• The manufacture of vinyl chloride
• Polymerisation types of vinyl chloride
  • Emulsion polymerisation
  • Microsuspension polymerisation
  • Suspension polymerisation 
• Production of grafted copolymer or copolymer resins 

PVC or polyvinyl chloride, is a thermo-plastic material derived from crude petroleum and salt. It is obtained by the polymerisation of vinyl chloride (VC) or monochloroethylene.

The manufacturing process is in two stages, starting from ethylene and chlorine:

manufacture of monomeric vinyl chloride or VC
polymerisation of the monomeric vinyl chloride.
 

The manufacture of vinyl chloride

1. Chlorinating of ethylene and pyrolysis of the resulting 1.2-dichloroethane :
   
   
   
   
   
2. Oxychlorination of the ethylene with the hydrochloric acid obtained during the preceding reaction, in the presence of oxygen, followed by pyrolysis of the resulting 1.2-dichloroethane :
   

Emulsion polymerisation

This process is used to manufacture most of the homopolymer resins in the SolVin 100 and 300 series.
Polymerisation is carried out in an autoclave which generally contains the following substances:

• demineralised water
• monomeric vinyl chloride
• a water-soluble initiator (e.g. persulphate, hydrogen peroxide,...)
• an emulsifier (e.g. a soap)

At the end of the polymerisation stage, the autoclave contains a stable dispersion of fine PVC particles in water (emulsion). This milky emulsion is commonly called a "latex". The diameter of the PVC particles in this latex is generally between 0.1 and 2 µm.

The PVC is separated from the water by pulverising the latex into fine droplets in a current of hot air in installations known as "atomiser" dryers.

The resin retains most of the emulsifiers used during polymerisation. These impart, in certain conditions, special properties such as improved thermal stability and greater ease of processing.

This process is used for producing certain resins for plastisols in the SolVin 300 series.
Polymerisation is carried out in an autoclave which generally contains the following substances:

• demineralised water
• monomeric vinyl chloride
• an initiator soluble in the monomer
• an emulsifier

The mixture is transferred to the polymerisation autoclave via a homogeniser which causes it to disperse into very fine droplets.

At the end of the polymerisation process, the autoclave contains a stable dispersion of fine particles of PVC in water. This liquid is commonly called "latex". The diameter of the PVC particles in this latex is generally between 0.1 and 3 µm (process giving a continuous particle size distribution).

The subsequent operations for obtaining the final product are the same as for the emulsion polymerisation process.

This manufacturing process is used for producing vinyl resins in the SolVin 200, 400 and 500 series.
Suspension polymerisation is carried out in an autoclave, which generally contains the following substances:

• demineralised water
• monomeric vinyl chloride
• an initiator soluble in the monomer (for example an organic peroxide)
• a protective colloid (e.g. polyvinyl alcohols, cellulose derivates, etc.).

Depending on the dosage and nature of the protective colloid and the stirring conditions, the monomer droplets can agglomerate to a greater or lesser extent in the course of the polymerisation.

The suspension of PVC particles obtained at the end of the polymerisation process is commonly known as a "slurry". After the polymerisation, the slurry is transported to centrifugal dryers for washing and removal of the greater part of the mother liquor.

Lastly the dry product is sieved and bagged. In general, the average size of PVC grains in suspension is about 125 microns.

Suspension resins are compatible with all compounding ingredients (stabilisers, lubricants, fillers, etc.)

The copolymers in the SolVin 400 and 500 series are prepared using the same process as that used for manufacturing suspension homopolymers.

The grafted copolymers in the 400 series, obtained by vinyl chloride (VC) polymerisation and polyacrylic elastomer grafting, make it possible to produce finished products offering high impact strength without adding modifiers.

Vinyl chloride - vinyl acetate copolymers (VC-VAC) in the 500 series generally contain 5-15 % of vinyl acetate.
The properties of these copolymers are appreciably different from those of the homopolymers:

• can be processed at considerably lower temperatures and pressures than those needed for vinyl chloride and homopolymers of the same molecular weight;
• particularly suited for thermoforming;
• can be used to obtain highly transparent ("crystal-clear") finished products.