Method of making tissue sheets with textured woven fabrics having highlighted design elements

Abstract

A method of making tissue sheets is disclosed in which three-dimensional woven papermaking fabrics, such as throughdrying fabrics, are provided with woven highlight areas, particularly woven highlight areas containing design elements which make the design elements more visible in the resulting tissue product.

Description

BACKGROUND OF THE INVENTION

Throughdrying is a well known method of drying tissue sheets, such as those useful for facial tissue, bath tissue, paper towels and the like. In general, the method involves supporting a wet web on a throughdrying fabric and passing hot air through the web/fabric structure to dry the web with minimal compaction. Throughdrying fabrics have evolved into more three-dimensional structures in order to provide texture and bulk to the tissue sheet, which is often perceived as advantageous by consumers. Examples of such relatively three-dimensional throughdrying fabrics are disclosed, for example, in U.S. Pat. No. 5,429,686 to Chiu et al., U.S. Pat. No. 5,672,248 to Wendt et al., and U.S. Pat. No. 6,398,910 B1to Burazin et al., all of which are hereby incorporated by reference.

Although such three-dimensional throughdrying fabrics have many advantages, the texture imparted to the dried tissue sheet can detract from the visibility of any decorative elements which may also be imparted to the tissue sheet. Therefore there is a need for a throughdrying fabric that can impart texture to the tissue sheet while also imparting distinctive design elements as well.

SUMMARY OF THE INVENTION

It has now been discovered that tissue sheets can be made by using a woven papermaking fabric, such as an air-laid forming fabric or throughdrying fabric, having a three-dimensional topography with “highlight areas” that surround or otherwise outline “design elements”. The highlight areas are imparted to the resulting tissue sheets such that the design elements are more clearly visible. In addition, the presence of the highlight areas enhances roll bulk for tissue products sold in roll form and increases the bulk of multi-ply tissue products by reducing nesting between adjacent plies.

Hence in one aspect, the invention resides in a tissue sheet having a textured background surface (hereinafter defined) which contains a highlight area (hereinafter defined) surrounding a design element (hereinafter defined).

In another aspect, the invention resides in a woven papermaking fabric, particularly a throughdrying fabric, having a sheet-contacting textured background surface which contains a highlight area or a highlight area surrounding a design element.

In another aspect, the invention resides in a method of making a tissue sheet comprising: (a) depositing an aqueous suspension of papermaking fibers onto a forming fabric, thereby forming a wet tissue web; (b) transferring the wet tissue web to a papermaking fabric having a textured sheet-contacting surface containing a highlight area surrounding a design element; and (c) drying the wet tissue web.

In another aspect, the invention resides in a method of forming an air-laid tissue sheet comprising depositing a pneumatic suspension of fibers onto a woven papermaking fabric having a textured background surface containing a highlight area surrounding a design element.

As used herein, the term “tissue sheet” means a low density paper sheet, such as sheets used for facial tissue, bath tissue, paper towels, table napkins and the like. Such sheets are characterized by a bulk of about 4 cubic centimeters or greater per gram as measured under a load of about 90 grams per square inch by conventional methods.

As used herein, the term “papermaking fabric” means any woven fabric used for making a tissue sheet, either by a wet-laid process or an air-laid process. Specific papermaking fabrics within the scope of this invention include wet-laid throughdrying fabrics and air-laid forming fabrics.

As used herein, the term “textured background surface” means a background surface having a three-dimensional topography with z-directional elevation differences of about 0.2 millimeter or greater. The background surface is the overall predominant surface of the sheet or fabric, excluding the portions of the surface occupied by the highlight areas and design elements, and is provided by the general weave pattern. Suitable textured background surfaces include surfaces generally having alternating ridges and valleys or bumps and depressions formed by the knuckles or other structures formed by overlapping warp and shute filaments. Since the texture of the background surface of a tissue sheet generally corresponds to the negative image of the background surface of the throughdrying fabric on which it is dried, or the air-laid forming fabric on which it is formed, the term “textured background surface” applies to both the papermaking fabric and the tissue sheet. For tissue sheets, the textured background surface can also be embossed.

As used herein, the term “surface plane of the textured background surface” means the plane formed by the highest points of the textured background surface.

As used herein, the term “design element” means a decorative figure, icon or shape such as a flower, heart, puppy, logo, trademark, word(s) and the like. The design element can be formed by raised areas, depressed areas or a combination of raised and depressed areas within the highlight area which give the design element a topography that distinguishes the design element from the surrounding highlight area. These raised and/or depressed areas can suitably be one or more curvilinear segments or other shapes. For tissue sheets, the design element can be the same or different color as the textured background surface or highlight area.

As used herein, the term “highlight area” means a woven surface area that either has substantially less surface texture than the surrounding background surface area, or has a texture that is substantially different in character than the surrounding background surface area, or has no texture, so that the design elements are easily distinguishable by the user of the tissue sheet product. It can be particularly advantageous for the highlight areas to be “substantially flat”, meaning they have substantially no elevational differences or few elevational differences in order to enable the design elements to be easily seen. Suitably, such flat areas have z-directional elevation differences of about 0.5 millimeter or less. However, as stated above, the woven highlight areas alternatively can be textured, provided they have a texture that is significantly different in character than the surrounding textured background surface area. Specific examples include, without limitation, a textured background surface area having substantially machine direction ridges and valleys, while the highlight areas comprise relatively flat regions, cross-machine direction ridges or lines, concentric circles or a series of dots. The highlight area can be woven or embroidered, stitched, extruded or embossed. For tissue sheets, the highlight area can be the same or different color as the textured background surface or design element. The highlight area can be raised above the mid-plane of the textured background surface, or it can be depressed below the mid-plane of the textured background surface, or it can be at the same level as the mid-plane of the textured background surface. In each case, the design element can be raised above the surface of the highlight area or depressed below the surface of the highlight area.

As used herein, the term “surface plane of the highlight area” means the plane formed by the highest points of the highlight area.

The area of the highlight area largely depends on the area of the design element. In general, the area of the highlight area can be about 3 square centimeters or greater, more specifically from about 3 to about 1200 square centimeters, more specifically from about 3 to about 150 square centimeters, and still more specifically from about 3 to about 18 square centimeters. The highlight area can substantially be in the shape of the periphery of the design element or it can be substantially different in shape than the periphery of the design element. The shape can be regular or irregular. Specific regular shapes include, without limitation, shapes that are substantially circular, square, triangular, rectangular, or otherwise polygonal or the like. For most applications, the highlight areas will be self-contained and substantially well-defined, although in instances with multiple highlight areas the highlight areas may be interconnected if desired. For most applications, the spacing of the highlight areas (center-to-center) will be about 24 inches or less, more specifically about 6 inches or less, more specifically from about 1 to about 6 inches, and still more specifically from about 1 to about 3 inches. For many design elements, the area of the highlight areas, which includes the area occupied by the design element, will be from about 125 to about 600 percent of the area of the design element, more specifically from about 125 to about 400 percent, more specifically from about 125 to about 300 percent, more specifically from about 125 to about 200 percent of the area of the design element. (The area of the design element is the surface area within a continuous line drawn around the periphery of the design element as a whole.)

Air-permeable highlight areas and design elements are particularly suitable for throughdrying fabrics. The flatness of the highlight areas can be enhanced by depositing an air-permeable material onto the woven highlight areas to fill in the low spots and/or build up the highlight area surface. Particularly suitable air-permeable materials include non-woven fibers and open-celled foam materials. The design elements can be created by extruding a material, such as a thermoplastic material, on top of the highlight areas in the form of the desired design element. Alternatively, design elements can be woven or embroidered, stitched, or embossed. Alternatively, the design elements can recessed within the highlight area and be created by selectively removing portions of the highlight area by cutting, embossing or grinding. In addition, the highlight areas can be created by sanding, grinding, or embossing selected raised areas of the woven fabric.

In developing the various products and methods of this invention, it has also been determined that tissue sheets and papermaking fabrics can benefit by having highlight areas, even without design elements. These highlight areas can serve to build bulk in multi-ply products or roll products and can also provide attractive products in their own right.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photograph of a papermaking fabric in accordance with this invention, in which a relatively flat highlight area has been woven into the three-dimensional background weave pattern.

FIG. 2 is a photograph of a tissue sheet made using the papermaking fabric shown in FIG. 1.

FIG. 3 is a photograph of a papermaking fabric in accordance with this invention comprising a woven textured background surface containing a depressed woven highlight area surrounding a raised extruded design element.

FIG. 4 is a photograph of a tissue sheet in accordance with this invention made using the papermaking fabric of FIG. 3.

FIG. 5 is a photograph of another papermaking fabric in accordance with this invention comprising a woven textured background surface and a woven highlight area overlaid with a foam material, from which a heart-shaped design element was sculpted.

FIG. 6 is a photograph of a tissue sheet in accordance with this invention made using the papermaking fabric of FIG. 5.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1, the invention will be further described in greater detail. Shown is a photograph of a papermaking fabric in accordance with this invention wherein the fabric comprises a woven textured background surface containing a woven highlight area. For this photograph and those that follow, lighting was provided from the top and side, so that depressed areas are dark and raised areas are light. The space between each of the vertical lines in the scale at the bottom of the photograph (and the following photographs) represents one millimeter. The highlight area is made of the same material as, and has distinctively less texture than, the textured background surface. The area of the highlight area is about 3.4 square centimeters. The surface plane of the woven highlight area is at about the same level as the mid-plane of the textured background surface.

FIG. 2 is a photograph of a tissue sheet made using the papermaking fabric shown in FIG. 1.

FIG. 3 is a photograph of a papermaking fabric in accordance with this invention. The design element has been created by extruding a silicone material onto the woven highlight area of the fabric shown in FIG. 1. The area of the highlight area was about 340 percent of the area of the design element. In this embodiment, the surface plane of the highlight area is at about the same level as the mid-plane of the textured background surface, and the design element is raised above the surface plane of the highlight area and is raised above the surface plane of the textured background surface.

FIG. 4 is a plan view photograph of a tissue sheet in accordance with this invention made using the papermaking fabric of FIG. 3.

FIG. 5 is a photograph of another papermaking fabric in accordance with this invention comprising a woven textured background surface containing a raised foam highlight area surrounding a depressed design element sculpted into the highlight area. The surface plane of the highlight area is raised above the mid-plane of the textured background surface and is even with the surface plane of the textured background surface. The design element is depressed below the surface plane of the highlight area and is about even with the mid-plane of the textured background surface. The area of the highlight area was about 520 percent of the area of the design element.

FIG. 6 is a plan view photograph of a tissue sheet in accordance with this invention made using the papermaking fabric of FIG. 5. In this case, the texture of the highlight area of the tissue is relatively flat compared to the texture of the textured background surface. The surface plane of the highlight area is even with the lowest points of the textured background surface. The design element is raised above the surface plane of the highlight area and is below the surface plane of the textured background surface. The fine-line pattern seen in the highlight area is texture remaining from the basesheet tissue.

EXAMPLES

Example 1

In order to further illustrate the method of this invention, a papermaking fabric was produced comprising a woven textured background sheet-contacting surface and a woven highlight area which had substantially less texture than the background texture. The fabric was woven using thermally stable polyester, allowing the fabric to be used as a throughdrying fabric. The fabric is substantially the same as that shown in FIG. 1. An RTV silicone (Ultra Black by Permatex, Inc., Solon, Ohio) was applied via extrusion within the highlight area on one side of the fabric. The silicone was applied to form a design element raised above the surface plane of the highlight area, as shown in FIG. 3.

Tissue handsheet blanks, subsequently used in order to simulate papermaking using the above-described fabric, were made using a process similar to that disclosed in U.S. Pat. No. 5,672,248 to Wendt et al., which is hereby incorporated by reference. In particular, a fiber furnish comprising 100% bleached northern softwood Kraft fiber was fed to a Fourdrinier former using a Voith Fabrics 2164-B33 forming fabric (commercially available from Voith Fabrics in Raleigh, N.C.). The speed of the forming fabric was about 0.33 meters per second. The newly-formed wet tissue web was then dewatered to a consistency of about 30 percent using vacuum suction before being transferred to transfer fabric which was traveling at about 0.33 meters per second. The transfer fabric was a Voith Fabrics 2164-B33 fabric. A vacuum shoe pulling about 15 centimeters of mercury vacuum was used to transfer the wet tissue web to the transfer fabric.

The wet tissue web was then transferred to a Voith Fabrics t807-1 throughdrying fabric. The throughdrying fabric was traveling at a speed of about 0.25 meters per second (about 30% rush transfer). A vacuum shoe pulling about 34 centimeters of mercury vacuum was used to transfer the wet tissue web to the throughdrying fabric. The wet tissue web was carried over a throughdryer operating at a temperature of about 107° C. and dried to final dryness of at least 96 percent consistency. The resulting uncreped throughdried tissue basesheet had the following properties, with conditioning: bone dry Basis Weight, 37 grams per square meter; CD Stretch, 6.0 percent; CD Tensile Strength, 3073 grams per 76.2 millimeters of sample width; MD Stretch, 18.7 percent; and MD Tensile Strength, 2881 grams per 76.2 millimeters of sample width.

The uncreped throughdried tissue basesheet was cut into handsheet blanks which were then molded into the papermaking fabric of FIG. 3. In particular, the handsheet was made by taking a pre-made blank sheet and laying it on the sheet-contacting surface of the fabric. A water mist was added to the sheet to reduce the solids content of the wet sheet to 25%. The wet sheet, still on top of the papermaking fabric, was then molded by traversing a vacuum slot (about 12.7 mm slot width) at a vacuum of about 61 cm water column. The fabric and handsheet were about 11.5 cm wide and 18 cm long in the traversing direction. The fabric and sheet together were moved back and forth over the vacuum slot until the solids content was about 95%. The dry sheet was then removed from the papermaking fabric. The resulting tissue product, shown in FIG. 4, exhibits the negative image of the background texture, highlight area, and design element of the papermaking fabric.

Example 2

In order to further illustrate the method of this invention, a papermaking fabric was produced comprising a woven textured background sheet-contacting surface and a woven highlight area which had substantially less texture than the background texture. The fabric was woven using thermally stable polyester, allowing the fabric to be used as a throughdrying fabric. The fabric is substantially the same as that shown in FIG. 1. A one component, polyurethane foam (Great Stuff manufactured by Dow Chemical, Inc., of Midland, Mich.) was applied to the highlight area of the fabric. After curing, excess foam was removed to a level substantially the same as the surface plane of the woven textured background sheet-contacting surface, creating a filled highlight area. A design element in the shape of a heart was then sculpted into this filled highlight area by removing selected areas of foam using a high-speed rotary tool (Dremel hand tool with attached cutter bit #125 by Robert Bosch Tool Co. of Mount Pleasant, Ill.). The design element is depressed below the height of the foamed highlight area and is essentially co-planar with the woven highlight area in the original fabric. The resultant fabric is shown in FIG. 5.

Tissue handsheet blanks were made as described in Example 1 except that a fiber furnish comprising about 65% bleached eucalyptus fiber and about 35% bleached northern softwood Kraft fiber was utilized. The resulting uncreped throughdried tissue basesheet had the following properties, with conditioning: bone dry Basis Weight, 29.4 grams per square meter; CD Stretch, 6.5 percent; CD Tensile Strength, 1080 grams per 76.2 millimeters of sample width; MD Stretch, 20.4 percent; and MD Tensile Strength, 1256 grams per 76.2 millimeters of sample width.

Following the handsheet procedure described in connection with Example 1, a handsheet was made using the papermaking fabric shown in FIG. 5, except that the molding vacuum was about 56 cm water column, and the fabric and handsheet were about 9 cm wide and 13 cm long in the traversing direction. The resultant sheet is shown in FIG. 6.

It will be appreciated that the foregoing description and examples, given for purposes of illustration, are not to be construed as limiting the scope of the invention, which is defined by the following claims and all equivalents thereto.

Claims

1. A method of making a tissue sheet comprising:

(a) depositing an aqueous suspension of papermaking fibers onto a forming fabric, thereby forming a wet tissue web;

(b) transferring the wet tissue web to a woven papermaking fabric having a textured background sheet-contacting surface containing a woven highlight area surrounding a design element; and

(c) drying the wet tissue web.

2. The method of claim 1 wherein the shape of the highlight area is substantially the same as the periphery of the design element.

3. The method of claim 1 wherein the shape of the highlight area is substantially different than the shape of the periphery of the design element.

4. The method of claim 1 wherein the area of the highlight area is from about 125 to about 600 percent of the area of the design element.

5. The method of claim 1 wherein the design element comprises an extruded material on top of the highlight area.

6. The method of claim 1 wherein the design element is raised above the surface plane of the highlight area.

7. The method of claim 1 wherein the design element is depressed below the surface plane of the highlight area.

8. The method of claim 1 wherein the design element is air-permeable.

9. The method of claim 1 wherein the design element is higher than the surface plane of the textured background surface.

10. The method of claim 1 wherein the woven highlight area is overlaid with a foam material and the design element comprises an extruded material on top of the foam material.

11. The method of claim 10 wherein the woven highlight area is overlaid with a foam material and the design element is recessed within the foam material.

12. A method of making a tissue sheet comprising:

(a) depositing an aqueous suspension of papermaking fibers onto a forming fabric, thereby forming a wet tissue web;

(b) transferring the wet tissue web to a woven papermaking fabric having a textured background sheet-contacting surface containing a woven highlight area; and

(c) drying the wet tissue web.

13. The method of claim 1 or 12 wherein the highlight area is textured.

14. The method of claim 1 or 12 wherein the highlight area is substantially flat.

15. The method of claim 1 or 12 wherein the shape of the highlight area is substantially circular.

16. The method of claim 1 or 12 wherein the shape of the highlight area is substantially rhomboid.

17. The method of claim 1 or 12 having a plurality of highlight areas wherein the center-to-center spacing of the highlight areas is from about 1 to about 6 inches.

18. The method of claim 1 or 12 wherein the area of the highlight area is about 3 square centimeters or greater.

19. The method of claim 1 or 12 wherein the highlight area is air-permeable.

20. The method of claim 1 or 12 wherein the surface plane of the highlight area is higher than the surface plane of the textured background surface.

21. The method of claim 1 or 12 wherein the highlight area is overlaid with an air-permeable open-cell foam material.

22. A tissue sheet made by the method of claim 1 or 12.

23. A method of forming an air-laid web comprising depositing a pneumatic suspension of fibers onto a woven papermaking fabric having a textured background surface containing a woven highlight area.

24. The method of claim 23 wherein the woven highlight area contains a design element.

25. A woven papermaking fabric having a textured background sheet-contacting surface containing a woven highlight area.

26. The fabric of claim 25 wherein the woven highlight area further contains a design element.

27. The fabric of claim 26 wherein the shape of the highlight area is substantially the same as the periphery of the design element.

28. The fabric of claim 26 wherein the shape of the highlight area is substantially different than the shape of the periphery of the design element.

29. The fabric of claim 26 wherein the area of the highlight area is from about 125 to about 600 percent of the area of the design element.

30. The fabric of claim 26 wherein the design element comprises an extruded material on top of the highlight area.

31. The fabric of claim 26 wherein the design element is raised above the surface plane of the highlight area.

32. The fabric of claim 26 wherein the design element is depressed below the surface plane of the highlight area.

33. The fabric of claim 26 wherein the design element is air-permeable.

34. The fabric of claim 26 wherein the design element is higher than the surface plane of the textured background surface.

35. The fabric of claim 26 wherein the woven highlight area is overlaid with a foam material and the design element comprises an extruded material on top of the foam material.

36. The fabric of claim 26 wherein the woven highlight area is overlaid with a foam material and the design element is recessed within the foam material.

37. The fabric of claim 25 or 26 wherein the highlight area is textured.

38. The fabric of claim 25 or 26 wherein the highlight area is substantially flat.

39. The fabric of claim 25 or 26 wherein the shape of the highlight area is substantially circular.

40. The fabric of claim 25 or 26 wherein the shape of the highlight area is substantially rhomboid.

41. The fabric of claim 25 or 26 having a plurality of highlight areas wherein the center-to-center spacing of the highlight areas is from about 1 to about 6 inches.

42. The fabric of claim 25 or 26 wherein the area of the highlight area is about 3 square centimeters or greater.

43. The fabric of claim 25 or 26 wherein the highlight area is air-permeable.

44. The fabric of claim 25 or 26 wherein the surface plane of the highlight area is higher than the surface plane of the textured background surface.

45. The fabric of claim 25 or 26 wherein the highlight area is overlaid with an air-permeable open-cell foam material.