Different diameter tubing and manufacturing method of different diameter tubing

Abstract

To provide high-strength different diameter tubing and a manufacturing method of the same.SOLUTION: According to an aspect of the present invention, different diameter tubing is provided. The different diameter tubing contains thermoplastic fluoropolymer and has a thin diameter and a large diameter portions, and compared to the thin diameter portion, the large diameter portion has a crystallinity of 200% or higher. According to another aspect of the present invention, a method for manufacturing different diameter tubing is provided. The manufacturing method includes extruding thermoplastic fluororesin into a tubular shape to obtain a tube precursor, heating a portion of the tube precursor to soften the same, pressurizing the tube precursor from inside and expanding a part of the softened tube precursor to form a large diameter portion, while maintaining the other portion as a thin diameter portion and cooling the enlarged large diameter portion.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a reduced diameter tube and a method for manufacturing a reduced diameter tube. [Background technology]

[0002] Fluorine resin-containing tubes are mainly formed by melt molding, but the strength of the fluororesin tubes produced by melt molding is insufficient. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-024308 [Patent Document 2] JP 2008-030471 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a different-diameter tube having a small diameter portion and a large diameter portion, the large diameter portion having a high strength, and a manufacturing method for manufacturing a different-diameter tube having a large diameter portion having a high strength. [Means for solving the problem]

[0005] According to one aspect of the present invention, there is provided a variable-diameter tube comprising a thermoplastic fluororesin, a thin diameter portion and a thick diameter portion, and the thick diameter portion has a degree of crystallinity 200% or more higher than that of the thin diameter portion.

[0006] According to another aspect of the present invention, there is provided a method for producing a variable diameter tube, the method including: extruding a thermoplastic fluororesin into a tubular shape to obtain a tube precursor, heating and softening a portion of the tube precursor, applying pressure to the tube precursor from within the tube to expand a portion of the heated tube precursor to form a large diameter portion while maintaining the remaining portion as a small diameter portion, and cooling the expanded large diameter portion. Effect of the Invention

[0007] According to the present invention, it is possible to provide a different-diameter tube having a small diameter portion and a large diameter portion, the large diameter portion being strong, and a manufacturing method capable of manufacturing a different-diameter tube having a large diameter portion being strong. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a cross-sectional view showing a schematic state of a tube precursor before blow molding. [Diagram 2] FIG. 11 is a cross-sectional view that illustrates a process of heating a tube precursor. [Diagram 3] 1A to 1C are cross-sectional views each showing a schematic process of blow molding a tube precursor. [Figure 4] FIG. 4 is a cross-sectional view illustrating a cooling process after blow molding. [Diagram 5] FIG. 11 is a cross-sectional view illustrating a process of removing a reduced diameter tube. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments will be described with reference to the drawings as appropriate. Note that the same reference numerals are used to designate common components throughout the embodiments, and duplicated descriptions will be omitted. Also, each figure is a schematic diagram for explaining the embodiments and for facilitating understanding thereof, and the shapes, dimensions, ratios, etc. may differ from those of the actual device, but these can be appropriately modified in design by taking into consideration the following explanation and known techniques.

[0010] In this specification, the operation of expanding the diameter of a tube precursor by applying pressure from within the tube may be referred to as "blow molding".

[0011] The reduced diameter tube according to the embodiment and the manufacturing method thereof will be further described with reference to the drawings.

[0012] Since the variable diameter tube according to the embodiment is manufactured by processing a tube precursor, the tube precursor will be described first.

[0013] The variable diameter tube according to the embodiment is manufactured from a tube precursor containing a thermoplastic fluororesin. The crystallinity of the tube precursor is preferably 5% or less.

[0014] The tube precursor used in the manufacture of the variable diameter tube according to the embodiment may be manufactured, for example, by melt molding, and may have a tube shape having a circular cross-sectional shape. The outer diameter of the tube precursor is D0. The cross-sectional shape of the tube precursor is not limited to a circle, and may be other shapes, such as a substantially circular shape or an elliptical shape. In addition, the side shape of the tube precursor is not limited to a straight tube shape, and may be an uneven shape such as a bellows shape. The dimensions of the tube precursor, for example, the outer diameter D0 and the length in the longitudinal direction, are not particularly limited, and may be appropriately set according to the application.

[0015] An example of a thermoplastic fluororesin contained in the tube precursor used in the production of the variable diameter tube according to the embodiment is perfluoroalkoxyalkane (PFA).

[0016] A method for manufacturing a variable diameter tube according to an embodiment includes extruding a thermoplastic fluororesin into a tubular shape to obtain a tube precursor, heating and softening a portion of the tube precursor, applying pressure to the tube precursor from within the tube to expand a portion of the softened tube precursor to form a large diameter section while maintaining the remaining portion as a small diameter section, and cooling the expanded large diameter section.

[0017] In the tube precursor formed into a tubular shape by extrusion, there is a part where the molecular chains of the thermoplastic fluororesin are densely packed together in a folded state. In the large-diameter part formed by heating and softening a part of the tube precursor and applying pressure from inside the tube to expand the diameter, the folded molecular chains are stretched. That is, the molecules of the thermoplastic fluororesin are oriented along the radial direction. When the large-diameter part thus formed is cooled, the softened thermoplastic fluororesin is solidified again. Therefore, in the large-diameter part, the molecules of the thermoplastic fluororesin are fixed in a state oriented in the radial direction. If the molecular orientation in the large-diameter part is perpendicular to the axial direction, when a crack occurs in the tube, the crack can be prevented from progressing in the axial direction. Therefore, according to the manufacturing method of the embodiment, a tube with a different diameter having a high strength in the large-diameter part can be manufactured.

[0018] Furthermore, by heating a portion of the tube precursor, the molecular chains in the amorphous portion of the portion can be easily untangled, and therefore the crystallinity of the molecular chains can be improved in the thicker portion formed by heating the portion of the tube precursor and then expanding the diameter as described above.

[0019] The heating temperature is preferably equal to or higher than the softening point and lower than the melting point of the thermoplastic fluororesin. If the heating temperature is lower than the melting point of the thermoplastic fluororesin, the increase in crystallinity of the large diameter portion after diameter expansion is likely to be 200% or more higher than that of the small diameter portion.

[0020] Furthermore, by carrying out the diameter expansion after heating by applying pressure from inside the tube, the diameter can be expanded efficiently even if the heating temperature is below the melting point of the thermoplastic fluororesin.

[0021] The expanded large diameter portion can be cooled by a known method such as air cooling or water cooling, but is preferably cooled rapidly. For example, it is preferable to lower the temperature of the tube precursor by water cooling at a rate of 70° C. / min or more.

[0022] A specific method for producing a tube according to an embodiment will be described with reference to FIGS. FIG. 1 is a cross-sectional view along the axial direction of a tube precursor, showing a state in which a portion of the tube precursor 1 is housed in a metal pipe 2. The outer diameter of the tube precursor 1 is indicated as D0, and the inner diameter of the metal pipe 2 is indicated as D2. One end of the tube precursor 1 is sealed with a sealant 3. The other end of the tube precursor 1 is sealed with a sealant 4. One end of a tubular nozzle 5 is attached to the sealant 4, which communicates with the inside of the tube precursor 1 from the outside. The other end of the nozzle 5 is connected to an air introduction device (not shown).

[0023] The tube precursor 1 is obtained, for example, by extruding molten resin with a screw extruder and forming it into a tubular shape. The outer diameter D0 of the tube precursor 1 is set to be smaller than the outer diameter D1 of the desired large diameter portion. The outer diameter D1 is preferably 10 mm or more and 30 mm or less.

[0024] FIG. 2 shows a state in which a heater 6 is provided on the outer periphery of a metal pipe 2 . The shape of the metal pipe 2 can be such that its internal structure has a desired tube shape, for example, a cylindrical shape. The dimensions of the metal pipe 2 are such that its inner diameter D2 corresponds to the outer diameter D1 of the desired large diameter portion. The longitudinal dimension of the metal pipe 2 is not particularly limited, but corresponds to the desired length of the large diameter portion. The heater 6 heats the metal pipe 2 to a temperature equal to or higher than the softening point and lower than the melting point of the resin constituting the tube precursor 1, thereby softening a portion of the tube precursor 1.

[0025] Heating may be performed, for example, using a hot air blower (for example, manufactured by Leister). By attaching an attachment in the form of a cylinder with a part cut out to the hot air blower and moving the attachment along the longitudinal direction of the tube precursor 1, parts of the tube precursor 1 can be heated sequentially along the longitudinal direction and softened.

[0026] FIG. 3 shows the softened tube precursor 1 in a state where pressure is applied from inside the tube to expand the diameter. After the heating is completed, the air introducing device connected to the nozzle 5 is driven to send pressurized air into the tube precursor 1, thereby pressurizing the tube precursor 1 from within the tube. In this way, a portion of the softened tube precursor 1 is expanded in diameter to form a large diameter portion 12, while the other portion is maintained as a small diameter portion 11.

[0027] The pressure applied to the tube precursor 1 from inside the tube is set to, for example, 2 MPa or more and 10 MPa or less. By such a pressurizing treatment, the tube precursor can be expanded in diameter.

[0028] 4 shows a state in which cold water is poured onto the metal pipe 2 to rapidly cool it. Alternatively, the metal pipe 2 may be immersed in a water tank for cooling. While the tube precursor 1 is pressurized from within the tube, cold water is sprayed onto the metal pipe 2 from a spray 7 installed on the outside of the metal pipe 2 to quench a portion of the tube precursor 1 softened by heating and fix the shape. By cooling a portion of the tube precursor 1 to room temperature in this manner, a variable-diameter tube having a small diameter portion 11 and a large diameter portion 12 and a desired degree of crystallinity is obtained.

[0029] FIG. 5 shows a schematic diagram of the process of removing the reduced diameter tube. After cooling is completed, the air is removed from the reduced diameter tube 10, the pressure inside the reduced diameter tube 10 is returned to normal pressure, and the reduced diameter tube 10 is then removed from the metal pipe 2. If necessary, the reduced diameter tube 10 may be cut to a desired length.

[0030] (Measurement method) The methods for measuring the heat of fusion, the degree of crystallinity, the tensile strength and the burst pressure are described below.

[0031] <Heat of fusion> The heat of fusion can be measured using, for example, a differential scanning calorimeter DSC-60 (manufactured by Shimadzu Corporation).

[0032] A measurement sample is weighed out to 5.0±0.5 mg, placed in an aluminum cell and crimped. The aluminum cell is set in a differential scanning calorimeter, and cycle measurements are performed under the measurement conditions shown in Table 1. The peaks obtained by the measurement are analyzed in the range of 300°C to 340°C to obtain the heat of fusion of the sample. For the analysis, for example, the analysis software attached to the DSC-60 can be used.

[0033] [Table 1]

[0034] <Crystallization degree> The degree of crystallinity (DC) can be calculated by the following formula (1), where Ha is the measured value of the heat of fusion of the thermoplastic fluororesin and Hb is the theoretical value of the heat of fusion when the thermoplastic fluororesin is completely crystalline. DC(%)=(Ha / Hb)×100 (1) The Hb value can be a known value. For example, when the thermoplastic fluororesin is PFA, the Hb value can be 22.2 cal / g described in paragraph 0013 of JP 2007-093650 A.

[0035] <Tensile strength> The tensile strength can be measured by a measurement method in accordance with JIS K 7137-2.

[0036] <Burst pressure> The burst pressure can be measured as follows. One end of the tube is sealed, the other end is connected to a fluid coupling, and water or air is pumped in to apply pressure from the inside of the tube. The pressure is increased at a rate of 0.1 MPa / sec, and the maximum pressure at which the tube breaks is taken as the breaking pressure.

[0037] (Example) The different diameter tube according to the embodiment will be described together with the manufacturing method thereof. PFA was fed into the extruder as the resin material for the tube. The melt temperature was set at 385°C and the extrusion speed was set at 1.0 m / min. The tube-shaped extrusion extruded from the extruder was wound up on a winder and slowly cooled by air, yielding a tube precursor with an outer diameter of 30 mm and a length of 100 cm.

[0038] The obtained tube precursor was subjected to a diameter expansion treatment as follows. First, a metal pipe having a length of 100 cm and an inner diameter of 40 mm was prepared for use in the diameter expansion process.

[0039] The two ends of the tube precursor were sealed with a sealant. A nozzle connected to an air introduction device was inserted into the sealant at one end and fixed so that no air leaked. Next, the tube precursor was inserted into a metal pipe. A heater was also placed around the outer periphery of the metal pipe.

[0040] The tube precursor inside the metal pipe was heated to 300°C by a heater, and part of the tube precursor was softened.

[0041] After the heating was completed, the air introduction device was driven to supply air into the tube precursor through the nozzle. The pressure inside the tube precursor was set to 2.0 to 2.5 MPa. The pressure outside the tube was set to atmospheric pressure (1 atm = 101.325 kPa). The large diameter part was then cooled while maintaining the internal pressure. Cooling was performed by spraying cold water onto the metal pipe, and quenching was performed at a rate of 80°C / min. In this way, the different diameter tube of the example was obtained.

[0042] (Comparative Example) A specific example of manufacturing a tube according to a comparative example will be described. PFA was fed into the extruder as the resin material for the tube. The melting temperature was set at 385°C and the extrusion speed at 1.0 m / min. The extruder was connected to a corrugating device consisting of a die that would form the thin and thick diameter sections. The molten resin extruded from the extruder was rapidly cooled by applying internal pressure to the inner surface of the die while in the molten state, resulting in a tube with a different diameter that had a thin and thick diameter section.

[0043] (result) The measurement results of the physical properties of the tubes of the examples and comparative examples are shown in Tables 2 and 3 below.

[0044] [Table 2]

[0045] [Table 3]

[0046] As shown in Table 2, the reduced diameter tube of the embodiment had a high degree of crystallinity, which was 200% or more higher than that of the reduced diameter tube of the comparative example.

[0047] This is believed to be because the large diameter portion of the reduced diameter tube of the embodiment was formed by blow molding at a temperature lower than the melting point. The manufacturing method of the reduced diameter tube of the embodiment includes heating a tube precursor containing a thermoplastic fluororesin at a temperature equal to or higher than the softening point and lower than the melting point to expand the diameter. Therefore, it is believed that a microstructure in which the molecules of the thermoplastic fluororesin are oriented in the radial direction is formed. Furthermore, since it is quenched in this state, it is believed that the microstructure of the large diameter portion of the reduced diameter tube of the embodiment is fixed in a state in which the molecules of the thermoplastic fluororesin are oriented.

[0048] In this way, it is considered that the large diameter portion of the reduced diameter tube of the example has a fine structure in which the molecules of the thermoplastic fluororesin are oriented, and therefore the degree of crystallinity is high.

[0049] In addition, from the results of Table 3, the large diameter portion of the reduced diameter tube of the embodiment had a higher tensile strength and burst pressure than the comparative example, despite the tube having a thinner wall thickness. Therefore, it is clear that the large diameter portion of the reduced diameter tube of the embodiment has a higher strength than the comparative example.

[0050] From the above results, it is clear that the large diameter portion of the variable diameter tube of the embodiment has a higher degree of crystallinity and is stronger than the tube of the comparative example formed by melt molding.

[0051] In contrast, in the comparative example, the material resin is heated above its melting point and melt-blowing processed to form a tube. In the forming method of melting the material resin, the molecules of the material resin do not stretch. Therefore, the molecules of the material resin are not oriented. Also, the degree of crystallinity is usually determined by the cooling speed from the molten state to a temperature below the melting point. For this reason, the cooling speed of the thick-diameter portion, which becomes thinner than the thin-diameter portion, is faster than that of the thin-diameter portion, and the degree of crystallinity is lower. This is thought to have resulted in the tube of the comparative example having a lower degree of crystallinity and lower strength.

[0052] As described above, a method for producing a variable diameter tube, which includes the steps of extruding a thermoplastic fluororesin into a tubular shape to obtain a tube precursor, heating and softening a portion of the tube precursor, applying pressure to the tube precursor from within the tube to expand a portion of the softened tube precursor to form a large diameter section while maintaining the other portion as a small diameter section, and cooling the expanded large diameter section, is a method capable of producing a tube whose large diameter section has a high strength.

[0053] The present invention is not limited to the above-mentioned embodiment, and can be modified in various ways without departing from the gist of the present invention. The embodiments may be combined as appropriate, and in that case, the combined effect can be obtained. Furthermore, the above-mentioned embodiment includes various inventions, and various inventions can be extracted by combinations selected from the multiple components disclosed. For example, if the problem can be solved and the effect can be obtained even if some components are deleted from all the components shown in the embodiment, the configuration from which the components are deleted can be extracted as an invention. [Explanation of symbols]

[0054] 1...tube precursor, 2...metal pipe, 3, 4...sealing material, 5...nozzle, 6...heater, 7...spray, 10...different diameter tube, 11...thin diameter section, 12...large diameter section, D0...outer diameter of tube precursor, D1...outer diameter of large diameter section, D2...inner diameter of metal pipe.

Claims

1. A tube having a small diameter portion and a large diameter portion, the large diameter portion having a degree of crystallinity 200% or more higher than that of the small diameter portion.

2. The reduced diameter tube according to claim 1 , wherein the thermoplastic fluororesin comprises a perfluoroalkoxyalkane.

3. extruding the thermoplastic fluororesin into a tubular shape to obtain a tube precursor; heating and softening a portion of the tube precursor; applying pressure to the tube precursor from inside the tube to expand a portion of the softened tube precursor to form a large diameter portion while maintaining the remaining portion as a small diameter portion; Cooling the expanded large diameter portion. A method for manufacturing a tube having a different diameter, comprising:

4. The method according to claim 3 , wherein the tube precursor is heated to a temperature equal to or higher than the softening point and lower than the melting point of the thermoplastic fluororesin.

5. The method according to claim 3 or 4, wherein the tube precursor is pressurized from inside the tube at a pressure of 2 MPa or more.

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