PVC PPRODUCTION GREEN PROCESS

CONTENTS

1. Introduction 2. History 3. PVC’s proprieties 4. PVC process

Row material Chemical process PVC production

5. Application 6. Green process 7. Eco-profiles and LCA8. Benefits of useing PVC9. References

1. INTRODUCTION

Poly Vinyl Chloride (abbreviated PVC), is the third-most widely produced polymer, after

polyethylene and polypropylene.

PVC comes in two basic forms: rigid (sometimes abbreviated as RPVC) and flexible. The

rigid form of PVC is used in construction for pipe, and in profile applications such as doors and

windows. It is also used for bottles and other non-food packaging, and cards (such as bank or

membership cards). It can be made softer and more flexible by the addition of plasticizers, the

most widely used being phthalates. In this form, it is also used in plumbing, electrical cable

insulation, imitation leather, signage, inflatable products and many applications where it replaces

rubber.

2. HISTORY

PVC was discovered accidentally on at least two occasions in the 19th century. The first, in

1838, was by the French physicist and chemist Henri Victor Regnault and the second in 1872 by

the German Eugen Baumann. On both occasions, the polymer appeared as a white solid inside

flasks of the newly discovered vinyl chloride gas that had been left exposed to sunlight. The

material was difficult to work with and no one mastered the challenge of commercial

applications.

In 1913, German inventor Friedrich Heinrich August Klatte took out a patent on PVC. His

method used polymerization of vinyl chloride with sunlight.

3. PVC's PROPRIETIES

PVC, PE, PP and PS are general purpose plastics. The features of the particular plastic are

determined by its chemical composition and type of molecular structure (molecular formation:

crystalline/amorphous structure)

Fire retarding properties

PVC has inherently superior fire retarding properties due to its chlorine content, even in

the absence of fire retardants. For example, the ignition temperature of PVC is as high as 455°C,

and is a material with less risk for fire incidents since it is not ignited easily.

Furthermore, the heat released in burning is considerably lower with PVC, when

compared with those for PE and PP. PVC therefore contributes much less to spreading fire to

nearby materials even while burning.

Durability

Under normal conditions of use, the factor most strongly influencing the durability of a

material is resistance to oxidation by atmospheric oxygen. PVC, having the molecular structure

where the chlorine atom is bound to every other carbon chain, is highly resistant to oxidative

reactions, and maintains its performance for a long time. Other general purpose plastics with

structures made up only of carbon and hydrogen are more susceptible to deterioration by

oxidation in extended use conditions (such as, for example, through repeated recycling).

Oil/Chemical resistance

PVC is resistant to acid, alkali and almost all inorganic chemicals. Although PVC swells

or dissolves in aromatic hydrocarbons, ketones, and cyclic ethers, PVC is hard to dissolve in

other organic solvents. Taking advantage of this characteristic, PVC is used in exhaust gas

ducts, sheets used in construction, bottles, tubes and hoses.

Mechanical stability

PVC is a chemically stable material, which shows little change in molecular structure,

and also exhibits little change in its mechanical strength. However, long chain polymers are

viscoelastic materials and can be deformed by continuous application of exterior force, even if

the applied force is well below their yield point. This is called creep deformation. Although

PVC is a viscoelastic material, its creep deformation is very low compared with other plastics

due to limited molecular motion at ordinary temperature, in contrast to PE and PP, which have

greater molecular motion in their amorphous sections.

Processability and mouldability

The processability of a thermoplastic material depends largely on its melt viscosity.

PVC is not suitable for injection moulding of large sized products, since its melt viscosity is

comparatively high. On the other hand, the viscoelastic behaviour of molten PVC is less

dependent on temperature and is stable. Therefore PVC is suitable for complex shaped

extrusion profiling (e.g., housing materials), as well as calendaring of wide films and sheets

(e.g., agricultural films and PVC leather).

Other properties that make PVC versatile

PVC has polar groups (chlorine), and is amorphous, therefore mixes well with various

other substances. The required physical properties of end products (e.g., flexibility, elasticity,

impact resistance, anti-fouling, prevention of microbial growth, anti-mist, fire retarding) can be

freely designed through formulation with plasticisers and various additives, modifiers, and

colouring agents. PVC is the only general purpose plastic that allows free, wide and seamless

adjustment of the required physical properties of products such as flexibility, elasticity, and

impact resistance, by adding plasticisers, additives and modifiers. Since the physical properties

of end products are adjustable through compounding with additives, only a few types of resin are

required to cover all applications (fibre, rigid and flexible plastic, rubber, paint, and adhesive).

This controllability is also extremely beneficial for recycling.

4. PVC PROCESS

PVC manufacturing process

From a chemical viewpoint, PVC is a thermoplastic polymer based on chlorinated hydrocar-

bons. This figure provides an overview of the production processes leading from raw materi-

als to finished products.

PVC is produced from two primary raw materials, ethylene and chlorine. These react to form

ethylene dichloride (EDC) which, upon cracking, yields vinyl chloride monomer (VCM). Free

radical polymerisation is used to produce the PVC polymer itself.

The two most important polymerisation techniques are suspension polymerisation and emul-sion polymerisation, leading to the production of S-PVC and E-PVC, respectively. These two types of PVC polymer have different properties and are used for distinct applications. The S-PVC process yields granules of polymer of 100 to 200 microns in diameter, which are used in processes such as injection moulding, extrusion and PVC film manufacture. Here, S-PVC is analysed in more detail, as it is more commonly used. The differ-ence between S- and E-PVC is rather small, as the type of polymerisation has a low impact on the overall performance of the PVC over its life cycle.

Row Material

Row material for PVC industry are: Chlorine and Ethylene

Production of ethylene and chlorine

Definition: The raw materials for PVC are petroleum (which contributes to 43% of the polymer

weight) and rock salt (57%). Petroleum is refined to naphtha, which is then cracked to form

ethylene. Chlorine is obtained from rock salt through an electrolytic process.

Manufacture: Ethylene is produced, together with a variety of co-products, by the steam cracking of naphtha or natural gas liquids. The natural gas liquids contain ethane, butane and propane and when they are pyrolysed the products are ethylene and propylene. Ethylene production via steam cracking is a basic chemical process. The ethylene used as an interme-diate in PVC production is the minor portion of the chemicals produced during this process. Products from the steam cracker are used as intermediates for a variety of other products.

Thirty percent of the chlorine produced in Germany is used for Vinylchloride (VCM) and EDC (dichloroethane) production. Chlorine is produced by the electrolysis of a salt solution or brine. During electrolysis chlorine is produced at the anode while sodium or caustic soda and hydrogen are produced at the cathode. The products of the electrode processes must be kept separately; otherwise they will react to form unwanted by-products. Either chemical or physi-cal separation is employed. Today, there are three different commercial electrolysis proc-esses available: the amalgam process, the diaphragm process and the membrane process.

The amalgam process requires a higher consumption of electrical power than the diaphragm or membrane processes but produces a purer and more concentrated caustic soda solution. Substantial quantities of steam are required to concentrate the caustic soda solutions, pro-duced by the diaphragm and membrane cells, to the concentration levels that are produced by the amalgam process. The Best Available Technology (BAT) for chlorine manufacture is recognised to be the membrane process, which consumes less electricity compared to the amalgam and diaphragm processes.

Environmental impact: Emissions from ethylene production are released to air and water.

They consist primarily of ethylene and propylene emissions to air, and methanol and pro-

pane/butane emissions to water. Other emissions, such as Total Organic Compound (TOC),

Sodium Hypochlorite (NaOCl), etc. are also present.

Environmental Impact and sources:

100%Ethylene supply (for S-PVC)

80%

Naphtha

NL: Nat. Gas

NO: Nat. Gas

60% Methanol

NaOH

40% Steam Cracker (process)Electricity

20% Thermal energy (process)

Steam (process)

0%y ] ] ] ] ] ] ]

. . . . . . .

nerg -Eq -Eq -Eq -Eq -Eq -Eq -Eq

DCB

at

DCB

n

DCB

2 2E e O Oy h h

r

sp Et CS

a gim [kg

o

[kg [kg [kgPr

ETP

Ph

HTP

[kg

TETP

0 [k

AP[kg

POCP

01

A P P

EGW

Environmental Impact of Ethylene Production

During chlorine production, emissions of chlorine and hydrogen are possible from all three processes (amalgam, diaphragm and membrane). Mercury can be emitted from the amalgam process only. Asbestos fibres within the diaphragm process are a potential workplace hazard but the existence of the fibres as such presents no environmental problem, since the fibres are chemically inert and no release during regular use appears. The diaphragm keeps the products of electrolysis separate while allowing the passage of electric current. A matter of concern is the handling and disposal of the diaphragm. Mercury disposal on-site can affect the water, air and soil in the plant neighbourhood, posing a hazard to plant operators and to the people and animal life living near the plant. Chlorine as a toxic gas has a potential environmental impact, if released to the environment.

Environmental Impact and sources:

100%Chlorine supply (for S-PVC)

NaCl salt80% Soda

60% Sulphuric acid

40%HCl

Steam (process)20%

Elektrolysis

0% Electricity (process)

] ] ] ] ] ] ]

ergy

. . . . . . .

-Eq -Eq -Eq -Eqq q q

E -E -E-

nCB

Phosphat

DCB

nCB

2O2E e O

rimary

D th D C S

[kg [kg [kgE

[kg [kg [kg0 PP

P TPETP [kg HTP

0 AC E 1

AEP

O T PP W

G

Environmental Impact of Chlorine Production

These figures show the environmental profile of these materials in impact catego-ries. In the

case of ethylene, naphtha occupies a major part in all impact categories, espe-cially

Photochemical Ozone Creation Potential (POCP). This is mainly due to the processing of

crude oil, which causes VOC emissions.

The high consumption of electricity is the main characteristic of the electrolysis process for

the production of chlorine (see Figure 4-4), causing CO2 and SO2 emissions, which result in a high Global Warming Potential (GWP) and Acidification Potential (AP). In comparison to the other process steps, the electricity production of the electrolysis process also results in a high Human Toxicity Potential (HTP). The German Environmental Protection Agency considers the mercury emission from the production of chlorine with the amalgam process and the elec-tricity consumption (its production and supply for the electrolysis) as the main environmental factor of concern for the chlorine production process. New installations of electrolysis processes have be operated with the membrane process.

A step-by-step shift to the membrane process for chlorine electrolysis is in progress. This is

seen as a major step to further reduce environmental impacts of chlorine production.

Risk characterisation: In the case of PVC, the production of chlorine plays a very important role and it is a continuing topic of discussion in the assessment of risk. Information regarding exposure: limits and areas of exposure, risks to the environment and health should be men-tioned. Moreover, the production of the petrochemical part of PVC, as for all plastics, includes various risks: sea pollution from drilling to shipping, and risks associated with

explosive gases such as ethylene.Risk characterisation is not a primary task within LCA, as LCA deals with potential impacts of regular operation. Today, initial approaches are in development that address the integration of risk aspects into LCA. Nevertheless, existing methods, such as Risk Assessment, are more suitable to answer specific questions related to the risks of chlorine.

Chemical Process

The chemical process for making PVC involves taking the simplest unit, called the

monomer, and linking these monomer molecules together in the polymerization process. Long

molecular chains are formed called polymers (which are also called macromolecules).

This is the case for PVC, which is made from vinyl chloride monomer known usually by

its initials VCM through polymerization. Some monomers exist in the form of reactive gaseous

chemical substances, and some of these may cause health hazards when in direct contact with

humans. In these cases they are manufactured and processed under strict control for health,

safety and environmental protection. On the other hand, polymers such as PVC, which are

manufactured from monomers through polymerization, are solid and chemically stable

substances, therefore do not affect human health. VCM, which is the raw material for PVC, is a

gas at ambient temperature but is usually stored in liquid form under pressure. Ethylene and

chlorine are raw materials for PVC. Upstream industries are those that provide these materials

and include producers of basic petrochemicals (sometimes known as feedstock’s’), which

supply ethylene, and the chlor-alkali (caustic soda) industry, which supplies chlorine.

At a first stage in the PVC production process ethylene and chlorine are combined to

produce an intermediate product called 1.ethylene dichloride; this is then transformed into vinyl

chloride, the basic building block of polyvinyl chloride or PVC. The process of `polymerization'

links together the vinyl chloride molecules to form chains of PVC. The PVC produced in this

way is in the form of a white powder. This is not used alone, but blended with other ingredients

to give formulations for a wide range of products.

PVC is a thermoplastic made of 57% chlorine (derived from industrial grade salt) and 43% carbon (derived predominantly from oil / gas via ethylene). It is less dependent than other polymers on crude oil or natural gas, which are nonrenewable, and hence can be regarded as a natural resource saving plastic, in contrast to plastics such as PE, PP, PET and PS, which are totally dependent on oil or gas.

PVC production

The process that take place are

1 Row material depozitation 9 Polyerasition

2 Chlorination 10 Stripping

3 Oxichlorination and Cracking 11 Centrifuging

4 Quenching 12 Drying

5 Cooling 13 Sieving

6 Purifiction 14 VSN storage

7 VCM purified 15 PVC recovery

8 Control room 16 Packing

First, the raw material VCM is pressurized and liquefied, and then fed into the polymerization

reactor, which contains water and suspending agents in advance. Through high-

speed agitation within the reactor, small droplets of VCM are obtained. Next, the initiator for

polymerizations is fed into the reactor, and PVC is produced by reaction under a few bar at 40 -

60°C.

PVC obtained through suspension polymerization is suspended in water as particles of

50~200 μm diameter (in slurry form). Thereafter the slurry discharged from the polymerization

reactor is stripped of residual monomer, dehydrated, dried and the particle size controlled by

screening to yield PVC in the form of a white powder. The un-reacted VCM is entirely

recovered through the stripping process, and after purification, recycled as raw material for reuse

in this process. PVC resin produced via this ‘suspension’ process is referred to within the

industry using the abbreviation S-PVC.

Emulsion polymerization and bulk polymerization are alternative, much less extensively

employed, technologies to manufacture PVC. Emulsion polymerization produces finer resin

grades having much smaller particles, which are required by certain applications. This type of

resin is sometimes called ‘paste’ PVC and referred to within the industry using the abbreviation

P-PVC to distinguish it from S-PVC.

5. APPLICATION

PVC is one of the most used plastic materials in the world. At global level, demand for

PVC exceeds 35 million tonnes per annum and it is in constant growth (+5% on global

average), with higher growth rates in the developing countries.

In Europe (EU-32), the production of PVC products – including exports – totals about 8

million tonnes per year. European PVC resin consumption totals some 6.5 million tonnes

per year, or 15% of all plastics use in Europe, with an average growth of 2-3% per year.

6. GREEN PROCESSThe concept of sustainability is often stated in a number of ways but four core principles appear throughout: Protect the environment, promote human health, conserve resources, and assure social and economic well-being to the global population. PVC resin has intrinsic properties that allow finished products to meet all four of these objectives. PVC resin and products compare favorably to other materials in life cycle assessments when reviewing key impacts of resource and energy conservation, and greenhouse gas emissions.

The 12 Principles of Green Chemistry

Those principles designated with an ‘*’ illustrate at least seven areas with which PVC resin production conforms.

Principle No.2, “Atom Economy”, refers to the conversion of raw materials into finished products. Overall conversion efficiency for ethylene dichloride to vinyl chloride to PVC is estimated to be 94% , which puts it among the highest for polymer resins. Key to achieving this is steam stripping of PVC resin that removes unreacted monomer and recycles it back to the front of the polymerization process which drives the polymerization (step 5) to nearly complete utilization of monomer feedstock.

As shown in Figure 1, PVC has one of the lowest embodied energy profiles for a polymer because of its composition with chlorine, use of catalysts in feedstock preparation, and exothermic monomer polymerization reaction, which all combine to adhere to Principle No.6 “Design for Energy Efficiency.” A further look at embodied energy is warranted since it should be basic to any material sustainability evaluation due to the amount of GHG emitted to produce the material. In the case of PVC, replacement of ethylene with chlorine in the polymer matrix creates an interesting tradeoff between the electrical energy intensive derivative chlorine (total energy for process and transportation = 17.67 MJ/Kg including salt mining) versus the fuel and electrical energy intensive derivative ethylene (total energy for process and transportation = 17.73 MJ/Kg), with the net result of PVC having a low total embodied energy. It should be pointed out that comparisons of polymers or other materials on a unit basis would only be an

indication of certain intrinsic attributes, and may not be representative of actual impacts of any material when a complete cradle to grave life cycle assessment (LCA) is performed.

Figure 1: Resin GHG Emissions vs. Embodied Energy, Data Reference: ACC Cradle to Gate LCI Report

Principles No. 3 and 12, “Less Hazardous Chemical Syntheses” and “Inherently Safer Chemistry for Accident Prevention” intend to reduce environmental and workplace hazards through chemical selection. But all organic raw materials, whether in a solid or liquid form, can present combustible dust or flammable liquid hazards which require responsible care during handling and processing, and whether derived from biomaterials or fossil fuels, cause issues when released into the environment. Alternatively, process safety practices and workplace monitoring are ways to accomplish the same end result. The PVC industry has a history of implementing safeguards and a proven record of achieving both of these aforementioned green chemistry principles through sophisticated process monitoring and controls. Year over year reductions in criteria emissions for vinyl chloride and dioxin are shown in Figures 2 and 3 respectively.

PVC plants are equipped with an elaborate array of continuous air samplers that alert employees quickly in the event of any monomer leak. These monitors and the continual emphasis by the industry for safety has resulted in an illness and injury rate that is one-third that of the overall chemical industry, and one-sixth that of overall manufacturing, as recorded in Figure 4.

Figure 2: PVC Industry Cradle to Resin Vinyl Chloride Emissio Figure 3: PVC Industry Cradle to Resin Dioxin Emission

Principle No. 8 “Reduce Derivatives” can be shown to be met by the examining the block flow diagram in Figure 5 which depicts the relatively simple route to manufacture PVC resin in just 5 steps.

Several steps incorporate catalysts which drive reactions more effectively as required by Principle No. 9 “Catalysis.”

Each step is computer controlled and continuous process parameter monitors assure optimal operations, which meets the requirement of Principle No.11 “Real-time Analysis of Pollution Prevention.”

Figure 4: Illness and Injury Rate, PVC Resin

Figure 5: Cradle-to-Resin Flow Diagram of PVC Production

7. ECO-PROFILES AND LCA

Life Cycle Assessment (LCA): Method to evaluate the magnitude of resources

consumption and impacts on the environment for a material or product throughout its whole

life cycle (production, use, waste disposal and recycling) .Rather than focusing on the

environmental load alone, it evaluates from a comprehensive viewpoint. It has been highlighted

as one of the guidelines for material comparison and green procurement.

By using LCAs correctly it can be ensured that:

Product systems are not erroneously favored or condemned on the basis of

individual results.

Developments do not inadvertently shift or even increase environmental impact but

in fact reduce it.

The resources available are directed in such as way that they achieve the

greatest environment benefit for the entire system.

PVC product systems have been investigated using LCA methodology in almost all

significant application areas in terms of production quantity.

Eco-profiles

Eco-profiles form part of Life-Cycle Assessment (LCA). Whereas LCAs are cradle-to-grave

analyses of the environmental impact of a product, eco-profiles stop at the factory gate

("Cradle-to-gate"). The Eco-profiles of PVC were fully updated in 2006. They can be

downloaded here .

The key impacts calculated in these eco-profiles are aggregated according to a standard

methodology and published in Environmental Declarations.

8. BENEFITS OF USEING PVC

9. REFERENCES

O. Y. S. Palacios , P. C. Narva´ez Rinco´n , J.-P. Corriou , M. C. Pardo, C.Fonteix,

“Multicriteria optimization of production conditions for a new phthalate-free PVC plasticizer”

Journal of Industrial and Engineering Chemistry, 2014,

G.G. Liang, W. D. Cook, H. J. Sautereau, A. Tcharkhtchi, “Diallyl orthophthalate as a reactive plasticizer for improving PVC processibility,Part II: Rheology during cure”, Polymer2009, 2635–2642

M. Balkaya , I. D. Moore, A. S.˘lamer. “Study of non-uniform bedding support under continuous PVC water,distribution pipes”, Tunnelling and Underground Space Technology,2013.

S. Z.Gaoa, J. S. Wangb, X. W. Gaoc,” Modeling and advanced control method of PVC polymerization Process” Journal of Process Control 23 (2013) 664– 681