Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Nonwoven fabric
Reexamination Certificate
1998-11-13
2004-02-03
Morris, Terrel (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Nonwoven fabric
C442S334000, C442S352000, C442S353000, C442S356000, C442S361000, C442S362000, C442S400000, C442S401000, C442S413000, C442S414000, C442S417000
Reexamination Certificate
active
06686303
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to bicomponent nonwoven webs containing splittable thermoplastic filaments and a third component selected from fibers, particles and combinations thereof. The splitting of bicomponent filaments into smaller filaments helps to contain the third component, and may add softness to the composite product. Also, better capillary may result from the increased filament surface area.
BACKGROUND OF THE INVENTION
Bicomponent nonwoven filaments are known in the art generally as thermoplastic filaments which employ at least two different polymers combined together in a heterogeneous fashion. Instead of being homogeneously blended, two polymers may, for instance, be combined in a side-by-side configuration, so that a first side of a filament is composed of a first polymer “A” and a second side of the filament is composed of a second polymer “B.” Alternatively, the polymers may be combined in a sheath-core configuration, so that an outer sheath layer of a filament is composed of a first polymer “A,” and the inner core is composed of a second polymer “B.” Alternatively, the polymers may be combined in an islands-in-the-sea configuration in which one or more islands of a first polymer “A” appear in a sea of a second polymer “B.” Other heterogeneous configurations are also possible.
Splittable nonwoven bicomponent filaments are disclosed in U.S. Pat. No. 5,759,926, issued to Pike et al. These filaments contain at least two incompatible polymers arranged in distinct segments across the cross-section of each filament. The incompatible segments are continuous along the length of each filament. The individual segments of each filament split apart from each other when the filament is contacted with a hot aqueous fibrillation-inducing medium, resulting in finer individual filaments formed from the segments. Other techniques for splitting bicomponent filaments include mechanical agitation and spontaneous splitting caused by differential shrinkage of the components.
Bicomponent filaments have been disclosed in combination with carbon particles, zeolites, ion exchange resins, carbon fibers, stabilizing fibers, and/or gas absorbing fibers for use in specialized filters. U.S. Pat. No. 5,670,044, issued to Ogata et al., discloses the use of bicomponent meltblown filaments in these combinations, for use in cylindrical filters. In that case, the bicomponent filaments contain high and low melting polymers. The filaments of the filter are stacked and bonded together by melting only the lower melting component. However, Ogata et al. does not suggest splitting the bicomponent filaments.
Pulp fibers have been employed in certain absorbent applications, to enhance the absorbency. U.S. Pat. No. 4,530,353, issued to Lauritzen, discloses pulp fibers in combination with staple length bicomponent fibers used in the manufacture of absorbent bandages. In that case, the fibers also contain high and low melting polymers. The staple length fibers are bonded together by melting only the lower melting component. Again, there is no suggestion to split the bicomponent filaments.
In the field of absorbent articles, and other fields where thermoplastic nonwoven webs are combined with a third component selected from other fibers and/or particles, there is a need or desire for techniques which better contain the third component within the thermoplastic nonwoven filaments. There is also a need or desire for techniques which increase the maximum amount of the third component that can be ensnared, entangled, or otherwise contained within the matrix of thermoplastic nonwoven filaments.
SUMMARY OF THE INVENTION
The present invention is directed to an improved nonwoven composite wherein thermoplastic nonwoven filaments are utilized as a matrix for ensnaring, containing and restraining a component selected from other fibers and/or particles. The nonwoven composite provides improved containment of the other fibers and/or particles, and effectively contains higher levels of the other fibers and/or particles within a thermoplastic nonwoven filament matrix. The improved performance is accomplished using splittable thermoplastic bicomponent filaments, whose first and second polymers split apart into a larger number of finer filaments. The resulting finer filaments, in the increased number, provide better containment of the third component selected from other fibers and/or particles.
The present invention is also directed to an absorbent article, including a personal care absorbent article, which utilizes the improved nonwoven web composite of the invention.
The splittable bicomponent filaments contain at least first and second mutually incompatible thermoplastic polymer components, arranged in distinct segments across the width of the filament. Each polymer component is preferably continuous along the length of each splittable filament. Preferably, the splitting of the segments is controllable, so that the third component (other pulp or particles) can be combined relatively easily with the bicomponent filaments before they are split. Thereafter, the bicomponent filaments are responsive to a control mechanism which induces splitting of the filaments into finer filaments corresponding to each segment, to more firmly entrap and ensnare the third component within the matrix of thermoplastic filaments. Preferably, the splittable bicomponent filaments, and the thermoplastic segment components thereof, are substantially continuous in length.
With the foregoing in mind, it is a feature and advantage of the invention to provide an improved nonwoven web composite which exhibits improved containment of a third component selected from fibers and/or particles, within a matrix of thermoplastic nonwoven filaments.
It is also a feature and advantage of the invention to provide a nonwoven web composite having a latent controlled containment mechanism, which improves the ensnaring and entrapment of the third component after the third component enters the thermoplastic filament matrix.
It is also a feature and advantage of the invention to provide an absorbent article made using the improved nonwoven web composite.
Definitions
The term “nonwoven fabric or web” means a web having a structure of individual fibers or threads which are interlaid, but not in a regular or identifiable manner as in a knitted fabric. Nonwoven fabrics or webs have been formed from many processes such as, for example, meltblowing processes, spunbonding processes, air laying processes, and bonded carded web processes. The basis weight of nonwoven fabrics is usually expressed in ounces of material per square yard (osy) or grams per square meter (gsm) and the fiber diameters useful are usually expressed in microns. (Note that to convert from osy to gsm, multiply osy by 33.91.)
The term “microfibers” means small diameter fibers having an average diameter not greater than about 75 microns, for example, having an average diameter of from about 1 micron to about 50 microns, or more particularly, microfibers may have an average diameter of from about 1 micron to about 30 microns. Another frequently used expression of fiber diameter is denier, which is defined as grams per 9000 meters of a fiber. For a fiber having circular cross-section, denier may be calculated as fiber diameter in microns squared, multiplied by the density in grams/cc, multiplied by 0.00707. A lower denier indicates a finer fiber and a higher denier indicates a thicker or heavier fiber. For example, the diameter of a polypropylene fiber given as 15 microns may be converted to denier by squaring, multiplying the result by 0.89 g/cc and multiplying by 0.00707. Thus, a 15 micron polypropylene fiber has a denier of about 1.42 (15
2
×0.89×0.00707=1.415). Outside the United States the unit of measurement is more commonly the “tex,” which is defined as the grams per kilometer of fiber. Tex may be calculated as denier/9. The foregoing range refers to diameters existing before any splitting. The splitting of bicomponent microfibers would result in correspondingly smaller
Arnold Billy Dean
Clark Darryl Franklin
Creagan Christopher Cosgrove
Duellman Justin Max
Frank Ryan Clinton
Kimberly--Clark Worldwide, Inc.
Morris Terrel
Pauley Peterson & Erickson
Pratt Christopher C.
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