MANUFACTURING PROCESS OF PVCBy Rajat Agarwal
Presented to: Dr. A.N. Sawarkar
INTRODUCTION Polyvinyl chloride is third largest and most
versatile of all thermoplastics. Global production and consumption of Polyvinyl
Chloride PVC in 2010 was approx. 34 million metric tons.
Polyvinyl chloride (PVC) was first manufactured in Germany in 1931 as a robust and lightweight new plastic.
Manufacturing of polyvinyl chloride (PVC) in India started 60 years ago with the country’s first PVC plant set up in Mumbai in 1951
The plant operated by Calico had a capacity of 6000 mt/year.
At present, the Indian PVC industry boasts of a production capacity of 1.3 million mt/year.
In India the total PVC capacity is expected to reach 1635 KTA by 2016-17.
Reliance Industries Ltd has planned capacity expansion to 735 KTA by 2016-17 followed by Finolex at 270 KTA, Chemplast 250 KTA, DCW90 KTA and Shriram70 KTA.
WHAT IS PVC ? PVC is a thermoplastic made of 57% chlorine and
43% hydrocarbon. With the addition of plasticizers, fillers,
reinforcements, lubricants and stabilizer, PVC may be formulated into flexible, rigid, elastomer or foamed compound.
PVC has outstanding combination of durability, stability, flame retardancy, heat-electrical insulation properties, recyclability, excellent long term weather ability and lower price.
PVC comes in two basic forms: rigid and flexible.
PROPERTIES OF PVC Weathering stability. PVC is resistant to aggressive
environmental factors is therefore the material of choice for roofing.
Versatility. PVC can be flexible or rigid. Fire protection. PVC is a material resistant to ignition due
to its chlorine content. Longevity. PVC products can last up to 100 years and even
more. Hygiene. PVC is the material of choice for medical
applications, particularly blood and plasma storage containers.
Barrier properties. PVC can be made impervious to liquids, vapors and gases.
Recyclability. PVC is very recyclable, more so than many other plastics.
Economical efficiency. PVC is the cheapest of large-tonnage polymers providing many products with the best quality-price ratio.
PROPERTIES (CONTD…)
Property Rigid PVC Flexible PVC
Density(g/cm3) 1.3-1.45 1.1-1.35
Thermal Conductivity[W/(m.K)]
0.14-0.28 0.14-0.17
Yield Strength[psi] 4500-8700 1450-3600
Young’s Modulus[psi] 490,00
Comprssion Strength 9500
Resistivity 1016 1012-1015
#source: http://en.wikipedia.org/wiki/Polyvinyl_chloride
APPLICATIONS AND USES
Pipes Clothing and Furniture Plasticizers Flooring Healthcare
Source: http://www.lenntech.com/polyvinyl-chloride-pvc.htm
MANUFACTURE PROCESS
The suspension polymerization process is most widely used process to manufacture PVC.
Manufacturing polyvinyl chloride (PVC) is a three-step process. Producing ethylene dichloride (EDC) Producing vinyl chloride monomer(VCM) Manufacturing polyvinyl chloride (PVC)
http://www.pvc.org/upload/images/Chart_02WEB_imagelarge.jpg
PRODUCING ETHYLENE DICHLORIDE
Chlorine is extracted from sea salt via electrolysis.
Ethylene is derived from hydrocarbon raw materials.
These are reacted to produce ethylene dichloride (1,2-dichloroethane).
C2H4 + Cl2 C2H4Cl2ethylene + chlorine = ethylene dichloride
#source: http://guichon-valves.com/wp-content/uploads/dichlorethane-process.jpg
PRODUCING VINYL CHLORIDE MONOMER
The ethylene dichloride is then decomposed by heating in a high temperature furnace or reactor.C2H4Cl2 C2H3Cl + HClethylene dichloride = vinyl chloride monomer + hydrogen chloride
The hydrogen chloride is reacted with more ethylene in the presence of oxygen (oxychlorination). This produces further ethylene dichloride.
The resultant ethylene dichloride is decomposed according to the above equation, and the hydrogen chloride is again returned for oxychlorination.
2HCl + C2H4 + ½ O2 C2H4Cl2 + H2O C2H3Cl + HCl + H2O
The overall reaction can be shown by adding together the above equations:2C2H4 + Cl2 + ½ O2 2C2H3Cl +H2Oethylene + chlorine + oxygen = VCM + water
#source: http://www.asc.co.id/uplimg/Image/edc.jpg
MANUFACTURING POLYVINYL CHLORIDE PVC is made using a process called addition
polymerisation. This reaction opens the double bonds in the vinyl
chloride monomer (VCM) allowing neighbouring molecules to join together creating long chain molecules.
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There are four polymerization routes for the manufacture of PVC.
Suspension Polymerization
Emulsion Polymerization
Bulk or Mass Polymerization
Solution Polymerization
SUSPENSION POLYMERIZATION
Vinyl chloride is dispersed into very fine droplets by vigorous stirring in water.
Protective colloids like polyvinyl, are added to prevent coalescing of the droplets.
Vinyl-soluble free radical initiators like lauryl are added and polymerization occurs around 50oC.
The polymer is centrifuged from the reaction mixture, washed, and dried.
Applications include injection molding and extrusion (film, tubes).
EMULSION POLYMERIZATION
Vinyl chloride is emulsified in water by adding surfactants and emulsifiers with vigorous stirring
Water soluble initiators like persulfates are used for polymerization.
Purification and drying of the resulting polymer results in a material that is more expensive than a resin produced by suspension polymerization.
However, the polymer in the emulsified state (also known as a plasticol) also can be used.
Examination and surgical gloves use plasticols for their manufacture.
BULK POLYMERIZATION Bulk polymerization is a two-stage process. In the first stage, pure vinyl chloride monomer is
polymerized up to 10% conversion using monomer-soluble free radical initiators.
In the second stage, more monomer is added and the mixture is polymerized with up to 80-85% yield. The excess monomer is stripped off using a vacuum and dried.
PVC obtained from this process is pure, crystal clear, with a narrow particle size distribution. Applications include blow molded bottles.
SOLUTION POLYMERIZATION In solution polymerization, vinyl chloride is
dissolved in organic solvents and polymerized with an organic soluble initiator.
The polymer precipitates from the solution is filtered, washed, and dried.
This process is used to make specialty copolymers with vinyl acetate.
ADDITIVES USED
Additive Properties Achieved
Anti-oxidants & other stabilizers
Slow down the rate at which the polymer will be degraded by oxygen, heat, visible light or UV radiation
Compatibilizers Enable PVC to be mixed with other plastics and helps plastic recycling
Flame retardants Reduce flammability of plastic
Pigments To color the plastic
Plasticizers To produce flexible and manageable plastic
Impact modifiers To absorb shock without damage
Fillers Inexpensive, inert materials that simply add bulk to the plastic
DISADVANTAGES OF PVC
Sensitive to UV and oxidative degradation Limited thermal capability Thermal decomposition evolves HCI Higher density than many plastics
REFERENCES Vinny R. Sastri, Plastics in Medical Devices, Second
Edition, Applied Science Publishers, 2014, Pages 73-120
http://cpmaindia.com/pvc_about.php http://nptel.ac.in/courses/103107082/module8/
lecture3/lecture3.pdf Thornton Joe, “Environmental Impacts of Polyvinyl
Chloride (PVC) Building Materials” http://www.pvc.org/ http://www.vinyl.org.au/pvc-safe-manufacturing/
manufacturing-process http://www.lenntech.com/polyvinyl-chloride-pvc.htm http://en.wikipedia.org/wiki/Polyvinyl_chloride