Multi-ply tissue paper product and method for manufacturing the same

Abstract

A multi-ply tissue paper product includes at least two plies made of tissue paper base-sheet with at least one outer ply being a structured outer ply produced by a structuring manufacturing method. The structured outer ply includes a microstructure pattern on substantially at least 80% of the structured outer ply surface. The microstructure pattern is applied by micro-embossing during a converting operation. The structured outer ply is chosen from a through air dried ply produced by a through air drying (TAD) manufacturing method; a dried ply produced by an advanced tissue molding system (ATMOS), or a dried ply produced by a structured tissue technology (SST) manufacturing method. The microstructure pattern includes a first series of protuberances having a density ranging from approximately 30 to 100 protuberances/cm.sup.2. The softness property of the structured outer ply is adjusted during a micro-embossing step.

Claims

1. A multi-ply tissue paper product comprising: a first structured outer ply of tissue paper base-sheet being produced by a structuring manufacturing method selected from the group consisting of through air dried ply produced by a through air drying (TAD) manufacturing method, a dried ply produced by an advanced tissue molding system (ATMOS), and a dried ply produced by a structured tissue technology (SST) manufacturing method; and a second structured ply of tissue paper base-sheet being through air dried ply produced by a structured manufacturing method selected from the group consisting of: TAD manufacturing method, ATMOS, and SST manufacturing method, wherein: the first structured outer ply comprises a first micro-embossed microstructure pattern on substantially at least 80% of the first structured outer ply surface, said micro-embossed microstructure pattern being applied by micro-embossing during a converting operation, the second structured ply comprises a second micro-embossed microstructure pattern on substantially at least 80% of the second structured ply surface, and the first micro-embossed microstructure pattern comprises a first series of protuberances having a density ranging from approximately 30 to 100 protuberances/cm.sup.2.

2. The multi-ply tissue paper product of claim 1, further comprising at least another ply being a wet pressed ply produced by a conventional wet press (CWP) manufacturing method.

3. The multi-ply tissue paper product according to claim 2, wherein the wet pressed ply comprises another micro-embossed microstructure pattern.

4. The multi-ply tissue paper product according to claim 1, wherein the first microstructure pattern comprises a second series of protuberances forming a decorative motif, the protuberances of the second series having a height approximately 1 to 3 times greater than the height of the protuberances of the first series.

5. The multi-ply tissue paper product according to claim 4, wherein the first microstructure pattern further comprises a third series of elongated protuberances having a density ranging from approximately 30 to 100 protuberances/cm.sup.2, the elongated protuberances having a length approximately 3 to 20 times longer than the length of the protuberances of the first or second series.

6. The multi-ply tissue paper product according to claim 4, wherein the protuberances of the first microstructure patterns are chosen from the group of microstructure patterns consisting of corrugations, undulations, wave-like profiles, pyramid or cone based micro-embossments, and truncated pyramid or truncated cone micro-embossments.

7. The multi-ply tissue paper product according to claim 1, wherein the first structured outer ply and the second structured ply are bonded together according to a nested or random nested manufacturing process.

8. A roll of sheet material comprising the multi-ply tissue paper product according to claim 1 wound onto a core.

9. A folded sheet material comprising the multi-ply tissue paper product according to claim 1 cut, stacked and folded into a package.

10. The multi-ply tissue paper product according to claim 1 in the form of a paper towel, toilet tissue roll, bathroom tissue, wiping tissue, kitchen tissue roll, facial tissue, or handkerchief.

11. A multi-ply tissue paper product comprising: a first structured outer ply of tissue paper base-sheet being produced by a structuring manufacturing method selected from the group consisting of through air dried ply produced by a through air drying (TAD) manufacturing method, a dried ply produced by an advanced tissue molding system (ATMOS), and a dried ply produced by a structured tissue technology (SST) manufacturing method; and a second structured ply of tissue paper base-sheet being through air dried ply produced by a structured manufacturing method selected from the group consisting of: TAD manufacturing method, ATMOS, and SST manufacturing method, wherein: the first structured outer ply comprises a first or second micro-embossed microstructure pattern on substantially at least 80% of the first structured outer ply surface, said first or second micro-embossed microstructure pattern being applied by micro-embossing during a converting operation, the second structured ply comprises the first microstructure pattern when the first structured outer ply comprises the second microstructure pattern, or the second structured ply comprises the second microstructure pattern when the first structured outer ply comprises the first microstructure pattern, the first microstructure pattern comprises a first series of protuberances having a density ranging from approximately 30 to 100 protuberances/cm.sup.2 and a second series of protuberances having a height different from the height of the first series of protuberances, and the second microstructure pattern comprises a third series of protuberances.

12. The multi-ply tissue paper product of claim 11, further comprising at least another ply being a wet pressed ply produced by a conventional wet press (CWP) manufacturing method.

13. The multi-ply tissue paper product according to claim 11, wherein the first microstructure pattern further comprises series of elongated protuberances having a density ranging from approximately 30 to 100 protuberances/cm.sup.2, the elongated protuberances having a length approximately 3 to 20 times longer than the length of the protuberances of the first or second series.

14. A roll of sheet material comprising the multi-ply tissue paper product according to claim 11 wound onto a core.

15. A folded sheet material comprising the multi-ply tissue paper product according to claim 11 cut, stacked and folded into a package.

16. The multi-ply tissue paper product according to claim 11 in the form of a paper towel, toilet tissue roll, bathroom tissue, wiping tissue, kitchen tissue roll, facial tissue, or handkerchief.

17. A method for manufacturing a multi-ply tissue paper product comprising a first structured ply and a second structured ply each of which is made of tissue paper base-sheet, wherein the manufacturing method comprises: manufacturing the first structured outer ply by a structuring manufacturing method selected from the group consisting of through air dried ply produced by a through air drying (TAD) manufacturing method, a dried ply produced by an advanced tissue molding system (ATMOS), and a dried ply produced by a structured tissue technology (SST) manufacturing method; and manufacturing a second structured ply of tissue paper base-sheet being through air dried ply produced by a structured manufacturing method selected from the group consisting of: TAD manufacturing method, ATMOS, and SST manufacturing method, micro-embossing a first micro-embossed microstructure pattern on the first structured outer ply on substantially at least 80% of the first structured outer ply surface during a converting operation, micro-embossing a second micro-embossed microstructure pattern on the second structured ply on substantially at least 80% of the second structured ply surface, wherein the first structured outer ply is microembossed between a first cylinder and a second cylinder engraved with a first microstructure pattern comprising a series of protuberances having a density ranging from approximately 30 to 100 protuberances/cm.sup.2, and wherein the first and second micro-embossed structured plies are joined to form the multi-ply tissue paper.

18. The multi-ply tissue paper product manufacturing method of claim 17, further comprising, during the micro-embossing of the first structured outer ply, adjusting a micro-embossing pressure applied to the first structured outer ply such as to adjust a softness related property relative to a strength related property of the first structured outer ply in a defined range.

19. The multi-ply tissue paper product manufacturing method of claim 18, wherein the micro-embossing pressure ranges from approximately 10 to 40 kg/cm linear such as to adjust the softness related property of the first structured outer ply between approximately 83 and 87 according to measurements provided by an EMTEC tissue softness analyzer, and a machine direction strength MDT related property of the first structured outer ply between approximately 90 and 130 N/m measured according to the standard EN ISO 12625-4:2005.

20. The multi-ply tissue paper product manufacturing method according to claim 17, further comprising manufacturing at least another ply as a wet pressed ply produced by a wet press manufacturing method.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention are illustrated by way of examples and not limited to the accompanying drawings, in which like references indicate similar elements:

(2) FIGS. 1 to 4 are side cross-section views of four embodiments of multi-ply tissue paper product, respectively;

(3) FIG. 5 is a graphic illustrating the effect of the micro-embossing pressure onto the hand-feel/softness;

(4) FIG. 6 is a graphic illustrating the effect of the micro-embossing onto the machine direction strength;

(5) FIG. 7 is a graphic illustrating the effect of various micro-embossing patterns onto the hand-feel/softness;

(6) FIG. 8 is a graphic illustrating the softness gain with the third embodiment;

(7) FIG. 9 schematically and partially illustrates an example of a converting assembly and method for manufacturing the multi-ply tissue paper product according to the first, second and third embodiment;

(8) FIG. 10 is a top view of an embodiment of a multi-ply tissue paper product schematically illustrating an example of aesthetic pattern;

(9) FIG. 11 is a top picture obtained with a microscope of a multi-ply tissue paper product according to the prior art; and

(10) FIG. 12 is top picture obtained with a microscope of an embodiment of a multi-ply tissue paper product.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(11) FIGS. 1 to 4 are side cross-section views schematically illustrating the layer structure of embodiments of multi-ply tissue paper products.

(12) FIG. 1 schematically illustrates a first embodiment of a multi-ply tissue paper product 1. It includes a first structured ply 2 and a second wet press ply 3. Each of these plies is made of tissue paper base-sheet having a low basis weight, in the range from 10 to 45 g/m.sup.2. The structured ply 2 may be a through air dried ply produced by a through air drying TAD manufacturing method. Alternatively to the through air drying TAD manufacturing method, other manufacturing method like the advanced tissue molding system ATMOS manufacturing method that generate a similarly structured ply may be used. The wet pressed ply 3 is produced by a wet press CWP manufacturing method.

(13) After the structured ply 2 has been produced by a paper making machine, a converting operation takes place. The converting operation includes micro-embossing the structured ply 2 on substantially at least 80% of its surface. The structured ply 2 may be embossed on substantially all its surface.

(14) The structured ply 2 may be provided with a first microstructure pattern at two levels, namely combining a series of first 7 and second 8 protuberances. For example, the second protuberances 8 may be obtained by embossing the structured ply 2 at a second height h2 ranging from 1 to 3 times greater than the first height h1, for example 1.4 times greater. The density of the first protuberances 7 is greater than the density of the second protuberances 8.

(15) The wet pressed ply 3 may be provided with a second microstructure pattern at one level, namely with a series of third protuberances 9. The third protuberances 9 may have a third height h3 that may be for example substantially identical to the first height h1.

(16) As an example, the first height h1 may range from approximately 0.5 to 0.7 mm and the second height h2 from approximately 0.7 to 1 mm. The density of the series of first protuberances 7 and third protuberances 9 may range from approximately 30 to 100 protuberances/cm.sup.2. The density of the series of second protuberances 8 may be 5 to 10 times less than the density of the series of first protuberances 7. The surface of a second protuberance 8 may be approximately between 0.5 to 2 mm.sup.2. The series of second protuberances 8 may form a decorative motif (flower, leaf, brand name, etc. . . . ) that may be repeated on the surface of the outer ply.

(17) Alternatively, one of the microstructure pattern may include a series of elongated protuberances having a density ranging from approximately 30 to 100 protuberances/cm.sup.2. The elongated protuberances may have a length approximately 3 to 20 times longer than the length of the protuberances of the first series of protuberances.

(18) FIG. 2 schematically illustrates a second embodiment of a multi-ply tissue paper product 1. The second embodiment differs from the first embodiment in that the first structured ply 2 is provided with the second microstructure pattern at one level (series of third protuberances 9), while the second wet press ply 3 is provided with the first microstructure pattern at two levels (combining a series of first 7 and second 8 protuberances).

(19) FIG. 3 schematically illustrates a third embodiment of a multi-ply tissue paper product 1. The third embodiment differs from the first embodiment in that the wet press ply 3 has been replaced by a second structured ply 4.

(20) FIG. 4 schematically illustrates a fourth embodiment of a multi-ply tissue paper product 1. The fourth embodiment includes two structured plies 2 and 4 and one wet press ply 5. The two structured plies 2 and 4 form the outer plies of the multi-ply tissue paper product 1. The wet press ply 5 is positioned as an intermediate and central ply within the multi-ply tissue paper product 1. The wet press ply 5 may be not-embossed (as illustrated in FIG. 4) or, alternatively, embossed with any of the microstructure patterns hereinbefore presented (not shown).

(21) Surprisingly, it was found that if the outer structured TAD ply is micro-embossed during the converting operation once dried after the tissue paper has been produced by the paper machine, the suppleness and/or softness would be substantially improved. This surprising effect is in contradistinction with the common knowledge until now as hereinafter illustrated by the graphics.

(22) FIG. 5 is a graphic illustrating the effect of the micro-embossing pressure (charge in kg/cm linear) onto the hand-feel/softness HF. The protocol of test includes embossing the TAD structured ply between a steel cylinder and a rubber cylinder with a micro-embossing pattern having a density of 80 protuberances/cm.sup.2. Firstly, a reference is produced by processing the tissue product into a converting assembly (as depicted in FIG. 9) without embossing the tissue product. This reference relates to hand-feel/softness measurement made at 0 kg/cm linear. Subsequently, multiple samples are produced by processing the tissue product into a converting assembly (as depicted in FIG. 9) and embossing the tissue product by applying an increasing embossing pressure.

(23) The softness of the resulting tissue product is measured by a tissue softness analyzer of the company EMTEC. The tissue softness analyzer operates as follows in order to determine a softness value or a hand-feel value combining real softness, smoothness/roughness and stiffness. The tissue product sample is positioned and secured in a measuring cell, e.g. like a drumhead. Below is placed a vibration sensor, above is placed a vertical movable measuring head with a rotating blade, which is pushed onto the tissue product sample with a defined load. Then a rotation of the rotating blades with a defined speed is executed. The motion of the blades over the tissue product sample generates different types of vibrations/noise, which are detected by means of the vibration sensor. The resulting vibrations/noise spectrum is an overlapping of two single spectra. The first peak of the spectrum represents the smoothness/roughness (vertical vibrations of the tissue product sample like a membrane, caused by the motion of the blades over the tissue product sample surface). The second peak of the spectrum represents the real softness (horizontal vibrations of the blades itself caused by momentary blocking and swinging back of the blades by the fibers of the tissue product sample, when moving over the surface). Further, the tissue product sample is deformed to measure elastic, visco-elastic and plastic properties (stiffness). The three parameters softness, smoothness and stiffness are combined together with the caliper, grammage and number of plies with different algorithms and results in a hand-feel value HF. In particular, an algorithm used for the measurements is referred as the QA1 algorithm by EMTEC. The higher the hand-feel value, the softer is the tissue product. A mathematical equation can be created such that the results correlate with a certain reference panel of consumers by using specific algorithms for each material (base tissue, toilet paper, facials, etc. . . . ).

(24) The graphic illustrates that an equivalent hand-feel/softness can be reached with an embossed standard TAD ply compared to a soft TAD ply (though having less strength) obtained through the paper making process. Further, by embossing the soft TAD ply, a gain in hand-feel/softness is also to be noticed. Furthermore, by embossing the TAD ply over a determined embossing pressure, namely around 10 and 20 kg/cm linear for soft TAD ply and standard TAD ply, respectively, the effect on hand-feel/softness is nil, at least decreases significantly.

(25) FIG. 6 is a graphic illustrating the effect of the micro-embossing onto the strength (Machine Direction Tensile MDT). The MD strength (dry strength) is measured according to the standard EN ISO 12625-4:2005. The graphic shows that, for an equivalent hand-feel/softness, an embossed standard TAD ply has more strength than an embossed soft TAD. Though not shown, the effect on the cross machine CD strength is similar. Thus, with the described method, it is possible to adjust the strength related property of the TAD ply in a given range without modifying the hand-feel/softness of the resulting product.

(26) FIG. 7 is a graphic illustrating the effect of various micro-embossing patterns onto the softness. Various microstructure patterns have been tested with the same tissue product, namely a first pattern ME80 including a density of 80 protuberances/cm.sup.2, a second pattern ME51 including 51 protuberances/cm.sup.2 and a third pattern Mixte1 including a combination of a series of elongated protuberances and a series of rounded protuberances. The graphic illustrates that independently of the pattern used to micro-emboss the TAD structured ply, the softness of the TAD structured ply is improved by the micro-embossing. The graphic is coherent with the graphic of FIG. 5 and further shows that greater is the micro-embossing pressure, greater is the softness in a limited range (above approximately 30 kg/cm linear, there is a stabilization in the softness improvement).

(27) FIG. 8 is a graphic illustrating the softness gain with a third embodiment a multi-ply tissue paper product. In this graphic, the softness value is obtained from a blind test using a panel of consumers testing various multi-ply tissue paper products. Similar results are obtained by means of a measurement by the tissue softness analyzer of the company EMTEC. The reference point RE indicates the softness related property relatively to the strength related property of a tissue product including two standard TAD plies (namely including TAD plies obtained with a standard through air drying manufacturing process). The point SO indicates the softness related property relatively to the strength related property of a tissue product including two softest possible TAD plies (namely including TAD plies obtained with a softest possible papermaking manufacturing process). The point ME indicates the softness related property relatively to the strength related property of a tissue product including two micro-embossed TAD plies obtained according to the described method. With the described method, a significant gain in softness is obtained while maintaining the strength (Cross Machine Tensile CD) at an acceptable value. The CD strength (dry strength) is measured according to the standard EN ISO 12625-4:2005. Though not shown, the effect on the Machine Direction Tensile MDT strength is similar. Further, with the described method, it is possible to adjust the strength related property of the TAD ply in a determined range (70 to 105 N/m) while maintaining the softness of the resulting product in an softness range (2.1 to 2.3) better than standard TAD ply or softest possible TAD ply resulting only from the papermaking process.

(28) The softness improvement that has been noticed as a surprising effect seems to result from the micro-embossing step that mechanically breaks the link between the fibers.

(29) FIG. 9 schematically and partially illustrates an example of a converting assembly and method for manufacturing the multi-ply tissue paper product 1 of the first to third embodiment (depicted in FIGS. 1-3). The converting assembly includes a glue dispenser 20, a first embossing unit 30, a second embossing unit 40 and a joining unit 50. The converting assembly and the converting method for manufacturing such a multi-ply tissue paper product that will be explained in details hereinafter is based on a facility designed for manufacturing a conventional, nested two or three ply paper product without requiring substantial changes in components or adjustments (nested flat internal ply process as described in EP 1 081 284). Thus, manufacturing the multi-ply tissue paper product based on an existing converting assembly is particularly cost effective.

(30) The first embossing unit 30 includes an engraved cylinder 31 and a mating rubber cylinder 32, both rotating in opposite directions. The cylinder 31 is engraved with a microstructure pattern combining first embossing tips of height H1 and second embossing tips of height H2. The first embossing tips are shallower than the second embossing tips. The first outer ply 2 (embodiment of FIG. 1), 3 (embodiment of FIG. 2) or 4 (embodiment of FIG. 3) is embossed in the first embossing apparatus 30. The engraved cylinder 31 enables performing a double-level engraving. The obtained embossed first outer ply 2 (embodiment of FIG. 1), 3 (embodiment of FIG. 2) or 4 (embodiment of FIG. 3) includes at least partly high discrete protuberances of height h2 (for example discrete truncated protuberances and/or linear protuberances such as flowers), and low protuberances of height h1 (for example discrete truncated protuberances). The heights h1 and h2 depend on the heights H1 and H2 of the engravings and also on the other embossing parameters, namely pressure, rubber quality, etc. . . . .

(31) The microstructure pattern may include punctual or elongated corrugations, undulations, wave-like profiles, pyramid or cone based micro-embossments, truncated pyramid or truncated cone micro-embossments.

(32) As an example, the first embossing tips on the cylinder 31 have an engraving height H1 between 0.2 and 2 mm and the second embossing tips on the cylinder 31 have an engraving height H2 such that the height difference H2H1 is between 0.1 and 0.7 mm. The microstructure patterns may have a density higher than 30 protuberances/cm.sup.2.

(33) The glue dispenser 20 applies an adhesive 22 to the external side of the outer ply 2 (embodiment of FIG. 1), 3 (embodiment of FIG. 2) or 4 (embodiment of FIG. 3). The adhesive 22 may be applied to the external side of the outer ply opposite the distal areas of the protuberances of height h2 of the embossed first outer ply.

(34) The glue dispenser 20 includes a vat 21, an applicator cylinder 23 and a dipping cylinder 24. The applicator cylinder 23 abuts the superposed through air dried ply 10 and the embossed first outer ply 2 (embodiment of FIG. 1), 3 (embodiment of FIG. 2) or 4 (embodiment of FIG. 3) against the engraved cylinder 31. The dipping cylinder 24 picks up the adhesive 22 in the vat 21 and transfers the adhesive 22 to the applicator cylinder 23. The applicator cylinder 23 is arranged to exercise a determined pressure on the engraved cylinder 31 at the distal area of the protuberances of height h2 of the embossed first outer ply. At said determined pressure, the adhesive 22 crosses the embossed first outer ply. Alternatively, the applicator cylinder 23 may be fitted with an engraved surface so as to apply the adhesive 22 only to part of the protuberances. This enables providing smoothness to the multi-ply tissue paper product 1.

(35) Because the gluing areas are limited to the distal planar areas of the high protuberances of the embossed first outer ply, the resulting stiffness of the multi-ply tissue paper product 1 can be predetermined. Thus, the resulting stiffness may be adjusted. FIG. 9 only illustrates a particular example including a rate of one high protuberance for three shallow protuberances.

(36) The adhesive 22 may be a polyvinyl acetate glue or a hot-melt glue. The adhesive may be diluted in water according to a proportion enabling an appropriate transfer to the various plies.

(37) Substantially simultaneously to the formation of the embossed first outer ply 2 (embodiment of FIG. 1), 3 (embodiment of FIG. 2) or 4 (embodiment of FIG. 3), the second outer ply 3 (embodiment of FIG. 1) or 2 (embodiments of FIGS. 2 and 3) is embossed in the second embossing apparatus 40.

(38) The second embossing unit 40 includes an engraved cylinder 41 and a mating rubber cylinder 42, both rotating in opposite directions. The cylinder 41 is engraved with a microstructure pattern having embossing tips of height H3. The height H3 may be substantially equal to the height H1.

(39) The resulting second outer ply 3 (embodiment of FIG. 1) or 2 (embodiments of FIGS. 2 and 3) includes at least partly low discrete protuberances of height h3. The second engraved cylinder 41 may also include an aesthetic pattern (for example a decorative motif comprising flowers).

(40) FIG. 10 is a top view of the resulting second outer ply 2 schematically illustrating an example of such an aesthetic pattern including a first series of protuberances 7 (protuberances of important density) and a second series of protuberances 8 (flower).

(41) Subsequently, the embossed first outer ply 2 (embodiment of FIG. 1), 3 (embodiment of FIG. 2) or 4 (embodiment of FIG. 3), and the embossed second outer ply 3 (embodiment of FIG. 1) or 2 (embodiments of FIGS. 2 and 3) are joined together in a nesting mode in the joining unit 50.

(42) The joining unit 50 includes a marrying cylinder 51 working in cooperation with the engraved cylinder 31 of the first embossing unit 30. The surface of the marrying cylinder 51 may be smooth. Alternatively, it may also be engraved and may include gaps in order to adjust the surface of joining and the final multi-ply tissue paper product smoothness.

(43) The joining of the embossed first outer ply to the embossed second outer ply is carried out in such a manner that: on the one hand, the distal areas of the high protuberances of the embossed first outer ply nest at least partly with the distal areas of the protuberances of the embossed second outer ply, and on the other hand, sufficient pressure is applied to bond the two plies 3 and 2, 2 on one side, and 3, or 2 and 4 on the other side with the help of the adhesive 22.

(44) As an alternative to the glue dispenser 50 as illustrated in FIG. 9, the adhesive (e.g. a hot melt glue, an aqueous glue, etc. . . . ) may be sprayed by appropriate means on each of the sides of the first outer ply before it is joined with the second outer ply.

(45) Then, the multi-ply tissue paper product may be wound onto a core 71 as a roll of sheet material 70, or may be stacked and folded into a package 81 as a folded sheet material 80. These operations are not germane to the present invention and will not be further described. The multi-ply tissue paper product may be used as paper towel, toilet tissue rolls, bathroom tissue, wiping tissue, kitchen tissue rolls, facial tissue or handkerchiefs, etc. . . . .

(46) The converting assembly and method hereinbefore described can be easily adapted to manufacture the embodiment depicted in FIG. 4. The CWP intermediate ply 5 may be superposed on the protuberances of the embossed first outer ply 4 at the level of the engraved cylinder 31. The CWP intermediate ply 5 fits closely onto the high protuberances of the embossed first outer ply 4. It further remains substantially planar between two consecutive high protuberances. Alternatively, it may be supported by the planar areas of the shallow protuberances. Thus, the corresponding converting assembly and method will not be further described as it is based on the converting assembly and method depicted in FIG. 9.

(47) FIGS. 11 and 12 are top pictures obtained with a microscope of a multi-ply tissue paper product.

(48) FIG. 11 shows the multi-ply tissue paper product manufactured according to the prior art. One can notice a regular pattern namely that all the protuberances are distributed along equidistant lines. Some of those equidistant lines are emphasized by dotted lines 14 in FIG. 11. This pattern results from the structuring manufacturing method (e.g. a through air drying TAD manufacturing method).

(49) FIG. 12 shows a multi-ply tissue paper product manufactured according an embodiment of the invention. One can notice an irregular pattern, namely that the distances between lines of protuberances are irregular. Some of those lines are emphasized by dotted lines 17 in FIG. 12. This is due to the interference between the pattern resulting from the fabric used by the structuring manufacturing method (e.g. a through air drying TAD manufacturing method) and the pattern resulting from the additional micro-embossing operation taking place during the converting operation.

(50) Thus, with the manufacturing method described herein, the papermaking process stays advantageously unchanged, only the converting process is affected by the additional micro-embossing operation. Thus, the described method enables a significant gain in softness of the final product is quite easy to implement on an existing industrial manufacturing line.

(51) The drawings and their descriptions hereinbefore illustrate rather than limit the invention.

(52) Though the invention has been described with respect to various embodiments of multi-ply tissue paper products including two and three plies, these are not limitative examples. The skilled person will readily recognize that the multi-ply tissue paper product may include more plies, e.g. four, five, six, etc. . . . provided that the structured outer ply is micro-embossed so as to confer a soft hand-feel to the tissue paper product.

(53) The numbers, densities, positions and shapes of the micro-embossments in the depicted embodiments are non-limitative examples. The skilled person will readily recognize that these numbers, densities, positions and shapes may be changed if desired or deemed necessary with respect to, for example, the desired aesthetic effect to be achieved by the multi-ply tissue paper products.

(54) Any reference sign in a claim should not be construed as limiting the claim. The word comprising does not exclude the presence of other elements than those listed in a claim. The word a or an or at least one preceding an element does not exclude the presence of a plurality of such element.