Dryers for foamed polymers

A very successful application of STALAM’s RF technology is the drying of foamed natural or synthetic polymers (mainly natural latex, also blended in various proportions with SBR, and hydrophilic polyurethane) after vulcanisation and washing / squeezing or wet casting.

Foam products are quite difficult to dry by means of conventional hot air systems due to several reasons: they are good thermal insulators, so heat conduction within the substrate is extremely slow; their physical-morphological structure make them little permeable to fluids, so air convection is also heavily hindered; for the same reason and due to their chemical nature, the water vapour migration from the centre towards the surface of the product is intrinsically slow; in many cases the items produced are thick, bulky, shaped, dense, etc.

The radio frequency technology can overcome all these inconveniences because: it does not rely on heat transmission, so even thick, shaped and dense items (casted blocks, mattresses, anatomic pillows, etc.) dry quickly with no surface overheating or yellowing effects; it is selective towards water, so even that contained in the core absorbs the RF energy instantly and migrates quickly towards the surface, leaving no wets spots anywhere in the product; the energy delivered to (absorbed by) the product can be adjusted as required, thus enabling to control accurately both the evaporation rate and the residual moisture content.

Added benefits of the RF drying technology are:

- instantaneous operation (no pre-heating)
- no heat dispersion to the environment, no dust, no fumes
- little noise
- little maintenance

STALAM in the last 20 years has developed and supplied a large number of RF dryers featuring specific technical solutions for natural or synthetic latex products (mainly mattresses, pillows, anatomic seats and LPC), highly hydrophilic polyurethane foam for health-care and medical uses, and other high-porosity polymeric substrates. STALAM machines can accomplish the entire drying process or work in conjunction with existing tunnel or cabinet type hot air dryers (ie. for partial drying) to increase the capacity (speed) of the production line, maximise the energetic efficiency and, especially, improve the quality of the end product.

More recently, STALAM RF equipment has also been successfully applied to the vulcanisation process of natural and blended latex sheets and pillows inside suitably designed moulds made of composite materials compatible with the dielectric heating technology.

PRODUCTION CAPACITY DATA FOR NATURAL LATEX / SBR & POLYURETHANE FOAM


* 60-105 kW output power

Download "Drying of foamed latex products" (160 kB)