What’s The PVC Compounding Extrusion Process?

Posted by Andy

As we know, most of the PVC product was made by rigid PVC or soft PVC. According to the content of plasticizer, PVC plastic is often divided into:

  1. No plasticized PVC, plasticizer = 0%.
  2. Rigid PVC, plasticizer < 10%. Using for making PVC pipe, profile, plate, sheet etc.
  3. Semi-rigid PVC, 10% < plasticizer < 30%.
  4. Soft PVC, 30% < plasticizer < 70%. Using for making PVC sealing strips, hoses, cables, film, artificial leather, soles, toys etc.
  5. And above 80%

Rigid PVC product mostly made by conical twin screw extruder machine line. Soft PVC product mostly made by parallel twin screw extruder machine line. Here we just introduce parallel twin screw extruder extrusion process.

Machine Flowchart: Hot and cold mixing unit — Parallel twin screw extruder — Single screw extruder — Air cooling hot cutting system — Pellets sifting and packing. (Ps: the extruder is double-stage mother & baby design)

  1. According to the formulation, put the PVC resin, plasticizer, CaCO3, stabilizer and other auxiliaries into hot mixer mixing. After 6-10 mins discharge into the cold mixer (6-10 mins) for premixing. PVC compounding must use the cold mixer to prevent material stick together after the hot mixer.
  2. Feeding the mixture material into first stage KTE-65 twin screw extruder through the screw loader and metering twin screw feeding hopper.
  3. The mixture material finished plasticizing, mixing and dispersing evenly in the KTE-65 twin screw extruder with around 155°C-165°C. And then the melting PVC compounding (150°C-160°C) following into the second SE-150 single screw extruder directly.
  4. The melting PVC compounding finished extruding and pelletizing by the single screw extruder with low speed, high pressure and cooling state. And the extrusion temperature has dropped to 110°C-120°C. At this time the air cooling die-face hot cutting system can be easy working and make sure the material will not stick to the cutting blade. (Ps: 1.Due to the high rotate speed of twin screw extruder, PVC compounding normally cannot be direct pelletizing. The pressure of die-head will be very high;   2.Long time at high temperature, PVC easily carbonized)
  5. After pelletizing, the granules temperature can be dropped to 35°C-40°C after two stages cyclone cooling system. Then after the wind-cooled vibrating sieve, the particle temperature drops below room temperature to be sent to the final product silo for packaging.

Basic working condition:

  1. Power supplier: 380V(-/+5%), 50Hz(-/+2%), 3 Phase (Customer)
  2. Factory temperature: around 10°C-40°C
  3. Air relative humidity: max. 80%, no condensation
  4. Inner cycle water: soft water, for extruder barrel cooling
  5. External cycle water: cooling the inner cycle water. Can build a 25-30m3 pool outside the workshop, water pump to form outside circulating water

Reference formulation:

1.Non-toxic Hose
PVC SG-2:           100
DNOP:                 45
ESO:                    5
DOTL:                  2
Ca-Zn:                  1

2.Cable Wire Casing
PVC SG-2:           100        100
DOP:                    42           16   
DBP:                      –             16
M50/T50:            –             13 
DOS:                     –               5 
TBLS:                  2.5            3
DBLPP:                1               –
BsSt2:                  1.5            1.5

3.Heat-resistant Cable Material
PVC, XS-2:          100
DOP:                     48
CP:                         20
TBLS:                     4
DBLPP:                 2.5
BaSt2:                   1.5
PbSt2:                   0.5
Wax:                       2
CaCO3:                 100

More details please contact:
Mr.Andy, WhatsApp +86-18550112020, Email weishunzhou@gmail.com




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