Surgery – Respiratory method or device – Means for removing substance from respiratory gas
Reexamination Certificate
2000-05-11
2001-05-22
Dawson, Glenn K. (Department: 3761)
Surgery
Respiratory method or device
Means for removing substance from respiratory gas
C128S206210
Reexamination Certificate
active
06234171
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to shaped fibrous respirators which can be worn to protect the wearer or surrounding personnel against air pollutants and other airborne agents, and to processes for producing such respirators. This invention also relates to multilayer shaped respirators that contain active sorbent particles in one or more of the respirator layers.
BACKGROUND OF THE INVENTION
Disposable cup-shaped multilayer fibrous respirators are described, for example, in U.S. Pat. No. 4,536,440 (Berg), U.S. Pat. No. 4,807,619 (Dyrud et al.), and U.S. Pat. No. 5,307,796 (Kronzer et al). Respirators for protection against nuisance gases or vapors typically contain one or more fibrous web layers containing sorbent particles such as activated carbon or alumina, and are described, for example, in U.S. Pat. No. 3,971,373 (Braun), U.S. Pat. No. 4,384,577 (Huber et al.), U.S. Pat. No. 4,454,881 (Huber et al.), U.S. Pat. No. 4,729,371 (Krueger et al.), and U.S. Pat. No. 4,873,972 (Magidson et al.).
Fibrous webs containing sorbent particles have been employed for a variety of other uses including vacuum cleaner bags, diapers and oil sorbents. Patents mentioning such particle-containing fibrous webs include U.S. Pat. No. 2,988,469 (Watson), U.S. Pat. No. 3,801,400 (Vogt et al.), U.S. Pat. No. 5,149,468 (Hershelman), U.S. Pat. No. 5,486,410 (Groeger et al.), U.S. Pat. No. 5,662,728 (Groeger), and International Application No. WO 97/30199 (Danaklon A/S et al.). Elastomeric or extensible webs containing particulate materials are described in U.S. Pat. No. 4,741,949 (Morman et al.), U.S. Pat. No. 5,190,812 (Joseph et al.), U.S. Pat. No. 5,238,733 (Joseph et al.), U.S. Pat. No. 5,258,220 (Joseph et al.), U.S. Pat. No. 5,248,455 (Joseph et al.), and U.S. Pat. No. 5,560,878 (Dragoo et al.). Pillowed microfiber webs containing sorbent particles are described in U.S. Pat. No. 4,103,058 (Humlicek). A particle-laden meltblown material said to be useful for gas/vapor filtering and/or absorbing, and specifically for disposable vacuum cleaner bags, is described in U.S. Pat. No. 4,797,318 (Brooker et al.). A particle-laden coating employing pressure-sensitive adhesive microfibers said to be useful for absorbent products, such as sanitary napkins, pantyliners, incontinence products, diapers and to such related absorbent products, is described in U.S. Pat. No. 5,462,538 (Korpman).
SUMMARY OF THE INVENTION
The above-mentioned U.S. Pat. No. 3,971,373 avers that particle-loaded microfiber sheet products may be incorporated into cup-like molded respirators “in the same ways as conventional non-particle-loaded web are included” (Col. 7, lines 31 et seq.). The assignee of the present invention has found it difficult reliably to mold respirators from web sheet materials containing high particle loading levels. The particles tend to drop from the web during handling or storage, thereby leading to waste and dust formation. In addition, the molding step can cause the web to tear or the particles to become consolidated or otherwise redistributed within the respirator, thereby creating regions having lower particle loading, and sometimes causing unexpectedly early respirator failure.
Web tearing, and particle loss, consolidation or redistribution can be reduced by welding together two particle-containing layers along a sinusoidal weld line, and then cutting and opening the resulting welded part to form a substantially cup-shaped preform. A similar procedure using non-particle-containing filtration layers is described in Example 22 of the above mentioned U.S. Pat. No. 4,807,619. The shape-retaining layers of the respirator are molded in mating male and female mold halves. The opened preform is then draped over the molded shape-retaining layers and welded or otherwise assembled to the molded layers to form the finished respirator. Converting processes employing such a preform exhibit fewer tears, thin spots and lost particles than converting processes involving molding of a conventional flat particle-containing web. However, formation of the preform requires extra manufacturing machinery and process steps, and causes undesirable material waste.
The present invention provides, in one aspect, a respirator comprising multiple layers including an air-permeable sorbent-particle-containing layer between air-permeable particle-retaining layers, at least one of the layers of such respirator being a shape-retaining layer, wherein the particle-containing layer has a generally cup-like shape, the particle-containing layer was stretchable during shaping to such cup-like shape without tearing or significant loss of particles, and at least some of the fibers in the particle-containing layer are sufficiently tacky after being formed by themselves into a particle-free web and cooled to room temperature so that the web will adhere to itself.
The present invention provides, in another aspect, a method for making such respirators.
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Barrett Leonard W.
Harper Roberta C.
Springett James E.
3M Innovative Properties Company
Cleveland David R.
Dawson Glenn K.
Mitchell Teena
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