Adhesives Mag logo
search
cart
facebook twitter linkedin youtube
  • Sign In
  • Create Account
  • Sign Out
  • My Account
Adhesives Mag logo
  • NEW PRODUCTS
  • NEWS
    • Adhesives & Sealants Headlines
    • Mergers/Acquisitions
    • Events Calendar
    • Market Trends
  • TOPICS
    • Finished Adhesives and Sealants
    • Pressure-Sensitive Adhesives (PSAs)
    • Coatings
    • Raw Materials and Chemicals
    • Materials Handling/Processing
    • Meter/Mix/Dispense
    • Curing
    • Testing/Quality Control
    • Packaging of Adhesives & Sealants
    • Converting/Packaging
    • Composites
    • Sustainability
  • COLUMNS
    • European Perspectives
    • Strategic Solutions
    • Supply Chain Strategies
    • Tape Talk
  • TOP 20
  • MULTIMEDIA
    • Videos
    • Podcasts
    • Webinars
    • eBooks
  • EXPLORE
    • Adhesives in Action
    • Blog
    • ASI Store
    • Industry Links
    • Market Research
    • Classifieds
  • DIRECTORIES
    • Buyers' Guide
    • Global Adhesives & Sealants Directory
    • Raw Materials, Chemicals, Polymers and Additives Handbook
    • Equipment Handbook
    • Distributor Directory
  • EMAGAZINE
    • EMAGAZINE
    • ARCHIVE ISSUES
    • ADVERTISE
      • Custom Content & Marketing Services
    • CONTACT
  • SIGN UP!

ONLINE EXCLUSIVE: A Novel Approach to the Synthesis of Aromatic and Aliphatic Isocyanates

July 1, 2004
Aromatic, as well as aliphatic di- and poly-, isocyanates are used in the production of polyurethane foams, elastomers, fibres, adhesives and coatings. The most widespread application outlets are found in industries such as construction, furniture, automotive, refrigeration and footwear.

A very good insight on polyurethane chemistry and technology is given in References 1-2; Reference 3 explores the chemistry of isocyanates. Additional publications not cited in this article can be traced in the relevant literature.

The global plant capacity of di- and poly- (methylene diphenyl isocyanates) is estimated at around 2.3 million tons, including new investments in the Far East. Major producers are BASF, Bayer, Dow and Huntsman.

Figure 1. Synthesis of Polymeric Aromatic Isocyanates
Starting from benzene, the current synthesis of isocyanates of the MDI type are represented by the four steps in Figure 1.

The phosgenation reaction, which is expressed in an ideal form in Step 4, has very often been a source of research programs aimed at the substitution of phosgene gas by easier-to-handle chemicals.

A few examples of amine (either aliphatic or aromatic) conversion into a mono-isocyanate through the use of phosgene alternatives, along with some references, are given in Figure 2.

Figure 2. Conversion of Amines into Isocyanates without Phosgene
Most reactions in this figure involve the formation of an intermediate component (carbamate, anilide, urea derivatives), which must be thermally dissociated to the corresponding isocyanate. This means an additional manufacturing step is added to the existing process, thus increasing its costs. On the other hand, the interesting aspect of such a process is the attractive price of urea (or dimethyl carbonate) compared to that of phosgene. In addition, both urea and dimethyl carbonate are considered to be more environmentally friendly than phosgene.

Other patented, synthetic approaches that avoid the passage through the amine are shown in Figure 3.

Figure 3. Synthetic Paths to Aromatic Isocyanates
In this article, we would like to propose a different synthetic method, which offers the following advantages.
  • The reduction of the steps involved in the current industrial production processes (Figure 1) - a welcome advantage considering the ever-increasing prices of the raw materials and the subsequent pressures they exercise on the profit margins of companies.
  • Avoiding the hazardous phosgenation step, part of a continuing search for safer production methods.

Such a synthetic route is represented in a simplified form in Figure 4.

Figure 4. New Route to Isocyanate Synthesis
When the reaction shown in Figure 4 is carried out on a laboratory scale (in an alcoholic medium and in the presence of a catalyst), a carbamate is formed.

This is shown on the infrared spectra, sections of which are shown in Figures 5a-5b.

When the same reaction is carried out with a different set of catalysts - and in an aprotic solvent, thus eliminating the possibility of carbamate formation - the only product is an isocyanate.

The latter is identified by the NCO group absorption at 2250 cm-1 (see Figures 6a-6b).

Future work will involve the following.
  • Improvement of the reaction yield.
  • Synthesis of methylene diphenyl isocyanate.
  • Synthesis of linear aliphatic diisocyanates.
  • Eventual scaleup of the process.


For more information, contact Demosthenes (Deny) Kyriacos, GEM-Chem, Avenue G. Mullie 25, 1200 Brussels- Belgium, phone 011-32-2-7710649; or e-mail GEM-Chem@skynet.be .

Share This Story

Looking for a reprint of this article?
From high-res PDFs to custom plaques, order your copy today!

Recommended Content

JOIN TODAY
to unlock your recommendations.

Already have an account? Sign In

  • mouse in hole

    Using Foam Sealants for Pest Prevention

    According to the National Pest Management Association,...
    Adhesives and Sealants Topics
    By: Kevin Corcoran
  • linked network nodes

    Using the Power of AI for Adhesive and Sealant Formulation

    With the help of software solutions, adhesive formulators...
    Raw Materials and Chemicals
    By: Karen Parker
  • top20-hero.jpg

    2024 ASI Top 20: Leading Global Manufacturers of Adhesives and Sealants

    ASI's annual ranking of the top 20 global adhesive and...
    Pressure-Sensitive Adhesives (PSAs)
Manage My Account
  • eMagazine Issues
  • eNewsletter
  • Online Registration
  • Manage My Preferences
  • Subscription Customer Service

More Videos

Popular Stories

Picture of three men and one woman cutting a ribbon

H.B. Fuller Opens Adhesives and Sealants Facility in UAE

Picture of Noelle Sieradzki

Mactac Announces Changes to Leadership Team

Aerial view of Bostik manufacturing facility

Bostik Invests in Added Capacity at Massachusetts Manufacturing Plant

ASI Top 20 website

Events

January 1, 2030

Webinar Sponsorship Information

For webinar sponsorship information, visit www.bnpevents.com/webinars or email webinars@bnpmedia.com.

View All Submit An Event

Products

Structural Adhesives: Properties, Characterization and Applications

Structural Adhesives: Properties, Characterization and Applications

See More Products

ASI CASE EBOOK

Related Articles

  • ONLINE EXCLUSIVE: An Analysis of Aromatic Polyisocyanates

    See More
  • Enabling Innovation in the Chemical Industry: A Novel Approach

    See More
  • Online Exclusive: Automating Adhesive Application - A Case Study

    See More
×

Keep the info flowing with our eNewsletters!

Get the latest industry updates tailored your way.

JOIN TODAY!
  • RESOURCES
    • Advertise
    • Contact Us
    • Directories
    • Store
    • Want More
  • SIGN UP TODAY
    • Create Account
    • eMagazine
    • eNewsletters
    • Customer Service
    • Manage Preferences
  • SERVICES
    • Marketing Services
    • Reprints
    • Market Research
    • List Rental
    • Survey & Sample
  • STAY CONNECTED
    • LinkedIn
    • Facebook
    • Youtube
    • X (Twitter)
  • PRIVACY
    • PRIVACY POLICY
    • TERMS & CONDITIONS
    • DO NOT SELL MY PERSONAL INFORMATION
    • PRIVACY REQUEST
    • ACCESSIBILITY

Copyright ©2025. All Rights Reserved BNP Media.

Design, CMS, Hosting & Web Development :: ePublishing