JP2019182728A - Heat insulation material and method for manufacturing the same - Google Patents

Abstract

An object of the present invention is to provide a heat insulating material which does not use rivets and has improved adhesion between silica airgel and a coating layer, and a method for manufacturing the same. The heat insulating material includes a composite layer containing fibers and silica airgel, and a coating layer covering the surface of the composite layer, wherein a crack is formed on the surface of the composite layer. An impregnation step of impregnating the fibers with a silica sol solution, a gel step of converting the silica sol to silica gel, a curing step of growing the silica gel, a hydrophobizing step of hydrophobizing the silica gel, and forming a crack on the surface of the silica gel And a drying step of drying the silica gel. [Selection diagram] Fig. 1

Description

  The present invention relates to a heat insulating material and a method for manufacturing the same. In particular, the present invention relates to a heat insulating material using a hydrophobic airgel and a method for producing the same.

  As a method for preventing a temperature rise on the surface of the device, there is a method using a heat insulating material that exhibits a sufficient heat insulating effect even in a narrow space inside the casing of the electronic device. This heat insulating material is a composite of silica airgel and non-woven fiber. This heat insulating material has improved handling properties and is a thin and homogeneous sheet (Patent Document 1). As shown in FIG. 2, the silica aerogel is composed of silica primary particles 201 having a diameter of about 1 nm, and the silica secondary particles 202 having a diameter of about 10 nm are formed with an interparticle distance of about 10 to 60 nm. It is an aggregate of a network structure having a plurality of voids 203.

  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.

  However, a silica airgel sheet in which a silica airgel having a nano-sized porous structure is supported on a nonwoven fabric has a small bonding force between the silica secondary particles 202 of the silica airgel and is extremely fragile. For this reason, when a 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.

  Therefore, when at least one or both surfaces of the airgel sheet have an 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.

  As a method for solving the problem, an example of fixing with a rivet through the laminate is shown because the adhesion with dust generated by silica airgel resulting from the weakness of silica airgel particles is poor (see, for example, Patent Document 2).

Japanese Patent No. 6064149 JP 2010-167585 A

  However, in Patent Document 2, a through-hole is mechanically provided in a layer coated on one surface of an airgel sheet and bonded with a rivet. However, since the heat of the heat generating part is conducted to the surface through the rivet through which the heat passes, there is a problem that the heat insulating property is deteriorated. In addition, the thickness of the airgel sheet and the layer coated on one surface varies by using rivets. As a result, there is a problem that the heat insulation is deteriorated due to a decrease in adhesion between the heat generating portion and the airgel sheet.

  Therefore, an object of the present invention is to provide a heat insulating material that improves the adhesion between the silica airgel and the coating layer without using rivets, and a method for producing the same.

  In order to solve the above problems, a heat insulating material including a composite layer containing fibers and silica airgel and a coating layer covering the surface of the composite layer, in which a crack is formed on the surface of the composite layer, is used.

  In addition, an impregnation step for impregnating the fiber with a silica sol solution, a gel step for converting the silica sol to silica gel, a curing step for growing the silica gel, a hydrophobization step for hydrophobizing the silica gel, and a crack on the silica gel surface The manufacturing method of the heat insulating material containing the cracking process which forms and the drying process which dries the said silica gel is used.

As described above, according to the heat insulating material of the present invention and the manufacturing method thereof, the adhesion between the heat insulating material in which the silica airgel is supported on the fiber and the coating layer is improved. For this reason, it can suppress that the silica airgel piece near the surface of a heat insulating material detaches | leaves and destroys. As a result, it is possible to realize a heat insulating material that can suppress the thickness variation of the heat insulating material at a low cost and that has a low thermal conductivity and can significantly suppress the amount of silica fine powder desorption.

Figure of heat insulation material of embodiment The schematic diagram which expanded a part of silica airgel of embodiment Figure of crack surface of silica airgel of embodiment Figure of cross section of silica airgel of embodiment Manufacturing flow chart of the heat insulating material of the embodiment (A) Surface view of the heat insulating material of the comparative example (b) Surface view of the heat insulating material of the embodiment

  Embodiments will be described below with reference to the drawings. FIG. 1 shows a cross-sectional view of a heat insulating material in an embodiment of the present invention.

<Configuration of heat insulating material 100>
In FIG. 1, the heat insulating material 100 is composed of a composite layer 101 and a coating layer 106 formed of a coating material 105.

  In the composite layer 101, the silica airgel 102 having a nano-sized porous structure is supported on the fibers 103. A surface of an arbitrary silica airgel 102 has a crack 104, the fiber 103 is exposed, and is bonded to the coating material 105.

  The crack 104 is a recess that is split in a mesh shape so that a plurality of lines intersect the surface of the silica airgel 102. A part of the crack 104 may reach the back surface of the silica airgel.

<Composite layer 101>
The composite layer 101 impregnates the fiber 103 with a gel raw material in the process of manufacturing the silica airgel 102. Thereafter, the gel raw material is reacted to form a wet gel. Finally, the wet gel surface is hydrophobized and dried with hot air. The fibers 103 are preferably resin-based PET (polyethylene terephthalate) or polypropylene (PP), and inorganic fibers such as acrylic oxide, glass wool, and glass paper that are subjected to flame-retardant treatment from the viewpoint of safety.

  The diameter of the fiber 103 is desirably 0.1 to 30 um. When the diameter of the fiber 103 is larger than 30 μm, heat is easily transferred through the fiber 103, so that the thermal conductivity is increased and the heat insulating property is deteriorated.

<Silica airgel 102>
FIG. 2 illustrates the structure of the silica airgel. The silica airgel 102 is a network in which silica secondary particles 202 having a diameter of about 10 nm formed by aggregating silica primary particles 201 having a diameter of about 1 nm have voids 203 having an interparticle distance of about 10 to 60 nm. A collection of structures.

  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 203 and does not function as a heat insulating material. Therefore, it is necessary to hydrolyze the silanol groups on the surface of the wet gel by silylation using a silylating agent and then dry with hot air.

<Crack 104>
FIG. 3 shows a photograph of the silica airgel 102 with a crack 104.
FIG. 3 shows a state in which the composite layer 101 of the heat insulating material 100 is viewed from above. In the drying process for manufacturing the composite layer 101, the composite layer 101 is subjected to drying by applying a weight. That is, when the composite layer 101 is dried and the surface is covered and applied with a load, insufficient drying occurs, and irregularities are formed on the surface of the composite layer 101 by the cracks 104. The coating material 105 can be brought into close contact with the fibers 103 of the composite layer 101 by applying and soaking the coating material 105 into the uneven portions generated by the crack 104.

  The crack 104 is a recess that is split in a mesh shape so that a plurality of lines intersect the surface of the silica airgel. As for the crack 104, the crack 104 arises in the site | part to which the weight was applied, and its vicinity. The crack area changes due to the load. If the weight is light, the crack will be smaller than the weighted area, and if the weight is heavy, the crack will be larger than the weighted area. Moreover, you may make the depth of a crack reach | attain the back surface of a silica airgel.

  Note that the crack 104 has the same shape as the fiber 103. Similar means similarity. The crack 104 preferably has a width of 5 μm or more in order to soak the coating material 105, and the depth is preferably deeper than the diameter of the fiber 103. That is, it is to a place deeper than the surface fiber 103. As a result, it is possible to prevent the coating material 105 from peeling off by covering the fiber 103 with the coating material 105. The crack 104 is a line-shaped recess. There are straight and curved parts.

FIG. 4 shows the cross-sectional structure of the silica airgel crack 104.
The surface of the fiber 103 appears due to the crack 104 in the silica airgel of the composite layer 101. As a result, the coating material 105 adheres to the fiber 103 to obtain adhesion strength.
Simply applying irregularities to the surface of the silica airgel 102, which is the surface of the composite layer 101, is ineffective if there is no adhesion to the fibers 103. Therefore, it is desirable that the coating material 105 exists so as to cover a part of the surface of the fiber 103 exposed by the crack 104.

The weight is preferably 0.8 g / cm ² or more. This is because if the weight is light, the silylating agent volatilizes simultaneously with other sites in the drying process. That is, the volatilization timing of the silylating agent is delayed by applying a weight. As a result, a crack 104 is generated at the portion to which the weight is applied.

  It is preferable to generate the crack 104 at a plurality of locations and avoid the heat generating portion. This is because if the crack 104 is generated on the heat generating portion, the thermal characteristics may be deteriorated due to the solid heat conduction of the coating material 105 entering the crack 104.

<Coating material 105>
In order to prevent the silica airgel 102 from being detached when an external stress is applied to the heat insulating material 100, a coating layer 106 is formed on the surface by the coating material 105 including the crack 104.

  The coating material 105 is selected in consideration of heat resistance, flame retardancy, flexibility, heat insulation, and thickness uniformity, without the silica airgel 102 being detached. In particular, water-based polyester, fluororesin, etc. are desirable as materials.

  The thickness of the coating layer 106 is preferably about several um to 50 um. This is because if the thickness is thin, it is easy to peel off during bending, and if the thickness is thick, the thermal conductivity is lowered.

<The manufacturing method of the heat insulating material 100>
FIG. 5 shows a manufacturing flowchart of the heat insulating material. The fiber 103 is uniformly impregnated with the sol solution in the impregnation step.

  Thereafter, the sol is gelled and a gel (solid) is grown in the fiber 103 in a curing process.

  Thereafter, in the hydrophobizing step, the surface of the silica nanoparticles in the wet gel is hydrophobized.

  After the hydrophobization treatment, the solvent is removed by heating in the drying step. In this embodiment, a crack 104 is generated by causing a cohesive failure in the process of volatilization of the solvent by applying a weight when removing the solvent in the drying step.

  By applying the resin in the next coating process, the fiber 103 exposed from the crack 104 and the coating material 105 are brought into close contact with each other.

  An example of the manufacturing method of the heat insulating material 100 is shown.

<Impregnation step>
First, the fiber 103 (weight per unit area 12 g / m 2, thickness 0.07 mm, dimension 12 cm □) is impregnated using a sol solution. Here, the sol solution is prepared by adding 1.4 wt% concentrated hydrochloric acid (12N) as a catalyst to high molar sodium silicate (silicic acid aqueous solution, Si concentration 14%) and stirring.

<Gelification process>
Next, the sol is allowed to gel at room temperature 23 ° C. for about 20 minutes. At this time, in order to promote gelation and shorten the time, heating may be performed with a heater (about 50 ° C. to 130 ° C.).

  Next, it forms in desired thickness using a biaxial roll.

<Curing process>
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. .

<Hydrophobicization process>
Next, after immersing the gel sheet in hydrochloric acid (6 to 12 N), 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), placed in a constant temperature bath at 55 ° C., and allowed to react 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.

<Crack process>
The surface of the gel sheet is partially pressurized to form a crack 104 on the surface. In addition, partial pressurization is pressing a pressurization member to a part of surface of a gel sheet, and compressing a gel sheet. The pressure member is a metal plate, a roller, or the like. In addition, a crack is made in the pressurized part.

<Drying process>
Next, the heat insulating material 100 having the composite layer 101 in which the silica aerogel 102 is supported on the fiber 103 having a nano-sized porous structure by transferring the gel sheet to a constant temperature bath at 150 ° C. and drying for 2 hours. I can do it.

  Note that the crack 104 may be formed on the surface by partial pressurization during the drying process without dividing the cracking process and the drying process.

<Example>
In the manufacturing process of the heat insulating material in which silica aerogel is supported on the fiber, the gel sheet is immersed in a mixed solution of octamethyltrisiloxane and 2-propanol (IPA) as a silylating agent and put in a constant temperature bath at 55 ° C. The reaction was performed for 2 hours.

  When the trimethylsiloxane bond began to form, hydrochloric acid water was discharged from the gel sheet, and two liquids were separated (siloxane in the upper layer, hydrochloric acid in the lower layer, 2-pronol). The heat insulating sheet was obtained by moving the gel sheet to a thermostat set at 150 ° C. and drying it in an air atmosphere for 2 hours.

Before drying, a weight of 1 g / cm ² per unit area is set on the composite layer 101 at an arbitrary place.
It was made to dry for 2 hours in the thermostat set to 150 to 200 degreeC in the set state.

  FIG. 6A and FIG. 6B show photographs of the surface state after drying. FIG. 6A is a photograph of the surface state without weight (no weight), and FIG. 6B is a photograph of the surface condition after weighting. A crack 104 is formed on the surface from the surface state after the load, and the fiber 103 in the silica airgel is exposed inside the crack 104. The coating layer 106 is formed using the coating material 105 so that the surface may become uniform using the hydrophobic coating material 105 (for example, aqueous | water-based polyester, a fluororesin etc.) there. Thereafter, in order to cure the coating layer 106, the coating layer 106 is dried at 100 to 400 ° C. in a thermostatic bath.

(as a whole)
The silica airgel may be another type of airgel.

The heat insulating material and the manufacturing method thereof of the present invention are widely used in electronic devices. Used for products related to heat, such as in-vehicle devices, information devices, mobile phones, displays, etc.

DESCRIPTION OF SYMBOLS 100 Heat insulating material 101 Composite layer 102 Silica airgel 103 Fiber 104 Crack 105 Coating material 106 Coating layer 201 Silica primary particle 202 Silica secondary particle 203 Void

Claims (11)

A composite layer comprising fibers and silica airgel;
A coating layer covering the surface of the composite layer,
A heat insulating material in which a crack is formed on the surface of the composite layer. The heat insulating material according to claim 1, wherein the crack is a line-shaped recess. The heat insulating material according to claim 1, wherein the crack has a width of 5 μm or more. The depth of the said crack is a heat insulating material of any one of Claims 1-3 deeper than the diameter of the said fiber. The heat insulating material according to any one of claims 1 to 4, wherein the crack has a shape similar to the fiber. The heat insulating material according to any one of claims 1 to 5, wherein the fiber is exposed at a part of the crack. The heat insulating material according to claim 1, wherein the coating layer is formed by filling the crack. The heat insulating material according to any one of claims 1 to 7, wherein the crack exists in a part of a surface, and a plurality of the cracks exist. An impregnation step of impregnating the fiber with a silica sol solution;
A gel step for converting the silica sol to silica gel;
A curing process for growing the silica gel;
A hydrophobizing step of hydrophobizing the silica gel;
A cracking process for forming a crack in the surface of the silica gel;
And a drying step of drying the silica gel. The method for manufacturing a heat insulating material according to claim 9, wherein the cracking step is a step of partially pressing the surface of the silica gel to cause cracking in the pressed portion. The manufacturing method of the heat insulating material of Claim 9 or 10 which performs the said crack process in the said drying process.

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