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Methylene diphenyl diisocyanate

January 01, 1970

Methylene diphenyl diisocyanate (MDI) is an aromatic diisocyanate. Three isomers are common, varying by the positions of the isocyanate groups around the rings: 2,2′-MDI, 2,4′-MDI, and 4,4′-MDI. The 4,4′ isomer is most widely used, and is also known as 4,4′-diphenylmethane diisocyanate.[3] This isomer is also known as Pure MDI. MDI reacts with polyols in the manufacture of polyurethane. It is the most produced diisocyanate, accounting for 61.3% of the global market in the year 2000.[4]

4,4′-Methylene diphenyl diisocyanate
Names
Preferred IUPAC name
1,1′-Methylenebis(4-isocyanatobenzene)
Other names
  • Bis(4-isocyanatophenyl)methane
  • 1-Isocyanato-4-[(4-isocyanatophenyl)methyl]benzene
  • 4,4′-Methylene diphenyl diisocyanate
  • 4,4′-Diphenylmethane diisocyanate
  • Bayer Desmodur 44
  • Methylene bis(4-phenyl isocyanate)
  • Pure MDI
Identifiers
  • 101-68-8 Y
3D model (JSmol)
  • Interactive image
  • Interactive image
ChEBI
  • CHEBI:53218 N
ChemSpider
  • 7289 Y
ECHA InfoCard 100.043.361
EC Number
  • 4,4'-: 202-966-0
  • 7570
RTECS number
  • NQ9350000
UNII
  • B0LO6BBS8C N
  • InChI=1S/C15H10N2O2/c18-10-16-14-5-1-12(2-6-14)9-13-3-7-15(8-4-13)17-11-19/h1-8H,9H2 N
    Key: UPMLOUAZCHDJJD-UHFFFAOYSA-N N
  • O=C=NC(C=C2)=CC=C2CC1=CC=C(N=C=O)C=C1
  • O=C=N\c1ccc(cc1)Cc2ccc(\N=C=O)cc2
Properties
C15H10N2O2
Molar mass 250.25 g/mol
Appearance White or pale yellow solid
Density 1.230 g/cm3, solid
Melting point 40 °C (104 °F; 313 K)
Boiling point 314 °C (597 °F; 587 K)
Reacts
Vapor pressure 0.000005 mmHg (20 °C)[1]
Hazards
GHS labelling:
Danger
H315, H317, H319, H332, H334, H335, H351, H373
P201, P202, P260, P261, P264, P271, P272, P280, P281, P285, P302+P352, P304+P312, P304+P340, P304+P341, P305+P351+P338, P308+P313, P312, P314, P321, P332+P313, P333+P313, P337+P313, P342+P311, P362, P363, P403+P233, P405, P501
Flash point 212–214 °C (Cleveland open cup)
Lethal dose or concentration (LD, LC):
2200 mg/kg (mouse, oral)[2]
31,690 mg/kg (rat, oral)[2]
  • 369 mg/m3 (rat, 4 hr)
  • 380 mg/m3 (rat, 4 hr)
  • 178 mg/m3 (rat)[2]
NIOSH (US health exposure limits):
PEL (Permissible)
 C 0.2 mg/m3 (0.02 ppm)[1]
REL (Recommended)
 TWA 0.05 mg/m3 (0.005 ppm) C 0.2 mg/m3 (0.020 ppm) [10-minute][1]
IDLH (Immediate danger)
 75 mg/m3[1]
Related compounds
Related Isocyanates
Related compounds
 Polyurethane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)

Production edit

Total world production of MDI and polymeric MDI is over 7.5 million tonnes per year (in 2017).

As of 2019, the largest producer was Wanhua Chemical Group.[5] Other major producers are Covestro,[6] BASF, Dow, Huntsman, Tosoh, Kumho Mitsui Chemicals. All major producers of MDI are members of the International Isocyanate Institute, whose aim is the promotion of the safe handling of MDI and TDI in the workplace, community and environment.

The first step of the production of MDI is the reaction of aniline and formaldehyde, using hydrochloric acid as a catalyst to produce 4,4'-Methylenedianiline and other diamine precursors, as well as their corresponding polyamines:

 

Then, these diamines are treated with phosgene to form a mixture of isocyanates, the isomer ratio being determined by the isomeric composition of the diamine. Two different reaction mechanisms for this transformation are possible, namely "phosgenations first" and "step-wise phosgenations".[7]

 

Distillation of the mixture gives a mixture of oligomeric polyisocyanates, known as polymeric MDI, and a mixture of MDI isomers which has a low 2,4′ isomer content. Further purification entails fractionation of the MDI isomer mixture.[8]

Reactivity of the isocyanate group edit

The positions of the isocyanate groups influences their reactivity. In 4,4′-MDI, the two isocyanate groups are equivalent but in 2,4′-MDI the two groups display highly differing reactivities. The group at the 4-position is approximately four times more reactive than the group at the 2-position due to steric hindrance.[4]

 
MDI isomers and polymer

Applications edit

The major application of 4,4′-MDI is the production of rigid polyurethane.[9] These rigid polyurethane foams are good thermal insulators and used in nearly all freezers and refrigerators worldwide, as well as buildings. Typical polyols used are polyethylene adipate (a polyester) and poly(tetramethylene ether) glycol (a polyether).

4,4′-MDI is also used as an industrial strength adhesive, which is available to end consumers as various high-strength bottled glue preparations.[10]

Safety edit

MDI, like the other isocyanates, is an allergen and sensitizer. Persons developing sensitivity to isocyanates may have dangerous systemic reactions to extremely small exposures, including respiratory failure. Handling MDI requires strict engineering controls and personal protective equipment.[11] It is a potentially violently reactive material towards water and other nucleophiles.

References edit

  1. ^ a b c d NIOSH Pocket Guide to Chemical Hazards. "#0413". National Institute for Occupational Safety and Health (NIOSH).
  2. ^ a b c "Methylene bisphenyl isocyanate". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  3. ^ Pubchem. "4,4'-Diphenylmethane diisocyanate | C15H10N2O2 - PubChem". pubchem.ncbi.nlm.nih.gov. Retrieved 2017-06-25.
  4. ^ a b Randall, D.; Lee, S. (2003). The Polyurethanes Book. New York: Wiley. ISBN 978-0-470-85041-1.
  5. ^ Tullo, Alexander H. (29 July 2019). "C&EN's Global Top 50 chemical companies of 2018". Chemical & Engineering News. Vol. 97, no. 30. Retrieved 15 January 2020.
  6. ^ Gal, J. (2012-02-20). . ICIS Chemical Business. Archived from the original on 2012-03-26. Retrieved 2020-01-15.
  7. ^ Boros, R. Zsanett; Koós, Tamás; Wafaa, Cheikh; Nehéz, Károly; Farkas, László; Viskolcz, Béla; Szőri, Milán (2018-08-16). "A theoretical study on the phosgenation of methylene diphenyl diamine (MDA)". Chemical Physics Letters. 706: 568–576. doi:10.1016/j.cplett.2018.06.024. ISSN 0009-2614. S2CID 102682388.
  8. ^ Six, C.; Richter, F. "Isocyanates, Organic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a14_611. ISBN 978-3527306732.
  9. ^ Boustead, I. (2005). (PDF). Eco-Profiles of the European Plastics Industry. Brussels: PlasticsEurope. Archived from the original (PDF) on 2013-09-25.
  10. ^ US patent 6884904, Smith, A. K.; Goddard, R. J.; Paulsen, E. J. L., "MDI-based polyurethane prepolymer with low monomeric MDI content", issued 2005-04-26 
  11. ^ Almaguer, D.; et al. (September 2006). "Preventing Asthma and Death from MDI Exposure During Spray-on Truck Bed Liner and Related Applications" (PDF). NIOSH Alert. The National Institute for Occupational Safety and Health. DHHS (NIOSH) Publication No. 2006–149. Retrieved 2012-08-14.

External links edit

  • International Chemical Safety Card 0298
  • IARC Monograph: "4,4'-Methylenediphenyl Diisocyanate"
  • NIOSH Safety and Health Topic: Isocyanates, from the website of the National Institute for Occupational Safety and Health (NIOSH)
  • Isofact American Chemistry Council Diisocyanates Panel
  • Azom Chemical database on Polyurethane chemistry
  • International Isocyanate Institute
  • Concise International Chemical Assessment Document 27

January 01, 1970
methylene, diphenyl, diisocyanate, aromatic, diisocyanate, three, isomers, common, varying, positions, isocyanate, groups, around, rings, isomer, most, widely, used, also, known, diphenylmethane, diisocyanate, this, isomer, also, known, pure, reacts, with, pol. Methylene diphenyl diisocyanate MDI is an aromatic diisocyanate Three isomers are common varying by the positions of the isocyanate groups around the rings 2 2 MDI 2 4 MDI and 4 4 MDI The 4 4 isomer is most widely used and is also known as 4 4 diphenylmethane diisocyanate 3 This isomer is also known as Pure MDI MDI reacts with polyols in the manufacture of polyurethane It is the most produced diisocyanate accounting for 61 3 of the global market in the year 2000 4 4 4 Methylene diphenyl diisocyanate Names Preferred IUPAC name 1 1 Methylenebis 4 isocyanatobenzene Other names Bis 4 isocyanatophenyl methane1 Isocyanato 4 4 isocyanatophenyl methyl benzene4 4 Methylene diphenyl diisocyanate4 4 Diphenylmethane diisocyanateBayer Desmodur 44Methylene bis 4 phenyl isocyanate Pure MDI Identifiers CAS Number 101 68 8 Y 3D model JSmol Interactive imageInteractive image ChEBI CHEBI 53218 N ChemSpider 7289 Y ECHA InfoCard 100 043 361 EC Number 4 4 202 966 0 PubChem CID 7570 RTECS number NQ9350000 UNII B0LO6BBS8C N InChI InChI 1S C15H10N2O2 c18 10 16 14 5 1 12 2 6 14 9 13 3 7 15 8 4 13 17 11 19 h1 8H 9H2 NKey UPMLOUAZCHDJJD UHFFFAOYSA N N SMILES O C NC C C2 CC C2CC1 CC C N C O C C1O C N c1ccc cc1 Cc2ccc N C O cc2 Properties Chemical formula C15H10N2O2 Molar mass 250 25 g mol Appearance White or pale yellow solid Density 1 230 g cm3 solid Melting point 40 C 104 F 313 K Boiling point 314 C 597 F 587 K Solubility in water Reacts Vapor pressure 0 000005 mmHg 20 C 1 Hazards GHS labelling Pictograms Signal word Danger Hazard statements H315 H317 H319 H332 H334 H335 H351 H373 Precautionary statements P201 P202 P260 P261 P264 P271 P272 P280 P281 P285 P302 P352 P304 P312 P304 P340 P304 P341 P305 P351 P338 P308 P313 P312 P314 P321 P332 P313 P333 P313 P337 P313 P342 P311 P362 P363 P403 P233 P405 P501 Flash point 212 214 C Cleveland open cup Lethal dose or concentration LD LC LD50 median dose 2200 mg kg mouse oral 2 LDLo lowest published 31 690 mg kg rat oral 2 LC50 median concentration 369 mg m3 rat 4 hr 380 mg m3 rat 4 hr 178 mg m3 rat 2 NIOSH US health exposure limits PEL Permissible C 0 2 mg m3 0 02 ppm 1 REL Recommended TWA 0 05 mg m3 0 005 ppm C 0 2 mg m3 0 020 ppm 10 minute 1 IDLH Immediate danger 75 mg m3 1 Related compounds Related Isocyanates Toluene diisocyanateNaphthalene diisocyanateHexamethylene diisocyanateIsophorone diisocyanate Related compounds Polyurethane Except where otherwise noted data are given for materials in their standard state at 25 C 77 F 100 kPa N verify what is Y N Infobox references Contents 1 Production 2 Reactivity of the isocyanate group 3 Applications 4 Safety 5 References 6 External linksProduction editTotal world production of MDI and polymeric MDI is over 7 5 million tonnes per year in 2017 As of 2019 the largest producer was Wanhua Chemical Group 5 Other major producers are Covestro 6 BASF Dow Huntsman Tosoh Kumho Mitsui Chemicals All major producers of MDI are members of the International Isocyanate Institute whose aim is the promotion of the safe handling of MDI and TDI in the workplace community and environment The first step of the production of MDI is the reaction of aniline and formaldehyde using hydrochloric acid as a catalyst to produce 4 4 Methylenedianiline and other diamine precursors as well as their corresponding polyamines nbsp Then these diamines are treated with phosgene to form a mixture of isocyanates the isomer ratio being determined by the isomeric composition of the diamine Two different reaction mechanisms for this transformation are possible namely phosgenations first and step wise phosgenations 7 nbsp Distillation of the mixture gives a mixture of oligomeric polyisocyanates known as polymeric MDI and a mixture of MDI isomers which has a low 2 4 isomer content Further purification entails fractionation of the MDI isomer mixture 8 Reactivity of the isocyanate group editThe positions of the isocyanate groups influences their reactivity In 4 4 MDI the two isocyanate groups are equivalent but in 2 4 MDI the two groups display highly differing reactivities The group at the 4 position is approximately four times more reactive than the group at the 2 position due to steric hindrance 4 nbsp MDI isomers and polymerApplications editThe major application of 4 4 MDI is the production of rigid polyurethane 9 These rigid polyurethane foams are good thermal insulators and used in nearly all freezers and refrigerators worldwide as well as buildings Typical polyols used are polyethylene adipate a polyester and poly tetramethylene ether glycol a polyether 4 4 MDI is also used as an industrial strength adhesive which is available to end consumers as various high strength bottled glue preparations 10 Safety editMDI like the other isocyanates is an allergen and sensitizer Persons developing sensitivity to isocyanates may have dangerous systemic reactions to extremely small exposures including respiratory failure Handling MDI requires strict engineering controls and personal protective equipment 11 It is a potentially violently reactive material towards water and other nucleophiles References edit a b c d NIOSH Pocket Guide to Chemical Hazards 0413 National Institute for Occupational Safety and Health NIOSH a b c Methylene bisphenyl isocyanate Immediately Dangerous to Life or Health Concentrations IDLH National Institute for Occupational Safety and Health NIOSH Pubchem 4 4 Diphenylmethane diisocyanate C15H10N2O2 PubChem pubchem ncbi nlm nih gov Retrieved 2017 06 25 a b Randall D Lee S 2003 The Polyurethanes Book New York Wiley ISBN 978 0 470 85041 1 Tullo Alexander H 29 July 2019 C amp EN s Global Top 50 chemical companies of 2018 Chemical amp Engineering News Vol 97 no 30 Retrieved 15 January 2020 Gal J 2012 02 20 To the Rescue ICIS Chemical Business Archived from the original on 2012 03 26 Retrieved 2020 01 15 Boros R Zsanett Koos Tamas Wafaa Cheikh Nehez Karoly Farkas Laszlo Viskolcz Bela Szori Milan 2018 08 16 A theoretical study on the phosgenation of methylene diphenyl diamine MDA Chemical Physics Letters 706 568 576 doi 10 1016 j cplett 2018 06 024 ISSN 0009 2614 S2CID 102682388 Six C Richter F Isocyanates Organic Ullmann s Encyclopedia of Industrial Chemistry Weinheim Wiley VCH doi 10 1002 14356007 a14 611 ISBN 978 3527306732 Boustead I 2005 Polyurethane rigid foam PDF Eco Profiles of the European Plastics Industry Brussels PlasticsEurope Archived from the original PDF on 2013 09 25 US patent 6884904 Smith A K Goddard R J Paulsen E J L MDI based polyurethane prepolymer with low monomeric MDI content issued 2005 04 26 Almaguer D et al September 2006 Preventing Asthma and Death from MDI Exposure During Spray on Truck Bed Liner and Related Applications PDF NIOSH Alert The National Institute for Occupational Safety and Health DHHS NIOSH Publication No 2006 149 Retrieved 2012 08 14 External links editInternational Chemical Safety Card 0298 IARC Monograph 4 4 Methylenediphenyl Diisocyanate NIOSH Safety and Health Topic Isocyanates from the website of the National Institute for Occupational Safety and Health NIOSH Isofact American Chemistry Council Diisocyanates Panel Azom Chemical database on Polyurethane chemistry MDI and the Environment 2005 presentation by Center for the Polyurethanes Industry International Isocyanate Institute Concise International Chemical Assessment Document 27 Retrieved from https en wikipedia org w index php title Methylene diphenyl diisocyanate amp oldid 1182928127, wikipedia, wiki, book, books, library,

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