Document KzewMj7BE8zb206BZdmkMQxbw

FILE NAME: BF Goodrich (BFG) DATE: 1952 DOC#: BFG029 DOCUMENT DESCRIPTION: Report - by William McCormick - Industrial Health Problems in the Rubber Industry Industrial Health Problems in the Rubber Industry W ILLIA M E. M cC O R M IC K The B. F. Goodrich Company Akron, Ohio The American rubber industry is com plex and diversified. Its raw materials and products com e from, and are used 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 es sentially all of the 787,000 long tons of rub ber consumed in the U.S.A. were imported natural crude. In 1950, nearly half of the 1,258,000 long tons used came from domes tic 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 rele vant to GR-S production, and GR-S and natural crude processing, follows. I. GR-S Manufacture 'J 'HE MANUFACTURE of GR-S rubber con sists of copolymerizing two compounds, butadiene and styrene, to form a finely dis persed 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 pres sures, different butadiene-styrene ratios, various catalysts, modifiers, polymerization accelerators, and anti-oxidants. A flow dia gram 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 CH._.:CH.CH:CH.;. It is a gas which Presented a t the F ourth Regional Gulf C oast Indus trial H ealth Conference. H ouston. Texas. S ep tem b er 28. 1951. in, Fig. I. Flow Diagram of G R-S Manufacture liquifies at --4.4 C. It is highly flamma ble, 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 in sulation. 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 wher ever it is used. Butadiene tends to spon taneously form explosive peroxides upon ageing. Hence an inhibitor such as tertiary butyl catechol, must be incorporated into the commercially produced product.- The health hazards of butadiene are mild. It has a narcotic effect at high concentra tions, but has little if any cumulative ac tion.:* Atmospheric concentrations up to at least 1000 p.p.m. can be tolerated for pro longed periods of time without ill effects. Sty r en e: Styrene, CfiHr,.CH:CH2 is a liquid, boiling at 145C. Its limits of flammability are 1.1% (29.3cC) 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 lab oratory animals exposed to vapor concen ' Page 3S INDUSTRIAL HYGIENE QUARTERLY March, 1052 trations of 650 p.p.m. up to six months5 but subjective symptoms in humans have been found3 after several hours' exposure to 800 p.p.m. The vapors become quite irri tating above 400 p.p.m. It is therefore de sirable to maintain workroom atmospheres below 200 p.p.m. Minor co m po n en ts: A large number of substances are used in more or less minor quantities for GR-S manufacturing. Among these are the various catalysts, emulsifiers, polymerization accelerators, short-stopping agents, anti-oxidants, and dusting materi als. Fortunately very few of these sub stances 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 elabo rate precautions must be taken to prevent skin contact. If it does occur accidentally, immediate removal from the skin is neces sary. In addition to its dermatitis produc ing potentialities, it is also systemically toxic. The degree of this, however, is not fully established, but is believed to be more severe than nitrobenzene.0 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, sul furic acid is used. If sodium sulfide is pres ent, 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 in stallation of process ventilation to satis factorily control this hazard. EFED is a relatively new compound in dustrially. 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 dry ing areas in sufficient amounts to require the use of process ventilation. II. 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 prob lems. 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 prob lem of dermatitis. This in many cases is the more difficult of the two to control. A romatic hydrocarbons: Benzol, toluol, and xylol (the names for the commercial grades of benzene, toluene, and xylene) are used quite extensively as solvents for rub ber 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 physiologi cal effects of these materials, some of which is conflicting, to say the least. The chemical formulas of the three compounds are C6He, CcH5.CH3, and C6H5(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 per centages 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 : ' Ch: Ho I.in' Tir. EU: Met SellSell* Tell Teilt B ar.. Ol. Calc: Steo: Mac: M.O. an. Anti. An Ben:. Vuitr An-. Aeeto Benz. Butyl Carbi Ethyl Ethyl. Gaso : Hept: Glue Aluir. Antin ltenzi. Benzi. Csdm: Cadmi Cadm: ChronLead Mona. Calciu Hard Aldehi Proc Altax Butyl C a p ta : Dibenz Diortli Erie ( Ethyl Ethyl E.hylo. fide) 195 been able, pical any trial any iical hich e of i, as new >ber i in reat rse, no robT Of and i as * I juld ous use *ob1 is uol, cial are tib ies, ree lth not 3 a -gi- ich cal H. :ng to ith ish to ies er* lol irs jse ial fly V O L.'13, No. 1 INDUSTRIAL HYGIENE QUARTERLY Page 3!) Components Used in the Manufacture of Rubber Products R ubber 1. .tmrnruii Made C.R-I N itriles (R-S ("H o t" and "C old"! N eoprene i;R-S Latex Hycar Pa Thiokol 2. S u t u r a l Fine Para Pale Crepe (iuayule Ribbed Smoked Sheets N atural I.atex Uechtim Inner Tube (N atural Butyl) No. 2Peel Meehnnical Blend I Black. L ight) Pure Gum No. 1 Peel Whole T ire T kxtii.es Chafers (P rim arily Cotton) Hose and Blet Ducks (R ayon. Cotton. Nylon) Liners ( P rim arily C otton) Tire Cord (Rayon. Cotton. Nylon) V ulcanizing Agents Ethyl T uads (T etraeth y lth iu ram Disulfide) Methyl T uads ( A e tram ethylthiuram Disulfide) Selenite (Selenium D iethyldithiocarbam ate) Selenium S u lfu r Tollurac (T ellurium D iethyldithiocarbam ate) T ellu riu m T etram ethylthiuram Monosulfide Activators Darak (D ibutyl Am m onium Para-A m ino Phenol O leate) Polyac ( Polydinitrosobenzene) Calcium H ydroxide L ith arg e Sodium A cetate Stearic Acid Magnesium Oxide Triethanolam ine M.O.D.X. (M ixed O rganic and Inorganic Acetates) R etarders Antiscorch Essen (Phthalic Phthalic Anhydride A nhydride) Salicylic Acid Benzoic Acid Dclac J -- Trichloro M elamine Vultrol--Diphenyl N itroso A m ine S olvents Acetone Amyl A cetate Isopropyl Acetate Benzol Isopropyl Alcohol K erosene Butyl A cetate Butyl Alcohol M ethyl Alcohol Carbon T etrachloride M ethyl E thyl Ketone Ethyl A cetate E thyl Alcohol Methyl Isobutyl Ketone Ethylene Dichloride Monochlorobenzene Gaso'ine (U nleudcd) P ropylene Dichloride Toluol H eptane H exane T richloroethylene Xylol Stifteners and An ti Softeners Glue Shellac Color P igments Aluminum Fow der P erm anent Green Antimony Sulfide Perm anent Orange Benzidine O range Perm anent Red Benzidine Yellow Red Iron Oxide Cadmium Lithoponc Red Lithol Toner Cadmium Selenide Rubber Green Cadmium Sulfide T itanium Dioxide Chrome Green U ltram arine Blue Lead C hrom ate Yellow Iron Oxide M onostral Green I nert F illers Calcium S ilicate Cork Ground W hiting Hard Clay Precipitated W hiting Soft Clay Accelerators Aldehyc A m m onia (A m m onia-A cetaldehyde C ondensation Product) Altax ( Benzothiazyl Disulfide) Butyl Eight Butyl Z im ate (Z inc D ibutyldithiocarbam ate) Captax (M ercaptobenzothiazole) Dibenzo G M F ( P, P* D ibenzoyl Q uinonedioxim e) Diortho Toylyl G uanadine Diphenyl Guanadine Erie (B is 4. 5 Dimethyl-Thiazyldisulfide) Ethyl Tuads (T etraeth y lth iu ram Disulfide) Ethyl Z im ate (Zinc D iethyldithiocarbam ate) E.hylac (2-Bcnzothiazyl-N ,N -D iehyI Thiocarbaxnyl Sul fide) GMF ( P-Quinonedioxime) G uantal (D iphenyl Guanidine Phthalatc) H cpteen. Hepteen Base ( Heptaldehyde-Aniline Conden sation Product) Kexa ( Hexam ethylene Tetram ine) Ledatc (L ead Dim ethyldithiocarham atct M ercaptothiazoline Methyl T uads. Monrx, T h'onex ( T etram ethylthiurtin Disulfide) . Methyl Z im ate (Zinc D inu-hyl) M ethylene P a ra Toluidine Na-22 A ccelerator (2-M ercaptoimidazoline) Para Nitrosodimethylnniline Polyac Potassium Pcntam ethyiene Ditliiocarbamate Pullman ( Butyraldehyde-Aniline Condensation Product) Safex (2. 4-Diniti-ophenyl D im ethyl-Thiocarbam ate) Santocure (Bcnzothiazyi-2-M onocyclohexyI-Sulfanamide) SPDX (Lead Dithiocarbamate) T etrone (C ipentam ethylene T hiuram Tetrasulfidel Texas (M ixed Mercapto Alkyl Thiazole) T h io c arb a n ilid e T rim en e. T rim e n e Base <K orm aidehydc-M onethylanuc; Condensation Product) ZBX (Zinc Butyl Zcnthatel F atty Acids C ottonseed F a tty Acid Low Acid Palm Oil Fatty Acid E ster S tearic Acid Laurie Acid Wool Grease Reinforcing F illers Barytes. Blanc Fixe Channel C arbon Blacks (V arious Types) Furnace C arbon Blacks (V arious Types) L ith o p o n e Zinc Oxide . Precipitated o r Fumed Silica ("W h ite Carbon Black") A n t i-Oxidants or Age Resistors A gerite Alba (Monobenzyl E ther o r Hydroquinone) A gerite Pow der (Phenyl Beta N aphthylam ine) A gerite Resin (Polymerized Aldol A lpha N aphthylam ine) A gerite Resin D (Polymerized T rim ethyl Dihydrvquino- line) A gerite W hite (Di-Beta N aphthyl P ara Phenylene- diamine) BLE (A Ketone-Am ine Reaction Product Flectol B (C o n d en satio n P roduct c-f A cetone a n d A niline) Flectol H (Condensation Product of Acetone and Aniline) Flectol W hite (1. 1-Bi P a ra H ydroxyphenyl Cyclohexane) Hoboken (D iphenyl P ara Phenylene Diamine) Iso Proposy Diphenylamine Neozone D (P h en y l Beta N aphthylam ine) PBNA (P h en y l Beta N aphthylam ine) Santoflex B (Condensation Product of P-Aminodiphenyl and Acetone) Stalite (M ono a n d Diheptyl D uuhines) z -' Dusting Materials ^ Corn S tarch Mica Soapstone Talc Potato Starch Zinc Stearate P lasticizers and Softeners A sphaitum Oil Bardol Paraffin Wax Black P etrolatum l'uraflux Pine T ar Coal T a r B ase Oil Soft Asphalt Soft Coal T ar Dibutyl P h th alate D ip en ter.e Extending Resin Fuctice Soft Cum ar Stabelite Hydrogenated Rosin Synccra W ax Tergum M ineral R ubber Tricresyl Phosphate Paraffin Base Oil R .P.A . # 3 (Xylyl M ercsptan in In e rt Oil) W etting A sents _ AIpbasol O T Aquarex D O ivus Paste Tergitol Nacconol T u rk ey Red Oil Miscellaneous Ammonia Asbestos G raphite Calcium Chloride Caustic Soda Hydrochloric Acid C opper Cyanide Chlorine Pum ice Soda Ash Cobalt S te a ra te Sodium liicar Donate D iatom nceous E a rth Sodium C yanide Sulfuric Acid Diazo A m ino Benzene T ri Stdium Phosphate Form alin G lycerin Zinc Cyai.ide Zinc Chloride l'ayv 40 INDUSTRIAL HYGIENE QUARTERLY M arch, 1952 by a damage to the blood forming processes, and may be permanently injurious or fatal. The symptomatology and treatment has been adequately discussed previously7 and will not be repeated here. The working environment of the employee must be so controlled that excessive exposure to any of these solvents will not occur. Suggested maximum vapor concentrations are 50 p.p.m. for benzol and 200 p.p.m. for toluol and xylol. In addition, the personnel so exposed should be examined regularly, with a complete blood count made at two or three month intervals. Any abnormal trend in one or more of the blood values should in dicate the need for possible removal of the individual from exposure and correc tion of operating procedures. P etroleum h y d r o c a r b o n s (distil lates) : Members of this group of solvents which find common usage in the rubber in dustry are gasoline (unleaded), hexane, heptane, and kerosene. Hexane and hep tane are chemical compounds, with chemical formulas of CH3.(CH2).,.CH3 and CH3.(CH2).,.CH3 respectively. Gasoline and kerosene are commercial blends of a num ber of different compounds. Boiling points range from 70sC upwards. All are flammable, with low explosive ranges and with flash points beginning at --45C. . The physiological action of these solvents is that of a narcotic. They are mildly toxic as compared to the aromatic hydrocarbons. However, some, particularly gasoline, may contain appreciable quantities of benzol, and if so the handling hazard will be pro portionately increased. They possess irri tant properties to the eyes and respiratory passages, which in most cases will serve as a controlling indicator of excessive ex posure. Atmospheric concentrations in the 500-1000 p.p.m. range can be tolerated with safety, unless one or more of the aromatic hydrocarbons as impurities are present in appreciable quantities. In this case a work ing level based upon the specific aromatic hydrocarbon concentration present should be usee. Ketones: The ketones are excellent rub ber solvents, and especially find uses in the processing of the nitrile rubbers. Acetone, methyl ethyl ketone (butanone), and methyl isobutvl ketone are of the most importance'. Their chemical formulas are: acetone--CH3.CO.CH3; methyl ethyl ketone --CH3.CO.C2H5; and methyl isobutyl ke tone--CH3.CO.C4H9. Their boiling points range from 568C to 118C, respectively. All are flammable with flash points rang ing from --18C to 23C. The toxicities of these compounds are mild. In high concentrations, their effects are those of a narcotic. Chronic intoxica tion is unknown. Atmospheric concentra tions much in excess of 500 p.p.m. for acetone and 200 p.p.m. for methyl ethyl ketone and methyl isobutyl ketone produce uncomfortable eye and respiratory irrita tion and should be avoided. Chlorinated hydrocarbons: Of this general class of solvents, carbon tetra chloride, ethylene dichloride, trichloroethyl ene, perchloroethylene, propylene dichloride, and monochlorobenzene find the most use in the rubber industry. This use varies. Some are used as rubber solvents, others as degreasers, and as fire extinguishing agents. Carbon tetrachloride, trichloro ethylene, and perchloroethylene are non flammable. The three others are. Their chemical formulas and boiling points are as follows: Carbon tetrachloride--CC14. 77C. Ethylene dichloride, (1,2 dichloroethane) --Cl.CHo.CHo.Cl. 84C. Trichloroethylene--CHC1: CC12. 87 C. Propylene dichloride (1,2 dichloropro- pane)--CH3.CHC1.CH2C1 97C. Perchloroethylene (tetrachloroethylene) --CLC: C: CL. 12lC. Monochlorobenzene--C6H5C1. 132 C. The chlorinated hydrocarbons possess varying degrees of toxicity. Of the above named, carbon tetrachloride is the most severe. Serious injury and death may result from exposure. Individual suscepti bility varies widely. It produces chronic effects, primarily to the kidneys and the liver. It is an insidiously dangerous sol vent and requires careful handling. Tri chloroethylene an d . perchloroethylene are considerably less toxic than the others men tioned above, but still need -to be handled with discretion. Unfortunately, there are no reliable simple indices useful for clinical evaluations of over-exposure to the chlori nated hydrocarbons. Rigid inspections of h. 1952 is are: ketone :yl kepoints :tively. rang- ds are effects toxica* '.entran. for ethyl roduce irrita : this tetra>ethylloride, st use ,'aries. others ishing hlorononTheir s are hane) C. opro- dene) assess above most may ceptironic I the ' sol- Tri are menldled are nical llori.3 of VOL. 13, N o. 1 INDUSTRIAL HYGIENE QUARTERLY Page 41 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.7 Alcohols: Alcohols used by the rubber industry are methyl, ethyl, isopropyl, n- butyl, and n-amyl. The chemical formulas and boiling points of these compounds are as follows: Methyl--CH.{OH. 65cC. Ethyl--C..H,OH. 78eC. Isopropyl--(CH;,) ..CHOH. 83CC. n-Butvl--C..Hv CH...CH..OH. 117CC. n-Amyl--CH;. (CH2).vCH3OH. 13S5C. All are inflammable, with flash points of 12CC 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 poison ings from the drinking of methyl alcohol (wood alcohol) frequently occur, but in dustrial poisonings are rare. Atmospheric concentrations should generally be main tained below 200' p.p.m., and skin contact prevented. Both n-butyl and n-amyl alcohol are in herently more toxic than their lower homo logs." However, because of their lower vola tilities, and their irritant properties, little hazard is encountered in their use. Ster ner" 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 impor tance are methyl, ethyl, n-propyl, isopropyl, n-butyl and isoamyl. Their chemical form ulas and boiling points are as follows: Methyl--CH3CO...CH3. 57C. Ethyl--CH3.COo.CoH5. 77C. N-propyl--CH3.CO..CH...CoH0. 102C. Isopropyl--CH3.C0'...CH(CHS!... 88C. N-butvl--CH3.COo.CH...CHo.C..Hv 125cC. Iso a m y l--CH3.C6...CH..CH...GH.(CH3)._.. 142C. All are flammable wi.h flash points of 9CC 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 characteris tic. They are considered to be among the safest of the solvents. Summary . 'J 'HE preceding discussion should not con vey an idea of hazardous working con ditions existing in the rubber industry. However, it does indicate a few of the prob lems 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 materi als, with their unknown hazards, are con stantly 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 1. J ones, G. W ., an d Kennedy. K. K .: Ilur. o f M ines R ept. o f I n f e s t . , No. 3565 (1941). 3. pK iu.iril. P . K., and Mokkell. C. E.: (Slum. a n d K a y . S r i r n . 21:1138-1145 (Ju ly 25. 104:). :t. Carpenter, C. P.. e t a l: Studies on the In h a la tio n o f 1.3 B u tad ie n e, w ith a C om parison of Its N a rco tic Krfect w ith Benzol. Toluol and Styrene, and a N ote on the E lim in atio n of S tyrene by th e H um an. Jour, o f h id . Hull. <C- Tax.. 26:69-7S (1944). 4. J ones, G, W ,, Siott. G. S. a n d Miller, W . E .: Lim its' of Inflammability and Ignition Tem perature of Styrene in A ir. Bar. of M im a R rpt. o f areal.. No. 3630 11942). 5. Spencer. H. C.. et al: T he Response of L aboratory A nim als to M onom eric S ty ren e. Jour. Iud. Hup. Tox., 24:295-301 (1942). 6. F airhaLL, L awrence T . : In d u strial Toxicology. The W illiam s and W ilkins Com pany, Baltimore, M ary land (1949), P. 266. 7. Wilson, R ex H ,, H occ.h, Glen V., and McCormick, William E .: Medical Problem s E ncountered in th e M anufacture o f Am erican-m ade Rubber. Ind. Med., 17: 199-207 ( J u n e . 1948). 8. Patty. F rank A.: In d u strial Hygiene and Toxi cology, Interscience Publishers, Inc., New York. N .Y . (1949). V olum e II, C hap. 26. 9. Sterner. J ames H.. e t a l: A Ten-year S tu d y o f Butyl A lcohol E xposures. Ind. Huff. Q uarterly. 10:53-59 (Septem ber 1949).