Compounding of sealing compounds

Twin screw extruders from Coperion are particularly suitable for the production of sealing compounds. Sealing compounds mainly describe chemically hardening single component systems in which the networking of the substrate is initiated by moisture in the air. This splits off reaction products. After fast formation of a surface skin, the networking continues inside the compound until complete hardening. Silicon sealing compounds (RTV) are distinguished from PUR sealing compounds for polymers.

Typical set-up of a plant for the production of sealing compounds

Typical structure of a plant for the production of reactive sealing compounds

In the production of RTV compounds, the silicon polymer is fed gravimetrically into the first barrel of the twin screw extruder. This supports the feeding of the extremely light fumed silica which tends to fluidize into the second barrel. The other liquid components such as silicon oil, networker and catalyst are fed successively into the barrels downstream.

An atmospheric venting is provided after the first compounding zone and a vacuum degassing unit in the penultimate barrel to remove air. Discharge takes place through a melt pump with downstream heat exchanger into the cartridge filling station. The compounds can also be strained.

Raw materials

Silicon polymer30 - 50 %
PUR prepolymer30 - 50 %
Fumed silica5 - 10 %
Chalk25 - 45 %
Soot0 - 3 %
Softeners15 - 40 %
Catalyst1 - 2 %

Throughput rates*

ZSK 43 Mv200 - 300 kg/h
ZSK 54 Mv350 - 600 kg/h
ZSK 62 Mv600 - 900 kg/h
ZSK 76 Mv900 – 1,500 kg/h
ZSK 98 Mv2,000 – 3,200 kg/h
ZSK 125 Mv3,500 – 6,000 kg/h

* depending on raw materials and recipes