U.S. patent application number 11/300750 was filed with the patent office on 2007-06-21 for durable hand towel.
Invention is credited to Malcolm C. Halls, Thomas Hampshire Schulz.
Application Number | 20070137807 11/300750 |
Document ID | / |
Family ID | 38068712 |
Filed Date | 2007-06-21 |
United States Patent
Application |
20070137807 |
Kind Code |
A1 |
Schulz; Thomas Hampshire ;
et al. |
June 21, 2007 |
Durable hand towel
Abstract
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.
Inventors: |
Schulz; Thomas Hampshire;
(Roswell, GA) ; Halls; Malcolm C.; (Alpharetta,
GA) |
Correspondence
Address: |
KIMBERLY-CLARK WORLDWIDE, INC.
401 NORTH LAKE STREET
NEENAH
WI
54956
US
|
Family ID: |
38068712 |
Appl. No.: |
11/300750 |
Filed: |
December 15, 2005 |
Current U.S.
Class: |
162/109 |
Current CPC
Class: |
D21H 27/005
20130101 |
Class at
Publication: |
162/109 |
International
Class: |
D21F 11/14 20060101
D21F011/14 |
Claims
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 claim 1, where the ratio of CDTEA*1000 to CD
tensile is between about 6 and about 9.
3. The paper towel of claim 1, where the CD stretch is between
about 6 percent and about 20 percent.
4. The paper towel of claim 3, where the CD stretch is between
about 7 percent and about 15 percent.
5. The paper towel of claim 4, where the CD stretch is between
about 8 percent and about 12 percent.
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 claim 6, where the ratio of CDTEA*1000 to CD
tensile is between about 6 and about 9.
8. The paper towel of claim 7, where the CD stretch is between
about 8 percent and about 15 percent.
9. The paper towel of claim 8, where the CD stretch is between
about 9 percent and about 13 percent.
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 claim 10, where the ratio of CDTEA*1000 to
CD tensile is between about 6 and about 9.
12. The paper towel of claim 11, where the CD stretch is between
about 7 percent and about 15 percent.
13. The paper towel of claim 12, where the CD stretch is between
about 8 percent and about 12 percent.
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 claim 14, where the
transfer fabric has an increased CD strain.
16. A towel prepared by a process as in claim 14, where the
throughdrying fabric has an increased CD strain.
17. A towel prepared by a process as in claim 16, where the
transfer fabric does not have any appreciable CD strain.
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 claim 18, where the
throughdrying fabric has an increased CD strain.
20. A towel prepared by a process as in claim 19, where the
transfer fabric does not have any appreciable CD strain.
Description
BACKGROUND
[0001] 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.
[0002] 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.
[0003] 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.
[0004] 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.RTM. 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.
[0005] 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.
[0006] 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.
[0007] 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.
SUMMARY OF THE INVENTION
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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.
Test Procedures
[0017] 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.RTM. 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.
[0018] In addition to tensile strength, the stretch and tensile
energy absorbed (TEA) are also reported by the MTS TestWorks.RTM.
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.
[0019] 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/cm.sup.2. The TEA is measured
in the MD and the CD of the samples.
[0020] 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.
[0021] 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.
[0022] 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 ft.sup.2). To convert the
results to grams per square meter, multiply the results by
1.6953.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a schematic of a papermaking apparatus.
[0024] FIG. 2 is a plot showing percentage of dispensing failures
versus geometric mean total energy absorbed (GMTEA) for examples
produced in accordance with this invention.
DETAILED DESCRIPTION
[0025] 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.
[0026] Referring to FIG. 1, a process of carrying out using the
present invention will be described in greater detail. The process
shown depicts an uncreped through dried process, but it will be
recognized that any known papermaking method or tissue making
method can be used in conjunction with the non-woven tissue making
fabrics of the present invention. Related uncreped through air
dried tissue processes are described in U.S. Pat. No. 5,656,132
issued on Aug. 12, 1997 to Farrington et al. and in U.S. Pat. No.
6,017,417 issued on Jan. 25, 2000 to Wendt et al. Both patents are
herein incorporated by reference to the extent they are not
contradictory herewith.
[0027] In FIG. 1, a twin wire former having a papermaking headbox
10 injects or deposits a furnish of an aqueous suspension of
papermaking fibers onto a plurality of forming fabrics, such as the
outer forming fabric 5 and the inner forming fabric 3, thereby
forming a wet tissue web 6. The forming process of the present
invention may be any conventional forming process known in the
papermaking industry. Such formation processes include, but are not
limited to, Fourdriniers, roof formers such as suction breast roll
formers, and gap formers such as twin wire formers and crescent
formers.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.RTM.), Henkel Corp. (Fibrabond.RTM.), Borden
Chemical (Cascamide.RTM.), 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.RTM. 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] 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.
[0041] 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] 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.
[0046] 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.
[0047] 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.
[0048] 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.
[0049] 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.
[0050] 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.
[0051] 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.
[0052] 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.
[0053] 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.
[0054] 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.
[0055] 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.
EXAMPLES
Examples 1-8
[0056] To further illustrate the invention, a pilot uncreped
throughdried tissue machine was configured similarly to that
illustrated in FIG. 1 and was used to produce multiple examples of
the one-ply, uncreped throughdried paper towel basesheets of the
present invention.
[0057] 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.
[0058] Wet strength resin (Kymene.RTM.) 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.
[0059] 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.
[0060] Paper towel basesheets were produced with an oven-dry basis
weight of approximately 16.3 lb/2880 ft.sup.2 (27.6 g/m.sup.2). 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.
[0061] 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. TABLE-US-00001 TABLE 1 Wet Dry Strength
Strength Fabric Fabric Additive Additive Refining Example Transfer
TAD (kg/MT) (kg/MT) (HPDT) 1 2164 t124-13 13.3 3.3 0.08 2 2164
t124-13 13.3 2.5 0.00 3 t1207-6 t124-13 13.0 3.3 3.88 4 t1207-6
t124-13 13.0 3.0 1.49 5 t1207-6 t1207-6 13.0 3.3 4.05 6 t1207-6
44GST 13.0 3.3 3.86 7 2164 44GST 12.0 3.3 0.32 8 2164 t1207-6 13.2
2.5 2.03
[0062] TABLE-US-00002 TABLE 2 BD Basis CD CDTEA/ GMTEA/ Weight CD
tensile stretch CDTEA CDT GMTEA GMT caliper Example (lb/2800
ft.sup.2) (g) (%) (g-cm/cm.sup.2) (.times.1000) GMT (g-cm/cm.sup.2)
(.times.1000) (mil) 1 19.68 3518.7 7.0 18.53 5.27 4285.3 29.17 6.81
20.2 2 15.95 3282.4 6.0 15.84 4.83 3832.5 26.49 6.91 19.1 3 15.82
3350.9 12.1 26.16 7.81 4082.5 35.48 8.69 25.5 4 16.50 3453.0 12.0
27.2 7.88 4050.1 34.67 8.56 26.6 5 16.19 3642.2 16.8 28.24 7.75
4667.7 41.84 8.96 28.9 6 16.35 3305.2 11.3 27.47 8.31 4142.3 37.88
9.15 19.1 7 16.43 3976.0 4.6 15.98 4.02 4765.2 29.35 6.16 13.9 8
15.13 3434.2 10.0 20.88 6.08 4137.1 33.27 8.04 23.5
[0063] TABLE-US-00003 TABLE 3 BD Basis CD CDTEA/ GMTEA/ Weight CD
tensile stretch CDTEA CDT GMTEA GMT caliper Example (lb/2800
ft.sup.2) (g) (%) (g-cm/cm.sup.2) (.times.1000) GMT (g-cm/cm.sup.2)
(.times.1000) (mil) 1 15.58 3094.1 6.2 15.17 4.90 3807.1 22.03 5.79
11.2 2 15.72 2877.6 5.8 13.74 4.77 3542.6 21.02 5.93 11.0 3 15.61
3001.8 9.4 20.04 6.68 3885.6 27.11 6.98 13.3 4 15.59 2682.4 9.2
17.68 6.59 3447.5 22.94 6.65 12.5 5 15.90 2037.3 11.0 13.62 6.69
3249.8 23.79 7.32 11.7 6 15.83 3196.8 10.7 24.95 7.80 4074.3 32.56
7.99 11.8 7 16.02 3432.5 4.4 12.62 3.68 4354.3 25.45 5.84 10.8 8
14.89 2803.9 8.1 16.3 5.81 3605.7 23.69 6.57 11.9
[0064] 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.RTM.
Sanitouch.RTM. 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.
[0065] 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.
[0066] 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.
[0067] The results of the dispensability of the paper towels for
Examples 1-8 is given in Table 3. Additionally, FIG. 2 shows the
percentage of failure versus the GMTEA for the Examples.
TABLE-US-00004 TABLE 3 Dispensing GMTEA Example Failures (%)
(g-cm/cm.sup.2) 1 8.33 22.03 2 16.25 21.02 3 10.00 27.11 4 14.79
22.94 5 13.54 23.79 6 7.08 32.56 7 2.08 25.45 8 14.90 23.69
[0068] As can be seen in FIG. 2, there is a clear correlation
between the increase in GMTEA and a decrease of dispensing
failures.
[0069] 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.
* * * * *