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With China Plastic Machinery
With China Plastic Machinery
PVC (Polyvinylchloride), the main component of which is polyvinyl chloride, is bright in color, corrosion-resistant, strong and durable. Since some toxic auxiliary materials such as plasticizers and anti-aging agents are added in the manufacturing process to enhance its heat resistance, toughness, ductility, etc., its products generally do not store food and medicine.
It is a synthetic material that is popular and widely used in the world today. Its global usage ranks second among various synthetic materials. According to statistics, in 1995 alone, the production of PVC in Europe was about 5 million tons, and its consumption was 5.3 million tons. In Germany, the production and consumption of PVC averaged 1.4 million tons. PVC is being produced and used worldwide at a growth rate of 4%. In recent years, the growth rate of PVC in Southeast Asia has been particularly significant, thanks to the urgent need for infrastructure construction in Southeast Asian countries. Among the materials that can produce three-dimensional surface films, PVC is the most suitable material. PVC (polyvinyl chloride), the structural formula of its monomer is CH2=CHClPVC. PVC material has a wide range of uses, with good processing performance, low manufacturing cost, corrosion resistance, insulation and other good characteristics. It is mainly used to make: Prewin PVC cards; PVC OEM; PVC wire; PVC curtains; PVC plastic-coated welded mesh; PVC foam board, PVC ceiling, PVC water pipe, PVC skirting, etc., as well as threading pipes, cable insulation, plastic doors and windows, plastic bags, etc. PVC products can be seen everywhere in our daily life. PVC is used to make various imitation leathers, used in luggage bags, sports products such as basketballs, footballs and rugby. It can also be used to make uniforms and belts for special protective equipment.
China's PVC pipes have developed rapidly in recent years, with an annual growth rate of 8%, while the annual demand growth rate is 2%. Among plastic pipes, PVC pipes have always been far ahead in terms of usage, and they are widely used in water supply and drainage pipes. Due to the relatively mature technology, the investment in product innovation of PVC water supply pipes in recent years is not large, and there are relatively few new products. There are more ordinary products on the market, and fewer high-tech and high-value-added products. Similar general products and low-end products account for the majority, and there are fewer high-end products.
At present, China's plastic pipe production capacity has reached 3 million tons, mainly including three categories of PVC, PE and PP-R pipes. Among them, PVC pipes are the plastic pipes with the largest market share, accounting for nearly 70% of plastic pipes. There are more than 1,600 PVC pipe production lines. The annual production capacity is more than 2.5 million tons. In 2003, the annual output of PVC pipes (pipe fittings) reached more than 1.2 million tons. Among plastic pipes, PVC accounts for 70%, PE accounts for 25%, PP-R accounts for 4%, and others account for 1%.
Process flow of PVC pipe production line
Production processRaw materials + additives preparation ¡ú mixing ¡ú conveying and feeding ¡ú forced feeding ¡ú conical twin-screw extruder ¡ú extrusion die ¡ú sizing sleeve ¡ú spray vacuum shaping box ¡ú immersion cooling water tank ¡ú ink printer ¡ú crawler tractor ¡ú knife lifting and cutting machine ¡ú pipe stacking rack ¡ú finished product inspection and packaging
(1) Raw materials mixing: PVC stabilizer, plasticizer, antioxidant and other auxiliary materials are added to the high-speed mixer in proportion and process. The material is heated to the set process temperature through self-friction between the material and the machine, and then the material is cooled to 40-50 degrees through the cold mixer; then it can be added to the hopper of the extruder.
(2) Extruder part: This machine is equipped with a quantitative feeding device to match the extrusion amount with the feeding amount to ensure stable extrusion of the product. Due to the characteristics of the conical screw, the feeding section has a larger diameter, and the heat transfer area and shear rate of the material are relatively large, which is conducive to the plasticization of the material. The diameter of the screw in the metering section is small, which reduces the heat transfer area and the shear rate of the melt, so that the melt can be extruded at a lower temperature. When the screw rotates in the barrel, the PVC mixture is plasticized and pushed to the die, thereby achieving compaction, melting, mixing and homogenization; and achieving the purpose of exhaust and dehydration. The feeding device and the screw drive device adopt variable frequency speed regulation, which can achieve synchronous speed regulation.
(3) Extrusion die part: After compaction, melting, mixing and homogenization of PVC, subsequent materials are pushed to the die through the screw. The extrusion die is a key component for pipe forming.
(4) The vacuum shaping water tank is used for shaping and cooling of pipes. The vacuum shaping water tank is equipped with a vacuum system and a water circulation system for shaping and cooling. The stainless steel tank is cooled by circulating water spraying. The vacuum shaping water tank is equipped with a forward and backward moving device and a left and right, height adjustment manual device.
(5) The traction machine is used to continuously and automatically lead the cooled and hardened pipes out of the machine head, and the speed is adjusted by frequency conversion.
(6) The cutting machine: After being controlled by the travel switch according to the required length, it automatically cuts and delays the turning of the frame to implement flow production. The cutting machine uses the fixed length switch signal as an instruction to complete the entire cutting process. During the cutting process, it keeps synchronization with the pipe operation. The cutting process is completed by electric and pneumatic drives. The cutting machine is equipped with a dust suction device to suck out the debris generated by cutting in time and recycle it.
(7) The turning action of the turning rack is realized by the cylinder through the air circuit control. The turning rack is equipped with a limit device. When the cutting saw cuts the pipe, the pipe continues to be transported. After a delay, the cylinder starts working to realize the turning action and achieve the purpose of unloading. After unloading, it automatically resets after a delay of several seconds and waits for the next cycle.
(1) PVC pipe refers to the main raw material of the pipe made of PVC resin powder. The types of PVC pipes are generally divided according to the purpose of the pipe: drainage pipes, water supply pipes, wire pipes, cable sheath pipes...
Because the raw material formula is different, the pressure resistance and other indicators of various types of pipes are different.
PVC water supply pipes are used in water supply projects of buildings with water supply accessories.
PVC drainage pipes are used for sewage discharge...
IV. Methods for distinguishing the quality of PVC pipes
(1) First look at the surface finish and whiteness.
(2) Drop the sample. Those that break easily are usually high-calcium products. Of course, it is acceptable if it meets your requirements and the price is right.
(3) Use your feet to step on the edge of the sample to see if it can be cracked, or the elongation at break after cracking.
(4) Weather resistance is quite troublesome. The most direct way is to put it in a high temperature and high light place for a few days to see the surface change rate, but it is too time-consuming. Just focus on the first three items.
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