The manufacture of CFC-free Polyurethane Rigid Foam using the THANOZON® Process

Goal of the project was the industrial-scale demonstration of the developed THANOZON procedure for the production of CFC-free polyurethane rigid foams using pentane as propellant. Thus the industrial fabrication of a completely CFC and/or halogen-free polyurethane rigid foam of unchanging quality according to DIN (German Institute for Standards) should be proven.



At the manufacture of PUR rigid foam boards the CFC-containing propellant R22 used so far, which contains ozone layer-diminishing halogen hydrocarbons, was replaced by pentane. The aim was an as large as possible preservation of the good heat damming characteristics of CFC driven PUR-rigid foam. 

Above all the project demonstrated the ecological advantages of the application of pentane as propellant compared with the partially halogenated CFC (R 22, R 142b), whose application is aimed at by some manufacturers of PUR rigid foam boards because of the only little prescription and plant adjustments necessary in that case. For the application of pentane as propellant the existing double-belt plant was reequipped or supplemented in substantial parts:

  • extension of the conveyor installation to reach the necessary higher speed and sufficient hardening by precipitation, 
  • adjustment of explosion prevention of the belt drive and the belt exhaust, 
  • adjustment of the sawing mechanism including piling device, 
  • new application mechanism with special metering controller, 
  • stocking of the propellant in an underground pentane tank, 
  • explosion-proof daily provision with stocks (ex area) and 
  • new building of a climatic chamber.

It could be shown that from the basic materials isocyanates and polyoles, catalysts like tertiary amines and a halogen-free propellant with 80% pentane portion a PUR rigid foam of the demanded quality can be made. As emission pentane (1.2 t/h) arose.


The ecological aim of the development was the complete elimination of the ozone-damaging chloroflourocarbons (CFCs) as propellant at the production of polyurethane rigid foam as well as the substitution of halogenated flame protection means. 

The project should demonstrate the commercial-scale efficiency of the procedure for the production of CFC-free PUR rigid foam developed by Thanex. Thus the conditions for the quick spreading of this rigid foam system in important ranges of application should be created. To realize the division of tasks existing basic formulations for rigid foam of different ranges of application were to be developed further and optimized. The existing manufacturing plant was to be converted to the requirements of the new technology and extended.

The design of the plant should correspond to the newest state of the art at that time while keeping to all safety-relevant regulations. The efficiency of the new production technology had to be proven by testing operation and manufacture of sample quantities under industrial conditions. On the basis the compiled product solutions the industrial fabrication of CFC and HCFC-free rigid foam of unchanging quality was to be proven.

Realization of the project 

All partial goals specified above could be achieved. 

The THANOZON® procedure is based on the application of pentane as propellant for the manufactured PUR rigid foam. This exhibits in principle the same good technical characteristics of conventional PUR rigid foam. The foam is completely CFC and HCFC-free. It does not exhibit any ozone damage potential. The greenhouse potential of pentane is extraordinarily small. The complete renouncement of halogenated flame protection means is likewise noticeable.

Meaning of the project for environmental protection 

The development of the procedure and the mechanical engineering for the manufacture of CFC and HCFC-free PUR rigid foams according to DIN (German Institute for Standards) is of great importance primarily for the following reasons:  

The used propellants on the basis of chlorofluorocarbons had a proven environmental damage potential (ozone depletion, global warming). 

The prohibition of CFC-containing propellants for the production of foamed plastics, effective in Germany from 01.01.1995, motivated raw material manufacturers, machine suppliers and processing plants to develop environmentally more compatible and nevertheless technically efficient alternatives.

Project Participants

Implementing Institution

Thanex GmbH u. Co.KG

More Project Informations

Project title:  Herstellung von FCKW-freiem PUR-Hartschaum nach dem Thanozonverfahren

Project number:  2063

Reference number:  FKZ: 50441-5/202

Project period:  1991 - 1993

Project region:  Germany (North Rhine-Westphalia)

Project contact:

Frau Fischer

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+49 (340) 2103 3067

+49 (340) 2104 3067

Source: Environmental library of the Federal Environment Agency (UBA)