ES2209555T3 - PAPER OF GREAT THICKNESS AND TAPE FOR THE MANUFACTURE OF PAPER FOR THE PRODUCTION OF 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

Thick paper and manufacturing tape of paper for its production.

Field of the Invention

The present invention relates to tapes for papermaking useful in machines for manufacturing paper to make absorbent paper products, soft, low density and the paper products produced by these. Plus particularly, this invention relates to tapes for papermaking comprising patterned armor and a reinforcement structure and high paper products Thickness / low density produced by these.

Background of the invention

Cellulosic fiber bands such as paper are well known in the art. Such fibrous bands are of use common for paper towels, toilet paper, napkins and Similar. The great demand for such paper products has created a demand for improved versions of products and methods for its manufacture.

To meet the needs of the consumer, the cellulosic fibrous bands must have different features. They must have sufficient tensile strength to prevent structures from tearing or fragmenting during ordinary use or when tensile forces are applied relatively small The cellulosic fiber bands must be absorbents, so that liquids are quickly absorbed and completely retained by the fibrous structure.

Tensile strength is the ability to the cellulosic fibers band to maintain its physical integrity during use Tensile strength is a function of the base weight of the cellulosic fiber band.

Absorbency is the property of the fibers cellulosic that allows them to attract and retain fluids in contact. The absorbency is influenced by the density of the band of cellulosic fibers If the band is too dense, the interstices between the fibers may be too small and the absorption rate may not be large enough for the intended use If the interstices are too large, capillary attraction of contact fluids is minimized preventing fluids from being retained by the fibrous band cellulosic because of tension limitations superficial.

Also, the band should present softness, of so that it is pleasant to the touch and not rough and hard during the utilization. Softness is the quality of cellulosic fiber that imparts a particularly pleasant skin sensation of the user or the user. The softness is universally proportional to the capacity of the cellulosic fiber band for resist deformation in the normal direction to the plane of the band cellulosic fibrous

Caliber is the apparent thickness of a band cellulosic fibrous measured at a certain mechanical pressure and is a function of the base weight and the structure of the band. The resistance, absorbency, and softness are influenced by the thickness of the cellulosic fibrous band.

The procedures for manufacturing paper products generally involve the preparation of a aqueous slurry of cellulosic fibers and the subsequent removal of grout water while simultaneously reordering the fibers to form an embryonic band. Several types can be used of machinery to assist in the dehydration procedure. A Typical manufacturing procedure employs a machine for the Fourdonier papermaking in which the paper grout is fed on a surface of an endless belt that displaces in which dehydration and rearrangement take place fiber initials.

After the initial formation, the band of paper goes through a drying procedure on another fabric called drying cloth that has the form of endless tape. The Drying procedure may involve mechanical compaction of The paper band, vacuum dehydration, by drying air and other types of procedures. During the procedure of dried, the embryonic band adopts a specific model or shape originated by the arrangement and deviation of the fibers cellulosic

U.S. Pat. No. 4,529,480, issued to Trokhan on July 16, 1985, introduced a tape for the papermaking comprising a woven member filled with holes that was surrounded by a resin armor hardened photosensitive. The elastomeric resin armor was provided with a plurality of discrete channels, known isolates as diversion ducts. The tape for papermaking used in the procedure was called a deviation member because the papermaking fibers were diverted within the ducts and became reorganized in the themselves after the application of a fluid pressure differential. The use of the tape in the procedure for papermaking provides the possibility to create a paper having certain desired resistance characteristics, absorption and softness.

Paper produced using the procedure described in US Pat. No. 4,529,480 is described in the U.S. Patent No. 4,637,859, issued to Trokhan. The paper is characterized by having two physically distinct regions distributed across their surfaces. A region is a region of continuous network that has a relatively high and high density intrinsic resistance The other region is one that is composed of a plurality of vaults that are completely surrounded by the network region The vaults in the last region have densities relatively low and relatively low resistance compared with the network region.

The vaults are produced by fibers that fill the ducts of diversion of the tape for the manufacture of paper during the papermaking process. The diversion ducts prevent the fibers deposited in them are compacted when the paper web is compressed during drying procedure As a result, the vaults are thicker  for having lower density and intrinsic resistance in comparison with the compacted regions of the band. Consequently, the Paper band gauge is limited by resistance intrinsic of the vaults.

Once the drying phase of the procedure Papermaking is over, the layout and deviation of The fibers is complete. However, depending on the type of finished product, treatments can be applied to paper additional such as calendering, softener application and the conversion. These procedures tend to compact the paper dome regions and reduce thickness. Therefore, the production of high thickness finished paper products that have two physically distinct regions requires the formation of cellulosic fibrous structures in the vaults that have resistance to mechanical pressure.

As the fibrous band forms cellulosic, the fibers are predominantly oriented in the plane X-Y of the band providing stiffness negligible structural in the Z direction. Once the fibers oriented in the X-Y plane are compacted by mechanical pressure, the fibers are compressed together increasing the density of the paper band while decreasing the thickness. The fibers oriented in the Z direction of the band, improve the structural rigidity in the Z direction of the band and its corresponding resistance to mechanical pressure. Consequently, maximize fiber orientation in the Z direction, maximize the thickness.

Bypass ducts provide some means for producing an orientation of the fibers in the Z direction allowing the fibers to deflect along the periphery of diversion ducts. The total fiber deviation depends of the size and shape of the diversion ducts in relation to The length of the fibers.

Large ducts allow them to accumulate minor fibers at the bottom of the duct which in turn limit the deviation of the fibers that are subsequently deposited in they. Conversely, small ducts allow fibers large bridges in the opening of the ducts with minimal deviation of the fibers. In EP 0135231A, Trokhan P. are described also deviation members and a method to manufacture the same.

The shape of the ducts also influences the fiber deflection. For example, diversion ducts defined by a periphery that forms abrupt corners or small radius increase the possibility of bridging fibers that Minimizes fiber deflection. See US Pat. No. 5,679,222, issued to Rasch et al. On October 21, 1997, for see examples of various forms of duct that can affect the fiber bridging

Consequently, the present invention provides a papermaking belt comprising a common crosslinked region and a plurality of ducts of discrete deviation that are sized and formed to optimize fiber deflection and corresponding orientation of the fibers in the Z direction.

The invention further provides a band of paper comprising a macroscopically crosslinked region essential flat, essentially continuous and a plurality of vaults discrete arranged through it. The vaults are sized and formed to produce the optimum thickness.

Summary

The present invention relates to a tape d papermaking that has a patterned armor capable of produce a low density / high thickness paper web and at paper band produced by this. The tape for the manufacture of paper comprises a reinforcing structure that has a reinforcement modeled arranged on it. The patterned structure includes a continuous network region and a plurality of conduits of discrete deviation, in which the diversion ducts are isolated from each other by the region of continuous network.

The deflection ducts are generally of elliptical shape and dimensioned in relation to a fiber length middle band, \ upbar {L}, so that the average width, \ upbar {W}, of the ducts is \ upbar {L} <\ upbar {W} <3 \ upbar {L}. The ducts of deviation have an aspect ratio that varies from at least around 1.0 to about 2.0 and a minimum radius of curvature in which the ratio of radius of minimum curvature to average width It varies from minus 0.29 to 0.50.

The deflection ducts may be arranged in an exagonal model in order to maximize the duct concentration per unit area while at the same time the area of the continuous network region is minimized. The region Continuous network provides an articulation area that has a width that varies from 0.178 mm to 0.51 mm.

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The paper produced on that tape for the papermaking comprises a flat web region and a plurality of discrete vaults scattered throughout it and isolated from each other by the continuous network region. The vaults they have the shape and arrangement of the diversion ducts generally elliptical described above.

Brief description of the ducts

These and other characteristics, aspects and advantages of the present invention will be better understood with with respect to the following description, appended claims and accompanying drawings, in which:

Figure 1 is a side elevation view schematic of a papermaking machine that uses the papermaking tape of the present invention;

Figure 2 is a top view of a portion of the papermaking tape of the present invention, showing the structure-bound armor of reinforcement and having openings in the paper side of form elliptical deviation ducts;

Figure 3 is a cross-sectional view. vertical of a portion of the papermaking tape shown in figure 2 taken along the line 3-3;

Figure 4 is a cross-sectional view. of a portion of the papermaking tape shown in Figure 3 depicting fibers that bridge the conduit of deviation;

Figure 5 is a cross-sectional view. vertical of a portion of the papermaking tape shown in figure 3 representing fibers collected at the bottom of the diversion duct;

Figure 6 is a cross-sectional view. vertical of a portion of the papermaking tape shown in figure 3 representing a cantilever fiber over the opening of the deflection duct to illustrate the deflection of the fibers;

Figure 7 is a cross-sectional view. vertical of a portion of the papermaking tape shown in figure 3 representing a fiber that bridges the deflection duct opening to illustrate the deflection of the fibers;

Figures 8a and 8b are plan views from up duct shapes that have small radii or corners abrupt that makes them prone to fiber bridging;

Figure 9 is a schematic representation of an elliptical duct that has a periphery rectilinear;

Figure 10 is a schematic representation of an elliptical duct that has a periphery curvilinear;

Figure 11 is a schematic representation, in plan, top view of bypass ducts arranged in an exagonal model with the major axes oriented parallel to the machine address of the tape;

Figure 12 is a schematic representation, in plan, top view of bypass ducts arranged in an exagonal model with the diagonally oriented major axes with respect to the machine direction of the tape;

Figure 13 is a cross-sectional view. vertical of a portion of the papermaking tape shown in figure 3 representing fibers that deviate inside of the diversion duct and illustrating the relationship between the duct width, height in the Z direction of the duct, and the stretching of the band;

Figure 14 is a cross-sectional view. vertical of a portion of the papermaking tape shown in figure 3 representing fibers that deviate inside of the diversion duct and illustrating the relationship between the deviation angle of the band and the angle that forms the interface joint / duct opening;

Figure 15 is a schematic representation, in plan, seen from above, of a paper band that has vaults arranged in a hexagonal model; Y

Figure 16 is a cross-sectional view. vertical of a portion of the paper web shown in the figure 15, taken along line 16-16.

Detailed description of the invention Definitions

The following terms, as used in this memory, have the following meanings:

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Machine address, designated MD, is the direction parallel to the circulation of the paper web through of papermaking equipment.

Transverse machine direction, designated CD is the direction perpendicular to the machine direction in the plane X-Y.

Area center, is a point inside the duct deviation that should coincide with the center of mass of a uniform thin distribution of matter bound by the periphery of the diversion duct.

Major axis, is the longest axis that crosses the center of the duct area and joining two points along the duct perimeter.

Minor axis, is the shortest axis or width that crosses the center of the duct area and that joins two points to the duct perimeter length.

Aspect ratio is the ratio of the length of the major axis to the length of the minor axis.

The average width of the duct is the average length of straight lines drawn through the center of the duct area and that join two points on the perimeter of it.

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

Curvilinear, belongs to curved lines.

Rectilinear, belongs to straight lines.

Height in the Z direction is the portion of the resin armor that extends from the face facing the Role of the reinforcement structure.

Average fiber length, is the weighted length of the average fiber length.

The memory contains a detailed description of (1) the papermaking tape of the present invention, and (2) the finished paper product of the present invention.

(1) Tape for Paper Making

In the papermaking machine representative schematically illustrated in figure 1, the tape for the papermaking of the present invention has the shape of an endless belt, tape 10 for papermaking. The papermaking belt 10 has a face 11 of paper contact and a rear face 12 opposite the face 11 of paper contact The tape 10 for papermaking is carrier of a paper band (or "fiber band") in several stages of its formation (an embryonic band 27 and a band intermediate 29). Embryonic band formation procedures are described in many references, such as US Pat. No. 3,301,746, issued to Sanford and Sisson on January 31, 1974, and U.S. Patent No. 3,994,771, issued to Morgan and Rich on 30 November 1976. Tape 10 for papermaking is shifts in the direction indicated by the directional arrow B around the return rollers 19a and 19b, the roller 20 of print narrowing, rollers 19c, 19d, 19e, 19f, and the emulsion distribution roller 21. The loop around which belt 10 is shifted for papermaking includes about means for applying a fluid pressure difference to the band embryonic 27, such as a vacuum pickup shoe (PUS) 24a and a 24 slot multi-slot vacuum box. In figure 1, the tape 10 for papermaking also moves around of a pre-dryer such as a dryer 26 by means of blowing, and passes through a narrowing formed by the roller 20 of print narrowing and a drum 28 Yankee drying.

Although the preferred embodiment of the tape for The papermaking of the present invention has the form of an endless belt 10, can be incorporated in other ways numerous that include, for example, stationary plates, to be used in the manufacture of handkerchiefs, or rotating drums, for be used with other types of continuous procedures. Regardless of the physical form that has tape 10 for the manufacture of paper for the execution of the invention which is it claims, it generally has certain characteristics that are set forth below. Tape 10 for paper making The present invention can be manufactured according to the Patent of USA No. 5,334,289, assigned jointly, issued in the name of Trokhan and others.

As shown in Figure 2, the tape 10 according to The present invention comprises primary components: an armor 30 and a reinforcement structure 32. Armor 30 comprises preferably a cured polymer photosensitive resin. The armor 30 and tape 10 have a first surface 11 that defines the paper contact side 11 of the tape 10 and a second surface 12 oriented towards the machine for manufacturing paper on which tape 10 is used.

As used herein, the X, Y addresses and Z are orientations that refer to tape 10 for paper making of the present invention (or paper strip 27 arranged on the tape) in a coordinate system Cartesian The tape 10 for paper making according to the The present invention is macroscopically flat. The tape plane 10 for papermaking defines their addresses X-Y. The perpendicular to the directions X-Y and to the plane of the tape 10 for the manufacture of paper is the Z direction of the tape 10. Also, the band 27 according to the present invention can be considered macroscopically flat and extending in an X-Y plane. The Z direction of the band is perpendicular to the directions X-Y and the plane of the band 27.

Preferably, the armature 30 defines a model default and provides an articulation area 36 that prints a similar model on the band 27 of the present invention. A particularly preferred model for armor 30 is a net essentially continuous. If the network model is selected essentially continuous preferred for armor 30, the ducts 34 discrete deviation will extend between the first surface 11 and the second surface 12 of the tape 10. The net essentially continuous surrounds and defines the ducts 34 of deviation.

Armor 30 prints a corresponding model that of the armor 30 on the band 27 transported thereon. Printing occurs at any time when the tape 10 and the band 27 passes between two rigid surfaces that have the game Enough to originate printing. This usually happens in a narrowing between two rollers and with the maximum frequency produced when the tape 10 transfers the paper to a drum 28 of Yankee drying. Printing is caused by the compression of the Armor 30 against paper 27 in the pressure roller 20.

The first surface 11 of the tape 10 of contact with band 27 is the carrier of it, during papermaking the first surface of the tape 10 can print a model on band 27 corresponding to the model of the armor 30.

The second surface 12 of the tape 10 is the belt machine contact surface 10. The second surface can be manufactured with a rear net that has passages in it that are different from conduits 34 of deviation. The passages provide irregularities in texture on the back side of the second surface of the tape 10. The passages allow air leakage in the X-Y plane of the tape 10, whose leakage does not necessarily circulate in the Z direction through ducts 34 of belt deflection 10. Tapes 10 incorporating that type of back texture can be done according to any of US Pat. assigned in common: Nº 5,098,522, issued on March 24, 1992 to Smurkoski and others; No. 5,364,504, issued on November 15, 1994 to Smurkoski et al .; and No. 5,260,171 issued on November 9, 1993 to Smurkoski and others.

The second basic component of the tape 10 according The invention is reinforcement structure 32. The structure 32 of reinforcement, like armor 30, has a first surface 13 facing the paper and a second surface 12 facing the machine, opposite the surface facing the paper. The structure 32 reinforcement is basically arranged between the surfaces opposite of the tape 10 and may have a surface coinciding with the back side of the tape 10. The reinforcement structure 32 provides support to the armor 30. The reinforcement component is typically woven, as is well known in the art. Portions of the reinforcement structure 32 aligned with the conduits 34 of deviation prevents the fibers used in papermaking pass completely through diversion ducts 34 and that way they reduce the production of small holes. If I dont know you want to use a woven fabric to reinforce structure 32, you can provide a nonwoven element, grid, mesh or plate having a plurality of holes by means of which provide adequate strength and support for armor 30 The present invention.

As shown in Figure 3, the armor 30 is attached to the reinforcement structure 32. Armor 30 se extends outward from face 13 facing the role of the reinforcement structure 32. The reinforcing structure 32 reinforces the 30 resin armor and has an open area that protrudes suitable to allow vacuum dehydrator machinery used in the papermaking process perform suitably its function of removing water from the embryonic band 27, and to allow water removed from the embryonic band 27 pass through the papermaking tape.

The tape 10 according to the present invention can be manufactured according to any of US Pat. assigned in Common: No. 4,514,345, issued on April 30, 1985 to Johnson and others; No. 4,528,239, issued July 9, 1983 to Trokhan; No. 5,098,522, issued March 24, 1992; No. 5,260,171, issued on November 9, 1993 to Smurkoski and others; No. 5,275,700, Issued on January 4, 1994 to Trokhan; No. 5,328,565, issued on July 12, 1994 to Rasch and others; No. 5,334,289, issued on 2 August 1992 to Trokhan and others; No. 5,431,786, issued on 11 July 1995 to Rasch and others; No. 5,496,624, issued on March 5 from 1996 to Stelljes, Jr. and others; No. 5,500,277, issued on 19 March 1996 to Trokhan and others; No. 5,514,523, issued on May 7 from 1996 to Trokhan and others; No. 5,554,467, issued on 10 September 1996, to Trokhan and others; No. 5,566,724, issued on 22 from October 1996 to Trokhan and others; No. 5,624,790, issued on 29 April 1997 to Trokhan and others; No. 5,628,876, issued on 13 May 1997 to Ayers and others; No. 5,679,222, issued on 21 October 1997 to Rasch and others; and No. 5,714,041, issued on 3 February 1998 to Ayers and others.

The ability to produce a paper band that having a particular thickness is a function of the thickness of the band. The thickness is the apparent thickness of a cellulosic fibrous band measured at a certain mechanical pressure. The thickness is a function of base weight of the band and the structure of the band. Base weight It is the weight in pounds of 3,000 square feet of paper. The Band structure refers to the orientation and density of the fibers that constitute the band 27.

The fibers that constitute the band 27 are typically oriented in the X-Y plane and provide minimal structural support in the Z direction. therefore, as the band 27 is compressed by the armature 30 modeled, band 27 is compacted creating a high region density, modeled that is of reduced thickness. Inversely, portions of the band 27 covering the diversion ducts 34 they are not compacted and as a result there are low regions density, thicker.

Low density regions, called vaults, give the band 27 an apparent thickness. Since the fibers that constitute a vault are oriented predominantly in the X-Y plane of band 27, the fibers provide a negligible support in the Z direction. Consequently, the vaults are very likely to be deformed and reduced thickness during operations for subsequent papermaking. Therefore, the thickness of the band 27 is generally limited by the ability of the vaults to Resist a mechanical pressure.

However, the diversion ducts 34 provide means for diverting fibers in the Z direction to along the periphery 38. The deflection of the fibers produces a fiber orientation that includes a steering component Z. That fiber orientation not only creates a thickness of apparent band but also provides some degree of stiffness structural in the Z direction that helps the band 27 maintain its thickness through the papermaking process. Consequently, for the present invention, the ducts 34 of deviation are sized and configured to maximize the fiber deflection along the peripheries 38.

Water removal from the embryonic band 27 begins as the fibers 50 are deflected within the ducts 34. The removal of water results in a decrease in fiber mobility that tends to fix the fibers in place after they have been diverted and redisposed. The deflection of the fibers in the ducts 34 of deflection can be induced by applying a pressure of differential fluid to the embryonic band 27. A preferred method to apply the pressure difference is to expose the embryonic band 27 at a vacuum through conduits 34 of deviation. Figure 1 illustrates the preferred method by the use of a recovery shoe 24.

Without having been proven by the theory, it considers that the redisposition of the fibers in the embryonic band 27 in relation to the diversion ducts 34 may adopt one of two models, which depend on a certain number of factors that They include the length of the fibers. As shown schematically in figure 4, the fiber ends 50 plus long can be stopped on top of the joints 36 allowing the middle parts of the fibers 50 are curved inside ducts 34 without being completely deviated Therefore, the "bridging" of the ducts occurs 34 deviation. Alternatively, as shown in Figure 5, 50 fibers (predominantly the shortest) can really be completely deposited in conduit 34 with little, if there is some, deviation that creates a stack of fibers 50 in it and minimize the deviation of subsequent fibers deposited in and around the duct 34.

The fiber deviation is a function of the resistance of the band to bending. The higher the rigidity at band bending, the greater the resistance to deviation. The Bending stiffness of a band is dominated by two factors: (1) the bending stiffness of the individual fibers; and (2) the fiber bond strength with fiber. However, the band in the pickup shoe 24a is wet and the fiber links with fiber are not well established due to the presence of large amounts of water in the band. Therefore, the dominant factor is the individual stiffness of the fibers. The more rigid the fiber The smaller the deviation.

Although the deflection of the fibers depends on the inherent stiffness of the fibers 50, the magnitude of the deviation It is mainly determined by the length of the fibers 50, depending on whether they are long enough to bypass the width of a duct 34. Figures 6 and 7 show two possible fiber deviation scenarios. In figure 6, fiber 50 it is fixed at a point A and is flown over the opening of the conduit 34. When this fiber 50 is subjected to a load uniform, such as a vacuum, the result is a bending moment high at point A and a deviation at point B defined by:

(1) f_ {B} = F \ L 3 / 8EI

where,

f_ {B} - deviation at point B;

F - Force evenly distributed on the fiber length;

L - Length of a fiber from the support point (s);

E - Elasticity Module;

I - Moment of inertia

In Figure 7, fiber segment 50 is more long than the width of the duct, with the result of two points A and fixed B. If fiber segment 50 experiences the same vacuum, the support forces in A and B create displaced bending moments with the result of a fiber deviation at point C defined by

(2) f_ {C} = F \ L3 / 384EI

where f_ {C} is the fiber deviation in the point C

Assuming that parameters F, L, E, and I are the same for the fibers shown in figures 6 and 7, is It is evident that the deviation f_ {B} is 48 times greater than the deviation f_ {C}.

(3) f_ {B} = 48f_ {C}

Consequently, fiber deflection can be improved by dimensioning the deflection ducts 34 to minimize the production of fiber bridges. However, the duct size is also limited by the number of small fibers in the supply capable of accumulating in ducts 34 and consequently, to prevent longer fibers from deviating in the same.

The supply usually includes hardwood and softwood. An example of hardwood fiber is Eucalyptus (EUC) while an example of softwood fiber is Pasta to North Soft Wood Sulfate (NSK). An example of a supply comprises 30% by weight of softwood and 70% by weight of hardwood. Since the average fiber length of softwood It is about three times the average length of wood fiber hard, sizing the deflection ducts in relation to the medium soft fiber length are very susceptible ducts to the accumulation of shorter hardwood fibers, limiting from that way the deviation of the longer fibers. Therefore, it prefers that the width, W, of the duct be sized with relation to the length of the average fiber of the supply, \ upbar {L}, where

(4) W \ geq \ overline {L}

For the present invention, the fiber length weighted average is determined by

(5) \ overline {L} = \ frac {\ sum n_ {i} \ overline {L} _ {i} ^ {2}} {\ sum n_ {i} \ overline {L} i {}

where

L_ {i} = Average fiber lengths in class i

n_ {i} = Number of fibers measured in the class i

The weighted length of the fiber length Average for the present invention is about 1.09 mm.

As shown in Figures 9 and 10, the ducts 34 can have a variety of different forms that have variable or constant widths. Duct forms that have variable widths defined in terms of major axis 40, minor axis 42, and average width 46. The major axis 40 is defined as the longer or wider axis that crosses the center of the duct area, the minor axis 42 is the shortest width that crosses the center of the area of the conduit, and the average width 46 is the average width that crosses the duct area center.

The average width 46 is determined by first measuring the length of a line drawn through the center of the area in the CD address joining two points on the perimeter of the duct. Lengths of similar lines oriented with increments angular Δ \ with respect to the CD (such as 15 degrees or less, varying from 0º to 165º, where 0º represents the CD) they are measured and averaged to determine the average width.

Since bridging is more likely to occur of fibers along the minor axis 42, it is preferred that the size of the minimum width of the conduit 34 relative to the length of middle fiber, \ upbar {L}, be

(6) W_ {min} \ geq \ overline {L}

Therefore, for the present invention, the Minimum preferred duct width is at least about 1.09 mm

Since the accumulation of smaller fibers it can occur along the major and minor axes 40, 42 of the conduit, it is difficult to define an upper limit for each or both axes 40, 42 which resulted in an accumulation of fibers minimum and maximum fiber deviation. However, for the In the present invention, it has been found that sizing the conduits 34 so that the average width 46 varies between the length \ upbar {L} of medium fiber and three times the length of average fiber, 3 \ upbar {L}, with it that the maximum thickness is generated

\ overline {L} < 3 \ overline {W} < 3 \ overline {L}

Consequently, for the present invention, prefers that the size of the ducts be such that the width of middle duct vary from 1.09 mm to 3.28 mm.

Band 27 is approximately a fiber network two-dimensional An ideal fiber network comprises a distribution random fiber in which the orientation of the fibers does not favor a particular direction. For that type of ideal network, the length, \ upbar {L}, of medium fiber, is the same in all addresses.

However fiber networks are typically arranged in the band with an orientation of the fibers that is charged to a particular address. For such charged networks, the average fiber length will vary relative to orientation angular in the X-Y plane of the band 27. Theoretically, that average fiber length is designated, \ upbar {L} _ {\ theta}, where

(7) \ overline {L} _ {\ theta} = \ frac {1} {n} \ sum_ {i = 1} ^ {n} l _ {\ theta i}

Y

the = angular orientation in the plane X-Y in relation to the CD address.

\ upbar {L} _ {\ theta i} = Component lengths of fibers with an angular orientation, the, in the plane X-Y.

\ upbar {L} _ {\ theta} Average fiber length with angular orientation, the, in the plane X-Y.

n = Number of fibers measured in orientation angular, the, in the X-Y plane.

For the present invention, the fibers 50 that constitute the network of two-dimensional fibers are oriented of predominant mode in the machine MD direction. Consequently, The average length of fiber in the machine direction is greater than the average fiber length in the transverse CD direction of machine.

(8) \ overline {L} MD> \ overline {L} _{CD}

From equation 4 it follows that

(9) W_ {MD}> W_ {CD}

Therefore, as shown in Figure 11, it prefers to orient the conduits 34 so that the major axes 40 run parallel to the machine direction of the belt. Do not However, since fiber orientation typically favors MD, a person skilled in the art should appreciate that the major axis 40 it can also be oriented in a diagonal direction, in which, As illustrated in Figure 12, the diagonal is defined as a angle 54 oriented 22.5 ° ± 22.5 ° relative to MD.

The shape of the duct is defined in terms of an aspect ratio R_ {A}, which is defined as the ratio of major axis 40 to minor axis 42. For deviation fiber maximum, it follows from equations (8) and (9) that the aspect ratio R_ {A}, is defined as

(10) R_ {A} = \ frac {\ overline {L_ {MD}}} {\ overline {L_ {CD}}} = \ frac {W_ {MD}} {W_ {CD}}

However, it is not practical to measure the length of medium fiber in a particular direction of the band in the plane X-Y for a just previous band condition to the fibers having deviated into the ducts 34 of deviation. Therefore, the inherent physical properties of the band that are a function of fiber length have to be considered to determine a relationship, R_ {A}, of aspect preferred, for a duct shape that provides the deflection of maximum fibers.

The physical properties of a paper band 27 are greatly influenced by the orientation of the fibers in the X-Y plane of band 27. For example, a band 27 that has a fiber orientation that favors the direction MD, has a higher tensile strength in the MD than in the CD, a higher stretch in CD than in MD, and a stiffness to the higher flexion in MD than in CD.

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

(11) T_ {MD, CD} (Resistance \ to \ the \ tradition) \ propto \ overline {L} MD, CD

Consequently, from equation 8 it follows what

(12) T_ {MD}> T_ {CD}

In addition, substituting \ frac {T_ {MD}} {T_ {CD}} for \ frac {\ overline {L_ {MD}}} {\ overline {L_ {CD}}} in equation 10, the aspect ratio R_ {A}, which defines the shape of the ducts is expressed as

(13) R_ {A} = \ frac {T_ {MD}} {T_ {CD}} = \ frac {W_ {MD}} {W_ {CD}}

The tensile strengths of the band 27 in MD and CD are measured using an Intelect II Standard Voltage Meter from Thwing-Albert manufactured by Thwing-Albert Instrument Co., of Philadelphia, PA. Consequently, the preferred duct form that provides optimal fiber deviation and the corresponding generation of thickness has an aspect ratio that measures 1 to 2. One way Most preferred has an aspect ratio that measures from 1.3 to 1.7. A form of maximum preference has an aspect ratio that It measures from 1.4 to 1.6.

The shape of the diversion duct 34 is not only significant to minimize bridging through the duct width but also to minimize bridging of fibers along the perimeter 38 of the duct walls. The duct walls that form abrupt corners of small radius They provide additional places for fiber bridging. Examples unfavorable duct shapes for this purpose are shown in figures 8a and 8b.

As shown in Figures 9 and 10, a form of preferred duct by the present invention is one that is generally elliptical that includes, but is not limited to, circles, ovals and polygons of six or more sides. Figure 9 illustrates a elliptical duct that has a rectilinear periphery that It comprises individual wall segments 44. For that kind of way duct, the bridging of fibers along the periphery is minimizes by providing an angle 39 between wall segments adjacent that is at least about 120 degrees.

Figure 10 illustrates a duct of form elliptical that has a concave curvilinear periphery towards the center duct The curvilinear periphery includes a minimum radius of curvature 48. Similarly, the bridging of fibers along the periphery is minimized by limiting the way so that the ratio of the minimum radius of curvature 48 to the width The average duct is at least 0.29 and not greater than 0.50.

(14) 0.29 \ leq \ frac {r_ {curv (mini)}} { \ overline {W}} \ leq0.50

As illustrated in Figure 13, ideally, the band 27 experiences on top of the joints 36 a zero elongation, while above ducts 34 the band 27 deforms completely experiencing elongation medium \ varepsilon

where

(15) \ varepsilon = \ frac {2 \ OB} {W}

Y

\ varepsilon = Average elongation

OB = is the height in the Z direction

W = is the duct width

Critical elongation determines when band 27 will break. If the elongation is greater than the critical elongation in band 27, the network will break causing Small holes in the band. The critical elongation in the band 27 depends on network properties such as length of the fibers and fiber orientation. The fiber link with fiber does not they play a role in critical lengthening because the band in the pickup shoe is wet and the fiber links with fiber They are not well established.

The total distance that band 27 deviates inside ducts 34 depends on height 60 in the direction Z. Since the critical stretch of the band is directly proportional to OB 60, it follows that OB is limited by the critical stretching of the band 27. Consequently, according to the equation 15 a reasonable margin for OB 60 is expressed as

(16) OB \ leq \ frac {\ varepsilon_ {critical}} {2} W

The critical elongation \ varepsilon_ {critical} it is a complicated function of fiber length, the fiber orientation and base weight. Qualitatively, at Critical elongation increases when the fiber length and / or the base weight increases. For the present invention, the height 60 in the Preferred Z address for maximum network deviation varies from to minus 0.127 mm to about 0.99 mm.

The total deviation a band will experience in the diversion ducts it is also determined in great part by the angle that forms the joint / duct interface of the reticulated armor. The deviation angle 62 of the band is defined as the angle of the band in the joint / interface of conduit with respect to the Z direction. An illustration of the deviation of the band is shown in figure 14. The fibers 50 that accumulate in the joint / duct interface are oriented with a Z direction component that allows them to provide the support structure capable of resisting compressive forces outside The oriented fibers parallel to the Z direction in the articulation / duct interface provide maximum support. However, since a band is not infinitely flexible, no is able to completely follow the contour of the duct 34. In addition, due to manufacturing limitations the walls of the deflection ducts are inclined forming an angle 64 of Resin in the joint / duct interface. The angle 64 of resin also limits the deviation of the band since the angle Deviation 62 cannot be smaller than resin angle 64. For the present invention, the resin angle measures preferably from 5 degrees to 10 degrees. The deviation angle of The band typically measures from 20 degrees to 50 degrees.

Since the external force applied to the paper during the various treatments the reaction of the force of fiber support in the articulation / hollow interface, how much The greater the number of fibers in this region, the greater the force of support and the corresponding thickness.

The number of fibers 50 on the surface of transition can be optimized by maximizing the total 38 perimeter of the interface. This is equivalent to maximizing the number of ducts 34 deviation for the unit area or to minimize the percentage of joint area 36. Theoretically, ducts 34 They can be packed at one end. However, as I know shown in figures 11 and 12, the joints are required 36 separating the ducts 34 have a minimum width 52 for that allow the resin to fix firmly to the structure secondary 32. For the present invention, the width 52 of Minimum preferred joint measures at least 0.178 mm to 0.51 mm

In addition, the number of ducts per unit area it can be maximized by packing conduits 34 in more arrangements efficient. A preferred arrangement of the ducts 34 is a which forms an exagonal model as shown in figures 11 and 12.

(2) The Paper

The paper 80 of the present invention has two basic regions The first region comprises a printed region 82 which is printed against the armor 30 of the tape 10. The region printed 82 preferably comprises a network essentially keep going. The continuous network 82 of the first paper region 80 is made on the essentially continuous armor 30 of the tape 10 and its geometry will generally correspond to it and will be arranged very close to it during manufacturing of paper.

The second region of paper 80 comprises a plurality of vaults 84 scattered across the network region 82 printed. Vaults 84 generally correspond to geometry, and during papermaking, in position, with the ducts 34 of deviation in the belt 10. Forming the ducts 34 of deviation during the papermaking process, the fibers are deflected in vaults 84 in the Z direction between the surface facing the role of armor 30 and the surface faced with the role of reinforcement structure 32. As a As a result, vaults 84 protrude outward from region 82 of the essentially continuous network of paper 80. Vaults 84 are preferably discrete, isolated from each other by region 82 of continuous network.

Without it having been theoretically proven, it considers that vaults 84 and regions 82 of the network essentially continuous paper 80 have base weights generally equivalent. By diverting vaults 84 in ducts 34 of deviation, the density of the vaults 84 is diminished in relation to at the density of region 82 of the essentially continuous network. In addition, the essentially continuous network region 82 (or other model that can be selected) can finally be printed, by example, against a Yankee drying drum. Such impression increases the density of the essentially continuous network region 62  in relation to that of vaults 84. The resulting paper 80 may be enhanced later as is well known in the art.

The paper 80 according to the present invention can be manufactured according to any of US Pat. assigned in Common: No. 4,529,480, issued July 16, 1985 to Trokhan; No. 4,637,859, issued on January 20, 1987 to Trokhan; No. 5,364,504, issued on November 15, 1994 to Smurkoski et al .; and No. 5,529,664, issued June 25, 1996 to Trokhan et al. and No. 5,679,222 issued October 21, 1997 to Rasch et al.

The shapes of vaults 84 in the plane X-Y include, but not limited to, circles, ovals and polygons of six or more sides. Preferably, the Vaults 84 are generally of an elliptical shape comprising peripheries 86 curvilinear or rectilinear. The curvilinear periphery 86 it comprises a minimum radius of curvature such that the ratio of the minimum radius of curvature to the average width of the vault vary from at least about 0.29 to about 0.50. The periphery 86 rectilinear can comprise a certain number of wall segments in which the angle included between adjacent wall segments be at least about 120 degrees.

Provide a paper 80 that has high thickness requires maximizing the number of fibers in the Z direction per unit of area in the band. Most fibers in the Z direction are oriented along the periphery 86 of the vaults 84 in the that fiber deflection occurs. Therefore, the orientation of fibers in the Z direction and the corresponding thickness of the web  of paper depend largely on the number of vaults per unit of area.

As shown in Figure 15, the number of Vaults 84 per unit area is maximized by minimizing the distance between adjacent vaults, which is achieved by arranging the vaults according to efficient distribution models. For the present invention, the preferred minimum distance 88 between vaults 84 is at least 0.178 mm and not larger than 0.51 mm. The distribution preferred of vaults 84 is a model formation hexagonal.

The number of vaults 84 per unit area of the 80 paper depends largely on the size and shape of the deflection ducts described above. For the present invention, the preferred average width of the vaults 84 is at least 1.09 mm and less than 3.28 mm. The generally elliptical shape preferred for vaults is one that has an aspect ratio ranging from 1 to 2. A generally more preferred elliptical shape It has an aspect ratio that varies from 1.3 to 1.7. Form generally elliptical of the highest preference has a relationship in appearance that varies from 1.4 to 1.6.

The thickness of the paper band is measured typically at a pressure of 14.7 grams / cm2 using a foot of round pressure having a diameter of 50.8 mm, after a application time of 3 seconds. The thickness can be measured using a Thwing-Albert thickness gauge, Model 89-100, manufactured by the Thwing-Albert Instrument Company of Philadelphia, Pennsylvania. The thickness is measured in temperature conditions and TAPPI moisture (Technical Association of the Pulp Industry and the Paper).

For the present invention, the gauge was measured in a paper band that comprised two layers. The thickness of the two-layer paper band is preferably between 0.508 mm and 1.016 mm. More preferably the thickness of the band of Two-layer paper is between 0.965 mm and 1.168 mm. With the maximum preference the thickness of the two-layer paper band It is between 0.635 mm and 762 mm.

Although they have been illustrated and described Particular embodiments of the present invention will be apparent. for those skilled in the art than other various changes and modifications can be made without leaving the spirit and scope of the invention. It is intended that the appended claims cover all those changes and modifications that are within reach of the invention.

Claims (10)

1. A tape (10) for papermaking which has a paper web contact surface (11) for transport a band of papermaking fibers that they have a length, \ upbar {L}, of medium fiber, and a surface (12) of contact of machine for the manufacture of paper opposite to said band contact surface (11), said said comprising papermaking tape: a reinforcing structure (32) having a patterned armature (30) disposed thereon, said armature (30) comprising a continuous network region and a plurality of discrete deflection ducts (34); said deflecting ducts (34) being isolated from each other by said continuous network region, characterized in that said deflecting ducts have a generally elliptical curvilinear periphery with a mean width \ upbar {W}, where \ upbar {L} < \ upbar {W} <3 \ upbar {L}, is an aspect ratio that varies from at least about 1 to about 2.0, and a minimum radius of curvature in which the minimum radius ratio of curvature to average width varies from at least 0.29 to 0.50. 2. The papermaking belt of claim 1, characterized in that said patterned reinforcement (30) extends outward from said reinforcing structure (32) a distance measuring at least about 0.127 mm to 0.99 mm . 3. The papermaking belt of claim 1, characterized in that the deflection ducts (34) are inclined from about 5 degrees to about 10 degrees. 4. The papermaking belt of claim 1, characterized in that said deflection ducts (34) are arranged according to a hexagonal model. 5. The papermaking belt of claim 4, characterized in that the continuous web region provides an articulation area (36) having a minimum width measuring at least about 0.178 mm to about 0.51 mm. 6. The papermaking tape of claim 5, characterized in that said articulation area (36) measures from about 25% to about 50% of the band contact surface (11) of said tape. 7. The papermaking belt of claim 1, characterized in that said deflection ducts (34) include major axes and said belt includes a machine direction in the XY plane, and because said major axes are oriented parallel to said direction of machine 8. The papermaking belt of claim 1, characterized in that said deflection ducts (34) include major axes and said belt includes a machine direction in the XY plane, and wherein said major axes are oriented diagonally with relation to said machine address. 9. The papermaking belt of claim 1, characterized in that the aspect ratio of said deflection ducts (34) ranges from 1.3 to 1.7. 10. A tape (10) for papermaking which has a paper web contact surface (11) for transport a band of papermaking fibers that they have a length, \ upbar {L}, of medium fiber, and a surface (12) of machine contact opposite said contact surface band, said belt comprising for the manufacture of paper: a reinforcing structure (32) having a patterned armature (30) disposed thereon, said armature (30) comprising a region of continuous network and a plurality of discrete diversion ducts (34), said ducts (34) being of deflection separated from each other by said region of continuous network, characterized in that said deflection ducts (34) have a rectilinear periphery comprising wall segments that have a generally elliptical shape with a mean width, barbar, a ratio aspect ranging from at least 1.0 to 2.0 and an angle (39) included between adjacent wall segments of at least 120 degrees.