Generally, high-molecular-weight polyethylene oxide (PEO) can present processing challenges due to its high melt viscosity and poor melt drawability; it can be difficult to form into fine-gauge film or small-diameter fibers. There is the alternative technology of solution casting, which has occasionally been utilized to cast thin films; however, solution casting may not always be practical for large-scale, economically viable film production.
One approach to improve the processability of PEO has been to blend the PEO with a second polymer, a copolymer of ethylene and acrylic acid, in order to increase the melt strength. The PEO/ethylene acrylic acid copolymer blend is capable of being processed into films of about 1.2 mils in thickness. However, the blend and resulting film may not be entirely water-soluble.
This new technology is a method for modifying PEO, and is intended to impart melt-processability so that the modified PEO may be drawn into thin films and fine fibers. The modification may be accomplished by mixing the PEO, a polar vinyl monomer additive, and an initiator, and applying heat. This may be conveniently achieved using a reactive-extrusion process. The method is particularly suited to allow fibers with fine-scale diameters (e.g., less than 30 microns) and fine-gauge film (e.g., less than 1 mil thick) to be spun or extruded from PEO. These fine-scale fibers and thin films may have potential use in applications such as packaging, personal care products, and medical products, where water solubility is desired and melt extrusion processes are preferred. By grafting judiciously selected polar vinyl monomer group(s) onto a PEO polymer backbone, melt-processability may be improved. Polymer molecular weight, polydispersity, and chemistry may be controlled to yield material with a balance of tensile strength and toughness properties that is more suited to melt extrusion than unmodified PEO.
Using this grafting method, the melt viscosity may be significantly reduced, which may improve processability and drawability, enabling the production of fine gauge (less than 1 mil thickness) polymer films that exhibit improved mechanical properties as well as water solubility. The technology is believed to be economical in that only small amounts of monomer need to be added to achieve significant property modification.
Modification of PEO resins with initial molecular weights of between about 50,000 g/mol to about 200,000 g/mol are preferred for fiber making. The modified PEO may be processed into water-soluble fibers using both melt-blown and spun-bond processes, which may be useful for many products.
Commercially available equipment, for example a twin-screw extruder, may be used for the reactive extrusion process. PEO resins, suitable monomers, and initiators are all available commercially.
This technology is offered by Kimberly-Clark Corp. For more information, view the yet2.com TechPak at http://info.hotims.com/28057-156.