Patent Application
20090117331
This invention relates generally to a paper product, more specifically, a bathroom tissue product having two or more plies with surface features wherein the two or more plies have surface features that have been optimized for improved aesthetics and firmness.
Absorbent paper products are well known in the art. Such products may include, for example, sanitary tissue products, facial tissues, paper toweling, bath tissue, napkins, etc. Frequently, these products are provided with textured surfaces or other features to enhance product performance and/or to enhance consumer appeal.
It is known that simply providing a product with improved properties is not enough for a product to be successful because a consumer may not fully appreciate the actual benefits of the product unless there is some sort of visual trigger that communicates the benefits to the consumer. For example, the pattern that appears on the surface of a paper product may not only impact the paper's performance, but may also affect how a consumer will perceive that product.
Texture may be imparted to the surface of an absorbent paper product in many ways. For example, a textured or patterned belt may be used to form the paper web during the papermaking process. Alternatively, an absorbent paper product may be embossed to provide texture to the surface of a paper product. It is known in the art that consumers prefer paper products having embossments, or other surface features, that are clear and pronounced, but wherein the paper product is also smooth, soft, strong, and a good value. Thus, it is highly desired to provide paper products having clear and pronounced embossments or surface features wherein the paper products also provide, or appear to provide, the benefits of smoothness, softness, strength, and value.
It is known that in a multi-ply paper product, the characteristics of the surface features that appear on one ply of the absorbent paper product actually impacts the appearance of the surface features on an opposing ply. Specifically, in a multi-ply paper product, such as bath tissue, wherein it is known for the plies have different patterns embossed, or formed, onto each ply, it is possible for the resultant paper product to exhibit “show through” of one ply's surface features onto the surface of the adjacent ply. This “show through” effect may have a negative effect on the softness and/or smoothness of the paper product and cause consumers to mistakenly believe that the paper product is of inferior smoothness, softness, strength or value. More surprisingly, Further, this “show through” effect is especially detrimental in a multi-ply paper product having highly pronounced features (such as deep embossments) because in addition to having a negative effect on the appearance and texture of the product, the firmness of the paper product when in roll form may be negatively impacted. Thus, there exists the need for a multi-ply paper product wherein surface features of one ply are optimized to compliment the surface features on an adjacent ply, wherein the paper product has clear and pronounced surface features, and exhibits a relatively high level of firmness when in roll form.
It has been surprisingly discovered that optimizing the number density, size, and height of the surface features on opposing plies of a multi-ply paper product patterns increases the firmness of the paper product when in roll form and prevent, or eliminate altogether, the “show through” effect.
Therefore, the present invention overcomes the disadvantages of the prior art by providing a multi-ply paper product with deep, pronounced, embossments or other surface features, wherein the embossments, or surface features, of one ply of the multi-ply paper product compliment the embossments, or surface features, of an adjacent ply of the paper product.
In one embodiment, the present invention is directed to a multi-ply paper product comprising a first ply and a second ply. The first ply comprises a plurality of first surface features wherein there are from about 5 first surface features/cm2 to about 20 first surface features/cm2, the first surface features have a surface area of from about 0.3 mm2 to about 4 mm2, and the first surface features have a height of from about 600 microns to about 2500 microns. The second ply comprises a plurality of second surface features wherein there are from about 30 second surface features/cm2 to about 80 second surface features/cm2, the second surface features have a surface area of from about 0.03 mm2 to about 1.2 mm2, and the surface features have a height of from about 400 microns to about 1600 microns.
In another embodiment, the present invention is directed to a multi-ply paper product in roll form comprising a first ply and a second ply. The first ply comprises a plurality of first surface features wherein there are from about 5 first surface features/cm2 to about 20 first surface features/cm2, the first surface features have a surface area of from about 0.3 mm2 to about 4 mm2, and the first surface features have a height of from about 600 microns to about 2500 microns. The second ply comprises a plurality of second surface features wherein there are from about 30 second surface features/cm2 to about 80 second surface features/cm2, the second surface features have a surface area of from about 0.03 mm2 to about 1.2 mm2, and the surface features have a height of from about 400 microns to about 1600 microns. The paper product has a firmness of about 10% greater than a comparable paper product having one embossed ply and one unconverted ply in roll form.
In another embodiment, the present invention is directed to a multi-ply paper product in roll form comprising a first ply and a second ply. The first ply comprises a plurality of first surface features wherein there are from about 5 first surface features/cm2 to about 20 first surface features/cm2 the first surface features have a surface area of from about 0.3 mm2 to about 4 mm2, and the first surface features have a height of from about 600 microns to about 2500 microns. The second ply comprises a plurality of second surface features wherein there are from about 30 second surface features/cm2 to about 80 second surface features/cm2, the second surface features have a surface area of from about 0.03 mm2 to about 1.2 mm2 and the surface features have a height of from about 400 microns to about 1600 microns. The paper product has a basis weight of from about 12 to about 50 lbs/3000 ft2 and a firmness of about 10% greater than a comparable paper product having one embossed ply and one unconverted ply in roll form.
While the specification concludes with claims that particularly point out and distinctly claim the present invention, it is believed that the present invention will be understood better from the following description of embodiments, taken in conjunction with the accompanying drawings, in which like reference numerals identify identical elements.
Without intending to limit the invention, embodiments are described in more detail below:
As used herein, “fibrous structure” means an arrangement of fibers produced in any papermaking machine known in the art to create a ply of paper. “Fiber” means an elongate particulate having an apparent length exceeding its apparent width. More specifically, and as used herein, fiber refers to such fibers suitable for a papermaking process.
As used herein, “paper product” refers to any formed, fibrous structure products, traditionally, but not necessarily, comprising cellulose fibers. In one embodiment, the paper products of the present invention include bath tissue products.
As used herein, “conventional paper web” refers to a paper web which has not been textured by a papermaking belt, wire, fabric, and the like during the papermaking process. In one embodiment, conventional paper web refers to a paper web which has been dried only by contact with the Yankee dryer. In another embodiment, a conventional paper web does not have any texture imparted onto the surface, although it may be textured during a converting process.
As used herein, “ply” or “plies” means an individual fibrous structure or sheet of fibrous structure, optionally to be disposed in a substantially contiguous, face-to-face relationship with other plies, forming a multi-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. In one embodiment, the ply has an end use as a tissue-towel paper product. A ply may comprise one or more wet-laid layers, air-laid layers, and/or combinations thereof. If more than one layer is used, it is not necessary for each layer to be made from the same fibrous structure. Further, the layers may or may not be homogenous within a layer. The actual makeup of a tissue paper ply is generally determined by the desired benefits of the final tissue-towel paper product, as would be known to one of skill in the art. The fibrous structure may comprise one or more plies of non-woven materials in addition to the wet-laid and/or air-laid plies.
As used herein, “basis weight” or “BW” is the weight per unit area of a sample reported in lbs/3000 ft2 or g/m2.
As used herein, “caliper” or “sheet caliper” is the macroscopic thickness of a product sample under load.
As used herein, “machine direction” or “MD” refers to the direction parallel to the flow of the fibrous structure through the papermaking machine and/or product manufacturing equipment.
As used herein, “cross machine direction” or “CD” refers to the direction perpendicular to the machine direction in the same plane of the fibrous structure and/or fibrous structure product comprising the fibrous structure.
As used herein, “Z-direction” refers to the direction normal to a plane formed by machine direction and cross machine directions.
As used herein, “surface feature” refers to a structured element on the surface of a paper web. In some embodiments, surface features may be formed using any known converting process, such as embossing. In other embodiments, surface features may be formed during the papermaking process, such as by using a textured belt to mold the paper. In one embodiment, a surface feature is an embossment.
As used herein, “show through” refers to the ends of the surface features or embossments from one ply becoming visible through the surface of an opposing ply. Without wishing to be limited by theory, in addition to affecting the aesthetic qualities of the paper product, it is thought that show through may affect texture of the paper product by causing a consumer to feel that the surface of the paper product is rough or bumpy.
As used herein, “embossing” refers to the process of deflecting a relatively small portion of a cellulosic fibrous structure normal to its plane and impacting the projected portion of the fibrous structure against a relatively hard surface to permanently disrupt the fiber to fiber bonds.
As used herein, “laminating” refers to the process of firmly uniting superimposed layers of paper with or without adhesive, to form a multi-ply sheet.
As used herein, “textured surface,” when referring to the surface of a paper product refers to the incorporation of texture into the fibrous structure product via the converting end of the papermaking process and/or the during the wet end stage of papermaking, including embossing, wet microcontraction, creping, the use of papermaking belts to effect a pattern densified structure, etc., and combinations thereof.
As used herein, “comparable roll paper product” refers to a paper product in roll form that has the same roll diameter, sheet count (roll length), basis weight, and identical core as another paper product in roll form.
As used herein, “densified” means a portion of a fibrous structure product that 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. One embodiment of a method of making a pattern densified fibrous structure and devices used therein are described in U.S. Pat. Nos. 4,529,480 and 4,528,239.
As used herein, “non-densified” means a portion of a fibrous structure product that exhibits a lesser density than another portion of the fibrous structure product.
As used herein, “firmness” refers to the roll's compressibility, or non-susceptibility to compression under the influence of the external, especially radial, force. The roll compressibility can be measured according to the Roll Firmness Test method described below.
The forming section 41 of the papermaking machine 21 comprises a headbox 50; a loop of fine mesh backing wire or fabric 51 which is looped about a vacuum breast roll 52, over vacuum box 70, about rolls 55 through 59, and under showers 60. Intermediate rolls 56 and 57, backing wire/fabric 51 is deflected from a straight run by a separation roll 62. Biasing means not shown are provided for moving roll 58 as indicated by the adjacent arrow to maintain fabric/wire 51 in a slack obviating tensioned state.
The intermediate carrier section 42 comprises a loop of forming and carrier fabric 26 which is looped about rolls 62 through 69 and about a portion of roll 56. The forming and carrier fabric 26 also passes over vacuum boxes 70 and 53, and transfer head 25; and under showers 71. Biasing means are also provided to move roll 65 to obviate slack in fabric 26. Juxtaposed portions of fabrics 51 and 26 extend about an arcuate portion of roll 56, across vacuum box 70, and separate after passing over an arcuate portion of separation roll 62. In one embodiment, forming and carrier fabric 26 is identical to backing wire/fabric 51 except for the lengths.
The pre-dryer/imprinting section 43 of papermaking machine 21 comprises a loop of transfer fabric or imprinting fabric 28. Transfer/imprinting fabric 28 is looped about rolls 77 through 86; passes across transfer head 25 and vacuum box 29; through a blow-through pre-dryer 88; and under showers 89. Additionally, not shown is a biasing mechanism for biasing roll 79 towards the adjacent Yankee dryer 91 with a predetermined force per lineal inch to effect imprinting the knuckle pattern of fabric 28 in paper web 30 in the manner of, and for the purpose disclosed in, U.S. Pat. No. 3,301,746. Not shown is a biasing mechanism for moving roll 85 as indicated by the adjacent arrow to obviate slack in fabric 28.
The drying/creping section 44 of papermaking machine 21 comprises Yankee dryer 91, adhesive applicator 92, creping blade 93, and reel roll 94.
V1 is the velocity of the papermaking fabrics 51 and 26. V2 is the velocity about the transfer/printing rolls 77 through 86. V3 is the velocity of the calendar assembly 45. V4 is the reel velocity of the reel roll 94.
The present invention contemplates the use of a variety of paper making fibers, such as natural fibers, synthetic fibers, as well as any other suitable fibers, starches, and combinations thereof. Paper making 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, groundwood, thermomechanical pulp, chemically modified, and the like. Chemical pulps may be used in tissue towel embodiments since they are known to those of skill in the art to impart a superior tactical sense of softness to tissue sheets made therefrom. Pulps derived from deciduous trees (hardwood) and/or coniferous trees (softwood) can be utilized herein. Such hardwood and softwood fibers can be blended or deposited in layers to provide a stratified web. Exemplary layering embodiments and processes of layering are disclosed in U.S. Pat. Nos. 3,994,771 and 4,300,981. Additionally, fibers derived from wood pulp such as cotton linters, bagesse, and the like, can be used. Additionally, fibers derived from recycled paper, which may contain any of all of the categories as well as other non-fibrous materials such as fillers and adhesives used to manufacture the original paper product may be used in the present web. In addition, fibers and/or filaments made from polymers, specifically hydroxyl polymers, may be used in the present invention. Non-limiting examples of suitable hydroxyl polymers include polyvinyl alcohol, starch, starch derivatives, chitosan, chitosan derivatives, cellulose derivatives, gums, arabinans, galactans, and combinations thereof. Additionally, other synthetic fibers such as rayon, polyethylene, and polypropylene fibers can be used within the scope of the present invention. Further, such fibers may be latex bonded.
Other materials are also intended to be within the scope of the present invention as long as they do not interfere or counteract any advantage presented by the instant invention.
The paper product may comprise any tissue-towel paper product known in the industry. Embodiment of these substrates may be made according U.S. Pat. Nos. 4,191,609, 4,300,981, 4,191,609, 4,514,345, 4,528,239, 4,529,480, 4,637,859, 5,245,025, 5,275,700, 5,328,565, 5,334,289, 5,364,504, 5,527,428, 5,556,509, 5,628,876, 5,629,052, 5,637,194, and 5,411,636; EP 677612, and U.S. Pat. App. No. 2004/0192136A1.
The substrates used to make the present invention paper product may be manufactured via a wet-laid making process where the resulting web is through-air-dried or conventionally dried. Optionally, the substrate may be foreshortened by creping or by wet microcontraction. Creping and/or wet microcontraction are disclosed in commonly assigned U.S. Pat. Nos. 6,048,938, 5,942,085, 5,865,950, 4,440,597, 4,191,756, and 6,187,138.
Conventionally pressed paper and a method for making such is described infra and is also exemplified in U.S. Pat. No. 6,547,928. Uncompacted, non pattern-densified paper products are also contemplated within the scope of the present invention and are described in U.S. Pat. Nos. 3,812,000 and 4,208,459. Uncreped paper products as defined in the art are also contemplated. The techniques to produce uncreped paper products in this manner are exemplified in European Pat. App. Nos. 0 677 612A2 and 0 617 164 A1; and in U.S. Pat. No. 5,656,132.
Uncreped paper product, in one embodiment, refers to a paper product which is non-compressively dried. In one embodiment, an uncreped paper product is dried by through air drying. Resultant through air dried paper products may be pattern densified such that zones of relatively high density are dispersed within a high bulk field, including pattern densified tissue wherein zones of relatively high density are continuous and the high bulk field is discrete. The techniques to produce uncreped paper product in this manner are taught in the prior art. For example, Wendt, et. al. in European Pat. App. Nos. 0 677 612A2 and 0 617 164 A1; and U.S. Pat. No. 5,656,132
The substrate which comprises the paper product of the present invention may be cellulosic, or a combination of both cellulose and non-cellulose. The substrate may be conventionally dried using one or more press felts. If the substrate which comprises the paper product according to the present invention is conventionally dried, it may be conventionally dried using a felt which applies a pattern to the paper as taught by commonly assigned U.S. Pat. No. 5,556,509; and PCT App. No. WO 96/00812. Other exemplary paper products may be made according to U.S. Pat. Nos. 4,528,239, 4,529,480, 5,275,700, 5,364,504, 5,527,428, 5,609,725, 5,679,222, 5,709,775, 5,795,440, 5,900,122, 5,906,710, 5,935,381, and 5,938,893.
In one embodiment the plies of a multi-ply paper product may be the same substrate respectively or the plies may comprise different substrates combined to create desired consumer benefits. In one embodiment the paper products comprise two plies. In another embodiment the paper product comprises a first ply, a second ply, and at least one inner ply.
In one embodiment, the paper product has a basis weight of from about 12 to about 50 lbs/3000 ft2, in another embodiment from about 18 lbs/3000 ft2 to about 40 lbs/3000 ft2. In another embodiment the basis weight is about 18 lbs/3000 ft2 to about 30 lbs/3000 ft2; and in yet another embodiment the basis weight is about 18 lbs/3000 ft2 and about 26 lbs/3000 ft2 as measured by the Basis Weight Method described herein. The basis weight claimed is for the multi-ply paper product. In one embodiment, each ply has the same basis weight. In another embodiment, the basis weight of one ply is at least about 15% greater than the basis weight of an adjacent ply. In another embodiment still, the basis weight of one ply is from about 15% to about 75% greater than the basis weight of an adjacent ply. In one embodiment, in a multi-ply paper product wherein one ply has a different basis weight than the adjacent ply, there is a lower embossment number density on the ply having a higher basis weight.
In one embodiment the paper product is in roll form. When in roll form, the paper product may be wound about a core or may be wound without a core. It should be understood by one of skill in the art that, when discussed comparatively, paper products in roll form are wound about comparable cores.
It is known in the art that the substrate which comprises a paper product may be made by through-air drying. An exemplary through air dried substrate may be made according to U.S. Pat. No. 4,191,609. Without wishing to be limited by theory, those of skill in the art will appreciate that paper products made with through-air-dried substrates generally have relatively high caliper and are relatively firm. Surprisingly, it was found that some embodiments of the present invention product provides a conventional substrate with levels of firmness and caliper that are comparable to a paper product made using a through-air-dried substrate.
The surface of the paper product may be textured by any means known in the art. In some embodiments the texture may be imparted into the surface of the paper product during converting (for example, embossing). In other embodiments, the texture may be imparted into the surface of the paper product during forming (for example, using a textured fabric or patterned belt) to provide a paper product having densified regions and non-densified regions. Suitable means of introducing textured surfaces into a paper web during forming include those exemplified in U.S. Pat. Nos. 4,514,345, 4,528,239, 5,098,522, 5,260,171, 5,275,700, 5,328,565, 5,334,289, 5,431,786, 5,496,624, 5,500,277, 5,514,523, 5,554,467, 5,566,724, 5,624,790, 5,628,876, 5,679,222, 5,714,041, and 5,906,710. Suitable means of embossing include those exemplified in U.S. Pat. Nos. 3,323,983, 5,468,323, 5,693,406, 5,972,466, 6,030,690, and 6,086,715. In one embodiment at least two plies have surface features that are embossments. In another embodiment, at least one ply has surface features that are embossments, and at least one ply has surface features which are formed into the surface of the paper web. In another embodiment still, at least two plies have surface features which are formed into the surface of the paper web.
It should be noted that one of skill in the art may use any method known in the art, such as textured belts, to form surface features instead of embossments into the surface of a paper web.
An exemplary process for embossing a paper web in accordance with the present invention incorporates the use of a knob-to-rubber impression embossment technology. By way of a non-limiting example, a tissue ply structure is embossed in a gap between an embossing roll and a backside impression roll. The embossing roll may be made from any material known for making such rolls, including, without limitation, steel, ebonite, hard rubber and elastomeric materials, and combinations thereof. The backside impression roll may be made from any material for making such rolls, including, without limitation soft rubber. As known to those of skill in the art, the embossing roll may be provided with a combination of emboss protrusions and gaps. Each emboss protrusion comprises a base, a face, and one or more sidewalls. An exemplary process for achieving deep embossments is exemplified in U.S. Pat. Pub. No. 2007/0062658A1.
In one embodiment, a first ply 30a may be embossed such that the first ply 30a may have relatively large and a relatively low number of embossments. In another embodiment, a second ply 30b may be embossed such that the second ply 30b may have relatively smaller, and a relatively higher number of, embossments compared to the first ply 30a. It should be noted that the plies 30a, 30b of a multi-ply web product may be made from different materials, such as from different fibers, different combinations of fibers, natural and synthetic fibers or any other combination of materials making up the base plies.
The benefits of having complimentary surface features on adjacent plies in a multi-ply paper product having a per-ply basis weight of between 10 and 40 gsm (16.3 lbs/3000 ft2 and 65.2 lbs/3000 ft2, respectively) are known in the art, such as is described in U.S. Pat. No. 6,916,403. It is surprisingly found that using one textured ply having a high density of surface features with another textured ply having a low density of surface features, the absorbent paper product that provides an effective visual embodiment of the surface texture of the paper product and increases the firmness and caliper of the paper product when in roll form. Without wishing to be limited by theory, it is thought that by using nested embossing for multi-ply paper products, or if the size of the surface features is too high on one ply and the number density and size of surface features is too low on an adjacent ply, the surface features from one ply may show through on any low density regions in an adjacent ply and cause the resultant paper product to lose its smoothness and aesthetic appeal. Despite these effects, it is thought that nested embossing or texturing two or more plies in a multi-ply product may provides the desirable benefit of increasing the caliper of the resultant multi-ply paper product. In addition, it is even more surprisingly found that optimizing the surface features and/or patterns on adjacent plies having a relatively low basis weight produces product having the relatively high roll firmness and/or caliper.
As described supra, it has been found that by providing a high number density of surface features having a relatively small surface area on one ply, and providing a relatively lower number density of surface features having a larger surface area on an adjacent ply, and wherein the features are deep and well-defined, the resulting paper product exhibits a greatly reduced, or no, show through effect while having a relatively high firmness when in roll form given a specific roll diameter and sheet count (roll length). In one embodiment, the surface features are provided to one or more plies by embossing a conventional paper web. In another embodiment, the surface features are provided to one or more plies by forming a paper web during the papermaking process. In one embodiment, a conventional paper web is embossed. Without wishing to be limited by theory, it is thought that by embossing a conventional paper web, the embossing pattern more easily stands out from the surface of the substrate because of the high level of contrast between the embossed and unembossed areas.
Surprisingly, it was discovered that the paper products of the present invention showed a markedly increased firmness over paper products having comparable roll diameter, sheet count (roll length), and basis weight. Without wishing to be limited by theory, it is thought that the high embossments provide additional caliper to the paper product than a paper product having shorter embossments or no embossments. As a result, for products with the same number of sheets, but wherein one product has a higher caliper, the higher caliper product may be wound more tightly to achieve a consumer-acceptable roll diameter than a paper product having shorter embossments or no embossments at all. More surprisingly, it was found that a roll having comparable roll diameter, basis weight, sheet count (roll length), and with an optimized texture, but that had less deep embossments exhibited a lower firmness than the roll products of the present invention. It should be noted that nested embossing is known to achieve high caliper, but exhibits the show through effect that is overcome by the present invention.
In one embodiment, the paper product in roll form has a relative roll firmness that is about 10% greater than a comparable paper product having one embossed ply and one unconverted ply in roll form. In another embodiment, the roll has a relative roll firmness that is from about 10% to about 50% greater than a comparable paper product having one embossed ply and one unconverted ply in roll form. In another embodiment, the roll has a relative roll firmness that is from about 20% to about 40% greater than a comparable paper product having one embossed ply and one unconverted ply in roll form.
The following table illustrates an exemplary embodiment of the present invention paper product as compared to prior art paper products. In the exemplary embodiment, each paper product is in roll form having the same total length (unwound), two conventional plies, a basis weight of about 10 lbs/3000 ft2 per ply, and the same composition. Each sample is wound such that each roll has a final roll diameter of about 4.56 inches and cut to a width of about 4.25 inches. The samples are as follows: (1) The present invention product has a feature density of about 42.98 embossments/in2 (each embossment having a diameter of about 0.052″) on one ply and a feature density of about 284.801 embossments/in2 (each embossment having a diameter of about 0.0283″) on the adjacent ply; (2) a nested emboss pattern wherein both the front and back ply have a feature density of about 28 elements/in2 (each embossment having a diameter of about 0.052″); (3) a feature density of about 42.98 embossments/in2 (each embossment having a diameter of about 0.052″) on a first ply, and the adjacent ply is brought through the same nip as the first ply; (4) a feature density of about 42.98 embossments/in2 (each embossment having a diameter of about 0.052″) on one ply and no features on the adjacent ply. Five identical exemplary rolls of each sample (present invention included) were measured and the average of the five rolls was recorded. The relative firmness is measured by taking the firmness of the standard (in this case, Sample 4) and dividing the firmness of the sample by the firmness of the standard and subtracting that result from 1. The resulting number is recorded as the relative roll firmness. The firmness and caliper of a prior art through air dried sample (5, Kleenex Cottennelle™ Linea Dorada) having the same roll diameter and basis weight. The compressibility and caliper of the present invention paper product made using a conventional substrate are comparable to the similar through-air-dried substrate (Sample 5).
The firmness is measured by the Roll Firmness Test Method described infra. The caliper is measured by the Sheet Caliper Test Method described infra. The basis weight is measured by the Basis Weight Test Method described infra.
One fibrous structure useful in achieving the fibrous structure paper product of the present invention is a conventional paper web described supra. Such a structure may be formed by the following process.
A conventional papermaking machine is used. A slurry of papermaking fibers is pumped to the headbox at a consistency of about 0.15%. The slurry consists of about 70% Northern Softwood Kraft fibers, about 30% unrefined Eucalyptus fibers, a cationic polyamine-epichlorohydrin wet burst strength resin at a concentration of about 25 lbs per ton of dry fiber, and carboxymethyl cellulose at a concentration of about 5 lbs per ton of dry fiber, as well as DTDMAMS at a concentration of about 6 lbs per ton of dry fiber.
Dewatering occurs through the Fourdrinier wire and is assisted by vacuum boxes. The embryonic wet web is transferred from the Fourdrinier wire at a fiber consistency of about 20% at the point of transfer, to a transfer fabric. The wire speed is about 620 feet per minute. The carrier fabric speed is about 600 feet per minute. Since the wire speed is faster than the carrier fabric, wet shortening of the web occurs at the transfer point. Thus, the wet web foreshortening is about 3%.
An aqueous solution of creping adhesive is applied to the Yankee surface by spray applicators before the location of the sheet transfer from the fabric to the Yankee. The fiber consistency is increased to an estimated 95.5% before creping the web with a doctor blade. The doctor blade has a bevel angle of about 25 degrees and is positioned with respect to the Yankee dryer to provide an impact angle of about 81 degrees. The Yankee dryer is operated at about 360° F., and Yankee hoods are operated at about 350° F.
The dry, creped web is passed between two calendar rolls and rolled on a reel operated at 560 feet per minute so that there is about 7% foreshortening of the web by crepe. The paper web resultant paper web is the first ply for a multi-ply paper product.
The process described supra is repeated for a second paper web to provide a second ply.
The paper described above is then subjected to a knob-to-rubber impression embossing process as follows. An emboss roll is engraved with a nonrandom pattern of protrusions. The emboss roll is mounted, along with a backside impression roll, in an apparatus with their respective axes being generally parallel to one another. The emboss roll comprises embossing protrusions which are frustaconical in shape. The backside impression roll is made of Valcoat™ material from Valley Roller Company, Mansfield, Tex. The paper web is passed through the nip to create a first embossed ply.
The first ply is embossed such that there is a feature density of about 42.98 embossments/in2 (each embossment having a diameter of about 0.052″). The second ply is not embossed.
Adhesive is applied to the tips of the embossments of the first ply and the second ply is joined with the first ply a zero clearance marrying nip, so that a unitary laminate is formed.
The resulting multi-ply paper product is wound such that it has a roll diameter of about 4.56 inches and cut to a width of about 4.25 inches. The firmness of this product is about 5.05%.
One fibrous structure useful in achieving the fibrous structure paper product of the present invention is a conventional paper web described supra. Such a structure may be formed by the following process.
A conventional papermaking machine is used. A slurry of papermaking fibers is pumped to the headbox at a consistency of about 0.15%. The slurry consists of about 70% Northern Softwood Kraft fibers, about 30% unrefined Eucalyptus fibers, a cationic polyamine-epichlorohydrin wet burst strength resin at a concentration of about 25 lbs per ton of dry fiber, and carboxymethyl cellulose at a concentration of about 5 lbs per ton of dry fiber, as well as DTDMAMS at a concentration of about 6 lbs per ton of dry fiber.
Dewatering occurs through the Fourdrinier wire and is assisted by vacuum boxes. The embryonic wet web is transferred from the Fourdrinier wire at a fiber consistency of about 20% at the point of transfer, to a transfer fabric. The wire speed is about 620 feet per minute. The carrier fabric speed is about 600 feet per minute. Since the wire speed is faster than the carrier fabric, wet shortening of the web occurs at the transfer point. Thus, the wet web foreshortening is about 3%.
An aqueous solution of creping adhesive is applied to the Yankee surface by spray applicators before the location of the sheet transfer from the fabric to the Yankee. The fiber consistency is increased to an estimated 95.5% before creping the web with a doctor blade. The doctor blade has a bevel angle of about 25 degrees and is positioned with respect to the Yankee dryer to provide an impact angle of about 81 degrees. The Yankee dryer is operated at about 360° F., and Yankee hoods are operated at about 350° F.
The dry, creped web is passed between two calendar rolls and rolled on a reel operated at 560 feet per minute so that there is about 7% foreshortening of the web by crepe.
The process described supra is repeated for a second paper web to provide a second ply.
The paper described above is then subjected to a knob-to-rubber impression embossing process as follows. An emboss roll is engraved with a nonrandom pattern of protrusions. The emboss roll is mounted, along with a backside impression roll, in an apparatus with their respective axes being generally parallel to one another. The emboss roll comprises embossing protrusions which are frustaconical in shape. The backside impression roll is made of Valcoat™ material from Valley Roller Company, Mansfield, Tex. The paper web is passed through the nip to create a first embossed ply.
The first ply is embossed such that there is a feature density of about 42.98 embossments/in2 (each embossment having a diameter of about 0.052″). The second ply is embossed such that there is a feature density of about 284.801 embossments/in2 (each embossment having a diameter of about 0.0283″).
Adhesive is applied to the tips of the embossments of the first ply and the second ply is joined with the first ply a zero clearance marrying nip, so that a unitary laminate is formed.
The resulting multi-ply paper product is wound such that it has a roll diameter of about 4.56 inches and cut to a width of about 4.25 inches. The compressibility of this product is about 6.44%.
The following describe the test methods utilized herein to determine the values consistent with those presented herein.
The geometric characteristics of the embossment structure of the present invention are measured using an Optical 3D Measuring System MikroCAD compact for paper measurement instrument (the “GFM MikroCAD optical profiler instrument”) and ODSCAD Version 4.14 software available from GFMesstechnik GmbH, Warthestraβe E21, D14513 Teltow, Berlin, Germany. The GFM MikroCAD optical profiler instrument includes a compact optical measuring sensor based on digital micro-mirror projection, consisting of the following components:
The GFM MikroCAD optical profiler system measures the height of a sample using the digital micro-mirror pattern projection technique. The result of the analysis is a map of surface height (Z) versus XY displacement. The system should provide a field of view of 160×120 mm with an XY resolution of 21 μm. The height resolution is set to between 0.10 μm and 1.00 μm. The height range is 64,000 times the resolution. To measure a fibrous structure sample, the following steps are utilized:
Embossments are often based on standard plane geometry shapes such as circles, ovals, various quadrilaterals and the like, both alone and in combination. For such plane geometry figures, the area of an individual embossment can be readily derived from well known mathematical and geometric formulas. For more complex shapes, various area calculation methods may be used. One such technique follows: Start with an image of a single embossment at a known magnification of the original (for example 100×) on an otherwise clean sheet of paper, cardboard or the like. Calculate the area of the paper (“Paper Area”) and weigh it (“Paper Weight”). Cut out the image of the embossment and weigh it (“Embossment Image Weight”). With the known weight and size of the whole paper, and the known weight and magnification of the embossment image, the area of the actual embossment may be calculated using the formula below. Note that magnification must be multiplied twice because both the x and y dimensions of the paper area have been magnified:
Embossment Area={[(Embossment Image Weight)/Paper Weight]*Paper Area}/Magnification2
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 fibrous structure 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). This method is herein referred to as the Basis Weight Method.
The Roll Diameter Tester comprises a vertical stand having a horizontal roll core support. A roll of paper product is placed on the roll core support such that the end of the roll is flush with the vertical stand of the tester. A perforated edge of a tail sheet (the last sheet in the roll) should come off the top of the roll such that the perforated edge of the tail sheet is closest to the analyst testing the roll firmness. The diameter and circumference of the roll are then measured using a diameter tape (Lufkin™ Chrome Clad Diameter Tape, Model C120TP) which does not have a loop at one end, but having a loop at the opposite end.
The diameter tape is wrapped around the roll of paper product in the machine direction such that the diameter tape is wrapped approximately around the center of the roll in the machine direction by passing the end of the diameter tape which does not have a loop through the loop at the opposite end of the diameter tape. The diameter tape is drawn through the loop such that that the diameter tape forms a true circle around the roll of paper product. A 100-gram weight is attached to the free end of the diameter tape. The weight and Roll Diameter Tester is positioned such that the weight is hanging freely. After three seconds, the diameter (“original roll diameter”) and circumference (“original roll circumference”) are recorded to the nearest 0.01 inch (about 0.1 mm).
With the diameter tape still in place, an additional 1000-gram weight (for a total of 1100 grams) is added on the end of the tape. After three seconds, the diameter (“Compressed Roll Diameter”) and circumference (“Compressed Roll Circumference”) are measured the nearest 0.01 inch (about 0.000254 mm) and recorded. The roll firmness, in terms of percentage of compressibility (% Compressibility), can be calculated to the nearest 0.1%, according to the following formula:
% Compressibility=[Original Roll Diam.−Compressed Roll Diam.]/(Original Roll Diam.)×100
All measurements referred to herein are made at 25° C. unless otherwise specified.
The Roll Diameter Tester comprises a vertical stand having a horizontal roll core support. A roll of paper product is placed on the roll core support such that the end of the roll is flush with the vertical stand of the tester. A perforated edge of a tail sheet (the last sheet in the roll) should come off the top of the roll such that the perforated edge of the tail sheet is closest to the analyst testing the roll firmness. The diameter and circumference of the roll are then measured using a diameter tape (Luflin™ Chrome Clad Diameter Tape, Model C120TP) which does not have a loop at one end, but having a loop at the opposite end.
Samples are conditioned at 23+/−1° C. and 50% relative humidity for two hours prior to testing. Sheet Caliper or Loaded Caliper of a sample of fibrous structure product is determined by cutting a sample of the fibrous structure product 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 14.7 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 mils.
All measurements referred to herein are made at 25° C. unless otherwise specified.
Herein, “comprising” means the term “comprising” and can include “consisting of” and “consisting essentially of.”
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.
