U.S. patent application number 15/110450 was filed with the patent office on 2016-12-15 for durable and soft wet pressed tissue.
The applicant listed for this patent is Kimberly-Clark Worldwide, Inc.. Invention is credited to Michael Alan HERMANS, Kayla Elizabeth ROUSE, Richard Louis UNDERHILL.
Application Number | 20160362843 15/110450 |
Document ID | / |
Family ID | 56689113 |
Filed Date | 2016-12-15 |
United States Patent
Application |
20160362843 |
Kind Code |
A1 |
HERMANS; Michael Alan ; et
al. |
December 15, 2016 |
DURABLE AND SOFT WET PRESSED TISSUE
Abstract
The present invention relates to soft, durable wet pressed
tissue products comprising Southern softwood fibers and more
particularly low-coarseness Southern softwood fibers. The inventive
tissue products generally comprise little or no Northern softwood
kraft fibers yet have comparable or better tissue product
properties such as a TS7 value (a measure of tissue softness) less
than about 20.0 dB V2 rms and a CD Durability Index (a measurement
of tissue durability) greater than about 14.0.
Inventors: |
HERMANS; Michael Alan;
(Neenah, WI) ; UNDERHILL; Richard Louis; (Neenah,
WI) ; ROUSE; Kayla Elizabeth; (Appleton, WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kimberly-Clark Worldwide, Inc. |
Neenah |
WI |
US |
|
|
Family ID: |
56689113 |
Appl. No.: |
15/110450 |
Filed: |
February 19, 2016 |
PCT Filed: |
February 19, 2016 |
PCT NO: |
PCT/US2016/018684 |
371 Date: |
July 8, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62118489 |
Feb 20, 2015 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D21H 27/30 20130101;
D21H 11/04 20130101; D21H 27/002 20130101; D21H 27/005 20130101;
D21H 27/38 20130101 |
International
Class: |
D21H 27/00 20060101
D21H027/00; D21H 11/04 20060101 D21H011/04; D21H 27/30 20060101
D21H027/30 |
Claims
1. A single ply wet pressed tissue product having a TS7 value less
than about 20.0 dB V2 rms a CD Tensile strength greater than about
400 g/3'' and a CD Durability Index greater than about 14.0.
2. The tissue product of claim 1 having a Burst Index greater than
about 5.0.
3. The tissue product of claim 1 having a CD TEA Index greater than
about 6.0.
4. The tissue product of claim 1 having a CD Durability Index
greater than about 15.0 and a CD Tensile strength from about 400 to
about 600 g/3''.
5. The tissue product of claim 1 wherein the TS7 value is from
about 18.0 to about 20.0 dB V2 rms.
6. The tissue product of claim 1 having a GMT from about 700 to
about 1200 g/3'' and a basis weight from about 15 to about 20
gsm.
7. The tissue product of claim 1 comprising at least about 5
percent, by weight of the tissue product, Southern softwood kraft
fibers.
8. The tissue product of claim 1 comprising at least about 5
percent, by weight of the tissue product, Southern softwood kraft
fibers having a coarseness less than about 21 mg/100 m, such as
from about 17 to about 21, and a fiber length greater than about
2.2 mm.
9. The tissue product of claim 1 comprising less than about 5
percent, by weight of the tissue product, NSWK fibers.
10. The tissue product of claim 1 wherein the tissue product is
substantially free from NSWK fibers.
11. The tissue product of claim 1 having a CD Stretch from about
4.0 to about 6.0.
12. The tissue product of claim 1 consisting essentially of EWHK
and SSWK and having a basis weight from about 10 to about 20
gsm.
13. A single ply wet pressed tissue product having improved
formation the product comprising at least about 20 percent, by
weight of the product, SSWK and having a TS7 value less than about
20.0 dB V2 rms and a CD Durability Index greater than about 14.0
wherein the PPF value is greater than a comparable tissue
substantially free from SSWK.
14. The tissue product of claim 13 having a Burst Index greater
than about 5.0.
15. The tissue product of claim 13 having a CD TEA Index greater
than about 6.0.
16. The tissue product of claim 13 having a GMT from about 700 to
about 1200 g/3'' and a basis weight from about 15 to about 20
gsm.
17. A wet pressed tissue product comprising at least one
multi-layered tissue web comprising a first and a second layer, the
second layer consisting essentially of low-coarseness SSWK fibers,
the tissue product having a CD Durability Index greater than about
14.0 and a TS7 value less than about 20.0 dB V2 rms.
18. The tissue product of claim 17 having a basis weight less than
about 20 gsm and CD Tensile from about 400 to about 600 g/3''.
19. The tissue product of claim 17 having a Burst Index greater
than about 30, a CD TEA Index greater than about 6.5 and a GMT from
about 600 to about 1000 g/3''.
20. The tissue product of claim 17 comprising at least about 5
percent, by weight of the tissue product, Southern softwood kraft
fibers having a coarseness less than about 21 mg/100 m and a fiber
length greater than about 2.2 mm.
Description
BACKGROUND OF THE DISCLOSURE
[0001] Tissue products, such as facial tissues, paper towels, bath
tissues, napkins, and other similar products, are designed with
several important properties in mind. For example, the products
should have good bulk, a soft feel, and should be strong and
durable. Unfortunately, however, when steps are taken to increase
one property of the product, other properties are often adversely
affected.
[0002] To achieve the optimum product properties, tissue products
are typically formed, at least in part, from pulps containing wood
fibers and often a blend of hardwood and softwood fibers to achieve
the desired properties. Typically when attempting to optimize
surface softness, as is often the case with tissue products, the
papermaker will select the fiber furnish based in part on the
coarseness of pulp fibers. Pulps having fibers with low-coarseness
are desirable because tissue paper made from fibers having a
low-coarseness can be made softer than similar tissue paper made
from fibers having a high coarseness. To optimize surface softness
even further, premium tissue products usually comprise layered
structures where the low-coarseness fibers are directed to the
outside layer of the tissue sheet with the inner layer of the sheet
comprising longer, coarser fibers.
[0003] Unfortunately, the need for softness is balanced by the need
for durability. CD Durability in tissue products can be defined in
terms of tensile strength, tensile energy absorption (TEA), burst
strength and tear strength. Typically tear, burst and TEA will show
a positive correlation with tensile strength while tensile
strength, and thus durability, and softness are inversely related.
Thus the paper maker is continuously challenged with the need to
balance the need for softness with a need for durability.
Unfortunately, tissue paper durability generally decreases as the
fiber length is reduced. Therefore, simply reducing the pulp fiber
length can result in an undesirable trade-off between product
surface softness and product durability.
[0004] Besides durability long fibers also play an important role
in overall tissue product softness. While surface softness in
tissue products is an important attribute, a second element in the
overall softness of a tissue sheet is stiffness. Stiffness can be
measured from the tensile slope of stress--strain tensile curve.
The lower the slope the lower the stiffness and the better overall
softness the product will display. Stiffness and tensile strength
are positively correlated, however at a given tensile strength
shorter fibers will display a greater stiffness than long fibers.
While not wishing to be bound by theory, it is believed that this
behavior is due to the higher number of hydrogen bonds required to
produce a product of a given tensile strength with short fibers
than with long fibers. Thus, easily collapsible, low-coarseness
long fibers, such as those provided by Northern softwood kraft
(NSWK) fibers typically supply the best combination of durability
and softness in tissue products when those fibers are used in
combination with hardwood kraft fibers such as eucalyptus hardwood
kraft fibers (EHWK). While NSWK fibers have a higher coarseness
than EHWK fibers, their small cell wall thickness relative to lumen
diameter combined with their long length makes them the ideal
candidate for optimizing durability and softness in tissue.
[0005] Unfortunately supply of NSWK is under significant pressure
both economically and environmentally. As such, prices of NSWK have
escalated significantly creating a need to find alternatives to
optimize softness and strength in tissue products. Alternatives,
however, are limited. For example, Southern softwood kraft (SSWK)
may only be used in limited amounts in the manufacture of tissue
products because its high coarseness results in stiffer, harsher
feeling products than NSWK. Thus, to-date SSWK is not widely used
in the manufacture of premium tissue products, which must be both
soft and strong.
[0006] Therefore, what is needed is a long fiber having relatively
low-coarseness that may be used to manufacture a tissue product
that is both soft and strong.
SUMMARY OF THE DISCLOSURE
[0007] The present inventors have surprisingly discovered that a
soft and strong tissue product may be produced using a fiber
furnisher comprising Southern softwood (SSW) fibers and more
particularly low-coarseness Southern softwood (low-coarseness SSW)
fibers and still more preferably low-coarseness Southern softwood
kraft (low-coarseness SSWK) fibers. The tissue products of the
present invention have properties comparable or better than those
produced using conventional softwood fibers, such as Northern
softwood kraft (NSWK) fibers. Accordingly, in certain preferred
embodiments, SSW fibers may replace at least about 50 percent of
the NSWK in the tissue product, more preferably at least about 75
percent and still more preferably all NSWK without negatively
effecting the tissue product's softness and durability.
[0008] Accordingly, in certain embodiments the tissue products may
comprise a multi-layered tissue web where one or more of the layers
comprise low-coarseness SSW fibers and NSWK fibers and/or
conventional SSWK fibers. Blending low-coarseness SSW fibers with
NSWK fibers and/or conventional SSWK fibers may improve the
physical properties of the tissue product, such as increased
softness and durability, while reducing the cost of manufacture.
Thus, in certain embodiments, the invention provides a tissue
product comprising from about 5 to about 30 percent, by weight of
the product, low-coarseness SSW fibers and from about 5 to about 30
percent, by weight of the product, conventional SSW fibers.
[0009] The blend of low-coarseness SSW fibers and conventional SSW
fibers may be selectively incorporated into the non-skin contacting
layer of a multi-layered product, such as the middle layer of a
three layered tissue product. Moreover, the blend of low-coarseness
SSW fibers and conventional SSW fibers may displace substantially
all of the NSWK in a tissue product while improving the product
properties, such as improved durability and increased softness.
[0010] In other embodiments the present invention provides for a
soft and durable wet pressed tissue web comprising SSW fibers and
more preferably low-coarseness SSW fibers, where the SSW fibers
displace substantially all of the NSWK fibers. The inventive wet
pressed tissue webs may be converted into single or multiply tissue
products comprising from about 5 to about 30 percent, by weight of
the product, low-coarseness SSW fibers. Thus, in one embodiment the
present invention provides a multi-ply tissue product comprising at
least one wet pressed tissue ply comprising from about 5 to about
30 percent, by weight of the ply, low-coarseness SSW fibers.
[0011] In still other embodiments the present invention provides a
single ply wet pressed tissue product that is soft, such as a
tissue product having a TS7 value less than about 20.0 dB V2 rms
and more preferably less than about 18.0 dB V2 rms, such as from
about 15.0 to about 20.0 dB V2 rms, and durable, such as a tissue
product having a CD Durability Index greater than about 14.0 and
more preferably greater than about 15.0.
[0012] In another embodiment the present invention provides a
single ply wet pressed tissue product having a CD Tensile greater
than about 400 g/3'', a CD Durability Index greater than about 14.0
and a TS7 value from about 15.0 to about 20.0 dB V2 rms.
[0013] In still other embodiments the present invention provides a
single ply wet pressed tissue product having a GMT from about 700
to about 1100 g/3'' and more preferably from about 750 to about 900
g/3'', a CD Durability Index greater than about 14.0 and a TS7
value less than about 20.0 dB V2 rms.
[0014] In yet another embodiment the present invention provides a
single ply wet pressed tissue product comprising at least about 5
percent, by weight of the product, such as from about 5 to about 30
percent, low-coarseness SSWK fibers, the tissue product having a
GMT from about 700 to about 1000 g/3'', a CD Tensile greater than
about 400 g/3'', a CD Durability Index greater than about 14.0 and
a TS7 value less than about 20.0 dB V2 rms.
[0015] In still other embodiments the present invention provides a
single ply wet pressed tissue product having improved formation,
the tissue product comprising at least about 5 percent, by weight
of the product, such as from about 5 to about 30 percent,
low-coarseness SSWK fibers, and having a PPF value less than about
33 and a C5 value less than about 18.
Definitions
[0016] As used herein, the term "fiber length" refers to the length
weighted average length of fibers determined utilizing a Kajaani
fiber analyzer model No. FS-100 available from Kajaani Oy
Electronics, Kajaani, Finland. According to the test procedure, a
pulp sample is treated with a macerating liquid to ensure that no
fiber bundles or shives are present. Each pulp sample is
disintegrated into hot water and diluted to an approximately 0.001
percent solution. Individual test samples are drawn in
approximately 50 to 100 ml portions from the dilute solution when
tested using the standard Kajaani fiber analysis test procedure.
The weighted average fiber length may be expressed by the following
equation:
x i = 0 k ( x i .times. n i ) / n ##EQU00001##
where k=maximum fiber length [0017] x=fiber length [0018] n=number
of fibers having length x.sub.i [0019] n=total number of fibers
measured.
[0020] As used herein, the term "coarseness" refers to the fiber
mass per unit of unweighted fiber length reported in units of
milligrams per one hundred meters of unweighted fiber length
(mg/100 m) as measured using a suitable fiber coarseness measuring
device such as the above mentioned Kajaani FS-200 analyzer. The
coarseness of the pulp is an average of three coarseness
measurements of three fiber specimens taken from the pulp. The
operation of the analyzer for measuring coarseness is similar to
the operation for measuring fiber length described above.
[0021] As used herein, the term "basis weight" generally refers to
the bone dry weight per unit area of a tissue and is generally
expressed as grams per square meter (gsm). Basis weight is measured
using TAPPI test method T220. Tissue products of the present
invention may be produced in a wide range of basis weights, such as
from about 10 to about 60 gsm and more preferably from about 15 to
about 30 gsm and in particularly preferred embodiments from about
15 to about 20 gsm.
[0022] As used herein, the term "Burst Index" refers to the dry
burst peak load (typically having units of grams) at a relative
geometric mean tensile strength (typically having units of g/3'')
as defined by the equation:
Burst Index = Dry Burst Peak Load ( g ) GMT ( g / 3 '' ) .times. 10
##EQU00002##
While Burst Index may vary, tissue products prepared according to
the present disclosure generally have a Burst Index greater than
about 5.0, more preferably greater than about 6.0 and still more
preferably greater than about 7.0, such as from about 5.0 to about
8.0.
[0023] As used herein, the term "caliper" is the representative
thickness of a single sheet (caliper of tissue products comprising
two or more plies is the thickness of a single sheet of tissue
product comprising all plies) measured in accordance with TAPPI
test method T402 using an EMVECO 200-A Microgage automated
micrometer (EMVECO, Inc., Newberg, Oreg.). The micrometer has an
anvil diameter of 2.22 inches (56.4 mm) and an anvil pressure of
132 grams per square inch (per 6.45 square centimeters) (2.0
kPa).
[0024] As used herein, the term "CD TEA Index" refers the CD
tensile energy absorption (typically having units of gcm/cm.sup.2)
at a given CD tensile strength (typically having units of g/3'') as
defined by the equation:
CD TEA Index = CD TEA ( g cm / cm 2 ) CDT ( g / 3 '' ) .times. 1 ,
000 ##EQU00003##
While the CD TEA Index may vary, tissue products prepared according
to the present disclosure generally have a CD TEA Index greater
than about 6.0, more preferably greater than about 7.0 and still
more preferably greater than about 7.5, such as from about 6.0 to
about 8.0.
[0025] As used herein, the term "CD Tear Index" refers to the CD
Tear Strength (typically expressed in grams) at a given CD tensile
strength (typically having units of g/3'') as defined by the
equation:
CD Tear Index = CD Tear ( g ) CDT ( g / 3 '' ) .times. 100
##EQU00004##
While the CD Tear Index may vary, tissue products prepared
according to the present disclosure generally have a CD Tear Index
greater than about 1.5, more preferably greater than about 1.8 and
still more preferably greater than about 2.0 such as from about 1.5
to about 2.5.
[0026] As used herein, the term "CD Durability Index" refers to the
sum of the CD Stretch, CD Tear Index and the CD TEA Index, and is
an indication of the durability of the product at a given CD
tensile strength. CD Durability Index is defined by the
equation:
Durability Index=CD Tear Index+CD TEA Index+CD Stretch
While the CD Durability Index may vary, tissue products prepared
according to the present disclosure generally have a CD Durability
Index greater than about 14.0, more preferably greater than about
14.5 and still more preferably greater than about 15.0, such as
from about 14.0 to about 18.0.
[0027] As used herein, the term "machine direction (MD) tensile
strength" is the peak load per 3 inches of sample width when a
sample is pulled to rupture in the machine direction. Similarly,
the "cross-machine direction (CD) tensile strength" is the peak
load per 3 inches of sample width when a sample is pulled to
rupture in the cross-machine direction. The percent elongation of
the sample prior to breaking is the "stretch" and may be specified
according to the orientation of the sample as either "MD stretch"
or "CD stretch". The MD tensile strength, CD tensile strength and
stretch are in the course of determining tensile strength as
described in the Test Methods section.
[0028] As used herein, the terms "geometric mean tensile" and "GMT"
refer to the square root of the product of the machine direction
tensile strength and the cross-machine direction tensile strength
of the tissue product. While the GMT may vary, tissue products
prepared according to the present disclosure generally have a GMT
greater than about 700 g/3'', more preferably greater than about
750 g/3'' and still more preferably greater than about 800 g/3'',
such as from about 700 to about 1200 g/3''.
[0029] As used herein, the term "layer" refers to a plurality of
strata of fibers, chemical treatments, or the like within a
ply.
[0030] As used herein, the terms "layered tissue web,"
"multi-layered tissue web," "multi-layered web," and "multi-layered
paper sheet," generally refer to sheets of paper prepared from two
or more layers of aqueous papermaking furnish which are preferably
comprised of different fiber types. The layers are preferably
formed from the deposition of separate streams of dilute fiber
slurries, upon one or more endless foraminous screens. If the
individual layers are initially formed on separate foraminous
screens, the layers are subsequently combined (while wet) to form a
layered composite web.
[0031] The term "ply" refers to a discrete product element.
Individual plies may be arranged in juxtaposition to each other.
The term may refer to a plurality of web-like components such as in
a multi-ply facial tissue, bath tissue, paper towel, wipe, or
napkin.
[0032] As used herein, the term "slope" refers to slope of the line
resulting from plotting tensile versus stretch and is an output of
the MTS TestWorks.TM. in the course of determining the tensile
strength as described in the Test Methods section herein. Slope is
reported in the units of grams (g) per unit of sample width
(inches) and is measured as the gradient of the least-squares line
fitted to the load-corrected strain points falling between a
specimen-generated force of 70 to 157 grams (0.687 to 1.540 N)
divided by the specimen width. Slopes are generally reported herein
as having units of grams (g).
[0033] As used herein, the term "geometric mean slope" (GM Slope)
generally refers to the square root of the product of machine
direction slope and cross-machine direction slope. GM Slope
generally is expressed in units of kilograms (kg).
[0034] As used herein, the term "low-coarseness Southern softwood"
(low-coarseness SSW) refers to a fiber derived from a pine in the
Pinus subgenus including, for example, P. taeda, P. elliotti, P.
palustris, P. pungens, P. rigida, P. serotina, P. muricata and P.
radiate, the fiber having a coarseness less than about 21 mg/100 m,
such as from about 16 to about 21 mg/100 m, and more preferably
from about 17 to about 20.5 mg/100 m, and a fiber length from about
2.0 to about 3.0 mm, and more preferably from about 2.2 to about
2.7 mm.
[0035] As used herein, the term "Stiffness Index" refers to GM
Slope (typically having units of kg), divided by GMT (typically
having units of g/3'').
Stiffness Index = MD Tensile Slope ( kg ) .times. CD Tensile Slope
( kg ) GMT ( g / 3 '' ) .times. 1 , 000 ##EQU00005##
While the Stiffness Index may vary, tissue products prepared
according to the present disclosure generally have a Stiffness
Index less than about 25.0.
[0036] As used herein, the term "sheet bulk" refers to the quotient
of the caliper (generally having units of .mu.m) divided by the
bone dry basis weight (generally having units of gsm). The
resulting sheet bulk is expressed in cubic centimeters per gram
(cc/g). Tissue products prepared according to the present invention
generally have a sheet bulk greater than about 6 cc/g, more
preferably greater than about 8 cc/g such as from about 6 to about
10 cc/g.
[0037] As used herein, the terms "T57" and "TS7 value" refer to the
output of the EMTEC Tissue Softness Analyzer (commercially
available from Emtec Electronic GmbH, Leipzig, Germany) as
described in the Test Methods section. TS7 has units of dB V2 rms,
however, TS7 may be referred to herein without reference to
units.
[0038] As used herein, a "tissue product" generally refers to
various paper products, such as facial tissue, bath tissue, paper
towels, napkins, and the like.
[0039] As used herein the formation measurement values "PPF" and
"C5" refer to the output of the Paper PerFect Formation Analyzer
(commercially available from OpTest Equipment Inc., Hawkesbury
Ontario). The results of the formation analysis are expressed
relative to perfect paper formation, the PPF value, and the
formation value as measured in the range from about 2.6 to about
4.5 mm ('C5''). The test method is described in detail in U.S. Pat.
No. 6,301,373, the contents of which are incorporated herein in a
manner consistent with the present disclosure.
[0040] As used herein the term "wet-pressed tissue" generally
refers to a tissue product manufactured by a conventional
wet-pressed method in which prior to the nascent tissue web being
transferred to the surface of a rotating drying cylinder, such as a
Yankee dryer, water is expressed from the web and absorbed by a
felt. The dewatered web, typically having a consistency of about 40
percent, is then dried while on the hot surface of the dryer. The
web is then creped from the surface of the dryer.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0041] It has now been discovered that manufacturing wet-pressed
tissue products using Southern softwood kraft ("SSWK") may improve
softness without compromising perceived in-use strength,
particularly in the CD direction of the sheet, compared to
comparable products manufactured with Northern softwood kraft
("NSWK"). Having improved CD properties at a given tensile
strength, the tissue products of the present disclosure have
improved cross-machine durability and toughness.
[0042] Thus, in certain embodiments the present disclosure relates
to tissue products, and more particularly single ply wet pressed
tissue products, comprising Southern softwood (SSW) fibers and more
preferably low-coarseness SSW fibers. The SSW fibers used in the
manufacture of the inventive tissue products may displace a
portion, and in certain embodiments all, of the long fiber length
fibers, such as NSWK fibers, without significantly impairing
important tissue physical properties such as durability, strength
and softness. For example, in certain embodiments the inventive
tissue products comprise low-coarseness SSW fibers and less than
about 5 percent, by weight of the tissue product,
[0043] NSWK, yet have improved durability and softness relative to
a comparable tissue product comprising 20 percent NSWK. Even more
surprising is that in certain embodiments NSWK may be entirely
replaced by low-coarseness SSWK fibers and the tissue product
properties may be improved.
[0044] The ability to replace a significant amount of NSWK, and in
certain embodiments all of the NSWK, with SSW and maintain or
improve tissue product properties is surprising provided that SSW
has traditionally been unsuitable for use in manufacturing premium
tissue products because of its high coarseness. However, it has now
been discovered that a SSW having reduced coarseness may be used in
the manufacture of soft and strong tissue products. The discovery
is particularly surprising because the reduction in fiber
coarseness is only moderate, such as less than about 10 percent,
compared to conventional SSWK. While being reduced relative to
conventional SSWK, the coarseness of low-coarseness SSW fibers is
still greater than NSWK as can be seen in Table 1, below.
TABLE-US-00001 TABLE 1 Fiber Length Coarseness Fiber Type (mm)
(mg/100 m) Conventional SSWK 2.35 21.3 Low-coarseness SSWK 2.53
19.3 NSWK Pulp Fiber 2.25 14.8 Eucalyptus Kraft Pulp Fiber 0.76
8.95
[0045] While the low-coarseness SSW fibers are higher in coarseness
compared to NSWK fibers they may replace NSWK fibers in tissue
products without impairing important physical properties such as
durability, strength and softness. Even more surprisingly, in
certain embodiments, substitution of NSWK fibers with
low-coarseness SSW fibers may actually increase softness (measured
as TS7) while also maintaining or improving durability (measured as
CD Durability Index).
[0046] The surprising increase in softness without a corresponding
decrease in durability is not found in prior art single ply wet
pressed tissue products. With reference to Table 2, below, tissue
products of the present disclosure generally have comparable or
improved durability at a given tensile strength compared to
commercially available single ply wet pressed tissue products. In
addition to having comparable or better durability, the instant
tissue products are of comparable softness (measured as TS7).
TABLE-US-00002 TABLE 2 CD CD CD CD GMT CDT CDS CD TEA TEA Tear Tear
Burst Burst Durability Product (g/3'') (g/3'') (%) (g *
cm/cm.sup.2) Index (g) Index (g) Index Index TS7 Great Value .TM.
668 458 4.4 3.04 6.638 11.04 2.41 430 6.44 13.4 22.3 1000 Family
Dollar .TM. 714 488 4.5 2.79 5.717 10.1 2.07 420 5.88 12.3 18.6
1000 Scott .TM. 1000 889 582 5.1 4.28 7.354 9.98 1.71 488 5.49 14.2
18.6 Inventive 826 523 5.3 3.88 7.419 11 2.10 538 6.51 14.8
19.2
[0047] Thus, the instant tissue products are generally soft, having
a TS7 value less than about 20.0, and durable, such as a product
having a CD Durability Index greater than about 14.0, more
preferably greater than about 14.5 and still more preferably
greater than about 15.0, such as from about 14.0 to about 18.0. The
foregoing values are generally achieved at relatively modest
tensile strengths, such as from a GMT from about 700 to about 1000
g/3'' and a CD tensile strength greater than about 400 g/3'', such
as from about 400 to about 800 g/3'' and more preferably from about
450 to about 600 g/3''. Moreover, in a particularly preferred
embodiment, the tissue products have relatively low basis weights,
such as less than about 20 gsm, such as from about 10 to about 20
gsm and more preferably from about 12 to about 18 gsm.
[0048] Accordingly, in one embodiment the present invention
provides a wet pressed tissue product comprising at least about 10
percent, by weight, SSWK and more preferably low-coarseness SSWK,
the tissue product having a CD Tensile from about 400 to about 600
g/3'', a CD Durability Index greater than about 14.0 and a TS7 less
than about 20.0. In a particularly preferred embodiment the
foregoing tissue product is produced without the addition of NSWK,
thus the resulting tissue product is substantially free of NSWK,
but has softness and durability comparable or better than a similar
tissue product comprising NSWK.
[0049] In other embodiments the tissue product comprises a single
ply wet pressed tissue product comprising less than about 5
percent, by weight of the tissue product, NSWK, the tissue product
having a TS7 value from about 16.0 to about 20.0, a CD tensile
greater than about 450 g/3'' and a CD Durability
[0050] Index from about 14.0 and more preferably greater than about
14.5 and still more preferably greater than about 15.0. In still
other embodiments the invention provides a single ply wet pressed
tissue product comprising from about 10 to about 40 percent, by
weight of the web, SSW fibers, the tissue product having a TS7 from
about 16.0 to about 20.0, a CD tensile greater than about 450 g/3''
and a CD Durability Index from about 14.0 to about 18.0.
[0051] In still other embodiments the single ply wet pressed tissue
products of the present invention have a CD stretch from about 4.0
to about 6.0 percent, a CD TEA from about 4.0 to about 6.0
(gcm/cm.sup.2) and a CD Tensile from about 400 to about 600 g/3''.
In still other embodiments the tissue products have a CD Tear
greater than about 10 g, such as from about 10 to about 12 g at a
CD Tensile strength greater than about 400 g/3'', such as from
about 400 to about 600 g/3''.
[0052] Not only do the instant tissue webs and products have
improved durability and softness, but may also display improved
formation. The improved formation of the instant webs is surprising
as formation tends to correlate with fiber length and coarseness
with furnishes having shorter fiber lengths and lower coarseness
having better formation. Here however, substitution of NSWK with
low-coarseness SSWK may actually improve formation despite the low
coarseness and longer fiber length relative to
[0053] NSWK. For example, in certain embodiments the use of
low-coarseness SSWK may improve formation, compared to a comparable
web substantially free from low-coarseness SSWK, by at least about
10 percent and more preferably by at least about 15 percent when
measured as PPF. Accordingly, in one embodiment the present
invention provides a single ply wet pressed tissue product
comprising less than about 5 percent, by weight of the tissue
product, NSWK, the tissue product having a PPF greater than about
30 and still more preferably greater than about 32 and a C5 value
greater than about 17 and more preferably greater than about
18.
[0054] In a particularly preferred embodiment the tissue product
comprises a multi-layered wet pressed tissue web wherein
low-coarseness SSW fiber is selectively disposed in only one of the
layers such that the low-coarseness SSW fiber is not brought into
contact with the user's skin in-use. For example, in one embodiment
the tissue web may comprise a two layered web wherein the first
layer consists essentially of hardwood kraft pulp fibers and is
substantially free of low-coarseness SSWK and the second layer
comprises low-coarseness SSW, wherein the low-coarseness SSWK
comprises at least about 50 percent by weight of the second layer,
such as from about 50 to about 100 percent by weight of the second
layer. It should be understood that, when referring to a layer that
is substantially free of low-coarseness SSW fibers, negligible
amounts of the fiber may be present therein, however, such small
amounts often arise from the low-coarseness SSW fibers applied to
an adjacent layer, and do not typically substantially affect the
softness or other physical characteristics of the web.
[0055] The tissue webs may be incorporated into tissue products
that may be either single or multi-ply, where one or more of the
plies may be formed by a multi-layered tissue web having
low-coarseness SSW fibers selectively incorporated in one of its
layers. In one embodiment the tissue product is constructed such
that the low-coarseness SSW fibers are not brought into contact
with the user's skin in-use. For example, the tissue product may
comprise two wet pressed tissue webs wherein each web comprises a
first fibrous layer substantially free from low-coarseness SSW
fibers and a second fibrous layer comprising low-coarseness SSW
fibers. The webs are plied together such that the outer surface of
the tissue product is formed from the first fibrous layers of each
web and the second fibrous layer comprising the low-coarseness SSW
fibers is not brought into contact with the user's skin in-use.
[0056] In those embodiments where the inventive wet pressed webs
are converted into multi-ply products the products may comprise
two, three or four plies where at least one of the plies comprise
low-coarseness SSW fibers and have comparable or better durability
and softness compared to a comparable web comprising NSWK. The
multi-ply tissue products may have a basis weight greater than
about 20 gsm, such as from about 20 to about 60 gsm and more
preferably from about 30 to about 40 gsm.
[0057] Generally low-coarseness SSW fibers useful in the present
invention are derived from pines in the Pinus subgenus. Suitable
species within the Pinus subgenus include, for example, P. taeda,
P. elliotti, P. palustris, P. pungens, P. rigida, P. serotina, P.
muricata and P. radiata. Particularly preferred are P. taeda, P.
elliotti, and P. palustris. Further, it is to be understood that
the compositions disclosed herein are not limited to containing any
one species of low-coarseness SSW fiber and may comprise a blend of
low-coarseness SSW fibers derived from two or more species, such as
a blend of fibers derived from P. taeda, P. elliotti, and P.
palustris.
[0058] In certain embodiments the low-coarseness SSW fibers are
derived from pines within the Pinus subgenus which are less than
about 14 years old and more preferably less than about 12 and still
more preferably less than about 10 years, such as from about 8 to
about 12 years. Generally pines within the
[0059] Pinus subgenus less than 14 years old comprise a large
percentage of juvenile wood and as such have fibers with lower
coarseness relative to more mature pines. In other embodiments
low-coarseness SSW fibers are derived from the corewood portion of
the tree, i.e., the portion of the tree comprising the first 10 to
12 growth layers from the pith. Corewood may be produced by
selectively removing the outer portion of the tree, such as by
removing the corewood, or by selecting the top portion of the tree
which is generally less than about 10 to 12 growth layers from pith
to bark.
[0060] Once the appropriate fiber source is identified suitable
low-coarseness SSW fiber may be produced by any appropriate method
known in the art. In one embodiment low-coarseness SSW fiber is
produced by well-known chemical pulping methods such as kraft,
sulfite or soda/AQ pulping methods. In one preferred embodiment
low-coarseness SSW fibers are produced by kraft pulping and have a
fiber length greater than about 2.2 mm and more preferably greater
than about 2.4 mm, such as from about 2.2 to about 2.8 mm. Further,
the foregoing fibers preferably have a coarseness less than about
21 mg/100 m, such as from about 16 to about 21 mg/100 m, more
preferably from about 17 to about 20.5 mg/ 100 m and still more
preferably from about 18 to about 19.5 mg/100 m.
[0061] In a particularly preferred embodiment low-coarseness SSW
fibers are utilized in the tissue web as a replacement for high
fiber length wood fibers such as softwood fibers and more
specifically NSWK. In one particular embodiment the low-coarseness
SSW fibers are substituted for NSWK such that the total amount of
NSWK, by weight of the tissue product, is less than about 10
percent and more preferably less than about 5 percent. In other
embodiments it may be desirable to replace all of the NSWK with
low-coarseness SSW fibers such that the tissue product is
substantially free from NSWK. In other embodiments low-coarseness
SSW fibers may be blended with conventional SSW fibers and the
blended SSW fibers may be substituted for NSWK such that the total
amount of NSWK, by weight of the tissue product, is less than about
10 percent and more preferably less than about 5 percent. The blend
of low-coarseness SSW fibers and conventional SSW fibers may be
such that the tissue product comprises, by weight of the tissue
product, from about 5 to about 30 percent low-coarseness SSW fibers
and from about 5 to about 30 percent conventional SSW fibers.
[0062] Generally the base webs and tissue products of the present
disclosure are prepared by a conventional wet pressed tissue
manufacture. For example, tissue webs may be manufactured using a
twin wire machine comprising a wet end and a dry section. The wet
end includes a headbox, a movable carrying forming wire, a movable
covering forming wire and a forming roll which may be perforated
and provided with suction means. Alternatively, the forming roll
may be smooth. The headbox supplies a single or multi-layer flow of
stock between the two moving forming wires for forming a paper web
by dewatering the stock. The two forming wires run together over
the forming roll and then in individual loops over a plurality of
rolls arranged to impel, guide, align and stretch the carrying
forming wire and the covering forming wire. The rolls defining the
path of the covering forming wire include a breast roll and, a
short way after the forming roll, a guide roll which can be termed
a forward drive roll. The covering forming wire leaves the carrying
forming wire and the paper web either immediately before the wire
and paper web diverge from the forming roll, or at a transfer
suction box, not shown, or other transfer means located between the
forming roll and forward drive roll. The carrying forming wire runs
to the drying section where it leaves the paper web by changing its
direction of travel around a guide roll.
[0063] The drying section comprises a Yankee dryer having a
relatively large diameter and a polished cylindrical surface. The
Yankee dryer, preferably consisting of a cylinder covered by a
hood, in which hot air is blown at high speed against the paper
web. The paper web is creped from the Yankee dryer by means of a
creping doctor blade to obtain the desired creping, after which the
finished creped paper web is wound onto a roll. Further, the drying
section includes a felt disposed upstream of the Yankee dryer and
travelling in a loop around several rolls and around a pick-up
means, suitably in the form of a roll, located nearest the wet end
and thereby in the vicinity of said guide roll for the carrying
forming wire, and a press roll which presses against the Yankee
dryer and is provided with suction means to dewater the paper web
before the latter comes into contact with the Yankee dryer. The
pick-up means may alternatively consist of a shoe. Further, two
guide rolls are disposed between the pick-up roll and press roll,
said guide rolls deflecting with a small angle the direction of
travel of the felt. A blind-drilled roll is disposed after the
press roll, in contact with the Yankee dryer. The paper web is
transferred to the felt at the point where this and the carrying
forming wire converge at the pick-up roll and thereafter
immediately diverge from each other.
[0064] As described above the web is mechanically dewatered by a
compression nip while the wet web is in contact with a papermaking
felt and thereafter dried with the aid of a Yankee dryer. As used
herein, a "felt" is an absorbent papermaking fabric designed to
absorb water and remove it from a tissue web. Papermaking felts of
various designs are well known in the art. The water expressed from
the wet web during compression is absorbed and carried away by the
felt. Commonly, the compression nip is formed between a press roll
and the surface of the Yankee dryer. Particularly suitable
wet-pressed tissue products in accordance with this invention are
mechanically dewatered, final-dried on a Yankee dryer and
once-creped.
[0065] Preferably the formed web is dried by transfer to the
surface of a rotatable heated dryer drum, such as a Yankee dryer.
In accordance with the present disclosure, the creping composition
may be applied topically to the tissue web while the web is
traveling on the fabric or may be applied to the surface of the
dryer drum for transfer onto one side of the tissue web. In this
manner, the creping composition is used to adhere the tissue web to
the dryer drum. In this embodiment, as the web is carried through a
portion of the rotational path of the dryer surface, heat is
imparted to the web causing most of the moisture contained within
the web to be evaporated. The web is then removed from the dryer
drum by a creping blade. Creping the web, as it is formed, further
reduces internal bonding within the web and increases softness.
Applying the creping composition to the web during creping, on the
other hand, may increase the strength of the web.
[0066] In a particularly preferred embodiment the formed web is
transferred to the surface of the Yankee dryer by a suction
pressure roll. Particularly suitable press loads for purposes of
this invention can have a peak pressure of about 1.4 MPa or
greater, more specifically from about 4 to about 8 MPa, and still
more specifically from about 4 to about 6 MPa. The wet tissue web
can be dewatered to a consistency of about 30 percent or greater,
more specifically about 40 percent or greater, more specifically
from about 40 to about 50 percent, and still more specifically from
about 45 to about 50 percent. As used herein and well understood in
the art, "consistency" refers to the bone dry weight percent of the
web based on fiber.
[0067] In order to adhere the web to the surface of the dryer drum,
a creping adhesive may be applied to the surface of the dryer drum
by a spraying device. The spraying device may emit a creping
composition made in accordance with the present disclosure or may
emit a conventional creping adhesive. The web is adhered to the
surface of the dryer drum and then creped from the drum using the
creping blade. If desired, the dryer drum may be associated with a
hood. The hood may be used to force air against or through the
web.
Test Methods
Tissue Softness
[0068] Tissue softness was measured using an EMTEC Tissue Softness
Analyzer ("TSA") (Emtec
[0069] Electronic GmbH, Leipzig, Germany). The TSA comprises a
rotor with vertical blades which rotate on the test piece applying
a defined contact pressure. Contact between the vertical blades and
the test piece creates vibrations, which are sensed by a vibration
sensor. The sensor then transmits a signal to a PC for processing
and display. The signal is displayed as a frequency spectrum. For
measurement of TS7 values the blades are pressed against the sample
with a load of 100 mN and the rotational speed of the blades is 2
revolutions per second.
[0070] The frequency analysis in the range of approximately 200 to
1000 Hz represents the surface smoothness or texture of the test
piece. A high amplitude peak correlates to a rougher surface. A
further peak in the frequency range between 6 and 7 kHZ represents
the softness of the test piece. The peak in the frequency range
between 6 and 7 kHZ is herein referred to as the TS7 Softness Value
and is expressed as dB V2 rms. The lower the amplitude of the peak
occurring between 6 and 7 kHZ, the softer the test piece.
[0071] Test samples were prepared by cutting a circular sample
having a diameter of 112.8 mm. All samples were allowed to
equilibrate at TAPPI standard temperature and humidity conditions
for at least 24 hours prior to completing the TSA testing. Only one
ply of tissue is tested. Multi-ply samples are separated into
individual plies for testing. The sample is placed in the TSA with
the softer (dryer or Yankee) side of the sample facing upward. The
sample is secured and the measurements are started via the PC. The
PC records, processes and stores all of the data according to
standard TSA protocol. The reported values are the average of five
replicates, each one with a new sample.
Sheet Bulk
[0072] Sheet Bulk is calculated as the quotient of the dry sheet
caliper (.mu.m) divided by the basis weight (gsm). Dry sheet
caliper is the measurement of the thickness of a single tissue
sheet measured in accordance with TAPPI test methods T402 and T411
om-89. The micrometer used for carrying out T411 om-89 is an Emveco
200-A Tissue Caliper Tester (Emveco, Inc., Newberg, Oreg.). The
micrometer has a load of 2 kilo-Pascals, a pressure foot area of
2500 square millimeters, a pressure foot diameter of 56.42
millimeters, a dwell time of 3 seconds and a lowering rate of 0.8
millimeters per second.
Tear
[0073] Tear testing was carried out in accordance with TAPPI test
method T414 "Internal Tearing Resistance of Paper (Elmendorf-type
method)" using a falling pendulum instrument such as Lorentzen
& Wettre Model SE 009. Tear strength is directional and MD and
CD tear are measured independently.
[0074] More particularly, a rectangular test specimen of the sample
to be tested is cut out of the tissue product or tissue basesheet
such that the test specimen measures 63 mm .+-.0.15 mm (2.5 inches
.+-.0.006'') in the direction to be tested (such as the MD or CD
direction) and between 73 and 114 millimeters (2.9 and 4.6 inches)
in the other direction. The specimen edges must be cut parallel and
perpendicular to the testing direction (not skewed). Any suitable
cutting device, capable of the prescribed precision and accuracy,
can be used. The test specimen should be taken from areas of the
sample that are free of folds, wrinkles, crimp lines, perforations
or any other distortions that would make the test specimen abnormal
from the rest of the material.
[0075] The number of plies or sheets to test is determined based on
the number of plies or sheets required for the test results to fall
between 20 to 80 percent on the linear range scale of the tear
tester and more preferably between 20 to 60 percent of the linear
range scale of the tear tester. The sample preferably should be cut
no closer than 6 mm (0.25 inch) from the edge of the material from
which the specimens will be cut. When testing requires more than
one sheet or ply the sheets are placed facing in the same
direction.
[0076] The test specimen is then placed between the clamps of the
falling pendulum apparatus with the edge of the specimen aligned
with the front edge of the clamp. The clamps are closed and a
20-millimeter slit is cut into the leading edge of the specimen
usually by a cutting knife attached to the instrument. For example,
on the Lorentzen & Wettre Model SE 009 the slit is created by
pushing down on the cutting knife lever until it reaches its stop.
The slit should be clean with no tears or nicks as this slit will
serve to start the tear during the subsequent test.
[0077] The pendulum is released and the tear value, which is the
force required to completely tear the test specimen, is recorded.
The test is repeated a total of ten times for each sample and the
average of the ten readings reported as the tear strength. Tear
strength is reported in units of grams of force (gf). The average
tear value is the tear strength for the direction (MD or CD)
tested. The "geometric mean tear strength" is the square root of
the product of the average MD tear strength and the average CD tear
strength. The Lorentzen & Wettre Model SE 009 has a setting for
the number of plies tested. Some testers may need to have the
reported tear strength multiplied by a factor to give a per ply
tear strength. For basesheets intended to be multiple ply products,
the tear results are reported as the tear of the multiple ply
product and not the single ply basesheet. This is done by
multiplying the single ply basesheet tear value by the number of
plies in the finished product. Similarly, multiple ply finished
product data for tear is presented as the tear strength for the
finished product sheet and not the individual plies. A variety of
means can be used to calculate but in general will be done by
inputting the number of sheets to be tested rather than number of
plies to be tested into the measuring device. For example, two
sheets would be two 1-ply sheets for 1-ply product and two 2-ply
sheets (4-plies) for 2-ply products.
Tensile
[0078] Tensile testing was done in accordance with TAPPI test
method T576 "Tensile properties of towel and tissue products (using
constant rate of elongation)" wherein the testing is conducted on a
tensile testing machine maintaining a constant rate of elongation
and the width of each specimen tested is 3 inches. More
specifically, samples for dry tensile strength testing were
prepared by cutting a 3.+-.0.05 inches (76.2.+-.1.3 mm) wide strip
in either the machine direction (MD) or cross-machine direction
(CD) orientation using a JDC Precision Sample Cutter (Thwing-Albert
Instrument Company, Philadelphia, Pa., Model No. JDC 3-10, Serial
No. 37333) or equivalent. The instrument used for measuring tensile
strengths was an MTS Systems Sintech 11S, Serial No. 6233. The data
acquisition software was an MTS TestWorks.RTM. for Windows Ver.
3.10 (MTS Systems Corp., Research Triangle Park, N.C.). The load
cell was 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 to 90 percent of the
load cell's full scale value. The gauge length between jaws was
4.+-.0.04 inches (101.6.+-.1 mm) for facial tissue and towels and
2.+-.0.02 inches (50.8.+-.0.5 mm) for bath tissue. The crosshead
speed was 10.+-.0.4 inches/min (254.+-.1 mm/min), and the break
sensitivity was set at 65 percent. The sample was placed in the
jaws of the instrument, centered both vertically and horizontally.
The test was then started and ended when the specimen broke. The
peak load was recorded as either the "MD tensile strength" or the
"CD tensile strength" of the specimen depending on direction of the
sample being tested.
[0079] Ten representative specimens were tested for each product or
sheet and the arithmetic average of all individual specimen tests
was recorded as the appropriate MD or CD tensile strength of the
product or sheet in units of grams of force per 3 inches of sample.
The geometric mean tensile (GMT) strength was calculated and is
expressed as grams-force per 3 inches of sample width. Tensile
energy absorbed (TEA) and slope are also calculated by the tensile
tester. TEA is reported in units of gcm/cm.sup.2. Slope is recorded
in units of kg. Both TEA and Slope are directional dependent and
thus MD and CD directions are measured independently. Geometric
mean TEA and geometric mean slope are defined as the square root of
the product of the representative MD and CD values for the given
property.
[0080] Multi-ply products were tested as multi-ply products and
results represent the tensile strength of the total product. For
example, a 2-ply product was tested as a 2-ply product and recorded
as such. A basesheet intended to be used for a 2-ply product was
tested as two plies and the tensile recorded as such.
Alternatively, a single ply may be tested and the result multiplied
by the number of plies in the final product to get the tensile
strength.
Burst Strength
[0081] Burst strength herein is a measure of the ability of a
fibrous structure to absorb energy, when subjected to deformation
normal to the plane of the fibrous structure. Burst strength may be
measured in general accordance with ASTM D-6548 with the exception
that the testing is done on a Constant-Rate-of-Extension (MTS
Systems Corporation, Eden Prairie, Minn.) tensile tester with a
computer-based data acquisition and frame control system, where the
load cell is positioned above the specimen clamp such that the
penetration member is lowered into the test specimen causing it to
rupture. The arrangement of the load cell and the specimen is
opposite that illustrated in FIG. 1 of ASTM D-6548. The penetration
assembly consists of a semi spherical anodized aluminum penetration
member having a diameter of 1.588.+-.0.005 cm affixed to an
adjustable rod having a ball end socket. The test specimen is
secured in a specimen clamp consisting of upper and lower
concentric rings of aluminum between which the sample is held
firmly by mechanical clamping during testing. The specimen clamping
rings has an internal diameter of 8.89.+-.0.03 cm.
[0082] The tensile tester is set up such that the crosshead speed
is 15.2 cm/min, the probe separation is 104 mm, the break
sensitivity is 60 percent and the slack compensation is 10 gf and
the instrument is calibrated according to the manufacturer's
instructions.
[0083] Samples are conditioned under TAPPI conditions and cut into
127.times.127 mm.+-.5 mm squares. For each test a total of 3 sheets
of product are combined. The sheets are stacked on top of one
another in a manner such that the machine direction of the sheets
is aligned. Where samples comprise multiple plies, the plies are
not separated for testing. In each instance the test sample
comprises 3 sheets of product. For example, if the product is a
2-ply tissue product, 3 sheets of product, totaling 6 plies are
tested. If the product is a single ply tissue product, then 3
sheets of product totaling 3 plies are tested.
[0084] Prior to testing the height of the probe is adjusted as
necessary by inserting the burst fixture into the bottom of the
tensile tester and lowering the probe until it was positioned
approximately 12.7 mm above the alignment plate. The length of the
probe is then adjusted until it rests in the recessed area of the
alignment plate when lowered.
[0085] It is recommended to use a load cell in which the majority
of the peak load results fall between 10 and 90 percent of the
capacity of the load cell. To determine the most appropriate load
cell for testing, samples are initially tested to determine peak
load. If peak load is <450 gf a 10 Newton load cell is used, if
peak load is >450 gf a 50 Newton load cell is used.
[0086] Once the apparatus is set-up and a load cell selected,
samples are tested by inserting the sample into the specimen clamp
and clamping the test sample in place. The test sequence is then
activated, causing the penetration assembly to be lowered at the
rate and distance specified above.
[0087] Upon rupture of the test specimen by the penetration
assembly the measured resistance to penetration force is displayed
and recorded. The specimen clamp is then released to remove the
sample and ready the apparatus for the next test.
[0088] The peak load (gf) and energy to peak (g-cm) are recorded
and the process repeated for all remaining specimens. A minimum of
five specimens are tested per sample and the peak load average of
five tests is reported as the burst strength.
Opacity
[0089] Opacity was measured using a TECHNIBRITE Micro TB-1C testing
instrument, available from Technidyne Corporation, New Albany, IND
according to the manufacturer's instructions and is reported as ISO
Opacity (%).
Formation
[0090] Tissue web and product formation was measured using the
PaperPerFect Formation (PPF) Analyzer (OpTest Equipment Inc.
Ontario, Canada). The PaperPerFect analyzer is a light-transmission
formation meter and is capable of measuring the formation scale of
paper ranging from 0.5 to 60 mm. The PPF analyzer measures the
formation characteristics of a sample by partitioning the sample
into its components as a function of scale of formation, over scale
of formation range indicated above. In making the measurement, the
instrument uses Fourier Transform-based power spectrum analysis in
partitioning the intensity of the non-uniformity of the formation
into its components as a function of the scale of formation.
Normally, a 256 by 256 pixel image is extracted from the original
sample, and subjected to the mirroring and Fast Fourier Transform
(FFT) subroutines of the machine. The machine then provides
wavelength numbers which directly relate to the dimension of the
local non-uniformity in the plane of the sheet. The results are
then expressed as PPF Formation Values (PPF) which are relative to
a "perfect paper" (having formation value of 1000 at each
component, e.g. different C size range)" and C5 value, which
measures formation in the range from 2.6 to 4.5 mm.
EXAMPLES
[0091] A blended single ply wet pressed tissue product was produced
from various fiber furnishes including, eucalyptus hardwood kraft
(EHWK), NSWK, conventional SSWK and low-coarseness SSWK ("LC SSWK).
The NSWK had a length-weighted fiber length of about 2.25 mm and a
fiber coarseness of about 14.8 mg/100 m. The low-coarseness SSWK
had a length-weighted fiber length of about 2.5 mm and a fiber
coarseness of about 19 mg/100 m. Starch and/or refining was used to
control the target geometric mean tensile strength of the resulting
product. The furnish blends and target strengths are summarized in
Table 3, below.
TABLE-US-00003 TABLE 3 Sample Furnish (wt %) 7 68% EHWK/20%
NSWK/12% SSWK 8 68% EHWK/20% LC SSWK/12% SSWK 9 68% EHWK/32% LC
SSWK
[0092] The stock solutions were pumped to a headbox after dilution
to 0.75 percent consistency to form a blended tissue web comprising
80 percent EHWK and 20 percent softwood kraft, either NSWK or
LC
[0093] SSWK. The target basis weight for all codes was about 16
gsm. The formed web was pressed against a Yankee dryer and adhered
thereto using a mixture of polyvinyl alcohol, water and
Kymene.RTM.. The dried web was subsequently removed from the Yankee
dryer by creping. The crepe ratio was set at 1.20-1.25.
[0094] To produce one-ply tissue product, the base sheets, produced
above, were calendared using a steel-on-rubber roll combination (40
P&J hardness rubber roll) to a thickness of 6.6.+-.1.1 mils and
the product wound into bath-tissue rolls of constant firmness,
diameter and sheet count. The resulting one-ply tissue products
were tested and exhibited the properties as shown in the tables
below.
[0095] The effect of LC SSWK fibers on various tissue product
strength and durability properties is summarized in the tables
below.
TABLE-US-00004 TABLE 4 Basis Weight GMT Sheet Bulk ISO Opacity
Sample (gsm) (g/3'') (g/cm.sup.3) (%) PPF C5 7 16.7 918 6.6 45.42
30.8 16.4 8 17.1 779 6.6 45.28 33.2 18.4 9 16.9 826 6.5 45.19 32.5
17.2
TABLE-US-00005 TABLE 5 CD CD Tensile Stretch CD Tear CD TEA GM
Slope Burst Sample (g/3'') (%) (g) (g * cm/cm.sup.2) (kg) (g) 7 592
5.11 12.87 4.280 14.1 578 8 522 5.22 9.19 3.731 12.1 479 9 523 5.32
10.98 3.888 13.0 538
TABLE-US-00006 TABLE 6 CD CD Tear TEA Burst CD Durability Stiffness
TS7 Sample Index Index Index Index Index (dB V2 rms) 7 2.17 7.23
6.30 14.51 24.96 18.74 8 1.76 7.15 6.15 14.13 22.75 18.12 9 2.10
7.43 6.51 14.85 24.51 19.19
[0096] While tissue webs, and tissue products comprising the same,
have been described in detail with respect to the specific
embodiments thereof, it will be appreciated that those skilled in
the art, upon attaining an understanding of the foregoing, may
readily conceive of alterations to, variations of, and equivalents
to these embodiments. Accordingly, the scope of the present
invention should be assessed as that of the appended claims and any
equivalents thereto and the foregoing embodiments:
[0097] In a first embodiment the present invention provides a
single ply wet pressed tissue product having a TS7 value less than
about 20.0 dB V2 rms, a CD Tensile strength greater than about 400
g/3" and a CD Durability Index greater than about greater than
about 14.0, more preferably greater than about 14.5 and still more
preferably greater than about 15.0, such as from about 14.0 to
about 20.0.
[0098] In a second embodiment the present invention provides the
tissue product of the first embodiment having a Burst Index greater
than about 5.0.
[0099] In a third embodiment the present invention provides the
tissue product of the first or the second embodiments having a CD
TEA Index greater than about 6.0.
[0100] In a fourth embodiment the present invention provides the
tissue product of any one of the first through the third
embodiments having a CD Durability Index greater than about
15.0.
[0101] In a fifth embodiment the present invention provides the
tissue product of any one of the first through the fourth
embodiments wherein the TS7 value is from about 18.0 to about 20.0
dB V2 rm.
[0102] In a sixth embodiment the present invention provides the
tissue product of any one of the first through the fifth
embodiments having a GMT from about 700 to about 1200 g/3'' and
more preferably from about 700 to about 1000 g/3'' and still more
preferably from about 750 to about 900 g/3''.
[0103] In a seventh embodiment the present invention provides the
tissue product of any one of the first through the sixth
embodiments comprising at least about 5 percent, by weight of the
tissue product, Southern softwood kraft fibers.
[0104] In an eighth embodiment the present invention provides the
tissue product of any one of the first through the seventh
embodiments comprising Southern softwood kraft fibers having a
coarseness less than about 21 mg/100 m, such as from about 17 to
about 21, and a fiber length greater than about 2.2 mm.
[0105] In a ninth embodiment the present invention provides the
tissue product of any one of the first through the eighth
embodiments wherein the tissue product comprises less than about 5
percent, by weight of the tissue product, NSWK fibers.
[0106] In a tenth embodiment the present invention provides the
tissue product of any one of the first through the ninth
embodiments wherein the tissue product is substantially free from
NSWK fibers.
[0107] In an eleventh embodiment the present invention provides the
tissue product of any one of the first through the tenth
embodiments wherein the tissue product has a CD Stretch from about
4.0 to about 6.0.
[0108] In a twelfth embodiment the present invention provides the
tissue product of any one of the first through the eleventh
embodiments wherein the tissue product has a CD TEA from about 3.5
to about 5.0 gcm/cm.sup.2.
[0109] In a thirteenth embodiment the present invention provides
the tissue product of any one of the first through the twelfth
embodiments wherein the tissue product has a CD Tear from about 10
to about 12 grams.
[0110] In a fourteenth embodiment the present invention provides
the tissue product of any one of the first through the thirteenth
embodiments wherein the tissue product consists essentially of EWHK
and SSWK and has a basis weight less than about 20 gsm, such as
from about 10 to about 20 gsm.
[0111] In a fifteenth embodiment the present invention provides the
tissue product of any one of the first through the fourteenth
embodiments wherein the tissue product has a PPF value greater than
about 32 and a C5 value greater than about 16.
[0112] In a sixteenth embodiment the present invention provides a
wet pressed tissue product comprising at least one multi-layered
tissue web comprising a first and a second layer, the second layer
consisting essentially of low-coarseness SSWK fibers, the tissue
product having a CD Durability Index greater than about 14.0, such
as from about 14.0 to about 20.0 and more preferably from about
15.0 to about 18.0, and a TS7 value less than about 20.0 dB V2 rms,
such as from about 18.0 to about 20.0 dB V2 rms.
[0113] In a seventeenth embodiment the present invention provides
the wet pressed tissue product of the sixteenth embodiment wherein
the tissue product has a basis weight less than about 20 gsm, such
as from about 10 to about 20 gsm and CD Tensile greater than about
400 g/3''.
[0114] In an eighteenth embodiment the present invention provides a
multi-ply tissue product comprising at least one wet pressed tissue
ply having a TS7 value less than about 20.0 dB V2 rms, a CD Tensile
strength greater than about 400 g/3'' and a CD Durability Index
greater than about greater than about 14.0, more preferably greater
than about 14.5 and still more preferably greater than about 15.0,
such as from about 14.0 to about 20.0.
[0115] In a nineteenth embodiment the present invention provides
the tissue product of the eighteenth embodiment wherein the least
one wet pressed tissue ply has a Burst Index greater than about
5.0.
[0116] In a twentieth embodiment the present invention provides the
tissue product of the eighteenth or the nineteenth embodiments
wherein the least one wet pressed tissue ply has a CD TEA Index
greater than about 6.0.
[0117] In a twenty-first embodiment the present invention provides
the tissue product of any one of the eighteenth through twentieth
embodiments having a CD Durability Index greater than about 15.0
and a TS7 value from about 18.0 to about 20.0 dB V2 rm.
[0118] In a twenty second embodiment the present invention provides
the tissue product of any one of the eighteenth through
twenty-first embodiments having a GMT from about 700 to about 1200
g/3'' and more preferably from about 700 to about 1000 g/3'' and
still more preferably from about 750 to about 900 g/3'' and a basis
weight greater than about 30 gsm
* * * * *