Document npwZ7EV6yZZkkxQeqV6G4YZG6

A CRITICAL REVIEW OF METHODS FOR CONTROLLING EMISSIONS OF VINYL CHLORIDE INTO THE WORKPLACE AND COMMUNITY A Thesis submitted to the Division of Graduate Studies of the University of Cincinnati in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in the Department of Environmental Health of the College of Medicine 1976 by Thomas E. Kupferer B.S. ChE. University of Louisville, 1971 CTL030574 ACKNOWLEDGEMENTS The following work would not have been possible if it were not for the timely and unselfish assistance which this writer received from many individuals and organizations. Special thanks are due my advisor, Mr. Lawrence J. Schafer, whose guidance, assistance and friendship have been of con stant benefit in the course of my studies. This author also wishes to express deep appreciation to the B. F. Goodrich Chemical Company and its employees, especially Mr. Ken Pember, Mr. James D. Fannin, Mr. Ronald L. Martin, Mr. Daniel P. Anderson, and Mr. William C. O'Brien. This organization and these men, accorded me the great service of spending many man-hours candidly discussing the vinyl chloride problem and providing a first-hand view of control techniques in use in the industrial environment. Special thanks are also due the Air Products and Chemicals Company and their representative, Mr. Thomas W. Herbig, for providing a complete file on their training and control program. The author would also like to take this opportunity to express appreciation for assistancein locating information to Mr. Loren Anderson and Dr. Martha* Radike of the Kettering Laboratory, Captain Phil Brown of the U. S. Air Force, Mr. Clifford Shotwell, Mr. Bob Hughes and Mr. Jay Jones of the U. S. National Institute for ^^030575 /i ACKNOWLEDGEMENTS (continued) Occupational Safety and Health, and Mr. John Knight of the U. S. Environmental Protection Agency. Acknowledgement is also paid to the Air Force Institute of Technology whose sponsorship has made ray studies possible. Finally, the greatest appreciation goes to my wife, Sylvia, for having constantly provided support and encouragement throughout this entire project. CTL03057 6 /< Chapter I II. III. IV. TABLE OF CONTENTS Title__________________________________________ INTRODUCTION 1 A. Background of the Vinyl Chloride Problem 1 B. Brief History of Vinyl Chloride 4 C. Methods of Production of Vinyl Chloride 6 D. Methods of Production of Polyvinyl Chloride 15 E. Health Effects of Vinyl Chloride 28 METHODS OF CONTROL IN THE WORKPLACE 34 A. Previous Control Practices and Exposures 34 B. Methods of Control in the Vinyl Chloride Monomer Industry 38 C. Methods of Control in the Polyvinyl Chloride Industry 67 D. Methods of Control in Polyvinyl Chloride Fabrication 76 ENVIRONMENTAL CONTROLS 83 A. Concern for Possible Effects on The Community 83 B. EPA Surveys for Vinyl Chloride in the Vicinity of Plants 85 C. Methods for Abating Emissions 93 SUMMARY 107 A. Review of the Current State-of-theArt for Vinyl Chloride Control 107 B. Review of the Effectiveness of Controls CTL030577 112 Table 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. LIST OF TABLES Title_________________________________________ Properties of Vinyl Chloride 7 Vinyl Chloride Production Processes 8 Polyvinyl Chloride Production Processes 18 Signs and Symptoms of Vinyl Chloride Disease in a 1972 Survey of 70 Patients 31 Respiratory Protection Requirements Respirator Cartridge Test Data for 50 ppm Vinyl Chloride Respirator Canister Test Data for 100 ppm Vinyl Chloride Effects of Aspiration and Air Stripping in Reducing Vinyl Chloride Residuals Results of Grab Samples Taken by the EPA Near Vinyl Chloride Plants Results of Integrated Samples Taken by the EPA Near Vinyl Chloride Plants 45 46 47 80 87 91 P ^ CTL030578 /< Figure 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. /< LIST OF FIGURES Title Simplified Flow Sheet for Production of Vinyl Chloride from Acetylene and Hydrogen Chloride Paqe 10 Simplified Flow Sheet for Production of Vinyl Chloride by Direct Chlorination of Ethylene with Dehydrochlorination 11 Simplified Flow Sheet for Production of Vinyl Chloride by Oxychlorination of Ethylene with Air Followed by Dehydrochlorination 14 Simplified Flow Sheet for Production of Vinyl Chloride by Oxychlorination of Ethylene with Oxygen Followed by Dehydrochlorination 16 Simplified Flow Sheet for Polymerization of Vinyl Chloride by the Suspension Pro cess 20 Simplified Flow Sheet for Polymerization of Vinyl Chloride by the Emulsion Process 23 Simplified Flow Sheet for Polymerization of Vinyl Chloride by the Bulk Process 25 Simplified Flow Sheet for Polymerization of Vinyl Chloride by the Solution Process 27 Closed Loop Sampling System 52 Closed System for Tank Car Loading 54 Equipment Maintenance Clearing System 55 Tapered-thread Pipe Joints 57 Examples of Flanged Pipe Joints 58 Chempumps Canned-Motor Pump 60 CTL030579 Figure 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. LIST OF FIGURES (continued) Title Standard Single Mechanical Seal for a Rotating Shaft Typical Double Mechanical Seal for a Rotating Shaft Typical Diaphragm Valve Layout and Sampling System for Polymerization Plant GAF Solvent Reactor Cleaning System Exhaust Hood for Blender as Recommended by Tribukh Aspiration System for Dry Blender Typical Improved Stripping Process Parameters Effects of Increased Temperature in Stripping of Polyvinyl Chloride Resin Simplified Flow Sheet for Activated Carbon Adsorption System Solvent Absorption System for Vinyl Chloride Control Refrigerated Vent System for Vinyl Chloride Control Page 61 62 64 69 74 78 79 98 99 101 103 106 CTL030580 CHAPTER I INTRODUCTION My purpose in the following pages is to review the technology available for the control of vinyl chloride, as it relates to preventing hazards in the environment of both the workplace and the community. I will first review the processes involving vinyl chloride, then briefly describe its hazards, and finally discuss, in detail, the methods and equipment used for its effective control. This first section will acquaint, or reacquaint, the reader with the vinyl chloride industry and with the vinyl chloride problem. It will also serve the reader as a ready reference for processes and items of equipment discussed in the main sections of this work. A. BACKGROUND OF THE VINYL CHLORIDE PROBLEM: In the past two decades, vinyl chloride has become one of the world's most economically significant chemicals. Although it is used in its pure form, its polymer, poly- . vinyl chloride, is one of the most important of all plastics. This polymer may be fabricated into sheets, extruded, molded, vacuum formed, or used as a coating. In short, it can be fabricated in any way applicable to thermoplastics. In CTL030581 addition, it has excellent properties for resisting attack by many chemicals and has good electrical resistance. Also, it may be processed for a wide range of rigidities and strengths. Its uses vary tremendously, with the polymer being used for such diverse applications as clothing, floor tile, shoes, pipes, building materials, wire insulation, paints and coatings, unbreakable bottles, credit cards, phonograph records, upholstery and automobile tops.(73) Vinyl chloride may also be polymerized with other materials such as vinyl acetate or vinyl ether, or vinylidene chlorid to form plastics with even more varied properties.(29) The monomer's only commercial use which directly reached the public was as a propellant in aerosol cans. One can then see that since the major portion of vinyl chloride monomer is consumed in producing the polymer, the main exposure has been an industrial one, where for many years, vinyl chloride was thought to present no serious hazard other than that of fire or explosion. In fact, it was even briefly tried as an anesthetic. As it came into general industrial use in the nineteen-fifties, more of its chronic effects became known, and hygienists began to recognize that there were certain characteristic chronic effects. Studies concerning these effects in the early seventies yielded the first hints of vinyl chloride CTL030582 /< X -3- carcinogenicity. It was not until early 1974, the B. F. Goodrich Chemical Company announced that the health and safety personnel at their Louisville, Kentucky polyvinyl chloride plant had determined that it was probable that a rare form of liver cancer seen in several workers at the plant might be related to vinyl chloride exposure. Within a very short time, a European group which was a following-up to the earlier studies suggesting carcinogenicity, released some of its preliminary data which showed a relationship in laboratory animals between cancer incidence and vinyl chloride exposure. These test animals developed a variety of cancers, which included the type of liver cancer seen in the Louisville polymerization workers. These revelations set off a whole series of regulatory and investigative actions, leading to an emergency temporary standard of one tenth of the previous standard for human exposure, and later to another even more drastic lowering of the allowable exposures. As a result, industry has been faced with a standard that is, in effect, three orders of magnitude lower than it was only two years ago. In addition., new environmental regulations for controlling emissions have been proposed, and, in all likelihood, will soon be adopted. This has placed a great demand on emission control technology in an industry where process losses were previously acceptable CTL30583 /i -4- at levels as high as six percent. B. BRIEF HISTORY OF VINYL CHLORIDE: Vinyl chloride is not a new chemical by any means, having been first synthesized and reported by Regnault in 1833. He also observed the polymer during the same time period, but did not fully recognize its character. It was not until 1911, however, that a process of commercial potential was discovered, when Klatte and Roulette developed a method of synthesizing vinyl chloride from acetylene and hydrogen chloride on a mercuric chloride catalyst. The first commercial plant was completed in the United States in 1928, followed some five years later by another small operation in Germany. Still, there was no significant interest in vinyl chloride until World War II created a pressing need for substitutes for natural rubber. By 1950, world-wide vinyl chloride pro duction had not yet reached two million tons per year. Between 1950 and 1960, demands began to grow very rapidly as more and more practical applications were discovered, with ' the result that production increased four-fold by 1960. (28,43) United States production for 1973 was 2.6 million tons of vinyl chloride and 2.3 million tons of polyvinyl chloride and copolymers. The average annual increase in production from 1968 through 1973 was fourteen percent, and this growth rate is not expected to slacken more than CTL030584 /' 5- moderately over the next four years. The only brake on further increases has been a short supply of the petroleum- based raw material, ethylene, and uncertainty over new federal regulations. In the United States in 1973 there were fifteen vinyl chloride plants with 1000 to 1500 employees, and thirty-seven polymerization plants with about 5000 em ployees. As of that time, new plants and expansions of older ones were being constructed to add another 1.378 billion pounds per year to the United States' vinyl chloride capacity. In addition to these, there were about 7500 plants performing fabrication of the polymer, employing about 350,000 workers.(73) Figures for the summer of 1975 con firm that this growth rate has continued in spite of the new regulatory requirements, with U.S. vinyl chloride capacity at 3.42 million tons per year and polymer capacity up to 3.03 million tons per year (about 27 pounds per capita per year). (74) It has been estimated that between 1,700,000 and 2,200,000 jobs ultimately depend upon the vinyl chloride/ polyvinyl chloride industry when one considers those employ ed in using fabricated materials such as automobile up- , holstery and some construction items.(76) -_ With this background on the significance of vinyl chlo ride and polyvinyl chloride, it can be seen why the discovery of its carcinogenicity caused such concern. The population of CTL030585 /< 6- - industrial workers is large, and since the polymer is a part of almost every American's daily life, essentially all persons are exposed to the polymer at least to some minute degree. Further, vinyl chloride is a chemical of vital economic importance, which has a profound impact on the nation's way of life. The consequences of the illness which it causes are very grave, yet the importance of the con tinued production of the chemical is also tremendous. Thus, clearly, it is indicated that the problem must be solved such that production may continue while the potential for harm to workers and the community is eliminated. The chemical and physical properties are listed in Table I. C. METHODS OF PRODUCTION OF VINYL CHLORIDE; There are currently four processes used in the United States for the synthesis of vinyl chloride monomer. These are shown in Table II. Hydrochlorination of Acetylene: This is the oldest of the commercial methods for preparing vinyl chloride, and until rather recently it was the primary production route in the United States.(21,28) The economics of this process are inferior to those based on ethylene and it has thus lost favor in industry. As of August, 1975, the Environ mental Protection Agency reported that the last of these plants was shut down.(74,76) The basic reaction is that * of acetylene and hydrogen chloride: /< CTL030586 TABLE I PROPERTIES OF VINYL CHLORIDE (27,28,29,34,74) SYNONYMS: Chloroethylene, Monochloroethylene, Chloro- ethene, VC, VCM FORMULA: CH2CHC1 molecular weight = 62.5 STRUCTURE: HH C=C H Cl BOILING POINT: -13.37 at 760 mm Hg SPECIFIC GRAVITY: 0.99 at -25C DENSITY: 2.55 grams/liter at 25C and 760 mm Hg VAPOR PRESSURE: 10 mm Hg -87.5C 100 mm Hg @ -55.8C 692 mm Hg e -15.8C 2660 mm Hg @ +25.0C SOLUBILITY: Slightly soluble in water (0.11%) Soluble in alcohols and mineral oil Very soluble in ether or carbon tetrachloride Solubility of water in vinyl chloride is 0.03% HAZARD DATA: Flashpoint = -108F (Cleveland open cup) Auto ignition temperature = 472C Lower explosive limit = 1.2% by volume in air Upper explosive limit = 22% by volume in air CONVERSION FACTORS: At 25C and 760 mm Bg 1 ppm = 0.00256 mg/l= 2.56 mg/m"* 1 mg/1 * 391 -ppm 1 mg/ra3 = 0.391 ppm PHYSICAL APPEARANCE: Colorless, in either gaseous or liquid form ODOR: Usually described as sweet or pleasant, sometimes as etherical. Those familiar with odor may first detect it at 1200 to 2000 ppm. CtL030587 -8- TABLE II I ' VINYL CHLORIDE PRODUCTION PROCESSES (12,74,76) Number of Process______________________________________ 1. Hydrochlorination of acetylene 2 Percent of Plants (1975) 1975 C 8 2. Chlorination-Oxychlorination of ethylene with air with dehydro chlorination 3. Chlorination-Oxychlorination of ethylene with oxygen with dehydro chlorination 10 1 77.5 4*5 4. Direct chlorination of ethylene with dehydrochlorination 3 10 C-IL030588 -9- HC s CH + HC1 -* H2C = CHC1 A schematic representation of the process is shown in Figure 1. The hydrogen chloride and acetylene are dried and introduced into a bed of activated carbon upon which a catalyst (tradi tionally mercuric chloride) is absorbed. The reactants are then passed through a two stage distillation process. In the first stage the lower boiling point impurities (mostly acetylene and hydrogen chloride) are allowed to boil off, while in the second, the vinyl chloride goes overhead leaving the higher boiling point impurities (mostly ethylidene chloride and aldehydes). The yield is very high, and the separation clean enough to yield vinyl chloride at better than 99% purity. (21,28,76) Dehydrochlorination of 1,2 Dichloroethane (Ethylene Dichloride or EDC: There are three different processes used which depend on the process of dehydrochlorination of ethy lene dichloride to produce vinyl chloride. These vary only in the use made of the hydrogen chloride which is formed during cracking, and how, if at all, it is returned to the process. The simplest process is direct chlorination of ethylene, followed by dehydrochlorination (cracking), which is sche matically represented in Figure 2. In this process, the CTL030589 /J VENT t \ -01 CTL030590 FIGURE I: Simplified Flow Sheet for Production of Vinyl Chloride From Acetylene and Hydrogen Chloride. (73) V I H M I CTL030591 FIGURE 2: Simplified Flow Sheet for the Production of Vinyl Chloride by s Direct Chlorinction of Ethylene, Followed by Dehydrochlorlnotion. (73) I 'it FI* JHC3 V.KTL CKIQTCC UC5t -12- basic materials are chlorine and ethylene. These are fed into the reactor where they are contacted with either iron chloride or calcium chloride catalyst. The following reaction then occurs: h2c = ch2 + ci2 -* cih2c - ch2ci This reaction is normally run at about 125C at seven to ten atmospheres, yielding nearly theoretical conversions. Following the ethylene dichloride synthesis, the product is washed twice with water in counter-current columns, then dis tilled in two successive columns to separate the low and high boiling impurities. The purified ethylene dichloride is then fed to a cracking furnace where it is contacted with pumice or charcoal catalyst at about fifty pounds pressure and 480 to 510C. About 94 to 97% of the ethylene dichloride is thus converted to vinyl chloride in each pass by the following reaction: CIH^C - CH2C1 heat- h2C = CHC1 + HC1 The reactor products stream is introduced into a distilla tion column where it is quenched with liquid ethylene dichlo ride, which separates the components with the vinyl chloride and the hydrogen chloride going overhead. The bottoms are then chilled, and either returned to the quenching column, or recycled back to the start of the process or to the initial CTL030592 -13- distillation step. This step, while essential from the engineering standpoint, does present the unfortunate con sequence of introducing vinyl chloride into the process streams even at the earliest stages. The distillate is then charged to a second column where the-vinyl chloride is separated with the bottoms, while the hydrochloric acid goes overhead. In the direct chlorination process, this acid is not reintroduced into the process, and is considered a by product. The final step in the process, then, is to distill the vinyl chloride stream in a final column in which the nearly pure vinyl chloride goes overhead, with the higher boiling impurities being removed in the bottoms.(1,2,7,12, 28,76) The most common process used in the United States is the chlorination-oxychlorination of ethylene with air, followed by dehydrochlorination, as shown schematically in Figure 3. The main difference between this procedure and the direct chlorination procedure is that the hydrogen chloride from the cracking process is reacted with air and ethylen in the presence of a ferric chloride catalyst to yield additional ethylene dichloride by the following reactions: 4 HCl + 2 2C12 + 2H20 h2c = CH2 + Cl2 C1H2C - ch2ci CTL030593 /i VIMT (ntioto TO ccovtr V I M u I CTL030594 FIGURE 3: Snp5f:ed Flowsheet for the Production of Vinyl Chloride by Oxychlorinotion of Elhylene with Air, Followed by Dehydrochlorinolion (73). *** to -15- The product stream from this reaction is washed in a counter-current column/ with hot water, after which the water and the ethylene dichloride are separated by virtue of their being essentially insoluble in one another. The ethylene dichloride stream from this process is then combined with that from a simultaneous direct chlorination process. The ethylene dichloride is then processed as in the direct chlorination process, except that the hydrogen chloride formed in the cracking process is returned to the oxychlorination reactor.(1,2,7,12) One manufacturer is currently using a modified oxychlorination process in which oxygen is used in place of air, as shown schematically in Figure 4. The process after that point is essentially the same as for oxychlorination of ethylene with air. (12) The primary advantages of this pro cess are the tremendous reduction of the gas stream leaving the reactor and the reduction of subsequent processing re quirements for separating the inert components such as nitro gen which would be present if air were used. This also re sults in decreased emissions from the oxychlorination reactor and provides a vent stream which is combustible without supplementary fuel.(74,75) D. METHODS OF PRODUCTION OF POLYVINYL CHLORIDE: * The vast majority, over 97%, of the vinyl chloride produced iv / < CTL030595 CTL030596 FIGURE 4: Simplified Flow Sheet for the Production of Vinyl Chloride by Oxychiorinotion of Ethylene with Oxygen, Followed by Dehydrochlorinction C73). -17- ha s been polymerized to make polyvinyl chloride or one of its copolymers.(73) Since the banning of the use of vinyl chloride as an aerosol propellant, it is likely that even this high percentage will increase, as this will leave only uses as a pharmaceutical base and as' a chemical intermediate in trichloroethane and pesticide production as significant uses of the monomer.(76) Currently four basic processes are in use in the United States for the production of polyvinyl chloride, as shown in Table III. The reaction in all processes is similar, with the basic mechanism being the joining of the monomer molecules through cleavage of the double bond, as shown: H NC H H 's Cl HH i - c - c- II H Cl H i C i H H f CI Cl n The reaction, its kinetics, and its endpoints have been well characterized,(11) but are not relevant to this dis cussion. The vinyl chloride may also be combined with anoth r monomer to produce copolymers.. An example of one of the more common of these is its copolymer with vinylidene chloride, which is formed as follows: Cl Cl *-< HH C H Cl I --c I H H Cl ii C-c II Cl H H i Cf H n CTL030597 -18- TABLE III POLYVINYL CHLORIDE PRODUCTION PROCESSES (12) 1973 Process Suspension Number of Plants 34 Percent of Total 78 Dispersion (emulsion) 11 12 Bulk 36 Solution 34 CTL030598 The typical polyvinyl chloride process is of a batch type and the plant will normally include the following operations: (3,4,5,12) 1. Receiving and storage of vinyl chloride monomer. 2. Polymerization to polyvinyl chloride 3. Stripping of the product stream and recovery of the unreacted monomer, slurry handling. 4. Centrifugation of filtration of the slurry. 5. Drying of the polymer. 6. Pneumatic conveying, and storage of the product. 7. Packaging and shipping. 8. Blending. 9. Waste treatment. The mostly widely used polymerization process in the United States is the suspension process, which is shown sche matically in Figure 5. The first step in the reaction is to introduce water, vinyl chloride, initiator, suspending agent and buffering agent into the reactor, which is normally a glass-lined agitated vessel of from 2000 to 6000 gallon capacity. The ratios used are generally on the order of two parts water per one of monomer (with a range of 1.5:1 to 4:1) which would be varied according to the polymer qualities desired. The initiators are usually organic peroxides such as dibenzoyl peroxide, acetyl benzoyl peroxide, or dibutyl / I CTL030599 20- CTL030600 WATER >1SUSPENSION AGENT INITIATOR RECYCLE I ^ACCUMULATOR) v%nt 4 OAT TANK RE ACTOR c>'.: woUr- CONDENSER -S .vnt watt* woUr | RECOVERY 'ACCUMULATOR Will [4 CONDENSER COMPRESSOR PHASE SEPARATOR KNOCK OUT POT STRIPPER Uam- liom olhf tn ppr BLENO tank L AIR FIGURE 5! Simplified Flow Sheet for Polymerisation of Vinyl Chloride by the Suspension Proces* (73). "I ,,WET -O AIR BLOWER DUST COLLECTOR SIZING ivtnl FINISHED POLYMER STORAGE PACKING AND SHIPPING \ I peroxide, and are added at about 0.03 to 0.2 pounds per hundred pounds of vinyl chloride. The suspending agent acts to stabilize the suspension, and is usually polyvinyl alcohol added at about 0.005 to 0.5 pounds per hundred pounds of vinyl chloride. As the reactants are' introduced into the reactor, they are vigorously agitated to create a very fine suspension of vinyl chloride droplets. The reactor is con trolled at between 35 and 50C by passing cooling water through its integral cooling jacket. Once initiated, the reaction is self-catalyzing and is allowed to run to about 90% of completion. At this point the batch is discharged from the reactor to a stripper or dump tank and is there stripped of unreacted vinyl chloride monomer by application of vacuum or injection of steam. These monomer vapors are carried, along with any noncondensable gases to a monomer recovery system. This system uses chillers and compressors to recover the unreacted monomer, but must be routinely vented to release any buildup . of the noncondensable gases. (76) After stripping, the polymer suspension is discharged to a blend tank where several batches may be accumulated and mixed. The slurry is centrifuged, and then dried,usually by a rotary drier using heated air. The dried polymer is then screened for sizing and sent to be stored or packaged.(3,11,12) CTL030601 -22- The second most widely used polymerization process in this country is the dispersion (emulsion) process, a schematic of which is shown in Figure 6. This process is similar to the suspension process, except that the vinyl chloride is dispersed in the water in a non-settling emulsion,stabilized by surface active agents. Another difference is that the initiators are dissolved in the water phase, whereas in the suspension process, they are dissolved in the vinyl chloride phase. The emulsifiers usually preferred are alkyl sulfates, alkane sulfonates, or fatty acid soaps. These are added at just above a critical concentration at which the emulsifiers form microscopic sized agglomerates called micelles. The reaction is triggered by initiators in the aqueous phase, usually peroxides or peroxydisulfates. The free radical so created migrates to the micelles where the polymer molecule begins to grow. At about one to two percent conversion of the vinyl chloride charge, the micelles disappear as the emulsifier is all used at the surface of the growing polymer particles. At about 60 percent conversion, essentially all the monomer is in the polyvinyl chloride. The batch is discharged to a spray drier when the solids content reaches about 50 to 55 percent. The water and unreacted monomer are removed in the drier. The polyvinyl chloride so produced as a high molecular weight t CTL030602 3 Ot* CJ o FIGURE 6: Simplified Flow Sheet for Polymerization of Vinyl CT\ o Chloride by the Dispersion (Emulsion) Process(73). CJ -24- and small particle size (50 to 150 microns). (5,11,12) The next most important, and the newest, process in this country is the bulk (Pechiney-St. Gobain) process. This process is considered desirable because there are no foreign substances such as emulsifiers or water added to the process which must be either removed at some stage, or left as con taminants in the final product. The process was only recently made practical by the introduction of a prepolymeri- zer as shown in the schematic in Figure 7. The first step in the process is to introduce monomer into the prepolymerizer with very small quantities of initiator (usually about 0.02 pounds of azo-bis-isobutyronitrile and 0.00005 pounds of di-isopropyl percarbonate per one hundred pounds of vinyl chloride). This is agitated for about three hours at 40 to 70C, with cooling being provided mainly through the vapori sation of unreacted monomer. At about seven to ten percent conversion, this charge is transferred to the main reactor (or autoclave) where it is slowly agitated for ten to fifteen more hours at about 50C. The reaction is one of heterogeneous phases, since the polymer is insoluble in the monomer, and, - in fact, the reaction mass.is basically a powder after about twenty percent conversion. Since the reaction is strongly exothermic, cooling is provided to the reactor jacket, the agitator shaft, 4 k ,I and by a reflux condenser. Once initiated, CTL030604 \ Vint CTL030605 -26- the reaction is self-catalyzing, and the rate of reaction increases with increasing percentages of polymer. The re action is halted at about 90% conversion by vacuum stripping the unreacted monomer directly from the autoclave. The pro duct is then drawn out of the reactor by an air eductor and air conveyed to processing and storage.(5,7,11,12) The final process used for polymerization of vinyl chlo ride in the United States is the solution process, which is shown schematically in Figure 8. In this process, the vinyl chloride monomer is dissolved in a solvent such as n-butane, cyclohexane, tetrahydrofuran or 1,2 dichloroethane. As the polymerization proceeds, the polymer precipitates, but is held in a slurry by agitation. The slurry is discharged to a steam stripper from which the unreacted vinyl chloride is returned to the reactor. The polymer and solvent are blended with other batches then centrifuged and dried in a manner similar to the suspension process. The product so produced has very few impurities and is characterized by a low mole- \ cular weight.(5,7,11,12) There is a wide variety in the details of equipment and exposures, even for plants using the same type process for production. Variations which especially affect the work environment are those such as the age of the equipment and the quality of housekeeping and maintenance. One serious CTLoaoeoe 21- CTL030607 FIGURE 8: Simplified Flow Sheet for Polymerization of Vinyl Chloride by the Solution Process (73). I V I -28- problem in all of these polymerization processes is the buildup of polymer on the reactor walls, which necessitates the periodic cleaning which has historically resulted in the most serious worker exposures. No continuous process of the classic type has been developed for the polymerization of vinyl chloride with the main deterent being the long residence time required for the reaction. E. HEALTH EFFECTS OF VINYL CHLORIDE: The vinyl chloride problem has been a very emotionally charged issue since the announcement of its implication as a carcinogen in January, 1974, and it is likely to remain so for some -time yet to come. One of the major reasons for this reaction has been that for many years, toxicologists had not related any serious health threat to occupational vinyl chlo ride exposure. Much has been said about how new chemicals should be pre-tested before being used or produced on any large scale.(42) However, it is important to note that vinyl chloride has been known as a commercial product for over forty years, and had been examined for health effects for many years by various researchers, and was repeatedly certi fied as having a very low hazard except for fire and explosion potential. Early research centered mainly on central nervous system effects, since vinyl chloride has obvious effects on that i CTL030608 ,i -29- system in acute exposures. In fact, vinyl chloride was proposed and studied for use as a general anesthetic during the 1930's and 1940's. These early studies concluded that the primary effect was acute central nervous system depression, and that essentially no chronic effects were found.(43,55) In 1949 one researcher in the U.S.S.R. did find certain chronic changes including "more-or-less profound hepatitis" in some vinyl chloride fabrication workers, but he attributed the changes to the plasticizers which were being added to the polymer.(72) In the late 1950's and the early 1960's, researchers began to become aware that vinyl chloride did indeed have chronic effects. Some of the problems noted were circulatory disorders, skin problems, liver damage, and a peculiar skeletal defect known as acroosteolysis. One of the earliest of these problems to be noted was angioneurosis, an irregu larity of the circulatory and nervous systems of the extremi ties. (23) These symptoms are generally referred to as Reynaud's syndrome, and involve spastic behavior of the arterial system which results in numbness and pallor or cyanosis of the fingers or.toes. (78) This is apparently related to a characteristic deformation of the terminal digits of the fingers, in the form of pseudo-clubbing and acroosteolysis. * i /< Acroosteolysis in vinyl chloride workers CTL030609 -30- was first observed as a resorption of bone in the terminal digits of the fingers, with the pseudo-clubbing, and a de formation of the nails. This defect has been epidemiologically related to high exposures especially as in reactor cleaning. (16,37,67,78) Table IV gives a summary of the signs and symptoms found in a survey of seventy patients from a German study (78) which more-or-less illustrate the effects of chronic vinyl chloride poisoning, or what h?s become known as "Vinyl Chloride Disease". Another more serious aspect of chronic vinyl chloride exposure began to emerge during this same period, that is, chronic liver injury. The injury is characterized by portal fibrosis, a nodular surface on the liver, enlargement of the liver, and elevated hepatic venous pressure. The injury is apparently either very slow healing, or does not heal.(28) Unfortunately, no completely reliable screening test has been determined as a means of ascertaining if injury is being done, or if it already exists in such cases. (80) The most significant development in vinyl chloride toxi cology was first suggested when one researcher announcedthat he had observed an increase in cancer incidence in animals exposed to 30,000 parts per million for four hours per day, five days a week, for ten to twelve months. The tumors observed did not, * k ,J however, include angiosarcoma.(40) However, CTL030610 -31- TABLE IV SIGNS AND SYMPTOMS OF VINYL CHLORIDE DISEASE IN A 1972 SURVEY OF 70 PATIENTS (67) Sign or Symptom Number of Patients Upper abdominal complaints Tiredness Frequent dizziness Numbness or tingling of fingers and toes Increased perspiration Sensation of coldness in fingers and toes Pain in the joints Impotency. Head pain Pain in the calves Low platelet count Increased BSP retention time Enlarged Spleen Reticulocytosis Increased SGOT, SGPT, AP or SP Scleredema-like skin chances Varices of the esophagus or fundus Acroosteolysis Raynaud's syndrome Low white cell count 42 27 26 22 19 18 17 13 9 9 57 45 39 24 10 8 8 6 6 5 Percent Patienl 60 39 37 31 27 26 24 19 13 13 81 67 57 41 14 11 11 9 9 7 CTL030611 -32- in December 1973, angiosarcoma was diagnosed as the cause of death in a vinyl chloride worker in Louisville, Kentucky. This represented the third such case of this rare cancer at the same plant, and thus the possibility of an occupationally related cancer was announced. Resulting epidemiological data established that while the expected death rate for angio sarcoma of the liver in the general population was about 0.0014 cases per 100,000 persons, thirteen cases of it had been found among vinyl chloride workers, who number less than 20,000. The incidence was thus about 400 times that of the general population.(30) These announcements also prompted the release of some preliminary data by Maltoni which showed angiosarcoma, and other cancers being related to vinyl chloride exposure in several laboratory animals. Maltoni has since found some increases in tumor incidence down to exposure levels as low as 50 parts per million. (40,41) More recent epidemiological research has indicated that there may indeed be other carcinomas occuring at greater than expected rates among vinyl chloride workers.(70) Other current subjects of interest which are at present unresolved are the potentials for mutagenesis and teratogenesis. A preliminary report of a teratogenicity test done on rabbits, rats, and mice did not show any such effect. (65) Testing for mutagenicity in bateriological systems has shown i CTL030612 /i V -33- some possibility that there may be some mutagenetic potential, but no definitive results are yet available.(60) Thus, as research has progressed, and the number of per sons exposed has increased, vinyl chloride has been found to be anything but the innocuous compound that it was first thought to be. The one undetermined fact that can be expect ed to continue to cause controversy is at what level risk is incurred. This has not been experimentally determined, and, in all likelihood, cannot be reliably measured.(63) CTL030613 -34- CHAPTER II METHODS OF CONTROL IN THE WORKPLACE A. PREVIOUS CONTROL PRACTICES AND EXPOSURES: In the past, relatively little attention was given to control of vinyl chloride in the workplace, since the toxico logic data of the time indicated that there was little hazard. As mentioned earlier in this paper, the first to actually observe the chronic effects were the Soviet re searchers Tribukh, Tikhomiroun, and Levin. In their 1949 survey of a vinyl chloride fabrication plant they observed exposures' from 1 to 470 parts per million of chlorinated hydrocarbons in various work areas, however, they attributed the health effects which they observed to the plasticizers which were being added instead of the residual monomer being released from the heated polymer.(72) In the United States, the earliest apparent efforts to determine exposures were those done by Dow Chemical, who started routine monitoring in about 1950. At that time, analytical techniques did not differentiate between vinyl chloride and other chlorinated . hydrocarbons, such as vinylidene chloride. Prior to 1960, exposures were generally fairly high, but mostly below a time weighted average of 500 parts per million. However, expo sures as high as 4000 parts per million were measured under ; 1 CTL030614 r( Hydrogen chloride CTL030862 <T$3tEimrr stiascsoisarts CTO-'* fOtTi'ISS --tNU lAum MAT m cc^r-jriita At tr'tr.iNt Ativj or CIOI MAftllAlt l**`|TM|t trtf ah m n| fotM of t'A^;AtD ilVK utlt 01 Mtll tux ai: fiown *h{ ia.vi iauc r<mi. *.tt ah*ovcw coMfo^awc new. RCVll MAI VAir - t*-cw o.\o6a*c UCi 01 0>lt0;v( (ION 'OAT. mil *r 111vamo fiuMitijin Kf 0 *M Ol'ff TKft A11 T*| MOtf MfOMAH i*C riOM'l mini ftCMimt O* 1h| (Oa*OaD All 0(r|rCt*t V'Om f**|M T*l amCvnII IMIO 9II*"N| ?*| lO^Mtt AN) fit ns/utr r i [_ i'l t I'! r K!VG&S5M P. POILYR'IG&S EM PiLASTBCS THE ING.PEO'ENTS APE FICfST BLENDED IC-GETHEJ AFTLICATlON Of HEAT ANO PRES SURE SUPPLIED DUPING PROCESSING FUSE AND XN.'T THE MIXTURE INTO A HOMO GENEOUS .MASS OR SHAPE. THE NEED FOR PRESSURE usuAur determined or THE PHYSICAL FORM OF THE GECN POLYMER AND METHOD Of PROCESSING KIOTO co.v.r-cuwos , TMIII Aft |T0* fiato . riAjrici o/ vu-jtvw ia. 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Xf ATJ8 di!p:2o*i op A piooipisd roirvriTi chiox:o: t:six o;cm plastic iattx is a stash rAi:c o.;.'j";iox op a JKOPIPISD V!im CNlOilC-J PIASTIC. PASIlCll V2S l> i:ss TKAff c 1 wic*ox | ,'C.r. i | * A VARifTY op STA.'.O. cs?3p5 { /ACD OfCN riASTICS ACI CO*lPOUK3(D r\A\/)*-ij and sold sr r. *7 1 oocja.cn c>i:*'?cai co V. ceh\ ft I ^--W) (1* to) ; !< Dr*" : CSISSrlJ c\iz;:i z?a::g, ejitcusion, molding <c COATING (IOIV1MT fOiUTIONS; cc/.ti^o, i.V:Pr.cc:;AnrJG# Cfrn::o r. r;LU gvst:::o OIOM PAST! tt^'S *r.:^4 PSOTSIIT ccapo'jxdid nti: ;tuir pastii CO'IA-TO U7TVI 01 > YOIAT-J Cuy;:.",S Tx v. PiOtCi; \*o n i-y.r^u, Icr*.3M c>i. a: d tz:`. t:j-> jO\. v;:.*: hapao; um ati |XT3IM(tT P-M <1-4 t-.CCO'TSI C5Ir_(,_^.CZ->^ C-3 co.'.n::c, irr.:c:nr:a, tOV/ FOc-"On /.-.OLDirro, crrrmo o c/jrn.no "r v la tO : < ii : ' .: -. ./ r!'Oi;uf;.: or; x. 4l ^ (i y i'L li ll !j d b: Li 8/- L-- a tJ 3 y L; \J iV Jj \^iy * NATURAL / . LiivLESTO^/ Abater y/ 'V XO VacstyiesV,? ! G V9 CU.fcrS.'c V >J i/frJ ft | HTtfyiEr/^ ./ "K 6 G`rt/0^l ; J-.;.;. rO-OLVO-Hj %1* x/ 'j 5 , j / I. ! r'\.E^.--.'T.- iTOf* rf..OJOi^n iwwinut wiri7l*| e?.Ta..4w*i\v.J.^>. ~ uc-xjli* iPXP'Ii*T-**Tr!-iA.1;'F--J TLs- 2Sj ^iT<wvw'e/>iw*gKm?<cn o o L r. e. .) . r_<.r? ii ; I C0P0LYtwER!ZAT!0;S TAKES PLACE ^Ccf'O M ' Oi j HEAT AUTOCLAVE^/ fLO"V~^ >;|! i(m: / . y i WHEN K0N0?JiERS OF DIFFERENT i p, uvjiiir^^prsj rrcjpncmn-.i ppr"os?.:p Os li~JtiOo.vi. OOi i Iuiy ul/uiuitYu ' ............. I ^ p _o0 pp:o :o co 1CTL030865 U -c COTW/i 'CHIrtR-HE ACETATE FLASliC ' 'X. \* \> /1 i\\ \ H f-i ?\i C h- : HSTA ;) 1.1 a> tc ; Li j] tj ij W I M c., fi li