„Dry Foam“ Prevention in
Suspension Polymerisation
Process
Polymerization processes
Emulsion Polymerization
Suspension Polymerization
Emulsifier:
• Sodium alkylsulfate
• Sodium alkylsulfonate
• Ammonium alkylcarboxy acid
• Sodium sulfosuccinate
•Dosage: ~ 1%
Suspension Aid:
• Polyvinylalcohol
• Methylhydroxycellulose
•Dosage: ~ 0,1%
Foam in the Production of PVC
Polymerization
Reactor
Blowdown
Vessel
Monomer
Recovery
(VCM, water,
surfactants, etc.)
Storage
Tank
Str
ipp
ing
Co
lum
n
Points where foam may occure
Production Problems caused by Foam
An increased foam build up
• reduces the space time yield of the reactor
• may increase fouling in the reactor which results
in higher maintenance and cleaning costs
• reduces the cooling capacity and may build up
layers on the cooling surface of reflux condensers
• may slow down the speed of demonomerisation
Evonik Antifoams for PVC
Designed for E-PVC and Micro S-PVC:
-TEGO Antifoam KS 53
-TEGO Antifoam KS 95
Designed for S-PVC:
-TEGO Antifoam KE 600
-TEGO Antifoam 2280
Sintered glass
To start, the cycliner is filled
with 1 l of surfactant solution
+ defoamer
Time is noted when foam
reaches 2 l mark
The Sintered Glass Test
Test Results in Suspending Agent and
Emulsifier Solution
0.1% PVOH solution 1% DBS solution
TEGO Antifoam KS 53
TEGO Antifoam KS 95
TEGO Antifoam KE 600
TEGO Antifoam 2280
120 s
150 s
600 s
660 s
960 s
840 s
300 s
240 s
Wet and Dry Foam
Wet foam Dry foam
Gas Bubbles in Pure Liquids
When the bubble reaches the
surface it bursts immedeately
No stable foam can be build
Foam Formation
Introduction and dispersion of
gas or air - formation of bubbles
Stabilisation by dissolved
amphiphilic molecules
Rising of stabilised bubbles
Penetration of the surface
formation of the double
layer
1
2
3
4
Defoaming: Mechanism Theory
Defoaming: Entering-Spreading
Entering - E
Spreading - S
Destabilisation
+ viscous drag on the
underlying liquid
E = g w/a + g w/o - g o/a > 0
S = g w/a - g w/o - g o/a > 0
wo
a
Dry Foam in S-PVC
Bubble
PVC particles
Dry foam
Standard Antifoams can not enter the
Surface
TEGOPREN 5890
TEGOPREN 5890
• is based on organomodifies siloxane (OMS)
• is a 100 % product
• is selfdispersable. Dilutions are long term stable
• can be used in food contact application
(EU Regulation 10/2011)
TEGOPREN 5890
TEGOPREN 5890 will be
added
Tests with PVC Slurry
Glass pipe
To start, the cycliner is filled
with 1000 ml of PVC Slurry
Antifoam is added hwen the
foam reaches 1500 ml mark
Test Results in Dry Foam
0
100
200
300
400
500
600
700
800
900
1000
0 5 10 15 20 25 30
ml fo
am
time (min)
TA KS 95
TA KS 53
TA KE 600
TA 2280
TP 5890