Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Reexamination Certificate
1999-04-12
2001-10-02
Morris, Terrel (Department: 1771)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
C604S367000, C604S374000, C604S375000
Reexamination Certificate
active
06296929
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an absorbent member having a high absorbent capacity and exhibiting exceptional expansion properties when wetted. More specifically, this invention relates to an absorbent member exhibiting exceptional expansion properties when wetted by an aqueous solution.
BACKGROUND OF THE INVENTION
Most traditional absorbent structures consist of a static network of fibers which contain a plurality of open areas located between the fibers. The open areas retain aqueous fluid which is absorbed by the absorbent structure. The majority of fluid is not absorbed into each individual fiber but instead most fluid is retained within the empty spaces which are formed in the network of cellulosic fibers. If the traditional absorbent member has a high absorbent capacity it usually does not have a high wicking rate. The reason for this is that the first attribute is in conflict with the second attribute.
Efforts to find absorbent members which have both a high absorbent capacity as well as a high wicking rate have only been marginally successful. It has been recognized that the dynamic properties of the fibers themselves somehow have to be changed. Some success has been obtained in calendering a wet laid network of bleached chemi-thermo-mechanical pulp (BCTMP). For this material, small expansion or release of potential energy upon wetting of the absorbent fibers was observed which can enhance the absorbent capacity and wicking rate of the absorbent member. It is believed that this occurs because the absorbent fibers are oriented, to a large extent, in the horizontal plane but with some modest “z” direction to the fiber axis as they conform to an irregular surface of the forming wire. The high to low position of the forming wires is about 0.020 to about 0.025 inches (about 0.508 mm to about 0.635 mm). When the tissue sheet is hot calendered at high pressure, this high to low shaping (or bumps in the sheet) is smoothed out. It is believed that the heat mobilizes any water present in the fibers, and the close proximity of fiber surfaces (intra and inter) allows hydrogen bonds to form with very little water present. When the flattened sheet is exposed to water, the hydrogen bonds break and the fibers return to their original shape. Since the wet laid sheet has a wet strength agent added, e.g., Kymene, the fibers stay attached to each other in the network therefore the sheet returns to its original bumpy state before calendering. These bumps or pockets on the surfaces hold more moisture than the flat sheet but a large portion of that moisture is not bound within the sheet structure.
It has also been observed that the open spaces within the fiber structure (void volume) of most traditional absorbent members, such as a paper towel, is limited. This is primarily due to two characteristics. First, the traditional absorbent member is restricted from expanding by the presence of wet strength bonds which limit or reduce the ability of the absorbent member to expand. Second, the axis of fibers of a traditional absorbent member are essentially oriented in only the x and y directions, not in the z-direction. This limits the absorbent member from being able to expand in three directions, thus reducing both its absorbent capacity and wicking rate.
Other attempts to increase the absorbent capacity and wicking rates of a traditional absorbent member have included the addition of superabsorbent particles (SAP). Superabsorbent particles have the ability to expand in size as they absorb fluid and also have the ability to retain fluid. However, the use of superabsorbent particles is disadvantageous in that most are very expensive and some of them tend to be rather slow in absorbing fluid. In addition, the relative absorbent capacity of most superabsorbent material is adversely affected by pressure and by ionic salts which are present in certain aqueous fluids, such as urine. Therefore, they present certain drawbacks to being used in disposable absorbent products such as diaper, training pants, incontinence garments, feminine napkins, meat and poultry pads, and the like.
Now it has been recognized that there is a real need for an absorbent member which has both a high absorbent capacity and a high wicking rate as well as the ability to rapidly expand in at least one direction when wetted by an aqueous fluid.
SUMMARY OF THE INVENTION
Briefly, this invention relates to an absorbent member which has a high absorbent capacity and which exhibits exceptional expansion properties when wetted by an aqueous solution. The absorbent member is constructed from a multitude of randomly oriented cellulosic fibers containing at least about 20% lignin within the fibers. The fibers have an average length of from between about 1 mm to about 5 mm. The absorbent member can have a moisture content of between about 1% to about 20% water by weight of fiber and has a density in the range of between about 0.2 g/cc to about 1 g/cc. The fibers are stressed or strained and bonded together by hydrogen bonds (both intra and inter fiber bonds) which constrain the fibers in an elastically stressed condition.
The general object of this invention is to provide an absorbent member having a high absorbent capacity and which exhibits exceptional expansion properties when wetted. A more specific object of this invention is to provide an absorbent member which exhibits exceptional expansion properties when wetted by an aqueous solution.
Another object of this invention is to provide an absorbent member which is capable of rapidly expanding in a selected direction opposite to the direction of a force vector used to induce the stressed or strained condition.
A further object of this invention is to provide an absorbent member which can expand against significant resisting force or pressure.
Still another object of this invention is to provide an absorbent member which is easy to construct and relatively inexpensive.
Still further, an object of this invention is to provide an absorbent member which exhibits a rapidly changing capillary structure when wetted by an aqueous solution.
Other objects and advantages of the present invention will become more apparent to those skilled in the art in view of the following description and the accompanying drawings.
REFERENCES:
patent: 3512530 (1970-05-01), Jones, Sr.
patent: 3736931 (1973-06-01), Glassman
patent: 3844288 (1974-10-01), Kiela
patent: 4057061 (1977-11-01), Ishikawa et al.
patent: 4100324 (1978-07-01), Anderson et al.
patent: 4215212 (1980-07-01), Franks
patent: 4275811 (1981-06-01), Miller
patent: 4321997 (1982-03-01), Miller
patent: 4382507 (1983-05-01), Miller
patent: 4410578 (1983-10-01), Miller
patent: 4537655 (1985-08-01), Henriksson et al.
patent: 4544596 (1985-10-01), Holtman
patent: 4560527 (1985-12-01), Harke et al.
patent: 4619862 (1986-10-01), Sokolowski et al.
patent: 4621011 (1986-11-01), Fleischer et al.
patent: 4735846 (1988-04-01), Larsonneur
patent: 4770920 (1988-09-01), Larsonneur
patent: 4822452 (1989-04-01), Tse et al.
patent: 4879170 (1989-11-01), Radwanski et al.
patent: 4931355 (1990-06-01), Radwanski et al.
patent: 4940621 (1990-07-01), Rhodes et al.
patent: 4950262 (1990-08-01), Takagi
patent: 5022945 (1991-06-01), Rhodes et al.
patent: 5055332 (1991-10-01), Rhodes et al.
patent: 5137537 (1992-08-01), Herron et al.
patent: 5183707 (1993-02-01), Herron et al.
patent: 5242435 (1993-09-01), Murji et al.
patent: 5295986 (1994-03-01), Zehner et al.
patent: 5320895 (1994-06-01), Larsonneur et al.
patent: 5374260 (1994-12-01), Lemay et al.
patent: 5387385 (1995-02-01), Murji et al.
patent: 5399412 (1995-03-01), Sudall et al.
patent: 5409572 (1995-04-01), Kershaw et al.
patent: 5415644 (1995-05-01), Enloe
patent: 5466232 (1995-11-01), Cadieux et al.
patent: 5484896 (1996-01-01), Naieni et al.
patent: 5492753 (1996-02-01), Levy et al.
patent: 5549791 (1996-08-01), Herron et al.
patent: 5582606 (1996-12-01), Bruemmer et al.
patent: 5620431 (1997-04-01), LeMahieu et al.
patent: 5634915 (1997-06-01), Osterdahl
patent: 5649918 (1997-07-01), Schleinz
pa
Gentile Victor Michael
Tanner James Jay
Connelly Thomas J.
Kimberly--Clark Worldwide, Inc.
Morris Terrel
Pratt Christopher C.
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