PVC double wall corrugated pipe

DATE：2022/5/24 9:59:05 / READ： / SOURCE：This station

PVC double wall corrugated pipe

As a light pipe, PVC double wall corrugated pipe is composed of inner and outer layers. The inner wall is smooth and the outer wall is hollow corrugated. Because its appearance structure can be changed, it has the advantages of high ring stiffness, high external pressure and 60% saving of raw materials compared with ordinary PVC pipes. With the localization of corrugated pipe production equipment and raw materials, PVC double wall corrugated pipe has gradually replaced metal pipe, cement pipe and ordinary plastic pipe in low pressure pipelines such as post and Telecommunications set line, building drainage and exhaust, farmland drainage and irrigation. Embossed film production line www.handern.com com
1. Material selection and formula design
PVC resin has poor thermal stability, poor fluidity and poor toughness of materials. In addition, the internal and external flow channels of double wall bellows head are long and the gap is small, and the outlet gap is less than 1mm. Therefore, the quality requirements of materials are extremely strict and easy to process. Therefore, corresponding additives must be added to meet the requirements of processing and products.
(1) the quality of selected materials has a great impact on the quality of double wall bellows. PVC is required to be 60~68mlg, and the thermal decomposition temperature is not less than 140 ℃. In order to improve its thermal stability, tribasic lead sulfate and dibasic lead phosphite with synergistic effect are added, and calcium stearate (cast) with improved thermal stability and lubricity of the system is added. Its calcium content (quantity) is 6.5%7.0%. Cast can improve the gel speed and plasticization, If the calcium content is low, the plasticization of the material is not good and the forming is difficult. Chlorinated polyethylene (CPE) is selected as the impact modifier, and Methacrylate Butadiene Styrene Copolymer (MBS) is used as the processing modifier. Due to the large friction heat and resistance between materials and materials, between materials and barrel and screw, internal and external lubricants must be added to the system, but the dosage must be strictly controlled to balance the internal and external lubrication. The lubricant is added to the machine head at the maximum torque of about 30MPa ~ 75%. Embossed film production line www.handern.com com
2. Main equipment
The unit for producing PVC double wall bellows consists of the following seven parts
(1) The mixing system is composed of high-speed kneader and low-speed kneader. Its function is to mix various raw and auxiliary materials into a uniform multiphase system and discharge the water and volatiles in the materials.
(2) The function of vibrating screen is to screen out impurities and foreign matters in materials. Embossed film production line www.handern.com com
(3) Twin screw extruder is the main equipment for material plasticization. At present, extruder can be divided into parallel twin screw and conical twin screw according to screw structure. Due to the narrow and long die flow channel, large screw torque and head melt pressure, the parallel twin-screw extruder generally can not meet the requirements, so the conical twin-screw extruder is selected. φ 65 / 120 conical twin-screw extruder is selected for bellows below 200mm, and 80 / 145 conical twin-screw extruder is selected for bellows above 200mm.
(4) The core component of the forming of double wall bellows of the machine head lies in the structure and design of the machine head. The mold structure is shown in Figure 1-25. The main feature is that the same model is divided twice at the same time to form two layers of internal and external flow channels. Compressed air is required between the interlayer of the inner and outer flow channels to form an outer ripple on the molding machine module. The inner core mold is provided with compressed air, 5 ~ 10 ℃ cooling water and heater. The inner layer is cooled and formed by the inner sizing sleeve. The surface of the die is externally heated, and the head is connected with the extruder in the form of huff block.
The inner and outer layers of double wall bellows have traction effect.
(5) The forming machine is a special machine tool for forming corrugated pipes. It is used for forming outer corrugated pipes and welding the inner and outer layers of double wall corrugated pipes. It has the function of traction.
(6) The fixed length cutting machine automatically cuts off the pipe in a fixed length.
(7) The pipe expander is mainly used to expand the mouth and shape of plastic pipes, and can also form the socket.
3. Preparation process
(1) process flow: batching - high speed mixing - low speed mixing - Screening - Twin Screw Extruder - head forming - Corrugated forming - fixed length cutting - pipe expansion - finished product.
(2) Process parameters and control points embossed film production line www.handern.com com
1. Kneading process kneading quality directly affects the product quality. The kneading process shall be carried out in strict accordance with the feeding sequence and specified temperature to maintain the consistency and uniformity of materials. The general feeding sequence is: PVC resin powder, stabilizer, impact modifier, processing modifier, filler and lubricant. The discharge temperature of high-speed kneading is about 120 ℃ and that of low-speed cold kneading is below 40 ℃. If the moisture content is too high, the hot kneading temperature shall be appropriately increased, but the agglomeration and agglomeration of materials due to too high temperature must be prevented. After cold mixing, the material barrel must be cleaned to remove the adhered blocks and impurities. If the production material is stored for a long time, it must be stirred again, and its temperature can be controlled at about 110 ℃.
2) Extrusion process. The matching of extrusion process such as temperature, speed and pressure is the key to control product quality. Taking + 110mm pipe as an example, the process is as follows: barrel temperature is 170 ℃ in zone 1, 180 ℃ in zone 2, 185 ℃ in zone 3, 19 in zone 4, 190 ℃ in feed Zone 2, 210 ℃ in die and 190 ℃ in core die; Screw oil temperature 100 ℃; The speed of the main engine is 25 ~ 28R min, and the torque is 75% of the maximum torque; Head melt pressure 25 ~ 30MPa, internal and external air pressure
0.060MPao
4. Precautions
1) Before start-up, the heating areas of the extruder connector and the head of the molding machine should be preheated first. The barrel rises in temperature half an hour later than the head. After the temperature rises to 160 ~ 170 ℃, start the extruder, add cleaning materials, gradually increase the screw speed, pay attention to the torque change at any time, and continue to rise to the normal production temperature. After the cleaning materials clean all the residues in the barrel and screw and the decomposed and discolored materials in the heating process, Observe the material extruded from the die. If it reaches the melting and plasticizing state, there is no powder, uniform color and no decomposition and discoloration, stop the machine and correct the concentricity of the machine head and the forming module again. After correction, it can be added to the production material for production.
2) When the machine is shut down, the hopper stops adding production material and replaces it with cleaning material to make each section of the embossed film production line of the machine barrel and mold www.handern.com Com the temperature drops by 5 ~ 10 ℃, but the die should be heated immediately and maintained at a temperature of about 160 ℃. After all the inner and outer layers of the cleaning materials come out, remove the die heating ring, stop the heating cylinder, control the die body temperature at 160 ~ 170 ℃, and stop the machine immediately after the materials in the standby cylinder are extruded.
3) The temperature of cleaning material and production material must be strictly controlled. When starting up, the material temperature of the inner layer is low, the discharging is slow, and the discharging of the outer layer is fast. Pay attention to extruding and heating the core die at the same time, and strictly control the discharging of the outer layer not too fast. If the discharge of the inner layer is fast and the outer layer is slow, the mandrel stops heating, and cooling water is supplied to the core mold to heat the outer mold and keep the temperature at 160 ~ 167 ℃.

Author：admin

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