Patent Grant
12134863
In the manufacture of paper products, particularly tissue products, it is generally desirable to provide an aesthetically pleasing final product with as much bulk as possible without compromising other product attributes, including softness, flexibility, absorbency, hand feel, and durability. However, most papermaking machines operating today utilize a process known as “wet-pressing”. In “wet-pressing” a large amount of water is removed from the newly-formed web of paper by mechanically pressing water out of the web in a pressure nip. A disadvantage of the pressing step is that it densifies the web, thereby decreasing the bulk and absorbency of the sheet. One problem encountered in the past by first we web pressing and/or then dry embossing is the difficulty in obtaining a tissue basesheet with good functionality, such as absorbency and softness, in combination with a pleasant appearance. This wet-pressing step, while an effective dewatering means, compresses the web and causes a marked reduction in web thickness, thus reducing bulk. In addition, using embossing to apply signature designs to a dry web generally results in a paper product that is gritty to hand feel, stiffer at the pattern edges, and with decreased absorbency.
Alternatives to wet-pressing such as through-air drying generally subject the web to less compression during manufacturing. For example, through-air drying typically involves forming a wet web from a papermaking furnish on a forming media, such as a forming fabric or wire. Then, the wet web is transferred to a permeable through-air-drying fabric around an open drum and non-compressively dried by passing hot air through the web while in intimate contact with the fabric. Through-air drying is a preferred method of drying a web because it avoids the compressive force of the dewatering step used in the conventional wet press method of tissue making. The resulting web optionally may be transferred to a Yankee dryer for creping. Such processes are typically referred to as creped through-air dried (CTAD). Because the web is substantially dry when transferred to the Yankee dryer, the process does not densify the sheet as much as the wet press process, however, embossing may still be needed to provide a tissue product having consumer preferred sheet bulk and designs. As with wet pressed webs, embossing has the drawback of a product that is gritty to hand feel, stiffer at the pattern edges, and with decreased absorbency.
An alternative to CTAD is the uncreped through-air dried (UCTAD) process described in U.S. Pat. Nos. 5,591,309 and 5,593,545. By eliminating the creping step the resulting web has relatively high bulk, good compressibility, and high resiliency, with the attendant benefits of increased absorbency and improved fiber utilization. While the web's improved bulk and resiliency may be desirable traits from a consumer perspective, they make the web difficult to emboss. Often patterns imparted by embossing an UCTAD web are poorly defined and fade over time as the resilient web relaxes.
Because it is poorly suited to embossing, tissue makers wishing to create UCTAD webs with design motifs have often resorted to using patterned through-air drying fabrics. For example, U.S. Pat. Nos. 6,749,719 and 7,624,765 disclose fabrics useful in the formation of tissue webs having design elements using the UCTAD process. While these fabrics may provide webs having design elements, they also impart the web with an overall textured background pattern. Thus, it may be difficult to discern the design elements. Further, the addition of design elements to the through-air drying fabrics reduces their air permeability, which in-turn reduces manufacturing efficiency.
Accordingly, there remains a need in the art for imparting molded through-air dried webs with an embossing design without negatively affecting the web's physical properties or the efficiency with which the webs are manufactured. There also remains a need for an embossing method, particularly a method for embossing high bulk, molded through-air dried tissue webs that provides both an aesthetically appealing multi-ply product and improved sheet bulk.
It has now been discovered that embossed multi-ply through-air dried products can be improved by providing the two outer most plies with different embossing patterns that result in the plies having different tensile strengths. For example, in certain instances the first ply may be embossed with the first pattern comprising line emboss elements and the second ply may be embossed with a second embossing pattern comprising dot emboss elements. The resulting multi-ply tissue products have plies of differing tensile strength, such as a first ply having a geometric mean tensile (GMT) strength greater than 500 g/3″, such as from about 500 to about 600 g/3″ and a second ply having a GMT less than 500 g/3″, such as from about 300 to about 500 g/3″. Preferably the difference in the GMT between the first and second plies is at least about 20 percent, such as from about 20 to about 50 percent.
Accordingly, in one embodiment the present invention provides an embossed multi-ply tissue product comprising: a first embossed tissue ply; a second embossed tissue ply, wherein the first embossed tissue ply has a geometric mean tensile strength that is at least about 20 percent greater than the geometric mean tensile (GMT) strength of the second embossed tissue ply. For example, the first ply may have a GMT from about 550 to about 600 g/3″ and the bottom ply may have a GMT from about 300 to about 400 g/3″.
In another embodiment the present invention provides an embossed multi-ply tissue product having a first and a second outer surface comprising: a first embossed through-air dried tissue ply having a molded topographical pattern and a first embossed pattern; a second embossed through-air dried tissue ply having a molded topographical pattern and a second embossed pattern, wherein the first outer surface of the tissue product has a TS7 value that is at least about 10 percent greater than the TS7 value of the second outer surface of the tissue product. For example, the first ply may have a TS7 greater than about 11.5, such as from about 11.5 to about 13.0 and the second ply may have a TS7 less than about 11, such as from about 10 to about 11.
In still another embodiment the present invention provides an embossed multi-ply tissue product having a first and a second outer surface comprising: a first embossed through-air dried tissue ply having a molded topographical pattern, a first embossed pattern consisting essentially of line emboss elements and a GMT from about 500 to about 600 g/3″; a second embossed tissue ply having a molded topographical pattern, a second embossed pattern consisting essentially of dot emboss elements and a GMT that is at least about 20 percent less than the GMT of the first embossed tissue ply; and wherein the first outer surface of the tissue product has a TS7 value that is at least about 10 percent greater than the TS7 value of the second outer surface of the tissue product.
In yet other embodiments present invention provides a method of making an embossed tissue product comprising the steps of: (a) depositing an aqueous suspension of papermaking fibers (furnish) onto an endless forming fabric to form a wet web; (b) at least partially dewatering the wet web; (c) transferring the partially dewatered web to a through-air drying fabric having a pattern thereon; (d) molding the web to the patterned through-air drying fabric to impart a first molded topographical pattern on the web; (e) through-air-drying the patterned web; (f) embossing the patterned web to impart a first embossed pattern on the web and provide a first embossed tissue ply; (g) embossing the patterned web to impart a second embossed pattern on the web and provide a second embossed tissue ply; and (h) plying the first and second embossed plies together to produce a multi-ply tissue product, wherein the first embossed tissue ply has a geometric mean tensile strength that is at least about 20 percent greater than the geometric mean tensile (GMT) strength of the second embossed tissue ply.
In certain embodiments the first molded topographical pattern, the first embossed pattern and the second embossed pattern are different, but visually related to one another. For example, the first molded topographical pattern may comprise a plurality of continuous, substantially machine direction (MD) oriented wave-like line elements, the second embossing pattern may comprise a plurality of substantially cross-machine direction oriented wave-like curvilinear elements consisting of embossed line elements, and the third embossing pattern may comprise a plurality of wave-like curvilinear elements consisting of dot emboss elements. Surprisingly, providing the second ply with wave-like curvilinear elements consisting of dot emboss elements, particularly a pattern having a pattern density from about 5 to about 15 embossments per square centimeter, provides the desired level of tensile degradation and also increases the bulk of the tissue product.
Accordingly, in another embodiment, the present invention provides an embossed multi-ply tissue product comprising a first tissue ply having a first side and an opposite second side, the first side having a molded topographical pattern and a first embossed pattern comprising a plurality of embossed elements disposed thereon, the first ply having a first GMT of 500 or greater g/3″, such as from 500 to about 600 g/3″; a second tissue ply having a first side and an opposite second side, the first side having a molded topographical pattern and a second embossed pattern comprising a plurality of dot emboss elements disposed thereon, the second ply having a second GMT less than 500 g/3″, such as from about 300 to less than 500 g/3″.
As used herein the term “Basesheet” refers to tissue web formed by any one of the papermaking processes described herein, but has not been subjected to further processing to convert the sheet into a finished product, such as embossing, calendering, perforating, plying, folding, or rolling into individual rolled products.
As used herein the term “Tissue Product” refers to products made from tissue webs and includes, bath tissues, facial tissues, paper towels, industrial wipers, foodservice wipers, napkins, medical pads, and other similar products. Tissue products may comprise one, two, three or more plies.
As used herein the term “Ply” refers to a discrete tissue web used to form a tissue product. Individual plies may be arranged in juxtaposition to each other.
As used therein, the term “Background Pattern” generally refers to a predominant overall pattern disposed on one surface of a tissue product, such as a molded topographical pattern or an embossed pattern.
As used herein, the term “Surface Plane” generally refers to the plane formed by the highest points of an object, such as the upper most surface of an engraved embossing roll, or the upper most surface of a tissue product. The surface plane may be determined by imaging a cross-section of the object, such as a tissue product, and drawing a line tangent to the highest point of its upper surface where the line is generally parallel to the x-axis of the object's surface and does not intersect any portion of the object.
As used herein the term “Pattern” generally refers to the arrangement of one or more design elements. Within a given pattern the design elements may be the same or may be different, further the design elements may be the same relative size or may be different sizes. For example, with reference to
As used herein the term “Motif” generally refers to the recurrence of one or more design elements within a pattern. The recurrence of the design element may not necessarily occur within a given tissue product sheet, for example, in certain embodiments the design element may be a continuous design element extending across two adjacent sheets separated from one another by a line of perforations. Motifs are generally non-random repeating units that form a pattern.
As used herein the term “Linear Element” refers to an element in the shape of a line, which may be continuous, discrete, interrupted, or a partial line with respect to a tissue product on which it is present. The linear element may be of any suitable shape such as straight, curled, curvilinear, and mixtures thereof. In one example, the linear element may comprise a plurality of discrete elements, such as dots, dashes or broken lines for example, that are arranged relative to one another to form a linear element having a substantially connected visual appearance.
As used herein the term “Curvilinear Element” refers to any curved linear element having at least one inflection point. A curvilinear element need not be a line element, but rather may comprise discrete dots, dashes or line segments that are substantially connected visually. For example, with reference to
Curvilinear elements may be used to form one or more design elements according to the present invention. In certain embodiments a design element may be formed from a single curvilinear element or by a plurality of similarly shaped and spaced apart curvilinear elements.
As used herein the term “Continuous” when referring to an element disposed on the surface of a tissue product, such as a linear element, a design element or a pattern, means that the element extends throughout one dimension of the tissue product surface. One non-limiting example of a continuous pattern is illustrated in
As used herein the term “Discrete” when referring to an element disposed on the surface of a tissue product, such as a line emboss element, a dot emboss element, a molded element, or a pattern, means that the element is visually unconnected from other elements. For example,
As used herein, the term “Embossing Pattern” generally refers to arrangement of one or more design elements on the surface of a tissue product, resulting from the tissue product being conveyed through a nip comprising an engraved embossing roll. The design elements may be discrete, semi-continuous or continuous and may comprise a line emboss element, a dot emboss element, or combinations thereof. The embossing pattern generally comprises a portion of the tissue product lying below the upper most surface plane of the tissue product.
As used herein the term “Dot embossment” generally refers to an embossment having a ratio of embossment length, measured along the longest dimension of the embossment, to embossment width, measured along the shortest dimension of the embossment, of about 1:1. Non-limiting examples of dot embossments are embossments that are shaped like circles, squares, rectangles, rectangles or diamonds. A plurality of spaced apart dot embossments that are substantially visually connected may form a linear element despite the embossments being spaced apart from one another.
A used herein the term “Line emboss element” generally refers to an embossment having a ratio of embossment length, measured along the longest dimension of the embossment, to embossment width, measured along the shortest dimension of the embossment, of greater than 1.
As used herein, the term “Embossment Plane” generally refers to the plane formed by the upper surface of the depressed portion of the tissue product forming the embossment. Generally the embossing element plane lies below the tissue product's surface plane. In certain embodiments the tissue product of the present invention may have a single embossing element plane, while in other embodiments the structure may have multiple embossing element planes. The embossing element plane is generally determined by imaging a cross-section of the tissue product and drawing a line tangent to the upper most surface of an embossment where the line is generally parallel to the x-axis of the tissue product.
As used herein the terms “Protuberance” and “Embossing Element” generally refer to any protuberance, boss, lug, finger, head, step, surface, or the like, having a z-directional height when measured from the axis of the roll, or some other common reference point. Generally the height is measured from the “base surface” of the roll, which is understood to be the peripheral surface of the roll having the least radial height when measured from the axis of the roll, or some other common reference point.
As used herein the term “Basis Weight” (BW) generally refers to the bone dry weight per unit area of a tissue and is generally expressed as grams per square meter (gsm). Basis weight is measured using TAPPI test method T-220. While basis weight may be varied, tissue products prepared according to the present invention generally have a basis weight greater than about 10 gsm, such as from about 10 to about 80 gsm and more preferably from about 30 to about 60 gsm.
As used herein, the term “Caliper” is the representative thickness of a single sheet (caliper of tissue products comprising two or more plies is the thickness of a single sheet of tissue product comprising all plies) measured in accordance with TAPPI test method T402 using a ProGage 500 Thickness Tester (Thwing-Albert Instrument Company, West Berlin, NJ). The micrometer has an anvil diameter of 2.22 inches (56.4 mm) and an anvil pressure of 132 grams per square inch (per 6.45 square centimeters) (2.0 kPa). The caliper of a tissue product may vary depending on a variety of manufacturing processes and the number of plies in the product, however, tissue products prepared according to the present invention generally have a caliper greater than about 600 μm, more preferably greater than about 700 μm and still more preferably greater than about 800 μm, such as from about 600 to about 900 μm.
As used herein the term “Sheet Bulk” refers to the quotient of the caliper (generally having units of μm) divided by the bone dry basis weight (generally having units of gsm). The resulting sheet bulk is expressed in cubic centimeters per gram (cc/g). While sheet bulk may vary depending on any one of a number of factors, tissue products prepared according to the present invention may have a sheet bulk greater than about 15.0 cc/g, such as from about 15.0 to about 20.0 cc/g, such as from about 16.0 to about 18.0 cc/g.
As used herein, the term “Geometric Mean Tensile” (GMT) refers to the square root of the product of the machine direction tensile strength and the cross-machine direction tensile strength of the tissue product. While the GMT may vary, tissue products prepared according to the present invention may have a GMT greater than about 700 g/3″, such as from about 700 to about 1,400 g/3″, such as from about 800 to about 1,200 g/3″.
As used herein, the term “Stretch” generally refers to the ratio of the slack-corrected elongation of a specimen at the point it generates its peak load divided by the slack-corrected gauge length in any given orientation. Stretch is an output of the MTS TestWorks™ in the course of determining the tensile strength as described in the Test Methods section herein. Stretch is reported as a percentage and may be reported for machine direction stretch (MDS), cross-machine direction stretch (CDS) or as geometric mean stretch (GMS), which is the square root of the product of machine direction stretch and cross-machine direction stretch. While the stretch of tissue products prepared according to the present invention may vary, in certain embodiments tissue products prepared as disclosed herein have a GMS greater than about 8 percent, more preferably greater than about 10 percent and still more preferably greater than about 12 percent, such as from about 8 to about 14 percent, such as from about 10 to about 12 percent.
As used herein, the terms “T57” and “TS7 value” refer to the output of the EMTEC Tissue Softness Analyzer (commercially available from Emtec Electronic GmbH, Leipzig, Germany) as described in the Test Methods section. TS7 has units of dB V2 rms, however, TS7 may be referred to herein without reference to units. The TS7 value is the frequency peak that occurs around 6.5 kHz on the noise spectrum graph output from the EMTEC Tissue Softness Analyzer. This peak represents the softness of the sample. Generally, softer samples produce a lower TS7 peak.
As used herein, the term “Average TS7” generally refers to the TS7 value for a first and a second side of a tissue product. In certain embodiments the invention provides an embossed multi-ply tissue product, such as a through-air dried tissue product, having an Average TS7 less than about 12.0 and more preferably less than about 11.0, such as from about 10.0 to about 12.0. The foregoing Average TS7 values may be obtained at a product GMT from about 800 to about 1,200 g/3″, such as from about 800 to about 1,000 g/3″.
The present inventors have now discovered that tissue products, particularly multi-ply through-air dried tissue products having a three-dimensional surface topography, having improved softness and sheet bulk may be produced by embossing each of the plies. More particularly, the inventors have discovered that it may be useful to provide a tissue product having a first tissue ply having a molded topographical pattern and a first embossed pattern comprising a plurality of embossed elements disposed thereon, and a second tissue ply having a molded topographical pattern and a second embossed pattern comprising a plurality of dot emboss elements disposed thereon.
Providing the first and second plies with different embossing patterns not only provides an aesthetically pleasing tissue product, the resulting product may also have certain improved physical properties. For example, the tissue product may have plies of differing strengths, such as a first ply that is stronger than the second ply. Accordingly, in certain embodiments the invention provides a tissue product having a first ply having a geometric mean tensile (GMT) strength greater than 500 g/3″, such as from about 500 to about 600 g/3″ and a second ply having a GMT less than 500 g/3″, such as from about 300 to about 500 g/3″. Preferably the difference in the GMT between the first and second plies is at least about 10 percent, more preferably at least about 20 percent and still more preferably at least about 30 percent, such as from about 10 to about 50 percent and more preferably from about 20 to about 50 percent and still more preferably from about 30 to about 50 percent.
In other embodiments the invention provides a tissue product having a first ply having a machine direction tensile (MDT) strength greater than 700 g/3″, such as from 700 to about 900 g/3″ and a second ply having a MDT of about 600 g/3″ or less, such as from about 400 to about 600 g/3″. Preferably the difference in the MDT between the first and second plies is at least about 10 percent, more preferably at least about 20 percent and still more preferably at least about 30 percent, such as from about 10 to about 50 percent and more preferably from about 20 to about 50 percent and still more preferably from about 30 to about 50 percent.
The difference in tensile strength between the first and second plies may result in a product having different softness on each of its outer surface. For example, in certain embodiments the multi-ply tissue product of the present invention has a first stronger ply having an outer surface having a first softness value, generally measured as TS7, and a second weaker ply having an outer surface having a second softness value that is less than the first softness value. In one embodiment the first outer surface of the tissue product has a TS7 value that is at least about 10 percent greater than the TS7 value of the second outer surface of the tissue product. For example, the first ply may have a TS7 greater than about 11.5, such as from about 11.5 to about 13.0 and the second ply may have a TS7 less than about 11, such as from about 10 to about 11.
In still other embodiments the multi-ply tissue products generally have improved sheet bulk, such as a sheet bulk greater than about 15 cubic centimeters per gram (cc/g), and improved softness, such as an Average TS7 less than about 12.0 and more preferably less than about 11.0, such as from about 10.0 to about 12.0. The foregoing Average TS7 values may be obtained at a product geometric mean tensile strength (GMT) from about 800 to about 1,200 g/3″, such as from about 800 to about 1,000 g/3″.
The inventive tissue products differ from commercially available multi-ply tissue products, which generally have plies of similar tensile strength and softness. The table below compares several commercially available tissue products and various inventive tissue products in this regard. A comparison of inventive and commercially available tissue products is further illustrated in
In certain preferred embodiments the improved products may be achieved by embossing the first and second plies with different embossing patterns, such as embossing patterns having different element shapes, size, scale or density. The use of two different embossing patterns may also provide the benefit of producing a product having differing patterns that provide a distinctive look and appeal to consumers.
Generally the first and second embossing patterns are combined with a tissue product having a molded pattern. The molded pattern, which may comprise a plurality of parallel, spaced apart linear elements, may form an overall background pattern over which the embossing pattern may be applied. For example, the tissue product may comprise a first and a second ply, where each ply comprises a molded background pattern consisting essentially of a plurality of parallel substantially machine direction (MD) oriented, continuous, wave-like ridges spaced apart from one another by valleys. The first ply may further comprise a first embossed pattern consisting essentially of line elements, such as continuous curvilinear elements. The second ply may comprise a second embossed pattern consisting essentially of a plurality of dot emboss elements, which in certain instances may be arranged to form a curvilinear element.
Thus, in certain preferred embodiments, the tissue products may be manufactured using a first and a second embossing roll having first and second embossing patterns that are different. For example, the first embossing pattern may comprise linear elements, which may be discrete or continuous, and the second embossing pattern may comprise non-linear elements. While in certain instances the first and second embossing patterns may be different, they may be related to one another. For example, the patterns may both comprise curvilinear elements that are visually related and provide the tissue product with an overall aesthetic that is desirable to a consumer.
In addition to at least partially forming the first and second embossing patterns from curvilinear elements, it may be advantageous to further relate the patterns by providing the elements with a similar scale. For example, the first embossing pattern may comprise a curvilinear line element having a first shape, such as a wave, with two points of inflection that define a segment length from about 30 to about 60 mm and the second embossing pattern may comprise a plurality of dot emboss elements arranged to form a curvilinear element also having a wave-like shape with two points of inflection and a segment length from about 30 to about 60 mm.
In still other instances the first and second embossing patterns may be further related to a molded topographical pattern disposed on the tissue ply. For example, the molded topographical pattern may comprise a plurality of parallel, spaced apart curvilinear elements, such as MD oriented sinusoidal waves, and both the first and second embossing patterns may also comprise curvilinear elements, such as sinusoidal waves.
The patterns may also be visually related to one another by forming the patterns with curvilinear elements having related weights or widths. For example, where the molded topographical pattern and the first embossing patterns are formed from curvilinear elements consisting of line elements the patterns may be related to one another by using similar line widths to form the curvilinear elements.
By providing patterns with similar shapes, scale, and line weights the patterns may appear complementary to one another and enhance the overall aesthetic of the tissue product, making it more visually appealing to consumers. Further, by relating the patterns in terms of shape, scale and line weight, the overall design connotations such as femininity, softness and cleansing are enhanced.
One skilled in the art will appreciate that a wide breadth of design elements may be used to create the various patterns, such as the molded topographical pattern, the first embossing pattern and the second embossing pattern. For example, in certain embodiments the patterns may consist essentially of curvilinear elements. In other embodiments the patterns may comprise a combination of curvilinear and rectilinear or straight elements. In still other embodiments the patterns may consist essentially of rectilinear or straight elements.
Several non-limiting examples of curvilinear elements are illustrated in the attached figures. For example, with reference to
With continued reference to
With reference now to
Two or more patterns, such as a molded pattern and an embossed pattern may combined in a single tissue product, such as the product illustrated in
The embossed elements are generally formed by embossing a tissue ply using an embossing roll having a pattern corresponding to a first embossing pattern engraved thereon. As such, the embossed element is generally a depression having a bottom surface lying below the surface plane of the ply. The shape and depth of the embossment may be controlled by the shape and height of the protuberances on the engraved embossing roll which form the embossment. Further, according to the present invention the embossed elements generally overlay a background pattern, which is preferably formed by molding the ply prior to drying in the web manufacturing process. The molded topographical pattern generally has a three-dimensional shape, such as an upper most surface plane and a lower surface plane. In certain instances the upper most surface plane may correspond to molded peaks and the lower surface plane may corresponded to molded valleys.
With continued reference to
With reference now to
As further illustrated in
Referring now to
In those embodiments where one or more of the patterns consist of wave-like shape, such as a sinusoidal wave, the amplitude may range from about 10 to about 40 mm and still more preferably from about 18 to about 22 mm, and the wavelength may range from about 50 to about 200 mm and still more preferably from about 80 to about 120 mm. For example, in one particular embodiment, the second ply may comprise a molded background pattern and a dot emboss pattern where both patterns comprises a plurality of sinusoidal wave elements having an amplitude ranging from about 10 to about 40 mm and a wavelength ranging from 80 to about 120 mm. The amplitude and wavelength of the patterns may be the same for the molded and embossed patterns, or they may be different. Further, the molded and embossed patterns may be continuous or they may be discrete.
Another embodiment of a dot emboss pattern 140 is shown in
Still another embodiment of a dot emboss pattern 140 is shown in
In addition to curvilinear design elements, particularly wave-like elements such as sine waves, other the dot emboss patterns disposed on the second ply may include other shapes such as zigzag or helix-like designs. In still other embodiments the dot emboss pattern may not be an overall pattern disposed substantially uniformly across the surface of the second tissue ply. Rather, the dot emboss pattern may include additional designs and patterns incorporated into the background pattern.
In the embodiment illustrated in
In certain embodiments both the spacing between dot emboss elements within a given linear element and dot embossments in adjacent elements may be substantially uniform for a given pattern. In other embodiments the spacing may be varied amongst intra-element dot emboss elements and inter-element dot emboss elements. Accordingly, in certain instances the dot emboss element density may be substantially uniform throughout a given pattern and in other instances the density may vary within a given pattern to have areas of high and lower density.
The various illustrated dot emboss patterns are merely a few examples of patterns that may be used in accordance with the present invention. In certain embodiments the dot embossments are disposed in a pattern such that at least about 2 percent, and more preferably at least about 5 percent, of the tissue surface area is covered by dot embossments. In other embodiments the percentage of the tissue surface area covered by dot embossments may range from about 2 to about 15 percent, such as from about 5 to about 10 percent.
In other instances the size of the pattern created by the dot embossments may be increased and decreased. For example, the density of dot emboss elements within a pattern may range from about 7.5 to about 20, particularly from about 7.5 to about 15 embossments per square centimeter and still achieve a soft and high bulk tissue product according to the present invention. Further, dot emboss elements themselves may take various shapes such as, for example, circles, ovals, diamonds, hexagons, triangles or any other suitable geometric formation. In particularly preferred embodiments the dot emboss elements are circular and have a diameter from about 0.075 to about 0.25 cm.
The multi-ply tissue products of the present invention may be manufactured using the apparatus shown in
The engraved embossing roll 212 is generally a hard and non-deformable roll, such as a steel roll, and comprises a plurality of protuberances 216, also referred to herein as embossing elements, extending radially from a first peripheral surface 219. The protuberances are arranged so as to form at least a first embossing pattern. One example of an embossing pattern formed on the outer surface of the first engraved embossing roll is shown in
The protuberances of the first engraved roll may comprise a first pattern consisting of linear elements, and more preferably continuous line elements, where the linear elements are spaced apart from one another to form land areas there between. The land areas may be continuous or discontinuous within a given dimension of the engraved roll depending on the arrangement of linear elements forming the first pattern. The pattern may be continuous along at least one dimension of the engraved roll and even more preferably is a regular, repeating pattern disposed across at least one dimension of the engraved roll.
The spacing and arrangement of the elements forming the first pattern may vary depending on the desired tissue product properties and appearance. The shape of the element may also be varied to provide the desired tissue product properties and appearance. For example, in one embodiment, the linear elements forming the first pattern are curvilinear and more preferably sinusoidal and are arranged substantially parallel to one another such that none of the elements intersect one another. In other embodiments the linear elements may occur as wave-like patterns that are arranged in-phase with one another such that the spacing between adjacent elements is substantially constant. In other embodiments the linear elements may form a wave pattern where adjacent elements are offset from one another.
Regardless of the particular first element shape and the resulting motif and pattern, or whether adjacent elements within a pattern are in or out of phase with one another, it is generally preferred that there is some portion of the roll surface along which adjacent elements within a pattern are separated from one another. In this manner the roll comprises land areas between adjacent elements. In a particularly preferred embodiment the first pattern comprises a plurality of spaced apart linear elements where the pattern is disposed continuously across both the x and y dimensions of the engraved roll surface and adjacent linear elements are spaced apart from one another in the y-dimension at least about 1.0 cm, such as from about 1.0 to about 5.0 cm and more preferably from about 2.0 to about 4.0 cm.
With reference again to
The first impression roll 211 and the first engraved embossing roll 212 are urged together to form a first embossing nip 210 through which the first tissue ply 201 passes to impose a first embossing pattern thereon. Generally a force or pressure is applied to one or both of the rolls such that the rolls are urged against one another causing the impression roll to deform about the protuberances such that when the ply is pressed about the protuberances and onto the landing areas (i.e. the outer surface areas of the roll surrounding the protuberances) an embossment results. As the embossed first tissue ply 205 exits the first embossing nip 210 it comprises a plurality of embossments 230 having distal ends 232.
To form a two-ply tissue product, a second parent roll 202 is unwound and the second tissue ply 204 is conveyed around an idler roller 220 and is then passed into a second embossing nip 215 formed between a second impression roll 217 and a second engraved embossing roll 213. The second impression roll generally has a smooth outer surface, which may be deformable. In certain instances the second impression roll has an outer covering comprising a natural or synthetic rubber and may have a hardness greater than about 40 Shore (A), such as from about 40 to about 100 Shore (A). The second engraved embossing roll 213 generally comprises a plurality of protuberances 222 extending from its peripheral surface 221. The protuberances are generally in the form of dot elements and form a second embossing pattern. In certain embodiments the protuberances disposed on the second engraved embossing roll may have a height of at least about 0.4 mm, such as from about 0.4 to about 2.0 mm.
As the second ply 204 passes through the second embossing nip 215 it is imparted with a plurality of dot emboss elements 231, which may be arranged to form a pattern. The embossed second ply 224 is then conveyed and brought into facing relation with the embossed first ply 205 using a marrying roll 240, as will be described in more detail below. While in certain instances the second engraved embossing roll 213 and impression roll 217 may be arranged relatively close to the first pair of rolls 211, 212 and the marrying roll 240, this is not necessary as the present method does not relying upon registration of the first and second embossing patterns with one another. In this manner, the present method differs from so called nested-method embossing, such as that described in U.S. Publ. No. 20120156447, where the embossing elements of the first embossing roll and the embossing elements of the second embossing roll are arranged such that the embossed elements of the first embossed ply and the embossed elements of the second embossed ply fit into each other similar to a gearing system.
After the embossed second ply 224 leaves the second embossing nip 215 it is brought into facing relationship with the embossed first ply 205. The two embossed plies 205, 224 are conveyed through a third nip 242 formed between the first engraved embossing roll 212 and a marrying roll 240, which may be a steel roll having a substantially smooth outer surface. The first and second embossed plies 205, 224 are joined together as they pass through the third nip 242 to form a multi-ply tissue product 280.
With continued reference to
The resulting two-ply tissue product 280 comprises embossed first and second plies 205, 224 with the first embossed ply 205 forming the upper most surface of the tissue product 280 and the second ply 224 forming the bottom most surface. In certain embodiments the first embossed ply may comprise a first embossed pattern consisting essentially of a plurality of continuous, curvilinear line element embossments and the second ply may comprise a plurality of dot emboss elements disposed thereon in a pattern consisting essentially of curvilinear elements. Further, although not illustrated in
In certain embodiments, to improve processability and one or more physical properties, one or more of the fibrous plies may be subjected to preconditioning to impart moisture and/or heat to the tissue plies prior to entering an embossing nip. For example, preconditioning mechanisms may be positioned upstream of the nip located between the engraved roll and the impression role to introduce moisture and/or heat to the first tissue ply prior to embossing. Methods and arrangements for applying moisture and heat (e.g., steam) to tissue webs are known to skilled artisans, and can be employed and fall within the scope of the present invention. By way of example, steam can be applied to either or both sides of a web prior to embossing.
Tissue webs useful in forming the multi-ply tissue products of the present invention may be formed using any one of several well-known manufacturing processes. For example, in certain embodiments, tissue products may be produced by a through-air drying (TAD) manufacturing process, an advanced tissue molding system (ATMOS) manufacturing process, a structured tissue technology (STT) manufacturing process, or belt creped. In particularly preferred embodiments the tissue product is manufactured by a creped through-air dried (CTAD) process or uncreped through-air dried (UCTAD) process.
Tissue webs produced by the foregoing processes may be imparted with a first pattern by wet molding. For example, one or more design elements may be formed by wet molding the web during manufacture using a patterned papermaking fabric, such as a patterned through-air drying fabric which imparts the pattern on the tissue web as it is dried. The dried web, which retains the molded pattern, may then be subjected to converting, such as embossing, to impart a second pattern on the web.
In one embodiment, tissue webs useful in the present invention are formed by the UCTAD process of: (a) depositing an aqueous suspension of papermaking fibers (furnish) onto an endless forming fabric to form a wet web; (b) at least partially dewatering the wet web; (c) transferring the partially dewatered web to a through-air drying fabric having a pattern thereon; (d) molding the web to the patterned through-air drying fabric to impart a first pattern on the web; (e) through-air-drying the web; and (f) embossing the web to impart a second pattern on the web.
Multi-ply tissue products produced according to the present invention not only have first and second patterns that may be aesthetically pleasing to a consumer, they may also have favorable physical properties, such as sufficient strength to withstand use while also being soft and having good hand-feel. Accordingly, in one embodiment the present invention provides an embossed multi-ply tissue product comprising: a first tissue ply having a first side and an opposite second side, the first side having a molded topographical pattern and a first embossed pattern comprising a plurality of embossed elements disposed thereon; a second tissue ply having a first side and an opposite second side, the first side having a molded topographical pattern and a second embossed pattern comprising a plurality of dot emboss elements disposed thereon, wherein the tissue product has a basis weight from about 10 to about 100 gsm, and more preferably from about 15 to about 60 gsm and a sheet bulk greater than about 15.0 cc/g and more preferably greater than about 16.0 cc/g, and still more preferably greater than about 17.0 cc/g, such as from about 15.0 to about 20.0 cc/g.
In addition to having the foregoing basis weights and sheet bulks, multi-ply tissue products prepared according to the present invention may have a geometric mean tensile (GMT) greater than about 700 g/3″, such as from about 700 to about 1,400 g/3″, and more preferably from about 800 to about 1,200 g/3″ and still more preferably from about 800 to about 1,000 g/3″. At these tensile strengths the tissue webs and products have relatively low Average TS7 values, such as less than about 12.0 and more preferably less than about 11.0, such as from about 10.0 to about 12.0.
In one particularly preferred embodiment of the present invention an embossed multi-ply tissue product comprising: a first tissue ply having a first side and an opposite second side, the first side having a molded topographical pattern and a first embossed pattern comprising a plurality of embossed elements disposed thereon; a second tissue ply having a first side and an opposite second side, the first side having a molded topographical pattern and a second embossed pattern comprising a plurality of dot emboss elements disposed thereon, wherein the tissue product has a basis weight of about 45 gsm or greater, a GMT from about 700 to about 1,000 g/3″, an Average TS7 less than about 12.0 and a sheet bulk greater than about 15.0 cc/g.
Sheet Bulk
Sheet Bulk is calculated as the quotient of the dry sheet caliper (μm) divided by the bone dry basis weight (gsm). Dry sheet caliper is the measurement of the thickness of a single sheet of tissue product (comprising all plies) measured in accordance with TAPPI test method 1402 using a ProGage 500 Thickness Tester (Thwing-Albert Instrument Company, West Berlin, NJ). The micrometer has an anvil diameter of 2.22 inches (56.4 mm) and an anvil pressure of 132 grams per square inch (per 6.45 square centimeters) (2.0 kPa).
Tensile
Tensile testing was done in accordance with TAPPI test method T-576 “Tensile properties of towel and tissue products (using constant rate of elongation)” wherein the testing is conducted on a tensile testing machine maintaining a constant rate of elongation and the width of each specimen tested is 3 inches. More specifically, samples for dry tensile strength testing were prepared by cutting a 3±0.05 inch (76.2±1.3 mm) wide strip in either the machine direction (MD) or cross-machine direction (CD) orientation using a JDC Precision Sample Cutter (Thwing-Albert Instrument Company, Philadelphia, PA, Model No. JDC 3-10, Serial No. 37333) or equivalent. The instrument used for measuring tensile strengths was an MTS Systems Sintech 11S, Serial No. 6233. The data acquisition software was an MTS TestWorks® for Windows Ver. 3.10 (MTS Systems Corp., Research Triangle Park, NC). The load cell was selected from either a 50 Newton or 100 Newton maximum, depending on the strength of the sample being tested, such that the majority of peak load values fall between 10 to 90 percent of the load cell's full scale value. The gauge length between jaws was 4±0.04 inches (101.6±1 mm) for facial tissue and towels and 2±0.02 inches (50.8±0.5 mm) for bath tissue. The crosshead speed was 10±0.4 inches/min (254±1 mm/min), and the break sensitivity was set at 65 percent. The sample was placed in the jaws of the instrument, centered both vertically and horizontally. The test was then started and ended when the specimen broke. The peak load was recorded as either the “MD tensile strength” or the “CD tensile strength” of the specimen depending on the direction of the sample being tested. The geometric mean tensile (GMT) strength was calculated and is expressed as grams-force per 3 inches of sample width. Tensile energy absorbed (TEA) and slope are also calculated by the tensile tester. TEA is reported in units of gm·cm/cm2. Slope is recorded in units of kg. Both TEA and Slope are directionally dependent and thus MD and CD directions are measured independently. Geometric mean TEA and geometric mean slope are defined as the square root of the product of the representative MD and CD values for the given property.
The product tensile strength, and related tensile properties, were tested as multi-ply products and results represent the tensile strength of the total product. For example, a two-ply product was tested as a two-ply product and recorded as such. Five representative specimens were tested for each multi-ply product and the arithmetic average of all individual specimen tests was recorded as the appropriate tensile property of the sample.
The tensile strength, and related tensile properties, of individual plies of a multi-ply product were tested as individual single plies. Prior to testing each individual ply, care was taken to separate each ply of a multi-ply product to ensure that the ply was undamaged. Plies having any tears or defects were discarded. Five representative specimens were tested for each multi-ply product, with each ply being tested individually, and the arithmetic average of all individual specimen tests was recorded as the appropriate tensile property of the given ply.
Tissue Softness
Tissue softness was measured using an EMTEC Tissue Softness Analyzer (“TSA”) (Emtec Electronic GmbH, Leipzig, Germany). The TSA comprises a rotor with vertical blades which rotate on the test piece applying a defined contact pressure. Contact between the vertical blades and the test piece creates vibrations, which are sensed by a vibration sensor. The sensor then transmits a signal to a PC for processing and display. The signal is displayed as a frequency spectrum. For measurement of TS7 values the blades are pressed against the sample with a load of 100 mN and the rotational speed of the blades is two revolutions per second.
The frequency analysis in the range of approximately 200 to 1000 Hz represents the surface smoothness or texture of the test piece. The peak in the frequency range between 200 to 1000 Hz is herein referred to as the TS750 value and is expressed as dB V2 rms. A high amplitude peak correlates to a rougher surface.
A further peak in the frequency range between 6 and 7 kHz represents the softness of the test piece. The peak in the frequency range between 6 and 7 kHz is herein referred to as the TS7 value and is expressed as dB V2 rms. The lower the amplitude of the peak occurring between 6 and 7 kHz, the softer the test piece.
In addition to TS750 and TS7, the analyzer reports a stiffness parameter (D) having units of mm/N. The stiffness parameter (D) is the deformation of the sample under a defined load.
Test samples were prepared by cutting a circular sample having a diameter of 112.8 mm. All samples were allowed to equilibrate at TAPPI standard temperature and humidity conditions for at least 24 hours prior to completing the TSA testing. The softness of the outer most surface of each ply is tested separately. As illustrated in
The sample is secured and the measurements are started via the PC. The PC records, processes and stores all of the data according to standard TSA protocol. The reported values are the average of five replicates, each one with a new sample.
Basesheets were made using a through-air dried papermaking process commonly referred to as “uncreped through-air dried” (“UCTAD”) and generally described in U.S. Pat. No. 5,607,551, the contents of which are incorporated herein in a manner consistent with the present disclosure. Basesheets with a target bone dry basis weight of about 26 grams per square meter (gsm) were produced. The base sheets were then converted by calendering, embossing, plying and winding to yield embossed two-ply tissue products.
In all cases the base sheets were produced from a furnish comprising northern softwood kraft and eucalyptus kraft using a layered headbox fed by three stock chests such that the webs having three layers (two outer layers and a middle layer) were formed. The two outer layers comprised eucalyptus kraft pulp (each layer comprising 30 percent weight by total weight of the web) and the middle layer comprised northern softwood kraft pulp (comprising 30 percent weight by total weight of the web). The center layer contained temporary wet strength, Fennobond 3000 (commercially available from Kemira, Atlanta, GA), which was added at 2 kg per metric ton of furnish. In certain instances the softwood furnish was refined to control strength.
The tissue web was formed on a Voith Fabrics TissueForm V forming fabric, vacuum dewatered to approximately 25 percent consistency and then subjected to rush transfer when transferred to the transfer fabric. The transfer fabric was the fabric described as “Fred” in U.S. Pat. No. 7,611,607 (commercially available from Voith Fabrics, Appleton, WI). The web was then transferred to a through-air drying fabric comprising a printed silicone pattern disposed on the sheet contacting side. The silicone formed a wave-like pattern on the sheet contacting side of the fabric. The pattern had a height of about 0.6 mm, a wavelength of about 100 mm and an amplitude of about 10 mm. The elements within the pattern were spaced apart from one another about 3.08 mm (center-to-center spacing). Transfer to the through-drying fabric was done using vacuum levels of greater than 10 inches of mercury at the transfer. The web was then dried to approximately 98 percent solids before winding.
The basesheet was calendered using two conventional polyurethane/steel calenders. The first calender comprised a 40 P&J polyurethane roll on the air side of the sheet and a standard steel roll on the fabric side at a load of 75 pli. The second calender comprised a 15 P&J polyurethane roll on the air side of the sheet and a standard steel roll on the fabric side at a load of 50 pli.
The calendered basesheet was then converted into two-ply rolled tissue products, substantially as illustrated in
The two-ply tissue product was subjected to physical testing, the results of which are shown in Table 3, below.
Embossing the second ply increased tensile degradation, particularly when the second ply was embossed with a pattern in the form of a sinusoidal wave. Embossing the plies also had the effect of providing each ply with different tensile and softness properties. For example, as illustrated in Tables 4 and 5 below, the first ply was generally at least about 10 percent stronger than the second ply, while the second ply was generally softer than the first ply.
Embossing the second ply with a patterned embossment, particularly a wave-like embossing pattern, was also particularly effective in increasing the sheet bulk of the finished product as illustrated in Table 6, below. Generally, providing the second ply with a wave-like embossing pattern increased sheet bulk from about 8 to about 11 percent compared to a similar product comprising an unembossed second ply. The increase in bulk was also observed compared to embossing the second ply with an overall background pattern.
First embodiment: An embossed multi-ply tissue product comprising: a first embossed tissue ply; a second embossed tissue ply, wherein the first embossed tissue ply has a geometric mean tensile strength that is at least about 20 percent greater than the geometric mean tensile (GMT) strength of the second embossed tissue ply.
Second embodiment: The product of the first embodiment wherein both the first embossed tissue ply comprises a molded topographical pattern and a first embossed pattern and wherein both patterns comprise a plurality of line elements.
Third embodiment: The product of the first or second embodiments wherein the first and second plies comprise an embossed pattern comprising a plurality of wave-like linear elements.
Fourth embodiment: The product of any one of the first through third embodiments wherein the molded topographical pattern, the first embossed pattern and the second embossed pattern are different.
Fifth embodiment: The product of any one of the first through fourth embodiments wherein the product has a GMT from about 700 to about 1,200 g/3″.
Sixth embodiment: The product of any one of the first through fifth embodiments wherein the first embossed tissue ply has a GMT greater than about 500 and the second embossed tissue ply has a GMT less than about 500.
Seventh embodiment: The product of any one of the first through sixth embodiments wherein the first embossed tissue ply has a MD Tensile greater than about 750 g/3″ and the second embossed tissue ply has a MD Tensile less than about 550 g/3″.
Eighth embodiment: The product of any one of the first through seventh embodiments having basis weight from about 20 to about 60 grams per square meter (gsm) and a bulk greater than about 15 cubic centimeters per gram (cc/g).
Ninth embodiment: The product of any one of the first through eighth embodiments wherein the first embossed tissue ply has a CD TEA greater than about 2.0 gf*cm/cm2 and the second embossed tissue ply has a CD TEA less than about 1.0 gf*cm/cm2.
Tenth embodiment: The product of any one of the first through ninth embodiments wherein the first embossed tissue ply has a first embossed pattern consisting essentially of line emboss elements and the second embossed tissue ply has a second embossed pattern consisting essentially of dot emboss elements.
Eleventh embodiment: The product of any one of the first through tenth embodiments wherein the first and the second tissue plies each comprise a through-air dried tissue ply having a molded topographical pattern.
Twelfth embodiment: The product of any one of the first through eleventh embodiments wherein the first and the second tissue plies are through-air dried tissue webs and comprise a molded topographical pattern is imparted by molding of the web to a through-air drying fabric.
Thirteenth embodiment: The product of any one of the first through twelfth embodiments wherein the first and second tissue plies are adhesively bonded to one another at a plurality of bonded regions.
Fourteenth embodiment: The product of any one of the first through thirteenth embodiments wherein at least a portion of the bonded regions are formed between the embossed area of the first ply and the embossed area of the second ply.
Fifteenth embodiment: The product of any one of the first through fourteenth embodiments wherein the first ply comprise a first embossing pattern that is substantially free from dot emboss elements and covers from about 10 to about 30 percent of the first ply surface area; and wherein the second ply comprises a second embossing pattern that is substantially free from line emboss elements and covers from about 2 to about 15 percent, and more preferably from about 5 to about 10 percent, of the second ply surface area.
Sixteenth embodiment: The product of any one of the first through fifteenth embodiments wherein the first outer surface of the tissue product has a TS7 value that is at least about 10 percent greater than the TS7 value of the second outer surface of the tissue product.
Seventeenth embodiment: The product of any one of the first through sixteenth embodiments wherein the second outer surface of the tissue product has a TS7 value from about 9.0 to about 11.0.
Eighteenth embodiment: The product of any one of the first through sixteenth wherein first embossing consists essentially of line emboss elements and covers from about 10 to about 30 percent of the first ply surface area; and wherein the second embossing pattern consists essentially of dot emboss elements having a shape a shape selected from the group consisting of circles, squares, rectangles, diamonds and combinations and wherein the dot emboss elements cover from about 5 to about 10 percent of the second ply surface area.
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| WO2020/180316 | 9/10/2020 | WO | A |
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