Polytetrafluoroethylene hose and process for the production thereof

Abstract

The application belongs to the technical field of polytetrafluoroethylene pipe preparation, and particularly relates to a polytetrafluoroethylene hose and a preparation process thereof, which comprises the following steps: mixing modified polytetrafluoroethylene particles, perfluoroalkoxy resin and a first conductive agent, and then feeding the mixture into an extruder to extrude a pipe embryo; adding methanol and octenyl trimethylsilane into a sodium hydroxide solution, stirring, adding glacial acetic acid, stirring, obtaining a modified solution, immersing the pipe embryo in the modified solution, reacting, taking out, washing, drying, cooling, and obtaining a modified pipe embryo; coating the modified pipe embryo with conductive glue, and performing heating and curing treatment on the conductive glue to obtain a polytetrafluoroethylene hose; mixing and stirring methyl methacrylate, 2-hydroxyethyl acrylate, dipropylene glycol butyl ether and hydroquinone, adding a second conductive agent and an initiator, and stirring uniformly to obtain conductive glue. The application can shorten the charge migration path, accelerate the charge leading-out speed, avoid the accumulation of charges on the pipeline, and maintain production safety.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polytetrafluoroethylene pipe preparation, and particularly relates to a polytetrafluoroethylene hose and a preparation process thereof. BACKGROUND

[0002] The chemical stability of the polytetrafluoroethylene pipe is strong, and when the pipe is applied to a conveying system in the fields of chemical industry and pharmaceutical industry, flammable and explosive materials such as gasoline and metal dust can be transported. When the materials flow at a high speed in the pipe, the materials will rub against the pipe wall to generate static charges on the pipe wall. Since there is a lack of conductive channels in the polytetrafluoroethylene pipe, the charges are difficult to be released through a natural way, and a high potential difference is easily formed. When the potential difference reaches a certain value, electrostatic discharge will be triggered, increasing the risk of explosion. Although the pipe can be grounded, since the resistivity of the polytetrafluoroethylene pipe is high, a large number of grounding points need to be set, and a grounding device needs to be independently installed at each grounding point and checked regularly, resulting in a significant increase in labor and maintenance costs.

[0003] A Chinese patent document with the publication number CN118126478B discloses a wear-resistant anti-static polytetrafluoroethylene composite material, which comprises 70-90 parts by weight of polytetrafluoroethylene, 10-30 parts by weight of fluorine-containing polyimide, and 1-8 parts by weight of fluorine-modified graphene. In the pipe prepared from the polytetrafluoroethylene composite material related to the above patent, the volume resistivity of the polytetrafluoroethylene is reduced due to the introduction of the fluorine-modified graphene, the overall conductivity and anti-static performance of the pipe are improved, and thus the number of required grounding points is reduced. However, in actual application, the charges generated in the pipe still need to migrate to the grounding points to be released. Since the migration path of the charges is long, the release speed of the charges is slow, and when flammable and explosive materials are transported, the charges are difficult to dissipate in time, and the charges may accumulate on the pipe, which poses a safety hazard and is not conducive to production safety. SUMMARY

[0004] The application provides a polytetrafluoroethylene hose and a preparation process thereof. In the preparation process of the pipe blank, a conductive material is added, and a conductive adhesive is coated on the outer wall of the pipe blank. The charges can be released by migrating from the inner wall of the pipe blank to the outer wall of the pipe blank, the migration path of the charges is shortened, the static dissipation capacity is improved, the accumulation of the charges on the pipe is avoided, and the production safety is maintained.

[0005] To solve the above problems, the application provides a polytetrafluoroethylene hose and a preparation process thereof, which adopts the following technical scheme:

[0006] A preparation process of a polytetrafluoroethylene hose, comprising the following steps:

[0007] S1, the polytetrafluoroethylene particles are subjected to plasma treatment by water vapor to obtain modified polytetrafluoroethylene particles; the modified polytetrafluoroethylene particles, a perfluoroalkoxy resin and a first conductive agent are uniformly mixed and then fed into an extruder to be extruded to obtain a tube embryo;

[0008] S2, methanol and octenyl trimethylsilane are added to a sodium hydroxide solution, stirred, glacial acetic acid is added, stirred, to obtain a modified solution, the tube embryo is soaked in the modified solution, reacted, taken out, washed, dried, cooled, to obtain a modified tube embryo;

[0009] S3, conductive glue is coated on the outer surface of the modified tube embryo, and the conductive glue is subjected to heating and curing treatment to obtain a polytetrafluoroethylene hose;

[0010] The conductive glue is prepared by mixing and stirring methyl methacrylate, 2-hydroxyethyl acrylate, dipropylene glycol butyl ether and hydroquinone, uniformly stirring a second conductive agent and an initiator to obtain the conductive glue.

[0011] In the polytetrafluoroethylene hose prepared by the application, the first conductive agent is contained in the tube embryo, and the conductive glue is coated on the outer surface of the tube embryo, thereby constructing an efficient and rapid charge dissipation system. The electric charge generated on the inner wall of the tube embryo can be quickly migrated to the outer wall of the tube embryo due to the conductivity of the carbon black. The setting of the conductive glue is equivalent to setting a large number of grounding points on the outer surface of the tube embryo. The electric charge migrated to the outer wall of the tube embryo can be directly discharged through the conductive glue. The electric charge migration distance is short, the discharge speed is fast, the static charge dissipation capacity is strong, and the accumulation of static charge in the polytetrafluoroethylene hose can be effectively avoided.

[0012] In the application, the polytetrafluoroethylene particles are subjected to surface modification treatment by water vapor to introduce a large number of hydroxyl functional groups on the surface of the polytetrafluoroethylene particles. The modified polytetrafluoroethylene particles are used to prepare the tube embryo, so that the outer surface of the tube embryo has a large number of hydroxyl functional groups, thereby providing reaction sites for the formation of siloxane bonds with silanol groups in the subsequent process.

[0013] In the preparation of the modified solution, octenyl trimethoxysilane is hydrolyzed to generate silanol under alkaline conditions. The silanol has an octenyl group, which is a long and flexible chain organic group. The octenyl group can produce a certain steric hindrance around the silicon atom, reduce the effective contact between the silanol groups, reduce the probability of self-condensation of the silanol groups, and improve the reactivity between the silanol groups and the hydroxyl groups on the outer surface of the tube embryo.

[0014] The pipe embryo is placed into the modified solution, the silanol group and the hydroxyl group on the surface of the modified pipe embryo are dehydrated and condensed, the silanol containing octenyl group is grafted on the surface of the pipe embryo through the silicon-carbon-oxygen bond, the pipe embryo is modified, and the surface of the modified pipe embryo is rich in carbon-carbon double bonds; the conductive adhesive is sprayed on the outer wall of the modified pipe embryo, under the action of heating and an initiator, the carbon-carbon double bonds on the surface of the modified pipe embryo and the carbon-carbon double bonds of methyl methacrylate and 2-hydroxyethyl acrylate are subjected to free radical polymerization, a network structure polymer is formed, the conductive adhesive is firmly attached to the surface of the modified pipe embryo, the interfacial bonding strength of the modified pipe embryo and the conductive adhesive is increased, and the adhesion stability of the conductive adhesive in the long-term use process of the polytetrafluoroethylene hose is improved.

[0015] The conductive adhesive contains 2-hydroxyethyl acrylate and dipropylene glycol butyl ether, the 2-hydroxyethyl acrylate has a hydroxyethyl group, the hydroxyethyl group serves as a long flexible side chain, the crosslinking density of the polymer network is reduced, the flexibility of the cured conductive adhesive is improved, and the conductive adhesive is prevented from being broken in the process of bending the hose; the dipropylene glycol butyl ether has high viscosity, the conductive adhesive sprayed on the outer surface of the modified pipe embryo is not prone to sagging, and a dense and uniform conductive coating is formed on the modified pipe embryo.

[0016] Further, in the step S1, the flow rate of water vapor is 150-155 mL / min, the plasma treatment is performed under the conditions that the vacuum degree is 20-25 Pa and the temperature is 90-110 ℃, and the plasma treatment time is 15-25 min.

[0017] Further, in the step S2, methanol and octenyltrimethylsilane are added to the sodium hydroxide solution with a pH of 8-9, stirring is performed at 120 rpm for 2 h, glacial acetic acid is added and uniformly mixed to obtain a modified solution with a pH of 5-6, the pipe embryo is immersed in the modified solution for dynamic impregnation, the reaction time is 6.0-6.5 h, methanol is used for cleaning, the drying temperature is 100 ℃, and the drying time is 1 h.

[0018] Under the weak acid condition, the hydroxyl groups on the surface of the modified pipe embryo are not protonated, the silanol groups in the silanol are partially protonated, the unprotonated hydroxyl groups contain lone pair electrons and can act as nucleophiles, the protonated silanol groups have stronger electrophilicity and are easily attacked by nucleophiles to form silicon-oxygen bonds, the reaction between the silanol groups and the hydroxyl groups on the outer surface of the pipe embryo is promoted, the density of the carbon-carbon double bonds grafted on the surface of the modified pipe embryo is increased, meanwhile, the dynamic impregnation treatment mode can constantly update the modified solution around the pipe embryo, improve the contact probability between the silanol groups and the hydroxyl groups on the surface of the pipe embryo, increase the grafting efficiency, and further increase the density of the carbon-carbon double bonds on the surface of the modified pipe embryo.

[0019] Further, the step of heating and curing the conductive glue in step S3 is: 38-40℃ for 2-2.5h, then 55-60℃ for 2.3-2.5h, then 100-105℃ for 1.5-2h, and then 150-155℃ for 0.5-0.7h.

[0020] The long-time heat preservation treatment at 38-40℃ and 55-60℃ after spraying the conductive glue on the surface of the modified pipe blank is conducive to the full infiltration of methyl methacrylate, 2-hydroxyethyl acrylate and initiator into the surface of the modified pipe blank, improves the contact degree between the components of the conductive glue and the carbon-carbon double bonds on the surface of the modified pipe blank, promotes the polymerization reaction between methyl methacrylate, 2-hydroxyethyl acrylate and the carbon-carbon double bonds on the surface of the modified pipe blank, and improves the interfacial bonding strength between the conductive glue and the modified pipe blank.

[0021] Further, a heat-shrinkable tube is sleeved on the cured conductive glue, heated, and cooled to obtain a polytetrafluoroethylene hose.

[0022] The heat-shrinkable tube provides a physical barrier for the conductive glue, avoiding scratching the conductive glue during the transportation and installation of the polytetrafluoroethylene hose and damaging the integrity and continuity of the conductive glue. The heat-shrinkable tube shrinks under heating, applies a radial pre-stress to the conductive glue, enhances the interfacial bonding strength between the conductive glue and the modified pipe blank, inhibits the transverse tensile deformation of the conductive glue when the polytetrafluoroethylene hose is bent, reduces the risk of cracking or peeling of the conductive glue caused by bending stress, and improves the overall structural reliability and long-term stability of the antistatic performance of the polytetrafluoroethylene hose.

[0023] Further, the first conductive agent is carbon black.

[0024] Further, the second conductive agent is carbon fiber and copper powder, the average particle size of the copper powder is 30-50nm, and the average diameter of the carbon fiber is 7-9μm with an aspect ratio of 3:1.

[0025] Since the orientation of the carbon fiber is random during stirring, part of the carbon fiber may be distributed obliquely or vertically to the outer wall of the pipe blank. After the conductive glue is cured, the ends or edges of these carbon fibers form a peak-valley rough structure on the outer surface of the conductive glue, so that the heat-shrinkable film can be embedded in the conductive glue when it shrinks, the friction between the conductive glue and the heat-shrinkable film is increased through the mechanical interlocking effect, the physical bonding strength between the heat-shrinkable film and the conductive glue is improved, the heat-shrinkable film is prevented from easily separating from the conductive glue, and the heat-shrinkable film always applies a radial pressure to the conductive glue, thereby improving the interfacial bonding strength between the conductive glue and the pipe blank.

[0026] Further, the carbon fiber is a modified carbon fiber obtained by plasma modification treatment using oxygen, and the copper powder is a modified copper powder obtained by surface silane modification treatment using gamma-aminopropyl triethoxysilane.

[0027] Further, the modified carbon fiber is prepared by the following method: under the conditions of a vacuum degree of 60 Pa and a temperature of 90 DEG C, plasma treatment is performed on the carbon fiber using oxygen with a flow rate of 100 mL / min for 25 min to obtain the modified carbon fiber; and the modified copper powder is prepared by the following method: gamma-aminopropyl triethoxysilane and deionized water are added to anhydrous ethanol, glacial acetic acid is added and mixed, the pH value is adjusted to 4, stirring is performed at 110 rpm for 5 min, copper powder is added multiple times under continuous stirring, after the copper powder is completely added, stirring is performed at 200 rpm for 30 min, anhydrous ethanol is used for washing, and vacuum drying is performed to obtain the modified copper powder.

[0028] The carbon fiber is subjected to plasma modification treatment, which effectively improves the roughness of the surface of the carbon fiber without significantly affecting the conductivity of the carbon fiber, and increases the binding force between the carbon fiber and the cured methyl methacrylate and 2-hydroxyethyl acrylate; the surface of the copper powder subjected to silane treatment forms a monomolecular organic film layer, which improves the corrosion resistance of the copper powder without affecting the conductivity of the copper powder, adjusts the surface properties of the copper powder, and enables the copper powder to be uniformly dispersed in the conductive adhesive.

[0029] A polytetrafluoroethylene hose is prepared by the above polytetrafluoroethylene hose preparation process and includes the following raw materials in parts by mass: 69-70 parts of polytetrafluoroethylene particles, 23-24 parts of perfluoroalkoxy resin, 5-6 parts of carbon black, and 3.3-3.4 parts of conductive adhesive; the conductive adhesive includes the following raw materials in parts by mass: 29-30 parts of methyl methacrylate, 14-15 parts of 2-hydroxyethyl acrylate, 13-14 parts of dipropylene glycol butyl ether, 0.08-0.09 parts of hydroquinone, 5-6 parts of carbon fiber, 19-20 parts of copper powder, and 1-1.1 parts of initiator; the initiator is one or both of dibenzoyl peroxide and dicumyl peroxide.

[0030] The polytetrafluoroethylene hose prepared by the method has the following advantages:

[0031] In the polytetrafluoroethylene hose prepared by the method, the pipe embryo is doped with carbon black, and the outer part of the pipe embryo is coated with conductive adhesive; during use of the hose, static charges generated during use of the hose are quickly migrated to the outer surface of the pipe embryo through the carbon black and are efficiently released through the conductive adhesive, the charge migration path is short, the discharge efficiency is high, and accumulation of charges on the hose is avoided.

[0032] The surface of the polytetrafluoroethylene particles is modified by water vapor to introduce hydroxyl groups on the surface of the pipe embryo. The silanol generated by hydrolysis of octenyltrimethoxysilane reacts with the hydroxyl groups on the surface of the pipe embryo under weak acid conditions to introduce carbon-carbon double bonds on the outer surface of the pipe embryo through silicon-carbon-oxygen bonds. Under the action of an initiator and heat, methyl methacrylate and 2-hydroxyethyl acrylate can be covalently bonded to the pipe embryo, thereby enhancing the interfacial bonding force between the conductive adhesive and the pipe embryo. A heat-shrinkable film is wrapped around the outer surface of the conductive adhesive. The heat-shrinkable film not only provides a physical barrier for the conductive adhesive but also applies radial pressure to the conductive adhesive, thereby further enhancing the interfacial bonding strength and stability between the conductive adhesive and the pipe embryo. Even when the polytetrafluoroethylene tube is bent and deformed, the conductive adhesive is not easily detached, ensuring that the polytetrafluoroethylene tube has long-term stable anti-static performance.

[0033] The conductive adhesive contains 2-hydroxyethyl acrylate and dipropylene glycol butyl ether. The 2-hydroxyethyl acrylate can increase the flexibility and ductility of the cured conductive adhesive, thereby preventing the conductive adhesive from cracking or breaking during bending of the hose. The dipropylene glycol butyl ether can prevent the conductive adhesive sprayed on the outer surface of the modified pipe embryo from sagging, thereby helping to form a dense and uniform conductive coating on the modified pipe embryo. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 A schematic diagram of the change in voltage over time on the inner wall of the polytetrafluoroethylene hose prepared in Example 6 and Comparative Examples 1 to 3. DETAILED DESCRIPTION

[0035] Preparation Example 1

[0036] 1.5 g of γ-aminopropyltriethoxysilane and 2 mL of deionized water were added to 40 mL of anhydrous ethanol, and glacial acetic acid was added to adjust the pH to 4. The mixture was stirred at 110 rpm for 5 min, and then 22 g of copper powder with a diameter of 40 nm was added at 550 rpm every 3 min for a total of 5 times. After all the copper powder was added, the mixture was stirred at 200 rpm for 30 min, washed with anhydrous ethanol 3 times, and vacuum dried to remove the ethanol, thereby obtaining modified copper powder. 100 g of carbon fibers with a diameter of 7 μm and an aspect ratio of 3:1 were placed in the vacuum chamber of a NE-PE10F type low-temperature plasma surface treatment instrument, the vacuum degree of the vacuum chamber was adjusted to 60 Pa, the temperature was adjusted to 90℃, and oxygen was introduced at a flow rate of 100 mL / min. After 25 min of treatment, the modified carbon fibers were obtained. 58 g of methyl methacrylate, 30 g of 2-hydroxyethyl acrylate, 28 g of dipropylene glycol butyl ether, and 0.16 g of hydroquinone were mixed and stirred at 1200 rpm for 10 min. Then, 40 g of the modified copper powder was added and stirred at 1200 rpm for 15 min. Subsequently, 10 g of the modified carbon fibers was added and stirred at 1500 rpm for 10 min. Finally, 2 g of dibenzoyl peroxide was added and stirred at 800 rpm for 5 min, thereby obtaining the conductive adhesive.

[0037] Preparation Example Two

[0038] Into 40 mL of anhydrous ethanol, 1.5 g of γ-aminopropyl triethoxysilane and 2 mL of deionized water were added, glacial acetic acid was added, the pH value was adjusted to 4, stirring was carried out at 110 rpm for 5 min, 22 g of copper powder with a diameter of 40 nm was added every 3 min under stirring at 550 rpm, a total of 5 times, after all were added, stirring was carried out at 200 rpm for 30 min, washing was carried out with anhydrous ethanol for 3 times, anhydrous ethanol was removed by vacuum drying, modified copper powder was obtained; 100 g of carbon fibers with a diameter of 8 μm and an aspect ratio of 3:1 were placed into a vacuum chamber of a NE-PE10F type low-temperature plasma surface treatment instrument, the vacuum degree of the vacuum chamber was adjusted to 60 Pa, the temperature was 90 ℃, oxygen was introduced, the flow rate was 100 mL / min, after treatment for 25 min, the modified carbon fibers were taken out; 59 g of methyl methacrylate, 29 g of 2-hydroxyethyl acrylate, 26 g of dipropylene glycol butyl ether, and 0.18 g of hydroquinone were mixed, stirring was carried out at 1200 rpm for 10 min, 38 g of modified copper powder was added, stirring was carried out at 1200 rpm for 15 min, 11 g of modified carbon fibers was added, stirring was carried out at 1500 rpm for 10 min, 2.1 g of dibenzoyl peroxide was added, stirring was carried out at 800 rpm for 5 min, conductive adhesive was prepared.

[0039] Preparation Example Three

[0040] Into 40 mL of anhydrous ethanol, 1.5 g of γ-aminopropyl triethoxysilane and 2 mL of deionized water were added, glacial acetic acid was added, the pH value was adjusted to 4, stirring was carried out at 110 rpm for 5 min, 22 g of copper powder with a diameter of 40 nm was added every 3 min under stirring at 550 rpm, a total of 5 times, after all were added, stirring was carried out at 200 rpm for 30 min, washing was carried out with anhydrous ethanol for 3 times, anhydrous ethanol was removed by vacuum drying, modified copper powder was obtained; 100 g of carbon fibers with a diameter of 8 μm and an aspect ratio of 3:1 were placed into a vacuum chamber of a NE-PE10F type low-temperature plasma surface treatment instrument, the vacuum degree of the vacuum chamber was adjusted to 60 Pa, the temperature was 90 ℃, oxygen was introduced, the flow rate was 100 mL / min, after treatment for 25 min, the modified carbon fibers were taken out; 59 g of methyl methacrylate, 29 g of 2-hydroxyethyl acrylate, 26 g of dipropylene glycol butyl ether, and 0.18 g of hydroquinone were mixed, stirring was carried out at 1200 rpm for 10 min, 38 g of modified copper powder was added, stirring was carried out at 1200 rpm for 15 min, 11 g of modified carbon fibers was added, stirring was carried out at 1500 rpm for 10 min, 2.1 g of dibenzoyl peroxide was added, stirring was carried out at 800 rpm for 5 min, conductive adhesive was prepared.

[0041] Example One

[0042] Put 200 g of polytetrafluoroethylene particles into the vacuum chamber of a low-temperature plasma surface treatment instrument of NE-PE10F type, adjust the vacuum degree of the vacuum chamber to 20 Pa, the temperature to 100 ℃, and the water vapor flow to 150 mL / min, take out after plasma treatment for 15 min, and obtain modified polytetrafluoroethylene particles; mix 140 g of the modified polytetrafluoroethylene particles and 47 g of perfluoroalkoxy resin, stir at 500 rpm for 5 min, add 10 g of carbon black, stir at 1500 rpm for 15 min, and send into a double-screw extruder for extrusion, use a core rod with an outer diameter of 4 cm and a pipe mold with an inner hole diameter of 5 cm, the extrusion temperature is 360 ℃, and the screw rotation speed is 30 rpm, and obtain a pipe embryo; add sodium hydroxide to 30 L of deionized water, adjust the pH to 8, and then add 1.5 L of methanol and 4.5 L of octenyltrimethoxysilane, stir at 120 rpm for 2 h under the protection of nitrogen, add glacial acetic acid and mix well, adjust the pH to 5, and obtain a modified solution, use a circulating pump to control the flow rate of the modified solution to be 10 L / h, block the openings at both ends of the pipe embryo after opening, immerse it in the modified solution for 6 h, clean it with methanol after taking it out, dry it at 100 ℃ for 1 h, and naturally cool to obtain a modified pipe embryo.

[0043] Put the conductive adhesive into the storage tank of a YMUS-ZS400 type spraying machine, set the nozzle aperture to 1.3 mm, the air pressure to 0.5 MPa, the conductive adhesive flow to 2.5 mL / s, the spraying distance to 10 cm, and the nozzle moving speed to 30 cm / s, use the layered spraying method to spray the outer wall of the modified pipe embryo, spray every 10 min, a total of three times, send the modified pipe embryo after spraying into a drying box, heat at 40 ℃ for 2 h, heat at 60 ℃ for 2 h at a speed of 10 ℃ / h, heat at 100 ℃ for 2 h at a speed of 15 ℃ / h, heat at 150 ℃ for 0.5 h at a speed of 20 ℃ / h, take it out, naturally cool, put it into an FEP heat-shrinkable tube, send it into an oven, heat at 120 ℃ for 15 min, and naturally cool to obtain a polytetrafluoroethylene hose. The conductive adhesive in this embodiment is prepared by Preparation Example One.

[0044] Example Two

[0045] Put 200 g of polytetrafluoroethylene particles into the vacuum chamber of a low-temperature plasma surface treatment instrument of NE-PE10F type, adjust the vacuum degree of the vacuum chamber to 22 Pa, the temperature to 100 ℃, and the water vapor flow to 150 mL / min, take out after plasma treatment for 15 min, to obtain modified polytetrafluoroethylene particles; mix 140 g of modified polytetrafluoroethylene particles and 46 g of perfluoroalkoxy resin, stir at 500 rpm for 5 min, add 12 g of carbon black, stir at 1500 rpm for 15 min, and send into a double-screw extruder for extrusion, using a core rod with an outer diameter of 4 cm and a pipe mold with a hole diameter of 5 cm, the extrusion temperature is 360 ℃, the screw rotation speed is 30 rpm, to obtain a pipe embryo; add sodium hydroxide to 30 L of deionized water, adjust the pH to 8, then add 1.5 L of methanol and 4.5 L of octenyltrimethoxysilane, stir at 120 rpm for 2 h under the protection of nitrogen, add glacial acetic acid to adjust the pH to 6, to obtain a modified solution, use a circulating pump to control the flow rate of the modified solution to be 10 L / h, put the pipe embryo into the modified solution after blocking the openings at both ends, immerse for 6 h, then take out and clean with methanol, dry at 100 ℃ for 1 h, and naturally cool to obtain a modified pipe embryo.

[0046] Put the conductive adhesive into the storage tank of a YMUS-ZS400 type spraying machine, set the nozzle aperture to 1.3 mm, the air pressure to 0.5 MPa, the conductive adhesive flow to 2.5 mL / s, the spraying distance to 10 cm, and the nozzle moving speed to 30 cm / s, use the way of layered spraying to spray the outer wall of the modified pipe embryo, spray every 10 min, a total of three times, put the sprayed modified pipe embryo into a drying oven, heat at 39 ℃ for 2 h, increase the temperature to 59 ℃ at a rate of 9 ℃ / h, heat for 2.5 h, increase the temperature to 100 ℃ at a rate of 13 ℃ / h, heat for 2 h, increase the temperature to 155 ℃ at a rate of 20 ℃ / h, heat for 0.5 h, take out, naturally cool, put into a FEP heat-shrinkable tube, heat at 120 ℃ for 15 min, and naturally cool to obtain a polytetrafluoroethylene hose.

[0047] The conductive adhesive in this example is prepared by Preparation Example One.

[0048] Example Three

[0049] Put 200 g of polytetrafluoroethylene particles into the vacuum chamber of a low-temperature plasma surface treatment instrument of NE-PE10F type, adjust the vacuum degree of the vacuum chamber to 23 Pa, the temperature to 90℃, and the water vapor flow to 155 mL / min, take out after plasma treatment for 20 min to obtain modified polytetrafluoroethylene particles; mix 139 g of modified polytetrafluoroethylene particles and 47 g of perfluoroalkoxy resin, stir at 500 rpm for 5 min, add 12 g of carbon black, mix at 1500 rpm for 15 min, and send into a double-screw extruder for extrusion, use a core rod with an outer diameter of 4 cm and a pipe mold with an inner hole diameter of 5 cm, the extrusion temperature is 360℃, the screw rotation speed is 30 rpm, and the processing obtains a pipe embryo; add sodium hydroxide to 30 L of deionized water, adjust the pH to 8, then add 1.5 L of methanol and 4.5 L of octenyltrimethoxysilane, stir at 120 rpm for 2 h under the protection of nitrogen, add glacial acetic acid to adjust the pH to 5.5, and obtain a modified solution, use a circulating pump to control the flow rate of the modified solution to be 10 L / h, block the openings at both ends of the pipe embryo after opening, and then immerse it in the modified solution for 6.2 h, then clean it with methanol, dry it at 105℃ for 1 h, and naturally cool it to obtain a modified pipe embryo.

[0050] Put the conductive adhesive into the storage tank of a YMUS-ZS400 type spraying machine, set the nozzle aperture to 1.3 mm, the air pressure to 0.5 MPa, the conductive adhesive flow to 2.5 mL / s, the spraying distance to 10 cm, and the nozzle moving speed to 30 cm / s, use a layered spraying method to spray the outer wall of the modified pipe embryo, spray every 10 min, a total of three times, send the modified pipe embryo after spraying into a drying oven, heat at 40℃ for 2.3 h, heat at 58℃ for 2.4 h at a rate of 9℃ / h, heat at 102℃ for 1.7 h at a rate of 14℃ / h, heat at 153℃ for 0.6 h at a rate of 19℃ / h, take out, naturally cool, put into an FEP heat-shrinkable tube, heat at 120℃ for 15 min, and naturally cool to obtain a polytetrafluoroethylene hose.

[0051] The conductive adhesive in this example is prepared by Preparation Example Two.

[0052] Example Four

[0053] Put 200 g of polytetrafluoroethylene particles into the vacuum chamber of a low-temperature plasma surface treatment instrument of NE-PE10F type, adjust the vacuum degree of the vacuum chamber to 20 Pa, the temperature to 90°C, and the water vapor flow to 155 mL / min, take out after plasma treatment for 20 min, and obtain modified polytetrafluoroethylene particles; mix 139 g of the modified polytetrafluoroethylene particles and 46 g of perfluoroalkoxy resin, stir at 500 rpm for 5 min, add 11 g of carbon black, mix at 1500 rpm for 15 min, and send into a double-screw extruder for extrusion, use a core rod with an outer diameter of 4 cm and a pipe mold with an inner hole diameter of 5 cm, the extrusion temperature is 360°C, and the screw rotation speed is 30 rpm, and obtain a pipe embryo; add sodium hydroxide to 30 L of deionized water, adjust the pH to 8, and then add 1.5 L of methanol and 4.5 L of octenyltrimethoxysilane, stir at 120 rpm for 2 h under the protection of nitrogen, add glacial acetic acid, and adjust the pH to 5.5 to obtain a modified solution, use a circulating pump to control the flow rate of the modified solution to be 10 L / h, block the openings at both ends of the pipe embryo after opening, immerse it in the modified solution for 6.3 h, clean it with methanol after taking it out, dry it at 105°C for 1 h, and naturally cool it to obtain a modified pipe embryo.

[0054] Put the conductive adhesive into the storage tank of a YMUS-ZS400 type spraying machine, set the nozzle aperture to 1.3 mm, the air pressure to 0.5 MPa, the conductive adhesive flow to 2.5 mL / s, the spraying distance to 10 cm, and the nozzle moving speed to 30 cm / s, use a layered spraying method to spray the outer wall of the modified pipe embryo, spray every 10 min, a total of three times, send the modified pipe embryo after spraying into a drying oven, heat at 39°C for 2.3 h, increase the temperature to 56°C at a speed of 10°C / h, heat at 56°C for 2.3 h, increase the temperature to 104°C at a speed of 14°C / h, heat at 104°C for 1.8 h, increase the temperature to 154°C at a speed of 18°C / h, heat at 154°C for 0.6 h, take it out, naturally cool it, put it into an FEP heat-shrinkable tube, heat at 120°C for 15 min, and naturally cool it to obtain a polytetrafluoroethylene hose. The conductive adhesive in this example is prepared by Preparation Example Two.

[0055] Example Five

[0056] Put 205 g of polytetrafluoroethylene particles into the vacuum chamber of a low-temperature plasma surface treatment instrument of NE-PE10F type, adjust the vacuum degree of the vacuum chamber to 25 Pa, the temperature to 110℃, and the water vapor flow to 150 mL / min, take out after plasma treatment for 25 min, to obtain modified polytetrafluoroethylene particles; mix 138 g of modified polytetrafluoroethylene particles and 48 g of perfluoroalkoxy resin, stir at 500 rpm for 5 min, add 11 g of carbon black, mix at 1500 rpm for 15 min, and send into a double-screw extruder for extrusion, use a core rod with an outer diameter of 4 cm and a pipe mold with an inner hole diameter of 5 cm, the extrusion temperature is 360℃, the screw rotation speed is 30 rpm, to obtain a pipe embryo; add sodium hydroxide to 30 L of deionized water, adjust the pH to 8, then add 1.5 L of methanol and 4.5 L of octenyltrimethoxysilane, stir at 120 rpm for 2 h under the protection of nitrogen, add glacial acetic acid to adjust the pH to 6, to obtain a modified solution, use a circulating pump to control the flow rate of the modified solution to be 10 L / h, put the pipe embryo into the modified solution after blocking the openings at both ends, and immerse for 6.5 h, then clean with methanol, dry at 110℃ for 1 h, and naturally cool, to obtain a modified pipe embryo.

[0057] Put the conductive adhesive into the storage tank of a YMUS-ZS400 type spraying machine, set the nozzle aperture to 1.3 mm, the air pressure to 0.5 MPa, the conductive adhesive flow to 2.5 mL / s, the spraying distance to 10 cm, and the nozzle moving speed to 30 cm / s, use a layered spraying method to spray the outer wall of the modified pipe embryo, spray every 10 min, a total of three times, send the modified pipe embryo after spraying into a drying oven, heat at 38℃ for 2.5 h, increase the temperature to 57℃ at a speed of 8℃ / h and heat for 2.5 h, increase the temperature to 105℃ at a speed of 13℃ / h and heat for 1.5 h, increase the temperature to 155℃ at a speed of 18℃ / h and heat for 0.7 h, take out, naturally cool, put into an FEP heat-shrinkable tube, heat at 120℃ for 15 min, and naturally cool, to obtain a polytetrafluoroethylene hose. The conductive adhesive in this example is prepared by Preparation Example Three.

[0058] Example Six

[0059] Put 205 g of polytetrafluoroethylene particles into the vacuum chamber of a low-temperature plasma surface treatment instrument of NE-PE10F type, adjust the vacuum degree of the vacuum chamber to 25 Pa, the temperature to 110 ℃, and the water vapor flow to 150 mL / min, take out after plasma treatment for 25 min to obtain modified polytetrafluoroethylene particles; mix 138 g of modified polytetrafluoroethylene particles and 48 g of perfluoroalkoxy resin, stir at 500 rpm for 5 min, add 12 g of carbon black, mix at 1500 rpm for 15 min, and then send into a double-screw extruder for extrusion; use a core rod with an outer diameter of 4 cm and a pipe mold with a hole inner diameter of 5 cm, the extrusion temperature is 360 ℃, and the screw rotation speed is 30 rpm to obtain a pipe embryo; add sodium hydroxide to 30 L of deionized water, adjust the pH to 8, and then add 1.5 L of methanol and 4.5 L of octenyltrimethoxysilane; under the protection of nitrogen, stir at 120 rpm for 2 h, add glacial acetic acid, and adjust the pH to 6 to obtain a modified solution; use a circulating pump to control the flow rate of the modified solution to be 10 L / h, block the openings at both ends of the pipe embryo, and then immerse the pipe embryo in the modified solution for 6.5 h; after taking out, wash with methanol, dry at 110 ℃ for 1 h, and naturally cool to obtain a modified pipe embryo.

[0060] Put the conductive glue into the storage tank of a YMUS-ZS400 type spraying machine, set the nozzle aperture to 1.3 mm, the air pressure to 0.5 MPa, the conductive glue flow to 2.5 mL / s, the spraying distance to 10 cm, and the nozzle moving speed to 30 cm / s, use a layered spraying method to spray the outer wall of the modified pipe embryo, spray once every 10 min, a total of three times, send the modified pipe embryo after spraying into a drying box, heat at 38 ℃ for 2.5 h, heat at 55 ℃ for 2.5 h at a speed of 9 ℃ / h, heat at 105 ℃ for 1.5 h at a speed of 15 ℃ / h, and heat at 150 ℃ for 0.7 h at a speed of 19 ℃ / h to obtain a polytetrafluoroethylene hose. The conductive glue in this embodiment is prepared by Preparation Example Three.

[0061] The present application also sets up a comparative example and carries out related tests.

[0062] Comparative Example One

[0063] Mix 140 g of polytetrafluoroethylene particles and 47 g of perfluoroalkoxy resin, stir at 500 rpm for 5 min, mix at 1500 rpm for 15 min, and then send into a double-screw extruder for extrusion; use a core rod with an outer diameter of 4 cm and a pipe mold with a hole inner diameter of 5 cm, the extrusion temperature is 360 ℃, and the screw rotation speed is 30 rpm to obtain a polytetrafluoroethylene hose.

[0064] Comparative Example Two

[0065] 140 g of modified polytetrafluoroethylene particles and 47 g of perfluoroalkoxy resin were mixed at 500 rpm for 5 min, 10 g of carbon black was added, mixed at 1500 rpm for 15 min, and then fed into a twin-screw extruder for extrusion. A core rod with an outer diameter of 4 cm and a tube die with a hole diameter of 5 cm were used, the extrusion temperature was 360 °C, and the screw rotation speed was 30 rpm. A polytetrafluoroethylene hose was obtained.

[0066] Comparative Example Three

[0067] Comparative Example Three and Example Five differ in that no carbon black was added during the preparation of the tube blank, and the other components and preparation process were the same as in Example Five. A polytetrafluoroethylene hose was obtained.

[0068] Comparative Example Four

[0069] Comparative Example Four and Example Six differ in that the tube blank was not placed in the modification solution for modification treatment, and the other components and preparation process were the same as in Example Six. A polytetrafluoroethylene hose was obtained.

[0070] Electrostatic voltage decay test

[0071] The samples prepared in each example and each comparative example were placed in a constant temperature and humidity chamber at 25 °C and a relative humidity of 60% for 24 hours, then removed. For the hose samples prepared in Examples One to Five and Comparative Example Three, the heat-shrinkable tube at one end of the hose was peeled off to expose the conductive adhesive, and the conductive adhesive was grounded. For the hose samples prepared in Example Six, Comparative Example One and Comparative Example Two, a conductive copper foil was wrapped around the middle of the hose sample, and was connected to the ground through a wire to simulate a local grounding condition. An electrostatic generator was used to apply a 320 V electrostatic voltage to 15 different points on the inner wall of each sample. An electrostatic potentiometer was used to record the change in voltage at each point over time. At the same time point, the average voltage of the 15 points was calculated. The results are shown in Tables 1 and 2. The voltage change over time on the inner wall of the samples of Example Six, Comparative Examples One to Three is shown in the graph of Figure 1 .

[0072] Table 1

[0073]

[0074] Table 2

[0075]

[0076] Analysis of Tables 1, 2 and Figure 1It can be seen that the static voltage half-life period of the sample of example one to example six is between 0.1-0.2s, the static voltage half-life period of the sample of comparative example one is more than 4s, the static voltage half-life period of the sample of comparative example two is between 1s-2s, and the static voltage half-life period of the sample of comparative example three is between 2s-3s, thus it can be known that adding carbon black in the process of making the tube blank or coating the conductive adhesive on the outside of the tube blank can improve the charge release speed, shorten the static half-life period of the polytetrafluoroethylene hose and improve the static dissipation capacity, but when only one of the two ways is used, the charge release speed is far less than that of the polytetrafluoroethylene hose containing both carbon black and conductive adhesive, and the specific reason is that the charge can be quickly migrated from the inner wall of the tube blank to the outer wall of the tube blank under the action of the carbon black, the outer wall of the tube blank is uniformly coated with the conductive adhesive, which is equivalent to setting up countless grounding points on the surface of the tube blank, the charge migration path is short and the migration speed is fast, and the static dissipation capacity of the polytetrafluoroethylene hose is greatly improved.

[0077] Bending fatigue test

[0078] The hose samples prepared in example one to six and comparative example four are respectively fixed on a dynamic bending tester, the bending radius is set to 15cm, and the bending is repeated at a speed of 30 times per minute, after 100,000 times of bending, the peeling area of the bending area and the static voltage half-life period of the hose sample are respectively detected, and the detection results are shown in table 3.

[0079] Table 3

[0080]

[0081] As can be seen from table 2, after 100,000 times of bending, the conductive adhesive structure of example one to five still maintains good integrity, and the polytetrafluoroethylene hose also maintains good static dissipation capacity; compared with example one to five, the conductive adhesive in example six appears partial peeling phenomenon after bending, and the static dissipation capacity is reduced, which shows that the heat-shrinkable tube sleeved on the conductive adhesive can effectively improve the structural stability and static dissipation capacity of the polytetrafluoroethylene hose in the long-term dynamic bending process; compared with example six, the conductive adhesive of comparative example four appears serious peeling phenomenon, and the static dissipation capacity is greatly reduced, which shows that the bonding force between the unmodified tube blank and the conductive adhesive is weak, and the modified tube blank can form a more firm interfacial bonding with the conductive adhesive, thereby improving the adhesion stability of the conductive adhesive in the long-term use process of the polytetrafluoroethylene hose.

[0082] The above is the preferred embodiment of the present application, it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can also be made, which should be considered as the protection scope of the present application.

Claims

1. A process for preparing a polytetrafluoroethylene hose, characterized in that: The following steps are involved: S1. plasma-treating polytetrafluoroethylene particles with water vapor to obtain modified polytetrafluoroethylene particles; The modified polytetrafluoroethylene particles, perfluoroalkoxy resin and the first conductive agent are mixed and then fed into an extruder for extrusion to obtain a tube blank; S2. Add methanol and octenyltrimethylsilane to a sodium hydroxide solution, stir, add glacial acetic acid and mix well to obtain a modified solution, immerse the tube embryo in the modified solution, react, remove, wash, dry, and cool to obtain a modified tube embryo; S3, coating the modified tube embryo with a conductive adhesive, and heating and curing the conductive adhesive to obtain a polytetrafluoroethylene hose; The conductive adhesive is prepared by the following method: methyl methacrylate, 2-hydroxyethyl acrylate, dipropylene glycol butyl ether, and hydroquinone are mixed and stirred, and a second conductive agent and an initiator are added and stirred evenly to obtain the conductive adhesive.

2. The process for preparing a polytetrafluoroethylene hose according to claim 1, characterized in that: In step S1, the flow rate of water vapor is 150-155 mL / min, and the plasma treatment is performed under the conditions of a vacuum degree of 20-25 Pa and a temperature of 90-110° C. The plasma treatment time is 15-25 min.

3. The process for preparing a polytetrafluoroethylene hose according to claim 2, characterized in that: In step S2, methanol and octenyltrimethylsilane are added to a sodium hydroxide solution with a pH of 8 to 9, and the mixture is stirred at 120 rpm for 2 hours. Glacial acetic acid is added and mixed to obtain a modified solution with a pH of 5 to 6. The embryonic tube is immersed in the modified solution for dynamic immersion, the reaction time is 6.0 to 6.5 hours, and the tube is washed with methanol. The drying temperature is 100° C. and the drying time is 1 hour.

4. The process for preparing a polytetrafluoroethylene hose according to claim 3, characterized in that: In step S3, the conductive adhesive is heated and cured as follows: keeping the temperature at 38-40°C for 2-2.5 hours, heating to 55-60°C for 2.3-2.5 hours, heating to 100-105°C for 1.5-2 hours, and heating to 150-155°C for 0.5-0.7 hours.

5. The process for preparing a polytetrafluoroethylene hose according to claim 4, characterized in that: A heat shrink tube is sheathed over the solidified conductive adhesive, heated, and cooled to obtain a polytetrafluoroethylene hose.

6. The process for preparing a polytetrafluoroethylene hose according to claim 5, characterized in that: The first conductive agent is carbon black.

7. The process for preparing a polytetrafluoroethylene hose according to claim 6, characterized in that: The second conductive agent is carbon fiber and copper powder, the average particle size of the copper powder is 30-50 nm, the average diameter of the carbon fiber is 7-9 μm, and the aspect ratio is 3:

1.

8. The process for preparing a polytetrafluoroethylene hose according to claim 7, characterized in that: The carbon fibers are modified carbon fibers obtained by plasma modification with oxygen, and the copper powder is modified copper powder obtained by surface silanization modification with gamma-aminopropyltriethoxysilane.

9. The process for preparing a polytetrafluoroethylene hose according to claim 8, characterized in that: The modified carbon fiber is prepared by the following method: under the conditions of a vacuum degree of 60 Pa and a temperature of 90° C., the carbon fiber is plasma treated with oxygen at a flow rate of 100 mL / min for 25 minutes to obtain the modified carbon fiber; the modified copper powder is prepared by the following method: γ-aminopropyltriethoxysilane and deionized water are added to anhydrous ethanol, glacial acetic acid is added and mixed, the pH value is adjusted to 4, and the mixture is stirred at 110 rpm for 5 minutes. The copper powder is added multiple times under continuous stirring. After all the copper powder is added, the mixture is stirred at 200 rpm for 30 minutes, washed with anhydrous ethanol, and vacuum dried to obtain the modified copper powder.

10. A polytetrafluoroethylene hose, prepared by the polytetrafluoroethylene hose preparation process according to any one of claims 7 to 9, characterized in that: The invention comprises the following raw materials in parts by mass: 69-70 parts of polytetrafluoroethylene particles, 23-24 parts of perfluoroalkoxy resin, 5-6 parts of carbon black and 3.3-3.4 parts of conductive adhesive; the conductive adhesive comprises the following raw materials in parts by mass: 29-30 parts of methyl methacrylate, 14-15 parts of 2-hydroxyethyl acrylate, 13-14 parts of dipropylene glycol butyl ether, 0.08-0.09 part of hydroquinone, 5-6 parts of carbon fiber, 19-20 parts of copper powder and 1-1.1 parts of initiator; the initiator is one or both of dibenzoyl peroxide and dicumyl peroxide.

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