ming process of CPVC pipe#pipe extrusion#CPVC pipe#PVC pipe

The extrusion forming process conditions of CPVC pipe are similar to those of ordinary PVCpipe , but the difference is that the quality requirement of the equipment parts for extrusion forming are higher; The fluctuation range control requirement of the process temperature is more stringent.

(1)The sequence of CPVC pipe extrusion forming process:

 measure all kinds of raw materials according to the formula of CPVC pipe forming material→Put the raw materials into the mixing machine and mix evenly→Mix well, cool and stir→make the plasticized raw materials show a molten state→Mold forming tube blank→Vacuum setting diameter cooling setting→Cool down the pipe with the cooling water tank→haul off→ identification marking→cutting→Pipe end expansion→check out→Packaging into the warehouse

(2)Equipment selection: 

Mix the ingredients with a high-speed mixer，the required rotation speed is from 800 to 1,000 r/min, covered with exhaust device. After the raw materials are mixed evenly, enter the cooling mixer, the speed is low, can be cooled by circulating cooling water.

Single screw extruder or double screw extruder can be used to plasticize the raw materials.If using a single screw extruder , the screw structure should be gradually deepened in thread depth.

If using a double-screw extruder. The co-rotation type shall be selected.

When the single screw extruder extrzes plasticizing raw materials, the equipment should have better exhaust device;It is suitable to cool down with circulating water or circulating oil. The temperature fluctuation of the process should be controlled at about ± 5℃.CPVC extruder is suitable. No porous plate between the barrel of the extruder and the molding mold; overload protection device shall be provided at the screw work.

(3) Molding process operation and temperature control:

①CPVC resin should be dried in 80 oven for 2~4h to remove moisture from the raw material

②After metering, the raw materials are mixed into the high-speed mixing machine, and the material temperature is about 115℃.

③The high speed mixing high temperature material is cooled in the low speed mixer until the material temperature reaches about 40℃.

⑷Process operation key points:

The extrusion molding of CPVC pipe is more difficult compared with the extrusion molding of PVC pipe.Due to the high viscosity and poor fluidity of chlorinated PVC melt, it is difficult to form.And the melt is easy to decompose in the production process, so the following problems should be paid attention to in the extrusion molding production of chlorinated polyvinyl chloride resin:

①The chlorinated PVC resin must be dried before it is put into production. It should be dried in an 80℃ oven for 2 ~4h. When necessary, the raw materials should be screened with a 40 mesh screen once, and then put into the hopper of the extruder for production.

②Attention should be paid to the selection of raw materials formula of molding pipe, stabilizers and other processing additives, which should strengthen the melt fluidity and improve the thermal stability of raw materials. Mix the formula well first if necessary. Take the sample test in a 230℃ oven for 2h. If there is no obvious discoloration and decomposition phenomenon, it indicates that the auxiliary material selection is reasonable and reasonable.

③The extrusion process temperature of CPVC pipe is slightly higher than the extrusion process temperature of PVC pipe. However, it should be noted that the temperature control fluctuation should not be greater than ± 5℃.

④In the process of producing CPVC pipe, if there is power failure, equipment failure, signs of melt decomposition or flue gas from the mold mouth, it should immediately stop feeding to the cylinder, use PVC resin to remove CPVC melt in the mold, and then stop down to eliminate the fault.

⑤ HCI gas released during CPVC melt decomposition is harmful to human body,so pay attention to the production workshop through

⑥For the extruder cylinder used to produce CPV resin, the melt flow in the screw and molding mold shall be treated with corrosion protection to prolong the service life of equipment parts.

⑦The cover should cover the exhaust outlet to facilitate the discharge of water vapor.

⑧Use the extruder for CPVC tube extrusion molding. Should pay attention to the performance conditions such as exhaust and process temperature control stability of the extruder cylinder. If these two conditions can not meet the production requirements, the extrusion molding of CPVC tube should be more difficult, or even impossible.

⑨When producing CPVC pipe, the screw shall have heating and cooling device, and the stability of the process temperature should be adjusted and controlled reasonably, so as to improve the fluidity of molten material and ensure the forming quality of products.

⑩When the inner wall of the forming pipe is uneven, the acrylate processing additives (or copolymers) should be added to the raw material formula to improve the melting temperature of CPVC and PVC; meanwhile, the stability control of the mandrel temperature.