Biosoluble glass fiber filtration media

Details Biosoluble glass fiber filtration media Biosoluble glass fiber filtration media

1999-07-08

2001-07-17

Upton, Christopher (Department: 1724)

Gas separation

Specific media material

Fibrous or strand form

C210S505000, C210S509000

Reexamination Certificate

active

06261335

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to glass fiber filtration media and, in particular glass fiber filtration media made from glass fibers that are rapidly solubilized in biological fluids.
Glass fiber filtration media are commonly used in air filtration applications. These filtration media can be classified in two groups namely, i.e. filtration media having an average efficiency between about 25% and about 60% (low efficiency filtration media) and filtration media having an average efficiency between about 65% and about 95% (intermediate and high efficiency filtration media) based on ASHRAE—52.1 test method.
While the air filtration media currently in commercial use performs well, the manufacture and/or subsequent handling of these glass fiber filtration media may result in the formation of loose fibers which can be inhaled. As it is impractical or impossible to remove such fibers from the body, it is important to make glass fiber filtration media from glass fibers having a high degree of biosolubility, i.e. fibers which are rapidly solubilized in biological fluids, while still maintaining the physical properties and performance characteristics required of such filtration media. Since the fine diameter glass fibers (glass fibers having a mean diameter between about 2.5×10
−5
inches and about 12.0×10
−5
inches) used in these air filtration media are normally made in a flame attenuation process, preferably, a glass composition should be used to form the fibers that can be fiberized by flame attenuation processes and still be rapidly solubilized in biological fluids.
SUMMARY OF THE INVENTION
The biosoluble glass fiber filtration media of the present invention includes a fibrous filtration layer of randomly oriented, entangled glass fibers which, when made into a suitable air cleaning device, has an initial efficiency of 25% or greater as measured by ASHRAE 52.1 test method. The glass fibers forming the media have a mean diameter between about 2.5×10
−5
inches and about 11.0×10
−5
inches. Typically, the filtration layer has a thickness ranging from about 0.12 inches to about 0.35 inches and a weight ranging from about 3.0 g/ft
2
(grams per square foot) to about 8.0 g/ft
2
. The filtration media has an initial flat sheet pressure drop of about 0.35 inches of water or less, with lower efficiency filtration media generally having lower initial pressure drops, and a dirt holding capacity of about 1.5 g/ft
2
(grams per square foot) or greater, with lower efficiency filtration media generally having the higher dirt holding capacities.
In addition to the above, the glass fibers of the filtration media of the present invention have a biodissolution rate in excess of 150 ng/cm
2
/hr, preferably equal to or greater than 200 ng/cm
2
/hr, more preferably equal to or greater than 300 ng/cm
2
/hr, and most preferably equal to or greater than 400 ng/cm
2
/hr, so that the fibers rapidly solubilize in biological fluids. Preferably, the glass fibers of the filtration media of the present invention are made from a glass composition that can be fiberized by flame attenuation processes and still retain the biodissolution rates stated above, i.e. rates in excess of 150 ng/cm
2
/hr.


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