Document RJD53Bmx6Gaxxq6Jjd1yoo2YV

FILE NAME: &'ZZ&' DATE: DOC#: &' DOCUMENT DESCRIPTION:ZZtDZ/, WZZ/ 1932 Our haneers fork nor;amEn- get ders law in- of the odes tion heir over in meions the the by mith hytion ing ent, ic -ousted e in :ons ark- of less uch rks. rem1.118 1 Industrial Health Problems in the Rubber Industry WILLIAM E. McCORMICK The B. F. Goodrich Company Akron, Ohio T HE AMERICAN rubber industry is complex and diversified. Its raw materials and products come from, and are used in, many parts of the world. Many of its processes require the use of potentially hazardous materials. Recent years have seen many changes in this industry. One of the most significant of these has been the development of American-made rubbers from domestic raw materials. In 1941 essentially all of the 787,000 long tons of rubber consumed in the U.S.A. were imported natural crude. In 1950, nearly half of the 1,258,000 long tons used came from domestic synthetic production. Many types of American-made rubber are commercially available, but GR-S (Government RubberStyrene) is the chief product. Others are butyl, nitrile types, neoprene, and thiokol. In the production of all of them certain health hazards exist. In the processing of them, as well as of natural crude, similar problems arise. A discussion of those relevant to GR-S production, and GR-S and natural crude processing, follows. I. GR-S Manufacture THE MANUFACTURE of GR-S rubber consists of copolymerizing two compounds, butadiene and styrene, to form a finely dispersed latex. This is then subsequently coagulated, filtered, dried and .baled for processing operations. Various types of GR-S are produced, depending upon the physical properties desired in the final product. This variation requires the use of different operating temperatures and pressures, different butadiene-styrene ratios, various catalysts, modifiers, polymerization accelerators, and anti-oxidants. A flow diagram of the general process is shown in Fig. 1. BUTADIENE: The butadiene used for GR-S manufacture is the 1,3 isomer, with the formula C112 :CH.CH:C}12. It is a gas which Presented at the Fourth Regional Gulf Coast Industrial Health Conference. Houston. Texas. September 28. 1951. wax= aierriel /snag= 1 (LCICTC Iltss) ILLINCLITIGI STUMM (0:11ILLA1011 411:00O11111 sem wan= WILLA 10110 4 Se.77110 Fig. I. Flow Diagram of GR-S Manufacture liquifies at --4.4 C. It is highly flammab:e, with an explosive range of 2.0-11.5 percent in air.1 Because of these physical characteristics, storage and transportation are accomplished under pressure and insulation. Upon its arrival at a GR-S plant, it is handled in a closed system. Necessary precautions must be taken to insure against the possibility of fire and explosion wherever it is used. Butadiene tends to spontaneously form explosive peroxides upon ageing. Hence an inhibitor such as tertiary butyl catechol, must be incorporated into the commercially produced product.2 The health hazards of butadiene are mild. It has a narcotic effect at high concentrations, but has little if any cumulative action." Atmospheric concentrations up to at least 1000 p.p.m. can be tolerated for prolonged periods of time without ill effects. STYRENE: Styrene, Calf 5.CH:CH. is a liquid, boiling at 145C. Its limits of flammability are 1.1% (29.3C) to 6.1% (65.2C).4 As in the case of butadiene, rigid precautions are necessary to protect against fire. Physiologically, styrene does not produce the serious effects of the closely related aromatic hydrocarbon, benzene. No significant changes have been found in laboratory animals exposed to vapor concen- ' Page 38 INDUSTRIAL HYGIENE QUARTERLY March, 1952 trations of 650 p.p.m. up to six months5 but subjective symptoms in humans have been found after several hours' exposure to SOO p.p.m. The vapors become quite irritating above 400 p.p.m. It is therefore desirable to maintain workroom atmospheres below 200 p.p.m. MINOR COMPONENTS: A large number of substances are used in more or less minor quantities for GP.-S manufacturing. Among these are the various catalysts, emulsifiers, polymerization accelerators, short-stopping agents, anti-oxidants, and dusting materials. Fortunately very few of these substances in their specific use present health problems. Exceptions are dinitrochlorobenzene, sodium sulfide, and EFED (triphenyl phosphite). Dinitrochlorobenzene is a hazardous com- pound. It is a severe sensitizer and elaborate precautions must be taken to prevent skin contact. If it does occur accidentally, immediate removal from the skin is necessary. In addition to its dermatitis producing potentialities, it is also systemically toxic. The degree of this, however, is not fully established, but is believed to be more severe than nitrobenzene. In the industrial use of this compound, the dermatitis hazard is by far the more important, and because of its severity, more or less controls the systemic hazard automatically. During the coagulation of the latex, sulfuric acid is used. If sodium sulfide is present, hydrogen sulfide is produced. The high degree of toxicity of this compound is well known. The manufacturing operations at which this evolution occurs are essentially open, and most of them require the installation of process ventilation to satisfactorily control this hazard. EFED is a relatively new compound industrially. Little is 'known regarding its toxicity. However, upon hydrolysis phenol is one of the products. This, together with EFED, may be present in the workroom air around the coagulation, filtering, and drying areas in sufficient amounts to require the use of process ventilation. AII. Processing Operations LARGE RUBBER industry in its processing of crude rubber into finished products uses a tremendous variety and quantity of different materials. An attempt has been made to list-these in the-accompanying table. This list is obviously intended to be typical of the industry and is not complete for any one manufacturer. Professional industrial health personnel will recognize here many materials with well-known physiological characteristics, as well as many about which little or nothing is known. It is because of the use of this vast array of substances, as well as the constant introduction of new ones, that industrial hygiene in the rubber industry is a necessity. It obviously is impossible to discuss in detail the health hazards of any great number of these materials. Many of course, are relatively innocuous and require no discussion. Others present numerous problems. From the standpoints of severity of hazard, number of personnel exposed, and quantity of material used, the solvents as a class are of major importance. These I shall attempt to discuss briefly. It should be realized that in addition to the various systemic problems associated with the use of these solvents, there is always the problem of dermatitis. This in many cases is the more difficult of the two to control. AROMATIC HYDROCARBONS: Benzol, toluol, and xylol (the names for the commercial grades of benzene, toluene, and xylene) are used quite extensively as solvents for rubber cements and for tackifying purposes. By far the most important of the three from the standpoint of hazards to health is benzol, although the other two are not without danger. The literature contains a large amount of information on physiological effects of these materials, some of which is conflicting, to say the least. The chemical formulas of the three compounds are C6H6, C6H5.CH3, and C6I15 (CH3)2. Their boiling points are 80.2C, 110.4C, and 138C to 144C respectively. All are flammable, with quite low explosive levels, and with flash points of-12C, and 4C, and 18 to 20C, respectively. The commercial grades of each contain as impurities minor percentages of each of the other two, and xylol contains all three of the xylene isomers (meta, ortho, para). Acute poisonings rarely result from these solvents, but chronic poisoning is a real probability. This is characterized chiefly V 1. 3. 1- Chr. Ho- Tir. Ettr, Met Stile: Tell, Tell, Bar:. 01, Cale! Sten: Magi M.O. an. Antis An Benz. Vultr An: Aeeto Benz, Butyl Carb< Ethyl Ethyl, Gaso Hept: Glue Alum Antin Renzi, Benzi, Cadet: Cadmi Cadmi Chrorr Lead Mona.- Cakiu Hard Mdeh) Pro Attu Butyl Capta, Dibenz Diorth Erie 1 Ethyl Ethyl E.hyla, fide, 1952 been able. pica' any trial iany ;ical hich e of (, as new )ber in reat rse, no robr of and t as le I mid ous use ob- is uol, dal are ub3e3. ree 1th not s a igiich cal EIp :ng to ith tsh les er101 ars !se ?al fly Vol.,. 13, No. 1 INDUSTRIAL HYGIENE QUARTERLY Page 39 COMPONENTS USED IN THE MANUFACTURE OF RUBBER PRODUCTS RUDDER I. .1merirctm .~fade Nitriler CR-S ("Hot" and "Cold") Neoprene GR-S Latex Hycar Pa Thiokol 2. Nature/ Fine Para Pale Crepe t;uayule Ribbed Smoked Sheets Natural Latex Reclaim Inner Tube (Natural Butyl) No. 2 Peel Mechanical Blend (Black. Light) Pure Gum Nu. 1 Peel %Thole Tire TEXTILES Chafers (Primarily Cotton) Hose and Islet Ducks (Rayon, Cotton. Nylon) Liners (Primarily Cotton) Tire Cord (Rayon. Cotton. Nehn) VULCANIZING AGENTS Ethyl Tunds (Tetraethylthiuram Disulfide) Methyl Tuads (Aetramethylthiuram Disulfide) Selenac (Selenium Diethyldithiocarbamate) Selenium Sulfur Tellurac (Tellurium Diethyldithiocarbamate) Tellurium Tetramethylthiuram Monosulfide ACTIVATORS Barak (Dibutyl Ammonium Para-Amino Phenol Oleate) l'olyac (Polydinitrosobenzene) Calcium Hydroxide Litharge Sodium Acetate Stearic Acid Magnesium Oxide Triethanolamine M.O.D.X. (Mixed Organic and Inorganic Acetates) RETARDERS Antiscoreh Essen (Phthalic Phthalic Anhydride Anhydride) Salicylic Acid Benzoic Acid Dclac J-- Trichloro Melamine Vultrol--Diphenyl Nitroso Amine SOLVENTS Acetone Amyl Acetate Isopropyl Acetate Benzol Isopropyl Alcohol Kerosene Butyl Acetate Butyl Alcohol Methyl Alcohol Carbon Tetrachloride Methyl Ethyl Ketone Ethyl Acetate Ethyl Alcohol Methyl Isobutyl Ketone Ethylene Dichloride Monochlorobenzene Gaso'ine (Unleaded) Propylene Dichloride Toluol Heptane Hexane Trichloroethylene Xylol STIFFENERS AND ANTI SOFTENERS Glue Shellac COLOR PIGMENTS Aluminum Powder Permanent Green Antimony Sulfide Permanent Orange Benzidine Orange Permanent Red Benzidine Yellow Red Iron Oxide Cadmium Lithopone Red Lithol Toner Cadmium Selenide Rubber Green Cadmium Sulfide Titanium Dioxide Chrome Green Ultramarine Blue Lead Chromate Yellow Iron Oxide Monastral Green INERT FILLERS Calcium Silicate Cork Ground Whiting Hard Clay Precipitated Whiting Soft Clay ACCELERATORS Lldehye Ammonia (Ammonia-Acetaldehyde Condensation Product) Altax (Benzothiazyl Disulfide) Butyl Eight Butyl Zimate (Zinc Dibutyldithiocarbamate) Captax (Mercaptobenzothiazole) Dibenzo GMF (P. P' Dibenzoyl Quinonedioxime) Diortho Toylyl Guanadine Diphenyl Guanadine Erie (Bis 4. 5 Dimethyl-Thiazyldisulfide) Ethyl Tuads (Tetraethylthiuram Disulfide) Eth) I Zimate (Zinc Diethyldithiocarbamate) E.hylac (2-Benzothiazyl-N,N-Diehyl Thiocarbamyl Sul- fide) GMF (P-Quinonedioxime) Guantal (Diphenyl Guanidine Phthalate) Hepteen. Hepteen Base (Heptaldehyde-Aniline Conden- sation Product Hexa ( Hexamethylene Tetraniinel Ledate (Lead Dimethyldithiovarlatmatei Mercaptothiazoline Methyl Toads. Moues. Th'onex Tetramethylthiurwn Disulfide) Meth) I Zimate ( Zinc Dime hyl) Methylene Para Toluidine Na-22 Accelerator (2-Mercaptoimidawline) Para Nitrosodimethyhtniline Polyac Potassium Pentamethylene L4ithiocarbamate Pu:lman (Butyraklehyde-Aniline Condensation Product) Safex (2. 4-Dinitrophenyl Dimethyl-Thiocarbamate) Santocure (Benzothiazyl-2-Monocyclohexyl-Sulfanaraidel SPDX (Lead Dithiocarbamate) Tetrone (Cipentamethylene Thiuram Tetrasulfidel Texas (Mixed Mercapto Alkyl Thiazole) Thiocarbanilide Trimene. Trimene Base (Formaldehyde-Monethylantic Condensation Product) ZBX (Zinc Butyl Zenthatei FATTY ACIDS Cottonseed Fatty Acid Low Acid Palm Oil Fatty Acid Ester Stearic Acid Laurie Acid Wool Grease REINFORCING FILLERS Barytes. Blanc Fixe Channel Carbon Blacks (Various Types) Furnace Carbon Blacks (Various Types) Lithopone Zinc Oxide . Precipitated or Fumed Silica ("White Carbon Black") ANTI-OxIoa.Nrs OR AGE RESISTORS Agerite Alba (Monobenzyl Ether or Hydroquinone) Agerite Powder (Phenyl Beta Naphthylamine) Agerite Resin (Polymerized Aldol Alpha Naphthylarnine) Agerite Resin D (Polymerized Trimethyl Dihydruquino- line) Agerite White (Di-Beta Naphthyl Para Pheny/ene- diamine) BLE (A Ketone-Amine Reaction Product Flectol 11 (Condensation Product of Acetone and Aniline) Flectol H (Condensation Product of Acetone and Aniline) Flectol White (1. 1-Di Para Hydroxyphenyl Cyclohexane) Hoboken (Diphenyl Pars Phenylene Diamine) Iso Proposy Diphenylamine Neozone D (Phenyl Beta Naphthylamine) PBNA (Phenyl Beta Naphthylamine) Santofiex B (Condensation Product of P-Aminodiphenyl and Acetone) Stelae (Mono and Diheptyl Dimninms) DUSTING M4TERIA LS Corn Starch Mica Soapstone Talc Potato Starch Zinc Stearate PLASTICIZERS AN 3 SOFTENERS Asphaltum Oil Bardol Paraffin Wax Black Petrolatum Paraflux Pine Tar Coal Tar Base Oil Soft Asphalt Soft Coal Tar Dibutyl Phthalate Extending Resin Dipentere Factice Soft Cumar Stabelite Hydrogenated Rosin Syncera Wax Tergum Mineral Rubber Tricresyl Phosphate Paraffin Base Oil R.P.A. #3 (Xylyl Merciptan in Inert Oil) WETTING A 3ENTS Alphasol OT Aquarex D vas Paste Tergitol =7 Nacconol Turkey Red Oil MISCELLAN SOUS Ammonia Asbestos Graphite Calcium Chloride Caustic Soda Hydrochloric Acid Copper Cyanide Chlorine Pumice Soda Ash Cobalt Stearate Sodium Iiicar)onate Diatomaceous Earth Sodium Cyanide Sulfuric Acid Diazo Amino Benzene Tri Sodium Phosphate Formalin Glycerin Zinc Cyar.ide Zinc Chloride Page 40 INDUSTRIAL HYGIENE QUARTERLY March. 1952 by a damage to the blood forming processes, importance. Their chemical formulas are: t. and may be permanently injurious or fatal. acetone--CH3.CO.CH3; methyl ethyl ketone r. The symptomatology and treatment has --CH3.CO.C2H5 ; and methyl isobutyl ke- S. been adequately discussed previously and tone--CH3.CO.C4H9. Their boiling points c. will not be repeated here. The working range from 56C to 118C, respectively. c: environment of the employee must be so All are flammable with flash points rang- controlled that excessive exposure to any ing from --18C to 23C. of these solvents will not occur. Suggested The toxicities of these compounds are PS maximum vapor concentrations are 50 mild. In high concentrations, their effects ir p.p.m. for benzol and 200 p.p.m. for toluol are those of a narcotic. Chronic intoxica- bt and xylol. In addition, the personnel so tion is unknown. Atmospheric concentra- exposed should be examined regularly, with tions much in excess of 500 p.p.m. for as a complete blood count made at two or three acetone and 200 p.p.m. for methyl ethyl month intervals. Any abnormal trend in ketone and methyl isobutyl ketone produce one or more of the blood values should in- uncomfortable eye and respiratory irrita- dicate the need for possible removal of tion and should be avoided. the individual from exposure and correc- CHLORINATED HYDROCARBONS: Of this tion of operating procedures. general class of solvents, carbon tetra- PETROLEUM HYDROCARBO NS (DISTIL- chloride, ethylene dichloride, trichloroethyl- 12 LATES) : Members of this group of solvents ene, perchloroethylene, propylene dichloride, which find common usage in the rubber in- and monochlorobenzene find the most use ha dustry are gasoline (unleaded), hexane, in the rubber industry. This use varies. ME heptane, and kerosene. Hexane and hep- Some are used as rubber solvents, others pr, tane are chemical compounds, with chemical as degreasers, and as fire extinguishing op. formulas of CH3.(CH2) 4.CH3 and CH3.- agents. Carbon tetrachloride, trichloro- ins. (CH3) 5.CH3 respectively. Gasoline and ethylene, and perchloroethylene are non- kerosene are commercial blends of a num- flammable. The three others are. Their du ber of different compounds. Boiling points chemical formulas and boiling points are col range from 70C upwards. All are as follows: tai flammable, with low explosive ranges and Carbon tetrachloride--CCI4. 77C. prc with flash points beginning at --45C. Ethylene dichloride, (1,2 dichloroethane) .- The physiological action of these solvents --CI.C112.C112.C1. 84C. hei is that of a narcotic. They are mildly toxic Trichloroethylene--CHCI: CC12. 87 C. log as compared to the aromatic hydrocarbons. Propylene dichloride (1,2 dichloropro- tili However, some, particularly gasoline, may pane)--CH3.CHCI.CH2C1 97C. haz contain appreciable quantities of benzol, Perchloroethylene (tetrachloroethylene) ner and if so the handling hazard will be pro- --C12C: C: C13. 121C. wo! portionately increased. They possess irri- Monochlorobenzene--C6H5C1. 132C. ill tant properties to the eyes and respiratory The chlorinated hydrocarbons possess thi: passages, which in most cases will serve varying degrees of toxicity. Of the above 100 as a controlling indicator of excessive ex- named, carbon tetrachloride is the most ..t posure. Atmospheric concentrations in the severe. Serious injury and death may ruL 500-1000 p.p.m. range can be tolerated with result from exposure. Individual suscepti- tan, safety, unless one or more of the aromatic bility varies widely. It produces chronic hydrocarbons as impurities are present in effects, primarily to the kidneys and the ula: appreciable quantities. In this case a work- liver. It is an insidiously dangerous sol- ing level based upon the specific aromatic vent and requires careful handling. Tri- E hydrocarbon concentration present should chloroethylene and perchloroethylene are N be used. considerably less toxic than the others men- KETONES: The ketones are excellent rub- tioned above, but still need .to be handled N ber solvents, and especially find uses in with discretion. Unfortunately, there are 1: the processing of the nitrile rubbers. no reliable simple indices useful for clinical 142 Acetone, methyl ethyl ketone (butanone), evaluations of over-exposure to the chlori- and methyl isobutyl ketone are of the most nated hydrocarbons. Rigid inspections of h. 1952 is are: ketone :yl kepoints :tively. rang- is are effects toxica:entran. for ethyl roduce i rrita- this tetra)ethylloride, 3t use ;aries. others ishing :hloro- nonTheir s are hane) C. -opro- lene) )ssess above most may :eptironic I the ; sol- Triare menidled are nical iloriof VOL. 13, No. 1 INDUSTRIAL HYGIENE QUARTERLY Peas 11 the working environment are necessary to maintain atmospheric concentrations at safe levels. These vary with the individual compounds, ranging from 50 p.p.m. for carbon tetrachloride to 200 p.p.m. for perchloroethylene. The treatment of cases of poisoning has been discussed elsewhere.? ALCOHOLS: Alcohols used by the rubber industry are methyl, ethyl, isopropyl, nbutyl, and n-amyl. The chemical formulas and boiling points of these compounds are as follows: Methyl-CH3OH. 65C. Ethyl-C2H7,0H. 78C. Isopropyl-(CH3 ) 2CHOH. 83C. n-Butyl-C..1-15.CH...C1120H. 117`C. n-Amyl-C1-13.( CH..1 3.C1120H. 138C. All are inflammable, with flash points of 12'C and upwards. From the standpoint of industrial health hazards, those of most significance are methyl, butyl, and amyl. Methyl alcohol produces its ill-effects primarily on the optic nerve. Accidental and suicidal poisonings from the drinking of methyl alcohol (wood alcohol) frequently occur, but industrial poisonings are rare. Atmospheric concentrations should generally be maintained below 200 p.p.m., and skin contact prevented. Both n-butyl and n-amyl alcohol are in- herently more toxic than their lower homologs.% However, because of their lower volatilities, and their irritant properties, little hazard is encountered in their use. Sterner9 has reported, in a ten year study of workers exposed to butyl alcohol vapors, no ill effects at levels up to 100 p.p.m. Above this level irritation existed. He suggests 100 p.p.m. as a safe working level. ACETATES: Acetates are useful as general rubber solvents. Those of primary importance are methyl, ethyl, n-propyl, isopropyl, n-butyl and isoamyl. Their chemical formulas and boiling points are as follows: Methyl-CH3CO2.CH3. 57C. Ethyl-CH3.00..C2H3. 77C. N-propyl-CH3.00...CH2.C.J15. 102C. Isopropyl-CH3.00..CH (CH3) 2. 88C. N-butyl-CH3.0O2.C1-12.CH2.C2H,. 125C. Isoa m yl-CHn.00...CH...CH...CH. ( CHO 142C. All are flammable wi :h flash points of 9C and upwards. As a group these compounds are only mildly toxic, and their industrial health hazards are few. The vapors are irritating in . concentrations above 200 p.p.m. The suggested maximum working levels are based largely on this irritating characteristic. They are considered to be among the safest of the solvents. Summary THE PRECEDING discussion should not convey an idea of hazardous working con- ditions existing in the rubber industry. However, it does indicate a few of the problems which may arise if improper handling precautions are used. We believe we have done, and are doing, a good job. However, ours is a rapidly changing industry. It is not only a huge consumer of chemicals, but a large producer as well. New materials, with their unknown hazards, are constantly being developed. Toxicological and industrial hygiene studies for them must likewise be made if they are to be used safety. This offers a challenging opportunity for industrial health. References I. JONES. G. W.. and KHNres:py. R. E.: Bur. of Mince Rcpt. of Invest.. No. 3565 (1941). 2. FROLICII. P. K., and MORRELL. C. E.: Cu in. and News. 21:1138-1145 (July 25. 1943). 3. CARPENTER. C. P., et al: Studies on the Inhalation of 1.3 Butadiene. with a Comparison of Its Narcotic Effect with Remo!. Toluol and Styrene. and a Note on the Elimination of Styrene by the Human. Jour. of Ind. 140. & Tor.. 26:69-7S (1944). 4. Jteet:s., C. W., SCOTT. C. S. and MILLER. W. E.: Limits' of Inflammability and Ignition Temperature of Styrene in Air. Bar. of Mines Rcpt. of Invest.. No. 3630 (1942). 5. SPENCER.. H. C.. et al: The Response of Laboratory Animals to Monomeric Styrene. Jour. lad. Hug. Tos., 24:295-301 (1942). 6. FAIRM ALL, LAN RENCK T.: Industrial Toxicology. The Williams and Wilkins Company, Baltimore. Maryland (1949). P. 266. 7. WILSON, REX H., ROUGH, GLEN V., and McCoRMICK, WILLIAM E.: Medical Problems Encountered in the Manufacture of American-made Rubber. Ind. Med., 17: 199-207 (June. 1948). S. PATTY. FRANK A.: Industrial Hygiene and Toxi- cology. Interscience Publishers. Inc., New York. N.Y. (1949). Volume II. Chap. 26. 9. STERNER. JAMES H.. et al: A Ten-year Study of Butyl Alcohol Exposure,. lad. Ilya. Quarterly, 10:53-59 (September 1949).