1999 - Volume 2 - Journal of Engineered Fibers and Fabrics

Patent Review
thickness of the filter media is preferably about 0.5 to 2 mm. The electret filter medium and the resin
from which it is produced should not be subjected to any unnecessary treatment which might increase its
electrical conductivity, e.g., exposure to gamma rays, ultraviolet radiation, pyrolysis, oxidation, etc.
Hydrocharging of the web is carried out by impinging fine jets of water onto the web at a pressure
sufficient to provide the web with a filtration enhancing electric charge. The pressure necessary to
achieve optimum results will vary depending on the type of jet used , the type of polymer, the type and
concentration of additives, the thickness and density of the web and whether pre-treatment such as
corona surface treatment, is carried out prior to hydrocharging. Generally, pressures in the range of about
10 to 500 psi (69 to 3450 kPa) are suitable. An apparatus suitable for hydraulically entangling fibers is
generally useful in the method of hydrocharging the nonwoven web, although the operation is carried out
at lower pressures in hydrocharging than generally used in hydroentangling.
The inventors suggest the technique of measuring the filtration performance of the web before and after
hydrocharging as the method to determine the effectiveness of electret formation. An increase in the
filtration performance is indicative of the trapped charge. This can be confirmed by subjecting the treated
web to a charge destroying procedure, such as exposure to x-ray radiation, alcohol treatment
(isopropanol) or heat treatment at a temperature about 30 0 C. below the melting point to near the melting
point and again measuring the filtration performance.
The inventors point out that staple fibers can also be introduced into the web. Further, sorbent particulate
material, such as activated carbon or aluminum, may also be incorporated.
The enhanced performance of the filter media can often be further improved by annealing, i.e., heating
for a sufficient time at a sufficient temperature to cause the additive to bloom to the surface of the fibers.
Generally, about one 1 to 10 minutes at about 140 0 C is sufficient for a polypropylene filter medium.
U.S. 5,908,598 (June 1, 1999); filed August 14, 1995. Assignee: Minnesota Mining and Manufacturing
Company. Inventors: Alan D. Rousseau, Marvin E. Jones, Seyed A. Angadjivand.
Lotion Wipe with Inverse Emulsion
This patent is directed toward a special type of disposable wipe, containing a lotion used to soothe the
skin. Such a wipe can be a special type of facial tissue or more substantial nonwoven wipe intended for
multiple uses. Some aspects of the patent disclosure are directed toward personal wipes, such as
wet-wipes used to cleanse the perianal area, premoistened baby wipes, adult incontinence wipes or as a
form of premoistened bathroom tissue.
The performance of such wiping products is enhanced if the wipe releases a significant quantity of water
during use for comfort and more effective cleansing. Such a wipe is even more effective when a
controlled amount of a lotion or emollient ingredient is deposited. In the case of both liquids, however,
the quantities involved must be controlled, as an excess of either the water or oil is unacceptable.
This patent discloses the use of a high internal phase inverse emulsion applied to a nonwoven substrate to
give a superior wiping product. This type of an emulsion is referred to a regular emulsion, since the
system consists of a discontinuous water phase dispersed in an emulsion of a continuous oleophilic
phase. Emulsions that are normally encountered consist of the water phase being the major and
continuous component, with a small amount of the oil or lipid phase dispersed as emulsified particles
within the water phase. Such an inverse emulsion can have much of the physical character of the major
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