HS Code for Crude MDI

Crude MDI, technically known as poly(methylene phenyl isocyanate) or polymeric MDI, is classified under HS code 3909.31. This classification is situated within Chapter 39 of the Harmonized System, which covers plastics and articles thereof. Heading 3909 specifically addresses amino-resins, phenolic resins, and polyurethanes in primary forms. Crude MDI is a complex mixture containing 4,4'-diphenylmethane diisocyanate along with its isomers and higher molecular weight oligomers. Unlike pure MDI, which is a chemically defined compound with a specific molecular structure, crude MDI is considered a polymer in primary form due to its variable composition and polymerization. The classification under 3909.31 is precise because the subheading explicitly names poly(methylene phenyl isocyanate). This follows the legal notes of Chapter 39, which define "primary forms" as liquids, pastes, blocks, lumps, or similar bulk forms. Because crude MDI is typically traded as a dark, viscous liquid mixture used primarily in the production of rigid polyurethane foams for insulation and construction, it meets the criteria for primary forms. It is distinguished from the pure isocyanates of Chapter 29 (specifically 2929.10) because it is a mixture of polymers and not a single, isolated organic compound. The presence of multiple isocyanate groups and the polymeric nature of the substance are the deciding factors that move it from the chemical chapter (29) to the plastics chapter (39).

Products Included

• Polymeric MDI (PMDI)
• Crude diphenylmethane diisocyanate
• Poly(methylene phenyl isocyanate) in liquid form
• Technical grade MDI mixtures

Common Misclassification

Crude MDI is often misclassified under HS code 2929.10, which is reserved for pure, chemically defined isocyanates like pure MDI or TDI. Another common error is using 3824.99 for chemical mixtures, but since crude MDI is a polymer in primary form, Chapter 39 takes precedence according to the General Interpretative Rules.

FAQ

What is the HS code for crude MDI?

The HS code for crude MDI (polymeric MDI) is 3909.31.

Why is crude MDI not in Chapter 29?

Chapter 29 is for separate chemically defined organic compounds. Crude MDI is a mixture of polymers and oligomers, which qualifies it as a plastic in primary form under Chapter 39.