JP5093129B2 - Vacuum heat insulating material, manufacturing apparatus and manufacturing method thereof - Google Patents

Description

  The present invention relates to a vacuum heat insulating material, a manufacturing apparatus and a manufacturing method thereof.

  In the conventional vacuum heat insulating material, since the internal space is already held, the decompression space is easily subdivided, and the bending and torsional rigidity is higher than that of ordinary yarn of the same thickness. Use hollow fiber for the reason that it can be maintained and retained, or the adhesion and contact between yarns is reduced, the space is easily subdivided and the rigidity is improved, so the space is stably maintained. For the reason that it can be held, for example, a modified cross-section yarn having a cross section of T-type, Y-type, three-leaf type, four-leaf type or five-leaf type is used as the material of the fiber structure (for example, patent Reference 1).

JP 2002-58604 A (4th tribute)

  In a conventional fiber structure using irregular cross-section yarns, if the yarns are stacked while crossing each other to form a fiber structure, the adhesion and contact between the yarns is reduced, but the yarns face the same direction. If the fiber structure is formed by laminating each other in a state, the uneven portions of the irregularly shaped cross section yarns are bitten and the contact area becomes rather large, and there is a drawback that sufficient heat insulating performance cannot be obtained. In addition, the ratio of facing the same direction as the ratio of crossing is not constant, and there is a drawback that the heat insulation performance is greatly influenced by these ratios.

  Further, in a fiber structure using hollow fibers, the strength of the fibers themselves is weakened, so that the contact strain at the portion where the fibers are in contact with each other under vacuum pressure is large, and conversely, the contact surface area is large. As a result, solid heat conduction from the inter-fiber contact portion is increased, and there is a drawback that sufficient heat insulation performance cannot be obtained.

  The present invention has been made to solve the above-described problems, and even when yarns are laminated in any direction to form a fiber structure, An object of the present invention is to obtain a vacuum heat insulating material having a substantially constant heat insulating performance as well as being able to reduce the adhesion and contact portion between them and obtain a higher performance vacuum heat insulating material.

  The vacuum heat insulating material according to the present invention is a vacuum heat insulating material comprising a fiber sheet, a core material in which a plurality of the fiber sheets are laminated, and a jacket material that covers the core material in a vacuum-sealing manner. The sheet is formed by mixing at least one kind of irregularly-shaped cross-section fibers having a plurality of protruding shapes and circular cross-section fibers having a substantially circular cross section.

  In the vacuum heat insulating material according to the present invention, since the fiber sheet is composed of the irregular cross-section fiber and the circular cross-section fiber, the fiber sheets are formed by stacking the yarns in any direction. Even in this case, the fibers hardly come into contact with each other on the surface, resulting in point or line contact. For this reason, contact heat conduction between fibers can be suppressed, the heat insulating performance of the vacuum heat insulating material can be improved, and a vacuum heat insulating material with a substantially constant heat insulating performance can be obtained.

It is sectional drawing which showed typically the structure of the vacuum heat insulating material in Embodiment 1 of this invention. It is sectional drawing which showed typically a set of fiber which comprises the fiber sheet of the vacuum heat insulating material in Embodiment 1 of this invention. It is sectional drawing which showed typically the irregular cross-section fiber which has the some protrusion shape which comprises the fiber sheet of the vacuum heat insulating material in Embodiment 1 of this invention. It is the characteristic figure which showed the result of having simulated the relationship between the fiber diameter of a circular cross-section fiber, and thermal conductivity, and the relationship between the protrusion diameter of a modified cross-section fiber, and thermal conductivity. It is sectional drawing which showed typically the fiber at the time of comprising a fiber sheet only with the 3 processus | protrusion deformed cross-section fiber in the conventional invention. It is the figure which showed nozzle arrangement | positioning of the die for melt spinning used for manufacture of the fiber sheet which concerns on this Embodiment 1. FIG. It is sectional drawing which showed typically a set of fiber which comprises the fiber sheet of the vacuum heat insulating material by Embodiment 2 of this invention. It is sectional drawing which showed typically a set of fiber which comprises the fiber sheet of the vacuum heat insulating material by Embodiment 3 of this invention.

Embodiment 1 FIG.
1 is a cross-sectional view schematically showing the structure of a vacuum heat insulating material according to Embodiment 1 of the present invention. In FIG. 1, the vacuum heat insulating material in the first embodiment is formed by laminating a fiber sheet 3 composed of a modified cross-section fiber having a plurality of protrusion shapes and a circular cross-section fiber having a substantially circular cross section, and the fiber sheet 3. It has a core material 4 configured and a jacket material 5 that covers and seals the core material 4.

  FIG. 2 is a cross-sectional view schematically showing a set of fibers constituting the fiber sheet of the vacuum heat insulating material according to Embodiment 1 of the present invention. In FIG. 2, a modified cross-section fiber 1 having a plurality of projections 11 on the outer periphery of a circular portion 10 (for example, the modified cross-section fiber 1 shown here has six projections 11 having six projections 11. The irregular cross-section fibers 6) and the circular cross-section fibers 2 having a substantially circular cross section are rarely in contact with each other on the surface, and are mixed in a state where they are in contact with each other by dots or lines.

  FIG. 3 is a cross-sectional view schematically showing a modified cross-section fiber having a plurality of protrusion shapes constituting the fiber sheet of the vacuum heat insulating material according to Embodiment 1 of the present invention. In FIG. 3, the modified cross-section fiber 1 of the first embodiment (for example, the modified cross-section fiber 1 shown here is a five-protrusion modified cross-section fiber 12 having five protrusions 11) has a protrusion height. The projection 11 is composed of hk7, a projection tip width dk8, and a circular portion 10 having a reference circle diameter ds9.

  Next, the manufacturing method of the vacuum heat insulating material in this Embodiment 1 is demonstrated. First, a method for producing the fiber sheet 3 will be described. For example, pellets of polyethylene terephthalate resin (hereinafter referred to as PET resin) are dissolved while being heated to the melting point, and the obtained liquid (or gel) PET resin is sent out by a gear pump. The liquid PET resin is discharged from a plurality of nozzles and cooled to form a spinning. The spun yarn thus formed is further drawn to a diameter of about 10 μm by a spunbond method or a melt blow method to obtain a fiber. The drawn fibers are discharged onto a conveyor to form a sheet. In the subsequent stage of this conveyor, using a roll that is flat or embossed as necessary, the fibers are partially heat-sealed to increase the tensile strength of the fibers and to suppress the fluffing of the fibers on the surface of the sheet. Thereby, roll winding and roll rewinding of the sheet can be facilitated.

  Next, a fiber sheet 3 is obtained by drawing out a sheet of a necessary size from the rolled sheet (hereinafter referred to as a sheet roll) and cutting the sheet. A plurality of fiber sheets 3 are stacked to obtain a core material 4. After that, the core material 4 is covered with two or one outer cover materials 5 and placed in a vacuum chamber to reduce the pressure so that the space covered with the outer cover material 5 is in a vacuum state. The outer periphery of the jacket material 5 is sealed in a state where the space covered with the jacket material 5 is at a predetermined pressure, for example, a vacuum pressure of about 0.1 to 3 Pa, and the pressure in the vacuum chamber is at atmospheric pressure. Return to. As described above, the vacuum heat insulating material in Embodiment 1 of the present invention is completed. The internal space of the vacuum heat insulating material is maintained in a vacuum state, and the jacket material 5 and the core material 4 receive a compressive force due to a pressure difference with the outside.

  In addition, when it is assumed that gas is generated from the core material 4 or the jacket material 5 or the like by being placed under a long-term vacuum, when gas is mixed from the outside, or when moisture is mixed, An appropriate gas adsorbent may be inserted into the space covered with the jacket material 5 as necessary.

  In addition, about the water | moisture content contained in the fiber sheet 3, you may provide the process of decompressing, heating the fiber sheet 3 before and behind cutting, etc., and you may remove this water | moisture content. In addition, a mechanism for heating the inside of the vacuum chamber is provided in a state where the core material 4 covered with the jacket material 5 is decompressed in the vacuum chamber, and the fiber sheet 3 is subjected to a thermal load such as thermal contraction or thermal decomposition. The moisture of the fiber sheet 3 may be removed under appropriate conditions, such as by setting the pressure at a temperature that does not apply and a pressure that does not induce vacuum discharge.

  Here, in the vacuum heat insulating material of the first embodiment, a vacuum heat insulating material having a fiber sheet 3 composed of a modified cross-section fiber 1 having a plurality of protrusions and a circular cross-section fiber 2 having a substantially circular cross section as a core material 4. The smaller the respective fiber diameters of the irregular cross-section fiber 1 and the circular cross-section fiber 2, the smaller the contact area between the fibers and the fibers, and the greater the contact thermal resistance. As a result, solid heat conduction is reduced and performance is improved. However, when the fiber sheet 3 is manufactured from a resin material by the melt spinning method, it is necessary to increase the fiber diameter to some extent in order to continuously manufacture the circular cross-section fiber 2 without breaking the yarn. For example, when a fiber sheet 3 using a circular cross-section fiber 2 was manufactured by a spunbond melt spinning method using a pellet material of PET resin, continuous production was possible up to a fiber diameter of about 10 μm. If it was less than that, thread breakage occurred and stable production could not be achieved.

  Based on the above, the relationship between the fiber diameter of the circular cross-section fiber 2 and the thermal conductivity and the relationship between the projection diameter of the irregular cross-section fiber 1 and the thermal conductivity were simulated. Here, assuming that a modified cross-section fiber 1 having three protrusions that are Y-shaped as a modified cross-section fiber 1, this is ideally in contact with the circular cross-section fiber 2, that is, laminated so that the fibers cross each other. It is assumed that it is in a state. FIG. 4 is a characteristic diagram showing the simulation result. In FIG. 4, the thermal conductivity is calculated by calculating the thermal conductivity in the thickness direction of the vacuum heat insulating material, and the vertical axis indicates the thermal conductivity of the vacuum heat insulating material when the fiber diameter of the circular cross-section fiber 2 is φ10 μm. As a reference value, the difference in thermal conductivity from the reference value was taken. Further, the irregular cross-section fiber 1 is assumed to have a shape in which a fiber diameter is a reference circle diameter ds9, a circular portion 10 having a reference circle diameter ds9, and a protrusion portion 11 having a protrusion height hk7 and a protrusion tip width dk8 are combined. .

  As is clear from this result, it can be expected that the thermal conductivity is lowered by reducing the fiber diameter of the circular cross-section fiber 2, but even if the fiber diameter of the circular cross-section fiber 2 cannot be reduced in production, the tip of the protrusion By forming the core material 4 in combination with the modified cross-section fiber 1 having a reduced width dk8, it is configured with a geometric shape so that the circular cross-section fiber does not enter the recess of the modified cross-section fiber, and is expected to lower the thermal conductivity. I understand that I can do it. On the other hand, it has been found that if the protrusion tip width dk8 is made too small, the strain increases due to the stress concentration on the protrusion 11 and as a result, the contact area increases, and the effect is annihilated. Therefore, it is desirable that the protrusion tip width dk8 be in the range of about 3 μm to about 8 μm.

  In addition, in order to clarify the difference in effect from the conventional example, the fiber sheet 3 was produced using only the three-protrusion deformed cross-section fibers 13 in the conventional invention, and the heat insulation performance was evaluated. FIG. 5 is a cross-sectional view schematically showing a fiber in the case where the fiber sheet 3 is configured by only the three-protrusion deformed cross-section fiber 13 in the conventional invention. The three-protrusion irregular cross-section fiber 13 in FIG. 5 is made of PET resin pellets, and a fiber sheet 3 using only the three-protrusion irregular cross-section fiber 13 is manufactured by a spunbond melt spinning method, and 25 sheets of these are laminated. A core material 4 was produced. The core material 4 is inserted into an aluminum laminate sheet (nylon 15 μm + polyethylene terephthalate 12 μm + aluminum sheet 6 μm + polyethylene 50 μm) with an adsorbent, and the pressure is reduced to about 1 Pa in a vacuum chamber. The part was sealed by heat sealing to produce a vacuum heat insulating material.

  Here, the adsorbent retains the degree of vacuum by adsorbing moisture, external gas, or outgas generated from the core material 4 entering the interior through defects such as the seal part of the outer cover material 5 or the aluminum laminate sheet itself. For example, a CaO system, an activated carbon system, a zeolite system, and a mixture of Li and Ba may be used.

  As a result of measuring the thermal conductivity of the vacuum heat insulating material manufactured according to this conventional example, the value was equal to or higher by several points than when the fiber sheet 3 was composed of only the circular cross-section fibers 2 having a fiber diameter of about φ10 μm. In order to investigate this cause, the cross section of the core material 4 simulating a vacuum state was observed. As a result, the reference circle diameter ds9 was about 10 μm, and the protrusion tip width dk8 was about 4 μm. Although explanation is omitted, even when manufacturing with a design target set, the material expands and contracts due to the stretching process using the spunbond method and the core drying process. However, with regard to the arrangement of the fibers, the three-protrusion modified cross-section fibers 13 adjacent to the recesses 14 between the protrusions 11 of the three-protrusion modified cross-section fibers 13 are shown in FIG. Many protrusions 11 were engaged with each other, and a large number of locations where the contact portions 15 of the fibers were in wide contact with each other were observed. That is, when the fiber sheet 3 is produced with the configuration of only the three-protrusion deformed cross-section fibers 13, not only the expected performance may not be obtained, but also there may be a large variation in performance. Easily recalled.

  The method of observing the cross section of the core material 4 by simulating the vacuum state is to compress the vacuum heat insulating material before being put in the vacuum chamber from both sides with a pressure equivalent to 1 atm, and solidify this with a resin and then cross section. Is observed with an electron microscope or the like.

  As is clear from the results of FIG. 4, the heat insulation performance improves as the fiber diameter is smaller, that is, the fiber cross-sectional area is smaller. Therefore, if the reference circle diameter ds9 is the same diameter, it can be easily predicted that the heat insulation performance is further improved when the projection height hk7 is smaller. Therefore, in consideration of the influence of the protrusion tip width dk8, conditions were examined so as to obtain a geometric shape in which the circular cross-section fiber 2 does not enter the recesses 14 between the protrusions 11 of the irregular cross-section fiber 1. As a result, the 6-protrusion modified cross-section fiber 6 combined with the circular cross-section fiber 2 having a fiber diameter of 10 μm is circular in the recess of the irregular cross-section fiber when the reference circle diameter ds9 is 10 μm and the protrusion height hk7 is 2.5 μm, for example. It has been found that a relatively good characteristic can be obtained with a geometrical shape that does not allow cross-sectional fibers to enter.

  On the other hand, the case where the circular cross-section fiber 2 is a hollow fiber was also examined separately, but as a result of the hollow fiber being compressed and deformed by the pressure from the atmosphere in a vacuum environment and the contact area increased, the effect of reducing the thermal conductivity is hardly obtained. It has been found.

  Here, in order to make a prototype of the fiber sheet 3 according to Embodiment 1, a melt spinning die 15 was produced. FIG. 6 is a view showing the nozzle arrangement of the melt spinning die 15 used for manufacturing the fiber sheet according to the first embodiment. In FIG. 6, a circular cross-section nozzle that is a nozzle corresponding to the cross-section fiber 1 and a cross-section nozzle 16 that is a nozzle corresponding to the cross-section fiber 1, so that adjacent fibers are the cross-section fiber 1 and the circular cross-section fiber 2. The 17 nozzles are arranged alternately so that every other nozzle has the same shape.

  Using the melt spinning die 15 shown in FIG. 6, a fiber sheet 3 was produced in the same procedure as the trial production procedure of the three-protrusion modified cross-section fiber 13. As a result, a circular cross-section fiber 2 having a fiber diameter of 10 μm, six protrusions having six protrusions 11 having a reference circle diameter ds9 of approximately 8 μm, a protrusion tip width dk8 of approximately 4 μm, and a protrusion height hk7 of approximately 2.5 μm. A fiber sheet 3 having a thickness of about 0.5 mm was produced with the modified cross-section fibers 6. The core material 4 was produced by laminating 25 sheets. The core material 4 is inserted into an aluminum laminate sheet (nylon 15 μm + polyethylene terephthalate 12 μm + aluminum sheet 6 μm + polyethylene 50 μm) with an adsorbent, and the pressure is reduced to about 1 Pa in a vacuum chamber. The part was sealed by heat sealing to produce a vacuum heat insulating material.

  As a result of measuring the thermal conductivity of the vacuum heat insulating material thus manufactured, the vacuum heat insulating material using a conventional fiber sheet as a core material has a thermal conductivity of about 0.0018 W / (m · K). On the other hand, the vacuum heat insulating material according to Embodiment 1 using the melt spinning die 15 shown in FIG. 6 has a thermal conductivity of about 0.0015 W / (m · K), and the heat insulating effect is improved by about 20%. . Moreover, when the cross section of the fiber sheet 3 was observed, the surface contact and meshing | engagement of protrusions in each fiber contact part were hardly seen. Therefore, the vacuum heat insulating material in this invention can obtain a higher heat insulation effect by reducing the contact area where fibers overlap and lowering the thermal conductivity.

  Similarly, a six-protrusion modified cross-section fiber 6 having six protrusions 11 as the irregular cross-section fiber 1 has a reference circle diameter ds9 of about 8 μm, a protrusion tip width dk8 of about 3 μm, and a protrusion height hk7 of about 2 μm. When the fiber sheet 3 was prototyped as described above, the thermal conductivity increased by about 30%, that is, the heat insulating effect was deteriorated by about 30%. As a result of cross-sectional observation, it was confirmed that this was because the circular height was in contact with the recess 14 between the protrusions 11 because the protrusion height hk7 was low. Therefore, it is desirable that the 6-protrusion modified cross-section fiber 6 has a protrusion height of 2 μm or more.

  In FIG. 6, the nozzles of the modified cross-section nozzle 16 and the circular cross-section nozzle 17 are arranged so that the nozzles are arranged in the same shape every other nozzle, but this arrangement is not particularly required. When such mutual arrangement is taken, there is a high probability that adjacent fibers in the manufactured fiber sheet 3 will be the irregular cross-section fiber 1 and the circular cross-section fiber 2, and it is easy to manufacture the fiber sheet 3 having good characteristics. I can imagine. However, when such mutual arrangement is not used, for example, even when the irregular cross-section nozzle 16 and the circular cross-section nozzle 17 are randomly arranged, it is obvious that the effect of improving the heat insulating characteristics of the fiber sheet 3 can be achieved. .

  FIG. 6 shows the case where the numbers of the modified sectional nozzles 16 and the circular sectional nozzles 17 are substantially the same. However, depending on the manufacturing conditions, the numbers of the modified sectional nozzles 16 and the circular sectional nozzles 17 may be different. It may be better to take the arrangement. As such an arrangement, for example, a case where a circular cross-section nozzle 17 that is easy to process is arranged in the peripheral portion and arranged so as to be mutually arranged in the central portion can be considered.

  Further, FIG. 6 shows a single type of nozzle having the same cross-sectional shape with respect to the modified cross-section nozzle 16, but a plurality of different cross-section nozzles 16 having different cross-sectional shapes may be combined depending on the manufacturing conditions to further form a circular cross section. A combination of the nozzle 17 and the fiber sheet 3 with better characteristics can be considered.

  In addition, there is a possibility that the fiber sheet 3 having better characteristics can be obtained by combining only a plurality of types of irregular cross-section nozzles 16 having different cross-sectional shapes depending on the manufacturing conditions. As described when the fiber sheet 3 is produced only with the three-protrusion modified cross-section fibers 13 in the invention, the protrusions 11 of the other modified cross-section fibers 1 mesh with the recesses 14 between the protrusions 11 of the deformed cross-section fibers 1, The standard circular diameter ds9 is used for the modified cross-section fibers 1 having different cross-sectional shapes to be combined so that many contact portions 15 of the fibers are widely in surface contact and good characteristics cannot be obtained. Therefore, it is necessary to sufficiently examine the protrusion tip width dk8 and the protrusion height hk7.

  As described above, the nozzle arrangement of the fiber sheet melt spinning die 15 according to the first embodiment shown in FIG. 6 is an example, and the present invention is not limited to this. If the arrangement conditions such that adjacent nozzle shapes are different are satisfied, it is easy to obtain better characteristics under general manufacturing conditions, but even if not all nozzle arrangements satisfy this arrangement condition, the manufacturing conditions Depending on the case, a better effect can be easily assumed. That is, it is obvious that the fiber sheet according to the first embodiment of the present invention can be obtained by satisfying this arrangement condition even with some nozzle arrangements.

Embodiment 2. FIG.
FIG. 7 is a cross-sectional view schematically showing a set of fibers constituting a fiber sheet of a vacuum heat insulating material according to Embodiment 2 of the present invention. In FIG. 7, the fiber sheet 3 is configured such that a circular cross-section fiber 2 and a seven-protrusion modified cross-section fiber 18 having seven protrusions 11 as the irregular cross-section fiber 1 coexist.

  A fiber sheet 3 having a thickness of about 0.5 mm is formed using 7-protrusion deformed cross-section fibers 18 having a reference circle diameter ds9 of about 8 μm, a protrusion tip width dk8 of about 3 μm, and a protrusion height hk7 of about 2 μm. . Other configurations and the manufacturing method are the same as those of the first embodiment, and thus description thereof is omitted. The core material 4 was produced by laminating 25 sheets. The core material 4 is inserted into an aluminum laminate sheet (nylon 15 μm + polyethylene terephthalate 12 μm + aluminum sheet 6 μm + polyethylene 50 μm) with an adsorbent, and the pressure is reduced to about 1 Pa in a vacuum chamber. The part was sealed by heat sealing to produce a vacuum heat insulating material.

  As a result of measuring the thermal conductivity of the vacuum heat insulating material manufactured as described above, the vacuum heat insulating material according to the second embodiment of the present invention has a heat conductivity equal to that of the first embodiment 0.0015 W / (m · K). ) Degree was obtained. Moreover, when the cross section of the fiber sheet 3 was observed, the surface contact and meshing | engagement of the projection parts 11 in each fiber contact part were hardly seen. Therefore, the vacuum heat insulating material in the second embodiment of the present invention can obtain the same heat insulating effect as that in the first embodiment.

  Similarly, the modified cross-section fiber 1 is a seven-protrusion modified cross-section fiber 18 having seven protrusions 11, a reference circle diameter ds9 of about 8 μm, a protrusion tip width dk8 of about 3 μm, and a protrusion height hk7 of about 1. When the fiber sheet 3 was prototyped so as to have a thickness of 5 μm, the thermal conductivity increased by about 30%, that is, the heat insulating effect deteriorated by about 30%. As a result of cross-sectional observation, it was confirmed that this was because the circular height was in contact with the recess 14 between the protrusions 11 because the protrusion height hk7 was low. For this reason, it is desirable that the height of the protrusions in the seven-protrusion deformed cross-section fiber 18 is 1.5 μm or more.

Embodiment 3 FIG.
FIG. 8 is a cross-sectional view schematically showing a set of fibers constituting a fiber sheet of a vacuum heat insulating material according to Embodiment 3 of the present invention. In FIG. 8, the fiber sheet 3 is configured such that a circular cross-section fiber 2 and an eight-protruded modified cross-section fiber 19 having eight projecting portions 11 as the modified cross-section fiber 1 are mixed.

  A fiber sheet 3 having a thickness of about 0.5 mm is formed by using the eight-protrusion deformed cross-section fiber 19 having a reference circle diameter ds9 of about 8 μm, a protrusion tip width dk8 of about 3 μm, and a protrusion height hk7 of about 1.5 μm. ing. Other configurations and the manufacturing method are the same as those of the first embodiment, and thus description thereof is omitted. The core material 4 was produced by laminating 25 sheets. The core material 4 is inserted into an aluminum laminate sheet (nylon 15 μm + polyethylene terephthalate 12 μm + aluminum sheet 6 μm + polyethylene 50 μm) with an adsorbent, and the pressure is reduced to about 1 Pa in a vacuum chamber. The part was sealed by heat sealing to produce a vacuum heat insulating material.

  As a result of measuring the thermal conductivity of the vacuum heat insulating material thus manufactured, the vacuum heat insulating material according to the third embodiment of the present invention has a heat conductivity equal to that of the first embodiment 0.0015 W / (m · K). ) Degree was obtained. Moreover, when the cross section of the fiber sheet 3 was observed, the surface contact and meshing | engagement of the projection parts 11 in each fiber contact part were hardly seen. Therefore, the vacuum heat insulating material in the third embodiment of the present invention can obtain the same heat insulating effect as that in the first embodiment.

  Similarly, an eight-protruded modified cross-section fiber 19 having eight protrusions 11 as the modified cross-section fiber 1 has a reference circle diameter ds9 of about 8 μm, a protrusion tip width dk8 of about 3 μm, and a protrusion height hk7 of about 1. When the fiber sheet 3 was prototyped so as to have a thickness of 0 μm, the thermal conductivity increased by about 40%, that is, the heat insulating effect deteriorated by about 40%. As a result of cross-sectional observation, it was confirmed that this was because the circular height was in contact with the recess 14 between the protrusions 11 because the protrusion height hk7 was low. For this reason, it is desirable that the protrusion height of the eight-protrusion deformed cross-section fiber 19 is 1.0 μm or more.

  In the above embodiment, polyethylene terephthalate fiber is used as the fiber material. However, polyester-based or other organic fibers such as polypropylene, polystyrene, or polyethylene may be used. The same effect can be obtained by using the circular cross-section fiber 2 and the modified cross-section fiber 1 as separate materials.

  In the above embodiment, the melt spinning method is used as a method for producing the fiber sheet 3. However, the method is not limited to this, and other methods such as dry spinning can be used as long as the fiber sheet 3 can be formed. A method, a wet spinning method, a wet manufacturing method, and the like may be used.

  DESCRIPTION OF SYMBOLS 1 Abnormal cross-section fiber, 2 Circular cross-section fiber, 3 Fiber sheet, 4 Core material, 5 Cover material, 6 Protrusion irregular cross-section fiber, 7 Protrusion height hk, 8 Protrusion tip width dk, 9 Reference | standard circle diameter ds, 10 circular Part, 11 protrusion part, 125 protrusion irregular cross-section fiber, 13 3 protrusion irregular cross section fiber, 14 recess, 15 melt spinning die, 16 irregular cross section nozzle, 17 circular cross section nozzle, 187 protrusion irregular cross section fiber, 188 protrusion irregular shape Cross-section fiber

Claims (6)

  In a vacuum heat insulating material provided with a core material in which a plurality of fiber sheets are laminated and a jacket material that covers the core material by vacuum-sealing, the fiber sheet is formed on a circular portion and a circumference of the circular portion. A vacuum heat insulating material, characterized in that it is formed by mixing irregular cross-section fibers composed of a plurality of arranged protrusions and circular cross-section fibers having a substantially circular cross section.   The planar geometric arrangement in which the irregular cross-section fiber and the circular cross-section fiber are adjacent to each other, wherein at least one tip portion of the protrusion is in contact with a part of the circumference of the circular cross-section fiber. Item 1. The vacuum heat insulating material according to Item 1.   The vacuum heat insulating material according to claim 1 or 2, wherein a width of a tip portion of the protrusion is smaller than a diameter of the circular cross-section fiber.   The vacuum heat insulating material according to any one of claims 1 to 3, wherein the number of protrusions of the protrusions is 6 or more.   The spinning die according to claim 1, further comprising: a spinning die in which the odd-shaped cross-section nozzle that discharges the irregular-shaped cross-section fibers and the circular cross-section nozzle that discharges the circular cross-section fibers are alternately arranged. The apparatus for manufacturing a vacuum heat insulating material according to any one of claims 1 to 4.   The spinning die in which the odd-shaped cross-section nozzle that discharges the irregular-shaped cross-section fibers and the circular cross-section nozzle that discharges the circular cross-section fibers are alternately arranged. The manufacturing method of the vacuum heat insulating material as described in any one of Claim 1 thru | or the said Claim 4.

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