WO2007016941A1

WO2007016941A1 - Multi-ply tissue paper product and method for producing same

Info

Publication number: WO2007016941A1
Application number: PCT/EP2005/008580
Authority: WO
Inventors: Heinz-Jürgen Müller
Original assignee: SCA Hygiene Products GmbH
Current assignee: Essity Germany GmbH
Priority date: 2005-08-08
Filing date: 2005-08-08
Publication date: 2007-02-15
Anticipated expiration: 2008-02-08
Also published as: MX2008000632A; AU2005335397A1; AU2005335397B2

Abstract

The invention relates to a multi-ply tissue paper product (10) and a method for producing same. The multi-ply paper has at least three structured plies of paper, whereas a first outer ply (12) has a first microstructure pattern with first protuberances (18) having a first height (h1), a second outer ply (14) having a second microstructure pattern with second protuberances (22) having a second height (h2) and at least one middle ply (16) sandwiched between the first outer ply (12) and the second outer ply (14) having a third structure pattern being an embossed pattern with third protuberances (17). The first and second outer plies and the at least one middle ply are ply bonded together in a non-registered manner and a décor embossing in the first outer ply (12) and/or second outer ply (14) with décor protuberances (21) having a fourth height (h4. h4’), whereas the difference in height (Δh, Δh’) between the first height (h1) and/or the second height (h2) and the fourth height (h4, h4’) is between 0.4 mm and 1 mm. All three plies are ply bonded (24) together after the first outer ply, the second outer ply and the middle ply have been structured separately.

Description

109 503 v5/t6/stl

Multi-ply tissue paper product and method for producing same

Field of the invention

The invention relates to a multi-ply tissue paper product comprising at least three structured plies of paper and a method for producing same.

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

General goals with respect to multi-ply paper are to provide softness, an improved feel, good mechanical strength and the desired absorption properties.

Description of the prior art

In multilayer products, tissue plies can be structured by different methods. A first method for providing a structured ply of paper is the use of a TAD (through air drying) process, which gives the paper a three-dimensional structure already in the paper machine.

A further method involves the embossing of tissue using a single nip or multi-nip embossing. The ply bonding of the single plies is provided by a mechanical embossing or by using an adhesive. In the case of three or multi -ply products, a plurality of plies are generally embossed together to provide a volume to the product. However, the embossing usually hardens the product and contributes to a rough feeling of the product. On the other hand, it is possible to use a micro embossing with a high density of protuberances of more than 40 protuberances/cm^ . A micro embossed product feels soft. However, micro embossed paper feels as if it could not absorb enough liquid.

Therefore, there is a constant desire to provide a tissue product with a high softness surface and a sufficient bulk.

WO 99/45205 describes a multi-ply tissue product with two embossed outer plies and a middle ply without embossing. The outer plies are embossed so that the protuberances are arranged with a density of more than 30 protuberances/cm^ . Each of the outer plies is glue bonded to the middle ply.

US 5,382,464 and US 5,736,223 both relate to specific nested configurations of a three-ply, embossed paper. The multi-ply paper according to US 5,736,223 is composed of two external plies the embossing protuberances of which are arranged in a foot-to-foot configuration. A third embossed middle ply is provided, the embossing protuberances of which nest between the protuberances of one of the two external plies. US 5,382,464 uses a different approach by providing embossed plies having protuberances of two different heights wherein the protuberances having a greater height alternate with more shallow protuberances. When the embossed ply is used to form a multi-ply paper, the small protuberances are arranged in a foot-to-foot configuration with the protuberances of a second embossed ply, so that the big protuberances of the first ply are positioned to nest between the protuberances of the second ply.

WO 02/103112 describes a multi-ply tissue paper product having at least three structured plies of paper with a first outer ply with a first microstructure pattern and a second outer ply with a second microstructure pattern and at least one middle ply with a third embossed pattern whereas the at least one middle ply is sandwiched between the first and second outer plies. Summary of the invention

It is the object of the invention to provide a multi-ply tissue paper which combines in an advantageous way a high softness and a necessary bulk to provide a good feeling to the user. Moreover, the product should be appealing to the eye and have a characteristic appearance.

This object is solved by a multi-ply tissue paper with the features of claim 1. The method for producing such a multi -ply tissue paper is characterized by the features of claim 20.

The invention resides in the provision of at least three embossed plies of paper and the provision of an additional decor embossing. Both, the first and the second outer ply are provided with a microstructure pattern with protuberances with a first height hi and second height h2 , respectively. At least one middle ply is sandwiched between the first outer ply and the second outer ply with a third structure pattern being an embossed pattern with third protuberances. By bonding the first and second outer plies and the at least one middle ply together in a non-registered manner, the resulting tissue combines soft outer plies with a volume producing inner ply. To achieve a product appealing to the eye, with a characteristic appearance and a high volume, an additional decor embossing is provided either in the first outer ply or second outer ply or in both plies with decor protuberances having a fourth height h4 and/or h4 ' , respectively, whereas the difference in height Δh and/or Δh¹, respectively, between the first height hi and/or the second height h2 and the fourth height h4 and/or h4 ' , respectively, is between 0.4 mm and 1 mm, preferably between 0.5 mm and 0.9 mm.

The resulting tissue paper combines the advantages of high softness, a high volume and a good ply bonding with a flexible decor embossing which gives the tissue product a unique appearance and additional volume. The additional volume emerges from the additional height or thickness that is introduced by the decor embossing pattern of the present invention. Due to the volume generating decor embossing in addition to the embossing of the middle ply, there is a considerable saving of fibres which contributes to the cutting down of the production costs.

The method of producing a multi-ply tissue paper comprises the steps of structuring a first outer ply with a first microstructure pattern with first protuberances having a first height hi, structuring a second outer ply with a second microstructure pattern with second protuberances having a second height h2 , embossing the first outer ply and/or second outer ply with a decor embossing pattern with protuberances having a fourth height h4 and/or h4 ' , respectively, whereas the difference in height Δh and/or Δh', respectively, between the first height hi and/or the second height h2 and the fourth height h4 and/or h4 ' , respectively, is between 0.4 mm and 1 mm, preferably between 0.5 mm and 0.9 mm and embossing a middle ply with a third structure pattern being an embossing pattern. When combining together the three plies so that the third pattern is in an unregistered way, the middle ply imparts volume to the multi-ply tissue whereas the two outer plies with the microstructure pattern contribute to the softness of the product. Furthermore, the decor embossing pattern provides additional volume of the multi-ply tissue product which leads to an improved feel and contributes to a reduction in production cost.

Preferred embodiments of the invention are characterized by the dependent claims.

According to a first preferred embodiment, the first protuberances have a first density of more than 40 protuberances/cm^ , the second protuberances have a second density of more than 40 protuberances/cm^ and the third protuberances have a density of less than 40 protuberances/cm^ . This specific selection of densities of protuberances provides a tissue paper with a soft feel and a high volume due to the additional bulk imparted by the middle layer.

According to a second preferred embodiment, the protuberances of the third structure pattern of the at least one middle ply have a height H which is at least 1.3 times greater than hi and h2 , respectively, preferably at least 1.5 times greater and most preferably at least 2.0 times greater than hi and h2. This is a further measure to impart bulk to the middle ply and to a multi-ply tissue paper product.

Preferably the decor protuberances consist of elongated structures, line segments, dots or combinations thereof. The line segments may have a length of from 2 mm up to 20 mm and a width of from 0.1 mm up to 2 mm. With an elongate shape it is possible to provide a design pattern which is easier discernible for a user and, thus, more complicated designs can be provided on the same scale of the design pattern compared to the use of single dots to generate a design pattern. It is, furthermore, possible to provide a free combination of multi-ply tissue paper with a decor embossing pattern on one or both outer surfaces. The decor embossing pattern on the first and second outer plies can be identical or disparate.

In a preferred embodiment, the decor protuberances and the first protuberances and/or second protuberances extend essentially in the same direction relative to the plane of the respective first outer ply and/or second outer ply. This can be the direction to the side of the respective first outer ply and/or second outer ply that is opposite the side contacting the middle ply. This leads to an even softer feel of the tissue product. According to another preferred embodiment, the first outer ply as well as the second outer ply carry the decor protuberances of the decor embossing pattern. These decor protuberances of the first outer ply and the second outer ply can be essentially identical.

According to a preferred embodiment of the invention, the ply bonding is generated by glue lamination using a lamination pattern. The height of the lamination pattern must be the sum of the individual heights of the microstructure pattern of the outer plies (hl+h2) and the height of the third pattern (H) . This ply bonding technique using a separate lamination pattern can be used to provide a design lamination to the product. It is possible to use e.g. discreet design lamination dots which are arranged to resemble the shape of a desired design like a flower. In order to provide a good ply bonding in the inventive multi-ply tissue paper, the glue lamination is preferably deep embossed to provide a sufficient ply bonding despite of the volume embossed middle ply.

The adhesives used can be all adhesives usually used in the art, e.g. starch or polyvinylalcohol .

According to an alternative embodiment of the invention, the ply bonding is generated by a mechanical ply bonding technique. Such a mechanical ply bonding technique could be the pressing of the multi-ply tissue with some small protrusions on a roller, like needle-tips. These protrusions run with high pressure against a suitable anvil roller. This pressing provides for a ply bonding between the individual tissue paper plies. An example for such a mechanical ply bonding is edge embossing.

According to preferred embodiments of the inventive method, the step of combining together the three plies so that the protuberances lie in an unregistered way can be carried out by first combining the first outer ply and the middle ply to a combined tissue web, the application of a laminating agent to the combined tissue web and the marrying of the combined tissue web and the second outer ply. As outlined above, the lamination can be provided according to a preferred embodiment of the invention using a design pattern of lamination dots.

In another preferred embodiment, the paper has at least four structured plies of paper and comprises two middle plies. In a variation of this embodiment, the structure patters of the two middle plies have third protuberances of different heights. The tissue paper of this embodiment and the variation provide even more volume due to the second middle (volume) ply that provides additional volume. Due to this additional volume, the tissue provides improved production efficiency since the material necessary per volume is reduced further.

In a further embodiment, a multi-ply tissue paper product is provided in which at least one ply is made of a different material with respect to the remaining plies. The first and/or second outer plies can be made of soft fibers and/or at least one middle ply can be made from slush pulp and/or recycling fibers. Such combination of materials leads to improved feel and volume of the tissue paper and results in reduced cost for materials at the same time.

For all above described embodiments, at least one of the first and second outer plies is micro-embossed. Alternatively, one of the first and second outer plies is structured by a TAD process. In other words, all combinations of outer plies which are structured by a TAD process or micro-embossed are within the scope of the invention.

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:

Figs. Ia to Id are diagrammatic illustrations of a tissue paper product according to a first embodiment of the invention, wherein Figs. Ib, Ic and Id show the first outer ply, middle ply and the second outer ply, respectively and Fig. Ia is a cross- sectional view of the three-ply tissue product along the lines A-A in Figs. Ib to Id;

Fig. 2 is a schematic representation of a paper converting device for producing the multi-ply tissue paper product according to Fig. 1;

Figs. 3a to 3d are diagrammatic illustrations of a tissue paper product according to a second embodiment of the invention, wherein Figs. 3b, 3c and 3d show the first outer ply, middle ply and the second outer ply, respectively and Fig. 3a is a cross-sectional view of the three-ply tissue product along the lines B-B in Figs. 3b to 3d;

Fig. 4 is a schematic representation of a paper converting device for producing the multi-ply tissue paper product according to Fig. 3;

Figs. 5a to 5d are diagrammatic illustrations of a tissue paper product according to a third embodiment of the invention, wherein Figs. 5b, 5c and 5d show the first outer ply, middle ply and the second outer ply, respectively and Fig. 5a is a cross- sectional of the three-ply tissue product along the lines C-C in Figs. 5b to 5d;

Fig. 6 is a schematic representation of a paper converting device for producing the multi-ply tissue paper product according to Fig. 5;

Fig. 7 is a schematic cross section of a tissue paper according to a fourth embodiment of the invention having four plies,-

Fig. 8 is a schematic representation of the production process of the four ply tissue product of Fig. 7; and

Fig. 9 is a schematic representation of a paper machine for producing the tissue paper of Fig. 7.

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. In the schematic drawings according to Fig. Ia, 3a and 5a, the heights of the protuberances of the microstructure patterns and the heights of the decor protuberances of the decor embossing were selected to clarify the invention and are not drawn to scale.

In the following embodiments, the outer plies are micro-embossed and at least one outer ply carries an additional decor embossing. However, it should be apparent to those skilled in the art that it is also possible to structure one or both outer plies using a TAD process.

Figs. Ia to Id describe a first embodiment of a three ply- tissue paper product which can be used as a toilet paper, a kitchen roll or a handkerchief. However, the use of the multi-ply tissue paper is not limited to these exemplified uses. Same applies to the number of plies in all exemplified embodiments which is not limited to three. If it is desired to provide more bulk it is easily possible to add one or more further volume embossed middle plies to the product.

Fig. Ib shows the first outer ply from above, whereas Fig. Id shows the second outer ply from below.

In the embodiment according to Fig. Ia, there are first and second outer plies which, in the product 10 according to Fig. Ia, are the first outer ply 12 and the second outer ply 14.

Between the first outer ply 12 and the second outer ply 14 there is sandwiched a middle ply 16, the protuberances of which are not in registration with the protuberances of the first outer ply 12 and the second outer ply 14. The first outer ply 12 and the second outer ply 14 are also combined so that a random configuration of the micro embossing pattern described later on the first outer ply 12 and the second outer ply 14 results.

As can be best seen from Figs. Ia and Ib, the first outer ply 12 is provided with a first micro embossing pattern 18 in the shape of little protrusions having a height hi of between 0.1 and 1.5 mm, and more preferably between 0.1 to 1.0 mm. The density of the protuberances of the first micro embossing pattern 18 is greater than 40 protuberances/cm^ , preferably greater than 60 protuberances/cm^ . The first outer ply 12 is additionally provided with a decor embossing pattern 21 with decor protuberances 21 having a fourth height h4. The fourth height h4 is chosen such that the difference in height Δh between the first height hi of the micro embossing pattern 18 of the first outer ply 12 and the fourth height h4 of the decor protuberances 21 is in a range between 0.4 mm and 1 mm. In other words, the decor protuberances are raised over the protuberances of the micro embossing pattern 18 of the first outer ply 12 such that they are clearly distinguishable from the micro embossing pattern.

The height difference Δh between decor protuberances 21 and micro embossing protuberances 18 of between 0.4 mm and 1 mm ensures that the decor embossing pattern is clearly visible and can be haptically experienced. The decor embossing pattern in this configuration, furthermore, provides the multi-ply tissue paper with even more volume compared to a multi-ply tissue paper without the described decor embossing protuberances .

The decor embossing pattern can either be formed by elongate protuberances which act as a line segment or by discrete dot- like protuberances which are assembled to form an aesthetic decor pattern. In particular, the decor embossing can have a shaping of aesthetic motives, such as flowers, or can consist of logos or trademarks of the manufacturer or retailer.

The second outer ply 14 (see also Fig. Id) is provided with a second micro embossing pattern 22 having a height h2 which can be different from the height hi. In any case, the height h2 is preferably between 0.1 and 1.5 mm and, preferably between 0.1 and 1.0 and therefore, in the same range as the height hi. The micro embossing pattern of the second outer ply 14 has a density of the protuberances of greater than 40 protuberances/cm-^ and preferably greater than 60 protuberances/cm^ • Even though in the present embodiment the decor embossing pattern is only shown on the first outer ply 12, it is conceivable that such decor embossing pattern could be provided on the second outer ply 14 instead or in a combined configuration on the first outer ply 12 as well as on the second outer ply 14 (such configuration is shown in figs. 3a- 3d below) . In the latter case, the decor patterns of the first and second outer plies can be identical or disparate.

The middle ply 16 according to Fig. Ic is also provided with an embossing. The embossing with a height H has a big ^• embossing pattern 17 with a density of the protuberances of less than 40 protuberances per cm^ .

The height H ranges between 0.3 and 3.0 mm and preferably between 0.7 and 2.5 mm.

In a preferred embodiment of the invention, the volume embossing of the middle ply has a density of about 30 or less than 30 protuberances/cm^ in combination with a density of the micro embossing pattern of the first outer ply and second outer ply of about 60 protuberances/cm^ .

As outlined above, the middle ply is not in registration with the first or second outer plies 14 so that a random configuration of the individual protuberances in the three plies occurs.

The ply bonding is performed by using small lamination dots 24 in combination with a small lamination embossing pattern 26 which is applied from the second outer ply 14.

The manufacturing method of the product 10 according to Fig. Ia is schematically described in Fig. 2. The first outer ply 12, middle ply 16 and second outer ply 14 are fed to the apparatus in the direction of arrows A, B and C. The first outer ply 12, middle ply 16 and second outer ply 14 are separately embossed between a pair of rollers wherein a usual combination of rollers, like a rubber rollers 31a, 31b, 31c in cooperation with steel rollers 28a, 28b, 28c is used. The tissue plies are embossed in the nip between the corresponding rubber roller and engraved steel roller.

The embossing pattern for the three separate plies is different for the product shown in Fig. Ia. Wherein the second outer ply 14 is provided with an micro embossing pattern only, the middle ply is volume embossed with a higher height of the protuberances and a lower density of protuberances per area and the first outer ply is both provided with a micro embossing pattern with geometrically regularly oriented small protuberances and a decor embossing pattern to provide the first outer ply with a decor distributed in a regular pattern over the surface of the first outer ply 12.

The volume embossed middle ply 16 and the micro embossed and design embossed first outer ply 12 are combined together by means of a roller 32 whereas the second outer ply 14. is separately fed around a rubber anvil roller 38 and through the nip between the rubber anvil roller 38 and a lamination embossing roller 40 with a lamination embossing pattern 26 at a lamination station 34 where a small lamination embossing pattern for the subsequent ply bonding with the first outer ply 12 and middle ply 16 is made. The application of the adhesive by means of the rollers 36 can be carried out using a standard technique.

The second outer ply 14 and the combined first outer ply and middle ply 12, 16 are brought in contact to another and bonded together between a marrying roller 44 and a lamination embossing roller 40 with a lamination embossing pattern. The combined three ply tissue product 10 leaves the apparatus in the direction of arrow D. Figs. 3a to 3d relate to a further product according to a slightly different embodiment of the invention. However, the same elements as those shown in Figs. Ia to Id are given the same reference numerals. The first outer ply 12 according to Fig. 3b is embossed with the micro embossing pattern 18 with the height hi corresponding to the micro embossing pattern explained in more detail for the product 10 above. The middle ply 16 according to Fig. 3c is also volume embossed with a big embossing pattern having a density of the protuberances of less than 40 dots/cm^ and a height H. The second outer ply 14 according to Fig. 3d is micro embossed with a micro embossing pattern 22 with a height h2.

A decor embossing pattern with decor protuberances 21 having a height h4 is provided on the first outer ply 12. The height difference Δh between the height hi of the micro embossing pattern 18 and the height h4 of the decor protuberances is between 0.4 mm and 1 mm. Additionally, a decor embossing pattern with decor protuberances 21' having a height h4 ' is provided on the second outer ply 14. The height difference Δh ' between the height h2 of the micro embossing pattern 22 and the height h4 ' of the decor protuberances is between 0.4 mm and 1 mm.

The height differences Δh, Δh¹ can be equal or disparate.

The decor protuberances 21, 21' in the current embodiment do not have the same length and are thus disparate, but it is conceivable that the decor protuberances on the first outer ply 12 as well as on the second outer ply 14 can be identical .

In any case, the decor protuberances add additional volume to the multi-ply tissue paper product in that they increase the felt thickness of the product by Δh + Δh¹. This gives more volume to the product, especially when it is rolled onto a bobbin. A further difference between the product 10 diagrammatically shown in Fig. Ia above and product 20 according to the present embodiment lies in the ply bonding used. There is a separate ply bonding using a deep embossing 42. This deep embossing 42 could also carry a design pattern, e.g. with discrete flower design lamination dots or with deep spots.

As can be best seen from a comparison between Figs. 2 and 4, the first outer ply 12 and the middle ply 16 can be created in a similar way to that already described in connection with Fig. 2. The first outer ply and middle ply are combined at the roller 32 to a combined, two-ply web 15 which passes between a rubber roller 38 and a lamination embossing roller 40 with a lamination embossing pattern which are parts of the lamination station 34 also comprising with the lamination rollers 36. In this lamination station the lamination is performed by deep embossing and could be provided with a desired design, e.g. flowers. Then the two-ply intermediate product 15 is combined with the second outer ply 14 which is being embossed by the rollers 28c, 31c with the micro embossing pattern as well as with the decor embossing pattern. The second outer ply 14 is then brought in contact to the two-ply intermediate product 15 between the spot lamination roller and a further marrying roller 44.

The difference between the products 10 and 20 resides in that in the product 10 according to Fig. Ia, the first outer ply is provided with a micro embossing and a decor pattern embossing, and the second outer ply is provided with a micro embossing and a lamination pattern, whereas in the product 20 according to Fig. 3a, the second outer ply is micro embossed and carries a decor embossing pattern and additionally to the decor embossing pattern in the first outer ply 12 a design embossing in the first outer ply 12 is performed by way of the design lamination dots 42. Figs. 5a to 5d show another embodiment of the invention. The first outer ply 12 of the product 30 according to Fig. 5b is provided with a micro embossing pattern 18 with the height hi and with a decor embossing pattern with decor protuberances 21 having a height h4. The density of the protuberances of the micro embossing pattern 18 corresponds to that of the products 10 and 20 according to Figs. Ia and 3a. The decor embossing pattern can consist of elongate, line segment-like and/or dot-like protuberances.

The difference in height Δh between the height hi of the micro embossing pattern and the height h4 of the decor protuberances 21 is between 0.4 mm and 1 mm. In other words, the decor protuberances 21 overtop the micro embossing pattern 18 by the height difference Δh.

The second outer ply 14 according to Fig. 5d is also provided with a micro embossing pattern with a height h2 and under the same conditions as outlined above with reference to Figs. Ia to Id. Same applies to the middle ply 16 according to Fig. 5c which is volume embossed with a big embossing pattern with a density of the protuberances 17 of less than 40 protuberances/cm² and preferably in a range of 30 or less than 30 protuberances/cm².

The ply bonding of the product 30 is generated without the use of an adhesive. The mechanical ply bonding system by means of which the three plies are bonded together in the regions 46 uses small needles or spikes to press together the three plies.

Fig. 6 gives the schematic production process of the three ply product 30 shown in Fig. 5a. The first outer ply 12, middle ply 16 and second outer ply 14 are all provided with a desired embossing pattern. The first outer ply 12 receives a micro embossing pattern and a decor embossing pattern as described above, both of which are applied in the nip between a steel engraved roller 28a and a rubber roller 31a. The middle ply 16 is volume embossed between a steel roller 28b and a rubber roller 31b and the second outer ply 14 is only provided with a micro embossing pattern by means of a steel roller 28c cooperating with a rubber roller 31c. All three separately embossed plies are combined at the roller 32 and receive the mechanical ply bonding in the nip between a structured steel embossing roller 50 and a corresponding counter roller 52. The counter roller 52 can be a smooth steel roller. The structured steel embossing roller can be provided with needle-like protrusions which press together the combined three-ply tissue paper and generate a mechanical ply bonding to the product 30 before leaving the apparatus.

Fig. 7 is a schematic cross-section through a four ply tissue product 10' of a fourth embodiment comprising a first outer ply 12 and a second outer ply 14. The first outer ply 12 and the second outer ply 14 may have all features of the first and second outer plies of the embodiments described above.

Between the first outer ply 12 and the second outer ply 14 are sandwiched two middle plies 16, 16', the protuberances of which are not in registration with the first outer ply 12 and the second outer ply 14. The heights H, H¹ of the protuberances of the middle plies 16, 16' drawn to be equal in the schematic figure but can be chosen such that in a preferred alternative of this embodiment the heights are different from each other.

The additional middle layer 16' introduces, compared to the first to third embodiments, additional volume to the tissue which results in an tissue paper with improved properties and less material usage due to the additionally introduced volume .

As to the materials, diverse materials can be used for the plies. For example, the first and second outer plies can be made from soft fibers and/or at least one middle ply can be made from slush pulp and/or recycling fibers. Such a combination provides the advantage of a tissue product with a soft feel and high volume which is at the same time, due to the middle plies, cost efficient. With the tissue paper of this embodiment the optimal fiber usage under a cost saving aspect as well as under a comfort aspect can be achieved. A comfort tissue paper can be achieved by reducing the fiber usage at the same time.

Fig. 8 shows schematically the production process of the four ply tissue 10' of the fourth embodiment shown in Fig. 7. The first outer ply 12, the second outer ply 14 and the two middle plies 16, 16 ' are fed from the left side of the figure to an embossing station 100 comprising combinations of rollers 112, 114, 116, 116', each embossing one of the plies 12, 14, 16, 16'. The combinations of rollers comprise rubber rollers in cooperation with steel rollers which carry the embossing pattern.

The embossed plies 12, 14, 16, 16 ' are then fed from the embossing station 100 into a combination station 120 where the plies are combined to the four ply tissue 10' .

Fig. 9 shows an apparatus for producing the four ply tissue paper 10'. The apparatus comprises an embossing station 100 and a combination station 120'. The first outer ply 12, the second outer ply 14 and the two middle plies 16, 16' are fed from the right side of the figure to the apparatus . Each ply is fed separately to the embossing station 100 and to the appropriate roller combination 112, 114, 116, 116'. The roller combinations typically comprise a rubber roller and a steel roller which carries the embossing pattern.

The readily embossed plies 12, 14, 16, 16' are then transported to the combination station 120' where in a first step the first outer ply 12 and the two middle layers 16, 16' are combined in a combination stage 121. After these upper three plies have been combined, the second outer ply is added to the three readily combined upper plies in a second combination stage 122.

In all embodiments, the heights H, H¹ of the middle plies can be at least 1.3 times greater than the heights hi, h2 of the first outer ply or second outer ply, respectively, and preferably 1.5 times greater and most preferably 2.0 times greater than the heights hi, h2 of the first and second outer plies .

All above described embodiments have in common that the multi-ply tissue paper product is a combination of micro embossed first and second outer plies where at least one of the outer plies carries a decor embossing pattern with decor protuberances in combination with a middle ply which is volume embossed using a big embossing pattern. The difference in height Δh, Δh¹ between the height h4 , h4 ' of the decor protuberances and the height of the respective outer ply is between 0.4 mm and 1 mm. The three plies are combined in an unregistered way wherein different types of ply bonding and different types of graphic embossing can be used. In general, the micro-embossed outer plies provide softness to the multiply product and the volume-embossed middle ply generates bulk to the product, whereas the decor embossing pattern gives additional feel and appearance to the product while providing additional volume.

Claims

1. Multi-ply tissue paper product (10; 20; 30), comprising: at least three structured plies of paper; a first outer ply (12) with a first microstructure pattern with first protuberances (18) having a first height (hi) ; a second outer ply (14) with a second microstructure pattern with second protuberances

(22) having a second height (h2) ; at least one middle ply (16) sandwiched between the first outer ply (12) and the second outer ply (14) with a third structure pattern being an embossed pattern with third protuberances (17) ; at least one additional decor embossing in the first outer ply (12) and/or second outer ply (14) with decor protuberances (21, 21') having a fourth height (h4, h4 ' ) , whereas the difference in height

(Δh, Δh¹) between the first height (hi) and/or the second height (h2) and the fourth height (h4, h4 ' ) is between 0.4 mm and 1 mm; wherein the first and second outer plies and the at least one middle ply are ply bonded together in a non-registered manner.

2. Multi-ply tissue paper product according to claim 1, characterized in that the first protuberances (18) have a first density of more than 40 protuberances/cm^ , the second protuberances (22) have a second density of more than 40 protuberances/cm^ and the third protuberances (17) have a density of less than 40 protuberances/cm².

3. Multi-ply tissue paper product according to claim 1 or 2, characterized in that the protuberances (17) of the third structure pattern have a height (H) which is at least 1.3, preferably 1.5 times and most preferably 2.0 times greater than (hi) and (h2) , respectively.

4. Multi-ply tissue paper product according to any of the preceding claims, characterized in that the decor protuberances (21, 21') consist of elongated structures, line segments, dots or combinations thereof.

5. MuIti -ply tissue paper product according to claim 4,' characterized in that the length of the line segments being 2 mm - 20 mm and the width of the line segments being 0.1 mm - 2 mm.

6. Multi-ply tissue paper product according to any of the preceding claims, characterized in that the decor protuberances (21, 21') and the first protuberances (18) and/or second protuberances (22) extend essentially in the same direction relative to the plane of the respective first outer ply (12) and/or second outer ply (14) .

7. Multi-ply tissue paper product according to claim 6, characterized in that the decor protuberances (21, 21') and the first protuberances (18) and/or second protuberances (22) extend essentially to the side of the respective first outer ply (12) and/or second outer ply (14) that is opposite the side contacting the middle ply( 16) .

8. Multi-ply tissue paper product according to any of the preceding claims, characterized in that the first outer ply (12) as well as the second outer ply (14) carry the decor protuberances (21, 21') of the decor embossing.

9. Multi-ply tissue paper product according to claim 7, characterized in that the decor protuberances (21, 21') of the first outer ply (12) and the second outer ply (14) are essentially identical.

10. Multi-ply tissue paper product according to any of the preceding claims, characterized in that the ply bonding is generated by adhesive lamination using a lamination pattern (24) .

11. Multi-ply tissue paper product according to any of the claims 1 to 9, characterized in that ply bonding is generated by a mechanical ply bonding technique.

12. Multi-ply tissue paper product according to any of the preceding claims, characterized in that at least one of the first and second outer plies is a TAD-paper.

13. Multi-ply tissue paper according to any of claims 1 to 11, characterized in that at least one of the first and the second outer plies is micro-embossed.

14. Multi-ply tissue paper product according to any of the preceding claims, characterized in that the decor protuberances (21, 21') have a dot-like shape arranged in a way to form an aesthetic pattern.

15. Multi-ply tissue paper product according to any of the preceding claims, characterized in that the paper has at least four structured plies of paper and comprises two middle plies (16, 16').

16. Multi-ply tissue paper product according to claim 15, characterized in that the structure patters of the two middle plies (16, 16') have third protuberances of different heights (H, H¹).

17. Multi-ply tissue paper product according to any of the preceding claims, characterized in that all plies of the paper are structured.

18. Multi-ply tissue paper product according to any of the preceding claims, characterized in that at least one ply is made of a different material with respect to the remaining plies.

19. Multi-ply tissue paper product according to claim 18, characterized in that the first and/or second outer plies (12, 14) are made of soft fibers and/or at least one middle ply (16, 16') is made from slush pulp and/or recycling fibers.

20. Method of producing a multi-ply tissue paper comprising the steps : a) structuring a first outer ply (12) with a first microstructure pattern with first protuberances (18) having a first height (hi) ; b) structuring a second outer ply (14) with a second microstructure pattern with second protuberances (22) having a second height (h2) ; c) embossing the first outer ply (12) and/or second outer ply (14) with decor protuberances (21, 21') having a fourth height (h4, h4 ^■ ) , whereas the difference in height (Δh, Δh¹) between the first height (hi) and/or the second height (h2) and the fourth height (h4, h4 ' ) is between 0.4 mm and 1 mm; d) embossing a middle ply (16, 16') with a third structure pattern being an embossing pattern; and e) combining together the three plies in an unregistered way.

21. Method of producing a multi-ply tissue paper according to claim 20, wherein in step a) the first protuberances (18) are structured such as having a first density of more than 40 protuberances/cm², in step b) the second protuberances (22) are structured such as having a second density of more than 40 protuberances/cm² and in step d) the embossing pattern having a density of less than 40 protuberances/cm².

22. Method of producing a multi-ply tissue paper according to claim 20 or 21, wherein the step e) comprises: el) providing a separate mechanical ply bonding of all three plies using exclusively a mechanic ply bonding technique without the use of adhesive.

23. Method of producing a multi-ply tissue paper according to any of the claims 20 to 22, wherein step e) is further subdivided into el) combining the first outer ply (12) and the middle ply (16) to a combined tissue web (15); e2) applying an adhesive to the combined tissue web (15) ; and e3) marrying the combined tissue web (15) and the second outer ply (14) .

24. Method of producing a multi-ply tissue paper according to claim 23, wherein in step e2) the lamination is provided using a design pattern of lamination dots.

25. Method of producing a multi-ply tissue paper according to any of the claims 20 to 24, characterized in that the structuring of at least one of the first outer ply and second outer ply is performed by embossing a micro- embossing pattern.

26. Method of producing a multi-ply tissue paper according to any of the claims 20 to 25, characterized in that the structuring of at least one of the first outer ply and second outer ply is performed by a TAD process.

27. Method of producing a multi-ply tissue paper according to any of the claims 20 to 26, characterized in that in step d) two inner plies (16, 16 ') are embossed with a third structure pattern.

28. Method of producing a multi-ply tissue paper according to claim 27, characterized in that the structure patterns of the two middle plies (16, 16') have third protuberances of different heights (H, H¹).

29. Method of producing a multi-ply tissue paper according to any of the claims 20 to 28, characterized in that the plies are embossed separately before being combined together.