EP1319748A1 - Multiply sheet of absorbent paper - Google Patents

Abstract

The multilayer absorbent paper sheet, comprising two layers (12, 14) of cellulose wadding, each with a weight of 15 - 35 g/sq m, has the first layer embossed with a first set of motifs in selected zones (16), made from embossed protuberances (18) projecting towards the second layer (14) and forming open cells in the sheet's outer surface. <??>At least some of the protuberances (18) have their tips (19) attached to the inner surface of the second layer. The first layer of the paper has a second set of motifs made from a series of smaller embossed protuberances (38) of smaller dimensions than the first and having a higher density. The second set of protuberances are set in recesses (36) so that their tips (39) are in contact with the second layer and some are attached to it.

Description

The invention relates to the field of absorbent papers for use sanitary or domestic, and in particular to cellulose wadding paper crimped.

It relates in particular to the field of papers intended for wiping in household, domestic or industrial use. For this application, papers with resistance to humidity imparted by the addition of a specific resin in the pulp containing the fibers paper mills in suspension, before leaf formation. This resin, a once crosslinked, forms a network resistant at least temporarily to disintegrating power of water.

In this field, it is known to make sheets of paper composed of several creped plies of grammage between 12 and 30-35 g / m ² provided with protuberances which are obtained by embossing.

Indeed, embossing gives bulk to the sheet and it induces improved absorption of liquids, touch and softness. We have sought to further increase absorption capacity by creating multilayer sheets obtained by combining at least two plies, made up each of at least one of said embossed sheets.

A multiple sheet is thus obtained which has characteristics mechanical, such as tensile strength, as well as a capacity of absorption determined.

There are two ways of embossing and assembling the plies. works according to the desired characteristics of the final product.

The first is known in the field under the designation "nested" or nesting. It consists first of embossing each of the folds separately from so as to form generally substantially protuberances on the surface frustoconical or in pyramid trunks. Then, we put glue on the top of the protrusions of one of the folds after it has been embossed but before it is detached from the embossing cylinder. The folds are placed so that the faces having the protrusions come opposite, the protuberances of one between the protuberances of the other. We put them together finally by bringing them together. So the two folds are linked by glue films between the tops of the protrusions of a fold and non-embossed areas between the protrusions of the other fold. The voids provided by this structure are suitable for ensuring the sheet a improved absorption. In addition, the exterior faces have a smooth feel and soft due to the alveoli formed by the back of the protuberances. This technique is illustrated by US patent 3,867,225.

The second method of assembly is known in the field under the designation "point to point". It differs from the previous one by the relative arrangement of the two folds. After they have been embossed separately, we bring these one on the other so as to make the vertices coincide protuberances, all or at least in part. The folds are linked together by the tops of the protuberances, points against points. This technique is illustrated by US Patent 3,414,459.

Products made using these techniques have long had a pattern of simple embossing in which the protrusions were aligned according to two directions crossed, uniformly. Such a pattern allows to obtain homogeneous properties but has little visual appeal.

However, in recent years, we have sought to make the appearance of less commonplace product by distributing the protrusions differently. The plaintiff thus markets a paper towel whose cells in surface are arranged in concentric circles evoking the propagation of the absorption of a liquid which is poured on a leaf absorbent or the propagation of waves on the surface when a drop of water falls into a liquid. This pattern in particular is composed of first distinct disc-shaped areas defined by three or four concentric circles. The discs are themselves arranged regularly in crossed directions. Second zones, defined between the discs adjacent, have a general diamond shape.

A motif of this type is of interest insofar as it is clearly visible by the consumer.

The applicant has set itself the objective of producing products with patterns whose relief was accentuated and whose perception was improved.

It managed to achieve this objective with a multiple sheet comprising a first ply and a second ply of cellulose wadding, each of grammage between 12 and 35 g / m ² , the first ply comprising a first embossing pattern consisting of first protuberances protruding on the internal face of the first ply which in particular form alignments and at least part of the vertices of which is linked to the internal face of the second ply opposite, characterized in that said first ply comprises a second pattern embossing consisting of second protrusions projecting from the inner face of the first fold of lower height whose density is higher and at least part of the vertices of which is in the same plane as the vertices of the first protuberances and is linked to the face internal of the second fold.

Thanks to the structure thus defined, the visual perception of the first motif by creating on the external face of the second zones whose level is different from that of the first zones with the first pattern. The three-dimensional effect is reinforced. We also observe that the thickness of the sheet remains more homogeneous. This effect is further accentuated by the higher density of the pattern of the protrusions of the second zones.

The invention also includes other features taken individually or in combination.

The protrusions arranged on the first zones have a density of less than 20 per cm ² , preferably less than 12 per cm ² . Such a distribution of the first protrusions corresponds to heights of protrusions between 1 and 2 mm. This makes it possible to create spaces between the first embossed ply and the second ply ensuring good absorption without losing resistance to crushing. This is particularly true when the second ply is not embossed in the areas facing said first and second areas.

The protrusions disposed on the second zones have a lower height than the first protrusions and a density greater than 30 per cm ² , preferably greater than 40 per cm ² . By their higher density and their different height, the second protrusions form plates which improve the contrast effect with the first zones.

The first zones and the second zones are adjacent.

Third low wall-shaped protrusions connect two first adjacent protrusions of an alignment. In order to further improve the visibility of the pattern of the first protuberances, we create protuberances in the form of a low wall which reinforces the layout of the alignments without necessarily impair tear resistance.

The second fold is of the through blow-drying type. The combination of an embossed ply of cellulose wadding, obtained by pressing conventional wet, with a blow drying type pleat crossing is particularly advantageous in the context of the invention. We thus optimizes absorption compared to mechanical resistance.

The invention also provides a cylinder on which the first ply is embossed. This includes first spikes forming alignments in first zones and second spikes whose height is lower and the higher density. The vertices of the first and second spikes are located in the same tangent planes along the generatrices of the cylinder.

The invention also provides a method of manufacturing a product according to the invention.

• la figure 1 représente, vu de dessus, un exemple de réalisation d'une feuille de papier multiple gaufré conforme à l'invention,
• la figure 2 est une vue schématique, en coupe et en perspective cavalière, d'une feuille de papier multiple conforme à l'invention,
• la figure 3 est une vue schématique, en perspective, montrant la surface d'un cylindre de gaufrage,
• la figure 4 est une vue agrandie de la surface du cylindre de la figure 3.
• la figure 5 est une vue, en perspective, d'un autre mode de réalisation des picots de la première zone selon l'invention,
• la figure 6 est une représentation photographique d'une feuille de l'invention.

Other characteristics and advantages of the invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

• FIG. 1 represents, seen from above, an exemplary embodiment of a sheet of multiple embossed paper according to the invention,
• FIG. 2 is a schematic view, in section and in perspective view, of a multiple sheet of paper according to the invention,
• FIG. 3 is a schematic perspective view showing the surface of an embossing cylinder,
• FIG. 4 is an enlarged view of the surface of the cylinder of FIG. 3.
• FIG. 5 is a perspective view of another embodiment of the pins of the first zone according to the invention,
• Figure 6 is a photographic representation of a sheet of the invention.

There is shown in Figures 1 and 2 an embodiment of a multiple sheet 10 of absorbent paper. This sheet comprises two folds arranged one on the other: a first fold called upper 12 and a second fold 14 called lower. This sheet is intended for general wiping, and for use as a household paper towel in particular. Such a product is in the form of a roll comprising around fifty pre-cut coupons. The paper is cellulose wadding weighing between 12 and 35 g / m ² . The upper fold 12 is, for example, of the type obtained according to a method with conventional wet pressing, and known in the field under the acronym "CWP". The fold 14 is preferably of the type obtained according to a process with drying through air and known in the field under the acronym "TAD". according to another embodiment the two folds are of the "TAD" type

According to the embodiment shown, the second fold is not embossed.

A CWP type paper manufacturing process consists of depositing the fibers suspended in water on a canvas to form a sheet. We drain the sheet, then transfer it to a felt which will allow apply it with a press against a drying cylinder. The leaf is peeled off and creped using a doctor blade. She is finally re-reel awaiting transformation into a finished product. Such a technique, presented here in summary, is said to be conventional. he There are of course variants.

A TAD type technique consists, after draining, of drying the sheet. without applying pressure, at least in part, to a sufficient dryness to freeze the fibers within the sheet. If necessary, we end the drying by applying the sheet to a heated cylinder. Thanks to this first drying, you can press the sheet on the cylinder. She keeps part of its volume. This cylinder also allows its creping. We achieves pressure-free drying by blowing hot air through the leaf after draining. This technique, which is designated in the domain under the acronym TAD, allows to obtain a thicker leaf, greater mass volume than conventional technique.

The sheet 10 is oriented in two directions, one longitudinal and the other transverse, represented in FIGS. 1 and 2 by the arrows L and T which correspond respectively to the direction of scrolling of the sheet during its manufacture, direction of travel, and the direction perpendicular thereto, cross direction.

The first embossing pattern 16 on the upper fold generally appears in Figure 1 and in more detail in Figure 2. It is composed of first protrusions 18 of generally frustoconical shape projecting inside the sheet. Each protuberance corresponds to a cell on the other face of the fold 12, facing outwards. The protrusions are arranged in alignments, here concentric circles, within the first zones. The protrusions 18 have a first height H1 which is between 0.5 mm and 1.5 mm. Their number within the first zones is between 6 per cm ² and 20 per cm ² , preferably between 9 and 12 per cm ² . The vertices 19 of the protrusions are in contact with the lower fold 14.

These first zones 16 are therefore here in the form of discs. The latter are themselves ordered in two crossed directions of a square mesh network, here at 45 ° relative to the direction of travel L. Inside each mesh, formed by the discs of the first zones, there are seconds protrusions 38 forming second zones 36. These protrusions 38 have a height H2 lower than that of the first protrusions 18. It is between 0.2 mm and 1.5 mm as can be seen in FIG. 2. The second protrusions form a plate of smaller thickness. From the external face, we see a cell at the right of each protuberance 38. The distribution of the protrusions 38 in the second zones 36 is tighter than those of the first zones 16. The density of the pattern is between 30 per cm ² and 80 per cm ² , preferably between 40 and 60 per cm ² . The tray-like appearance comes from the relatively tight arrangement of the second protuberances which are distributed substantially uniformly in this area. At the edge of this zone which is adjacent to the first zones, there is a very marked enhancement. The apex of the second protuberances is in contact with the fold 14. At least for some, and in particular for the assembly, a film of adhesive forms a bond between the apex 39 of the protrusions and the fold 14. The same is true of the peaks of the protrusions 18 of the first zones. It is understood that the vertices 19 and 39 are in the same plane as the fold 14.

The second fold 20 is not embossed. The height difference between H1 and H2 is between 0.3 mm and 1.3 mm.

To emboss the upper fold, we use an engraved cylinder as we can see Figures 3 and 4. Figure 3 shows the general appearance of the surface of the cylinder with the lines of pins 28 and 48 arranged according to the pattern of the figure 1. The detail of figure 4, corresponding to the reference D4 on the Figure 3 shows the first tapered pins 28 with a vertex 29 forming a flat. The protrusions have a fairly steep slope, between 70 ° and 75 °. The height H '1 of the pins between the flats 29 and the bottom of the engraving 28 is at least equal to H1: H'1> = H1. The protrusions 48 also have a frustoconical shape, with a vertex forming a flat 49. The flats 49 are at the same altitude with respect to the axis of rotation of the cylinder as the vertices 29. On the other hand, the depth of the etching H'2 is less H'2 <H'1. The protrusions 48 are distributed so homogeneous in the second zones.

In the example shown, the pins have a frustoconical shape based circular. Other forms are possible, in particular diamond or pyramid trunk with a polygonal base or a linear base.

The method of manufacturing a sheet 10 as claimed is to emboss a ply of crepe cellulose wadding on the cylinder by pressing the ply on the cylinder by means of a rubber cylinder or another resilient material. The embossing pressure must be sufficient for the cellulose wadding enters the space between the pins of the first areas. In particular, in the first zones, the paper must go down to a depth greater than H'2. The tray shape, with a tight pattern, second zones, on the other hand, limit the penetration of paper between the second zone pins. The rubber is rather pushed back towards the periphery of the second zones. This results in an increased marking effect in this border part between the first zones and the second zones.

To make a two-ply sheet according to the teaching of the invention, glue is placed on the flats 29 and 49. As they are at the same height, you can simply put it down using a glue applicator cylinder. Then we approach an unembossed fold and the press on the tops to form bonds between the two folds along of these peaks. Once assembled, we cut the sheet, and roll it up to make it a finished product as is common.

According to this process, the bond between the plies is increased relative to a two-level embossing process of the prior art because all of the peaks of the spikes are linked.

In the above description, the sheet is double. It falls within the framework of the invention to provide more than two folds. For example, the embossed fold can to be himself double; the non-embossed fold also. Of course, the reason shown is only given as an example. Other reasons are conceivable insofar as they take up the teaching of the invention. In particular, a particular embodiment comprises a pattern consisting at least in part of second profile protrusions linear, drawing for example a flower.

FIG. 5 represents another embodiment of the first zones which allows to further improve the visible character of the embossed decoration.

We represented a part of the spikes of the first zone, in fact spikes on one of the alignments in this area. According to this embodiment we have arranged in reliefs in the form of walls 30 between the adjacent pins 28 of a alignment. The pins 28 are frustoconical or in the form of a pyramid trunk with a flat at the top 29. The top 31 of the walls 30 is at a level lower than the vertices 29. The chosen distance is between 0.4 mm and 0.9 mm. In other words, it's also the difference between their height H'1 and H'3.

The thickness “e” of the walls 30 is less than that of the pins 28. say at the same height, it is less than the diameter of the pins. The thickness walls is thus 10 to 50% lower than that of the studs, so as in particular to limit the additional embossing pressure resulting the presence of low walls. Their slope is preferably the same as that spikes.

The distance between the heights H'1 and H'3 is sufficient for the rubber comes into contact with the upper surface 31 of the wall at the time of embossing and thus conform the sheet to the wall at least partially.

Claims (10)

Multiple sheet comprising a first ply (12) and a second ply (14) of cellulose wadding, each of grammage between 12 and 35 g / m ² , the first ply comprising a first embossing pattern on first areas (16) consisting of first protrusions (18), projecting from the internal face of the first ply corresponding to cells on the external face, which in particular form first alignments and at least part of the vertices (19) of which is linked to the internal face of the second fold (14) facing each other, characterized in that said first fold (12) comprises a second embossing pattern (36) consisting of second protrusions (38) projecting from the internal face of the first fold (12 ) whose height (H2) relative to that (H1) of the first protuberances is lower, whose density is higher, and at least part of the vertices (39) of which is in the same plane as the vertices (19) of the first protrusions (18) and is linked to the inner face of the second fold (14). Multiple sheet according to claim 1, characterized in that the first protuberances (18) are arranged on first zones (16), their density being less than 20 protuberances per cm ² preferably less than 12 per cm ² . Sheet according to one of the preceding claims, characterized in that the second protrusions (38) are arranged on second zones (36), their density being greater than 30 per cm ² , preferably greater than 40 per cm ² . Sheet according to claims 2 and 3, characterized in that the first zones and the second zones are adjacent. Sheet according to claim 1, characterized in that third protrusions (30) in the form of walls connect two adjacent first protrusions of an alignment. Sheet according to one of the preceding claims, characterized in that the second ply (14) is of the through-blow-drying type. Sheet according to one of the preceding claims, characterized in that the second ply (14) is not embossed. Embossing cylinder engraved with a pattern corresponding to the pattern of one of the sheets according to any one of the preceding claims, characterized in that it comprises first pins (26) forming alignments in first zones and second pins (46) whose height is lower and the density higher, the vertices of the first and second spikes being located in the same tangent planes along the generatrices of the cylinder. Method for manufacturing a sheet by means of an installation comprising an embossing cylinder according to the preceding claim, characterized in that it consists in embossing a first ply (12) of creped cellulose wadding on said cylinder then in apply a film of glue to the tops of the protrusions by means of a glue applicator cylinder, then bond said ply to a second ply. Manufacturing method according to the preceding claim, characterized in that said second ply (14) is not embossed.

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