Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates t:o a method of and apparatus for
teY~uxizing untex~urcd dry tissue web, and in particular is directed to
proclucing bulk and softness in tlle tissue web sheet.
I-leretofore texturizing of tissue web has generally been effectecl
in colmection with a Yankee dryer which is Q large and costly high
pressure steam vessel in ~he form of a drum on the periphery of which
the web is dried. 13ulk and softness in the tissue sheet is produced by
creping, that is scraping the slightly adhered sheet from the Yankee
xoll surface by means of a doctor blade. Inas~uch as the adhesion
of the tissue sheet to the Yankee drum surface is intimately associated
with the drying process, the drying and creping are inseparable
functions on the Yankee dryex drum.
.
Alternatively, some bulkiness may be produced in the tissue
sheet by passing heated air through the tissue sheet, referred to as
through-drying which is very satisfactory for drying the tissue in lieu
-oP mechanical pressingl Such through-drying, as well as other tissue -~
~ . . - : :
- drying methods suffer from ~he limitation that there is no built in
generation of bulk or softness equivalent to the process of creping
,
from the Yankee dryer. As an order of mag~itude estirnate, a t]lrOUgh-
- dryer tissue sheet rnay have only 1/3 to 1/2 tlle bulk of à tissue sheet
creped frorrl a Yankee dryer~
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An important object of tlie present invention is to attain good
bulk and softness generation in tissue sheet, avoidirlg tlle need for
and great cost of a Yankee dryer an~ permittin~ drying of the sheet
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353
to be effected by method alternative to Yankee dryer, such
as through-drying.
In accordance with the present invention, there is
provided a method of texturizing untextured dry tissue web,
comprising advancing the untextured dry tissue web through a
mechanical texturizing device such as the nip of grooved
rotary texturizing rolls having complementary substantially
interdigitated texturizing ribs and grooves, and mechanically
working and texturizing the dry tissue web as by driving the
ribs into engagement with both faces of the dry tissue web
as the web advances through the nip of the rolls, thereby
generating bulk and softness in the resulting tissue sheet.
Also according to features of the invention there is
provided apparatus for texturizing untextured dry tissue web,
comprising a mechanical texturiæing device such as rotary ;
texturizing rolls disposed in nip relation and adapted to
have the untextured dry tissue web advanced through the nip
of the rotating rolls, and the device having means for mecha-
nically working and texturizing the advancing web, such as
rolls which have complementary substantially interdigitated
texturizing ribs and grooves for driving in texturizing rela-
tion against both faces of the dry tissue web as it advances
through the nip of the rolls, whereby to generate bulk and
so~tness in the resulting tissue sheet.
The invention provides in combination with a conti-
nuous strip of low bulk about 85% to 97~ dry originally un-
textured tissue sheet web of about .115 mm thickness formed
from a water slurry o~ tissue quality ~ellulose fibers
hydrogen bonded by drying of the web to said about 85% to
97% dry condition, apparatus for texturing said tissue sheet
web into bulky, soft sanitary tissue. The apparatus comprises
cooperating grooved rotary texturing rolls each o~ which has
generally radially projecting texturing ribs separated by
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grooves, the ribs on each of the rolls being the same and
there being from 4 to 30 equally spaced ribs per centimeter-
measured across said ribs, each of said ribs having a line
contact crest. The rolls are oriented in nip relation with
the texturing ribs and grooves of each roll partially inter-
digitated with the ribs and grooves of the other of said rolls.
The dry tissue sheet web under tension runs longitudinally
through the rib and groove nip of said rolls at a substantially
common linear speed with rotation o said rolls. The partially
interdigitated ribs of each roll are spaced apart from the
ribs of the other roll a distance greater than the thickness
of said dry tissue sheetweb, so that there is complete free-
dom from any squeezing of said web between any surface of the
ribs. The rib crests are oriented by their spaced interdigi-
tated relation, so that they thrust a limited distance into
the opposite faces of the tensioned running dry tissue sheet
web and effect just enough progressive limited wave-stretch
deformation of the dry tissue sheet web areas engaged by and
thrust by the rib crests in successive opposite directions
out of the original plane of the tensioned web to cause mecha
nical breaking of the hydrogen bond of and partial loosening
of fibers at both faces of the dry tissue sheet web, resul-
ting in fluffy surface tex~ure on the dr~ tissue sheet web
and imparting desired tissue bulk and softness to the web
while retaining satisfactory web integrity, and elasticity
and breaking length characteristics in the textured web. The
rib crests separate in the rotation of said rolls after said
limited wave-stretch deormation of the web by said crests
so that said textured dry tissue sheet web is released from
3~ said crests and said web areas permitted to return elastically
toward said original plane of the web.
Other object features, and advantages of the inven-
tion will be readily apparent from the following description
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of certain representative embodiments thereof, taken in
conjunction with the accompanying .......................
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drawing altllougll variat:ions and modifications may be e~fected without
departillg from tl~e spirit ancl scope of the novel concepts embodied in
the disclosure and in wllicll:
FIG; 1 îs a schematic illustration detnonstrating practice
Oe the invention in association with a tissue web former and dryer.
,
. FlG. 2 is a sche~atic illustration demonstrating practice
of the invention on dry untextured web unwound from reels or logs
as, for example, in a converting room.
- ~ FIG. 3 is a schematic illustration of complementary substantially
interdigitated texturizing ribs and ~-ooves of rotary texturizing rolls.
FIG. 4 is a diagram showing bulk attainable by various roll
separations; and
FIG. S is a diagram showing test results a~tained by the
number of passes of a tissue web through the texturizing rolls.
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On reference to Fig. 1, a tis.sue sheet web W is produced by
.delivering tissue stock ~rom a headbox 10 to a forliler 11 comprising
~ foraminous forming belt 12 such as a fourdrinier wire which tra~els
over or past a dewatering device such as a suction box 13-and then
delivers the formed wet web to a tllrough-dxyer 14. ~rllis dryer
desirably comprises a porous dryer belt 15 whicll picks ~ e formed
wet web from tlle ~ormer belt 12 and carries the wet web in drying
relation about ~a sul)stall~ial c~tent of tlle perimcter of a porous (lrying roll
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or clrulll 17 fxom \vhich llea~d drying air is driven tllrough the beit 14
and the wel~- as sllown l~y the arrows 17a. Beyond tlle dryer 1~
tlle dry ~mtextured ~issue web W leaves l:lle belt 15 ancl may l)e eithe.
reelcd into logs for future converting, Ol- as depicted in l;ig. 1 may
pass througll a slitter 18 wllicll divides tlle l:elatively wide web as formed
illtO the desired narrower widths before tlle we~ sections arc further
processecl e.g.ultimately reeled into rolls such ~s ~oilet tissue rolls.
In order to provide tlle untextured dry tissue web W witll ciesirable
bulk and softness, i~ is advanced througll a mechanical texturizing device
19 comprisiIlg in a simple and efficient form grooved rotary texturizing
rolls of wllicll there may be one or more sets to provide one or more
.
texturizing passes of the web through the nips of tlle rolls. The texturizing
rolls 19 have complementary substantially interdigitated texturizing ribs 20
(Eig. 3) and grooves 21 ox driving iII texturizing rel~tion against both
faces of the dry tissue web ~s it advances through the nip of the rolls,
whereby to generate bulk and so~tness in tlle resulting tissue sheet. ~he
ribs and grooves 20 ancl 21 may e~tend circum~e~entially or longitudinally
xelative to the axis of the rolls 19, or a combinativn of the ciL-cumferential
and longitudinal orientations. In a desirable form, tlle ribs and grooves
20,21 may be of generally screw thread form of substantially triangular
cross secl:ion formed as a xight hand thread on ol~ of the ~lls 19 and as
a left lland thread on tlle companion roll 19 in tlle set so that Wit]l tlle
rolls rotating in unisoll tlle ril~s 20 ~vill uniformly sul~stantially interdi~ita-
~at tlle nip of tlle rolls~
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110r tc~t~lri%ing treat:ing of untextured ~ry tissue sh~et ~Jeb
of about .115 mm calipered-average tllickness, the number of ribs
and grooves 20, 21 may range between 10 and 28 per cm (~5 to 70 per
inch~. 13y experimeDting,it has been deterlnilled that to attain the
besti.results in proclucing su~ficient deformation of tlle dry tissue sheet
passillg tllrougll tlle nip of the rolls to pxoduce tlle desir~d ]~ulk and
soitness, at least a .Smm ( 020 incll) rlb lleigllt and groove deptil sllould
be present. In adclition, the cle~ree or deptll of engagement between the
nip~ of the grooved. I-olls 19 has l~een foun~ to result in a fairly predictable
resulting bulkmess and softness in tlle rcsulting texture in tlle slleet web.
~or example, having reference to Fig. 4~ maximum bulk cm3/gm is
attained wllere the spacing l)ctween the ribs 20 is minimum. For example
where tlle caliper thickness of untextured dry tissue web is about .115.mm
tlle greatest bulldness is attained where the nip of tlle rolls is spaced
at about .20mm, snd tlle bulkiness declines relatively sharply as indicated -
by the descending curve in Fig. ~ as tlle separation is increased, for
example by-.OS mm increments. It will be understood, of course, that -.
the tear strength of tlle ultimately textured sileet will be substantially
proportionate to the severity of tc~;turizing treatment to which tlle. dry
web is subjected as a result of spacing of tl~e roll nip. Excellellt. .
results for toilet tissue arc attail~ed where tlle otller parameters for tlle
ribs and grooves are substan~ially.as alre~dy described and tlle Sp~Cillg
of tlle roll nip is abou~ .275 mm, .and wherein tl~e attained te~;turi~.ed
bulk is substantially as inclic.ltecl at point 22 on tl~e c~lrve in Eiig. .~J
namely abou~ 8.5Cm3/glll ill one passtllrough tl~e rolls 19.
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Where greater bulk is desired, the dry tis ue we~ may
be advanced through a plurality of texturizing roll passes, two
such passes being shown in Fig. 1 and a third indicated as
optional if even greater bulk is desired. By way of example
reference is made to Fig. 5 showing that the bulk rate attained
is according to a straight line ascending curve as the web pro-
gresses through each successive pass, and assuming the texturizing
rolls to be substantially the same for each pass. Thus, where a
bulk of about 8.5cm3/gm may be expected in one pass, the bulk
rate becomes about 9.5cm3/gm in a second pass having substantially
the same texturizing roll nip parameters. By advancing the web
through a plurality of such texturizing passes, loss in strength
is minimized.
Where it is preferred to effect texturizing in the
converting room of a plant rather than as a continuous process
following the slitter after the dryer of a papermaking machine
installation, the arrangement demonstrated in Fig. 2 may be
employed. In this mode, the untextured dry tissue web is reeled
into rolls or logs 23, one of which is depicted and from which
t~e web W' is advanced through one or more sets of texturizing
rolls 19' having characteristics such as described for the
texturizing rolls 19. Beyond the texturizing rolls the textured
web is advanced to other converting operations such as rolling
into tissue rolls and wrapping, and the like.
By way of illustrating comparatively the results attained
by texturizing of untextured dry tissue web in accordance with the
present invention with average textured tissue produced according
to prior art technique such as Yankee dryer creping, reference
may be had to the following chart:
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, _ I
13asi s l'i~icliness 13ulk Breaking Softness
Weight ( Ca liper) cln3/gm I,c-~ngtll, m Rating
. gm/m~ mm , ,
.,_ _ . ... . . . .
Average properties
of pl: ior ~rt tissue 2~. 2 , 20 9 400 t l1,astro
Untexturecl clry
tissue 20 , 115 5.75 1957 _
l~ibbed and Grooved .
roll treated dry .
20 ~.l7 8.~ ~ L
As will be observed in this ch~r~, wllen starting with an unte~tured
clry tissue ~vel which may have been produced by through-dryin~ ancl
having a basis weight o about 20 grn/m2 as cornpared to prior art
(e.g~ Yankee dryer creped) tissue, tlle dry tissue web after treatment
according to the present invention remains at substantially a basis weight
. . . .~,
of 20 gm/m2. Wllere the calipered thickness of the ull~exturecl dry
. tissue web IS about .115 mm, aIter treatment it calipers at about .17 mm
in comparison tO albou~ a D2() mm tilickness fol tl~e prior art tissuer
~-~owever,where the prior art tissue has a bulk o 9 cm3/gmj tlle dr~ tlssue
web textured according-to tlle present inven~ioll llas a closel~ similar
bulk of 8~5 cm3/gm. ~Iso tlle compara~ive bre~king len~ is closèl~
approachecl in the textured dry tissue web as compa1ecl to tlle prior art
tis6ue in that as sllowrl tl~e bre~king lengtll of tll~ te~tllrecl clry tiSSll~ ~'eb
.; ~,,
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accordillg to the prcsent inventioll is reduce~ to only 377 m frc~m 1~7 m
and wl~ich comparcs qulte fa~oI-rll)ly with the 400 m breaking lengtl-ls of
tlle prior art l:issue. Finally, in the softnessrating wherein the prior
art tissue may rate from 1 to 9 that is from harsh to very soft, a softness
rating of about 4 is attained by practice of the present invention.
It will thus l~e apparent that according to the present invention
it is possible to start with a very low bulk dry sheet of tissue and produce
a final bulk comperable to tissue produced by prior art techniques such
as Yankee dryer and creping. Qui~e substantial economies in original
equipment and production are attained by the present invention by the
abillty to transform untextured dry tissue web produced by the most
- economical metho(l such as by through-drying and without any need for the
costly Yankee dryer or creping technigue. The tex~ured tissue sheet
has, nevertheless, comparal~le l~ulk, tear strength and softness to the
more costly prior art tissue,
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It will be ~inderstood that variations and modifications may
.
be effected without departing ~rom the spirit and scope of the novel
concepts of this invention.
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