EP1996395A1

EP1996395A1 - Method for producing a multi-ply paper product, tissue paper product and apparatus for producing a multi-ply paper product

Info

Publication number: EP1996395A1
Application number: EP06723517A
Authority: EP
Inventors: Emmanuelle Morin; Günther Zöller
Original assignee: SCA Hygiene Products GmbH
Current assignee: Essity Germany GmbH
Priority date: 2006-03-17
Filing date: 2006-03-17
Publication date: 2008-12-03
Anticipated expiration: 2026-03-17
Also published as: EP1996395B1; ES2333463T3; PL1996395T3; WO2007107167A1; ATE445497T1; DE602006009847D1

Abstract

The invention concerns a method for producing a multi-ply paper product (4), comprising the steps of feeding an upper ply (1) with a first feeding velocity (V4) into a stuffing nip (5), the upper ply having cushion recesses (10) embossed therein and feeding a middle ply (2) with a second feeding velocity (V2) into the stuffing nip for stuffing at least a portion of the middle ply into the cushion recesses of the upper ply, the second feeding velocity being higher than the first feeding velocity.

Description

Method for producing a multi-ply paper product, tissue paper product and apparatus for producing a multi-ply paper product

Description

Technical Field

The present invention relates to a method for producing a multi-ply paper product according to the preamble of claim 1, a tissue paper product according to the preamble of claim 13 and an apparatus for producing a multi-ply paper product according to the preamble of claim 22.

Multi-ply tissue paper for various uses such as kitchen paper, toilet paper or a handkerchief involve a plurality of plies of paper which are bonded together to form a multi-ply paper product .

General goals with respect to multi-ply papers are to provide softness, an improved hand-feel, good mechanical strength and the desired absorption properties. It is, furthermore, desired to improve the perceived thickness of the tissue paper product in order to give the user a comfortable feeling and to suggest superior qualities of the paper product in combination with increased absorption properties.

Description of the Prior Art

In multi-layer products, tissue plies can be structured by different methods. One of those methods is to structure the tissue plies by surface embossing using single nip or multi nip embossing. The ply bonding of the single plies is then usually provided by using an adhesive or by pressure bonding of the plies.

In order to increase the perceived thickness of multi-ply paper products, one method is to increase the volume of the tissue plies by embossing cushion-like embossings in the surface of at least one of the outer plies. The cushions are usually filled with air only. Accordingly, the stability of such cushions is never guarantied, they may collapse easily and the finished product does not feel as thick as it appears to be.

Multi-ply paper products are known which provide cushions that are supported by a second layer that has protrusions nested with the cushions in order to support extension of the cushions perpendicular to the general plane of the paper. The additional layers comprising the supporting protrusions suffer, however, the same problem in that they are not supported themselves but only filled with air.

One problem associated with cushions in multi-ply paper products is, that the cushions are not stable and collapse easily.

US 4,543,142 shows a two-ply nested paper towel in which the protrusions of the respective layers are supported by protrusions of the respective second layer. The protrusions of the first and the second layer are such that in every protrusion of the first layer exactly one protrusion of the second layer is nested.

EP 1 239 079 Al describes a two-ply paper product with a first, substantially flat, layer and a second layer that comprises cushions and a design pattern that is imprinted in the areas of the cushions . Between the cushions and the substantially flat layer there is no support for the cushions at all. Summary of the Invention

It is an object of the invention to improve the perceived thickness of a multi-ply paper product, in particular when compared to its optical appearance.

This object is solved by a method for producing a multi-ply paper product with the features of claim 1. A tissue paper product is characterized by the features of claim 13. An apparatus for producing a multi-ply paper product comprises the features of claim 22.

The invention according to the method resides in the provision of different feeding velocities of an upper ply having cushion recesses embossed therein into a stuffing nip and a middle ply into the same stuffing nip. In particular, the upper ply is fed with a first feeding velocity into the stuffing nip whereas the upper ply has cushion recesses embossed therein. The middle ply is fed with a second feeding velocity into the stuffing nip in order to stuff at least a portion of the middle ply into the cushion recesses of the upper ply, whereas the second feeding velocity of the middle ply is higher than the first feeding velocity of the upper ply.

This method results in a multi-ply paper product which comprises cushions on its upper side, said cushions being at least partially filled with the middle ply whereas the length of tissue the cushions are filled with is considerably longer than the length of tissue used in the upper cushion layer. In other words, the middle ply is stuffed into the cushion recesses of the upper ply such that the middle ply exhibits wrinkles and/or a creped appearance in the portions of the cushion recesses. This leads to a situation in which a big portion, if not all, of the volume of the cushion is filled with the middle ply stuffing. The structure obtained by the method results in a multi-ply paper product which has cushions that are supported by the material of the middle ply that is stuffed into them such that the cushions do not easily collapse but are supported by the respective middle layer material. Thus, the optical appearance of the cushions conforms to the thickness of the tissue paper product that is haptically perceived since the cushions do not collapse when touched by a user. Furthermore, the absorption properties of the resulting tissue paper products are considerably improved since the tissue paper product carries a higher amount of fibres which, consequently, leads to a higher absorption quality of the resulting tissue paper.

In order to provide an efficient method, the upper ply is passed through a cushion embossing nip before entering the stuffing nip in order to emboss the cushion recesses into the upper ply.

A tissue paper product comprising three layers can be manufactured by the step of laminating together the upper ply, the middle ply and a lower ply in a laminating nip whereas the middle ply is arranged between the upper ply and the lower ply. This particular arrangement has the advantage that the middle ply, which exhibits wrinkles or has a creped appearance, is covered on both sides by plies that carry a controlled embossing pattern. In particular, the upper ply carries the cushion embossing pattern and the lower ply may carry a micro-embossing pattern in order to increase the softness of the resulting multi-ply paper product.

In a preferred embodiment of the method, the middle ply is fed through the stuffing nip such that it develops wrinkles within the cushion recesses. A further advantageous variant is that the middle ply is fed through the stuffing nip such that it wrinkles/crepes within the cushion recesses. This contributes to the above-mentioned structure in which the cushion recesses are filled with the stuffing structure of the middle ply.

In order to further increase the volume of the resulting tissue ply paper product and in order to encourage the folding, wrinkling or creping of the middle ply, the middle ply may carry a volume embossing pattern. This volume embossing pattern is advantageously provided by the step of embossing the middle ply with a volume embossing pattern before feeding it to the stuffing nip.

The volume embossing pattern may carry a pattern that comprises volume embossed protrusions and un-embossed areas. In other words, the volume embossed pattern is only provided in selected areas of the middle ply. In an advantageous variant the step of synchronizing the areas of volume embossed protrusions of the middle ply with the cushion recesses of the upper ply is provided such that un-embossed areas of the middle ply are situated in the same positions as un-embossed areas of the upper ply. In other words, in the areas in which a bonding between the upper ply and the middle ply and, optionally, a lower ply, takes place, the middle ply should not be embossed but substantially flat. Thiø improves the reliability of a bonding between the layers and adds to the optical appearance of the resulting multi-ply tissue paper product since the embossing edges in the area of the bonding can be made sharp and exact. This is particularly the case since the bonding does not take place in an area of the middle ply where lots of wrinkles are present as a substrate .

In a further preferred variant of this method, the step of synchronizing the areas of the volume embossing protrusions of the middle ply with the cushion recesses of the upper ply is provided such that at least one un-embossed area of the middle ply is situated inside a cushion recess. Such un- embossed area of the middle ply situated inside the cushion recess helps the actual manufacturing process in that such un-embossed area of the middle ply can interact with the respective summit portion of the protrusions of a male embossing roll. The interplay between the male embossing roll and the female embossing roll that is responsible for embossing the cushion recesses into the upper ply, with the respective un-embossed areas of the middle ply adds to the reliability of the process since neither of the summit portions of the protrusions comes into contact with wrinkled areas of the middle ply.

In a further embodiment of the method, the volume embossing pattern of the middle ply is matched to the cushion embossing pattern of the upper ply.

In order to laminate the layers together, glue is preferably applied onto the summit portions of the upper ply before it enters the stuffing nip.

A tissue paper product according to the invention comprises an upper ply comprising cushion protrusions formed therein, a lower ply, and a middle ply being situated between the upper ply and the lower ply. The middle ply comprises wrinkled areas matched with the cushion protrusions of the upper ply such as to fill at least a portion of the cushion protrusions with the middle ply.

In a preferred embodiment, the middle ply comprises volume embossed protrusions. In a further preferred embodiment, the middle ply fills most of the cushion protrusions. These embodiments add to an improved stability of the cushion protrusions and/or the cushions and thus contribute to an improved haptic appearance of the tissue paper product such that the cushion protrusions are less inclined to collapse. In order to enhance the optical appearance of the finished tissue paper product, the upper ply, the middle ply and the lower ply are laminated together in laminating areas that correspond to un-embossed areas of the upper ply. Advantageously, the middle ply exhibits un-embossed areas in said lamination areas in a further improved embodiment, the middle ply comprises un-embossed areas within the cushion protrusions. These different embodiments of the middle ply which exhibit un-embossed areas at least in the position in which the layers are bonded together, result in an improved optical appearance since the bonding portions are substantially flat.

This principle can be further applied by synchronizing the feeding of the plies such that un-embossed areas of the middle ply are in register with the cushion protrusions of the upper ply. This leads to a tissue paper product in which all cushion protrusions are stuffed or filled with the middle ply, but the areas between the cushion protrusions, namely the areas in which the plies are bonded together, do not comprise such wrinkled or creped paper plies which consequently leads to sharp embossing edges.

In a further preferred embodiment, also the lower ply carries cushion protrusions that are substantially filled with the stuffing of the middle ply. The lower ply can be mirror- inverted with regard to the upper ply which consequently leads to a perfectly symmetrical tissue paper product which has an identical appearance on its upper and lower side.

The invention, furthermore, pertains to an apparatus for producing a multi-ply paper product, preferably according to the method described above. Such apparatus comprises a cushion embossing nip for embossing cushion recesses in an upper ply, the cushion embossing nip being formed between a female embossing roll and a counter roll, said counter roll having a lower surface hardness than that of the female embossing roll. The apparatus, furthermore, includes a stuffing nip for stuffing a middle ply into the cushion recesses of the upper ply, the stuffing nip being formed between a male embossing roll and a female embossing roll, the male embossing roll and the female embossing roll being arranged in a nested arrangement. The apparatus, furthermore, includes a feeding means for feeding the middle ply into the stuffing nip with a feeding velocity higher than the circumferential speed of the female embossing roll.

Such an apparatus enables the user to produce a multi-ply paper product with improved perceived thickness. In particular, the feeding of the middle ply through the feeding means with a higher feeding velocity than that of the circumferential speed of the female embossing roll leads to a wrinkling or creping of the middle ply when it enters into the stuffing nip. Consequently, the material amount, or ply length that is stuffed into the cushion recesses is higher than the amount of ply used to constitute the cushion protrusions themselves. In other words, a longer length of ply is stuffed into the cushion recesses of the upper ply which consequently leads to an arrangement in which the cushion protrusions are filled to a considerable amount with the middle ply material .

The apparatus, advantageously, comprises a volume embossing nip for embossing a volume pattern into the middle ply whereas the volume embossing nip is located upstream of a stuffing nip and, at the same time, constitutes the feeding means. In a preferred embodiment, the volume embossing pattern of the volume embossing nip comprises areas of embossing protrusions and un-embossed areas. In a further preferred embodiment, the un-embossed areas of the middle ply are synchronized with un-embossed areas of the upper ply. The provision of un-embossed areas as well as the provision of a synchronization of the un-embossed areas with the un- embossed areas of the upper ply leads to an arrangement in which un-embossed areas are present in the areas in which the actual lamination of the plies to one another takes place.

In a preferred embodiment, the apparatus furthermore includes a lamination nip for laminating a lower ply together with the upper ply and the middle ply, said lamination nip being provided downstream of the stuffing nip. This laminating nip can preferably be formed between the female embossing roll and a lamination roll (Marrying roll) . This embodiment ensures an efficient lamination of the three plies together.

A background embossing nip -for embossing the lower ply can be provided upstream the laminating nip such that a pre-embossed lower ply is fed into the lamination nip. Such additional background embossing of the lower ply contributes to a higher perceived softness of the tissue paper product.

In a preferred variant, the embossing pattern of the male embossing roll is arranged such that it contributes to the retracting of the middle ply into the cushion recesses of the upper ply and supports the necessary wrinkling and/or σreping of the middle ply within a cushion recesses of the upper ply. Preferably, the protrusions of the male embossing pattern have a shape like an asymmetric pyramid. Such embossing protrusions of the male embossing roll could comprise three surfaces that extend in a radial direction of the embossing roll and one surface that is situated in a negative angle with respect to the radial direction. Such male embossing pattern contributes to retracting the middle ply into the cushion recesses of the upper ply and supports the wrinkling or filling in of the middle ply into the cushion recesses.

Brief Description of the Drawings

In the following, the invention is described by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic illustration of an apparatus that is able to carry out the method for producing a multi-ply paper product ;

Figure 2 is a schematic representation of a second embodiment of the apparatus for carrying out the method for producing a multi-ply paper product;

Figure 3 is a schematic illustration of the stuffing nip and a magnified portion of the stuffing nip;

Figure 4 is a magnified representation of the stuffing nip through which an upper ply and a middle ply is fed and additionally a lamination is shown in which a lower ply is laminated to the upper and middle plies;

Figure 5 is yet another enlargement of the stuffing nip with the upper ply and the middle ply arranged therein;

Figure 6 is a perspective schematic representation of an embossing roll with male protrusions;

Figure 7 is a perspective schematic representation of an embossing protrusion in a second embodiment;

Figure 8 is a schematic cross-section through a tissue paper product in a first embodiment;

Figure 9 is a schematic cross-section through a tissue paper product of a second embodiment; and

Figure 10 is a schematic cross-section through a tissue paper product according a third embodiment . Detailed Description of Preferred Embodiments

In the following description of preferred embodiments of the invention, corresponding parts or elements in the different drawings will be denoted by the same reference numerals.

Figure 1 schematically shows an apparatus for producing a multi-ply paper product. It, furthermore, schematically shows the method for producing a multi-ply paper product.

According to the method, an upper ply 1 is fed with a feeding velocity V^ into a cushion embossing nip 6 which is formed between a female embossing roll 50 and a counter roll 60. The female embossing roll 50 is typically made from a steel material, or has at least a steel surface in which the female embossing pattern is present. The female embossing pattern corresponds basically to the desired cushion pattern which is to be imprinted into the upper layer 1.

The cushion pattern is embossed into the upper layer 1 by the counter roll 60 which exhibits an elastic surface such as to press the upper layer 1 into the female embossing pattern of the female embossing roll 50. The female embossing pattern on the female embossing roll 50 is the negative equivalent to the desired upper/outer surface of the finished multi-ply tissue paper product. In other words, the pattern that is intended to show cushion protrusions in the finished paper product are cushion recesses in the female embossing roll. In the following, even though the embossing pattern will be visible as cushion protrusions in the finished paper product, it will be referred to as cushion recesses since the cushion protrusions are visible as cushion recesses on the outer side of the female embossing roll 50.

The female embossing roll 50 is rotated with a rotation velocity that results in a surface velocity of the female embossing roll of V₄. Accordingly, the counter roll 60 is rotated with the corresponding surface velocity and there is no slip between the two rolls.

The feeding velocity V]_ of the upper ply can be set to be a little higher than the surface velocity V4 of the female embossing roll 50 since, due to the cushion recesses of the female embossing roll 50, the length of ply needed to cover all recesses of the embossing roll 50 might require more material. The feeding velocity V₁ of the upper ply can, however, be identical to the surface velocity V4 of the female embossing roll. Then, the upper ply is slightly stretched in the areas of the cushion recesses.

The upper ply 1 that now adheres to the surface of the female embossing roll 50 is conveyed to a stuffing nip 5. The stuffing nip 5 is formed between_, the female embossing roll 50 and a male embossing roll 52. The male embossing roll 52 is, preferably, made from the same material as the female embossing roll 50 and has a high surface hardness. The male embossing roll 52 carries a male embossing pattern on its surface which is in register with the embossing recesses of the female embossing roll 50. The pattern could be, for example, a Union embossing pattern or a waffle pattern.

The female embossing pattern of the female embossing roll 50 is defined as being a cylinder composed of cavities, the roll of which is to be filled with tissue. The male pattern of the male embossing roll 52 is defined to be a cylinder composed of knobs, the goal of which is to push the tissue into a cavity of the female pattern.

A middle ply 2 is fed into the stuffing nip with a feeding velocity V2 which is considerably higher than the surface velocity V4 of the female embossing roll 50. The female embossing roll 50 and the male embossing roll 52 are rotated together with identical velocities since they are in a registered arrangement. The middle ply 2 is thus fed into the stuffing nip 5 with a higher velocity which, consequently, leads to a wrinkling or creping of the middle ply in the stuffing nip which, subsequently, leads to a situation in which the middle ply 2 fills at least parts of the cushion recesses situated on the surface pattern of the female embossing roll 50. The male embossing roll 52 supports this wrinkling and stuffs the middle ply 1 into these recesses, as will become more apparent in the description with regard to Figures 4 and 5.

The middle ply 2 can be fed into the stuffing nip 5 by a feeding means which in Figure 1 is constituted by a volume embossing nip 8 which is formed between a volume embossing roll 80 and a counter roll 82, the volume embossing roll 80 having a surface of a higher surface hardness than that of the counter roll 82. The counter roll 82 is, preferably, made of a rubber material. However, it is also possible that the volume embossing roll 80 and the counter roll 82 are both made of steel (Union embossing) .

Before the upper ply 1 enters into the stuffing nip 5, it passes through a gluing nip 9 in which an adhesive is applied onto the summit portions of the embossing pattern of the female embossing roll 50. The gluing nip 9 is formed between the female embossing roll 50 and a glue application roll 90 which is in contact with a second glue application roll 92 and a third glue application roll 94. The second and third glue application rolls 92 and 94 contribute to an even and sparing application of the glue onto the upper ply 1.

After passing through the stuffing nip 5, the upper ply with the cushion recesses embossed therein and the middle ply which is stuffed into the cushion recesses of the upper ply are fed together towards a lamination nip 7 which is formed between the female embossing roll 50 and a lamination roll (Marrying roll) 70. The lamination roll 70 preferably has a surface hardness lower than that of the female embossing roll 50. The lamination roll 70 preferably exhibits a surface made from a rubber material .

Through the lamination nip 7, a lower ply 3 is fed together with the upper ply 1 and the middle ply 2 such that the three plies are laminated together in the summit portions of the female embossing pattern of the female embossing roll 50. The resulting multi-ply tissue paper product 4 comprises three layers, namely an upper layer 1, a middle layer 2 and a lower layer 3 , whereas the upper layer 1 carries a cushion pattern comprising cushion protrusions which are filled or stuffed with wrinkled or creped material of the middle ply 2.

The resulting multi-ply tissue paper product exhibits a high stability of the cushions since the cushions are supported by the wrinkled material in the cushion protrusions .

The lower ply 3 is fed into the lamination nip 7 with a feeding velocity V3 which corresponds to the surface velocity V4 of the female embossing roll 50. In other words, there is no slip between the upper ply 1 and the middle ply 2 which are conveyed on the surface of the female embossing roll 50 on the one hand and the added lower ply 3 in the lamination nip 7 on the other hand.

Figure 2 shows a second embodiment of the apparatus for producing a multi-ply paper product and also illustrates the method of producing the multi-ply paper product. The apparatus shown in Figure 2 has the same structure as that shown and described with regard to Figure 1. The only difference is that the lower ply 3 is fed through a pre- embossing nip 86 which is formed between an embossing roll 88 and a counter roll 89 before it is fed through the lamination nip 7. The embossing pattern which is embossed into the lower layer 3 in the pre-embossing nip 86 contributes to a soft feel of the lower side of the resulting tissue ply paper product 4 especially if the embossing pattern is a micro embossing pattern. Such embossing could also be provided on the upper ply 1.

Figure 3 shows a schematic illustration of the stuffing nip which is formed between the female embossing roll 50 and the male embossing roll 52. Figure 3 shows the rotation directions of the female embossing roll 50, the male embossing roll 52 and the counter roll 60. Furthermore, there is an enlargement of the stuffing nip which clearly shows the registered engagement of the female embossing roll 50 and the male embossing roll 52. The female embossing roll exhibits recesses 502 and protrusions 500. The recesses 502 are separated from each other by the protrusions 500.

The male embossing roll 52 carries protrusions 520 and recesses 522. The protrusions 520 are separated from each other by the recesses 522. In the Figure, it is clearly visible that the protrusions 520 of the male embossing roll 52 extend into the recesses 502 of the female embossing roll 50. Vice versa the protrusions 500 of the female embossing roll 50 extend into the recesses 522 of the male embossing roll 52.

Figure 4 shows the stuffing nip 5 in a yet enlarged illustration. The female embossing roll 50 shows recesses 502 and protrusions 500 and the male embossing roll 52 shows protrusions 520 and recesses 552. The male embossing roll 52 and the female embossing roll 50 are synchronized such that they are in a registered engagement. A first ply 1 is shown that covers the surface of the female embossing roll 50 such that cushion recesses 10 are present in the areas of the recesses 502 of the embossing pattern and un-embossed areas 12 are present in the areas of the protrusions 500 of the embossing pattern of the female embossing roll 50. A middle ply 2 is shown that carries a volume embossing structure 21. The middle ply 2 is fed into the stuffing nip 5 with a velocity higher than that actually present in the stuffing nip 5. Consequently, the middle ply 2 develops wrinkles 20 and, consequently, fills in, at least parts, of the cushion recesses 10 in the stuffing nip 5. The wrinkling is eased, among other things, by the presence of glue 96 which is applied onto the summit portions of the protrusions 500 or, more precisely, on the un-embossed areas 20 of the upper ply 1 which reside on the summit portions of the protrusions 500 of the female embossing roll 50. The glue 96 in these portions automatically binds the middle ply 2 and conveys it further on.

The upper ply 1 and the middle ply 2 are then carried together into a lamination nip 7 which is formed between a lamination roll 70 and the female embossing roll 50. Through the lamination nip 7, a lower ply 3 is fed together with the upper ply 1 and the middle ply 2 such that a multi-ply paper product 4 comprising the upper ply 1, the middle ply 2 and the lower ply 3 is laminated.

Figure 5 shows the situation in the lamination nip more clearly. In the lamination nip, the middle ply 2 comprises wrinkled and/or creped portions 20 and also un-embossed portions 24 and 26. In the embodiment shown in Figure 5, the middle ply 2 carries a pre-embossing which can, for example, be embossed in the volume embossing nip 80 as shown in Figures 1 and 2. The volume embossing 80 is, in this embodiment, made such that embossed areas and un-embossed areas are present in the middle ply 2. The un-embossed areas 24 and 26 are synchronized with the protrusions 520 of the male embossing roll 52 and the protrusions 500 of the female embossing roll 50. In other words, the un-embossed areas 24 are positioned in the area of the protrusions 500 of the female embossing roll 50 and the un-embossed area 26 are present in the area of the protrusions 520 of the male embossing roll 52. As will be seen with reference to Figures 9 and 10 in the following this makes a special contribution to the reliability of the bonding of the three plies and, additionally, to the optical appearance of the embossing sharpness .

Figure 6 schematically shows a perspective view of the male embossing roll 52 comprising protrusions 520 which have a top side 527 which is parallel to the cylinder surface of the male embossing roll 52, side surfaces 525 facing in the axial direction of the cylinder, the side surfaces 525 extending in a radial direction, and front surfaces 524 and back surfaces 526 which are inclined with respect to the radial direction of the cylinder. The front surfaces 524 and the back surfaces 526 are inclined such that they both together form an equilateral triangle.

Figure 7 shows an improved protrusion 520' to be used with a male embossing roll the protrusions 520' has a front surface 524' which is inclined with respect to the radial direction of the cylinder and a back surface 526' which extends in the radial direction, namely perpendicular to the cylinder surface of the male embossing roll 52. This supports the retracting in of the middle ply 2 into the stuffing nip 5 and encourages the wrinkling of the middle ply in order to fill at least parts of the cushion recesses of the upper ply 1.

Figure 8 shows a multi-ply tissue paper product which comprises an upper ply 1, a middle ply 2 and a lower ply 3. The upper ply 1 has, embossed therein, cushion protrusions 10 and also carries un-embossed areas 12 which extend in the original plane of the previously un-embossed upper ply 1. The middle ply 2 is stuffed into the cushion protrusions 10 or, when seen from the upper side of the finished paper product, into the cushion recesses 10 of the upper ply 1. The middle ply 2 shows a wrinkled structure with wrinkles 20 all over its extension. The lower ply 3 is substantially flat and is laminated together with the first and the second ply at positions that correspond to the un-embossed areas 12 of the upper ply 1. The filling in of the protrusions with the wrinkled middle ply material leads to a cushion 10 of the resulting multi-ply tissue paper product 4 in which the cushion exhibits a significant resistance against collapsing.

Figure 9 shows a second embodiment of a multi-ply tissue paper product with a first ply 1, a middle ply 2 and a lower ply 3. The middle ply 2 shows, in this embodiment, portions 22 which are wrinkled and un-embossed portions 24. The un- embossed portions 24 are situated in the same areas as the un-embossed areas 12 of the upper ply 1. In other words, at the location where the upper ply, the middle ply and the lower ply 3 are laminated together, the three plies are substantially flat which, on the one hand, increases the lamination reliability since the glue only has to travel through one layer, namely the middle layer 2 in order to laminate all three layers together and, on the other hand, the sharpness of the embossing lines, which are represented by the un-embossed areas 12 of the upper ply 1, exhibits an increased sharpness when compared to the embodiment of Figure 8 since the imprinting is done on a flat "substrate" surface.

Figure 10 shows yet another embodiment of a multi-ply tissue paper product 4 in which a first ply 1, a middle ply 2 and a lower ply 3 are laminated together. The middle ply 2, in this embodiment, shows areas 25, 27 which exhibit wrinkles and areas 24, 26 which are completely flat. One of those flat areas, namely the area 26, is inside the cushion recess 10 of the upper layer 1. This particular embodiment is advantageous in the production process since the synchronization between the middle ply 2 and the respective protrusions of the male embossing roll and the female embossing roll is eased due to the presence of the un- embossed areas 24, 26. The stuffing in the wrinkled areas 25, 27 can, thus, be controlled in an easier way.

Claims

1. Method for producing a multi-ply paper product (4), comprising the steps: feeding an upper ply (1) with a first feeding velocity (V4) into a stuffing nip (5) , the upper ply having cushion recesses (10) embossed therein; feeding a middle ply (2) with a second feeding velocity (V2) into the stuffing nip for stuffing at least a portion of the middle ply into the cushion recesses of the upper ply, the second feeding velocity being higher than the first feeding velocity.

2. Method according to claim 1, comprising the step of passing the upper ply through a cushion embossing nip

(6) before entering the stuffing nip to emboss the cushion recesses into the upper ply.

3. Method according to claim 1 or 2 , comprising the step of laminating the upper ply, the middle ply and a lower ply (3) together in a laminating nip (7) , whereas the middle ply is arranged between the upper ply and the lower ply.

4. Method according to any of the preceding claims, characterised in that the middle ply is fed through the stuffing nip such that it develops wrinkles (20) and/or a creped appearance within the cushion recesses.

5. Method according to any of the preceding claims, characterised in that the middle ply is fed through the stuffing nip such that it crepes within the cushion recesses .

6. Method according to any of the preceding claims, characterised in that the middle ply carries a volume embossing pattern.

7. Method according to claim 6, comprising the step of embossing- the middle ply with a volume embossing pattern before feeding it to the stuffing nip.

8. Method according to claim 6 or 7 , characterised in that the volume embossing pattern comprises areas carrying volume embossing protrusions and un-embossed areas.

9. Method according to claim 8, comprising the step of synchronising the areas of the volume embossing protrusions of the middle ply with the cushion recesses of the upper ply such that un-embossed areas (24) of the middle ply are situated in the same position as un- embossed areas of the upper ply.

10. Method according to claim 8 or 9 , comprising the step of synchronising the areas of the volume embossing protrusions of the middle ply with the cushion recesses of the upper ply such that at least one embossed area of the middle ply is situated inside a cushion recess.

11. Method according to any one of claims 6 to 10, characterised in that the volume embossing pattern of the middle ply is matched with the cushion embossing pattern of the upper ply.

12. Method according to any of the preceding claims, comprising the step of applying glue onto the summit portions of the embossing pattern of the female embossing roll.

13. Tissue paper product comprising an upper ply (1) comprising cushion protrusions (10) formed therein; a lower ply (3) ; and a middle ply (2) being situated between the upper ply and the lower ply, the middle ply comprises wrinkled areas (20, 25, 27) matched with the cushion protrusions of the upper ply such as to fill at least a portion of the cushion protrusions with the middle ply.

14. Tissue paper product according to claim 13, characterised in that the middle ply comprises volume embossing protrusions.

15. Tissue paper product according to claim 13 or 14, characterised in that the middle ply fills most of the cushion protrusions .

16. Tissue paper product according to any one of claims 13 to 15, characterised in that the upper ply, the middle ply and the lower ply are laminated together in laminating areas that correspond to un-embossed areas (12) of the upper ply.

17. Tissue paper product according to claim 16, characterised in that the middle ply exhibits un- embossed areas (24) in the lamination areas.

18. Tissue paper product according to any one of claims 13 to 17, characterised in that the middle ply comprises un-embossed areas (26) within the cushion protrusions.

19. Tissue paper product according to claim 17 or 18, characterised in that the un-embossed areas of the middle ply are synchronised with the un-embossed areas of the upper ply.

20. Tissue paper product according to any one of claims 13 to 19, characterised in that the lower ply also carries cushion protrusions that are substantially filled with the wrinkled middle ply.

21. Tissue paper product according to claim 20, characterised in that the lower ply is mirror-inverted with regard to the upper ply.

22. Apparatus for performing the method according to claims 1 to 12 comprising

a cushion embossing nip (6) for embossing cushion recesses (10) in an upper ply (1) , the cushion embossing nip being formed between a female embossing roll (50) and a counter roll (60) having a lower surface hardness than that of the female embossing roll; a stuffing nip (5) for stuffing a middle ply (2) into the cushion recesses of the upper ply, the stuffing nip being formed between a male embossing roll (52) and the female embossing roll, the male embossing roll and the female embossing roll being arranged in a nested arrangement ; a feeding means (80) for feeding the middle ply to the stuffing nip with a feeding velocity (V2) higher than the circumferential speed (V4) of the female embossing roll.

23. Apparatus according to claim 22, characterised in that the feeding means is a volume embossing nip (8) for embossing a volume pattern into the middle ply, the volume embossing nip being located upstream of the stuffing nip.

24. Apparatus according to claim 23, characterised in that the volume embossing pattern of the volume embossing nip comprises areas of embossing protrusions and un- embossed areas.

25. Apparatus according to claim 24, characterised in that the un-embossed areas of the middle ply are synchronised with un-embossed areas of the upper ply.

26. Apparatus according to any one of the claims 22 to 25, characterised in that a laminating nip (7) for laminating a lower ply (3) together with the upper ply and the middle ply is provided downstream of the stuffing nip.

27. Apparatus according to claim 26, characterised in that a background embossing nip (86) for embossing the lower ply is provided upstream the laminating nip.

28. Apparatus according to any one of claims 22 to 28, characterised in that the embossing pattern of the male embossing roll is such that it contributes in retracting the middle ply into the cushion recesses of the female embossing roll .

29. Apparatus according to claim 28, characterised in that the protrusions of the male embossing pattern have a shape of an asymmetric pyramid.

30. Apparatus according to claim 28 or 28, characterised that the embossing protrusions of the male embossing roll comprise three surfaces (525', 526') extending substantially in a radial direction of the male embossing roll and one surface (524') in a negative angle with respect to the radial direction of the male embossing roll.