Note: Descriptions are shown in the official language in which they were submitted.
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MULTIPLE SUBSTRATE PLY ATTACHMENT UTILIZING A
FLEXOGRAPHIC PRINTING PROCESS TO APPLY CHEMICAL
ADHESIVES ONTO TISSUE
Field of the Invention
The present invention is directed to a process for attaching two
or more artwork-printed plies together through the use of an adhesive.
Background of the Invention
In the past, most of the multiple-ply tissue products known in
the art have been flawed in that the multiple plies of tissue are often
inadequately bonded together and the two plies frequently become
unattached on the roll as it is being used. This results in the potential
for the user to tear off a tissue sheet and utilize the reverse or back
side. When tissue plies are reversed, the consumer inadvertently
uses the harsh, rough, and scratchy side of the tissue rather than the
soft and smooth side, thus causing consumer dissatisfaction.
In order to improve the quality of multiple-ply tissue products as
it relates to ply reversal, improved ply attachment processes are
needed. Such an attachment process optimally has a low operational
cost, a low capital cost, and a minimal negative impact on the product.
Typically, when two or more artwork-printed plies of tissue are
being attached together by adhesive glue, two completely separate
processes are necessary. One process is needed to mechanically
apply the printed ink artwork design to the tissue while a second
process is necessary to apply an adhesive to the tissue. The use of
two separate processes results in increased production costs and
maintenance costs as well as increased machine clean-up time.
U.S. Patent No. 3,414,459 to Wells, for example, employs the
steps of separately embossing each of two paper sheets and then
adhesively joining them to form a laminated paper structure.
Similarly, U.S. Pat. No. 5,858,554 to Neal et al. is directed to a multi-
ply paper product wherein the plies are joined together through the
use of an aqueous adhesive composition. The specification of this
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patent reveals that the plies are embossed, but such embossing takes
place after the plies are formed but before the adhesive composition
is applied to one or both plies.
Likewise, U.S. Pat. No. 5,874,157 to Robinson et al. discloses
a laminated paper product comprising a plurality of laminae that are
joined with a laminating adhesive. The laminae may have interlocking
embossments or embossed sites; however, the embossing of the
laminae occurs prior to the joining process involving the laminating
adhesive. Comparably, WO 98/50482 to Nunes et al. is directed to an
adhesive composition for laminating an absorbent paper product and
a method for making the same. This patent also claims the paper
product wherein embossed plies are laminated using this adhesive
composition. However, the plies are already embossed prior to being
treated with the adhesive composition. Thus, these patents illustrate
how the two processes of imprinting an artwork design onto a tissue
and applying an adhesive to the same tissue are traditionally separate
processes.
Methods other than those employing an adhesive solution are
known in the art for bonding plies of tissue laminae together to form a
single laminate. For example, U.S. Pat. Nos. 4,806,418 and
4,867,831 to Sic. I, both assigned to the assignee of the present
invention, provide for ply attachment through the distribution of
thermoplastic particles between the plies and the subsequent melting
of these particles to bond together the fibers of the plies.
Furthermore, U.S. Pat. No. 5,143,776 to Givens is directed to a
laminate of two tissue laminae adhesively joined by hot melt
adhesive. In this patent, the hot melt adhesive forms the pattern of a
single longitudinally or transversely oriented stripe. The patent states
that the stripe of adhesive is interposed between the laminae, but it
does not suggest that the application of this hot melt adhesive could
simultaneously involve the printing of an artwork design.
Also, U.S. Pat. No. 4,816,320 to St. Cyr describes a process
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wherein the outer surface of one tissue layer is dotted or stippled with
fine dots or atomized droplets of adhesive material mist-sprayed
thereon. The multiple plies are then bonded together to form integral
improved tissue sheets. Thus, the methods described for joining
multiple plies of tissue together to form a tissue laminate do not
contemplate the combination of a process for applying an adhesive
solution with a process for imparting a printed artwork design to the
same tissue plies.
Flexographic processes have been used frequently in the
printing industry, and such flexographic printing processes have
proven to have a negligible impact on increasing tissue ply stiffness.
Various products are known in the art that may be used as
flexographic and/or magnetic printing plate assemblies. A European
patent, EP 0058737/A1, discloses a photosensitive flexographic
element. The flexographic element in this reference comprises a
layer of a photosensitive, elastomeric composition attached to a
flexible support. This element is useful in the preparation of
flexographic printing plates.
Similarly, U.S. Pat. No. 3,670,646 to Welch, Jr. is directed to a
flexible printing plate-saddle assembly into which magnetic particles
are incorporated in order to provide an improved means for securing
the printing plate to a printing press. Also, U.S. Patent No. 3,824,927
to Pugh et al. provides for a printing member in which the printing
element is held in position on a conventional roll by magnetic means.
Such printing assemblies are useful in printing an artwork design onto
a tissue laminate; however, they do not provide any means for
simultaneously applying an adhesive solution to tissue plies.
Therefore, a need currently exists for a single, more efficient
process that combines the application of a printed ink artwork design
to a tissue with the application of an adhesive to a tissue.
Summary and Objects of the Invention
It is an object of the present invention to combine the process
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of applying a printed ink artwork design to a tissue and the process of
applying an adhesive to a tissue into a single, more efficient process.
This and perhaps other objects of the present invention are
accomplished through the use of a flexographic magnetic printing roll
that applies either an ink, adhesive, and water mixture or an adhesive
and water mixture onto tissue between the plies for the purpose of ply
attachment and/or artwork application. In certain embodiments of the
present invention, the flexographic magnetic printing roll is in the
shape of a desired artwork and uses the artwork design to apply the
chemical mixture of adhesive to the tissue.
In contrast to the above-described processes and products, the
process of the present invention does not involve a flexographic
element coated with the elastomeric composition described in EP
0058737/A1. The invention contemplated herein, in fact, goes
beyond the creation of either a new flexographic element or a new
printing plate assembly and seeks to combine two traditionally
separate processes (the application of a printed artwork design to a
tissue and the application of an adhesive to that tissue) into a single,
more efficient process. The patent references described above do
not contemplate such a combination of two separate processes with
the use of one flexographic printing roll.
In certain embodiments of this process, the chemical mixture is
1 part water, 1 part adhesive, and 0.0302 parts full concentrated ink.
In other embodiments, a mixture of only adhesive and water
containing 1 part adhesive and 1 part water is used. These and other
features, aspects and advantages of the present invention will
become better understood with reference to the following description
and appended claims.
Brief Description of the Drawings
FIG. 1 shows a schematic diagram of the flexographic printing
process described herein.
FIG. 2 shows the orchid print pattern used in the flexographic
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process described here.
FIG. 3 shows a dotted print pattern with a low print area used
in the process of the present invention.
FIG. 4 shows a dotted print pattern with medium print area
5 used in the process of the present invention.
Detailed Description of Representative Embodiments
Reference now will be made in detail to the embodiments of
the invention, one or more examples of which are set forth below.
Each example is provided by way of explanation of the invention, not
limitation of the invention. In fact, it will be apparent to those skilled in
the art that various modifications and variations can be made in the
present invention without departing from the scope or spirit of the
invention. For instance, features illustrated or described as part of
one embodiment, can be used on another embodiment to yield a still
further embodiment.
Thus, it is intended that the present invention cover such
modifications and variations as come within the scope of the
appended claims and their equivalents. Other objects, features and
aspects of the present invention are disclosed in or are obvious from
the following detailed description. It is to be understood by one of
ordinary skill in the art that the present discussion is a description of
exemplary embodiments only, and is not intended as limiting the
broader aspects of the present invention, which broader aspects are
embodied in the exemplary constructions.
The process of the present invention attaches two-ply bath
tissue together using a flexographic magnetic printing roll to apply
either an ink, adhesive, and water mixture or an adhesive and water
mixture onto tissue between the sheets for the purpose of ply
attachment with or without simultaneous artwork application. This
flexographic magnetic printing roll provides the desired artwork and
utilizes its artwork design capabilities to apply this chemical mixture to
the tissue. Thus, the process combines two manufacturing processes
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into a more efficient process. This combination of two processes into
one results in increased efficiency because production and
maintenance costs are reduced. Also, machine clean-up time is
reduced through this combination.
Various tissue-making processes are known to those in the art.
In particular, U.S. Patent No. 5,129,988 to Farrington, Jr. and U.S.
Patent No. 5,494,554 to Edwards et al. disclose various tissue-making
methods and processes for forming multi-layered paper webs. Such
patents are incorporated herein in their entireties by reference thereto.
These tissue-making processes and the tissue products resulting
thereby may be utilized in the process of the present invention for
forming the plies of tissue that are then printed with artwork and
joined together by the flexographic printing roll described herein.
Furthermore, processes for forming uncreped through-air dried
webs are described in U.S. Patent Nos. 5,779,860 to Hollenberg et al.
and 5,048,589 to Cook et al., both of which are assigned to the
assignee of the present invention and both of which are incorporated
herein in their entireties by reference thereto. In such processes,
through-air drying is employed as shown in the Figures of Cook et al.
As described and shown therein, a web is prepared by: (1 ) forming a
furnish of cellulosic fibers, water, and a chemical debonder; (2)
depositing the furnish on a traveling foraminous belt, thereby forming
a fibrous web on top of the traveling foraminous belt; (3) subjecting
the fibrous web to noncompressive drying to remove the water from
the fibrous web; and (4) removing the dried fibrous web from the
traveling foraminous belt. The process described therein does not
include creping and is, thus, referred to as an uncreped through-air
drying process.
Tissue products prepared from this uncreped through-air drying
process will typically possess relatively high levels of absorbent
capacity, absorbent rate and strength. In addition, because the
process avoids the use of costly creping steps, tissue products
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formed according to such a process will generally be more
economical to produce than creped towels of similar composition and
basis weight.
A process that produces a noncompressed sheet using can
drying which may be employed in the present invention is described in
U.S. Patent No. 5,336,373 to Scattolino et al., which is incorporated
herein in its entirety by reference thereto.
Embodiments of the present invention are represented by the
process diagramed in FIG. 1. In such embodiments, ply attachment
using an ink, adhesive, and water mixture may be achieved by mixing
1 part water with 1 part adhesive and 0.0302 parts full concentrate ink
to yield the final chemical solution. This adhesive solution is pumped
into a reservoir or doctor chamber 8 and then applied onto antilox roll
10 by doctor chamber 8 using two doctor blades that keep the doctor
chamber 8 sealed. Antilox roll 10 functions similarly to a gravure roll
except that antilox roll 10 is more durable and has a much longer
production life in commercial applications. Antilox roll 10, used in
certain embodiments of the present invention, is made by placing a
coating (approximately 0.020 inches thick in some cases) of
chromium oxide on the outer perimeter of a round steel roll. The
chromium oxide may then be etched with a laser. The laser burns
microscopic "pot-holes" called gravure cells onto the surface of the
chromium oxide.
Thus, these microscopic pores along antilox roll 10 fill up with
the above-described mixture of ink, adhesive, and water as roll 10 is
rotated about its centerline. The adhesive solution is then
mechanically transferred onto flexographic printing roll 12. The now-
filled gravure cells or microscopic pores are rotated around until they
contact rubber flexographic printing roll 12. A specific metered
amount of the chemical mixture is then transferred, due to capillary
forces, out of the gravure cells on antilox roll 10 and onto flexographic
rubber roll 12.
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This printing roll 12 has an engraved raised artwork pattern on
its surface, and it contacts the inside of first sheet 20 of two tissue
sheets and applies or prints the mixture onto first sheet 20. This first
sheet 20, now containing the mixture of ink, adhesive, and water on
its surface, is then met by untreated tissue sheet 22, and the two
sheets 20 and 22 are "married" together by the backing roll or
marrying roll 14. The two-ply sheet 24 then passes over another
rubber roll 16 and may be further converted in additional processes.
Thus, the present invention produces a tissue product wherein
the ink, adhesive, and water mixture is between the layers and not on
the exterior as in known products.
In alternative embodiments of the present invention, the above-
described process is performed with a mixture of only adhesive and
water, containing, for example, 1 part adhesive and 1 part water.
In certain embodiments of the present invention, a towel may
be the substrate rather than a tissue. The towel is likewise able to
undergo the above-described flexographic printing process.
In one embodiment of the present invention, the engraved
raised artwork design located on the flexographic roll includes floral
designs such as orchid shapes, which apply the chemical mixture of
either ink, adhesive, and water or adhesive and water to the tissue or
towel.
Examples
The present invention may be understood by reference to the
following Examples, without being limited thereto. Two experimental
trial runs were performed in accordance with the present invention.
These two experiments investigated the feasibility of obtaining ply
attachment for a two-ply uncreped through-air dried bath tissue using
the flexographic gluing process described herein. Both the
effectiveness of the adhesive process and the effects on the tissue
products' quality were studied. In both Examples, the process of the
present invention was performed on the bath tissue at a speed of 350
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feet per minute, and pilot plant scale equipment was used during
these experiments.
Specific descriptions of the trial runs and the results of each
Example are fully described below. Generally, the experiments
described in these examples showed successful ply attachment at
converting speeds of 350 feet per minute. Also, the quality of the
tissue products formed according to the present invention proved to
be comparable to the quality of tissue products laminated together by
other ply attachment methods such as the use of a crimping wheel.
Example 1
During this Example, the adhesive used was product number
48037 made by Reichold Chemicals, Inc. in Durham, NC. This
adhesive is a cornstarch- based adhesive with a viscosity of
approximately 70cp. Although this particular adhesive was utilized in
the examples, any adhesive such as cellulose-based, polyvinyl-
based, etc. could be employed. In addition, adhesives having a
viscosity of from about 20 to about 200 centipoises would generally
meet the requirements of an adhesive sufficient to bond the The final
glue or adhesive that was applied to the sheet during this Example
was a 50 percent by volume glue and 50 percent by volume water
mixture.
During this experimental trial, ink was added to the glue and
water mixture. The ink used herein was a dark charcoal grey water-
based ink (product number 430-Z-4, color code "Butterfly Grey")
made by Daw A J Printing Co. in Appleton, WI. However, alternative
water-based inks of any color and any concentration level may be
used in the process of the present invention. The ink was mixed with
the glue and water in the following manner: 1.75 gallons of the
Reichold 48037 adhesive, 1.75 gallons of water, and 200 mL of the
grey ink. All of the chemicals used were 100% water-soluble.
A flexographic gluing process was performed. The converting
equipment used in this experiment was set up in the following order:
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first unwind, second unwind, large roll calendar, coater (modified to
become a flexographic printer), small roll calendar, and rewinder. The
converting speed was 350 feet per minute using two-ply uncreped
through-air dried bath tissue with a total weight of 20 Ibs./2880 ft2.
5 The process was performed in order to laminate two plies of bath
tissue together using the above-described water-soluble, starch
based adhesive.
The process settings for this Example are described below in
Table I:
10 Table I
0.0048 in print area per
1 inl of
Low Print Area tissue
0.0276 in' print area per
1 in' of
High Print Area tissue
Machine Speed 350 feet/minute
Uncreped through-air dried
tissue
Bath Tissue Basesheet sheet
Bath Tissue Weight per Ply 10 Ibs./2880 ft'
Reichold 48037, Diluted
to 50
Adhesive Used volume % water, Viscosity
70 cp
Nip Width between Antilox 13 mm of interference
Roll
and Flexographic Printing
Roll
Nip Width between Flexographic
Printing Roll and Steel Marrying9 mm of interference
Roll
Nip Width between Steel Marrying9 mm of interference
and Urethrane Backing Roll
Glue Add-on Onto Sheet 5 weight % solids
The flexographic print pattern used during this experiment was
an orchid pattern, shown in Figure 2. This orchid pattern results in a
high adhesive add-on relative to the tissue sheets because the
pattern has a high contact area. Thus, an optimal balance between
liquid glue solids concentration and print area was achieved as print
area increased, glue solids concentration decreased and vice versa.
It was found in the experiments done according to Example 1 that
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glue add-on of 5 weight percent solids in conjunction with the orchid
print pattern produced sufficient ply attachment.
The test method used for determining the success of the ply
attachment was Standard Test Method 814-W in which a Slip/Peel
tester (manufactured by Instrumentors, Inc.) was used. The peel
tester was used in the peak load setting.
In general, the results of the experiments run in accordance
with Example 1 resulted in high quality ply attachment at a machine
speed of 350 feet per minute. Also, the overall product quality of the
resulting two-ply tissue product produced by the flexographic gluing
process was comparable to the product quality of tissue products
produced using prior art control processes. For example, tissue
products formed according to the flexographic process of the present
invention had similar softness, stiffness, and drapeability as tissue
products in which ply attachment was facilitated by a crimping wheel.
Furthermore, with the flexographic gluing process, it was found that
absorbency, bulk, wet and dry strength, opacity, and brightness did
not appear to differ significantly from other prototypes made without
the flexographic process. Thus, the flexographic adhesive process
did not negatively impact the overall products quality.
Tests were also conducted to compare the glued product
produced according to the present invention with a non-glued
prototype. Several softness tests (such as hand ranking and
simulated use panel) showed that the prototypes formed according to
the present invention demonstrated comparable characteristics.
Example 2
During this Example, the adhesive used was product number
18-1537 made by National Starch and Chemical Co. of Bridgewater,
NJ. This adhesive is also cornstarch-based with a viscosity of
approximately 70cp and is 100% water-soluble. The final glue or
adhesive that was applied to the sheet during this experiment was a
70 percent by weight glue and 30 percent by weight water mixture.
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No ink was incorporated into the mixture used herein.
The overall flexographic process used in Example 2 was
identical to that used in Example 1 except the use of a different
adhesive without the addition of an ink. The process settings for this
experiment are set forth below in Table II:
Table II
Low Print Area 0.0048 in' print area per
1 in' of
tissue
High Print Area 0.0276 in' print area per
1 in' of
tissue
Machine Speed 350 feet/minute
Bath Tissue Basesheet Uncreped through-air dried
tissue
sheet
Bath Tissue Weight per Ply 10 Ibs./2880 ft'
National Starch 18-1537,
Diluted
Adhesive Used to 30 weight % water, Viscosity
60
cp
Nip Width between Antilox 13 mm of interference
Roll
and Flexographic Printing
Roll
Nip Width between Flexographic
Printing Roll and Steel 9 mm of interference
Marrying
Roll
Nip Width between Steel g mm of interference
Marrying
and Urethrane Backing Roll
Glue Add-on Onto Sheet 5 weight % solids
One of the flexographic print patterns used in this Example was
the orchid print pattern, shown in Figure 2. It was determined during
the process of this Example that the glue add-on level relative to the
tissue sheet should approximate 5 weight percent solids to obtain
acceptable ply attachment when using the orchid print pattern.
Attempts were made during the process of this Example to use
two other flexographic printing plates with varying print areas. These
other printing plates were used in order to minimize the glue add-on
relative to the tissue sheets by reducing the contact area of the
flexographic printing plates. A dotted print pattern with a low print
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area (seen in Figure 3) and a dotted print pattern with a medium print
area (seen in Figure 4) were used. The dots imprinted onto the tissue
sheets in both Figs. 3 and 4 were 3/64 inches in diameter. The
pattern with the low print area had dots spaced 1 inch apart in a 45
degree diamond pattern. The print pattern with the medium print area
had dots spaced 1/2 inch apart also in a 45 degree diamond pattern.
These and other modifications and variations to the present
invention may be practiced by those of ordinary skill in the art, without
departing from the spirit and scope of the present invention, which is
more particularly set forth in the appended claims. In addition, it
should be understood that aspects of the various embodiments may
be interchanged both in whole or in part. Furthermore, those of
ordinary skill in the art will appreciate that the foregoing description is
by way of example only, and is not intended to limit the invention so
further described in such appended claims. Therefore, the spirit and
scope of the appended claims should not be limited to the description
of the preferred versions contained therein.
