„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