Anti-static Teflon hose with flat inside and corrugated outside

Abstract

The invention discloses an anti-static inner-flat outer-wave Teflon hose, and belongs to the technical field of high-performance fluid conveying. The smooth lining layer is made of melt-processable fluorine-containing polymer blends in a specific proportion, so that the anti-static effect of a body is achieved; the smooth lining layer is made of melt-processable fluorine-containing polymer blends in the radial direction from inside to outside; the continuous conductive grounding grid is coated outside the lining layer; and an outer corrugated reinforcement layer formed by sintering PTFE powder by vacuum adsorption. The core of the invention is that the outer surface of the lining layer is provided with anchoring micro-grains, and the PTFE material of the outer corrugated layer is embedded into the micro-grains and coats the conductive grid during sintering, so that a firm mechanical interlocking composite structure is formed. The key of the preparation method comprises the following steps: co-extruding the sizing lining pipe, weaving the conductive net, and performing vacuum rotary corrugated forming and sintering. The hose has the advantages of ultrahigh smoothness of the inner wall, excellent flexibility, lasting and reliable static conductivity and strong interlayer binding force.

Description

Technical Field

[0001] This invention relates to the field of pipeline structure technology, specifically to an antistatic Teflon flexible hose with an inner flat and outer wave. Background Technology

[0002] Polytetrafluoroethylene (PTFE) and its copolymers have become the preferred material for hoses used in high-end manufacturing industries such as semiconductors, photovoltaics, and biopharmaceuticals for conveying high-purity, highly corrosive chemicals due to their excellent chemical inertness, wide temperature range, and non-stick properties. To meet the flexibility requirements of pipeline installation, hoses are typically made with a flexible corrugated structure. However, achieving ultra-high cleanliness of the inner wall, durable and reliable antistatic properties, and excellent mechanical durability within this structure has always been a technical challenge for the industry.

[0003] In existing technologies, the following solutions exist to address the flexibility and functionality issues of Teflon hoses: First, pure PTFE hoses with a corrugated inner wall are directly extruded. While this solution ensures flexibility, the corrugated inner wall easily traps trace particles or microorganisms in the fluid, creating a source of contamination and failing to meet the stringent cleanliness requirements for ultrapure fluid transport. Second, to address static electricity buildup, metal wires are typically braided or a conductive coating is applied to the outer periphery of smooth or corrugated hoses. However, for "flat-inner-corrugated-outer-corrugated" hoses processed from smooth tubing, the outer metal braid and the PTFE surface have weak bonding due to significant differences in physicochemical properties. Under frequent dynamic bending conditions, they are prone to loosening or even peeling, leading to interruption of the static electricity conduction path and unreliable antistatic performance. Third, to further enhance interlayer bonding, some technologies have attempted to use adhesives or roughen the PTFE surface. However, adhesives may introduce leached substances that contaminate the fluid, while mechanical roughening may damage the integrity of the hose wall, creating a potential leakage hazard. Summary of the Invention

[0004] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides an antistatic inner flat outer wave Teflon flexible hose, which solves the problems mentioned in the background art.

[0005] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: an antistatic Teflon flexible hose with an inner flat and outer wave, comprising, from the inside to the outside in the radial direction: The inner liner is made of a melt-processable fluoropolymer composition comprising: 70–90 wt% of a first melt-processable fluoropolymer selected from one or more of perfluoroalkoxyalkanes, fluorinated ethylene-propylene copolymers, ethylene-tetrafluoroethylene copolymers, and polyvinylidene fluoride; and 10–30 wt% of a second melt-processable fluoropolymer, which is a functionalized fluoropolymer having 0.5–5 mol% of monomer units containing polar functional groups covalently bonded to its main chain, wherein the polar functional groups are selected from one or both of hydroxyl and cyano groups. The volume resistivity of the inner lining layer, measured at 23°C and 50% relative humidity, is 1×10⁻⁶. 6 Ω·cm to 1×10 9 Ω·cm, thereby achieving moderate charge dissipation through the bulk material; A continuous conductive grounding grid is constructed of metal wires in a braided or spirally wound manner and tightly wrapped around the outer surface of the inner lining layer; The outer corrugated reinforcement layer is formed on the outer periphery of the inner liner layer by vacuum adsorption and sintering process using non-conductive polytetrafluoroethylene material, and forms a mechanical interlocking structure with the outer surface of the inner liner layer. The outer surface of the inner liner layer has anchoring micro-textures formed by a sizing process. The PTFE material is partially embedded in the anchoring micro-textures during sintering and also covers and fills the mesh structure of the continuous conductive grounding grid, so that the outer corrugated reinforcement layer forms a composite structure of mechanical interlocking and physical covering with the inner liner layer and the continuous conductive grounding grid.

[0006] Preferably, the second melt-processable fluoropolymer is a copolymer of tetrafluoroethylene and perfluorinated monomers, wherein the content of the perfluorinated monomer units is 0.8–1.2 mol.

[0007] Preferably, the thickness of the inner lining layer is 0.2–0.8 mm, and its outer surface is treated with hot air at 300–350°C to form a micro-melting activation layer with a thickness of 20–30 µm, which is used to enhance the bonding strength with the continuous conductive grounding grid.

[0008] Preferably, the continuous conductive grounding grid is woven from 316L stainless steel wire, with a single wire diameter of 0.08–0.15 mm and a weaving angle of 45°±5°.

[0009] Preferably, the corrugation depth of the outer corrugated reinforcement layer is 1.5–3.0 mm, the wave pitch is 4–7 mm, and the ratio of wave depth to wave pitch is between 0.3 and 0.5.

[0010] Preferably, the outer wall of the outer corrugated reinforcing layer is wrapped with a transparent outer sheath, which is made of fluorinated ethylene propylene copolymer heat shrink tubing, with a wall thickness of 0.1–0.3 mm after shrinkage, and an outer surface resistivity of not less than 1×10¹³ Ω㎡.

[0011] Preferably, the hose is provided with flanged metal joints at both ends, and the end of the continuous conductive grounding grid is flanged and clamped between the flange of the metal joint and the outer wall of the hose, to ensure that the contact resistance of the electrical continuity connection is less than 1 milliohm and can withstand a sealing test of not less than 1.5 times the nominal pressure.

[0012] Preferably, the hose can withstand 10,000 bending cycles at a bending radius of 1.5 times the nominal inner diameter without cracking, leaking, or delamination.

[0013] Preferably, in a dynamic particle precipitation test, the fluid contact surface of the inner wall of the hose exhibits a precipitation amount of no more than 5 particles / mL for particles with a diameter of not less than 0.5µm, making it suitable for conveying ultrapure chemicals, photoresists, pharmaceutical water, or new energy battery electrolytes.

[0014] A method for preparing an antistatic inner flat outer wave Teflon flexible hose, applicable to the aforementioned antistatic inner flat outer wave Teflon flexible hose, includes the following steps: S1. Prepare the inner liner by mixing the first and second melt-processable fluoropolymers in an environment with a moisture content of ≤100ppm, melting and extruding them at 320-375℃ using a single screw extruder, and sizing them by vacuum sizing sleeve to form a smooth inner liner with anchoring micro-textures on the outer surface. S2 braided conductive layer, braided or spirally wound metal wire on the outer surface of the inner liner tube to form a continuous conductive grounding grid; S3 Forming the outer corrugated layer: The inner liner tube covered with the conductive grounding grid is placed in a vacuum rotary corrugated forming equipment. PTFE fine powder is evenly sprinkled on the outside of the tube blank. Under negative pressure, the PTFE powder passes through the mesh of the conductive grounding grid and is adsorbed onto the anchoring micro-texture of the inner liner layer. Then, after heating and sintering and cooling, an outer corrugated reinforcing layer that is mechanically interlocked with the inner layer is formed.

[0015] (III) Beneficial Effects This invention provides an antistatic Teflon flexible hose with an inner flat and outer wave design, which has the following beneficial effects: This invention employs a melt-processable fluoropolymer blend extruded into the inner liner, ensuring absolute smoothness and chemical inertness of the inner wall, thus eliminating the defect of easy material accumulation on the corrugated inner wall from the source. Secondly, an anchoring micro-texture is formed in situ on the outer surface of the inner liner using a vacuum sizing process. Furthermore, a functionalized fluoropolymer is preferred, allowing PTFE powder to embed into the micro-texture at the molecular level and interact strongly with functional groups during the subsequent sintering of the outer corrugated layer, forming a "mechanical-chemical" interlocking structure far exceeding physical bonding. This integrated molding technology from the inside out ensures extremely high peel strength (≥30 N / cm) between the outer corrugated layer and the inner liner, avoiding the risk of interlayer separation. This provides the hose with excellent flexibility while ensuring its integrity and reliability as an ultrapure fluid channel.

[0016] 2. This invention cleverly places a conductive grounding mesh made of metal wire between the inner lining layer and the outer corrugated layer. A unique corrugated forming process completely encapsulates and fills the gaps in the metal mesh with PTFE material, firmly anchoring the conductive mesh inside the pipe wall. This protects it from direct mechanical stresses such as external friction and bending, preventing loosening or peeling. When static charge is generated, it can be slowly dissipated through the inner lining layer with a certain volume resistivity, or quickly guided to the grounding connector through the tightly contacting conductive mesh. This dual-path electrostatic discharge mechanism, combined with the permanent protection provided by the embedded structure, ensures that the antistatic performance of the hose remains stable and reliable throughout its service life, fully meeting the safety requirements for transporting flammable and explosive environments and electrostatically sensitive ultrapure chemicals. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a cross-sectional schematic diagram of the present invention.

[0018] The components include: 1. Inner lining layer; 2. Continuous conductive grounding grid; 3. Outer corrugated reinforcement layer; 4. Flanged metal joint; 5. Transparent outer sheath. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: like Figure 1-2As shown, this embodiment of the invention provides an antistatic inner flat outer wave Teflon flexible hose. The preparation process of this antistatic inner flat outer wave Teflon flexible hose includes raw material preparation, preparation process, post-processing and assembly, and performance testing.

[0021] Raw material preparation: Inner liner composition: Weigh 85 wt% PFA (first melt-processable fluoropolymer) and 15 wt% tetrafluoroethylene-perfluoro(4,7-dioxa-8-hydroxyoctene) copolymer (second melt-processable fluoropolymer, with 1.0 mol% functional group monomer unit content). Mix thoroughly in dry air with a dew point below -40°C.

[0022] Conductive grounding grid: Prepare 316L stainless steel wire with a diameter of 0.10mm.

[0023] Outer corrugated layer material: Prepare suspension polymerized PTFE fine powder with an average particle size of 30μm.

[0024] Preparation process: S1. Preparation of the inner liner tube: The mixed inner liner composition was fed into a single-screw extruder with a length-to-diameter ratio of 36:1. The tube blank was extruded at a melt temperature of 350°C and sizing was performed using a sizing sleeve with a vacuum of -0.07 MPa (water temperature controlled at 22°C) to form a smooth inner liner tube with an inner diameter of 12.0 mm and a wall thickness of 0.5 mm. Anchoring micro-textures of approximately 10-15 μm naturally formed on the outer surface of the tube blank. Subsequently, the tube blank underwent three-stage gradient water cooling at 55°C-35°C-18°C, and finally annealed in a clean oven at 125°C for 35 minutes to eliminate internal stress. The volume resistivity of the resulting inner liner tube was measured to be 5.2 × 10⁻⁶. 7 The inner wall roughness Ra is 0.12 μm, with a diameter of Ω·cm.

[0025] S2. Braided conductive layer: On the outer surface of the above-mentioned inner liner tube, a conductive grounding mesh with a coverage of about 75% is formed by braiding 316L stainless steel wire at a braiding angle of 46°.

[0026] S3. Forming the Outer Corrugated Layer: The tube blank covered with a conductive grounding mesh is fixed in a vacuum rotary corrugated forming machine. Fine PTFE powder is evenly sprinkled onto the rotating tube blank. Under a negative pressure of -0.08 MPa, the PTFE powder is adsorbed and passes through the mesh of the conductive mesh, tightly adhering to the anchoring micro-textures of the inner liner tube. Subsequently, the tube blank enters a sintering furnace and is sintered at 380℃. After cooling, an outer corrugated reinforcing layer with a corrugation depth of 2.0 mm and a corrugation pitch of 5.0 mm (corrugation depth-to-pitch ratio of 0.4) is formed. This outer layer is firmly bonded to the inner liner and the conductive mesh, and the peel strength is tested to reach 38 N / cm.

[0027] Post-processing and assembly: Flanged stainless steel connectors were installed at both ends of the flexible hose, and the ends of the conductive grounding grid were flanged and reliably clamped. The contact resistance at the connector was measured to be 0.8 mΩ.

[0028] The hose was subjected to a 2.0MPa (nominal pressure of 1.3MPa) air pressure tightness test, and no leakage was observed after holding the pressure for 5 minutes.

[0029] Performance testing: Bending fatigue test: Under a bending radius of 18 mm (1.5 times the nominal inner diameter), the hose was subjected to 10,000 cycles of bending test, and no cracks, leaks or delamination were observed.

[0030] Particle precipitation: The tubing was flushed with ultrapure water at a flow rate of 1 m / s, and the liquid sample was collected for testing. The amount of particles ≥0.5 μm precipitated was 3 particles / mL.

[0031] Electrostatic discharge decay: According to the IEC61340-5-1 standard test, the time for electrostatic discharge to decay from ±1000V to ±100V is less than 0.03 seconds.

[0032] Example 2: The difference between this embodiment and Embodiment 1 lies in the raw materials and the preparation process.

[0033] Differences between the raw materials and those in Example 1: The inner liner composition is a blend of 80 wt% FEP and 20 wt% functionalized ETFE (cyano functional group content is 0.9 mol%).

[0034] Outer sheath: Prepare transparent FEP heat shrink tubing.

[0035] Differences in preparation process: S1. Preparation of inner liner tube: After extrusion molding, the outer surface of the inner liner tube is briefly treated with hot air at 330°C to form a micro-melt activation layer of about 25μm thickness to further enhance the adhesion with the subsequent conductive layer.

[0036] S2. Braided conductive layer: Same as in Example 1.

[0037] S3. Molding the outer corrugated layer: The process is the same as in Example 1.

[0038] Additional step S4. Install outer sheath: Place the transparent FEP heat-shrink tubing over the formed corrugated pipe and heat-shrink it to form a dense outer sheath with a wall thickness of approximately 0.2 mm. The surface resistivity of this sheath is greater than 10¹³ Ω㎡, which can effectively prevent the adsorption of external environmental pollutants and facilitate visual inspection of the internal condition.

[0039] Performance results: In addition to possessing the excellent performance of Example 1, the flexible tube obtained in this embodiment has a lower risk of particle contamination and precipitation in cleanroom environments due to its smooth outer sheath surface, making it particularly suitable for the extremely high cleanliness requirements in semiconductor photolithography processes.

[0040] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An antistatic inner flat outer corrugated Teflon flexible hose, characterized in that, From the inside to the outside along the radial direction, it includes: The inner liner (1) is made of a melt-processable fluoropolymer composition comprising: (A) 70–90 wt% of a first melt-processable fluoropolymer selected from one or more of perfluoroalkoxyalkane (PFA), fluorinated ethylene propylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), and polyvinylidene fluoride (PVDF); and (B) 10–30 wt% of a second melt-processable fluoropolymer, which is a functionalized fluoropolymer having 0.5–5 mol% of monomer units containing polar functional groups covalently bonded to its main chain, wherein the polar functional groups are selected from one or both of hydroxyl and cyano groups. The continuous conductive grounding grid (2) is made of metal wires in a braided or spirally wound manner and tightly wrapped around the outer surface of the inner lining layer (1); The outer corrugated reinforcement layer (3) is formed on the outer periphery of the inner liner layer (1) by vacuum adsorption and sintering process of non-conductive polytetrafluoroethylene (PTFE) material, and forms a mechanical interlocking structure with the outer surface of the inner liner layer (1). The outer surface of the inner liner layer (1) has anchoring micro-textures formed by sizing process. The PTFE material is partially embedded in the anchoring micro-textures during sintering and covers and fills the mesh structure of the continuous conductive grounding grid (2), so that the outer corrugated reinforcement layer (3) forms a composite structure of mechanical interlocking and physical covering with the inner liner layer (1) and the continuous conductive grounding grid (2).

2. The antistatic inner flat outer corrugated Teflon flexible hose according to claim 1, characterized in that: The second melt-processable fluoropolymer is a copolymer of tetrafluoroethylene and perfluorinated (4,7-dioxa-8-hydroxyoctene), wherein the content of the perfluorinated (4,7-dioxa-8-hydroxyoctene) monomer unit is 0.8–1.2 mol.

3. The antistatic inner flat outer corrugated Teflon flexible hose according to claim 1, characterized in that: The inner lining layer (1) has a thickness of 0.2–0.8 mm, and its outer surface is treated with hot air at 300–350°C to form a micro-melting activation layer with a thickness of 20–30 µm, which is used to enhance the bonding strength with the continuous conductive grounding grid (2).

4. The antistatic inner flat outer corrugated Teflon flexible hose according to claim 1, characterized in that: The continuous conductive grounding grid (2) is woven from 316L stainless steel wire with a single wire diameter of 0.08–0.15 mm and a weaving angle of 45°±5°.

5. The antistatic inner flat outer corrugated Teflon flexible hose according to claim 1, characterized in that: The outer corrugated reinforcement layer (3) has a corrugation depth of 1.5–3.0 mm and a wave pitch of 4–7 mm, with the ratio of wave depth to wave pitch between 0.3 and 0.

5.

6. The antistatic inner flat outer corrugated Teflon flexible hose according to claim 1, characterized in that: The outer corrugated reinforcing layer (3) is wrapped with a transparent outer sheath (5) on its outer side wall. The transparent outer sheath (5) is made of fluorinated ethylene propylene copolymer heat shrink tubing, with a wall thickness of 0.1–0.3 mm after shrinkage, and its outer surface resistivity is not less than 1×10¹³Ω㎡.

7. The antistatic inner flat outer corrugated Teflon flexible hose according to claim 1, characterized in that: The hose is provided with flanged metal connectors (4) at both ends. The end of the continuous conductive grounding grid (2) is flanged and clamped between the flange of the metal connector and the outer wall of the hose to ensure that the contact resistance of the electrical continuity connection is less than 1 milliohm and can withstand a sealing test of not less than 1.5 times the nominal pressure.

8. A method for preparing an antistatic inner flat outer corrugated Teflon flexible hose, applied to the antistatic inner flat outer corrugated Teflon flexible hose as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Prepare the inner liner by mixing the first and second melt-processable fluoropolymers in an environment with a moisture content of ≤100ppm, melting and extruding them at 320-375℃ using a single screw extruder, and sizing them by vacuum sizing sleeve to form a smooth inner liner with anchoring micro-textures on the outer surface. S2 braided conductive layer, braided or spirally wound metal wire on the outer surface of the inner liner tube to form a continuous conductive grounding grid (2). S3 Forming the outer corrugated layer: The inner liner tube covered with the conductive grounding grid is placed in a vacuum rotary corrugated forming equipment. PTFE fine powder is evenly sprinkled on the outside of the tube blank. Under the action of negative pressure, the PTFE powder passes through the mesh of the conductive grounding grid and is adsorbed onto the anchoring micro-texture of the inner liner (1). Then, after heating and sintering and cooling and shaping, an outer corrugated reinforcing layer (3) mechanically interlocked with the inner layer is formed.

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