Manufacture of PVC

Ethylene Dichlonde and Vinyl Chloride. In the United States, all ethylene dichloride [107-60-2] (EDC) is produced from ethylene, either by chlorination or oxychlorination (oxyhydrochlorination). The oxychlorination process is particularly attractive to manufacturers having a supply of by-product HCl, such as from pyrolysis of EDC to vinyl chloride [75-01-4] monomer (VCM), because this by-product HCl can be fed back to the oxychlorination reactor. EDC consumption follows demand for VCM which consumed about 87% of EDC production in 1989. VCM is, in turn, used in the manufacture of PVC resins. Essentially all HCl generated during VCM production is recycled to produce precursor EDC (see Chlorocarbons and Cm OROHYDROCARBONS ViNYLPOLYAffiRS). 

The European Pharmacopoeia identifies di(2-ethylhexyl) phthalate as a substance that may be used in the manufacture of PVC plasticized containers and tubing for human blood and blood components, at a level of not more than 40% in the plastic (Council of Europe, 1997). 

In the manufacture of PVC plastisol propellants, the usual care is taken to assure that all ingredients meet specifications for chemical composition, dryness, and particle size. Since PVC plastisol propellants do not involve chemical reaction in their curing process, however, the presence of certain impurities in the ingredients is far less critical than with those propellant systems that are solidified by polymerization reaction. Ammonium perchlorate, the most common oxidizer, can normally be procured from the supplier with the required low moisture content. If not, it is dried immediately before use. Tray dryers or other drying means may be used, depending upon the quantity of material. Normally, some or all of the oxidizer must be ground to achieve the desired mean particle size and particle-size distribuion. High speed hammer mills have proved... 

Ethylhexanol. Use of 2-ethylhexanol in the manufacture of PVC plasticizers, most notably DOP (di-2-ethylhexyl phthalate), has historically accounted for over 70 percent of U.S. demand for this alcohol. DOP has been the most widely used general purpose PVC plasticizer for close to half a century and is considered the "workhorse" of the industry. The material is used in a wide variety of PVC resin applications including flooring, wire and cable, packaging and coated fabrics. In the past, DOP has represented the industry cost/ performance standard against which all competing plasticizers were measured. 

The biorientation process is also used in the manufacture of PVC-U sheet (64). 

Extrusion and biaxial orientation processes used by Solvay subsidiary Ondex in the manufacture of PVC sheets are described, and the properties and applications of these sheets are examined. 

EXTRUSION MANUFACTURE OF PVC-O AND PVC-M PIPES WITH ORGANIC STABILISERS -THE PACIFIC PERSPECTIVE... 

The production of plastics also involves the use of potentially harmful chemicals under the name of stabilizers or colorants. Many of these stabilizers/additives have not undergone environmental risk assessment and their impact on human health and the environment is currently uncertain and doubtful. Phthalates, as additives, are widely used in the manufacturing of PVC products, and risk assessments of the effects of phthalates on the environment are currently being carried out. Recent research for the Community Recycling Network casts doubt on whether pyrolysis and gasification are the right processes for dealing with the residual municipal waste. 

Much of the ethylene dichloride produced is used to make polyvinyl chloride (PVC or vinyl). In fact, in the United States, about 40 percent of the chlorine produced goes to the manufacture of PVC. In addition to piping, tubing, flooring, siding, film, coatings, and many other products, PVC is also used in the production of prosthetic (artificial) limbs. 

Worldwide, chlorine is mainly utilized in the manufacture of PVC, for pulp and paper bleaching, water treatment and... 

A significant increase is expected in chlorine utilization in the manufacture of PVC and phosgenes for isocyanate manufacture. 

Vinyl chloride Manufacture of PVC resins, adhesives, environmental decomposition of trichloroethylene... 

The manufacture of PVC is very important commercially [2,18,213,248,249] and the synthesis of the monomer, vinyl chloride is therefore an important step in this synthesis (see Sect. 6.4.3) ... 

The Danish minister of environment in 1988 announced that within a few years the manufacture and use of polyvinyl chloride (PVC) products had to be reduced as much as technically and economically possible due to their environmental impacts of production, use, and disposal. This preventive environmental policy was mainly based on the emission of hydrogen chloride and dioxins from waste incineration. A study of the technical, economic, and environmental consequences of a substitution was initiated by the National Agency of Environmental Protection. The goal was to collect background data for the upcoming negotiations between the environmental authorities and PVC-industry and manufacturers of PVC products in Denmark. The environmental assessment focused on PVC and 11 alternative materials, such as polyethylene (PE), polypropylene (PP), polyethylene terephtalate (PET), polystyrene (PS), polyurethane (PUR), synthetic rubbers (EPDM, CR and SBR), paper, impregnated wood, and aluminum. ... 

PVC pipe first developed by German scientists during World War II has grown by leaps and bounds. A total of 6.6 bilUon kg of PVC resin was produced in 1998 in the United States of which 907 kg are used toward manufacture of PVC pipe. For buried pipes, 10.2 cm in diameter and larger, which includes water, sanitary, and storm sewers, 137,500 km of PVC were produced in 1997 at a total worth of 1 billion. 

Aromatic and aliphatic hydrocarbons are used as extenders, particularly in the manufacture of PVC plastisols that must maintain as stable a viscosity as possible for relatively long periods of time (dip and rotational molding). The petroleum industry offers imprecisely defined products with an aliphatic-aromatic structure for use as extenders. They are added to plastisols in small amounts as viscosity regulators. Dibenzyl toluene also serves the same purpose. A disadvantage of this type of extenders is the risk of exudation if excessive quantities are used. 

Diglycol benzoates are liquid plasticizers rather like benzyl butyl phthalate (BBP) in their plasticizing action in PVC. In the manufacture of PVC floor coverings, the benzoates offer the advantage of a highly soil resistant surface. In this respect, they are even superior to BBP, which itself performs well here. 

Different processes are nsed in industry for the manufacture of polymers by fi-ee-radical chain polymerization. Among them homogeneous bulk polymerization is economically the most attractive and yields products of higher purity and clarity. But it has problems associated with the heat of polymerization, increases in viscosity, and removal of unreacted monomer. This method is nevertheless used for the manufacture of PVC, polystyrene, and poly(methyl methacrylate). More common processes are homogeneous solution polymerization and heterogeneous suspension polymerization. 

Waste PVC materials, at the end of their useful life, can continue to cause problems. They are likely to be powerful sources of POP if their waste is incinerated, and dioxins can be produced easily by unregulated burning. The environmental group Greenpeace has advocated the global phase-out of PVC with the claim that dioxins are produced as by-products during the manufacture of PVC, as well as from the incineration of waste PVC in domestic garbage. 

EDC is produced in very large quantities as a raw material for the manufacture of PVC. As a result it is a relatively low-cost solvent. This simultaneously reduces the incentive for the original user to recover it and for the customer of a merchant recoverer to buy recovered rather than virgin material. However, EDC s high chlorine content makes it expensive to incinerate and this factor subsidizes recovery. 

As part of the discussion on the use of textile construction membranes, it should be made clear what happens at end-of-Ufe for materials used so far for building construction. Thermoplastic membrane components like PVC can be processed after each utilization period under certain conditions and be supplied for reuse in the raw material cycle. Leading European manufacturers of PVC/PES membranes and roofing sheets have united in order to recycle post-consumer waste, disused membranes and PVC materials (ref. Vinyl) in most modem plants with approved thermo-physical procedures. The output of this recycling process is then used for new products. An important factor in the operation of these and other environmental raw-material recovery procedures is logistics, which includes the materials being carefully prepared and sorted prior to delivery. The processing plants are potentially able to achieve a turnover of more than one ton per hour (ref. recovinyl). 

Phthalate esters are a key additive in many plastics, therefore are an important constituent of numerous consumer products. Most of the mid- to high-molecular weight phthalate esters are used in the manufacturing of PVC to impart flexibility," while DBP is used in epoxy resins and cellulose esters and specialized adhesive formulations, DEHP is used extensively in disposable medical devices made of PVC. Plasticizers are also used in consumer products such as food packaging, bottled water, and children toys. 

Water-soluble substituted celluloses are another class of stabilizers used in the suspension polymerization, mainly in the manufacture of PVC. These stabilizers are soluble in both the vinyl chloride and the aqueous phase [20]. Ckjnsequently, the stabilizer can also affect the stabihty of the primary particles inside the polymerizing monomer droplets and, thus, the final porosity of the PVC particles. Hydroxypropyl methylcellulose (HPMC) is a cellulose ether, produced byreacting cellulose with propylene oxide and methyl chlorine in an alkaline medium. As a result, a fraction of the hydroxyl groups (hydrophilic groups) of the cellulose... 

Vinyl chloride monomer used for the manufacture of PVC plastics intended for contact with foods provides an example where there is a low specific migration limit , plus a low limit on the level allowed to be present in the packaging material. These limits are contained in an EC Directive 78/142/EEC on PVC plastics and are 0.01 milligrams per kilogram of food (lOppb), and 1 milligram per kilogram of polyvinyl chloride. 

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