U.S. patent application number 12/728352 was filed with the patent office on 2010-11-25 for apparatus suitable for extended nip embossing.
Invention is credited to Kevin Benson McNeil.
Application Number | 20100294449 12/728352 |
Document ID | / |
Family ID | 43123781 |
Filed Date | 2010-11-25 |
United States Patent
Application |
20100294449 |
Kind Code |
A1 |
McNeil; Kevin Benson |
November 25, 2010 |
APPARATUS SUITABLE FOR EXTENDED NIP EMBOSSING
Abstract
An apparatus suitable for use with a web substrate embossing
system is disclosed. The apparatus comprises at least two rolls
juxtaposed in an axially parallel relationship and a continuous
belt capable of providing a compressive force to a corresponding
embossing surface. The continuous belt is disposed about the at
least two rolls. The at least two rolls and continuous belt have an
axis generally corresponding to the corresponding embossing
surface. A first surface of the continuous belt is capable of being
disposed proximate to at least a portion of the corresponding
embossing surface and forming an elongate nip therebetween.
Inventors: |
McNeil; Kevin Benson;
(Loveland, OH) |
Correspondence
Address: |
THE PROCTER & GAMBLE COMPANY;Global Legal Department - IP
Sycamore Building - 4th Floor, 299 East Sixth Street
CINCINNATI
OH
45202
US
|
Family ID: |
43123781 |
Appl. No.: |
12/728352 |
Filed: |
March 22, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12722739 |
Mar 12, 2010 |
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12728352 |
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12469715 |
May 21, 2009 |
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12722739 |
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Current U.S.
Class: |
162/358.3 |
Current CPC
Class: |
B31F 1/07 20130101; B31F
2201/0738 20130101; B31F 2201/0754 20190101 |
Class at
Publication: |
162/358.3 |
International
Class: |
D21F 3/00 20060101
D21F003/00 |
Claims
1. An apparatus suitable for use with an extended nip web substrate
embossing system, the apparatus comprising: at least two rolls
juxtaposed in an axially parallel relationship; and, a continuous
belt capable of providing a compressive force to a corresponding
embossing surface, said continuous belt being disposed about said
at least two rolls, the at least two rolls and continuous belt
having an axis generally corresponding to said corresponding
embossing surface, a first surface of said continuous belt capable
of being proximately disposed to at least a portion of said
corresponding embossing surface and forming an elongate nip
therebetween.
2. The apparatus of claim 1 wherein said first surface of said
continuous belt is deformable.
3. The apparatus of claim 1 wherein said first surface of said
continuous belt further comprises a relieved surface.
4. The apparatus of claim 1 wherein said first surface of said
continuous belt further comprises a first embossing pattern
disposed thereon.
5. The apparatus of claim 4 wherein said first embossing pattern is
disposable upon a web substrate disposed within said elongate
nip.
6. The apparatus of claim 4 wherein said corresponding embossing
surface has a second embossing pattern disposed thereon.
7. The apparatus of claim 6 wherein said second embossing pattern
is disposable upon said web substrate within said elongate nip.
8. The apparatus of claim 6 wherein said first embossing pattern
and said second embossing pattern disposed upon said corresponding
embossing surface are complementary.
9. The apparatus of claim 6 wherein said second embossing pattern
is disposed upon a pattern roll.
10. The apparatus of claim 6 wherein said second embossing pattern
is disposed upon a second continuous belt.
11. The apparatus of claim 1 wherein said axis of said continuous
belt is adjustable relative to said corresponding embossing surface
in order to provide said continuous belt with a compressive force
upon said corresponding embossing surface.
12. The apparatus of claim 11 wherein said compressive force
provided by said continuous belt differs incrementally along said
corresponding embossing surface.
13. The apparatus of claim 1 wherein said axis of said continuous
belt is adjustable relative to said corresponding embossing surface
in order to provide a known position of said continuous belt
relative to said corresponding embossing surface.
14. The apparatus of claim 13 wherein said known position of said
continuous belt relative to the surface of said pattern roll
differs incrementally along said corresponding embossing
surface.
15. The apparatus of claim 1 wherein said axis of said continuous
belt is at least incrementally adjustable relative to said
corresponding embossing surface in order to provide said continuous
belt with a compressive force upon said corresponding embossing
surface.
16. The apparatus of claim 1 wherein said axis of said continuous
belt is at least incrementally adjustable relative to said
corresponding embossing surface in order to provide said continuous
belt with a known position relative to said corresponding embossing
surface.
17. The apparatus of claim 1 wherein said corresponding embossing
surface and said continuous belt are adapted to receive a web
substrate at said elongate nip.
18. The apparatus of claim 1 further comprising a pressure assist
device, said pressure assist device being disposed proximate to a
second surface of said continuous belt, said second surface being
disposed opposite said first surface, said pressure assist device
being adjustable relative to at least one of said second surface of
said continuous belt and said surface of said corresponding
embossing surface.
19. The apparatus of claim 1 further comprising a first positioning
device, said first positioning device controlling a position of
said continuous belt relative to said corresponding embossing
surface.
20. The apparatus of claim 19 further comprising a second
positioning device, said second positioning device controlling a
position of said continuous belt relative to said corresponding
embossing surface.
Description
PRIORITY
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 12/722,739 filed on Mar. 12, 2010 which is a
continuation-in-part of, and claims priority to, U.S. patent
application Ser. No. 12/469,715 filed on May 21, 2009.
FIELD OF THE INVENTION
[0002] The present invention relates to embossing a web substrate
and particularly to decorative embossing a single ply, or multiple
plies, of bath tissue or paper toweling.
BACKGROUND OF THE INVENTION
[0003] Embossing and embossing technology is well known in the
prior art. Embossing is a common technique used for a plurality of
reasons. In a first instance, embossing is a common technique used
to join two plies of paper together in order to form a multi-ply
laminate. The resulting laminate has properties such as caliper,
flexibility, and absorbency not attainable from a single ply having
twice the basis weight of either constituent ply. In this regard,
embossing can be accomplished by one of several known embossing
processes such as knob-to-knob embossing or dual-ply lamination.
Such processes are disclosed in U.S. Pat. Nos. 3,414,459 and
5,294,475. Yet another embossing process for joining two plies
together is called nested embossing and is well known in the
art.
[0004] Also known is the embossing of a single-ply product in order
to provide a decorative appeal to the final embossed product. The
embossment of a single-ply paper product can make the resulting
product more absorbent, softer, and bulkier over a comparative
unembossed product. The embossing of single-ply products can be
accomplished by the use of pin-to-pin embossing where protrusions
on the respective embossing rolls are matched so that the tops of
the corresponding protrusions contact each other through the paper
product. This process results in the compression of the fibrous
structure of the product. Similarly, embossing single-ply products
can be accomplished by the use of male/female embossing (also
called nested embossing) where the protrusions of one or both rolls
are aligned with each a non-protrusion area or a female recession
in the other rolls. Such processes are shown in U.S. Pat. No.
4,921,034.
[0005] With each of the foregoing embossing processes, embossments
are deflected out of the plane of the paper. Such deflection may
desirably increase the caliper of that ply. For example,
conventional embossing may increase caliper 25 to 135% as the
emboss pressures deform the fibers out of the plane of the
paper.
[0006] By embossing out of the plane of the paper, it is meant that
the embossments extend outwardly from the original thickness of the
unembossed paper product. Thus, embossments which are deformed out
of the plane of the paper extend outwardly from the surface of the
paper, thereby increasing its caliper. The aesthetic clarity of the
embossed pattern is directly proportional to the magnitude of the
out-of-plane deformation of these embossments.
[0007] Typical prior art embossing processes can rely upon a
conventional rubber anvil roll and a steel pattern roll to form the
aesthetic pattern. This type of embossing is known to those of
skill in the art as knob-to-rubber embossing (also known as
rubber-to-steel). In knob-to-rubber embossing, a hard embossing
roll having emboss protrusions or emboss knobs disposed in a
desired pattern thereon mates with the surface of a soft impression
roll. As a paper web is passed through the nip formed between these
rolls, the emboss knobs impress the web against and into a soft
impression roll to deform the overall structure and resulting
appearance of the web. In other words, the aesthetic pattern
results from the deformation of the fibers out of the plane of the
paper when the plies are embossed against the deformable anvil
roll. Such a process and apparatus are shown in U.S. Pat. No.
5,436,057.
[0008] The conventional wisdom by users of such rubber-to-steel
techniques provides for the use of a relatively large soft rubber
roll in conjunction with the steel pattern roll. Without desiring
to be bound by theory, the large soft rubber roll deforms
significantly under the pressures developed and necessary to emboss
a paper substrate. This deformation of the large soft rubber roll
provides for nip widths that are significantly greater than a mere
tangential relationship of the lightly contacting rolls forming the
rubber-to-steel system. By providing for a large nip width, the
paper product being deformed therein is provided with a longer
duration in between the two rolls and undergoes significant product
deformation to provide a product having relatively deep
embossments. These embossments have been found to be highly
desirable to consumers.
[0009] However, it is also known to these practitioners that there
is an associated loss in tensile strength caused by these
out-of-plane embossments. It is not uncommon for certain substrates
to suffer a 20 to 40% tensile loss during such conventional
embossing processes. Additionally, such systems have been found to
degrade the apparent softness of the resulting structure. This
softness degradation has been attributed to the tactile sensation
caused by these out-of-plane embossments.
[0010] In light of these defects in the known prior art, it was
surprisingly found that providing a high level of visual contrast
between the embossment and un-embossed regions of a paper structure
surrounding the embossment can communicate depth and effective
embossing to these consumers. Even more surprising, it was found
that this high level of visual contrast between the embossment and
un-embossed regions of a paper structure can be provided at a
significantly higher line speed if the emboss process utilizes a
first relatively hard anvil roll followed by a relatively soft
emboss roll.
SUMMARY OF THE INVENTION
[0011] An exemplary embodiment of the present invention provides
for an apparatus suitable for use with a web substrate embossing
system. The apparatus comprises at least two rolls that are
juxtaposed in an axially parallel relationship and a continuous
belt capable of providing a compressive force to a corresponding
embossing surface. The continuous belt is disposed about the at
least two rolls. The at least two rolls and continuous belt have an
axis generally corresponding to the corresponding embossing
surface. A first surface of the continuous belt is capable of being
disposed proximate to at least a portion of the corresponding
embossing surface and forming an elongate nip therebetween.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a schematic side elevational view of an apparatus
for embossing paper according to the present invention.
[0013] FIG. 1A is an enlarged view of the region labeled 1A of FIG.
1;
[0014] FIG. 2 is a schematic side elevational view of an
alternative embodiment for embossing paper;
[0015] FIG. 3 is a schematic side elevational view of yet another
alternative embodiment for embossing paper;
[0016] FIG. 3A is a schematic side elevational view of still
another alternative embodiment for embossing paper;
[0017] FIG. 3B is a schematic side elevational view of still yet
another alternative embodiment for embossing paper;
[0018] FIG. 3C is a schematic side elevational view of yet another
alternative embodiment for embossing paper;
[0019] FIG. 4 is a schematic side elevational view of still another
alternative embodiment for embossing paper and,
[0020] FIG. 5 is a schematic side elevational view of another
alternative embodiment for embossing paper.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The instant invention can be neatly parsed into three easily
recognizable portions. These are: 1) the apparatus for producing an
embossed substrate; 2) the process for making an embossed
substrate; and 3) the unique embossed substrate produced by the
described apparatus. The description of each section of the claimed
apparatus is described forthwith.
Apparatus
[0022] Referring to FIGS. 1 and 1A, the embossing apparatus of the
present invention can be provided with at least two cylindrical
axially parallel rolls juxtaposed to form a nip therebetween. The
first roll is a corresponding embossing surface such as a pattern
roll 12 that has protuberances 30 extending radially outward from
the periphery of the roll 12. The second roll is an anvil roll 14
and has a surface which is generally smooth to the naked eye.
Preferably, the anvil roll 14 has a machined surface with a finish
of 32 micro inches or less.
[0023] The pattern roll 12 can comprise any combination of `line`
emboss elements and `dot` emboss elements. A line emboss element
can be characterized by having a depth relative to the surface of
the respective surface of a web material. A line emboss element can
also characterized by having a total embossment length to total
embossment width (or an aspect ratio) of greater than 1. A dot
emboss element can be characterized by having a depth relative to
the surface of the web material. A dot emboss element can also be
characterized by having a total embossment length to total
embossment width (or an aspect ratio) of 1.
[0024] In a preferred embodiment, neither the pattern roll 12 nor
the anvil roll 14 deform during the embossing process. However,
while some theoretical deformation in response to an applied load
may be predicted, the pattern roll 12 and the anvil roll 14 are
sufficiently non-deformable and rigid to obviate deformation which
permits out-of-plane embossments to be formed in the paper web 18.
In one embodiment, the anvil roll 14 may be a crowned roll. In a
preferred embodiment, deflection of the pattern roll 12 and anvil
roll 14 is minimized and controlled in a predictable manner.
[0025] Each of the pattern rolls 12 and anvil rolls 14 is
preferably formed from steel and more preferably hardened, although
any relatively non-deformable rigid material may be used. It is
preferred that the anvil roll 14 not be provided with a softer
rubber cover. In stark contrast, a very hard roll, such as an anvil
roll 14 having a cover with a hardness of less than about 40
P&J, more preferably less than about 30 P&J, even more
preferably less than about 20 P&J, and yet more preferably less
than about 10 P&J as measured with a 1/8-inch diameter ball
under a constant load of one kilogram at a temperature of
70.degree. F. after sixty seconds, is best suited for the instant
application. By way of non-limiting example, it was found suitable
that the pattern roll 12 is provided with a 14-inch diameter and
the corresponding anvil roll 14 is provided with a 7-inch
diameter.
[0026] Preferably, the pattern roll 12 is stationary, and the anvil
roll 14 is loaded although, if desired, the opposite arrangement
could be used. Alternatively, each of the pattern roll 12 and anvil
roll 14 could be pneumatically, hydraulically, or linear actuator
loaded and biased towards the other pattern 12 or anvil roll 14.
Load cells may be incorporated into the mounting of each of the
pattern roll 12 and anvil roll 14 to equalize loading across the
nip to allow for monitoring pressure fluctuations during
embossing.
[0027] Alternatively, the pattern roll 12 and the anvil roll 14 are
diametrically loaded together along the plane connecting the
centers of the pattern roll 12 and anvil roll 14. The pattern roll
12 and anvil roll 14 may be loaded together by pneumatic, or
preferably hydraulic, loading cylinders, or more preferably by
linear actuators. Preferably, there is one loading cylinder at each
end of the pattern roll 12 and anvil roll 14 to be pneumatically,
or more preferably is hydraulically or via linear actuator loaded.
However, one of skill in the art will understand that engagement
between the pattern roll 12 and anvil roll 14 may be controlled by
pneumatic loading cylinders, hydraulic loading cylinders, rotation
of a ball/screw mechanism in a linear actuator, or any other
suitable means, to load both ends of the anvil roll 14 against both
ends of the pattern roll 12 with a desired first force or to a
desired first amount of engagement.
[0028] An exemplary, but non-limiting, embossing process of the
present invention may comprise any form of dual or multi-nip
configurations. These processes may comprise unwinding a sheet of
web substrate 26, such as a paper web, from a supply roll,
controlling the speed of the web substrate, directing the web
substrate 26 into the embossing nips, and then subsequently
transporting the final web product to any additional desired
converting operations. Such additional converting operations may
include printing, coating, perforating, folding, cutting, winding,
and the like. In a preferred embodiment, the tension of the web
substrate 26 can be controlled relative to a target tension.
[0029] Embossing, according to the present invention, occurs at an
embossing pressure of at least about 1,000 psi and preferably
between about 1,000 psi to about 10,000 psi, even more preferably
between about 1,000 psi and about 5,000 psi, and more preferably
from about 1,000 psi to about 3,000 psi. The desired embossing
pressure is dependent upon the substrate, particularly the caliper,
surface topography, and furnish of the paper web 18 to be embossed.
As the surface texture topography increases, generally greater
embossing pressure is required according to the present
invention.
[0030] It is known that embossing pressure can be determined by the
following formula:
EP=AL/(NA.times.PLA)
[0031] Where:
[0032] EP is the embossing pressure;
[0033] AL is the applied load;
[0034] NA is the nip area; and,
[0035] PLA is the pattern land area
[0036] The applied load is the sum of the weight of the upper
embossing roll (either the pattern roll 12 or the anvil roll 14, as
the case may be) and the pressure applied through the loading
cylinders used to compress the pattern roll 12 and anvil roll 14
together. If the loading plane connecting the centers of the anvil
roll 14 and the pattern roll 12 is not vertical, only the vertical
component of the weight of the upper embossing roll (either pattern
roll 12 or anvil roll 14) that is applied to the paper web 18 is
considered in determining the applied load.
[0037] The nip area is the multiple of the nip width (NW) and the
lesser of the width of the pattern roll 12 and anvil roll 14. The
width of the paper web 18 is taken parallel to the axes of the
pattern roll 12 and anvil roll 14. The nip width (NW) is taken
parallel to the machine direction.
[0038] It has been surprisingly found that the nip width (NW) can
be estimated by the following relationship:
NW = [ 5.8 .times. 10 - 6 LTD 1 D 2 P 1.35 D 1 + D 2 ] 0.81 D 1 -
0.232 ##EQU00001##
[0039] Where:
[0040] D1 is the anvil roll 14 diameter in units of inches;
[0041] D2 is the pattern roll 12 diameter in units of inches;
[0042] L is the nip load in pounds per linear inch;
[0043] T is the thickness of the anvil roll 14 cover in units of
inches; and,
[0044] P is the rubber hardness in units of P&J.
[0045] Referring again to FIG. 1, the exemplary embodiment of the
present invention shown in plan view of the embossing apparatus 10
provides for a pattern roll 12, an anvil roll 14, and an embossing
roll 16. The paper web 18 is passed between the nip formed between
anvil roll 14 and pattern roll 12 and subsequently the nip formed
between embossing roll 16 and pattern roll 12. In a preferred
embodiment, as the paper web 18 passes between pattern roll 12 and
anvil roll 14, the paper web 18 is disposed onto the protuberances
30 disposed about pattern roll 12.
[0046] In a preferred embodiment of the present invention, passing
the paper web 18 between anvil roll 14 and pattern roll 12 prior to
any additional steps is believed to be beneficial because the paper
web is placed in a position relative to the protuberances 30
disposed upon the pattern roll in a position that effectively
reduces the movement of the paper web 18 relative to the pattern
roll 12. In other words, the paper web 18 is locked onto each of
the protuberances 30 disposed upon pattern roll 12 due to a
pressure exerted by anvil roll 14 upon pattern roll 12 and the
protuberances 30 disposed thereon.
[0047] Without desiring to be bound by theory, it is believed that
providing the embossing step, as that claimed by the instant
invention, prior to any additional embossing or gluing steps can
provide for final web product 28 having a better embossed quality
and better consumer acceptance.
[0048] Referring again to FIG. 1, the paper web 18 is first passed
between anvil roll 14 and pattern roll 12. At that point, the paper
web 18 is effectively pressed onto the protuberances 30 disposed
upon pattern roll 12. The paper web 18 then proceeds upon the
surface of rotating pattern roll 12 to embossing roll 16 which can
then further emboss and/or densify the paper web 18 in the region
disposed between embossing roll 16 and pattern roll 12. Preferably
embossing roll 16 has a hardness of greater than about 40 P&J,
more preferably greater than about 70 P&J, even more preferably
greater than about 90 P&J, even yet more preferably greater
than about 100 P&J, yet still more preferably greater than
about 120 P&J, and yet even more preferably greater than about
130 P&J. The resulting final web product 28 can be provided
then with embossments having a very high level of contrast between
the embossed and unembossed areas disposed upon paper web 18 as
formed into final web product 28. It was surprisingly found that
the arrangement of anvil roll 14, embossing roll 16, and pattern
roll 12 can provide a better quality embossed final web product 28
at significantly higher line speeds than a final product produced
from the systems described in the known prior art. Naturally, the
production of a final web product 28 having high quality
embossments produced at a very high line speed compared to those of
the prior art can significantly reduce the cost associated with
producing the final web product 28 as compared with those systems
of the known prior art.
[0049] It was also found that the anvil roll 14 and embossing roll
16 can be produced to have a smaller diameter than the rolls used
with equipment associated with the known prior art. In a preferred
embodiment of the present invention, the anvil roll 14 and
embossing roll 16 are provided with a diameter less than about 19
inches, preferably less than about 15 inches, yet more preferably
less than about 10 inches, more preferably 5 inches to 10 inches,
and most preferably about 7 inches.
[0050] In a preferred embodiment of the present invention, the
protuberances 30 disposed upon the pattern roll 12 are provided
with a transition region having a known radius of curvature. Such a
transition region disposed upon protuberance 30 of pattern roll 12
is disposed between the distal end of the protuberance and the
known sidewall of the protuberance. In a preferred embodiment of
the present invention, the radius of curvature of the transition
region disposed upon protuberance 30 of pattern roll 12 has a
radius of greater than about 0.075 mm. In other embodiments of the
present invention, the radius of curvature of the transition region
disposed upon protuberance 30 of pattern roll 12 is greater than
about 0.1 mm, more preferably greater than about 0.25 mm. even more
preferably greater than about 0.5 mm, and most preferably ranges
from between about 0.075 mm and about 0.5 mm. In any regard, it is
preferred that the radius of curvature disposed upon protuberance
30 of pattern roll 12 be less than about 1.8 mm. In other preferred
embodiments of the present invention, the radius of curvature of
protuberance 30 disposed upon pattern roll 12 is less than about
0.75 mm, more preferably ranges from between about 0.10 mm and
about 0.50 mm, yet more preferably ranges from between about 0.20
mm and about 0.50 mm, and most preferably ranges from between about
0.20 mm and about 0.30 mm.
[0051] It was found that providing the protuberance 30 with a
radius of curvature proximate to the distal end of the protuberance
30 disposed upon pattern roll 12 can result in a circular arc from
which the radius of curvature can be determined as a traditional
radius of curvature of an arc. However, it should be realized by
one of skill in the art that the present invention also
contemplates transition region configurations which are proximate
and are ground by having the edge of the transition region of the
protuberance 30 disposed upon pattern roll 12 removed by one or
more straight line or irregular cut lines. In such a case, the
release of curvature of the protuberance 30 can be determined by
measuring the radius of curvature of a circular arc that includes a
portion which approximates the curve of the transition region of
the protuberance 30.
[0052] In other embodiments, at least a portion of the distal end
of the protuberance 30 disposed upon pattern roll 12 (other than
the transition region) can be generally non-planar (i.e., generally
curved or rounded). It is in this way that the entire surface of
the protuberance 30 disposed upon pattern roll 12 spanning between
the sidewalls of the protuberance 30 can be non-planar. Such
non-planar surfaces can take any shape, such as curved or rounded,
but are not necessarily limited to smooth curves or curves as
described above. This may include a number of straight line or
irregular cuts to provide a non-planar surface. While not desiring
to be bound by theory, it is believed that rounding the transition
regions of the protuberances 30 or any portion of the distal end of
the protuberances 30 can provide the final web product 28 with
embossments that are more blunt with fewer rough edges, thereby
preventing tearing of the web and providing the resulting embossed
final web product 28 with a smoother and/or softer look and/or
feel.
[0053] As shown in FIG. 2, exemplary apparatus 10A for embossing a
paper web 18 can comprise a pattern roll 12 and any number of
additional rolls as required by the process to produce final web
product 28. As shown, pattern roll 12 is accompanied by anvil roll
14, embossing roll 16, and a secondary roll 20 that can provide
embossments upon paper web 18 to produce final web product 28. As
shown, it is preferred that anvil roll 14 have a hardness of less
than about 40 P&J, more preferably less than about 30 P&J,
even more preferably less than about 20 P&J, and yet more
preferably less than about 10 P&J in order to lock the unformed
web substrate 26 upon the protuberances 30 disposed upon pattern
roll 12. As the paper web 18 progresses through the apparatus 10A,
embossing roll 16 can further compress the paper web 18 upon the
protuberances 30 disposed upon pattern roll 12. Similarly,
secondary roll 20 can provide yet further embossment of the paper
web 18 as may be required to produce final web product 28. It has
been found that embossing a paper web 18 with two or more nips
while the paper web 18 remains in contact with the pattern roll 12
can provide a deeper, more appealing emboss impression with less
degradation to the paper web 18 strength than embossing the paper
web 18 in a single nip as in the prior art.
[0054] In the alternative embodiment provided in FIG. 3, a belt
mechanism 22 can be utilized to form an extended emboss nip in
order to provide embossments upon paper web 18 to produce final web
product 28. A belt 24 can be positioned adjacent to pattern roll 12
such that the surface of the pattern roll 12 and the surface of the
belt 24 are in contact or overlap one another. The belt 24 contact
or overlap with the pattern roll 12 surface may extend for a
portion of the pattern roll 12 circumference to provide increased
distance and time for more effective image formation in a web
substrate 26 disposed between the pattern roll 12 and the belt 24.
The portion of the pattern roll 12 surface contacting the belt 24
may range from 2 degrees of the pattern roll 12 circumference to as
much as 200 degrees of the pattern roll 12 circumference. In a
preferred embodiment, the belt 24 and the pattern roll 12 may be
driven by means known in the art such that their surface speeds are
essentially equal. Additionally, the belt 24 may be loaded against
the pattern roll 12 by pressure regulation means known in the art,
such as air cylinders, hydraulic cylinders, load sensing linear
actuators, mechanical springs, and the like. Alternatively, the
belt 24 may be loaded against the pattern roll 12 by displacement
regulation means known in the art, such as air cylinder loading
against mechanical stops, linear actuators, ball/screw mechanisms,
and the like. In any regard, the belt 24 operates in cooperation
with the pattern roll 12 to impart an image corresponding to the
pattern on the pattern roll 12 into a web substrate 26 disposed
between the pattern roll 12 and the belt 24.
[0055] As shown in FIG. 3, unformed web substrate 26 in the form of
paper web 18 can be transported into contact with pattern roll 12
and belt mechanism 22 comprising belt 24. In a preferred
embodiment, the belt 24 is driven at a surface speed that
corresponds to the speed of the incoming paper web 18. A
positioning device (not shown), such as linear actuators, servo
motors, cams, links, and the like known by those of skill in the
art as useful for such a result, can to be provided for control of
the position of the belt 24 relative to pattern roll 12. It is
believed in this way the position of the belt 24 of belt mechanism
22 can provide the required contact, clearance, and/or pressure
between the belt 24 and the pattern roll 12 in order to provide
embossments upon paper web 18 to form final web product 28. Such
contact, clearance, and/or pressure may be uniform throughout the
length of contact of pattern roll 12 and belt 24.
[0056] Alternatively, the contact, clearance (i.e., distance),
and/or pressure between the belt 24 and the pattern roll 12 may
differ incrementally throughout the length of contact of pattern
roll 12 and belt 24. Such incremental differences may constitute
desired differential profiles of contact, clearance, and/or
pressure between the belt 24 and the pattern roll 12. For example,
the contact, clearance, and/or pressure at the beginning of the nip
formed between the belt 24 and the pattern roll 12 may be less than
the contact, clearance, and/or pressure at the end of the nip
formed between the belt 24 and the pattern roll 12. Alternatively,
the contact, clearance, and/or pressure at the beginning of the nip
formed between the belt 24 and the pattern roll 12 may be less than
the contact, clearance, and/or pressure in a central portion of the
nip formed between the belt 24 and the pattern roll 12 and yet
again different than the contact, clearance, and/or pressure at the
end of the nip formed between the belt 24 and the pattern roll
12.
[0057] Optionally, belt mechanism 22 can maintain a fixed position
and pattern roll 12 can be adjusted relative to the belt 24
disposed about belt mechanism 22 in order to provide the desired
contact, clearance, and/or pressure between the belt 24 and pattern
roll 12. In any regard, it is preferable that the belt 24 be loaded
against the pattern roll 12 in order to achieve the embossment
desired in a final web product 28.
[0058] The belt 24 may comprise a deformable surface such as a
synthetic rubber as known in the art which, when loaded against the
pattern roll 12 with a web substrate 26 disposed on the pattern
roll 12 surface, deforms the sheet on and around the protuberances
30 disposed about the pattern roll 12 surface, thereby imparting
the desired emboss pattern image onto the web substrate 26.
[0059] If so desired, the belt 24 disposed about belt mechanism 22
may be provided with a relieved surface or complimentary to the
embossing pattern disposed upon the pattern roll 12. In this
embodiment, the relief portions can be provided as a pattern
disposed upon or within the material comprising belt 24. Such a
pattern may be disposed upon or otherwise associated with belt 24
by laser engraving, mechanical implantation, polymeric curing, or
the like. In an exemplary, but non-limiting embodiment, such a
pattern, relieved or otherwise, may correspond to the individual
protuberances forming the embossment pattern disposed about pattern
roll 12. The belt 24 pattern may be registered to the pattern roll
12 embossing pattern and driven by means known in the art to
maintain the registration at all times. The belt 24 position may be
controlled such that the distal ends of the belt 24 pattern
elements extend into any relieved portion corresponding to any
protuberances 30 disposed upon the pattern roll 12. The depth of
engagement between the belt 24 pattern elements and the
protuberances 30 disposed upon pattern is roll 12, as well as any
clearance between mating pattern elements, can be controlled to
impart a desired embossing image onto the web substrate 26. The
depth of engagement between the pattern roll 12 and the belt 24 may
be controlled by adjusting the distance between the pattern roll 12
and the belt 24 by rotation of a ball/screw mechanism in a linear
actuator, wherein the linear actuator is coupled to the pattern
roll 12 or belt 24, or by other suitable means.
[0060] As shown in FIG. 4, unformed web substrate 26 in the form of
paper web 18 can be transported into contact with belt mechanism 22
comprising belt 24 and another form of corresponding embossing
surface--here embossing belt mechanism 38 comprising pattern belt
40. In a preferred embodiment, the belt 24 and belt 40 are both
driven at a surface speed that corresponds to the speed of the
incoming paper web 18. Positioning devices (not shown), such as
linear actuators, servo motors, cams, links, and the like known by
those of skill in the art as useful for such a result, can be
provided to control of the position of the belt 24 relative to
pattern belt 40. It is believed in this way the position of the
belt 24 of belt mechanism 22 can provide the required contact,
clearance, and/or pressure between the belt 24 and the pattern belt
40 in order to provide embossments upon paper web 18 to form final
web product 28. Such contact, clearance, and/or pressure may be
uniform throughout the length of contact of pattern belt 40 and
belt 24.
[0061] Alternatively, the contact, clearance (i.e., distance),
and/or pressure between the belt 24 and the pattern belt 40 may
differ incrementally throughout the length of contact of pattern
belt 40 and belt 24. Such incremental differences may constitute
desired differential profiles of contact, clearance, and/or
pressure between the belt 24 and the pattern belt 40. For example,
the contact, clearance, and/or pressure at the beginning of the nip
formed between the belt 24 and the pattern belt 40 may be less than
the contact, clearance, and/or pressure at the end of the nip
formed between the belt 24 and the pattern belt 40. Alternatively,
the contact, clearance, and/or pressure at the beginning of the nip
formed between the belt 24 and the pattern belt 40 may be less than
the contact, clearance, and/or pressure in a central portion of the
nip formed between the belt 24 and the pattern belt 40 and yet
again different than the contact, clearance, and/or pressure at the
end of the nip formed between the belt 24 and the pattern belt
40.
[0062] Optionally, belt mechanism 22 can maintain a fixed position
and pattern belt 40 can be adjusted relative to the belt 24 in
order to provide the desired contact, clearance, and/or pressure
between the belt 24 and pattern belt 40. In any regard, it is
preferable that the belt 24 be loaded against the pattern belt 40
in order to achieve the embossment desired in a final web product
28.
[0063] Both belt 24 and pattern belt 40 may comprise a deformable
surface such as a synthetic rubber as known in the art which, when
loaded against each other with a web substrate 26 disposed on the
pattern belt 40 surface, deforms the web substrate 26 on and around
any is protuberances 30 disposed about the pattern belt 40 surface,
thereby imparting the desired emboss pattern image onto the web
substrate 26.
[0064] If so desired, the belt 24 may be provided with a relieved
surface complimentary to the embossing pattern or relieved surface
disposed upon the pattern belt 40. In this embodiment, the relief
portions can be provided as a pattern disposed upon or within the
material comprising belt 24 and/or pattern belt 40. Such a pattern
may be disposed upon or otherwise associated with belt 24 and/or
pattern belt 40 by laser engraving, mechanical implantation,
polymeric curing, or the like. In an exemplary, but non-limiting
embodiment, such a pattern, relieved or otherwise, may correspond
to the individual protuberances forming the embossment pattern
disposed about pattern belt 40. The belt 24 pattern may be
registered to the pattern belt 40 embossing pattern and driven by
means known in the art to maintain the registration at all times.
The belt 24 position may be controlled such that the distal ends of
the belt 24 pattern elements extend into any relieved portion
corresponding to any protuberances 30 disposed upon the pattern
roll 12. The depth of engagement between the belt 24 pattern
elements and the protuberances 30 disposed upon pattern belt 40, as
well as any clearance between mating pattern elements, can be
controlled to impart a desired embossing image onto the web
substrate 26. The depth of engagement between the pattern belt 40
and the belt 24 may be controlled by adjusting the distance between
the pattern belt 40 and the belt 24 by rotation of a ball/screw
mechanism in a linear actuator, wherein the linear actuator is
coupled to the pattern belt 40 or belt 24, or by other suitable
means.
[0065] In an alternative embodiment of a dual or multi-nip
embossing process, the web substrate 26 may be embossed in a first
emboss nip, formed by engagement between a first pattern roll 12
and a second pattern roll (not shown). The first pattern roll 12
and second pattern roll may have complementary patterns wherein the
raised elements on one pattern roll may be registered and engaged
with corresponding recesses in the opposing pattern roll. Passing
the web substrate 26 between the first pattern roll 12 and the
second pattern roll while the two pattern rolls are engaged at a
first depth of engagement can provide a desired emboss impression
in the web substrate 26. Engagement between the first pattern roll
12 and the second pattern roll may be controlled by adjusting the
distance between the center of the first pattern roll 12 and the
center to of the second pattern roll by rotating a ball/screw
mechanism in a linear actuator, wherein the linear actuator is
coupled to one of the pattern rolls, to load the first pattern roll
12 and second pattern roll toward one another to a desired first
depth of engagement. After passing through the first emboss nip
formed by the first pattern roll 12 and the second pattern roll,
the web substrate 26 may be further embossed in a second nip,
formed by engagement between the first pattern roll 12 and a third
pattern roll (not shown), wherein the third pattern roll also has a
pattern complementary to the first pattern roll 12, to a desired
second depth of engagement. In an alternative embodiment, three or
more complementary pattern rolls may be used to emboss the web
substrate 26 while the web substrate 26 is in contact with the
first pattern roll 12. In yet another embodiment, the web substrate
26 may be embossed in two or more nips while the web substrate 26
remains in contact with a first pattern roll 12 wherein the first
nip may comprise either an anvil roll 14 or a second pattern roll
and the second nip may comprise either a second pressure roll or a
third pattern roll.
[0066] As would be known to one of skill in the art, a pattern
disposed upon belt 24 may be formed by first applying a synthetic
rubber surface to the belt 24 and subsequently laser engraving the
rubber surface to create the desired pattern. Other suitable
materials may also be used for the belt 24 surface, such as metals,
photopolymers, and the like. Other means known in the art may also
be used to create the desired pattern upon belt 24, such as
machining, photo engraving, and the like. It is believed that such
an exemplary pattern associated with belt 24 may be registered with
respect to any direction or directions of paper web 18,
particularly the machine and cross-machine direction of paper web
18.
[0067] As shown in FIG. 3A, a pressure assist device 30 is
preferably disposed adjacent the inwardly facing surface of the
belt 24. It is preferred that pressure assist device 30 be
positioned in order to support conveyor belt 24 as conveyor belt 16
contacts pattern roll 12.
[0068] It was found in certain embodiments that belt 24 tended to
deflect away from the pattern roll 12 when belt 24 was engaged with
the pattern roll 12. In other words, as the total surface area of
belt 24 that was conformably disposed about pattern roll 12 and any
web substrate 26 disposed thereabout, the desired pressure per unit
area at the point where web substrate 26 contacted the surface of
belt 24 to the pattern roll 12 decreased.
[0069] Thus, the surprising solution was to provide for a pressure
assist device 30 with belt 24. It was surprisingly found that
pressure assist device 30 reduced the deformation of belt 24 away
from pattern roll 12. This allowed belt 24 to be moved relative to
pattern roll 12 in order to more accurately apply the desired
amount of pressure or distance between belt 24 and pattern roll 12
to more precisely. It was also surprisingly found that the
incorporation of pressure assist device 30 with belt 24 could
facilitate the application of pressure, or force, between belt 24
and pattern roll 12 in better conformity with a desired wind
profile of a final web product 28.
[0070] As shown in FIGS. 3A and 4, pressure assist device 30 (30a)
could be provided by one of skill in the art as a flat plate 32 (or
plurality of flat plates comprising first flat plate 34 and second
flat plate 36). As shown in FIG. 3B, pressure assist device 30
could be provided by one of skill in the art as a series of flat
plates 34. Such a flat plate 32 or series of flat plates 34 could
be fixably mounted relative to the inside of belt 24 according to
methods known to those of skill in the art. One of skill in the art
will readily recognize that by providing pressure assist device 30
as a plurality or series of plates can also assist in the providing
the pressure assist device 30 with the capability of applying an
incrementally differing the contact, clearance (i.e., distance),
and/or pressure between the belt 24 and the pattern roll 12
throughout the length of contact of pattern roll 12 and belt 24. If
such an incrementally different contact, clearance (i.e.,
distance), and/or pressure between the belt 24 and the pattern roll
12 is desired, one of skill in the art would be able to adapt each
of the plurality or series of plates with the capability of
independent movement relative to each other as well as relative to
the inside of belt 24.
[0071] Additionally, it should be understood that pressure assist
device 30 could move relative to the inside of belt 24 by the use
of a positioning device (not shown), such as linear actuators,
servo motors, cams, links, and the like known by those of skill in
the art as useful for such a result, to control of the position of
pressure assist device 30 relative to belt 24. Suitable positioning
devices (not shown) associated with pressure assist device 30
should preferably be capable of moving either end of pressure
assist device 30 relative to belt 24 generally parallel to the
Z-direction relative to web substrate 26 as web substrate 26 passes
proximate to, and in eventual contacting engagement with, pattern
roll 12. Either the leading edge or trailing edge of pressure
assist device 30 is preferably positionable either jointly or
severally. However, it should be realized that pressure assist
device 30 can have a respective axis in virtually any direction
required to provide the required contact clearance, and/or pressure
between the belt 24 and the pattern roll 12.
[0072] In such an embodiment as shown in FIGS. 3A-3B it can be
preferred to provide the surface of pressure assist device 30
contacting the inwardly facing surface of belt 24 as a surface
having reduced friction in order to extend belt 24 life. Manners
and processes of providing a reduced friction surface would be
known to those of skill in the art of reducing the frictional
forces of contacting surfaces. Such methods may incorporate the
application of lubricants to the surface of pressure assist device
30. Another embodiment may provide for the incorporation and/or
deposition of materials having known low coefficients of friction
upon the surface of pressure assist device 30. Yet another
embodiment to reduce frictional forces may provide for the
application and/or injection of air into the interstice formed
between the outwardly facing surface of pressure assist device 30
and belt 24. Still yet another embodiment to reduce frictional
forces may provide for the provision of pressurized air to be
emitted from the surface of pressure assist device 30 from the
interior of pressure assist device 30 through a plurality of holes
connecting the interior of pressure assist device 30 and the outer
surface of pressure assist device 30 that contacts belt 24. In a
preferred embodiment, the tension of belt 24 could be minimized to
reduce any resulting frictional forces disposed upon pressure
assist device 30.
[0073] The pressure assist device 30 may be provided as a plate
having chamfered trailing and/or leading edges. It was surprisingly
found that providing pressure assist device 30 in the form of a
plate having chamfered trailing and leading edges can significantly
increased belt 24 life by reducing the opportunity for
imperfections present upon the belt 24 from impacting a hard
trailing and/or leading edge present upon pressure assist device
30.
[0074] Alternatively and as shown in FIG. 3C, it should also be
realized by one of skill in the art that the surface of pressure
assist device 30 contacting belt 24 can be provided as a
curvilinear surface 34 forming an arc of a circle (or a hyperbola)
in the MD direction. Such an arc of a curvilinear surface 34
forming pressure assist device 30 should conform, or be conformable
with, the surface of pattern roll 12. In yet another alternative
embodiment, pressure assist device 30 could be provided as a roller
(not shown). It would also be appreciated by one of skill in the
art that pressure assist device 30 could be provided as a plurality
of rollers (not shown) that are displaced in a collectively linear
manner along the inner surface of belt 24. Disposing a plurality of
rollers in this manner cold result in the application of a
consistent pressure along the inner surface of belt 24 and a
resulting consistent pressure being applied to the surface of
pattern roll 12 by belt 24. Alternatively, each roller of a
plurality of rollers could be provided with an incrementally
different pressure being applied to selected regions of the inner
surface of belt 24. This could result in the application of a
corresponding differential pressure being applied to the surface of
pattern roll 12 by belt 24. In any regard, it should be realized by
one of skill in the art that any combination of pressure assist
devices can be used (i.e., plates, curvilinear surfaces, and
rollers, and the like, and combinations thereof) in order to
provide the desired pressure (i.e., constant, fixed, variable, and
combinations thereof) or the desired displacement (i.e., constant,
fixed, variable, and combinations thereof) on the second surface of
the continuous belt 24.
[0075] As shown in FIG. 5, an alternative apparatus 10C is shown in
its simplest form. As depicted, pattern roll 12 is accompanied by a
singular roll--in this case, anvil roll 14. Thus, it should be
realized that as paper web 18 approaches the interstice formed
between pattern roll 12 and anvil roll 14, the anvil roll 14 is
provided with sufficient pressure in order to confine paper web 18
against individual protuberances 30 disposed about pattern roll 12
to provide the unformed web substrate 26 to be converted to final
web product 28 having the desired embossments disposed
thereupon.
Process
[0076] A preferred soft tissue paper of the present invention
further comprises papermaking fibers of both hardwood and softwood
types wherein at least about 50% of the papermaking fibers are
hardwood and at least about 10% are softwood. The hardwood and
softwood fibers are most preferably isolated by relegating each to
separate layers wherein the tissue comprises an inner layer and at
least one outer layer. It should be realized by one of skill in the
art that any substrate suitable for providing a product consistent
with the present invention may be suitable for use herein.
[0077] A preferred tissue paper product of the present invention is
preferably creped, i.e., produced on a papermaking machine
culminating with a Yankee dryer to which a partially dried
papermaking web is adhered and upon which it is dried and from
which it is removed by the action of a flexible creping blade.
[0078] Creping is a means of mechanically compacting paper in the
machine direction. The result is an increase in basis weight (mass
per unit area) as well as dramatic changes in many physical
properties, particularly when measured in the machine direction.
Creping is generally accomplished with a flexible blade, a
so-called doctor blade, against a Yankee dryer in an on machine
operation.
[0079] A Yankee dryer is a large diameter, generally 8-20 foot drum
which is designed to be pressurized with steam to provide a hot
surface for completing the drying of papermaking webs at the end of
the papermaking process. The paper web which is first formed on a
foraminous forming carrier, such as a Fourdrinier wire, where it is
freed of the copious water needed to disperse the fibrous slurry is
generally transferred to a felt or fabric in a so-called press
section where de-watering is continued either by mechanically
compacting the paper or by some other de-watering method such as
through-drying with hot air, before finally being transferred in
the semi-dry condition to the surface of the Yankee for the drying
to be completed.
[0080] While the characteristics of the creped paper webs,
particularly when the creping process is preceded by methods of
pattern densification, are preferred for practicing the present
invention, un-creped tissue paper is also a satisfactory substitute
and the practice of the present invention using un-creped tissue
paper is specifically incorporated within the scope of the present
invention. Un-creped tissue paper, a term as used herein, refers to
tissue paper which is non-compressively dried, most preferably by
through-drying. Resultant through air dried webs are pattern
densified such that zones of relatively high density are dispersed
within a high bulk field, including pattern densified tissue
wherein zones of relatively high density are continuous and the
high bulk field is discrete.
[0081] To produce un-creped tissue paper webs, an embryonic web is
transferred from the foraminous forming carrier upon which it is
laid, to a slower moving, high fiber support transfer fabric
carrier. The web is then transferred to a drying fabric upon which
it is dried to a final dryness. Such webs can offer some advantages
in surface smoothness compared to creped paper webs.
[0082] Tissue paper webs are generally comprised essentially of
papermaking fibers. Small amounts of chemical functional agents
such as wet strength or dry strength binders, retention aids,
surfactants, size, chemical softeners, crepe facilitating
compositions are frequently included but these are typically only
used in minor amounts. The papermaking fibers most frequently used
in tissue papers are virgin chemical wood pulps. Additionally,
filler materials may also be incorporated into the tissue papers of
the present invention.
[0083] Preferably, softening agents such as quaternary ammonium
compounds can be added to the papermaking slurry. Preferred
exemplary quaternary compounds have the formula:
(R.sub.1).sub.4-m--N.sup.+--[R.sub.2].sub.mX.sup.- [0084] wherein:
[0085] m is 1 to 3; [0086] R.sub.1 is a C.sub.1-C.sub.6 alkyl
group, hydroxyalkyl group, hydrocarbyl or substituted hydrocarbyl
group, alkoxylated group, benzyl group, or mixtures thereof; [0087]
R.sub.2 is a C.sub.14-C.sub.22 alkyl group, hydroxyalkyl group,
hydrocarbyl or substituted hydrocarbyl group, alkoxylated group,
benzyl group, or mixtures thereof; and [0088] X.sup.- is any
softener-compatible anion are suitable for use in the present
invention.
[0089] Preferably, each R.sub.1 is methyl and X.sup.- is chloride
or methyl sulfate. Preferably, each R.sub.2 is C.sub.16-C.sub.18
alkyl or alkenyl, most preferably each R.sub.2 is straight-chain
C.sub.18 alkyl or alkenyl. Optionally, the R.sub.2 substituent can
be derived from vegetable oil sources.
[0090] Such structures include the well-known
dialkyldimethylammonium salts (e.g. ditallowedimethylammonium
chloride, ditallowedimethylammonium methyl sulfate, di(hydrogenated
tallow)dimethyl ammonium chloride, etc.), in which R.sub.1 are
methyl groups, R.sub.2 are tallow groups of varying levels of
saturation, and X.sup.- is chloride or methyl sulfate.
[0091] Particularly preferred variants of these softening agents
are what are considered to be mono- or di-ester variations of these
quaternary ammonium compounds having the formula:
(R.sub.1).sub.4-m--N.sup.+--[(CH.sub.2).sub.n--Y--R.sub.3].sub.mX.sup.-
[0092] wherein: [0093] Y is --O--(O)C--, or --C(O)--O--, or
--NH--C(O)--, or --C(O)--NH--; [0094] m is 1 to 3; [0095] n is 0 to
4; [0096] each R.sub.1 is a C.sub.1-C.sub.6 alkyl group,
hydroxyalkyl group, hydrocarbyl or substituted hydrocarbyl group,
alkoxylated group, benzyl group, or mixtures thereof; [0097] each
R.sub.3 is a C.sub.13-C..sub.21 alkyl group, hydroxyalkyl group,
hydrocarbyl or substituted hydrocarbyl group, alkoxylated group,
benzyl group, or mixtures thereof; and [0098] X.sup.- is any
softener-compatible anion.
[0099] Preferably, Y.dbd.--O--(O)C--, or --C(O)--O--; m=2; and n=2.
Each R.sub.1 substituent is preferably a C.sub.1-C.sub.3, alkyl
group, with methyl being most preferred. Preferably, each R.sub.3
is C.sub.13-C.sub.17 alkyl and/or alkenyl, more preferably R.sub.3
is straight chain C.sub.15-C.sub.17 alkyl and/or alkenyl,
C.sub.15-C.sub.17 alkyl, most preferably each R.sub.3 is
straight-chain C.sub.17 alkyl. Optionally, the R.sub.3 substituent
can be derived from vegetable oil sources.
[0100] Specific examples of ester-functional quaternary ammonium
compounds having the structures detailed above and suitable for use
in the present invention may include the diester dialkyl dimethyl
ammonium salts such as diester ditallow dimethyl ammonium chloride,
monoester ditallow dimethyl ammonium chloride, diester ditallow
dimethyl ammonium methyl sulfate, diester di(hydrogenated)tallow
dimethyl ammonium methyl sulfate, diester di(hydrogenated)tallow
dimethyl ammonium chloride, and mixtures thereof. Diester ditallow
dimethyl ammonium chloride and diester di(hydrogenated)tallow
dimethyl ammonium chloride are particularly preferred. These
particular materials are available commercially from Witco.
Chemical Company Inc. of Dublin, Ohio under the trade name "ADOGEN
SDMC".
[0101] Typically, half of the fatty acids present in tallow are
unsaturated, primarily in the form of oleic acid. Synthetic as well
as natural "tallows" fall within the scope of the present
invention. It is also known that depending upon the product
characteristic requirements desired in the final product, the
saturation level of the ditallow can be tailored from non
hydrogenated (soft) to touch, partially or completely hydrogenated
(hard). All of above-described levels of saturations are expressly
meant to be included within the scope of the present invention.
[0102] It will be understood that substituents R.sub.1, R.sub.2 and
R.sub.3 may optionally be substituted with various groups such as
alkoxyl, hydroxyl, or can be branched. As mentioned above,
preferably each R.sub.1 is methyl or hydroxyethyl. Preferably, each
R.sub.2 is C.sub.12-C.sub.18 alkyl and/or alkenyl, most preferably
each R.sub.2 is straight-chain C.sub.16-C.sub.18 alkyl and/or
alkenyl, most preferably each R.sub.2 is is straight-chain C.sub.18
alkyl or alkenyl. Preferably R.sub.3 is C.sub.13-C.sub.17 alkyl
and/or alkenyl, most preferably R.sub.3 is straight chain
C.sub.15-C.sub.17 alkyl and/or alkenyl. Preferably, X.sup.- is
chloride or methyl sulfate. Furthermore the ester-functional
quaternary ammonium compounds can optionally contain up to about
10% of the mono(long chain alkyl) derivatives, e.g.,
(R.sub.2).sub.2--N.sup.+--((CH.sub.2).sub.2OH)
((CH.sub.2).sub.2OC(O)R.sub.3)X.sup.- as minor ingredients. These
minor ingredients can act as emulsifiers and can be useful in the
present invention.
[0103] The use of quaternary ammonium ingredients before is most
effectively accomplished if the quaternary ammonium ingredient is
accompanied by an appropriate plasticizer. The plasticizer can be
added during the quaternizing step in the manufacture of the
quaternary ammonium ingredient or it can be added subsequent to the
quaternization but prior to the application in the papermaking
slurry as a chemical softening agent. The plasticizer is
characterized by being substantially inert during the chemical
synthesis, but acts as a viscosity reducer to aid in the synthesis
and subsequent handling, i.e. application of the quaternary
ammonium compound to the tissue paper product. Preferred
plasticizers are comprised of a combination of a non-volatile
polyhydroxy compound and a fatty acid. Preferred polyhydroxy
compounds include glycerol and polyethylene glycols having a
molecular weight of from about 200 to about 2000, with polyethylene
glycol having a molecular weight of from about 200 to about 600
being particularly preferred. Preferred fatty acids comprise
C.sub.6-C.sub.23 linear or branched and saturated or unsaturated
analogs with isostearic acid being the most preferred.
[0104] While not wishing to be bound by theory, it is believed that
a synergism results from the relationship of the polyhydroxy
compound and the fatty acid in the mixture. While the polyhydroxy
compound performs the essential function of viscosity reduction, it
can be quite mobile after being laid down thus detracting from one
of the objects of the present invention, i.e. that the deposited
softener be. The inventors have now found that the addition of a
small amount of the fatty acid is able to stem the mobility of the
polyhydroxy compound and further reduce the viscosity of the
mixture so as to increase the processability of compositions of a
given quaternary ammonium compound fraction.
[0105] It is anticipated that wood pulp in all its varieties will
normally comprise the tissue papers with utility in this invention.
However, other cellulose fibrous pulps, such as cotton linters,
bagasse, rayon, etc., can be used and none are disclaimed. Wood
pulps useful herein include chemical pulps such as, sulfite and
sulfate (sometimes called Kraft) pulps as well as mechanical pulps
including for example, ground wood, ThermoMechanical Pulp (TMP) and
Chemi-ThermoMechanical Pulp (CTMP). Pulps derived from both
deciduous and coniferous trees can be used.
[0106] Hardwood pulps and softwood pulps, as well as combinations
of the two, may be employed as papermaking fibers for the tissue
paper of the present invention. The term "hardwood pulps" as used
herein refers to fibrous pulp derived from the woody substance of
deciduous trees (angiosperms), whereas "softwood pulps" are fibrous
pulps derived from the woody substance of coniferous trees
(gymnosperms). Blends of hardwood Kraft pulps, especially
eucalyptus, and northern softwood Kraft (NSK) pulps are
particularly suitable for making the tissue webs of the present
invention. A preferred embodiment of the present invention
comprises the use of layered tissue webs wherein, most preferably,
hardwood pulps such as eucalyptus are used for outer layer(s) and
wherein northern softwood Kraft pulps are used for the inner
layer(s). Also applicable to the present invention are fibers
derived from recycled paper, which may contain any or all of the
above categories of fibers.
[0107] In one preferred embodiment of the present invention, which
utilizes multiple papermaking furnishes, the furnish containing the
papermaking fibers which will be contacted by the particulate
filler is predominantly of the hardwood type, preferably of content
of at least about 80% hardwood.
[0108] Other materials can be added to the aqueous papermaking
furnish or the embryonic web to impart other characteristics to the
product or improve the papermaking process so long as they are
compatible with the chemistry of the softening agent and do not
significantly and adversely affect the softness, strength, or low
dusting character of the present invention. The following materials
are expressly included, but their inclusion is not offered to be
all-inclusive. Other materials can be included as well so long as
they do not interfere or counteract the advantages of the present
invention.
[0109] It is common to add a cationic charge biasing species to the
papermaking process to control the zeta potential of the aqueous
papermaking furnish as it is delivered to the papermaking process.
These materials are used because most of the solids in nature have
negative surface charges, including the surfaces of cellulosic
fibers and fines and most inorganic fillers. One traditionally used
cationic charge biasing species is alum. More recently in the art,
charge biasing is done by use of relatively low molecular weight
cationic synthetic polymers to preferably having a molecular weight
of no more than about 500,000 and more preferably no more than
about 200,000, or even about 100,000. The charge densities of such
low molecular weight cationic synthetic polymers are relatively
high. These charge densities range from about 4 to about 8
equivalents of cationic nitrogen per kilogram of polymer. One
example material is Cypro 514.RTM., a product of Cytec, Inc. of
Stamford, Conn. The use of such materials is expressly allowed
within the practice of the present invention.
[0110] The use of high surface area and high anionic charge
microparticles for the purposes of improving formation, drainage,
strength, and retention is taught in the art. Common materials for
this purpose are silica colloid, or bentonite clay. The
incorporation of such materials is expressly included within the
scope of the present invention.
[0111] If permanent wet strength is desired, the group of
chemicals: including polyamide-epichlorohydrin, polyacrylamides,
styrene-butadiene latices; insolubilized polyvinyl alcohol;
urea-formaldehyde; polyethyleneimine; chitosan polymers and
mixtures thereof can be added to the papermaking furnish or to the
embryonic web. Polyamide-epichlorohydrin resins are cationic wet
strength resins which have been found to be of particular utility.
Suitable types of such resins are described in U.S. Pat. Nos.
3,700,623 and 3,772,076. One commercial source of useful
polyamide-epichlorohydrin resins is Hercules, Inc. of Wilmington,
Del., which markets such resin under the mark Kymene
557H.RTM.).
[0112] Many paper products must have limited strength when wet
because of the need to dispose of them through toilets into septic
or sewer systems. If wet strength is imparted to these products, it
is preferred to be fugitive wet strength characterized by a decay
of part or all of its potency upon standing in presence of water.
If fugitive wet strength is desired, the binder materials can be
chosen from the group consisting of dialdehyde starch or other
resins with aldehyde functionality such as Co-Bond 1000.RTM.
offered by National Starch and Chemical Company, Parez 750.RTM.
offered by Cytec of Stamford, Conn. and the resin described in U.S.
Pat. No. 4,981,557.
[0113] If enhanced absorbency is needed, surfactants may be used to
treat the tissue paper webs of the present invention. The level of
surfactant, if used, is preferably from about 0.01% to about 2.0%
by weight, based on the dry fiber weight of the tissue paper. The
surfactants preferably have alkyl chains with eight or more carbon
atoms. Exemplary anionic surfactants are linear alkyl sulfonates,
and alkylbenzene sulfonates. Exemplary nonionic surfactants are
alkylglycosides including alkylglycoside esters such as Crodesta
SL-40.RTM. which is available from Croda, Inc. (New York, N.Y.);
alkylglycoside ethers as described in U.S. Pat. No. 4,011,389,
issued to W. K. Langdon, et al. on Mar. 8, 1977; and
alkylpolyethoxylated esters such as Pegosperse 200 ML available
from Glyco Chemicals, Inc. (Greenwich, Conn.) and IGEPAL
RC-520.RTM. available from Rhone Poulenc Corporation (Cranbury,
N.J.).
[0114] The present invention is further applicable to the
production of multi-layered tissue paper webs. Multi-layered tissue
structures and methods of forming multi-layered tissue structures
are described in U.S. Pat. Nos. 3,994,771; 4,300,981; 4,166,001;
and European Patent Publication No. 0 613 979 A1. The layers
preferably comprise different fiber types, the fibers typically
being relatively long softwood and relatively short hardwood fibers
as used in multi-layered tissue paper making. Multi-layered tissue
paper webs resultant from the present invention comprise at least
two superposed layers, an inner layer and at least one outer layer
contiguous with the inner layer. Preferably, the multi-layered
tissue papers comprise three superposed layers, an inner or center
layer, and two outer layers, with the inner layer located between
the two outer layers. The two outer layers preferably comprise a
primary filamentary constituent of relatively short paper making
fibers having an average fiber length between about 0.5 and about
1.5 mm, preferably less than about 1.0 mm. These short paper making
fibers typically comprise hardwood fibers, preferably hardwood
Kraft fibers, and most preferably derived from eucalyptus. The
inner layer preferably comprises a primary filamentary constituent
of relatively long paper making fiber having an average fiber
length of least about 2.0 mm. These long paper making fibers are
typically softwood fibers, preferably, northern softwood Kraft
fibers. Preferably, the majority of the particulate filler of the
present invention is contained in at least one of the outer layers
of the multi-layered tissue paper web of the present invention.
More preferably, the majority of the particulate filler of the
present invention is contained in both of the outer layers.
[0115] Alternatively, as shown in FIG. 3, the embossing process may
comprise an extended embossing nip. This process may comprise
unwinding a web substrate 26, such as a formed paper web, from a
supply roll, controlling the speed of the web substrate 26,
directing the web substrate 26 into an extended embossing nip, and
then subsequently transporting the final web product to any
additional desired converting operations. Exemplary, but
non-limiting, additional converting operations may include
printing, coating, perforating, folding, cutting, winding, and the
like.
[0116] In a preferred embodiment, the tension of the web substrate
26 is controlled relative to a target tension. An extended
embossing nip may be used to emboss the web substrate 26 while the
web substrate 26 remains in contact with a pattern roll 12. Such an
extended emboss nip may comprise a pattern roll 12 and a belt 24.
Passing the web substrate 26 between the pattern roll 12 and the
belt 24 can provide a desired emboss impression in the web
substrate 26. In one embodiment, the belt 24 may be a flexible and
compressible material (such as a polymer or an elastomer) that is
loaded against the pattern roll 12 to form an extended embossing
nip. In a preferred but non-limiting embodiment, such an extended
embossing nip is greater than 5 cm in length, or greater than 10 cm
in length, or greater than 20 cm in length. The loading force
between the pattern roll 12 and the belt 24 may be the same
throughout the extended nip, or it may be controlled to increase
from the beginning of an extended nip to the end of an extended
nip, or it may be controlled to decrease from the beginning of an
extended nip to the end of an extended nip.
[0117] In an alternative embodiment, the loading between the
pattern roll 12 and the belt 24 may be controlled to any desired
level at all points within such an extended nip. The belt 24 may be
loaded against the pattern roll 12 by pneumatic loading cylinders,
hydraulic loading cylinders, rotation of a ball/screw mechanism in
a linear actuator, or any other suitable means. The belt 24 may be
slave driven by mechanical means, such as gears, that are coupled
to the pattern roll 12. Alternatively, the belt 24 may be driven by
a separate servo drive, or the like, that is controlled in relation
to the speed of the pattern roll 12. In a preferred embodiment, the
surface speed of the pattern roll 12 and the surface speed of the
belt 24 are the same.
[0118] It has been found that embossing a web substrate 26 with an
extended emboss nip can provide a deeper, more appealing emboss
impression with less degradation to the web substrate 26 strength
than embossing the web substrate 26 in a relatively short, single
nip as in prior art which utilizes two rolls to form an embossing
nip. In an alternative embodiment of the extended embossing nip,
the belt 24 surface may comprise a pattern complementary to pattern
roll 12 or pattern belt 40. The depth of engagement may be the same
throughout the extended nip, or it may be controlled to increase
from the beginning of the extended nip to the end of the extended
nip, or it may be controlled to decrease from the beginning of the
extended nip to the end of the extended nip. In an alternative
embodiment, the depth of engagement between the pattern roll
12/pattern belt 40 and the belt may be controlled to any desired
level at all points within the extended nip.
Product
[0119] The soft tissue paper of the present invention preferably
has a basis weight ranging from between about 5 g/m.sup.2 and about
120 g/m.sup.2, more preferably between about 10 g/m.sup.2 and about
75 g/m.sup.2, and even more preferably between about 10 g/m.sup.2
and about 50 g/m.sup.2. The soft tissue paper of the present
invention preferably has a density ranging from between about 0.01
g/cm.sup.3 and about 0.19 g/cm.sup.3, more preferably between about
0.02 g/m.sup.3 and about 0.1 g/cm.sup.3, and even more preferably
between about 0.03 g/cm.sup.3 and about 0.08 g/cm.sup.3.
Analytical and Testing Procedures
[0120] The following test methods are representative of the
techniques utilized to determine the physical characteristics of
the multi-ply tissue product associated therewith.
1. Sample Conditioning and Preparation
[0121] Unless otherwise indicated, samples are conditioned
according to Tappi Method #T402OM-88. Paper samples are conditioned
for at least 2 hours at a relative humidity of 48% to 52% and
within a temperature range of 22.degree. C. to 24.degree. C. Sample
preparation and all aspects of testing using the following methods
are confined to a constant temperature and humidity room.
2. Basis Weight
[0122] Basis weight is measured by preparing one or more samples of
a certain area (m.sup.2) and weighing the sample(s) of a fibrous
structure according to the present invention and/or a paper product
comprising such fibrous structure on a top loading balance with a
minimum resolution of 0.01 g. The balance is protected from air
drafts and other disturbances using a draft shield.
[0123] Weights are recorded when the readings on the balance become
constant. The average weight (g) is calculated and the average area
of the samples (m.sup.2). The basis weight (g/m.sup.2) is
calculated by dividing the average weight (g) by the average area
of the samples (m.sup.2).
3. Density
[0124] The density of multi-layered tissue paper, as that term is
used herein, is the average density calculated as the basis weight
of that paper divided by the caliper, with the appropriate unit
conversions incorporated therein. Caliper of the multi-layered
tissue paper, as used herein, is the thickness of the paper when
subjected to a compressive load of 95 g/in.sup.2 (14.7
g/cm.sup.2).
4. Reflected Light Intensity
[0125] Measure the reflected light intensity from the embossment
using lighting normal to the surface and collecting the reflected
light at 45 degrees from the normal.
[0126] a. Equipment
[0127] A Diagnostics Instruments Spot Insight color camera Model
320 with a Cosmicar 50 mm 1:1.8 lens, along with the SPOT v4.0.8
software was used to acquire sample images. The lens was set to an
F stop of 16. The working distance to the center of the sample from
the face of the lens was 29.5 cm. The field of view of the camera
system was 68 mm. The sample was placed on a 45 degree inclined
glass plate that had a white heavy card stock paper glued to the
surface. Lighting was provided by a Bausch and Lomb FiberLight,
with a bifurcated fiber optic, adjusted to approximately 60%
output. The two heads of the fiber optic were attached in parallel
and aimed normal to the inclined sample stage. The working distance
from the fiber optic tip to the sample was 21.5 cm. A Stouffer
Cameraman's Sensitivity Guide (8 gray level steps) Part #R1215 was
used to accurately adjust the light intensity (see procedure).
[0128] b. Procedure:
[0129] The white paper of the sample stage was used to obtain the
flat field correction and carry out the color balance procedure as
described in the SPOT software guide. The camera settings were:
Exposure 80 milliseconds, Gain 4.0 and Gamma 1.0. Typical color
balance values were: R=1.236, G=1.000, B=2.848. The flat field data
image was stored in a separate image file. Light intensity was
adjusted such that the grayscale reading from an image acquired of
the Stouffer Guide read as follows for the six brightest steps
(151, 112, 84, 60, 44, 32, all +/-2 gray level). The optical
densities of the six Stouffer Guide steps measured with an X-Rite
418 densitometer were 0.042, 0.170, 0.313, 0.458, 0.608, and 0.755.
The final image of the Stouffer target was recorded as a
calibration reference. A flat field corrected image of the sample
stage was also recorded for reference. Images were then captured of
each sample. Images of the Stouffer target were also captured every
tenth sample to confirm stability of the lighting and camera.
[0130] Image analysis was carried out using a MathWorks, Inc MatLab
2008b script (see d. Calculation Script) that first converted the
color image to grayscale using mean luminance and then allowed ten
embossments to be hand outlined, the outlined portion excluded the
majority of the embossment transition area from the top surface to
the bottom of the embossment, the embossment wall area more
specifically. If the paper sample contained different types of
embossments, a separate image centering on each type was acquired
and quantified separately. To avoid as much of the perspective
distortion as possible due to the 45 degree incline relative to the
camera, only embossments near the center of the image were used for
analysis. An estimate of the background brightness is obtained by
drawing a large area outline of non-embossed and non-emboss
transition region. The outlined areas are then used to determine
the mean gray levels within the MatLab script and the output
written directly to an Excel spreadsheet.
[0131] c. Results
[0132] The contrast ratio is determined by dividing the mean emboss
brightness (n=10) as measured above by the background mean
brightness.
[0133] d. Calculation Script
TABLE-US-00001 function GreyValueKnob(num_knobs) % GrayValueKnob -
This function accepts tif images from an open dialog box % and
allows the user to zoom in on a specific area, then hand identify %
areas for calculation of a mean gray value. A background area is
also % manually indicated and the values are all stored in an Excel
spreadsheet. % Usage % GreyValueKnob(7) - use for grayscale
verification % GreyValueKnob(10) - use for knob quantitation %
Input: % num_knobs - number of areas to manually draw. The
background area is % extra and not included in this count % Output:
% Excel spreadsheet with raw and calculated data % Setup output
Excel file xls_Name=[`EmbossLumSummary_` datestr(now,
`yyyymmdd-HHMMSS`) `.xls`]; d={`Image`, `Mean GS`, `Std`, `Bkgrnd
GS`, `Std`, `Contrast`, `Knob Lum->`}; x_status =
xlswrite(xls_Name, d,`Data`,`A1`); num=1; % Get tif file name, loop
until cancel dialog box while num>=1
[FileName,PathName,FilterIndex] = uigetfile(`*.tif`,`Open towel
image file`); if FilterIndex==0, return; end; cd (PathName); % read
file and convert to grayscale [t_color] = imread (FileName); t_gray
= rgb2gray(t_color); % display image and pause to zoom
imagesc(t_gray); colorbar; colormap(`jet`); title(`Towel grey
image`); xlabel(`Zoom area of interest, then hit Return`); zoom on;
beep; pause; zoom off; % Get polyroi for each knob for knob =
1:num_knobs xlabel([`Draw emboss ` num2str(knob)]); bw = roipoly;
gs(knob)= mean(t_gray(find(bw>0))); % find the perimeter points
bwe=imerode(bw,ones(5,5)); bwp=bw-bwe; per_pts=find(bwp>0); %
burn perimeter into image t_gray(per_pts)=0.95*min(t_gray(:)); end
% Get background area xlabel(`Draw background`); bw = roipoly; %
calc background values bgrnd = mean(t_gray(find(bw>0))); stdbg =
std(double(t_gray(find(bw>0)))); % calcualte contrast value
tcontrast = mean(gs)/bgrnd; % find the background perimeter points
bwe=imerode(bw,ones(5,5)); bwp=bw-bwe; per_pts=find(bwp>0); %
burn background perimeter into image darker than knobs
t_gray(per_pts)=0.75*min(t_gray(:)); imagesc(t_gray); xlabel
([`Segmented image: ` FileName]); colormap(gray(256)); beep; pause;
% wait for manual figure save if needed... beep; % format output
results for Excel d={FileName, mean(gs), std(gs), bgrnd, stdbg,
tcontrast}; for j=1:num_knobs d(j+6)={gs(j)}; end % Write data to
Excel in next row x_status = xlswrite(xls_Name, d,`Data`,[`A`
num2str(num+1)]); num=num+1; display(`Done...next image`); end
return
5. Embossment Structure Measurement
[0134] The geometric characteristics of the embossment structure of
the present invention are measured using an Optical 3D Measuring
System MikroCAD compact for paper measurement instrument (the "GFM
MikroCAD optical profiler instrument") and ODSCAD Version 4.14
software available from GFMesstechnik GmbH, Warthestra.beta.e E21,
D14513 Teltow, Berlin, Germany. The GFM MikroCAD optical profiler
instrument includes a compact optical measuring sensor based on
digital micro-mirror projection, consisting of the following
components: [0135] A) A DMD projector with 1024.times.768 direct
digital controlled micro-mirrors. [0136] B) CCD camera with high
resolution (1280.times.1024 pixels). [0137] C) Projection optics
adapted to a measuring area of at least 160.times.120 mm. [0138] D)
Recording optics adapted to a measuring area of at least
160.times.120 mm; [0139] E) Schott KL1500 LCD cold light source.
[0140] F) A table stand consisting of a motorized telescoping
mounting pillar and a hard stone plate; [0141] G) Measuring,
control and evaluation computer. [0142] H) Measuring, control and
evaluation software ODSCAD 4.14. [0143] I) Adjusting probes for
lateral (XY) and vertical (Z) calibration.
[0144] The GFM MikroCAD optical profiler system measures the height
of a sample using the digital micro-mirror pattern projection
technique. The result of the analysis is a map of surface height
(Z) versus XY displacement. The system should provide a field of
view of 160.times.120 mm with an XY resolution of 21 .mu.m. The
height resolution is set to between 0.10 .mu.m and 1.00 .mu.m. The
height range is 64,000 times the resolution. To measure a fibrous
structure sample, the following steps are utilized: [0145] 1. Turn
on the cold-light source. The settings on the cold-light source are
set to provide a reading of at least 2,800 k on the display. [0146]
2. Turn on the computer, monitor, and printer, and open the
software. [0147] 3. Verify calibration accuracy by following the
manufacturers instructions. [0148] 4. Select "Start Measurement"
icon from the ODSCAD task bar and then click the "Live Image"
button. [0149] 5. Obtain a fibrous structure sample that is larger
than the equipment field of view and conditioned at a temperature
of 73.degree. F..+-.2.degree. F. (about 23.degree. C..+-.1.degree.
C.) and a relative humidity of 50% .+-.2% for 2 hours. Place the
sample under the projection head. Position the projection head to
be normal to the sample surface. [0150] 6. Adjust the distance
between the sample and the projection head for best focus in the
following manner. Turn on the "Show Cross" button. A blue cross
should appear on the screen. Click the "Pattern" button repeatedly
to project one of the several focusing patterns to aid in achieving
the best focus. Select a pattern with a cross hair such as the one
with the square. Adjust the focus control until the cross hair is
aligned with the blue "cross" on the screen. [0151] 7. Adjust image
brightness by increasing or decreasing the intensity of the cold
light source or by altering the camera gains setting on the screen.
When the illumination is optimum, the red circle at the bottom of
the screen labeled "I.O." will turn green. [0152] 8. Select
"Standard" measurement type. [0153] 9. Click on the "Measure"
button. The sample should remain stationary during the data
acquisition. [0154] 10. To move the data into the analysis portion
of the software, click on the clipboard/man icon. [0155] 11. Click
on the icon "Draw Cutting Lines." On the captured image, "draw" a
cutting line that extends from the center of a negative embossment
through the centers of at least six negative embossments, ending on
the center of a final negative embossment. Click on the icon "Show
Sectional Line Diagram." Move the cross-hairs to a representative
low point on one of the left hand negative embossments and click
the mouse. Then move the cross-hairs to a representative low point
on one of the right hand negative embossments and click the mouse.
Click on the "Align" button by marked point's icon. The Sectional
Line Diagram is now adjusted to the zero reference line. [0156] 12.
Measurement of Emboss Height, h. Using the Sectional Line Diagram
described in step 11, click the mouse on a representative low point
of a negative emboss, followed by clicking the mouse on a
representative point on the nearby upper surface of the sample.
Click the "Vertical" distance icon. Record the distance
measurement. Repeat the previous steps until the depth of six
negative embossments have been measured. Take the average of all
recorded numbers and report in mm, or .mu.m, as desired. This
number is the embossment height. [0157] 13. Measurement of Wall
Angle, a. Using the Sectional Line Diagram of step 11, select with
the mouse two points on the wall of a negative embossment that
represent respectively 33% and 66% of the depth measured in step
12. Click the "Angle" icon. The ODSCAD software calculates the
angle between a) the straight line connecting the two selected
points and b) the zero reference line described in step 11. This
angle is the wall angle. Repeat these steps for the six negative
embossments measured in step 12. [0158] 14. Measurement of Emboss
Area, A. Using the Sectional Line Diagram of step 11, select with
the mouse two points on each wall of a negative embossment that
represents 50% of the depth measured in step 12. Click the
"horizontal distance" icon. The horizontal distance is the diameter
of an equivalent circle. The area of that circle is calculated
using the formula Area=2*pi*(d/2) 2 and is recorded as the
Equivalent Emboss Area. If the embossment shape is elliptical or
irregular, more sectional lines are needed, cutting through the
embossment from different directions, to calculate the equivalent
area. Repeat these steps for the six negative embossments measured
in step 12.
EXAMPLES
A. Example 1
[0159] One fibrous structure useful in achieving the embossed
multi-ply paper product of the present invention is the
through-air-dried (TAD), differential density structure described
in U.S. Pat. No. 4,528,239. Such a product may be formed by the
following process.
[0160] A Fourdrinier, through-air-dried papermaking machine is
used. A slurry of papermaking fibers is pumped to the headbox at a
consistency of about 0.15%. The slurry consists of about 70%
Northern Softwood Kraft fibers, about 30% unrefined Eucalyptus
fibers, a cationic polyamine-epichlorohydrin wet burst strength
resin at a concentration of about 25 lbs per ton of dry fiber, and
carboxymethyl cellulose at a concentration of about 5 lbs per ton
of dry fiber, as well as DTDMAMS at a concentration of about 6 lbs
per ton of dry fiber.
[0161] Dewatering occurs through the Fourdrinier wire and is
assisted by vacuum boxes. The embryonic wet web is transferred from
the Fourdrinier wire at a fiber consistency of about 20% at the
point of transfer, to a TAD carrier fabric. The wire speed is about
620 feet per minute. The carrier fabric speed is about 600 feet per
minute. Since the wire speed is faster than the carrier fabric, wet
shortening of the web occurs at the transfer point. Thus, the wet
web foreshortening is about 3%.
[0162] The consistency of the web is about 60% after the action of
the TAD dryers operating about a 400.degree. F., before transfer
onto the Yankee dryer. An aqueous solution of creping adhesive is
applied to the Yankee surface by spray applicators before the
location of the sheet transfer. The fiber consistency is increased
to an estimated 95.5% before creping the web with a doctor blade.
The doctor blade has a bevel angle of about 25 degrees and is
positioned with respect to the Yankee dryer to provide an impact
angle of about 81 degrees. The Yankee dryer is operated at about
360.degree. F., and Yankee hoods are operated at about 350.degree.
F.
[0163] The dry, creped paper web is passed between two calendar
rolls and rolled on a reel operated at 560 feet per minute so that
there is about 7% foreshortening of the web by crepe.
[0164] The paper web described above is then subjected to a
knob-to-rubber impression embossing apparatus and process as
follows: A 14'' diameter embossing roll is engraved with a
nonrandom pattern of embossing protrusions. The embossing
protrusions have a wall angle of 102.5.degree. and a round or oval
surface with a major/minor axis of 0.1'', and a height of 0.065''.
There are 30 embossing protrusions per square inch. The paper web
passes a 0.63'' nip formed between to the embossing roll and a
first pressure roll having a hardness of about 17 P&J and a
diameter of about 7 inches that is juxtaposed in an axially
parallel arrangement with the embossing roll. The resultant paper
product is passed through a 1.50'' nip formed between the embossing
roll and a second pressure roll having a hardness of about 125
P&J and a diameter of about 7 inches that is juxtaposed in an
axially parallel arrangement with the embossing roll. The above
converting is operations are carried out at a constant sheet
velocity of about 1000 fpm.
[0165] Surprisingly, the resultant embossed multi-ply paper product
has a more pronounced emboss pattern than products of the prior
art. In addition, the resultant embossed product exhibits emboss
registration which is greatly improved over that produced by prior
art embossing processes.
B. Example 2
[0166] A product produced as detailed in Example #1 supra is ply
bonded to a second product produced as detailed in Example #1
supra. The resulting 2-ply substrate is processed as detailed
infra.
[0167] The paper web described above is then subjected to a
knob-to-rubber impression embossing apparatus and process as
follows: A 14 inch diameter embossing roll is engraved with a
nonrandom pattern of embossing protrusions. The embossing
protrusions have a wall angle of 102.5.degree., round or oval
surface with a major/minor axis of 0.1'', and a height of 0.130''.
There are 18 embossing protrusions per square inch.
[0168] The paper web passes a 0.63'' nip formed between the
embossing roll and a first pressure roll having a hardness of about
17 P&J and a diameter of about 7 inches that is juxtaposed in
an axially parallel arrangement with the embossing roll. After
undergoing an initial embossing transformation, the paper web
passes a second 1.5'' nip formed between the embossing roll and
pressure roll having a hardness of 125 P&J and a diameter of
about 7 inches that is juxtaposed in an axially parallel
arrangement with the embossing roll. After undergoing the second
embossing transformation, the paper web passes a an adhesive
application roll that is juxtaposed in an axially parallel
arrangement with the embossing roll such that the adhesive
application roll contacts the distal end of the embossing
protrusions, and therefore adhesive is only applied to the embossed
areas of the paper web. Once adhesive has been applied to the
embossed areas, the paper web then passes between a nip formed
between the embossing roll and a marrying roll, which marries the
paper web to a different paper web, which is also as described
above, and is also passed through the nip formed between the
embossing roll and the marrying roll. The above converting
operations are carried out at a constant sheet velocity of about
1000 fpm.
[0169] Again surprisingly, the resultant embossed multi-ply paper
product has a more pronounced emboss pattern than products of the
prior art. In addition, the resultant embossed multi-ply paper
product exhibits registration which is greatly improved over that
produced by prior art embossing processes.
[0170] Both products produced above are tested according to the
intensity method detailed herein. The resulting intensity data is
provided in Table 1.
TABLE-US-00002 TABLE 1 Product intensity measurement data Sample
Contrast Example 1 (1-ply) 1.31 Example 2 (2-ply) 1.24 Vanity Fair
Napkins (1-ply) 1.22 Brawny (2-ply) 1.20 Famliy Dollar towel
(2-ply) 1.18 Publix towel (2-ply) 1.16 Quilted Nothern Ultra Plush
tissue (3-ply) 1.15 1st Quality towel (2-ply) 1.14 Kroger Nice
& Strong napkin (1-ply) 1.14 Shoppers Value towel (2-ply) 1.14
Bounty towel (2-ply) 1.14 Angel Soft tissue (2-ply) 1.14 Thrifty
Made towel (2-ply) 1.13 Dixie napkins (1-ply) 1.13 Target Premium
towel (2-ply) 1.12 Charmin Ultra Strong (2-ply) 1.12 Kroger Nice
& Soft tissue (2-ply) 1.10 Mardi Gras napkins (1-ply) 1.03
Kroger Nice & Elegant napkins (2-ply) 1.03
[0171] A preferred embodiment of the present invention provides a
single ply paper product having a contrast ratio greater than about
1.25 as measured according to the Reflected Light Intensity test
method, more preferably greater than about 1.30, even more
preferably ranging from about 1.25 to about 1.5, yet more
preferably ranging from about 1.25 to about 1.35, and most
preferably ranging from about 1.30 to about 1.35.
[0172] A preferred embodiment of the present invention provides a
two-ply paper product having a contrast ratio greater than about
1.22 as measured according to the Reflected Light Intensity test
method, more preferably greater than about 1.25, even more
preferably greater than about 1.30, yet more preferably ranging
from about 1.25 to about 1.50, and most preferably ranging from
about 1.25 to about 1.35.
[0173] The embossments of the product of the present invention have
an embossment height, h, of greater than about 800 microns,
preferably greater than about 1000 microns, and more preferably
greater than about 1100 microns. The embossment height is measured
using the Embossment Structure Measurement Method described in the
test methods herein. The embossment height, h, is a measure from
the top of the unembossed structure to the bottom of the embossment
as described in the test method.
[0174] While particular embodiments of the present invention have
been illustrated and described herein, it would be obvious to those
skilled in the art that various other changes and modifications can
be made without departing from the spirit and scope of the
invention. It is therefore intended to cover in the appended claims
all such changes and modifications that are within the scope of
this invention.
[0175] The dimensions and values disclosed herein are not to be
understood as being strictly limited to the exact numerical values
recited. Instead, unless otherwise specified, each such dimension
or value is intended to mean both the recited dimension or value
and a functionally equivalent range surrounding that dimension or
value. For example, a dimension disclosed as "40 mm" is intended to
mean "about 40 mm."
[0176] Every document cited herein, including any cross referenced
or related patent or application, is hereby incorporated herein by
reference in its entirety unless expressly excluded or otherwise
limited. The citation of any document is not an admission that it
is prior art with respect to any invention disclosed or claimed
herein or that it alone, or in any combination with any other
reference or references, teaches, suggests or discloses any such
invention. Further, to the extent that any meaning or definition of
a term in this document conflicts with any meaning or definition of
the same term in a document incorporated by reference, the meaning
or definition assigned to that term in this document shall
govern.
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