Application Example: Feeding & Conveying in PVC Production

Polyvinyl chloride, commonly known as PVC, is one of the most widely used thermoplastics for several good reasons. PVC has an excellent cost/benefit ratio when compared to other polymer resins.

PVC Production Process
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PVC is used in the manufacture of end-use products for a wide range of applications in the consumer, construction, food and medical industries. Products made with PVC exhibit good impact strength, stiffness and strength-to-weight ratio. PVC products offer good dimensional stability at ambient temperatures, resistance to chemicals and oils, durability, and non-flammability character.

PVC Production Plant

PVC Production

PVC is produced by the polymerization of VCM (vinyl chloride monomer). This reaction is carried out in an autoclave where the raw materials (VCM, emulsifiers and chemical initiators) are dispersed in demineralized water under vigorous agitation. There are four well known methods for the production of PVC: suspension (S-PVC), emulsion (E-PVC), micro suspension and mass polymerization. The suspension polymerization process is the most commonly used.

Material Profiles

PVC is a thermoplastic with a Glass Transition Temperature (Tg) of about 82°C [180°F] and a density of 1.38 g/cm3 [86.15 lb/ft3].

Plastics need to be plasticized to enhance their flexibility, resiliency and melt flow. Without the addition of plasticizers, it may not be possible to make plastics sheeting, tubing, film and other flexible forms of plastics.

Heat Stabilizers
PVC is vulnerable to degradation during processing, and is therefore a prime consumer of heat stabilizers.

The use of fillers in the manufacturingof PVC parts is very common as they are used to extend the resin, thus reducing the cost of the final plastic part.

Other Materials Utilized

Materials Used
  • PVC Regrind
  • Additives
  • Antioxidants
  • Flame Retardants
  • Blowing Agents
  • Pigments

Bulk Unloading and Storage Systems

Pneumatic Transfer of Raw Materials
The delivery of PVC resin to a compounding or manufacturing plant is traditionally carried out by rail cars or tank trucks. Tank trucks are equipped with an onboard pressure blower to convey the resin to storage silos. The process of transferring PVC from rail cars to silos is achieved using a combination of pressure and vacuum pneumatic transfer in dilute phase.

State-of-the Art Feeding and Metering Solutions

In batch feeding operations, all materials are metered in Gain-in- Weight (GIW) batch mode. GIW batching uses individual volumetric feeders to feed ingredients into a common weigh hopper.

Choosing the Right Feeder
The choice of raw materials, the size of the compounding operation and an end-product formula or recipe, determine whether the material is fed gravimetrically or volumetrically, the type of feeder used (single or twin screw or rotary valve), and the order in which the materials are added to the highintensity mixer.

Feeding, Blending and Metering
In batch feeding operations, all materials are metered in Gain-in- Weight (GIW) batch mode. GIW batching uses individual volumetric feeders to feed ingredients into a common weigh hopper.

Dry-Blend Production
The intermediate compound known as a ‘dry-blend’ is generated by mixing together the ingredients according to predetermined formulations. The different materials are brought together in a high-intensity (high speed) hot mixer.

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  • Comprehensive product line with all necessary accessory products such as filters, level indicators, diverter valves, rotary valves, coolers, piping and blowers
  • Experience loading into transport forms such as sea/land shipping containers, trucks, railcars, boxes and bags
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