Polyethylene composite belt for long-distance pipeline and preparation method thereof

Abstract

The invention relates to the technical field of steel pipeline protection, in particular to a polyethylene composite belt for a long-distance pipeline and a preparation method of the polyethylene composite belt. The polyethylene composite belt for the long-distance pipeline comprises a polyolefin base material and an adhesive layer coated on the surface of the polyolefin base material, the adhesive layer is prepared from the following raw materials: ethylene propylene diene monomer, low-density polyethylene, an ethylene-octene copolymer, maleic anhydride grafted polyethylene, a lubricant, nano silicon dioxide and an antioxidant; the polyolefin base material is prepared from the following raw materials: high-density polyethylene, ethylene propylene diene monomer, hyperbranched polyesteramide, graphene oxide, urea resin, an antioxidant, an ultraviolet stabilizer and a silane coupling agent. The working condition requirement of field joint coating can be met, the lap joint shear strength is effectively enhanced, the peel strength is excellent, the problem of interface debonding under the cambered surface stress of the bent pipe is effectively solved, and the preparation method is simple and suitable for large-scale application and popularization.

Description

Technical Field

[0001] The present invention relates to the technical field of steel pipe protection, and particularly to a polyethylene composite tape for long-distance pipelines and a preparation method thereof. Background Art

[0002] In long-distance oil and gas pipeline projects, for the anti-corrosion of steel pipes, due to the special shape of hot-bent elbows, the coating operation of the external anti-corrosion layer is difficult, and it is often the weak link of the external anti-corrosion layer of the whole pipeline.

[0003] The anti-corrosion performance of steel pipes is directly related to the service life and safety of the pipes. At present, the external anti-corrosion of hot-bent elbows mainly relies on materials such as epoxy coatings and polyethylene adhesive tapes, but it is significantly affected by environmental humidity, and there are also problems such as high curing internal stress and easy failure of the bonding interface. The coating performance mismatch and lap joint failure risks have long been faced in the joint filling process, becoming the weak link of pipeline corrosion protection. In addition, the hot-melt adhesive based on EVA has poor compatibility with the polyethylene substrate, and the peel strength decays significantly during long-term service, and it is easy to debond due to soil stress or temperature alternation.

[0004] At present, a polyethylene composite tape has emerged in the market for elbow anti-corrosion and steel pipe joint filling. The polyethylene composite tape consists of a double-layer structure, one layer is a radiation-crosslinked high-density polyolefin substrate, and the other layer is a polyolefin adhesive. However, during the construction of the joint filling technology with the polyethylene composite tape, due to insufficient material ductility or uneven heat shrinkage, the performance difference between the elbow anti-corrosion layer and the straight pipe section is extremely large. The peel strength of the elbow joint filling heat shrinkage tape decreases significantly due to local stress concentration, becoming the area where corrosion occurs preferentially.

[0005] In view of this, there are significant shortboards in the adaptability of elbow anti-corrosion materials, the bonding strength of the joint filling interface, and the construction reliability, which need to be solved urgently. Summary of the Invention

[0006] The purpose of the present invention is to solve the disadvantages existing in the prior art, and to provide a polyethylene composite tape for long-distance pipelines and a preparation method thereof.

[0007] A polyethylene composite tape for long-distance pipelines includes a polyolefin substrate and an adhesive layer coated on the surface of the polyolefin substrate.

[0008] Among them, the raw materials of the adhesive layer include, by mass: 20-40 parts of ethylene propylene diene monomer rubber, 40-60 parts of low-density polyethylene, 5-15 parts of ethylene-octene copolymer, 1-10 parts of maleic anhydride grafted polyethylene, 1-2 parts of lubricant, 1-2 parts of nano-silica, and 1-3 parts of antioxidant; The raw materials of the polyolefin substrate include, by mass parts: 5-15 parts of ethylene-propylene-diene monomer rubber, 40-60 parts of high-density polyethylene, 5-10 parts of hyperbranched polyamide ester, 1-2 parts of graphene oxide, 0.5-1 part of urea-formaldehyde resin, 1-3 parts of antioxidant, 0.1-1 part of ultraviolet stabilizer, and 1 part of silane coupling agent.

[0009] Preferably, the thickness ratio of the polyolefin substrate to the adhesive layer is 1-2:0.5-1.

[0010] Preferably, the density of the high-density polyethylene is 0.95-0.98 g / cm 3 。

[0011] Preferably, the density of the low-density polyethylene is 0.923-0.927 g / cm 3 。

[0012] Preferably, the ultraviolet stabilizer is a hindered amine light stabilizer, preferably light stabilizer 944.

[0013] Preferably, the maleic anhydride grafting rate in the maleic anhydride grafted polyethylene is 1.5-2%.

[0014] Preferably, the antioxidant is antioxidant 1010 or / and antioxidant 1076.

[0015] Preferably, the lubricant includes: calcium stearate and ethylene bisstearamide, and the mass ratio of calcium stearate to ethylene bisstearamide is 1:0.1-0.5.

[0016] The preparation method of the polyethylene composite tape for long-distance pipelines described above includes the following steps: S1. Premix ethylene-propylene-diene monomer rubber, high-density polyethylene, hyperbranched polyamide ester, graphene oxide, urea-formaldehyde resin, antioxidant, and ultraviolet stabilizer, extrude and form at 160-200 °C, cool to room temperature, etch one side surface with high-pressure water jet for 2-5 s, the water flow pressure is 50-150 MPa, the water flow speed is 3-5 m / s, spray an ethanol solution containing silane coupling agent on the surface, pre-dry at 80-100 °C, and perform electron beam radiation treatment and drying to obtain a polyethylene substrate; Among them, using the three-dimensional dendritic molecular chain of hyperbranched polyamide ester, multiple hydrogen bond networks are formed through its hydroxyl groups with lamellar graphene oxide and urea-formaldehyde resin, and cooperating with the action of ethylene-propylene-diene monomer rubber, it promotes the corrosion protection performance to remain stable under the dynamic stress of the elbow arc surface; S2. Mix ethylene-propylene-diene monomer rubber, low-density polyethylene, ethylene-octene copolymer, maleic anhydride grafted polyethylene, lubricant, nano-silica, and antioxidant evenly, and melt and extrude and coat on one side surface of the polyethylene substrate after being etched by high-pressure water jet, and cool by vacuum adsorption.

[0017] Preferably, in S1, during the electron beam radiation treatment, the irradiation dose is 10 - 15 kGy.

[0018] Preferably, in S1, the ethanol solution containing silane coupling agent is prepared from silane coupling agent and absolute ethanol according to a mass ratio of 1:5 - 10.

[0019] Beneficial effects: The present invention uses ethylene propylene diene monomer (EPDM) to be compounded and blended with low - density polyethylene, maleic anhydride - grafted polyethylene, and ethylene - octene copolymer. The anhydride groups of maleic anhydride - grafted polyethylene form a reinforcing phase in the system, which can effectively avoid peeling failure caused by thermal expansion mismatch. With the cooperation of ethylene - octene copolymer, it can effectively resist fatigue cracking caused by stress.

[0020] In the polyolefin substrate of the present invention, EPDM is compounded with high - density polyethylene. The different glass transition temperatures of the two lead to the formation of a multiphase dispersion structure, which can effectively absorb the load generated by stress and relieve the internal stress concentration caused by the thermal shrinkage of the elbow pipe. Then, with the cooperation of hyperbranched polyamide ester, its three - dimensional dendritic structure can effectively improve the bonding strength of EPDM in high - density polyethylene, effectively transfer dynamic stress, and reduce the stress concentration caused by bending deformation. Subsequently, after roughening treatment on one side and binding silane coupling agent on the surface, it can effectively enhance the bonding strength with the adhesive layer, greatly promote the interfacial shear strength, and effectively solve the problem of the attenuation of the peel strength at the lap joint interface of the repair joint.

[0021] The present invention can meet the working condition requirements of on - site repair joints, effectively enhance the lap shear strength, and has excellent peel strength, effectively solving the problem of interfacial debonding under the stress of the elbow pipe arc surface. The present invention can ensure the stable performance of the adhesive layer in the production of composite tapes and pipeline repair joints, eliminate the difference in anti - corrosion quality between elbow pipes and straight pipes, and has a simple preparation method, which is suitable for large - scale popularization and application. Description of the drawings

[0022] Figure 1 It is a comparison chart of the tensile strength and lap shear strength of the polyethylene composite tapes obtained in Example 5 and Comparative Examples 1 - 3.

[0023] Figure 2 It is a comparison chart of the peel strength of the polyethylene composite tapes obtained in Example 5 and Comparative Examples 1 - 3.

[0024] Figure 3 It is a graph showing the change of the peel strength of the polyethylene composite tapes obtained in Example 5 and Comparative Examples 1 - 3 with the hot water bath treatment time. Detailed implementation manners

[0025] The following further explains the present invention with specific examples.

[0026] The high-density polyethylene used below is sourced from Jilin Petrochemical, with the grade of HDPE HA7260 and a density of 0.957 g / cm 3 。The low-density polyethylene used below is sourced from Yanshan Petrochemical, with the grade of LDPE LD104 and a density of 0.925 g / cm 3 。The ethylene propylene diene monomer (EPDM) used below is sourced from Dow Chemical of the United States, with the grade of EPDM IP 3430. The hyperbranched polyamide ester used below has the trade name of Hybrane® PS 2550. The ethylene-octene copolymer used below is sourced from Dow Chemical of the United States, with the grade of ENGAGE™ POE8842. The maleic anhydride grafted polyethylene used below is purchased from Wuhan Mouxiang Kejie Biotechnology Co., Ltd., with a maleic anhydride grafting rate of 1.76%. The urea-formaldehyde resin used below is purchased from Jinan Mouguang Chemical Co., Ltd.

[0027] Example 1 A polyethylene composite tape for long-distance pipelines, comprising: a polyolefin substrate with a thickness of 1 mm, and an adhesive layer (with a thickness of 0.5 mm) coated on the surface of the polyolefin substrate.

[0028] Among them, the raw materials of the adhesive layer include: 20 g of ethylene propylene diene monomer (EPDM), 40 g of low-density polyethylene, 5 g of ethylene-octene copolymer, 1 g of maleic anhydride grafted polyethylene, 1 g of lubricant (composed of calcium stearate and ethylene bisstearamide in a mass ratio of 1:0.1), 1 g of nano-silica, and 1 g of antioxidant 1076; while the raw materials of the polyolefin substrate include: 5 g of ethylene propylene diene monomer (EPDM), 40 g of high-density polyethylene, 5 g of hyperbranched polyamide ester, 1 g of graphene oxide, 0.5 g of urea-formaldehyde resin, 1 g of antioxidant 1010, 0.1 g of light stabilizer 944, and 1 g of KH560 coupling agent.

[0029] The preparation method of the above polyethylene composite tape for long-distance pipelines includes the following steps: S1. Premix ethylene propylene diene monomer (EPDM), high-density polyethylene, hyperbranched polyamide ester, graphene oxide, urea-formaldehyde resin, antioxidant 1010, and light stabilizer 944 in a mixer, then feed them into a twin-screw extruder for extrusion molding. The extrusion temperature is 160 °C, and then it is cooled to room temperature; on one side surface, it is etched by high-pressure water jet for 2 s, the water flow pressure is 50 MPa, and the water flow speed is 3 m / s. Then, an ethanol solution containing KH560 coupling agent (the mass ratio of silane coupling agent to absolute ethanol is 1:5) is sprayed on the surface after high-pressure water jet etching, pre-dried at a temperature of 80 °C, and then treated by electron beam radiation (the irradiation dose is 10 kGy), and finally dried to obtain the polyethylene substrate; S2. Mix ethylene propylene diene monomer (EPDM), low density polyethylene (LDPE), ethylene-octene copolymer, maleic anhydride grafted polyethylene, lubricant, nano-silica, and antioxidant 1076 evenly, feed them into a twin-screw extruder for melt extrusion, and then coat one side surface of the polyethylene substrate after high-pressure water jet etching. The coating temperature is 190 °C; cool by vacuum adsorption, and control the wind speed to be 0.5 m / s.

[0030] Example 2 A polyethylene composite tape for long-distance pipelines, comprising: a polyolefin substrate with a thickness of 2 mm, and an adhesive layer (with a thickness of 1 mm) coated on the surface of the polyolefin substrate.

[0031] Among them, the raw materials of the adhesive layer include: 40 g of ethylene propylene diene monomer (EPDM), 60 g of low density polyethylene (LDPE), 15 g of ethylene-octene copolymer, 10 g of maleic anhydride grafted polyethylene, 2 g of lubricant (composed of calcium stearate and ethylene bisstearamide in a mass ratio of 1:0.5), 2 g of nano-silica, and 3 g of antioxidant 1076; while the raw materials of the polyolefin substrate include: 15 g of ethylene propylene diene monomer (EPDM), 60 g of high density polyethylene (HDPE), 10 g of hyperbranched polyamide ester, 2 g of graphene oxide, 1 g of urea-formaldehyde resin, 3 g of antioxidant 1010, 1 g of light stabilizer 944, and 1 g of KH560 coupling agent.

[0032] The preparation method of the above-mentioned polyethylene composite tape for long-distance pipelines includes the following steps: S1. Premix ethylene propylene diene monomer (EPDM), high density polyethylene (HDPE), hyperbranched polyamide ester, graphene oxide, urea-formaldehyde resin, antioxidant 1010, and light stabilizer 944 in a mixer, feed them into a twin-screw extruder for extrusion molding, the extrusion temperature is 200 °C, and cool to room temperature; etch one side surface with high-pressure water jet for 5 s, the water pressure is 150 MPa, the water flow rate is 5 m / s, spray an ethanol solution containing KH560 coupling agent (the mass ratio of silane coupling agent to absolute ethanol is 1:10) on the surface after high-pressure water jet etching, pre-dry at a temperature of 100 °C, and perform electron beam radiation treatment (the irradiation dose is 15 kGy), and dry to obtain the polyethylene substrate; S2. Mix ethylene propylene diene monomer (EPDM), low density polyethylene (LDPE), ethylene-octene copolymer, maleic anhydride grafted polyethylene, lubricant, nano-silica, and antioxidant 1076 evenly, feed them into a twin-screw extruder for melt extrusion, and then coat one side surface of the polyethylene substrate after high-pressure water jet etching. The coating temperature is 200 °C; cool by vacuum adsorption, and control the wind speed to be 0.8 m / s.

[0033] Example 3 A polyethylene composite tape for long-distance pipelines, comprising: a polyolefin substrate with a thickness of 1.5 mm, and an adhesive layer (with a thickness of 0.75 mm) coated on the surface of the polyolefin substrate.

[0034] Among them, the raw materials of the adhesive layer include: 25 g of ethylene propylene diene monomer rubber, 55 g of low-density polyethylene, 12 g of ethylene-octene copolymer, 2 g of maleic anhydride grafted polyethylene, 1.3 g of lubricant (composed of calcium stearate and ethylene bisstearamide in a mass ratio of 1:0.4), 1.8 g of nano-silica, and 1.5 g of antioxidant 1076; while the raw materials of the polyolefin substrate include: 12 g of ethylene propylene diene monomer rubber, 45 g of high-density polyethylene, 7 g of hyperbranched polyamide ester, 1.7 g of graphene oxide, 0.7 g of urea-formaldehyde resin, 2.5 g of antioxidant 1076, 0.3 g of light stabilizer 944, and 1 g of KH560 coupling agent.

[0035] The preparation method of the polyethylene composite tape for long-distance pipelines described above includes the following steps: S1. Feed ethylene propylene diene monomer rubber, high-density polyethylene, hyperbranched polyamide ester, graphene oxide, urea-formaldehyde resin, antioxidant 1076, and light stabilizer 944 into a mixer for premixing, then feed them into a twin-screw extruder for extrusion molding. The extrusion temperature is 190 °C, and then it is cooled to room temperature; on one side surface, perform high-pressure water jet etching for 3 s, the water flow pressure is 120 MPa, and the water flow rate is 3.5 m / s. Spray an ethanol solution containing KH560 coupling agent (the mass ratio of silane coupling agent to absolute ethanol is 1:9) on the surface after high-pressure water jet etching, pre-dry at a temperature of 85 °C, and perform electron beam radiation treatment (the irradiation dose is 13 kGy), and then dry to obtain the polyethylene substrate; S2. Mix ethylene propylene diene monomer rubber, low-density polyethylene, ethylene-octene copolymer, maleic anhydride grafted polyethylene, lubricant, nano-silica, and antioxidant 1076 evenly, then feed them into a twin-screw extruder for melt extrusion, and immediately coat on one side surface of the polyethylene substrate after high-pressure water jet etching. The coating temperature is 192 °C; perform vacuum adsorption cooling, and control the wind speed to be 0.7 m / s.

[0036] Example 4 A polyethylene composite tape for long-distance pipelines includes: a polyolefin substrate with a thickness of 1.5 mm, and an adhesive layer (with a thickness of 0.75 mm) coated on the surface of the polyolefin substrate.

[0037] Among them, the raw materials of the adhesive layer include: 35 g of ethylene propylene diene monomer rubber, 45 g of low-density polyethylene, 8 g of ethylene-octene copolymer, 8 g of maleic anhydride grafted polyethylene, 1.7 g of lubricant (composed of calcium stearate and ethylene bisstearamide in a mass ratio of 1:0.2), 1.2 g of nano-silica, and 2.5 g of antioxidant 1076; while the raw materials of the polyolefin substrate include: 8 g of ethylene propylene diene monomer rubber, 55 g of high-density polyethylene, 9 g of hyperbranched polyamide ester, 1.3 g of graphene oxide, 0.8 g of urea-formaldehyde resin, 1.5 g of antioxidant 1076, 0.7 g of light stabilizer 944, and 1 g of KH560 coupling agent.

[0038] The preparation method of the polyethylene composite tape for long-distance pipelines described above includes the following steps: S1. Premix ethylene propylene diene monomer (EPDM), high-density polyethylene (HDPE), hyperbranched polyamide ester, graphene oxide, urea-formaldehyde resin, antioxidant 1076, and light stabilizer 944 in a mixer, and then feed them into a twin-screw extruder for extrusion molding. The extrusion temperature is 170 °C, and then it is cooled to room temperature. Etch one side surface with high-pressure water jet for 4 s, with the water pressure of 80 MPa and the water flow rate of 4.5 m / s. Spray an ethanol solution containing KH560 coupling agent (the mass ratio of silane coupling agent to absolute ethanol is 1:7) on the surface after high-pressure water jet etching, pre-dry at 95 °C, and then conduct electron beam radiation treatment (the irradiation dose is 11 kGy), and finally dry to obtain the polyethylene substrate. S2. Mix EPDM, low-density polyethylene (LDPE), ethylene-octene copolymer, maleic anhydride grafted polyethylene, lubricant, nano-silica, and antioxidant 1076 evenly, and then feed them into a twin-screw extruder for melt extrusion. Immediately coat the mixture on one side surface of the polyethylene substrate that has been etched by high-pressure water jet, and the coating temperature is 198 °C. Cool it by vacuum adsorption, and control the wind speed to be 0.6 m / s.

[0039] Example 5 A polyethylene composite tape for long-distance pipelines includes a polyolefin substrate with a thickness of 1.5 mm and an adhesive layer (with a thickness of 0.75 mm) coated on the surface of the polyolefin substrate.

[0040] Among them, the raw materials of the adhesive layer include: 30 g of EPDM, 50 g of LDPE, 10 g of ethylene-octene copolymer, 5 g of maleic anhydride grafted polyethylene, 1.5 g of lubricant (composed of calcium stearate and ethylene bisstearamide with a mass ratio of 1:0.3), 1.5 g of nano-silica, and 2 g of antioxidant 1010; while the raw materials of the polyolefin substrate include: 10 g of EPDM, 50 g of HDPE, 8 g of hyperbranched polyamide ester, 1.5 g of graphene oxide, 0.75 g of urea-formaldehyde resin, 2 g of antioxidant 1010, 0.5 g of light stabilizer 944, and 1 g of KH560 coupling agent.

[0041] The preparation method of the polyethylene composite tape for long-distance pipelines described above includes the following steps: S1. Premix ethylene propylene diene monomer (EPDM), high-density polyethylene (HDPE), hyperbranched polyamide ester, graphene oxide, urea-formaldehyde resin, antioxidant 1010, and light stabilizer 944 in a mixer, then feed them into a twin-screw extruder for extrusion molding at an extrusion temperature of 180 °C, and cool to room temperature. Etch one side surface with high-pressure water jet for 4 s, with a water flow pressure of 100 MPa and a water flow velocity of 4 m / s. Spray an ethanol solution containing KH560 coupling agent (the mass ratio of silane coupling agent to absolute ethanol is 1:8) on the surface after high-pressure water jet etching, pre-dry at a temperature of 90 °C, and perform electron beam radiation treatment (irradiation dose is 12 kGy), then dry to obtain a polyethylene substrate; S2. Mix EPDM, low-density polyethylene (LDPE), ethylene-octene copolymer, maleic anhydride grafted polyethylene, lubricant, nano-silica, and antioxidant 1010 evenly, then feed them into a twin-screw extruder for melt extrusion, and immediately coat on one side surface of the polyethylene substrate that has been etched by high-pressure water jet at a coating temperature of 195 °C. Cool by vacuum adsorption, and control the wind speed at 0.65 m / s.

[0042] Comparative Example 1 A polyethylene composite tape for long-distance transportation pipelines includes: a polyolefin substrate with a thickness of 1.5 mm, and an adhesive layer (with a thickness of 0.75 mm) coated on the surface of the polyolefin substrate.

[0043] Among them, the raw materials of the adhesive layer include: 30 g of EPDM, 50 g of LDPE, 10 g of ethylene-octene copolymer, 5 g of maleic anhydride grafted polyethylene, 1.5 g of lubricant (composed of calcium stearate and ethylene bisstearamide with a mass ratio of 1:0.3), 1.5 g of nano-silica, and 2 g of antioxidant 1010; while the raw materials of the polyolefin substrate include: 10 g of EPDM, 50 g of HDPE, 8 g of hyperbranched polyamide ester, 1.5 g of graphene oxide, 0.75 g of urea-formaldehyde resin, 2 g of antioxidant 1010, 0.5 g of light stabilizer 944, and 1 g of KH560 coupling agent.

[0044] The preparation method of the above-mentioned polyethylene composite tape for long-distance transportation pipelines includes the following steps: S1. Premix EPDM, HDPE, hyperbranched polyamide ester, graphene oxide, urea-formaldehyde resin, antioxidant 1010, and light stabilizer 944 in a mixer, then feed them into a twin-screw extruder for extrusion molding at an extrusion temperature of 180 °C, and cool to room temperature. Etch one side surface with high-pressure water jet for 4 s, with a water flow pressure of 100 MPa and a water flow velocity of 4 m / s. Spray an ethanol solution containing KH560 coupling agent (the mass ratio of silane coupling agent to absolute ethanol is 1:8) on the surface after high-pressure water jet etching, pre-dry at a temperature of 90 °C, and then dry to obtain a polyethylene substrate; S2. Mix ethylene propylene diene monomer (EPDM), low density polyethylene (LDPE), ethylene-octene copolymer, maleic anhydride grafted polyethylene, lubricant, nano-silica, and antioxidant 1010 evenly, feed them into a twin-screw extruder for melt extrusion, and then coat one side surface of the polyethylene substrate after being etched by high-pressure water jet. The coating temperature is 195 °C; cool by vacuum adsorption, and control the wind speed to be 0.65 m / s.

[0045] Comparative Example 2 A polyethylene composite tape for long-distance transmission pipelines, comprising: a polyolefin substrate with a thickness of 1.5 mm, and an adhesive layer (with a thickness of 0.75 mm) coated on the surface of the polyolefin substrate.

[0046] Among them, the raw materials of the adhesive layer include: 30 g of ethylene propylene diene monomer (EPDM), 50 g of low density polyethylene (LDPE), 10 g of ethylene-octene copolymer, 5 g of maleic anhydride grafted polyethylene, 1.5 g of lubricant (composed of calcium stearate and ethylene bisstearamide in a mass ratio of 1:0.3), 1.5 g of nano-silica, and 2 g of antioxidant 1010; while the raw materials of the polyolefin substrate include: 18 g of ethylene propylene diene monomer (EPDM), 50 g of high density polyethylene (HDPE), 1.5 g of graphene oxide, 0.75 g of urea-formaldehyde resin, 2 g of antioxidant 1010, 0.5 g of light stabilizer 944, and 1 g of KH560 coupling agent.

[0047] The preparation method of the above-mentioned polyethylene composite tape for long-distance transmission pipelines includes the following steps: S1. Premix ethylene propylene diene monomer (EPDM), high density polyethylene (HDPE), graphene oxide, urea-formaldehyde resin, antioxidant 1010, and light stabilizer 944 in a mixer, feed them into a twin-screw extruder for extrusion molding, the extrusion temperature is 180 °C, and cool to room temperature; etch one side surface with high-pressure water jet for 4 s, the water pressure is 100 MPa, the water flow rate is 4 m / s, spray an ethanol solution containing KH560 coupling agent (the mass ratio of silane coupling agent to absolute ethanol is 1:8) on the surface after high-pressure water jet etching, pre-dry at 90 °C, and perform electron beam radiation treatment (the irradiation dose is 12 kGy), and dry to obtain a polyethylene substrate; S2. Mix ethylene propylene diene monomer (EPDM), low density polyethylene (LDPE), ethylene-octene copolymer, maleic anhydride grafted polyethylene, lubricant, nano-silica, and antioxidant 1010 evenly, feed them into a twin-screw extruder for melt extrusion, and then coat one side surface of the polyethylene substrate after being etched by high-pressure water jet. The coating temperature is 195 °C; cool by vacuum adsorption, and control the wind speed to be 0.65 m / s.

[0048] Comparative Example 3 A polyethylene composite tape for long-distance transmission pipelines, comprising: a polyolefin substrate with a thickness of 1.5 mm, and an adhesive layer (with a thickness of 0.75 mm) coated on the surface of the polyolefin substrate.

[0049] Among them, the raw materials of the adhesive layer include: 30 g of ethylene propylene diene monomer (EPDM), 50 g of low-density polyethylene (LDPE), 10 g of ethylene-octene copolymer, 5 g of maleic anhydride grafted polyethylene, 1.5 g of lubricant (composed of calcium stearate and ethylene bisstearamide with a mass ratio of 1:0.3), 1.5 g of nano-silica, and 2 g of antioxidant 1010; while the raw materials of the polyolefin substrate include: 10 g of EPDM, 50 g of high-density polyethylene (HDPE), 8 g of hyperbranched polyamide ester, 1.5 g of graphene oxide, 0.75 g of urea-formaldehyde resin, 2 g of antioxidant 1010, 0.5 g of light stabilizer 944, and 1 g of KH560 coupling agent.

[0050] The preparation method of the polyethylene composite tape for long-distance pipelines described above includes the following steps: S1. Premix EPDM, HDPE, hyperbranched polyamide ester, graphene oxide, urea-formaldehyde resin, antioxidant 1010, and light stabilizer 944 in a mixer, and then feed them into a twin-screw extruder for extrusion molding. The extrusion temperature is 180 °C, and then it is cooled to room temperature; spray an ethanol solution containing KH560 coupling agent (the mass ratio of silane coupling agent to absolute ethanol is 1:8) on one side surface, pre-dry at 90 °C, and perform electron beam radiation treatment (the irradiation dose is 12 kGy), and then dry to obtain the polyethylene substrate. S2. Mix EPDM, LDPE, ethylene-octene copolymer, maleic anhydride grafted polyethylene, lubricant, nano-silica, and antioxidant 1010 evenly, and then feed them into a twin-screw extruder for melt extrusion, and immediately coat it on the surface of the polyethylene substrate on the side sprayed with KH560 coupling agent. The coating temperature is 195 °C; cool it by vacuum adsorption, and control the wind speed to be 0.65 m / s.

[0051] Refer to GB / T 1040.2-2022 "Plastics - Determination of tensile properties - Part 2: Test conditions for moulding and extrusion plastics" to measure the tensile strength of the polyethylene composite tapes obtained in Example 5 and Comparative Examples 1-3.

[0052] Refer to GB / T 7124-2008 "Adhesives - Determination of tensile shear strength (rigid-to-rigid)" to measure the lap shear strength of the polyethylene composite tapes obtained in Example 5 and Comparative Examples 1-3.

[0053] Refer to GB / T 2790-1995 "Test method for 180° peel strength of adhesives - Flexible-to-rigid" and SY / T0315 "Technical specification for fusion-bonded epoxy powder external coating for steel pipelines" to measure the peel strength of the polyethylene composite tapes obtained in Example 5 and Comparative Examples 1-3.

[0054] Such as Figure 1 and Figure 2As shown, the tensile strength, lap shear strength, and peel strength of the polyethylene composite tape obtained in Example 5 are all the highest, superior to those of Comparative Examples 1-3 (P < 0.05).

[0055] The polyethylene composite tapes obtained in Example 5 and Comparative Examples 1-3 were wound around the elbow pipe in a cold tape and hot winding manner. The elbow pipe with the polyethylene composite tape (without edge sealing treatment) was immersed in a constant temperature water bath at 50 ± 3 °C for a period of time, and then the specimen was taken out of the water bath for peel strength testing.

[0056] As Figure 3 shown, after the polyethylene composite tape obtained in Example 5 was treated in a hot water bath, the peel strength was still always the highest, superior to those of Comparative Examples 1-3 (P < 0.05).

[0057] As described above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A polyethylene composite belt for long-distance pipelines, characterized in that: It includes a polyolefin substrate and an adhesive layer coated on the surface of the polyolefin substrate; The raw materials of the adhesive layer include, by mass: 20-40 parts of EPDM rubber, 40-60 parts of low-density polyethylene, 5-15 parts of ethylene-octene copolymer, 1-10 parts of maleic anhydride grafted polyethylene, 1-2 parts of lubricant, 1-2 parts of nano-silicon dioxide, and 1-3 parts of antioxidant; The raw materials of the polyolefin substrate include, by mass, 5-15 parts of EPDM rubber, 40-60 parts of high-density polyethylene, 5-10 parts of hyperbranched polyamide ester, 1-2 parts of graphene oxide, 0.5-1 parts of urea-formaldehyde resin, 1-3 parts of antioxidant, 0.1-1 parts of ultraviolet stabilizer, and 1 part of silane coupling agent.

2. The polyethylene composite belt for long-distance pipeline according to claim 1, characterized in that: The thickness ratio of the polyolefin substrate to the adhesive layer is 1-2:0.5-1.

3. The polyethylene composite belt for long-distance pipeline according to claim 1, characterized in that: The density of high-density polyethylene is 0.95-0.98g / cm 3 .

4. The polyethylene composite belt for long-distance pipeline according to claim 1, characterized in that: The density of low-density polyethylene is 0.923-0.927 g / cm 3 .

5. The polyethylene composite belt for long-distance pipeline according to claim 1, characterized in that: The UV stabilizer is a hindered amine light stabilizer.

6. The polyethylene composite belt for long-distance pipeline according to claim 1, characterized in that: The maleic anhydride grafting rate in maleic anhydride grafted polyethylene is 1.5-2%.

7. The polyethylene composite belt for long-distance pipeline according to claim 1, characterized in that: The antioxidant is antioxidant 1010 and / or antioxidant 1076.

8. The polyethylene composite belt for long-distance pipeline according to claim 1, characterized in that: The lubricant includes: calcium stearate and ethylene bisstearamide, and the mass ratio of calcium stearate to ethylene bisstearamide is 1:0.1-0.

5.

9. A method for preparing a polyethylene composite tape for a long-distance pipeline according to any one of claims 1 to 8, characterized in that: The steps include: S1. Premix EPDM rubber, high-density polyethylene, hyperbranched polyamide ester, graphene oxide, urea-formaldehyde resin, antioxidant and UV stabilizer, extrude and mold at 160-200° C., cool to room temperature, etch one side surface with high-pressure water jet for 2-5 seconds, with a water flow pressure of 50-150 MPa and a water flow velocity of 3-5 m / s, spray an ethanol solution containing a silane coupling agent on the surface, pre-dry at 80-100° C., treat with electron beam radiation, and dry to obtain a polyethylene substrate; S2. Evenly mix EPDM rubber, low-density polyethylene, ethylene-octene copolymer, maleic anhydride grafted polyethylene, lubricant, nano-silica and antioxidant, melt-extrude and coat on the surface of a polyethylene substrate after high-pressure water jet etching, and cool by vacuum adsorption.

10. The method for preparing a polyethylene composite tape for a long-distance pipeline according to claim 9, characterized in that: In S1, during the electron beam radiation treatment, the radiation dose is 10-15 kGy.

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