EP1646745A1

EP1646745A1 - Method and device for hydroentangling a web made of a fibrous cellulose product, and a web of this type

Info

Publication number: EP1646745A1
Application number: EP04767371A
Authority: EP
Inventors: Bernard Louis Dit Picard; Philippe Gregoire
Original assignee: Georgia Pacific France SAS
Current assignee: Essity Operations France SAS
Priority date: 2003-06-18
Filing date: 2004-06-17
Publication date: 2006-04-19
Anticipated expiration: 2024-06-17
Also published as: RU2352696C2; US20060137155A1; US20090113680A1; RU2005138594A; FR2856414A1; AU2004249920A1; US7467445B2; WO2004113602A1; AU2004249920B2; US7669304B2; CA2529028A1; EP1646745B1; CA2529028C; FR2856414B1

Abstract

The invention relates to a method for hydroentangling a web (N) during which the web is placed on a porous support (10) that moves translationally or rotates about an axis, and at least one face of the web is processed by means of a number of water jets arranged in a row perpendicular to the advancing direction of the web. The invention is characterized by the fact that the row contains jets having a first section (14A) and at least jets having a second section (24A) that differs from the first. The invention also relates to a method involving the processing of the web by means of a number of water jets arranged in at least two rows that are perpendicular to the advancing direction of the web. The rows contain jets having a first section (14, 16, 17, 18, 19) and at least jets having a second section (24, 26, 27, 28, 29, 39) that differs from the first. At least one row contains jets whose distance from one another is not constant. This method makes it possible to produce webs whose surface condition is varied. The invention also relates to a device for implementing said method and to a web having grooves of different depths and spacing.

Description

Method and device for hydroliaging a sheet of fibrous cellulosic product and such a sheet

The present invention relates to the technique of hydraulic bonding or hydroliage of a sheet of fibers, and is aimed in particular at a means for obtaining a determined surface condition on a sheet of cellulosic fibers, in particular hydrophilic cotton, optionally in admixture with artificial or synthetic fibers. The present invention also relates to a hydraulically linked ply. A known hydroliage process consists in treating a sheet of fibers using high-pressure water jets, with the aim of entangling all or part of the fibers and modifying some of its characteristics. This process seeks in particular to modify its mechanical strength and linting. The fiber sheet is supported by a porous fabric which moves in a direction perpendicular to the alignments of the water jets. The latter are produced by an apparatus comprising one or more injectors arranged transversely with respect to the direction of movement of the sheet of fibers. Usually, an injector comprises a high pressure chamber in the form of a channel communicating on one side with a blade provided with calibrated perforations, of circular shape, all of the same diameter and of suitable profile. The blade is designated in the present field by the term strip. It is this term which is used subsequently. The distribution channel is supplied by pumps supplying water at a high pressure, from a few bars to 300 bars.

The perforations commonly have a diameter of between 80 μm and 200 μm and are regularly spaced along the strip. The spacing is between 0.2 and 10 mm. There are commercially available metal strips with one to three rows of perforations. In the case of more than one row, the perforations are staggered.

The porous fabric, on which the sheet of fibers is extended, is driven along a flat table or else on a cylinder set in rotation. The fabric allows water to pass through the fibrous web, and a suction means provided under the fabric ensures its evacuation.

From a certain grammage or thickness of the sheet, this device has the immediately visible result of producing a relief formed by continuous lines, generally rectilinear, parallel to each other, and regularly spaced on the surface of the sheet. The lines are particularly visible when the jets are spaced from each other by at least one millimeter and with sufficient pressure. These lines are aligned in the direction of travel of the web.

These lines are in fact grooves formed on the surface of the water table, the depth, the spacing between them and the width depend essentially on the arrangement of the water jets, the pressure of the water admitted to the injectors, the diameter and the profile of the perforations as well as the speed of movement of the sheet with respect to the jets.

For cosmetic use, make-up and / or make-up removal from the skin, the sheet of fibers is preferably made up of cellulosic fibers and in particular hydrophilic cotton fibers, optionally mixed with other fibers, artificial or synthetic.

Patent EP 1 106 723 in the name of the applicant, describes a tampon cut from a sheet of hydrophilic cotton having a grammage of at least 150 g / m ² comprising recessed ridges spaced 1 to 8 mm apart and a streak depth at least 0.25 mm. This tablecloth also has a certain tensile strength. The other side also includes streaks but their spacing and depth are different from those of the first. This type of sheet is produced, for example, by hydroliage. The sheet is entrained under jets having an appropriate spacing and energy according to the relief which it is desired to obtain.

According to a variant of the process, repeated in patent application EP 010121057 (1,167,605), the water jets of the hydraulic binding means form groups with jets spaced apart by a distance of between 0.4 and 1 , 2 mm, the groups of jets being spaced from each other by a distance of between 1, 2 and 4 mm. It is thus possible to produce plies having different reliefs between the two faces while avoiding the problem of linting for large gaps between the streaks. A cotton product is obtained, the two faces of which are distinguished from each other, which retains its qualities of mechanical resistance: resistance to fluffing, resistance to delamination in particular, and softness. One side has a more itchy effect than the other for cleaning.

The Applicant constantly pursues the objective of offering the user improved products.

In particular, it has set itself as its first objective, the development of hydroliage means making it possible to produce products whose surface condition, in particular the relief, is more elaborate than those currently known.

Indeed, the most widespread state of the art aims to produce, for each face of a product, surfaces striated regularly or with a sequence of spaces between the ridges, the latter all being identical, even if a distinction is made between opposite each other.

To meet the needs of the user in terms of makeup or make-up removal, the applicant has set itself as another objective the production of a sufficiently thick product with a relief which would make it possible to provide the skin with the quantity of cleansing milk. or necessary lotion but also to strengthen their make-up removing action, by friction without irritating the skin. In particular, it is aimed at a thick fibrous product which keeps bulking, a good level of resistance in both walking and cross direction, and good absorption while being hydraulically linked. These objectives can be achieved with a hydraulic bonding process of a sheet of fibers, consisting of placing the sheet on a porous support movable in translation or in rotation around an axis, treating at least one face of the sheet with means of a plurality of water jets arranged in a row perpendicular to the direction of travel of the sheet, characterized in that the row comprises jets with a first section and at least jets with a second section different from the first .

We also manage to achieve these objectives with a hydraulic bonding process of a sheet of fibers, consisting of placing the sheet on a porous support movable in translation or in rotation around an axis, treating the sheet using a plurality of water jets arranged in at least two rows perpendicular to the direction of travel of the web, characterized in that the rows include jets with a first section and at least jets with a second section different from the first, at at least one row comprising jets whose spacing between them is not constant. While the prior art taught manufacturing methods allowing the production of products little different from standard products, the Applicant noted with surprise that one could considerably increase the number of product qualities by playing on the jets section. water along the row of perforations. In particular, the hydraulic diameter is not constant. By hydraulic diameter is understood the diameter of the circle having the same area as the section considered. For example for an oval or polygonal section, the hydraulic diameter is the diameter of the circle which has the same area.

Advantageously, the web is treated with jets arranged in at least two rows parallel to each other. Preferably, the number of rows is at most equal to four.

The process is particularly advantageous when the jets are produced by the same injector. This ensures good synchronization between the steps of the successive rows. We master the patterns on the tablecloth and therefore on the finished products.

This arrangement allows a large number of combinations. According to an advantageous solution to at least two rows of jets, a row comprises jets forming groups spaced from each other, the next row having jets not aligned in the direction of travel of the web with the jets of the first row .

According to another embodiment, a row comprises jets forming groups spaced from one another, the row which follows has jets partly aligned in the direction of travel of the web, with those of the first row. Advantageously, the first row comprises jets of a first section and the next row of jets of a second section. Advantageously still, according to another embodiment, the first row comprises jets of a first section and jets of a second section, the next row comprising jets of a second section or else jets of a second section and jets from a third section.

The process is applied to one side of the web. It can also be applied on both sides. The patterns on both sides can be the same or different.

Advantageously, the fibers are essentially cellulosic fibers, in particular cotton. For example, the tablecloth comprises from 70 to 100% of cotton fibers and from 0 to 30% of artificial or synthetic fibers. The sheet can have a weight up to 400 g / m ² ; preferably the grammage is greater than 150 g / m ² . After the binding treatment, the sheet is transformed into products in the form of round, oval, square or rectangular pads or any other shape for cosmetic or other use as is known.

The invention also relates to a device for implementing the method, in which the jets are produced by perforations or orifices formed along a strip arranged opposite a water distribution channel. This device is characterized by the fact that the perforations are arranged along the same strip and have different sections.

Advantageously, the strip has at least two rows of perforations. According to one embodiment, the perforations of the same row have the same section, this section being different from the perforations of the other row. The invention also relates to a sheet of fibers hydraulically linked by water jets comprising on at least one face grooves formed by said hydraulic bonding. It is characterized by the fact that it comprises at least first deep grooves of 50 to 600 μm with a spacing between a first groove and an adjacent groove of between 0.2 and 5 mm, and at least a second deep groove of 200 at 1000 μm with a spacing between the second groove and an adjacent groove of between 2 and 9 mm, the depth and the spacing of the second groove being greater than that of the first grooves. The depth of the grooves is defined from a cross section perpendicular to their direction, on one face. A groove has two sides, a right side and a left side. Each flank extends between the bottom of the groove and the first vertex encountered from the bottom. The depth of a groove is the difference in level between the top of one of the flanks and the bottom of the latter.

In practice, for grooves of average or surface depth, the depth is defined as an average value from the two values measured on either side of a vertex between two adjacent grooves. When the groove is deep, we measure the two values on each side of the vertex and retain the greater of the two values.

It is noted that whatever the depth of the groove, the measurement is made relative to its adjacent vertex, a distant vertex is not taken into account even if it is at a higher level.

The spacing is defined by the distance between the bottom of two adjacent grooves. This bottom is generally in the form of N. We know patent application EP 1310226. It relates to a cotton wool pad for cosmetic use, the two faces of which have fine parallel grooves having a depth of 0.1 to 0.2 mm and a spacing of 0.5 to 0.7 mm formed by water needling, and at least one face also has wide grooves having a depth of about 0.3 to 0.8 mm and a spacing d '' about 9.0 to 15.0 mm. It is noted that this product is obtained by a first passage of the fiber web under an injector forming the fine furrows then under a second injector forming the broad and deep furrows. It follows that the broad grooves are formed in overprint after a first binding by the fine-jet injectors.

The ply of the invention differs from the subject of the previous patent application by the fact that the second deeper grooves are visually distinct and spaced from the fine grooves. They form separate groups. By the presence of unbound zones, the advantages of softness, absorption and thickness of an unbound web are combined with the mechanical strength and the lint-free surface of a hydraulically linked web. According to another characteristic, the sheet comprises groups of at least two second adjacent grooves and preferably at most six second adjacent grooves. Strip-shaped zones are thus created with an apparent relief comprising non-hydrolated surfaces where the fibers are not hydraulically associated, giving greater softness to the touch. Preferably the first grooves have a depth of between 50 and 250 μm. They form areas of higher binding density than the previous ones.

Preferably, the spacing between a first groove and the adjacent groove closest to the latter is between 0.2 and 2 mm, and more particularly between 1 and 2 mm. Furthermore, the spacing between a second groove and the closest adjacent groove thereof is preferably between 3 and 5 mm.

According to another embodiment, the ply has third grooves different from the first and second grooves. In particular, the third grooves differ from the other two by the depth. In particular, the third grooves differ from the other two also by the spacing.

The invention will now be described in more detail, with reference to the accompanying drawings in which: FIG. 1 schematically represents a conventional hydraulic binding installation, FIG. 2 schematically represents and in section an injector with a perforated strip, FIG. 3 represents schematically a sectional view of a sheet treated with a profile at different levels, FIGS. 4 to 9 schematically represent different arrangements of perforations according to the different rows, FIGS. 10 and 10A respectively show the pattern of the perforations of an injector and the profile as measured after carrying out hydraulic tying tests, FIGS. 11 and 11 A respectively show a pattern of perforations of an injector and the profile as measured after carrying out second hydraulic tying tests, FIGS. 12 and 12A show respectively an injector perforation pattern and the profile as measured has after completion of third hydraulic tying tests, FIGS. 13 and 13A respectively show a pattern of perforations of an injector and the profile as measured after completion of fourth hydraulic tying tests, FIG. 14 shows another variant of arrangement of the orifices .

In Figure 1, there is shown schematically an installation for hydraulic bonding of a sheet of fibers. The sheet N, whose grammage is preferably greater than 150 g / m ² , is supported and driven on an endless belt 10. It is then transferred to a perforated cylinder 20 rotating around a horizontal axis. The sheet then passes in front of an injector 22 arranged perpendicular to the direction of travel of the sheet. The injector perforations, distributed over the entire width of the sheet, are supplied with pressurized water from a pump, and deliver water jets towards the sheet N. On the opposite side of the sheet, at the inside the cylinder, a vacuum slot 24 has been provided to ensure the evacuation of the water once it has passed through the sheet and the porous fabric forming the envelope of the cylinder. After treatment, the sheet is taken to a drying station, for example. A single injector has been shown; according to other embodiments, there is a second or more injectors in parallel with the first, and this on each of the two faces of the sheet preferably.

The injector is shown in more detail in Figure 2; it includes a distributor 221 in the form of a rectilinear channel, here in cross-section. This channel comprises a grid 224 for distributing fluid along its axis. On this grid, a strip 30 has been mounted comprising the perforations. The strip is interchangeable and held by jaws along its axis. Pressurized water fills the distribution channel from a supply duct, not shown. The water is guided through the grid 224 then passes through the strip 30 in as many jets as there are openings in the strip. These perforations or orifices have a profile formed in the thickness of the strip which is adapted to produce stable jets in the form of cylindrical needles. Such a profile may successively include, for example, a cylindrical portion and a divergent portion. To the knowledge of the applicant, the injection orifices of the prior art all have a circular section. In addition, their diameter is constant from one end to the other of the strip. According to the prior art also, the strip can comprise up to three rows of injection orifices staggered. The purpose of the arrangement in two or three rows is to allow greater resistance to the web, with the same injector.

In accordance with the invention, a complex relief structure is produced on the surface of the nonwoven resulting from the binding of the web. An example of a profile of such a structure is shown in FIG. 3. There are zones at different levels in the sheet N: a first zone A, for example at a first deeper level and a zone B at a shallower level. In an application where the sheet N has been transformed into a make-up removal pad, the deeper zones A serve as a reservoir for make-up removal products or for care milks to be applied to the skin. The less deep areas B are the active parts for removing make-up due to the close contact with the skin. They are reinforced by the intermediate zones between zones A and zones B. In addition to the levels, zones A and B may have different widths. The type of structure such as that shown in FIG. 3 is obtained by means of perforations provided on the strip according to the process of the invention. The perforations are assimilated to the jets produced.

There is shown in Figure 4 the arrangement of perforations to obtain a profile of the type shown in Figure 3. This representation and the following are not to scale. The diameter of the perforations has been enlarged for a better understanding of the invention. They are arranged in two rows parallel to each other perpendicular to the direction of travel of the sheet of fibers. A first row is composed of circular perforations 14 with a first diameter. They are grouped by five with a first spacing between them. The perforations produce defined jets from their section.

Each group is spaced from its adjacent group by a distance greater than the first spacing. For example, the spacing between the perforations of a group can be 0.2mm or more and the spacing between two adjacent groups can be greater than 2mm, the diameter of the perforations being 80 to 300μm. On the next row there are perforations 24 whose diameter is different from that of the perforations 14. They are here arranged in the interval between two adjacent groups of the first row. Each group in the second row has two perforations arranged so as to be inserted between the groups in the first row. Preferably, the two rows are arranged on the same strip because the perforations are then supplied under the same hydraulic conditions, in particular pressure. The jets from the larger diameter perforations therefore have greater energy since the energy in this case is related to the flow rate. The ridges or grooves formed by the latter are deeper than the ridges formed by the first row. There is no interference between the jets from the perforations of the two rows. The streaks are well separated. It is the best solution to properly synchronize the water jets and master the final pattern.

FIG. 4A shows the arrangement of the perforations in a single row. This comprises perforations with a first section 14A and perforations according to a second section 24A, different from the first.

FIG. 5 shows another arrangement of perforations. It differs from the previous one by adding perforations 15 'opposite the perforations 25 in the next row. These perforations 15 ′ differ from the perforations 15 by their longitudinal profile, not shown. They produce more diffuse jets and therefore less marked grooves. The hydraulic characteristics of these perforations are for example degraded with respect to those of the perforations 15 so that the jets produced have little effect on the surface of the sheet. Their function is to prepare the tablecloth to receive the jets of the next row which score better.

In Figure 6 there are shown perforations 26 on the second row which have a non-circular section. The shape is oval with an axis inclined with respect to the alignment of the perforations 16. However, the shape of the section may still be different; you can also remove the tilt.

In FIG. 7, the perforations in the first row are of circular section. However, there are perforations 17 with a first section and perforations 17 'with a second section of larger diameter. The perforations 17 are grouped here by 5 with a first spacing therebetween. Between these groups, the perforations 17 'have been arranged here, two in number.

The second row comprises perforations 27 with a section, here, identical to the first. They are aligned in the direction of travel (which is perpendicular to the rows) with the perforations 17. Two perforations 27 'are arranged in alignment with a perforation 17'. This arrangement makes it possible to make streaks on several levels: a first level is obtained by the jets of the perforations 17 and 27 aligned, a second level obtained by the alignment of the jets from the perforations 17 'and 27', and a third level is obtained by a 17 'hole only.

Figure 8 shows 2 rows. Compared to the direction of travel, the layout is reversed when compared to the layout in Figure 4. The largest perforations are at the front. FIG. 9 shows an example of a strip with three rows, 19, 29 and 39. The sections of the perforations 19 are the largest; the perforations of the second row 29 have an intermediate dimension between that of the perforations 19 and 39 of the third row. It can therefore be seen that the process makes it possible to produce sheets of cotton or other striated cellulosic fibers, the profile of which can be varied.

Combinations other than those shown here can be designed without departing from the scope of the invention by playing on both the arrangement of the perforations and their section.

Products in accordance with the invention have been produced with binding water injectors comprising orifices on the same "strip" arranged in different patterns. FIG. 10 shows an injector, the strip of which has orifices distributed in two rows: a first row of orifices 110 with a diameter of 140 μm and a second row of orifices 210 of oval shape with a large diameter of 700 μm. The holes are shown in enlargement with respect to their spacing. The repeating pattern here consists of five holes 110 with a diameter of 140 μm, spaced from each other by 4.8 mm and an oval hole. The distance between the center of the oval hole 210 and that of the adjacent hole 110 is 7.2 mm. This pattern repeats over the entire width of the injector. Four sheets, of the same weight Pds, of hydrophilic cotton were subjected to a hydroliage treatment with such an injector, the water supply of which was regulated at a different pressure P for each: 20, 40, 64 and 84 bars respectively. After treatment, the thickness of the ply EP was measured in mm, its swelling G in mm, the resistances direction of movement Rsm and direction across Rst in Newton per inch wide (N / inch). The thickness EP of the sheet is the measurement of a stack of 20 formats cut from the sheet with the application of a pressure of 2.25 g / cm ² . The bulking G or thickness potential corresponds to the increase in height of the stack of formats when the above pressure is removed.

The depth of the grooves was measured using the following method:

A sample is placed under a 3 CCD digital camera, ensuring that it is well level and well centered. We make an image. By means of appropriate software, Optocat for example, the image is acquired and processed in the determined area of interest by combining the Gray code and phase shift techniques. Automatic masking removes points with poor contrast or with ambiguities. Then by software, Toposurf for example, we analyze the image obtained and we create a profile of its relief. The relief is measured on the curve obtained.

For a zone examined, a curve as shown in FIG. 10A is obtained with the distance along the profile on the abscissa in mm, and the height on the ordinate in μm.

As can be seen in FIG. 10A, the area measured is cut into segments here from A to F. Each of the segments frames a bell profile with a peak between two grooves. The spacing between the grooves corresponds to that of the orifices provided on the strip of the injector used, which can easily be checked. For each segment, the height of the peak is determined relative to each of the two low points. Two heights of the same peak are therefore obtained respectively with respect to the low level of the two lateral grooves.

Then for each of the peaks which does not correspond to a deep groove (here the grooves other than that between the segments C and D), the average value of the two values is determined. For deep grooves, the value used is the maximum of the values measured on their highest side. In the present case, there is only one deep groove in the measured area between C and D. A value is obtained for each of the segments. There are three values respectively Hs low, Hp high, and Hm medium and: the value Hs corresponding to the depth of the surface grooves which form said first grooves. the value Hp corresponding to the maximum depth of the deep grooves which form said second grooves, the value Hm corresponding to the depth of the average grooves which form said third grooves or else said first grooves in the absence of an Hs value,

In the present example, only Hp and Hm values could be determined due to the nature of the pattern.

From the pressure P and the flow rate, the energy EN (in 10 ^"3 kWh / m ² ) applied to the sheet can be determined.

A control sheet T was also produced with an injector having only one kind of regularly spaced orifices according to the prior art.

We note that for an applied energy value comparable to that of the control (between 1 and 2 10 ^"3 kWh / m ² ), we obtain by this technique deep groove depths between 600 and 850 μm for a pressure between 40 and 64 bars only, this value should be compared with the average depth of 250 μm on the control sheet.

It is also observed that the thickness of the sheet is greater (63-66 mm compared to 58 mm) and the swelling improved (6 compared to 4).

The results have been collated in the table below.

Reason 1

In this example the first grooves are the grooves defined by the segments A, B, C; D, E, F and the second groove is formed between segments C and D.

In FIG. 11 another test arrangement is shown.

This pattern comprises, on a first row, a first group of five circular orifices 111 of diameters 140 μm spaced 1.2 mm apart, and, on a second row, a second group of three circular orifices of diameter 200 μm. The spacing between the orifices 211 is 2.4 mm. The second group is at a distance of 4.8 mm from the first group on both sides. This pattern repeats throughout the strip.

The profile, as measured according to the method recalled above, is shown in Figure 11 A.

In the zone examined, we note the presence of segments that have been designated from A to O. We distinguish first surface grooves of depth Hs whose value is determined from the sides of the segments [C, D, E, F , K, L, M, N]. second deep grooves between segments A and B, G and H, and I and J [A, B, G, H; I, J] The depth Hp value is determined from the values measured respectively on the right flanks of A, left flank of B, right flank of G and left flank of J. [A, B; G, J]. We retain the maximum value for Hp. Third grooves of depth Hm whose value is determined from the segments H and I [H, I].

The values determined are shown in the table below. Note that this pattern allows for second deep grooves up to 774 μm. This depth is to be related to the spacing of 4.8 mm between the first group and the second group of orifices

Pattern 2

According to a variant of the pattern, a pattern is provided for example with a group of five first orifices 111 1 mm apart and a group of three second orifices 4 mm apart. FIG. 12 shows the pattern of the injector orifices chosen for a third test.

The injector has

On a first row, a group of four circular orifices 112: diameter 140 μm, spacing 2 mm; In a second row, a group of three circular orifices 212: diameter 180 μm, spacing 3 mm;

In a third row, a single circular opening 312: diameter 200 μm, spacing 6 mm.

The profile of the relief, in a cross section to the direction of the grooves, determined by the measurements carried out is shown in FIG. 12A. We distinguish the segments referenced from A to K with first, superficial grooves, defined by the segments [G on the right, H, I, J], a second, deep groove, defined by the right flank of C, and the left flank of D, third grooves, of medium or intermediate depth, defined by the sides of segments E, F, and the left side of G

The table below brings together the values Pattern 3

FIG. 13 shows the injector pattern for a fourth test.

The injector has

On a first row, a group of four circular orifices 113: diameter 140 μm, spacing 1.2 mm; In a second row, a group of two circular holes 213: diameter

180 μm, spacing 2.4 mm;

In a third row, a single third circular opening 313: diameter 200 μm, spacing 4.8 mm.

The profile determined by the measurements carried out is shown in FIG. 13 A. a distinction is made between the segments referenced from A to N with first surface grooves defined by the segments [C, D, E, J, K, L], three second grooves deep [left flank of A; between G and H; and right flank of N] and of the third middle grooves defined by the segments [B, F, I, M].

The table below collects the measured values.

Pattern 4

The grooves are for example rectilinear but they can also be at least partly broken, wavy, sinusoidal in particular or even interrupted.

According to a variant of this motif, not shown, a group of five or four orifices 113 (140 μm) spaced 1.2 mm each is provided, a group of two orifices 213 (180 μm) with a spacing of 3.6 mm and a third orifice 313 (200 μm) also 3.6 mm apart.

FIG. 14 shows another variant of the pattern for distributing orifices on the same injector strip. The pattern successively comprises on a row a group of three orifices 114 (140 μm) spaced 1 mm apart, on another row a group of two orifices 214 (180 μm) with a spacing of 3 mm and on another row still a single orifice 314 (200μm) with a spacing of 3 mm with the orifices 214 and 4 mm with the orifices 114.

As can be seen, the arrangements of orifices of different diameters and different spacing can be varied on separate rows or on the same row.

Claims

claims

I. Method of hydraulically bonding a sheet (N) of fibers, consisting in placing the sheet on a porous support (10) movable in translation or in rotation about an axis, treating at least one face of the sheet with means of a plurality of water jets arranged in a row perpendicular to the direction of travel of the sheet, characterized in that the row comprises jets with a first section (14A) and at least jets with a second section ( 24A) different from the first.

2. Method of hydraulic bonding of a sheet of fibers, consisting of placing the sheet on a porous support movable in translation or in rotation about an axis, treating the sheet using a plurality of water jets arranged along at least two rows perpendicular to the direction of travel of the web, characterized in that the rows include jets with a first section (14, 16, 17, 18, 19) and at least jets with a second section (24 , 26, 27, 28, 29, 39) different from the first, at least one row comprising jets whose spacing between them is not constant.

3. Method according to the preceding claim according to which the web is treated by means of jets arranged in a number of rows ranging from two to four.

4. Method according to claim 2 or 3, the rows of jets are produced by the same injector (22).

5. Method according to one of claims 3 to 4, one row of which comprises jets (14, 18) forming groups spaced from one another, the next row having jets which are not aligned in the direction of travel of the web. with the jets in the first row (24, 28).

6. Method according to one of claims 3 to 4, one row of which comprises jets (17) forming groups spaced from one another, the next row having jets (27, 27 ') partly aligned in the direction of scrolling of the tablecloth, with those of the first row.

7. Method according to one of claims 5 and 6, the first row comprising jets of a first section and the next row of jets of a second section.

8. Method according to one of claims 5 and 6, the first row comprising jets of a first section and jets of a second section, the next row comprising jets of a second section or jets of a second and third section jets.

9. Method according to one of the preceding claims in which the two faces of the sheet are treated.

10. Method according to one of the preceding claims, in which essentially cellulosic fibers are treated, in particular cotton fibers.

I I. Device for implementing the method according to one of the preceding claims, in which the jets are produced by perforations formed along a strip disposed opposite a water distribution channel, characterized by the fact that the perforations on the same strip (30) have different sections.

12. Device according to the preceding claim, in which the strip (30) has at least two rows of perforations. 13. Device according to the preceding claim, in which the perforations of the same row have a first section, this section being different from the section of the perforations of the other row.

14. Sheet of fibers hydraulically linked by water jets comprising on at least one face grooves formed by said hydraulic bonding characterized in that it comprises at least first deep grooves of 50 to 600 μm with a spacing between a first groove and an adjacent groove between 0.2 and 5 mm, and at least one second deep groove of 200 to 1000 μm with a spacing between a second groove and an adjacent groove between 2 and 9 mm, the depth and the spacing of the second groove being greater than those of the first grooves.

15. A web of fibers according to claim 14 comprising at least one group of at least two second adjacent grooves and preferably at most five second adjacent grooves.

16. A sheet of fibers according to claim 15 comprising at most six second adjacent grooves. 17. A fiber sheet according to claim 14, 15 or 16, the first grooves of which have a depth of between 50 and 250 μm.

18. A sheet of fibers according to one of claims 14 to 17 comprising at least one group of at least two first adjacent grooves and preferably at most twenty first adjacent grooves.

19. A sheet of fibers according to one of claims 14 to 18, the spacing between a first groove and an adjacent groove is between 0.2 and 2 mm, preferably between 1 and 2 mm.

20. fiber mat according to one of claims 14 to 19, the spacing between a second groove and an adjacent groove is between 3 and 5 mm.

21. A sheet of fibers according to one of claims 14 to 20 comprising third grooves different from the first and second grooves.

22. A sheet of fibers according to claim 21, the third grooves of which differ from the other two by the depth. 23. a sheet of fibers according to claim 22, the third grooves of which differ from the other two by the spacing.

24. Tablecloth according to one of claims 14 to 23 obtained according to the method of one of claims 1 to 10.

5. Fibrous pad intended for skin care produced from a sheet according to one of claims 14 to 24.