EP1455014A1 - Embossed absorbent paper sheet - Google Patents

Abstract

The absorbent paper, especially of cellulose wadding, consists of two or more layers, at least one of which is embossed in a pattern with protuberances (1, 2, 3) having a density of 30 per sq cm or more. The embossed pattern has at least two adjacent zones with different protuberance densities and/or heights to produce a relief effect. The tips of the protuberances, which have a surface area of at least 0.03 sq mm for small ones and up to about 0.80 sq mm for large ones, occupy between 7 and 45 per cent of the embossed area of the paper, and the difference in their densities and/or heights is between 7 and 45 per cent. The embossed pattern comprises at least one first zone (1) with protuberances of one density, surrounded by at least one second zone (2, 3) with protuberances having a greater density than the first zone. The pattern can have a geometrical or aesthetic design. The layers of the paper are joined together by adhesive, and one variant of the design can have a non-embossed layer between two embossed ones.

Description

The present invention relates to the field of absorbent papers for sanitary or domestic use, and relates to a product comprising at least an embossed fold, intended for the production of toilet paper essentially but also handkerchiefs, napkins or possibly paper towels.

In the sanitary and household paper industry, uses for the realization of this type of products, an absorbent product generally creped, light weight, designated: cellulose wadding or cotton fabric. We take advantage of the elongation capacity of the structure, conferred for example by creping, for embossing the sheet. This operation consists in permanently deforming the latter between a non-deformable cylinder provided with reliefs and a counter-cylinder, by example with resilient coating. This produces protrusions on a face corresponding to cavities on the other face.

Indeed the trend of recent years, with regard to Hygiene products made of cellulose wadding was to make them softer, more soft by working their characteristics of thickness and resistance, especially by embossing. The latter also improves the attractiveness visual of the product. The embossing operation is carried out on paper with low humidity level, i.e. in transformation. We then work a dry sheet, unwound from a mother roll from the machine paper.

The most common embossing patterns consist of a repetition on a geometric basis of elementary protuberances of small cross section and simple geometric shape. An example is described in US Pat. No. 3,414,459 which relates to a laminated sheet made up of a plurality of elementary sheets, called plies, glued together. The pleats were embossed with a frequency of distribution and a height of the protrusions adapted to the production of water-absorbing products, paper towels for example. The number of elements ranges from 5 to 30 per cm ² .

For its part, the Applicant has developed, for toilet paper in particular, patterns whose number of elements is greater, ranging from 30 to 80 per cm ² . This type of embossing is usually called "micro-embossing". The elements in relief forming the embossing necessarily have a very small elementary surface at the top, less than 1 mm ² . An aspect which imitates that of a woven product is obtained for these latter embodiments. An example has been described in patent EP 426 548.

However, this type of product has limited visual appeal. In in addition when combining two plies thus embossed, the softness of the product obtained is not optimal.

The solution presented in patent FR 2 728 152 makes it possible to improve the softness of a double-ply sheet with this type of embossing, by producing a combined pattern, comprising a graphic pattern and a background pattern. The first consists of protuberances whose shape is linear with a width of between 0.1 and 2 mm, and the second comprises small generally frustoconical protuberances distributed at a rate of at least 30 per cm ² (micro-embossing). The folds are combined on the linear shape pattern, thus limiting the extent of the surfaces bonded together and the stiffening induced.

In accordance with this embodiment, the proportion of embossed surface depending on the background pattern is largely in the majority: 80% of the surface in convenient. It is he who provides most of the functional characteristics related to embossing, namely thickness and absorption.

We also know US Patent 5,620,776 which describes sheets of absorbent absorbent paper in a pattern forming a network of diamonds with a pattern inside made up of elements linear, or formed by protuberance alignments. This is about invention of obtaining sheets with improved bulkiness with respect to sheets not embossed, and whose patterns stand out well. However, the densities of protuberances used do not relate to micro-embossing.

We also know the patent application EP 1 073 797 which describes a sheet of absorbent paper, having a pattern formed only of protrusions of the same size, distributed at almost identical densities so as to obtain a uniform marking and a good definition of said pattern, while having characteristics of thickness and resistance comparable to that of a sheet having a uniform embossing.

The embossing motif disclosed in this patent includes a network of cells with little or no embossing inside.

It is therefore most often a question of finding a compromise between density of the pattern-forming element (s), the surface they occupy, their shape, their marking ...

According to the effects that one seeks to obtain: softness, thickness, absorption, aesthetics, resistance, we can act on the parameters mentioned above.

The known micro-embossments have equal densities and / or substantially equal over the entire surface of the products.

In accordance with the present invention, it is sought to obtain a embossed product with improved relief in itself, without that its other properties are not diminished or altered.

According to the invention, the improved relief is obtained essentially thanks to a characteristic embossing.

Furthermore, the product according to the invention advantageously has a relatively large thickness and in no case gives a impression (neither visual nor touch) of crushing, or flattening.

Thus, the subject of the invention is a product made of absorbent paper, in particular of cellulose wadding comprising at least two plies, at least one of which is embossed according to an embossing pattern comprising protuberances of density greater than or equal to 30 per cm ² .

According to the invention, said embossing pattern comprises at at least two juxtaposed zones whose protuberances have respectively a different density and / or a surface at the top different in order to obtain a relief effect on said product.

Without departing from the scope of the invention, the ratio between the area occupied by the tops of said protrusions and the embossed surface, that is to say occupied by one or more embossed areas of the sheet is between 1 and 60% preferably between 7 and 45%.

Advantageously, the difference in density and / or surface at apex of protrusions is greater than 7 and preferably greater than 15%.

In addition, the surface at the top of the smallest protrusions is at least 0.03 mm ² .

Furthermore, the surface at the top of the largest protuberances is at most of the order of 0.80 mm ² .

According to one embodiment of the invention, the embossing pattern comprises at least a first zone whose protuberances have a first density, said zone being surrounded by at least one second zone whose protuberances have a second density greater than the first density.

According to an additional characteristic of the invention, the pattern of embossing further includes linear elements.

More specifically, the linear elements define a second geometric network and / or aesthetic patterns.

Preferably, the folds are assembled together by gluing.

According to a preferred embodiment of the invention, the product includes at least two embossed pleats.

Without departing from the scope of the invention, the product can comprise three folds: two outer embossed folds and a central non-embossed fold.

• la figure 1 illustre une vue de dessus d'un produit gaufré selon un mode de réalisation de l'invention ;
• la figure 2 illustre une vue de dessus d'un produit gaufré selon un autre mode de réalisation de l'invention ;
• la figure 3 a trait à une vue de dessus d'un produit gaufré selon encore un autre mode de réalisation de l'invention ;
• la figure 4 est un graphique montrant la relation entre l'épaisseur et l'empreinte pour des produits de même densité ayant des protubérances de surface au sommet différente ; et

Other characteristics, details, advantages of the invention will appear better on reading the description which follows, given by way of illustration and in no way limiting, with reference to the appended drawings in which:

• FIG. 1 illustrates a top view of an embossed product according to an embodiment of the invention;
• FIG. 2 illustrates a top view of an embossed product according to another embodiment of the invention;
• Figure 3 relates to a top view of an embossed product according to yet another embodiment of the invention;
• Figure 4 is a graph showing the relationship between thickness and footprint for products of the same density with different surface protrusions at the top; and

Figure 5 is a graph showing the relationship between thickness and the footprint for products of different densities with surface protrusions with identical apex.

In the rest of this text, as in the usual language of the paper technique in question, the "protuberances" are elements in relief on the sheet or fold in cellulose wadding, while the "spikes" are elements in relief on the cylinder intended to form the protrusions on the product of cellulose wadding.

Furthermore, a micro-embossing usually includes protuberances with a density greater than 30 or even 50 protuberances / cm ² .

FIG. 1 relates to an embossing pattern produced on a product according to the invention.

More precisely, this pattern comprises a first zone 1 provided of a micro-embossing having a first density, said first zone being surrounded by other micro-embossed areas 2,3 having respectively a second density different from the first density and a third density still different.

Similarly, the surfaces at the top of the protrusions of the zones juxtaposed can be of different values.

• le premier microgaufrage 1 présente par exemple une densité de 32 protubérances/cm² et forme des hexagones ;
• le deuxième microgaufrage 2 est doté d'une densité de protubérances de 72 protubérances/cm² et est inscrit dans des étoiles.
• le troisième microgaufrage 3 est le plus dense puisque les protubérances ont ici une densité de 157 protubérances/cm².

According to the embodiment of Figure 1:

• the first micro-embossing 1 has for example a density of 32 protuberances / cm ² and forms hexagons;
• the second micro-embossing 2 has a density of protuberances of 72 protuberances / cm ² and is inscribed in stars.
• the third micro-embossing 3 is the densest since the protuberances here have a density of 157 protuberances / cm ² .

The third micro-embossing is inscribed in diamonds.

The three types of embossing 1, 2, 3 are juxtaposed on at least one fold, and they make it possible to obtain a sheet with well pronounced relief.

For the density calculation, the following calculation method was used:

The "embossed surface" corresponds to the area delimited by a line passing through the center of gravity of the protrusions forming the contour outside the chosen area.

The “number of protrusions” is equal to the number of protrusions located inside the area, to which we add half the number of protrusions located on the aforementioned contour line.

The density is equal to the ratio of the “number of protrusions” to the "Embossed surface".

In the context of the invention, a “zone” comprises at least 10 protuberances aligned in at least two rows.

FIG. 2 illustrates another embodiment of the invention according to which the embossing pattern comprises two types of micro-embossing: the first is formed of first zones 1 provided with protuberances having a first density of 61 protuberances / cm ² and a first surface at the top of 0.23 mm ² ; these zones are here in the form of an octagon.

Interspersed between the first zones there are second micro-embossed zones 2, of square shape and the protuberances of which have a second density (81 1 protuberances / cm ² ) and a second surface at the top: 0.13 mm ² .

The two types of zones are juxtaposed. We thus obtain a relief well marked on each sheet of cellulose wadding.

There is no linear protuberance in this embossing pattern.

Figure 3 shows yet another embossing pattern according to the invention.

The motif shown here is made up of 3 zones juxtaposed delimited by both first linear elements 5 and seconds zones 2 consisting of protuberances having a high density.

On all or part of their surface, zones 3 include uniformly distributed protuberances of density less than the density of protrusions forming the zones 2.

According to the invention, the difference in density of protrusions between the different areas is greater than 15%.

Furthermore, second linear elements 4 define at inside certain areas 3, aesthetic patterns, here in the form of tulips.

Of course, the pattern illustrated in Figure 3 is only an example in no way limiting.

In particular, the linear elements 1,4 are not necessarily present. When they are present, they reinforce the relief.

In all cases, a micro-embossing such as the sheet is carried out presents a clearly visible and well defined relief.

In addition, a bonding can take place to assemble the folds: preferably bonding is carried out on all or part of the zones micro-embossed and / or linear pattern.

In addition, tests have been carried out by embossing a sheet (or fold) of cellulose wadding between an engraved cylinder with a pattern according to the invention and a rubber cylinder. This sheet was then associated by bonding to an unembossed sheet. The thickness of the structure thus obtained was measured using a micrometer device LORENTZEN & WETTRE reference SE050 used according to standard NF EN 12625-3.

Five different embossing pressures were applied between the steel and rubber, these pressures were recorded using carbon paper. For each press, a sheet of carbon paper was placed between the engraved cylinder and rubber. The rubber crashes on contact with engraved cylinder and “prints” the pattern on carbon paper. PIN or imprint corresponds to the width of the mark left by the cylinder engraved on carbon paper. This mark will be more or less wide in depending on the embossing pressure applied.

FIG. 4 illustrates a first series of tests intended to show the effect of the surface at the top (or dimension) of the pins of the cylinder on the thickness of the product obtained. Starting from the same density of spikes, here 60 spikes / cm ² , tests were carried out on patterns having the same depth and respectively spikes with a diameter at the top equal to 0.4 mm and 0.6 mm. On the ordinate, there are thicknesses of the products and on the abscissa the PIN or imprint left by the cylinder on the carbon paper.

Curve A corresponds to products formed on cylinders having pins of diameter at the top substantially equal to 0.4 mm while that curve B relates to products formed on cylinders whose the pins have a diameter substantially equal to 0.6 mm. The comparison of these curves shows that for the same footprint, we obtains a greater thickness of the structure when it is obtained with an engraved cylinder whose pins have the surface at least important summit.

In FIG. 5, resulting from a second series of tests such as defined above, curves C, D and E were obtained for three products whose embossing patterns have three densities of protuberances different. Three different cylinders were used.

Starting from pins of the same diameter on the cylinders, here 0.4 mm, tests were carried out on patterns having the same depth and respectively pin densities of 50, 60 and 80 protuberances / cm ² .

We observe that, with equal footprint, the higher the density of the pins decreases the more the thickness of the product obtained increases.

Thus, by juxtaposing zones of embossing patterns having densities and / or different top surfaces, we can get different product thicknesses, allowing to have the relief effect desired, on the final product.

The relationship between the variation in thickness of the product and the effect of relief is therefore well established.

Claims (13)

Absorbent paper product, in particular of cellulose wadding comprising at least two plies, at least one of which is embossed according to an embossing pattern comprising protrusions (1,2,3) of density greater than or equal to 30 per cm ² , characterized in that said embossing pattern comprises at least two juxtaposed zones, the protrusions (1,2,3) of which have respectively a different density and / or a different top surface in order to obtain a relief effect on said product. Product according to claim 1 characterized in that the ratio between the surface occupied by the vertices of said protrusions (1,2,3) and the embossed surface of the sheet is between 1 and 60%. Product according to claim 2 characterized in that the ratio between the surface occupied by the tops of said protrusions and the embossed surface of the sheet is between 7 and 45%. Product according to any one of the preceding claims, characterized in that the difference in density and / or surface at the top of the protuberances is greater than 7% and preferably greater than 15%. Product according to any one of the preceding claims, characterized in that the surface at the top of the smallest protrusions is at least equal to 0.03 mm ² . Product according to any one of the preceding claims, characterized in that the surface at the top of the largest protuberances is at most of the order of 0.80 mm ² . Product according to any one of the preceding claims, characterized in that the embossing pattern comprises at least a first zone (1) whose protrusions have a first density, said zone being surrounded by at least a second zone (2,3) the protrusions of which have a second density greater than the first density. Product according to any one of the preceding claims, characterized in that the embossing pattern further comprises linear elements (4,5). Product according to claim 8 characterized in that the linear elements (5) define a geometric network. Product according to any one of claims 9 or 10 characterized in that the linear elements (4) define aesthetic patterns. Product according to any one of the preceding claims, characterized in that the plies are joined together by gluing. Product according to any one of the preceding claims, characterized in that it comprises at least two embossed plies. Product according to claim 12 characterized in that it further comprises a third non-embossed ply disposed between the two embossed plies.

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