CA1094853A - Method of and apparatus for texturizing untextured dry tissue web - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Untextured dry tissue web is advanced through the nip of grooved rotary texturizing rolls having complementary substantially interdigitated texturizing ribs and grooves, and driving the ribs into texturizing engagement with both faces of the dry tissue web as the web advances through the nip of the rolls.

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Description

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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.
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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 -~
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- 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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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

-2-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 ,~ ., ~
-2a-~9~8~3 of certain representative embodiments thereof, taken in conjunction with the accompanying .......................

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~L09~853 , 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.
, ' 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 ~0~8~3 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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~!94~3~3 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.

___ 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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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 .; ~,, L8~3 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, .- - ~' . , .
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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Claims (19)

1. THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
   OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
   l. A method of producing bulky, soft sanitary tissue, comprising:
   providing in a continuous strip a low bulk dry untextured tissue sheet web of about .115 mm thickness from a water slurry of tissue quality cellulose fibers hydrogen bonded by drying of the web to from about 85% to 97% dry condition;
   providing cooperating grooved rotary texturing rolls each of which has generally radially projecting texturing ribs sep-arated by grooves, the ribs on each of the rolls being the same and having from 4 to 30 equally spaced ribs per centimeter measured across the ribs, each rib being of generally triangular shape with a line contact crest;
   orienting said rolls in nip relation with the texturing ribs and grooves of each roll partially interdigitated with the ribs and grooves of the other of the rolls, and with the spacing between the partially interdigitated ribs greater than the thickness of said web;
   guiding said dry web under running tension through the rib and groove nip of said rolls;
   effecting longitudinal running of said dry web and rotation of said rolls at a common speed;
   thrusting said rib crests into the opposite faces of the running dry web and effecting progressive wave-stretch deforma-tion of the web areas engaged by the thrusting crests out of the original plane of the tensioned web, and thereby mechanically breaking the hydrogen bond of and partially loosening some of the fibers of the dry web and texturing and imparting desired tissue bulk and softness to the running dry web while retaining satisfactory web integrity, and elasticity and breaking length characteristics in the textured web;
   and after said stretch deformation releasing said web areas from said rib crests and permitting said web areas to return elastically toward said original plane of the web;
   
   whereby, the loosened fibers at both faces of the web provide a fluffiness which imparts the desired bulk and softness to the textured dry web.
2. 2. A method according to claim 1, comprising advancing the dry untextured tissue sheet web through a plurality of said grooved rotary texturing roll nips, and thereby increasing the bulk and softness in the resulting tissue sheet.
3. 3. A method according to claim l, comprising providing the texturing rolls with texturing ribs at least .5 mm in height and intervening grooves about .5 mm deep, and spacing the rolls apart at the nip within a range of .20 mm to .40 mm.
4. 4. A method according to claim 1, comprising effecting the texturing to attain a bulk of about 8.5 cm3/gm.
5. 5. A method according to claim 1, comprising forming the untextured dry tissue web to a basis weight of 20 gm/m and texturing the dry tissue web to a caliper thickness of about .17 mm, a bulk of about 8.5 cm3/gm and a breaking length of about 377 m with a softness rating of about 4.
6. 6. A method according to claim l, wherein the untextured dry tissue web is of a basis weight of about 20 gm/m , and texturing the dry tissue web to a bulk within a range of about 6 cm /gm to about 10.5 cm3/gm.
7. 7. A method according to claim 1, comprising after advancing the untextured dry tissue web through the nip of said first mentioned set of grooved rotary texturing rolls, successively thereafter advancing the dry tissue web through the nip of a second set of grooved rotary texturing rolls having complementary substantially interdigitated texturing ribs and grooves, and thereby increasing the bulk of the dry textured web.
8. 8. A method according to claim 1, comprising forming said texturing ribs on said texturing rolls to run axially on the perimeter of the rolls, and dry texturing said web entirely across its width.
9. 9. A method according to claim 1, comprising forming said texturing rolls with said ribs running circumferentially on the rolls, and dry texturing the web entirely across its width.
10. 10. A method according to claim 1, comprising providing said texturing ribs on said texturing rolls to extend axially along the perimeters of the rolls, and providing texturing rolls having the same characteristics except that the texturing ribs extend circumferentially on the perimeters of the rolls, and treating the same web successively between the rolls having the ribs running axially and between the rolls having the ribs running circumferentially.
11. 11. In combination with a continuous strip of low bulk about 85% to 97% dry originally untextured tissue sheet web of about .115 mm thickness formed from a water slurry of tissue quality cellulose 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:
    said apparatus comprising cooperating grooved rotary texturing rolls each of which has generally radially projecting texturing ribs separated by 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;
    said rolls being oriented in nip relation with the texturing ribs and grooves of each roll partially interdigitated with the ribs and grooves of the other of said rolls;
    said dry tissue sheet web under tension running longitu-dinally through the rib and groove nip of said rolls at a sub-stantially common linear speed with rotation of said rolls;
    said partially interdigitated ribs of each roll being spaced apart from the ribs of the other roll a distance greater than the thickness of said dry tissue sheet web, so that there is complete freedom from any squeezing of said web between any surface of the ribs;
    said rib crests being oriented by their spaced interdigitated 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 mechanical breaking of the hydrogen bond of and partial loosening of fibers at both faces of the dry tissue sheet web, resulting in fluffy surface texture on the dry 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;
    and said rib crests separating in the rotation of said rolls after said limited wave-stretch deformation of the web by said crests so that said textured dry tissue sheet web is released from said crests and said web areas permitted to return elastically toward said original plane of the web.
12. 12. A combination according to claim 11, wherein a plurality of pairs of said cooperating groove rotary texturing rolls are located to act successively on the running dry tissue sheet web, so that the fluffiness and the bulk and softness is increased in the textured web.
13. 13. A combination according to claim 11, wherein said ribs are of substantially triangular shape in cross section.
14. 14. A combination according to claim 3, wherein said ribs are of substantially triangular shape in cross section.
15. 15. A combination according to Claim 11, wherein said texturing ribs are at least .5 mm in height, said separating grooves are about .5 mm deep, and spacing of the rolls at the nip is within a range of .20 mm to .40 mm.
16. 16. A combination according to Claim 11, including a second set of grooved rotary texturing rolls having comple-mentary substantially interdigitated texturing ribs and grooves through which the dry tissue web advances from said first rolls for thereby increasing the bulk of the dry tex-tured web.
17. 17 A combination according to Claim 11, wherein said texturing ribs on said texturing rolls extend axially on the perimeters of the rolls, and said ribs texturing said dry tissue sheet web entirely across the web width.
18. 18. A combination according to Claim 11, wherein said ribs extend circumferentially on said rolls, and said ribs texturing the dry tissue web entirely across the web width.
19. 19. A combination according to Claim 11, wherein said texturing ribs on said texturing rolls extend axially along the perimeters of the rolls, and additional texturing rolls having the same characteristics except that the texturing ribs thereof extend circumferentially on the perimeters of the rolls, and the web runs successively between the rolls having the ribs extending axially and between the rolls having the ribs extending circumferentially.