The IP.com Prior Art Database
Copyright © 2006, Kimberly-Clark Worldwide
English (United States)
7 pages / 168.0 KB
Scarfing Clump Buster
Mike Venturino, David Heyn, Randy Burr, John De Vos, Paul Olmstead, Sara Schewe, Glenn Thomsen
Kimberly-Clark Corporation, Neenah, Wisconsin
Absorbent products like infant diapers, training pants, incontinence and feminine care products typically have an absorbent core that comprises cellulose pulp fibers (fluff) and polyacrylate superabsorbent particulate (SAP). If more absorbent material is present in the product, the product is capable of absorbing more fluids. Similarly if an absorbent core is deficient in absorbent material, it can not absorb as much. For these reasons it is desirable to maintain a consistent amount of fluff and SAP within the absorbent core such that the desired level of absorbency is provided.
The authors of this publication have determined that the root cause of weight variability and poor ZA (zoned absorbent) target area pocket filling are associated with large clumps of fluff within the fibrous matrix. This publication teaches how to diminish the largest contributor of fluff clumps, the scarfing return.
Scarfing is the process of machining the backside of an absorbent core while the front side of the absorbent is in contact with a vacuum drum or screen. Typically a rotating pin roll is used to remove the high spots from the backside of absorbent and the excess material is then recycled into the process. Scarfing clumps are formed as the recycle is pneumatically conveyed to the process. The weight variability problem is compounded when the absorbent core is formed with clumps; as the scarfing roll tends to extract the entire clump out of the absorbent core, leaving a divot, as well as further populating the scarfing return ductwork with additional clumps.
The authors consider the scarfing operation a vital step in the forming process. It is key to maintaining weight variability and controlling the absorbent basis weight, measured in grams per square meter. We do not consider the absence of scarfing a viable option.
Historically when the scarfing return was processed through the fiberizer, fibrous clumps were effectively dispersed; unfortunately this also caused excessive fracturing of superabsorbent (SAP). Analysis of the fractured SAP showed significant reduction of the absorbent properties as well as increased quantities of potentially respirable sized SAP. To resolve those issues the scarfing return was relocated from the hammermill to the forming chamber. The scarfing relocation successfully decreased potentially respirable SAP in the range of 50 to 90%, but it had the adverse effect of increasing weight variability by 10%. The problem is exasperated when more of the absorbent is concentrated into a zoned area (ZA) within the fluid intake target area. The greater the basis weight (g/m2) difference between the ZA and the rest of the pad, the greater the scarfing...