Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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MULTI-PLY ABSORBENT PAPER PRODUCT
HAVING IMPRESSED PATTERN
FIELD OF THE INVENTION
This invention generally relates 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.
DACKGROUND OF THE INVENTION
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.
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.
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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
puffmess, 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.
U.S. Patent 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.
F
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.
A need also exists for a tissue that is heavily embossed, but which does not
1
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.
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
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the one ply embossed tissue creates undesirable paper dust and has a tendency
to
damage the steel emboss rolls.
SUMMARY OF THE INVENTION
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.
According to another aspect of the invention, a method of producing a two
ply tissue 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.
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
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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
5 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.
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
10 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.
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
15 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
4 20 embossed tissue.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
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
4 25 which like elements are designated by like reference
numerals and wherein:
Fig. 1 is a schematic illustration of an apparatus for embossing a paper
product in accordance with one aspect of the present invention;
"i
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Fig. 2 is a front view of the roller arrangement used in the apparatus
- 4
4 shown in Fig, 1;
Fig. 3A is a schematic illustration of an alternative arrangement for
carrying out double depth embossing in accordance with the present invention;
5 Fig. 3B is a cross-sectional view of a portion of the interface
between one
X of the pattern rolls and one of the impression rolls shown
in Fig. 3A;
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;
Fig. 4A is a schematic illustration of a multi-ply paper product produced in
10 accordance with the present invention;
; Fig. 4B is a schematic illustration of a multi-ply tissue product
produced in
accordance with known methods;
Fig. 5 is a schematic illustration of another apparatus for embossing a
paper product in accordance with another aspect of the present invention;
15 Fig. 6A is an illustration of one emboss pattern used in conjunction
with
the present invention;
Fig. 6B is an enlarged illustration of one portion of the emboss pattern
1
shown in Fig. 6A;
Fig. 7 is an illustration of a different emboss pattern used in connection
20 with the present invention;
'a'41 Fig. 8 is an illustration of a further emboss pattern used in
connection with
the present application;
Fig. 9 is a graph of GM tensile strength versus caliper comparing the
embossing technique of the present invention versus conventional embossing;
25 Fig. 10 is a graph of GM tensile strength versus GMMMD (friction)
comparing the embossing technique of the present invention versus conventional
embossing;
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Fig. 11 is a graph of GM Tensile Strength versus tensile modulus
comparing the embossing technique of the present invention and conventional
embossing;
= Fig. 12 is a graph of GM tensile strength versus sensory panel softness
for
5 the present invention and for conventional embossing;
Fig. 13 is a graph of GM tensile strength versus visual test comparing the
embossing technique of the present invention and conventional embossing;
Fig. 14 is a graph of GM tensile strength versus caliper comparing the
embossing technique of the present invention versus conventional embossing;
A
10 Fig. 15 is a graph of GM tensile strength versus GMMMD comparing the
embossing technique of the present invention and conventional embossing;
= Fig. 16 is a graph of GM tensile strength versus tensile modulus
comparing
the embossing technique of the present invention and conventional embossing;
Fig. 17 is a graph of GM tensile strength versus sensory softness value
1 15 comparing the embossing technique of the present
invention and conventional
embossing;
Fig. 18a is a magnified cross-section of a multi-ply tissue produced in
accordance with the embossing technique of the present invention;
1 Fig. 18b is a magnified cross-sectional view of a
multi-ply tissue formed in
20 accordance with conventional embossing;
Fig. 19a is a magnified cross-sectional view of a multi-ply tissue produced
in accordance with the embossing technique of the present invention;
Fig. 19b is a magnified cross-sectional view of a multi-ply tissue produced
in accordance with conventional embossing;
25 Fig. 20a is a magnified cross-sectional view of a multi-ply tissue
produced
in accordance with the embossing technique of the present invention;
4 Fig. 20b is a magnified cross-sectional view of a
multi-ply tissue produced
4 in accordance with conventional embossing;
4
4
4
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Fig. 21a is a magnified cross-sectional view of a multi-ply tissue produced
4 in accordance with the embossing technique of the present
invention;
Fig. 21b is a magnified cross-sectional view of a multi-ply tissue produced
in accordance with conventional embossing;
5 Fig. 22 is a graph of GM tensile illustrating the effect of
different rubber
hardness of the impression roll;
Fig. 23 is a graph of GM tensile strength versus tensile modulus
illustrating the effect of different rubber hardness of the impression roll;
Fig. 24 is a graph of GM tensile strength versus GMMMD illustrating the
10 effect of rubber hardness of the impression roll on the tissue product;
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;
Fig. 26 is a graph of GM tensile strength versus caliper illustrating the
15 effect of adhesive on a tissue product produced in accordance with the
embossing
technique of the present invention;
4 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;
20 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;
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
25 with the embossing technique of the present invention;
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
:1!
the present invention;
'
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,i
ki
,
; -8-
,
' I 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;
Fig. 32 is a graph of GM tensile strength versus GMIAMD illustrating the
effect of adhesive on a tissue product produced in accordance with the
embossing
A technique of the present invention;
v411 Fig. 33 is a graph of GM tensile strength versus sensory
panel softness
!.:11
illustrating the effect of adhesive on a tissue product produced in accordance
with
)4 the embossing technique of the present invention;
10 Fig. 34 is a graph of GM tensile strength versus caliper
illustrating the
i'
/4 effect of the emboss pattern and emboss process of the present
invention on a two-
4
4 ply tissue product;
A Fig. 35 is a graph of GM tensile strength versus tensile
modulus
1
it ' illustrating the effect of the emboss pattern and the emboss process
of the present
15 invention on the fabrication of a two-ply tissue product;
Fig. 36 is a graph of GM tensile strength versus GMMMD illustrating the
41
effect of the emboss pattern and the emboss process of the present invention
on
i fabrication of a two-ply tissue product;
Fig. 37 is a graph of GM tensile strength versus sensory panel softness
4 20 illustrating the effect of the emboss pattern and the emboss
process of the present
invention on the fabrication of a two-ply tissue product;
It Fig. 38 is a graph of GM tensile strength versus caliper
illustrating the
A
effect of emboss pattern on a tissue product produced in accordance with the
A emboss technique of the present invention;
ji 25 Fig. 39 is a graph of GM tensile strength versus tensile
modulus
*
14 illustrating the effect of the emboss pattern and the emboss
process on the
ji fabrication of a two-ply tissue product;
1
1,
*
4
li
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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 ittvention;
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
41.!
fabrication of a two-ply tissue product;
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;
1.0 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
1
tissue product in accordance with the =I- \ssing technique of the present
µr.4
'1=11 invention;
0.1.6
9 Fig. 44 is a graph of GM tensile strength versus GMAMD
illustrating the
.44
effect of steam preconditioning on the fabrication of a two-ply tissue product
produced using the embossing technique of the present invention;
-4 Fig. 45 is a graph of GM tensile strength versus
sensory softness
4.1 illustrating the effect of the emboss pattern used in the
prior art on a two-ply tissue
product using various emboss:
1 20 Fig. 46 is a graph of GM tensile strength versus GMNIMD
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;
Fig. 47 is a graph of GM tensile strength versus caliper illustrating the
4 effect of the emboss pattern used in the prior art on the
fabrication of a two-ply
tissue product using diffeient emboss techniques;
Fig, 4F 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 rwo-ply tissue product using different emboss techniques;
4
441
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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;
Fig. 50 is an enlarged cross-sectional view of a portion of a multi-ply
product produced using the apparatus shown in Fig. 49;
5 Fig. 51 is an enlarged cross-sectional view of a portion of another
multi-
ply product produced in accordance with the present invention;
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;
10 Fig. 53 is a side view of a portion of a tissue product having a
different
H. depth or double depth emboss pattern;
= 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
Fig. 55 is a schematic illustration of an apparatus used to produce a one
15 ply tissue product in accordance with another aspect of the invention.
DETAILED DESCRIPTION OF THE INVENTION
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
20 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
-c 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
25 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
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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
5 second nip which imparts shallower embossing through lower penetration
depth or
lower nip pressure.
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
10 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
15 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
20 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
25 possessing strength characteristics not commonly found in tissue paper
having
such attributes.
The present invention as described in more detail below has application to
multi-ply paper products in which characteristics such as are softness,
puffiness,
.,!
CA 02835786 2013-12-10
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1 =
VI
,
1
1
V
¨12-
4
4 bulk and emboss definition contribute to perceived product
desirability. The paper
,
i
k ,
i
products include absorbent paper, bathroom and facial tissue, napkins and
towels.
1 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
ii 5 types of multi-ply paper products.
1 The multi-ply tissue product according to the present
invention is
I fabricated using the apparatus shown in Fig. I. To produce the
differential depth
kli
,A embossed tissue, a first tissue ply 20 is conveyed past a
series of idler rollers 22
1
4i towards the nip that is located between a pattern roll 24 which
may be made of
Aoli
I 10 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
i counterclockwise direction. The first tissue ply 20 forms the
bottom ply in the
Lfr4
M resulting multi-ply tissue.
i.4 A second tissue ply 28 is conveyed around an idler roller
32 and is then
,41 15 passed into a nip located between an impression roll 34 which
may be made of
fl rubber and the pattern roll 24. The second tissue ply 28 is
adapted to form the top
1 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
t
ply 28 passes through the nip between the pattern roll 24 and the impression
roll
,41 20 34, the second tissue ply 28 is heavily embossed. This heavy
embossing of the
1
second tissue ply imparts a high degree of emboss definition and perceived
1
* puffiness to the second tissue ply 28.
A
.i.,i In contrast, the first tissue ply 20 that is fed through
the nip between the
)1 pattern roll 24 and the impression roll 26 is only lightly embossed.
That is, the
25 first tissue ply is embossed to a lesser degree than the second tissue
ply 28. The
Ilightly 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
1 .
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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
,4 the impression roll 26, the bottom side or inside of the two-
ply tissue possesses a
5 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).
As mentioned above, the second tissue ply 28 is rather heavily embossed
10 whereas the first tissue ply 20 is rather lightly embossed. This
difference in the
degree of embossment can be achieved in several ways, For ex pie, 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
15 pattern roll 24 and the impression roll 26. Alternatively, water
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
20 Shore Durometer A).
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
25 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
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41
11
I
4
A
il -14-
11
4
..1 advantageous attributes of the multi-ply tissue will be
discussed in more detail
1 below.
iFig. 3A illustrates a slightly modified form of the apparatus for carrying
41 out the differential depth embossing. Here, the first
tissue ply 20 is fed from an
41 5 unwinder 40 to the nip located between an impression roll
42 which may be made
if
l, of rubber and a first pattern roll 44 which may be made of
steel. The first tissue
1 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
4
1 10 may be made of rubber and a second pattern roll 50 which
may be made of steel.
ill The nip between the impression roll 48 and the second
pattern roll 50 is designed
A
4 to impart a heavy emboss to the second tissue ply 28.
41
11 Fig. 3B illustrates that the light emboss can be
achieved by allowing the
4 engravings on the first pattern roll 44 to penetrate into
the impression roll 42 to a
$ 15 lesser extent as compared to the heavy emboss that is
applied to the second tissue
1
,N ply 28. This can be accomplished by using less pressure or
by using an
LI
impression roll 42 made of a material that is not as easily penetrated as the
411 impression roll 48, and/or by using a pattern roll 44 less
engraved than the pattern
,14,;11 roll 50. As shown in Fig. 3C, the heavy emboss applied to
the second tissue ply
: 20 28 can be achieved by the engravings on the pattern roll
50 penetrating more
Itl 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
'4 roller 50.
A
4
After the heavily embossed second tissue ply 28 passes through the nip
4
A 25 between the impression roll 48 and the pattern roll 50, a
gluing unit 52 applies
0
A glue to the projections that are formed on the exterior
surface of the embossed
0 second tissue ply 28 by virtue of the embossing. The
heavily embossed second
,
1St
4 tissue ply 28 with the applied glue then advances further
to a nip between the
I
:
1
)1
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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
.1/411 conveyed around a marrying roll 54 and subsequently wound.
Fig. 4A generally illustrates the multi-ply tissue that results from the
5 differential depth embossing technique illustrated in Fig. 3A. For
comparison
_
purposes, Fig. 4B illustrates a conventional multi-ply tissue formed by
conveying
04
two tissue plies through the nip formed between a steel engraved roll and a
rubber
1
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
10 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
X possess desirable strength characteristics by virtue of the
lightly embossed first
15 tissue ply 20.
Fig. 5 illustrates another variation on the apparatus shown in Fig. 1. In
this version shown in Fig. 5, 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
4t 20 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
1'4 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
25 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.
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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.
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.
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.
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
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= -17-
illustrate three different emboss patterns that, in combination with the
differential
depth emboss, provide particularly advantageous results.
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
= 5 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. 68 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
10 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
15 approximately 2 provides a smoother and puffier structure that is
pleasing to the
touch and thus perceived to be of softer quality.
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
20 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.
25 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
CA 02835786 2013-12-10
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= 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
5 heart.
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,
= 10 with the resulting data being summarized in various
graphs and tables set forth
below and in the drawing figures.
Example 1
This example provides a comparison between tissue product converted
using the conventional emboss process and that converted using the
differential
15 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
20 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. Figures 9-13 show the
test results. It can be seen from Figure 9 that the differential depth emboss
25 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
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the conventional emboss process. Figure 10 shows that the differential depth
emboss process resulted in product with lower friction or GMIVIMD (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
5 strength as shown in Figure 11. The high tensile modulus is caused by
light
embossing on the bottom ply. Figure 12 shows that the differential depth
emboss
process made product with better sensory softness at equal GM tensile
strength.
4
Compared to the conventional product, the overall softness value of the
differential depth embossing product is 0.4 or more units higher which is
10 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 Figure 13.
Example 2
15 This example compares and illustrates the differences between the
4
differential depth emboss product and the conventional tissue product. Tissue
4 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
20 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
25 ft. Physical test results are plotted in Figures 1446. Figures 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
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using the conventional process. Figure 16 shows that the differential depth
embossing product has higher tensile modulus than the conventional product.
The
sensory softness result is shown in Figure 17. The differential depth emboss
product has a overall softness value 0.2 to 0.4 units higher than the
conventional
4 5 product.
Example 3
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. Ease sheets were made at basis
10 weight of 9.3 lbs/3000 square ft using a square crepe blade at 72
degrees creping
A 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
15 using the conventional emboss process at penetration depth 0.085 inches.
For
tm/0-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.
Table 1 below lists all of the physical properties and sensory softness
20 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.
Compared to the conventional emboss product, the differential depth
25 emboss product has higher caliper, higher tensile modulus, and lower
friction.
The differential depth emboss product has a overall sensory softness value
0.74
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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 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 Ast) 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
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
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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 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"/8st) 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 (gt% 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
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
CA 02835786 2013-12-10
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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.
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 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"/8st) 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
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Example 6
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.
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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"/8st) 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/311) 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
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
CA 02835786 2013-12-10
4
1 -26-
2
4
4 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
5 has higher caliper, lower tensile modulus and lower friction. Based on
sensory
1 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
10 differential depth emboss process.
Table 5: Properties of Two-Ply Tissue Products
Differential Depth Differential
Depth
Emboss Product Emboss Product
(with Glue Applied)
Basis Weight (lbs/ream) 18.01 18.5
Caliper (0,001"/8st) 80.0 81.8
MD Dry Tensile (g/3") 965 1034
15 CD Dry Tensile (g/3") 430 424
GM Dry Tensile (g/3") 644 662
Peri% Tensile (g/3") 404 410
Tensile Modulus (g/% strain) 23.4 21.7
Friction 0.189 0.176
20 Roll Diameter (inch) 4A0 4.53
Roll Compressibility (%) 20.5 20.3
Sensory Softness 17.18 17.85
;
4
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Example 8
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.
CA 02835786 2013-12-10
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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"/8st) 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
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.
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=
-29-
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 7: Physical Properties of Two-Ply Tissue Products
Conventional Differential Depth
Emboss Product Emboss Product
(40/80 Sha)
Pene. Depth (x0.001") 95 100/65
Basis Weight (lbs/ream) 26.5 26.4
Caliper (0.001"/8st) 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 (gi% strain) 14.1 13.86
Friction 0.168 0.162
Sensory Softness 20.24 20.44
Example 10
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
CA 02835786 2013-12-10
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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 8: Physical Properties of Two-Ply Tissue Products
Conventional Differential Depth
Emboss Product Emboss Product
(40/80 Sha)
Pene. Depth (x0.001") 100 100/65
Basis Weight (lbs/ream) 26.5 26.8
Caliper (0.001"/8st) 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 1915
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Example 11
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 50x. 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 defmition 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
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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 9: Physical Properties of Two-Ply Tissue Products
Conventional Differential Depth
Emboss Product Emboss Product
(40/40 Sha)
Pene. Depth (x0.001") 75 85/50
Basis Weight (lbs/ream) 18.95 18.94
Caliper (0.001 "/8st) 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
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. I3oth processes
CA 02835786 2013-12-10
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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 50x. 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 10: Physical Properties of Two-Ply Tissue Products
Conventional Differential Depth
Emboss Product Emboss Product
(40/40 Sha)
Pene. Depth (x0.001") 85 100/65
Basis Weight (lbs/ream) 17.65 18.2
Caliper (0.001"/8st) 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/To strain) 19.83 23.39
Friction 0.167 0.166
Sensory Softness 17.13 17.58
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Example 13
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
Figures
22-25. Figure 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.
The effect of rubber roll hardness on the tensile modulus and friction are
not significant as shown in Figures 23 and 24. A similar trend is observed for
the
sensory softness result as shown in Figure 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. Patent No. 3,708,366. U.S. Patent 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
CA 02835786 2013-12-10
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results between the present invention and the disclosure in U.S. Patent 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
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. Figures 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. Figure 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 Figure 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.
CA 02835786 2013-12-10
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Example 15
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
5 pattern like that shown in Fig. 6A was used. Four different penetration
depths
were run for each condition. Figure 30 shows that the adhesive did provide a
little advantage for generating bulk. Figure 31 shows that both differential
depth
A
embossing products with and without adhesive applied have a similar tensile
modulus at equal GM tensile strength. As the penetration depth increases, the
10 differential depth embossing product without adhesive applied has lower
friction
as shown in Figure 32. Figure 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.
15 Thus, by applying adhesive for running the differential depth embossing
process,
the tissue softness may be reduced.
Example 16
This example presents a comparison between tissue product converted
using the differential depth emboss process and that converted using the
20 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
= 25 has a higher caliper than the differential depth
embossing product at equal GM
tensile strength as shown in Figure 34 Figure 35 shows that the differential
depth
embossing product has a higher tensile modulus at equal GM tensile strength
CA 02835786 2013-12-10
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because of the light emboss at the second nip. Figure 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 Figure 37.
Example 17
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 Figure 38. The test results
of
tensile modulus, friction and sensory softness are plotted in Figures 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
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
CA 02835786 2013-12-10
g
11
4
4
;0
-38-
pattern illustrated in Fig. 8. Table 11 below lists the physical properties
and
ti sensory softness result, The differential depth embossing
product has higher
0
1 caliper, lower friction, higher tensile modulus and better
softness. The difference
i-I in softness value is greater than 0.4 units which is
significant difference at 95%
il.
:$ 5 confidence level. The results for commercially made products
are consistent with
1 those observed for pilot products used in Examples 3, 4 and 5.
N
N
s Table 11; Physical Properties of Two-Ply Tissue
Products
kj
i Conventional Differential
Depth
'4
Emboss Product Emboss
Product
(40/40 Sha)
41
4 Pene. Depth (x0.001") 47 75/35
ii
,.,
'I Basis Weight (lbs/ream) 18.7 18.8
1 10 Caliper (0.001"/8st) 72.6 73.3
4 MD Dry Tensile (g/3") 1065 1056
4
..1
Cl) Dry Tensile (g/3") 417 405
J4
i;. GM Dry Tensile (g/3") 666 654
'10t
II Tensile Modulus (g/% strain) 19.0 21.1
jt 15 Friction 0.154 0.151
;I Roll Diameter (inch) 4.2 4.19
141
Roll Compressibility (%) 19.0 21.1
. Sensory Softness 17.16 17.72
0
11
4
Example 19
kd
0
A 20 This example illustrates a comparison between the
differential depth
4
A 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.
41
,
.,
CA 02835786 2013-12-10
i
.1
4
1:1
7
0,
1
11.
0 Base sheets were made from a furnish containing 60% Northern
hardwood haft
hi
N and 40% Northern softwood haft. Two-ply tissue was converted
using the
i conventional emboss process at a penetration depth of 0.057
inches. For the
differential depth embossing tissue product, the penetration depth was 0.088
'i
'I 5 inches for the top ply, and then the top and bottom plies were
embossed together
1 at a penetration depth of 0.038 inches. Table 12 below lists
the physical
=
properties and sensory softness result. The differential depth embossing
product
1 has a higher caliper, lower friction, and better softness. The
difference in softness
SI value is greater than 0.4 units which is significant difference
at 95% confidence
1
1 10 level. Both tissue products have similar tensile modulus
value. The sensory
softness result is thus consistent with those found in Example 10.
Table 12: Physical Properties of Two-Ply Tissue Products
,
_______________________________________________________________________________
Conventional Differential
Depth
I Emboss Product Emboss Product
(40/80 Sha)
1 Pene. Depth (x0.001") 57 88/38
M
Basis Weight (lbs/ream) 26.6 26.6
1
$1 15 Caliper (0.001"/8st) 102.9 106.1
Al MD Dry Tensile (g/3") 896 868
R.
41. CD Dry Tensile (g/3") 346 332
A
41 GM Dry Tensile (g/3") 557 537
,4
4 Tensile Modulus (gi% strain) 13.2 13.4
t -
il.
N 20 Friction 0.159 0.156
N Roll Diameter (inch) 4.15 4.18
Roll Compressibility (%) 22.2 21.1
1 Sensory Softness 19.15 19.91
.:
i
A
CA 02835786 2013-12-10
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Example 20
= 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
= 5 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
10 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 Figures 42 and 43. Figure 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.
15 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
This example provides a comparison between the differential depth
20 embossing product and the conventional product converted using the
emboss
pattern described in U.S. Patent 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
25 product was also studied. The sensory softness test result is plotted in
Figure 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
CA 02835786 2013-12-10
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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 Figures 46-48. Figure 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.
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. Patent 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.
CA 02835786 2013-12-10
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Table 13: Comparison between The Current Invention and The Prior Art
Emboss Pattern Aspect Ratio Radius
Sensory Softness Sensory Softness
(Length /Width) (x 0.001") (DDE) (Cony.)
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. Patent No.
3,708,366
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.
Patent 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.
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
CA 02835786 2013-12-10
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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.
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.
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.
CA 02835786 2013-12-10
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The engraved roll 118 can be heated, preferably to a temperature lying
within the range of approximately 50 C-100 C, or preferably approximately
75 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.
The first and second receiving rolls 114, 120 possess a high hardness,
greater than Shore-D 80 and preferably greater than Shore-D 90.
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.
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.
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.
CA 02835786 2013-12-10
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The adhesive applying device 204 includes an adhesive supply 206 and a
rotatable
application roller 208.
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.
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.
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
CA 02835786 2013-12-10
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controlling the relative feed rates of the two sheets, so that one sheet is
fed at a
faster rate than the other.
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.
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.
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.
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
CA 02835786 2013-12-10
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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.
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.
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.
CA 02835786 2013-12-10
-48-
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.
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.
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.
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 to
the particular embodiments may be made by others, and equivalents employed,
without departing from the scope of the present invention. Accordingly, it is
expressly intended that all such variations, changes and equivalents which
fall within
the scope of the invention be embraced thereby.
