material is smooth, when the heat insulating material is used, there is no space between the wall surface of the housing for storing the heat insulating material, and thus heat insulation is also performed from this point. The property is remarkably improved.

Next, the present invention will be described in more detail with reference to examples and comparative examples.
Example 1
First, a glass fiber mat (thickness of about 300 mm, density of about 3 kg / m ³ ) obtained by spraying a glass fiber having an average fiber diameter of 4 μm with a phenol resin binder so that Igros is 1% by mass is first put on a pair of rolls. Press at a density of 150 kg / m ^{3 when} pressurized, and then continue to be sandwiched by a conveyor with a clearance of about 8 mm above and below in a hot air passing oven at 260 ° C., an oven residence time of about 90 seconds, and a density of 120 kg when pressurized / M ³ was heated and compressed, and further pressed with a pair of rolls under a pressure density of 150 kg / m ³ . As a result, a core material for a vacuum heat insulating material having a thickness of about 30 mm and a density of about 35 kg / m ³ was obtained. Three cores are stacked and inserted into a highly gas barrier coated bag and sucked with a vacuum seal device for 20 minutes so that the pressure in the bag is 3.9 Pa. Then, the opening of the bag is thermocompression bonded, A vacuum heat insulating material having a thickness of 12 mm and a density of 250 kg / m ³ was obtained.

Example 2
First, a glass fiber mat (thickness of about 300 mm, density of about 3 kg / m ³ ) obtained by spraying a glass fiber having an average fiber diameter of 4 μm with a phenol resin binder so that Igros is 1% by mass is first put on a pair of rolls. Pressing at a pressure density of 80 kg / m ³ , followed by a hot air passage oven, sandwiched by a conveyor having a clearance of about 11 mm above and below, 260 ° C., oven dwell time of about 90 seconds, pressure density of 80 kg / M ³ was heated and compressed, and further pressed with a pair of rolls under a pressure density of 80 kg / m ³ . As a result, a core material for a vacuum heat insulating material having a thickness of about 40 mm and a density of about 26 kg / m ³ was obtained. Using this core material, a vacuum heat insulating material was obtained in the same manner as in Example 1.

Example 3
First, a glass fiber mat (thickness of about 300 mm, density of about 3 kg / m ³ ) obtained by spraying a glass fiber having an average fiber diameter of 4 μm with a phenol resin binder so that Igros is 1% by mass is first put on a pair of rolls. Press at a density of 150 kg / m ³ under pressure, and continue to be sandwiched by a conveyer having a clearance of about 11 mm above and below in a hot air passing oven, at 260 ° C., an oven residence time of about 90 seconds, and a density of 80 kg under pressure / M ³ was heated and compressed, and further pressed with a pair of rolls under a pressure density of 150 kg / m ³ . As a result, a vacuum heat insulating core material having a thickness of about 35 mm and a density of about 30 kg / m ³ was obtained. Using this core material, a vacuum heat insulating material was obtained in the same manner as in Example 1.

Comparative Example 1
The glass fiber mat obtained by spraying a glass fiber having an average fiber diameter of 4 μm with a phenol resin binder so that the gloss is 1% by mass is sandwiched by a conveyor having a clearance of about 8 mm above and below in a hot air passing oven. Heat compression was performed under the conditions of 260 ° C., density at press time of about 120 kg / m ³ , and pressurization time of 5 minutes. As a result, a vacuum heat insulating core material having a thickness of about 45 mm and a density of about 23 kg / m ³ was obtained. Using this core material, a vacuum heat insulating material was obtained in the same manner as in Example 1.

Comparative Example 2
The glass fiber mat obtained by spraying a glass fiber having an average fiber diameter of 4 μm with a phenol resin binder so that the amount of gloss is 1% by mass is sandwiched by a conveyer having a clearance of about 11 mm above and below in a hot air passing oven. Heat compression was performed under the conditions of 260 ° C., density during pressing of about 80 kg / m ³ , and pressing time of 5 minutes. As a result, the binder was cured to obtain a core for vacuum heat insulating material having a thickness of about 50 mm and a density of about 21 kg / m ³ . Using this core material, a vacuum heat insulating material was obtained in the same manner as in Example 1.

Comparative Example 3
A glass fiber mat (thickness of about 300 mm, density of about 3 kg / m ³ ) obtained by spraying a phenol resin binder on glass fibers having an average fiber diameter of 4 μm so that the gloss is 1% by mass is heated in a hot air passing oven. While being sandwiched by a conveyor having a clearance of about 8 mm above and below, it is heated and compressed under the conditions of 260 ° C., oven residence time of about 5 minutes, density at pressurization of 120 kg / m ³ , and density at pressurization with a pair of rolls of 80 kg / m It pressed on condition of ³ . Thereby, a core material for vacuum heat insulating material having a thickness of about 43 mm and a density of about 24 kg / m ³ was obtained. Using this core material, a vacuum heat insulating material was obtained in the same manner as in Example 1.

Comparative Example 4
A glass fiber mat (thickness: 300 mm, density: about 3 kg / m ³ ) obtained by spraying a phenol resin binder on glass fibers having an average fiber diameter of 4 μm so that the gloss is 6% by mass is firstly used with a pair of rolls. Pressing at a pressure density of 150 kg / m ³ , followed by a hot air passage oven, sandwiched by a conveyor having a clearance of about 8 mm above and below, 260 ° C., oven dwell time 90 seconds, pressure density 120 kg / m ³ Pressed under conditions. As a result, a vacuum heat insulating core material having a thickness of 8 mm and a density of about 35 kg / m ³ was obtained. Using this core material, a vacuum heat insulating material was obtained in the same manner as in Example 1.

[Evaluation]
The surface smoothness and thermal conductivity of the vacuum heat insulating materials of the above Examples and Comparative Examples were evaluated by the following evaluation methods, and the results shown in Table 1 below were obtained.
[Evaluation methods]
1. Vacuum device: Vacuum device manufactured by Furukawa Seisakusho (trade name FVS-500 × 150)
2. Surface smoothness (measurement method is as follows):
A: There are few irregularities and the depth of the concave portion is less than 1 mm. O: There are slight irregularities, the depth of the concave portion is 1 mm or more and less than 2 mm. Δ: The irregularity is slightly large and the depth of the concave portion is 2 mm or more and less than 3 mm. Large, depth of recess is 3mm or more

"Measurement method of surface smoothness"
As shown in FIG. 2, a hard flat plate, a sample vacuum heat insulating material (200 × 200 mm), a pin (a round bar with a diameter of 3 mm and a pointed tip) and a gauge (size 150 mm × 150 mm, weight 100 ± 1 g) A pin gauge comprising a knob and a hole having a diameter of 3.5 mm in the center is prepared. The sample is placed on a hard flat plate, the center of the gauge is placed about 50 mm or more inside from the end of the test piece, and the pin is dropped. Gently lower the gauge onto the specimen. Grab the gauge knob with the thumb of one hand and the tip of the index finger to fix the pin and gauge, and pick up the integrated pin gauge from the specimen. While holding the pin gauge knob firmly, apply a straight scale and measure the distance between the bottom of the gauge and the tip of the pin in units of 0.5 mm. This is repeated and ten dents are measured. The average value at 10 locations is defined as the dent of the test specimen.
3. Thermal conductivity: Measured with a thermal conductivity meter (HC-074-300) manufactured by Eihiro Seiki Co., Ltd.

  According to the present invention as described above, it is possible to provide a core material for a vacuum heat insulating material excellent in heat insulating properties in which the fiber orientation is perpendicular to the heat transfer direction and the surface is smooth. By using this core material, it is possible to obtain a vacuum heat insulating material excellent in heat insulating performance with good workability.

The figure which illustrates the method of this invention illustratively. The figure explaining the measurement of surface smoothness.

Claims (5)

An inorganic fiber mat formed by collecting inorganic fibers to which an uncured thermosetting organic binder is attached in an amount of 0.5 to 3.0% by mass in a solid content is 1 so that the density is 50 to 1,000 kg / m ^3. A first step of pressurizing using a pair of rollers, a second step of forming by heating while pressing so that the density is 50 to 150 kg / m ³ between the upper and lower conveyors in the hot-air passing oven , Further, after the second step, a third step of pressurizing so that the density is 50 to 1,000 kg / m ³ using a pair of rollers is continuously performed in this order, and the density is 20 to 60 kg / A method for producing an inorganic fiber mat for a vacuum heat insulating material, comprising obtaining an inorganic fiber mat having a thickness of 1.2 times or more of m ³ and the thickness of the second step. The manufacturing method of the inorganic fiber mat for vacuum heat insulating materials of Claim 1 pressurized so that a density may be set to 100-300 kg / m < ³ > at said 1st process. The method for producing an inorganic fiber mat for a vacuum heat insulating material according to claim 1, wherein the pressure and heating time in the second step is 30 seconds to 200 seconds. The manufacturing method of the inorganic fiber mat for vacuum heat insulating materials of Claim 1 which pressurizes so that a density may be set to 100-300 kg / m < ³ > at a said 3rd process. The method for producing an inorganic fiber mat for a vacuum heat insulating material according to claim 1, wherein the inorganic fiber mat is obtained by adding an uncured thermosetting organic binder to the inorganic fiber and then collecting the inorganic fibers into a mat shape. .

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