DE1965716C3 - Absorbent cellulosic sheet and process for making it '' - Google Patents

Description

The invention relates to an absorbent cellulose fiber web with a basis weight of 8.5-85 g / m ² for the consistently preferably single-layer paper towel goods, the web being embossed in a predetermined pattern covering part of the web surface and the thickness of the web being embossed in in the embossed areas is lower than in the non-embossed areas. Such absorbent webs made of cellulose fibers are used for the production of numerous disposable products, especially in the sanitary sector, such as. B. wipes, towels or facial tissues.

The most widespread method for producing such webs is based on the principle of conventional paper production. A fiber pulp normally obtained from wood pulp is applied wet to a storage screen, and the fiber web that forms on the screen is then watered down by pressing and / or drying enable the fibers resting against one another and lead to a correspondingly strong bond between the fibers. This also applies if the web was not or only slightly pressed for dewatering. Because of this strong bond between the fibers, such a wet-laid web naturally has only a poor grip ( ie it is hard, stiff and not very bulky) and also only a low absorbency, ie it is not readily suitable for production suitable for towels or corresponding disposable products. Rather, it is necessary to additionally crepe such a wet-deposited web by removing it from the drying drum of the paper machine by means of a creping blade. By creping, the bonds of the fibers to one another are broken again to a certain extent, so that the grip and the absorbency of the web are somewhat improved.

However, there are several limits to creping. First, it is only effective for a web with a low basis weight of less than about 25 g / m ² , since wet deposited webs with higher basis weights are completely stiff and generally unsuitable for use as a disposable towel. In order to produce an end product of sufficient bulk and softness even with a web of low basis weight, two or more layers of the material must normally be placed on top of one another and connected to one another, which means additional work and, as a result of the measures necessary to connect the layers, also in particular does not benefit the handle and the softness of the material. A second limit imposed on creping is that even with a low basis weight web, the detrimental properties resulting from the strong bonding of the fibers to one another are not completely eliminated, since creping does not by any means make the fiber bonds much Scope cancels.

In addition, a wet deposited web is usually a preferred fiber orientation in the machine direction of the discharge screen. As a result, the tear strength is in the Machine direction always higher than in the transverse direction perpendicular to it. Since the material is also available in the transverse direction must have sufficient strength for use, it means that the strength is always disproportionately large in the machine direction, which is also the formation of an optimal grip

counteracts

In order to improve the grip and the absorbency of wet-deposited webs, it is from the CH-PS 4 34 957 also already known, the wet deposited web initially thermally on a Water content, which is less than the water content of a usually on the drying drum one Paper machine transferred web to pre-dry, then the web pre-dried in this way by means of to bind an embossing roller by embossing and only then to dry it finally. In this way it arises an improvement in the properties, but it is by no means optimal. even when dried without pressing, a wet-deposited web has a relatively strong bond the fibers on each other, get the remaining between the embossed areas loose, uncompressed areas lack their maximum possible bulk, softness and absorbency as a result, it is normally necessary here too in practice to crepe the web again in order to by breaking further fiber bonds in the uncompressed areas, the bulkiness and softness (i.e. the grip) and improve absorbency. Otherwise there are also restrictions here with regard to the basis weight of the web, so that two-layered ones continue to be used for many areas of application Materials are necessary.

Besides wet-deposited webs, dry-deposited webs made of cellulose fibers are also known. With such dry deposited webs there are no problems whatsoever with regard to a to strong self-binding of the fibers to one another, as there is no water at all during the deposition due to the lack of water significant binding forces can be effective. As a result, however, dry deposited webs have also the fundamental disadvantage that they have no strength of their own, but rather through additional strength Measures need to be consolidated. These additional measures are in accordance with the intended use selected. If it is essentially due to good tear resistance matters and does not depend too much on the handle and absorbency, the solidification takes place by adding an adhesive to the web. Mu an adhesive can be, combined with the fact that dry deposited fibers generally more randomly oriented and not as strongly oriented in the machine direction Like wet-deposited fibers, they are quite good and, above all, largely in all web directions achieve uniform strengths, but not sufficient values in terms of grip and absorbency, so that the adhesively attached, dry deposited webs for the ones at issue here Use cases are generally not suitable.

If the solidification of the dry deposited webs, however, is more in the direction of a possible good absorbency is selected, such as the z. B. required for absorbent pads or the like then there is normally insufficient intrinsic strength of the web. It must then, such as B. the AT-PS 2 65 841 shows that the solidification takes place through a separate carrier material, which with the dry deposited cellulose web is connected and surrounds it. However, this affects the grip of the Material quite considerably, because then the grip is only provided by the carrier material and not by the dry peeled cellulose layer determined. That

However, the carrier material is always inevitably made in such a way that that it feels much harder and stiffer than a cellulose web. This also includes the well-known cellulose webs that have been deposited dry and are consolidated by a carrier material despite their good absorbency not suitable for disposable towels or similar products

The object of the invention is to produce disposable towels or similar products to create a suitable web of cellulose fibers with optimal strength properties in terms of height and isotropy connects with an optimal grip and optimal absorbency, and thus the hitherto known materials for the production of such disposable products is superior

This object is achieved according to the invention in that the path is a continuum of dry deposited, is essentially unbonded fibers with a length of less than 1.27 cm, which by embossing, which cover 5 to 40% of the web surface and have a smaller distance from one another than the length corresponds to the individual fibers, is connected to form a coherent web in such a way that the thickness of the web in the non-embossed areas is at least 2.5 times that in the embossed areas Areas.

The invention is thus based on a dry deposited cellulose fiber web. So far has been believed that dry deposited cellulosic fibrous webs bring advantages in many respects, but not used in the manufacture of disposable products can be. However, the invention now makes such an application possible, namely by that the solidification of the dry deposited fibers takes place through a precisely defined embossing process. This makes it possible to consolidate the dry deposited fibers into a web in such a way that the properties can be made fully usable in terms of grip and absorbency, d. H. through the Solidification no longer adversely affects the grip and / or the absorbency.

Compared to webs of wet-deposited cellulose fibers, as they have been used so far for the production of disposable doors When products or similar products have been used, the invention has many advantages. First is im In the initial state of the web there is no fiber bond at all, so that no more or less excessive fiber binding must be subsequently reduced again by creping. An optimal grip and an optimal absorbency is therefore mapped out from the start and does not need to be added afterwards to be discontinued through additional measures. Furthermore, a dry deposited web can also be used without others can be manufactured with higher basic weights, so that heavier products can now also be used in single-layer execution are possible. Ultimately, however, it also arises because of the markedly indiscriminate Distribution of the fiber orientation, a very uniform strength in all web directions, so it is not more is necessary to accept an excessive strength in the machine direction in order to move in the direction perpendicular to this, to obtain a reasonably sufficient strength.

The embossing of the dry deposited webs is carried out so that the embossed areas have less Have a distance from each other than corresponds to the average fiber length, so that on average all Fibers are well integrated into the web. the

Embossed areas are dimensioned in such a way that their total area does not cover 40% of the total web surface exceeds that there is still a sufficient area for the formation of not embossed and thus the properties of the dry deposited original web having -. Areas is available. This ensures that the good grip and high absorbency that are drawn in the initial path, are also retained in the end product.

From a procedural point of view, it has proven expedient to guide the continuum of dry deposited, essentially unbonded fibers through the gap between an embossing roller and a smooth counter roller and to adjust it beforehand to a moisture content of 6 to 35%, r, where the pressure im Embossing gap is kept to at least 140 kg / cm ² . This measure enables sufficient fiber bonds to be formed in the area of the embossed areas in a particularly simple manner. 2 "

The invention is described in more detail below in exemplary embodiments and with reference to the drawings. It represents

F i g. 1 schematically shows a view of an apparatus for producing the cellulose fiber 2 "> according to the invention train,

F i g. 2 schematically shows the view of a section from a cellulose fiber web according to the invention,

F i g. 3 shows the photomicrograph of a cellulose fiber web according to FIG. 2 in cross section, jo

4 shows a schematic view of a modification of the device for producing the device according to the invention Cellulose fiber web,

F i g. 5 shows the photomicrograph of a section from a single-layer cellulose according to the invention fiber web that can be used as towel fabric,

6 in microphotography a section of a two-layer cellulose fiber web according to the invention, which can be used as a towel,

F i g. 7 in microphotography a section of a single-layer cellulose fiber web according to the invention, which can be used as a face towel,

8 schematically shows the view of a device for applying additives during the production of the cellulose fiber web according to the invention,

9 shows an electron micrograph of a cellulose fiber web according to the invention, and

10 schematically, on an enlarged scale, the cross section of a cellulose fiber web according to the invention.

The product created according to the invention is shown in FIG. 2. It consists of a soft, absorbent web with a basis weight of 8.5 to 85 g / m ² , which is produced by using cellulose fibers with an average length of less than 1.27 cm are initially laid down dry to form a continuum of essentially unconnected fibers and then connected to a coherent structure by means of an embossing applied in a uniform pattern. The areas connected by embossing take up 5 to 40% of the web surface and are arranged at a distance from one another which is less than the average length of the individual fibers. The b5 thickness of the continuum is at least two times greater than the thickness of the connected areas.

For the continuous or semi-continuous production of the product according to FIG. 2, the in F i g. The device shown is used, a substantially dry cellulose mat 10, which is obtained in the usual way from wood and consists of firmly interconnected cellulose fibers, is unwound from a roll 12 and fed to a picker chamber 14 via feed rollers 16. A picker roller 18 provided with teeth around its circumference is provided there, which divides the mat 10 into the individual fibers 20. These are conveyed to a moving storage screen 24 via an air duct 22. By means of an air supply 26 and a vacuum housing 28, a downwardly directed air flow is generated in the air duct 22, so that a cellulose fiber web 30 of essentially unbonded fibers is formed on the storage screen 24.

This cellulose fiber web 30 is then passed through calender rolls 32, between which it is easily compressed so far that they are sufficient for transfer to a conveyor belt 34 Cohesion gets. No ^ h can be made from one Nozzle 36 water can be sprayed onto the web 30 to create a static attraction between the web and counteract the sieve. After the web 30 has been transferred onto the conveyor belt 34, the depositing screen runs 24 between an air blower 38 and a vacuum housing 40 to remove any remaining loose fibers from the sieve 24 to remove.

On the conveyor belt 34, the moisture content the cellulose web 30 is adjusted to 6 to 35% by means of a water spray device 42 Web 30 by passing it through the gap between a smooth, hard roller 44 and a * · Steel embossing roller 46 bound. The bonded web 30 can then be dried and rolled up or on stored in another way until needed. There is no need for the web 30 is creped.

It is important for the properties of the end product that the fibers are removed from the cellulosic web 30 prior to bonding are indiscriminately oriented and essentially not interconnected. In principle, this can be done with everyone conventional air laying techniques, shown in FIG. 1 blow channel shown is particularly good for this suitable. As will be described below, the random orientation of the unbonded fibers in the Bahn significantly contributes to this. that the end product has reasonable strength along with a good grip and a high absorbency

Another important measure that affects the properties of the end product is the Adjust the moisture content of the cellulosic web 30 prior to bonding. It has been found that the web 30 a moisture content of 6 to 35% prior to binding (based on the weight of the moistened web) should own. Higher moisture levels, i.e. moisture levels to the extent that the Moisture completely fills the open pore volume, as it affects the grip and the absorbency of the End product deteriorate, probably because the web 30 is then in the gap between the rollers 44 and 46 are so strongly compressed that that fiber bonds can also arise in the unembossed areas. On the other On the other hand, if the moisture contents are too low, it is very difficult to give the web 30 sufficient strength obtain. Preferably, the moisture content of the web 30 is adjusted to 10 to 30% prior to bonding

Finally, the manner in which the cellulose web 30 is bound is also of considerable importance for the properties of the end product. It has been shown that the area, the pressure and the spacing of the embossing are influencing factors. In this regard, the embossing protrusions on the embossing roller 46 must be such that the bond area produced by the embossing in the finished web makes up from 5 to 40%, and preferably from 8 to 20% of the total web surface. Too large a surface area of the entire binding area has a detrimental effect on absorbency and grip, while if the area of the entire binding area is too small, the strength of the end product is insufficient. The optimal surface area of the entire binding area depends somewhat on the weight of the web. For webs with a basis weight of less than 34 g / m ² , i.e. with a basis weight of 8.5 to 34 g / m ² , surface proportions of the entire bond area of 10 to 40% are most favorable, values of 10 to 20% being preferred will. On the other hand, for webs with basis weights greater than 34 g / m ² , i.e. for basis weights of 34 to 85 g / m ² , surface proportions of the total bond area of 5 to 25% and preferably 8 to 15% are most useful.

In addition to the area proportion of the total binding area, the binding frequency is also very important. In order to achieve a sufficient strength of the final product should be ^"1, the distances between the individual binding areas be less than the average length of the cellulose fibers from which the web is composed Further, a regularly recurring weave pattern preferable to obtain a uniform strength over the entire surface of the web With an area proportion of the total bond area of 5 to 40%, there are preferably 4 to 16 individual bond areas per centimeter of length in both directions of the web. A frequency of 6 to 14 individual bond areas per centimeter of length is generally preferred. The area of a single bond area then results from the area share of the entire binding area and the frequency of the individual binding areas.

Sufficient pressure must be applied during bonding to keep the fibers in the individual Formation areas of hydrogen bonds. The term »hydrogen bridge« is used to describe the Understood bonding commonly present in self-bonded wet-deposited paper products iii and which is probably due to secondary valence bonds between OH groups and Η atoms of the touching fibers is based on the F i g. 9 shows how the bond areas in the according to the following Example II, look under an electron microscope at a magnification of one hundred times. The bond areas appear as highly compressed fibers.

In order to achieve a sufficient bond, the pressure exerted on the individual bond areas should be at least 140 kg / cm ^2. To a large extent, the maximum pressure is given by the load limit of the corresponding rollers. For practical purposes this pressure will generally not exceed ^{2100 kg / cm 2.} It is particularly useful, with the embossing roller, a flexible, z. B. made of nylon, smooth roller to work together, since then the wear on the embossing roller is reduced.

The design of the embossing protrusions on the embossing roller is not particularly critical, although up to ^r i it can influence the directional resistance of the final product to some extent. However, in order to avoid a noticeable compression of the cellulose web 30 outside the bonding areas during embossing, it is expedient to use the

ui embossing projections with comparatively steep flanks to provide. The height of the embossing projections, which is preferably in the range from 0.38 to 0.76 mm, must also be in in each case be such that there is no excessive compaction of the web, which leads to binding of the fibers

is outside of the binding areas, can occur. A certain compaction of the entire web, the z. B. can be around 50% and of the basis weight and depends on the frequency of binding, usually occurs during embossing, but is of the order of magnitude no further harmful.

The bond areas of the final product generally have a thickness of less than 40% and preferably less than 20% of the thickness of the unbound areas. In other words it is Thickness of the final web in the unbonded areas at least 2.5 times and preferably at least 5 times as large as the thickness of the bond areas. It is believed that this thickness ratio along with the fact that essentially none

jo binding of the fibers is present except in the intended binding areas, to the handle and to the The absorbency of the finished web contributes significantly.

It should also be pointed out that the web for binding with relatively low pressure by several

J5 nip is passed through. Surprisingly becomes essentially the same when passing the web through two nips, for example Tear resistance is achieved as if the web were subjected to double pressure through a single nip is passed through. If desired, more than two nips can be used accordingly lower pressure can be used. In this way, the process speed can be increased significantly and the wear on the embossing roller can be substantially reduced. However, the effects are modest multiple nips not strictly additive. Rather, there is a minimum pressure below which the desired compaction is not obtained regardless of the number of nips used.

This minimum pressure is 140 kg / cm ² and accordingly, if, for example, two roll nips are used, the pressure in the second roll nip should be at least 140 kg / cm ² .
In a number of use cases such as B.

Generally with facial tissues and hand towels, paper products still have to increase wet strength Additives such as urea-formaldehyde resins, melamine-formaldehyde resins, Polyamides or polyimines are added. This also applies to the one according to the invention Product Such additives can be added either before or after binding, e.g. by spraying on take place. However, an arrangement according to FIG. 8 used to reduce the effects of the Additions in terms of absorbency and grip are kept as small as possible. According to FIG. 8 is a Roller 48 is provided, which is partially immersed in a container 50 which is filled with a solution 52 of a wet strength-increasing Resin is filled The roller 48 takes the

Resin on and leads it over rollers 54 and 56 of the Embossing roller 46 closed. This ensures that the resin is only fed to the web in the bond areas will. In this way, but also by spraying on before or after binding, for example on the spray devices 42 or 58 in FIG. 1, starch or another binding agent can also be incorporated into the web, to prevent "lint".

The type of cellulose fiber used is not! particularly critical. It can be relatively thin-walled, κι long fibers from cedar to coarse, thick-walled fibers from pine trees can be used. The kind of Fibers will generally result from cedar fibers determined by the type of B3hn desired a soft, looser web, while pine fibers make a more woolly web. Long fibers become preferred, because then the distance between the individual bonding areas can be increased and that End product becomes more flexible. Additionally, thin-walled fibers have been found to add a little softness contribute to the product. In any case, the cellulose fibers you use have a maximum length 1.27 cm and preferably a length in the range 1 to 5 mm; so they are shorter than normal ones Textile fibers whose length is in the order of magnitude 2> of at least 1.9 cm.

Cellulose mats obtained using the. "Π Kraft process have proven to be a very useful starting material for the product according to the invention. So long however, the fibers separated from the mats then subsequently in the manner described above can be tied, the manner in which the mats are obtained is not significant. Especially with Continuous production of the product according to the invention is the selection of suitable cellular fiber mat- s-i depends on how easy it can be to defiber. In such a case it is appropriate that Low density mats made from unground fibers can be used. To make the shredding even further can facilitate a delivery agent or a -tu mechanical delivery surgery can be used. The use of a delivery agent should only be used in to such an extent that not the subsequent binding of the product according to the invention is hindered. · »">

The basis weight of the product according to the invention depends somewhat on the intended use. With basic weights between 8.5 and 34 g / cm ² , the product can be used in particular in the bathroom and for facial tissues, while with -> u higher basic weights up to 50 g / cm ² and possibly even above it is preferably suitable for towels. Quite surprisingly, the product can be used in a single layer for many areas of application, although it has a basic weight similar to ή conventional products that have to be composed of several layers.

As shown in FIG. 2, the product according to the invention is characterized by a continuum of randomly oriented fibers 60, which is interrupted by a pattern wi of bonding areas 62. 3 is a cross-section taken along a series of binding areas, it can be seen that between the binding areas loosely bulky and thus very soft areas of essentially b ·; Form unconnected fibers. From Fig.9 is the character of the loose baus; can also be seen ELIGIBLE areas.

Another property of the product according to the invention is shown schematically in FIG. 10 for the cross section of part of the web produced according to Example I. As can be seen there, they are close to each other fibers located on the surface of the loose, bulky areas when leaving the bonding area an orientation away from the base plane of the web (i.e. orientation in the Z direction). These relatively large z-directional alignment also appears to give the web grip desired to contribute.

Apart from the areas with unconnected fibers, which also have a high orientation in the Z-direction have, sii-! i distinguishes what is according to the invention Also product of conventional products is that the fibers are more indiscriminate in the base plane of the web are aligned and the Bahr; with the same basic weight is less dense. Both of these latter metrics also seem to be important to help give the product the desired combination of strength, absorbency and improvement tempting to give a grip.

The fiber alignment in the web ground plane is at the product according to the invention in fact completely indiscriminately. As a result, the track has. ci.iu im substantially uniform tear strength in all directions. In particular, the tear strength is in Machine direction uuu pretty much the same in the direction perpendicular to it. The ratio of tear strength between these two directions, d. H. the orthotropic tenacity ratio (ORV), generally exceeds not 1.5 and is usually less than 1.2. As a result, the railway only needs to be tied so far that the required tear strength results for the specific application. It takes As a result, there is no excessive bond in one of the directions to be accepted, which is naturally has an effect on an improved grip. Due to the random fiber orientation in the web a desirable isotropic absorbency is also obtained.

The density of the web, which serves as a further parameter, can be used both as "real web density (RBD)" and as "Apparent web density (SBD)" can be measured. The real web density refers to that Volume of a trajectory of a given area, which is caused by the opposite real Surfaces of the web is included. The apparent track density, on the other hand, is based on a fictitious one Volume of such a track section by adding the two outermost surface elevations to the track touching tangential planes are created and the resulting volume is used as a basis will. In the case of the apparent web density, all those outside the real web surface also count Unevenness, such as the valleys between the crepe folds in creped products or in the one according to the invention Product, the depressions in the area of the binding areas, with the volume.

Two methods (A and B) are suitable for determining the real web density (RBD) A becomes a pre-weighed single-ply sheet cut from the sheet concerned Saturated with a low viscosity mineral oil suitable for pharmaceutical use The excess oil is saturated by repeatedly placing the sheet on a layer of polyethylene removed from both surfaces, with

the excess oil remains on the polyethylene. As soon as all excess oil has been removed from the surfaces (and it has been checked by observation with a stereomicroscope that the oil remaining in the sample is in the fine, inner capillary system and no longer, for example, in any crepe folds or in the depressions of the "'end areas ), the sheet is weighed again. Since the specific gravity of the cellulose fiber and the oil is known, the rrs.ie sheet density (in g / cm ³ ) can be calculated.

In method B, the sheet is embedded in resin and then, with a microtome, 80 slices, zersctir.iti-ü, successive in the direction of the marchine, each of which is 0.025 mm thick. The contours of the projected images of these sections are planimetrized, and the total area of the 80 sections times the thickness of the sections then results in the volume - Jes surface area. The mass of the area is calculated from the average green weight of the underlying web, and this ultimately results in the ic <i! E web density in ^ cm ³ . Of these two methods, method A is the least time consuming and arguably the most accurate.

The characterization of a web by specifying the apparent web density (SBD) is: particularly useful for uncreped webs, since there is no additional volume due to crepe creases. An Instron test device of the type used for measuring web thicknesses is expediently used to measure the apparent web density. This testing device has two plates which can be moved relative to one another and between which the piece of surface cut out of the path to be examined is placed. The plates are then moved against the flat piece in such a way that they rest against the flat piece with a predetermined low pressure without compressing it. The resulting plate spacing indicates the thickness. ^{The apparent sheet density in g / cm 3} is then calculated from this thickness, the known area and the known basis weight of the sheet.

The values for the real web density and for the apparent web density are determined by the area percentage of the entire binding area, the distance between the individual binding areas and the basic weight of the Affected orbit. Large proportions of the entire binding area, small distances between the individual Bonding areas or large basis weights lead to greater densities and vice versa. Thus, with the given basic weight the desired density of the web by suitable selection of the surface area of the entire binding area and the distances between the

Table 1

individual binding areas are preserved.

In the case of the product according to the invention with basic weights between 8.5 and 85 g / cm ² , a real weight of 0.05 to 0.5 g / cm ³ and an apparent weight can be achieved

■> sheet density of 0.02 to 0.1 g / cm ^J can be achieved. In particular, webs have a basic weight of 17 to 34 g / cm ² , a surface area of the entire bond area of 8 to 20% and a number of 6 to 10 individual bond areas per centimeter

Hi long? in both directions of the web a real web density of 0.10 to 0.23 g / cm 'and an apparent web density of 0.03 to 0.07 g / cm ³ . In general, the change in density within the specified range is directly proportional to the change in the

ι % basic weight and the area of the entire binding area and inversely proportional to the distance between the individual! Is binding areas. As can be seen from Table 2 below, the product according to the invention has a lower real web density in comparison with conventional products of the same basic weights. The ^ hoinbare web density Linn cannot be compared, since the conventional products are creped. However, it can be assumed that if such a comparison is made prior to creping the conventional products, the products of the invention will also have a lower apparent web density.

Numerical examples now follow, in particular for

jo illustration of the advantages of the invention.

Examples IbisVI

The following Examples I to VI relate to

ji products which are produced with the device and the method according to FIG. 1 are made. Table 1 gives the basic procedural conditions. The cellulose mat fed to the picker roller 18 consisted of bleached Kraft cellulose (a mixture of North American black spruce, bush pine and balsam fir) and had a density of 0.6 g / cm ³ and a basis weight of about 120 g / m ² . The calender rolls 32 were operated with a line pressure of about 2 kg / cm, and the roll 44 became a smooth one

4 ·> nylon roller used. After passing through the Bond nip had run. The embossing roller 46 had diamond-shaped embossing projections in one Patterns were arranged according to a 60 ° triangle.

The sieve 24 was at a speed of 8.22 m per minute in Examples I and II and with a speed of 4.12 meters per minute in Examples III to VI.

example Il III IV V Vl I. 22.05 28.83 43.25 43.25 28.83 Basis weight (g / m ² ) 18.65 8th 8th 8th 8th 8th Moisture content before the 8th Rollers 32 (%) 20th 24 30th 30th 24 Moisture content before 20th Tie (%) 33.6 26.6 26.6 26.6 26.6 Binding pressure (kg / cm) 26.6 10 7th 7th 7th 7th Number of binding areas 7th per centimeter of length

continuation example 19 65 716 14th IV V VI 13th I. 10 10 10 10 Area of the total - 0.2 0.2 Congestion area (%) - Il 111 Wet strength additive *) 10 10 03 (% accumulated solids) Strength") - - hand hand Facial (% accumulated solids) Bathroom cloth cloth cloth Intended use of the cloth single layer web Bathroom Bathroom cloth cloth

Sprayed on before binding
Sprayed on after binding

The webs made according to these examples were rated for tear strength and feel compared to conventional products. The evaluation was carried out as follows:

The tear strength was measured with an Instron tester on sections of web of predetermined size 23.9 ° C and a relative humidity of 50% and is measured in grams per centimeter of sample width specified.

The grip is based on the general aesthetic impression when touching a web and cannot really be represented in a really representative manner with a single objective measurement. As part of an approximation of an objective representation of the handle, the measurement of the compression work (VA), the measurement of the fold recovery angle (FEW) and the measurement of the coefficient of friction (Q) were used.

The compression work is an indicator of the softness of the web and is intended to express the work (in cm χ g) that a person has to exert to get an impression of its softness by pressing the surface of a sheet between thumb and forefinger. Greater work is associated with greater softness. To measure the compaction work, a web section of a predetermined size is compacted in an Instron test device with a ^{pressure gradually increasing to 15.5 g / cm 2} , a force-time curve being recorded and then integrated. Prior to the measurement of the samples, these eight hours, brought to a temperature of 23.9 ⁰ C and a relative humidity of 50% long.

The fold recovery angle was determined according to the ASTM

Table 2

Test D 1295 (ASTM Standards part 24; 274 to 278

2 (October 1968). This test uses a Section folded and held under a load of 500 g for 5 minutes. Then the load is removed! and given the material 5 minutes to recover. Dei The angle then established is the Falterholungswin angle. This gives you the slackness and resilience Web again, with a low value reflecting the fact that the kinks in the crumple a material yield easily and do not give a hard sensation.

in The coefficient of friction is similar to the compression work is a measure of the softness of the web and indicates the work (in cm χ g) that goes into compacting the Bahr by friction between the web surface and a substantially smooth gliding object

r> must be. This measurement is therefore representative of in the event that a person rubs the material between his thumb and forefinger. As with the Verdich work, a higher coefficient of friction is associated with a softer material. To carry out de!

Tests will be an area cut out of the web piece on a smooth piece of plywood and clamped at one end to the wood. On the fest jammed end of the track section is a lightweight loaded carriage with one 3 Teflon sliding surface placed. This end would then be slowly lifted up until the slide zi begins to move, and the angle of inclination of the plywood is then adjusted so that the carriage mi a constant speed of 2.54 to 5.08 cm /:

^r > o slides downwards. This slope is a direct measure of the coefficient of friction of Teflon on the sample material.

train Orund RBD *) SBD Tear Strength, g / cm to ORV VA FEW to O weight Maschi vertical Maschi vertical nen direction nen direction g / m ² g / cm ³ g / cm ³ direction 66.5 cm ■ g direction example 1 18.65 0.136 0.04 66.5 87.4 1 0.59 80 Example III 28.83 0.144 0.06 88.9 51.9 1 0.7 73 87 0.272 Creped bath 29.68 0.271 104.7 1.95 0.45 75 0.233 room towel according to CH-PS 4 34 957 42.1 70 Creped bath 16.96 0.276 89.7 2.1 0.48 70 0.233 room towel appropriate CH-PS 4 34 957

Continuation reason
weight
g / m- ' RBD ")
g / cm ' SBD RciUfcsiigkcit, g / etii
Machine / .u
non- scnkr.
g / cm ¹ direction direction 66.1
31.5 ORV VA
cm · g FEW
Maschi
nen
direction to
vertical
direction C ₁ train 27.98
30.53 0.251
0.499 112.6
1023 1.7
3.25 0.62
038 86
101 83
78 033
0.225 Creped Ge
face cloth according to
CH-PS 4 34 957
Commercially available
creped
Face towel ··)

*) Method A applied, measurement carried out on two-layer products only on one layer · *) Fibers laid wet.

Table 2 gives the results of the measurements discussed above for webs according to FIG Examples I and III in comparison to different> o State-of-the-art products. The orthotropic tear strength ratios and the sheet densities are also noted in Table 2

As can be seen from Table 2, the webs according to Examples I and III essentially have the following:> same tear strength in the machine direction and in the perpendicular direction. Also are with the two Orbits the densities low. With regard to the measurements representing the handle, the two have Orbits continue a clear trend toward m toward better appearance. This is particularly evident from the measurements of the compaction work and the Coefficient of friction can be seen and was also confirmed by a subjective grip test.

For the web according to Example III, the r> Absorbency determined by the method of capillary tension. In doing so, the from B u r g e η i and Kapor (Textile Research, Journal 37, No. 5. 356-366 May 1967) to this effect modified that for this test water as a liquid -in and an equilibrium time of 100 minutes was used. With the method of capillary tension can the suction pressure exerted by a web at different levels of saturation can be measured. The suction pressure, in turn, is an indication of the inclination of the -r. Web to absorb even more water at a certain saturation level, because at the same saturation level, the web absorbs with the higher suction pressure more active additional water than the track with the lower suction pressure. This type of measurement is known draws the absorbency particularly well, since when a product is actually used it hardly reaches the level total saturation is reached

At saturation levels of 2 or 4 or 6 g of H ₂ CVg fibers, the suction pressures for a web according to r, Example III were 40 or 20 or 11 cm H ₂ O. Such pressures are characteristic of a good absorbency of the web. It should also be mentioned that a web produced in the manner described above using Kraft pulp has a higher suction pressure and a higher saturation capacity than conventional products, especially those made with sulphite pulp and for at least several months at the same t, <> saturation level have aged. The good absorbency of the web produced according to the invention is probably due to the fine pore structure of the loose puffy areas between the binding areas. It it is assumed that the distribution of the pore size in these loose bulky areas is such that a large proportion of the total pore volume of the The web consists of pores that are particularly effective in absorbing liquid at intermediate levels of web saturation.

Examples VIlbisX

Examples VII to X do not apply to the device according to FIG. 1 for the large-scale production of cellulose webs, but from the in F i g. 4 which delivered only single sheets instead of longer webs. The cellulose fibers were placed in a container 64 which has a grid 66 at its lower end. Not from one Compressed air was passed through the grid from the source shown, so that any remaining lumps of fiber were removed were cut into small pieces so that they could pass the grate. After passing the grate, they arrived individual fibers 68 through a metal funnel 70 down through a cylindrical chamber 72 and a down widening chamber part 74 through onto a fine storage sieve 76, which is located at the bottom of chamber part 74 was arranged. A suction pressure was generated by a fan 78, so that through the under the Grille 76 lying grille 80 resulted in a uniform flow of air.

The tear strength of the sheets produced in this way was measured in the manner described above, for the handle, however, more subjective measurement methods were used.

A hardness test was used to determine the unevenness and roughness of the sample surfaces. After this the samples were adapted to the conditions of the test room, each sample was for this purpose with one hand of the Examiner pressed against a flat surface while using the sensitive areas of the fingers of the other hand a pressure that corresponded to the pressure normally applied when the product was used, in Machine direction passed across the center of the sample. The sample was then processed in the same manner in the in the opposite direction and then compared in hardness with the other samples. Of the The examiner felt the samples to be tested as often as necessary to determine the relative hardnesses. Samples were then classified in values from 1 to 10, the hardness increasing with increasing values.

The crease resistance was also determined with a stiffness test. This was done with a sample in a UanH nnrl oino other PrrtKe in rlttt * anXoren

Hand slightly wrinkled. During testing were

the samples were held at arm's length with the pressures applied to crumple them roughly equivalent to those the product is typically exposed to The classification is the same as for the endurance test, with the stiffness increasing with increasing values increases

Finally, the overall softness was determined by handling a sample with both hands and Compare the quality with the quality of another sample determined. The examiner observed in particular> special dip deflection of the sample and its smoothness after brushing it with your fingers.

Example VII

Bleached pine kraft pulp was dispersed in water and formed into sheets 30.48 cm wide and about 510 g / m ^{2 basis} weight. The sheets were formed on a conventional paper machine with minimal wet pressure so as to obtain a low density. After drying on a steam-heated drying drum, each sheet was cut into strips 4.45 cm wide and divided into its individual fibers with a picker roller

About 2.1 g of the fibers thus obtained were placed in the container 64 (Fig. 4) and closed with air shaped into a sheet of 8 "x 8". This Sheet was made in a hydraulic press with a

Plate 3

Physical properties

Force compressed by 101 after that it was then compressed for 2 '/ 2 Hours exposed to an atmosphere of 97% relative humidity with approximately 20% humidity (on the basis of the wet leaf) ingested.

The moistened sheet was then bound by embossing in a two-roll calender, the rolls of which had a diameter of 7.62 cm. The top roll was checked with 8 embossing protrusions per centimeter of length in the machine direction and 10 embossing protrusions per centimeter of length in the perpendicular direction, each embossing protrusion having an area of 0.168 mm ² . The lower roller was a smooth steel roller. The calender was run with a line pressure of about 16 kg / cm. The layer was guided so that it could pass through the nip twice. Assuming that three rows of dots were in contact with one another in the nip, the bonding pressure per pass was 703 kg / cm ² .

A photomicrograph (20 times magnification) of the product thus produced is shown in FIG physical properties of this product were compared to a commercially available two-layer material made from wet-deposited fibers and had been creped off a drying drum. The two-layer material was with the addition of Polyvinyl alcohol made so the layers could stick together better. The results are in the Plate 3 shown:

Dry-laid, single-layer material according to Example VII Commercially available, wet-laid,
two-layer
material

Basis weight, g / cm ² 48.7 Tear Strength, g / cm Machine direction 172.3

to vertical Direction 167.3

Strain, %

Both material samples and a sample of a towel available from Hai IeI were subjectively tested for their grip. The towel was helge provides two VirVnden by wet-laid and creped Zeil 1 osefaser layers by pin-to-pin-Prägui ι. A polyvinyl alcohol solution

Plate 4

46.5

433.1

221.8

32

4) was the contact surfaces of the two layers was added in order to obtain an adhesion of the layers to one another. The two-layer material possessed impressions on both sides with capillaries between the two layers. The results are in

Vi panel 4 shown:

sample

handle hardness

stiffness

Dry laid, one

layered material according to Example VII

Wet laid, tenon

two-ply hand towel embossed on cones Wet laid, two-layer material

Example VIII

Pc ttriirAr * \ tr \ r \ Aort n \ ** in \\ e * n 7 «* lliilr \ c« »facprn a

as in Example VII. Approximately 1.1 g of the fibers were placed in the container 64 (FIG. 4) and then formed into a sheet with a basis weight of about 23.8 g / m ² by means of air. The leaf

would then be bound as in Example VII.

Two of these sheets were then combined with one hydraulic press connected to each other. The press arrangement consisted of a flat one Metal plate, a rubber cushioned disc, a brass spacer disc with a thickness of 0.00254 cm, a coarse, eight-meshed net, the two leaves, and a second flat metal plate. This press assembly was placed in a hydraulic press and compressed with a force of 301 F i g. 6 shows a photomicrograph (12.6X) of a portion of the two-layer product so produced.

Physical properties were compared with those of a wet-laid two-layer material according to Example VII compared. The results can be seen from Table 5:

Plate 5

Physical properties

Dry laid- Commercially available, laid, two- wet laid, layered two-layered

Material according to material Example VIII

46.5

46.5

433.1

221.8

32

Basis weight, g / cm ² tear strength, g / cm

Machine direction 93.5

to vertical Direction 109.8 Elongation,% 6

RBD, g / cm3 0.212

(Method B)

As in Example ViI, the grip was determined for both samples and for the commercially available cone-on-cone embossed, two-layer towel. The results are shown in Table 6:

Plate 6

handle Hardness

stiffness

4.5

8.0

7.0

Two-layer material laid dry in accordance with Example VIII Wet-filed, tenon-on-tenon embossed two-layer towel Wet laid, two-layer 6.5 hand towel

Example IX

Relatively long, thin fibers of cedarwood were dispersed in water and formed into 30.48 cm wide sheets with a basis weight of about 510 g / m ² . These were cut into 4.45 cm strips and frayed into individual fibers as in Example VII. Approximately 1.4 grams of the fibers were placed in container 64 and aired into a sheet having a basis weight of 30 pg / m ² shaped. The sheet was then wetted for 2 hours at 97% relative humidity so that it reached a moisture content of approximately 20%.

The moistened sheet was bound as in Example VII to make it soft, smooth, and flexible Product made. To the touch, this product conveyed a slightly slippery or silky feel. The Fi g. 7 shows a photomicrograph (20x magnification) of the product from which the three-dimensional

Structure can be seen that gives the impression of whether it is a finely woven cloth. The F i g. Figure 3 also shows a photomicrograph (30x magnification) of a cross section through the bound sheet

■> which is laid through the midpoints of the binding areas The bulky structure can be seen from this. The education areas have an average thickness of 0.0406 mm, while the unbonded areas are relatively free of inter-fiber bonds and

ι ο have an average thickness of 0.2769 mm.

The physical properties of such a material, which is suitable as a facial tissue, are with im Commercially available facial tissues have been compared, which are stored wet in the usual way. the Commercial cloths were folded in order to obtain a two-layer product. The results are given in Table 7:

Plate 7

Physical properties

Product stored dry according to Example IX

Basis weight g / m ² 31.4

Tear Strength, g / cm Machine direction 80.5

to vertical Direction 80.5

Elongation,% 6

RBD, g / cm3 (Method B) 0.205

Commercially available, wet filed product

31.9

216.5
52.5
10-15

The handle of the sample obtained according to this example was compared with the handle of a wet-laid sample Web that is partially dried without compaction, then placed on a knitted fabric and then on a Dryer had been pressed, whereby the surface pattern of the fabric was transferred to the web. The results can be seen from Table 8:

Plate 8

handle

Dry-laid product, wet-laid product Example IX

Overall softness

hardness

stiffness

1.0

Example X

2.8

Bleached pine kraft pulp was turned into a sheet having a basis weight of about 30.5 g / m "was formed as described in Example VII. This sheet was bound exactly as in Example VII, but with the addition of a A solution with 5 wt .-% solids of a wet strength-increasing adhesive on the rubber roller Embossing projections of the embossing roller was applied.

Two of the sheets thus prepared were in one Instron tester dry and three other sheets were tested wet for strength. The wet ones Samples were placed dry on the Instron jaws, then soaked with water, followed by could adjust for at least 45 to 60 seconds. The dry tear strength was average 498 g / cm and the wet tear strength was 110 g / cm.

For this purpose 4 sheets of drawings

Claims (7)

. Patent claims: 1. Absorbent cellulose fiber web with a basis weight of 83-85 g / m ² for the production of preferably single-layer paper towel goods, the web being embossed in a predetermined pattern covering part of the web surface and the thickness of the web being smaller in the embossed areas than in the non-embossed areas, characterized in that the web is a! Continuum of dry-deposited, essentially unbonded fibers less than 1.27 cm in length, which by embossings covering 5 to 40% of the web surface and a have a smaller distance from one another than corresponds to the length of the individual fibers, is connected to form a coherent web in such a way that the thickness in the non-embossed areas is at least 2.5 times as great as in the embossed areas. 2. Web according to claim 1, characterized in that it consists of wood pulp fibers, the basis weight is about 17 to 51 g / m ² and preferably 17 to 34 g / m ² , the embossed areas about 8 to 20% of the total web surface cover and the thickness of the web in the non-embossed areas is at least five times as great as in the embossed areas. 3. Web according to one of the preceding claims, characterized in that the embossed Areas in both directions of extension of the web at a frequency of about 6-14 per Centimeters in length are arranged. 4. Web according to one of the preceding claims, characterized in that its real density (RBD) is approximately 0.05 to 0.5 g / cm ¹ and preferably 0.1 to 0.23 g / cm ³ 5. Web according to one of the preceding claims, characterized in that its apparent density (SBD) is about 0.02 to 0.1 g / cm 'and is preferably 0.03 to 0.07 g / cm '. 6. Web according to one of the preceding claims, characterized in that its orthotropes Tensile Strength Ratio (ORV) is less than 1.5 and preferably less than 1.2. 7. A method for producing a cellulose fiber web according to any one of the preceding claims, characterized in that the Konlinuum of dry deposited, essentially unbonded fibers passed through the gap between an embossing roller and a smooth counter roller and is previously set to a moisture content of 6 to 35% The pressure in the embossing gap is kept at least 140 kg / cm ² and the embossing projections of the embossing roller are designed and distributed such that 5-40% of the web surface is covered by embossings and the distance between two embossings is less than 1.27 cm . ίο