JP2005265038A - Vacuum heat insulating material and method for manufacturing inorganic fiber sheet for vacuum heat insulating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide vacuum heat insulating material having improved heat insulating effect by aligning fiber in a direction vertical to a heat transmission direction from a sheet front surface to a back surface, namely, in a horizontal direction to the sheet surface with aiming at fiber structure (fiber arrangement) improving heat insulating effect to remarkably reducing shot and using inorganic fiber of small fiber diameter, and a method for manufacturing inorganic fiber sheet for vacuum heat insulation. <P>SOLUTION: Laminated plural sheets of inorganic fiber sheet made by a wet papermaking method with using inorganic fiber as a main component is used as a core material in this vacuum heat insulating material. Content of shots of particle diameter 30 μm or greater in the inorganic fiber is 0.1 mass% or less, average fiber diameter of the inorganic fiber is 0.2-6 μm, and the inorganic fiber is aligned in the horizontal direction to the sheet surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a vacuum heat insulating material manufactured using inorganic fibers. Specifically, the heat transfer distance is reduced by significantly reducing the shot content and improving the structure of the fibers constituting the vacuum heat insulating material. It is related with the manufacturing method of the vacuum heat insulating material which lengthens and improves heat insulation, and the inorganic fiber sheet for vacuum heat insulating materials.

Conventionally, as a vacuum heat insulating material, a needling mat, felt, wool or the like made of an inorganic fiber is molded using a binder, stored in a heat insulating container, and then sealed in a vacuum.
In order to improve the heat insulation of the vacuum heat insulating material made of the inorganic fiber, the heat insulating material in which the content of shots (non-fibrous granular material) in the inorganic fiber is reduced, or the inorganic fiber is perpendicular to the heat transfer direction. Various vacuum heat insulating materials have been proposed, such as heat insulating materials arranged in a row.

  For example, if the size of the shot of inorganic fibers constituting the heat insulating material is large and the number is large, the size and number of voids in the heat insulating material increase, and heat conductivity is increased by heat transfer due to air convection in the large air gap. It has been found that it increases and the thermal insulation decreases. For this reason, Patent Document 1 includes a shot containing ratio of an inorganic fiber containing a shot, an inorganic powder, and a binder, the average fiber length of the inorganic fiber being 1 mm or less, and a particle diameter of 45 μm or more contained in the inorganic fiber. Is 30% by weight or less, and a heat insulating material in which the weight average diameter of the inorganic powder is 1 to 30 μm has been proposed. Further, Patent Document 2 proposes a heat insulating material in which the shot content with a particle diameter of 50 μm or more contained in the inorganic fibers constituting the heat insulating material is 1% by weight or less.

  In addition, when the inorganic fibers constituting the vacuum heat insulating material are arranged in parallel with the direction of the heat transferred from one surface to the other surface, heat transfer is easy along the gaps of the inorganic fibers, so the thermal conductivity is high. It is known that the heat insulating property is reduced. For this reason, Patent Document 3 discloses that a water dispersion medium having a constant concentration by crushing fiber cotton is continuously dehydrated in several times while dewatering, and gradually forming a fiber layer, thereby transferring the heat transfer direction. On the other hand, a vacuum heat insulating material in which fibers are arranged in a vertical direction has been proposed.

  In addition, as a vacuum heat insulating material in which glass fibers are arranged in a direction perpendicular to the heat transfer direction, Patent Document 4 discloses that glass wool raw cotton having an average fiber diameter of about 4 to 6 μm is cut into a predetermined size. A predetermined amount of cotton collection is laminated, ion-exchanged water having a pH value near neutral is sprayed on the surface of this cotton collection laminate, compressed at room temperature, and diffused and penetrated into the cotton collection laminate, then heated. There has also been proposed a vacuum heat insulating material in which glass fibers are arranged in a direction perpendicular to the heat transfer direction by high-temperature compression with a press and repeating this compression.

In addition, as a vacuum heat insulating material in which fibers are arranged in a direction perpendicular to the heat transfer direction, Patent Document 5 describes that a plurality of paper-making papers made of inorganic fibers having an average fiber diameter of 2 μm or less are laminated, and inorganic fibers are bonded together. There has also been proposed a vacuum heat insulating material in which inorganic fibers are arranged in a direction perpendicular to the heat transfer direction by binding at each intersection with components eluted from these fibers.
JP 2001-192278 A JP 2001-48672 A Japanese Patent Laid-Open No. 9-4785 JP 2004-11709 A JP 7-139691 A

However, since the heat insulating material described in Patent Document 1 is not obtained by completely removing shots, the heat conductivity is about 0.046 W / m · K, which is a relatively high heat insulating material. There was an inconvenience. Further, the heat insulating material described in Patent Document 2 also has a disadvantage in that the shot has not been completely removed, so that the heat conductivity is relatively high.
In addition, the vacuum heat insulating material described in Patent Document 3 is, for example, a vacuum heat insulating material obtained by compressing and dewatering glass fibers having an average fiber length of 2 mm, with a vacuum thermal conductivity of 0.015 W / m · K, fiber It is described that the thermal conductivity is higher than the vacuum thermal conductivity of 0.007 W / m · K of a vacuum heat insulating material obtained by compressing and dewatering a glass fiber having a length of 1 mm. This is presumed that when relatively long fibers were subjected to compression dehydration, the fiber structure was rough, so that the structure of the fibers was deformed during vacuum heating and the heat insulation was reduced. However, it is presumed that the glass fibers are not surely arranged in the direction perpendicular to the heat transfer direction.
In addition, as in the vacuum heat insulating material described in Patent Document 4, when trying to move fibers by pressing without destroying the glass fibers in the wet sheet, the space of the glass fiber structure is usually used. Since the amount is 90% or more, the sheet moisture amount is 80% or more, that is, the moisture amount is 8 times or more that of glass fiber. However, in the case of the vacuum heat insulating material of Patent Document 4, the maximum is 2 at the time of high-temperature compression. Since only double the amount of moisture is attached, it is not considered that the glass fiber moves in the horizontal direction by pressing, the glass fiber breaks and shortens by pressing, and the finely broken glass fiber has a dense structure. The heat insulating property is enhanced, and it is estimated that the heat insulating effect due to the fiber structure (fiber arrangement) is small.
Moreover, in the vacuum heat insulating material of the said patent document 5, an inorganic fiber is perpendicular | vertical with respect to the thickness direction of a vacuum heat insulating material as a whole vacuum heat insulating material by laminating | stacking several layers of the inorganic fiber paper obtained by wet papermaking. However, there is no special control (special control of jet / wire ratio, etc.) to arrange the fibers in the horizontal direction with respect to the paper surface during wet paper making of paper. When viewed in paper units, the fibers are not surely arranged in the horizontal direction with respect to the paper surface.
Therefore, the present invention pays attention to the fiber structure (fiber arrangement) that enhances the heat insulation effect, significantly reduces shots, and uses the inorganic fiber having a small fiber diameter to transfer heat from the front surface to the back surface of the sheet. It aims at providing the manufacturing method of the vacuum heat insulating material which arranged the fiber in the orthogonal | vertical direction, ie, the horizontal direction with respect to the sheet | seat surface, and improved the heat insulation effect, and the inorganic fiber sheet for vacuum heat insulating materials. .

In order to achieve the above object, the vacuum heat insulating material of the present invention is a vacuum heat insulating material obtained by using a laminate of a plurality of inorganic fiber sheets made mainly of inorganic fibers and wet-made as described in claim 1 as a core material. And the shot fiber content of a particle diameter of 30 μm or more in the inorganic fiber is 0.1% by mass or less, the average fiber diameter of the inorganic fiber is 0.2 to 6 μm, and the inorganic fiber is on the sheet surface. On the other hand, it is arranged in a horizontal direction.
The vacuum heat insulating material according to claim 2 is characterized in that, in the vacuum heat insulating material according to claim 1, the inorganic fiber sheet is composed of only inorganic fibers.
The vacuum heat insulating material according to claim 3 is the vacuum heat insulating material according to claim 1 or 2, wherein the average fiber diameter of the inorganic fibers is 2 μm or less.
Moreover, the vacuum heat insulating material of Claim 4 is a vacuum heat insulating material in any one of Claims 1 thru | or 3, The said inorganic fiber is glass fiber, It is characterized by the above-mentioned.
In order to achieve the above object, the method for producing an inorganic fiber sheet for a vacuum heat insulating material according to the present invention has inorganic fibers dispersed in a dispersion medium on a forming wire that travels in a certain direction as described in claim 5. A method for producing an inorganic fiber sheet for vacuum heat insulating material, in which an inorganic fiber is deposited on the forming wire while dewatering the paper-making raw material liquid and wet-making, and the average fiber is used as the inorganic fiber. Use of inorganic fibers having a diameter of 0.2 to 6 μm and a particle content of 30 μm or more and a shot content of 0.1% by mass or less, and a speed ratio between the flow speed of the papermaking raw material liquid and the traveling speed of the forming wire The jet / wire ratio is 0.5 to 0.8.
Moreover, the manufacturing method of the inorganic fiber sheet for vacuum heat insulating materials of Claim 6 is a manufacturing method of the inorganic fiber sheet for vacuum heat insulating materials of Claim 5, The average fiber diameter of the said inorganic fiber is 2 micrometers or less. Features.
Moreover, the manufacturing method of the inorganic fiber sheet for vacuum heat insulating materials of Claim 7 is a manufacturing method of the inorganic fiber sheet for vacuum heat insulating materials of Claim 5 or 6, The said inorganic fiber is glass fiber, It is characterized by the above-mentioned. To do.

The vacuum heat insulating material of the present invention is a vacuum heat insulating material using as a core a material obtained by laminating a plurality of wet-made inorganic fiber sheets mainly composed of inorganic fibers, and the inorganic fiber sheet has a particle diameter of 30 μm or more. It consists of a sheet made by wet papermaking mainly composed of inorganic fibers having a shot content of 0.1% by mass or less and an average fiber diameter of 0.2 to 6 μm (preferably 0.2 to 2 μm). Are arranged in the horizontal direction. As described above, the vacuum heat insulating material of the present invention is almost free of shots and uses an inorganic fiber sheet formed mainly of very fine inorganic fibers as a core material. A large number of voids are formed, heat transfer due to convection of air in the voids is small, thermal conductivity is lowered, and heat insulation can be improved. Moreover, since the inorganic fiber sheet in which the fibers are arranged in the horizontal direction with respect to the sheet surface is used as the core material, heat transfer from the front surface to the back surface of the heat insulating material can be inhibited, and the gap between the fibers serving as the heat transfer path Complicated and maze, heat conduction time becomes longer and heat insulation effect can be improved.
Further, when glass fiber is used as the inorganic fiber, it is highly useful because a glass fiber having a fine diameter can be easily obtained industrially. Sheets made by wet papermaking of glass fibers should be made of inorganic fiber sheets for vacuum insulation with a stable quality, with improved accuracy in thickness and density, compared to those formed by compressing cotton wool laminates made of glass wool. Can do.
Further, the method for producing an inorganic fiber sheet for vacuum heat insulating material according to the present invention comprises ejecting a papermaking raw material liquid in which inorganic fibers are dispersed in a dispersion medium onto a forming wire running in a certain direction, and dehydrating the papermaking raw material liquid. However, it is a manufacturing method in which inorganic fibers are deposited on the forming wire to perform wet papermaking, and the inorganic fibers have an average fiber diameter of 0.2 to 6 μm and a shot content of 0.1 to 30 μm. Since the inorganic fiber which is less than mass% is used, and the jet / wire ratio, which is the speed ratio of the flow speed of the papermaking raw material liquid and the traveling speed of the forming wire, is set to 0.5 to 0.8, the papermaking raw material liquid The traveling speed of the forming wire is faster than the flow velocity of the paper, and the inorganic fibers in the papermaking raw material liquid are pulled in the traveling direction of the forming wire. It can be arranged in a horizontal direction with respect to the surface.

The vacuum heat insulating material of the present invention is formed by using, as a core material, a laminate of a plurality of inorganic fiber sheets made by wet papermaking mainly composed of inorganic fibers.
The inorganic fibers need to be arranged in the horizontal direction with respect to the sheet surface of the inorganic fiber sheet. By doing so, the fibers can be arranged in the vertical direction with respect to the heat transfer direction of the heat insulating material, thereby inhibiting the thermal conductivity and, as a result, improving the heat insulating performance of the vacuum heat insulating material. Can do.
The inorganic fiber must have an average fiber diameter of 0.2 to 6 μm. Because, if the average fiber diameter is less than 0.2 μm, it is possible to make a sheet by wet papermaking, but there is a disadvantage that the material cost becomes high and it is not suitable for practical use as an industrial product, and if it exceeds 6 μm, This is because there is an inconvenience that the entangled structure between the fibers decreases and sufficient sheet strength cannot be obtained. In addition, since the one where the average fiber diameter of the said inorganic fiber is smaller can refine | miniaturize the space | gap of an inorganic fiber sheet and gas heat conduction is reduced, the heat insulation performance of a vacuum heat insulating material improves. From this point, the average fiber diameter of the inorganic fibers is preferably 2 μm or less.

As the inorganic fiber, glass fiber, ceramic fiber, slag wool fiber, rock wool fiber and the like can be used. However, glass fiber is preferred because fine fibers can be easily obtained industrially.
The inorganic fiber of the fine diameter contains non-fibrous particles usually called shots because of its production method, but these shots do not function as fibers but also have high heat conductivity. Is preferable. In particular, a large shot having a particle size of 30 μm or more generates large pores in the heat insulating material and promotes heat transfer due to gas convection heat transfer and gas molecule collision, so that the heat insulating performance of the heat insulating material is greatly hindered. For this reason, as an inorganic fiber used for the vacuum heat insulating material of the present invention, a fiber having a shot content of 30 μm or more and 0.1% by mass or less is used.
In the present invention, in particular, in order to obtain a high-quality inorganic fiber sheet that does not cause surface irregularities or the like, it is produced by a wet papermaking method rather than a dry method (such as a cotton collection lamination method) that has been the mainstream in the past. Yes. For example, if the papermaking raw material liquid in which inorganic fibers are dispersed in a dispersion medium is centrifuged and passed through a screen filter, the shot content with a particle diameter of 30 μm or more in the inorganic fibers becomes substantially zero. It can be reduced to 1% by mass or less.
As the glass fiber, for example, a short glass fiber obtained by melting and spinning an acid-resistant C glass, applying energy with a flame of a burner and blowing it, or a long glass fiber spun after melting the C glass is suitable. Used for. Glass fiber obtained by such a flame method or other methods such as centrifugation is formed in a columnar shape with a small surface area and is not branched (fibrillated) like pulp fibers. During wet papermaking, even if the fibers in the papermaking raw material are pulled by a forming wire that runs in a certain direction, there are no inconveniences such as the fibers being caught and the sheet surface being crushed or having holes. .

  In addition to the inorganic fibers, the inorganic fiber sheet includes inorganic materials such as organic binders, inorganic binders, organic fibers, and other binder-functional materials, organic powders, inorganic powders, microcapsule granules, and the like. An auxiliary material such as a material that can improve the strength, uniformity, and handleability of the fiber sheet can be mixed. In addition, it is also possible to obtain an inorganic fiber sheet composed only of inorganic fibers by the wet papermaking method and not including the auxiliary material as described above. In this case, the vacuum deterioration due to the gas generated from the auxiliary material is caused. In addition to being able to prevent the accompanying decrease in heat insulation performance, there is no merit between fibers due to the binder, so that there is a merit that it is possible to have flexibility that can cope with deformation according to the use of the vacuum heat insulating material.

The method for producing an inorganic fiber sheet for a vacuum heat insulating material according to the present invention is characterized in that a papermaking raw material liquid in which inorganic fibers are dispersed in a dispersion medium is jetted onto a forming wire running in a certain direction, and the papermaking raw material liquid is dehydrated. Inorganic paper is deposited on the forming wire and wet-made, and in particular, in order to reliably arrange the fibers in the horizontal direction with respect to the sheet surface of the wet-made inorganic fiber sheet, The jet / wire ratio, which is the speed ratio between the flowing speed and the traveling speed of the forming wire, is controlled in the range of 0.5 to 0.8. In order to perform such control, in the present invention, as the paper machine, a part of the inclined paper machine (for example, a sealed inclined paper machine equipped with a pound regulator) whose jet / wire ratio can be adjusted relatively easily or a long machine is used. It is preferable to use a net paper machine. When the jet / wire ratio is 0.8 or less, the traveling speed of the forming wire is clearly faster than the speed at which the papermaking raw material liquid flows. Therefore, the inorganic fibers are all pulled in the forming wire flow direction. Thus, an inorganic fiber sheet in which inorganic fibers are reliably arranged in the horizontal direction with respect to the sheet surface can be obtained. If the jet / wire ratio is less than 0.5, the forming wire travel speed is too high relative to the speed at which the papermaking raw material liquid flows, that is, the raw material supply speed. It is not possible to obtain a sheet with a uniform texture.
Hereinafter, as an example, a specific method for producing the inorganic fiber sheet for vacuum heat insulating material of the present invention using the hermetic inclined paper machine equipped with the pound regulator shown in FIG. 1 will be described with reference to the drawings.
(1) First, as a raw material, for example, a predetermined amount of fine glass fiber having an average fiber diameter of 1 μm is weighed, and the fiber is uniformly dispersed and mixed in water by a separator such as a mixer or a pulper to obtain a papermaking raw material liquid . Since glass fiber is not fibrillated unlike pulp, it is broken into powder when using a beating machine equipped with a blade such as a beater, so a pulper is used. This papermaking raw material liquid is transported and stored in a storage tank.
(2) Next, since it is presumed that a small amount of shot is mixed in the glass fiber in the papermaking raw material liquid, the papermaking raw material liquid is centrifuged with a centrifuge, and then a screen filter is used. By passing, the shot content with a particle diameter of 30 μm or more in the glass fiber contained in the papermaking raw material liquid is made 0.1 mass% or less.
(3) Next, the supply amount of the papermaking raw material liquid is controlled by a seed valve / white water valve (not shown), and the papermaking raw material liquid is ejected from the head box 3 via a step diffuser or the like, and the papermaking raw material liquid pool (water pool) ) 5 is formed. The glass fibers 4 in the pool 5 are deposited on the forming wire 6 that runs obliquely upward, and dehydrated from below to form the wet glass web sheet 2. The sealed inclined paper machine 1 can easily adjust the flow rate of the papermaking raw material liquid by adjusting the area of the raw material input opening of the head box 3 by pressing the liquid level of the pool 5 with the pound regulator 8. By adjusting the traveling speed of the forming wire 6 with respect to this flow velocity, the jet / wire ratio, which is the speed ratio between the flow rate of the papermaking raw material liquid and the traveling speed of the forming wire 6, is in the range of 0.5 to 0.8. Can be adjusted.
(4) Next, the glass fiber sheet 2 in the wet paper state is passed through a dryer that dries moisture to obtain a base paper of the inorganic fiber sheet for vacuum heat insulating material, which is wound into a roll. If this base paper is developed and cut into a desired size, an inorganic fiber sheet for vacuum heat insulating material is obtained.

Next, although the Example of this invention is described with a comparative example and a prior art example, this invention is not limited to this Example.
(Example)
100 mass% of short glass fibers made of C glass having an average fiber diameter of 1 μm are dispersed and mixed in water using a pulper device, and then stored in a storage tank as a papermaking raw material liquid. Thereafter, the papermaking raw material liquid is centrifuged by a centrifuge and passed through a screen filter to remove shots in the papermaking raw material liquid. Next, using the hermetic inclined paper machine equipped with the above-described pound regulator, the above-described jet / wire ratio is adjusted to 0.7 to form a wet fiberglass sheet on the forming wire, 220 It dried through the hot-air dryer of 0 degreeC, and obtained the inorganic fiber sheet for vacuum heat insulating materials of thickness 2.0mm and density 0.18g / cm < ³ >. In order to set the jet / wire ratio to 0.7, the spout valve / white water valve is adjusted so that the ejection amount of the papermaking material liquid ejected from the head box onto the forming wire is 70 m ³ / min. By adjusting the area of the raw material input opening of the head box to 10 m ² with a pound regulator to adjust the flow rate of the papermaking raw material liquid to 7 m / min, the traveling speed of the forming wire is adjusted to 10 m / min. / The wire ratio was adjusted to 0.7.
When the directionality of the fibers of the obtained inorganic fiber sheet for vacuum heat insulating material was observed, almost all the fibers were arranged in the horizontal direction with respect to the sheet surface.
Next, 5 sheets of the inorganic fiber sheet for vacuum heat insulating material are stacked to form a laminated body having a thickness of 10 mm, and this laminated body is inserted into a gas barrier film bag as a core material for vacuum insulating material, and evacuated to 10 ⁻³ Torr. Thus, a vacuum heat insulating material was obtained. At this time, no ripples or wrinkles were observed on the appearance of the vacuum heat insulating material. With respect to this vacuum heat insulating material, the thermal conductivity at room temperature was measured to be 0.0020 W / m · K. Moreover, when the shot content rate in the said core material for vacuum heat insulating materials was measured by 30 micrometer sieve residual amount, it was 0.01 mass% or less.

(Conventional example)
Ion exchange water is sprayed twice on the surface of glass wool obtained by centrifugation with an average fiber diameter of 2 μm and no resin is adhered, and the glass wool is sandwiched between SUS plates and pressurized, and heated at 380 ° C. After heating in a furnace for 60 minutes and cooling, an inorganic fiber sheet for vacuum heat insulating material having a thickness of 10 mm and a density of 0.20 g / cm ³ was obtained.
When the directionality of the fiber of the obtained inorganic fiber sheet for vacuum heat insulating materials was observed, the directionality of clear fiber was not seen, but between fibers became narrower than before pressurization by pressurization.
Next, the inorganic fiber sheet for vacuum heat insulating material was inserted into a gas barrier film bag as a core material for vacuum heat insulating material, and evacuated to 10 ⁻³ Torr to obtain a vacuum heat insulating material. At this time, no ripples or wrinkles were observed on the appearance of the vacuum heat insulating material. With respect to this vacuum heat insulating material, the thermal conductivity at room temperature was measured to be 0.0030 W / m · K. The shot content in the core for vacuum heat insulating material was 0.5% by mass when measured by the residual amount of 30 μm sieve.

(Comparative example)
An inorganic fiber sheet for vacuum heat insulating material having a thickness of 2.0 mm and a density of 0.14 g / cm ³ was obtained in the same manner as in Example 1 except that the jet / wire ratio was 1.0. In order to set the jet / wire ratio to 1.0, the ejection amount of the papermaking raw material liquid ejected from the head box onto the forming wire is set to 100 m ³ / min. The flow rate of the papermaking raw material liquid was adjusted to 10 m / min by adjusting the area to 10 m ² , while the traveling speed of the forming wire was adjusted to 10 m / min to adjust the jet / wire ratio to 1.0.
When the directionality of the fibers of the obtained inorganic fiber sheet for vacuum heat insulating material was observed, the fibers were randomly oriented in the vertical and horizontal directions with respect to the sheet surface.
Next, 5 sheets of the inorganic fiber sheet for vacuum heat insulating material are stacked to form a laminated body having a thickness of 10 mm, and this laminated body is inserted into a gas barrier film bag as a core material for vacuum insulating material, and evacuated to 10 ⁻³ Torr. Thus, a vacuum heat insulating material was obtained. At this time, no ripples or wrinkles were observed on the appearance of the vacuum heat insulating material. With respect to this vacuum heat insulating material, the thermal conductivity at room temperature was measured to be 0.0030 W / m · K. Moreover, when the shot content rate in the said core material for vacuum heat insulating materials was measured by 30 micrometer sieve residual amount, it was 0.01 mass% or less.

  Next, for the inorganic fiber sheet for vacuum heat insulating material, the core material for vacuum heat insulating material, and the vacuum heat insulating material of Examples, Conventional Examples and Comparative Examples obtained above, thickness, basis weight, density, fiber direction Table 1 shows the results of measuring the properties, shot content, and thermal conductivity.

From the results shown in Table 1, the following was found.
(1) In the inorganic fiber sheet used for the vacuum heat insulating material of the example, since the shot content with a particle diameter of 30 μm or more, which is a factor for forming a large void, is substantially zero with 0.01 mass% or less, air Heat transfer due to convection is small, and almost all the glass fibers are arranged in the horizontal direction with respect to the sheet surface. It was confirmed that a vacuum heat insulating material having low heat conductivity and excellent heat insulating properties can be obtained because the gaps between fibers serving as heat paths are complicated and mazes.
(2) In the inorganic fiber sheet used for the vacuum heat insulating material of the conventional example, the shot content is relatively high, and there is no clear fiber orientation in which the fibers are arranged in the horizontal direction with respect to the sheet surface. In comparison, the heat insulating property of the vacuum heat insulating material was high and the heat insulating property was poor. In addition, it was speculated that the manufacturing cost would be increased because a step of evaporating the water adhering to the glass wool in a heating furnace after batching water on the glass wool in the sheet manufacturing method is required.
(3) In the inorganic fiber sheet used for the vacuum heat insulating material of the comparative example, the shot content is low (substantially zero), but the fibers have no orientation with respect to the sheet surface and are randomly oriented. Since there are a relatively large number of fibers oriented in the direction perpendicular to or close to the sheet surface, the fiber gap formed from the front surface to the back surface of the heat insulating material becomes a heat transfer path, and heat is easily transferred. Compared with the above, the heat conductivity of the vacuum heat insulating material was high, and the heat insulating property was inferior.

Explanatory drawing which shows schematic structure of the sealed inclination paper machine provided with the pound regulator which manufactures the inorganic fiber sheet for vacuum heat insulating materials of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sealing type inclined paper machine 2 Glass fiber sheet in wet paper state 3 Head box 4 Glass fiber 5 Pool 6 Forming wire 8 pound regulator

Claims (7)

  A vacuum heat insulating material using as a core a material obtained by laminating a plurality of inorganic fiber sheets made mainly from inorganic fibers, and the shot content of the inorganic fibers having a particle diameter of 30 μm or more is 0.1% by mass A vacuum heat insulating material, wherein the inorganic fiber has an average fiber diameter of 0.2 to 6 μm, and the inorganic fibers are arranged in a horizontal direction with respect to a sheet surface.   The vacuum heat insulating material according to claim 1, wherein the inorganic fiber sheet is composed only of inorganic fibers.   The vacuum heat insulating material according to claim 1 or 2, wherein an average fiber diameter of the inorganic fibers is 2 µm or less.   The vacuum heat insulating material according to any one of claims 1 to 3, wherein the inorganic fiber is a glass fiber.   A vacuum for performing wet papermaking by ejecting a papermaking raw material liquid in which inorganic fibers are dispersed in a dispersion medium onto a forming wire that travels in a certain direction, and depositing the inorganic fibers on the forming wire while dehydrating the papermaking raw material liquid. A method for producing an inorganic fiber sheet for a heat insulating material, wherein an inorganic fiber having an average fiber diameter of 0.2 to 6 μm and a shot content ratio of a particle diameter of 30 μm or more is 0.1% by mass or less is used as the inorganic fiber. In addition, a jet / wire ratio, which is a speed ratio between the flow rate of the papermaking raw material liquid and the forming wire, is set to 0.5 to 0.8. Method.   The average fiber diameter of the said inorganic fiber is 2 micrometers or less, The manufacturing method of the inorganic fiber sheet for vacuum heat insulating materials of Claim 5 characterized by the above-mentioned.   The said inorganic fiber is a glass fiber, The manufacturing method of the inorganic fiber sheet for vacuum heat insulating materials of Claim 5 or 6 characterized by the above-mentioned.

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