Patent Application
20210018135
The present disclosure relates to a thermal insulator to be used for thermal insulation, a thermal insulation sheet using the thermal insulator, and a method for manufacturing a thermal insulator.
In recent years, there has been a great demand for energy saving, and methods for achieving the energy saving include improvement of energy efficiency by heat-retention of equipment. To achieve the heat-retention, a thermal insulation sheet having an excellent thermal insulation effect is required. Thus, a thermal insulator may be used in which silica xerogel is carried on a nonwoven fabric to make the coefficient of thermal conductivity lower than that of air.
As prior art document information related to this technique, for example, Patent Literature 1 is known.
However, the thermal insulator has a basically flat structure, and therefore when an attempt is made to adjust a position of the thermal insulator in equipment, the position adjustment may be difficult to perform because the thermal insulator is stuck on an area where the thermal insulator has been initially placed.
In order to solve the above-described problem, the thermal insulator of the present disclosure includes a nonwoven fabric carrying xerogel in interior spaces, and a plurality of projections provided on at least one surface of the nonwoven fabric.
With the above-described configuration, it is possible to obtain a thermal insulator and a thermal insulation sheet which are easily position-adjusted, and a thermal insulation effect can be enhanced by means of the projections.
Hereinafter, a thermal insulation sheet according to an exemplary embodiment of the present disclosure will be described with reference to drawings.
Thermal insulator 12 is formed by carrying silica xerogel (not shown) in spaces of nonwoven fabric 11 made of polyethylene terephthalate (hereinafter, referred to as PET) having spaces inside the PET. Nonwoven fabric 11 includes PET fiber having an average fiber thickness of about 10 μm, and the spaces occupy about 90% of nonwoven fabric 11. Since this silica xerogel has nano-sized spaces inside the silica xerogel, a coefficient of thermal conductivity of a part filled with the silica xerogel is 0.018 to 0.024 W/m·K, smaller than a coefficient of thermal conductivity of air. The silica xerogel is broad-sense xerogel with the gel being in a dried state, and may be obtained not only by ordinary drying but also by supercritical drying, freeze drying or the like.
Here, thermal insulator 12 has a thickness of about 0.3 mm and a size of about 100 mm square. One surface of thermal insulator 12 is provided with projections 13 formed by raising a part of the surface. Projections 13 have a height of about 0.03 mm from the one surface, and a diameter of about 3 mm, and are arranged in such a manner that a shortest distance between centers of projections 13 is about 15 mm.
This ensures that when the surface provided with projection 13 is placed at an installation position, contact occurs only with the projections, and therefore the thermal insulator is prevented from sticking at the installation position. Thus, fine positioning or the like is easily performed. Further, a thickness increases by the height of projections 13, so that a thermal insulation effect can be improved.
Preferably, the height of projections 13 ranges from 0.05 t to 0.15 t inclusive, where t is a thickness of thermal insulator 12. This is because when the height is less than 0.05 t, an effect of an invention according to the present disclosure is reduced, and when the height is more than 0.15 t, it is difficult to maintain a shape.
Preferably, projections 13 are arranged in such a manner that a shortest distance between projections 13 ranges from 30 t to 80 t inclusive, where t is the thickness of thermal insulator 12. This is because when the distance is less than 30 t, a contact area increases, resulting in reduction of the effect of the invention according to the present disclosure, and when the distance is more than 80 t, thermal insulator 12 bends, resulting reduction of the effect of the invention according to the present disclosure.
Projections 13 may be provided on both surfaces of thermal insulator 12 as in
Next, a method for manufacturing the thermal insulator according to the exemplary embodiment of the present disclosure will be described.
First, a nonwoven fabric made of PET having a thickness of about 0.3 mm is prepared. This nonwoven fabric is immersed in a sol solution obtained by, for example, adding hydrochloric acid to a sodium silicate aqueous solution, so that the interior spaces of the nonwoven fabric are impregnated with the sol solution. The sol solution is gelled, hydrophobized and dried to fill the interior spaces of the nonwoven fabric with silica xerogel. Before the sol solution is completely dried, a surface of the nonwoven fabric is only partially suctioned under vacuum, and the suctioned part is raised to form a projection. By completely drying the nonwoven fabric, a thermal insulator having a plurality of projections on a surface of the thermal insulator can be obtained.
A size, an arrangement, a height and the like of projections can be set to a predetermined size, arrangement, height and the like according to a shape and an arrangement of holes of a vacuum suction plate.
Thereafter, two thermal insulators 12 are superposed, and wholly covered with insulating film 14. In this way, thermal insulation sheet 15 is obtained.
In the exemplary embodiment, materials of nonwoven fabric 11, projections 13 and insulating film 14 are PET, but may be resin materials other than PET. The materials of nonwoven fabric 11, projections 13 and insulating film 14 may be mutually different.
The thermal insulator according to the present disclosure and the thermal insulation sheet using the thermal insulator can be easily position-adjusted, and are industrially useful.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-067343 | Mar 2018 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/009556 | 3/11/2019 | WO | 00 |
