PDF Publication Title:
Text from PDF Page: 045
164 E.J. Beckman / J. of Supercritical Fluids 28 (2004) 121–191 its use is not sustainable (the same can be said for CO2 !). Major challenges remaining in this process are in many ways ‘mechanical’—how does one design a treatment chamber that allows fast charging, fast sam- ple changeover, and rapid dying? Is there sufficient thermodynamic and transport information available to model and hence scale-up the process? Note that this situation is analogous to that described for continuous polyurethane production using carbon dioxide—the chemical challenges were overcome long before the mechanical issues were settled. A further challenge would include redesigning conventional dyes to allow for higher CO2 solubility, which would provide for more even coating. Applying the concept of carbon dioxide as ‘re- versible plasticizer’, Shine and Gelb [203] showed that one could mix a thermally labile bioactive com- pound (here a vaccine) into polycaprolactone. Howdle et al. [204] recently expanded this work into the tis- sue engineering field. Here, CO2 was used to swell an aliphatic polyester, depressing its Tg to well below room temperature. A temperature and shear-sensitive enzyme was then mixed with the swollen poly- mer; upon depressurization the enzyme was found to be dispersed throughout the now foamed poly- mer and to have retained its activity. Such a process allows the blending of temperature sensitive com- pounds with polymers without the need for additional solvent-based processing. Powder coating processing provides another poten- tial application for CO2 as a sustainable and reversible plasticizer. Powder coatings (blends of low molec- ular weight functional polymer, crosslinking agent, pigments, and stabilizers) are themselves considered green materials, as they can be applied directly to automobile and appliance bodies without any sol- vent. However, the means for production of powder coatings is itself wasteful and expensive. The raw materials are charged to an extruder for high shear mixing; the resulting pellets are then ground and sieved to create the proper size distribution. Waste from the grinding process cannot be re-extruded, as the polymers are quite naturally thermally sensitive. Ferro Corporation [205] first patented a process where CO2 is used to swell the polymer, depressing its Tg (normally 310–320 K) to well below 270 K. The addi- tives (pigments, etc.) are then mixed with the swollen polymer. Finally, the material is rapidly depressurized through a nozzle to form a granular mixture. Note that material processed in this way can actually be recycled if necessary, as temperatures employed are low (313 K). PPG Corporation [206] also supported work in this area using hydrofluorocarbon fluids; this work was targeted at small colored batches. Other patents have also appeared recently [207]. Challenges remaining here include elimination of a significant degassing problem upon film formation and the need to lower the operating pressure as much as possible to remain economical. Regarding the degassing prob- lem, conventional powder coating formulations use benzoin as the degassing agent (to help eliminate air during film formation). However, it is not currently known why benzoin is effective as a degassing aid in conventional formulations, and hence the design of analogs for use in material processed in CO2 is not currently possible. Indeed, both Ferro Corporation and PPG have ceased (at least for now) their research and development efforts in this area, owing to an inability to rapidly overcome these technical hurdles. 3.9. Extrusion-foaming using CO2 The extrusion-based foaming of polymers [41] is inherently sustainable in that small amounts of raw material (the polymer) are used to create valuable, lightweight parts. The low weight and/or low thermal conductivity of these parts ultimately saves energy in applications ranging from home and appliance insula- tion to transportation components. Although the parts themselves can be considered sustainable, the conven- tional method of fabrication releases a large volume of solvent to the atmosphere. Prior to the late 1980s, chlorofluorocarbons (CFCs) were often employed as blowing agents (pore-forming agents), as these sol- vents are low boiling, non-toxic, and non-flammable. Subsequent to the acceptance of the Montreal Pro- tocols (1986), most foam producers switched from CFCs to hydrofluorocarbons, hydrocarbons, or mix- tures of hydrocarbons and CO2. There is generally a desire within the foam producing industry to move to 100% CO2 as the blowing agent in extrusion foaming, although some serious technical hurdles remain. A variety of polymers are extrusion-foamed, including polyolefins, polystyrene and polyesters. It should be noted that while injection of a volatile blowing agentPDF Image | Supercritical and near-critical CO2 in green chemical synthesis and processing
PDF Search Title:
Supercritical and near-critical CO2 in green chemical synthesis and processingOriginal File Name Searched:
sos.pdfDIY PDF Search: Google It | Yahoo | Bing
NFT (Non Fungible Token): Buy our tech, design, development or system NFT and become part of our tech NFT network... More Info
IT XR Project Redstone NFT Available for Sale: NFT for high tech turbine design with one part 3D printed counter-rotating energy turbine. Be part of the future with this NFT. Can be bought and sold but only one design NFT exists. Royalties go to the developer (Infinity) to keep enhancing design and applications... More Info
Infinity Turbine IT XR Project Redstone Design: NFT for sale... NFT for high tech turbine design with one part 3D printed counter-rotating energy turbine. Includes all rights to this turbine design, including license for Fluid Handling Block I and II for the turbine assembly and housing. The NFT includes the blueprints (cad/cam), revenue streams, and all future development of the IT XR Project Redstone... More Info
Infinity Turbine ROT Radial Outflow Turbine 24 Design and Worldwide Rights: NFT for sale... NFT for the ROT 24 energy turbine. Be part of the future with this NFT. This design can be bought and sold but only one design NFT exists. You may manufacture the unit, or get the revenues from its sale from Infinity Turbine. Royalties go to the developer (Infinity) to keep enhancing design and applications... More Info
Infinity Supercritical CO2 10 Liter Extractor Design and Worldwide Rights: The Infinity Supercritical 10L CO2 extractor is for botanical oil extraction, which is rich in terpenes and can produce shelf ready full spectrum oil. With over 5 years of development, this industry leader mature extractor machine has been sold since 2015 and is part of many profitable businesses. The process can also be used for electrowinning, e-waste recycling, and lithium battery recycling, gold mining electronic wastes, precious metals. CO2 can also be used in a reverse fuel cell with nafion to make a gas-to-liquids fuel, such as methanol, ethanol and butanol or ethylene. Supercritical CO2 has also been used for treating nafion to make it more effective catalyst. This NFT is for the purchase of worldwide rights which includes the design. More Info
NFT (Non Fungible Token): Buy our tech, design, development or system NFT and become part of our tech NFT network... More Info
Infinity Turbine Products: Special for this month, any plans are $10,000 for complete Cad/Cam blueprints. License is for one build. Try before you buy a production license. May pay by Bitcoin or other Crypto. Products Page... More Info
| CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com | RSS | AMP |