Chemical Industry-Polyvinyl chloride

Polyvinyl chloride

Polyvinyl chloride, also known as PVC, is a thermoplastic that is obtained via polymerisation of vinyl chloride. PVC is naturally a rigid thermoplastic polymer but it can be plasticized.

PVC is one of the most commonly used plastics. Light, strong, non-flammable, impermeable, hardwearing, easily processed by any means, simple to recycle (Vinyloop^®) and inexpensive, PVC is ideal for a range of uses. Solvay markets both resins and ready-to-use formulations: premix powders and granulated compounds under its tradename Benvic^®  

See for further information http://www.benvic.com/.

Solvay cooperates with BASF via their joint-venture Solvin.

See also http://www.solvinpvc.com/.

For the construction industry , PVC is shaped into piping, window frames, doors, guttering, clading or floor and wall coverings.

In automobiles, it protects the underside and bodywork, contributes to sound insulation and is molded to produce dashboard panels and interoir trim.

In the packaging sector, PVC is used to make full range of films, sheets, bottles and thermoformed trays.

Farmers have it to thank for irrigation pipes, sheeting for greenhouses , waterproofing for reservoirs, etc.

In hospitals it is used for blood and plasma bags and protective drawsheets.

It provides the safety sheeting of wires in the electrical industry, and is also widely used for tou and household appliances of all kind.

Production process

The production of polyvinyl chloride is by far the most important end-use of chlorine. The production process can be devided into 3 steps:

• production of 1,2-dichloroethane (EDC) with chlorine (Cl₂) and ethene (CH₂=CH₂) or with gaseous hydrochloric acid (HCl), oxygen (O₂), and ethylene
• formation of vinyl chloride monomer (VCM) via pyrolyses of EDC
• formation of PVC via polymerisation of VCM

Production of 1,2-dichloroethane (EDC or DCE )

DCE can be obtained via direct chlorination:

CH₂=CH₂ + Cl₂ -> CH₂Cl-CH₂Cl

or via oxychlorination:

CH₂=CH₂ + 2 HCl + ½ O₂ -> CH₂Cl-CH₂Cl + H₂O

Direct chlorination is performed at 50 °C and oxychlorination at 220 to 240 °C and at 4 bars.

Production of vinyl chloride monomer (VCM)

The obtained EDC undergoes subsequently a thermal decomposition (pyrolysis) at 500 °C at 10 bars that produces vinyl chloride monomer and gaseous hydrochloric acid according to the reaction:

CH₂Cl-CH₂Cl  -> CH₂=CHCl + HCl

The produced hydrochloric acid can be re-used in the oxychlorination process or be absorbed in water and sold as aqueous hydrochloric acid (HCl 34 %).

Production of polyvinyl chloride (PVC)

Subsequently VCM undergoes a polymerisation reaction, resulting in the production of PVC according to the reaction:

n CH2=CHCl  -> (-CH2-CHCl-CH2-CHCl-)n/2

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