Textile structure product comprising layers each having different levels of cellulose nanoparticles

Abstract

A fibrous structure is disclosed having at least two layers. Each of the at least two layers comprises a blend of structural fibers selected from the group consisting of softwood fibers, non-wood fibers, natural non-cellulose fibers, man-made cellulose or non-cellulose fibers, hardwood fibers, recycled fibers, and mixtures thereof. Each of the at least two layers is arranged in a facing relationship. The second layer of the at least two layers comprises about 0.05 weight percent to about 20 weight percent cellulose nanoparticles of the second layer.

Description

[Technical Field]

[0001] The present disclosure relates to a paper web product containing cellulose nanoparticles. More specifically, the product is a layered paper fiber structure in which the layers have non-uniform levels of cellulose nanoparticles. The use of selected non-uniform levels of cellulose nanoparticles provides product designers with additional flexibility in optimizing the user performance benefits of the manufactured product. [Background technology]

[0002] Paper products such as fine paper, printing paper, paperboard, cement / fiber composites, decorative paper, paper towels, bath tissue, napkins, and other similar products are designed to balance several important properties specific to each product type. For example, tissue products should have good bulk, good absorbency, a soft feel, and good strength and durability. In another example, fine printing paper should have high smoothness, optimal whiteness, and good printability / ink retention.

[0003] Unfortunately, the balance of performance properties is generally contained within a limited formulation space or box. Within a product type, when steps are taken to increase one property of the product, other properties of the product are often adversely affected. For example, product designers of tissue products have long attempted to balance lower levels of softwood fibers in their paper structures while attempting to obtain sufficient strength, while at the same time minimizing the adverse effects on softness, sheet bulk, or absorbency that typically result from the refining of higher levels of these softwood fibers.

[0004] In another example, in multi-use fibrous sheets, particularly those used for paper toweling, napkins, and handkerchiefs, increased softwood content, increased refining, and cationic / anionic polymer additions have been required to achieve strength targets required for durability requirements, however, all of these effects can adversely affect sheet feel and product absorbency.

[0005] In yet another example, printing papers used for commercial or office printing or personal handwriting still need increased strength without a corresponding decrease in ink penetration / absorbency. This need increases as environmental benefits drive higher percentages of recycled pulp and / or higher levels of filler in fine paper products. Higher percentages of recycled pulp, especially repeatedly recycled pulp, result in fiber degradation and, as a result, lower strength and quality of the resulting paper product. Traditionally, this strength loss has been compensated for by significantly increasing synthetic strength additives and resins, which in turn often results in lower ink absorption in the product. Similarly, higher levels of filler have also been compensated for by significantly increasing synthetic strength additives and / or increased refining levels, which in turn often results in a paper structure with lower bulk and / or lower performance, with increased print pick-up.

[0006] There remains a continuing, and in fact growing, need to be able to develop printing paper products that have high strength and impermeability while maintaining cost and ink absorbency.

[0007] In other paper segments, there is also a need for more environmentally friendly and compostable barrier properties. Today, these barrier properties can only be achieved using chemical and other non-organic barrier coatings. The targeted use of cellulose nanoparticles within specific product layers can create structures that meet product needs while using a higher percentage of recyclable, compostable, and natural materials.

[0008] Similarly, paperboard products are also being affected by increased levels of recycled pulp. For example, board products used for food storage may experience a decrease in strength if the fibers are less strong, but may also result in greater permeability of the paper structure. This increased packaging permeability may result in a decrease in the antimicrobial protection of the product, resulting in a shorter product shelf life. Traditionally, this is compensated for by increasing the use of expensive synthetic additives or by thicker, less permeable plastic coatings, which hinder recyclability and compostability.

[0009] Thus, there remains a need for novel fibrous structures that further optimize the physical product performance of textiles without sacrificing other performance properties such as softness, permeability, printability, ink absorption, barrier properties, absorbency, and paper machine / nonwoven machine reliability. Those skilled in the art will recognize that all fibrous sheet making processes can benefit from the selective addition of cellulose nanoparticles; non-limiting examples of such structures are structures and products made on conventional papermaking assets, conventional dry creped tissue machines, differential density or structured tissue papermaking processes, and air-laid papermachine assets. Summary of the Invention

[0010] The present disclosure provides a fibrous structure comprising at least two layers. Each of the at least two layers comprises a blend of structural fibers selected from the group consisting of softwood fibers, non-wood fibers, natural non-cellulose fibers, man-made cellulose or non-cellulose fibers, hardwood fibers, recycled fibers, and mixtures thereof. Each of the at least two layers is arranged in a facing relationship. The second of the at least two layers comprises cellulose nanoparticles in an amount of about 0.05 weight percent to about 20 weight percent of the second layer.

[0011] The present disclosure also provides a fibrous structure having a surface layer comprising high aspect ratio nanofilaments.

[0012] The present disclosure further provides a fibrous structure comprising at least two plies arranged in contact with each other in a facing relationship, each ply having a longitudinal grain and a transverse, coplanar longitudinal grain. Each of the at least two plies comprises a blend of structural fibers selected from the group consisting of softwood fibers, non-wood fibers, natural non-cellulose fibers, man-made cellulose or non-cellulose fibers, hardwood fibers, recycled fibers, and mixtures thereof. A first ply of the at least two plies comprises a first layer comprising about 0.05 weight percent to about 20 weight percent cellulose nanoparticles of the first layer. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is an illustrative cross-sectional view of a two-layer embodiment of a fibrous substrate of the present disclosure. FIG. [Figure 2] FIG. 2 is an illustrative cross-sectional view of a three-layer embodiment of a fibrous substrate according to the present disclosure, wherein the outer layer of the substrate comprises cellulose nanoparticles. [Figure 3] FIG. 2 is an illustrative cross-sectional view of a three-layer embodiment of a fibrous substrate according to the present disclosure, wherein the inner layer of the substrate comprises cellulose nanoparticles. [Figure 4] 1 is an illustrative cross-sectional view of a two-layer embodiment of a fibrous substrate fabricated on the illustrated forming wire according to the present disclosure, in which the first layer comprising cellulose nanoparticles is the layer formed on the forming wire surface. [Figure 5] 1 is an illustrative cross-sectional view of a two-layer embodiment of a fibrous substrate fabricated on an illustrated forming wire according to the present disclosure, in which the first layer comprising cellulose nanoparticles is a layer formed without contact with the forming wire. [Figure 6] 1 is an illustrative cross-sectional view of a two-layer embodiment of a fibrous substrate made with a process including two parallel forming wires according to the present disclosure. FIG. [Figure 7] FIG. 1 is an illustrative cross-sectional view of a two-layer embodiment of a fibrous substrate according to the present disclosure, in which the first layer comprising high aspect ratio cellulose nanofilaments is the concentrated layer and therefore the thinner layer. [Figure 8]1 is an illustrative cross-sectional view of a three-layer embodiment of a fibrous substrate fabricated on the forming wire shown in accordance with the present disclosure, in which a first layer comprising cellulose nanoparticles is the layer formed on the forming wire surface. [Figure 9] 1 is an illustrative cross-sectional view of a three-layer embodiment of a fibrous substrate made with a process including two parallel forming wires according to the present disclosure. FIG. [Figure 10] 1 is an illustrative cross-sectional view of a three-layer embodiment of a fibrous substrate according to the present disclosure, in which a first layer comprising cellulose nanoparticles is a concentrated, and therefore thinner, layer and is shown in opposing relationship to the second and third layers of the substrate. [Figure 11] 1 is an exemplary flow diagram of a typical paper machine. [Figure 12] 12A-12E. An illustrative flow diagram of a typical converting operation suitable for combining two separate layered plies of fibrous material. DETAILED DESCRIPTION OF THE INVENTION

[0014] Despite numerous publications on the use of cellulose nanoparticles in fibrous structures, cellulose nanoparticle terminology remains fragmented, and inconsistent terminology is used to describe cellulose particles. The term "cellulose nanoparticles" as used herein refers to cellulose particles with at least one nanoscale dimension. Examples of cellulose nanoparticles include, but are not limited to, microfibrillated cellulose (MFC), nanofibrillated cellulose (NFC), algal cellulose particles (AC), bacterial cellulose particles (BC), and high-aspect-ratio cellulose nanofilaments (CNF).

[0015] The present disclosure relates to a fibrous substrate 100 comprising at least two layers. A first layer 110 and a second layer 120 of the layers are disposed in contact with each other in a face-to-face relationship. Each of the first and second layers is formed from a plurality of overlapping fibers and other components as required for the end use of the particular substrate. The first layer comprises a plurality of cellulose nanoparticles 150. The layers of the paper web substrate 100 are formed from a plurality of overlapping fibers selected from the group consisting of softwood fibers, non-wood fibers, natural non-cellulose fibers, man-made cellulose or non-cellulose fibers, hardwood fibers, and mixtures thereof, fillers, active ingredients, and combinations thereof. Preferably, the first layer of the paper web substrate comprises at least about 0.05 weight percent nanoparticles, and the second layer does not comprise directly added cellulose nanoparticles. In another embodiment, at least two layers each contain cellulose nanoparticles, but the composition of the cellulose nanoparticles in the layers is different, with each layer having at least about 0.05 weight percent cellulose nanoparticles.

[0016] As used herein, "paper web substrate" traditionally refers to any wet-formed or dry-laid fibrous structure product that includes, but is not necessarily, cellulose fibers. Paper web substrate embodiments may include, but are not limited to, tissue products such as sanitary tissue products, toweling products such as absorbent towels, paperboard grades, paper packaging substrates, paper used in high-pressure laminate construction, paper used for printing and writing, and fibrous substrates used in airlaid nonwoven products. Other paper web substrate embodiments contemplated by the present disclosure also include, but are not limited to, embryonic dry webs such as those used in airlaid fabrication processes, which include a loosely bonded, "fluffy" structure of desired fibers.

[0017] "Fiber structure," as used herein, refers to a structure comprising one or more fiber layers. In one example, a fiber structure according to the present disclosure refers to an ordered arrangement of fibers within a structure to perform a function. Non-limiting examples of fibrous structures of the present disclosure may include all forms of paper substrates, nonwoven substrates, and composite materials (including reinforced plastics and reinforced cement).

[0018] As used herein, "converting operations" means additional processing steps in which a fibrous structure is coated, combined, embossed, cut, or otherwise treated to create a product better suited to the task it is designed to perform. These operations may occur either immediately after the web is formed on the paper machine, or after it has been passed through separate processes and machines.

[0019] Non-limiting examples of processes for producing fibrous web structures include the well-known wet-laid and air-laid (also known as nonwoven) papermaking processes. Those skilled in the art will recognize that such processes typically involve preparing a fibrous composition in the form of a suspension in either a wet, more specifically, aqueous, or dry, more specifically, gaseous, i.e., air-based, medium. The aqueous medium used in wet processes is often referred to as a fibrous slurry. The fibrous suspension is then used to deposit a plurality of fibers onto a forming wire or belt to form an initial fibrous structure, after which the fibers are dried and / or bonded to produce the fibrous structure. Further processing of the fibrous structure may be performed to form a final fibrous structure. For example, in papermaking processes, finishing may include localized treatments, either on-line or off-line, to create an intermediate structure, and / or one or more plies may be combined to create a final substrate. In many fibrous web production processes, the final fibrous structure may be wound or sheeted and subsequently converted into a final product through additional "converting operations."

[0020] Figure 11 shows a non-limiting example of a wet paper machine. In a typical paper machine, there are at least five distinct operating sections: The forming section, commonly called the wet end, takes an aqueous solution of fibers and other constituents and creates the embryonic web (in a drylay paper machine, the fibers are dispersed in air before creating the embryonic web). The press section removes a significant amount of residual water through a system of nips formed by rolls pressing against each other, assisted by press felts which support the sheet and absorb the forced out water. The dryer section of a paper machine, as the name suggests, dries the paper, either by a series of internal steam-heated cylinders that evaporate the water, or by other external means that dry the web. (In a dry-type paper machine, the press and dryer sections are replaced by a bonding and curing process, in which heat and / or chemicals are used to treat the web and create the final structure.) The finishing section is where the paper is smoothed and / or coated / treated to provide specific surface or structural changes such as coating, sizing, surface modification, and / or calendering under high load and pressure. In the reeling section, the paper coming out of the paper machine is wound onto spools for further processing.

[0021] There may also be a coating section to modify the surface properties with a coating, a non-limiting example of a coating is kaolin clay.

[0022] The papermaking process can be adapted to allow the addition of any number of specialty materials or chemicals to provide specialized functionality to the finished paper. Sizing agents, such as resins, glues, or starches, can be added to the web to alter the paper's properties by improving its water resistance, reducing its ability to fluff, reducing abrasion, and improving its printability and surface bond strength. These sizing agents may be applied at the wet end (internal sizing), the dry end (surface sizing), or both. At the dry end, sizing is typically applied using a size press. The size press may be a roll applicator (flooded nip) or a nozzle applicator, typically located before the final dryer section. Some papermakers also use a "coater" to apply a coating of pigments, such as calcium carbonate or china clay, suspended in a binder of digested starch and styrene-butadiene latex. The coating creates a very smooth, bright surface with excellent print quality. Some paper machines may also use calendering or supercalendering to enhance surface structure, improve printability, and / or alter sheet stiffness.

[0023] Those skilled in the art will recognize that the process for making fibrous webs is highly adaptable and customizable, allowing for the creation of structures for various end uses by varying either the base materials and / or unit operations to better create the desired structure. A non-limiting example of this customization is the addition of creping blades and larger dryer rolls (Yankees) to some types of tissue machines. Another non-limiting example is the use of dry fiberization (i.e., hammer mills to "fluff" dry fibrous webs) equipment and air delivery systems to create dry / airlaid structures.

[0024] In a traditional papermaking machine's forming section, or wet end, a dilute aqueous mixture of fibers and other product materials is fed to a headbox before being deposited onto the wire. The purpose of the headbox is to create turbulence, prevent fibers from clumping together, and create a material with a uniform basis weight across the papermaking machine. The headbox may contain one or more layers, which may have the same or different aqueous solutions fed to them. From the headbox, the aqueous slurry is deposited onto a moving wire or fabric loop. The slurry is then optionally dewatered to create the desired structure.

[0025] Again, those skilled in the art will recognize that paper machines can be varied depending on the desired paper feed material, basis weight, and sheet construction. One non-limiting example modification is the addition of a second headbox, which is added to the wet end to lay a different fiber blend on top of the partially formed base layer. The secondary headbox is usually located at the point where the base sheet completely drains. It is not considered a separate ply because the action of water works to mix the fibers of the top and bottom layers. Secondary headboxes are common in the production of linerboard.

[0026] Another non-limiting example of a forming / wet end section modification is the addition of a second wire above the drainage table. The bottom and top wires meet, creating some drainage from both sides of the sheet. The top wire improves formation and also provides more drainage, helping the machine increase speed and produce a particular paper grade at an economical rate. Twin-wire machines, or gap formers, use two vertical wires in the forming section, which increases the dewatering rate of the fiber slurry while also providing uniform two-sidedness.

[0027] tissue products "Tissue" or "towel" paper products refer to products made by paper tissue or toweling techniques, including, but not limited to, conventional felt-pressed or conventional wet-pressed tissue, pattern-densified tissue, and through-air-drying paper with or without creping. For example, the papermaking process of the present disclosure can utilize adhesive creping, wet-creping, double creping, embossing, wet-pressing, air-pressing, through-air drying, through-air drying with creping, through-air drying without creping, and other steps in forming a paper web. Some examples of such techniques are disclosed in U.S. Patent Nos. 4,529,480, 5,048,589, 5,399,412, 5,129,988, 5,494,554, 5,607,511, 6,398,916, 7,744,726, and 8,388,803, all of which are incorporated herein in a manner consistent with this disclosure. When forming multi-ply tissue products, the separate plies can be made from the same or different processes, as desired.

[0028] For example, in one embodiment, the tissue web may be a creped through-air-dried web formed using processes known in the art. In other embodiments, the base web is formed by a non-creped through-air-drying process. Related non-creped through-air-drying tissue processes are described, for example, in U.S. Patent Nos. 5,656,132 and 6,017,417, both of which are incorporated herein by reference in a manner consistent with this disclosure.

[0029] Tissue embodiments of fibrous structures according to the present disclosure may be in the form of through-air dried fibrous structures, differential density fibrous structures, differential basis weight fibrous structures, wet-laid fibrous structures, air-laid fibrous structures, creped or uncreped fibrous structures, pattern densified or non-pattern densified fibrous structures, compressed or non-compressed fibrous structures, double recreped fibrous structures, as are known in the art, as exemplified in U.S. Pat. Nos. 3,301,746, 3,974,025, 4,191,609, 4,637,859, 6,398,906, and 8,388,803.

[0030] Airlaid Process "Air-laying" is a well-known process by which fibrous nonwoven layers can be formed. In the air-laying process, individual fibers or bundles of fibers, typically having lengths ranging from about 0.5 to about 52 millimeters (mm), are separated and entrained in an air supply and then deposited onto a forming screen, usually with the assistance of a vacuum. The randomly deposited fibers are then bonded together, for example, using hot air to activate a binder component or latex adhesive. Air-laying is taught, for example, in U.S. Pat. Nos. 4,640,810; 4,494,278; 5,527,171; 4,375,448; or other similar methods. Webs produced by these methods may subsequently be bonded together by heat fusion, latex bonding, or a combination thereof to form webs of sufficient tensile strength, as is well known in the art. The webs produced in this document are best exemplified by, but not limited to, the DANWEB process.

[0031] Airlaid nonwovens are particularly well suited for use as wet wipes. Airlaid nonwovens may have a basis weight ranging from about 30 to about 350 grams per square meter (gsm), with staple fibers of about 0.5 to 10 denier and about 6 to 15 millimeters in length. Wet wipe substrates generally may have a dry fiber density of about 0.025 g / cc to about 0.2 g / cc.

[0032] "Layer," as used herein, means that portion of a ply having some thickness and containing natural or artificial fibers, fillers, and / or other necessary additives. The layers may be supplied from different sources. For example, different furnishes may be supplied from the same or different headboxes to a single ply structure having multiple separate layers of intermingled fibers. Each furnish may contain any combination of natural or synthetic fibers, as discussed above. Also, without wishing to be limited by theory, it is believed that the layers are not completely separate, but rather that there is some intermixing of the components between the different layers at the boundary between the two layers.

[0033] Because the layers are constructed into a single fiber structure, they are arranged in a face-to-face relationship, i.e., each longitudinal x transverse face of one layer is adjacent to the parallel faces of another layer.

[0034] As used herein, a "ply" refers to a fibrous substrate containing one or more layers. The plies may be processed through a conversion process and embossed, laminated, or bonded together to create a final fibrous structure. The fibrous structures of the present disclosure contemplate one or more plies arranged in a facing relationship relative to one another. Specifically, a fibrous structure containing two plies may have a first ply having one or more layers and a second ply having one or more layers, each engaged in a facing relationship. Each ply may be formed from multiple layers, each containing overlapping fibers. However, each ply may contain different components, creating a fibrous structure with a structure including non-uniform layers. The first ply of the at least two plies may contain multiple cellulose nanoparticles and / or other fibers. The second ply of the at least two plies may be essentially nanoparticle-free or may contain the same or a different amount of cellulose nanoparticles as the first ply.

[0035] "Fiber," as used herein, refers to an elongated physical structure whose apparent length significantly exceeds its apparent diameter, i.e., having a length-to-diameter ratio of at least about 10 and less than 200. Fibers having noncircular cross-sections and / or tubular shapes are common; the "diameter" in this case can be considered to be the diameter of a circle having a cross-sectional area equal to that of the fiber. More specifically, as used herein, "fiber" refers to fibers that make up fibrous structures. The present disclosure contemplates the use of various fibrous structure-making fibers (also referred to herein as "structural fibers"), such as, for example, softwood fibers, non-wood fibers, natural non-cellulosic fibers, man-made cellulose or non-cellulosic fibers, hardwood fibers, recycled fibers, or any suitable fibers, and mixtures thereof. The fibers can be natural or man-made fibers, and further, the fibers can be virgin or recycled fibers. Man-made fibers can include both those composed of cellulosic materials and those composed of non-cellulosic materials. These fibers can be created / manufactured by any of the processes known to those skilled in the art. Additionally, fibers contemplated by this disclosure include non-wood fibers, hardwood fibers, softwood fibers, and man-made fibers, recycled fibers, and combinations thereof.

[0036] Recycled fibers may be added to the furnish in any amount. Recycled fibers contemplated in this disclosure include both pre-consumer and post-consumer sources. Any suitable recycled fiber may be used, although recycled fibers having relatively low levels of groundwood pulp may be used.

[0037] The term "cellulose nanoparticles," as used herein, refers to cellulose particles having at least one nanoscale dimension. Cellulose nanoparticles include, but are not limited to, microfibrillated cellulose (MFC), nanofibrillated cellulose (NFC), algal cellulose particles (AC), bacterial cellulose particles (BC), and high-aspect-ratio cellulose nanofilaments (CNF). As used in this disclosure, "cellulose nanoparticles" may be derived from either softwood and / or hardwood and may therefore contain fibrous elements of softwood or hardwood.

[0038] Microfibrillated cellulose (MFC) is defined herein as a fibrous material composed of cellulose fibrils, which are very thin, with diameters of about 5-100 nm, averaging about 20 nm, and fibril lengths of about 20 nm-200 μm, but typically 100 nm-100 μm.

[0039] Nanofibrillated cellulose (NFC) is a specific class of MFC with fiber dimensions at the lower end of the aforementioned fibril size range. In MFC, individual microfibrils are partially or completely separated from one another. Fibers that are fibrillated and have microfibrils on their surface, as well as microfibrils that are separated into the aqueous phase of the slurry, are included in the definition of MFC. The cellulose nanoparticles in this disclosure can be produced by any process known to those skilled in the art. Processes used to create cellulose nanoparticles include, but are not limited to, modified refiners, homogenizers, ultrasonic fiber treatment, and chemical fiber treatment, including enzyme fiber modification.

[0040] The components of microfibrillated cellulose are: [Table 1] See Gary Chinga-Carrasco, “Cellulose fibers, nanofibrils and microfibrils: The morphological sequence of MFC components from a plant physiology and fiber technology point of view,” Table 1, Nanoscale Res Lett. 2011; 6(1): 417, published online June 13, 2011.

[0041] "High aspect ratio cellulose nanofilaments" are another subset of MFCs with unique dimensions. A high aspect ratio means that the fiber length divided by the fiber width is at least about 200 to about 5,000, or about 600 to about 1,000. These cellulose nanofilaments have an average width in the nanometer range, e.g., about 30 nm to about 500 nm, and an average length in the micrometer range or greater, e.g., about 6 μm to about 2.5 mm. Cellulose nanofilaments can have an average thickness in the range of about 20 nm to about 600 nm, or about 30 nm to about 500 nm. Such cellulose nanoparticles can be obtained, for example, by mechanical processes. Exemplary processes are described in U.S. Patent Application Publication Nos. 2013 / 0017394 and 2015 / 0057442.

[0042] Those skilled in the art will recognize that cellulose nanoparticles are difficult to obtain as a homogeneous material or "pure form," and thus nanoparticle materials contain many-fold mixtures of material lengths as a result of the mechanical or chemical processes by which they are produced. For example, exemplary cellulose nanoparticles have at least about 40% by weight, or at least about 75% by weight, or at least about 90% by weight of the cellulose nanoparticles in the purified mixture with an average particle length of greater than 6 μm and a diameter of about 30-500 nm.

[0043] Another anticipated use of cellulose nanoparticles possible with embodiments contemplated by this disclosure is the inclusion of a small percentage of either pure cellulose nanoparticles and / or a mixture of cellulose nanoparticles with other refined products in virgin or recycled pulp streams before transport to the papermaking site. In this way, a virgin fiber source can be enriched through the addition of cellulose nanoparticles, and the cellulose nanoparticles can then be added to the papermaking process without introducing a new fiber input stream. By dosing nanoparticles with cellulose at the pulp manufacturing facility, it would be possible to produce what might be called a "super pulp" with properties only possible with the inclusion of cellulose nanoparticles. Thus, many different methods for adding cellulose nanoparticles are contemplated by this disclosure, including, but not limited to, the direct inclusion of pure cellulose nanoparticles, mixtures of cellulose nanoparticles with other refined by-products having nanoparticle contents greater than 50%, and the inclusion of cellulose nanoparticles in virgin or recycled fibers before inclusion at the paper mill.

[0044] The phrase "fibrillated cellulose fibers," as used herein, refers to cellulose fibers that have undergone a mechanical or chemical treatment during which individual cellulose filaments or bundles of cellulose filaments are liberated from the body of the fiber but remain attached to the fiber at one end, creating a larger bond area and increased fiber-to-fiber contact. The extent of the treatment determines the number of cellulose nanoparticles released from the fiber.

[0045] Algal cellulose particles (AC) are microfibrils extracted from the cell walls of various algae by acid hydrolysis and / or mechanical purification. The resulting microfibrils are micron-long in length and have a high aspect ratio.

[0046] Bacterial cellulose particles (BC) are microfibrils secreted by various bacteria isolated from bacterial bodies and growth media. The resulting microfibrils are micron-long in length and have a high aspect ratio.

[0047] Those skilled in the art will recognize that the fibers of the fibrous structures contemplated in this disclosure can include fibers created from multiple sources and base materials. "Fibrillated man-made non-cellulosic fibers" are contemplated, along with "synthetic polymer fibers" and similar terminology, which refer to non-cellulosic fibers made from synthetic polymers such as polyester, nylon, and polyolefins. Splittable fiber preparation for creating splittable fibers is generally known in the context of thermoplastic fibers, where the fibers have segments formed from different polymers. See U.S. Patent Nos. 5,759,926, 5,895,710, and U.S. Patent Application Publication No. 2003 / 0203695.

[0048] Splittable fibers produced and utilized in connection with the present disclosure may have a split pie shape, an islands-in-the-sea configuration, a side-by-side configuration, a hollow configuration, etc. See U.S. Patent No. 4,735,849 and U.S. Patent Application Publication No. US 2002 / 0168912, Figures 2-9. Splittable fibers are preferably disintegrated prior to incorporation into the furnish, as discussed below.

[0049] During the preparation of some fibers for wet papermaking operations, softwood fiber pulps and some hardwood fiber pulps are optionally subjected to mechanical or chemical processing, whereby the fibers are compressed, subjected to high shear, and / or chemically treated to make them softer and create increased fiber-to-fiber bond areas through fiber fibrillation, fiber swelling, and / or increased fiber flexibility. Those skilled in the art will recognize that the three main products of pulp fiber refining are: 1) a percentage of fibers that are completely unaffected by refining intensity and consistency; 2) a significant percentage of fibers are fibrillated, thereby stripping the fiber cell walls and exposing microfibrils that remain attached to the original fiber; and 3) a percentage of fibers and microfibrils are cut or mechanically broken into very small pieces (<74 microns in length); this fraction is referred to as the fines fraction. These fines can be either primary (those present in natural wood sources) or secondary (those created during the refining process).

[0050] The fibrous substrate 100 of the present disclosure can include at least one layer comprising nanoparticles 150. The second layer 110 can include a plurality of cellulose nanoparticles. This second layer 110 can include at least about 0.05 weight percent of the nanoparticles, or from about 0.05 weight percent to about 20 weight percent, or from about 0.1 weight percent to about 5 weight percent of the nanoparticles.

[0051] The first layer 120 of the at least two layers 120 may be free of cellulose nanoparticles. Specifically, the first layer 120 may not contain directly added cellulose nanoparticles. The first layer 120 may not contain intentionally or deliberately added cellulose nanoparticles. "Intentionally" and / or "intentionally," as used herein, refer to a voluntary, deliberate act with the specific intent of adding cellulose nanoparticles to the first layer 120. Such a first layer 120 free of intentionally added cellulose nanoparticles may be observed in that the first layer 120 may contain less than about 0.50 weight percent, or less than about 0.25 weight percent, or less than about 0.10 weight percent, or less than about 0.05 weight percent cellulose nanoparticles of the first layer 120.

[0052] One skilled in the art can envision that first layer 120 also contains nanoparticles, either at the same or a significantly different loading than second layer 110. Specifically, first layer 120 may contain more or less cellulose nanoparticles, depending on the desired characteristics of the final product. First layer 120 may include more than about 0.05 percent, or more than about 0.10 percent cellulose nanoparticles.

[0053] By layering fibrous structured products to vary the level of cellulose nanoparticle concentration throughout the thickness of the structure, formulation options for achieving higher performance paper products are dramatically expanded.

[0054] "Basis weight" as used herein means lbs / 3000ft 2 or g / m 2 The weight per unit area of ​​the sample is reported in gsm. Fibre web-based tissue embodiments of the present disclosure have a mass of about 5 g / m 2 ~about 150g / m 2 , preferably about 10 g / m 2 ~Approx. 120g / m 2 , more preferably about 20 g / m 2 ~about 100g / m 2The paper embodiment of the fibrous web structure of the present disclosure may exhibit a basis weight of about 25 g / m 2 ~Approx. 350g / m 2 , preferably about 50 g / m 2 ~about 300g / m 2 , more preferably about 75 g / m 2 ~about 250g / m 2 The paperboard embodiment of the fibrous web structure of the present disclosure may exhibit a basis weight of about 300 g / m 2 ~About 1000g / m 2 , preferably about 400 g / m 2 ~about 800g / m 2 , more preferably about 400 g / m 2 ~about 600g / m 2 The amount may be shown.

[0055] The weight is calculated based on a certain area (m 2 ), and weighing the sample(s) of fibrous structure and / or paper product comprising such fibrous structure according to the present disclosure on a top-loading balance with a minimum resolution of 0.01 g. The balance is protected from air currents and other disturbances using a draft shield. The weight is recorded when the balance reading is constant. The average weight (g) and the average area (m) of the sample are then calculated. 2 ) is calculated. 2 ) is the average weight (g) multiplied by the average area (m 2 ) is calculated by dividing by

[0056] FIG. 1 illustrates a cross-sectional view of an exemplary embodiment of a fibrous structure or ply 100 of the present disclosure, including a second layer 110 and a first layer 120. In some embodiments, the second layer 110 may include a specific blend of fibers, fillers, active ingredients, other fibers, and combinations thereof selected from the group consisting of softwood fibers, non-wood fibers, natural non-cellulose fibers, man-made cellulose or non-cellulose fibers, hardwood fibers, recycled fibers, and mixtures thereof. In some embodiments, the first layer 120 may also include a specific blend of fibers, fillers, active ingredients, other fibers, and combinations thereof selected from the group consisting of softwood fibers, non-wood fibers, natural non-cellulose fibers, man-made cellulose or non-cellulose fibers, hardwood fibers, and mixtures thereof. The second layer 110 may include at least about 0.05% (i.e., greater than about 0.05%), or between about 0.05% and about 20%, or between about 0.1% and about 5% nanoparticles by weight of the second layer 110.

[0057] 2 shows a cross-sectional view of an exemplary embodiment of a fibrous structure or ply 100 of the present disclosure, including a second layer 110, a first layer 120, and a third layer 130 disposed adjacent the outer surface of the fibrous structure. Each of the three layers (110, 120, and 130) may include softwood fibers, non-wood fibers, natural non-cellulose fibers, man-made cellulose or non-cellulose fibers, hardwood fibers, recycled fibers, and mixtures thereof, fillers, active ingredients, other fibers, and combinations thereof. In one embodiment, the second layer 110 may include greater than about 0.05%, or between about 0.05% and about 20%, or between about 0.1% and about 5% nanoparticles by weight of the second layer 110.

[0058] 3 shows a cross-sectional view of an exemplary embodiment of a fibrous structure or ply 100 of the present disclosure, including a second layer 110, a first layer 120, and a third layer 130, each of which serves as one of the inner layers of the fibrous structure. In some embodiments, each layer (110, 120, 130) of the fibrous structure may include softwood fibers, non-wood fibers, natural non-cellulose fibers, man-made cellulose or non-cellulose fibers, hardwood fibers, recycled fibers, and mixtures thereof, fillers, active ingredients, other fibers, and combinations thereof. In one embodiment, the second layer 110 may include greater than about 0.05%, or between about 0.05% and about 20%, or between about 0.1% and about 5% nanoparticles by weight of the second layer 110.

[0059] 4 shows a cross-sectional view of an exemplary embodiment of a fibrous structure or ply 100 of the present disclosure, including a first layer 120 and a second layer 110, where the structure is formed with the second layer 110 formed directly on the forming belt / fabric / wire 200 of a paper machine or nonwoven machine. The first layer 120 and / or the second layer 110 may comprise softwood fibers, non-wood fibers, natural non-cellulose fibers, man-made cellulose or non-cellulose fibers, hardwood fibers, recycled fibers, and mixtures thereof, fillers, active ingredients, other fibers, and specific mixtures thereof. In one embodiment, the second layer 110 may comprise greater than about 0.05%, or between about 0.05% and about 20%, or between about 0.1% and about 5% nanoparticles by weight of the second layer 110.

[0060] 5 shows a cross-sectional view of an exemplary embodiment of a fibrous structure or ply 100 of the present disclosure, including a second layer 110 and a first layer 120, where the structure is formed with the second layer 110 formed in a layer away from a forming belt / fabric / wire 200 of a papermaking machine. The first layer 110 and / or the second layer 120 may comprise softwood fibers, non-wood fibers, natural non-cellulose fibers, man-made cellulose or non-cellulose fibers, hardwood fibers, recycled fibers, and mixtures thereof, fillers, active ingredients, other fibers, and specific mixtures thereof. In one embodiment, the second layer 110 may comprise greater than about 0.05%, or between about 0.05% and about 20%, or between about 0.1% and about 5% nanoparticles by weight of the second layer 110.

[0061] 6 shows a cross-sectional view of an exemplary embodiment of a fibrous structure or ply 100 of the present disclosure, where the fibrous structure 100 includes a first layer 120 and a second layer 110 formed in a dual-belt / wire fabrication process, where both the first layer 120 and the second layer 120 are formed in contact with one of two forming belts / fabrics 200 and 210 of a paper machine / nonwoven machine. In some embodiments, the first layer 120 and / or the second layer 110 may comprise softwood fibers, non-wood fibers, natural non-cellulose fibers, man-made cellulose or non-cellulose fibers, hardwood fibers, recycled fibers, and mixtures thereof, fillers, active ingredients, other fibers, and combinations thereof. In one embodiment, the second layer 110 may comprise greater than about 0.05%, or between about 0.05% and about 20%, or between about 0.1% and about 5% nanoparticles by weight of the second layer 110.

[0062] FIG. 7 shows a cross-sectional view of an exemplary embodiment of a fibrous structure or ply 100 of the present disclosure, including a first layer 110 and a second layer 120, where the second layer 110 is a high concentration of high-aspect ratio cellulose nanofilaments. Such structures may be produced by directly adding a high concentration of high-aspect ratio cellulose nanofilaments, such as via a headbox, spraying, coating, gravure application, or other direct application process. In some embodiments, the second layer 120 may contain a specific mixture of softwood fibers, recycled material fibers, hardwood fibers, man-made cellulose or non-cellulose fibers, fillers, and / or active ingredients, and / or other fibers. As shown in FIG. 7, the second layer 120 comprises at least about 40.0% (greater than about 40.0%), or greater than 50.0%, or between about 55.0% and about 100% high-aspect ratio cellulose nanofilaments 150 by weight of the second layer 110.

[0063] 8 shows a cross-sectional view of an exemplary embodiment of a fibrous web structure or ply 100 of the present disclosure, including a first layer 120, a second layer 110, and a third layer 130, where the structure is formed with the second layer 110 formed directly on a papermaking machine forming belt / fabric 200. In some embodiments, the first layer 120, the second layer 110, and / or the third layer 130 may comprise softwood fibers, non-wood fibers, natural non-cellulose fibers, man-made cellulose or non-cellulose fibers, hardwood fibers, recycled fibers, and mixtures thereof, fillers, active ingredients, other fibers, and combinations thereof. In one embodiment, the second layer 110 may comprise greater than about 0.05%, or between about 0.05% and about 20%, or between about 0.1% and about 5% nanoparticles by weight of the fibrous structure. One skilled in the art can envision the second layer 110 being formed on either the wire side (150) or the opposite side of the fiber structure (130). In yet another embodiment, the first layer 110 can include greater than about 0.05% by weight of the second layer 110, or between about 0.05% and about 20% by weight, or between about 0.1% and about 5% by weight of nanoparticles.

[0064] 9 shows a cross-sectional view of an exemplary embodiment of a fibrous structure or ply 100 of the present disclosure, where the fibrous structure 100 includes a first layer 120, a second layer 110, and a third layer 130 formed in a dual belt / wire making process, where both the first layer 120 and the third layer 130 are formed in contact with one of a paper machine's two forming belts / fabrics 200 and 210. In some embodiments, the first layer 120, the second layer 110, and the third layer 130 may comprise specific mixtures of softwood fibers, non-wood fibers, natural non-cellulosic fibers, man-made cellulose or non-cellulosic fibers, hardwood fibers, recycled fibers, and mixtures thereof, fillers, active ingredients, other fibers, and combinations thereof. In one embodiment, the second layer 110 can include greater than about 0.05% nanoparticles by weight of the second layer 110, or between about 0.05% and about 20%, or between about 0.1% and about 5% nanoparticles by weight of the second layer 110.

[0065] 10 shows a cross-sectional view of an exemplary embodiment of a fibrous structure or ply 100 of the present disclosure, including a second layer 110, a first layer 120, and a third layer 130, where the second layer 110 has a high concentration of high-aspect-ratio cellulose nanofilaments. Such a fibrous structure 100 may be produced by directly adding a high concentration of cellulose nanoparticles and / or high-aspect-ratio cellulose nanofilaments, such as by headbox, spraying, coating, gravure application, or other direct application processes. The first layer 120 and the third layer 130 may contain specific mixtures of softwood fibers, recycled material fibers, hardwood fibers, man-made cellulose or non-cellulose fibers, fillers, and / or active ingredients, and / or other fibers. In one embodiment shown in FIG. 10, the second layer 110 comprises at least about 40.0% (greater than about 40.0%) by weight of the second layer 110, or greater than about 50.0% by weight, or between about 55.0% and about 100% by weight of the second layer 110, of cellulose nanoparticles and / or cellulose nanofilaments and / or high aspect ratio cellulose nanofilaments 150.

[0066] FIG. 12A shows a cross-sectional view of an exemplary embodiment of a fibrous structure 100A of the present disclosure, including a first ply 210 and a second ply 220, where the first ply 210 has a layered, similar or different concentration of cellulose nanoparticles than the second ply. Once combined, the two plies, each with three layers, create a structure and function different from a single-ply structure. In some embodiments, each ply may also contain layers that may contain specific mixtures of softwood fibers, recycled fibers, hardwood fibers, man-made cellulose or non-cellulose fibers, fillers, and / or active ingredients, and / or other fibers. In one embodiment shown in FIG. 12A, the first ply 210 may include three layers. Layer #1 contains at least about 40.0% (greater than about 40.0%), or greater than 50.0%, or between about 55.0% and about 100% cellulose nanoparticles 150 by weight of layer #1. Similarly, the second ply 220 may include three layers, with layer #1 containing at least about 40.0% (greater than about 40.0%), or greater than 50.0%, or about 55.0% to about 100% cellulose nanoparticles 150 by weight of the first layer of ply 220. Additionally, the first ply 210 may further include a second layer (e.g., layer #2). The second layer may not contain intentionally added cellulose nanoparticles.

[0067] Another contemplated embodiment is the combination of layered and non-layered plies to create a final fibrous structure. Those skilled in the art will recognize that layered plies contain at least one layer containing a specific mixture of softwood fibers, recycled fibers, hardwood fibers, man-made cellulose or non-cellulose fibers, fillers, and / or active ingredients, and / or other fibers. In one embodiment, the first ply includes at least two layers. Layer #1 contains at least about 0.05% (greater than about 0.05%), or 0.05% to about 20.0% cellulose nanoparticles by weight of Layer #1. The second ply is a homogeneous fibrous structure containing 0.05% to 20% cellulose nanoparticles by weight of the ply. In another embodiment, the second homogeneous fibrous ply may contain less than 0.05% cellulose nanoparticles.

[0068] In yet another embodiment, the first ply can include nanoparticles in at least one layer, and the nanoparticles can be loaded at the same or different loadings in different layers. Those skilled in the art can envision numerous structures that can be created by independently varying the furnish composition of each ply, each layer in ply 1, the cellulose nanoparticle content in each layer of ply, and the number of plies combined to create the final structure. In addition to combining homogeneous plies with or without cellulose nanoparticles, those skilled in the art can further envision that applying cellulose nanoparticles in a separate layer of ply 1 allows formulators to further optimize the attributes of the final product. In many applications, the nanoparticle loading can be 0.05-20% by weight of the layer in ply 1 or homogeneous ply 2, although surface layers containing more than 40% nanoparticles by weight of the surface layer are also envisioned.

[0069] Those skilled in the art will also recognize that there are countless possible structures that can be created by independently varying the furnish composition of the layers within each ply, the cellulose nanoparticle content in each layer of plies, and the number of plies combined to create the final structure. Those skilled in the art will further envision methods of applying the cellulose nanoparticles in separate layers that allow formulators to optimize the attributes of the final product. Non-limiting examples of possible structures are shown in Figures 12B, 12C, 12D, and 12E. Nanoparticles are envisioned to be present in at least one layer in at least one ply, and may be present in different layers at the same or different loadings. In many applications, nanoparticle loadings may be 0.05-20% of the layer in which they are incorporated. In other applications, nanoparticle loadings may comprise less than 0.05% of the layer in which they are incorporated.

[0070] Optional Ingredients - Chemical Papermaking Additives If desired, various chemical additive compositions may optionally be used to further enhance consumer-desired benefits such as softness, low lint, absorbency, sheet flexibility, and temporary and / or permanent wet strength additives. Those skilled in the art will recognize that different materials may be added to the papermaking / nonwoven process depending on the papermaking / nonwoven process and the end use of the product, non-limiting examples include, but are not limited to, mineral additives, optical brighteners, sizing agents, coatings, debonders, silicone softening additives, non-silicone softening additives, strength additives, absorbency additives, biocides, retention aids, and aesthetic additives.

[0071] Mineral Additives Many fiber-based products contain mineral additives called fillers. A non-limiting example is a paper product that may contain a primarily cellulose fiber web and a specified amount of mineral and / or organic fillers. Fillers, as the name suggests, are used to fill the spaces enclosed by the cellulose fibers of the web. Fillers also improve certain paper properties, including opacity, whiteness, and printability. Other additives, such as pigments, dyes, starches, sizing agents, and strength-enhancing polymers, can also be used to form paper with desired end-product properties. Traditionally, minerals such as kaolin clay (hydrated aluminum silicate), chalk, ground limestone or marble (calcium carbonate), talc (hydrated magnesium silicate), gypsum (calcium sulfate), diatomaceous earth (silicon dioxide), and titanium dioxide have been used as fillers. Most other fillers are inorganic materials produced synthetically from minerals (e.g., titanium dioxide, synthetic silica, barium sulfate) or by regeneration after purification (e.g., limestone-lime-precipitated calcium carbonate). Fillers used to form paper products using methods developed prior to the present disclosure decrease the strength properties, such as the breaking length in kilometers (tensile strength divided by basis weight x 102, per TAPPI method T494), of the product as the percentage of filler used to make such products increases. Depending on the desired properties of the desired paper product, fillers can be incorporated in any amount from 0% to about 75%, preferably from about 5% to about 60.0%, more preferably from about 10% to about 50.0%, and even more preferably from about 20% to about 40%, by weight on a dry fiber basis of the paper web structure. Fillers can be incorporated into a single layer sheet or into any layer of a multilayer web product.

[0072] Strength Additives—The process of the present application also includes adding a strength additive to the papermaking furnish. Generally, the strength additive may be applied in various amounts depending on the desired properties of the web. Strength additives useful in the present disclosure include, but are not limited to, cationic water-soluble resins. These resins impart wet strength to paper sheets and are well known in the papermaking art. Such resins include, but are not limited to, polyamide epichlorohydrin (PAE), urea-formaldehyde resins, melamine formaldehyde resins, polyacrylamide resins, dialdehyde starch, and mixtures thereof.

[0073] In some embodiments, other strength agents may be utilized to further improve the strength of the fibrous web product. The listing of optional chemical components is intended to be merely exemplary in nature and is not intended to limit the scope of the present disclosure. Other materials are also contemplated as long as they do not interfere with or negate the benefits of the present disclosure.

[0074] The fibrous structure may include at least two plies arranged in contact with each other in a facing relationship. Each of the at least two plies may include at least two layers arranged in a facing relationship. Each of the at least two layers in each ply may include structural fibers selected from the group consisting of softwood fibers, non-wood fibers, man-made cellulose or non-cellulose fibers, hardwood fibers, recycled fibers, and mixtures thereof. Each multi-layer ply may include a surface layer comprising cellulose nanoparticles. The fibrous structure may be bonded, as discussed above, such that the surface layer of each ply is the surface layer of the fibrous structure. The surface layer may comprise more than about 40 weight percent cellulose nanoparticles of the surface layer. The cellulose nanoparticles may be applied to the surface layer of a first ply by the process described above before placing the first ply in contact with the surface of a second ply of the at least two plies in a facing engagement. Furthermore, the cellulose nanoparticles may be applied to create a surface layer comprising cellulose nanofilaments.

[0075] Any dimension and / or value disclosed herein should not be understood to be strictly limited to the exact numerical value recited. Instead, unless otherwise specified, each such dimension and / or value is intended to mean both the recited dimension and / or value and a functionally equivalent range surrounding that dimension and / or value. For example, a dimension disclosed as "40 mm" is intended to mean "about 40 mm."

[0076] All documents cited herein, including cross-referenced or related patents or applications, and patent applications or patents to which this application claims priority or benefit, are incorporated herein by reference in their entirety unless expressly excluded or otherwise limited. The citation of a document is not an admission that it is prior art to any invention disclosed or claimed herein, or that it alone, or in combination with other reference(s), teaches, suggests, or discloses such invention. Furthermore, to the extent that a meaning or definition of a term herein conflicts with a meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term herein shall govern.

[0077] 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 in the appended claims to cover all such changes and modifications that are within the scope of this invention.

Claims

1. A fibrous structure comprising a first fibrous layer and a second fibrous layer, the first fibrous layer and the second fibrous layer being disposed in opposing relationship, the first and second fibrous layers each comprising a mixture of structural fibers selected from the group consisting of softwood fibers, non-wood fibers, natural non-cellulosic fibers, man-made cellulose or non-cellulosic fibers, hardwood fibers, recycled fibers, and mixtures thereof; each of the first and second fibrous layers comprising at least 0.05 wt. % cellulose nanoparticles; the weight percentage of cellulose nanoparticles in the first fibrous layer is different from the weight percentage of cellulose nanoparticles in the second fibrous layer; Fiber structures.

2. The fibrous structure of claim 1 , wherein the first fibrous layer comprises 0.05 weight percent to 20 weight percent cellulose nanoparticles.

3. The fibrous structure of claim 2 , wherein the second fibrous layer comprises 0.05 weight percent to 20 weight percent cellulose nanoparticles.

4. 10. The fibrous structure of claim 1, wherein the first fibrous layer does not contain intentionally added cellulose nanoparticles, and the first and second fibrous layers are manufactured by airlaid technology.

5. The fibrous structure of claim 1 , wherein the first fibrous layer is an outer layer of the fibrous structure.

6. The fibrous structure of claim 1 , wherein the second fibrous layer comprises 0.1 weight percent to 5 weight percent of the cellulose nanoparticles.

7. The fibrous structure of claim 1 , wherein the second fibrous layer comprises a high concentration of high aspect ratio cellulose nanofilaments.

8. The fibrous structure of claim 1 , further comprising a fiber surface layer comprising high aspect ratio nanofilaments.

9. 9. The fibrous structure of claim 8, wherein the fiber surface layer comprises at least 40 weight percent of the high aspect ratio nanofilaments.

10. 9. The fibrous structure of claim 8, wherein the fiber surface layer comprises greater than 50 weight percent of the high aspect ratio nanofilaments.

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