Note: Descriptions are shown in the official language in which they were submitted.
~^ ``
llSSO~)7
PATTERN DENSIFIED FIBROUS WEB
HAVING SPACED, BINDER IMPREGNATED HIGH
DENSITY ZONES, AND METHOD QF MAKING SUCH A WEB
. Peter Graves Ayers
. John Michael Raley
. " ~ - ' , ,
~ Te`chni'c'al' Fi'e'ld
- .
This invention relates to soft fibrous webs such'as
'-, paper for,paper towels and tissue-paper, and a method of
making such a web which'is reinforced at least in part by
binder material. -
~ .
B'a'ck~'roun't':~rt
. ' In general, thé exemplary paten~s described below
tisclose soft, re~atively hi'gh'bulk webs such'as paper, and .
concomltant processes, some'of which.inclute'pattern app}ied
~ 10 binder:materials such'as elastomers for the'purpose o -
.~ s;trengthening the'fibrous webs without making them inordinately
: .- inflexible'or hard or harsh to feeI.
:
: . U-.'S. Patent No. 2,.039,312 which issued May 5, 1936 to
.~ . , J~.,H. Goldman discloses a Re~nforced Carded Web which may be
. ~ }5~ reinforced by.a reticulated network of narrow lines of
~ impregnation with a suitable'binder which lines are preferabl~.~ spaced slightly less than the'average fiber length of the
fibers constituting the web.
: ~ U.S'. Patents ~o. 2,880,111 and No. 3,009,822 which
issued to A. H. Drelich et al. on March 31, 1959 and
November 21, 1961, respectively, disclose fibrous Textile-
.Like Nonwoven Fabrics. wherein the fibexs are held together
by an adhesive or bonding material distributed amongst them
in predetermined patterns of closely spaced discrete areas.
The latter patent also diæcloses lined patterns of binder as
: well as a rotogravure method.of making such fabrics which
. .
~r ~ ' 1~
,
~'~S50~)7
- 2 -
includes the step of wetting a fibrous web prior to rotogravure
printing a predetermined pattern of spaced binder segments.
U.S. Patent No. 3,301,746 which issued January 31, 1967
to Lawrence H. Sanford and James B. Sisson covers a Process
For ~orming Absorbent Paper By Imprinting A Fabric Knuckle
Pattern Thereon Prior To Drying And Process Thereof. Briefly,
a high bulk fibrous web-is wet formet and predried to a
fiber consistency of from about 30 to about 80 pçrcent by
avoiding substantial mechanical compression until the web is
'10 predried; then a knuckle pattern of an imprinting fabric is
imprintet in the predried web while the remainder remains
substantially uncompacted. The web may also be somewhat
molded to the surface of the imprinting fabric by differential
fluid forces prior to the predrying. Upon being imprinted,
the imprinted ~ones become'compacted and relatively highly
hydrogen bonded due to the'imprinting pressure'and the water
remaining in the predried web prior to final drying. Thus,
upon ~inal drying, the'resulting paper is pattexn compacted
and bonded in the'image of the knuckle'pattern of the
imprinting fabric.' It is be'Iieved that such paper i8 so~t
and bulky because'of not befng com~acted overall and because
the'fibers disposed in the uncompacted portion~ do not
become highly hydrogen bonded a~ in theretofore conventional
felt-pressing papermaking. U.S'. Patent No. 3,994,771 which
issued November 30, 1976 to George Morgan, Jr., et al.
extended this technology to a Process For Forming A Layered
Paper We~ Having Improved Bulk, Tactile Impression And
Absorbency And Paper Thereof.
U.S'. Patent No. 4,158,594 which was filed June 24, 1971
and issued June 19, 1979 to Henry E. Becker et al. tiscloses
Bonded, Differentially Creped, Fibrous Webs And Method of
Making Same wherein creping bonding material such as latex
is pattern graw re printed onto a dried, self-supporting
fibrous web having relatively low intesfiber bonding strength.
The web is preferably creped prior to printing, and is
printed while being ~orwarded onto a crep~ng cylinder from
w&ich it is subsequentlY ~dlfferentially creped. This
.
1~55007
-- 3 --
patent recites that it is particularly desirable to apply
the bonding material in a reticular pattern so that the
bonding material forms a net-like web of strength over the
fibrous web. Indeed, all of the disclosed examples were
printed with a reticular pattern although both discrete spot
bonding and reticular pattern bonding are shown in the
figures. 'This technology was apparently bxoadened somewhat
by the following commonly assigned patents although all
commonly show gravure printing of bonding material onto
dried, self-supporting fibrous webs: U.S'. Patents No.
' 3,.879,257 which issuet April 22, 1975; No. 3,903,342 which
'' issued Sep'tember 2, 1975;' ant No. 4,000,237 w~ich issued
December 28, 1976.
. .
U.S'. Patent No. 3,'812,000.which'is3ued ~ay 21, 1974 to
J.L. 5al~ucci et al. discloses a Soft, Absorbent, ~ibrous,
Sheet Material Formed By Avoiding Mechanical Compression Of'
The Elastomer.Containing Fiber Furni~h Until The Sheet Is At
Least 80X Dry. As tisclosed, an el'astomeric bonting material
i8 i'ncluded in the fiber fuxnish ~o that it ~s distributed
throughout the finished sheet. Attitionally, re such
bonding material may be'applied to the sheet in a predetermined
~pattern by a patterned gravure'roll while the shee~ is being
forwarded thro.ugh'a paper mach~ on a foraminous drying
fabric. The pattern 18 stated to preferably be.a reticular
hexagonal pattern. As compared to the Sanford-Sisson patent
des'cr.ibed.above,' Sal w cci'et al. include.el'astomeric material
in a low-bont ~urnish; predry to a greater extent; and may
gravure'print a pattern of additional binder material on the
web with a patterned gravure rolL. However, Salvucci et al.
expresslr teach away from pattern knuckle.compaction as
taught by Sanford-Sisson because "the pres'sures generated by
the knuckle pattern of the woven wire are'so high as to
create hart portions of the web which glve a feeling of
harshness.to the resulting protuct."
U.S. Patent No. 3,898,123 which issued August 5, 1975
to Charles H. PhillipY et al. di~closes a Method For Wet
Print-Bonding Light-Weight Wet-Formed Fibrous Webs wherein a
~55007
- 4 -
self-supporting, wet-formed web has an aqueous resin binder
applied by print-bonding rolls having etched or engraved
printing surfaces, and which binder material is applied
~ intermediate two open draw free spans of the we~ prior to
drying the web.
i U.. S. Patent No. 4,127,637 which issued November 28,
1978.to Eugene J. Pietreniak et al. discloses a Method Of
I Manuaeturing A Dry-Formed, Embossed Adhesively Bonded,
1 Nonwaven Fibrous Sheet having spaced uncompacted fibrous
zones on a compacted reticulated ibrous network wherein
I binder m~terial is preferably.disposed in the ~ncompacted
zones and through the compacted network.
. .
U.S. Patent No. 4,159,355 which issued June 26, 1979 to
Kenneth Kaufman discloses Foam Bonding method and apparatus
for applying a foamed binder in a uniorm and controlled
metered flow t~ a.surface.of a.moving substrate such as a
nonwoven web.
~dditi~nally, a paper titled Forming Of Lo~ Denæity
Nonwoven Fabrics: Technology And Direction was presented by
G.A.M. Butterworth on Nove~ber 13, 1979 at the International
Air Laid And Low Density.Forming Seminar at the Hyatt Regency
Hotel in Atlanta, Georgia. This paper provides a consolidated
discussion of patents pertaining to low density webs including
we~s which are at least part1ally impregnated with, for
instance, binder materia~.
While no~ intend~ng to limit the present invention to
the following generalized distinctions, the present invention
provides, as compared to the foregoing background art, a
generally relati~ely low bond, high bulk, highly flexible
pattern densiiet web such as a paper sheet ha~ing spaced
discrete ~ones o relatively high fiber density which zones
are suficiently impregnated with binder material to provide
adequate sheet tens~le strength without compacting or impregnat-
ing the surrounding low density portions o the web; ant the
present invention provides a concomitant method of making
.
- - .. .....
~55(~)7
- 5 -
such a web. That is, the background art does not disclose
applying binder material to only relatively dense-zones of a
fibrous web having a patterned array of spaced discrete high
fiber density zones as provided by the present invention.
,
, 5 Disclosure Of The'Invention
In accordance with one broad aspect of the present
invention there is provided a pattern densified fibrous web
Iand concomitant method of making such a web which web has a
¦relatiuely high bulk field of relat:ively low fiber density,
and a patterned array of spaced æones of relatively high
fiber density at least a substantial proportion of which
'~' zones are at least partially impregnated with'binder material,
and in which web'the high bulk field is substantiall~
uncompacted and devoid of such binder material. The con-
comitant method comprises the steps o~ forming a.pattern
densified embryonic we~'having an arra~ of discrete high
density ~ones disposed in a predetermined pattern; supporting
the'embryonlc web on a eorresponding array of spaced supports
80 that at least each.'of a predet'ermined sub-array of t~e
dense ~ones i~ ~uxtaposed one of a corresponding sub-array
of the support's; and biasing the ~ub-array of supports
towards a contacting type'impregnating means with the'sub-
array of dense'zones disposed therebetween so that, through
.~' coincidence of at least a substantial number of $he supports
~'25 of the sub-array and binder transfer portians of the
~mpregnatin~ means, at least a s~ubstantial proportion of the
dense ones become at least partially impregnated. In the
method, the array of spaced supports may be the knuckles of.
'' an endless imprinting carrier ~abric and the sub-array of
such supports may be only the top-surface-plane knuckles of
.. the fabric in fabrics ha~ing both top-surface-plane knuckles
and sub-top-surface knuckles.. In fabrics having no sub-top-
surface knuckles the sub-array of supports would in fact be
the array of s~pports. For.maximum strength, all of the
135 high density zones are impregnated with binder material
!whereas only some may only be partially impregnated
in sheets wherein partial impregnation provid~s sufficient
sheet strength for the intended use of the sheets.
' ~ .
-
~55()()7
-- 6 --
Impregnating means such as a full field gravure applicatormay be used to impregnate the dense zones of the web biased
against it whereas less-than-full-field gravure applicators
may be used to only partially impregnate all or some of the
dense zones of the web, or wholly impregnate only some of
the dense zones. Moreover, the method may further comprise
the step of subjecting the impregnated zones to further
mechanical pressure/compaction after they are impregnated to
increase the binder penetration and interfiber bonding
therein.
More particularly, the present invention, in its
product aspect, resides in a pattern densified fibrous web
comprising a relatively high bulk field having a relatively low
fiber density, and a patterned array of spaced discrete zones
of relatively high fiber density integrated with said rela-
tively high bulk field, said high bulk field comprising a
multiplicity of arched spans which corporately coact with said
high density zones to provide said web with a vaulted, charac-
ter, and at least a substantial proportion of said high density
zones being at least partially impregnated with inter-fiber
binder material through the full thickenss of said web, and
said high bulk field being substantially devoid of said
binder material.
Brief Description of the Drawings
While the specification concludes with claims par-
ticularly pointing out and distinctly claiming the subject
matter regarded as forming the present invention, it is
believed the invention will be better understood from the
following description taken in conjunction with the accompanying
drawings in which corresponding features are indentically
designated, and in which:
Figure l is an enlarged photographic sectional
view of a fragmentary sheet of paper embcdying the present invention.
~, .
- 6a - ~sso~7
Figure 2 is a fragmentary plan view drawing.of a sheet
of paper embodying the present invention which sheet comprises
a predetermined pattern of spaced high density zones disposed
on a relatively high bulk field.
Figure 3 is a fragmentary ~ectional view drawing of a
sheet of paper embodying the present invention which sectional
view is taken along line 3-3 of Figure 2, and which sectional
vie* generally corresponds to the photographic sectional
view of Figure 1.
Figure 4 i9 a fragmentary sectional view drawing of a
sheet of paRer~hich is substantially identical to that
64DWn in Figure 3 except the.1at, high tensity zones of the
Figure 4 s;heet are not impregnated with binder material.
1155~(~7
-- 7 --
Figure 5 is a side elevational, somewhat schematic view
of a papermaking machine for manufacturing a wet laid fibrous
web such as paper in accordance with the present invention.
Figure 6 is a fragmentary plan view of an exemplary
imprinting carrier fabric such as may be used on the papermaking
machine shown in Figure S and which imprints its top-surface-
plane knuckle pattern into a web such as a sheet of paper to
precipitate a pattern of co,mpacted zones.
,Figure 7 is a radially i~wardlY looking, fragmentary
''10 view of the surface of a rotogravure eylinder ha~ing a full
fiel'd of truncated pyramidal reservoirs ~ormed therein, and
having a partiall~ peeled b'ack opaque overlay disposed
thereon which overlay is apertured ~n the knuckle pattern of
the'imprinting carrier fabric shown in Figure 6.
.
Figures 8 through'l2 are partially masked fragmentary
rotogravure cylinders which''are'substantially identical to
that shown in Figure 7 except the'cylinders of Figures 8
th~ough'l2 are'less-than-full-fieId micropatter'ned to provide
reservoirs over only about 75, 50, 50, 50, and 25 percent,
respective}y, o their cylindrical surface areas.
Figure'13'is a somewhat schematic side elevational view
of a handsheet impregnating apparatus~
Figure 14 i9 an enlarged scale,' fragmentary view of the
roller-nip portion of the apparatus shown in Figure 13 and
through which nip portion a handsheet disposed on an ~mprint-
ing carrier fabric, and a flat gravure plate are being
forwarded in ~uxtaposed relation.
.
Figure 15 is an enlarged scale, fragmentary view similar
to Figure 14 except the handsheet of Figure 15 is not disposed
on an imprinting carrier fabric as shown in Flgure 14.
J
-
` l~SSO(~7
- 8 -
De`tailed De'scrip'tion'Of'The' Invention
A fragmentary po~tion of a microtomed section of a
paper sheet embodying the present invention is shown in the
- photographic Figure 1 to comprise a fibrous web 20 comprising
a multiplicity of fibers 21 which are disposed in relatively
high density zones 22 and 23, and arcuate-shape relatively
~- low density span portions 24, and in which web the high
density ~ones 22 and 23 are impregnated with a latex fiber
. binder material 25.
'10 Briefly, as described more fully hereinafter in conjunction
wi'th'diecusging web 20, Figures 2, 3 and 4, the present
invention provides a soft, pattern densified fibrous web
such as a.paper sheet whi'ch comprises a relatively low
density fibrous fie~d.and a mNltiplicity of relatively high
density fibrous zones disposed in a predetermined array, and
in which'web ;each'of at least a substantial proportion of
such'dehse zones are at least partially impregnated with a
binder material of a type'which provides interfiber bonds
which'are'preferably substantially more. flexible than.ordinary
interfiber hydrogen bonds which occur between cellulosic
fibers in ordinary papermaXing.. The web com~rises a principal
. web'-strength fiber con'stituent comprising fibers of sufficient
, average length with respect to the spacing of the impregnated
high density zones that a substantial fraetion of the fibers
wi'll have'spaced portions thereof disposed in adjacent
~mpregnated dense zones and in.overlapping bonded relation
.. with portions of other fibers 80 that the bonded principal
web-s~trength fiber~ constitute` a strength-skeletal-network
: - of the web. Preferably, the low density field comprises
arcuate-sha~e spans which are so disposed with respect to
the dense zones that.the web has a ~aulted character. Also,
preferably: the principal web-strength fibers have average
lengths of about 2.0 mm or greater (e.g., softwood fibers);
but for the impregnated dense zones, the web is characterized
by a relatively low degree of interfiber bonding which may
be achieved by including debonders in the furnish, or through
the use of low bond fibers; and the dense zonee preferably
~ .
. ~
~55~7
. _ 9
are qual in number to the number of imprinting knuckles of
an imprinting fabric having a mesh count of from about 10-
MD/10-CD to about 60-MD/60-CD filaments per inch ~from about
4 by 4 to about 24 by 24 machine direction filaments and
cross machine direction filaments per centimeter, respectively)
and more preferably from about 20-MD~20-CD to about 50-
MD/50-CD filaments per inch (from about 8 by 8 to about 20
i by 20 machine dixection filaments and cross machine direc~ion
j filaments per centimeter, respectiveIy).
Briefly, a web embodiment of the present invention as
described above is preferably made by forming a pattern
densified web of flbers of appropriate lengths, flexibility,
and bonding propensity; supporting high density zones of the
web 'on an array of spaced supports which'are'preferabl~
! ~5 generally coplanar; deflecting the webs low density span
po~tions out o the plane of the supports; and im~regnating
at least a substantial proportion o~ the dense'~ones. The
degree of ~mpregnation andlor bonding may be'increased by
' sub~'ect~ng the'high'density zones to mechanical compression
after the'basic impregnation has been effected. For ins~ance,
a wet formed ~mbryonic web may be'so pattern densified and
defl'ected by a differential fluid pressure while the embryonic
i, web is disposed on an appropriate imprinti~g carr*er fabric
as described hereinafter in conjunction with discussing
Figure'6; and the impregnating may be effected, for instance,
by a pressure biaæed gravuxe apparatus a3 also des'cribed
hereinater. Preferably, the web i9 also creped, calendered
and reeled after being impregnated and dried to further
increase'its stretch, bulk and softness, and to control its
3Q caliper.
Referring again to ~igure 1, web 20 and the preferred
process for making it in accordance with the present invention
'are described hereinafter as paper sheet 20 and papermaking
processes, respectively, although it is not intended to
thereby limit the pre~ent invention.
-7
` - 10 - `
Figure 3 is a fragmentary sectional view drawing of a
paper sheet 20 embodying the present invention which view is
taken along line 3-3 of Figure 2, and which sectional view
drawing generally corresponds to the photographic sectional
. 5 view of Figure 1. That is, paper sheet 20 is shown in
Figure 3 to comprise arcuate-shape low density span portions
i 24 which are alternately spaced by relatively long and short
1 high density zones 22 and 23, respectively, which dense zones
j ' are generally planar and are impregnated with binder material
3 io 2~. As may be 3een in Figure 2, a mul.tiplicity of dense
zones 22 and 23'are disposed in a predetermined pattern or
! arra~ on a generally low'density field o~ which portions 24,
- Figure 3, are'representative.
j Figu~e 4 is a fragmentary sectional view drawing of.a
15' pattern densified paper sheet 20a which generally corresponds
with'paper sheet 20, Figure'3, except paper sheet 20a i9
not impregnated with binder material'. That is, paper sheet
20a ~8 a pattern tensified web which'has not.had lts high '
density ~ones impregnated with binder material in accordance
20 with'the present invention. Also, the'reIative fiber density
. of zones 22a and 23a of unimpregnated sheet 20a is shown to
¦ be somewhat less tha'n the fiber densi~y of zones 22 and 23 ~
' o æheet 20 because ~ones 22a and 23a have not been subjected
... ~- : to the'mechanical compaction experienced by zones 22 and ~3
through the practice'of the present invention.as hereinbefore
- des'cribed,
.
. - Figure 5 is a fragmentary, somewhat schematic side
elevational view of an exemplary paperm2king machine 30
- through the use of which paper sheet embodiments of the
present invention can be made and the proce~ of the present
invention can be'practiced. Papermaking machlne 30 is a
. fixed roof former type papermaking machine wherein a ~ibrous
slurry is delivered from a headbox 32 onto a Fourdrinier
wire 33 passing over a vacuum type breast roll 34. The
Fourdrinier wire then passes,over a forming board 35 and
suction box 36 and is further looped about turning roll~ 41
through 46. The slurry i~ partially dewatered by the vacuum
_ ___ __ _,_ . . ., , .. . . .. . .... : . . .
1155(~7
- 11 -
and table roll action of the breast roll. Further dewatering
is precipitated by forming board 35 and suction box 36 so
that an embryonic fibrous web 20e is formed and forwarded on
the Fourdrinier wire to a first transfer station generally
designated 50 where it is transferred from Fourdrinier wire
33 to an endless intermediate carrier fabric 51 which
' paxtially wraps roll 42, passes over suctio'n boxes 52 and
53, then over vacuum transfer box 54, and thèn is looped
about rolls 55, 56, 57 and 58. Dewatering is furthered as
the'embryonic web' 20e'is forwarded in sandwiched relation
- bet'ween Fourdrinier wire'33 and.fabric 51 past suction boxes
52 and 53, and then over a portion of vacuum transfer box 54
after which the'embryonic web 20e is disposed and forwarded
on abric 51 to an endless imprinting carrier fabric 59 at a
second transfer station des~gnated 60. At the second transfer
station 60, embryonic web' 20e ~s trans~erred.by the action
of vacuum transfer box'61 from the'intermediate.'carrler
fabric 51 to the'imprinting carrier fabric 59 which'is
looped.paat/about suction box 62,.turn~ng roll 63, blow '
through predryer 64, impregnating means 6~, turning roll 66,
pressure roll 67, turning roll 68, showers 69, suction box
7~-, and turning rolls 71 and 72~ At this time,rformation of
the web' continues due'to the'differential fluid pressure ,
applied to the web to effect the'second transfer and fiber
mobility enabled by a sufficientlr high water content
~preferably a fiber consistency of 30 percent or less), the
. embryonic web'becomea' pattern densified with'denae ~ones of
fibers juxtaposed the knucklea of the imprinting carrier
fabric 59. After being tranaferred to ~he ~mprin~ing carrier
fabric 59, the embryonic web i9 further dewatered by suction
- box 62 and blow-through'predryer 64; then partially impregnated
with binder material. 25 by pressure biased impregnating
means 65; and then transferred to Yankee dryer 75 by the
action o pressure roll 67 which is biased towards the
Yankee dryer by biasing means 76. Transfer of the web to
the Yankee dryer and adherence thereto is enabled by creping
adhesive applied through'applicator 77. Finally, upon being
fully dried on the Yankee dryer~ the transformation of
. ~ .
~ .
~s~
- 12 -
embryonic web 20e to paper sheet 20 is completed as the
final drying thereof is effected and, preferably, it is
creped from the Yankee dryer by the action of doctor blade
78. Preferably, the paper sheet 20 is then calendered and
reeled to control its caliper and enable its subsequent
conversion from reels into paper products such as paper
towels, and toilet and facial tissue paper. Also, in the
event the binder material requires curing, such curing may
be effected at least in part after the paper sheet has been
removed from the papermaking machine.
Figure 6 is a plan view of the top, outwardly facing
surface of an exemplary imprinting carrier fabric 59 which
may be used on a papermaking machine such as papermaking
machine 30, Figure 5, to practice the present invention.
Fabric 59 is a five-shed satin weave of polyester monofila-
ments which were woven using a 1, 4, 2, 5, 3 warp pick sequence
and wherein the filaments 90-1 through 90-5 which extend in
the machine direction, MD, alternately pass over four and
under one of the filaments 91-1 through 91-5 which extend in
the cross machine direction, CD; and wherein the CD filaments
alternately pass over one and under four MD filaments.
Fabric 59 has been stressed, heat set, and sanded to provide
coplanar sets of long MD imprinting knuckles 92, and rela-
tively short l-over CD imprinting knuckles 93. The outwardly
facing surfaces of coplanar sets of knuckles 92 and 93
corporately define a top-surface-plane of fabric 59. Fabric
59 also has adjacent pairs of sub-top-surface filament
crossovers designated 94 which, by virtue of the weave,
stressing, and heat setting are recessed below the top-
surface-plane of the fabric. Such a fabric is described
more fully in the commonly assigned U.S. Patent No.
4,239,065 of Paul Dennis Trokhan, granted December 16,
1980. Also, such a fabric is particularly useful
for making soft and absorbent imprinted paper having
uncompressed portions circumscribed by picket-like lineaments
of alternatiely spaced areas of compacted fibers and non-
compacted fibers which compacted fiber areas or zones are
- 13 - 1~55~7
precipitated by imprinting the top-surface-plane knuckles of
the fabric into a relatively uncompacted, low density, high
bulk paper sheet. This is more fully described in the
commonly assigned U.S. Patent No. 4,191,609 of Paul
Dennis Trokhan, issued March 4, 1980. While the 5-shed
fabric 59, Figure 5, has been described above as exemplary
with respect to the present invention it is not intended
to thereby limit the present invention to any particular
fabric weave, or knuckle geometry or disposition.
Impregnating means 65, Figure 5, comprises roto-
gravure cylinder 81, backing roll 82, biasing means 83, and
reservoir 85 which is adapted by means not shown to maintain a
relatively constant predetermined level of liquid impregnating
material 25 therein. This level insures that a downwardly
facing arcuate portion of rotogravure cylinder 81 is immersed
in the impregnating material. Doctor means, not shown, are
provided for removing the excess impregnating material from
the rotogravure cylinder as it rotates upwardly towards the
traveling embryonic web. Synchronous drive means, not
shown, may also be provided as needed to obviate deleterious
drag on the embryonic web as it passes through the nip
between rotogravure cylinder 81 and backing roll 82. While,
as described, impregnating means 65 of papermaking machine
30 is a gravure type applicator, it is not intended to thereby
limit the present invention to gravure applicators or
impregnators. Rather, it is believed that other contacting
type applicators such as, for instance, foam applicators
may be used to practice the present invention.
Figure 7 is an enlarged scale, radially inwardly
looking view of a fragmentary portion of an exemplary rotogra-
vure cylinder 81 which has its cylindrical surface covered by
a partially peeled back, opaque mask 96 which is apertured in
the top-surface-plane knuckle pattern of imprinting carrier
fabric 59, Figure 6. That is, apertures 92a and 93a in mask
.'i
.~
115S~7
- 14 -
96 are sized and dis?osed in the image of the top-surface-
plane knuckle pattern of fabric 59, Figure 6. The entire
gravure surface of rotogravure cylinder 81 is defined by a
~ full field pattern of truncated pyramidal cavities or
reservoirs 100. In use, as an em~ryonic web 20e is carried
through the nip of impregnating means 65 of papermaking
machine 30, Figure 4, only the dense zones-of the web which
are Juxtaposed top-suxface-plane knuckles 92 and 93 of
fabric 59 are biased against the rotogra~ure cylinder 81.
This substantially limits the pattern of impregnation to the
pattern of the high density zones ~uxtaposed the top-surface-
plane knuckles 92 and 93 of fabric 59. Thus, the pattern of
impregnation is determined by the patterned array of top-
surface-plane knuckles of the imprinting carrier fabric
rather than a pattern on the. rotogravure cylinder. Also,
the p~ttern of impregnation of the web' is in registration
with the pattern of dense ~ones; of the web.as illustrated in
web''20, Figures 1 and 3. However, the area of the web'which
. becomes impregnated may in fact be substantially larger than
20 the'sanded areas of knuc~Ies.92 and 93 because the filament~
of the woven fabric 59 gradually slope away from the sanded
areas of the knuckle~ and thus cause web.portions contiguous
thereto to be'impregnated along with the web port~ons
~mmediately ~uxtaposet the sanded areas of the knuckles.
- 25 Furthermore, it i8 believed that the absence of biasing of
.' . the'unsupported span portions of the embryonic web substantially
obviates transfer of binding material thereto from rotogravure
cylinder 81. Moreover,' displacement of the unsupported span
portions into the ~nterilamentary spaces of the imprinting
fabric may be effected to virtually totally obviate their
being impregnated by rotogravure cylinder Bl-
Figures 8 through 12 are simllar to Figure 7 except thealternate embodiment rotograVure cylinders 81a through 81e
of Figures 8 through 12, respectively, are provided with
less-than-full-field-checkerboard type patterns of reservoirs
100 which reservoirs cover 75, 50, 50, 50, and 25 percent,
respectively, of the working surfaces of cylinders 81a, 81b,
81c, 81d, and 81e. Thu~, s~ch les~-than-full-field patterned
~ : .
.. _ . . . ..
c. ! ~
115i5~7
- 15 -
rotogravure cyiinders will coact with a patterned imprinting
fabric to apply impregnating material to only the surface
portions of an embryonic web which are in registered relation
with top-surface-plane knuckles and adjacent reservoir
5 portions of the rotograVure cylinder pattern. Such patterned
cylinders are useful with respect to providing various
degrees of web strength through binder impregnation while
preserving various complementary- degrees of binter free
surface areas. Thus, strength may be increased by ~mpregnating
10 larger percentages of web surface area. Furthermore, whereas
the alternate embodiment, less-than-full-field, rotogravure
cylinders 81a through'81e have relativel~ small checkerboard-
type patterns with'respect to the knuckle pattern of fabric 59,
Figure'6, less-than-full-field patterns (not shown) having
15 larger open (non-printing~non-~mpregnating) areas may be used
to assure not impregnating a substantial proportion of the
dense zonei as weIl as concurrently assuring that a substantial
proportion of the dense'zones will be.impregnated.. This is
useful w~en, for instance,' creping of the'finished web is
20 desired and the binder substantially vitiates the'intended
function of a creping athesi~e'(e.g.: polyvinyl alcohol
applied by spray applicators 77, Figure 5), the proportion
of binder impregnated zones is maintained great enough to
provide adequate web strength'while the proportion of
25 non-binder-~mpregnated zones is.made great enough to enable
the'creping adhesive to securely affix those zones to the
Yankee'tryer (creping cylinder) to control the web ant the
.creping thereof in substantlally the manner disclosed.in the
hereinbefore referenced Sanford-Sisson patent (u~s. Patent No.
3,3~1,746).
Figure 13 is a somewhat schematic side elevational view
of a handsheet impregnating apparatus 106 which comprise~
rotatably mounted', rubber covered rolls 107 ant 108, a
slanted feed plate 109, a horizontal feed plate 110, and a
~eceiving plate 111. Means not shown are provided to pressure
35 bias rolls 107 and 108 together, and to synchronously rotate
rolls 107.and 108 in the directlons indicated by the arrows
drawn thereon.
~ `
~550~7
- 16 -
Figure 14 is a fragmentary enlarged scale view of the
nip portion of apparatus 106, Figure 13, which view shows
fragmentary sections of rolls 107 and 108, a gravure plate
115, and a paper handsheet 116 disposed on the under side of
an imprinting carrier fabric 117. Figure 15 is substantially
identical to Figure 14 except the handsheet 116 in Figure 15
is self-supported; i.e., not disposed on an`imprinting
carrier fabric.
!
In use, referring to handsheet impregnating apparatus
~, '10 106, Figures 13'~hrough 15, a gravure'plate 115 is placed on
j 'plate 110 with its pattern side'up and with its cells filled
wi'th binder material. Then, a handsheet 116 is placed on
plate 109. Handsheet 116 may be associated with an imprinting
carrier fabric 117 as indicated in Figure'14, or not so
associated as indicated by the'absence of such'a fabric 117
from Figure 1~. Then, rolls 107 and 108 are biased together
wi'th'a predetermined force'and rotated s~nchronously while
t~e ~andsheet 116 and the gravure'plate 115 are simNltaneously
moved 90 that their leading edges enter the nip between the'
rolls. Thus, as the'handsheet and gravure'plate pass through
~he'nip, the'handsheet becomes impregnated. When the web is
associated with'a fabric durinz impregnation as shown in
,~ Figure14, the pattern of web impregnation is the knuckle
:! -pattern of the fabric when a full f~eld gravure plate is
used. Therefore, when the handsheet has been pattern
den~ified by formation on an imprinting carrier fabric so
that the dense zones of the handsheet are ~uxtaposed the
knuckles of the imprinting~carrier fabric, only the dense
zones of the handsheet become impregnated by a full ield
graw re pLate through the use of handsheet impregnating
apparatus 106.
Briefly, referring back to Figure 5, an embryonic web
20e is preferabLy formed and forwarded without sub~ecting it
to substantial mechanical'compaction until it reaches the
impregnating means 65. By including a principal web-strength
fiber constituent in the'furn~sh which constituent cQnsists of
fibers having a predetermined average length relation with respect
. - ,
. ...
.. _ ___ __. . ... . _ _ . _., _ ... _ .~ .. ., , _ , .. . . ..... . . .
' ' 1 ~5 5 0n7
- 17 -
to the knuckle pattern of the imprinting carrier fabric 59,
` and by controlling dewatering, a pattern densified embryonic
web may be formed in which web relatively high fiber density
zones are juxtaposed the outwardly facing knuckles of
imprinting carrier fabric 59, and in which web the remaining
portions which are unsupported and span the spaces between
the knuckles have relatively low fiber density. Preferably,
the unsupported spans.are also acted on by sufficient
differential fluid pressure while the web'i~ at a sufficiently
l~w fiber consistency to sufficiently displace the unsupported
spans intc the'interfilamentary spaces between ~he knuckles
¦ of the imprinting carrier fabric.to obviate their being
impregnated by impregnating means 65 although'it is not
intended to thereby limit the present invention. The embryonic
web''is pxeerabI~ predried to from about 30 to about 95
. percent fiber consistency ant more'preferably to from about
60 to about 90 percent fiber consistenc~ prior to being
im~regnated. ~Lso, preferably the drying is suficiently
asymmetrical to try the'unsupported portions of the web
substantially more than the'dense portions. This may be
effected, for instance,' by blow through predrying of the web
. while'it i8 disposed on the'imprinting carrier fabric of -~
papermaking machine'30. Thi8 enhances the'Z-direction
penetration of the binder material through the thicknes's of
- 2S the web and lessens the propensity o~ the binder material to
migrate laterally in the X-Y direc~ions into the low density
porti.on~ of the web. Such X-Y migration into the low
density por~ions of the web from the high density zones i8
further inhibited tue to their relative capillary st~uctures:
' 30 i.e.', normal~iy capillary flow is greater from low density to
. . hi'gh density ~nes than from high density to low density
zones. Moreo~er, with respect to latex type binder emulsions
in particular, i~ is beii~ved that the.commencement.of X-Y
migration from relatively wet zones into dry areas acts to
¦ 35 dewater such emulsions and cause them to coagulate rather
than migrate very far into the dry areas.
, - , , :, .
. ~
.
... . , . , . , ... _ _._ __._....... _, _ .. _ __ _ _ . . . .. .. ... ... .... .. . . .... .
~SSC~7
- 18 -
.,.-`
In addition to the impregnation of the high density
zones which is effected as the web is carried on the
imprinting carrier fabric 59 through the pressure biased
impregnating means 65, Figure 5, the biasing also precipitates
some compaction of and bonding within the high density zones
of the web. Subsequently, as the high density zones of the
web are again sub~ected to knuckle pressure~between pressure
roll 67 and Yankee'dryer 75, the'penetration.of the binder
is enhanced, and the degree of compaction and bonding within
the high density ~ones i~ 'increased.
A number of handsheet examples as we~l as papermaking
machine examples are described be~ow. Brie1y, the'handsheet
examples evidence the benefits of impregnating only dense
zones of a pattern densified paper sheet in accordance with
the present invention; and the'papermaking machine examples
evide'nce'the-benefit of sub~-ecting impregnated high density
- zones to further mechanical pressur.e.after the impregnating,
and the'benefits which may be derived from the'present
in~ention through-'the use'of different impregnating materials.
. .
'HANDSHEE~ ~XAMPLE' I
A pattern densifi'ed, one'foot square'(about 30 cm
square) handsheet having a basis weight of about 16.5 pounds
per 3000 square feet (about 27 grams per. square meter) was
ormed from a fibrous furnish on a fo.raminous polye~ter
25- fabric of the 5-shed satin weave'shown in Figure 6 and
. having a 36-MDl32-CD filaments per inch (about 14-MD by
12~6-CD fiIaments per centimeter) mesh count. The'urnish
comprised about 60 percent by fiber weight of Tongacel
~registered t~ademark of'Lo~isiana Pacific Corporat~-on)
. 30 K 324N, a relatively low bond, long fiber, post bleach cold
caustic extracted dissolving grade Worthern Softwood Sulfite
which is available from Louisiana Pac~fic Corporation,
and about 40 percent by fiber weight of relati~ely long
softwood fibers which were obtained from The Buckeye Cellulose
: 35 Corporation under the designation Grand Prairie Prime, a
Northern Softwood Kraft. After formation and draining., the
.... . . .. . ~ ... . . . , __ . ... _ _ ... .
sson7. '
- 9 -
handsheet was further dewatered by pulling the fabric with
-the handsheet disposed thereon over a vacuum slot having 10
inches (about 25.4 centimeters) of mercury vacuum applied
~ thereto. The handsheet was then dried on a can type dryer
while still disposed on the fabric and in its original
relation thereto. The dried handsheet was then ~mpregnated
in its zones ~uxtaposed the top-surface-plane knuckles of
the fabric by passing the fabric/sheet c~mbination and a
full-field gravuxe plate through'the handsheet impregnating
apparatus 106 as indicated in the enlarged scale'Figure 14
- and as hereinbefore described. The latex binder comprised a
25 percent solids, self-crosslink~ng acrylic latex emulsion
whi'ch was obtained from R~hm and Haas Company, Philatelphia,
Pennsylvania, and which was designated TR-520. The'latex
binder further comprised ammonium nitrate (NH4N03), a latent
acid catalyst, in the amount of about 0.5 percent by weight
of latex solids;"Pluronic L-92"of about 1.0 percent by
weight of latex solids, which is a nonionic surfactant sold
by BASF Wyandotte Corporation, Parsippany, New Jersey, and
which was added to serve as a finishéd product wetting
agent; ammonium hydroxide (NH40H) in sufficient ~mount to
raise the pH of the binder solution to about 5.0; Lithium
'Acetate (CH3C021i) in the a~ount of 200 ppm Lithium based on
the weight of latex solids to serve as a tracer to facilitate
analysis of samples to ascertain their latex content; and an
anio~ic ~ater soluble dye was added to allow visual lnspection
of the impregnation patter~. The grawre'plate was etched
to provide a full field o~ reservoirs which numbered abou~
2~,500 reservoirs per square lnch (about 3500 reservoirs per
sqUare centimeter) and the corporate volume of the reservoirs
Wa8 ~bout 1.2 microliters per square centimeter of etched
area.
'HANDSHEET'E~AMPLE'2
Hantsheet Example 2 was a replicate of Handsheet Example
1 insofar a3 variables in ~he making thereof permitted.
* Trademark 0
.. . . _ . ..
1155(~-)7
- 20 -
'HAND'SHEE~ EXAMPLE' 3
Handsheet Example 3 was prepared like Handsheet Examples
1 and 2 except for Number 3 the etched, full field gravure
pattern comprised about 40,000 reservoirs per square inch
(about 6200 reservoirs per square centimeter), and the
corporate volume of the reservoirs was about 2.2 microliters
per square centimeter.
. 'HAND'SHEE~ EXAMPEE 4 . -:
Handsheet Example 4 was prepared like Handshe~t Example
1 except that after-it was dried on.its forming fabric it
was removed therefrom, rotated 90 degrees with'respect
; thereto, and reassociated.therewith with'adhesive tape.
Thus, the pattern of the ~one'densified handsheet was pIaced
out of registration with the'knuckle patte~n of the fabric
`15 prior to impregnation 90 that comparative'data could be
obtained with respect to out-of-registration impregnation-
~Handsheet Example 4) versu~ in-registration im~regnation
(Hand~heet Examples 1, 2 and 3) of pattern densified fibrous
webs .
' ........................ '.. '
. ' ~NDSHEE~ EXAMPLE 5
I Handsheet Example'5 was prepared like Handsheet Example
j 4 except, prior to impregnation, the densified structure of
i the handshee~ was placed out of registration with the '
knuckle pattexn of the fabric by removlng the handsheet rom
the'fabric and t~rning thè handsheet over prior to reassociating
it with the fabric with adhesive tape.' Thls hantsheet
provided fuxther out-of-reg~stxation-impregnation data which
is tabulated along with the corresponding data from Handsheet
Examples 1 through 4 in Table I.
' HAND'SHEET'EXAMPLE' 6
Whereas Handsheet Examples ~ through 5 were'pattern
densified during their formation on relatively coarse 36 X 32
mesh fabrics o the 5-shed satin weave shown in Figure 6,
Handsheet Example 6 was ~ormed with relatively uniform
density on a relat~vely fine mesh fabric having llO'X 95,
~' :' ~
.
` 13L55~)7
. - 21 -
.
MD X CD filaments per inch (about 43 X 37, MD X CD filaments
per centimeter), and woven with a 4-shed satin weave using a
1, 2, 3, 4 warp pick sequence. But fox the different forming
fabrics, Handsheet Example 6 was made and dried in the same
manner and of the same furnish as Handsheet Example 1.
However, because the relatively fine mesh 4-shed satin weave
j fabric described above is much smoother than the relatively
coarse 5-shed fabric shown in Figure 6, and because the
fibers of the furnish were very long with'respect to the
knuckle-to-knuckIe span of the 110 X 95, 4-shed as compared
. to the coarser 36 X 32, 5-shed fabric, the handsheet formed
I . on the'4-shed was reIatively uniformly dense as compared to
1 ' the'pattern densified Handsheet Examples 1 through 5, inclusive.
But, it is not intended to thereby imply th~t pattern densified
sheets cannot be formed on fine mesh fabrics such as the 4-
shed satin weave des'cribed above. After being dried,
Handfiheet Example 6 was removed from the 110 X 95 forming
. fabric and taped onto a 36 X 32 mesh,' 5-shed fabric identical
to thoQe.used for Handsheet Examples 1 through 5 prior to
bein~ ~mpregnated by passing it through handsheet impregnating
apparatus 106 in the manner indicated in Figure 14. The
gravure plate and the latex binder composition were also the
same'for Handsheet Example 6 as for Handsheet Examples 1, 2,
4 and 5. Thus, Handsheet Example 6 was a pattern impregnated
sheet of relatively uniform density which yielded data which
is also tabulated in Table 1 or conveniently comparing the
pattern densified/pattern impregnated Handsheet Examples 1
through 3 embodying the pres~nt invention with the unio~m
densitylp~ttern impregnated Handsheet Example 6.
. 30 Referring now to Table I, the Handsheet Examples 1
through 3 embodying the present invention clearly ~a~e
superior (lower) bending modulus ti.e., greater flexibility)
as compared to.the out-of-registration impregnated/pattern
. 'densified Handsheet Examples 4 and 5, and as compared to the
pattern impregnated/uniform density Handsheet Example 6.
..'.'
...
~155(~7
- 22 -
TABLE I
Binder Wet Total
on Product, Total DryTotal Wetrenslle,
Handsheet Percent of Area Tensile Tensile Percent of Bending
5ExampleWeight of Covered, Strength,Strength, Dry Total Modulus,
Number Fibers_ Percentg/inch g/inch Tensile Kg/cm2
7 . 82 39 . 1 986 414 42. 0 31 . 9
' 2 8.32 38.2 sos 355 39.2 21.3
3 10.56 51. 61379 598 43.4 31.9
.
¦ 10 4 9.17 65.41093 415 38.0 45.9
8.48 6~.3 948 399 42.1 43.6
6 9.68 58.41089 416 38.2 67.4
HAND~HEE~ EXAMPLE~''7'AND' 8
~ Two additional Handsheet Examples embodying the present
¦ 15 invention were'prepared in the'same'manner and with the same
furnish as Handsheet Examples 1 through 3 except the gra w re
plates were engraved to provide'different levels of binder
-addition. Pert~nent data from.these two examples are
tabulated in Tabt'e II; in particulax, comparative dry strength
and we~ strength'data which'evidences that embodiments of
the present invention have'greater strength'derived from a
. given amount of binder than the'non-pattern densified
Handsheet Example 9 described next.
. HAND'SHEET EX~MPLE 9
. 25 This handsheet was of relatively uniform density and
. ' was formed~ dewatered and dried substantially identlcally to
.Handsheet Example 6 uqing the same furnish as for Handsheet
Examples 1 through 8. Howe~er, whereas Handsheet Example 6.
was impregnated by a full-field gra w re plate while backed
by a 36 X 32 5-shed fabric in the manner shown in Figure 14,
Handsheet Example 9 was impregnated in the manner shown in
Figure 15; that is, not backed'by a fabric. In this instance,
the gravure plate 115 was prepared with a pattern identical
in size and geometry to the top-surface-plane knuckles of a
36 X 32 5-shed fabric, Figure 6. The gravure pattern
comprised abou~ 22,500 reservoirs per s~uare inch of reservoirs
,
.
_.. _. . _ ...... . . . __._ ._ _ . .
- 1~55(~)7
- 23 -
(about 3,500 reservoirs per square centimeter of reservoirs)
and was derived from a 150 X 150 lines per inch (about 59 X
59 lines per centimeter) screen which was superimposed on a
knuckle-pattern print made from the 36 X 32 5-shed fabric
59, Figure 6, to make a negative which was then used in
producing an acid etched gravure plate. Therefore, the
uniform density Handsheet Example 9 was pattern impregnated
in the sa~e pattern as Handsheet Examples 7 and 8 embodying
the present invention. However, whereas Handshe~t Examples
7 and 8 were pattern densified prior to their being impregnated
in their dense ~onesj Handsheet ~xample 9 was of uniform
density; i.e., having no dense zones.
'TAB~E'II
. W~t Total
- Tensile,
.Blnder' Total Dry Total ~et Percent
, Percent o~ Tensile Tensile of Dry
~andsheet - Basis Weight Weight Strength~ Strength, Total
Example lbs/3000 sq.ft. of Fibers g/ibch '~/inch Tens~le
7 16.2 . '4.64 . 703 ,258 '36.7
20 8~ ' 16.0 5.40 ' .834'317 38.0
9 15.4 5.02 540 175 31.6
. ,.
; Another benefit which ma~ be derived from the present
invention is precipitated by the application of pressure to
the.binder impregnated de~se zones as, referring to F~gure
25 5, the pattern densified embryonic web 20e ~backed by fabr~c
. 59) passes through the pressure biased nip intermediate
pressure roll 67 and Yankee dryer 75 prior to the inal
. drying and creping of the web. The following example,
. Example I0, illustrates this.
..........
EXAMPLF 10
Basically, a papermaking machine of the general
configuration as papermaking machine 30, Figure 5, was run
to produce two families of samples. during which run: the
percent of latex solids in the binder emulsion in reservoir
35 85 was incremented fxom 10 to 25 and then to 40 pereent; the
after predryer (APD) iber consistency was varied from about
.. .. . _ . , . . _ ~ ._.. ... __ . ... _ _ . _ .... _ _ . .. ._ _ . ._ _. . . _ .. _ . : .. .
l~sson7
- 24 -
68 percent to about 91 percent; and samples were taken from
adjacent the- doctor blade 7~ which samples had about zero
crepe, and from intermediate roll 66 and pressure roll 67.
~ In the data tabulated in ~able IIIa and IIIb, the former
samples are designated Pressed Samples, and the latter `
samples are designated Unpressed Samples; and pairs of
samples are designated by pair numbers which pairs each
comprise a Pressed Sample and an Unpressed Sample.
, . ......................... - .
TABEE Illa
EXAMPLE 10
POST INPREGNATION PRESSING OF DENS~ ZONES
PRESSED S~MPLES VS. UNPRESSED SAMPLES
. Total Wet Ratio,
T~sile Strength, Pressed To
j 15Perce~t APDX OP Total Dry Unpressed
Sample Sollds Piber. Tensile Strength (Ratlo of
Pair In Latex Conaistency, - - Column 4 toNo. Binder Percent `PresSed UnPressed Column 5)
1 10 76.0~8.~ 28.3 .99
2 10 88.927.6 26.1 - 1.06
3 25 67.639.7 32~4 1.23
4 25- 88.740.2 27.9 1.44
67-.639.0 31`.4 1.24
6 40 90.931.4 21.5 1.46
.., -
~ 25 - ~ABLE IIIb
:~ EXAMPLE 10
POST IMPREaN~TION PRESSING OF DENSE ZONES
_ PRESSED.SAMPLES VS. UNPRESSED SAMPLES
Wet Tensile Strength, g/inch
Pair Pressed - Unpressed
- No. MD CD Total MD CD Total
1 46 39 85 83 50 133
2 74 44 118 66 41 107
3 115 80 195 99 63.162
4 111 83 194 76 44 120
72 167 85 60 145
. 6 - 43 54 97 56 41 97
_ _ ,,, _, ., . . , _ _, . . _ . . . _ , . . . . ... . . . ...... . ~ . . .
~s50n7
25 -
The s~amples of Example 10 were made on a papermaking
machine of the general geome~ry of machine 30, Figure 5,
using the 60 percent Tongacel/40 percent Grand Prairie Prime
(low bond/kraft softwood fibers, respectively), long fiber
furnish as used to make Handsheet ~xamples 1 through 9
descxibed above. This furnish was chosen to produce, if not
impregnated in accordance with the present invention, a weak
web with less than 150 grams per inch total tensile strength
(the sum of t~e machine direction tensile strength plus the
cross machine direction strength). A 0.12 percent fiber
consistency pulp slurry of this furnish was distributed on a
Fourdrinier wire 33 of a 4-shed satin weave having a 78 X
60, MD X CD filament mesh count per inch (about 31 by 24
filaments per centimeter). Dewatering was progressiveIy
effected while the web was being forwaxded on the 78 X 60
Fourdrinier wire, and then on intermediate carrier wire 51
of the same mesh, weave, and material as the Fourdrinier
wire to increase the fiber consistency of the web to about
22 percent prior to being transferred to the ~mpr~nt~ng
carrier fabric 59 which was a 5-shed satin weave of the type
shown in Figure 6 and having 31 X 25, MD ~ CD filaments per
inch (about 12 X 10 filaments per centimeter). Further
dewatering was precipitatet by vacuum transfer box 61 and
the triple vacuum box 62 to provide a fiber consistency of
about 32 percent. `The resu~t of vacuum transferring from
the 78 X 60 intermediate carrier fabric 51 to the 31 X 25
imprinting carrier fabric 59 and the vacuum dewatering
thereon caused the web to become pattern densified thereby
completing the formation of the pattern densified web:
discrete spaced dense zones ~uxtaposed top-surface-plane
knuckles of imprinting carrier fabric 59. and relatively low
de~sity spans or portions between those knuckles. These
conditions also caused the unsupported portions of the web
to be displaced by the vacuum induced differential fluid
(air) pressure into the interfilamentary voids of fabric 59.
The web was then predried by blow through predryer 64 to an
APD fiber consistency in the range stated sbove: about 68
percent to about 91 percent. The web, still disposed on
abric 59 then was forwarded thereon through a full-field
... ... . .
;55
26 -
pattern, pressure biased gravure impregnating means of the
type described hereinbefore which caused the dense zones of
the web to be pressed against the gra wre cylinder 81 and
- thereby become impregnated; however, the low density span
portions were not so impregnated by virtue of having been
sufficiently displaced into the interfilamentary spaces of
fabric 59 to substantially obviate their being impregnated
by the impregnating means. Additionall~, binder impregnation
of the low density ~pan portions was substantiaIly;obviated
by not press~ng them against the rotogravure cylinder'81.
' Rotogravure cylinder 81 was engraved with a full-field
pattern of'reservoirs (cells) number~ng about 3500 per
~quare'centimeter ant ha~ing a total volume of about 1.4
microliters per square centimeter.
The binder material used to impregnate the sample~ of
Example'10 was the same'latex emu'lsion as for the hereinbefore
described handsheets except: the'percent solids was
incremented from 10 to 25 and then to 40 percent; and very
law'levels of commercial deoamers"(Foammastes 160L"~and
20~Colloid 694~were'added to suppress foaming of the latex
emulsion 25 in reservoir 85 as cylinder 81 rotated therethrough
and the'excess latex was doctored therefrom. "Fozmmaster
160L'was obtained from Diamond Shamrock Co~poration, Cleveland,
Ohi'o; and Colloid 694 was obtained from Colloids, Inc.,
Newark, New Jersey.
.
' Further with'respect'to Example 10, backing roll'82,
Figure 5, was an 80 Shore A Durometer rubber covered roll;
'' and pressure roll 67 was an 85 Shore A ~urometer rubber -
coveret roll. Roll 82 was biased`towards cylinder 81 with a
.
orce of about 20 pounds per lineal inch (about 3.5 Xilograms
per lineal centimeter); and pressure roll 67 was'biased
towards Yankee cylinder 75 at about 440 pounds per lineal
inch (about 78 kilograms per lineal cent~meter). The creping
adhesive which was applie~ to Yankee dryer 75 via spray
applicators 77 to enable creping wa~"Gel~atol 20-90"*~a*
polyvinyl alcohoilacetate manufactured by Monsanto Co., St.
- Louis, Mi~souri. After being creped from the Yankee dryer
* Trademark
** Trademark
; *** Trademark
1~55~7
_ 27 -
75 by doctor blade 78, the paper web from which the pressed
samples were taken was reeled at the same speed as the
Yankee; thus the samples exhi~ited virtually zero residual
~ crepe so that residual crepe would not be a substantial
difference between the pressed samples and the unpressed
~samples which were obtained as follows. The unpressed
' samples of Example 10 were obtained by pressing a sheet
width, adhesive coated, rotatabl~ mounted spool against the
web' on fabric 59 running from roll 66 towards pressure roll
1~ 67 to accumulate sufficient web on the'spool to run samples
i - thereof which were not adulterated by.the adhesive on the
¦ spool. The'samples were tested to obtain the TabIes IIIa.and
IIIb data after being cured for about 5 minutes at about
300F.. (about 150C.~'). . '
'15 Generally, the data in Tables IIIa and IlIb indicate
that post-impregnation pressing as described hereinbefore
precipitates improved wet tensile strength;' and greater wet
tensile'strength'for a 25 percent level of solids in a latex
' binder emulsion thaff for either a 10 percent-or 40 percent
level of solids. Furthermore,' post-~mpregnation pressing
aIso generally improves the ratio of total wet stxength to
total dry strength of-the paper which is generally regarded
as a performance parameter for paper towels and the like.
. _ . ,
. Three more papermaking experiments which'are designated
25~ and described below a~ Examples 11, 12, and 13 were conducted
. to produce papers embodying the present invention: that is,
pattern dens.ified papers having discrete, spaced, binder
impregnated zones of h~gh fiber tenslty and otherwise being .
s~bstantially low bond, high bulk, unimpregnated structures.
Data from these examples are'tabulated in Table IV~
. ' ' ' ' .
. .
1~5501)7
TABLE IV
EXAMPLE 11 EXAMPLE 12 EXAMPLE 13
2-Ply Paper 2-Ply Paper 3-Layer
Towel TowelToilet Tissue
Basis Weight: pounds per 3000 34.2 39.2 16.8
sq.ft. (grams per square meter) (55-8) (63~9) (27.4)
Caliper: mils t.~. ) 33.1 30.0 10.7
(0.83) tO.76) tO.27)
Dry MD Tensile Strength: 465 924 196
. 10 grams~inch (græms/cent~meter~ (183) (364) (77)
Dry CD Tensile Strength: 346 559 144
grams/inch (gra~s/centimeter) (136) (220) (57)
Wet CD Tensile Strength: 157 176 Not
græms~inch (grams/centimeter) (62) (69) Measured
Wet/Dry CD T~n5ile S~rength 47X 31Z
I .. : , . .
Wet Tear Strength: grams 56.0 53.0Not Measured
Stretch KD l9X 35X 23
Stretch CD llZ 9% 7X
Softness: .Sub~ective Panel Score
Unit~, Example Versu~
-Contemporary Paper Product Of
Comparable Ba~is Weight ~1.7 +1.0 +1.7
. Spill Wipe-Up:
3 Sub~ective Panel Score Units,
:~ 25 Example ~ersus a Contemporary
Paper Product of Ccmparable -
Basi~ Weigbt -0.4 ~0.9Not Mea~uret
Binder Content, Estimated As
. Percent Of Fiber We~ght 62 n 2.4X
30 Binder: Type Latex Emulsion Polymeric Latex Emulsion
Solution
. Concentration 40Z Solids lOX Solu~ion 5Z Solids
.. . ., .. .. ... , ,,, , _,,, , . ,, ,, _ _ ...... .. . _ .,, _ ._ ._. . . .. -- --.. _ _ . . . . .
55~f)7
29 -
Briefly, Exa~ples 11 and 12 were made using low bond
Tongacel, described hereinbefore, in the furnishes to provide
low bond webs, and the process conditions were so çontrolled
that the webs were pattern densified when fully formed, and
then impregnated with binder material in their dense ~ones
to enhance both their wet and dry strengths: a latex emulsion
binder for Example 11 and a polymeric solution type binder
I for Example 12.
¦ ~Iore specifically, Example 11 was ma~e from the same
60% Tongacel/40% Northern Softwood Kraft and in thè same`
I manner as Example 10 except for a reIatively constant APD
'i fiber consistency of 78 percent; and except for the'latex
binder having 40 percent solids and containing no lithium
tracer or dye.' After the'paper web was creped and doctored
rom the'Yankee dryer, Example-'ll was calendered by a
rubberlsteel calender roll pair at about 58 pounds per
square'inch (about 400 kPa) and reeled at a speed of 75
percent of the Yankee to provide a relatively high degree of
' residual crepe. The'reels of pap'er were then combined into
2-ply paper towels with the non-~ankee-contactin~ sides of
both plies in face-to-face reIation, and embossed and
athesively secured together as taught by U.S. Patent ~o.
3 3,414,4S9 which issued December 3, 1968 to E. R. Wells, and
shown in sectional-view Figure 6 thereof. The combined
25 product was cured at 350F. for about 3'seco~ds, reeled, and
then tested. The data are tabulated on Table IV. These
paper towels exhibited ~igh strength and an extràordinary
ratio of wet/dry CD tensile strength as compared to a variety
of contemporary paper towels yet scored substantially higher
30 in subJectively percei~ed softness. Also, the data evidences
thst the converting process removed a substantial portion of
the residual crepe'in the paper.
. .. .
Example 12 was also made on a papermaking machine of
the same'general geometry as machine 30, Figure 5, except, a
three'chamber divided headbox (not shown) was used to deliver
two types of flber slurries onto the Fourdrinier wire 33 in
superposed relation. The first-down slurry ~uxtaposed the
. , ., __ _ . , . ~ _ .. ,, .. . _ _. _ . _ . . . _ . . . . ..... ., _ . . ..
~5S0~7
- 30 -
Fourdrinier wire was identical to the low bonding pulp
slurry o~'Tongace~'/Northern Softwood Kraft which was used to
make Examples 10 and 11, and was issued from the bottom
chamber of the headbox at a fiber consistency of about 0.20
percent. Northern Softwood Kraft slurries were simultaneously
issued from both the center and top headbox chambers at a
fiber consistency of about 0.12 percent. The Fourdrinier
wire 33, and intermediate carrier fabric 51 were the same 78
X 60 mesh and wea~e,' respectlvely, as used for Examples 10
and 11. However, the imprinting carrier fabric 59 was the
same 36 X 32, 5-shed mesh'and weave as used for Handsheet
Example 1. Fiber consistency was 13 percent prior to transfer
to fabric 59; 29 percent before p~edryer (BPD); and about 96
percent APD.
The binder used for Example 12 was a 10 percent solution
of'Parez 63I NC'*a papermaking wet strength resin sold by
Amer'ica~ Cyanamid Company, Wayne, ~ew Jersey. Thls is
beIieved to be a reaction product of glyoxal wi'th a copolymer
of dialkyl dimethyl ammonium chloride and acrylamide.
The rotograVure cylinder used for Example'12 was the
same as for Examples 10 and 11; and the web was finished,
creped, calendered, reeled, converted to 2-ply paper towels,
and tested to the'same degree and in the same manner as
Example ll except both plies were oriented to place their
low bond layers on the outside of the structure. The
re~ulting data are tabulated in Table I~.
Example 13 was formed as a 3-layer structure'using the
3-compartment headbox described above and in the same general
manner in the same papermaking machine as Example 12. The
three'layers consisted o Champion Eucalyptus on the top and
bottom and Grsnd Prairie Prime .~orthern Softwood Kraft in
the middle. The Champion ~ucalyptus was obtained rom
Champ~on International Corporation, Stamford, Connecticut.
All pulps were at 0.13 percent consistency when distributed
at three equal basis weight3 to produce a web on the machine
of 17 7 pounds per 3000 square feet ~about 28.9 grams per
8quare meter) bagis weight. The kraft layer was made from
* Trademark
.
.. . . .. . .. ~ .,, ~ . . . .
- 31 -
low bonding pulp furnish whic~ had Quaker 200~*(a stearyl
imidazoline made by Quaker Chemical Company, Consh~hocken,
Pennsylvania) added at a level of about 0.25 weight percent
of the kraft. The web was initially formed on the same 78 X
60 Fourdrinier wire used for Exam~les 10, 11, and 12, and
subsequently transferred and dewatered as generally described
with respect to those Examples. The imprinting carrier
fabric wa~ a 3-shed semi-twill having a mesh c~unt of 31 X
25, MD X CD filaments/inch, and was treated to provide
10. ~mprinting knuckles as described in U.S. Patent No. 3,905,863
which issued September 16, 1975 to P. G. Ayers. The net
result of vacuum transferring from a 78 X 60 intermediate
fabric to a 31 X 25 imprinting carrier fabric and subsequent
dewatering was to produce a web'on the 31 X 25 mesh imprinting
carrier fabric of non-uniform density having l~w density
portions ~uxtaposed the voids in the fabric, and high density
zones iuxtaposed the fabric knuck$es.
The latex binder used was"Airflex 402'which was obtained
from Air Products And Chemicals Inc., Allentown, Pennsylvania;
a dry strength vinyl-acetate ethylene emulsion. This was
ad~usted to have'a 5Z leveI of sol~ds, and applied by the
same rotogravure'cylinder of Example 10. The impregnated
we~,' still tisposed on and in register with the 31 X 25
imprinting carrier fabric, was then pressed at about 440 pli
~about 78 kilogramæ per lineal centimeter) against the'
Yankee'dryer, using'a rubber covered pressure roll with a
Shore A Durometer hardness of 85 loaded against the dryer to
impr~nt the ~nuckle pattern of the fabric into the web and
thereby compaet the dense zones thereof. Gelvatol 20-90
polyvinyl alcohol/acetate manufactured by ~onsanto was
applied to the Yankee dryer upstream from the pressure roll
to adhere the web to the Yankee and allow creping at the
doctor blade after the web was dried. The web was then run
through a rubber roll/steel roll papermaking calendering nip
at a light load and wound up on a reel at 82% of the Yankee
speed. The reels of paper thus obtained were rewound and
slit into standard toilet tissue rolls and tested. The
test da.a are tabulated in Table IV.
* Trademark
** Trademark
. . _ . . . _ , . . .
r
1~5SO~)7
- 32 -
While particular embodiments of the present invention
have been illustrated and described, it would be obvious to
those skilled in the art that various other changes and
modifications can be made without departing from the spirit
and scope of the invention. Therefore, it is intended to
cover in the appended claims all such changes and
modifications that are within the scope of this invention.
~ .................. - __ . ., . __ __ ... _ . ..... . .
