EP1239079A1 - Paper sheet with small cushions - Google Patents

Abstract

The paper consists of at least two layers of crepe cellulose wadding weighing 10 - 40 g/sq m, the upper layer being between 0.6 and 2 per cent longer than the lower one and embossed to form protuberances (12) in rows (14) that are joined to the lower layer to make cushions (16) of 1 - 20 sq cm in area. The cushions have a length to width ratio of preferably 1 - 1.5 : 1, and the protuberances are truncated conical in shape with bases of 1 - 1.5 mm diameter and preferably not more than 1.5 mm apart. The two-layer paper is made from two separate rolls of paper, with the upper layer taken round an embossing roller and past an adhesive application roller before the two layers are joined together and made into rolls of smaller diameter.

Description

Disclosed is a sheet of paper made up of at least two folds of cellulose wadding forming pads.

The field of the invention is that of papers for sanitary use or domesticated. It includes in particular absorbent paper products whose shape, the composition and structure are determined according to their application. So non-limiting examples that may be mentioned include toilet paper, handkerchiefs, facial tissues, napkins, tablecloths, household paper towels, industrial wiping wadding, etc.

Toilet paper, for example, comes in the form of coupons precut in a continuous strip wrapped around a mandrel. Coupons can also come in an individual form and be entangled. Leaf can be simple, but most often it is made up of two or more thicknesses, also called plies, of cellulose wadding. In a sheet the folds can just be juxtaposed, free from each other but, the most often they are embossed and bonded together by bonding or mechanically by knurling.

Cellulose wadding is a paper of low grammage: 10 to 40 g / m ² , consisting essentially or exclusively of paper fibers and optionally comprising one or more additives to reinforce one or other of its characteristics. Depending on the applications, one can emphasize one or other of its properties and make it more soft, absorbent, resistant or a more marked textile appearance to make it more attractive. For example, the incorporation of resins serves to improve the tear resistance when the sheet is wet.

Furthermore the cellulose wadding can be creped, that is to say include undulations which give it a certain capacity of elongation in the direction market. The creping can be obtained, for example, at the time of drying of the leaf. This is applied while still wet on a cylinder heated to a sufficient temperature to extract moisture. We take off the sheet by means a doctor blade placed between the latter and the surface of the cylinder. This operation, properly conducted, results in the formation of arranged waves perpendicular to the direction of travel of the sheet, known as the running direction. We characterizes the creping of the sheet by the number of peaks counted in the direction step reduced to a unit of length.

We know the US patent 3,673,060; he describes a product, a napkin for example, formed of two plies of creped cellulose wadding bonded together by adhesive. The latter is distributed according to a pattern made up of point surfaces close together. from each other and leaving substantial parts of the two folds unbound. From 4 to Only 8% of the surface is bound and the two folds, whose creping lines are parallel, are not stretched in the same way. This voltage difference is obtained by stretching the two folds differently before they are tied together along the said pattern. Such tension control allows, after the adhesive has been attached, that one of the folds contracts more than the other. This results in a tendency to separate folds in the non-bonded parts between the areas with adhesive.

Patent teaches applying the adhesive to a fold using a roller applicator suitably engraved. Then put the second fold on the first then we train the two folds between two calendering cylinders, one of which is engraved and in phase with the applicator roller. Finally the sheet is entrained between two engraved steel cylinders, to be embossed along the edges of what will be the towel after cutting. This process thus appears to be of limited application to the manufacture of a towel-like product with an embossed edge.

In addition, the recommended area of the unbound part between two adjacent linked areas is around 0.65 cm ² . It is relatively small. According to the example given, the surface of the point connection zones is of the order of 2 mm ² with a spacing of 4.75 mm. It is mentioned in the patent that the sheet thus imitates the appearance and texture of a textile product. Preferably, the pins are distributed uniformly on the sheet.

French patent 70 35063 describes a process for manufacturing a several thicknesses of flexible material, paper or plastic, depending on which prints an adhesive material on one of the pleats along a so-called peripheral pattern open, representing diamonds or squares. The two folds have been previously embossed in a uniform pattern of protrusions and one of them is put under tension longitudinally so as to give the sheet, after cutting into towels, a "padded" look. We observe that the diamonds are very wide otherwise probably the glue deposited along continuous lines would create a product relatively rigid. This patent thus applies to products such as towels or table tablecloths.

US Patent 3,650,882 describes a paper, composed of three plies of cotton wool cellulose, in which the central pleat is stretchy and elastic and the outer pleats are embossed and less stretchy. The folds are linked along spaced areas so that leave unrelated parts. In the wet state the internal fold can thus be relax and occupy the space of unrelated parties. We plan to tie the central fold to external folds while it is extended relative to these. During the relaxation of the tensions to which the sheet is subjected, the central fold retracts and the other folds are set in volume in the unbound parts. Linked areas and unrelated parties appear to be of the same extent.

US Patent 4,469,735 also describes a product with several plies of cotton wool. cellulose with different elongation characteristics to allow the formation of bags and an increase in their absorption volume in the wet state.

The present invention aims to produce a product, consisting of at least at least two plies of creped cellulose wadding, with an attractive appearance for the consumer, in particular an aspect akin to that of a textile product and which is improved compared to the state of the art.

The subject of the invention is therefore a product composed of at least two plies, an upper ply and a lower ply, of creped cellulose wadding, each of grammage between 10 and 40 g / m ² , the upper ply of which comprises first protuberances on the side facing the inner fold, through the top of which they are linked. This product is characterized in that the said first protuberances are distributed in alignments which delimit between them cells with an area between 1 and 20 cm ² , the upper fold being longer in the forward direction than the lower fold by 0.6 at 2% and being linked to the lower fold by the tops of said first protuberances, so that pads are formed inside the cells.

By pad, according to the patent, there is an area whose two folds do not are not related to each other, and that is bounded by alignments of firsts protrusions forming a closed contour. The bearing is characterized by the fact that the upper fold appears detached from the lower fold and creates a domed effect.

Thanks to the invention, a product is obtained having a raised surface with pads inside the cells defined by the protuberance alignments, and whose appearance is similar to that of textile products, fleece in particular. Of advantageously when the product is in roll form, the effect of embossed pads is particularly visible when unrolling it.

According to another characteristic, said alignments are constituted first protuberances spaced from each other by a distance less than 3 mm. Indeed beyond this spacing the pads do not form properly. The ripples tend to extend in the cross direction. The first protrusions constituting the contours of the pads are preferably frustoconical shape with a circular or oval base. However, this base can also be polygonal. It can also have a very elongated shape giving footprints in continuous or discontinuous lines.

According to a preferred embodiment, the protrusions have a shape frustoconical, in particular of circular section, and their spacing along the alignments is very low. It is preferably less than the diameter of the section of protuberance.

The alignments can be straight or wavy. According to a mode of particular realization they form a network, of which the said cells are defined by their intersections. In particular, they have a substantially diamond-shaped shape and the sides of the latter are wavy. Such an example of pattern is described in the patent US 5,436,057.

According to another embodiment, inside said cells, the fold upper is embossed according to a pattern consisting of second protuberances. These are frustoconical or have a vertex of linear shape. The summit of second protuberances is free, i.e. it is not glued or otherwise bound in the second fold.

The second fold is embossed or not.

The present invention also relates to a process making it possible to produce a product with at least two plies of creped cellulose wadding, of grammage between 10 and 40 g / m ² .

• on déroule une première bande d'ouate de cellulose depuis une bobine mère et on la gaufre sur un cylindre de gaufrage gravé selon un motif constitué au moins de premières protubérances formant des alignements qui définissent entre eux des cellules fermées,
• on déroule une deuxième bande d'ouate de cellulose depuis une bobine mère, on applique la deuxième bande sur la première, et
• on lie les deux bandes en mettant en contact les deux bandes par les sommets des premières protubérances de telle sorte qu'au moment de la liaison des plis, ceux-ci sont différenciés de manière à ce que, au repos, la longueur des plis soit différente de plus de 0,6%, de préférence de 0,6 à 2%. On enroule ensuite la bande obtenue autour d'un mandrin -et on tronçonne le dit rouleau en rouleaux plus petits.

The method of the invention is characterized in that it comprises at least the following steps:

• a first strip of cellulose wadding is unwound from a mother roll and it is embossed on an embossing cylinder engraved according to a pattern consisting of at least first protuberances forming alignments which define closed cells between them,
• a second strip of cellulose wadding is unwound from a mother reel, the second strip is applied to the first, and
• the two bands are linked by bringing the two bands into contact by the vertices of the first protrusions so that at the time of the binding of the plies, these are differentiated so that, at rest, the length of the plies is different by more than 0.6%, preferably from 0.6 to 2%. The strip obtained is then wound around a mandrel - and the said roll is cut into smaller rolls.

The two bands differ from one another by one or other of the following characteristics taken alone or in combination: the speed of unwinding, the tension in the direction of travel, the level or depth of the embossing, and the elasticity.

La figure 1 représente une vue de dessus d'une feuille conforme à l'invention

La figure 2 est une vue en coupe selon II-II de la figure 1

La figure 3 représente de façon schématique une installation permettant de réaliser une feuille conforme à l'invention.

Other characteristics and advantages of the invention will emerge from the description which follows, by way of nonlimiting example, of an embodiment with reference to the appended drawings in which

Figure 1 shows a top view of a sheet according to the invention

Figure 2 is a sectional view along II-II of Figure 1

Figure 3 shows schematically an installation for producing a sheet according to the invention.

The sheet, represented in FIGS. 1 and 2, is composed of two plies of creped cellulose wadding. The cellulose wadding can be of the type obtained according to a conventional wet pressing process of the sheet, and designated in the field by CWP or else according to a process comprising a drying step by blowing through air of the TAD type. The grammage for each of the plies is between 10 and 40 g / m ² . For an application as toilet paper, a grammage preferably between 15 and 24 g / m ² is chosen. There is a top fold (10) and a so-called bottom fold (20). The cellulose wadding is crimped with the corrugations, as is known, all oriented, perpendicular to the direction of travel of the machine. The number of creping lines is between 40 and 80 lines per cm.

Thus the folds have a rate of elongation at break of at least 25%. Preferably it is not less than 20%.

According to the invention, the upper fold comprises protrusions (12) on the face of the fold which is turned towards the lower fold. These protuberances being formed by embossing, a cavity corresponds to them on the face turned towards the outside of the leaf. They have a section in the plane of the sheet which can be circular, oval or polygonal. A film of glue applied between the top of these first protuberances and the lower fold makes the two folds integral with one another.

The protrusions form alignments (14). We can define a alignment as a succession of protrusions presenting consecutively the smaller spacings. In the embodiment shown, the alignments are arranged in two directions substantially 90 ° from each other so that they intersect, forming a network and regular cells (16).

According to a preferred embodiment of the invention, the cells (16) have a preferably a rhomboid parallelogram shape. The ratio of length, its largest dimension, across the width, the largest dimension measured transversely to the first, is not greater than 5, preferably it is not greater than 1.5. The sides of the parallelogram are straight or shaped wavy as shown in Figure 1.

The upper fold remains detached from the lower fold at the cell level. it means that its dimension in the forward direction is greater than that of the lower fold. Analysis shows that the length of the upper fold must at least be greater than that of the lower fold by at least 0.6% so that the formation of pads on the upper fold.

Another necessary condition is the distance between two protrusions adjacent along an alignment. Indeed if the spacing exceeds a certain threshold, the pads do not form. Certainly ripples exist, due to the difference in length between the two folds, but they are irregular. We observed that the pads only form if this distance between the protrusions remains less than 3 mm.

Inside the cells (16), one can provide as shown in the figures, a secondary embossing formed by second protrusions (18). These protrusions (18) have an embossing height lower than that of the first protrusions (12). They do not form areas of connection of the upper fold with the lower fold.

A method of manufacturing a sheet according to the invention and corresponding to an embodiment as shown in Figure 3 is described below. A first continuous strip of cellulose wadding (10) is unwound from a mother coil (100) which is mounted on a rotating support. We train this band to a certain speed through an embossing group comprising a cylinder (102) to rigid and etched surface and a cylinder (104) with a surface of resilient material such as rubber. The pattern of the engraving of the rigid cylinder is for example that of the Figure 1, with first elements in relief or spikes at a first level of engraving for the realization of the first protrusions and of the second elements in relief at a level lower than the first for the realization of the second protuberances. The engravings of two-level embossing cylinders are known to the man of art.

The strip after embossing receives a film of adhesive which is deposited on the raised surfaces, i.e. those of the embossing pattern, by a cylinder (106) applicator known per se. The pattern of the engraving of the rigid cylinder corresponds to first protuberances. It can also consist of protrusions of different depths. In this case, the adhesive film is deposited only on the protrusions in the highest relief. The adhesive is a water-based glue, for example a polyvinyl adhesive common in the field of the invention.

According to another embodiment, the connection of the folds is obtained so mechanical or in any other way known to those skilled in the art.

The second fold is then applied to the first by means of a cylinder matchmaker (108). The second fold (20) comes from a mother reel (200) which is unwound at a determined speed. The pressure exerted by the matching cylinder ensures the connection folds to each other. The double sheet is then driven while being held under voltage towards the "logs" manufacturing station. A "log" is a roll intermediate to the diameter of the product after it has been finished and of width equal to the width from the mother coil. Once formed, the log is led to a sawing station where it is sawed. Finally the rolls obtained are guided to the packing stations, packaging and storage.

According to the invention, the tension of one of the two bands is adjusted cellulose wadding relative to the other upstream of the station where the folds are bound to one another. This is to allow the lower fold to retract more than the other when the tensions are released. To this end, a drawing group can be provided (arranged upstream of the station where the two folds are linked to each other). Slowing down for example the speed of the lower fold from 0.6% to 2% compared to the speed of the embosser, we remain in the elastic deformation range and we increase the level of fold tension. When this tension is subsequently released, the lower fold proportionally retracts and the pads form on the surface of the upper fold. In particular, when the bottom fold is not embossed as shown in the figure 3. The tension difference between the lower fold and the upper fold is then created by embossing which changes the physical characteristics of the top fold. The lower fold retaining its elasticity, it will retract more.

We produced products according to this process, and measured the differences in length between the two folds.

• mesurer la longueur de 10 coupons consécutifs sur un rouleau,
• séparer les deux en faisant attention à ne pas déchirer le papier aux points de collage ni l'étirer au-delà de sa limite de déformation élastique, et
• étaler les deux plis sous une règle métallique et mesurer l'écart de longueur en sens marche.

The measurement method consisted in:

• measure the length of 10 consecutive coupons on a roll,
• separate the two, being careful not to tear the paper at the gluing points or stretch it beyond its limit of elastic deformation, and
• spread the two folds under a metal ruler and measure the length difference in the running direction.

To calculate the relative percentage deviation (ER) of length between the folds, we has taken into account that the outer fold is longer when winding.

L1 est la longueur de 10 coupons, et D1 le diamètre initial du rouleau.

L2 est l'écart de longueur mesuré entre les deux plis, D2 le diamètre après avoir enlevé 10 coupons.

Din est le diamètre du mandrin, N le nombre de feuilles initial, et L la longueur unitaire d'un coupon.

We apply the formula: ER = (100 / L1x {L2-L1x (D1 2 -DIN 2 ) / [(D1 + D2) x2xNxL]}, where the parameters are defined below:

L1 is the length of 10 coupons, and D1 the initial diameter of the roll.

L2 is the length difference measured between the two folds, D2 the diameter after removing 10 coupons.

Din is the diameter of the mandrel, N the initial number of sheets, and L the unit length of a coupon.

Example 1

Grammage 40.3 g/m².

Résistance sens marche : 215 N/m. Il s'agit de la valeur de la force nécessaire pour rompre une éprouvette découpée dans le sens marche de la feuille, ramenée à un mètre de largeur.

Résistance sens travers : 75 N/m. idem ci-dessus, mais l'éprouvette a été découpée dans le sens perpendiculaire au précédent.

Taux d'allongement à la rupture : 16 %.(mesuré dans le sens marche)

Two products were made with the same cellulose wadding, the characteristics of which are as follows (measurements made on 2 plies):

Weight 40.3 g / m ² .

Resistance in running direction: 215 N / m. This is the value of the force necessary to break a test piece cut in the running direction of the sheet, reduced to one meter in width.

Cross direction resistance: 75 N / m. same as above, but the test piece was cut in the direction perpendicular to the previous one.

Elongation rate at break: 16%. (Measured in the running direction)

The products were produced according to the process described above. The fold upper was embossed according to the pattern shown in Figure 1, the lower fold was not waffle.

We made a first product by applying a voltage difference between the folds, so that the final product has a marked cushioning effect. We have manufactured a second product by reducing the tension difference between the two plies of such so that the final product does not have a cushioning effect.

Premier produit : 1.12%

Second produit : 0.23%

Ten measurements were made on each of the products. The relative mean deviations measured are as follows:

First product: 1.12%

Second product: 0.23%

Example 2

In order to evaluate the previous analysis method and to check if the result obtained is significant, a third product was produced by embossing two plies together according to the pattern in Figure 1. The cellulose wadding had the following characteristics: grammage , 40.3 g / m ² ; resistance MD, 215 N / m; CD resistance, 75 N / m; with an elongation rate at break of 16%.

Ten measurements were made on the product. Relative average deviations measured were 0.15%. This allows to conclude that the difference in length measured between two products, one of which has a cushioning effect and the other is not significant.

Claims (10)

Sheet of paper consisting of at least two plies (10, 20) of creped cellulose wadding, an upper ply (10) and a lower ply (20), each of grammage between 10 and 40 g / m ² , the upper fold (10) being embossed and provided with first protrusions (12), characterized in that said first protrusions (12) are distributed in alignments (14) which delimit between them cells (16) having a surface area between 1 and 20 cm ² , the upper fold (10) being longer in the forward direction than the lower fold (20) by at least 0.6%, preferably from 0.6 to 2%, and linked to it by the top of the first protrusions (12) in such a way that pads are formed inside the cells (16). Sheet of paper according to the preceding claim, characterized in that the cells (16) have a length / width ratio of between 1 and 5, preferably between 1 and 1.5. Sheet of paper according to one of the preceding claims, characterized in that the distance between two adjacent protrusions (12) along an alignment (14) is not more than 3 mm, preferably not more than 1.5 mm. Sheet of paper according to the preceding claim, characterized in that the protrusions (12) are of frustoconical shape, with a diameter at the base between 1 and 3 mm, preferably between 1 and 1.5 mm. Sheet of paper according to one of the preceding claims, characterized in that the alignments (14) are arranged in two different directions defining between them said cells (16). Sheet of paper according to one of the preceding claims, characterized in that it is in the form of a roll. Method for manufacturing a sheet according to one of the preceding claims, characterized in that it comprises the following steps: a first strip (10) of cellulose wadding is unwound from a master roll and it is embossed on an embossing cylinder (102) in a pattern with first protuberances forming alignments which define closed cells therebetween, a second strip (20) of cellulose wadding is unwound from a mother reel, the second strip is applied to the first and the two strips are linked by the tops of the first protrusions (12), the two strips (10, 20) being differentiated at the time of the connection of the folds so that, at rest, the length of the pleats is different by at least 0.6%, preferably from 0.6 to 2%, the double strip obtained is wound around a mandrel by exerting a tension, and the said roll is cut into smaller rolls. Method according to the preceding claim, characterized in that the folds are differentiated from one another according to the following characteristics taken individually or in combination: the speed of unwinding, the tension in the running direction, the depth of the embossing, elasticity. Method according to one of claims 7 or 8, characterized in that the two plies are bonded by applying glue (106) to the tops of the first protrusions. Method according to one of claims 7 or 8, characterized in that the two plies are bonded by mechanical pressure on the tops of the first protrusions.

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