A SHEET OF ABSORBENT MATERIAL, ROLL, LOG AND METHOD FOR MANUFACTURING THE SAME

Abstract

A sheet of absorbent material having opposite sheet side edges spaced apart from one another to define an overall width of the absorbent sheet, the sheet of absorbent material including zones of weakness spaced along the sheet of absorbent material according to a machine direction, each zone of weakness extending substantially transversally to said machine direction, each zone of weakness defining two adjacent individual absorbent sheet portions, each zone of weakness being a tear line. The tear line comprises two edge regions and a central region, a first edge region beginning at one of the sheet side edges towards the central region, a second edge region beginning at the other sheet side edges towards the central region, the central region including alternating perforated segments and unperforated segments. The edge regions are unperforated so as to constitute attachment areas within the tear line between two adjacent individual absorbent sheet portions.

Claims

1. A sheet of absorbent material having opposite sheet side edges spaced apart from one another to define an overall width of the sheet of absorbent material, the sheet of absorbent material comprising zones of weakness spaced along the sheet of absorbent material according to a machine direction, each zone of weakness extending substantially transversally to said machine direction, each zone of weakness defining two adjacent individual absorbent sheet portions, each zone of weakness being a tear line, wherein: the tear line comprises two edge regions and a central region, a first edge region beginning at one of the sheet side edges towards the central region, a second edge region beginning at the other sheet side edges towards the central region, the central region comprising alternating perforated segments and unperforated segments, said edge regions are unperforated so as to constitute attachment areas within the tear line between two adjacent individual absorbent sheet portions.

2. The sheet of absorbent material of claim 1, wherein a width ratio of the edge regions relatively to the central region ranges from about 4% to about 20%

3. The sheet of absorbent material of claim 1, wherein an edge region width ranges from about 3 mm to about 10 mm.

4. The sheet of absorbent material according to claim 1, wherein the central region comprises alternating perforated segments and unperforated segments according to a perforation pattern comprising at least two perforated segments separated by one unperforated segment, each segment having substantially an identical width.

5. The sheet of absorbent material according to claim 1, wherein the central region comprises alternating perforated segments and unperforated segments according to a perforation pattern comprising multiple perforated segments, two adjacent perforated segments being separated by one unperforated segment, each perforated segment having a width increasing from one side edge towards the opposite side edge, each unperforated segment having a constant width.

6. The sheet of absorbent material according to claim 1, wherein the central region comprises alternating perforated segments and unperforated segments according to a perforation pattern comprising multiple perforated segments, two adjacent perforated segments being separated by one unperforated segment, each unperforated segment having a width increasing from one side edge towards the opposite side edge, each perforated segment having a constant width.

7. A roll of sheet of absorbent material comprising a sheet of absorbent material according to claim 1 wound onto a core or on itself.

8. An absorbent sheet product comprising the sheet of absorbent material according to claim 1, wherein the absorbent sheet is chosen among the group consisting of napkins, towels, kitchen towels, hand towels, toilet papers, wipes and facial tissues.

9. A log base sheet made of absorbent material having opposite log side edges spaced apart from one another to define an overall width of the log base sheet, the log base sheet comprising zones of weakness spaced along the log base sheet according to a machine direction of the log base sheet, each zone of weakness extending substantially transversally to said machine direction, each zone of weakness being a tear line, the log base sheet comprising multiple phantom lines parallel to the machine direction representing imaginary lines for cutting the log base sheet, wherein: the tear line comprises multiple successions of first edge region, a central region and a second edge region from one of the log side edge towards the other log side edge, the central region comprising alternating perforated segments and unperforated segments, said edge regions are unperforated, and each phantom line is positioned at a boundary between two adjacent edge regions so as to constitute attachment areas within said tear line between two adjacent central regions.

10. The log base sheet of claim 9, wherein a central region out of two in each tear line is replaced by an unperforated region, and wherein two consecutive tear lines are staggered according to a cross-machine direction such that all the central region are positioned between two adjacent phantom lines.

11. A log of sheet of absorbent material comprising a log base sheet made of absorbent material according to claim 9 wound onto a core or on itself.

12. A method for manufacturing a roll of sheet of absorbent material comprising the steps of: feeding a log base sheet made of absorbent material into a perforating unit, the log base sheet having opposite log side edges spaced apart from one another to define an overall width of the log base sheet; defining zones of weakness spaced along the log base sheet according to a machine direction of the log base sheet, each zone of weakness extending substantially transversally to said machine direction, by pinching each zone of weakness as a tear line; defining multiple phantom lines in the log base sheet parallel to the machine direction representing imaginary lines for cutting the log base sheet; wounding the pinched log base sheet onto a core or on itself to form a log; cutting the pinched log base sheet once a desired log diameter is reached; cutting the log into multiple and individual rolls of absorbent material sheet; the manufacturing method is characterized in that it further comprises: pinching each tear line as multiple successions of first edge region, a central region and a second edge region from one of the log side edge towards the other log side edge, the central region comprising alternating perforated segments and unperforated segments; unperforating said edge regions; and positioning each phantom line at a boundary between two adjacent edge regions so as to constitute attachment areas within said tear line between two adjacent central regions.

13. The manufacturing method of claim 12, wherein a central region out of two in a tear line is replaced by an unperforated region, and wherein two consecutive tear lines are staggered according to a cross-machine direction such that all the central region are positioned between two adjacent phantom lines.

Description

DETAILED DESCRIPTION

[0048] FIG. 2 schematically and partially illustrates the method for manufacturing a log of sheet of absorbent material according to a first exemplary embodiment of the invention. More precisely, FIG. 2 schematically and partially shows a converting operation taking place after a base sheet 1 has been produced by a paper making machine. At this stage, the base sheet 1 is fed into a converting line.

[0049] In FIG. 2, multiple phantom lines 20-27 parallel to the machine direction MD are also represented on the base sheet 1 for the sole purpose of illustration. The phantom lines 20-27 are spaced apart in the cross-machine direction CD. Each phantom line schematically represents an imaginary line where the base sheet 1 will be cut at the end of the converting process in order to form a plurality of individual rolls of sheet of absorbent material. Thus, two adjacent phantom lines define the future edges of the individual roll. The distance between two consecutive phantom lines is equal to the full width of the individual roll.

[0050] The base sheet 1 is fed into the space of the perforating unit 10, namely between a perforator roll 11 and an anvil roll 12 of the perforating unit 10. The perforating unit 10 will be described in details in relation with FIGS. 5 and 6. The base sheet 1 is pinched (step S1) with the tear lines 50 (schematically represented by dotted lines). The tear line 50 is a line according to a cross-machine direction CD (i.e. transversally to the machine direction MD) made in the thickness of the base sheet 1 that constitutes a zone of weakness. According to an embodiment of the invention, the tear line 50 comprises two edge regions 56 and a central region 55. A first edge region begins at one of the sheet side edges towards the central region 55. A second edge region begins at the other sheet side edges towards the central region 55. The central region 55 comprises alternating perforated segments and unperforated segments. The two edge regions 56 are short unperforated segments. The central region 55 comprises alternating perforation segments having a particular perforating pattern. The perforating pattern of the perforation segments 55 will be described in details in relation with FIGS. 7 to 11. The short unperforated segments of the two edge regions 56 are crossed substantially in the middle by a corresponding phantom line 20-27 or, in other word, each phantom line 20-27 is positioned at a boundary between two adjacent edge regions 56. Each perforation segment 55 is positioned in the middle of the full width defined by two adjacent phantom lines (e.g., 21 and 22), more precisely at a distance a from both phantom lines that defines the future edges of the individual roll. Thus, the length of the short unperforated segments 56 in the cross direction CD is noted 2. The length of the perforation segments 55 in the cross direction CD is noted . Two consecutive tear lines 50 define the individual sheet length L in the rolls 4 (e.g., a length around 33 cm).

[0051] The short unperforated segments 56 of length 2 form attachment areas within the tear line 50 according to the cross-machine direction CD of the base sheet. The short unperforated segments form a plurality of attachment areas between two consecutive portions according to the machine direction MD of the base sheet. With an appropriately chosen length 2, the resulting tensile strength of the tear lines 50 is significantly improved. This avoids, at least considerably reduces, the blowouts in the base sheet during production. Indeed, breaks in the base sheet cannot propagate, at least with difficulty, along the tear line 50. As a non-limitative example, the length 2 may be chosen around or superior to 8 mm (i.e. 4 mm).

[0052] After the pinching step (S1), the perforated base sheet 1 is wound (step S2) onto a core 3 (or alternatively on itself for coreless log) in order to form a wound log 2 by means of the rewinding unit 11. Then, though not represented and similarly to the method for manufacturing a roll of sheet of absorbent material represented in FIG. 1, once the desired log diameter is reached: [0053] the base sheet 1 is cut; [0054] the produced log 2 is separated from the base sheet 1 and subsequently a new log begins to be produced; [0055] a loose end forming a tail of the base sheet of the produced log 2 is adhered to the log; and [0056] the produced log 2 is cut into multiple and individual rolls 4.

[0057] Considering the size of the individual roll, a width ratio of the edge regions relatively to the central region may range from about 4% (i.e. 2=24 mm for a sheet width of the individual roll of 200 mm) to about 20% (i.e. 2=210 mm for a sheet width of the individual roll of 100 mm).

[0058] FIG. 3 schematically and partially illustrates the method for manufacturing a log of sheet of absorbent material according to a second exemplary embodiment of the invention. The second exemplary embodiment differs from the first exemplary embodiment in that the base sheet 1 is pinched (step S1) with staggered tear lines 51 and 52 (schematically represented by dotted lines). One central region out of two in each tear line is replaced by an unperforated region, and two consecutive tear lines are staggered according to a cross-machine direction CD such that all the central region are positioned between two adjacent phantom lines. More precisely, two identical adjacent tear lines 50 in the first exemplary embodiment are replaced by a first tear line 51 adjacent to a second tear line 52, the first tear line 51 being staggered or offset according to the CD direction relatively to the second tear line 52. Further, the tear line 51 or 52 comprises alternating perforation segments 55 having a particular perforating pattern and long unperforated segments 56 (corresponding to two edge regions and one unperforated central region). The perforating pattern of the perforation segments 55 will be described in details in relation with FIGS. 7 to 11. The perforated segments 55 are positioned in the middle of the full width defined by two adjacent phantom lines (e.g., 20 and 21 for the first tear line 51), more precisely at a distance a from both phantom lines that defines the future edges of the individual roll. Still, the length of the perforation segments 55 in the cross direction CD is noted . Compared to the first exemplary embodiment, in the second exemplary embodiment each long unperforated segment 56 has the length 2 increased from the length of a roll width, or a length 2++2=4+. Two consecutive tear lines 51 or 52 define the individual sheet length L in the rolls of sheet of absorbent material 4 (e.g., a length around 33 cm). Two adjacent tear lines 51 and 52 are separated by a distance 6 in the machine direction MD.

[0059] The long unperforated segments 56 of length 4+ form attachment areas within the tear line 51, 52 according to the cross-machine direction CD of the base sheet. The long unperforated segments form a plurality of attachment areas between two consecutive portions according to the machine direction MD of the base sheet. Thus, the resulting tensile strength of the tear lines 51, 52 is significantly improved. This avoids, at least considerably reduces, the blowouts in the base sheet during production. The breaks in the base sheet cannot propagate, at least with difficulty, along the tear line 51 or 52. As a non-limitative example, the length 2 may be chosen around or superior to 8 mm (i.e. 4 mm).

[0060] FIG. 4 is a perspective view schematically illustrating the individual roll of sheet of absorbent material 4 manufactured according to the first embodiment of FIG. 2 or the second embodiment of FIG. 3. The roll 4 may be a roll of paper, for example a roll of toilet paper or a roll of kitchen towels. The roll may comprise a core or may be coreless. The roll has evenly spaced-apart transverse tear lines 50, 51, 52 which extend across the width of individual sheet of absorbent material 59 (e.g., a paper web). The tear lines 50, 51, 52 enable tearing off and separation of individual sheets of paper 19 of a predetermined length L when the roll is unwound in the direction of the arrow. The two attachment areas between two consecutive individual sheets 19 (according to the machine direction MD of the sheet) resulting from the short unperforated segments of length a on each edge of the individual roll do not impair the separation of each individual sheet 19 from the roll 4 when the dimension is appropriately chosen.

[0061] FIG. 5 is a perspective view schematically illustrating a perforating unit 10 used for pinching the base sheet 1 according to the manufacturing method of the first exemplary embodiment.

[0062] The perforating unit 10 comprises the perforator roll 11 and the anvil roll 12. The space 18 is defined therebetween. The perforator roll 11 carries at least one knife, for example two knifes 14, 15. In this non limitative example, the first knife 14 is positioned at 180 degrees relatively to the second knife 15. More knifes and different positioning angle are possible. The anvil roll 12 carries a spiral blade 13. The perforator roll 11 and the anvil roll 12 are both rotating so that when the base sheet 1 is fed into the space 18, it is pinched according to a scissors like movement between one of the knife 14 or 15 and the spiral blade 13.

[0063] In the embodiment of FIG. 5, each knife 14, 15 extends all along the width of the perforator roll 11. This width corresponds at least to the width of the base sheet 1 or the width of the log 2. Each knife is used to cut the tear line 50 (see FIG. 2) in the base sheet 1. Each knife 14, 15 comprises multiple zones 16, each zone corresponding to a perforation segment 55 having a defined perforating pattern that may be chosen among the represented perforating pattern of FIGS. 7 to 11. Each zone 16 is separated from an adjacent zone by the distance 2..

[0064] FIG. 6 is a perspective view schematically illustrating another perforating unit 10 used for pinching the base sheet 1 according to the manufacturing method of the second exemplary embodiment. The embodiment of FIG. 6 differs from the embodiment of FIG. 5 in that both knifes 14 and 15 comprises segmented zones 16. Similarly, each segmented zone 16 corresponds to a perforation segment 55 having a defined perforating pattern that may be chosen among the represented perforating pattern of FIGS. 7 to 11. The first knife 14 is used to cut the first tear line 51 (see FIG. 3) in the absorbent base sheet 1.The second knife 15 is used to cut the second tear line 52 (see FIG. 3) in the absorbent base sheet 1. A zone 16 of the first knife 14 is shifted relatively to a zone 16 of the second knife 15 by the distance 2. (corresponding to the two adjacent unperforated edge regions) so as to pinch the base sheet 1 according to staggered tear lines 51 and 52.

[0065] FIG. 7 schematically illustrates a first exemplary perforating pattern of a perforation segment 55A (top part) and the corresponding zone 16A of the knife 14, 15 (bottom part). The perforation segment 55A comprises two perforated segments 60 separated by one unperforated segment 61. The unperforated segment 61 forms an attachment area between two consecutive portions (according to the machine direction MD) of the base sheet. Each perforated segment 60 forms a detachment area between two consecutive portions (according to the machine direction MD) of the base sheet. The zone 16A of the knife 14, 15 comprises a succession of blade elements and notch corresponding to the first exemplary perforating pattern.

[0066] FIG. 8 schematically illustrates a second exemplary perforating pattern of a perforation segment 55B (top part) and the corresponding zone 16B of the knife 14, 15 (bottom part). The perforation segment 55B comprises four perforated segments 62, two adjacent perforated segments 62 being separated by an unperforated segment 63. The zone 16B of the knife 14, 15 comprises a succession of blade elements and notches corresponding to the second exemplary perforating pattern.

[0067] FIG. 9 schematically illustrates a third exemplary perforating pattern of a perforation segment 55C (top part) and the corresponding zone 16C of the knife 14, 15 (bottom part). The perforation segment 55C comprises eighteen perforated segments 64, two adjacent perforated segments 64 being separated by an unperforated segment 65. The zone 16C of the knife 14, 15 comprises a succession of blade elements and notches corresponding to the second exemplary perforating pattern.

[0068] FIG. 10 schematically illustrates a fourth exemplary perforating pattern of a perforation segment 55D (top part) and the corresponding zone 16D of the knife 14, 15 (bottom part). The perforation segment 55D comprises multiple perforated segments 66, two adjacent perforated segments 66 being separated by an unperforated segment 67. The width of the perforated segments 66 increases along the perforation segment 55D, as depicted from the left to the right (or conversely). The width of the unperforated segment 67 is constant along the perforation segment 55D. The zone 16D of the knife 14, 15 comprises a succession of blade elements and notches corresponding to the second exemplary perforating pattern. The width of the blade elements increases along the zone 16D of the knife while the width of the notch is constant.

[0069] FIG. 11 schematically illustrates a fifth exemplary perforating pattern of a perforation segment 55E (top part) and the corresponding zone 16E of the knife 14, 15 (bottom part). The perforation segment 55E comprises multiple perforated segments 68, two adjacent perforated segments 68 being separated by an unperforated segment 69. The width of the perforated segments 68 is constant along the perforation segment 55E. The width of the unperforated segment 69 increases along the perforation segment 55D, as depicted from the left to the right (or conversely). The zone 16E of the knife 14, 15 comprises a succession of blade elements and notches corresponding to the second exemplary perforating pattern. The width of the blade elements is constant along the zone 16D of the knife while the width of the notch increases.

[0070] In the represented perforating pattern of FIGS. 7 to 11, the numbers of perforated segments and unperforated segments are given as non-limitative examples, other numbers would also be satisfactory in the context of embodiments of the present invention.

[0071] The roll of sheet of absorbent product of an embodiment of the invention can be dispensed in various dispensers, for example in center-feed dispensers for dispensing sheets from the center of the roll or in tangential dispensers for tangentially dispensing sheets from the roll.

[0072] Tensile strength measurements according to the standard CEN 12625-4 (determination of tensile strength, stretch at break and tensile energy absorption of tissue paper and tissue products) have been performed on sheets according to the prior art and according to an embodiment of the invention. The characteristics of the central region comprising alternating perforated segments 60, 62, 64, 66, 68 of dimension and unperforated segments 61, 63, 65, 67, 69 of dimension US around 4 mm PS around 1 mm gives an unperforated ratio or bond ratio of 20% (1 mm over 5 mm). The perforating pattern is the one of FIG. 9.

Tensile Strength Measurements:

[0073]

TABLE-US-00001 Prior Art Invention Invention Invention US = 1 mm = 0 mm = 3 mm = 5.5 mm = 8 mm PS = 4 mm N/m N/m N/m N/m Single ply 64 56 63 71 Two plies 132 124 132 142
The log base sheet according to an embodiment of the invention can be converted at speeds typical in the industry, e.g., up to 650 m/min without the occurrence of sheet blowouts. This shows an improved tensile strength of each zone of weakness (tear line) of the log base sheet when runs into the converting machine. Further, the tensile strength of the sheet (e.g., wound as an individual roll) is similar, even less, to the one of the prior art, thus showing an easy dispensing. In particular, an edge region having a width () ranging from about 3 mm to about 5 mm gives excellent results in term of tensile strength, thus allowing easy dispensing. This is a surprising results because whatever the size of the edge zone (within said range) and at equivalent unperforated ratio, the tensile strength of the tear line of the sheet is identical or at least quite similar, while one could have expected an increased tensile strength resulting in poor dispensing.

[0074] The drawings and their descriptions hereinbefore illustrate rather than limit the embodiments of the invention.

[0075] In the description and the drawings, each zone of weakness (being a tear line) have been described and/or shown as extending substantially transversally to the machine direction. This should be interpreted in a broad sense, meaning that the zone of weakness may be inclined relatively the cross-machine direction CD, as an example according to angle in a range of 10.

[0076] The application of the absorbent sheet product is broad and encompasses numerous away-from-home, domestic or sanitary applications, e.g., towels, kitchen towels, hand towels, toilet papers, wipes, facial tissues, bath tissues, napkins etc.

[0077] 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.