What is polyol?

What is Polyol?

A polyol is the main raw material in any flexible foam formulation.

Two types of feedstock are used in the manufacture of a polyol: an initiator and an alkylene oxide. In the case of flexible slabstock polyols, the initiator is usually glycerol. The main alkylene oxide is propylene oxide (PO), but usually some ethylene oxide (EO) is used as well .The hydroxyl groups at the end of each chain can react with di-isocyanates, such as TDI to give polyurethane polymer.

Manufacture of Propylene oxide

Propylene oxide is the major feedstock for polyols. There are two basic commercial routes for the manufacture of PO, per oxidation process and the chlorhydrin process. Per-oxidation process produces both styrene monomer (SM) and PO.

Peroxidation Process (1)

In this process, the first step is per oxidation of ethyl benzene.

Ethyl benzene + Oxygen = Ethyl benzene Hydro peroxide


Peroxidation Process (2)

The ethyl benzene hydro peroxide is then used to oxidize propylene to give PO.

Ethyl benzene hydro peroxide + Propylene = Propylene Oxide + Methyl Phenyl Carbinol

Peroxidation Process (3)

The methyl phenyl carbinol, produced at the same time as the PO, is dehydrated to styrene monomer, an important raw material for the polystyrene industry

Methyl Phenyl Carbinol = Styrene Monomer + Water

Chlorhydrin Process

In the Chlorhydrin process, propylene is reacted with hypochlorous acid to give propylene chlorhydrin. In the presence of calcium hydroxide the chlorhydrin is converted to PO. The main by-product of this process is calcium chloride, which represents a disposal challenge making this process less attractive than the direct per oxidation route.

Propylene + Hypochlorous acid = Propylene Chlorhydrin

Propylene Chlorhydrin + Calcium Hydroxide = Propylene oxide + Calcium Chloride

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