EP2170596A2

EP2170596A2 - Creped absorbent paper sheet, roll for embossing such a sheet and embossing process

Info

Publication number: EP2170596A2
Application number: EP08826682A
Authority: EP
Inventors: Pierre Graff
Original assignee: Georgia Pacific France SAS
Current assignee: Essity Operations France SAS
Priority date: 2007-07-13
Filing date: 2008-06-23
Publication date: 2010-04-07
Anticipated expiration: 2028-06-23
Also published as: HUE031819T2; FR2918598A1; US20100136291A1; ES2592685T3; WO2009016274A3; WO2009016274A2; US8216664B2; CA2692830A1; EP2170596B1; EA201000001A1; FR2918598B1; EA016514B1; WO2009016274A4

Abstract

The invention provides an embossed sheet composed of at least a first and a second ply of creped cellulose wadding having a basis weight between 12 and 30 g/m2 according to which the first ply (4) has a first embossed pattern composed of a series of first aligned protrusions (20) of frustoconical overall shape, the tops of which are oriented towards the inside of the sheet, the second ply (2) comprises a first and a second series of protrusions, the tops of which are oriented towards the inside of the sheet, the first series (5) having a height greater than that of the second series of protrusions (3). According to the invention, the protrusions (20) of the first ply (4) and the highest protrusions (5) of the second ply (2) are nested inside one another, and the lowest protrusions (3) of the second ply (2) are arranged between the protrusions of the first ply so as to create empty spaces (6) between the two plies that promote a rapid absorption of liquid. The invention furthermore relates to a pair of rolls and to the associated process for producing such embossed sheets.

Description

ABSORBENT PAPER SHEET CREPE,

CYLINDER FOR EMBOSSING SUCH SHEET AND METHOD OF EMBOSSING

The invention relates to a sheet of paper, in particular an absorbent paper sheet of creped cellulose wadding, comprising an embossing pattern.

The invention particularly relates to a sheet of paper, composed of at least a first and a second ply of creped cellulose wadding, intended for the field of wiping in household, domestic or industrial use, that is to say may be used as a paper towel, cloth etc.

In the field of sanitary or domestic papers such as toilet paper or paper towel, it is known to produce sheets of paper composed of several folds of absorbent paper, for example creped cellulose wadding of grammage between 12 and 30 g / m ² , provided with protuberances which are obtained by embossing.

Indeed the embossing gives bouffant to the sheet and it induces an improvement in the absorption of liquids, touch and softness. It has been sought to further increase the absorption capacity by creating multilayer sheets obtained by combining at least two layers, also called folds, each consisting of at least one of said embossed sheets. This gives a multilayer sheet (or multi-ply) which has mechanical characteristics such as tensile strength, as well as a specific absorption capacity.

Two modes of embossing and ply assembly are commonly implemented 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 protuberances that are generally substantially frustoconical or pyramid trunks. Then glue is deposited on the top of the protuberances of one of the folds, and the folds are arranged so that the faces having the protuberances come opposite, the protuberances of the one between the protuberances of the other . The folds are finally assembled so that the protuberances having been glued together fit between the protuberances of the other fold. Thus the two plies are linked by glue points between the tops of the protuberances of a fold and unembossed areas between the protuberances of the other fold. A structure is produced whose voids thus formed are suitable for ensuring the sheet an improved absorption. In addition, the outer faces have a smooth and soft feel due to the recessed areas formed by the back of the protuberances. This technique is illustrated for example by US-A-3,867,225. The second method of assembly is known in the field under the designation "tips / tips". It differs from the previous one by the relative disposition of the two folds. These, after they have been embossed separately, are brought one on the other so as to coincide the tops of the protuberances, or at least part of these vertices. The folds are linked together by the tops of the protuberances, tips against points. This technique is illustrated by US-A-3,414,459.

When considering the practical achievements of these structures, whether nested or spikes / points, the protuberances obtained during embossing are most often made to be distributed in a pattern in which the protuberances are generally aligned in a manner. or more directions, evenly. Such a pattern makes it possible to obtain a sheet which is homogeneous as regards its mechanical characteristics.

However, in order to improve user satisfaction, it is important to increase the flexibility, also called the "hand" of the sheet. The flexibility of the leaf can be defined as its ability to deform in a regular fashion when it is placed in a user's hand, his fingers being stretched in line with his palm and the user then folding his fingers. .

A sheet of paper that has a high flexibility will then deform and bend or arch so as to remain substantially parallel to the shape determined by the interior of the palm of the hand of the user. A sheet of paper that has low flexibility will bend along one or more lines, each portion of the sheet extending between two fold lines remaining substantially flat.

A sheet of paper with high flexibility is more enjoyable to use.

An embossed multilayer sheet is also known, as described in patent application EP 1 236 830 A1, in which at least one first ply comprises a first embossing pattern consisting of a first series of first protuberances, of generally frustoconical shape projecting from the surface. internal face of the first fold, which form in particular first alignments and whose vertices are connected to the inner face of the second fold vis-à-vis; the two plies each comprise a second embossing pattern consisting of a second series of second protuberances of generally frustoconical shape projecting on the inner face of the corresponding ply, and in that the vertices of the second protuberances of a pleat extend in vis-à-vis and near the vertices of the second protuberances of the other fold. The object of the invention is to propose a new embossed paper sheet design which notably makes it possible to improve the absorption of the sheet without diminishing its mechanical characteristics and which remains visually attractive. - AT -

For this purpose, the invention proposes an embossed sheet composed of at least a first and a second ply of creped cellulose wadding of weight of between 12 and 30 g / m ² according to which the first ply comprises a first embossing pattern. consisting of series of first aligned protuberances of generally frustoconical shape whose vertices are oriented towards the inside of the sheet, the second fold comprises a first and a second series of protuberances whose vertices are oriented towards the inside of the sheet of the first series and have a height greater than that of the second series of protuberances.

According to the invention, the protuberances of the first ply and the highest protuberances of the second ply are nested one inside the other, and the lower protuberances of the second ply are arranged between the protuberances of the first ply so as to create between the two folds of the empty spaces favoring rapid absorption of liquid. According to other features of the invention:

the protuberances of the first fold form series of circles;

preferably, said circles are concentric per set of at least 3, preferably 4 circles;

according to a preferred embodiment of the invention, the outermost circles of the sets have tangents;

- Advantageously, the first fold further comprises embossing protrusions arranged between the series of circles, preferably forming squares alignments;

according to the invention, the lower protuberances of the second ply have a density greater than 30 protuberances / cm ² ;

according to an advantageous embodiment of the invention, the highest protuberances of the second fold form in particular series of circles, preferably concentric, per set of at least 3;

- thus, the series of circles are juxtaposed and tangent, the lower protuberances are juxtaposed in said spaces between the series of circles;

- Preferably, some of the highest protuberances of the second ply are arranged among the lower protuberances of the second ply, nested vis-à-vis the first ply protuberances arranged between the series of concentric circles;

- Finally, the second fold further comprises a third series of protuberances in the general shape of a wall projecting on the inner face of the sheet, and each of which connects between them two protuberances of greater height which form concentric circles.

The invention also proposes a pair of engraved rolls for embossing an embossed sheet whose first roll comprises a first series of large pins of generally frustoconical shape and forming first juxtaposed sets of concentric circular alignments and second large pins arranged between said concentric assemblies, and whose second cylinder comprises a series of large generally frustoconical studs forming second juxtaposed sets of concentric circular alignments, and a series of small pins arranged between said second sets.

According to the invention the second cylinder further comprises third pins generally disposed in the center of the small pins, and to perform the embossing of the folds, the second cylinders are keyed so that the large pins of each cylinder are nested (nested) and the third pins of the second cylinder and the second large pins of the first cylinder are also nested. The invention finally proposes a method of manufacturing an embossed sheet by means of a pair of rolls as defined above.

Other features, details 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 among which:

- Figure 1 is a schematic section in the thickness of a sheet of cellulose wadding according to the prior art; - Figure 2 is a schematic section in the thickness of a multi-ply sheet according to one embodiment of the invention;

FIG. 3 is an illustrative flat view of the etching of an embossing cylinder used according to the invention;

FIG. 4 is a plan view of the etching of the other embossing roll used according to the invention; and

FIG. 5 gives comparative curves relating to the absorption of a sheet according to the prior art and of a sheet according to the invention.

FIG. 1 thus shows in section a sheet according to the prior art, as described in the European patent application EP 1 236 830 A1.

The sheet 10 of embossed paper comprises a first upper ply 12 and a second lower ply 14 of creped cellulose wadding, intended for all types of hygiene or household products. Cellulose wadding, weighing between 12 and

30 g / m ² , is preferably of the type obtained by conventional wet pressing, known as CWP.

More particularly, the paper sheet 10 shown in Figure 1 is for example intended to be incorporated in a roll of paper towels.

A first embossing pattern of each fold 12 and 14, of known general design, consists of first series of first protuberances 18 and 20, of generally frustoconical shape. protruding on the inner face of the fold 12, 14 corresponding thereby extending inwardly of the sheet 10.

The first protuberances 18 and 20 form in particular first alignments according to figures, in particular in closed loops which are here circles.

Here, according to FIG. 1, associated series of the first protuberances 18, 20 of the one and the other fold 12, 14 are nested, concentrically, between the associated series of the protuberances 20, 18 of the other 14, 12 of the two folds. The first series of first protuberances 18 and 20 may be aligned in two main directions so as to define a grid. The two main directions here are perpendicular to each other, and are inclined at 45 degrees relative to the longitudinal directions L and transverse T of the sheet 10 as will be explained in more detail below.

According to a known technique, the first protuberances 18, 20 constituting the elements of the first pattern are obtained by embossing the first 12 and the second ply 14 of the sheet 10 respectively, by means of a pair of rolls as is common.

Thus pins corresponding to the protuberances that are desired on the first 12 and the second ply 14 of the sheet 10 are formed in relief on the convex cylindrical outer face of the associated cylinder. For the realization of the series of first protuberances

18 on the first fold 12 of the sheet 10, the embossing roll comprises on its convex cylindrical face a first homologous series of embossed pins of generally frustoconical relief shape, which are distributed in concentric circles according to the first alignments of the first protuberances 18 , so as to realize the corresponding part of the first pattern of the first fold 12.

Similarly, the series of protuberances 20 on the second fold 14 of the sheet 10 is made by another cylinder embossing whose punctured relief pins may be, are distributed in concentric circles.

In accordance with the teachings of this prior art, the first ply 12 comprises a second embossing pattern consisting of second series of second protuberances 38 of generally frustoconical shape projecting on the internal face of the first ply.

12, thus extending inwardly of the sheet 10.

The second protuberances 38 are made similarly to the first protuberances 18 and 20, in particular by a second series of second frustoconical shaped pegs which extend to the convex surface of the second embossing roll.

When arranged in front of the protuberances 20 of the second ply 14, the protuberances 38 tend to reduce the height of the protuberances 20: such protuberances are referenced 20 'in FIG.

The protuberances 18 of the first ply 12 and the protuberances 20 of the second ply 14 are nested one inside the other. The present invention, including an embodiment of a sheet cut according to its thickness, is shown in FIG. 2 and has the following characteristics:

The first fold 4 comprises a first series of protuberances 20 of generally frustoconical shape whose vertices are oriented towards the inside of the fold 1 and which can be arranged as illustrated in FIG. 3, namely by forming alignments.

By way of example, the protuberances 20 may have a height of approximately 0.8 mm and an area at the apex of approximately 2 mm ² with an average density of the order of 4 / cm ² . In the particular case shown here, between the series of circles there are about eight first protuberances 20 grouped on an area of about 1 cm ² . The second ply 2 comprises a first and a second series of protuberances respectively marked 3 and 5, whose vertices are all oriented towards the inside of the sheet, the first series of protuberances 5 having a height greater than that of the second series 3 .

Illustratively, the first protuberances 3 with a rounded top surface have a height of about

0.4 mm and a density of about 30 / cm ² . The second protuberances 5 have a geometry and a density closer to those of the protuberances 20 of the first ply 4.

According to an interesting aspect of the invention, the first protuberances 5 (the highest) of the second ply 2 are positioned nested vis-à-vis the protuberances

20 of the first fold 4. A particularly favorable disposition will be described in connection with FIGS. 3 and 4.

In addition, the second protuberances (the lower ones)

3 of the second ply 2 are placed between the protuberances 20 of the first ply, so as to form voids or pockets 6 between the folds that promote the rapidity of absorption of liquids as evidenced in particular the curve of Figure 5.

Such an arrangement of the protuberances improves the maintenance of the "small" protuberances 3 of the second ply 2 which are here closely held between the larger protuberances 5. The structure thus formed collapses less rapidly in the wet state, which accelerates the passage liquid inside the structure, thus accelerating the rate of absorption of the sheet.

Figures 3 and 4 illustrate a particularly favorable arrangement of the pins of each of the cylinders used to form each of the outer plies of the embossed sheet according to the invention.

According to FIG. 3 which illustrates the embossing pattern of the first ply 4 seen from above, spikes 200 are mainly aligned in circles and more precisely concentric circles. C1, C2, C3, C4, here sets of four concentric circles.

The sets of circles being generally juxtaposed, the outermost circles C4 of said sets tangent in certain places.

Moreover, pins 201 of the same type as those (200) forming circles are provided between the sets of circles, and preferentially form squares.

FIG. 4 shows the embossing pattern of the second ply 2, comprising in particular a set of large studs 50 which form the highest protuberances 5 on the second ply, and a set of small studs 30 which create the "small" protuberances 3 of the second fold.

Large studs 50 form here sets of three concentric circles juxtaposed.

The small spikes 30 are arranged in the surfaces between the sets of concentric circles; they are inscribed in kinds of squares whose center includes a large pin 50.

Figure 2 is a section of a sheet obtained by the cylinders of Figures 3 and 4, according to section AA.

To simplify to the extreme, it can be considered that Figures 3 and 4 show the embossing patterns respectively of the first and second fold.

Thus, the concentric circles C1, C2, C3, C4 correspond to the sets of circles C'1, C'2, C'3, C'4, formed by the protuberances 20 of the first fold 4.

Thus, according to the invention, the patterns of each of the folds 2, 4 are complementary, and adapted to each other so as to promote rapid absorption of liquid inside the folds, as clearly shown by the curves of Figure 5.

The two curves of FIG. 5 are given by absorption A in g / g of a sheet as a function of time t in s.

According to the absorption tests, the sample is laid flat on a porous sintered glass plate. whose pore size was determined at 40 μm. A plate carrying weights is placed on the sample to keep the sample flat. The sample is thus slightly compressed. The porous plate rests on a plate which comprises in its center an orifice of diameter equal to 3 mm into which a flexible tube opens out from below which in this way puts the volume of the porous plate in communication with a liquid reservoir whose level can be adjusted in height compared to that of the porous plate. The tank itself is placed on a scale. This means makes it possible to know the quantity of liquid which has passed into the sample when the reservoir has been raised relative to the porous plate.

The liquid is water with 9 g / l of sodium chloride.

The procedure involves impregnating the sample through the porous plate by lowering the level of the sample relative to the reservoir. The amount of liquid absorbed is measured every ten seconds simply by measuring the loss of water in the tank. We proceed with different weights. Measurements of absorption capacity can also be carried out without pressure.

In FIG. 5, the curve I relates to the invention and the curve A to the prior art, more exactly a sheet as shown in cross section in FIG.

It can be seen that the curve I has a slope that is larger than the curve A, which means that the sheet according to the invention has a higher absorption rate than a sheet according to the prior art.

This characteristic is very important, even determining for buyers, users of this type of product.

Furthermore, the protuberances 20 of the first ply 4 can be interconnected by relief elements as disclosed for example in the application EP 1 101 866 A1. This characteristic makes it possible to obtain a more pronounced embossing pattern.

Claims

1. Embossed sheet composed of at least a first and a second ply of creped cellulose wadding of a weight of between 12 and 30 g / m ² in which the first ply (4) has a first embossing pattern consisting of series of first protuberances (20) aligned, frustoconical general shape whose vertices are oriented towards the inside of the sheet, the second fold (2) comprises a first and a second series of protuberances whose vertices are oriented towards the inside of the sheet, the first series (5) having a height greater than that of the second series of protuberances (3), characterized in that the protuberances (20) of the first ply (4) and the highest protuberances (5) of the second ply ( 2) are nested one inside the other, and in that the protuberances (3) of the lower height of the second ply (2) are arranged between the protuberances of the first ply so as to create spaces between the two plies. ides (6) favoring rapid absorption of liquid.

2. Sheet according to claim 1, characterized in that the protuberances of the first fold (4) form a series of circles (C ¹ I, C'2, C'3, C'4).

3. Sheet according to claim 2, characterized in that said circles are concentric per set of at least 3, preferably 4 circles.

4. Sheet according to any one of claims 2 or 3, characterized in that the outermost circles (C'4) sets have tangents.

5. Sheet according to any one of claims 2 to 4, characterized in that the first ply (4) further comprises embossing protuberances (20) disposed between the series of circles, preferably forming squared alignments.

6. Sheet according to any one of the preceding ications, characterized in that the protuberances (3) of the lower second ply (2) have a density greater than 30 protuberances / cm ² .

7. Sheet according to any one of the preceding claims, characterized in that the protuberances (5) the highest of the second fold (2) form in particular series of circles, preferably concentric, for a set of at least 3.

8. Sheet according to claim 7, characterized in that the series of circles are juxtaposed and tangent, the protuberances (3) the least high of the second fold (2) being disposed in said spaces between the series of circles.

9. Sheet according to any one of claims 3 to 8, characterized in that some of the highest protuberances (5) of the second ply are arranged among the protuberances (3) of the lower second ply, nested vis-à- screw protrusions (20) of the first ply and arranged between the series of concentric circles.

10. Sheet according to any one of claims 3 to

9, characterized in that the second fold (2) further comprises a third series of protuberances generally shaped wall projecting on the inner face of the sheet, and each of which connects two protuberances (20) of high height which form concentric circles.

1 1. Pair of engraved rolls for embossing a multiply sheet of cellulose wadding according to any one of the preceding claims, the first roll comprising a first series of large pins of generally frustoconical shape and forming first juxtaposed sets of concentric circular alignments. and second large pins disposed between said sets of concentric circles, and whose second cylinder comprises a series of large pins of generally frustoconical shape forming second sets juxtaposed concentric circular alignments, and a series of small pins arranged between said second sets, characterized in that the second cylinder further comprises third pins generally arranged in the center of the small pins, and in that to perform the embossing of the pleats , the second cylinders are set so that the large pins of each cylinder are nested and in that the third pins of the second cylinder and the second large pins of the first cylinder are also nested.

12. Process for embossing sheets of cellulose fiber wadding by means of a pair of rolls according to claim 11.