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Isocyanate Exposure Assessment Techniques Dr. Stepan Reut

Isocyanate Exposure Assessment Techniques Dr. Stepan Reut. Industrial Hygiene Conquest After an Old Dragon. © OSHTECH Inc. 2006. How to deal with isocyanate issues?. ISOCYANATES. OSHTECH Inc. 2006. What's in a name ?. Cyanides R-C N

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Isocyanate Exposure Assessment Techniques Dr. Stepan Reut

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  1. Isocyanate Exposure Assessment Techniques Dr. Stepan Reut Industrial Hygiene Conquest After an Old Dragon © OSHTECH Inc. 2006

  2. How to deal with isocyanate issues? ISOCYANATES OSHTECH Inc. 2006

  3. What's in a name ? • Cyanides R-CN 1704 Berlin - JC Dippel and H. Diesbach. Studied reaction of blood with potash • Cyanates R-O-CN 1824 Wohler. Discovered “organic chemistry” by 1828 • Isocyanate R-N=C=O 1824 Liebeg worked with inorganic isocyanates – Fulminates Along with Wohler co-discovered Chemical Structure OSHTECH Inc. 2006

  4. How it all started? • 1848 – Wurtz. First to synthesize isocyanates by alkylating calcium cyanate with organic sulfuric acid esters. • 1937- Otto Bayer. Discovered the first diisocyanate synthesis and diisocyanate polyaddition processes, otherwise regarded as scientific curiosities only. Otto Bayer 1902-1982 OSHTECH Inc. 2006

  5. Otto Bayer’s Resin OCN-(CH2)6-NCO + H2N-(CH2)6- NH2 OCN-(CH2)6-NH(CO)NH-(CH2)6- NH2 OSHTECH Inc. 2006

  6. Chemical Structure of Selected Diisocyanates 4’4-MDI IPDI OSHTECH Inc. 2006

  7. Reactivity of Isocyanates • Reaction with Alcohols (Glycols): RNCO+ R1OH→ RNH-CO-O-R1 (Urethane) • Reaction with Amines: RNCO+ R1NH2→ RNH-CO-NH-R1 (Urea) • Reaction with Water: RNCO+ HOH→ RNH2+CO2 RNCO+ RNH2→ RNH-CO-NH-R OSHTECH Inc. 2006

  8. Relative reactivity of isocyanates with active hydrogen compounds OSHTECH Inc. 2006

  9. Stability of Isocyanates(half-life) • Reaction with Water: • RNCO+ HOH→ RNH2+CO2 • RNCO+ RNH2→ RNH-CO-NH-R OSHTECH Inc. 2006

  10. Diisocyanates on the World Market • MDI - Rigid Foams, Fibres • TDI - Flexible Foams, Paints, Coating • HDI- Paints & Coatings • IPDI -Elastomers • NDI-Elastomers OSHTECH Inc. 2006

  11. MDI Usage in North America http://www.polyurethane.org/ OSHTECH Inc. 2006

  12. Commercial Diisocyanate Monomers TWA 5 ppb OSHTECH Inc. 2006

  13. Poly- Isocyanates • Oil-like or solid products • Products of homo-oligomerization • vapour pressure (typically <5ppb) • Less reactive (more stable) • Less toxic (Manufacturers’ limits range from 0.5-1 mg/m3) • Diisocyanate Contamination ( 0.5%) • Contains mixture of 2-, 3-, ....... –mers • Exposure limit in μmol –NCO groups Department of Public Health – Australia. Community Air Pollution from Crash Repair Workshops OSHTECH Inc. 2006

  14. Blocked Isocyanates Many isocyanate reactions are reversible when Isocyanate adduct is heated RNCO+ R1OH→ RNH-CO-O-R1 RNH-CO-O-R1 → RNCO → polymerization Blocked Isocyanate – Safer to handle and work with TDI, HDI, IPDI in situ t airborne OSHTECH Inc. 2006

  15. Relative toxicity of poly-isocyanates Boundaries OSHTECH Inc. 2006

  16. Di- Isocyanates Arch, BASF, Bayer, Degusa, Dow, Huntsman, Lyondell, Shell , Rhodia Poly- Isocyanates Air Products, Autotravi, BASF, Bayer, Degussa,Ecopur, HuntsmanTolling, Uniroyal Major Manufacturers OSHTECH Inc. 2006

  17. Sampling = Derivatization Problem: • Isocyanates are unstable • Can be Vapour or Solid • Low concentrations must be traced • Derivatization: • Stabilizes (neutralize) Isocyanate • Turns it into non-volatile product • Tags isocyanate group with easy detectable chemical OSHTECH Inc. 2006

  18. Derivatization Reaction +2 OSHTECH Inc. 2006

  19. Sampling Tools Sampling Pump (0.5-2.0 L/min) Sampling Cassettes suitable for the application Impinger OSHTECH Inc. 2006

  20. Collection: Vapour vs. Particulates Vapour • any sampler with right derivatizer Particles • Inhalable Sampler (e.g., IOM): <100 μm • 37-mm filter (closed face): < 20 μm • Impinger: < 20 μ m OSHTECH Inc. 2006

  21. Derivatization: Vapour vs. Particulates Filter with derivatizer • Vapour • Particles < 2 μ m Filter with derivatizer. Extracted on site • Slow-cure particles > 2 μ m Impinger • Vapour and particles < 20 μ m OSHTECH Inc. 2006

  22. Standard Analytical Methods: Overview • Colorimetric (Old MOL method for TDI, MDI) • HPLC methods with identification based on retention time. • monomers: NIOSH, OSHA, EPA, • polymers: OSHA, Bayer • HPLC methods with identification based on selective detector response. • monomers and polymers: NIOSH, ASTM, MDHS OSHTECH Inc. 2006

  23. Isocyanate determination by HPLC based on retention time OSHA PV 2125 Derivatizer Impurity OSHTECH Inc. 2006

  24. Isocyanate determination by HPLC based on detector response Derivatizer is unique, and detector is selective. Any signal detected is isocyanate Derivatizer Iso-ChekTM manual OSHTECH Inc. 2006

  25. Practical Limitations Cassette • Limited shelf life • Volatility of derivatizers • Interferences Impinger • Solvent problems • Glassware in industrial environment • Shipping inconvenience OSHTECH Inc. 2006

  26. Comparison of Methods OSHTECH Inc. 2006

  27. Recommendations • Is the Isocyanate an issue? • MSDS is good, but not enough. Some manufacturers do not disclose composition. Read between lines. • The word “Isocyanate” in MSDS does not necessary mean it will be released into the air. • Also recognize Isocyanate closest “relatives”. • Watch for symptoms. • Smaller production scale, larger chance of exposure. • Are you dealing with “normal” operation or “extreme” conditions? • Normal – MSDS is your friend. • Extreme – assume the worst. • Fire – take into account Isocyanate half-life. • Do not let “Isocyanates” mask other problems. • Solvents, Isocyanate derivatives (i.e. MDA), housekeeping. OSHTECH Inc. 2006

  28. “Isocyanate” Problems? For Help Analytical Services: • OSHA 18, 42,47, PV2030, PV2034, PV2125 • NIOSH 2535 and Bayer’s “Nitro” methods Material Study: • Product decomposition simulation and tests Equipment Rentals: • Pumps, cassettes, impingers, vials & solutions Visit us at http://www.oshtechinc.com/ OSHTECH Inc. 2006

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