EP1236830A1 - Creped and embossed absorbent paper, embossing cylinder and process - Google Patents

Abstract

The embossed absorbent paper is made from at least two layers (12, 14) of creped cellulose wadding with a weight of between 12 and 30 g/sq m. Each layer has two embossed patterns with truncated conical protuberances - one with large protuberances (18) with summits (32) extending as far as the inner surface (24) of the opposite layer, and the other with smaller protuberances (38, 40) with summits (42, 44) that meet in the middle between the layers but are not linked. The larger protuberances are in a pattern of concentric rings, while the smaller ones fill the spaces between them. The layers of the paper are formed between pairs of rollers with projecting studs and then assembled.

Description

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

The invention relates in particular to a sheet of paper, composed of at least first and second plies of cotton wool creped cellulose, intended for wiping in a household, domestic or industrial use, i.e. can be used as a paper towel, cloth etc.

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

Indeed, the embossing gives bulk to the sheet and it induces improved absorption of liquids, touch and sweetness. We tried to further increase the capacity absorption by creating multilayer sheets obtained by associating at least two layers, also called folds, each consisting of at least one of said embossed sheets.

A multilayer sheet is thus obtained which has mechanical characteristics such as resistance to traction, as well as a determined absorption capacity.

Two modes of embossing and assembling the plies are commonly implemented according to the desired characteristics of the final product.

The first is known in the field under the designation "nested" or interlocking. It consists first of all in embossing folds separately so as to form on the surface protrusions generally substantially frustoconical or in pyramid trunks. Then we put glue on the top protrusions of one of the folds, and we have the folds of so that the faces with the protrusions come in screw with screw, the protuberances of one between the protuberances of the other. We finally assemble the folds so that the protuberances having been glued come to fit between the protrusions of the other fold. So the two folds are linked by glue points between the vertices of the protrusions of a fold and non-embossed areas between the protrusions of the other ply. A structure is produced whose voids thus formed are able to provide the sheet with improved absorption. In addition, the outer sides have a smooth and fluffy feel due recessed areas formed by the back of the protrusions. This technique is illustrated by US-A-3,867,225.

The second method of assembly is known in the field under the designation "spikes / spikes". It differs from preceded by the relative arrangement of the two folds. These, after they have been embossed separately, are brought one on the other so as to make the vertices of the protrusions coincide, or at least some of these peaks. The folds are linked between them by the tops of the protuberances, points against points. This technique is illustrated by patent US-A-3,414,459.

When we consider the practical achievements of these structures, whether of the nested or spike / spike type, the protrusions obtained during embossing are most often made so as to be distributed according to a pattern in which the protrusions are generally aligned in one or more multiple directions, evenly. Such a pattern allows to obtain a uniform sheet with regard to its characteristics mechanical.

However, in order to improve the satisfaction of user it is important to increase the flexibility of the leaf.

We can define the flexibility of the sheet as its ability to deform regularly when laid in the hand of a user, his fingers stretched out in the extension of his palm and the user then folds his fingers.

A sheet of paper with high flexibility will then deform and bend or arch so as to remain substantially parallel to the shape determined by inside the palm of the user's hand.

A sheet of paper with low flexibility will fold along one or more lines, each portion of the sheet that extends between two remaining fold lines substantially flat.

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

Generally speaking, increasing the flexibility of the leaf causes in particular a decrease in its mechanical characteristics.

The object of the invention is to propose a new embossed sheet design that allows for increased the flexibility of the sheet without reducing its characteristics mechanical.

To this end, the invention provides an embossed sheet composed of at least a first and a second ply of creped cellulose wadding with a grammage between 12 and 30 g / m ² of the type of which at least one first ply has a first embossing pattern consisting of a first series of first protuberances, of generally frustoconical shape projecting from the internal face of the first fold, which in particular form first alignments and the vertices of which are linked to the internal face of the second fold opposite screw, characterized in that these two folds each comprise a second embossing pattern consisting of a second series of second protrusions projecting from the internal face of the corresponding fold, and in that the vertices of the second protrusions of a fold s 'extend opposite and near the tops of the second protuberances of the other fold.

• des sommets des deuxièmes protubérances d'un pli sont en contact avec des sommets des deuxièmes protubérances en vis-à-vis de l'autre pli ;
• les sommets en contact des deuxièmes protubérances ne sont pas liés ;
• les hauteurs des deuxièmes protubérances des deux plis sont sensiblement égales ;
• chacun des deux plis comporte une première série de premières protubérances, de forme générale tronconique en saillie sur la face interne du pli, qui forment des premiers alignements ;
• les protubérances alignées de la première série forment des figures du type en boucle fermée ;
• chacun des deux plis comporte une première série de premières protubérances, et des séries associées des premières protubérances de l'un et de l'autre pli sont imbriquées entre les séries associées des protubérances de l'autre des deux plis ;
• des deuxièmes protubérances sont à sommets ponctuels;
• des deuxièmes protubérances sont à sommets linéaires.

According to other characteristics of the invention:

• vertices of the second protrusions of a ply are in contact with vertices of the second protrusions facing the other ply;
• the vertices in contact with the second protrusions are not linked;
• the heights of the second protrusions of the two plies are substantially equal;
• each of the two folds comprises a first series of first protuberances, of generally frustoconical shape projecting from the internal face of the fold, which form first alignments;
• the aligned protrusions of the first series form figures of the closed loop type;
• each of the two plies has a first series of first protrusions, and associated series of the first protrusions of one and the other ply are nested between the associated series of protrusions of the other of the two plies;
• second protrusions are at point vertices;
• second protrusions are with linear vertices.

The invention also provides a pair of engraved cylinders for embossing an embossed sheet according to any one of previous claims including at least one of the cylinders includes a first series of first shaped pins general frustoconical and forming first alignments, characterized in that the two engraved cylinders include each a second series of second raised pins, at point and / or linear vertices with each second spike of a cylinder corresponds substantially with a second spike of the other cylinder and whose sum of the heights of the second corresponding pins is substantially equal to the height of the first pimples.

The invention finally proposes a method for manufacturing a embossed sheet by means of a pair of cylinders according to the previous claim, characterized in that it consists of emboss the two folds to form the first and second embossing patterns, then to assemble the two folds so that the vertices of the first protuberances are linked to the face internal fold opposite and that the vertices of the second protrusions of a fold extend opposite and near the vertices of the second protuberances of the other fold.

• la figure 1 illustre en vue de dessus un exemple de réalisation d'une feuille de papier gaufré conforme aux enseignements de l'invention, et plus particulièrement une feuille de papier essuie-tout ;
• la figure 2 est une vue schématique en coupe et en perspective d'une feuille de papier gaufré réalisée conformément aux enseignements de l'invention ;
• la figure 3 est une vue schématique en section d'une feuille de papier gaufré qui est réalisée conformément aux enseignements de l'invention et qui est légèrement cambrée ;
• les figures 4 et 5 sont des vues schématiques en section d'une feuille de papier gaufré réalisée selon des variantes de réalisation de l'invention ;
• la figure 6 est une vue schématique en perspective illustrant la surface cylindrique convexe d'un cylindre de gaufrage d'un pli d'une feuille selon la figure 1 ;
• la figure 7 est une vue à grande échelle du détail D7 de la figure 6.

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 among which:

• Figure 1 illustrates a top view of an embodiment of a sheet of embossed paper according to the teachings of the invention, and more particularly a sheet of paper towel;
• Figure 2 is a schematic sectional and perspective view of a sheet of embossed paper made in accordance with the teachings of the invention;
• Figure 3 is a schematic sectional view of a sheet of embossed paper which is produced in accordance with the teachings of the invention and which is slightly arched;
• Figures 4 and 5 are schematic sectional views of a sheet of embossed paper produced according to alternative embodiments of the invention;
• Figure 6 is a schematic perspective view illustrating the convex cylindrical surface of an embossing cylinder with a fold of a sheet according to Figure 1;
• FIG. 7 is a large-scale view of detail D7 in FIG. 6.

FIGS. 1 and 2 show an example of production of a sheet 10 of embossed paper, in particular a sheet of paper consisting of a first upper fold 12 and a second lower ply 14 of absorbent paper, wadding creped cellulose, intended for all types of hygiene products or cleaning.

The cellulose wadding, with a basis weight between 12 and 30 g / m ² , is of the type obtained by conventional wet pressing, called "CWP", or of the type obtained by drying by through air, called "TAD".

More particularly, the sheet of paper 10 shown in Figures 1 and 2 is for example intended to be incorporated in a paper towel roll.

Sheet 10 is oriented in two directions longitudinal and transverse, shown in Figure 2 by the arrows L and T, which correspond to the direction of scrolling of sheet 10 during its manufacture, also called "on" direction and to the perpendicular direction respectively, also called direction "Travers".

After embossing, a first pattern 16 is apparent and is visually detaches from the first 12 and the second fold 14 of the sheet 10.

The first embossing pattern 16 of each fold 12 and 14, of known general design, consists of first series of first protrusions 18 and 20, of general shape frustoconical projecting from the internal face 22, 24 of the fold 12, 14 corresponding, thus extending towards the inside of the sheet 10.

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

Here, in accordance with Figure 1, associated series of first protrusions 18, 20 of one and the other fold 12, 14 are nested, concentrically, between series associated with protuberances 20, 18 on the other 14, 12 on both folds.

The first series of first protrusions 18 and 20 are aligned in two main directions so as to define a grid. The two main directions are here perpendicular to each other, and are inclined at 45 degrees by with respect to the longitudinal L and transverse directions T of the sheet 10.

The vertices 32, 34 of the first protrusions 18, 20 are linked to the internal face 24, 22 of the fold 14, 12 opposite (see figure 2).

According to a known technique, the first protuberances 18, 20 constituting the elements of the first motif 16 are obtained by embossing the first 12 and the second folds 14 of sheet 10 by means of a pair of cylinders, one of which them 26 is shown in FIGS. 6 and 7.

"Protuberances" homologous to those desired get on the first 12 and the second folds 14 of the sheet 10 are formed in relief on the convex cylindrical external face 28 of the associated cylinder 26.

For the realization of the series of first protuberances 18 on the first fold 12 of the sheet 10, the embossing cylinder 26 has on its convex cylindrical face 28 a first homologous series of pins in relief 30 of general shape tapered in relief, which are distributed in concentric circles according to the first alignments of the first protrusions 18, so as to make the corresponding part of the first pattern 16 of the first fold 12.

Similarly the series of first protuberances 20 on the second fold 14 of the sheet 10 is produced by another similar embossing cylinder with raised pins tapered are distributed in concentric circles according to the first alignments of the first protrusions 20, so to make the corresponding part of the first pattern 16 of the second fold 14.

When the first 12 and the second folds 14 are embossed, they are assembled together by gluing vertices 32 or 34 first protuberances 18 or 20 on the internal face 24 or 22 of the second 14 or of the first fold 12 opposite.

In accordance with the teachings of the invention, and in order improve the flexibility of the sheet 10 without reducing its mechanical characteristics and its absorption capacity, two folds 12, 14 have a second embossing pattern 36 consisting of second series of second protrusions 38, 40 which are for example of generally frustoconical shape, it is say at point vertices, projecting from the internal face 22, 24 of the fold 12, 14 corresponding, thus extending towards the inside of the sheet 10.

The axes A1 and A2 of the second protrusions 38 and 40 the first 12 and the second folds 14 are substantially aligned.

The second protrusions 38 and 40 are made of similar to the first protrusions 18 and 20, in particular by a second series of second pins 46 of frustoconical shape which extend to the convex surface 28 of the embossing cylinder 26.

Each second pin of a cylinder corresponds to preferably with a second matching spike on the other cylinder, and the sum of the heights of the second spikes correspondents is substantially equal to the height of the first pimples.

The second protrusions 38, 40 form in particular second alignments according to figures, in particular in closed loops, which are arranged between the first series first protuberances 18 and 20.

Here, the closed loops have the general shape of a square the edges of which are substantially curved and concave parallel to the circles defined by the first protrusions 18 and 20.

However, the second alignments may consist in other shapes, geometric or not, such as diamonds or flowers.

It is also possible that the second alignments of the second protrusions 38 and 40 have circles which are arranged concentrically with the circles of the first series of first protrusions 18 and 20.

As a variant not shown, the second protrusions are not necessarily protuberances frustoconical with point vertices, but can also be type with linear vertices defining more or less linear patterns less complex.

The second protrusions can also be combinations of point vertices and linear vertices on the same fold, on the two folds or respectively on one and the other of the two folds.

When the second protuberances are frustoconical, they are preferably micro protuberances, by comparison with the first frustoconical protuberances, with a density of micro protuberances between 30 and 80 protuberances per cm ² .

The diameter of the peaks of the pins to burn the micro protrusions is for example of the order of 0.4 mm while that of the first (macro) protuberances is of the order of 1.0 mm.

By way of example, if we consider the corresponding heights of the first pins 30 and second pins 46 formed in relief on the cylinder 26, intended for embossing a first fold 12 of a sheet of paper for a used as a paper towel, the height of the first pins 30 is equal to 1.3 millimeters while the height of the second pins 46 is equal to 0.7 millimeters. With a cylinder thus defined, associated with a cylinder with an appropriate rubber coating, a ply of cellulose wadding of 22 g / m ² was embossed and an average thickness H of the first ply 12 was obtained of the order of 0.8 millimeter.

The first 30 and the second pins 46 are shaped frustoconical with circular, oval, polygonal or other cross section, and preferably with a steep slope, between 60 and 70 °.

The vertices 42, 44 of the second protrusions 38, 40 of the first 12 and second folds 14 extend opposite and proximity to opposite and substantially aligned vertices axially 44, 42 of the second protrusions 40, 38 of the other fold 14, 12.

Such an embossed sheet 10 has flexibility greater than that of an embossed sheet produced according to the state of the technical while having mechanical characteristics and a absorption capacity which are not reduced.

The flexibility of the sheet 10 is improved because, when bending of the sheet 10, the vertices 42 and 44 of the seconds protrusions 38 and 40 can move slightly one by relation to the other, that is to say tilt and shift in accordance in Figure 3.

Mutual support of summits 42 and 44 of the second protrusions 38 and 40 prevent the formation of a line of folding detrimental to the flexibility of the sheet and promotes bending the sheet 10.

Mutual support of summits 42 and 44 of the second protrusions 38 and 40 also minimizes crushing of sheet 10 which allows sheet 10 to keep its bouffant, that is to say its absorption capacity.

In accordance with FIG. 2, the vertices 42 and 44 of the second protrusions 38 and 40 may be in contact. They are not related to each other.

According to a variant, represented in FIG. 4, the vertices 42 and 44 of the second protrusions 38 and 40 are separated axially by a slight clearance J.

The two figures 2 and 4 represent second protrusions 38 and 40 which are symmetrical with respect to a median plane of the sheet 10, that is to say that their heights H1, H2 are equal just like the heights H1 ', H2'.

However, according to a variant shown in FIG. 5, the second protrusions 38 and 40 can be unsymmetrical.

Without departing from the scope of the invention, it is not necessary that the vertices of the second protrusions opposite are perfectly aligned.

Nor is there a requirement that there be a full correspondence of the second protrusions of a fold with second protrusions of the other fold.

Regarding the performance of a sheet according to the invention, they are analogous to those of the product corresponding to the state of the art with only first protrusions, except for the flexibility of the sheet which is greatly improved.

Tests have shown that the stiffness of the sheet according to the invention, that is to say the inverse of the flexibility, (measured according to the geometric mean method called "Geometric Mean Stiffness "), is reduced by more than 20% compared to the sheet stiffness according to the state of the art.

Claims (11)

Embossed sheet (10) composed of at least first and second plies (12, 14) of creped cellulose wadding weighing between 12 and 30 g / m ² of the type of which at least one first ply (12) has a first embossing pattern (16) consisting of a first series of first protuberances (18), of generally frustoconical shape projecting from the internal face (22) of the first fold (12), which in particular form first alignments and whose vertices (32) are linked to the internal face (24) of the second fold (14) opposite, characterized in that these two folds (12, 14) each comprise a second embossing pattern (36) consisting of '' a second series of second protrusions (38, 40) projecting from the internal face (22, 24) of the corresponding fold, and in that vertices (42, 44) of the second protrusions (38, 40) of a fold (12, 14) extend opposite and near the tops (44, 42) of the second protrusions (40, 38) of the other fold (14, 12). Embossed sheet (10) according to the preceding claim, characterized in that vertices (42, 44) of the second protrusions (38, 40) of a fold (12, 14) are in contact with vertices (44, 42) of the second protrusions (40, 38) facing the other fold (14, 12). Embossed sheet (10) according to the preceding claim, characterized in that the vertices (42, 44) in contact with the second protrusions (38, 40) are not linked. Embossed sheet (10) according to any one of the preceding claims, characterized in that the heights (H1, H2) of the second protrusions (38, 40) of the two plies (12, 14) are substantially equal. Embossed sheet (10) according to any one of the preceding claims, characterized in that each of the two folds (12, 14) comprises a first series of first protuberances (18, 20), of generally frustoconical shape projecting from the internal face (22, 24) of the fold (12, 14), which form the first alignments. Embossed sheet (10) according to any one of the preceding claims, characterized in that the aligned protrusions (18, 20) of the first series form figures of the closed loop type. Embossed sheet (10) according to the preceding claim, characterized in that each of the two plies (12, 14) comprises a first series of first protrusions (18, 20), and in that associated series of the first protrusions (18, 20 ) of one and the other fold (12, 14) are nested between the associated series of protrusions (20, 18) of the other (14, 12) of the two folds. Embossed sheet (10) according to any one of the preceding claims, characterized in that second protrusions are at point vertices. Embossed sheet (10) according to any one of the preceding claims, characterized in that second protrusions are with linear vertices. Pair of cylinders (26) engraved for embossing an embossed sheet (10) according to any one of the preceding claims, at least one of the cylinders (26) of which comprises a first series of first pins (30) of general shape frustoconical and forming first alignments, characterized in that the two engraved cylinders (26) each comprise a second series of second raised pins, with linear and / or point vertices (46) including each second pin (46) of a cylinder corresponds substantially with a second pin (46) of the other cylinder and the sum of the heights of the corresponding second pins (46) being substantially equal to the height of the first pins (30). Method for manufacturing an embossed sheet (10) by means of a pair of cylinders (26) according to the preceding claim, characterized in that it consists in embossing the two plies (12, 14) so as to form the first (16) and the second embossing patterns (36), then assembling the two folds (12, 14) so that the vertices (32, 34) of the first protrusions (18, 20) are linked to the internal face (24, 22) of the fold (14, 12) opposite and that the vertices (42, 44) of the second protrusions (38, 40) of a fold (12, 14) extend opposite and near the tops (44, 42) of the second protrusions (40, 38) of the other ply (14, 12).

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