Polyurethane CoatingsPerformance, Quality, Safety Bayer ~

/VL~t/~2/Professional Answers To Questions About /

Safe Application Of High-Performance Polyurethane Maintenance Coatings

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Neededby industriesthroughoutthe world.

B ridges, industrial plants and otherstructures of all kinds are exposed

to temperature extremes, radiationfrom the sun, chemical attack, abra-sion, fumes, marine atmospheres. andocher sources of corrosive damage. Leftunchecked,thesehostilefactorsinflictseriousdamagethat can result in thelossesthat are associatedwith col-lapsedstructures and the need to repairor replacetherm

Throughout the world, heavydutypolyurethanemaintenancecoatingsareusedto protect bridgesand the build-ingsandstructuresof chemical plants,petroleumrefineries,pulp and papermills andother industrial facilities. IntheU.S.A. alone,millions of gallons ayear are usedbecausepolyurethanepaints andcoatingsare recognized asthe cost-effectiveleaders in providinglong-lastingprotectionand long-termdurability.

ChemistryMakesFblyurethanesWorkPolyurethanes are reaction products.The material of the protective film isformed by a chemicalreactionbetweena polyisocyanate curing agent and ei-ther a resin (two-component system)orwater in theatmosphere (moisture-cure system). The reaction results ina polymer—a material with extreme-1y large molecules crosslinked into adense barrier against corrosive ele-ments.

lblyurethanesCan & Tailor MadeThe polyisoc~natecan react with resintypes such as polyesters, acrylics andpolyethers. As a result, polyurethanecoatings are unsurpassed in the abilityto be formulated to meet specific en-vironmental and performance re-quirements.

fblyurethanesCan Be Applied by StandardMethods, SafelyAlthough polyurethane paints and coat-ings provide an unusual degree ofsuperior performance, the’ can beapplied by conventional methods:conventional-air, airless and electro-static spraying,brushing, and rolling.Since polyisocyanates. like other paintand coating ingredients. involve poten-tial health hazards, they require protec-tive measures during application.

MobaySuppliesPolyisocyanatesfor PolyurethaneCoatingsMobay Corporation does not makepaints or coatings. The companymanufactures and supplies poly-isocyanate chemicals used by themanufacturers of polyurethane paintsand coatings.

Choosing a paint or coating involvestwo fundamental concerns: perfor-mance and safety inapplication. Thefoll~’ingpages provide informationabout both concerns with expert tes-timony. explanatory information andsupporting data. This information re-lates only to Mobay products: inforrna-tion about specific paints or coatingsshould be obtained from the paint orcoatings manufacturer.

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Ferjorrnance and QualityPolyurethanesare wnong the lowest costcoatingswith durability and long life.

Q. How manydifferent main’tenancecoating mateflaisarecurrentlyin use?

A. A wide ~riery of coatings arecurrently being specified. Theseinclude alkyds. chlorinated rub-bers, vinyls. the inorganic sines.the epoxies, the acrylics and thepolyurethanes.

Q. Wliatconsiderarionsgointospecifying a maintenancecoatingsy~rem?

A. Corrosion resistance is, ofcourse, one of the prime consider-ations. Corttsicc resistance relaxesto the ability to protect the struc-ture. And it’s also related to theresistance of a coating to abra-sion—it’s toughness—and also thefilm thinning. The better a filmresists chalking, the longer its lifeand the greater its corrosion resis-tance for that reason.

Q. w,iat about longevityof thecoating?A Longevity is extremely im-

portant. For example. if t’*o coat-ing systerts cost roughly the samething initially bat one Lasts twice aslong as the other, then the coatingwhich lasts twice as long is roughlyone-half the cost of the other coat-ing system in terms ofservice Ilk.

Q. on ic/tat basis are coatingcosts estimated?

A. Costs are estimated today,many tint, on the basis ofsquare foot per year o(service Ilk.And again, it is seen that serviceuk is ethical in order to ~in lo.w-cost coating systert~%r a plans.

~. Whataboutappeorunce?

- Appearance is critical also.Certain areas in a plant requiringhighlighting need the resistance tochalking and ~dinfand the colorretention offered b~.the polyure-thane type coatings—the alipitaticpcrlyurethanes. Either. the acrylicsor the polyesters, is excellent andmust be rated highly.

Q. is there anyra’dng elseruwould like to add. Dr.Roebuck?

A. I’d like to add one additionalactor. which ~t have not dis’cussed, and that ~culd be thecleanability of polyurethaneswhich they offer because of theirtightness and ability to resist Silk-ing. Excellent cleanability. Theycan be readily washed and k’r thisreason are widely used by certainindustries requiring this char-acteristic.

ICorrosion Resistanceesting and experience have

demonstrated the superiority ofpolyurethane coatings in their resis-tance to attack from v.cathering. abra-sion. acids, alkalis. sol~ents. andmarine atmosphere. Documented casehistories show that polyurethane coat-ings made with Mobay polvisocyanateproducts have outperformed othertypes of coatings in a sulfisric acid plantin Louisiana. a wastewater plant thattreats seawater. trans-Alaska pipelinepumping stations, chemical and fertil-izer plants. tanks for holding carbontetrachioride and other solvents, and awide range of other facilities.

Long-Term Serviceand Low Life-Cycle CostsPolyurethane’s protection lasts a longtime with minimum maintenance. Lifeexpectancy of polyurethane coatings insome applications is as high as 10 to 12

Over the course ofhis career. Dr. Roebr.rck has hadcor.sider~.lec.penencrin q,eofiingn-cinzenance coaxing materials jail rspes. A rrczpjenr cf the Site!Straciures Pointing Council ‘if olin D. Keene A..ord. he is bio..m ..orld.wtdeforhis expertise in corrosion con:rot He has authored owrJ~pubiicartons.readiesa grodice level course at the Universit jSowhent *nua on cor-rosion control in petroleumprocessing, and is active in theNaxionci Associ-asloti ofCorrosion Engineers and the Steel Structures Pointing Council.

years.

Appearance

Dr. Albert H. Roebuckdiscusseshigh-pe’fonnancecoatings.

Although polyurethanes are usedprimarily for corrosion protection. ap-pearance is also a consideration. Light-stable aliphatic polyurethanes provideretention of color and gloss where sur-face appearance is important.

Figure 1.

Taut I.TestOn: Comparative Cumulative Resistancelturibility RatligsSystem A F C 0 E F B H I r k

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TestPtnedwn: b meastjre wheat, base. and acid ,tsstance, et,ti ~f1erentpant ~~ernswere sajb-ected to lcurMour spot tests Test reageilts were paced ma tos-caw pocket in steel panels panted wet?,one of the test coatings. apobed m accordance with manufacturers mstnjctions Alter four hours, theel‘ects of the ccaos’w tu,d on the panted panel were rated EaCh reaçertt was talcated oil a scale tt1-5(5 ~ effect I = completeta,Jijre) A ra,nç p1 ISo the rnasrn,m obtalnatie or each cuss ofreagents Sail sony Ie~n~‘as conducted according to frSTM B 117 Ealeno, OurasiLty things werebased oil etnoencal opsenations The results of the tests ace stow’t m the chart abc-e The tests wereccMuctec -r M0t

1aDoratones

Coatings Cost GuideThe basic objective of the coatings specifier is toachieve maximum protection and appearance at theleast possible cost. As Table II shows, urethane coat-ing systems are among themost cost-effectivesystemswhen compared on a long-term basis.

Table II.Comparative Cost of Elena Coating Slstemt

System Catlic

CostOct $~1t/Mitt Mit

TensAfl4ledC~tilt’

USehpc-~cy~tss5

L~CjteCa~Sfit’)

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A k~gh.8uiIdUrethane %pCoa 65 0037 723 10 0,12

lragan,czinc Pnnrer 25 0025I k4.gP-8oiCEpa~ bpCoat 50 0019 138 6 023

2-Component Ep~ nternlediate 1 8 0419Inlorganc Zinc Prtrtm 25 0~5

CNW,c bpcoal 300021 07t 2 035~C Pnnw 15 0018

0 3%SikconcAkyc boCcat 18 0033 070 2 035~pd Prime, 13 0018

EFogh-Sorcyirtyl boCoal 50 004 089 6 015Ymbi Pnirer 20 0037

F ChlonnstedRubber bpCoat 40 0031 080 6 073

Ch(rtnats~ubbe, Primer 20 0028GEpoxyMastic 1-Coat 60 002 05~ 6 010

H 2-Component High.BoddEpoxyMasl,c boCoat 60 0019 ill 6 019

Zjnc-R’CtrEpay Primer 25 0032I 2-Component Aapttatic

Actyicureth.ane 1,oCot iS 0295 144 10 014

2-CompcnerrlN.gt-Bur~Epoxy lrfern’cAate 1 0 0019

c-PachE~y Pnrr,en 25 0032

J 2-OmpcrentAiplstcPotsesterurethane boCoat IS 0036 1219 10 0.12

UrethaneMo.SIL’re-ctre InterrT,edla?e 25 0027

UrethaneMoisture-Cure Primer 25 0 ~7

K 2-Component MpltatcPof)vsteruremane boCoat iS 0036 145 10 0.74

2i-ligt.Boid Epoxy rn1ern~ate40 0019

1st-Pact, Epoxy Primer 2.5 0032

Mat: ~aapøal ~ msIt’ .t~esft - pa-i trda~ecoa ~ration. arid apgbCatOl costs Satiate p(tpara~SC pnre roe at flQ~icEedrtern~atea-c toncos are fi~ ac~4edThese ~3 icer bornbIACE paper No 183. 1988 Pant and team’gsSelecoona-C Cost &a’ P~y’urethane coatings stow an addmp~4 of ~5ifl1~g C re%~~— laippirec res~ra1ors.Mt’cegtl a~gIcatomcosts for r1utt~~aeeritatyapoeax t1.ghec nnany cantors friare Ctnd actual cot rn be Ower ~ Cm-creased prhou~wltytewef appicaDon WXlet~.and less recrt

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Application 3aJeiyAll chemicals,including isocyanates,can be usedsafelyby limiting etposure.

HealthEffectsereare four typesof ingredients

in industrial coatings:resins,pig-rnents. volatile solvents,and additives.Substanceswithin eachof thesegroupscan affect the body through one ormore of four routes: inhalation, skincontact/absorption. eye contact or in-gestion. Substancesvary considerablyin the seriousnessof their effects andthe concentration levelsthat presentahazard,

With respectto polyisocyanates,ingeneral,overexposurecanirritate eyes.nose, throat, skin and lungs. An ex-posed person may experienceskinsensitization and/or respiratorysensitization resulting in asthmaticsymptomswhichcouldbepermanent.Overexposuremay causelungdamageandaSuctionin lung functionwhichcould also be permanent.Overexpo-sure can also result in flu-like symp-toms such as fever, chills, or an achyfeeling. But the key to avoiding adversehealtheffects lies in applying one sim-ple rule: preventoverexposure. (For amore detailed discussion of healtheffects, consult the Mobay MaterialSafetyData Sheet for the specific prod-uct involved.)

By and large, ingestion is not a com-mon route of exposure in the work-place. Skin contact or absorption aswell aseyecontact can be prevented bywearing proper work apparel and eyeprotection, and by careful handling toprevent spills and splashes. Inhalationis the most prenlent route of exposureand requires the most skill, caution,knowledge and equipment.

VaporPressureTheconcentrationof a substance in theair apaintermay breatheis of criticalimportancein preventingoverexposurethroughinhalation.The concentrationdepends upon the application technique(i.e. spray vs. non-spray) and the ma-terial’s vapor pressure—the ability ofa liquid to evaporate into the air. Thehigher the vapor pressure. the moreeasily the liquid evaporates: the lower

the vapor pressure. the less readily itevaporates.

Table III on page 5 shows the room-temperature vapor pressure (measuredin millimetersof mercury)of a few per-tinent chemicals. For comparison pur-poses. the table also list,s the chemicalsin order of their relative vaporpres-sures with MDI having the basevalueof I.

Monitoring SurveysDeterminePolyisocyanate Exposure LevelsThe monitoring survey-s reported hereinvolved solvent-borne polyurethanepaints containing Mobay poly-isocy-anate products that are based onHDI (hexarnethylene diisocyanate)(i.e. Desmodur N-75) and MDI(diphenylmethane diisocyanate) (i.e.Desmodur E-2l). In addition to thepolyisocyanate products in the systemsevaluated here, the two-componentpaint systemscontainedtracesof HDImonomer while the one-componentmoisture-cure system contained signi-ficant amounts of MDI monomer.Furthermore,aspreviously indicated.these systems contain organic solvents.All these contaminants should alwaysbe included in a monitoring program.

Etposurecriteria forevaluatingmonitoringresults

HDI and HDI PolyisocyanateExposureLimitsTo protect the worker against airborneexposures to chemicals, the Occupa-tional Safety and Health Administra-tion (OSHA) and the AmericanConferenceof Gaemmenul IndustrialHygienists(ACGIH) have established.respectively. Permissible ExposureLimits (PELs) or Threshold LimitValues (TLV5) fora number of chemi-cals, According to ACGIH: TLVs

refer to airborneconcentrations ofsubstances and represent conditionsunder ‘~hichit is believed that nearlyall workers may be repeatedly exposed.day after day, without adverse healtheffects”

The ACGIH has established a TLVfor hexamethylene dilsoc nate (HDI,monomer of 0.005 ppm as an eight-hour time-weighted average (TWA~.Although PELs have been establishedfor severaiof thediis cyanates, federalOSHA has not establishedone forHDI, Mobay endorsesthe ACGIHTLV-TWA. andrecommendsa Ceilinglevel (C) for HDI of 0,02ppm (Mobay’GuidelineLevel, MGL). Thisconcen-trationshouldnot beexceededevenforbrief periods.

ACGIH andfederalOSHA have notestablisheda TCV or PELfor theHDI-basedpolyisocy~anates.However, therecommended MobayGuidelineLevel(MGL) for the UDI-based poly-isocy-anates is 0.5 mgim3 (TWA—averagedover S hours) anda ID mglrn3

Short-TermExposureLimit (STEL—averagedover 15 minutes). On TablesV throughX. the 1.0 mg/rn3 STEL isusedas the most appropriateguidelinesince samplesweretakenonly duringsprayingor mixing and large unsarn-pled partsof the workshift involved nopotential for isocyanateexposure.

MDI Exposure LimitsThe current ACGIH TLV-TWA forMDI is 0AD51 mglm3. Currently. theOSHA PEL is ~2 mg/m’ as a ceilingvalue (29 CFR-~9l0.lCXXJ)-At present.no allowable limit has been establishedfor the Desrnodur E-2l polyisocyanate.which is based on MDI.

Solvent Exposure LimitsPELsand/orTL\~have beenestab-lished for most solvents used in paints.These limits, or manu~cturer’sguide-lines. were used for the organic solventsassociated with the coating systemsevaluated at the time of these surveys.

Whensubstances present together intheworkplaceair havedifferenthealtheffects,they shouldbe consideredsep-aratelvwith respectto their TLVS

When they have similar effects (aswith the organicsolvents associatedwith the coating systemsevaluated inthesesurveys)their combined effect

should be given primary consideration.TLVs can be substituted in the follow-ing formula for this purpose:

%TLV (mixture) =

ioo Conc1 + Conc2 + ,•, + _____‘ft’]1 TLV2 TLVR

Sun-ey of Painting of a BridgeSuperstructure and DeckThroughout the summer of 1988. Mo-bay’s Occupational and Product SafetyDepartment. Coatings Product Safetygroup, conducted a series of industrialhygiene surveys during the painting ofthe Fleming Park bridge, Neville Is-land, Pennsylvania. The purpose wasto determine airborne isocyanate andsolvent vapor concentrations duringbrush-and-roll application of a Des-modur E-21 based polyurethane primerand during airless spray of DesrnodurN-75 based two-partpolyurethane in-termediate and top coats. The resultsappearin Tables IV, V. and VI.

Table Iii.Vapot Nessum Compadsal

VP, RelativeChemical mmHq VPMDI (Monomerand Polymer) 0.~1 1PoJyisocyanate(Desrrcdur N) 0.~75 75IIMOI (Desmodur W) O.X1 IXHOt 0025 2.SXTOt 0025 - 25CCxyse~e(xy3oi) BWater 180MElt (Methyl Ethyl Ket~Ie) 91 9,1X.~

Table ItBnaà-R&t Applicatic. ~ Cot-Pail, Mo4slwe-Cw,P~IywethaswPilmer (Desmodw E-21)

Airbaoe Caaceatntioes

P~ntMDI Solvent

Sample Monomesic (Desmodur E-211 IndexSit.. MDI (mg/rn’) (mg/n’) ~4)Painterll 0.011 0.07 118

Pajnterf2 0.005 003 69Patnters3 0,001 <001 —

Deck <0011 <0~ —

Onsnore <0013 <007 —

Aoo.e OpenPaintCaii <0013 <007 —

Threshold UnitValue (TiMO Goidel me 0051 — 100%

TaSty.S~ytqTwo-Pail Polywethan. Intermediate Coat(DesmedcrN.7s~

AIrborn Ciii catratioss1401 PWy-

Sample MonnericSIt. 1101 (ppb)

Isocyieate(Desmodur N)

(mg/rn’)

SolvedIndex100%

Painterhl 24 25 151Pamterl2 1.9 2.2 117Paintert3 4.1 52 151DeenwindSott, 0.5 <002 cliDeck 06 009 26UndecBridge <0.4 002 —

Tbiubold UnitValue (TIM)

Gmdeline 5-0 1~0t I00%- ~ct art atn~t ~m~q ~ ~te‘pta, 5fl~

I sti, w ——_ I ‘5 ~a onira ~ c.aavc ‘UWTQ 1S~

~teru Ca.cntan

Saniple MoaomencSI~ HOt (ppb~

NOISy-~a

(Desmedw N)(mglm’)

SolveEbidet1~%

Paintertl 46 166 133Paanterl2 40 181 224

riSupen’sor 0 7 003 <20

Deck <06 <003 —

kikuck <06 <0.03 —

Unier8rtdge2slt <07 <0.03 —

underBndge2stt’ <07 <007 —

UnderBndgel5tt’ 16 0~ —

Oo.mwnd.~1t’ 13 08 —

MixinQ Aea - 08 004 —

Tbn$hoId UmitVain (TLV)V Goideline 51 1.t~ 100’-.)carcr~itt —~ ‘umber ~ t1 -roll’ ~a

511L SttrarL txxsa ~raa r.aaWTtlvolT~4tt

Figure 2.

FIgure 1

Table VI.Spnyl.g ~n-PaI Potywethae b~(Desmodur N’75)

Application .‘)(~tCtivcontinued

Dr. Dotill, a medical doctor, is aprofessorcu the C’u’erntv c/KansasMedical center He is a vrçrld it-

,wwned roxrcologtsr ..ho has cc-aushoreda szandardrexthookonrox-ico1og’c He is a chartermetreeroftheSonervof Jazicologs- and serwdas itspresadena’froni/986 to SC He is aconsultantto the A1z’ionattademvcfSciences, the US. Ennmnmenzalhotecrion ,4gencv and main’ otherhealth related o,~aniations.

Dr John Doull answersquestionsaboutapplication safety.

Q-With all the stories abouttoxicity lately, it seems thateverything is hazardous,eveiything is toxic. ts thattrue?

A. Well, it’s true in a sense thatevery chemical is capable of pro-ducing injury if the dose is suffi-ciently high.

Too many vitamins can causepoisoning. Paracelsus. who is thepatron saint oftoxicology. said over400 years ago, “All substances arcpoisonous. There are no excep-tions, It is only the dose that distin-guishes between the poison andtheremedyr Noi. the good news fromthat is that every chemical, includ-ing the isocyanates. can be usedsafely by limiting exposure.

Somepainters are concernedaboutthe hazards associatedwith isocyunates. For exam-ple, can isoqcnates causeasthma?

A. Yes, overexposure to isocy-anates can cause Sensitization.which in turn can produce asthma.In addition, there are certain in-dividuals who ate more susceptibkto this effect than others. Also, pro-ple.who have been re~atedlvmr.exposed or who have been exposedto a single large dose, such in-dividuals may develop isixyanatesensitization and this in turn mz~-cause them to react to future ex-posures to very low levels, evenbelow the levels that might be con-sudered safe for ocher individuals.

Q. Are the effects of over-exposure pennanent’

A. Lsocyanates produce satraJeffects, First, the irritationresponse—burning of the eyes,the nose, the throat, tightness inthe chest, difficulty in breathing.These tts alt usually temporaryand they do not persist once over-exposure isdiscominuel. Now, thescott response is the sensitizationand this does tend to be jxrmaicnt,Although in scene cases peoplehave recovered from sensitizabon,Repeated overexposure to isocy-anates, above the acceptable a-posure level s. can cause eventuallung damage irrludirq decmases inlung function and these effects un-fortunately can be permanent.

Q, Do isoc’ycnatescausecancer?

A ~ll. they are not known tocause cancer in humans, in onelifetime animal study in which ratsand mice were exposed by inhala-tion to toluene diisoc..arate or TI)!,they did not cause cancer. How-ever, in another lifetime study inwhich the rats were given massivedoses oCT01 by tube directly intothe stomach, there was an increasein tumors. We don’t really havecomparable studies with all of theother iSOCyanaits Of at least theyhave not yet been reported.

Do isc’cyanates cause steril-ity, birth defects or repro-ductive problems?

A- l’rnnota’*areofan scientificevidence, either human or animale idence. that isoc’,anates causesterility or birth defects or repro-ductive problems.

co.njou aiways teu witenjcuare being overexposed?

A. Unfortunately you can’t be-cause you can’t smell or you can’tdetect isocy-anates at concentn-tionswt,ich in bce may be hann&l.This is why you must always wearpro~crrespiratory protective e-quiprnent unless you have actual‘monitoring data which indicatesthat the contaminant levels are wellwithin the acceptable limits.

Q, wizycanpoi~w’ethanepaintsbe used safely?

A- ‘mere are several reasons.First, most of these coatings aremade with the polyisocyanateswhich are the less hazardous £,nn,The amount of monomers is keptquite low, in fact, some of thesepolyisocyanates were deliberatelyprepared for usc in paints.

Second. if you have good venti-lation and you use good work peac-tices, then the contaminant levelin the air will be reasonably low,And third, and most important.your protective equipment andyour respirator can protect you.

Q. wirnt is proper protectionagainst isocya nate-cost-wining paints?

A. The lord ofrespiratory protec-tion that you need really dependson the concentration of ismxyanacein the air in some cases, a vaporparticulate or cartridge respiratorma’ be adequate. In other cases.you ma’ need to have a full air-

supplied respirator. You shouldconsult the paint manufacturer’slabels, the MSDS—the MaterialSafety Data Sheet—feir advice inthis regard. However, it is irnpor’tant to remember that if you don’tknow what the concentration ofisocyanate is, then you have to usethe air supplied respirator to besure that you’re getting enoughprotection.

How great is the danger ofoverexposure to isoc>cnatefrom an open can of poly-urethane paint?

A. Oh, I would way that it’s min-imal’ assuming that the person usnot sensitized to the isocvanates inwhich ~e the risk ‘Maid be small.However, skin contact with themixed paint or with the activatorcan cause dermatitis. The paintershould also wtjr safety glasses andshould wear reéomxnended gloveswhen handling the mixed paint.

A! what point in the use ofpaints containing poly

4.so-

tyanatnis there thegreatestdanger oj’overexposure?

A. Certainly during spray paintapplication, particularly in con-fined spaces where the ventilationis poor. This certainly would be theworst case.

Monitoring Suneyof Paintingof Chemical Plant FacilitiesThe Mobay Occupational and ProductSafety Department also monitoredspray painting of chemical processtanks and brush-and-rollerpainting ofhandrails at the Mobay New Martins-vile. WV plant, The results are pre-sented in Tables Vii, VIII. and IX.

table VII.Air Spraying at Desmodur Il-iS Based bp Coaton Chemical Stonge Tank

Airborne Co.cenlntioasHOt Paly- SoiwatIsocpaate Index

Sample Monomeric (Desinodur N) Cumulative54e HOt (9Db) (mglm’) ¼TiMSprayPainter 09 014 <22Painter Helper <0 2 <0 02 <22Dcwnvnnd(No.t) 25 It.’Above PaintersEast 25 It.Downwind SOIl.West 15 II.lJ~*,nd15 ft.Threshold LimitValue (R.Y)K Goideline

<0.2 <002 <22<0.2 <002 <24<0.2 <002 <22<0.2 <0.02 <25<0.2 <002 <24<0.3 <003 —

s.c u’ ir~‘ens Ii 0171 Wci~~It

tStE. Oact 4. ‘tx~sunOttf%d v eatiç ‘o~trc ‘~

Table VIII.trash-and-Roll Application ofOew,odtn Ff15 Based isp Coat on Handrails

Airborne ConcentrationsHUh NI)- Solventisocyanate Index

Sample Monomeric (Desmodur N) CumulativeSite 1401 (ppb) (mg/rn’) ½ThYPainter <0 3 <003 <25ThgStaircase <03 <003

2ndLandtng 13 005 <25lsiLandtnç <03 <003 <25Threshold LimitValue (TIMK Guideline 5.0 1.0’ 100¼5TEL ieraçe4 E’xs~rr lr’a’c.n.,J:r; -o-4oniç-o,.,

Table IX.Air Spray Application at Oesmodor N’Th BasedTop Coat on Waste Treatment Tank

- Airborne Concentrations

MDI Poly- Solventisocyonate Index

Sample Monomeric (flesmodur N) CumulatIveSite HUh (ppb~ (mg/rn

1) ½TI,V

Painter 0 9 0 16 <28

Upwind 151V 09 <00~ <28Downwind 15ft 14 024 —— <28Doniwind 3511’ <04 <00’ <2!Threshold LimitValue (TLV)~rGuideline 5.0 IC’ 100¼

Monitoring Survey ofPaint Mixing in a LaboratoryControlled laboratory monitoringwhile paint was mixed showed that airconcentrations of HDI monomer.polv-isocyanate,and solvents were not de-tectable. The limits of detectionwere03 ppb. Oft mg/m& and 23% of thecumulative TLV, respectively.

Table X.Mixing at Desinodur N-IS Based Paint in a Ubot-atory

Airborne Concenbations

Sample MonomericSite MDI (ppblA~Mimr <07PoiniA <07

Point 9 <0 7Point C <0 7Point 0’ <0 7Threshold LimitValue (TIMa Guideline

MDI NI)-~nate

(Des4nodw N)(mglm1)

<0 01<001<001<0 0’<001

SolventIndex

Cismglatiw½TIM

<23

<23<23<23<23

5.0 1.0’ 100¼- Dcaxt~ alec i,w~.‘ r tu ~ -— ‘r~rn ‘,,r

- Si. set sa~t4 Esxs.e rip’s ~ eas~ç -~-TtrY.c‘et.n

Monitoring ConsiderationsThe monitoring surveysreportedhereinvolved polyurethane paints contain-ing Moba polyisocyanate productsbased on HDI~examethylene diiso-cyanate) and ?vTDI (diphenylmethanediisocyanate). As thetablesax left show.it is important to measure both theair-borne isocyanate monomers and thepolvisocyanates. IT MUST BEREMEMBERED HOWEVER,THAT CONDITIONS VARYWIDELY FROM JOB TO JOB,AND PAINT SPECWIERS, PAINT-ING CONTRACTORS,OR FACIL-ITY OWNERS MUST OBTAINSUFFICIENT MONITORINGDATA FOR MAKING THEIROWNINFORMED JUDGMENT AS 10RESPIRATORY PROTECTIONREQUIREMENTS FOR A GIVENAPPLICATION -

Figure 4~

~aJeo’rroceauresaim equipment

II paints are potentially hazard-ous during application because

they contain four classes of chem-icals—pigments. solvents, resins, andmiscellaneous additives. To one extentor another, these materials presentpotential health hazards when a painteris overexposed to them. That is why it

is necessary to employ all reasonableprecautions and protective equipmentto prevent overexposure during ap-plication.

Painters must use protective equip-ment when spraying any reactive coat-ing system. Particularly important, theymust read the paint-can label andapplicable Material Safety Data Sheetand carefully folloc~- the paint manu-facturer’s recommendations printedthere.

Monitoring should be done so thatlevels of exposure are known; when a-posure levels are not known, hazardouslevels must be assumed and the maxi-mum protective equipment must beemployed. In Mobay’s monitoring ex-perience, cases have been observedin which contamination levels greatlyexceeded permissible limits, makingsupplied-air respiratory equipmentmandatory.

Monitoring the ExposureAreaIn the Fleming Park bridge study, theoutdoor space potentially exceedingpermissible limitsof aircontaminationhad anellipsoidal shape (see Figure 5)-

The dimensions of the ellipsoid, in thiscase, were 20 feet upwind. 20 feet toeach side, and 50 feet downwind fromthe spray gun. These dimensions cor-responded well to the area where spraymist could be seen depositing onsuthces and solvents could be smelled.

Figure 5.

Mobay industrial hygienists refer to thisas the area of sprayapplication—thespace inside which all workers neededto have thesame respiratory protectionas the painters themselves. The shapeand dimensions of thisarea ofspra)-ap-plicazion depend on several factors:number and nearness of painters. windspeed and directiofl, type of paint ap-plication. spraying rate and amount ofmisting and bounceback caused by thevarious surface shapes being painted,and degree of enclosure. The greatvariability of these factors makes it im-possible to generalize or develop a stan-dard size and shape of the area of sprayapplicationand therefore this area mustbedetermined in the field on a case-by-case basis. Monitoring should alwaysbe carried out by properly trained per-sonnel employing the appropriatemeasuring instruments, accuratelycalibrated.

Q. ima: measuresdo jvu he-poseWpyterJolt? wor*elsfrom the ‘potential hazardsUn-cOed in using polyure-

A. ~ll. basically you have twochoices. One is the air-fed maskand the second is the cartridgetype- Your choice is based onwhere you’re going to tise it andbow youre going to aççly the ~u-tens]. If at are insolved in spr~#-ing materials indoors or outdoors.at use the air-S. it ae’re doingwork in enclosed ar~ssud~asbuildinp. taAks, and so forth, atuse the air-S whether at arebrushing or spr~’ing.AM if .a— mixi~material orbrushing inopen areas, then we use just the

plain camidge type mask.

Q. Are there situations whereyu nquirefrnh-afr.nipp~,espinion when sprayingothersolvent-based paInts?

A. t. v.1-aweget imolveri ind&wkbnh~oqtthnginc3-clcsedar~~ieciaBy when wtre—- v.~~bavebind that ahtzh airx~,inIoris & ary togo.It pwMa the proper atrscspbere

a man to do hisjob dYicieunly.

Q~SUice~nadeal withpotentialhazards in ajçdytng poly-rzrethanaa wed a odinrateriais, what do you thhzkyour inthzstzy needs to in-creaseworker safrly?

A. i ~aie.t e~axü,e more tnowl-* otis at ate given relitheto the haranis and how to dal withthoce hat, the brna~acnv.~believe that at need mc tnia-

R,rmarioo relative to types o(pto-tecthe devices, types dclothing.saF,a, -r And at aiM ~ ~kethis information and cnnsznit ixefficiendy to cur people. If at dothat, at an handle these hanrdsin a manic that will pw.-ide satryto worker Ma quality job Isthe owner.

1JohnSConomosPvrsidens, John S Conmnos. Inc&idgMUe. h,inj3tc-ua

Painting contractordiscussesprotectionon thejob-

Wind

4

t

Boundary 04hna & Spray Appkatiec

Respiratory ProtectionMobay fully endorses use of respiratorsnot only for protection from polyiso-cyanates. but also for protection fromsolvent vapors and other paint ingre-dients.

A wide variety of respirators isa\azl-able from industrial safety equipmensuppliers. They are available in twogeneral types: air-purifying respiratorsand supplied-air reSpirators. The selec-tion depends upon the level of airborneexposure, the type of isocyanate in-volved, and the application conditions.Here too, painters must consult paint-can labels and Material Safety DataSheets from the paint manufacturer forassistance. In addition, product safetyliterature, including Material SafetyData Sheets, is published by Mobay foreach of its products.

Respirators should be used strictly inaccordance with the manufacturer’s in-structions and the 051-iA respiratoryprotection standard § 1910.134. (seeAppendix B. page 12). Air-purifyingrespirators must be properly fitted.Respirator users must be medicallyapproved to wear respirators. Filtersand organic-vapor cartridges must bechanged as frequently as recommendedby the respirator manufacturer.

The concentration at which the odorofdiisocyanates is detectable is higherthan allowable limits. Therefore thesense of smell does not provide a suit-able warning. Breakthrough couldoccur during use of an air-purifyingrespirator without immediate detec-tion, and an individual could be ex-posed in excess of alIoc%-able limits.However~solvent-vapor breakthroughwill be detectable by odor well beforeisocyanates break through in concentra-tions above their TLVs.

With supplied-air respirators, it is es-sential that the blower or other airsource draw the air from outside thecontaminated area so the painter is sup-plied with clean respirable air. If com-pressor air is used, it must be properly

filtered and monitored to ensure a con-tinuous supply of grade D breathing airto the respirator.

The spray painter in Figure 6. apply-ing a Desruodur N-75 based coating.used an air-supplied respirator becausecontaminant levels of paint ingredientswere unknown at the time.

In Figure 7, the spray painter, apply-ing a Desmodur N-75 based top coat.has fresh-air protection through an air-supplied hood. Because hoods coverthe head and shoulders, they can pro-vide added protection from eye andskin contact with paint mist.

Figure 6

Figure 7

3ajery Proceduresand Lquipmentcontinued

In the application of a DesmodurN-75 based top coat, shown in Figure8, monitoring results during both brushand roller use indicated airborne levelsof paint ingredients at that time (seeTable VEil) to be such that an air-purifying respirator afforded adequateprotection. This type of respirator.commonly called a vapor-particulaterespirator, has a cartridge that absorbsorganic vapors and a prefilter that re-moves particulates from the air.

Contact ProtectionBecause isocyanates and the other in-gredients in polyurethane paints cancause dermatitis and eye irritation,painters should wear chemical gogglesor glasses with side shields andchemical-resistantgloves (butyl rubberis recommended). Barrier creams forapplication to the skin are available;these offer limited protection andshould be used only to supplement thecoverage afforded by protectiveclothing.

OtherSourcesof InformationOther sources of information are Mo-bay’s product data sheets, MaterialSafety Data Sheets, and labels. If youneed any of this literatureor further in-formation, contact your Mobayrepresentative or call Mobay’s Cor-porate Occupational and ProductSafety Department at (412) 777-2867.

Figure &

AppenaixAGlossary

Airless Spraying PolymerSpray application of paint with equip. A large-molecule chemical compoundment that uses direct pump pressure in- consisting of repeating structural unitsstead of compressed air to atomize the (monomers).paint.Asthma Partsper billion.A condition of continuous or intermit- ppmtent labored breathing accompanied by parts per million.wheezing, a sense of constriction in thechest, and often attacks of coughing or Resin~asnin~ A semisolid or solid flowable ortanic

c’ , material used as a binder in a coating.DermatitisIntlarnmation, irritation or reddening Sensitizationof the skin. The body’s hyperactive (allergy-like)

response to a substance that has beenElectrostatic Spraying touched or inhaled by a susceptibleA system of applying paint by spray Ut individual,which the paint and the painted objecthave opposite electrical charges, caus- S’TELing the paint to be attracted to ~ Short-Term Exposure Limit (an OSHA

standard), the maximum contaminantconcentration to which a worker may

HD1 be exposed for 15 minutes.Hexamethylene diisocyanate. TLV

MDI Threshold Limit Value (published byDiphenylmethane diisocyanate. the American Conference of Govern-

Monomer mental Industrial Hygienists), theThe smallest, simplest molecule of an airborne-contaminant concentrationorganic chemical compound that is below which nearly all workers may becapable of conversion to polymers by’ repeatedly exposed day-after-day with-combination with itself or other simi- out adverse effects.tar molecules or compounds. 1”VA

OSHA flme Weighted Average, the arithmet’Occupational Safety and Health ical mean concentration over an 8-hourMministration period.

Vapor PressurePigment The pressure that causes a liquid toA substance that imparts black, white evaporate. It is measured when the liq-or color to paint. uid and vaporare in equilibrium and is

PEL expressed in millimeters of mercuryPermissible Exposure Limit; an ex-posure limit established by OSHA’sregulatory authority. May be a Time-Weighted Average (TWA) limit or amaximum-concentration exposurelimit.

.1-ippenazxiiOSHA Regulations

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Parts oIOSHA regulations relevant to respiratory protectionare printed below as they appear in 29 CFR Ch. XVII.§ 191(1134. These regulations were in effect on the date of pub-lication of this booklet (June 1989). Since subsequent revi-sions may have occurred, the reader is cautioned to followcurrent regulations.

b~eI-ikmcNS.et 0511mm to be putted aGre Cobe, angad’

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