A wear-resistant polyethylene gas pipe and preparation method thereof

Abstract

The present invention relates to a wear-resistant polyethylene gas pipe and a preparation method thereof, and belongs to the technical field of steel-plastic composite pipes. The pipe comprises a wear-resistant inner layer, an alloy seamless steel pipe and an outer anti-corrosion layer, wherein the wear-resistant inner layer comprises, by weight, 100 parts of high-density polyethylene, 14-18 parts of triallyl isocyanurate, 10-15 parts of maleic anhydride grafted polyethylene, 15-22 parts of wear-resistant weathering aid, 0.4-0.5 parts of electric enhancer, 0.2-0.3 parts of antioxidant and 1-1.3 parts of defoamer; the wear-resistant weathering aid is a low cross-linking material, which can form secondary cross-linking with the main material, uniformly disperse silica fume in the main material and combine with the main material by forming a covalent bond, and form a high-strength cross-linked polymer after the coating is cured, and at the same time, the wear-resistant weathering aid also introduces fluorine groups into the coating to improve the corrosion resistance of the coating. After testing, the wear resistance and corrosion resistance of the pipe are significantly better than those of the existing 3PE pipe.

Description

Technical Field

[0001] The invention belongs to the technical field of steel-plastic composite pipes, and in particular relates to a wear-resistant polyethylene gas pipe and a preparation method thereof. Background Art

[0002] Natural gas is an efficient and clean energy source with good fluidity, strong compressibility, gas at room temperature and pressure, and low energy density. Compared with other energy sources such as coal and oil, it can be transported through pipelines, making it more convenient to use, and its proportion in the energy structure is increasing year by year.

[0003] Pipeline natural gas contains impurities such as sand and gravel particles, sulfides, water and oil. Under the high-speed flow of natural gas, the inner wall of the pipeline is physically eroded and chemically corroded, increasing the transportation resistance and affecting the safety of pipeline transportation. Therefore, existing natural gas pipelines are generally coated with inner coatings to improve the smoothness of the inner wall and slow down the corrosion of impurities on metal-based pipelines. In the prior art, common inner coating materials are mainly epoxy coatings and polyolefin coatings. Among them, epoxy coatings have high adhesion, high hardness, good wear resistance and corrosion resistance, but they are brittle and the coating is prone to coating damage during installation and service. Polyolefin coatings have good toughness and good adhesion, but low strength and poor wear resistance. In order to obtain good comprehensive performance, there are currently products that combine the two materials, such as 3PE anti-corrosion steel pipes, which use epoxy coatings as the bottom layer and polyethylene as the surface layer. The two are combined through a compatible material as a bonding layer to obtain a relatively stable coating, but the manufacturing process of this type of pipe is complicated and fails to overcome the problem of poor wear resistance of polyethylene. Combined with the existing polyolefin strengthening and modification technology, it mainly involves doping certain inorganic rigid particles into the polyolefin matrix, which can improve the strength and wear resistance of polyolefin to a certain extent. However, the bonding strength between these inorganic rigid particles and polyolefin is low. When polyolefin corrodes, the inorganic rigid particles act as surface defects, increase the friction resistance of the airflow, and also cause incidental tearing problems during the shedding process, resulting in a sharp deterioration in coating performance. Summary of the invention

[0004] In order to solve the technical problems mentioned in the background technology, the object of the present invention is to provide a wear-resistant polyethylene gas pipe and a preparation method thereof.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A wear-resistant polyethylene gas pipe comprises, from inside to outside, a wear-resistant inner layer, an alloy seamless steel pipe and an outer anti-corrosion layer, wherein the wear-resistant inner layer is formed by curing a composite polyethylene coating, and comprises the following raw materials in parts by weight:

[0007] 100 parts of high-density polyethylene, 14-18 parts of triallyl isocyanurate, 10-15 parts of maleic anhydride grafted polyethylene, 15-22 parts of wear-resistant and weather-resistant additives, 0.4-0.5 parts of charge enhancer, 0.2-0.3 parts of antioxidant and 1-1.3 parts of defoaming agent.

[0008] The wear-resistant and weather-resistant additive is prepared by the following method:

[0009] Step A1: prepare an acidic ethanol solution using ethanol, acetic acid and water, add silica fume and silane coupling agent KH570, stir and mix to hydrolyze for 40min-1h, then add ammonia water until the pH value is above 6.0 with ultrasonic vibration, stand for coupling for 12h, take the bottom precipitate, wash, centrifuge and dry to obtain a coupling filler;

[0010] Furthermore, the pH value of the acidic ethanol solution is 3-4, and the mass fraction of ethanol in the acidic ethanol solution is 25-35%. Under this condition, the silane coupling agent KH570 is hydrolyzed and coupled evenly, and the loading rate is high.

[0011] Furthermore, the dosage ratio of silica ash, silane coupling agent KH570 and acidic ethanol solution is 100g:12-15mL:500-600mL, the ultrasonic oscillation frequency is 25-33kHz, the silane coupling agent KH570 is hydrolyzed in the ethanol solution of organic acid, and then coupled with silica ash to graft organic groups with unsaturated double bonds onto the surface of silica ash.

[0012] Step A2: 2,6-dichlorofluorobenzene, triethylamine and tetrahydrofuran are mixed, nitrogen is introduced for protection, the temperature is pre-heated to 45-55°C and mixed, diallylamine is added, the stirring rate is controlled to 240-360rpm, the temperature is continued to be raised to 68-75°C, and the reaction is refluxed for 1.5-2h. After the reaction is completed, the tetrahydrofuran is removed by vacuum rotary evaporation, boiling water is added for washing, and the organic phase is dried to obtain a fluorinated monomer;

[0013] Furthermore, the dosage ratio of 2,6-dichlorofluorobenzene, diallylamine, triethylamine and tetrahydrofuran is 0.1 mol: 0.22-0.24 mol: 5-6 mL: 60-80 mL, and triethylamine is used as an acid binding agent to promote the substitution reaction of 2,6-dichlorofluorobenzene and diallylamine to form a compound with a terminal branched double bond and a rigid benzene ring structure and a fluorine group in the molecule.

[0014] Step A3: Mix the fluorinated monomer, coupling filler, calcium stearate and azobisisobutylimidazoline hydrochloride, protect with nitrogen, heat to 155-165° C., control the stirring rate to 80-120 rpm, and mix for 1.6-2.3 h. After cooling the discharged material, crush it to obtain a wear-resistant and weather-resistant additive;

[0015] Furthermore, the usage ratio of the fluorinated monomer, the coupling filler, calcium stearate and azobisisobutylimidazoline hydrochloride is 100g:35-55g:5-8g:1.6-2.2g, and azobisisobutylimidazoline hydrochloride is used as an initiator to promote the coupling filler and the fluorinated monomer to form a polymer with a low crosslinking degree.

[0016] Preferably, the charge enhancing agent is the charge regulator H308.

[0017] Preferably, the antioxidant is the antioxidant DLTP.

[0018] Preferably, the defoaming agent is defoaming agent 4420.

[0019] The preparation method of the composite polyethylene coating comprises the following steps: mixing various raw materials at high speed, feeding the raw materials into a twin-screw extruder for extrusion and tableting, crushing the raw materials after cooling to room temperature, and grinding and crushing the raw materials after freezing and embrittlement to prepare the composite polyethylene coating.

[0020] Furthermore, the barrel temperature of the twin-screw extruder is: 120°C in zone 1, 140°C in zone 2, 150°C in zone 3, 140°C in zone 4, and the head temperature is 155°C.

[0021] Furthermore, the grinding fineness of the composite polyethylene coating is 80-100 meshes.

[0022] A method for preparing a wear-resistant polyethylene gas pipe comprises the following steps:

[0023] Step S1: Derusting, degreasing and ceramic coating the inner and outer walls of the alloy seamless steel pipe, installing a protective card cover at the end to obtain a clean prefabricated pipe;

[0024] Step S2: electrostatically spraying the composite polyethylene coating onto the inner wall of the clean prefabricated pipe, controlling the electrostatic voltage of the powder spray gun to 65-80 kV, the air pressure to 0.13-0.18 MPa, and the distance between the nozzle and the inner wall to 25-35 cm, to obtain a pre-coated pipe;

[0025] Step S3: placing the pre-coated tube in an oven, controlling the temperature to 185-200° C., and heat preservation and curing time to 25-35 min. After cooling, a wear-resistant inner layer is formed to obtain an outer blank tube;

[0026] Step S4: Brushing zinc-rich primer on the outer surface of the outer blank pipe forms an outer anti-corrosion layer after curing to obtain a wear-resistant polyethylene gas pipe.

[0027] Beneficial effects of the present invention:

[0028] The invention provides a steel-plastic composite pipe with good wear resistance and natural gas corrosion resistance. The inner wall coating of the pipe is mainly made of high-density polyethylene. The comprehensive performance of the coating is greatly improved by adding a self-made wear-resistant and weather-resistant additive for blending and modification. The wear-resistant and weather-resistant additive is made of silica ash as a reinforcing base material, treated with a silane coupling agent KH570, and an organic group with an unsaturated double bond is grafted onto the surface to obtain a coupling filler. 2,6-dichlorofluorobenzene is used as a bridging material, and a substitution reaction is performed with diallylamine to form a compound with a terminal branched double bond to obtain a fluorinated monomer. Azobisisobutylimidazoline hydrochloride is used as an initiator. Through reasonable process control, the coupling filler and the fluorinated monomer are promoted to form an organic-inorganic polymer with a low crosslinking degree. The organic polyolefin structure has good compatibility with high-density polyethylene and can be evenly dispersed in the main material during powder making and plasticizing. , giving full play to the strengthening effect of silica fume; the wear-resistant and weather-resistant additive is a low-cross-linked product, and its cross-linked structure extends to the main material, forming a snap-in effect in the physical structure, and strengthening the bonding strength between the silica fume and the main material; in addition, the structure of the wear-resistant and weather-resistant additive contains a certain amount of unsaturated bonds, which can form secondary cross-linking with the main material and triallyl isocyanurate during the plasticizing process. In addition, the wear-resistant and weather-resistant additive contains a large number of rigid benzene ring structures, which can form high-strength cross-linked polymers. At the same time, the silica fume is combined with the main material through covalent bonds, and the bonding strength between the silica fume and the main material is strengthened in the chemical structure; in addition, the fluorinated monomer also introduces fluorine groups into the coating to improve the corrosion resistance of the coating. The bonding mechanism is the same as that of silica fume. The fluoride is uniform and has a high bonding strength with the main material. Compared with external preservatives, it is not easy to migrate and segregate during the powder making and plasticizing process, and exerts a stable corrosion resistance. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Example 1

[0031] This embodiment prepares a wear-resistant polyethylene gas pipe, which specifically includes the following steps:

[0032] 1) Preparation of wear-resistant and weather-resistant additives

[0033] 1.1. Take ethanol, acetic acid and water to prepare an acidic ethanol solution, control the pH to be about 4, the mass fraction of ethanol to be about 35%, then add silica ash (SF90 type is used in the embodiment, and the particle size is about 0.1 μm) and silane coupling agent KH570, and stir and mix at 300 rpm for hydrolysis for 1 hour, then apply ultrasonic oscillation with a frequency of 25 kHz, slowly add industrial ammonia water to the hydrolyzate, the dropping time is about 20 minutes, adjust the pH value of the mixed solution to 6.0, and stand for coupling for 12 hours. In the reaction, the amount ratio of silica ash, silane coupling agent KH570 and acidic ethanol solution is 100 g: 12 mL: 500 mL. After standing, take the bottom precipitate, add 10 times the mass of water to wash, centrifuge and take the precipitate again in vacuum to obtain a coupling filler.

[0034] 1.2. Take 2,6-dichlorofluorobenzene, triethylamine and tetrahydrofuran and mix them. Nitrogen is introduced into the reactor until a stable airflow is discharged. The reaction system is preheated under nitrogen protection and stirred at 120 rpm until the temperature reaches 45°C. Diallylamine is then added, the stirring rate is increased to 240 rpm, the temperature is continued to rise to 68°C, and the reaction is refluxed for 2 hours. During the reaction, the amount ratio of 2,6-dichlorofluorobenzene, diallylamine, triethylamine and tetrahydrofuran is 0.1 mol: 0.22 mol: 5 mL: 60 mL. After the reaction is completed, the tetrahydrofuran is removed by rotary evaporation under reduced pressure, and then boiling water 1.5 times the mass of the rotary evaporation substrate is added for washing. The organic phase is vacuum dried to obtain a fluorinated monomer.

[0035] 1.3. Take fluorinated monomer, coupling filler, calcium stearate and azobisisobutylimidazoline hydrochloride, add them into a stirrer and mix them, then add them into a reactor, introduce nitrogen protection, raise the temperature to 155°C, control the stirring rate to 80rpm, and knead for 2.3h. During the reaction, the amount ratio of fluorinated monomer, coupling filler, calcium stearate and azobisisobutylimidazoline hydrochloride is 100g:35g:5g:1.6g. After the reaction is completed, discharge and cool, and grind into micro powder with a fineness of not less than 30 mesh to obtain a wear-resistant and weather-resistant additive.

[0036] 2) Preparation of composite polyethylene coating

[0037] 2.1. Take the following raw materials according to weight:

[0038] 100 parts of high-density polyethylene, model DMDA-8008, provided by Dushanzi Petrochemical Company;

[0039] 16 parts of triallyl isocyanurate, industrial grade raw material, provided by Guangzhou Xinda Fine Chemical Co., Ltd.;

[0040] 10 parts of maleic anhydride grafted polyethylene, the model is maleic anhydride grafted polyethylene, provided by Nanjing Feiteng New Material Technology Co., Ltd.;

[0041] 15 parts of wear-resistant and weather-resistant additive, prepared in this example;

[0042] 0.4 parts of charge enhancer, selected from charge regulator H308, provided by Hubei Laisi Chemical New Materials Co., Ltd.;

[0043] 0.2 parts of antioxidant, selected from antioxidant DLTP, provided by Qingdao Xunneng Technology Co., Ltd.;

[0044] 1 part of defoamer, selected from defoamer 4420, provided by Hubei Laisi Chemical New Materials Co., Ltd.;

[0045] The raw materials purchased in the following examples are all from the same batch.

[0046] 2.2. Add the above raw materials into the mixer according to the weight ratio, stir and mix at a high speed of 1500rpm for 10min, then add the mixture into the twin-screw extruder, control the barrel temperature as follows: 120℃ for zone 1, 140℃ for zone 2, 150℃ for zone 3, 140℃ for zone 4, and the head temperature as 155℃, extrude the mixture into a tablet press for compaction, cool to room temperature, crush with a blade, freeze and embrittle with liquid nitrogen, and then grind and crush until the fineness of the powder reaches 80 mesh to obtain a composite polyethylene coating.

[0047] 3) Preparation of wear-resistant polyethylene gas pipes

[0048] 3.1. Take the alloy seamless steel pipe for gas, carry out conventional rust removal, degreasing and ceramic coating treatment on the inner and outer walls, install the protective card cover at the pipe port to prevent the coating from adhering to the end and affecting the welding, and obtain a clean prefabricated pipe.

[0049] 3.2. The composite polyethylene coating is electrostatically sprayed on the inner wall of the clean prefabricated pipe, the static voltage of the powder spray gun is controlled to be 80 kV, the air pressure is controlled to be 0.18 MPa, and the distance between the nozzle and the inner wall is 35 cm to obtain a pre-coated pipe.

[0050] 3.3. Place the pre-coated tube in an oven, control the temperature to 185°C, keep the temperature for 35 minutes, and form a wear-resistant inner layer after cooling to obtain an outer tube.

[0051] 3.4. Apply zinc-rich primer to the outer surface of the outer blank pipe, which forms an outer anti-corrosion layer after curing to obtain a wear-resistant polyethylene gas pipe.

[0052] Example 2

[0053] This embodiment prepares a wear-resistant polyethylene gas pipe, which specifically includes the following steps:

[0054] 1) Preparation of wear-resistant and weather-resistant additives

[0055] 1.1. Prepare an acidic ethanol solution with ethanol, acetic acid and water, control the pH to be about 4, the mass fraction of ethanol to be about 25%, then add silica ash and silane coupling agent KH570, stir and mix at 300rpm for hydrolysis for 40min, then apply ultrasonic oscillation with a frequency of 33kHz, slowly add industrial ammonia water to the hydrolyzate, the dropping time is about 20min, adjust the pH value of the mixed solution to 7.0, and let it stand for coupling for 12h. During the reaction, the amount ratio of silica ash, silane coupling agent KH570 and acidic ethanol solution is 100g:15mL:600mL. After standing, take the bottom precipitate, add 10 times the mass of water to wash, centrifuge and take the precipitate again, vacuum dry, and obtain a coupling filler.

[0056] 1.2. Take 2,6-dichlorofluorobenzene, triethylamine and tetrahydrofuran and mix them. Nitrogen is introduced into the reactor until a stable airflow is discharged. The reaction system is preheated under nitrogen protection and stirred at 120 rpm until the temperature reaches 55°C. Diallylamine is then added, the stirring rate is increased to 360 rpm, the temperature is continued to rise to 75°C, and the reaction is refluxed for 1.5 hours. During the reaction, the amount ratio of 2,6-dichlorofluorobenzene, diallylamine, triethylamine and tetrahydrofuran is 0.1 mol: 0.24 mol: 6 mL: 80 mL. After the reaction is completed, tetrahydrofuran is removed by reduced pressure rotary evaporation, and then 1.5 times the mass of boiling water of the rotary evaporation substrate is added for washing. The organic phase is vacuum dried to obtain a fluorinated monomer.

[0057] 1.3. Take fluorinated monomer, coupling filler, calcium stearate and azobisisobutylimidazoline hydrochloride, add them into a stirrer and mix them, then add them into a reactor, introduce nitrogen protection, raise the temperature to 165°C, control the stirring rate to 120rpm, and knead for 1.6h. During the reaction, the amount ratio of fluorinated monomer, coupling filler, calcium stearate and azobisisobutylimidazoline hydrochloride is 100g:55g:8g:2.2g. After the reaction is completed, discharge and cool, and grind into micro powder with a fineness of not less than 30 mesh to obtain a wear-resistant and weather-resistant additive.

[0058] 2) Preparation of composite polyethylene coating

[0059] 2.1. Take the following raw materials according to weight:

[0060] 100 parts of high-density polyethylene, 14 parts of triallyl isocyanurate, 13 parts of maleic anhydride grafted polyethylene, 22 parts of wear-resistant and weather-resistant additives, 0.4 parts of charge enhancer, 0.3 parts of antioxidant, and 1.3 parts of defoaming agent.

[0061] 2.2. Add the above raw materials into the mixer according to the weight ratio, stir and mix at a high speed of 1500rpm for 10min, then add the mixture into the twin-screw extruder, control the barrel temperature as follows: 120℃ for zone 1, 140℃ for zone 2, 150℃ for zone 3, 140℃ for zone 4, and the head temperature as 155℃, extrude the mixture into a tablet press for compaction, cool to room temperature, crush with a blade, freeze and embrittle with liquid nitrogen, and then grind and crush until the fineness of the powder reaches 100 mesh to obtain a composite polyethylene coating.

[0062] 3) Preparation of wear-resistant polyethylene gas pipes

[0063] 3.1. Take the alloy seamless steel pipe for gas, carry out conventional rust removal, degreasing and ceramic coating treatment on the inner and outer walls, install the protective card cover at the pipe port to prevent the coating from adhering to the end and affecting the welding, and obtain a clean prefabricated pipe.

[0064] 3.2. The composite polyethylene coating is electrostatically sprayed on the inner wall of the clean prefabricated pipe, the static voltage of the powder spray gun is controlled to be 65 kV, the air pressure is controlled to be 0.13 MPa, and the distance between the nozzle and the inner wall is controlled to be 25 cm to obtain a pre-coated pipe.

[0065] 3.3. Place the pre-coated tube in an oven, control the temperature to 200°C, keep it warm and solidify for 25 minutes, and form a wear-resistant inner layer after cooling to obtain an outer tube.

[0066] 3.4. Apply zinc-rich primer to the outer surface of the outer blank pipe, which forms an outer anti-corrosion layer after curing to obtain a wear-resistant polyethylene gas pipe.

[0067] Example 3

[0068] This embodiment prepares a wear-resistant polyethylene gas pipe, which specifically includes the following steps:

[0069] 1) Preparation of wear-resistant and weather-resistant additives

[0070] 1.1. Prepare an acidic ethanol solution with ethanol, acetic acid and water, control the pH to be about 3, the mass fraction of ethanol to be about 30%, then add silica ash and silane coupling agent KH570, stir and mix at 300rpm for hydrolysis for 1h, then apply ultrasonic oscillation with a frequency of 28kHz, slowly add industrial ammonia water to the hydrolyzate, the dropping time is about 20min, adjust the pH value of the mixed solution to 7.0, and let it stand for coupling for 12h. During the reaction, the amount ratio of silica ash, silane coupling agent KH570 and acidic ethanol solution is 100g:13mL:520mL. After standing, take the bottom precipitate, add 10 times the mass of water to wash, centrifuge and take the precipitate again and vacuum dry to obtain a coupling filler.

[0071] 1.2. Take 2,6-dichlorofluorobenzene, triethylamine and tetrahydrofuran and mix them. Nitrogen is introduced into the reactor until a stable airflow is discharged. The reaction system is preheated under nitrogen protection and stirred at 120 rpm until the temperature reaches 48°C. Diallylamine is then added, the stirring rate is increased to 300 rpm, the temperature is continued to rise to 72°C, and the reaction is refluxed for 1.6 hours. During the reaction, the amount ratio of 2,6-dichlorofluorobenzene, diallylamine, triethylamine and tetrahydrofuran is 0.1 mol: 0.22 mol: 6 mL: 70 mL. After the reaction is completed, tetrahydrofuran is removed by reduced pressure rotary evaporation, and then 1.5 times the mass of boiling water of the rotary evaporation substrate is added for washing. The organic phase is vacuum dried to obtain a fluorinated monomer.

[0072] 1.3. Take fluorinated monomer, coupling filler, calcium stearate and azobisisobutylimidazoline hydrochloride, add them into a stirrer and mix them, then add them into a reactor, introduce nitrogen protection, raise the temperature to 160°C, control the stirring rate to 80rpm, and knead for 1.8h. During the reaction, the amount ratio of fluorinated monomer, coupling filler, calcium stearate and azobisisobutylimidazoline hydrochloride is 100g:50g:7g:2g. After the reaction is completed, discharge and cool, and grind into micro powder with a fineness of not less than 30 mesh to obtain a wear-resistant and weather-resistant additive.

[0073] 2) Preparation of composite polyethylene coating

[0074] 2.1. Take the following raw materials according to weight:

[0075] 100 parts of high-density polyethylene, 18 parts of triallyl isocyanurate, 15 parts of maleic anhydride grafted polyethylene, 20 parts of wear-resistant and weather-resistant additives, 0.5 parts of charge enhancer, 0.2 parts of antioxidant, and 1.2 parts of defoaming agent.

[0076] 2.2. Add the above raw materials into the mixer according to the weight ratio, stir and mix at a high speed of 1500rpm for 10min, then add the mixture into the twin-screw extruder, control the barrel temperature as follows: 120℃ for zone 1, 140℃ for zone 2, 150℃ for zone 3, 140℃ for zone 4, and the head temperature as 155℃, extrude the mixture into a tablet press for compaction, cool to room temperature, crush with a blade, freeze and embrittle with liquid nitrogen, and then grind and crush until the fineness of the powder reaches 80-100 mesh to obtain a composite polyethylene coating.

[0077] 3) Preparation of wear-resistant polyethylene gas pipes

[0078] 3.1. Take the alloy seamless steel pipe for gas, carry out conventional rust removal, degreasing and ceramic coating treatment on the inner and outer walls, install the protective card cover at the pipe port to prevent the coating from adhering to the end and affecting the welding, and obtain a clean prefabricated pipe.

[0079] 3.2. The composite polyethylene coating is electrostatically sprayed on the inner wall of the clean prefabricated pipe, the static voltage of the powder spray gun is controlled to be 70 kV, the air pressure is controlled to be 0.15 MPa, and the distance between the nozzle and the inner wall is 30 cm to obtain a pre-coated pipe.

[0080] 3.3. Place the pre-coated tube in an oven, control the temperature to 195°C, keep the temperature for 32 minutes, and form a wear-resistant inner layer after cooling to obtain an outer tube.

[0081] 3.4. Apply zinc-rich primer to the outer surface of the outer blank pipe, which forms an outer anti-corrosion layer after curing to obtain a wear-resistant polyethylene gas pipe.

[0082] Comparative Example

[0083] This comparative example is an existing 3PE coated gas pipe, provided by a pipeline company in Cangzhou.

[0084] In order to explore the wear resistance of the wear-resistant inner layer, the pipes prepared in Examples 1 to 3 and the pipes provided in the comparative example were sampled and subjected to wear coefficient tests and simulated micropowder scouring tests, respectively, as follows:

[0085] Wear coefficient test: refer to ASTM D968-93 standard, use falling sand method to test, each time the amount of falling sand is 10L, record 7 times the coating thickness change, take the average value to ensure the accuracy of the measured coating thickness, and calculate the wear coefficient;

[0086] Simulated micro powder scouring test: 800 mesh silica micro powder is used as abrasive and sprayed into the test tube through a venturi tube. The micro powder concentration is controlled to be 5g / m 3 , the flow rate in the tube is 15m / s, and a 30d scouring test is carried out to detect the surface roughness and thickness changes of the coating before and after the test;

[0087] The specific test results are shown in Table 1:

[0088] Table 1

[0089]

[0090] It can be seen from the data in Table 1 that the inner wall wear coefficient of the pipe prepared by the present invention is 46.9-54.1 L / mil, the thickness is reduced by 0.8-1.1 μm after simulated micropowder scouring, and the wear resistance of the inner wall coating is significantly better than that of the existing 3PE coated gas pipe.

[0091] In order to study the corrosion of natural gas on the inner wall of the pipe, the sample was cut according to the ASTM D968-93 standard, and self-sealing joints were installed on both ends of the sample pipe. After vacuuming, natural gas was injected and pressurized to 0.6MPa to simulate the internal state of the sub-high pressure gas pipeline. After standing for 6 months, the natural gas was discharged using a nitrogen return device, and the wear coefficient test was performed again. Compared with the test data in Table 1, the corrosion resistance rate = wear coefficient after corrosion / wear coefficient before corrosion × 100%. The specific test data are shown in Table 2:

[0092] Table 2

[0093]

[0094] It can be seen from the data in Table 2 that natural gas has a certain degree of corrosiveness to polyethylene coatings. Among them, the corrosion resistance rate of the pipe prepared by the present invention reaches more than 98%, which is significantly better than the existing 3PE coated gas pipe.

[0095] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0096] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A wear-resistant polyethylene gas pipe, comprising a wear-resistant inner layer, an alloy seamless steel pipe and an outer anti-corrosion layer, characterized in that: The wear-resistant inner layer is formed by curing a composite polyethylene coating, which comprises the following raw materials in parts by weight: 100 parts of high-density polyethylene, 14-18 parts of triallyl isocyanurate, 10-15 parts of maleic anhydride grafted polyethylene, 15-22 parts of wear-resistant and weather-resistant additives, 0.4-0.5 parts of charge enhancer, 0.2-0.3 parts of antioxidant and 1-1.3 parts of defoamer; The wear-resistant and weather-resistant additive is prepared by the following method: Step A1: prepare an acidic ethanol solution, add silica fume and silane coupling agent KH570, stir and hydrolyze for 40min-1h, then add ammonia water until the pH value is above 6.0 with ultrasonic vibration, stand for coupling for 12h, take the bottom precipitate, wash, centrifuge and dry to obtain a coupling filler; Step A2: 2,6-dichlorofluorobenzene, triethylamine and tetrahydrofuran are mixed, preheated to 45-55°C under nitrogen protection, and then diallylamine is added, stirred and the temperature is continued to rise to 68-75°C, and refluxed for 1.5-2h. After the reaction is completed, tetrahydrofuran is removed by vacuum rotary evaporation, and boiling water is added for washing. The organic phase is taken and dried to obtain a fluorinated monomer; Step A3: Mix the fluorinated monomer, coupling filler, calcium stearate and azobisisobutylimidazoline hydrochloride, protect with nitrogen, heat to 155-165° C., stir and knead for 1.6-2.3 hours, cool and crush the discharged material to obtain a wear-resistant and weather-resistant additive.

2. The wear-resistant polyethylene gas pipe according to claim 1, characterized in that: The dosage ratio of silica fume, silane coupling agent KH570 and acidic ethanol solution is 100g:12-15mL:500-600mL, the pH value of the acidic ethanol solution is 3-4, and the mass fraction of ethanol is 25-35%.

3. The wear-resistant polyethylene gas pipe according to claim 1, characterized in that: The usage ratio of 2,6-dichlorofluorobenzene, diallylamine, triethylamine and tetrahydrofuran is 0.1 mol: 0.22-0.24 mol: 5-6 mL: 60-80 mL.

4. A wear-resistant polyethylene gas pipe according to any one of claims 2-3, characterized in that: The usage ratio of the fluorinated monomer, the coupling filler, the calcium stearate and the azobisisobutylimidazoline hydrochloride is 100g: 35-55g: 5-8g: 1.6-2.2g.

5. The wear-resistant polyethylene gas pipe according to claim 4, characterized in that: The preparation method of the composite polyethylene coating is as follows: the raw materials are mixed and then extruded and sheeted. The barrel temperature of the extruder is: 120°C for zone one, 140°C for zone two, 150°C for zone three, 140°C for zone four, and the head temperature is 155°C. The composite polyethylene coating is then cooled, crushed, and freeze-ground to obtain the composite polyethylene coating.

6. The wear-resistant polyethylene gas pipe according to claim 5, characterized in that: The grinding fineness of the composite polyethylene coating is 80-100 mesh.

7. The method for preparing a wear-resistant polyethylene gas pipe according to claim 6, characterized in that: The steps include: Step S1: Derusting, degreasing and ceramic coating the inner and outer walls of the alloy seamless steel pipe, installing a protective card cover at the end to obtain a clean prefabricated pipe; Step S2: electrostatically spraying the composite polyethylene coating onto the inner wall of the clean prefabricated pipe, controlling the electrostatic voltage of the powder spray gun to 65-80 kV, the air pressure to 0.13-0.18 MPa, and the distance between the nozzle and the inner wall to 25-35 cm, to obtain a pre-coated pipe; Step S3: placing the pre-coated tube in an oven, controlling the temperature to 185-200° C., and heat preservation and curing time to 25-35 min. After cooling, a wear-resistant inner layer is formed to obtain an outer blank tube; Step S4: Brushing zinc-rich primer on the outer surface of the outer blank pipe forms an outer anti-corrosion layer after curing to obtain a wear-resistant polyethylene gas pipe.

8. The method for preparing a wear-resistant polyethylene gas pipe according to claim 7, characterized in that: The charge enhancer is the charge regulator H308.

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