Patent US4084949A successfully refreshed from Google Patents.
US4084949A
Expired / Lapsed
US
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Surgical face mask filtering medium
Assignee: Dexter Corp
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Filing: 1975-11-06
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Granted: 1978-04-18
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Expires: 1995-11-06
Abstract
Abstract A porous bacteria filter medium of reduced binder content is provided in flexible fibrous sheet form comprised of micron-diameter glass fibers and less than about 30 percent by weight of a polyolefin heat sealable binder fiber randomly dispersed throughout the sheet and fused therein. This filter medium has a bacteria filtration efficiency of at least 96 percent and a porosity in excess of 25 cfm at only two thirds the weight resulting in breathability within comfortable limits over prolonged periods of time. The polyolefin fibers used in the sheet exhibit a surface area greater than 25 square meters per gram and are formed of polymeric material having a molecular weight of 500,000 and a melt index less than 0.5.
Inventors
- 👤 Walter F. Biggins
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 12:02
CPC Classifications
B; B01; B01D; B01D39/00; B01D39/14; B01D39/20; B01D39/2003; B01D39/2017; B01D39/2024; A; A62; A62B; A62B23/00; A62B23/02; A62B23/025
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
165 words
A porous bacteria filter medium in flexible fibrous sheet form consisting essentially of thermostable micron-diameter filtering fibers and containing from about 5 to about 30 percent by weight of a hot water insoluble heat sealable thermoplastic polymeric binder in fibrous form having a microfibrillar structure made up of microfibrils similar to wood pulp, said binder fibers being randomly dispersed throughout the sheet and fused to the thermostable fibers at the cross-over points of the thermostable fibers to eliminate its fibrous structure and coat said thermostable fibers to provide an effective fiber diameter only slightly greater than the diameter of said thermostable fibers, said filter medium having a bacteria filtration efficiency of at least about 96 percent and sufficient porosity to permit breathability within comfortable limits, the binder fibers prior to fusion exhibiting an average length of about 1- 4 mm, a surface area of at least 1 square meter per gram and being comprised of a high molecular weight, low melt index thermoplastic polymeric material.
Claim 2
Dependent Claim
165 words
A porous bacteria filter medium in flexible fibrous sheet form consisting essentially of thermostable micron-diameter filtering fibers and containing from about 5 to about 30 percent by weight of a hot water insoluble heat sealable thermoplastic polymeric binder in fibrous form having a microfibrillar structure made up of microfibrils similar to wood pulp, said binder fibers being randomly dispersed throughout the sheet and fused to the thermostable fibers at the cross-over points of the thermostable fibers to eliminate its fibrous structure and coat said thermostable fibers to provide an effective fiber diameter only slightly greater than the diameter of said thermostable fibers, said filter medium having a bacteria filtration efficiency of at least about 96 percent and sufficient porosity to permit breathability within comfortable limits, the binder fibers prior to fusion exhibiting an average length of about 1- 4 mm, a surface area of at least 1 square meter per gram and being comprised of a high molecular weight, low melt index thermoplastic polymeric material.
Claim 3
Dependent Claim
24 words
The filter medium of claim 1 wherein the binder fibers are polyolefin fibers having a surface area greater than 25 square meters per gram.
Claim 4
Dependent Claim
22 words
The filter medium of claim 1 wherein the binder fibers are selected from the group consisting of polyethylene, polypropylene and combinations thereof.
Claim 5
Dependent Claim
27 words
The filter medium of claim 1 wherein the melt index of the polymeric material is less than 0.5 and the average molecular weight is greater than 800,000.
Claim 6
Dependent Claim
39 words
The filter medium of claim 1 wherein the binder fiber content is about 20 percent by weight, the porosity of the medium exceeds 25 cfm and the pressure drop across the medium is less than 4.5 millimeters of water.
Claim 7
Dependent Claim
36 words
The filter medium of claim 1 wherein the porosity falls within the range of 44-65 cfm and the thermostable fibers are glass fibers having an average diameter falling within the range of .5 to 2.6 microns.
Claim 8
Dependent Claim
58 words
The filter medium of claim 1 wherein the binder fibers are polyolefin fibers comprising up to about 20 percent by weight of the fiber content, said binder fibers having the morphology of wood fibers, a surface area greater than 25 square meters per gram, a melt index less than 0.5 and an average molecular weight greater than 800,000.
Claim 9
Dependent Claim
22 words
The filter medium of claim 1 wherein said thermostable fibers are inorganic fibers have a fiber diameter of less than 14 microns.
Claim 10
Dependent Claim
43 words
The filter medium of claim 8 wherein said inorganic fibers have an average fiber diameter within the range of 0.5 to 5.0 microns, the melt index of the polymeric material is less than 0.1 and the average molecular weight is greater than 500,000.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-04-17 | 1981-10-17 | 1982-04-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-04-17 | 1985-10-17 | 1986-04-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-04-17 | 1989-10-17 | 1990-04-18 | $7700.00 | Window Closed / Lapsed |