U.S. patent number 3,905,863 [Application Number 05/457,043] was granted by the patent office on 1975-09-16 for process for forming absorbent paper by imprinting a semi-twill fabric knuckle pattern thereon prior to final drying and paper thereof.
This patent grant is currently assigned to The Procter & Gamble Company. Invention is credited to Peter G. Ayers.
United States Patent |
3,905,863 |
Ayers |
September 16, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
Process for forming absorbent paper by imprinting a semi-twill
fabric knuckle pattern thereon prior to final drying and paper
thereof
Abstract
A low-density, soft, bulky and absorbent paper sheet exhibiting
a diamond-shaped pattern in its surface after creping, said paper
being characterized by having a cross-directional stretch of from
about 3.5 percent to about 6 percent, as well as improved softness,
surface feel and drape, said paper sheet being particularly
suitable for use in tissue, toweling and sanitary products. The
aforesaid paper sheets are produced by impressing a dot-dash
knuckle pattern, wherein the long axis of the dash impressions is
aligned parallel to the machine direction of papermaking, using the
back side of a monofilament, polymeric fiber, semi-twill fabric of
selected coarseness, the knuckle imprint area of which constitutes
between about 20 percent and about 50 percent of the total fabric
surface area, as measured in the plane of the knuckles, on an
uncompacted paper web at selected fiber consistencies, induced by
thermal predrying, prior to final drying and creping.
Inventors: |
Ayers; Peter G. (West Chester,
OH) |
Assignee: |
The Procter & Gamble
Company (Cincinnati, OH)
|
Family
ID: |
27004184 |
Appl.
No.: |
05/457,043 |
Filed: |
April 1, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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368440 |
Jun 8, 1973 |
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Current U.S.
Class: |
162/113; 156/183;
162/117; 139/425A; 162/116 |
Current CPC
Class: |
D21F
11/006 (20130101); D21F 11/14 (20130101) |
Current International
Class: |
D21F
11/14 (20060101); D21F 11/00 (20060101); D21H
005/24 () |
Field of
Search: |
;162/113,116,117,109
;139/425A,383R ;161/128 ;156/183 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bashore; S. Leon
Assistant Examiner: Corbin; Arthur L.
Attorney, Agent or Firm: Linman; E. Kelly Braun; Frederick
H. Gorman; John V.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of my copending
application, Ser. No. 368,440, filed June 8, 1973, entitled
"PROCESS FOR FORMING ABSORBENT PAPER BY IMPRINTING A SEMI-TWILL
FABRIC KNUCKLE PATTERN THEREON PRIOR TO FINAL DRYING AND PAPER
THEREOF", now abandoned.
Claims
Having thus defined and described the invention, what is claimed
is:
1. A process for the manufacture of a soft, bulky and absorbent
paper sheet which comprises the steps of:
a. forming an uncompacted paper web having a uniform basis weight
of about 5 to about 40 pounds per 3000 square feet,
b. supporting said uncompacted paper web on the back side of a
semi-twill imprinting fabric having about 20 to about 60 meshes per
inch, the knuckle imprint area on the back side of said fabric
constituting between about 20 and about 50 percent of the total
fabric surface area, as measured in the plane of the knuckles, said
imprinting fabric being formed from filaments having a diameter of
about 0.008 to about 0.025 inches,
c. thermally pre-drying said uncompacted paper web to a fiber
consistency between about 30 and about 98 percent,
d. imprinting a dot-dash knuckle pattern with said semi-twill
imprinting fabric such that the long axis of the dash impressions
in said pattern is aligned parallel to the machine direction of the
pre-dryed, uncompacted paper web, and
e. final drying and creping the paper sheet so formed.
2. The process for the manufacture of a soft, bulky and absorbent
paper sheet as described in claim 1 wherein the final drying of the
paper sheet is performed on the imprinting fabric.
3. The process for the manufacture of a soft, bulky and absorbent
paper sheet as described in claim 1 wherein the final drying of the
paper sheet is performed on a Yankee dryer drum and the creping is
performed by means of a doctor blade.
4. The process for the manufacture of a soft, bulky and absorbent
paper sheet as described in claim 1 wherein the uncompacted paper
web formed in step (a) is molded to conform to the pattern of the
imprinting fabric prior to thermally pre-drying the uncompacted
paper web in step (c).
5. A process for the manufacture of a soft, bulky and absorbent
paper sheet which comprises the steps of:
a. forming an uncompacted paper web having a uniform basis weight
of about 9 to about 25 pounds per 3000 square feet,
b. supporting said paper web on the back side of a semi-twill
imprinting fabric having about 20 to about 60 meshes per inch, the
knuckle imprint area on the back side of said fabric constituting
between about 20 and about 50 percent of the total fabric surface
area, as measured in the plane of the knuckles, said imprinting
fabric being formed from filaments having a diameter of about 0.008
to about 0.025 inches,
c. thermally pre-drying said uncompacted paper web to a fiber
consistency between about 40 and about 98 percent,
d. imprinting a dot-dash knuckle pattern with said semi-twill
imprinting fabric such that the long axis of the dash impressions
in said pattern is aligned parallel to the machine direction of the
pre-dryed, uncompacted paper web, and
e. final drying and creping the paper sheet so formed by means of a
Yankee dryer drum and a doctor blade.
6. The process for the manufacture of a soft, bulky and absorbent
paper sheet as described in claim 5 wherein the uncompacted paper
web formed in step (a) is molded to conform to the pattern of the
imprinting fabric prior to thermally pre-drying the uncompacted web
in step (c).
7. A soft, bulky and absorbent paper sheet characterized by having
a uniform basis weight of about 5 to about 40 pounds per 3000
square feet, by having imprinted in its surface, to a depth of at
least 30 percent of its machine glazed caliper, the knuckle pattern
of the back side of a semi-twill imprinting fabric having about 20
to about 60 meshes per inch, by having about 20 to about 50 percent
of its surface compressed in said dot-dash knuckle pattern such
that the long axis of the dash impressions in said pattern is
aligned parallel to the machine direction during the formation of
said paper sheet, said paper sheet being further characterized by
having a cross-directional stretch of from about 3.5 percent to
about 6 percent.
8. The soft, bulky and absorbent sheet described in claim 7 which
sheet exhibits a diamond-shaped pattern in its surface after
creping.
Description
FIELD OF THE INVENTION
This invention relates to improvements in papermaking and non-woven
web manufacturing operations and particularly to the provision of a
low-density, soft, bulky and absorbent paper sheet characterized by
having significantly greater cross-directional stretch, as well as
improved softness, surface feel and drape when compared to paper
sheets produced by prior art papermaking and non-woven web
manufacturing methods.
More particularly, in one important embodiment, the present
invention consists of a monofilament, polymeric fiber, semi-twill
fabric which when used to imprint an uncompacted paper web at
selected fiber consistencies, induced by thermal pre-drying, will
produce a dot-dash pattern wherein the long axis of the dash
impressions is aligned parallel to the machine direction of
paper-making and the long axis of the dot impressions is aligned
parallel to the cross-machine direction. The aforesaid imprinting
fabric is especially suitable for use in papermaking and non-woven
web manufacturing operations, such as the papermaking operation
disclosed in U.S. Pat. No. 3,301,746, issued to Sanford et al. on
Jan. 31, 1967, said patent being incorporated herein by reference,
wherein the surface characteristics of such fabrics are of
operational and product characteristic importance.
In one preferred embodimen, the present invention consists of a
monofilament, polymeric fiber, semi-twill fabric of the type
normally used for transporting a moist web through the forming,
pressing and drying sections of a papermaking machine, which
monofilament, polymeric fiber, semi-twill fabric is woven and
thereafter shrunk by heat treatment to result in a dimensionally
heat stable fabric having uniform knuckle heights in conjunction
with minimum "free" or interstitial area on the surface of the
fabric which will contact the uncompacted paper web, said fabric
having been further improved by abrading its web contacting surface
with a fine abrasive medium to increase its knuckle imprint
area.
BACKGROUND OF THE INVENTION
In a Fourdrinier paper machine, paper stock is fed onto a traveling
endless belt that is supported and driven by rolls associated with
the machine and which serves to the papermaking surface of the
machine. Foundrinier belts are commonly formed from a length of
woven Fourdrinier fabric with its ends joined together in a seam to
provide an endless belt. Fourdrinier fabrics of this type generally
comprise a plurality of spaced longitudinal warp filaments and a
plurality of spaced transverse woof or weft filaments which have
been woven together on a suitable loom. It should be noted that the
warp filaments of the fabric are, for purposes of this
specification, defined as those which run parallel to the machine
direction of papermaking and non-woven web manufacturing machines
to form a continuous carrier belt; woof or weft filaments are, for
purposes of this specification, defined as those which run in the
cross-machine direction.
Although the weaving and fabric treatment criteria of the present
invention are applicable in other areas of monofilament, polymeric
fiber fabric use, the instant features will be most readily
understood in respect to the use of such fabrics for imprinting
purposes in web formation operations. In these operations, for
example in the operation of a paper machine according to the
teachings of U.s. Pat. 3,301,746, improved web transferability and
dryer surface contact are desirable in an imprinting fabric, and
the monofilament, polymeric fiber fabric used should not contribute
factors to the final paper product other than those desired by the
papermaker and designed into the paper product.
In referring to monofilament, polymeric fiber fabrics herein,
applicant intends reference to moist web carrier fabrics woven, for
example, from the polyamide fibers, vinyl fibers, acrylic fibers
and polyester fibers sold under the respective trade names of
"nylon," "Saran," "Orlon," "Dacron," and "Treviera." While both
warp and woof filaments in fabrics can be made up of a multiplicity
of fibers, the present invention is concerned with warp and woof
filaments comprised of one fiber, i.e., monofilaments.
While a number of different weaves have been proposed for
Fourdrinier fabrics, two weaves which find extensive use today are
the so-called "plain" weave and the "semi-twill" (sometimes also
called "long crimp") weave. In the plain weave, each weft filament
passes successively under one warp filament and then over the next
warp filament, whereas in the semi-twill weave each weft filament
passes over two warp filaments, under the next warp filament, and
then over the next two warp filaments in a repeated pattern. Of
these two weaves, the semi-twill weave is the most widely used.
The imprinting fabric suggested for use in U.S. Pat. 3,301,746, to
which the present invention has particular relevance, may be of
square or diagonal weave, and can be of any specific construction
including, for example, plain or semi-twill weave. A preferred
imprinting fabric, according to the teachings of the aforesaid
Sanford et al. patent, has about 20 to about 60 meshes per inch and
is formed from filaments having a diameter of from about 0.008 to
about 0.02 inches.
Paper sheets produced in accordance with the teachings of U.S. Pat.
No. 3,301,746 utilizing a monofilament, polymeric fiber, semi-twill
imprinting fabric exhibit properties similar in most respects to
paper sheets produced utilizing a plain weave imprinting fabric
having filaments of approximately the same diameter when the
semi-twill fabric is installed so that its conventional "face" side
is used to imprint the uncompacted paper web. This is due to the
fact that the conventional face side of the semi-twill fabric,
assuming the fabric has uniform knuckle heights on its web
contacting side, will produce a dot-dash pattern wherein the long
axis of the dash impressions is aligned parallel to the
cross-machine direction and the long axis of the dot impressions is
aligned parallel to the machine direction. The dash impressions
result from each weft filament passing in a repeated pattern under
one warp filament and then over the next two warp filaments, while
the dot impressions result from each warp filament passing in a
repeated pattern over one weft filament and then under the next two
weft filaments on the conventional face side of the fabric.
When paper sheets imprinted by the conventional face side of a
semi-twill fabric, as described above, are doctored from the drying
drum, the dot-dash knuckle impressions are aligned essentially
between the creping folds. The resulting creping folds are,
therefore, substantially uninterrupted across the sheet's surface.
Thus paper sheets produced utilizing the conventional face side of
a semi-twill imprinting fabric exhibit properties substantially
similar to paper sheets produced utilizing a plain weave imprinting
fabric, i.e., a low-density, soft, bulky and absorbent paper sheet
characterized by having uniform creping folds which extend
substantially uninterrupted across the width of the sheet.
On the other hand, utilization of the "back" side of a monofilament
polymeric fiber, semi-twill fabric to imprint an uncompacted paper
web in accordance with the teachings of U.S. Pat. No. 3,301,746
will, assuming the fabric has uniform knuckle heights on its web
contacting side, produce a dot-dash pattern wherein the long axis
of the dash impressions is aligned parallel to the machine
direction of the paper machine and the long axis of the dot
impressions is aligned parallel to the cross-machine direction. The
dash impressions result from each warp filament passing in a
repeated pattern under one weft filament and then over the next two
weft filaments, while the dot impressions result from each weft
filament passing in a repeated pattern over one warp filament and
then under the next two warp filaments on the back side of the
fabric.
Paper sheets imprinted with the back side of a conventional
semi-twill, monofilament, polymeric fiber fabric, unlike paper
sheets imprinted with either a plain weave fabric or the
conventional face side of a semi-twill fabric, exhibit a
diamond-shaped pattern after creping.
Applicant has discovered that by increasing the knuckle imprint
area on the back side of a conventional semi-twill, monofilament,
polymeric fiber fabric in accordance with the teachings of U.S.
Pat. No. 3,573,164 issued to Friedberg et al. on Mar. 30, 1971,
said patent being incorporated herein by reference. unexpected
improvments in paper sheet characteristics can be realized. These
unexpected advantages take the form of improved cross-directional
stretch, softness, surface feel and drape. The improvements become
more pronounced as the knuckle area on the back side of the
semi-twill fabric is increased.
Although improved web transfer characteristics and improved drying
of the web are realized when the web contacting knuckle surfaces of
nearly any monofilament, polymeric fiber fabric are abraded in
accordance with the teachings of U.S. Pat. No. 3,573,164, applicant
has learned that the aforementioned improvements in
cross-directional stretch, softness, surface feel and drape are
realized only with respect to the back side of a semi-twill
imprinting fabric, such as is described above.
In order to maximize the beneficial effects of abrading the knuckle
surfaces on the back side of a semi-twill imprinting fabric,
applicant has found it desirable to obtain a semi-twill fabric
having uniform knuckle heights and minimum free area on its back
side prior to initiating any abrading process. Uniform knuckle
heights permit a greater increase in knuckle imprint area while
minimizing the danger of abrading completely through any particular
filament. In addition, if knuckle heights are uniform prior to
initiating any abrading process, the resulting imprint pattern
after abrading will be more uniformly consistent.
Because a fabric such as is utilized for imprinting purposes in
U.S. Pat. No. 3,301,746 is subjected to elevated temperatures
during use, it is desirable to dimensionally heat stabilize the
fabric prior to subjecting it to an abrading process to increase
its knuckle imprint area. If this is not done, the uniform
imprinting surface produced by carefully weaving the fabric and
abrading the web contacting surface of the fabric prior to use will
tend to warp as the temperature of the fabric becomes elevated,
thereby losing most of the benefits to be obtained by such careful
pre-treatment.
A means of preparing a dimensionally heat stable, plain weave,
monofilament, polymeric fiber fabric having uniform knuckle heights
and minimum free area on each side of the fabric is disclosed in
U.S. Pat. No. 3,473,576 issued to Amneus on Oct. 21, 1969, said
patent being incorporated herein by reference. A plain weave fabric
is prepared by selecting polymeric warp monofilaments having a
relatively high heat-induced shrinkage potential and further
selecting an initial warp monofilament spacing in the loom
according to a mathematical equation disclosed in the
aforementioned Amneus patent. Polymeric woof monofilaments are then
selected which have a relatively low heat induced shrinkage
potential, and these woof monofilaments are woven and beaten in the
weaving process into a plain weave fabric having an initial caliper
calculated according to yet another mathematical equation disclosed
in the aforementioned Amneus patent. After the initial weaving
process, the fabric knuckles are brought to uniform on both sides
of the fabric and the minimum free area of the fabric is set by a
heat shrinkage treatment which maintains the fabric in warp tension
while allowing it to shrink in the woof direction. Successive heat
treatments are repeated until the monofilament, polymeric fiber,
plain weave fabric does not shrink further at the treating
temperature, at which point it is said to be "locked-up", i.e., no
further shrinkage will occur if the fabric is later subjected, in
use, to elevated tempeatures equivalent to the treating
temperature.
It is important to note that due to the symmetry of the plain
weave, uniform knuckle heights and minimum free area are achieved
simultaneously on both sides of the fabric when the weaving and
heat treatment processes described in the aforementioned Amneus
Patent are utilized. This is not the case with a semi-twill weave
fabric. If a monofilament, polymeric fiber, semi-twill fabric is
subjected to a heat treatment process similar to that disclosed in
the Amneus patent, the knuckles on the conventional face side of
the fabric will become coplanar before the knuckles on the back
side of the fabric have reached a uniform height. Thus, in order
for the knuckles on the back side of the fabric to become coplanar,
the fabric must be subjected to further heat treatment. The
additional heat treatment required to make the knuckle heights on
the back side of the fabric uniform causes the knuckle heights on
the conventional face side of the fabric to again become
non-uniform.
Therefore, the initial warp filament spacing and caliper of a
semi-twill fabric necessary to produce minimum free area and
uniform knuckle heights on the back side of the fabric after heat
treatment are determined experimentally by trial and error.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide a low-density,
bulky and absorbent creped paper structure exhibiting a
diamond-shaped pattern in its surface, said paper structure having
significanty improved softness, surface feel and drape, as well as
significantly improved cross-directional stretch.
It is a further object of the present invention, in a preferred
embodiment, to produce the above mentioned paper structure in
accordance with the teachings of U.S. Pat. No. 3,301,746 by
utilizing the back side of a conventional, monofilament, polymeric
fiber, semi-twill fabric which has been abraded in accordance with
the teachings of U.S. Pat. No. 3,573,164 to imprint the uncompacted
paper web prior to creping.
It is a further object of the present invention, in a preferred
embodiment, to produce a paper structure in accordance with the
teachings of U.S. Pat. No. 3,301,746 wherein a dot-dash pattern is
imprinted on the uncompacted paper web, prior to creping, such that
the long axis of the dash impressions is aligned parallel to the
machine direction and the long axis of the dot impressions is
aligned parallel to the cross-machine direction.
It is another object of the present invention, in a preferred
embodiment, to provide dimensionally heat stable, monofilament,
polymeric fiber, semi-twill fabrics for use in fibrous web
carrying, imprinting, and other fabric using operations, which
monofilament, polymeric fiber, semi-twill fabrics are characterized
by having uniform knuckle heights and minimum free area on their
back side, thus contributing materially to the avoidance of
transfer and contact problems in papermaking and web formation
operations.
It is a further object of the present invention, in a preferred
embodiment, to provide a process for the production of
dimensionally heat stable, monofilament, polymeric fiber,
semi-twill fabrics, which process sets criteria for the weaving and
heat treating operations necessary to achieve uniform knuckle
heights and minimum free area on the back side of said fabrics.
Another object of the present invention, in a preferred embodiment,
is to provide a monofilament, polymeric fiber, semi-twill fabric
for use in papermaking and non-woven web manufacturing operations,
the back surface of which fabric has a total knuckle imprint area
of from about 20 percent to about 50 percent of the total fabric
surface area, as measured in the plane of the knuckles, and which
knuckle imprint area has a surface finish at least equal in
smoothness to the surface finish induced by abrasion with an
abrasive medium having an effective abrasive grain size of less
than about 300 mesh.
It is yet another object of the present invention, in a preferred
embodiment, to provide a monofilament, polymeric fiber, semi-twill
fabric for use in the imprinting and drying sections of a
papermaking machine, the back side of which fabric presents an
increased knuckle area to the moist paper web for use in pressing
the web onto the surface of a dryer while it contributes materially
to the final tensile strength of the dried paper product by
avoiding the rupture of fiber bonds.
SUMMARY OF THE INVENTION
In a preferred embodiment of the present invention, a low density,
soft, bulky and absorbent paper sheet is provided, said paper sheet
exhibiting a diamond-shaped pattern in its surface after creping,
said paper sheet being characterized by having a cross-directional
stretch of from about 2 percent to about 6 percent, as well as
improved softness, surface feel and drape, said paper sheet being
particularly suitable for use in tissue, toweling, and sanitary
products.
The soft, bulky and absorbent paper sheets of the present invention
are produced, in a preferred embodiment, generally in accordance
with the teachings of U.S. Pat. No. 3,301,746 by forming an
uncompacted paper web, supporting said uncompacted paper web on the
back side of a monofilament, polymeric fiber, semi-twill imprinting
fabric having about 20 to about 60 meshes per inch, said imprinting
fabric having been formed from filaments having a diameter of from
about 0.008 inches to about 0.025 inches, the back side of said
fabric having had its knuckle imprint area increased in accordance
with the teachings of U.S. Pat. No. 3,573,164, thermally pre-drying
said uncompacted paper web to a fiber consistency of about 30
percent to about 98 percent, imprinting a dot-dash knuckle pattern
with the back side of said semi-twill imprinting fabric such that
the long axis of the dash impressions in said pattern is aligned
parallel to the machine direction and the long axis of the dot
impressions is aligned parallel to the cross-machine direction of
the pre-dried uncompacted paper web, and final drying and creping
the paper sheet so formed.
In a preferred embodiment of the present invention, the back side
of the monofilament, polymeric fiber, semi-twill imprinting fabric
is prepared in accordance with the teachings of U.S. Pat. No.
3,573,164 by abrading the knuckle surfaces to increase the knuckle
imprint area to between about 20 percent and about 50 percent of
the total fabric surface area, as measured in the plane of the
knuckles, as well as to polish the knuckle surfaces.
In yet another preferred embodiment of the present invention, the
monofilament, polymeric fiber, semi-twill fabric is woven and heat
treated so as to produce a dimensionally heat stable fabric having
uniform knuckle heights and minimum free area on its back side
prior to abrading the knuckle surfaces on the back side of the
fabric.
BRIEF DESCRIPTION OF THE DRAWINGS
While the specification concludes with claims particularly pointing
out and distinctly claiming the subject matter which is regarded as
the present invention, it is believed that the invention will be
better understood from the following description taken in
connection with the accompanying drawings in which:
FIG. 1 is a plan view of an enlarged portion of a conventional
right-hand semi-twill, monofilament, polymeric fiber fabric as
viewed from the back side, i.e., that side of the fabric which
according to the teachings of the prior art does not normally
contact the web. The monofilament, polymeric fiber, semi-twill
fabric is shown prior to any abrasion treatment and prior to use as
an endless or continuous fabric belt in papermaking or non-woven
web manufacturing operations.
FIG. 2 is an enlarged cross-sectional view of the semi-twill fabric
illustrated in FIG. 1, taken looking in the cross-machine direction
(CD) along line 2--2 in FIG. 1, which cross-sectional view
illustrates the higher relative elevation and the smooth knuckle
surfaces of the warp filaments on each side of the fabric.
FIG. 3 is an enlarged cross-sectional view of the semi-twill fabric
illustrated in FIGS. 1 and 2, taken looking in the machine
direction (MD) along line 3--3 in FIG. 1, which cross-sectional
view illustrates the lower relative elevation and the smooth
knuckle surfaces of the woof or weft filaments.
FIG. 4 is a simplified illustration of an enlarged partial plan
view of an uncreped paper sheet which has been imprinted utilizing
the conventional face side of a semi-twill fabric such as is shown
in FIGS. 1 through 3. The long axis of the dot impressions formed
by the warp filaments is aligned parallel to the machine
direction.
FIG. 5 is a simplified illustration of an enlarged partial plan
view of an uncreped paper sheet which has been imprinted utilizing
the back side of a semi-twill fabric such as is shown in FIG. 1
through 3. The long axis of the dash impressions formed by the warp
filaments is aligned parallel to the machine direction.
FIG. 6 is an enlarged cross-sectional view of a monofilament,
polymeric fiber, semi-twill fabric such as is illustrated in FIGS.
1 through 3, taken looking in the cross-machine direction at a
point corresponding to line 2--2 in FIG. 1, after the fabric has
been subjected to a heat treatment process sufficient to produce
uniform knuckle heights on the conventional face side of the
fabric.
FIG. 7 is an enlarged cross-sectional view of the semi-twill fabric
illustrated in FIG. 6, taken looking in the machine direction at a
point corresponding to line 3--3 in FIG. 1.
FIG. 8 is a simplified illustration of an enlarged partial plan
view of an uncreped paper sheet which has been imprinted utilizing
the conventional face side of a monofilament, polymeric fiber,
semi-twill fabric such as is illustrated in FIGS. 6 and 7. The long
axis of the dash impressions formed by the woof or weft filaments
is aligned parallel to the cross-machine direction, while the long
axis of the dot impressions formed by the warp filaments is aligned
parallel to the machine direction.
FIG. 9 is a simplified illustration of an enlarged partial plan
view of an uncreped paper sheet which has been imprinted utilizing
the back side of a semi-twill fabric such as is illustrated in
FIGS. 6 and 7. The long axis of the dash impressions formed by the
warp filaments is aligned parallel to the machine direction.
FIG. 10 is an enlarged cross-sectional view of a monofilament,
polymeric fiber, semi-twill fabric such as is illustrated in FIGS.
1 through 3 and 6 and 7, taken looking in the cross-machine
direction at a point corresponding to line 2--2 in FIG. 1, after
the fabric has been subjected to a heat treatment process
sufficient to produce uniform knuckle heights and minimum free area
on the back side of the fabric. It should be noted that at this
point, the knuckle heights on the conventional face side of the
fabric are no longer uniform.
FIG. 11 is an enlarged cross-sectional view of the semi-twill
fabric illustrated in FIG. 10, taken looking in the machine
direction at a point corresponding to line 3--3 in FIG. 1.
FIG. 12 is a simplified illustration of an enlarged partial plan
view of an uncreped paper sheet which has been imprinted utilizing
the conventional face side of a semi-twill fabric such as is
illustrated in FIGS. 10 and 11. The long axis of the dash
impressions formed by the woof or weft filaments is aligned
parallel to the cross-machine direction.
FIG. 13 is a simplified illustration of an enlarged partial plan
view of an uncreped paper sheet which has been imprinted utilizing
the back side of a semi-twill fabric such as is illustrated in
FIGS. 10 and 11. The long axis of the dash impressions formed by
the warp filaments is aligned parallel to the machine direction,
while the long axis of the dot impressions formed by the woof or
weft filaments is aligned parallel to the cross-machine direction.
The dot impressions are present at this stage due to the fact that
the knuckles on the back side of the fabric are of uniform
height.
FIG. 14 is an enlarged cross-sectional view of a monofilament,
polymeric fiber, semi-twill fabric such as is illustrated in FIGS.
10 and 11, taken looking in the cross-machine direction at a point
corresponding to line 2--2 in FIG. 1, after the back side of the
fabric has been abraded to increase its knuckle imprint area.
FIG. 15 is an enlarged cross-sectional view of the semi-twill
fabric illustrated in FIG. 14, taken looking in the machine
direction at a point corresponding to line 3--3 in FIG. 1.
FIG. 16 is a plan view of an enlarged portion of the monofilament,
polymeric fiber, semi-twill fabric illustrated in FIGS. 14 and 15,
as viewed from the back side of the fabric.
FIG. 17 is a plan view photograph, enlarged about 12 times actual
size, of an uncreped paper sheet which has been imprinted utilizing
the back side of a semi-twill fabric such as is shown in FIGS. 14,
15, and 16. The pattern produced is similar to that shown in FIG.
13, but the dot-dash impressions constitute a greater percentage of
the surface area of the paper due to the increased knuckle imprint
area of the fabric.
FIG. 18 is an illustration of an enlarged cross-sectional view of
the uncreped paper sheet of FIG. 17, taken looking in the
cross-machine direction along line 18--18 in FIG. 17.
FIG. 19 is a plan view photograph, enlarged about 6 times actual
size, of a paper sheet such as is shown in FIGS. 17 and 18 after
creping. The long axis of the impressions visible after creping is
oriented generally in the cross-machine direction, while the
overall surface of the paper exhibits a diamond-shaped pattern
characteristic of paper sheets made in accordance with the present
invention.
FIG. 20 is an illustration of an enlarged cross-section view of the
creped paper sheet of FIG. 19, taken looking in the cross-machine
direction along line 20--20 in FIG. 19.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In describing preferred embodiments of the invention disclosed
herein, specific terminology will be adhered to for the sake of
clarity in referring to the features of the monofilament, polymeric
fiber fabrics for use in papermaking and non-woven web
manufacturing processes. The conventional face side of the
semi-twill fabrics referred to herein refers to that side of the
fabric which, according to the teachings of the prior art, would
normally come in contact with the paper web, i.e., the sides of the
semi-twill fabric which would, depending upon its particular
condition, produce one of the imprint patterns illustrated in FIGS.
4, 8 or 12 (assuming it is a right-hand semi-twill fabric). In the
aforementioned FIGS. the long axis of the dash impressions 9, where
present, is aligned parallel to the cross-machine direction, while
the long axis of the dot impressions 3, where present, is aligned
parallel to the machine direction. The "back" side of the
semi-twill fabrics referred to herein shall be defined as that side
which would not normally contact the paper web according to the
teachings of the prior art, i.e., the side of the semi-twill fabric
which would, depending upon its particular condition, produce one
of the imprint patterns illustrated in FIGS. 5, 9, 13, or 17
(assuming it is a right-hand semi-twill fabric). In the
aforementioned figures, the long axis of the dash impressions 8 is
aligned parallel to the machine direction, while the long axis of
the dot impressions 10, where present, is aligned parallel to the
cross-machine direction.
It should be noted that although a right-hand semi-twill fabric is
utilized for purposes of illustration throughout this
specification, the benefits disclosed can also be obtained
utilizing a left-hand semi-twill fabric, which is woven as a mirror
image of a right-hand semi-twill fabric.
FIG. 1 represents an enlarged plan view of a portion of a
conventional right-hand, monofilament, polymeric fiber, semi-twill
fabric as viewed from the back side. The semi-twill fabric
illustrated in FIG. 1 has not been used on a paper machine nor has
it been accorded any special abrading treatment. The warp
monofilaments 1 are aligned parallel to the machine direction,
while the woof or weft monofilaments 2 are aligned parallel to the
cross-machine direction. In a preferred embodiment of the present
invention, the imprinting fabric illustrated in FIG. 1 has about 20
to about 60 meshes per inch and is formed from monofilament
polymeric fibers having diameters ranging from about 0.008 inches
to about 0.025 inches. Both warp and woof monofilaments may, but
need not necessarily be of the same diameter. FIGS. 2 and 3 are
cross-sectional views of the semi-twill fabric illustrated in FIG.
1, taken looking respectively in the cross-machine and machine
directions. The knuckles formed at the cross-over points of the
warp filaments 1 and the woof filaments 2 are not coplanar on
either the face or the back side of the fabric. As can be seen in
FIGS. 2 and 3, the warp filaments 1 are at a higher relative
elevation than the woof filaments 2 on both sides of the fabric.
This is termed, for purposes of this specification, a "warp-high"
condition of the fabric.
FIG. 4 is a simplified illustration of the knuckle imprint pattern
which would result if a semi-twill fabric such as is illustrated in
FIGS. 1 through 3 were installed so that the conventional face side
of the fabric were utilized to imprint an uncreped paper web
produced in accordance with the teachings of U.S. Pat. No.
3,301,746 issued to Sanford et al. on Jan. 31, 1967, said patent
being incorporated herein by reference. The dot impressions 3
visible on the surface of such an uncreped paper sheet after
imprinting form a pattern corresponding to the knuckles 4 of the
warp filaments 1 on the conventional face side of the fabric. Since
the dot impressions 3 are formed by the warp filaments 1, the long
axis of the dot impressions is aligned parallel to the machine
direction. The knuckles 7 formed by the woof filaments 2 on the
conventional face side of the fabric do not form a corresponding
impression in the uncompacted paper web due to the fact that they
are at a lower relative elevation than the warp filament knuckles
4.
FIG. 5 illustrates the knuckle imprint pattern which would result
if an uncompacted paper web produced in accordance with the
teachings of U.S. Pat. No. 3,301,746 were imprinted utilizing the
back side of an imprinting fabric such as is illustrated in FIGS. 1
through 3. Because the warp filaments 1 are at a higher relative
elevation than the woof filaments 2 on the back side of the fabric,
only the peaks of the knuckles 5 formed by the warp filaments are
impressed into the paper web during the imprinting process. Since
the warp filaments 1 run in the machine direction, the resulting
pattern consists of a series of relatively long dash impressions 8,
wherein the long axis of the impressions is aligned parallel to the
machine direction.
The imprint pattern illustrated in FIG. 5 differs from the imprint
pattern illustrated in FIG. 4 in two important respects. First,
since each warp filament 1 passes over two woof filaments 2 on the
back side of the semi-twill fabric as compared to only one woof
filament 2 on the face side of the fabric, the length of the
impressions is approximately twice as great when the web is
imprinted with the back side of the fabric. Secondly, when a paper
web imprinted with the pattern illustrated in FIG. 5 is removed
from the drying drum by means of a conventional doctor blade, a
diamond-shaped pattern is imparted to the surface of the paper,
whereas when a paper web imprinted with the pattern illustrated in
FIG. 4 is removed from the drying drum by means of a conventional
doctor blade, a regulated creping pattern results in which the
crepe ridges are substantially unbroken across the width of the
sheet. This characteristic difference in finished product appears
to be due to the fact that the web illlustrated in FIG. 4 is
adhered to the dryer drum only at interrupted intervals, i.e., by
the dot impressions 3, which impressions are not sufficiently long
to overlap each other in the machine direction. The paper web
illustrated in FIG. 5, on the other hand, is adhered to the dryer
drum in a continuous fashion, i.e., by the dash impressions 8,
which impressions are sufficiently long to overlap each other in
the machine direction.
Based on the teachings of the prior art, and particularly on U.S.
Pat. No. 3,473,576 issued to Amneus on Oct. 21, 1969, said patent
being incorporated herein by reference, it is recognized that
smooth web transfers and maximum drying effectiveness are not
realized with fabrics having rough or inconsistent web contacting
surfaces. Smooth web transfers are particularly desirable where, as
in the case of the papermaking process disclosed in U.S. Pat. No.
3,301,746, the imprinting fabric is of product characteristic
importance. It has, therefore, been found desirable to utilize
imprinting fabrics having uniform knuckle heights and minimum free
or interstitial area on the side of the fabric contacting the
uncompacted paper web. Because such imprinting fabrics are
subjected to elevated temperatures during use, it has also been
found desirable to dimensionally heat stabilize such fabrics prior
to use to prevent warpage.
It is important to note that due to the symmetry of a plain weave
fabric, uniform knuckle heights and minimum free area achieved
simultaneously on both sides of the fabric when the fabric is
subjected to a heat treatment process such as that disclosed in
U.S. Pat. No. 3,473,576. This is not the case with a semi-twill
weave fabric. If a monofilament, polymeric fiber, semi-twill fabric
is subjected to a heat treatment process such as that disclosed in
U.S. Pat. No. 3,473,576, the knuckles 4 and 7 on the conventional
face side of the fabric will become coplanar before the knuckles 5
and 6 on the back side of the fabric. In order for the knuckles 5
and 6 on the back side of the fabric to reach uniform heights, the
fabric must be subjected to further heat treatment. The additional
heat treatment in turn causes the heights of the knuckles 4 and 7
on the conventional face side of the semi-twill fabric to again
become non-uniform.
Therefore, the initial warp filament spacing and caliper of a
semi-twill fabric necessary to produce minimum free area and
uniform knuckle heights on the back side of the fabric after heat
treatment is determined experimentally by trial and error.
In a preferred embodiment of the present invention, a monofilament,
polymeric fiber, semi-twill fabric is prepared by selecting warp
monofilaments having a relatively high heat-induced shrinkage
potential in the range of about 10 percent to about 30 percent,
preferably about 16 percent. After selecting and spacing the warp
monofilaments, polymeric woof monofilaments are selected which have
a relatively low heat-induced shrinkage potential in the range of
about 2 percent to about 8 percent, preferably about 4 percent. The
heat shrinkage treatment takes advantage of the aforementioned
shrinkage characteristics of the warp and woof monofilaments. The
heat shrinkage treatment comprises subjecting the initially woven
fabric to a series of heat applications as it is stretched and
secured at its ends in the lengthwise or warp direction, while it
is free to shrink in the woof direction.
The heat shrinkage treatment is conveniently applied to the
initially woven semi-twill fabric while the fabric is mounted as an
endless belt on a finishing table such as those conventionally used
in finishing metal Fourdrinier wires. A conventional wire finishing
table consists of two adjustable rolls for supporting, tensioning
and driving the wire or fabric to be finished as an endless belt.
The heat shrinkage can be induced conveniently by an infrared
source mounted as a bank above and across the initially woven
fabric. The infrared source heats areas of the initially woven
fabric as the fabric slowly revolves on the rolls of the wire
finishing table. Heat is applied to the fabric in successive
treatments of about 5 seconds to about 40 seconds, preferably about
15 seconds, per treatment. The fabric temperatures during the
successive applications of heat approach gradually the softening
point of the selected monofilament polymeric fibers. Multiple
passes are used to avoid sudden shrinkage which induces fabric
wrinkles. Successive heat treatments are repeated until the knuckle
heights on the back side of the fabric reach uniformity, which
condition should also correspond to minimum free or interstitial
area if the initial warp filament spacing and caliper of the fabric
have been properly determined. A semi-twill fabric which has been
subjected to the aforementioned heat treatment process, although
not locked-up as in the case of a plain weave fabric subjected to
such a heat treatment process, is dimensionally heat stable at the
temperatures encountered in the web imprinting process disclosed in
U.S. Pat. No. 3,301,746. 3,301,746.
The temperature of the fibers in the successive heat treating
passes is increased to a maximum temperature immediately below the
softening point of the selected fibers. For example, the heat
treating temperature used with Treviera fibers is about 360.degree.
to about 400.degree.F, preferably about 375.degree.F. For
dimensional heat stability in use as an imprinting fabric is
accordance with the teachings of U.S. Pat. No. 3,301,746, a
sufficient number of successive heating treatments or passes are
employed to insure that the monofilament polymeric fibers making up
the fabric structure have been at the highest heat treating
temperature for a total time of about 15 to about 120 seconds.
Contrary to expectation, a weaving procedure wherein polymeric warp
and woof monofilaments are merely woven as tightly as possible to
insure a minimum free area will not result in a fabric with uniform
knuckle heights after heat treating or use in web drying systems.
Polymeric fibers in general exhibit heat shrinkage, and if such a
tight weaving procedure involving initial minimum spacing in both
polymeric warp and woof monofilaments is attempted, the resulting
heat treated and heat stabilized fabric will exhibit non-uniform
knuckle heights. Therefore, in a preferred embodiment of the
present invention, an initial warp filament spacing in the loom and
an initial caliper of the semi-twill fabric are determined
experimentally by trial and error to take into account the
heat-induced shrinkage which occurs during the above described
dimensional heat stabilization process.
FIGS. 6 and 7 are enlarged cross-sectional views of a monofilament,
polymeric fiber, semi-twill fabric such as is illustrated in FIGS.
1 through 3 after a heat treatment process such as that described
above has been initiated. FIG. 6 is taken looking in the
cross-machine direction at a point corresponding to line 2--2 in
FIG. 1, while FIG. 7 is taken looking in the machine direction at a
point corresponding to line 3--3 in FIG. 1. FIGS. 6 and 7 represent
an intermediate condition of the fabric which occurs during the
heat treatment process, prior to achieving uniform knuckle heights
and minimum free area on the back side of the fabric. FIG. 6
represents the condition which results when the warp filaments 1
tend to draw themselves closer to a straight line due to the heat
induced shrinkage. The tendency of the warp filaments 1 to assume a
lower total amplitude, due to the heat-induced shrinkage, forces
the woof monofilaments 2 on the conventional face side of the
fabric downwardly and the woof monofilaments 2 on the back side of
the fabric upwardly since the ends of the woof monofilaments are
not restrained. This is more clearly illustrated in FIG. 7, wherein
the woof monofilaments 2 tend to wrap themselves more completely
about the warp monofilaments 1. As a result, the knuckles 7 formed
by the woof monofilaments 2 become coplanar with the knuckles 4
formed by the warp monofilaments 1 located on the conventional face
side of the fabric. It should be noted that, at this particular
point, the knuckles 5 formed by the warp monofilaments 1 remain at
a higher relative elevation than the knuckles 6 formed by the woof
monofilaments 2 on the back side of the fabric.
FIG. 8 is a simplified illustration of an enlarged partial plan
view of an uncreped paper sheet produced in accordance with the
teachings of U.S. Pat. No. 3,301,746, which uncreped paper sheet
has been imprinted utilizing the conventional face side of a
monofilament, polymeric fiber, semi-twill fabric such as is
illustrated in FIGS. 6 and 7. The knuckle imprint pattern is
similar to that shown in FIG. 4 wherein the dot impressions 3
formed by the knuckles 4 of the warp monofilaments 1 on the
conventional face side of the fabric are illustrated, but the dash
impressions 9 formed by the knuckles 7 of the woof monofilaments 2
are also present. Because the woof monofilaments 2 are aligned
parallel to the cross-machine direction, the long axis of the dash
impressions 9 is also aligned parallel to the cross-machine
direction.
FIG. 9 is a simplified illustration of an enlarged partial plan
view of an uncreped paper sheet produced in accordance with the
teachings of U.S. Pat. No. 3,301,746, which uncreped paper sheet
has been imprinted utilizing the back side of a semi-twill fabric
such as is illustrated in FIGS. 6 and 7. As in FIG. 5, the long
axis of the dash impressions 8 formed by the knuckles 5 of the warp
monofilaments 1 is aligned parallel to the machine direction.
As with paper sheets imprinted with the pattern illustrated in FIG.
4, paper sheets utilizing the imprinting pattern illustrated in
FIG. 8 exhibit a basic regularity of creping wherein the crepe
ridges extend substantially uninterrupted across the entire width
of the sheet. Addition of the dash impressions 9 to the imprinting
pattern does not alter the fact that the imprinted paper sheet is
adhered to the dryer drum only at interrupted intervals
corresponding to the spacing, in the machine direction, of the dot
impressions 3. Paper sheets imprinted with the pattern illustrated
in FIG. 9, on the other hand, exhibit a diamond-shaped pattern
characteristic of paper sheets made in accordance with the present
invention when doctored from the dryer drum.
In order to obtain uniform knuckle heights and minimum free area on
the back side of a semi-twill fabric such as is illustrated in
FIGS. 6 and 7, as is desired in a preferred embodiment of the
present invention, the heat treatment process is continued until a
condition similar to that illustrated in FIGS. 10 and 11 is
achieved. FIG. 10 is taken looking in the cross-machine direction
at a point corresponding to line 2--2 in FIG. 1, while FIG. 11 is
taken looking in the machine direction at a point corresponding to
line 3--3 in FIG. 1. Heat-induced shrinkage of the warp
monofilaments 1, as shown in FIG. 10, has produced a lower total
amplitude causing the woof monofilaments 2 on the back side of the
fabric to move upwardly and the woof monofilaments 2 on the
conventional face side of the fabric to move downwardly. As can be
seen in FIG. 11, the woof monofilaments 2 which, unlike the warp
monofilaments 1, are not subjected to tension tend to wrap
themselves more completely about the warp monofilaments 1 located
on the conventional face side of the fabric. Simultaneously, the
woof monofilaments 2 tend to "belly" or gradually wrap themselves
about the two adjacent warp monofilaments 1 located on the back
side of the fabric. As a result, the heights of the warp
monofilament knuckles 5 on the back side of the fabric and the woof
monofilament knuckles 6 on the back side of the fabric become
uniform, while the heights of the woof monofilament knuckles 7 on
the conventional face side of the fabric and the warp monofilament
knuckles 4 on the conventional face side of the fabric become
non-uniform. If the initial warp filament spacing in the loom and
the initial caliper or thickness of the semi-twill fabric have been
properly determined to take into account the heat-induced
shrinkage, the condition illustrated in FIGS. 10 and 11 should
result, i.e., a dimensionally heat stabilized semi-twill fabric
having uniform knuckle heights as well as minimum free area on its
back side.
FIG. 12 is a simplified illustration of an enlarged partial plan
view of an uncreped paper sheet made in accordance with the
teachings of U.S. Pat. No. 3,301,746, which uncreped paper sheet
has been imprinted utilizing the conventional face side of a
semi-twill fabric such as is illustrated in FIGS. 10 and 11. The
imprinting pattern is basically similar to that shown in FIG. 8,
but the dot impressions 3 formed by the warp monofilament knuckles
4 on the conventional face side of the fabric are no longer present
due to the fact that the warp monofilament knuckles 4 are at a
lower relative elevation than the woof monofilament knuckles 7 on
the conventional face side of the fabric. Paper sheets imprinted
with the pattern illustrated in FIG. 12 exhibit properties
substantially similar to sheets imprinted with the patterns shown
in FIGS. 4 and 8 after creping.
FIG. 13 is a simplified illustration of an enlarged partial plan
view of an uncreped paper sheet produced in accordance with the
teachings of U.S. Pat. No. 3,301,746, which uncreped paper sheet
has been imprinted utilizing the back side of a semi-twill fabric
such as is illustrated in FIGS. 10 and 11. The dash impressions 8
formed by the warp filament knuckles 5 on the back side of the
fabric are essentially the same as those illustrated in FIG. 8, but
the dot impressions 10 formed by the woof monofilament knuckles 6
on the back side of the fabric are also present due to the fact
that the warp filament knuckles 5 and the woof filament knuckles 6
on the back side of the fabric are of uniform height. Paper sheets
produced utilizing the back side of a semi-twill fabric such as is
illustrated in FIGS. 10 and 11 for imprinting purposes exhibit a
diamond-shaped surface appearance after creping, which surface
appearance is characteristic of paper sheets made in accordance
with applicant's invention. As the knuckle imprint area on the back
side of such a monofilament, polymer fiber, semi-twill fabric is
increased, the diamond-shaped pattern becomes more pronounced.
Applicant has discovered that increasing the knuckle imprint area
on the back side of such a fabric also produces certain unexpected
improvements in finished sheet characteristics. These unexpected
improvements take the form of greater cross-directional stretch, as
well as improved softness, surface feel and drape. Increasing the
knuckle imprint area on the convenional face side of a similar
monofilament, polymeric fiber, semi-twill imprinting fabric does
not, however, yield similar improvements in finished sheet
characteristics. This is likewise true of plain weave imprinting
fabrics. Applicant has thus learned unexpectedly that the above
mentioned improvements in sheet characteristics are uniquely
achievable by increasing the knuckle imprint area on the back side
of a conventional monofilament, polymeric fiber, semi-twill
imprinting fabric.
One method of increasing the knuckle imprint area of a
monofilament, polymeric fiber fabric is disclosed in U.S. Pat. No.
3,573,164 issued to Friedberg et al. on Mar. 30, 1971, said patent
being incorporated herein by reference, wherein the knuckle
surfaces are abraded with a fine abrasive medium to improve web
transfer, web drying, web product characteristics and general
machine operation. In a preferred embodiment of the present
invention, the monofilament, polymeric fiber, semi-twill imprinting
fabric to be abraded is brought to the condition illustrated in
FIGS. 10 and 11, i.e., uniform knuckle heights and minimum free
area on its back side, prior to initiating any abrading treatment.
Although the abrasion treatment disclosed in the aforementioned
Friedberg et al. patent will produce uniform knuckle heights on a
fabric which does not initially have uniform knuckle heights, it is
most desirable, in a preferred embodiment of the present invention,
to utilize a fabric initially having uniform knuckle heights on the
side to be treated to minimize the possibility of abrading
completely through one or more monofilaments during the abrading
process. Therefore, the back side of a fabric such as is shown in
FIGS. 10 and 11 can undergo a more extensive abrading process, thus
producing a greater increase in knuckle imprint area than is
permissible with a fabric initially having non-uniform knuckle
heights on the side to be treated.
As mentioned earlier in this specification, it has been found
desirable that monofilament, polymeric fiber fabrics be
dimensionally heat stabilized prior to use. Failure to do so can
cause warpage after the fabric has been placed in service and
subjected to elevated temperatures. Thus, to realize the full
benefits to be obtained by the abrading process, it is most
desirable, in a preferred embodiment of the present invention, that
the semi-twill fabric be dimensionally heat stabilized in
accordance with the procedures described in this specification
prior to initiating the abrading treatment.
In accordance with the teachings of the aforementioned Friedberg et
al. patent, the back side of a monofilament, polymeric fiber,
semi-twill imprinting fabric, in a preferred embodiment of the
present invention, is subjected to a treatment wherein the knuckle
surfaces of the fabric are abraded using either a wet or dry
sandpaper having an effective abrasive grain size of about 300 mesh
to about 500 mesh as an abrasive medium. The abrasive media can be
mounted on drums for rotative application to the fabric knuckle
surfaces. The abrading process can be performed while continuously
showering the fabric with water or other cleansing and lubricating
fluid, for example light oil, to remove abraded particles and
facilitate the polishing operation.
In a preferred embodiment of the present invention, a total knuckle
imprint area of about 20 percent to about 50 percent of the total
fabric surface area, as measured in the plane of the knuckles, is
developed on the treated surface. Increasing the knuckle imprint
area beyond the 50 percent level greatly increases the danger of
abrading completely through particular monofilaments and is also
likely to have a detrimental effect on the fabric life.
In yet another preferred embodiment of the present invention, it is
desirable to form a smooth and polished surface on the knuckles on
the back side of the monofilament, polymeric fiber semi-twill
fabric. To this end, the above described abrading operation can be
conducted in several stages. For example, the initial abrasion can
be carried out with an abrasive medium having an effective abrasive
grain size of about 300 mesh, and this initial abrading operation
can be followed by an abrasive polishing treatment using a water
lubricated wet sandpaper having an effective abrasive grain size of
about 500 mesh. Polishing abrasives such as talc, rouge and crocus
cloth can also be used to further polish the knuckle surfaces.
FIGS. 14 and 15 are enlarged cross-sectional views of a
monofilament, polymeric fiber, semi-twill fabric such as is
illustrated in FIGS. 10 and 11 after the back side of the fabric
has been abraded to increase its knuckle imprint area to between
about 20 percent and about 50 percent of the total fabric surface
area, as measured in the plane of the knuckles. FIG. 16 is a plan
view of an enlarged portion of the fabric illustrated in FIGS. 14
and 15, as viewed from the back side of the fabric. The fabric
illustrated in FIGS. 14 through 16 represents a preferred
embodiment of the present invention, wherein uniform knuckle
heights and minimum free area were achieved on the back side of the
fabric prior to initiating the abrading process. An inherent
advantage associated with obtaining uniform knuckle heights and
minimum free area prior to initiating the abrading treatment is in
the uniform consistency of the knuckle imprint pattern which
results after the abrading process has been completed. This latter
feature is most clearly illustrated in FIG. 16.
FIGS. 14 and 15, taken looking in the cross-machine and machine
directions respectively, illustrate the fabric profile which is
presented to an uncompacted paper web when the fabric is utilized
for imprinting purposes in accordance with the teachings of U.S.
Pat. No. 3,301,746. The warp filament knuckles 5 and the woof
filament knuckles 6 as shown in FIGS. 10 and 11 have been abraded
to form the plateau-like warp filament knuckles 5' and woof
filament knuckles 6' illustrated in FIGS. 14 and 15. In addition to
improving web transfer and web drying characteristics, the
plateau-like knuckle surfaces 5' and 6' impress an uncompacted
paper web to a uniform depth, thus producing a more distinct
imprint pattern.
The moist paper web carried on an imprinting fabric of the present
invention can be thermally pre-dryed by means of passing hot gases,
for example air, through the moist paper web and the imprinting
fabric. One suitable apparatus for pre-drying the moist paper web
is disclosed in U.S. Pat. No. 3,303,576 issued to Sisson on Feb.
14, 1967, which patent is incorporated herein by reference.
Although the means by which thermal pre-drying is accomplished is
not critical, it is critical that the relationship of the moist web
to the imprinting fabric be maintained once established.
According to the teachings of U.S. Pat. No. 3,301,746, thermal
pre-drying is used to effect a fiber consistency in the moist paper
web from about 30 percent to about 80 percent, preferably about 40
percent to about 80 percent. The aforementioned Sanford et al.
patent further teaches that at fiber consistencies less than about
30 percent, the desirably balanced sheet characteristics of
softness, bulk and absorbency suffer because the sheet and the
fibers thereof are two moist, and yielding occures during the
imprinting step. The aforementioned Sanford et al. patent also
teaches that pre-drying to fiber consistencies above about 80
percent precludes the development of effective tensile strengths in
the imprinted paper sheet.
Based on the Sanford et al. patent and the application of Gregory
A. Bates, Ser. No. 452,610 filed Mar. 19, 1974 and entitled
TRANSFER AND ADHERENCE OF RELATIVELY DRY PAPER WEB TO A ROTATING
CYLINDRICAL SURFACE, said application being commonly owned by the
assignee of the present invention and incorporated herein by
reference, it is now known that fiber consistencies between about
30 percent and about 98 percent prior to transfer of the web to the
drying drum are possible without adversely affecting the tensile
strength of paper sheets thus produced. Fiber consistencies in the
higher end of the range, i.e., above about 80 percent, are now
known to be a function of the adhesive sprayed on the surface of
the drying drum prior to web transfer, as explained in detail in
the aforementioned application of Bates.
Imprinting the fabric knuckle pattern in the moist web by pressing
the pre-dryed web against a relatively non-yielding surface, for
example, an unheated steel roll or a Yankee dryer surface, while
the pre-dryed web is yet carried on the imprinting fabric results
in a paper sheet having impressed in its surface, to a depth of at
least 30 percent of its machine glazed caliper the knuckle pattern
of the imprinting fabric. Machine glazed claiper refers to the
caliper of the paper sheet taken directly from the Yankee dryer,
before creping. Thus, the knuckle surfaces 5' and 6', illustrated
in FIGS. 14 through 16 in a preferred embodiment of the present
invention, are impressed to a uniform depth of at least 30 percent
of the machine glazed caliper of the uncreped paper sheet.
The pressure required for the imprinting of the imprinting fabric
pattern can be provided, in a preferred embodiment of the present
invention, by one or more pressure rolls operating on the
imprinting fabric to force the knuckles of the fabric into the
surface of the pre-dryed web and to force the pre-dryed web surface
under the knuckles against a Yankee dryer surface.
It should be understood that it is critical to the practice of the
present invention that the imprinting step described above be the
first substantial overall mechanical compaction step which the
paper web has received during formation and pre-drying.
FIG. 17 is a photograph of an enlarged partial plan view of an
uncreped paper sheet made in accordance with the teachings of U.S.
Pat. No. 3,301,746, utilizing the back side of a semi-twill fabric
such as is illustrated in FIGS. 14 through 16 to imprint the
uncompacted paper web. The resulting knuckle imprint pattern is
basically similar to that shown in FIG. 13. However, the dash
impressions 8 formed by the warp filament knuckles 5' and the dot
impressions 10 formed by the woof filament knuckles 6' constitute a
greater percentage of the sheet's surface area due to the increase
in the size of the fabric knuckles. In addition, the impressions 8
and 10 are more distinct due to the fact that they are of
substantially uniform depth, having been produced by the
plateau-like surfaces of the knuckles 5' and 6'.
FIG. 18 is an illustration of an enlarged cross-sectional view of
the uncreped paper sheet of FIG. 17, taken looking in the
cross-machine direction along line 18--18 in FIG. 17.
FIG. 19 is a photograph of an enlarged partial plan view of a
creped paper sheet made in accordance with the teachings of U.S.
Pat. No. 3,301,746, utilizing the back side of a semi-twill fabric
such as is illustrated in FIGS. 14 through 16 to imprint the
uncompacted paper web prior to creping. The long axis of the
impressions 11 visible after creping appears to be oriented
generally in the cross-machine direction. Unlike paper sheets made
in accordance with the teachings of the aforementioned Sanford et
al. patent utilizing either a similarly prepared plain weave
imprinting fabric or the conventional face side of a similarly
prepared semi-twill imprinting fabric, the overall surface of the
paper exhibits a diamond-shaped pattern rather than uniform
unbroken creping ridges extending across the width of the
sheet.
FIG. 20 is an illustration of an enlarged cross-sectional view of
the paper sheet of FIG. 19, taken looking in the cross-machine
direction along line 20--20 in FIG. 19.
A finished paper sheet such as is illustrated in FIGS. 19 and 20,
produced in accordance with the present invention, exhibits
improvements in cross-directional stretch, softness, surface feel
and drape which are not achievable by the paper manufacturing
process disclosed in U.S. Pat. No. 3,301,746 when a similarly
prepared plain weave fabric or when the conventional face side of a
similarly prepared semi-twill fabric are utilized to imprint an
uncompacted paper web prior to creping. Increasing the knuckle
imprint area on a plain weave fabric or on the conventional face
side of a semi-twill fabric, although improving web transfer and
web drying characteristics, does not produce the improvements in
cross-directional stretch, softness, surface feel and drape which
are realized by increasing the knuckle imprint area on the back
side of a semi-twill imprinting fabric.
From the foregoing general and specific description of the present
process, it is apparent that the critical procedures to be carried
out are the formation of an uncompacted paper web at a specified
range of fiber consistency and the imprinting thereof by the
knuckles on the back side of a monofilament, polymeric fiber,
semi-twill imprinting fabric, said fabric having a knuckle imprint
area constituting about 20 percent to about 50 percent of the total
surface area on the back side of the fabric, as measured in the
plane of the knuckles. The formation of the paper web and the final
drying techniques together with the pre-drying imprinting and
creping procedures can be varied by one skilled in the art to
produce distinctive papers for various uses while remaining within
the scope of this invention.
By the foregoing procedures, creped paper sheets exhibiting a
diamond-shaped surface appearance, composed substantially of
cellulosic fibers, having basic weights of from about 5 to about 40
pounds per 3000 square feet, and exhibiting a repeating pattern of
discrete impressed areas are produced.
In order to demonstrate the improvements characteristic of finished
product made in accordance with applicant's invention, a series of
test runs were made to compare the characteristics of paper sheets
made in accordance with the teachings of U.S. Pat. No. 3,301,746,
utilizing different sides of a monofilament, polymeric fiber,
semi-twill fabric. Paper machine conditions, with the exception of
the imprinting fabric, were maintained constant for the entire
series of tests.
Furnish comprised of a 50 percent softwood kraft and a 50 percent
hardwood sulfite stock was utilized throughout the entire series of
tests.
An adhesive coat was applied to the Yankee dryer surface by
utilizing a wire glue roll of approximately 40 mesh turning at a
lineal speed of approximately 9 feet per minute at its periphery in
an open glue pot and then spraying the glue picked up on the wire
mesh glue roll onto the surface of the Yankee dryer drum by means
of a series of air jets located interiorly of the glue roll and
operating continuously at an air pressure of 75 p.s.i.g. The glue
utilized was purchased under the specification Peter Cooper IX from
the Peter Cooper Corporation of Gowanda, New York. The mixture, as
applied, contained 1 part glue and 99 parts water. The pre-dryed
and imprinted web was caused to part from the imprinting fabric at
the pressure nip exit and adhere to the Yankee dryer surface by
means of the adhesive coat described above.
The dry creped sheet was removed from the Yankee dryer by means of
a conventional doctor blade so that the finished product had 12
percent stretch as crepe folds.
Two separate monofilament, polymeric fiber, semi-twill fabrics were
utilized during the test runs. The fabrics were both 31 (machine
direction) by 28 (cross-machine direction) mesh utilizing warp and
woof monofilaments having a diameter of 0.45 mm. (about 0.018
inches). One of the fabrics was woven so as to present its back
side as a web contacting surface and the other was woven so as to
present its conventional face side as a web contacting surface.
Both of the fabrics, as received, were in a configuration similar
to that illustrated in FIGS. 10 and 11, i.e., the heights of the
warp filament knuckles 5 and the woof filament knuckles 6 on the
back side of each fabric were approximately equal, while the warp
filament knuckles 4 were at a lower relative elevation than the
woof filament knuckles 7 on the conventional face side of each
fabric.
In order to isolate the effect of the imprinting fabrics on
finished sheet characteristics, the fabrics were installed
successively on the same paper machine in the as-received
condition, and paper sheets were produced in accordance with the
teachings of U.S. Pat. No. 3,301,746.
The fabric woven so as to present its back side as a web contacting
surface was found to have an initial knuckle imprint area of about
21.2 percent in the as-received condition, while the fabric woven
so as to present its conventional face side as a web contacting
surface was found to have a knuckle imprint area of about 23.4
percent in the as-received condition.
Data taken from paper samples made utilizing the imprinting fabric
having its back side in contact with the uncompacted paper web is
reported hereinbelow under Example I. Data taken from paper samples
made utilizing the imprinting fabric having its conventional face
side in contact with the uncompacted paper web is reported
hereinbelow under Example II. With the exception of the imprinting
fabrics, the paper machine conditions were unchanged between
Examples I and II.
To illustrate the effect of increasing the knuckle imprint area on
the web contacting side of the imprinting fabrics, each fabric was
abraded in accordance with the teachings of U.S. Pat. No.
3,573,164. The knuckle imprint area on the fabric utilizing its
back side as a web contacting surface was increased from
approximately 21.2 percent to approximately 28.4 percent, while the
knuckle imprint area of the fabric utilizing its conventional face
side as a web contacting surface was increased from approximately
23.4 percent to approximately 34.1 percent. The tests were repeated
keeping all paper machine conditions, other than the increased
knuckle imprint area of the fabrics, unchanged. The results of
tests performed on sample paper sheets taken during each run are
tabulated hereinbelow under Examples III and IV. The data set forth
in Example III is taken from sample sheets made utilizing the
semi-twill imprinting fabric which presented its back side to the
uncompacted paper web, while the data set forth in Example IV is
taken from sample sheets made utilizing the semi-twill fabric which
presented its conventional face side to the uncompacted paper
web.
Finally, the knuckle imprint area of each fabric was further
increased in accordance with the teachings of U.S. Pat. No.
3,573,164 until the fabric utilizing its back side as a web
contacting surface achieved a total knuckle imprint area of 37.3
percent, while the fabric utilizing its conventional face side as a
web contacting surface achieved a total knuckle imprint area of
40.0 percent. The tests were repeated keeping all paper machine
conditions, other than the knuckle imprint area of the fabrics,
unchanged. The results of tests performed on sample paper sheets
taken during each run are tabulated hereinbelow under Examples V
and VI. Data set forth in Example V is taken from paper sheets made
utilizing the semi-twill fabric which presented its back side to
the uncompacted paper web, while data set forth in Example VI is
taken from paper sheets made utilizing the semi-twill fabric which
presented its conventional face side to the uncompacted paper
web.
The caliper of a paper sheet at 80 grams per square inch, as
tabulated in the Examples hereinbelow, is the thickness of that
sheet when subjected to a compressive load of 80 grams per square
inch.
The tensile strengths in the machine direction (MD) and
cross-machine direction (CD), as tabulated in the Examples
hereinbelow, are reported as the force in grams that a 1 inch wide
sample with a 4 inch span between the tensile tester clamps, cut in
the MD or CD direction, can withstand before breaking, as measured
on a standard Thwing-Albert Tensile Tester such as is available
from the Thwing-Albert Instrument Company of Philadelphia,
Pennsylvania.
The percentage stretch data tabulated in the Examples hereinbelow
was determined concurrently with the determination of MD and CD
tensile strengths as described above.
A Thwing-Albert Handle-O-Meter, catalogue number 211-3, such as is
available from the Thwing-Albert Instrument Company of
Philadelphia, Pennsylvania, was used to measure a combination of
stiffness and sliding friction of the paper samples. A high
Handle-O-Meter or H-O-M reading indicates a lack of softness and
is, therefore, undesirable. A lower H-O-M reading indicates a
softer sheet. Two 41/2 inch by 41/2 inch paper samples were placed
side by side over the 0.25 inch wide Handle-O-Meter slot located
beneath the blade of the unit. To determine the machine direction
Handle-O-Meter reading of the sheets, the machine direction of the
paper samples was aligned parallel to the Handle-O-Meter blade. To
determine the cross-machine direction Handle-O-Meter reading, the
machine direction of the sample sheets was aligned perpendicular to
the blade of the Handle-O-Meter. Readings taken directly from the
standard 50 micro-ampere meter mounted on the Handle-O-Meter are
reported in the Examples hereinbelow.
In order to quantify sheet properties relating to surface feel and
drape, resort was had to the principles of textile testing. Fabric
handle, as its name implies, is concerned with the feel of the
material and so depends on the sense of touch. When the handle of a
fabric is judged, the sensations of stiffness or limpness, hardness
of softness, and roughness or smoothness are all made use of. Drape
has a rather different meaning and very broadly is the ability of a
fabric to assume a graceful appearance in use. Experience in the
textile industry has shown that fabric stiffness is a key factor in
the study of handle and drape.
One instrument devised by the textile industry to measure stiffness
is the Shirley Stiffness Tester. In order to compare the drape and
surface feel properties of paper samples made utilizing different
sides of a semi-twill imprinting fabric, a Shirley Stiffness Tester
was constructed to determine the "bending length" of the paper
samples, and hence to calculate values for "flexural rigidity" and
"bending modulus".
The Shirley Stiffness Tester is described in ASTM Standard Method
No. 1388. The horizontal platform of the instrument is supported by
two side pieces made of plastic. These side pieces have engraved on
them index lines at the standard angle of deflection of
411/2.degree.. Attached to the instrument is a mirror which enables
the operator to view both index lines from a convenient position.
The scale of the instrument is graduated in centimeters. The scale
may be used as a template for cutting the specimens to size.
To carry out a test, a rectangular strip of paper, 6 inches by 1
inch, is cut to the same size as the scale and then both scale and
specimen are transferred to the platform with the specimen
underneath. Both are slowly pushed forward. The strip of paper will
commence to droop over the edge of the platform as the scale and
specimen are advanced. Movement of the scale and the specimen is
continued until the tip of the specimen viewed in the mirror cuts
both of the index lines. The amount of overhang, " ", can
immediately be read off from the scale mark opposite a zero line
engraved on the side of the platform.
Due to the fact that paper assumes a permanent set after being
subjected to such a stiffness test, four individual specimens were
utilized to test the stiffness of the paper along a given axis, and
an average value for the particular axis was then calculated.
Samples were cut both on and across the cross-machine direction
(CD) axis, on and across the CD+30.degree. axis, and on and across
the CD+135.degree. axis. From the data collected both on and
perpendicular to each of three aforementioned axes, an average
overhang value, , was calculated for the particular paper
sample.
The bending length, c, for purposes of these tests, shall be
defined as the length of paper that will bend under its own weight
to a definite extent. It is a measure of the stiffness that
determines draping quality. The calculation is as follows:
c = cm. .times. f(.theta.) where f(.theta.) = [cos 1/2 .theta.
.div. 8 tan .theta.].sup.1/3, and = the average overhang value of
the particular paper sample as determined above.
In the case of the Shirley Stiffness Tester, the angle .theta. =
411/2.degree., at which angle f(.theta.) or f(411/2.degree.) = 0.5.
Therefore, the above calculation simplifies to:
c = .times. (0.5) cm.
Flexural rigidity, "G", is a measure of stiffness associated with
handle. The calculation of flexural rigidity, G, in the present
instance is as follows:
G = 0.1629 .times. (basis weight of the particular paper sample in
pounds per 3,000 sq. ft.) .times. c.sup.3 mg. cm., where c = the
bending length of the particular paper sample as determined above,
expressed in cm.
The bending modulus, q, as reported in the Examples hereinbelow, is
independent of the dimensions of the strip tested and may be
regarded as the "intrinsic stiffness" of the material. Therefore,
this value may be used to compare the stiffness of materials having
different thicknesses. For its calculation, the thickness or
caliper of the paper sample must be measured at a pressure of 1
pound per square inch.
The bending modulus, q, is then given by:
q = 732 .times. G .div. g.sup.3 kg./sq.cm., where G is the flexural
rigidity of the particular paper sample as determined above,
expressed in mg. cm., and g is the thickness or caliper of the
particular paper sample, expressed in mils, when subjected to a
pressure of 1 pound per square inch.
The results of tests performed on sample paper sheets produced
during the runs described above are reported in the Examples
hereinbelow in terms of bending modulus, q, which has relevance
with respect to both drape and surface feel. A lower bending
modulus corresponds to increased drape, and hence to improved
surface feel.
The knuckle imprint areas referred to in the Examples hereinbelow
were determined by making an impression with pressure sensitive
paper in each of four areas on the web contacting surface of the
imprinting fabric utilized in the particular Example. Enlarged
photographs were taken of each of the four impressions, and a
"unit-cell" of knuckles, i.e., one repeating pattern of knuckles,
was enclosed in each photograph. The total area of each enclosed
unit-cell and the total area of the knuckles inside each such
unit-cell were then measured, and the results were expressed in
terms of the percentage of knuckle area. The average value for the
four discrete unit-cells was taken to be the knuckle imprint area
for the particular Example.
The Examples below compare the finished sheet properties of paper
samples produced in accordance with the present invention with the
sheet properties of paper samples produced utilizing the
conventional face side of a similar imprinting fabric at various
stages of fabric treatment.
__________________________________________________________________________
EXAMPLE I Back side of imprinting fabric contacting web Cal- Basis
Sample no. iper at Knuckle weight Bending (for indenti- 80 gm/
imprint pounds/ Tensile Tensile Handle- Handle- Stretch Stretch
Modulus fication pur- sq.in., area, 3,000 MD,gm./ CD,gm./ O-Meter
O-Meter MD, CD, "q",kg./ poses only) inches percent sq.ft. in. in.
MD CD % % sq.cm.
__________________________________________________________________________
1 0.0106 21.2 15.4 251 224 8.25 3.0 16.5 2.0 10.27 2 0.0104 21.2
16.5 259 170 6.25 2.75 17.0 3.0 10.25 3 0.0106 21.2 15.5 325 161
11.25 3.0 18.0 3.0 10.38 4 0.0108 21.2 15.0 268 116 8.5 2.5 19.0
3.0 9.00 5 0.0116 21.2 15.8 181 114 6.25 2.75 19.0 3.0 7.38 6
0.0107 21.2 15.0 251 248 10.5 3.0 20.0 2.5 9.08 7 0.0107 21.2 15.5
219 183 9.5 3.0 16.5 3.0 8.38
__________________________________________________________________________
EXAMPLE II Conventional face side of imprinting fabric contacting
web Cal- Basis Sample no. iper at Knuckle weight Bending (for
indenti- 80 gm/ imprint pounds/ Tensile Tensile Handle- Handle-
Stretch Stretch Modulus fication pur- sq.in., area, 3,000 MD,gm./
CD,gm./ O-Meter O-Meter MD, CD, "q",kg./ poses only) inches percent
sq.ft. in. in. MD CD % % sq.cm.
__________________________________________________________________________
1 0.0100 23.4 15.8 209 144 7.0 2.0 20.0 3.0 11.33 2 0.0102 23.4
15.5 199 147 8.25 2.0 21.0 2.0 11.04 3 0.0106 23.4 15.1 155 130
8.50 2.0 20.5 2.0 8.60 4 0.0105 23.4 15.3 175 141 8.25 2.0 20.0 2.0
12.27 5 0.0091 23.4 15.4 331 241 11.5 3.0 21.0 2.0 21.60 6 0.0097
23.4 15.2 350 194 10.5 2.5 19.5 3.0 22.01 7 0.0107 23.4 15.3 266
194 10.5 3.0 22.0 2.5 10.21
__________________________________________________________________________
EXAMPLE III Back side of imprinting fabric contacting web Cal-
Basis Sample no. iper at Knuckle weight Bending (for indenti- 80
gm/ imprint pounds/ Tensile Tensile Handle- Handle- Stretch Stretch
Modulus fication pur- sq.in., area, 3,000 MD,gm./ CD,gm./ O-Meter
O-Meter MD, CD, "q",kg./ poses only) inches percent sq.ft. in. in.
MD CD % % sq.cm.
__________________________________________________________________________
1 0.0097 28.4 16.9 278 218 7.0 2.3 18.5 3.5 10.53 2 0.0105 28.4
15.7 280 159 5.80 2.0 19.5 3.5 8.41 3 0.0099 28.4 15.2 300 221 10.5
2.0 19.0 3.5 11.12 4 0.0105 28.4 14.7 199 153 6.5 2.0 19.0 4.0 5.76
5 0.0105 28.4 15.1 193 150 6.80 2.0 18.0 3.5 5.76 6 0.0103 28.4
15.4 299 266 10.0 2.5 20.5 3.0 10.50 7 0.0105 28.4 16.0 275 190 5.3
2.0 20.5 4.5 8.37
__________________________________________________________________________
EXAMPLE IV Conventional face side of imprinting fabric contacting
web Cal- Basis Sample no. iper at Knuckle weight Bending (for
indenti- 80 gm/ imprint pounds/ Tensile Tensile Handle- Handle-
Stretch Stretch Modulus fication pur- sq.in., area, 3,000 MD,gm./
CD,gm./ O-Meter O-Meter MD, CD, "q",kg./ poses only) inches percent
sq.ft. in. in. MD CD % % sq.cm.
__________________________________________________________________________
1 0.0089 34.1 15.4 410 241 11.5 2.0 26.5 2.0 19.64 2 0.0087 34.1
15.9 471 295 16.5 3.0 26.5 2.0 26.35 3 0.0091 34.1 15.6 330 201
14.5 2.0 24.0 2.5 20.11 4 0.0090 34.1 14.9 291 174 9.75 2.0 21.5
3.0 20.68 5 0.0093 34.1 15.3 255 196 15.5 2.5 21.5 2.0 18.41 6
0.0097 34.1 15.5 290 191 12.5 2.0 25.0 2.5 14.82 7 0.0093 34.1 14.7
263 190 9.5 2.0 24.0 3.0 16.00
__________________________________________________________________________
EXAMPLE V Back side of imprinting fabric contacting web Cal- Basis
Sample no. iper at Knuckle weight Bending (for indenti- 80 gm/
imprint pounds/ Tensile Tensile Handle- Handle- Stretch Stretch
Modulus fication pur- sq.in., area, 3,000 MD,gm./ CD,gm./ O-Meter
O-Meter MD, CD, "q",kg./ poses only) inches percent sq.ft. in. in.
MD CD % % sq.cm.
__________________________________________________________________________
1 0.0092 37.3 15.5 269 188 6.0 2.5 19.2 5.0 8.75 2 0.0099 37.3 16.4
268 164 5.5 2.0 21.5 5.0 6.07 3 0.0098 37.3 15.6 338 243 7.0 2.5
20.5 5.5 10.48 4 0.0093 37.3 15.1 271 171 5.5 2.0 19.5 5.5 6.73 5
0.0099 37.3 15.9 206 136 5.80 2.0 19.5 5.0 6.03 6 0.0107 37.3 16.1
265 191 9.0 2.5 21.0 5.5 9.25 7 0.0099 37.3 15.8 259 200 5.5 2.0
20.5 5.5 6.80
__________________________________________________________________________
EXAMPLE VI Conventional face side of imprinting fabric contacting
web Cal- Basis Sample no. iper at Knuckle weight Bending (for
indenti- 80 gm/ imprint pounds/ Tensile Tensile Handle- Handle-
Stretch Stretch Modulus fication pur- sq.in., area, 3,000 MD,gm./
CD,gm./ O-Meter O-Meter MD, CD, "q",kg./ poses only) inches percent
sq.ft. in. in. MD CD % % sq.cm.
__________________________________________________________________________
1 0.0085 40.0 15.4 315 216 10.25 2.0 24.0 2.0 26.53 2 0.0087 40.0
14.3 303 209 12.5 2.0 23.5 2.0 22.04 3 0.0088 40.0 14.8 300 228
14.5 2.0 23.0 2.0 20.66 4 0.0091 40.0 14.5 304 213 12.25 2.0 23.0
2.0 15.66
__________________________________________________________________________
The data presented in the Examples above clearly show the
advantages of the present invention in producing a paper sheet
characterized by having significantly improved cross-directional
stretch, softness, surface feel and drape.
It is to be understood that the forms of the invention herein
illustrated and described are to be taken as preferred embodiments.
Various changes or omissions may be made in the weaving process,
the heat treating process, or in the process for increasing the
knuckle imprint area of the fabric without departing from the
spirit or scope of the invention as defined in the attached
claims.
* * * * *