U.S. patent application number 12/774829 was filed with the patent office on 2010-08-26 for micro fiber textured paper tissue and method of making it.
Invention is credited to Bruno Johannes Ehrnsperger, Klaus Hilbig.
Application Number | 20100212848 12/774829 |
Document ID | / |
Family ID | 29404023 |
Filed Date | 2010-08-26 |
United States Patent
Application |
20100212848 |
Kind Code |
A1 |
Hilbig; Klaus ; et
al. |
August 26, 2010 |
MICRO FIBER TEXTURED PAPER TISSUE AND METHOD OF MAKING IT
Abstract
Paper tissues and paper tissue products such as disposable
handkerchiefs, kitchen paper towels, toilet paper and facial
tissues exhibiting a soft and smooth surface, and a high bulkiness
together with a high strength, in order to provide to the user an
enhanced functionality and a high degree of comfort during usage.
The present invention also relates to the process of making paper
tissue and paper tissue products presenting such
characteristics.
Inventors: |
Hilbig; Klaus; (Frankfurt am
Main, DE) ; Ehrnsperger; Bruno Johannes; (Bad Soden
am Taunus, DE) |
Correspondence
Address: |
THE PROCTER & GAMBLE COMPANY;Global Legal Department - IP
Sycamore Building - 4th Floor, 299 East Sixth Street
CINCINNATI
OH
45202
US
|
Family ID: |
29404023 |
Appl. No.: |
12/774829 |
Filed: |
May 6, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10430918 |
May 7, 2003 |
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12774829 |
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Current U.S.
Class: |
162/109 |
Current CPC
Class: |
D21F 11/006 20130101;
B31F 2201/0784 20130101; B31F 2201/0758 20130101; B31F 2201/0728
20130101; B31F 2201/0725 20130101; D21F 11/14 20130101; B31F 1/07
20130101; B31F 2201/0761 20130101 |
Class at
Publication: |
162/109 |
International
Class: |
D21H 27/02 20060101
D21H027/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 14, 2002 |
EP |
02010577.1 |
Apr 25, 2003 |
EP |
03009391.8 |
Claims
1. A paper tissue, said tissue comprising: paper fibers and having
a first surface, a second surface and an embossing pattern disposed
thereon, said embossing pattern having raised regions surrounded by
depressed regions on said first surface, said first surface having
extending paper fibers wherein said extending paper fibers have a
first end and a second end, said first end being un-bonded to said
tissue and said second end being integral with, and bonded to, said
tissue; wherein more of said extending paper fibers are disposed in
said raised regions than in said depressed regions; and, wherein
said embossing pattern comprises at least 30 embossing elements per
square centimeter.
2. The tissue of claim 1 further comprising extending paper fibers
on said second surface.
3. The tissue of claim 1 comprising at least 25% more of said
extending paper fibers in said raised regions of said first surface
than in said depressed regions.
4. The tissue of claim 3 comprising at least 50% more of said
extending paper fibers in said raised regions of said first surface
than in said depressed regions.
5. The tissue of claim 1 in which said embossing pattern further
comprises a micro-embossing pattern.
6. The tissue of claim 1 further comprising an interconnected
network formed by said depressed regions.
7. The tissue of claim 1 wherein said first surface forms an outer
surface.
8. A paper-product including at least two plies, each of which
includes the tissue of claim 1, wherein said embossing patterns of
each of said tissues are registered.
9. A process for making a paper tissue, the process including the
following steps: providing a tissue, said tissue having a first and
a second surface, embossing said tissue by passing said tissue
between two rolls forming an embossing nip, and brushing at least
one of said surfaces of said tissue, wherein said brushing process
step is subsequent to said embossing step.
10. The process of claim 9 in which said embossing step comprises a
micro-embossing step created by stretch deformation of said tissue
without creating local tissue breakage.
11. The process of claim 9 in which said brushing process step
comprises the use of a brushing tool on said first surface without
a counter-surface being applied to said second surface of said
tissue.
12. The process of claim 9 wherein said brushing process step uses
a brushing tool on said first surface with a counter-surface being
applied to said second surface of said tissue.
13. The process of claim 12 wherein the counter-surface is a
counter-roll, said first surface of said tissue is in contact with
said counter-roll while said second surface of said tissue is in
contact with said brushing tool, and said second surface of said
tissue contacting said brushing tool is convex.
14. The process of claim 10 wherein said tissue is moving at a
first surface speed and the brushing tool has a second surface
speed that is been 1.5 and 20 times faster than the first surface
speed of said tissue.
15. An article comprising: paper fibers and having a first surface,
a second surface, and an embossing pattern disposed thereon; said
embossing pattern having raised regions surrounded by depressed
regions on said first surface; said first surface having extending
paper fibers wherein said extending paper fibers have a first end
and a second end, said first end being unbonded to said tissue and
said second end being integral with, and bonded to, said tissue;
wherein more of said extending paper fibers are disposed in said
raised regions than in said depressed regions; and wherein said
depressed regions have a depth of less than 260 micrometers.
16. The article of claim 15 wherein said embossing pattern
comprises at least 30 embossing elements per square centimeter.
17. The article of claim 15 wherein said embossing pattern further
comprises a micro-embossing pattern.
18. The article of claim 15 wherein said extending paper fibers
disposed in said raised regions comprise at least 25% more of said
extending paper fibers than said extending paper fibers disposed in
said depressed regions.
19. The article of claim 15 further comprising an interconnected
network formed by said depressed regions.
20. The article of claim 15 wherein said first surface forms an
outer surface of said article.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. application Ser.
No. 10/430,918, filed 7 May 2003, pending.
FIELD OF THE INVENTION
[0002] The present invention relates to paper tissues and paper
tissue products, such as disposable handkerchiefs, kitchen paper
towels, toilet paper and facial tissues. The present invention also
relates to the process of making paper tissue and paper tissue
products having such improved characteristics.
BACKGROUND OF THE INVENTION
[0003] Paper tissues sometimes called paper webs or sheets,
tissues, tissue layers, paper plies or paper tissue webs, and
products made there from, such as paper handkerchiefs, paper
kitchen towel or toilet paper, find extensive use in modern society
and are well known in the art. Such paper tissues are generally
made by the layering of cellulose fibers, in a wet form, onto a
screen, with the addition of various additives or other
ingredients, followed by a drying step. Other process steps,
before, during or after the above-mentioned paper making steps are
generally targeted at giving the desired properties to the tissue.
Converting steps are aimed at creating a finished product from the
paper tissue(s).
[0004] Products made from paper tissues can be made by the
association of multiple layers of tissues, also called plies, or
can comprise a single tissue layer (single ply products). Those
plies can be combined and held together in different ways to form
the finished product. For example, plies may be held together by
embossing and/or by gluing.
[0005] It has long been recognized that important physical
attributes of these paper tissues are strength,
thickness/bulkiness, softness, smoothness, and absorbency. Softness
and smoothness relate to the tactile sensation perceived by the
consumer when holding a particular product, rubbing it across the
skin, or crumpling it within the hands. The tactile sensation is a
combination of several physical properties. The tactile sensation
can be well captured by the objective parameter of the
physiological surface smoothness (PSS) parameter as known e.g. from
U.S. Pat. No. 5,855,738. As important for the tactile sensation of
consumers is the thickness/caliper of a tissue product also called
bulkiness. Strength is the ability of the product to maintain
physical integrity and to resist tearing, bursting, and shredding
under conventional use conditions. Absorbency is the measure of the
ability of a tissue or product to absorb quantities of liquid,
particularly aqueous solutions or dispersions. Overall absorbency
as perceived by the consumer is generally considered to be a
combination of the total quantity of a liquid a given mass of paper
tissue or product will absorb at saturation as well as the rate at
which the mass absorbs the liquid.
[0006] Relatively thick and yet soft disposable paper products,
namely in the form of paper handkerchiefs, are known. For example,
Tempo.TM., sold by The Procter & Gamble Company, is a multi-ply
paper product experienced as thick and soft and having a caliper of
about 0.3 mm. A high caliper conveys the idea of high dry and wet
strength to the consumer. A high wet strength, also referred to as
wet burst strength, in particular prevents tearing or bursting
which for a paper handkerchief in turn results in contamination of
the user's hand with mucus or other body fluids.
[0007] A common way to enhance the smoothness of the tissue surface
is to calender the material. For example U.S. Pat. No. 5,855,738
issued to Weisman et al. describes a calendering step that helps in
the manufacture of a smooth high-density tissue. This manufacturing
step flattens the surface of the tissue, thus re-orienting and
re-bonding the paper fibers at the surface of the paper web.
However, calendaring reduces considerably the caliper of the paper
web, impairing the desired bulkiness of the final product. Methods
for creating tissues with high bulkiness have been described, for
example in U.S. Pat. No. 5,702,571 and EP 0 696 334 B1, both by
Kamps et al. In these references, the tissue's bulkiness is
enhanced by embossing the tissue between a nip formed by one male
engraved roll and one female engraved roll. Another example is
given in the patent application EP 01103798.3 by K. Hilbig, M.
Liplijn and H. Reinheimer, filed on Feb. 16, 2001, and includes the
creation of a tri-dimensional structure at the paper surface (via
micro-embossing, also called stretch deformation before a
calendering step). However, the above-mentioned methods still
submit the paper to a calendering step that can reduce the
thickness of the paper versus a micro-embossed paper tissue.
[0008] Another way to obtain a smooth paper tissue surface is to
submit the paper tissue to a step of brushing. Brushing of tissue
is described, for example, in U.S. Pat. No. 3,592,732 issued to
Wand et al. in which the tissue is brushed by a rotating brush
using an engraved or dented roll as a counter surface. In U.S. Pat.
No. 5,180,471, Sauer et al. describes a multi-ply tissue and
related method in which the inward surfaces have been brushed. It
is believed that the brushing of the paper surface acts on the
paper fibers (cellulose fibers) by unbonding one end of the paper
fibers close to the surface of the tissue, herein referred to as
extending fibers, thus allowing the extending fibers to raise above
the paper web surface, thus creating a surface which is smooth to
the touch. However, brushing can reduce the strength of the paper
web as it modifies the structure of the fibre network forming the
paper web and reduces the bonding between the fibers making up the
surface of the tissue.
[0009] Despite the efforts in the prior art, each of the above
methods present disadvantages affecting one or more of the key
characteristics of the paper tissue when trying to improve another
one. Thus, there remains a need for paper tissues which combine one
or more apparently incompatible features such as a high surface
smoothness, a high strength, and a high thickness/bulkiness.
SUMMARY OF THE INVENTION
[0010] The present invention relates to paper tissues comprising
cellulose fibers. The tissues have a first and a second surface,
and an embossing pattern, which form raised regions surrounded by
depressed regions on the first surface. The regions coincide with
the respective opposite regions on the second surface of the
tissue. The first surface has extending fibers, which have a first
and a second end, with the first end being un-bonded to the tissue
and the second end being bonded to the tissue. The unbounded ends
of the extending fibers are obtainable by brushing of the first
surface, such that there are more extending fibers in the raised
regions than in the depressed regions.
[0011] The present invention also relates to the process for making
a paper tissue according to the above. The process comprises the
steps of embossing the tissue by passing it between two rolls
forming an embossing nip and brushing at least one of the surfaces
of the tissue.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 represents a paper handkerchief composed of 3 paper
tissues (also called plies or layers), and exhibiting a
substantially non-flat/non-uniform surface.
[0013] FIG. 2 is a magnified portion of FIG. 1, on which the 3
paper tissues are seen.
[0014] FIG. 3 shows the process for making a tissue as shown in
FIG. 1.
[0015] FIG. 4 shows an enlarged portion of the paper tissue at
location I of FIG. 3.
[0016] FIG. 5 shows an enlarge portion of the paper tissue at
location II of FIG. 3.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The present invention provides a paper tissue exhibiting a
high level of surface smoothness, softness, strength and/or
bulkiness.
[0018] The present invention provides a paper tissue surface which
is not uniform and presents the desired characteristics in separate
regions as well as a method to form such a paper tissue.
Specifically, one region is relatively smooth and soft. The
smoothness/softness is provided by the presence of loose paper
fibre ends, which supports the tactile benefits of the tissue.
Strength is provided in a region having a substantially non-altered
network of fibers. Bulkiness can be created by the presence of
raised and depressed regions and conserved through the process of
converting the paper tissue, by both the nature of these process
steps and preferably by their determined sequence.
Embossing
[0019] Although any known-in-the-art type of embossing can be
practiced within the present invention, one preferred embossing
step is a so-called micro-embossing or stretch embossing step, also
called stretch deformation. One example of a suitable embossing
step is described in the European patent application EP 01103798.3
by K. Hilbig, M. Liplijn and H. Reinheimer, filed on Feb. 16, 2001,
in which a very fine pattern is embossed using a low pressure.
Embossing can be carried out on one tissue, such as the tissue (13)
of FIG. 3, 4, or 5 or the tissue (2), (3), (4) of FIGS. 1 and 2.
Alternatively embossing can be carried out on a multi-ply entity,
such as the tissue (1) of FIG. 1. For simplicity, the tissue (13)
of FIG. 3 is described below as a tissue (i.e. a single-ply
entity), but the skilled person understands that it can be replaced
by a multi-ply entity such as the multi-ply tissue (1) of FIG. 1,
without deviating from the present invention.
[0020] As shown in FIG. 3, embossing of a paper tissue is generally
achieved by passing the tissue or the multiply entity through a nip
(8) formed between two embossing rolls (9), (10), at least one
embossing roll (9) comprising embossing elements (12). An embossing
roll typically comprises a smooth surface and embossing elements
(12). Embossing elements (12) are protrusions raising above this
surface and having a certain height as measured in a radial
direction of the axis of the embossing roll above the smooth roll
surface to the utmost point of the protrusion. Embossing elements
(12) also have width in a direction parallel to the roll axis and a
length in a radial direction. The term width and length as used
herein can be the diameter of a round embossing element (12). Such
a diameter needs not be constant from the bottom of the embossing
element (12) to its top. Preferably, the largest width of an
embossing element (12) is on said smooth surface.
[0021] The embossing elements (12) can have any shape, such as
pyramidal or half spherical, and the cross section of the embossing
elements (12) can be circular, oval or square. The embossing
elements (12) may form a continuous pattern, but preferably are
distinct from each other, such as the smooth surface of the roll
forms a continuous plane. In one embodiment of the present
invention, the embossing elements (12) are disposed over at least
one embossing roll in a very fine pattern, comprising at least 30,
50, 60, 70 or even at least about 80 embossing elements per square
centimetre surface area of the embossing roll. The embossing
elements (12) are preferably less than about 1 mm in height, but
can be less than about 0.8 mm in height, less than about 0.6 mm in
height, less than about 0.5 mm in height, less than about 0.4 mm in
height, or even less than about 0.3 mm in height.
[0022] Preferably the stretch embossing has a ratio of embossed
areas to un-embossed areas from about 5% to about 95%, about 20% to
about 80% or about 40% to about 60% of the total surface area of
the tissue paper are embossed.
[0023] Any known type of embossing roll and mode of operation of
such roll is within the scope of the present invention. For
example, two hard metal embossing rolls can be used, wherein a
first roll comprises protruding embossing elements, referred to as
the male roll, and a second roll comprises matching recesses,
referred to a the female roll. The recesses may be mirror images of
the protruding embossing elements or may be adapted to be slightly
smaller than exact mirror images, e.g. due to a slight difference
in size or shape (e.g. slope) of those recesses in the female roll.
It is also possible to use so called pin-to-pin embossing where two
rolls are used with matching protrusions. Alternatively, a first
embossing roll comprising a web contacting surface made from a hard
material comprising protruding embossing elements can be made to
contact a second roll comprising a web contacting surface
comprising a relatively softer material (e.g. rubber), in which
recesses are formed upon sufficiently close contact with the
protruding embossing elements. Providing an embossing nip from a
relatively hard roll in combination with a softer roll has numerous
advantages, such as cheaper and easier production and operation,
since the adjustment of the rolls is much less critical than for
two hard rolls or two rolls of equal hardness.
[0024] The size of the nip formed between the two embossing rolls
may be adapted depending on the tissue paper to be processed and
depending on the embossing pattern used. Also depending on those
considerations no pressure or some pressure may be applied to urge
the first embossing roll and the second embossing roll together.
When two hard rolls are employed in the process, a male and a
female role, the rolls can be operated so as to leave a space
corresponding to about 60% to about 140%, preferably about
80%-about 120% of the calliper of the un-embossed tissue paper
between the protruding embossing elements of the male role and the
bottom of the recesses of the female role. When a hard roll is used
in combination with a softer roll, the rolls can be pressed against
each other with a pressure of about 10 N/square centimetre to about
1000 N/square centimetre, about 20 N/square centimetre to about 200
N/square centimetre, about 50 N/square centimetre to about 100
N/square centimetre or any other desired pressure. Further, any of
the embossing rolls may be heated or not heated and run at the same
speed or different speeds.
[0025] The above described embossing with a fine pattern, in one
important aspect serves to increase the caliper, or in other words
the bulk of the paper tissue. Therefore, in one mode of the present
invention a single tissue is passed through the embossing nip. In
alternative modes of operation, a multitude of plies of paper
tissues may be passed through the nip at the same time. This will
results in embossments which initially match or nest between the
tissues.
Brushing
[0026] According to one aspect of the present invention, the
brushing of the paper tissue(s) is performed after the embossing
step, but can also be considered as an independent step provided it
delivers the intended result described. The terms brush and
brushing are being used in the present document as an example, but
without limiting the scope of this invention. In accordance with
the present invention are any tool, equipment or means able to
provide the desired modification on the surface and structure of
the paper tissue (i.e. to lift fiber ends up without complete
detachment). Conventionally such means include any type of abrasive
surface such as those provided by the bristles of a brush or by
sand paper. Useful structures providing abrasive functionability
can be made from natural or artificial materials such as foam,
metal or polymers. To create the desired abrasion a relative
movement between the surface of the paper tissue and means of
abrasion can be provided. As alternatives, chemical, optical, or
physical processes resulting in the described modification of the
surface and/or structure of the tissue, are considered within the
scope of the present invention.
[0027] Preferably, the modification on the surface and structure of
the paper tissue is achieved with a rotating tool which is in
abrasive contact with the surface of the tissue(s), typically a
brush cylinder comprising brushing bristles along its full
circumference is used. The bristles can be polymeric or from
natural origins such as animal hair or fur. The brushing step can
be performed on one side of the paper tissue or on both, depending
on the intended benefits desired, by a combination of one, two or
more brushes. One brush (or brush cylinder) or more can be applied
to each tissue side. For simplicity, the embodiment of the
invention is described in the following with one brush cylinder
(identified in the FIG. 3 by the reference numeral 11) acting on
one tissue side. Alternative configurations can be practiced also.
For example, two or more brushes acting on the same tissue side,
brushing of the first and second surfaces simultaneously or
consecutively, are envisioned. In one embodiment, five pairs of
brushes are used, providing five brushing operations on each side
of the web.
[0028] One result of the brushing step is a modification of the
most outwardly lying fibers on the surface of the tissue. The
tissue fibers are generally bonded by hydrogen bridges to each
other during the tissue making, drying or subsequent calendering at
a multitude of points where the fibers intersect. It is believed
that, during the brushing step, the paper fibers are provided with
sufficient energy to break some of the hydrogen bonds linking the
fibers together and insuring the cohesion of the paper structure.
This energy is provided by the tear force or shear force of the
individual bristles when colliding with the fibers. Without being
bound by the theory, the inventors believe that the energy should
be sufficient to break some of the bond between the fibers but low
enough not to break all of the bonds which would provoke a complete
dislocation of the fibers from tissue surface (also known as
Tinting), and to not break the fiber structure itself.
[0029] The brushing step of the present invention creates extending
fibers (7), as shown in FIGS. 2 and 5, i.e. fibers having one fiber
end still bonded to other fibers while the other fiber end is
freed, and able to raise above the surface of the tissue. These
extending fibers (7) can help provide tactile smoothness and
softness to the tissue.
[0030] The process according to the present invention is believed
to loosen or free only one end of the fibers by breaking their
bonds to the other fibers at one end. It is however observed that
the brushing step may also induce a complete release of some
complete fibers or fiber breakage. These fibers or pieces of fibers
can be removed from the tissue thereby helping to reduce Tinting.
They can be recycled. Schematically the process according to the
present invention can be seen in FIG. 3: first a tissue web (13) is
provided, usually unwound from a roll of tissue web. The tissue web
(13) is guided to an embossing station where the tissue web is
guided through a nip (8) between two embossing rolls (9), (10). The
tissue (13), after embossing is then guided toward a brushing
station where at least one side is exposed to a brushing cylinder
(11). The brushing cylinder can be operated to rotate so that its
surface moves with or against the tissue movement or simply stands
still. The setting of the equipment, particularly the brushing
cylinder, such as rotation speed, distance of the brush to the
tissue web, extend of wrapping of the tissue web around the brush,
and the design of the brush, such as the nature of the bristles,
their length, the bending moment of the bristles, the density and
the diameter of the bristles, the treatment or coating of the
bristles, are optimized to deliver the best results for the quality
of the paper tissue after brushing (analyzed by strength,
smoothness, softness and bulk of the tissue), the stability of the
process, and the life of the equipment.
[0031] The brushing step can be performed with only the inherent
force of the moving paper tissue web acting on the brush, i.e.
without the use of a counter-roll or counter-surface to apply
pressure and/or guide the paper tissue onto the brush. Only the
tension of the paper tissue web and to a much lesser extent the own
weight of the paper tissue applies a pressure on the rotating brush
(11), as shown in FIG. 3. When more than one brush cylinder are
used in the process, some of the brushes may, or may not, be
positioned in such a way that they brush the two sides of the paper
web simultaneously. In one embodiment, the brush rotates in the
direction of the web movement on the converting line. However,
rotation in the opposite direction is also contemplated.
Alternatively, a counter surface (often in the form of a counter
roll, rotating at a surface speed close to the surface speed of the
web) is used. The counter surface may be positioned as such as a
portion of the web is simultaneously both in contact with both the
brush and with the counter surface. The position of the counter
roll and path of the web may be such that a convex surface of the
web is exposed to the action of the brush. Without being bound by
the theory it is believed that this configuration "opens up" the
micro-structure of the web and consequently enhance the action of
the brush on to the web tissue fibers. This configuration is
achieved by having for example a partial wrapping of the web around
the counter roll (the surface of the web not in contact with the
counter roll has, therefore, a convex surface that is in contact
with the brush).
[0032] Together with the design of the brush, its speed of rotation
is a factor in the effectiveness of the brushing step, affecting
the wearing of the equipment as well end results of the process
step. In certain preferred embodiments, the speed of the brushing
cylinder relatively to the tissue web surface is higher than about
1,000 m/min (linear velocity of point of contact to the paper web),
higher than about 1,500 m/min, higher than about 2,000 m/min or
higher than about 3,000 m/min. The relative surface speed of the
brush can also be calculated in relationship to the surface speed
of the web. The surface speed of the brush being between 1.5 and 20
times faster than the surface speed of the web, between 2 and 15
times, and between 5 and 10 times should all provide suitable
results.
[0033] The brush 11 as used in the present invention can be of very
wide nature and design, including synthetic, metallic or natural
hair, over a wide range of dimension and density. In a preferred
way to conduct the invention, brushes made of horsehair have been
used, as sold by Mink GmbH (Goeppingen, Germany) under the
reference ZZB 12528-K2509. Such brushes are used conventionally in
the treatment of textiles. The brush may be substantially circular
and operate by rotation around one axis. The inventors, however,
contemplate as being part of the present invention the use of other
types of brushes (for example, fixed brushes or brushes operating
by translation of the brush surface or abrasive surface over the
surface of the paper tissue), provided the action of the brush
induces the described modification on the surface and structure of
the paper tissue.
[0034] In one preferred way to practice the invention, the embossed
paper tissue web is wrapped around two brush rolls without being
fixed on a guide roll. Each brushing roll brushes one surface of
the tissue. The travel distance of the paper tissue on the surface
of the brush (i.e. the wrapping of the paper tissue around the
brush or in other words, length of contact between the brush and
the paper tissue) can vary over a wide range. It has been found
useful to set this length to less than about 20 cm in some
embodiments, less than about 5 cm in other embodiments, and less
than about 1 cm in yet other embodiments, although a wider range of
length is contemplated.
[0035] For paper tissue, which has been made in the paper making
operation as a non-homogeneous mixtures of long and short fibers,
with one side of the tissue presenting more short fibers than the
other side, the present invention contemplates a preferred
orientation of the paper web on the brush. Preferably the paper
tissue or the brush are orientated as such as the short fibers of
the paper tissue are brought to contact with the brush. Without
wishing to be bound by the theory, it is believed that the short
fibers present less bonding to each other. It may thus be easier to
loosen more fiber ends out of short fiber side than out of long
fiber side of a tissue.
[0036] It has been observed that the brushing step of a paper
tissue tends to increase its caliper and increases in the range of
about 1% to about 25% have been measured, averaging to about 5%.
Importantly, this increase in caliper, leading to a high bulk, is
additive to the caliper increase created by the embossment step or
the stretch deformation process step. The stretch deformation
itself generally adds about 50% to about 200% of caliper to the
paper tissue, according to the European patent application EP
01103798.3 supra.
[0037] One advantage of the present invention in comparison to the
process described in European patent application EP 01103798.3
supra, is the possibility to eliminate the conventional calendering
step after the stretch deformation step. This conventional
calendaring generally results in a decrease of the stretch deformed
paper tissue caliper, which led to a total caliper increase (after
both steps: stretch deformation and smooth calendering) of about
10% to about 100%. The elimination of the calendering after the
embossing but the use of brushing allows achieving an exceptionally
high-end caliper of the treated tissue web, in the range of about
51% to about 225% in the examples given above.
[0038] In one embodiment as shown on FIG. 3, the tissue (13) of
FIGS. 3, 4, 5 has been previously submitted to an embossing step,
most preferably the micro-embossing (or stretch embossing or
stretch deformation step) described under the "Embossing" headline
in this document. In that case, the paper tissue (13) enters the
brushing step being an essentially non-flat surface, i.e.
presenting raised regions (6) and depressed regions (5), relatively
to each other, created by the embossing step. The effect of
brushing on this pre-deformed paper tissue is unexpected and acts
preferentially on the raised regions (6) while leaving the
depressed regions (5) substantially un-altered. Thus, more
extending fibers (7) are created on the raised regions (6) relative
to those created in the depressed regions (5). A network of
substantially unaltered depressed regions is thereby created. This
network substantially conserves the strength and tensile
characteristics of the un-treated tissue. This delivers the
intended results of creating a paper tissue with a high degree of
softness and smoothness (provided in particular by the extending
fibers of the raised regions), a high strength (in particular
provided by the network of unaltered depressed regions) and
bulkiness (provided by the presence of raised and depressed
regions).
Optional Process Steps
[0039] The method for making a paper product according to the
present invention may comprise a number of further optional steps.
For example, a lotion may be applied to the tissue by any suitable
means, such as, but not limited to printing or spraying, onto one
or more surfaces of the paper tissue or paper product, or a portion
of these surfaces. Further, juxtaposed plies of the paper tissue
may be joined so as to provide a multi-ply paper product,
preferably by attachment embossing. "Attachment embossing", as used
herein, refers to an embossing by which all plies of a multi-ply
product according to the present invention are embossed in one
process step. "Attachment embossing" has been described by H.
Reinheimer, K. Hilbig and W. Schmitt in WO 95/27429. Preferably the
attachment embossing does not or at least not to a large extent
affects the smoothness of any calendered tissue. Therefore,
preferably the paper product has an un-embossed surface over a
major part of the surface area of the tissue, preferably on the
first and the second surface. As used herein, this means that the
tissue has one or more regions not comprising an attachment
embossing and, optionally, one or more regions comprising an
attachment embossing, and that the region not comprising an
attachment embossing is at least about 50%, at least about 80% or
in some embodiments as much as 99%, of the surface area of the
tissue. Most commonly the regions comprising an attachment
embossing lie close to the edge of the tissue (for example along
two or four edges). Attachment embossing may also be used for
decorative purposes (for example to create a pattern or to spell
out a logo or brand name). In one example embodiment, the
attachment embossing may be done by pin-to-pin embossing and with
10 to 40 embossing elements per square-centimetre having a height
from 0.01 mm to 1 mm, or 0.05 mm to 0.2 mm. The percentage of
attachment embossed areas to un-embossed or fine embossed areas of
the total surface area of a paper tissue product can be about 0.01%
to about 5%. Attachment embossing involves as substantive
densification of the paper tissue products as to achieve the
attachment. Therefore the nip or space between one embossing
element and its counterpart, e.g. two pins where pin-to-pin
embossing is employed, is less that the caliper of the paper tissue
to be embossed, typically about 5% to about 50%, about 10% to about
20% of the calliper of the paper tissue to be embossed, which leads
to embossing pressures of about 10,000 to about 50,000
N/square-centimetre.
[0040] The method of the present invention may further comprise a
step of sizing the paper tissue web or paper product to the desired
dimensions. Further if desired, the paper products according to the
present invention may be provided with functional or aesthetic
indicia. The indicia may be applied to either or both of the
surfaces of the paper products. The indicia may cover all or part
of the paper products and be applied in a continuous or
discontinuous pattern. The indicia may be applied to the paper
tissue products by any means well known in the art, such as
spraying, extruding, and preferably printing.
Examples
Paper Tissue
[0041] A piece of paper tissue according to the present invention
is cut from a paper tissue web and presents a non-uniform surface,
obtainable for example by a process step of micro-embossing. It has
typically 30 to 100 depressed regions per cm.sup.2 and the
depressed regions have typically a depth of less than 260.mu. and
typically a diameter of more than 20.mu.. The thickness of the
tissue depends highly on the manufacturing process and is typically
100.mu. per native paper tissue ply, 150.mu. to 200.mu. when
embossed or stretch deformed. This results in about 400.mu. to
500.mu. when 3 plies are combined (after embossing) to form a
finished product. The dimensions of the paper tissue are not
relevant as it depends almost only on the setting of the cutting
equipment on a manufacturing machine.
[0042] As it can be seen in FIG. 5, the raised regions (6) of the
paper tissue (13) show extending fibers (7), visible under a
microscope or magnifier lens. The ends of the fibers are non-bonded
to the other fibers and thus have the ability to stick out of the
surface of the paper tissue. These extending fibers are believed to
provide the particular characteristics, according to the present
invention, which are responsible for the benefits described above,
in particular softness, smoothness and bulkiness of a tissue. The
strength characteristics of the tissue, on the other hand is
substantially not altered because the number of extending fibers in
the depressed regions is smaller than in the raised regions.
[0043] Counting of the extending fibers can be made under light
magnification (for example 10 times magnifier lens) by estimating
the density or the number of extending fibers or by numerical
counting of those, both in the raised regions and in the depressed
regions.
Paper Handkerchiefs
[0044] In the particular example of Tempo.TM. paper handkerchiefs,
the handkerchiefs include 3 or 4 plies of paper tissues. Each
handkerchief has a basis weigh of about 50 to 80 g/sqm (i.e. about
18 g/sqm per ply) and a caliper of 400.mu. to 600.mu. (about
140.mu. per ply). The plies are linked together by a particular
embossing, according to WO95/27429, and possibly gluing, which
keeps the plies together and enable the design of a particular
pattern at the surface of the paper handkerchief. In a particular
example, only the 2 outside surfaces of the handkerchiefs (after
combining the plies) have unbonded fiber ends in the raised regions
of the tissues in accordance with the present invention. The other
surfaces of the tissues (inwardly oriented surfaces of the outside
tissue and internal tissue's surfaces) present raised regions and
depressed regions providing bulkiness and caliper, but an about
equal quantity of unbonded fibers on the raised and depressed
regions.
Absorbent Article
[0045] In another example, the paper tissue according to the
present invention is in an absorbent article. The term "absorbent
article" refers to devices that absorb and contain liquid, and more
specifically, refers to devices that are placed against or in
proximity to the body of the wearer to absorb and contain the
various exudates discharged from the body. Absorbent articles
include but are not limited to diapers, adult incontinence briefs,
training pants, diaper holders and liners, sanitary napkins and the
like.
[0046] Absorbent articles typically comprise an absorbent core, a
topsheet and a backsheet. The absorbent core generally is disposed
between the topsheet and the backsheet. The absorbent core may
comprise an acquisition system, which includes an upper acquisition
layer facing towards the wearer's skin and a lower acquisition
layer facing the garment of the wearer. In one embodiment, the
upper acquisition layer comprises a non-woven whereas the lower
acquisition layer comprises a mixture of chemically stiffened,
twisted and curled fibers, high surface area fibers and
thermoplastic binding fibers. In another embodiment, both
acquisition layers are provided from a non-woven material.
Alternatively, one or all layers of the acquisition system may be
provided from a tissue paper in accordance with the present
invention. For example, the storage layer may be wrapped by a core
wrap material. In one such embodiment the core wrap material
comprises a top layer and a bottom layer. The core wrap material,
the top layer or the bottom layer can be provided by a paper tissue
according to the present invention. The top layer and the bottom
layer may be provided from two or more separate sheets of materials
of they may be alternatively provided from a unitary sheet of
material. Such a unitary sheet of material may be wrapped around
the storage layer e.g. in a C-fold.
[0047] While particular embodiments of the present invention have
been illustrated and described, it would be obvious to those
skilled in the art that various other changes and modifications can
be made without departing from the spirit and scope of the
invention. It is therefore intended to cover in the appended claims
all such changes and modifications that are within the scope of
this invention.
[0048] All documents cited herein are, in their relevant part,
incorporated herein by reference; the citation of any document is
not to be construed as an admission that it takes away
patentability of the present invention.
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