Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – Bulk deposition of particles by differential fluid pressure
Reexamination Certificate
1999-10-20
2001-03-27
Theisen, Mary Lynn (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
Bulk deposition of particles by differential fluid pressure
C264S113000, C264S121000, C425S081100, C425S083100
Reexamination Certificate
active
06207099
ABSTRACT:
THE FIELD OF THE INVENTION
The present invention relates to a method for forming a substantially uniform distribution of particulate material within a fibrous web. More particularly, the present invention relates to a method for forming a substantially uniform distribution of superabsorbent polymer particles within the cross direction of an absorbent pad composed of hydrophilic fibers.
BACKGROUND OF THE INVENTION
Absorbent articles, such as disposable infant diapers, feminine care products, incontinence garments and the like, have included high absorbency superabsorbent polymers to increase the absorbent capacity of the article and to reduce the bulkiness of the article.
Various devices and processes have been employed to manufacture absorbent article designs. Air forming techniques for forming webs of hydrophilic fibers, such as woodpulp fibers, are well known in the art. In addition, it is well known that superabsorbent polymers may be mixed with the hydrophilic fibers during an airlaying process to form an absorbent web. For example, see the Sanyo Technical Bulletin entitled “SAP SHEET”, dated October 1982.
Various methods and apparatus have been employed to manufacture absorbent articles. For example, U.K. Patent Application, No. GB 2,150,033 A published Jun. 26, 1985, describes a suction drum apparatus for making an absorbent pad wherein an integrated shell of flocculent material surrounds an internal absorbent layer. U.S. Pat. No. 4,087,508 issued May 2, 1978 to Cook et al. describes a method which includes applying hydrocolloid polymer particles onto the surface of a central zone of a moving web, and distributing the applied particles into the body of the moving web by air-pressure means. International Patent Application No. WO 88/04165 published Jun. 16, 1988 describes a method and apparatus for forming a nonwoven pad consisting of fibrous material in which highly moisture-absorbent particles are intermixed with the fibrous material throughout a predetermined portion of the thickness of the nonwoven pad. It further describes a spray gun or an extension thereof positioned within the chamber relative to the fibrous material atop a conveyor and that is operated to discharge moisture-absorbent material at a predetermined velocity, such that the moisture-absorbent material is intermixed with the fibrous material throughout a central layer of the thickness of the nonwoven pad while forming boundary layers on either side of the center layer which are substantially free of moisture-absorbent material. Additionally, the spray gun preferably operates intermittently to form spaced, sharply defined areas along the length and width of the nonwoven pad wherein each area has moisture absorbent material interspersed throughout a portion of the thickness thereof.
Conventional methods, such as those described above, have not been sufficiently satisfactory. For example, the methods may be overly complex and expensive and may not provide desired uniform deposition for particulate materials, such as superabsorbent granules. The rate of delivery of the superabsorbent particles may not be adequately controlled, and the systems may be excessively sensitive to changing bulk densities in the particulate material.
BRIEF DESCRIPTION OF THE INVENTION
The present invention provides a method for forming a substantially uniform (zoned or otherwise) distribution of particulate material within a fibrous web. Generally stated, a method of the present invention may be practiced using an apparatus as described below. The conveying means provides a gas entrained supply stream of the particulate material. The transferring means directs the particulate material into a delivery gas stream to provide a constant or intermittent flow of a selected quantity of particulate material, a delivery conduit, and a delivery nozzle into a web forming chamber. The fiberizing means provides a flow of a selected fibrous material into the web forming chamber, and directing means controls the flow of the particulate material from the delivery conduit, through the delivery nozzle, into the web forming chamber. A foraminous forming layer is disposed within the web forming chamber for receiving the fibrous material and the particulate material to form a fibrous web having a substantially uniform distribution of the particulate material. Such a distribution may include zoned regions having selected, different amounts of the particulate material therein.
The present invention can further provide a method for forming a substantially uniform distribution of particulate material within the cross direction of a fibrous web. In this aspect of the present invention, the method comprises the steps of providing a gas entrained supply stream of the particulate material. The particulate material is transferred into a delivery gas stream to provide a flow of particulate material through a delivery conduit and delivery nozzle into a web forming chamber. A flow of a selected fibrous material is provided into the web forming chamber, and the flow of particulate material from the delivery nozzle into the forming chamber. The fibrous material and particulate material are received on a foraminous forming layer located within the forming chamber to produce a fibrous web.
Another aspect of the present invention is a distinctive absorbent article comprising a substantially unitary web composed of a mass of hydrophilic fibers, and a quantity of superabsorbent polymer particles substantially uniformly located in the cross direction of the fibrous mass. The superabsorbent particles may have a distinctive, non-uniform distribution along a longitudinal, length dimension of the web. The weight percentage of superabsorbent (per unit weight of the combined particles and fiber) also may be non-uniformly distributed along the length dimension and in the thickness dimension. In particular aspects of the present invention, the absorbent article can also include a longitudinal, length-wise particle distribution that is substantially configured in the form of two or more stepped stages.
The present invention can advantageously provide a method which, when compared to conventional devices, can more efficiently substantially uniformly distribute the particulate material within the cross direction of a fibrous web, and can position the particulate material in a manner which is generally independent of the flow of fibrous material employed to form the web. In the present invention, the method provides a substantially uniform cross-direction particulate distribution within the fibrous web. A further advantage of the present invention is that the method can operate at high speeds. The method also prevents the non-uniform distribution of the particulate material within cross direction of the absorbent article wherein the absorbent article includes a region with a zoned application in the machine direction. The method also prevents a non-uniform distribution of the particulate matter within the cross direction of the absorbent article wherein the absorbent article includes a non-uniform basis weight of fibers in the machine direction and cross direction (pocket forming and profiles). It has been noted that using current method causes a non-uniform distribution of the particulate material in the cross direction.
The distinctive absorbent article of the present invention can advantageously provide a more efficient use of the absorbent material and provide a more effective, localized placement of superabsorbent particles within a web or pad composed of hydrophilic fibers.
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patent: 4087508 (1978-05-01), Slaughter et al.
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patent: 4551191 (1985-11-01), Kock et al.
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patent: 5028224 (1991-07-01), Pieper et al.
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patent: 5248524 (1993-09-01), Soderlund
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patent: 3417700 A1 (1985-11-01), None
Fell David Arthur
Halloran Thomas Joel
Niemi Paul Martin
Olsen Martin Karl
Rooyakkers John Anthony
Charlier Patricia A.
Connelly Thomas J.
Kimberly--Clark Worldwide, Inc.
Theisen Mary Lynn
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