Paper making and fiber liberation – Processes and products – Pore forming in situ
Reexamination Certificate
2000-09-18
2003-10-07
Fortuna, Jose A. (Department: 1731)
Paper making and fiber liberation
Processes and products
Pore forming in situ
C162S190000, C162S157600, C162S132000, C162S125000, C162S164600
Reexamination Certificate
active
06630054
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods for forming an absorbent composite and, more particularly, to methods for forming a fluted absorbent composite that includes superabsorbent material.
BACKGROUND OF THE INVENTION
Cellulose fibers derived from wood pulp are used in a variety of absorbent articles, for example, diapers, incontinence products, and feminine hygiene products. It is desirable for the absorbent articles to have a high absorbent capacity for liquid, rapid liquid acquisition, low rewet, as well as to have good dry and wet strength characteristics for durability in use and effective fluid management. The absorbent capacity of articles made from cellulose fibers is often enhanced by the addition of absorbent materials, such as superabsorbent polymers. Superabsorbent polymers known in the art have the capability to absorb liquids in quantities from 5 to 100 times or more their weight. Thus, the presence of superabsorbent polymers greatly increases the liquid holding capacity of absorbent articles made from cellulose.
Because superabsorbent polymers absorb liquid and swell upon contact with liquid, superabsorbent polymers have heretofore been incorporated primarily in cellulose mats that are produced by the conventional dry, air-laid methods. Wet-laid processes for forming cellulose mats have not been used commercially because superabsorbent polymers tend to absorb liquid and swell during formation of the absorbent mats, thus requiring significant energy for their complete drying.
Cellulose structures formed by the wet-laid process typically exhibit certain properties that are superior to those of an air-laid structure. The integrity, fluid distribution, and the wicking characteristics of wet-laid cellulosic structures are typically superior to those of air-laid structures. Attempts to combine the advantages of wet-laid composites with the high absorbent capacity of superabsorbent materials has led to the formation of various wet-laid absorbent composites that include superabsorbent polymers. These structures can be generally characterized as structures that either have superabsorbent polymers distributed on the surface of a wet-laid composite, laminates, or, alternatively, structures that have superabsorbent material distributed relatively uniformly throughout the composite.
However, absorbent composites that contain superabsorbent materials commonly suffer from gel blocking. Upon liquid absorption, superabsorbent materials tend to coalesce and form a gelatinous mass which prevents the wicking of liquid to unwetted portions of the composite. By preventing distribution of acquired liquid from a composite's unwetted portions, gel blocking precludes the effective and efficient use of superabsorbent materials in fibrous composites. The wicking capacity of conventional fibrous composites that include relatively homogeneous distributions of superabsorbent material is generally significantly restricted after initial liquid insult. The diminished capacity of such fibrous composites results from narrowing of capillary acquisition and distribution channels that accompanies superabsorbent material swelling. The diminution of absorbent capacity and concomitant loss of capillary distribution channels for conventional absorbent cores that include superabsorbent material is manifested by decreased liquid acquisition rates and far from ideal liquid distribution on successive liquid insults.
Accordingly, there exists a need for methods for forming an absorbent composite that includes superabsorbent material and that effectively acquires and wicks liquid throughout the composite and distributes the acquired liquid to absorbent material where the liquid is efficiently absorbed and retained without gel blocking. The present invention seeks to fulfill these needs and provides further related advantages.
SUMMARY OF THE INVENTION
The present invention provides methods for forming an absorbent fibrous composite containing absorbent material dispersed in bands through the composite and along the composite's length. The methods generally include depositing a fibrous slurry on a foraminous support to form a web and depositing or injecting absorbent material to the web across the its width to provide a web having absorbent material in bands along the composite's length. Drying the web provides a fluted absorbent composite. In one embodiment, the method is a wet-laid method and in another embodiment, the method is a foam-forming method. Preferably, the methods are twin-wire forming methods.
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Bolstad Clifford R.
Bunker Daniel T.
Graef Peter A.
Howard Fred B.
Miller Charles E.
Christensen O'Connor Johnson & Kindness PLLC
Fortuna Jos'e A.
Weyerhaeuser Company
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