CZ164499A3 - A paper web having a relatively thinner continuous web area and discrete relatively thicker areas in the continuous web area - Google Patents

Abstract

A paper web and method of making the paper web are disclosed. In one embodiment the paper web includes a continuous relatively thinner region and a plurality of discrete relatively thicker regions. The relatively thicker regions are disposed in the plane of the relatively thinner region. The paper web can have a relatively patterned face and a relatively smooth face. The paper structures can be dried relatively quickly and efficiently, and can provide enhanced absorbency and bulk density while having a relatively smooth face.

Description

A paper web having a relatively thinner continuous web region and discrete relatively thicker regions in the plane of the continuous web region

Technical field

This invention relates to paper material and in particular to a tissue paper web having both bulk and smoothness and to methods of producing such a tissue paper web.

State of the art

Paper materials such as toilet paper, paper towels and napkins are widely used in both households and industries. Many attempts have been made to make these products more preferred by consumers.

One approach to obtaining tissue paper products preferred by consumers that have both bulk and flexibility is shown in U.S. Patent 3,994,771, issued November 30, 1976 to Morgan et al., which is hereby incorporated by reference into this specification. Greater bulk and flexibility can also be achieved by juxtaposing compressed and uncompressed zones, as shown in U.S. Patent 4,191,609, issued March 4, 1980 to Trokhan, which is also hereby incorporated by reference into this specification.

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Another approach to making paper products more palatable to consumers is to dry the paper material to provide greater bulk, tensile strength, and reduced tearing. Examples of paper materials made in this manner are shown in U.S. Patent 4,637,859, issued January 20, 1987 to Trokhan, which patent is hereby incorporated by reference into this specification. U.S. Patent 4,637,859 shows discrete, dome-shaped protrusions that are dispersed throughout a continuous web, which patent is also hereby incorporated by reference into this specification. The continuous web can provide strength, while the relatively thicker domes can provide softness and absorbency.

One disadvantage of the papermaking method described in U.S. Patent 4,637,859 is that drying such a web can be relatively energy intensive and expensive and typically involves the use of a cross-flow air dryer. In addition, the papermaking method described in U.S. Patent 4,637,859 may be limited in terms of the speed at which the web can be finally dried on a Yankee dryer drum. This limitation appears to be due at least in part to the pattern formed on the web before it is transferred to the Yankee dryer drum. In particular, the spaced-apart domes described in U.S. Patent 4,637,859 may not be dried on the surface of the Yankee dryer drum as effectively as the continuous web described in U.S. Patent 4,637,859. Therefore, for a given level of consistency and basis weight, there is a limit to the speed at which the Yankee dryer drum can be operated.

The following publications show other methods of making paper web and are hereby incorporated by reference into this specification. WO 95/17548 published June 29, 1995 in the name of Ampulski et al. and having a US priority date of December 20, 1993, WO 96/00812 published January 11, 1996 in the name of Trokhan et al. with a US priority date of June 29, 1994, WO 96/00814 ····· ·· · · · ·

- 3 published on January 11, 1996 in the name of Phan and having a priority date of June 29, 1994, U.S. Patent 5,556,509 issued on September 17, 1996 to Trokhan et al. and U.S. Patent 5,549,790 issued to Phan

August 27, 1996.

U.S. Patents 4,326,000, 4,000,237 and 3,903,342 describe sheet materials having elastomeric bonding materials bonding the surfaces of the sheet together in a pattern. Such a method has the disadvantage that the use of bonding materials can be relatively expensive and difficult to control at production speeds. In addition, the elastomeric bonding material can reduce the absorbency of the web.

Conventional tissue paper, produced by compressing a web using one or more compression felts in a nip, can be produced at relatively high speeds. A pattern can be embossed into a web of conventionally compressed paper after drying, and the macro thickness of the web can be increased. For example, embossed patterns are common in tissue paper products after they have been dried.

However, extrusion processes generally impart a certain aesthetic appearance to the paper material at the expense of other material properties. In particular, extrusion into a dried paper web disrupts the bonds between the pulp fibers in the material. This disruption occurs because bonds are formed and fixed during drying of the germinal pulp of fibers. The displacement of the fibers perpendicular to the plane of the paper structure after drying of the paper material disrupts the bonds between the fibers. The disruption of the bonds results in a reduction in the tensile strength of the dried paper web and, in addition, extrusion is usually carried out after the dried paper web has been creped in a drying drum, creping can disrupt the creping pattern,

Extrusion along the supplied belt.

For example, extrusion can cancel out at some points on the strip • · • fcfc

crepe pattern by compacting or stretching the crepe pattern. Such a result is undesirable because the crepe pattern improves the softness and flexibility of the dried web.

Scientists and papermaking engineers continue to seek improved methods for producing soft, strong, and absorbent tissue paper that can be dried efficiently at reduced costs.

Therefore, it is one object of the present invention to provide a paper web and a method of manufacturing a paper web with multiple regions that allows for relatively rapid drying with relatively low energy consumption and at low cost.

Another object of the present invention is to provide a method of producing multi-region paper that can be produced on an existing paper machine (having conventional or cross-flow air drying) without the need for substantial modification of the paper machine.

Another object of the present invention is to provide a paper web and a method of making a paper web, wherein the web has at least two distinct non-embossed regions differing in one or more of the following properties: thickness, height, density and basis weight.

Another object is to provide a paper web and a method of making a paper web, wherein the web has increased thickness (gauge), bulk density, and absorbency with a relatively patterned face and a relatively smooth reverse surface, thereby imparting both the bulkiness and softness desired by consumers of paper products.

Another object of the present invention is to provide a method of making a paper web, wherein the web is a paper web and is substantially free of • · materials, • 0 0 0 0 0 0 •00 00 0 000 0 000 0 000 00 • • 0 0 0 0 000 000 000 000 binding materials such as elastomeric binding materials that negatively affect absorbency.

The essence of the invention

The invention includes a wet-laid paper web having first and second oppositely facing surfaces. The paper comprises a relatively thinner region and a relatively thicker region, the relatively thicker region being located in the plane of the relatively thinner region. The ratio of the thickness P of the relatively thicker region to the thickness K of the relatively thinner region may be at least about 1.5.

In one embodiment, the paper web comprises a relatively thinner continuous web region, which may have a relatively high density, and a plurality of relatively thicker discrete regions dispersed throughout the continuous web region. The discrete regions are located in the plane of the continuous web region and may have a density that is lower than the density of the continuous web region. In one embodiment, each relatively thicker discrete region may surround at least one discrete densified region.

The paper web may have a basis weight ranging from about 7 to about

about 70 g/m2 and a macro thickness of at least about 0.1 mm and more preferably at least about 0.2 mm and a bulk density of less than or equal to about 0.12 g/ ^cm3 . The paper web may also have an absorbency of at least about 20 g/g.

The paper web may have a surface smoothness ratio of greater than about 1.15, preferably greater than about 1.20, particularly preferably greater than about 1.25, even more preferably greater than 1.30, and most preferably greater than about 1.40. One surface of the web may have a surface smoothness value of less than about 900, and more preferably less than about 850. The opposite surface of the web may have a smoothness value of

« ·· surface of at least about 900 and more preferably at least about 1000. Procedures for measuring area thickness, web macro thickness, web basis weight, web bulk density and surface smoothness ratio are described below.

Overview of images in drawings

While the description concludes with claims which particularly point out and clearly define the invention, the invention will be better understood from the following description, which is accompanied by the drawings, in which like elements are identified by the same reference numeral, wherein:

Figure 1 shows a plan view of a first surface of a paper material according to one embodiment of the present invention, the paper material having a first, relatively thinner continuous web region and a plurality of relatively thicker, spaced apart regions dispersed throughout the continuous web region.

Figure 2 shows the paper material of Figure 1 in cross-section taken along lines 2-2 in Figure 1 and showing relatively thicker discrete regions located in the plane of the continuous web region.

Figure 3 is a micrograph of a section through a paper material of the type shown in Figures 1 and 2.

Figure 4 is a photograph of the first surface of a paper material of the type shown in Figures 1 and 2.

Figure 5 is a photograph of the second surface of a paper material of the type shown in Figures 1 and 2.

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Figure 6 shows a cross-section of prior art paper of the type disclosed in U.S. Patent 4,637,859.

Figure 7A is a microphotograph of a section of a paper strip of the type from U.S. Patent 4,637,859.

Figure 7B is a plan view of one side of a paper web of the type shown in U.S. Patent 4,637,859. Figure 7C is a plan view of the other side of the paper web of Figure 7B.

Figure 8A is a plan view of an apparatus used to produce a paper web of the type shown in Figures 1 and 2, the apparatus including a drainage felt layer and a web patterning layer attached to the drainage felt layer and having a continuous web-contacting upper surface.

Figure 8B shows the apparatus of Figure 8A in cross-section taken along lines 8B shown in Figure 8A.

Figure 8C shows in plan view an apparatus including a drainage felt layer and a patterning layer strip, wherein the patterning layer strip includes a discrete surface contacting strip.

Figure 9A shows a paper machine for producing a paper web with the apparatus of Figures 8A and 8B.

Figure 9B shows a paper web being transferred to the apparatus shown in Figure 8B to form a paper web having a first surface substantially conforming to the apparatus and a second surface substantially smooth.

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Figure 9C shows a paper web on the apparatus shown in Figure 8B supported between a vacuum nip roller and a Yankee dryer drum so that a pattern is formed on a first surface of the paper web and the second surface of the paper web is adjacent the Yankee drum.

Figure 9D shows a cross-sectional view of a two-ply tissue paper comprising two webs of the type shown in Figure 2 with relatively smoother second surfaces of the webs facing outwardly.

Figure 10 is a cross-sectional view of a paper web made in accordance with an alternative embodiment of the present invention showing relatively thicker discrete regions located in the plane of a continuous network region, each discrete region surrounding one or more discrete densified regions.

Figure 11 is a micrograph of a section through a paper material of the type shown in Figure 10.

Figure 12 is a photograph of the first surface of a paper material of the type shown in Figure 10.

Figure 13 is a photograph of the second surface of a paper material of the type shown in Figure 10.

Figure 14A is a plan view of an apparatus for use in making a paper web of the type shown in Figure 10, the apparatus including a web patterning layer attached to a perforated element formed from woven fibers.

Figure 14B shows a cross-sectional view of the apparatus of Figure 14.

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Figure 15A shows a paper machine with the apparatus of Figures 14A and 14B.

for belt production

Figure 15B shows a web of paper being conveyed to the apparatus shown in Figure 14B to form a web of paper having a first surface conforming to the apparatus and a second surface that is substantially smooth.

Figure 15C shows a paper web on the apparatus shown in Figure 14B being carried between a nip roll and a Yankee dryer drum so that a pattern is impressed on a first surface of the paper web and the second surface of the web adheres to the Yankee drum.

Figure 16 shows a cross-sectional view of a paper web produced in accordance with one embodiment of the present invention, the web comprising multiple layers of fibers including a debonding layer.

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Figures 1 and 2 illustrate a paper web 20 made in accordance with one embodiment of the present invention, and Figures 3 through 5 are photographs of a paper structure of the type shown in Figures 1 and 2. For comparison purposes, Figures 6 and 7A through 7C illustrate a paper web of the type described in U.S. Patent 4,637,859.

A paper web made in accordance with one embodiment of the present invention comprises a relatively thinner region and a relatively thicker region, wherein the relatively thicker region is located in the plane of the relatively thinner region. The paper web is laid wet and may be substantially free of dry areas. Referring to Figures 1 to 5, the paper web 20 has a first surface 22 and a second facing surface 24.

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The paper web 20 includes a relatively thinner region 30 having a thickness indicated by 32, bordering the region 30, and a thickness indicated by 34.

continuous mesh K. Part of the surface 22 and part of the surface 2 4

The belt 20 also includes a plurality of relatively thicker regions 50 dispersed throughout the continuous mesh region 30. The relatively thicker regions 50 have a thickness designated P and extend from the surface 32 of the continuous mesh region 30. The portion of the surface 22 bordering the regions 50 is designated 52 and the portion of the surface 24 bordering the regions 50 is designated 54 . The thickness P is greater than the thickness K. Preferably, the ratio P/K is at least about 1.5. Referring to Figure 3 , P may be at least about 0.3 mm and preferably at least about 0.40 mm. K may be less than about 0.25 mm and more preferably less than about 0.20 mm.

The continuous web region and the discrete, relatively thicker regions 50 may both be pre-shortened, for example by creping. In Figures 1 and 2, the creping combs of the continuous web region are indicated by the numeral 35 and extend generally in the cross-machine direction. The discrete, relatively thicker regions 50 may also be similarly pre-shortened to have creping combs 55.

The continuous network region 30 may be a relatively high density, macroscopically monoplanar continuous network region of the type described in U.S. Patent 4,637,859. The relatively thicker regions 50 may have a relatively low density and may be distributed bilaterally alternately as described in U.S. Patent 4,637,859, but the relatively thicker regions 50 are not domes of the type shown in U.S. Patent 4,637,859.

The relatively thicker regions 50 are located in the plane of the continuous mesh region 30. The height of the mesh region plane 30 • to this·· * · ··· « to · ··· ·· ·· ·· • to· to « to · ··· ··· • · to ·· is schematically represented by surface 23 (appearing as a straight line in Figure 2). Surface 23 is located midway between surfaces 32 and 34. While the mesh plane 30 is shown in Figure 2 as being flat, it is understood that the mesh plane 30 may include surface 23 having a curvature.

By the term located in the plane of the continuous mesh region 30 is meant that the relatively thicker region 50 includes a portion extending both above and below the surface 23. As can be seen from Figure 2, a portion of the thicker region 50 extends along an imaginary line 25. The portion of the region 50 extending along an imaginary line 25 is located both above and below the surface 23 such that the intersection of line 25 with surface 52 is above the surface 23 and the intersection of line 25 with surface 54 is below the surface 23.

The procedure for measuring the thicknesses P and K and the procedure for determining the location of the surface 23 to determine whether the region 50 is located in the plane of the region 30 are described below in the Thickness and Height Measurement section.

Unlike the paper web shown in Figures 1 and 2, the paper web 80 shown in Figure 6, which is described in U.S. Patent No. 4,637,859, does not have relatively thicker regions located in the plane of the continuous web. U.S. Patent No. 4,637,859 describes domes 84 dispersed throughout the continuous web 83. In Figure 6, the domes 84 are not located in the plane of the web 83. Instead, as can be seen in Figure 6, the lower surface of the domes 84 is located above the surface 23 shown in Figure 6. A micrograph of a paper web of the type described in U.S. Patent No. 4,637,859 is shown in Figure 7A, and the oppositely facing surfaces of such a paper web are shown in Figures 7B and 7C.

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Accordingly, the paper web 20 shown in Figures 1 and 2 can have the strength advantages of the continuous web region 30, bulk density, macrothickness, absorbency, and softness derived from the relatively thicker regions 50 and yet still have a relatively smooth surface 24 compared to paper of the type shown in U.S. Patent 4,637,859.

In particular, the paper web 20 may have a surface smoothness ratio greater than about 1.15, preferably greater than about 1.20, even more preferably about 1.25, even more preferably 1.30, and most preferably about 1.40, where the surface smoothness ratio is the surface smoothness value of surface 22 divided by the surface smoothness value of surface 24.

In one embodiment, surface 24 of strip 20 may have a surface smoothness value of less than about 900, and more preferably less than about 850. Opposite surface 22 may have a surface smoothness value of at least about 900, and more preferably at least about 1000.

The method for measuring the surface smoothness value of a surface is described below in the Surface Smoothness section. The surface smoothness value of a surface increases as the surface becomes more textured and less smooth. A relatively low surface smoothness value then results in a relatively smooth surface.

In contrast to the paper webs 20 of the present invention, a paper pattern of the type described in U.S. Patent 4,637,859 may exhibit a surface smoothness ratio of about 1.07 and smoothness values on opposite surfaces of about 993 and 1065.

One advantage of the paper web 20 is the combination of a relatively smooth surface 24 to provide softness, relatively thicker areas 50 to provide relatively high

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bulkiness and absorbency and compacted relatively thinner, relatively high density web regions 30 for strength. In addition, the paper web 20 can be formed and dried relatively quickly and efficiently as described below.

A paper web 20 having a relatively smooth surface 24 may be useful in the manufacture of multi-ply folded tissue paper having smooth outwardly facing surfaces. For example, two or more webs 20 may be combined to form a multi-ply folded tissue paper such that the two outwardly facing surfaces of the multi-ply folded tissue paper include surfaces 24 of the webs 20 and the surfaces 22 of the outer plies face inwardly. Such a multi-ply folded tissue paper may have the strength and bulk advantages associated with relatively thicker areas dispersed throughout the continuous web area while still presenting a relatively smooth and soft outer surface to the touch of the customer.

An example of such a two-ply tissue paper is shown in Figure 9D. The two webs 20 can be joined together by placing them side by side in any suitable manner, including, but not limited to, bonding by adhesive, mechanical, ultrasonic, and combinations of these methods.

The paper web 20 may have a basis weight of about 7 to about 70 g/m2. The paper web 20 may have a macro-thickness of at least about 0.1 mm, and preferably at least about 0.2 mm, and a bulk density of at least about 0.12 g/cm3 (basis weight divided by macro-thickness). Methods for measuring the basis weight, macro-thickness, and bulk density of the web are described below.

The paper web 20 of the type shown in Figures 1 and 2 may also have an absorbent capacity of at least about 20 g/g. A method for measuring absorbent capacity is described below. The paper web 20 exhibits the advantages of absorbent capacity as paper webs of high bulk combined with the advantages of a relatively smooth surface typically associated with conventional tissue papers that are conventionally pressed with felt.

Belt supporting the apparatus

Figures 8A and 8B illustrate a web support apparatus 200 for use in making a paper web of the type shown in Figures 1 and 2. The web support apparatus 200 includes a drainage felt layer 220 and a patterning belt, layer 2.50. The web support apparatus 200 may be in the form of a continuous belt for drying and imparting patterning to a paper web in a papermaking machine. The web support apparatus 200 has a first face side 202 of the web and a second face side 204 facing away from the other side. The web support apparatus 200 is shown in Figure 8A with the first face side 202 facing the viewer. The first face side 202 of the web includes a first surface that contacts the web and a second surface that contacts the web.

In Figures 8A and 8B, the first surface contacting the belt is a first felt surface 230 of the felt layer 220. The first felt surface 230 is positioned at a first height 231. The first felt surface 230 is the felt surface that contacts the belt. The felt layer 220 also has a second felt surface 232 facing the opposite side.

In Figures 8A and 8B, the second web contacting surface is provided with a patterning layer 250. The patterning layer 250, which is attached to the felt layer 220, has a web contacting upper surface 260 at a second height 261. The difference between the first height 231 and the second height 261 is less than the thickness of the paper web when the paper web is transferred to the web supporting apparatus 200. The surfaces 260 and 230 can be positioned at the same height, such that the heights 231 and 261 are the same. Alternatively, the surface 260 may be slightly above the surface 230, or the surface 230 may be slightly above the surface 260.

The difference in height is greater than or equal to 0.0 mil and less than about 8.0 mils (0.20 mm). In one embodiment, the difference in height is less than about 6.0 mils (0.15 mm), more preferably less than about 4.0 mils (0.10 mm), and most preferably less than about 2.0 mils (0.05 mm), to maintain a relatively smooth surface 24 as described below.

The drainage felt layer 220 is permeable to water and is capable of receiving and containing water extruded from a wet web of paper-forming fibers. The web patterning layer 250 is impermeable to water and does not receive or contain water extruded from the web of paper-forming fibers. The web patterning layer 250 may have a continuous top surface 260 that is in contact with the web, as shown in Figure 8A. The web patterning layer may alternatively be discontinuous or semi-continuous. The discontinuous top layer 260 is shown in Figure 8C.

The strip patterning layer 250 preferably includes a photosensitive resin that can be deposited on the first surface 230 as a liquid and subsequently crosslinked by radiation such that a portion of the strip patterning layer 250 penetrates and is thereby securely attached to the first felt surface 230. The strip patterning layer 250 preferably does not extend through the entire thickness of the felt layer 220, but instead extends into less than about half of the thickness of the felt layer 220 to maintain the flexibility and compressibility of the strip support apparatus 200 and, in particular, the flexibility and compressibility of the felt layer 220.

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A suitable drainage felt layer 220 comprises a nonwoven web 240 of natural or synthetic fibers needled * to a carrier material formed of woven fibers 244 . Suitable materials from which the nonwoven web may be formed may * include, but are not limited to, natural fibers such as wool and synthetic fibers such as polyester and nylon. The fibers from which the web 240 is formed may have a denier of between about 3 and about 20 grams per 9000 meters of fiber length.

The felt layer 220 may have a layered construction and may include a mixture of fiber types and sizes. The felt layer 220 is configured to assist in transporting water received from the web away from the first felt surface 230 and toward the second felt surface 232. The felt layer 220 may have finer, relatively more densely packed fibers located proximate the first felt surface 230. The felt layer 220 preferably has a relatively high density and a relatively small pore size proximate the first felt surface 230 compared to the density and pore size of the felt layer 220 at the second felt surface 232, such that water entering the first surface 230 is carried away from the first surface 230.

The drainage felt layer 220 may have a thickness greater than about 2 mm. In one embodiment, the drainage felt layer 220 may have a thickness ranging from about 2 mm to about 5 mm.

PCT Publication WO 96/00812 published January 11, 1996, WO 96/22555, published August 22, 1996, and WO 96/25547 published August 22, 1996, all to Trokhan et al., U.S. Patent Application Serial No. 08/701,600 Method of Applying Resin to Papermaking Materials, filed August 22, 1996, U.S. Patent Application Serial No. 08/640,452 High Absorbency/Low Reflectivity Felts with Patterned Layer, filed April 30, 1996, and U.S. Patent Application Serial No. 08/672,293 Method

- 17 * «« • 4 · • 444 9 4 4 4 4 4 4 949 49 49 4449 4 4 4 4 • 44 4 4 4 9 4 4 4 4 49 4 49 4 4 4 44 4 • 4 4 9 · 4 • 9 94 94 wet production expelled silk paper with felts having chosen permeability, filed on the 28th June 1996 is this includes in the form of a link for the purpose description use

photosensitive resins for felt drainage and for the purpose of describing suitable drainage felts.

The drainage felt layer 220 may have an air permeability of less than about 200 standard cubic feet per minute (scfm) (60.96 Nm3/min am), where air permeability in scfm is a measure of the number of cubic feet of air per minute that will pass through an area of one square foot (0.093 ^m2 ) of the felt layer at a pressure differential across the drainage felt thickness of about 0.5 inches (1.34 mm) of water column. In one embodiment, the drainage felt layer 220 may have an air permeability in the range of about 5 to about 200 scfm (1.52 to 60.96 ^Nm3 /min ^am2 ), preferably less than about 100 scfm (30.48 ^Nm3 /min ^am2 ).

The drainage felt layer 220 may have a basis weight in the range of between about 800 and about 2000 g/m ² , an average density (basis weight divided by thickness) in the range of between about 0.35 g/cm 3 and about 0.45 g/cm 3 . The air permeability of the belt support apparatus 200 for supporting the belt is less than or equal to the permeability of the felt layer 220.

One suitable felt layer 220 is Amflex 2 Press Felt manufactured by Appleton Mills Company, Appleton, Wisconsin, USA. Felt layer 220 is Amflex 2 Press Felt manufactured by Appleton Mills Company, Appleton, Wisconsin, USA. Felt layer 220 may have a thickness of about 3 mm, a basis weight of about 1400 g/m ² , an air permeability of about 30 scfm (9.14

Nm ^J /min am ² ) and have a two-layer support structure having a three-ply or more fiber top and warp bottom and a 4-ply cable monofilament weft across the machine. The 240 web may include polyester fibers having a denier of about 3 on the first • ·· ·· *· · · · · • ··· » 9 • · · · · · · • 9 · W · »«· 99 99 ··· 99 99

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The belt support apparatus 200 shown in Figure 8A has a belt patterning layer 250 having a continuous mesh top surface 260 that is in contact with the belt and having a plurality of discrete apertures 270 therein. Suitable shapes of apertures 270 include, but are not limited to, circles, machine direction elongated ovals (designated MD in Figure 8A), polygons, irregular shapes, or mixtures thereof. The projected surface area of the continuous mesh top surface 260 can range from about 5 to about 75 percent of the projected surface area of the belt support apparatus 200 as shown in Figure 8A, and is preferably between about 25 percent and about 50 percent of the projected surface area of the apparatus 200.

In the embodiment shown in Figure 8a, the continuous upper mesh surface 260 may have less than about 700 spaced apart openings per square inch (109/ ^cm2 ) of the projected area of the apparatus 200, and preferably about 10 to about 400 spaced apart openings 270 per square inch (1.5 to 62/cm2) of the projected area of the apparatus as shown in Figure 8A. The spaced apart apertures 270 may be arranged in a bilateral alternating zigzag pattern in the machine direction (MD) and cross-machine direction (CD) as described in U.S. Patent 4,637,859 issued January 20, 1987. In one embodiment, the apertures 270 may be overlapping and arranged in a bilateral alternating zigzag pattern with apertures sized and spaced such that in both the machine direction and cross-machine direction the edges of the apertures 270 overlap one another and such that any line drawn parallel to the machine direction or the cross-machine direction will pass through at least some of the apertures 270.

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Description of the paper production method

The paper material 20 of the present invention can be made on a papermaking machine as shown in Figures 9A, 9B and 9C. Referring to Figure 9A, the method of making the paper material 20 of the present invention begins by taking an aqueous dispersion of papermaking fibers in the form of a paper pulp and placing it from a headbox 500 onto a foraminous, liquid-permeable forming member such as a forming belt 542, followed by forming a seed belt of papermaking fibers 543 supported by the forming belt 542. For simplicity, the forming belt is shown as a single Fourdrinier wire. It is understood that any of a variety of double forming wires may be used.

It is contemplated that the paper forming fibers used in the present invention may be wood pulp pulps in all their varieties. However, other cellulosic fibrous pulps such as those from cotton, bagasse, rayon, etc. may also be used and none are excluded. Wood pulps that may be used herein include chemical pulps such as Kraft kraft pulp, kraft and kraft pulps, as well as mechanical pulps including, for example, ground wood, thermomechanical pulps, and chemical thermomechanical pulps (CTMP). Pulps from both deciduous and coniferous trees may be used.

Both hardwood pulps and softwood pulps can be used, as well as mixtures of the two. The term hardwood pulp as used herein refers to fibrous pulp derived from woody material from broadleaf trees (angiosperms), while softwood pulps are fibrous pulps derived from • · · • · ··· ·

- 20 woody material of coniferous trees (gymnosperms). Hardwood pulps such as eucalyptus, having an average fiber length of about 1.00 mm, are particularly suitable for the tissue paper webs described below where softness is important, while Northern Softwood Kraft pulps having an average fiber length of about 2.5 mm are preferred where strength is required. Also useful in the present invention are fibers derived from recycled paper, which may include any or all of the above categories, as well as other non-fibrous materials such as fillers and adhesives used to facilitate the original papermaking process.

The paper coating may include a variety of additives, including, but not limited to, fibrous binders such as wet strength binders, dry strength binders, and chemical plasticizers. Suitable wet strength binders include, but are not limited to, polyamide-epichlorohydrin resins sold under the trade name KYMENE® 557H by Hercules Inc., Wilmington, Delaware, USA. Suitable temporary wet strength binders include, but are not limited to, modified starch binders such as NATIONAL STARCH® 78-0080 sold by National Starch Chemical Corporation, New York, New York, USA. Suitable dry strength binders include, but are not limited to, carboxymethyl cellulose and cationic polymers such as ACCO® 711. The xACCO® dry strength family of materials is available from American Cvanamid Company. Wavne, New Jersey, USA.

The paper coating deposited on the forming wire preferably includes a debonding agent to inhibit some of the bonds between the fibers as the web is dried. The debonding agent, in combination with the energy supplied to the web by the dry creping process, results in a portion of the web being densified. In one embodiment, it may be • fefe • · fefefefe fe • ·

debonding agent applied to the fibers forming the interlayer of fibers, located between two or more layers. The interlayer acts as a debonding layer between the outer layers of fibers. The creping energy can therefore lead to a loosening of the portion between the outer layers of fibers. The creping energy can therefore compact a portion of the web along the debonding layer. The loosening of the web can lead to voids 310 (Figure 16).

As a result, the web can be formed to have a relatively smooth surface for efficient drying on a Yankee dryer drum. However, due to compaction on the creping blade, the dried web can also have regions of varying density, including a continuous reticulated relatively high density region and discrete relatively low density regions that are created by the creping process.

Suitable debonding agents include chemical softening compounds such as those described in U.S. Patent 5,279,767, issued January 18, 1994 to Phan et al. Suitable biodegradable chemical softeners are described in U.S. Patent 5,312,522, issued May 17, 1994 to Phan et al. U.S. Patents 5,279,767 and 5,312,522 are hereby incorporated by reference into this specification. Such chemical softeners can be used as debonding agents to break the bonds between fibers in one or more layers of fibers forming a web.

One suitable plasticizer for providing for the disruption of interfiber bonds in one or more layers of fibers forming the web 20 is a papermaking additive comprising diester-di(contact-hardened) thallium dimethylammonium chloride. A suitable plasticizer used in papermaking is the brand name ADOGEN® additive sold by Witco Company, Greenwich, CT, USA.

• ·· • · · ··· ··· • ί · ·

M ·· ··

The seed web 543 is preferably prepared from an aqueous dispersion of the papermaking fibers, although dispersions in liquids other than water may be used. The fibers are dispersed in a carrier liquid to have a consistency of from about 0.1 to about 0.3 percent. The percent consistency of a dispersion, pulp, web, or other system is defined as 100 times the coefficient obtained when the weight of the dry fibers in the system under consideration is divided by the total weight of the system. The weight of the fibers is always expressed on a completely dry fiber basis.

The seed web 543 can be formed in a continuous papermaking process as shown in Figure 9A or alternatively in a batch process such as manual papermaking. After the dispersion of papermaking fibers is deposited on the forming web 542, the seed web 543 is formed by removing a portion of the aqueous dispersion medium by methods well known to those skilled in the art. The seed web is generally monoplanar and is formed to have substantially smooth, macroscopically monoplanar first and second surfaces using any suitable forming web 542.

Vacuum boxes, forming plates, hydrofoils, etc. can be used to remove water from the dispersion. The seed belt 543 advances together with the forming belt 542 around the return roller 502 and comes into proximity with the belt support apparatus 200.

The next step in the production of the germ belt 543 supporting the transferred paper material 20 involves transferring the belt from the forming belt 542 to the apparatus 200 and the belt (designated 545 in the figure)

9B) on the first side 202 of the apparatus 200. The germinal band at the transition to the apparatus 200 preferably has a consistency ranging from about to about 20 percent.

The web is transferred to the apparatus 200 such that the first face 547 of the transferred web 545 is supported and follows the surface 202 of the apparatus 200 with portions of the web 545 supported on surface 260 and portions of the web supported on felt surface 230. The second surface 549 of the web is maintained in a substantially smooth, macroscopically monoplanar configuration. Referring to Figure 9B, the height difference between surface 260 and surface 230 of the web support apparatus 200 is sufficiently small such that the second back side of the germ web remains substantially smooth and macroscopically monoplanar as the web is transferred to the apparatus 200. In particular, the height difference between surface 260 and surface 230 should be less than the thickness of the germ web at the point of transfer.

The steps of transferring the seed strip 543 to the apparatus 200 may be provided at least in part by applying a fluid pressure differential to the seed strip 543. For example, the seed strip 543 may be a vacuum transferred from the forming strip 542 to the apparatus 200 by a vacuum source 600, such as a vacuum foot or vacuum cylinder, as shown in Figure 9A. One or more additional vacuum sources 620 may also be provided downstream of the seed strip transfer point to provide additional dewatering.

The belt 545 is carried on the apparatus 200 in the machine direction (MD in FIG. 9A) to a nip 800 existing between the vacuum press cylinder 900 and the hard surface 875 of the heated Yankee dryer drum 880. Referring to FIG. 9C, a steam trap 2800 is positioned directly in front of the nip 800. The steam trap 2800 directs steam directly onto the surface 549 of the belt 545 as the surface 547 of the belt 545 is conveyed through the vacuum providing portion 920 of the vacuum press cylinder 900.

The steam trap 2800 is mounted opposite the vacuum providing portion 920. The vacuum providing portion 920 draws steam into the web 545 and the felt layer 220. The steam provided by the steam trap 2800

• to to · ·· · · ι to · · » ·· · • · · to · · • · to· ·· heats the water in the paper web 545 and the felt layer 220, thereby reducing the viscosity of the water in the web and the felt layer 220. This causes the water in the web and the felt layer 220 to be more easily removed by the vacuum provided by the cylinder 900.

The steam hood 2800 can provide about 0.3 pounds (0.14 kg) of saturated steam per pound (0.45 kg) of dry fiber at a pressure of less than about 15 psi (0.1 MPa). The vacuum providing portion 920 provides a vacuum on the surface 204 in the range of about 1 to about 15 inches (25.4 to 381 mm) of mercury, and preferably in the range of about 3 to about 12 inches (76 to 305 mm) of mercury. A suitable vacuum nip 900 is a suction nip manufactured by Winchester Roli Products. A suitable steam hood 2800 is a type D5A manufactured by Measurex-Devron Company, North Vancouver, British Columbia, Canada.

The vacuum providing portion 920 is in communication with a vacuum source (not shown). The vacuum providing portion 920 is stationary relative to the rotating surface 910 of the cylinder 900. The surface 910 may be a drilled or grooved surface through which a vacuum is applied to the surface 204. The surface 910 rotates in the direction shown in Figure 9C. The vacuum providing portion 920 provides a vacuum to the surface 204 of the belt supporting apparatus 200 as the belt and apparatus 200 are carried through the steam trap 2800 and through the gap 800. While only the vacuum providing portion 920 is shown, in other embodiments it may be desirable to provide separate vacuum providing portions, each providing a different vacuum to the surface 204 as the apparatus 200 passes around the cylinder 900.

A Yankee dryer typically includes a steam-heated steel or iron drum. Referring to Figure 9C, a belt 545 is carried in a gap 800 on the apparatus 200 such that the substantially smooth second surface 549 of the belt can be conveyed to surface 875. Before • · · •9 ··»·

- 25 » 99 • 9 4 • 9 I »9 9 9 4

4 > 99 gap, before the point where the web is transferred to surface 875, nozzle 890 applies adhesive to surface 875.

The adhesive may be a polyvinyl alcohol-based adhesive. Alternatively, the adhesive may be a CREPTROL® type adhesive manufactured by Hercules Company, Wilmington, Delaware, USA. Other adhesives may be used. Generally, in embodiments where the web is transferred to a Yankee 880 dryer drum at a consistency greater than about 40

percent is it possible use glue such as CREPTROL® adhesive. Glue can to be applied on the belt directly or indirectly a number of ways (as is it the case with application on the surface of the drying drum Yankee 875) . For example, it can to have glue sprayed on belt in

in the form of microdroplets or on the surface of the Yankee dryer drum 875. Alternatively, the adhesive could also be applied to the surface 875 by a coating roller or brush. In yet another embodiment, the creping adhesive could be added to the paper coating at the wet end of the paper machine, for example by adding the adhesive to the paper coating in the headbox 500. On the Yankee dryer drum 880, from about 2 pounds to about 4 pounds of adhesive can be applied per ton of dried paper fibers.

900

As the web is supported on the apparatus 200 through the gap 800, the vacuum providing portion 920 of the roller 900 provides a vacuum on the surface 204 of the web supporting apparatus 200. Also, as the web is supported on the apparatus 200 through the gap 800 between the vacuum pressure roller and the dryer surface 800, the web patterning layer 250 of the web supporting apparatus 200 imprints therein a pattern corresponding to the surface 260 of the first surface 547 of the web 545. Since the second back surface 549 is a substantially smooth, macroscopically monoplanar surface, substantially the entire second surface 549 is positioned against and adjacent to the dryer surface 875 as the web is supported through the gap 800. As the web is supported through the gap, the second surface 549 is supported against the smooth surface 875 to maintain it in

9999

9

99 «9 9

9 9

999 999

9

99 substantially smooth, macroscopically monoplanar. Accordingly, the first surface 547 of the strip 545 is provided with a preselected pattern, while the second surface 549 remains substantially smooth. The strip 545 preferably has a consistency in the range of about 20 percent to about 60 percent when the strip 545 is transferred to the surface 875 and the surface pattern 260 is formed on the strip.

As the web is carried through the gap 800, it is believed that the heated surface 875 may boil the water in the web 545. It is believed that the vacuum created by the vacuum nip roll 900 draws the boiling water from the web through the portions of the felt layer 220 that are not covered by the layer 250 extruded into the web.

Without being limited by theory, it is believed that the result of substantially the entire second surface 549 being positioned against the surface 87 of the Yankee drum is that drying of the web 545 on the Yankee dryer drum is more efficient than would be possible with a web having only selected portions of the second surface against the Yankee dryer drum. In particular, it is contemplated that by positioning substantially all of the second surface 549 against the Yankee surface 875, the above-described patterned paper having both bulk and smoothness and having a basis weight of at least about 8 lbs (3.6 kg) per 3000 square feet (279 m ² ) and preferably at least about 10 lbs (4.5 kg) per 3000 square feet (279 m ² ), can be dried on the Yankee dryer 880 from a consistency of at least about 50 percent and preferably less than 30 percent to a consistency of at least about 90 percent and more preferably at least about 95 percent, while removing water at a rate of at least about 11 tons of water per hour at a belt speed of at least about 4500 feet (1372 m)/minute and more preferably at least about 5000 feet (1524 m)/minute.

In particular, it is contemplated that the present invention allows a web 545 having a basis weight of at least about 8 pounds (3.6 kg) per 3000 square feet (279 m), and preferably at least about 10 pounds (4.5 kg) per 3000 square feet (279 m), to be dried from a relatively low consistency to a relatively high consistency on a Yankee dryer drum at a drum speed of at least about 4500 feet (1372 m) per minute. In particular, it is contemplated that the present invention allows web 545 having the above basis weight parameters to be dried from a consistency of less than about 30 percent and preferably greater than about 25 percent (when the web is transferred to drum 880) to a consistency of at least about 90 percent and more preferably at least about 95 percent (when the web is removed from the drum by creping) at a web speed of at least about 4500 feet (1372 m) per minute, more preferably at least about 5000 feet (1524 m) per minute, and most preferably at least about 6000 feet (1829 m) per minute on a Yankee dryer drum.

In comparison, it is believed that the drying rate of paper on a Yankee dryer drum having a continuous web and discrete domes as described in U.S. Patent 4,637,859 and a basis weight of at least about 10 pounds (4.5 kg) per 3,000 square feet (279 m ² ) cannot be as high as 3,500 ft/min (1,067 m/min) if the paper is to be dried on the Yankee drum from a consistency of about 30 percent to about 90 percent. Paper of the type illustrated in U.S. Patent 4,637,859 is typically predried prior to the Yankee drum so that it has a consistency of about 60 percent to about 70 percent after passing to the dryer drum. Without being bound by theory, it is believed that if the paper illustrated in U.S. Patent 4,637,859 is dried without the use of a pre-dryer, then the Yankee dryer drum speed is limited to less than about 3000 feet/min (914 m/min).

The final step in forming the paper structure 20 is to crepe the web 545 from the surface 875 using a doctor blade 1000 as shown in Figure 9A. Without being limited by theory, it is believed that the energy imparted by the doctor blade 1000 to the web 545 increases the volume or removes compaction.

B

- 28 ·· *· ···· »· ·· • · « ···· ··· ·· · Β·«· • · · · · · » · · · Β · · • · · · · · « ♦·· ·· * ·· ·· at least some portions of the web, particularly those portions of the web on which the patterned surface 260 of the web is not embossed. Accordingly, the step of creping the web with the surface 875 by the doctor blade 1000 ensures that the web has a first, compacted, relatively thinner region corresponding to the pattern, provided to the first face of the web and a second relatively thicker region. Generally, the doctor blade has a bevel angle of about 25 degrees and is positioned relative to the Yankee dryer drum to provide a cut angle of about 81 degrees.

The paper material 20 shown in Figure 2 exhibits shortening due to creping in both the continuous region 30 and the discrete regions 50. The creping frequency in the region 30 is different than that in the regions 50. Generally, the creping frequency in the regions 50 is lower than the creping frequency in the continuous web 30.

In an alternative embodiment, the belt extrusion apparatus 200 may include a resin pattern layer 250 that defines a plurality of discrete raised surfaces 260 that are in contact with the belt and that are connected to the drainage felt layer 220 as shown in the plan view of Figure 8C. In Figure 8C, the felt surface 230 that is in contact with the belt is in the form of a continuous line.

Which surrounds the discrete surfaces 260. Such an apparatus can be used to form a paper web according to the present invention, wherein the paper material comprises many relatively thinner discrete regions which are dispersed within a relatively thicker continuous network region.

0· 00 · 0 0 0 0 • ♦ 4 0 0 «

0« · 000 004

- 29 0· ··'· • ·♦· * • · · · * • · · ·

In another alternative embodiment of the present invention, the belt supporting apparatus 200 may include a resin layer disposed on a foraminous member in the background that includes a woven fiber fabric. Referring to Figures 14A-15C, the apparatus 200 may include a resin layer 250 disposed on a woven fabric 1220.

The resin layer 250 has a continuous web-like web contacting surface 260 defining discrete apertures 270 as shown in Figure 14A. The woven fabric 1220 includes machine direction fibers 1242 and cross-machine direction fibers 1241.

In Figures 14A and 14B, the first surface that contacts the belt is provided at a first height 1231 with discrete bump-like surfaces 1230 located at the intersection of fibers 1241 and 1242. The upper surfaces of fibers 1241 and 1242 may be sandblasted or otherwise abraded to provide relatively flat, generally oval-shaped bump surfaces 1230 (detail of the oval shapes is not shown in Figure 14A). The second surface that contacts the belt is provided with a belt patterning layer 250. The belt patterning layer 250, which is bonded to the woven fabric 1220, has an upper surface 260 that contacts the belt at a second height

261.

The difference between the first height 1231 and the second height 261 is less than about the thickness of the paper web when the paper web is transferred to the belt supporting apparatus 200. The continuous surface 260 and • ·· * * · • tttt· • tttt tt · tt • tttt tttt *♦ tt*tttt tt tttt ♦ » ♦ ♦

tt tt • ř · · • ··% ··· • tt tttt tttt discrete surfaces 1230 may be placed at the same height such that the heights 1231 and 261 are the same. Alternatively, surface 260 may be slightly above surfaces 1230 or surfaces 1230 may be slightly above surface 260.

The difference in height is greater than or equal to 0.0 mil and less than about 5.0 mil. In one embodiment, the difference in height is less than about 4.0 mil (0.10 mm), more preferably less than about 2.0 mil (0.05 mm), and most preferably less than about 1.0 mil (0.025 mm), to maintain a relatively smooth surface 24 as described below.

The web support apparatus 200 shown in FIGS. 14A and 14B can be used to form the paper web shown in FIGS. 10-13. Referring to FIG. 10, the paper web 20 includes a continuous web, a relatively thinner region 30 corresponding to a surface 260, and a plurality of discrete relatively thicker regions 50 dispersed throughout the continuous web region 30. The regions 50 correspond to openings 270 in the surface 260. Each of the relatively thicker regions 50 surrounds at least one densified region.

70. The densified areas 70 correspond to the surfaces 1230 of the woven fabric

1220.

Referring to Figure 11, P may be at least about 0.35 mm and preferably at least about 0.44 mm. K may be less than about 0.20 mm and more preferably less than about 0.10 mm.

• · · • ·♦· • · ·· ♦··· • · • 4 •

Figures 15A-15C illustrate the formation of the strip 20 shown in Figure 10 using the strip support apparatus 200. As described above with respect to Figures 9A-9C, the germ strip

543 having first and second smooth surfaces is formed on a forming screen 542 and is transferred to a belt supporting apparatus 200. The belt 543 is vacuum transferred to the apparatus 200 to produce a belt 545 supported on the apparatus 200. As seen in Figure 15B, the first surface 547 is formed according to surface 260 and surfaces 1230 and the second surface 549 is maintained as a substantially smooth, macroscopically monoplanar surface.

Unlike FIGS. 9A-9C , the web 545 and the web supporting apparatus 200 are then carried through a cross-flow air drying apparatus 650 , with heated air directed across the web 545 while the web 545 is supported on the apparatus 200 .

The heated air is directed to enter the surface 545 and pass across the belt 545 and then through the apparatus 200.

A cross-flow air drying apparatus 650 can be used to dry the web 545 to a consistency of from about 30 percent to about 70 percent. U.S. Patent 3,303,576 to Sisson and U.S. Patent 4,303,576 to Sisson

247,930, issued to Ensign et al., are hereby incorporated by reference for the purpose of showing suitable cross-flow air dryers for use in practicing the present invention.

• flfl flflfl · · • flflfl · · • · · ♦ · fl • flfl flfl • flfl ·· flfl • * flfl·· • » fl flfl ♦ * ♦ fl flfl • flfl fl • fl • fl ♦

fl • flfl «

lol

The partially dried web 545 and apparatus 200 are directed to pass through a nip 800 formed between a nip roll 900 and a Yankee dryer drum 880. The continuous mesh surface 260 and discrete surfaces 1230 are impressed into the surface 547 of the web 545 as the web is carried through the nip 800. Adhesive supplied by a nozzle 890 is used to adhere substantially all of the substantially smooth surface 549 to the surface 875 of the heated Yankee dryer drum 880.

Figure 16 is a cross-sectional view of a paper web 20 showing a paper web in accordance with the invention, the paper web having three fibrous layers designated 301, 302 and 303. A paper web having a layered structure can be made using the papermaking equipment and methods shown in Figures 8A and 8B and 9A to 9C or alternatively those shown in Figures 14A, 14B and 15A to 15C.

While the individual forming screen 542 is shown in the figure

9A, it is understood that other configurations of the forming screen may be used in combination with one or more headboxes capable of providing one or more layers of fiber deposition to provide a multi-layered web. U.S. Patent 3,994,771 issued to Morgan et al. and U.S. Patent 4,300,981 issued to

Carstens et al. and common US patent application

Laminated tissue paper having improved functional properties filed on October 24, 1996 in the names of Phan and Trokhan describes φ

φφφ φ

• Φ φφφφ

* φφφφ • φφφ φφφ φ φ layering and is incorporated herein by reference. Various types of forming wire configurations can be used, including double forming wire. Furthermore, various types of headbox construction can be used to obtain a web having one or more layers of fibers.

Referring to Figure 16, one or more headboxes may be used to form three layers of the deposit corresponding to layers 301, 302, and 303 on the forming wire 542, such that the seed belt includes layers 301, 302, and 303. The first layer 301 may include relatively long paper-forming fibers located adjacent the first surface 22 of the belt. The relatively long paper-forming fibers in the first layer 301 may include softwood fibers, such as northern softwood fibers, having an average fiber length of about 3 mm or more. The second layer 302 may include relatively short paper-forming fibers located adjacent the second surface 24 of the belt. The relatively short paper-forming fibers in the second layer 302 may include hardwood fibers, such as eucalyptus fibers, having an average fiber length of about 1.5 mm or less.

A third layer 303 is disposed between the first layer 301 and the second layer 302. The third layer may be a bond-breaking layer characterized by having voids 310 that are substantially free of fibers. These voids are illustrated in the photomicrographs of Figures 3 and 11.

• ·♦ ·· · · » • ··· · · • · · · · · · · · · · · · ·· ·· ·*· ·« *· • «· • · · · • ·· · «

···

The voids may be located particularly in the relatively thicker regions 50. The third layer may include a debonding agent such as an ADOGEN® type additive to reduce fiber-to-fiber bonds in the third layer 303, thereby facilitating the opening of the fiber structure in the layer 303 to provide voids.

310. The third layer 303 may include softwood or hardwood fibers or a combination of hardwood and softwood.

In another embodiment, each of the layers 301 and 302 may include relatively short hardwood fibers, and the third layer 303 may include relatively long softwood fibers.

For example, layers 301 and 302 may be predominantly formed from eucalyptus fibers and the third layer 303 may be predominantly formed from relatively long Northern Softwood fibers.

Alternatively, other methods may be used to facilitate reduction of belt compaction or to remove fiber bonds in the middle layer of the belt. U.S. Patent 4,225,382 to Kearney et al. is hereby incorporated by reference into this specification for purposes of describing multi-layer belts consisting of highly bonded layers separated by an inner layer.

• · ·· ··· ·· • ··· • · · · · ··· ·« • ·

Examples

All percentages given are weight percentages based on the weight of dry fibers unless otherwise stated.

Example 1

This example shows the preparation of a three-ply tissue paper web produced with the papermaking machine shown in Figures 14A, 14B and 15A-15C.

A 3% by weight aqueous kraft pulp of Northern Softwood Kraft (NSK) is prepared in a conventional pulping machine. A 2% by weight aqueous solution of wet strength resin (i.e., National Starch 78-0080 sold by National Starch and Chemical Corporation, New York, NY, USA) is added to the feed tube of the NSK at a rate of 0.2% by weight based on the weight of the dry fibers (the ratio of the weight of wet strength resin to the weight of the dry fibers is 0.002). The NSK pulp is diluted to about 0.2% consistency in a centrifugal pump. Second, a 3% by weight aqueous eucalyptus pulp is prepared in a conventional pulping machine. A 2% by weight solution of debonding agent (i.e. ADOGEN®442) is added to the eucalyptus feed tube at a rate of 0.1% by weight of dry fibers. The eucalyptus pulp is diluted to a consistency of about 0.2% by centrifugal pump.

Three individually treated streams for each layer (stream 1 = 100% NSK, stream 2 = 100% eucalyptus, stream 3 = 100% eucalyptus) are kept separate as they pass through the headbox and are deposited on the Fourdrinier screen to form a three-layer seed belt containing two outer eucalyptus layers and a central NSK layer. Dewatering occurs on the Fourdrinier screen and is assisted by a deflector and vacuum boxes. The Fourdrinier screen has a 5-shed, satin weave configuration and has 110 threads per inch in the machine direction and 95 threads per inch in the cross-machine direction.

The germ paper web is transferred by vacuum from a Fourdrinier screen, at a fiber consistency of about 8% at the transfer point, to a web support apparatus 200 having an apertured backing element comprising a woven fabric 1220 and a web patterning layer 250 made of a photosensitive resin. The web is transferred to the web support apparatus 200 by a pressure differential of about 16 inches (406.4 mm) of mercury. The apertured backing element is arranged as a 5-shed satin fabric having 68 monofilaments per inch in the machine direction and 51 monofilaments per inch in the cross-machine direction, the machine direction fibers having a diameter of about 0.22 mm and the cross-machine direction fibers having a diameter of about 0.29 mm. Such an apertured backing element is manufactured by Appleton Wire Company, Appleton, Wisconsin, USA.

The web patterning layer 250 has a continuous web-contacting surface 260 with a raised area that is in the range of about 30 to about 40 percent of the raised area of the apparatus 200. The difference between the elevation 1231 of the web-contacting surface of the apertured backing element and the height 261 of the continuous web-contacting surface 260 is about 0.001 inch (0.0254 mm).

The web is transferred to apparatus 200 to obtain a web 545 supported on apparatus 200 and having a substantially smooth second surface 549 as shown in Figure 15B. Further dewatering is achieved by vacuum assisted dewatering and cross-flow air drying as represented by devices 600, 620 and 650 until the web has a fiber consistency of about 65%.

• ·· ·· » · · • ··· · · • · · · · · ·*· ·· • fc fc··* ·· ·· • * * · • 9 ♦ · • · · fcfcfc • « • fc fcfc

Transfer to the Yankee dryer drum at nip 800 is accomplished by a pressure roller 900. Surface 250 and surfaces 1230 are impressed onto the first surface 547 of the belt 545 to provide a patterned surface 547. Substantially all of the second surface 549 is adhered to the surface 875 of the Yankee dryer drum 880 using a polyvinyl alcohol-based creping adhesive. The pressure in nip 800 is at least about 400 pli (10.7 kg/linear cm).

Before the web is dry creped with the surface 875 by the doctor blade 1000, the consistency of the web is increased to about 90% to about 100%. The doctor blade has a bevel of about 25 degrees and is positioned with respect to the Yankee dryer drum to provide a cutting angle of about 81 degrees. The Yankee dryer drum is operated at about 800 fpm (feet per minute) (about 244 meters per minute). The dry web is wound into a roll at a speed of 650 fpm (200 meters per minute).

The web produced by the above process is converted into a single tissue toilet paper having three layers. This single sheet tissue toilet paper has a basis weight of about 17.5 pounds per 3000 square feet, contains about 0.02% by weight of temporary wet strength resin and about 0.01% by weight of bond disrupting agent.

It is important that the resulting single-sheet tissue paper is absorbent and suitable for use as toilet tissue paper and has the following characteristics:

basic weight: 1-7 C 1 / f vj lb/3000 sq ft. (28 macrothickness: 13, 6 miles (0, 0136 inches= bulk density: 0.08 g/black ³ surface smoothness 22 : 8 90 surface smoothness 24 : 1071 3 smoothness ratio: 1.20

• fc • fc fcfc • fc · fc • fcfc » fcfcfc • fcfc

Example 2

This example provides a two-ply tissue paper web produced on the paper machine shown in Figures 14A, 14B and 15A-15C.

A 3% by weight aqueous kraft pulp of NSK (Northern Softwood Kraft) is produced in a conventional pulping machine. A 2% solution of a temporary wet strength resin (e.g., PAŘEZ® 750 sold by American Cyanamid Company, Stanford, Ct, USA) is added to the NSK feed tube at a rate of 0.2% by weight, based on dry fibers. The NSK pulp is diluted to about 0.2% density in a centrifugal pump. A second 3% by weight aqueous eucalyptus pulp is prepared in a conventional pulping machine. A 2% solution of a bond-breaking agent (i.e., ADOGEN® 442 sold by Witco Corporation, Dublin, OH, USA) is added to the eucalyptus feed tube at a rate of 0.1% by weight, based on dry fibers. Eucalyptus pulp is diluted to a consistency of about 0.2% in a centrifugal pump.

The streams of the two applied layers (stream 1 = 100 NSK /stream 2 = 100% eucalyptus) are mixed in a headbox and deposited on a Fourdrinier screen 542, where they form a seed belt containing NSK and eucalyptus fibers. Dewatering occurs through the Fourdrinier screen and is assisted by a deflector and vacuum boxes. The Fourdrinier screen is constructed of a 5-shed satin fabric having 110 monofilaments per inch in the machine direction and 95 monofilaments per inch in the cross-machine direction.

The wet seed web is transferred from a Fourdrinier screen at a fiber consistency of about 8% at the transfer point to a belt supporting apparatus 200 comprising a woven fabric 1220 and a belt patterning layer 250 having a continuous mesh-like surface 260.

The wet seed web is transferred from the Fourdrinier belt at a fiber consistency of about 8% at the transfer point to the apparatus 200 to provide a web 545 having a substantially smooth, macroscopically monoplanar surface 549 and a surface 547 corresponding to surfaces 1230 and surface 260. A pressure differential of about 16 inches of mercury is used to transfer the web to the apparatus 200. The woven fabric 1220 is of a three-shed satin weave configuration having 79 machine direction and 67 monofilament fibers per inch in the cross-machine direction, with the machine direction fibers having a diameter of about 0.18 mm and the cross-machine direction fibers having a diameter of about 0.21 mm. Such an apertured backing element is manufactured by Appleton Wire Company, Appleton, Wisconsin.

The belt patterning layer 250 has an upper belt contacting surface 260 having a raised area that is in the range of about 30 to about 40% of the raised area of the apparatus 200. The difference between the elevation 1231 of the belt contacting surface 1230 and the elevation 261 of the surface 260 is about 1 mil (0.001 inch, i.e. 0.0254 mm).

Further dewatering of the web 545 is accomplished by vacuum assisted dewatering and drying air passing across, as represented by devices 600, 620 and 650, until the web has a fiber consistency of about 65%. Transfer to the Yankee dryer drum occurs at the nip 800 formed between the nip roll 900 and the Yankee dryer drum 880.

Surface 250 and surfaces 1230 are embossed into the first surface 547 of the belt 545 to form the patterned surface 547. Substantially all of the second surface 549 adheres to the surface 875 of the Yankee dryer drum.

880 using a creping adhesive based on • ··

Λ η ···♦·· · — 4 ν — ··· ·· ·· ·· ·· polyvinyl alcohol. The contact pressure in the gap 800 is at least about 400 pli.

Before the web is dry-creped with a 1000 doctor blade, the web consistency is increased to a value between about 90% and 100%. The doctor blade has a bevel angle of about 25 degrees and is positioned relative to the Yankee dryer drum to provide a cut angle of about 81 degrees. The Yankee dryer drum is operated at about 800 fpm (feet per minute) (about 244 meters per minute). The dry web is formed into a roll at a speed of 650 fpm (200 meters per minute).

The web is treated to form two folded sheets of bath tissue paper. Each sheet has a basis weight of about 12.8 pounds per 3000 square feet and contains about 0.02% resin for temporary wet strength and about 0.01% bond-breaking agent.

The resulting double-ply tissue paper is soft, absorbent and suitable for use as a paper towel. Each sheet has the following properties:

base weight: 12.8 lb/3000 sq ft. macro thickness: 11.4 mi 1 (0.185 mm) bulk density: 0.07 g/ ^cm2 surface smoothness 22: 850 surface smoothness 24: 100 6 smoothness ratio: 1.18

g/ ^m2 )

Example 3

This example provides a two-sheet tissue paper, with each sheet having 3 layers and each sheet being made on a paper mill.

a machine of the type shown in Figures 8A, 8B and 8A to 9C.

A 3% by weight aqueous pulp of Northern Softwood Kraft fibers is made using a conventional pulper. A 2% solution of temporary wet strength resin (e.g., National Starch 78-0080, sold by National Starch and Chemical Corporation, New York, New York, USA) is added to the NSK in the feed tube at a rate of 0.2% by weight based on dry fibers. The Northern Softwood Kraft pulp is diluted to a consistency of about 0.2% by weight in a centrifugal pump. A second 3% by weight aqueous eucalyptus pulp is made using a conventional pulper. A 2% solution of a bond disrupting agent (e.g., ADOGEN® 442, available from Witco Corporation of Dublin, OH, USA) is added to one of the eucalyptus pulp feed lines at a rate of 0.1% by weight based on dry fibers. The eucalyptus pulp is diluted to about 0.2% consistency with a centrifugal pump.

Three individually treated ply streams (Stream 1 = 100% NSK (Northern Softwood Kraft); Stream 2 = 100% Eucalyptus coated with bond-breaking agent; Stream 3 = 100% Eucalyptus) are kept separate in the headbox and are deposited onto a Fourdrinier screen to form a three-layer seed web containing an outer eucalyptus layer, a separated eucalyptus layer and a NSK (Northern Softwood Kraft) layer. Dewatering occurs on the Fourdrinier screen and is assisted by a deflector and vacuum boxes. The Fourdrinier screen has a 5-shed satin weave configuration and has 110 monofilaments per inch in the machine direction and 95 monofilaments per inch in the cross-machine direction.

9 9 · · 9 9 · 9 · • ··· 9 9 9 9 9 9 9 •9 999 · 9 9 999999

9····· · ·

99999 ·9 9 99 99

The wet seed web is transferred from the Fourdrinier screen at a fiber consistency of about 8% at the transfer point to a web support apparatus 200 having a drainage felt layer 220 and a photosensitive resin layer 250 for patterning the web.

Dewatering felt 220 is an Amflex 2 Press Felt product manufactured by Appleton Mills, Appleton, Wisconsin, USA. Felt 220 comprises a polyester fiber web. The web has a surface denier of 3, a substrate denier of 10-15. Felt layer 220 has a basis weight of 1436 g/m 2 , a thickness of about 3 mm, and an air permeability of about 30 to about 40 scfm (9.1 to 12.2 Nm ³ /m ² ).

The patterning belt layer 250 includes a belt contacting a continuous mesh surface 260 having a raised area of about 30 to about 40 percent of the raised area of the belt support apparatus 200. The difference between the elevation 261 of the surface 260 and the elevation 231 of the felt surface 230 is about 0.005 inches (0.127 mm).

The seed strip is transferred to apparatus 200 to obtain a strip 545 supported on apparatus 200 and having a macroscopically monoplanar, substantially smooth surface 549. The transfer is provided at a vacuum transfer location with a pressure differential of about 20 inches (50.8 mm) of mercury.

Further dewatering is provided by vacuum assisted dewatering, such as in apparatus 620, until the web has a fiber consistency of about 25%. The web 545 is then carried past the steam trap 2880 and into the gap 800 formed between the vacuum nip roll 900 and the Yankee dryer drum 880.

Surface 260 is pressed into surface 547 of web 545 in nip 800 by compressing web 545 and web support apparatus 200 between vacuum nip roll 900 and Yankee dryer drum 880 at a nip pressure of about 400 pli (71.4 kg/linear cm). The creping adhesive is

used to adhere the web to the Yankee dryer drum. Before the web is creped with a doctor blade, the fiber consistency is increased to at least about 90%. The doctor blade has a bevel angle of about 25 degrees and is positioned relative to the Yankee dryer drum to provide a cut angle of about 81 degrees. The Yankee dryer drum is operated at about 800 fpm (feet per minute) (about 244 meters per minute). The dry web is formed into rolls at a speed of 650 fpm (198 m/min).

The web is converted into a two-ply bathroom facial tissue paper, each sheet having three layers. The two-ply toilet tissue paper includes about 1.0% resin for temporary wet strength and about 0.1% bond disrupting agent.

Each sheet has the following properties;

Basis Weight: 9.8 lb/3000 sq ft. (15.9 g/m ² ) Macro Thickness: 6 mil (0.15 mm) Bulk Density: 0.10 g/cm ^J Surface Smoothness 22: 740 Surface Smoothness 24: 960 Smoothness Ratio: 1.30

Example 4

This example provides a tissue paper web produced on a paper machine of the type shown in Figures 8A, 8B and 9A to 9C.

A 3% by weight aqueous NSK (Northern Softwood Kraft) pulp is prepared in a conventional pulper. A 2% solution of temporary wet strength resin (PAŘEZ® 750) is added to the NSK feed pipe at a rate of 0.2% by weight of dry fibers. The NSK pulp is diluted to a consistency of about 0.2% by weight in a circulation pump. Secondly, a 2% by weight

A 3% aqueous solution of conventional fibers (ADOGEN®442 Eucalyptus consistency) is added to the eucalyptus fiber dosing tube at a rate of 0.1% by weight of dry fibers, and the pulp is diluted to about 0.2% by weight with a circulation pump.

These two individually treated layers (stream 1 = 100% NSK, stream 2 = 100% eucalyptus) are mixed in a headbox and are deposited on a Fourdrinier screen to form a single-layer web of NSK fibers and covered with eucalyptus fibers, the eucalyptus fibers being coated with a debonding agent. Dewatering occurs through the Fourdrinier screen and is assisted by a deflector and vacuum boxes. The Fourdrinier

the screen has a 5-shed satin fabric configuration having 110 monofilaments in the cross-machine direction. to the inch in along the machine and 95 in Germical moist zone is transmitted from Fourdrinier sieve at fiber consistency about 8% at the crossing point to belt

a backing 200 having a drainage felt layer 220 and a photosensitive resin strip patterning layer 250.

The drainage felt 220 is Amflex 2 Press Felt manufactured by Appleton Mills of Appleton, Wisconsin, USA. The belt patterning layer 250 includes a continuous belt contacting surface 260. The belt patterning layer 250 has a raised area equal to about 35 percent of the raised area of the belt supporting apparatus 200. The difference in height between the upper belt contacting surface 260 and the first felt surface 230 is about 0.005 inches (0.127 mm).

The germ strip is transferred to the strip supporting apparatus 200 and is bent in a first bending stage to form a generally ·· 99 • 0 0 0 0 0

0 0 · 0 0 • 0 · 900 009 • · 4 0

40 49 • · • 00 monoplanar belt 545. Transfer is effected at the vacuum transfer location by a pressure differential of about 20 inches of mercury. Further dewatering is accomplished by vacuum assisted dewatering until the belt has a fiber consistency of about 25%. The belt 545 is supported by a belt support apparatus which is adjacent to the steam trap 2800 and into the gap 800 formed between the vacuum nip roll 900 and the Yankee dryer drum 880. The belt 545 is then compacted against the compaction surface 875 of the Yankee dryer drum 880 by a nip pressure of at least about 400 pli (71.4 kg/linear cm). A polyvinyl alcohol based creping adhesive is used to adhere the compacted belt to the Yankee dryer drum. Before the web is dry-creped from the surface of the dryer drum 880 by a doctor blade, the fiber consistency is increased to at least about 90%. The doctor blade has a bevel angle of about 25 degrees and is positioned relative to the Yankee dryer drum to provide a cut angle of about 81 degrees. The Yankee dryer drum is operated at about 800 fpm (feet per minute) (about 244 meters per minute). The dry web is formed into a roll at a speed of 650 fpm (200 meters per minute).

The web is converted into a single-ply, two-ply paper towel, each sheet of two-ply bath tissue paper having a basis weight of about 12.6 pounds per 3000 square feet and containing about 0.2% by weight of temporary wet strength resin and about 0.1% by weight of bond-breaking agent.

The resulting double-ply tissue paper is soft, absorbent, and suitable for use as a paper towel.

Tissue paper has the following properties:

basis weight: 12.6 lb/3000 sq ft. (20.5 g/m ² ) macro thickness: 8.8 mil (0.22 mra) bulk density: 0.092 g/cm ³ surface smoothness 22: 890 surface smoothness 24: 1050 • ··· φ φ φ · φφφ φ φφφ φ · φφφ φφ φφ φΦΦ· φφφ φφφ smoothness ratio: 1.18

Hypothetical example:

The following hypothetical example illustrates a method of producing two-ply tissue paper using a commercial-sized papermaking plant of the type shown in Figures 8A, 8B and 9A-9C.

A 3% by weight aqueous NSK (Northern Softwood Kraft) pulp is prepared in a conventional pulper. A 2% solution of temporary wet strength resin (PAŘEZ® 750 manufactured by American Cyanamid Corporation of Stanford, CT, USA) is added to the NSK feed tube at a rate of 0.2% by weight of dry fibers. The NSK pulp is diluted to a consistency of about 0.2% by weight with a circulation pump. Second, a 3% by weight aqueous eucalyptus pulp is prepared using a conventional pulper. A 2% solution of bond-breaking agent (ADOGEN® 442, manufactured by Witco Corporation of Dublin, OH, USA) is added to the eucalyptus feed tube at a rate of 0.1% by weight of dry fibers.

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about 0.2%.

These two individually adjusted / , , <1 _ 1 Λ fi Q. U o TZ woro uu ± — ± d υ ό Ixl úi\ _r p j- vu u. no.

mixed in a headbox and are screened to form single-layer streams into individual layers — cuj\a±y^L.uo) ó-c j oOa and deposited on a Fourdrinier belt of NSK fibers and covered with eucalyptus fibers, the eucalyptus fibers being coated with a debonding agent. Dewatering occurs through the Fourdrinier screen and is aided by the effect of a vacuum box. The Fourdrinier screen has a 5-shed satin fabric configuration having 110

- 47 • φ» φ· · • φφφ ·♦ φφφφ φφ > · φ φ > φ φ •φφ φφφ • φ ·· monofilaments per inch in the machine direction and 95 in the cross-machine direction (43.3 and 37.4/cm, respectively).

The wet seed web is transferred from the Fourdrinier screen at a fiber consistency of about 10% at the transition point to a belt supporting apparatus 200 having a drainage felt layer 220 and a photosensitive resin belt patterning layer 250.

The drainage felt 220 is Amflex 2 Press Felt manufactured by Appleton Mills, Appleton, Wisconsin, USA. The patterning layer 250 comprises a continuous patterning strip having 2 oval-shaped holes 270 per square inch (10.7/cm ) of the strip contacting surface 220. The patterning layer 250 has a raised area equal to about 35 percent of the raised area of the strip supporting apparatus 200. The difference in height between the upper strip contacting surface 260 and the felt surface 230 is about 0.005 inches (0.127 mm).

The germ strip is transferred to a strip support apparatus 545, forming a generally monoplanar strip 545. The transfer is effected at the vacuum transfer location by a pressure differential of about 20 inches (508 mm) of mercury. Further dewatering is accomplished by vacuum assisted dewatering until the strip has a fiber consistency of about 30%.

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The vacuum pressure roller 900 has a pressure surface 910, having a 545 is then compacted against a Yankee hardness of about 1000.

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875 drying drum

880 pressing the waist 545 and the waist of the piracicaba apparatus between

ΓΛ r i ř 1 a r η v η η ητ r r c h Q 1 0 povnch Ysnkoo 830 dryer drum with a contact pressure of at least about 400 pli (71.4 kg/linear cm). A polyvinyl alcohol-based creping adhesive is used to adhere the compacted web to the Yankee dryer drum. Before creping the Z 3 dry web from the surface of the dryer drum 880 with a doctor blade •tt ··»· • tt • tttt • tt ttt • ♦ * · · tt tt tt · · · · • tt · ··· ··· ttt ttt • tttt tttt the fiber consistency is increased to at least about 90%. The doctor blade has a bevel angle of about 20 degrees and is positioned relative to the Yankee dryer drum to provide a cutting angle of about 76 degrees. The Yankee dryer drum is operated at about 4500 fpm (feet per minute) (about 1372 meters per minute). The dry web is formed into a roll at a speed of 3690 fpm (1125 meters per minute).

The web is converted into a two-ply paper towel. Each sheet of two-ply bath tissue has a basis weight of about 12.5 pounds (5.67 kg) per 3000 square feet (278.7 m ² ) and contains about 0.2% by weight of temporary wet strength resin and about 0.1% by weight of bond-breaking agent.

The resulting double-ply tissue paper is soft, absorbent, and suitable for use as a paper towel.

Analytical procedures

Thickness and height measurements for paper properties:

The location of the plane 23 of the regions 30, the thickness of the region 30 and the thickness of the region 50 are determined using micrographs of cross-sections of the paper web. An example of such a micrograph is shown in Figure 3, where the location of the plane 23 is shown together with the thickness P of the regions 50 and the thickness K of the region 30.

Ten samples, each measuring approximately 2.54 x 5.1 cm (1 inch x 2 inches), are randomly selected from a sheet or roll of tissue paper. If it is not possible to obtain ten samples from a single sheet, then additional sheets made under the same conditions (preferably from the same original roll) may be used.

• fc • fcfc ·· ffcfcfc

fcfc fcfc • · · · fc fc fcfcfcfc • · fcfcfc fcfcfc fc fcfc • fcfc fcfc

Microsections of the same sample are made by stacking each sample on a rigid cardboard holder. The cardboard holder is placed in a silicone mold. The paper sample is immersed in a resin such as Merigraph photopolymer, manufactured by Hercules, Inc.

The sample is vulcanized to cure the resin. The sample is removed from the silicone mold. Before being placed in the photopolymer, the sample is marked with a reference point to determine exactly where the microcuts were made.

Preferably, the same reference point is used for both the plan view (i.e., Figure 4) and the various cross-sections (i.e., Figure 3) of the strip sample 20.

The sample is placed in a type 860 microslitter manufactured by American Optical Company, Buffalo, New York, USA and leveled. The edge of the sample is removed from the sample in slices using the microslitter until a smooth surface appears.

A sufficient number of microsections are removed from the sample so that the different areas of the paper web can be accurately reconstructed (i.e. 30 and 50). For the embodiment described herein, slices having a thickness of about 60 microns per slice are taken from the smooth surface. Multiple slices may be required so that the thicknesses of P and K can be determined.

The sample slice is mounted on a microscope slide using oil and a coverslip. The slide and sample are mounted in a beam microscope and observed at 40x magnification. Photomicrographs are taken along the slice and the individual photomicrographs are arranged in a series to reconstruct the section profile. Thicknesses and heights can be determined from the reconstructed profile as shown in Figure 3, which is a photomicrograph of a cross-section through the structure of a paper of the type shown in Figures 1 and 2.

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9 9 9 9 fl • flfl flfl • fl « 99 99

Thicknesses are determined using a Hewlett Packard ScanJet IIC flatbed color scanner to scan the microphotographs and save them as a graphic file on a personal computer. The scanning software from Hewlett Packard is DeskScan II version 1.6. The scanner is set to scan black and white photographs. The path is Laser Writer NT, NTX. The brightness and contrast settings are 125. The scale is 100%. The file is scanned and saved as an image file on a Macintosh IlCi computer. The image file is opened with a suitable image software package or CAD program such as PowerDraw version 6.0, available from Engineering Software, North Carolina, USA.

Referring to Figure 3, the thicknesses of areas 30 and 50 are indicated by circles having their diameters marked K and P respectively. First, the largest circle that can be inscribed in the area 50 being examined is drawn using the PowerDraw software. The diameter of this circle is marked P. The thickness P of area 50 is the diameter of this circle multiplied by the appropriate magnification factors. (The magnification factor is the magnification of the micrograph multiplied by the magnification of the scanned image).

Next, the smallest circles that can be inscribed in the parts of area 30 on both sides of area 50 are drawn. The diameters of these circles are denoted by K. The thickness K of area 30 next to area 50 is the average of the two diameters multiplied by the scale factor mentioned above.

The plane of region 30 adjacent to region 50 is located by drawing a line connecting the centers of two rings having diameter K as shown in Figure 3.

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9 9 9 9

9,999,999

9 9

99 99 • ·· ♦ ♦ ♦ · · • ··· * · • · · » ·

9 9 9 9

999 99 99 ·· ····

For each of the ten samples, a line representing plane 23 is drawn for each occurrence of the relatively thicker region 50. If this line intersects region 50 in at least 25 percent of the occurrences, then the paper from which the samples were taken has relatively thicker regions located in the plane of the relatively thicker region according to the present invention. For example, if ten samples yield 50 occurrences of relatively thicker regions 30 on each side of relatively thicker regions 50, then relatively thicker regions 50 are considered to be located in the plane of relatively thinner regions 30 if and only if the drawn line representing plane 23 intersects thicker regions 50 in at least 13 of the 50 occurrences.

Surface smoothness:

The surface smoothness of the paper web side is measured according to the method for measuring physiological surface smoothness (PSS) established at the International Paper Physics Conference, TAPPI in 1991 in the article on page 19 of book I, entitled "Methods for Measuring the Mechanical Properties of Tissue Paper", by Ampulski et al., which article is hereby incorporated by reference into this specification. The PSS measurement as used herein is a point-by-point summation of amplitude values as described in the aforementioned article. The measurement procedures set forth in the article are also generally described in U.S. Patent 4,959,125 to Spendel and U.S. Patent 5,059,282 to Ampulski et al., which patents are hereby incorporated by reference into this specification.

For the purposes of testing paper samples according to the present invention, the PSS measurement method in the above article is used to measure surface smoothness with the following modifications to the procedure:

Instead of importing pairs of digitized data (amplitude and time) into SAS software for 10 samples as described in • ·· • · · • ·*· • 0 · · ···

400 00

0000 • ♦ 0

0 4 • 00 0 0 0 • 0 0

00 0 0 0 0 0 0 0 0

000 000 0 0

00 above sample, the surface smoothness measurement is performed by acquiring, digitizing and statistically processing data for 10 samples using LABVIEW software, which is available from National Instruments, Austin, Texas, USA. Each amplitude spectrum is created using the Amplitude and Phase Spectrum.vi module in the LABVIEW software package, with Amp Spectrum mag Vrms selected as the output spectrum. The output spectrum is obtained for each of the 10 samples.

Each output spectrum is then smoothed using the following weighting coefficients in LABVIEW: 0.000246, 0.000485, 0.00756, 0.062997. These weighting coefficients are chosen to mimic the smoothing provided by the coefficients 0.0039, 0.0077, 0.120, 1.0 specified in the SAS article above.

After smoothing, each spectrum is filtered using the frequency filters specified in the above article. The PSS value in microns is then calculated as described in the above article for each individually filtered spectrum. The surface smoothness of a side of the paper web is the average of 10 PSS values measured from 10 samples taken from the same side of the paper web. Similarly, the surface smoothness of the opposite side of the paper web can be measured. The smoothness ratio is obtained by dividing the higher surface smoothness value corresponding to the more textured side of the paper web by the lower surface smoothness value corresponding to the smoother side of the paper web.

Basic weight:

The basic weight is measured according to the following procedure:

The paper to be measured is conditioned for a minimum of 2 hours at 71-75 degrees Fahrenheit (21.7 to 23.9 °C) to a relative ♦ ♦ • · ♦ • ·· · « • · 111 1

111 11

111 11 11

11 1 1111 1 1111 1 1 111 111 1 11 11 humidity 48 to 52 percent. The conditioned paper is cut to produce twelve samples measuring 3.5 inches by 3.5 inches (8.9 x 8.9 cm). The samples are cut, six samples at a time, with a suitable pressure slicer, such as the Thwing-Albert Alfa Hydraulic Pressure Sample Cutter, type 240-10. The two stacks of six samples are then combined into 12 sheets containing the stack and conditioned for at least 15 additional minutes at 71 to 75 F (21.7 to 23.9 °C) and 48 to 52 percent humidity.

The stack of 12 sheets is then weighed on a calibrated analytical balance. The balance is maintained in the same room in which the samples were prepared. A suitable balance is manufactured by Sartorius Instrument Company as the A200S. The weight thus obtained is the weight in grams for a stack of 12 sheets of paper, each sheet having an area of 12.25 square inches (79 ^cm2 ).

The basis weight of a paper web (the weight per unit area of one sheet) is calculated in units of pounds per 3000 square feet using the following equation:

weight of a 12-sheet stack (grams x 3000 x 144 sq. in. per sq. ft. (453.6 g/lb)x(12 sheets) x (12.25 sq. in. per sheet) or simply: basis weight (lb/3000 ft ² ) = weight of a 12-sheet stack (g) x 6.48

Macro thickness dimension or dry thickness dimension

The macrothickness dimension or dry thickness dimension is measured using the dry thickness measurement procedure described in U.S. Patent 4,469,735, issued September 4, 1984 to Trokhan, which patent is hereby incorporated by reference into this specification.

9

9 9 9 9

9,999,999

9 9

99 99 ·· 9 9 9

999 9 9

9 9 9 9 9

9 9 9 9

999 99 99

9999

99

9 9

Bulk density

Bulk density is the basis weight of the strip divided by the macrothickness of the strip.

Absorption capacity

The absorbency of the web is measured using the horizontal absorbency test described in the cited U.S. Patent 4,469,735.

Height measurement of the belt supporting apparatus

The height difference between the height 231 of the first felt surface and the height 261 of the strip contacting surface 260 is measured using the following procedure. The strip supporting the apparatus is supported on a flat horizontal surface with the strip patterning layer facing upward. A stylus having a circular contact surface of about 1.3 mm and a vertical length of about 3 mm is mounted on a thickness gauge from Federal Products Company (type 432B-81 amplifier modified for use with the EMD4320 Wl tear-off sensor), Providence, Rhode Island, USA. The instrument is calibrated by determining the voltage difference between two precision inserts of known thickness that provide a known height difference. The instrument is zeroed at a height slightly lower than the surface 230 of the first felt to ensure unrestricted travel of the stylus. The stylus is positioned above the appropriate height and lowered to make the measurement. The touch tip exerts a pressure of about 0.24 g/mm at the measurement point. At least three measurements are taken at each height. The measurements for each height are averaged. The difference between the average values is calculated, which gives the height difference.

The same procedure is used to measure the difference between heights 1231 and 261 as shown in Figure 14B.

Claims (7)

PATENT CLAIMS A wet-laid paper web having first and second oppositely facing surfaces having a relatively thinner, continuous network region and a plurality of relatively thicker discrete regions dispersed in the continuous network region, wherein the relatively thicker discrete regions are disposed in a continuous plane. network area. 2. The paper web of claim 1 having a basis weight in the range of about 7 to about 70 g / m @ ² . The third paper web according to claim 1 or 2, characterized in that the paper web has a macro caliper of at least about 0.1 mm and a bulk density less than about 0.12 g / ^cc. Paper web according to claim 1, 2 or 3, characterized in that both the continuous network and discrete areas are shortened beforehand. The paper web of claim 1, 2, 3, or 4, wherein the surface smoothness ratio of the web is greater than about 1.15, preferably greater than 1.20, and most preferably greater than 1.25. The paper web of claim 1, 2, 3, 4 or 5, wherein the second surface of the web has a surface smoothness value of less than about 900. The paper web of claim 1, 2, 3, 4, 5, or 6, wherein each discrete relatively thicker region surrounds at least one discrete densified region.