WO2002068758A1

WO2002068758A1 - A sheet of creped and embossed absorbent paper, an embossing roll for one such sheet and an embossing method

Info

Publication number: WO2002068758A1
Application number: PCT/FR2002/000673
Authority: WO
Inventors: Pierre Graff
Original assignee: Georgia-Pacific France
Priority date: 2001-02-23
Filing date: 2002-02-22
Publication date: 2002-09-06
Also published as: DE60127806D1; CA2406577A1; NO332242B1; PT1236830E; ATE359396T1; DK1236830T3; DE60127806T2; EP1236830B1; ES2284600T3; EP1236830A1; NO20025046D0; CA2406577C; NO20025046L

Abstract

The invention relates to an embossed sheet (10) consisting of at least one first and one second ply (12, 14) of creped cellulose wadding. Said sheet is of the type that has at least one first ply (12) comprising a first embossing pattern (16) made up of a first series of first protrusions (18) which form, in particular, first alignments and the peaks (32) of which are linked to the inner face (24) of the second ply (14) with both surfaces facing each other. Said invention is characterised in that each of the two plies (12, 14) comprise a second embossing pattern (36) made up of a second series of second protrusions (38, 40) and in that the peaks (42, 44) of the second protrusions (38, 40) of one ply (12, 14) extend opposite and close to the peaks (44, 42) of the second protrusions (40, 38) of the other ply (14, 12).

Description

_FE _U _L PAPER AND ABSORBENT crimped GAUFREE, cylinder EMBOSSING SUCH A SHEET AND METHOD FOR EMBOSSING

The invention relates to a sheet of paper, in particular a sheet of absorbent crepe cellulose wadding paper, having an embossing pattern.

The invention relates in particular to a sheet of paper, composed of at least a first and a second pl is of cotton wool cre creped, intended for the field of wiping in a household, domestic or industrial use , i.e. likely to be used as a paper towel, cloth etc.

In the field of papers for sanitary or domestic use such as toilet paper or paper towels, it is known to make sheets of paper composed of several plies of absorbent paper, for example in creped cel lulose wadding grammage between 1 2 and 30 g / m ² , provided with protuberances which are obtained by embossing.

In fact, the embossing gives bulk to the film and it induces an improvement in the absorption of the liquids, the feel and the smoothness. Attempts have been made to further increase the absorption capacity by creating layers the multilayers obtained by associating at least two layers, also called plies, each consisting of at least one of said embossed sheets.

A multilayer laminate is thus obtained which has mechanical characteristics such as tensile strength, as well as a determined absorption capacity.

Two modes of embossing and assembly of the plies are commonly implemented according to the desired characteristics of the final product.

The first is known in the field under the designation "nested" or interlocking. It consists first of embossing each of the folds separately so as to form on the surface protuberances generally substantially conical or in pyramid trunks. Then we put glue on the top of the protrusions of one of the folds, and we place the folds so that the faces having the protuberances come opposite, the protuberances of one between the protuberances of the other. Finally, the folds are assembled in such a way that the protuberances having been glued come to fit between the protuberances of the other fold. Thus the two plies are linked by glue points between the tops of the protuberances of a pl i and non-embossed areas between the protuberances of the other ply. A structure is made of which the voids thus formed are suitable for ensuring that the sheet has improved absorption. In addition, the exterior faces have a smooth and soft feel due to the recessed areas formed by the back of the protrusions. This technique is illustrated by patent US-A-3,867,225.

The second method of assembly is known in the field under the designation "points / points". It differs from the previous one by the relative arrangement of the two folds. These, after they have been embossed separately, are brought one on the other so as to make the vertices of the protrusions coincide, or at least part of these vertices. The folds are linked together by the tops of the protuberances, points against points. This technique is illustrated by patent US-A-3,414,459.

When we consider the practical achievements of these structures, whether of the nested or point / point type, the protuberances obtained during embossing are most often made so as to be distributed according to a pattern in which the protuberances are generally aligned according to a or more directions, evenly. Such a pattern makes it possible to obtain a uniform film with regard to its mechanical characteristics.

However, in order to improve user satisfaction, it is important to increase the flexibility of the sheet. We can define the flexibility of the sheet as its ability to deform regularly when it is placed in the hand of a user, his fingers being stretched in line with his palm and the user then folds his fingers.

A sheet of paper which has a high flexibility will then deform and bend or arch so as to remain substantially parallel to the shape determined by the inside of the palm of the user's hand.

A sheet of paper which has low flexibility will fold along one or more lines, each portion of the sheet which extends between two fold lines remaining substantially planar.

A sheet of paper that has high flexibility is more pleasant to use.

In general, the increase in the flexibility of the sheet notably causes a reduction in its mechanical characteristics.

The object of the invention is to propose a new design of embossed paper sheet which makes it possible to increase the flexibility of the sheet without reducing its mechanical characteristics.

For this purpose, the invention provides an embossed sheet composed of at least a first and a second pl is of cotton wool creped crêpe of grammage between 12 and 30 g / m ² of the type of which at least one first fold comprises a first embossing pattern consisting of a first series of first protuberances, of generally frustoconical shape projecting from the internal face of the first fold, which in particular form first alignments and the vertices of which are connected to the internal face of the second fold in opposite, characterized in that these two folds each comprise a second embossing pattern consisting of a second series of second protrusions in raised edges the internal face of the corresponding ply, and in that the vertices of the second protuberances of a pl i extend opposite and near the vertices of the second protuberances of the other ply.

According to other characteristics of the invention:

- vertices of the second protrusions of a fold are in contact with vertices of the second protrusions facing the other fold;

- the vertices in contact with the second protrusions are not linked;

- The heights of the second protrusions of the two plies are substantially equal;

each of the two folds comprises a first series of first protuberances, of generally frustoconical shape projecting from the internal face of the fold, which form first alignments;

- the aligned protrusions of the first series form figures of the closed loop type;

- Each of the two folds comprises a first series of first protrusions, and associated series of the first protrusions of one and the other fold are nested between the associated series of protrusions of the other of the two folds;

- second protrusions are at point vertices;

- second protuberances have linear l vertices. The invention also provides a pair of engraved cylinders for the embossing of an embossed sheet according to any one of the preceding claims, at least one of the cylinders of which comprises a first series of first pins of generally frustoconical shape and forming first alignments. , characterized in that the two engraved cylinders each comprise a second series of second raised pins, with point and / or linear vertices, each second pin of a cylinder corresponds substantially with a second pin of the other cylinder and the sum of the heights of the corresponding second spikes is substantially equal to the height of the first spikes.

The invention finally proposes a method of manufacturing an embossed sheet by means of a pair of cylinders according to the preceding claim, characterized in that it consists in embossing the two plies so as to form the first and second patterns. embossing, then to assemble the two folds so that the tops of the first protuberances are tied to the internal face of the pl i opposite and that the tops of the second protuberances of a pl i extend opposite opposite and near the tops of the second protrusions of the other fold.

Other characteristics and advantages of the invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

- Figure 1 it luster a top view of an embodiment of a sheet of embossed paper according to the teachings of the invention, and more particularly a sheet of paper towel;

- Figure 2 is a schematic sectional and perspective view of a sheet of embossed paper made in accordance with the teachings of the invention;

- Figure 3 is a schematic sectional view of a sheet of embossed paper which is produced in accordance with the teachings of the invention and which is slightly arched;

- Figures 4 and 5 are schematic sectional views of a sheet of embossed paper produced according to alternative embodiments of the invention;

- Figure 6 is a schematic perspective view illustrating the convex indric cylindrical surface of an embossing cylinder with a fold of a sheet according to Figure 1; FIG. 7 is a large-scale view of the detail D7 of FIG. 6.

There is shown in Figures 1 and 2 an embodiment of a sheet 1 0 of embossed paper, in particular a sheet of paper consisting of a first upper fold 12 and a second lower fold 14 of absorbent paper, wadding crêped cellulose, intended for all types of hygiene or household products.

The cellulose wadding, with a basis weight between 12 and 30 g / m ² , is of the type obtained by conventional wet pressing, called "CWP", or of the type obtained by drying by through air, called "TAD".

More particularly, the sheet of paper 10 shown in Figures 1 and 2 is for example intended to be incorporated in a roll of paper towel.

The sheet 10 is oriented in two longitudinal and transverse directions, represented in FIG. 2 by the arrows L and T, which correspond to the direction of travel of the sheet 1 0 during its manufacture, also called "On" direction and to the perpendicular direction respectively, also called "Travers" direction.

After embossing, a first pattern 16 is apparent and detaches visually from the first 12 and the second fold 14 of the sheet 1 0.

The first embossing pattern 16 of each ply 12 and 14, of known general design, consists of first series of first protrusions 1 8 and 20, of generally frustoconical shape projecting on the internal face 22, 24 of the ply 12, 14 corresponding, thus extending towards the inside of the sheet 10.

The first protrusions 18 and 20 in particular form first alignments according to figures, in particular in closed loops which are here circles. Here, in accordance with FIG. 1, associated series of the first protrusions 1 8, 20 of one and the other fold 12, 14 are nested, concentrically, between the associated series of protrusions 20, 1 8 of l 'other 14, 12 of the two folds.

The first series of first protrusions 18 and 20 are aligned in two main directions so as to define a grid. The two main directions are here perpendicular to each other, and are inclined at 45 degrees relative to the longitudinal L and transverse T directions of the sheet 10.

The vertices 32, 34 of the first protrusions 18, 20 are linked to the internal face 24, 22 of the fold 14, 12 opposite (see Figure 2).

According to a known technique, the first protrusions 18, 20 constituting the elements of the first pattern 16 are obtained by embossing the first 12 and the second folds 14 of the sheet 10 by means of a pair of cylinders, one of which 26 is shown in FIGS. 6 and 7.

"Protrusions" homologous to those which it is desired to obtain on the first 12 and the second folds 14 of the sheet 10 are formed in relief on the external convex cylindrical face 28 of the associated cylinder 26.

For the production of the series of first protuberances 18 on the first fold 12 of the sheet 10, the embossing cylinder 26 has on its convex cylindrical face 28 a first homologous series of raised pins 30 of generally frustoconical shape in relief, which are distributed in concentric circles according to the first alignments of the first protrusions 18, so as to make the corresponding part of the first pattern 16 of the first fold 12.

Similarly, the series of first protrusions 20 on the second fold 14 of the sheet 10 is produced by another similar embossing cylinder, the frustoconical raised pins of which are distributed in concentric circles according to the first alignments of the first protrusions 20, so as to produce the corresponding part of the first pattern 16 of the second pl i 14.

When the first 12 and the second folds 14 are embossed, they are assembled together by bonding the tops 32 or 34 of the first protrusions 18 or 20 on the internal face 24 or 22 of the second 14 or of the first fold 12 facing each other. -screw.

In accordance with the teachings of the invention, and in order to improve the flexibility of the sheet 1 0 without reducing its mechanical characteristics and its absorption capacity, the two plies 12, 14 comprise a second embossing pattern 36 consisting of second series of second protrusions 38, 40 which are for example of generally frustoconical shape, that is to say with point vertices, projecting from the internal face 22, 24 of the corresponding fold 12, 14, thus extending towards the interior of the sheet 10.

The axes A1 and A2 of the second protrusions 38 and 40 of the first 12 and the second pl is 14 are substantially aligned.

The second protrusions 38 and 40 are produced in a similar fashion to the first protrusions 18 and 20, in particular by a second series of second pins 46 of frustoconical shape which extend to the convex surface 28 of the embossing cylinder 26.

Each second spike of a cylinder preferably corresponds with a second corresponding spike of the other cylinder, and the sum of the heights of the corresponding second spikes is substantially equal to the height of the first spikes.

The second protrusions 38, 40 form in particular second alignments according to figures, in particular in closed loops, which are arranged between the first series of first protrusions 18 and 20.

Here, the closed loops have the general shape of a square, the edges of which are curved and concave in a manner substantially parallel to the circles defined by the first protrusions 18 and 20.

However, the second alignments can consist of other shapes, geometric or not, such as diamonds or flowers.

It is also possible that the second alignments of the second protrusions 38 and 40 include circles which are arranged concentrically with the circles of the first series of first protrusions 18 and 20.

As a variant not shown, the second protuberances are not necessarily frustoconical protuberances with point vertices, but can also be of the type with linear vertices defining more or less complex linear patterns.

The second protuberances can also be combinations of point vertices and linear vertices on the same fold, on the two folds or respectively on one and the other of the two folds.

When the second protuberances are frustoconical, they are preferably micro protuberances, by comparison with the first frustoconical protuberances, with a density of micro protuberances between 30 and 80 protuberances per cm ² .

The diameter of the peaks of the pins for etching the micro protuberances is for example of the order of 0.4 mm while that of the first (macro) protuberances is of the order of 1.0 mm.

By way of example, if we consider the corresponding heights of the first pins 30 and of the second pins 46 formed in relief on the cylinder 26, intended for embossing a first fold 12 of a sheet of paper for use as a paper towel, the height of the first pins 30 is equal to 1, 3 mid llimeter while the height of the second pins 46 is equal to 0.7 millimeter. With a cylind indre thus defined, associated with a cyl indre with an appropriate rubber coating, a ply of cotton wool of cel lulose of 22 g / m ² was embossed and an average thickness H of the first ply 12 was obtained of the order of 0.8 millimeter.

The first 30 and the second pins 46 are of frustoconical shape with circular, oval, polygonal or other section, and preferably with a steep slope, between 60 and 70 °.

The vertices 42, 44 of the second protrusions 38, 40 of the first 12 and second plies 14 extend opposite and near the opposite and substantially axially aligned vertices 44, 42 of the second protrusions 40, 38 of the other pl i 14, 12.

Such an embossed sheet has a flexibility greater than that of an embossed sheet produced according to the state of the art while having mechanical characteristics and an absorption capacity which are not reduced.

The flexibility of the sheet 1 0 is improved because, when bending the sheet 1 0, the vertices 42 and 44 of the second protrusions 38 and 40 can move slightly relative to each other, that is to say - say tilt and shift according to figure 3.

The mutual support of the vertices 42 and 44 of the second protuberances 38 and 40 prevents the formation of a fold line detrimental to the flexibility of the sheet and promotes the bending of the sheet 1 0.

The mutual support of the vertices 42 and 44 of the second protrusions 38 and 40 also makes it possible to minimize the crushing of the sheet 1 0 which allows the sheet 1 0 to retain its bulk, that is to say its absorption capacities. According to Figure 2, the vertices 42 and 44 of the second protrusions 38 and 40 may be in contact. They are not related to each other.

According to a variant, represented in FIG. 4, the vertices 42 and 44 of the second protrusions 38 and 40 are separated axially by a slight clearance J.

The two figures 2 and 4 represent second protrusions 38 and 40 which are symmetrical with respect to a median plane of the film on the 10th, that is to say that their heights H 1, H2 are equal just like the heights H 1 ', H2'.

However, according to a variant shown in Figure 5, the second protrusions 38 and 40 may be asymmetrical.

Without departing from the scope of the invention, it is not necessary for the vertices of the second opposite protuberances to be perfectly aligned.

Nor is it compulsory that there is a complete correspondence of the second protrusions of a fold with second protrusions of the other fold.

As regards the performances of a sheet according to the invention, they are analogous to those of the corresponding product according to the state of the art with only first protuberances, with the exception of the flexibility of the sheet which is greatly improved.

Tests have in fact shown that the stiffness of the sheet according to the invention, that is to say the inverse of the flexibility, (measured according to the method of the geometric mean known as "Geometry Mean Stiffness"), is reduced more 20% compared to the stiffness of the sheet according to the state of the art.

Claims

REVEN DICATIONS

1. Embossed sheet (1 0) composed of at least a first and a second ply (12, 14) of creped cel lulose wadding with a grammage between 12 and 30 g / m ² of the type including at least a first ply (12 ) comprises a first embossing pattern (16) consisting of a first series of first protuberances (1 8), of generally frustoconical shape in sail binds on the internal face (22) of the first pl i (12), which form first alignments and the vertices (32) of which are connected to the internal face (24) of the second fold (14) opposite, characterized in that these two folds (12, 14) each have a second pattern (36 ) of embossing consisting of a second series of second protrusions (38, 40) projecting from the internal face (22, 24) of the corresponding fold, and in that vertices (42, 44) of the second protrusions (38, 40 ) of a fold (12, 14) extend opposite and near the tops (44, 42) of the second protrusions (40, 38) of the other fold (14, 12) .

2. Embossed sheet (10) according to the preceding claim, characterized in that the tops (42, 44) of the second protrusions (38, 40) of a fold (12, 14) are in contact with the tops (44, 42) of the second protuberances (40, 38) facing the other fold (14, 12).

3. Embossed sheet (10) according to the preceding claim, characterized in that the vertices (42, 44) in contact with the second protuberances (38, 40) are not linked.

4. Embossed sheet (10) according to any one of the preceding claims, characterized in that the heights (H 1, H2) of the second protrusions (38, 40) of the two plies (12, 14) are substantially equal.

5. Feuil the embossed (10) according to any one of the preceding claims, characterized in that each of the two folds (12, 14) comprises a first series of first protuberances (1 8, 20), of generally frustoconical projecting shape on the internal face (22, 24) of the fold (12, 14), which form the first alignments.

6. Embossed sheet (10) according to any one of the preceding claims, characterized in that the protuberances (1 8, 20) aligned from the first series form figures of the closed loop type.

7. Embossed sheet (10) according to the preceding claim, characterized in that each of the two folds (12, 14) comprises a first series of first protuberances (1 8, 20), and in that associated series of the first protuberances ( 18, 20) of one and the other pl i (12, 14) are nested between the associated series of protrusions (20, 1 8) of the other (14, 12) of the two folds.

8. Embossed sheet (10) according to any one of the preceding claims, characterized in that second protrusions are at point vertices.

9. Embossed sheet (10) according to any one of the preceding claims, characterized in that second protrusions are with linear vertices.

1 0 Pair of cylinders (26) engraved for the embossing of an embossed sheet (1 0) according to any one of the preceding claims, at least one of the cylinders (26) of which comprises a first series of first pins (30 ) of generally frustoconical shape and forming first alignments, characterized in that the two engraved cylinders (26) each comprise a second series of second raised pins, with linear and / or punctual vertices (46) including each second pin (46) of a cylinder corresponds substantially with a second spike (46) of the other cylinder and the sum of the heights of the corresponding second spikes (46) being substantially equal to the height of the first spikes (30).

1 1. Method of manufacturing an embossed film (10) by means of a pair of cylinders (26) according to claim previous, characterized in that it consists in embossing the two plies (12, 14) so as to form the first (16) and the second patterns (36) of embossing, then assembling the two plies (12, 14) so that the vertices (32, 34) of the first protrusions (18, 20) are linked to the internal face (24, 22) of the pl i (14, 12) opposite and that the vertices (42, 44) of the second protuberances (38, 40) of a fold (12, 14) extend opposite and near the vertices (44, 42) of the second protrusions (40, 38) of the other fold (14, 12).