TISSUE PRODUCT AND METHOD AND APPARATUS FOR PRODUCING SAME

Abstract

A multi-ply tissue paper product includes at least three plies. The tissue paper product includes a first inner ply being a creped ribbed ply and having a basis weight of 10 to 30 gsm, and a first outermost ply and a second outermost ply on each side of said inner ply, the first and second outermost plies being non-ribbed plies, wherein a creped ribbed ply is a ply including ribs and valleys providing an average core roughness Rk in the range 10 to 300 μm, and peaks being 4 to 12 per cm as measured along said first direction; and wherein a non-ribbed ply is a ply displaying no parallel ribs and valleys extending continuously along any direction of the ply or displaying parallel ribs and valleys extending continuously along any direction of the ply, the ribs and valleys providing peaks being less than 4 per cm.

Claims

1. A multi-ply tissue paper product, comprising at least three plies wherein the tissue paper product comprising a first inner ply being a creped ribbed ply and having a basis weight of 10 to 30 gsm, and a first outermost ply and a second outermost ply on each side of said inner ply, said first and second outermost plies being non-ribbed plies, wherein a creped ribbed ply is defined as a ply comprising creping lines extending along a first direction, and parallel ribs and valleys extending continuously along a second direction being substantially perpendicular to said first direction, said ribs and valleys providing an average core roughness Rk in the range 10 to 300 μm, and a number of peaks being 4 to 12 per cm as measured along said first direction; and wherein a non-ribbed ply is defined as a ply displaying no parallel ribs and valleys extending continuously along any direction of the ply or displaying parallel ribs and valleys extending continuously along any direction of the ply, said ribs and valleys providing a number of peaks being less than 4 per cm.

2. Multi-ply tissue paper product according to claim 1, wherein said ribs and valleys of said first inner ply provides a number of peaks as measured along said first direction being 6 to 12 per cm, preferably 8 to 12 per cm and/or said ribs and valleys of said first inner ply providing an average core roughness Rk in the range to 150 μm.

3. Multi-ply tissue paper product according to claim 1, wherein said first inner ply has a basis weight of 12 to 28 gsm, preferably 14 to 24 gsm.

4. Multi-ply tissue paper product according to claim 1, wherein, on at least one side of said first inner ply, preferably on each side of said first inner ply, the tissue paper product comprises no more than two plies being non-ribbed plies external of said first inner ply.

5. Multi-ply tissue paper product according to claim 1, wherein on at least one side of said first inner ply, preferably on each side of said first inner ply, the tissue paper product comprises no more than one outer ply being a non-ribbed ply external of said inner ply.

6. Multi-ply tissue paper product according to claim 1, wherein said outermost ply or plies being a non-ribbed ply external of said inner ply has/each have a basis weight being less than 30 gsm.

7. Multi-ply tissue paper product according to claim 1, wherein said outermost ply or plies being a non-ribbed ply displays no parallel ribs and valleys extending continuously along any direction of the ply or each display parallel ribs and valleys extending continuously along any direction of the ply, said ribs and valleys providing a number of peaks being less than 2 per cm.

8. Multi-ply tissue paper product according to claim 1, wherein said outermost ply or plies being a non-ribbed ply displays no parallel ribs and valleys extending continuously along any direction of the ply or each display parallel ribs and valleys extending continuously along any direction of the ply, said ribs and valleys providing said ribs and valleys providing an average core roughness Rk less than 10 μm.

9. Multi-ply tissue paper product according to claim 1, wherein said multi-ply tissue paper product comprises an adhesive joining at least two of the plies of said multi-ply tissue product, said adhesive being applied over a total adhesive area being less than 10% of a total area of said multi-ply tissue product.

10. Multi-ply tissue paper product according to claim 1, wherein said multi-ply tissue paper product comprises construction embossments joining at least two of the plies of said multi-ply tissue product, said construction embossments being applied over a total construction embossment area being less than 10% of a total area of said multi-ply tissue product.

11. Multi-ply tissue paper product according to claim 1, wherein said multi-ply tissue paper product comprises no more than five plies.

12. Multi-ply tissue paper product according to claim 1 wherein said multi-ply tissue paper product comprises four plies only.

13. Multi-ply tissue paper product according to claim 1, wherein said multi-ply tissue paper product comprises three plies only.

14. Multi-ply tissue paper product according to claim 1, wherein said first and/or second outermost ply is a creped ply, preferably said creped ply is produced by CWP technology.

15. Multi-ply tissue paper product according to claim 1, wherein said first and/or second outermost ply is a structured ply.

16. Multi-ply tissue paper product according to claim 1, wherein the first and/or second outermost ply is/are a pre-embossed plie(s).

17. Multi-ply tissue paper product according to claim 1, wherein the product comprises at least a second inner ply.

18. Multi-ply tissue paper product according to claim 17, wherein the second inner ply is a pre-embossed ply.

19. Multi-ply tissue paper product according to claim 17 or 18, wherein said second inner ply is a creped ribbed ply.

20. Multi-ply tissue paper product according to claim 17 or 18, wherein the second inner ply is a non-ribbed ply.

21. Multi-ply tissue paper product according to claim 17, wherein said first inner ply is non-embossed, and said second inner ply is micro-embossed.

22. Multi-ply tissue paper product according to claim 17, wherein said first and second inner plies are adjacent plies in the product.

23. Multi-ply tissue paper product according to claim 17, wherein said first inner ply is non-embossed.

24. Multi-ply tissue paper product according to claim 17, wherein at least one, preferably both of two adjacent plies to the first inner ply is/are construction embossed to join to the first inner ply.

25. Multi-ply tissue paper product according to claim 24, wherein said adjacent ply or plies are joined to the first inner ply by adhesive and/or mechanical ply-bonding.

26. Multi-ply tissue paper product according to claim 22, wherein at least one, preferably both of said two adjacent plies to the first inner ply are pre-embossed.

27. Method for manufacturing a multi-ply tissue paper web for tissue paper products comprising: providing a first inner web having a basis weight of 10 to 30 gsm, and being a creped ribbed web, a creped ribbed web being defined as a web comprising creping lines extending along a first direction, and parallel ribs and valleys extending continuously along a second direction being substantially perpendicular to said first direction, said ribs and valleys providing an average core roughness Rk in the range 10 to 300 μm, and a number of peaks being 4 to 12 per cm as measured along said first direction; providing a first and a second outermost web being non-ribbed webs, wherein a non-ribbed web is defined as a web displaying no parallel ribs and valleys extending continuously along any direction of the web or displaying parallel ribs and valleys extending continuously along any direction of the web, said ribs and valleys providing a number of peaks being less than 4 per cm; positioning said first inner web between said first and second outermost webs; ply-bonding said webs to a form a multi-ply web wherein said first and second outermost webs form the outermost plies of the multi-ply web.

28. Method according to claim 27, wherein said step of providing said at least first inner web comprises providing a web manufactured by use of a creping blade provided with a rake edge comprising indentations.

29. Method according to claim 28, wherein said rake edge comprises indentations in a number of 4 to 12 per cm over the rake edge length, and/or said indentations having a depth of 0.1 to 1.0 mm.

30. Multi-ply tissue product manufactured by the method of claim 27.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0145] With reference to the appended drawings, below follows a more detailed description of multi-ply products cited as examples.

[0146] In the drawings:

[0147] FIG. 1 schematically illustrates a ply being a creped ribbed ply,

[0148] FIG. 2 illustrates an Abbott-Firestone curve as used for defining roughness parameters;

[0149] FIG. 3a illustrates roughness measurements made on a creped ribbed ply in the cross-direction CD;

[0150] FIG. 3b illustrates roughness measurements made on a standard creped ply made by CWP (Conventional Wet Pressing) in the machine direction MD;

[0151] FIG. 4 schematically illustrates a multi-ply product,

[0152] FIG. 5 schematically illustrates another multi-ply product;

[0153] FIG. 6 schematically illustrates a manufacturing method suitable for achieving a multi-ply product;

[0154] FIG. 7 schematically illustrates yet another multi-ply product;

[0155] FIG. 8 schematically illustrates a manufacturing method for achieving a multi-ply product;

[0156] FIG. 9 schematically illustrates yet another multi-ply product having four plies;

[0157] FIG. 10 schematically illustrates a manufacturing method suitable for achieving a multi-ply product.

DETAILED DESCRIPTION

[0158] FIG. 1 is a perspective view schematically illustrating a ply being a creped ribbed ply as described herein.

[0159] The creped ribbed ply displays creping lines as is typical for creped products. The creping lines extend generally along a first direction, which is the cross-direction of the ply. Creping lines, being the result of wrinkling when the creped product is removed from the dryer by the doctor blade, are usually slightly irregular in their nature.

[0160] The creped ribbed ply also displays ribs and valleys extending continuously and in parallel along a second direction perpendicular to the first direction of the ply. The second direction would hence be the machine direction of the ply. The structure of the creped ribbed ply is regular, meaning that the distribution and shape of the ribs have a regular appearance over the ply.

[0161] If seen from a top side of the creped ribbed ply (with reference to FIG. 1) a plurality of ribs 300 extend in parallel forming valleys 400 between them. The ribs 300 and valleys 400 extend regularly and continuously all over the ply. As seen in FIG. 1, the ribs and valleys are apparent also on a bottom side of the product, where the bottom side of the upwardly directed ribs 300 form bottom-side valleys 400′ and the bottom side of the upwardly directed valleys 400 form bottom-side ribs 300′. Generally, the top side and the bottom side ribs 300, 300′ may not be identical, but the height of the ribs may be greater on one of the sides.

[0162] As proposed herein, at least one inner ply of the multi-ply product claimed should be a creped ribbed ply as defined herein and as illustrated in FIG. 1.

[0163] Hence, creped ribbed ply is a ply comprising creping lines extending along a first direction, and parallel ribs and valleys extending continuously along a second direction being substantially perpendicular to said first direction, said ribs and valleys providing an average core roughness Rk in the range 10 to 300 μm, preferably 20 to 150 μm, and a number of peaks being 4 to 12 per cm as measured along said first direction.

[0164] Core Roughness Rk is defined according to ISO 13565-1 and ISO 13565-2.

[0165] The roughness profile as per ISO 13565-1 is generated by a special filtering technique minimizing profile distortions due to deep valleys in plateau profiles. A straight line divides the Abbott-Firestone curve (See FIG. 2) into three areas from which the parameters are then computed as per ISO 13565-2.

[0166] Core roughness depth Rk is the depth of the roughness core profile. In other words, it is the core height of the profile along the Y-axis of the Abbott-Firestone curve generated by placing a 40% line on the curve at the minimum slope point and extending the lines to the 0% and the 100% points.

[0167] Reduced peak height Rpk is the mean height of the protruding peaks above the roughness core profile.

[0168] Reduced valley depth Rvk is the mean depth of the valleys protruding from the roughness core profile.

[0169] Mr1 and Mr2 are the smallest and the highest material ratios of the roughness core profile.

[0170] Evaluation length is the length over which the values of surface parameters are evaluated. It is recommended that the evaluation length consists of five sampling lengths although it may comprise any number of sampling lengths.

[0171] Mean Line M is the reference line about which the profile deviations are measured. The mean line of the roughness profile is usually established by analogue or digital filters with the selected cut-off corresponding to the roughness sampling length.

[0172] Profile Peak is the point of maximum height on a portion of a profile that lies above the mean line and between two intersections of the profile with the mean line.

[0173] Profile valley is the point of maximum depth on a portion of a profile that lies below the mean line and between two intersections of the profile with the mean line.

[0174] With number of peaks per cm is meant herein the number of Profile Peaks as defined in the above per cm.

[0175] For determining the relevant parameters, an Alicona Infinite Focus SL was used with the software IF-Measure Suite Version 5.1.

[0176] pictures were taken of each ply to be examined. On each picture, 10 lengths, each length being 1 cm, were drawn at different positions on the ply. Accordingly, 50 measurements (10 lengths on 5 pictures) were used for calculating the different parameters, and an average of all measurements was formed.

[0177] FIG. 3a is a graph illustrating roughness measurements on a ply being a creped ribbed ply, as measured along the cross-direction of the ply. The regular ribs and valleys are clearly visible from the graph, and the number of peaks per cm—corresponding to the number of ribs per cm—may be counted. In this sample, there are 8 peaks/cm.

[0178] FIG. 3b is a graph illustrating roughness measurements on a ply being an ordinary CWP ply, i.e. a creped ply not being defined as a creped ribbed ply. The measurement is made along the machine direction of the ply, and hence illustrates the appearance of the creping lines. It is seen how the creping lines lack the regular appearance of the ribs-and-valleys in FIG. 3a.

[0179] For a creped ribbed ply, the appearance of the ply if roughness is measured along the machine direction, i.e. parallel to the ribs and valleys, may be found to be similar to the one in FIG. 3b, namely to display conventional creping lines.

[0180] A non-ribbed ply is defined herein as a ply displaying no parallel ribs and valleys extending continuously along any direction of the ply or displaying parallel ribs and valleys extending continuously along any direction of the ply, said ribs and valleys providing a number of peaks being less than 4 per cm. For variants of non-ribbed plies displaying no parallel ribs and valleys extending continuously along any direction of the ply, it will be sufficient to determine that no such continuous structures exist. For the case where the non-ribbed ply displays ribs and valleys continuously along any direction of the ply, but with a number of peaks less than 4 per cm, peaks-per-cm measurements such as those laid out in the above may be performed.

[0181] FIG. 4 schematically illustrates a variant of a multi-ply tissue paper product 1. It includes three plies, namely a first outermost ply 2, a second outermost ply 3 and an inner ply 100.

[0182] The inner ply 100 is a creped ribbed ply as described above, as illustrated by the undulations in the drawing forming ribs and valleys.

[0183] With “outermost ply” is meant an outermost ply of the multi-ply tissue paper product 1. For example, the first outermost ply 2 may be a top ply of the tissue paper product 1, and the second outermost ply 3 may be a bottom ply of the tissue paper product 1.

[0184] The outermost plies 2, 3 are non-ribbed plies as described above.

[0185] A multi-ply tissue paper product 1 may be a three-ply product consisting of three plies being said first outermost ply 2, second outermost ply 3 and said inner ply 100. In such a product the inner ply 100 being a creped ribbed ply is sandwiched between the first and second outermost plies 2, 3.

[0186] However, and as will be demonstrated in the following examples, variants with more than three plies are readily conceivable.

[0187] Regardless of the number of plies, the plies of the tissue product may be combined together by a combining operation of a chemical nature (e.g. by adhesive bonding), or of a mechanical nature (e.g. by knurling or edge-embossing), or a combination of both as mentioned in the above.

[0188] The first and/or second outermost ply may be embossed.

[0189] The first and/or second outer ply 2, 3 may be creped plies.

[0190] The first and/or second outer ply 2, 3 may be TAD plies.

[0191] FIG. 5 is a schematic side view of another variant of a multi-ply tissue paper product 1 comprising a first outermost ply 2, a second outermost ply 3 and an inner ply 100. The inner ply 100 is, although not illustrated in the drawing, a creped ribbed ply. The first and second outermost plies 2, 3 are non-ribbed plies.

[0192] In this tissue paper product 1, the first outer ply 2, the second outer ply 3 and the inner ply 100 are all construction embossed to achieve the bonding between the plies 2, 3, 100.

[0193] The first and second outermost plies 2, 3 may be non-embossed, i.e. they may have no other embossments than said construction embossments. Alternatively, the first and second outer plies 2,3 may be pre-embossed

[0194] FIG. 6 schematically illustrates a variant of a manufacturing method which may be used to provide a multi-ply tissue product.

[0195] A first web 2′ and a second web 100′ are directed together through a nip between an embossing roll 101 and an anvil roll 102. In this nip the first web 2′ and the second web 100′ are simultaneously provided with an embossing pattern.

[0196] Thereafter, an application roll 103 for adhesive applies adhesive to those parts of the second web 100′ at which there are protruding embossing elements in the embossing roll 101. (The adhesive is transported from an adhesive batch via an adhesive transfer roll to the application roll.) A third web 3′ is transported to the second web 100′ and adhesively bonded to the second web 100′ in a nip 110 between the embossing roll 101 and a marrying roll 111. The adhesive bonding takes place at those portions of the webs at which the adhesive was applied.

[0197] The resulting multi-ply web 1′ comprises three correspondingly embossed plies, bonded together by embossing and adhesive bonds. As will be understood from the above description, if the multi-ply web 1′ is formed to multi-ply tissue products e.g. by continued converting, in the tissue product 1 the first web 2′ forms the first outermost ply 2, the second web 100′ forms the inner ply 100 and the third web 3′ forms the second outermost ply 3.

[0198] The manufacturing method principally described in FIG. 6 is not limited to manufacturing of webs or products comprising three plies only. Instead, more than three plies may be achieved, for example four plies or five plies.

[0199] In particular, a four-ply web or product may be achieved, in which the two inner plies are both creped ribbed plies as described in the above.

[0200] FIG. 7 is a schematic side view of yet another multi-ply tissue product 1, which is assembled according to the method of the type referred to herein as “Nesfip” and as described in more detail in EP 1 081 284 A1. The product 1 comprises a first outermost ply 2, a second outermost ply 3, and an inner ply 100. The inner ply 100 is, although not illustrated in the drawings, a creped ribbed ply. The first and second outer plies 2, 3 are non-ribbed plies.

[0201] The first outermost ply 2 and the second outermost ply 3 are embossed with patterns 5, 7, 9 at least in part composed of discrete protrusions 6, 8, and 10. The protrusions face the inner ply 100.

[0202] The inner ply 100 is non-embossed. As such, the inner ply 100 may serve to hinder unintentional nesting between the adjacent layers, i.e. the first and second outer plies 2, 3.

[0203] The first outer ply 2 comprises a first embossment pattern 5 and a second embossment pattern 7. The height h of the second pattern 7 is less than the height H of the first pattern 5. The first pattern 5 comprises relatively high protrusions 6 with and the second pattern 7 comprises relatively low protrusions, the high protrusions 6 of the first pattern 5 being of heights H and the low protrusions 8 of the second pattern 7 having the height h less than those of the high protrusions, H>h.

[0204] Advantageously and as shown in FIG. 1, the second outer ply 3 comprises a single pattern 9, for example implemented by protrusions 12 of the height h′.

[0205] The plies 2, 3, and 100 are combined by joining the distal areas of at least part of the high protrusions 6 of the first outermost ply 2 and of at least part of the second outermost ply 3 with the inner ply 100.

[0206] At least one of the outer plies 2, 3 may comprise a pattern with a pattern density larger than 30 protrusions/cm.sup.2.

[0207] FIG. 8 illustrates schematically a variant of a method for producing a multi-ply tissue product being a Nesfip-type method.

[0208] In FIG. 8, a first web 2′ to form the first outer ply 2 is embossed in a first embossing apparatus 12 including an engraved cylinder 13 and a mating rubber cylinder rotating in the opposite direction. The cylinder 13 is engraved in a first relatively high pattern having embossing tips of height H1 and a relatively shallower pattern of embossing tips of height h1.

[0209] Thanks to the double-level engraving by the cylinder 13, a first pattern 5 and a second pattern 7 is made on the first outermost ply 2. The first pattern 5 is composed at least partly of high discrete protrusions 6 of height H. This pattern 5 with a relatively high embossment height H1 may form decorative elements, for example picots and/or flowers. The second pattern 7 is composed of relatively low protrusions 8 of height h, for example micro dots. The heights H and h depend on the depths H1 and h1 of the engravings and also on the other embossing parameters, such as pressure, rubber quality, etc.

[0210] Preferably, the inner web 100′, being a creped ribbed web as explained in the above, is previously non-embossed. The inner web 100′ is moved into position and superposed on the protrusions 6′, 8′ of the first embossed outermost web 2′ at the level of the engraved cylinder 13. In this manner, the web 100′ hugs the high protrusions 6′ of the embossed outer web 2′ while remaining substantially planar between two consecutive high protrusions 6′, the planar areas of the low protrusions 8′ being able to act as intermediary supports.

[0211] At the level of this junction between the embossed outer web 2′ and the inner web 100′, an adhesive 11 is applied to the outer side of the inner web 100′ using a glue dispenser 15.

[0212] In parallel, a second outer web 3′ is embossed separately by means of a second embossing apparatus 19 into an embossment pattern 9 at least in part composed of discrete protrusions 10′ of height h′. The apparatus 19 includes a cylinder 20 engraved with a pattern of embossing tips of height h4′ a and a mating rubber cylinder.

[0213] FIG. 9 is a schematic side view of another multi-ply tissue product 1. The tissue product 1 has a first outermost ply 2 which is a bottom ply and a second outermost ply 3 which is a top ply. The tissue product of FIG. 9 may be produced in accordance with a method of the type denoted herein as “NoveFip” and described in PCT/IB2018/001556.

[0214] The first outermost ply 2 and the second outermost ply 3 are both provided with an embossing pattern including micro-embossed protrusions 8a, 8b.

[0215] However, it is also possible to provide first and/or the second outermost ply 2, 3, as so-called structured plies, for example manufactured by means of a Through Air Drying Process (TAD).

[0216] In the example according to FIG. 9, two inner plies 4 and 100 are provided. The first inner ply 100 is a creped ribbed ply. The first inner ply 100 is un-embossed (which means that first inner ply 100 is not embossed by means of a contact with an embossing roll before it is fed to the final ply-bonding).

[0217] In the illustrated embodiment the first inner ply 100 being a creped ribbed ply is adjacent to the bottom ply being the first outermost ply 2.

[0218] The second inner ply 4 between the first inner ply 100 and the second outermost ply 3 is a non-ribbed ply. The second inner ply 4 is micro-embossed in order to increase the bulk of the tissue product 1.

[0219] The first outermost ply 2 comprises a micro-embossed pattern comprising embossed protrusions 8b having a height h1. The second outermost ply 3 comprises a micro-embossed pattern comprising embossed protrusions 8a having a height h3. The height h3 of the micro-embossed pattern of the second outermost ply 3 may be different from the height h1 of the micro-embossed pattern of the first outermost ply 2.

[0220] In addition to the micro-embossed pattern comprising the embossed protrusions 8a, the second outermost ply 3 may comprise a décor embossed pattern comprising decor embossed protrusions 9. The décor embossed protrusions 9 may have a height h2 higher than the height of the micro-embossed protrusions 8a of the second outermost ply 3. At the décor embossed protrusions 9 with said height h2, ply-bonding between all of the plies is achieved.

[0221] The application of adhesive may be restricted to an overall surface fraction of less than 10% of a total area of said multi-ply tissue product 1, preferably less than 6% of a total area of said multi-ply tissue product 1, most preferred 3 to 6%.

[0222] The restricted amount of adhesive is beneficial for the perceived softness of the product.

[0223] The micro-embossed protrusions 19 of the second inner ply 4 and the micro-embossed protrusions 8a of the adjacent second outermost ply 3 are not in register with one another. This increases the bulk and absorbency of the tissue product 1 because the protrusions 19, 8a cannot nest one into the other which would reduce the thickness of the tissue product.

[0224] Also, the micro-embossed protrusions 19 of the second inner ply 4 and the micro-embossed protrusions 8a of the adjacent second outermost ply 3 may have different densities so as to avoid/limit unintentional nesting between the protrusions 19, 8a which would reduce the thickness of the tissue product.

[0225] As may be seen in FIG. 9, the protrusions 19 of the micro-embossed second inner ply 4 cannot nest with the protrusions of the first outermost ply 2 as in between there is the non-embossed first inner ply 100. The thickness is not reduced which is positive for the bulk and absorbency of the tissue product 1.

[0226] FIG. 10 schematically shows a device for manufacturing a multi-ply tissue product according a method of the type referred to herein as Novefip. The first outermost web 2, the second outermost web 3, the first inner web 100 and the second inner web 4 are directed into the device 30.

[0227] The central element of the device 30 is the embossing roll S1 which is an engraved steel roll. The second outermost web 3 is directed into the nip between the embossing roll S1 and a counter roll 32 in order to emboss the second outermost web 3. After having been embossed, the second inner web 4 joins the second outermost web 3. Before joining the second outermost web 3 at the embossing roll S1, the second inner web 4 is micro-embossed in the nip between the engraved steel embossing roll S3 and the counter roll 34.

[0228] After the second outermost web 3 and the second inner web 4 have been joined at the embossing roll S1, glue is applied towards the second inner web 4 by means of a glue application device GU. Since the embossing roll S1 has micro-embossing protrusions of a smaller height and décor embossing protrusions of a greater height, the glue is only applied towards the second inner web 4 at the décor embossing protrusions with the greater height.

[0229] The first inner web 100 is non-embossed and fed towards the embossing roll S1 downstream of the glue application device GU. The first inner web 100 is directed into the gap between the embossing roll S1 and a second embossing roll S2 which also runs against the counter roll 38. The second embossing roll S2 is also an engraved steel roll with a micro-embossing pattern. In the nip between the second embossing roll S2 and the counter roll 38, the first outermost web 2 is embossed. The first inner web 100 joins the second inner web 4 and the first outermost web 2 and becomes sandwiched between these two.

[0230] After leaving the gap between the embossing roll S1 and the second embossing roll S2, the multi-ply structure is directed into the nip between the embossing roll S1 and a marrying roll M1 where the final ply bonding takes place. Downstream of the marrying roll M1, the multi-ply tissue web 1 can be directed to a perforating unit 40 at which the tissue web 1 receives perforation lines which are provided at regular intervals in a direction perpendicular to the longitudinal direction of the multi-ply tissue web 1.

[0231] Downstream of the perforating unit 40, the tissue web 1 can be wound to a roll or folded to a stack. Instead of perforations, the web 1 could be separated into individual pieces and optionally be folded to become a stack of individual sheets.

Detailed Examples

[0232] In the examples in the below, comparative examples are made between products including an inner ply being a creped ribbed ply as defined herein, and products without such a creped ribbed ply.

[0233] In the examples, the different plies are combined using different ply-bonding methods.

[0234] Non-ribbed plies used as outer plies:

TABLE-US-00001 Basis Thickness, MD tensile CD tensile MD weight mm strength, strength, stretch, Product gsm (12 ply) N/m N/m N/m TAD 19.3 2.9 95 53 11.8 Omega 20.1 1.67 135 60 22.7 Trio 18.8 1.75 91 51 24.1 Reference 17.7 1.25 206 147 21.5

[0235] Non-ribbed ply used as outer or inner ply:

TABLE-US-00002 MD CD Basis Thickness, tensile tensile MD weight mm strength, strength, stretch, Softness Product gsm (12 ply) N/m N/m N/m (TSA) Reference 17.7 1.25 206 147 21.5 2.0

[0236] Creped ribbed ply:

TABLE-US-00003 MD CD Basis Thickness, tensile tensile MD weight mm strength, strength, stretch, Softness Product gsm (12 ply) N/m N/m N/m (TSA) Thunder E 16.4 1.95 158 120 24.0 0.7

[0237] For the creped ribbed ply “Thunder E”, the number of peaks in the cross direction coming from the ribs and valleys is 9/cm, and Rk in cross direction is 70.7 μm. These measurements were made on the Yankee side of the ply, and in general, the ribs and valleys are slightly more pronounced on the Yankee side than on the Hood side of a ply.

[0238] The number of crepe lines of the Thunder E ply were 61/cm as measured in MD on the Hood side.

[0239] The non-ribbed plies TAD, Omega, Trio and Reference, were all found to have Rk values of at least 0.35 μm. However, none of them displayed any parallel ribs and valleys extending continuously along the plies.

[0240] In the below, the methods used for determining the various parameters were the following:

[0241] Firmness:

[0242] Firmness is a compression value measured on roll radius with a compression mass of 1 kg. The roll is positioned on a core support, and with a measurement plate for applying 1 kg weight to the middle of the roll. The 1 kg weight is slowly put on the measurement plate. 5 s after applying the roll, the movement of the measurement plate is recorded.

[0243] The firmness unit is 1/10 mm. For each roll, an average of 2 measurements is reported.

[0244] The rolls are conditioned for 24±4 h at 50±10% r. h. and 23±1° C.

[0245] The values in the table below indicate the firmness of the rolls from which the samples were taken. Firmness of the roll could influence the thickness of the product. To exclude this effect, comparison have been made between rolls having a similar firmness. As a consequence, sheet count and roll diameter of compared rolls are different.

[0246] Further details regarding firmness may be found in EP 1 541 756 A1

[0247] Basis Weight:

[0248] Basis weight is determined in accordance with ISO 12625-6: 2016.

[0249] The basis weight is determined in g/m.sup.2.

[0250] Thickness Per Sheet:

[0251] Thickness is determined in accordance with ISO 12625-3.

[0252] Dry Tensile Strength (MD, CD) and Tensile Stretch:

[0253] Dry tensile strength and tensile stretch are determined in accordance with ISO 12625-4.

[0254] A load cell of 100N was used.

[0255] Absorption:

[0256] Absorption is herein the water absorption capacity of the tissue paper. Water absorption capacity is the amount of water the sample is able to absorb, reported in g/g (i.e. g water/g material in sample).

[0257] Absorption was measured according to ISO12625-8:2011,

[0258] The water is deionized water, conductivity 0.25 mS/m at 25° C., in accordance with ISO14487.

[0259] Tsa Softness:

[0260] TSA indicates herein measurements of softness made with a softness test method (TSA—Tissue Softness Anlalyzer), that uses acoustic waves and has demonstrated to correlate well with hand panel tests for thin materials like tissue. The test method follows the general outline of the TSA instrument manual dated 2013 Jul. 8 (Collection of the TSA Operating instruction, Multi Functional Measuring system, Tissue Softness Analyzer, 2012 Dec. 12, available from EMTEC electronic GMBH with the settings as set forth therein or in WO 2019/221647 A1 by Essity Hygiene and Health Aktiebolag.

[0261] The Tissue Softness Analyzer TSA simultaneously gathers the essential single relevant parameters which have an influence on the tissue softness, and provides a comfort prediction.

[0262] The comfort prediction may be used to determine the softer one out of two tissues being compared. A higher value indicates a higher softness.

[0263] For the purpose of this application, the result of TSA measurements of “Thunder E” being a creped ribbed ply, and “Reference”, being a non-ribbed ply are comparable results, showing that the “Reference” ply is indeed a softer ply than “Thunder E”.

[0264] Softness Panel:

[0265] Panel softness is determined by evaluation made by panel members. The panelists rank products in terms of softness. The Softness Panel values are therefore comparative values enabling a comparison between the samples tested, rather than an absolute parameter.

[0266] The softer the product/tissue base sheet is rated the higher the value will be.

[0267] Softness values of tissue products (finished goods) and tissue base sheets are not directly comparable as there are different scales/reference products.

[0268] Each sample is composed of one product, i.e. a multi-ply tissue paper product.

[0269] The dimensions of the samples are therefore the dimensions of the finished products.

[0270] Samples are placed in MD before the panelists.

[0271] Samples are conditioned for minimum 2 hours in a controlled area at 23° C. and 50% relative humidity.

[0272] The different samples are comfort rated by ten panelists, and an average comfort rating for each product is determined over the panelists.

[0273] Hence, softness panel values are comparative values within a test and indicate the perceived softness of a product.

[0274] For the purpose of this application, softness panel values given in one and the same table are comparable and indicate the perceived relative softness of the products tested. The higher the value of the rating, the more comfortable is the product.

[0275] Tests: Nesfip

[0276] Three-ply products were produced using the Nesfip-technology.

[0277] Nesfip 3-Ply Products

[0278] Outer plies: Omega

[0279] Inner ply: Thunder E compared to Reference

TABLE-US-00004 Dry Dry tensile tensile Roll Basis Thickness strength strength Absorption Plies in No of diameter Firmness weight (1 sheet) MD CD Softness CEN order sheets (mm) (mm) (g/m.sup.2) (mm) (N/m) (N/m) panel (g/g) Omega 132 120.0 56 55.8 0.62 400 230 1.6 8.8 Reference Omega Omega 121 118.3 57 55.3 0.68 357 202 1.6 9.4 Thunder E Omega

[0280] Outer plies: Trio and TAD

[0281] Inner ply: Thunder E compared to Reference

TABLE-US-00005 Dry Dry tensile tensile Roll Basis Thickness strength strength Absorption Plies in No of diameter Firmness weight (1 sheet) MD CD Softness CEN order sheets (mm) (mm) (g/m.sup.2) (mm) (N/m) (N/m) panel (g/g) Trio 132 120.8 66 53.2 0.63 282 204 1.6 10.5 Reference TAD Trio 121 118.0 68 53.3 0.64 231 206 1.6 10.8 Thunder E TAD

[0282] Outer plies: TAD

[0283] Inner ply: Thunder E compared to Reference

TABLE-US-00006 Dry Dry tensile tensile Roll Basis Thickness strength strength Absorption Plies in No of diameter Firmness weight (1 sheet) MD CD Softness CEN order sheets (mm) (mm) (g/m.sup.2) (mm) (N/m) (N/m) panel (g/g) TAD 125 120.0 66 53.7 0.65 296 192 1.7 11.8 Reference TAD TAD 121 120.0 70 51.7 0.68 242 180 1.8 12.1 Thunder E TAD

[0284] The sample tests confirmed that thickness is increased in samples comprising the Thunder E ply being a creped ribbed ply compared to the samples having no creped ribbed ply. Moreover, absorption increased in all of the samples comprising the Thunder E ply compared to the reference ply.

[0285] Moreover, the basis weight decreased or was not significantly affected in the samples comprising the Thunder E ply compared to the samples comprising the Reference ply.

[0286] Accordingly, an increased thickness is achieved using the inner ply(-ies) being a creped ribbed ply, although the basis weight of the multi-ply product is lower. This means that an increased thickness results using less material than in the reference sample.

[0287] In addition, the softness of the samples including the Thunder E inner ply was the same or not significantly affected as compared to the samples including the Reference inner ply. This was surprising since it was expected that the ribbed structure of the ribbed ply would have a negative impact on softness.

[0288] Accordingly, the results displayed in the above demonstrates how surprisingly soft products may be achieved with the advantages of higher thickness and less or the same fibre consumption, by using a inner ply being a ribbed ply as proposed herein.

[0289] Further tests have been made investigating the influence of nip size when forming products using the Nesfip method. Nip sizes 30/30 mm, 32/31 mm and 34/32 mm were compared. As expected, with increased embossing nips for the outer plies the thickness of the total product increases, both for products including an inner ply being a ribbed ply and for products not including such a ply. However, for the same nip size, the product with an inner ply being a ribbed ply was always found to be thicker than the product without a ribbed ply.

[0290] Novefip 4-Ply Products

[0291] Four-ply products were produced using the Novefip method.

[0292] Outer plies: Trio

[0293] Two inner plies: Reference+Reference or Reference+Thunder E

TABLE-US-00007 Dry Dry tensile tensile Roll Basis Thickness strength strength Absorption Plies in No of diameter Firmness weight (1 sheet) MD CD Softness CEN order sheets (mm) (mm) (g/m.sup.2) (mm) (N/m) (N/m) panel (g/g) Trio 113 120.0 59 69.8 0.72 519 337 1.6 9.0 Reference Reference Trio Trio 105 119.8 62 69.1 0.78 485 352 1.7 9.4 Reference Thunder E Trio

[0294] Again, the results of the measurements performed on the tested samples confirm that good softness may be combined with increased absorption and thickness, this time with a slightly reduced basis weight.

[0295] Further, four-ply products were tested with both inner plies being ribbed plies, wherein the ribbed plies were oriented with the Yankee side of the plies upwards or downwards, respectively. The orientation of the ribbed ply was not found to have any influence on the thickness, strength, softness or absorption.

[0296] Novefip 5-Ply Products

[0297] Five-ply products were produced using the Novefip method.

[0298] Sample 1: 5 reference plies

[0299] Sample 2: 4 reference plies and 1 inner ply being a Thunder E ply

[0300] Sample 3: 5 Thunder E plies

TABLE-US-00008 Dry Dry tensile tensile Roll Basis Thickness strength strength Absorption Plies in No of diameter Firmness weight (1 sheet) MD CD Softness CEN order sheets (mm) (mm) (g/m.sup.2) (mm) (N/m) (N/m) panel (g/g) Reference 105 120.0 52 86.9 0.78 888 681 1.3 8.3 Reference Reference Reference Reference Reference 100 120.8 59 86.1 0.81 858 626 1.4 8.6 Reference Reference Thunder E Reference Thunder E  95 120.0 59 78.0 0.88 769 581 0.9 8.9 Thunder E Thunder E Thunder E Thunder E

[0301] Also for-five ply Novefip products there is an increase in thickness without significant impact on softness or absorption when a product including an inner ply being a ribbed ply is compared to a product with no ribbed ply.

[0302] A product with only creped ribbed plies, i.e. where also the outermost plies are creped ribbed plies as defined herein, displays significantly reduced softness as compared to the products with non-ribbed outermost plies.

[0303] In all, the above tests of sample products confirm that products comprising an inner ply being a creped ribbed ply as described herein may provide higher thickness even with slightly lower weight than previous products, while still achieving at least satisfactory values for strength.

[0304] For all comparisons, the roll firmness was kept the same or at least on a similar level.

[0305] It is to be understood that the present disclosure is not limited to the variants described above and illustrated in the drawings; rather, the skilled person will recognise that many changes and modifications may be made within the scope of the amended claims. In particular, methods as proposed herein may be varied and adapted to produce variants of the products proposed herein.