JPH0540388Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] This invention can be used to transfer various fluids over a wide temperature range, from cryogenic fluids such as liquid nitrogen to high-temperature fluids such as high-temperature oil. Regarding hoses that can be used.

[Conventional technology]

Recently, the development of materials that exhibit superconductivity at liquid nitrogen temperatures (boiling point -196°C) is progressing rapidly. When using such superconducting materials, it is necessary to constantly cool the material formed into cotton material or thin film with liquid nitrogen.
A closed system is adopted due to running costs and other considerations. In this case, after the liquid nitrogen cools the superconducting material, it returns to the refrigerator, where it is cooled again and circulated. Here, a metal pipe such as stainless steel is used as the liquid nitrogen piping material, and the metal pipe is covered with a heat insulating material to block heat from the outside.

[The problem that the idea aims to solve]

However, since the metal pipes mentioned above lack flexibility, it is difficult to pipe them compactly, and in terms of heat retention, since they are made of metal, it is necessary to coat them with a thick insulation material, which increases piping costs, running costs, etc. There are some problems from this point of view. Therefore, the use of hoses as a piping material to compensate for these drawbacks of metal pipes was considered, but conventional hoses are made of plastic such as polyamide or rubber, so they cannot be used at temperatures such as liquid nitrogen. At extremely low temperatures, the elasticity of any material decreases significantly, and the flexibility that is the advantage of these hoses is lost, and the material itself becomes brittle, making it unusable in terms of mechanical strength. However, there are still no hoses capable of transporting cryogenic fluids that have been developed.

In view of these problems of the prior art, the object of this invention is to provide a hose that is capable of transporting cryogenic fluid and has excellent flexibility and heat retention.

[Means to solve the problem]

In order to achieve the above object, the hose according to this invention has a structure including an inner tube made of a thermoplastic fluororesin and a heat insulating layer made of a foamed thermoplastic fluororesin integrally provided on the outside of the inner tube. do.

[Action]

The hose of this invention has an inner tube made of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP), etc. whose minimum operating temperature is -250℃ or less. This inner layer tube is covered with a heat insulating layer made of foamed thermoplastic fluororesin such as PFA or FEP, which has a minimum operating temperature of -250℃ or less, similar to the inner layer tube. Because of this structure, it has excellent mechanical properties at extremely low temperatures, and the presence of the foamed heat insulating layer thermally isolates the inner tube from the outside, resulting in extremely good heat retention. Therefore, when a cryogenic fluid such as liquid nitrogen is passed through the hose, low-temperature embrittlement does not occur in the material constituting the hose, and mechanical strength is maintained satisfactorily. Furthermore, since the heat insulating layer made of the foamed thermoplastic fluororesin has a high heat insulating effect, it can effectively prevent the temperature of the internal fluid from rising due to the outside temperature. Therefore, this hose is particularly suitable as a piping material used in equipment in which cryogenic fluid is distributed, such as superconducting equipment that operates while being cooled with liquid nitrogen.

Furthermore, the heat insulating layer made of foamed thermoplastic fluororesin is flexible and has a suitable shape retention property, and is made of the same or similar material as the inner tube, and is heated during extrusion to form a heat insulating layer on the outer circumferential surface of the inner tube. Because they are joined and integrated, they have the effect of improving the kink resistance of the inner tube without adversely affecting the flexibility of the hose. Therefore, it is possible to reliably cope with bent piping without buckling and to reduce the piping space, which is extremely convenient since there is a high degree of freedom in piping.

〔Example〕

The figure is a perspective view with the end cut away showing an embodiment of the hose 1 according to this invention. This hose 1
is on the outer periphery of the inner layer tube 2 made of PFA,
A heat insulating layer 3 made of foamed FEP is bonded and integrated with the outer peripheral surface of the inner tube 2, and furthermore, in the embodiment, an intermediate layer 4 made of FEP and a heat insulating layer 5 made of foamed polyurethane are provided on the outside of the heat insulating layer 3. and a protective outer cover 6 made of soft polyurethane are sequentially provided.

In this case, as the foamed thermoplastic fluororesin forming the heat insulating layer 3, foamed PFA may be used instead of foamed FEP, and from the viewpoint of bonding strength to the inner layer tube 2, it is preferable to use the same material. In order to form these heat insulating layers 3, for example, chemical foaming using a foaming agent or physical foaming in which a gas such as Freon is blown into a molten fluororesin to foam it, etc.
It can be formed by known foaming means. Note that in order to integrate the inner tube 2 and the heat insulating layer 3, two extruders are used instead of extruding the heat insulating layer 3 in a separate process, and one extruder is equipped with a foam containing a foaming agent. It is preferable to put the base resin pellets into the extruder and at the same time, put the fluororesin pellets containing no foaming agent into the other extruder, and coextrude both in a concentric manner to form an integral product.

In addition, the material for the inner tube 2 is PFA.
In addition, it is of course possible to use FEP, etc.
This material, together with the material of the heat insulating layer 3, is appropriately selected depending on the type of fluid to be transferred.

As described above, in the hose 1 according to the present invention, the inner layer tube 2 is made of a fluororesin whose mechanical properties do not deteriorate much even at extremely low temperatures of -250°C, and this inner layer tube is made of a similar thermoplastic fluororesin. Because it is integrally surrounded by a heat insulating layer formed by foaming, it maintains its flexibility even at extremely low temperatures, and can be used, for example, to transfer cryogenic fluids such as liquid nitrogen or liquefied natural gas. Optimal.

In addition, in the embodiment, an intermediate layer 4, a heat insulating layer 5, and a protective jacket 6 are further provided outside the heat insulating layer 3, but these layers are not the essence of the present invention.
It is not necessarily necessary to provide it. That is, the hose 1 according to the present invention has a heat insulating layer 3 made of a foamed fluororesin having excellent mechanical properties at low temperatures in its structure.
exists, so by increasing the thickness of the heat insulating layer 3, the outer heat insulating layer 5 can be omitted. Also,
If the outer circumferential surface of the heat insulating layer 3 is made non-porous by heat treatment, the intermediate layer 4 and the protective jacket 6 can be omitted.

In the hose 1 of the present invention, the foamed fluororesin 3 alone has a sufficient heat insulating effect, so even if cryogenic fluid is passed through the inner tube 2, the outer peripheral surface of the heat insulating layer 3 will not be as cold. No. Therefore, as shown in the examples, although it is significantly inferior to foamed fluororesin in terms of mechanical properties at low temperatures,
It is possible to use other foamed plastic materials, such as foamed polyurethane, which is inexpensive and has excellent flexibility. In this case, by reducing the thickness of the insulation layer 3 on the outside of the inner tube 2 to a certain extent, the flexibility of the hose can be reduced. Further improvement.

In addition, the hose 1 according to the present invention has an inner tube 2.
The heat insulating layer 3 is made of the same or similar thermoplastic fluororesin, and these fluororesins have excellent heat resistance properties not found in other resins, so they are suitable not only for cryogenic fluids but also for cryogenic fluids. It can also be applied to transfer high temperature fluids of 200℃ or higher.

[Effect of idea]

As explained above, according to this invention, the hose is made up of an inner tube made of fluororesin with excellent temperature characteristics, and a heat insulating layer made of foamed fluororesin is integrally provided on the outside, which is not possible with conventional hoses. It can be used to transfer cryogenic fluids such as liquid nitrogen or liquefied natural gas, and is resistant to buckling and has good flexibility, so it has a high degree of freedom when piping, and is compact with a small bending radius. Piping becomes possible.

In addition, the fluororesin that makes up the hose has excellent heat resistance, and the outside of the inner tube is covered with a heat insulating layer made of a similar resin foam.
Even when applied to high-temperature fluids of 200℃ or higher, the hose can be safely transferred without damage, making it an extremely versatile hose.

Note that this invention is not limited to the above-mentioned embodiments; for example, a braided layer or a spirally wound layer made of metal wire, synthetic fiber thread, glass fiber thread, etc. for pressure-resistant reinforcement may be provided on the outside of the heat insulating layer of the hose. It is of course possible to make various changes within the technical concept of this invention.

[Brief explanation of the drawing]

The figure is a perspective view with the end cut away showing an embodiment of the hose according to this invention. 2... Inner layer tube, 3, 5... Heat insulation layer, 4...
...middle layer, 6...protective outer covering.

Claims (1)

[Scope of utility model registration request] an inner tube made of thermoplastic fluororesin;
The hose includes a heat insulating layer made of a foamed thermoplastic fluororesin that is integrally provided on the outside of the inner tube.