U.S. patent application number 11/465837 was filed with the patent office on 2006-12-21 for multi-ply absorbent paper product having impressed pattern.
This patent application is currently assigned to FORT JAMES CORPORATION. Invention is credited to Thomas N. Kershaw, Galyn A. Schulz, Gary L. Worry, Kang C. Yeh.
Application Number | 20060283538 11/465837 |
Document ID | / |
Family ID | 34555124 |
Filed Date | 2006-12-21 |
United States Patent
Application |
20060283538 |
Kind Code |
A1 |
Schulz; Galyn A. ; et
al. |
December 21, 2006 |
MULTI-PLY ABSORBENT PAPER PRODUCT HAVING IMPRESSED PATTERN
Abstract
A multi-ply tissue includes a first cellulosic embossed ply
having an emboss pattern applied over a portion of its surface and
a second cellulosic embossed ply of tissue. The first ply is
contact laminated to the second ply so that the primary adhesion
between the plies of tissue is the result of contact between
cellulosic fibers. The first and second plies contact one another
in contact-areas, with the contact areas between the first and
second plies defining compliant voids. The contact areas between
the first ply and the second ply are elongated and/or rounded
contact areas. A method of forming a multi-ply tissue involves
conveying a base sheet through a nip between an impression roll and
a pattern roll to produce an embossed base sheet having a back side
possessing projections, applying adhesive to the back side of the
embossed base sheet at spaced apart locations, and applying a flat
backing sheet to the back side of the embossed base sheet so that
the backing sheet adheres to the back side of the embossed base
sheet at said spaced apart locations. A method of producing an
embossed tissue involves successively conveying a base sheet
through a nip between a first impression roll and a pattern roll,
and conveying the base sheet through another nip between the
pattern roll and a second impression roll, wherein the second
impression roll is made of rubber having a lower hardness than the
rubber from which the first impression roll is made.
Inventors: |
Schulz; Galyn A.;
(Greenville, WI) ; Worry; Gary L.; (Appleton,
WI) ; Yeh; Kang C.; (Neenah, WI) ; Kershaw;
Thomas N.; (Neenah, WI) |
Correspondence
Address: |
PATENT GROUP GA030-43;GEORGIA-PACIFIC CORPORATION
133 PEACHTREE STREET, N.E.
ATLANTA
GA
30303-1847
US
|
Assignee: |
FORT JAMES CORPORATION
133 Peachtree Street NE
Atlanta
GA
|
Family ID: |
34555124 |
Appl. No.: |
11/465837 |
Filed: |
August 21, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11002651 |
Dec 3, 2004 |
7118796 |
|
|
11465837 |
Aug 21, 2006 |
|
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09564800 |
May 5, 2000 |
|
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11002651 |
Dec 3, 2004 |
|
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60162981 |
Nov 1, 1999 |
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Current U.S.
Class: |
156/219 ;
156/209; 162/117; 162/132 |
Current CPC
Class: |
D21H 27/002 20130101;
B31F 2201/0728 20130101; B31F 2201/0784 20130101; B31F 2201/0725
20130101; B31F 2201/0733 20130101; B32B 38/06 20130101; B32B 23/02
20130101; B32B 5/26 20130101; B32B 37/12 20130101; B31F 2201/0758
20130101; Y10T 428/24463 20150115; D21H 27/40 20130101; B31F
2201/0774 20130101; B31F 2201/0743 20130101; B31F 1/07 20130101;
Y10T 156/1039 20150115; D21H 27/02 20130101; Y10T 156/1023
20150115; B31F 2201/0789 20130101; B32B 3/26 20130101; B31F
2201/0738 20130101; D21H 27/32 20130101; B31F 2201/0787 20130101;
B32B 3/30 20130101; Y10T 428/24612 20150115; B32B 23/10 20130101;
B31F 2201/0764 20130101; B32B 2262/062 20130101; B31F 2201/0792
20130101; Y10T 428/24562 20150115 |
Class at
Publication: |
156/219 ;
162/132; 162/117; 156/209 |
International
Class: |
B31F 1/07 20060101
B31F001/07; D21F 11/00 20060101 D21F011/00 |
Claims
1. A method of forming a two-ply tissue comprising: producing a
first ply of tissue having an emboss pattern; producing a second
ply of tissue having an emboss pattern, the first ply being more
heavily embossed than the second ply; resting the first and second
plies together to contact laminate the first ply to the second ply
with contact areas between the first and second plies, the contact
areas being elongated or gently rounded.
2. The method according to claim 1, wherein the emboss patterns on
the first ply and the second ply are formed by emboss elements
having an aspect ratio greater than one.
3. The method according to claim 1, wherein the emboss patterns on
the first ply and the second ply are formed by emboss elements
having an aspect ratio greater than 5.
4. The method according to claim 1, including preconditioning the
first ply and the second ply before embossing through use of heat
and moisture.
5. The method according to claim 1, including preconditioning the
first ply and the second ply before embossing through use of
steam.
6. A method of producing an embossed tissue comprising: conveying a
base sheet through a nip between a first impression roll made of
rubber and a pattern roll to push portions of the base sheet into
indented portions of the pattern roll; conveying the base sheet
through a nip between the pattern roll and a second impression roll
made of rubber having a lower hardness than the rubber from which
the first impression roll is made to push the portions of the base
sheet further into the indented portions of the pattern roll to
produce an embossed tissue.
7. The method according to claim 6, including conveying the base
sheet between the first impression roll and another impression roll
prior to conveying the base sheet through the nip between the first
impression roll and the pattern roll.
8. A method of forming a two-ply tissue comprising: conveying a
base sheet through a nip between an impression roll and a pattern
roll to emboss a pattern on the base sheet, the engagement of the
impression roll with the pattern roll producing an embossed base
sheet having a back side possessing projections produced by the
pattern roll; and apply a flat backing sheet to the back side of
the embossed base sheet by contact lamination to cause the backing
sheet to adhere to the back side of the embossed base sheet and
thereby form a two-ply tissue.
9. The method according to claim 8, wherein the base sheet and the
backing sheet are conveyed at different speeds.
10. The method according to claim 8, wherein the projections on the
embossed base sheet include projections with differing heights.
Description
[0001] This application is a division of U.S. application Ser. No.
09/564,800, filed May 5, 2000, which claims priority to and the
benefits under 35 U.S.C. .sctn.119(e) of U.S. application Ser. No.
60/162,981, filed Nov. 1, 1999, both of which are incorporated
herein by reference in their entireties.
FIELD OF THE INVENTION
[0002] This invention generally related to absorbent paper
products, including tissue paper, towels, wipes and napkins. More
particularly, the present invention pertains to an embossed
multi-ply absorbent paper product.
BACKGROUND OF THE INVENTION
[0003] Consumer acceptance of absorbent paper products such as
tissue paper products and the like is influenced by the perceived
softness of the tissue product. Indeed, the consumer's perception
of the desirability of one tissue product over another is based in
significant respects on the perceived relative softness of the
tissue products; the tissue product that is perceived to be more
soft is typically perceived to be more acceptable.
[0004] Thus, tissue paper should ideally possess a relatively high
emboss definition and bulk, and a relatively high degree of
perceived puffiness and softness. The emboss definition and bulk of
the tissue paper is commonly found to affect the perceived softness
of the tissue paper. In addition, the tissue paper should possess
sufficient strength. However, it is typically the case that
improving one or more of these parameters of the tissue paper
adversely affects one or more of the other parameters. For example,
applying a very heavy embossing to the tissue product increases the
embossing definition and bulk of the tissue paper, but also
increases the friction so that the perceived softness is reduced.
Also, a reduction in the strength of the tissue product results. On
the other hand, a less heavily embossed tissue product might
possess better strength characteristics and smoothness attributes,
but the perceived puffiness and softness of the tissue product
would be adversely affected.
[0005] Conventional deep embossing of two-ply tissue paper involves
conveying two plies of tissue paper through a nip formed between a
steel roll and a rubber roll. While this type of embossing is able
to provide better emboss definition and puffiness, it also
increases the back side friction which thus reduces tissue
softness. Also, the rather heavy embossing adversely affects the
strength of the resulting multi-ply tissue.
[0006] U.S. Pat. No. 3,708,366 describes a method of producing
two-ply paper towel in which one ply is more severely embossed than
the other ply. This patent is not specifically related to the
manufacture of tissue paper products. Moreover, the patent
describes that the preferred embossments are in the shape of a
frustum of a cone. This embossment shape produces non-elongated and
rather sharply defined contact regions between the two plies which
have been found to result in a paper towel product having a rather
harsh feel. While this resulting feel of the product may be
acceptable from the standpoint of paper towel products such as that
with which the aforementioned patent is concerned, it is a result
that is not well suited for tissue paper products.
[0007] There thus exists a need for a tissue product having better
perceived softness and bulk along with better emboss definition,
without unduly degrading the strength characteristics of the tissue
product.
[0008] A need also exists for a tissue that is heavily embossed,
but which does not have the roughened characteristics typically
associated with such heavily embossed tissue. When multiple sheets
are embossed together, the nubs or protuberances on the back side
of the tissue are perceived as being rough by the consumer.
[0009] A need also exists for a one ply embossed sheet that does
not possess a two-sided look or appearance. One ply embossed sheets
are typically embossed with matched steel-to-steel rolls and this
produces the undesirable two sided look or appearance. Aside from
this, the use of steel-to-steel emboss rolls to produce the one ply
embossed tissue creates undesirable paper dust and has a tendency
to damage the steel emboss rolls.
SUMMARY OF THE INVENTION
[0010] According to one aspect of the invention, a multi-ply tissue
includes a first cellulosic embossed ply having an emboss pattern
applied over from three to twelve percent of its surface to a depth
of at least about thirty thousandths of an inch, and a second
cellulosic embossed ply of tissue in which the depth of emboss
applied to the second ply is no more than about 80% of the depth of
emboss applied to the first ply. The first ply is contact laminated
to the second ply, with the primary adhesion between the plies of
tissue being the result of contact between cellulosic fibers rather
than through an intermediate adhesive. The first and second plies
contact one another in contact areas, with the contact areas
between the first and second plies defining compliant voids and
with the total contact area being no more than about fifteen
percent of the area of the tissue sheets.
[0011] According to another aspect of the invention, a method of
producing a two ply issue involves embossing a first ply of tissue
so that the first ply of tissue possesses an emboss pattern and
embossing a second ply of tissue so that the second ply of tissue
possesses an emboss pattern, with the first ply being more heavily
embossed than the second ply. The first and second plies are nested
together to contact laminate the first ply to the second ply with
contact areas between the first and second plies, the contact areas
being elongated or gently rounded.
[0012] In accordance with another aspect of the invention, a method
of producing a two ply tissue involves conveying a base sheet
through a nip between an impression roll sometimes made of rubber
and a pattern roll sometimes made of steel to emboss a pattern on
the base sheet and produce an embossed base sheet having a back
side possessing projections produced by the pattern roll, applying
adhesive to the back side of the embossed base sheet at spaced
apart locations so that portions of the back side of the embossed
base sheet between the projections are devoid of adhesive, and
applying a flat backing sheet that is devoid of embossing to the
back side of the embossed base sheet to cause the backing sheet to
adhere to the back side of the embossed base sheet at the spaced
apart locations.
[0013] A still further aspect of the invention involves a multi-ply
sheet that includes an embossed base sheet having a back side
possessing projections, adhesive on the back side of the embossed
base sheet at spaced apart locations so that portions of the back
side of the embossed base sheet between the projections are devoid
of adhesive, and a flat backing sheet devoid of embossing and
adhered to the back side of the embossed base sheet at the spaced
apart locations.
[0014] Another aspect of the invention involves a method of
producing an embossed tissue that involves conveying a base sheet
through a nip between a first impression roll and a pattern roll to
push portions of the base sheet into indented portions of the
pattern roll, conveying the base sheet through a nip between the
pattern roll and a second impression roll made of rubber having a
lower hardness than the rubber from which the first impression roll
is made to push the portions of the base sheet further into the
indented portions of the pattern roll to produce an embossed
tissue.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The foregoing and additional details and features associated
with the present invention will become more apparent from the
following detailed description considered with reference to the
accompanying drawing figures in which like elements are designated
by like reference numerals and wherein:
[0016] FIG. 1 is a schematic illustration of an apparatus for
embossing a paper product in accordance with one aspect of the
present invention;
[0017] FIG. 2 is a front view of the roller arrangement used in the
apparatus shown in FIG. 1;
[0018] FIG. 3A is a schematic illustration of an alternative
arrangement for carrying out double depth embossing in accordance
with the present invention;
[0019] FIG. 3B is a cross-sectional view of a portion of the
interface between one of the pattern rolls and one of the
impression rolls shown in FIG. 3A;
[0020] FIG. 3C is a cross-sectional view of a portion of the
interface between the other pattern roll and impression roll used
in the apparatus shown in FIG. 3A;
[0021] FIG. 4A is a schematic illustration of a multi-ply paper
product produced in accordance with the present invention;
[0022] FIG. 4D is a schematic illustration of a multi-ply tissue
product produced in accordance with known methods;
[0023] FIG. 5 is a schematic illustration of another apparatus for
embossing a paper product in accordance with another aspect of the
present invention;
[0024] FIG. 6A is an illustration of one emboss pattern used in
conjunction with the present invention;
[0025] FIG. 6B is an enlarged illustration of one portion of the
emboss pattern shown in FIG. 6A;
[0026] FIG. 7 is an illustration of a different emboss pattern used
in connection with the present invention;
[0027] FIG. 8 is an illustration of a further emboss pattern used
in connection with the present application;
[0028] FIG. 9 is a graph of GM tensile strength versus caliper
comparing the embossing technique of the present invention versus
conventional embossing;
[0029] FIG. 10 is a graph of GM tensile strength versus GMMMD
(friction) comparing the embossing technique of the present
invention versus conventional embossing;
[0030] FIG. 11 is a graph of GM Tensile Strength versus tensile
modulus comparing the embossing technique of the present invention
and conventional embossing;
[0031] FIG. 12 is a graph of GM tensile strength versus sensory
panel softness for the present invention and for conventional
embossing;
[0032] FIG. 13 is a graph of GM tensile strength versus visual test
comparing the embossing technique of the present invention and
conventional embossing;
[0033] FIG. 14 is a graph of GM tensile strength versus caliper
comparing the embossing technique of the present invention versus
conventional embossing;
[0034] FIG. 15 is a graph of GM tensile strength versus GMMMD
comparing the embossing technique of the present invention and
conventional embossing;
[0035] FIG. 16 is a graph of GM tensile strength versus tensile
modulus comparing the embossing technique of the present invention
and conventional embossing;
[0036] FIG. 17 is a graph of GM tensile strength versus sensory
softness value comparing the embossing technique of the present
invention and conventional embossing;
[0037] FIG. 18a is a magnified cross-section of a multi-ply tissue
produced in accordance with the embossing technique of the present
invention;
[0038] FIG. 18b is a magnified cross-sectional view of a multi-ply
tissue formed in accordance with conventional embossing;
[0039] FIG. 19a is a magnified cross-sectional view of a multi-ply
tissue produced in accordance with the embossing technique of the
present invention;
[0040] FIG. 19b is a magnified cross-sectional view of a multi-ply
tissue produced in accordance with conventional embossing;
[0041] FIG. 20a is a magnified cross-sectional view of a multi-ply
tissue produced in accordance with the embossing technique of the
present invention;
[0042] FIG. 20b is a magnified cross-sectional view of a multi-ply
tissue produced in accordance with conventional embossing;
[0043] FIG. 21a is a magnified cross-sectional view of a multi-ply
tissue produced in accordance with the embossing technique of the
present invention;
[0044] FIG. 21b is a magnified cross-sectional view of a multi-ply
tissue produced in accordance with conventional embossing;
[0045] FIG. 22 is a graph of GM tensile illustrating the effect of
different rubber hardness of the impression roll;
[0046] FIG. 23 is a graph of GM tensile strength versus tensile
modulus illustrating the effect of different rubber hardness of the
impression roll;
[0047] FIG. 24 is a graph of GM tensile strength versus GMMMD
illustrating the effect of rubber hardness of the impression roll
on the tissue product;
[0048] FIG. 25 is a graph of GM tensile strength versus sensory
panel softness illustrating the effect of rubber hardness of the
impression roll on the tissue product formed in accordance with the
present invention;
[0049] FIG. 26 is a graph of GM tensile strength versus caliper
illustrating the effect of adhesive on a tissue product produced in
accordance with the embossing technique of the present
invention;
[0050] FIG. 27 is a graph of GM tensile strength versus tensile
modulus illustrating the effect of adhesive on the tissue product
produced in accordance with the embossing technique of the present
invention;
[0051] FIG. 28 is a graph of GM tensile strength versus GMMMD
illustrating the effect of adhesive on the tissue product produced
in accordance with the embossing technique of the present
invention;
[0052] FIG. 29 is a graph of GM tensile strength versus sensory
panel softness illustrating the effect of adhesive on the tissue
product produced in accordance with the embossing technique of the
present invention;
[0053] FIG. 30 is a graph of GM tensile strength versus caliper
illustrating the effect of adhesive on the tissue product produced
using the embossing technique of the present invention;
[0054] FIG. 31 is a graph of GM tensile strength versus tensile
modulus illustrating the effect of adhesive on the tissue product
produced in accordance with the embossing technique of the present
invention;
[0055] FIG. 32 is a graph of GM tensile strength versus GMMMD
illustrating the effect of adhesive on a tissue product produced in
accordance with the embossing technique of the present
invention;
[0056] FIG. 33 is a graph of GM tensile strength versus sensory
panel softness illustrating the effect of adhesive on a tissue
product produced in accordance with the embossing technique of the
present invention;
[0057] FIG. 34 is a graph of GM tensile strength versus caliper
illustrating the effect of the emboss pattern and emboss process of
the present invention on a two-ply tissue product;
[0058] FIG. 35 is a graph of GM tensile strength versus tensile
modulus illustrating the effect of the emboss pattern and the
emboss process of the present invention on the fabrication of a
two-ply tissue product;
[0059] FIG. 36 is a graph of GM tensile strength versus GMMMD
illustrating the effect of the emboss pattern and the emboss
process of the present invention on fabrication of a two-ply tissue
product;
[0060] FIG. 37 is a graph of GM tensile strength versus sensory
panel softness illustrating the effect of the emboss pattern and
the emboss process of the present invention on the fabrication of a
two-ply tissue product;
[0061] FIG. 38 is a graph of GM tensile strength versus caliper
illustrating the effect of emboss pattern on a tissue product
produced in accordance with the emboss technique of the present
invention;
[0062] FIG. 39 is a graph of GM tensile strength versus tensile
modulus illustrating the effect of the emboss pattern and the
emboss process on the fabrication of a two-ply tissue product;
[0063] FIG. 40 is a graph of GM tensile strength versus GMMMD
illustrating the effect of emboss pattern on a tissue product
produced in accordance with the emboss technique of the present
invention;
[0064] FIG. 41 is a graph of GM tensile strength versus sensory
panel softness illustrating the effect of the emboss pattern and
the emboss process on the fabrication of a two-ply tissue
product;
[0065] FIG. 42 is a graph of GM tensile strength versus caliper
illustrating the effect of steam preconditioning on the production
of a two-ply tissue product in accordance with the embossing
technique of the present invention;
[0066] FIG. 43 is a graph of GM tensile strength versus tensile
modulus illustrating the effect of steam preconditioning on the
fabrication of a two-ply tissue product in accordance with the
embossing technique of the present invention;
[0067] FIG. 44 is a graph of GM tensile modulus versus GMMMD
illustrating the effect of steam preconditioning on the fabrication
of a two-ply tissue product produced using the embossing technique
of the present invention;
[0068] FIG. 45 is a graph of GM tensile strength versus sensory
softness illustrating the effect of the emboss pattern used in the
prior art on a two-ply tissue product using various emboss;
[0069] FIG. 46 is a graph of GM tensile strength versus GMMMD
illustrating the effect of the emboss pattern used in the prior art
on the production of a two-ply tissue product using different
emboss techniques;
[0070] FIG. 47 is a graph of GM tensile strength versus caliper
illustrating the effect of the emboss pattern used in the prior art
on the fabrication of a two-ply tissue product using different
emboss techniques;
[0071] FIG. 48 is a graph of GM tensile strength versus GM tensile
modulus illustrating the effect of the emboss pattern used in the
prior art on the fabrication of a two-ply tissue product using
different emboss techniques;
[0072] FIG. 49 is a schematic illustration of an apparatus used to
impress a pattern on a multi-ply paper product in accordance with
another aspect of the invention;
[0073] FIG. 50 is an enlarged cross-sectional view of a portion of
a multi-ply product produced using the apparatus shown in FIG.
49;
[0074] FIG. 51 is an enlarged cross-sectional view of a portion of
another multi-ply product produced in accordance with the present
invention;
[0075] FIG. 52 is a schematic illustration of an apparatus used to
produce a two-ply tissue product having a heavily embossed pattern
in accordance with another aspect of the invention;
[0076] FIG. 53 is a side view of a portion of a tissue product
having a different depth or double depth emboss pattern;
[0077] FIG. 54 is a schematic illustration of an apparatus used to
produce a one ply tissue product in accordance with another aspect
of the invention; and
[0078] FIG. 55 is a schematic illustration of an apparatus used to
produce a one ply tissue product in accordance with another aspect
of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0079] Generally speaking, one aspect of the present invention
relates to a multi-ply absorbent paper product possessing what is
termed a differential depth emboss that contributes to imparting
highly desirable characteristics and properties to the multi-ply
paper product. One of the plies forming the multi-ply paper product
is embossed relatively heavily while the other ply is relatively
lightly embossed. By embossing one ply more heavily than the other,
the resulting multi-ply paper product possesses better perceived
softness and bulk along with better emboss definition, yet the
strength of the resulting multi-ply paper product is not unduly
degraded. The preservation of product strength results from less
emboss damage of the lightly embossed ply. In accordance with the
present invention, the differential depth emboss maintains a good
emboss definition on the outside of the multi-ply paper product by
virtue of the heavily embossed ply while at the same time reducing
the backside friction. The differential depth embossing process
deeply embosses the top ply first through higher penetration depth
or higher nip pressure. The top ply is then joined to or nested
with the bottom ply through a second nip which imparts shallower
embossing through lower penetration depth or lower nip
pressure.
[0080] The improved properties and characteristics of the multi-ply
paper product associated with the present invention is also
achieved by using the differential depth embossing in conjunction
with an embossing pattern having particular characteristics. When
the first and second plies are nested together, the plies become
contact laminated to one another so that the primary adhesion
between the sheets is the result of contact between cellulosic
fibers rather than through an intermediate adhesive. The embossed
pattern is specifically designed to avoid non-elongated sharply
defined contact regions as it has been found through developmental
efforts that contact regions having these characteristics produce a
rather harsh feeling sheet. In the present invention, the embossed
pattern is configured so that the contact region is either
elongated and sharply defined (having a small radius of curvature
along the edge between the emboss and the background) or
non-elongated and gently rounded. The voids defined by these
contact regions are thus compliant. The combination of the
differential depth embossing and the particular characteristics of
the embossed pattern together results in a multi-ply paper product
such as tissue paper having significantly increased softness and
puffiness characteristics, and improved bulk and emboss definition
as compared to other known tissue products while at the same time
possessing strength characteristics not commonly found in tissue
paper having such attributes.
[0081] The present invention as described in more detail below has
application to multi-ply paper products in which characteristics
such as are softness, puffiness, bulk and emboss definition
contribute to perceived product desirability The paper products
include absorbent paper, bathroom and facial tissue, napkins and
towels. The detailed description set forth below makes reference to
tissue paper, but it is to be understood that the present invention
is equally applicable to these other types of multi-ply paper
products.
[0082] The multi-ply tissue product according to the present
invention is fabricated using the apparatus shown in FIG. 1. To
produce the differential depth embossed tissue, a first tissue ply
20 is conveyed past a series of idler rollers 22 towards the nip
that is located between a pattern roll 24 which may be made of
steel and an impression roll 26 which may be made of rubber. The
pattern roll 24 rotates in the clockwise direction while the
impression roll 26 rotates in the counterclockwise direction. The
first tissue ply 20 forms the bottom ply in the resulting multi-ply
tissue.
[0083] A second tissue ply 28 is conveyed around an idler roller 32
and is then passed into a nip located between an impression roll 34
which may be made of rubber and the pattern roll 24. The second
tissue ply 28 is adapted to form the top ply in the resulting
multi-ply tissue. The second tissue ply 28 is rewound around the
pattern roll 24 to form the outside of the multi-ply tissue. As the
second tissue ply 28 passes through the nip between the pattern
roll 24 and the impression roll 34, the second tissue ply 28 is
heavily embossed. This heavy embossing of the second tissue ply
imparts a high degree of emboss definition and perceived puffiness
to the second tissue ply 28.
[0084] In contrast, the first tissue ply 20 that is fed through the
nip between the pattern roll 24 and the impression roll 26 is only
lightly embossed. That is, the first tissue ply is embossed to a
lesser degree than the second tissue ply 28. The lightly embossed
first tissue ply 20 is joined to or nested with the heavily
embossed second tissue ply 28 at the nip between the pattern roll
24 and the impression roll 26. By virtue of being rewound on the
pattern roll 24 and joined to the first tissue ply, the relatively
high friction on the heavily embossed second tissue ply 28 faces
towards the lightly embossed first tissue ply 20. By virtue of the
relatively light embossing that occurs at the nip between the
pattern roll 24 and the impression roll 26, the bottom side or
inside of the two-ply tissue possesses a relatively low friction
and thus a better perceived softness. The resulting multi-ply
tissue exiting from the nip between the pattern roll 24 and the
impression roll 26 is passed around a series of idler rolls 36 and
is then wound on a take-up roll (not shown).
[0085] As mentioned above, the second tissue ply 28 is rather
heavily embossed whereas the first tissue ply 20 is rather lightly
embossed. This difference in the degree of embossment can be
achieved in several ways. For example, the impression rolls 26, 34
can be made of materials having different degrees of softness to
allow a higher penetration depth in the case of the nip between the
pattern roll 24 and the impression roll 34 as compared to the nip
between the pattern roll 24 and the impression roll 26.
Alternatively, greater pressure can be applied at the nip between
the pattern roll 24 and the impression roll 34 as compared to the
nip between the pattern roll 24 and the impression roll 26. With
the use of more pressure to achieve the different penetration
depth, the impression rolls 26, 34 can have the same hardness or
softness characteristics (e.g., 40-80 Shore Durometer A).
[0086] FIG. 2 illustrates the emboss roll 24 situated between the
two impression rolls 26, 34. FIG. 2 also illustrates one example of
the pattern on the pattern roll 24 that has been found to produce,
in conjunction with the differential depth emboss described above,
multi-ply paper products such as tissues having better perceived
softness and bulk along with better emboss definition yet without
unduly degrading the strength of the multi-ply tissue. The
characteristics of the emboss pattern and the way in which such
characteristics contribute to the overall advantageous attributes
of the multi-ply tissue will be discussed in more detail below.
[0087] FIG. 3A illustrates a slightly modified form of the
apparatus for carrying out the differential depth embossing. Here,
the first tissue ply 20 is fed from an unwinder 40 to the nip
located between an impression roll 42 which may be made of rubber
and a first pattern roll 44 which may be made of steel. The first
tissue ply 20 is lightly embossed as it passes through the nip
between the impression roll 42 and the first pattern roll 44. At
the same time, the second tissue ply 28 is fed from an unwinder 46
towards the nip located between an impression roll 48 which may be
made of rubber and a second pattern roll 50 which may be made of
steel. The nip between the impression roll 48 and the second
pattern roll 50 is designed to impart a heavy emboss to the second
tissue ply 28.
[0088] FIG. 3B illustrates that the light emboss can be achieved by
allowing the engravings on the first pattern roll 44 to penetrate
into the impression roll 42 to a lesser extent as compared to the
heavy emboss that is applied to the second tissue ply 28. This can
be accomplished by using less pressure or by using an impression
roll 42 made of a material that is not as easily penetrated as the
impression roll 48, and/or by using a pattern roll 44 less engraved
than the pattern roll 50. As shown in FIG. 3C, the heavy emboss
applied to the second tissue ply 28 can be achieved by the
engravings on the pattern roll 50 penetrating more deeply into the
impression roll 48 through the use of greater pressure of a softer
material for the impression roll 48, and/or deeper embossment on
the pattern roller 50.
[0089] After the heavily embossed second tissue ply 28 passes
through the nip between the impression roll 48 and the pattern roll
50, a gluing unit 52 applies glue to the projections that are
formed on the exterior surface of the embossed second tissue ply 28
by virtue of the embossing. The heavily embossed second tissue ply
28 with the applied glue then advances further to a nip between the
pattern roll 44 and the pattern roll 50. At this point, the lightly
embossed first tissue ply 20 is nested with the heavily embossed
second tissue ply 28 and are then conveyed around a marrying roll
54 and subsequently wound.
[0090] FIG. 4A generally illustrates the multi-ply tissue that
results from the differential depth embossing technique illustrated
in FIG. 3A. For comparison purposes, FIG. 4B illustrates a
conventional multi-ply tissue formed by conveying two tissue plies
through the nip formed between a steel engraved roll and a rubber
roll. As can be seen, the two tissues forming the conventional
multi-ply tissue are deeply nested within one another. In this
conventional multi-ply tissue, the tissue may possess desirable
emboss definition and perceived puffiness characteristics, but the
tissue will be rather rough. In contrast, in the multi-ply tissue
of the present invention as shown in FIG. 4A, the tissue will not
only possess better perceived softness and bulk along with better
emboss definition, but will also possess desirable strength
characteristics by virtue of the lightly embossed first tissue ply
20.
[0091] FIG. 5 illustrates another variation on the apparatus shown
in FIG. 1. In this version shown in FIG. 55, two preconditioning
mechanisms 60, 62 are provided for preconditioning each of the
tissue plies 20, 28 prior to entering the respective nips. The
preconditioning mechanisms 60, 62 are designed to impart moisture
and/or heat to the tissue plies 20, 28. The preconditioning
mechanisms 60, 62 can be designed to apply moisture and heat to the
tissue plies 20, 28 at the same time or can be designed to
individually apply steam or moisture and heat to the tissue plies
20, 28 in successive stages. As a further alternative, the
preconditioning mechanisms 60, 62 can be designed to apply only
moisture or only heat to the tissue plies 20, 28. In a preferred
form of the invention, the preconditioning mechanisms 60, 62 are in
the form of steam showers that apply a combination of moisture and
heat to the tissue plies 20, 28.
[0092] A first one of the preconditioning mechanisms 60 is
positioned upstream of the nip located between the pattern roll 24
and the impression role 26 and a second one of the preconditioning
mechanisms 62 is positioned upstream of the nip located between the
pattern roll 24 and the impression roll 34. An additional idler
roll 56 is also provided at the position shown in FIG. 5. The
second tissue ply 28 is conveyed around this idler roll 56 prior to
being subjected to the preconditioning treatment (i.e., moisture
and/or heat) by the second preconditioning mechanism 62.
[0093] Although the arrangement shown in FIG. 5 has been found
advantageous from the standpoint of enhancing product quality,
other methods and arrangements for applying moisture and heat
(e.g., steam) to the tissue plies 20, 28 that are known to skilled
artisans can be employed and fall within the scope of the present
invention. By way of example, steam can be applied to either or
both sides of the plies 20, 28, and steam can be applied to the ply
28 ahead of the idler roller 56. Also, the idler roller 56 shown in
FIG. 5 is not necessary for practicing the invention when steam is
applied to the tissue ply 28 at a point between the idler roll 32
and the impression roll 34.
[0094] The arrangement shown in FIG. 5 has been found to be quite
advantageous in that steam preconditioning each of the tissue plies
20, 28 prior to embossing provides a much higher caliper and lower
tensile modulus as compared to tissue plies not subjected to steam
preconditioning. Without being bound by theory, it is believed that
preconditioning one or both of the plies with steam enables the
plies to become more compliant and this allows an improved emboss
definition to be imparted to the web. Better emboss definition is
highly desirable as it helps enhance sheet caliper.
[0095] As mentioned above, the present invention is based on the
discovery that unexpectedly advantageous results can be achieved by
combining differential depth emboss with an emboss pattern having
certain characteristics. FIGS. 6A, 7 and 8 illustrate three
different emboss patterns that, in combination with the
differential depth emboss, provide particularly advantageous
results.
[0096] The emboss pattern 70 shown in FIG. 6A is in the form of a
series of spaced apart flowers 72. The pattern also includes dots
arranged in the shape of diamonds, at least some of which surround
the flowers 72. Each of the flowers 72 is defined by emboss
elements 74, substantially all of which are elongated in shape.
FIG. 6B illustrates an enlarged version of one of the elongated
emboss elements 74'. As can be seen, the elongated emboss element
74' is dimensioned so that the dimension y is significantly greater
than the dimension x. The emboss element thus possesses an aspect
ratio (i.e., y/x) greater than 1 (if the dimensions x and y were
equal, the aspect ratio would be 1). The aspect ratio of the emboss
element is preferably between about 1 and about 10, preferably
greater than about 2. Without being bound by theory, it is believed
that using emboss elements with aspect ratios between approximately
1 and approximately 10, greater than approximately 2 provides a
smoother and puffier structure that is pleasing to the touch and
thus perceived to be of softer quality.
[0097] FIG. 7 illustrates another preferred emboss pattern 80.
Here, the emboss pattern is in the form of alternating and spaced
apart flowers 72, like those shown in FIG. 6A, and hearts 82. The
hearts provide an open emboss pattern. The aspect ratio of an
individual heart is the contact area weight average of the
individual aspect ratios of the components making up the heart. The
pattern shown in FIG. 7 also includes dots arranged in the form of
diamonds, with each diamond shaped arrangement of dots surrounding
one of the flowers 72 and hearts 82.
[0098] FIG. 8 illustrates another preferred emboss pattern 90.
Here, the emboss pattern is in the form of alternating and spaced
apart flowers 72, like those shown in FIG. 6A, and double hearts 92
defined by a heart shaped emboss positioned within another heart
shaped emboss. The pattern further includes dots likes those shown
in FIG. 7 that are arranged in the form of diamonds each
surrounding one of the flowers and double hearts. The double hearts
provide an open emboss pattern. The aspect ratio of an individual
double heart is the contact area weight average of the individual
aspect ratios of the components making up the double heart.
[0099] A variety of tests were conducted on different tissue
samples produced according to the differential depth emboss (DDE)
of the present invention and tissue samples produced according to
the conventional process in which two tissue plies are conveyed
between a steel/rubber nip. The tests are discussed below, with the
resulting data being summarized in various graphs and tables set
forth below and in the drawing figures.
EXAMPLE 1
[0100] This example provides a comparison between tissue product
converted using the conventional emboss process and that converted
using the differential depth embossing process. Tissue base sheets
were made on a crescent former pilot paper machine using 15 degree
bevel at a percent crepe of 22%. The base sheet furnish contains
65% Southern hardwood kraft and 35% Northern softwood kraft. Base
sheets were converted to two-ply tissue using the conventional
steel-to-rubber process and the differential depth emboss process.
The rubber rolls with hardness 40 Shore Durometer A were used in
both processes. Both processes used the same emboss pattern shown
in FIG. 7. Each process converted base sheets at three or four
penetration depths (or nip pressures). Physical properties of
various tissue products were measured and compared. FIGS. 9-13 show
the test results. It can be seen from FIG. 9 that the differential
depth emboss process made product with slightly lower caliper at
equal GM tensile strength (geometric mean strength which is equal
to the square root of the product obtained by the multiplying MD
dry tensile and CD dry tensile) than those converted using the
conventional emboss process. FIG. 10 shows that the differential
depth emboss process resulted in product with lower friction or
GMMMD (friction deviation from the mean) at equal GM tensile
strength. The differential depth emboss process produced product
with higher tensile modulus at equal GM tensile strength as shown
in FIG. 11. The high tensile modulus is caused by light embossing
on the bottom ply. FIG. 12 shows that the differential depth emboss
process made product with better sensory softness at equal GM
tensile strength. Compared to the conventional product, the overall
softness value of the differential depth embossing product is 0.4
or more units higher which is significant at the 95% confidence
level. The visual tests were performed on selected prototypes. The
results indicate that the differential depth emboss process
produced product with better visual perception at equal penetration
depth as shown in FIG. 13.
EXAMPLE 2
[0101] This example compares and illustrates the differences
between the differential depth emboss product and the conventional
tissue product. Tissue base sheets were made from a furnish
containing 60% Southern hardwood kraft, 30% Northern softwood kraft
and 10% Broke. Base sheets were made with square blade at 20% crepe
ratio and converted into two-ply tissue using the conventional
process and the differential depth emboss process. The hardness of
rubber rolls used in both processes is 40 Shore Durometer A. Both
processes used the same emboss pattern corresponding to the emboss
pattern shown in FIG. 8. Each process converted base sheets at two
penetration depths (or nip pressures). The basis weight of two-ply
tissue product is 17 to 20 lbs/3000 square ft. Physical test
results are plotted in FIGS. 14-16. FIGS. 14 and 15 indicate that
two-ply tissue converted using the differential depth emboss
process has higher caliper and lower friction at equal GM tensile
strength than that converted using the conventional process. FIG.
16 shows that the differential depth embossing product has higher
tensile modulus than the conventional product. The sensory softness
result is shown in FIG. 17. The differential depth emboss product
has a overall softness value 0.2 to 0.4 units higher than the
conventional product.
EXAMPLE 3
[0102] This example illustrates the effect of the emboss process on
two-ply tissue. The furnish of tissue base sheets contains 30%
Northern softwood kraft, 60% Southern hardwood kraft and 10% trial
broke. Base sheets were made at basis weight of 9.3 lbs/3000 square
ft using a square crepe blade at 72 degrees creping angle. The
conventional process and the differential depth emboss process were
used to converted base sheet to two-ply tissue. The rubber rolls
with hardness 40 Shore Durometer A were used in both processes. The
same emboss pattern used in Example 2 above was used in this
example. Two-ply tissue was converted using the conventional emboss
process at penetration depth 0.085 inches. For two-ply tissue
converted using the differential depth emboss process, the
penetration depth is 0.095 inches for top ply (or outside) and then
the top and bottom (or inside) plies are embossed together at
penetration depth 0.065 inches.
[0103] Table 1 below lists all of the physical properties and
sensory softness values for the differential depth embossing tissue
product and the tissue product produced using the conventional
method. The way in which the properties and values shown in FIG. 1,
as well as subsequent tables, are obtained is known in the art and
so a detailed description is not provided here.
[0104] Compared to the conventional emboss product, the
differential depth emboss product has higher caliper, higher
tensile modulus, and lower friction. The differential depth emboss
product has a overall sensory softness value 0.74 units higher than
the conventional emboss product. The difference in softness value
is 0.4 units or more which is significant at 95% confidence level.
TABLE-US-00001 TABLE 1 Physical Properties of Two-Ply Tissue
Products Conventional Differential Depth Emboss Product Emboss
Product Basis Weight (lbs/ream) 18.1 18.4 Caliper (0.001''/8 st)
78.3 84.8 MD Dry Tensile (g/3'') 990 934 CD Dry Tensile (g/3'') 421
430 GM Dry Tensile (g/3'') 646 634 Tensile Modulus (g/% strain)
19.4 20.5 Friction 0.189 0.181 Roll Diameter (inch) 4.42 4.56 Roll
Compressibility (%) 19.1 19.7 Sensory Softness 16.89 17.63
EXAMPLE 4
[0105] This example compares and illustrates the differences
between the differential depth emboss tissue product and the
conventional product. Tissue-base sheets similar to those used in
the example 3 were converted to 2-ply tissue. An emboss pattern
similar to that illustrated in FIG. 8 was used in the present
example. The rubber rolls with hardness 40 Shore Durometer A were
used in both processes. Two-ply tissue was converted using the
conventional emboss process at penetration depth 0.080 inches. For
two-ply tissue converted using the differential depth emboss
process, the penetration depth is 0.090 inches for top ply and then
the top and bottom plies are embossed together at a penetration
depth of 0.060 inches. The physical properties of the tissue
products were measured and compared. Table 2 below lists all of
test results including sensory softness value. Compared to the
conventional emboss product, the differential depth emboss product
has higher caliper, higher tensile modulus, and lower friction.
Also, the differential depth emboss product has a sensory softness
value 0.4 units higher than the conventional emboss product.
TABLE-US-00002 TABLE 2 Physical Properties of Two-Ply Tissue
Products Conventional Differential Depth Emboss Product Emboss
Product Basis Weight (lbs/ream) 18.4 18.7 Caliper (0.001''/8 st)
74.5 78.3 MD Dry Tensile (g/3'') 1044 1075 CD Dry Tensile (g/3'')
432 447 GM Dry Tensile (g/3'') 672 693 Tensile Modulus (g/% strain)
20.2 24.3 Friction 0.172 0.158 Roll Diameter (inch) 4.33 4.46 Roll
Compressibility (%) 19.2 19.6 Sensory Softness 17.35 17.75
EXAMPLE 5
[0106] This example illustrates that the effect of the emboss
process on two-ply tissue. The furnish of tissue base sheet
contains 30% Northern softwood kraft, 60% Southern hardwood kraft,
and 10% trial broke. An emboss pattern similar to that shown in
FIG. 8 was used in the present example. Two-ply tissue was
converted using the conventional emboss process at a penetration
depth of 0.095 inches. For two-ply tissue converted using the
differential depth emboss process, the penetration depth is 0.090
inches for top ply and then top and bottom plies were embossed
together at a penetration depth of 0.065 inches. Rubber rolls with
hardness 40 Shore Durometer A were used in both processes. Table 3
below lists all of test results including sensory softness
value.
[0107] Compared to the conventional emboss product, the
differential depth emboss product has higher tensile modulus, and
lower friction. Both products have similar caliper. The
differential depth emboss product has a sensory softness value 0.68
units higher than the conventional emboss product. Thus, the
difference in softness value is greater than 0.4 units which is
significant at 95% confidence level. TABLE-US-00003 TABLE 3
Properties of Two-Ply Tissue Products Conventional Differential
Depth Emboss Product Emboss Product Basis Weight (lbs/ream) 18.6
18.8 Caliper (0.001''/8 st) 72.9 73 MD Dry Tensile (g/3'') 1129
1111 CD Dry Tensile (g/3'') 438 455 GM Dry Tensile (g/3'') 703 711
Tensile Modulus (g/% strain) 21.15 24.75 Friction 0.161 0.144 Roll
Diameter (inch) 4.31 4.25 Roll Compressibility (%) 19.7 20 Sensory
Softness 17.55 18.23
EXAMPLE 6
[0108] This example illustrates that the effect of adhesive and the
emboss process on two-ply tissue. Tissue base sheets similar to
those used in Example 5 were converted using both the differential
depth emboss process and the conventional process. The rubber rolls
with hardness 40 Shore Durometer A were used in both processes.
Both processes used the same emboss pattern similar to that shown
in FIG. 8. Two strips of adhesive per embossed sheet at 4.5
mg/linear meter per strip were applied on the back side of the top
ply to improve the ply-bond. For the differential depth embossing
process, the two-ply tissue with adhesive applied was embossed at a
penetration depth of 0.090 inches for the top ply, and then the top
and bottom plies were embossed together at a penetration depth of
0.060 inches. A two-ply tissue converted using the conventional
emboss process was embossed at a penetration depth of 0.085 inches.
Compared to the conventional product, the differential depth
embossing product has higher caliper, higher tensile modulus and
higher friction. Higher friction for the differential depth
embossing product is inconsistent with the results observed in
previous examples. The sensory softness result indicates that the
differential depth embossing product and the conventional product
have similar softness. Based on physical attributes and softness
results, applying adhesive for running the differential depth
embossing process is not preferred. TABLE-US-00004 TABLE 4
Properties of Two-Ply Tissue Products Conventional Differential
Depth Emboss Product Emboss Product (with Glue Applied) (with Glue
Applied) Basis Weight (lbs/ream) 17.9 18.0 Caliper (0.001''/8 st)
75.7 80.0 MD Dry Tensile (g/3'') 1001 965 CD Dry Tensile (g/3'')
444 430 GM Dry Tensile (g/3'') 667 644 Perf. Tensile (g/3'') 434
410 Tensile Modulus (g/% strain) 20.6 23.4 Friction 0.175 0.189
Roll Diameter (inch) 4.29 4.40 Roll Compressibility (%) 18.9 20.5
Sensory Softness 17.0 17.16
EXAMPLE 7
[0109] This example illustrates the effect of adhesive on two-ply
tissue converted using the differential depth emboss process.
Tissue base sheets similar to those used in Example 5 were
converted to two-ply tissue using the differential depth emboss
process. An emboss pattern similar to that shown in FIG. 8 was used
in the present example. The rubber rolls with hardness 40 Shore
Durometer A were used. Two strips of adhesive per embossed sheet at
4.5 mg/linear meter per strip were applied on the top ply. The
differential depth embossing product with adhesive applied was
embossed at a penetration depth of 0.090 inches for the top ply,
and then the top and bottom plies were embossed together at a
penetration depth of 0.060 inches. The differential depth embossing
product without adhesive applied was embossed at a penetration
depth of 0.095 inches for the top ply and embossed at a penetration
depth of 0.065 inches as the top and bottom plies were joined
together. Table 5 below lists the physical attributes and softness
value results. The effect of adhesive on the perforated tensile
strength of two-ply tissue is not significant. The differential
depth embossing product without glue applied has higher caliper,
lower tensile modulus and lower friction. Based on sensory softness
results, the differential depth embossing product without adhesive
applied is softer than that with adhesive applied. The difference
in sensory softness value is greater than 0.4 units which is
significant at the 95% confidence level. As mentioned in the
Example 6, the adhesive is not preferred when running the
differential depth emboss process. TABLE-US-00005 TABLE 5
Properties of Two-Ply Tissue Products Differential Depth Emboss
Product Differential Depth (with Glue Applied) Emboss Product Basis
Weight (lbs/ream) 18.01 18.5 Caliper (0.001''/8 st) 80.0 81.8 MD
Dry Tensile (g/3'') 965 1034 CD Dry Tensile (g/3'') 430 424 GM Dry
Tensile (g/3'') 644 662 Perf. Tensile (g/3'') 404 410 Tensile
Modulus (g/% strain) 23.4 21.7 Friction 0.189 0.176 Roll Diameter
(inch) 4.40 4.53 Roll Compressibility (%) 20.5 20.3 Sensory
Softness 17.18 17.85
EXAMPLE 8
[0110] This example illustrates that the effect of the emboss
process on two-ply tissue. Tissue base sheet was made using
undulatory creping blades. The blade was undulated at a spacing of
20 undulations/inch and a depth of 0.020'' and had a 25 degree
bevel angle. The furnish of base sheet was 30% Northern softwood
kraft, 60% Southern hardwood kraft, and 10% trial broke. The rubber
rolls with hardness 40 Shore Durometer A were used in both
processes. Two-ply tissue converted using the conventional emboss
process was embossed at a penetration depth of 0.095 inches. For
two-ply tissue converted using the differential depth emboss
process, the penetration depth was 0.095 inches for the top ply,
and then the top and bottom plies were embossed together at a
penetration depth of 0.065 inches. An emboss pattern similar to
that shown in FIG. 8 was employed in the present example. Table 6
below lists all of the physical properties and sensory softness
value. Compared to the conventional product, the differential depth
emboss product has lower caliper, higher tensile modulus, and lower
friction. The differential depth emboss product has an overall
sensory softness value 0.65 units higher than the conventional
embossing product. The difference in sensory softness value is
greater than 0.4 units which is significant at the 95% confidence
level. TABLE-US-00006 TABLE 6 Physical Properties of Two-Ply Tissue
Products Conventional Differential Depth Emboss Product Emboss
Product Basis Weight (lbs/ream) 18.4 18.6 Caliper (0.001''/8 st)
71.3 69.2 MD Dry Tensile (g/3'') 1043 1001 CD Dry Tensile (g/3'')
441 456 GM Dry Tensile (g/3'') 678 676 Tensile Modulus (g/% strain)
19.81 22.18 Friction 0.154 0.149 Roll Diameter (inch) 4.23 4.16
Roll Compressibility (%) 21.5 18.5 Sensory Softness 17.62 18.27
EXAMPLE 9
[0111] This example illustrates that the effect of emboss process
on stratified tissue base sheet with basis weight ranging from 11
to 13 lbs/3000 square ft. Tissue base sheet is in stratified mode
and the layer split of base sheet was 65% (100% Northern hardwood
kraft) to the Yankee side and 35% (100% Northern softwood kraft) to
the air side. Base sheets were converted to two-ply tissue using an
emboss pattern similar to that illustrated in FIG. 8. The rubber
rolls with hardness 40 Shore Durometer A were used in both
processes. Two-ply tissue was converted using the conventional
emboss process at penetration depth 0.095 inches. For two-ply
tissue converted using the differential depth emboss process, the
penetration depth was 0.100 inches for the top ply, and then the
top and bottom plies were embossed together at a penetration depth
of 0.065 inches. Table 7 below lists all of the test results
including sensory softness value. Compared to the conventional
product, the differential depth embossing product has lower
friction and higher caliper at the similar GM tensile strength. The
differential depth embossing product has lower tensile modulus
which differs from previous examples. The differential depth emboss
product has a better sensory softness (20.44 vs. 20.24 units).
TABLE-US-00007 TABLE 7 Physical Properties of Two-Ply Tissue
Products Differential Depth Conventional Emboss Product Emboss
Product (40/80 Sha) Pene. Depth (.times.0.001'') 95 100/65 Basis
Weight (lbs/ream) 26.5 26.4 Caliper (0.001''/8 st) 105.7 112.2 MD
Dry Tensile (g/3'') 960 921 CD Dry Tensile (g/3'') 412 381 GM Dry
Tensile (g/3'') 629 592 Tensile Modulus (g/% strain) 14.1 13.86
Friction 0.168 0.162 Sensory Softness 20.24 20.44
EXAMPLE 10
[0112] This example illustrates the effect of the emboss process on
homogeneous tissue base sheet with basis weight ranging from 11 to
13 lbs/3000 square feet. Base sheets were in the homogeneous mode
containing 35% Northern softwood kraft and 65% Northern hardwood
kraft. Base sheets were converted to two-ply tissue using an emboss
pattern similar to that shown in FIG. 8. Rubber rolls with hardness
40 Shore Durometer A were used in both processes. Two-ply tissue
was converted using the conventional emboss process at a
penetration depth 0.100 inches. For two-ply tissue converted using
the differential depth emboss process, the penetration depth was
0.100 inches for the top ply, and then the top and bottom plies
were embossed together at a penetration depth of 0.065 inches.
Table 8 below lists all of the test results including sensory
softness value. Compared to the conventional product, the
differential depth emboss product has lower friction and higher
caliper at equal GM tensile strength. The differential depth
embossing product has lower tensile modulus which is consistent
with the results in example 9. The differential depth emboss
product has a better sensory softness value that is 0.56 units
higher than the conventional products. TABLE-US-00008 TABLE 8
Physical Properties of Two-Ply Tissue Products Differential Depth
Conventional Emboss Product Emboss Product (40/80 Sha) Pene. Depth
(.times.0.001'') 100 100/65 Basis Weight (lbs/ream) 26.5 26.8
Caliper (0.001''/8 st) 104.6 108.6 MD Dry Tensile (g/3'') 1097 1046
CD Dry Tensile (g/3'') 426 447 GM Dry Tensile (g/3'') 684 683
Tensile Modulus (g/% strain) 17.13 16.52 Friction 0.177 0.175
Sensory Softness 19.19 19.75
EXAMPLE 11
[0113] This example compares and illustrates the differences
between the microstructure between the differential depth emboss
product and the conventional tissue product. The base sheet furnish
contained 65% Southern hardwood kraft and 35% Northern softwood
kraft. Two-ply tissue was converted using the conventional emboss
process at a penetration depth of 0.075 inches. For the
differential depth embossing product, the penetration depth was
0.085 inches for the top ply, and then the top and bottom plies
were embossed together at a penetration depth of 0.050 inches. Both
processes used the same emboss pattern depicted in FIG. 7. The
rubber rolls with hardness 40 Shore Durometer A were used in both
processes. FIGS. 18a, 18b and 19a, 19b are cross-sectional views
taken at two different places of products produced conventionally
and according to the present invention. The illustrations in FIGS.
18a, 18b and 19a, 19b are magnified at 50.times.. Compared to the
cross-sectional structure of the conventional product, the bottom
ply of the differential depth embossing product possesses less
curvature because of the light emboss as the top and bottom plies
are joined together. Based on the physical test results listed in
Table 9 below, less curvature explains that the differential depth
embossing product has much lower friction than the conventional
product. The contours of the top ply for both the differential
depth embossing product and the conventional product are similar.
The differential depth embossing product can maintain an emboss
definition as good as the conventional product. The softness pocket
between the top and bottom plies for the differential depth
embossing product is larger than that for the conventional product.
The larger softness pocket can improve puffiness feel which may
provide a two-ply tissue with better softness. Based on sensory
softness results, the differential depth embossing product has
better sensory softness than the conventional product. The
differential depth embossing product has larger softness pocket
between plies and less curvature on the bottom ply which contribute
better softness and lower friction. In previous examples, the
differential depth embossing product always has lower friction and
better sensory softness than the conventional product.
TABLE-US-00009 TABLE 9 Physical Properties of Two-Ply Tissue
Products Differential Depth Conventional Emboss Product Emboss
Product (40/80 Sha) Pene. Depth (.times.0.001'') 75 85/50 Basis
Weight (lbs/ream) 18.95 18.94 Caliper (0.001''/8 st) 64.2 67.0 MD
Dry Tensile (g/3'') 1127 1154 CD Dry Tensile (g/3'') 518 541 GM Dry
Tensile (g/3'') 764 790 Tensile Modulus (g/% strain) 24.5 25.42
Friction 0.152 0.139 Sensory Softness 17.1 18.0
EXAMPLE 12
[0114] This example compares microstructure between the
differential depth emboss product and the conventional tissue
product. Tissue base sheets were made from a furnish containing 60%
Southern hardwood kraft, 30% Northern softwood kraft and 10% Broke
and with square blade at 20% crepe ratio. Two-ply tissue was
converted using the conventional emboss process at a penetration
depth of 0.085 inches. For the differential depth embossing
product, the penetration depth was 0.100 inches for the top ply,
and then the top and bottom plies were embossed together at a
penetration depth of 0.065 inches. The rubber roll hardness used in
both processes was 40 Shore Durometer A. Both processes used the
same emboss pattern illustrated in FIG. 8. Table 10 below lists the
physical properties and sensory softness results. FIGS. 20a, 20b
and 21a, 21b show the cross-sectional structure taken at two
different positions. The illustrations in FIGS. 20a, 20b and 21a,
21b are magnified at 50.times.. The gap (or softness pocket)
between top and bottom for the differential depth embossing product
is much larger than that for the conventional product. Because of
the wider softness pocket, the differential depth embossing product
has a higher caliper than that of the conventional product. The
larger gap between the top and bottom plies can also improve tissue
softness. As can be seen from table 10 below, the differential
depth embossing product has higher softness than the conventional
product. The results are consistent with those observed in the
example 11. TABLE-US-00010 TABLE 10 Physical Properties of Two-Ply
Tissue Products Differential Depth Conventional Emboss Product
Emboss Product (40/80 Sha) Pene. Depth (.times.0.001'') 85 100/65
Basis Weight (lbs/ream) 17.65 18.2 Caliper (0.001''/8 st) 72.3 79.2
MD Dry Tensile (g/3'') 929 894 CD Dry Tensile (g/3'') 411 415 GM
Dry Tensile (g/3'') 618 609 Tensile Modulus (g/% strain) 19.83
23.39 Friction 0.167 0.166 Sensory Softness 17.13 17.58
EXAMPLE 13
[0115] This example illustrates the effect of rubber roll hardness
on the tissue product converted using the differential depth emboss
process. A base sheet similar to that used in example 12 was used
here. The base sheets were converted to two-ply tissue using the
differential depth emboss process. Instead of using the same
hardness (i.e., 40 Shore Durometer A) of rubber rolls for both
nips, a harder rubber roll (i.e., greater than 40 Shore Durometer
A) was used at the light emboss nip (or the second nip) where the
two plies are joined or nested together. The rubber roll hardness
ranged from 40 to 80 Shore Durometer A at the light emboss nip. For
one condition, both softer rubber rolls (i.e., 40 Shore Durometer
A) were replaced by harder rubber rolls (i.e., 55 Shore Durometer
A). The emboss pattern shown in FIG. 8 was used in this example.
Four different penetration depths were run in each condition. The
basis weight of the converted two-ply tissue was 18 to 20 lbs/3000
square ft. Physical test results are plotted in FIGS. 22-25. FIG.
22 shows that the effect of rubber roll hardness on the caliper of
differential depth embossing products is not significant. The
difference in caliper among differential depth embossing products
is within 0.003'' per 8 sheets.
[0116] The effect of rubber roll hardness on the tensile modulus
and friction are not significant as shown in FIGS. 23 and 24. A
similar trend is observed for the sensory softness result as shown
in FIG. 25. The difference in softness value among differential
depth embossing products is less than 0.4 units which is
significant difference at 95% confidence level. Based on results,
the harder rubber roll (i.e., greater than 40 Shore Durometer A)
can replace the softer roll (i.e., 40 Shore Durometer A) at the
light emboss nip. The aforementioned result differs from that
described in U.S. Pat. No. 3,708,366. U.S. Pat. No. 3,708,366
states that the rubber roll used as the light emboss nip is
preferred to be softer than the rubber roll used at the heavy
emboss nip. While not wishing to be bound by theory, it is believed
that the likely explanation for the difference in results between
the present invention and the disclosure in U.S. Pat. No. 3,708,366
is due to elongated/non-elongated and gently rounded emboss
patterns used in the present invention. These patterns are less
likely to form sharp embossments in the ply when using hard rubber
rolls.
EXAMPLE 14
[0117] This example illustrates the effect of adhesive on tissue
product converted using the differential depth emboss process.
Rubber rolls with 40 Shore Durometer A were used. The base sheet
was similar to that used in Example 12 and was converted to two-ply
tissue using the differential depth emboss process. Adhesive was
applied on extrusions at the back side of the top ply across the
web. The adhesive was applied using an apparatus similar to that
shown in FIG. 3A. The emboss pattern illustrated in FIG. 8 was used
in this example and four different penetration depths were run for
each condition. FIGS. 26 and 27 show that the effects of adhesive
on the caliper and the tensile modulus of the differential depth
embossing tissue product are not significant. FIG. 28 shows that
the differential depth embossing product without adhesive applied
has a lower friction than the differential depth embossing product
with adhesive applied. The differential depth embossing product
without adhesive applied has better softness as shown in FIG. 29.
The difference in softness value is more than 0.4 units which is a
significant difference at 95% confidence level. Compared to the
product with adhesive applied, the product without adhesive applied
has lower friction and better softness. The aforementioned results
are consistent with those found in Examples 6 and 7. Thus, applying
adhesive is not preferred for running the differential depth
embossing process.
EXAMPLE 15
[0118] This example illustrates the effect of adhesive on a tissue
product converted using the differential depth emboss process. The
only difference between Example 14 and Example 15 is the emboss
pattern. In this example, an emboss pattern like that shown in FIG.
6A was used. Four different penetration depths were run for each
condition. FIG. 30 shows that the adhesive did provide a little
advantage for generating bulk. FIG. 31 shows that both differential
depth embossing products with and without adhesive applied have a
similar tensile modulus at equal GM tensile strength. As the
penetration depth increases, the differential depth embossing
product without adhesive applied has lower friction as shown in
FIG. 32. FIG. 33 shows that the differential depth embossing
product without adhesive applied has better softness. The
difference in softness value is more than 0.4 units which is
significant difference at 95% confidence level. The sensory
softness result is consistent with that found in Example 14. Thus,
by applying adhesive for running the differential depth embossing
process, the tissue softness may be reduced.
EXAMPLE 16
[0119] This example presents a comparison between tissue product
converted using the differential depth emboss process and that
converted using the conventional emboss process. Rubber rolls with
40 Shore Durometer A were used for both processes. The base sheet
was similar to that used in Example 12. Four penetration depths
were run for each process and the emboss pattern used for each
emboss process was similar to that shown in FIG. 6A. The basis
weight of the two-ply tissue product was 18 to 20 lbs/3000 square
ft. The conventional product has a higher caliper than the
differential depth embossing product at equal GM tensile strength
as shown in FIG. 34 FIG. 35 shows that the differential depth
embossing product has a higher tensile modulus at equal GM tensile
strength because of the light emboss at the second nip. FIG. 36
shows that the differential depth embossing product has lower
friction at equal GM tensile strength. Compared to the conventional
product, the differential depth embossing product has better
softness as shown in FIG. 37.
EXAMPLE 17
[0120] This example presents a comparison between the differential
depth emboss product and the conventional tissue product. The only
difference between Example 16 and 17 is the emboss pattern. The
emboss pattern shown in FIG. 8 was used in this example. The
differential depth embossing product has higher caliper at equal GM
tensile strength as shown in FIG. 38. The test results of tensile
modulus, friction and sensory softness are plotted in FIGS. 39-41.
Compared to Example 16, the results are consistent with the
differential depth embossing product having lower friction, higher
tensile modulus, and better softness. Although different emboss
pattern were used in Examples 16 and 17, the differential depth
emboss product always has better softness than the conventional
product.
EXAMPLE 18
[0121] This example compares the differential depth emboss product
and the conventional tissue product. Both products were converted
on the commercial machine. Tissue base sheets were made from a
furnish containing 30% Southern hardwood kraft, 20% Northern
softwood kraft and 50% recycled fibers. Two-ply tissue was
converted using the conventional emboss process at a penetration
depth 0.047 inches. For the differential depth embossing product,
the penetration depth was 0.075 inches for the top ply and then the
top and bottom plies were embossed together at a penetration depth
of 0.035 inches. The rubber roll hardness used in both processes is
40 Shore Durometer A. Both processes used the same emboss pattern
illustrated in FIG. 8. Table 11 below lists the physical properties
and sensory softness result. The differential depth embossing
product has higher caliper, lower friction, higher tensile modulus
and better softness. The difference in softness value is greater
than 0.4 units which is significant difference at 95% confidence
level. The results for commercially made products are consistent
with those observed for pilot products used in Examples 3, 4 and 5.
TABLE-US-00011 TABLE 11 Physical Properties of Two-Ply Tissue
Products Differential Depth Conventional Emboss Product Emboss
Product (40/40 Sha) Pene. Depth (x0.001'') 47 75/35 Basis Weight
(lbs/ream) 18.7 18.8 Caliper (0.001''/8 st) 72.6 73.3 MD Dry
Tensile (g/3'') 1065 1056 CD Dry Tensile (g/3'') 417 405 GM Dry
Tensile (g/3'') 666 654 Tensile Modulus (g/% strain) 19.0 21.1
Friction 0.154 0.151 Roll Diameter (inch) 4.2 4.19 Roll
Compressibility (%) 19.0 21.1 Sensory Softness 17.16 17.72
EXAMPLE 19
[0122] This example illustrates a comparison between the
differential depth emboss product and the conventional tissue
product. The differences between Example 18 and Example 19 involve
the base sheet and the penetration depth. The basis weight of the
tissue base sheet ranges from 11-13 lbs/3000 square feet. Base
sheets were made from a furnish containing 60% Northern hardwood
kraft and 40% Northern softwood kraft. Two-ply tissue was converted
using the conventional emboss process at a penetration depth of
0.057 inches. For the differential depth embossing tissue product,
the penetration depth was 0.088 inches for the top ply, and then
the top and bottom plies were embossed together at a penetration
depth of 0.038 inches. Table 12 below lists the physical properties
and sensory softness result. The differential depth embossing
product has a higher caliper, lower friction, and better softness.
The difference in softness value is greater than 0.4 units which is
significant difference at 95% confidence level. Both tissue
products have similar tensile modulus value. The sensory softness
result is thus consistent with those found in Example 10.
TABLE-US-00012 TABLE 12 Physical Properties of Two-Ply Tissue
Products Differential Depth Conventional Emboss Product Emboss
Product (40/80 Sha) Pene. Depth (x0.001'') 57 88/38 Basis Weight
(lbs/ream) 26.6 26.6 Caliper (0.001''/8 st) 102.9 106.1 MD Dry
Tensile (g/3'') 896 868 CD Dry Tensile (g/3'') 346 332 GM Dry
Tensile (g/3'') 557 537 Tensile Modulus (g/% strain) 13.2 13.4
Friction 0.159 0.156 Roll Diameter (inch) 4.15 4.18 Roll
Compressibility (%) 22.2 21.1 Sensory Softness 19.15 19.91
EXAMPLE 20
[0123] This example illustrates the effect of steam preconditioning
on two-ply tissue converted using the differential depth emboss
process. Base sheets were made from a furnish containing 35%
Northern hardwood kraft and 65% Northern softwood kraft. The emboss
pattern shown in FIG. 8 was used in this example. The base sheets
were converted using the differential emboss process with steam
preconditioning at both nips as shown in FIG. 5. The set-up was
substantially the same as that shown in FIG. 5. Three penetration
depths were run for each condition. Compared to the differential
depth embossing product without steam preconditioning, the
differential depth embossing product with steam preconditioning has
a much higher caliper and lower tensile modulus at equal GM tensile
strength as shown in FIGS. 42 and 43. FIG. 44 shows that the effect
of friction on both products are not obvious. The friction for the
differential depth embossing product with steam preconditioning is
quite variable as shown in FIG. 44. Running the differential depth
emboss process with steam preconditioning can provide two-ply
tissue with more bulk and lower modulus which can improve tissue
softness.
EXAMPLE 21
[0124] This example provides a comparison between the differential
depth embossing product and the conventional product converted
using the emboss pattern described in U.S. Pat. No. 3,708,366. A
base sheet similar to that used in Example 17 was converted to
2-ply tissue using the differential depth emboss process and the
conventional emboss process. Each process was run at four
penetration depths. The effect of adhesive on the differential
depth embossing product was also studied. The sensory softness test
result is plotted in FIG. 45. The difference in softness value
between the differential depth embossing product and the
conventional product is less than 0.4 units which is significant
difference at 95% confidence level. In the previous examples, the
differential depth embossing product always possessed better
softness and 0.4 units or more higher than the conventional
product. The differential depth embossing product with adhesive
applied has lower softness value than the differential depth
embossing product without adhesive applied. The aforementioned
result is consistent with the results observed in Example 13.
Applying adhesive when running the differential depth emboss
process decreases tissue softness. The physical attributes are
measured and plotted in FIGS. 46-48. FIG. 46 shows no significant
difference between the differential depth embossing product and the
conventional product. In previous examples, the differential depth
embossing product had lower friction than the conventional product.
Thus, as can be seen, improving tissue softness requires not only
the differential depth emboss process but also a specific emboss
pattern as described above.
[0125] Table 13 below sets forth a comparison of the aspect ratio
of the three emboss patterns shown in FIGS. 6A, 7 and 8 as well as
the emboss pattern described in U.S. Pat. No. 3,708,366. The table
also sets forth a comparison of the sensory softness for tissue
embossed using differential depth embossing as well as the
conventional process for each of the emboss patterns.
TABLE-US-00013 TABLE 13 Comparison between The Current Invention
and The Prior Art Sensory Sensory Aspect Ratio Radius Softness
Softness Emboss Pattern (Length/Width) (x0.001'') (DDE) (Conv.)
FIG. 8 emboss 4.01 10 17.6 17.2 design FIG. 7 emboss 5.08 10 18.1
17.0 design FIG. 6A emboss 6.58 10 17.8 17.1 design Prior art
emboss 1.0 5 16.9 16.7 design embodied in U.S. Pat. No.
3,708,366
[0126] It is apparent from the foregoing that utilizing the
differential depth embossing technique with a known emboss pattern
such as that described in U.S. Pat. No. 3,708,366 does not improve
sensory softness. It is only when the differential depth embossing
technique is combined with the unique emboss patterns having the
characteristics described above and illustrated by way of example
in the drawing figures that an improvement in sensory softness is
achieved.
[0127] The embodiment of the present invention described above
involves treatment of the paper product utilizing an embossing
technique. However, a different type of paper treatment can also be
utilized to apply a marking to the paper having the characteristics
shown in FIGS. 6A, 7 and 8. For example, a debossing paper
treatment can be employed to produce a multi-ply paper product as
shown in FIG. 50. The multi-ply paper product 100 includes at least
two plies 102, 104. The two plies 102, 104 are bonded or connected
together by the pattern 106 that is impressed upon the multi-ply
paper product. The pattern 106 that is impressed upon the
multi-plies 102, 104 advantageously has the shape and
characteristics of any one of the emboss patterns described above
and illustrated in FIGS. 6A, 7 and 8. The impressed pattern is
applied to the paper product so one surface 105 of the paper
product is essentially flat and the other is impressed with the
pattern 106.
[0128] The multi-ply paper product 100 shown in FIG. 50 can be
produced using an apparatus similar to that shown in FIG. 49. The
apparatus includes an unwind roll 110 on which is wound a multi-ply
paper product such as tissue 112. As the sheet passes from the
unwind roll 110 to a first receiving roll 114, the multi-ply paper
product 112 can be brought into contact with water. The water can
be applied to the sheet 112 in the form of steam by passing the
sheet 112 over a tank 116 containing water that is heated to a
temperature greater than or equal to the boiling point of water.
Steam is thus released from the tank and comes into contact with
the surface of the sheet 112. The amount of steam applied can vary,
although it is preferably less than approximately 3% by weight of
the sheet 112, more preferably less than 2% by weight. The small
amount of water in the form of steam that is applied to the sheet
constitutes a preparatory step for the next step in the formation
of the impressed pattern on the multi-ply sheet that is designed to
considerably improve the quality of the impressed pattern. In this
regard, the steam has an advantageous affect on the definition and
uniformity of the pressed pattern. Of course, liquid can be applied
to the sheet 112 in forms other than steam, such as, for example,
by spraying fine droplets.
[0129] The sheet 112 is conveyed to the first receiving roll 114,
and is then passed between the first receiving roll 114 and a steel
engraved roll 118. The steel engraved roll 118 is a hard and
non-deformable roll. The first receiving roll 114 is substantially
elastic. The sheet 112 then makes a second pass between the
engraved roll 118 and a second receiving roll 120. The second
receiving roll 120 is preferably substantially elastic.
[0130] The engraved roll 118 can be heated, preferably to a
temperature lying within the range of approximately 50.degree.
C.-100.degree. C., or preferably approximately 75.degree. C. It has
been found that the combination of the application of water in the
form of steam and the use of a heated engraved roll provides an
advantageous impressed pattern upon the multi-ply sheet 100 shown
in FIG. 50.
[0131] The first and second receiving rolls 114, 120 possess a high
hardness, greater than Shore-D 80 and preferably greater than
Shore-D 90.
[0132] FIG. 51 illustrates a slightly different two-ply paper
product in which a pattern is impressed upon the two-ply paper
product in a slightly different manner from that described above.
Once again, the impression or marking that is applied to the paper
product advantageously possesses the shape and characteristics of
any one of the embossed patterns described above and illustrated in
FIGS. 6A, 7 and 8.
[0133] As seen in FIG. 51, the paper product includes two plies
120, 122. The sheet is provided with a series of impressed regions
124 having the shape and characteristics of any one of the embossed
patterns described above and illustrated in FIGS. 6A, 7 and 8. The
sheet is produced by passing the two-ply paper product through a
nip formed between an engraved roll and a back up roll. As the two
plies 120, 122 pass into the nip, portions of the two-ply paper
product corresponding to the projections on the engraved roll are
impressed. This compression causes the cellulosic fibers in the two
plies 120, 122 to become intermingled and connected with one
another.
[0134] Another aspect of the present invention illustrated in FIGS.
52 and 53 relates to a different process for producing for
producing a two-ply tissue. This method involves the production of
a tissue having a heavily embossed pattern, but which is not
perceived as being rough to the consumer. Referring to FIG. 52, a
rubber roll 200 is positioned in abutting relation to a steel
engraving roll 202. An adhesive applying device 204 is positioned
adjacent the steel engraving roll 202. The adhesive applying device
204 includes an adhesive supply 206 and a rotatable application
roller 208.
[0135] A base sheet or substrate 210 is conveyed around the rubber
roll 200 and then enters a nip 212 between the rubber roll 200 and
the steel engraved roll 202. The rubber roll 200 presses the base
sheet 210 into the pattern formed on the engraved steel roll 202 to
produce the desired embossing pattern. The rubber roll 200 can be a
relatively soft rubber having a low durometer to thereby impart a
heavy boss to the base sheet 210. As the base sheet 210 is conveyed
around the outer surface of the steel engraved roll 202, the
backside of the embossed base sheet 210 passes by the adhesive
application roller 208 which applies adhesive only to the
protuberances or nips on the back of the heavily embossed
sheet.
[0136] As the embossed base sheet 210 is being conveyed, an
essentially or substantially flat backing sheet 214 is conveyed
past a roller 216 and then into engagement with the back surface of
the embossed base sheet 210. As a result, the backing sheet 214 is
adhered to the embossed base sheet 210. A marrying roll 218 is
preferably provided adjacent the outer surface of the steel
engraved roll 202 to facilitate adherence between the two sheets
210, 214. Because the adhesive is only applied to the nips or
projections on the embossed sheet 210, the flat backing sheet 214
is adhered to the embossed base sheet 210 only at those places.
This selective positioning of the adhesive is advantageous from the
standpoint of not excessively interfering or hindering the
perceived softness of the resulting sheet. At the same time, the
perceived strength of the sheet is increased significantly.
[0137] It is also possible with this method to improve the
perceived quilted appearance of the resulting product by making it
appear puffier. This can be achieved by utilizing mismatch in the
stretch between the two sheets 210, 214. This mismatch in the
stretch of the two sheets can be achieved or controlled by
controlling the relative feed rates of the two sheets, so that one
sheet is fed at a faster rate than the other.
[0138] In the resulting product, the protuberances or nubs on the
backside of the heavily embossed sheet 210 are masked or covered by
the substantially flat un-embossed backing sheet. The perceived
softness of the resulting two-ply tissue is thus improved. This
method also makes it possible to easily color decorate the
resulting tissue product by using colored adhesive to join the
sheets.
[0139] A further advantage associated with this method is
illustrated in FIG. 53. In this variation, dual depth embossing is
employed. With dual depth embossing, some of the embossments 220
are deeper than other embossments 222. This could be easily
achieved by appropriately configuring the outer surface of the
steel engraved roll 202. In addition to different depth embossing,
the different depth embossments 220, 222 can be of a different
configuration to impart an attractive appearance to the finished
tissue product. For example, the deeper embossments 220 can be in
the form of tulip-shaped embossments while the shallower
embossments 222 can be dot-shaped embossments.
[0140] A further refinement provided by the variation shown in FIG.
53 is that adhesive can be applied even more selectively to only
portions of the backing side of the embossed sheet 210'. That is,
through use of an adhesive application device such as that shown in
FIG. 52, adhesive is applied to only the longest protuberances or
nubs forming a part of the embossed pattern. Thus, adhesive is only
applied in very small selected areas between the two sheet 210',
214 so as not to significantly interfere with the perceived
softness of the resulting sheet, while at the same time allowing
realization of an increase in the perceived strength of the
resulting sheet.
[0141] Another aspect of the present invention illustrated in FIGS.
54 and 55 relates to a different process for producing a single ply
tissue having a one-sided finished product appearance. In
accordance with this aspect of the present invention, double nip
embossing is carried out through use of one steel roll and two
rubber rolls possessing different durometer or hardness
characteristics. As illustrated in FIG. 54, the arrangement for
producing double nip embossing on the same steel engraved roll
includes a first rubber roll 300, a second rubber roll 302 and a
steel engraved roll 304 located between the first and second rubber
rolls 300, 302. The first rubber roll 300 and the second rubber
roll 302 possess different hardness or durometer characteristics.
The, first rubber roll 300 is made of a rubber material possessing
relatively medium durometer characteristics while the second rubber
roll 302 is made of a rubber possessing relatively soft durometer
characteristics. Both the first and second rubber rolls 300, 302
engage the steel engraved roll 304 and press against the steel
engraved roll. The steel engraved roll 304 is preferably engraved
so that between 5% and 50% of its exterior surface constitutes an
indented pattern while the remaining portion is not indented.
[0142] As further illustrated in FIG. 54, a single base sheet or
substrate 306 is conveyed around the exterior surface of the first
rubber roll 300 and is then conveyed into the nip 308 between the
first rubber roll 300 and the steel engraved roll 304. As the
substrate 306 is conveyed into the nip 308, the first rubber roll
300 starts forming the base sheet or substrate 306 around the
protruding elements of the steel engraved roll 304 or presses the
base sheet 306 into the indented portions of the steel engraved
roll 304.
[0143] The base sheet 306 continues to be conveyed along the
rotating exterior surface of the steel engraved roll 304 and then
enters a second nip 310 formed between the second rubber roll 302
and the steel engraved roll 304. Because the second rubber roll 302
is made of a softer rubber material having a lower durometer, the
rubber will flow more deeply into the steel engraved roll 304. The
embossed sheet exiting the second nip 310 will possess a one-sided
appearance.
[0144] The use of this arrangement involving two rubber-to-steel
nips improves the softness perception of the resulting tissue
product, imparts more bulk to the resulting tissue product,
contributes to providing a tissue product having a better
appearance, and creates a truer looking one-sided tissue
product.
[0145] A variation on the arrangement shown in FIG. 54 is
illustrated in FIG. 55 and involves the use of the first rubber
roll 300, the second rubber roll 302, and the steel engraved roll
304. In addition, a third rubber roll 320 is employed and is
positioned adjacent the first rubber roll 300. Thus, the same
effects and advantages discussed above in connection with the
arrangement shown in FIG. 54 are achieved. In addition, the
inclusion of the third rubber roll 320 provides a rubber-to-rubber
station that imparts additional calendering and softness treatment
to the base sheet 306.
[0146] It is thus possible in accordance with this aspect of the
present invention to produce a one ply embossed tissue having a
one-sided finished product appearance. The first rubber roll is
designed to emboss in a way that begins to set the desired pattern
while the softer second rubber roll causes the sheet to flow deeper
into the indented pattern on the engraved roll, thus developing the
one-sidedness required and desired for a premium single ply
product.
[0147] The principles, preferred embodiments and modes of operation
of the present invention have been described in the foregoing
specification. However, the invention which is intended to be
protected is not to be construed as limited to the particular
embodiments described. Further, the embodiments described herein
are to be regarded as illustrative rather than restrictive.
Variations and changes may be made by others, and equivalents
employed, without departing from the spirit of the present
invention. Accordingly, it is expressly intended that all such
variations, changes and equivalents which fall within the spirit
and scope of the invention be embraced thereby.
* * * * *