Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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ABSORBENT COMPOSITE SHEET, ROLL OF SUCH A SHEET, PACKET OF
SHEETS, AND MANUFACTURING PROCESS
BACKGROUND OF THE INVENTION
[0001 ] The present disclosure relates to a so-called composite sheet for
domestic
or away from home use.
[0002] Numerous examples are known of so-called "multi-ply" sheets, also
known as sheets of tissue paper, having at least two separate plies of which
at least one is
an absorbent ply, especially made of cellulose wadding.
[0003] The so-called "tissue" paper in accordance with an embodiment of the
invention is defined in the standard NF EN ISO 12625-1.
[0004] Multi-ply sheets are very commonly used and are in particular available
packaged as rolls of pre-cut sheets, especially in the form of rolls for
wiping known as
"kitchen towel paper" or else as "kitchen towel" rolls.
[0005] These products are much appreciated for their various parameters such
as
their flexibility, their softness, their strength in the dry and wet state,
their liquid
absorption capacity, etc.
[0006] While composite sheets having the main characteristics and qualities
mentioned above may be suitable for their intended purpose, improvements in
the art may
be realized by providing a novel product of the composite sheet type which,
while having
the main characteristics and qualities mentioned above, makes it possible, in
addition, to
package hot or cold food products while effectively protecting them,
especially with a
view to easily producing a complete or partial packaging of the food which may
then be
almost impermeable to liquids and to provide a thermal barrier function, and
which may
in addition be folded and unfolded several times without however
deteriorating.
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BRIEF DESCRIPTION OF THE INVENTION
[0007] An embodiment of the invention provides a composite sheet for domestic
or away from home use, the composite sheet including:
-a first ply of paper with a degree of absorption of liquids equal to or
greater
than around 5 (g/g CEN standard),
-a second superposed ply which is composed of a metal-containing layer, the
thickness of which is equal to or less than around 10 m (microns).
[0008] In an embodiment, the second ply is a metal foil, and the second ply is
joined to the first ply by an adhesive.
[0009] Such an example product essentially has the advantages of being able to
be smoothed out and therefore reused, which is not the case for a conventional
aluminium
foil, of which the thickness is around 11 microns to around 13 microns.
[0010] A product according to an embodiment of the invention is however
stiffer
than such an aluminium foil. The example composite product according to an
embodiment of the invention thus keeps both its flexibility and its stiffness.
[0011 ] According to an embodiment of the invention, the composite sheet
product
is as absorbent as a multi-ply tissue sheet, but it is stronger.
[0012] Such a product may, in addition, be packaged in the form of a roll of
pre-
cut or non-pre-cut composite sheet, which may be used in existing dispensers
for
aluminium foil (also known as "aluminium paper") and/or kitchen towel that
equip, in
particular, numerous domestic or professional kitchens.
[0013] According to other features of an example embodiment of the invention:
-the thickness of the second ply is equal to or less than around 7 microns
( m);
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-the basis weight (weight per unit area) of the second ply is between around
13 and around 19 grams per square meter (g/m2), desirably equal to around 17
grams per
square meter (g/m2);
-the first ply is a tissue paper sheet, an embossed tissue paper sheet, a
machine gloss paper sheet a machine glaze paper sheet; or a machine finish
paper sheet;
-the thickness of the sheet forming the first ply is between around 0.25 and
around 0.45 millimeter (mm), desirably equal to around 0.35 millimeter (mm);
-the basis weight of the sheet forming the first ply is between around 17 and
around 50 grams per square meter (g/m2), desirably equal to around 19 grams
per square
meter (g/m2);
-the basis weight of the composite sheet is between around 30 and around 69
grams per square meter (g/m2);
-the adhesive is a vinyl type adhesive;
-the adhesive is desirably deposited on one of the faces of the metal foil
forming the second ply; and
-the metal-containing layer forming the second ply is an aluminium layer.
[0014] An embodiment of the invention also provides a roll composed of a
composite sheet according to the invention, formed from a continuously wound
strip of
composite sheet.
[0015] According to one feature of the roll, the strip of composite sheet
wound as
a roll includes pre-cut regions.
[0016] An embodiment of the invention also provides a packet of individual
sheets composed of a stack of individual composite sheets according to an
embodiment
of the invention, which may be stacked up, or folded and/or interfolded.
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[0017] An embodiment of the invention also provides a process for
manufacturing a sheet according to an embodiment of the invention, including
the
process of joining the first ply and the second ply by bonding and pressing
between two
rolls.
BRIEF DESCRIPTION OF THE FIGURES
[0018] Other features and advantages of an embodiment of the invention will
appear on reading the description which follows, for an understanding of which
reference
will be made to the appended drawings in which:
[0019] Figure 1 is a schematic perspective view of a composite sheet according
to
an embodiment of the invention;
[0020] Figure 2 is a diagram illustrating an example first installation for
implementing a process according to an embodiment of the invention;
[0021 ] Figure 3 is a diagram illustrating an example second installation for
implementing a process according to an embodiment of the invention;
[0022] Figure 4 is a schematic perspective view of a composite sheet according
to
an embodiment of the invention;
[0023] Figure 4A is an expanded cross section view of the composite sheet of
Figure 4;
[0024] Figure 5 is a diagram illustrating an example third installation for
implementing a process according to an embodiment of the invention; and
[0025] Figure 6 is a diagram illustrating an example fourth installation for
implementing a process according to an embodiment of the invention.
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DETAILED DESCRIPTION OF THE INVENTION
[0026] According to an embodiment of the invention, a composite sheet CS is
provided which has two plies, a first ply P1 and a second ply P2, of which
one, P1, is a
sheet of so-called "tissue" paper made of cellulose wadding, a sheet of
machine gloss or
machine glaze (MG) paper, or a sheet of machine finish (MF) paper, and of
which the
other, P2, is a metal-containing layer, and for example a metal foil such as
an aluminium
foil for example, the two plies being joined together by a vinyl adhesive ADH
when each
ply is one sheet.
[0027] The first ply P 1 is chosen with consideration to its mechanical
strength
and its high degree of absorption of liquids g/g: equal to or greater than
around 5 (CEN
standard) for example.
[0028] In an embodiment, the first ply P 1 is a tissue ply produced in the wet
state,
and desirably a so-called TAD (Through Air Dry process) product obtained
according to
the known techniques described and represented, for example, in documents WO-
AI-
01/44568, EP-A1-631 014 or FR-A1-2 481 328.
[0029] In an embodiment, the first ply P 1 made of a TAD tissue sheet is
embossed in the wet state according to techniques known in the field and
desirably by
means of a so-called "imprinting" fabric.
[0030] Features of an example sheet forming the first ply are, for example,
the
following:
-Basis weight: around 20 g/m2 (grams per square meter).
-Thickness: around 0.35 mm (millimeter).
[0031 ] Embossing carried out by marking by means of a fabric in the wet
state.
[0032] MD (machine direction of the sheet) tensile strength: around 300 N/m
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(Newtons per meter).
[0033] CD (cross direction of the sheet) tensile strength: around 260 N/m.
-MD (machine direction) elongation: around 20%.
-CD (cross direction) elongation: around 9%.
-CD (cross direction) wet strength: around 75 N/m.
-Liquid absorption capacity g/g: around 15 (CEN standard).
-Liquid absorption capacity g/m2: around 315 g/m2.
[0034] In an embodiment, the composition of the sheet is 100% pure cellulose
wadding including around 90% based on resinous paper-making fibers and around
10%
based on hardwood papermaking fibers.
[0035] In accordance with an embodiment of the invention, a first ply P1 is
characterized by a high flexibility, a large absorption capacity, good wet
strength, and a
"cloth-like" visual appearance.
[0036] In an embodiment, the first ply P1 is a machine gloss or a machine
glaze
(MG) paper, or a machine finish (MF) paper. These papers are smoother than the
aforementioned tissue paper and provide better printing surfaces. The physical
properties
of the MG or MF papers are similar to those of the aforementioned tissue
paper, with the
exception of the elongation, which in this case is around 1/3 the value of the
tissue paper,
and the thickness, which would be around 10% of the value of the tissue paper.
In
contrast to the tissue paper, which contains 100% cellulose, the MG or MF
papers could
contain inorganic fillers in the range of around I% to around 30% by weight.
These
fillers improve the optical properties and lower the cost of the paper.
[0037] In comparison with the aforementioned tissue paper, which is 100%
cellulose wadding including around 90% based on resinous papermaking fibers
and
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around 10% based on hardwood papermaking fibers, the MG and MF sheets can
contain
around 20% to around 90% resinous fibers and around 80 to around 10% hardwood
fibers. In applications where the release coating is utilized, around 0.1% to
around 5% by
weight will be coating material with the remaining fiber sheet composed as
described
above.
[0038] The second ply P2 is for example an annealed aluminium foil having a
small thickness and with its surface degreased, of which the main
characteristics are the
following:
[0039] Thickness: less than around 7 .tm (microns), for example equal to
around
6.0 pm (microns) around 8%.
-Basis weight: around 17 g/m2.
-Elongation: around 1%.
[0040] The aluminium foil forming the second ply P2 is desirably for food
contact or use, and desirably conforms to the 2004/1935/EC and 89/109/EEC
directives
and regulations.
[0041 ] By comparison, an aluminium foil - conventional aluminium paper for
household use, for example - has a thickness of around 11 m (microns) to
around 13 m
and, relative to such a "thick" conventional foil, the very thin foil or layer
of the second
ply P2 according to an embodiment of the invention, used alone would be too
fragile for
packaging and would withstand with great difficulty the mechanical stresses
inherent to
the various handlings.
[0042] And with regard to a process for manufacturing a composite sheet
according to an embodiment of the invention, it is only through the teachings
disclosed
herein that one skilled in the art is taught to combine two plies such as
plies P 1 and P2,
especially due to the very small thickness of the ply P2, and due to
respecting the
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standards relating to food contact which impose restrictions to the choice of
adhesive.
[0043] As disclosed herein, the combination of the two plies P1 and P2 is
carried
out in an embodiment of the invention by application of a specific adhesive
ADH,
suitable for food contact (for example an aqueous dispersion of a vinyl
polymer), which
in an embodiment is deposited on one face of the second ply P2. The adhesive
ADH is,
for example, an adhesive with the reference SUBO DA 37M sold by Bostik (trade
mark).
The adhesive used desirably respects the national and international
regulations regarding
the contact of materials with foodstuffs, and desirably conforms to the
national and
international standards and regulations on that subject.
[0044] The second ply P2, of which one face is coated with adhesive, is for
example applied to/pressed on the first ply P1 by a pressure roll known as a
marrying
roll.
[0045] By way of example, the main characteristics of the composite sheet CS
thus obtained in accordance with an embodiment of the invention are the
following:
-Basis weight: around 39 g/m2.
-Thickness: around 0.29 mm.
[0046] Dry strength: MD (machine direction): around 363 N/m and CD (cross
direction): around 369 N/m.
-Elongation: around 3%.
-Liquid absorption capacity g/g: around 9 (CEN standard).
[0047] Furthermore, in an embodiment, the wet (tensile) strength of the
composite sheet CS is around 279 N/m [MD (machine direction)] and around 294
N/m
[CD (cross direction)]. The wet strength/dry strength ratio is between around
0.77 and
around 0.80.
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[0048] The invention is not limited to the design of the second ply in the
form of
an aluminium foil.
[0049] It may, for example, be a foil of another metal or of another metal
alloy.
[0050] Similarly, the metal-containing layer forming the second ply is not
necessarily a metal foil.
[0051 ] The metal-containing layer may also be produced by deposition,
spraying
or coating over one of the faces of the first ply P1.
[0052] The metal-containing layer may also be a layer of material containing
metal particles embedded therein, such as metal particles embedded in a
curable resin or
polymer material for example.
[0053] The composite sheet according to an embodiment of the invention may,
for example, be produced in the form of a strip wound continuously as a roll,
for example
according to the following specifications:
-Outer diameter of the "new" roll: around 80 mm.
-Length of the wound strip of composite sheet: around 20 m.
-Width of the roll: around 230 mm or around 300 mm.
[0054] Outer diameter of the mandrel on which the strip of sheet is wound:
around 27 mm.
[0055] The strip of composite sheet wound as a roll may comprise perforations
or
"pre-cuts" along the cross direction in order to facilitate the delivery of
the roll as
individual sheets of predetermined length.
[0056] The composite sheet according to an embodiment of the invention may
also be sold in the form of a packet of individual sheets, for example of
substantially
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square shape, which may be stacked, or folded and/or interfolded, for example.
[0057] By way of non-limiting example and with reference to Figure 2, one
example of a process for producing a composite sheet CS according to an
embodiment of
the invention will now be described.
[0058] Represented in Figure 2 is a first conversion line 10 composed of two
motorized reels 12 and 14.
[0059] The first reel 12 is intended to receive the spool of cellulose wadding
raw
material 16, for example of TAD type. The cellulose wadding raw material 16 in
this
instance being the first ply P 1 in accordance with an embodiment of the
invention.
[0060] The second reel 14 receives the spool of aluminium foil 18. The foil 18
forms in this instance the second ply P2 in accordance with an embodiment of
the
invention.
[0061 ] The width of the spools may be defined as a function of customary
dimensional standards.
[0062] Downstream of the reels 12 and 14, considering the running direction of
the sheets from the reels, the conversion line 10 includes a unit 20 for
bonding the two
plies constituting the composite sheet CS according to an embodiment of the
invention,
and also a unit 22 for converting the sheet 16 in order to form the first ply
P 1 in
accordance with an embodiment of the invention.
[0063] In a known manner, the unit 22 includes a rubber roll 24 and an
engraved
roll 26, the latter also constituting the marrying roll of the bonding unit
20.
[0064] After passing between the rolls 24 and 26, the embossed sheet 16 forms
the first ply P 1 in accordance with an embodiment of the invention.
[0065] The unit 20 for bonding the two plies P1 and P2 includes in this
instance a
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bonding station 28 having a chambered doctor blade system 30 containing the
adhesive
ADH, and an applicator roll 32 for transfer of the adhesive to the opposite
face of the
second ply P2 (sheet 18).
[0066] The unit 20 also includes a combining roll 34 made of hard rubber.
[0067] During their passage between the combining rolls 26 and 34, the two
plies
PI and P2 are joined together to form the composite sheet CS which is then
continuously
wound on a winding machine 38.
[0068] In order to absorb the possible disturbances linked to the differences
in
elongation between the two plies P 1 and P2, an embodiment includes a draw-
control
group 36 arranged upstream of the roll 24.
[0069] The plies P1 and P2 joined together pass towards draw rolls 40 that
enable
homogeneous feeding, without a problem of folds, at the inlet of the winding
machine 38.
[0070] Represented in Figure 3 is a second example conversion line 10'.
[0071] This line 10' will be described in comparison with the first line 10
illustrated in Figure 2, the identical, analogous or similar components being
denoted by
the same reference numbers.
[0072] The composite sheet CS obtained due to this second line 10' is
characterized in that the sheet 16 which forms the first ply P 1 in accordance
with an
embodiment of the invention is not embossed.
[0073] For the purpose of the second line 10', the engraved roll 26 from the
first
line 10 is removed.
[0074] In order to be assembled, the sheets 16 and 18 thus pass between the
combining roll 34 and the marrying roll 24 which is, in the instance of second
conversion
line 10', smooth. In an embodiment, the rolls 34 and 24 between which the two
sheets are
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pressed are desirably made of steel.
[0075] In an embodiment, and in addition to the foregoing, a non-stick coating
Cl
is applied to the outside surface of the first ply P1, as illustrated in
Figures 4 and 4A,
where Figure 4A depicts an expanded cross section view of the composite sheet
CS of
Figure 4 with coating C 1 added. Coating C 1 may be continuous or non-
continuous.
[0076] If continuous, then coating Cl is porous, thereby allowing the passage
of
water vapor and/or condensed liquid into the cellulose structure of first ply
P 1. In an
embodiment, coating Cl is a hydrophobic moisture-vapor-permeable coating
formed
using a hydrophobe precursor, such as: alkyl ketene dimers (AKD's) from
Hercules, Inc.;
alkenyl succinic anhydride (ASA) from American Cyanamid; and, Werner chromium
complexes from du Pont, for example.
[0077] If non-continuous, then the material forming coating C 1 is not
necessarily
porous, as long as there is sufficient exposure of the underlying first ply P
1 to permit the
passage of water vapor and/or condensed liquid into the cellulose structure of
first ply P 1.
In an embodiment, coating Cl is a hydrophobic moisture-vapor-impermeable
coating
formed using: wax/polymer blends; polyethylene, polyvinylidene chloride;
ethylene
acrylic acid copolymer, polypropylene, polyester, poly lactic acid,
polyisobutylene,
nylon, polymethylpentene, ethylene vinyl acetate; hot melts; and, fluorinated
molecules,
for example. When used in accordance with an embodiment of the invention, the
layer
including coating Cl is considered to be permeable even though the material
forming
coating Cl may itself not be permeable, as the layer including coating Cl
permits the
passage of water vapor and/or condensed liquid into the cellulose structure of
first ply P 1.
[0078] While embodiments disclosed herein refer to specific materials useful
for
coating Cl, it should be appreciated that the scope of the invention is not
limited only to
those materials listed, but may also include any hydrophobic moisture-vapor-
permeable
material, or any hydrophobic moisture-vapor-impermeable material, suitable for
the
purposes disclosed herein.
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[0079] Reference is now made to Figures 5 and 6, which depict similar
conversion lines to those of Figure 2 (conversion line 10) and Figure 3
(conversion line
10'). In Figures 5 and 6, the illustrated processes and associate equipment
are referred to
as third conversion line 50 and fourth conversion line 50', respectively.
[0080] In Figures 5 and 6, the coating Cl and the associated operations for
applying the coating Cl are collectively referred to and designated by CA.
While two
locations are illustrated in each of Figures 5 and 6 for CA, only one location
is needed to
produce the composite sheet CS with the non-stick coating Cl in accordance
with an
embodiment of the invention. That is, coating Cl may be applied in one of two
general
locations, before the first and second plies P 1 and P2 are combined (before
marrying roll
24 for example), or after composite sheet CS is formed (after marrying roll 24
for
example). Notwithstanding the foregoing, it will be appreciated that a two-
stage
application process for applying coating Cl, both before and after marrying
roll 24 for
example, is not outside the scope of the claimed invention. The coating
application CA
could be accomplished inline during the lamination process, as illustrated in
Figures 5
and 6, but could also be accomplished as a secondary offline operation. For
example, the
coating application CA could be accomplished as part of a post-lamination
printing
operation using rotogravure or anilox application methods, which would allow
flexibility
in the manufacturing process.
[0081 ] In addition to the foregoing, it will be appreciated that any of the
above-
noted functional chemistries may be added to the paper during the production
of the
paper (wet end or internal application), intermediate in the process (size
press
application), or post production (any of a variety of coating techniques
applied after the
paper sheet is formed, including in-line coating).
[0082] Additionally, the surface of the coated first ply P 1 may be altered
through
oxidation by flame or corona discharge treatments, which will result in a
higher surface
energy and better ink adhesion if printing on the coated surface is desired.
While
embodiments of the invention are described employing certain techniques to
alter the
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surface energy of the coated first ply, it will be appreciated that the scope
of the invention
is not limited to only those techniques mentioned, but also encompasses any
other
technique suitable for the purposes disclosed herein.
[0083] As discussed above, the release coating Cl may be applied in such a way
that does not form a continuous barrier to the passage of water vapor, or to
the passage of
condensed liquid, into the cellulose structure of the first ply Pl I. As such,
technologies
that deposit discrete portions of coating Cl are desirable, although methods
producing a
continuous film may be used at low solids content.
[0084] From the foregoing, it will be appreciated that the release coating C I
can
be applied by any suitable technique known to those skilled in the art, such
as a size press
or coater, spraying, powder coating, chemical vapor deposition, and physical
vapor
deposition. In general, any coating technique suitable for the purposes
disclosed herein
(for example, permitting conveyance of moisture to the absorptive parts of the
first ply
P 1) may be used. Suitable coating methods known in the art and contemplated
for use in
accordance with an embodiment of the invention, are further described and
discussed in
U.S. Patent No. 5,582,674.
[0085] In addition to the actual coating process, it is contemplated that
additional
operations such as drying may be employed. As such, reference herein to
coating
application CA also encompasses any additional operation employed in
accordance with
an embodiment of the invention.
[0086] While certain combinations of features have been described herein, it
will
be appreciated that these certain combinations are for illustration purposes
only and that
any combination of any of the disclosed features may be employed in accordance
with an
embodiment of the invention. Any and all such combinations are contemplated
herein
and are considered within the scope of the invention disclosed.
[0087] While certain locations for coating application CA have been described
and illustrated herein, it will be appreciated that these certain locations
are for illustration
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purposes only and that any location for coating application CA suitable for
the purposes
disclosed herein may be employed in accordance with an embodiment of the
invention.
Any and all such locations are contemplated herein and are considered within
the scope
of the invention disclosed.
[0088] As disclosed, some embodiments of the invention may include some of the
following advantages: a composite paper wrap that could be used with the paper
side in
or the paper side out, depending on the particular type of food that is being
wrapped, such
as hot or cold food, or wet or dry food; a composite sheet wrap having a foil
side that is
capable of being smoothed out and reused; a composite sheet utilizing MG or MF
paper
that provides an improved printing surface over tissue paper; and, a composite
sheet
utilizing MG or MF paper having inorganic fillers for improved optical
properties and
lower cost.
[0089] While the invention has been described with reference to exemplary
embodiments, it will be understood by those skilled in the art that various
changes may
be made and equivalents may be substituted for elements thereof without
departing from
the scope of the invention. In addition, many modifications may be made to
adapt a
particular situation or material to the teachings of the invention without
departing from
the essential scope thereof. Therefore, it is intended that the invention not
be limited to
the particular embodiment disclosed as the best or only mode contemplated for
carrying
out this invention, but that the invention will include all embodiments
falling within the
scope of the appended claims. Also, in the drawings and the description, there
have been
disclosed exemplary embodiments of the invention and, although specific terms
may
have been employed, they are unless otherwise stated used in a generic and
descriptive
sense only and not for purposes of limitation, the scope of the invention
therefore not
being so limited. Moreover, the use of the terms first, second, etc. do not
denote any
order or importance, but rather the terms first, second, etc. are used to
distinguish one
element from another. Furthermore, the use of the terms a, an, etc. do not
denote a
limitation of quantity, but rather denote the presence of at least one of the
referenced
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item.
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