Polyvinyl vinyl chloride monomer process

Vinyl chloride monomer (VCM) is one of the leading chemicals used mainly for manufacturing polyvinyl chloride (PVC). The PVC worldwide production capacity in 2005 was of about 35 million tons per year, with an annual growth of about 3%, placed after polyolefines but before styrene polymers. In the 1990s the largest plant in the USA had a capacity of about 635 ktons [1], but today there are several plants over one million tons. At this scale even incremental improvements in technology have a significant economic impact. Computer simulation, process optimization and advanced computer-control techniques play a determinant role. 

A polymer is a large molecule built up by a repetition of small simple chemical units. These large molecules are formed by the reaction of a monomer.72 For example, the monomer for the plastic polyvinyl chloride (PVC) is vinyl chloride. When the vinyl chloride monomer is subjected to heat and pressure it undergoes a process called polymerization (Table 1.3) the joining together of many small molecules in repeat units to make a very large molecule. Structural representations of the monomer repeat unit and polymer are shown below. 

Application A process to produce polyvinyl chloride (PVC) from vinyl chloride monomer (VCM) using suspension polymerization. Many types of PVC grades are produced including commodity, high K-value, low K-value, matted type and co-polymer PVC. The PVC possesses excellent product qualities such as easy processability and good heat stability. 

Application Production of suspension polyvinyl chloride (PVC) resins from vinyl chloride monomer (VCM) using the Vinnolit process. 

Application Adding a stripping column to existing polyvinyl chloride (PVC) plants to remove vinyl chloride monomer (VCM) from PVC slurry. The recovered VCM can be reused in the PVC process, without any deterioration of PVC polymer quality. 

Vin Tec GmbH/Krupp Uhde Polyvinyl chloride (emulsion) Vinyl chloride monomer Batch process uses 2 or more reactors special coating/buildup suppressant allows many batch operations before cleaning NA NA... 

Chisso Polyvinyl chloride (suspension) Vinyl chloride monomer Batch process manufactures many PVC grades including commodity, high/low K values, matted type and copolymer PVC 12 2000... 

Presence of impurities in excipients can have a dramatic influence on the safety, efficacy or stability of the drug product. Monomers or metal catalysts used during a polymerization process are toxic and can also destabilize the drug product if present in trace amounts. Due to safety concerns, the limit of vinyl chloride (monomer) in polyvinyl pyrrolidone is nmt 10 ppm, and for hydrazine (a side product of polymerization reaction) nmt 1 ppm. Monomeric ethylene oxide is highly toxic and can be present in ethoxylated excipients such as PEGs, ethoxylated fatty acids, etc. 

Polyvinyl Chloride. Vinyl chloride monomer is produced industrially by three processes ... 

Vinyl chloride monomer (VCM) is a typical high tonnage chemical and most of the production is converted into polymers, particularly polyvinyl chloride (PVC). The processes and routes of manufacture of VCM have changed significantly over the years and these are summarized in section 12.3.3.2. However, we will look here at the pre-petrochemical days and also in more detail at the processes and the reasons why they changed. 

Ethylene dicldoride (EDC) is made by the direct chlorination of ethylene [8] in the presence of a catalyst such as iron (III) chloride or copper (II) chloride. EDC is also made by oxychlorination, a process where ethylene reacts with HCl and oxygen in the presence of a catalyst, often copper (II) chloride [9,10]. The EDC is then converted to vinyl chloride, commonly called vinyl chloride monomer (VCM) by a dehydrohalogenation reaction. The VCM is then polymerized to polyvinyl chloride (PVC). 

In the manufacture of polyvinyl chloride (PVC), an offgas stream is produced that contains unreacted vinyl chloride monomer. This stream is usually compressed and condensed to recover as much monomer as possible. However, the vent stream from the condenser still contains a significant amount of monomer. Baker et al. (1991) described an installation that recovers 100 to 200 Ib/hr of monomer from a condenser vent stream. The process vent stream is compressed to 63 psig and sent to a condenser operating at 14°F. The condenser vent stream, containing 30% vinyl chloride monomer, is sent to the membrane unit. The... 

In the polymerization of polyvinyl chloride, unwanted gas is generated by side reactions, and some small amounts of air leak into the reactors. These inerts must be vented from the process. Because vinyl chloride monomer (VCM) is extremely volatile, the purge gas, although it is typically at 4-5 bars pressure, can contain as much as 50vol% monomer. As a consequence, the vented gas stream, although small, may contain several hundred thousand dollars worth of monomer values. A typical process flow scheme to recover VCM is shown in Figure 21.10 (Lahierc et al., 1993). 

Vinyl chloride has been known for over a hundred years and its polymerization to polyvinyl chloride (PVC) was achieved in 1912. Industrial-scale production of this plastic began in 1927. PVC is still the most versatile plastic. One of the reasons for this is the numerous variations made possible by the method of manufacture of the polymer, namely by copolymerization with other monomers and their processing. Thus, PVC can be thermoformed on all conventional processing machines if the slight thermal damage is taken into consideration. Machining is easy and the material can be bonded, bent, welded, printed and thermoformed. 

POLYVINYL CHLORIDE (PVC). [CAS 9002-86-2], The manufacture of polyvinyl chloride resins commences with the monomer, vinyl chloride, which is a gas, shipped and stored under pressure to keep it in a liquid state bp —14°C, fp —160°C, density (20°C), 0.91. The monomer is produced by the reaction of hydrochloric acid with acetylene. This reaction can be carried out in eidier a liquid or gaseous state. In another technique, ethylene is reacted with chlorine to produce ethylene dichloride. This is then cataiytically dehydrohalogcnatcd to produce vinyl chloride. The byproduct is hydrogen chloride. A later process, oxychlorination, permits the regeneration of chlorine from HC1 for recycle to the process. 

In addition polymerization, monomers react to form a polymer chain without net loss of atoms. The most common type of addition polymerization involves the free-radical chain reaction of molecules that have C = C bonds. As in the chain reactions considered in Section 18.4, the overall process consists of three steps initiation, propagation (repeated many times to build up a long chain), and termination. As an example, consider the polymerization of vinyl chloride (chloro-ethene, CH2 = CHC1) to polyvinyl chloride (Fig. 23.1). This process can be initiated by a small concentration of molecules that have bonds weak enough to be broken by the action of light or heat, giving radicals. An example of such an initiator is a peroxide, which can be represented as R—O—O—R, where R and R represent alkyl groups. The weak 0—0 bonds break... 

Addition polymerization takes place for unsaturated monomers. In the presence of a catalyst, such as a free radical, a pi bond in the monomer is disturbed, and the resulting molecule is. itself, a chemically active free radical. This first step of the process is called initiation. The process may then continue, with the new molecule bonding with additional monomers in the same manner, thus forming a chain. Following this propagation step, free radicals may combine, thus forming a more stable polymer chain. This final step is called termination. Peroxides, such as benzoyl peroxide, are common agents that, when heat is applied, form free radicals that can initiate the polymerization process. An example of addition polymerization is shown below for the monomer vinyl chloride, which forms polyvinyl chloride. 

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