A high-voltage and heat-resistant polyethylene resin composition pipe and a manufacturing method and application thereof

Abstract

The application provides a high-voltage and heat-resistant polyethylene resin composition pipe and a manufacturing method and application thereof. The pipe is made of a high-voltage and heat-resistant polyethylene resin composition, wherein the high-voltage and heat-resistant polyethylene resin composition comprises 100 parts by weight of heat-resistant polyethylene, 0.3-0.8 parts by weight of a composite additive and 10-30 parts by weight of a pre-dispersed carbon nanotube master batch; the composite additive comprises an antioxidant, a halogen absorbent and a fluorine processing aid, and the weight ratio of the three is 1:0.1-1:0.1-0.5; and the pre-dispersed carbon nanotube master batch comprises surface-modified carbon nanotubes and heat-resistant polyethylene powder, and the weight ratio of the two is 0.01-0.1:1. The pipe provided by the application, especially a large-diameter pipe, has excellent processing performance, such as anti-sagging performance, and the pipe also has excellent pressure and heat resistance.

Description

Technical Field

[0001] This invention relates to a high-pressure and heat-resistant polyethylene resin composition pipe, its manufacturing method and application, belonging to the field of polymer materials technology. Background Technology

[0002] Heat-resistant polyethylene pipe material, abbreviated as PE-RT pipe material, is a type of non-crosslinked polyethylene with advantages such as good heat-fusion bonding, excellent high-temperature resistance, and long service life. In recent years, PE-RT pipe material, with its excellent physical properties, corrosion resistance, flexibility, processability, and construction and installation characteristics, has endowed the pipe material with good performance stability, high safety, and repairability. It can replace random copolymer polypropylene (PPR), polybutene (PB), chlorinated polyvinyl chloride (PVC-C), and crosslinked polyethylene (PEX) in applications such as underfloor heating pipes, heat exchangers, and hot and cold water transportation. The international standard ISO22391-2:2009 classifies PE-RT pipe materials into two types: Type I and Type II. According to the standard requirements, Type I PE-RT pipe materials are allowed to undergo brittle fracture at all temperatures below 110℃, meaning the hydrostatic pressure curve can show an inflection point, while Type II PE-RT pipe materials are not allowed to undergo brittle fracture at all temperatures below 110℃, meaning the hydrostatic pressure curve cannot show an inflection point. It is evident that Type II PE-RT pipes outperform Type I products in terms of pressure resistance and slow crack growth resistance. Their application areas have rapidly expanded to secondary heating network construction and renovation, industrial heat medium transportation, and other fields. In particular, under the same transportation pressure, the pipe wall can be thinned, saving raw materials, and it is more suitable for making larger diameter pipes. It has now become the development direction of the PE-RT pipe market.

[0003] The special resin used in Type II PE-RT pipes needs to possess excellent heat resistance and pressure resistance, with a pressure rating no lower than PE100. It also needs excellent processability and anti-sagging properties to meet the requirements for processing large-diameter pipes. Current research mainly focuses on introducing long branches into the molecular chain during polymerization by adjusting catalysts and polymerization conditions to improve the material's pressure resistance. However, this technology is complex, the molecular chain structure is difficult to control, and the cost is high. Furthermore, processing problems such as gel points on the inner wall are prone to occur during processing.

[0004] Carbon nanotubes (CNTs) are one-dimensional nanomaterials composed of several to dozens of layers of coaxial cylindrical tubes arranged in a hexagonal pattern. CNTs possess excellent mechanical properties; their tensile strength reaches 50-200 GPa, 100 times that of steel, while their density is only 1 / 6 that of steel, at least an order of magnitude higher than conventional graphite fibers. Furthermore, their elastic modulus can reach 1 TPa, comparable to that of diamond and approximately five times that of steel. Carbon nanotubes exhibit elasticity through volume changes, capable of withstanding tensile strain greater than 40%. In material composites, they can significantly absorb energy, increasing strength and toughness, making them a current research hotspot in the field of polyolefin composites. However, the strong van der Waals forces between carbon nanotubes cause them to easily entangle or aggregate into bundles, making uniform dispersion in polymers difficult and greatly limiting their application in polyolefin materials.

[0005] In summary, current technologies for improving the pressure resistance of heat-resistant pipe materials typically involve controlling the polymerization process to increase the content of long-chain branches and the number of tie molecules. The more tie molecules present, the greater the resistance to pull-out under external force, resulting in better high-temperature and pressure resistance. However, adjusting the polymerization process is complex and difficult to control precisely. Furthermore, in existing pipe production processes, carbon black is generally added to the raw material composition to improve weather resistance and electrical conductivity, but this does not improve the mechanical properties of the pipe. Additionally, in the production of large-diameter heat-resistant pipes, the slower processing speed leads to significant pipe sagging. Moreover, current technologies using carbon nanotubes to modify pipes typically involve directly blending and extruding carbon nanotubes with polyethylene base material online. However, this method results in poor dispersion of carbon nanotubes, making it difficult to guarantee the quality of the resulting pipes.

[0006] Therefore, providing a novel high-pressure and heat-resistant polyethylene resin composition pipe, its manufacturing method, and its application has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To address the aforementioned shortcomings and deficiencies, one objective of this invention is to provide a high-pressure-resistant and heat-resistant polyethylene resin composition pipe.

[0008] Another object of the present invention is to provide a method for manufacturing the high pressure-resistant and heat-resistant polyethylene resin composition pipe described above.

[0009] Another object of the present invention is to provide the above-described high pressure-resistant and heat-resistant polyethylene resin composition pipes as connecting fittings between pipes.

[0010] To achieve the above objectives, on the one hand, the present invention provides a high pressure-resistant and heat-resistant polyethylene resin composition pipe, wherein the pipe is made of a high pressure-resistant and heat-resistant polyethylene resin composition, wherein the high pressure-resistant and heat-resistant polyethylene resin composition comprises: 100 parts by weight of heat-resistant polyethylene, 0.3-0.8 parts by weight of composite additives, and 10-30 parts by weight of pre-dispersed carbon nanotube masterbatch.

[0011] The composite additive includes antioxidants, halogen absorbers, and fluorine processing aids, with a weight ratio of 1:0.1-1:0.1-0.5.

[0012] The pre-dispersed carbon nanotube masterbatch comprises surface-modified carbon nanotubes and heat-resistant polyethylene powder, with a weight ratio of 0.01-0.1:1.

[0013] This invention uses a high-pressure-resistant and heat-resistant polyethylene resin composition as raw material to produce high-pressure-resistant and heat-resistant polyethylene resin composition pipes. The high-pressure-resistant and heat-resistant polyethylene resin composition includes heat-resistant polyethylene, composite additives, and pre-dispersed carbon nanotube masterbatch. The presence of composite additives and pre-dispersed carbon nanotube masterbatch can bring out the excellent properties of the high-pressure-resistant and heat-resistant polyethylene resin composition, giving it excellent processing performance when producing large-diameter pipes. This meets the national standard requirements for the pressure resistance of heat-resistant pipe materials, thus enabling the produced pipes, especially large-diameter pipes, to have excellent processing performance, such as anti-sagging performance, while also possessing excellent pressure and heat resistance.

[0014] As a specific embodiment of the pipe material described above in this invention, the composite additive is a cylindrical composite additive, which is prepared by mixing and extruding antioxidants, halogen absorbents and fluorine processing aids in a weight ratio of 1:0.1-1:0.1-0.5.

[0015] In one specific embodiment of the pipe material described above in this invention, the extrusion is cold extrusion;

[0016] Preferably, the extrusion speed is 0.5-1 kg / min.

[0017] In some embodiments of the present invention, the preparation method of the composite additive specifically includes: uniformly mixing antioxidants, halogen absorbents and fluorine processing aids in a weight ratio of 1:0.1-1:0.1-0.5 and then placing them into an auxiliary cold extrusion machine for processing and extrusion at room temperature at an extrusion speed of 0.5-1 kg / min to form a composite additive.

[0018] In one specific embodiment of the pipe material described above in this invention, the antioxidant is a mixture of hindered phenolic antioxidants and phosphite antioxidants, wherein the weight ratio of hindered phenolic antioxidants to phosphite antioxidants is 1:1-5, preferably 1:1-3.

[0019] As a specific embodiment of the pipe material described above in this invention, the hindered phenolic antioxidant includes one or a combination of several of the following: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], (2,4,6-trioxo-1,3,5-triazine-1,3,5(2H,4H,6H)-triyl)trivinyltris[3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate and 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene;

[0020] The phosphite antioxidants include one or a combination of several of the following: tris(2,4-di-tert-butylphenyl)-phosphite, bis[2-methyl-4,6-bis(1,1'-dimethylethyl)phenol] ethyl phosphate, and (2,4,6-tri-tert-butylphenyl-2-butyl-2-ethyl)-1,3-propanediol phosphite.

[0021] When using two or more hindered phenolic antioxidants or phosphite antioxidants, the hindered phenolic antioxidants or phosphite antioxidants can be mixed in any proportion.

[0022] In one specific embodiment of the pipe material described above in this invention, the halogen absorbent includes calcium stearate and / or zinc stearate.

[0023] In one specific embodiment of the pipe material described above in this invention, the weight ratio of antioxidant to halogen absorbent is 1:0.1-0.5.

[0024] In one specific embodiment of the pipe material described above in this invention, the fluorinated processing aid includes a fluorinated elastomer.

[0025] In one specific embodiment of the pipe material described above in this invention, the weight ratio of antioxidant to fluorinated processing aid is 1:0.1-0.3. The fluoroelastomer is a conventional substance and is commercially available. In some embodiments of this invention, the fluoroelastomer may be, for example, PPAFX-5920 manufactured by 3M Company, USA.

[0026] In one specific embodiment of the tubing described above in this invention, the pre-dispersed carbon nanotube masterbatch is obtained by mixing surface-modified carbon nanotubes treated with titanate coupling agent and heat-resistant polyethylene powder at a weight ratio of 0.01-0.1:1, followed by melt extrusion. In some embodiments of this invention, the pre-dispersed carbon nanotube masterbatch is obtained by mixing surface-modified carbon nanotubes and heat-resistant polyethylene powder at a weight ratio of 0.01-0.1:1, continuously mixing them in a high-speed mixer at room temperature for 15-20 minutes, and then melt extruding them in a twin-screw extruder.

[0027] In one specific embodiment of the pipe material described above in this invention, the temperature of the melt extrusion is 190-230°C.

[0028] In one specific embodiment of the pipe material described above in this invention, the heat-resistant polyethylene powder used in the pre-dispersed carbon nanotube masterbatch, i.e., the heat-resistant polyethylene resin base material, is the same as the heat-resistant polyethylene used in the high-pressure heat-resistant polyethylene resin composition. Both are ethylene-1-hexene copolymers, with a melt flow rate of 0.4-0.8 g / 10 min under 2.16 kg conditions and a density of 0.940-0.945 g / cm³. 3 In some embodiments of the present invention, the ethylene-1-hexene copolymer is produced using a gas-phase process and a metallocene catalyst.

[0029] As a specific embodiment of the tubing described above in this invention, the carbon nanotubes surface-modified with the titanate coupling agent are prepared by a method comprising the following steps:

[0030] 1) Add carbon nanotubes to a mixture of potassium permanganate and concentrated sulfuric acid and disperse the carbon nanotubes evenly. Reflux the evenly dispersed mixture at 115-125℃ (preferably 120℃) and then filter and wash until the filtrate is neutral. Dry the solid product obtained by filtration to constant weight under vacuum to obtain dried carbon nanotubes.

[0031] 2) Add the titanate coupling agent and the dried carbon nanotubes to ethanol and disperse the carbon nanotubes evenly. Reflux the evenly dispersed mixture at 78-80℃ to remove the ethanol and obtain carbon nanotubes with titanate coupling agent surface modification.

[0032] As a specific embodiment of the tubing material described above in this invention, in step 1) of the preparation method of carbon nanotubes with surface modification treatment by titanate coupling agent, carbon nanotubes are added to a mixture of potassium permanganate and concentrated sulfuric acid, and ultrasonic treatment is performed at room temperature for 2 hours to make the carbon nanotubes dispersed evenly.

[0033] As a specific embodiment of the tube material described above in this invention, in step 2) of the preparation method of carbon nanotubes with surface modification treatment by titanate coupling agent, titanate coupling agent and dried carbon nanotubes are added to ethanol and ultrasonically treated at room temperature for 1 hour to make the carbon nanotubes uniformly dispersed.

[0034] As a specific embodiment of the tube material described above in this invention, in step 2) of the preparation method of carbon nanotubes with surface modification treatment by titanate coupling agent, the reflux time is 2 hours.

[0035] As a specific embodiment of the pipe material described above in this invention, the pipe material is a large-diameter pipe material with a diameter ≥ 50 mm.

[0036] As a specific embodiment of the pipe material described above in this invention, the pipe material is subjected to hydrostatic strength test according to GBT6111-2016 "Thermoplastic Pipes for Fluid Transportation - Resistance to Internal Pressure". The test results show that under the conditions of 80℃ and 5MPa ring stress, the test time is greater than 3000h, and the pipe material does not leak or crack.

[0037] According to GB / T28799.2-2020 "Heat-resistant polyethylene (PE-RT) piping systems for hot and cold water", the hydrostatic strength test was conducted on the pipe material. The test results showed that under the conditions of 95℃ and hoop stress of 3.8MPa, the test time was greater than 5000h, and the pipe material did not leak or crack.

[0038] The tensile yield stress of the pipe is ≥25.0 MPa, and the cantilever beam impact strength is ≥27.0 kJ / m. 2 ;

[0039] For pipes with a diameter ≥ 50 mm, the ratio of the difference in wall thickness between the upper and lower walls of the pipe in the direction perpendicular to the ground is ≤ 5‰.

[0040] The ratio of the difference in wall thickness between the upper and lower walls of the pipe in the direction perpendicular to the ground is: (lower wall thickness - upper wall thickness) / standard outer diameter of the pipe.

[0041] On the other hand, the present invention also provides a method for manufacturing the high pressure-resistant and heat-resistant polyethylene resin composition pipe described above, wherein the manufacturing method includes:

[0042] At room temperature, heat-resistant polyethylene, composite additives and pre-dispersed carbon nanotube masterbatch are mixed evenly in a high-speed mixer. Then, the evenly mixed powder is put into a twin-screw extruder and melt-extruded at 160-210℃ to obtain high pressure-resistant and heat-resistant polyethylene resin composition granules.

[0043] The high-pressure and heat-resistant polyethylene resin composition particles are then fully mixed using an extrusion screw and extruded. The extrusion zone of the extrusion screw includes 6-8 sections. The first two sections are the feeding sections, with an extrusion temperature of 165±5℃, preferably 160-165℃. The last two sections are the output sections, with an extrusion temperature of 180±10℃, preferably 175-185℃. The middle sections are the melting sections, with an extrusion temperature of 170±5℃, preferably 170-175℃.

[0044] The processing line speed is 15-50 m / min, preferably 20-30 m / min.

[0045] In another aspect, the present invention also provides the application of the high pressure-resistant and heat-resistant polyethylene resin composition pipes described above as connecting fittings between pipes.

[0046] Compared with the prior art, the beneficial technical effects that the high pressure-resistant and heat-resistant polyethylene resin composition pipe, its manufacturing method, and its application provided by the present invention can achieve include:

[0047] The high-pressure-resistant and heat-resistant pipe was subjected to hydrostatic strength testing according to GB / T6111-2016 "Thermoplastic Pipes for Fluid Transportation - Internal Pressure Resistance". The test results showed that the pipe did not leak or crack after a test time of more than 3000 hours at a temperature of 80℃ and a ring stress of 5MPa. The high-pressure-resistant and heat-resistant pipe was also subjected to hydrostatic strength testing according to GB / T28799.2-2020 "Heat-resistant Polyethylene (PE-RT) Piping Systems for Hot and Cold Water". The test results showed that the pipe did not leak or crack after a test time of more than 5000 hours at a temperature of 95℃ and a ring stress of 3.8MPa. This indicates that the high-pressure-resistant and heat-resistant pipe provided by this invention has excellent high-pressure resistance, superior to the performance of polyethylene pipes with an MRS classification of PE100 in GB / T6111-2016.

[0048] Furthermore, for high pressure and heat resistant pipes with a diameter ≥ 50 mm, the ratio of the wall thickness difference between the upper and lower walls of the pipe in the direction perpendicular to the ground is ≤ 5‰, indicating that the high pressure and heat resistant pipes provided by the present invention have excellent processing performance, especially anti-sagging performance. Detailed Implementation

[0049] It should be noted that the term "comprising" and any variations thereof in the specification and claims of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products, or devices.

[0050] The "range" disclosed in this invention is given in the form of a lower limit and an upper limit. It can be one or more lower limits and one or more upper limits, respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges defined in this way are composable, meaning that any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for specific parameters, it is also expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if the listed minimum range values ​​are 1 and 2, and the listed maximum range values ​​are 3, 4, and 5, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5.

[0051] In this invention, unless otherwise specified, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this invention, and "0-5" is simply a shortened representation of these numerical combinations.

[0052] In this invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in this invention can be combined with each other to form new technical solutions.

[0053] In this invention, unless otherwise specified, all technical features and preferred features mentioned in this invention can be combined with each other to form new technical solutions.

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the appendices and embodiments. The embodiments described below are some, but not all, embodiments of this invention, and are only used to illustrate the invention, and should not be considered as limiting the scope of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0055] Example 1

[0056] This embodiment provides a high-pressure and heat-resistant pipe, which is manufactured by a method including the following specific steps:

[0057] At room temperature, 100 parts by weight of heat-resistant polyethylene, 0.5 parts by weight of composite additives and 30 parts by weight of pre-dispersed carbon nanotube masterbatch are mixed in a high-speed mixer for 15 minutes. Then, the uniformly mixed powder is put into a twin-screw extruder and melt-extruded at 160°C, 175°C, 185°C, 185°C, 175°C and 165°C (taking a six-stage heated twin-screw extruder as an example) to obtain high pressure-resistant and heat-resistant polyethylene resin composition granules.

[0058] High pressure-resistant and heat-resistant polyethylene resin composition particles are placed in a feeding system, fully mixed by an extrusion screw, and then extruded to obtain the high pressure-resistant and heat-resistant pipe.

[0059] The pipe extrusion temperature is set in 8 stages according to the temperature gradient. The first two stages are the feeding stages with an extrusion temperature of 160℃, the last two stages are the output stages with an extrusion temperature of 170℃, and the middle stages are the melting stages with an extrusion temperature of 165℃. The processing line speed is 15m / min.

[0060] The composite additive is a cylindrical composite additive obtained by uniformly mixing antioxidants, halogen absorbers, and fluorinated processing aids in a weight ratio of 1:0.5:0.25 and then extruding the mixture in an additive cold extruder at room temperature. The extrusion speed is 0.5 kg / min. The antioxidant is a combination of 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene and tris(2,4-di-tert-butylphenyl)-phosphite in a weight ratio of 1:1. The halogen absorber is zinc stearate, and the fluorinated processing aid is PPA FX-5920, a fluoroelastomer manufactured by 3M Company, USA.

[0061] The pre-dispersed carbon nanotube masterbatch is prepared by mixing carbon nanotubes with surface modification of titanate coupling agent and heat-resistant polyethylene powder at a weight ratio of 0.01:1, continuously mixing them at room temperature for 20 minutes in a high-speed mixer, and then melt-extruding them in a twin-screw extruder. The melt extrusion temperature is 200°C.

[0062] The carbon nanotubes surface-modified with the titanate coupling agent are prepared by a method comprising the following steps:

[0063] 1) Add carbon nanotubes to a mixture of potassium permanganate and concentrated sulfuric acid, and treat with ultrasound at room temperature for 2 hours to disperse the carbon nanotubes evenly. After refluxing the evenly dispersed mixture at 120°C, filter and wash until the filtrate is neutral. Dry the filtered solid product to constant weight under vacuum to obtain dried carbon nanotubes.

[0064] 2) Add titanate coupling agent and dried carbon nanotubes to ethanol, sonicate at room temperature for 1 h to make carbon nanotubes uniformly dispersed, and reflux the uniformly dispersed mixture at 78 °C for 2 h to remove ethanol, and obtain carbon nanotubes with titanate coupling agent surface modification.

[0065] The heat-resistant polyethylene base material is a copolymer of ethylene and 1-hexene, with a melt flow rate (2.16 kg) of 0.6 g / 10 min and a density of 0.9425 g / cm³. 3 It is produced using a gas-phase process and under the catalysis of a metallocene catalyst.

[0066] Example 2

[0067] This embodiment provides a high-pressure and heat-resistant pipe, which is manufactured by a method including the following specific steps:

[0068] At room temperature, 100 parts by weight of heat-resistant polyethylene, 0.3 parts by weight of composite additives and 10 parts by weight of pre-dispersed carbon nanotube masterbatch are mixed in a high-speed mixer for 15 minutes. Then, the uniformly mixed powder is put into a twin-screw extruder and melt-extruded at 160°C, 175°C, 185°C, 185°C, 175°C and 165°C (taking a six-stage heated twin-screw extruder as an example) to obtain high pressure-resistant and heat-resistant polyethylene resin composition granules.

[0069] High pressure-resistant and heat-resistant polyethylene resin composition particles are placed in a feeding system, fully mixed by an extrusion screw, and then extruded to obtain the high pressure-resistant and heat-resistant pipe.

[0070] The pipe extrusion temperature is set in 8 stages according to the temperature gradient. The first two stages are the feeding stages with an extrusion temperature of 165℃, the last two stages are the output stages with an extrusion temperature of 180℃, and the middle stages are the melting stages with an extrusion temperature of 175℃. The processing line speed is 20m / min.

[0071] The composite additive is a cylindrical composite additive obtained by uniformly mixing antioxidants, halogen absorbers, and fluorinated processing aids in a weight ratio of 1:0.1:0.1 and then extruding them in an additive cold extruder at room temperature. The extrusion speed is 1 kg / min. The antioxidant is a combination of 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene and tris(2,4-di-tert-butylphenyl)-phosphite in a weight ratio of 1:1. The halogen absorber is zinc stearate, and the fluorinated processing aid is PPA FX-5920, a fluoroelastomer manufactured by 3M Company, USA.

[0072] The pre-dispersed carbon nanotube masterbatch is prepared by mixing carbon nanotubes with surface modification of titanate coupling agent and heat-resistant polyethylene powder at a weight ratio of 0.05:1, continuously mixing them at room temperature for 15 minutes using a high-speed mixer, and then melt-extruding them in a twin-screw extruder. The melt extrusion temperature is 210°C.

[0073] The carbon nanotubes surface-modified with the titanate coupling agent are prepared by a method comprising the following steps:

[0074] 1) Add carbon nanotubes to a mixture of potassium permanganate and concentrated sulfuric acid, and treat with ultrasound at room temperature for 2 hours to disperse the carbon nanotubes evenly. After refluxing the evenly dispersed mixture at 120°C, filter and wash until the filtrate is neutral. Dry the filtered solid product to constant weight under vacuum to obtain dried carbon nanotubes.

[0075] 2) Add titanate coupling agent and dried carbon nanotubes to ethanol, sonicate at room temperature for 1 h to make carbon nanotubes uniformly dispersed, and reflux the uniformly dispersed mixture at 80℃ for 2 h to remove ethanol, to obtain carbon nanotubes with titanate coupling agent surface modification.

[0076] The heat-resistant polyethylene base material is a copolymer of ethylene and 1-hexene, with a melt flow rate (2.16 kg) of 0.4 g / 10 min and a density of 0.940 g / cm³. 3 It is produced using a gas-phase process and under the catalysis of a metallocene catalyst.

[0077] Example 3

[0078] This embodiment provides a high-pressure and heat-resistant pipe, which is manufactured by a method including the following specific steps:

[0079] At room temperature, 100 parts by weight of heat-resistant polyethylene, 0.8 parts by weight of composite additives and 10 parts by weight of pre-dispersed carbon nanotube masterbatch are mixed in a high-speed mixer for 15 minutes. Then, the uniformly mixed powder is put into a twin-screw extruder and melt-extruded at 160°C, 175°C, 185°C, 185°C, 175°C and 165°C (taking a six-stage heated twin-screw extruder as an example) to obtain high pressure-resistant and heat-resistant polyethylene resin composition granules.

[0080] High pressure-resistant and heat-resistant polyethylene resin composition particles are placed in a feeding system, fully mixed by an extrusion screw, and then extruded to obtain the high pressure-resistant and heat-resistant pipe.

[0081] The pipe extrusion temperature is set in 8 stages according to the temperature gradient. The first two stages are the feeding stages with an extrusion temperature of 170℃, the last two stages are the output stages with an extrusion temperature of 185℃, and the middle stages are the melting stages with an extrusion temperature of 175℃. The processing line speed is 40m / min.

[0082] The composite additive is a cylindrical composite additive obtained by uniformly mixing antioxidants, halogen absorbers, and fluorinated processing aids in a weight ratio of 1:0.1:0.5 and then extruding them in an additive cold extruder at room temperature. The extrusion speed is 0.75 kg / min. The antioxidant is a combination of 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene and tris(2,4-di-tert-butylphenyl)-phosphite in a weight ratio of 1:1. The halogen absorber is zinc stearate, and the fluorinated processing aid is PPA FX-5920, a fluoroelastomer manufactured by 3M Company, USA.

[0083] The pre-dispersed carbon nanotube masterbatch is prepared by mixing carbon nanotubes with surface modification of titanate coupling agent and heat-resistant polyethylene powder at a weight ratio of 0.1:1, continuously mixing them at room temperature for 18 minutes using a high-speed mixer, and then melt-extruding them in a twin-screw extruder. The melt-extrusion temperature is 230°C.

[0084] The carbon nanotubes surface-modified with the titanate coupling agent are prepared by a method comprising the following steps:

[0085] 1) Add carbon nanotubes to a mixture of potassium permanganate and concentrated sulfuric acid, and treat with ultrasound at room temperature for 2 hours to disperse the carbon nanotubes evenly. After refluxing the evenly dispersed mixture at 120°C, filter and wash until the filtrate is neutral. Dry the filtered solid product to constant weight under vacuum to obtain dried carbon nanotubes.

[0086] 2) Add titanate coupling agent and dried carbon nanotubes to ethanol, sonicate at room temperature for 1 h to make carbon nanotubes uniformly dispersed, and reflux the uniformly dispersed mixture at 80℃ for 2 h to remove ethanol, to obtain carbon nanotubes with titanate coupling agent surface modification.

[0087] The heat-resistant polyethylene base material is a copolymer of ethylene and 1-hexene, with a melt flow rate (2.16 kg) of 0.8 g / 10 min and a density of 0.945 g / cm³. 3 It is produced using a gas-phase process and under the catalysis of a metallocene catalyst.

[0088] Example 4

[0089] This embodiment provides a high-pressure and heat-resistant pipe, which is manufactured by a method including the following specific steps:

[0090] At room temperature, 100 parts by weight of heat-resistant polyethylene, 0.4 parts by weight of composite additive and 20 parts by weight of pre-dispersed carbon nanotube masterbatch are mixed in a high-speed mixer for 15 minutes. Then, the uniformly mixed powder is put into a twin-screw extruder and melt-extruded at 160°C, 175°C, 185°C, 185°C, 175°C and 165°C (taking a six-stage heated twin-screw extruder as an example) to obtain high pressure-resistant and heat-resistant polyethylene resin composition granules.

[0091] High pressure-resistant and heat-resistant polyethylene resin composition particles are placed in a feeding system, fully mixed by an extrusion screw, and then extruded to obtain the high pressure-resistant and heat-resistant pipe.

[0092] The pipe extrusion temperature is set in 8 stages according to the temperature gradient. The first two stages are the feeding stages with an extrusion temperature of 160℃, the last two stages are the output stages with an extrusion temperature of 175℃, and the middle stages are the melting stages with an extrusion temperature of 170℃. The processing line speed is 25m / min.

[0093] The composite additive is a cylindrical composite additive obtained by uniformly mixing antioxidants, halogen absorbers, and fluorinated processing aids in a weight ratio of 1:0.1:0.2 and then extruding them in an additive cold extruder at room temperature. The extrusion speed is 0.5 kg / min. The antioxidant is a combination of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl)phosphite in a weight ratio of 1:1. The halogen absorber is zinc stearate, and the fluorinated processing aid is PPA FX-5920, a fluoroelastomer manufactured by 3M Company, USA.

[0094] The pre-dispersed carbon nanotube masterbatch is prepared by mixing carbon nanotubes with surface modification of titanate coupling agent and heat-resistant polyethylene powder at a weight ratio of 0.03:1, continuously mixing them at room temperature for 20 minutes using a high-speed mixer, and then melt-extruding them in a twin-screw extruder. The melt-extrusion temperature is 190°C.

[0095] The carbon nanotubes surface-modified with the titanate coupling agent are prepared by a method comprising the following steps:

[0096] 1) Add carbon nanotubes to a mixture of potassium permanganate and concentrated sulfuric acid, and treat with ultrasound at room temperature for 2 hours to disperse the carbon nanotubes evenly. After refluxing the evenly dispersed mixture at 120°C, filter and wash until the filtrate is neutral. Dry the filtered solid product to constant weight under vacuum to obtain dried carbon nanotubes.

[0097] 2) Add titanate coupling agent and dried carbon nanotubes to ethanol, sonicate at room temperature for 1 h to make carbon nanotubes uniformly dispersed, and reflux the uniformly dispersed mixture at 78 °C for 2 h to remove ethanol, and obtain carbon nanotubes with titanate coupling agent surface modification.

[0098] The heat-resistant polyethylene base material is a copolymer of ethylene and 1-hexene, with a melt flow rate (2.16 kg) of 0.7 g / 10 min and a density of 0.940 g / cm³. 3 It is produced using a gas-phase process and under the catalysis of a metallocene catalyst.

[0099] Example 5

[0100] This embodiment provides a high-pressure and heat-resistant pipe, which is manufactured by a method including the following specific steps:

[0101] At room temperature, 100 parts by weight of heat-resistant polyethylene, 0.6 parts by weight of composite additives, and 20 parts by weight of pre-dispersed carbon nanotube masterbatch are mixed in a high-speed mixer for 15 minutes. Then, the uniformly mixed powder is fed into a twin-screw extruder and melt-extruded at 160°C, 175°C, 185°C, 185°C, 175°C, and 165°C (taking a six-stage heated twin-screw extruder as an example) to obtain high-pressure heat-resistant polyethylene resin composition granules.

[0102] High pressure-resistant and heat-resistant polyethylene resin composition particles are placed in a feeding system, fully mixed by an extrusion screw, and then extruded to obtain the high pressure-resistant and heat-resistant pipe.

[0103] The pipe extrusion temperature is set in 8 stages according to the temperature gradient. The first two stages are the feeding stages with an extrusion temperature of 160℃, the last two stages are the output stages with an extrusion temperature of 170℃, and the middle stages are the melting stages with an extrusion temperature of 170℃. The processing line speed is 30m / min.

[0104] The composite additive is a cylindrical composite additive obtained by uniformly mixing antioxidants, halogen absorbers, and fluorinated processing aids in a weight ratio of 1:0.2:0.2 and then extruding them in an additive cold extruder at room temperature. The extrusion speed is 1 kg / min. The antioxidant is a combination of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl)phosphite in a weight ratio of 1:1. The halogen absorber is zinc stearate, and the fluorinated processing aid is PPA FX-5920, a fluoroelastomer manufactured by 3M Company, USA.

[0105] The pre-dispersed carbon nanotube masterbatch is prepared by mixing carbon nanotubes with surface modification of titanate coupling agent and heat-resistant polyethylene powder at a weight ratio of 0.02:1, continuously mixing them at room temperature for 15 minutes in a high-speed mixer, and then melt-extruding them in a twin-screw extruder. The melt extrusion temperature is 190°C.

[0106] The carbon nanotubes surface-modified with the titanate coupling agent are prepared by a method comprising the following steps:

[0107] 1) Add carbon nanotubes to a mixture of potassium permanganate and concentrated sulfuric acid, and treat with ultrasound at room temperature for 2 hours to disperse the carbon nanotubes evenly. After refluxing the evenly dispersed mixture at 120°C, filter and wash until the filtrate is neutral. Dry the filtered solid product to constant weight under vacuum to obtain dried carbon nanotubes.

[0108] 2) Add titanate coupling agent and dried carbon nanotubes to ethanol, sonicate at room temperature for 1 h to make carbon nanotubes uniformly dispersed, and reflux the uniformly dispersed mixture at 78 °C for 2 h to remove ethanol, and obtain carbon nanotubes with titanate coupling agent surface modification.

[0109] The heat-resistant polyethylene base material is a copolymer of ethylene and 1-hexene, with a melt flow rate (2.16 kg) of 0.5 g / 10 min and a density of 0.941 g / cm³. 3 It is produced using a gas-phase process and under the catalysis of a metallocene catalyst.

[0110] Comparative Example 1

[0111] This comparative example provides a heat-resistant pipe, which is manufactured by a method including the following specific steps:

[0112] At room temperature, 100 parts by weight of heat-resistant polyethylene and 0.5 parts by weight of composite additives are mixed in a high-speed mixer for 15 minutes. Then, the uniformly mixed powder is put into a twin-screw extruder and melt-extruded at 160°C, 175°C, 185°C, 185°C, 175°C and 165°C (taking a six-stage heated twin-screw extruder as an example) to obtain polyethylene resin composition granules.

[0113] The heat-resistant pipe is obtained by placing polyethylene resin composition particles into a feeding system, fully mixing them through an extrusion screw, and then extruding them.

[0114] The pipe extrusion temperature is set in 8 stages according to the temperature gradient. The first two stages are the feeding stages with an extrusion temperature of 165℃, the last two stages are the output stages with an extrusion temperature of 180℃, and the middle stages are the melting stages with an extrusion temperature of 175℃. The processing line speed is 20m / min.

[0115] The composite additive is a cylindrical composite additive obtained by uniformly mixing antioxidants, halogen absorbers, and fluorinated processing aids in a weight ratio of 1:0.1:0.1 and then extruding them in an additive cold extruder at room temperature. The extrusion speed is 1 kg / min. The antioxidant is a combination of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl)phosphite in a weight ratio of 1:1. The halogen absorber is zinc stearate, and the fluorinated processing aid is PPA FX-5920, a fluoroelastomer manufactured by 3M Company, USA.

[0116] The heat-resistant polyethylene base material is a copolymer of ethylene and 1-hexene, with a melt flow rate (2.16 kg) of 0.7 g / 10 min and a density of 0.940 g / cm³. 3 It is produced using a gas-phase process and under the catalysis of a metallocene catalyst.

[0117] Comparative Example 2

[0118] This comparative example provides a heat-resistant pipe, which is manufactured by a method including the following specific steps:

[0119] At room temperature, 100 parts by weight of heat-resistant polyethylene, 0.3 parts by weight of composite additives and 0.1 parts by weight of carbon nanotubes are mixed in a high-speed mixer for 15 minutes. Then, the uniformly mixed powder is put into a twin-screw extruder and melt-extruded at 160°C, 175°C, 185°C, 185°C, 175°C and 165°C (taking a six-stage heated twin-screw extruder as an example) to obtain polyethylene resin composition granules.

[0120] The heat-resistant pipe is obtained by placing polyethylene resin composition particles into a feeding system, fully mixing them through an extrusion screw, and then extruding them.

[0121] The pipe extrusion temperature is set in 8 stages according to the temperature gradient. The first two stages are the feeding stages with an extrusion temperature of 165℃, the last two stages are the output stages with an extrusion temperature of 180℃, and the middle stages are the melting stages with an extrusion temperature of 175℃. The processing line speed is 20m / min.

[0122] The composite additive is a cylindrical composite additive obtained by uniformly mixing antioxidants, halogen absorbers, and fluorinated processing aids in a weight ratio of 1:0.1:0.1 and then extruding them in an additive cold extruder at room temperature. The extrusion speed is 1 kg / min. The antioxidant is a combination of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl)phosphite in a weight ratio of 1:1. The halogen absorber is zinc stearate, and the fluorinated processing aid is PPA FX-5920, a fluoroelastomer manufactured by 3M Company, USA.

[0123] The heat-resistant polyethylene base material is a copolymer of ethylene and 1-hexene, with a melt flow rate (2.16 kg) of 0.7 g / 10 min and a density of 0.940 g / cm³. 3 It is produced using a gas-phase process and under the catalysis of a metallocene catalyst.

[0124] Test Example 1

[0125] The high pressure and heat resistant pipes provided in Examples 1-5 of the present invention and the heat resistant pipes provided in Comparative Examples 1-2 were subjected to hydrostatic strength, tensile yield stress and cantilever beam impact strength tests, respectively. The standards referenced for the tests and the test results are shown in Table 1 below.

[0126] Table 1

[0127]

[0128]

[0129] As can be seen from the above, the high-pressure and heat-resistant pipes provided in Examples 1-5 of this invention are respectively made from corresponding high-pressure and heat-resistant polyethylene resin compositions. The heat-resistant pipe provided in Comparative Example 1 is made from a composition of heat-resistant polyethylene and composite additives, without the addition of pre-dispersed carbon nanotube masterbatch. The heat-resistant pipe provided in Comparative Example 2 is made from a composition of heat-resistant polyethylene, composite additives, and carbon nanotubes, with the carbon nanotubes being directly added without the preparation of masterbatch. Analysis of the data in Table 1 shows that, in terms of impact strength, the cantilever beam impact strength of the high-pressure and heat-resistant pipes provided in Examples 1-5 is significantly improved compared to the heat-resistant pipes provided in Comparative Examples 1-2, indicating a significant improvement in the mechanical properties of these pipes. The results of the two hydrostatic strength tests also show that these pipes have high pressure resistance. According to the classification standards in GB / 6111, the failure time of the high-pressure and heat-resistant pipes provided in Examples 1-5 greatly exceeds the performance of polyethylene pipes with an MRS classification of PE100.

[0130] Furthermore, it can be seen from Table 1 that for the high pressure and heat resistant pipes provided in Examples 1-5 with a pipe diameter ≥ 50 mm, the ratio of the wall thickness difference between the upper and lower walls of the pipe in the direction perpendicular to the ground is ≤ 5‰, indicating that compared with the heat resistant pipes provided in Comparative Examples 1-2, the high pressure and heat resistant pipes provided in the embodiments of the present invention have excellent processing performance, especially anti-sagging performance.

[0131] In summary, the high-pressure and heat-resistant pipes provided in this embodiment of the invention were subjected to hydrostatic strength tests according to GB / T6111-2016 "Thermoplastic Pipes for Fluid Transportation - Internal Pressure Resistance". The test results show that the pipes did not leak or crack after a test time of more than 3000 hours at a temperature of 80℃ and a ring stress of 5MPa. Furthermore, the high-pressure and heat-resistant pipes provided in this embodiment of the invention were subjected to hydrostatic strength tests according to GB / T28799.2-2020 "Heat-resistant Polyethylene (PE-RT) Piping Systems for Hot and Cold Water". The test results show that the pipes did not leak or crack after a test time of more than 5000 hours at a temperature of 95℃ and a ring stress of 3.8MPa. This indicates that the high-pressure and heat-resistant pipes provided in this embodiment of the invention have excellent high-pressure resistance performance, superior to the performance of polyethylene pipes with an MRS classification of PE100 in GB / T6111-2016.

[0132] Furthermore, for the high pressure-resistant and heat-resistant pipes provided in the embodiments of the present invention with a pipe diameter ≥ 50 mm, the ratio of the wall thickness difference between the upper and lower walls of the pipe in the direction perpendicular to the ground is ≤ 5‰, indicating that the high pressure-resistant and heat-resistant pipes provided by the present invention have excellent processing performance, especially anti-sagging performance.

[0133] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical inventions, and technical inventions in this invention can be freely combined and used.

Claims

1. A high-pressure-resistant and heat-resistant polyethylene resin composition pipe, characterized in that, The pipe is made of a high pressure-resistant and heat-resistant polyethylene resin composition, wherein the high pressure-resistant and heat-resistant polyethylene resin composition comprises: 100 parts by weight of heat-resistant polyethylene, 0.3-0.8 parts by weight of composite additives, and 10-30 parts by weight of pre-dispersed carbon nanotube masterbatch. The composite additive includes antioxidants, halogen absorbers, and fluorine processing aids, with a weight ratio of 1:0.1-1:0.1-0.

5. The pre-dispersed carbon nanotube masterbatch comprises carbon nanotubes surface-modified with titanate coupling agent and heat-resistant polyethylene powder, with a weight ratio of 0.01-0.1:

1. The heat-resistant polyethylene and the heat-resistant polyethylene powder are both copolymers of ethylene and 1-hexene, with a melt flow rate of 0.4-0.8 g / 10 min and a density of 0.940-0.945 g / cm³ under 2.16 kg conditions. 3 .

2. The pipe according to claim 1, characterized in that, The composite additive is a cylindrical composite additive, which is prepared by mixing and extruding antioxidants, halogen absorbers and fluorine processing aids in a weight ratio of 1:0.1-1:0.1-0.

5.

3. The pipe according to claim 2, characterized in that, The extrusion is cold extrusion.

4. The pipe according to claim 2, characterized in that, The extrusion speed is 0.5-1 kg / min.

5. The pipe according to any one of claims 1-4, characterized in that, The antioxidant is a mixture of hindered phenolic antioxidants and phosphite antioxidants, wherein the weight ratio of hindered phenolic antioxidants to phosphite antioxidants is 1:1-5.

6. The pipe according to claim 5, characterized in that, The weight ratio of hindered phenolic antioxidants to phosphite antioxidants is 1:1-3.

7. The pipe according to claim 5, characterized in that, The hindered phenolic antioxidants include one or a combination of several of the following: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], (2,4,6-trioxo-1,3,5-triazine-1,3,5(2H,4H,6H)-triyl)trivinyltris[3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate and 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene; The phosphite antioxidants include tris(2,4-di-tert-butylphenyl)-phosphite, bis[2-methyl-4,6-di(1,1-di-tert-butylphenyl)-phosphite, and bis[2-methyl-4,6-di(1,1-di-tert-butylphenyl)-phosphite. ’ One or a combination of several of the following: (-dimethylethyl)phenol ethyl phosphate and (2,4,6-tri-tert-butylphenyl-2-butyl-2-ethyl)-1,3-propanediol phosphite.

8. The pipe according to any one of claims 1-4, characterized in that, The halogen absorbent includes calcium stearate and / or zinc stearate.

9. The pipe according to any one of claims 1-4, characterized in that, The fluorinated processing aids include fluoroelastomers.

10. The pipe according to claim 1, characterized in that, The pre-dispersed carbon nanotube masterbatch is prepared by mixing carbon nanotubes with a surface-modified titanate coupling agent and heat-resistant polyethylene powder at a weight ratio of 0.01-0.1:1, followed by melt extrusion.

11. The pipe according to claim 10, characterized in that, The temperature of the melt extrusion is 190-230℃.

12. The pipe according to claim 10 or 11, characterized in that, The carbon nanotubes surface-modified with the titanate coupling agent are prepared by a method comprising the following steps: 1) Add carbon nanotubes to a mixture of potassium permanganate and concentrated sulfuric acid and disperse the carbon nanotubes evenly. Reflux the evenly dispersed mixture at 115-125℃, then filter and wash until the filtrate is neutral. Dry the filtered solid product to constant weight under vacuum to obtain dried carbon nanotubes. 2) Add the titanate coupling agent and the dried carbon nanotubes to ethanol and disperse the carbon nanotubes evenly. Reflux the evenly dispersed mixture at 78-80℃ to remove the ethanol and obtain carbon nanotubes with surface modification by titanate coupling agent.

13. The pipe according to any one of claims 1-4, characterized in that, The pipe is a large-diameter pipe with a diameter ≥ 50 mm.

14. The pipe according to any one of claims 1-4, characterized in that, The hydrostatic strength test of the pipe was conducted according to GBT6111-2016 "Thermoplastic Pipes for Fluid Transportation - Resistance to Internal Pressure". The test results showed that the pipe did not leak or crack after a test time of more than 3000 hours under the conditions of 80℃ and 5MPa hoop stress. According to GB / T28799.2-2020 "Heat-resistant polyethylene (PE-RT) piping systems for hot and cold water", the hydrostatic strength test was conducted on the pipe material. The test results showed that under the conditions of 95℃ and hoop stress of 3.8MPa, the test time was greater than 5000h, and the pipe material did not leak or crack. The tensile yield stress of the pipe is ≥25.0 MPa, and the cantilever beam impact strength is ≥27.0 kJ / m. 2 ; For pipes with a diameter ≥ 50 mm, the ratio of the difference in wall thickness between the upper and lower walls of the pipe in the direction perpendicular to the ground is ≤ 5‰.

15. A method for manufacturing a high-pressure-resistant and heat-resistant polyethylene resin composition pipe according to any one of claims 1-14, characterized in that, The manufacturing method includes: At room temperature, heat-resistant polyethylene, composite additives and pre-dispersed carbon nanotube masterbatch are mixed evenly in a high-speed mixer. Then, the evenly mixed powder is put into a twin-screw extruder and melt-extruded at 160-210℃ to obtain high pressure-resistant and heat-resistant polyethylene resin composition granules. The high pressure-resistant and heat-resistant polyethylene resin composition particles are then fully mixed using an extrusion screw and then extruded. The extrusion zone of the extrusion screw includes 6-8 sections. The first two sections are the feeding sections with an extrusion temperature of 165±5℃, the last two sections are the output sections with an extrusion temperature of 180±10℃, and the middle sections are the melting sections with an extrusion temperature of 170±5℃. The processing line speed is 15-50 m / min.

16. The use of the high pressure-resistant and heat-resistant polyethylene resin composition pipe according to any one of claims 1-14 as a connecting pipe between pipes.

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