Note: Descriptions are shown in the official language in which they were submitted.
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CHEMICALLY ENHANCED MULTI-DENSITY PAPER
STRUCTURE AND METHOD FOR MAKING SAME
FIELD OF THE INVENTION
This invention relates to a chemically enhanced paper structure
comprising a cellulose substrate and a chemical papermaking additive.
More particularly, this invention relates to a paper structure comprising a
cellulose substrate containing at least two micro-regions of density or basis
weight, wherein the chemical papermaking additives are incorporated in
register with the micro-regions of the paper structure.
~ b BACKGROUND OF THE INVENTION
Consumer products such as toilet tissue, toweling and facial tissue
made from cellulosic webs are a pervasive part of modern society. In
general, these products need to possess certain key physical properties to
be considered acceptable to consumers. While the exact mix of key
properties and the absolute value of the individual properties will vary
depending on the nature of the product, nonetheless, softness, wet and dry
strength, absorbency, and pleasing aesthetic nature are universally
desirable properties. Softness is that aspect of the fibrous web that elicits
a
pleasing tactile response and insures that the product is not harsh or
abrasive when it contacts human skin or other fragile surfaces. Strength is
the ability of the structure to retain its physical integrity during use.
Absorbency is the property of the fibrous structure which allows it to acquire
and retain contacted fluids in an acceptable time. Aesthetic nature refers to
the psycho-visual response that occurs when the consumer views the
product either alone or in the context of the product's surroundings.
The most common method for the manufacture of tissue products is
the wet laid papermaking process. In such a process, individual fibers are
first suspended in a dilute slurry with water. This slurry is then laid on a
foraminous screen to remove a large portion of the water and to form a thin,
relatively uniform-weight embryonic web. This embryonic web is then
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molded and/or dried in a variety of ways to form the final tissue web. As
part of this process the molded and/or dried web is usually glued to a drying
drum and subsequently creped from the surface of the dryer to impart
desirable properties.
Products made by many existing wet laid processes fall under the
above description. Examples of such webs that are soft, strong, and
absorbent and contain at least two micro regions of density can be found in,
U.S. Patents: 3,301,746 which issued January 31, 1967, to Lawrence H.
Sanford and James B. Sisson; 3,974,025 which issued August 10, 1976, to
Peter G. Ayers; 3,994,771 which issued November 30, 1976, to George
Morgan, Jr. and Thomas F. Rich; 4,191,609 which issued March 4, 1980, to
Paul D. Trokhan; and 4,637,859 which issued January 20, 1987, to Paul D.
Trokhan. Each of these papers is characterized by a repeating pattern of
dense areas and less dense areas. The dense areas can be either discrete
or continuous. These dense areas result from localized compaction of the
web during papermaking by raised areas of an imprinting carrier fabric or
belt.
Other high-bulk, soft tissue papers are disclosed in U.S. Patent
4,300,981 which issued November 17, 1981, to Jerry E. Carstens; and
4,440,597 which issued April 3, 1984, to Edward R. Wells and Thomas A.
Hensler.
Chemically enhanced paper structures comprising a cellulose
substrate and having chemical enhanced features applied thereto are
known in the art. For example, achieving high-bulk, soft and absorbent
tissue paper through the avoidance of overall compaction in combination
with the use of debonders and elastomeric bonders in the papermaking
furnish is disclosed in U.S. Patent 3,812,000 which issued May 21, 1974, to
J. L. Salvucci, Jr.
Chemical debonders such as those contemplated by Salvucci,
referred to above, and their operative theory are disclosed in such
representative U.S. Patents as 3,755,220 which issued August 28, 1973, to
Friemark et al.; 3,844,880 which issued October 29, 1974, to Meisel et al.;
and 4,158,594 which issued January 19, 1979, to Becker et al.
Tissue paper has also been treated with cationic surfactants, as well
as noncationic surfactants to enhance softness. See, for example, U. S.
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Patent 4,959,125 which issued September 25, 1990, to Spendei; and U. S.
Patent 4,940,513 which issued July 10, 1990, to Spendel, that disclose
processes for enhancing the softness of tissue paper by treating it with
noncationic, preferably nonionic, surfactants.
It has been found that the softness of tissue paper, in particular, high-
bulk pattern densified tissue papers, can be improved by treatment with
various agents such as vegetable, animal or synthetic oils, and especially
polysiloxane materials typically referred to as silicone oils. See, for
example, U. S. Patent 5,059,282 which issued October 22, 1991, to
Ampulski et al. The Ampulski patent discloses a process for adding a
polysiloxane compound to a wet tissue web (preferably at a fiber
consistency of between about 20% and about 35%). These polysiloxane
compounds impart a silky, soft feeling to the tissue paper.
While the processes described above generally make acceptable
product properties, the product properties can be further enhanced.
However, processes to make current products and potentially enhanced
products suffer from several drawbacks. For example, the chemicals used
to strengthen tissue webs are often added to the dilute slurry of water and
fibers prior to the initial lay down on the forming screen. This is a
relatively
convenient and cost effective way to introduce additives. However, other
chemicals to aid absorbency or to improve softness are also commonly
added to the so called wet end of the tissue making process. Because of
the complex nature of the individual chemicals used to generate the key
properties, they often interact with each other in an adverse manner. They
can compete with each other for the desired retention on the cellulose fibers
as well as destroy properties that are inherent in the fibers. For example
softening chemicals often reduce the natural tendency of fibers to bond to
other fibers and hence reduce the functional strength of the resulting web.
Both the process and the product benefit if the chemical papermaking
additives introduced in the wet end are kept to a minimum.
Additives introduced in the wet end of the process must be retained by
the cellulose frbers if the chemicals are to be functional. This is generally
done by using chemicals that possess an ionic charge; most preferably a
positive ionic charge which is attracted to the inherent negative ionic charge
of cellulose. Many additives which could improve the properties of the web
are not charged. Introduction of such chemicals into the dilute fiber slurry
at
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the wet end of the process results in poor retention and exacerbates the
interference problems described above.
Examples of patents that disclose processes for adding strength and
softness agents to the wet end of the papermaking process include U.S.
Patents 5,223,096 which issued June 29, 1993 to Phan and Trokhan, and
5,217,576 which issued June 8, 1993 to Phan. These wet end processes
typically result in a uniform addition of the strength and softening agents to
the tissue paper, and thus, will not prevent any potential undesirable
interaction of the chemicals.
Another drawback to adding any chemical to the wet end of the
process is that the chemical, if retained, is distributed throughout the web.
In many instances it is desirable to apply active ingredients) only to the
surface of the web. This may, for instance, be desirable with lubricious
softening materials. Application only to the surface insures efficient use of
the material since consumers only tactilely interact with the surface.
Application to the surface also avoids interference with other materials, such
as strength additives, that might best be included in the center of the sheet.
The chemical papermaking additives can also be added to the
cellulose substrate subsequent to formation of the wet web. For example,
the chemical additives may be applied to the cellulose substrate from an
aqueous chemical solution, then dried to form a chemically enhanced paper
structure. Unfortunately, previous methods of adding chemicals to a
cellulose substrate result in a uniform or homogeneous distribution of the
chemicals on the substrate. This uniform or homogeneous distribution of
chemicals can negate many of the performance advantages offered by
cellulose substrates containing at least two micro-regions of density.
The present invention overcomes all of the above mentioned
drawbacks and generates desirable additional benefits. in particular, it has
been found that the addition of functional chemicals in register with the
micro-regions of the cellulose substrate can maximize the performance
advantages of multi-region paper. For example, as will be discussed in
detail hereinafter, chemical softeners are optimally added to the low density
micro-regions of the web to further enhance that function.
Typically, the chemical composition is applied to the cellulose
substrate by spraying or printing. Unfortunately, it is difficult to spray the
chemical composition onto the substrate in a precise pattern. Printing the
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chemical composition onto the substrate may result in a pattern having
greater definition and precision than obtainable by spraying, but requires
a printing roll having raised protuberances or gravure cells. Printing rolls
having raised protuberances and gravure plates limit the pattern of the
5 applied chemical composition to that pattern corresponding to the
protuberances of the printing roll or the gravure plates, regardless of
which pattern may be desirable for a particular capillary substrate. Also, it
can be very difficult to register the printed pattern with the micro-regions
of the substrate.
This problem may be overcome by providing a plethora of printing
rolls and gravure plates, one for each desired pattern. However, such
provision increases the expense of the apparatus to a point where it may
not be economically feasible to provide a printing roll or a gravure plate
for each desired pattern if only a short production run is desired.
Accordingly, it would be desirable to be able to chemically enhance
predetermined micro-regions of tissue paper, in particular high bulk,
pattern densified tissue papers, by a process that: (1 ) can be carried out
in a commercial papermaking system without significantly impacting on
machine operability; (2) uses chemical compositions that are nontoxic and
environmently friendly; and (3) can be carried out in a manner so as to
maintain desirable tensile strength, absorbency and low lint properties of
the tissue paper.
Importantly, by adding functional chemicals in register with desired
micro-regions in accordance with teachings of the present invention, the
desired functional property can be enhanced without adveresly affecting
other properties. For example, tensile strength can be increased without
negatively impacting softness; or, alternatively, softness can be improved
without negatively impacting tensile strength.
It is an object of an aspect of this invention to provide soft,
absorbent toilet tissue paper products.
It is an object of an aspect of this invention to provide soft,
absorbent facial tissue paper products.
It is an object of an aspect of this invention to provide soft,
absorbent paper towel products.
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It is an object of an aspect of the present invention to provide a
paper structure, such as a tissue web, comprising a cellulose substrate
containing at least two micro-regions of density, wherein chemical
papermaking additives are incorporated in register with the micro-regions
of the paper structure.
It is a further object of an aspect of this invention to provide an
improved process to incorporate chemical papermaking additives into the
tissue web that enhance softness, strength, absorbency, and aesthetics
or combinations of these properties.
It is a further object of an aspect of this invention to provide an
improved process to incorporate chemical papermaking additives in
register with the micro-regions of the tissue web to maximize the
performance advantages of mufti-region paper.
These and other objects of aspects are obtained using the present
invention, as will be seen from the following more detailed disclosure.
SUMMARY OF THE INVENTION
The invention is a chemically enhanced paper structure comprising
a cellulose substrate having first regions of relatively high density and
second regions of relatively low density. The regions of relatively high
density and relatively low density are each disposed in a nonrandom,
repeating pattern. An immobilized chemical papermaking additive is
disposed on the regions of relatively high density or the regions of
relatively low density.
In a particularly preferred embodiment, the regions of relatively
high density form an essentially continuous network, and the regions of
relatively low density are discrete. In this embodiment, the immobilized
chemical papermaking additive is preferably disposed, for example, on
the discrete low density regions if it is intended to improve softness and/or
absorbency. Likewise, the immobilized chemical papermaking additive
can be added to the continuous high density regions if it is intended, for
example, to improve strength. In addition, as will be discussed in detail
hereinafter, the chemically enhanced paper structure of the present
invention is preferably through-air-dried.
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6a
According to an aspect of the present invention, there is provided a
chemically enhanced paper structure comprising:
a cellulosic substrate having first regions of high density and
second regions of low density, the regions of high density and low density
each being disposed in a non random, repeating pattern; and
an immobilized chemical papermaking additive disposed on one of
the regions of the high density or one of the regions of low density.
According to a further aspect of the present invention, there is
provided a chemically enhanced paper structure comprising:
a cellulosic substrate having first regions comprising an essentially
continuous high density network and second discrete regions of low
density; and
an immobilized chemical papermaking additive disposed on the
low density regions.
According to another aspect of the present invention, there is
provided a through air-dried chemically enhanced paper structure
comprising:
a cellulosic substrate comprising an essentially continuous high
density network region, and discrete low density regions disposed therein,
the high density essentially continuous network region and the low density
discrete regions each being disposed in a non random repeating pattern,
wherein the high density essentially continuous network region defines a
first elevation and the low density discrete regions defines a second
elevation; and
an immobilized chemical papermaking additive disposed on one of
the regions of high density or one of the regions of low density.
BRIEF DESCRIPTION OF THE DRAWINGS
While the Specification concludes with claims particularly pointing
out and distinctly claiming the present invention, it is believed the present
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invention will be better understood from the following description taken in
conjunction with the accompanying drawings in which:
Figure 1 is a fragmentary top plan view of an paper structure according
to the present invention having a continuous cellulose network
and discrete sites of a chemical papermaking additive therein;
Figure 2 is a fragmentary side elevational view taken along line 2-2 of
Figure 1; and
Figure 3 is a schematic vertical elevational view of one apparatus
which may be used to produce the structure of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
As illustrated in Figure 1, a chemically enhanced paper structure 20
according to the present invention comprises a generally planar cellulose
15. substrate 22 and a chemical papermaking additive 24. The chemical
papermaking additive 24 is applied to the cellulose substrate 22, typically in
the form of a aqueous solution 40 as shown in Figure 3. Referring to Figure
3, the aqueous solution 40 is applied to the cellulose substrate 22 in a
particular pattern. Once the aqueous solution 40 is disposed on the
cellulose substrate 22, the water is ultimately removed by drying, with the
chemical papermaking additive 24 remaining on the cellulose substrate.
Referring back to Figure 1, the cellulose substrate 22 is a cellulose
structure, preferably a tissue paper web. The cellulose substrate 22
comprises multiple micro-regions 34 and 38 having different basis weights
and/or densities. Any arrangement of regions 34 and 38 in the cellulose
substrate 22 is acceptable, so long as the cellulose substrate 22 is
macroscopically planar and the chemical papermaking additive 24 may be
immobilized in register with one of the micro-regions.
The cellulose substrate 22 according to the present invention has
distinguishable micro-regions 34 and 38 defining two mutually different
densities. Preferably, the regions 34 and 38 are disposed in an
arrangement comprising an essentially continuous network region 32 and
discrete regions 36 within the essentially continuous network. As used
herein, a region 32 which extends substantially throughout the cellulose
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substrate 22 in one or both of the principal dimensions is considered to be
"an essentially continuous network." Conversely, regions 36 which are not
contiguous, are considered to be "discrete." The discrete regions 36 project
outwardly to a distal end from the region 32 defining the essentially
continuous network.
Preferably, the discrete regions 36 and the essentially continuous
network region 32 are disposed in a nonrandom, repeating pattern. By
being "nonrandom" the regions 32 and 36 are considered to be predictable
and may occur as a result of known and predetermined features of the
manufacturing process. By "repeating", the pattern is formed more than
once in the cellulose substrate 22. However, it is to be understood that if
the cellulose substrate 22, as presented to the consumer, is relatively small
and the pattern is relatively large or the paper structure 20 is presented to
the consumer as an integral unit, the pattern may appear to occur only once
in the cellulose substrate 22. More preferably the regions 34 and 38 of
the cellulose substrate 22 are disposed in an arrangement having a high
density essentially continuous network region 32 and discrete low density
regions 36 within the essentially continuous network region 32. Preferably,
the discrete low density regions 36 and the essentially continuous network
region 32 lie in a different plane, as will be discussed hereinafter.
For the embodiments described herein, a cellulose substrate 22
having about 2 to about 155 low density discrete regions 36 (preferably with
chemical papermaking additive 24 thereon) per square centimeter (10 to
1000 discrete regions 36 per square inch) and more, particularly, about 16 to
about 109 low density discrete regions 36 per square centimeter (100 to
700 discrete regions 36 per square inch) has been found suitable.
Furthermore, the cellulose substrate 22 according to the present
invention may comprise two different elevations 26. The "elevation" of a
cellulose substrate 22 is its local deviation from planarity. The elevation 26
of a substrate is determined by laying it on a flat, horizontal surface, which
serves as a reference plane. Different elevations 26 of the cellulose
substrate 22, which may or may not be coincident with the regions 34 and
38 of differing density described above, are determined by the difference in
height above the reference plane, taken orthogonal the reference plane and
principal dimensions of the cellulose substrate 22.
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Preferably the regions 34 and 38 defined according to differing
densities and differing elevations 26 are coincident. Thus the discrete low
density regions 36 are also raised in elevation 26 (or lowered in elevation 26
if the cellulose substrate 22 is inverted) from the high density regions 34 of
the essentially continuous network region 32. However, it is to be
recognized that suitable embodiments may exist wherein such discrete
regions 36 of a particular density are not coincident with a particular
elevation 26.
The cellulose substrate 22 according to the present invention may be
comprised of cellulosic fibers having one very large dimension (along the
longitudinal axis of the fiber) compared to the other two relatively very
small
dimensions (mutually perpendicular, and . being both radial and
perpendicular to the longitudinal axis of the fiber), so that linearity is
approximated. UVhile microscopic examination of the fibers may reveal the
other two dimensions are small compared to the principal dimension of the
fibers, such other twD small dimensions need not be substantially equivalent
nor constant throughout the axial length of the fiber. It is only important
that
the fiber be able to bend about its axis, be able to bond to other fibers and
be distributed onto a forming wire (or its equivalent) by a liquid carrier.
The cellulose substrate 22 may be creped or be uncreped, as desired.
Creping the cellulose substrate 22 foreshortens it producing undulations in
the Z-direction throughout the essentially continuous network region 32.
Such undulations yield cross machine ripples which are considered too
minor to be differences in elevation 26 as compared to the differences in
elevation 26 obtainable by the methods described hereinbelow. However, it
is to be recognized that a creped cellulose substrate 22 may be embossed,
through-air-dried, etc. to produce differences in elevation 26 which are
large, relative to the creping undulations and ripples. An example of a
method of making an uncreped, through-air dried tissue paper product is
described in European Patent Application No. 0 677 612 A2 assigned to
Kimberly-Clark Corporation, published October 18, 1995. Such uncreped,
through-air dried structures are suitable for the practice of this invention.
The fibers comprising the cellulose substrate 22 may be synthetic,
such as polyolefin or polyester; are preferably cellulosic, such as cotton
linters, rayon or bagasse; and more preferably are wood pulp, such as soft
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woods (gymnosperms or coniferous) or hard woods {angiosperms or
deciduous), may be cross-linked, and may comprise combinations of
synthetic and cellulosic materials. As used herein, a cellulose substrate 22
is considered "ceilulosic" if the cellulose substrate 22 comprises at least
5 about 50 weight percent or at least about 50 volume percent ceilulosic
fibers, including but not limited to those fibers listed above. A cellulosic
mixture of wood pulp fibers comprising softwood fibers having a length of
about 2.0 to about 4.5 millimeters and a diameter of about 25 to about 50
micrometers, and hardwood fibers having a length of less than about 1
10 millimeter and a diameter of about 12 to about 25 micrometers has been
found to work well for the cellulose substrates 22 described herein.
If wood pulp fibers are selected for the cellulose substrate 22, the
fibers may be produced by any pulping process including chemical
processes, such as sulfite, sulfate and soda processes; and mechanical
processes such as stone groundwood. Alternatively, the fibers may be
produced by combinations of chemical and mechanical processes or may
be recycled. The type, combination, and processing of the fibers used are
not critical to the present invention.
A cellulose substrate 22 according to the present invention is
macroscopically two-dimensional and planar, having some thickness in the
third dimension. However, the thickness in the third dimension is relatively
small compared to the first two dimensions or to the capability to
manufacture a cellulose substrate 22 having relatively large measurements
in the first two dimensions.
The cellulose substrate 22 according to the present invention
comprises a single lamina and may be layered or stratified as to fiber type.
However, it is to be recognized that two or more single laminae, any or all
made according to the present invention, may be joined in face-to-face
relation to form a unitary laminate.
Of course, it is to be recognized that a woven or nonwoven material
may be adequately utilized as a cellulose substrate 22, providing it meets
the density requirements specified above.
A cellulose substrate 22 having regions 34 and 38 of different
densities may be achieved by locally densifying certain areas through
embossing as is well known in the art, or by dedensifying certain areas by
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vacuum or pressure deflection into a suitable mold followed by through-air
drying as is well known in the art. Similarly, a cellulose substrate 22 having
different elevations 26 in the direction generally normal to the plane of the
cellulose substrate 22 may be accomplished by embossing as is well known
in the art, or again accomplished by vacuum or pressure deflection into a
suitable mold followed by through-air drying as is well known in the art.
Preferably, the chemically enhanced paper structure of the present
invention is through-air-dried. A particularly preferred through-air dried
cellulose substrate 22 is produced in accordance with commonly assigned
U.S. Patent 4,529,480 issued July 16, 1985 to Trokhan, for the purpose of
showing a through-air-dried cellulose substrate 22 having discrete regions 36
and an essentially continuous pattern region 32 and for the purpose of
showing how to make a particularly preferred cellulose substrate 22
,15 according to the present invention having different elevations 26. A
cellulose
substrate 22 made according to U.S. Patent 4,529,480 issued to Trokhan
has mutually coincident discrete regions 36, which regions 36 are both
relatively low in density and raised (or lowered) in elevation 26.
The cellulose substrate 22 preferably has a difference in elevation 26
between the different regions 34 and 38 of at least about 0.13 millimeters
(0.005 inches). The elevation 26 is measured without a confining pressure,
using microtomoscopy or stereoscopic three-dimensional scanning electron
microscopy imaging, as are well known in the art.
The chemical papermaking additive 24 may be applied to the cellulose
substrate in an aqueous solution, emulsion; suspension, etc. For example,
an aqueous solution 40 containing the chemical papermaking additive 24,
can be applied to the cellulose substrate 22 as illustrated in Figure 3.
The specific type of chemical papermaking additive 24 is not critical to
the invention, so Tong as the chemical papermaking additive 24 rnay be
applied in the desired pattern, and immobilized, so that it does not flow,
migrate, or otherwise transport to different parts of the cellulose substrate
22 and transmogrify the desired pattern into a less useful disposition of the
chemical papermaking additive 24 (such as a uniform coating). The
chemical papermaking additive 24 is preferably immobilized in both the dry
condition and while wetted in use.
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Referring to Figure 2, the aqueous solution 40 containing the chemical
papermaking additive 24 is preferably disposed upon, registered with, and
immobilized at the discrete low density regions 38 of the cellulose substrate
22 in a particular predetermined pattern. Although other patterns, such as
semicontinuous patterns which form lines extending throughout
substantially only one principal dimension of the cellulose substrate 22
(i.e.,
the machine direction, the cross machine direction, or diagonals thereof) are
possible, a pattern having the chemical papermaking additive 24 disposed
on only the discrete low density regions 38 is preferred. In this preferred
embodiment, the relatively high density region is substantially free of the
immobilized chemical papermaking additive 24.
Referring again to Figure 3, the chemically enhanced paper structure
according to the present invention may be made according to the
illustrated apparatus 50. The illustrated apparatus 50 comprises three
15 axially rotatable rolls 52, 54 and 56, preferably having mutually parallel
longitudinal axes, a metering roll 52, a transfer roll 54, and an anvil roll
56.
The three rolls 52, 54 and 56 form a nip 58 and a gap 60. The nip 58 is
between the metering roll 52 and the transfer roll 54. The gap 60 is
between the transfer roll 54 and the anvil roll 56.
20 The metering roll 52 is a gravure roll disposed in a reservoir 62 of the
liquid precursor 40. Upon axial rotation, the metering roll 52 acquires liquid
precursor 40 from the reservoir 62, precisely levels the fill in the
individual
cells of the metering roll 52 by means of doctor blade 41 and then transfers
a particular quantity of the aqueous solution 40 to the transfer roll 54. The
cellulose substrate 22 passes through the gap 60 between the transfer roll
54 having aqueous solution 40 uniformly disposed thereon and the anvil roll
56. Importantly the topographically elevated regions 36 and 38 of the
cellulose substrate 22, to which it is desired to apply the aqueous solution
40 containing the chemical papermaking additive 24, project toward and
contact the transfer roll 54, with the balance of the cellulose substrate 22
resting against the anvil roll 56. It will be apparent to one skilled in the
art
that by increasing or decreasing the clearance in the gap 60 between the
transfer roll 54 and the anvil roll 56, smaller and larger amounts of the
aqueous composition 40 may be printed upon and applied to the
topographically elevated regions of the cellulose substrate 22, respectively,
upon contact therewith. Likewise, changing the design of the metering roll
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52 can alter the amount of aqueous solution 40 applied to the cellulose
substrate 22 at a constant gap 60. Alternatively, it will be apparent the
aqueous solution 40 may be applied to the transfer roll 54 by spraying,
submerging the transfer roll 54 in the aqueous composition 40, etc., and
thereby eliminating the necessity for a metering roll 52, or by printing
directly from the metering roll 52 to the substrate 22 in the gap 60 formed
between the metering roll 52 and the anvil roll 56.
As the cellulose substrate 22 passes through the gap 60 between the
transfer roll 54 and the anvil roll 56, aqueous solution 40 is applied to only
the regions of the cellulose substrate 22 which have an elevation 26
sufficient to contact the periphery of the transfer roll 54. The transfer roll
54,
does not contact the portions of the cellulose substrate 22 which rest
against the anvil roll 56. Accordingly, no aqueous solution 40 is applied to
these portions of the cellulose substrate 22.
By adjusting the clearance in the gap 60, different quantities of the
aqueous solution 4D, and ultimately dried chemical papermaking additive
24, may be applied to the elevated regions of the cellulose substrate 22.
Generally, for the embodiments described herein, aqueous composition 40
applied in the range of about 1 to about 500 milligrams per square
centimeter of discrete region 36 has been found suitable.
Once the cellulose substrate 22 to be utilized in the paper structure 20
is selected based upon consumer preferences, certain benefits become
apparent. Particularly, the cellulose substrate 22 according to the present
invention, having regions 34 and 38 of different elevations 26 (one region
34 in contact with the anvil roll 56, the other region 38 in contact with the
transfer roll 54) provides several advantages not found in the prior art.
First,
a particular pattern of the aqueous solution 40 containing the chemical
papermaking additive 24 may be deposited onto the cellulose substrate 22,
without requiring the transfer roll 54 to have a gravure pattern or have
radially extending protuberances. Typically, metering rolls 54 having
patterns are more difficult and expensive to manufacture, than nonpatterned
metering rolls 54.
A second benefit of the claimed invention is the flexibility which allows
one who may not wish to use a transfer roll 54 having a pattern, to achieve
registration of the pattern with the regions of the cellulose substrate 22 to
which it is desired to apply the chemcial papermaking additive 24. Such
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registration can be extremely difficult to achieve under even ideal
manufacturing conditions, as the different regions of the cellulose substrate
22 may occur on near microscopic scale. Actual manufacturing is even
more complex, because the pitch of the different regions 32 and 36, and
hence the opportunity of misregistration may change with ordinary
variations in tension as the cellulose substrate 22 is drawn through the
apparatus 50, the basis weight of the cellulose substrate 22, and other
manufacturing parameters. Production of the invention by the process
described in Figure 3 ensures exact registration of the chemical
papermaking additive 24 with the desired regions of the cellulose substrate
22.
Third, if it is desired to change the pattern of the chemical
papermaking additive 24 applied to the cellulose substrate 22, a single
apparatus 50 having a transfer roll 54 with a smooth unpatterned periphery
may be utilized for multiple patterns. A cellulose substrate 22 having a
different topography is inserted in the gap 60 between the transfer roll 54
and anvil roll 56, and the clearance of the gap 60 adjusted as appropriate.
The transfer roll 54 may continue to be provided with a smooth surface and
any desired pattern achieved by simply changing the cellulose substrate 22.
Once a particular cellulose substrate 22 is selected, such flexibility in
manufacturing was unattainable in the prior art.
Several variations according to the present invention are feasible. For
example, if desired, one may construct a cellulose substrate 22 having an
essentially continuous network region 32 and discrete regions 36 which
differ according to basis weight rather than density, if such a cellulose
substrate 22 is selected, it may be advantageously made using a forming
wire according to Figure 4 of commonly assigned U.S. Patent 4,514,345
issued April 30, 1985 to Johnson et al. or commonly assigned U.S. Patent
5,245,025 issued September 14, 1993 to Trokhan et af., for the purpose of
showing how to make a cellulose substrate 22 having regions which differ
according to basis weight. Alternatively, discrete regions 36 having plural
different elevations 26 above (or below) the essentially continuous network
region 32 are feasible. The chemical composition 24 may be applied to only
' the discrete regions 36 having a particular minimum elevation 26, or to each
of the discrete regions 36 in elevation-dependent quantities.
CA 02257691 2003-07-07
CHEMICAL PAPERMAKING ADDITIVES
The chemical papermaking additives for use in the multi-density paper
structures of the present invention are preferably selected from the group
5 consisting of strength additives, absorbency additives, softener additives,
aesthetic additives, and mixtures thereof. Each of these types of additives
will be discussed below.
A) Strength Additives
The strength additive is selected from the group consisting of
10 permanent wet strength resins, temporary wet strength resins, dry strength
additives, and mixtures thereof.
If permanent wet strength is desired, the chemical papermaking
additive can be chosen from the following group of chemicals: polyamid-
epichlorohydrin, polyacrylamides; insoiubifized polyvinyl alcohol; urea-
15 _ formaldehyde; - polyethyleneimine; and chitosan polymers. Polyamide-
epichlorohydrin resins are cationic wet strength resins which have been
found to be of particular utility. Suitable types of such resins are described
in U.S. Patent Nos. 3,700,623, issued on October 24, 1972, and 3,772,076,
issued on November 13, 1973, both issued to Keim. One commercial source
of a useful polyamide-epichlorohydrin resins is Hercules, Inc. of Wilmington,
Delaware, which markets such resin under the mark Kymene~ 557H.
Polyacrylamide resins have also been found to be of utility as wet
strength resins. These resins are described in U.S. Patent Nos. 3,556,932,
issued on January 19, 1971, to Coscia, et al. and 3,556,933, issued on
January 19, 1971, to Williams et al. One commercial source of
polyacrylamide resins is American Cyanamid Co. of Stanford, Connecticut,
which markets one such resin under the mark Parez~ 631 NC.
Still other water-soluble cationic resins finding utility in this invention
are urea formaldehyde and melamine formaldehyde resins. The more
common functional groups of these polyfunctional resins are nitrogen
containing groups such as amino groups and methylol groups attached to
nitrogen. Polyethylenimine type resins may also find utility in the present
invention.
CA 02257691 2003-07-07
16
If temporary wet strength is desired, the chemical papermaking
additive can be chosen form the following group of chemicals: cationic
dialdehyde starch-based resin (such as CaIdasT"" produced by Japan Carlet,
National Starch 78-0080 or CobondT"" 1000, both produced by National
Starch and Chemical Corporation); and dialdehyde starch. Modified starch
temporary wet strength resins are also described in U.S. Patent No.
4,675,394, Solarek, et al. issued June 23, 1987. Preferred temporary wet
strength resins include those described in U.S. Patent No. 4,981,557 issued
on January 1, 1991, to Bjorkquist. Another example of a preferred temporary
wet strength resin is Parez~ 7508, a commercially available modified
polyacrylamide resin manufactured by CyTec.
If dry strength is desired, the chemical papermaking additive can be
chosen from the following group of chemicals. Polyacrylamide (such as
combinations of CyproT"" 514 and AccostrengthT"" 711 produced by American
Cyanamid of Wayne, N.J.), starch (such as com starch or potato starch);
polyvinyl alcohol (such as AirvoIT"" 540 produced by Air Products Inc of
Allentown, PA); guar or locust bean gums; andlor carboxymethyl cellulose
(such as AqualonT"" CMC-T from Aqualon Co., Wilmington, DE). In general,
suitable starch for practicing the present invention is characterized by water
solubility, and hydrophilicity. Exemplary starch materials include corn starch
and potato starch, albeit it is not intended to thereby limit the scope of
suitable starch materials; and waxy corn starch that is known industrially as
amioca starch is particularly preferred. Amioca starch differs from common
com starch in that it is entirely amylopectin, whereas common corn starch
contains both amplopectin and amylose. Various unique characteristics of
amioca starch are further described in "Amioca - The Starch From Waxy
Corn", H. H. Schopmeyer, Food Industries, December 1945, pp. 106-108
(Vol. pp. 1476-1478). The starch can be in granular or dispersed form albeit
granular form is preferred. The starch is preferably sufficiently cooked to
induce swelling of the granules. More preferably, the starch granules are
swollen, as by cooking, to a point just prior to dispersion of the starch
granule. Such highly swollen starch granules shall be referred to as being
"fully cooked." The conditions for dispersion in general can vary depending
upon the size of the starch granules, the degree of crystallinity of the
granules, and the amount of amylose present. Fully cooked amioca starch,
for example, can be prepared by heating an aqueous slurry of about 4%
CA 02257691 1998-12-10
WO 97/47809 PCTIUS97110177
17
consistency of starch granules at about 190°F (about 88°C) for
between
about 30 and about 40 minutes. Other exemplary starch materials which
may be used include modified cationic starches such as those modified to
have nitrogen containing groups such as amino groups and methylol groups
attached to nitrogen, available from National Starch and Chemical
Company, (Bridgewater, New Jersey). Such modified starch materials have
heretofore been used primarily as a pulp furnish additive to increase wet
and/or dry , strength. However, when applied in accordance with this
invention by application to a tissue paper web they may have reduced effect
on wet strength relative to wet-end addition of the same modified starch
materials. Considering that such modified starch materials are more
expensive than unmodified starches, the latter have generally been
preferred. These wet and dry strength resins may be added to the pulp
furnish in addition to being added by the process described in this invention.
It is to be understood that the addition of chemical compounds such as the
wet strength and temporary wet strength resins discussed above to the pulp
furnish is optional and is not necessary for the practice of the present
development.
The strength additive may be applied to the tissue paper web alone,
simultaneously with, prior to, or subsequent to the addition of softener,
absorbency, and/or aesthetic additives. At least an effective amount of a
strength additive, preferably starch, to provide lint control and concomitant
strength increase upon drying relative to a non-binder treated but otherwise
identical sheet is preferably applied to the sheet. Preferably, between about
0.01 % and about 2.0% of a strength additive is retained in the dried sheet,
calculated on a dry fiber weight basis; and, more preferably, between about
0.9 % and about 1.0% of a strength additive material, preferably starch-
based, is retained.
B) Softener Additives
The chemical softener additives are selected from the group
consisting of lubricants, plasticizers, cationic debonders, noncationic
debonders and mixtures thereof. Suitable debonders for use as softener
additives in the present invention include both cationic and noncationic
surfactants, with cationic surfactants being preferred. Noncationic
surfactants include anionic, nonionic, amphoteric, and zwitterionic
surfactants. Preferably, the surfactant is substantially nonmigratory in situ
CA 02257691 2003-07-07
18
after the tissue paper has been manufactured in order to substantially
obviate post-manufacturing changes in the tissue paper's properties which
might otherwise result from the inclusion of surfactant. This may be
achieved, for instance, through the use of surfactants having melt
temperatures greater than the temperatures commonly encountered during
storage, shipping, merchandising, and use of tissue paper product
embodiments of the invention: for example, melt temperatures of about
50°C or higher.
The level of noncationic surfactant applied to tissue paper webs to
provide the aforementioned softness/tensile benefit ranges from the
minimum effective level needed for imparting such benefit, on a constant
tensile basis for the end product, to about 2°!0: preferably between
about
0.01 °lo and about 2% noncationic surfactant is retained by the web;
more
preferably, between about 0.05% and about 1.0%; and, most preferably,
between about 0.05% and about 0.3%. The surfactants preferably have
alkyl chains with eight or more carbon atoms. Exemplary anionic
surfactants are linear alkyl sulfonates, and alkylbenzene sulfonates.
Exemplary nonionic surfactants are alkylglycosides including alkylglycoside
esters such as Crodesta~ SL-40 which is available from Croda, inc. (New
York, NY); alkylglycoside ethers as described in U.S. Patent 4,011,389,
issued to W. K. Langdon, et al. on March 8, 1977; alkylpolyethoxylated
esters such as Pegosperse~' 200 ML available from Glyco Chemicals, Inc.
(Greenwich, CT); alkylpolyethoxylated ethers and esters such NeodoIRT~" 25-
12 available from Shell Chemical Co; sorbitan esters such as SpanTM 60
from ICI America, Inc, ethoxylated sorbitan esters, propoxylated sorbitan
esters, mixed ethoxylated/propoxylated sorbitan esters, and polyethoxylated
sorbitan alcohols such as TweenT"" 60 also from ICI America, Inc.
Alkylpolyglycosides are particularly preferred for use in the present
invention.
The above listings of exemplary surfactants are intended to be merely
exemplary in nature, and are not meant to limit the scope of the invention.
Any surfactant other than the chemical papermaking additive
emulsifying surfactant material, is hereinafter referred to as "surfactant,"
and
any surfactant present as the emulsifying component of emulsified chemical
papermaking additives is hereinafter referred to as "emulsifying agent". The
surfactant may be applied to the tissue paper alone or simultaneously with,
CA 02257691 2003-07-07
19
after, or before other chemical papermaking additives. In a typical process,
. if another additive is present, the surfactant is applied to the cellulosic
substrate simultaneously with the other additive(s). It may also be desirable
to treat a debonder containing tissue paper with a relatively low level of a
binder for lint control and/or to increase tensile strength. As used herein
the
term "binder" refers to the various wet and dry strength additives known in
the art. The binder may be applied to the tissue paper simultaneously with,
after or before the debonder and an absorbency aid, if used. Preferably,
binders are added to the tissue webs simultaneously with the debonder
(e.g., the binder is included in the dilute aqueous solution applied to the
tissue web).
If a chemical softener that functions primarily by imparting a lubricous
feel is desired, it can be chosen from the following group of chemicals.
Organic materials (such as mineral oil or waxes such as paraffin or carnuba,
or lanolin); and polysiloxanes (such as the compounds described in U.S.
Patent No. 5,059,282 issued to Ampulski. Suitable polysiloxane compounds
for use in the present invention are described in detail below.
The level of polysiloxane compounds applied to tissue paper webs to
provide the aforementioned softness/lubricous feel benefit ranges from the
minimum effective level needed for imparting such benefit, on a constant
tensile basis far the end product, to about 2%, by weight on a dry fiber
basis: preferably between about 0.01 % and about 2% polsiloxane
compound is retained by the web; more preferably, between about 0.02%
and about 1.0%; and, most preferably, between about 0.03% and about
0.3%. The polysiloxane compounds preferably have monomeric siloxane
- units of the following structure:
R1
I
-[- Si-O-]-
I
R2
CA 02257691 2003-07-07
wherein, R1 and R2, for each independent siloxane monomeric unit can
each independently be hydrogen or any alkyl, aryl, afkenyl, alkaryl, arakyl,
cycloalkyl, halogenated hydrocarbon, or other radical. Any of such radicals
can be substituted or unsubstituted. R1 and R2 radicals of any particular
5 monomeric unit may differ from the corresponding functionalities of the next
adjoining monomeric unit. Additionally, the polysiloxane can be either a
straight chain, a branched chain or have a cyclic structure. The radicals R1
and R2 can additionally independently be other silaceous functionalities
such as, but not limited to siloxanes, polysiloxanes, silanes, and
10 polysilanes. The radicals R1 and R2 may contain any of a variety of organic
functionalities including, for example, alcohol, carboxylic acid, aldehyde,
ketone and amine, amide functionalities, with amino functional silicone
compounds being preferred. Exemplary alkyl radicals are methyl, ethyl,
propyi, butyl, pentyl, hexyl, octyl, decyl, octadecyl, and the like. Exemplary
15 alkenyl radicals are vinyl, allyl, and the like. Exemplary aryl radicals
are
phenyl, Biphenyl, naphthyl, and the like. Exemplary aikaryl radicals are toyt,
xylyl, ethylphenyl, and the like. Exemplary arakyl radicals are benzyl, alpha-
phenylethyl, beta-phenylethyl, alpha-phenylbutyl, and the like. Exemplary
cycloalkyl radicals are cyclobutyl, cyclopentyl, cyclohexyl, and the tike.
20 Exemplary halogenated hydrocarbon radicals are chloromethyl, bromoethyl,
tetrafluorethyl, fluorethyl, trifluorethyl, trifiuorotoyl, hexafluoroxylyl,
and the
like. References disclosing polysiloxanes include U. S. Patent No.
2,826,551, issued March 11, 1958 to Geen; U. S. Patent No. 3,964,500,
issued June 22, 1976 to Drakoff; U.S. Patent No. 4,364,837, issued
December 21, 1982, Pader, U.S. Patent No. 5,059,282, issued October 22,
1991 to Ampulksi et al.; and British Patent No. 849,433, published
September 28, 1960 to Woolston. Also, Silicon Com oo unds9 pp 181-217,
distributed by Petrarch Systems, Inc., 1984, contains an extensive fisting and
description of polysiloxanes in general.
If a chemical softener that functions primarily by plasticizing the
structure is desired, it can be chosen from the following group of chemicals:
polyethylene glycol {such as PEG 400); dimethylamine; and/or glycerine.
If a cationic chemical softener that functions primarily by debonding is
desired, it can be chosen from the following group of chemicals. Cationic
CA 02257691 2003-07-07
21
quaternary ammonium compounds (such as dihydrogenated tallow dimethyl
ammonium methyl sulfate (DTDMAMS) or dihydrogenated tallow dimethyl
ammonium chloride (DTDMAC) both produced by Witco Corporation of
Greenwich, Connecticut; BerocelT"" 579 (produced by Eka Nobel of
Stennungsund, Sweden); materials described in U.S. Patent No.'s 4,351,699
and 4,447,294 issued to Osborn; and/or diester derivatives of DTDMAMS or
DTDMAC.)
In particular, quaternary ammonium compounds having the formula:
(R1)4-m - N+ - ~R2Jm X-
wherein
m is 1 to 3;
each R1 is a C1-Cg alkyl group, hydroxyalkyl group, hydrocarbyl or
substituted hydrocarbyl group, alkoxylated group, benzyl group, or
mixtures thereof;
each R2 i5 a Cg-C41 alkyl group, hydroxyalkyl group, hydrocarbyl or
substituted hydrocarbyl group, alkoxylated group, benzyl group, or
mixtures thereof; and
X- is any softener-compatible anion are suitable for use in the present
invention.
Preferably, each R2 is C1s-C18 alkyl, most preferably each R2 is
straight-chain C18 alkyl. Preferably, each R1 is methyl and X- is chloride or
methyl sulfate. Optionally, the R2 substituent can be derived from vegetable
oil sources.
Biodegradable ester-functional quaternary ammonium compound
having the formula:
(R1 )4-m vN+ - ~(CH2)n - Y - R2Jm X-
wherein
each Y = -0-(O)C-, or -C(O)-O-;
m = 1 to 3; preferably, m=2;
each n = 1 to 4; preferably, n=2;
each R1 substituent is a short chain C1-C6, preferably C1-C3, alkyl
group, e.g., methyl (most preferred), ethyl, propyl, and the tike,
hydroxyafkyf group, hydrocarbyl group, benzyl group or mixtures
thereof;
CA 02257691 2003-07-07
22
each R2 is a long chain, at least partially unsaturated (IV of greater
than about 5 to less than about 100, preferably from about 10 to about
85), C11-C23 hydrocarbyl, or substituted hydrocarbyl substituent and
the counter-ion, X-,- can be any softener-compatible anion, for
example, acetate, chloride, bromide, methylsulfate, formate, sulfate,
nitrate and the like can also be used in the present invention.
Preferably, the majority of R2 comprises fatty acyls containing at least
90% C1g-C24 chainlength. ~Itore preferably, the majority of R2 is
selected from the group consisting of fatty acyls containing at least
90% Clg, C22 and mixtures thereof.
Other types of suitable quaternary ammonium compounds are
described in European Patent No. 0 688 901 A2, assigned to Kimberly-Clark
Corporation, published December 12, 1995.
Tertiary amine softening compounds can also be used in the present
invention. Examples of suitable tertiary amine softeners are described in
U.S. Patent 5,399,241, assigned to James River Corporation, issued March
21, 1995.
~1 Absorbency Additives
if an absorbency aid is desired that enhances the rate of absorbency
it can be chosen from the following group of chemicals: polyethoxylates
(such as PEG 400); alkyl ethoxylated esters (such as Pegosperse 200ML
from Lonza Inc.); alkyl ethoxylated alcohols (such as Neodol); alkyl
polyethoxylated nonylphenols (such as IgepaIT"" CO produced by Rhone
Poulenc/GAF), ethoxylate trimethyl pentanediol, andlor materials described
_ in U.S. Patent No.'s 4,959,125 and 4,940,513 issued to Spendel. In those
instances where the surfactant debonder softener decreases wetting, a
wetting agent, e.g., a second surfactant, may be added to the application
solution. For example, a sorbitan stearate ester can be mixed with an alkyl
polyethoxylated alcohol to produce a soft wettable paper.
Water soluble poiyhydroxy compounds can also be used as
absorbency aids andlor wetting agents. Examples of water soluble
polyhydroxy compounds suitable far use in the present invention include
glycerol, polyglycerols having a weight average molecular weight of from
CA 02257691 2003-07-07
23
about 150 to about 800 and polyoxyethylene and polyoxypropylene having
a weight-average molecular weight of from about 200 to about 4000,
preferably from about 200 to about 1000, most preferably from about 200 to
about 600: Polyoxyethyfene having an weight average molecular weight of
from about 200 to about 600 are especially preferred. Mixtures of the
above-described polyhydroxy compounds may also be used. For example,
mixtures of glycerol and polyglycerols, mixtures of glycerol and
polyoxyethylenes, mixtures of polyglycerols and polyoxyethylenes, etc... are
useful in the present invention. A particularly preferred polyhydroxy
compound is polyoxyethylene having an weight average molecular weight of
about 400. This material is available commercially from the Union Carbide
Company of Danbury, Connecticut under the trade name "PEG-400".
If an absorbency aid is desired that decreases the rate of absorbency
it can be chosen from the following group of chemicals. Alkytketenedimers
(such as AquapeIRT"" 360XC Emulsion manufactured by Hercules Inc.,
Wilmington, DE.); fluorocarbons (such as Scotch GuardT"" by 3M of
Minneapolis, MN) hydrophobic silicones (such as PDMSTM DC-200 by Dow
Corning of Midland, MI), fluorotelomers (such as ZonyIT"" 7040 by Dupont of
Wilmington, DE.), etc.
The absorbency additive can be used alone or in combination with a
strength additive. Starch based strength additives have been found. to be
the preferred binder for use in the present invention. Preferably, the tissue
paper is treated with an aqueous solution of starch. In addition to reducing
tinting of the finished tissue paper product, low levels of starch also
imparts
a modest improvement in the tensile strength of tissue paper without
imparting boardiness (i.e., stiffness) which would result from additions of
- high levels of starch. Also, this provides tissue paper having improved
strengthlsoftness relationship compared to tissue paper which has been
strengthened by traditional methods of increasing tensile strength: for
example, sheets having increased tensile strength due to increased refining
of the pulp; or through the addition of other dry strength additives. This
result is especially surprising since starch has traditionally been used to
build strength at the expense of softness in applications wherein softness is
not an important characteristic: for example, paperboard. Additionally,
parenthetically, starch has been used as a filler for printing and writing
paper to improve surface printability.
CA 02257691 1998-12-10
WO 97/47809 PCT/US97/I0177
24
D) Aesthetic Additives
If an aesthetic additive is desired, it can be chosen from the following
group of chemicals: inks; dyes; perfumes; opacifiers (such as Ti02 or
calcium carbonate), optical brighteners, and mixtures thereof.
The aesthetics of the paper can also be improved utilizing the process
described in this invention. Inks, dyes, and/or perfumes are preferably
added to the aqueous composition which is subsequently applied to the
tissue paper web. The aesthetics additive may be applied alone or in
combination with the wetting, softening, and/or strength additives.
Analytical Methods
Analysis of the amounts of treatment chemicals herein retained on
tissue paper webs can be performed by any method accepted in the
applicable art. For example, the level of polysiloxane retained by the tissue
paper can be determined by solvent extraction of the polysiioxane with an
organic solvent followed by atomic absorption spectroscopy to determine
the level of silicon in the extract; the level of nonionic surfactants, such
as
alkylglycosides, can be determined by extraction in an organic solvent
followed by gas chromatography to determine the level of surfactant in the
extract; the level of anionic surfactants, such as linear alkyl sulfonates,
can
be determined by water extraction followed by colorimetry analysis of the
extract; the level of starch can be determined by amylase digestion of the
starch to glucose followed by colorimetry analysis to determine glucose
level. These methods are exemplary, and are not meant to exclude other
methods which may be useful for determining levels of particular
components retained by the tissue paper.
Hydrophilicity of tissue paper refers, in general, to the propensity of
the tissue paper to be wetted with water. Hydrophilicity of tissue paper may
be somewhat quantified by determining the period of time required for dry
tissue paper to become completely wetted with water. This period of time is
referred to as "wetting time." In order to provide a consistent and
repeatable test for wetting time, the following procedure may be used for
wetting time determinations: first, a conditioned sample unit sheet (the
environmental conditions for testing of paper samples are 23~1 °C and
50~
CA 02257691 1998-12-10
WO 97/47809 PCT/US97/10177
2% RH as specified in TAPPI Method T 402), approximately 4-3/8 inch x 4-
3/4 inch (about 11.1 cm x 12 cm) of tissue paper structure is provided;
second, the sheet is folded into four (4) juxtaposed quarters, and then
crumpled into a ball approximately 0.75 inches (about 1.9 cm) to about 1
5 inch (about 2.5 cm) in diameter; third, the balled sheet is placed on the
. surface of a body of distilled water at 23 ~ 1 °C and a timer is
simultaneously
started; fourth, the timer is stopped and read when wetting of the balled
sheet is completed. Complete wetting is observed visually.
The preferred hydrophilicity of tissue paper depends upon its intended
10 end use. It is desirable for tissue paper used in a variety of
applications,
e.g., toilet paper, to completely wet in a relatively short period of time to
prevent clogging once the toilet is flushed. Preferably, wetting time is 2
minutes or less. More preferably, wetting time is 30 seconds or less. Most
preferably, wetting time is 10 seconds or less.
15 Hydrophilicity characters of tissue paper embodiments of the present
. invention may, of course, be determined immediately after manufacture.
However, substantial increases in hydrophobicity may occur during the first
two weeks after the tissue paper is made: i.e., after the paper has aged two
{2) weeks following its manufacture. Thus, the above stated wetting times
20 are preferably measured at the end of such two week period. Accordingly,
wetting times measured at the end of a two week aging period at room
temperature are referred to as "two week wetting times."
The density of tissue paper, as that term is used herein, is the average
density calculated as the basis weight (mass/unit area) of that paper divided
25 by the caliper, with the appropriate unit conversions incorporated therein.
Caliper of the tissue paper, as used herein, is the thickness of the paper
when subjected to a compressive load of 95 glint (15.5 g/cm2). A suitable
instrument for measurement is the thickness tester model 89-100 made by
Twing-Albert Instrument Co. of Philadelphia, PA 19154.
The following examples illustrate the practice of the present invention
but are not intended to be limiting thereof.
EXAMPLE 1
CA 02257691 2003-07-07
26
A pilot scale Fourdrinier papermaking machine is used in the practice
of the present invention. A 3% by weight aqueous slurry of NSK (Northern
Softwood Kraft (such as Grand Prairie from Weyerhaeuser Corporation of
Tacoma Washington)) is made up in a conventional re-pulper. A 2%
solution of the temporary wet strength resin (i.e., National starch 78-0080
marketed by National Starch and Chemical corporation of New-York, NY) is
added to the NSK stock pipe at a rate of 0.75% by weight of the dry fibers.
The adsorption of the temporary wet strength resin onto NSK fibers is
enhanced by an in-fine mixer. The NSK slurry is diluted to about 0.2%
consistency at the fan pump. A 3% by weight aqueous slurry of Eucalyptus
(such as Aracruz of Brazil) fibers is made up in a conventional re-pulper.
The Eucalyptus slurry is diluted to about 0.2% consistency at the fan pump.
The individual furnish components are sent to separate layers (i.e., Euc. to
the outer layers and NSK in the center layer) in the head box and deposited
onto a Foudrinier wire to form a three-Payer embryonic web. Dewatering
occurs through the Fourdrinier wire and is assisted by a deflector and
vacuum boxes. The Fourdrinier wire is of a 5-shed, satin weave
configuration having 33 machine-direction and 30 cross-machine-direction
monofilaments per centimeter, respectively. The embryonic wet web is
transferred from the Fourdrinier wire, at a fiber consistency of about 18% at
the point ~ of transfer, to a second papermaking belt. Th~second
papermaking belt is an endless belt having the preferred network surface
and deflection conduits. The papermaking belt is made by forming a photo-
polymeric network on a foraminous woven element made of polyester and
having 20 (MD) by 18 (CD) filaments per centimeter in a four shed dual
layer design according to the process disclosed in U.S. Patent No.
5,334,289 issued to Trokhan. The filaments are about .22 mm in diameter
machine-direction and .28 mm in diameter cross-machine-direction. The
photo-polymer fabric has about 35 percent knuckle area and has 562 Linear
Idaho Cells per square inch (87 cells per square cm), the Linear Idaho cell
pattern is described in detail in Figure 19 of U.S. Patent 5,514,523, issued
to
Trokhan et al. on May 7, 1996. The photosensitive resin used in the process
is MEHT""-1000, a methacrylated-urethane resin marketed by MacDermid
Imaging Technology lnc., Wilmington, Delaware. The papermaking belt has
a total thickness of about 1.2 mm with 0.2 mm of photopolymer pattern
extending above the woven foraminous element.
CA 02257691 2003-07-07
27
The- embryonic web is carried on the papermaking belt past the
vacuum dewatering box, through blow-through predryers after which the
web is transferred onto a Yankee dryer. The other process and machine
conditions are listed below. The fiber consistency is about 27% after the
vacuum dewatering box and, by the action of the predryers, about 65% prior
to transfer onto the Yankee dryer; creping adhesive comprising a 0.25%
aqueous solution of polyvinyl alcohol is spray applied by applicators; the
fiber consistency is increased to be an estimated 98% before dry creping
the web with a doctor blade. The doctor blade has a bevel angle of about
25 degrees and is positioned with respect to the Yankee dryer to provide an
impact angle of about 81 degrees; the Yankee dryer is operated at about
350°F (177°C); the Yankee dryer is operated at about 800 fpm
(feet per
minute) (about 244 meters per minute). The dry creped web is then passed
between two calender rolls. The two calender rolls, are biased together at
roll weight and operated at surface speeds of 660 fpm (about 201 meters
per minute). The calendered web is wound on a reel (which is also
operated at a surface speed of 660 fpm) and is then ready for use.
An aqueous solution containing a chemical additive composition is
continuously applied onto the paper-contacting surface of the papermaking
belt via an emulsion distribution roll before the papermaking belt comes in
contact with the embryonic web. The aqueous chemical additive
composition applied by the distribution roll onto the deflection member
contains five ingredients: water, Regal Oil (a high-speed turbine oil marketed
by the Texaco Oil Company), ADOGENT"' TA 100 (a distearyldimethyl
ammonium chloride surfactant marketed by the Witco Corporation, cetyl
alcohol (a C~s linear fatty alcohol marketed by The Procter & Gamble
- Company) and glycerol. The relative proportions of the five ingredients are
as follows: 6.1 % by weight Regal Oil, 0.3% by weight Adogen, 0.2% by
weight cetyl alcohol, 31.1 % by weight of glycerol, and the remainder water.
The volumetric flow rate of the aqueous chemical additive composition
applied to the papermaking belt is about 0.50 gal/hr.-cross-direction ft.
(about
6.21 liters/hr-meter). The wet web has a fiber consistency of about 25%, total
web weight basis, when it comes in contact with the aqueous chemical
additive composition.
The web is converted into a single ply tissue paper product. The
tissue paper has about 18 #l3M Sq Ft basis weight, contains about 1 % of
CA 02257691 2003-07-07
28
the glycerol and about 1 % of the Regal oil primarily on the knuckle areas of
the tissue paper, and about 0.2% of the temporary wet strength resin
distributed throughout the tissue paper. Importantly, the resulting tissue
paper is soft, absorbent and is suitable for use as facial andlor toilet
tissues.
EXAMPLE 2
A pilot scale Fourdrinier papermaking machine is used in the practice
of the present invention. A 3% by weight aqueous slurry of NSK (Northern
Softwood Kraft (such as Grand Prairie from Weyerhaeuser Corporation of
Tacoma Washington)) is made up in a conventional re-pulper. A
2°l°
solution of the temporary wet strength resin (i.e., National starch 78-0080
marketed by National Starch and Chemical corporation of New-York, NY) is
added to the NSK stock pipe at a rate of 0.75% by weight of the dry fibers.
The adsorption of the temporary wet strength resin onto NSK fibers is
enhanced by an in-line mixer. The NSK slurry is diluted to about 0.2%
consistency at the fan pump. A 3% by weight aqueous slurry of Eucalyptus
(such as Aracruz of Brazil) fibers is made up in a conventional re-pulper.
The Eucalyptus slurry is diluted to about 0.2% consistency at the fan pump.
The individual furnish components are sent to separate layers (i.e., Euc. to
the outer layers and NSK in the center layer) in the head box and deposited
onto a Foudrinier wire to form a three-layer embryonic web. Dewatering
occurs through the Fourdrinier wire and is assisted by a deflector and
vacuum boxes. The Fourdrinier wire is of a 5-shed, satin weave
configuration having 33 machine-direction and 30 cross-machine-direction
monofilaments per centimeter, respectively. The embryonic wet web is
_ transferred from the Fourdrinier wire, at a fiber consistency of about 18%
at
the point of transfer, to a second papermaking belt. The second
papermaking belt is an endless belt having the preferred network surface
and deflection conduits. The papermaking belt is made by forming a photo
polymeric network on a foraminous woven element made of polyester and
having 20 (MD) by 18 (CD) filaments per centimeter in a four shed dual
layer design according to the process disclosed in U.S. Patent No.
5,334,289 issued to Trokhan. The filaments are about .22 mm in diameter
machine-direction and .28 mm in diameter cross-machine-direction. The
photo-polymer fabric has about 35 percent knuckle area and has 562 Linear
Idaho Cells per square inch (87
CA 02257691 2003-07-07
29
cells per square cm), the Linear Idaho cell pattern is described in detail in
Figure 19 of U.S. Patent 5,514,523, issued to Trokhan et al. on May 7, 1996.
The photosensitive resin used in the process is MEH-1000, a methacrylated-
urethane resin marketed by MacDermid Imaging Technology Inc.,
Wilmington, Delaware. The papermaking belt has a total thickness of about
1.2 mm with 0.2 mm of photopolymer pattern extending above the woven
foraminous element.
The embryonic web is carried on the papermaking belt past the
vacuum dewatering box, through blow-through predryers after which the
web is transferred onto a Yankee dryer. The other process and machine
conditions are listed below. The fiber consistency is about 27% after the
vacuum dewatering box and, by the action of the predryers, about 65% prior
to transfer onto the Yankee dryer; creping adhesive comprising a 0.25%
aqueous solution of polyvinyl alcohol is spray applied by applicators; the
fiber consistency is increased to be an estimated 98% before dry creping
the web with a doctor blade. The doctor blade has a bevel angle of about
degrees and is positioned with respect to the Yankee dryer to provide an
impact angle of about 81 degrees; the Yankee dryer is operated at about
350°F (177°C); the Yankee dryer is operated at about 800 fpm
(feet per
20 minute) (about 24.4 meters per minute). The dry creped web is then passed
between two calender rolls. The two calender rolls are biased together at
roll weight and operated at surface speeds of 660 fpm (about 201 meters
per minute). The calendered web is wound on a reel (which is also
operated at a surface speed of 660 fpm) and is then ready for use.
25 An aqueous solution containing a chemical additive composition is
continuously applied onto the upper portion of the calender rolls. The
- aqueous chemical additive composition applied by the calender roll contains
three ingredients: water, a quartenary ammonium compound (such as
di(hydrogenated)tallow dimethyl ammonium methyl sulfate marketed by the
Witco Corporation under the trade name "VarisoftT"" 137" and glycerol. The
relative proportions of the three ingredients are as follows: 10% by weight
"Varisoft 137", 40% by weight of glycerol, and the remainder water. The web
has a fiber consistency of about 98%, total web weight basis, when it comes
in contact with the aqueous chemical additive composition.
The web is converted into a single ply tissue paper product. The
tissue paper has about 18 #/3M Sq Ft basis weight, contains about 1 % of
CA 02257691 2003-07-07
the glycerol and about 0.2% of the quaternary ammonium compound
softener primarily on the pillow areas of the tissue paper, and about 0.2% of
the temporary wet strength resin distributed throughout the tissue paper.
Importantly, the resulting tissue paper is soft, absorbent and is suitable for
5 use as facial and/or toilet tissues.
EXAMPLE 3
A pilot scale Fourdrinier papermaking machine is used in the practice
of the present invention. A 3% by weight aqueous slurry of NSK (Northern
10 Softwood Kraft (such as Grand Prairie from Weyerhaeuser Corporation of
Tacoma Washington) is made up in a conventional re-pulper. A 2% solution
of the temporary wet strength resin (i.e., National starch 78-0080 marketed
by National Starch and Chemical corporation of New-York, NY) is added to
the NSK stock pipe at a rate of 0.75% by weight of the dry fibers. The
15 adsorption of the temporary wet strength resin onto NSK fibers is enhanced
by an in-line mixer. The NSK slurry is diluted to about 0.2% consistency at
the fan pump. A 3% by weight aqueous slurry of Eucalyptus (such as
Aracruz of Brazil) fibers is made up in a conventional re-pulper. The
Eucalyptus slurry is diluted to about 0.2% consistency at the fan pump. The
20 individual furnish components are sent to separate layers (i.e., Euc. to
the
outer layers and NSK in the center layer) in the head box and deposited
onto a Foudrinier wire to form a three-layer embryonic web. Dewatering
occurs through the Fourdrinier wire and is assisted by a deflector and
vacuum boxes. The Fourdrinier wire is of a 5-shed, satin weave
25 configuration having 33 machine-direction and 30 cross-machine-direction
monofilaments per centimeter, respectively. The embryonic wet web is
- transferred from the Fourdrinier wire, at a fiber consistency of about 18%
at
the point of transfer, to a second papermaking belt. The second
papermaking belt is an endless belt having the preferred network surface
30 and deflection conduits. The papermaking belt is made by forming a photo
polymeric network on a foraminous woven element made of polyester and
having 20 (MD) by 18 (CD) filaments per centimeter in a four shed dual
layer design according to the process disclosed in U.S. Patent No.
5,334,289 issued to Trokhan. The filaments are about .22 mm in diameter
machine-direction and .28 mm in diameter cross-machine-direction. The
photo-polymer fabric has about 35 percent knuckle area and has 562 Linear
Idaho Cells per square inch (87
CA 02257691 2003-07-07
31
cells per square cm), the Linear Idaho cell pattern is described in detail in
Figure 19 of IJ.S. Patent 5,514,523, issued to Trokhan et al. on May 7, 1996.
The photosensitive resin used in the process is MEH-1000, a methacrylated-
urethane resin marketed by MacDermid Imaging Technology Inc.,
Wilmington, Delaware. The papermaking belt has a total thickness of about
1.2 mm with 0.2 mm of photopolymer pattern extending above the woven
foraminous element.
The embryonic web is carried on the papermaking belt past the
vacuum dewatering box, through blow-through predryers after which the
web is transferred onto a Yankee dryer. The other process and machine
conditions are listed below. The fiber consistency is about 27% after the
vacuum dewatering box and, by the action of the predryers, about 65% prior
to transfer onto the Yankee dryer; creping adhesive comprising a 0.25%
aqueous solution of polyvinyl alcohol is spray applied by applicators; the
fiber consistency is increased to be an estimated 98% before dry creping
the web with a doctor blade. The doctor blade has a bevel angle of about
degrees and is positioned with respect to the Yankee dryer to provide an
impact angle of about 81 degrees; the Yankee dryer is operated at about
350°F (177°C); the Yankee dryer is operated at about 800 fpm
(feet per
20 minute) (about 244 meters per minute). The dry creped web is then passed
between two calender rolls. The two catender rolls are biased together at
roll weight and operated at surface speeds of 660 fpm (about 201 meters
per minute). The calendered web is wound on a reel (which is also
operated at a surface speed of 660 fpm) and is then ready for use.
25 An aqueous solution containing a chemical additive composition is
continuously applied onto the knuckle areas of the papermaking belt via an
emulsion distribution roll before the papermaking belt comes in contact with
the embryonic web. The aqueous chemical additive composition applied by
the distribution roll onto the knuckle areas of the papermaking belt contains
five ingredients: water, Regal Oil (a high-speed turbine oil marketed by the
Texaco Oil Company), ADOGEN TA 100 (a distearyldimethyl ammonium
chloride surtactant marketed by the Witco Corporation, cetyl alcohol (a C16
linear fatty alcohol marketed by The Procter & Gamble Company) and a
water soluble dye composition. The relative proportions of the five
ingredients are as follows: 6.1 % by weight Regal Oil, 0.3% by weight
Adogen, 0.2% by weight cetyl alcohol, 0.2% by weight of water soluble dye
CA 02257691 1998-12-10
WO 97/47809 PCT/US97110177
32
composition, and the remainder water. The volumetric flow rate of the
aqueous chemical additive composition applied to the papermaking belt is
about 0.50 gallhr.-cross-direction ft. (about 6.21 liters/hr-meter). The wet
web has a fiber consistency of about 25%, total web weight basis, when it
comes in contact with the aqueous chemical additive composition.
The web is converted into a single ply tissue paper product. The
tissue paper has about 18 #/3M Sq Ft basis weight and contains about
0.2% of a temporary wet strength resin. Importantly, the resulting tissue
paper is soft, absorbent, has improved aesthetics and is suitable for use as
facial and/or toilet tissues.
EXAMPLE 4
A pilot scale Fourdrinier papermaking machine is used in the practice
of the present invention. A 3% by weight aqueous slurry of NSK (Northern
Softwood Kraft (such as Grand Prairie from Weyerhaeuser Corporation of
Tacoma Washington) is made up in a conventional re-pulper. A 2% solution
of the temporary wet strength resin (i.e., National starch 78-0080 marketed
by National Starch and Chemical corporation of New-York, NY) is added to
the NSK stock pipe at a rate of 0.75% by weight of the dry fibers. The
adsorption of the temporary wet strength resin onto NSK fibers is enhanced
by an in-line mixer. The NSK slurry is diluted to about 0.2% consistency at
the fan pump. A 3% by weight aqueous slurry of Eucalyptus {such as
Aracruz of Brazil) fibers is made up in a conventional re-pulper. The
Eucalyptus slurry is diluted to about 0.2% consistency at the fan pump. The
individual furnish components are sent to separate layers (i.e., Euc. to the
outer layers and NSK in the center layer) in the head box and deposited
onto a Foudrinier wire to form a three-layer embryonic web. Dewatering
occurs through the Fourdrinier wire and is assisted by a deflector and
vacuum boxes. The Fourdrinier wire is of a 5-shed, satin weave
configuration having 33 machine-direction and 30 cross-machine-direction
monofilaments per centimeter, respectively. The embryonic wet web is
transferred from the Fourdrinier wire, at a fiber consistency of about 18% at
the point of transfer, to a second papermaking belt. The second
papermaking belt is an endless belt having the preferred network surface
CA 02257691 2003-07-07 I
33
and deflection conduits. The papermaking belt is made by forming a photo-
polymeric network on a foraminous woven element made of polyester and
having 20 (MD) by 18 (CD) filaments per centimeter in a four shed dual layer
design according to the process disclosed in U.S. Patent No. 5,334,289
issued to Trokhan. The filaments are about .22 mm in diameter machine-
direction and .28 mm in diameter cross-machine-direction. The photo-
polymer fabric has about 35 percent knuckle area and has 562 Linear Idaho
Cells per square inch (87 cells per square cm), the Linear Idaho cell pattern
is described in detail in Figure 19 of U.S. Patent 5,514,523, issued to
Trokhan et al. on May 7, 1996. The photosensitive resin used in the process
is MEH-1000, a methacrylated-urethane resin marketed by MacDermid
Imaging Technology Inc., Wilmington, Delaware. The papermaking belt has
a total thickness of about 1.2 mm with 0.2 mm of photopolymer pattern
extending above the woven foraminous element.
The embryonic web is carried on the papermaking belt past the
vacuum dewatering box, through blow-through predryers after which the
web is transferred onto a Yankee dryer. The other process and machine
conditions are listed below. The fiber consistency is about 27% after the
20 vacuum dewatering box and, by the action of the predryers, about 65% prior
to transfer onto the Yankee dryer; creping adhesive comprising a 0.25%
aqueous solution of polyvinyl alcohol is spray applied by applicators; the
fiber consistency is increased to be an estimated 98% before dry creping
the web with a doctor blade. The doctor blade has a bevel angle of about
25 25 degrees and is positioned with respect to the Yankee dryer to provide an
impact angle of about 81 degrees; the Yankee dryer is operated at about
_ 350°F (177°C); the Yankee dryer is operated at about 800 fpm
(feet per
minute) (about 244 meters per minute). The dry creped web is then passed
between two calender rolls. The two calender rolls are biased together at
30 roll weight and operated at surface speeds of 660 fpm (about 201 meters
per minute). The calendered web is wound on a reel (which" is also
operated at a surface speed of 660 fpm) and is then ready for use.
An aqueous solution containing a chemical additive composition is
continuously applied to the surface of the Yankee dryer by a spray system
35 prior to the transfer of the embryonic web. The aqueous chemical additive
composition applied by the spray system onto the surface of the Yankee
CA 02257691 1998-12-10
WO 97/47809 PCT/IJS97/10177
34
dryer contains three ingredients: water, Airvol 540 (a polyvinyl alcohol
marketed by Air Products and Chemicals of Allentown, PA) and Cypro 711
(a poiyacrylamid dry strength resin supplied by American Cyanamid of
Wayne, N.J). The relative proportions of the three ingredients are as
follows: 0.125% by weight polyvinyl alcohol, 0.125% by weight
polyacrylamid dry strength resin, and the remainder water. The volumetric
flow rate of the aqueous chemical additive composition applied to the
surface of the Yankee Dryer is about 0.11 gallons/i~ninute/cross direction
foot. The wet embryonic web has an overall average water content of about
0.67 pounds of water per pound of fiber.
The web is converted into a single ply tissue paper product. The
tissue paper has a basis weight of about 1$ pounds of fiber per 3000
square feet of area and contains about 0.01 % of the dry strength resin
distributed primarily on the high density regions of the tissue product.
Importantly, the resulting tissue paper is soft, absorbent, has improved
aesthetics and is suitable for use as facial and/or toilet tissues.
