CA2149512A1 - A method for the manufacturing of an absorbent structure and an absorbent article comprising an absorbent structure manufactured according to this method (iii) - Google Patents

Abstract

A method for manufacturing of an absorbent structure in an absorbent article, such as a sanitary napkin, tampon, panty protector, incontinence guard, diaper, bed protector, wound or sore dressing, saliva absorbent and like articles is comprising the use of absorbent material in roll form directly in the product without first defibrating the material and then forming a mat. The material possesses good aquisition properties, which are meaningful to the function of the product. A high surface dryness is obtained, among other things. In addition to cellulose fibres, the absorbent structure may also include superabsorbent material and/or binding fibres, among other ingredients. The pulp mat is very thin, therewith obviating the need to compress the mat further in the product. In the case of certain product applications, the material is softened mechanically prior to its use as an absorbent material.

Description

WO 94/11)954 b~i~ 214 9 512 P~cr/sE93/00972 A ME~THC)D FOR THE MANUFACTURING OF AN ABSORBENl STRUCIURE AND AN ABSORBENT ARTICLE COMPRISING AN
ABSORBE~ STRU~ MANUFACIIJRED ACCORDING TO T~S
ME~OD
: ' Ba~k~Q~
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The present invention relates to a method for manufacturi~g o~ an absorbent structure in an absorbent article, such as a sanitary ~apkin, a tampon, a panty prot~ctor, an incontinence guard, a diaper, a '~ ~ound or ~ore dressing, a saliva absorbent and like articles.

Many di~erent types of absorbent ar~cles of this kind are ~ow~ to the art. The absor~ent bodies of such article~ are typically produced by dry-defibering and flufElng cehulose pulp in roll, bale or sheet fo~ for instance, to form a pulp mat, sometimes a~i~ed with so-calle~
superabsorbent material in the pulp mat, these absorbe~ts being :
: polymers which ar~ capable of absorbing many times ~eir OWIl weight : of water or ~dy fluid.

. The pulp body is often compressed so as to enhance its fluid-wicking : ability and also in order to reduce pulp body bull{ and therewi1~h obtain : an article which is as compact as possible.
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The absorbeIlt body ~nay also include other cons~tuents, for instance :: - constituents which will improve its flli~d aquisitioIl propert;ie~ or its :
fluid~wicking properlies) or which ~ increase its cohere~ st;re~ , i.e.
its coheren~, and its ability to withstand deIormatioIl in use.

C)ne serious drawback with products of this natvre is found irl the tQ$al absorption capacity of the articies and also in the fact that the articles will ofl;en leak long before their total absorp~ioIl capacity h~s been fully u~lized. Among other t~ings, :~his is because the body fluid discharged by the we~er is unable to penetrate into the absorption matenal and to spread to hitherto~ unused: ~reas of the article quiekly enough, but instead leaks f~om the sides of the saI~itary napkin, the diaper or the incontinence guard. The ability of the materials used iIl ~e artide to :

~ -~ 1 WO 94/109S4 ~ 9 ~J 1 2 PCl/SE93/0o977 -disperse the absorbed fluid throughout the entire absorbent body i3 thus highly important. -Another problem resides in so-called rewetting, i.e. the transference of body fluid that has already been absorbed back into coIltact t~vitb the wearer's skin as a result of external forc~s, ~ar instance when the wearer sits down. It is generally desired that the surface of the article that lies pro~imal to the wearer in use will re~ as dry as possible.

~other desideraltum with regard to the majority of hygiene produc~s iB
that the article shall be thin, so that it can be wom as discretely as possible.

A very large par~ of the production plants used in the manufac~ure of the aforesaid hygiene articles is comprised of defibrating equipment, pneumatic conveying systems and mat-forming ~l~pment. This eqwpment is also the source of serious faults iIl the productioIl plants.
Equipment iEor cornpressing the finished pulp mat or the finished hygiene product is furthe~ore often included downstream of the production plants.

A separate prohIem is related to the use of superabsor~nt matenal in a~sorbent articles. The superabsorbent material is normally available in the form of granules, which are di~ficult to bi~d lto the absorbe~t st;ructure.
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It is known ~rom International Patent Application WO 90/05808 to produce ~ pulp web by dry-fo~g, which is later defilbered, go-called dr~T-f`ormed roll or reel pulp. Flash-dried paper-pulp fibres, which may consist of thermomechanical pulp, chemi-thermomechanical pulp, ` i CTMP, or chemical p~per pulp, sulphite or sulphat~ pulp iwith ~ dry solids content of sbout 80% is delivered by me~s of ~ air ~tream in a cont~olled flow to a ~orming hsad arranged above a ~rIni~g wire ~d there ~ormed into a web that ha~ a surface weight of 3û0-1500 glm2 and a density of 550-1000 k~m3. Air i~ sucked away through a ~uc~on box placed beneath the wire. The moisture co~tent in t~e pro~ess 8 be 5-30~.

_~ WO 94/109~4 j 21 4 9 ~12 PCI`/SE93/00972 The web is pre-pressed to a density of 550-1000 kg/m3 in order to slightly reduce the bulk of the web prior to the final pressing stage. The presse~ web has a mechanical strength which enables the web to be rolled-up or handled in sheet form for storage and transportation purposes. The web can be readily defibered and is intended to be converted into fluff for use iIl the manufacture of absorbent bodies or pads ~or diapers, sanitary napkins and like articles.

Another method ~or the manufacturing of an absorbent structure is described in European Patent Q 12~ 042, where a mixture of hydrophilic fibres and water insoluble particles of insoluble hydrogel is airlaid into a web and compressed to a density of 0.15 to about 1.0 g/cm3. This method howev~r comprises several production steps, where the dry lap base material is first disintegr~ted into cellulose fibres by use of a hammer mill, whereafter the fibres are deposited on a screen sur~ace and formed to the absorbent structure, which is then compressed. These maTlufacturing steps make this process rather complicated an~ expensive.

mmar~of th~e Invention The object of the present invention is to provide in an absorbent article of the aforedescribed kind an absorbent structure which exhibits extremely good absorption properties9 both with respect to îts ability to quickly take up fluid and also with respect to its ability to spread fluid throughout the material. The material will preferably exhibit low rewetting tendencies as well as being capable of being made very thin.
It is also desired to provide a simplified method o~ manufacturing absorbent articles of the kind defined in the introduction. These objects and desiderata are achieved with a manufactunng method in which particulate material comprising 30-100%, preferably at least 50~o and most preferably at least 70% flash-dried cellulose fibres is dry-fQrmed to a web wi~h a surface weight of between 50-1500 g/m2 and compressed to a density~of between 0.2-0.8 gicm3 and that the web without subsequent defibration and flu~fing is incorporated as an absorbent structure in an absorbent article..

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RECrIFIED SHEET (RULE 91) WO 94/10954 21~ 9 ~12 P~/SE93/0097? -Non-defibered, dry-~or$ned roll pulp has been found to be an extremely -~
good absorption material and can be used directly as aIl absorbent ma~rial in hygiene articles, without being defibered. The matenal also has good fluid wicking properties and swelling properties, which are meaning~ul to the function of the product. The pulp mat is very thin and therefore need not be fs~rther compressed ir~ the product or article.

In the case of certain product applications in hygiene articles, it is convenient to soften dry-formed roll pulp prior to its u~e a~ an absorption material. The earlier mentioIled good absorption properties, ;~
fluid wicking proper1;ies and swelling properties are not in~uenced by the so~tening process to any great extent. One method to soften an absorbent sheet is described in European Patent ~pplication EP 0 360 472, where the compres~ed absorbe~t material is worked between partially cutting rollers and thereby gaining sof~ness. This method however leads among other things to decreased strength ill the softened material..
~rief De~çription of the Dr~p~

The invention will now be described in more detail wi~ reference to a number of exemplifying embodiments thereof and also with reference ~ the accompanying drawings, in which:

Figure 1 illustrates the absorption proper~es of a dry-formed CTMP-material subsequent to being worked betwee~ rolls at di~erent roll spaMngs. Conventionally formed aIld compressed pulp mats of CTMP-pulp snd chemical pulp respec~vely were used as references.

Figure 2 illustrates the absorption properties of a dry-formed CTMP-materi~l~subsequent to being softened. aonvenl;ionally forme~ d compressed mats comprised o~ CTMP-pulp and chemical pulp respectively were used as references.
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Figure 3 illustrates the absorp~or~ properties of a complete absor~ent article manufa~ctured with dry-formed CTMP in the core.
Conventionally manufactured produc~s of corresponding compo~itions were used as references.
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~ WO 94/10954 ~14 9 51 2 PCr/SE93/00972 . .
Figure 4 illustrates the fluid aquisition time of a complete absorbent article produced with dry-fo~med CTMP in the core. Conventionally manufactured products of corresponding compositions were used as ; re~erences.

Figure 5 illustrates the degree of utilization of a complete absorbent a~icle produced with dry-formed CTMP in the core. Conventionally manufactured prod~cts of corresponding compositions were used as re~erenFes Fi~gure 6 illustrates ~he absorption properties of an absorbent structure produced with dry-fo~med CTMP, both with and without a superabsorbent admixture. Conventionally manufactured pulp cores both with and without a superabsorbent admixture were used as references, Figure 7 illustrates rewetting of a complete absorbent article produced with dry-formed CTMP in the core. ~onventionally manufactured products of co~esponding compositions were used as r~ferences.
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:~ Figure 8 illustrates the:respecti~e rewetting of an unsoftened and a softened absorbent structure in connection with blood absorption which was produced with dry-formed CTMP in the core, both with and with-out a superabsorbent admi~ture.

:Figure 9 illustrates rewetting of ~ a completely absorberlt arti~le in : ~ comlection with blood absorp~on which was produced from dry-~ormed CTMP in the core. ConveIltionally manufac~ured products of corresponding composition were used as references.

Figure~ 10-11 illustrate schematically t~e composition of ~arious exemplif~ying:eDlbodiments of in~entive absorbent ar~cles.
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Figure 12 illustrates the structure of a cross section of the material in ~^ : unsoftenedcondi~on.

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21~51 ~ I
Figure 13 illustrates the structure of a cro~ section of the material in sof~ened condition.

Des~ription Qf the Invention As before mentioIled, important properties of a material us d in the manu~cture of a hygiene article are its absorbent capacity, absorptian rate, wicking capacity, drainagé capacity, retentio~
capacity, rewetting, softness and smoothness.

The fluids concerned are ~e, menstruat;ion blood, blood, flwd matter ~om wounds and sores, ~g fl~ud and saliva.

The object of the present invention is to provide in aIl absorbent ar~cle such as a sanitary napkin, tarnpon, panty protector, incont;inence guard, diaper, bed protector, wourld or sore dressi~g, saliva a~sorbent and like afficles, an absorbent structure which e~chibits ~3igbly ef~c~ve absorption properties, especially with regard to its fll~id-aquusitio:tl rate ~d its ability to wick fll~id throughout the m~terial. The ~tenal will also preferably have low r ewetting and be capable of being made very thin and smo~th. It is also desired to simp)ify the manu~acturing process. A finished absorbent material in roll form which can be used without needing to be defibered would partially reduce t~ie need for the earlier mentioned defibering equipment, pneuma~c conveying systsms and mat-formLng equipment, a~d conse~uently there is a de~and for such material.

The aforesaid obiects and desiderata haYe been achie~ed in accordance with the invention by using a manufactu~Ilg method in which particulate material comprising 30-100%, preferably at least ~0~ ~d most preferably at least 70% 1ash-dried cellulose fibres is dry-formed to ~ web with a surface weight of between ~0-1500 g/m2 a~d compre~sed to a density of between 0.2-0.~ g/cm3 and that the web :withollt subsequent defibration and fluf~mg is incorporated as an absorbent structure in an absorbent ~rticle.

In accordance with the invention, there is used a dr~-forrned prodllct which is m~ufactured ~om particlllate mate~i~ as mechanical pulp 21~51~
WO 94/1û954 . ; ~ Pt~1SE93/00972 . ;: ` !
or chemi-thermomechanical pulp (CTMP) or a corresponding product manu~actured from sulphite pulp or sulphate pulp, so-called chemical cellulose pulp. C~ellu~ose fibres which have been sti~ened chemically may also be used. In the dry-formed product c~ also ~e included other particulate m~tter as superabsorbents, thermoplastic bi~ding fibre and other kind of fibres.
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Non-treated dry-formed roll pulp has e2tremely good absorption, wicking and swelling properties, aIld it has been found possible to use the material immediately as an absorption material in hygiene ar~cles without defibrating the pulp. In the case of certain a~sorbent articles, it has been found suitable to soften the material slightly p ior to its use. One method of sof~ening the~ mate~al is des~d below.

Dry-formed roll pulp has a good integrity whieh means t~at!in the case of use of superabsorbent matenals in dr~-formed:roll pulp tlt~e granules will be well bound to the absorbent ætructure and will not spread during : further conversion into absorbent hygiene products.
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DIy-formed cellulose pulp can be produced, for instance, by formLng a web of fl~sh-dried paper pulp fibreæ in accordance with the method described in :lnternational Patexlt Applicaf;ion ~O 9Qio5808.
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Cellulose:pulp fibres have a so-called curl ~alue which defi~es~the crookedness of the fibre. Curl ~lue can be measured according to the method described by BD. JordaIl, N.~G. Nguyen in Papper och Ir~
411986~ page~313.

Sof~çnin,~~ M~

The mat~n~3~ can be given a sof~ness whi~h rènders the mate~ial highly suitable :~r use a8~ ~ sbsorption material in the majori~y of hyg~e~e articles, ~by ~working dry-formed :roll pulp betwee~ for iIlstaDce cor~ugated~ rolls. ~ The materi~l can be: brought to dif~erent degr~es of sof~ess~fa~ different product upplications, by working the mate~ial b~tween~ ~ff~ent ~ypes of rolls and at dil3`erent roli ~pacings.

2 1 ~ 9 5 1 ~ PCI~SE93/00972 ~`

Dry-formed roll pulp which has been softened in this way exhibits very good product properties, and the earlier mentioned good absorption properties are not influenced by the so~tening process to any great extent.

The material is delaminated in the softening process as illustrated in figures 12 and 13. The unsoftened material has normally an even high density throughout the whole the thickness of the material (61). As a result of the softening process the mate~al is delaminated so as to form a plurality of partially s~parated (63), thin fibre layers (62).
Softening and delamination of the material reduces its total density to some e~ctent, aXthough the original density is essentially retained in each individual layer. Because a very high density is retained in the individual layers, the good fluid wicking properties of the material are retained despite the increase in bulk obtained in conjunction with the softening process. The total bulk is increased by up to 300GJo, normally 1-100%, as a result of the softening process, depending on the method used and the extent to which ~e material is softened.
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It will be understood that the aforesaid material so~tening method has been given solely by way of example and that corresponding results can be achieved with the aid of other methods. For instance, the material could eventually be softened by means of ultrasonic energy, microwaves, by moisturizing the material, or with the aid of chernical additives.

Inv~eation of ~erial Pro~

The test e4uipment described below was used to evaluate ahsorption properties.

Method l. Ahsorption Prope~ties U~l~j~

rectangular test ~ody was punched from the material and a line was drawn transversely across the test body at a point 11 cm from one short end of the body. A flui~ container was placed ~djacent laboratory scales and both the scales and the container were adjusted $o a horizontal posit~on. A plexiglass plate was placed on the scales at a 30 .

;~ : 8 RCTIFIED SHEE~ ~RU

--~ W0 94/}0954 214 9 51 2 PCl`/SE93/00972 . : , slope, with one free edge of the plate e~tending slightly down into the container. A line had been drawn transversely across the plai~ ~.t a point 11 cm from the lower edge of said plate. Test fluid (0.9% NaCl-solution) was poured into the container, until 20 mm of the ple~nglass plate was located beneath the surface of the fluid. The test body was secured on the plexi~lass plate so that the ~ine drawIl on the test body coincided unth the line drawn on the plate while, at the ~ame time, folding away the lower part of the test body 80 as to prevent it from coming into contact with the test liquid. A cIock wa~ ~tarted at the same time as the test body was laid onto thè plate~ with the test body e2tended:down iIltO the solution to:the same e~tent as the plate. The increase in weight of the test body wi~ time wa9 recorded.

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Ut;iliz~tion ~ :

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A test product was secured in a ~ture. Test fll~id (O.9~b NaCl-~olution) was del*ered to the wetting point of the product over a period of 60 minutes at the rate at~which the f~uid wns absorbed. The amo~mt of fluid absorbed was mensured contlnuously and the total amount of fluid absorbed by the product constitutes the utilized absorption capacity of the test product. ~The test product was then placed in a fluid bath, in : which it had~ maYimum opportunity of absorbing test fluid. The test product was then~ again weighed and the total absorption capaoity : c~cula~d. The d~gree of utilization is given by the :quotie~t between the~ utilized ab~orption capaci~y:of the test product arld the total:
nbsorp~on capacity.~

Four bat~hes of sample ;~luid (0.9% NnCl-solution], each ~omprising 28 ml, were delive~ed at 20-minute intervals. The t;ime measurement was co~ ued u~ all fluid: had bee~::absorbed. The ~tent to w~ he fluid had dispersed in t~e~dinper was noted after each batch. Sub~equent to delivering ~the lnst~ batch of fluid, filter paper wns placed over the we~ting~point and loaded with:a weight of 1.1 kg fo~ 15 secoxlds. The wo 94~109~4 2 1 4 ~ 5 1 2 PCI/SE93/OGs77 ~~

filter paper was weighed both before and a~r applying the load and rewetting was recorded.

Methnd 41 D~t~ninin~ Rewettin~ Meas~mQ~

A diaper intended for a given weight range was weighed and then placed on a flat supporS sur~ace. An adapted quantity of t~st fluid (û.9% NaCl-solution, 100 rnl for a diaper intended for a weight r ange of 7-15 kg) was delivered to the wetf;ing point of the diaper. A ~urther 100 ml of fluid was delivered after 20 minutes. When all fluid had been absorbed, a i;lter paper was placed over the we~ng poirl$ and loaded with a ~veight of 1.1 kg fior 15 seconds. The filter paper was weighed both ~efore and af~er applying the load and the result was recorded as a first rewet~g instance. After a further 20 minutes, arlother 100 ml of fluid was delivered and when all fluid had been absorbed, the procedure was repeated with a fresh filter paper and the result recorded as a second xewetting Lnstance.

MethQ~ ~ Determinin~ BlnQ~ AI
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A test body, 65 x 200 mm, was puIlched from the material. 5 ml t~st fluid (O.9~o NaCl-solution~ were delivered to the wet~ng point on the test body. Dispersion of the fluid was measured after about 30 minutes. A further ~ ml of test fluid (0.9% NaCl-~olution) were then deliYered to the wetting point and f~uid dispersion was measured af~er about a`filrther 30 minutes. Subsequent to ~e last delivery, eight filter papers were placed over the wet~ng pOiXlt and loaded ~th a weight of 4.875 kg for 15 secon~s. The filter papers were weighed both ~ore and 8f~er applying t~e load and rewetting was recorded.

T~st Res~lts With the intention of investigatiIlg how ~he material was ~ected at different sof~eI~ing roll ~pa~ings when ~of~ning the material, a material was tested ur~der dif~erent sQftening conditions. For i~ta~ce7 in the case of a dry-formed CTMP~mate~ial having a sur~ace weight o~ 900 i 2149~12 . ~ WO 94/lOs54 pcrtsEs3/oo972 . ` .. ` ~ . !

g/m2 and a density of 0.63 ~/cm3, a suitable roll spacing is 1.7-2.4 mm during the softening process. The material is not influenced to any great extent at roll spacings whicb lie within this range. Figure 1 illustrates the absorption properties at different roll spacings. The ` : results were dete~nined in accordance with Method 1.
A Material according to the invention, roll spacing 1.7 mm.
; :E3 Material accor~ing to the inven~on, roll spacing 2.0 mm.
C Material according to the invenhon, roll spacing 2.4 mm.
D Mate~al according to the invention, roll spacing 2.0 mm, softened : twice. ~ ~
:: E M~terial according to the invention, ro~l spacing 2.0 mm, sof~ened : four ~mes. : ~ :
: F CTMP-p~p, density 0.125 g/cm3. ~
G Chemical sulphate p~p, density 0.125 g/cm3.

~bso~tion Proverties_Qf ~nt ~t~E
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: ~ The abs~rption properties of an inventive CTMP-material having a sur~ace weight Of goo g~2 and a~ density of O.~3 g/cm3 compared untl those of:~co~responding pulp~ ~cores produced from conventlonally~
:defibred and web-ormed CTMP::and correspo~ding chemical pulp are :~ : ~ shown in~FIgure~2. In:the absence of superabsorbent mate~al, the : : ~ absorption;capacity is a~out 9~g o f fluid for each~gram of absorbent~
: ;materia.The~resu~tswere~determinedLn:accordancew:ithMe~odl.
: ~ : A: Materialaccording~tothe:inven~:on.:
~ ~ B CTMP-pulp,~ density 0.l25 ~3. ~
;~ ~ ~ C ¢hemical~sulp~atepulp, densityO.125 ~/cm3.:

It~ the m~ntioniof studyi~g other prope~s of co~nplet~ abso~ent ; `: ~ : a~icles,~test products were:prepared in~ the ~form~ of ~con~e~tioIlal~
~ :ch;ldren's~diapers~which cornprised;a~T-shaped abso~bentsb~dy (T-COFe),:
"~ which`~lies;n~est~he~wearer,:and~a:rectangul~rabsorbent:body~R
" ~ :corè)~which~lies beneath the T-core, where the re~gul~s absorbent:
~ body~in~he~test~products~was:producedfrvmar~inventive~CTMP-```~ materLal. ln~the~con~srention~ products, the T-shaped a~sorbe~t~body WO 94/10954 2 1 4 9 ~1 2 PCIISE93/01)97~ -(T-core) and the rectanguiar absorbent body (R-core) were comprised of conventional defibred CTMP ~d chemical pulp.

Me~suremen~s_of ~he Abso~on C;~a~ci~y Products which comprised an inventive CTMP-matenal e~hibited an absorption in grams which was equivalent to the reference produc$s which had corresponding pulp cores that were comprised of con:ventionally defibred and mat-~ormed CTMP and chemical pulp. The results are set forth in Figu~e 3. The results were determi~ed in accordanc0 with Method 2.
A Reference diaper I,ibero GLrl.
B ~ference diaper Libero Boy.
C Child diaper comprising irlventive material.

Measurements of Fluid Aquisition Time : :
Products in which the R-core comprised a~ inventive CTMP-material e2~hibited a shorter fluid aguisition time than ~he ref`ere~ce product.
T~s implies that an R-core which contains in~entive CTMP-material : is ~ble tb drain the T-core more ef~ec~ely. The results can be seen from Figure ~. The results were determined in ac~ordance with Method A Reference diaper Iiibero Gi~l.
: B Reference diaper Libero Boy.
C Child diaper comprising i~ventive mate~ial.

: ~ Mea~rçm~s~h~l~ll~
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A comparison between the degree of` utilization of 'che ~sor~ellt body ` in an absorbent art;cle which coIltained an inventive CTMP-mat~rial and a corresponding absorbent article which co~tained convention ~: CTMP and :chemical pulp sh~wed t~at Ule degree of utiliz~o~ is about the same, although ~lightly on the plus: side for an inve~tive CTMP-:: ~ matenal. The results can be: seen from Figure 5. The results were ~: . detenr~ined in accordance with~Method 2.
A Re~erence diaper Libero Girl.
B Reference diaper Libero 130y.
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-? w~ 95~ Z I ~ 9 S 1 ~ Pcr/SE93/00972 C Child diaper comprising inven~Ye material.

Admixin~ Su~erabsorbenl; Mate al ; The presence of superabsorbent material in an absorbent body will influence the absorption properties of the body. Superabsorbent ; material can be incorporated in the absorbent body in di~erent ways.
For instance it may be admi~ed with the body material, laid in layers in the body, or disposed therein in some other way. This admi~ture of superabsorbent material can be effected in conjuIlction with manufacturiIlg the dry-~rmed material7 although it may also be effected durin~ some other part of the manufacturing process. The absorption properties ~ere compared with an inventive CTMP-material to which no superabsorbent material had beeIl added and also with corresponding pulp cores comprised of conveIltional defibred CTMP and chemical pulp. The results of this comparison are showil in Fi,~,ure 6. The results were determined in accordance wit~ Method 1.
; A Chemical sulphate pulp containing 30% superabsorbent and having a density of 0.125 g/cm3.
B Inventiv~ material containing 30% superabsorbent.
:: ~ C Reference diaper containing 301rO superabsorbent.
: D Inven~ve material containing no sup~rabsorbent.

~: : wet~ en~
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Products which ~comprised an inventive CTMP-matenal in the ~ core exhibited better rewetting ~alu~s than the reference product. Thi~ o implies that an-~R-core which contair~ ven~ve ~MP-material is able to drain the T-core more ef~ectively. The results can be seen frarn Figure 7. The results were dete~mined in accordarlce with Method 4.
A ~/ Reference diaper Libero Girl.
B Reference diaper Libero Boy. ~
C ahild diaper comprising inYelltive matenal.
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In ~e case of blood absorption, products which compri~ed ~n inyehtive softened CTMP-material showed better rewetting ~alue~ than noll-WO 94~10954 2 14 9 S 12 PCI /SE93/00972 - !

softened products. The results also showed that when absorbing blood, products which lacked superabsorbent material e:~:hibi~ed lower rewetting values than material which contained superabsorbent material. Material which lacks superabsorbent material also disperses blood much more ef~ectively. The results can be ~een ~rom Figures 8 and 9. The reference products comprised two different products frequently found on the market. The results were determined in accordance with Method 5. The prerequisites for this ef~ect are that at lesst one layer of the pulp mat is free from superabsorbent material.
Of course, this does not exclude the presence of such material in ot~er parts of the absorbent article.
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Figure 8 A Inventive material 350 g/m2.
B Invenhve material 350 g/m~, sof~ened.
C InveIltive material ~50 g/m2 + 5% superabsorbent.
D Inventive material 360 g/m2 + 5% superabsorbent, s~flGened.

Figure 9 A Reference product 1.
B Reference product 2.
C Product containing inventive material.

Netw~rk ~n~h Dry-fo~med roll pulp will nor~ally have suf~i~ent mat st~e~gth for the product applications intended here. If the networ!~ stre~gth of ce~n product applica~ons should be found insuf~lcient, the networl3; ~t;rength ca~ be increased by reinforcing the structure in some suitable manner, by adding reinforcing fibres, binding fibres or binding agent to the cellulose fibre mi~ture. The network streng~h can alS'Q be increase~ by incorporating a reinforcing layer of, for instance, plLastioD non-wove~, net or ~reads in the absorbent structure, or by ~asteining a rein~orcing layer or an ou~r sheet on one or bot~ sides of the matenal.

wo 94/109~4 ~ 1 4 9 ~ 1 2 PC~/SE93/00972 .
The softened pulp mat is still very thin, and consequently it i8 unnecessary in many cases to further compress the mat prior to its use in an absorbent article. A suitable density is 0.2~0.8 g/cm3, preferably 0.25-0.7 g/cm3 and most preferably 0.3-û.6 g/cm3. A
: suitable sur~ace weight is between 50-1500 &/m2, preferably 80-lOaO
g/m~ and most pre~erably 100-800 g/crn2. When calculating ~he . density, the thickne3s of the material was measured with the aid of a Mitutoyo thickness meter.

D~sçri;~tion Q~iLin~mbo~im.~t Figure 10 illustrates a diaper const~cted in accordance with one embodiment of the inventioIl. The diaper includes, in a conve~tio:llal manner, an absorbent body 11 wh;ch is enclosed betwee~ a fluid-permeable top sheet 12, which conveniently comprises a sof~ non-woven material, a perforated plastic film or the like a~d which is intended to lie proximal to the wearer in ~;e, a~d a fluid-impermeable bottom sheet 13. The sheets 12 and 13 have parts which e~tend beyond the absorbent body 11 and the sheets ~e joined together at these protruding parts. The bottom sheet 13 is comprised of a suitable plastic material, for instance polyethylene. It will be understood, however, that other known materials can be used ~or the top and bottom sheets, wi~hin the scope of the invention.

The absorbent body is comprised of two or more layers, an upper fluid aquisition layer 14 and one or two lower wicl~ng layers a~d storag~
layers 15 and 16. The inventive rnaterial is used mainly as a~
aquisition layer 14. Those layers in which inYenti~e material is no~
used may be comprised of other types materials? fo~ instance : conven~onal cellulose fibre matenaL

The purpose of:the a~uisition layer 14 is to rapidly take-up a g~ve ~:: quanti~ of ~luid. Thi~ flui~ shall solely be held 1008e~ly in the fibr~
s~cture ~and quickl~ drairled ~herefrom. The aquisition layer 14 is comprised of dryformed matenal in aceordance with the iIlYe~1;;on and ~: has a relati~eb open fibre~ structure of relati~ely low den~ity a~d contains 0-lO~ ~uperabsorbent material. The superabaorbe t material used in the aquisition layer 14 will prei~erably haYe a high gel : ~ :
~:
: 1 5 ', W O 94/10954 2 1 ~ 9 5 1 2 P~'r/S~93/00972 ~~

strength, so that an open three-dimensional fibre structure will be ~etained in this layer a~ter becoming wet. A suitable density range ~or the aquisition }ayer 14 is 0.20-0.70 g/cm3. A suitable surface weight range for the aquisition layer 14 is 80-1000 ~lm~.

The main purpose of the wicking layer 15 is to transport the fluid received in the aquisition layer 14 effectively to the storage layer 16 located beneath the wicking layer 16 and to ensure that the greatest possible part of the storage layer 16 is utilized for absorption purposes.
The wicking layer 15 may be comprised of dif~erent type~ materials, and has a rela~vèly low superabsorbent content.

The purpose of the storage layer 16 is to absorb and bmd the fluid which is dispersed to the storage layer 16 through the wicking layer 15.
The storage layer 16 may be comprised of dif~reIlt types materials and has a relabvely high superabsorbent content.

The wicking layer 15 and the storage layer 16 may optionally be combined to form a single layer. In this case, the single layer will have a relatively high superabsorbent content and a ~elat;ively high dellsity.

W hen ~he unckinglayer 1~ and the storagelayer 16 are combinedin a single layer, the superabsorbent content of the layer c ~ be valied throughoutthe product,so as to obtain a superabsorbe~t gradie~tin ~he dep~h,length andVorthe bread~h direc~on of~he product.

The VaUiQUS layers m ay have di~erentforrns and sizes. Norma~ly,the absorbent structureis combined ~th some fiDrnn ofelas~cation,inter alia in ~he crotch reg~on ofthe product,i~ order tn im prove product e~i~ency.
~ f Figllre 11 illustrates an exennpli ~ n~ e m bodiment of an inven~ve ~;' wound or sore dressing. The dressing i~cludes, in a con~en~o~al ~:; m ~ ner,~ an absor~ent body 41 ~vhich is enclo~ed betwee~ a ~uid-perm eable top sheet:42, which is suutably com prised of a ~oft non-woven m ate~al, a per~orated plas~c film or the lik~, and w~ich is ~J ~ : .

~ wo g4/l0954 21~ 9 5 :~ 2 PCr/SE93~00972 intended to lie proximal to the wearer in use, and a fl~.1id-repellent bottom sheet 43. The sheets 42 and 43 have parts which protrude beyond the a~sorbent body 41 and are joined together at these protruding parts. The bottom sheet 43 is comprised of a sui~ble fluid-repellent material, for instance a non-woven material that has been made hydrophobic. It will be understood, however, that the top and bottom sheets may compnse other known materials, wi~hin the scope of the invention.

The absorbent body 41 is comprised of oI~ly one single layer. This layer may consist of inventive dry-~Imed material and may be constructed with a relatively open fibre structure of relatively low density and with a superabsorbent content of 0-10%. A suitable density range in respect of the absorbent body 41 is 0.20-0.50 g/cm3 and a suitable sur~ace weight is 200-700 glm2.

It will be understood that the invention is not restricted to the illustrated and described exemplifying embodiments thereof and that other embodiments are conceivable within the scope OI the following Claims.
: .

Claims (22)

Claims

1. A method for the manufacturing of an absorbent structure (11,41) in an absorbent article, such as a diaper, sanitary napkin, tampon, panty protector, incontinence guard, bed protector, wound or sore dressing, saliva absorbent and like articles, wherin particulate material comprising 30-100%, preferably at least 50% and most preferably at least 70%
cellulose fibres is dry-formed to a web (14,15,16,41) that is compressed to a density of between 0.2-0.8 g/cm3, charac-terized in that the cellulose fibres used has been flash-dried; the web is dry formed to a web with a surface weight of between 50-1500 g/m2; and in that the web without subse-quent defibration and fluffing is incorporated as an absor-bent structure in an absorbent article.

2. A method for the manufacturing of an absorbent structure according to Claim 1, characterized in that said web is compressed to a density of between 0.25-0.8 g/cm3, preferably 0.3-0.7 g/cm3.

3. A method for the manufacturing of an absorbent structure according to any of Claims 1 or 2, characterized in that the web in connection to the compression has a moisture content of between 3-20%, preferably between 4-18% and most prefer-ably 11-16% calculated on the total weight of the web.

4. A method for the manufacturing of an absorbent structure according to any of the preceding Claims, characterized in that the web before being incorporated as an absorbent structure in an absorbent article is mechanically softened and therewith delaminated, so as to exhibit a plurality of partially separated (63) thin fibre layers (62), which in themselves exhibit a density which corresponds to the first density.

5. An absorbent structure, characterized in that it has been manufactured according to the method claimed in one of more of Claims 1-4.

6. An absorbent structure manufactured according to Claim 5, characterized in that the surface weight of the structure is between 80-1000 g/m2, preferably 100-800 g/m2.

7. An absorbent structure according to Claims 5 or 6, characterized in that the cellulose fibres are mainly comprised of fibres of chemi-thermomechanically produced pulp.

8. An absorbent structure according to Claim 7, charac-terized in that the chemi-thermomechanical pulp fibres have a curl value of between 0.20 and 0.40.

9. An absorbent structure according to any of Claims 5-6, characterized in that the cellulose fibres are mainly com-prised of fibres of chemically produced pulp.

10. An absorbent structure according to any of Claims 5-9, characterized in that at least an amount of the fibres are chemically stiffened cellulose fibres.

11. An absorbent structure according to any of Claims 5-10, characterized in that the structure includes between 0-20%
superabsorbent material, preferably between 0.5-10%, and most preferably 1-5%, calculated on the total weight of the structure in a dry state.

12. An absorbent structure according to any of the prece-ding Claims, characterized in that the structure includes a reinforcing means, for instance binding agent, reinforcing fibres or thermoplastic binding fibres.

13. An absorbent structure according to any of the prece-ding Claims, characterized in that the structure includes a reinforcing layer of non-woven, tissue, plastic or net mate-rial for instance.

14. An absorbent article such as a diaper, sanitary napkin, panty protector, incontinence guard, bed protector, wound or sore dressing, saliva absorbent and like articles comprising a liquid-permeable top sheet (12,42), an essentially liquid-impermeable bottom sheet (13,43), and an absorbent body enclosed between said sheets, characterized in that the absorbent body includes an absorbent structure according to any of Claims 5-12.

15. An absorbent article according to Claim 14, in which the absorbent body includes at least two layers, a aquisition layer (14) and one or more wicking and/or storage layers (15,16), wherein the aquisition layer is intended to quickly take up and deliver fluid to the wicking and/or storage layer or layers, characterized in that the aquisition layer com-prises an absorbent structure according to Claim 5 having a surface weight of between 50-1500 g/m2 and a density of bet-ween 0.20-0.80 g/cm3.

16. An absorbent article according to Claim 15, character-ized in that the cellulose fibres in the aquisition layer are comprised mainly of fibres of chemi-thermomechanically pro-duced pulp.

17. An absorbent article according to Claim 16, character-ized in that the absorbent structure in the aquisition layer is covered with a layer of chemical pulp on one side thereof.

18. An absorbent article according to any oh Claims 15-17, characterized in that at least an amount of the cellulose fibres in the aquisition layer are chemically stiffened cel-lulose fibres.

19. An absorbent article according to any of Claims 15-18, characterized in that the density of the aquisition layer is between 0.25-0.70 g/cm3, preferably between 0.30-0.60 g/cm3.

20. An absorbent article according to any of Claims 15-19, characterized in that the surface weight of the aquisition layer is between 80-1000 g/m2, preferably between 100-800 g/m2.

21. An absorbent article according to any of Claims 15-20, characterized in that the aquisition layer includes between 0-20% superabsorbent material, preferably between 0.5-10%, and most preferably 1-5%, calculated on the total weight of the structure in a dry state.

22. The use, in absorbent structures incorporated in absor-bent articles such as diapers, sanitary napkins, tampons, panty protectors, incontinence guards, bed protectors, wound or sore dressings, saliva absorbents and like articles, of a dry-formed web with a surface weight of between 50-2000 g/m2 and a density of between 0.2-0.8 g/cm3 made of particulate material comprising 30-100%, preferably at least 50% and most preferably at least 70% flash-dried cellulose, without any defibration and fluffing of the web.