EP1455014B1 - 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 aims at a product comprising at least one embossed fold, intended for the production of toilet paper essentially but also tissues, napkins or paper towels .

In the paper industry for sanitary and domestic use, is used for the realization of this type of product, a generally creped absorbent product, of low basis weight, designated: cellulose wadding or wadded fabric. We take advantage of the capacity of lengthening of the structure, conferred for example by creping, to emboss the sheet. This operation consists in deforming the latter permanently between a non-deformable cylinder provided with reliefs and a counter-cylinder, for example with resilient coating. Thus, protuberances are obtained on one face corresponding to cavities on the other face.

Indeed the trend in recent years, as regards the hygiene products in cellulose wadding has been to make them softer, more soft by working their characteristics of thickness and strength, including embossing. The latter also makes it possible to improve the visual appeal of the product. The embossing operation is performed on paper with low humidity, that is to say in transformation. We then work a dry sheet unwound from a mother reel from the paper machine.

The most widespread 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 the U.S. Patent 3,414,459 which is on a laminated sheet consisting of a plurality of elementary sheets, called folds, glued together. The folds were embossed with a frequency of distribution and a height of the protuberances 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 referred to as "microgolding". The relief elements forming the embossing necessarily have an elementary surface at the very low vertex, less than 1 mm ² . For these last embodiments, an aspect is obtained which mimics that of a woven product. An example has been described in the patent EP 426,548 .

This type of product, however, has a limited visual appeal. In addition, when two plies thus embossed are bonded together, the softness of the product obtained is not optimal.

The solution presented in FR 2,728,152 allows to improve the softness of a double-folded 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). Folds are associated with the pattern of linear shape, thus limiting the extent of the surfaces bonded together and the stiffening induced.

According to this embodiment, the proportion of embossed surface according to the background pattern is largely the majority: 80% of the surface in practice. It is he who provides most of the functional characteristics related to embossing, namely thickness and absorption.

We also know the U.S. Patent 5,620,776 which discloses sheets of absorbent paper embossed in a pattern forming an array of lozenges whose interior comprises a pattern of either linear elements or protrusion alignments. In this invention it is a question of obtaining sheets with improved swelling with respect to non-embossed sheets, and whose patterns stand out well. However, the densities of protrusions used do not concern microgaufrages.

We still know the demand for patent EP 1 073 797 which discloses a sheet of absorbent paper, having a pattern consisting only of similarly sized protuberances, distributed in almost identical densities so as to obtain a homogeneous marking and a good definition of said pattern, while having characteristics of thickness and strength comparable to those of a sheet having uniform embossing.

The embossing pattern disclosed in this patent includes an array of cells whose interior is little or not embossed.

It is therefore most often to find a compromise between the density of the element or elements forming patterns, the surface they occupy, their shape, their marking ...

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

The known microgauferings have densities equal and / or substantially equal over the entire surface of the products, as illustrated for example in the document EP 1081284 .

According to the present invention, it is sought to obtain an embossed product having in itself an improved relief, without its other properties being reduced or altered.

According to the invention, the improved relief is obtained essentially by means of a characteristic embossing.

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

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

According to the invention, said embossing pattern comprises at least two juxtaposed zones whose protuberances respectively have a different density and / or a different top surface 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 peaks of said protuberances and the embossed surface, that is to say occupied by one or more embossed areas of the sheet is between 1 and 60% of preferably between 7 and 45%.

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

In addition, the top surface of the smaller protuberances is at least 0.03 mm ² .

In addition, 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 a second zone whose protuberances have a second density greater than the first density.

According to an additional feature of the invention, the embossing pattern further comprises linear elements.

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

Preferably, the plies are assembled together by gluing.

According to a preferred embodiment of the invention, the product comprises at least two embossed folds.

Without departing from the scope of the invention, the product may comprise three plies: two embossed outer plies and a non-embossed central 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:

• the figure 1 illustrates a top view of an embossed product according to one embodiment of the invention;
• the figure 2 illustrates a top view of an embossed product according to another embodiment of the invention;
• the figure 3 relates to a top view of an embossed product according to yet another embodiment of the invention;
• the figure 4 is a graph showing the relationship between thickness and footprint for products of the same density having surface protuberances at different apex; and

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

In the remainder of this text, as in the usual language of the papermaking technique in question, the "protuberances" are elements in relief on the sheet or the ply of cellulose wadding, while the "spikes" are elements in relief. on the cylinder intended to form the protuberances on the product made of cellulose wadding.

Furthermore, microembossing usually comprises protuberances with a density greater than 30 or even 50 protuberances / cm ² .

The figure 1 relates to an embossing pattern made on a product according to the invention.

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

Likewise, the surfaces at the top of the protuberances of the juxtaposed zones may 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.

In accordance with the embodiment of the figure 1 :

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

The third microgaufrage is written 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 pronounced relief.

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

The "embossed surface" corresponds to the zone delimited by a line passing through the center of gravity of the protuberances forming the outer contour of the chosen zone.

The "number of protuberances" is equal to the number of protuberances within the zone, to which is added half the number of protuberances on the above-mentioned contour line.

The density is equal to the ratio of the "number of protuberances" on the "embossed surface".

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

The figure 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 areas are here in octagon shape.

Intercalated between the first zones are second microgaufrées zones 2, of square shape and whose protuberances 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. A well marked relief is thus obtained on each sheet of cellulose wadding.

There is no linear protuberance in this embossing pattern.

The figure 3 shows yet another embossing pattern according to the invention.

The pattern represented here is composed of juxtaposed zones 3 delimited by both first linear elements 5 and second zones 2 consisting of protuberances having a high density.

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

According to the invention, the density difference of the protuberances between the different zones is greater than 15%.

Furthermore, second linear elements 4 define, within certain zones 3, aesthetic patterns, here in the form of tulips.

Of course, the pattern illustrated by the figure 3 is only a non-limiting example.

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

In all cases, a microembossing is performed such that the sheet has a well-visible and well-defined relief.

In addition, a bonding can take place to assemble the folds: preferentially the bonding is performed on all or part of the microgaufrées zones and / or the linear pattern.

Furthermore, tests were carried out by embossing a sheet (or fold) of cellulose wadding between a cylinder engraved with a pattern according to the invention and a rubber cylinder. This sheet was then bonded to a non-embossed sheet. The thickness of the structure thus obtained was measured using a LORENTZEN & WETTRE micrometer device, reference SE050, used according to standard NF EN 12625-3.

Five different embossing pressures between the steel and the rubber were applied and these pressures were measured using carbon paper. For each pressure, a sheet of carbon paper was placed between the engraved cylinder and the rubber. The rubber crushes in contact with the engraved cylinder and "print" the pattern on the carbon paper. The PIN or imprint is the width of the mark left by the engraved cylinder on the carbon paper. This mark will be more or less wide depending on the embossing pressure applied.

The figure 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 pins, here 60 pins / cm ² , tests were carried out on patterns having the same depth and respectively of peak diameter dots equal to 0.4 mm and 0.6 mm. On the ordinate, we find thicknesses of products and on the abscissa the pin or impression left by the cylinder on the carbon paper.

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

On the figure 5 , resulting from a second series of tests as defined above, curves C, D and E were obtained for three products whose embossing patterns have three different densities of protuberances. 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 densities of pins of 50, 60 and 80 protuberances / cm ² .

It is observed that, with an equal footprint, the higher the density of the pins, the more the thickness of the product obtained increases.

Thus, by juxtaposing areas of embossing patterns having different densities and / or top surfaces, different product thicknesses can be obtained to provide the desired relief effect on the final product.

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

Claims (12)

1. Absorbent paper product, in particular made of cellulose wadding, which includes at least two plies, at least one of which is embossed according to an embossing pattern including protrusions (1, 2, 3) at a density of equal to or greater than 30 per cm², characterized in that said embossing pattern includes at least two adjoining regions whereof the protrusions (1, 2, 3) are at different densities and/or have different surface areas at the peaks, in order to achieve a relief effect on said product.
2. Product according to Claim 1, characterized in that the ratio of the surface area occupied by the peaks of said protrusions (1, 2, 3) to the embossed surface area of the sheet is between 1 and 60%.
3. Product according to Claim 2, characterized in that the ratio of the surface area occupied by the peaks of said protrusions to the embossed surface area of the sheet is between 7 and 45%.
4. Product according to any one of the preceding claims, characterized in that the difference in density and/or surface area at the peaks of the protrusions is greater than 7% and preferably greater than 15%.
5. Product according to any one of the preceding claims, characterized in that the surface area at the peaks of the smallest protrusions is at least equal to 0.03 mm².
6. Product according to any one of the preceding claims, characterized in that the surface area at the peaks of the largest protrusions is at most around 0.80 mm².
7. Product according to any one of the preceding claims, characterized in that the embossing pattern includes at least one first region (1) whereof the protrusions are at a first density, said region being surrounded by at least one second region (2, 3) whereof the protrusions are at a second density which is greater than the first density.
8. Product according to any one of the preceding claims, characterized in that the embossing pattern further includes linear elements (4, 5).
9. Product according to Claim 8, characterized in that the linear elements (5) define a lattice.
10. Product according to any one of the preceding claims, characterized in that the plies are joined together by adhesive bonding.
11. Product according to any one of the preceding claims, characterized in that it includes at least two embossed plies.
12. Product according to Claim 11, characterized in that it further includes a third unembossed ply disposed between the two embossed plies.

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