PVC pipe production process

日期:2022/3/2 8:45:55 / 閱讀: / 來源:本站

PVC pipe production process
PVC resin
A high-speed mixing a low-speed mixing a recycled material
auxiliary
Finished product - flaring - cutting - drawing - cooling and shaping - extrusion figure 1-3 production process flow chart of rigid PVC pipe
The production process of rigid PVC pipe can be divided into three processes: forming material preparation process (also known as extrusion front stage), including proportioning (pretreatment, metering and transportation of raw materials and auxiliary materials), mixing (high speed and low speed), screening (forming powder) or granulation (granular material); Extrusion process; Shaping packaging process (also known as post extrusion stage). The production process conditions are as follows:
(1) At present, most enterprises use high-speed mixer (hot mixer) to mix raw materials, and then use low-speed mixer (cold mixer) to cool the mixed materials.
During high-speed mixing, the heat generated by external heating and shear friction gradually infiltrates the additives into the voids of PVC resin. On the one hand, the additives can be evenly dispersed in the resin. On the other hand, the resin is semi gelatinized, forming loose powder. At 80 ~ 120 ℃, the PVC resin particles swell and the particle size tends to be uniform. At the same time, considering that the temperature is above 100 ℃, there is pressure and the melt is formed into the required shape. The extruder head of rigid PVC pipe is generally thread head. The process parameters of each part are: die connector temperature 165 ℃, die temperature 170 ℃, 170C, 165 ℃, 180 ℃, 190 ℃, melt pressure 250Mpa and melt temperature 195 ℃.
(3) The tube from the process machine mould is cooled to harden and set. Generally, sizing sleeve is used for outer diameter sizing and inner diameter sizing. The outer diameter setting structure is relatively simple and easy to operate, which is widely used in China. The length of the sizing sleeve with fixed outer diameter is generally 3 times of its inner diameter, and the inner diameter of the sizing sleeve shall be slightly larger than (generally no more than 2mm) the nominal size of the outer diameter of the pipe. The cooling methods of pipes include water immersion cooling and spray cooling, and the more commonly used is spray cooling.
(4) The operation of the traction device of the traction process provides a certain traction force and traction speed for the pipe extruded by the machine head, leads out the pipe evenly, and adjusts the wall thickness of the pipe by adjusting the traction speed. The traction speed is required to be very uniform and stepless speed regulation. The traction speed depends on the extrusion speed. Generally, the traction speed is 1% ~ 3% faster than the extrusion speed.
3. Performance index
The performance indexes of pipes are divided into appearance quality and internal quality. The appearance quality requirements are: the surface is smooth and flat, there is no shunting trace, the section bubble is dense and uniform, and the size meets the tolerance requirements. The internal quality of pipes is mainly tested as follows: ① Vicat softening temperature is greater than 79 ℃; The yield tensile stress is greater than 40MPa; The flat test is pressed to the outer diameter of 112 without fracture, and the hydraulic test is qualified; ② The drop hammer impact test is qualified if the drop hammer is 1.0kg and falls freely from a height of 1000mm, and the products do not show cracks, crazing and cracking; ③ The dichloroethylene immersion test is qualified if there is no hair. Example 8r-pvc flared pipe is light and beautiful, acid and alkali resistant, especially the drinking polyvinyl chloride (R-PVC) flared pipe with simple connection, excellent pressure resistance and water tightness, which fully shows its application advantages in construction and other industries. This example introduces the flared pipe produced by introducing foreign equipment and selecting all domestic raw materials.

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