CA2309998C - Method and device for producing a fiber web consisting of cellulose fibers for use in hygiene products - Google Patents

Abstract

The invention relates to a method for producing a strip of absorbent, rollable cellulose fibre material (100) which is suitable for use in the hygiene sector. A fibre layer consisting of cellulose fibres is placed on a base layer (8) and pre-compressed to form a loose non-woven fabric which is introduced into a gap between a pair of calender rollers (6.1, 6.2) and which is used to produce a pattern of dotted or lined print areas (17) in which the fibres (1) are disposed in a random manner and are compressed against each other at a pressure ranging from 150 to 600 MPa, resulting in a non-solvent fusion of said fibres and the production of a strip of fibre material (100) with an imprinted pattern.

Description

MET1iOD AND DEVICE FOR PRODUCING A FIBER WEA CONSISTING OF CELLULOSE
FIBERS FOR USE IN HYGIENE PRODUCTS

'rhe invention relates to a method for producing an absorbent fiber web and a device for producing a fiber web consisting of cellulose fibers for use in hygiene products, in particular, personal, absorbing hygiene products. The invention further relates to an absorbant fiber web manufactured according to this method.

It is known to combine cellulose-containing material such as wood or plant fibers into a fiber web by employing a combindtiun of inechanical and chemtcal processing strps under intensive lwaung while excluding oxygen. The aim of such a process is to avoid rhe use of binding agent additives Cuher conzpletely or to a larbe extent According to one of these known methods (US A
1 4,111,744), ceAulose fibers wich a rnoisture content of 3 to 12 percent in weight are subjected to pressurr in an oxygen-free aunosphere at a temperature of 450 to 800 F (= 232 to 426 C), which is a high temperature environment beyond the cellulose carbontzing temperature and cellulose combustibility trmperature.
Paper-type products may also br manufactured usiug the aforementioned lmowu tnetftod, but, aniy that of stiff cardboard The disadvantage of Llus method is that a considerable technological effort needs to be invested to heat the pressuri2ed spacc and to prevent combustion of the material through oxygen-free tnanufacturing.
Also known is a methocl (WO 94/10956) for producing under pressure absorbetu web products from dry cellulose fibers and additives by compressing a material with a weight per tuut area of 30-2000 g/cm' to a producc with a dCnsity of 0.2-1.0 glcm'. Compressing is carried out using stnooth calettdcr rollers. The disadvantage of this method is rhat although rhe density is increased, the tear strength of the tuateiial icself is low. Synthenc additives, especially theromplasts, must be added to increase the tear suength.

It is further knowu from US-A 3 692 622 to initially fornr an irregular cellulose fiber l8yer and under relatively low pressure to produce a lcxnc non-woveti fabric with a low density and tear strength. The loose non-woven is theu entered into the gap of an additional pair of caleader rolls and embossed with a pattrru of point- or lute-shaped pressure zottes_ The result is a soft, absorbent web utaterial with a base weight of about 16.9 to 50.9 g/m'. The tear strength of this fiber web is about 0.09 !cN/m. Thus, it is a materixl that rears easily as is the case witn iacia! tissaes, for example.
The calender pressures applied for this known product axe about 2,000 to 10,000 psi corresponding to 14 to 69 MPa. Thr US-A
docurnent speaks of resultant hydrogen bundtng, as is also the result in self-bonding conventional paper products.

MAY-24-00 04:16PM FR0M-STIKEMAN, ELLIOTT +6132308677 T-698 P 15/27 F-325

2 The fiber web manufactured by the mCthod is said to be particularly suitable for manufacturing hygiene products. it is said to be vCry absorbing, soft and capable for processing as a web. Single-use hygiene articles such as diaper panties and such are tnanufactured in high volume. The core absorbing layers used for these products should be tolerated well by the body, the absorbed liquids well distributed, and after use, thr products should rot in landfills without residue. A known method is to manufacnue the absorbing layer of a wood cellulosr fiber rnatrix, where so-called superabsorbers can be added to this fiber matrix to increase rbe liquid absorption capacity. Superabsorbers are polymers that can absorb water by building hydrogels It is the objective io specify a method for producing a fiber web made of cellulose fibers, where essentially no btnding agents need to br used, and were the process can be carried out ai room temperaturCs under normal atmospheric pressure and with thC oxygen content of ambient air.

This objective is accomplished with the method for manufacturing a fiber web made of cellulose fibers, which is largely tear resistant, absorbent and rollable, using the processing steps according to the features of claizn 1.

It is assumed that in the technology of producing cellulose fibers it is known to make them of a wood derivative known in the industry as "fluff pulp". This material is a standardized wood product made of cellulose material shtpped in boards or webs, so-called wood pulp cardboards, where said material is crushed in a hammer mill and separated into fibers until it turns into a cotton-like product of ceiluiose fibers, namely fluff pulp. A description of such a standardized crushing process can be found, for exainple, in the brochure of the company Dan-Webforming International A/S.
Risskov, Denmark.
This wood derivative called "tluff pulp" is a product that is used in large quaatities in the so-called water-less paper production. Preferably, the fibers have a length of about 1 to 5 rtun as they exit the bammer inill. According to the first step of the aforementioned process, they are embedded irregularly in a cellulose riber layer with a height of 5 to 15 mm and are preferably sent on a conveyor belt io a movable strainer tluough a pre-condenser station that consists preferably of a pair of calender rolls with low pressure, such tl-at the result is a loose non-woven with low density and tear strength. The tear strength is dimensioned such that the non-woven can sag over a lerigth of 0.1 to 1 m without tearing. It can also withstand air pressures that occur during the production_ This essentially known and still very loose non-woven is inserted into a gap of a pair of calender roAs, where a sigruricant pressure is applied in the point-shaped pressure zones.
The pressure must be at least 100 and should be about 520 MPa (MPa = N/mm) The liquid limit of the material used for the rollers is geucrally the upper pressure limit. Acuording to the state-of-the-an, such high pressures have not been MAY-24-00 04:16PM FROM-STIKEMAN, ELLIOTT +6132308677 T-698 P 16/27 F-325

3 used until now. To produce such a pressure, rollers may be used with studs, with line patterns offset from one anozher or wirh other protruding point- or line-shaped pressure surfaces, where the array density of the point-shaprd pressure zones is between 1 and 16 array points per cm2.

A fiber web, preferably with a m= weight between 50 g and 1500 g, is produced according to the method. Due to the discribution of the cotulecting points, this new fiber web has become so strong that a tear suengih of at least 0.12 kN/m, preferably of up to 0.65 kN/m, is achieved. The thickness of the fiber web is dependent on the desired metrage.

The size of the pressure area of the puint-shaped pressure zones is dependent on the pressure that can be achievzd between the second calender rollers. Poini-shaped pressure zones with areas between 0.05 and mm= have proven sutficient.

As has already been emphasized, the tCtnperature of the second pair of calender rolls should be maintained at room temperature, that is, between 19 and 25 C. The operation can also take place at higher tempcrarures. It should be noted that the temperature will increase in the pressure zones due to the significant use of power.
Pre-:ompression should talce place at a tool crmperature of between 18 and 320 C, preferably between 250 and 300 C. Preferably, thz pre-compression tool is a pair of calender rolls that can be heated_ The fiber and/or the loose non-woven are brougtu to a certain moisture content before entering the calender rolls, whrrr preferably the moisture conteni should be set to between 2 and 9 percent in weight, at a rqinimum to 1 5 percent in weight.

Starting triaterial is thC aforemei-tioned iluff pulp wood derivative.
Preferably, this is a srandardizA
dehbered product, such as the one also used in rnanufaczuring fiber webs according to lactowu methods.
Sulfite or sulfate bleached long fiber cellulose of northern wood appears very advan,tageous.

It has also proven ac3vantageous, when r.he cellulose fibers were not bleached to totai whiteness but instead when they still contained a certain content on natural wood materials.
The degree of whiteness should be between 80 and 92 %, preferably between 85 and 89 %. A certain remaining lignin contetu has shown to be advantageous as well, for example if it is between 0.5 and 5 percent in weight of the starting matzrial_ Non-binding, tnorganic pigments or tillers, such as titanium oxide, kaolin or zeolithe can be added ta the stdrting material.

Ir1AY-24-00 04:17PM FROtI-STIKEI4AN, ELLIOTT +6132308877 T-698 P.17/27 F-325

4 A certain amount of superabsorbers can be added to the starting fibers as well, where the acrylate composites known as superabsorbers can be added in powder forYn to the fluff pulp in an atnouru of, for example, 0.5 to 70 percent in wright (in relation to the total arnount) and where the manufacturing process is not significantly influCnczd by this.

In the pressure zone of the second calender roll, the radial distance of the calender roll pair beyond the actual point-shaped pressure zones should be about 1 to 15 mm such that the material beyond the pressure zorie is not squashed during the pressure application, but is rather fluffed and somewhat compressed.

The gap in ttie pressure zone of the second pair of calencler rolls is dependent on the metrage and the thickness of the inscrted loose non-woven. In general, the gap should not exceed a clear width of 0.45 to 1 tnttt.

A signifrcant part of the device for carrying out the method is formed by tbe second pair of ealetalrr rolls, whtch is prrterably made up of two steel calender rollers both provided with nwnerous studs distributed across the outer surfaces of ttie rollers corresponding ta point-shaped pressure zones that are surrounded by indentations tlhat rxhibit d rnultiple of the volume of the raised areas. In the operacing gap, the raised areas of the two rollers are opposite one another, and a pressure of at least 200 MPa up to the maximum liquid lirnit of the materiat used for the studs is exerted on the nnn-woven located in the point-shaped pressure zones.

The preferable heighr of the studs or other pressure zones is between 0.5 and 15 mm from the roller base. The studs are preferably shaped as pyramzds or truncated cones with a snul coat angle of 10 to 45 in relation to the radius. Line-shaped or similar pressure zones are possible as well.

The irregularly arranged fibers are compressed under very high localized pressure in line or point-shaped pressure zones, such that a multitudr of close fusions of the fiber bodies occur that will not separate after the pressure is released. A product of numerous irregular cellulose fibers is produced, where said fibers are connected in the pressure zones through fiber bonding.
The fiber web has sufficient tear strength and also a high absorption capacity such that it is ideally suited for hygiene products.

It has shown that in order to meet the specific requirements of the hygiene industry, the web of fiber materials must subsequently be combined with suitable materials in a labor-intensive manner. Thus, the additional objective is given to specify au addttionat method for producing a fiber web consisting of cellulose fibers rhat is e9uipped with, for example, increased tear strength, densiry or breathing and/or insulating capacities.

The methods and apparatus in the claims will become more readily apparent through the description of exemplary enibodiments with reference being made to the accompanying drawings, wherein Fig. 1 shows a schCmat:c presentation of a device for producing a fiber web made of cellulose fibers;
Fig. 2 shows in an enlarged presentation according to Fig. 1, the cross-section of the pressure zone of two rollers with pyratnid=shaped studs;

Fig. 3 shows a perspective prCnientation of a section of the product truuutfaetured according to the method;

Fig. 4 shows an enlarged presentation of the pressure zones of the fiber web;

Fig. 5 shows a schematic presentatton of a different device for producing a fiber web with two additional synshetic layers, Fig. 6 shows a schematic prrseniation of yet another device for producing a fiber web with a synthetic coatinb;

Fig. 7 shows a presentation sunilar to Fig. 2 of a cross-section of the pressure zone of two rollers with an inserted fibrr web with a foil placed on it.

Fig. I shows in a schrmatic sequence an arrangement of roAers and rolls for carrying out the tnethod.
The production process starts with cellulose fibers made of fluff pulp, preferably of dry wood pulp cardboards by means of a hammer mill, which is described in great detail in the state-of-the-art presented in the aforeinentioned brochure of Dan Webforming international A/S.

A layer of irregular fibers 1 in a height of about 20 mm is conveyed to a first pair of calender rollers 4.1, 4.2 on a strainer conveyer belt 8. The upper roller 4.1 has a surface temperature of about 220 C, whiie the bottora roIler is unheated. The web is tnoisturized by spraying from above using a moisturizing device 3 prior to entering the gap between the two rollers 4.1 and 4.2. The rrsuitauc moisture of the material is about 5 to 10 percent in weight.

A portion of the moisture is elirninated biltween the calender rollers 4.1 and 4.2, aad the irregular eellulose fiber layer is corupressrd to a loosc uon-woven with low density and tear strength. However, the tear strength is sufficient that ttie non-woven 2 does not tear when bridging the distance between the end of the strarrrer beli 8 and rhe reversing roll 7 to the inlet into the gap between the two additiondl calendCr rolls 6.1 and 6.2, which is about SU cm.

The first processing step is simply a prC-compresston or compacting of the aon-woven from the irregularly arranged tibers. A fixcd web is not produced and it is entirely possible to remove thx fibers iadividually, piece by piece. Thr tear strength of the non-woven is very low, prrferably at least 8 N/tn wide.

The non-wovert 2 providCd by the strainer belt 8 is again rwisturrzed from top and bottom (maisturizing device 5) prior to entering the gap between the two calender rolls 6_ 1 and 6.2.

Between the calender rolls 6.1 and 6.2, the inuially loose non-woven is subjected to an array of point-shapod pressure zones, where the irregularly arranged fibers are pressed onto each other under high pressure, such that a close fusion of the tiber bodies occurs and a fiber web 100 with an etnbossed pattera is created that will not separate etier the pressure is released. The roller arrangement cau also be termed as "pixel rollers".

Carbonization of the fiber material is avoided. However, it is obvious that the pressure is sufficiently high to practically melt the matertals constituting the fibers, ihat is, cellulose and reniaining ligniit and other materials, wlterr such close bonding occurs that goes beyond the bond of simple adhesion.
Through point-tocused high pressure and crowding of the fibers, the loose c.ellulose or pulp fibers are bonded together in all existltig free spaces, additionally glued and interlocked, resulting in an overail very strong fiber web.

Rolls 6.1 and 6.2 are operated at regular room temperatures, thar is, between 18 and 25 C, however it should not be rxcluded ehat tha rollers may be heated or that a higher temperattue may be reached at the point-shaped and also point-focused pre ure zones due to the high mechanical energy. The pressure affectutg the cellulose fiber layer in the puitu-shaped pressure zones 17 (cf.
Fig. 2) is preferably above 500 MPa, but defittitely in a range of 100 to 600 MPa, even higher with a respective technoiogical effort.

With this method, fiber webs with a mZ weighr between 50 and 1500 g, for exaruple, can be produced.
The fiber web exiting the calenders is significantly tttore tear resistaru than the web eatering the caleader rolis 6.1 atu16.2 The material is treated with broad drawing roller 9.
Thereafrer, it is wrapped otuo a take-up rolirr 11 with the use of a driver roller 10.

MAY-24-00 04:18PM FROIA-STIKEfrIAN, ELLIOTT +6132308877 T-698 P.20/27 F-325 Foremost, the material used should be an inexpensive mass material that is available in large amounts.
Fluff pulp witti a whiteacss of 85 to 89 % is the preferred choice, which in turn means thaz a signific,ant lignin and residue content is still present. It has been shown that such residues significantly improve the bonding behavior. Experience shows thar cellulose bleached entirely has a worse bonding behavior ihau less pure cellulose. The titer should nor be below a certain length because fibers that are too short cannot bridge the distance between the point-thaped pressure zones such that low rear szrength is achieved with low titer.

SuppleAaentary additives are also dirtwnsionrd according to the desired tear strength. The addition of so-called super-absorbers, as described in the document WO 94/10596, for example, is relarively uneritieal.
Fluff pulp can be supplemented with superabsorbers with 0S to 70 percent in weight, preferably 5 to 30 percent in weight, and thereafter sent through the high-pressure calender rolls 6. The superabsorbers have tuw bonding effect; tou large an amounr will reduce the tear strength.

However, the addition of crushed non-bonding inorganic materials, such as the whire pigrnent titanium oxide, reduces the tear strength such that, in general, a percentage of 25 percent in weight of titanium oxide should noi be exceeded. A similar rule applies to fillers such as kaolin and zeolithe.

It is important that binding agents such as are lcnown from the state-of-the-an, which are generally required, can be avoided almost entirely. "T'his significantly improves the recycleability and cornpostability of thr product. The production becomes less expensive and is simpler because stations for applying and curing are not required. However, it shall not be precluded that the finishad product can be provided with a surface tinish or larninated with a film on one or both sides afier running through the calender rollers 6.1 and 6.2.

Fig. 2 shows an exemplary embodiment of a high pressure zone between the two calender rollers 6.1 and 62. As can be sren, thr outer roller surface is provided wirh studs 14, shown in an enlarged presentation. The numerous studs distributed across the entire outer roller surface result, preferably, in an array density of thr point-shaped pressure regions of between 1 and 16 array points per cm2 for the fuzished fiber web. The studs have the shape of a truncated pyramid with a stud coat angle of 10 to 45 in relation to the radius. A calculated pressure of a bout 520 MPa, which leads to the aforementioned fusion of thC celiuluse fibers in the gap, is present in the gap 12, where the pressure zone 17 is created.
Other shapes of the pressure zones, such as truncat.ed cones, cylinders or cubes are possible and are selected according ro professional opinions according to the required pressure, thc respective stanitig material and the material uf the rullers, the temperatures that occur, etc.

_ ... __ _.-_-._.~...~.,.... _,.., _.__ _. _. ,.. _,~.
~.....__ MAY-24-00 04:18PI4 FROii-STIKEMAN, ELLIOTT +6132308877 T-698 P.21/27 F-325 In the preseut case, the direction of the operation is from left tv right.
Thus, the fuushed product exhibits almost lucid fusion zones 18, thai alternate with sonwwhat tluffy loose regions 19 that are, however, compressr,d when compared to the starting non-woven.

Fig. 3 shows the finished product, consisting of nurmerous irregular cellulose fibers that arr connected by fusion in the pressure zones 18. The niaterial itself has a high tear strength and, in addirion, a high absorption capacity, which is increased evrn further through thr use of superabsorbers such that it can be used as packagitig material, for hygiene products, lining ruaterial, pillow filler and similar products. The material can also be used in the construction industry as a well as replacernent for paper and cardboard.
The aforCmentioned products can also be used for napkins, tampons, baby diaper panties, slip inserts, sanitary napkins, and incontinence products Fig. 4 shows an enlarged przsentation of a pressure zone 17 in an electron microscope image. In this case, the pressure 2one has a hexagonal shape that has been caused by the insertion of a stud 14 into the non-woven. The pressure applied in this case is 190 MPa (= 190 N/mm). It can be seen that the initially routui and undamaged fibers 29 are flat and smooth in the pressure zone dtre to the pressure.
The superabsorber particles that were present are optically no longer recognizable, because they have obviously been pressrd into the surface. The fiber structure can still be recognized sotnewhat in the portion of the zones 27 inside the pressurC zone 17, while other zones 28 are present where a fiber structure can no longer be recognized. Ttie fibers pressed onto one another can no longer be separated from one another when trying to do so with a dissecting needle. Thus, a fusiou, compacting and gluing with surface bonding of thr fiber and/or cellulose substance has occurred with the pressure being kept under the carbouization limit of the fibers 29.

Fig. 5 shows a schematic sequence of an arrangement of rollers and rolls where the method is carried out using a second embodimCnt. A layer of irregular fibers 1 in a height of about 20 mm is conveyed to a first pair of calendrr rollers 4.1, 4.2 on a strainer conveyer belt 8. The upper roller 4.1 has a surface temperature of about 250 C, while the bottom roller is unheated. The web is moisturized by spraying from above using moisturiztng device 3 prior to entering the gap between the two rollers 4.1 and 4.2.
The resu]tant moisture of the material is about 5 to 10 percent in weight.

A portion of the moisture is elimir,ated between the calender rollers 4.1 and 4.2 and the irregular cellulose fiber layer is compressed w a loose non-woven with low densiry aud tear strengrh_ 8etween the calender rolls 6.1 and 6.2, the initially loose non-woven is subjected to an array of point-shaped pressure zones where thC irregularly arranged fibers are pressed onto each other under high pressure such that a close fusion of the fiber bodies occurs and a fiber web 100 with an embossed pattern MAY-24-00 04:18P14 FROM-STIKEMAN, ELLIOTT +6132308877 T-698 P.22/27 F-325 is created that will not separatr after the pressure is released.

After passing the calender rollers 6.1 and 6.2, the fiber web 40 is on both sides glued to, welded to attdlor mechanically connected to wCbs 20.1 and 20.2 made of textile, non-woven-type ar foil-type tnaterial. ThC pre-fabricated coating webs 20.1, 20.2 have - as far as necessary - already been coated with adhesive, and are guided from above and below onto the fiber web that exits from the calender roller pair 6.1, 6.2 and fused to it using the pressure roll pair 9.1, 9.2. A
mechanical connection of the coating with thz fiber material is also possible using pressure rollers 9.1, 9.2 provided with embossing elements. Gluing with a hot adhesivC is possible as well. The composite is wrapped onto a take-up roller 11 with the use of a driver rollrr 10_ Fig. 6 shows in a schematic sequence an arrangement of rollers and rolls for carrying out the method in an additional embodiment. The production process stans with cellulose fibers utade of fluff pulp that has been made of dry "wood pulp" using hammer mills.

Similar to Fig. 1, a IayCr of irregular fibers 1 in a height of about 20 mm is conveyed to a first pair of calertder rollers 4.1, 4.2 on a strainer conveyer brlt 8. The upper roll 4.1 has a surface temperature of about 180 C, while the bottom roller is unheated.

The irregular cellulose fiber web is cornpressed between the calender rollers 4.1 and 4.2 to a loose non-woven with low density and tear strength. Prior to entering the gap between the two calender rolls 6.1 and 6.2, the non-woven 2 provided by ttie strairier belt 8 is covered from the top with a tlun (10 m) foil 30 made of PTFE that initially is not perforated (PTFE = polyfluorethylen).

Between the calender rolls 6.1 and 6.2, the non-woven covered with the PTFE
foil is subjected to an array of point-shaped pressure zones where the irregularly arranged fibers are pressed onto each other under high pressure such that a close fusion of the fiber bodies occurs and a fiber web 100 with an embossed panern is created that will not separatC after the pressure is released; the foil, which is relatively heat-resistant is included in the composite. Carbonization of thC
fiber or foil material is prevented. The sintering or bcbinning-to-rnelt foil material achieves additional bonding.

Rolls 6.1 and 6.2 are operated ar regular room temperatures, that is, between 18 and 26 C, however it should not be precluded that the rolls rnay be hearxd or that a higher temperature may be reached at the poitu-shaped and point-focused pressure zonzs due to the high mechanical energy.

The pressurt affecting the cellulose fiber layer with the foil placed on it in the point-shaped pressure zones 17 (cf. Fig. 4) is preferably above 300 to 400 MPa . After passing through the calender rollers 6.1, _ .._...~-...-......N_,....~._ MAY-24-00 04:19Pi4 FROfrI-STIKEfrIAN, ELLIOTT +6132308877 6.2, the fiber web is on one side connect,ed with a foil web. The composite is wrapped onto a talce-up roller 11 with the use of a driver roller 10, An additional coating web 20.2 has - as far as necessary - already been c:oated with adhesive, and is guided from below onto the wCb that zxits from the calender roller pair 6.1, 6.2 and fused to it using the pressure roll pair 9.1, 9.2 (cf. Figure 6). The composite is wrapped onto a take-up roller 11 with the use of a driver roller 10.

Fig. 7 shows an exemplary erubodiruent of a high pressure 2one between rhe two calender rollers 6.1 and 6.2. As can be seen, the outer roller surface is provided with studs 14 shown in an enlarged presentation.
The numerous studs 14 distributed across the entire outer roller surface preferably result in an array densiry of the point-shaped pressure regions of between I and 16 array points per em' for the finished fiber web. The studs have the shape of a truncated pyramid with a stud coat angle of 10 te 45 in relation to rhe radius. A calculated pressure of a bout 520 MPa, which leads to the aforementioned fusion of the cellulose 2ibers in the gap, is present in the gap 12, where the pressure zone 17 is created.
Other shapes of the pressure zones, such as truncated cones, cylinders or cubes are possible and are selected according to professional opiruons according to the required pressure, the respective starting material and the material of che rollers, the temperatures that occur, etc.
Foi130 can be calendered or laminated ai the samr time.

For Fig. 7, iaie direction of the operation is from left to right. Thus, ihe finished product exhibiis almost lucid fusion zoi,es 18, that alternate with somewhat fluffy loose regions 19 that are, however, compressed when compared to ttie starting non-woven.

The coating methods are described in greater detail based on the following examples:
Example 1 A fiber web 100 (cf. Fib. 3) is combined on one side with a web of woven textile material. On the surface pointing t.o the fiber web, the textile web is provided with a Hotmeit adhesive, such that a good adhesive bond is produced after passing through the pressure rolls 9.1, 9.2.
Because of the fiber material, such a composite exhibits good heai insulating effecis and can withstand greater rnechanical forces due to the woven textile web.

Exemple 2 The fiber web 100 produced according to the description of Figures 1 to 3 is at its uncoated surface additionally bonded to a foil-type, settu-permCable climattc membrane made of polytetrafluorethylen using an adhesive. The climatic membrane is water resistant but permrabie to water steam. When used _...._..r.~.,.._ ...............~._.W.,..~._.~ _...
----.~......._.._ ._._.___._ _.._.._.____ MAY-24-00 04:19Ptv1 FROM-STIKEMAN, ELLIOTT +6132308877 T-698 P.24/27 F-325 as liner material for hygietx garments, the water vapor ernittrd by the user can be taken up by the fiber fabric and then dissipated by the climatic membrane. At the same time, the fiber layer is protected from moisture.

Example 3 A non-woven web 100 is combined with a polytetrafluorethylen foil with a thicltness of 20 m, which is coated on one side with an adhesive free of solvents. The calender rolls 6.1, 6.2 create a composite. At its uncoated side, an additional polyethylene foil is placed on the composite before it enters the calender rollers 9_1, 9.2. The needle rollers (not shown) apply a perforation to the second polyethylene foil. The foil particles intilirating the fiber web during the perforation procedure cause a mechanical anchoring between the fiber web with a first foil glued to it and the second foil. The result is a mat,erial 200 thai is absorbent towards one surface and tight to liquid towards the other surface, which is particularly suited for use in hygiene products_ In recycling, the soiled fiber web can be cotnposied aftrr tearing off the top foil coatings. The composite material subject to the inveniion is more rnvironmetually fiiendly than, for example, the cellulose with polymeric superabsorbers used for disposable dtapers.

Claims (24)

What is claimed is:

1. A method for producing an absorbent fiber web which is tear resistant, and rollable, from cellulose fibers, cellulose pulp or of wood pulp cardboard without the use of additional binding agents, where said fiber web is suitable for use in the hygiene sector comprising the following processing steps:

(a) providing an irregular cellulose fiber layer and pre-compressing it under relatively low pressure to produce a loose non-woven web with low density and tear strength; and (b) providing a pair of calender rolls having a pattern of point or line-shaped studs, defining a gap therebetween, and inserting the loose non-woven web into the gap of the calender rolls to create a pattern of point- or line-shaped pressure zones under relatively high pressure, where the irregularly arranged fibers are pressed onto each other, wherein (1) the loose non-woven web has a moisture content of up to 5 percent by weight when it is inserted, (2) the irregularly arranged fibers are pressed onto each other under a pressure in a range between 250 and 600 MPa such that non-separating fusion of the fibers occurs and a fiber web with an embossing pattern is created, and (3) the tear strength of the fiber web is at least 0.12 kN/m.

2. A method according to claim 1, wherein a fiber web is produced with a weight per m2 of between 50 g and 500 g.

3. A method according to claims 1 or 2, wherein a fiber web is produced with an array density of the point-shaped pressure zones between 1 and 16 per cm2.

4. A method according to any one of claims 1 to 3, wherein the point-shaped pressure zones have an area of between 0.05 and 10 mm2.

5. A method according to any one of claims 1 to 4, wherein the temperature of the calender rolls is maintained at approximately room temperature, that is, between 18 and 26° C.

6. A method according to any one of claims 1 to 5, wherein pre-compression occurs at a temperature of 18 to 320° C.

7. A method according to any one of claims 1 to 6, wherein a second pair of calender rolls is used as pre-compressing tool.

8. A method according to any one of claims 1 to 7, wherein the fiber layer provided in step (a) is a mixture of fiber material and superabsorber, and where the superabsorber content is between 0.5 and 70 percent by weight of the mixture.

9. A method according to any one of claims 1 to 8, wherein the cellulose fibers used as starting material have a degree of whiteness of 80 to 90%.

10. A method according to any one of claims 1 to 9, wherein cellulose fibers with a residual content of lignin of 0.5 to 5 percent by weight are used as starting material.

11. A method according to any one of claims 1 to 10, wherein the irregular cellulose fiber web of step (a) contains supplementary filler materials.

12. A method for producing an absorbent fiber web which is tear resistant, and rollable, from cellulose fibers, cellulose pulp or of wood pulp carboard without the use of additional binding agents, where said fiber web is suitable for use in the hygiene sector comprising the following processing steps:

(a) providing an irregular cellulose fiber layer and pre-compressing it under relatively low pressure to produce a loose non-woven web with low density and tear strength; and (b) providing a pair of calender rolls having a pattern of point or line-shaped studs, defining a gap therebetween said calender rolls having a radial distance, beyond the actual point-shaped pressure zone of 1 to 5 mm in the pressure zone;
and inserting the loose non-woven web into the gap of the calender rolls to create a pattern of point- or line-shaped pressure zones under relatively high pressure, where the irregularly arranged fibers are pressed onto each other, wherein (1) the loose non-woven web has a moisture content of up to 5 percent by weight when it is inserted, (2) the irregularly arranged fibers are pressed onto each other under a pressure in a range between 250 and 600 MPa such that a non-separating fusion of the fibers occurs and a fiber web with an embossing pattern is created, and (3) the tear strength of the fiber web is at least 0.12 kN/m.

13. A method according to any one of claims 1 to 12, wherein the gap in the pressure zone of the calender rolls, between opposing point-shaped pressure zones, exhibits a clear width of 0.05 to 1 mm.

14. A device for producing an absorbent fiber web which is tear resistant, and rollable, from cellulose fibers, cellulose pulp or of wood pulp carboard without the use of additional binding agents, where said fiber web is suitable for use in the hygiene sector, said device comprising;

(a) a pair of calender rolls having a pattern of point or line-shaped studs, defining an operational gap therebetween, and (b) means for providing an irregular cellulose fiber layer and pre-compressing it under relatively low pressure; and means for providing the loose non-woven web having a moisture content of up to 5 percent by weight before it is inserted into the operational gap, wherein the pair of calender rolls consist of two calender rolls that are both provided with numerous studs distributed across the outer surface of the rollers and surrounded by indentations that exhibit a multiple of the volume of the studs wherein the studs are opposite one another in the operational gap and where a pressure of at least 200 MPa up to the maximum liquid salt limit of the material used for the studs can be applied in point-shaped pressure zones to the loose non-woven, which is located between the studs, to create a pattern of point- or line-shaped pressure zones where the irregularly arranged fibers are pressed onto each other, such that a non-separating fusion of the fibers occurs and a fiber web with an embossing pattern is created, having a tear strength of at least 0.12 kN/m.

15. A device according to claim 14, wherein the height of the studs form the roller base is between 0.5 and 5 mm.

16. A device according to claim 14, wherein the studs have the shape of truncated pyramids.

17. A device according to claim 16, wherein the truncated zone shapes or pyramid shapes have a stud coat angle between 10 and 45° in relation to the radius.

18. An absorbent fiber matt which is tear resistant, and rollable, from cellulose fibers, cellulose pulp or of wood pulp carboard without the use of additional binding agents, and has a tear strength of the fiber web is at least 0.12 kN/m, which is suitable for use in hygiene products, made by the following processing steps:

(a) providing an irregular cellulose fiber layer and pre-compressing it under relatively low pressure to produce a loose non-woven web with low density and tear strength; and (b) providing a pair of calender rolls having a pattern of point or line-shaped studs, defining a gap therebetween, and inserting the loose non-woven web into the gap of the calender rolls to create a pattern of point- or line-shaped pressure zones under relatively high pressure, where the irregularly arranged fibers are pressed onto each other, wherein (1) the loose non-woven web has a moisture content of up to 5 percent by weight when it is inserted into the gap, (2) the irregularly arranged fibers are pressed onto each other under a pressure in a range between 250 and 600 MPa; such that a non-separating fusion of the fibers occurs creating a fiber web with an embossing pattern.

19. A method according to any one of claims 1 to 13, wherein the fiber web provided in step (a) is a mixture of fiber material and superabsorbent, and where the superabsorbent content is between 5 and 30 percent by weight of the mixture.

20. A method according to any one of claims 1 to 13, wherein the cellulose fibers used as starting material have a degree of whiteness of 85 to 89%.

21. A method according to any one of claims 1 to 13, wherein a starting material is used that contains supplementary filler materials selected from the group of filler materials consisting of titanium oxide, chalk and kaolin.

22. A method according to any one of claims 1 to 13, wherein a starting material is used that contains supplementary filler materials selected from the group of filler materials consisting of titanium oxide, chalk and kaolin.

23. A device according to claim 14, wherein the angle of the stud coat in relation to the radius is between 10 and 45.

24. A device according to claim 14, wherein the studs are cube-shaped.