Production process of Krah pipe and equipment adopted by production process

Abstract

The invention discloses a Krah pipe production process and equipment adopted by the Krah pipe production process, and relates to the field of pipeline production. The production technology of the Krah pipe comprises the following steps that S1, core mold preheating and inner layer winding forming operation are conducted on a first machining station; s2, transferring the inner layer formed by winding and the core mold to a second processing station; s3, a polypropylene single-wall corrugated pipe is introduced to serve as an auxiliary support of the outer layer, a polyethylene material belt is extruded out, and after the surface of the polypropylene single-wall corrugated pipe is completely wrapped with the polyethylene material belt, the polypropylene single-wall corrugated pipe wrapped with the polyethylene material belt is wound and connected to the blank seam of the inner layer in a lap joint mode; s4, uniformly cooling and shaping the finished product in the step S3; and when the polyethylene material belt is wound, the temperature of the polyethylene material belt is 25-35 DEG C higher than that of the inner layer. The problems that the outer wall of the Krah pipe is oval, and the inner layer is thinned can be solved, the structural height and the ring stiffness of the pipe can be improved, and meanwhile stable combination of the inner layer and the outer layer can be guaranteed.

Description

Technical Field

[0001] The present application relates to the field of pipe production, and in particular to a production process of carat pipes and equipment used therein. Background Art

[0002] High-density polyethylene (HDPE) winding structural wall pipe B type pipe, commonly known as "carat pipe". Carat pipe is made of high-density polyethylene resin as the main raw material. After the inner layer is formed by hot winding molding process, the polyethylene tape is wrapped with a polypropylene single-wall corrugated pipe (i.e. the outer layer) and wrapped around the outer circumference of the inner layer as a special structural wall pipe as an auxiliary support structure.

[0003] At present, the existing process adopts the method of winding the inner and outer layers simultaneously when producing carat tubes, that is, the inner and outer layers are wound at the same station, almost at the same time. The advantage of this method is that the inner and outer layers can be firmly combined. However, there are also the following disadvantages: the shrinkage rate of high-density polyethylene resin is 2-4%. During the molding stage of the outer layer of the tube wall material, since the tube wall material is still in a molten state, the tube wall material cools and shrinks to produce stress, causing the outer layer of the tube wall to shrink from the outside to the inside, and finally causing the polypropylene single-wall corrugated tube to sink, squeezing the inner layer of the carat tube material, so that the actual produced tube is like Figure 1 :The outer wall of the pipe is oval, and the outer layer of polypropylene single-wall corrugated pipe is embedded in the inner layer, causing the inner layer to become thinner, and excess material is accumulated under the oval outer wall. This situation seriously reduces the structural height of the outer pipe wall, which greatly reduces the ring stiffness of the pipe. At the same time, the inner layer of the pipe is too thin and is easily damaged by external forces, affecting the overall quality and service life of the pipe, and cannot fully meet the engineering needs. Summary of the invention

[0004] In order to improve the problem that the existing process easily produces carat tubes with elliptical outer walls and thin inner layers, resulting in greatly reduced performance of the carat tubes, the present application provides a production process for carat tubes and equipment used therein.

[0005] A production process of a carat tube comprises the following steps: S1, perform core mold preheating and inner layer winding molding operations at processing station No. 1; S2, transfer the inner layer and the core mold of the winding molding to the second processing station as a whole, and the transfer process should be smooth; S3, introducing a polypropylene single-wall corrugated tube as an auxiliary support for the outer layer, and extruding a polyethylene tape, so that the polyethylene tape completely covers the surface of the polypropylene single-wall corrugated tube, and then wrapping the polypropylene single-wall corrugated tube covered with the polyethylene tape around the seam of the inner layer blank, thus completing the winding and forming operation of the outer layer; S4, uniformly cooling and shaping the finished product of step S3; When the polyethylene tape is wound, the temperature of the polyethylene tape is 25-35° C. higher than the temperature of the inner layer.

[0006] Different from the existing production process of winding the inner and outer layers of the carat tube at the same time, the winding of the inner layer of the carat tube and the polyethylene tape (outer tube wall) of the present application is carried out after the overall winding of the inner layer of the carat tube is completed, and when the polyethylene tape is wound, the temperature difference between the polyethylene tape and the inner layer is controlled within the range of 25-35°C, the purpose is to allow the inner layer material to cool to a certain extent first, so that the texture of the inner layer becomes slightly harder, so that when the polyethylene tape is wound, the influence of the cooling shrinkage of the polyethylene tape on its own non-roundness and the thickness of the inner layer structure can be reduced, which can improve the problem of "oval outer wall and thin inner layer" of the carat tube, which is beneficial to improve the structural height and ring stiffness of the tube, and at the same time, the appropriate temperature difference can also ensure the stable combination of the inner layer and the outer layer.

[0007] Among them, the temperature difference between the polyethylene strip and the inner layer should not be too large, otherwise it will easily lead to a loose bond between the outer layer and the inner layer, and the outer layer and the inner layer will be easily delaminated due to external force impact during subsequent use. The temperature difference between the polyethylene strip and the inner layer should not be too small, otherwise it will easily increase the shrinkage stress of the outer wall, which will affect its own non-roundness and the thickness of the inner layer structure. When the outer wall is elliptical, the structural height of the pipe will decrease, affecting the ring stiffness of the pipe. When the inner layer is too thin, the pipe is easily damaged by external forces, affecting the overall quality and service life of the pipe, and cannot fully meet the engineering needs.

[0008] Preferably, the polyethylene material strip comprises a surface layer and an inner layer, the shrinkage rate of the surface layer is 1.5-1.7%, and the shrinkage rate of the inner layer is 2-2.5%.

[0009] In the present application, it is preferred to use a two-layer polyethylene tape, and the shrinkage rates of the two layers are inconsistent. The shrinkage rate of the surface layer is smaller than that of the inner layer, but the toughness is slightly worse than that of the inner layer. The combination of the surface layer and the inner layer with different shrinkage rates is conducive to taking into account the low radial shrinkage and high impact resistance of the polyethylene tape. Among them, the shrinkage rate of the surface layer of the polyethylene tape is low, so that the deformation ability of the polyethylene tape to resist external shrinkage is enhanced. During the cooling process, it is preferentially shaped and forms a rigid skeleton, which constrains the radial shrinkage of the entire polyethylene tape, thereby reducing the elliptical deformation of the outer wall caused by uneven shrinkage. In addition, after the surface layer is shaped, the inner layer shrinks mainly in the axial direction to release stress, rather than radially extruding the surface layer, thereby reducing the compression effect of the surface layer on the inner layer of the carat tube, further improving the problem of thinning of the inner layer of the carat tube.

[0010] Preferably, the difference in shrinkage between the inner layer and the surface layer is 0.3-0.8%.

[0011] In the present application, the difference in shrinkage between the inner layer and the surface layer is controlled between 0.3-0.8%, which is beneficial to reduce the risk of interlayer separation between the inner layer and the surface layer, and is beneficial to further reduce the out-of-roundness of the outer wall.

[0012] Preferably, the raw materials for preparing the surface layer include 1.5-2wt% aminosilane coupling agent modified calcium carbonate, 2.5-3wt% PE organic masterbatch, 0.5-1wt% ultra-high molecular weight polyethylene, 1-2wt% olefin wax and the balance high-density polyethylene, and the raw materials for preparing the inner layer include 2-3wt% epoxy modified polyolefin elastomer, 2-3wt% PE organic masterbatch and the balance high-density polyethylene.

[0013] In the present application, the shrinkage rate of the surface layer is in the range of 1.5-1.7%, and the shrinkage rate of the inner layer is in the range of 2-2.5%, and the aminosilane coupling agent modified calcium carbonate in the surface layer can form a chemical bond with the epoxy-modified polyolefin elastomer in the inner layer, thereby improving the bonding stability between the surface layer and the inner layer and preventing the delamination problem caused by the difference in shrinkage rate or interface between the surface layer and the inner layer.

[0014] Wherein, the preparation method of the aminosilane coupling agent modified calcium carbonate is as follows: 0.2-0.3 parts by weight of aminosilane coupling agent is added to 100 parts by weight of ethanol solution with a mass concentration of 70-80%, and after stirring evenly, 8-10 parts by weight of calcium carbonate is added, and then the temperature is raised to 55-65° C. and heated under reflux for 1-1.5 hours, followed by filtering, washing and drying the filter residue to obtain aminosilane coupling agent modified calcium carbonate.

[0015] Preferably, the molecular weight of the ultra-high molecular weight polyethylene is 4 million to 6 million.

[0016] Preferably, the epoxy-modified polyolefin elastomer is POE graft-modified with glycidyl methacrylate.

[0017] The raw materials for preparing the glycidyl methacrylate graft-modified POE include glycidyl methacrylate, POE elastomer, peroxidation initiator and antioxidant in a weight ratio of (2.5-3.5):100:(0.03-0.05):(0.1-0.2).

[0018] In the present application, controlling the grafting rate of methacrylate carboxylic acid glyceride is beneficial to taking into account both the low radial shrinkage and high impact resistance of the polyethylene tape, and preventing the problem of decreased interface bonding strength between the surface layer and the inner layer caused by too high or too low grafting rate.

[0019] Further preferably, the thickness ratio of the surface layer to the inner layer is 1:(3-4).

[0020] In the present application, the thickness of the surface layer and the inner layer is controlled to be 1: (3-4), which is beneficial to taking into account both the low radial shrinkage and high impact resistance of the polyethylene tape.

[0021] The melt extrusion temperatures of the inner layer, the surface layer and the inner layer are all 180-190°C.

[0022] In the second aspect, the equipment used in the production process of a carat tube provided by the present application adopts the following technical solution: A device used in a carat tube production process includes: A base frame, wherein one side of the base frame is provided with a No. 1 processing station, and the other side of the base frame is provided with a No. 2 processing station; the No. 1 processing station is provided with a core mold, the core mold is connected to a heating mechanism for heating the core mold, and the No. 2 processing station is provided with a core mold for completing inner layer winding; An inner layer extrusion mechanism, the inner layer extrusion mechanism is used for heating, melting and extruding the inner layer raw material; A first moving mechanism, wherein the first moving mechanism controls the inner layer extrusion mechanism to move along the length direction of the core mold, and through the cooperation of the winding mechanism, the extruded inner layer raw material is wound around the surface of the core mold at the first processing station; A polypropylene single-wall corrugated pipe feeding mechanism, wherein the polypropylene single-wall corrugated pipe feeding mechanism conveys the polypropylene single-wall corrugated pipe to the core mold for inner layer winding at the second processing station; A polyethylene material strip extrusion mechanism, wherein the polyethylene material strip extrusion mechanism comprises an inner layer extrusion mechanism and a surface layer extrusion mechanism, wherein the inner layer material extruded by the inner layer extrusion mechanism is firstly used to coat the polypropylene single-wall corrugated pipe internally, and then the surface layer material extruded by the surface layer extrusion mechanism is used to coat the polypropylene single-wall corrugated pipe externally to obtain an outer layer material; A second moving mechanism, wherein the second moving mechanism controls the polyethylene strip extrusion mechanism to move along the length direction of the core mold, and through the cooperation of the winding mechanism, the outer layer material is wound on the core mold where the inner layer winding is completed at the second processing station; A cooling station is used to naturally cool the pipe after the outer layer winding is completed.

[0023] In summary, this application at least includes the following beneficial technical effects: (1) The winding of the inner layer of the carat tube and the polyethylene tape (outer tube wall) of the present application is carried out after the overall winding of the inner layer of the carat tube is completed. When the polyethylene tape is wound, the temperature difference between the polyethylene tape and the inner layer is controlled within the range of 25-35°C. The purpose is to allow the inner layer material to cool to a certain extent first, so that the texture of the inner layer becomes slightly harder, so that when the polyethylene tape is wound, the effect of the cooling shrinkage of the polyethylene tape on its own non-circularity and the thickness of the inner layer structure can be reduced, which can improve the problem of "oval outer wall and thin inner layer" of the carat tube, which is conducive to improving the structural height and ring stiffness of the tube. At the same time, the appropriate temperature difference can also ensure the stable combination of the inner layer and the outer layer.

[0024] (2) In this application, a two-layer polyethylene tape is preferably used, and the shrinkage rates of the two layers are inconsistent. The shrinkage rate of the surface layer is smaller than that of the inner layer, but the toughness is slightly worse than that of the inner layer. The combination of the surface layer and the inner layer with different shrinkage rates is conducive to taking into account the low radial shrinkage and high impact resistance of the polyethylene tape. Among them, the shrinkage rate of the surface layer of the polyethylene tape is low, which enhances the deformation ability of the polyethylene tape to resist external shrinkage. During the cooling process, it is preferentially shaped and forms a rigid skeleton, which constrains the radial shrinkage of the entire polyethylene tape, thereby reducing the elliptical deformation of the outer wall caused by uneven shrinkage. In addition, after the surface layer is shaped, the inner layer shrinks mainly in the axial direction to release stress, rather than radially squeezing the surface layer, thereby reducing the compression effect of the surface layer on the inner layer of the carat tube, further improving the problem of thinning of the inner layer of the carat tube.

[0025] (3) In the present application, the shrinkage rate of the surface layer is in the range of 1.5-1.7%, and the shrinkage rate of the inner layer is in the range of 2-2.5%, and the aminosilane coupling agent-modified calcium carbonate in the surface layer can form a chemical bond with the epoxy-modified polyolefin elastomer in the inner layer, thereby improving the bonding stability between the surface layer and the inner layer and preventing the delamination problem caused by the difference in shrinkage rate or interface between the surface layer and the inner layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a cross-sectional view of a carat tube obtained by the existing carat tube production process.

[0027] Figure 2 It is a structural schematic diagram of the carat tube production equipment of the present application.

[0028] Figure 3 It is a cross-sectional view of a carat tube obtained by the carat tube production process of the present application.

[0029] Description of reference numerals: 1. Base frame; 11. Processing station No. 1; 12. Processing station No. 2; 13. Core mold; 2. Inner layer extrusion mechanism; 3. First moving mechanism; 4. Polypropylene single-wall corrugated pipe feeding mechanism; 5. Polyethylene material strip extrusion mechanism; 51. Inner layer extrusion mechanism; 52. Surface layer extrusion mechanism; 6. Second moving mechanism; 7. Cooling station. DETAILED DESCRIPTION

[0030] The present application embodiment discloses a carat tube production device, such as Figure 2 ,include: A bottom frame 1, one side of the bottom frame 1 is provided with a No. 1 processing station 11, and the other side of the bottom frame 1 is provided with a No. 2 processing station 12; the No. 1 processing station 11 is provided with a core mold 13, and the core mold 13 is connected to a heating mechanism for heating the core mold 13, and the No. 2 processing station 12 is provided with the core mold 13 after the inner layer winding is completed; Inner layer extrusion mechanism 2, the inner layer extrusion mechanism is used for heating, melting and extruding the inner layer raw materials; The first moving mechanism 3 controls the inner layer extrusion mechanism 2 to move along the length direction of the core mold 13, and through the cooperation of the winding mechanism, the extruded inner layer raw material is wound around the surface of the core mold 13 of the first processing station 11; The polypropylene single-wall corrugated pipe feeding mechanism 4 conveys the polypropylene single-wall corrugated pipe to the second processing station 12 to complete the inner layer winding on the core mold 13; The polyethylene material strip extrusion mechanism 5 includes an inner layer extrusion mechanism 51 and a surface layer extrusion mechanism 52. The inner layer material extruded by the inner layer extrusion mechanism 51 is firstly used to coat the polypropylene single-wall corrugated tube, and then the surface layer material extruded by the surface layer extrusion mechanism 52 is used to coat the polypropylene single-wall corrugated tube to obtain an outer layer material. The second moving mechanism 6 controls the polyethylene strip extrusion mechanism 5 to move along the length direction of the core mold 13, and through the cooperation of the winding mechanism, the outer layer material is wound on the core mold 13 where the inner layer is wound at the second processing station 12; The cooling station 7 is used to hold the pipe that has completed the outer layer winding, so that the pipe can be cooled naturally.

[0031] The present application is further described below in conjunction with specific experiments.

[0032] Preparation Example [Preparation Example 1] A glycidyl methacrylate grafted modified POE comprises 2.5 kg glycidyl methacrylate, 100 kg POE elastomer (Mitsui DF710 from Japan), 0.03 kg diisopropylbenzene peroxide and 0.1 kg antioxidant 1010.

[0033] In this preparation example, the preparation method of glycidyl methacrylate graft-modified POE is as follows: Glycidyl methacrylate, POE elastomer, dicumyl peroxide and antioxidant 1010 are put into an extruder according to a proportion, melt-extruded at 170-190° C., and granulated to obtain glycidyl methacrylate graft-modified POE.

[0034] [Preparation Example 2] A glycidyl methacrylate grafted modified POE comprises 3.5 kg glycidyl methacrylate, 100 kg POE elastomer (Mitsui DF710 from Japan), 0.05 kg dicumyl peroxide and 0.2 kg antioxidant 1010.

[0035] In this preparation example, the preparation method of glycidyl methacrylate graft-modified POE is as follows: Glycidyl methacrylate, POE elastomer, dicumyl peroxide and antioxidant 1010 are put into an extruder according to a proportion, melt-extruded at 170-190° C., and granulated to obtain glycidyl methacrylate graft-modified POE.

[0036] [Preparation Example 3] A POE grafted with glycidyl methacrylate, which is different from [Preparation Example 1] in that the amount of glycidyl methacrylate used is 10 kg.

[0037] [Preparation Example 4] An aminosilane coupling agent KH550 modified calcium carbonate, the preparation method of which is as follows: 0.25 kg of aminosilane coupling agent KH550 was added to 100 kg of ethanol solution with a mass concentration of 75%, and after stirring evenly, 8 kg of calcium carbonate was added, and then the temperature was raised to 60°C and heated to reflux for 1 hour, followed by filtering, washing and drying the filter residue to obtain aminosilane coupling agent KH550 modified calcium carbonate. Example

[0038] [Example 1] A production process of a carat tube comprises the following steps: S1, preheating the core mold at the No. 1 processing station, and then feeding 98wt% high-density polyethylene (Taiwan Formosa Plastics 8001 from Taiwan Province of China) and 2wt% PE organic masterbatch (solvent black 7 mass content of 40%) into the inner layer extrusion mechanism, melt extruding at 180-190°C to obtain the inner layer sheet, and then controlling the inner layer sheet to be wound along the length direction of the core mold through the winding mechanism and the first moving mechanism; S2. After the inner layer winding operation is completed, the core mold with the inner layer wound is transferred as a whole to the No. 2 processing station. The transfer process should be smooth. S3, 1.5wt% of aminosilane coupling agent KH550 modified calcium carbonate prepared in [Preparation Example 4], 2.5wt% PE organic masterbatch (solvent black 7 mass content is 40%), 1wt% ultra-high molecular weight polyethylene (Korea Petrochemical U050), 1wt% low molecular weight polyethylene wax (polyethylene wax A-C6A) and the remaining high-density polyethylene (Taiwan Formosa Plastics 8001 from Taiwan Province, China) are put into the surface extrusion mechanism, and 2wt% of methacrylate glycidyl graft modified POE prepared in [Preparation Example 1], 2wt% PE organic masterbatch (solvent black 7 mass content is 40%) and the remaining high-density polyethylene (China Taiwan Formosa Plastics 8001 in Taiwan Province) is put into the inner layer extrusion mechanism. When the temperature of the inner layer on the core mold is 30℃ lower than the temperature of the surface layer, the inner layer raw material extruded by the inner layer extrusion mechanism at 180-190℃ is first used to coat the polypropylene single-wall corrugated pipe internally, and then the surface layer raw material extruded by the surface layer extrusion mechanism at 180-190℃ is used to coat the polypropylene single-wall corrugated pipe externally. Among them, the extrusion speed of the inner layer raw material is 3 times that of the surface layer raw material, and the outer layer material is obtained. Then, the outer layer material is controlled to be wound along the length direction of the core mold by the winding mechanism and the second moving mechanism, and it is ensured that the outer layer material overlaps the seam of the inner layer blank to complete the outer layer winding molding operation; S4, the finished product of step S3 is evenly cooled and shaped to avoid sudden cooling.

[0039] In this embodiment, the shrinkage rate of the surface layer is 1.5%, the shrinkage rate of the inner layer is 2.1%, and the difference in shrinkage rate between the inner layer and the surface layer is 0.6%.

[0040] [Example 2] A carat tube production process, which differs from [Example 1] in that: in step S3, a surface layer extrusion mechanism is charged with 2wt% of aminosilane coupling agent KH550 modified calcium carbonate prepared in [Preparation Example 4], 3wt% of PE organic masterbatch (solvent black 7 mass content is 40%), 0.5wt% of ultra-high molecular weight polyethylene (Korea Petrochemical U050), 2wt% of low molecular weight polyethylene wax (polyethylene wax A-C6A) and the balance of high-density polyethylene (Taiwan Formosa Plastics 8001 from Taiwan Province, China), and an inner layer extrusion mechanism is charged with 3wt% of methacrylic acid glycidyl graft modified POE prepared in [Preparation Example 2], 3wt% of PE organic masterbatch (solvent black 7 mass content is 40%) and the balance of high-density polyethylene (Taiwan Formosa Plastics 8001 from Taiwan Province, China).

[0041] In this embodiment, the shrinkage rate of the surface layer is 1.5%, the shrinkage rate of the inner layer is 2.1%, and the difference in shrinkage rate between the inner layer and the surface layer is 0.6%.

[0042] [Example 3] A production process for carat tubes, which differs from Example 1 in that: 3wt% of aminosilane coupling agent KH550 modified calcium carbonate prepared in Preparation Example 4, 3wt% of PE organic masterbatch (solvent black 7 mass content is 40%), 6wt% of ultra-high molecular weight polyethylene (Korea Petrochemical U050), 2wt% of low molecular weight polyethylene wax (polyethylene wax A-C6A) and the balance of high-density polyethylene (Taiwan Formosa Plastics 8001 from Taiwan Province, China) are put into a surface layer extrusion mechanism, and 3wt% of PE organic masterbatch (solvent black 7 mass content is 40%) and the balance of high-density polyethylene (Taiwan Formosa Plastics 8001 from Taiwan Province, China) are put into an inner layer extrusion mechanism.

[0043] In this embodiment, the shrinkage rate of the surface layer is 1.3%, the shrinkage rate of the inner layer is 2.5%, and the difference in shrinkage rate between the inner layer and the surface layer is 1.2%.

[0044] [Example 4] A carat tube production process, which differs from [Example 1] in that: in step S3, the raw material glycidyl methacrylate graft-modified POE fed into the inner layer extrusion mechanism is replaced by an equal amount of glycidyl methacrylate graft-modified POE prepared in [Preparation Example 3].

[0045] In this embodiment, the shrinkage rate of the surface layer is 1.5%, the shrinkage rate of the inner layer is 2%, and the difference in shrinkage rate between the inner layer and the surface layer is 0.5%.

[0046] Comparative Example [Comparative Example 1] A production process of a carat tube, which differs from [Example 1] in that: In step S3, when the outer layer material is wound, the temperature of the inner layer on the core mold is 10°C lower than the surface layer temperature.

[0047] [Comparative Example 2] A production process of a carat tube, which differs from [Example 1] in that: In step S3, when the outer layer material is wound, the temperature of the inner layer on the core mold is 45°C lower than the surface layer temperature.

[0048] Performance testing According to the methods of the above-mentioned Examples 1-4 and Comparative Examples 1-2, carat tube samples with a nominal size of 300 mm, an inner wall thickness of 2 mm, and a ring stiffness grade of SN12.5 were prepared respectively, and the carat tube samples were taken for the following performance tests.

[0049] (1) Cross-sectional shape of the outer tube wall: Cut the carat tube along the diameter direction, observe the cross-sectional shape of the outer tube wall of the carat tube, and record it in Table 1 below.

[0050] (2) Thinnest wall thickness of inner layer: The carat tube was cut in the diameter direction, and three samples were taken from each embodiment and comparative example. Three intersection points of the outer layer and the inner layer of each sample were sampled at equal intervals for testing, and the average value of the test data was recorded in the following Table 1.

[0051] (3) Ring stiffness: The test was conducted in accordance with GB / T9647-2015 "Determination of Ring Stiffness of Thermoplastic Pipes". Three samples were taken from each embodiment and comparative example for testing. The average value of the test data was recorded in Table 1 below.

[0052] (4) Oven test: After cutting the carat tube in the diameter direction, put the cut sample into an oven at a temperature of 110°C for 30 min. Observe whether delamination or cracking occurs at the weld joints between the inner layer and the surface layer, and between the outer layer and the inner layer in the outer tube wall. Record the results in Table 2 below.

[0053] Table 1

[0054] Table 2

[0055] The outer wall interface of the carat tubes obtained in Examples 1-4 and Comparative Example 2 of the present application is quasi-circular, such as Figure 3 The outer wall cross section of the carat tube obtained in comparative example 1 is elliptical, which is similar to Figure 1 similar.

[0056] Combining Example 1 with Comparative Examples 1-2 and the test data in Tables 1-2, it can be seen that when the outer layer winding operation of the carat tube is performed, controlling the temperature difference between the outer polyethylene tape and the inner layer of the carat tube within the range of 25-35° C. is beneficial to improving the problem that the outer layer wall of the carat tube is elliptical and the inner layer wall thickness is thinned at the fusion joint of the outer layer and the inner layer, while ensuring the stable bonding of the fusion joint of the outer layer and the inner layer of the carat tube, which can effectively improve the ring stiffness of the carat tube and extend the service life of the carat tube.

[0057] Combining Example 1 with Example 3 and the test data in Table 1-Table 2, it can be seen that the surface layer in Example 3 increases the amount of aminosilane coupling agent KH550 modified calcium carbonate and ultra-high molecular weight polyethylene, and the inner layer is not mixed with glycidyl methacrylate grafted modified POE, the shrinkage difference between the surface layer and the inner layer of the polyethylene material strip increases, the surface layer and the inner layer are prone to delamination after heat treatment, and the ring stiffness of the carat tube is also reduced.

[0058] Combining the test data in Example 1 and Example 4 and Table 1-Table 2, it can be seen that the grafting rate of glycidyl methacrylate in the glycidyl methacrylate graft-modified POE incorporated into the inner layer of Example 4 is increased. Combining the data in the table, it can be seen that the surface layer and the inner layer of the polyethylene material strip in Example 4 are prone to delamination after heat treatment, and the ring stiffness of the carat tube is also reduced, so it is preferred to control the grafting rate of glycidyl methacrylate in the glycidyl methacrylate graft-modified POE within a reasonable range.

[0059] This specific implementation manner is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the specific implementation manner as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A production process for carat tubes, characterized in that: The following steps are involved: S1, perform core mold preheating and inner layer winding molding operations at processing station No. 1; S2, transfer the winding core mold with the inner layer to the second processing station as a whole, and the transfer process should be smooth; S3, introducing a polypropylene single-wall corrugated tube as an auxiliary support for the outer layer, and extruding a polyethylene tape, so that the polyethylene tape completely covers the surface of the polypropylene single-wall corrugated tube, and then wrapping the polypropylene single-wall corrugated tube covered with the polyethylene tape around the seam of the inner layer blank, thus completing the winding and forming operation of the outer layer; S4, uniformly cooling and shaping the finished product of step S3; When the polyethylene tape is wound, the temperature of the polyethylene tape is 25-35° C. higher than the temperature of the inner layer.

2. A carat tube production process according to claim 1, characterized in that: The polyethylene material strip comprises a surface layer and an inner layer, the shrinkage rate of the surface layer is 1.5-1.7%, and the shrinkage rate of the inner layer is 2-2.5%.

3. A carat tube production process according to claim 2, characterized in that: The difference in shrinkage between the inner layer and the surface layer is 0.3-0.8%.

4. A carat tube production process according to claim 2 or 3, characterized in that: The raw materials for preparing the surface layer include 1.5-2wt% aminosilane coupling agent modified calcium carbonate, 2.5-3wt% PE organic masterbatch, 0.5-1wt% ultra-high molecular weight polyethylene, 1-2wt% olefin wax and the balance high-density polyethylene, and the raw materials for preparing the inner layer include 2-3wt% epoxy modified polyolefin elastomer, 2-3wt% PE organic masterbatch and the balance high-density polyethylene.

5. A carat tube production process according to claim 4, characterized in that: The molecular weight of the ultra-high molecular weight polyethylene is 4 million to 6 million.

6. The production process of a carat tube according to claim 4, characterized in that: The epoxy-modified polyolefin elastomer is POE graft-modified by glycidyl methacrylate.

7. A carat tube production process according to claim 6, characterized in that: The raw materials for preparing the glycidyl methacrylate graft-modified POE include glycidyl methacrylate, POE elastomer, peroxidation initiator and antioxidant in a weight ratio of (2.5-3.5):100:(0.03-0.05):(0.1-0.2).

8. The production process of a carat tube according to claim 4, characterized in that: The thickness ratio of the surface layer to the inner layer is 1:(3-4).

9. The production process of a carat tube according to claim 4, characterized in that: The melting extrusion temperatures of the inner layer, the surface layer and the inner layer are all 180-190°C.

10. An apparatus used in the production process of a carat tube according to any one of claims 1 to 9, characterized in that: include: A base frame, wherein one side of the base frame is provided with a No. 1 processing station, and the other side of the base frame is provided with a No. 2 processing station; the No. 1 processing station is provided with a core mold, the core mold is connected to a heating mechanism for heating the core mold, and the No. 2 processing station is provided with a core mold for completing inner layer winding; An inner layer extrusion mechanism, the inner layer extrusion mechanism is used for heating, melting and extruding the inner layer raw material; A first moving mechanism, wherein the first moving mechanism controls the inner layer extrusion mechanism to move along the length direction of the core mold, and through the cooperation of the winding mechanism, the extruded inner layer raw material is wound around the surface of the core mold at the first processing station; A polypropylene single-wall corrugated pipe feeding mechanism, wherein the polypropylene single-wall corrugated pipe feeding mechanism conveys the polypropylene single-wall corrugated pipe to the core mold for inner layer winding at the second processing station; A polyethylene material strip extrusion mechanism, wherein the polyethylene material strip extrusion mechanism comprises an inner layer extrusion mechanism and a surface layer extrusion mechanism, wherein the inner layer material extruded by the inner layer extrusion mechanism is firstly used to coat the polypropylene single-wall corrugated pipe internally, and then the surface layer material extruded by the surface layer extrusion mechanism is used to coat the polypropylene single-wall corrugated pipe externally to obtain an outer layer material; A second moving mechanism, wherein the second moving mechanism controls the polyethylene strip extrusion mechanism to move along the length direction of the core mold, and through the cooperation of the winding mechanism, the outer layer material is wound on the core mold where the inner layer winding is completed at the second processing station; A cooling station is used to naturally cool the pipe after the outer layer winding is completed.

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