US 20070137807 A1
A durable single-ply uncreped paper towel having an increased level of geometric mean total energy absorbed (GMTEA) per geometric mean tensile (GMT) and an increased level of cross-machine direction total energy absorbed (CDTEA) per cross-machine direction tensile strength is disclosed. A method of making such a paper towel is also disclosed.
1. A durable paper towel comprising a single throughdried uncreped tissue ply having a GMT of about 2700 grams or greater per 7.62 centimeters and a ratio of GMTEA*1000 to GMT of about 7 or greater.
2. The paper towel of
3. The paper towel of
4. The paper towel of
5. The paper towel of
6. A durable paper towel comprising a single throughdried uncreped tissue ply having a GMT of about 2700 grams or greater per 7.62 centimeters, a ratio of GMTEA*1000 to GMT of about 7 or greater, and a CD stretch between about 6 percent and about 20 percent.
7. The paper towel of
8. The paper towel of
9. The paper towel of
10. A durable paper towel comprising at least one throughdried uncreped tissue ply having a GMT of about 2700 grams or greater per 7.62 centimeters, and a CD stretch between about 6 percent and about 20 percent.
11. The paper towel of
12. The paper towel of
13. The paper towel of
14. A durable paper towel having a GMT of about 2700 grams or greater per 7.62 centimeters, a ratio of GMTEA*1000 to GMT of about 7 or greater, and a CD stretch between about 6 percent and about 20 percent, prepared by a process comprising the steps of:
forming a furnish of cellulosic fibers and water;
depositing the furnish on a forming fabric thereby forming a fibrous web on top of the forming fabric;
transferring the fibrous web from the forming fabric to a transfer fabric;
transferring the fibrous web from the transfer fabric to a throughdrying fabric;
subjecting the fibrous web to non-compressive through-air drying to remove the water from the fibrous web; and
removing the dried fibrous web from the throughdrying fabric without creping the fibrous web,
where at least one of the transfer and throughdrying fabrics of the process has a topography in CD such that increased CD strain is imparted to the fibrous web.
15. A towel prepared by a process as in
16. A towel prepared by a process as in
17. A towel prepared by a process as in
18. A method for making a durable uncreped throughdried paper towel having a GMT of about 2700 grams or greater per 7.62 centimeters, a ratio of GMTEA*1000 to GMT of about 7 or greater, and a CD stretch between about 6 percent and about 20 percent, comprising the steps:
depositing an aqueous suspension of papermaking fibers onto a forming fabric to form a wet web,
transferring the wet web to a transfer fabric,
transferring the wet web from the transfer fabric to a throughdrying fabric,
throughdrying the web to form a tissue sheet, and
removing the tissue sheet from the throughdrying fabric,
where at least one of the transfer fabric and throughdrying fabric has an increased CD strain which imparts CD strain to the tissue sheet.
19. A towel prepared by a process as in
20. A towel prepared by a process as in
Tabbing is a critical dispensing failure in which a small piece is pulled from a paper towel when it is desired to dispense the entire towel. This typically occurs because the user's hands are wet and the tensile force required to pull a towel from the dispenser is high. The wet tensile strength of a paper towel is typically about 30 percent to 35 percent of the towel's dry tensile strength. Thus the paper towel is put at a disadvantage when encountering the user's wet hands and the towel will often fail to dispense and leave the user holding only a small piece of the paper towel.
One method that has attempted to resolve this tabbing issue has been modifications to the towel dispensers that reduce the force required to dispense such towels. Another method of addressing the issue of tabbing has been through the modification of the towel physical properties such as tensile strength and stretch, to help increase the towel durability. The increase of towel strength has generally been directed to increasing the machine direction (MD) tensile strength and MD stretch. As used herein, the term “machine direction” or “MD” means the length of a web or towel in the direction in which it is produced. The term “cross machine direction” or “CD” means the width of fabric or towel, i.e. a direction generally orthogonal to the MD.
Finally, tabbing has also been addressed by improving the folding of the towel such that multiple plies of the towel material are presented to the user desiring to dispense the towel, thus multiplying the strength of the towel being dispensed.
All of these methods have helped reduce the level of tabbing experienced, however, it has been found that the levels of tabbing are still unacceptable. One factor that magnifies the problem is the many towel put-ups and dispenser types from which such paper towels are dispensed. Paper towels dispense in either the MD or the CD directions depending on the format of the dispenser. Additionally, stresses that occur on all towels during dispensing impact both the MD and CD of the towel. For instance, when pulling on a hard roll towel which dispenses in the MD (i.e., the towel is dispensed in the same general direction as it was produced), stress is put primarily in the MD of the towel with secondary stresses acting in the CD of the towel. A towel dispensed in the CD, such as the SCOTTFOLD® Towel available from the Kimberly-Clark Corporation (Roswell, Ga.), experiences its primary stress in the CD of the towel with secondary stresses being applied in the MD of the towel.
One limitation that is faced in addressing these issues is that paper towel basesheet manufacturing and the subsequent physical properties of such paper towels are kept the same for many towel formats and dispensers in which such towels may be used. The goal of such uniformity is often an attempt to provide one type of towel that meets the needs of as many dispensing needs and formats as possible.
Another issue is that a paper towel will generally be stronger in MD compared to the CD of the same towel. As discussed, this will compromise towels dispensed in the CD and will contribute to failures when such towel is dispensed in the MD. Additionally, it has traditionally been easier to increase the MD stretch of a towel rather than increasing the CD stretch.
Due to these directional forces that are applied to paper towels amongst differing dispensing formats, it has been difficult to produce a single towel basesheet that is durable enough to be reliably dispensed in these different dispenser formats with minimal tabbing.
In view of the issues stated above it is desired to produce a towel that has increased durability in the CD to improved the ability of the towel to dispense in the CD, and in the MD, with reduced instances of dispensing failures. The inventors have discovered an unexpected result that makes up the present invention that produces such a towel.
This invention is directed to a durable paper towel made of a single throughdried uncreped tissue ply having a GMT of about 2700 grams or greater per 7.62 centimeters and a ratio of GMTEA*1000 to GMT of about 7 or greater. In some embodiments the ratio of CDTEA*1000 to CD tensile is between about 6 and about 9. In some embodiments, the stretch of the paper towel may be between about 6 percent and about 20 percent.
The invention is also directed to a durable paper towel comprising a single throughdried uncreped tissue ply having a GMT of about 2700 grams or greater per 7.62 centimeters, a ratio of GMTEA*1000 to GMT of about 7 or greater, and a CD stretch between about 6 percent and about 20 percent. In some embodiments, the paper towel may have a ratio of CDTEA*1000 to CD tensile between about 6 and about 9. In some embodiments, the paper towel may have a CD stretch between about 7 percent and about 15 percent. In further embodiments, the paper towel may have a CD stretch between about 8 percent and about 12 percent.
The invention is also directed to a durable paper towel comprising at least one throughdried uncreped tissue ply having a GMT of about 2700 grams or greater per 7.62 centimeters, and a CD stretch between about 6 percent and about 20 percent. In some embodiments, the towel may have a ratio of CDTEA*1000 to CD tensile between about 6 and about 9.
Another aspect of the invention is a durable paper towel having a GMT of about 2700 grams or greater per 7.62 centimeters, a ratio of GMTEA*1000 to GMT of about 7 or greater, and a CD stretch between about 6 percent and about 20 percent. The towel prepared by forming a furnish of cellulosic fibers and water and depositing that furnish on a forming fabric to form a fibrous web. The fibrous web is transferred from the forming web to a transfer fabric and from the transfer fabric to a throughdrying fabric. The fibrous web is then subjected to non-compressive through-air drying to remove the water from the fibrous web. Finally, the fibrous web is removed from the throughdrying fabric without creping the fibrous web.
At least one of these fabrics (transfer and throughdrying) has a topography in the CD such that CD strain is imparted to the fibrous web. In some embodiments, the transfer fabric has an increased CD strain. In other embodiments, the throughdrying fabric has an increased CD strain. In one embodiment, the throughdrying fabric has an increased CD strain and the transfer fabric does not have any appreciable CD strain.
Finally, the invention is also directed to a method for making a durable uncreped throughdried paper towel having a GMT of about 2700 grams or greater per 7.62 centimeters, a ratio of GMTEA*1000 to GMT of about 7 or greater, and a CD stretch between about 6 percent and about 20 percent. The method includes the steps of depositing an aqueous suspension of papermaking fibers onto a forming fabric to form a wet web, transferring the wet web to a transfer fabric, transferring the wet web from the transfer fabric to a throughdrying fabric, throughdrying the web to form a tissue sheet, and removing the tissue sheet from the throughdrying fabric.
At least one of these fabrics (transfer and throughdrying) has a topography in the CD such that CD strain is imparted to the fibrous web. In some embodiments, the throughdrying fabric has an increased CD strain. In one embodiment, the throughdrying fabric has an increased CD strain and the transfer fabric does not have any appreciable CD strain.
In the interests of brevity and conciseness, any ranges of values set forth in this specification contemplate all values within the range and are to be construed as support for claims reciting any sub-ranges having endpoints which are whole number values within the specified range in question. By way of a hypothetical illustrative example, a disclosure in this specification of a range of from 1 to 5 shall be considered to support claims to any of the following ranges: 1-5; 1-4; 1-3; 1-2; 2-5; 2-4; 2-3; 3-5; 3-4; and 4-5.
Tensile testing is conducted in the manner which is well known. More particularly, samples for tensile strength testing are prepared by cutting a 3 inches (76.2 mm) wide by 5 inches (127 mm) long strip in either the machine direction or cross-machine direction orientation using a JDC Precision Sample Cutter (Thwing-Albert Instrument Company, Philadelphia, Pa., Model No. JDC3-10). The instrument used for measuring tensile strengths is an constant-rate-of-extension (CRE) testing machine with a computer-based data acquisition and frame control system, such as an MTS Systems Sintech 11S (MTS Systems Corporation, Eden Prairie, Minn.). The data acquisition software is MTS TestWorks® for Windows (MTS Systems Corp., Research Triangle Park, N.C.). The load cell is selected from either a 50 Newton or 100 Newton maximum, depending on the strength of the sample being tested, such that the majority of peak load values fall between 10 and 90 percent of the load cell's full scale value. Primarily a 100 Newton load cell was used for this testing. The gauge length between jaws is 4+/−0.04 inches (101.6+/−1 mm). The jaws are operated using pneumatic-action and are rubber coated. The minimum grip face width is 3 inches (76.2 mm), and the approximate height of a jaw is 0.5 inches (12.7 mm). The crosshead speed is 10+/−0.4 inches/min (254+/−1 mm/min), and the break sensitivity is set at 65 percent. The sample is placed in the jaws of the instrument, centered both vertically and horizontally. The test is then started and ends when the specimen breaks. The peak load is recorded as either the “MD tensile strength” or the “CD tensile strength” of the specimen depending on the sample being tested. At least six (6) representative specimens are tested for each product, taken “as is”, and the arithmetic average of all individual specimen tests is either the MD or CD tensile strength for the product.
In addition to tensile strength, the stretch and tensile energy absorbed (TEA) are also reported by the MTS TestWorks® for Windows program for each sample measured. Stretch (either MD stretch or CD stretch) is reported as a percentage and is defined as the ratio of the slack-corrected elongation of a specimen at the point it generates its peak load divided by the slack-corrected gauge length.
Total energy absorbed (TEA) is calculated as the area under the stress-strain curve during the same tensile test as has previously described above. The area is based on the strain value reached when the sheet is strained to rupture and the load placed on the sheet has dropped to 65 percent of the peak tensile load. Since the thickness of a paper sheet is generally unknown and varies during the test, it is common practice to ignore the cross-sectional area of the sheet and report the “stress” on the sheet as a load per unit length or typically in the units of grams per 3 inches of width. For the TEA calculation, the stress is converted to grams per centimeter and the area calculated by integration. The units of strain are centimeters per centimeter so that the final TEA units become g-cm/cm2. The TEA is measured in the MD and the CD of the samples.
Additionally, the geometric mean tensile strength (GMT) is calculated from the tensile strength measurements. The GMT is calculated as the square root of the product of the MD tensile strength and the CD tensile strength.
The caliper of the sheet is measured as the thickness of a single sheet using a controlled loading micrometer. The caliper is measured using a micrometer having an anvil diameter of 56.42 millimeters and a loading pressure is 2.0 kPa. The results are reported in mil (0.001 inches). To convert the results to microns multiply by 25.4.
The basis weight is calculated by measuring the weight of a sample of known area after it is “bone dry”. Nine 4-inch by 4-inch (101.6 by 101.6 mm) samples are die cut and conditioned in a 105 degree C. (+/−2 degrees) oven for eight minutes and allowed to cool no more than eight minutes prior to weighing. The results are reported in pounds per ream (lb/2880 ft2). To convert the results to grams per square meter, multiply the results by 1.6953.
Suitable papermaking processes useful for making tissue sheets in accordance with this invention include uncreped throughdrying processes which are well known in the tissue and towel papermaking art. Such processes are described in U.S. Pat. No. 5,607,551 issued Mar. 4, 1997 to Farrington et al., U.S. Pat. No. 5,672,248 issued Sep. 30, 1997 to Wendt et al. and U.S. Pat. No. 5,593,545 issued Jan. 14, 1997 to Rugowski et al., all of which are hereby incorporated by reference.
The wet tissue web 6 forms on the inner forming fabric 3 as the inner forming fabric 3 revolves about a forming roll 4. The inner forming fabric 3 serves to support and carry the newly-formed wet tissue web 6 downstream in the process as the wet tissue web 6 is partially dewatered to a consistency of about 10 percent based on the dry weight of the fibers. Additional dewatering of the wet tissue web 6 may be carried out by known paper making techniques, such as vacuum suction boxes, while the inner forming fabric 3 supports the wet tissue web 6. The wet tissue web 6 may be additionally dewatered to a consistency of at least about 20 percent, more specifically between about 20 percent to about 40 percent, and more specifically about 20 percent to about 30 percent.
The forming fabric 3 can generally be made from any suitable porous material, such as metal wires or polymeric filaments. For instance, some suitable fabrics can include, but are not limited to, Albany 84M and 94M available from Albany International (Albany, N.Y.); Asten 856, 866, 867, 892, 934, 939, 959, or 937; Asten Synweve Design 274, all of which are available from Asten Forming Fabrics, Inc. (Appleton, Wis.); and Voith 2184 available from Voith Fabrics (Appleton, Wis.). Other suitable fabrics are described in U.S. Pat. Nos. 6,120,640 to Lindsay, et al. and 4,529,480 to Trokhan. Forming fabrics or felts comprising nonwoven base layers may also be useful, including those of Scapa Corporation made with extruded polyurethane foam such as the Spectra Series.
Suitable cellulosic fibers for use in connection with this invention include secondary (recycled) papermaking fibers and virgin papermaking fibers in all proportions. Such fibers include, without limitation, hardwood and softwood fibers as well as nonwoody fibers. Noncellulosic synthetic fibers can also be included as a portion of the furnish. It has been found that a high quality product having a unique balance of properties may be made using predominantly secondary fibers or all secondary fibers.
Wet strength resins may be added to the furnish as desired to increase the wet strength of the final product. Presently, the most commonly used wet strength resins belong to the class of polymers termed polyamide-polyamine epichlorohydrin resins. There are many commercial suppliers of these types of resins including Hercules, Inc. (Kymene®), Henkel Corp. (Fibrabond®), Borden Chemical (Cascamide®), Georgia-Pacific Corp. and others. These polymers are characterized by having a polyamide backbone containing reactive crosslinking groups distributed along the backbone. Other useful wet strength agents are marketed by American Cyanamid under the Parez® tradename as well as materials described in U.S. Pat. Nos. 5,085,736; 5,088,344 and 4,981,557 issued to Procter & Gamble.
Similarly, dry strength resins can be added to the furnish as desired to increase the dry strength of the final product. Such dry strength resins include, but are not limited to carboxymethyl celluloses (CMC), any type of starch, starch derivatives, gums, polyacrylamide resins, and others as are well known. Commercial suppliers of such resins are the same those that supply the wet strength resins discussed above.
The wet web 6 is then transferred from the forming fabric 3 to a transfer fabric 8 while at a solids consistency of between about 10 percent to about 35 percent, and particularly, between about 20 percent to about 30 percent. As used herein, a “transfer fabric” is a fabric that is positioned between the forming section and the drying section of the web manufacturing process.
Transfer to the transfer fabric 8 may be carried out with the assistance of positive and/or negative pressure. For example, in one embodiment, a vacuum shoe 9 can apply negative pressure such that the forming fabric 3 and the transfer fabric 8 simultaneously converge and diverge at the leading edge of the vacuum slot. Typically, the vacuum shoe 9 supplies pressure at levels between about 10 to about 25 inches of mercury. As stated above, the vacuum transfer shoe 9 (negative pressure) can be supplemented or replaced by the use of positive pressure from the opposite side of the web to blow the web onto the next fabric. In some embodiments, other vacuum shoes can also be used to assist in drawing the fibrous web 6 onto the surface of the transfer fabric 8.
Typically, the transfer fabric 8 travels at a slower speed than the forming fabric 3 to enhance the “MD stretch” of the web, which generally refers to the stretch of a web in its machine or length direction (expressed as percent elongation at sample failure). For example, the relative speed difference between the two fabrics can be from 0 percent to about 80 percent, in some embodiments from about 5 percent to about 50 percent, and in some embodiments, from about 8 percent to about 18 percent. This is commonly referred to as “rush” transfer. During “rush transfer”, many of the bonds of the web are believed to be broken, thereby forcing the sheet to bend and fold into the depressions on the surface of the transfer fabric 8. Such molding to the contours of the surface of the transfer fabric 8 may increase the MD and CD stretch of the web.
Rush transfer from one fabric to another can follow the principles taught in any one of the following patents, each of which is herein incorporated by reference to the extent it is not contradictory herewith: U.S. Pat. No. 5,667,636 to Engel et al.; U.S. Pat. No. 5,830,321 to Lindsay et al.; U.S. Pat. No. 4,440,597 to Wells et al.; U.S. Pat. No. 4,551,199 to Weldon; and U.S. Pat. No. 4,849,054 to Klowak.
The wet tissue web 6 is then transferred from the transfer fabric 8 to a throughdrying fabric 11. While supported by the throughdrying fabric 11, the wet tissue web 6 is dried to a final consistency of about 94 percent or greater by a throughdryer 13. The dried tissue web 15 is then removed from the throughdrying fabric 11 and traverses an open draw 20, before passing through a pair of steel calender rolls 16, 18 which adjust the web 15 to the desired finished caliper. The web 15 then passes through the winding nip between the reel drum 22 and the reel 23 and is wound into a roll of tissue 25 for subsequent converting, such as slitting cutting, folding, and packaging.
In transferring the wet tissue web from the transfer fabric 8 to the throughdrying fabric 11, the wet tissue web 6 may be macroscopically rearranged to conform to the surface of the throughdrying fabric 11 with the aid of a vacuum transfer roll 12 or a vacuum transfer shoe like the vacuum shoe 9. If desired, the throughdrying fabric 11 can be run at a speed slower than the speed of the transfer fabric 8 to further enhance MD stretch of the resulting absorbent tissue product. The transfer may be carried out with vacuum assistance to ensure conformation of the wet tissue web 6 to the topography of the throughdrying fabric 11.
The drying process can be any noncompressive drying method which tends to preserve, or increase, the caliper or thickness of the wet web including, without limitation, throughdrying, infra-red radiation, microwave drying, etc. Because of its commercial availability and practicality, throughdrying is well-known and is a preferred means for noncompressively drying the web for purposes of this invention. The throughdrying process and tackle can be conventional as is well known in the papermaking industry. Suitable throughdrying processes are described in U.S. Pat. No. 5,048,589 to Cook et al. (1991) entitled “Non-Creped Hand or Wiper Towel” and U.S. Pat. No. 4,440,597 to Wells et al. (1984) entitled “Wet-Microcontracted Paper and Concomitant Process”, which are herein incorporated by reference.
Once the wet tissue web 6 has been non-compressively dried, thereby forming the dried tissue web 15, it is possible to crepe the dried tissue web 15 by transferring the dried tissue web 15 to a Yankee dryer prior to reeling, or using alternative foreshortening methods such as microcreping as disclosed in U.S. Pat. No. 4,919,877 issued on Apr. 24, 1990 to Parsons et al.
The finished basis weight of the individual throughdried sheet or ply used for purposes of this invention can preferably be from about 20 to about 50 gsm, and more particularly from about 28 to about 38 gsm.
Optionally, in some embodiments, multiple throughdried sheet can be plied together to form a multi-ply product having two, three, four or more plies. These multi-ply products have unexpectedly high caliper and absorbency characteristics for the amount of fiber involved. The basis weight of a multi-ply products depend upon the number of plies and the basis weight of each ply.
The geometric mean tensile strength (GMT) of the tissue sheets of this invention can be about 2700 grams per 7.62 centimeters (hereinafter designated simply as “grams”), more specifically from about 3400 grams to about 4200 grams.
It has been found that by increasing the GMTEA of the paper towel, the durability of the towel increases such that the occurrence of dispensing defects (i.e., tabbing) decreases. As defined earlier, GMTEA is the square root of the product of the MD TEA and the CDTEA. Also, as discussed above, TEA is calculated as the area under the stress-strain curve provided by tensile testing of the paper towel material. As such, TEA can be increased by increasing the tensile strength of the material (i.e., increasing possible stress), increasing the stretch of the material (i.e., increasing possible strain), or by increasing a combination of strength and stretch. Increases in these characteristics in the MD, CD or both the MD and CD of the towel will increase the respective TEA, the subsequent GMTEA, and will thus improve the dispensability of the paper towel.
Various methods, as are well known, have previously been used and are available to increase the tensile strength of a paper product in both the MD and the CD. However, it has been found that methods used to increase the strength of the paper product also contribute to increased costs to the process and materials, as well as undesirable tactile characteristics. As the tensile strength of the paper product is increased (at a constant caliper), the stiffness of the product increases to undesirable levels for a paper towel.
The present invention increases the dispensability of the paper products (i.e., increased GMTEA) by increasing the CDTEA of the product through increased CD stretch, while keeping the MD tensile, CD tensile, and MD stretch constant. This increase in CD stretch is imparted to the fibrous web during the production of the tissue sheet through the use of fabrics with topographical structure. To normalize the increase in CDTEA for various levels of CD tension, the ratio of CDTEA to CD tensile strength helps characterize the nature of the invention. The ratio of GMTEA to GMT similarly characterizes the invention by normalizing effects that could be attributed to increases in tensile strength. The desired ratio of CDTEA (*1000) to CD tensile for the tissue sheets of the present invention is between about 6 and about 9. The desired ratio of GMTEA (*1000) to GMT for the tissue sheets of the present invention is about 7 or greater.
The various fabrics used to produce the towels of the present invention, particularly the throughdrying fabric and the transfer fabric, have a topographical structure that imparts three-dimensionality to the resulting tissue sheet or ply. This three-dimensionality in turn imparts CD stretch to the sheet because the three-dimensional bumps and/or ridges can be pulled out when the sheet is stressed. This increased “topography” of the fabric is often interchangeably referred to as increased “strain”, with respect to the fabric, and reflects the increased strain that is imparted to the material webs that are formed thereon.
The MD stretch is also enhanced in part by the three-dimensionality, but to a greater extent the MD stretch is provided by the “rush” transfer of the newly-formed web from the faster moving forming fabric to the slower moving transfer fabric, or by creping if present.
Suitable three-dimensional fabrics useful for purposes of this invention are those fabrics having a top surface and a bottom surface. During wet molding and/or throughdrying, the top surface supports the wet tissue web. The wet tissue web conforms to the top surface and during molding is strained into a three-dimensional topographic form corresponding to the three-dimensional topography of the top surface of the fabric. Adjacent the bottom surface, the fabric has a load-bearing layer which integrates the fabric and provides a relatively smooth surface for contact with various tissue machine elements.
Fabrics can be woven or non-woven, or a combination of a woven substrate with an extruded sculpture layer which provides the topographical sculptured layer. Fabrics may also be finished so the warps are parallel to the cross-machine direction when run on a tissue machine, creating a series of substantially continuous cross-machine direction ridges separated by valleys.
The transfer and TAD fabrics used herein have textured sheet-contacting surfaces comprising of substantially continuous machine-direction ridges separated by valleys and are similar to those described in U.S. Pat. No. 6,673,202 to Burazin et al., herein incorporated by reference. Furthermore, such fabrics with ridged sculpted layers can be extended to include ridges having a height of from 0.4 mm to about 5 millimeters, a ridge width of 0.5 mm or greater and a CD ridge frequency of from about 1.5 to about 8 per centimeter. Specific fabric styles described in this manner include Voith Fabrics t1205-1, t1207-6, t1203-1, and t1203-8. As a means of illustration, the t1205-1 fabric has 3.02 ripples/cm and a ridge height of approximately 0.8 mm. The t1203-1 fabric has 2.03 ripples/cm and a ridge height of approximately 1.1 mm. The t1207-6 fabric has a high degree of topography, similar to the t125-1 and t1203-1, but with a more uniform CD strain profile than either of the t1203-1 or t1205-1 fabrics.
Other fabrics with a lower degree of topography are also available. For example, Voith t124-13 has a medium level topography compared to the high topography fabrics discussed above and the low level of topography of flat fabrics. The t124-13 has MD and CD elements, but not the level of MD-oriented structure present for the t1207-6 fabric. Thus, this medium level topography fabric will impart less CD strain into the fiber web than the high topography fabric.
By comparison, a flat fabrics that are commonly used in paper product manufacturing, such as the 44GST fabric pattern (available from Voith Fabrics, among others), have much less topography than either the high topography fabrics (such as t1207-6) or medium topography fabrics (such as t124-13). Such flat fabrics have no appreciable topography. Subsequently, a low topography (or “flat”) fabric will impart very little CD strain to the fiber web.
Other suitable fabrics with topographical features are described by U.S. Pat. No. 5,429,686 issued on Jul. 4, 1995 to Chiu et al., of which fabric style Voith Fabrics t807-1 is one embodiment. Additional topographical fabrics with MD dominant features which can be utilized are described in U.S. Pat. No. 6,706,152 to Burazin et al., herein incorporated by reference. Alternately, the TAD fabric may have topography produced by compounds applied to the fabric, such as discussed in U.S. patent application Ser. No. 11/020,932 to Krautkramer et al., filed Dec. 23, 2004.
Other fabrics suitable for use as the transfer fabric or the TAD fabric can have textured sheet-contacting surfaces comprising of a waffle-like pattern consisting of both machine-direction and cross-machine direction ridges with sculpted layers which have a peak height (from lowest element contacted by the tissue to the highest element) ranging from 0.5 mm to about 8 millimeters, and a frequency of occurrence of the two-dimensional pattern from about 0.8 to about 3.6 per square centimeter of fabric.
To further illustrate the invention, a pilot uncreped throughdried tissue machine was configured similarly to that illustrated in
The furnish used was a mixture of 50 percent recycled fiber, 30 percent northern softwood kraft fibers (NSWK), and 20 percent southern softwood kraft (SSWK) fiber. The recycled fibers were dispersed in a pulper for 30 minutes at a consistency of 3 percent. Similarly, the NSWK and SSWK fibers were dispersed in a pulper for 30 minutes at a consistency of 3 percent and then refined. The level of refining (in units of horsepower-day per ton of fiber) of the softwood kraft fibers for each of the Examples is given in Table 1. The fibers were then blended in a 50/50 ratio and the thick stock was sent to a machine chest and diluted to a consistency of 3 percent.
Wet strength resin (Kymene®) and dry strength resins (CMC) were added to the furnish prior to delivering the furnish to the forming fabric. The strength resins were added in the amounts (in units of kg per metric ton of fiber) as given in Table 1.
The machine chest furnish was diluted to approximately 0.1 percent consistency and delivered to a forming fabric using a three-layered headbox in a blended configuration. The forming fabric speed was approximately 1700 fpm. The resulting web was then transferred to a transfer fabric traveling approximately 15 percent slower than the forming fabric using a vacuum shoe (at 8-10 mm Hg) to assist the transfer. A molded vacuum roll (at 20-25 mm Hg) was used to deliver the web onto a throughdrying fabric. The web was dried with a throughdryer operating at a temperature of 350 degrees F. (177 degrees C.). The paper towel basesheet was then directed through a calender nip formed by two steel calender rolls set to deliver the desired finished caliper of the material.
Paper towel basesheets were produced with an oven-dry basis weight of approximately 16.3 lb/2880 ft2 (27.6 g/m2). All testing was performed on basesheets from the pilot machine without further processing and on finished (calendered) products. All codes were produced to strength targets of 5100 g for MD tensile, 4150 g for GMT, and MD tensile to CD tensile ratio of 1.5.
Each of the examples were produced with various combinations of transfer and throughdrying (“TAD”) fabrics having various degrees of topography. The different three TAD fabrics and two different transfer fabrics used for the examples were all obtained from Voith Fabrics (Appleton, Wis.) and included two low topography fabrics (2164 and 44GST), a medium topography fabric (t124-13) and a high topography fabric (t1207-6). The fabrics used for each Example are given in Table 1. The resulting basesheet properties are given in Table 2 and the resultant finished product properties are given in Table 3.
The finished hardroll towels produced for Examples 1-8 were additionally tested for dispensability. Each test roll was placed in a standard wall-mounted dispenser (K-C Insight® Sanitouch® Hard Roll Towel Dispenser, available from Kimberly-Clark Corporation, Roswell, Ga.) for testing by a human test subject using a metronome to ensure reproducibility of the rate at which the dispensing action is performed. On the first beat the test subject dipped their hands into a tub of water up to their second knuckles. On the second beat, the hands were removed from the water and excess water is shaken from the thumb and fingers. The towel was grasped with the thumb and pad of three fingers on the third beat. On the fourth beat the towel is pulled from the dispenser. The test procedure is performed 40 times per testing cycle.
For each Example, rolls were tested using four different dispensing cycles: one-hand fast, one-hand slow, two-hand fast, two-hand slow. The fast test cycles were performed with the metronome set to 105 beats per minute and the slow test cycles were performed with the metronome set to 80 beats per minute. For “two-handed” test cycles, the towel was grasped on the left and right edges of the towel protruding from the dispenser. For “one-handed” test cycles, the towel was grasped on the right edge of the towel protruding from the dispenser by the subject's right hand. The testing cycles are randomized amongst 12 rolls per Example such that only two testing cycles were tested on each test roll. In total, 240 sheets are dispensed for each testing cycle for a total of 960 sheets for each Example.
The total number of dispensing failures (e.g., tabbing, tears, and any other non-whole sheets of towel from the dispenser) were recorded and reported as the percentage of failures based on the number of dispensing attempts.
The results of the dispensability of the paper towels for Examples 1-8 is given in Table 3. Additionally,
As can be seen in
It will be appreciated that the foregoing examples and discussion, given for purposes of illustration, are not to be construed as limiting the scope of this invention, which is defined by the following claims and all equivalents thereto.