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Water-Absorbent, Melt-Processed Compositions

IP.com Disclosure Number: IPCOM000032981D
Publication Date: 2004-Nov-19
Document File: 8 page(s) / 79K

Publishing Venue

The IP.com Prior Art Database

Related People

Dave Soerens: AUTHOR

Related Documents

US 6117947: PATENT [+2]

Abstract

Improved melt-processable compositions are made by graft polymerization of PEO with alkoxy silane followed. The process yields a modified resin, which, while kept relatively dry, can be fabricated into useful structures, and then, when exposed to humid air, becomes crosslinked. The result is a material that retains the versatility of thermal processability into a variety of structures along with the capability of using those structures for absorbency. This unusual combination of features is available because the crosslinked, hydrophilic network is generated after the structure is fabricated.

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Water-Absorbent, Melt-Processed Compositions

   Dave A. Soerens Kimberly-Clark Corporation Neenah, Wisconsin

Superabsorbents are widely utilized in personal care and health care industries due to their ability to absorb large quantities of aqueous fluid. However, the common particulate form of superabsorbents imparts a significant limitation for fabricating discrete structures of designed size and shape that retain a high degree of integrity, even after absorbing significant amount of aqueous fluid.

The fabrication of structures of discrete size and shape is generally most economical and environmentally friendly with a melt process. Consequently, there is a need for materials that can be relatively easily processed, such as by thermal processing, so that it can be easily fabricated into a wide range of structures, such as films, foams, and fibrous webs. Most currently available water-soluble resins are not practical for melt processing into thin films or fibers for personal care or medical applications. A water soluble resin that overcomes the difficulties associated with melt processing while also possessing good aqueous fluid absorption characteristics is highly desirable. Even more desirable are functional forms made from a water-soluble resin that are still absorbent, flexible and retain high integrity, even after absorbing fluid.

Poly(ethylene oxide) (PEO) is one of the very few polymers which is both water-soluble and thermally processable (for molecular weight less than 400,000 g/mole). By grafting polar monomers onto the PEO backbone through the reactive extrusion process, the inherent deficiencies in melt processing and weak film properties of commercial grades of PEO were overcome, as described in US Pat. Nos. 6,117,947 B1; 6,172,177 B1; and 6,372,850 B1.

Reactive modification of PEO provided superior melt-processable, water-soluble films and fibers. However, with the ongoing need for aqueous fluid absorbents there was a desire to find a way to crosslink PEO so that the water-soluble material would become a water-absorbent material. Furthermore, it is highly desirable to maintain the thermal processability of PEO so that it can be easily fabricated in to a wide range of structures such as films, foams, and fibrous webs. It is also highly desirable to have a facile method to crosslink the polymer and avoid the more exotic and costly methods for crosslinking PEO such as gamma radiation or UV radiation.

US Pat. No. 6,596,402 B2 describes graft polymerization of PEO with a trialkoxy silane functional group. The silane graft modified PEO resin can be thermally processed into functional forms, such as films, fibers and foams. When these functional forms are exposed to moist air, a crosslinking reaction occurs, by the mechanism shown below, to provide a gel structure capable of absorbing relatively large amounts of water, such as more than 15 grams of 0.9% saline solution per gram of polymer under free swell conditions (i.e., with...