Internal oxygen resistance type heat-resistant polyethylene pipeline and preparation method thereof

Abstract

The invention discloses an internal oxygen resistance type heat-resistant polyethylene pipeline and a preparation method thereof. The internal oxygen resistance type heat-resistant polyethylene pipeline comprises a PE-RT outer pressure-bearing layer, a first bonding layer, an EVOH layer, a second bonding layer and a PE-RT inner pressure-bearing layer, and the PE-RT outer pressure-bearing layer, the first bonding layer, the EVOH layer, the second bonding layer and the PE-RT inner pressure-bearing layer are sequentially arranged from outside to inside. The EVOH layer is basically located in the middle of the pipeline, the wall thicknesses of the inner pressure-bearing layer and the outer pressure-bearing layer are basically the same, and compared with structural optimization of a traditional five-layer oxygen-resisting heat-resisting polyethylene pipe, the overall pressure resistance, high temperature resistance, scraping resistance, aging resistance, pollution resistance and scale resistance of a pipeline system are remarkably improved; meanwhile, the problems that the overall wall thickness of the pipe is too large due to only one pressure-bearing layer, connection of a water dividing and collecting device is difficult, and direct hot melting connection of the pipe and the pipe fitting cannot be achieved are solved, and the construction efficiency is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyethylene pipes, and particularly relates to an oxygen-inside-resistant heat-resistant polyethylene pipe and a preparation method thereof. Background Art

[0002] The oxygen-inside-resistant heat-resistant polyethylene (PE-RT) pipe is a special floor heating pipe, and its main function is to prevent oxygen from entering the inside of the pipe, preventing the metal components at the pipe connection from undergoing chemical reactions, resulting in corrosion and damage. Under normal conditions, metal components will corrode under the action of high temperature, high pressure, water and oxygen, reducing the service life. In a heating system, temperature, pressure and water are inevitable, so the oxygen content will determine the service life of the system. When oxygen penetrates into the pipe material, an oxidation reaction will occur, resulting in corrosion and reducing the service life of the system. Especially in a floor heating system, due to its large pipe heat exchange area, the oxygen penetration situation is more serious. Using an oxygen barrier pipe can effectively reduce this kind of corrosion and extend the service life of the system. In addition, the heat-resistant polyethylene (PE-RT) oxygen barrier pipe can also prevent the problem of bacteria easily growing due to the prevention of oxygen from penetrating into the inside of the pipe, so as not to reduce the water flow rate and flow in the pipe and thus affect the heating effect.

[0003] At present, the structures of heat-resistant polyethylene (PE-RT) oxygen barrier pipes are usually divided into two types: three-layer and five-layer. The outer layer of the three-layer heat-resistant polyethylene (PE-RT) oxygen barrier pipe is an EVOH oxygen barrier layer, the inner layer is a heat-resistant polyethylene (PE-RT) pressure-bearing layer, and the middle is an adhesive layer (hot melt adhesive layer). The five-layer heat-resistant polyethylene (PE-RT) oxygen barrier pipe is based on the three-layer oxygen barrier pipe, and an additional adhesive layer (hot melt adhesive layer) and a heat-resistant polyethylene layer are added outside, making the oxygen barrier effect more reliable. The five-layer oxygen barrier pipe is superior to the three-layer oxygen barrier pipe in performance because its oxygen barrier layer is inside and is not easily damaged due to friction.

[0004] Although the oxygen barrier pipe has its advantages, the currently common three-layer oxygen barrier or five-layer oxygen barrier both have their disadvantages:

[0005] First, for the three-layer heat-resistant polyethylene (PE-RT) oxygen barrier pipe, since the EVOH layer is located on the outermost layer of the pipe, it will be damaged and peeled off due to friction during transportation, resulting in a reduction or even loss of the oxygen barrier effect;

[0006] Second, for the ordinary five-layer heat-resistant polyethylene (PE-RT) oxygen barrier pipe, in order to ensure the pipe pressure-bearing quality, the wall thickness of the pressure-bearing layer is generally made larger. Therefore, in order to ensure the welding quality and use stability, the outer layer needs to be peeled off during installation, which greatly increases the operation time, and there are often problems of size mismatch when the pipe with a relatively thick production wall thickness is connected to the manifold, affecting the overall construction progress;

[0007] Thirdly, for the heat-resistant polyethylene (PE-RT) pipe used in floor heating, due to its connection with the copper water distribution device, copper ions will accelerate the aging of the PE-RT material, thus accelerating the decline of the oxidation induction time of the material, resulting in the decline of the long-term heat and pressure resistance performance and causing the pipe to age and rupture.

[0008] Fourthly, due to the pollution of the water source, the backward technology of the waterworks and the outdated and unreasonable pipe network, scaling is likely to occur inside the heat-resistant polyethylene (PE-RT) pipe, seriously affecting the water flow in the pipe. Summary of the Invention

[0009] In view of this, the present invention aims to provide an internal oxygen-resistant heat-resistant polyethylene pipe and its preparation method to solve at least one of the technical problems in the background technology.

[0010] To achieve the above object, the technical solution of the present invention is realized as follows:

[0011] An internal oxygen-resistant heat-resistant polyethylene pipe includes a PE-RT outer pressure-bearing layer, a first bonding layer, an EVOH layer, a second bonding layer, and a PE-RT inner pressure-bearing layer. The PE-RT outer pressure-bearing layer, the first bonding layer, the EVOH layer, the second bonding layer, and the PE-RT inner pressure-bearing layer are arranged in sequence from the outside to the inside. The end of the internal oxygen-resistant heat-resistant polyethylene pipe is provided with a first safety gasket or a second safety gasket.

[0012] Further, the thickness ratio of the PE-RT outer pressure-bearing layer, the first bonding layer, the EVOH layer, the second bonding layer, and the PE-RT inner pressure-bearing layer is 45-50:1-1.5:1.3-2.0:1-1.5:45-50.

[0013] Further, the PE-RT outer pressure-bearing layer includes heat-resistant polyethylene, a PE-RT silicone anti-scratch masterbatch, and a PE-RT metal passivator;

[0014] The mass ratio of heat-resistant polyethylene, the PE-RT silicone anti-scratch masterbatch, and the PE-RT metal passivator is 100:(1-5):(1-6);

[0015] The PE-RT silicone anti-scratch masterbatch includes polysiloxane, silica, heat-resistant polyethylene, and a hot melt adhesive (maleic anhydride grafted polyethylene); the mass ratio of polysiloxane, silica, heat-resistant polyethylene, and the hot melt adhesive (maleic anhydride grafted polyethylene) is 40:30:30:(1-3);

[0016] The PE-RT silicone anti-scratch masterbatch is granulated by a twin-screw granulator, and the process temperature is 180°C - 190°C;

[0017] The PE-RT metal passivator includes heat-resistant polyethylene and antioxidant 1024 (N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine); the mass ratio of heat-resistant polyethylene to antioxidant 1024 (N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine) is 100:5;

[0018] The PE-RT metal passivator is pelletized by a twin-screw granulator, and the process temperature is 180°C - 200°C.

[0019] Further, the first adhesive layer includes hot-melt adhesive (maleic anhydride grafted polyethylene) and masterbatch, and the mass ratio of hot-melt adhesive (maleic anhydride grafted polyethylene) to masterbatch is 100:(5 - 15);

[0020] The second adhesive layer includes hot-melt adhesive (maleic anhydride grafted polyethylene) and masterbatch, and the mass ratio of hot-melt adhesive (maleic anhydride grafted polyethylene) to masterbatch is 100:(5 - 15).

[0021] Further, the PE-RT internal pressure-bearing layer includes heat-resistant polyethylene, PE-RT silicone anti-scratch masterbatch, and PE-RT metal passivator;

[0022] The mass ratio of heat-resistant polyethylene, PE-RT silicone anti-scratch masterbatch, and PE-RT metal passivator is 100:(1 - 5):(1 - 6)

[0023] The PE-RT silicone anti-scratch masterbatch includes polysiloxane, silica, heat-resistant polyethylene, and hot-melt adhesive (maleic anhydride grafted polyethylene);

[0024] The mass ratio of polysiloxane, silica, heat-resistant polyethylene, and hot-melt adhesive (maleic anhydride grafted polyethylene) is 40:30:30:(1 - 3);

[0025] The PE-RT silicone anti-scratch masterbatch is pelletized by a twin-screw granulator, and the process temperature is 180°C - 190°C;

[0026] The PE-RT metal passivator includes heat-resistant polyethylene and antioxidant 1024 (N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine); the mass ratio of heat-resistant polyethylene to antioxidant 1024 (N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine) is 100:5;

[0027] The PE-RT metal passivator is pelletized by a twin-screw granulator, and the process temperature is 180°C - 200°C;

[0028] Further, the first safety cushion ring is provided with hand-held rods distributed in a conical shape, and the ends of the hand-held rods converge into a connecting block; the material of the safety cushion ring is heat-resistant polyethylene; the vertical projection length of the hand-held rod is 3 mm - 4 mm; the inner diameter of the safety cushion ring corresponds to the inner diameter of the oxygen-resistant heat-resistant polyethylene pipe, and the outer diameter of the safety cushion ring corresponds to the outer diameter of the oxygen-resistant heat-resistant polyethylene pipe;

[0029] The first safety cushion ring is hot-melt butt welded to the oxygen-resistant heat-resistant polyethylene pipe through a hot plate;

[0030] The inner diameter of the second safety cushion ring corresponds to the inner diameter of the oxygen-resistant heat-resistant polyethylene pipe, and the outer diameter of the safety cushion ring corresponds to the inner diameter of the socket fitting corresponding to the oxygen-resistant heat-resistant polyethylene pipe. When in use, the cushion ring is lined to the inner bottom of the socket fitting, and a polyolefin special welding machine is used to perform hot-melt socket welding on the pipe and fitting.

[0031] A preparation method of an oxygen-resistant heat-resistant polyethylene pipe includes the following steps:

[0032] S1: Batching and stirring, and extrusion is carried out by an extruder. A five-layer co-extrusion die head is selected for the extruder. From the outside to the inside, the pipe is successively a PE-RT outer pressure-bearing layer, a first bonding layer, an EVOH layer, a second bonding layer, and a PE-RT inner pressure-bearing layer;

[0033] S2: After the extruded pipe is cooled for the first time in a vacuum box, it then enters a spray cooling water tank in sequence, and after post-treatment, an oxygen-resistant heat-resistant polyethylene pipe is obtained.

[0034] Further, in step S1, the processing temperature of the PE-RT outer pressure-bearing layer is 200 - 210 °C, the processing temperature of the first bonding layer is 180 - 190 °C, the processing temperature of the EVOH layer is 180 - 200 °C, the processing temperature of the second bonding layer is 180 - 190 °C, and the processing temperature of the PE-RT inner pressure-bearing layer is 200 - 210 °C.

[0035] Further, in step S2, the cooling water temperature of the spray cooling water tank is 15 - 25 °C;

[0036] The thickness of the EVOH layer is 0.06 mm - 0.08 mm;

[0037] The thickness of the first bonding layer is 0.03 mm - 0.07 mm, and the thickness of the second bonding layer is 0.03 mm - 0.07 mm

[0038] The PE-RT outer pressure-bearing layer and the PE-RT inner pressure-bearing layer each account for about 50% of the nominal wall thickness of the corresponding specification required by the national standard.

[0039] Furthermore, after post-processing in step S2, an internal oxygen-resistant heat-resistant polyethylene pipe is obtained, including inkjet printing, traction by a traction machine, and cutting by a cutting machine to obtain a product according to the required length, and then measuring and testing. If the measurement and test results are qualified, it is packaged and stored, and if not, it is scrapped and crushed.

[0040] Compared with the prior art, the internal oxygen-barrier heat-resistant polyethylene pipe and the preparation method thereof described in the present invention have the following advantages:

[0041] 1. This application is a five-layer structure. Through the function of the EVOH layer, the pipeline has the function of resisting oxygen penetration and thus metal corrosion. At the same time, the unique anti-scratch formula protection and anti-aging formula of the outermost heat-resistant polyethylene (PE-RT) layer not only solves the problem of direct hot-melt connection, but also avoids the damage to the heat-resistant polyethylene (PE-RT) pressure-bearing layer and EVOH layer during the production, transportation, installation and long-term heat-resistant and pressure-resistant use of the pipe, resulting in pipe failure. At the same time, the inner pressure-resistant heat-resistant polyethylene (PE-RT) anti-fouling and anti-scaling layer delays the scaling time, thereby extending the cleaning cycle of the pipeline and reducing the risk of plugging and bursting.

[0042] The EVOH layer of the present application is basically located in the middle of the pipe, and the wall thickness of the inner and outer pressure-bearing layers is basically the same. Compared with the structural optimization of the traditional five-layer oxygen-barrier heat-resistant polyethylene pipe, the overall pressure resistance and high temperature resistance of the pipeline system are significantly improved. At the same time, it also eliminates the problem of only one pressure-bearing layer causing the overall wall thickness of the pipe to be too thick and the difficulty in connecting the manifold, thereby greatly reducing the construction time.

[0043] 2. This application is an innovation in system safety. Compared with the ordinary five-layer oxygen-barrier heat-resistant polyethylene pipe whose EVOH layer is biased towards the outside of the pipe, the EVOH layer of the inner oxygen-barrier heat-resistant polyethylene pipe will be better protected, and no peeling treatment is required during construction and welding, which will speed up the construction progress and greatly improve labor efficiency.

[0044] This application uses an EVOH layer as the oxygen barrier layer and, after adjustment, places the EVOH layer in the exact middle of the pipe. To prevent the EVOH layer from hydrolyzing during use and causing the separation of the inner and outer pressure-bearing layers, leading to the risk of pipe bursting, two innovative safety gasket rings are also invented and fused with the pipe ends. The two designed safety gasket rings use different welding methods: when the first safety gasket ring is used, it is heat-melted and butt-welded to the pipe through a hot plate; when the second safety gasket ring is used, the gasket lining is inserted into the inner bottom of the socket fitting, and on the premise of not affecting the water flow rate of the pipeline system, a polyolefin special-purpose welder is used for heat-melt socket welding of the pipe and fitting. The function of the first safety gasket ring or the second safety gasket ring is to completely wrap the EVOH layer at the pipe end face, eliminating the risk of hydrolysis caused by the contact between EVOH and water. Through either of the above two welding methods, it is system-connected to a five-layer oxygen-barrier heat-resistant polyethylene (PE-RT) pipe, which not only ensures that the pipe does not need to be peeled during construction but also ensures the safety of the pipe during long-term use.

[0045] 3. Under the condition of the same oxygen permeability, the cost of the oxygen barrier agent and the hot-melt adhesive material in this application is lower. During the extrusion process of the pipe, through the lean-designed extruder die and screw structure, the plasticization effect of the melt is better, so that the inner and outer surfaces of the pipe are smooth and flat, the overall structure of the pipe is stable, the five layers are more precisely separated, and the error is less, avoiding the phenomenon that the oxygen barrier effect of the pipe decreases due to wall thickness deviation or the stress concentration and breakage of the pipe during use caused by the wall thickness fluctuation of the pressure-bearing layer.

[0046] At the same time, through the adjustment of the pipe structure in this invention, the oxygen barrier layer and the bonding layer (hot-melt adhesive layer) are moved to the center part of the pipe. Under the condition of the same oxygen permeability of the pipe, due to the inward movement of the oxygen barrier layer and the bonding layer (hot-melt adhesive layer) along the circumference, the cross-sectional area decreases, and raw materials are saved. Taking a dn32 pipe as an example, for a five-layer oxygen-barrier heat-resistant polyethylene pipe with the oxygen barrier layer usually on the outside, the proportion of the oxygen barrier layer is 2%, while the proportion of the oxygen barrier layer in this invention is 1.5%, a decrease of 0.5%. Since the prices of EVOH and hot-melt adhesive materials are expensive, the overall production material cost of the pipe is reduced by more than 5%, truly achieving the effect of improving quality and reducing costs.

[0047] 4. The present application innovates in the glue layer identification technology. To avoid potential quality hazards caused by uneven extrusion or non-extrusion of hot melt adhesive during the extrusion of conventional five-layer oxygen barrier pipes, and since there is no suitable means on the market to monitor the thickness of the bonding layer (hot melt adhesive layer), there are significant safety hazards in the pipes. Water pipes are concealed works, and once problems occur, they are not easy to detect in time, which can easily cause significant losses to users. Therefore, to address this problem, we innovate in the identification of the bonding layer (hot melt adhesive layer), adjust the formula of the bonding layer (hot melt adhesive layer), and achieve the visualization of the color of the hot melt adhesive bonding layer through the adjustment of the formula and process. When the bonding layer is extruded normally, it shows a colored appearance. If it is abnormal (such as non-extrusion or deviation in the extrusion size of the pipe glue layer), the appearance color of the pipe will change significantly, facilitating the real-time monitoring of production quality. This avoids the errors of traditional visual inspection, improves the yield rate, and ensures the safety of the user's pipeline system. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0049] Figure 1 It is a schematic flow chart of a method for preparing an internal oxygen barrier heat-resistant polyethylene pipe according to an embodiment of the present invention;

[0050] Figure 2 It is a schematic structural diagram of an internal oxygen barrier heat-resistant polyethylene pipe according to an embodiment of the present invention;

[0051] Figure 3 It is a schematic diagram of a first safety gasket ring of an internal oxygen barrier heat-resistant polyethylene pipe according to an embodiment of the present invention;

[0052] Figure 4 It is a schematic diagram of a second safety gasket ring of an internal oxygen barrier heat-resistant polyethylene pipe according to an embodiment of the present invention;

[0053] Figure 5 It is an installation schematic diagram of a first safety gasket ring of an internal oxygen barrier heat-resistant polyethylene pipe according to an embodiment of the present invention;

[0054] Figure 6 It is a photo of a second safety gasket ring of an internal oxygen barrier heat-resistant polyethylene pipe according to an embodiment of the present invention;

[0055] Figure 7 It is a photo of a first safety gasket ring of an internal oxygen barrier heat-resistant polyethylene pipe according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0056] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0057] The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0058] Embodiment 1

[0059] The oxygen barrier type heat-resistant polyethylene (PE-RT) pipe has a five-layer structure: counting from the outside to the inside of the pipe, the first layer is the outer pressure-bearing layer of PE-RT, which mainly plays the roles of wear resistance, scratch resistance, heat resistance, pressure resistance and aging resistance. The formula is PE-RT (grade: Lanzhou Petrochemical mPE 3010 or Daqing Petrochemical 3711): PE-RT silicone anti-scratch masterbatch [polysiloxane: silicon dioxide: PE-RT is Lanzhou Petrochemical 3010 or Daqing Petrochemical 3711: compatibilizer (hot melt adhesive, i.e., maleic anhydride grafted polyethylene) is Basell PX3060) = 40:30:30:2]: PE-RT metal deactivator = 100:3:3.

[0060] The second layer is the first bonding layer (hot melt adhesive layer), which mainly plays the roles of bonding and marking. The formula is that the mass ratio of hot melt adhesive (maleic anhydride grafted polyethylene) Basell PX3060 and color masterbatch is 100:10;

[0061] The third layer is the EVOH (grade: SoarnoL TM DC3205HB) layer, which mainly plays the role of weather-resistant oxygen barrier, reducing the oxygen permeation rate;

[0062] The fourth layer is the second bonding layer (hot melt adhesive layer), which mainly plays the roles of bonding and marking. The formula is that the mass ratio of hot melt adhesive (maleic anhydride grafted polyethylene) Basell PX3060 and color masterbatch is 100:10;

[0063] The fifth layer is the inner pressure-bearing layer of PE-RT, which mainly plays the roles of heat resistance, pressure resistance, hydrophobicity, scale prevention and aging resistance. The formula is PE-RT (grade: Lanzhou Petrochemical mPE 3010 or Daqing Petrochemical 3711): PE-RT silicone anti-scratch masterbatch [polysiloxane: silicon dioxide: PE-RT is Lanzhou Petrochemical 3010: compatibilizer (hot melt adhesive, i.e., maleic anhydride grafted polyethylene) is Basell PX3060) = 40:30:30:2]: PE-RT metal deactivator = 100:3:3.

[0064] Among them, the formula of the PE-RT silicone anti-scratch masterbatch is: polysiloxane: silicon dioxide: PE-RT (Lanzhou Petrochemical 3010 or Daqing Petrochemical 3711): compatibilizer (hot melt adhesive Basell PX3060) = 40:30:30:2, and it is granulated by a twin-screw granulator with the process temperature between 180°C and 190°C.

[0065] The PE-RT metal passivator is: PE-RT (Lanzhou Petrochemical 3010 or Daqing Petrochemical 3711): antioxidant 1024 (N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoyl]hydrazine) = 100:5. Granulation is carried out by a twin-screw granulator, and the process temperature is between 180°C and 200°C.

[0066] Step 1, batching and stirring, and extrusion is carried out through a Battenfeld Cincinnati extruder. A five-layer coextrusion die head is selected for the equipment. Counting from the outside to the inside of the pipe, the first layer is the PE-RT outer resin layer, the second layer is the first bonding layer (hot melt adhesive layer), the third layer is the EVOH layer, the fourth layer is the second bonding layer (hot melt adhesive layer), and the fifth layer is the PE-RT outer resin layer.

[0067] Step 2, traction and cooling. After the extruded pipe is cooled for the first time in a vacuum box, it then enters three conventional spray cooling water tanks in sequence. The oxygen-barrier type heat-resistant polyethylene pipe includes inkjet printing, traction by a tractor, and cutting by a cutting machine according to the required length to obtain the product, and then measurement and inspection are carried out. If the measurement and inspection results are qualified, it is packaged and stored in the warehouse; if not, it is scrapped and pulverized.

[0068] Extrusion process parameter requirements: The processing temperature of the PE-RT outer pressure-bearing layer is 200 - 210°C, the processing temperature of the first bonding layer is 180 - 190°C, the processing temperature of the EVOH layer is 180 - 200°C, the processing temperature of the second bonding layer is 180 - 190°C, the processing temperature of the PE-RT inner pressure-bearing layer is 200 - 210°C, and the cooling water temperature is 15 - 25°C. The thickness of the oxygen-barrier layer is 0.06mm, the thicknesses of the first and second bonding layers (hot melt adhesive layers) are 0.04mm respectively, and the thicknesses of the inner and outer PE-RT layers each account for about 50% of the nominal wall thickness of the corresponding specifications required by the national standard.

[0069] Table 1. Processing temperature of PE-RT

[0070]

[0071]

[0072] Table 2. Comparison of hydrostatic pressure and other properties of PE-RT pipes

[0073]

[0074]

[0075] The following is the comparison of the copper aging resistance effect after adding the metal passivator to PE-RT:

[0076] Comparison of the copper aging resistance effect of PE-RT: 0.1% copper salt powder was added to the PE-RT raw material by the internal mixing method in a rheometer, and antioxidant 1024 (N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine) was added at a mass fraction of 0 - 0.3% respectively, and numbered respectively.

[0077] Table 3 Comparison table of copper aging resistance effect

[0078]

[0079] Table 4 OIT data after thermal oxygen aging in an oven at 100°C

[0080]

[0081]

[0082] Adding copper ions to the PE-RT material in the form of copper salt can significantly reflect the catalytic oxidation effect of copper ions. Adding antioxidant 1024 (N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine) according to the required content can significantly achieve the shielding effect on copper ions to prevent it from catalytically accelerating the thermal oxygen aging problem of PE-RT.

[0083] Comparative Example 2

[0084] The difference from Example 1 is that there is no outer pressure-bearing layer and the first bonding layer of PE-RT. During transportation, the oxygen barrier layer will be damaged and peeled off due to friction, resulting in a reduction or failure of the oxygen barrier effect.

[0085] Comparative Example 3

[0086] The difference from Example 1 is that the PE-RT organosilicon anti-scratch masterbatch in the outer pressure-bearing layer of PE-RT includes silica, heat-resistant polyethylene and hot melt adhesive (maleic anhydride grafted polyethylene), and the mass ratio is 70:30:2, and polysiloxane is not added. As a result, the contact angle cannot reach 110°, and the hydrophobic (anti-fouling) and anti-scratch effects are not good.

[0087] Comparative Example 4

[0088] The difference from Example 1 is that the PE-RT organosilicon anti-scratch masterbatch in the inner pressure-bearing layer of PE-RT includes silica, heat-resistant polyethylene and hot melt adhesive (maleic anhydride grafted polyethylene), and the mass ratio is 70:30:2, and polysiloxane is not added. As a result, the contact angle cannot reach 110°, and the hydrophobic (scale prevention) effect is not good.

[0089] Comparative Example 5

[0090] The difference from Example 1 is that the PE-RT silicone anti-scratch masterbatch in the outer pressure-bearing layer of PE-RT comprises polysiloxane, heat-resistant polyethylene and hot melt adhesive (maleic anhydride grafted polyethylene), and the mass ratio is 70:30:2, and silicon dioxide is not added.

[0091] It leads to a decrease in the hydrophobic (anti-fouling) anti-scratch performance effect and stability.

[0092] Comparative Example 6

[0093] The difference from Example 1 is that the PE-RT silicone anti-scratch masterbatch in the inner pressure-bearing layer of PE-RT comprises polysiloxane, heat-resistant polyethylene and hot melt adhesive (maleic anhydride grafted polyethylene), and the mass ratio is 70:30:2, and silicon dioxide is not added;

[0094] It leads to the contact angle not reaching 110°, and the hydrophobic (scale prevention) performance effect and stability decrease.

[0095] Comparative Example 7

[0096] The difference from Example 1 is that the PE-RT metal passivator is not added to the outer pressure-bearing layer of PE-RT;

[0097] And the mass ratio of heat-resistant polyethylene to PE-RT silicone anti-scratch masterbatch is 100:6.

[0098] It leads to a significant decrease in OIT after thermal-oxidative aging in an oven at 100 °C, and the heat-resistant and pressure-resistant time is reduced.

[0099] Comparative Example 8

[0100] The difference from Example 1 is that the PE-RT metal passivator is not added to the inner pressure-bearing layer of PE-RT;

[0101] And the mass ratio of heat-resistant polyethylene to PE-RT silicone anti-scratch masterbatch is 100:6.

[0102] It will also lead to a significant decrease in OIT after thermal-oxidative aging in an oven at 100 °C, and the heat-resistant and pressure-resistant time is reduced.

[0103] Comparative Example 9

[0104] The difference from Example 1 is that the PE-RT silicone anti-scratch masterbatch is not added to the outer pressure-bearing layer of PE-RT;

[0105] And the mass ratio of heat-resistant polyethylene to PE-RT metal passivator is 100:6.

[0106] It leads to a significant reduction in the hydrophobic (anti-fouling) scratch-resistant effect.

[0107] Comparative Example 10

[0108] The difference from Example 1 is that the PE-RT silicone anti-scratch masterbatch is not added to the inner pressure-bearing layer of PE-RT;

[0109] And the mass ratio of heat-resistant polyethylene to the PE-RT metal passivator is 100:6.

[0110] This results in a significant reduction in the hydrophobic (scale prevention) performance.

[0111] Table 5 Comparison table of the effects of examples and comparative examples

[0112]

[0113] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An internal oxygen-resistant heat-resistant polyethylene pipe, characterized in that: It includes a PE-RT outer pressure-bearing layer, a first bonding layer, an EVOH layer, a second bonding layer, and a PE-RT inner pressure-bearing layer. The PE-RT outer pressure-bearing layer, the first bonding layer, the EVOH layer, the second bonding layer, and the PE-RT inner pressure-bearing layer are arranged in sequence from the outside to the inside. The end of the internal oxygen-barrier heat-resistant polyethylene pipe is provided with a first safety gasket or a second safety gasket.

2. The internal oxygen-barrier heat-resistant polyethylene pipe according to claim 1, characterized in that: The thickness ratio of the PE-RT outer pressure-bearing layer, the first bonding layer, the EVOH layer, the second bonding layer and the PE-RT inner pressure-bearing layer is 45-50: 1-1.5: 1.3-2.0: 1-1.5: 45-50.

3. The internal oxygen-barrier heat-resistant polyethylene pipe according to claim 1, characterized in that: The PE-RT outer pressure-bearing layer includes heat-resistant polyethylene, PE-RT silicone anti-scratch masterbatch, and PE-RT metal passivator; The mass ratio of heat-resistant polyethylene (PE-RT), PE-RT silicone anti-scratch masterbatch, and PE-RT metal passivator is 100:(1-5):(1-6); The PE-RT silicone anti-scratch masterbatch includes polysiloxane, silica, heat-resistant polyethylene (PE-RT) and hot melt adhesive (maleic anhydride grafted polyethylene), and the mass ratio of polysiloxane, silica, heat-resistant polyethylene (PE-RT) and hot melt adhesive (maleic anhydride grafted polyethylene) is 40:30:30:(1-3); PE-RT silicone anti-scratch masterbatch is granulated by a twin-screw granulator, and the process temperature is 180℃-190℃; The PE-RT metal passivator includes heat-resistant polyethylene and antioxidant 1024 (N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine); the mass ratio of heat-resistant polyethylene and antioxidant 1024 (N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine) is 100:5; PE-RT metal passivator is granulated by a twin-screw granulator with a process temperature of 180℃-200℃.

4. The internal oxygen-barrier heat-resistant polyethylene pipe according to claim 1, characterized in that: The first adhesive layer comprises hot melt adhesive (maleic anhydride grafted polyethylene) and masterbatch, and the mass ratio of the hot melt adhesive (maleic anhydride grafted polyethylene) to the masterbatch is 100:(5-15); The second adhesive layer comprises hot melt adhesive (maleic anhydride grafted polyethylene) and masterbatch, and the mass ratio of the hot melt adhesive (maleic anhydride grafted polyethylene) to the masterbatch is 100:(5-15).

5. The internal oxygen-barrier heat-resistant polyethylene pipe according to claim 1, characterized in that: The PE-RT inner pressure-bearing layer includes heat-resistant polyethylene (PE-RT), PE-RT silicone anti-scratch masterbatch, and PE-RT metal passivator; The mass ratio of heat-resistant polyethylene, PE-RT silicone anti-scratch masterbatch, and PE-RT metal passivator is 100:(1-5):(1-6) The PE-RT silicone anti-scratch masterbatch includes polysiloxane, silica, heat-resistant polyethylene and hot melt adhesive (maleic anhydride grafted polyethylene), and the mass ratio of polysiloxane, silica, heat-resistant polyethylene and hot melt adhesive (maleic anhydride grafted polyethylene) is 40:30:30:(1-3); PE-RT silicone anti-scratch masterbatch is granulated by a twin-screw granulator, and the process temperature is 180℃-190℃; The PE-RT metal passivator includes heat-resistant polyethylene and antioxidant 1024 (N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine); the mass ratio of heat-resistant polyethylene and antioxidant 1024 (N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine) is 100:5; PE-RT metal passivator is granulated by a twin-screw granulator with a process temperature of 180℃-200℃.

6. The internal oxygen-barrier heat-resistant polyethylene pipe according to claim 1, characterized in that: The first safety washer is provided with a hand-held rod distributed in a cone shape, and the ends of the hand-held rods converge into a connecting block; the material of the safety washer is heat-resistant polyethylene; the vertical projection length of the hand-held rod is 3mm-4mm; the inner diameter of the safety washer corresponds to the inner diameter of the internal oxygen-resistant heat-resistant polyethylene pipe, and the outer diameter of the safety washer corresponds to the outer diameter of the internal oxygen-resistant heat-resistant polyethylene pipe; The first safety washer is connected to the internal oxygen-resistant heat-resistant polyethylene pipe by heating with a hot plate; The inner diameter of the second safety washer corresponds to the inner diameter of the internal oxygen-resistant heat-resistant polyethylene pipe, and the outer diameter of the safety washer corresponds to the inner diameter of the socket fitting corresponding to the internal oxygen-resistant heat-resistant polyethylene pipe. When in use, the second safety washer is lined to the bottom of the socket fitting and welded using a special polyolefin welder.

7. A method for preparing an internal oxygen-barrier heat-resistant polyethylene pipe according to claims 1-6, characterized in that: The steps include: S1: Mix the ingredients and extrude them using an extruder. The extruder uses a five-layer co-extrusion die head. The pipe is composed of a PE-RT outer pressure-bearing layer, a first adhesive layer, an EVOH layer, a second adhesive layer, and a PE-RT inner pressure-bearing layer from the outside to the inside. S2: After extrusion, the pipe is cooled in a vacuum box for the first time, and then enters a spray cooling water tank in turn. After post-treatment, an internal oxygen-resistant heat-resistant polyethylene pipe is obtained.

8. The method for preparing an internal oxygen-barrier heat-resistant polyethylene pipe according to claim 7, characterized in that: In step S1, the processing temperature of the PE-RT outer pressure-bearing layer is 200-210°C, the processing temperature of the first adhesive layer is 180-190°C, the processing temperature of the EVOH layer is 180-200°C, the processing temperature of the second adhesive layer is 180-190°C, and the processing temperature of the PE-RT inner pressure-bearing layer is 200-210°C.

9. The method for preparing an internal oxygen-barrier heat-resistant polyethylene pipe according to claim 7, characterized in that: The cooling water temperature of the spray cooling water tank in step S2 is 15-25°C; The thickness of the EVOH layer is 0.06mm to 0.08mm; The thickness of the first adhesive layer is 0.03 mm to 0.07 mm, and the thickness of the second adhesive layer is 0.03 mm to 0.07 mm. The PE-RT outer pressure-bearing layer and the PE-RT inner pressure-bearing layer each account for about 50% of the nominal wall thickness of the corresponding specifications required by the standard.

10. The method for preparing an internal oxygen-barrier heat-resistant polyethylene pipe according to claim 7, characterized in that: After post-processing in step S2, an internal oxygen-resistant heat-resistant polyethylene pipe is obtained, including inkjet printing, traction, and cutting to the required length by a cutting machine, and then measuring and testing. If the measurement and test results are qualified, it is packaged and stored; if not, it is scrapped and crushed.

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