Flame-retardant heat insulation pipe

Abstract

To provide a flame-retardant heat insulation pipe with high flame retardant performance and heat insulation performance, and good flexibility.SOLUTION: A flame-retardant heat insulation pipe H1 comprises: a pipe body 1 composed of a soft flexible pipe; a foam layer 2 which is a sheet formed by extrusion-molding and foaming of a mixture containing a polyolefin resin and a flame retardant agent, and which is formed of an elastically deformable foam material laminated so as to cover the exterior of the pipe body 1; and a protection layer 3 composed of a protection film which is laminated so as to cover the exterior of the foaming layer 2. A tear strength of the foam material in the extrusion direction of extrusion molding as measured conforming to JIS-K-6767 is equal to or higher than 15 N / cm, and a residual elongation rate of the form material when the pipe is pulled at 500 mm / min until reaching an elongation deformation amount of 100% in the extrusion direction and is left to stand is equal to or lower than 10%. The pipe body 1 and the foam layer 2 are not adhered to each other and are laminated so as to be movable relative to each other in the pipe axis direction of the pipe body 1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a flame-retardant thermal insulation pipe having excellent heat insulation properties, flame retardancy and good flexibility and usable in fields such as semiconductor manufacturing, medical care, food industry and industrial parts. [Background technology]

[0002] Tubes and hoses used in fields such as semiconductor manufacturing, medical care, the food industry, and industrial parts require insulation to prevent the quality of the transported fluids, such as chemical raw materials, from deteriorating due to temperature changes and to prevent energy loss, and therefore insulated pipes covered with foam material are used.

[0003] In addition, there is an increasing need to make devices, factory facilities, and their components flame-retardant in order to prevent damage from spreading when a fire breaks out in a building or factory. Generally, foamed sheets or tubes made of foamed polyolefin resins such as polyethylene are used as the foamed materials for covering the thermal insulation pipes. However, these are flammable, and foamed materials containing flame retardants are used instead to meet the demand for flame retardancy.

[0004] For example, Patent Document 1 discloses a hot and cold water pipe having a circular sheath pipe, a circular insulating material inserted into the sheath pipe, and one circular resin pipe inserted into the insulating material, the outer circumferential surface of the insulating material being covered with a film, the hot and cold water pipe being characterized in that the difference (DC) between the inner diameter D of the sheath pipe and the outer diameter C of the insulating material is 2 to 10 mm, and the outer circumferential surface of the insulating material is an uneven surface. Patent Document 2 discloses a method for producing a polyethylene-based flame-retardant resin foam by supplying a blowing agent to a kneaded material containing a polyethylene-based resin and an organic flame retardant, and extruding and foaming the mixture, the method being characterized in that the melting peak (RTm) of the polyethylene-based resin and the upper limit (ATm) of the melting range of the organic flame retardant have a relationship of 0≦RTm-ATm≦40 as determined by differential thermal analysis. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2007-205551 A [Patent Document 2] JP 2006-199760 A Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, the demand for flame retardancy has been increasing even in semiconductor manufacturing factories, and flame-retardant thermal insulation pipes are also used for the cooling flow passages of various semiconductor manufacturing equipment. For example, semiconductor manufacturing equipment that requires precise operation, such as an electron beam lithography equipment that forms circuit patterns on semiconductor devices, is equipped with a cooling flow passage through which cooling water circulates in order to prevent the operating accuracy from decreasing due to driving heat, and requires insulation to keep the temperature of the cooling water constant and flame retardancy to prevent the spread of fire. These equipment also require flexibility to allow narrow piping even with complex internal structures, and flexible hoses and tubes that are more flexible than the conventional metal pipes and cross-linked polyolefin resin pipes described in Patent Document 1 and Patent Document 2 are preferably used as the inner pipe of the flame-retardant thermal insulation pipe.

[0007] However, when these hoses or tubes are used as inner pipes, they are bent at a much smaller bending radius than conventional flame-retardant thermal insulation pipes, and the foam material, which is pulled strongly around the outer periphery of the bend, stretches and thins, causing problems such as loss of flame retardancy and thermal insulation. In addition, in applications where the flame-retardant thermal insulation pipe is repeatedly bent and stretched, the stretched and thinned foam material does not return to its original shape, and the slack and wrinkles may be damaged by friction with equipment, etc., and fragments of the foam material may be generated as foreign matter. [Means for solving the problem]

[0008] As a result of extensive investigations, the present inventors have found that the above problems can be solved by the flame-retardant thermal insulation pipe of the present invention. The flame-retardant thermal insulation pipe of the present invention comprises a pipe body made of a flexible pipe, a foamed layer made of an elastically deformable foamed material which is in the form of a sheet obtained by extrusion molding and foaming a mixture containing a polyolefin resin and a flame retardant, and which is laminated so as to cover the outside of the pipe body, and a protective layer made of a protective film which is laminated so as to cover the outside of the foamed layer, wherein the foamed material has a tear strength of 15 N / cm or more in the extrusion direction of the extrusion molding measured in accordance with JIS-K-6767, and when a test piece cut into a dumbbell-shaped No. 1 shape as specified in JIS-K-6251 is pulled in the extrusion direction at 500 mm / min until it reaches an elongation deformation of 100% and then allowed to stand, the residual elongation is 10% or less as calculated by the formula (YX) / (X)×100 from the gauge length (X) in the initial state and the gauge length (Y) after being allowed to stand, and the pipe body and the foamed layer are not bonded to each other and are laminated so as to be freely movable relative to each other. Effect of the Invention

[0009] According to the present invention, it is possible to provide a flame-retardant, thermally insulated pipe which is excellent in flame retardancy, heat insulation, and flexibility. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a partially cutaway front view of a flame-retardant thermal insulation pipe according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to Fig. 1. A flame-retardant thermal insulation pipe H1 (see Fig. 1) according to an embodiment of the present invention comprises a pipe body 1 made of a flexible pipe, a foamed layer 2 made of an elastically deformable foaming material in a sheet shape formed by extrusion molding and foaming a mixture containing a polyolefin resin and a flame retardant, laminated so as to cover the outside of the pipe body 1, and a protective layer 3 made of a thermoplastic resin film laminated so as to cover the outside of the foamed layer 2.

[0012] The foamed material constituting the foamed layer 2 has a tear strength of 15 N / cm or more in the extrusion direction during extrusion molding (hereinafter referred to as the "extrusion direction") measured in accordance with JIS-K-6767, and a residual elongation of 10% or less after 100% tension in the extrusion direction. The pipe body 1 and the foamed layer 2 are not bonded, and are laminated so as to be able to move freely relative to each other.

[0013] By setting the tear strength (measured according to JIS-K-6767) of the foam material constituting the foam layer 2 of the flame-retardant thermal insulation pipe H1 of this embodiment to 15 N / cm or more, the flame-retardant thermal insulation pipe H1 has durability without cracks or other damage even in areas where stress is repeatedly applied, such as the outer periphery of bending, and can have long-term flame retardancy and thermal insulation. If the tear strength is less than 15 N / cm, the foam material will crack due to repeated bending and stretching, making it easy to conduct heat, or the internal resin will melt in the event of a fire, making it impossible to prevent the spread of fire, making it impossible to realize a flexible flame-retardant thermal insulation pipe H1. In order to achieve higher durability, the tear strength is preferably 18 N / cm or more, and more preferably 20 N / cm or more.

[0014] In addition, by setting the residual elongation rate of the foaming material constituting the foaming layer of the flame-retardant thermal insulation pipe H1 of this embodiment to 10% or less after 100% tension, the flame-retardant thermal insulation pipe H1 has durability without thickness change or slackness even in areas where stress is repeatedly applied, such as the outer periphery of bending, and can have long-term flame retardancy and thermal insulation. If the residual elongation rate after 100% tension is greater than 10%, the foaming material caused by repeated bending and stretching does not recover from thickness change or slackness, and heat is easily conducted, or damage is caused by friction with equipment and facilities, resulting in the generation of foreign matter, making it impossible to realize a flexible flame-retardant thermal insulation pipe H1. In order to improve durability, the residual elongation rate is preferably 8% or less, and more preferably 5% or less.

[0015] For such applications, the foam material is formed by extrusion molding for the convenience of continuous molding of a sufficient length, but it is generally known that the foam material obtained by extrusion molding has anisotropy in its physical properties due to the bias in the aspect ratio of the bubbles. The foam material constituting the foam layer 2 of the flame-retardant thermal insulation pipe H1 of this embodiment is laminated during molding so that the extrusion direction coincides with the pipe axis direction of the flexible pipe, and the above-mentioned excellent characteristics can be obtained by specifying the tear strength and residual elongation rate in the extrusion direction of the foam material.

[0016] In addition, the flexible pipe constituting the pipe body 1 in such applications is constructed of a material that can be stretched or compressed in the axial direction so as to bend flexibly while maintaining its flow path, and in particular, flexible pipes formed by extrusion molding of plasticized thermoplastic resins or thermoplastic elastomers are remarkably flexible compared to conventional polyolefin resin pipes and the like, and can be used with a very small bending radius. It is generally known that for the same pipe diameter, the smaller the bending radius, the greater the elongation rate on the outer periphery of the bend, and therefore the greater the stress applied to the foamed material laminated on the outside of the flexible pipe. The flame-retardant thermal insulation pipe H1 of this embodiment can obtain the above-mentioned excellent characteristics even when used with a very small bending radius compared to conventional flame-retardant thermal insulation pipes, by specifying the tear strength and residual elongation rate in the extrusion direction of the foamed material constituting the foamed layer 2.

[0017] Furthermore, by laminating the pipe body 1 and the foamed layer 2 of the flame-retardant thermal insulation pipe H1 of this embodiment so that they are not bonded and can freely move relative to each other in the axial direction of the pipe body 1, it is possible to prevent the foamed material from being subjected to stress due to expansion and compression of the pipe body 1, and it is possible to prevent cracks and wrinkles in the foamed material due to repeated bending and stretching, thereby making it possible to provide the flame-retardant thermal insulation pipe H1 with long-term flame retardancy and thermal insulation properties.

[0018] If the pipe body 1 and the foam layer 2 of the flame-retardant thermal insulation pipe H1 are bonded, the pipe body 1 and the foam layer 2 are repeatedly stretched and compressed together by repeated bending and stretching, and cracks and wrinkles occur in the foam material, making it impossible to realize a flexible flame-retardant thermal insulation pipe H1. Even if the pipe body 1 and the foam layer 2 of the flame-retardant thermal insulation pipe H1 are not bonded, but are attached to the pipe body with tape or heat-shrink tubing so that they do not move freely, the foam material follows the expansion and compression of the pipe body and is subjected to stress, causing similar problems and making it impossible to realize a flexible flame-retardant thermal insulation pipe H1. When connecting the end of the pipe body 1 of the flame-retardant thermal insulation pipe H1 to another device using a joint or the like, the pipe body 1 and the foam layer 2 are not bonded, so they can be easily removed, which is advantageous in construction work.

[0019] The clearance between the pipe body 1 and the foamed layer 2 of the flame-retardant thermal insulation pipe H1 of this embodiment can be determined by the ratio (B) / (A) of the outer circumference (A) of the pipe body 1 to the inner circumference (B) of the foamed layer 2. (B) / (A) is preferably in the range of 1.01 to 1.15, and more preferably 1.05 to 1.10. When the clearance is within this range, the pipe body 1 and the foamed layer 2 can move freely relative to each other, there is little excess foaming material that can cause slack or wrinkles, and the productivity when laminating the foamed layer 2 is good.

[0020] The flexible tube constituting the tube body 1 of this embodiment is formed by extrusion molding of a mixture of either a plasticized thermoplastic resin or a thermoplastic elastomer, or a combination thereof, and tubes of various structures can be used as required.

[0021] Examples of the plasticized thermoplastic resin include vinyl chloride resin, urethane resin, and polyamide resin.

[0022] Examples of the thermoplastic elastomer include silicone, urethane, nitrile rubber, styrene-butadiene rubber, chloroprene, phosphazene, fluoroelastomer, perfluoroelastomer, perfluoropolyether elastomer, methylsilicone, phenylsilicone, fluorosilicone, or a combination thereof.

[0023] Examples of the structure of the flexible tube include a single-layer tube made of a single material, a multi-layer tube in which a plurality of layers with different physical properties are laminated, and a hose provided with a reinforcing material between layers.

[0024] Examples of the reinforcing material include multiple or single braids made of polyester, PET, nylon (registered trademark), aramid fibers, etc.; monofilaments made of olefin resin, polyester resin, etc.; multifilaments woven from thin monofilaments (single fibers); flat yarns (or tape yarns) made of tape-shaped threads; metal wires made of stainless steel, etc., or coils made of hard materials similar to stainless steel; and combinations of these.

[0025] The foam material constituting the foam layer 2 in this embodiment is formed into a sheet-like shape by extruding a mixture containing a polyolefin resin and a flame retardant, and is laminated so as to cover the outside of the pipe body 1.

[0026] Examples of the polyolefin resin include polyethylene resin and polypropylene resin.

[0027] Examples of the polyethylene resin include low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymers, ethylene-acrylate copolymers such as ethylene-methyl acrylate copolymers and ethylene-ethyl acrylate copolymers, ethylene-methacrylate copolymers such as ethylene-methyl methacrylate copolymers and ethylene-ethyl methacrylate copolymers, and combinations thereof.

[0028] Examples of the polypropylene resin include homopolypropylene, a propylene-α-olefin copolymer containing 50% by mass or more of propylene, and combinations thereof.

[0029] Examples of the flame retardant include halogen compounds containing bromine or chlorine, phosphorus compounds, hydrated compounds, zinc borate, etc. In addition, a flame retardant assistant that improves flame retardancy when used in combination with the flame retardant can be used. Examples of the flame retardant assistant include antimony trioxide, antimony pentoxide, zinc stannate, zinc sulfide, zinc borate, molybdenum compounds, iron oxides, etc. Because of their cost and excellent compatibility with polyolefin resins, halogen compounds are preferred as flame retardants, and antimony trioxide and antimony pentoxide are preferred as flame retardant assistants because of their large synergistic effect with halogen compounds.

[0030] Examples of methods for producing the foam include a method in which a molten resin mixed with a volatile foaming agent consisting of a linear or branched aliphatic hydrocarbon or an alicyclic hydrocarbon is extruded into a sheet or tube, and a method in which a molten resin mixed with an organic or inorganic thermally decomposable foaming agent is extruded into a sheet, which is then crosslinked by irradiating with ionizing radiation, and the crosslinked sheet is further heated to cause foaming.

[0031] The foam has sufficient thermal insulation properties and has an apparent density of 0.065 g / cm 3 It is preferable that the foaming ratio is 0.05 g / cm or less (approximately 15.4 times or more in terms of foaming ratio). 3 It is more preferable that the expansion ratio is about 20 times or more.

[0032] Examples of methods for laminating the foam layer 2 in this embodiment include a method in which a foam material is extruded into a tubular shape to cover the outside of the pipe body 1 and then laminated, and a method in which a foam material that has been extruded into a sheet shape in advance is rolled so as to cover the outside of the pipe body 1, and the butted end faces are heat-sealed to form a tubular shape and then laminated.

[0033] In order for the foam layer 2 to have sufficient flame retardancy, heat insulation, and flexibility, the thickness of the foam layer 2 is preferably 1 to 15 mm, and more preferably 3 to 10 mm.

[0034] Examples of methods for laminating the protective layer 3 in this embodiment include a method in which a protective film made of a thermoplastic resin or a thermoplastic elastomer is formed by a T-die method or an inflation extrusion method, etc., is wrapped around the outside of the foamed layer 2 to cover it, and a method in which the protective film is formed directly on the surface of a foamed material extruded into a sheet shape by an extrusion lamination method in advance.

[0035] The flame-retardant thermal insulation pipe H1 of this embodiment can be used as piping for various chemical raw materials, medicines, air, various gases, water, etc. in the fields of food, beverages, semiconductor manufacturing, medical equipment, chemistry, and other industries. It is particularly suitable as a hose for cooling water.

[0036] The flame-retardant thermal insulation pipe H1 according to the present embodiment described above can provide the following effects: In other words, the flame-retardant thermal insulation pipe H1 of the present embodiment is flexible, has excellent flame retardancy and thermal insulation properties, and does not lose its flame retardancy and thermal insulation properties over a long period of time because the foamed layer 2 is not damaged, even when used with a very small bending radius or when repeatedly bent and stretched, compared to conventional flame-retardant thermal insulation pipes, and can be used as a pipe with a much longer life than conventional products.

[0037] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present invention. EXAMPLES

[0038] The present invention will be described in more detail below with reference to examples and comparative examples. In the examples and comparative examples, the physical properties of the foaming material used in the flame-retardant thermal insulation pipe were measured by the following method. The foaming material was prepared by melt-kneading a mixture of 15 parts by weight of a bromine-based flame retardant, 2 parts by weight of antimony trioxide, and 1 part by weight of titanium dioxide with respect to 100 parts by weight of polyethylene, and then extruding the mixture from the die of an extrusion molding machine to foam the mixture and form a foamed sheet having a thickness of 5 mm. In addition, a polyethylene resin was melt-extruded onto the surface of the foamed sheet by extrusion lamination to form a protective layer having a thickness of 85 μm.

[0039] A commercially available flexible hose was used for the flexible tube, and in Examples 1 to 6 and Comparative Examples 1 to 4, a Toyolon (registered trademark) hose manufactured by Toyox Corporation (inner diameter: 19 mm, outer diameter: 26 mm, main material: soft polyvinyl chloride, reinforcing material: polyester thread) was used as the tube body, and in Example 7, a Hybrid Toyolon (registered trademark) hose manufactured by Toyox Corporation (inner diameter: 19 mm, outer diameter: 26 mm, main material: soft polyvinyl chloride, reinforcing material: special PET resin and polyester thread) was used as the tube body. The foamed sheet was rolled and the butted end faces were heat welded together so that the extrusion direction of the molded foamed sheet matched the axial direction of the flexible tube, to form a tubular foam layer and protective layer covering the outside of the flexible tube.

[0040] 1. Tear strength The tear strength was measured by conducting a test in accordance with JIS-K-6767.

[0041] 2. Residual elongation The residual elongation was determined by the following procedures (i) to (iv). (i) The foamed sheet was cut into a dumbbell shape No. 1 as specified in JIS-K-6251 to prepare a test specimen, and the distance between the gauge lines in the initial state was designated as (X). The test specimen was cut so that the longitudinal direction (tensile direction) coincided with the extrusion direction of the foamed sheet. (ii) The test piece was pulled vertically from bottom to top at 500 mm / min in an environment of 23°C and 50 RH% humidity using a tensile testing machine (Tensilon RTF235 manufactured by A&D Corporation) until it reached an elongation deformation of 100% (gauge length = 80 mm), and then left in that state for 30 seconds. (iii) After the test piece was elongated, it was removed from the tensile tester and allowed to stand for 1 minute in an environment of a temperature of 23° C. and a humidity of 50 RH%, and the gauge length (Y) was measured. (iv) Residual elongation was calculated from the gauge length in the initial state (X) and the gauge length after standing (Y) using the following formula. Residual elongation rate (%) = (YX) / (X) x 100

[0042] In Examples 1 to 7, the foam material constituting the foam layer has a tear strength of 15 N / cm or more and a residual elongation rate of 9% or less, and the pipe body and the foam layer are laminated so as to be non-bonded and move freely relative to each other. In Comparative Example 1, the foam material constituting the foam layer has a tear strength of less than 15 N / cm. In Comparative Examples 2 and 3, the foam material constituting the foam layer has a residual elongation rate of more than 10%. In Comparative Example 4, an adhesive is applied to the inner surface of the foam material constituting the foam layer, and the pipe body and the foam material are bonded together so that they do not move freely relative to each other. The following 1 shows the characteristics and physical properties of Examples 1 to 6 and Comparative Examples 1 to 4.

[0043] [Table 1]

[0044] (Measurement results) The state of the foamed material after carrying out the following operations (i) to (iii) on each of the flame-retardant thermal insulation pipes of Examples 1 to 7 and Comparative Examples 1 to 4 was checked and each of the items of "breakage," "thickness," and "slackness" was evaluated. The evaluation results are shown in Table 2 below. (i) In an environment of 23°C, the flame-retardant thermal insulation pipe was bent so as to form a circle with a diameter ratio of 1:1 in two perpendicular directions, and the minimum bending was reached when the outer diameter was flattened to 90% of the normal diameter, and the pipe was left in that state for 30 seconds. The radius of the circle drawn by the flame-retardant thermal insulation pipe at the minimum bending (minimum bending radius) was 95 mm for Examples 1 to 6 and Comparative Examples 1 to 4, and 90 mm for Example 7. (ii) After bending the flame-retardant thermal insulation pipe, it was fully extended to its original state and then left in that state for 30 seconds. (iii) The above steps (i) and (ii) were repeated 200 times without any time interval, and the foam material was then cut open along the axial direction of the tube to check the condition of the foam material.

[0045] <Tear> The inner surface of the foam material was visually inspected for cracks and rated according to the following criteria. ○: No cracks on the inner surface. △: There is a crack on the inner surface, and the depth is less than 30% of the original foam thickness. ×: There is a crack on the inner surface, and the depth of the crack is 30% or more of the original foam thickness.

[0046] <Thickness> The thickness of the expanded and thinned portion of the foam material was measured and evaluated according to the following criteria. ○: The thickness of the thinned area is 90% or more of the original thickness. △: The thickness of the thinned area is between 70% and 90% of the original thickness. ×: The thickness of the thinned area is less than 70% of the original thickness.

[0047] <Slack> The width of the cut-open foam material in the direction perpendicular to the axial direction of the tube was measured and evaluated according to the following criteria. Good: The width of the foam is less than 110% of the original width. △: The width of the foam is between 110% and 120% of the original width. ×: The width of the foam is more than 120% of the original width.

[0048] [Table 2]

[0049] As shown in Table 2, the flame-retardant thermal insulation pipes of the Examples did not show any breaks in the foam material, no changes in thickness, and no slack, compared to Comparative Examples 1 to 4. These evaluation results show that the flame-retardant thermal insulation pipes of the Examples do not lose their flame retardancy or thermal insulation properties even when repeatedly bent at unprecedentedly small bending radii over a long period of time, and there is no risk of foreign matter being generated due to damage to the foam material.

[0050] In Comparative Example 1, the tear strength was as low as 13 N / cm, and therefore the compression and tension caused by repeated bending caused cracks in the foam material, resulting in a decrease in flame retardancy. In Comparative Examples 2 and 3, the residual elongation was large at 12% or more, and the foam material, which was pulled strongly especially on the outer periphery of the bend, did not return to its original shape after elongation, and the foam material became larger relative to the pipe body, causing slack and wrinkles that could cause damage to the flame-retardant thermal insulation pipe. In particular, in Comparative Example 3, thin-walled parts occurred in the foam material, and the thermal insulation properties were reduced.

[0051] In Comparative Example 4, the pipe body and the foam layer were bonded together and did not stretch or sag, but because they could not move freely relative to each other, the effects of compression and tension due to repeated bending were greater than in the other Examples and Comparative Examples, causing cracks in the foam material and reducing flame retardancy.

[0052] As a result, the flame-retardant thermal insulation pipe of the present invention does not lose its flame retardancy or thermal insulation properties even when repeatedly bent at unprecedentedly small bending radii over a long period of time, and there is no risk of foreign matter being generated due to damage to the foam. Therefore, the pipe can be suitably used in equipment that requires facilities or narrow piping, and in applications requiring repeated bending and straightening, in the food, beverage, semiconductor manufacturing, medical equipment, chemical and other industries. [Explanation of symbols]

[0053] 1 Tube body 2 Foam layer 3 Protective layer H1 Flame retardant thermal insulation pipe

Claims

1. A tube body made of a flexible tube; a foam layer formed of an elastically deformable foam material in a sheet shape obtained by extruding a mixture containing a polyolefin resin and a flame retardant and laminated so as to cover the outside of the pipe body; A flame-retardant thermal insulation pipe having a protective layer made of a protective film laminated so as to cover the outer side of the foam layer, The foamed material has a tear strength of 15 N / cm or more in the extrusion direction of the extrusion molding measured in accordance with JIS-K-6767, and when a test piece cut into a dumbbell-shaped No. 1 shape as specified in JIS-K-6251 is pulled in the extrusion direction at 500 mm / min until it reaches an elongation deformation of 100% and then left to stand, the residual elongation calculated from the gauge length (X) in the initial state and the gauge length (Y) after standing to stand by the formula (Y-X) / (X) x 100 is 10% or less; and the pipe body and the foamed layer are not bonded to each other and are laminated so as to be freely movable relative to each other. Flame retardant thermal insulation pipe.

2. 2. The flame-retardant thermal insulation pipe according to claim 1, characterized in that the ratio (B) / (A) of the outer circumference (A) of the pipe body to the inner circumference (B) of the foamed layer satisfies 1.05 to 1.

1.

3. 3. The flame-retardant thermally insulated pipe according to claim 2, wherein the flexible pipe is a soft flexible pipe formed by extrusion molding of a mixture of either a plasticized thermoplastic resin, a thermoplastic elastomer, or a combination thereof.

4. The flame-retardant thermal insulation pipe according to any one of claims 1 to 3, which is used for cooling water.

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