US20080008853A1

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Publication number: US20080008853A1
Application number: US11/820,509
Authority: US
Inventors: Matthew Todd Hupp; Charles Allen Redd; Steven Lee Barnholtz
Original assignee: Procter and Gamble Co
Current assignee: Procter and Gamble Co
Priority date: 2006-07-05
Filing date: 2007-06-20
Publication date: 2008-01-10
Also published as: WO2008005500A2; CA2656631A1; MX2009000078A; EP2035608A2; WO2008005500A3

Abstract

Webs, such as fibrous structures, having a tuft, sanitary tissue products employing same and methods for making same are provided. More particularly, webs, such as fibrous structures, having a tuft employing a non-extensible material, such as non-extensible fibers, sanitary tissue products employing same and methods for making same are provided.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/854,843 filed Oct. 27, 2006 and U.S. Provisional Application No. 60/818,701 filed Jul. 5, 2006.

FIELD OF THE INVENTION

The present invention relates to webs, such as fibrous structures, comprising a tuft, sanitary tissue products comprising same and methods for making same. More particularly, the present invention relates to webs, such as fibrous structures, comprising a tuft comprising a non-extensible material, such as non-extensible fibers, sanitary tissue products comprising same and methods for making same.

BACKGROUND OF THE INVENTION

Webs, especially fibrous structures, comprising tufts are known in the art. Such fibrous structures utilize extensible fibers and/or films to form tufts within the fibrous structures. For example, in one prior art execution, polypropylene fibers are meltblown onto a cellulosic pulp fibrous structure and then subjected to a tuft generating process which pushes the polypropylene fibers through the cellulosic pulp fibers thereby creating a polypropylene fiber tuft (an extensible fiber tuft).

Formulators of such webs and/or fibrous structures apparently never believed that tufts could be formed out of a non-extensible material, especially non-extensible fibers. Some of their concerns included the non-extensible fibers breaking during the tuft generating process before a tuft could be formed. As a result, a web comprising a tuft comprising a non-extensible material, especially non-extensible fibers, has never before been achieved.

Since extensible fiber and/or film materials are typically thermoplastic polymers, the cost of such materials is significant for use in fibrous structures that are incorporated into sanitary tissue products, such as bath tissue, facial tissue and paper towels, in particular, thus making it difficult for sanitary tissue product manufacturers to utilize such thermoplastic polymers.

Accordingly, there has been a need for webs, especially fibrous structures, comprising a non-extensible material, especially non-extensible fibers, wherein the fibrous structure comprises a tuft comprising a non-extensible material, especially non-extensible fibers, sanitary tissue products comprising same and methods for making same.

SUMMARY OF THE INVENTION

The present invention fulfills the needs described above by providing a web, such as a fibrous structure, comprising a tuft comprising a non-extensible material, especially non-extensible fibers.

In one example of the present invention, a web, such as a fibrous structure, comprising a tuft comprising a non-extensible material, such as non-extensible fibers, is provided.

In another example of the present invention, a method for making a web according to the present invention, wherein the method comprises the steps of:

- a. forming a web comprising a non-extensible material, such as non-extensible fibers;
- b. imparting extensibility into the web, or at least a portion of the web, to form an extensible web or portion of the web, for example such that the web exhibits a stretch of less than 800% as measured by the Short Span Tensile Test Method; and
- c. subjecting the extensible web or portion of the web to a tuft generating operation such that a tuft comprising a non-extensible material (for example non-extensible fibers) is formed in the web, is provided.

In yet another example of the present invention, a single- or multi-ply sanitary tissue product comprising a web according to the present invention is provided.

Accordingly, the present invention provides a web comprising a tuft comprising a non-extensible material, especially non-extensible fibers, a sanitary tissue product comprising such a web and a method for making such a web.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a fibrous structure in accordance with the present invention;

FIG. 2 is a perspective view of an apparatus for forming a fibrous structure according to the present invention;

FIG. 3 is a cross-sectional depiction of the apparatus shown inFIG. 2;

FIG. 4 is a perspective view of a portion of the apparatus ofFIG. 2 for forming a fibrous structure of the present invention;

FIG. 5 is an enlarged perspective view of a portion of the apparatus ofFIG. 4;

FIG. 6 is a schematic representation of a portion of a multi-ply fibrous structure according to the present invention;

FIG. 7 is a schematic representation of a portion of a multi-ply fibrous structure according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

“Web” as used herein means a substantially planar structure, for example a film and/or a fibrous structure. The web may comprise a surface comprising undulations. Such undulations may be formed by creping of the web and/or rush transferring of the web during the web-making process.

“Tuft,” for purposes of this present invention only, means a region, in the form of a continuous loop, of the fibrous structure and/or sanitary tissue product that is extended from the fibrous structure and/or sanitary tissue product along or substantially along the z-axis (“z-axis” as used herein is commonly understood in the art to indicate an “out-of-plane” direction generally orthogonal to the x-y plane as shown inFIG. 1, for example). In one example, a tuft according to the present invention is a continuous loop that extends along the z-axis from the x-y plane of the fibrous structure and/or sanitary tissue product, wherein the tuft comprises a non-extensible material, such as non-extensible fibers. In another example, a tuft according to the present invention is a continuous loop that extends along the z-axis from the x-y plane of the fibrous structure and/or sanitary tissue product, wherein the tuft comprises at least 10% and/or at least 20% and/or at least 30% and/or at least 50% and/or 100% or less and/or 90% or less and/or 70% or less by weight of the total fibers present in the tuft of non-extensible fibers. In another example, the tuft comprises 100% by weight of total fibers present in the tuft of non-extensible fibers, in other words in this example, the tuft is made up entirely of non-extensible fibers.

The tuft may define an interior open or substantially open void area that is generally free of fibers. In other words, the tufts of the present invention may exhibit a “tunnel-like” structure, instead of a “tent-like” rib-like element that exhibits continuous side walls as is taught in the prior art. In one example, the tunnel is oriented in the MD of the fibrous structure. If the web comprises a surface having undulations that are oriented in the CD direction, then the tuft may be oriented perpendicular to such undulations. In another example, as a result of the tuft, a discontinuity is formed in the fibrous structure and/or sanitary tissue product in its x-y plane. A “discontinuity” as used herein is an interruption along the side/surface of the fibrous structure and/or sanitary tissue product opposite the tuft. In other words, a discontinuity is a hole and/or recess and/or void on a side/surface of the fibrous structure that is created as a result of the formation of the tuft on the opposite side/surface of the fibrous structure and/or sanitary tissue product. In one example, a deformation in a surface of fibrous structure and/or sanitary tissue product such as a bulge, bump, loop or other protruding structure that extends from a surface of the fibrous structure and/or sanitary tissue product of the present invention.

In one example, the tufts of the fibrous structure of the present invention may increase the caliper (wet and/or dry) and/or bulk (wet and/or dry) of the fibrous structure and/or sanitary tissue product. For example, the tufts of the fibrous structure of the present invention may increase the caliper by at least about 10% and/or at least about 20% relative to the fibrous structure and/or sanitary tissue product prior to formation of the tufts.

In another example, the tufts may be oriented inward in a multi-ply fibrous product, they may be oriented outward on a multi-ply sanitary tissue product, and they may be oriented such that one ply has the tufts oriented inward and another ply has the tufts oriented outward in/on the multi-ply sanitary tissue product.

In yet another example, the tufted fibrous structure and/or sanitary tissue product of the present invention may be convolutedly wound to form a roll of the fibrous structure and/or sanitary tissue product. Such a roll may exhibit an effective caliper that is greater than the combined caliper of the untufted fibrous structure and/or sanitary tissue product.

In still another example, the tufts of the fibrous structure and/or sanitary tissue product may be phased to embossing, printing and/or perforations on and/or within the fibrous structure and/or sanitary tissue product.

In yet another example, the tufts of the fibrous structure and/or sanitary tissue product may generate enhanced aesthetics through creating differential height/elevation and/or differential texture regions, differential opacity regions, differential color (when tufts have colors (same or varied)), phasing with ink or emboss or other indicia within the fibrous structure and/or sanitary tissue product.

“Non-extensible material” as used herein means a material that is present within a portion of a web, such as a fibrous structure, wherein the web exhibits a stretch of less than 800% and/or less than 700% and/or less than 600% and/or less than 500% and/or less than 400% and/or less than 300% as measured according to the Short Span Tensile Test Method described herein. In one example, a surface of a web according to the present invention comprises a non-extensible material. In addition to a non-extensible material, such as non-extensible fibers, a surface of a web according to the present invention may comprise extensible fibers, such as thermoplastic polymer fibers. Such thermoplastic polymer fibers may comprise a thermoplastic polymer thermoplastic polymers selected from the group consisting of: polypropylene, copolymers of polypropylene, polyethylene, copolymers of polyethylene, polyethylene terephthalate, copolymers of polyethylene terephthalate and mixtures thereof.

“Non-extensible fibers” as used herein means fibers that are present within a portion of a web, such as a fibrous structure, wherein the web exhibits a stretch of less than 800% and/or less than 700% and/or less than 500% and/or less than 400% and/or less than 300% as measured according to the Short Span Tensile Test Method described herein. In one example, one or more of the non-extensible fibers exhibits a length of less than about 7 mm and/or less than about 6.5 mm and/or less than about 6 mm and/or less than about 5 mm and/or less than about 3 mm and/or less than about 2.5 mm and/or from about 0.4 mm to about 7 mm and/or from about 0.5 mm to about 6.5 mm and/or from about 0.5 mm to about 6 mm and/or from about 0.6 mm to about 5 mm.

In one example, one or more of the non-extensible fibers comprises a naturally occurring fiber.

“Fiber” as used herein means an elongate physical structure having an apparent length greatly exceeding its apparent diameter, i.e. a length to diameter ratio of at least about 10. Fibers having a non-circular cross-section and/or tubular shape are common; the “diameter” in this case may be considered to be the diameter of a circle having cross-sectional area equal to the cross-sectional area of the fiber. More specifically, as used herein, “fiber” refers to fibrous structure-making fibers. The present invention contemplates the use of a variety of fibrous structure-making fibers, such as, for example, natural fibers or synthetic fibers, or any other suitable fibers, and any combination thereof.

Natural fibrous structure-making fibers (“naturally occurring fibers”) useful in the present invention include animal fibers, mineral fibers, other plant fibers (such as trichomes and/or seed hairs) and mixtures thereof. Animal fibers may, for example, be selected from the group consisting of: wool, silk and other naturally occurring protein fibers and mixtures thereof. The other plant fibers may, for example, be derived from a plant selected from the group consisting of: wood, cotton, cotton linters, flax, sisal, abaca, hemp, hesperaloe, jute, bamboo, bagasse, kudzu, corn, sorghum, gourd, agave, loofah and mixtures thereof.

Wood fibers; often referred to as wood pulps include chemical pulps, such as kraft (sulfate) and sulfite pulps, as well as mechanical and semi-chemical pulps including, for example, groundwood, thermomechanical pulp, chemi-mechanical pulp (CMP), chemi-thermomechanical pulp (CTMP), neutral semi-chemical sulfite pulp (NSCS). Chemical pulps, however, may be preferred since they impart a superior tactile sense of softness to tissue sheets made therefrom. Pulps derived from both deciduous trees (hereinafter, also referred to as “hardwood”) and coniferous trees (hereinafter, also referred to as “softwood”) may be utilized. The hardwood and softwood fibers can be blended, or alternatively, can be deposited in layers to provide a stratified and/or layered web. U.S. Pat. No. 4,300,981 and U.S. Pat. No. 3,994,771 are incorporated herein by reference for the purpose of disclosing layering of hardwood and softwood fibers. Also applicable to the present invention are fibers derived from recycled paper, which may contain any or all of the above categories as well as other non-fibrous materials such as fillers and adhesives used to facilitate the original papermaking.

The wood pulp fibers may be short (typical of hardwood fibers) or long (typical of softwood fibers). Nonlimiting examples of short fibers include fibers derived from a fiber source selected from the group consisting of Acacia, Eucalyptus, Maple, Oak, Aspen, Birch, Cottonwood, Alder, Ash, Cherry, Elm, Hickory, Poplar, Gum, Walnut, Locust, Sycamore, Beech, Catalpa, Sassafras, Gmelina, Albizia, Anthocephalus, and Magnolia. Nonlimiting examples of long fibers include fibers derived from Pine, Spruce, Fir, Tamarack, Hemlock, Cypress, and Cedar. Softwood fibers derived from the kraft process and originating from more-northern climates may be preferred.

In addition to the various wood pulp fibers, other cellulosic fibers such as cotton linters, rayon, and bagasse can be used in this invention. Synthetic fibers (“non-naturally occurring fibers”), such as polymeric fibers, can also be used. Elastomeric polymers, polypropylene, polyethylene, polyester, polyolefin, polyvinyl alcohol and nylon, can be used. The polymeric fibers may comprise natural polymers from sources such as starch sources, protein sources and/or cellulose sources. The polymeric fibers can be produced by suitable methods known in the art.

An embryonic fibrous web can be typically prepared from an aqueous dispersion of papermaking fibers, though dispersions in liquids other than water can be used. The fibers are dispersed in the carrier liquid to have a consistency of from about 0.1 to about 0.3 percent. It is believed that the present invention can also be applicable to moist forming operations where the fibers are dispersed in a carrier liquid to have a consistency of less than about 50% and/or less than about 10%.

“Fibrous structure” as used herein means a structure that comprises one or more fibers. In one example, a fibrous structure according to the present invention means an orderly arrangement of fibers within a structure in order to perform a function. Nonlimiting examples of fibrous structures of the present invention include composite materials (including reinforced plastics and reinforced cement), paper, fabrics (including woven, knitted, and non-woven), and absorbent pads (for example for diapers or feminine hygiene products). A bag of loose fibers is not a fibrous structure in accordance with the present invention.

Nonlimiting examples of processes for making fibrous structures include known wet-laid papermaking processes and air-laid papermaking processes. Such processes typically include steps of preparing a fiber composition in the form of a suspension in a medium, either wet, more specifically aqueous medium, or dry, more specifically gaseous, i.e. with air as medium. The aqueous medium used for wet-laid processes is oftentimes referred to as a fiber slurry. The fibrous suspension is then used to deposit a plurality of fibers onto a forming wire or belt such that an embryonic fibrous structure is formed, after which drying and/or bonding the fibers together results in a fibrous structure. Further processing the fibrous structure may be carried out such that a finished fibrous structure is formed. For example, in typical papermaking processes, the finished fibrous structure is the fibrous structure that is wound on the reel at the end of papermaking, and may subsequently be converted into a finished product, e.g. a sanitary tissue product.

The fibrous structures of the present invention may be homogeneous or may be layered. If layered, the fibrous structures may comprise at least two and/or at least three and/or at least four and/or at least five layers.

“Sanitary tissue product” as used herein means a soft, low density (i.e. <about 0.15 g/cm3) web useful as a wiping implement for post-urinary and post-bowel movement cleaning (toilet tissue), for otorhinolaryngological discharges (facial tissue), and multi-functional absorbent and cleaning uses (absorbent towels). The sanitary tissue product may be convolutedly wound upon itself about a core or without a core to form a roll of sanitary tissue product.

“Basis Weight” as used herein is the weight per unit area of a sample reported in lbs/3000 ft²or g/m². Basis weight is measured by preparing one or more samples of a certain area (m²) and weighing the sample(s) of a fibrous structure according to the present invention and/or a paper product comprising such fibrous structure on a top loading balance with a minimum resolution of 0.01 g. The balance is protected from air drafts and other disturbances using a draft shield. Weights are recorded when the readings on the balance become constant. The average weight (g) is calculated and the average area of the samples (m²). The basis weight (g/m²or gsm) is calculated by dividing the average weight (g) by the average area of the samples (m²).

“Caliper” or “Sheet Caliper” as used herein means the macroscopic thickness of a single-ply fibrous structure, web product or film according to the present invention. Caliper of a fibrous structure, web product or film according to the present invention is determined by cutting a sample of the fibrous structure, web product or film such that it is larger in size than a load foot loading surface where the load foot loading surface has a circular surface area of about 3.14 in². The sample is confined between a horizontal flat surface and the load foot loading surface. The load foot loading surface applies a confining pressure to the sample of 15.5 g/cm²(about 0.21 psi). The caliper is the resulting gap between the flat surface and the load foot loading surface. Such measurements can be obtained on a VIR Electronic Thickness Tester Model II available from Thwing-Albert Instrument Company, Philadelphia, Pa. The caliper measurement is repeated and recorded at least five (5) times so that an average caliper can be calculated. The result is reported in millimeters.

In one example, the single-ply fibrous structure and/or sanitary tissue product according to the present invention exhibits a sheet caliper of at least about 0.508 mm (20 mils) and/or at least about 0.762 mm (30 mils) and/or at least about 1.524 mm (60 mils).

“Effective Caliper” as used herein means the radial thickness a layer of fibrous structure and/or sanitary tissue product occupies within a convolutely wound roll of such fibrous structure and/or sanitary tissue product. In order to facilitate the determination of effective caliper, an Effective Caliper Test Method is described herein. The effective caliper of a fibrous structure and/or sanitary tissue product can differ from the sheet caliper of the fibrous structure and/or sanitary tissue product due to winding tension, nesting of deformations, etc.

“Density” or “Apparent density” as used herein means the mass per unit volume of a material. For fibrous structures, the density or apparent density can be calculated by dividing the basis weight of a fibrous structure sample by the caliper of the fibrous structure sample with appropriate conversions incorporated therein. Density and/or apparent density used herein has the units g/cm³.

“Dry Tensile Strength” (or simply “Tensile Strength” as used herein) of a fibrous structure and/or sanitary tissue product is measured as follows. One (1) inch by five (5) inch (2.5 cm×12.7 cm) strips of fibrous structure and/or sanitary tissue product are provided. The strip is placed on an electronic tensile tester Model 1122 commercially available from Instron Corp., Canton, Mass. in a conditioned room at a temperature of 73° F.±4° F. (about 28° C.±2.2° C.) and a relative humidity of 50%±10%. The crosshead speed of the tensile tester is 4.0 inches per minute (about 10.2 cm/minute) and the gauge length is 4.0 inches (about 10.2 cm). The Dry Tensile Strength can be measured in any direction by this method. The “Total Dry Tensile Strength” or “TDT” is the special case determined by the arithmetic total of MD and CD tensile strengths of the strips.

“Absorbent” and “absorbency” as used herein means the characteristic of the fibrous structure which allows it to take up and retain fluids, particularly water and aqueous solutions and suspensions. In evaluating the absorbency of paper, not only is the absolute quantity of fluid a given amount of paper will hold significant, but the rate at which the paper will absorb the fluid is also. Absorbency is measured here in by the Horizontal Full Sheet (HFS) test method described in the Test Methods section herein. In one example, the fibrous structures and/or sanitary tissue products according to the present invention exhibit an HFS absorbency of greater than about 5 g/g and/or greater than about 8 g/g and/or greater than about 10 g/g up to about 100 g/g. In another nonlimiting example, the fibrous structures and/or sanitary tissue products according to the present invention exhibit an HFS absorbency of from about 12 g/g to about 30 g/g.

“Machine Direction” or “MD” as used herein means the direction parallel to the flow of the fibrous structure through the papermaking machine and/or product manufacturing equipment.

“Cross Machine Direction” or “CD” as used herein means the direction perpendicular to the machine direction in the same plane of the fibrous structure and/or paper product comprising the fibrous structure.

“Ply” or “Plies” as used herein means an individual fibrous structure optionally to be disposed in a substantially contiguous, face-to-face relationship with other plies, forming a multiple ply fibrous structure. It is also contemplated that a single fibrous structure can effectively form two “plies” or multiple “plies”, for example, by being folded on itself.

As used herein, the articles “a” and “an” when used herein, for example, “an anionic surfactant” or “a fiber” is understood to mean one or more of the material that is claimed or described.

All percentages and ratios are calculated by weight unless otherwise indicated. All percentages and ratios are calculated based on the total composition unless otherwise indicated.

Unless otherwise noted, all component or composition levels are in reference to the active level of that component or composition, and are exclusive of impurities, for example, residual solvents or by-products, which may be present in commercially available sources.

Fibrous Structure

The fibrous structure and/or sanitary tissue product of the present invention may be made from any suitable precursor fibrous structure (a fibrous structure that has not be subjected to a tuft generating operation) known to those skilled in the art. In one example, the precursor fibrous structure may be made by an air-laid process. In another example, the precursor fibrous structure may be made by a wet-laid process.

The precursor fibrous structure may be made with a fibrous furnish that produces a single layer embryonic fibrous web or a fibrous furnish that produces a multi-layer embryonic fibrous web.

In one example, the air laid fibrous structure is selected from the group consisting of thermal bonded air laid (TBAL) fibrous structures, latex bonded air laid (LBAL) fibrous structures and mixed bonded air laid (MBAL) fibrous structures.

The precursor fibrous structures may exhibit a substantially uniform density or may exhibit differential density regions, in other words regions of high density compared to other regions within the patterned fibrous structure. Typically, when a fibrous structure is not pressed against a cylindrical dryer, such as a Yankee dryer, while the fibrous structure is still wet and supported by a through-air-drying fabric or by another fabric or when an air laid fibrous structure is not spot bonded, the fibrous structure typically exhibits a substantially uniform density.

In one example, the precursor fibrous structure of the present invention comprises 100% or about 100% by weight, on a dry precursor fibrous structure basis of wood pulp fibers.

In another example, the precursor fibrous structure of the present invention comprises from about 100% to about 10% and/or from about 100% to about 30% and/or from about 100% to about 50% and/or from about 100% to about 75% by weight, on a dry precursor fibrous structure basis of wood pulp fibers. The other fibers, if any, in this type of precursor fibrous structure may be synthetic fibers, continuous, substantially continuous or staple synthetic fibers.

Extensibility sufficient to form a tuft comprising otherwise non-extensible material may be imparted to a precursor web (fibrous structure) by any suitable means such as by forming the web on a structured through-air-drying fabric, foreshortening, creping, wet microcontracting, and/or rush transferring. Alternatively, the precursor web (e.g., fibrous structure) may not be foreshortened.

The precursor fibrous structure may be pattern densified. A pattern densified fibrous structure is characterized by having a relatively high-bulk field of relatively low fiber density and an array of densified zones of relatively high fiber density. The high-bulk field is alternatively characterized as a field of pillow regions. The densified zones are alternatively referred to as knuckle regions. The densified zones may be discretely spaced within the high-bulk field or may be interconnected, either fully or partially, within the high-bulk field.

The precursor fibrous structure may be uncompacted, non pattern-densified. The precursor fibrous structure may be of a homogenous or multilayered construction. The precursor fibrous structure may be made with a fibrous furnish that produces a single layer embryonic fibrous web or a fibrous furnish that produces a multi-layer embryonic fibrous web.

The precursor fibrous structures of the present invention may comprise any suitable ingredients known in the art. Nonlimiting examples of suitable ingredients that may be included in the precursor fibrous structures include permanent and/or temporary wet strength resins, dry strength resins, softening agents, wetting agents, lint resisting agents, absorbency-enhancing agents, immobilizing agents, especially in combination with emollient lotion compositions, antiviral agents including organic acids, antibacterial agents, polyol polyesters, antimigration agents, polyhydroxy plasticizers, opacifying agents, bonding agents, debonding agents, colorants, soil release polymers (polymeric hydrophilizing agents), wetting agents and mixtures thereof. Such ingredients, when present in the fibrous structure of the present invention, may be present at any level based on the dry weight of the fibrous structure. Typically, such ingredients, when present, may be present at a level of from about 0.001 to about 50% and/or from about 0.001 to about 20% and/or from about 0.01 to about 5% and/or from about 0.03 to about 3% and/or from about 0.1 to about 1.0% by weight, on a dry precursor fibrous structure basis.

The fibrous structures of the present invention and/or sanitary tissue products comprising such fibrous structures may have a basis weight of between about 10 g/m²to about 120 g/m²and/or from about 14 g/m²to about 80 g/m²and/or from about 20 g/m²to about 60 g/m².

The fibrous structures of the present invention and/or sanitary tissue products comprising such fibrous structures may have a total dry tensile strength of greater than about 59 g/cm (150 g/in) and/or from about 78 g/cm (200 g/in) to about 394 g/cm (1000 g/in) and/or from about 98 g/cm (250 g/in) to about 335 g/cm (850 g/in).

The fibrous structures of the present invention and/or sanitary tissue products comprising such fibrous structures may have a density of about 0.60 g/cc or less and/or about 0.30 g/cc or less and/or from about 0.04 g/cc to about 0.20 g/cc.

The fibrous structures of the present invention and/or sanitary tissue products comprising such fibrous structures may have a lint of about 2 or more and/or about 4 or more and/or from about 6 or more to about 12 or less and/or about 10 or less and/or about 8 or less.

As shown inFIG. 1, a fibrous structure and/orsanitary tissue product10 comprising atuft12 is provided. Thetuft12 comprises anon-extensible material14, such asnon-extensible fibers16. As a result of the creation of thetuft12, anopen void area20 is formed within thetuft12 and adiscontinuity22 is formed on thenon-tufted surface24 of the fibrous structure and/orsanitary tissue product10. Even though the schematic example doesn't show it, thediscontinuity22 may be smaller in width in the x-plane than the maximum x-plane width of thetuft12. The fibrous structure and/orsanitary tissue product10 may be made offibers26, which may be extensible or non-extensible.

The fibrous structure of the present invention may be combined with an additional fibrous structure the same or different from the fibrous structure of the present invention. Tufts present in the fibrous structure of the present invention may protrude at least into the additional fibrous structure. In addition, the tufts present in the fibrous structure of the present invention may protrude through the additional fibrous structure as a result of the additional fibrous structure breaking at the point of the tuft.

When combined with one or more additional fibrous structures, the same or different from the fibrous structures of the present invention to form a multi-ply sanitary tissue product, the tufts may be oriented either inwardly such that the tufts do not form part of an external surface of the sanitary tissue product or outwardly such that the tufts do form part of an external surface of the sanitary tissue product. In one example, tufts of two different fibrous structures of the present invention of a multi-ply sanitary tissue product may contact one another by being oriented inwardly such that the tufts do not form part of an external surface of the sanitary tissue product. However, the tufts of the fibrous structures may be separated from one another by one or more additional fibrous structures the same or different from the fibrous structures of the present invention. Alternatively, tufts of two different fibrous structures of the present invention of a multi-ply sanitary tissue product may be oriented differently, one fibrous structure having the tufts oriented outwardly such that the tufts form part of an external surface of the sanitary tissue product and one fibrous structure having tufts oriented inwardly such that the tufts do not form part of an external surface of the sanitary tissue product. In another example, tufts of two different fibrous structures of the present invention of a multi-ply sanitary tissue product may both be oriented outwardly such that the tufts form a part of the external surfaces of the sanitary tissue product.

The additional fibrous structure may be combined with the fibrous structure of the present invention by any suitable means. The fibrous structure may be combined before or after tufts are present in the fibrous structure of the present invention.

The fibrous structure of the present invention and the additional fibrous structure may exhibit different stretch properties at peak load. For example the fibrous structure of the present invention may exhibit a stretch at peak load that is less than the stretch at peak load of the additional fibrous structure.

In another example, a fibrous structure of the present invention or portions thereof may exhibit a pre-tuft stretch at peak load that is less than the stretch at peak load of the additional web or portions of the additional web. The pre-tuft stretch at peak load of the fibrous structure of the present invention or portions thereof may be influenced, especially immediately before and/or during being subjected to a tuft generating process, such that the stretch at peak load of the fibrous structure of the present invention or portions thereof is greater than (at the time of being subjected to the tuft generating process) the stretch at peak load of the additional fibrous structure thus allowing the fibrous structure of the present invention or portions thereof to be imparted tufts.

In other examples, the fibrous structure of the present invention or portions thereof may exhibit a greater stretch at peak load than the additional fibrous structure or portions thereof.

In one example, the fibrous structure and/or sanitary tissue product of the present invention may comprise 100% by weight of fibers of wood pulp fibers. In another example, the fibrous structure and/or sanitary tissue product of the present invention may comprise 100% by weight of fibers of a mixture of wood pulp fibers and staple synthetic fibers.

The fibrous structure of the present invention may be formed by any suitable process known in the art.

Tuft Generating Process

Referring toFIG. 2, there is shown a nonlimiting example of an apparatus and method for making a fibrous structure of the present invention. Theapparatus100 comprises a pair of intermeshing rolls102 and104, each rotating about an axis A, the axes A being parallel in the same plane.Roll102 comprises a plurality ofridges106 andcorresponding grooves108 which extend unbroken about the entire circumference ofroll102.Roll104 is similar to roll102, but rather than having ridges that extend unbroken about the entire circumference,roll104 comprises a plurality of rows of circumferentially-extending ridges that have been modified to be rows of circumferentially-spacedteeth110 that extend in spaced relationship about at least a portion ofroll104. The individual rows ofteeth110 ofroll104 are separated by correspondinggrooves112. In operation, rolls102 and104 intermesh such that theridges106 ofroll102 extend into thegrooves112 ofroll104 and theteeth110 ofroll104 extend into thegrooves108 ofroll102. The intermeshing is shown in greater detail in the cross sectional representation ofFIG. 3, discussed below.

InFIG. 2, theapparatus100 is shown having one patterned roll, e.g., roll104, and one non-patternedgrooved roll102. However, in certain examples it may be desirable to use twopatterned rolls104 having either the same or differing patterns, in the same or different corresponding regions of the respective rolls. Such an apparatus can produce fibrous structures with tufts protruding from both sides of the fibrous structure.

The process of the present invention is similar in many respects to a process as described in U.S. Pat. No. 5,518,801 entitled “Web Materials Exhibiting Elastic-Like Behavior” and referred to in subsequent patent literature as “SELF” webs, which stands for “Structural Elastic-like Film”. However, there are significant differences between the apparatus of the present invention and the apparatus disclosed in the above-identified '801 patent. These differences account for the novel features of the web of the present invention. As described below, theteeth110 ofroll104 have a specific geometry associated with the leading and trailing edges that permit the teeth, e.g.,teeth110, to essentially “punch” through the precursorfibrous structure28 as opposed to, in essence, emboss the web. The difference in theapparatus100 of the present invention results in a fundamentally different fibrous structure.

Precursor fibrous structure

28 is provided either directly from a web making process or indirectly from a supply roll (neither shown) and moved in the machine direction to the nip116 of counter-rotating intermeshing rolls102 and104.Precursor fibrous structure28 can be any suitable fibrous structure that exhibits or is capable of exhibiting sufficient stretch at peak load to permit formation of tufts in the fibrous structure.Precursor fibrous structure28 can be plasticized by any means known in the art, such as by subjecting the precursor web to a humid environment. As precursorfibrous structure28 goes through thenip116 theteeth110 ofroll104

enter grooves

108 ofroll102 and simultaneously urge fibers out of the plane of plane of precursorfibrous structure28 to formtufts12 anddiscontinuities22, not shown inFIG. 2. In effect,teeth110 “push” or “punch” through precursorfibrous structure28. As the tip ofteeth110 push through precursorfibrous structure28 the portions of fibers that are oriented predominantly in the CD and acrossteeth110 are urged by theteeth110 out of the plane of precursorfibrous structure28 and are stretched, pulled, and/or plastically deformed in the z-axis, resulting in formation of thetuft12. Fibers that are predominantly oriented generally parallel in the machine direction of precursorfibrous structure28 as shown inFIG. 2, are simply spread apart byteeth110 and remain substantially in the non-tufted region of thefibrous structure10. The number, spacing, and size of tufts can be varied by changing the number, spacing, and size ofteeth110 and making corresponding dimensional changes as necessary to roll104 and/orroll102. This variation, together with the variation possible in precursorfibrous structures28 and line speeds, permits many varied fibrous structures to be made for many purposes. For example, a fibrous structure made from a high basis weight textile fabric having MD and CD woven extensible threads could be made into a soft, porous ground covering, such as a cow carpet useful for reducing udder and teat problems in cows. A fibrous structure made from a relatively low basis weight nonwoven web of extensible spunbond polymer fibers could be used as a terry cloth-like fabric for semi-durable or durable clothing.

FIG. 3 shows in cross section a portion of the intermeshing rolls102 and104 includingridges106 andteeth110. As shownteeth110 have a tooth height TH (note that TH can also be applied toridge106 height; in a preferred example tooth height and ridge height are equal), and a tooth-to-tooth spacing (or ridge-to-ridge spacing) referred to as the pitch P. As shown, depth of engagement E is a measure of the level of intermeshing of

rolls

102 and104 and is measured from tip ofridge106 to tip oftooth110. The depth of engagement E, tooth height TH, and pitch P can be varied as desired depending on the properties of the precursor web and the desired characteristics of fibrous structure. Also, the greater the density of the tufted regions desired (tufted regions per unit area of fibrous structure), the smaller the pitch should be, and the smaller the tooth length TL and tooth distance TD should be, as described below.

FIG. 4 shows one example of aroll104 having a plurality ofteeth110 useful for making a fibrous structure of the present invention having a basis weight of between about 15 gsm and 100 gsm and/or from about 25 gsm to about 90 gsm and/or from about 30 gsm to about 90 gsm. In one example, the resulting fibrous structure exhibits a basis weight of from about 15 gsm to about 50 gsm and/or from about 15 gsm to about 40 gsm. An enlarged view ofteeth110 shown inFIG. 4 is shown inFIG. 5. In this example ofroll104

teeth

110 have a uniform circumferential length dimension TL of about 1.25 mm measured generally from the leading edge LE to the trailing edge TE at the tooth tip111, and are uniformly spaced from one another circumferentially by a distance TD of about 1.5 mm. For making a fibrous structure from a precursor web having a basis weight in the range of about 15 gsm to 100 gsm,teeth110 ofroll104 can have a length TL ranging from about 0.5 mm to about 3 mm and a spacing TD from about 0.5 mm to about 3 mm, a tooth height TH ranging from about 0.5 mm to about 10 mm, and a pitch P between about 1 mm (0.040 inches) and 2.54 mm (0.100 inches). Depth of engagement E can be from about 0.5 mm to about 5 mm (up to a maximum approaching the tooth height TH). Of course, E, P, TH, TD and TL can each be varied independently of each other to achieve a desired size, spacing, and area density of tufts (number of tufts per unit area of fibrous structure).

As shown inFIG. 5, eachtooth110 has a tip111, a leading edge LE and a trailing edge TE. The tooth tip111 is elongated and has a generally longitudinal orientation, corresponding to the longitudinal axes L of tufted regions. It is believed that to get the tufts of the fibrous structure that can be described as being terry cloth-like, the LE and TE should be very nearly orthogonal to the localperipheral surface120 ofroll104. As well, the transition from the tip111 and the LE or TE should be a sharp angle, such as a right angle, having a sufficiently small radius of curvature such that, in use theteeth110 push through precursor web at the LE and TE. Without being bound by theory, it is believed that having relatively sharply angled tip transitions between the tip oftooth110 and the LE and TE permits theteeth110 to punch through precursor web “cleanly”, that is, locally and distinctly, so that the resulting fibrous structure can be described as “tufted” in tufted regions rather than “embossed” for example. When so processed, the fibrous structure is not imparted with any particular elasticity, beyond what the precursor web may have possessed originally.

Although the fibrous structure of the present invention is disclosed in preferred examples as a single ply fibrous structure made from a single ply precursor web, it is not necessary that it be so. For example, a laminate or composite precursor web having two or more plies can be used so long as one of the plies is a fibrous structure according to the present invention. In general, the above description for the fibrous structure holds, recognizing that tufted, aligned fibers, for example, formed from a laminate precursor web would be comprised of fibers from both (or all) plies of the laminate. In such a fibrous structure, it is important, therefore, that all the fibers of all the plies have sufficient diameter, elongation characteristics, and fiber mobility, so as not to break prior to extension and tufting. In this manner, fibers from all the plies of the laminate may contribute to the tufts. In a multi-ply fibrous structure, the fibers of the different plies may be mixed or intermingled in the tuft and/or tufted regions. The fibers may not protrude through but combine with the fibers in an adjacent ply.

Multi-ply fibrous structures can have significant advantages over single ply fibrous structures. For example, a tuft from a multi-ply fibrous structure made of two or more precursor plies is shown schematically inFIGS. 6-7. As shown inFIG. 6, the multi-plyfibrous structure10′ comprises ply28′ and ply28″.Ply28″ is a precursor ply in accordance with the present invention.Ply28″ comprises atuft12 comprising a non-extensible material. Thetuft12 protrudes throughprecursor web28′.

As shown inFIG. 7, the multi-plyfibrous structure10′ comprises three plies,28′,28″,28′″. One or bothplies28′ and28′″ may be a precursor ply in accordance with the present invention.Plies28′ and28′″ contribute material, such as fibers, to formtuft12, which comprises a non-extensible material, in a “nested” relationship that “locks” the two precursor plies together, forming a laminate fibrous structure without the use or need of adhesives or thermal bonding or ultrasonic bonding or hydroentangling between the plies. However, if desired an adhesive, chemical bonding, resin or powder bonding, or thermal bonding or ultrasonic bonding or hydroentangling and combinations thereof between the plies can be selectively utilized to certain regions or all of the precursor plies. In addition, the multiple plies may be bonded during processing by any suitable bonding method by applying an adhesive or by thermal bonding without the addition of a separate adhesive. Also, bonding may be achieved by physically subjecting the two plies to the tuft generating process such that tufts, especially tufts from at least one ply protrude through the other ply. In one example, thetuft12 retains the ply relationship of the laminate precursor web, as shown inFIG. 7, wherein the upper ply (specifically ply28′ inFIG. 7, remains substantially intact. As shown, thetuft12 protrudes throughprecursor web28″ and only into theprecursor web28′ (not throughprecursor web28′).

In a multi-ply fibrous structure, for example10′ inFIGS. 6-7, each precursor ply can have different properties. For example, as shown inFIGS. 6-7, multi-plyfibrous structures10′ can comprise two (or more) precursor fibrous structures (at least one of the precursor fibrous structures is a fibrous structure according to the present invention), e.g., first andsecond precursor webs28′ and28″.

In the multi-ply fibrous structures examples illustrated inFIGS. 6-7, the formation of thetufts12 results in adiscontinuity22 on thenon-tufted surface24 and anopen void area20.

The fibrous structures of the present invention, addition to being used as web products, may also be used for a wide variety of other applications. Nonlimiting examples of such other applications include various filter sheets such as air filter, bag filter, liquid filter, vacuum filter, water drain filter, and bacterial shielding filter; sheets for various electric appliances such as capacitor separator paper, and floppy disk packaging material; beach mat; various industrial sheets such as tacky adhesive tape base cloth, oil absorbing material, and paper felt; various wiper sheets such as wipers for homes, services and medical treatment, printing roll wiper, wiper for cleaning copying machine, and wiper for optical systems; hygiene or personal cleansing wiper such as baby wipes, feminine wipes, facial wipes, or body wipes, various medicinal and sanitary sheets, such as surgical gown, gown, covering cloth, cap, mask, sheet, towel, gauze, base cloth for cataplasm, diaper, diaper core, diaper acquisition layer, diaper liner, diaper cover, base cloth for adhesive plaster, wet towel, and tissue; various sheets for clothes, such as padding cloth, pad, jumper liner, and disposable underwear; various life material sheets such as base cloth for artificial leather and synthetic leather, table top, wall paper, shoji-gami (paper for paper screen), blind, calendar, wrapping, and packages for drying agents, shopping bag, suit cover, and pillow cover; various agricultural sheets, such as cow carpets, cooling and sun light-shielding cloth, lining curtain, sheet for overall covering, light-shielding sheet and grass preventing sheet, wrapping materials of pesticides, underlining paper of pots for seeding growth; various protection sheets such as fume prevention mask and dust prevention mask, laboratory gown, and dust preventive clothes; various sheets for civil engineering building, such as house wrap, drain material, filtering medium, separation material, overlay, roofing, tuft and carpet base cloth, wall interior material, soundproof or vibration reducing sheet, and curing sheet; and various automobile interior sheets, such as floor mat and trunk mat, molded ceiling material, head rest, and lining cloth, in addition to a separator sheet in alkaline batteries.

Another advantage of the process described to produce the fibrous structures of the present invention is that the fibrous structures can be produced in-line with other fibrous structure production equipment. Additionally, there may be other solid state formation processes that can be used either prior to or after the process of the present invention. Nonlimiting examples of suitable solid state formation processes include printing, embossing, laminating, slitting, perforating, cutting edges, stacking, folding, mechanical softening, and the like.

As can be understood from the above description of the fibrous structures and methods for making such fibrous structure of the present invention, many various fibrous structures can be made without departing from the scope of the present invention as claimed in the appended claims. For example, fibrous structures can be coated or treated with lotions, medicaments, cleaning fluids, anti-bacterial solutions, emulsions, fragrances, surfactants.

EXAMPLESExample 1

A fibrous structure in accordance with the present invention is made on a pilot wet-laid papermaking machine. A homogeneous blend of 70% NSK fibers, 20% Eucalyptus fibers and 10% Co-PET/PET (sheath/core) staple fibers is used to make the fibrous structure. 25#/ton of Kymene (permanent wet strength agent), 6#/ton carboxymethylcellulose and 4#/ton of DTDMAMS is mixed into the fiber slurry. The fibrous structure is formed on a three-dimensional molded through-air-dried belt. The papermaking machine is run at 3% wet microcontraction (i.e., a papermaking belt that transfers the web to a through-air-dried fabric is running faster than the through-air-dried fabric) and 20% crepe off a Yankee dryer. The fibrous structure is then passed through a tuft generating operation wherein the tuft generating roll has a depth of engagement of about 0.042″. Two plies of the fibrous structures comprising tufts are combined using an embossing process. The resulting fibrous structure is a non-extensible tufted fibrous structure wherein the tuft comprises a non-extensible material. The stretch of the fibrous structure according to the Short Span Tensile Test Method is 227%.

Example 2

A fibrous structure in accordance with the present invention is made on a pilot wet-laid papermaking machine. A homogeneous blend of 75% NSK fibers and 25% SSK fibers is used to make the fibrous structure. 25#/ton of Kymene (permanent wet strength agent), 6#/ton carboxymethylcellulose and 4#/ton of DTDMAMS is mixed into the fiber slurry. The fibrous structure is formed on a three-dimensional molded through-air-dried belt. The papermaking machine is run at 3% wet microcontraction and 20% crepe off a Yankee dryer. The fibrous structure is then passed through a tuft generating operation wherein the tuft generating roll has a depth of engagement of about 0.032″. The resulting fibrous structure is a non-extensible tufted fibrous structure wherein the tuft comprises a non-extensible material. The stretch of the fibrous structure according to the Short Span Tensile Test Method is 230%.

Example 3

A fibrous structure in accordance with the present invention is made on a pilot wet-laid papermaking machine. A homogeneous blend of 70% NSK fibers and 30% SSK fibers is used to make the fibrous structure. 25#/ton of Kymene (permanent wet strength agent), 6#/ton carboxymethylcellulose and 4#/ton of DTDMAMS is mixed into the fiber slurry. The fibrous structure is formed on a three-dimensional molded through-air-dried belt. The papermaking machine is run at 3% wet microcontraction and 10% crepe off a Yankee dryer. The fibrous structure is then passed through a tuft generating operation wherein the tuft generating roll has a depth of engagement of about 0.052″. The resulting fibrous structure is a non-extensible tufted fibrous structure wherein the tuft comprises a non-extensible material. The stretch of the fibrous structure according to the Short Span Tensile Test Method is 230%.

Comparative Example 4

A multi-ply sanitary tissue product comprising a tuft consisting of extensible material is formed by sandwiching between two existing wood pulp fiber fibrous structures a 12 gsm meltblown synthetic bicomponent (80% PET core/20% CoPET sheath) fiber layer. Prior to thermally bonding the multi-ply sanitary tissue product, the multi-ply sanitary tissue product is passed through a tuft generating operation wherein the tuft generating roll has a depth of engagement of about 0.060″. The resulting multi-ply sanitary tissue product is a tufted multi-ply sanitary tissue product wherein the tufts consist of extensible material. The stretch of the multi-ply sanitary tissue product according to the Short Span Tensile Test Method is 1026%.

Comparative Example 5

A multi-ply sanitary tissue product is formed by sandwiching between two existing wood pulp fiber fibrous structures a 6 gsm meltblown synthetic bicomponent (80% PET core/20% CoPET sheath) fiber layer. Prior to thermally bonding the multi-ply sanitary tissue product, the multi-ply sanitary tissue product is then passed through a tuft generating operation wherein the tuft generating roll has a depth of engagement of about 0.060″. The resulting multi-ply sanitary tissue product is a tufted multi-ply sanitary tissue product wherein the tufts consist of extensible material. The stretch of the multi-ply sanitary tissue product according to the Short Span Tensile Test Method is 828%.

Test Methods

Unless otherwise indicated, all tests described herein including those described under the Definitions section and the following test methods are conducted on samples that have been conditioned in a conditioned room at a temperature of 73° F.±4° F. (about 23° C.±2.2° C.) and a relative humidity of 50%±10% for 2 hours prior to the test. Further, all tests are conducted in such conditioned room. Tested samples should be subjected to 73° F.±4° F. (about 23° C.±2.2° C.) and a relative humidity of 50%±10% for 24 hours prior to testing.

Short Span Tensile Test Method

Suitable equipment for this test could include a Thwing Albert EJA or Instron tensile tester. The tester must have modified grips, with rubber pieces added both grips on the edge closest to the corresponding grip. Secondly, the grip must be level to each other and any equipment to load the grips must not interact with the opposing grip. The zero height between the grips is set by bringing the grips together until the first substantial force is measured, the cross hairs are zeroed. The sample gauge length is set by increasing the gap between the grips to the desired distance (0.100 cm). The cross hairs are re-zeroed.

In this test, modified grips are used to pull one inch strips of fibrous structures and/or sanitary tissue products comprising one or more tufts apart at a speed of 2.54 cm/min. The load is captured as the grips are separating until the peak load is reached and then continued until only 2% of the peak load is remaining. The grips were then returned to the initial position or gauge length describe above. Strain at break was determined as the strain at 2% of the peak load after the peak load had been achieved. Four repeats were performed on separate sample pieces and the four results were averaged. The samples tested were 1 inch strips in the machine direction. The samples tested were after the tufting process. If a sample exhibits a stretch according to this test method of less than 800% and/or less than 700% and/or less than 600% and/or less than 500% and/or less than 400% and/or less than 300% to 0%, then the sample is deemed to contain a tuft that comprises a non-extensible material, such as non-extensible fibers.

Effective Caliper Test

Effective caliper of a fibrous structure and/or sanitary tissue product in roll form is determined by the following equation:

EC=(RD²−CD²)/(0.00127×SC×SL)

wherein EC is effective caliper in mils of a single sheet in a wound roll of fibrous structure and/or sanitary tissue product; RD is roll diameter in inches; CD is core diameter in inches; SC is sheet count; and SL is sheet length in inches.

Horizontal Full Sheet (HFS) Absorbency Test:

The Horizontal Full Sheet (HFS) test method determines the amount of distilled water absorbed and retained by the paper of the present invention. This method is performed by first weighing a sample of the paper to be tested (referred to herein as the “Dry Weight of the paper”), then thoroughly wetting the paper, draining the wetted paper in a horizontal position and then reweighing (referred to herein as “Wet Weight of the paper”). The absorptive capacity of the paper is then computed as the amount of water retained in units of grams of water absorbed by the paper. When evaluating different paper samples, the same size of paper is used for all samples tested.

The apparatus for determining the HFS capacity of paper comprises the following: An electronic balance with a sensitivity of at least ±0.01 grams and a minimum capacity of 1200 grams. The balance should be positioned on a balance table and slab to minimize the vibration effects of floor/benchtop weighing. The balance should also have a special balance pan to be able to handle the size of the paper tested (i.e.; a paper sample of about 11 in. (27.9 cm) by 11 in. (27.9 cm)). The balance pan can be made out of a variety of materials. Plexiglass is a common material used.

A sample support rack and sample support cover is also required. Both the rack and cover are comprised of a lightweight metal frame, strung with 0.012 in. (0.305 cm) diameter monofilament so as to form a grid of 0.5 inch squares (1.27 cm²). The size of the support rack and cover is such that the sample size can be conveniently placed between the two.

The HFS test is performed in an environment maintained at 23±1° C. and 50±2% relative humidity. A water reservoir or tub is filled with distilled water at 23±1° C. to a depth of 3 inches (7.6 cm).

The paper to be tested is carefully weighed on the balance to the nearest 0.01 grams. The dry weight of the sample is reported to the nearest 0.01 grams. The empty sample support rack is placed on the balance with the special balance pan described above. The balance is then zeroed (tared). The sample is carefully placed on the sample support rack. The support rack cover is placed on top of the support rack. The sample (now sandwiched between the rack and cover) is submerged in the water reservoir. After the sample has been submerged for 60 seconds, the sample support rack and cover are gently raised out of the reservoir.

The sample, support rack and cover are allowed to drain horizontally for 120±5 seconds, taking care not to excessively shake or vibrate the sample. Next, the rack cover is carefully removed and the wet sample and the support rack are weighed on the previously tared balance. The weight is recorded to the nearest 0.01 g. This is the wet weight of the sample.

The gram per paper sample absorptive capacity of the sample is defined as (Wet Weight of the paper−Dry Weight of the paper).

The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm”.

All documents cited in the Detailed Description of the Invention are, in relevant part, incorporated herein by reference; the citation of any document is not to be construed as an admission that it is prior art with respect to the present invention. To the extent that any meaning or definition of a term in this written document conflicts with any meaning or definition of the term in a document incorporated by reference, the meaning or definition assigned to the term in this written document shall govern.

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.