Published on: Mar 4, 2016
Transcripts - Polyol Unit
Polyol production = 16,000 MT/PA
Products: Nine polyols and Ten premix formulations.
Starter: Glycerine, dipropylene glycol, sucrose
Initiator: Dried KOH
Prepolymer or Base: Low Molecular weight Polymer, Intermediates
from Initiators & various EO/PO mixtures.
HMW prepolymer: For manufacturing polyols above 4200 MW
Crude polyol: Polyol before potassium removal and stripping.
Initiation: Addition of KOH to glycerine
C3H8O3 + KOH C3H5(OH)2OK+ + H2O
Removal of water for efficient polyol was preferred. Impurity of
polyols were removed as unsaturates.
C3H6O(propylene oxide) Allyl Alcohol
Allyl Alcohol+m(PO) Monol
Factors Affecting production:
Ethylene oxide, Propylene Oxide, Activated Glycerine &
Unsaturated level of final product polyols. Polyol molecular weight is
inversely proportional to polyol product hydroxyl number. Low
functionality leads to unsaturation due to isomerisation of Propylene
Crude containing Alkoxide (ROK+H2O ROH+KOH) were
removed by hydrolysing were sodium pyrophosphate were used to
Raw material specification:
1) Propylene Oxide
2) Ethylene Oxide
3) Starters: Glycerine/Triethanolamine
4) Potassium Hydroxide
Glycerine is saponified with KOH and the initiator formed is
treated with propylene oxide to form prepolymer. The prepolymer
thus formed is treated with propylene oxide and/or ethylene oxide to
form polyols mixture which is then separated from impurities by
filtration to obtain the desired polyol product.
Glycerine is mixed with potassium hydroxide to form initiator in
the mix drum which is provided with a vent.
Reactor (Prepolymer Step):
Then the initiator from mix drum is treated with propylene oxide
in the reactor. This step is called as Prepolymer step.
Prepolymer thus formed is allowed to soak for a certain time in the
reactor and then send to storage tank.
The prepolymer stored in storage tank is sent to the second
reactor. A part of the prepolymer is sent to the mix drum for
Reactor (Polymer Step):
This reactor is also provided with a vent where propylene oxide
and/or ethylene oxide is added for noncapped products.
For capped products, an additional step is required where ethylene
oxide is added after stripping unreacted propylene oxide in the
Treater is used to remove KOH and unreacted oxides. It is also
provided with a vent.
The polyols mixture formed in the reactor is sent to the treater where
the KOH present in the mixture is neutralized by adding a neutralizer.
Sodium phrophospate powder is used as neutralizer.
Dimineralised water and antioxidants are also added to the treater. By
using filter aid, the polyols is then separated from other components
and sent to day tanks for storage. Leaf type filtration is employed.
Water washing is done to prevent cross contamination of the products.
Vacuum system is used for product types drying, stripping of PO
Blend drums are used for agitation of polyol products. Internal and
external agitation additive pots are used as the medium of agitation.