Isocyanate
Polyurethanes were synthesized from polyester and butanediol with three different diisocyanates as following : 4,4´‐diphenylmethane diisocyanate (MDI), m‐xylene diisocyanate (XDI), and 2,4‐toluene diiscynate (TDI).Toluene diisocyanate
Toluene diisocyanate (TDI) is a member of isocyanates which are widely used today in the manufacture of polyurethane. In a process for TDI preparation, first Dinitrotoluene (DNT) is reacted with hydrogen in the presence of a suitable catalyst and produce toluenediamine (TDA). Then TDA is converted to TDI by reaction with Carbonyldicoloride (CDC).
TDI is commonly used to manufacture:
Flexible foams – used for the fabrication of bedding, furniture, automotive seating, flexible packaging and carpet underlay; this is the largest market application for TDI
“Foamed-in-place” polyurethane plastics – ranging from soft and sponge-like to hard and porous for use in furniture, packaging, insulation and boat building
Polyurethane coatings – used on leather, wire, tank linings and masonry
Elastomers – used to produce adhesives, films and linings, and abrasive wheels and other mechanical items that require abrasion and solvent resistance
Rigid, “pour-in-place” foams – for use in appliances, and, in smaller amounts, packaging
Urethane sealants – used in construction applications
Cast elastomers – for production of articles such as roller blade wheels
| TDI Properties | ||
|---|---|---|
| Properties | SPECIFICATION | TEST METHOD |
| Appearance @ 30 ˚C | Clear liquid | Visual |
| Purity, %wt. | Min. 99.5 | GC |
| 2,4-TDI Content, %wt. | 80.0 ± 1.0 | ASTM D4660.00 |
| 2,6-TDI Content, %wt. | 20.0 ± 1.0 | ASTM D4660.00 |
| Total Acidity, ppm by wt. | Max. 40 | ASTM D5629.05 |
| Hydrolysable chlorine, ppm by wt. | Max. 100 | ASTM D4663.98 |
| Total chlorine, ppm by wt. | Max. 500 | ASTM D4661.03 |
| Color (APHA) | Max.25 | ASTM D4877.04 |
| Sp.gr @ 25 ˚C | 1.22 ± 0. | ASTM D4659.03 |
| Nitro Isocyanate compounds, ppm | Max.30 | H900.5800 |
Applications
Methylene diphenyl diisocyanate
Methylene diphenyl diisocyanate, most often abbreviated as MDI, is an aromatic diisocyanate. It exists in three isomers, 2,2′-MDl,2,4′-MDI, and 4,4′-MDI. The first step of the production of MDI is the conversion of Benzene into nitrobenzene. Next, in the presence of a suitable catalyst, aniline is produced. Then, Aniline is reacted with Formaldehyde in the presence of Hydrochloric acid 32%Wt., produce PMA (Polymeric di-phenyl Methyl Amine). Finally, by the effect of carbonyl chloride, PMA produce MDI. MDI Application MDI is reacted with Polyol to produce polyurethane. These rigid polyurethane foams are good thermal insulators and are used in nearly all freezers and refrigerators worldwide, as well as buildings. It is also used in industry-leading adhesives, leather and automotive industries such as car seats and dashboards and car interior panels, and the production of bedding and footwear of various types of shoes.
