JPS6313077B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bonded heat-insulating material for a multilayer heat-insulating body that is simple and has excellent heat-insulating performance. Multilayer insulation has the best insulation performance and can be made lightweight, so it has been developed as an insulation method for cryogenic refrigerant containers that require high-performance insulation, including fuel tanks for space exploration rockets. The general structure of multilayer insulation is one in which radiation shielding films (such as aluminum foil or aluminum-deposited polyester) and net-like spacers for isolating them are alternately laminated, and the entire film is evacuated. Although this type of multilayer insulation has excellent insulation performance, it requires a complicated installation process because it uses materials with different mechanical properties, such as the radiation shield film and the spacer. Furthermore, since these materials generally require a considerable amount of processing steps to make, they have drawbacks such as higher costs than insulating materials such as powder, various fibers, and foam materials. For this reason, the application of multilayer insulation has been limited to applications that require particularly high performance. A combined heat insulating material A, which has improved the above-mentioned drawbacks and integrates a radiation shield and a spacer, has been developed as an inexpensive and simple heat insulating material without significantly impairing the performance of the multilayer heat insulating member. Using this insulation material makes the installation process much easier than with conventional methods.
In addition, it has become possible to significantly reduce material costs.
However, the heat insulation performance is inferior by an order of magnitude compared to conventional types with good characteristics, and sufficient performance is not necessarily obtained. A conventional example will be explained based on the drawings. FIG. 1 is a diagram schematically showing a cross section of a conventional simple bonded heat insulating material A for a multilayer heat insulating body, in which 1 is a multilayer heat insulating sheet member with low thermal conductivity, and 2 is a fiber constituting it. Element 3 is a metal film with a low emissivity that is deposited thereon by means such as vapor deposition. In this case, the underlying sheet is a fibrous material such as various papers, nonwoven fabrics, fiberglass, and paper. This is because these materials are generally porous and have air permeability, which makes it easy to remove gas between layers when laminated in multiple layers. A detailed analysis of the heat inflow into multilayer insulation using such insulation materials revealed that radiation heat transfer accounts for the majority of the heat transfer factors. This fact indicates that the cause of the poor characteristics is the deterioration of the emissivity compared to the conventional multilayer insulation consisting of a shield and a spacer. The reason for this is that, as can be easily understood from FIG. 1, the metal film has at least asperities depending on the thickness of the cellulose 2, which causes diffuse reflection of the radiant heat. The appearance also has a dull luster. In order to eliminate the conventional drawbacks, the present invention provides a combined heat insulating material for a multilayer heat insulating body in which a radiation shield metal film is attached to one side of a heat insulating sheet material laminated with fibrous materials. It is characterized by providing an intermediate layer with a smooth surface to which it adheres to the metal film, and its purpose is to improve the emissivity of the radiation shield metal film with a simple configuration. The present invention will be explained using the drawings. Figure 2 shows the bonded insulation material B for multilayer insulation of the present invention.
shows. In the figure, 4 is the base insulation sheet,
5 is cellulose constituting the underlying heat insulating sheet 4; 6
7 indicates a metal film for radiation shielding, 7 indicates an intermediate processed layer, and 8 indicates small holes for ventilation. The manufacturing process of the bonded heat insulating material for the multilayer heat insulating body of the present invention is to compensate for the unevenness caused by the cellulose 5 on the underlying heat insulating sheet 4 so as not to damage its porosity, and to make the surface flat. The intermediate processed layer 7 is formed using suitable means and materials. By attaching a radiation shield film thereon, a shield surface with low emissivity can be formed without impairing air permeability. The intermediate processing layer is made of polyester, polyethylene,
It is required to be a polymeric material such as nylon, which has the necessary mechanical elasticity even at extremely low temperatures, and which does not peel off from the base sheet 4 and the shield film 6. When the base sheet 4 is made of polyester, the combination of polyester as the intermediate layer and aluminum as the radiation shielding film will satisfy the above conditions. FIG. 3 is also a conceptual diagram of another embodiment of the present invention. The structure is similar to that shown in FIG. 2, except that the intermediate processed layer 7 is formed by processing the cellulose 5 itself near the surface of the base sheet 4.
That is, when the cellulose material 5 is a polymeric material, the cellulose material near the surface is softened or melted by applying a pressure bonding treatment to the base sheet 4 for a short time using a high-temperature roll system with a smooth surface. It is characterized by forming a smooth surface. When the base sheet material 4 is paper, it is not expected to have the same effect as the above-mentioned polymeric material, but it is expected that a fairly smooth surface can be obtained by processing such as passing it through a hot rolling roll.
However, when the base sheet material is paper or fiberglass, the method of attaching the intermediate layer to obtain a smooth surface is considered suitable. The porosity of the bonded heat insulating material C is effective in exhausting residual gas between layers when multiple layers are laminated. However, if the vent hole is too large, radiant heat will pass through. There is no problem as long as the diameter of the ventilation hole is less than half the short wavelength of the radiant heat that you want to block, and it is generally considered that if the diameter of the equivalent small hole is a few μm or less, it will have little effect. Therefore, the intermediate processing layer 7
Even when forming by adhesion processing, it is desirable that small air permeable pores of several micrometers or less be formed. FIG. 4 shows a bonded heat insulating material D without ventilation holes. In the manufacturing process, the intermediate processed layer 7 is formed on the base sheet 4 using means and materials that compensate for the unevenness caused by the cellulose 5 and make the surface flat. By attaching and processing the radiation shield film 6 thereon, a shield surface with a low emissivity can be formed. As explained above, the present invention makes the surface of the heat insulating sheet material on which the radiation shielding metal film is adhered smooth, thereby making the radiation shielding metal film adhered thereon smooth and achieving high performance. Since it is a bonded heat insulating material with a radiation shield surface formed, it solves the problems of complicated handling and high cost, which were the drawbacks of conventional bonded heat insulating materials for multilayer insulation consisting of a radiation shield film and a spacer. In addition to this, it is possible to significantly improve the poor radiation performance that was a defect of the existing simple bonded insulation material for multilayer insulation shown in Figure 1, which is simply a radiation shielding film attached directly to the insulation sheet. There are advantages. Therefore,
The present invention can provide a high-performance, simple, and inexpensive bonded insulation material for multilayer insulation used in containers for cryogenic refrigerants and other cryogenic equipment. Due to this advantage, the field of application is extremely wide; It produces great effects where it benefits people.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of a cross section of a conventional simplified bonded heat insulating material for a multilayer heat insulating body, FIG. 2 is a cross sectional view of a bonded heat insulating material for a multilayer heat insulating body of the present invention, and FIG. 3 is another embodiment of the present invention. FIG. 4 shows a cross-sectional view of a second embodiment without ventilation holes. 1, 4: heat insulating sheet material, 2, 5: cellulose of heat insulating sheet material, 3, 6: radiation shield metal film,
7: Intermediate processing layer, 8: Breathable small holes.

Claims (1)

[Scope of Claims] 1. A bonded heat insulating material for a multilayer heat insulating body in which a radiation shielding metal film is attached to one side of a heat insulating sheet material laminated with fibrous materials, wherein the heat insulating sheet material and the radiation shielding metal film are bonded together. A bonded heat insulating material for a multilayer heat insulating body, characterized in that an intermediate layer with a smooth surface to which it adheres to the metal film is provided between the layers. 2. The bonded heat insulating material for a multilayer heat insulating body according to claim 1, wherein the intermediate layer is a layer formed by softening or melting the surface of the heat insulating sheet material. 3. The bonded heat insulating material for a multilayer heat insulating body according to claim 1, wherein the intermediate layer is a layer made of a new polymeric material laminated on the heat insulating sheet material.