The invention also relates to a method of embossing layers and joining them by lamination-for the-production of a web material comprising at least two layers; for example, but not exclusively, made of paper material, in which at least one of the layers is embossed, and a method in which both layers are embossed separately and then joined with at least partial nesting of the protuberances of one layer between corresponding protuberances of the other layer.

Finally, the invention relates to a web material comprising at least two layers, at least one of which is embossed, joined together.

Prior art In many applications, particularly in the production of toilet paper, absorbent paper, paper towels and other paper products, especially, but not exclusively, made from what is known as"tissue"paper, in order to obtain a web material of sufficient strength, thickness, softness and absorption characteristics, at least two layers are embossed separately from each other to produce corresponding sets of protuberances in any pattern on them. When thus embossed, the two layers are then joined and laminated, following the application of an adhesive to the protuberances of one of the layers.

According to a first method, the two layers are joined with the protuberances of one layer coinciding with the protuberances of the other.

This is known as tip-to-tip joining.

According to a different method, to which the present invention relates, the two layers are joined and laminated with the protuberances of one layer positioned so that they are nested between the protuberances of the other layer. In this case a so-called a nested product is obtained. A device, a

method and the corresponding product obtainable by this second method are described, for example, in US-A-3, 556, 907 and US-A-3, 694, 300.

In practice, a device for embossing and lamination by the nesting method comprises: a first embossing cylinder provided with a first set of points on its surface and interacting with a first pressure roller; a second embossing cylinder provided with a second set of points on its surface and interacting with a second pressure roller, positioned with its axis parallel to the axis of the first embossing cylinder. The two embossing cylinders are close to, but separated from, each other. The first embossing cylinder is also associated with an adhesive dispenser which is used to apply an adhesive to the protuberances of a first layer, embossed between the first embossing cylinder and the first pressure roller. Downstream of the nip between the two embossing cylinders there is a laminating roller (called a"marrying roll') which interacts with the first embossing cylinder. A second layer, embossed between the second embossing cylinder and the second pressure roller, is detached from the second embossing cylinder and supported on the layer running around the first embossing cylinder before the two layers pass into the laminating nip between the first embossing cylinder and the laminating roller.

The arrangement is such that the protuberances of the second embossed layer become nested between the protuberances of the first embossed layer and in this configuration the two layers are laminated and therefore permanently joined together by the action of the adhesive applied to the protuberances of the first layer and by the lamination.

Objects of the invention Particularly in the field of the production of tissue paper articles, a high degree of softness and yieldingness of the product is required at the present time. This requirement is limited by the need to fix the embossed layers together permanently to prevent one layer from being detached from the other before use. For this purpose, the adhesive is applied and the lamination of the two layers is then carried out. The application of the adhesive and the subsequent lamination on all the points make the product relatively stiff and hard.

The object of the present invention is to provide a device and a process which can be used to obtain an embossed product, for example, but not exclusively, of the nested type, which is softer than the conventional products and which at the same time ensures a permanent fixing between the layers.

Brief description of the invention This and other objects and advantages, which the following text will make clear to those skilled in the art, are obtained according to the invention with an embossing and laminating device comprising: -at least a first embossing cylinder provided with a first set of points on its surface and interacting with a first pressure roller; -an adhesive dispenser interacting with said first embossing cylinder; -a laminating roller interacting with said first embossing cylinder, for laminating said layers between the laminating roller and the points of the first embossing cylinder and for joining them together, characterized in that the laminating roller has a cylindrical surface with at least one recessed area, in which it does not press on the points of the first embossing cylinder.

Thus, after the adhesive has been applied to the protuberances obtained by embossing on one of the two layers, the two superimposed layers are laminated in areas, and more precisely in the non-recessed areas of the laminating roller. At the positions of the recessed areas of the cylindrical surface of the laminating roller, there is no lamination and therefore no adhesion of the two layers to each other. The adhesive, which can also be applied to all the protuberances of the first layer, penetrates between the fibers of the two layers, causing them to adhere to each other, only in the areas which are laminated by the laminating roller and therefore not at the positions of the recessed area or areas of the laminating roller. In these areas, although the adhesive is present, it does not cause stiffening of the material, or causes it only to a negligible extent, thus producing a softer and more yielding material.

In an improved and preferred embodiment, the device also has a

second embossing cylinder, provided with a second set of points on its surface, and a second pressure roller interacting with this. The device formed in this way is capable of separately embossing two layers, which are then superimposed on each other with one of the two layers retained on the first embossing cylinder and the second layer detached from the second embossing cylinder in such a way that it is superimposed on the first layer, with at least partial nesting of the protuberances, in other words with at least some protuberances of the second layer nested between protuberances of the first layer. If the second_ layer is not passed between the second embossing cylinder and the second pressure roller there will be a product in which one of the layers is embossed and the other is smooth. In this case also, the advantages of the present invention are at least partially obtained.

Essentially, the invention provides a method of embossing and lamination for producing a laminated material with at least two layers of web material, comprising the steps of: -embossing at least a first of the two layers to create a first set of protuberances on it; -applying an adhesive to at least some of the protuberances of said first layer; -positioning said layers one above the other; -laminating said two layers to join them by gluing; characterized in that said two layers are not laminated along at least one of their portions.

In a particularly advantageous embodiment of the method according to the present invention, both the layers are embossed with a first and a second set of protuberances respectively, and are then joined with at least some protuberances of one layer nested between protuberances of the other layer.

The non-laminated area can comprise, for example, between 30% and 70% of the total surface of the laminated material, although values outside this range can be used in some cases. An increase in the non- laminated surface is accompanied by an increase in the yieldingness of the

material.

Essentially, the invention is used to produce a web material comprising at least two layers, at least one of which is embossed, and which are joined together by gluing and lamination, characterized in that at least one portion of said layers is not subject to lamination, and in this portion the two layers are not glued to each other. The term"lamination"denotes the passage of the layers between two members which exert a pressure for joining the layers to each other by gluing.

In a possible embodiment, a first layer is embossed while the other is smooth, but in a preferred embodiment both layers are embossed with a first and a second set of protuberances respectively; at least some of the protuberances of one set are nested between protuberances of the other set.

It is also possible to prevent the application of the adhesive in the non-laminated areas, for example by a suitable configuration of the adhesive dispenser.

Further advantageous characteristics and embodiments of the invention are indicated in the attached claims.

Brief description of the drawings The invention will be more clearly understood from the description and the attached drawings which show a possible non-restrictive embodiment of the invention. More particularly, the drawings show the following: in Fig. 1, a schematic side view of an embossing and laminating device; in Fig. 2, a perspective view of a portion of the laminating roller; in Fig. 3, a schematic, highly enlarged, local section of a portion of web material according to the invention; in Fig. 4, a perspective view of a portion of the laminating roller in a different and improved embodiment; and in Fig. 5, a schematic, highly enlarged, local section of a portion of web material produced by the laminating rol ! er of Fig. 4.

Detailed description of the preferred embodiment Fig. 1 shows schematically the general structure of the embossing

and laminating device. It comprises a first and a second embossing cylinder 1, 3, each of which is provided with a corresponding set of first and second points indicated by 1 P and 3P. The first embossing cylinder 1 interacts with a first pressure roller 5, for example a rubber-coated roller, while the second embossing cylinder 3 interacts with a second pressure roller 7. The two embossing cylinders 1, 3 are positioned with their axes parallel in such a way as to form a nip between them, indicated by 8, but are positioned with a spacing between the axes 1A and 3A and/or a timing arrangement such that the points 1 P and 3P do not touch each other.

The first embossing cylinder 1 is also associated with an adhesive applicator, indicated in a general way by 9, and a laminating roller 11.

A first layer V1 of material to be embossed is fed around the first pressure roller 5 and is embossed between this roller and the embossing cylinder 1, in such a way as to form a set of protuberances P1 on the layer.

Similarly, a second layer V2 is run around the second pressure roller 7 and is embossed between this and the second embossing cylinder 3 to form a plurality of protuberances P2 on this layer (Fig. 3).

Along its path around the circumferential development of the first embossing cylinder 1, the layer V1 receives, on the protuberances formed by embossing, an adhesive applied by the applicator 9. This applicator has, in the illustrated example, a roller 9A which collects the adhesive from a vessel 9B and transfers it to an application roller 9C. The rollers 9A and 9C can be such that the adhesive is applied to all the protuberances of the layer V1 or to only some of them, for example by making the roller 9C have recessed annular areas which do not receive the adhesive from the roller 9A and therefore do not transfer adhesive to the layer V1.

In the area of the nip 8 between the embossing cylinders 1 and 3, the second layer V2 embossed between the second embossing cylinder 3 and the second pressure roller 7 is detached from the second embossing cylinder 3 and placed on the first layer V1 which. is still on the surface of the first embossing cylinder 1. The timing between the two cylinders 1, 3 is such that the protuberances P2 formed on the second layer V2 become nested between

the protuberances P1 formed on the first layer V1. Alternatively, it is possible to arrange for the two embossing cylinders 1, 3 to be spaced apart sufficiently in such a way that the layer which is detached from the embossing cylinder 3 comes to have at least some of its protuberances nested between corresponding protuberances of the layer which is located on the first embossing cylinder 1, as a result of the tension and elasticity of the layer. In this case it is not necessary for the two cylinders 1, 3 to be timed precisely, but it is also possible that they may be connected mechanically by a belt transmission which does not provide precise timing of the two cylinders.

The two layers superimposed in this way are then laminated between the first embossing cylinder 1 and the laminating roller 11, the latter exerting a pressure on the points 1 P of the first embossing cylinder 1.

Characteristically, according to the invention, the laminating roller 11 has a discontinuous cylindrical surface, with recessed areas, as shown schematically by way of example in Fig. 2. In this example of embodiment, the laminating roller 11 has a recessed helical strip 11A. Thus the action of lamination of the two layers V1 and V2 takes place only at the position of the non-recessed surface of the roller 11, in other words with the exclusion of the recessed strip 11A. In the area where the two layers V1 and V2 are not laminated together, there is no adhesion of the layers to each other, despite the presence of adhesive on the protuberances P1 of the first layer V1. The result of this is shown schematically in Fig. 3, where the lamination of the two layers and consequently their adhesion to each other has taken place at the positions of the protuberances P1 indicated by"A", by the action of the adhesive C which has penetrated into the fibers forming the two layers.

Conversely, at the positions of the protuberances P1 indicated by"NA", there has been no lamination of the layers V1 and V2 to each other-the adhesive C has remained essentially wholly on the layer V1 and has dried there without penetrating between the fibers of the two layers, and particularly without penetrating between the fibers of the layer V2.

The two layers V1, V2 thus have no adhesion to each other within strips inclined with respect to the direction of feed, and corresponding to the

recessed helical strip 11A of the laminating roller 11. This makes the web material M softer and more yielding than is the case with conventional methods and devices, where the lamination takes place over the whole surface of the layers, with consequent adhesion of all the protuberances P1 to the layer V2.

The recessed area of the laminating roller 11 can also have a different shape from the helical shape shown in Fig. 2. For example, recessed strips with an annular development can be provided. In this case, it is possible to provide a similar configuration of the adhesive applicator roller 9C, so that the protuberances P1 corresponding to the recessed annular strips are free of adhesive. This provides a saving of adhesive and a further improvement (although only a modest one) in the softness and yieldingness of the product.

However, the improvement is limite, since the positive effect of an increase in the softness and yieldingness of the web material depends primarily on the absence of lamination and not on the absence of application of adhesive.

On the other hand, the use of recessed areas with a helical development has the advantage of making the operation of the machine more uniform and of preventing wear and concentrated accumulations of residues on the embossing cylinder 1.

In a preferred embodiment, shown in detail in Fig. 4, the laminating roller 11 has a series of recessed areas 11 A configured as a series of helical grooves, in other words as a multiple-start helix, in order to achieve a greater uniformity of the characteristics of softness and yieldingness of the product, and also in order to ensure adhesion between the two layers over the whole development of the web material. Each recessed area thus has a limited width, but the sum of the recessed areas is approximately of the same order of magnitude as the sum of the non-recessed areas, in other words those at the position of which the lamination of the two layers takes place. Ultimately, given a sufficiently small dimension of the lowered areas (in respect of width) it is possible to reach a situation in which there is a 1: 1 ratio between the laminated and non-laminated protuberances in cross section, as shown schematically in Fig. 5. This can be achieved, for example, with a recessed

area in the form of a helix with approximately fifty starts, with a transverse dimension of, for example, 5-10 mm. Advantageously, it is possible to have the laminating roller 11 divided transversely into two equal parts, provided with recessed helical areas 11A orientated in opposite directions, so that it also has a widening action.

The illustrated device can also produce a web material in which the layer V2 is not embossed. This is achieved by feeding the layer V2 directly to the cylinder 1, downstream of the point of application of the adhesive. In a simplifie version, the second embossing cylinder 3 and the corresponding pressure roller can be eliminated, if a machine which always produces material with only a single embossed layer is required.

It is to be understood that the drawing shows only an example of embodiment of the invention, which can be varied in its forms and arrangements without departure from the fundamental principle of the invention.