KR20010075403A - High caliper paper and papermaking belt for producing the same - Google Patents

Abstract

A papermaking belt for producing a high caliper web of papermaking fibers and the paper web produced thereby. The papermaking belt comprises a reinforcing structure having a continuous network region and a plurality of discrete deflection conduits disposed thereon. The deflection conduits are sized, shaped, and arranged to maximize fiber deflection along the periphery of the conduits. The conduits are generally elliptical in shape having a mean width sized relative to mean fiber length. The conduits are arranged to maximize perimeter and corresponding fiber deflection per unit area.

Description

[0001] DESCRIPTION [0002] HIGH CALIPER PAPER AND PAPERMAKING BELT FOR PRODUCING THE SAME [0003]

Cellulosic fibrous webs, such as paper, are known in the art. Such fibrous webs have recently been used in ordinary paper towels, toilet paper, facial tissues, napkins, and the like. Due to the high demand of such paper products, there has been a demand for improved paper and its manufacturing method.

In order to meet the needs of consumers, cellulose fiber webs must have various characteristics. The cellulosic fibrous web should have sufficient strength to prevent the structure from tearing or tearing during normal use or when relatively low tensile strength is applied. In addition, the cellulosic fibrous web should be absorbent so that it can rapidly absorb the liquid and retain it sufficiently by the fibrous structure.

Tensile strength is the ability of the cellulose fibrous web to maintain physical integrity during use. Tensile strength is also related to the basis weight of the cellulosic fibrous web.

Absorbency is a property that makes it possible to absorb and retain the fluid that the cellulosic fibrous web contacts. Absorbency is affected by the density of the cellulosic fibrous web. If the web is too dense, the crevices between the fibers become too narrow and the absorption rate may not be high enough for the intended use. If the clearance is too wide, the capillary suction of the contacting fluid is minimized and the fluid is not retained in the cellulosic fibrous web due to surface tension limitations.

In addition, the web should be soft and non-tacky during use. Generally, softness is proportional to the ability of a cellulosic fibrous web to withstand deformation in a direction perpendicular to its plane.

The caliper is a clear thickness of the cellulose fibrous web measured at some mechanical compression and is related to the basis weight and the structure of the web. The strength, absorbency and softness are influenced by the caliper of the cellulosic fibrous web.

The process of making a paper product includes providing an aqueous slurry of cellulose fibers, then removing water from the slurry and rearranging the fibers to form an unformed web. Various types of machinery can be used to assist in the dehydration process. In a typical manufacturing process, a Fourdrinier wire papermaking machine is used which supplies a paper sliver on the surface of a moving endless belt where initial dewatering and fiber rearrangement is performed.

After the initial forming, the paper web is subjected to a drying process and is placed on another fibrous layer called dry fiber in the form of an endless belt. The drying process may include mechanical compression of paper webs, vacuum dewatering, air drying, and other types of processes. During the drying process, the non-formed web takes a special pattern or shape caused by the arrangement and deflection of the cellulose fibers.

U.S. Patent No. 4,529,480 issued to Trokhan on July 16, 1985, discloses a papermaking belt comprising a porous nonwoven member surrounded by a cured photosensitive resin skeleton. The resin framework is provided with a number of individual separation channels known as deflection conduits. Because the papermaking fibers were deflected into the conduit and repositioned therein when applying the fluid pressure differential, the papermaking belts used in the process were referred to as deflecting members. The use of belts in the papermaking process has provided the possibility to produce paper with the desired strength, absorbency and flexibility properties.

The paper produced using the process disclosed in U.S. Patent No. 4,529,480 is disclosed in US Pat. No. 4,637,859 issued to Trokans, which is incorporated herein by reference. Such paper is characterized in that two physically distinct regions are distributed along its surface. One region is a contiguous network region with relatively high density and high intrinsic strength. The other area is an area made up of a number of dome completely surrounded by a network area. The dome of the latter region has a relatively low density and a relatively low intrinsic strength compared to the network region.

During the papermaking process, the dome is formed as the deflection conduit of the papermaking belt is filled with fibers. The deflection conduit prevents the fibers disposed therein from being compressed when the paper web is compressed during the drying process. As a result, the dome becomes thicker and has lower density and intrinsic strength as compared to the compressed area of the web. Thus, the caliper of the paper web is limited by the intrinsic strength of the dome.

Once the drying phase of the papermaking process is complete, the arrangement and deflection of the fibers is completed. However, depending on the type of finished product, the paper may be subjected to further processing such as claning, application of flexibilizer, and modification. These processes compress the dome area of the paper and reduce the thickness. Thus, in the production of finished paper products having two physically distinct regions, it is necessary to form a cellulose fibrous structure resistant to mechanical compression on the dome.

When the cellulosic fibrous web is formed, the fibers are oriented mainly in the X-Y plane of the web, so that the structural strength in the Z direction can be neglected. When the fibers oriented in the X-Y plane are compressed by mechanical pressure, the fibers are compressed in unison to increase the density of the paper web and decrease the thickness. When the fibers are oriented in the Z direction of the web, the structural strength in the Z direction of the web and the resistance to the corresponding mechanical pressure are improved.

The deflection conduit provides a means for providing fiber orientation in the Z direction by enabling it to deflect the fiber along its circumference. The total fiber deflection depends on the size and shape of the deflection conduit with respect to the length of the fiber.

The large conduit enables small fibers to accumulate on the bottom of the conduit and thereby limits the deflection of subsequent fibers disposed therein. Conversely, small conduits enable large fibers to connect the openings of the conduits and less deflection of the fibers.

Also, the shape of the conduit affects the deflection of the fiber. For example, a deflection conduit defined by the outer periphery forming sharp edges or small radii increases the possibility of fiber bridging, thereby minimizing fiber deflection. See, for example, U.S. Patent No. 5,679,222, issued October 21, 1997 to Rasch et al., Which provides examples of various conduit configurations that may affect fiber connections.

Accordingly, the present invention provides a papermaking belt comprising a continuous network area and a plurality of individual deflection conduits having a size and shape that optimizes fiber deflection and corresponding Z orientation fiber orientation.

The present invention further provides a paper web comprising an essentially continuous, essentially macroscopic unidirectional network region and a plurality of individual domes diffused therethrough. The size and shape of the dome are made to form an optimal caliper.

SUMMARY OF THE INVENTION

The present invention relates to a papermaking belt with a skeleton of a predetermined pattern capable of producing a paper web of low density / high caliper, and a paper web produced thereby. The papermaking belt includes a reinforcing structure having a skeleton of a predetermined pattern disposed thereon. The skeleton of the predetermined pattern includes a continuous network skeleton and a plurality of individual deflection conduits, wherein the deflection conduits are separated from each other by a continuous network area.

The deflection conduits are generally elliptical and have a size such that the average width (W) of the conduits is L < W < 3L as compared to the length (L) of the average web fibers.

The aspect ratio of the deflection conduit is in the range of about 1.0 to about 2.0 and the radius of curvature radius of the minimum curvature radius to the average width is in the range of about 0.29 to about 0.50.

In order to maximize the concentration of conduits per unit area while minimizing the area of the continuous network area, the deflection conduits may be arranged in a hexagonal pattern. The pattern of continuous network provides a knuckle region having a width ranging from at least about 0.007 inches to about 0.020 inches.

The paper produced on such a papermaking belt comprises essentially macroscopic unidirectional network regions and a plurality of individual domes dispersed throughout and separated from each other by the continuous network region. This dome takes the shape and arrangement of the aforementioned generally elliptical deflection conduits.

These and other features, aspects and advantages of the present invention will become better understood with regard to the following detailed description, the appended claims and the accompanying drawings.

The present invention relates to a papermaking belt useful in a papermaking machine for making low density soft paper products and a paper product produced thereby. More particularly, the present invention relates to a papermaking belt comprising a framework and a reinforcing structure of a predetermined pattern, and a high caliper / low density paper product produced thereby.

Figure 1 is a schematic side view of one embodiment of a papermaking machine using the papermaking belt of the present invention,

Fig. 2 is a plan view of a portion of a papermaking belt of the present invention, showing a skeleton that is joined to a stiffening structure and has an elliptical paper-

3 is a vertical cross-sectional view of a portion of a papermaking belt shown along line 3-3 of FIG. 2,

Fig. 4 is a vertical cross-sectional view of a portion of the papermaking belt shown in Fig. 3 showing the fibers connecting deflection conduits,

Figure 5 is a vertical cross-sectional view of a portion of the papermaking belt shown in Figure 3 showing that the fibers are collected on the bottom of the deflection conduit,

Figure 6 is a vertical cross-sectional view of a portion of the papermaking belt shown in Figure 3 showing that the fibers are cantilevered above the openings of the deflection conduit to show deflection of the fibers,

Fig. 7 is a vertical cross-sectional view of a portion of the papermaking belt shown in Fig. 3 showing the fibers connecting the openings of the deflection conduit to show deflection of the fibers,

Figures 8a and 8b are plan views of a tubular shape with a tight radius or sharp edges to facilitate fiber connection,

9 is a schematic view of an elliptical conduit having a rectangular outer periphery,

Figure 10 is a schematic view of an elliptical conduit having a curved outer periphery,

Figure 11 is a plan view schematic of the batch thermal deflection conduit in a hexagonal pattern with the main axis oriented parallel to the machine direction of the belt,

Figure 12 is a plan view schematic of a deflection conduit arranged in a hexagonal pattern in which the main axes are oriented diagonally in the machine direction of the belt,

Figure 13 is a vertical cross-sectional view of a portion of the papermaking belt shown in Figure 3 showing fibers deflected into the deflection conduit and showing the relationship between the width of the conduit, the height of the conduit in the Z direction, and the stretch of the web,

Fig. 14 is a vertical cross-sectional view of a portion of the papermaking belt shown in Fig. 13 showing the fibers deflected into the deflection conduit and showing the relationship between the angle of bending of the web and the angle forming the interface of the nodal /

Figure 15 is a schematic plan view of a paper web with a dome arranged in a hexagonal pattern,

16 is a vertical cross-sectional view of a portion of the paper web shown along line 16-16 of Fig.

Term Definition

The meaning of the following terms used in this specification will be described.

The machine direction (MD) is parallel to the flow of the paper web through the paper making plant.

The cross machine direction (CD) means the direction perpendicular to the machining direction in the X-Y plane.

The center of the area is the point in the deflection conduit that coincides with the center of mass of a thin, uniformly distributed object tangent to the periphery of the deflection conduit.

The major axis is the longest axis that traverses the area center of the conduit and connects two points along the circumference of the conduit.

The minor axis is the shortest axis that traverses the area center of the conduit and connects two points along the circumference of the conduit.

The aspect ratio is the ratio of the length of the major axis to the length of the minor axis.

The average width of the conduit is the average length of the straight line connecting the two points of his attention, drawn through the center of the area of the conduit.

The radius of curvature is the instantaneous radius of curvature at a point on the curve.

The curve belongs to a curved line.

A straight line belongs to a straight line.

The height in the Z direction is the portion of the resin skeleton extending from the side of the reinforcing structure facing the paper.

The average fiber length is the length of the average fiber length.

The following detailed description includes (1) the papermaking belt of the present invention, and (2) the detailed description of the completed paper product of the present invention.

(1) Paper belt

In the exemplary papermaking apparatus shown schematically in Figure 1, the papermaking belt of the present invention takes the form of an infinite papermaking belt 10. The paper belt 10 has a paper contacting side 11 and a back side 12 opposite thereto. The papermaking belt 10 carries a paper web (or " fibrous web ") from various forming steps (unformed web 27 and intermediate web 29). The formation process of the unformed web is described in U.S. Patent No. 3,301,746 issued to Sanford and Sisen on Jan. 31, 1974, and U.S. Patent No. 3,994,771 issued to Morgan and Ritchie on Nov. 30, Are disclosed in various references. The paper belt 10 is conveyed in the direction indicated by the arrow B around the return rolls 19a and 19b, the printing nip roll 20, the return rolls 19a, 19d, 19e and 19f and the oil distributing roll 21 . The loop through which the papermaking belt 10 travels is provided with means for applying a fluid pressure differential to the unformed webs, such as vacuum pick-up shoe (PCU) 24a and multi-slot vacuum box 24 and the like. 1, the papermaking belt 10 moves around a pre-dryer such as the blow dryer 26 and passes between a nip formed by the printing nip roll 20 and the Yankee dryer drum 28 .

Although the preferred embodiment of the papermaking belt of the present invention is in the form of an endless belt 10, it can be used in a number of different forms, such as, for example, a fixed plate used in the manufacture of a handsheet or a rotary drum for use in other types of continuous processes Lt; / RTI &gt; Regardless of the physical form in which the papermaking belt 10 is believed to be the practice of the present invention, it generally has any of the physical properties described below. The papermaking belt 10 of the present invention may be manufactured according to U.S. Patent No. 5,332,889 issued to Trokhan (herein incorporated by reference).

2, the belt 10 according to the present invention comprises two main components: a skeleton 30 and a stiffening structure 32. As shown in Fig. The skeleton 30 preferably comprises a cured polymeric photosensitive resin. The skeleton 30 and the belt 10 comprise a first surface 11 defining a paper contacting side 11 of the belt 10 and an opposing second surface 12 facing the papermaking apparatus in which the belt 10 is used ).

The X, Y, and Z directions used herein are orientations relative to the papermaking belt (or paper web 27 disposed on the belt) of the present invention in a Cartesian coordinate system. The papermaking belt 10 according to the present invention is macroscopically flat. The plane of the paper belt 10 defines the X-Y direction. The Z direction is perpendicular to the X-Y direction and the plane of the paper belt 10. Likewise, the web 27 according to the invention can be considered to be macroscopically flat and lying in the X-Y plane.

Preferably, the skeleton 30 provides a node region 36 that defines a predetermined pattern and prints a similar pattern on the web 27 of the present invention. A particularly preferred pattern of framework 30 is essentially a continuous network. The individual deflection conduits 34 will extend between the first surface 11 and the second surface 12 of the belt 10 when essentially selecting a pattern of continuous meshwork on the skeleton 30. [ In essence, the continuous meshwork surrounds the deflection conduit 34 and defines it.

The skeleton 30 provides a node region 36 that defines a predetermined pattern and prints a pattern corresponding thereto on a web 27 supported thereon. Printing is always performed when the belt 10 and the web 27 pass between two rigid surfaces having a clearance sufficient for printing. Printing is generally performed in the nip between the two rolls and is most commonly performed when the belt 10 carries the paper to the Yankee dryer drum 28. Printing is performed by compressing the skeleton 30 against the paper 27 in the pressure roll 20.

The first surface 11 of the belt 10 contacts the web 27 supported thereon. During the papermaking, the first surface of the belt 10 may print a pattern corresponding to the pattern of the skeleton 30 on the web 27.

The second surface 12 of the belt 10 is the surface in contact with the machine. The second surface may be fabricated to have a backside network with a passageway different from the deflection conduit 34. The conduit provides irregularities in the texture of the back surface of the second surface of the belt 10. The passage allows leakage of air in the X-Y plane of the belt 10, and such leakage does not necessarily flow in the direction through the deflection conduit 34 of the belt 10. The belt 10 having such a backing structure is described in U.S. Patent No. 5,098,522, issued March 24, 1992 to Smurkoski et al., And U.S. Patent No. 5,364,504, issued November 15, 1994 to Smurker Koski et al. And 5,260,171, issued November 11, 1993 to Schumerkoski et al., The disclosures of which are incorporated herein by reference.

The second major component of the belt 10 in accordance with the present invention is the reinforcing structure 32. The reinforcing structure 32 has a first or paper-facing surface 13, such as a skeleton 30, and a surface facing the second or papermaking device. The reinforcing structure 32 is disposed primarily between the opposing surfaces of the belt 10 and may have a surface that coincides with the back surface of the belt 10. [ The reinforcing structure 32 supports the frame 30. The reinforcing structure is typically woven as is known in the art. A portion of the stiffening structure 32 that mates with the deflection conduit 34 prevents fibers used for papermaking from fully passing through the deflection conduit 34 and thereby reducing the occurrence of pinholes. A nonwoven element, screen, net or plate with a plurality of holes may provide adequate strength and support to the framework 30 of the present invention, if it is not desired to use woven fibers in the reinforcement structure 32.

3, the skeleton 30 is joined to the stiffening structure 32. The skeleton 30 extends outward from the side 13 facing the paper of the stiffening structure 32. As shown in Fig. The reinforcing structure 32 reinforces the resin skeleton 30 and the vacuum dewatering device used in the papermaking process removes water from the unformed web 27 and also removes water removed from the unformed web 27. [ And has a protruding opening area suitable for being passed through the belt 10.

The belt 10 in accordance with the present invention is described in U.S. Patent No. 4,514,345 issued to Johnson et al. On Apr. 30, 1985, U.S. Patent 4,528,239 issued Jul. 9, 1985 to Trokhan, 5,298,722, issued November 9, 1993, 5,260,171 issued November 9, 1993, 5,275,700 issued January 4, 1994 to Trokhan, 5,328,565 issued to Lash et al, July 12, 1994, U.S. 5,334,289 issued to Trocane et al. On Mar. 2, U.S. 5,431,786 issued to Lash et al. On Jul. 11, 1995, U.S. 5,496,624 issued March 5, 1996 to Steljes Jr., et al., March 19, 1996 5,500,277 issued to IJA Trocane et al., 5,514,523 issued to Trocane et al. On May 7, 1996, 5,554,467 issued to Trocane et al on Sep. 10, 1996, No. 5,566,724 issued to Khan et al., Issued on April 29, 1997 to Trokhan et al. 5,628,876 issued May 13,1997 to Aries et al., 5,679,22 issued to Lash et al. On October 21,1997, 5,714,041 issued to Aries et al. On Feb. 3, 1998 , &Lt; / RTI &gt; The entire disclosure of which is incorporated herein by reference.

The ability to produce paper with a certain thickness is related to the caliper of the web. The caliper is the thickness of the cellulosic fibrous web measured at any mechanical pressure. The caliper is related to the web's basic weight and web configuration. The basis weight is a pound unit weight of 3,000 ft ² of paper. The composition of the web is related to the orientation and density of the fibers making up the web 27.

The fibers that make up the web 27 are typically oriented in the X-Y plane and provide minimal structural support in the Z direction. Accordingly, as the web 27 is compressed by the skeleton 30 of a predetermined pattern, the web 27 is densified to form a high-density region of a predetermined pattern of reduced thickness. Conversely, a portion of the web 27 covering the deflection conduit 34 is not compressed and thus forms a thick, low density region.

The low density region, called the dome, gives the web 27 an accurate thickness. Since the fibers constituting the typical dome are oriented mainly in the X-Y plane of the web 27, the support of the fibers in the Z direction is negligible. Conversely, the dome is deformed during subsequent papermaking operations and tends to decrease in thickness. Thus, the caliper of the web 27 is generally limited by the ability of the dome to withstand mechanical pressure.

However, the deflection conduit 34 provides a means for bending the fibers along the periphery 38 in the Z direction. By the deflection of the fibers, a fiber orientation including the component in the Z direction is generated. The orientation of such fibers not only forms a clear web thickness but also provides a certain amount of structural strength in the Z direction, which helps the web 27 maintain its thickness through the papermaking process. Thus, in the present invention, the size and shape of the deflection conduit 34 is set to maximize the deflection of the fiber along the periphery 38.

As the fibers 50 are deflected into the deflection conduit 34, removal (dehydration) of water from the unformed web 27 is initiated. Dehydration reduces the mobility of the fibers, which makes it easier to fix the fibers in place after being deflected and rearranged. By applying different fluid pressures to the unformed web 27, deflection of the fibers into the deflection conduit 34 can be reduced. One preferred method of applying different pressures is to expose the unformed web 27 to a vacuum through the deflection conduit 31. In Figure 1, a preferred method is shown using a pick-up shoe 24.

Without being limited by theory, it is common to arrange the fibers of the unformed web 27 with respect to the deflection conduit 34 to take one of two models depending on the number of tolerances, including the length of the fibers. As shown schematically in Figure 4, the distal end of the elongate fibers 50 is constrained on the upper portion of the knob 36 to enable bending into the conduit 34 without bending the central portion of the fiber 50 completely. Thus, the " connection " of the deflection conduit 34 is achieved. 5, the fibers 50 (primarily short fibers) are arranged such that a slight deflection forms a pile of fibers 50 and is disposed within and around the conduits 34 Can be sufficiently disposed within the conduit 34 with minimized deflection of the next fiber to be treated.

The deflection of the fiber is related to the bending resistance of the web. The higher the bending hardness of the web, the greater the bending resistance. The bending hardness of the web is dominated by two factors: (1) the bending hardness of the individual fibers, and (2) the bond strength between the fibers. However, in the pick-up shoe 24, the web is wetted and the inter-fiber joint is not well attained due to the presence of a large amount of water in the web. Therefore, the main factor is the hardness of the individual fibers. The harder the fiber, the less deflection.

Although the deflection of the fibers is dependent on the intrinsic hardness of the fibers 50, the magnitude of the deflection is largely determined by whether the fibers 50 are sufficiently long in length to be as wide as the conduits 34. Figures 6 and 7 show two possible outlines of fiber deflection. In Fig. 6, the fibers 50 are fixed at point A and are cantilevered above the openings of the conduit 34. In Fig. When a uniform load such as vacuum is applied to the fiber 50, a high bending moment is generated at the point A, and the deflection at the point B is defined by the following equation (1).

Here, f _B is biased at point B, F are uniformly distributed over the length of the fiber strength, L is the fiber from the supporting point (s) in length, E is Young's modulus, I is moment of inertia.

In Fig. 7, the fibers 50 are longer than the width of the conduit, so they are fixed at two points (A, B). If the same vacuum is applied to the fibers 50, the bearing forces at points A and B will result in deflecting the bending moment and deflecting the fibers at point C (equation 2).

Where f _C is the fiber deflection at point C.

Assuming that the variables (F, L, E) are the same for the fibers shown in Figures 6 and 7, the deflection (f _B ) of the fiber is 48 times greater than the deflection (f _C ) of the fiber.

Thus, the deflection of the fiber can be improved by setting the size of the deflection conduit 34 to minimize the occurrence of the connection. However, the size of the conduit is limited by the number of small fibers in the feed that can accumulate in the conduit 34 and thereby inhibit large fibers from deflecting therein.

The feed usually includes both hardwoods and softwoods. An example of a broad-leaved tree is eucalyptus (EUC), and an example of a conifer is northern softwood kraft (NSK). An example of a feedstock is 30 wt.% Conifer and 70 wt.% Hardwood. By setting the average fiber length of softwoods to about three times the average fiber length of hardwoods and by setting the size of the deflection conduits to the average softwood length, the conduits are easy to accumulate short hardwood fibers, Limit. Therefore, it is desirable to set the width W of the conduit to be equal to the average fiber length of the feed L.

In the present invention, the average fiber length is a weighted average fiber length obtained by the following equation (5).

Where L _i is the average length of fibers of species i and n _i is the number of fibers measured in species i .

The length-weighted average fiber length in the present invention is about 0.043 inches.

As shown in Figs. 9 and 10, conduit 34 may take a variety of different shapes with variable widths or constant widths. The shape of the conduit with variable width is defined by the main axis 40, the minor axis 42 and the average width 46. The major axis 40 is the longest axis or width traversing the area center of the conduit and the minor axis 42 is the shortest width traversing the area center of the conduit and the average valley 46 is the area of the conduit It is the average width across the center.

The average width 46 is determined by first measuring the length of the line drawn through the area center of the CD connecting the two points on the periphery of the conduit. The average width is determined by measuring and averaging the lengths of similar lines oriented at an angle increase of .DELTA..theta. For CD (for example, when 0 represents CD, in the range of 0 to 165).

It is preferable to set the minimum width of the conduit 34 with respect to the average fiber length L as shown in Equation (6), since the fiber connection is most likely to occur along the minor axis 42.

Thus, a preferred minimum conduit width in the present invention is at least about 0.043 inches.

The accumulation of small fibers can occur along both the main axis 40 and the minor axis 42 of the conduit so that it is difficult to define the upper limit with respect to the two side shafts 40 and 42. As a result, Deflection occurs. However, in the present invention, it has been found that the maximum caliper is formed by setting the size of the conduit 34 such that the average width 46 is in the range from the average length L to three times the average fiber length (3L) .

L? W? 3L

Therefore, it is desirable to set the size of the conduit so that the range of average conduit width in the present invention is about 0.043 inches to about 0.129 inches.

The web 27 is an approximately two-dimensional fiber network. The ideal fiber network comprises an arbitrary distribution of fibers in which the orientation of the fibers does not favor a particular orientation. For such an ideal network, the average fiber length L is the same in all directions.

However, it is common that the network of fibers is arranged in a web having the orientation of fibers deflected in a particular direction. For such a deflected network, the average fiber length will vary with respect to the oblique orientation in the XY plane of the web 27. Theoretically, such average fiber length is denoted by L _?.

ΘIs the respective orientation of the X-Y plane with respect to the CD,L _Θi Is the component length of the fiber in each direction of the X-Y plane,L _Θ Is the average fiber length in each direction in the X-Y plane, and n is the average fiber length in the X-Y plane in each directionΘ) &Lt; / RTI &gt;

In the present invention, the fibers 50 constituting the two-dimensional fiber network are oriented mainly in the machining direction MD. Therefore, the average fiber length in the machining direction is longer than the average fiber length in the transverse working direction (CD).

From Equation (4):

Therefore, as shown in Fig. 11, it is preferable to orient the conduit 34 so that the main shaft 40 is parallel to the working direction of the belt. However, since it is usual for the direction of the fibers to prefer the working direction MD, those skilled in the art will appreciate that the main axes are oriented diagonally and this diagonal line is oriented at 22.5 DEG +/- 22.5 DEG with respect to the working direction Angle &lt; RTI ID = 0.0 &gt; 54. &lt; / RTI &gt;

The shape of the conduit is defined by the aspect ratio R _A defined as the ratio of the major axis 40 to the minor axis 42. For the maximum deflection of the fiber, it follows equations (8) and (9) in which the aspect ratio ( R _A ) is defined as:

However, it is impractical to measure the average fiber length in a specific direction of the web in the XY plane in the web state immediately before the fiber is deflected into the deflection conduit 34. [ It is therefore necessary to determine the preferred aspect ratio ( R _A ) for the shape of the conduit providing maximum fiber deflection, taking into account the inherent physical properties of the web that are related to the length of the fiber.

The physical properties of the paper web 27 are primarily influenced by the orientation of the fibers in the X-Y plane of the web 27. For example, the web 27 having a fiber direction favoring the machining direction MD has a tensile strength higher than that of CD, a stretched CD is higher than MD, and a bending hardness of MD is higher than that of CD.

In addition to the orientation of the fibers, the tensile strength of the web is proportional to the corresponding length of the fibers oriented in a particular direction of the X-Y plane. Thus, the tensile strength of the web in MD and CD is proportional to the average fiber length in MD and CD.

Therefore, Equation (8) becomes as follows.

Further, by replacing L _MD / L _CD in Equation (10) with T _MD / T _CD , the aspect ratio R _A defining the shape of the conduit can be expressed as follows.

The tensile strength of web 27 on MD and CD was measured using an Intelect II Standard Tensile Tester manufactured by Thwing-Albert Instrument Co. of Philadelphia, PA. As a result of the experiment, the shape of the preferred conduit providing optimal fiber deflection and corresponding caliper formation has an aspect ratio of 1 to 2. The preferred shape has an aspect ratio of about 1.3 to 1.7. The most preferred shape has an aspect ratio of 1.4 to 1.6.

The shape of the deflection conduit 34 is important to minimize the connection of the fibers across the width of the conduit as well as to minimize the connection of the fibers along the perimeter 38 of the conduit wall. The duct wall, which forms tight radii or sharp edges, provides an additional place for fiber connections. The shape of the conduit which is undesirable for this purpose is shown in Figures 8a and 8b.

As shown in Figures 9 and 10, the shape of the conduit preferred for the present invention is generally oval, including, but not limited to, circular, oval, and polygons of six or more sides. 9 illustrates an elliptical conduit having a rectangular outer periphery including an individual wall portion 44. Fig. With respect to the shape of such a conduit, the connection of fibers along the periphery is minimized by providing a narrowed angle 39 between adjacent wall portions of at least 120 [deg.].

Figure 10 shows an elliptical conduit with a concave outer circumference of a curve toward the center of the conduit. The curved circumference includes a minimum radius of curvature 48. Likewise, the connection of the fibers along the circumference is minimized by limiting the shape so that the ratio of the minimum radius of curvature (48) to the average duct width is at least 0.29 and is only 0.50 or less.

13, ideally the web 27 on top of the knob 36 is stretched to zero while the conduit 34 applies an average stretch? To the web 27, Bend.

? is the average elongation, OB is the height in the Z direction, and W is the width of the conduit.

The critical elongation is obtained when the web 27 is broken. If the elongation is greater than the critical elongation of the web 27, the network is broken and a pinhole is generated in the web. The critical elongation of the web 27 depends on the nature of the network, such as the length of the fibers and the orientation of the fibers. Since the web is wetted in the pick-up shoe and the inter-fiber joint is not well formed, the inter-fiber joint has no effect on the critical elongation.

The total distance the web 27 is bent into the conduit 34 follows the height 60 in the Z direction. Since the critical elongation of the web is directly proportional to OB, OB is defined by the critical elongation of the web 27. [ Therefore, the preferable range of OB (0) from Equation (15) is expressed as follows.

Renal threshold _(threshold ε) is the fiber length, fiber orientation and basis weight and complex relationships. Qualitatively, the critical elongation increases as the fiber length and / or basis weight increases. In the present invention, the preferred range of height in the Z direction for maximum web deflection is at least about 0.005 inches to about 0.039 inches.

The overall deflection the web will undergo in the deflection conduit is also determined by the angle that forms the node / conduit interface of the skeleton of a given pattern. The deflection angle 62 of the web is defined as the angle of the web at the interface of the node / conduit with respect to the Z direction. The deflection of the web is shown in Fig. The fibers 50 deposited at the interface of the nodule / conduit are oriented by a component in the Z direction that makes it possible to provide a support structure that is able to withstand external compressive forces. The fibers oriented parallel to the Z direction at the interface of the nodule / conduit provide maximum support. However, since the web 27 is not infinitely flexible, it is not possible to follow the contour of the conduit 34 completely. Also, due to manufacturing limitations, the walls of the deflection conduit are inclined to form a resin angle 64 at the interface of the nodes / conduits. Since the deflection angle 62 is not less than the resin angle 64, the resin angle 64 further restricts the deflection of the web. In the present invention, it is preferable that the resin angle is inclined between 5 and 10 degrees. The deflection angle range of the web is typically from about 20 [deg.] To about 50 [deg.].

The external force applied to the paper during the various processes reacts by the support force from the fibers at the interface of the nodule / pocket, so the greater the number of fibers in this area, the higher the bearing capacity and corresponding caliper. The number of fibers 50 at the deformation interface can be optimized by maximizing the total periphery 38 of the interface. This is the same as maximizing the number of deflection conduits 34 per unit area or minimizing the proportion of the node region 36. Theoretically, the conduit 34 can be compressed to an extreme state. However, as shown in Figures 11 and 12, there is a need for a knob 36 to separate the conduit 34 to have a minimum width 52 to enable firm attachment of the resin to the stiffening structure 32 . In the present invention, the preferred minimum node width 52 is at least about 0.007 inches to about 0.020 inches.

In addition, the conduit 34 can be compressed in a more efficient arrangement to maximize the number of conduits per unit area. A preferred arrangement of the conduits 34 is to form a hexagonal pattern as shown in Figs.

(2) Paper

The paper 80 of the present invention has two main areas. The first region includes a printing area 82 that is printed against the skeleton 30 of the belt 10. It is preferred that the print region 82 essentially comprises a continuous network. The continuous network 82 of the first region of the paper 80 is formed on the intrinsic continuous network 30 of the belt 10 and generally conforms to its geometric shape and is very close to it As shown in FIG.

The second area of paper 80 includes a plurality of domes 84 distributed throughout the printed network area 82. The dome 84 is generally coincident with the geometry of the deflection conduit 34 of the belt and substantially coincides with its position during retraction. By matching the deflection conduit 34 during the papermaking, the fibers in the dome 84 are deflected in the Z direction between the surface facing the paper of the skeleton 30 and the surface facing the paper of the stiffening structure 32. As a result, the dome 84 protrudes outward from the intrinsic continuous network region 82 of the paper 80. Preferably, the dome 84 is separated and separated from each other by a continuous network region 82. Without being limited by theory, the dome 84 of paper 80 and the intrinsic continuous network region 82 may have substantially the same basis weight. By deflecting the dome 84 into the deflection conduit 34, the density of the dome 84 is reduced relative to the intrinsic continuous networked tissue region 82. In addition, the intrinsic continuous network region 82 (or other pattern that may be selected) may be subsequently pressed against the Yankee dryer drum, for example. By such pressing, the density of the intrinsic continuous network region 82 is increased relative to the density of the dome 84. The resulting paper 80 may be embossed later, as is known in the art.

The paper 80 in accordance with the present invention is described in U.S. Patent 4,529,480, Trokhan, July 16, 1985, U.S. Patent 4,637,859, January 20, 1987, Trokhan, U.S. 5,364,504, November 15, 1994, 5,529,664 issued June 25,1996 to Trokhan et al, and 5,679,222 issued to Lash et al. On October 21, 1997, the entire contents of which are incorporated herein by reference.

The shape of the dome 84 in the X-Y plane includes, but is not limited to, circular, oval, and polygons of six or more sides. Preferably, the dome 84 is generally elliptical in shape, including a curved or straight perimeter 86. Curved perimeter 86 includes a minimum radius of curvature such that the ratio of the ratio of the minimum curvature radius to the average width of the dome is at least about 0.29 to about 0.50. The straight peripheries 86 may include a plurality of wall portions with a narrowed angle between adjacent wall portions of at least about 120 [deg.].

To provide paper 80 with a high caliper it is necessary to maximize the number of fibers in the Z direction per unit area of web. The majority of the Z-direction fibers are oriented along the outer circumference 86 of the dome 84 where fiber deflection occurs. Therefore, the orientation of the fibers in the Z direction and the corresponding caliper of the paper web will depend primarily on the number of dome per unit area.

As shown in FIG. 15, the number of dome 84 per unit area is maximized by minimizing the distance between adjacent dams achieved by arranging the dome in an effective pattern. In the present invention, the preferred minimum distance 88 between the dome 84 is at least 0.007 inches and only 0.020 inches. A preferred arrangement of the dome 84 is to form a hexagonal pattern.

The number of dome 84 per unit area of the paper 80 depends mainly on the size and shape of the deflection conduit described above. In the present invention, the preferred average width of the dome 84 is at least about 0.043 inches, and not more than about 0.129 inches. A preferred generally elliptical shape for the dome is an aspect ratio of about 1 to 2. [ More preferably, the generally elliptical shape aspect ratio is about 1.3 to about 1.7, and the most preferred generally elliptical shape aspect ratio is about 1.4 to 1.6.

The caliper of the paper web is typically measured at a pressure of 95 grams per square inch using a circular press foot with a diameter of 2 inches after a 3 second pause. The caliper can be measured using a Thwing-Albert Thickness Tester model 89-100 manufactured by Thwing-Albert Instrument Company of Philadelphia, Pa. Calipers are measured under TAPPI temperature and humidity conditions.

In the present invention, the caliper was measured on a paper web containing two piles. Preferably the caliper of the double ply paper web is 20 to 40 mils. The caliper of the double ply paper web is more preferably 38 to 46 mils, and most preferably 25 to 30 mils.

While particular embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various other changes and modifications may be made without departing from the spirit and scope of the invention. All such variations and modifications falling within the scope of the invention are included in the scope of the appended claims.

Claims (10)

A papermaking belt having a paper web contacting surface for supporting a web of papermaking fibers having an average fiber length (L) and a papermaking device contacting surface opposite the paper web contacting surface, Wherein the skeleton of the predetermined pattern comprises a continuous network region and a plurality of discrete deflection conduits, wherein the deflection conduits are separated from one another by the continuous network region , Said deflection conduits having an average width (W) of L < W < 3L , an aspect ratio in the range of at least about 1.0 to about 2.0, and a minimum curvature radius range of at least about 0.29 to about 0.50 Comprising a reinforcing structure having a generally elliptical curved perimeter having a radius Paper belt. The method according to claim 1, The skeleton of the predetermined pattern extends outwardly from the reinforcement structure at a distance ranging from at least about 0.005 inches to about 0.039 inches Paper belt. The method according to claim 1, The deflection conduit is inclined at about 5 [deg.] To about 10 [deg.] Paper belt. The method according to claim 1, The deflection conduits are arranged in a hexagonal pattern Paper belt. 5. The method of claim 4, Wherein the continuous network region provides a node region having a minimum width in the range of at least about 0.007 inch to about 0.020 inch Paper belt. 6. The method of claim 5, Wherein the nodal region is between about 25% and about 50% of the web contacting surface of the belt Paper belt. The method according to claim 1, Said deflection conduit having a main axis, said belt having a machining direction in the X-Y plane, said main axis being oriented parallel to said machining direction Paper belt. The method according to claim 1, Wherein the deflection conduit has a major axis and the belt has a machining direction in the X-Y plane, the major axis being oriented diagonally to the machining direction Paper belt. The method according to claim 1, Wherein the aspect ratio of the deflection conduit is from about 1.3 to about 1.7 Paper belt. A papermaking belt having a paper web contacting surface for supporting a web of papermaking fibers having an average fiber length (L) and a papermaking device contacting surface opposite the paper web contacting surface, Wherein the skeleton of the predetermined pattern comprises a continuous network region and a plurality of discrete deflection conduits, the deflection conduits being separated from each other by the continuous network region, The deflection conduit having a rectangular outer periphery including a wall portion forming a generally elliptical shape, the rectangular outer periphery having an average width (W) of L < W < 3L , an aspect ratio of at least about 1.0 to about 2.0, Having a narrowed angle between adjacent wall portions of at least about 120 [deg.], Paper belt.