EP1472411B1 - Absorbent embossed paper sheet, embossing cylinder, and method for the production thereof - Google Patents

Abstract

Absorbent paper, from a cellulose pulp, has at least one embossed zone (A1,A2) with projections on one surface matching the honeycomb recesses on the other surface. The honeycomb has a polygonal shape, and there is at least one zone (B) which is not embossed. The honeycombs (101,102) are deployed along at least one alignment. Absorbent paper, from a cellulose pulp, has at least one embossed zone (A1,A2) with projections on one surface matching the honeycomb recesses on the other surface. The honeycomb has a polygonal shape, and there is at least one zone (B) which is not embossed. The honeycombs (101,102) are deployed along at least one alignment. The sides of the facing honeycombs define a bridge with straight edges in a longer length than the width. They span preferably two non-embossed zones separated by an embossed zone.

Description

The invention relates to the field of absorbent papers for sanitary or domestic use. It includes single use products such as napkins, tablecloths, paper towels or toilet paper, made of cellulose wadding.

Cellulose wadding is an absorbent paper of grammage preferably between 15 and 35 g / m ² , which can be manufactured so as to have a certain elongation capacity. A common technique is to apply and paste the still wet sheet on a drying cylinder, and then detach it by means of a doctor blade to create crepe corrugations. It can then be reeled pending processing into a finished product. This technique presented in a summary way is called conventional. It is designated in the domain by (CWP).

Another technique is to dry the sheet after dewatering without exerting pressure, in part at least 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. Thanks to this first drying, the sheet can be pressed onto the cylinder without destroying its structure. It retains part of its volume. This cylinder also allows its creping. The first drying is carried out without pressure by blowing hot air through the sheet after it has drained. This technique, which is designated in the field under the acronym (TAD), makes it possible to obtain a thicker sheet, and a larger volume mass than the conventional technique. It is characterized by a more open structure and greater permeability.

Then, by the known technique of embossing, it can improve or at least change one or the other of its characteristics, such as softness, flexibility, absorption, thickness or appearance . The mode of transformation is then a function of the use for which it is intended. The embossing pattern is most commonly constituted protrusions or bosses in the form of pyramids round section, oval or square, regularly distributed on the surface of the sheet. It is observed that a protuberance on one side of the sheet corresponds to a cavity or cell on the other side. For embossing the cellulose wadding, a rigid roll is generally used which has on the surface spikes, obtained by etching or by machining, of suitable shape, size and density. The sheet is applied to the roll and is pressed by means of another roll having a deformable coating, eg rubber. She thus marries the relief. For the same reason, we obtain a deformation more or less important according to the parameters we have chosen, such as the flexibility of the rubber, for its ability to deform and conform to the relief of the etching, and the embossing pressure.

The Applicant markets a paper towel product whose protuberances are distributed in concentric circles. The paper towel is composed of two plies of cellulose wadding which have been separately embossed and assembled so that the protuberances are in a position known as "nested". The protuberances of one fold face the other fold and are placed between the protuberances of the latter. The two folds are nested in this way one into the other, and provide pockets of air, improving absorption. The sheet has cavities on both sides visible. By ignoring the state of the surface at the microscopic level, but considering its appearance with the naked eye, the sheet has a relief with two levels. A first level is defined by the bottom of the cells (the bottom of the cells is in a single plane if the embossing pins were all at the same level). The second level corresponds to that of the part of the sheet which is not embossed.

A variant of this product is described in the application EP 1 101 867-A1 .

To improve the absorption capacity of a paper towel product, it is possible to work on the sheet at the time of its manufacture, that is to say at the level of the paper machine, on its formation, its mode of drying. or the additives that are incorporated for example.

We also know the US Patent 6,173,496 which shows a cylinder equipped with an external embossing liner whose relief is formed by laser. This technique makes it possible to form very precise profile pins.

The document is still known FR 2,773,564 which shows in particular a sheet of absorbent paper, one of whose faces has an embossing consisting of two types of protuberances of different frustoconical shape and height.

The prior art also includes the US Patent 3,867,225 which discloses a process of embossing and association of nested folds, each of the plies having embossing in a regular mesh network.

The embossing mode of the sheet is also an important parameter on which one can act for this purpose.

The Applicant has set itself the objective of creating an embossing mode that improves the absorption properties of paper made of cellulose wadding.

The Applicant has also set itself the goal of creating an embossing mode producing an attractive and attractive visual effect at a time.

• les alvéoles sont disposés selon au moins un alignement
• les côtés en vis à vis de deux alvéoles adjacentes définissent un pont à bords rectilignes ou sensiblement rectilignes, de longueur L supérieure à sa plus grande largeur D, un ou plusieurs ponts reliés les uns aux autres déterminant un chemin entre préférentiellement deux secondes zones non gaufrées séparées par au moins une première zone gaufrée.

According to the invention, this objective is achieved with a sheet of cellulose wadding comprising at least a first embossed zone having protuberances on one face corresponding to cells on the other face, the cells having a base of substantially polygonal shape, and at least a second non-embossed zone, characterized in that:

• the cells are arranged in at least one alignment
• the sides opposite two adjacent cells define a bridge with straight or substantially rectilinear edges, of length L greater than its greatest width D, one or more bridges connected to each other determining a path between preferably two second non-embossed zones separated by at least one first embossed zone.

The term "bridge" is the part that lies between two adjacent cells. In a preferred arrangement of the invention, the bridges have straight edges. The edges of the bridges can be curved without departing from the scope of the invention. The edges are preferably parallel but they can also be slightly inclined relative to each other, as will be explained in more detail below.

The width D of the bridge is defined by the distance separating the edges of two adjacent cells. When the edges are not parallel, consider the average distance along the bridge.

In this case, the width may vary in a plane parallel to the surface of the sheet. The width of the bridge may also vary in a plane perpendicular to the surface of the sheet, between the surface of the sheet at the top of the cell and the bottom of the cell. The greatest width is determined both in the plane parallel to the surface of the sheet and in the plane perpendicular to the surface of the sheet.

This width can be very small when the bridges are not planar but are curved transversely, which is the most common.

The structure according to the invention is new compared to that which can be found in the state of the art. Surprisingly, it is found that the bridges stand out visually and create a pattern distinct from the pattern from the cells, while in the patterns of the prior art, the apparent pattern was exclusively that of the cells themselves. The embossed pattern of the invention evokes a textile product with an embroidered ornament. Indeed, the bridge with its straight edges, evokes the gathering of several fibers or son of a woven product or simply textile.

In particular, the sheet of the invention has at least three distinct levels of relief which highlight the pattern defined by the cell alignments.

A first level corresponds to the bottom of the cells, a second level corresponds to the non-embossed zone and a third level to the surface of the bridges.

This solution differs from the prior art where the cells, respectively protuberances, forming alignments, have exclusively an oval or round base. Admittedly, in this case too, it is found that between two adjacent cells, the level of the sheet is lower than that of the second zone, but this part has a rounded hollow shape which can not be likened to a bridge. The invention makes it possible to create fractures of level, sources of contrast. The edges formed by these surroundings, rectilinear or substantially rectilinear, also contribute to enhancing the contrast effect.

Preferably, the sheet of cellulose wadding is such that the L / D ratio is greater than 1, preferably greater than 1.5, and especially greater than 3.

The sheet may further be characterized in that the distance between two adjacent first zones (A ₁ , A ₂ ) separated by a non-embossed zone (B) is between one and three times, preferably between one and two times the width of said first zones (A ₁ , A ₂ ).

An embossed paper whose pattern includes square cells is already known. For example, the patent US 4,293,990 discloses an embossed paper sheet for wiping. Embossing is composed of flat portions separated by valleys. The distance (width and length) between the cells is always the same in this case. Bridges do not exist. In addition, although the blanks of the valleys are rectilinear, there is not in this part pattern corresponding to the second zones of the invention, therefore a fortiori three zones at different levels.

In particular, according to one embodiment, the section of the cells can be triangular with the advantage of being able to arrange them in alignments forming portions of curves without losing the property of the bridges.

Advantageously, the slope (α) of at least one of the walls of the cells measured relative to the vertical to the plane of the sheet is between 20 ° and 45 °.

In addition, the linear density of the cells is between 2 and 20 per cm; their surface density is between 4 and 50 per cm ² , preferably between 4 and 20 per cm ² .

The sheet according to the invention may be associated with a second sheet of cellulose wadding to form a double-thickness sheet.

Thus, the second sheet may be a sheet of cellulose wadding, of the throughdried drying type.

According to an interesting feature of the invention, the alignments are concentric.

The embossing roll of a sheet comprises polygonal base-shaped pegs forming alignments in which two adjacent pegs are arranged so that two respective sides of the polygonal base of said two pegs are disposed opposite one of the other and are substantially parallel to each other.

Preferably, the pins are triangular based.

The cylinder according to the invention is characterized in particular by the fact that the angle (β) defined by said two sides of the substantially parallel pins is between 0 and 35 °.

Preferably, each of the faces of the pins forms an angle (α) of between 20 and 45 ° with a plane perpendicular to a generatrix of the cylinder defined at the level of said face.

The process for making a sheet, in which a sheet is pressed onto an embossed embossing cylinder, is, of course, part of the present invention.

The invention also relates to the process for obtaining in particular the product defined above. Surprisingly, it is found that it is possible to produce a pattern comprising cell alignments forming such a three-level relief, by embossing the cellulose wadding on a cylinder engraved with a single level of etching depth. This avoids the complex and expensive engraving of the cylinders.

• la figure 1 représente schématiquement une installation de gaufrage ;
• la figure 2 représente une partie d'un exemple de motif de gaufrage du cylindre conforme à l'invention ;
• la figure 2 A est une partie agrandie de la figure 2 ;
• la figure 3 est une représentation en perspective d'un picot du motif de la figure 2 ;
• la figure 4 représente une vue partielle photographique, en perspective, d'un produit gaufré selon le motif de la figure 2 ;
• la figure 5 représente une vue photographique, en perspective, d'un produit gaufré de l'art antérieur ;
• la figure 6 représente une vue photographique, en perspective, d'un produit gaufré selon un autre mode de réalisation de l' invention ;
• la figure 7 est un dessin d'un motif réalisé sur un cylindre selon encore un autre mode de réalisation de l'invention ;
• la figure 8 est un dessin d'un autre motif de cylindre selon l'invention ; et
• la figure 9 montre un graphique sur lequel on a reporté des vitesses d'absorption mesurées sur un produit de l'invention et sur un produit de l'art antérieur.

Other advantages and characteristics will emerge on reading the following description of a non-limiting embodiment of the invention, accompanied by drawings in which:

• the figure 1 schematically represents an embossing installation;
• the figure 2 represents a part of an exemplary embossing pattern of the cylinder according to the invention;
• the figure 2 A is an enlarged part of the figure 2 ;
• the figure 3 is a perspective representation of a picot of the motive of the figure 2 ;
• the figure 4 represents a photographic partial view, in perspective, of an embossed product according to the pattern of the figure 2 ;
• the figure 5 represents a photographic view, in perspective, of an embossed product of the prior art;
• the figure 6 is a photographic perspective view of an embossed product according to another embodiment of the invention;
• the figure 7 is a drawing of a pattern made on a cylinder according to yet another embodiment of the invention;
• the figure 8 is a drawing of another cylinder pattern according to the invention; and
• the figure 9 shows a graph on which the absorption rates measured on a product of the invention and on a product of the prior art have been reported.

The figure 1 gives a schematic representation of an element of an industrial unit for embossing folds of cellulose wadding and transforming them into a sheet of product for sanitary or domestic use. This element comprises a embossing cylinder 1, usually of metal, with a surface engraved according to the desired embossing pattern, and a cylinder 2 with a rubber coating or any other material liable to deform. The two cylinders have parallel axes of rotation and roll one over the other. The sheet 3 of cellulose wadding is guided between the two rolls at the same time as driving means rotate the two rolls in opposite directions with respect to each other, and pushing means bring the two rolls closer together. from one another under a determined effort. By deforming in the contact zone, the rubber comes to marry the relief of the etching of the first cylinder 1. The sheet 3 placed between the two cylinders undergoes the same deformation. The etching consists of pins 10, which can be seen on a scale enlarged with respect to the diameter of the cylinder, distributed according to the chosen pattern. The width of the contact zone between the two cylinders, which forms a rectangular band, is designated by the term imprint and is expressed in centimeters.

On the figure 2 a top view of a portion of the pattern engraved on the cylinder 1 and in accordance with one embodiment of the invention is shown.

This pattern may preferentially consist of triangular-based pins 10. The pins are placed in alignments A ' ₁ , A' ₂ which in this example are essentially circular arcs and constitute on the sheet of the first embossed areas A ₁ , A ₂ . Between two alignments A ' ₁ , A' ₂ , there is a second zone B 'which has no pins 10.

The pins have, preferably, a pyramidal shape with a triangular base as seen more precisely on the figure 3 . Their summit is not in peak and is truncated. It forms a flat surface. The height (H) of the spikes is measured from their top to the bottom of the engraving and varies from 0.1 to 2.5 mm approximately. It depends on the intended application.

Preferably, a lower height is chosen for products that aim for a soft touch such as toilet paper or napkins. On the other hand, for a product whose absorption capacity of the cellulose wadding is best exploited, a higher height H is chosen.

The faces of the adjacent pyramid-shaped pins may have different or identical slopes. Their base is polygonal or substantially polygonal and two adjacent pins are arranged so that their bases have two straight sides parallel or substantially parallel as defined below.

The angle (α) (as visible on the figure 3 ) slopes of the pins are preferably between 20 ° and 45 °, measured relative to the vertical of the base of the pin and on the cylinder is perpendicular to the axis of the latter.

Finally although the pin 10 of the figure 3 for example has sharp edges, it is also within the scope of the invention to provide pyramidal pins whose edges are rounded. Other forms of polygonal-based pins can be considered as trapezes, rhombuses ...

According to the embodiment shown, the pins on the same alignment are arranged such that the sums 101, 102 of any two adjacent pins may be slightly offset from the general direction of the alignment, as illustrated in particular on the figure 2 at the alignment areas A ' ₁ or A' ₂ .

Considering the space between two pins, it is observed that it is defined by the sides 101m and 102m of their triangular base. Preferably, the two adjacent sides 101m, 102m of two pins between them form an angle (β) which in accordance with a feature of the invention is between 0 ° and 35 °: cf. Figure 2A .

Here, in the case of triangular base pins arranged in an arc, two adjacent pins are oriented in an opposite direction. In other words, a first and a third pin of the alignment are oriented towards the center of the circle defined by the alignment whereas the second pin disposed between the first and the third is oriented towards the outside of the circle defined by alignment and is interposed between the first and second pins.

The angle (β) formed by the two sides is preferably less than 35 ° so that it can form a bridge on the embossed product. The distance between two successive pins is quite small. It is such that, on the embossed product, the length L of the bridge portion is in a ratio with its width D greater than 1; but the result is more marked with a higher ratio, 1.5 for example, 2 or 3 in particular.

By the width D, it is necessary to understand the distance between two sides of two adjacent cells. This width can be taken at any level between the base and the top of the cell; the width D thus varies according to the angle (α).

The length L of a bridge substantially corresponds to the length of two adjacent sides 101m, 102m of two adjacent pins 10.

The embodiment of the patterns of the invention is of particular interest when the plies are arranged in nested mode and the first areas separated from each other by substantially unaffected second zones. The widths are preferably equal in this arrangement because there is then a clear difference in level between the first and second zones.

Without departing from the scope of the invention, two or more alignments may be adjacent, i.e., close to one another, to form an embossed area which itself is surrounded by non-embossed areas. . Bridges are thus created, between the cells, different alignments, which allow communication from a non-embossed zone to another non-embossed zone disposed on the other side of the embossed zone.

The figure 7 illustrates an exemplary embodiment of this type. Indeed, one can see in this figure an engraved cylinder portion on which appear in particular corrugated alignments A ' ₃ of pins. With this type of cylinder, it is possible to produce sheets comprising alignments cells such as two interconnected bridges determine a path between two non-embossed areas.

Alignment alignments include a set of at least two adjacent cells that delimit at least one bridge.

The alignments may consist of sets of cells with a polygonal base, juxtaposed with other types of cells corresponding for example to conventional protuberances having a circular base. This variant is not illustrated.

On the figure 4 , there is shown a partial view, in perspective, of a product obtained by embossing on a cylinder having the pattern of the figure 2 .

We recognize the cells 101 'and 102' arranged in alignments A ₁ , A ₂ here in the form of circles. The cells are separated by portions forming bridges P in zigzag according to the pattern of the embodiment shown. It is observed that the bridges P are curved and do not have a flat upper surface. This comes from the small spacing between the protuberances placed along the alignments. When embossing, the paper does not touch the background of the engraving. The rows of protuberances are separated by non-embossed B areas. It is observed that the bridges are at a slightly lower level than that of the zones B. This relief accentuates the contrast between the embossed zones A ₁ , A ₂ and non-embossed zones B.

Thus (cf. figures 4 and 6 ), we observe the formation of very visible bridges. Each bridge P has a length L and a width D. Additional patterns thus created give a new effect to the product.

Without departing from the scope of the invention, the pattern may be as schematized on the figure 8 corresponding to the surface of a cylinder, that is to say with not only alignments A ' ₄ of polygonal base pins defining first circles, but also with other alignments A "formed of conventional circular section pins which define concentric circles at the first circles, other elements of pattern C 'formed by a polygonal-based (here triangular) pin alignment can also be envisaged, in view of the relative arrangement of the pins forming the latter alignment, the adjacent sides two spikes form here an angle β (as illustrated on the Figure 2A ). As a result, on the embossed product, the bridge thus formed does not have a constant width. In this type of pattern, the width the non-embossed area may be the same or less than the width of the cell alignments.

A first sheet may be embossed in a pattern of polygonal shaped cell alignment. This first sheet may be associated with a second embossed sheet following the same type of pattern so that the two sheets are assembled in a known position under the name of "nested".

According to other embodiments of the invention, a first sheet may be embossed according to the principle of the variants represented in FIGS. figures 4 (sheet), 7 or 8 (cylinder). This first sheet may be associated with a second embossed sheet or according to a pattern of the state of the art, that is to say without bridges, for example of the type illustrated by the figure 5 or in a pattern combining bridge alignments and bridges-free alignments, as illustrated for example by figure 8 .

According to the invention, not only a visual contrast effect is obtained but a technical improvement of the product has been demonstrated concerning the absorption properties.

It has been surprisingly observed that the products according to the invention have significantly improved absorption properties.

This effect is very advantageous especially for the use of the sheet as a paper towel.

Thus, it has been possible to demonstrate by different tests that not only is the absorption capacity increased, the diffusion of the liquid is thus improved both in the transverse direction and in the operating direction and finally, the rate of absorption of the liquids by the sheet according to the invention is superior to the products of the prior art.

• Référence L1, un papier essuie-tout gaufré, composé de deux plis de grammage 23 g/m² chacun disposés en position nested l'un par rapport à l'autre commercialisé par la Demanderesse. Le produit est représenté en photographie sur la figure 5. Les alvéoles PA₁ sont circulaires et disposés en cercles concentriques laissant entre eux des zones non gaufrées PA₂.
  • Diamètre des alvéoles : 1 mm, mesuré au fond.
  • Nombre d'alvéoles par cm² : 7 environ.
  • Nombre d'alvéoles le long d'un alignement : environ 4 par cm linéaire.
• Référence M1, même papier de base que celui de la référence L1, mais gaufré suivant des alignements d'alvéoles de section triangulaire tel qu'illustré par la figure 4 et composé également de deux plis ainsi gaufrés.
  Les alvéoles ont une base triangulaire équilatérale dont les côtés ont 1 mm de long. Le produit est celui représenté en photographie à la figure 4.
  Les alvéoles sont disposés en cercles concentriques selon le motif de la figure 2. La densité du motif est la même que pour la référence L1. On trouve le même nombre par unité de surface et le même nombre par unité de longueur, le long des alignements.
• Référence N1, on fabrique une feuille composée de deux plis à partir du même papier et avec un motif unitaire composé des mêmes alvéoles que dans le cas M1, mais la disposition des alignements n'est plus en cercles. Les cercles sont remplacés par des hexagones. Le produit est représenté sur la figure 6 et donne un effet de motif différent.

Le tableau ci-dessous rapporte les valeurs de l'absorption mesurée successivement pour des pressions croissantes de 5, 55 et 105 g/cm² puis revenant à une pression de 5 g/cm². On note que la valeur de 5 g/cm² correspond, estime-t-on, à la pression à laquelle est soumis le papier essuie-tout en utilisation normale.
Les caractéristiques du papier tissue, de base avant gaufrage, papier 1 ainsi que celles des papiers en ouate de cellulose L1, M1, N1 sont rassemblée-, sur le tableau ci-dessous. Gram - age g/m² Ep. mm Résistance à la traction sèche N/m/2plis Résistance à la traction humide N/m/2 plis Absorption (g/g) sous différentes pressions (glcm²) SM ST SM ST 5 55 105 5 Papier 1 46 0,18 1151 627 307 174 3,8 3,2 2,9 3,4 L1 6,2 3,2 2,7 3,8 M1 6,7 3,4 2,8 4,0 N1 6,6 3,4 2,8 4,0
Le grammage est exprimé en g/m². L'épaisseur est mesurée sur une pile de 12 feuilles et ramenée à une feuille. La résistance à la traction est mesurée sur des éprouvettes, découpées dans une feuille à deux plis, de 5 cm de large, et est rapportée en N/m. L'absorption est mesurée en gramme de liquide absorbé par gramme de papier (g/g).
On observe pour les références M1 et N1 de l'invention une amélioration de l'absorption par rapport à un motif constitué d'alvéoles à base circulaire (réf. L1). L'amélioration est plus marquée à faible charge soit 5 g/cm². Cela s'explique par le fait que l'effet du motif diminue avec l'augmentation de la pression d'appui sur la feuille d'essuie-tout. On constate cette même différence entre les feuilles gaufrées et le même papier non gaufré.
2) On a procédé à un deuxième test, dit de diffusion, destiné à évaluer la capacité de mouillage d'un échantillon par diffusion de liquide. En général, le liquide est de l'eau salée à 0,9 %. Les échantillons de forme rectangulaire (par exemple 12 cm x 2,5 cm) sont placés sur un plateau inclinable et des électrodes (espacées d' 1 cm) sont disposées sur chaque échantillon dont une extrémité est plongée dans l'eau. L'ensemble des électrodes est relié à un ordinateur qui enregistre notamment le temps à chaque cm mouillé. Un programme met en forme ces données, ce qui permet d'obtenir le tableau suivant : la première ligne de chiffres (de 1 à 9) correspond au nombre de cm mouillés. Dans ce tableau, L correspond à un produit connu ; M et N correspondent respectivement aux produits M1 et N1 du test d'absorption. Temps de diffusion sens SM (s) Temps de diffusion sens ST (s) 1 2 3 4 5 6 8 9 1 2 3 4 5 6 8 9 L 0,8 3,3 7,7 16 25 36 64 86 0,7 2,5 5 7,7 12 16 28 36 M 1,1 3,9 6,9 15 21 28 52 66 1 2,9 5,5 10 14 19 34 43 N 1,2 3,7 8,8 13 21 29 56 68 0,9 2,6 4,6 8 14 20 33 42
On observe que pour les produits M et N, comportant le motif de l'invention, les temps de diffusion dans le sens marche et dans le sens travers sont plus proches l'un de l'autre que ceux du produit L. Cela signifie que le liquide diffuse plus efficacement dans toutes les directions que sur un produit L présentant un motif de gaufrage de l'art antérieur.
3) On a procédé à un test de vitesse d'absorption visant à vérifier dans quelle mesure la géométrie des alvéoles et leur alignement permettant la création de ponts intervenaient dans le processus d'absorption.Tests have been carried out to show that products in accordance with the invention have an improved absorption capacity compared with products of the prior art.
1) Measurement test of the absorption capacity and the rate of absorption under pressure.
For this test, the sample is laid flat on a porous sintered glass plate whose pore size has been determined at 40 μm. A tray carrying weights is placed on the sample. The sample is thus slightly compressed. The porous plate rests on a plate which has an orifice in its center into which a flexible tube opens from below. The flexible tube thus puts the volume of the plate porous communication with a liquid reservoir whose level can be adjusted in height relative 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 usually water at 9 g / l 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 simply by measuring the loss of water in the tank. We proceed with different weights.
Absorption capacity measurements can also be performed without pressure.
The samples were as follows:

• Reference L1, an embossed paper towel, consisting of two plies of weight 23 g / m ² each arranged nested position relative to each other marketed by the Applicant. The product is represented in a photograph on the figure 5 . The cells PA ₁ are circular and arranged in concentric circles leaving between them non-embossed areas PA ₂ .
  • Diameter of the cells: 1 mm, measured at the bottom.
  • Number of cells per cm ² : 7 approx.
  • Number of cells along an alignment: about 4 per linear cm.
• Reference M1, same base paper as that of the reference L1, but embossed according to triangular section alveolar alignments as illustrated by the figure 4 and also composed of two folds thus embossed.
  The cells have an equilateral triangular base whose sides are 1 mm long. The product is the one represented in photograph at figure 4 .
  The cells are arranged in concentric circles according to the pattern of the figure 2 . The density of the pattern is the same as for the reference L1. The same number per unit area and the same number per unit length are found along the alignments.
• Reference N1, a sheet made of two plies is made from the same paper and with a unitary pattern composed of the same cells as in the case M1, but the arrangement of the alignments is no longer in circles. Circles are replaced by hexagons. The product is represented on the figure 6 and gives a different pattern effect.

The table below reports the values of the measured absorption successively for increasing pressures of 5, 55 and 105 g / cm ² then returning to a pressure of 5 g / cm ² . It is noted that the value of 5 g / cm ² corresponds, it is estimated, to the pressure to which the paper towel is subjected in normal use.
The characteristics of tissue paper, base before embossing, paper 1 as well as those of cellulose wadding paper L1, M1, N1 are shown in the table below. Gram - age g / m ² Ep. Mm Tensile strength dry N / m / 2plis Tensile strength wet N / m / 2 ply Absorption (g / g) under different pressures (gcm ² ) SM ST SM ST 5 55 105 5 Paper 1 46 0.18 1151 627 307 174 3.8 3.2 2.9 3.4 L1 6.2 3.2 2.7 3.8 M1 6.7 3.4 2.8 4.0 N1 6.6 3.4 2.8 4.0
The grammage is expressed in g / m ² . The thickness is measured on a stack of 12 leaves and brought back to a leaf. The tensile strength is measured on specimens, cut from a two-ply sheet, 5 cm wide, and reported in N / m. Absorption is measured in grams of absorbed liquid per gram of paper (g / g).
For the M1 and N1 references of the invention, an improvement in absorption is observed with respect to a circular base pattern (item L1). The improvement is more marked at low load or 5 g / cm ² . This is because the effect of the pattern decreases with increasing pressure on the paper towel. This same difference is observed between the embossed sheets and the same non-embossed paper.
2) A second diffusion test was conducted to evaluate the wetting capacity of a sample by diffusion of liquid. In general, the liquid is 0.9% salt water. Rectangular samples (eg 12 cm x 2.5 cm) are placed on a tilting tray and electrodes (spaced 1 cm apart) are placed on each sample with one end immersed in water. All of the electrodes is connected to a computer that records the particular time each wet cm. A program formats these data, which gives the following table: the first digit line (from 1 to 9) corresponds to the number of wet cms. In this table, L corresponds to a known product; M and N respectively correspond to products M1 and N1 of the absorption test. Diffusion time meaning SM (s) Diffusion time sense ST (s) 1 2 3 4 5 6 8 9 1 2 3 4 5 6 8 9 The 0.8 3.3 7.7 16 25 36 64 86 0.7 2.5 5 7.7 12 16 28 36 M 1.1 3.9 6.9 15 21 28 52 66 1 2.9 5.5 10 14 19 34 43 NOT 1.2 3.7 8.8 13 21 29 56 68 0.9 2.6 4.6 8 14 20 33 42
It is observed that for the products M and N, comprising the ground of the invention, the diffusion times in the forward direction and in the cross direction are closer to one another than those of the product L. This means that the liquid diffuses more efficiently in all directions than on a product L having an embossing pattern of the prior art.
(3) An absorption rate test was performed to verify the extent to which cell geometry and their alignment for bridging were involved in the absorption process.

There is a horizontal cylinder above a Teflon coated blade. A sheet of paper is attached to the cylinder facing the blade. Drop a drop of colored water on the blade and slowly approach the latter of the sheet which is on the cylinder. We strongly illuminate the drop and record with a camera that triggers just before absorption. The maximum recording time is 5.4 seconds with one image every 4 ms.

The images obtained make it possible to measure the evolution of the diameter of the drop over time.

The time taken by a droplet on the slide is measured to pass inside the paper substrate, and the operation is repeated as many times as is necessary to obtain a statistically representative sample of results. These measurements were made on samples of the same papers as in the previous examples in two different places. The absorption time was first measured by the paper at points PI ₁ ( figure 4 ) and PA ₁ ( figure 5 ) in the central area of the patterns, then at points PI ₂ ( figure 4 ) and PA ₂ ( figure 5 ) that is to say in the non-embossed zone (but corresponding to an embossed zone of the second fold).

It was thus possible to measure the average time of absorption of the drops. On the figure 9 the absorption curves of the diameter of a drop were plotted over time.

• Courbe 1 est la trace pour une goutte initiée au point PA₁ de la figure 5.
• Courbe 2 est la trace pour une goutte initiée au point PI₁ de la figuré. 4.
• Courbe 3 est la trace pour une goutte initiée au point PA₂.
• Courbe 4 est la trace pour une goutte initiée au point PI₂.

These four curves each indicate the evolution as a percentage of the diameter of a drop as a function of time, the drop being initiated at different locations of two types of leaves.

• Curve 1 is the trace for a drop initiated at point PA ₁ of the figure 5 .
• Curve 2 is the trace for a drop initiated at point PI ₁ of the figurative. Four.
• Curve 3 is the trace for a drop initiated at point PA ₂ .
• Curve 4 is the trace for a drop initiated at the point PI ₂ .

Thus, it appears that, at comparable points of initiation, the diameter of a drop decreases more rapidly when it is applied to a product of the invention. It can be deduced that the rate of absorption of liquids applied on the surface is faster.

It is observed that the improvement of the absorption speed is obtained at the surface of the fold both on an embossed zone and on an area which itself is not embossed. In fact, it is necessary to take into consideration the underlying fold which is respectively embossed and unembossed. The invention therefore has an overall effect on the double sheet (comprising two folds).

Claims (15)

1. Sheet of tissue paper comprising at least one first embossed zone (A₁, A₂) with protuberances on one face corresponding to cells (101', 102') on the other face, the cells having a base with a substantially polygonal shape, and at least one second unembossed zone (B), characterized in that:

   - the cells (101', 102') are placed in at least one alignment;

   - the facing sides of two adjacent cells define a bridge (P) with rectilinear or substantially rectilinear edges with a length L greater than its greatest width D, one or more bridges connected to one another determining a path preferably between two second unembossed zones (B) separated by at least one first embossed zone (A₁, A₂)
2. Sheet of tissue paper according to the preceding claim, characterized in that L/D is greater than 1, preferably greater than 1.5, and notably greater than 3.
3. Sheet according to one of the preceding claims, characterized in that the distance between first two adjacent zones (A₁, A₂), separated by an unembossed zone (B), is between one and three times, preferably between one and two times, the width of the said first zones (A₁, A₂).
4. Sheet of tissue paper according to any one of the preceding claims, characterized in that the base of the said cells (101', 102') is triangular.
5. Sheet of tissue paper according to one of the preceding claims, characterized in that the slope (α) of at least one of the walls of the cells measured relative to the vertical to the plane of the sheet is between 20° and 45°,
6. Sheet of tissue paper according to one of the preceding claims, characterized in that the surface density of the cells is between 4 and 50 per cm² and preferably between 4 and 20 per cm².
7. Sheet of tissue paper according to any one of the preceding claims, characterized in that the linear density of the cells is between 2 and 20 per cm.
8. Sheet of tissue paper according to one of the preceding claims, characterized in that it is associated with a second sheet of tissue paper to form a double-thickness sheet.
9. Sheet of tissue paper according to the preceding claim, characterized in that the second sheet is a sheet of tissue paper, of the through-air dried type.
10. Sheet of tissue paper according to any one of the preceding claims, characterized in that the said alignments are concentric.
11. Cylinder for the embossing of a sheet according to one of the preceding claims, characterized in that it comprises pins (10) with a polygonal base forming alignments (A₁, A₂), in which two adjacent pins(101, 102) are placed in such a manner that two respective sides (101m, 102m) of the polygonal base of the said two pins are placed facing one another and are substantially parallel with one another.
12. Cylinder according to the preceding claim, characterized in that the pins (10) have a triangular base.
13. Cylinder according to one of Claims 11 and 12, characterized in that the angle (β) between the said two substantially parallel sides (101m, 102m) of the pins(101, 102) is between 0 and 35°.
14. Cylinder according to one of Claims 11 to 13, characterized in that each of the faces of the pins form an angle (α) of between 20 and 45° with a plane perpendicular to a generatrice of the cylinder defined on the said face.
15. Method for manufacturing a sheet according to one of Claims 1 to 10, according to which the sheet is pressed on an engraved embossing cylinder (1), characterized in that the cylinder (1) is defined according to any one of Claims 11 to 14.

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