WO2009113115A1

WO2009113115A1 - Embossed multi-ply paper material and embossing unit for the production thereof

Info

Publication number: WO2009113115A1
Application number: PCT/IT2009/000079
Authority: WO
Inventors: Mauro Gelli
Original assignee: Fabio Perini S.P.A.
Priority date: 2008-03-11
Filing date: 2009-03-03
Publication date: 2009-09-17
Also published as: EP2252455B1; ES2635962T3; ITFI20080047A1; EP2252455A1

Abstract

The web material comprises an edge area with preferably linear protuberances (PA, PC), disposed so as to mutually intersect and be joined tip-to-tip. In the central. area, inside a frame or parallel longitudinal edges embossed tip-to-tip, the material presents a decorated embossed area (PD). In the central area and in the edge area glues with different chromatic characteristics are used to mu¬ tually join the plies obtaining a chromatic decorative effect.

Description

ΈMBOSSED MULTI-PLY PAPER MATERIAL AND EMBOSSING UNIT FOR

THE PRODUCTION THEREOF" DESCRIPTION

Technical Field The present invention relates to a new multi-ply paper material, in particular made of tissue paper, for the production of napkins, handkerchiefs, rolls of toilet paper or kitchen towel and the like.

The invention also relates to improvements to embossing units for embossing sheets of tissue paper intended for the production of an embossed multi-ply paper material. State of the art

In the field of disposable paper materials, such as disposable napkins and handkerchiefs, toilet paper, kitchen towels for domestic or industrial use, the production of multi-ply materials is known, i.e. materials composed of two or more plies typically bonded by gluing, in which one or more of the plies forming the paper material are embossed to obtain decorative and/or technical- functional effects.

In the production of napkins of other products formed by folded sheets one of the problems that occurs is represented by the uneven thickness of the paper material, which causes difficulties in forming piles of folded napkins and consequently in their packaging. Moreover, in this type of article there is the further drawback of accidental reciprocal detachment of the plies along the edges with consequent forming of portions, which can bend accidentally during packaging, giving rise to defects in the finished pack. Moreover, in the production of disposable articles, there is a tendency to design versatile machines, i.e. which with minimum modifications on the production line can supply products with different aesthetic appearances, to modify the production in time or also to simultaneously produce products with aesthetic appearances varying from one another, so as to produce multi-product packs with particular aesthetic appeal characterized by the presence of articles with colors and/or patterns differing from one another. Objects and summary of the invention

According to one aspect, the invention proposes a new multi-ply embossed paper material, which entirely or partly overcomes one or more of the drawbacks of known materials and/or which provides improved aesthetic and/or technical-functional characteristics.

According to one embodiment the multi-ply material comprises at least a first ply and at least a second tissue ply embossed and bonded by gluing, wherein: along at least one edge portion the first ply and the second ply have a tip- to-tip embossing, at which said first and second ply are bonded with a first glue at protuberances facing each other and inside the multi-ply material; in a central portion the first ply is provided with a central embossing with protuberances facing the inside of the multi-ply material and the second ply is provided with a decorative embossing with protuberances facing the inside of the multi-ply material, in said central portion the two plies being glued tip-to-tip with a second glue at mutually coinciding contact surfaces of protuberances of the central embossing of the first ply and protuber- ances of the decorative embossing of the second ply; the first glue and the second glue have different characteristics to each other.

The edge portions can form a frame which delimits a central portion, or two bands parallel to two edges, between which a central area is arranged. The glues can advantageously have different chromatic characteristics, for example different colors or different densities of the same color, to obtain particularly interesting decorative effects, and a considerable variety of products also with a single pair of embossing rollers. According to a different embodiment, however, the glues can differ from each other with regard to other technical and func- tional characteristics. For example, a first glue can be denser and more adhesive to obtain more effective adhesion of the two plies also in the presence of reciprocal contact surfaces of limited extension. The other glue can instead be less dense, i.e. obtained with a greater dilution in water or other solvent, to obtain weaker adhesion. This can be useful in areas that are highly embossed which receive the second glue and where, if the second glue were as dense as the first, the finished product would be excessively stiff.

As it is known to those skilled in the art, tip-to-tip embossing or joining of two or more embossed plies is intended as joining or embossing in which the protuberances of one ply, oriented towards the inside of the multi-ply material, are placed directly opposite and coinciding with protuberances of the other ply, also oriented towards the inside of the multi-ply article. In other terms, the two plies are in contact at the front surfaces of directly opposite protuberances ori- ented towards the inside of the product.

The definition of tip-to-tip embossing or joining also includes cases in which only some of the tips or protuberances of one ply coincide with tips or protuberances of the other, and also cases in which the protuberances of the two plies coincide only in areas, i.e. in the case in which the protuberances of one and/or the other ply are composed of projecting linear elements which mutually intersect and are superimposed in delimited areas of intersection.

Each ply can have a typical grammage of the plies of tissue paper, for example between 15 and 80 g/m² and more preferably between 30 and 60 g/m². Each ply can in turn be composed of one or more layers of tissue paper depending on the characteristics of weight, strength, absorption capacity, thickness and the like required of the finished product.

It would also be possible for one or more intermediate plies, either smooth or in turn embossed, for example, with background embossing or mi- croembossing, to be interposed between the first ply and the second ply of tis- sue paper embossed and bonded by gluing.

The multi-ply material can be manufactured in individual folded sheets, for example in the form of handkerchiefs, napkins or the like. In this case the tip-to-tip embossed edge portion can preferably surround a central area on the four sides. In this manner the folded article is glued stably and effectively along the entire perimeter edge by tip-to-tip joining of the respective protuberances of the first and of the second ply.

In other embodiments the multi-ply paper material can be manufactured in a roll. In this case the tip-to-tip embossed edge portion is preferably composed of two longitudinal bands extending along the longitudinal edges of the roll of material. It would also be possible to provide further tip-to-tip embossed areas along the transverse perforations which in the roll of product divide one sheet of paper material from the next, where the sheets are individually detachable by tearing along perforation lines. In this last case each sheet is thus glued along the four sides at the tip-to-tip embossing areas of the two. plies with the - A - advantage that the individual sheet does not tend to delaminate, i.e. the risks of one ply becoming detached from the other along the edge area of the single sheet detached from the roll of continuous web material are avoided or in any case limited. With the characteristics of the multi-ply paper material embossed according to the invention, as well as obtaining effective joining along the edge of the article, there is also the further advantage that the various portions of the mate-

,) rial, both the edge and the central portion, substantially present more or less the same thickness, as both along the edge and in the central area both plies of the multi-ply material are preferably embossed with protuberances of the same height. This prevents the typical drawbacks of some folded sheet multi-ply paper materials, in which the edges are thicker than the central area, or vice- versa, due to the technique with which they are embossed and bonded together. The use of colored glues with different chromatic characteristics for the edge portion and for the central portion allows articles characterized by considerable variability of decoration to be obtained. As will be clear from the description below of some embodiments of the invention, it is also possible to obtain embossing units that produce from the same plies, coming from one or more reels, products differing from one another as far as pattern and color distribution is concerned.

Chromatic characteristics of the colored glues must generically be intended as any characteristic of chromatic differentiation, whether determined by the use of different colors, determined by the use of different shades of the same color, or yet again by a greater or lesser intensity, for example obtained with a different dosage of glues of the same color in the different areas or portions of the multi-ply paper material. However, the two glues are preferably differentiated by a different color, thus obtaining an improved effect of chromatic characterization of the finished product. In some embodiments, both glues are colored. Instead, in other embodiments one of the glues can be colorless, while the other glue is colored.

In some embodiments the tip-to-tip embossing of the edge portion of both plies is preferably composed of protuberances of simple and repetitive geometric shape. For example, the protuberances of the two plies in the edge portion can be formed by truncated-cone or truncated-pyramid shaped protuberances. However, in a preferred embodiment the protuberances of the areas with tip-to-tip embossing are composed on both plies or at least on one of the plies by linear protuberances, i.e. characterized by a dimension in length sub- stantially greater than the dimension in width and typically with a length at least ten times, preferably at least 20 times, and more preferably at least 50 times greater than the transverse dimension, i.e. the width. By using linear embossing, adjustment of the embossing unit is simplified, as the difficulties of phasing the embossing rollers that emboss the two plies to be joined are eliminated or substantially reduced.

In fact, when tip-to-tip embossing is composed of single isolated protuberances, for example truncated-cone or truncated-pyramid in shape, the embossing rollers must be phased precisely so that the protuberances of one roller coincide with the protuberances of the other so as to generate plies which are joined correctly tip-to-tip. Instead, when the protuberances are linear, preferably on both plies and thus on both embossing rollers which emboss them, no precise phasing of the embossing rollers is necessary, as in any case the linear protuberances of one roller intersect the linear protuberances of the other, as these linear protuberances are oriented with distinct angular orientations. In this way areas of tip-to-tip superimposition are generated, composed of the intersections of the linear protuberances generated on the two plies and formed by the two embossing rollers. For example, if the linear protuberances have a rectilinear shape, the tip-to-tip joining areas will be composed, for each linear protuberance of one ply, by the points or areas of intersection of this linear protu- berance with coinciding linear protuberances with a different angular orientation of the other ply.

To reduce the transverse stresses which can be generated on the single ply during embossing by linear projections inclined with a helical orientation on the embossing roller, necessary to generate linear and rectilinear embossing protuberances on the embossed ply, in an advantageous embodiment the linear protuberances are oriented with different angular, preferably opposed, orientations in the edge portion and in the central portion respectively.

According to some embodiments, the edge portion can be divided into two areas advantageously separated from each other and the linear protuber- ances can have different and preferably opposed angular orientations in the two separate areas of the edge portion. According to some embodiments, the edge portion can be divided into possibly continuous areas, characterized by linear embossing protuberances oriented according to different and preferably opposed angles, again in order to generate on the ply being embossed a lateral traction force with a substantially null or in any case limited resultant, so that the ply does not tend to pull excessively in transverse direction during embossing.

The background embossing of the central portion of the first ply can advantageously be formed by a simple and repetitive embossing of geometric shape, such as truncated-pyramid or truncated-cone shaped protuberances, but will preferably be composed of protuberances of linear shape and in particular, for example, of rectilinear shape, with an appropriate angular orientation to exert on the ply material during embossing a limited transverse force and preferably tending towards zero. According to a further aspect the invention relates to an embossing unit comprising: a first path for a first ply and a second path for a second ply to be embossed; a first embossing roller cooperating with a first pressure roller; a second embossing roller cooperating with a second pressure roller, said first and second embossing roller being provided with projections defining emboss- ing patterns for a first ply and for a second ply, respectively, fed along said first path and said second path; and said embossing rollers being adjustable in tip- to-tip arrangement to laminate the two plies between the respective projections in a lamination nip defined between said first and said second embossing roller; a first glue dispenser cooperating with said first embossing roller and provided with a first applicator roller to apply a first glue in specific areas of the first ply at projections of the first embossing roller, a second glue dispenser cooperating with said second embossing roller and provided with a second applicator roller to apply a second glue to specific areas of the second ply at projections of the second embossing roller. Further advantageous characteristics of the multi-ply paper material and of the embossing unit according to the invention are indicated in the appended claims and will be described in greater detail with reference to some non- limiting examples of embodiments of the invention. Brief description of the drawings The invention will be better understood by following the description and accompanying drawings, which show practical non-limiting embodiments of the invention. More in particular, in the drawings:

Fig.1 shows a diagram of a possible embodiment of an embossing unit according to the invention

Figs.2 and 3 show side views of the two embossing rollers of the embossing unit of Fig. 1 in a possible schematic embodiment;

Figs.2A, 3A, 3B show enlarged local sections according to the lines HA- HA, IIIA-IIIA and IHB-IIIB respectively of Figs. 2 and 3; Figs.4 and 5 show side views of two cliche rollers of the two glue dispensers of the embossing unit of Fig.1 in a possible embodiment;

Fig.4A shows an enlarged local section according to the line IVA-IVA of Fig.4;

Fig.5A shows an enlarged local section according to the line VA-VA of Fig.5;

Fig.6 shows a plan view of a portion of the first ply embossed with an embossing unit according to Figs.1 to 5;

Fig.7 shows a plan view of the second ply embossed with an embossing unit according to Figs. 1 to 5, Figs. 6 and 7 being in different scales; Fig.8 shows a cross section, schematic and not in scale, of the multi-ply material obtained from joining the plies of Figs.6 and 7;

Fig.δA shows a plan view of a napkin obtained with the multi-ply material of Figs.6 to 8;

Fig.9 shows a plan view of a portion of a second ply embossed with a dif- ferent decorative pattern, usable with the embossed ply of Fig.6;

Figs.10A and 10B show side views of a different embodiment of two embossing rollers usable in combination on an embossing unit of the type shown in Fig.1 for the production of a multi-ply web material, specifically intended for the formation of rolls; Figs.11 A and 11B show side views of the cliche rollers of the glue dispensers associated with the embossing rollers of Figs.10A and 10B respectively;

Figs.12A to 12E show schematic views of portions of multi-ply web material obtained with the embossing rollers of Figs.10A and 10B; Fig.13 shows portions of two embossing rollers in a different embodiment; and

Fig.14 shows an enlarged schematic local section of a paper web material produced with an embossing unit similar to that of Fig. 1 , but with the rollers of Fig.13.

Detailed description of embodiments of the invention

With initial reference to Fig.1 , in an embodiment of the invention, an embossing unit generically indicated with 1 can comprise a first embossing roller 3 cooperating with a first pressure roller 5. The first pressure roller 5 has, for ex- ample, a cylindrical surface coated by an elastically yielding material. On the first ply V1 fed along a first feed path into the nip defined by the rollers 3 and 5 an embossing is thus generated as a result of projections provided on the cylindrical surface of the first embossing roller 3 penetrating the elastically yielding layer of the pressure roller 5. The shape of the projections of the embossing roller 3 can be of the type shown in greater detail with reference to the subsequent Figs. 2 to 5.

The embossing unit 1 advantageously includes a second embossing roller 7 provided, similarly to the embossing unit 3, with embossing projections of appropriate shape, which will be described in possible examples of embodi- ment below with reference in particular to Fig.3 and to Figs. 7 and 9. The second embossing roller 7 cooperates with a second pressure roller 9 which, similarly to the pressure roller 5, can be provided with a cylindrical surface coated by an elastically yielding material to emboss a second ply V2 fed along a second feed path through the embossing nip defined by the rollers 7 and 9. A lamination nip 11 , through which the two plies V1 , V2, previously embossed in the embossing nips 3, 5 and 7, 9 respectively, are fed, is defined between the embossing rollers 3 and 7. A respective glue is applied to the protuberances generated by the embossing rollers 3 and 7 on the plies V1 and V2 respectively, to obtain bonding by lamination of the plies V1 and V2 in the lami- nation nip 11.

In some embodiments, for this purpose the embossing unit 1 has a first glue dispenser 13 and a second glue dispenser 15 associated respectively with the first embossing roller 3 and with the second embossing roller 7.

In some embodiments the glue dispensers 13 and 15 have the same config u ration, except as regards the pattern of the cliche rollers, as described below, although it would also be possible to provide glue dispensers 13 and 15 with different configurations from each other.

In some embodiments, each of the glue dispensers 13 and 15 includes a glue reservoir 13A, 15A, in which a respective glue is contained. Advantageously, the two glues have different chromatic characteristics. For example, the two glues can have different colors, one can be colored and the other colorless, or they can present different shades of a same color. The glue is picked up from the reservoir 13A, 15A by means of an anilox roller indicated with 13B for the dispenser 13 and with 15B for the dispenser 15. The anilox roller 13B, 15B transfers the glue to a printing roller or cliche roller indicated with 13C for the glue dispenser 13 and with 15C for the glue dispenser 15.

The cliche rollers 13C and 15C have a surface shaped with raised and lowered portions according to a particular pattern so that instead of applying the glue to all the protuberances generated on the respective plies V1 , V2, it is only applied to some of said protuberances, as will be better explained hereunder with reference to Figs. 4 to 8.

Fig.2 shows a schematic side portion of the first embossing roller 3 in a possible embodiment. One or more areas A1 substantially quadrangular in shape (in the planar development of the cylindrical surface of the roller) are provided along the circumferential extension of the roller 3, wherein the roller has incisions and projections of linear shape and helical inclination. The projections are indicated with 3A. Fig.2A shows an enlargement in a cross section according to line MA-IIA of a portion of the surface of the roller. In this section the structure of the projections 3A can be seen, spaced from one another by notches, grooves or incisions 3B.

The shape of the projections 3A is such that embossing projections with an inclined rectilinear shape, for example with an angle between 20° and 80° and preferably between 30° and 60°, even more preferably around 45° with re- spect to the edges of the ply V1 , will be generated in the area A1 of the ply V1 embossed by the roller 3.

The linear projections 3A have a height H, for example, between 0.5 and 1.8 mm. The width L of the single projection 3A can, for example, be between 0.3 and 1.5 mm. The pitch P between the projections 3A can be between 1 and 5 mm. According to some embodiments, the projections 3A can be arranged with a density between 2 and 10 projections/cm.

On the surface of the embossing roller 3 the areas or portions A1 can be arranged in a number equivalent to one or more along the circumferential ex- tension and in a number of one or more along the longitudinal extension, according to the diamet ric and longitudinal dimension of the embossing roller 3 and to the width of the plies V1 and V2.

According to some embodiments, in the area indicated with B1 surrounding the areas A1 the embossing roller 3 has a plurality of projections 3C which can have, similarly to the projections 3A, a simple geometric configuration. In some embodiments, such as the one shown, the projections 3C have a linear configuration similar to the projections 3A. The dimensions and the pitch, as well as the density of the projections 3C can substantially be of the same order of size as those of the projections 3A. However, the projections 3C are prefera- bly inclined with an opposite angle with respect to that of the projections 3A. For example, if the projections 3A are inclined by 45° with respect to the axis A-A of the roller, the projections 3C can be inclined by 135°.

According to some advantageous embodiments the projections 3A in the areas A1 are separated from the projections 3C in the areas B1 , i.e. the projec- tions 3A and 3C are not mutually joined but preferably spaced apart by a distance, for example corresponding to their width. In this manner a discontinuity is formed substantially having the shape of a square indicated with R which surrounds each area or portion A1. This square R without projections, which can have the shape of a frame, for example 0.01 - 5 mm in width, makes phasing of the rollers less critical, as will be clear from the description below.

Engraving of the cylindrical surface of the embossing roller 7 is described below with reference to Figs. 3, 3A and 3B.

In a similar manner to the embossing roller 3, the embossing roller 7 is also divided into areas or portions, indicated with C1 and Dl More in particular, the areas C1 are composed of squares of shape and dimensions substantially identical to those of the areas A1 , while the area D1 surrounds the areas or squares C1 and extends in a substantially similar manner to the area B1 of the embossing roller 3. In this manner, the embossing rollers 3 and 7 can be phased so that in the lamination nip 11 the areas C1 coincide with the areas A1.

Linear projections 7C are provided in the area D1 surrounding the squares C1 of the roller 7. In some embodiments said projections 7C are substantially equivalent to the projections 3C of the embossing roller 3, but oriented in the opposite direction. In this manner in the lamination nip 11 the linear projections 3C and 7C coincide mutually in intersection areas, each linear projection 7C intersecting a plurality of linear projections 3C and vice versa.

Projections 7B of complex shape, defining decorative patterns, are instead provided in the squares or areas C1. Purely by way of example, in Fig.3 the projections 7B are elliptical in shape, but it must be understood that they can have any pattern. In some embodiments, the projections 7B have a linear extension that is preferably non-rectilinear, i.e. they have a lengthwise extension much greater than the width or thickness. They can define open lines or closed lines, as shown in the example of Fig.3. The height of the projections 7C and 7B, indicated with H1 in Figs. 3A and 3B, is identical, and can be identical or different with respect to the height H of the projections 3A, 3C of the roller 3.

Figs.4 and 5 show a possible embodiment of the cliche rollers 13C and 15C of the two glue dispensers 13 and 15 respectively, suitable to cooperate with embossing rollers designed as shown in Figs. 2 and 3. The cliche roller 13C shown in Fig.4 and in the enlarged detail of Fig.4A has recesses 11 quadrangular in shape (in planar development), the dimension of which substantially corresponds to the dimension of the areas A1 of the embossing roller 3. The surrounding surface indicated with S1 of the cliche roller 13C projects with re- spect to the recesses 11 and surrounds them. In this manner the cliche roller 13C receives the glue from the anilox roller 13B only on the surface S1 and therefore transfers the glue only in the area B1 of the embossing roller 3, the areas A1 remaining without glue. In this manner the ply V1 is embossed by the embossing roller 3 in the nip between the roller 3 and the roller 5 and the protu- berances generated thereon coinciding with the projections 3C of the embossing roller 3 receive glue from the surface S1 of the cliche roller 13C, while the protuberances generated by the projections 3A in the areas A1 remain without glue.

Instead, the cliche roller 15C of the glue dispenser 15 has a surface con- figuration complementary to that of the cliche roller 13C, with projecting portions I2 in the form of squares coinciding according to position and dimension with the squares C1 of the embossing roller 7. The projecting areas I2 of the side surface of the cliche roller 15C are surrounded by a lowered surface S2 which does not receive glue from the anilox roller 15B, which instead distributes a layer of glue on the projecting surface of the raised areas I2. Consequently, the ply V2 embossed in the nip between the embossing roller 7 and the pressure roller 9 receives the glue dispensed from the dispenser 15 on the protuberances generated by the projections 7B, as a result of contact with the projecting surfaces 12, while the protuberances generated by the linear projections 7C of the area D1 of the embossing roller 7 remain without glue.

In the lamination nip 11 between the embossing rollers 3 and 7, the projections 7C and 3C are pressed against each other in a tip-to-tip arrangement compressing, i.e. laminating, the two plies V1 and V2 together. This ensures that the colored glue applied by the cliche roller 13C of the dispenser 13 reciprocally bonds the portions of the plies V1 and V2 corresponding to the surfaces B1 , D1 of the rollers 3 and 7. Instead, the areas of the plies V1 and V2 corresponding to the areas A1 and C1 of the embossing rollers 3 and 7 are bonded by the glue applied by the cliche roller 15C in the areas in which the projections 7B of the embossing roller 7 and the linear projections 3A of the embossing roller 3 coincide.

The multi-ply web material which is obtained by embossing through the embossing unit 1 described above is shown in particular in Figs. 6, 7 and 8.

Fig.6 shows a portion of the ply V1 embossed in the embossing unit 1. In this portion of ply V1 , which could, for example, be a part of a napkin obtained by joining the plies V1, V2, linear protuberances PA generated by the linear projections 3C of the embossing roller 3 are present, inclined by an angle of approximately 45° with respect to the machine direction MD, i.e. the direction of feed of the ply V1 in the embossing unit. The ply V1 also has linear protuber- ances PB inside a frame delimited externally by the protuberances PA. The protuberances PB have a linear shape more or less corresponding to that of the protuberances PA (in particular with regard to pitch and dimension), but an inclination preferably identical and opposite. The square containing the protuberances PB is separated from the frame defined by the protuberances PA by an intermediate area without protuberances. This area corresponds to the area R without projections 3C, 3A of the embossing roller 3.

Fig.7 shows a portion of the ply V2. This has a frame in which linear protuberances PC are distributed, generated by projections 7C of the embossing roller 7. This frame has a dimension substantially equivalent to that of the frame defined by the linear protuberances PA on the ply V1. As can be observed from comparing Figs. 6 and 7, the protuberances PA and the protuberances PC are inclined in opposite directions, so that when they are superimposed they mutually intersect in quadrangular points or areas with dimensions equivalent to the transverse dimensions of the protuberances PA and PC. In these areas reciprocal tip-to-tip bonding of the two plies is obtained.

In the area inside the square formed by the linear protuberances PC the ply V2 has protuberances PD of a shape corresponding to the projections 7B of the embossing roller 7. These protuberances PD have a more complex shape than the linear protuberances PA, PB and PC, as they must form the decorative part of the product. In the example shown in Fig.7 these are lines with a raised circular and/or elliptical shape, projecting towards the inside of the multi-ply material, i.e. towards the ply V1. The protuberances PD are bonded at the front surfaces thereof where these surfaces coincide with the protuberances PB of the ply V1 below. Joining takes place through lamination in the nip 11 between the embossing rollers 3 and 7 in a similar manner, and thus with tip-to-tip bonding, to the mutually intersecting protuberances PC and PA.

Fig.8 shows a greatly schematized and enlarged cross section of the article obtained by joining the plies V1 and V2. The section has been taken along a line parallel to a protuberance PA and thus orthogonal to the protuberances PB of the ply V1 , and to the protuberances PC of the ply V2. CA indicates the reciprocal bonding points along the area of superimposition of the frames defined by the protuberances PA and PC (bonding in the intersections of the linear protuberances PA, PB). CB indicates the areas of superimposition and bonding between the protuberances PD of the ply V2 and the protuberances PB of the ply V1, where bonding between the plies V1 and V2 is obtained with the glue dispensed by the dispenser 15.

Fig.δA schematically shows a plan view of an article M in the form of a napkin formed by a portion of multi-ply web material composed by joining plies V1 and V2 embossed as described above. The napkin, which can be folded along the two fold lines L1 and L2, has a frame embossed and glued tip-to-tip with the protuberances PA, PC and a central square with the protuberances PD on the ply V2 and PB on the ply ,V1. In Fig.δA a portion of the ply V1 in the cen- tral area is removed to show embossing PB of the ply V2 below.

The article thus obtained has: uniform thickness due to the equal heights of the protuberances in the various areas of the ply V1 and of the ply V2; particularly stable gluing along the edges, due to superimposition in very dense points of the lines formed by the protuberances PA and PC; and a central area decorated on one face with the protuberances PD, in which adequate reciprocal gluing of the plies V1, V2 is achieved. Moreover, the article has a particular decorative-aesthetic effect obtained as a result of the chromatic difference between the glues dispensed by the dispensers 13 and 15. More in particular, a first coloration characterizes the frame in which the protuberances PA and PC are located and a second color characterized the central patterns PD.

Besides the advantages mentioned above, the embossing unit 1 also allows articles M differing from one another to be produced, for example by producing the projections 7B of consecutive squares C1 of the embossing roller 7 of different shape and/or dimension and/or distribution from one another. More- over, if the decorative pattern is to be changed between one production batch and the next, it is sufficient to replace the embossing roller 7 with another having projections 7B of another shape, maintaining the embossing roller 3. This substantially simplifies operations to change the product, increasing the flexibility of the machine. Purely by way of example, Fig. 9 shows a portion of a ply V2 similar to the portion shown in Fig.7, but with a different decoration defined by decorative embossing protuberances again indicated with PD, surrounded by a frame defined by linear protuberances PC; the protuberances PD can be surrounded, again in the area surrounded by the frame defined by the protuberances PC, by a background of protrusions of lesser height (not shown in Fig.9), which do not receive glue, but nonetheless ensure that the product has a certain structure after the plies are joined.

Advantageously, the projections 3A and 3C of the roller 3 are both linear and with inverse helical orientation, so that no significant lateral pulling forces are generated on the ply V1. Nonetheless, in some embodiments, it would also be possible to produce in the areas 3A projections of other shapes, not linear and helical, but for example truncated-pyramidal or truncated-conical in shaped, with suitable dimensions, for example densities between 15 and 70 projec- tions/cm² and front surfaces between 0.1 and 1 mm². In this case, the quadran- gular areas A1 in which no helical projections are present are sufficient to prevent generation on the ply V1 of relevant transverse thrusts.

Figs.1OA to 12D show a different embodiment of the invention. In particular, Figs.1OA and 10B schematically show the surface structure of the two embossing rollers of an embossing unit which can be designed, for example, as shown in Fig.1. In the embodiment of Figs.10A and 10B each of the two embossing rollers 3 and 7 is divided into a plurality of portions or sections aligned along the longitudinal extension of the roller. More in particular, the roller 7 has twelve sections or portions indicated with the letters A-M and similarly twelve portions A1-M1 are provided on the embossing roller 3. It must be understood that in actual fact the number of portions into which each roller is divided can differ from that indicated, as the figure shows only one part of the longitudinal extension of the embossing rollers. In the example shown, projections of simple geometric shape forming a background embossing on the respective ply V1 or V2 are provided in the sections A, B, C, D, E, F, H, I, K, L and M of the embossing roller 7 and in the sections A1 , C1 , E1 , F1 , G1 , H1 , 11 , J1 , K1 and L1 of the embossing roller 3. Schematically and by way of example, the portions A, C and A1 , C1 have projections of inclined linear shape and thus extending helically. The sections or portions B, D, E, I, K, L, M, E1 , G1 , 11, J1 , K1 , L1 have individual projections, for example truncated-conical or truncated-pyramidal in shape, while again by way of example the sections or portions F, H, F1 and H1 have protuberances of simple geometric shape extending rectangularly with different orientations (respectively tangential and axial). In the sections or areas G, J, B1 , D1 and M1 projections according to a pattern are instead provided, i.e. of large dimension and with a substantially linear extension identical or similar to the projections 7B of the example of embodiment shown in Fig.3.

The cliche roller 13C of the glue dispenser 13, shown schematically in Fig. 11B and which cooperates with the embossing roller 3 has a series of annular portions of larger diameter indicated with B13, D13, F13, H 13, K13 and M13, which are located in positions coinciding with the sections or portions B1 , D1 , F1 , H1 , K1 and M1 indentified on the embossing roller 3 and have the same axial dimension as these. In this manner, the ply V1 which is embossed by the embossing roller 3 receives glue on the embossing protuberances gen- erated by the projections which are located in the sections B1 , D1 , F1 , H1 , K1 and M1 of the embossing roller 3, while the remaining areas remain without glue.

In a complementary manner, the cliche roller 15C (Fig.11A) of the glue dispenser 15 has annular sections or areas A15, C15, E15, G15, 115 and L15 of larger diameter, with dimension and position corresponding to the sections A, C, E, G, I, J and L identified on the embossing roller 7. In this manner, the ply V2 embossed by the embossing roller 7 will receive glue on the protuberances formed on the ply by the projections which are located in the sections A, C, E, G, I, J and L of the embossing roller 7, while the remaining areas will remain without glue.

Therefore, it can be seen that one or other of the two glues dispensed by the glue dispensers 13, 15 respectively is applied to each longitudinal band defined on the web material V1 , V2 by the areas or sections A-M or A1-M1 identified on the embossing rollers 3, 7. As these glues have different chromatic characteristics, on the multi-ply web material formed by the plies V1 , V2 alternate areas are generated with different colors obtained by the use of colored glues with distinct chromatic characteristics. By winding the multi-ply web material V1 , V2 in an individual log and cutting this into a number of rolls according to equidistant planes T1-T5 (Fig.10A), or cutting the plies V1 , V2 along lines in the positions T1-T5 and winding individual axially aligned rolls, rolls are obtained which, as Figs. 12A-12E show, are characterized by colored embossed patterns with different colors and with different patterns on each roll, due to the different shape of the projections which are found on the various sections of the embossing rollers 3 and 7. In Figs.12A-12E the rolls obtained by cutting the log formed by winding of the multi-ply web material V1 , V2 are indicated with R1-R5. For example, the roll R1 is formed by cutting along the planes T1 , T2 indicated in Fig. 10A and has two longitudinal edge areas formed by geometric embossing of linear shape on the two plies generated by the protuberances of the sections respec- tively A, A1 and C, C1 of the embossing rollers 7 and 3. In these areas the embossing is substantially equivalent to that defined by the protuberances PA and PC of Figs. 6 and 7 described previously; in this particular example, the two longitudinal edge areas have angles opposed to each other. In the central area between the two edge areas embossed and joined tip-to-tip, the ply V1 has the embossing pattern formed by the projections in the section B1 of the embossing roller 3, while the ply V2 has a background microembossing formed by the small projections of geometric shape in the section B of the embossing roller 7. In this area gluing between the two plies is obtained in the positions in which the protuberances of the area B1 and of the area B coincide, the protuberances of the area B1 having received glue from the annular section B13 of the cliche roller 13C.

The rolls R2, R3, R4 and R5 are configured in a similar manner, each having two opposite longitudinal edge areas bonded tip-to-tip with protuber- ances of small dimensions and a central area with protuberances according to a pattern on one ply and background protuberances of small dimensions on the other.

As can be seen from Figs.12A-12E, the edge areas of the rolls can also vary in shape, both on the upper and on the lower ply. For example, in Fig.12A the lines are orientated in opposite directions from one band to the other; in Fig.12B the bands are of different width and have a different subject; in Fig.12C they are wider; in Fig.12D they are of different width but have the same subject. In the same manner the cuts according to the cutting lines TI ₁ T2, T... can be made approximately along the center line of a band with a single subject (such as the cut T2 in Fig.10A) or in proximity of a change of subject (as in the case of cuts T3 or T4). In this latter case it would also be possible to have, on the theoretical cutting line, a neutral area, i.e. without glue and approximately 3-8 mm in width to hide a small inaccuracy in the cut, if this diverges from the theoretical cutting line. It must be understood that the shapes of the protuberances of the plies

V1 and V2 and thus of the corresponding projections of the embossing rollers 3 and 7 can differ with respect to those shown purely by way of example in Figs.10A-12E. For example, linear projections of helical shape similar to those indicated with 3A for the roller 3 in Fig.2 could be provided in the areas B and D of the embossing roller 7. This is also the case for the projections in the areas G1 and J1 of the embossing roller 3.

The embossing rollers 3 and 7, and the respective cliche rollers 13C, 15C can also be inverted to modify the appearance of the finished product, whether this is in the form of folded article or a roll. By way of example, with the embossing rollers engraved as in Figs. 2 and 3, if the roller 7 is considered to emboss the upper ply and the roller 3 to emboss the lower ply, a napkin or a roll is obtained in which the central pattern is visually pronounced, while the frame or side bands are more visually subtle, as the colored glue is distributed on the lower ply.

Instead, by inverting the rollers, or folding or winding the paper in the opposite direction, products are obtained with the central part decorated in transparency, but with improved sensorial effect due to the lack of glue in the more widely used central part, and perfectly defined side bands. In general, a multi-ply web material is obtained in which edge areas and central areas are reciprocally bonded with glues of different chromatic characteristics and the edge areas are bonded tip-to-tip with protuberances of geometric shape, preferably simple and repetitive such as isolated truncated-cone or truncated-pyramid shaped protuberances, or straight lines. The central areas preferably have on one ply a geometric background embossing and on the other a decorative embossing of large dimensions.

In particular, when the embossing rollers are designed with bands as shown by way of example in Figs. 1OA, 1OB, the projections of a same roller can be provided with different heights to one another. In this case, the use of cliche glue applicator rollers 13C, 15C is unnecessary, as smooth glue applicator rollers, i.e. with a substantially cylindrical continuous outer surface, can be used. Figs. 13A, 13B show portions of embossing rollers, once again indicated with 3 and 7, in which bands of protuberances of different heights are provided. For example, protuberances 3A of height hi and protuberances 3C of height h2, distributed in bands, are provided on the embossing roller 3. Similarly, protuberances 7B of height h2 and protuberances 7C of height hi are provided on the embossing roller 7. In the lamination nip the protuberances 7C press against the protuberances 3C in tip-to-tip arrangement. Similarly, the protuberances 7B press against the protuberances 3A. In this manner a multi-ply paper article of the type indicated schematically in Fig.14 is obtained, in which central areas with protuberances PB, PD are intercalated between edge areas formed by the reciprocal pressure of the projections 7C, 3C with protuberances PA, PC on the plies V1 and V2. The different height of the projections 7B, 7C, 3A, 3C of the two embossing rollers 3 and 7 makes it possible to use smooth glue applicator rollers 13C, 15C, i.e. not according to a pattern, due to the fact that distribution of the glue in areas is obtained through the different height of the protuberances generated in the different areas of the plies V1 and V2.

It is understood that the heights of the projections 7A, 7B, 3A, 3C of the rollers 7 and 3 are in any case such as to obtain tip-to-tip joining in the lamination nip between the two rollers, so as to cause lamination of the two plies and gluing thereof with the two glues of different chromatic characteristics, one applied to the projections 7B of greater height of the embossing roller 7 (by the applicator roller 15C) and the other to the projections 3C of greater height of the roller 3 (using the applicator roller 13C). In substance, the sum of the heights of the projections that coincide in tip-to-tip arrangement remains the same.

The projections with different heights on the same roller can be obtained by grinding in a particularly simple manner when the projections are arranged in annular bands, as shown in Figs. 10A-10B, as in this way it is possible to grind all the projections of a same annular band to the same height, and the projections of the adjacent bands to a different height.

It is understood that the drawing shows just one example, provided merely as a practical demonstration of the invention, which can vary in its forms and arrangements, without however departing from the scope of the concept underlying the invention.

Claims

CLAlMS

1. An embossed multi-ply paper material comprising at least a first ply and a second ply of tissue paper, embossed and bonded by gluing, wherein: along at least one edge portion the first ply and the second ply have a tip- to-tip embossing, at which said first and second ply are glued with a first glue at protuberances facing one towards the other inside the multi-ply material; in a central portion the first ply is provided with a central embossing with protuberances facing the inside of the multi-ply material and the second ply is provided with a decorative embossing with protuberances facing the inside of the multi-ply material, in said central portion the two plies being glued tip-to-tip with a second glue at mutually coinciding contact surfaces of protuberances of the central embossing of the first ply and protuberances of the decorative embossing of the second ply; - the first glue and the second glue have different characteristics to each other.

2. Multi-ply material as claimed in claim 1 , wherein said first and second glue have different chromatic characteristics to each other.

3. Multi-ply material as claimed in claim 1 or 2, wherein said central em- bossing of the first ply is a background embossing.

4. Multi-ply material as claimed in claim 3, wherein said central embossing of the first ply is composed of protuberances of simple and repetitive geometric shape.

5. Multi-ply material as claimed in one or more of the preceding claims, wherein said tip-to-tip embossing of the edge portion is composed on both plies of protuberances of simple and repetitive geometric shape.

6. Multi-ply material as claimed in one or more of the preceding claims, wherein said tip-to-tip embossing of the edge portion is composed, on each of said first and second ply, of linear protuberance^ oriented with different inclina- tions on the two plies, the two plies being mutually glued at the intersections of the linear protuberances of the first and of the second ply.

7. Multi-ply material as claimed in claim 6, wherein said linear protuberances comprise mutually parallel rectilinear protuberances on each of said first and second ply.

8. Multi-ply material as claimed in claim 6 or 7, wherein said linear protuberances have a density between 2 and 10 lines/cm.

9. Multi-ply material as claimed in claim 6, 7 or 8, wherein said linear protuberances have a front surface of a width between 0.3 and 1.5 mm and preferably a pitch between 1 and 5 mm.

10. Multi-ply material as claimed in one or more of the preceding claims, wherein said edge portion extends along two parallel and opposite longitudinal edges of the material, between which the central portion is arranged.

11. Multi-ply material as claimed in one or more of the preceding claims, wherein said edge portion defines at least one quadrangular frame which delimits the central portion therewithin.

12. Multi-ply material as claimed in one or more of claims 3 to 11 , wherein said central embossing of the first ply is formed by linear protuber- ances oriented with an opposite orientation with respect to linear protuberances of the corresponding embossing of the edge portion of the first ply.

13. Multi-ply material as claimed in claim 12, wherein the linear protuberances of the central embossing of the first ply comprise mutually parallel rectilinear protuberances.

14. Multi-ply material as claimed in claim 12 or 13, wherein said linear protuberances of the central embossing of the first ply have a density between 2 and 10 lines/cm.

15. Multi-ply material as claimed in claim 12, 13 or 14, wherein said linear protuberances of the central embossing of the first ply have a front surface with a width between 0.3 and 1.5 mm and preferably a pitch between 1 and 5 mm.

16. Multi-ply material as claimed in one or more of claims 12 to 15, wherein the linear protuberances of the edge portions and the linear protuberances of the central portion of said first ply are mutually separated by an unem- bossed area.

17. Multi-ply material as claimed in one or more of the preceding claims, wherein said decorative embossing comprises protuberances with a density no greater than 20 protuberances/cm².

18.An embossing unit comprising: a first path for a first ply and a second path for a second ply to be embossed; a first embossing roller cooperating with a first pressure roller; a second embossing roller cooperating with a second pressure roller, said first and second embossing roller being provided with projections defining embossing patterns for a first ply and for a second ply, respectively, fed along said first path and said second path; and said embossing roll- ers being adjustable in tip-to-tip arrangement to laminate the two plies between the respective projections in a lamination nip defined between said first and said second embossing roller; a first glue dispenser cooperating with said first embossing roller and equipped with a first applicator roller to apply a first glue in specific areas of the first ply at projections of the first embossing roller, a sec- ond glue dispenser cooperating with said second embossing roller and equipped with a second applicator roller to apply a second glue to specific areas of the second ply at projections of the second embossing roller.

19. Embossing unit as claimed in claim 18, wherein said first and second applicator roller have respective cliches to apply glue in defined areas of the re- spective ply.

20. Embossing unit as claimed in claim 18 or 19, wherein: said first embossing roller comprises first projections defining on the first ply at least one edge portion and second projections defining at least one central portion; said first applicator roller of the first glue dispenser is configured to apply the first glue at the first projections, but not at the second projections; the second embossing roller comprises third projections in phase with the first projections of the first embossing roller defining said edge portion and fourth projections in phase with the second projections of the first embossing roller defining said central portion; said second applicator roller of the second glue dispenser is configured to apply the second glue at the fourth projections of the second embossing roller, but not at the third projections of the second embossing roller.

21. Embossing unit as claimed in claim 19, wherein said first projections and said second projections of the first embossing roller define respective background embossing.

22. Embossing unit as claimed in one or more of claims 18 to 21 , wherein: said first embossing roller comprises first projections defining on the first ply at least one edge portion and second projections defining at least one central portion, said first projections and said second projections having different heights from each other; the second embossing roller comprises third pro- jections in phase with the first projections of the first embossing roller defining said edge portion and fourth projections in phase with the second projections of the first embossing roller defining said central portion, said third and fourth projections having different heights from each other, the heights of the first, sec- ond, third and fourth projections being such that the first and third projections press against each other and the second and fourth projections press against each other in the lamination nip between the embossing rollers.

23. Embossing roller as claimed in claim 22, wherein the first glue applicator roller and the second glue applicator roller have substantially smooth and continuous cylindrical surfaces. i,

24. Embossing roller as claimed in claim 22 or 23, wherein said first, second, third and fourth projections are disposed according to annular bands.