EP1319748B2 - 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 sanitary or domestic use, including papers creped cellulose wadding.

It relates in particular to the field of paper intended for wiping in domestic, domestic or industrial use. For this application, papers having a moisture resistance imparted by the addition of a specific resin in the pulp containing the suspended paper fibers before the formation of the sheet are used. This resin, once cured, forms a network resistant at least temporarily to the disintegrating power of water.

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

In fact, the embossing gives the leaf a bouffant and induces an improvement in the absorption of the liquids, the touch and the softness. It has been sought to further increase the absorption capacity by creating multilayer sheets obtained by combining at least two plies, each consisting of at least one of said embossed sheets.

This gives a multiple sheet which has mechanical characteristics, such as tensile strength, as well as a specific absorption capacity.

Two modes of embossing and ply assembly are commonly employed depending on the desired characteristics of the final product.

The former is known in the field as "nested" or interlocking. It consists first of embossing each of the plies separately so as to form on the surface protrusions generally substantially frustoconical or truncated pyramid. Then, glue is deposited on the top of the protuberances of one of the folds after it has been embossed but before it is detached from the embossing roll. The pleats are placed so that the faces having the protuberances come opposite, the protuberances of the one between the protuberances of the other. We assemble them finally by bringing them closer to one another. Thus the two plies are bonded by adhesive films between the tops of the protuberances of a fold and non-embossed areas between the protuberances of the other fold. The voids provided by this structure are adapted to ensure the sheet improved absorption. In addition, the outer faces have a smooth and soft feel due to the cells formed by the back of the protuberances. This technique is illustrated by the patent US 3,867,225 .

The second mode of assembly is known in the field under the designation "tip to point". It differs from the previous one by the relative disposition of the two folds. After they have been embossed separately, these are brought together so as to make the tops of the protuberances coincide, all or at least in part. The folds are linked together by the tops of the protuberances, tips against points. This technique is illustrated by the patent US 3,414,459 .

The products made by these techniques have long exhibited a simple embossing pattern in which the protuberances were aligned in two crossed directions, uniformly. Such a pattern provides homogeneous properties but has little visual appeal.

However, in recent years, attempts have been made to make the appearance of the product less ordinary by distributing the protuberances differently. The applicant thus markets a paper towel whose surface cells are arranged in concentric circles evoking the propagation of the absorption of a liquid that is poured onto an absorbent sheet or the propagation of surface waves when a drop of water falls into a liquid. This particular pattern is composed of first distinct disk-shaped areas defined by three or four concentric circles. The discs are themselves arranged regularly in crossed directions. Second zones, defined between the adjacent disks, have a general diamond shape.

A pattern of this type is of interest to the extent that it is clearly visible to the consumer.

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

It has achieved this goal with a multiple sheet according to claim 1.

By virtue of the structure thus defined, the visual perception of the first pattern is increased by creating on the outer face second zones whose level is different from that of the first zones comprising the first pattern. The three-dimensional effect is reinforced. It is also observed that the thickness of the sheet remains more homogeneous. This effect is further accentuated by the higher density of the pattern of the protuberances of the second zones.

The US Patent 2177490 door on a packing sheet consisting of two embossed folds each of which has protuberances on both sides. The protuberances are divided into distinct zones with shapes and / or different dimensions.

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

The protuberances disposed on the first zones have a density of less than 20 cm ² , preferably less than 12 cm ² . Such a distribution of the first protuberances corresponds to heights of protuberances of between 1 and 2 mm. This creates 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 protuberances disposed on the second zones have a smaller height than the first protuberances and a density greater than 30 cm ² , preferably greater than 40 cm ² . By their higher density and their different height, the second protuberances form trays that improve the contrast effect with the first zones.

The first zones and the second zones are adjacent.

Third wall-shaped protuberances connect two adjacent first protuberances of an alignment. In order to further improve the visibility of the pattern of the first protuberances, wall-shaped protuberances are created which reinforce the layout of the alignments without affecting the tear resistance.

The second ply is of the through-blow drying type. The combination of a wadded fold of cellulose wadding, obtained by conventional wet pressing, with a fold of the through-blow drying type is particularly advantageous in the context of the invention. This optimizes the absorption with respect to the mechanical strength.

The invention also proposes a cylinder on which the first ply is waffled. This comprises first pins forming alignments in first zones and second pins having a lower height and a higher density. The vertices of the first and second pins 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 non selon la revendication 1.
• 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:

• the figure 1 represents, seen from above, an embodiment of a sheet of embossed multiple paper according to the invention,
• the figure 2 is a schematic view, in cross-section and in perspective view, of a sheet of multiple paper according to the invention,
• the figure 3 is a schematic view, in perspective, showing the surface of an embossing cylinder,
• the figure 4 is an enlarged view of the cylinder surface of the figure 3 not according to claim 1.
• the figure 5 is a view, in perspective, of another embodiment of the pins of the first zone according to the invention,
• the figure 6 is a photographic representation of a sheet of the invention.

We have shown on figures 1 and 2 an exemplary embodiment of a multiple sheet of absorbent paper. This sheet comprises two folds arranged one on the other: a first so-called upper fold 12 and a second fold 14 said lower. This sheet is intended for wiping on a general plan, and for use as a household paper towel in particular. Such a product is in the form of a roll comprising 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 by a method with conventional wet pressing, and known in the field under the acronym "CWP". The fold 14 is preferably of the type obtained by a method with through air drying and known in the field under the acronym "TAD". according to another embodiment the two folds are of type "TAD"

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

A method of making paper, CWP type consists of depositing the fibers in suspension in water on a fabric to form a sheet. The sheet is drained and then transferred to a felt which will allow to apply it with a press against a drying cylinder. The sheet is peeled off and is creped by means of a doctor blade. It is finally reeled waiting for a transformation into a finished product. Such a technique, presented here in a summary way, is said to be conventional. There are of course variants.

A technique of TAD type after draining to dry the sheet without exerting pressure, at least in part, to a sufficient dryness to freeze the fibers within the sheet. If necessary, the drying is completed by applying the sheet to a heated cylinder. With this first drying, the sheet can be pressed onto the cylinder. It retains part of its volume. This cylinder also allows its creping. The drying is carried out without pressure by blowing hot air through the sheet after draining. This technique, which is designated in the field under the acronym TAD, makes it possible to obtain a thicker sheet with a greater mass volume than the conventional technique.

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

The first embossing pattern 16 on the upper fold generally appears at the figure 1 and more in detail on the figure 2 . It is composed of first protuberances 18 of generally frustoconical shape projecting inside the sheet. Each protuberance corresponds to a cell on the other side of the fold 12, facing outwards. The protuberances are arranged in alignments, here concentric circles, inside first zones. The protuberances 18 have a first height H1 which is between 0.5 mm and 1.5 mm. Their number inside 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 protuberances are in contact with the lower fold 14.

These first areas 16 are here in the form of disks. The latter are themselves arranged according to two crossed directions of a square-meshed network, here at 45 ° with respect to the running direction L. Inside each mesh, formed by the disks of the first zones, there are seconds protuberances 38 forming second zones 36. These protuberances 38 have a height H2 lower than that of the first protuberances 18. It is between 0.2 mm and 1.5 mm, as can be seen in FIG. figure 2 . The second protuberances form a plate of smaller thickness. From the outer face, we see a cell to the right of each protrusion 38. The distribution of the protuberances 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-shaped appearance comes from the relatively tight arrangement of the second protuberances which are distributed substantially uniformly in this area. On the edge of this zone, which is adjacent to the first zones, there is a very marked enhancement. The top of the second protuberances is in contact with the fold 14. At least for some, and in particular for the assembly, a film of glue forms a connection between the vertex 39 of the protuberances and the fold 14. It is the same for vertices of the protuberances 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 difference in height 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 on the Figures 3 and 4 . The 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 the figure 4 , corresponding to reference D4 on the figure 3 shows first frustoconical studs 28 with a vertex 29 forming a flattened surface. The protuberances have a rather steep slope, between 70 ° and 75 °. The height H'1 of the pins between the flats 29 and the bottom of the etching 28 is at least equal to H1: H'1> = H1. The protuberances 48 also have a frustoconical shape, with a top forming a flattened surface 49. The flats 49 are at the same altitude relative to the axis of rotation of the cylinder as the peaks 29. On the other hand, the depth of the etching H ' 2 is less H'2 <H'1. The protuberances 48 are distributed homogeneously in the second zones.

In the example shown, the pins have a frustoconical shape with a circular base. Other forms are possible, including rhombus or truncated pyramid polygonal base or linear basis.

The method of making a sheet as claimed is to emboss a fold of creped cellulose wadding on the roll by pressing the fold on the roll by means of a rubber roll or other resilient material. The embossing pressure must be sufficient for the cellulose wadding to enter the space between the pins of the first zones. In particular, in the first zones, the paper must descend to a depth greater than H '2. The tray shape, with a tight pattern, second zones on the other hand limits the penetration of paper between the pins of the second zones. The rubber is rather pushed towards the periphery of the second zones. This results in an increased marking effect in this boundary portion between the first zones and the second zones.

To manufacture a two-ply sheet according to the teaching of the invention, glue is deposited on the flats 29 and 49. Since they are at the same height, it can simply be deposited by means of a cylinder. glue applicator. Next, we approach a non-embossed fold and press it on the vertices to form bonds between the two folds along these vertices. Once assembled, cut the sheet, and wind it to make a finished product as is common.

According to this method, the binding of the folds is increased with respect to a two-level embossing method of the prior art because all the peaks of the pins are linked.

In the foregoing description, the sheet is double. It is within the scope of the invention to provide more than two folds. For example, the embossed fold may itself be double; the non-embossed fold also. Of course, the pattern shown is given only as an example. Other reasons are conceivable insofar as they repeat the teaching of the invention. In particular, a particular embodiment comprises a pattern consisting at least in part of second protuberances linear profile, for example drawing a flower.

The figure 5 represents another embodiment of the first zones which makes it possible to further improve the visible character of the embossed decoration.

A portion of the pins of the first zone is represented, in fact, pins on one of the alignments of this zone. According to this embodiment, wall-shaped reliefs 30 have been disposed between the adjacent pins 28 of an alignment. The pins 28 are frustoconical or truncated pyramid with a flat at the top 29. The top 31 of the walls 30 is at a lower level with respect to the vertices 29. The difference chosen is between 0.4 mm and 0.9 mm . In other words, it is 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. That is to say, same height, it is smaller than the diameter of the pins. The thickness of the walls is thus 10 to 50% lower than that of the pins, in particular to limit the additional embossing pressure resulting from the presence of low walls. Their slope is preferably the same as that of the pins.

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

Claims (9)

1. A multi-ply sheet for wiping comprising a first ply (12) and a second ply (14) incorporating a wet strength resin, each ply being made of tissue paper and exhibiting a specific surface weight between 12 and 35 g/m², the first ply comprising a first embossing pattern in first zones (16) including first protrusions (18) projecting from an inner surface of the first ply and having corresponding alveoles on an opposite side, said first protrusions having tops (19) of which at least more than one is connected to an opposite inner surface of the second ply (14), and wherein said first ply (12) further comprises a second embossing pattern (36) including second protrusions projecting (38) from the inner surface of the first ply (12), said second protrusions having a height (H2) which is less than a height (H1) of said first protrusions characterized by the fact that the density of said first protrusions is less than 20/cm², said second protrusions (38) are configured in second zones (36) and have a density greater than 30 protusions/cm², and at least more than one top (39) of said second protrusions situated in a plane also containing tops (19) of the first protrusions (18) and is connected to an inside surface of the second ply (14), third protrusions (30) wall shaped connect two first protuberances adjacent in line.
2. Multi-ply sheet as claimed in claim 1, wherein the first protrusions have a density of less than 12/cm².
3. Multi-ply sheet according to any of the preceding claims, wherein the second protrusions have a density more than 40/cm².
4. Sheet as claimed in claim 2 or 3, wherein the first zones and the second zones are adjacent.
5. Sheet as claimed in claim 1, further comprising third protrusions (30) configured as partitions linking two adjacent first protrusions.
6. Sheet according to any of the preceding claims, wherein the second ply (14) is made by a through-air-drying method.
7. An embossing cylinder engraved with a pattern corresponding to a pattern of the sheet according to any of the preceding claims, wherein the cylinder comprises first embossing tips (26) constituting arrays in first zones and second embossing tips (46) of a shallower height than said first embossing tips and exhibiting a greater density per unit area, tops of the first embossing tips and of the second embossing tips being situated in a same plane extending tangentially along generatrices of the cylinder.
8. A method for manufacturing a sheet using an assembly including the embossing cylinder of claim 8, wherein said method comprises embossing a first creped tissue paper ply (12) on said cylinder, applying an adhesive film onto the tops of the first protrusions and the second protrusions using an adhesive depositing cylinder, and linking said first ply to said second ply.
9. Manufacturing method as claimed in claim 8, wherein said second ply (14) is unembossed.

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