VINYL CHLORIDE MONOMER EMISSIONS
FROM THE POLYVINYL CHLORIDE PROCESSING INDUSTRIES
U. S. Environmental Protection Agency
Research Triangle Park, North Carolina
Arthur D Little, Inc
This paper was produced from a copy of the original document by mindfully.org
The success of this program was totally dependent upon our being able to obtain data from resin manufacturers, compounders, and fabricators. Most manufacturers were extremely cooperative, both in allowing us to inspect their operations and in giving us their. data. We would like to acknowledge this help and to thank these manufacturers for their time and effort.
Page SUMMARY S-1 I. INTRODUCTION I-1 A. BACKGROUND: THE VCM PROBLEM I-1 B. SCOPE OF STUDY I-1 C. METHODS I-2 II. POLYVINYL CHLORIDE MANUFACTURING: PROCESSES & APPLICATIONS II-1 A. GENERAL II-1 B. POLYVINYL CHLORIDE POLYMERIZATION PROCESSES II-4 C. COMPOUNDING OF PVC RESINS II-5 D. FABRICATION PROCESSES II-8 III. END-USE MARKETS AND STRUCTURE OF THE FABRICATION INDUSTRY III-1 A. AN OVERVIEW III-1 B. STRUCTURE OF THE COMPOUNDING INDUSTRY III-1 C. STRUCTURE OF THE FABRICATING INDUSTRIES III-5 D. FUTURE TRENDS III-22 E. SUBSTITUTION OF OTHER RAW MATERIALS FOR PVC RESIN III-24 IV. DESCRIPTION OF PROCESSES AND EMISSION POINTS IV-1 A. COMPOUNDING IV-1 B. EXTRUSION IV-18 C. CALENDERING IV-29 D. BLOW MOLDING IV-31 E. INJECTION MOLDING IV-34 F. COMPRESSION MOLDING IV-35 G. SOLVENT CAST FILM IV-35 V. TOTAL U.S. EMISSIONS OF VINYL CHLORIDE MONOMER FROM POLYVINYL CHLORIDE COMPOUNDING AND FABRICATING V-1
TABLE OF CONTENTS (continued)
Page VI. CURRENT STATUS OF CONTROLS TO LIMIT VCM EMISSIONS FROM THE PVC FABRICATION INDUSTRIES VI-1 A. CURRENT CONTROL TECHNIQUES VI-1 B. FUTURE CONTROL TECHNIQUES VI-2 APPENDICES
LIST OF FIGURES
II-la. Polyvinyl Chloride Manufacturing Processes II-2 II-lb. Polyvinyl Chloride Manufacturing Processes II-3 IV-1. Continuous Hot Compounding Line IV-3 IV-2. Batch Hot Compounding Operation IV-4 IV-3. Banbury Mixer IV-5 IV-4. Dry Blend Compounding IV-14 IV-5. Typical Double Batch Compounding of Pipe Resin IV-16 IV-6. Schematic of Wire and Cable Coating Process IV-21 IV-7. Crosshead Die for Wire Coating IV-22 IV-8. Flexible PVC Film Extrusion with In-Plant Compounding IV-24 IV-9. Typical PVC Pipe Extrusion Operation IV-26 IV-10. Rigid Profile Extrusion IV-30 IV-11. Typical Calendering Operation IV-32 IV-12. Solvent Cast PVC Film Production IV-36
LIST OF TABLES
Page S-1. Total U.S. Emission Rate of VCM from Polyvinyl Chloride S-3 Processing S-2. Annual Vinyl Chloride Emissions - 1974 S-4 II-1. U.S. Production of PVC Resins II-6 II-2. Domestic Consumption of PVC Resins II-16 II-3. U.S. Consumption of PVC Resins II-18 III-1. Domestic End Use Breakdown of PVC Resin - 1974 III-2 III-2. U.S. Consumption of PVC Resins by End Use III-4 III-3. Estimated Consumption of Resin for Rigid Compound in 1974 III-6 III-4. Estimated Consumption of Resin for Flexible Compound in III-7 1974 III-5. Estimated Consumption of Paste Resin in 1974 III-8 III-6. Estimated PVC Consumption in Pipe and Conduit III-10 III-7. End Use Market for Siding and Other Extruded Profiles III-12 III-8. Market Shares for Major Suppliers of PVC Floor Covering III-14 III-9. PVC Wire and Cable Usage (1973) III-16 III-10. PVC Usage in Soft Trim for Average Automobile III-10 III-11. Substitution Aspects of Fabricated Vinyl Products III-32 IV-1. VCM Levels in Resin at Points along Compounding Process IV-7 (ppm by weight) IV-2. Vinyl Chloride Concentrations in Film Processing IV-8 IV-3. Flexible VCM Compound Production IV-9 IV-4. Percent Vinyl Chloride Monomer in PVC Homopolymer IV-11 IV-5. Percent Vinyl Chloride Monomer in PVC-PVA Copolymer IV-12 IV-6. VCM Loss During Dry Blend Compounding of Rigid PVC IV-17 Formulations IV-7. Typical Extruder Temperatures for PVC IV-19 IV-8. VCM Losses from Flexible PVC Calendering IV-33 V-1. Total U.S. Emission Rate of VCM from Polyvinyl Chloride V-2 Processing V-2. Annual Vinyl Chloride Emissions - 1974 V-3 VI-1. Anticipated Future VCM Loss Rates from Compounding and VI-1 Fabrication
LIST OF TABLES (continued)
Page Appendix A-I. Major U.S. Producers of Raw PVC Resin A-1 A-II. Major Merchant PVC Resin Consumers A-2 A-III. List of Suppliers of PVC Compound A-7 A-IV. Producers of PVC Pipe and Fittings A-20 A-V. Suppliers of Resin or Compound to PVC Pipe A-22 Fabricators A-VI. Film and Sheeting Calenders in Operation in the USA A-25 A-VII. Manufacturers of Flexible (Plasticized) PVC Sheet A-28 A-VIII. Manufacturers of Rigid PVC Sheet A-32 A-IX. U.S. Producers of PVC Film (Calendered and Extruded) A-35 A-X. U.S. Producers of Cast PVC Film and Sheet A-38
The recognition of the potential link between the exposure of workers to
vinyl chloride monomer (VCM) and the development of angiosarcoma of the
liver has resulted in the Occupational Safety and Health Administration
setting standards to limit the exposure of plant workers to VCM. These
standards are expected to result in controls which reduce the concentration
of VCM in plant air to very low levels. However, the ventilation
methods used as one major route to meeting the OSHA regulations in no
way reduce the total aunt of VCM emitted from the plants to the
atmosphere. There is therefore still concern about the effects of VCM
emissions on the non-worker population in communities surrounding PVC
production and fabrication plants.
The purpose of this present study was to attempt to quantify the extent of VCM emissions from polyvinyl chloride processing plants, including both compounders and fabricators who process the compound--through the melt or solvent phase-into semi-finished products.
In this report, we discuss the structure of the PVC processing industry, and document the emissions from each segment of the processing industry. Emissions are categorized primarily by the type of fabrication process. Data on emissions were obtained from interviews with resin producers, compounders, and fabricators. The primary approach to the estimation of emissions was the classic material balance. The VCM content of resins entering each process step was estimated, and the amount of monomer in the product emerging from each process step was separately estimated. The difference in VCM concentration between the material entering and exiting from each process step was used to estimate the VCM losses. Total nationwide emissions, by process, were then obtained by multiplying the VCM lost per kilogram at each process step by the total amount of material processed each year by that process. Since the residual VCM levels in resin are constantly changing as manufacturers seek to minimize them in order to minimize worker exposure to the monomer in fabrication plants, we used late 1974 levels of residual monomer as the basis of these calculations.
Table S-1 shows the total U.S. emissions of VCM from polyvinyl chloride processing, categorized by process. As shown by this table, the predominant emissions arise from the compounding portions of the processing operations. VCM emissions from later processing operations are negligible. Table S-2 compares the annual VCM emission rates from PVC processing with the emissions from vinyl chloride monomer production and from polyvinyl chloride polymerization. Emissions from compounding and subsequent fabrication processes together account for less than one-half of one percent of the total U.S. emissions.
At present there is no external control equipment used to limit VCM emissions from
compounding and fabricating facilities. Although such controls as carbon adsorption
and scrubbing have been considered for VCM emissions from polymerization plants,
their application to compounding and fabricating facilities appears impractical
because of the low levels of VCM in exiting air from these facilities. Compounding
is the only step in the fabrication process where some external controls may be
warranted practical, specifically in the dry-blending portion of the operation.
However, such controls as may be practical run counter to the current
high-ventilation trend in operation used to limit in-plant emissions.
The most promising control technique to limit VCM emissions to the atmosphere from compounding and fabricating facilities appears to be further reduction of residual monomer levels is resin input to these operations. At present, resin manufacturers are modifying their processes to reduce these levels in order to comply with OSHA regulations. The effect on external emissions from compounding and fabricating facilities is expected to be substantial. Table S-3 shows the estimated average residual VCM levels which manufacturers expect to achieve by 1975 and by 1980; the total annual U.S. emissions of VCM expected from compounding and fabricating facilities using those resins is also shown.
Estimated VCM Emission Rate* Process kg/year (lbs/yr)
A. Flexible PVC 1. Compounding 220,000 (480,000) 2. Extrusion <3,000 (<6,000) 3. Calendering <4,000 (<1,000) 4. Molding <400 (<800) B. Rigid PVC 1. Compounding 300,000 (660,000) 2. Extrusion <4,000 (<10,000) 3. Molding <1,000 (<2,000) C. Plastisols, Organosols, 2,000 (4,500) Solution and Latex Fabrication
* Based on 1974 production rates and late 1974 VCM contents of resins.
Subtotal of Amount U.S. Emissions Total U.S. Percent of Total Emissions Produced by Process Emissions U.S. Emissions Process (kg/kg produced) (kg) (kg) (kg)
A. Monomer Production 2.5 x 10-3 2.2 x 109 - 5.7 x 106 4.0 B. Polymerization - 2.4 x 109 - 1.3 x 108 95.4 Suspension Process 3.9 x 10-2 1.9 x 109 7.6 x 107 - - Dispersion Process 6.0 x 10-2 2.8 x 108 1.7 x 107 - - Solution Process 1.8 x 10-2 5.9 x 107 1.0 x 106 - - Bulk Process 2.4 x 10-2 1.2 x 108 2.9 x 106 - - C. Fabrication Processes - 2.3/x 109 - 5-6 x 105 0.4
A. BACKGROUND: THE VCM PROBLEM
In early 1974 the potential link between the exposure of polyvinyl chloride
industry workers to high concentrations of vinyl chloride monomer (VCM) and their development of angiosarcoma of the liver began to achieve
widespread recognition. The Occupational Safety and Health Administration
(OSHA) of the U.S. Department of Labor acted rapidly to set temporary
and then permanent safety standards to limit the exposure of plant workers
to VCM. Although the acceptability of the permanent standards is currently
under dispute, there is little doubt the result of these standards will
be to reduce to very low levels the VCM in the air which workers breathe.
Since the ventilation methods used. as one major route to meeting the OSHA regulations in no way reduce the total amount of VCM emitted from the plants to the atmosphere, there is still concern about the effects of VCM emissions on the non-worker population in communities surrounding such plants. Although there is little data available at this time as to the actual levels at which VCM emissions to the atmosphere would be of danger to such populations, the Environmental Protection Agency believes it to be important to quantify the extent of these emissions in order to begin to set guidelines governing them.
B. SCOPE OF STUDY
The purpose of this current program is to quantify the extent of VCM emissions from one segment of the polyvinyl chloride (PVC) industry: the processors of the resin. For the purposes of this study, these processors are defined as those manufacturers who work with polymerized polyvinyl chloride resins and, by suitable manipulations involving either a melt, latex or solvent phase, produce finished or semi-finished products. These processors include both compounders (who blend raw resin with additives prior to fabrication to produce a feed "compound" with the desired properties) and fabricators who process compound--through the melt or solvent phase--into semi-finished products. (Compounding may be done by the fabricators themselves, prior to "fabrication", or these fabricators may purchase compound from the resin manufacturers or from independent compounders.)
The PVC fabricating industry is highly diversified, fabricating over 4.5 billion pounds of resin per year into-a myriad of product and end-use applications. Many of the twenty-one raw resin producers also compound some of their own resin, some even purchase resin from other resin producers, and many are also fabricators of finished or semi-finished products. In addition, several dozen independent compounders supply compound to fabricators. The fabricators themselves number several thousand, ranging from
small businesses to fabricators of several hundred million pounds per year of product.
In Sections II and III following, we describe the structure of the PVC processing industry, and the size of each segment. In those sections, the industry is described according to two major categorization schemes: the end products produced and the major type of process used to produce the product. In Sections IV and V, we describe the processes used to fabricate polyvinyl chloride, and document the major points of VCM emission from each process, and estimates of the amount of VCM emitted. Section VI discusses control measures.
Our most important tool for estimating VCM emissions was the classic material balance. By knowledge of the VCM content of resins entering and exiting from each process step, we were able to estimate the amount of monomer lost at each step. "Total nationwide emissions" were then obtained by multiplying the VCM lost per kilogram, at each process step by the total amount of material processed each year by that method.
We should emphasize that no experimental work was done by us during this program. All data used to estimate VCM emissions were obtained by interviews with resin producers, compounders and fabricators. For some processes, data on VCM content of resins at each step were extremely sparse or inconsistent. Concern with monomer emissions in the PVC industry is of relatively recent origin, and manufacturers have not yet had the time to obtain complete data. An additional complication in these estimates arises from recent changes in raw resin manufacturing processes. Because of the OSHA regulations, resin manufacturers are devoting considerable efforts to reducing the monomer contents of their resins in order to reduce VCM emission in compounding and fabricating plants. Thus, "the VCM content" of a particular grade of resin is a changing quantity. In general, the residual VCM levels in most grades of resin were considerably lower in late 1974 than they were in early 1974; they are expected to be even lower in 1975 if resin producers' predictions are correct. For the purposes of this study, we have attempted to use the typical late 1974 VCM levels in resins for each process.
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