JP2017036745A - Heat insulation material, apparatus made by using the same and manufacturing method of heat insulation material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat insulation material capable of suppressing that silica aerogel pieces existing on opening parts of nonwoven fabric are released and destroyed on a heat insulation material surface and a large amount of silica aerogel fine particles are scattered into an electronic apparatus without deteriorating heat conductivity, in the heat insulation material to which silica aerogel is deposited among fibers.SOLUTION: A heat insulation material has a second composite layer 105 different in basic weight, at least on one surface of a first composite layer 103 which has silica aerogel deposited among fibers. Therein, second fibers 104 of the second composite layer 105 are larger in basic weight than first fibers 101 of the first composite layer 103, the basic weight of the second fibers 104 is 34 to 53 g/m, a fiber layer having a thickness of the second fibers 104 of 0.02 to 0.05 mm is formed and, thereby, powder dropping is suppressed by means of the second composite layer 105.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a heat insulating material used by being laminated with a heat radiating material among heat insulating materials used in electronic devices and the like.

In recent years, ICT (Information and
As the performance of electronic devices in the information and communication technology field called Communication Technology) increases, the heat generation density from heat-generating components such as CPUs has increased rapidly, and heat diffusion technology in these electronic devices has become essential. It is coming.

  Conventionally, a composite sheet in which a silica airgel sheet and a graphite sheet are laminated is conceivable as a heat insulating material capable of dissipating the heat of heat-generating components inside the apparatus while keeping the temperature rise on the apparatus surface low (Patent Document 1).

  Since the graphite sheet has an in-plane thermal conductivity higher than the thermal conductivity in the thickness direction and has anisotropy of 10 times or more, the heat generated from the heat-generating component can be scattered in the plane. In addition, the silica airgel sheet is obtained by carrying a silica airgel having a nano-sized porous structure on a nonwoven fabric.

  As shown in FIG. 3, the silica aerogel is composed of silica primary particles 301 having a diameter of about 1 nm, and the silica secondary particles 302 having a diameter of about 10 nm formed by aggregating the silica primary particles 301 have an interparticle distance of about 10 to 60 nm. It is an aggregate of a network structure having the voids 303.

  Since this interparticle distance is less than the mean free path of air (nitrogen molecules), the thermal conductivity is as low as 0.015 to 0.024 W / mK, which is 0. 0 which is the thermal conductivity of still air at room temperature. 026 W / mK or less. Therefore, by laminating the airgel sheets having low thermal conductivity, it is possible to suppress the heat scattered in the plane by the graphite sheet from being transmitted to the casing.

  However, since the silica airgel sheet in which the silica airgel having a nano-sized porous structure is supported on the nonwoven fabric has a small bonding force between the silica secondary particles 302 of the silica airgel and is extremely fragile, when stress is applied from the outside The 100 μm to 200 μm square silica airgel pieces present in the openings of the nonwoven fabric on the surface of the silica airgel sheet are detached into the electronic apparatus.

  Furthermore, since the silica airgel pieces desorbed in the electronic device are not carried by the nonwoven fabric that relieves external stress, they are crushed into a large amount of silica particles and scattered in the electronic device. Cause problems such as poor contact.

  Therefore, when at least one or both surfaces of the airgel sheet have external stress applied to the nonwoven fabric in which the nonwoven fabric is supported by a silica airgel having a nano-sized porous structure, the silica airgel is detached. It is necessary to suppress this.

In order to prevent the fine powder of silica particles from scattering, it is conceivable to dispose the heat dissipating material and the heat insulating material in a state of being laminated with an insulating film as in Patent Document 2.
Moreover, like patent document 3, a heat insulating material can also be coat | covered with the coating layer which consists of alumina.

Japanese Patent Laying-Open No. 2015-84402 Japanese National Patent Publication No. 11-513431 JP 2011-162902 A

  However, when an insulating film material is used on the surface of the heat insulating material as in Patent Document 2, an increase in the thermal conductivity of the heat insulating material through the insulating film material, or the operating temperature range is limited by the type of the laminate material, etc. There is a problem.

  Further, as in Patent Document 3, when a coating layer made of alumina is provided on the surface of the heat insulating material, when a coating solution containing a surfactant added for the purpose of improving the wettability to the heat insulating material is applied, Water having a large surface tension penetrates into the pores of the silica airgel.

  When the water in the pores is volatilized in the subsequent drying step, the capillary force that promotes the shrinkage of the silica airgel skeleton acts and shrinks. As a result, the pores are crushed, so that there is a problem that the solid thermal conductivity is increased and the thermal conductivity is deteriorated.

  Therefore, in the present invention, in view of the above problems, the structure of the silica airgel is maintained to suppress the deterioration of the thermal conductivity, and the silica airgel pieces existing on the nonwoven fabric surface are detached and destroyed on the surface of the heat insulating material, and a large amount of It aims at providing the heat insulating material which can suppress that silica airgel fine powder disperses in an electronic device.

  The heat insulating material of the present invention is a laminate of a first composite layer in which silica aerogel is supported on first fibers and a second composite layer in which silica aerogel is supported on second fibers, and the first fibers The basis weight is different between the second fiber and the second fiber.

Specifically, the basis weight of the second fiber is larger than the first fiber, the basis weight of the second fiber is 34 g / m ² or more and 53 g / m ² or less, and the thickness of the second fiber Is 0.02 mm to 0.05 mm.

  According to the present invention, it is possible to prevent the silica airgel pieces near the surface of the first composite layer from detaching and breaking while maintaining the structure of the thermal conductivity silica airgel by the laminate and the thermal conductivity associated therewith. Can be suppressed. As a result, it is possible to realize a heat insulating material having a low thermal conductivity and capable of greatly suppressing the amount of silica fine particles detached.

The expanded sectional view of the heat insulating material of Embodiment 1 of this invention Cross-sectional view of the smartphone housing Schematic diagram enlarging a part of silica airgel Expanded cross-sectional view of the heat insulating material of the comparative example (A)-(d) The figure which shows the surface state which carry | supported the silica airgel on the fiber from which a basis weight differs. The figure which shows the manufacturing method of the heat insulating material of (a)-(c) embodiment. The figure which shows another manufacturing method of the heat insulating material of embodiment The figure which shows the relationship between the fabric weight of a fiber in a heat insulating material, and thermal conductivity The figure which shows the relationship between the fabric weight of a fiber in a heat insulating material, and the desorption number of silica airgel The expanded sectional view of the heat insulating material of Embodiment 2 of this invention

Embodiments of the present invention will be described below with reference to the drawings.
(Embodiment 1)
FIG. 1 shows an example of a heat insulating material 100 according to an embodiment of the present invention.

  The heat insulating material 100 includes a first composite layer 103 in which a silica airgel 102 having a nano-sized porous structure is supported on a first fiber 101 of a nonwoven fabric, and a second composite provided on the surface of the first composite layer 103. The layer 105 is combined. The 2nd composite layer 105 is comprised by making the silica airgel 102 which has a nano-sized porous structure carry on the 2nd fiber 104 of a nonwoven fabric.

The first fibers 101 constituting the first composite layer 103 and the second fibers 104 constituting the second composite layer 105 are composed of fibers having different basis weights. The basis weight is the weight of the fiber per unit area 1 m ² .

<Thermal conductivity of heat insulating material 100>
In this embodiment, the heat insulating material 100 is used for an electronic device having a limited space in the housing, such as an ICT portable device. Here, FIG. 2 shows a cross-sectional view of a smartphone as an example.

  In this smartphone, the liquid crystal panel 202, the substrate 203, and the CPU 204 and the IC component 205, which are the heat generating components installed therein, are arranged in contact with the CPU 204 in a housing surrounded by the upper case 201a and the lower case 201b. A graphite sheet 206 as a heat dissipating material is disposed. In this example, two heat insulating materials 100 are used. Let this be the heat insulating materials 100a and 100b.

  The heat insulating material 100 a interposed between the upper case 201 a and the graphite sheet 206 is in close contact with the upper case 201 a and the graphite sheet 206. The first composite layer 103 of the heat insulating material 100 a is in close contact with the graphite sheet 206. The thickness of the gap between the upper case 201a and the graphite sheet 206 is required to be 0.5 mm or less.

  The heat insulating material 100b interposed between the lower case 201b and the IC component 205 mounted on the back side of the substrate 203 is in close contact with the IC component 205 and the lower case 201b. The first composite layer 103 of the heat insulating material 100 b is in close contact with the IC component 205. The thickness of the gap between the lower case 201b and the graphite sheet 206 is required to be 0.5 mm or less.

  Therefore, from the condition of the heat insulating material 100 to be used in a space of 0.5 mm or less, the heat conductivity of the heat insulating material 100 is preferably 0.05 W / m · K or lower. When the heat conductivity of the heat insulating material 100 is larger than 0.05 W / m · K, the heat insulating effect of heat generated from the heat-generating component is low.

<Configuration of first composite layer 103>
The first composite layer 103, which is a main part of the heat insulating material 100, impregnates the first fiber 101 with the gel raw material in the manufacturing process of the silica airgel 102. Thereafter, the gel raw material is reacted to form a wet gel. Finally, it is obtained by hydrophobizing the wet gel surface and drying with hot air.

  The fiber diameter of the first fiber 101 is desirably 0.1 to 30 μm. This is because when the fiber diameter of the first fiber 101 is larger than 30 μm, heat is easily transferred through the first fiber 101, so that the thermal conductivity is increased and the heat insulation is deteriorated. When the fiber diameter of the first fiber 101 is smaller than 0.1 μm, when an external force is applied to the heat insulating material 100, it is not possible to relax the stress applied to the silica airgel, and the silica airgel is easily destroyed. .

The basis weight of the first fiber 101 is desirably ²⁰ to 30 g / m ² .
This is because when the basis weight of the first fibers 101 is larger than 30 g / m ² , the silica airgel 102 that can be filled between the first fibers 101 is reduced, so that the thermal conductivity is increased and the heat insulation is deteriorated.

Further, when the basis weight of the first fiber 101 is smaller than 20 g / m ² , when an external force is applied to the heat insulating material 100, it is not possible to mitigate the stress applied to the silica airgel, and the silica airgel is destroyed. It becomes easy to be done.

  Examples of the material of the first fiber 101 include inorganic fiber glass wool and rock wool, natural wool heat insulating material and cellulose heat insulating material, foam ceramics, carbonized foam cork, urethane foam, phenol foam, polystyrene foam as resin heat insulating material. Etc. can be used. Among these, a resin-based heat insulating material is more preferable in consideration of good adhesiveness with the graphite sheet 206 as a heat radiating material.

<Second composite layer 105>
The second composite layer 105 has an effect of preventing the silica airgel pieces from being detached from the first composite layer 103 while maintaining heat insulation performance as much as possible.

  The thickness of the second fiber 104 is preferably 0.02 mm to 0.05 mm. When the thickness is smaller than 0.02 mm, it is difficult to ensure the basis weight of the fiber. This is because when the thickness is larger than 0.05 mm, the thermal conductivity is deteriorated.

The fiber diameter of the second fiber 104 is desirably 0.1 to 30 μm for the same reason as in the case of the first fiber 101.
(Comparative example)
FIG. 4 shows an example of a heat insulating material that is different in configuration from the first embodiment shown in FIG. 1 and that can dissipate heat from heat-generating components inside the device while keeping the temperature rise on the device surface low. Show. This comparative example is a composite sheet in which a silica airgel sheet and a graphite sheet are laminated, and the silica airgel pieces are prevented from being detached as follows.

  The surface of the graphite layer 403 of the composite sheet of the graphite layer 403 and the heat insulating layer 402 is in close contact with the heat-generating component 405 mounted on the substrate 406 via the double-sided tape 404, and the surface of the heat insulating layer 402 of the composite sheet is the insulating film. It is in contact with the housing 400 via 401.

  The insulating film 401 is effective for preventing the separation of the silica airgel pieces, but has a drawback that the heat conductivity is high and the heat insulating effect is lowered. For example, as shown in FIG. 2, when the thickness of the gap between the upper case 201a, the lower case 201b and the CPU 204 is 0.5 mm or less, the thermal conductivity when a 0.05 mm insulating film is used is 0.08 W / m.・ It becomes K and the heat insulation effect is greatly reduced.

<Silica airgel 102>
Next, the structure of the silica airgel carried on the first fiber 101 and the second fiber 104 of the first embodiment will be described in detail.

  As shown in FIG. 3, the silica airgel 102 is composed of silica primary particles 301 having a diameter of about 1 nm. The silica secondary particles 302 having a diameter of about 10 nm formed between the particles are about 10 to 60 nm. It is an aggregate of a network structure having a gap 303 of distance.

  Silica airgel 102 uses water alkoxide such as water glass or tetramethoxysilane as a gel raw material, and mixes a solvent such as water or alcohol with a catalyst as necessary to react with the gel raw material in the solvent to form a wet gel. It is formed and the solvent inside is dried.

  However, when the wet gel is normally dried with hot air, it shrinks due to the surface tension when the solvent dries, crushes the gap 303, and does not function as a heat insulating material. Therefore, so that the surface tension hardly works when the solvent dries, it is supercritical drying, or the silanol group on the surface of the wet gel is hydrophobized by silylation using a silylating agent and then dried with hot air. Is required.

<The basis weight and thermal conductivity of the second fiber 104>
As the material of the second fiber 104, as with the first fiber 101, inorganic fiber glass wool or rock wool, natural wool heat insulating material or cellulose heat insulating material, foam ceramics, carbonized foam cork, resin heat insulating material Urethane foam, phenol foam, polystyrene foam, etc. can be used.

  Table 1 below shows the thermal conductivity due to the difference in the basis weight of the second fibers 104 in the second composite layer 105.

FIG. 8 shows the relationship between the basis weight and the thermal conductivity. Surface states when the basis weight is changed to 20, 35, 40, 45 are shown in FIGS. 5 (a) to 5 (d). The magnifications in FIG. 5 are the same and are 20 times.

  As the basis weight increases, the distance between fibers becomes shorter and denser. As a result, the silica airgel 102 that can be filled between the second fibers 104 is reduced. For this reason, thermal conductivity is rising. The thermal conductivity of the single fiber is 0.05 W / m · K. From this result, it is understood that the thermal conductivity of the single fiber is not more than that of the insulating film. As described above, the thermal conductivity may be 0.05 W / m · K or less.

  Therefore, there is no problem even if the second composite layer 105 is a single fiber not containing silica gel. That is, the basis weight is not limited from the thermal conductivity. However, the lower the thermal conductivity, the better the heat insulation. Therefore, it is desirable to support the silica airgel on the second fibers 104.

As can be seen from FIG. 8, the thermal conductivity is constant at a basis weight of 24 to 34 g / m ² . When the thermal conductivity does not change, the silica airgel pieces can be prevented from being detached by increasing the basis weight. Therefore, it is preferable to use a basis weight of 34 g / m ² or more and 53 g / m ² or less.

Next, the relationship between the basis weight and the desorption of the silica airgel pieces is shown.
<Weight per unit of second fiber 104 and suppression of dust generation>
FIG. 9 shows the basis weight and the number of desorption of silica airgel pieces. The number of desorptions of each silica airgel piece was measured with the number of powder falling off with a basis weight of 20 g / m ² as 1.

As the basis weight increases, the number of detached silica airgel pieces decreases.
As the reason for the decrease in the number of detached silica airgel pieces as the basis weight increases, the size of the silica airgel pieces decreases as the basis weight increases, as shown in FIGS. 5 (a) to 5 (d). This is because the structure becomes intertwined with the fibers.

The effect of changing the basis weight of the first fiber 101 and the second fiber 104 will be described.
In order to improve the heat insulation property of the first composite layer 103, the heat insulation property is improved as the basis weight of the first fiber 101 is decreased and the silica airgel is increased. On the other hand, there is a drawback that the mechanical strength is reduced with the increase of silica airgel and the silica airgel pieces are detached. Therefore, by increasing the basis weight of the second fiber 104, the silica airgel is entangled with the second fiber 104 and has an effect of suppressing the separation of the silica airgel piece.

<The manufacturing method of the heat insulating material 100>
An example of the manufacturing method of the heat insulating material 100 is shown in FIG.
First, as shown in FIG. 6 (a), the first fibers 101 having different basis weights (basis weight 12g / m ² , thickness 0.07mm, dimensions 12cm □) and second fibers 104 (weight per unit area 34g / m ²⁾ , The thickness is 0.04 mm and the dimensions are 12 cm □), and the first fiber 101 is immersed downward in the sol solution 602 of the water tank 604 to impregnate the sol solution 602.

  When immersed in the sol solution 602, the impregnation time can be shortened by immersing the first fiber 101 downward in the sol solution 602 rather than immersing in the sol solution 602 with the second fiber 104 facing down.

Or when supplying the sol liquid 602 using the dispenser 601 as shown in FIG.6 (b), it is good to impregnate the 2nd fiber 104 below.
In both cases of FIG. 6A and FIG. 6B, the sol solution 602 is obtained by adding 1.4 wt% of concentrated hydrochloric acid (12N) as a catalyst to high molar sodium silicate (silicic acid aqueous solution, Si concentration 14%). And then mix by stirring.

  6A and 6B, after impregnating the sol solution 602, the sol is allowed to stand for about 20 minutes at a room temperature of 23 ° C. to gel the sol. At this time, in order to accelerate the gelation and reduce the time, it may be heated to about 50 ° C. to 130 ° C. with a heater or the like. Next, as shown in FIG.6 (c), it passes between biaxial rolls 603 grade | etc., And forms in desired thickness.

  Next, pure water is poured into the container to prevent drying and placed in a thermostatic bath at 80 ° C. for 12 hours to promote silanol dehydration condensation reaction to grow silica particles to form a porous structure. .

Next, after immersing the gel sheet in hydrochloric acid (6 to 12N), the gel sheet is left at room temperature of 23 ° C. for 1 hour to incorporate hydrochloric acid into the gel sheet.
Next, the gel sheet is immersed in, for example, a mixed solution of octamethyltrisiloxane, which is a silylating agent, and 2-propanol (IPA), and placed in a constant temperature bath at 55 ° C. for 2 hours. When the trimethylsiloxane bond starts to form, hydrochloric acid is discharged from the gel sheet, and the upper layer is separated into trisiloxane and the lower layer is separated into hydrochloric acid water.

  Next, the gel sheet was transferred to a constant temperature bath at 150 ° C. and dried for 2 hours, so that the silica airgel was supported on the fibers having the nano-sized porous structure such as the first fibers 101 and the second fibers 104. A heat insulating material 100 having the first composite layer 103 and the second composite layer 105 is formed.

As a method for producing the sheets of the first composite layer 103 and the second composite layer 105, there is another method described below.
As shown in FIG. 7, the first fiber 101 of the first composite layer 103 is impregnated with a sol liquid 602 having a bulk density higher than that of the first fiber 101. Thereafter, at the same time as the gelation progresses, the first fiber 101 is overlaid with the second fiber 104 that does not contain the silica airgel 102 or the sol solution 602 to gel the sol, and pass between the biaxial rolls 603. And a desired thickness.

  As described above, the heat insulating material 100, which is a feature of the present invention, has a basis weight of the first composite layer 103 on the surface of the first composite layer 103 in which silica aerogel is supported on fibers having a nano-sized porous structure. A thermal insulation with a different second composite layer 105 can be made.

  This keeps the structure of the silica airgel and prevents the silica airgel fragments from detaching and destroying on the surface of the heat insulating material without deteriorating the thermal conductivity, and preventing a large amount of silica airgel fine particles from scattering in the electronic device. Can do.

The adhesion between the first composite layer 103 and the second composite layer 105 is connected by the silica airgel 102 located in both layers.
(Embodiment 2)
In the first embodiment, the second composite layer 105 is formed on one surface of the first composite layer 103, but the second composite layer 105 is formed on both surfaces of the first composite layer 103 as shown in FIG. You can also

  The manufacturing method in this case is to create a laminate in which the first fibers 101 and the second fibers 104 having different basis weights are sandwiched between the first fibers 101 and the second fibers 104 are laminated on both sides, and this is used as a sol. Immerse in the solution, gel the sol solution impregnated in the laminate, shape it to a desired thickness, form a porous structure in which the silica particles in the laminate are grown, and support the silica aerosol .

  As another method, the first fibers 101 of the second fibers 104 and the first fibers 101 having different basis weights are impregnated with a sol solution having a bulk density or higher, and the first fibers 101 in which the gelation of the sol solution is in progress. The second fibers 104 that do not carry silica aerosol are overlapped on both sides and formed to have a desired thickness, and the second fibers 104 are impregnated with the sol solution of the first fibers 101. It is also possible to form a porous structure in which silica particles in the first fiber 101 are grown and to carry a silica aerosol.

  The heat insulating material 100 of FIG. 10 can be used as the heat insulating materials 100a and 100b of the smartphone shown in FIG.

  The heat insulating material manufactured by the manufacturing method of the present invention can suppress detachment of the silica airgel pieces on the surface while maintaining the thermal conductivity, and can be widely used for various electronic devices. It can be applied to products that generate heat, such as information equipment, mobile phones, and displays.

DESCRIPTION OF SYMBOLS 100 Heat insulating material 101 1st fiber 102 Silica airgel 103 1st composite layer 104 2nd fiber 105 2nd composite layer 201a Upper case 201b Lower case 202 Liquid crystal panel 203 Substrate 204 CPU
205 IC component 206 Graphite sheet 301 Silica primary particle 302 Silica secondary particle 303 Void 601 Dispenser 602 Sol solution 603 Biaxial roll

Claims (8)

A first composite layer in which silica aerogel is supported on the first fibers;
It is a laminate with a second composite layer in which silica aerogel is supported on the second fiber,
The basis weight is different between the first fiber and the second fiber.
Insulation. The basis weight of the second fiber is larger than the first fiber, and the basis weight of the second fiber is 34 g / m ² or more and 53 g / m ² or less.
The heat insulating material according to claim 1. The thickness of the first composite layer is thicker than the second composite layer, and the thickness of the second composite layer is 0.02 mm to 0.05 mm,
The heat insulating material according to claim 1 or 2. The first fiber and the second fiber have a fiber diameter of 0.1 to 30 μm,
The heat insulating material according to any one of claims 1 to 3. Between the heat generation location and the housing, a heat dissipating material and the heat insulating material according to any one of claims 1 to 4 are stacked and disposed.
machine. A laminate in which the second fibers are laminated on at least one side of the first fibers and the first fibers having different basis weights is immersed in a sol solution,
After the sol solution impregnated in the laminate is gelled, it is molded to a desired thickness,
Forming a porous structure in which the silica particles in the laminate are grown, and supporting silica aerosol on the porous structure;
A method of manufacturing a heat insulating material. Impregnating a first fiber having a smaller basis weight of the first fiber and the second fiber having a different basis weight with a sol solution having a bulk density or more,
At least one surface of the first fiber in which gelation of the sol solution is in progress is overlaid with a second fiber not containing silica aerosol to have a desired thickness, and the second fiber is impregnated with the sol solution of the second fiber,
Forming a porous structure in which silica particles in the second fiber and the first fiber are grown, and supporting the silica aerosol on the porous structure;
A method of manufacturing a heat insulating material. The basis weight of the second fiber is larger than the first fiber, and a fiber having a basis weight of 34 g / m ² or more and 53 g / m ² or less is used as the ^second fiber.
The manufacturing method of the heat insulating material of Claim 6 or Claim 7.