Polymeric diphenylmethane diisocyanate

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General structure of PMDI with n = 0, 1, 2… 6. There are different constitutional isomers with regard to the isocyanate groups.

Polymeric diphenylmethane diisocyanate ( PMDI ), also known as technical MDI , is a mixture of methylene diphenyl isocyanates and homologous aromatic polyisocyanates . However, the term “polymeric diphenylmethane diisocyanate” is technically incorrect, since it is not a polymer but a mixture of compounds with several (typically up to 6) phenylene groups , each of which has an isocyanate group. A common trade name is also polymethylene polyphenyl isocyanate .

PMDI is used as a binder in wood -based panels , especially OSB panels , and is a starting material for the production of polyurethanes .

Manufacturing

The industrial production takes place from 4,4'-diaminodiphenylmethane (a methylenedianiline , MDA) or from its homologues with phosgene as reactant . The starting materials are first by condensation of aniline with formaldehyde produced.

Composition and properties

safety instructions
Surname

Technical MDI

CAS number

9016-87-9

EC number

618-498-9

ECHA InfoCard

100.112.554

GHS labeling of hazardous substances
08 - Dangerous to health 07 - Warning

danger

H and P phrases H: 315-317-319-332-334-335-351-373
P: 260-280-284-304 + 340-305 + 351 + 338-342 + 311
Toxicological data

49000 mg kg −1 ( LD 50 ,  rat ,  oral )

The properties of the PMDI in terms of reactivity and thus its usability as a binder are essentially influenced by the following factors:

PMDI is a brown, very difficult to ignite liquid ( flash point above 200 ° C), which has a higher density than water. The melting point is around −24 ° C. At 20 ° C the density is around 1.23 g · cm −3 .

Wood chipboard

PMDI, in comparison to others in the wood products industry adhesives used some advantages, particularly in applications with higher requirements for moisture resistance or the higher price formaldehyde - emission justify:

Individual evidence

  1. ↑ a b c d Entry on Technical MDI in the GESTIS substance database of the IFA , accessed on December 22, 2019(JavaScript required) .