DE1965716A1 - Absorbent cellulosic sheet and process for making same - Google Patents

Description

DR. KURT-RUDOLF EIKENBERG PATENT ADVOCATE

3 HANNOVER · SCHACKSTRASSE 1 · TELEFON (0811) 8140 88 · KABEL PATENTION HANNOVER

Kimberly-Clark Corporation 240/451

Cellulosic fiber absorbent web and process for making the same

The invention relates to paper products and, more particularly, to sanitary paper wipes and paper hands cloths.

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Conventionally, such disposable products are in papermaking facilities has been shaped, in = cltL "a fibrous wood pulp layer was applied by means of water and then the water either by drying or by pressing and Drying was removed. During the removal of the water, strong surface tension forces develop between the fibers, so that there is inevitably a bond between the fibers everywhere. This happens even if the layers are not pressed hard. Because of this ubiquitous bond, have such Water-formed webs inherently have very undesirable feel properties (i.e. hardness, stiffness, lower Circumference and little softness) and low absorbency. As a result, in order to avoid the aforementioned, undesirable Properties the water-formed sheets are creped, i.e. the paper web is removed from the drying drum by means of scraped off with a stripping knife. This creping artificially improves the feel and absorbency enlarged, in-which an excess bond between the fibers is interrupted again.

Creping to improve the properties mentioned however, there are several limits. Above all, creping is only effective on webs with a low overall weight less than 6.8 kg. Conventionally made creped webs with higher basis weights are entirely stiff and generally unsuitable, for example as a face towel to be used. As a result, it is conventional practice that two layers of low Base weight can be used for these purposes. Only in this way can a sufficiently bulky product come with sufficient softness can be produced »

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A second limit imposed on creping "is that even with a low basis weight material, the detrimental properties inherent in all of the original bonding are not entirely eliminated. In water-forming processes, preferred fiber orientation is the machine direction As a result, the tear strength in this direction is always higher than in the perpendicular direction. Thus, creped products with sufficient tear strength perpendicular to the machine direction have an excess tear strength in the machine direction. Because of this excess tear strength, which is necessary to have sufficient tear strength transversely to get to the machine direction, achieving prevents optimal feel characteristics. Thus, also have creped B _a hnen of gringem basis weight than optimal feel properties.

It has been suggested that the tactile properties of water-formed sheets by thermally pre-drying a sheet to a fiber consistency is much better than that of the sheets usually fed to the dry surface of a paper machine The partially dried sheet is then provided with a hump pattern by means of a printing fabric and then dried, without destroying the bonds imprinted by the hump pattern. Although by this process the softness can be improved a little bit, the bulkiness and the absorbency of the product made in this way are between the humps due to the occurrence of water removal Surface tension forces are pretty bad, because the lines are still connected to each other in these areas

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are. As a result, creping is still necessary, to get the maximum benefits of the proposed method. For many areas of application are still two-layer membranes necessary.

As can be seen from the above,

"Possess the conventional water-forming papermaking processes the undesirable disadvantage that the ^ asern originally be excessively connected to each other and then have to be detached from each other again by creping. Additionally is the necessity that a large amount of water must be removed, disadvantageous particularly with regard to the therewith associated water pollution problems. Furthermore, it would be very desirable if products could be obtained which have sufficient tear resistance, improved feel properties and improved absorbency as opposed to have those hitherto commercially available, it would be particularly desirable if these products consist of only one single layer.

Many years ago, wood pulp fiber webs were produced by means of air. The resulting But only used for those purposes where either a low tear resistance was required, for example for absorbent pillows or the like, or where a certain minimum tear strength was required the feel and absorbency were unimportant (e.g. for various special papers). In the US patents 2,447,161 and 2,810,940 and British Patent Specification 1,088,991 are methods of air forming such Described tracks for corresponding areas of application. To

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today it has not been believed that an air formation process Can advantageously be used for making paper products that can be used as sanitary wipes and towels can be used.

It is the aim of the invention to be aesthetic

creating effective, paper-like webs that are more desirable Way have an improved combination of tear resistance, absorbency and feel properties.

According to the invention, such an absorbent web made of cellulose fibers is characterized in that the web has a basis weight of 2.27 to 22.7 kg per 267.6 m ² and consists of a continuum of essentially unbonded fibers with a length of less than 1.27 cm, the continuum is interrupted by a pattern of areas in which the fibers are connected to one another, these binding areas covering 5 to 40% of the entire web area, the binding areas at a smaller distance than the average length of the individual fibers $ are separated from one another and the web has a thickness which is at least 2.5 times as great as the thickness of the bond areas.

The basis weight is preferably about 4.54 to 13.6 kg, the fibers being wood pulp fibers which make up bond areas 8 to 20 % of the total web area and the web has a thickness which is at least 5 times the thickness of the Attachment areas.

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BATH ORIGINAL

A method according to the invention for producing such webs consists in that a layer of cellulose fibers is formed by means of air, which has a length of less than 1.27 cm, the layer having a basis weight of 2.27 to 22.7 leg / 267, 6 m, then the layer is given a coherent structure by connecting the fibers to one another in areas arranged in a pattern, with the bonding areas covering 5 to 40 fo of the web area and being less spaced from one another than corresponds to the average length of the individual fibers, and the The thickness of the web is such that it is at least 2.5 times as great as the thickness of the bond areas.

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ORIGINAL

The invention is described in more detail below with reference to the drawings. In the drawings:

Fig. 1 is a schematic view of a

Device with which the products according to the invention on continuous or semi-continuous ./ege can be produced,

Fig. 2 is a schematic view of part of an inventive, single-layer track, with the loose, hilly structure guü you can see,

Figure 3 is a photomicrograph of a part a cross-section through a web as shown in Fig. 2, wherein the cross-section extends through a bond line,

^J FIG. 4 is a schematic view of an apparatus with which the method according to the invention can be carried out,

Figure 5 is a photomicrograph of a part

a single-layer according to the invention Web that can be used as towel fabric,

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Pig. 6 is a photomicrograph of a part

a two-layer according to the invention] Web used as towel fabric can be,

Pig. 7 is a photomicrograph of a part

a single-layer according to the invention Web that can be used as a face towel,

Pig. 8 is a schematic view of a device used for applying adhesive agents can be used during the manufacturing process,

9 shows an electron micrograph a web according to the invention and

10 is a photomicrograph of a cross section through a device according to the invention Train.

A preferred example of one according to the invention built product is in Pig. 2 shown. It comprises a soft, absorbent sheet with a basis weight of 2.27 to 22.7 kg / 267.6 m obtained by making a continuum of essentially unbound wood pulp fibers

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is formed, after which the fibers are formed by joining in united in a uniform pattern into a coherent structure will. The connected areas take 5 to 4Ö? U des Area of the web and are arranged at a distance from one another which is less than the average length of the individual pasers. The thickness of the continuum is at least ' 2.5 times greater than the thickness of the connected areas. '

The device shown in FIG. 1 can be used to produce the product shown in FIG. 2; continuously or semi-continuously. A substantially dry wood pulp sheet 10 is taken from a roll 12 unwound and fed via feed rollers 16 to a picker chamber. Around the pulp arch into its individual fibers separate, a conventional picker roller 18 is provided which is provided with teeth around its circumference. The picker roller 18 separates the pulp sheet into its individual fibers 20, which are fed via a form feed 22 to a holey, moving one Network 24 are promoted. A downward flow of air is established through air from a source 26 and a vacuum housing 28. generated by a path 30 on the moving Ne ^ z 24 is molded.

After its formation, the web is passed through calender rolls 32, between which it is slightly compressed is so that it "oekommt a sufficient cohesion to be fed to a conveyor belt 34 can. Aue of a nozzle 36 water can be sprayed on in order to thereby

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a static attraction between the train and the rush to counteract. An air blower 38 and a vacuum housing 40 serve to remove loose fibers from the web 24 after from which the web has been transported, so that an accumulation of fibers is prevented.

After the web is fed to the conveyor belt 34, the moisture content of the web is measured by means of a water spray device 42 is set to 6 "to $ 35. After that, the web by passing it through the nip between a smooth, hard roll 44 and a patterned steel roll bound. The bonded web can then be dried; and rolled up or otherwise stored until needed. There is no need for the baan to be creped will.

There are several important considerations in performing the method described above directly the touch, the drunkenness and the resilience of the resulting product can be influenced. Above all else, it is important that the fibers are removed before binding the Bahn are randomly oriented and essentially not connected to one another. Although conventional air shaping techniques are used to Producing a web with such properties can be used can, the mold feed shown in Fig. 1 is particularly suitable for producing a special, suitable web. As will be described below, the random fiber orientation in the web contributes significantly to the fact that a

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useful resilience together with a desirable one Palpability and absorbency can be achieved.

Another important aspect of the process is the moisture content of the web prior to bonding. It has been found that the web should have a moisture content of $ 6 to $ 35 (based on the weight of the wetted web) prior to bonding. Higher moisture contents, i.e. moisture contents up to an extent to which the moisture fills the previously empty volume, are detrimental as they normally do not compress the feel and drinkability of the finished product - probably due to the greater compression of the web and its binding Bodies-influencing. On the other hand, at lower moisture levels, it is very difficult to obtain sufficient resistance * Preferably a moisture level prior to binding of $ 10 to $ 30 is preferred.

The manner in which the web is bonded constitutes a third important aspect of the process. In order to obtain a product with the desired properties, the area, pressure and spacing of the bond has been found to be important. With reference to Fig. 1, the steel roll 46 should have a raised pattern such that the total bonded area in the finished web occupies an area of 5 to 40 ½ and more specifically 8 "to 20 ½ of the total web area. As affecting moisture content

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larger bound areas adversely affect absorbency and the tactile properties while tied at lower levels Areas the resistance of the railway is insufficient. The optimal bound area for a given web is based on the weight of the web. For sheets with a basic weight of less than 9t07 kg / 267.6 m, e.g. with a basic weight from 2.27 to 9.07 kg, bound areas of $ 10 to $ 40 are most useful, with bound areas of $ 10 to 20 ^ are preferred. On the other hand are for Lanes with basic weights greater than 9.07 kg, e.g. basic weights from 9.07 to 22.7 kg, bound areas from 5 to $ 25 and specifically $ 8 to $ 15 most satisfactory.

Apart from the total bound area, the binding frequency is also very important. To be adequate To achieve resilience, the distances between the bound areas should be less than the average length 'of the wood pulp fibers that make up the track exists. Furthermore, a regularly recurring weave pattern is preferred in order to ensure uniform resistance to get the train. With a total bound area of $ 5 to $ 40, each own bound area preferably a frequency of 10 to 40 per 2.54 cm in either direction of the web. A frequency of 15 to 35 / 2.54 cm areas is generally preferred. The area of a single bond can be from the entire bound area and the frequency of the individual bound areas can be determined.

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Sufficient pressure must be applied during bonding so that the fibers form hydrogen bonds in the individual areas. The term hydrogen bond should be understood to mean the bond that is usually present in self-bonded, customary paper products. It is assumed that such bonds are secondary Yalenz bonds between OH groups and Η atoms of touching fibers. FIG. 9 shows how the bond areas in the web produced according to Example II below look under λ 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 with the method described, the should be applied to the individual Pressure applied to the binding areas should be at least 140 kg / cm. To a large extent, the maximum pressure is through given the yield point of the corresponding rollers. For practical

For technical purposes, this pressure is generally 2100 kg / cm

do not exceed. In ¹ this regard, it is desirable to use together with the patterned roll has a resilient, for example made of nylon, smooth roll. This reduces the wear on the patterned roller.

The design of the raised parts on the patterned roller is not considered particularly critical, although to a certain extent it can influence directional resistance. However, to a noticeable To avoid pinching the web outside of the areas to be bound, it is desirable that the pages of the sublime part are comparatively 8th part. With regard to

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at the height of the raised parts it should be noted that a certain Compaction of the entire web, e.g. by 50%, depending on the basis weight and the binding frequency occurs while the binding is being performed. Excessive compaction leading to binding of the fibers outside the However, it should be avoided. Raised portion heights between 0.015 and 0.030 are generally useful.

The bound through hydrogen bonding regions of the hergestell-th with the above-described process products generally have a thickness which is less than 40% of the thickness of the final sheet, the thickness of the bonding areas is preferably less than 20 i>. In other words, the thickness of the final web will be at least 2.5 times and generally at least 5 times the thickness of the bond areas. It is believed that this ratio of the thickness of the finished web to the thickness of the bond areas, together with the fact that there is essentially no bond of the fibers other than the intended bond areas, contributes significantly to the feel and absorbency of the finished web.

Another process aspect of the present invention is that the bond by reducing pressure and passing the web through a plurality of nips. Surprisingly, for example when passing the web through two nips essentially ' lent the same tensile strength achieved as when the web through a single nip, in which the double Pressure is applied, is carried out. If desired,

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can have more than two nips with a correspondingly lower one Pressure can be used. In this way, the process speed can be increased significantly and the wear and tear of the patterned Roll can be reduced significantly. The whole

ρ nip pressure should however be at least 140 kg per cm be. For example, when using two nips

2, the additive amount of pressure should be 140kg per cm.

It should be noted, however, that the effects of multiple nips are not strictly additive. Ea is consequently a minimum pressure below which the desired \ compression is not obtained regardless of the number of nips used.

As is well known, certain applications of paper products for which the webs discussed herein can be used require the use of moisture resistant resins such as urea formaldehyde, melamine formaldehyde, polyamides or polyimines. This applies generally to face towels and hand towels. In the method described here, the moisture-proof additives can end either before or after binding e.g. B. be added by spraying. Preferably, however, an arrangement according to Fig. 8 a used so that the effect of the addition with respect to the absorbency and feel properties is kept as small as possible. According to FIG. 8, a roller 48 is provided which rotates in a container 50 filled with a moisture-proof solution 52. The roller 48 is partially immersed in the solution 52 and picks up the resin which is fed to the patterned roller 46 via the rollers 54 and 56. In this arrangement, the moisture-proof resin is _a B hn only fed into the Bindungebieten. As with that

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feuchtigkeitBfesten Z _u, starch or other binder of the web satz.kann be supplied in order to prevent "fiddle about". In the method described, this can be done by spraying on before or after binding, for example at the spray devices 42 or 58 in Pig. I applied.

In the process described, the wood pulp used is not particularly critical. As a result, pulps with relatively thin-walled, long fibers (cedar) can be used to coarse pulps with thick-walled fibers (pine). The type of pulp is generally determined by the type of web desired. Cedar pulps make a soft, loose sheet, while pine pulps make a more woolly sheet. Long fibers are preferred because the distance between the individual bonding areas can be increased, making the finished product more flexible. In addition, it has been found that thin-walled fibers contribute somewhat to the softness of the product. In any event, it should be emphasized that the present invention is concerned with products which consist essentially of cellulose fibers, in particular of wood pulp, of short length. Compared to normal textile fibers, the fibers used here are considerably shorter. While the length of dextile fibers is on the order of at least 1.9 cm, the fibers used here have a length of less than 1.3 cm. In general, the length of the fibers used here is in the range of 1 to 5 mm.

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Pulp sheets made by the Kraft process have been found to be very useful for the invention. However, as long as the separated sheet of your fibers may be then bonded in the above beschreibenen ¥ _e ise, the manner of manufacture of the pulp is not particularly critical. In particular, when the process is carried out continuously, the selection of suitable pulp sheets depends on how easily the defibration can be carried out. Accordingly, it is initially desirable that low density sheets made of unground fibers be used. To further facilitate grasping, a debonding agent or mechanical debonding operation can be used. However, if a debonding agent is used, it should be done only to the extent that it does not prevent subsequent bonding in the process.

As already stated, the products made by the process described are particular suitable as sanitary wipes and towels and have basic weights of 2.27 to 22.7 kg and

2 preferably 4 »54 to 13.6 kg per 267.6 m. With basic weights between 2.27 and 9.07 kg, the products can be used in particular in the bathroom and as face towels, while with higher basic weights they are preferably suitable as towels. Quite surprisingly, the webs can be used in a single layer for many areas of application, whereby they have similar basic properties as conventional products, which are composed of several layers in order to obtain the necessary softness and absorbency. It is believed that this is due to the uniform structure of the webs of the invention.

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As can be seen from Fig. 2, indicates the new product can be found randomly through a continuum of * * directed fibers 60, which is interrupted by a pattern of bond areas 62. If, as shown in Fig. 3, When a cross-section is taken along a number of the bond areas, it can be seen that the bond areas interrupted by loose "mounds" of essentially unbound fibers. The fact that in the "Hill areas" is essentially no bond, results from the lack of strong surface tension forces, which normally form between the fibers in aqueous processes when the water is removed will. From Fig. 9 the character of the loose "hilly areas" can be seen in which there is essentially no binding is available. Since there is no bond, these areas are very soft.

Another property of the webs produced as described can be seen from FIG Microphotography with a hundredfold enlargement of a cross-section represents part of the web produced according to Example I. As can be seen here, the an alignment close to the surface of the loose "mound" when leaving the binding area, which points away from the base plane of the path (i.e. orientation in the Z direction). This relatively large alignment in the Z-direction also looks to the desired feel properties to contribute to the railway.

Except for the fact that the B _a hnen areas of unbound fibers and fibers having a high orientation shown having Z-direction, the webs also different zu_herkömmlichen products since the fibers

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are aligned more indiscriminately in the ground plane of the web and the web "is less dense for the same basis weight. Both of these latter distinguishing features seem also to an important extent to contribute to the product the desired combination of firmness and absorbency and to give improved tactile properties.

The Ifaser orientation in the ground plane of the new

Bahn is completely indiscriminate. As a result, the railway has a " essentially uniform tear strength in all directions. In particular, tear strength is in the machine direction unä perpendicular to it pretty much the same. The maximum ratio of tensile strength between these two directions, i.e., the orthotropic tenacity ratio (ORV) generally does not exceed 1.5 and is usually less than 1.2. As a result, the webs only need to be bonded to the extent necessary to maintain their tear strength for the special end use. As a result, there is no need for an excessive bond in one of the Directions to be made. Of course, this has an effect on improved feel. Because of the irregular paser alignment of the webs also obtain a desired iaotropic absorbency. How much these properties are desirable and required is detailed in U.S. Patent 3,455,778 executed.

Sheets produced in the manner described have a lower density at equivalent basis weights than conventional products. Such a lower density results from the measurement of both the real leaf

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density (RBD) as well as the apparent sheet density (SBD). The real sheet density refers to the volume, which is trapped by the opposing surfaces of the web. This density is different from that Apparent sheet density, which refers to the volume between two flat plates used to determine the sheet diameter be used.

Two methods have been used to determine actual sheet density. A procedure (procedure A) is based on the measurement of the absorption of oil, taking a pre-weighed sample with the size of 7.44 cm by 7 »44 cm of a single layer web with one for pharmaceutical Use suitable mineral oil (e.g. Wheiterex 318) of low viscosity to be saturated. After saturation will the excess oil from the surfaces by repeatedly laying the sheet on the surface of a polyethylene layer removed. The excess oil from the surfaces remains on the polyethylene. When there's no more oil left it is believed that substantially all of the excess oil has been removed from the surfaces. this can be proven by observation with a stereo microscope. Such observation shows that this is in the sample remaining oil is in the fine, inner capillary system and not on the surfaces, for example in crepe folds or binding impressions. After removing the Surface oil, the sample is weighed again. Since the specific gravity of the cellulose fibers and the oil is known, the real sheet density can thus be calculated.

Method B uses a sample in resin embedded and microtomized in the machine direction so that eighty cuts are created, each of which is 0.025mm thick. is.

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The outlines of the projected images of these sections are then planimized. The entire G _e Bidding the eighty-sections times the thickness of the sections then obtains the volume of the sample. The mass of the sample is calculated from the average basis weight of the pre-cut web. The weight per unit volume (RBD) of the sample is reported in grams per cm. Of the two methods described above, method A is the least time consuming and is considered to be the most accurate.

Characterizing a web by specifying the apparent sheet density (SBD) is particularly useful for uncreped Orbits useful as there is no additional volume

due to crepe wrinkles. Here is the apparent one

ρ sheet density has been measured by placing a 25.81 cm

large piece of web is placed in an Instron test facility equipped with an apparatus for continuous Record the pressure and yield of the sample is provided. The cross head is then lowered to 0.05 cm / mm until a compressive stress of 0.25 g per 6.45 cm is indicated will. This value is taken to indicate the thickness of the uncompacted sample. The sample is then taken from the Test device removed, whereupon the crosshead is lowered further and its movement is recorded simultaneously until a Contact has been made between the crosshead and the pressure plate. The distance of the crosshead by which it moves The thickness of the specimen is taken as the thickness of the specimen. The apparent leaf density (SBD) is then calculated using this thickness, the known Size of the sample and the known basis weight of the sample is used.

BATH ORIGINAL

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The "treated densities of the webs, i.e. the real sheet density and the apparent sheet density become influenced by the entire bond area of the web, the distance between the bond regions and the basic weight of the web. Large bonding areas, small distances between the bonding areas or large basis weights create greater densities. On the On the other hand, lower densities can be obtained by using small bonding areas, a large distance between the Binding areas and a low basis weight is chosen. Thus, for a given basis weight, the desired Obtain density of the web by suitable selection of the entire bond area and the spacing of the individual bond areas will.

Using the method described herein, webs with basis weights between 2.27 and 22.7 kg, which has a real sheet density of

2
0.05 to 0.5 g per cm and an apparent sheet density of

ρ
0.02 to 0.1 g per cm. In particular _, webs with a basis weight of 4> 54 to 9.07 kg, a total pas bond area of 8 to 20 $ and a frequency of the bond areas of 15 to 35 per 2.54 cm in both directions of the web have a real sheet density of 0.10 to 0.23 and an apparent sheet density of 0.03 to 0.07. The change in density in the above range is directly dependent on the change in the basis weight and the entire bond area and, conversely, depends on the distance between the bond areas. As will be seen here, _a T fel II, according to the invention possess Webs made in comparison with conventional webs of the same basis weights less real leaf density. The apparent sheet density cannot be compared because conventional products are creped. However, it is believed that if such a comparison

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before creping the conventional products would be carried out that the webs of the invention have a lower would have apparent sheet density.

The following Examples I "to TI show the production of webs made with the apparatus and method described with reference to Figure 1. Table I gives the basic process conditions for the production of these webs. Those of the picker roller 18 feed pulp consisted of sheets of a weight of 31 _f 8 kg of bleached Packpapierpulpe from northern softwoods (a mixture of North American Black spruce, Bush jaw and Balsam fir) having a density of 0.6 g per cm. The calender rolls 32 were at a pressure of 5> 44 kg per straight 2.54 cm, a smooth nylon roller being used as roller 44. The webs according to the examples were dried by surface heating after they had run through the binding roller gap. diamond-shaped dots arranged in a pattern according to a 60 ° triangle The net 24 was moved at a speed of 8.22 m per Minute in Examples I and II and driven at a speed of 4112 meters per minute in Examples III to VI.

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Panel I.

Example I. II III 17th Y TI Basic weight
kg / 267.6 m ^e.g. 4.99 5.90 7.71 11.53 11.53 7.71 Moisture
keep the gate
. Rollers 32 8th 8th 8th 8th 8th 8th ο moisture
^ salary before
"Tie (#)
ύ. . 20th 20th 24 30th 30th 24 ** Binding printing
^ kg / straight 2.54 cm 67.6 85.3 67.6 67.6 67.6 67.6 O tie pattern
μ (points per 2.54 cm) 19th 25th 19th 19th 19th 19th Total bond
i area in i » the railway 10 10 10 10 10 10 j ffaßfeatigkeit *
j (? 6 attached solid
i substance) __— 0.2 0.2 ■ Strength ** (# ap-
i stored solid matter)
• ^; Intended use
the single-layer track Badim
mer cloth Bathroom
cloth Badim
mer cloth hand
cloth hand
cloth 0.3
Facial
cloth

CO CD cn

* sprayed on before binding **. sprayed on after binding

CT)

The webs of the various examples above were rated for tear strength and feel compared to conventional products. The evaluation was carried out as follows.

Tear resistance

Tear strength was measured on an Instron tester (Model No. TM-M) "on web samples as large as 1.27 cm 7> 62 cm measured. The measurements were made with a Crosshead speed of 0.170 cm / min at 23.9 ° 0 and performed at a relative humidity of $ 50. The tear resistance is given as the gram load per 2.54 cm of the sample width.

Tactile properties

The tactile characteristics are with the general

aesthetic effect connected, given someone the web is, if he like to handle. As a result, it cannot be assumed that a single objective test can truly be representative of these properties. However, the following 3 tests were selected as part of an attempt to objectively present the tactile properties:

The measurement of the compression work (VA), the measurement of the fold recovery angle (FEW) and the measurement of the

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Coefficient of friction (G ^).

The importance of compression work as a

An indication of the softness of the web is given in U.S. Patent No. 3,301 dealt with. As pointed out here, 'the compaction work is the one inch-by-g work that it takes to make a web up compress to a load of 100 g / 6.452 cm with a

Contact area of 25.81 cm. It is believed that this work is like work done by one person that squeezes the surface of a sheet of paper between his thumb and forefinger to create an impression from its softness. A greater work is associated with a greater softness. The measurement of the Compaction work is in accordance with that of San Ford described method using an Instron tester (model TM-M) was performed with the samples

2
had a size of 25> 81 cm and the cross head with a

Speed of 0.05 cm / min was moved. Before the measurement the samples were brought to a temperature of 23.9 ° 0 and a relative humidity of $ 50 for 8 hours.

The pallet recovery angles were measured in accordance with the procedure described in ASTM Test D 1 295 (ASTM Standards part 24; 274-278, October 1968). In this test, a sample of material is folded and held under a load of 500 g for 5 minutes. Thereafter, the stress is removed and the material is given 5 minutes to recover.

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The recovery angle (FEW) is then measured. It is believed, that this test reflects the slack and compliance of the web. It is also assumed that a minor Recovery angle reflects the fact that when a material is crumpled, the pressure points give way easily and no hard impression is created.

A third user test that can be used to indicate softness is the measurement of C _f between the web surface and a substantially smooth gliding object. As with the measurement of compaction work, the slip coefficient indicates the work that is performed when the web is compacted. However, since this measurement is not made precisely in a normal direction of compaction, this test also indicates the work done when rubbing the material as if someone were sliding the material between the thumb and forefinger. As with compaction work, it is believed that a higher coefficient of friction is associated with a softer material. The test is carried out by carefully laying a piece of the sheet on a piece of smooth plywood and clipping the sheet to the wood at one end. A slide (6.35 cm in the direction of movement and 4.76 cm in the perpendicular direction with a weight of 53.5 g and a sliding surface made of Teflon) is placed on the clamped end of the track. The end is then slowly lifted up until the carriage begins to move. The angle of inclination of the plywood will be

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then adjusted so that the carriage slides downwards at a constant speed of 2.54 "to 5» 08 cm / sec. This slope is a direct measure of the coefficient of friction of Teflon on the test material. Table II gives the results of the properties discussed for webs according to the examples I and III and on various conventional products. The orthotropic tear strength ratios and the mentioned densities are also given.

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Plate II

train Basic weight
kg / 267.6 m RBD * SBD - Tear-resistant
g / 2.54 cm
Machine"
direction , speed
to vertical
direction ORV VA FEW
machinery
direction to vertical
Deer. ^C f Example I. 4.99 0.136 0, o4 I69 I69 1 o £ 9 Example III 7.71 0.144 0.06 226 222 1 0.7 73 80 0.272 conventional ,
^ creped bath
C, zinan cloth 7.94 o, 271 266 132 i, S5T o, 45 75 87 0.233 J? conventional,
^ creped bath
OQ room towel 4.54 o, 276 228 Io7 2.1 0 ^ 8 7o 7o 0.233 ^ ₄ conventional,
_ ». creped facial
O cloth 7.49 o, 251 286 168 1.7 Ci62 86 83 0.233 T * conventional,
; creped
S face towel 8.16 o, 499 260 80 3.25 0.58 lol 78 0.225

* Measurement carried out on only one layer of two-layer products
Method A applied for RBD

CD CJl

As can be seen from Table 2, "own

the webs of Examples I and III had substantially the same tear strength in the machine direction and more perpendicular thereto Direction . Also, "in" both examples are the densities small amount. In terms of feel properties "own the orbits a clear trend towards one better appearance. This is particularly evident from the measurements of the compression work and the coefficient of friction evident. Furthermore, controlled subjective testing also indicated that the webs of Examples I and III did better Possessed tactile properties.

The absorbency of the web according to Example III was also determined by the method of capillary tension. The method used was a modification of the method described by Burgeni and Kapor (Textil Research Journal 37, No. 5, 356-366, May 1967). For this test water and an equilibrium time of 100 minutes were used. This method can be used to measure the suction pressure exerted by a web at different levels of saturation. Of the Suction pressure is in turn an indication of the tendency of the web to absorb more water at the particular saturation level. For example, at the same saturation levels, the web with the higher suction pressure becomes more active additional Absorb water than the web with the lower suction pressure. These measurements are believed to be the Particularly mark absorbency, since the real

109828/1102

"Ϊ9657Τ6"

need a product hardly reaches the level of total saturation.

At saturation levels (g HpO / g

Fibers) of 2, 4 and 6 were the suction pressures (cm H ₂ O) for a web according to Example III 40, 20 and 11. Such pressures are characteristic of a good absorbency of the web. In this regard, it has been found that webs made according to the above-described method using a packing paper pulp have a higher suction pressure at the same saturations and have higher saturation capacities than conventional products, in particular those made with a sulfite pulp which is suitable for at least several Has been aged months.

The described absorbency properties of the webs produced according to the invention are probably based on the pore structure of the loose "hills" of the tracks. Since these "hills" have a very low density and in the I consist essentially of unbound fibers, they have j "fine pores. It is assumed that the distribution of the pores' size in the "mounds" is such that a large amount of the total pore volume of the web consists of pores i especially with liquid absorption at intermediate levels the orbit saturation are effective.

The remaining Examples VII to X.

IQ 9 8 2.8 / .1.1 02.

also illustrate the invention. The tracks according to this Examples were made with an apparatus shown in Fig. 4 in the following manner:

Pulp, previously divided into its individual fibers, is placed in the container 64 at its lower Has a grid 66 at the end. From a feed, not shown, compressed air is passed through the grid, so Lumps of fiber are broken up until they are so small that they can pass the grid. After passing the grid the fibers 68 pass through the metal funnel 70 down through the cylindrical chamber 72 and the widening Chamber part 74 The fibers are then collected on the fine grid 76, which is at the bottom of the chamber part 74 is arranged. A suction pressure is generated by a fan 78, with the grille lying under the grille 76 80 a uniform air flow is obtained.

The tear strength of the webs in these examples was measured as described above and reported as g / 7 »62 cm width. Various tests have been used to illustrate the tactile properties. The feel properties were determined subjectively. A hardness test was used to determine the roughness and roughness of the sample surfaces. After the samples had been adapted to the conditions of the test room, the sample was placed against a flat one with one hand of the experimenter

9628/1102

Surface pressed while the sensitive areas of the Finger of the other hand over the center of the web in the machine direction pressure applied normal to the pressure to which the product was subjected are cared for. The sample is swept in the same way in the opposite direction and the direction of the Hardening machine compared with the powder sample or samples. The Expertimentator touches the samples to be tested as often as necessary to determine the relative hardness. The samples are then classified in values of 1 ^ 10, with the hardness with increasing values.

A stiffness test is used to determine crease resistance. This test is done by one sample is easily wrinkled in one hand and another sample in the other hand. During testing will be the samples held at arm's length, the pressures applied to wrinkle normal to those who received the product should be exposed. The rating is the same as for the endurance test, with the stiffness increasing with increasing values increases.

Overall softness is determined by grasping a bow with both hands and comparing the quality of one bow with the quality of another bow. The tester observed, in particular, the deflection of the arc and its smoothness after recoating with the

44-0-2-

Fingers.

Example VII

Bleached pine packing paper pulp was dispersed in water and formed into sheets with a width of 30.48 cm and a basis weight of about 136 kg / 267 _} 6 m. The sheets were formed on a conventional papermaking machine with minimal moisture pressing so as to obtain a low sheet density. After drying on a steam-heated drying drum, the sheet was cut into 4> 45 cm strips and divided into its individual fibers on a picker roller.

Approximately 2.1 grams of the shredded pulp was placed in container 64 (Fig. 4) and air closed molded into a layer 8 "x 8". This layer was made in a hydraulic press with a force of 10 t compressed. The densified layer was then left in a 97% relative humidity atmosphere for 2 1/2 hours during which time the web is exposed to approximately 20% moisture (based on the wet web).

The moistened web was then bound by embossing in a two-roll calender, the rollers of which are one. Diameter of 7.62 om beBaßen. The top roller had a checkered pattern of 21 points / 2.54 om in MaBohinenriohtung

and 25 in the direction perpendicular thereto, each

ρ point comprised an area the size of 0.00168 cm. the bottom roll was a smooth steel roll. The calender was run with a load of 40.8 kg / straight 2.54 cm. The sheet was guided so that it could pass through the nip twice. Assuming three rows of points in which the nips were in contact with each other, the bonding pressure per pass was 703 kg / cm

A photomicrograph (20X) of the bonded web is in Pig. 5 shown.

The physical properties of the web thus formed were compared with a conventional two-layer material prepared by conventional water forming and scraping the dried web from the drying drum with a doctor blade. The two-layer material was made with the addition of polyvinyl alcohol so that the layers could adhere better to one another. The '. Results are shown on Table III: \

Plate III

physical properties

air-formed,

single layer

hand towel

10982 8 / 1IQ 2.

water-formed, two-layer towel

Basic weight kg / 267.6m 13.02 12.4 Tear strength g / 7.62cm broad Machine direction 1313 3300 in addition vertical direction 1275 1690 Strain (%) 5 32

The two towel samples were subjectively tested for their feel properties with a sample of an im Tested commercially available water-molded towels. The latter was made by joining two layers together by tenon-on-tenon embossing. A polyvinyl alcohol solution was added to the points of contact of the two layers in order to allow the layers to adhere to one another to obtain. The two-layer sheet had impressions on both sides with capillaries between the two layers. The results are shown in! Table IV:

Plate IV.

sample Tactile properties
Hardness stiffness 1 air formed single layer
hand towel 1 8th water-formed, tenon-on- -
Tenon-embossed two-layer
good towel 8th 9 water-formed, two-layer
good towel 9

109828/1 10 2

It is a low density sheet of bleached pack paper pulp formed from pine trees, cut into strips and divided into its individual fibers as in Example VII. Approximately 1.1 g of the fibers are then in the container 64 (Fig. 4) brought and then by means of air to sheet shaped, which has a basis weight of about 6.35 kg per 267.6 m had. The air-formed sheets were then patterned as in Example VII.

Two of these sheets were then connected to one another with a hydraulic press The arrangement consisted of a flat metal plate, a rubber-damped disc and a brass spacer disc with a thickness of 0.00254 cm, a coarse, eight-mesh net, the two arches or layers and a second flat metal plate. This stacked arrangement was put into a hydraulic press given and pressed together with a force of 30 t. Fig. 6 shows a photomicrograph (12.6 times magnification) of a portion of the two-layer web so produced.

The physical properties were compared with those of a water-formed two-layer towel according to Example VII compared. The results are shown in Table V:

109828/1102

BAD ORlGlNAl,

-38 panel Y

phyaikal.Properties air-formedea water-formedtea

two-layer two-layer towel towel

Basic weight kg / 267.6m ² 12.4 12.4 Tear strength g / 7.62cm
broad
Machine direction
in addition vertical direction 713
838 3300
1690 Stretching (*? <>)
RBD g / cm ⁵ (method B) 6th
0.212 32

The tactile properties of both samples were compared with those of a tenon-on-tenon embossed two-layer towel made according to Example VII was. The results are shown in Table VI:

Plate VI

sample ischich- Feel
hardness Properties
stiffness - air-formed two
good towel Tenon-on-
two-layer 1 1 water-molded,
Tenon-embossed β
good towel two-way 4.5 0.0 water-molded,
good towel 10982! 6.5 7.0 / 1102

BATH ORIGINAL

109828/1102

BATH ORIGINAL Belspiel IX

Cedar pulp with relatively long, thin fibers was dispersed in water and formed into 30.48 cm wide sheets formed with a basic weight of 136 kg / 267.6 m. These were cut into 4.45 cm strips and cut into individual fibers frayed as in Example VII. Approximately 1.4 grams of the fluffed pulp was placed in container 64 and by means of air to arches with a total weight of 8.16 kg / 267, 6 m shaped. The sheets were wetted within 2 hours at 97% relative humidity so that they reached a moisture content of about $ 20.

The wetted sheets were bound as in Example VII to form a web that was soft, smooth, and flexible. When touched, these arches gave a slightly slippery or silky feel. Figure 7 shows a microphotograph (20x magnification) · g of such a web, from which the three-dimensional structure is visible, which gives the impression as if we are dealing with a finely woven cloth.

Fig. 3 shows a photomicrograph (30x magnification) of a cross section through the bonded web which is passed through the centers of the bond areas. It can be seen therefrom the flaky, undulating structure of the web.

The bond areas have an average thickness of 0.00406 cm, while the unbound areas are relatively free of bonds between the fibers and have an average thickness of 0.02769 cm.

The physical properties of the sheet useful as a facial tissue are those commercially available Facial towels have been compared to those in more common ones Way are made by shaping water. The conventional webs have been folded to form a two-layer product to obtain. The results are given in Table VII:

Plate VII

physical properties air-formedβ
product sample water-molded
product 8.39 · 8.52 Basic weight kg / 267.6m Tear strength g / 7.62cm
broad 613 1650 Machine direction 613 400 in addition vertical direction 6th
0.205 10-15 Elongation ($)
RBD g / cm ⁵ (method B)

109828/1 102

19657 TB

The feel of the air-molded samples are compared with those of water-formed webs that are partially dried without compaction, then placed on a knitted fabric and then pressed on a dryer in order to transfer the humped pattern of the fabric onto the web. This procedure is detailed in U.S. Patent 3 501 746. The results are from Olafe 1 VIII evident:

Plate VIII

Feel properties

sample

air-molded water-molded Product product

general softness hardness

Stiffness

2.8

Example X

A bleached packing paper pulp made from pine trees

was aired into a sheet having a basis weight of about 0.16 kg / 267.6 m according to the procedure of Example VII

109828/1102

shaped.

The sheets were as in Example VII with a diamond-shaped pattern with 21 × 25 digits per 2.54 cm (0.00168 cm / bond) bound. A solution with 5 percent solids by weight of a moisture-proof Adhesives were fed to the diamond-shaped pattern by means of a rubber roller. A pressure of 40.8 kg / straight 2.54 cm (this corresponds to a pressure on the individual points of 703 kg / cm) exerted, with the arch was passed twice through the nip.

Two sheets were tested dry in an Instron tester, while three samples were tested wet. The wet samples were placed dry on the Instron jaws, then soaked in water, whereupon they were left for at least 45 to 60 seconds could adapt. The tear loads of the wet and dry samples were below the following Conditions tested:

Span 5 * 08 cm; Width 7.62 cm; Crosshead speed 1 cm / min; Feed speed 50 cm / min.

The dry tear load averaged 498 g and the wet 110 g. As from the examples above VII through X, the present invention provides new air-formed webs or sheets that are very have advantageous properties for use as a wipe or towel.

-Patent claims-

10 9 8 2 8/1102

Claims (1)

Patent claims: 1. Absorbent web made of cellulose fibers, characterized in that the web has a basis weight of 2.27 to 22.7 kg / 267.6 m and consists of a continuum of essentially unbonded fibers with a length of less than 1.27 cm , the continuum is interrupted by a pattern of areas in which the pasers are connected to each other, these bonding areas covering 5 to 40% of the entire web area, the bonding areas at a distance less than the average length of the individual pasers from each other are separated, and the web has a thickness which is at least 2, finally as great as the thickness of the bond areas. 2. Absorbent web made of cellulose fibers, characterized in that the web is air-formed and patterned and has hydrogen bonds, the cellulose fibers are shorter than 1.27 cm, the basis weight is 2.27 to 22.7 kg / 267.6 m and the hydrogen bonds be spaced closer to each other than the average length of each 109828/1 102 BATH ORIGINAL Fibers debioht, with the entire bond area about $ 5 to $ 40 of the railroad area covered. 5 «web according to claim 1 or 2, characterized in that the basic weight is about 4.54 to 13.6 kg} the fibers consist of wood pulp fibers, the bonding areas cover about 8 to 20 $ of the entire web area and the web has a thickness that is at least five times the thickness of the bond areas. 4. Web according to one of the preceding claims, characterized. that the bond areas are arranged in both directions of extension of the web at a frequency of about 15 to 35 per 2.54 cm. 5. Web according to one of the preceding claims, characterized in that the pasers are aligned essentially randomly in the base plane of the web. 6. Web according to one of the preceding claims, characterized It is known without t that the real sheet thickness of the web is approximately 0.05 to 0.5 g / cm, the change in density in this area being directly dependent on the change in the basis weight and the total binding area and vice versa from the distance between the Binding areas depends. 7. Web according to claim 6, characterized in that the web has a real sheet density of 0.1 to 0.23. 109828/1102 8. Web according to one of the preceding claims, characterized in that the apparent sheet density of the web is un- ^; about 0.02 to 0.1 g / cm2, the change in density in this area being directly dependent on the change in the basis weight and the total bond area and vice versa depends on the distance between the binding areas. 9. Web according to claim 8, characterized gekennzelohnet that the ■ basis weight is about 4 »54 to 9.07 kg, wherein the cellulose fibers consist of wood pulp fibers occupy the bonding areas 8 to 2Q $ of the web area and in both directions of the web at a frequency from 15 to 35 p ^ o 2.54 cm and the sheet has a thickness which is at least five times greater than the thickness of the binding ^: areas and the apparent sheet density is 0.03 to 0.07. , 10. Absorbent web made of cellulose fibers, characterized in that the orthotropic tear strength ratio (ORV) is less than 1.5, the basis weight 2.27 to 22.7 kg ο
per 267.6 m and the orbit consists of a continuum Holzpulpefaeern consists, the continuum in a regular Pattern of binding areas is interrupted, which take up 5 to 40 $ of the railway area, the binding areas have a smaller distance from each other than the ■ average length of the pasern and the web has a thickness that is at least 2.5 times greater than the thickness of the bond regions. 109828/1102 11. Web according to claim 1O, characterized in that the basis weight amounts to 4 »54 to 13.6 kg, whereby the binding areas make up 8 to 20 $ of the entire railway area and the web has a thickness which is about five times greater than the thickness of the bond areas. 12. The web of claim 11, characterized in that the orthotropic tear strength ratio is less than 1.2. 13. A method for producing a web according to any one of the preceding claims, characterized in that a layer of cellulose fibers is formed by means of air, which have a length of less than 1.27 cm, the layer having a basis weight of 2.27 to 22, 7 kg / 267.6 m ² , after which the layer is given a coherent structure by connecting the fibers to one another in areas arranged in a pattern, the bonding areas covering 5 to 40 $ of the web area and being spaced apart from one another by a smaller distance than the average length of the corresponds to individual strands, and the thickness of the web is such that it is at least 2.5 times as great as the thickness of the bond areas. 14. The method according to claim 13, characterized in that the fibers bind wood pulp fibers, the layer has a basis weight of 4.54 to 13.6 kg and the connection is made in this way 109828 / TT Q2 is carried out that the binding areas 8 "to 20 $ des Make up the railway area and the path has a thickness that is at least five times the thickness of the bond areas. 15. Method according to claim 13 or 14 » characterized in that the joining is carried out by passing the layer through a nip between a smooth roll and a patterned roll, the moisture content of the layer before passage through the nip being 6 to 35 $ and the pressure in the nip is at least 140.6 kg / cm ² . I. Bm / kä / bö 109828 / 1-1 0.2 Blank page