Injection molding process method for flaring of large steel strip reinforced polyethylene spiral corrugated pipe

Abstract

The invention belongs to the technical field of plastic processing, and particularly relates to an injection molding process method for flaring a large steel strip reinforced polyethylene spiral corrugated pipe. The process method comprises the following key steps: firstly, selecting a recycled material for blending linear polyethylene, and performing thorough drying treatment to ensure the drying degree of the material; then, the treated recycled material is mixed with high-density polyethylene; and then, the mixed material is subjected to injection molding. Particularly, injection molding is subdivided into six stages, then a pressure maintaining molding stage is carried out, and the pressure maintaining stage is divided into three stages. The refined control not only significantly improves the quality and performance of the product, but also greatly improves the stability and yield of the reclaimed material for polyethylene blending in the injection molding process. And an efficient and reliable novel method is provided for flaring manufacturing of the large steel strip reinforced polyethylene spiral corrugated pipe.

Description

Technical Field

[0001] The invention relates to the technical field of plastic pipe processing, in particular to a high-efficiency injection molding process for a flared portion of a large steel-belt reinforced polyethylene spiral corrugated pipe. Technical Background

[0002] In the plastic pipe manufacturing industry, large steel-reinforced polyethylene spiral corrugated pipes are widely used due to their excellent corrosion resistance, light weight, high strength and good drainage performance. However, this type of pipe faces many technical challenges in the manufacturing process of the flared part. The flared part is the key area of ​​the pipe connection, and its quality and performance are directly related to the stability and safety of the entire pipe system.

[0003] When dealing with the expansion manufacturing of large steel-reinforced polyethylene spiral corrugated pipes, the traditional injection molding process often causes defects such as poor coating, weak bonding, and unstable dimensions at the expansion part due to problems such as low melt flow rate, uneven filling, and fast cooling speed. These problems not only affect the appearance and service life of the pipe, but may also cause safety hazards such as leakage in actual applications.

[0004] In particular, for large pipes with specifications of DN800 and above, the injection weight of the flared part is large and the dimensional accuracy is high, which places more stringent requirements on the injection molding process. How to ensure the uniform flow and full filling of the melt in the mold while avoiding shrinkage and deformation during the cooling process has become a key problem that needs to be solved urgently in current technology.

[0005] In view of this, the present invention proposes an injection molding process method for the expansion of large steel belt reinforced polyethylene spiral corrugated pipes, aiming to achieve high-quality and high-efficiency production of the expansion part by optimizing injection molding parameters, improving mold design and adopting advanced material blending technology. This method can not only improve the overall performance and service life of the pipe, but also provide strong technical support for the sustainable development of the plastic pipe manufacturing industry.

[0006] However, the existing molding process cannot meet this demand, so a new injection molding process is needed to solve this problem. Summary of the invention

[0007] Based on the above technical background, the main purpose of the present invention is to provide an injection molding process method for expanding the mouth of a large steel-reinforced polyethylene spiral corrugated pipe. The injection molding process method aims to improve the structural strength and sealing performance of large plastic pipes by optimizing the injection molding process, meet the needs of various infrastructure and industrial applications for high-quality, large-diameter plastic pipes, and overcome the shortcomings of the prior art.

[0008] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0009] The present invention provides an injection molding process for expanding a large steel-belt reinforced polyethylene spiral corrugated pipe, the injection molding process comprising the following steps:

[0010] Step 1, drying the linear polyethylene blended with recycled materials;

[0011] Step 2: Add high-density polyethylene to the dried linear polyethylene blending recycled material, and then perform injection molding and pressure holding molding in sequence to obtain a large steel belt reinforced polyethylene spiral corrugated pipe expansion.

[0012] In step 1,

[0013] Preferably, the linear polyethylene blending recycled material is dried at 100-120° C. for 3-5 hours.

[0014] In step 2,

[0015] Preferably, the ratio of the amount of the recycled material for linear polyethylene blending to the amount of high-density polyethylene added is 10-20%:1.

[0016] Preferably, the injection molding adopts six-stage segmented injection: the pressure of the first-stage injection is 60-80%, the speed of the first-stage injection is 70-80%, and the position of the first-stage injection is 300-400 mm;

[0017] The pressure of the second-stage injection is 80-100%, the speed of the second-stage injection is 90-100%, and the position of the second-stage injection is 100-200mm;

[0018] The pressure of the third-level injection is 50-70%, the speed of the third-level injection is 50-70%, and the position of the third-level injection is 80-100mm;

[0019] The pressure of the fourth-level injection is 30-50%, the speed of the fourth-level injection is 20-40%, and the position of the fourth-level injection is 60-80 mm;

[0020] The pressure of the fifth-stage injection is 20-30%, the speed of the fifth-stage injection is 5-20%, and the position of the fifth-stage injection is 40-50 mm;

[0021] The pressure of the sixth-stage injection is 20-25%, the speed of the sixth-stage injection is 3-7%, and the position of the sixth-stage injection is 30-50 mm.

[0022] More preferably, the pressure of the first injection is 70%, the speed of the first injection is 75%, and the position of the first injection is 350 mm;

[0023] The pressure of the second injection is 90%, the speed of the second injection is 95%, and the position of the second injection is 150mm;

[0024] The pressure of the third-level injection is 60%, the speed of the third-level injection is 60%, and the position of the third-level injection is 90mm;

[0025] The pressure of the fourth-level injection is 40%, the speed of the fourth-level injection is 30%, and the position of the fourth-level injection is 70mm;

[0026] The pressure of the fifth-stage injection is 25%, the speed of the fifth-stage injection is 10%, and the position of the fifth-stage injection is 45 mm;

[0027] The pressure of the sixth-level injection is 21%, the speed of the sixth-level injection is 5%, and the position of the sixth-level injection is 40mm.

[0028] Preferably, the three stages of pressure holding molding include: the pressure of the first stage is 20-40%, the speed of the first stage is 20-40%, and the pressure holding time of the first stage is 5-20s;

[0029] The pressure of the second stage is 60-70%, the speed of the second stage is 10-30%, and the holding time of the second stage is 20-40s;

[0030] The pressure of the third stage is 10-30%, the speed of the third stage is 3-7%, and the holding time of the third stage is 50-70s.

[0031] More preferably, the three stages of pressure holding molding include: the pressure of the first stage is 30%, the speed of the first stage is 30%, and the holding time of the first stage is 10s;

[0032] The pressure in the second stage is 65%, the speed in the second stage is 20%, and the holding time in the second stage is 30s;

[0033] The pressure in the third stage is 20%, the speed in the third stage is 5%, and the holding time in the third stage is 60s.

[0034] The beneficial effects of the present invention are:

[0035] (1) The present invention divides injection molding into six stages, each of which is carefully designed to ensure that the material can fill the mold evenly and smoothly. Next, it enters the pressure-maintaining molding stage, which is also scientifically divided into three stages. It aims to further optimize the molding effect and dimensional stability of the product through continuous pressure control, and effectively reduce the occurrence of surface defects of the product, such as shrinkage holes and bubbles. This refined control not only significantly improves the quality and performance of the product, but also greatly improves the stability and yield rate of recycled materials for polyethylene blending during the injection molding process. It provides an efficient and reliable new method for the expansion of large steel belt reinforced polyethylene spiral corrugated pipes.

[0036] (2) The polyethylene blend used in the present invention complies with the CJ / 225-2011 standard, ensuring that it has both good rigidity and toughness, as well as excellent resistance to environmental stress cracking, resistance to slow crack growth, and resistance to rapid crack propagation.

[0037] (3) During the injection process, the present invention effectively solves the problems of poor melt fluidity and insufficient mold filling capacity by precisely controlling the injection speed and pressure. By properly adjusting the injection speed, unstable melt flow caused by too fast injection and too fast melt cooling caused by too slow injection are avoided, thereby ensuring that the melt can evenly and stably fill the mold cavity.

[0038] (4) During the pressure holding stage, the present invention adopts a refined control strategy. By setting the appropriate pressure holding pressure and time in stages, it effectively prevents quality problems such as shrinkage and deformation of the product during the cooling and solidification process, and further improves the dimensional stability and overall performance of the product.

[0039] (5) The present invention significantly improves the stability and yield rate of recycled polyethylene blending materials during the injection molding process by optimizing the process parameters of injection molding and pressure-holding molding, and provides an efficient and reliable new method for the expansion production of large steel belt reinforced polyethylene spiral corrugated pipes.

[0040] At the same time, the molding process of the present invention does not require special equipment and process conditions. The obtained large steel belt reinforced polyethylene spiral corrugated pipe expansion has good mechanical properties, meets production standards and use standards, and has good application prospects in the field of injection molding. DETAILED DESCRIPTION

[0041] The present invention will be described in detail below, and the characteristics and advantages of the present invention will become clearer and more distinct with the description.

[0042] The present invention provides an injection molding process for expanding a large steel-belt reinforced polyethylene spiral corrugated pipe, the injection molding process comprising the following steps:

[0043] Step 1, drying the linear polyethylene blended with recycled materials;

[0044] Step 2: Add high-density polyethylene to the dried linear polyethylene blending recycled material, and then perform injection molding and pressure-holding molding in sequence to obtain a large steel belt reinforced polyethylene spiral corrugated pipe expansion.

[0045] The above steps are described in detail below.

[0046] In step 1, drying is performed in an oven.

[0047] The linear polyethylene blended recycled material is dried at 100-120°C for 3-5 hours.

[0048] Preferably, the linear polyethylene blending recycled material is dried at 110° C. for 4 hours to remove moisture and other impurities therein.

[0049] In step 2, the ratio of the amount of the recycled linear polyethylene blending material to the amount of the high-density polyethylene pipe material added is 10-20%:1.

[0050] The recycled materials for polyethylene blending meet the standards.

[0051] Before the injection molding operation, the mold needs to be cleaned, dried and heated to ensure that the mold is in good working condition.

[0052] The barrel temperature of the injection molding machine is set to six zones, from the hopper to the storage cylinder, which are set to 180-195°C, 195-205°C, 200-210°C, 205-215°C, 210-220°C, and 215-225°C respectively. The storage cylinder temperature is set to four zone temperatures, which are set to 195-205°C, 200-210°C, 205-215°C, and 210-220°C respectively. The nozzle temperature is set to two zone temperatures, which are set to 205-215°C and 210-220°C respectively. The mold is not heated.

[0053] Preferably, the barrel temperature of the injection molding machine is set to six zones, from the hopper to the storage cylinder, which are set to 190°C, 200°C, 205°C, 210°C, 215°C, and 220°C in sequence; the storage cylinder temperature is set to four zone temperatures, which are set to 200°C, 205°C, 210°C, and 215°C in sequence; the nozzle temperature is set to two zone temperatures, which are set to 210°C and 215°C in sequence; the mold is not heated to ensure that the raw material is plasticized and melted in the barrel.

[0054] The injection molding adopts six-stage segmented injection: the pressure of the first-stage injection is 60-80%, the speed of the first-stage injection is 70-80%, and the position of the first-stage injection is 300-400 mm.

[0055] The pressure of the second-stage injection is 80-100%, the speed of the second-stage injection is 90-100%, and the position of the second-stage injection is 100-200 mm.

[0056] The pressure of the third-level injection is 50-70%, the speed of the third-level injection is 50-70%, and the position of the third-level injection is 80-100 mm.

[0057] The pressure of the fourth-stage injection is 30-50%, the speed of the fourth-stage injection is 20-40%, and the position of the fourth-stage injection is 60-80 mm.

[0058] The pressure of the fifth-stage injection is 20-30%, the speed of the fifth-stage injection is 5-20%, and the position of the fifth-stage injection is 40-50 mm.

[0059] The pressure of the sixth-stage injection is 20-25%, the speed of the sixth-stage injection is 3-7%, and the position of the sixth-stage injection is 30-50 mm.

[0060] Preferably, the pressure of the first-stage injection is 70%, the speed of the first-stage injection is 75%, and the position of the first-stage injection is 350 mm.

[0061] The pressure of the second-stage injection is 90%, the speed of the second-stage injection is 95%, and the position of the second-stage injection is 150mm.

[0062] The pressure of the third-level injection is 60%, the speed of the third-level injection is 60%, and the position of the third-level injection is 90mm.

[0063] The pressure of the fourth-level injection is 40%, the speed of the fourth-level injection is 30%, and the position of the fourth-level injection is 70mm.

[0064] The pressure of the fifth-level injection is 25%, the speed of the fifth-level injection is 10%, and the position of the fifth-level injection is 45 mm.

[0065] The pressure of the sixth-level injection is 21%, the speed of the sixth-level injection is 5%, and the position of the sixth-level injection is 40mm.

[0066] The injection molding of the present invention is carried out by adjusting the injection parameters according to the method of filling at a slow speed at the beginning, a fast speed in the middle and a slow speed at the end. The injection molding adopted by the present invention can control the water ripple defect of the melt at the gate of the product at the beginning of injection, the fast speed in the middle can avoid the melt temperature from dropping too fast, and the slow speed at the end can avoid defects such as poor exhaust of trapped air, material shortage caused by burning, welding marks, etc., thereby ensuring the filling effect of the product and reducing surface defects.

[0067] After the injection is completed, the product is kept under pressure to prevent deformation or shrinkage. During the pressure holding process, the nozzle of the injection molding machine continuously feeds material into the cavity, and the pressure holding time is set according to the thickness of the product. In the later stage of pressure holding, the material density continues to increase, and the plastic part is gradually formed. The pressure holding stage should continue until the gate is solidified and sealed.

[0068] The pressure holding molding includes three stages: the first stage is to solidify the outer surface of the expanded injection part, the second stage is to prevent shrinkage, and the third stage is to solidify the cooling of the annular point gate of the branch runner. The best product quality can be obtained by controlling the pressure holding time and pressure in each stage.

[0069] The three stages of pressure-holding molding include: the pressure of the first stage is 20-40%, the speed of the first stage is 20-40%, and the pressure-holding time of the first stage is 5-20s.

[0070] The pressure in the second stage is 60-70%, the speed in the second stage is 10-30%, and the holding time in the second stage is 20-40s.

[0071] The pressure of the third stage is 10-30%, the speed of the third stage is 3-7%, and the holding time of the third stage is 50-70s.

[0072] Preferably, the three stages of pressure-holding molding include: the pressure of the first stage is 30%, the speed of the first stage is 30%, and the pressure-holding time of the first stage is 10s.

[0073] The pressure in the second stage is 65%, the speed in the second stage is 20%, and the holding time in the second stage is 30s.

[0074] The pressure in the third stage is 20%, the speed in the third stage is 5%, and the holding time in the third stage is 60s.

[0075] After the mold is closed, the injection pressure holding process starts immediately, and this stage needs to continue until the gate is completely solidified and sealed. The present invention not only greatly reduces the risk of defects such as water ripples on the surface of the product by finely controlling key parameters such as injection speed and temperature, but also effectively avoids the occurrence of burning by optimizing the material flow characteristics.

[0076] During the injection molding process, the present invention focuses on the control of the filling and shrinkage compensation stages to ensure sufficient filling and density of each part of the product. At the same time, through the use of multi-stage injection molding and multi-stage pressure holding technology, the residual stress is further reduced and the overall quality and performance of the product are improved. During the injection and pressure holding process, the nozzle of the injection molding machine continuously feeds material into the cavity, and the pressure holding time is set according to the thickness of the product. In the later stage of pressure holding, the material density continues to increase, and the plastic part is gradually formed. The pressure holding stage must continue until the gate is solidified and sealed. The present invention reduces the possibility of surface defects such as water ripples on the product by accurately controlling parameters such as injection speed and temperature. The use of a diverter annular point gate is conducive to the uniform flow of materials and prevents the occurrence of burning.

[0077] In addition, the injection molding process of the present invention also cleverly combines the rear-end exhaust technology to further optimize the molding process and ensure the high-quality output of polyethylene blended recycled material products. This series of innovations not only significantly improves production efficiency, but also significantly improves product quality.

[0078] It is worth mentioning that the molding process of the present invention does not require special equipment or harsh process conditions, has extremely high versatility and applicability, and can be widely extended to all aspects of the injection molding field, providing strong support for the efficient and high-quality development of the industry.

[0079] Example

[0080] The present invention is further described below by means of specific examples. These embodiments are only intended to illustrate the present invention but are not intended to limit the scope of the present invention.

[0081] The technical parameters of the injection molding machine used in the embodiments of the present invention are: injection device: screw diameter 120mm, plunger diameter 175mm, theoretical volume 27901g, injection stroke 1160mm, injection rate 997g / s. The barrel temperature is set to six zones from the hopper to the storage cylinder, the storage cylinder temperature is set to four zones, and the nozzle temperature is set to two zones.

[0082] The performance parameters of the linear polyethylene recycled material used in the embodiments of the present invention are as follows: melt index: 1.5-2.5 g / 10 min (test method GB / T 3682);

[0083] Density: 0.917~0.923g / cm 3 (Test method GB / T 1033);

[0084] Mechanical properties:

[0085] Tensile breaking stress: ≥12MPa (test method GB / T 1040);

[0086] Tensile yield stress: ≥8.3MPa (test method GB / T 1040);

[0087] Elongation at break: ≥500% (test method GB / T 1040).

[0088] The performance parameters of the YGH051T high-density polyethylene pipe material ("North Star Double Peak" produced by Borealis) used in the embodiments of the present invention are as follows:

[0089] Melt flow rate (MFR190℃, 5kg): 0.75g·(10min) -1 ;

[0090] Density: 0.94g / cm 3 ;

[0091] Elongation at break:>600%;

[0092] Tensile yield strength: 23MPa;

[0093] Tensile modulus: 1000MPa;

[0094] Thermal stability: stable at 210℃ for 15min;

[0095] Resistance to environmental stress cracking: >10000h.

[0096] Example 1: DN800 pipe

[0097] An injection molding process for expanding a large steel-belt reinforced polyethylene spiral corrugated pipe comprises the following steps:

[0098] The recycled linear polyethylene blending material was placed in an oven and heated to 85°C for 1.5 hours to remove moisture and other impurities.

[0099] Add high-density polyethylene to the dried linear polyethylene blending recycled material, then add it to the injection molding machine, and start the injection molding machine to start injection. The ratio of the amount of the linear polyethylene blending recycled material to the high-density polyethylene pipe material (YGH051T) is 11:89. Before the injection molding operation, the mold needs to be cleaned, dried and heated to ensure that the mold is in good working condition. The barrel temperature of the injection molding machine is set to six zones, starting from the hopper to the storage cylinder, set to 190℃, 200℃, 205℃, 210℃, 215℃, and 220℃ in sequence. The storage cylinder temperature is set to four zone temperatures, which are set to 200℃, 205℃, 210℃, and 215℃ in sequence. The nozzle temperature is set to two zone temperatures, which are set to 210℃ and 215℃ in sequence. The mold is not heated to ensure that the raw materials are plasticized and melted in the barrel.

[0100] Injection molding adopts six-stage injection: the pressure of the first-stage injection is 60%, the speed of the first-stage injection is 70%, and the position of the first-stage injection is 300mm.

[0101] The pressure of the second-stage injection is 90%, the speed of the second-stage injection is 95%, and the position of the second-stage injection is 150mm.

[0102] The pressure of the third-level injection is 60%, the speed of the third-level injection is 60%, and the position of the third-level injection is 90mm.

[0103] The pressure of the fourth-level injection is 40%, the speed of the fourth-level injection is 30%, and the position of the fourth-level injection is 70mm.

[0104] The pressure of the fifth-level injection is 25%, the speed of the fifth-level injection is 10%, and the position of the fifth-level injection is 45 mm.

[0105] The pressure of the sixth-level injection is 21%, the speed of the sixth-level injection is 5%, and the position of the sixth-level injection is 40mm.

[0106] After the injection is completed, the product is kept under pressure to prevent deformation or shrinkage. During the pressure holding process, the nozzle of the injection molding machine continuously feeds material into the cavity, and the pressure holding time is set according to the thickness of the product. In the later stage of pressure holding, the material density continues to increase, and the plastic part is gradually formed. The pressure holding stage should continue until the gate is solidified and sealed.

[0107] The pressure holding molding includes three stages: the pressure of the first stage is 30%, the speed of the first stage is 30%, and the holding time of the first stage is 10s.

[0108] The pressure in the second stage is 65%, the speed in the second stage is 20%, and the holding time in the second stage is 30s.

[0109] The pressure in the third stage is 20%, the speed in the third stage is 5%, and the holding time in the third stage is 60s.

[0110] The finished product is taken out of the mold and quality checked. If there are defects on the product, such as surface water ripples, burning phenomenon, weld lines, etc., the injection molding process needs to be adjusted and optimized.

[0111] Example 2: DN1000 pipe as an example

[0112] An injection molding process for expanding a large steel-belt reinforced polyethylene spiral corrugated pipe comprises the following steps:

[0113] The recycled linear polyethylene blending material was placed in an oven and heated to 100°C for 5 hours to remove moisture and other impurities.

[0114] Add high-density polyethylene to the dried linear polyethylene blending recycled material, then add it to the injection molding machine, and start the injection molding machine to start injection. The ratio of the amount of the linear polyethylene blending recycled material to the high-density polyethylene pipe material (YGH051T) is 13:87. Before the injection molding operation, the mold needs to be cleaned, dried and heated to ensure that the mold is in good working condition. The barrel temperature of the injection molding machine is set to six zones, starting from the hopper to the storage cylinder, and set to 190°C, 200°C, 205°C, 210°C, 215°C, and 220°C in sequence. The storage cylinder temperature is set to four zone temperatures, which are set to 200°C, 205°C, 210°C, and 215°C in sequence. The nozzle temperature is set to two zone temperatures, which are set to 210°C and 215°C in sequence. The mold is not heated to ensure that the raw materials are plasticized and melted in the barrel.

[0115] Injection molding adopts six-stage injection: the pressure of the first-stage injection is 70%, the speed of the first-stage injection is 75%, and the position of the first-stage injection is 350mm.

[0116] The pressure of the second-level injection is 80%, the speed of the second-level injection is 90%, and the position of the second-level injection is 100mm.

[0117] The pressure of the third-level injection is 50%, the speed of the third-level injection is 50%, and the position of the third-level injection is 80mm.

[0118] The pressure of the fourth-level injection is 30%, the speed of the fourth-level injection is 20%, and the position of the fourth-level injection is 60mm.

[0119] The pressure of the fifth-level injection is 20%, the speed of the fifth-level injection is 5%, and the position of the fifth-level injection is 40mm.

[0120] The pressure of the sixth-level injection is 20%, the speed of the sixth-level injection is 3%, and the position of the sixth-level injection is 30mm.

[0121] After the injection is completed, the product is kept under pressure to prevent deformation or shrinkage. During the pressure holding process, the nozzle of the injection molding machine continuously feeds material into the cavity, and the pressure holding time is set according to the thickness of the product. In the later stage of pressure holding, the material density continues to increase, and the plastic part is gradually formed. The pressure holding stage should continue until the gate is solidified and sealed.

[0122] The pressure holding molding includes three stages: the pressure of the first stage is 20%, the speed of the first stage is 20%, and the holding time of the first stage is 20s.

[0123] The pressure in the second stage is 60%, the speed in the second stage is 10%, and the holding time in the second stage is 40s.

[0124] The pressure in the third stage is 10%, the speed in the third stage is 3%, and the holding time in the third stage is 70s.

[0125] The finished product is taken out of the mold and quality checked. If there are defects on the product, such as surface water ripples, burning phenomenon, weld lines, etc., the injection molding process needs to be adjusted and optimized.

[0126] Example 3: Taking DN1200 pipe as an example

[0127] An injection molding process for expanding a large steel-belt reinforced polyethylene spiral corrugated pipe comprises the following steps:

[0128] The recycled linear polyethylene blending material was placed in an oven and heated to 120°C for 3 hours to remove moisture and other impurities.

[0129] Add high-density polyethylene to the dried linear polyethylene blending recycled material, then add it to the injection molding machine, and start the injection molding machine to start injection. The ratio of the amount of the linear polyethylene blending recycled material to the high-density polyethylene pipe material (YGH051T) is 16:84. Before the injection molding operation, the mold needs to be cleaned, dried and heated to ensure that the mold is in good working condition. The barrel temperature of the injection molding machine is set to six zones, starting from the hopper to the storage cylinder, and set to 190℃, 200℃, 205℃, 210℃, 215℃, and 220℃ in sequence. The storage cylinder temperature is set to four zone temperatures, which are set to 200℃, 205℃, 210℃, and 215℃ in sequence. The nozzle temperature is set to two zone temperatures, which are set to 210℃ and 215℃ in sequence. The mold is not heated to ensure that the raw materials are plasticized and melted in the barrel.

[0130] Injection molding adopts six-stage injection: the pressure of the first-stage injection is 80%, the speed of the first-stage injection is 80%, and the position of the first-stage injection is 400mm.

[0131] The pressure of the second-level injection is 100%, the speed of the second-level injection is 100%, and the position of the second-level injection is 200mm.

[0132] The pressure of the third-level injection is 70%, the speed of the third-level injection is 70%, and the position of the third-level injection is 100mm.

[0133] The pressure of the fourth-level injection is 50%, the speed of the fourth-level injection is 40%, and the position of the fourth-level injection is 80mm.

[0134] The pressure of the fifth-level injection is 30%, the speed of the fifth-level injection is 20%, and the position of the fifth-level injection is 50mm.

[0135] The pressure of the sixth-level injection is 25%, the speed of the sixth-level injection is 7%, and the position of the sixth-level injection is 50mm.

[0136] After the injection is completed, the product is kept under pressure to prevent deformation or shrinkage. During the pressure holding process, the nozzle of the injection molding machine continuously feeds material into the cavity, and the pressure holding time is set according to the thickness of the product. In the later stage of pressure holding, the material density continues to increase, and the plastic part is gradually formed. The pressure holding stage should continue until the gate is solidified and sealed.

[0137] The pressure holding molding includes three stages: the pressure of the first stage is 40%, the speed of the first stage is 40%, and the holding time of the first stage is 5s.

[0138] The pressure in the second stage is 70%, the speed in the second stage is 30%, and the holding time in the second stage is 20s.

[0139] The pressure in the third stage is 30%, the speed in the third stage is 7%, and the holding time in the third stage is 50s.

[0140] The finished product is taken out of the mold and quality checked. If there are defects on the product, such as surface water ripples, burning phenomenon, weld lines, etc., the injection molding process needs to be adjusted and optimized.

[0141] Experimental example

[0142] Experimental Example 1 Mechanical Properties Test

[0143] The MFR (melt index) value and mechanical property test were performed on the expansion of the large steel belt reinforced polyethylene spiral corrugated pipe obtained in Examples 1-3. The tensile strength was tested according to GB / T8804.3, and the tensile strength must be ≥20.7MPa to meet the production standard, the elastic modulus was tested according to GB / T 9341, and the elastic modulus must be ≥758MPa to meet the production standard, and the MFR (melt index) was tested according to GB / T 3682, and MFR (5kg, 190°C) / (g / 10min) must be ≤1.0 to meet the production standard. The test results are shown in Table 1. In Table 1, YGH051T is a high-density polyethylene pipe material.

[0144] Table 1

[0145]

[0146] It can be seen from Table 1 that the melt index of Examples 1-3 is ≤1.0g / 10min, the tensile strength of the expanded large steel belt reinforced polyethylene spiral corrugated pipes prepared in Examples 1-3 is ≥20.7MPa, and the elastic modulus is ≥758MPa, indicating that the expanded large steel belt reinforced polyethylene spiral corrugated pipes prepared in the present invention meet the production standards.

[0147] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A large steel belt reinforced polyethylene spiral corrugated pipe expansion injection molding process, characterized in that: The injection molding process comprises the following steps: Step 1, drying the linear polyethylene blended with recycled materials; Step 2: Add high-density polyethylene to the dried linear polyethylene blending recycled material, and then perform injection molding and pressure holding molding in sequence to obtain a large steel belt reinforced polyethylene spiral corrugated pipe expansion.

2. The injection molding process according to claim 1, characterized in that: In step 1, The linear polyethylene blended recycled material is dried at 100-120°C for 3-5 hours.

3. The injection molding process according to claim 1, characterized in that: In step 2, The ratio of the added amount of the recycled material for linear polyethylene blending to the high-density polyethylene is 10-20%:

1.

4. The injection molding process according to claim 1, characterized in that: In step 2, The injection molding adopts six-stage segmented injection: the pressure of the first-stage injection is 60-80%, the speed of the first-stage injection is 70-80%, and the position of the first-stage injection is 300-400mm; The pressure of the second-stage injection is 80-100%, the speed of the second-stage injection is 90-100%, and the position of the second-stage injection is 100-200mm; The pressure of the third-level injection is 50-70%, the speed of the third-level injection is 50-70%, and the position of the third-level injection is 80-100mm; The pressure of the fourth-level injection is 30-50%, the speed of the fourth-level injection is 20-40%, and the position of the fourth-level injection is 60-80 mm; The pressure of the fifth-stage injection is 20-30%, the speed of the fifth-stage injection is 5-20%, and the position of the fifth-stage injection is 40-50 mm; The pressure of the sixth-stage injection is 20-25%, the speed of the sixth-stage injection is 3-7%, and the position of the sixth-stage injection is 30-50 mm.

5. The injection molding process according to claim 4, characterized in that: The pressure of the first injection is 70%, the speed of the first injection is 75%, and the position of the first injection is 350mm; The pressure of the second injection is 90%, the speed of the second injection is 95%, and the position of the second injection is 150mm; The pressure of the third-level injection is 60%, the speed of the third-level injection is 60%, and the position of the third-level injection is 90mm; The pressure of the fourth-level injection is 40%, the speed of the fourth-level injection is 30%, and the position of the fourth-level injection is 70mm; The pressure of the fifth-stage injection is 25%, the speed of the fifth-stage injection is 10%, and the position of the fifth-stage injection is 45 mm; The pressure of the sixth-level injection is 21%, the speed of the sixth-level injection is 5%, and the position of the sixth-level injection is 40mm.

6. The injection molding process according to claim 1, characterized in that: In step 2, The three stages of pressure holding molding include: the pressure of the first stage is 20-40%, the speed of the first stage is 20-40%, and the pressure holding time of the first stage is 5-20s; The pressure of the second stage is 60-70%, the speed of the second stage is 10-30%, and the holding time of the second stage is 20-40s; The pressure of the third stage is 10-30%, the speed of the third stage is 3-7%, and the holding time of the third stage is 50-70s.

7. The injection molding process according to claim 6, characterized in that: The three stages of pressure holding molding include: the pressure of the first stage is 30%, the speed of the first stage is 30%, and the pressure holding time of the first stage is 10s; The pressure in the second stage is 65%, the speed in the second stage is 20%, and the holding time in the second stage is 30s; The pressure in the third stage is 20%, the speed in the third stage is 5%, and the holding time in the third stage is 60s.

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