JP2019151765A - Manufacturing method of crosslinked fluorine resin tube, crosslinked fluorine resin tube, and heat recovery article - Google Patents

Abstract

To provide a manufacturing method of a crosslinked fluorine resin tube capable of manufacturing the crosslinked fluorine resin tube sufficiently high in abrasion resistance.SOLUTION: The manufacturing method of a crosslinked fluorine resin tube has a coating process for coating inside of a cylindrical body with a resin composition containing a fluorine resin, an irradiation process for irradiating the cylindrical body after the coating process with radiation ray under low oxygen atmosphere at a temperature of melting point of the fluorine resin or higher, and a separation process for separating a molded body from the cylindrical body after the irradiation process, the fluorine resin is a tetrafluoroethylene-perfluoro alkyl vinyl ether copolymer or a tetrafluoroethylene-hexafluoropropylene copolymer, and the cylindrical body contains aluminum or nickel on a surface layer in an inner side.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a crosslinked fluororesin tube, a crosslinked fluororesin tube, and a heat recovery article.

  Fluoropolymers such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polytetrafluoroethylene (PTFE), etc. are heat resistant, slippery, mechanical Excellent in mechanical strength. For this reason, the use of heat-shrinkable tubes containing these fluororesins has been studied today.

  However, among the above-mentioned fluororesins, PFA and FEP have low melt viscosity. Therefore, when heated to the melting point or higher, they are melt-deformed and it is difficult to maintain a desired shape. Therefore, it has been proposed today to irradiate these fluororesins with radiation at a temperature below the melting point (see Patent Document 1 and Non-Patent Document 1).

Japanese Patent Laid-Open No. 2006-135862

Hitoshi Imamura: Molding, 29 (9), 336 (2017)

  However, when the method described in the above publication is used, the cross-linking of the fluororesin does not proceed or becomes insufficient, so that it is difficult to sufficiently enhance the wear resistance of the molded product. That is, according to the conventional method, it is difficult to promote the crosslinking of the fluororesin and maintain the wear resistance while maintaining the desired shape.

  The present invention has been made based on such circumstances, and a method for producing a crosslinked fluororesin tube capable of producing a crosslinked fluororesin tube having a sufficiently high wear resistance, and a crosslinked fluorine having a sufficiently high wear resistance. It is an object to provide a resin tube and a heat recovery article.

  A method for producing a crosslinked fluororesin tube according to an aspect of the present invention, which has been made to solve the above-described problems, includes an application step of applying a resin composition containing a fluororesin to an inner surface of a cylindrical body, and a step after the application step. An irradiation step of irradiating the cylindrical body with radiation at a temperature equal to or higher than a melting point of the fluororesin, and a separation step of separating the molded body from the cylindrical body after the irradiation step; , Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or tetrafluoroethylene-hexafluoropropylene copolymer, and the cylindrical body contains aluminum or nickel in the surface layer on the inner surface side.

  A cross-linked fluororesin tube according to another embodiment of the present invention, which has been made to solve the above problems, is based on a cross-linked fluororesin, and the fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. Or it is a tetrafluoroethylene-hexafluoropropylene copolymer, and a heat shrinkage rate is 30% or more.

  A heat recovery article according to another embodiment of the present invention made to solve the above problems includes the crosslinked fluororesin tube and a primer layer laminated on at least one surface of the crosslinked fluororesin tube.

  The method for producing a crosslinked fluororesin tube of the present invention can produce a crosslinked fluororesin tube having sufficiently high wear resistance. Further, the crosslinked fluororesin tube and the heat recovery article of the present invention have sufficiently high wear resistance.

It is a flowchart which shows the manufacturing method of the crosslinked fluororesin tube which concerns on one Embodiment of this invention. It is a typical perspective view which shows the application | coating process of the manufacturing method of the crosslinked fluororesin tube of FIG. It is a typical perspective view which shows the irradiation process of the manufacturing method of the crosslinked fluororesin tube of FIG. It is a schematic plan view which shows the isolation | separation process of the manufacturing method of the crosslinked fluororesin tube of FIG. It is a flowchart which shows the manufacturing method of the crosslinked fluororesin tube which concerns on embodiment different from the manufacturing method of the crosslinked fluororesin tube of FIG. It is a typical perspective view which shows the crosslinked fluororesin tube which concerns on one Embodiment of this invention. It is a typical perspective view showing the heat recovery article concerning one embodiment of the present invention.

[Description of Embodiment of the Present Invention]
First, embodiments of the present invention will be listed and described.

  The method for producing a cross-linked fluororesin tube according to one aspect of the present invention includes a coating step of applying a resin composition containing a fluororesin to the inner surface of a cylindrical body, a low oxygen atmosphere on the cylindrical body after the coating step, and An irradiation step of irradiating radiation at a temperature equal to or higher than the melting point of the fluororesin; and a separation step of separating the molded body from the cylindrical body after the irradiation step, wherein the fluororesin is tetrafluoroethylene-perfluoroalkyl vinyl ether It is a copolymer or a tetrafluoroethylene-hexafluoropropylene copolymer, and the cylindrical body contains aluminum or nickel in the surface layer on the inner surface side.

  The method for producing the cross-linked fluororesin tube is such that a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or a tetrafluoroethylene-hexafluoropropylene copolymer is applied to the inner surface of the cylindrical body. By irradiating radiation in an oxygen atmosphere and at a temperature equal to or higher than the melting point of the fluororesin, the fluororesin can be sufficiently crosslinked. Moreover, since the said cylindrical body contains aluminum or nickel in the surface layer of an inner surface side, the manufacturing method of the said crosslinked fluororesin tube was bridge | crosslinked by cooling this fluororesin below to melting | fusing point after bridge | crosslinking of the said fluororesin. The molded body (tube body) containing the fluororesin can be separated from the cylindrical body. Accordingly, the method for producing the crosslinked fluororesin tube can produce a crosslinked fluororesin tube having sufficiently high wear resistance.

  The upper limit of the arithmetic average roughness Ra of the inner surface of the cylindrical body is preferably 100 μm. Thus, by setting the arithmetic average roughness Ra of the inner surface of the cylindrical body to the upper limit or less, the molded body can be easily separated from the cylindrical body in the separation step.

  The melt flow rate at 372 ° C. of the fluororesin is preferably 0.5 g / 10 min or more. Thus, the applicability | paintability of the said resin composition can be improved because the melt flow rate in 372 degreeC of the said fluororesin is more than the said minimum.

  The method for producing the cross-linked fluororesin tube may further include a diameter expanding step for expanding the molded body after the separation step and a cooling step for cooling the molded body after the diameter expanding step. Thus, the cross-linked fluororesin having a high thermal contraction rate is further provided by further including a diameter expansion step for expanding the molded body after the separation step and a cooling step for cooling the molded body after the diameter expansion step. The tube can be manufactured easily and reliably.

  A cross-linked fluororesin tube according to another embodiment of the present invention comprises a cross-linked fluororesin as a main component, and the fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or tetrafluoroethylene-hexafluoro. It is a propylene copolymer and has a heat shrinkage rate of 30% or more.

  The cross-linked fluororesin tube has sufficiently high wear resistance because it contains a cross-linked tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or tetrafluoroethylene-hexafluoropropylene copolymer as a main component.

The storage elastic modulus at 350 ° C. of the crosslinked fluororesin tube is preferably 1.0 × 10 ⁵ Pa or more. Thus, when the storage elastic modulus at 350 ° C. is not less than the above lower limit, the dimensional stability of the crosslinked fluororesin tube can be sufficiently enhanced.

  The limit PV value of the crosslinked fluororesin tube is preferably 200 MPa · m / min or more. Thus, the abrasion resistance of the said crosslinked fluororesin tube can be improved more because a limit PV value is more than the said minimum.

  The lower limit of the light transmittance of the crosslinked fluororesin tube is preferably 90%. Since the cross-linked fluororesin tube is excellent in heat resistance, it can be used as a protective tube for illumination members such as near-ultraviolet LEDs and laser illumination elements. In this case, when the light transmittance is equal to or higher than the lower limit, it is possible to sufficiently suppress a decrease in the light amount of the illumination member.

  A heat recovery article according to another embodiment of the present invention includes the crosslinked fluororesin tube and a primer layer laminated on at least one surface of the crosslinked fluororesin tube.

  Since the heat recovery article includes the crosslinked fluororesin tube, the wear resistance is sufficiently high.

  In the present invention, the “melting point” refers to a melting point peak temperature measured by a differential scanning calorimeter (DSC) in accordance with JIS-K7121: 2012 “Plastic transition temperature measurement method”. “Arithmetic average roughness Ra” means a value measured with a cutoff value (λc) of 0.25 mm and an evaluation length (l) of 10 mm in accordance with JIS-B0601: 2001. The “main component” refers to a component having the highest content ratio in terms of mass, for example, a component having a content of 50% by mass or more. “Heat shrinkage” refers to the rate of change from the diameter before heating based on the diameter after shrinkage heated at 350 ° C. “Light transmittance” is a transmittance of light having a wavelength of 400 nm measured in accordance with JIS-K7375: 2008 “Plastic—How to obtain total light transmittance and total light reflectance” in a sheet body having a thickness of 1 mm. Say. “Melt flow rate” refers to a value measured under the condition of a load of 21.6 kg in accordance with JIS-K-7210: 2014 using an extrusion plastometer. “Storage elastic modulus” is a term (real number term) constituting a complex elastic modulus representing the relationship between stress and strain when sinusoidal vibration strain is applied to a viscoelastic body. ). “Limit PV value” is measured in accordance with JIS-K7218: 1986 “Plastic sliding wear test method”, measured under two conditions: constant speed at 25 m / min and constant load at 10 MPa. Of the measured values, the lower measured value. Specifically, a metal (S45C) cylinder (outer diameter / inner diameter = 11.5 / 7.4) as a counterpart material is placed on the test piece, and a predetermined load (surface pressure: P) is obtained under dry lubrication conditions. ), The test piece is rotated at a predetermined speed (rotational speed: V), and the dynamic friction coefficient is measured by the reaction torque generated in the cylinder. At this time, one of the speed (V) and the load (P) is made constant, and the lower measured value (P · V value at which abrupt wear occurs) obtained by changing the other.

[Details of the embodiment of the present invention]
Preferred embodiments of the present invention will be described below with reference to the drawings.

[First embodiment]
<Method for producing crosslinked fluoropolymer tube>
As shown in FIG. 1, the method for producing the cross-linked fluororesin tube includes an application step of applying a resin composition containing a fluororesin to the inner surface of the cylindrical body, and a low oxygen atmosphere in the cylindrical body after the application step. And the irradiation process which irradiates a radiation at the temperature more than melting | fusing point of the said fluororesin, and the isolation | separation process which isolate | separates a molded object from the said cylindrical body after the said irradiation process. The fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) or a tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Moreover, the said cylindrical body contains aluminum or nickel in the surface layer of an inner surface side. The “surface layer on the inner surface side” means a layer exposed on the outermost surface on the inner surface side.

  The method for producing the cross-linked fluororesin tube is such that the fluororesin (PFA or FEP) is applied to the inner surface of the tubular body, and the tubular body is subjected to a low oxygen atmosphere at a temperature equal to or higher than the melting point of the fluororesin. By irradiation with radiation, the fluororesin can be sufficiently crosslinked. In the method for producing the crosslinked fluororesin tube, the radiation transmitted through the cylindrical body is irradiated with radiation from the outer surface side of the cylindrical body while heating the fluororesin to a temperature equal to or higher than the melting point. Is irradiated. In the method for producing the crosslinked fluororesin tube, the fluororesin is irradiated with radiation in a state where the outer surface side of the resin composition applied in the application step is supported by the cylindrical body. The fluororesin can be sufficiently crosslinked while maintaining the above. Moreover, since the said cylindrical body contains aluminum or nickel in the surface layer of an inner surface side, the manufacturing method of the said cross-linked fluororesin tube has cooled the said fluororesin below to melting | fusing point after bridge | crosslinking the said fluororesin cross-linked. The molded body (tube body) to be included can be separated from the cylindrical body. That is, since the linear expansion coefficient of the fluororesin is larger than the linear expansion coefficient of the forming material of the cylindrical body, the thermal contraction of the cylindrical body and the molded body is achieved by cooling the fluororesin to a melting point or less after crosslinking. By utilizing the difference in rate, the molded body can be easily separated from the cylindrical body. Accordingly, the method for producing the crosslinked fluororesin tube can produce a crosslinked fluororesin tube having sufficiently high wear resistance.

(Coating process)
As shown in FIG. 2, in the application step, a resin composition containing PFA or FEP is applied to the inner surface of the cylindrical body 1. In the application step, the resin composition is preferably applied to the inner surface of the cylindrical body 1 with a substantially uniform thickness. Thereby, the said resin composition is formed in the tubular coating film 2 whose outer diameter is equal to the internal diameter of the cylindrical body 1. FIG.

<Cylindrical body>
The cylindrical body 1 has a metal as a main component. Examples of the metal include aluminum and stainless steel. The shape of the cylindrical body 1 is not particularly limited as long as it is cylindrical, and examples thereof include a cylindrical shape and a polygonal cylindrical shape. Moreover, as the cylindrical body 1, it is also possible to use a cylinder whose diameter changes along the axial direction or a cylinder with a bottom.

  The cylindrical body 1 is preferably formed to have a substantially uniform thickness so that the amount of radiation transmitted is equal. The average thickness of the cylindrical body 1 is not particularly limited as long as it can appropriately transmit radiation while maintaining a necessary strength, and can be, for example, 100 μm or more and 1000 μm or less.

  As described above, the cylindrical body 1 includes aluminum or nickel in the surface layer on the inner surface side. The cylindrical body 1 preferably contains aluminum or nickel on the entire surface of the inner surface. It is thought that the cylindrical body 1 can separate easily the molded object obtained by bridge | crosslinking the said fluororesin by including aluminum or nickel in the surface layer of an inner surface side. As an example in which the surface layer on the inner surface side of the tubular body 1 contains aluminum, for example, a structure in which the entire tubular body 1 is made of aluminum, or a structure in which an aluminum layer is formed on the inner surface of another metal body such as stainless steel. Is mentioned. Moreover, as an example in which the surface layer on the inner surface side of the cylindrical body 1 contains nickel, for example, the configuration in which the entire cylindrical body 1 is made of nickel, or the inner surface of another metal main body such as stainless steel is subjected to alkaline electropolishing treatment. The structure which gives is mentioned. It is considered that by subjecting the inner surface of the main body to an alkaline electropolishing treatment, nickel is concentrated in the surface layer of the main body and the separability from the molded body is improved.

  The upper limit of the arithmetic average roughness Ra of the inner surface of the cylindrical body 1 is preferably 100 μm, more preferably 50 μm, and even more preferably 20 μm. When the arithmetic average roughness Ra exceeds the upper limit, it may be difficult to separate the molded body from the tubular body 1 in a separation step described later. On the other hand, the arithmetic average roughness Ra of the inner surface of the cylindrical body 1 is preferably as small as possible, and the lower limit thereof is not particularly limited, and may be 0 μm.

<Resin composition>
The resin composition may contain only one of PFA and FEP as the fluororesin, or may contain both PFA and FEP. Moreover, the said fluororesin may contain the polymer unit derived from another copolymerizable monomer in the range which does not impair the effect of this invention. The upper limit of the content ratio of the polymer units derived from the other copolymerizable monomers is, for example, 3 mol% with respect to all the polymer units constituting the fluororesin.

  The lower limit of the melt flow rate (MFR) of the fluororesin at 372 ° C. is preferably 0.5 g / 10 min, more preferably 10 g / 10 min, and further preferably 15 g / 10 min. If the MFR is less than the lower limit, applicability of the resin composition may be insufficient. In addition, although it does not specifically limit as an upper limit of said MFR, From a viewpoint that a coating film can be formed in the inner surface of the cylindrical body 1 easily and reliably, it can be 35 g / 10min, for example.

  The resin composition may contain a dispersant for uniformly dispersing the fluororesin. Examples of the dispersant include a mixed solution of water and an emulsifier, a mixed solution of water and alcohol, a mixed solution of water and acetone, a mixed solution of water, alcohol and acetone.

  As a minimum of content of the above-mentioned fluororesin in the above-mentioned resin composition except the above-mentioned dispersing agent, 60 mass% is preferred, 85 mass% is more preferred, and 98 mass% is still more preferred. The content is particularly preferably 100% by mass. If the content is less than the lower limit, heat resistance, slipperiness, mechanical strength and the like may be insufficient.

  The resin composition may contain other fluororesin and other optional components as long as the effects of the present invention are not impaired. Examples of the other fluororesins include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), and chlorotrifluoroethylene. -Ethylene copolymer (ECTFE), polyvinyl fluoride (PVF), fluoroolefin-vinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, and the like. Moreover, as said arbitrary component, a coloring agent, a electrically conductive material, a thermal radiation material, a fluorescent agent, a reflecting agent etc. are mentioned, for example.

<Application method>
As a coating method in the coating step, for example, a resin composition (dispersion) in which the cylindrical body 1 is arranged so that the axial direction is vertical, and the fluororesin powder is uniformly dispersed in the dispersant. Can be hung from above the cylindrical body 1, and a method of immersing the cylindrical body 1 in the dispersion.

(Irradiation process)
In the irradiation step, as shown in FIG. 3, the outer surface of the cylindrical body 1 is formed in a low oxygen atmosphere and at a temperature equal to or higher than the melting point of the fluororesin with the coating film 2 formed on the inner surface of the cylindrical body 1. Radiate from the side. Thus, in the irradiation step, the dispersion medium is evaporated and the fluororesin is crosslinked. As a result, a tubular molded body obtained by curing the fluororesin tree is obtained. In addition, when the said resin composition contains both PFA and FEP, in the said irradiation process, it is preferable to irradiate a radiation at the temperature more than melting | fusing point of the higher melting point (PFA) among PFA and FEP.

  When the fluororesin is PFA (melting point: 304 ° C. or higher and 310 ° C. or lower), the specific irradiation temperature in the irradiation step is 310 ° C. or higher, and the fluororesin is FEP (melting point: 270 ° C.). In some cases, it is 270 ° C or higher. As a minimum of the irradiation temperature of the radiation in the said irradiation process, the temperature 5 degreeC higher than the said melting | fusing point is preferable. On the other hand, as the upper limit of the irradiation temperature, a temperature 50 ° C. higher than the melting point is preferable, and a temperature 20 ° C. higher than the melting point is more preferable. By irradiating with radiation at the above temperature, cross-linking between molecules can be promoted while suppressing breakage of the main chain of the fluororesin.

  As an upper limit of the oxygen concentration in the said irradiation process, 100 volume ppm is preferable, 10 volume ppm is more preferable, and 5 volume ppm is further more preferable. When the oxygen concentration exceeds the upper limit, the fluororesin may be decomposed.

  Examples of the radiation include ionizing radiation such as γ rays, electron beams, X rays, neutron rays, and high energy ion rays. Moreover, as a minimum of the irradiation dose of ionizing radiation, 10 kGy is preferable, 70 kGy is more preferable, and 260 kGy is further more preferable. When the said irradiation dose is smaller than the said minimum, there exists a possibility that the crosslinking reaction of the said fluororesin may not fully advance. On the other hand, the upper limit of the irradiation dose is, for example, preferably 2000 kGy, more preferably 1200 kGy, and further preferably 400 kGy from the viewpoint of preventing an unnecessarily large irradiation amount.

(Separation process)
In the separation step, as shown in FIG. 4, the molded body 3 formed in the irradiation step is separated from the cylindrical body 1. In the separation step, the temperature heated to the melting point of the fluororesin or higher in the irradiation step is cooled below the melting point of the fluororesin, and the linear expansion coefficient of the fluororesin and the linear expansion coefficient of the metal forming the cylindrical body 1 are The molded body 3 is separated from the tubular body 1 using the difference. Specifically, in the separation step, the diameter of the molded body 3 is changed to the diameter of the cylindrical body 1 by cooling the temperature heated to the melting point of the fluororesin or higher in the irradiation step to less than the melting point of the fluororesin. The molded body 3 is separated from the cylindrical body 1 by relatively reducing the diameter.

  The cooling temperature in the separation step can be, for example, 10 ° C. or higher and 30 ° C. or lower.

  In the separation step, it is also possible to employ a method of separating the molded body 3 by dissolving or decomposing the base material with a chemical or the like.

[Second Embodiment]
The cross-linked fluororesin tube manufacturing method of FIG. 5 includes a coating step in which a resin composition containing a fluororesin is applied to the inner surface of the cylindrical body, and the cylindrical body after the coating step is subjected to a low oxygen atmosphere and the fluororesin. An irradiation step of irradiating radiation at a temperature equal to or higher than the melting point, a separation step of separating the molded body from the cylindrical body after the irradiation step, a diameter expanding step of expanding the molded body after the separation step, and the expansion. A cooling step for cooling the molded body after the diameter step. In the method for producing the cross-linked fluororesin tube, the fluororesin is PFA or FEP, and the cylindrical body contains aluminum or nickel in the surface layer on the inner surface side. The application process, the irradiation process, and the separation process in the method for manufacturing the crosslinked fluororesin tube are the same as the application process, the irradiation process, and the separation process in the method for manufacturing the crosslinked fluororesin tube in FIG. That is, the manufacturing method of the said crosslinked fluororesin tube is equipped with a diameter expansion process and a cooling process as a post process of the isolation | separation process of FIG. Therefore, only the diameter expansion process and the cooling process will be described below.

  Since the manufacturing method of the said crosslinked fluororesin tube is further equipped with a diameter expansion process and a cooling process after the said isolation | separation process, a crosslinked fluororesin tube with a high heat shrinkage rate can be manufactured easily and reliably.

(Diameter expansion process)
The diameter expansion process can be performed using, for example, a generally cylindrical known sizing tube (not shown) having an internal space through which the molded body 3 separated in the separation process passes. In the diameter expansion step, for example, gas is supplied into the molded body 3 that passes through the sizing tube while decompressing the internal space. Thereby, in the said diameter expansion process, the outer diameter of the molded object 3 can be expanded to the internal diameter of the said sizing pipe | tube.

(Cooling process)
In the cooling step, the molded body 3 expanded in the diameter expanding step is cooled and fixed. Thereby, the molded object 3 after cooling fixation is comprised as the crosslinked fluororesin tube 11 of FIG. The diameter of the cross-linked fluororesin tube 11 after cooling and fixing in the cooling process is substantially equal to the diameter after expanding in the diameter expanding process. Examples of the cooling source in the cooling step include water, cold air, and a refrigerant.

<Crosslinked fluoropolymer tube>
The cross-linked fluororesin tube 11 in FIG. 6 is obtained by the method for producing the cross-linked fluororesin tube. The cross-linked fluororesin tube 11 has a cross-linked fluororesin as a main component, the fluororesin is PFA or FEP, and the heat shrinkage rate is 30% or more.

  Since the cross-linked fluororesin tube 11 is mainly composed of cross-linked PFA or FEP, the wear resistance is sufficiently high.

  Moreover, since the said fluororesin is fully bridge | crosslinked, the said crosslinked fluororesin tube 11 can fully be expanded in the said diameter expansion process, and, thereby, heat shrinkage rate can be 30% or more. . Since the cross-linked fluororesin tube 11 has a thermal shrinkage rate equal to or higher than the lower limit, it can be easily shrunk into an irregular shape, and can appropriately cover members having various shapes.

  The lower limit of the heat shrinkage rate of the cross-linked fluororesin tube 11 is preferably 50% and more preferably 95%. When the thermal contraction rate is equal to or higher than the lower limit, it becomes easier to contract into an irregular shape. In addition, although it does not specifically limit as an upper limit of the said thermal contraction rate, From a viewpoint of performing the above-mentioned diameter expansion process easily and reliably, it can be set to 300%, for example.

The lower limit of the storage elastic modulus at 350 ° C. of the crosslinked fluororesin tube 11 is preferably 1.0 × 10 ⁵ Pa, and more preferably 1.2 × 10 ⁵ Pa. If the storage elastic modulus is less than the lower limit, the dimensional stability of the crosslinked fluororesin tube 11 may be insufficient. On the other hand, the upper limit of the storage elastic modulus at 350 ° C. of the cross-linked fluororesin tube 11 is not particularly limited, but may be, for example, 1.0 × 10 ⁹ Pa.

  The lower limit of the limit PV value of the crosslinked fluororesin tube 11 is preferably 200 MPa · m / min, more preferably 500 MPa · m / min, and still more preferably 800 MPa · m / min. If the limit PV value is less than the lower limit, the abrasion resistance of the crosslinked fluororesin tube 11 may be insufficient. On the other hand, the upper limit of the limit PV value of the cross-linked fluororesin tube 11 is not particularly limited, but may be, for example, 1000 MPa · m / min.

  The lower limit of the light transmittance of the crosslinked fluororesin tube 11 is preferably 90%, more preferably 95%. In the cross-linked fluororesin tube 11, the fluororesin crystals are subdivided by irradiation with radiation in the irradiation step, thereby increasing the light transmittance. Moreover, since the said crosslinked fluororesin tube 11 is excellent in heat resistance, it can be used as a protection tube of illumination members, such as near ultraviolet LED and a laser illumination element, for example. In this case, if the light transmittance is less than the lower limit, the light amount of the illumination member may be insufficient. Note that the upper limit of the light transmittance is not particularly limited, and may be, for example, 100%.

[Third embodiment]
<Heat recovery article>
A heat recovery article 21 in FIG. 7 includes the crosslinked fluororesin tube 11 in FIG. 6 and a primer layer 22 laminated on at least one surface of the crosslinked fluororesin tube 11. In the heat recovery article 21, a primer layer 22 is laminated on the outer peripheral surface of the crosslinked fluororesin tube 11. The primer layer 22 is preferably laminated on the entire outer peripheral surface of the cross-linked fluororesin tube 11. The heat recovery article 21 is a two-layer body of a cross-linked fluororesin tube 11 and a primer layer 22.

  Since the heat recovery article 21 includes the cross-linked fluororesin tube 11, the wear resistance is sufficiently high.

(Primer layer)
The primer layer 22 is disposed between the cross-linked fluororesin tube 11 and the article to be adhered (not shown), and improves waterproofness and adhesion between the cross-linked fluororesin tube 11 and the article to be adhered. That is, the primer layer 22 is an adhesive layer that bonds the cross-linked fluororesin tube 11 and the article to be adhered. Examples of the main component of the primer layer 22 include synthetic resins such as PFA, polyethersulfone (PES), and polyamide. The synthetic resin may be cross-linked by irradiation with ionizing radiation or the like. Further, the primer layer 22 may contain additives such as a viscosity property improver, a deterioration inhibitor, a flame retardant, a lubricant, a colorant, a heat stabilizer, an ultraviolet absorber, and an adhesive.

  Since the heat recovery article 21 includes the primer layer 22, the crosslinked fluororesin tube 11 mainly composed of a fluororesin that is crosslinked to the article to be adhered such as metal or rubber can be easily and reliably attached. Can do. More specifically, according to the conventional method, it is necessary to crosslink the fluororesin after coating the object to be adhered with the cross-linked fluororesin tube, so that the object to be adhered cannot withstand the heating temperature. It was difficult to obtain an adherend. On the other hand, since the heat recovery article 21 is preliminarily crosslinked with the fluororesin, the crosslinked fluororesin tube 11 can be easily and reliably applied to the article to be adhered while suppressing deterioration of the quality of the article to be adhered. Can be worn. In particular, since the primer layer 22 is laminated on the outer peripheral surface of the crosslinked fluororesin tube 11 in the heat recovery article 21, the crosslinked fluororesin tube 11 is easily and reliably laminated on the inner peripheral surface of the article to be adhered. Can do.

<Manufacturing method>
The manufacturing method of the heat recovery article 21 includes a stacking step of stacking the primer layer 22 on the cross-linked fluororesin tube 11.

  In the laminating step, the primer layer forming composition for forming the primer layer 22 on at least one surface of the cross-linked fluororesin tube 11 is applied, and the primer layer forming composition after the applying step is baked. And a firing step.

  The manufacturing method of the heat recovery article can easily and reliably manufacture the heat recovery article 21 having sufficiently high wear resistance.

[Other Embodiments]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is not limited to the configuration of the embodiment described above, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. The

  For example, the specific procedure of the said diameter expansion process and a cooling process is not specifically limited. Moreover, the manufacturing method of the said crosslinked fluororesin tube may have the winding-up process which winds up a molded object after cooling by the said cooling process.

  In the heat recovery article, the primer layer is not necessarily laminated on the outer peripheral surface of the cross-linked fluororesin tube, and may be laminated on the inner peripheral surface of the cross-linked fluororesin tube. Moreover, the said primer layer may be laminated | stacked on both surfaces of a crosslinked fluororesin tube.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

[Example]
[No. 1]
As the above-mentioned coating process, powder PFA (Mitsui Dupont Fluoro) is applied on the inner surface of an aluminum foil (1050) pipe having an average thickness of 200 μm, an average inner diameter of 30 mm, and an inner surface having a maximum height roughness Rz of 1 μm as defined in JIS B0601: 2013. Chemical powder “MP102”) was coated with electrostatic powder. The melting point of the PFA was 310 ° C., and the MFR at 372 ° C. was 20 g / 10 min. Next, after baking the above PFA at 350 ° C. for 20 minutes, as the above-described irradiation step, the PFA is heated to 330 ° C. in a low oxygen atmosphere having an oxygen concentration of 5 ppm by volume or less, and an electron beam accelerator manufactured by NHV Corporation is used. The electron beam was irradiated from the outer surface side of the aluminum pipe. The irradiation conditions were an acceleration voltage of 1160 kV and an irradiation dose of 300 kGy. Subsequently, as the above-described separation step, the tube-shaped molded body formed on the inner surface of the cylindrical body was separated by cooling to 25 ° C. and utilizing the difference in linear expansion coefficient between aluminum and PFA. As a result, a cross-linked fluororesin tube mainly composed of cross-linked PFA having an average thickness of 180 μm and an inner diameter of 30 mm was produced.

[Comparative example]
[No. 2]
No. except that the above irradiation process was not performed. In the same manner as in Example 1, a cross-linked fluororesin tube was produced.

[No. 3]
No. except that the heating temperature in the irradiation step was 200 ° C. and the electron beam irradiation amount was 50 kGy. In the same manner as in Example 1, a cross-linked fluororesin tube was produced.

<Quality of cross-linked fluoropolymer tube>
(Storage modulus)
No. 1 to No. A test piece was prepared by cutting the cross-linked fluororesin tube 3 into a rectangular shape having a length of 20 mm and a width of 10 mm. These test pieces were measured using a viscoelasticity measuring device (DMS) ("DVA-200" manufactured by IT Measurement & Control Co., Ltd.) in a nitrogen atmosphere, a measurement temperature range of 25 ° C to 400 ° C, and a temperature increase rate of 10 ° C / min. The measurement was performed at a strain amplitude of 5 μm, a measurement frequency of 1 Hz, a minimum tension of 9.8 mN, and a force amplitude initial value of 29.4 mN. Table 1 shows the measurement results of the storage elastic modulus at 350 ° C.

(Limit PV value)
No. 1-No. A test piece was cut out from the cross-linked fluororesin tube 3 and this test piece was thermally fused at 330 ° C. to a 2 mm thick aluminum plate (3003) in which uncrosslinked PFA was laminated to a thickness of 50 μm, followed by thrust wear. The limit PV value was obtained by setting in a testing machine. As the counterpart material, a cylinder having a material of S45C and a ring dimension (outer diameter / inner diameter) of Φ11.5 / Φ7.4 was used. The measurement results of the limit PV value are shown in Table 1.

(Heat shrinkage)
No. Fixing the cross-linked fluororesin tube No. 1 in an expanded state by applying an internal pressure of 0.1 MPa at a temperature of 320 ° C., expanding the inner diameter to 60 mm (expansion process), and water-cooling immediately after the expansion (cooling process). did. When the expanded cross-linked fluororesin tube was heated at 350 ° C., the inner diameter contracted to 31 mm.

(Heat recovery article)
The crosslinked fluororesin tube after the above-described cooling step was heated at 350 ° C. to coat the outer peripheral surface of an aluminum pipe having an inner diameter of 30 mm. A primer layer-forming composition containing PES and PFA at a ratio of 1: 1 is applied to the outer peripheral surface of the cross-linked cross-linked fluororesin tube after coating, and then baked at 330 ° C. for 20 minutes. A heat recovery article having a primer layer laminated on the surface was produced. In this heat recovery article, the crosslinked fluororesin tube and the primer layer were heat-sealed, and the peel strength at 25 ° C. between them was 10 N / cm.

(Adherent)
The heat recovery article was pulled out from the aluminum pipe and disposed on the inner peripheral surface of a SUS304 pipe having an inner diameter of 40 mm, and the inner surface was expanded by adding air at 350 ° C. As a result, an adherend was obtained in which the primer layer and the SUS304 pipe were bonded, and the pipe and the cross-linked fluororesin tube were bonded via the primer layer.

[Evaluation results]
As shown in Table 1, no. In the crosslinked fluororesin tube No. 1, the fluororesin is sufficiently crosslinked, so that the limit PV value and the storage elastic modulus at 350 ° C. are No. 1. 2 and no. 3 is larger than the cross-linked fluororesin tube. From this, No. 1 shows that the cross-linked fluororesin tube 1 has excellent wear resistance and dimensional stability.

  In addition, as described above, no. 1 cross-linked fluororesin tube has a high heat shrinkage rate. Furthermore, no. The heat recovery article using the 1 cross-linked fluororesin tube has a high peel strength between the cross-linked fluororesin tube and the primer layer, and an adherend excellent in adhesion is obtained.

  As described above, since the method for producing a crosslinked fluororesin tube according to the present invention can produce a crosslinked fluororesin tube having sufficiently high wear resistance, it is preferably used for OA equipment, lighting members and the like. It is suitable as a method for manufacturing a fluororesin tube.

DESCRIPTION OF SYMBOLS 1 Tubular body 2 Coating film 3 Molded body 11 Cross-linked fluororesin tube 21 Heat recovery article 22 Primer layer

Claims (9)

An application step of applying a resin composition containing a fluororesin to the inner surface of the cylindrical body;
An irradiation step of irradiating the cylindrical body after the application step with a radiation in a low oxygen atmosphere and at a temperature equal to or higher than the melting point of the fluororesin;
A separation step of separating the molded body from the cylindrical body after the irradiation step,
The fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or a tetrafluoroethylene-hexafluoropropylene copolymer,
The manufacturing method of the crosslinked fluororesin tube in which the said cylindrical body contains aluminum or nickel in the surface layer of an inner surface side.   The method for producing a crosslinked fluororesin tube according to claim 1, wherein the inner surface of the cylindrical body has an arithmetic average roughness Ra of 100 μm or less.   The method for producing a crosslinked fluororesin tube according to claim 1 or 2, wherein the fluororesin has a melt flow rate at 372 ° C of 0.5 g / 10 min or more. A diameter expansion step for expanding the diameter of the molded body after the separation step;
The method for producing a crosslinked fluororesin tube according to claim 1, further comprising a cooling step of cooling the molded body after the diameter expansion step. The main component is a cross-linked fluororesin,
The fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or a tetrafluoroethylene-hexafluoropropylene copolymer,
A crosslinked fluororesin tube having a heat shrinkage rate of 30% or more. The cross-linked fluororesin tube according to claim 5, wherein the storage elastic modulus at 350 ° C. is 1.0 × 10 ⁵ Pa or more.   The cross-linked fluororesin tube according to claim 5 or 6, wherein the limit PV value is 200 MPa · m / min or more.   The cross-linked fluororesin tube according to claim 5, wherein the light transmittance is 90% or more.   A heat recovery article comprising: the crosslinked fluororesin tube according to any one of claims 5 to 8; and a primer layer laminated on at least one surface of the crosslinked fluororesin tube.

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