Environmental Considerations in the Production of Flexible Slabstock

Total gas loss by the production of flexible polyether foam may range between 4–20 weight percent; higher densities are mainly blown with carbon dioxide – the lower densities partially with CO₂, partially with either fluorocarbon and/or methylene chloride. During blow-off approximately 30% of the total gas loss will escape spontaneously from the top surface, the other 70% being contained in the block will mainly diffuse via the vertical sides and the bottom of the block. The speed of diffusion depends upon a number of physical variables and was measured and determined respectively (a) from smaller lab tests, (b) a larger 2 × 2 × 1 metres box test and finally (c) from 20 metres long blocks (2 metres wide, 1 metre high) which were made on the pilot plant.

During these trials the installation and application of adequate chlorofluoro-carbon (or CFC 11) and/or methylene chloride recycling systems was made. For the block test 2 × 2 × 1 metres a 5 kgs capacity adsorption unit was installed; diffusion rates and fan capacities were determined and with this information a pilot plant for 20 metres long block was designed and built by Laader Berg.

The objectives for this newly developed foaming system were:

1. Producing emissions at environmentally acceptable limits with a controllable degree of adsorption and recovery which may vary from 0·99%.

2. Improved formulation accuracy achieved by application of the computer in combination with gas analysis equipment, resulting in a narrower spread of the properties.

3. Improved working atmosphere for the operators – TDI concentrations approaching to zero.

4. Remote controlled starts and stops using improved mechanical methods which can be controlled by microprocessors.

The existing situation with this project is as follows:

1. The pilot machine can produce a wide range of foams.

2. A filter adsorption system was operational at the end of Feb. 1987.

3. Various tests were carried out through 1987.

4. Cost-price comparison calculations indicate positive feasibility.