JP2006307921A - Vacuum thermal insulating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum thermal insulating material capable of preventing rupture of fibers in compression by atmospheric pressure applied in vacuum packing and suppressing heat conduction of a solid component to a low value. <P>SOLUTION: In this vacuum thermal insulating material constituted by covering a core material 4 with an outer covering material made of a laminate film and reducing pressure in the inside of the outer covering material and sealing it, the core material 4 is constituted by laminating glass fibers 2a, 2b having such characteristic that they are not easily broken off even when deformed by external force by increasing distortion limit of rupture like layers in such a way that the direction of length of the glass fibers 2a, 2b becomes substantially vertical to the direction of heat transfer and the glass fibers 2a, 2b being adjacent in the direction of heat transfer cross mutually. Since the glass fibers 2a, 2b are not easily broken off even when the core material 4 is compressed by atmospheric pressure, contact of a rupture part with the other fibers is suppressed and heat conduction of the solid component is suppressed. As a result, the vacuum thermal insulating material capable of suppressing heat conduction of the solid component to a low value can be manufactured. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vacuum heat insulating material having excellent heat insulating performance.

  As the core material used for the vacuum heat insulating material, an inorganic compound having a small thermal conductivity and less gas generation is suitable. In particular, a vacuum heat insulating material using a glass fiber laminate as a core material is known to have excellent heat insulating performance, and an example of the core material constituting the vacuum heat insulating material is shown in FIG. There is something.

  FIG. 5 shows that the inorganic fine fibers 1a are randomly laminated so that the length direction thereof is perpendicular to the heat transfer direction and the length directions of the inorganic fine fibers 1a intersect each other. Point-to-point contact with each other, driven into the laminated inorganic fine fiber 1a in parallel with the heat transfer direction, and provided with a penetration fiber 1b constituting the high-density inorganic fine fiber mat 1, an inorganic fine fiber mat It has been proposed to form a core material by superimposing a plurality of sheets 1 (for example, see Patent Document 1).

  In the conventional vacuum heat insulating material configured as described above, since the inorganic small-diameter fibers 1a are arranged at right angles to the heat transfer direction and randomly, the fibers are in point contact with each other. The contact thermal resistance at the contact point is large, and the amount of heat transfer in the core material thickness direction is small.

  However, with only the fibers arranged perpendicular to the heat transfer direction, the compression resistance against atmospheric pressure acting in the heat transfer direction decreases, and the core material is compressed by the atmospheric pressure acting after vacuum packaging, making it difficult to ensure thickness Therefore, the penetration fibers 1b are partially arranged in parallel with the heat transfer direction.

However, since the heat insulation performance is lowered by the penetration fibers 1b, a core material is formed by superimposing a plurality of inorganic fine fiber mats 1 and the amount of heat transferred by the penetration fibers 1b is reduced.
Japanese Examined Patent Publication No. 7-103955

  However, in the above conventional configuration, since the contribution of heat conduction by fibers horizontal in the heat transfer direction is large, it is difficult to sufficiently reduce heat conduction even when a plurality of inorganic thin fiber mats 1 are overlapped, There was a problem that the heat conduction of the solid component was increased.

  On the other hand, in the core material formed by laminating glass fibers, which are a kind of inorganic fine fiber, only in the heat transfer direction and the horizontal direction, the heat conduction of the solid component increases due to the following factors.

  A compressive force is applied to the glass fiber through the jacket material. Glass fibers are intertwined inside a core material made of glass fibers, and when compressive force is applied by atmospheric pressure, tensile stress and bending stress are applied to the glass fibers to cause distortion.

  If the strain limit of breakage of the glass fiber is small, it breaks with a slight strain, the space held by the presence of this fiber disappears, and heat is easily transferred by the fibers that are not in contact with each other Become. Furthermore, heat is easily transferred also when the broken portion of the fiber comes into contact with the nearby fiber.

  The present invention solves the above-mentioned conventional problems, and aims to provide a vacuum heat insulating material that suppresses heat conduction of a solid component caused by fibers in the heat transfer direction and the horizontal direction and has low heat conductivity. To do.

  In order to solve the above-mentioned conventional problems, the vacuum heat insulating material of the present invention is a glass fiber having a characteristic that the core material is not easily broken even if it is deformed by an external force by increasing the strain limit of breaking. The glass fiber is laminated in layers so that the length direction is substantially perpendicular to the heat transfer direction and the glass fibers adjacent to each other in the heat transfer direction intersect.

  As a result, the fibers are difficult to break even when compressed by atmospheric pressure, so that the surrounding space is maintained and the surrounding fibers are less likely to come into contact with each other, so that an increase in the heat conduction of the solid component is suppressed. Therefore, it becomes a vacuum heat insulating material which suppressed the heat conduction of the solid component low.

  The vacuum heat insulating material of this invention can obtain the vacuum heat insulating material which has the heat insulation performance outstanding compared with the vacuum heat insulating material using the core material produced using the glass which has the same thermal conductivity.

  The invention of the vacuum heat insulating material according to claim 1 is formed by covering the core material with a cover material made of a laminate film and sealing the cover material by reducing the pressure inside the cover material. The glass fiber having the characteristic that it is difficult to break even if deformed by an external force by increasing the limit, the length direction of the glass fiber is substantially perpendicular to the heat transfer direction, and the glass fibers adjacent to each other in the heat transfer direction are It is characterized by being laminated in layers so as to intersect.

  If the glass fiber is difficult to break even if it is deformed by an external force, even if the fiber entangled in the core material is distorted by atmospheric pressure, it is difficult to break, and the presence of this fiber keeps the space. As the core material, a vacuum heat insulating material in which the core material is hardly compressed by atmospheric pressure, heat is not easily transmitted by maintaining the space in the core material, and the heat conduction of the solid component is kept low can be obtained.

  According to a second aspect of the present invention, the core material according to the first aspect of the present invention is made of a glass fiber aggregate having a compression recovery rate of 70% or more.

  The compression restoration rate indicates a ratio of bulkiness before and after compression of the glass fiber aggregate. For example, when the bulkiness is 70 mm when a glass fiber aggregate having a bulkiness of 100 mm is compressed, the compression recovery rate of the glass fiber aggregate is 70%.

  Some glass fiber aggregates have various compression recovery rates depending on the degree of brittleness of the glass fibers constituting the glass fiber aggregate. The thermal conductivity of the vacuum heat insulating material decreases as the compression recovery rate of the glass fiber aggregate constituting the core increases. The heat conductivity of the vacuum heat insulating material produced with the glass fiber aggregate which has various compression recovery rates was measured. When the compression recovery rate is less than 70%, the thermal conductivity of the vacuum heat insulating material does not depend on the compression recovery rate, but when the compression recovery rate is 70% or more, the thermal conductivity decreases as the compression recovery rate increases. From this, when the compression recovery rate exceeds 70%, the heat transfer by the glass fiber inside the core material decreases, and the cause is estimated as follows.

  When the glass fiber breaks, the thermal conductivity increases because the broken portion comes into contact with other fibers. Therefore, the thermal conductivity can be reduced by using a glass fiber aggregate that is difficult to break the glass fiber as a core material.

  The glass fiber aggregate with a high compression recovery rate is used to increase the bulk of the glass fiber aggregate due to the force that breaks the unbroken fiber when the glass fiber inside is hard to break when compressed. is there. In order to restore the bulkiness of the compressed glass fiber aggregate, it is necessary that there are many unbroken glass fibers, and when the unbroken glass fibers increase, the compression recovery rate is 70% or more. Become.

  Therefore, a vacuum heat insulating material with reduced thermal conductivity can be obtained by using a glass fiber aggregate having a compression recovery rate of 70% or more as a core material.

When the compression recovery rate is measured, the pressure applied to the glass fiber aggregate is 20 kPa for 1 minute, and the bulk after compression is measured 24 hours after the pressure is released. Further, when there are glass fiber aggregates having various densities, and those having a low density are compressed, the bulkiness is not restored, and the compression restoration rate cannot be measured accurately. In order to accurately calculate the compression recovery rate, the glass fiber aggregate having a low density is temporarily compressed, and the bulkiness when the density is set to 20 kg / m ³ or more is defined as the bulkiness before compression.

Even if a core material formed by molding a glass fiber aggregate having the above characteristics is produced, the characteristics of the glass fiber are maintained. For this reason, the core material which shape | molded the said glass fiber assembly has a small ratio of what fractures | ruptures with the glass fiber in a core material, even when a big compressive force acts on the core material. The pressure of about 1 kg / cm ² is applied to the core material of the vacuum heat insulating material due to atmospheric pressure to increase the density. However, if the core material has the above characteristics, there are few fibers that break even when compressed by atmospheric pressure. A vacuum heat insulating material in which the heat conduction of the solid component is suppressed can be obtained.

  Therefore, the core material produced from the glass fiber aggregate having the above characteristics has a small percentage of fibers that are broken even when compression is repeated. That is, the compression strength is unlikely to be reduced by compression.

  Therefore, the value obtained by dividing the second compression strength by the first compression strength is increased. A value obtained by dividing the second compression strength by the first compression strength is defined as a compression strength ratio.

For example, when the core material is compressed so that the density becomes 350 kg / m ³ , the compression strength applied at 250 kg / m ³ is compressed again to 250 kg / m ³ after releasing the compression force. The compressive strength ratio is 35% or more.

Further, when the core material density relative to the compressive strength applied to at 250 kg / m ³ in the process of compressing so that 270 kg / m ^3, and compressed again become 250 kg / m ³ after opening the compressive force The compressive strength ratio is 80% or more. These are because the ratio of the glass fiber that breaks during the first compression is small, and the ratio of the fiber that contributes to the compressive strength is large during the second compression.

  According to a third aspect of the present invention, the glass fiber according to the first or second aspect of the present invention has a tensile elongation at break of 1% or more.

  When the thermal conductivity of a vacuum heat insulating material produced from glass fiber aggregates having various tensile breaking elongations is measured, when the tensile breaking elongation is less than 1%, the thermal conductivity of the vacuum insulating material is equal to the tensile breaking elongation. However, when the tensile elongation at break becomes 1% or more, the thermal conductivity decreases as the tensile elongation at break increases. From this, when the tensile elongation at break exceeds 1%, the heat transfer by the glass fiber inside the core material decreases, and the cause is estimated as follows.

  Since the fibers are intertwined in a complicated manner inside the core material, even when the core material is compressed with a uniform pressure, the way in which the force is applied to each fiber is different. For example, there are fibers that are mainly subjected to tensile force, fibers that are mainly subjected to compressive force, and fibers that are mainly subjected to bending force, and most of the fibers that break are due to tensile force. Further, the magnitude of the tensile force applied varies depending on each fiber, and the fiber exceeding the tensile elongation at break breaks due to the tensile force. If the tensile elongation at break of the fiber is 1% or more, most of the fibers are in the elastic deformation region, so that the proportion of the fibers that break is small. Since the ratio of the breaking fiber is small, heat transfer due to contact between the broken portion of the fiber and another fiber is suppressed.

  Accordingly, it is possible to obtain a vacuum heat insulating material in which the heat conduction of the solid component is kept low.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the present embodiment.

(Embodiment 1)
FIG. 1 is a cross-sectional view of the vacuum heat insulating material in the first embodiment. FIG. 2 is a cross-sectional view of a core material used for the vacuum heat insulating material in the same embodiment. FIG. 3 is a cross-sectional view showing a state after vacuum packaging of the concentric material.

  The vacuum heat insulating material 3 includes a core material 4, a jacket material 5, and an adsorbent 6. The core material 4 in which the adsorbent 6 is embedded is covered with a jacket material 5 made of a laminate film, and the inside of the jacket material 5 is decompressed. And sealed.

  The core material 4 includes a plurality of glass fibers 2a in which the fiber length direction is perpendicular to the heat transfer direction and substantially parallel to the cross section of the core material 4, and the fiber length direction is perpendicular to the heat transfer direction and the core material. A plurality of glass fibers 2b arranged substantially perpendicularly to the four cross sections are laminated alternately in the heat transfer direction, and the glass fibers 2a and 2b are formed into a plate shape.

  The jacket material 5 is a laminate film configured using linear low-density polyethylene as a sealant layer, aluminum as a metal foil, and nylon as an outermost layer. The adsorbent 6 is calcium oxide.

  The glass fibers 2a and 2b constituting the core material 4 are glass fibers having increased tensile elongation at break. The glass fibers 2a and 2b are produced by being discharged from a fiberizing apparatus that rotates at high speed in a molten state and stretched by a high-speed air flow. The lower the temperature of the air stream that stretches the melted fiber, the higher the tensile elongation at break due to the quenching effect of the glass fiber due to quenching. A core material 4 was produced by using a collection of the glass fibers 2a and 2b as raw cotton. In the present embodiment, the temperature of the air flow that stretches the glass fibers 2a and 2b is set to -20 ° C.

After the 100 mm bulk raw cotton produced by the above method was compressed at 20 kPa for 1 minute, the bulk after 24 hours was 75 mm, and the compression recovery rate was 75%. The density of the raw cotton before compression was 22 kg / m ³ . The high restoration rate of the compressed raw cotton is because there are many fibers that are not broken by compression.

  The core material 4 was formed and formed by compressing raw cotton while heating. The core material thus produced was inserted into the jacket material 5 which was made in advance by a three-side seal, and then the pressure was reduced to 13 Pa, followed by sealing, whereby the vacuum heat insulating material 3 was produced. About the vacuum heat insulating material comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  As shown in FIG. 3, the glass fiber 2 a facing the substantially horizontal section is in contact only through the glass fiber 2 b facing the substantially vertical section.

  Since the atmospheric pressure is applied to the jacket material, the core material 4 receives a compressive force from the jacket material. Since the point at which the glass fibers 2 are in contact with each other is pressed by the compressive force, the glass fiber 2 is fixed by the frictional force of the glass.

  Accordingly, when a force is applied in the direction in which the plurality of contacts are separated from each other in one glass fiber 2a, 2b, a tensile stress is applied to the glass fibers 2a, 2b. When the tensile breaking elongation of the glass fibers 2a and 2b is small, the glass fibers 2a and 2b are broken only when the contact points are slightly separated from each other. When the glass fibers 2a and 2b are broken, the broken portion becomes a free end. As a result, the heat conduction of the solid component increases due to the broken portion coming into contact with the other glass fibers 2a and 2b.

  Since the contact methods between the glass fibers 2a and 2b in the core material 4 are diverse, even when the same pressure is applied to the entire core material 4, the distance between the points where the fibers are fixed. The degree of change is diverse. If the tensile elongation at break of the glass fibers 2a and 2b is 1% or more, even if atmospheric pressure is applied, most of the fibers are not broken and an increase in heat conduction of the solid component can be suppressed.

  It was 0.0015 W / mK when the heat conductivity of the vacuum heat insulating material in this Embodiment was measured.

  The tensile breaking elongation of the glass fibers 2a and 2b of the raw cotton in the present embodiment was 1.5%. Further, the tensile breaking elongation of the glass fibers 2a and 2b as the core material is 1.4%, and it can be seen that the influence on the tensile breaking elongation by heating is small. The tensile elongation at break was calculated by applying a tensile force with the glass fibers 2a and 2b separated by 20mm and fixing at two points, and dividing the length increased until the break by 20mm. Since the tensile elongation at break was highly variable, the average value of those measured 100 times was used.

(Embodiment 2)
FIG. 4 is a cross-sectional view of the core material in the second embodiment.

  The glass fibers 2a and 2b are obtained by increasing the breaking limit by ion exchange. When ion exchange is performed, a compressive force is applied to the surface of the glass fiber, so that it is difficult to break when the outside of the bend is stretched. A vacuum heat insulating material was produced using this glass fiber.

The heat conductivity of this vacuum heat insulating material was 0.0015 W / mK. The vacuum heat insulating material was disassembled and a core material compression test was performed. Once the process of compressing such that the density is 350 kg / m ^3, the compressive strength when the density is 250 kg / m ^3, a 89KPa, compressed so again 250 kg / m ³ after opening the compressive force The compressive strength required to achieve this was 33 kPa, and the compressive strength ratio was 37.1%.

Also, once in the course of compression such that the density is 270 kg / m ^3, compression strength when the density is 250 kg / m ³ is 90 kPa, so that again a 250 kg / m ³ after opening the compressive force The compression strength required for compression was 74 kPa, and the compression strength ratio was 82.2%. Since it is difficult to make the density before compression in each part of the raw cotton uniform, the compressive force varies. For this reason, let the average value of what was measured 10 times be compression force.

  When compression is repeated, the reason why the required reduction in compression strength is small is that there are few fibers that break due to compression. When the number of fibers that breaks due to compression is small, an increase in the heat conduction of the solid component due to the broken portion coming into contact with other fibers is suppressed. Therefore, excellent heat insulation performance can be obtained.

  A method for producing a vacuum heat insulating material, such as a method for producing a core material from raw cotton, a bag making method for an outer covering material, and a method for measuring each physical property are the same as those in the first embodiment.

  In the present invention, the strain limit of breakage indicates the magnitude of strain until the glass fiber breaks due to the applied force. For example, in the tensile test, the length that is extended until the fracture occurs is divided by the initial length. The same applies to other tests such as bending.

  In the present invention, quenching by quenching and strengthening by ion exchange are performed as means for increasing the strain limit of breakage of glass fiber, but means for increasing the strain limit of breakage is not limited to these, If physical properties are obtained, excellent thermal conductivity can be obtained.

  In the calculation of the compression recovery rate, the bulkiness after compressing the raw cotton is a value measured after 24 hours have elapsed after compression.

  The compression test of the core material is performed at a compression speed of 5 mm / min, and the compression strength when the core material reaches a predetermined density is defined as the compression strength at each density.

  Example 1 to Example 4 show the results obtained by examining the temperature of the air flow extending from the fiberizing apparatus and extending the glass fiber in the molten state in the first embodiment. In each Example, a core material formed into a plate shape while heating raw cotton obtained by collecting glass fibers was covered with a jacket material, and the inside was sealed after decompression to prepare a vacuum heat insulating material. Example 5 shows the results of investigation by reinforcing the fiber by ion exchange in the second embodiment. The method for producing the vacuum heat insulating material is the same as in Examples 1 to 4.

(Example 1)
When the air flow for stretching the fibers was 90 ° C., the thermal conductivity of the vacuum heat insulating material was 0.0018 W / mK. The tensile elongation at break of the core fiber was 1.1%. Compressive strength ratio in 250 kg / m ³ when compressed to 350 kg / m ³ was 35.5%. Compressive strength ratio in 250 kg / m ³ when compressed to 270 kg / m ³ was 80.1%. Vacuum insulation that has excellent heat insulation performance because the fiber in the core material is not easily broken because the tensile breaking elongation of the fiber of the core material and the compression strength ratio of the core material are large, and the contact between the broken part and other fibers is suppressed. A material was obtained.

(Example 2)
When the air flow for stretching the fibers was 70 ° C., the thermal conductivity of the vacuum heat insulating material was 0.0018 W / mK. The fiber tensile elongation at break of the core material was 1.2%. Compressive strength ratio in 250 kg / m ³ when compressed to 350 kg / m ³ was 36.0%. Compressive strength ratio in 250 kg / m ³ when compressed to 270 kg / m ³ was 80.7%. Vacuum insulation that has excellent heat insulation performance because the fiber in the core material is not easily broken because the tensile breaking elongation of the fiber of the core material and the compression strength ratio of the core material are large, and the contact between the broken part and other fibers is suppressed. A material was obtained.

Example 3
When the air flow for stretching the fiber was 50 ° C., the thermal conductivity of the vacuum heat insulating material was 0.0016 W / mK. The fiber tensile breaking elongation of the core material was 1.3%. Compressive strength ratio in 250 kg / m ³ when compressed to 350 kg / m ³ was 36.8%. Compressive strength ratio in 250 kg / m ³ when compressed to 270 kg / m ³ was 80.9%. Vacuum insulation that has excellent heat insulation performance because the fiber in the core material is not easily broken because the tensile breaking elongation of the fiber of the core material and the compression strength ratio of the core material are large, and the contact between the broken part and other fibers is suppressed. A material was obtained.

Example 4
When the air flow for stretching the fibers was −20 ° C., the thermal conductivity of the vacuum heat insulating material was 0.0015 W / mK. The fiber tensile breaking elongation of the core material was 1.4%. Compressive strength ratio in 250 kg / m ³ when compressed to 350 kg / m ³ was 37.0%. Compressive strength ratio in 250 kg / m ³ when compressed to 270 kg / m ³ was 82.4%. Vacuum insulation that has excellent heat insulation performance because the fiber in the core material is not easily broken because the tensile breaking elongation of the fiber of the core material and the compression strength ratio of the core material are large, and the contact between the broken part and other fibers is suppressed. A material was obtained.

(Example 5)
When the strain limit of breakage of the glass fiber was reinforced by ion exchange, the thermal conductivity of the vacuum heat insulating material was 0.0015 W / mK. The fiber tensile breaking elongation of the core material was 1.4%. Compressive strength ratio in 250 kg / m ³ when compressed to 350 kg / m ³ was 37.1%. Compressive strength ratio in 250 kg / m ³ when compressed to 270 kg / m ³ was 82.2%. Vacuum insulation that has excellent heat insulation performance because the fiber in the core material is not easily broken because the tensile breaking elongation of the fiber of the core material and the compression strength ratio of the core material are large, and the contact between the broken part and other fibers is suppressed. A material was obtained.

  Table 1 shows the relationship between the thermal conductivity of the vacuum heat insulating material using the glass fiber reinforced under each condition as a constituent element of the core material, and the physical properties of the fiber and the core material.

急冷を行う条件を変えて作製したガラス繊維を芯材に用いた真空断熱材の熱伝導率測定結果と、芯材とガラス繊維の物性を説明する。

The thermal conductivity measurement result of the vacuum heat insulating material using the glass fiber produced by changing the conditions for rapid cooling as the core material, and the physical properties of the core material and the glass fiber will be described.

(Comparative Example 1)
When the air flow for stretching the fibers was 200 ° C., the thermal conductivity of the vacuum heat insulating material was 0.0020 W / mK. The tensile elongation at break of the core fiber was 0.8%. Compressive strength ratio in 250 kg / m ³ when compressed to 350 kg / m ³ was 33.3%. Compressive strength ratio in 250 kg / m ³ when compressed to 270 kg / m ³ was 78.8%. Since the temperature of the air flow that stretches the fiber is high, a sufficient quenching effect cannot be obtained, the tensile fracture elongation of the core fiber and the compressive strength ratio of the core material are not sufficient, the fiber breaks, the fracture part and others The thermal conductivity is increased by the contact of the fibers.

(Comparative Example 2)
When the air flow for stretching the fibers was 150 ° C., the thermal conductivity of the vacuum heat insulating material was 0.0020 W / mK. The tensile elongation at break of the core fiber was 0.8%. Compressive strength ratio in 250 kg / m ³ when compressed to 350 kg / m ³ was 33.7%. Compressive strength ratio in 250 kg / m ³ when compressed to 270 kg / m ³ was 79.3%. Since the temperature of the air flow that stretches the fiber is high, a sufficient quenching effect cannot be obtained, the tensile fracture elongation of the core fiber and the compressive strength ratio of the core material are not sufficient, the fiber breaks, the fracture part and others The thermal conductivity is increased by the contact of the fibers.

(Comparative Example 3)
When the air flow for stretching the fibers was 100 ° C., the thermal conductivity of the vacuum heat insulating material was 0.0020 W / mK. The tensile elongation at break of the core fiber was 0.8%. Compressive strength ratio in 250 kg / m ³ when compressed to 350 kg / m ³ was 34.7%. Compressive strength ratio in 250 kg / m ³ when compressed to 270 kg / m ³ was 79.5%. Since the temperature of the air flow that stretches the fiber is high, a sufficient quenching effect cannot be obtained, the tensile fracture elongation of the core fiber and the compressive strength ratio of the core material are not sufficient, the fiber breaks, the fracture part and others The thermal conductivity is increased by the contact of the fibers.

  Table 2 shows the relationship between the properties of glass fibers and thermal conductivity under each condition.

(表１)と（表２）に示しているように、冷却を行う空気の温度が低くなるに従って引張り破断伸度が大きくなっており、熱伝導率は小さくなっていることが判る。ここで、引張り破断伸度が１％以上になると真空断熱材の熱伝導率が低減することがわかる。また、３５０ｋｇ／ｍ³まで圧縮した場合の２５０ｋｇ／ｍ³における圧縮強度比が３５％以上、２７０ｋｇ／ｍ³まで圧縮した場合の２５０ｋｇ／ｍ³における圧縮強度比は８０％以上になると熱伝導率が低減することが判る。

As shown in (Table 1) and (Table 2), it can be understood that the tensile elongation at break increases as the temperature of the cooling air decreases, and the thermal conductivity decreases. Here, it can be seen that the thermal conductivity of the vacuum heat insulating material is reduced when the tensile elongation at break is 1% or more. Further, 350 kg / m ³ compression strength ratio in 250 kg / m ³ when compressed to 35% or more, the compressive strength ratio in 250 kg / m ³ when compressed to 270 kg / m ³ comes to 80% or more thermal conductivity Is found to be reduced.

  The same thermal conductivity is obtained both when the temperature of the air flow for stretching the fibers is set to -20 ° C and when ion exchange is performed. In addition, the tensile elongation at break of the glass fiber and the compressive strength ratio of the core material are the same, and if the physical properties of the glass fiber or the core material are obtained, it can be seen that it is not due to means for improving the strain limit of the glass fiber strain. .

  When the tensile elongation at break of the glass fiber is increased, the ratio of fracture when the core material is compressed by atmospheric pressure is reduced, the contact of the fractured part with other glass fibers is suppressed, and the heat conduction of the solid component is reduced. Can be suppressed.

  Moreover, the core material using the glass fiber which has been subjected to rapid cooling or ion exchange has a reduced compression strength reduction rate required for repeated compression to the same density. That is, the compressive strength ratio is increased. This is because glass that has been subjected to rapid cooling or ion exchange has a small proportion of fibers that break even when compressed, and therefore has a large proportion of fibers that contribute to compressive strength even after repeated compression. Therefore, in the core material having a large compressive strength ratio, the broken portion is prevented from coming into contact with other glass fibers, and the heat conduction of the solid component can be kept low. As a result, the thermal conductivity decreases as the compressive strength ratio of the core increases.

  From the above results, it can be seen that when the strain limit of the breakage of the glass fiber is increased, an increase in the heat conduction of the solid component due to the contact between the breakage part and other fibers is suppressed, and an excellent heat insulation performance is obtained.

  As mentioned above, since the vacuum heat insulating material concerning this invention has the outstanding heat insulation performance, high heat insulation performance is obtained by thinner thickness. Therefore, in addition to uses such as a refrigerator and a cooler box, the present invention can be applied to uses such as a liquid crystal projector, a copy machine, and a notebook computer that require high heat insulation performance in a narrow space.

Sectional drawing of the vacuum heat insulating material in Embodiment 1 of this invention Sectional drawing of the core material of the vacuum heat insulating material in Embodiment 1 of this invention Sectional drawing of the core material after vacuum packaging of the vacuum heat insulating material in Embodiment 1 of this invention Sectional drawing of the core material of the vacuum heat insulating material in Embodiment 2 of this invention Cross-sectional view of a conventional vacuum insulation core

Explanation of symbols

2a, 2b Glass fiber 3 Vacuum heat insulating material 4 Core material 5 Jacket material

Claims (3)

  The core material is covered with a cover film made of a laminate film, and the inside of the cover material is sealed under reduced pressure, and the core material breaks even if it is deformed by an external force by increasing the strain limit of breakage. The glass fiber having the characteristic that it is difficult to perform is laminated in layers so that the length direction of the glass fiber is substantially perpendicular to the heat transfer direction and the glass fibers adjacent to each other in the heat transfer direction intersect each other. Vacuum insulation material.   The vacuum heat insulating material according to claim 1, wherein the core material is a glass fiber aggregate having a compression recovery rate of 70% or more.   The vacuum heat insulating material according to claim 1 or 2, wherein the glass fiber has a tensile elongation at break of 1% or more.

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