Note: Descriptions are shown in the official language in which they were submitted.
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CU.T RES[STANT PAPER AND PAPER ARTICLES AND
METHOD FOR MAKING SAME
Field of the Invention
The invention relates to the papermaking arts and, in particular, to the
manufacture of paper products such as file folders and the like made of
relatively heavy
weight paper a/k/a paperboard for use in office and clerical environments.
ac ground of the Tnvention
The contemporary work office uses a myriad of paper products including, but
not limited to, writingpapers, notepads, and file folders and / orjackets to
organize and store
various paperwork. Such file folders and / orjackets (hereinafter referred to
collectively as
"folders") are typically made using a paper material which is rather stiff and
durable so as to
protect the contents of the file and to stand upright or remain relatively
flat and self-
supporting. Unforhmately, such products also typically have edges which have a
tendency
to inflict so called "paper cuts" upon personnel handling the files. While
rarely presenting
a case of serious injury, paper cuts are nonetheless an inconvenience and may
cause
considerable discomfort as such cuts are oftcn jagged and irregular and formed
across the
highly sensitive nerve endings of the fingers.
Accordingly, there exists aneed for improvedpaperproducts, and inparticular
paper based file folders, which reduce or eliminate paper cuts.
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Summarv of the Invention
With regard to the foregoing and other objects and advantages, the present
invention provides a method for making a paper material having a reduced
tendency to cut
human skin and tissue. The method includes providing a papermaking furnish
including
cellulosic fibers, from about 0.5 to about 5.0 wt% by weight dry basis
expanded or
expandable microspheres, and, optionally, conventional furnish additives
including fillers,
retention aids, and the like, forming a fibrous web from the papermaking
furnish, drying the
web, and calendaring the web to a caliper of from about 11.0 to about 18.0
mils and a density
ranging from about 7.0 to about 12.0 lb/3000ft~/mil .
In another aspect, the invention relates to a paper material for use in the
manufacture of paper articles such as file folders. The paper material
includes a paper web
including cellulosic fibers and expanded microspheres dispersed within the
fibers and,
optionally, conventional paper additives including one or more fillers and
starches. The
paper web has a density of from about 7.0 to about 12.0 lb/3000ft2/mil and a
caliper of from
about 11.0 to about 18.0 mils. In addition, the paper web has edges which
exhibit an
improved resistance to inflicting cuts upon human skin.
In still another aspect, the invention provides a file folder or jacket. The
file
folder ofjacket comprises a paper web including wood fibers and expanded
microspheres
dispersed within the fibers. The paper web has a density of from about 7.0 to
about 12.0
lb/3000ft2/mil and a caliper of from about 11.0 to about 18.0 mils. The paper
web is die cut
to provide exposed edges on the folder orjacket that exhibit improved
resistance to inflicting
cuts upon human skin.
In accordance with one preferred embodiment of the invention, the paper web
has a density of from about 7.5 lb/3000ft2/mil to about 9.01b/3000fta/mil. It
is also preferred
that the paper web have a caliper of about 14.0 to about 16.0 mils. The basis
weight of the
web is typically from about 80 lb/3000ft a to about 3001b/3000ft a, more
preferably from
about 120 lb/3000ft a to about 1501b/3000ft 2.
Typically the microspheres in the paper web comprise synthetic polymeric
microspheres and comprise from about 0.5 to about 5.0 wt.% of the total weight
of the web
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on a dry basis, more preferably from about 1.0 wt % to about 2.0 wt % of the
total weight of
the web on a dry basis. It is particularly preferred that the microspheres
comprise
microspheres made from a polymeric material selected from the group consisting
of methyl
methacrylate, ortho-chlorostyrene, polyortho-chlorostyrene, polyvinylbenzyl
chloride,
acrylonitrile, vinylidene chloride, para-tert-butyl styrene, vinyl acetate,
butyl acrylate, styrene,
methacrylic acid, vinylbenzyl chloride and combinations of two or more of the
foregoing.
The microspheres have a preferred expanded diameter of from about 30 to about
60 microns.
In addition, it may be preferred in some cases to initially disperse the
microspheres in the
furnish in an unexpanded state and subsequently expand the microspheres as the
paper web
dries.
The cellulosic fibers of the web may be provided from hardwoods, softwoods,
or a mixture of the two. Preferably, the fibers in the paper web include from
about 30% to
about 100 % by weight dry basis softwood fibers and from about 70% to about 0%
by weight
dry basis hardwood fibers.
Brief Description of the Drawings
The above and other aspects and advantages of the invention will now be
further described in conjunction with the accompanying drawings in which:
Fig. 1 is photomicrograph illustrating edges of conventional papers after
being
cut by various paper cutting techniques;
Fig. 2 is another photomicrograph comparing a die cut conventional paper and
a die cut paper according to one embodiment of the present invention;
Fig. 3 is a side elevational view illustrating diagrammatically a paper die
cutting apparatus for use in reverse die cutting paper samples;
Fig. 4 is a side elevational view illustrating diagrammatically a testing
apparatus for simulating paper cuts upon a finger; and
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Fig. 5 is a perspective view illustrating certain aspects of the testing
apparatus
of Fig. 4.
Detailed Description of the Invention
The invention provides a paper material having an improved cut
resistance, i.e., the edges of the paper have a reduced tendency to cut,
abrade, or damage
human skin. As used herein, "paper" refers to and includes both paper and
paperboard unless
otherwise noted.
The paper is provided as a web containing cellulosic pulp fibers such as fiber
derived from hardwood trees, softwood trees, or a combination of hardwood and
softwood
trees prepared for use in a papermaking furnish by any known suitable
digestion, refming,
and bleaching operations. In a preferred embodiment; the cellulosic fibers in
the paper
include from about 30% to about 100 % by weight dry basis softwood fibers and
from about
70% to about 0% by weight dry basis hardwood fibers. In certain embodiments,
at least a
portion of the fibers may be provided from non-woody herbaceous plants
including, but not
limited to, kenaf, hemp, jute, flax, sisal, or abaca although legal
restrictions and other
considerations may make the utilization of hemp and other fiber sources
impractical or
impossible. The paper may also include other conventional additives such as,
for example,
starch, mineral fillers, sizing agents, retention aids, and strengthening
polymers. Among the
fillers that may be used are organic and inorganic pigments such as, by way of
example,
polymeric particles such as polystyrene latexes and polymethylmethacrylate,
and minerals
such as calcium carbonate, kaolin, and talc. In addition to pulp fibers and
fillers,
the paper material also includes dispersed within the fibers and any other
components from
about 0.5 to about 5.0 wt % by dry weight expanded microspheres. More
preferably the
paper includes from about 1.0 to about 2.0 wt % expanded microspheres.
Suitable
microspheres include synthetic resinous particles having a generally spherical
liquid-
containing center. The resinous particles may be made from methyl
methacrylate, methyl
methacrylate, ortho-chlorostyrene, polyortho-chlorostyrene, polyvinylbenzyl
chloride,
acrylonitrile, vinylidene chloride, para-tert-butyl styrene, vinyl acetate,
butyl acrylate, styrene,
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methacrylic acid, vinylbenzyl chloride and combinations of two or more,of the
foregoing.
Preferred resinous particles comprise a polymer containing from about 65 to
about 90 percent
by weight vinylidene chloride, preferably from about 65 to about 75 percent by
weight
vinylidene chloride, and from about 3 5 to about 10 percent by weight
acrylonitrile, preferably
from about 25 to about 35 percent by weight acrylonitrile.
The microspheres preferably subsist in the paper web in an "expanded" state,
having undergone expansion in diameter in the order of from about 300 to about
600 % from
an "unexpanded" state in the original paperrnakin,g fiunish from which the web
is derived.
In their original unexpanded state, the center of the expandable microspheres
may include a
volatile fluid foaming agent to promote and maintain the desired volumeiric
expansion.
Preferably, the agent is not a solvent for the polymer resin. A particularly
preferred foamiag
agent is isobutane, which may be present in an amount rangiag from about 10 to
about 25
percent by weight of the total weight of the resinous particles. Upon
heating'to a temperature
in the range of from about 80 to about 190 C in the dryer unit of a
papermaking machine,
the resinous particles expand to a diameter ranging from about 30 to about 60
microns.
Suitable expandable microspheres are available from Akzo Nobel of 1Viarietta,
Georgia under
the tradename EXPANCEL. Expandable microspheres and their usage in paper
materials
are described in more detail in U.S. Patent Number 6;802,938.
Papers formed according to the present invention preferably have a final
caliper, after calendering ofthe paper, and any nipping or pressing such as
may be associated
with subsequent coating of from about 11.0 to about 18.0 mils, more preferably
from about
14.0 mils to about 16.0 mils. Papers of the invention also typically exhibit
basis weights of
firnn about 801b/3000ft a to about 3001b/3000ft2 , more preferably from about
1201b/3000ft
'to about 1501b/3000ft 2. The final density of the papers, that is, the basis
weight divided
by the caliper, is typically from about 7.01b/3000ft a/mil to about
12.01b/3000ft 2/n1i1, and
more preferably from about 7.51b/3000ft 2/mil to about 9.01b/3000ft 2/mil.
Thus, the paper
has a relatively larger caliper in relation to its weight compared to
conventional papers.
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The reduction in basis weight versus caliper is believed to be attributable at
least in part to the large number of tiny voids in the paper associated with
the expanded
microspheres interspersed in the fibers with the microspheres causing,
especially during the
expansion process, a significant increase in the void volume in the material.
In addition, the
paper after drying operations is calendered sufficient to achieve the final
desired calipers
discussed herein along with any desired surface conditioning of the web
associated with the
calendering operation. The impartation of a significantly increased void
volume along with
a relatively high caliper also has the effect of reducing the density of the
paper while
retaining good stiffness and other properties important for use as stock for
file folders and the
like.
The method of forming the paper materials of the present invention includes
providing an initial paper furnish. The cellulosic fibrous component of the
furnish is suitably
of the chemically pulped variety, such as a bleached kraft pulp, although the
invention is not
believed to be liinited to: kraft pulps, and may also be used with good effect
with other
chemical pulps such as sulfite pulps, mechanical pulps such as ground wood
pulps, and other
pulp varieties and mixtures thereof such as chemical-mechanical and thermo-
mechanical
pulps.
While not essential to the invention, the pulp is preferably bleached to
remove
lignins and to achieve a desired pulp brightness according to one or more
bleaching
treatments known in the art including, for example, elemental chlorine-based
bleaching
sequences, chlorine dioxide-based bleaching sequences, chlorine-free bleaching
sequences,
elemental chlorine-free bleaching sequences, and combinations or variations of
stages of any
of the foregoing and other bleaching related sequences and stages.
After bleaching is completed and the pulp is washed and screened, it is
generally subjected to one or more refining steps. Thereafter, the refmed pulp
is passed to a
blend chest where it is mixed with various additives and fillers typically
incorporated into a
papermaking furnish as well as other pulps such as unbleached pulps and/or
recycled or post-
consumerpulps. The additives may include so-called "internal sizing" agents
used primarily
to increase the contact angle of polar liquids contacting the surface of the
paper such as
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alkenyl succinic anhydride (ASA), alkyl ketene dimer (AKD), and rosin sizes.
Retention aids
may also be added at this stage. Cationic retention aids are preferred;
however, anionic aids
may also be employed in the furnish.
In addition, and prior to providing the furnish to the headbox of a
papermaking
machine, polymeric microspheres are added to the pulp furnish mixture. As
noted above, the
microspheres are added in an amount of from about 0.5% to about 5.0% based on
the total
dry weight of the furnish. The microspheres may be preexpanded or in
substantially their final
dimension prior to inclusion in the furnish mixture. However, it is preferred
that the
microspheres are initially added to the furnish in a substantially unexpanded
state and then
caused to expand as the paper web is formed and dried as described
hereinafter. It will be
appreciated that this expansion has the effect of enabling an increased
caliper and reduced
density in the final paper product. It is also within the scope of the
invention to include
mixtures of expandable and already-expanded microspheres (or microspheres that
are already
substantially in their final dimensional state) in the papermaking furnish so
that a portion of
the microspheres will expand to a substantial degree in drying operations
while the balance
will remain in substantially the same overall dimensions during drying.
Once prepared, the furnish is formed into a single or multi-ply web on a
papermaking machine such as a Fourdrinier machine or any other suitable
papermaking
machine known in the art, as well as those which may become known in the
future. The basic
methodologies involved in making paper on various papermaking machine
configurations are
well-known to those of ordinary skill in the art and accordingly will not be
described in detail
herein. In general, a so-called "slice" of furnish consisting of a relatively
low consistency
aqueous slurry of the pulp fibers (typically about 0.1 to about 1.0%) along
with the
microspheres and various additives and fillers dispersed therein is ejected
from a headbox
onto a porous endless moving forming sheet or wire where the liquid is
gradually drained
through small openings in the wire until a mat of pulp fibers and the other
materials is formed
on the wire. The still-wet mat or web is transferred from the wire to a wet
press where more
fiber-to-fiber consolidation occurs and the moisture is further decreased. The
web is then
passed to an initial dryer section to remove most of the retained moisture and
further
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consolidate the fibers in the web. The heat of the drying section also
promotes expansion
of unexpanded microspheres contained in the web.
After initial drying, the web may be further treated using a size press
wherein
additional starch, pigments, and other additives may be applied to the web and
incorporated
therein by the action of the press.
After treatment in the size press and subsequent drying, the paper is
calendered
to achieve the desired final caliper as discussed above to improve the
smoothness and other
properties ofthe web. The calendering may be accomplished by steel-steel
calendaring at nip
pressures sufficient to provide a desired caliper. It will be appreciated that
the ultimate
caliper of the paper ply will be largely determined by the selection of the
nip pressure.
Paper materials formed according to the invention may be utilized in a variety
of office or clerical applications. In particular, the inventive papers are
advantageously used
in forming Bristol board file folder or jackets for storing and organizing
materials in the
office workplace. The manufacture of such folders from paper webs is well
known to those
in the paper converting arts and consists in general of cutting appropriately
sized and shaped
blanks from the paper web, typically by "reverse" die cutting, and then
folding the blanks into
the appropriate folder shape followed by stacking and packaging steps. The
blanks may also
be scored beforehand if desired to facilitate folding. The scoring, cutting,
folding, stacking,
and packaging operations are ordinarily carried out using automated machinery
well-known
to those of ordinary skill on a substantially continuous basis from rolls of
the web material
fed to the machinery from an unwind stand.
A typical apparatus for "reverse" die cutting is illustrated diagrammatically
in
Fig. 3. Such die cutting is in contrast to so-called "guillotine" cutting
ofpaper. In guillotine
cutting, a paper to be cut is supported by a flat, fixed surface underneath
the paper, and the
paper is cut by the lowering of a movable cutting blade down through the
thickness of the
paper and into a slot in the fixed surface dimensioned to receive the cutting
blade. Guillotine
cutting typically produces relatively smooth paper edges; however, guillotine
cutting is
generally impractical for high speed, large volume cutting applications.
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In reverse die cutting, a cutting blade is fixed in an upright position
protruding
from a housing located beneath the paper to be cut. With the blade fixed and
the paper in a
cutting position above the blade, a contact plate is lowered against the top
of the paper and
presses the paper against the edge of the cutting blade causing the blade to
cut the paper.
The papers and the folders and other die cut articles formed therefrom, having
exposed edges have been observed to exhibit a significantly reduced tendency
to cut the skin
ofpersons handling the folders as compared to prior art papers and die cut
paper articles such
as folders. That is, the edges of the papers are less likely to cause cutting
or abrasion of the
skin if the fingers or other portions of the body are inadvertently drawn
against an exposed
edge of the material.
Without being bound by theory, it is believed the improvement in cut
resistance
derives from the combination of an increased caliper and a decreased density
as compared
to prior art papers and the effect of these attributes on how the paper reacts
to cutting
operations. As noted above, folder blanks are typically die cut. When die
cutting blanks
for conventional folders from prior art papers having a relatively small
caliper and a
relatively high density, it is believed that the die blade initially creates a
clean cut through a
portion of the thickness of the paper. However, before the die blade can
complete a clean cut
through the paper, the remainder of the paper thickness "bursts" or fractures
in a relatively
jagged and irregular manner. As a consequence, the resultant edge ofthe folder
is jagged and
includes a large number of very small, but very sharp paper shards. Contact
with these small
jagged sharp edges and shards is believed to be a primary cause of paper cut
incidents.
While the resultant paper edges from die cutting are more rough and jagged
than from, say, guillotine cutting, die cutting techniques are more easily
implemented in
large-scale, high speed manufacturing, and are therefore favored greatly in
modern practice.
Fig. 1 illustrates four samples of a conventional paper which have been cut by
different techniques. The foremost sample in the micrograph is a paper which
has been
guillotine cut. The two samples depicted in the center of the micrograph are
cut by a lab
bench die cutter described in further detail hereinafter. The fmal sample, in
the background
of the micrograph, is cut by a conventional, production scale die cutter. As
may be seen, the
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die cut conventional papers exhibit considerable roughness about the edges of
the paper
samples.
However, it has been determined that paper according to the invention having
a relatively high caliper and relatively low density has a considerably
reduced tendency to
fracture or burst prematurely when being die cut. The die blade is apparently
allowed to
complete a clean cut through the paper thickness and, consequently, the
resultant edge
exhibits significantly fewer jagged irregularities and shards which produce
paper cuts.
Therefore, folders for example made according to the invention exhibit a
significantly
reduced tendency to cause paper cuts as they are being handled.
The differences in the resultant die cut paper edges is dramatically
illustrated
in Fig. 2 which depicts on the right a die-cut edge ofpaper formed according
to the invention
and to the left a die-cut edge of a conventional paper of substantially the
same basis weight.
The inventive paper includes about 2 wt% expanded microspheres and has a
caliper of about
15 mils and a density of about 8.7 lb/3000 ft2 / mil. The conventional paper
does not include
any microspheres and has a caliper of about 11 mils and a density of about
11.31b/3000 ft2
/ mil. It may be seen that the edge of the inventive paper is significantly
smoother in
appearance and has a more beveled corner profile. It is believed that these
differences
account for the reduction in cutting tendency.
The following nonlimiting examples illustrate various additional aspects ofthe
invention. Unless otherwise indicated, temperatures are in degrees Celsius,
percentages are
by weight and the percent of any pulp additive or moisture is based on the
oven-dry weight
of the total amount of.material.
Example 1
A series of papers were formed from a mixture of about 40% softwood pulp
and about 60% hardwood pulp and having a Canadian Standard Freeness of about
450 and
incorporating amounts of expandable microspheres and being calendered to a
variety of
differing calipers. The resultant papers containing the expanded microspheres
were then
tested to determine the likelihood of an edge cutting a person's fmgers while
being handled.
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In place of actual human skin, the tests were performed using a rubberized
finger covered by
a latex glove material which served as an artificial "skin".
The samples for examination were die cut using a laboratory die cutter 20
illustrated in Fig. 3. The cutter includes a bottom housing 22 having a recess
24. A cutting
blade 26 is mounted in a supporting block 28 and the block is fixed in the
recess 24 so that
the cutting blade projects upward.
The die cutter 20 also includes an upper housing 30 which is held in alignment
with the lower housing by a plurality of bolts or rods 32 which are received
in a
corresponding plurality of holes in the upper housing 30. Over the cutting
blade 26, the
upper housing includes a contact surface 34. The paper sample 36 to be cut is
placed in the
gap between the cutting blade 26 and the contact surface 34. The contact
surface 34 is then
pressed downward by a hydraulic ram 3 8 or by other suitable driving means so
that the paper
sample 36 is pressed against the cutting blade and cut I burst in two.
The cutting tendencies of the edges of the paper samples were evaluated in a
testing procedure referred to hereinafter as the "Cutting Index 30" test (with
"30" indicating
the number of replicates of the test performed). The Cutting Index 30 test
uses an apparatus
similar to that depicted diagrammatically in Figs. 4 and 5. The testing
apparatus 50 includes
a frame 52 which supports a paper sample clamping device 54 and suspends the
clamping
device 54 from above. The clamping device 54 is suspended about a pivot point
56 which
allows the angle of the clamping device 54 to vary relative to horizontal. In
this manner, the
paper may be contacted against the simulated finger at different contact
angles. The paper
sample 60 to be tested is held in the clamping device 54 in a substantially
upright position.
The testing apparatus 50 also includes a simulated finger 62 which may be
drawn against the edge of the paper sample 60 in the apparatus. For instance,
the finger 62
may be removably affixed to a movable base 64 which slides along a rail or
track 66 by
means of hydraulic actuation so that the fmger 62 is drawn into contact with
the edge of the
paper sample 60. After the sample contacts the finger, the latex is examined
to determine
if a cut is produced and the cuts are then characterized according to size.
The simulated finger is preferably formed from an inner rod of metal or stiff
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plastic, which is covered by a somewhat flexible material such a neoprene
rubber and the
neoprene layer is preferably covered by a latex layer such as a finger from a
latex glove. In
this manner, the finger roughly simulates the bone, muscle, and skin layers of
an actual
finger. While the latex and neoprene structure does not exhibit the exact some
tendency to
be cut as an actual finger, it is believed that a relatively high incidence of
cuts in this structure
will generally correlate to a relatively high incidence of cuts in an actual
finger and a
relatively low incidence of cuts in this structure will generally correlate to
a relatively low
incidence of cuts in an actual finger.
In the experiments described herein, neoprene rubber layer employed has a
hardness of about Shore A 50, the latex "skin" is about 0.004 inches thick,
and the latex skin
is attached to the neoprene using double-sided tape. In order to better
simulate skin, the latex
is also allowed to condition by exposure to an elevated temperature of about
125 C for a
period of about 6 hours prior to testing. Because latex is a naturally
occurring substance,
latexes and products produced therefrom exhibit some degree ofvariation from
batch to batch
with respect to certain properties such as moisture content. It was found that
by conditioning
the latex at the elevated temperature for about 6 hours, the resultant latex
skins exhibited a
more uniform set of properties and accordingly the reproducibility of test
results improved.
The paper samples employed are cut to a size of about 1 inch by six inches and
a die cut edge is aligned in the bottom of the clamping device to contact the
finger. The
simulated finger is then drawn against the paper edge, then stopped and the
latex skin is
examined to determine if a cut has occurred and if so, the magnitude or size
of the cut.
A total of 30 replicates were performed for each paper sample. The results
were as follows:
Table I
Sample ID % Expancel Basis weight Final Density Total Cutting
(WMCF) (Wt %) (lb/3000ft2) Caliper (lb/3000ft2/mil) Cuts Index
(mils)
1A 0 127 11.9 10.7 19 45
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2 2 108 12.0 9.0 15 34
3 3 108 12.7 8.5 17 29
6A 0 148 12.1 12.3 22 56
6B 0 182 14.5 12.6 18 30
6C 0 200 16.2 12.4 13 16
124 2 131 15.8 8.3 7 15
143 2 143 17.0 8.4 3 5
In addition to measuring the number of cuts (out of 30 replicates), the size
of
each cut was characterized on a 1 to 5 scale with 1 being "very small" and 5
being "large".
Using this data, a "Cutting Index" was determined by summing the products of
the number
of cuts in each size category by the severity of the cut on the 1 to 5 scale.
These results are
shown in Table II:
Table II
Sample ID Total Cuts Large Med+ Med Small V. Small Cutting
(5) (4) (3) (2) (1) Index
1A 19 0 3 5 7 4 45
2 15 0 1 3 10 1 34
3 17 0 0 1 10 6 29
6A 22 0 4 8 6 4 56
6B 18 0 0 6 0 12 30
6C 13 0 0 0 3 10 16
124 7 0 0 3 2 2 15
143 3 0 0 0 2 1 5
As may be seen in samples 1- 3 and 6A, the density of the papers was varied
by addition ofvarying amounts of expanded microspheres while the paper
calipers were held
approximately constant at about 12 mils. These samples demonstrate that a
reduction of
density associated with inclusion of microspheres leads to a corresponding
reduction in the
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number and severity of cuts produced by the paper.
In samples 6A - 6C, the paper density was held approximately constant at about
12.5 lb/3000 ft2 / mil while the caliper of the papers was varied. The results
demonstrate a
clear correlation between increasing caliper and decreasing cuts and cut
severity in a paper
containing the microspheres.
Finally, in samples 124 and 143, papers were produced containing microspheres
and employing both a reduced density and a high caliper at the same time. The
results were
quite dramatic with number of cuts and the weight average cuts both being
reduced to
extremely low levels. Thus, it appears that while both caliper increase and
density reduction
in association with addition ofmicrospheres may individually reduce cutting to
some degree,
the combination of the two appears to provide a synergistic reduction in
cutting which is
surprising and quite unexpected.
Example 2
A similar set of tests were conducted using a series of papers formed from a
second pulp furnish, again formed from a mixture of about 40% softwood pulp
and about
60% hardwood pulp and having a Canadian Standard Freeness of about 450. In
these tests,
two sets of papers were produced, with each set of papers having approximately
the same
basis weight. For one group of papers, the basis weight was on the order of
about 130
lb/3000 ftz and for the second group, the basis weight was about 1501b/3000
ft2. Within each
group, various amounts of microspheres were added and the resultant paper
caliper varied.
Again, 30 replicates of each sample were tested for cutting tendency. The
results are shown
in Tables III and IV.
Table III
Sample ID % Expancel Basis weight Final Density Total Cutting
(Wt %) (lb/3000ft2) Caliper (lb/3000ft2/mil) Cuts Index
(Mils)
1 0 129 12.1 10.7 21 77
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3 2 133 15.5 8.58 15 34
4 3 128 17.2 7.46 10 16
0 153 13.8 11.1 25 80
7 2 149 14.6 10.2 16 36
8 3 150 18.4 8.15 7 12
These results show a clear trend toward decreases in total cuts as well as the
weighted average cuts with increasing amount ofmicrospheres where the basis
weight is held
about the same. It is seen that increasing the amount of microspheres while
holding the basis
weight the same can'be said to result in an increased caliper, decreased
density, and decreased
number and severity of cuts.
Table IV
Sample ID Total Cuts Large Med+ Med Small V. Small Cutting
(5) (4) (3) (2) (1) Index
1 21 7 5 5 3 1 77
3 15 0 2 1 8 3 34
4 10 0 0 0 6 4 16
5 25 2 9 6 8 0 80
7 16 0 0 4 12 0 36
8 7 0 0 0 5 2 12
Example 3
A similar set of tests were conducted using a series of papers formed from a
third pulp furnish including about 35% softwood fibers and about 65% hardwood
fibers.
Again, 30 replicates of each sample were tested for cutting tendency. The
results are shown
in Tables V.
CA 02443904 2003-10-10
WO 02/084026 PCT/US02/12264
Table V
Sample ID % Expancel Basis weight Final Density Total Cutting
(Wt. %) (lb/3000ft2) Caliper (lb/3000ft2/mil) Cuts Index
(Mils)
1241b 0 129 11.39 11.34 28 116
control
1431b 0 148 11.57 12.76 30 95
control
4 2 128 14.83 8.61 15 21
6 2 125 15.21 8.22 7 9
7 2 124 14.94 8.28 5 5
8 2 125 15.08 8.27 15 15
9 2 125 14.56 8.62 8 9
In these tests, the papers containing expanded microspheres were produced to
provide a target basis weight of about 1241b/3000 ft2 and compared to two
controls formed
with no microspheres and having basis weights of 124 lb/3000 ft2 and 143
lb/3000ft2
respectively. The expanded microsphere samples again showed dramatic
reductions in
cutting tendency as compared to the control papers. The total number of cuts
was reduced
by about 50% or more in each case and the reductions in average weighted cuts
was reduced
further still.
Having now described various aspects of the invention and preferred
embodiments thereof, it will be recognized by those of ordinary skill that
numerous
modifications, variations and substitutions may exist within the spirit and
scope of the
appended claims.
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