The present invention relates to a multilayer product of paper-like material, in particular of the cannete or of the corrugated cardboard type, that is particularly, but not exclusively, indicated for the provision of enclosures, containers and packaging.

It is known that a sheet of flat paper is extremely flexible along all directions.

For some time on the market there have been products, known as “cannete”, constituted by one tensioned layer of paper-like material and one corrugated layer bonded thereto, which generally are slender and have the advantage of high rigidity in the barrel direction of the flutes and great flexibility in the direction of undulation of the flutes, to the point where they can be easily rolled up.

If the cannete is covered with another flat layer, this results in the product that is normally known by the name “corrugated cardboard”, which has good rigidity but cannot be rolled up.

Another possible conventional solution is to superimpose multiple layers levels of cannete Bl, B2, B3 on each other so as to obtain a corrugated cardboard Al, A2 with several superimposed corrugations, wherein, in any case, each corrugation is formed from a single undulated flat sheet.

In the packaging sector, the need is felt to develop multilayer products of paper-like material of the corrugated cardboard or cannete type which have the best possible robustness.

As is known, the following three coefficients are normally used in measurements of robustness for this type of multilayer products made of paper-like material:

- The Edge Compression Test (ECT) coefficient, which serves to determine the capacity for resistance to vertical compression of a strip of corrugated cardboard in the barrel direction of the flutes;

- The Box Compression Test (BCT) coefficient, which, similarly to the previous coefficient, identifies the resistance to vertical compression of an empty box and therefore serves to correlate this value with the resistance to real-world stacking conditions that packaging materials are subjected to in a warehouse;

- The Flat Compression Test (FCT) coefficient, which is an index of the resistance of a corrugated cardboard to a force applied in a direction perpendicular to the flat surface under specific conditions.

The aim of the present invention consists of providing a multilayer product of paper-like material, in particular of cannete or of the corrugated cardboard type, that has better mechanical characteristics and, in particular, better robustness than the background art.

Within this aim, an object of the present invention is to provide a multilayer product of paper-like material, in particular of the cannete or of the corrugated cardboard type, that has a higher value for at least one of the ECT, BCT, and FCT coefficients than the prior art.

Another object of the invention consists of providing a multilayer product of paper-like material, in particular of the cannete or of the corrugated cardboard type, that is easy to implement and economically competitive.

Another object of the invention consists of making available a valid alternative to the prior art.

This aim and these and other objects which will become better apparent hereinafter are achieved by a multilayer product according to claim 1.

This aim and these and other objects which will become better apparent hereinafter are also achieved by a method according to claim 9.

Further characteristics and advantages of the invention will become better apparent from the description of some preferred, but not exclusive, embodiments of a multilayer product, which are illustrated by way of non limiting example with the aid of the accompanying drawings wherein:

Figure 1 is a cross-sectional view of a first multilayer product according to the prior art; Figure 2 is a cross-sectional view of a second multilayer product according to the prior art;

Figure 3 is a perspective view of a first embodiment of a multilayer product according to the invention;

Figure 4 is a cross-sectional view of the multilayer product of Figure 3;

Figure 5 is a cross-sectional view of a second possible embodiment of the multilayer product according to the invention;

Figure 6 is a cross-sectional view of a third possible embodiment of the multilayer product according to the invention; Figure 7 is a cross-sectional view of a fourth possible embodiment of the multilayer product according to the invention.

With reference to the figures, the multilayer product of paper-like material, generally designated by the reference numeral 1, 10, 100 or 1000 according to the embodiment, is “of paper-like material”, i.e. its main components (i.e. the sheets or layers of which is composed, which will be described below) are mainly made of paper-like material, which does not rule out the presence within it of other, complementary materials, such as for example adhesives or plastic materials.

The term “paper-like material” means any type of paper or cardboard made available by the state of the art.

In particular, the multilayer product 1, 10, 100 to which reference is made can be considered, according to the embodiments, to be of the cannete or of the corrugated cardboard type, and is therefore particularly adapted for providing packaging, boxes and similar applications.

Similarly to the prior art referred to, the multilayer product 1, 10, 100, 1000 can be made of panels or sheets of any extension. In some embodiments, like the one shown in Figure 5, the multilayer product 1 can be stored in rolls.

The multilayer product 1, 10, 100, 1000 comprises at least one corrugated layer 3, 3’ bonded to (i.e. fixed, preferably glued or heat- welded) to a first flat layer of cannete 2, 2’.

According to the invention, such at least one corrugated layer 3, 3’ is constituted in turn by a sheet of cannete which is shaped so as to form a wave (i.e. it has been fully undulated).

Therefore, the corrugated layer 3, 3’, does not consist of a single undulated flat sheet as in the background art, but of a sheet of cannete which has been shaped so as to form a wave.

As will be described below, this corrugated layer 3, 3’ is in practice obtained starting from a conventional sheet of cannete, which is undulated by shaping it so as to form a wave.

The Applicant has in fact experimentally discovered that by making the corrugated layer with material that is in turn corrugated, the mechanical characteristics of the multilayer product significantly improve.

As is known, a sheet of cannete is a sheet constituted by a tensioned layer of paper-like material and a corrugated layer bonded thereto.

Therefore, the sheet of cannete that constitutes the corrugated layer 3, 3’ and which is shaped so as to form a wave, comprises in turn a corrugated sheet 32 fixed to the surface of a tensioned sheet 31 which is in turn shaped so as to form a wave, and therefore the corrugated sheet 32 extends along a wave; it is to be noted that the amplitude and the wavelength of the wave of the tensioned sheet 31 are greater than the amplitude and the wavelength of the corrugated sheet 32.

All the corrugated layers 3, 3’ to which reference will be made from this point onward, and in the accompanying claims, have the above characteristics deriving from the fact that they are constituted by a sheet of cannete which has been shaped so as to form a wave.

In some embodiments, such as the one shown in Figure 5, there is a single corrugated layer 3 bonded to a single flat layer of cannete 2 and therefore the corrugated layer 3 is free on one of its two faces, and therefore, similarly to sheets of conventional cannete, the multilayer product 1 can be rolled up and therefore this embodiment can be likened, functionally, to cannete.

In other embodiments, like those illustrated in Figures 3, 4, 6 and 7, the at least one corrugated layer 3, 3’ is comprised between a first flat layer of cannete 2 and a second flat layer of cannete 4, 4’.

In practice, when a second flat layer of cannete 4 is added to the embodiment shown in Figure 5 by fixing it to the other side of the corrugated layer 3 opposite from the first flat layer 2, a multilayer product 10 in the embodiment of Figure 3 and 4 is obtained.

The multilayer product 10, 100 of the embodiments illustrated in Figures 3, 4 and 6, which comprise a single corrugated layer 3 comprised between two flat layers 2, 4 of cannete, can be functionally likened to corrugated cardboard with a single corrugated layer.

Note that in these embodiments, the corrugated layer 3 (constituted by a sheet of cannete) is fixed directly to the first flat layer of cannete 2 and to the second flat layer of cannete 4.

In yet other embodiments, such as for example that of Figure 7, the multilayer product 1000 comprises two or more superimposed corrugated layers 3, 3’ which are preferably comprised between a first 2 and a second 4’ flat layer of cannete.

Even more preferably, an intermediate flat layer of cannete T is interposed between the above mentioned two superimposed corrugated layers 3, 3’.

In more detail, in the embodiment shown in Figure 7, the multilayer product 1000 comprises, in this order: - a first flat layer of cannete 2;

- a first corrugated layer 3 fixed to the first flat layer of cannete 2;

- an intermediate flat layer of cannete T fixed to the first corrugated layer 3 ;

- a second corrugated layer 3’ fixed to the intermediate flat layer of cannete 2’;

- a second flat layer of cannete 4’ fixed to the second corrugated layer 3’.

As previously clarified, each one of the above mentioned corrugated layers 3, 3’ is constituted by a sheet of cannete which is shaped so as to form a wave.

In practice, by superimposing two multilayer products 1, 10, 100 which comprise a single corrugated layer 3 (like those of Figures 3-6) on each other and fixing them to each other, a multilayer product 1000 is obtained with two corrugated layers such as for example that of Figure 7.

Obviously other embodiments are also possible in which, in a manner that is obvious in light of the foregoing description, further corrugated layers and/or further flat layers of cannete are superimposed.

In any embodiment, the corrugated layer 3, 3’ can present the corrugations of the corrugated sheet 32 protruding toward the inside (as in Figure 6) or toward the outside (as in Figures 4 and 5) of the large wave formed by the tensioned sheet 31, according to the implementation choices.

In practice, in some embodiments (as in Figures 4 and 5), in the corrugated layer 3, the corrugated sheet 32 is fixed to an external surface of the tensioned sheet 31 so as to protrude toward the outside of the wave formed by the tensioned sheet 31; in this case the second flat layer of cannete 4, 4’ is fixed to the corrugated sheet 32 (to the crests of the wave thereof).

In other embodiments (as in Figure 6), in the corrugated layer 3, the corrugated sheet 32 is fixed to an internal surface of the tensioned sheet 31 so as to protrude toward the inside of the wave formed by the tensioned sheet 31; in this case the second flat layer of cannete 4, is fixed to the tensioned sheet 31 (to the crests of the wave thereof).

In a multilayer product 1000 with multiple superimposed corrugated layers 3, 3’, a first corrugated layer 3 can present the corrugations of the corrugated sheet 32 protruding toward the inside and a second corrugated layer 3’ can present the corrugations of the corrugated sheet 32’ protruding toward the outside.

The multilayer product 1, 10, 100, 100 can be easily produced by way of a method that comprises the following steps: a) supplying two or more flat sheets of cannete; b) undulating at least one of the flat sheets of cannete so as to obtain a sheet of cannete shaped so as to form a wave| this shaping of the flat sheets of cannete can for example be obtained by way of a corrugation process and an apparatus as described in EP16705439; c) fixing the sheet of cannete shaped so as to form a wave to a first flat sheet of cannete.

After these steps, a corrugated layer 3 is obtained which is constituted by the sheet of cannete shaped so as to form a wave, bonded to a first flat layer of cannete 2 constituted by the first flat sheet of cannete, and therefore a multilayer product 1 is obtained like that of Figure 5.

Optionally, the following further step can be performed: d) fixing a second flat sheet of cannete to the above mentioned corrugated layer 3 so as to form a second flat layer of cannete 4.

In this manner the corrugated layer 3 is comprised between the first 2 and second 4 flat layer of cannete, thus obtaining a multilayer product like that of Figures 3, 4, 6.

The steps just described can be repeated in order to superimpose more layers.

In order to obtain advantageously a multilayer product 1000 with two or more corrugated layers, such as for example that of Figure 7, the following step can be executed: e) superimposing and mutually bonding two or more multilayer products 1, 10, 100, each one of which is obtained by way of the steps a), b) c) and optionally d).

Preferably all the sheets and the layers are paper.

The operation and use of the multilayer product 1, 10, 100, 1000 according to the invention is entirely similar to that of conventional multilayer products of the cannete or corrugated cardboard type.

Advantageously, the present invention has values of the ECT, BCT, FCT coefficients indicating robustness which are significantly higher than the prior art.

By way of example, it is possible to provide a multilayer product according to the invention, like that of Figure 4, with thin paper of 40-50 g/sq.m., which has mechanical characteristics in terms of robustness that are similar to those that a traditional product made with paper of much greater thickness, of approximately 600 g/sq.m., would (theoretically) have, which - in the state of the art - is not technically possible in that today it cannot be corrugated according to the prior art.

In practice it has been found that the multilayer product according to the present invention achieves the intended aim and objects in that it has a better robustness than the background art, and in particular higher values for the ECT, BCT, FCT coefficients.

Another advantage of the multilayer product according to the invention consists in that it is easy to implement and economically competitive.

Another advantage of the multilayer product according to the invention consists in that it makes available a valid alternative to the prior art.

The multilayer product, thus conceived, is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

Moreover, all the details may be substituted by other, technically equivalent elements. In practice, the materials used, as well as the contingent shapes and dimensions, may be any according to the requirements and to the state of the art.

The disclosures in Italian Patent Application No. 102021000003278 from which this application claims priority are incorporated herein by reference.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs