EP1391174A1 - Roll of cellulose wadding sheets and process for producing the same - Google Patents

Abstract

The absorbent paper roll contains layers of cellulose wadding sheets (1a, 1b), each with at least one ply having a weight of between 10 and 40 g/sq m. The sheets have thicker zones (4) that are separated for at least 90 per cent of their periphery by thinner zones (5), and in the outer layers of the roll the thicker zones are positioned so that they at least partially overlap one another, creating a difference in height (H) on at least the outside of the roll. The thicker zones of the paper are produced by micro-embossing, forming projecting areas with at least 30 points per sq cm, with the point having areas of between 0.03 and 2 sq mm at their tips. The difference in thickness between the thicker and thinner zones of the paper is at least 10 per cent and preferably at least 20 per cent.

Description

The present invention relates to the field of absorbent paper sanitary or domestic use, more specifically cotton wool products cellulose, and more particularly targets rolls formed from absorbent papers as well as their manufacturing process.

Rolls of toilet paper or paper towels for example are preferred applications of the invention.

Specifically, the invention relates to rolls formed of sheets absorbent paper based on cellulose wadding which have zones thick separated by areas of lesser thickness.

Embossing is a known way to give thickness and relief to such leaves.

The embossing operation is performed on a sheet of paper with low humidity level, that is to say the so-called dry part of the installation, located in downstream of the wet part relative to the manufacturing process of the sheet of paper.

The present invention relates to the formation of the roll once the embossed sheet of paper in the dry part of the installation.

The embossing process allows you to distort locally and a fold forming part of a sheet, that is to say to obtain protrusions on one side corresponding to a hollow on the other side of said fold.

The association of two folds so that their protuberances are in contact is known as the "point-to-point" technique, while when the protrusions of a fold are nested in the recessed areas on the other fold, it is the technique called "nested" or "nested".

Anyway, the folds are embossed with a frequency of distribution of the protuberances, a height and a shape adapted to the realization of the final product; these parameters have a particular effect on the final thickness of the sheet, its softness, flexibility, qualities of absorption and its aesthetics.

The thickness of a cellulose wadding sheet can also be obtained by other means such as the superposition of a larger number of folds, for example 3 or 4 folds. However this technique has limits related to the assembly of folds. So, practically, we cannot assemble more than 4 folds to properly form a sheet in cellulose wadding.

Another known way to give bulk, or thickness to a sheet formed from cellulose wadding is to manufacture it according to a technique called TAD (Through Air Drying).

These different techniques therefore make it possible to give bulk and / or a particular external appearance to each of the sheets making up a roller. However, the external appearance of the roller does not reflect the bulking imparted to each sheet. Figure 1 is an example of a roller obtained according to the prior art, from sheets having in themselves a certain relief. The external appearance of such a roller is relatively flat, without specific relief or swelling, which is not very attractive for the buyer.

Indeed the current sheets of the rollers are subjected, during winding, to constraints such that the patterns are more or less crushed and therefore not visible from a distance.

Such a product is perceived as banal, of medium category by the buyer who, as a result, risks choosing another product.

Furthermore, we know US Patent 4,339,088 which describes a process to make a roll of absorbent paper sheets formed in such a way so that throughout the winding of the roller, we avoid mutual nesting of the leaf protrusions. This does not confer well heard no relief on the roller itself. This mutual interlocking of leaf relief is considered an adverse effect by humans of the trade, since it hinders the good winding of the product.

In a new and unexpected way, it has been discovered that the aspect outside of a roll made of cellulose wadding sheets could be significantly improved thanks to specific technical characteristics linked to the constitution of the roller.

Thus one of the objectives of the present invention is to achieve a pronounced relief on the outside of the roller, before first use.

Thus, the subject of the present invention is a roll formed from a plurality of cellulose wadding sheets each having at least one ply, the grammage of each of the plies being between 10 and 40 g / m ² , and the sheets having thick areas separated over at least 90% of their periphery by thinner areas.

According to the invention, on at least the most coils outside of the roller, thick areas are at least partially superimposed on each other so as to combine the thicknesses and create level differences at least on the outside of the roller.

Thus, by superimposing thick zones on other zones of same type, in particular at the level of the last turns of the roller, we obtains raised areas on the outside of the roller clearly visible at a distance of several meters.

More precisely according to the invention the difference in thickness between thick areas and thinner areas of said sheets is at least 10%, preferably at least 20%.

Thus, given the relative arrangement of the sheets forming the last turns of the roller, there is a significant difference in level H over the visible (outer) face of the roller between raised areas and hollow areas.

In accordance with an embodiment of the invention, the zones thick of said sheets are embossed.

According to a particular embodiment of the invention, at least 50% of the thick areas of said sheets are formed by a micro-embossing on at least one fold, said micro-embossing consisting of a set of protrusions of density at least equal to 30 spikes / cm ² and whose surface at the top is between 0.03 mm ² and 2 mm ² .

Thick areas and non-thick areas of the sheet define together at least one motif.

Advantageously, the pitch P machine direction of the pattern is such that NxP = ΠxD where N is a non-zero integer preferably greater than 1 and D is the outside diameter of said roller.

The machine direction P of the pattern is the smallest distance in the sheet running direction in the manufacturing machine, distance by which the pattern is reproduced identically.

By realizing on the one hand particular patterns and by choosing on the other hand, a step P as claimed, a new visual effect and unexpected is obtained.

According to an additional characteristic of the invention, the zones thick are spaced from each other by a distance greater than 2 mm and preferably greater than 4 mm.

More specifically, the thin areas may be non embossed or formed with protrusions at least 10% high less than the height of the protrusions forming the thick zones.

In addition, the areas of the thick zones are preferably greater than 2 cm ² .

These characteristics, considered alone or in combination, allow to create reliefs on the outside of the roller, that is to say create visual effects to amplify the perception of thickness, comfort, even absorption of the product.

Without departing from the scope of the invention, the thick zones are delimited by linear elements or not, of depth greater than the thickness of thick areas.

It is for example possible to form pads, or a quilted structure or any other motif whose relief stands out well on outside of the roller.

A particular form of the invention relates to a roller, the sheets comprise at least two folds, a first fold being embossed and a second fold not being embossed, the first fold being visible from outside of the roller.

Another form of the invention relates to a roller whose sheets comprise at least two folds, the folds being embossed according to different embossing patterns. In particular, the invisible fold of the outside of the roll may consist of a micro-embossing over its entire area.

A roll according to the invention can be formed from a plurality of cellulose wadding sheets each having at least one ply, the grammage of each of the plies being between 10 and 40 g / m ² , with differences in level H at least on the outside of the roller, formed by raised areas with a surface area of between 3 and 20 cm ² separated over at least 90% of their periphery by hollow areas.

By way of illustration, said differences in level H between the zones in relief and the recessed areas are at least 0.2 mm, preferably at least minus 0.4 mm.

The invention further relates to a method for producing a roller. consisting in winding on itself a strip formed of a plurality of cellulose wadding sheets juxtaposed, said sheets having thick areas separated by thinner areas.

According to a characteristic of the invention, the winding is such that the thick zones of the turns are at least partially superimposed more external of said roller.

In the context of the invention, the thick zones are partially superimposed, if at least 80% and preferably 90% of the surface of a thickest area of the outermost turn covers a thickest area of the nearest turn.

As already stated, the set of thick zones and zones thinner sheets define at least one relief pattern.

Advantageously, a step P direction of said pattern is determined. such that NxP = ΠxD or N is a non-zero integer preferably greater than 1 and D is the outside diameter of said roller.

In particular, the roll is formed from sheets made up at least two folds embossed and arranged according to the tip-tip process.

According to one embodiment of the invention, the roller is formed of sheets consisting of at least two folds, at least one of which is embossed, the folds that can be combined by gluing.

In addition, the folds can be embossed separately, with different embossing patterns.

Without departing from the scope of the invention, the method can also consist in pre-embossing at least one of the folds of said sheet by means of a uniform micro-embossing and then embossing said fold to form said less thick areas; said micro-embossed ply may for example have on all or part of its surface at least 30 protuberances per cm ² .

• La figure 1 est une photo d'un rouleau selon l'art antérieur ;
• La figure 2 est un schéma montrant la superposition théorique de deux feuilles selon l'invention ;
• La figure 3 est un schéma de même type que celui de la figure 2, montrant la position des feuilles sur un rouleau ;
• La figure 4 est un schéma d'un autre mode de réalisation de l'invention ;
• La figure 5 illustre encore un autre mode de réalisation de l'invention ;
• La figure 6 est une photo d'un rouleau obtenu selon l'invention ;
• La figure 7 est un dessin d'un motif de gaufrage d'une feuille faisant partie d'un rouleau selon l'invention ; et
• La figure 8 est un dessin d'un autre motif de gaufrage d'une feuille faisant partie d'un rouleau selon l'invention.

Other characteristics, advantages and details of the invention will appear better on reading the description which follows, given by way of illustration and in no way limiting with reference to the attached drawings in which:

• Figure 1 is a photo of a roller according to the prior art;
• FIG. 2 is a diagram showing the theoretical superposition of two sheets according to the invention;
• Figure 3 is a diagram of the same type as that of Figure 2, showing the position of the sheets on a roll;
• Figure 4 is a diagram of another embodiment of the invention;
• FIG. 5 illustrates yet another embodiment of the invention;
• Figure 6 is a photo of a roller obtained according to the invention;
• Figure 7 is a drawing of an embossing pattern of a sheet forming part of a roll according to the invention; and
• Figure 8 is a drawing of another embossing pattern of a sheet forming part of a roll according to the invention.

Figure 2 illustrates the theoretical positioning of sheets making part of a roller according to the invention, in particular at the level of the turns more external.

With such an arrangement, the thicknesses of the most thick 4 of the leaves accumulate while the thinner areas 5 remain spaced from each other.

More specifically, Figure 2 shows in section two sheets capable of being part of a roll according to the invention. Each sheet 1a, 1b here consists of thick areas 4, with an area for example of between 3 and 20 cm ² , separated by thin areas 5. The thick areas 4 are separated by a distance of at least 2 mm. The difference in thickness between these two types of zones is at least 10%. This difference in thickness on each sheet can for example be demonstrated using a micrometer, which will apply a pressure of 20 g / cm ² to a sample for 5 seconds. A thick zone 4 is then successively measured then a non-thick zone 5, in order to deduce therefrom the difference in thickness between these two zones.

Another way to measure this difference in thickness is to use non-contact surveying devices that provide the profile of each side of the sheet, such as for example the apparatus "Microtop" marketed by the company EOTECH.

In reality, that is to say on the last turns of a roll according to the invention, the superposition of two sheets 1a, 1b may resemble the diagram of FIG. 3. The thickest zones 4 are here in contact, with slight deformation, while the thinner areas 5 of the first sheet 1a (visible from the outside of the roll) are deformed and almost come into contact with the thinner areas 5 of the second sheet 1b (not visible from the outside of the roll). This "subsidence" thin outer areas is mainly due to the constraints that undergoes the sheet during winding. There is indeed a tension on the sheet, in order to obtain a good final roll. We thus create a difference in level H, for example of the order of half a millimeter, which provides relief visible from afar, as shown in Figure 6. A bump / hollow effect is thus obtained.

As it appears in Figures 3, 4 and 5, the difference in level H is the distance between the top of a thick area 4 and the bottom of an area thin 5 at the outermost turn of the roller, that is to say that which is visible from the outside.

FIG. 4 relates to another possible embodiment of the invention, according to which each sheet is made up of two folds, the outside fold 3a being embossed and the inside fold 3b being smooth or non-embossed. The thick zones 4 consist of micro-embossings on the outer ply 1a, with a density greater than 30 spikes / cm ² . The thick zones 4 are delimited by protrusions of larger diameter 6 or by linear protuberances and of depth equal to or preferably greater than the other protuberances forming the micro-embossing. The two plies can be combined by gluing at the level of the large protrusions 6. Examples of such an embossing pattern correspond to FIGS. 7 and 8.

The two sheets 1a, 1b are arranged as shown in the FIG. 4, that is to say with their thickest zones 4 superimposed, as well as their thin areas 5. The protrusions of the embossing can be identical or not. We easily obtain a difference in level H significant which therefore induces a particular effect on the outside of the roller.

The relief according to the invention can only be obtained under certain conditions: thick areas 4, for example embossed, are surrounded by thin zones 5, over most of their periphery, that is to say on at least 90% of their periphery.

Furthermore, the thick zones 4 must be at a certain distance from each other: minimum 2 mm, preferably 4 mm.

In addition, the step P in the running direction of the relief pattern is linked to the outer diameter D of the roller by the relation: NxP = ΠxD; N being a non-zero whole number preferably greater than one.

In a roll, there will therefore be several overlapping zones answering this equation, according to the value of N.

By way of illustration, the step P direction of the pattern can be of the order from 5 to 6 cm.

Advantageously, the thick zones have an area greater than 2 cm ² , for example between 3 and 20 cm ² . They can be constituted by a micro-embossing, that is to say a set of protrusions with a density at least equal to 30 spikes / cm ² , with for example a surface at the apex of between 0.03 mm ² and 2 mm ² .

FIG. 5 illustrates yet another embodiment of the invention that the outermost turns of the roller are consisting of sheets 1a, 1b each comprising two embossed plies 3a, 3b.

In this case, the two folds 3a, 3b are arranged so that their respective protuberances are in contact (tip-tip association). Thus, on the last turn, we obtain a difference in level H clearly visible from the outside of the roller. Of course, the difference H is to be considered as an average value because of manufacturing deviations may lead to slight differences in the value of H on the roller.

Any system known per se can be used to measure whether necessary the difference in level H on the outside of the roller: by example by image analysis from a photograph of the "crest" of the roller, or by topography with or without contact.

For this purpose it is possible to use a digital camera of visualization of the profile of the ridge of the roller which is illuminated in light grazing. Then, once this profile is saved on a computer, it is possible thanks to specialized software to measure differences in height H between the "top" of thick areas and the "bottom" of areas thin.

Without departing from the scope of the invention, the sheets may be each made up of several folds with different physical characteristics such as grammage, aspect ratio, thickness ...

The methods for obtaining the folds 3a, 3b forming the sheets 1a, 1b can be of any type known per se, example: CWP (Conventional Wet Press / Standard process with drying on heated cylinder), TAD (Through Air Drying / Drying process by blowing through air). We can also combine, within the framework of the invention, folds obtained according to different processes.

The photograph in FIG. 7 illustrates an embodiment where we see thick zones 4 micro-embossed, in the shape of diamonds, delimited by elements 6 such as pins of greater depth. The thinner zones 5 separate the zones 4; a spacing defined by zones 5 is thus achieved between zones 4. This spacing, combined in particular with the superposition of the most external of the roller, allows to obtain the relief according to the invention.

As can be seen in FIG. 8, the thick zones 4 can include linear protuberances 8, or a combination of linear protuberances 8 and micro-embossing. On the photograph of the Figure 8, the elements 6 which delimit the thick areas 4 formed essentially of a micro-embossing, can be formed of protuberances greater depth.

Of course, any form of pattern inside a thick area 4 can be imagined.

In the context of the invention, the thin zones 5 can be smooth areas, with no protuberances, but they can also be made up of protrusions giving little thickness to the product. Their thickness is preferably equal to the thickness of the material of departure.

One way to make this type of product can be to pre-embed one or more folds thanks to a micro-embossing then to “crush” by embossing or knurling certain areas which will become little areas thick 5.

Another embodiment of the invention may consist in creating by any means known per se, zones of lesser thickness on a product thick such as a sheet comprising 3 or 4 plies or of the T.A.D type such as defined above.

Regarding the assembly of the different folds forming a sheet cellulose wadding, several known possibilities are possible: gluing, knurling, cold or hot marking.

Preferably, the folds can be glued at the highest protrusions, delimiting thick areas. In that case, the folds can be combined using a matching cylinder or according to the tip-tip process.

Thick zones 4 are not necessarily separated on their entire periphery by thin areas. They can be "linked" to other thick areas. This is why it is expected that thick areas are surrounded on at least 90% of their periphery by areas thin 5.

Claims (19)

Roll formed from a plurality of cellulose wadding sheets (1a, 1b) each having at least one ply (3a, 3b), the grammage of each ply being between 10 and 40 g / m2, the sheets having thick areas (4) separated over at least 90% of their periphery by thinner areas (5), characterized in that on at least the outermost turns of the roller, the thick areas (4) are at least partially superimposed to each other so as to combine the thicknesses and to create differences in level H at least on the outside of the roll. Roll according to Claim 1, characterized in that the difference in thickness between the thick zone (4) and the thinner zone (5) of a sheet is at least 10%, preferably at least 20%. Roll according to any one of the preceding claims, characterized in that the thick zones (4) of the said sheets are embossed. Roll according to any one of the preceding claims, characterized in that at least 50% of the thick zones (4) of the said sheets are formed by a micro-embossing on at least one fold, the said micro-embossing consisting of a set protuberances with a density at least equal to 30 pins / cm ² and whose surface at the top is between 0.03 mm ² and 2 mm ² . Roller according to any one of the preceding claims, in which said thick zones (4) and said non-thick zones (5) define at least one relief pattern characterized in that the pitch P in the machine direction of said pattern is such that NxP = ΠxD where N is a non-zero integer preferably greater than 1 and D is the outside diameter of said roller. Roll according to any one of the preceding claims, characterized in that the thick zones (4) are spaced from each other by a distance greater than 2 mm and preferably greater than 4 mm. Roller according to any one of the preceding claims, characterized in that the thin zones (5) are unembossed or formed by protuberances the height of which is at least 10% less than the height of the protuberances forming the thick zones (4). Roller according to any one of the preceding claims, characterized in that the areas of the thick zones (4) are preferably greater than 2 cm ² . Roller according to any one of the preceding claims, characterized in that the thick zones (4) are delimited by elements (6) which are linear or not, of depth greater than the thickness of the thick zones (4). Roll according to any one of the preceding claims, characterized in that the sheets comprise at least a first embossed fold and a second non-embossed fold, the first fold being visible from the outside of the roll. Roll formed from a plurality of cellulose wadding sheets (1a, 1b) each having at least one ply (3a, 3b), the grammage of each of the plies being between 10 and 40 g / m ² , with differences at level H at least on the outside of the roller, characterized in that said differences in level H are formed by thick zones (4) with a surface preferably greater than ² cm ² separated over at least 90% of their periphery by zones not thick (5). Roller according to claim 11, characterized in that said level differences H between the thick areas and the non-thick areas are at least 0.2 mm, preferably at least 0.4 mm. Method for producing a roll according to any one of the preceding claims, consisting of winding on itself a strip formed of a plurality of sheets of cellulose wadding juxtaposed, said sheets having thick zones (4) separated on at minus 90% of their periphery by thinner zones (5) characterized in that the winding is such that the thick zones (4) of the outermost turns of the roller are at least partially superimposed. Method according to claim 13, in which said cellulose wadding sheets have on at least one of their faces thick zones (4) separated by thin zones (5) which together define at least one relief pattern, characterized in that a pitch P direction of said pattern is determined such that NxP = ΠxD where N is a non-zero integer preferably greater than 1 and D is the outside diameter of said roller. Method according to Claim 13 or 14, characterized in that the roller is formed from sheets (1a, 1b) made up of at least two embossed plies (3a, 3b) and arranged according to the tip-tip method. Method according to any one of Claims 13 to 15, characterized in that the roll is formed from sheets (1a, 1b) consisting of at least two plies, at least one ply of which is embossed (3a, 3b), and in that that we combine the folds by gluing. A method according to claim 16 characterized in that the plies are embossed separately with different embossing patterns. Method according to any one of Claims 13 to 17, characterized in that it also consists in pre-embossing at least one of the folds of said sheet by means of a uniform micro-embossing then in embossing said fold to form said thinner zones (5 ). Method according to claim 17, characterized in that the microgolded ply (s) have (s) on all or part of its surface at least 30 protuberances per cm ² .

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