LATEST MANUFACTURING SOLUTIONS FOR SLABSTOCK FOAMS

As environmental pressure increases worldwide, it is becoming necessar y for foamers to eliminate chlorinated products - such as chloro fluor o carbons (CFCs), methylene chloride, 1.1.1 trichloroethane - or any t ype of volatile organic compounds (VOC's) from their production. In so me countries these additives have already been banned: the impact on t he flexible foam industries would be to increase foam prices and to el iminate certain soft grades. The use of liquid carbon dioxide (CO2) as an expanding agent in a polyurethane foam is a good and well accepted idea. Handling this liquid, which gasses off at room temperature, has always been one of the main problems. Its use - although the subject of various patents - has been scarcely put into current practice, most ly because of inherent problems linked with the formation of typical ' 'chimneys'' in the foam, i.e. long, narrow cavities oriented in the ri se sense, generated by the uncontrolled expansion of carbon dioxide. P ossible solutions to this problem can be found by investigating severa l aspects of the process: chemicals selection, CO2 dispersion into the formulation, gas nucleation, metering equipment, mixing chamber's geo metry, foam's laydown, rise profile, but until now no suitable method was available and this interesting opportunity was left aside. Cannon started investigating this matter after having spent several years in the development of a suitable pre-mixing device for LBBA's (Low Boilin g Point Blowing Agents). The original program started in 1989 when liq uid carbon dioxide was tried for the expansion of low-density rigid fo ams for insulation applications (refrigerators, panels etc). Heavy fro thing effect was noticed when loading high amounts of CO2 in conventio nal polyols. Cell structure was acceptable, but frequent ''chimneys'' were still present. On top of that, the lambda value of a CO2-blown fo am was still not attractive for most of the applications.The project w as temporarily put on hold, giving priority to other more promising al ternative blowing agents (HCFC 22, 142b, HFC 134a, etc) because of the ir higher insulation capacity and better solubility in conventional po lyols. Now (after having successfully solved the problem of metering a nd mixing gaseous blowing agents with the EasyFroth(TM) unit and cyclo pentane with the Multi EasyFroth(TM) version) Cannon have developed an d patented a proprietary method for the addition of liquid CO2 to flex ible foam formulations for slabstock. This revolutionary new process - for which a patent is pending - is named CarDio(TM) from carbon dioxi de: it enables foamers to continue producing their existing foam grade s at a lower chemical cost, due to the significant price differential between CFC's, ABA's and CO2. Its peculiar foaming method can also - i f one likes - dramatically reduce the size of the foaming plants, ther eby deriving the advantages of reduced floor space and plant volume.