Nonwoven fibrous structure comprising a multifilament fiber
Fibrous structures including a fiber and/or a multifilament fiber, sanitary tissue products employing such fibrous structures and methods for making such fibrous structures are provided.
This application claims the benefit of U.S. Provisional Application No. 60/817,321 filed Jun. 29, 2006.
FIELD OF THE INVENTIONThe present invention relates to nonwoven fibrous structures, more particularly to nonwoven fibrous structures comprising multifilament fibers, methods for making such fibrous structures and sanitary tissue products employing such fibrous structures.
BACKGROUND OF THE INVENTIONUnlike woven fibrous structure, such as textiles, nonwoven fibrous structures have not employed multifilament fibers. Nonwoven fibrous structures have conventionally been made of monofilament fibers. Wood pulp fibers, staple synthetic fibers, continuous polymeric fibers all have been used in their monofilament form to produce fibrous structures. No multifilament fibers have been used in the past in nonwoven fibrous structures.
Accordingly, there is a need for nonwoven fibrous structures comprising multifilament fibers, methods for making such fibrous structures and sanitary tissue products comprising such fibrous structures.
SUMMARY OF THE INVENTIONThe present invention fulfills the needs described above by providing a fibrous structure comprising a multifilament fiber, a method for making such a fibrous structure and a sanitary tissue product comprising such a fibrous structure.
In one example of the present invention, a nonwoven fibrous structure comprising a multifilament fiber is provided.
In another example of the present invention, a nonwoven fibrous structure comprising a fiber and/or a multifilament fiber wherein the fiber and/or the multifilament fiber is associated with an ingredient (other than the fiber or multifilament itself) and/or characteristic present in the fibrous structure, is provided.
In yet another example of the present invention, a method for making a nonwoven fibrous structure, the method comprising the steps of incorporating a fiber and/or multifilament fiber into a fibrous structure wherein the fiber and/or multifilament fiber is associated with an ingredient and/or characteristic of the fibrous structure such that a consumer is able to determine by looking at the fiber and/or the multifilament fiber that the fibrous structure and/or sanitary tissue product comprising such fibrous structure contains a certain ingredient and/or exhibits a certain characteristic, is provided.
In another example of the present invention, a method for making a nonwoven fibrous structure comprising a multifilament fiber, wherein the method comprises forming a nonwoven fibrous structure from a fibrous slurry and/or fibrous composition comprising a multifilament fiber, is provided.
A fibrous slurry as used herein means a mixture of multifilaments and/or monofilaments. Such mixtures of multifilaments and/or monofilaments may be used in wet laid process or an air laid process
In yet another example of the present invention, a single- or multi-ply sanitary tissue product comprising a nonwoven fibrous structure according to the present invention, is provided.
Accordingly, the present invention provides nonwoven fibrous structures comprising a multifilament fiber, methods for making such a fibrous structure, and sanitary tissue products comprising such a fibrous structure.
“Multifilament fiber” as used herein means a fiber that comprises two or more monofilaments that are substantially unbonded, but physically associated with one another to form a unitary structure. Nonlimiting examples of suitable multifilament fibers may be derived from yarns (continuous strands of twisted monofilaments) or from tow (an untwisted bundle of continuous filaments) most preferably by cutting such yarns or tow into papermaking length. The dispersion energy from the papermaking operation is insufficient to separate the multifilament fibers. Groups of fibers with substantial bonding among the filaments, including but not limited to such as nits, shives, and flakes, are not multifilament fibers but rather are termed herein “bonded-multifilament fibers”.
The multifilament fiber may exhibit a length of at least about 1 mm. The multifilament fiber may exhibit any shape, for example it may be substantially cylindrical in shape. The multifilament fiber may exhibit an average effective diameter that is at least 1.2 times and/or at least 1.4 times and/or at least 1.5 times and/or at least 2 times and/or at least 10 times the average effective diameter of any monofilaments within a fibrous structure. Effective diameter means the calculated diameter based on the diameter of a circle having the same area as the area of the filament or multifilament in question. In one example, the multifilament fiber exhibits a length of less than about 12.70 cm (5 inches) and/or less than about 10.16 cm (4 inches) and/or less than about 7.62 cm (3 inches) and/or less than about 5.08 cm (2 inches) and/or less than about 2.54 cm (1 inch).
In one example, the multifilament fiber of the present invention exhibits an average effective diameter of at least about 30 microns and/or at least about 100 microns and/or at least about 500 microns.
The multifilament fibers of the present invention may comprise natural fibers, non-naturally occurring fibers, such as spun cellulose fibers and/or spun starch fibers, and/or other synthetic fibers, such as polymeric fibers including but not limited to nylon fibers, polyester fibers, polyolefin fibers and combinations thereof.
In one example, at least one type of multifilament fiber of the present invention is different in color than the other types of multifilament fibers and the monofilament fibers comprising the fibrous structure of the present invention. Preferably the color difference is sufficient to render the multifilament fiber visually discernible.
As shown in
A multifilament fiber may be a bonded multifilament fiber and/or a non-bonded multifilament fiber.
“Bonded multifilament fiber” is an assembly of monofilaments that are physically attached to one another directly or indirectly (such as via a bonding agent), to form a bonded multifilament fiber. Nonlimiting examples of bonded multifilament fibers include flakes, nit and shives.
“Non-bonded multifilament fiber” is an assembly of monofilaments that are in contact with one another at least one point along their lengths but are not physically attached to one another. Nonlimiting examples of non-bonded multifilament fibers include yarn (monofilaments twisted about one another along their lengths) and tow (monofilaments not twisted about one another along their lengths).
In one example, the multifilament fibers of the present invention are used in the fibrous structures of the present invention in the form of cut yarn and/or cut tow that exhibit suitable lengths for inclusion in the fibrous structures of the present invention.
“Monofilament Fiber” as used herein means an elongate particulate having an apparent length greatly exceeding its apparent width, i.e. a length to diameter ratio of at least about 10. More specifically, as used herein, “fiber” refers to papermaking fibers. The present invention contemplates the use of a variety of papermaking fibers, such as, for example, natural fibers or synthetic fibers, or any other suitable fibers, and any combination thereof. Papermaking fibers useful in the present invention include cellulosic fibers commonly known as wood pulp fibers. Applicable wood pulps include chemical pulps, such as Kraft, sulfite, and sulfate pulps, as well as mechanical pulps including, for example, groundwood, thermomechanical pulp and chemically modified thermomechanical pulp. 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 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.
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 and/or non-naturally occurring fibers, such as polymeric fibers, can also be used. Elastomeric polymers, polypropylene, polyethylene, polyester, polyolefin, and nylon, can be used. The polymeric fibers can be produced by spunbond processes, meltblown processes, and other 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 multifilament fibers. In one example, a fibrous structure according to the present invention means an orderly arrangement of multifilament fibers alone or in combination with monofilament 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.
“Nonwoven” or “Nonwoven fibrous structure” as used herein means a web that is produced by a process other than knitting or some other woven process. A nonwoven fibrous structure is a web that comprises a plurality of fiber and/or monofilaments and/or multi-filaments that is produced by a process other than knitting or some other woven process.
Nonlimiting examples of processes for making nonwoven 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.
In one example, the sanitary tissue product of the present invention comprises a fibrous structure according to the present invention.
“Basis Weight” as used herein is the weight per unit area of a sample reported in lbs/3000 ft2 or 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/m2) is calculated by dividing the average weight (g) by the average area of the samples (m2).
“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 StructureThe fibrous structures of the present invention comprise one or more fibers and/or one or more multifilament fibers.
When present, the fibrous structure may comprise at least about 0.1% by weight, on a dry fibrous structure basis of a multifilament fiber. In one example, the fibrous structure may comprise at least about 0.1% and/or at least about 0.2% and/or at least about 0.4% and/or at least about 1% to about 25% and/or to about 10% and/or to about 5% and/or to about 2.5% by weight, on a dry fibrous structure basis of a multifilament fiber.
In addition to the multifilament fiber, the fibrous structures of the present invention may comprise one or more monofilament fibers. In addition to the multifilament fiber and monofilament fibers, if any, the 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 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 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 fibrous structure basis.
The fibrous structures of the present invention may be of any type, including but not limited to, conventionally felt-pressed fibrous structures; pattern densified fibrous structures; and high-bulk, uncompacted fibrous structures. The fibrous structures may be creped or uncreped and/or through-dried or conventionally dried. The sanitary tissue products made therefrom may be of a single-ply or multi-ply construction.
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/m2 to about 120 g/m2 and/or from about 14 g/m2 to about 80 g/m2 and/or from about 20 g/m2 to 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.
As shown in
In one example, a multifilament fiber 10 can be used within a fibrous structure 20 to convey to a consumer of the fibrous structure 20 and/or sanitary tissue product comprising such fibrous structure 20 that the fibrous structure 20 exhibits a certain property or characteristic. In other words, the multifilament fiber 10 may function as a visual cue to inform a consumer that the fibrous structure contains or does not contain a particular ingredient (other than the fact that a multifilament fiber is present) and/or that the fibrous structure exhibits a certain property/characteristic such as softness.
In another example, a fibrous structure may comprise a fiber that provides a visual cue that is associated with the presence of a certain ingredient (other than the fact that a certain fiber is present) and/or characteristic (i.e., certain property) is provided. The fiber may be noticeable to a consumer of the fibrous structure by being colored, of a different size, of a different shape, of a different length, different texture from other fibers within the fibrous structure.
In one example, the fibrous structure of the present invention is a nonwoven fibrous structure.
Method for Making a Fibrous StructureA fibrous structure comprising a multifilament fiber may be made by any suitable method known in the art. In one example, a method for making a fibrous structure comprising a multifilament fiber comprises the step of forming a fibrous slurry and/or fibrous composition comprising a multifilament fiber and depositing the fibrous slurry and/or fibrous composition onto a forming belt such that a fibrous structure is formed.
NONLIMITING EXAMPLES Example 1This Example illustrates a process for making a multi-ply sanitary tissue product (i.e., a bathroom tissue) according to the present invention using a through-air dried process.
An aqueous slurry of Northern Softwood Kraft (NSK) of about 3% consistency is made up using a conventional pulper and is passed through a stock pipe toward the headbox of the Fourdrinier. A dispersion of Parez 750C (available from Kemira Corporation of Kennesaw, Ga.) wet strength resin about 1% in concentration is mixed with this stock in an amount sufficient to deliver a total of about 3 lb of resin per ton of finished paper product. Distribution of the Parez 750C is aided by an in-line mixer. This wet strength resin treated stock is diluted at the inlet of a first fan-pump with recycled white water to a consistency of about 0.2%.
An aqueous slurry of acacia fibers (from Riau Andalan—Indonesia) of about 3% by weight is made up using a conventional repulper. After the acacia fibers are added to the pulper, green cotton thread (spun cotton of 2 ply of 120×120 denier) cut to a length of ¼″ is added to the pulper in an amount to equal to about 1% of the final sheet weight. The pulping intensity is controlled to fibrillate the multifilament threads at the ends, but leaving the majority of the filament shaft intact. The frayed ends will add to the attractiveness of the finished product as well as improve the anchoring of the multifilaments in the structure. The acacia & cotton thread slurry passes to the second fan pump where it is diluted with white water to a consistency of about 0.2%.
The slurries of NSK and acacia/thread are directed into a multi-channeled headbox suitably equipped with layering leaves to maintain the streams as separate layers until discharged onto a traveling Fourdrinier wire. A three-chambered headbox is used. The acacia/thread slurry containing 70% of the dry weight of the ultimate paper is directed to the chambers leading to the two outer layers while the NSK slurry comprising 30% of the dry weight of the ultimate paper is directed to the chamber leading to the center layer. The NSK and acacia/thread slurries are combined at the discharge of the headbox into a composite slurry.
The composite slurry is discharged onto the traveling Fourdrinier wire and is dewatered assisted by a deflector and vacuum boxes. The embryonic wet web is transferred from the Fourdrinier wire, at a fiber consistency of about 17% by weight at the point of transfer, to a patterned drying fabric. The drying fabric is designed to yield a pattern-densified tissue with discontinuous low-density deflected areas arranged within a continuous network of high density (knuckle) areas. This drying fabric is formed by casting an impervious resin surface onto a fiber mesh supporting fabric. The supporting fabric is a 48×52 filament, dual layer mesh. The thickness of the resin cast is about 12 mil above the supporting fabric. The knuckle area is about 40% and the open cells remain at a frequency of about 400 per square inch. The open cells are generally elliptical in shape with the longer direction disposed in the machine direction and having an aspect ratio of 0.866.
Further de-watering is accomplished by vacuum assisted drainage until the web has a fiber consistency of about 22% by weight. While remaining in contact with the patterned forming fabric, the patterned web is pre-dried by air blow-through pre-dryer to a fiber consistency of about 58% by weight.
The semi-dry web is then adhered to the surface of a Yankee dryer with a sprayed creping adhesive comprising a 0.250% aqueous solution of polyvinyl alcohol. The creping adhesive is delivered to the Yankee surface at a rate of 0.1% adhesive solids based on the dry weight of the web.
The fiber consistency is increased to about 98% before the is dry creped from the Yankee with a doctor blade. The doctor blade has a bevel angle of about 20° and is positioned with respect to the Yankee dryer to provide an impact angle of about 76°. The Yankee dryer is operated at a temperature of about 350° F. (177° C.) and a speed of about 800 fpm (feet per minute) (about 244 meters per minute). The paper is wound in a roll using a surface driven reel drum having a surface speed of about 680 fpm (about 207 meters per minute), thus resulting in a crepe of about 15%.
After the doctor blade, the web is calendered across all its width with a steel to rubber calendar roll to achieve the caliper desired in the product. Resulting fibrous structure has a basis weight of about 20 g/m2; a 1-ply total dry tensile between 250 and about 300 g/in, a 1-ply initial total wet tensile between about 30 and about 35 g/in and a 1-ply caliper of about 0.018 inches. Resulting fibrous structure is then plied together with a like sheet to form a two-ply, creped, pattern densified fibrous structure so that the Yankee-contacting surface, which is the flatter surface, of each ply faces inward while the non-Yankee contacting surface face outward. The plies are minimally tacked together using about ½″ wide stripe of hot melt adhesive to prevent the plies from easily separating. The resulting two-ply fibrous structure has a) a total basis weight of about 40 g/m2 and a caliper of about 0.028 inches.
The cotton threads provide an attractive and prominent visual signal to consumers that a certain ingredient (not merely that a cotton thread is present) and/or a certain property is present in the fibrous structure.
Example 2Example 1 is repeated except that the chopped cotton thread is replaced with denim pulp. The denim pulp is made from recovered scraps from the manufacture of clothing articles such as jeans using denim fabric. It is processed by an entirely mechanical process using a refiner until the fibers are chopped to satisfactory papermaking lengths. Some of the denim filaments retain their multifilament character. The denim pulp is added to the pulper with the acacia fibers. Otherwise the practice of Example 1 is repeated. The denim pulp multifilaments provide an attractive and prominent visual signal to consumers that a certain ingredient (not merely that a denim pulp multifilament is present) and/or a certain property is present in the fibrous structure.
Example 3Example 1 is repeated except that the chopped cotton thread is replaced with green dyed polyester tow. The tow is 200 ends of 2 dpf polyester chopped to. Some of the tow bundles their multifilament character. The denim pulp is added to the pulper with the acacia fibers and the time and intensity of the pulping is moderated so that most of the tow bundles retain a multifilament character. The ends of the chopped tow segments tend to feather outward creating a sheave appearance. This adds to their appearance in the finished product as well as helping to anchor the tow in the fibrous structure. Otherwise the practice of Example 1 is repeated. The polyester tow multifilaments provide an attractive and prominent visual signal to consumers that a certain ingredient (not merely that a polyester tow multifilament is present) and/or a certain property is present in the fibrous structure.
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.
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”.
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.
Claims
1. A nonwoven fibrous structure comprising a multifilament fiber.
2. The fibrous structure according to claim 1 wherein the multifilament fiber is selected from the group consisting of: twisted multifilaments, tow multifilaments and mixtures thereof.
3. The fibrous structure according to claim 1 wherein the multifilament fiber comprises two or more monofilaments.
4. The fibrous structure according to claim 3 wherein the monofilaments are selected from the group consisting of natural fibers, non-naturally occurring fibers and mixtures thereof.
5. The fibrous structure according to claim 3 wherein the multifilament fiber exhibits an average fiber diameter of at least about 1.2 times the average fiber diameter of the largest average fiber diameter monofilament present in the fibrous structure.
6. The fibrous structure according to claim 1 wherein the multifilament fiber exhibits an average effective fiber diameter of at least about 30 microns.
7. The fibrous structure according to claim 1 wherein the multifilament fiber is associated with an ingredient and/or characteristic of the fibrous structure.
8. A single- or multi-ply sanitary tissue product comprising a fibrous structure according to claim 1.
9. A method for making a fibrous structure according to claim 1, the method comprising the step of depositing a fibrous slurry comprising a multifilament fiber on a forming belt such that the fibrous structure is formed.
10. A method for making a nonwoven fibrous structure according to claim 7, the method comprising the steps of incorporating a multifilament fiber into a fibrous structure wherein the multifilament fiber is associated with an ingredient and/or characteristic of the fibrous structure such that a consumer is able to determine by looking at the multifilament fiber that the fibrous structure and/or sanitary tissue product comprising such fibrous structure contains a certain ingredient and/or exhibits a certain characteristic.
11. A nonwoven fibrous structure comprising a fiber wherein the fiber is associated with an ingredient and/or characteristic of the fibrous structure.
12. A method for making a nonwoven fibrous structure according to claim 11, the method comprising the steps of incorporating a fiber into a fibrous structure wherein the fiber is associated with an ingredient and/or characteristic of the fibrous structure such that a consumer is able to determine by looking at the fiber that the fibrous structure and/or sanitary tissue product comprising such fibrous structure contains a certain ingredient and/or exhibits a certain characteristic.
Type: Application
Filed: Jun 20, 2007
Publication Date: Jan 3, 2008
Inventors: Kenneth Douglas Vinson (Toone, TN), Arnold William Trueman (Cedar Grove, TN)
Application Number: 11/820,511
International Classification: D04H 1/00 (20060101);
