Pipe joint and method of manufacturing a pipe joint

Abstract

The present application provides a pipe joint, which has a cylindrical hollow portion, wherein the wall thickness of the portion having the largest wall thickness of the pipe joint is 2 mm to 7 mm, the ratio L / D of the length L in the axial direction of the hollow portion to the diameter D of the hollow portion is 5 or less, the pipe joint contains a copolymer, the copolymer contains tetrafluoroethylene units and fluoro(alkyl vinyl ether) units, the content of the fluoro(alkyl vinyl ether) units of the copolymer is 2.8 mass% to 6.0 mass% with respect to the total monomer units, the melt flow rate of the copolymer at 372°C is 4.0 g / 10 minutes or more and less than 11.0 g / 10 minutes, and the number of functional groups of the copolymer is 50 or less.

Description

TECHNICAL FIELD

[0001] The present application relates to a pipe joint and a method for manufacturing a pipe joint. BACKGROUND

[0002] Conventionally, a pipe joint formed of a tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer has been known.

[0003] For example, Patent Literature 1 describes a joint for semiconductor device manufacturing obtained by molding a molding material for ozone-resistant articles, the molding material for ozone-resistant articles being composed of a copolymer (A) having a melt flow rate of 0.1 g / 10 minutes to 50 g / 10 minutes, the copolymer (A) being a copolymer composed of tetrafluoroethylene and perfluoro vinyl ether, containing 3.5% by mass or more of perfluoro vinyl ether units, having a melting point of 295°C or more, and having 50 or less unstable end groups per 1 x 10 6 carbon atoms in the copolymer (A).

[0004] Prior Art Documents

[0005] Patent Literature

[0006] Patent Literature 1: International Publication No. 2003 / 048214 SUMMARY

[0007] Problems to be Solved by the Invention

[0008] An object of the present application is to provide a pipe joint which can be easily manufactured even in the case of a large wall thickness and length, is excellent in deformation resistance to a fluid of high temperature and high pressure, and is excellent in appearance of a hollow portion and appearance.

[0009] Means for Solving the Problems

[0010] According to the present application, there is provided a pipe joint having a hollow portion in a cylindrical shape, wherein a wall thickness of a portion having the largest wall thickness of the pipe joint is 2 to 7 mm, a ratio (L / D) of a length (L) in an axial direction of the hollow portion to a diameter (D) of the hollow portion is 5 or less, the pipe joint contains a copolymer containing a tetrafluoroethylene unit and a fluoro(alkyl vinyl ether) unit, a content of the fluoro(alkyl vinyl ether) unit of the copolymer is 2.8 to 6.0% by mass with respect to all monomer units, a melt flow rate of the copolymer at 372°C is 4.0 g / 10 minutes or more and less than 11.0 g / 10 minutes, and a number of functional groups of the copolymer is 50 or less.

[0011] The length (L) in the axial direction of the hollow portion is preferably 20 mm or more.

[0012] The fluorinated (alkyl vinyl ether) unit of the copolymer is preferably a perfluoro(propyl vinyl ether) unit.

[0013] The content of the fluorinated (alkyl vinyl ether) unit of the copolymer is preferably 3.5 to 5.5 mass% relative to the total monomer units.

[0014] The melt flow rate of the copolymer at 372°C is preferably 5.0 to 9.0 g / 10 minutes.

[0015] The melting point of the copolymer is preferably 295 to 315°C.

[0016] The pipe joint of the present application is preferably an injection-molded body.

[0017] Further, the manufacturing method of the pipe joint of the present application provides a manufacturing method of a pipe joint, which is a manufacturing method of inserting a cylindrical core material into a mold cavity of a mold, filling a molten copolymer into the mold cavity of the mold from an injection molding machine, cooling the molten copolymer to solidify it, extracting the core material in the axial direction of the pipe joint, and taking out the pipe joint from the mold, wherein the ratio (L / D) of the length (L) in the axial direction of the hollow portion of the pipe joint formed by extracting the core material to the diameter (D) of the hollow portion is 5 or less, and the wall thickness of the portion where the wall thickness of the pipe joint is the thickest is 2 to 7 mm.

[0018] The length of the core material is preferably the same as the length (L) in the axial direction of the hollow portion of the pipe joint.

[0019] Effects of the Invention

[0020] According to the present application, it is possible to provide a pipe joint that can be easily manufactured even in the case of a large wall thickness and length, is beautiful in both the hollow portion and the appearance, and has excellent deformation resistance to fluids at high temperature and high pressure. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a plan view, a sectional view, and a side view that show one embodiment of the pipe joint of the present application. DETAILED DESCRIPTION

[0022] Hereinafter, a specific embodiment of the present application will be described in detail, but the present application is not limited to the following embodiment.

[0023] The pipe joint of the present application has a cylindrical hollow portion, and the wall thickness of the portion where the wall thickness of the pipe joint is the thickest is 2 to 7 mm.

[0024] Such a pipe joint with a large wall thickness is generally manufactured by injection molding of a copolymer using a core material for forming a hollow portion. If a pipe joint with a large wall thickness is manufactured by injection molding, molding defects such as sink marks, voids, and the like are easily generated, and therefore, in order to suppress the molding defects, the holding pressure (secondary pressure) needs to be increased. However, if the holding pressure is increased, other molding defects such as burrs are generated, or smooth extraction of the core material becomes difficult, and damage to the hollow portion (inner surface of the pipe joint) is caused. On the other hand, if these problems are to be solved, the extraction of the core material itself becomes difficult, or molding defects such as roughness, flow marks, and the like are generated.

[0025] In addition, if the wall thickness of the pipe joint is increased and the length of the pipe joint is increased, further problems are generated. That is, in the case where the length of the pipe joint (length (L) in the axial direction of the hollow portion of the pipe joint) is increased, the length of the core material to be extracted is also increased, and the core material becomes difficult to extract, and therefore, the diameter of the pipe joint (diameter (D) of the hollow portion of the pipe joint (inner diameter of the pipe joint)) needs to be increased. If the diameter (D) of the hollow portion of the pipe joint is increased, even if the pipe joint is deformed only by a small percentage, the shape of the entire pipe joint is greatly changed.

[0026] Therefore, a pipe joint is required which is excellent in deformation resistance to a fluid at high temperature and high pressure, and in which the hollow portion and the appearance are both beautiful even in the case where the wall thickness and the length are large, and the core material can be smoothly extracted, and which is excellent in productivity.

[0027] The pipe joint of the present application has a cylindrical hollow portion, the wall thickness of the portion where the wall thickness of the pipe joint is the largest is 2 mm to 7 mm, and the ratio (L / D) of the length (L) in the axial direction of the hollow portion to the diameter (D) of the hollow portion is 5 or less. Furthermore, the pipe joint of the present application contains a copolymer containing tetrafluoroethylene (TFE) units and fluoro(alkyl vinyl ether) (FAVE) units, the content of the FAVE units of the copolymer, the melt flow rate (MFR), and the number of functional groups are appropriately adjusted. Therefore, the pipe joint of the present application can be easily manufactured even in the case where the wall thickness and the length are large, the hollow portion and the appearance are both beautiful, and the deformation resistance to a fluid at high temperature and high pressure is excellent.

[0028] Figure 1 An embodiment of the pipe joint of the present application is shown. Figure 1 The pipe joint shown is a T-joint, and has a wall thickness (T) and a diameter (D).

[0029] The wall thickness of the portion where the wall thickness of the pipe joint is the largest is 2 mm to 7 mm, preferably 5 mm or less, and more preferably 3 mm or less. The wall thickness of the pipe joint of the present application is relatively large, and therefore, the rigidity and the impact resistance are excellent.

[0030] In the pipe joint of the present application, the wall thickness of the portion where the wall thickness of the pipe joint is the largest is 2 mm to 7 mm, and the ratio (L / D) of the length (L) in the axial direction of the hollow portion to the diameter (D) of the hollow portion is 5 or less. Figure 1The pipe fitting shown has a uniform wall thickness, but the thickness can also be varied so that the wall thickness at the thickest part of the pipe fitting is within the range of 2mm to 7mm. In one embodiment, the overall wall thickness of the pipe fitting can also be set within the range of 2mm to 7mm. The overall wall thickness of the pipe fitting is preferably 5mm or less, more preferably 3mm or less.

[0031] Figure 1 The pipe fitting shown has two hollow portions with different axial directions and different axial lengths. In this invention, when the pipe fitting has two or more hollow portions with different axial directions, the axial length of the hollow portion with the longest length is defined as "the axial length (L) of the hollow portion of the pipe fitting".

[0032] The ratio (L / D) of the axial length (L) of the hollow portion of the pipe fitting of the present invention to the diameter (D) of the hollow portion is 5 or less, preferably 4 or less, more preferably 3 or less, preferably 0.1 or more, and more preferably 1 or more. If the ratio (L / D) is too large, it is difficult to extract the core material during injection molding, making it difficult to manufacture the pipe fitting with high productivity. The pipe fitting of the present invention has excellent resistance to deformation of high-temperature and high-pressure fluids, so its dimensions are not easily changed. Therefore, although it has a relatively large diameter (D) relative to its length (L), it can reliably prevent fluid leakage from the connection between the piping and the pipe fitting, even under high-temperature and high-pressure fluid flow conditions.

[0033] The axial length (L) of the hollow portion of the pipe fitting of the present invention is preferably 20 mm or more, more preferably 25 mm or more, further preferably 30 mm or more, particularly preferably 35 mm or more, and most preferably 40 mm or more. Furthermore, the axial length (L) of the hollow portion of the pipe fitting of the present invention is preferably 80 mm or less, more preferably 70 mm or less, further preferably 60 mm or less, and particularly preferably 50 mm or less. Even with increased length, the core material of the pipe fitting of the present invention can be smoothly extracted during injection molding, enabling high-productivity manufacturing. The length of the pipe fitting of the present invention is not significantly limited; therefore, by using the pipe fitting of the present invention, the design freedom of piping can be improved.

[0034] The fitting of the present invention comprises a copolymer containing tetrafluoroethylene (TFE) units and fluorinated (alkyl vinyl ether) (FAVE) units. This copolymer is a melt-processable fluoropolymer. Melt-processability refers to the ability to melt and process the polymer using existing processing equipment such as extruders and injection molding machines.

[0035] As a FAVE constituting the above-mentioned FAVE unit, at least one of the groups consisting of the monomers shown in general formula (1) and the monomers shown in general formula (2) can be listed.

[0036] General formula (1):

[0037] CF2 = CFO(CF2CFY) 1 O) p -(CF2CF2CF2O) q -Rf (1)

[0038] (where Y) 1 (This indicates F or CF3, Rf indicates a perfluoroalkyl group with 1 to 5 carbon atoms, p indicates an integer from 0 to 5, and q indicates an integer from 0 to 5.)

[0039] General formula (2):

[0040] CFX = CXOCF2OR 1 (2)

[0041] (In the formula, X being the same or different represents H, F, or CF3, R) 1 This refers to a straight-chain or branched fluoroalkyl group having 1 to 6 carbon atoms and containing 1 to 2 atoms selected from the group consisting of H, Cl, Br, and I; or a cyclic fluoroalkyl group having 5 or 6 carbon atoms and containing 1 to 2 atoms selected from the group consisting of H, Cl, Br, and I.

[0042] Among them, the monomer represented by general formula (1) is preferred as the FAVE, more preferably at least one of the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether) (PEVE) and perfluoro(propyl vinyl ether) (PPVE), further preferably at least one of the group consisting of PEVE and PPVE, and particularly preferably PPVE.

[0043] The content of FAVE units in the copolymer is 2.8 to 6.0% by mass relative to all monomer units. More preferably, the content of FAVE units in the copolymer is 3.0% by mass or more, further preferably 3.2% by mass or more, even more preferably 3.3% by mass or more, particularly preferably 3.4% by mass or more, most preferably 3.5% by mass or more, more preferably 5.8% by mass or less, further preferably 5.7% by mass or less, even more preferably 5.6% by mass or less, and particularly preferably 5.5% by mass or less. If the content of FAVE units in the copolymer is too high, burrs will be generated during injection molding, or damage to the hollow portion (inner surface of the connector) will be caused when the core material is extracted. If the content of FAVE units in the copolymer is too low, the extraction of the core material itself becomes difficult, or excellent resistance to deformation under high temperature and high pressure fluids cannot be obtained.

[0044] The content of TFE units in the copolymer is preferably 94.0 to 97.2% by mass relative to all monomer units, more preferably 94.2% by mass or more, further preferably 94.3% by mass or more, even more preferably 94.4% by mass or more, particularly preferably 94.5% by mass or more, more preferably 97.0% by mass or less, further preferably 96.8% by mass or less, even more preferably 96.7% by mass or less, particularly preferably 96.6% by mass or less, and most preferably 96.5% by mass or less. If the content of TFE units in the copolymer is too low, burrs may be generated during injection molding, or damage may be caused to the hollow part (inner surface of the pipe fitting) when the core material is extracted. If the content of TFE units in the copolymer is too high, the extraction of the core material itself may become difficult, or excellent deformation resistance to high-temperature and high-pressure fluids may not be obtained.

[0045] In this invention, the content of each monomer unit in the copolymer is determined by... 19 Determined by F-NMR method.

[0046] The copolymer may also contain monomer units from monomers capable of copolymerizing with TFE and FAVE. In this case, the content of monomer units capable of copolymerizing with TFE and FAVE is preferably 0% to 3.2% by mass, more preferably 0.05% to 1.0% by mass, and even more preferably 0.1% to 0.3% by mass, relative to all monomer units of the copolymer.

[0047] Monomers capable of copolymerizing with TFE and FAVE include hexafluoropropylene (HFP) and CZ. 1 Z 2 =CZ 3 (CF2) n Z 4 (where Z) 1 Z 2 and Z 3 Same or different, represented by H or F, Z 4 Vinyl monomers (represented by H, F, or Cl, where n represents an integer from 2 to 10) and CF2=CF-OCH2-Rf 1 (where Rf) 1 This refers to perfluoroalkyl groups having 1 to 5 carbon atoms. Alkyl perfluorovinyl ether derivatives, etc., are also included. HFP is preferred.

[0048] The copolymer is preferably selected from at least one of the groups consisting of copolymers composed only of TFE units and FAVE units and TFE / HFP / FAVE copolymers, and more preferably copolymers composed only of TFE units and FAVE units.

[0049] The melt flow rate (MFR) of the copolymer is 4.0 g / 10 min or more and less than 11.0 g / 10 min. The MFR of the copolymer is preferably 4.5 g / 10 min or more, more preferably 5.0 g / 10 min or more, preferably 10.5 g / 10 min or less, more preferably 10.0 g / 10 min or less, further preferably 9.5 g / 10 min or less, and particularly preferably 9.0 g / 10 min or less. If the MFR of the copolymer is too low, molding defects such as roughness and flow marks will occur. If the MFR of the copolymer is too high, burrs will occur, or damage to the hollow portion (inner surface of the pipe fitting) will be caused when the core material is extracted. Furthermore, excellent resistance to deformation under high temperature and high pressure fluids cannot be obtained.

[0050] In this invention, every 10 of the copolymer 6 The number of functional groups per carbon atom in the main chain is 50 or less, preferably 40 or less, more preferably 30 or less, further preferably 20 or less, even more preferably 15 or less, particularly preferably 10 or less, and most preferably less than 6. If the number of functional groups in the copolymer is too high, poor molding results will occur, such as roughness and flow marks. In addition, excellent resistance to deformation under high temperature and high pressure fluids cannot be obtained.

[0051] The identification of the types of functional groups and the determination of the number of functional groups mentioned above can be achieved using infrared spectroscopy.

[0052] Regarding the number of functional groups, specifically, it was determined using the following method. First, the above copolymer was cold-pressed to produce a film with a thickness of 0.25 mm to 0.3 mm. The film was analyzed by Fourier transform infrared spectroscopy to obtain the infrared absorption spectrum of the above copolymer, and a differential spectrum was obtained compared with the background spectrum of a fully fluorinated copolymer without functional groups. The number of functional groups in the above copolymer was calculated from the absorption peaks of specific functional groups shown in the differential spectrum according to the following formula (A). 6 The number of functional groups N per carbon atom.

[0053] N = I × K / t(A)

[0054] I: Absorbance

[0055] K: Correction coefficient

[0056] t: Membrane thickness (mm)

[0057] For reference, the absorption frequencies, molar absorptivity, and correction factors for some functional groups are shown in Table 1. Furthermore, the molar absorptivity was determined using FT-IR measurements of low-molecular-weight model compounds.

[0058] [Table 1]

[0059] Table 1

[0060]

[0061] The absorption frequencies of -CH2CF2H, -CH2COF, -CH2COOH, -CH2COOCH3, and -CH2CONH2 are tens of Kaiser (cm) lower than those of -CF2H, -COF, free -COOH, and bonded -COOH, -COOCH3, and -CONH2, respectively, as shown in the table. -1 ).

[0062] For example, the number of functional groups in -COF refers to the number of functional groups originating from the absorption frequency of -CF2COF, which is 1883 cm⁻¹. -1 The number of functional groups derived from the absorption peak at 1840 cm⁻¹ and the absorption frequency originating from -CH₂COF were also analyzed. -1 The total number of functional groups obtained from the absorption peak at the given location.

[0063] Functional groups are those present at the ends of the main chain or side chains of the copolymer, and those present in the main chain or side chains. The number of functional groups can be the total number of -CF=CF2, -CF2H, -COF, -COOH, -COOCH3, -CONH2, and -CH2OH.

[0064] The aforementioned functional groups are introduced into the copolymer, for example, through chain transfer agents or polymerization initiators used in the manufacturing of the copolymer. For instance, when an alcohol is used as a chain transfer agent, or when a peroxide having a -CH2OH structure is used as a polymerization initiator, -CH2OH is introduced to the ends of the copolymer's main chain. Alternatively, the aforementioned functional groups are introduced to the ends of the copolymer's side chains by polymerizing monomers containing functional groups.

[0065] By fluorinating the copolymer having such functional groups, copolymers with the number of functional groups within the aforementioned range can be obtained. That is, the copolymer contained in the pipe fitting of the present invention is preferably a fluorinated copolymer. The copolymer contained in the pipe fitting of the present invention also preferably has a -CF3 terminal group.

[0066] The melting point of the copolymer is preferably 295–315°C, more preferably 300°C or higher, even more preferably 301°C or higher, particularly preferably 302°C or higher, more preferably 310°C or lower, and even more preferably 305°C or lower. By keeping the melting point within the above range, pipe fittings can be manufactured more easily even with large wall thicknesses and lengths, the hollow portion and appearance of the pipe fittings are more aesthetically pleasing, and the pipe fittings exhibit superior resistance to deformation from high-temperature and high-pressure fluids.

[0067] In this invention, the melting point can be determined using a differential scanning calorimeter (DSC).

[0068] The pipe fitting of the present invention may contain fillers, plasticizers, processing aids, mold release agents, pigments, flame retardants, lubricants, light stabilizers, weather stabilizers, conductive agents, antistatic agents, ultraviolet absorbers, antioxidants, foaming agents, fragrances, oils, softeners, defluorinating agents, and other components.

[0069] Examples of fillers include silica, kaolin, clay, organoclay, talc, mica, alumina, calcium carbonate, calcium terephthalate, titanium dioxide, calcium phosphate, calcium fluoride, lithium fluoride, cross-linked polystyrene, potassium titanate, carbon, boron nitride, carbon nanotubes, and glass fiber. Examples of conductive agents include carbon black. Examples of plasticizers include dioctyl phthalate and pentaerythritol. Examples of processing aids include carnauba wax, sulfone compounds, low molecular weight polyethylene, and fluorinated additives. Examples of defluorinating agents include organonium and amidines.

[0070] Other polymers besides the copolymers described above can also be used as other components. Examples of other polymers include fluoropolymers, fluororubbers, and non-fluorinated polymers, in addition to the copolymers described above.

[0071] The copolymer contained in the pipe fitting of the present invention can be manufactured by polymerization methods such as suspension polymerization, solution polymerization, emulsion polymerization, and bulk polymerization. As a polymerization method, emulsion polymerization or suspension polymerization is preferred. In these polymerization processes, conditions such as temperature and pressure, polymerization initiators, and other additives can be appropriately set according to the composition and amount of the copolymer.

[0072] Oil-soluble or water-soluble free radical polymerization initiators can be used as polymerization initiators.

[0073] Oil-soluble free radical polymerization initiators can be well-known oil-soluble peroxides, and the following substances can be cited as representative examples:

[0074] Dialkyl percarbonate esters, such as di-n-propyl percarbonate, diisopropyl percarbonate, disec-butyl percarbonate, and di-2-ethoxyethyl percarbonate;

[0075] Peroxide esters such as tert-butyl peroxide isobutyrate and tert-butyl perpentyl peroxide;

[0076] Dialkyl peroxides such as di-tert-butyl peroxide;

[0077] Di[fluoro(or fluorochloro)acyl] peroxides; etc.

[0078] Examples of diacyl peroxides include those represented by [(RfCOO)-]2 (where Rf is a perfluoroalkyl, ω-hydroperfluoroalkyl, or fluorochloroalkyl).

[0079] Examples of di[fluoro(or fluorochloro)acyl]peroxides include, for example, di(ω-hydro-dodecanoyl)peroxide, di(ω-hydro-tetradecanoyl)fluoroheptanoyl)peroxide, di(ω-hydro-hexadecanoyl)fluorononanoyl)peroxide, di(perfluoropropionyl)peroxide, di(perfluorobutyryl)peroxide, di(perfluoropentanoyl)peroxide, di(perfluorohexanoyl)peroxide, di(perfluoroheptanoyl)peroxide, di(perfluorooctanoyl)peroxide, di(perfluorononanoyl)peroxide, di(ω-chloro-hexafluorobutyryl)peroxide, and di... (ω-chloro-decafluorohexanoyl) peroxide, di(ω-chloro-tetrafluorooctanoyl) peroxide, ω-hydro-dodecanoheptafluorononanoyl-peroxide, ω-chloro-hexafluorobutyryl-ω-chloro-decafluorohexanoyl-peroxide, ω-hydro-dodecanoheptafluorobutyryl-perfluorobutyryl-peroxide, di(dichloropentafluorobutyryl) peroxide, di(trichlorooctafluorohexanoyl) peroxide, di(tetrachloroundecanoyl) peroxide, di(pentachlorotetrafluorodecanoyl) peroxide, di(undecachlorotetrafluorotetradecanoyl) peroxide, di(undecachlorotetrafluorotetradecanoyl) peroxide, etc.

[0080] Water-soluble free radical polymerization initiators can be well-known water-soluble peroxides, such as ammonium, potassium, and sodium salts of persulfate, perboric acid, perchloric acid, superphosphoric acid, and percarbonate; organic peroxides such as disuccinate peroxide and diglutaric acid peroxide; tert-butyl maleate peroxide; and tert-butyl hydroperoxide. Reducing agents such as sulfites can also be used in combination with peroxides, with the amount used relative to the peroxide ranging from 0.1 to 20 times.

[0081] In polymerization, surfactants, chain transfer agents, and solvents can be used, each of which can be existing and well-known substances.

[0082] As the surfactant, known surfactants can be used, such as nonionic surfactants, anionic surfactants, and cationic surfactants. Among these, fluorinated anionic surfactants are preferred, and more preferably, fluorinated anionic surfactants with straight or branched chains having 4 to 20 carbon atoms, with or without ether-bonded oxygen (i.e., oxygen atoms can be inserted between carbon atoms). The amount of surfactant added (relative to the polymerization water) is preferably 50 ppm to 5000 ppm.

[0083] Examples of chain transfer agents include: hydrocarbons such as ethane, isopentane, n-hexane, and cyclohexane; aromatics such as toluene and xylene; ketones such as acetone; acetates such as ethyl acetate and butyl acetate; alcohols such as methanol and ethanol; thiols such as methyl mercaptan; and halogenated hydrocarbons such as carbon tetrachloride, chloroform, dichloromethane, and chloromethane. The amount of chain transfer agent added varies depending on the chain transfer constant of the compound used, and is typically used in the range of 0.01% to 20% by mass relative to the polymerization solvent.

[0084] Examples of solvents include water and mixed solvents of water and alcohol.

[0085] In suspension polymerization, fluorinated solvents can be used in addition to water. Examples of fluorinated solvents include hydrochlorofluorocarbons such as CH3CClF2, CH3CCl2F, CF3CF2CCl2H, and CF2ClCF2CFHCl; chlorofluorocarbons such as CF2ClCFClCF2CF3 and CF3CFClCFClCF3; hydrofluorocarbons such as CF3CFHCFHCF2CF2CF3, CF2HCF2CF2CF2CF2H, and CF3CF2CF2CF2CF2CF2CF2H; and CH3OC2F5. Hydrofluoroethers such as CH3OC3F5CF3CF2CH2OCHF2, CF3CHFCF2OCH3, CHF2CF2OCH2F, (CF3)2CHCF2OCH3, CF3CF2CH2OCH2CHF2, and CF3CHFCF2OCH2CF3; perfluorocyclobutanes such as CF3CF2CF2CF3, CF3CF2CF2CF2CF3, and CF3CF2CF2CF2CF2CF3, with perfluoroalkanes being preferred. From the perspectives of suspension and economy, the amount of fluorinated solvent relative to the aqueous medium is preferably 10% to 100% by mass.

[0086] There is no particular limitation on the polymerization temperature, which can be 0 to 100°C. The polymerization pressure is appropriately determined according to the type, amount, vapor pressure, polymerization temperature, and other polymerization conditions used, and is usually 0 to 9.8 MPaG.

[0087] When an aqueous dispersion containing a copolymer is obtained through polymerization, the copolymer can be recovered by precipitating it, washing, and drying. Alternatively, when a copolymer is obtained as a slurry through polymerization, the copolymer can be recovered by removing the slurry from the reaction vessel, washing, and drying. The copolymer can also be recovered as a powder by drying.

[0088] The copolymer obtained through polymerization can also be granulated. There are no particular limitations on the granulation method; existing known methods can be used. For example, methods such as using a single-screw extruder, twin-screw extruder, or tandem extruder to melt-extrude the copolymer and cut it to a specified length to form granules can be employed. The extrusion temperature during melt extrusion needs to be varied depending on the melt viscosity of the copolymer and the manufacturing method; preferably, it is between the copolymer's melting point +20°C and the copolymer's melting point +140°C. There are no particular limitations on the copolymer cutting method; existing known methods such as wire cutting, thermal cutting, underwater cutting, and sheet cutting can be used. The volatile components in the granules can also be removed by heating (degassing treatment). Alternatively, the granules can be treated by contacting them with warm water at 30°C to 200°C, steam at 100°C to 200°C, or hot air at 40°C to 200°C.

[0089] The copolymer obtained by polymerization can also be fluorinated. Fluorination can be carried out by contacting the unfluorinated copolymer with a fluorinated compound. Through fluorination, thermally unstable functional groups such as -COOH, -COOCH3, -CH2OH, -COF, -CF=CF2, and -CONH2, as well as relatively thermally stable functional groups such as -CF2H, can be converted into extremely thermally stable -CF3. As a result, the total number of functional groups (-COOH, -COOCH3, -CH2OH, -COF, -CF=CF2, -CONH2, and -CF2H) of the copolymer can be easily adjusted to the above-mentioned range.

[0090] There are no particular limitations on fluorine-containing compounds; examples of fluorine radical sources that generate fluorine radicals under fluorination conditions can be cited. Examples of such fluorine radical sources include F2 gas, CoF3, AgF2, UF6, OF2, N2F2, CF3OF, and fluorinated halogens (e.g., IF5, ClF3).

[0091] Fluorine radical sources such as F2 gas can be 100% concentrated, but from a safety perspective, it is preferable to mix them with an inert gas and dilute them to 5% to 50% by mass before use, and more preferably to 15% to 30% by mass. Examples of such inert gases include nitrogen, helium, and argon; from an economic perspective, nitrogen is preferred.

[0092] The conditions for fluorination are not particularly limited; the molten copolymer can be brought into contact with a fluorinated compound. However, it is generally carried out at a temperature below the melting point of the copolymer, preferably between 20°C and 240°C, and more preferably between 100°C and 220°C. The fluorination treatment is typically carried out for 1 hour to 30 hours, preferably 5 hours to 25 hours. Fluorination is preferably carried out by bringing the unfluorinated copolymer into contact with fluorine gas (F2 gas).

[0093] The pipe fitting of the present invention can be manufactured, for example, by inserting a cylindrical core material into the cavity of a mold, filling the cavity of the mold with molten copolymer from an injection molding machine, cooling and solidifying the molten copolymer, pulling the core material out along the axial direction of the pipe fitting, and removing the pipe fitting from the mold.

[0094] The aforementioned manufacturing method involves injection molding a copolymer with appropriately adjusted FAVE unit content, MFR, and functional group number. Therefore, even when manufacturing pipe fittings with large wall thickness and length, the core material can be smoothly extracted without damaging the hollow portion, enabling high-productivity manufacturing of pipe fittings without observed molding defects such as roughness or flow marks. Furthermore, the resulting pipe fitting (injection molded body) exhibits excellent resistance to deformation under high-temperature and high-pressure fluids.

[0095] In the manufacturing method described above, a core material with the same axial length (L) as the hollow portion of the pipe fitting can be used. The core material can be one piece or multiple pieces. In the case of forming a hollow portion with a large axial length (L), it is necessary to extract the long core material during demolding. However, the manufacturing method described above is a copolymer injection molding method in which the content of FAVE units, MFR, and number of functional groups are appropriately adjusted, thus allowing the core material to be extracted smoothly without damaging the hollow portion.

[0096] The hollow portion (inner surface of the pipe fitting) of the present invention is smooth, and has excellent chemical resistance and heat resistance, thus making it suitable for use as piping for the flow of reagents.

[0097] The embodiments have been described above, but it is understood that various changes can be made to the methods and details without departing from the spirit and scope of the claims.

[0098] Example

[0099] Next, embodiments will be given to illustrate the implementation of the present invention, but the present invention is not limited to the embodiments described.

[0100] The values ​​in the examples were measured using the following methods.

[0101] (Monomer content)

[0102] The content of each monomer unit was determined by an NMR analyzer (e.g., an AVANCE300 high-temperature probe manufactured by Bruker BioSpin).

[0103] (Mel flow rate (MFR))

[0104] According to ASTM D1238, the mass (g / 10 min) of polymer flowing out of a nozzle with an inner diameter of 2.1 mm and a length of 8 mm per 10 minutes was determined using a melt indexer G-01 (manufactured by Toyo Seiki Co., Ltd.) at 372°C and a load of 5 kg.

[0105] (Melting point)

[0106] The first heating was performed using a differential scanning calorimeter (trade name: X-DSC7000, manufactured by Hitachi High-Tech Science) at a heating rate of 10°C / min, from 200°C to 350°C. Then, the temperature was cooled from 350°C to 200°C at a cooling rate of 10°C / min. The second heating was performed again at a heating rate of 10°C / min, from 200°C to 350°C. The melting point was determined from the peak value of the melting curve generated during the second heating process.

[0107] (Number of functional groups)

[0108] The copolymer granules were cold-pressed to produce films with a thickness of 0.25 mm to 0.3 mm. The films were then scanned 40 times using a Fourier transform infrared spectroscopy (FT-IR) device (Spectrum One, PerkinElmer) to obtain infrared absorption spectra. A differential spectrum was obtained between this spectrum and the background spectrum of the fully fluorinated film, which lacks functional groups. The concentration of the sample relative to each 1 × 10⁻⁶ functional group was calculated from the absorption peaks of specific functional groups observed in the differential spectrum according to the following formula (A). 6 The number of functional groups N per carbon atom.

[0109] N = I × K / t(A)

[0110] I: Absorbance

[0111] K: Correction coefficient

[0112] t: Membrane thickness (mm)

[0113] For reference, the absorption frequencies, molar absorptivity, and correction factors for the functional groups in this invention are shown in Table 2. The molar absorptivity was determined from FT-IR measurements of low-molecular-weight model compounds.

[0114] [Table 2]

[0115] Table 2

[0116]

[0117] Synthesis example 1

[0118] 51.8 L of pure water was added to a 174 L autoclave, and after thorough nitrogen purging, 40.9 kg of perfluorocyclobutane, 0.54 kg of perfluoropropyl vinyl ether (PPVE), and 5.10 kg of methanol were added. The system temperature was maintained at 35 °C, and the stirring speed was maintained at 200 rpm. Next, tetrafluoroethylene (TFE) was injected to 0.64 MPa, followed by 0.051 kg of a 50% methanol solution of di-n-propyl peroxide dicarbonate, to initiate polymerization. As the pressure in the system decreased during polymerization, TFE was continuously supplied to maintain a constant pressure, with 0.020 kg of PPVE added for every 1 kg of TFE supplied. Polymerization was terminated when the amount of TFE added reached 40.9 kg. Unreacted TFE was released, and the autoclave was restored to atmospheric pressure. The resulting reaction product was washed with water and dried to obtain 41.1 kg of powder.

[0119] The obtained powder was melt-extruded at 360°C using a screw extruder (trade name: PCM46, manufactured by Ikebe Co., Ltd.) to obtain TFE / PPVE copolymer granules. The PPVE content of the obtained granules was determined using the method described above.

[0120] The obtained granules were placed in a VVD-30 vacuum vibratory reactor (manufactured by Okawahara Seisakusho Co., Ltd.) and heated to 210°C. After evacuation, F2 gas diluted to 20% by volume with N2 gas was introduced to atmospheric pressure. 0.5 hours after the introduction of F2 gas, the reactor was temporarily evacuated, and F2 gas was introduced again. This process was repeated 0.5 hours later, followed by another evacuation and introduction of F2 gas. This process of introducing F2 gas and evacuating the reactor was repeated once every hour, and the reaction was carried out at 210°C for 10 hours. After the reaction was completed, the reactor was completely replaced with N2 gas to stop the fluorination reaction. Various physical properties of the fluorinated granules were measured using the above method.

[0121] Synthesis example 2

[0122] The amount of PPVE was changed to 3.47 kg, methanol to 3.28 kg, and the amount of 50% methanol solution of di-n-propyl peroxide dicarbonate to 0.026 kg. The amount of PPVE was changed to 0.071 kg added for every 1 kg of TFE supplied, resulting in 43.8 kg of dry powder. Otherwise, fluorinated granules were obtained in the same manner as in Synthesis Example 1.

[0123] Synthesis example 3

[0124] The amount of PPVE was changed to 2.69 kg, methanol to 0.10 kg, and the 50% methanol solution of di-n-propyl peroxide dicarbonate to 0.026 kg. The amount of PPVE was changed to 0.057 kg added for every 1 kg of TFE supplied, resulting in 43.2 kg of dry powder. Otherwise, fluorinated granules were obtained in the same manner as in Synthesis Example 1.

[0125] Synthesis example 4

[0126] The amount of PPVE was changed to 2.69 kg, the amount of methanol was changed to 2.48 kg, and the amount of PPVE was changed to an additional 0.057 kg for every 1 kg of TFE supplied, resulting in 43.2 kg of dry powder. Otherwise, fluorinated granules were obtained in the same manner as in Synthesis Example 1.

[0127] Synthesis example 5

[0128] The amount of PPVE was changed to 2.75 kg, the amount of methanol was changed to 0.88 kg, and the amount of PPVE was changed to 0.058 kg added for every 1 kg of TFE supplied, resulting in 43.3 kg of dry powder. Otherwise, unfluorinated granules were obtained in the same manner as in Synthesis Example 1.

[0129] Synthesis example 6

[0130] The amount of PPVE was changed to 1.49 kg, the amount of methanol was changed to 1.65 kg, and the amount of PPVE was changed to 0.036 kg added for every 1 kg of TFE supplied, resulting in 42.4 kg of dry powder. Otherwise, fluorinated granules were obtained in the same manner as in Synthesis Example 1.

[0131] Synthesis Example 7

[0132] The amount of PPVE was changed to 2.11 kg, the amount of methanol was changed to 1.28 kg, the amount of PPVE was changed to 0.047 kg added for every 1 kg of TFE supplied, the heating temperature of the vacuum vibrating reactor was changed to 170°C, and the reaction time at 170°C was changed to 5 hours, resulting in 42.8 kg of dry powder. Otherwise, fluorinated granules were obtained in the same manner as in Synthesis Example 1.

[0133] Synthesis example 8

[0134] The amount of PPVE was changed to 2.75 kg, the amount of methanol was changed to 0.60 kg, and the amount of PPVE was changed to 0.058 kg added for every 1 kg of TFE supplied, resulting in 43.3 kg of dry powder. Otherwise, fluorinated granules were obtained in the same manner as in Synthesis Example 1.

[0135] Using the granules obtained in the synthesis example, various physical properties were determined using the methods described above. The results are shown in Table 3.

[0136] [Table 3]

[0137] Table 3

[0138]

[0139] The “<6” in Table 3 refers to the number of functional groups being less than 6.

[0140] Using the granules obtained above, pipe fittings were fabricated using the following method. The resulting pipe fittings were evaluated. The results are shown in Table 4.

[0141] (Preparation of pipe fitting (1)) (Refer to example)

[0142] Using an injection molding machine (Sumitomo Heavy Industries, SE50EV-A), with the barrel temperature set to 400°C, the mold temperature set to 220°C, and the injection speed set to 5 mm / s, granules were injection molded to produce a cylindrical injection molded body (inner diameter Φ1.5cm (diameter (D) of the hollow part = 15mm), outer diameter Φ1.9cm, thickness 2mm, axial length of the tube 10.5cm (axial length (L) = 105mm)). A removable core material with a diameter of Φ1.5cm and a height of 10.5cm was mounted on the movable side of the mold.

[0143] Evaluate release properties based on the following criteria.

[0144] ○: Capable of extracting cylindrical injection-molded parts from the core material.

[0145] ×: Unable to extract the cylindrical injection molded part from the core material.

[0146] (Making pipe fitting 2)

[0147] Using an injection molding machine (Sumitomo Heavy Industries, SE50EV-A), with the barrel temperature set to 400°C, the mold temperature set to 220°C, and the injection speed set to 5 mm / s, granules were injection molded to produce a cylindrical injection molded body (inner diameter Φ1.5cm (diameter (D) of the hollow part = 15mm), outer diameter Φ1.9cm, thickness 2mm, axial length of the tube 4.5cm (axial length (L) = 45mm)). A core with a diameter of Φ1.5cm and a height of 4.5cm, which can be removed from the movable side of the mold, is installed in the inner cavity.

[0148] Pipe fittings (2) were used in the following evaluation.

[0149] (Appearance evaluation (rough edges))

[0150] Visually inspect the end of the hollow part of the pipe connector (2) (the part that forms the interface between the core and the mold) and evaluate it according to the following criteria.

[0151] ○: Observed rough edges

[0152] ×: No rough edges observed

[0153] (Appearance Evaluation (Hollow Section))

[0154] Visually inspect the hollow part (inner surface) of the pipe joint (2) and evaluate it according to the following criteria.

[0155] ○: No damage was observed in the hollow section.

[0156] ×: Damage observed in the hollow section

[0157] (Demolding performance evaluation)

[0158] The fabrication of the pipe fitting (2) was repeated 20 times according to the above method, and evaluated according to the following criteria.

[0159] ○: The core material can be extracted during the entire manufacturing process.

[0160] ×: Sometimes the core material cannot be extracted during more than one production attempt.

[0161] (Appearance evaluation (gate area))

[0162] Visually confirm the position of the joint corresponding to the gate of the mold of the pipe joint (2). Figure 1 The roughness of the inner wall around the location A shown is evaluated according to the following criteria.

[0163] ○: Surface roughness

[0164] ×: Surface is smooth

[0165] (Appearance evaluation (flow marks))

[0166] The appearance of the pipe fitting (2) is evaluated according to the following criteria.

[0167] ○: The surface is smooth overall, and no flow marks were observed on the entire molded body.

[0168] ×: Surface roughness or flow marks observed.

[0169] (Tensile creep test)

[0170] Tensile creep strain was determined using a Hitachi High-Tech TMA-7100. A sample 1 mm wide and 20 mm long was prepared from a pipe fitting (2). The sample was mounted in the measuring fixture with a 10 mm gap between the clamps. A cross-sectional load of 2.41 N / mm² was applied to the sample. 2The sample was subjected to a load at 240°C, and the displacement (mm) of its length was measured from 70 minutes to 300 minutes after the start of the test. The ratio of the displacement (mm) to the initial sample length (10mm) was calculated (tensile creep strain (%)). Injection-molded parts with low tensile creep strain (%) measured at 240°C for 300 minutes are difficult to elongate even when subjected to tensile loads in very high-temperature environments, exhibiting excellent resistance to deformation in high-temperature and high-pressure fluids.

[0171]

[0172] To manufacture pipe fittings with thick walls, molding defects such as shrinkage marks and voids are easily produced. Therefore, to manufacture pipe fittings with thick walls, it is necessary to increase the holding pressure (secondary pressure) during injection molding. As shown in Table 4, increasing the holding pressure during injection molding results in burrs or damage to the hollow portion (inner surface of the pipe fitting) when the core material is extracted (Comparative Examples 1 and 4). On the other hand, to eliminate these molding defects, core material extraction itself becomes difficult (Comparative Example 2), or molding defects such as roughness and flow marks occur (Comparative Examples 3 and 5).

[0173] Furthermore, if the ratio of the axial length (L) of the hollow portion to its diameter (D) is too large, core material extraction becomes difficult (see example). Therefore, to manufacture pipe fittings with a large axial length (L) of the hollow portion, the diameter (D) of the hollow portion needs to be increased. If the diameter (D) of the hollow portion is increased, even if the pipe fitting deforms by only a small proportion, the overall shape of the pipe fitting will change significantly, thus requiring excellent deformation resistance to high-temperature and high-pressure fluids. However, conventional pipe fittings have the problem of not necessarily having sufficient deformation resistance (comparative examples 2, 4, and 5).

[0174] In contrast, the pipe fitting of the present invention allows for smooth extraction of the core material during its manufacture, thus facilitating production (Examples 1-3). Furthermore, even with large wall thickness and length, the pipe fitting of the present invention maintains an aesthetically pleasing hollow portion and appearance, and exhibits excellent resistance to deformation under high temperature and high pressure fluids (Examples 1-3).

Claims

1. A pipe fitting having a cylindrical hollow portion, wherein, The wall thickness of the thickest part of the pipe joint is 2mm to 7mm. The ratio of the axial length L of the hollow portion to the diameter D of the hollow portion, L / D, is 5 or less. The fitting contains a copolymer containing tetrafluoroethylene units and fluorinated (alkyl vinyl ether) units. The copolymer contains fluorinated (alkyl vinyl ether) units at a rate of 2.8% to 6.0% by mass relative to all monomer units. The copolymer has a melt flow rate of 4.0 g / 10 min or more and less than 11.0 g / 10 min at 372°C. Every 10 of the copolymer 6 The total number of functional groups of -CF=CF2, -CF2H, -COF, -COOH, -COOCH3, -CONH2 and -CH2OH with a number of carbon atoms in the main chain is less than 50.

2. The pipe fitting as described in claim 1, wherein, The axial length L of the hollow part is 20 mm or more.

3. The pipe fitting as described in claim 1 or 2, wherein, The fluorinated (alkyl vinyl ether) unit of the copolymer is a perfluoro (propyl vinyl ether) unit.

4. The pipe fitting as described in claim 1 or 2, wherein, The content of the fluorinated (alkyl vinyl ether) unit in the copolymer is 3.5% to 5.5% by mass relative to all monomer units.

5. The pipe fitting as described in claim 1 or 2, wherein, The copolymer has a melt flow rate of 5.0 g / 10 min to 9.0 g / 10 min at 372 °C.

6. The pipe fitting as described in claim 1 or 2, wherein, The copolymer has a melting point of 295°C to 315°C.

7. The pipe fitting as described in claim 1 or 2, wherein, It is an injection-molded body.

8. A method for manufacturing a pipe fitting, comprising the following steps: inserting a cylindrical core material into a mold cavity; filling the mold cavity with molten copolymer from an injection molding machine; cooling the molten copolymer to solidify it; extracting the core material along the axial direction of the pipe fitting; and removing the pipe fitting from the mold, wherein... The ratio of the axial length L of the hollow portion of the pipe joint formed by extracting the core material to the diameter D of the hollow portion, L / D, is 5 or less. The wall thickness of the thickest part of the pipe joint is 2mm to 7mm.

9. The manufacturing method as described in claim 8, wherein, The length of the core material is the same as the axial length L of the hollow part of the pipe joint.

10. The manufacturing method as described in claim 8 or 9, wherein, The copolymer is a copolymer containing tetrafluoroethylene units and fluorinated (alkyl vinyl ether) units. The copolymer contains fluorinated (alkyl vinyl ether) units at a rate of 2.8% to 6.0% by mass relative to all monomer units. The copolymer has a melt flow rate at 372°C of 4.0 g / 10 min or more and less than 11.0 g / 10 min. The copolymer has a per 10 6 The total number of functional groups of -CF=CF2, -CF2H, -COF, -COOH, -COOCH3, -CONH2 and -CH2OH with a number of carbon atoms in the main chain is less than 50.

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